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

Abstract

This 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 a pore structure. When the adsorption amount of 100 g of the carbon material to linseed oil is A and the specific surface area of the carbon material is B, the carbon material satisfies 36 ≦ A×B ≦ 75. The unit of the adsorption amount A of 100 g of the carbon material to linseed oil is ml, and the unit of the specific surface area B of the carbon material is m 2 / g. The carbon material provided by this application can achieve both high initial Coulomb efficiency, high energy density, good cycle performance and storage performance in secondary batteries.

Description

Technical Field

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

Background Art

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

Summary of the Invention

[0003] An object of this application is to provide a carbon material, a method for manufacturing the same, a secondary battery including the same, and a power consumption device that can achieve both high initial Coulomb efficiency, high energy density, good cycle performance, and storage performance in a secondary battery.

[0004] A first aspect of this application provides a carbon material. The carbon material includes a pore structure. Let the adsorption amount of 100 g of the carbon material to linseed oil be A, and the specific surface area of the carbon material be B. Then, the carbon material satisfies 36 ≦ A × B ≦ 75. The unit of the adsorption amount A of 100 g of the carbon material to linseed oil is ml, and the unit of the specific surface area B of the carbon material is m 2 / g.

[0005] The carbon material provided by this application can effectively reduce the irreversible capacity loss of a secondary battery, improve the capacity performance of the secondary battery, and achieve high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance in the secondary battery simultaneously.

[0006] In any embodiment of this application, 38 ≦ A × B ≦ 65, preferably 39 ≦ A × B ≦ 55. In this case, it is advantageous for the secondary battery to better achieve high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance simultaneously.

[0007] In any embodiment of this application, the adsorption amount A of 100 g of the carbon material to linseed oil is 30 mL to 50 mL, preferably 35 mL to 47 mL. When the adsorption amount of the carbon material to linseed oil is within the above range, since the surface side reaction activity of the carbon material particles is low, the consumption of active ions due to the formation of the SEI film can be reduced, and the influence on the transport of active ions due to the overly dense particle surface can be avoided. Also, it is advantageous to form a reasonable pore structure between the particles of the negative electrode film layer and improve the wettability of the negative electrode sheet to the electrolyte.

[0008] In any embodiment of this application, the specific surface area B of the carbon material is 0.5 m 2 / g to 2.1 m 2 / g, preferably 0.7 m 2 / g to 1.8 m 2 / g. When the specific surface area of the carbon material is within the above range, the carbon material has low surface side reaction activity, which can reduce the consumption of active ions due to the formation of the SEI film and improve the initial Coulomb efficiency of the carbon material. On the other hand, it can also have high active ion transport performance.

[0009] In any embodiment of this application, the carbon material includes one or more pore structures with a pore area of 0.1 μm 2 or more, preferably with a pore area of 0.12 μm 2 to 2.5 μm 2It includes one or more pore structures. When the carbon material further includes a pore structure having the above pore area, the pore structure can ensure an expansion space necessary for the volume change of the carbon material particles, thereby further reducing the risk of generation of a new interface due to crushing of the carbon material particles, reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and further improving the cycle performance and storage performance of the secondary battery.

[0010] In any embodiment of the present application, the carbon material includes an external region and an internal region located inside the external region. The external region is a region extending 0.25L from the particle surface of the carbon material to the inside of the particle, where L is the minor axis length of the carbon material particle. Let the total pore area of the external region be S1 and the total pore area of the internal region be S2, and S2 > S1. When the carbon material particles further satisfy S2 > S1, the irreversible capacity loss of the secondary battery can be effectively reduced, the capacity performance of the secondary battery can be improved, and high initial Coulomb efficiency, high energy density, good cycle performance, and good storage performance of the secondary battery can be better balanced.

[0011] In any embodiment of the present application, 1.3 ≤ S2 / S1 ≤ 450, preferably 1.8 ≤ S2 / S1 ≤ 400. When S2 / S1 satisfies the above range, high initial Coulomb efficiency, high energy density, good cycle performance, and good storage performance of the secondary battery can be better balanced.

[0012] In any embodiment of the present application, 0.01 μm 2 ≤ S1 ≤ 12.0 μm 2 and preferably 0.02 μm 2 ≤ S1 ≤ 7.0 μm 2 When the total pore area of the external region of the carbon material is within the above range, the carbon material particles have fewer surface defects and a more stable structure, avoiding the penetration of the electrolyte into the pore structure inside the carbon material particles as much as possible, reducing the occurrence of side reactions, reducing the consumption of active ions due to the formation of the SEI film inside the carbon material particles, while not affecting the transport performance of active ions and electrons.

[0013] In any embodiment of the present application, 2.5 μm 2 ≦S2≦25.0 μm 2 and preferably, 3.0 μm 2 ≦S2≦20.5 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 can be ensured due to the volume change of the carbon material particles, the risk of generation of new interfaces due to crushing of the carbon material particles can be reduced, the occurrence of side reactions on the new interface surface can be decreased, and the consumption of active ions due to the formation of the SEI film on the new interface surface can be reduced. On the other hand, the capacity and initial Coulomb efficiency of the carbon material can be improved.

[0014] In any embodiment of the present application, L≥4 μm, and preferably, 6 μm≤L≤18 μm.

[0015] In any embodiment of the present application, the area of the pore structure in the external region of the carbon material is 0.2 μm 2 or less, and preferably 0.15 μm 2 or less. By controlling the size of 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 reducing the surface defects of the carbon material, improving the structural stability of the carbon material, avoiding the intrusion of the electrolyte into the pore structure inside the carbon material particles as much as possible, and further improving the cycle performance and storage performance of the secondary battery.

[0016] 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 preferably contains one or more pore structures with an area of 0.18 μm 2 to 2.5 μm 2 When the internal region of the carbon material contains pore structures of the above size, a sufficient and stable expansion space can be ensured due to the volume change of the carbon material particles, the risk of crushing of the carbon material particles can be reduced, and on the other hand, the compression density of the carbon material can be improved.

[0017] In any embodiment of the present application, when the interlayer distance of the external region of the carbon material is d1 and the interlayer distance of the internal region of the carbon material is d2, the carbon material satisfies d1≥d2, and preferably, d1>d2. Since the interlayer distance of the external region of the carbon material is large, which is advantageous for the rapid insertion and desorption of active ions, the kinetic performance of the secondary battery can be further improved. Since the interlayer distance of the internal region of the carbon material is small, which is advantageous for improving the gram capacity and compression density of the carbon material, the energy density of the secondary battery can be further improved.

[0018] In any embodiment of the present application, d1 is 0.33565 nm to 0.33610 nm.

[0019] In any embodiment of the present application, d2 is 0.33557 nm to 0.33585 nm.

[0020] In any embodiment of the present application, the graphitization degree of the carbon material is 94% to 98%, and preferably 95% to 97%. When the graphitization degree of the carbon material is within the above range, it is advantageous for improving the energy density of the secondary battery, and is also advantageous for improving the cycle performance, storage performance and / or rate performance of the secondary battery.

[0021] In any embodiment of the present application, La(110) of the carbon material is 100 nm to 150 nm, and preferably 110 nm to 130 nm.

[0022] In any embodiment of the present application, Lc(002) of the carbon material is 20 nm to 45 nm, and preferably 28 nm to 40 nm.

[0023] When the La(110) and / or Lc(002) of the carbon material is within an appropriate range, it is advantageous for the carbon material to have high crystallinity and / or graphitization degree, advantageous for improving the gram capacity of the carbon material, also advantageous for improving the active ion and electron transport performance of the negative electrode film layer, and further advantageous for improving the cycle performance, storage performance and / or rate performance of the secondary battery.

[0024] In any embodiment of the present application, the volume distribution particle size Dv50 of the carbon material is 8.0 μm to 24.0 μm, preferably 9.5 μm to 22.5 μm.

[0025] In any embodiment of the present application, the volume distribution particle size Dv10 of the carbon material is 5.0 μm to 15.0 μm, preferably 6.0 μm to 14.0 μm.

[0026] In any embodiment of the present application, the volume distribution particle size Dv90 of the carbon material is 16.0 μm to 35.0 μm, preferably 17.0 μm to 34.0 μm.

[0027] When the volume distribution particle sizes Dv10, Dv50 and / or Dv90 of the carbon material are within the above ranges, it is advantageous for improving the transport performance of active ions and electrons, also advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, and the cycle performance and / or rate performance of the secondary battery can be further improved.

[0028] In any embodiment of the present application, (Dv90 - Dv10) / Dv50 of the carbon material is 0.55 to 1.55, preferably 0.8 to 1.4. When (Dv90 - Dv10) / Dv50 of the carbon material is within the above range, its particle deposition performance is good, which is advantageous for improving the compression density of the negative electrode film layer, so the energy density of the secondary battery can be further improved. Also, it is advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer.

[0029] In any embodiment of the present application, the tap density of the carbon material is 0.80 g / cm3 ~1.32 g / cm 3 and preferably 0.82 g / cm 3 ~1.28 g / cm 3 When the tap density of the carbon material is within the above range, the compression density of the negative electrode sheet can be improved, and further the energy density of the secondary battery can be improved. It is also advantageous to form a reasonable pore structure between the particles of the negative electrode film layer, improve the transport performance of active ions and electrons, and improve the cycle performance and storage performance of the secondary battery.

[0030] In any embodiment of the present application, the gram capacity of the carbon material is 355 mAh / g to 371 mAh / g, preferably 360 mAh / g to 370 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be improved.

[0031] In any embodiment of the present application, the form of the carbon material includes one or more of massive, spherical and substantially spherical.

[0032] The second aspect of the present application is a method for producing a carbon material, including step 1 of supplying a raw material having a plurality of pore structures, step 2 of uniformly mixing the raw material and a filler at a predetermined ratio, and then holding at a first temperature T1 for a first time t1 to obtain an intermediate, and step 3 of holding the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material. The carbon material includes a pore structure. When the adsorption amount of 100 g of the carbon material to linseed oil is A and the specific surface area of the carbon material is B, the carbon material satisfies 36 ≦ A × B ≦ 75. The unit of the adsorption amount A of 100 g of the carbon material to linseed oil is ml, and the unit of the specific surface area B of the carbon material is m 2 / g. A method for producing a carbon material is provided.

[0033] In any embodiment of the present application, the raw material includes natural graphite, and preferably, the natural graphite includes one or more of flake graphite, natural spherical graphite and microcrystalline graphite.

[0034] In any embodiment of the present application, the volume distribution particle size Dv50 of the raw material is 8.5 μm to 24.0 μm, preferably 10.5 μm to 22.5 μm.

[0035] In any embodiment of the present application, the ash content in the raw material is 1 wt% or less. When the ash content in the raw material is low, it is advantageous for the carbon material to have low surface defects.

[0036] In any embodiment of the present application, the softening point temperature of the filler is 110°C to 175°C, preferably 120°C to 170°C. When the softening point temperature of the filler is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range.

[0037] In any embodiment of the present application, the coking value of the filler is 26% to 50%, preferably 33% to 45%. When the coking value of the filler is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range.

[0038] In any embodiment of the present application, the volume distribution particle size Dv50 of the filler is 6 μm or less, preferably 1 μm to 5 μm. Thereby, it is advantageous for the filler to be filled into the pore structure of the raw material after melting by heat, and it is also advantageous to improve the dispersion uniformity between the filler and the raw material.

