Carbon materials and methods for producing the same, as well as secondary batteries and power consumption devices containing the same.

Abstract

The present application provides a carbon material, a method for manufacturing the same, a secondary battery and a power consumption device including the same. The carbon material includes an external region and an internal region located inside the external region. The external region is a region extending from the particle surface of the carbon material to the particle interior at a distance of 0.25L, where L is the minor axis length of the particles of the carbon material. Let the total pore area of the external region be S 1 and the total pore area of the internal region be S 2 , and S 2 >S 1 . The carbon material according to the present application can endow the secondary battery with high initial Coulomb efficiency, high energy density and good cycle performance.

Description

[Technical Field]

[0001] This application relates to the field of battery technology, and more specifically to carbon materials and methods for manufacturing the same, as well as secondary batteries and power consumption devices containing the same. [Background technology]

[0002] In recent years, secondary batteries have been widely used in many fields, including energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. The negative electrode active material is a crucial component of secondary batteries and affects their performance and cost. Currently, negative electrode active materials mainly consist of graphite, and natural graphite is attracting widespread attention due to its relatively low cost. However, natural graphite has defects such as many voids, many defects, and poor compatibility with the electrolyte, resulting in poor cycle performance of secondary batteries. Therefore, we focused on how to improve the performance of natural graphite. [Overview of the project]

[0003] The present invention aims to provide a carbon material and a method for manufacturing the same that can be used in secondary batteries to combine high initial Coulomb efficiency, high energy density, and good cycle performance, as well as a secondary battery and a power consumption device containing the same.

[0004] A first aspect of the present invention provides a carbon material comprising an outer region and an inner region located inside the outer region, wherein the outer region is a region extending from the particle surface of the carbon material into the particle at a distance of 0.25 L, where L is the minor axis length of the particle of the carbon material, the total pore area of ​​the outer region is S1, the total pore area of ​​the inner region is S2, and S2 > S1.

[0005] The carbon material according to this application satisfies S2 > S1, in which case the particles of the carbon material may have the characteristic of having a large number of pores and / or large pore size in the internal region, but a small number of pores and / or small pore size in the external region. Because the particles of the carbon material have a large number of pores and / or large pore size in the internal region, the pore structure can secure the expansion space necessary for volume changes of the particles of the carbon material, thereby reducing the risk of new interfaces being generated due to the crushing of the particles of the carbon material, further reducing the occurrence of side reactions, reducing losses due to irreversible capacity of secondary batteries, and improving the cycle performance of secondary batteries; because the particles of the carbon material have a small number of pores and / or small pore size in the external region, the particles of the carbon material have a more stable structure, and it is possible to avoid as much as possible the electrolyte penetrating the pore structure inside the particles of the carbon material, thereby reducing the occurrence of side reactions, reducing the consumption of active ions due to the formation of SEI films inside the particles, further improving the initial Coulomb efficiency of the carbon material, and improving the cycle performance of secondary batteries.

[0006] Therefore, the carbon material relating to this application effectively reduces losses due to irreversible capacity in secondary batteries, improves the capacity performance characteristics of secondary batteries, and enables secondary batteries to possess high initial Coulomb efficiency, high energy density, and good cycle performance.

[0007] In any embodiment of the present application, 1.5 ≤ S2 / S1 ≤ 500, and selectively, 2.5 ≤ S2 / S1 ≤ 120. If S2 / S1 is further within the above range, the secondary battery can be made to better combine high initial Coulomb efficiency, high energy density, and good cycle performance.

[0008] In any embodiment of the present application, 0.01 μm 2 ≤S1 ≤ 10.0 μm 2 Therefore, selectively, 0.1 μm 2 ≤S1 ≤ 4.5 μm 2When the total pore area of the external region of the carbon material is within the above range, the particles of the carbon material can have a stable structure, and the electrolyte can be avoided from entering the pore structure inside the particles of the carbon material as much as possible to reduce the occurrence of side reactions and reduce the consumption of active ions due to the formation of the SEI film inside the particles of the carbon material, while not affecting the transport performance of active ions and electrons.

[0009] In any embodiment of the present application, 1.8 μm 2 ≦S2≦25.0 μm 2 and optionally, 2.1 μm 2 ≦S2≦20.0 μm 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 for the volume change of the particles of the carbon material can be ensured, the risk of generating a new interface due to the crushing of the particles of the carbon material can be reduced, the occurrence of side reactions on the surface of the new interface can be reduced, and the consumption of active ions due to the formation of the SEI film on the surface of the new interface can be reduced, while the capacity and the initial Coulomb efficiency of the carbon material can be improved.

[0010] In any embodiment of the present application, L is 5 μm or more, and optionally, 6 μm ≦ L ≦ 20 μm.

[0011] In any embodiment of the present application, the area of the pore structure in the external region of the carbon material is less than 0.15 μm 2 and optionally, 0.10 μm 2 or less. By controlling the area of the pore structure in the external region of the carbon material within the above range, the external region of the carbon material can have a dense structure, thereby effectively improving the structural stability of the carbon material, avoiding the electrolyte from entering the pore structure inside the particles of the carbon material as much as possible, and further effectively improving the cycle performance of the secondary battery.

[0012] In any embodiment of the present application, the internal region of the carbon material contains one or more pore structures with an area of 0.15 μm 2 or more, and optionally, an area of 0.15 μm 2 ~2.0 μm2 The material contains one or more pore structures of the above size. By including pore structures of the above size within the internal region of the carbon material, a sufficient and stable expansion space is secured for volume changes of the carbon material particles, reducing the risk of particle fragmentation of the carbon material while improving the compressive density of the carbon material.

[0013] In any embodiment of the present application, the interlayer distance of the outer region of the carbon material is d1, the interlayer distance of the inner region of the carbon material is d2, and the carbon material satisfies d1 ≥ d2, and selectively d1 > d2.

[0014] The large interlayer distance in the outer region of the carbon material is advantageous for the rapid insertion and removal of active ions, thus further improving the dynamic performance of the secondary battery. The small interlayer distance in the inner region of the carbon material is advantageous for improving the gram capacity (capacity per gram) and compressive density of the carbon material, thus further improving the energy density of the secondary battery.

[0015] In any embodiment of the present application, d1 is 0.33565 nm to 0.33615 nm.

[0016] In any embodiment of the present application, d2 is 0.33557 nm to 0.33595 nm.

[0017] In any embodiment of the present application, the specific surface area of ​​the carbon material is 2.1 m². 2 It is less than / g and selectively 0.7m 2 / g~1.8m 2 The value is / g. Because the carbon material of this application has a low specific surface area and low surface activity, it can reduce the consumption of active ions due to the formation of SEI films and improve the initial Coulomb efficiency of the carbon material.

[0018] In any embodiment of the present application, the volume-distributed particle size Dv50 of the carbon material is 8.0 μm to 25.0 μm, and selectively 9.0 μm to 22.0 μm.

[0019] In any embodiment of the present application, the volume-distributed particle size Dv90 of the carbon material is 16.0 μm to 35.0 μm, and selectively 17.0 μm to 34.0 μm.

[0020] If the volume distribution particle size Dv50 and / or Dv90 of the carbon material is within the above range, it is advantageous for improving the transport performance of active ions and electrons, and thus the cycle performance and / or rate performance of the secondary battery can be further improved.

[0021] In any embodiment of the present application, the particle size distribution (Dv90-Dv10) / Dv50 of the carbon material is 0.5 to 1.5, and selectively 0.7 to 1.3. This is advantageous for improving the compressive density of the carbon material, and therefore allows for further improvement of the energy density of the secondary battery.

[0022] In any embodiment of the present application, the topography of the carbon material includes one or more of the following: lumpy, spherical, and subspherical. This is advantageous for improving the compressive density of the negative electrode sheet and, consequently, the energy density of the secondary battery.

[0023] In any embodiment of the present application, the degree of graphitization of the carbon material is 91.5% to 98%, and selectively 92% to 98%. Having the degree of graphitization of the carbon material within this range is advantageous for achieving a combination of high energy density and good cycle performance, storage performance and / or rate performance in the secondary battery.

[0024] In any embodiment of the present application, the powder resistivity of the carbon material under a pressure of 8 MPa is 0.009 Ω·cm to 0.052 Ω·cm, and selectively 0.01 Ω·cm to 0.04 Ω·cm. Having the powder resistivity of the carbon material within this range is advantageous for improving electron transport performance, thereby further improving the cycle performance and rate performance of the secondary battery.

[0025] In any embodiment of the present application, the tap density of the carbon material is 0.80 g / cm³. 3 ~1.50g / cm 3Therefore, selectively, 0.85 g / cm³ 3 ~1.45g / cm 3 Therefore, if the tap density of the carbon material is within the above range, the compressive density of the negative electrode sheet can be improved, further increasing the energy density of the secondary battery, and is also advantageous for improving the transport performance of active ions and electrons, as well as the cycle performance and dynamic performance of the secondary battery.

[0026] In any embodiment of the present application, the gram capacity of the carbon material is 350 mAh / g to 372 mAh / g, and selectively 353 mAh / g to 371 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be improved.

