Artificial graphite, its preparation method, and a secondary battery and electrical device containing the artificial graphite.

Abstract

This application provides an artificial graphite material A, wherein the artificial graphite material A is a secondary particle, and the surface roughness η of the artificial graphite material A is... A Satisfy: 6≤η A ≤12. This application also provides an artificial graphite material B, wherein the artificial graphite material B is in the form of primary particles, and the surface roughness η of the artificial graphite material B is... B Satisfy: 2.5≤η B ≤5. This application also provides a secondary battery and an electrical device comprising the aforementioned artificial graphite material A and / or artificial graphite material B. The secondary battery provided by this application can achieve high energy density and good service life.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to an artificial graphite and its preparation method, as well as a secondary battery and electrical device containing the artificial graphite as a negative electrode active material. Background Technology

[0002] Secondary batteries are widely used due to their outstanding characteristics such as high energy density, no pollution, and long service life.

[0003] In secondary batteries, artificial graphite has been widely used as a negative electrode active material. However, existing artificial graphite cannot fully meet the requirements of high energy density batteries, nor can it meet the high requirements for battery life. Therefore, it is necessary to provide a new artificial graphite material that can further improve energy density without affecting battery life. Summary of the Invention

[0004] This application was made in view of the aforementioned issues, and its purpose is to provide an artificial graphite that achieves high energy density and good service life, a method for preparing the same, and a negative electrode sheet prepared from the artificial graphite as a negative electrode active material. Furthermore, this application also aims to provide a secondary battery with high energy density and good service life, a battery module comprising the secondary battery, a battery pack, and an electrical device.

[0005] To achieve the above objectives, the present invention provides the following technical solution.

[0006] The first aspect of this application provides an artificial graphite material A, wherein the artificial graphite material A is secondary particles, and the surface roughness η of the artificial graphite material A is... A Satisfy: 6≤η A ≤12. In some embodiments, the artificial graphite material A satisfies: 7≤η A ≤10.

[0007] In some embodiments, the true density ρ of the artificial graphite material A A ≥2.20g / cm 3 Optionally, ρ A ≥2.25g / cm 3 .

[0008] In some embodiments, the volume average particle size Dv50 of the artificial graphite material A A Satisfying: Dv50 A ≥10μm; optionally, 12μm≤Dv50 A ≤20μm.

[0009] In some embodiments, the specific surface area of ​​the artificial graphite material A is 1.5-4.0; optionally, it is 2.5-3.5.

[0010] In some embodiments, the tap density of the artificial graphite material A is 0.8-1.4; optionally, it is 0.9-1.1.

[0011] In some embodiments, the degree of graphitization of the artificial graphite material A is 92% or higher; optionally, it is 94%-97%.

[0012] In some embodiments, the specific capacity of the artificial graphite material A is 340 mAh / g or higher; optionally, it is 350-360 mAh / g.

[0013] A second aspect of this application provides an artificial graphite material B, wherein the artificial graphite material B is in the form of primary particles, and the surface roughness η of the artificial graphite material B is... B Satisfy: 2.5≤η B ≤5.

[0014] In some embodiments, the artificial graphite material B satisfies: 3≤η B ≤4.

[0015] In some embodiments, the true density ρ of the artificial graphite material B B ≥2.20g / cm 3 Optionally, ρ B ≥2.25g / cm 3 .

[0016] In some embodiments, the volume average particle size Dv50 of the artificial graphite material B B Satisfying: Dv50 B ≤15μm; optionally, 5μm≤Dv50 B ≤12μm.

[0017] In some embodiments, the specific surface area of ​​the artificial graphite material B is 0.5-3.0; optionally, it is 1.0-2.5.

[0018] In some embodiments, the tap density of the artificial graphite material B is 0.8-1.4; optionally, it is 1.1-1.3.

[0019] In some embodiments, the degree of graphitization of the artificial graphite material B is 91% or higher; optionally, it is 92%-94%.

[0020] In some embodiments, the specific capacity of the artificial graphite material B is 340 mAh / g or higher; optionally, it is 340-350 mAh / g.

[0021] A third aspect of this application provides a method for preparing artificial graphite material A, which includes the following steps in sequence:

[0022] (A1) Provide raw materials, crush them, and shape them;

[0023] (A2) Granulation;

[0024] (A3) Graphitization treatment;

[0025] (A4) Surface roughening treatment to obtain the artificial graphite material A;

[0026] Wherein, the artificial graphite material A is a secondary particle, and the surface roughness η of the artificial graphite material A is... A Satisfy: 6≤η A ≤12.

[0027] Regarding the preparation method of artificial graphite material A, in some embodiments, the surface roughness η of the secondary particles before graphitization treatment is... A It is 4-6.

[0028] Regarding the preparation method of artificial graphite material A, in some embodiments, the surface roughening treatment includes:

[0029] The materials are placed in the blending machine and processed at a specific rotation speed.

[0030] The specific rotational speed is 500-1000 r / m, optionally 600-800 r / m.

[0031] The processing time is 3-60 minutes, optionally 5-20 minutes.

[0032] Regarding the preparation method of artificial graphite material A, in some embodiments, the surface roughening treatment includes:

[0033] Place the material in the granulation vessel and continuously circulate dry air;

[0034] The temperature is raised to a processing temperature, and the processing is carried out at that temperature, which is 300-800℃, or optionally 400-600℃.

[0035] The processing time is 1-8 hours, optionally 2-4 hours.

[0036] A fourth aspect of the present invention provides a method for preparing artificial graphite material B, which comprises the following steps in sequence:

[0037] (B1) Provide raw materials, crush them, and shape them;

[0038] (B2) Graphitization treatment;

[0039] (B3) Surface roughening treatment to obtain the artificial graphite material;

[0040] Wherein, the artificial graphite material B is a primary particle, and the surface roughness η of the artificial graphite material B is... B Satisfy: 2.5≤η B ≤5.

[0041] Regarding the preparation method of artificial graphite material B, in some embodiments, the surface roughness of the primary particles before graphitization is 1.5-3.

[0042] Regarding the preparation method of artificial graphite material B, in some embodiments, the surface roughening treatment includes:

[0043] The materials are placed in the blending machine and processed at a specific rotation speed.

[0044] The specific rotational speed is 800-1000 r / m, optionally 850-950 r / m.

