Carbon material, its manufacturing method, and secondary battery and power consumption device including the same

Abstract

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

Description

[Technical Field]

[0001] The present application relates to the technical field of batteries, and more particularly to carbon materials and methods for producing the same, as well as secondary batteries and power consuming devices containing the same. [Background technology]

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in many fields, including power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As the range of applications for secondary batteries becomes increasingly broad, the performance requirements for secondary batteries also increase. For example, secondary batteries are required to combine various performance characteristics such as energy density, dynamic performance, and service life. The negative electrode active material is an important component of secondary batteries and affects their performance. Currently, negative electrode active materials mainly contain graphite. However, the prior art has faced challenges in combining high capacity graphite with high initial coulombic efficiency, and it is also difficult to achieve good cycling performance and dynamic performance in secondary batteries. Summary of the Invention

[0003] The present application aims to provide a carbon material that enables a secondary battery to have high initial coulombic efficiency and good cycle performance and kinetic performance, a method for producing the same, and a secondary battery and a power consuming device including the same.

[0004] A first aspect of the present application provides a carbon material comprising a pore structure, the carbon material comprising a 3R phase and a 2H phase simultaneously present, and a 0 3R(101) / I 2H(004) ≦0.100, where I 3R(101) is the peak intensity of the diffraction peak of the 3R phase 101 crystal plane in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 2H phase 004 crystal plane in the X-ray diffraction spectrum of the carbon material.

[0005] ​ In the course of their research, the inventors discovered that 3R-phase crystalline carbon and 2H-phase crystalline carbon exist simultaneously in a carbon material, and the ratio of the peak intensity of the diffraction peak of the 3R-phase 101 crystal plane to the peak intensity of the diffraction peak of the 2H-phase 004 crystal plane is 0.01 to 0.01. 3R(101) / I 2H(004) It has been discovered that when the ratio ≦0.100 is satisfied, there are many active sites on the surface of the carbon material particles, which can accelerate the transport of active ions and also ensure high surface stability of the carbon material particles, thereby effectively reducing surface side reactions and the consumption of active ions. The carbon material according to the present application has a pore structure, which provides the expansion space necessary for the volume change of the carbon material particles, thereby reducing the risk of new interfaces being generated due to the fracture of the carbon material particles, reducing the occurrence of side reactions and the consumption of active ions. Therefore, the carbon material according to the present application can combine high ion transport performance, high surface stability, and low volume change, and can further enable secondary batteries using the carbon material to combine high initial coulombic efficiency and good cycle performance and kinetic performance.

[0006] In any embodiment of the present application, 0.005≦I 3R(101) / I 2H(004) ≦0.100, and optionally, 0.008≦I 3R(101) / I 2H(004) ≦0.065. I of carbon materials 3R(101) / I 2H(004) If the value of the initial coulombic efficiency is within the above range, the secondary battery can be made to have a high initial coulombic efficiency, good cycle performance, and good dynamic performance.

[0007] In any embodiment of the present application, the X-ray diffraction spectrum of the carbon material does not have a peak at the 3R phase 012 crystal plane, and in this case, the carbon material particles have fewer internal defects, which can further reduce the consumption of active ions and improve the initial coulombic efficiency and cycle performance of the secondary battery.

[0008] In any embodiment of the present application, the carbon material has a pore area of ​​0.15 μm 2 ​and optionally, one or more pore structures having a pore area of ​​0.15 μm or greater. 2 ~2.0μm 2 In further research, the inventors found that when a carbon material includes a pore structure having the above pore area, the pore structure can ensure expansion space necessary for volume changes of the carbon material particles, thereby further reducing the risk of new interfaces being generated due to crushing of the carbon material particles, further reducing the occurrence of side reactions, reducing irreversible capacity loss in the secondary battery, and improving the cycle performance of the secondary battery.

[0009] In any embodiment of the present application, the carbon material includes an outer region and an inner region located inside the outer region, the outer region extending a distance of 0.25L from the particle surface of the carbon material to 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 denoted as S1, the total pore area of ​​the inner region is denoted as S2, and S2 > S1. When the carbon material further satisfies S2 > S1, it can effectively reduce irreversible capacity loss of secondary batteries, improve the capacity performance of secondary batteries, and more suitably combine high initial coulombic efficiency with good cycle performance and kinetic performance for secondary batteries.

[0010] In any embodiment of the present application, 1.5≦S2 / S1≦420, and optionally 2≦S2 / S1≦300. When S2 / S1 is within the above range, the secondary battery can more suitably combine high initial coulombic efficiency with good cycle performance and kinetic performance.

[0011] In any embodiment of the present application, 0.01 μm 2 ≦S1≦5.0μm 2 Meets the standard of 0.02μm. 2 ≦S1≦4.5μm 2In this case, the carbon material particles have a more stable structure, the electrolyte is prevented from penetrating into the pore structure inside the carbon material particles as much as possible, the occurrence of side reactions is reduced, and the consumption of active ions due to the formation of an SEI film inside the carbon material particles is reduced, without affecting the transport performance of active ions and electrons.

[0012] In any embodiment of the present application, 2.5 μm 2 ≦S2≦25.0μm 2 Selectable, 3.0μm 2 ≦S2≦22.5μm 2 In this case, a sufficient and stable expansion space is ensured to accommodate the volume change of the carbon material particles, the risk of new interfaces being generated due to the fracture of the carbon material particles is reduced, the occurrence of side reactions on the surface of the new interface is reduced, and the consumption of active ions due to the formation of an SEI film on the surface of the new interface is reduced, while the capacity and initial coulombic efficiency of the carbon material can be improved.

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

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

[0015] In any embodiment of the present application, the interior region of the carbon material may include a carbonaceous material having an area of ​​0.15 μm 2 and optionally one or more pore structures having an area of ​​0.15 μm or greater. 2 ~2.0μm 2When the internal region of the carbon material includes a pore structure of the above size, a sufficient and stable expansion space is secured for the volume change of the carbon material particles, reducing the risk of crushing the carbon material particles, while improving the compressed density of the carbon material and increasing the energy density of the secondary battery.

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

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

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

[0019] In any embodiment of the present application, the particle size distribution (Dv90-Dv10) / Dv50 of the carbon material is 0.90 to 1.50, and optionally 0.90 to 1.45, thereby improving the compressed density of the carbon material and further improving the energy density of the secondary battery.

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

[0021] In any embodiment of the present application, the topography of the carbon material comprises one or more of a blocky, spherical, and near-spherical shape.

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

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

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

[0025] A second aspect of the present application provides a method for producing a carbon material, the method comprising: step 1 of providing a raw material having a plurality of pore structures; step 2 of uniformly mixing the raw material and a filler material in a predetermined ratio, and then maintaining the temperature at a first temperature T1 for a first time t1 to obtain an intermediate; and step 3 of maintaining the temperature of the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material, the carbon material comprising a pore structure, the carbon material being a material in which a 3R phase and a 2H phase simultaneously exist, and which is 0. 3R(101) / I 2H(004) ≦0.100, where I 3R(101) is the peak intensity of the diffraction peak of the 3R phase 101 crystal plane in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 2H phase 004 crystal plane in the X-ray diffraction spectrum of the carbon material.

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

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

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

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

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

[0031] In any embodiment of the present application, the caulking value of the filler material is between 20% and 48%, and optionally between 25% and 40%.

[0032] ​In any embodiment of the present application, the filler material comprises one or more of coal pitch, petroleum pitch, polymers and resins, and optionally comprises petroleum pitch.

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

[0034] By adjusting one or more parameters of the type of filler material, softening point, caulking value, amount of addition, etc. within the above range, I 3R(101) / I 2H(004) It is advantageous to adjust the pore size and / or the number of pores in the outer and inner regions of the carbon material to be within an appropriate range. Furthermore, after the filler material is thermally melted, it does not have high viscosity, maintains good fluidity, and is less likely to adhere to raw material particles, reducing aggregation of the raw material particles in the subsequent manufacturing process. This reduces problems such as an increase in surface defects and side reactions in the carbon material particles, which are caused by the need to increase the depolymerization process.

