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

Abstract

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

Description

Technical Field

[0001] The present 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 an electric power consumption device.

Background Art

[0002] In recent years, secondary batteries have been widely used in many fields such as energy storage power systems such as hydraulic, thermal, wind, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. The negative electrode active material is an important component of the secondary battery and affects the performance and cost of the secondary battery. Currently, the negative electrode active material mainly contains graphite, and natural graphite has the advantage of relatively low cost, so it is currently widely concerned. However, since natural graphite has defects such as many voids, many defects, and poor compatibility with the electrolyte, the cycle performance of the secondary battery is deteriorated. Therefore, attention has been focused on how to improve the performance of natural graphite.

Summary of the Invention

[0003] An object of the present application is to provide a carbon material, a method for manufacturing the same, a secondary battery including the same, and an electric power consumption device that can endow the secondary battery with high initial Coulomb efficiency, high energy density, and good cycle performance.

[0004] The first aspect of the present application provides a carbon material, the carbon material includes an external region and an internal region located inside the external region, the external region is a region extending from the particle surface of the carbon material to the particle interior at a distance of 0.25L, L is the short axis length of the particles of the carbon material, the total pore area of the external region is denoted as S 1 and the total pore area of the internal region is denoted as S 2 and S 2 > S 1 is satisfied.

[0005] The carbon material according to the present application satisfies S 2 > S 1is satisfied. In this case, the particles of the carbon material can 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 particles 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 particles of the carbon material, thereby reducing the risk of generating a new interface due to the crushing of the particles of the carbon material. Furthermore, the occurrence of side reactions can be reduced, the loss due to the irreversible capacity of the secondary battery can be reduced, and the cycle performance of the secondary battery can be improved. Since the number of pores in the external region of the particles of the carbon material is small and / or the pore size is small, the particles of the carbon material can have a more stable structure, and the intrusion of the electrolyte into the pore structure inside the particles of the carbon material can be avoided as much as possible. Thereby, 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 furthermore, the initial Coulomb efficiency of the carbon material can be improved, and the cycle performance of the secondary battery can be improved.

[0006] Therefore, the carbon material according to the present application can effectively reduce the loss due to the irreversible capacity of the secondary battery, improve the capacity performance of the secondary battery, and enable the secondary battery to have high initial Coulomb efficiency, high energy density, and good cycle performance.

[0007] In any embodiment of the present application, 1.5 ≦ S 2 / S 1 ≦ 500, and optionally, 2.5 ≦ S 2 / S 1 ≦ 120. When S 2 / S 1 is further within the above range, the secondary battery can better have high initial Coulomb efficiency, high energy density, and good cycle performance.

[0008] In any embodiment of the present application, 0.01 μm 2 ≦ S 1 ≦ 10.0 μm 2 and optionally, 0.1 μm 2 ≦ S 1 ≦ 4.5 μm 2That is. When the total pore area of the external region of the carbon material is within the above range, the particles of the carbon material can have a stable structure, and the electrolyte can be prevented from entering the pore structure inside the particles of the carbon material as much as possible to reduce the occurrence of side reactions and reduce the consumption of active ions due to the formation of the SEI film inside the particles of the carbon material, while not affecting the transport performance of active ions and electrons.

[0009] In any embodiment of the present application, 1.8 μm 2 ≦S 2 ≦25.0 μm 2 That is, optionally, 2.1 μm 2 ≦S 2 ≦20.0 μm 2 That is. When the total pore area of the internal region of the carbon material is within the above range, a sufficient and stable expansion space for the volume change of the particles of the carbon material can be ensured, the risk of the generation of a new interface due to the crushing of the particles of the carbon material can be reduced, the occurrence of side reactions on the surface of the new interface can be reduced, and the consumption of active ions due to the formation of the SEI film on the surface of the new interface can be reduced, while the capacity and initial Coulomb efficiency of the carbon material can be improved.

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

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

[0012] In any embodiment of the present application, in the internal region of the carbon material, the area is 0.15 μm 2One or more of the above pore structures are included, and optionally, pores with an area of 0.15 μm 2 ~2.0 μm 2 One or more of the pore structures are included. By including the pore structures of the above size in the internal region of the carbon material, a sufficient and stable expansion space for the volume change of the carbon material particles is ensured, while reducing the risk of crushing of the carbon material particles, and the compression density of the carbon material can be improved.

[0013] In any embodiment of the present application, the interlayer distance of the external region of the carbon material is d 1 and the interlayer distance of the internal region of the carbon material is d 2 and the carbon material satisfies d 1 ≧d 2 and optionally, d 1 >d 2 is satisfied.

[0014] 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 (capacity per gram) and compression density of the carbon material, the energy density of the secondary battery can be further improved.

[0015] In any embodiment of the present application, d 1 is 0.33565 nm to 0.33615 nm.

[0016] In any embodiment of the present application, d 2 is 0.33557 nm to 0.33595 nm.

[0017] In any embodiment of the present application, the specific surface area of the carbon material is 2.1 m 2 / g or less, and optionally 0.7 m 2 / g to 1.8 m 2 / g. Since the carbon material of the present application has a low specific surface area and low surface activity, it 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.

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

[0019] 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, and optionally 17.0 μm to 34.0 μm.

[0020] When the volume distribution particle sizes 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, so that the cycle performance and / or rate performance of the secondary battery can be further improved.

[0021] In any embodiment of the present application, the particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is 0.5 to 1.5, and optionally 0.7 to 1.3. Thereby, it is advantageous for improving the compression density of the carbon material, so that the energy density of the secondary battery can be further improved.

[0022] In any embodiment of the present application, the topography of the carbon material includes one or more of massive, spherical and quasi-spherical shapes. Thereby, it is advantageous for improving the compression density of the negative electrode sheet, and thus for improving the energy density of the secondary battery.

[0023] In any embodiment of the present application, the graphitization degree of the carbon material is 91.5% to 98%, and optionally 92% to 98%. When the graphitization degree of the carbon material is within the above range, it is advantageous for achieving both high energy density and good cycle performance, storage performance and / or rate performance of the secondary battery.

[0024] In any embodiment of the present application, the powder resistivity of the carbon material under a pressure of 8 MPa is 0.009 Ω·cm to 0.052 Ω·cm, and optionally 0.01 Ω·cm to 0.04 Ω·cm. When the powder resistivity of the carbon material is within the above range, it is advantageous for improving the electron transport performance, so that the cycle performance and rate performance of the secondary battery can be further improved.

[0025] In any embodiment of the present application, the tap density of the carbon material is 0.80 g / cm 3 ~1.50 g / cm 3 and optionally 0.85 g / cm 3 ~1.45 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. Moreover, it is also advantageous for improving the transport performance of active ions and electrons, and the cycle performance and kinetic performance of the secondary battery.

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

[0027] The second aspect of the present application provides a method for manufacturing a carbon material. The manufacturing method includes: Step 1 of providing a raw material having a plurality of pore structures; after uniformly mixing the raw material and a filler at a predetermined ratio, holding at a first temperature T 1 for a first time t 1 to obtain an intermediate body (Step 2); and holding the obtained intermediate body at a second temperature T 2 for a second time t 2 to obtain a carbon material (Step 3). The carbon material includes an external region and an internal region located inside the external region. The external region is a region extending from the particle surface of the carbon material to a distance of 0.25L inside the particle, where L is the short axis length of the particle of the carbon material. Let the total pore area of the external region be S 1 and the total pore area of the internal region be S2 and S 2 >S 1 is true.

[0028] In any embodiment of the present application, the raw material includes natural graphite, and optionally, the natural graphite includes one or more of flake graphite, natural spherical graphite, and microcrystalline graphite.