[0045] The processing time is 20-60 minutes, optionally 30-50 minutes.

[0046] Regarding the preparation method of artificial graphite material B, in some embodiments, the surface roughening treatment includes:

[0047] Place the material in the granulation vessel and continuously circulate dry air;

[0048] The temperature is raised to a processing temperature, and the processing is carried out at that temperature, which is 300-800℃, or optionally 400-600℃.

[0049] The processing time is 1-8 hours, optionally 2-4 hours.

[0050] The fifth aspect of this application provides a secondary battery, wherein the secondary battery includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes the artificial graphite material A and / or the artificial graphite material B of this application, or includes the artificial graphite material A and / or B prepared by the methods provided in the third and / or fourth aspects of this application.

[0051] A sixth aspect of this application provides an electrical device including the secondary battery provided in the fifth aspect of this application.

[0052] The secondary battery provided in this application includes artificial graphite material A and / or artificial graphite material B as the negative electrode active material, preferably including both artificial graphite material A and artificial graphite material B. The artificial graphite materials A and B in this application appropriately set the surface roughness of the graphite, thereby improving the bonding force between graphite and the binder, increasing the interaction force between graphite particles, and thus reducing the rebound at the moment of ejection after cold pressing, extending the service life of the secondary battery and improving safety performance. Simultaneously, because it can improve the bonding force between graphite and the binder, and increase the interaction force between graphite particles, it can also achieve high energy density. The battery module, battery pack, and power device of this application include the secondary battery provided in this application, and therefore have at least the same advantages as the secondary battery. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of a secondary battery provided in an embodiment of this application.

[0055] Figure 2 This is a schematic diagram of a battery module provided in an embodiment of this application.

[0056] Figure 3 This is a schematic diagram of a battery pack provided in an embodiment of this application.

[0057] Figure 4 yes Figure 3 The exploded diagram.

[0058] Figure 5 This is a schematic diagram of an electrical device provided in an embodiment of this application.

[0059] The reference numerals in the attached figures are explained as follows:

[0060] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Secondary battery. Detailed Implementation

[0061] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the composite artificial graphite and its preparation method, secondary battery, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0062] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it 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.

[0063] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0064] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0065] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0066] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or several" means two or more.

[0067] Electrical energy, as an economical, practical, clean, and easily controlled and converted form of energy, is increasingly being used in various electrical devices. Secondary batteries, due to their advantages such as high energy density, portability, lack of memory effect, and environmental friendliness, have become a preferred power source for these devices. However, secondary batteries formed using existing natural or artificial graphite as the negative electrode active material do not have sufficiently high energy density to meet the demands for high energy density and long service life. Therefore, how to further improve the energy density and extend the service life of secondary batteries has become a focal point in the field of secondary battery technology.

[0068] Through extensive research, the inventors have noticed that when artificial graphite material is made into secondary or primary particles and the surface roughness of the artificial graphite material is set to a specific value, and when the artificial graphite material is used to prepare negative electrode active materials, it is beneficial for secondary batteries to maintain a high energy density and for improving the service life and safety performance of secondary batteries, as well as battery modules, battery packs and electrical devices including the secondary batteries.

[0069] [Artificial Graphite Material A and its Preparation Method]

[0070] The first aspect of this application provides an artificial graphite material A, wherein the artificial graphite material A is secondary particles, and the surface roughness η of the artificial graphite material A is... A Satisfy: 6≤η A ≤12, preferably 7≤η A ≤10. Appropriate surface roughness η of artificial graphite material A. A This process enhances the bonding strength between graphite and the binder, thereby increasing the interparticle force of graphite particles. This reduces the rebound during the roll ejection process after cold pressing, improving the lifespan and safety performance of the secondary battery. Furthermore, the increased bonding strength between graphite and the binder, and consequently the increased interparticle force, also contributes to achieving higher energy density.

[0071] In some embodiments, the true density ρ of the artificial graphite material A of this application A ≥2.20g / cm 3 Optionally, ρ A ≥2.25g / cm 3 The appropriate true density of artificial graphite material A enables it to have a high specific capacity, which is beneficial to improving the specific capacity of composite artificial graphite. It also inhibits the occurrence of cycle side reactions, extends the service life of secondary batteries, and improves safety performance.

[0072] In some embodiments, the volume average particle size Dv50 of the artificial graphite material A of this application is... A Satisfying: Dv50A ≥10μm; optionally, 12μm≤Dv50 A ≤20μm. An appropriate volume average particle size of artificial graphite material A can enable artificial graphite material A to have a high specific capacity, which is beneficial to improving the specific capacity of composite artificial graphite, and will also inhibit the occurrence of cycle side reactions, extend the service life of secondary batteries and improve safety performance.

[0073] In some embodiments, the specific surface area of ​​the artificial graphite material A in this application is 1.5-4.0; optionally, it is 2.5-3.5. If the specific surface area of ​​the artificial graphite material A is too high, the surface reactivity is strong, side reactions are prone to occur during cycling, and the lifespan performance is poor. If the specific surface area of ​​the artificial graphite material A is too low, there are few surface active sites, and the power performance of the material is poor.

[0074] In some embodiments, the tap density of the artificial graphite material A in this application is 0.8-1.4; optionally, it is 0.9-1.1. If the tap density of the artificial graphite material A is low, the slurry has poor stability and is difficult to process. There is no particular upper limit to the tap density of the artificial graphite material A; it can be set according to the extent achievable by conventional methods.

[0075] In some embodiments, the degree of graphitization of the artificial graphite material A in this application is 92% or higher; optionally, it is 94%-97%. If the graphitization of the artificial graphite material A is too low, the capacity is low; if the graphitization of the artificial graphite material A is too high, the interlayer spacing is narrow and the cyclic expansion is large.

[0076] In some embodiments, the specific capacity of the artificial graphite material A in this application is 340 mAh / g or higher; optionally, it is 350-360 mAh / g. The higher the appropriate specific capacity of the artificial graphite material A, the higher the energy density of the secondary battery containing it. The artificial graphite material A provided in this application has a high specific capacity, which enables the secondary battery provided in this application to have high energy density characteristics.

[0077] A third aspect of this application provides a method for preparing artificial graphite material A, which includes the following steps in sequence:

[0078] (A1) Provide raw materials, crush them, and shape them;

[0079] (A2) Granulation;

[0080] (A3) Graphitization treatment;

[0081] (A4) Surface roughening treatment to obtain the artificial graphite material.

