Graphite material and preparation method thereof, negative pole piece, battery and electric device

Abstract

The invention discloses a graphite material and a preparation method thereof, a negative pole piece, a battery and an electric device. The preparation method of the graphite material comprises the following steps: crushing a green coke raw material to obtain green coke granules; carrying out oxidation treatment on the green coke granules at the temperature of more than or equal to 600 DEG C to obtain an oxide material; and graphitizing the oxide material to obtain the graphite material. The graphite material prepared in the invention has good compaction density and good gram volume, and can improve the energy density of a battery when being used in a battery negative electrode, so the graphite material has good application prospects when being used as a battery negative electrode active material.

Description

Technical Field

[0001] The present application belongs to the technical field of battery materials, and specifically relates to a graphite material and a preparation method thereof, a negative electrode sheet, a battery, and an electrical device. Background Art

[0002] New energy vehicles have been developing rapidly in recent years. The battery drive system is the main factor affecting the performance and cost of new energy vehicles. Secondary batteries have become the preferred power supply solution in the current new energy vehicle battery drive system due to their high energy density, low memory effect and high operating voltage.

[0003] For lithium-ion batteries, graphite-based materials are primarily used as negative electrode active materials. Graphite is widely available, easy to prepare, and has relatively stable electrochemical properties. However, to further increase battery energy density, the compaction density of graphite materials used in negative electrodes needs to be improved. Summary of the Invention

[0004] In view of the above problems, the present application provides a graphite material and a preparation method thereof, a negative electrode plate, a battery and an electrical device, aiming to solve the technical problem of how to increase the compaction density of the graphite material to increase the energy density of the battery.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a graphite material, comprising:

[0006] Crushing the raw coke material to obtain coke pellets;

[0007] The coke particles are oxidized at a temperature greater than or equal to 600° C. to obtain an oxide material;

[0008] The oxide material is graphitized to obtain a graphite material.

[0009] By using green coke as a raw material for preparing graphite materials, crushing the green coke raw material into green coke particles, and then performing an oxidation treatment at a temperature greater than or equal to 600°C, the green coke raw material can not only be pre-calcined to reduce volatile matter, but also the surface of the green coke particles can be uniformly micro-oxidized, thereby improving the adhesion of the surface of the green coke particles and increasing the specific surface area. In this way, after the subsequent graphitization treatment, the finished graphite materials can be more tightly bonded, thereby increasing the compaction density of the graphite material. The graphite material prepared in this embodiment of the present application has a good compaction density and good gram capacity. It can be used in the negative electrode of a battery to improve the energy density of the battery. Therefore, it has a good application prospect as a negative electrode active material for a battery.

[0010] In some embodiments, the green coke particles are oxidized at a temperature of 600-900°C.

[0011] Under the temperature condition of 600-900℃, not only can the coke particles be oxidized better, but also the graphite material can have a good yield.

[0012] In some embodiments, the oxidation treatment step includes placing the green coke particles in an atmosphere containing an oxidant and subjecting them to heat treatment under the temperature conditions.

[0013] The coke particles are placed in an atmosphere containing an oxidant for heat treatment, so that oxidation can be more effectively achieved on the surface of the coke particles in an atmosphere of a solid-gas two-phase system.

[0014] In some embodiments, the oxidant comprises at least one of oxygen, chlorine, fluorine and nitric oxide; and / or,

[0015] The volume fraction of the oxidant in the atmosphere is 21-30%.

[0016] The above oxidant can effectively oxidize the surface of the coke particles, and the oxidant atmosphere with the above volume fraction can stably perform micro-oxidation.

[0017] In some embodiments, the heat treatment time is 0.5-2 hours.

[0018] The surface of the green coke particles can be slightly oxidized within the above time.

[0019] In some embodiments, the oxidation treatment frequency of the green coke particles is 200-500 kg / h, the oxidant-containing atmosphere is continuously introduced into the green coke particles, and the ventilation rate of the oxidant-containing atmosphere is 200-300 m / h. 3 / h.

[0020] Placing the coke particles in an atmosphere containing an oxidant for oxidation treatment under the above-mentioned parameter conditions can not only fully oxidize the coke particles, but also prevent them from being over-oxidized, thereby reducing the loss of the coke particles and improving their oxidation efficiency.

[0021] In some embodiments, the particle size Dv50 of the coke pellets obtained by crushing the coke raw material is 6-10 μm.

[0022] The green coke particles with the above parameters not only have obvious micro-oxidation effects, but also the obtained graphite material products are easy to recycle and the product particles are more regular.

[0023] In some embodiments, the coke raw material includes at least one of needle coke, petroleum coke, and pitch coke.

[0024] The above-mentioned types of raw coke materials are widely available and easy to obtain.

[0025] In some embodiments, the true density of the coke raw material is 1.2-1.5 g / c; or

[0026] The raw coke material includes at least one of low-sulfur coke and medium-sulfur coke. The sulfur content of the low-sulfur coke is lower than 0.1%, and the sulfur content of the medium-sulfur coke is 0.1-3%.