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

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

[0031] By adjusting the particle size and / or pore volume of the raw material within the above ranges, it is possible to reduce as much as possible the aggregation of the raw material during the subsequent manufacturing process, thereby reducing problems such as an increase in surface defects of carbon material particles and an increase in active sites of surface side reactions due to the need for a depolymerization step.

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

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

[0034] In any embodiment of the present application, the coking value of the filler is 15% to 40%, optionally 20% to 34%. When the coking value of the filler is within the above range, it is advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material within an appropriate range.

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

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

[0037] In any embodiment of the present application, after uniformly mixing the raw material and the filler at a predetermined ratio, the temperature rising process of rising to the first temperature T 1 is a stepwise temperature rising process, and optionally includes a first temperature rising process and a second temperature rising process.

[0038] In any embodiment of the present application, the first temperature rising process rises the temperature from 200°C to 250°C and holds the temperature at this level for 1 h to 3 h.

[0039] In any embodiment of the present application, the second temperature rising process rises the temperature to the first temperature T 1 and holds the temperature at this level for the first time t 1 for heat preservation.

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

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

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

[0043] 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 manufacturing a carbon material with a desired structure.

[0044] In any embodiment of the present application, the second temperature T 2 is from 1600 °C to 2620 °C, and optionally from 1800 °C to 2450 °C.

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

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

[0047] 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 manufactured by the method of the second aspect of the present application.

[0048] The fourth aspect of the present application provides a power consumption device including the secondary battery of the third aspect of the present application.

[0049] The carbon material according to the present application can effectively reduce the loss due to the irreversible capacity of the secondary battery, improve the capacity display characteristics of the secondary battery, and enable the secondary battery to have high initial Coulomb efficiency, high energy density and good cycle performance. Since the power consumption device of the present application includes the secondary battery of the present application, it has at least the same advantages as the secondary battery.

Brief Description of the Drawings

[0050] To more clearly explain the technical solution of the embodiments of the present application, the drawings necessary for the embodiments are briefly introduced below. It should be understood that the following drawings show only some embodiments of the present application, and those skilled in the art can obtain other related drawings based on these drawings without creative effort.

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Modes for Carrying Out the Invention

[0051] Hereinafter, embodiments of the carbon material, its manufacturing method, secondary battery, and power consumption device specifically disclosed in the present application will be described in detail with reference to the drawings as appropriate. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily 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.

[0052] The "range" disclosed in the present application 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 define the boundaries of a particular range. The range thus defined may be a range including or excluding 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 contemplated. 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 contemplated. In the present application, unless otherwise explained, the numerical range "a to b" is a shorthand notation for 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 that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is a shorthand notation for combinations of these numerical values. Also, the notation that a certain parameter is an integer of 2 or more (≧2) is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and selectable embodiments of the present application may be combined with each other to form a new technical solution. Also, such a technical solution is considered to be included in the disclosure content of the present application.

[0054] Unless otherwise specified, all technical features of this application and selectable technical features may be combined with each other to form a new technical solution. Moreover, such a technical solution is considered to be included in the disclosure content of this application.

[0055] Unless otherwise specified, all steps of this application may be performed in sequence or randomly, but it is preferred to be performed in sequence. For example, the fact that the 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 method may further include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0056] Unless otherwise specified, the terms "have", "comprise" and "include" described in this application are open-ended and may also be closed-ended. For example, the above-mentioned "have", "comprise" and "include" can represent further "having", "comprising" or "including" other components not listed, or only "having", "comprising" or "including" the components listed.

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

[0058] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0059] 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.

[0060] Unless otherwise specified, in this application, the term "active ion" refers to an ion that can reciprocally insert and desorb between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

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

[0062] Graphite can be classified into artificial graphite and natural graphite according to the manufacturing process and origin. 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 advantages of high capacity and high compression density.

[0063] Natural graphite mainly includes flake graphite, natural spherical graphite and microcrystalline graphite. Generally, different from artificial graphite, natural graphite has a very large number of voids and defects inside and outside the particles. In the initial charging process of a secondary battery, the electrolyte reacts with the particle surface and the pores inside the particles to cause many side reactions, resulting in a high irreversible capacity loss in the first charge 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 microstructure is often a layered structure. Due to such a structure, the volume change of natural graphite is large in the process of desorption and insertion of active ions, 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.

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

[0065] The particle surface coating treatment mainly uniformly mixes natural graphite and a coating agent (such as pitch, polymer compound, etc.) so as to coat a layer of amorphous carbon layer on the surface of natural graphite particles, and then performs heat treatment to slightly repair the defects on the particle surface. However, in the process of research, the inventors of the present application found that the amorphous carbon layer coated on the surface causes a decrease in the gram capacity and / or compression density of natural graphite, which affects the energy density of the secondary battery. At the same time, the amorphous carbon layer coated on the surface cannot effectively prevent the electrolyte from infiltrating into the pore structure inside the particles. Therefore, it is found that the improvement effect on the initial Coulomb efficiency, cycle performance and / or storage performance of the secondary battery is limited.

[0066] The particle internal filling treatment mainly mixes natural graphite and a filling agent (such as pitch, polymer compound, etc.), and fills the filling agent into the voids inside the particles by means of a predetermined pressure, vacuum pumping and temperature increase, etc., to obtain natural graphite without voids inside the particles. However, in the process of research, the inventors of the present application found that the carbon filled in a large amount inside the particles causes both the gram capacity and the compression density of natural graphite to decrease, which affects the energy density of the secondary battery. At the same time, since all the voids inside the natural graphite particles are filled with carbon, the volume change of natural graphite is large during the desorption and insertion process of active ions, and the particles are more likely to be crushed. Furthermore, the destruction and reconstruction of the SEI film on the particle surface are repeated, which further 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. In the prior art, since the surface of the natural graphite without voids inside the particles is continuously coated with an amorphous carbon layer, the gram capacity and / or compression density of natural graphite further decreases. At this time, since there are still many surface defects on the particles, the service life of the secondary battery cannot be effectively improved.

[0067] 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, the energy density of the secondary battery is also lost, and the capacity performance during long-term use of the secondary battery is still inferior.

[0068] In view of this, the inventors of the present application have, through a large amount of research, provided a novel carbon material that has a high gram capacity, a high initial Coulomb efficiency, and a small volume change, and can endow the secondary battery with a high initial Coulomb efficiency, a high energy density, and good cycle performance. Carbon material

[0069] The first aspect of the embodiment of the present application is a carbon material, the carbon material includes an external region and an internal region located inside the external region, the external region is a region extending from the particle surface of the carbon material to the particle interior at a distance of 0.25L, L is the short axis length of the particles of the carbon material, and the total pore area of the external region is S 1 is denoted as, and the total pore area of the internal region is S 2 is denoted as, and S 2 >S 1 and a carbon material satisfying this condition is provided.

[0070] The carbon material according to the present application has S 2 >S 1is satisfied, and in this case, the particles of the carbon material can 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 particles 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 particles of the carbon material, thereby reducing the risk of generation of new interfaces due to crushing of the particles of the carbon material, further reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and improving the cycle performance of the secondary battery; since the number of pores in the external region of the particles of the carbon material is small and / or the pore size is small, the particles of the carbon material can be given a more stable structure, and the electrolyte can be avoided from infiltrating into the pore structure inside the particles of the carbon material 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, further improving the initial Coulomb efficiency of the carbon material, and further improving the cycle performance of the secondary battery.