[0082] Wherein, the artificial graphite material A is a secondary particle, and the surface roughness η of the artificial graphite material A is... ASatisfy: 6≤η A ≤12.

[0083] In this application, one or more of the following can be used as raw materials for step (A1): raw coke and calcined coke; preferably, the raw materials include one or more of needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, needle-shaped coal-series raw coke, non-needle-shaped coal-series raw coke, calcined needle-shaped coke, and calcined petroleum coke.

[0084] In some embodiments, the raw materials can be crushed using equipment and methods known in the art in step (A1), such as air jet mills, mechanical mills, or roller mills. The crushing process often produces a large number of excessively small particles, and sometimes excessively large particles as well. Therefore, after crushing, grading can be performed as needed to remove excessively small and excessively large particles from the crushed powder. Grading results in particulate products with a better particle size distribution, facilitating subsequent shaping and / or granulation processes. Grading can be performed using equipment and methods known in the art, such as grading sieves, gravity classifiers, centrifugal classifiers, etc.

[0085] In some embodiments, in step (A1), equipment (e.g., shaping machine or other shaping equipment) and methods known in the art can be used to shape the granular product after crushing in step (A1), for example, to grind the edges of the obtained granular product, which facilitates subsequent operations and makes the obtained product have higher stability.

[0086] In some embodiments, granulation can be performed in step (A2) using equipment known in the art, such as a granulator. A granulator typically includes a stirred reactor and a module for temperature control of the reactor. Furthermore, by adjusting process conditions such as stirring speed, heating rate, granulation temperature, and cooling rate during the granulation process, the volume average particle size of the granulated product can be controlled. For example, in this application, the granulation conditions can be set as follows: stirring speed of 800 r / min-1500 r / min, heating rate of 8-15 °C / min, granulation temperature of 400 °C-650 °C, and granulation time of 6-10 hours.

[0087] In some embodiments, graphitization is performed in step (A3). Graphitization includes high-temperature graphitization and low-temperature graphitization. In some embodiments, any one or both of the high-temperature and low-temperature graphitization methods may be appropriately selected according to specific requirements, or the high-temperature and / or low-temperature graphitization processes may be repeated multiple times.

[0088] High-temperature graphitization can yield graphite with appropriate graphitization degree and interlayer spacing. In some embodiments, the high-temperature graphitization temperature in step (A3) can be 2800℃-3200℃, for example 2900℃-3100℃ or 3000℃-3200℃. Graphite prepared at appropriate graphitization temperatures can achieve appropriate graphitization degree and interlayer spacing, thereby enabling composite artificial graphite to obtain high structural stability and specific capacity.

[0089] Graphite with appropriate graphitization degree and interlayer spacing can also be obtained through low-temperature graphitization treatment. In some embodiments, the temperature for low-temperature graphitization treatment in step (A3) can be 2500℃-2700℃, for example 2500℃-2600℃ or 2600℃-2700℃. Graphite prepared at appropriate graphitization temperatures can achieve appropriate graphitization degree and interlayer spacing, thereby enabling composite artificial graphite to obtain high structural stability and specific capacity.

[0090] Regarding the preparation method of artificial graphite material A, in some embodiments, the surface roughness η of the secondary particles before graphitization treatment is... A It is 4-6.

[0091] In some implementations, the surface roughening process in step (A4) includes a method performed primarily by physical means (hereinafter referred to as "Method 1A"), specifically:

[0092] The materials are placed in the blending machine and processed at a specific rotation speed.

[0093] The specific rotational speed is 500-1000 r / m, optionally 600-800 r / m.

[0094] The processing time is 3-60 minutes, optionally 5-20 minutes.

[0095] In some embodiments, the surface roughening treatment in step (A4) includes a method primarily carried out by chemical means (hereinafter referred to as "Method 2A"), specifically:

[0096] Place the material in the granulation vessel and continuously circulate dry air;

[0097] The temperature is raised to a processing temperature, and the processing is carried out at that temperature, which is 300-800℃, or optionally 400-600℃.

[0098] The processing time is 1-8 hours, optionally 2-4 hours.

[0099] In some embodiments, the surface roughening process in step (A4) can be performed using any one or both of the methods 1A and 2A, or the process of method 1A and / or method 2A can be repeated multiple times.

[0100] [Artificial Graphite Material B and its Preparation Method]

[0101] A second aspect of this application provides an artificial graphite material B, wherein the artificial graphite material B is in the form of primary particles, and the surface roughness η of the artificial graphite material B is... B Satisfy: 2.5≤η B ≤5, preferably surface roughness η B Satisfy: 3≤η B ≤4. Appropriate surface roughness η of artificial graphite material B B This process enhances the bonding strength between graphite and the binder, thereby increasing the interparticle force of graphite particles. This reduces the rebound during the roll ejection process after cold pressing, improving the lifespan and safety performance of the secondary battery. Furthermore, the increased bonding strength between graphite and the binder, and consequently the increased interparticle force, also contributes to achieving higher energy density.

[0102] In some embodiments, the true density ρ of the artificial graphite material B B ≥2.20g / cm 3 Optionally, ρ B ≥2.25g / cm 3 The appropriate true density of artificial graphite material B enables it to have a high specific capacity, which is beneficial to improving the specific capacity of composite artificial graphite. It also inhibits the occurrence of cycle side reactions, extends the service life of secondary batteries, and improves safety performance.

[0103] In some embodiments, the volume average particle size Dv50 of the artificial graphite material B B Satisfying: Dv50 B ≤15μm; optionally, 5μm≤Dv50 B ≤12μm. The appropriate volume average particle size of artificial graphite material B enables it to have a high specific capacity, which is beneficial to improving the specific capacity of composite artificial graphite. It also inhibits the occurrence of cycle side reactions, extends the service life of secondary batteries, and improves safety performance.

[0104] In some embodiments, the specific surface area of ​​the artificial graphite material B is 0.5-3.0; optionally, it is 1.0-2.5. If the specific surface area of ​​the artificial graphite material B is too high, the surface reactivity is strong, side reactions are prone to occur during cycling, and the lifespan performance is poor. If the specific surface area of ​​the artificial graphite material B is too low, there are few surface active sites, and the power performance of the material is poor.