[0027] A second aspect of the present invention provides a method for manufacturing a carbon material, the manufacturing method comprising: step 1 providing a raw material having a plurality of pore structures; step 2 uniformly mixing the raw material and a filler in a predetermined ratio, and then maintaining the mixture at a first temperature T1 for a first time t1 to obtain an intermediate; and step 3 maintaining the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material, wherein the carbon material comprises an outer region and an inner region located inside the outer region, the outer region being a region extending from the particle surface of the carbon material into the particle at a distance of 0.25 L, where L is the short axis length of the particle of the carbon material, the total pore area of ​​the outer region being S1, the total pore area of ​​the inner region being S2, and S2 > S1.

[0028] In any embodiment of the present application, the raw material comprises natural graphite, optionally comprising one or more of the following: flake graphite, natural spheroidal graphite, and microcrystalline graphite.

[0029] In any embodiment of the present application, the volume distribution particle size Dv50 of the raw material is 8.0 μm to 25.0 μm, and selectively 9.0 μm to 22.0 μm.

[0030] In any embodiment of the present application, the pore volume of the raw material is 6.0 mm 3 / g or more, and selectively 6mm 3 / g~100mm 3 It is / g.

[0031] By adjusting the particle size and / or pore volume of the raw materials within the above range, aggregation of the raw materials in subsequent manufacturing processes can be reduced as much as possible. This reduces problems such as an increase in surface defects in carbon material particles and an increase in active sites for surface side reactions that would otherwise require a depolymerization step.

[0032] In any embodiment of the present application, the softening temperature (softening point) of the filler is 90°C to 150°C, and selectively 100°C to 140°C. Having the softening temperature of the filler within this range is advantageous for adjusting the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range.

[0033] In any embodiment of the present application, the volume distribution particle size Dv50 of the filler is 6 μm or less, and selectively between 2 μm and 5 μm. This is advantageous for the filler to fill the pore structure of the raw material after it has melted due to heat, and is also advantageous for improving the uniformity of the dispersion between the filler and the raw material.

[0034] In any embodiment of the present application, the caulking value of the filler is 15% to 40%, and selectively 20% to 34%. Having the caulking value of the filler within the above range is advantageous for adjusting the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range.

[0035] In any embodiment of the present application, the filler includes one or more of coal pitch, petroleum pitch, polymer compounds, and resins, and optionally includes one or more of coal pitch and petroleum pitch.

[0036] In any embodiment of the present application, the mass ratio of the filler to the raw material is (15-30):100, and optionally (18-28):100. This is advantageous for adjusting the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range.

[0037] In any embodiment of the present application, the heating process, which involves uniformly mixing the raw material and the filler in a predetermined ratio and then raising the temperature to a first temperature T1, is a stepwise heating process and optionally includes a first heating process and a second heating process.

[0038] In any embodiment of the present application, the first heating process involves heating to 200°C to 250°C and maintaining the temperature for 1 to 3 hours.

[0039] In any embodiment of the present application, the second heating process heats up to the first temperature T1 and maintains that temperature for a first time t1.

[0040] In any embodiment of the present application, the temperature is raised to the first temperature T1 at a rate of 1°C / min to 10°C / min, and selectively at 1.5°C / min to 8°C / min.

[0041] In any embodiment of the present application, the first temperature T1 is 700°C to 1150°C, and selectively 850°C to 1100°C.

[0042] In any embodiment of the present application, the first time t1 is 1h to 5h, and selectively 2h to 4h.

[0043] By adjusting one or more of the heating rate, first temperature, first time, heating process, etc., within the above range, it is advantageous to produce a carbon material with a desired structure.

[0044] In any embodiment of the present application, the second temperature T2 is 1600°C to 2620°C, and selectively 1800°C to 2450°C.

[0045] In any embodiment of the present application, the second time t2 is 1.5h to 6h, and selectively 2h to 5h.

[0046] By adjusting one or more of the second temperature and second time within the above range, it is advantageous to adjust the content of disordered carbon in the carbon material to an appropriate range, and is also advantageous for manufacturing carbon materials with desired structure and performance.

[0047] A third aspect of the present application provides a secondary battery comprising a negative electrode sheet containing the carbon material of the first aspect of the present application or a carbon material manufactured by the method of the second aspect of the present application.

[0048] A fourth aspect of the present application provides a power consumption device including a secondary battery as described in the third aspect of the present application.

[0049] The carbon material according to this application effectively reduces losses due to irreversible capacity in secondary batteries, improves the capacity performance characteristics of secondary batteries, and enables secondary batteries to possess high initial Coulomb efficiency, high energy density, and good cycle performance. The power consumption device according to this application, since it is equipped with the secondary battery according to this application, has at least the same advantages as a secondary battery. [Brief explanation of the drawing]

[0050] To more clearly explain the technical concept of the embodiments of this application, the necessary drawings for the embodiments are briefly introduced below. It should be understood that the following drawings show only a few embodiments of this application, and those skilled in the art can obtain other relevant drawings based on these drawings without requiring any creative effort. [Figure 1] This is a schematic diagram of a cross-sectional image of the carbon material particles of the present invention. [Figure 2] This is a schematic diagram of one embodiment of the secondary battery of the present invention. [Figure 3] This is an exploded schematic diagram of one embodiment of the secondary battery of the present invention. [Figure 4] This is a schematic diagram of one embodiment of the battery module of the present invention. [Figure 5] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 6] Figure 5 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 7] This is a schematic diagram of one embodiment of a power consumption device that includes the secondary battery of the present invention as a power source. [Figure 8] This is a scanning electron microscope image of the carbon material produced in Example 4. [Figure 9] This is a scanning electron microscope image of the carbon material manufactured in Comparative Example 1. In the drawing, the proportions are not necessarily drawn to the actual size. The symbols are explained below: 1 Battery pack, 2 Upper case, 3 Lower case, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate, 100 Carbon material, 101 External region, 102 Internal region [Modes for carrying out the invention]

[0051] The carbon material disclosed in this application, its manufacturing method, and embodiments of secondary batteries and power consumption devices incorporating the same will be described in detail below, with reference to the drawings as appropriate. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art. The accompanying drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter described in the claims.

[0052] The “range” disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting one lower limit and one upper limit, the selected lower limit and upper limit limit the boundary of a special range. The range thus limited may include or exclude endpoints, and may be any combination, that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are given for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Also, if minimum range values ​​1 and 2 and maximum range values ​​3, 4 and 5 are given, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 may all be expected. In this application, unless otherwise stated, the numerical range “a-b” is an abbreviation for 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 in this specification, all real numbers between "0 and 5" are listed, and "0 to 5" is an abbreviated notation for combinations of these numbers. Also, the notation that a parameter is an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of this Application may be combined to form new technical solutions. Such technical solutions are considered to be included in the disclosures of this Application.

[0054] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical concepts. Such technical concepts are considered to be included in the disclosures of this application.

[0055] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but it is preferable that they be performed sequentially. For example, if it is mentioned that the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if it is mentioned 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 steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0056] Unless otherwise specified, the terms "have," "equip," and "include" as used in this application mean open-ended, but may also mean closed-ended. For example, the aforementioned "have," "equip," and "include" may mean "have," "equip," or "include" other components not listed, or "have," "equip," or "include" only the listed components.

[0057] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the conditions A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist) all satisfy the condition "A or B."

[0058] Unless otherwise specified, terms used in this application have the common meanings that are ordinarily understood by those skilled in the art.

[0059] Unless otherwise specified, the numerical values ​​of each parameter mentioned herein can be measured by various test methods commonly used in the art, for example, according to the test methods provided herein.

[0060] Unless otherwise specified, the term "active ion" in this application refers to an ion that can reciprocate and be inserted into and removed from between the positive and negative electrodes of a secondary battery, and includes but is not limited to lithium ions.

[0061] In this application, the terms "multiple" and "multiple types" refer to two or more types.

[0062] Graphite can be classified into artificial graphite and natural graphite depending on the manufacturing process and origin. Artificial graphite generally requires a high-temperature graphitization process, which consumes a lot of energy and is therefore costly. Natural graphite, being naturally occurring, has the advantage of being relatively inexpensive. Furthermore, natural graphite has the advantages of high volume and high compressibility.

[0063] Natural graphite mainly consists of flake graphite, natural spheroidal graphite, and microcrystalline graphite. Generally, unlike artificial graphite, natural graphite particles have a large number of voids and defects both inside and outside the particles. During the initial charging process of a secondary battery, the electrolyte undergoes many side reactions with the particle surface and internal pores, resulting in high irreversible capacity loss during the first charge, low initial Coulomb efficiency, and poor cycle performance and storage performance. In particular, flake graphite and natural spheroidal graphite have high crystallinity and graphitization, and their microstructure is often layered. Due to this structure, the volume change of natural graphite is large during the desorption and insertion processes of active ions, which easily causes the graphite layered structure to break down and the particles to break down. After the particles are broken down, the exposed fresh surface continues to react with the electrolyte, further increasing the irreversible capacity loss of the secondary battery.

[0064] Currently, the performance of natural graphite is primarily improved through particle surface coating treatment and / or particle internal filling treatment.