[0027] By using the above-mentioned types of coke raw materials as raw materials for preparing graphite materials and following the process flow of the preparation method of the embodiments of the present application, graphite materials with significantly improved compaction density can be obtained, and the graphite material products have high purity and stable electrochemical properties.

[0028] In a second aspect, an embodiment of the present application provides a graphite material prepared by the preparation method provided in the first aspect of the embodiment of the present application.

[0029] The graphite material according to the embodiment of the present application is prepared by a preparation method unique to the embodiment of the present application. Therefore, the graphite material according to the embodiment of the present application has a good compaction density and good specific capacity, and can be used in the negative electrode of the battery to improve the energy density of the battery.

[0030] In some embodiments, the compacted density of the graphite material is 1.65-2.05 g / cm 3 , optionally, a compacted density of 1.85-2.05 g / cm 3 .

[0031] The compacted density of the graphite material is greater than that of conventional graphite, which can significantly increase the energy density of the battery.

[0032] In a third aspect, an embodiment of the present application provides a negative electrode plate, comprising a negative electrode current collector and a negative electrode active layer bonded to at least one surface of the negative electrode current collector, wherein the negative electrode active layer contains the graphite material provided in the second aspect of the embodiment of the present application.

[0033] Since the negative electrode plate contains the graphite material unique to the embodiment of the present application, the negative electrode plate of the embodiment of the present application has a good compaction density and can significantly improve the energy density of the battery when used in the battery.

[0034] In a fourth aspect, an embodiment of the present application provides a battery, characterized in that the battery includes the negative electrode plate provided in the third aspect of the embodiment of the present application.

[0035] The battery uses the negative electrode provided in the third aspect of the embodiment of the present application, and thus has a good energy density.

[0036] In a fifth aspect, an embodiment of the present application provides an electrical device, which includes the battery provided in the fourth aspect of the embodiment of the present application.

[0037] By adopting the battery provided in the fourth aspect of the embodiment of the present application, such an electrical device has a high energy density and can work better.

[0038] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0040] Figure 1 This is a schematic diagram of the battery cell structure of an embodiment of a secondary battery of the present application;

[0041] Figure 2 for Figure 1 An exploded schematic diagram of the battery cell shown;

[0042] Figure 3 This is a schematic structural diagram of an embodiment of a battery module of the present application;

[0043] Figure 4 This is a schematic structural diagram of an embodiment of a battery pack of the present application;

[0044] Figure 5 for Figure 4 Schematic diagram of the exploded structure of the battery pack shown;

[0045] Figure 6 Schematic diagram of an embodiment of an electrical device including the secondary battery of an embodiment of the present application as a power source.

[0046] Description of reference numerals:

[0047] 10 - battery cell; 11 - housing; 12 - top cover assembly; 13 - electrode assembly; 20 - battery module; 30 - battery pack; 31 - upper case; 32 - lower case. DETAILED DESCRIPTION

[0048] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0050] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0051] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0052] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0053] In the description of the embodiments of this application, the term "plurality" refers to two or more (including two). Similarly, "multiple groups" refers to two or more (including two groups), and "multiple sheets" refers to two or more (including two sheets). "At least one" refers to more than one (including one, two, three, etc.).

[0054] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0055] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0056] With the increasing depletion of traditional energy resources, the development of new energy storage devices is gaining increasing attention. Secondary batteries, in particular, have attracted considerable attention due to their high energy density, high theoretical capacity, excellent cycle stability, and environmentally friendly properties. Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles. As the application areas of secondary batteries as power batteries continue to expand, market demand is also growing, creating an urgent need to increase the energy density of secondary batteries.

[0057] Graphite is an allotrope of carbon, generally classified into two categories: natural graphite and artificial graphite. Natural graphite can be divided into flake graphite, earthy graphite, and block graphite. Because natural graphite primarily comes from graphite deposits, mined graphite contains a high level of impurities, requiring beneficiation to reduce its impurity content before use. Artificial graphite broadly refers to graphite materials obtained through organic carbonization followed by high-temperature graphitization. It is generally made from easily graphitizable materials such as petroleum coke, needle coke, and pitch coke. It undergoes a series of processes, including batching, kneading, molding, roasting, graphitization (high-temperature heat treatment), and machining, resulting in a relatively long production cycle.

[0058] For lithium-ion batteries that use graphite as the negative electrode active material, graphite is not only widely available and easy to prepare, but also has relatively stable electrochemical properties, is environmentally friendly, and is recyclable, so it can be used well in batteries; however, in order to further improve battery performance such as energy density, the graphite material used as the negative electrode active material still needs to be further improved.

[0059] Based on the above considerations, in order to improve the compaction density of graphite, the embodiment of the present application develops a method for preparing graphite material, by oxidizing the coke particles formed by crushing the coke under certain temperature conditions. Such a process can make the surface of the coke particles uniformly micro-oxidized, thereby improving the adhesion of the coke particles and increasing the specific surface area, thereby improving the cohesion and tightness of the finished graphite material after graphitization, thereby improving the compaction density of the graphite material. The graphite material prepared by this technical solution is not only simpler than the existing technical process, but also can improve the compaction density at the same time. When used in batteries, it can increase the energy density of the battery. The specific solution is as follows.