[0035] In any embodiment of the present application, after the raw material and the filling material are uniformly mixed in a predetermined ratio, the temperature-raising process of raising the temperature to the first temperature T1 is a stepwise temperature-raising process, which optionally includes a first temperature-raising process and a second temperature-raising process.

[0036] In any embodiment of the present application, the first temperature-raising process involves raising the temperature to 200° C. to 300° C. and maintaining the temperature at that temperature for 1 hour to 3 hours.

[0037] In any embodiment of the present application, the second temperature increase process increases the temperature to the first temperature T1 and maintains the temperature for a first time t1.

[0038] In any embodiment of the present application, the first temperature T1 is between 700°C and 1100°C, and optionally between 850°C and 1100°C.

[0039] In any embodiment of the present application, the first time period t1 is between 1 hour and 5 hours, and optionally between 2 hours and 4 hours.

[0040] By adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. to fall within the above ranges, it is advantageous to adjust the pore size and / or the number of pores in the outer region and the inner region of the carbon material to fall within an appropriate range.

[0041] In any embodiment of the present application, the second temperature T2 is between 1850°C and 2650°C, and optionally between 2100°C and 2480°C.

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

[0043] By setting the second temperature and / or the second time within the above range, I 3R(101) / I 2H(004) It is advantageous to adjust the value to be within an appropriate range, and it is also advantageous to improve the cycle performance and / or dynamic performance of the secondary battery.

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

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

[0046] The carbon material produced in the present application has few surface defects and / or bulk defects, and the carbon material can combine high ion transport performance, high surface stability, and low volume change, and secondary batteries using the carbon material can also combine high initial coulombic efficiency and good cycle performance and kinetic performance. The power consumption device of the present application includes the secondary battery of the present application and has at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0047] In order to more clearly explain the technical solutions of the embodiments of the present application, the drawings necessary for the embodiments of the present application will be briefly described below. It is clear that the drawings described below are only some embodiments of the present application. Those skilled in the art can further derive other drawings based on the drawings without the need for creative work. In the drawings, the drawings are not necessarily drawn to actual size. [Figure 1] FIG. 1 is a schematic diagram of a cross-sectional image of one of the particles of the carbon material of the present application. [Figure 2] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Figure 3] 1 is an exploded schematic view of an embodiment of a secondary battery of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 5] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 6] FIG. 6 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 5. [Figure 7] 1 is a schematic diagram of an embodiment of a power consuming device that includes a secondary battery of the present application as a power source. [Figure 8] 1 is an X-ray diffraction spectrum of the carbon material produced in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0048] Hereinafter, embodiments of the carbon material and its manufacturing method, as well as secondary batteries and power consumption devices including the carbon material and its manufacturing method specifically disclosed in the present application, will be described in detail with appropriate reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0049] "Ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of that particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 and maximum range values ​​of 3, 4, and 5 are recited, then ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, the numerical range "a to b" is an abbreviation indicating any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 and 5" are included herein, and "0 to 5" is an abbreviation for combinations of these numerical values. Furthermore, expressing a parameter as an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions are considered to be included in the disclosure content of the present application.

[0051] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions are considered to be included in the disclosure content of the present application.

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

[0053] Unless otherwise specified, the terms "comprise" and "include" used in this application mean open-ended and may also be closed-ended. For example, the terms "comprise" and "include" can mean "comprise" or "include" other components not listed, or "comprise" or "include" only the listed components.

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

[0055] Unless otherwise explained, terms used in this application have the well-known meanings commonly understood by those of ordinary skill in the art.

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

[0057] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be inserted and removed back and forth between the positive and negative electrodes of a secondary battery, including, but not limited to, lithium ions.

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

[0059] Depending on the manufacturing process or source, graphite can be divided into artificial graphite and natural graphite. The production of artificial graphite generally requires a high-temperature graphitization process, which consumes a lot of energy and is expensive, resulting in a high cost for the artificial graphite. Natural graphite, derived from nature, has the advantage of being inexpensive. Natural graphite also has the advantages of high capacity and high compaction density.

[0060] Natural graphite mainly includes flake graphite, natural spherical graphite, and microcrystalline graphite. Unlike artificial graphite, natural graphite typically has numerous voids and defects inside and outside the particles. During the initial charge process of a secondary battery, numerous side reactions occur between the electrolyte and the particle surface and the pores inside the particles, resulting in high initial irreversible capacity loss, low initial coulombic efficiency, and poor cycle performance. In particular, flake graphite and natural spherical graphite often have high crystallinity and graphitization, and a layered microstructure. This structure is prone to fracture of the graphite layer structure and particle crushing due to the large volume change that occurs during the desorption and intercalation processes of active ions in natural graphite. After particle crushing, 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 and slow diffusion of active ions, resulting in poor kinetic performance.

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

[0062] The particle surface coating process typically involves uniformly mixing natural graphite with a coating agent (e.g., pitch, a polymer compound, etc.) and then heat-treating the mixture to coat the surface of the natural graphite particles with a layer of amorphous carbon, thereby slightly repairing defects on the particle surface. However, the inventors of the present application discovered during their research that the amorphous carbon layer on the surface reduces the gram capacity and / or compaction density of the natural graphite, affecting the energy density of secondary batteries, and that the amorphous carbon layer on the surface cannot effectively prevent the electrolyte from penetrating into the pore structure inside the particles, thereby limiting the effects of improving the initial coulombic efficiency and cycle performance of secondary batteries.

[0063] The particle interior filling process mainly involves mixing natural graphite with a filler (e.g., pitch, a polymer compound, etc.), and then filling the voids inside the particles with the filler by applying a predetermined pressure, evacuation, heating, etc., to obtain natural graphite with no voids inside the particles. However, the inventors of the present application discovered during their research that a large amount of carbon filled inside the particles reduces both the gram capacity and compressed density of the natural graphite, affecting the energy density of secondary batteries. Furthermore, because all the voids inside the natural graphite particles are filled with carbon, the volume change of the natural graphite during the desorption and insertion of active ions is large, making the particles more fragile, and the SEI film on the particle surface is repeatedly destroyed and reconstructed, further increasing the consumption of active ions, increasing the capacity loss of secondary batteries, and shortening the service life of secondary batteries. In the prior art, the surface of natural graphite particles, which do not have voids inside, is coated with a single layer of amorphous carbon, which further reduces the gram capacity and / or compact density of the natural graphite. In addition, since there are still many defects on the particle surface, the service life of the secondary battery cannot be effectively improved.

[0064] Therefore, after natural graphite is modified by the above particle surface coating treatment and / or particle interior filling treatment, the irreversible capacity loss of the secondary battery can be reduced to some extent and the initial coulombic efficiency of the secondary battery can be improved, but there is a limit to the improvement in the initial coulombic efficiency of the secondary battery, and the energy density of the secondary battery is also lost. Furthermore, it is difficult to achieve both good cycle performance and good kinetic performance of the secondary battery.

[0065] Therefore, the inventors of the present application have conducted extensive research and have proposed a novel carbon material that can provide a secondary battery with high initial coulombic efficiency, as well as good cycle performance and kinetic performance. carbon materials

[0066] A first aspect of an embodiment of the present application provides a carbon material comprising a pore structure, wherein the carbon material simultaneously contains a 3R phase and a 2H phase, and 3R(101) / I 2H(004) ≦0.100, where I 3R(101) is the peak intensity of the diffraction peak of the 3R phase 101 crystal plane in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 2H phase 004 crystal plane in the X-ray diffraction spectrum of the carbon material.

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

[0068] 3R (Rhombohedral) phase crystalline carbon is rhombohedral phase crystalline carbon and has a stacking structure of ABCABC..., and 2H (Hexagonal) phase crystalline carbon is hexagonal crystalline carbon and has a stacking structure of ABAB.... In the course of their research, the inventors discovered that 3R phase crystalline carbon and 2H phase crystalline carbon exist simultaneously in a carbon material, and that the ratio of the diffraction peak intensity of the 3R phase 101 crystal plane to the diffraction peak intensity of the 2H phase 004 crystal plane is 0. 3R(101) / I 2H(004) ​​It was discovered that when the ratio is ≦0.100, there are many active sites on the surface of the carbon material particles, which can speed up the transport of active ions and also increase the surface stability of the carbon material particles, thereby effectively reducing surface side reactions and reducing the consumption of active ions.