[0039] In any embodiment of the present application, the content of quinoline insoluble matter in the filler is 1 wt% or less, preferably 0.8 wt% or less.

[0040] In any embodiment of the present application, the filler includes one or more of coal pitch and petroleum pitch.

[0041] In any embodiment of the present application, the mass ratio of the filler to the raw material is (10-32):100, preferably (10-25):100. Thereby, it is advantageous for the carbon material to have an appropriate adsorption amount A to linseed oil and / or an appropriate specific surface area B, and it is advantageous to make A×B of the carbon material within an appropriate range. It is also advantageous to adjust the size and / or the number of pores in the external region and the internal region of the carbon material within an appropriate range, and to adjust S2 / S1 within an appropriate range.

[0042] In any embodiment of the present application, after uniformly mixing the raw material and the filler at a predetermined ratio, the temperature-rising process of raising the temperature to the first temperature T1 is a stepwise temperature-rising process, preferably including a first temperature-rising process, a second temperature-rising process, and a third temperature-rising process.

[0043] In any embodiment of the present application, in the first temperature-rising process, the temperature is raised to 200°C to 250°C and kept at this temperature for 0.5 h to 2 h.

[0044] In any embodiment of the present application, in the second temperature-rising process, the temperature is raised to 450°C to 550°C and kept at this temperature for 0.5 h to 2 h.

[0045] In any embodiment of the present application, in the third temperature-rising process, the temperature is raised to the first temperature T1 and kept at this temperature for the first time t1.

[0046] 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, preferably 1.5°C / min to 8°C / min.

[0047] In any embodiment of the present application, the first temperature T1 is 700°C to 1100°C, preferably 750°C to 1100°C.

[0048] In any embodiment of the present application, the first time t1 is 0.5 h to 5 h, preferably 0.5 h to 3 h.

[0049] By adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. within the above ranges, it is advantageous for the production of the desired carbon material. For example, it is advantageous for the carbon material to have an appropriate adsorption amount A to linseed oil and / or an appropriate specific surface area B, and it is advantageous to make A×B of the carbon material within an appropriate range. It is also advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range.

[0050] In any embodiment of the present application, the second temperature T2 is 1920 °C to 2520 °C, preferably 2050 °C to 2400 °C.

[0051] In any embodiment of the present application, the second time t2 is 1 h to 6 h, preferably 2 h to 5 h.

[0052] By adjusting one or more of the second temperature and the second time within the above ranges, it is advantageous to reduce the content of irregular carbon in the carbon material, and it is advantageous for the carbon material to have an appropriate adsorption amount A to linseed oil and / or an appropriate specific surface area B, and it is advantageous to make A×B of the carbon material within an appropriate range.

[0053] The third aspect of the present application provides a secondary battery including a negative electrode sheet containing the carbon material of the first aspect of the present application or the carbon material produced by the method of the second aspect of the present application.

[0054] The fourth aspect of the present application provides a power consumption device including the secondary battery of the third aspect of the present application.

[0055] Since the power consumption device of the present application includes the secondary battery provided by the present application, it has at least the same advantages as the secondary battery.

Brief Description of the Drawings

[0056] To more clearly explain the technical solutions of the embodiments of this application, the drawings that need to be used in the embodiments of this application are briefly described below. Obviously, the drawings described below are only some embodiments of this application, and those skilled in the art can also obtain other drawings based on these drawings without creative efforts.

[0057]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0058] In the drawings, they are not necessarily drawn to actual scale. The description of the reference numerals is as follows. 1 Battery pack 2 Upper housing 3 Lower housing 4 Battery module 5 Secondary battery 51 Case 52 Electrode assembly 53 Cover plate 100 Carbon material 101 External region 102 Internal region

Embodiments for Carrying Out the Invention

[0059] Hereinafter, embodiments specifically disclosing the carbon material of the present application, a method for manufacturing the same, and a secondary battery and a power consumption device including the same will be described in detail with appropriate reference to the drawings. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of known matters or redundant descriptions of substantially the same configurations may be omitted. This is to avoid the following description from being unnecessary and redundant and to facilitate the understanding of those skilled in the art. Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0060] In the present application, the "range" disclosed is defined in the form of a lower limit and an upper limit. A predetermined range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit limit the boundary of a special range. The range thus limited may be a range including or not including the end values, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, when ranges of 60 to 120 and 80 to 110 are given for a specific parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also expected. Also, when the minimum range values 1 and 2 and the maximum range values 3, 4, and 5 are given, ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 may all be expected. In the present application, unless otherwise explained, the numerical range "a to b" is represented by an abbreviation of any combination of real numbers between a and b, and both a and b are real numbers. For example, the numerical range "0 to 5" indicates all real numbers between "0 to 5" in this specification, and "0 to 5" is an abbreviation of the combination of these numerical values. Also, when a certain parameter is expressed as an integer of 2 or more (≧2), it corresponds to disclosing that the parameter is, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0061] Unless otherwise specified, all embodiments and alternative embodiments of the present application may be combined with each other to form a new technical solution. Moreover, such a technical solution should be regarded as being included in the disclosure content of the present application.

[0062] Unless otherwise specified, all technical features and alternative technical features of the present application may be combined with each other to form a new technical solution. Moreover, such a technical solution should be regarded as being included in the disclosure content of the present application.

[0063] Unless otherwise specified, all steps of the present application may be performed in sequence or randomly, but it is preferred to be performed in sequence. For example, the fact that the above method includes steps (a) and (b) means that the above method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, when it is mentioned that the above method may further include step (c), it means that step (c) may be added to the above method in any order. For example, the above method may include steps (a), (b), and (c), may include steps (a), (c), and (b), may include steps (c), (a), and (b), etc.

[0064] Unless otherwise specified, the terms "comprising" and "including" described in the present application are open-ended and may also be closed-ended. For example, the above "comprising" and "including" can represent further "comprising" or "including" other components not listed, or "comprising" or "including" only the components listed.

[0065] Unless otherwise specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the following conditions is satisfied: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0066] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0067] Unless otherwise specified, the numerical values of each parameter mentioned in this application can be measured by various test methods commonly used in this field. For example, they can be measured according to the test methods provided in this application.

[0068] Unless otherwise specified, in this application, the term "active ion" refers to an ion that can be inserted and removed reciprocally between the positive electrode and the negative electrode of a secondary battery, and the ion includes, but is not limited to, lithium ions.

[0069] In this application, the terms "a plurality" and "a plurality of types" mean two or more.

[0070] Graphite is divided into artificial graphite and natural graphite according to the manufacturing process and the source. When manufacturing artificial graphite, it generally needs to go through a high-temperature graphitization treatment process. Since the energy consumption of this process is high and the cost is high, the cost of artificial graphite is high. Natural graphite is derived from nature, so it has the advantage of being relatively inexpensive. In addition, natural graphite also has the advantage of high capacity.

[0071] Natural graphite mainly includes flake graphite, natural spherical graphite and microcrystalline graphite. Usually, different from artificial graphite, natural graphite has a very large number of voids and defects inside and outside its particles. In the initial charging process of a secondary battery, the electrolyte generates many side reactions with the particle surface and the pores inside the particles, resulting in a high initial irreversible capacity loss of the secondary battery, a low initial Coulomb efficiency, and poor cycle performance and storage performance. In particular, flake graphite and natural spherical graphite have high crystallinity and high graphitization degree, and their microstructures are often layered structures. Due to such structures, the volume change occurring in the process of desorption and insertion of active ions in natural graphite is large, which is likely to cause the crushing of the graphite layered structure and the particles. After the particles are crushed, the exposed fresh surface continues to react with the electrolyte, so the irreversible capacity loss of the secondary battery further increases.

[0072] Currently, the performance of natural graphite is mainly improved by particle surface coating treatment and / or particle internal filling treatment.

[0073] In the particle surface coating treatment, mainly after uniformly mixing natural graphite and a coating agent (such as pitch, polymer compound, etc.), heat treatment is carried out to coat a layer of carbon layer on the surface of natural graphite particles to slightly repair the defects on the particle surface. However, the inventor of the present application has found in the research process that the amorphous carbon layer coated on the surface reduces the gram capacity (capacity per gram) and / or compression density of natural graphite, affects the energy density of the secondary battery, and at the same time, there are still many defects on the particle surface after being coated with the amorphous carbon layer, and the amorphous carbon layer coated on the surface cannot effectively prevent the electrolyte from penetrating into the pore structure inside the particles. As a result, the improvement effect on the initial Coulomb efficiency, cycle performance and / or storage performance of the secondary battery is limited.

[0074] In the particle internal filling process, natural graphite and a filler (such as pitch, polymer compound, etc.) are mainly mixed, and the filler is filled into the voids inside the particles by means such as a predetermined pressure, evacuation, and temperature increase, so as to obtain natural graphite without voids inside the particles. However, the inventor of the present application found in the research process that a large amount of carbon filled inside the particles, especially soft carbon, reduces the gram capacity (capacity per gram) of natural graphite, affects the energy density of the secondary battery, and at the same time, since all the voids inside the natural graphite particles are filled with carbon, the volume change occurring in the process of desorption and insertion of active ions of natural graphite becomes large, and the particles are more likely to be crushed. Furthermore, the destruction and reconstruction of the SEI film on the particle surface are repeated, further increasing the irreversible consumption of active ions, increasing the irreversible capacity loss of the secondary battery, and shortening the service life of the secondary battery. In the prior art, since a layer of amorphous carbon layer continues to be coated on the surface of the natural graphite without voids inside the particles, the gram capacity and / or compression density of the natural graphite are further reduced. At this time, since there are still many surface defects of the particles, the service life of the secondary battery cannot be effectively improved.

[0075] Therefore, after modifying natural graphite by the above particle surface coating treatment and / or particle internal filling treatment, the irreversible capacity loss of the secondary battery can be reduced to a certain extent, and the initial Coulomb efficiency of the secondary battery can be improved. However, the improvement effect on the initial Coulomb efficiency of the secondary battery is limited, and the energy density of the secondary battery is impaired. Moreover, the capacity performance during the long-term cycle and storage process of the secondary battery is still poor.

[0076] In view of this, the inventor of the present application has conducted a large amount of research and provides a novel carbon material that has both a high gram capacity and a high initial Coulomb efficiency, and can achieve both a high initial Coulomb efficiency, a high energy density, and good cycle performance and storage performance in the secondary battery.

[0077] Carbon material

[0078] The first aspect of the embodiment of the present application provides a carbon material.

[0079] The carbon material includes a pore structure. Let the adsorption amount of 100 g of the carbon material to linseed oil be A, and the specific surface area of the carbon material be B. Then, the carbon material satisfies 36 ≦ A×B ≦ 75. The unit of the adsorption amount A of 100 g of the carbon material to linseed oil is ml, and the unit of the specific surface area B of the carbon material is m 2 / g.

[0080] In the process of research, the inventor of the present application found that when the carbon material satisfies 36 ≦ A×B ≦ 75, it is possible to achieve both high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance in a secondary battery. The reasons are considered as follows.