[0060] Graphite material and preparation method thereof

[0061] In a first aspect, an embodiment of the present application provides a method for preparing a graphite material, comprising:

[0062] S01: crushing the raw coke material to obtain coke pellets;

[0063] S02: oxidizing the coke pellets at a temperature greater than or equal to 600° C. to obtain an oxide material;

[0064] S03: Graphitizing the oxide material to obtain a graphite material.

[0065] Green coke raw material generally refers to raw coke before calcination and can be divided into oil-based coke and coal-based coke. It is the raw material for producing artificial graphite. Green coke pellets refer to granular raw coke pellets formed after physical and mechanical crushing of raw coke raw materials. They differ from green coke raw materials in their apparent particle size. Oxide materials are oxidized materials obtained by surface oxidation of green coke pellets under certain temperature conditions. They differ from green coke pellets primarily in that their surface has been oxidized at a temperature of 600°C or higher.

[0066] The embodiment of the present application utilizes green coke as a raw material for preparing graphite materials. After the green coke raw material is crushed into green coke pellets, an oxidation treatment is performed at a temperature greater than or equal to 600°C. Under this temperature condition, not only can the green coke pellets be pre-calcined to reduce volatile matter, but the surface of the green coke particles can also be uniformly micro-oxidized, thereby improving the adhesion of the surface of the green coke particles and increasing the specific surface area. In this way, after subsequent graphitization treatment, the finished graphite materials can be more tightly bonded, thereby increasing the compaction density of the graphite material. The graphite material prepared in this embodiment of the present application has a good compaction density and good gram capacity. It can be used in the negative electrode of a battery to improve the energy density of the battery. Therefore, it has a good application prospect as a negative electrode active material for a battery.

[0067] In step S01:

[0068] Green coke raw material is the raw coke before calcination and generally contains a certain amount of ash, volatile matter, and sulfur. Ash content generally refers to the content of metals such as iron, calcium, and magnesium, as well as various metal oxides and inorganic salts in the green coke raw material. A higher ash content means a higher content of inorganic matter in the green coke raw material. Excessive ash content is difficult to completely eliminate during the graphitization process. Volatile matter generally refers to the content of organic matter such as resin and oil in the green coke. Excessive volatile matter may cause graphite agglomeration during graphitization, reducing the graphitization yield.

[0069] Therefore, in the embodiments of the present application, the raw coke material and the oxidized oxide material may include: ash content: ≤ 0.2%, illustratively, ash content: ≤ 0.1%; volatile matter: 5-9%, illustratively, volatile matter: 6-8%. The raw coke material with the above composition is well suited for preparing the graphite material product of the embodiments of the present application.

[0070] Specifically, raw coke materials can be classified into low-sulfur coke, medium-sulfur coke, and high-sulfur coke based on their sulfur content. Low-sulfur coke has a sulfur content of less than 0.1%, medium-sulfur coke has a sulfur content of 0.1-3%, and high-sulfur coke has a sulfur content of more than 3%. Excessively high sulfur content can affect graphite crystallite growth. Therefore, in the embodiments of the present application, the raw coke materials can include at least one of low-sulfur coke and medium-sulfur coke, which can better promote graphite crystallite growth.

[0071] Specifically, the true density of the raw coke material in the embodiments of the present application can be 1.2-1.5 g / cc. True density refers to the actual mass of solid matter per unit volume when the material is absolutely dense, and is referred to as true density. "cc" refers to cubic centimeters, a unit of volume, and "g" refers to grams, a unit of weight. "g / cc" represents the actual mass of the material per cubic centimeter. The raw coke material is oxidized at a temperature greater than or equal to 600°C to further reduce the volatile matter, resulting in a true density of 1.8-2.1 g / cc after oxidation.

[0072] In the embodiment of the present application, the true density test method comprises the following steps: (1) pre-treatment: taking a clean and dry sample cup and placing it on a balance, zeroing it, adding a powder sample into the sample cup, which occupies about 1 / 2 of the volume of the sample cup, and recording the sample mass; (2) placing the sample cup containing the sample in a true density tester, sealing the test system, introducing helium according to the program, detecting the pressure of the gas in the sample chamber and the expansion chamber, and then calculating the true volume according to Bohr's law (PV=nRT), thereby calculating the true density; wherein P is pressure (Pa), V is volume (m 3 ), n refers to the amount of gas substance (mol), T is the temperature (K), and R is the molar gas constant 8.31 J / (mol·K).

[0073] In some embodiments, the raw coke feedstock may include at least one of needle coke, petroleum coke, and pitch coke. Needle coke may include oil-based needle coke and coal-based needle coke. Petroleum coke is a product obtained by distilling crude oil to separate light and heavy oils, followed by thermal cracking of the heavy oil. Pitch coke is the solid residue obtained after high-temperature dry distillation or delayed coking of coal tar pitch.