[0105] In some embodiments, the tap density of the artificial graphite material B is 0.8-1.4; optionally, it is 1.1-1.3. A low tap density of the artificial graphite material B results in poor slurry stability and difficulty in processing. There is no particular upper limit to the tap density of the artificial graphite material B; it can be set according to what is achievable by conventional methods.

[0106] In some embodiments, the degree of graphitization of the artificial graphite material B is 91% or higher; optionally, it is 92%-94%. If the graphitization of the artificial graphite material B is too low, the capacity is low; if the graphitization of the artificial graphite material B is too high, the interlayer spacing is narrow and the cyclic expansion is large.

[0107] In some embodiments, the specific capacity of the artificial graphite material B is 340 mAh / g or higher; optionally, it is 340-350 mAh / g. The higher the appropriate specific capacity of the artificial graphite material B, the higher the energy density of the secondary battery containing it. The artificial graphite material B provided in this application has a high specific capacity, which enables the secondary battery provided in this application to have high energy density characteristics.

[0108] The fourth aspect of this application provides a method for preparing artificial graphite material B, which includes the following steps in sequence:

[0109] (B1) Provide raw materials, crush them, and shape them;

[0110] (B2) Graphitization treatment;

[0111] (B3) Surface roughening treatment to obtain the artificial graphite material B;

[0112] Wherein, the artificial graphite material B is a primary particle, and the surface roughness η of the artificial graphite material B is... B Satisfy: 2.5≤η B ≤5.

[0113] In this application, one or more of the following can be used as raw materials for step (B1): raw coke and calcined coke; preferably, the raw materials include one or more of the following: needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, needle-shaped coal-series raw coke, non-needle-shaped coal-series raw coke, calcined needle-shaped coke, and calcined petroleum coke.

[0114] In some embodiments, the raw materials can be crushed using equipment and methods known in the art in step (B1), such as air jet mills, mechanical mills, or roller mills. The crushing process often produces a large number of excessively small particles, and sometimes excessively large particles as well. Therefore, after crushing, grading can be performed as needed to remove excessively small and excessively large particles from the crushed powder. Grading results in particulate products with a better particle size distribution, facilitating subsequent shaping and / or granulation processes. Grading can be performed using equipment and methods known in the art, such as grading sieves, gravity classifiers, centrifugal classifiers, etc.

[0115] In some embodiments, in step (B1), equipment (e.g., shaping machine or other shaping equipment) and methods known in the art can be used to shape the granular product after crushing in step (B1), for example, to grind the edges of the obtained granular product, which facilitates subsequent operations and makes the obtained product have higher stability.

[0116] In some embodiments, graphitization is performed in step (B2). Graphitization includes high-temperature graphitization and low-temperature graphitization. In some embodiments, any one or both of the high-temperature and low-temperature graphitization methods may be appropriately selected according to specific requirements, or the high-temperature and / or low-temperature graphitization processes may be repeated multiple times.

[0117] High-temperature graphitization can yield graphite with appropriate graphitization degree and interlayer spacing. In some embodiments, the high-temperature graphitization temperature in step (B2) can be 2800℃-3200℃, for example 2900℃-3100℃ or 3000℃-3200℃. Graphite prepared at appropriate graphitization temperatures can achieve appropriate graphitization degree and interlayer spacing, thereby enabling composite artificial graphite to obtain high structural stability and specific capacity.

[0118] Graphite with appropriate graphitization degree and interlayer spacing can also be obtained through low-temperature graphitization treatment. In some embodiments, the temperature for low-temperature graphitization treatment in step (B2) can be 2500℃-2700℃, for example 2500℃-2600℃ or 2600℃-2700℃. Graphite prepared at appropriate graphitization temperatures can achieve appropriate graphitization degree and interlayer spacing, thereby enabling composite artificial graphite to obtain high structural stability and specific capacity.

[0119] Regarding the preparation method of artificial graphite material B, in some embodiments, the surface roughness of the primary particles before (B2) graphitization treatment is 1.5-3.

[0120] In some embodiments, a surface roughening treatment is performed in step (B3) to obtain artificial graphite material B.

[0121] In some implementations, the surface roughening process in step (B3) includes a method performed primarily by physical means (hereinafter referred to as "Method 1B"), specifically:

[0122] The materials are placed in the blending machine and processed at a specific rotation speed.

[0123] The specific rotational speed is 800-1000 r / m, optionally 850-950 r / m.

[0124] The processing time is 20-60 minutes, optionally 30-50 minutes.

[0125] In some implementations, the surface roughening treatment in step (B3) includes a method primarily carried out by chemical means (hereinafter referred to as "Method 2B"), specifically:

[0126] Place the material in the granulation vessel and continuously circulate dry air;

[0127] The temperature is raised to a processing temperature, and the processing is carried out at that temperature, which is 300-800℃, or optionally 400-600℃.

[0128] The processing time is 1-8 hours, optionally 2-4 hours.

[0129] In some embodiments, the surface roughening process in step (B3) can be performed using any one or both of the methods 1B and 2B, or the process of method 1B and / or method 2B can be repeated multiple times.

[0130] [Parameter Measurement of Artificial Graphite Materials A and B]

[0131] In the embodiments and comparative examples of this application, the surface roughness η of artificial graphite materials A and B is... A η B All of them were obtained using the following method.

[0132]

[0133] Where SSA is the specific surface area of ​​the artificial graphite material, ρ is the true density of the artificial graphite material, and D is the density of the artificial graphite material. k and V k Test data can be directly read from the testing equipment, a laser particle size analyzer (Malvern Master Size 3000); n represents the number of particle size ranges of the material, and n can be set according to the laser particle size analyzer (e.g., n=80). Where D...k V represents the average particle size within a certain particle size range of the material (i.e., (upper limit particle size + lower limit particle size) / 2); k This indicates the volume percentage of particles in this range among all particles.

[0134] In the embodiments and comparative examples of this application, the true density ρ of artificial graphite materials A and B is... A ρ B The density was measured using a true density tester (AccuPyc) in accordance with standard GB / T 24586-2009.

[0135] In the embodiments and comparative examples of this application, the volume average particle size Dv50 of artificial graphite materials A and B is... A Dv50 B According to standard GB / T 19077.1-2016, the particle size was determined using a laser particle size analyzer (such as Malvern Master Size3000).