[0081] First, at this time, since the surface of the carbon material particles is dense, the carbon material particles have a stable structure, and by avoiding the penetration of the electrolyte into the pore structure inside the carbon material particles as much as possible, the occurrence of side reactions can be reduced, the consumption of active ions due to the formation of the SEI film inside the particles can be reduced, and further, the initial Coulomb efficiency of the carbon material can be improved, and the cycle performance and storage performance of the secondary battery can be further improved.

[0082] Second, at this time, since there are few defects on the surface of the carbon material particles, the adsorption ability of the particles to oily substances is weak, which is advantageous for reducing side reactions in the battery.

[0083] Third, at this time, the carbon material particles can form a reasonable pore channel structure in the negative electrode film layer and improve the wettability of the negative electrode sheet to the electrolyte.

[0084] Therefore, the carbon material provided by the present application can effectively reduce the irreversible capacity loss of the secondary battery, improve the capacity utilization characteristics of the secondary battery, and achieve both high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance in the secondary battery.

[0085] When A×B is less than 36, the adsorption amount of the carbon material to linseed oil may be small and / or the specific surface area of the carbon material may be small. When the adsorption amount of the carbon material to linseed oil is small, the densification degree of the surface structure of the carbon material is high, and thus the volume change of the carbon material particles in the desorption and insertion process of active ions may be large. At this time, the particles are more likely to be crushed, and furthermore, the SEI film on the particle surface is likely to repeat destruction and reconstruction, which conversely increases the irreversible consumption of active ions, increases the irreversible capacity loss of the secondary battery, and shortens the service life of the secondary battery. When the specific surface area of the carbon material is small, it may be disadvantageous for the transport of active ions, thus affecting the capacity performance, cycle performance and / or rate performance of the secondary battery.

[0086] When A×B exceeds 75, the adsorption amount of the carbon material to linseed oil may increase and / or the specific surface area of the carbon material may increase. When the adsorption amount of the carbon material to linseed oil increases, there are many surface defects and / or pore structures of the carbon material particles, so there are many side reactions of the electrolyte, and the consumption of active ions due to the formation of the SEI film is large, which reduces the initial Coulomb efficiency of the secondary battery. At the same time, as the number of charge and discharge cycles of the secondary battery increases, the thickness of the SEI film on the surface of the carbon material particles continues to increase, thus also affecting the cycle performance and / or rate performance of the secondary battery. When the specific surface area of the carbon material increases, the side reaction activity on the surface of the carbon material particles is high, and the consumption of active ions due to the formation of the SEI film is large, so the initial Coulomb efficiency of the secondary battery is reduced, affecting the storage performance of the secondary battery.

[0087] In some embodiments, 38≦A×B≦65, preferably 38≦A×B≦60, 39≦A×B≦55, 39≦A×B≦52, 39≦A×B≦50. The inventor has found in further research that in this case, it is advantageous for the secondary battery to better balance high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance.

[0088] In some embodiments, the adsorption amount A of 100 g of the carbon material to linseed oil is 30 mL to 50 mL, preferably 35 mL to 47 mL. When the adsorption amount of the carbon material to linseed oil is within the above range, since the side reaction activity on the surface of the carbon material particles is low, the consumption of active ions due to the formation of the SEI film can be reduced, and the influence on the transport of active ions due to the overly dense particle surface can be avoided. Further, it is also advantageous to form a reasonable pore structure between the particles of the negative electrode film layer and improve the wettability of the negative electrode sheet to the electrolyte. Thereby, in the secondary battery, high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance can be better balanced.

[0089] In some embodiments, the specific surface area B of the carbon material is 0.5 m 2 / g to 2.1 m 2 / g, preferably 0.7 m 2 / g to 1.8 m 2 / g, 0.9 m 2 / g to 1.8 m 2 / g, 1.0 m 2 / g to 1.8 m 2 / g, 1.0 m 2 / g to 1.7 m 2 / g, 1.0 m 2 / g to 1.6 m 2 / g. When the specific surface area of the carbon material is within the above range, the carbon material has low surface side reaction activity, whereby the consumption of active ions due to the formation of the SEI film can be reduced, and the initial Coulomb efficiency of the carbon material can be improved. On the other hand, it can also have high active ion transport performance. Thereby, high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance can be better balanced in the secondary battery, and the secondary battery can also be provided with good rate performance.

[0090] The specific surface area of the carbon material is a meaning known in the art and can be measured by equipment and methods known in the art. For example, referring to GB / T 19587-2017, it can be measured by the nitrogen gas adsorption specific surface area analysis measurement method and calculated by the BET (Brunauer Emmett Teller) method. As the measuring instrument, the Tri-Star 3020 type specific surface area pore size analyzer of Micromeritics, USA can be used.

[0091] The adsorption amount A of 100 g of carbon material to linseed oil can be measured according to the following method. Referring to GB / T 3780.2-2017, a test sample dried with a certain mass (for example, 20 g) is weighed, and the weighed sample is placed in the mixing chamber of the oil absorption meter. The temperature of the mixing chamber is 23 °C and is covered with a lid. Align the constant-speed burette oil delivery port above the orifice of the lid of the mixing chamber. Start the oil absorption meter, the device starts to operate and drip linseed oil. As the oil absorption amount of the sample increases, the mixture material changes from a free-flowing state to a semi-plastic aggregate, and the viscosity of the mixture continuously increases. The viscosity is transmitted to the torque sensor system of the oil absorption meter. When the semi-plastic aggregate reaches a preset torque level due to the dropped oil, the oil absorption meter and the constant-speed burette automatically close. Read the value corresponding to 70% of the maximum torque of the fitting curve, and use the formula A = (V / m) × 100 to calculate the adsorption amount A of 100 g of carbon material to linseed oil. V represents the volume of linseed oil consumed by the sample corresponding to 70% of the maximum torque, with the unit of ml, and m is the mass of the added sample, with the unit of g.

[0092] In some embodiments, the carbon material includes one or more pore structures with a pore area of 0.1 μm 2 or more, preferably, the pore area is 0.12 μm 2 ~2.5 μm 2It includes one or more pore structures. When the carbon material further includes a pore structure having the above pore area, the pore structure can secure an expansion space necessary for the volume change of the carbon material particles, thereby further reducing the risk of generation of a new interface due to crushing of the carbon material particles, and further reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and further improving the cycle performance and storage performance of the secondary battery.

[0093] In some embodiments, the carbon material includes an external region and an internal region located inside the external region. The external region is a region extending 0.25L from the particle surface of the carbon material to the particle interior, where L is the minor axis length of the carbon material particles. Let the total pore area of the external region be S1 and the total pore area of the internal region be S2, and S2 > S1.

[0094] In the present application, the total pore area S1 of the external region and the total pore area S2 of the internal region of the first carbon-based material can be obtained by measurement from the cross-sectional image of the first carbon-based material.

[0095] In the present application, the cross-sectional image of the first carbon-based material includes a cross-sectional image passing through the center of the particles of the first carbon-based material. The "particle center" refers to the range within a radius extending 0.1 μm from the geometric center of the particle towards the particle surface.

[0096] In the present application, the minor axis length of the particle refers to the minimum value when the connecting line between two points on the particle surface passes through the geometric center of the particle.

[0097] FIG. 1 is a schematic diagram of a cross-sectional image of the particles of the carbon material 100 of the present application, and the cross-sectional image passes through the center of the particles of the carbon material 100. As shown in FIG. 1, L represents the minor axis length of the particles of the carbon material 100, and the region extending 0.25L from the particle surface of the carbon material 100 to the particle interior is the external region 101, and the region inside the external region 101 is the internal region 102.

[0098] The cross-section of the first carbon-based material can be manufactured by using a cross-section polisher (for example, the IB-09010 CP type argon ion cross-section polisher of JEOL Ltd.). Next, referring to JY / T 010-1996, the cross-section of the first carbon-based material is scanned by using a scanning electron microscope (for example, the Sigma 300 type scanning electron microscope of Carl Zeiss AG in Germany), and finally, the total pore area S1 of the external region and the total pore area S2 of the internal region of the first carbon-based material are calculated by using image processing software (for example, AVIZO).

[0099] When the carbon material further satisfies S2 > S1, the carbon material particles may have the characteristics that the number of pores in the internal region is large and / or the pore size is large, while the number of pores in the external region is small and / or the pore size is small. Since the number of pores in the internal region of the carbon material is large and / or the pore size is large, the pore structure can ensure the expansion space required for the volume change of the carbon material particles, thereby reducing the risk of generating a new interface due to the crushing of the carbon material particles, and thus reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and improving the cycle performance and storage performance of the secondary battery. Since the number of pores in the external region of the carbon material is small and / or the pore size is small, the carbon material particles can have fewer surface defects and a more stable structure, and can avoid the electrolyte from penetrating into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions, reducing the consumption of active ions due to the formation of the SEI film inside the particles, and thus improving the initial Coulomb efficiency of the carbon material and further improving the cycle performance and storage performance of the secondary battery. Therefore, when the carbon material particles further satisfy S2 > S1, the irreversible capacity loss of the secondary battery can be effectively reduced, the capacity performance of the secondary battery can be improved, and the secondary battery can better achieve high initial Coulomb efficiency, high energy density, good cycle performance and storage performance at the same time.

[0100] In some embodiments, 1.3 ≤ S2 / S1 ≤ 450, 1.8 ≤ S2 / S1 ≤ 400, 2.0 ≤ S2 / S1 ≤ 300, 2.5 ≤ S2 / S1 ≤ 200, 3.0 ≤ S2 / S1 ≤ 150. As a result of further study, the inventors have found that when S2 / S1 satisfies the above range, high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance can be better balanced in the secondary battery.

[0101] In some embodiments, 0.01 μm 2 ≤ S1 ≤ 12.0 μm 2 and preferably, 0.02 μm 2 ≤ S1 ≤ 10.0 μm 2 and 0.02 μm 2 ≤ S1 ≤ 8.0 μm 2 and 0.02 μm 2 ≤ S1 ≤ 7.0 μm 2 and 0.1 μm 2 ≤ S1 ≤ 10.0 μm 2 and 0.1 μm 2 ≤ S1 ≤ 7.0 μm 2 When the total pore area of the external region of the carbon material is within the above range, the carbon material particles have fewer surface defects and a more stable structure, and the electrolyte can be avoided from entering the pore structure inside the carbon material particles as much as possible, reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film inside the carbon material particles, while not affecting the transport performance of active ions and electrons.

[0102] In some embodiments, 2.5 μm 2 ≤ S2 ≤ 25.0 μm 2 and preferably, 3.0 μm 2 ≤ S2 ≤ 22.5 μm 2 and 3.0 μm 2 ≤ S2 ≤ 20.5 μm 2 and 4.0 μm 2 ≤ S2 ≤ 17.5 μm 2When the total pore area of the internal region of the carbon material is within the above range, a sufficient and stable expansion space can be ensured due to the volume change of the carbon material particles, the risk of generation of new interfaces due to crushing of the carbon material particles 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. On the other hand, the capacity and initial Coulomb efficiency of the carbon material can be improved.

[0103] In some embodiments, L≧4 μm, preferably 4 μm≦L≦20 μm, 6 μm≦L≦18 μm, 8 μm≦L≦18 μm, 8 μm≦L≦16 μm.