[0065] Particle surface coating treatment involves uniformly mixing natural graphite with a coating agent (e.g., pitch, polymer compounds, etc.) and then heat-treating it to slightly repair defects on the particle surface, thereby coating the surface of natural graphite particles with a single amorphous carbon layer. However, in the course of research, the inventors of this application discovered that the amorphous carbon layer coated on the surface leads to a decrease in the gram capacity and / or compressive density of the natural graphite, affecting the energy density of the secondary battery. At the same time, the amorphous carbon layer coated on the surface cannot effectively prevent the electrolyte from penetrating the pore structure inside the particles, thus limiting its effect on improving the initial Coulomb efficiency, cycle performance, and / or storage performance of the secondary battery.

[0066] The particle internal filling process mainly involves mixing natural graphite with a filler (e.g., pitch, polymer compounds, etc.) and filling the voids inside the particles with the filler using methods such as predetermined pressure, vacuum, and heating, to obtain natural graphite without internal voids. However, in the course of their research, the inventors of this invention found that the large amount of carbon filling inside the particles reduces both the gram capacity and compressive density of the natural graphite, affecting the energy density of the secondary battery; at the same time, because all the voids inside the natural graphite particles are filled with carbon, the volume change of the natural graphite is large during the desorption and insertion process of active ions, making the particles more easily fragmented, and further increasing the irreversible consumption of active ions by repeatedly destroying and rebuilding the SEI film on the particle surface, thereby increasing the irreversible capacity loss of the secondary battery and shortening the service life of the secondary battery. In conventional technology, an amorphous carbon layer is continuously applied to the surface of natural graphite particles that do not have internal voids. This further reduces the gram capacity and / or compressive density of the natural graphite, and because the surface defects of the particles remain numerous, the lifespan of secondary batteries cannot be effectively improved.

[0067] Therefore, after modifying natural graphite by the above-mentioned particle surface coating treatment and / or particle internal filling treatment, it is possible to reduce the irreversible capacity loss of the secondary battery to some extent and improve the initial Coulomb efficiency of the secondary battery. However, the improvement in the initial Coulomb efficiency of the secondary battery is finite, and the energy density of the secondary battery is also lost, and the capacity performance characteristics of the secondary battery during long-term use are still inferior.

[0068] In view of this, the inventors of the present invention, after extensive research, have provided a novel carbon material that combines high gram capacity, high initial Coulomb efficiency, and small volume change, and that can also provide secondary batteries with high initial Coulomb efficiency, high energy density, and good cycle performance. Carbon materials

[0069] A first embodiment of the present invention provides a carbon material comprising an outer region and an inner region located inside the outer region, wherein the outer region is a region extending from the particle surface of the carbon material into the particle at a distance of 0.25 L, where L is the minor axis length of the particle of the carbon material, the total pore area of ​​the outer region is S1, the total pore area of ​​the inner region is S2, and S2 > S1.

[0070] The carbon material according to this application satisfies S2 > S1, in which case the particles of the carbon material may have the characteristic of having a large number of pores and / or large pore size in the internal region, but a small number of pores and / or small pore size in the external region. Because the particles of the carbon material have a large number of pores and / or large pore size in the internal region, the pore structure can secure the expansion space necessary for volume changes of the carbon material particles, thereby reducing the risk of new interfaces being generated due to the crushing of the carbon material particles, further reducing the occurrence of side reactions, reducing irreversible capacity loss of secondary batteries, and improving the cycle performance of secondary batteries; because the particles of the carbon material have a small number of pores and / or small pore size in the external region, the particles of the carbon material have a more stable structure, and it is possible to avoid as much as possible the electrolyte penetrating the pore structure inside the particles of the carbon material, thereby reducing the occurrence of side reactions, reducing the consumption of active ions due to the formation of SEI films inside the particles, further improving the initial Coulomb efficiency of the carbon material, and further improving the cycle performance of secondary batteries.

[0071] Therefore, the carbon material relating to this application can effectively reduce irreversible capacity loss in secondary batteries, improve the capacity performance characteristics of secondary batteries, and enable secondary batteries to possess high initial Coulomb efficiency, high energy density, and good cycle performance.

[0072] In some embodiments, 1.5 ≤ S2 / S1 ≤ 500, and selectively, 1.8 ≤ S2 / S1 ≤ 250, 2 ≤ S2 / S1 ≤ 200, 2.2 ≤ S2 / S1 ≤ 150, 2.5 ≤ S2 / S1 ≤ 120, 4 ≤ S2 / S1 ≤ 120, 5 ≤ S2 / S1 ≤ 120, and 6 ≤ S2 / S1 ≤ 120. In further research, the inventors found that if S2 / S1 is also within the above range, the secondary battery can be made to better combine high initial Coulomb efficiency, high energy density, and good cycle performance.

[0073] In some examples, 0.01 μm 2 ≤S1 ≤ 10.0 μm 2 Therefore, selectively, 0.02 μm 2≤S1 ≤ 8.0 μm 2 , 0.03 μm 2 ≤S1 ≤ 7.0 μm 2 , 0.04μm 2 ≤S1 ≤ 6.0 μm 2 , 0.05 μm 2 ≤S1 ≤ 5.0 μm 2 , 0.06 μm 2 ≤S1 ≤ 4.5 μm 2 , 0.07μm 2 ≤S1 ≤ 4.5 μm, 0.09 μm 2 ≤S1 ≤ 4.5 μm, 0.1 μm 2 ≤S1 ≤ 4.5 μm 2 , 0.1 μm 2 ≤S1 ≤ 4.0 μm 2 , 0.1 μm 2 ≤S1 ≤ 3.5 μm 2 Therefore, when the total pore area of ​​the external region of the carbon material is within the above range, the carbon material particles can be given a more stable structure, thereby minimizing the penetration of the electrolyte into the pore structure inside the carbon material particles, reducing the occurrence of side reactions, and reducing the consumption of active ions due to the formation of SEI films inside the carbon material particles, while not affecting the transport performance of active ions and electrons.

[0074] In some examples, 1.8 μm 2 ≤S2 ≤ 25.0 μm 2 Therefore, selectively, 2.0 μm 2 ≤S2 ≤ 22.5 μm 2 , 2.1 μm 2 ≤S2 ≤ 20.0 μm 2 , 2.2 μm 2 ≤S2 ≤ 17.5 μm 2 , 3.0 μm 2 ≤S2 ≤ 15.0 μm 2 Therefore, 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 volume changes of the carbon material particles, reducing the risk of new interfaces being generated due to fragmentation of the carbon material particles, reducing the occurrence of side reactions on the surface of the new interfaces, and reducing the consumption of active ions due to the formation of SEI films on the surface of the new interfaces, while improving the capacity and initial Coulomb efficiency of the carbon material.

[0075] In this 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 measured by a cross-sectional image of the carbon material.

[0076] In this application, the cross-sectional image of the carbon material includes a cross-sectional image passing through the center of the carbon material particle. "Particle center" refers to the area within a radius of 0.1 μm extending from the geometric center of the particle toward the particle surface.

[0077] In this application, the minor axis length of a particle refers to the minimum value at which the line connecting two points on the surface of the particle passes through the geometric center of the particle.

[0078] Figure 1 is a schematic diagram of a cross-sectional image of a particle of the carbon material 100 of the present invention, and the cross-sectional image passes through the center of the particle of the carbon material 100. As shown in Figure 1, L represents the minor axis length 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 at a distance of 0.25L is the outer region 101, and the region inside the outer region 101 is the inner region 102.

[0079] After preparing a cross-section of a carbon material using a cross-section polisher (for example, the IB-09010 CP type argon ion cross-section polisher from JEOL Japan), the cross-section of the carbon material can be scanned using a scanning electron microscope (for example, the Sigma 300 scanning electron microscope from ZEISS Germany) by referring to JY / T010-1996, and finally, the total pore area S1 of the outer region and the total pore area S2 of the inner region of the carbon material can be calculated using image processing software (for example, AVIZO).

[0080] In some examples, L is 5 μm or greater, and selectively within the ranges of 5 μm ≤ L ≤ 20 μm, 6 μm ≤ L ≤ 20 μm, 8 μm ≤ L ≤ 20 μm, and 8 μm ≤ L ≤ 18 μm.

[0081] In some embodiments, the area of ​​the pore structure in the external region of the carbon material is 0.15 μm². 2 It is less than 0.10 μm, and selectively 0.10 μm 2The inventors, through further research, have found that by controlling the area of ​​the pore structure in the external region of the carbon material to within the above range, a dense structure can be created in the external region of the carbon material. This effectively improves the structural stability of the carbon material, minimizes the penetration of the electrolyte into the pore structure inside the carbon material particles, and effectively improves the cycle performance of the secondary battery. Of course, in this application, the area of ​​all pore structures in the external region of the carbon material is all 0.15 μm. 2 This does not limit the scope to the following, for example, an area of ​​0.15 μm² with 95% or more, or selectively 99% or more, of the pore structure. 2 The following are available, and selectively, 0.10 μm 2 It can be controlled as follows:

[0082] In some embodiments, the internal region of the carbon material has an area of ​​0.15 μm 2 The pore structure contains one or more of the above characteristics, and selectively has an area of ​​0.15 μm². 2 ~2.0μm 2 The material contains one or more pore structures. In further research, the inventors found that by incorporating pore structures of the above size into the internal region of the carbon material, a sufficient and stable expansion space can be secured for volume changes of the carbon material particles, reducing the risk of fragmentation of the carbon material particles while improving the compressive density of the carbon material.