[0069] The carbon material according to the present application has a pore structure. In the present application, "the carbon material has a pore structure" means that the carbon material has a pore structure that can be directly observed from a cross-sectional image (for example, a scanning electron microscope image with a particle magnification of 1000 times), i.e., the pore structure in the raw material for producing the carbon material is not completely filled. The pore structure in the carbon material can secure expansion space necessary for volume changes in the carbon material particles, thereby reducing the risk of new interfaces being generated due to the fracture of the carbon material particles, reducing the occurrence of side reactions, and reducing the consumption of active ions.

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

[0071] In some embodiments, 0.005≦I 3R(101) / I 2H(004) ≦0.100, and optionally, 0.006≦I 3R(101) / I 2H(004) ≦0.080 and 0.007≦I 3R(101) / I 2H(004) ≦0.072 and 0.008≦I 3R(101) / I 2H(004) ≦0.065 and 0.010≦I 3R(101) / I 2H(004) The inventors have conducted extensive research into the I of carbon materials. 3R(101) / I 2H(004) Furthermore, it has been found that when the ρ is within the above range, the secondary battery can be made to have a high initial coulombic efficiency and good cycle performance and kinetic performance at the same time.

[0072] In some embodiments, the X-ray diffraction spectrum of the carbon material does not have a peak corresponding to the 3R phase 012 crystal plane. The carbon material of the present application does not have a 3R phase 012 crystal plane, and the carbon material particles have fewer internal defects, which can further reduce the consumption of active ions and improve the initial coulombic efficiency and cycle performance of the secondary battery.

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

[0074] In some embodiments, the carbon material has a pore area of ​​0.15 μm 2 and optionally, one or more pore structures having a pore area of ​​0.15 μm or greater. 2 ~2.0μm 2 In further research, the inventors discovered that when a carbon material includes a pore structure having the above pore area, the pore structure can ensure expansion space necessary for volume changes of the carbon material particles, thereby further reducing the risk of new interfaces being generated due to 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 of the secondary battery.

[0075] In some embodiments, the carbon material comprises an outer region and an inner region located inside the outer region, the outer region refers to a region extending from the particle surface of the carbon material to the interior of the particle a distance of 0.25L, L refers to the length of the minor axis of the carbon material particle, the total pore area of ​​the outer region is denoted as S1, the total pore area of ​​the inner region is denoted as S2, and S2 > S1.

[0076] Through further research, the inventors discovered that when the carbon material further satisfies S2 > S1, the carbon material particles are characterized by a large number of pores and / or large pore size in the inner region and a small number of pores and / or small pore size in the outer region. The large number of pores and / or large pore size in the inner region of the carbon material provides the pore structure with the expansion space necessary for the volume change of the carbon material particles, thereby reducing the risk of new interfaces due to fracture of the carbon material particles, reducing the occurrence of side reactions, reducing irreversible capacity loss of secondary batteries, and improving the cycle performance and kinetic performance of secondary batteries. The small number of pores and / or small pore size in the outer region of the carbon material provides the carbon material particles with a more stable structure and minimizes the infiltration of the electrolyte into the pore structure of the carbon material particles, thereby reducing the occurrence of side reactions and the loss of active ions due to the formation of an SEI film inside the particles, further improving the initial Coulombic efficiency of the carbon material and further improving the cycle performance of secondary batteries.

[0077] Therefore, if the carbon material further satisfies S2>S1, it can effectively reduce the irreversible capacity loss of the secondary battery, improve the capacity performance characteristics of the secondary battery, and more favorably allow the secondary battery to have a high initial coulombic efficiency and good cycle performance and kinetic performance.

[0078] In some embodiments, 1.5≦S2 / S1≦420, 2≦S2 / S1≦300, 2.2≦S2 / S1≦250, 2.5≦S2 / S1≦150, or 2.8≦S2 / S1≦100. In further studies, the inventors found that when S2 / S1 is within the above range, the secondary battery can more favorably combine high initial coulombic efficiency with good cycle performance and kinetic performance.

[0079] In some embodiments, 0.01 μm 2 ≦S1≦5.0μm 2 and optionally 0.02 μm 2 ≦S1≦4.5μm 2 , 0.04 μm 2≦S1≦4.5μm 2 , 0.08 μm 2 ≦S1≦4.5μm 2 , 0.1 μm 2 ≦S1≦4.5μm 2 , 0.1 μm 2 ≦S1≦4.0μm 2 , 0.1 μm 2 ≦S1≦3.5μm 2 When the total pore area of ​​the outer region of the carbon material is within the above range, the carbon material particles have a more stable structure and the electrolyte is prevented from penetrating into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions and the consumption of active ions due to the formation of an SEI film inside the carbon material particles, without affecting the transport performance of active ions and electrons.

[0080] In some embodiments, 2.5 μm 2 ≦S2≦25.0μm 2 , selectable, 3.0 μm 2 ≦S2≦22.5μm 2 , 3.0 μm 2 ≦S2≦20.0μm 2 , 3.0 μm 2 ≦S2≦17.5μm 2 , 3.5 μm 2 ≦S2≦15.0μm 2 When the total pore area of ​​the internal region of the carbon material is within the above range, a sufficient and stable expansion space can be secured for the volume change of the carbon material particles, the risk of new interfaces being generated due to the fracture of the carbon material particles is reduced, the occurrence of side reactions on the surfaces of the new interfaces is reduced, and the consumption of active ions due to the formation of an SEI film on the surfaces of the new interfaces is reduced, while the capacity and initial coulombic efficiency of the carbon material can be improved.

[0081] In the present application, the total pore area S1 of the outer region and the total pore area S2 of the inner region of the carbon material can be obtained by measuring a cross-sectional image of the carbon material.

[0082] In this application, a cross-sectional image of a carbon material includes a cross-sectional image passing through the center of a carbon material particle. The "center of a particle" refers to an area within a radius extending 0.1 μm from the geometric center of the particle toward the particle surface.

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

[0084] 1 is a schematic diagram of a cross-sectional image of a particle of the carbon material 100 of the present application, and the cross-sectional image passes through the center of the particle of the carbon material 100. As shown in FIG. 1, L represents the length of the minor axis of the particle of the carbon material 100, and the region extending from the particle surface 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.

[0085] A cross section of the carbon material is prepared using a cross section polishing device (e.g., JEOL Corporation, Japan, IB-09010 CP type argon ion cross section polishing device), and then the cross section of the carbon material is scanned using a scanning electron microscope (e.g., ZEISS, Germany, Sigma 300 type scanning electron microscope) according to JY / T010-1996. Finally, the total pore area S1 of the outer region and the total pore area S2 of the inner region of the carbon material are calculated using image processing software (e.g., AVIZO).

[0086] In some embodiments, L≧4 μm, optionally 4 μm≦L≦20 μm, 6 μm≦L≦20 μm, 8 μm≦L≦20 μm, 8 μm≦L≦18 μm, 8 μm≦L≦16 μm.

[0087] In some embodiments, the area of ​​the pore structure in the outer region of the carbon material is 0.15 μm 2 less than, optionally 0.10 μm 2The inventors have further discovered through further research that by controlling the area of ​​the pore structure in the outer region of the carbon material to be within the above range, the outer region of the carbon material can have a dense structure, thereby effectively improving the structural stability of the carbon material, preventing the electrolyte from penetrating 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, the present application does not require that the areas of all pore structures in the outer region of the carbon material be less than 0.15 μm 2 For example, but not limited to, 95% or more, optionally 99% or more of the surface of the pore structure is 0.15 μm 2 Controlled to be less than 0.10 μm, selectable 2 It can be the following:

[0088] In some embodiments, the interior region of the carbon material has an area of ​​0.15 μm 2 and optionally one or more pore structures having an area of ​​0.15 μm or greater. 2 ~2.0μm 2 In further research, the inventors have further discovered that when the internal region of the carbon material includes a pore structure of the above size, a sufficient and stable expansion space can be secured for volume changes of the carbon material particles, reducing the risk of crushing the carbon material particles while improving the compressed density of the carbon material and improving the energy density of the secondary battery.