[0074] By using the aforementioned raw coke materials as raw materials for preparing graphite materials, and following the process flow of the preparation methods of the embodiments of the present application, graphite materials with significantly increased compaction density can be obtained. Furthermore, the graphite material products are high in purity and have stable electrochemical properties. Specifically, in the preparation methods of the embodiments of the present application, low-sulfur coke or medium-sulfur coke from petroleum coke can be used as raw materials for preparing the graphite materials.

[0075] In some embodiments, the particle size Dv50 of the green coke pellets obtained by the crushing of the green coke raw material is 6-10 μm, illustratively including but not limited to any one of 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, and 10 μm, or a range therebetween.

[0076] The size of a particulate material is called particle size, the percentage of particles within different size ranges is called particle size distribution, and volume distribution particle size is the cumulative particle size calculated based on particle volume. For example, Dv50 represents the particle size corresponding to the cumulative volume particle size distribution percentage of a sample reaching 50%. In specific embodiments, a particle size analyzer can be used to measure the average particle size. The specific surface area (BET) refers to the total surface area per unit mass of a material. The specific surface area of ​​the graphite in the examples of this application was measured using the BET method using a fully automatic BSD-BET-A nitrogen adsorption specific surface area analyzer.

[0077] Sphericity is an indicator used to describe spherical shapes, reflecting the uniformity and consistency of a material's particle shape. The higher the sphericity, the closer the particle shape is to a perfect sphere. The closer the particle's morphology is to a sphere, the closer its sphericity is to 1. Particle shape can generally be observed using an optical microscope or scanning electron microscope, and sphericity can be calculated using image processing algorithms.

[0078] For example, the raw coke material can be crushed using a mechanical mill or roller mill, followed by classification to adjust the particle size distribution of the resulting pellets, resulting in coke pellets with a Dv50 of 6-10 μm. This not only allows for good shaping, but also ensures that the final graphite material has a good compaction density, thereby improving battery kinetic performance. Furthermore, a shaping machine is used to shape the crushed material and remove fine powder to obtain coke pellets with good sphericity.

[0079] The green coke pellets with the above parameters have a small particle size, a large specific surface area, and a significant micro-oxidation effect. Moreover, through physical shaping, the green coke pellets are made more regular, with improved sphericity, making them easier to process.

[0080] In step S02:

[0081] In the embodiments of the present application, the oxidation treatment temperature of the green coke particles plays an important role. Pre-calcination at a temperature of 600°C or higher can reduce volatile matter and enhance the surface adhesion of the green coke particles, thereby increasing the compacted density of the graphite material. Examples of such temperatures include, but are not limited to, any of 600°C, 650°C, 700°C, 720°C, 750°C, 780°C, 800°C, 850°C, 900°C, 950°C, 980°C, and 1000°C, or a range of values ​​greater than or equal to any of these values. If the temperature is too low, for example, below 600°C, illustratively, the temperature is 300-500°C, and only very slight oxidation can occur on the surface of the particles, which is generally only beneficial for coating and modifying the surface of the particles, but the compaction density of the material is basically unchanged. If the temperature is too high, for example, above 900°C, the compaction density is difficult to increase further after reaching a certain level. As the temperature rises, energy loss is large, and the final yield of the graphite material is affected, thereby increasing the process cost. Therefore, when the oxidation treatment temperature is 600-900°C, a certain degree of oxidation occurs on the surface of the particles, and the specific surface area is greatly increased. At the same time, due to the increase in adhesion, the compaction density is significantly improved, and the yield is high and the energy consumption is low.

[0082] In some embodiments, the oxidation treatment step includes placing the green coke particles in an atmosphere containing an oxidant and heat treating them under the aforementioned temperature conditions. Heat treating the green coke particles in an atmosphere containing an oxidant allows for more effective surface oxidation of the green coke particles in a solid-gas two-phase atmosphere.

[0083] In some embodiments, the green coke pellets are placed in an atmosphere containing an oxidant and heat treated at a temperature for a time period of 0.5-2 hours, illustratively including but not limited to any one of 0.5 hours, 0.8 hours, 1 hour, 1.5 hours, 1.8 hours, and 2 hours, or any range therebetween. Micro-treatment within this time range can achieve micro-oxidation of the surface of the green coke pellets.

[0084] In some embodiments, the oxidant includes at least one of oxygen, chlorine, fluorine, and nitric oxide; the above oxidants can effectively oxidize the surface of the coke particles.

[0085] In some embodiments, an oxidant-containing atmosphere is an oxidizing atmosphere, comprising an oxidant gas; wherein the volume fraction of the oxidant in the atmosphere is 21-30%, i.e., the volume fraction of the oxidant gas in the entire oxidizing atmosphere mixture is 21-30%. For example, using an oxidant gas and a nitrogen carrier gas as an example, the oxidant gas and nitrogen constitute a mixed gas of the oxidizing atmosphere, and the volume fraction of the oxidant gas in the mixed gas is 21-30%. Oxidant atmospheres with these volume fractions can stably perform micro-oxidation.

