Graphite material and preparation method therefor, secondary battery, and electric device

Abstract

The present application provides a graphite material and a preparation method therefor, a secondary battery, and an electric device. The crystallite size La along the a-axis direction of the graphite material ranges from 135 nm to 150 nm.

Description

Graphite materials and their preparation methods, secondary batteries and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application filed on July 31, 2024, application number 202411045706X, entitled "Graphite Material and Preparation Method Thereof, Secondary Battery and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to a graphite material and its preparation method, a secondary battery, and an electrical device. Background Technology

[0004] In recent years, lithium-ion batteries and other batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. With the continuous expansion of the application scope of lithium-ion batteries and other batteries, correspondingly higher requirements are being placed on battery performance.

[0005] How to make secondary batteries simultaneously achieve multiple electrochemical properties remains a topic that needs further research in this field. Summary of the Invention

[0006] The first aspect of this application provides a graphite material in which the crystallite size La along the a-axis direction is 135 nm to 150 nm.

[0007] When La is less than 135 nm, the crystallinity of graphite materials is insufficient, and the crystal structure is incomplete, which may worsen the cycle performance of the battery when used in a secondary battery. When La is greater than 150 nm, the excessive crystallization of graphite materials leads to significant crystal expansion, which may also worsen the cycle performance of the battery when used in a secondary battery. When the La of graphite materials is in the range of 135 nm to 150 nm, the graphite materials have a suitable specific capacity and less expansion during cycling. Using this type of graphite material in a secondary battery can effectively improve the cycle performance of the battery while maintaining a high energy density.

[0008] In some implementations, La is 140nm to 148nm.

[0009] In some embodiments, the crystallite size Lc along the c-axis of the graphite material is 20 nm to 40 nm.

[0010] In some embodiments, the graphite particles have a porous structure. This porous structure can buffer the expansion of the graphite material during battery cycling, which is beneficial for further improving the battery's cycle performance.

[0011] In some implementations, the volume percentage of the pore structure in the graphite material is 8% to 15%.

[0012] In some embodiments, the pore volume of the graphite material is 0.006 cm³. 3 / g~0.015cm 3 / g.

[0013] In some embodiments, the graphitization degree of the graphite material is 91% to 95%. Graphite materials with a graphitization degree within this range have a higher specific capacity, which is beneficial for improving the energy density of the battery.

[0014] In some embodiments, the true density of the graphite material is 2.2 g / cm³. 3 ~2.3g / cm 3 Graphite materials with a true density within this range are suitable for use in secondary batteries, as they facilitate the development of a high compaction density in the negative electrode active layer, thereby promoting an increase in battery energy density.

[0015] In some embodiments, the tap density of the graphite material is 1.1 g / cm³. 3 ~1.4g / cm 3 Graphite materials with tap density within this range are suitable for use in secondary batteries, as they facilitate the development of a higher tap density in the negative electrode active layer, thereby promoting an increase in battery energy density.

[0016] In some embodiments, the specific capacity of the graphite material is 340 mAh / g to 360 mAh / g. Graphite materials with specific capacities within this range can enable secondary batteries to have higher energy densities.

[0017] In some embodiments, the graphite material I D / I G It is 0.01-0.13; where, I D This indicates that the Raman spectrum of the material is at 1350±50 cm⁻¹. -1 The intensity of peak D at I G This indicates that the Raman spectrum of the material is at 1580±50 cm⁻¹. -1 The intensity of the G peak at that location.

[0018] In some embodiments, the volumetric particle size distribution (Dv50) of the graphite material is 8 μm to 18 μm.

[0019] In some embodiments, the volumetric particle size distribution (Dv90) of the graphite material is 20 μm to 35 μm.

[0020] In some embodiments, the volumetric particle size Dv10 of the graphite material is 2 μm to 8 μm.

[0021] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the graphite material is 1.0 to 1.8.

[0022] Meeting the above conditions in terms of graphite particle size distribution is beneficial to promoting the compaction of graphite materials, thereby enabling secondary batteries to have higher energy density.

[0023] The second aspect of this application provides a method for preparing graphite materials, comprising the following steps: washing anthracite raw materials to obtain de-ashed anthracite, wherein the ash content of the de-ashed anthracite is less than or equal to 2%; holding the de-ashed anthracite at 1800℃~2000℃ for 10h~15h, and then holding it at 2800℃~3000℃ for 10h~50h. Anthracite is formed in rock strata under long-term high temperature and high pressure conditions, and its internal structure contains a partially cryptocrystalline structure, which can lay the foundation for obtaining graphite materials with a larger La content. The longer holding time can promote the development of carbon layers in the planar direction, increase La content, and promote the improvement of battery energy density and cycle performance.