[0089] In some embodiments, the carbon material has a layer spacing of d1 in an outer region thereof and a layer spacing of d2 in an inner region thereof, and the carbon material satisfies d1≧d2, and optionally d1>d2.

[0090] In the carbon material of the present application, the interlayer spacing in the outer region of the carbon material is large, which is advantageous for rapid insertion and desorption of active ions, thereby further improving the dynamic performance of the secondary battery.The interlayer spacing in the inner region of the carbon material is small, which is advantageous for improving the gram capacity and compressed density of the carbon material, thereby further improving the energy density of the secondary battery.

[0091] In some embodiments, d1 is between 0.33565 nm and 0.33600 nm.

[0092] In some embodiments, d2 is between 0.33553 nm and 0.33589 nm.

[0093] The interlayer distance of different regions of the carbon material can be examined using equipment and methods well known in the art. For example, it can be examined using a High Resolution Transmission Electron Microscope (HRTEM). The testing equipment can be a Thermo Fisher Spectra S / TEM scanning transmission electron microscope.

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

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

[0096] In some embodiments, the topography of the carbon material includes one or more of a blocky, spherical, and nearly spherical shape, which is advantageous for improving the compression density of the negative electrode sheet and improving the energy density of the secondary battery.

[0097] In some embodiments, the carbon material includes primary particles, and optionally, the proportion of the primary particles in the carbon material is 50% or more, for example, 55% to 95%, 60% to 100%, 65% to 90%, 65% to 80%, 70% to 100%, 75% to 90%, 80% to 100%, 90% to 100%, or 95% to 100%. The carbon material includes a suitable proportion of primary particles, which provides high structural stability and reduces the occurrence of side reactions. It can also improve the compression density of the negative electrode sheet and the energy density of the secondary battery.

[0098] In some embodiments, the carbon material may be all primary particles, i.e., the number percentage of the primary particles in the carbon material is 100%.

[0099] The terms primary particles and secondary particles both have the meanings well known in the art. 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 particles and secondary particles can be distinguished using scanning electron microscope (SEM) images.

[0100] In the present application, the proportion of the number of primary particles in the carbon material can be tested according to the following method: a test sample is randomly taken from the negative electrode film layer, multiple test areas are randomly selected from the test sample, images of the multiple test areas are obtained using a scanning electron microscope, and the proportion of the number of carbon material particles in the primary particle topography in each image to the total number of carbon material particles is calculated statistically; the average value of the multiple statistical results is the proportion of the number of primary particles in the carbon material.

[0101] In some embodiments, the specific surface area of ​​the carbon material is 0.6 m 2 / g~2.5m2 / g, optionally 0.8m 2 / g~2.4m 2 The carbon material of the present application has a low specific surface area and low surface activity, which reduces the consumption of active ions due to the formation of an SEI film, and can improve the initial coulombic efficiency of the carbon material and the cycle performance of a secondary battery.

[0102] The specific surface area of ​​a carbon material has a meaning well known in the art and can be measured using instruments and methods well known in the art. For example, it can be tested according to the nitrogen gas adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated by the Brunauer Emmett Teller (BET) method, where the nitrogen gas adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area pore size analyzer manufactured by Micromeritics, Inc., USA.

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

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

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

[0106] The volume distribution particle sizes Dv10, Dv50, and Dv90 of carbon materials have meanings well known in the art and refer to the particle sizes corresponding to the cumulative volume distribution percentages of the material reaching 10%, 50%, and 90%, respectively. These can be measured using instruments and methods well known in the art. For example, they can be easily measured using a laser particle size analyzer in accordance with GB / T 19077-2016, Particle Size Distribution Laser Diffraction Method. The testing instrument may be a Mastersizer 3000 laser particle size analyzer manufactured by Malvern Instruments, UK.

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

[0108] The tap density of a carbon material has a meaning well known in the art and can be measured by instruments and methods well known in the art, for example, by using a powder tap density tester in accordance with GB / T 5162-2006. The test instrument can be Dandong Baite's BT-301.

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

[0110] The compressed density of the powder of the carbon material has a meaning well known in the art and can be measured by an instrument and a method well known in the art. For example, it can be measured by an electronic pressure tester (e.g., a UTM7305 type electronic pressure tester) with reference to GB / T 24533-2009. As an exemplary test method, 1 g of the carbon material powder is weighed and the powder is measured to have a base area of ​​1.327 cm. 2 The powder is placed in a mold, pressurized to 5000 kg, and held for 30 seconds. The pressure is then released and held for 10 seconds, and the data is recorded. The powder compressed density of the carbon material at a pressure of 5000 kg is calculated.

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

[0112] The gram capacity of a carbon material is a well-known term in the art and can be tested by methods well-known in the art. An exemplary test method involves thoroughly mixing a carbon material sample with an adhesive (styrene butadiene rubber (SBR)), a thickener (sodium carboxymethyl cellulose (CMC)), and a conductive agent (carbon black) in a mass ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly applied to the surface of a copper foil negative electrode current collector, dried in an oven, and then pre-dried. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. LiPF6 is then dissolved in the organic solvent to prepare a 1 mol / L electrolyte. A lithium metal piece is then used as the counter electrode, and a polyethylene (PE) thin film is used as the separator. A CR2430-type coin cell is then assembled in an argon-protected glove box. At 25°C, the coin cell was first discharged to 0.005 V at a constant current of 0.15 mA, allowed to stand for 5 minutes, and then discharged again to 0.005 V at a constant current of 10 μA. The initial discharge capacity of the coin cell was recorded, and then charged to 2.0 V at a constant current of 0.3 mA. The charge capacity of the coin cell was recorded. The ratio of the charge capacity of the coin cell to the mass of the carbon material sample is the gram capacity of the carbon material. Manufacturing method

[0113] A second aspect of the present embodiment provides a method for producing a carbon material, which can produce the carbon material of the first aspect of the present embodiment.

[0114] The method for producing the carbon material includes step 1 of providing a raw material having a plurality of pore structures; step 2 of uniformly mixing the raw material and a filler material in a predetermined ratio, and then maintaining the temperature at a first temperature T1 for a first time t1 to obtain an intermediate; and step 3 of maintaining the temperature of the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material, wherein the carbon material includes a pore structure, and the carbon material is a material in which a 3R phase and a 2H phase simultaneously exist and are 0 3R(101) / I 2H(004) ​≦0.100, where I 3R(101) is the peak intensity of the diffraction peak of the 3R phase 101 crystal plane in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 2H phase 004 crystal plane in the X-ray diffraction spectrum of the carbon material.

[0115] In some embodiments, the raw material for producing the carbon material includes natural graphite, optionally including one or more of flake graphite, natural spheroidal graphite, and microcrystalline graphite, more preferably natural spheroidal graphite.

[0116] In this application, "natural spherical graphite" refers to spherical or nearly spherical natural graphite, and does not mean that all natural graphite particles are controlled to be ideal spheres. In some embodiments, flake graphite can be pretreated to obtain natural spherical graphite of a desired particle size and topography, and optionally, the pretreatment includes steps such as crushing, classification, spheroidization, and purification.

[0117] In some embodiments, the topography of the feedstock comprises one or more of spherical and near-spherical.