[0083] In some embodiments, the interlayer distance in the outer region of the carbon material is denoted as d1, the interlayer distance in the inner region of the carbon material is denoted as d2, and the carbon material satisfies d1 ≥ d2, and selectively, d1 > d2.

[0084] The large interlayer distance in the outer region of the carbon material is advantageous for the rapid insertion and deinsertion of active ions, thus further improving the dynamic performance of the secondary battery. The small interlayer distance in the inner region of the carbon material is advantageous for improving the gram capacity and compressive density of the carbon material, thus further improving the energy density of the secondary battery.

[0085] In some examples, d1 is between 0.33565nm and 0.33615nm.

[0086] In some examples, d2 is between 0.33557 nm and 0.33595 nm.

[0087] The interlayer distances in different regions of carbon material particles can be measured using known instruments and methods in this field. For example, it can be measured using a high-resolution transmission electron microscope (HRTEM). The test instrument can be a Thermo Fishers Spectra S / TEM scanning transmission electron microscope.

[0088] In some embodiments, the degree of graphitization of the carbon material is 91.5% to 98%, and selectively 92% to 98%, 93% to 98%, and 94% to 97.5%. Having the degree of graphitization of the carbon material within these ranges is advantageous for achieving a high energy density and good cycle performance, storage performance, and / or rate performance in secondary batteries.

[0089] The degree of graphitization of carbon materials is a well-known concept in this field and can be measured using well-known instruments and methods. For example, it can be tested using an X-ray diffractometer (e.g., Bruker D8 Discover), and the test is performed according to JIS K 0131-1996 and JB / T 4220-2011, measuring the average interlayer distance d of the (002) crystal plane in the crystal structure of the carbon material. 002 Obtain the Mering-Maire formula g=(0.344-d 002 The degree of graphitization can be calculated based on ) / (0.344-0.3354)×100%. In the above formula, d 002 This is the average interlayer distance of the (002) crystal plane in the crystal structure of a carbon material, expressed in nanometers (nm).

[0090] In some embodiments, the topography of the carbon material includes one or more of the following: lumpy, spherical, and subspherical. This is advantageous for improving the compressive density of the negative electrode sheet and, consequently, the energy density of the secondary battery.

[0091] In some embodiments, the carbon material contains primary particles, and selectively, the proportion of 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, containing an appropriate proportion of primary particles, can have high structural stability, reduce the occurrence of side reactions, improve the compressive density of the negative electrode sheet, and improve the energy density of the secondary battery.

[0092] In some embodiments, the carbon material may consist entirely of primary particles, i.e., the proportion of primary particles in the carbon material is 100%.

[0093] The terms primary and secondary particles are both well-known in this field. Primary particles are particles in a non-aggregated state. Secondary particles are particles in an aggregated state formed by the aggregation of two or more primary particles. Primary and secondary particles can be distinguished using scanning electron microscope (SEM) images.

[0094] In this application, the proportion of primary particles in a carbon material can be tested by selecting any one test sample in the negative electrode film layer, selecting any multiple test areas in the test sample, acquiring images of the multiple test areas using a scanning electron microscope, statistically calculating the ratio of the number of carbon material particles in the primary particle topography to the total number of carbon material particles in each image, and taking the average of the multiple statistical results as the proportion of primary particles in the carbon material.

[0095] In some embodiments, the specific surface area of ​​the carbon material is 2.1 m². 2It is less than / g and selectively 0.7m 2 / g~1.8m 2 The value is / g. Because the carbon material of this application has a low specific surface area and low surface activity, it can reduce the consumption of active ions due to the formation of SEI films and improve the initial Coulomb efficiency of the carbon material.

[0096] The specific surface area of ​​carbon materials is a well-known concept in this field and can be measured using well-known instruments and methods. For example, referring to GB / T 19587-2017, it can be tested using the nitrogen gas adsorption specific surface area analysis method and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen gas adsorption specific surface area analysis test can be performed using the Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, Inc., USA.

[0097] In some examples, the volume distribution particle size Dv50 of the carbon material is 8.0 μm to 25.0 μm, and selectively 9.0 μm to 22.0 μm.

[0098] In some embodiments, the volume distribution particle size Dv90 of the carbon material is 16.0 μm to 35.0 μm, and selectively 17.0 μm to 34.0 μm.

[0099] If the volume distribution particle size Dv50 and / or Dv90 of the carbon material is within the above range, it is advantageous for improving the transport performance of active ions and electrons, and thus the cycle performance and / or rate performance of the secondary battery can be further improved.

[0100] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the carbon material is 0.5 to 1.5, and selectively between 0.7 and 1.3. When the particle size distribution (Dv90-Dv10) / Dv50 of the carbon material falls within the above range, it is advantageous for improving the compressive density of the carbon material, and thus the energy density of the secondary battery can be further improved.

[0101] The volume distribution particle sizes Dv10, Dv50, and Dv90 of carbon materials have well-known meanings in this art, representing the particle sizes corresponding to when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, respectively, and can be measured using instruments and methods well-known in this art. For example, they can be conveniently measured using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The test instrument may be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0102] In some embodiments, the powder resistivity of the carbon material at a pressure of 8 MPa is between 0.009 Ω·cm and 0.052 Ω·cm, and selectively between 0.01 Ω·cm and 0.04 Ω·cm. When the powder resistivity of the carbon material falls within the above range, it is advantageous for improving electron transport performance, and thus the cycle performance and rate performance of the secondary battery can be further improved.

[0103] The powder resistivity of carbon materials is well known in the art and can be measured using well known instruments and methods in the art. For example, referring to GB / T 30835-2014, it can be measured using the four-probe method with a powder resistivity analyzer (e.g., Suzhou Crystal ST2722, Sansi Vertical UTM7305). As an exemplary measurement method, a fixed amount of test sample powder is weighed and placed in a special mold, and the measurement pressure is set to obtain powder resistivity at different pressures. In this application, the test pressure may be set to 8 MPa.

[0104] In some embodiments, the tap density of the carbon material is 0.80 g / cm³. 3 ~1.50g / cm 3 Therefore, selectively, 0.85 g / cm³ 3 ~1.45g / cm 3 Therefore, if the tap density of the carbon material is within the above range, the compressive density of the negative electrode sheet can be improved, further increasing the energy density of the secondary battery, which is also advantageous for improving the active ion and electron transport performance, as well as the cycle performance and dynamic performance of the secondary battery.

[0105] The tap density of carbon materials is a well-known concept in this art and can be measured using known instruments and methods. For example, it can be measured using a powder tap density tester, referring to GB / T 5162-2006. The Dandong Baite BT-301 can be used as the tester.

[0106] In some embodiments, the gram capacity of the carbon material is 350 mAh / g to 372 mAh / g, and selectively 353 mAh / g to 371 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be improved.

[0107] The gram capacity of carbon materials is a well-known concept in this field and can be measured by methods well known in this field. As an example test method, a carbon material sample was thoroughly mixed with styrene-butadiene rubber (SBR) as a binder, sodium carboxymethylcellulose (CMC) as a thickener, and carbon black as a conductive agent in a mass ratio of 96.2:1.8:1.2:0.8 with an appropriate amount of deionized water as a solvent, forming a uniform negative electrode slurry. This negative electrode slurry was then uniformly applied to the surface of copper foil used as a negative electrode current collector, dried in an oven, and used. 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 above organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Subsequently, a CR2430 type coin cell was assembled in a glove box protected by argon gas, using a metallic lithium sheet as the counter electrode and a polyethylene (PE) film as the separator. At 25°C, the fabricated coin cell is first discharged with a constant current of 0.15mA to 0.005V, left to stand for 5 minutes, then discharged again with a constant current of 10μA to 0.005V, and the initial discharge capacity of the coin cell is recorded. Subsequently, it is charged with a constant current of 0.3mA to 2.0V, and the charging capacity of the coin cell is recorded. The ratio of the charging capacity of the coin cell to the mass of the carbon material sample is the gram capacity of the carbon material. Manufacturing method

[0108] A second embodiment of the present invention provides a method for manufacturing a carbon material that can produce the carbon material of the first embodiment of the present invention.

[0109] The method for producing the carbon material includes: step 1 providing a raw material having a plurality of pore structures; step 2 uniformly mixing the raw material and a filler in a predetermined ratio, then maintaining the mixture at a first temperature T1 for a first time t1 to obtain an intermediate; and step 3 maintaining the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material, wherein the carbon material includes an outer region and an inner region located inside the outer region, the outer region being a region extending from the particle surface of the carbon material into the particle at a distance of 0.25 L, where L is the minor axis length of the particle of the carbon material, 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.

[0110] In some embodiments, the raw materials for producing the carbon material include natural graphite. Optionally, the natural graphite includes one or more of the following: flake graphite, natural spheroidal graphite, and microcrystalline graphite, and further optionally includes natural spheroidal graphite.

[0111] "Natural spheroidal graphite" refers to natural graphite that is spherical or near-spheroidal, and does not mean that all natural graphite particles are controlled to be ideal spheres. In some examples, natural spheroidal graphite with a desired particle size and topography can be obtained by pretreatment of flake graphite, and selectively, the pretreatment includes steps such as crushing, classification, spheroidization, and purification.

[0112] In some embodiments, the topography of the raw material includes one or more types of spherical and subspherical shapes.