[0071] Therefore, the carbon material according to the present application can effectively reduce the irreversible capacity loss of the secondary battery, improve the capacity performance of the secondary battery, and endow the secondary battery with high initial Coulomb efficiency, high energy density and good cycle performance.

[0072] In some embodiments, 1.5 ≦ S 2 / S 1 ≦ 500, and optionally, 1.8 ≦ S 2 / S 1 ≦ 250, 2 ≦ S 2 / S 1 ≦ 200, 2.2 ≦ S 2 / S 1 ≦ 150, 2.5 ≦ S 2 / S 1 ≦ 120, 4 ≦ S 2 / S 1 ≦ 120, 5 ≦ S 2 / S 1 ≦ 120, 6 ≦ S 2 / S 1 ≦ 120. The inventors have found in further research that S 2 / S 1When further satisfying that it is within the above range, it has been found that the secondary battery can better have high initial Coulomb efficiency, high energy density, and good cycle performance.

[0073] In some embodiments, 0.01 μm 2 ≦ S 1 ≦ 10.0 μm 2 and optionally, 0.02 μm 2 ≦ S 1 ≦ 8.0 μm 2 、0.03 μm 2 ≦ S 1 ≦ 7.0 μm 2 、0.04 μm 2 ≦ S 1 ≦ 6.0 μm 2 、0.05 μm 2 ≦ S 1 ≦ 5.0 μm 2 、0.06 μm 2 ≦ S 1 ≦ 4.5 μm 2 、0.07 μm 2 ≦ S 1 ≦ 4.5 μm、0.09 μm 2 ≦ S 1 ≦ 4.5 μm、0.1 μm 2 ≦ S 1 ≦ 4.5 μm 2 、0.1 μm 2 ≦ S 1 ≦ 4.0 μm 2 、0.1 μm 2 ≦ S 1 ≦ 3.5 μm 2 is. When the total pore area of the external region of the carbon material is within the above range, the particles of the carbon material can have a stable structure, and the electrolyte can be avoided from entering the pore structure inside the particles of the carbon material as much as possible, reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film inside the particles of the carbon material, while not affecting the transport performance of active ions and electrons.

[0074] In some embodiments, 1.8 μm 2 ≦ S 2 ≦ 25.0 μm 2 and optionally, 2.0 μm2 ≤ S 2 ≤ 22.5 μm 2 , 2.1 μm 2 ≤ S 2 ≤ 20.0 μm 2 , 2.2 μm 2 ≤ S 2 ≤ 17.5 μm 2 , 3.0 μm 2 ≤ S 2 ≤ 15.0 μm 2 That is. 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 for the volume change of the particles of the carbon material, the risk of generation of new interfaces due to crushing of the particles of the carbon material can be reduced, the occurrence of side reactions on the surface of the new interfaces can be reduced, and the consumption of active ions due to film formation of the SEI film on the surface of the new interfaces can be reduced. On the other hand, the capacity and initial Coulomb efficiency of the carbon material can be improved.

[0075] In the present application, the total pore area S of the external region of the carbon material 1 and the total pore area S of the internal region 2 can be measured from a cross-sectional image of the carbon material.

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

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

[0078] 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 indicates the minor axis length of the particles of the carbon material 100, and the region extending at a distance of 0.25L from the particle surface of the carbon material 100 toward the particle interior is the external region 101, and the region inside the external region 101 is the internal region 102.

[0079] After preparing a cross-section of the carbon material using a cross-section polisher (e.g., the IB-09010 CP type argon ion cross-section polisher from JEOL, Japan), referring to JY / T010-1996, the cross-section of the carbon material was scanned using a scanning electron microscope (e.g., the Sigma 300 type scanning electron microscope from ZEISS, Germany), and finally, the total pore area S of the external region of the carbon material was calculated using image processing software (e.g., AVIZO). 1 and the total pore area S of the internal region 2 can be calculated.

[0080] In some embodiments, L is 5 μm or more, and optionally, 5 μm ≤ L ≤ 20 μm, 6 μm ≤ L ≤ 20 μm, 8 μm ≤ L ≤ 20 μm, 8 μm ≤ L ≤ 18 μm.

[0081] In some embodiments, the area of the pore structure in the external region of the carbon material is less than 0.15 μm 2 and optionally less than 0.10 μm 2 The inventors further found in further research that by controlling the area of the pore structure in the external region of the carbon material within the above range, a dense structure can be formed in the external region of the carbon material, thereby effectively improving the structural stability of the carbon material, avoiding as much as possible the intrusion of the electrolyte into the pore structure inside the particles of the carbon material, and effectively improving the cycle 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 less than 0.15 μm 2 but can be controlled such that, for example, 95% or more, and optionally 99% or more, of the pore structure area is less than 0.15 μm 2 and optionally less than 0.10 μm 2 as follows.

[0082] 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, and optionally, with an area of 0.15 μm 2 to 2.0 μm 2It contains one or more pore structures. In further research, the inventors 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.

[0083] In some embodiments, the interlayer distance of the external region of the carbon material is d 1 and the interlayer distance of the internal region of the carbon material is d 2 and the carbon material satisfies d 1 ≧d 2 and optionally, d 1 >d 2 is satisfied.

[0084] Since the interlayer distance of the external region of the carbon material is large, it is advantageous for the rapid insertion and desorption of active ions, so 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, it is advantageous for improving the gram capacity and compression density of the carbon material, so the energy density of the secondary battery can be further improved.

[0085] In some embodiments, d 1 is 0.33565 nm to 0.33615 nm.

[0086] In some embodiments, d 2 is 0.33557 nm to 0.33595 nm.

[0087] 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 test equipment can use the Spectra S / TEM scanning transmission electron microscope of Thermo Fisher Scientific.

[0088] In some embodiments, the graphitization degree of the carbon material is 91.5% - 98%, optionally 92% - 98%, 93% - 98%, 94% - 97.5%. When the graphitization degree of the carbon material is within the above range, it is advantageous for the secondary battery to have both high energy density and good cycle performance, storage performance, and / or rate performance.

[0089] The graphitization degree of the carbon material is a well-known meaning in this field and can be measured by well-known equipment and methods in this field. For example, it can be tested using an X-ray diffractometer (e.g., Bruker D8 Discover), and the test refers to JIS K 0131-1996 and JB / T 4220-2011 to obtain the average interlayer distance d of the (002) crystal plane in the crystal structure of the carbon material. 002 to obtain, and then the graphitization degree can be calculated based on the Mering-Maire 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) crystal plane in the crystal structure of the carbon material, expressed in nanometers (nm).

[0090] In some embodiments, the topography of the carbon material includes one or more of massive, spherical, and quasi-spherical. This is advantageous for improving the compression density of the negative electrode sheet and thus the energy density of the secondary battery.

[0091] In some embodiments, the carbon material includes primary particles. Optionally, the proportion of the number of the primary particles in the carbon material is 50% or more, for example, 55% - 95%, 60% - 100%, 65% - 90%, 65% - 80%, 70% - 100%, 75% - 90%, 80% - 100%, 90% - 100%, or 95% - 100% may also be possible. The carbon material can include an appropriate proportion of primary particles, have high structural stability, reduce the occurrence of side reactions, improve the compression density of the negative electrode sheet, and improve the energy density of the secondary battery.

[0092] In some embodiments, the carbon materials may all be primary particles, that is, the proportion of the number of the primary particles in the carbon materials is 100%.

[0093] Both the primary particles and the secondary particles are in the well-known meaning in this field. The primary particles refer to non-aggregated particles. The secondary particles refer to aggregated particles in which two or more primary particles are aggregated. The primary particles and the secondary particles can be distinguished by using a scanning electron microscope (SEM) image.