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

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

[0120] In this application, the OI value of a raw material has a meaning well known in the art, and can be tested using equipment and methods well known in the art. For example, the test can be performed using an X-ray diffraction apparatus (e.g., Bruker D8 Discover). The test is performed by obtaining an X-ray diffraction spectrum of the raw material powder with reference to JIS K0131-1996 and JB / T 4220-2011, and determining the OI value = I 004 / I 110 The OI value of the raw material can be calculated from I 004 is the integrated area of ​​the diffraction peak of the crystalline carbon 004 crystal plane in the raw material, and I 110 is the integrated area of ​​the diffraction peak of the 110 crystal plane of the crystalline carbon in the raw material.

[0121] In some embodiments, the volume distribution particle size Dv50 of the filler material is 6 μm or less, and optionally 1 μm to 6 μm, 2 μm to 5 μm, or 3 μm to 5 μm, which is advantageous for the filler material to fill the pore structure of the raw material and for improving the dispersion uniformity of the filler material and the raw material.

[0122] In some embodiments, the softening point temperature of the filler material is 105°C to 190°C, optionally 105°C to 180°C, 105°C to 175°C, 105°C to 170°C, 105°C to 165°C, 105°C to 160°C, 105°C to 155°C, 105°C to 150°C, 110°C to 180°C, 110°C to 175°C, 110°C to 16 ... ℃ to 170℃, 110℃ to 165℃, 110℃ to 160℃, 110℃ to 155℃, 110℃ to 150℃, 115℃ to 180℃, 115℃ to 175℃, 115℃ to 170℃, 115℃ to 165℃, 115℃ to 165℃, 115℃ to 160℃, 115℃ to 155℃, 115℃ to 150℃, 115℃ to 145℃. In the course of research, the inventors have found that when the softening point temperature of the filler material is within the above range, 3R(101) / I 2H(004) to be within a suitable range, and it has also been found to be advantageous to adjust the pore size and / or number of pores in the outer and inner regions of the carbon material to be within a suitable range.

[0123] In some embodiments, the coking value of the filler material is 20% to 48%, and optionally 25% to 40%. In the course of research, the inventors have found that when the coking value of the filler material is within the above range, I 3R(101) / I 2H(004) to be within a suitable range, and to adjust the pore size and / or number of pores in the outer and inner regions of the carbon material to be within a suitable range.

[0124] In some embodiments, the filler material has a softening point temperature of 110°C to 165°C and a coking value of 25% to 40%.

[0125] In this application, the coking value of the filler material has the meaning known in the art and can be measured by instruments and methods known in the art, for example, by referring to GB / T 8727-2008.

[0126] In some embodiments, the filler material comprises one or more of coal pitch, petroleum pitch, polymers, and resins, optionally including petroleum pitch.

[0127] In some embodiments, the mass ratio of the filler material to the raw material is (10-40):100, and optionally (15-30):100. 3R(101) / I 2H(004)It is advantageous to adjust the pore size and / or number of pores in the outer and inner regions of the carbon material to be within an appropriate range. If the mass ratio of the filler material to the raw materials is too small, the dispersion uniformity between the filler material and the raw materials may be poor, in which case the filler material cannot effectively modify the defects inside the particles and cannot effectively prevent the electrolyte from penetrating into the pore structure inside the particles of the resulting carbon material, which affects the initial coulombic efficiency and cycle performance of the secondary battery. If the mass ratio of the filler material to the raw materials is too high, the pore structure inside the raw materials is likely to be completely filled, which results in a large volume change in the resulting carbon material, making the particles more prone to fracture, increasing the consumption of active ions due to the formation of the SEI film, and increasing the irreversible capacity loss of the secondary battery. If the mass ratio of the filler material to the raw materials is too high, a large amount of the filler material is likely to remain on the particle surface, which makes the particles more prone to agglomeration, increasing the depolymerization process and reducing the gram capacity and compressed density of the resulting carbon material.

[0128] By adjusting one or more parameters of the type of filler material, softening point, caulking value, amount of addition, etc. within the above range, I 3R(101) / I 2H(004) It is advantageous to adjust the pore size and / or the number of pores in the outer and inner regions of the carbon material to be within an appropriate range. Furthermore, after the filler material is thermally melted, it does not have a high viscosity, maintains good fluidity, and is less likely to adhere to raw material particles, reducing aggregation of the raw material particles in the subsequent manufacturing process. This reduces problems such as an increase in surface defects and side reactions in the carbon material particles due to the need to increase the depolymerization process.

[0129] In some embodiments, in step 2, after the raw material and the filling material are uniformly mixed in a predetermined ratio, the temperature-raising process of raising the temperature to the first temperature T1 is a stepwise temperature-raising process, which optionally includes a first temperature-raising process and a second temperature-raising process.

[0130] In some embodiments, the first temperature-raising process involves raising the temperature to 200°C to 300°C and maintaining the temperature for 1 hour to 3 hours. The inventors discovered during their research that maintaining the temperature for a period within the above range is advantageous for adjusting the pore size and / or number of pores in the outer and inner regions of the carbon material to fall within an appropriate range.

[0131] In some embodiments, the second heating process includes heating to the first temperature T1 and maintaining the temperature at that temperature for a first time t1.

[0132] In some embodiments, the first temperature T1 is between 700°C and 1100°C, optionally between 750°C and 1100°C, 800°C and 1100°C, 850°C and 1100°C, 900°C and 1100°C, or 950°C and 1100°C.

[0133] During the course of research, the inventors discovered that setting the first temperature within the above range is advantageous for adjusting the pore size and / or pore number in the outer and inner regions of the carbon material to fall within an appropriate range. If the first temperature is too low, some of the filler material may not be converted into a carbon material. When the heat treatment in the subsequent step 3 is performed, the filler material may subsequently be decomposed into small molecular substances, resulting in the actual residual carbon in the filler region having a large pore structure, which cannot effectively modify the internal defects of the particles and cannot effectively prevent the electrolyte from penetrating the pore structure inside the obtained carbon material particles, further affecting the initial coulomb efficiency and cycle performance of the secondary battery. This effectively avoids the following problems: if the first temperature is too high, the energy consumption in the carbon material production process may increase.

[0134] In some embodiments, the first time period t1 is between 1 hour and 5 hours. For example, the first time period t1 may be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or any range of greater than 1 hour. Optionally, the first time period t1 is between 2 hours and 4 hours.

[0135] During the course of research, the inventors discovered that if the first time is within the above range, it is advantageous to adjust the pore size and / or pore number in the outer and inner regions of the carbon material to be within an appropriate range. If the first time is too short, some of the filler material may not be converted into a carbon material, and when heat-treated in the subsequent step 3, it may be subsequently decomposed into small molecular substances, resulting in the actual residual carbon in the filler region having a large pore structure, which cannot effectively modify the internal defects of the particles and cannot effectively prevent the electrolyte from penetrating the internal pore structure of the obtained carbon material particles, further affecting the initial coulomb efficiency and cycle performance of the secondary battery. Also, if the first time is too long, it is possible to effectively avoid increased energy consumption in the carbon material production process.

[0136] In the stepwise heating process, the temperature is first raised to 200-300°C. Since the heating temperature is higher than the softening point temperature of the filler material, the filler material melts and softens due to the heating. After keeping the temperature for 1-3 hours, the filler material can flow into the pore structure of the raw material and fill it. After that, the temperature is raised to the first temperature. At this time, the filler material undergoes a carbonization reaction, effectively filling the pore structure occupied by the filler material.

[0137] In some embodiments, the heating rate of the first heating process may be 1°C / min to 10°C / min, and optionally 1.5°C / min to 8°C / min. The inventors have found in the course of their research that a heating rate within the above range is advantageous for adjusting the pore size and / or number of pores in the outer and inner regions of the carbon material within an appropriate range.

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

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

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

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

[0142] In some embodiments, the second temperature T2 is between 1850°C and 2650°C, and optionally between 1950°C and 2580°C, 1950°C and 2520°C, 1950°C and 2480°C, 1950°C and 2420°C, 1950°C and 2360°C, 2020°C and 2580°C, 2020°C and 2520°C, 2020°C and 2480°C, 2020°C and 2420°C, 2020°C and 2360°C, 2100°C and 2580°C, 2100°C and 2520°C, 2100°C and 2480°C, 2100°C and 2420°C, or 2100°C and 2360°C.