[0024] In some implementations, the ash content of the anthracite raw material is greater than 10%.

[0025] In some embodiments, the volatile matter content of the anthracite raw material is 3.5% to 6.5%.

[0026] In some implementations, the hydrogen content of the anthracite feedstock is 2% to 3%.

[0027] In some embodiments, the average maximum reflectance of the vitrinite in the anthracite raw material is 2% to 6%;

[0028] In some embodiments, the dry ash-free gross calorific value of the anthracite raw material is less than 34 MJ / kg to 35.1 MJ / kg.

[0029] A third aspect of this application provides a secondary battery, including a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, the negative electrode active layer including a negative electrode active material, the negative electrode active material including graphite material of any embodiment provided in the first aspect of this application.

[0030] The fourth aspect of this application provides an electrical device, including the secondary battery provided in the third aspect of this application. Attached Figure Description

[0031] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0032] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application.

[0033] Figure 2 is an exploded view of the secondary battery according to one embodiment of this application shown in Figure 1.

[0034] Figure 3 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0035] Figure 4 is a scanning electron microscope (SEM) image of the graphite material in Embodiment 1 of this application.

[0036] Figure 5 is a SEM image of the conventional petroleum coke graphite material in Comparative Example 3 of this application.

[0037] Explanation of reference numerals in the attached drawings: 1. Secondary battery; 11. Casing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device. Detailed Implementation

[0038] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] The "range" disclosed in this application can be defined in the form of 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 the specific range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently, and they can be combined arbitrarily; 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 also 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 "a–b" 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" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0041] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0044] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly. For example, a method including steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0045] In this application, unless otherwise stated, "A, such as B" means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0046] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0047] One embodiment of this application provides a graphite material. The crystallite size La along the a-axis of the graphite material is 135 nanometers (nm) to 150 nm. When La is less than 135 nm, the graphite material has insufficient crystallinity and incomplete crystal development, which may degrade the battery's cycle performance when used in a secondary battery. When La is greater than 150 nm, the excessive crystallization of the graphite material leads to significant crystal expansion, which may also degrade the battery's cycle performance when used in a secondary battery. When the La of the graphite material is in the range of 135 nm to 150 nm, the graphite material has a suitable specific capacity and exhibits less expansion during cycling. Using this graphite material in a secondary battery can enable the battery to achieve both high energy density and good cycle performance.

[0048] In some embodiments, as examples of choices for the graphite material La, the La value can be 135 nm, 135.9 nm, 136 nm, 137 nm, 138 nm, 139 nm, 139.7 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 145.6 nm, 146 nm, 147 nm, 148 nm, 149 nm, 149.4 nm, 150 nm, or any value within the range of any two of the above values. Optionally, La is between 140 nm and 148 nm. Graphite materials with La in the 140 nm to 148 nm range have higher capacity, which is beneficial for further improving the energy density of the battery.

[0049] In some embodiments, the crystallite size Lc along the c-axis of the graphite material is 20 nm to 40 nm. Optionally, the crystallite size Lc along the c-axis of the graphite material can be 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 26.6 nm, 26.8 nm, 27 nm, 27.2 nm, 27.7 nm, 28 nm, 29 nm, 29.1 nm, 30 nm, 31 nm, 31.7 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, or any value within the range of any two of the above values.

[0050] Understandably, the crystallite size La along the a-axis and Lc along the c-axis of graphite materials can be obtained through X-ray diffraction (XRD). Specifically, XRD analysis can be performed using an XRD instrument with the following settings: voltage: 40 kV; current: 40 mA; anti-scattering slit: 1 mm; measurement speed: 0.01671° step size and 0.24 s scan time within the 2θ range of 20° to 80°. The full width at half maximum (FWHM) of the peaks appearing near the 2θ range of 20° to 30° in the (002) crystal plane and the peaks appearing near the 2θ range of 38° to 50° in the (100) crystal plane were measured, and the La(100) and Lc(002) values ​​were obtained using the Scherrer equation. Optionally, the XRD instrument can be a Bruker D8 Discover.

[0051] In some embodiments, the graphite particles have a porous structure. This porous structure can buffer the expansion of the graphite material during battery cycling, which is beneficial for further improving the battery's cycle performance.