[0094] In the present application, the proportion of the number of the primary particles in the carbon materials can be tested by a method in which any one test sample is selected in the negative electrode film layer, any plurality of test regions are selected in the test sample, images of the plurality of test regions are obtained by using a scanning electron microscope, the proportion of the number of the carbon material particles of the primary particle topography to the total number of the carbon material particles in each image is statistically calculated, and the average value of the plurality of statistical results is taken as the proportion of the number of the primary particles in the carbon materials.

[0095] In some embodiments, the specific surface area of the carbon material is 2.1 m 2 / g or less, and optionally 0.7 m 2 / g to 1.8 m 2 / g. Since the carbon material of the present application has a low specific surface area and low surface activity, it 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.

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

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

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

[0099] When the volume distribution particle size Dv50 and / or Dv90 of the carbon material is within the above range, it is beneficial to improve the transport performance of active ions and electrons, so that the cycle performance and / or rate performance of the secondary battery can be further improved.

[0100] In some embodiments, the particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is 0.5 to 1.5, and optionally 0.7 to 1.3. When the particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is within the above range, it is beneficial to improve the compression density of the carbon material, so that the energy density of the secondary battery can be further improved.

[0101] The volume distribution particle sizes Dv10, Dv50, and Dv90 of the carbon material have the well-known meanings in this field, and respectively represent the particle sizes corresponding to when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, and can be measured by well-known equipment and methods 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 equipment may be a Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK.

[0102] In some embodiments, the powder resistivity of the carbon material at a pressure of 8 Mpa is 0.009 Ω·cm to 0.052 Ω·cm, and optionally 0.01 Ω·cm to 0.04 Ω·cm. When the powder resistivity of the carbon material is within the above range, it is beneficial to improve the electron transport performance, so that the cycle performance and rate performance of the secondary battery can be further improved.

[0103] The powder resistivity of the carbon material is a well-known meaning in this field and can be measured by well-known equipment and methods in this field. For example, referring to GB / T 30835-2014, it can be measured by the four-probe method using a powder resistivity measuring instrument (for example, it may be Suzhou Lattice ST2722 or Sansi Zongheng UTM7305). As an exemplary measurement method, a fixed amount of test sample powder can be weighed and put into a dedicated mold, and the measurement pressure can be set to obtain the powder resistivity at different pressures. In the present application, the test pressure may be set to 8 MPa.

[0104] In some embodiments, the tap density of the carbon material is 0.80 g / cm 3 ~1.50 g / cm 3 and, optionally, 0.85 g / cm 3 ~1.45 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, which is also advantageous for improving the active ion and electron transport performance, and the cycle performance and kinetic performance of the secondary battery.

[0105] The tap density of the carbon material is a well-known meaning in this field and can be measured by known equipment and methods in this field. For example, referring to GB / T 5162-2006, it can be measured using a powder tap density test instrument. As the test instrument, Dandong Baite BT-301 can be used.

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

[0107] The gram capacity of the carbon material is a well-known meaning in this field and can be measured by well-known methods in this field. As an exemplary test method, a carbon material sample, styrene-butadiene rubber (SBR) as a binder, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent are sufficiently stirred and mixed with deionized water as an appropriate amount of solvent at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on the surface of a copper foil as a negative electrode current collector, dried in an oven and used. After ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain an organic solvent, LiPF 6 is dissolved in the above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L. Then, a metal lithium sheet is used as a counter electrode, a polyethylene (PE) film is used as a separator, and a CR2430 coin cell is assembled in a glove box protected by argon gas. At 25 °C, first, the above-prepared coin cell 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 coin cell is recorded. Then, it is charged at a constant current of 0.3 mA to 2.0 V, and the charging capacity of the coin cell is recorded. The ratio of the charging capacity of the coin cell to the mass of the carbon material sample is the gram capacity of the carbon material. Manufacturing method

[0108] 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.

[0109] The manufacturing method of the carbon material includes Step 1 of providing a raw material having a plurality of pore structures, and after uniformly mixing the raw material and a filler at a predetermined ratio, keeping it warm at a first temperature T 1 for a first time t 1 to obtain an intermediate in Step 2, and heating the obtained intermediate at a second temperature T 2 for a second time t 2A step 3 of heat preservation to obtain a carbon material, wherein the carbon material includes an external region and an internal region located inside the external region, the external region is a region extending from the particle surface to the particle interior of the carbon material at a distance of 0.25L, L is the short axis length of the particles of the carbon material, and the total pore area of the external region is denoted as S 1 denoted as such, and the total pore area of the internal region is denoted as S 2 denoted as such, and S 2 >S 1 is satisfied.

[0110] In some embodiments, the raw material for manufacturing the carbon material includes natural graphite. Optionally, the natural graphite includes one or more of flaky graphite, natural spherical graphite, and microcrystalline graphite, and further optionally includes natural spherical graphite.

[0111] "Natural spherical graphite" means natural graphite having a spherical or quasi-spherical shape, and does not mean controlling 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 topography can be obtained. Optionally, the pretreatment includes processes such as crushing, classification, spheroidization, and purification.

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

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

[0114] In some embodiments, the pore volume of the raw material is 6.0 mm 3 / g or more, and optionally 6 mm 3 / g to 100 mm 3 / g, 7 mm 3 / g to 80 mm 3 / g, 8 mm 3 / g to 60 mm3 / g, 8 mm 3 / g to 40 mm 3 / g. When the pore volume of the raw material is within the above range, it is advantageous for subsequent filling processes.

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

[0116] In some embodiments, the softening temperature of the filler is 90°C to 150°C. For example, the softening temperature of the filler may be in a range consisting of any numerical value such as 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C or more. Optionally, the softening temperature of the filler is 95°C to 145°C, 95°C to 140°C, 95°C to 135°C, 100°C to 145°C, 100°C to 140°C, 100°C to 135°C, 105°C to 145°C, 105°C to 140°C, 105°C to 135°C, 110°C to 145°C, 110°C to 140°C, 110°C to 135°C.

[0117] In the research, the inventors found that when the softening temperature of the filler is within the above range, it is advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material within an appropriate range. Also, if the softening temperature of the filler is too high, after the filler is heated and melted, it is difficult to flow and fill the pore structure of the raw material, thereby unable to effectively modify the internal defects of the particles, and unable to effectively prevent the electrolyte from entering the pore structure inside the particles of the obtained carbon material. As a result, it affects the initial Coulomb efficiency and cycle performance of the secondary battery; if the softening temperature of the filler is too low, the filler contains many small molecular substances, and these small molecular substances are likely to volatilize due to heat. Therefore, after the filler is melted by heat, it is easy to flow and fill the pore structure of the raw material. However, when performing heat treatment in step 2 and / or step 3, the small molecular substances in the filler volatilize, so that the carbon actually remaining in the filling area cannot be effectively filled into the pore structure of the raw material, and an effective filling effect cannot be realized, or the carbon actually remaining in the filling area has many pore structures, thus unable to reduce the consumption of active ions due to SEI film formation and the irreversible capacity loss of the secondary battery, and at the same time, it can effectively avoid the situation of also affecting the cycle performance and / or storage performance of the secondary battery.

[0118] In some embodiments, the volume distribution particle size Dv50 of the filler is 6 μm or less, and optionally 1 μm to 6 μm, 1 μm to 5 μm, 2 μm to 5 μm, 3 μm to 5 μm. Thereby, it is advantageous for the filler to fill the pore structure of the raw material after being melted by heat, and it is also advantageous to improve the dispersion uniformity between the filler and the raw material.