[0104] In some embodiments, the area of the pore structure in the external region of the carbon material is 0.2 μm 2 or less, preferably 0.15 μm 2 or less. The inventor further studied and found that by controlling the size of 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 reducing the surface defects of the carbon material, improving the structural stability of the carbon material, and avoiding as much as possible the intrusion of the electrolyte into the pore structure inside the carbon material particles, and further improving the cycle performance and storage performance of the secondary battery. Of course, this application does not limit that the area of all pore structures in the external region of the carbon material is 0.2 μm 2 or less. For example, the area of 95% or more, preferably 99% or more of the pore structures can be controlled to be 0.2 μm 2 or less, preferably 0.15 μm 2 or less.

[0105] In some embodiments, the internal region of the carbon material contains one or more pore structures with an area of 0.15 μm 2 or more, preferably with an area of 0.18 μm 2 ~2.5 μm 2It contains one or more pore structures. In further research, the inventor found that by including pore structures of the above size in the internal region of the carbon material, a sufficient and stable expansion space can be ensured for the volume change of the carbon material particles, reducing the risk of crushing of the carbon material particles, while improving the compression density of the carbon material.

[0106] In some embodiments, when the interlayer distance of the external region of the carbon material is d1 and the interlayer distance of the internal region of the carbon material is d2, the carbon material satisfies d1≧d2, and preferably, d1>d2.

[0107] Since the interlayer distance of the external region of the carbon material is large, which is advantageous for the rapid insertion and desorption of active ions, the kinetic performance of the secondary battery can be further improved. Since the interlayer distance of the internal region of the carbon material is small, which is advantageous for improving the gram capacity and compression density of the carbon material, the energy density of the secondary battery can be further improved.

[0108] In some embodiments, d1 is 0.33565nm to 0.33610nm.

[0109] In some embodiments, d2 is 0.33557nm to 0.33585nm.

[0110] The interlayer distances of different regions of the carbon material particles can be measured by known devices and methods in this field. For example, it can be measured using a High Resolution Transmission Electron Microscope (HRTEM). The measuring device can use a Thermo Fisher Spectra S / TEM scanning transmission electron microscope.

[0111] In some embodiments, La(110) of the carbon material is 100nm to 150nm, and preferably 110nm to 130nm.

[0112] In some embodiments, the Lc(002) of the carbon material is 20 nm to 45 nm, preferably 28 nm to 40 nm.

[0113] When the La(110) and / or Lc(002) of the carbon material is within an appropriate range, it is advantageous for the carbon material to have high crystallinity and / or graphitization degree, advantageous for improving the gram capacity of the carbon material, also advantageous for improving the active ion and electron transport performance of the negative electrode film layer, and further advantageous for improving the cycle performance, storage performance and / or rate performance of the secondary battery.

[0114] La(110) represents the crystallite size along the a-axis on the (110) crystal plane of the carbon material, and Lc(002) can represent the crystallite size along the c-axis on the (002) crystal plane of the carbon material, and can be measured by known devices and methods in this field. For example, it can be measured using an X-ray diffractometer (for example, Bruker D8 Discover). The measurement can be obtained by referring to JIS K0131-1996 and JB / T 4220-2011, obtaining the peak intensity and full width at half maximum (FWHM) of the diffraction peak corresponding to the (110) crystal plane of the carbon material and the peak intensity and full width at half maximum (FWHM) of the diffraction peak corresponding to the (002) crystal plane, and then calculating based on Scherrer's formula.

[0115] In some embodiments, the graphitization degree of the carbon material is 94% to 98%, preferably 95% to 97%. When the graphitization degree of the carbon material is within the above range, it is advantageous for improving the energy density of the secondary battery, and also advantageous for improving the cycle performance, storage performance and / or rate performance of the secondary battery.

[0116] The graphitization degree of the carbon material has the meaning known in the art and can be measured by known devices and methods in the art. For example, it can be measured using an X-ray diffractometer (for example, Bruker D8 Discover). The measurement is based on the average interlayer distance d of the (002) crystal plane in the crystal structure of the carbon material by referring to JIS K 0131-1996 and JB / T 4220-2011002 is obtained, and then the graphitization degree can be calculated based on the formula g = (0.344 - d 002 ) / (0.344 - 0.3354) × 100%. In the above formula, d 002 is the average interlayer distance of the (002) plane in the crystal structure of the carbon material represented in nanometers (nm).

[0117] In some embodiments, the form of the carbon material includes one or more of massive, spherical, and substantially spherical. Thereby, it is advantageous for improving the compression density of the negative electrode sheet and thus the energy density of the secondary battery.

[0118] In some embodiments, the carbon material includes primary particles. Preferably, the proportion of the number of the primary particles in the carbon material is 50% or more. For example, it may be 55% - 95%, 60% - 100%, 65% - 90%, 65% - 80%, 70% - 100%, 75% - 90%, 80% - 100%, 90% - 100%, or 95% - 100%. The carbon material can include an appropriate proportion of primary particles, have high structural stability, can also reduce the occurrence of side reactions, and can improve the compression density of the negative electrode sheet and the energy density of the secondary battery.

[0119] In some embodiments, all of the carbon materials may be primary particles, that is, the proportion of the number of the primary particles in the carbon material is 100%.

[0120] Both primary particles and secondary particles have meanings known in the art. Primary particles refer to non-aggregated particles. Secondary particles refer to aggregated particles in which two or more primary particles are aggregated. Primary particles and secondary particles can be distinguished using a scanning electron microscope (SEM) image.

[0121] In this application, the ratio of the number of primary particles in the carbon material can be measured by taking any one test sample in the negative electrode film layer, taking any plurality of test regions in the test sample, acquiring images of the plurality of test regions using a scanning electron microscope, and counting the ratio of the number of carbon material particles in the primary particle form to the total number of carbon material particles in each image, and taking the average value of the plurality of statistical results as the ratio of the number of primary particles in the carbon material.

[0122] In some embodiments, the volume distribution particle size Dv50 of the carbon material is 8.0 μm to 24.0 μm, preferably 9.5 μm to 22.5 μm.

[0123] In some embodiments, the volume distribution particle size Dv10 of the carbon material is 5.0 μm to 15.0 μm, preferably 6.0 μm to 14.0 μm.

[0124] In some embodiments, the volume distribution particle size Dv90 of the carbon material is 16.0 μm to 35.0 μm, preferably 17.0 μm to 34.0 μm.

[0125] When the volume distribution particle sizes Dv10, Dv50 and / or Dv90 of the carbon material are within the above ranges, it is advantageous for improving the transport performance of active ions and electrons, and is also advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, and the cycle performance and / or rate performance of the secondary battery can be further improved.

[0126] In some embodiments, (Dv90 - Dv10) / Dv50 of the carbon material is 0.55 to 1.55, preferably 0.8 to 1.4. When (Dv90 - Dv10) / Dv50 of the carbon material is within the above range, its particle deposition performance is good, which is advantageous for improving the compression density of the negative electrode film layer, so the energy density of the secondary battery can be further improved, and it is also advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer.

[0127] The volume distribution particle sizes Dv10, Dv50, and Dv90 of the carbon material have meanings known in this field, and respectively indicate the particle sizes corresponding when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, and can be measured by devices and methods known in this field. For example, referring to GB / T 19077-2016 Laser Diffraction Method for Particle Size Distribution, it can be conveniently measured using a laser particle size analyzer. The test device may be a Mastersizer 2000E type laser particle size analyzer of Malvern Instruments Limited, UK.

[0128] In some embodiments, the tap density of the carbon material is 0.80 g / cm 3 ~1.32 g / cm 3 and preferably 0.82 g / cm 3 ~1.28 g / cm 3 When the tap density of the carbon material is within the above range, it is also beneficial to improve the compression density of the negative electrode sheet, further improve the energy density of the secondary battery, form a reasonable pore structure between the particles of the negative electrode film layer, improve the transport performance of active ions and electrons, and improve the cycle performance and storage performance of the secondary battery.

[0129] The tap density of the carbon material has a meaning known in this field and can be measured by devices and methods known in this field. For example, referring to GB / T 5162-2006, it can be measured using a powder tap density tester. As the test device, BT-301 of Dandong BET can be used.

[0130] In some embodiments, the gram capacity of the carbon material is 355 mAh / g to 371 mAh / g, and preferably 360 mAh / g to 370 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be improved.

[0131] The gram capacity of the carbon material is a meaning known in the art and can be measured by methods known in the art. An exemplary measurement method is to sufficiently stir and mix a carbon material sample, styrene-butadiene rubber (SBR) as an adhesive, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent in a mass ratio of 96.2:1.8:1.2:0.8 with deionized water as an appropriate amount of solvent to form a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on the surface of a copper foil, which is a negative electrode current collector, and dried in an oven for future use. After mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, LiPF6 is dissolved in the above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L. Then, a CR2430 type button battery is assembled in a box protected by argon gas, with a metal lithium sheet as the counter electrode and a polyethylene (PE) film as the separator. At 25 °C, first, the button battery manufactured above is discharged at a constant current of 0.15 mA to 0.005 V, allowed to stand for 5 min, and then discharged at a constant current of 10 μA to 0.005 V, and the initial discharge capacity of the button battery is recorded. Then, it is charged at a constant current of 0.3 mA to 2.0 V, and the charging capacity of the button battery is recorded. The ratio of the charging capacity of the button battery to the mass of the carbon material sample is the gram capacity of the carbon material.

[0132] Manufacturing method

[0133] The second aspect of the embodiment of the present application provides a manufacturing method of a carbon material capable of manufacturing the carbon material of the first aspect of the embodiment of the present application.

[0134] The method for manufacturing the carbon material includes step 1 of supplying a raw material having a plurality of pore structures, step 2 of uniformly mixing the raw material and a filler at a predetermined ratio and then holding at a first temperature T1 for a first time t1 to obtain an intermediate, and step 3 of holding the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material. The carbon material includes a pore structure. If the adsorption amount of 100 g of the carbon material to linseed oil is A and the specific surface area of the carbon material is B, the carbon material satisfies 36 ≦ A × B ≦ 75. The unit of the adsorption amount A of 100 g of the carbon material to linseed oil is ml, and the unit of the specific surface area B of the carbon material is m 2 / g.

[0135] In some embodiments, the raw material for manufacturing the carbon material includes natural graphite. Preferably, the natural graphite includes one or more of flaky graphite, natural spherical graphite, and microcrystalline graphite, and preferably includes natural spherical graphite.

[0136] "Natural spherical graphite" means natural graphite having a spherical or substantially spherical shape, and does not control all natural graphite particles into ideal spheres. In some embodiments, by performing pretreatment on flaky graphite, natural spherical graphite with a desired particle size and morphology can be obtained. Preferably, the pretreatment includes processes such as crushing, classification, spheroidization, and purification.

[0137] In some embodiments, the form of the raw material includes one or more of spherical and substantially spherical.

[0138] In some embodiments, the volume distribution particle size Dv50 of the raw material is 8.5 μm to 24.0 μm, preferably 10.5 μm to 22.5 μm.

[0139] By adjusting the particle size of the raw material within the above range, it is possible to reduce the aggregation of the raw material in the subsequent manufacturing process, thereby reducing problems such as an increase in surface defects of carbon material particles and an increase in surface side reaction sites due to the need to increase the depolymerization process.

[0140] In some embodiments, the ash content in the raw material is 1 wt% or less. When the ash content in the raw material is low, it is advantageous for the carbon material to have low surface defects.