[0136] Among them, Dv50 A Dv50 B The physical definition is as follows:

[0137] Dv50 A Dv50 B The particle size corresponding to a cumulative volume distribution percentage of 50% for artificial graphite materials.

[0138] In the embodiments and comparative examples of this application, the specific surface area of ​​artificial graphite materials A and B was tested using the nitrogen adsorption specific surface area analysis method according to GB / T19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc., USA.

[0139] In the embodiments and comparative examples of this application, the tap density of artificial graphite materials A and B was determined using a powder tap density tester (such as Dandong Baite BT-301) in accordance with standard GB / T 5162-2006.

[0140] In the embodiments and comparative examples of this application, the compaction density of artificial graphite materials A and B is tested using an electronic pressure testing machine (such as UTM7305) in accordance with GB / T 24533-2009: a certain amount M of the powder sample to be tested is placed on a compaction mold (bottom area S), different pressures are set, the pressure is held for 30s, the pressure is released, and after waiting for 10s, the thickness H of the powder after compaction under the pressure is read on the equipment, and the compaction density under the pressure can be calculated. The compaction density of the negative electrode active material under the pressure is M / (H×S).

[0141] Graphite interlayer spacing d 002 The degree of graphitization can be tested using methods known in the art. For example, the degree of graphitization can be tested using an X-ray diffractometer (such as a Bruker D8 Discover), and the testing method can be referenced in JIS K 0131-1996 and JB / T 4220-2011, to measure d. 002 The size is then determined according to the formula G = (0.344 - d). 002 The degree of graphitization is calculated using (0.344-0.3354) / (0.344-0.3354), where d 002 It is the interlayer spacing in the artificial graphite crystal structure, expressed in nanometers (nm).

[0142] The specific mass of artificial graphite materials A and B was determined using methods known in the art. For example, it was determined using the following method.

[0143] <Methods for determination of gram volume>

[0144] The prepared artificial graphite material, conductive agent Super P, thickener (CMC-Na), and binder (SBR) were mixed with deionized water in a mass ratio of 94.5:1.5:1.5:2.5 to form a slurry. The prepared slurry was coated onto a copper foil current collector and dried in an oven for later use. A lithium metal sheet was used as the counter electrode. A polyethylene (PE) film was used as the separator. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L. The above components were assembled into a CR2430 coin cell in an argon-protected glove box.

[0145] After the obtained coin cells were left to stand for 12 hours, they were discharged at a constant current of 0.05C to 0.005V, left to stand for 10 minutes, and then discharged at a constant current of 10μA to 0.005V. They were then charged at a constant current of 0.1C to 2V, and the charging capacity was recorded. The ratio of the charging capacity to the mass of the composite artificial graphite is the specific capacity of the prepared artificial graphite material.

[0146] [Rechargeable Battery]

[0147] The fifth aspect of this application provides a secondary battery comprising any one of the artificial graphite materials A provided in the first aspect of the present invention and / or any one of the artificial graphite materials B provided in the second aspect of the present invention.

[0148] This application provides a secondary battery in its embodiments. Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator is disposed between the positive and negative electrodes, primarily to prevent short circuits between the positive and negative electrodes while allowing ions to pass through.

[0149] [Negative electrode plate]

[0150] The negative electrode includes a negative current collector and a negative electrode film disposed on at least one surface of the negative current collector. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film is laminated and disposed on either or both of the two opposite surfaces of the negative current collector.

[0151] The negative electrode current collector can be made of a material with good conductivity and mechanical strength, serving both as a conductor and a current collector. In some embodiments, the negative electrode current collector can be made of copper foil.

[0152] The negative electrode film includes a negative electrode active material, which includes any one of the artificial graphite materials A provided in the first aspect of this application and / or any one of the artificial graphite materials B provided in the second aspect of this application. It can significantly reduce the instantaneous rebound of the negative electrode sheet including artificial graphite material during the manufacturing process after cold pressing and rolling, thereby effectively improving the service life and safety performance of the secondary battery.

[0153] In some embodiments, the step of preparing a negative electrode sheet using any one or more artificial graphite materials of this application may include: dispersing a negative electrode active material including any one or more artificial graphite materials A and / or B of this application, a binder, and optional thickeners and conductive agents in a solvent, the solvent being deionized water, to form a uniform negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and obtaining a negative electrode sheet after processes such as drying and cold pressing.

[0154] In some embodiments, the negative electrode sheet may optionally include other negative electrode active materials that can be used as the negative electrode of a secondary battery. Other negative electrode active materials may be one or more of other graphite materials (such as other artificial graphite or natural graphite different from those in this application), mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon-based materials, and tin-based materials.

[0155] In some embodiments, the adhesive may be selected from one or more of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0156] In some embodiments, the thickener may be sodium carboxymethyl cellulose (CMC-Na).

[0157] In some embodiments, the conductive agent used for the negative electrode sheet may be selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0158] [Positive electrode plate]

[0159] The positive electrode includes a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector and comprising a positive active material. As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film is laminated on either or both of the two opposite surfaces of the positive current collector.

[0160] The positive current collector can be made of a material with good conductivity and mechanical strength. In some embodiments, the positive current collector can be aluminum foil.

[0161] This application does not impose specific restrictions on the type of positive electrode active material. Materials known in the art that can be used as positive electrodes for secondary batteries can be used, and those skilled in the art can select them according to actual needs.

[0162] In some embodiments, the secondary battery may be a lithium-ion secondary battery. The positive electrode active material may be selected from lithium transition metal oxides and their modified materials, wherein the modified material may be a lithium transition metal oxide that has undergone doping modification and / or coating modification. For example, the lithium transition metal oxide may be selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium phosphates with an olivine structure.

[0163] As an example, the positive electrode active material of a secondary battery can be selected from LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2, LiFePO4 (LFP), and LiMnPO4.

[0164] In some embodiments, the positive electrode membrane may optionally include an adhesive. There is no specific limitation on the type of adhesive, and those skilled in the art can select one according to actual needs. As an example, the adhesive used for the positive electrode membrane may include one or more of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0165] In some embodiments, the positive electrode membrane may optionally include a conductive agent. There is no specific limitation on the type of conductive agent, and those skilled in the art can select it according to actual needs. As an example, the conductive agent used for the positive electrode membrane may include one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0166] [Electrolytes]

[0167] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0168] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0169] In some embodiments, the electrolyte salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate).