[0086] In order to reduce costs, the embodiment of the present application can directly use air as the oxidizing atmosphere, wherein the nitrogen volume fraction of the air is about 78%, and the oxygen volume fraction is about 21%.

[0087] In some embodiments, the oxidation frequency of the coke pellets is 200-500 kg / h, the oxidant-containing atmosphere is continuously introduced into the coke pellets, and the ventilation rate of the oxidant-containing atmosphere is 200-300 m / h. 3 / h; For example, the oxidation treatment frequency of the green coke pellets includes but is not limited to any one of 200kg / h, 220kg / h, 240kg / h, 250kg / h, 280kg / h, 300kg / h, 350kg / h, 380kg / h, 400kg / h, 450kg / h, 500kg / h or any range between two of them, and the ventilation rate of the atmosphere containing the oxidant includes but is not limited to 200m 3 / h、220m 3 / h、240m 3 / h、250m 3 / h、280m 3 / h、300m 3 / h, or any range between them. Under the aforementioned parameter conditions, oxidizing the coke pellets in an atmosphere containing an oxidant not only fully oxidizes the coke pellets but also prevents over-oxidation, thereby reducing coke pellet loss and improving oxidation efficiency.

[0088] In some embodiments, the continuous horizontal reactor is heated to 600-900°C, the furnace speed is 2-6 r / min, and the air flow rate is 200-300m 3 The raw coke pellets are oxidized at a rate of 200-500 kg / h. Material is fed into the feed port and fed into the chamber at a constant speed via a rotary feeder. After micro-oxidation within the chamber, the material cools and falls through the discharge port into a discharge bag, resulting in an oxide material with increased powder pressure.

[0089] In step S03:

[0090] The oxide material can be graphitized to obtain the final graphite material product. The graphitization temperature can be 1800-3000°C. Specifically, the oxide material obtained by heat treatment is added to a graphitization furnace and heated to 1800-3000°C for graphitization to obtain the artificial graphite material product.

[0091] In a second aspect, an embodiment of the present application provides a graphite material prepared by the preparation method provided in the first aspect of the embodiment of the present application.

[0092] The graphite material according to the embodiment of the present application is prepared by a preparation method unique to the embodiment of the present application. Therefore, the graphite material according to the embodiment of the present application has a good compaction density and good specific capacity, and can be used in the negative electrode of the battery to improve the energy density of the battery.

[0093] In some embodiments, the graphite material has a compacted density of 1.65-2.05 g / cm 3 ; Exemplarily, including but not limited to 1.65g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.05g / cm 3 Any point value or any range value between the above; Specifically, the compacted density is 1.85-2.05g / cm 3 Accordingly, energy density is the product of compacted density and gram capacity.

[0094] Negative electrode

[0095] In a third aspect, an embodiment of the present application provides a negative electrode plate, comprising a negative electrode current collector and a negative electrode active layer bonded to at least one surface of the negative electrode current collector, wherein the negative electrode active layer contains the graphite material provided in the second aspect of the embodiment of the present application.

[0096] Since the negative electrode plate contains the graphite material unique to the embodiment of the present application, the negative electrode plate of the embodiment of the present application has a good compaction density and can significantly improve the energy density of the battery when used in the battery.

[0097] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0098] In some embodiments, the negative electrode active layer of the negative electrode sheet may further include a conductive agent and a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] In some embodiments, the negative electrode active layer may optionally include other additives, such as a dispersant, a thickener (such as sodium carboxymethyl cellulose), and the like.

[0100] Battery

[0101] In a fourth aspect, an embodiment of the present application provides a battery, which includes the negative electrode sheet of the third aspect of the embodiment of the present application.

[0102] The battery of the embodiment of the present application uses the negative electrode plate provided in the third aspect of the embodiment of the present application, and thus has a good energy density. Therefore, such a battery is easy to mass-produce, has low cost, and is environmentally friendly.

[0103] In one embodiment, the battery is a secondary battery, including a lithium-ion battery or a sodium-ion battery.

[0104] In one embodiment, the secondary battery includes a positive electrode sheet and a negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet provided in the third aspect of the embodiment of the present application.

[0105] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode active layer provided on at least one surface of the positive electrode current collector. The positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0106] In some embodiments, the positive electrode active layer contains a positive electrode active material, and the positive electrode active material may include a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05At least one of lithium iron phosphate (LiFePO4) and its modified compounds. Examples of lithium phosphates containing an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. The weight ratio of the positive electrode active material in the positive electrode active layer is 80-100 weight percent, based on the total weight of the positive electrode active layer.

[0107] In some embodiments, the positive electrode active layer may further optionally include a binder. As an example, the binder in the positive electrode active layer may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode active layer is 0-20 weight %, based on the total weight of the positive electrode active layer.

[0108] In some embodiments, the positive electrode active layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, carbon black (e.g., acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode active layer is 0-20 weight %, based on the total weight of the positive electrode active layer.