[0141] In some embodiments, the softening point temperature of the filler is 110°C to 175°C. For example, the softening point temperature of the filler may be in a range consisting of any numerical values such as 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C or more. Preferably, the softening point temperature of the filler is 120°C to 170°C.

[0142] In the process of research, the inventor found that when the softening point temperature of the filler is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range. In addition, the following situations can be avoided. When the softening point temperature of the filler is too high, it becomes difficult for the filler to be fluid-filled into the pore structure of the raw material. As a result, the surface and internal defects of the obtained carbon material particles cannot be effectively reduced, and the electrolyte cannot be effectively prevented from entering the pore structure inside the obtained carbon material particles. At this time, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material easily increase, and A×B of the carbon material easily increases. Furthermore, it affects the initial Coulombic efficiency, cycle performance, and storage performance of the secondary battery. When the softening point temperature of the filler is too low, the filler contains relatively many small molecule substances, and these small molecule substances are easily volatilized by heat. Therefore, the filler is easily fluid-filled into the pore structure of the raw material. However, when heat-treated at a high temperature, the small molecule substances in the filler volatilize, so that the actually remaining carbon cannot be effectively filled into the pore structure of the raw material, and an effective filling effect cannot be realized, or the actually remaining carbon in the filling region has relatively many pore structures. At this time, the surface defects of the carbon material particles are numerous, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material easily increase, and A×B of the carbon material easily increases. Furthermore, it is impossible to reduce the consumption of active ions due to the formation of the SEI film and the irreversible capacity loss of the secondary battery, and at the same time, it affects the cycle performance and storage performance of the secondary battery.

[0143] In some embodiments, the coking value of the filler is 26% to 50%, preferably 33% to 45%. The inventor has found that during the research process, when the coking value of the filler is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range.

[0144] The coking value of the filler is a meaning known in the art and can be measured by equipment and methods known in the art. For example, it can be measured with reference to GB / T 8727-2008.

[0145] In some embodiments, the softening point temperature of the filler is 120°C to 170°C, and the coking value is 33% to 45%.

[0146] In some embodiments, the volume distribution particle size Dv50 of the filler is 6 μm or less, preferably 1 μm to 6 μm, 1 μm to 5 μm, 2 μm to 5 μm, or 3 μm to 5 μm. Thereby, it is advantageous for the filler to be filled into the pore structure of the raw material after melting due to heat, and it is also advantageous to improve the dispersion uniformity between the filler and the raw material.

[0147] In some embodiments, the content of quinoline insoluble matter in the filler is 1 wt% or less, preferably 0.8 wt% or less. If the content of quinoline insoluble matter is high, it will affect the actual remaining atomic arrangement of carbon in the filling area, and will also affect the powder compression density of the carbon material and the energy density of the secondary battery.

[0148] In some embodiments, the filler includes one or more of coal pitch and petroleum pitch.

[0149] In some embodiments, the mass ratio of the filler to the raw material is (10~32):100, preferably (10~25):100, (11~22):100, (11~20):100. Thereby, it is advantageous for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range. In addition, the following situations can be avoided. If the mass ratio of the filler to the raw material is too small, it becomes difficult for the filler to be fluid-filled into the pore structure of the raw material. As a result, the internal defects of the obtained carbon material particles cannot be effectively reduced, and the intrusion of the electrolyte into the pore structure inside the obtained carbon material particles cannot be effectively blocked. At this time, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material easily increase, A×B of the carbon material easily increases, and further, it affects the initial Coulomb efficiency, cycle performance, and storage performance of the secondary battery. If the mass ratio of the filler to the raw material is too large, the pore structure inside the raw material is likely to be completely filled. At this time, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material easily decrease, A×B of the carbon material easily decreases. Thereby, the volume change occurring in the process of desorption and insertion of active ions of the obtained carbon material becomes large, and the particles are more likely to be crushed. Furthermore, the consumption of active ions due to the formation of the SEI film increases, and the irreversible capacity loss of the secondary battery increases. Also, if the mass ratio of the filler to the raw material is too large, a large amount of the filler remains on the particle surface. At this time, the particles are more likely to aggregate, not only does the depolymerization process increase, but also the gram capacity and compression density of the obtained carbon material decrease.

[0150] By adjusting one or more parameters such as the type of filler, softening point, coking value, addition amount, etc. within the above ranges, it is advantageous for the carbon material to have an appropriate adsorption amount A to linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range. Further, after the filler melts due to heat, its viscosity does not increase, it maintains good fluidity, raw material particles are not easily adhered, and agglomeration in the subsequent manufacturing process of the raw material particles can be reduced. Thereby, problems such as an increase in surface defects of the obtained carbon material particles and an increase in surface side reaction sites due to the need to increase the depolymerization step can be reduced.

[0151] In some embodiments, in step 2, after uniformly mixing the raw material and the filler at a predetermined ratio, the temperature rising process of rising to the first temperature T1 is a stepwise temperature rising process, and preferably includes a first temperature rising process, a second temperature rising process, and a third temperature rising process.

[0152] In some embodiments, the first temperature rising process rises to 200°C to 250°C and holds at this temperature for 0.5 h to 2 h.

[0153] In the process of research, the inventor found that when the heat preservation time of the first heating process is within the above range, it is beneficial for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is beneficial to make A×B of the carbon material within an appropriate range. It is also beneficial to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range, and to adjust S2 / S1 within an appropriate range. In addition, the following situations can be avoided. If the heat preservation time is too short, it is difficult for the filler to be fluid-filled into the pore structure of the raw material, and there is a possibility of carbonization on the particle surface. Therefore, the internal defects of the obtained carbon material particles cannot be effectively reduced, and the electrolyte cannot be effectively prevented from entering the pore structure inside the obtained carbon material particles. In this case, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material are likely to increase, A×B of the carbon material is likely to increase, and further affect the initial Coulomb efficiency, cycle performance and storage performance of the secondary battery. If the heat preservation time is too long, the filler is likely to be fluid-filled into all the pore structures of the raw material, and the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material are likely to decrease, and A×B of the carbon material is likely to decrease. Therefore, the volume change occurring in the process of desorption and insertion of active ions of the carbon material becomes large, the particles are more likely to be crushed, the consumption of active ions due to the formation of the SEI film increases, the irreversible capacity loss of the secondary battery increases, and it also affects the cycle performance, storage performance and rate performance of the secondary battery.

[0154] In some embodiments, the second heating process raises the temperature to 450°C to 550°C and keeps the temperature for 0.5 h to 2 h.

[0155] In some embodiments, the third heating process raises the temperature to the first temperature T1 and keeps the temperature for the first time t1.

[0156] In the stepwise heating process, first, the temperature is raised to 200°C to 250°C. Since the heating temperature is higher than the softening point temperature of the filler, at this time, the filler is melted and softened by heat, and can be kept warm for 0.5 h to 2 h to be fluid-filled into the pore structure of the raw material. Then, the temperature is raised to 450°C to 550°C. At this time, the melted and softened filler undergoes a carbonization reaction and gradually becomes in a semi-coke state, turning into a viscous liquid or solid, thereby avoiding the filler from entering all the pore structures of the raw material. Finally, the temperature is raised to the first temperature T1. At this time, the filler undergoes a carbonization reaction, whereby the pore structure occupied by the filler is effectively filled, the surface defects are reduced, and furthermore, it is beneficial for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is beneficial to make A×B of the carbon material within an appropriate range, and it is also beneficial to adjust the pore size and / or the number of pores in the external region and the internal region of the carbon material within an appropriate range, and to adjust S2 / S1 within an appropriate range.

[0157] 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 consisting of any value such as 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 above. Preferably, the heating rate is 1.5°C / min to 8°C / min.

[0158] In some embodiments, the heating rate of the first heating process may be 1°C / min to 10°C / min, preferably 1.5°C / min to 8°C / min.

[0159] In the process of research, the inventors have found that when the heating rate of the first heating process is within the above range, it is advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range, and to adjust S2 / S1 within an appropriate range. In addition, the following situations can be avoided. 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 be fluid-filled into the pore structure of the raw material. As a result, the internal defects of the obtained carbon material particles cannot be effectively reduced, and the electrolyte cannot be effectively prevented from penetrating into the internal pore structure of the obtained carbon material particles, which will affect the initial Coulombic efficiency, cycle performance and storage performance of the secondary battery. If the heating rate is too low, the filler is likely to be fluid-filled into all the pore structures of the raw material. As a result, the volume change occurring in the process of desorption and insertion of active ions in the carbon material becomes larger, and the particles are more likely to be crushed. This increases the consumption of active ions due to the formation of the SEI film, increases the irreversible capacity loss of the secondary battery, and affects the cycle performance, storage performance and rate performance of the secondary battery.

[0160] In some embodiments, the heating rate of the second heating process may be 1 °C / min to 10 °C / min, preferably 1.5 °C / min to 8 °C / min.

[0161] In some embodiments, the heating rate of the third heating process may be 1 °C / min to 10 °C / min, preferably 1.5 °C / min to 8 °C / min.

[0162] In some embodiments, in step 2, the first temperature T1 is 700 °C to 1100 °C. For example, the first temperature T1 may be in the range consisting of any value such as 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C or more. Preferably, the first temperature T1 is 750 °C to 1100 °C.

[0163] In the process of research, the inventor has found that when the first temperature is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range, and to adjust S2 / S1 within an appropriate range. In addition, the following situations can be avoided. If the first temperature is too low, the filler may not be completely converted into the carbon material, and continue to decompose into small molecule substances during subsequent heat treatment. As a result, the carbon actually remaining in the filling region has many pore structures, and cannot effectively reduce the internal defects of the obtained carbon material particles, nor can it effectively prevent the electrolyte from entering the pore structure inside the obtained carbon material particles. At the same time, the surface defects of the obtained carbon material increase, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material easily increase, A×B of the carbon material easily increases, and further affect the initial Coulomb efficiency, cycle performance and storage performance of the secondary battery. If the first temperature is too high, the energy consumption and cost in the manufacturing process of the carbon material increase.

[0164] In some embodiments, the first time t1 is 0.5h to 5h. For example, the first time t1 may be in the range consisting of 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or any numerical value above. Preferably, the first time t1 is 0.5h to 3h.

[0165] In the process of research, the inventors have found that when the first time is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and it is advantageous to make A×B of the carbon material within an appropriate range. It is also advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range. In addition, the following situations can be avoided. If the first time is too short, the filler may not be completely converted into the carbon material, and by continuously decomposing into small molecule substances during subsequent heat treatment, the carbon actually remaining in the filling region has many pore structures, and the internal defects of the obtained carbon material particles cannot effectively reduce the internal defects of the obtained carbon material particles. It is also impossible to effectively prevent the electrolyte from entering the pore structure inside the obtained carbon material particles. At the same time, the surface defects of the obtained carbon material increase, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material easily increase, A×B of the carbon material easily increases, and further affects the initial Coulomb efficiency, cycle performance and storage performance of the secondary battery. If the first time is too long, the energy consumption and cost in the manufacturing process of the carbon material are likely to increase.

[0166] In some embodiments, in step 2, the heat treatment may be performed in an intermediate frequency furnace, a roller hearth kiln, a rotary kiln or a pusher kiln.

[0167] In some embodiments, in step 2, the heat treatment atmosphere may be a protective gas atmosphere. The protective gas may include one or more of nitrogen, argon, and helium.