[0170] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl 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).

[0171] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0172] [Isolation membrane]

[0173] Secondary batteries using electrolytes, and some secondary batteries using solid electrolytes, also include a separator. The separator is positioned between the positive and negative electrodes to provide isolation. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. In some embodiments, the separator material can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can 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 can be the same or different.

[0174] [Outer Packaging]

[0175] In some embodiments, the secondary battery may include an outer packaging for encapsulating a positive electrode, a negative electrode, and an electrolyte. As an example, the positive electrode, negative electrode, and separator may be stacked or wound to form a stacked or wound battery cell, with the cell encapsulated within the outer packaging; the electrolyte may be a liquid electrolyte that wets the cell. The number of cells in the secondary battery may be one or more, adjustable as needed.

[0176] In some embodiments, the outer packaging of the secondary battery can be a soft pack, such as a pouch. The soft pack can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). The outer packaging of the secondary battery can also be a hard shell, such as an aluminum shell.

[0177] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0178] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. Figure 1 This is an example of a square-structured secondary battery 5.

[0179] [Battery Module]

[0180] In a sixth aspect of this application, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0181] Figure 2 This is battery module 4, used as an example. (See reference...) Figure 2 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0182] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0183] [Battery Pack]

[0184] In a sixth aspect of this application, the battery module of this application can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0185] Figure 3 and Figure 4 This is battery pack 1 as an example. (See reference...) Figure 3 and Figure 4 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0186] [Electrical appliances]

[0187] A sixth aspect of this application also provides an electrical device comprising the secondary battery of this application, the secondary battery providing power to the electrical device. The electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0188] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0189] Figure 5 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0190] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0191] Example

[0192] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0193] Example 1a

[0194] Preparation of artificial graphite material A:

[0195] (A1): The calcined needle coke raw material was crushed by roller mill and then graded and shaped by centrifugal separator and shaping machine to obtain precursor 1;

[0196] (A2): The precursor 1 obtained in step (A1) is granulated to obtain intermediate 1; a binder is added during the granulation process, and the amount of the binder is 15% of the weight of the precursor 1 used in the granulation step (A2); granulation is carried out using a granulator with a stirring speed of 1000 r / min, a heating rate of 10℃ / min, a granulation temperature of 650℃, and a granulation time of 8 hours;

[0197] (A3): The intermediate 1 obtained in step (A2) is graphitized at a temperature of 3000℃;

[0198] (A4): The product obtained in step (A3) is placed in a granulation vessel and dry air is continuously introduced; the temperature is increased to 550℃ at a rate of 5℃ / min, and the temperature is maintained at this treatment temperature for 2 hours to obtain artificial graphite material A. The artificial graphite material A is a secondary particle with a surface roughness of 8.5.

[0199] Preparation of negative electrode sheet

[0200] The artificial graphite material A, conductive agent Super P, binder SBR, and thickener CMC-Na prepared above were mixed in a mass ratio of 96.2:0.8:1.8:1.2, and thoroughly stirred in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry was coated onto the surface of a copper foil current collector, and after drying and cold pressing (at a pressure of 70 tons and a speed of 35 m / s), the negative electrode sheet was obtained. The areal density of the negative electrode sheet was 10.7 mg / cm³. 2 The compaction density of the negative electrode film is 1.71 g / cm³. 3 .

[0201] Preparation of positive electrode sheet

[0202] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2 (NCM523), conductive agent (Super P), and binder PVDF are thoroughly mixed in an appropriate amount of NMP at a weight ratio of 96.2:2.7:1.1 to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto the surface of a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained. The compacted density of the positive electrode sheet is 3.45 g / cm³. 3 Its surface density is 18.8 mg / cm³. 2 .

[0203] Preparation of electrolyte

[0204] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L.

[0205] Separating membrane

[0206] Polyethylene (PE) film is used.

[0207] Preparation of secondary batteries

[0208] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain an electrode assembly. The electrode assembly is then placed in an outer package, and the electrolyte is added. After processes such as encapsulation, settling, formation, and aging, a secondary battery is obtained.

[0209] Examples 2a-17a and Comparative Examples 1a-2a

[0210] Examples 2a-17a and Comparative Examples 1a-2a are essentially the same as Example 1a, with the only differences being shown in Tables 1-3. For Examples 2a-17a and Comparative Examples 1a-2a, unless explicitly stated in Tables 1-3, they are considered to be the same as Example 1a.

[0211] The test results of the artificial graphite materials obtained in Examples 1a-13a and Comparative Examples 1a-5a are shown in Tables 1 to 3 below.

[0212] In Table 1, the processing method of step (A4) is "chemical", which means that step (A4) is performed as follows: the material is placed in the granulation vessel and dry air is continuously introduced; the temperature is increased to the specified processing temperature at 5°C / min and held at the specified processing temperature for a specified time. The processing temperature and processing time (i.e., the holding time) are shown in Table 1.

[0213] In Table 1, the processing method for step (A4) is "physical", which means that step (A4) is performed in the following manner: that is, the material is placed in the blending machine and processed at a specified speed, and the speed and processing time are shown in Table 1.

[0214] Performance Testing

[0215] (1) The method for determining the compaction density of the negative electrode film after cold pressing is as follows.

[0216] Take the negative electrode sheets from the above embodiments and comparative examples, and punch them into small circular sheets with an area of ​​S1 (the unit of area S1 is cm). 2 Weigh it and record its weight as M1 (M1 is in g).

[0217] Measure the thickness of the negative electrode film (here, the thickness of the negative electrode film layer on any surface of the negative electrode current collector can be measured; the unit of thickness is cm).

[0218] Wipe off the negative electrode membrane of the weighed negative electrode sheet, weigh the negative current collector, and record the weight as M0 (M0 unit: g). When the negative electrode membrane is only placed on one surface of the negative current collector, the weight of the negative electrode membrane = M1 - M0; when the negative electrode membrane is placed on both surfaces of the negative current collector, the weight of the negative electrode membrane = (M1 - M0) / 2.

[0219] The areal density of the negative electrode film = the weight of the negative electrode film / S1.

[0220] Based on the "area density of the negative electrode film" and the "thickness of the negative electrode film", the "compact density of the negative electrode film after cold pressing" is calculated using the following formulas and recorded in the tables below.