[0052] Understandably, the pore structure of graphite materials can be tested by preparing a cross-section of the graphite material using a cross-section polisher; then, referring to JY / T010-1996, a scanning electron microscope (SEM) can be used to scan the cross-section of the graphite material. The cross-section polisher can be an IB-09010CP type argon ion cross-section polisher, and the SEM can be a Sigma 300 type SEM from ZEISS GmbH, Germany.

[0053] Optionally, the volume percentage of the pore structure in the graphite material is 8% to 15%. For example, the volume percentage of the pore structure in the graphite material can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any value within the range of any two of the above values.

[0054] In some embodiments, the pore volume of the graphite material is 0.006 cubic centimeters per gram (abbreviated as cm). 3 / g)~0.015cm 3 / g. Optionally, the pore volume of the graphite material can be 0.006 cm³. 3 / g, 0.007cm 3 / g, 0.008cm 3 / g, 0.009cm 3 / g, 0.0097cm 3 / g, 0.01cm 3 / g, 0.0108cm 3 / g, 0.011cm 3 / g, 0.0111cm 3 / g, 0.0112cm 3 / g, 0.0115cm 3 / g, 0.012cm 3 / g, 0.0128cm 3 / g, 0.013cm 3 / g, 0.014cm 3 / g, 0.015cm 3 / g and any value within the range consisting of any two of the above values.

[0055] The pore volume of graphite materials refers to the total volume of pores per unit mass of material. It can generally be tested using nitrogen adsorption-desorption methods, for example, with a TRISTAR II 3020 surface area adsorption analyzer, according to GB / T 21650.2-2008.

[0056] The volume ratio of pore structure in graphite materials refers to the proportion of the volume occupied by the pore structure in the entire material. For example, a Thermo Fisher APREO 2S scanning electron microscope can be used, referring to the test method JY / T010-1996, to cut material particles with an ion beam, and then the proportion of the pore structure area on the cut surface to the total area of ​​the material particles can be calculated.

[0057] In some embodiments, the graphitization degree of the graphite material is 91% to 95%. Graphite materials with a graphitization degree within this range have a higher specific capacity, which is beneficial for improving the energy density of the battery. Optionally, the graphitization degree of the graphite material is 91%, 91.8%, 91.9%, 92%, 92.6%, 92.8%, 93%, 93.5%, 94%, 95%, or any value within the range of any two of the above values.

[0058] It is understandable that the degree of graphitization of graphite materials can be calculated using the following formula: Degree of graphitization = (0.344 - d) / ( ... 002 ) / (0.344-0.3354)×100%, where d 002 d represents the interlayer spacing of the (002) crystal plane of graphite material. 002 This information can be obtained through testing and analysis using an X-ray diffractometer. For example, an X-ray diffractometer can be used for testing, and the testing can be performed in accordance with JIS K 0131-1996 and JB / T 4220-2011, to obtain the average interlayer spacing d002 of the C(002) crystal plane in the material's crystal structure. An X-ray diffractometer such as a Bruker D8 Discover can be used.

[0059] In some embodiments, the true density of the graphite material is 2.2 g / cm³ (abbreviated as g / cm³). 3 )~2.3g / cm 3 Graphite materials with a true density within this range are suitable for use in secondary batteries, facilitating the achievement of a higher compaction density in the negative electrode active layer and promoting increased battery energy density. Optionally, the true density of the graphite material can be 2.2 g / cm³. 3 2.21 g / cm 3 2.22 g / cm 3 2.23 g / cm 3 2.24 g / cm 3 2.25g / cm 3 2.26 g / cm 3 2.27 g / cm 3 2.28g / cm 3 2.29 g / cm 3 2.3g / cm 3 And any value within the range consisting of any two of the above values.

[0060] Understandably, true density can be determined using a true density meter at 25°C. A true density meter such as the AccuPyc II 1340 can be used.

[0061] In some embodiments, the tap density of the graphite material is 1.1 g / cm³. 3 ~1.4g / cm 3 Graphite materials with tap densities within this range are suitable for use in secondary batteries, facilitating the development of a higher tap density in the negative electrode active layer and promoting increased battery energy density. Optionally, the tap density of the graphite material can be 1.1 g / cm³. 3 1.12 g / cm 3 1.15g / cm 3 1.18 g / cm 3 1.2g / cm 3 1.22g / cm 3 1.25g / cm 3 1.28g / cm 3 1.3g / cm 3 1.32g / cm 3 1.35g / cm 3 1.38g / cm 3 1.4g / cm 3 And any value within the range consisting of any two of the above values.