[0168] In Step 2, by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. within the above ranges, it is advantageous for the production of the desired carbon material. For example, it is advantageous for the carbon material to have an appropriate adsorption amount A to linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range and to adjust S2 / S1 within an appropriate range.

[0169] In some embodiments, the second temperature T2 is 1920°C to 2520°C. For example, the second temperature may be in the range consisting of 1950°C, 2000°C, 2050°C, 2100°C, 2150°C, 2200°C, 2250°C, 2300°C, 2350°C, 2400°C, 2450°C, 2500°C or any other numerical value thereabove. Preferably, the second temperature T2 is 2050°C to 2400°C.

[0170] The inventors have found that during the research process, when the second temperature is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A to linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous for the carbon material to have low surface defects, high gram capacity and / or high compression density. In addition, the following situations can be avoided. If the second temperature is too low, there are many surface defects in the obtained carbon material particles. In this case, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material are likely to increase, and A×B of the carbon material also easily increases, further affecting the initial Coulomb efficiency, cycle performance and storage performance of the secondary battery. If the second temperature is too high, the content of irregular carbon in the obtained carbon material is too low, and both the crystallinity and graphitization degree of the carbon material are high. In this case, it is disadvantageous for the rapid desorption and insertion of active ions, and the volume change of the carbon material during the charge and discharge process is large, thereby increasing the risk of crushing of the carbon material particles, affecting the cycle performance and / or kinetic performance of the secondary battery. Also, if the second temperature is too high, the energy consumption and cost in the production process of the carbon material increase.

[0171] In some embodiments, the second time t2 is 1 h to 6 h. For example, the second time t1 may be in the range consisting of any value such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h or more. Preferably, the second time t2 is 2 h to 6 h.

[0172] The inventor has found that during the research process, when the second time is within the above range, it is advantageous for the carbon material to have an appropriate adsorption amount A to linseed oil and / or an appropriate specific surface area B, and it is advantageous to keep A×B of the carbon material within an appropriate range. It is also advantageous for the carbon material to have low surface defects, high gram capacity and / or high compression density. In addition, the following situations can be avoided. If the second time is too short, there will be many surface defects in the obtained carbon material particles. In this case, the adsorption amount A of the carbon material to linseed oil and / or the specific surface area B of the carbon material will easily increase, and A×B of the carbon material will also easily increase, further affecting the initial Coulomb efficiency, cycle performance and storage performance of the secondary battery. If the second time is too long, the content of irregular carbon in the obtained carbon material will be too low, and both the crystallinity and graphitization degree of the carbon material will be high. In this case, it is disadvantageous for the rapid desorption and insertion of active ions, and the volume change of the carbon material during the charge and discharge process is large. As a result, the risk of crushing of the carbon material particles also increases, affecting the cycle performance and / or kinetic performance of the secondary battery. Also, if the second time is too long, the energy consumption and cost in the manufacturing process of the carbon material will increase.

[0173] In some embodiments, in step 3, the heat treatment can be carried out in an intermediate frequency furnace, a box-type graphitization furnace, an Acheson-type graphitization furnace, a continuous graphitization furnace or an in-line graphitization furnace.

[0174] In some embodiments, in step 3, for the intermediate frequency furnace and the continuous graphitization, the heat treatment atmosphere may be a protective gas atmosphere. The protective gas may include one or more of nitrogen, argon, and helium.

[0175] Adjusting one or more of the second temperature and the second time within the above ranges is advantageous for reducing the content of irregular carbon in the carbon material, for the carbon material to have an appropriate adsorption amount A of linseed oil and / or an appropriate specific surface area B, and for A×B of the carbon material to be within an appropriate range.

[0176] The method for manufacturing the carbon material of the present application has a simple process, high safety, does not require pre-setting of pressure or vacuum treatment, and does not require adding a depolymerization step in the heat treatment process. The carbon material manufactured in the present application has a small volume expansion, high structural stability, and few surface defects, so it can have a high gram capacity and a high initial Coulomb efficiency, and can also achieve both a high initial Coulomb efficiency, a high energy density, and good cycle performance and storage performance in a secondary battery.

[0177] The manufacturing method of the present application has a low cost, high practicality, and is suitable for large-scale production.

[0178] Secondary battery

[0179] The third aspect of the embodiment of the present application provides a secondary battery.

[0180] The present application does not particularly limit the type of secondary battery. For example, the secondary battery may be a lithium-ion battery or the like. Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and the like. In the charge and discharge process of the secondary battery, active ions reciprocate between the positive electrode sheet and the negative electrode sheet for insertion and desorption, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of the 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). In a secondary battery using an electrolyte solution and a secondary battery using some solid electrolytes, a separator may be further included, which is provided between the positive electrode sheet and the negative electrode sheet and plays a role in isolation.

[0181] [Negative electrode sheet]

[0182] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two surfaces facing each other in 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.

[0183] In some embodiments, the negative electrode film layer includes a carbon material according to the first aspect of the embodiments of the present application or a carbon material manufactured by the method described in the second aspect of the embodiments of the present application. Thereby, it is possible to achieve both high initial Coulomb efficiency, high energy density, and good cycle performance and storage performance in the secondary battery.

[0184] In some embodiments, the negative electrode film layer may further include other negative electrode active materials other than the above carbon materials. In some embodiments, the other negative electrode active materials include, but are not limited to, one or more of conventional natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include one or more of silicon alone, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include one or more of tin alone, tin oxide, and tin alloy material.

[0185] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. In the present application, the type of the negative electrode conductive agent is not particularly limited. By way of example, the negative electrode conductive agent can include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0186] In some embodiments, the negative electrode film layer may optionally contain a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. By way of example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0187] In some embodiments, the negative electrode film layer may optionally contain other auxiliaries. By way of example, the other auxiliaries may include a thickener, e.g., sodium carboxymethyl cellulose (CMC), PTC thermistor material, etc.

[0188] In some embodiments, a metal foil sheet or a composite current collector can be used as the negative electrode current collector. As an example of the metal foil sheet, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. By way of example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. By way of example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0189] The negative electrode film layer is usually formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional auxiliaries in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0190] The negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present application is sandwiched between the negative electrode current collector and the negative electrode film layer, and further includes a conductive undercoat layer (for example, composed of a conductive agent and an adhesive) provided on the surface of the negative electrode current collector. In some embodiments, the negative electrode sheet according to the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0191] [Positive electrode sheet]

[0192] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0193] The positive electrode current collector can use a metal foil sheet or a composite current collector. As an example of the metal foil sheet, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0194] The positive electrode film layer usually includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode film layer is usually formed by applying a positive electrode slurry to the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other components in a solvent and stirring uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). The adhesive used in the positive electrode film layer includes, for example, any one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. As an example, the conductive agent used in the positive electrode film layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0195] The positive electrode active material can employ a positive electrode active material for secondary batteries known in the art.

[0196] 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.

[0197] 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.

[0198] In some embodiments, for example, the positive electrode active material for the lithium-ion battery is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and / or LiMnPO4 may be included.

[0199] In the present application, the modified compound of each of the above cathode active materials can be subjected to doping modification and / or surface coating modification with respect to the cathode active material.

[0200] [Electrolyte]

[0201] In some embodiments, the electrolyte uses an electrolytic solution containing an electrolyte salt and a solvent.

[0202] The type of the electrolyte salt is not specifically limited and can be selected according to actual needs.

[0203] When the secondary battery of the present application is a lithium ion battery, for example, the electrolyte salt includes 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(oxalate)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorosulfate phosphate (LiTFOP).

[0204] The type of the solvent is not specifically limited and can be selected according to actual needs. In some embodiments, by way of example, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0205] In some embodiments, the electrolyte may optionally contain an additive. For example, the additive may include a negative electrode film-forming additive, may include a positive electrode film-forming additive, and may include an additive capable of improving certain performance of the secondary battery, such as an additive for improving the overcharge performance of the secondary battery, an additive for improving the high-temperature performance of the secondary battery, an additive for improving the low-temperature output performance of the secondary battery, and the like.

[0206] [Separator]

[0207] In the present application, the type of the separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0208] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0209] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be used to manufacture an electrode assembly by a winding process or a lamination process.

[0210] In some embodiments, the secondary battery can include an exterior. The exterior is used to seal the electrode assembly and the electrolyte described above.

[0211] In some embodiments, the exterior may be a rigid case such as a rigid plastic case, an aluminum case, or a steel case. The exterior may also be a soft pack, for example, a pouch soft pack. The material of the soft bag may be plastic, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0212] In the present application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other arbitrary shape. FIG. 2 shows, as an example, a secondary battery 5 having a rectangular structure.

[0213] In some embodiments, as shown in FIG. 3, the exterior may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates surround to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 covers the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted as needed.

[0214] The method for manufacturing the secondary battery of the present application is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolytic solution. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed as an electrode assembly by a winding process or a lamination process. The electrode assembly is placed in an exterior package, and after drying, the electrolytic solution is injected. Through processes such as vacuum sealing, standing, formation, and shaping, a secondary battery can be obtained.

[0215] In some embodiments of the present application, the secondary battery according to the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be plural. The specific number may be adjusted according to the use and capacity of the battery module.

[0216] FIG. 4 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 4, in the battery module 4, a plurality of secondary batteries 5 may be provided side by side in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by a fastener.

[0217] Alternatively, the battery module 4 may further include a housing having an accommodation space for accommodating a plurality of secondary batteries 5.

[0218] In some embodiments, the above battery module may be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the use and capacity of the battery pack.

[0219] FIGS. 5 and 6 are schematic diagrams of a battery pack 1 as an example. As shown in FIGS. 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms a sealed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0220] Power consumption device

[0221] This application further provides a power consumption device including at least one of a secondary battery, a battery module, or a battery pack of this application. The secondary battery, battery module, or battery pack may be used as a power source of the power consumption device, or may be used as an energy storage unit of the power consumption device. The power consumption device may be a mobile device (e.g., a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

[0222] The power consumption device can select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0223] FIG. 7 is a schematic diagram of a power consumption device as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements for high output and high energy density of the power consumption device, a battery pack or a battery module can be adopted.

[0224] Another example of the power consumption device may be a mobile phone, a tablet computer, a notebook computer, etc. This power consumption device is generally required to be thin, and a secondary battery can be used as a power source.

[0225] Embodiment

[0226] The following examples are used to explain the disclosure content of this application in more detail. Since it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the disclosure content of this application, these examples are only for illustrative purposes. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are based on mass. All reagents used in the examples are commercially available or obtained by synthesis according to conventional methods and can be used directly without further treatment. The equipment used in the examples is commercially available.

[0227] Example 1

[0228] (1) Preparation of carbon material

[0229] In step 1, mechanical grinding, classification, spheroidization, and purification treatments were performed on 100-mesh flaky graphite to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 μm and an ash content of 0.01%.

[0230] In step 2, the obtained natural spherical graphite and petroleum pitch (softening point temperature of 120 °C, volume distribution particle size Dv50 of 4.3 μm, coking value of 33%) were mixed in a VC mixer at a mass ratio of 100:15 for 30 min. After that, the mixed material was put into a roller hearth kiln, heated to 230 °C at a rate of 5 °C / min and held for 1 h (the first heating process), then heated to 500 °C at a rate of 5 °C / min and held for 1 h (the second heating process), and further heated to 1100 °C at a rate of 5 °C / min and held for 1 h (the third heating process). After completion, it was cooled to room temperature to obtain an intermediate.