[0113] In some embodiments, the volume distribution particle size Dv50 of the raw material is 8.0 μm to 25.0 μm, and selectively between 9.0 μm and 22.0 μm. When the volume distribution particle size of the raw material falls within the above range, it is advantageous for the subsequent filling process.

[0114] In some embodiments, the pore volume of the raw material is 6.0 mm 3 / g or more, and selectively 6mm 3 / g~100mm 3 / g, 7mm 3 / g~80mm 3 / g, 8mm 3 / g~60mm 3 / g, 8mm 3 / g~40mm 3 The value is / g. If the pore volume of the raw material is within the above range, it is advantageous for the subsequent filling process.

[0115] By adjusting the particle size and / or pore volume of the raw materials within the above range, it is possible to minimize aggregation of the raw materials in subsequent manufacturing processes. This reduces problems such as an increase in surface defects in carbon material particles and an increase in active sites for surface side reactions due to the need for a depolymerization step.

[0116] In some embodiments, the softening temperature of the filler is 90°C to 150°C. For example, the softening temperature of the filler may be in the range of any number of 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C or higher. Selectively, the softening temperature of the filler is 95°C to 145°C, 95°C to 140°C, 95°C to 135°C, 100°C to 145°C, 100°C to 140°C, 100°C to 135°C, 105°C to 145°C, 105°C to 140°C, 105°C to 135°C, 110°C to 145°C, 110°C to 140°C, or 110°C to 135°C.

[0117] In their research, the inventors found that when the softening temperature of the filler is within the above range, it is advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range. Furthermore, if the softening temperature of the filler is too high, it becomes difficult for the filler to flow and fill the pore structure of the raw material after it is heated and melted, thereby preventing effective modification of internal particle defects and effectively preventing the electrolyte from penetrating the pore structure inside the particles of the obtained carbon material, which in turn affects the initial Coulomb efficiency and cycle performance of the secondary battery. If the softening temperature of the filler is too low, the filler contains many small molecular substances, and these small molecular substances are easily volatile due to heat. Although the filler is easy to flow and fill the pore structure of the raw material after it is melted by heat, when heat treatment is performed in steps 2 and / or 3, the small molecular substances in the filler volatilize, preventing the carbon that actually remains in the filling area from effectively filling the pore structure of the raw material, thus preventing an effective filling effect from being achieved, or the carbon that actually remains in the filling area has many pore structures, which in turn prevents the consumption of active ions due to SEI film formation and irreversible capacity loss of the secondary battery from being reduced, and at the same time affects the cycle performance and / or storage performance of the secondary battery.

[0118] In some embodiments, the volume distribution particle size Dv50 of the filler is 6 μm or less, and is selectively 1 μm to 6 μm, 1 μm to 5 μm, 2 μm to 5 μm, or 3 μm to 5 μm. This is advantageous for the filler to fill the pore structure of the raw material after melting due to heat, and is also advantageous for improving the uniformity of dispersion between the filler and the raw material.

[0119] In several embodiments, the caulking value of the filler is 15-40%, and selectively 16-38%, 16-35%, 18-35%, and 20-34%. In their research, the inventors found that when the caulking value of the filler is within the above range, it is advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range.

[0120] In this application, the caulking value of the filler has a meaning well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured by referring to GB / T 8727-2008.

[0121] In some embodiments, the softening temperature of the filler is 100°C to 140°C, and the caulking value is 20% to 34%. This is advantageous for adjusting the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range.

[0122] In some embodiments, the filler includes one or more of coal pitch, petroleum pitch, polymer compounds, and resins, and may optionally include one or more of coal pitch and petroleum pitch.

[0123] In some embodiments, the mass ratio of the filler to the raw material is (15-30):100, and optionally (18-28):100. This is advantageous for adjusting the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range. Furthermore, if the mass ratio of filler to raw material is too small, the uniformity of dispersion between the filler and raw material may be poor. In this case, the filler will not easily flow and fill the pore structure of the raw material after melting due to heat, thereby preventing effective modification of defects inside the particles and preventing the electrolyte from penetrating the pore structure inside the particles of the resulting carbon material, which in turn affects the initial Coulomb efficiency and cycle performance of the secondary battery. If the mass ratio of filler to raw material is too large, it is likely to lead to complete filling of the pore structure inside the raw material. In this case, the volume change of the resulting carbon material will be large, the particles will be more easily crushed, the consumption of active ions due to the formation of the SEI film will increase, and the irreversible capacity loss of the secondary battery will increase. Also, if the mass ratio of filler to raw material is too large, a large amount of filler will remain on the particle surface. In this case, the particles will be more easily aggregated, the depolymerization process will increase, and the gram capacity and compressive density of the resulting carbon material will decrease.

[0124] By adjusting parameters such as the type of filler, softening point, coking value, and amount of additive within the above range, the filler can maintain good fluidity without high viscosity after melting due to heat, and the raw material particles can be less likely to adhere to each other, reducing aggregation of raw material particles in subsequent manufacturing processes. This reduces problems such as an increase in surface defects in carbon material particles and an increase in active sites for surface side reactions, which would otherwise require an increase in the depolymerization process.

[0125] In some embodiments, the heating process in step 2, in which the raw materials and the filler are uniformly mixed in a predetermined ratio and then heated to a first temperature T1, is a stepwise heating process and optionally includes a first heating process and a second heating process.

[0126] In some embodiments, the first heating process involves raising the temperature from 200°C to 250°C and maintaining the temperature for 1 to 3 hours.

[0127] In some embodiments, the second heating process raises the temperature to the first temperature T1 and maintains that temperature for a first time t1.

[0128] In the stepwise heating process, the temperature is first raised to 200°C to 250°C. Since the heating temperature is higher than the softening temperature of the filler, the filler melts and softens due to the heat at this time. After being kept warm for 1 to 3 hours, it can be fluidly filled into the pore structure of the raw material. Subsequently, the temperature is raised to the first temperature T1. At this time, the molten and softened filler undergoes a carbonization reaction, thereby effectively filling the pore structure occupied by the filler.

[0129] In some embodiments, in step 2, the first temperature T1 is 700°C to 1150°C. For example, the first temperature T1 may be in the range of any number of 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C or higher. Selectively, the first temperature T1 is 850°C to 1100°C.

[0130] In their research, the inventors found that when the first temperature is within the above range, it is advantageous for adjusting the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range. Furthermore, if the first temperature is too low, the filler may not be completely converted into carbon material, and during the subsequent heat treatment in step 3, it may continue to decompose into small molecular substances, resulting in a filler region with many pore structures that cannot effectively modify defects inside the particles, and thus failing to effectively prevent the electrolyte from penetrating the pore structure inside the particles of the resulting carbon material, thus affecting the initial Coulomb efficiency and cycle performance of the secondary battery; if the first temperature is too high, it is possible to effectively avoid a situation where energy consumption in the manufacturing process of the carbon material increases.

[0131] In some embodiments, the first time t1 is between 1h and 5h. For example, the first time t1 may be in the range of 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, or any of these values. Selectively, the first time t1 is between 2h and 4h.

[0132] The inventors found in their research that when the first time is within the above range, it is advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range. Furthermore, if the first time is too short, the filler may not be completely converted into carbon material, and during the subsequent heat treatment in step 3, it may continue to decompose into small molecular substances, resulting in a filler region with many pore structures that cannot effectively modify defects inside the particles, and thus the electrolyte cannot effectively prevent penetration into the pore structure inside the particles of the resulting carbon material, which in turn affects the initial Coulomb efficiency and cycle performance of the secondary battery; if the first time is too long, it is possible to effectively avoid a situation where energy consumption in the manufacturing process of the carbon material increases.

[0133] In some embodiments, in step 2, the temperature is raised to the first temperature T1 at a rate of 1°C / min to 10°C / min. For example, the heating rate may be in the range of 1.5°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any of the above values. Selectively, the heating rates are 1.5°C / min to 8°C / min, 1.5°C / min to 6°C / min, and 1.5°C / min to 5°C / min.

[0134] The inventors found in their research that when the heating rate is within the above range, it is advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material to an appropriate range. Furthermore, if the heating rate is too high, the filler may carbonize on the surface of the raw material particles, making it difficult for the filler to flow and fill the pore structure of the raw material after it has melted due to heat. This prevents effective modification of defects inside the particles and prevents the electrolyte from penetrating the pore structure inside the particles of the resulting carbon material, ultimately affecting the initial Coulomb efficiency and cycle performance of the secondary battery. If the heating rate is too low, the filler is more likely to flow and fill all the pore structures of the raw material after it has melted due to heat. This increases the volume change of the carbon material during the desorption and insertion process of active ions, making the particles more easily fragmented. This increases the consumption of active ions due to the formation of the SEI film, increasing irreversible capacity loss in the secondary battery and effectively avoiding the effects on the cycle performance, storage performance and / or rate performance of the secondary battery.

[0135] In some embodiments, the heating rate of the first heating process may be 1°C / min to 10°C / min, and selectively may be 1.5°C / min to 8°C / min, 1.5°C / min to 6°C / min, or 1.5°C / min to 5°C / min.

[0136] In some embodiments, the heating rate of the second heating process may be 1°C / min to 10°C / min, 1.5°C / min to 8°C / min, 1.5°C / min to 6°C / min, or 1.5°C / min to 5°C / min.