[0109] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0110] In one embodiment, the separator may be made of materials known in the art for battery separators. For example, the separator base film may include one or more of a polyethylene film, a polypropylene film, and a polyvinylidene fluoride film.

[0111] The electrolyte conducts ions between the positive and negative electrodes. The present invention does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0112] In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent. If the secondary battery is a lithium ion battery, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate. If the secondary battery is a sodium ion battery, the corresponding electrolyte salt is replaced with a sodium salt.

[0113] In some embodiments, the solvent in the electrolyte can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0114] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0115] In some embodiments, the secondary battery of the present application may include any one of a battery cell, a battery module, and a battery pack. A battery cell refers to a battery housing and a battery cell encapsulated in the battery housing. The shape of the battery cell is not particularly limited and may be cylindrical, square, or any other shape. Figure 1 The battery cell 10 shown has a square structure.

[0116] In some embodiments, as Figure 2 As shown, the outer packaging of the battery cell 10 may include a shell 11 and a top cover assembly 12. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the top cover assembly 12 is used to cover the opening to close the receiving cavity. The positive electrode, diaphragm and negative electrode sheet contained in the secondary battery of the embodiment of the present application can be formed into an electrode assembly 13 through a winding process and / or a lamination process. The electrode assembly 13 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 13. The number of electrode assemblies 13 contained in the battery cell 10 may be one or more, which can be adjusted according to actual needs.

[0117] The preparation method of the battery cell 10 is well known. In some embodiments, the positive electrode sheet, separator, negative electrode sheet, and electrolyte can be assembled to form the battery cell 10. As an example, the positive electrode sheet, separator, and negative electrode sheet can be wound or laminated to form the electrode assembly 13. The electrode assembly 13 is placed in an outer package, dried, and then injected with electrolyte. The battery cell 10 is then vacuum packaged, allowed to stand, formed, and shaped.

[0118] A battery module is assembled from the battery cells 10 , that is, it may contain a plurality of battery cells 10 , and the specific number can be adjusted according to the application and capacity of the battery module.

[0119] In some embodiments, Figure 3 FIG. 2 is a schematic diagram of a battery module 20 as an example. Figure 3 As shown, in the battery module 20, the plurality of battery cells 10 may be arranged in sequence along the length direction of the battery module 20. Of course, they may also be arranged in any other manner. The plurality of battery cells 10 may further be fixed by fasteners.

[0120] Optionally, the battery module 20 may further include a housing having an accommodation space, and the plurality of battery cells 10 may be accommodated in the accommodation space.

[0121] A battery pack is assembled from the battery cells 10 described above, and may contain multiple battery cells 10, wherein multiple battery cells 10 may be assembled into the battery module 20 described above. The specific number of battery cells 10 or battery modules 20 contained in a battery pack may be adjusted according to the application and capacity of the battery pack.

[0122] As in the embodiment, Figure 4 and Figure 5 The figure is a schematic diagram of an example battery pack 30. The battery pack 30 may include a battery box and multiple battery modules 20 disposed within the battery box. The battery box comprises an upper case 31 and a lower case 32. The upper case 31 covers the lower case 32 and forms an enclosed space for accommodating the battery modules 20. The multiple battery modules 20 may be arranged in any manner within the battery box.

[0123] In some embodiments, as Figure 4As shown, the outer packaging of the battery cell 20 may include a shell 21 and a top cover assembly 22. The shell 21 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 21 has an opening connected to the receiving cavity, and the top cover assembly 22 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the isolation membrane and the negative electrode sheet contained in the secondary battery of the embodiment of the present application can be formed into an electrode assembly 23 through a winding process and / or a lamination process. The electrode assembly 23 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 23. The number of electrode assemblies 23 contained in the battery cell 20 may be one or more, which can be adjusted according to actual needs.

[0124] The preparation method of the battery cell 20 is well known. In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be assembled with an electrolyte to form the battery cell 20. As an example, the positive electrode sheet, separator, and negative electrode sheet can be wound or laminated to form an electrode assembly 23. The electrode assembly 23 is then placed in an outer package, dried, and then injected with electrolyte. The battery cell 20 is then vacuum packaged, allowed to stand, formed, and shaped.

[0125] A battery module is assembled from the battery cells 20 , that is, it may contain a plurality of battery cells 20 , and the specific number can be adjusted according to the application and capacity of the battery module.

[0126] In some embodiments, Figure 5 FIG is a schematic diagram of a battery module 30 as an example. Figure 5 As shown, in the battery module 30, the plurality of battery cells 20 may be arranged in sequence along the length direction of the battery module 30. Of course, they may also be arranged in any other manner. The plurality of battery cells 20 may further be fixed by fasteners.

[0127] Optionally, the battery module 30 may further include a housing having an accommodation space, and the plurality of battery cells 20 may be accommodated in the accommodation space.

[0128] A battery pack is assembled from the battery cells 20 described above, and may contain multiple battery cells 20, wherein multiple battery cells 20 may be assembled into the battery module 30 described above. The specific number of battery cells 20 or battery modules 30 contained in a battery pack may be adjusted according to the application and capacity of the battery pack.