[0231] In step 3, the obtained intermediate was put into an Acheson graphitization furnace, heated to 2300 °C and held for 2 h. After completion, it was demagnetized and sieved to obtain a carbon material.

[0232] (2) Manufacture of button battery (half cell)

[0233] The carbon material produced above, styrene-butadiene rubber (SBR) as an adhesive, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent are sufficiently stirred and mixed with deionized water, which is an appropriate amount of solvent, in a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on the surface of a copper foil, which is a negative electrode current collector, and dried in an oven for future use. After mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, LiPF6 is dissolved in the above organic solvent to produce an electrolyte solution with a concentration of 1 mol / L. Then, using a lithium metal sheet as a counter electrode and a polyethylene (PE) thin film as a separator, a CR2430 type button battery is assembled in a glove box protected by argon gas.

[0234] (3) Fabrication of a secondary battery (full cell)

[0235] The carbon material produced above, carbon black (Super P) as a conductive agent, styrene-butadiene rubber as an adhesive, and sodium carboxymethyl cellulose as a thickener are sufficiently stirred and mixed in deionized water, which is an appropriate amount of solvent, in a weight ratio of 96:1:1:2 to form a negative electrode slurry. The negative electrode slurry is coated on two surfaces of a copper foil, which is a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0236] 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 coated on two surfaces of an aluminum foil, which is a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0237] A polypropylene film with a thickness of 12 μm was used as a separator, and the positive electrode sheet and the negative electrode sheet manufactured above were arranged in order. The separator was located between the positive electrode sheet and the negative electrode sheet to perform an isolation function, and then it was wound to obtain an electrode assembly. The electrode assembly was placed in an outer package, and after drying, the same electrolyte as the button battery manufactured above was injected. After passing through processes such as vacuum sealing, standing, formation, and capacity, a secondary battery was obtained.

[0238] Comparative Example 1

[0239] The manufacturing methods of the half-cell and the full-cell are the same as those in Example 1 except for the manufacturing process of the carbon material.

[0240] Mechanical grinding, classification, spheroidization, and purification treatments were performed on 100-mesh flaky graphite. After obtaining natural spherical graphite with a volume distribution particle size Dv50 of 17 μm and an ash content of 0.01%, the obtained natural spherical graphite was used as a carbon material to manufacture a half-cell and a full-cell.

[0241] Comparative Example 2

[0242] The manufacturing methods of the half-cell and the full-cell are the same as those in Example 1 except for the manufacturing process of the carbon material.

[0243] Mechanical grinding, classification, spheroidization, and purification treatments were performed on 100-mesh flaky graphite, and natural spherical graphite with a volume distribution particle size Dv50 of 17 μm and an ash content of 0.01% was obtained.

[0244] The obtained natural spherical graphite and petroleum pitch (softening point temperature 120 °C, volume distribution particle size Dv50 of 4.3 μm, coking value of 33%) were mixed in a VC mixer for 30 min at a mass ratio of 100:15, and then the mixed material was graphitized at 3200 °C for 10 h. After completion, it was cooled to room temperature to obtain a carbon material.

[0245] Comparative Example 3

[0246] The manufacturing methods of the half cell and the full cell are the same as those of Example 1 except for the manufacturing process of the carbon material.

[0247] Mechanical pulverization, classification, spheroidization, and purification treatments were performed on 100-mesh flaky graphite to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 μm and an ash content of 0.01%.

[0248] The obtained natural spherical graphite and petroleum pitch (softening point temperature 120°C, volume distribution particle size Dv50 of 4.3 μm, coking value of 33%) were mixed in a VC mixer at a mass ratio of 100:15 for 30 min, and then the mixed material was carbonized at 1300°C for 2 h and cooled to room temperature after completion to obtain a carbon material.

[0249] Comparative Example 4

[0250] The manufacturing methods of the half cell and the full cell are the same as those of Example 1 except for the manufacturing process of the carbon material.

[0251] Mechanical pulverization, classification, spheroidization, and purification treatments were performed on 100-mesh flaky graphite to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 μm and an ash content of 0.01%.

[0252] Asphalt was added to the wash oil and stirred at high speed to fully dissolve the asphalt, obtaining an asphalt solution. 100 g of natural stone spherical ink was put into the reaction kettle, and vacuum was applied for 60 min. When the vacuum degree of the reaction kettle reached 0.07 MPa, the asphalt solution suction valve was opened, and all the asphalt solution was sucked into the reaction kettle. After the liquid supply was completed, the suction valve was closed, the vacuum application was stopped, and at the same time, the mixture was stirred at high speed for 40 min. After the pressure application (12 MPa) immersion was completed, the pressure was reduced to make the pressure inside and outside the reaction kettle the same, and then nitrogen gas was introduced and heated to 230 °C to remove the wash oil. After all the wash oil in the reaction kettle was discharged, under the condition of a pressure of 1.5 MPa, the reaction kettle was heated to 410 °C at a heating rate of 5 °C / min, and the thermal polymerization reaction was carried out for 10 h, and then cooled to room temperature and discharged. The obtained material was kept under isostatic pressure (10 MPa) for 30 min, then treated at a high temperature of graphitization (2800 °C) for 4 h, cooled to room temperature, and pulverized. The pulverized material and asphalt were uniformly mixed at a ratio of 100:5, and carbonized at 1000 °C for 5 h under the protection of nitrogen gas, and then cooled to room temperature to obtain a carbon material without voids inside.

[0253] Examples 2 to 23

[0254] The manufacturing methods of the half-cell and the full-cell are the same as those in Example 1 except that the manufacturing process parameters of the carbon material are adjusted. For details, refer to Table 1.

[0255] Performance test

[0256] (1) Test of the adsorption amount of the carbon material to linseed oil

[0257] Refer to GB / T 3780.2-2017, weigh 20 g of the dried test sample, place the weighed sample in the mixing chamber of the oil absorption meter, cover it with a lid when the temperature of the mixing chamber is 23 °C. Align the constant-speed burette oil delivery port above the orifice of the mixing chamber lid. Start the oil absorption meter, the device starts to operate and drops linseed oil. As the oil absorption of the sample increases, the mixture changes from a free-flowing state to a semi-plastic aggregate, and the viscosity of the mixture continuously increases. This viscosity is transmitted to the torque sensor system of the oil absorption meter. When the semi-plastic aggregate reaches the preset torque level due to the dropped oil, the oil absorption meter and the constant-speed burette automatically close. Read the value corresponding to 70% of the maximum torque of the fitting curve, and use the formula A = (V / m)×100 to calculate the adsorption amount A of 100 g of the carbon material to linseed oil. Here, V represents the volume of linseed oil consumed by the sample at 70% of the maximum torque, with the unit of ml, and m is the mass of the added sample, with the unit of g.

[0258] (2) Test of the specific surface area of the carbon material

[0259] Refer to GB / T 19587-2017, test by the nitrogen gas adsorption specific surface area analysis measurement method, and calculate the specific surface area B of the carbon material by the BET (Brunauer Emmett Teller) method. As the test equipment, the Tri-Star 3020 type specific surface area and pore size analysis measurement instrument of Micromeritics, USA can be used.

[0260] (3) X-ray diffraction analysis test of the carbon material

[0261] With reference to JIS K0131-1996 and JB / T 4220-2011, tests were carried out using an X-ray diffractometer. After obtaining the peak intensity and full width at half maximum (FWHM) of the diffraction peak corresponding to the (110) crystal plane of the carbon material, and the peak intensity and full width at half maximum (FWHM) of the diffraction peak corresponding to the (002) crystal plane, La(110) and Lc(002) of the carbon material were calculated based on Scherrer's formula. La(110) indicates the crystallite size along the a-axis in the (110) crystal plane of the carbon material, and Lc(002) can indicate the crystallite size along the c-axis in the (002) crystal plane of the carbon material. The test equipment may be a Bruker D8 Discover X-ray diffractometer.

[0262] (4) Test of the total pore area in the external and internal regions of the carbon material

[0263] After uniformly mixing the adhesive for sample production with the carbon material powder, it was applied to a copper foil and dried at 60°C for 30 min for future use. The sample was cut into a size of 6 mm × 6 mm and attached to the sample stage of a CP type argon ion cross-section polisher. The sample was cut using a plasma beam to obtain the cross-section of the carbon material, and the cross-section of the carbon material particles passed through the center of the carbon material particles. As the test equipment, an IB-09010 CP type argon ion cross-section polisher of JEOL Ltd. can be used.

[0264] The cross-section of the carbon material was scanned using a scanning electron microscope. The test can refer to JY / T 010-1996. The test equipment may be a Sigma 300 type scanning electron microscope of ZEISS, Germany.

[0265] The region extending 0.25L from the particle surface to the particle interior of the carbon material was defined as the external region, and the region inside the external region was defined as the internal region, where L represents the short axis length of the carbon material particles. Using image processing software, the total pore area S1 of the external region and the total pore area S2 of the internal region of the carbon material particles were calculated. The image processing software may be AVIZO.

[0266] (5) Test of the initial Coulomb efficiency of carbon materials

[0267] At 25 °C, first discharge the button battery manufactured above at a constant current of 0.15 mA to 0.005 V, let it stand for 5 min, then discharge it at a constant current of 10 μA to 0.005 V, and record the initial discharge capacity of the button battery. Then, charge it at a constant current of 0.3 mA to 2.0 V, and record the initial charge capacity of the button battery. The initial Coulomb efficiency (%) of the carbon material = (initial charge capacity of the button battery) / (initial discharge capacity of the button battery) × 100%.

[0268] (6) Test of the cycle performance of secondary batteries

[0269] At 25 °C, charge the secondary battery manufactured above at a constant current of 1 C to the upper cut-off voltage (corresponding to 100% SOC), then charge it at a constant voltage until the current reaches 0.05 C, let it stand for 5 min, and then discharge the secondary battery at a constant current of 1 C to the lower cut-off voltage (corresponding to 0% SOC), and record the discharge capacity at this time as the first discharge capacity. Conduct a cycle charge-discharge test on the secondary battery according to the above method, and record the discharge capacity after one cycle. The capacity retention rate (%) of the secondary battery after 2000 cycles at 25 °C = (discharge capacity after 2000 cycles) / (first discharge capacity) × 100%.

[0270] (7) Test of the storage performance of secondary batteries

[0271] At 25 °C, charge the secondary battery manufactured above at a constant current of 1 C to the upper cut-off voltage (corresponding to 100% SOC), then charge it at a constant voltage until the current reaches 0.05 C, let it stand for 5 min, and then discharge the secondary battery at a constant current of 1 C to the lower cut-off voltage (corresponding to 0% SOC), and record the discharge capacity at this time as the discharge capacity before storage.

[0272] At 25°C, the secondary battery prepared above was charged at a constant current of 1C up to the upper cut-off voltage (corresponding to 100% SOC), and then charged at a constant voltage until the current reached 0.05 C. The secondary battery was then placed in a thermostatic chamber at 60°C and stored until the discharge capacity of the secondary battery after storage attenuated to 90% of the discharge capacity before storage, at which point the test was stopped and the number of days the secondary battery was stored was recorded.