[0137] In some embodiments, the heat treatment in step 2 can be carried out in a vertical granulation vessel, a horizontal granulation vessel, a vertical reaction vessel, a horizontal reaction vessel, or a roll furnace.

[0138] In some embodiments, the heat treatment atmosphere in step 2 may be a protective gas atmosphere. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0139] In step 2, adjusting one or more of the heating rate, first temperature, first time, heating process, etc., within the above range is advantageous for producing a carbon material having a desired structure.

[0140] In some embodiments, the second temperature T2 is between 1600°C and 2620°C. For example, the second temperature may be in the range of any number of 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, 2500°C, 2600°C or higher. Selectively, the second temperature T2 is between 1800°C and 2500°C, 1800°C and 2450°C, 2000°C and 2450°C, 2050°C and 2450°C, and 2100°C and 2450°C.

[0141] In their research, the inventors found that when the second temperature is within the above range, the carbon material has a stable structure, which is advantageous in avoiding particle fragmentation as much as possible. Furthermore, if the second temperature is too low, the resulting carbon material has a high content of disordered carbon, leading to a high defect content in the carbon material, which affects the initial Coulomb efficiency, cycle performance, and storage performance of the carbon material; if the second temperature is too high, the resulting carbon material has a low content of disordered carbon, resulting in high crystallinity and graphitization of the carbon material, which is unfavorable for the rapid desorption and insertion of active ions, and the volume change of the carbon material during the charge-discharge process becomes even larger, which increases the risk of particle fragmentation of the carbon material and thus affects the cycle performance of the secondary battery; and if the second temperature is too high, the energy consumption and cost in the manufacturing process of the carbon material also increase, which can be effectively avoided.

[0142] In some embodiments, the second time t2 is between 1.5h and 6h. For example, the second time t2 may be in the range of any number such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or higher. Selectively, the second time t2 is between 2h and 5h.

[0143] In their research, the inventors found that when the second time falls within the above range, it is advantageous for adjusting the degree of disorder in the carbon material, resulting in a stable structure for the carbon material and minimizing particle fragmentation. Furthermore, if the second time is too short, the resulting carbon material has a high content of disordered carbon, leading to a high defect content and affecting the gram capacity and initial Coulomb efficiency of the carbon material. If the second time is too long, the resulting carbon material has a low content of disordered carbon, resulting in high crystallinity and graphitization. In this case, it is disadvantageous for the rapid desorption and insertion of active ions, and the large volume change of the carbon material during the charge-discharge process increases the risk of particle fragmentation, thus affecting the cycle performance and storage performance of the secondary battery. Moreover, if the second time is too long, it is possible to effectively avoid the situation where energy consumption and costs increase during the manufacturing process of the carbon material.

[0144] In some embodiments, in step 3, the heat treatment can be carried out in a medium-frequency furnace, a box-type graphitizing furnace, an Acheson-type graphitizing furnace, a continuous graphitizing furnace, or an internal series graphitizing furnace.

[0145] In some embodiments, in step 3, the intermediate frequency furnace and the continuous graphitization heat treatment atmosphere may be a protective gas atmosphere. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0146] By adjusting one or more of the second temperature and second time within the above range, it is advantageous to adjust the content of disordered carbon in the carbon material to an appropriate range, and is also advantageous for manufacturing carbon materials with desired structure and performance.

[0147] The carbon material manufacturing method of this invention is simple, highly safe, does not require a predetermined pressure or vacuum treatment, and does not require an additional depolymerization step in the heat treatment process. The carbon material manufactured by this invention has low volume expansion, high structural stability, low surface activity, and can also combine high gram capacity, high initial Coulomb efficiency, and small volume change, making it possible to provide secondary batteries with high initial Coulomb efficiency, high energy density, and good cycle performance.

[0148] The manufacturing method of this invention is low-cost, highly practical, and suitable for large-scale production. secondary battery

[0149] A third aspect of the embodiments of the present invention provides a secondary battery.

[0150] This application does not particularly limit the type of secondary battery; for example, the secondary battery may be a lithium-ion battery. Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the secondary battery, active ions reciprocate between the positive electrode sheet and the negative electrode sheet for insertion and removal, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. This application does not particularly limit the type of electrolyte, and it 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 (i.e., an electrolyte solution). A secondary battery using an electrolyte solution and a secondary battery using a solid electrolyte may further include a separator that serves to isolate the positive electrode sheet and the negative electrode sheet. [Negative electrode sheet]

[0151] 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 opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0152] In some embodiments, the negative electrode film layer includes a carbon material according to the first embodiment of the present invention or a carbon material manufactured by the method described in the second embodiment of the present invention. This enables the secondary battery to combine high initial Coulomb efficiency, high energy density, and good cycle performance.

[0153] In some embodiments, the negative electrode film layer may further contain other negative electrode active materials besides the carbon material described above. In some embodiments, the other negative electrode active materials include, but are not limited to, one or more of the following: ordinary 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 the following: elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include one or more of the following: elemental tin, tin oxide, and tin alloy material.

[0154] In some embodiments, the negative electrode film layer may optionally contain a negative electrode conductive agent. In this application, the type of negative electrode conductive agent is not particularly limited, and as an example, the negative electrode conductive agent may include one or more types selected from superconducting carbon, conductive graphite, acetylene black, carbon black, kecheng black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0155] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. In this application, the type of negative electrode binder is not particularly limited, and examples include one or more types selected from styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0156] In some embodiments, the negative electrode film layer may optionally further contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor material, etc.

[0157] In some embodiments, the negative electrode current collector can be a metal foil sheet or a composite current collector. Copper foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more types of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more types of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0158] The negative electrode film layer is generally formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a selectable conductive agent, a selectable binder, and a selectable other auxiliary agent in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0159] The negative electrode sheet does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present invention further includes a conductive primer layer (e.g., consisting of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector, and in some embodiments, the negative electrode sheet according to the present invention further includes a protective layer covering the surface of the negative electrode film layer. [Positive electrode sheet]

[0160] 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 opposing surfaces in the direction of its own thickness, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0161] The positive electrode current collector can be a metal foil sheet or a composite current collector. An example of a metal foil sheet is aluminum foil. The composite current collector can include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more types of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more types of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0162] The positive electrode film layer generally comprises a positive electrode active material, a selectable binder, and a selectable conductive agent. The positive electrode film layer is generally formed by applying a positive electrode slurry to the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing the positive electrode active material, a selectable conductive agent, a selectable binder, and any other components in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP). For example, the binder used in the positive electrode film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a ternary copolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, and a fluorine-containing acrylate resin. For example, the conductive agent used in the positive electrode film layer may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0163] The positive electrode active material can be a positive electrode active material used in secondary batteries that are well known in this field.

[0164] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material includes, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their modified compounds. Examples of the lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of the lithium-containing phosphates include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds.

[0165] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery may include one or more of lithium transition metal oxides and their modified compounds having the general formula Li a Ni b Co c M d O e A f where 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M is one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is one or more selected from N, F, S, and Cl.

[0166] In some embodiments, the positive electrode active material used in the lithium-ion battery includes, for example, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 It may contain one or more of O2, LiFePO4, and LiMnPO4.

[0167] In the present application, the modified compound of each of the above cathode active materials may be obtained by performing doping modification and / or surface coating modification on the cathode active material. [Electrolyte]

[0168] In some embodiments, the electrolyte uses an electrolytic solution containing an electrolyte salt and a solvent.

[0169] The type of the electrolyte salt is not specifically limited and can be selected according to actual needs.

[0170] 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 (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro bis(oxalato)phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0171] The type of solvent is not particularly limited and can be selected according to actual needs. In some examples, the organic solvent may include, for instance, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0172] In some embodiments, the electrolyte may optionally further contain additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve some aspects of the secondary battery's performance, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature power performance of the secondary battery. [Separator]

[0173] In this application, the type of separator is not particularly limited, and any well-known porous structure separator having good chemical and mechanical stability can be selected.

[0174] In some embodiments, the material of the separator may include one or more of the following: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. If the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0175] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be manufactured into an electrode assembly by a winding process or a lamination process.

[0176] In some embodiments, the secondary battery may include an outer casing. This casing is used to seal the electrode assembly and electrolyte described above.

[0177] In some embodiments, the outer packaging may be a hard case such as a rigid plastic case, an aluminum case, or a steel case. The outer packaging may also be a soft bag, such as a bag package. The material of the soft package may be plastic, and may be one or more of the following: polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0178] The shape of the secondary battery of this application is not particularly limited and may be cylindrical, rectangular, or any other shape. Figure 2 shows a secondary battery 5 with a rectangular structure as an example.

[0179] In some embodiments, as shown in Figure 3, the exterior may include a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates enclose each other to form a housing chamber. The housing 51 has an opening that communicates with the housing chamber, and the cover plate 53 closes the opening so as to close the housing chamber. The positive electrode sheet, negative electrode sheet and separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged into the housing chamber. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and may be adjusted according to the needs.

[0180] The method for manufacturing the secondary battery of the present invention is well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly can be placed in an outer casing, the electrolyte can be injected after drying, and a secondary battery can be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0181] In some embodiments of the present invention, the secondary battery according to the present invention 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.

[0182] Figure 4 is a schematic diagram of an example battery module 4. As shown in Figure 4, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 5 may be fixed together with fasteners.