[0221] The compaction density of the negative electrode film after cold pressing = the areal density of the negative electrode film / the thickness of the negative electrode film.

[0222] (2) The method for determining the compaction density and cyclic expansion rate of the negative electrode film after cycling is as follows.

[0223] The secondary batteries prepared in each embodiment and comparative example were charged at a constant current rate of 1C to the charging cutoff voltage of 4.2V, then charged at a constant voltage until the current ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 1C to the discharge cutoff voltage of 2.8V, allowed to stand for 5 minutes. This constitutes one charge-discharge cycle. The batteries were subjected to 600 charge-discharge cycles according to this method. The negative electrode sheet was disassembled and tested according to the method steps given in section 1 above. The "compact density of the negative electrode film after cycling" was obtained and recorded in the following tables.

[0224] Based on the "compacted density of the negative electrode film after cold pressing" and the "compacted density of the negative electrode film after cycling", the "cycle expansion rate (600 cys) of the negative electrode film" is calculated using the following formula and recorded in the following tables.

[0225] Cyclic expansion rate of the negative electrode film (600 cys) = (Compacted density of the negative electrode film after cold pressing / Compacted density of the negative electrode film after cycling - 1) × 100%

[0226] The compaction density of the negative electrode film after cold pressing is the result of the test using method 1 above.

[0227]

[0228]

[0229] Example 1b

[0230] Preparation of artificial graphite material B:

[0231] (B1): Raw petroleum coke feedstock is crushed using a mechanical mill and then graded and shaped using a centrifugal separator and a shaping machine to obtain precursor 1;

[0232] (B2): The precursor 1 obtained in step (B1) is graphitized at a temperature of 3000℃;

[0233] (B3): The product obtained in step (B2) is placed in a fusion machine and processed at 1000 r / m for 30 minutes to obtain artificial graphite material B. The artificial graphite material B is a primary particle with a surface roughness of 3.5.

[0234] Preparation of negative electrode sheet

[0235] The artificial graphite material B, conductive agent Super P, binder SBR, and thickener CMC-Na prepared above were mixed at a mass ratio of 96.2:0.8:1.8:1.2, and thoroughly stirred in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry was coated onto the surface of a copper foil current collector, and after drying and cold pressing, a negative electrode sheet was obtained. The areal density of the negative electrode sheet was 10.7 mg / cm³. 2 The compaction density of the negative electrode film is 1.67 g / cm³. 3 .

[0236] Preparation of positive electrode sheet

[0237] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2 (NCM523), conductive agent (Super P), and binder PVDF are thoroughly mixed in an appropriate amount of NMP at a weight ratio of 96.2:2.7:1.1 to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto the surface of a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained. The compacted density of the positive electrode sheet is 3.45 g / cm³. 3 Its surface density is 18.8 mg / cm³. 2 .

[0238] Preparation of electrolyte

[0239] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L.

[0240] Separating membrane

[0241] Polyethylene (PE) film is used.

[0242] Preparation of secondary batteries

[0243] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain a battery cell. The battery cell is then placed in an outer packaging, and the electrolyte mentioned above is added. After processes such as encapsulation, settling, formation, and aging, a secondary battery is obtained.

[0244] Examples 2b-17b and Comparative Examples 1b-2b

[0245] Examples 2b-14b and Comparative Examples 1b-2b are essentially the same as Example 1b, with the only differences being shown in Tables 4-6. For Examples 2b-17b and Comparative Examples 1b-2b, unless explicitly stated in Tables 4-6, they are considered to be the same as Example 1b.

[0246] The test results of the artificial graphite materials obtained in Examples 1b-17b and Comparative Examples 1b-2b are shown in Tables 4-6 below.

[0247] In Table 4, the processing method of step (B3) is "chemical", which means that step (B3) is carried out in the following manner: the material is placed in the granulation vessel and dry air is continuously introduced; the temperature is increased to the specified processing temperature at 5°C / min and held at the specified processing temperature for a specified time. The processing temperature and processing time (i.e., the holding time) are shown in Table 4.

[0248] In Table 4, the processing method for step (B3) is "physical", which means that step (B3) is performed in the following manner: that is, the material is placed in the blending machine and processed at a specified speed, and the speed and processing time are shown in Table 4.

[0249]

[0250] Table 5

[0251]

[0252] Table 6

[0253]

[0254] Example 1c

[0255] Preparation of negative electrode sheet

[0256] The artificial graphite material A prepared in Example 1a, the artificial graphite material B prepared in Example 1b, the conductive agent SuperP, the binder SBR, and the thickener CMC-Na were mixed in a mass ratio of 48.1:48.1:0.8:1.8:1.2, and thoroughly stirred in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry was coated onto the surface of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet was obtained. The areal density of the negative electrode sheet was 10.7 mg / cm³. 2 The compaction density of the negative electrode film is 1.71 g / cm³. 3 .

[0257] Preparation of positive electrode sheet

[0258] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2 (NCM523), conductive agent (Super P), and binder PVDF are thoroughly mixed in an appropriate amount of NMP at a weight ratio of 96.2:2.7:1.1 to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto the surface of a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained. The compacted density of the positive electrode sheet is 3.45 g / cm³.3 Its surface density is 18.8 mg / cm³. 2 .

[0259] Preparation of electrolyte

[0260] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L.

[0261] Separating membrane

[0262] Polyethylene (PE) film is used.

[0263] Preparation of secondary batteries

[0264] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain a battery cell. The battery cell is then placed in an outer packaging, and the electrolyte mentioned above is added. After processes such as encapsulation, settling, formation, and aging, a secondary battery is obtained.

[0265] Table 7

[0266]

Claims

1. An artificial graphite material A, wherein the artificial graphite material A is composed of secondary particles, and the surface roughness η of the artificial graphite material A is... A Satisfy: 6 η A 12; The degree of graphitization of the artificial graphite material A is above 92%.

2. The artificial graphite material A as described in claim 1, wherein, 7 or A 10.

3. The artificial graphite material A as described in claim 1, wherein, The true density ρ of the artificial graphite material A A ≥2.20g / cm 3 .

4. The artificial graphite material A as described in claim 3, wherein, r A ≥2.25g / cm 3 。 5. The artificial graphite material A as described in claim 1, wherein, The volume average particle size Dv50 of the artificial graphite material A A Satisfying: Dv50 A ≥10μm.