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

[0120] In the present application, the coking value of the filler is the well-known meaning in this field and can be measured by the known equipment and methods in this field. For example, it can be measured with reference to GB / T 8727-2008.

[0121] In some embodiments, the softening temperature of the filler is 100°C to 140°C, and the coking value is 20% to 34%. Thereby, it is advantageous to adjust the size and / or the number of pores in the external region and the internal region of the carbon material to an appropriate range.

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

[0123] In some embodiments, the mass ratio of the filler to the raw material is (15 - 30):100, and optionally (18 - 28):100. Thereby, it is advantageous to adjust the size and / or the number of pores in the external region and the internal region of the carbon material to an appropriate range. Also, if the mass ratio of the filler to the raw material is too small, the dispersion uniformity between the filler and the raw material may deteriorate. In this case, after the filler is melted by heat, it is difficult to flow and fill the pore structure of the raw material, thereby the defects inside the particles cannot be effectively modified, and the electrolyte cannot be effectively prevented from penetrating into the pore structure inside the obtained carbon material particles. As a result, it will affect the initial Coulombic efficiency and cycle performance of the secondary battery; if the mass ratio of the filler to the raw material is too large, it is likely to cause the pore structure inside the raw material to be completely filled. In this case, the volume change of the obtained carbon material is large, the particles are more likely to be crushed, the consumption of active ions due to the formation of the SEI film increases, and the irreversible capacity loss of the secondary battery increases; and if the mass ratio of the filler to the raw material is too large, a large amount of filler remains on the particle surface. In this case, the particles are more likely to aggregate, not only the depolymerization process increases, but also the gram capacity and compression density of the obtained carbon material decrease, and this situation can be effectively avoided.

[0124] By adjusting parameters such as the type of filler, softening point, coking value, and addition amount within the above ranges, after the filler melts due to heat, its viscosity is not high, it maintains good fluidity, the raw material particles are not easily adhered, and the aggregation of raw material particles in the subsequent manufacturing process can be reduced. Thereby, problems such as an increase in surface defects of carbon material particles and an increase in active sites of surface side reactions due to the need to increase the depolymerization process can be reduced.

[0125] 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 T 1 is a stepwise temperature rising process, and optionally includes a first temperature rising process and a second temperature rising process.

[0126] In some embodiments, the first temperature rising process raises the temperature from 200 °C to 250 °C and holds the temperature at this level for 1 h to 3 h.

[0127] In some embodiments, the second temperature rising process raises the temperature to the first temperature T 1 and holds the temperature at this level for the first time t 1 for heat preservation.

[0128] In the stepwise temperature rising process, first, the temperature is raised from 200 °C to 250 °C. Since the heating temperature is higher than the softening temperature of the filler, at this time, the filler melts and softens due to heat, and it can be kept at this temperature for 1 h to 3 h to flow and fill the pore structure of the raw material. Then, the temperature is raised to the first temperature T 1 At this time, the melted and softened filler undergoes a carbonization reaction, whereby the pore structure occupied by the filler can be effectively filled.

[0129] In some embodiments, in step 2, the first temperature T 1 is 700 °C to 1150 °C. For example, the first temperature T 1may be in a range consisting of any value of 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C or more. Optionally, the first temperature T 1 is 850 °C to 1100 °C.

[0130] The inventors have found in their research that when the first temperature is within the above range, it is advantageous for adjusting the pore size and / or the number of pores in the external and internal regions of the carbon material within an appropriate range. Also, if the first temperature is too low, the filler may not be completely converted into the carbon material, and when performing heat treatment in subsequent step 3, it continues to decompose into small molecule substances, so that the filled region has many pore structures and cannot effectively modify the defects inside the particles, and the electrolyte cannot be effectively prevented from entering the pore structure inside the particles of the obtained carbon material, which affects the initial Coulomb efficiency and cycle performance of the secondary battery; if the first temperature is too high, the situation of increased energy consumption in the manufacturing process of the carbon material can be effectively avoided.

[0131] In some embodiments, the first time t 1 is 1 h to 5 h. For example, the first time t 1 may be in a range consisting of any value of 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or more. Optionally, the first time t 1 is 2 h to 4 h.

[0132] In the research, the inventors have found that when the first time is within the above range, it is advantageous to adjust the pore size and / or the number of pores in the external region and the internal region of the carbon material to an appropriate range. Also, if the first time is too short, the filler may not be completely converted into the carbon material, and when heat treatment is performed in the subsequent step 3, it continues to decompose into small molecule substances, so that the filling region has many pore structures and cannot effectively modify the defects inside the particles, and the electrolyte cannot be effectively prevented from entering the pore structure inside the particles of the obtained carbon material, which in turn affects the initial Coulomb efficiency and cycle performance of the secondary battery; if the first time is too long, the situation of increased energy consumption in the manufacturing process of the carbon material can be effectively avoided.

[0133] In some embodiments, in step 2, the first temperature T is raised at a rate of 1 °C / min to 10 °C / min. 1 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. Optionally, the heating rate is 1.5 °C / min to 8 °C / min, 1.5 °C / min to 6 °C / min, 1.5 °C / min to 5 °C / min.

[0134] In the research, the inventors have found that when the heating rate is within the above range, it is advantageous 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. Also, if the heating rate is too high, the filler may carbonize on the surface of the raw material particles, and after the filler melts due to heat, it becomes difficult to flow and fill into the pore structure of the raw material, thereby being unable to effectively modify the defects inside the particles, and also being unable to effectively prevent the electrolyte from infiltrating into the pore structure inside the particles of the obtained carbon material. As a result, it affects the initial Coulomb efficiency and cycle performance of the secondary battery; if the heating rate is too low, after the filler melts due to heat, it is likely to flow and fill into all the pore structures of the raw material, the volume change of the carbon material during the desorption and insertion process of active ions becomes large, and the particles are more likely to be crushed, thereby increasing the consumption of active ions due to the formation of the SEI film, increasing the irreversible capacity loss of the secondary battery, and also affecting the cycle performance, storage performance and / or rate performance of the secondary battery. This situation can be effectively avoided.

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

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

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

[0138] 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 gas, argon gas, and helium gas.

[0139] In step 2, it is advantageous to produce a carbon material having a desired structure by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. within the above ranges.

[0140] In some embodiments, the second temperature T 2 is 1600°C to 2620°C. For example, the second temperature may be in the range consisting of any value such as 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, 2500°C, 2600°C or more. Optionally, the second temperature T 2 is 1800°C to 2500°C, 1800°C to 2450°C, 2000°C to 2450°C, 2050°C to 2450°C, 2100°C to 2450°C.

[0141] The inventors have found in the research that when the second temperature is within the above range, the carbon material has a stable structure, which is advantageous for avoiding particle crushing as much as possible. Also, if the second temperature is too low, the content of irregular carbon in the obtained carbon material is high, so the defect content of the carbon material increases, affecting the initial Coulomb efficiency, cycle performance and storage performance of the carbon material; if the second temperature is too high, the content of irregular carbon in the obtained carbon material is too low, so both the crystallinity and graphitization degree of the carbon material increase. 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 becomes even larger, thereby increasing the risk of particle crushing of the carbon material and affecting the cycle performance of the secondary battery; and when the second temperature is too high, the energy consumption and cost in the manufacturing process of the carbon material also increase, and this situation can be effectively avoided.

[0142] In some embodiments, the second time t 2 is 1.5 h to 6 h. For example, the second time t 2It may be a range consisting of any numerical values such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h or more. Optionally, the second time t 2 is from 2h to 5h.