[0183] Optionally, the battery module 4 may further comprise a housing having a housing space for accommodating multiple secondary batteries 5.

[0184] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0185] Figures 5 and 6 are schematic diagrams of an example battery pack 1. As shown in Figures 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper case 2 and a lower case 3, the upper case 2 covering the lower case 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner. power consumption equipment

[0186] The present application further provides a power consumption device comprising 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 consumption device, or as an energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, tablet computers, laptop computers, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, and satellites, energy storage systems, etc.

[0187] The aforementioned power consumption device can be configured to use a secondary battery, battery module, or battery pack, depending on its usage needs.

[0188] Figure 7 is a schematic diagram of an example of a power consumption device. This power consumption device includes pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, etc. To meet the high power output and high energy density requirements of this power consumption device, a battery pack or battery module can be used.

[0189] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices generally require a thin design and can utilize rechargeable batteries as their power source. Examples

[0190] The following examples illustrate the contents of this application in more detail, but these examples are merely illustrative, and it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the disclosure. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are based on mass. Furthermore, all reagents used in the examples may be commercially available or synthesized according to conventional methods, and may be used as is without requiring further processing. Furthermore, all apparatus used in the examples are commercially available. Example 1 (1) Manufacturing of carbon materials

[0191] Step 1: 100-mesh flake graphite is subjected to mechanical grinding, classification, spheroidization, and purification. The volume distribution particle size Dv50 is 15 μm, and the pore volume is 18 mm². 3 Obtain natural spheroidal graphite at a concentration of / g.

[0192] Step 2: The obtained natural spheroidal graphite and petroleum pitch (softening temperature 120°C, volume distribution particle size Dv50 5 μm, coking value 30%) are mixed in a VC mixer at a mass ratio of 100:20 for 30 minutes. The mixed material is then placed in a roller hearth kiln and heated to 225°C at a rate of 5°C / min and held for 1 hour (first heating process). After that, the material is heated to 900°C at a rate of 5°C / min and held for 2 hours (second heating process). After completion, it is cooled to room temperature to obtain an intermediate.

[0193] Step 3: The obtained intermediate is placed in an Acheson graphitization furnace, heated to 1900°C and maintained for 3 hours. After completion, it is demagnetized and sieved to obtain the carbon material. (2) Manufacturing of coin cells (half cells)

[0194] The carbon material produced above, styrene-butadiene rubber (SBR) as a binder, sodium carboxymethylcellulose (CMC) as a thickener, and carbon black as a conductive agent are thoroughly mixed with an appropriate amount of deionized water as a solvent in a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. This slurry is then uniformly applied to the surface of the copper foil, which serves as the negative electrode current collector, and dried in an oven before use. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. LiPF6 is then dissolved in this organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Subsequently, a CR2430 type coin cell is assembled in a glove box protected by argon gas, using a metallic lithium sheet as the counter electrode and a polyethylene (PE) thin film as the separator. (3) Manufacturing of secondary batteries (full cells)

[0195] The carbon material prepared above, carbon black (Super P) as a conductive agent, styrene-butadiene rubber as a binder, and sodium carboxymethylcellulose as a thickener are thoroughly mixed in a weight ratio of 96:1:1:2 with an appropriate amount of deionized water as a solvent to form a negative electrode slurry. The negative electrode slurry is applied to two surfaces of copper foil, which serves as the negative electrode current collector, and after drying and cold pressing, a negative electrode sheet is obtained.

[0196] LiFePO4, conductive carbon black, and polyvinylidene fluoride are mixed in a weight ratio of 96:2.5:1.5, an appropriate amount of solvent NMP is added, and the mixture is uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry is applied to two surfaces of aluminum foil to be used as a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0197] A 12 μm thick polypropylene film is used as a separator. The positive electrode sheet and negative electrode sheet manufactured above are placed in order, with the separator positioned between the positive and negative electrode sheets to act as an isolation. The film is then wound to obtain an electrode assembly. The electrode assembly is placed in an outer casing and dried. After that, the same electrolyte as the coin cell manufactured above is injected, and a secondary battery is obtained through processes such as vacuum sealing, standing, chemical conversion, and capacitance adjustment. Comparative Example 1

[0198] The manufacturing methods for half-cells and full-cells are similar to those in Example 1, except for the carbon material manufacturing process.

[0199] Mechanical grinding, classification, spheroidization, and purification treatment were performed on 100-mesh flake graphite, resulting in a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm². 3 After obtaining natural spheroidal graphite at a concentration of / g, half-cells and full-cells are manufactured using the obtained natural spheroidal graphite as a carbon material. Comparative Example 2

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

[0201] Mechanical grinding, classification, spheroidization, and purification treatment were performed on 100-mesh flake graphite, resulting in a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm². 3 Natural spheroidal graphite is obtained at a concentration of / g. The obtained natural spheroidal graphite and petroleum pitch (softening temperature 120°C, volume distribution particle size Dv50 of 5 μm, coking value of 30%) are mixed in a VC mixer at a mass ratio of 100:20 for 30 minutes. The mixed material is then carbonized at 3200°C for 10 hours, and after completion, it is cooled to room temperature to obtain a carbon material. Comparative Example 3

[0202] The manufacturing methods for half-cells and full-cells are similar to those in Example 1, except for the carbon material manufacturing process.

[0203] Mechanical grinding, classification, spheroidization, and purification treatment were performed on 100-mesh flake graphite, resulting in a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm². 3 Natural spheroidal graphite is obtained at a concentration of / g. The obtained natural spheroidal graphite and petroleum pitch (softening temperature 120°C, volume distribution particle size Dv50 of 5 μm, coking value of 30%) are mixed in a VC mixer at a mass ratio of 100:20 for 30 minutes. The mixed material is then carbonized at 1300°C for 2 hours, and after completion, it is cooled to room temperature to obtain a carbon material. Comparative Example 4

[0204] The manufacturing methods for half-cells and full-cells are similar to those in Example 1, except for the carbon material manufacturing process.

[0205] Mechanical grinding, classification, spheroidization, and purification treatment were performed on 100-mesh flake graphite, resulting in a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm². 3 Natural spheroidal graphite is obtained at a concentration of / g. The obtained natural spheroidal graphite and petroleum pitch (softening temperature 120°C, volume distribution particle size Dv50 of 5 μm, coking value of 30%) are mixed in a VC mixer for 30 minutes. Subsequently, the mixed materials were added to the reaction vessel, and the vessel was heated gradually at a rate of 2°C / min. While heating, the reaction vessel was kept in a constant stirring state until it reached 190°C. The reaction vessel was then suctioned until the pressure was -0.1 MPa, and then kept warm for 2 hours. After the warming period, the reaction vessel was heated to 650°C and kept warm for 2 hours, and then cooled to approximately 160°C. After that, petroleum pitch was gradually added to the inside of the reaction vessel, with a mass ratio of 1:1 between the amount of petroleum pitch added this time and the amount added last time. After that, the reaction vessel was heated again to 190°C, and the reaction vessel was suctioned until the pressure was -0.1 MPa, and then kept warm for 2 hours. After the warming period, the reaction vessel was heated to 650°C and kept warm for 2 hours, and then cooled by condensation. Finally, the material processed in the above process is heat-treated at 1300°C for 2 hours, the heat-treated sample is pulverized and sieved to obtain a carbon material without internal voids. Example 2-28

[0206] The manufacturing methods for half-cells and full-cells are similar to those in Example 1, except that the parameters of the carbon material manufacturing process are adjusted. See Table 1 for details.

[0207] [Table 1] JPEG0007836421000002.jpg245170 Performance Test (1) Testing of the total pore area in the external and internal regions of carbon materials

[0208] After uniformly mixing the preparation binder with the carbon material powder, the mixture is applied to copper foil and dried at 60°C for 30 minutes before use. The sample is then cut into 6mm x 6mm pieces and attached to the sample stage of a CP-type argon ion cross-section polisher. The sample is cut using a plasma beam to obtain a cross-section of the carbon material, and the cross-section of the carbon material passes through the center of the carbon material particles. The test apparatus may be the IB-09010 CP-type argon ion cross-section polisher from JEOL Japan.

[0209] A scanning electron microscope is used to scan a cross-section of the carbon material. The test procedure can be described in JY / T010-1996. The test equipment may be a Sigma 300 scanning electron microscope from ZEISS GmbH, Germany.

[0210] The region extending 0.25 L from the surface of the carbon material particle into the particle's interior is defined as the outer region, and the region inside the outer region is defined as the inner region, where L represents the minor axis length of the carbon material particle. The total pore area S1 of the outer region and the total pore area S2 of the inner region of the carbon material are calculated using image processing software. The image processing software may be AVIZO. (2) Testing of the initial Coulomb efficiency of carbon materials

[0211] At 25°C, first discharge the coin cell manufactured above with a constant current of 0.15mA to 0.005V, let it stand for 5 minutes, then discharge it again with a constant current of 10μA to 0.005V and record the initial charge capacity of the coin cell. After that, charge it with a constant current of 0.3mA to 2.0V and record the initial charge capacity of the coin cell. Initial Coulomb efficiency (%) of the carbon material = Initial charge capacity of the coin cell / Initial discharge capacity of the coin cell × 100%. (3) Testing of the cycle performance of secondary batteries

[0212] At 25°C, the rechargeable battery manufactured as described above is charged with a constant current of 0.5C until it reaches the upper cutoff voltage (corresponding to 100% SOC), then charged with a constant voltage until the current reaches 0.05C, left to stand for 5 minutes, and then discharged with a constant current of 0.5C until it reaches the lower cutoff voltage (corresponding to 0% SOC). The discharge capacity at this time, i.e., the initial discharge capacity, is recorded. The rechargeable battery is subjected to a cycle charge-discharge test according to the above method, and the discharge capacity after each cycle until the discharge capacity of the rechargeable battery has decreased to 80% of the initial discharge capacity is recorded, and the number of cycles at this time is recorded.