[0143] In the course of their research, the inventors have found that when the second temperature is within the above range, I 3R(101) / I 2H(004) It is advantageous to adjust the second temperature to be within a suitable range, and it is advantageous to adjust the pore size and / or pore number in the outer and inner regions of the carbon material to be within a suitable range. If the second temperature is too low, the resulting carbon material will have many surface defects and / or bulk phase defects, and I 3R(101) / I 2H(004)If the second temperature is too high, the surface stability of the carbon material particles will decrease, causing side reactions on the particle surface to increase, which will affect the initial coulombic efficiency and cycle performance of the secondary battery. If the second temperature is too high, the obtained carbon material will not contain 3R-phase crystalline carbon, and the layer spacing of the carbon material will become small, which will be unfavorable for the transport of active ions and will affect the dynamic performance of the secondary battery.

[0144] In some embodiments, the second time period t2 is between 1.5 hours and 6 hours. For example, the second time period t1 may be in a range of any value, including 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, or more. Optionally, the second time period t2 is between 2 hours and 5 hours.

[0145] In the course of research, the inventors have found that if the second time is within the above range, 3R(101) / I 2H(004) It has been found that it is advantageous to adjust the pore size and / or the number of pores in the outer and inner regions of the carbon material to be within an appropriate range. If the second time is too short, the resulting carbon material will have many surface defects and / or bulk phase defects, and I 3R(101) / I 2H(004) If the second time is too long, the obtained carbon material will not contain 3R-phase crystalline carbon, and the layer spacing of the carbon material will be small, which will be unfavorable for the transport of active ions and will affect the dynamic performance of the secondary battery.

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

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

[0148] In step 3, the second temperature and / or the second time are adjusted to be within the above range, thereby obtaining I 3R(101) / I 2H(004) It is advantageous to adjust the pore size and / or the number of pores in the outer and inner regions of the carbon material to be within an appropriate range, and it is also advantageous to improve the cycle performance and / or kinetic performance of the secondary battery.

[0149] The method for producing a carbon material according to the present invention is simple and safe, does not require pressure or vacuum treatment, and does not require a separate depolymerization step during heat treatment. The carbon material produced according to the present invention has few surface defects and / or bulk defects, and can combine high ion transport performance, high surface stability, and low volume change. Furthermore, secondary batteries using the carbon material can combine high initial coulombic efficiency and good cycle and kinetic performance.

[0150] The manufacturing method of the present application is low cost, highly practical, and suitable for large-scale industrialization. secondary battery

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

[0152] The present application does not particularly limit the type of secondary battery, and the secondary battery may be, for example, a lithium-ion battery. Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charge / discharge process of a secondary battery, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet, and the electrolyte functions to conduct the active ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte in the present application is not particularly limited and can be selected according to actual needs. For example, the electrolyte may be at least one selected from a solid electrolyte and a liquid electrolyte (electrolytic solution). Secondary batteries using electrolytic solutions and some secondary batteries using solid electrolytes may further include a separator disposed between the positive electrode sheet and the negative electrode sheet to separate them. [Negative electrode sheet]

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

[0154] In some embodiments, the negative electrode film layer comprises the carbon material of the first aspect of the present application or the carbon material produced by the method of the second aspect of the present application, which allows the secondary battery to have both high initial coulombic efficiency and good cycle and kinetic performance.

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

[0156] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. In the present application, the type of the negative electrode conductive agent is not particularly limited, 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 may optionally further include a negative electrode adhesive. In the present application, the type of the negative electrode adhesive is not particularly limited, and for example, the negative electrode adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

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

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

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

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

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

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

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

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

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

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

[0168] In some embodiments, for example, the positive electrode active material used in the lithium-ion battery is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2Mn 0.3 O2(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 It may contain one or more of O2, LiFePO4 and LiMnPO4.

[0169] In the present application, the modified compounds of the positive electrode active materials are obtained by subjecting the positive electrode active materials to doping modification and / or surface coating modification. [Electrolytes]

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

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

[0172] When the secondary battery of the present application is a lithium-ion battery, for example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

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

[0174] In some embodiments, the electrolyte solution may optionally further include an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve some performance of the secondary battery, such as an additive that improves the overcharge performance of the secondary battery, an additive that improves the high-temperature performance of the secondary battery, or an additive that improves the low-temperature power performance of the secondary battery. [Separator]

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

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

[0177] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be wound or stacked to form an electrode assembly.

[0178] In some embodiments, the secondary battery may include an outer casing, which is used to seal the electrode assembly and electrolyte.

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

[0180] The shape of the secondary battery of the present application is not particularly limited, and may be cylindrical, prismatic, or any other shape. Figure 2 shows a secondary battery 5 having a prismatic structure as an example.

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

[0182] Methods for manufacturing the secondary battery of the present application are well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be wound or stacked to form an electrode assembly, which can then be placed in a housing and dried. The electrode assembly can then be infused with an electrolyte, and the secondary battery can be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

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

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

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

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

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

[0188] An embodiment of the present application provides a power consuming device including at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage means for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a tablet computer, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc.

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

[0190] 7 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the power consuming device, a battery pack or battery module may be employed.

[0191] Other examples of power consuming devices include mobile phones, tablet computers, laptops, etc. These power consuming devices are generally required to be thin and can employ secondary batteries as their power source. Example

[0192] The following examples are provided to more specifically describe the contents of the present application, but these examples are merely illustrative and will be apparent to those skilled in the art to make various modifications and variations within the scope of the disclosure of the present application. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are calculated on a mass basis. All reagents used in the examples are commercially available or may be synthesized according to conventional methods and can be used as is without further treatment. All devices used in the examples are commercially available. Example 1 (1) Manufacturing of carbon materials

[0193] Step 1: 100 mesh flake graphite is mechanically crushed, classified, spheroidized, and refined to obtain natural spherical graphite, whose volume distribution particle size Dv50 is 12 μm and OI value is 5.5.

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

[0195] Step 3: The obtained intermediate is placed in an Acheson graphitization furnace, heated to 2320°C, and kept at that temperature for 3 hours. After completion of this, the material is demagnetized and sieved to obtain a carbon material. (2) Coin cell (half cell) manufacturing

[0196] The carbon material sample prepared above, styrene butadiene rubber (SBR) as an adhesive, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent were thoroughly mixed in a mass ratio of 96.2:1.8:1.2:0.8 in deionized water to form a uniform anode slurry. The anode slurry was then uniformly applied to the surface of a copper foil anode current collector and dried in an oven. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. LiPF6 was then dissolved in the organic solvent to prepare a 1 mol / L electrolyte. A lithium metal piece was then used as the counter electrode, and a polyethylene (PE) thin film was used as the separator. A CR2430-type coin cell was then assembled in an argon-protected glove box. (3) Manufacturing of secondary batteries (full cells)

[0197] The carbon material prepared above, the conductive agent carbon black (Super P), the adhesive styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose were mixed in a weight ratio of 96:1:1:2 with an appropriate amount of deionized water as a solvent and stirred thoroughly to form a negative electrode slurry. The negative electrode slurry was then applied to two surfaces of copper foil as a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0198] LiFePO4, conductive carbon black, and polyvinylidene fluoride are mixed in a weight ratio of 96:2.5:1.5, and an appropriate amount of NMP solvent is added and stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry is then applied to two surfaces of aluminum foil, which serves as a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0199] A 12 μm thick polypropylene film is used as a separator, and the positive electrode sheet and negative electrode sheet prepared above are placed in order. The separator is positioned between the positive electrode sheet and the negative electrode sheet to separate them, and then rolled up to obtain an electrode assembly. The electrode assembly is placed in an outer casing and dried. After that, the same electrolyte as in the coin cell is injected, and the secondary battery is obtained through processes such as vacuum sealing, standing, chemical formation, and capacity. Comparative Example 1

[0200] The manufacturing method of the half-cell and full-cell is similar to that of Example 1, but the manufacturing process of the carbon material is different.