[0273] The parameters of the carbon materials produced in Examples 1 to 23, such as volume distribution particle size and tap density, are all within the ranges described in the present specification.

[0274] Considering the test results in Table 2, it can be seen that when the carbon material satisfies 36≦A×B≦75, the battery can achieve high initial coulombic efficiency, high energy density, and good cycle performance and storage performance. In addition, when the carbon material further satisfies 38≦A×B≦65, and preferably 39≦A×B≦55, the overall performance of the battery can be further improved.

[0275] None of the carbon materials produced in Comparative Examples 1 to 4 satisfied 36≦A×B≦75, and none of them could provide a battery with a high initial coulombic efficiency, high energy density, and good cycle performance and storage performance at the same time.

[0276] In Comparative Example 1, untreated natural spherical graphite was used as the carbon material, which had many voids inside. As can be seen from the measurement results in Table 2, the gram capacity, initial coulombic efficiency, cycle performance and storage performance of the battery manufactured using this were all poor, and when the number of cycles of the battery did not reach 2000, the discharge capacity decreased to 80% of the first discharge capacity.

[0277] The carbon materials produced in Comparative Examples 2 and 3 formed a carbon layer coating layer on the surface of natural spherical graphite, but the carbon layer was only present on the surface of the natural spherical graphite, and could not achieve a filling effect. In addition, the carbon layer could not effectively prevent the electrolyte from penetrating into the pore structure inside the particles, and further, the improvement effect on the initial coulombic efficiency, cycle performance and storage performance of the battery was limited.

[0278] In Comparative Example 4, when producing the carbon material, the filler is filled into all the pore structures inside the natural spherical graphite particles by isostatic pressing, which results in a large volume change of the carbon material particles during the process of desorption and insertion of active ions, making the particles more likely to be crushed, and further limiting the effect of improving the cycle performance and storage performance of the battery. In addition, the presence of a large amount of soft carbon inside and / or on the surface of the carbon material particles increases side reactions on the particle surface, further affecting the cycle performance and storage performance of the battery. At the same time, the production process is complicated and not suitable for large-scale production.

[0279] Considering the test results in Table 2, it can be seen that when the carbon material particles further satisfy S2>S1, preferably satisfy 1.3≦S2 / S1≦450, more preferably satisfy 1.8≦S2 / S1≦400, the overall performance of the battery is further improved. In this case, the carbon material particles further have the characteristics that the number of holes in the inner region is large and / or the size of the holes is large, but the number of holes in the outer region is small and / or the size of the holes is small. The pore structure in the inner region of the carbon material can ensure the expansion space required for the volume change of the carbon material particles, thereby reducing the risk of new interfaces caused by the crushing of the carbon material particles, reducing the occurrence of side reactions, and reducing the loss of irreversible capacity of the secondary battery. The small number of holes in the outer region of the carbon material and / or the small size of the pores can give the carbon material particles a more stable structure, and can prevent the electrolyte from penetrating the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film inside the particles. As a result, a carbon material that further satisfies the above structural features can further improve the overall performance of the battery.

[0280] Note that this application is not limited to the above embodiments. The above embodiments are examples, and those having a configuration substantially the same as the technical idea and exhibiting the same operational effects within the technical scope of this application are all included in the technical scope of this application. In addition, within the scope not departing from the gist of this application, various modifications conceivable by those skilled in the art made to the embodiments, and other forms constructed by combining some of the components in the embodiments are also included in the scope of this application.

Table 1

Table 2

Claims

1. A carbon material comprising a pore structure, When the adsorption amount of 100 g of the carbon material to linseed oil is A and the specific surface area of the carbon material is B, the carbon material satisfies 36 ≦ A × B ≦ 75. The unit of the adsorption amount A of 100 g of the carbon material to linseed oil is ml, and the unit of the specific surface area B of the carbon material is m ２ / g. Carbon material.

2. The carbon material according to claim 1, wherein 38 ≦ A × B ≦ 65, preferably 39 ≦ A × B ≦ 55.

3. The adsorption amount A of 100 g of the carbon material to linseed oil is 30 mL to 50 mL, preferably 35 mL to 47 mL, and / or The specific surface area B of the carbon material is 0.5 m ２ / g to 2.1 m ２ / g, preferably 0.7 m ２ / g to 1.8 m ２ / g, and the carbon material according to claim 1 or 2.

4. The carbon material contains one or more pore structures with a pore area of 0.1 μm ２ or more, preferably, contains one or more pore structures with a pore area of 0.12 μm ２ to 2.5 μm ２ The carbon material according to any one of claims 1 to 3, which contains one or more pore structures with a pore area of 0.12 μm to 2.5 μm.

5. The carbon material includes an outer region and an inner region located inside the outer region. The outer region is a region extending 0.25L in distance from the particle surface of the carbon material to the particle interior, where L is the minor axis length of the carbon material particle. Let the total pore area of the outer region be S １ and the total pore area of the inner region be S ２ and S ２ > S １ The carbon material according to any one of claims 1 to 4

6. 1.3 ≤ S ２ / S １ ≤ 450, preferably 1.8 ≤ S ２ / S １ ≤ 400, the carbon material according to claim 5

7. 0.01 μm ２ ≤ S １ ≤ 12.0 μm ２ wherein, preferably, 0.02 μm ２ ≤ S １ ≤ 7.0 μm ２ and / or 2.5 μm ２ ≤ S ２ ≤ 25.0 μm ２ wherein, preferably, 3.0 μm ２ ≤ S ２ ≤ 20.5 μm ２ and / or The carbon material according to claim 5 or 6, wherein L ≧ 4 μm, preferably 6 μm ≦ L ≦ 18 μm.

8. The area of the pore structure in the outer region of the carbon material is 0.2 μm ２ or less, preferably 0.15 μm ２ or less, and / or In the internal region of the carbon material, there is one or more pore structures with an area of 0.15 μm ２ or more, preferably, there is one or more pore structures with an area of 0.18 μm ２ to 2.5 μm ２ The carbon material according to any one of claims 5 to 7, which contains one or more of the pore structures.

9. Let the interlayer distance of the external region of the carbon material be d １ and the interlayer distance of the internal region of the carbon material be d ２ Then, the carbon material satisfies d １ ≧ d ２ and preferably satisfies d １ > d ２ The carbon material according to any one of claims 5 to 8

10. d １ is from 0.33565 nm to 0.33610 nm, and / or d ２ The carbon material according to claim 9, wherein d is from 0.33557 nm to 0.33585 nm.

11. The graphitization degree of the carbon material is 94% to 98%, preferably 95% to 97%, and / or La(110) of the carbon material is 100 nm to 150 nm, preferably 110 nm to 130 nm, and / or Lc(002) of the carbon material is 20 nm to 45 nm, preferably 28 nm to 40 nm. The carbon material according to any one of claims 1 to 10.

12. The carbon material according to any one of claims 1 to 11, satisfying at least one of the following: (1) The volume distribution particle size Dv50 of the carbon material is 8.0 μm to 24.0 μm, preferably 9.5 μm to 22.5 μm. (2) The volume distribution particle size Dv10 of the carbon material is 5.0 μm to 15.0 μm, preferably 6.0 μm to 14.0 μm. (3) The volume distribution particle size Dv90 of the carbon material is 16.0 μm to 35.0 μm, preferably 17.0 μm to 34.0 μm. (4) (Dv90 - Dv10) / Dv50 of the carbon material is 0.55 to 1.55, preferably 0.8 to 1.

4. (5) The tap density of the carbon material is 0.80 g / cm ３ to 1.32 g / cm ３ and preferably 0.82 g / cm ３ to 1.28 g / cm ３ is. (6) The gram capacity of the carbon material is 355 mAh / g to 371 mAh / g, preferably 360 mAh / g to 370 mAh / g. (7) The form of the carbon material includes one or more of massive, spherical and substantially spherical.

13. Step 1 of supplying a raw material having a plurality of pore structures, Mix the raw materials and the filler uniformly at a predetermined ratio, and then, at the first temperature T １ for the first time t １ Keep warm to obtain an intermediate in Step 2 The obtained intermediate is maintained at a second temperature T ２ for a second time t ２ to obtain a carbon material, and Step 3 of obtaining a carbon material, which is a method for producing a carbon material The carbon material includes a pore structure. Let the adsorption amount of 100 g of the carbon material to linseed oil be A, and the specific surface area of the carbon material be B. Then, the carbon material satisfies 36 ≦ A × B ≦ 75. The unit of the adsorption amount A of 100 g of the carbon material to linseed oil is ml, and the unit of the specific surface area B of the carbon material is m ２ / g. A method for producing a carbon material.

14. The raw material according to claim 13 satisfies at least one of the following: (1) The raw material contains natural graphite, preferably the natural graphite contains one or more of flaky graphite, natural spherical graphite and microcrystalline graphite. The volume distribution particle size Dv50 of (2) the raw material is 8.5 μm to 24.0 μm, preferably 10.5 μm to 22.5 μm. (3) The ash content in the raw material is 1 wt% or less.

15. The method according to claim 13 or 14, wherein the filler satisfies at least one of the following: (1) The softening point temperature of the filler is 110°C to 175°C, preferably 120°C to 170°C. (2) The coking value of the filler is 26% to 50%, preferably 33% to 45%. (3) The volume distribution particle size Dv50 of the filler is 6 μm or less, preferably 1 μm to 5 μm. (4) The content of quinoline-insoluble matter in the filler is 1 wt% or less, preferably 0.8 wt% or less.

16. The method according to claim 15, wherein the filler contains one or more of coal pitch and petroleum pitch.

17. The method according to any one of claims 13 to 16, wherein the mass ratio of the filler to the raw material is (10 to 32):100, preferably (10 to 25):

100.

18. After uniformly mixing the raw material and the filler at a predetermined ratio, the temperature increase process of increasing the temperature to the first temperature T １ The temperature increase process of increasing the temperature to the first temperature T is a stepwise temperature increase process, preferably including a first temperature increase process, a second temperature increase process, and a third temperature increase process. The method according to any one of claims 13 to 17.

19. The first heating process is to heat up to 200°C to 250°C and keep the temperature for 0.5 h to 2 h, and / or The second heating process is to heat up to 450°C to 550°C and keep the temperature for 0.5 h to 2 h, and / or The third temperature increase process raises the temperature to the first temperature T １ and holds the temperature for a first time t at that temperature, １ The method according to claim 18, wherein the method is to keep the temperature constant.

20. Heat the temperature to the first temperature T at a rate of 1 °C / min to 10 °C / min, preferably 1.5 °C / min to 8 °C / min. １ The method according to any one of claims 13 to 19.

21. The first temperature T １ is 700°C to 1100°C, preferably 750°C to 1100°C, and / or The first time t １ is from 0.5 h to 5 h, preferably from 0.5 h to 3 h, the method according to any one of claims 13 to 20.

22. The second temperature T ２ is from 1920°C to 2520°C, preferably from 2050°C to 2400°C, and / or Said second time t ２ is from 1 h to 6 h, preferably from 2 h to 5 h, the method according to any one of claims 13 to 21.

23. A secondary battery comprising a negative electrode sheet including a carbon material according to any one of claims 1 to 12 or a carbon material manufactured by the method according to any one of claims 13 to 22.

24. A power consumption device comprising the secondary battery according to claim 23.

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