[0129] As in the embodiment, Figure 6 Figure 4 is a schematic diagram of an example battery pack 40. The battery pack 40 may include a battery box and multiple battery modules 30 disposed within the battery box. The battery box comprises an upper case 41 and a lower case 42. The upper case 41 covers the lower case 42 and forms an enclosed space for accommodating the battery modules 30. The multiple battery modules 30 may be arranged in any manner within the battery box.

[0130] Electrical devices

[0131] In a fifth aspect, embodiments of the present application provide an electrical device comprising the battery of the fourth aspect of the present application. The battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device provided by embodiments of the present application is low-cost and environmentally friendly.

[0132] Electrical devices may include, but are 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, satellites, energy storage systems, etc. These electrical devices may be equipped with secondary battery cells, battery modules, or battery packs based on their intended use.

[0133] Figure 6 The diagram is a schematic diagram of an exemplary electric device. This device is 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 this device, a battery pack or battery module can be used.

[0134] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0135] Example

[0136] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0137] Example 1

[0138] A method for preparing a graphite material comprises the following steps:

[0139] 1) Crushing and shaping of raw materials:

[0140] A raw coke material (petroleum coke, ash content: ≤0.2%; volatile matter: 5-9%; sulfur content: 0.5-4%; true density 1.2-1.5 g / cc) is provided, the raw coke material is crushed by a mechanical mill, and then graded after crushing. A shaping machine is used to shape the crushed material and remove fine powder, ultimately obtaining a raw coke pellet with a particle size Dv50 of 8.5 μm.

[0141] 2) Micro-oxidation treatment:

[0142] The continuous horizontal reactor was heated to 800°C, the furnace speed was 2 r / min, and the air (containing 21% oxygen) flow rate was 200 m 3 / h. The green coke pellets obtained in step 1) are fed into the chamber at a rate of 200 kg / h through the feed port. The pellets enter the chamber at a constant speed via a rotary feeder. After 0.5 h of micro-oxidation treatment within the chamber, the pellets cool and fall through the discharge port into a discharge bag, yielding an oxide material with increased powder pressure.

[0143] 3) Graphitization:

[0144] The oxide material obtained in the above step 2) is added into a graphitization furnace, and the temperature is raised to 3000° C. for graphitization treatment to obtain a finished graphite material.

[0145] Example 2

[0146] A method for preparing a graphite material differs from Example 1 in that the temperature in the micro-oxidation treatment step is 600° C. Other steps are the same as Example 1.

[0147] Example 3

[0148] A method for preparing a graphite material differs from Example 1 in that the temperature in the micro-oxidation treatment step is 700° C. Other steps are the same as Example 1.

[0149] Example 4

[0150] A method for preparing a graphite material differs from Example 1 in that the temperature in the micro-oxidation treatment step is 900° C. Other steps are the same as Example 1.

[0151] Example 5

[0152] A method for preparing a graphite material, which differs from Example 1 in that the temperature in the micro-oxidation treatment step is 920° C. Other aspects are the same as Example 1.

[0153] Example 6

[0154] A method for preparing a graphite material, which differs from Example 1 in that, in the micro-oxidation treatment step, the heat treatment time is 2 hours. All other aspects are the same as Example 1.

[0155] Example 7

[0156] A method for preparing a graphite material differs from Example 1 in that, in the micro-oxidation treatment step, air is replaced with an atmosphere having an oxygen volume fraction of 30% (the carrier gas is nitrogen). Other aspects are the same as Example 1.

[0157] Example 8

[0158] A method for preparing a graphite material differs from Example 1 in that, in the micro-oxidation treatment step, air is replaced with an atmosphere containing 30% chlorine gas by volume (the carrier gas is nitrogen). Other aspects are the same as Example 1.

[0159] Example 9

[0160] A method for preparing a graphite material, which differs from Example 1 in that, in the micro-oxidation treatment step: the oxidation treatment frequency of the coke particles is 500 kg / h, the air ventilation rate is 300 m 3 / h. Other aspects are the same as in Example 1.

[0161] Example 10

[0162] A method for preparing a graphite material differs from Example 1 in that, in the steps of crushing and shaping the raw material, a coke pellet having a particle size Dv50 of 6 μm is obtained. All other aspects are the same as Example 1.

[0163] Example 11

[0164] A method for preparing a graphite material differs from Example 1 in that, in the steps of crushing and shaping the raw material, a coke pellet with a particle size Dv50 of 10 μm is obtained. All other aspects are the same as Example 1.

[0165] Comparative Example 1

[0166] A method for preparing a graphite material, which differs from Example 1 in that the temperature in the micro-oxidation treatment step is 580° C. Other aspects are the same as Example 1.

[0167] Comparative Example 2

[0168] A method for preparing a graphite material, which differs from Example 1 in that, before the micro-oxidation treatment step: the crushed and shaped green coke particles are first calcined at 1400° C. for 12 hours, and then the micro-oxidation treatment step and graphitization step of Example 1 are performed.