[0201] 100 mesh flake graphite is mechanically crushed, classified, spheroidized and refined to obtain natural spherical graphite, whose volume distribution particle size Dv50 is 12 μm and OI value is 5.5. Comparative Example 2

[0202] The manufacturing method of the half-cell and full-cell is similar to that of Example 1, but the manufacturing process of the carbon material is different.

[0203] 100 mesh flake graphite is mechanically crushed, classified, spheroidized and refined to obtain natural spherical graphite, whose volume distribution particle size Dv50 is 12 μm and OI value is 5.5.

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

[0205] The manufacturing method of the half-cell and full-cell is similar to that of Example 1, but the manufacturing process of the carbon material is different.

[0206] 100 mesh flake graphite is mechanically crushed, classified, spheroidized and refined to obtain natural spherical graphite, whose volume distribution particle size Dv50 is 12 μm and OI value is 5.5.

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

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

[0209] 100 mesh flake graphite is mechanically crushed, classified, spheroidized and refined to obtain natural spherical graphite, whose volume distribution particle size Dv50 is 12 μm and OI value is 5.5.

[0210] The obtained natural spherical graphite and petroleum pitch (having a softening point temperature of 142°C, a volume distribution particle size Dv50 of 5µm, and a coking value of 35%) are mixed in a VC mixer for 30 minutes. Then the mixed materials are put into the reactor, and the reactor is gradually heated, with a heating rate of 2°C / min. While heating, the reactor is kept in a constant stirring state, and the temperature is raised to 190°C, and the reactor is evacuated until the pressure reaches -0.1Mpa, and then kept warm for 2 hours. After the temperature is raised to 650°C and kept warm for 2 hours, the reactor is cooled to about 160°C, and then petroleum pitch is gradually added into the reactor, and the mass ratio of the petroleum pitch added this time to the petroleum pitch added last time is 1:1. Then the reactor is again heated to 190°C, and the reactor is evacuated until the pressure reaches -0.1Mpa, and then kept warm for 2 hours. After the temperature is raised to 650°C and kept warm for 2 hours, the reactor is cooled by condensation. Finally, the material processed in the above process is heat-treated at 1300°C for 3 hours, and the heat-treated sample is crushed and sieved to obtain a carbon material with no internal voids. Examples 2 to 17

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

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

[0213] Tests were conducted using an X-ray diffractometer in accordance with JIS K0131-1996 to obtain X-ray diffraction spectra of carbon materials. The test conditions were as follows: carbon materials were prepared into samples using the flat sample preparation method; CuKα radiation was used as the radiation source; a copper target was used as the anode target; voltage was 40 kV; current was 40 mA; anti-scatter slit was 1 mm; scanning 2θ angle range was 20° to 80°; step size was 0.01671°; step time was 0.24 s; and scanning speed was 4° / min. A Bruker D8 Discover X-ray diffractometer was used as the test equipment.

[0214] The 2θ of the diffraction peak of the 3R phase 101 crystal plane is in the range of 43° to 44°, the 2θ of the diffraction peak of the 2H phase 004 crystal plane is in the range of 53° to 55°, and the 2θ of the diffraction peak of the 3R phase 012 crystal plane is in the range of 46° to 47°. The peak intensity of the diffraction peak of the 3R phase 101 crystal plane and the peak intensity of the diffraction peak of the 2H phase 004 crystal plane are expressed as the integrated area of ​​the corresponding diffraction peak. (2) Testing the total pore area in the outer and inner regions of the carbon material

[0215] The adhesive and carbon powder were mixed uniformly and then coated onto copper foil. The mixture was then dried at 60°C for 30 minutes. The sample was 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 was then cut using a plasma beam to obtain a cross-section of the carbon material, with the cross-section passing through the center of the carbon particle. The test equipment used was a JEOL IB-09010 CP-type argon ion cross-section polishing machine.

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

[0217] The region extending from the particle surface to the interior of the carbon material particle a distance of 0.25L 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 minor axis of the carbon material particle. Image processing software is used to calculate the total pore area S1 of the outer region of the carbon material and the total pore area S2 of the inner region of the carbon material. The image processing software may be AVIZO. (3) Testing the initial coulombic efficiency of carbon materials

[0218] At 25°C, the coin cell was first discharged to 0.005 V at a constant current of 0.15 mA, allowed to stand for 5 minutes, and then discharged to 0.005 V at a constant current of 10 μA. The initial discharge capacity of the coin cell was recorded. It was then charged to 2.0 V at a constant current of 0.3 mA, and the initial charge capacity of the coin cell was recorded. Initial coulombic efficiency (%) of the carbon material = initial charge capacity of the coin cell / initial discharge capacity of the coin cell × 100%. (4) Testing the cycle performance of secondary batteries

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

[0220] At 25°C, the secondary battery was discharged at a constant current of 1C to the lower limit off-state voltage (corresponding to 0% SOC). It was then charged at a constant current of 1C to the upper limit off-state voltage (corresponding to 100% SOC), and constant voltage charging continued until the current reached 0.05C, at which point the secondary battery was fully charged. The fully charged secondary battery was allowed to stand for 5 minutes, and then discharged at a constant current of 1C to the lower limit off-state voltage (corresponding to 0% SOC). The discharge capacity at this point was the actual capacity of the secondary battery at a 1C rate, designated C0. The secondary battery is charged at a constant current of xC0 (a gradient charge rate, e.g., 1C0, 1.05C0, 1.1C0, 1.15C0, 1.2C0, 1.25C0, 1.3C0, 1.35C0, 1.4C0...) up to the upper limit of off-state voltage (corresponding to 100% SOC), and then the constant voltage charge is continued until the current reaches 0.05C0. After allowing to stand for 5 minutes, the secondary battery is disassembled and observed for lithium deposition on the surface of the negative electrode sheet. If lithium is not deposited on the surface of the negative electrode sheet, the charge rate is increased until lithium is deposited on the surface of the negative electrode sheet, and the test is repeated. The maximum charge rate at which no lithium is deposited on the surface of the negative electrode sheet is recorded.

[0221] [Table 2]

[0222] The carbon materials produced in Examples 1 to 17 had parameters such as specific surface area, volume distribution particle size, particle size distribution, graphitization degree, tap density, and powder compressed density within the ranges described in the specification of the present application.

[0223] FIG. 8 shows the X-ray diffraction spectrum of the carbon material produced in Example 1. As can be seen from the test results summarized in Table 2, the X-ray diffraction spectrum of the carbon material is 0 3R(101) / I 2H(004) When the X-ray diffraction spectrum of the carbon material satisfies 0.005≦I≦0.100, the battery can have a high initial coulombic efficiency and good cycle and dynamic performance. 3R(101) / I 2H(004) ≦0.100, optionally 0.008≦I 3R(101) / I 2H(004) ​When the ratio satisfies ≦0.065, the battery can be made to have a better combination of high initial coulombic efficiency, good cycle performance and good kinetic performance.

[0224] As can be seen from the test results summarized in Table 2, when the X-ray diffraction spectrum of a carbon material does not have a peak of the 3R phase 012 crystal plane, the battery can better combine high initial coulombic efficiency with good cycle performance and kinetic performance.

[0225] As can be seen from the test results summarized in Table 2, when the carbon material further satisfies S2 > S1, and optionally satisfies 1.5 ≦ S2 / S1 ≦ 420, the overall performance of the battery is further improved. In this case, the carbon material particles are further characterized by a large number of pores and / or large pore size in the inner region and a small number of pores and / or small pore size in the outer region. The pore structure in the inner region of the carbon material provides the expansion space necessary for the volume change of the carbon material particles, thereby reducing the risk of new interfaces being generated due to the fracture of the carbon material particles, reducing the occurrence of side reactions, and reducing irreversible capacity loss of the battery. The small number of pores and / or small pore size in the outer region of the carbon material provides the carbon material particles with a more stable structure and minimizes the infiltration of the electrolyte into the pore structure inside the carbon material particles, thereby reducing the occurrence of side reactions and the consumption of active ions due to the formation of an SEI film inside the particles. Therefore, carbon materials that further satisfy the above structural characteristics can further improve the overall performance of batteries.