[0143] The inventors have found in the research that when the second time is within the above range, it is advantageous for adjusting the irregularity of the carbon material, the carbon material has a stable structure, and it is also advantageous to avoid particle crushing as much as possible. Also, if the second time is too short, the content of irregular carbon in the obtained carbon material is high, so the defect content of the carbon material becomes high, affecting the gram capacity and initial Coulomb efficiency of the carbon material; if the second time is too long, the content of irregular carbon in the obtained carbon material is too low, so both the crystallinity and graphitization degree of the carbon material increase. At this time, it is disadvantageous for the rapid desorption and insertion of active ions, and the volume change of the carbon material during the charge-discharge process is large, so the risk of particle crushing of the carbon material also increases, thus affecting the cycle performance and storage performance of the secondary battery; and when the second time is too long, the situation where the energy consumption and cost in the manufacturing process of the carbon material increase can be effectively avoided.

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

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

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

[0147] The manufacturing method of the carbon material of the present application has a simple process, high safety, does not require a predetermined pressure or vacuum treatment, and does not require the addition of a depolymerization step in the heat treatment process. The carbon material manufactured in the present application has a small volume expansion, high structural stability, low surface activity, and can also have a high gram capacity, high initial Coulomb efficiency, and small volume change. It can also endow the secondary battery with high initial Coulomb efficiency, high energy density, and good cycle performance.

[0148] The manufacturing method of the present application has low cost, high practicability, and is suitable for large-scale production. Secondary battery

[0149] The third aspect of the embodiment of the present application provides a secondary battery.

[0150] The present application does not particularly limit the type of the secondary battery. For example, the secondary battery may be a lithium-ion battery or the like. Generally, the 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 of 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 electrolytic solution). In a secondary battery using an electrolytic solution and a secondary battery using a solid electrolyte, a separator may further be included between the positive electrode sheet and the negative electrode sheet to play a role of isolation. [Negative electrode sheet]

[0151] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two 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.

[0152] In some embodiments, the negative electrode film layer includes the carbon material of the first aspect of the embodiment of the present application or the carbon material manufactured by the method described in the second aspect of the embodiment of the present application. Thereby, the secondary battery can be provided with high initial Coulomb efficiency, high energy density, and good cycle performance.

[0153] 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 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.

[0154] 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 may include one or more selected from superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

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

[0156] In some embodiments, the negative electrode film layer may optionally further contain other auxiliaries. By way of example, the other auxiliaries may include thickeners such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0157] In some embodiments, the negative electrode current collector can use a metal foil sheet or a composite 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).

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

[0159] 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 further includes a conductive primer layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. 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. [Positive Electrode Sheet]

[0160] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in the self-thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0161] A metal foil sheet or a composite current collector can be used as the positive electrode 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).

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

[0163] The positive electrode active material can adopt a positive electrode active material used in well-known secondary batteries in this field.

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

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

[0166] In some embodiments, the positive electrode active material used in the lithium ion battery includes, for example, LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiNi 1 / 3 Co 1 / 3 Mn1 / 3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O 2 , LiFePO 4 , LiMnPO 4 may include one or more of these.

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

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

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

[0170] When the secondary battery of the present application is a lithium-ion battery, for example, the electrolyte salt is lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6) Lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate) borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ) may include one or more of lithium difluorobis(oxalate) phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0171] The type of the solvent is not particularly limited and can be selected according to actual needs. In some embodiments, by way of example, the organic 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).

[0172] In some embodiments, the electrolyte may optionally further include 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 additives that can improve some performance of the secondary battery, such as additives for improving the overcharge performance of the secondary battery, additives for improving the high-temperature performance of the secondary battery, and additives for improving the low-temperature power performance of the secondary battery. [Separator]

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

[0174] 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.

[0175] 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.

[0176] In some embodiments, the secondary battery may include an exterior. The exterior is used for sealing the above-described electrode assembly and electrolyte.

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

[0178] The shape of the secondary battery of the present application is not particularly limited, and it may be cylindrical, rectangular, or any other arbitrary shape. FIG. 2 shows, as an example, a rectangular-structured secondary battery 5.

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

[0180] The manufacturing method of the secondary battery of the present application is well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolytic solution. As an example, a positive electrode sheet, a separator, and a negative electrode sheet are formed into an electrode assembly by a winding process or a lamination process, the electrode assembly is placed in an exterior, and after drying, an electrolytic solution is injected, and through processes such as vacuum sealing, standing, forming, and shaping, a secondary battery can be obtained.

[0181] In some embodiments of the present application, the secondary battery according to the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be plural, and the specific number may be adjusted according to the use and capacity of the battery module.

[0182] 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 arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Further, these plurality of secondary batteries 5 may be fixed by fasteners.

[0183] Optionally, the battery module 4 may further include a housing having an accommodation space for accommodating a plurality of secondary batteries 5.

[0184] In some embodiments, the 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 application and capacity of the battery pack.

[0185] 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 case 2 and a lower case 3, and the upper case 2 covers the lower case 3 to form 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. Power consumption device

[0186] The present application further provides a power consumption device including at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source of the power consumption device or as an energy storage unit of the power consumption device. The power consumption device may be a mobile device (e.g., a mobile phone, tablet computer, notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, hybrid electric vehicle, plug-in hybrid electric vehicle, electric bicycle, electric scooter, electric golf cart, electric truck, etc.), a train, a ship, and a satellite, an energy storage system, etc., but is not limited thereto.

[0187] The power consumption device can select a secondary battery, battery module, or battery pack according to its usage needs.

[0188] FIG. 7 is a schematic diagram of a power consumption device as an example. This power consumption device is a pure electric vehicle, hybrid electric vehicle, plug-in hybrid electric vehicle, etc. In order to meet the requirements of high output and high energy density of this power consumption device, a battery pack or a battery module can be adopted.

[0189] The power consumption device as another example may be a mobile phone, a tablet computer, a notebook computer, or the like. This power consumption device is generally required to be thin and can adopt a secondary battery as a power source. Example

[0190] The following examples illustrate the content of the present application in more detail. However, these examples are merely illustrative and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the disclosure of the present application. Unless otherwise specified, all parts, percentages, and ratio values described in the following examples are all based on mass standards. Also, all reagents used in the examples may be commercially available or synthesized according to conventional methods, and can be used as they are without further treatment. Moreover, all devices used in the examples are commercially available. Example 1 (1) Manufacture of carbon material

[0191] Step 1: Mechanical pulverization, classification, spheroidization, and purification treatment are performed on 100-mesh flaky graphite to obtain natural spherical graphite with a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm 3 / g.

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

[0193] Step 3: The obtained intermediate is put into an Acheson graphitization furnace, heated to 1900 °C and held for 3 h. After completion, demagnetization and sieving are performed to obtain a carbon material. (2) Manufacture of coin cell (half cell)

[0194] The carbon material manufactured above, styrene-butadiene rubber (SBR) as a binder, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent are sufficiently stirred and mixed in deionized water as an appropriate amount of solvent at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on the surface of a copper foil which is a negative electrode current collector, dried in an oven, and then used. After mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio of 1:1:1 to obtain an organic solvent, LiPF 6 is dissolved in the above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L. Then, using a metal lithium sheet as a counter electrode and a polyethylene (PE) thin film as a separator, a CR2430 coin cell is assembled in a glove box protected by argon gas. (3) Manufacture of secondary battery (full cell)

[0195] The carbon material prepared above, carbon black (Super P) as a conductive agent, styrene-butadiene rubber as a binder, and sodium carboxymethyl cellulose as a thickener are sufficiently stirred and mixed in deionized water as an appropriate amount of solvent at 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.