[0169] Performance Testing

[0170] (1) Compaction density test

[0171] Refer to GB / T 24533-2009 and use an electronic pressure testing machine (such as UTM7305) to test. The steps include: placing graphite material powder on a special compaction mold, setting the pressure, and reading the thickness of the powder under pressure on the equipment to calculate the compaction density.

[0172] (2) Gram capacity test

[0173] The graphite material prepared above is mixed evenly with the conductive agent Super P, the binder PVDF (polyvinylidene fluoride) and the solvent NMP (N-methylpyrrolidone) in a mass ratio of 91.6:1.8:6.6 to prepare a slurry; the prepared slurry is coated on a copper foil current collector, dried in an oven and set aside; a metal lithium sheet is used as a counter electrode; a polyethylene (PE) film is used as an isolation membrane; ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is evenly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L; the above parts are assembled into a CR2430 button battery in an argon-protected glove box.

[0174] After the resulting button cell was left to rest for 12 hours, it was discharged at a constant current of 0.05C to 0.005V. After resting for 10 minutes, it was discharged at a constant current of 50μA to 0.005V. After resting for 10 minutes, it was discharged at a constant current of 10μA to 0.005V. The cell was then charged at a constant current of 0.1C to 2V, and the charge capacity was recorded. The ratio of the charge capacity to the mass of the graphite material is the gram capacity of the prepared graphite material.

[0175] The test results are shown in Table 1.

[0176] Table 1

[0177]

[0178] From the data in Table 1, we can see that:

[0179] Compared with Comparative Example 1, Examples 1-11 of the present application can significantly improve the compaction density and energy density of the graphite material by performing oxidation treatment at a temperature greater than or equal to 600°C. At the same time, after the oxidation treatment temperature exceeds 900°C, for example, in Example 5, the degree of improvement in the compaction density and energy density of the graphite material basically reaches the limit, and the final yield of the graphite material is reduced. By adjusting the parameters such as the time, feeding frequency, gas flow rate, and oxidant of the micro-oxidation treatment within the scope of the above embodiments, the compaction density and energy density of the graphite material can be improved. When the particle size and oxygen content of the coke particles are appropriately increased, the effect is better, and the above-mentioned Example 11 has the best effect.

[0180] In addition, in Comparative Example 2, the crushed and shaped green coke particles were first calcined at 1400°C for 12 hours, and then subjected to the same micro-oxidation treatment as in Example 1. The final compacted density and gram capacity of the graphite material obtained were basically equivalent to those in Example 1. However, because Comparative Example 2 had an additional calcination step before the micro-oxidation treatment, the complexity of the process was increased, and the energy consumption was increased, which was not conducive to large-scale production.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing a graphite material, characterized in that: include: Crushing the raw coke material to obtain coke pellets; The coke particles are oxidized at a temperature greater than or equal to 600° C. to obtain an oxide material; The oxide material is graphitized to obtain a graphite material.

2. The preparation method according to claim 1, wherein The green coke particles are oxidized at a temperature of 600-900°C.

3. The preparation method according to claim 1 or 2, wherein The oxidation treatment step includes placing the green coke particles in an atmosphere containing an oxidant and subjecting them to heat treatment under the temperature conditions.

4. The preparation method according to claim 3, wherein The oxidant comprises at least one of oxygen, chlorine, fluorine and nitric oxide; and / or, The volume fraction of the oxidant in the atmosphere is 21-30%.

5. The preparation method according to claim 3 or 4, characterized in that The heat treatment time is 0.5-2h.

6. The preparation method according to any one of claims 3 to 5, characterized in that The oxidation treatment frequency of the green coke particles is 200-500 kg / h, the oxidant-containing atmosphere is continuously introduced into the green coke particles, and the ventilation rate of the oxidant-containing atmosphere is 200-300 m / h. 3 / h.

7. The preparation method according to any one of claims 1 to 6, wherein The particle size Dv50 of the coke particles obtained by crushing the coke raw materials is 6-10 μm.

8. The preparation method according to any one of claims 1 to 7, wherein The raw coke material includes at least one of needle coke, petroleum coke and pitch coke.

9. The preparation method according to any one of claims 1 to 8, wherein The true density of the raw coke material is 1.2-1.5 g / cc; or The raw coke material includes at least one of low-sulfur coke and medium-sulfur coke. The sulfur content of the low-sulfur coke is lower than 0.1%, and the sulfur content of the medium-sulfur coke is 0.1-3%.

10. A graphite material, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 9.

11. The graphite material according to claim 10, wherein The compacted density of the graphite material is 1.65-2.05 g / cm 3 , optionally, a compacted density of 1.85-2.05 g / cm 3 .

12. A negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer bonded to at least one surface of the negative electrode current collector, characterized in that: The negative electrode active layer contains the graphite material according to claim 10 or 11.

13. A battery, characterized in that: The battery comprises the negative electrode sheet according to claim 12.

14. An electrical device, characterized in that: The electrical device comprises the battery according to claim 13.

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