[0226] The X-ray diffraction spectra of the carbon materials produced in Comparative Examples 1 to 4 were all 0 3R(101) / I 2H(004) ≦0.100, and neither of them can provide a battery with a high initial coulombic efficiency and good cycle and kinetic performance.

[0227] ​In Comparative Example 1, untreated natural spherical graphite was used as the carbon material, and there were many voids and defects inside the carbon material particles. As can be seen in combination with the test results in Table 2, the initial coulombic efficiency, cycle performance, and kinetic performance of the battery manufactured using this were all poor.

[0228] The carbon material prepared in Comparative Example 2 formed a carbon coating layer on the surface of natural spherical graphite. The high heat treatment temperature and long heat treatment time resulted in a small interlayer spacing of the carbon material, which was unfavorable for the transport of active ions. As can be seen in combination with the test results in Table 2, this resulted in poor dynamic performance of the prepared battery. Furthermore, the coating layer was present only on the surface of the natural spherical graphite, which did not achieve an effective filling effect and could not effectively prevent the electrolyte from penetrating into the pore structure inside the particles, and the improvement in battery cycle performance was limited.

[0229] In the carbon material produced in Comparative Example 3, a carbon layer was formed on the surface of natural spherical graphite. However, because the heat treatment temperature was low, the main component of the coating layer was amorphous carbon, resulting in numerous surface defects and / or bulk phase defects in the carbon material. Furthermore, the coating layer was present only on the surface of the natural spherical graphite, which prevented it from achieving an effective filling effect and effectively prevented the electrolyte from penetrating into the pore structure inside the particles, resulting in limited improvements in the cycle performance and dynamic performance of the battery.

[0230] When the carbon material was prepared in Comparative Example 4, the filler material was filled into all of the pore structures inside the natural spherical graphite particles by vacuum suction. Since the heat treatment temperature was low, a large amount of amorphous carbon was present inside and on the surface of the carbon material particles. Furthermore, since there was no pore structure inside the carbon material particles obtained in this case, the volume change that occurred during the desorption and insertion process of the active ions from the carbon material was large, making the particles more prone to fracture, and the effect of improving the cycle performance and kinetic performance of the battery was limited.

[0231] The present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea and that exhibits similar effects within the technical scope of the present application is included within the technical scope of the present application. Furthermore, various modifications to the embodiments that can be conceived by a person skilled in the art, and other forms constructed by combining some of the components of the embodiments, are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0232] 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 secondary battery, 51 housing, 52 electrode assembly, 53 cover plate, 100 carbon material, 101 outer region, 102 inner region.

Claims

1. A carbon material comprising a pore structure, The carbon material has a 3R phase and a 2H phase simultaneously present, and 0<I ３Ｒ（１０１） / I ２Ｈ（００４） ≦0.100, I ３Ｒ（１０１） is the peak intensity of the diffraction peak of the 3R phase 101 crystal plane in the X-ray diffraction spectrum of the carbon material, and I ２Ｈ（００４） is the peak intensity of the diffraction peak of the 2H phase 004 crystal plane in the X-ray diffraction spectrum of the carbon material, Carbon materials.

2. 0.005≦I ３Ｒ（１０１） / I ２Ｈ（００４） ≦0.100, The carbon material according to claim 1 .

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

4. The carbon material has a pore area of ​​0.15 μm ２ and one or more pore structures that are at least The carbon material according to claim 1 or 2.

5. the carbon material includes an outer region and an inner region located inside the outer region, the outer region is a region extending from the particle surface of the carbon material to the interior of the particle by a distance of 0.25L, L refers to the length of the minor axis of the carbon material particle, and the total pore area of ​​the outer region is S １ and the total pore area of ​​the inner region is S ２ and S ２ >S １ That is, The carbon material according to claim 1 or 2.

6. 1.5≦S ２ / S １ ≦420, The carbon material according to claim 5 .

7. 0.01 μm ２ ≦S １ ≦5.0 μm ２ and / or 2.5 μm ２ ≦S ２ ≦25.0 μm ２ and / or L≧4 μm; The carbon material according to claim 5 .

8. The area of ​​the pore structure in the outer region of the carbon material is 0.15 μm ２ is less than, and / or The inner region of the carbon material has an area of ​​0.15 μm ２ and one or more pore structures that are at least The carbon material according to claim 5 .

9. The carbon material satisfies at least one of the following: (1) The specific surface area of ​​the carbon material is 0.6 m ２ / g to 2.5m ２ / g, (2) The volume distribution particle size Dv50 of the carbon material is 6 μm to 30 μm, (3) the particle size distribution of the carbon material (Dv90-Dv10) / Dv50 is 0.90 to 1.50; (4) The degree of graphitization of the carbon material is 93% to 98.5%; (5) The topography of the carbon material includes one or more of a blocky, spherical, and approximately spherical shape. The carbon material according to claim 1 .

10. The carbon material satisfies at least one of the following: (1) The tap density of the carbon material is 0.8 g / cm ３ ~1.20 g / cm ３ and (2) The compressed density of the powder of the carbon material under a pressure of 5000 kg is 1.85 g / cm ３ ~2.10 g / cm ３ and (3) The gram capacity of the carbon material is 350 mAh / g to 370 mAh / g; The carbon material according to claim 1 .

11. A method for producing a carbon material, comprising: Step 1: providing a raw material having a plurality of pore structures; The raw material and the filler material are uniformly mixed in a predetermined ratio, and then heated to a first temperature T １ At the first time t １ Step 2: Incubating the mixture to obtain an intermediate; The obtained intermediate is heated to a second temperature T ２ At the second time t ２ and step 3 of obtaining a carbon material by keeping the temperature. The carbon material includes a pore structure, and the carbon material has a 3R phase and a 2H phase simultaneously present, and 0<I ３Ｒ（１０１） / I ２Ｈ（００４） ≦0.100, and I ３Ｒ（１０１） is the peak intensity of the diffraction peak of the 3R phase 101 crystal plane in the X-ray diffraction spectrum of the carbon material, and I ２Ｈ（００４） is the peak intensity of the diffraction peak of the 2H phase 004 crystal plane in the X-ray diffraction spectrum of the carbon material, The caulking value of the filler material is between 20% and 48%. A method for producing carbon materials.

12. The raw material satisfies at least one of the following: (1) The raw material contains natural graphite; (2) The volume distribution particle size Dv50 of the raw material is 6 μm to 30 μm, (3) The OI value of the raw material is 4 or more; The method of claim 11.

13. The filler material satisfies at least one of the following: (1) The softening point of the filler material is 105°C to 190°C; (2) the caulking value of the filler material is 25% to 40%; (3) The volume distribution particle size Dv50 of the filler material is 6 μm or less, (4) The filler material includes one or more of coal pitch, petroleum pitch, polymer compounds, and resins; 13. The method of claim 11 or 12.

14. The mass ratio of the filler material to the raw material is (10 to 40):100; 13. The method of claim 11 or 12.

15. After the raw material and the filling material are uniformly mixed at a predetermined ratio, the mixture is heated to a first temperature T １ The temperature increase process is a stepwise temperature increase process.

13. The method of claim 11 or 12.

16. The first temperature-raising process includes raising the temperature to 200°C to 300°C and maintaining the temperature for 1 hour to 3 hours, and / or The second heating process is performed by raising the temperature to the first temperature T １ and maintaining the temperature for a first time t １ Keep warm, 16. The method of claim 15.

17. The first temperature T １ is between 700°C and 1100°C, and / or The first time t １ is 1h to 5h, 13. The method of claim 11 or 12.

18. The second temperature T ２ is between 1850°C and 2650°C, and / or The second time t ２ is 1.5h to 6h, 13. The method of claim 11 or 12.

19. A secondary battery including a negative electrode sheet, wherein the negative electrode sheet includes the carbon material according to claim 1. Secondary battery.

20. 20. A power consuming device comprising the secondary battery of claim 19.

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