[0213] [Table 2]

[0214] Figure 8 is a scanning electron microscope image of the carbon material produced in Example 4. Figure 9 is a scanning electron microscope image of the carbon material produced in Comparative Example 1. As can be seen from the figures, Comparative Example 1 uses untreated natural spheroidal graphite as the carbon material, and has many voids inside its particles. As can be seen from the test results in Table 2, the initial Coulomb efficiency of the produced battery is low and the cycle life is short.

[0215] This invention allows for the formation of a carbon material in which the outer region is dense and the inner region still retains a small portion of the pore structure by mixing natural spheroidal graphite with a filler such as petroleum pitch, heat-treating the mixture, and then filling the pore structure of the natural spheroidal graphite with the filler. In both cases, the carbon material satisfies S2 > S1. The pore structure in the inner region can secure the expansion space necessary for volume changes of the carbon material particles, thereby reducing the risk of new interfaces being generated due to fragmentation of the carbon material particles, reducing the occurrence of side reactions, and reducing irreversible capacity loss of the battery. The outer region has a dense structure, which minimizes the penetration of the electrolyte into the pore structure inside the carbon material particles, thus reducing the occurrence of side reactions. Therefore, the carbon material according to this invention has small volume expansion, high structural stability, and low surface activity, enabling batteries to have high gram capacity, high initial Coulomb efficiency, and long cycle life.

[0216] None of the carbon materials produced in Comparative Examples 1-4 satisfy S2 > S1, and none of them can provide batteries with high gram capacity, high initial Coulomb efficiency, and long cycle life.

[0217] The carbon materials produced in Comparative Examples 2 and 3 consist of natural spheroidal graphite coated with a carbon layer. However, this carbon layer exists only on the surface of the natural spheroidal graphite, failing to achieve an effective filling effect. Furthermore, the carbon layer does not effectively prevent the electrolyte from penetrating the pore structure inside the particles. As a result, the improvement in the initial Coulomb efficiency and cycle performance of the battery is limited.

[0218] In Comparative Example 4, when manufacturing the carbon material, filling all the pore structures inside the natural spheroidal graphite particles with a filler by vacuum evacuation results in a large volume change of the carbon material during the desorption and insertion process of active ions, making the particles more easily fragmented. Consequently, the improvement effect on the battery's cycle performance is limited.

[0219] The carbon materials produced in Examples 1 to 28 have parameters such as specific surface area, volume distribution particle size, particle size distribution, degree of graphitization, powder resistivity, and tap density all within the ranges specified in this specification.

[0220] In summary, the test results from Examples 1 to 28 show that if the carbon material further satisfies 1.5 ≤ S2 / S1 ≤ 500 and selectively satisfies 2.5 ≤ S2 / S1 ≤ 120, the initial Coulomb efficiency and / or cycle performance of the battery can be further improved.

[0221] In summary, the measurement results from Examples 4, 25-28 show that when raw materials have different volume distribution particle sizes Dv50 and / or pore volumes, the manufacturing method of the present invention can yield carbon materials with excellent electrochemical properties in all cases.

[0222] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea of ​​the present invention and produces similar effects is included within the scope of the present invention. In addition, various modifications to the embodiments that a person skilled in the art could conceive, as long as they do not depart from the spirit of this invention, and other forms constructed by combining some of the components of the embodiments are also included within the scope of this invention.

Claims

1. A carbon material, It includes an external region and an internal region located inside the external region. The external region is a region that extends from the particle surface of the carbon material to the particle interior at a distance of 0.25L, where L is the minor axis length of the particles of the carbon material. Let the total pore area of the external region be S １ and the total pore area of the internal region be S ２ and S ２ > S １ and 0.01 μm ２ ≤ S １ ≤ 10.0 μm ２ and 1.8 μm ２ ≤ S ２ ≤ 25.0 μm ２ is satisfied. Carbon materials.

2. 1.5 ≤ S ２ / S １ ≤ 500 The carbon material according to claim 1.

3. 0.1 μm ２ ≤S １ ≤4.5 μm ２ and / or, 2.1 μm ２ ≤S ２ ≤20.0 μm ２ That is, The carbon material according to claim 1.

4. L is 5 μm or larger. The carbon material according to claim 1.

5. The area of ​​the pore structure in the external region of the carbon material is 0.15 μm². ２ Less than, The carbon material according to claim 1.

6. The internal region of the carbon material has an area of ​​0.15 μm². ２ It includes one or more pore structures that are as described above. The carbon material according to claim 1.

7. The interlayer distance in the outer region of the carbon material is d １ Let d be the interlayer distance in the internal region of the carbon material. ２ The carbon material is d １ ≥ d ２ Satisfying The carbon material according to claim 1.

8. d １ The wavelength is 0.33565 nm to 0.33615 nm, and / or d ２ The range is 0.33557 nm to 0.33595 nm. The carbon material according to claim 7.

9. The carbon material satisfies at least one of the following conditions: (1) The specific surface area of ​​the carbon material is 2.1 m². ２ / g or less, (2) The volume distribution particle size Dv50 of the carbon material is 8.0 μm to 25.0 μm. (3) The volume distribution particle size Dv90 of the carbon material is 16.0 μm to 35.0 μm. (4) The particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is 0.5 to 1.

5. (5) The topography of the carbon material includes one or more of the following: bulky, spherical, and subspherical. The carbon material according to claim 1.

10. The carbon material satisfies at least one of the following conditions: (1) The degree of graphitization of the carbon material is 91.5% to 98%, (2) The powder resistivity of the carbon material at a pressure of 8 MPa is 0.009 Ω·cm to 0.052 Ω·cm. (3) The tap density of the carbon material is 0.80 g / cm³. ３ ~1.50 g / cm ３ And, (4) The gram capacity of the carbon material is 350 mAh / g to 372 mAh / g. The carbon material according to claim 1.

11. A method for manufacturing carbon materials, Step 1 provides a raw material having multiple pore structures, After uniformly mixing the raw materials and filler in a predetermined ratio, the first temperature T １ Then the first time t １ Step 2 involves maintaining the temperature to obtain an intermediate, The obtained intermediate is heated to a second temperature T ２ Then the second time t ２ The process includes step 3, which involves maintaining the temperature to obtain a carbon material. The carbon material comprises an outer region and an inner region located inside the outer region, wherein the outer region is a region extending from the particle surface of the carbon material into the particle at a distance of 0.25 L, where L is the minor axis length of the carbon material particle, and S is the total pore area of ​​the outer region. １ The total pore area of ​​the internal region is set to S. ２ and S ２ > S １ And, 0.01 μm ２ ≤S １ ≤10.0 μm ２ It is 1.8 μm ２ ≤S ２ ≤25.0 μm ２ That is, A method for manufacturing carbon materials.

12. The aforementioned raw material satisfies at least one of the following conditions: (1) The raw material contains natural graphite, (2) The volume distribution particle size Dv50 of the raw material is 8.0 μm to 25.0 μm. (3) The pore volume of the raw material is 6.0 mm ３ It is 1 / g or more. The method according to claim 11.

13. The filler satisfies at least one of the following conditions: (1) The softening temperature of the filler is 90°C to 150°C. (2) The caulking value of the filler is 15% to 40%, (3) The volume distribution particle size Dv50 of the filler is 6 μm or less. The method according to claim 11.

14. The filler includes one or more of the following: coal pitch, petroleum pitch, polymer compounds, and resins. The method according to claim 13.

15. The mass ratio of the filler to the raw material is (15-30):

100. The method according to claim 11.

16. After uniformly mixing the raw materials and the filler in a predetermined ratio, the first temperature T １ The heating process that raises the temperature to a certain level is a stepwise heating process. The method according to claim 11.

17. The first heating process involves raising the temperature to 200°C to 250°C and maintaining that temperature for 1 to 3 hours, and / or The second heating process is performed when the temperature reaches the first temperature T １ The temperature is raised to a certain level, and the temperature is maintained at that level for a first time t １ The purpose is to keep it warm. The method according to claim 16.

18. The first temperature T is increased at a rate of 1°C / min to 10°C / min. １ Heat up to this point. The method according to claim 11.

19. The first temperature T １ The temperature is 700°C to 1150°C, and / or, The first time t １ It is 1 to 5 hours. The method according to claim 11.

20. The second temperature T ２ The temperature range is 1600°C to 2620°C, and / or, The second time t ２ It is 1.5 to 6 hours. The method according to claim 11.

21. A negative electrode sheet comprising a carbon material according to any one of claims 1 to 10, Secondary battery.

22. A secondary battery as described in claim 21, Power consuming device.

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