6. The artificial graphite material A as described in claim 5, wherein, 12 μm Dv50 A 20 μm。 7. The artificial graphite material A as described in claim 1, wherein, The specific surface area of ​​the artificial graphite material A is 1.5-4.

0.

8. The artificial graphite material A as described in claim 7, wherein, The specific surface area of ​​the artificial graphite material A is 2.5-3.

5.

9. The artificial graphite material A as described in claim 1, wherein, The tap density of the artificial graphite material A is 0.8-1.

4.

10. The artificial graphite material A as described in claim 9, wherein, The tap density of the artificial graphite material A is 0.9-1.

1.

11. The artificial graphite material A as described in claim 1, wherein, The degree of graphitization of the artificial graphite material A is 94%-97%.

12. The artificial graphite material A as described in claim 1, wherein, The specific capacity of the artificial graphite material A is above 340 mAh / g.

13. The artificial graphite material A as described in claim 12, wherein, The specific capacity of the artificial graphite material A is 350-360 mAh / g.

14. An artificial graphite material B, wherein the artificial graphite material B is in the form of primary particles, and the surface roughness η of the artificial graphite material B is... B Satisfies: 2.5 η B 5; The volume average particle size Dv50 of the artificial graphite material B B Satisfy: 5μm Dv50 B 12μm.

15. The artificial graphite material B as described in claim 14, wherein, 3 or B 4.

16. The artificial graphite material B as described in claim 14, wherein, The true density ρ of the artificial graphite material B B ≥2.20g / cm 3 .

17. The artificial graphite material B as described in claim 16, wherein, r B ≥2.25g / cm 3 。 18. The artificial graphite material B as described in claim 14, wherein, The specific surface area of ​​the artificial graphite material B is 0.5-3.

0.

19. The artificial graphite material B as described in claim 18, wherein, The specific surface area of ​​the artificial graphite material B is 1.0-2.

5.

20. The artificial graphite material B as described in claim 14, wherein, The tap density of the artificial graphite material B is 0.8-1.

4.

21. The artificial graphite material B as described in claim 20, wherein, The tap density of the artificial graphite material B is 1.1-1.

3.

22. The artificial graphite material B as described in claim 14, wherein, The degree of graphitization of the artificial graphite material B is above 91%.

23. The artificial graphite material B as described in claim 22, wherein, The degree of graphitization of the artificial graphite material B is 92%-94%.

24. The artificial graphite material B as described in claim 14, wherein, The specific capacity of the artificial graphite material B is above 340 mAh / g.

25. The artificial graphite material B as described in claim 24, wherein, The specific capacity of the artificial graphite material B is 340-350 mAh / g.

26. A method for preparing an artificial graphite material A, comprising the following steps in sequence: (A1) Provide raw materials, crush, and shape; (A2) Granulation; (A3) Graphitization treatment; (A4) Surface roughening treatment to obtain the artificial graphite material; in, The artificial graphite material A is composed of secondary particles, and the surface roughness η of the artificial graphite material A is... A Satisfy: 6 η A 12; The degree of graphitization of the artificial graphite material A is above 92%.

27. The method for preparing artificial graphite material A as described in claim 26, wherein, The surface roughness of the secondary particles before graphitization is 4-6.

28. The method for preparing artificial graphite material A as described in claim 26, wherein, The surface roughening treatment includes: The materials are placed in the blending machine and processed at a specific rotation speed. The specific rotational speed is 500-1000 r / m. The processing time is 3-60 minutes.

29. The method for preparing artificial graphite material A as described in claim 28, wherein, The specific rotational speed is 600-800 r / m.

30. The method for preparing artificial graphite material A as described in claim 28, wherein, The processing time is 5-20 minutes.

31. The method for preparing artificial graphite material A as described in claim 26, wherein, The surface roughening treatment includes: Place the material in the granulation vessel and continuously circulate dry air; The temperature is raised to the processing temperature, and the processing is carried out at this temperature, which is 300-800°C. C; The processing time is 1-8 hours.

32. The method for preparing artificial graphite material A as described in claim 31, wherein, The processing temperature is 400-600°C. C.

33. The method for preparing artificial graphite material A as described in claim 31, wherein, The processing time is 2-4 hours.

34. A method for preparing an artificial graphite material B, comprising the following steps in sequence: (B1) Provide raw materials, crush, and shape; (B2) Graphitization treatment; (B3) Surface roughening treatment to obtain the artificial graphite material; in, The artificial graphite material B is composed of primary particles, and the surface roughness η of the artificial graphite material is... B Satisfies: 2.5 η B 5; The volume average particle size Dv50 of the artificial graphite material B B Satisfy: 5μm Dv50 B 12μm.

35. The method for preparing artificial graphite material B as described in claim 34, wherein, The surface roughness of the primary particles before graphitization is 1.5-3.

36. The method for preparing artificial graphite material B as described in claim 34, wherein, The surface roughening treatment includes: The materials are placed in the blending machine and processed at a specific rotation speed. The specific rotational speed is 800-1000 r / m. The processing time is 20-60 minutes.

37. The method for preparing artificial graphite material B as described in claim 36, wherein, The specific rotational speed is 850-950 r / m.

38. The method for preparing artificial graphite material B as described in claim 36, wherein, The processing time is 30-50 minutes.

39. The method for preparing artificial graphite material B as described in claim 34, wherein, The surface roughening treatment includes: Place the material in the granulation vessel and continuously circulate dry air; The temperature is raised to the processing temperature, and the processing is carried out at this temperature, which is 300-800°C. C; The processing time is 1-8 hours.

40. The method for preparing artificial graphite material B as described in claim 39, wherein, The processing temperature is 400-600°C. C.

41. The method for preparing artificial graphite material B as described in claim 40, wherein, The processing time is 2-4 hours.

42. A secondary battery, wherein, The secondary battery includes a negative electrode sheet, and the negative electrode sheet includes a negative electrode active material. The negative electrode active material includes: artificial graphite material A according to any one of claims 1-13 and / or artificial graphite material B according to any one of claims 14-25; or, it includes: artificial graphite material A prepared by the method according to any one of claims 26-33 and / or artificial graphite material B prepared by the method according to any one of claims 34-41.

43. An electrical device comprising the secondary battery of claim 42.

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