[0196] LiFePO 4 and conductive carbon black and polyvinylidene fluoride are mixed at a weight ratio of 96:2.5:1.5, an appropriate amount of solvent NMP is added, and they are 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.

[0197] A polypropylene film with a thickness of 12 μm is used as a separator. The positive electrode sheet and the negative electrode sheet manufactured above are placed in order, and the separator is positioned between the positive electrode sheet and the negative electrode sheet to play a role of isolation. Then, it is wound to obtain an electrode assembly. The electrode assembly is placed in an exterior package, dried, and then the same electrolyte as the coin cell manufactured above is injected. After passing through processes such as vacuum sealing, standing, formation, and capacity, a secondary battery is obtained. Comparative Example 1

[0198] The manufacturing methods of the half cell and the full cell are similar to those of Example 1 except for the manufacturing process of the carbon material.

[0199] Mechanical grinding, classification, spheroidization, and purification treatments are performed on 100-mesh flaky graphite, and natural spherical graphite with a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm 3 / g is obtained. After that, the obtained natural spherical graphite is used as a carbon material to manufacture a half cell and a full cell. Comparative Example 2

[0200] The manufacturing methods of the half cell and the full cell are similar to those of Example 1 except for the manufacturing process of the carbon material.

[0201] Mechanical grinding, classification, spheroidization, and purification treatments are performed on 100-mesh flaky graphite, and natural spherical graphite with a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm 3 / g is obtained. The obtained natural spherical graphite and petroleum pitch (softening temperature 120 °C, volume distribution particle size Dv50 of 5 μm, coking value 30%) are mixed in a VC mixer at a mass ratio of 100:20 for 30 min, and then the mixed material is carbonized at 3200 °C for 10 h. After completion, it is cooled to room temperature to obtain a carbon material. Comparative Example 3

[0202] The manufacturing methods of the half cell and the full cell are similar to those of Example 1 except for the manufacturing process of the carbon material.

[0203] Mechanical crushing, classification, spheroidization, and purification treatments are performed on 100-mesh flaky graphite to obtain natural spherical graphite with a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm 3 / g. The obtained natural spherical graphite and petroleum pitch (softening temperature 120 °C, volume distribution particle size Dv50 of 5 μm, coking value 30%) are mixed in a VC mixer for 30 min at a mass ratio of 100:20. After that, the mixed material is carbonized at 1300 °C for 2 h, and after completion, it is cooled to room temperature to obtain a carbon material. Comparative Example 4

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

[0205] Mechanical crushing, classification, spheroidization, and purification treatments are performed on 100-mesh flaky graphite to obtain natural spherical graphite with a volume distribution particle size Dv50 of 15 μm and a pore volume of 18 mm 3 / g. The obtained natural spherical graphite and petroleum pitch (softening temperature 120 °C, volume distribution particle size Dv50 of 5 μm, coking value 30%) are mixed in a VC mixer for 30 min. Then, the mixed material is put into a reaction kettle, and the reaction kettle adopts a method of gradually increasing the temperature at a heating rate of 2 °C / min. While heating, the reaction kettle is kept in a constant-speed stirring state and heated to 190 °C. The reaction kettle is evacuated until the pressure reaches -0.1 Mpa. Then, it is kept warm for 2 h. After the heat preservation is completed, the reaction kettle is heated to 650 °C and kept warm for 2 h. Then, the reaction kettle is cooled down to about 160 °C. Then, petroleum pitch is gradually added to the inside of the reaction kettle. The mass ratio of the added amount of petroleum pitch this time to the previous petroleum pitch is 1:1. Then, the reaction kettle is heated to 190 °C again, and the reaction kettle is evacuated until the pressure reaches -0.1 Mpa. Then, it is kept warm for 2 h. After the heat preservation is completed, the reaction kettle is heated to 650 °C and kept warm for 2 h. Then, it is cooled by condensation and temperature reduction. Finally, the material processed in the above process is heat-treated at 1300 °C for 2 h. The sample after heat treatment is crushed and sieved to obtain a carbon material without internal voids. Example 2 - 28

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

[0207]

Table 1

[0208] After uniformly mixing the preparation binder with the carbon material powder, it is applied to a copper foil and dried at 60 °C for 30 min before use. The sample is cut into a size of 6 mm × 6 mm and pasted onto the sample stage of a CP type argon ion cross-section polisher. The sample is cut using a plasma beam to obtain the cross-section of the carbon material, and the cross-section of the carbon material passes through the center of the carbon material particles. The test apparatus may be an IB-09010 CP type argon ion cross-section polisher manufactured by JEOL, Japan.

[0209] The cross-section of the carbon material is scanned using a scanning electron microscope. The test can refer to JY / T010-1996. The test equipment may be a Sigma 300 type scanning electron microscope manufactured by ZEISS, Germany.

[0210] The region extending from the particle surface of the carbon material to a distance of 0.25L inside the particle is defined as the external region, and the region inside the external region is defined as the internal region, where L represents the minor axis length of the carbon material particles. Using image processing software, the total pore area S 1 of the external region of the carbon material, and the total pore area S 2 of the internal region of the carbon material are calculated. The image processing software may be AVIZO. (2) Test of the initial Coulomb efficiency of the carbon material

[0211] At 25°C, first discharge the coin cell manufactured above at a constant current of 0.15 mA until 0.005 V, let it stand for 5 minutes, then discharge it at a constant current of 10 μA until 0.005 V, record the initial charge capacity of the coin cell, and then charge it at a constant current of 0.3 mA until 2.0 V, and record the initial charge capacity of the coin cell. The initial Coulomb efficiency (%) of the carbon material = the initial charge capacity of the coin cell / the initial discharge capacity of the coin cell × 100%. (3) Test on the cycle performance of the secondary battery

[0212] At 25°C, charge the secondary battery manufactured above at a constant current of 0.5C until the upper cut-off voltage (corresponding to 100% SOC), then charge it at a constant voltage until the current reaches 0.05C, let it stand for 5 min, and then discharge the secondary battery at a constant current of 0.5C until the lower cut-off voltage (corresponding to 0% SOC), and record the discharge capacity at this time, that is, the initial discharge capacity. Perform a cycle charge and discharge test on the secondary battery according to the above method, record the discharge capacity after each cycle until the discharge capacity of the secondary battery decays to 80% of the initial discharge capacity, and record the number of cycles at this time.

[0213]

Table 2

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

[0215] This application can mix natural spherical graphite and fillers such as petroleum pitch and then heat-treat them, and then fill the fillers into the pore structure of natural spherical graphite to form a carbon material in which the external region is dense and the internal region still retains a small part of the pore structure. All carbon materials are S 2 >S 1is satisfied. The pore structure in the internal region can ensure the expansion space required for the volume change of the carbon material particles, thereby reducing the risk of generating new interfaces due to the crushing of the carbon material particles, reducing the occurrence of side reactions, and reducing the irreversible capacity loss of the battery. The external region has a dense structure, and since the electrolyte can be avoided from entering the pore structure inside the carbon material particles as much as possible, the occurrence of side reactions can be reduced. Therefore, the carbon material according to the present application has a small volume expansion, high structural stability, and low surface activity, and can endow the battery with high gram capacity, high initial Coulomb efficiency, and long cycle life.

[0216] All of the carbon materials produced in Comparative Examples 1 to 4 are S 2 >S 1 do not satisfy, and none of them can endow the battery with high gram capacity, high initial Coulomb efficiency, and long cycle life.

[0217] The carbon materials produced in Comparative Examples 2 to 3 are those with a carbon layer coating formed on the surface of natural spherical graphite. However, the carbon layer exists only on the surface of natural spherical graphite, and an effective filling effect cannot be realized. Moreover, the carbon layer cannot effectively prevent the electrolyte from entering the pore structure inside the particles. As a result, the improvement effect on the initial Coulomb efficiency and cycle performance of the battery is limited.

[0218] In Comparative Example 4, when manufacturing the carbon material, by evacuating and filling the filler into all the pore structures inside the natural spherical graphite particles, the volume change of the carbon material during the process of desorption and insertion of active ions is large, and the particles are more likely to be crushed. As a result, the improvement effect on the cycle performance of the battery is limited.

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

[0220] Summarizing the test results of Examples 1 to 28, when the carbon material satisfies 1.5 ≦ S 2 / S 1Further satisfying ≦500 and optionally 2.5≦S 2 / S 1 When ≦120 is satisfied, it can be seen that the initial Coulomb efficiency and / or cycle performance of the battery can be further improved.

[0221] When the measurement results of Examples 4 and 25 to 28 are combined, it can be seen that when the raw materials have different volume distribution particle sizes Dv50 and / or pore volumes, according to the manufacturing method of the present application, carbon materials with excellent electrochemical performance can be obtained in any case.

[0222] It should be noted that the present application is not limited to the above embodiments. The above embodiments are illustrative, and those having a configuration that is substantially the same as the technical idea and similar effects within the scope of the technical solution of the present application, no matter what they are, are included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications conceived by those skilled in the art applied to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application.

Claims

1. A carbon material, It includes an external region and an internal region located inside the external region. The external region is a region configured to extend from the particle surface of the carbon material to the particle interior at a distance of 0.25L, where L is the minor axis length of the particles of the carbon material. Let the total pore area of the external region be S １ and the total pore area of the internal region be S ２ , and S ２ > S １ is satisfied The carbon material.

2. 1.5 ≤ S ２ / S １ ≤ 500, and optionally, 2.5 ≤ S ２ / S １ ≤ 120 The carbon material according to Claim 1.

3. 0.01 μm ２ ≤ S １ ≤ 10.0 μm ２ wherein, optionally, 0.1 μm ２ ≤ S １ ≤ 4.5 μm ２ and / or 1.8 μm ２ ≤ S ２ ≤ 25.0 μm ２ and optionally, 2.1 μm ２ ≤ S ２ ≤ 20.0 μm ２ is The carbon material according to Claim 1 or 2.

4. L is 5 μm or more, and optionally, 6 μm ≤ L ≤ 20 μm, The carbon material according to any one of Claims 1 to 3.

5. The area of the pore structure in the outer region of the carbon material is less than 0.15 μm ２ and optionally less than 0.10 μm ２ or less. The carbon material according to any one of Claims 1 to 4.

6. The internal region of the carbon material contains one or more pore structures with an area of 0.15 μm ２ or more, and optionally contains one or more pore structures with an area of 0.15 μm ２ to 2.0 μm ２ or more. The carbon material according to any one of Claims 1 to 5.

7. 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 such that the carbon material satisfies d １ ≧ d ２ and Optionally, d １ > d ２ is such that The carbon material according to any one of Claims 1 to 6.

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

9. The carbon material satisfies at least one of the following, (1) The specific surface area of the carbon material is 2.1 m ２ / g or less, and optionally 0.7 m ２ / g to 1.8 m ２ / g, and (2) The volume distribution particle size Dv50 of the carbon material is 8.0 μm to 25.0 μm, and optionally 9.0 μm to 22.0 μm, (3) The volume distribution particle size Dv90 of the carbon material is 16.0 μm to 35.0 μm, and optionally 17.0 μm to 34.0 μm, (4) The particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is 0.5 to 1.5, and optionally 0.7 to 1.3, (5) The topography of the carbon material includes one or more of massive, spherical and spheroidal shapes, The carbon material according to any one of Claims 1 to 8.

10. The carbon material satisfies at least one of the following, (1) The graphitization degree of the carbon material is 91.5% to 98%, and optionally 92% to 98%, (2) The powder resistivity of the carbon material at a pressure of 8 MPa is 0.009 Ω·cm to 0.052 Ω·cm, and optionally 0.01 Ω·cm to 0.04 Ω·cm, (3) The tap density of the carbon material is 0.80 g / cm ３ to 1.50 g / cm ３ and optionally 0.85 g / cm ３ to 1.45 g / cm ３ and (4) The gram capacity of the carbon material is 350 mAh / g to 372 mAh / g, and optionally 353 mAh / g to 371 mAh / g, The carbon material according to any one of Claims 1 to 9.

11. A method for manufacturing a carbon material, Step 1 of providing a raw material having a plurality of pore structures, After uniformly mixing the raw materials and the filler at a predetermined ratio, keep them at the first temperature T １ for the first time t １ to obtain an intermediate product 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 includes Step 3 The carbon material includes an outer region and an inner region located inside the outer region. The outer region is a region extending from the particle surface of the carbon material to the particle interior at a distance of 0.25L, where L is the minor axis length of the particles of the carbon material. Let the total pore area of the outer region be S １ and the total pore area of the inner region be S ２ and S ２ > S １ is satisfied The method for manufacturing a carbon material.

12. The raw material satisfies at least one of the following, (1) The raw material contains natural graphite, and optionally, the natural graphite contains one or more of flake graphite, natural spherical graphite and microcrystalline graphite, (2) The volume distribution particle size Dv50 of the raw material is 8.0 μm to 25.0 μm, and optionally 9.0 μm to 22.0 μm, (3) The pore volume of the raw material is 6.0 mm ３ / g or more, and optionally 6 mm ３ / g to 100 mm ３ / g, The method according to Claim 11.

13. The filler satisfies at least one of the following, (1) The softening temperature of the filler is 90°C to 150°C, optionally 100°C to 140°C, (2) The coking value of the filler is 15% to 40%, optionally 20% to 34%, (3) The volume distribution particle size Dv50 of the filler is 6 μm or less, optionally 2 μm to 5 μm, The method according to claim 11 or 12.

14. The filler contains one or more of coal pitch, petroleum pitch, polymer compounds, and resins, and optionally contains one or more of coal pitch and petroleum pitch, The method according to claim 13.

15. The mass ratio of the filler to the raw material is (15 to 30):100, optionally (18 to 28):100, The method according to any one of claims 11 to 14.

16. After uniformly mixing the raw material and the filler at a predetermined ratio, the temperature rising process to raise the temperature to the first temperature T １ is a stepwise temperature rising process, and optionally includes a first temperature rising process and a second temperature rising process The method according to any one of claims 11 to 15.

17. The first heating process is to heat up to 200°C to 250°C and keep the temperature for 1 h to 3 h, and / or The second temperature rising process is to raise the temperature to the first temperature T １ and keep the temperature for a first time t １ at that temperature. The method according to claim 16.

18. Heat up to the first temperature T at a rate of 1 °C / min to 10 °C / min, optionally 1.5 °C / min to 8 °C / min １ ​ The method according to any one of claims 11 to 17.

19. The first temperature T １ is 700°C to 1150°C, optionally 850°C to 1100°C, and / or The first time t １ is 1 h to 5 h, and optionally 2 h to 4 h The method according to any one of claims 11 to 18.

20. the second temperature T ２ is from 1600°C to 2620°C, optionally from 1800°C to 2450°C, and / or the second time t ２ is 1.5 h to 6 h, and optionally 2 h to 5 h The method according to any one of claims 11 to 19.

21. A negative electrode sheet comprising the carbon material according to any one of claims 1 to 10 or the carbon material manufactured by the method according to any one of claims 11 to 20, A secondary battery.

22. Comprising the secondary battery according to claim 21, A power consumption device.

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