[0062] It is understood that tap density can be tested using methods known in the art. For example, it can be determined using a powder tap density tester, referring to standard GB / T 5162-2006. If an FZS4-4B type tap density tester is used, the test parameters are as follows: vibration frequency 250±15 times / minute, amplitude 3±0.1 mm, vibration count 5000 times, and measuring cylinder 25 mL.

[0063] In some embodiments, the specific capacity of the graphite material is between 340 mAh / g and 360 mAh / g. Graphite materials with specific capacities within this range can enable the secondary battery to have a high energy density. Optionally, the specific capacity of the graphite material can be 340 mAh / g, 342 mAh / g, 345 mAh / g, 348 mAh / g, 350 mAh / g, 352 mAh / g, 355 mAh / g, 358 mAh / g, 360 mAh / g, or any value within the range of any two of the above values.

[0064] In some embodiments, the graphite material I D / I GIt is 0.01-0.13; where, I D This indicates that the Raman spectrum of the material is at 1350±50 cm⁻¹. -1 The intensity of peak D at I G This indicates that the Raman spectrum of the material is at 1580±50 cm⁻¹. -1 The intensity of the G peak at that location.

[0065] Material I D / I G The values ​​can be measured using a Raman spectrometer. The test conditions are as follows: excitation wavelength 532 nm, grating 600 lines, objective lens 50x, integration time 10 s, cumulative count 3, area scan, obtaining the D and G peak intensities at 100 points, and calculating the I values ​​at 100 points. D / I G Remove the largest and smallest 25 I's. D / I G The average of the remaining 50 points is the material's I. D / I G The testing instrument can be a Horiba LabRAM HR800 Raman spectrometer.

[0066] In some embodiments, the volumetric particle size distribution (Dv50) of the graphite material is 8 micrometers (μm) to 18 μm. Optionally, the volumetric particle size distribution (Dv50) of the graphite material can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, or any value within the range of any two of the above values.

[0067] The volumetric particle size distribution (Dv90) of graphite materials ranges from 20 μm to 35 μm. The Dv90 can be any value within the range of 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, or any two of the above values.

[0068] The volumetric particle size distribution (Dv10) of graphite materials ranges from 2 μm to 8 μm. The Dv10 of graphite materials can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or any value within the range of any two of the above values.

[0069] The particle size distribution (Dv90-Dv10) / Dv50 of the graphite material is 1.0 to 1.8. The particle size distribution (Dv90-Dv10) / Dv50 of the graphite material can be 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or any value within the range of any two of the above values.

[0070] Meeting the above conditions in terms of graphite particle size distribution is beneficial to promoting the compaction of graphite materials, thereby enabling secondary batteries to have higher energy density.

[0071] It is understood that the volumetric distribution particle sizes Dv10, Dv50, and Dv90 represent the particle sizes corresponding to a cumulative volumetric distribution percentage of 10%, 50%, and 90%, respectively. These can be tested using methods known in the art. For example, they can be determined using a laser particle size analyzer, referring to standard GB / T 19077-2016. The laser particle size analyzer can be a Malvern Master Size 3000.

[0072] Another embodiment of this application provides a method for preparing a graphite material. The method includes the following steps: washing anthracite raw material to obtain de-ashed anthracite, wherein the ash content of the de-ashed anthracite is less than or equal to 2%; holding the de-ashed anthracite at 1800°C to 2000°C for 10 hours to 15 hours, and then holding it at 2800°C to 3000°C for 10 hours to 50 hours. Optionally, the holding temperature at 1800°C to 2000°C can be 1800°C, 1850°C, 1900°C, 1950°C, 2000°C, or any value within the range of any two of the above values. Optionally, the holding time at 1800°C to 2000°C can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or any value within the range of any two of the above values. Optionally, the holding temperature at 2800℃~3000℃ can be 2800℃, 2850℃, 2900℃, 2950℃, 3000℃, or any value within the range of any two of the above values. Optionally, the holding time at 2800℃~3000℃ can be 10h, 20h, 30h, 40h, 50h, or any value within the range of any two of the above values.

[0073] In the preparation method of this embodiment, anthracite is formed in rock strata under long-term high temperature and high pressure conditions. Its internal structure contains a partially cryptocrystalline structure, which lays the foundation for obtaining graphite materials with a large latitude (La). A longer holding time promotes the development of carbon layers in the planar direction, increasing La and improving the battery's energy density and cycle performance. By washing the anthracite raw material to reduce the ash content to less than or equal to 2%, and by holding it at different temperatures, the lamellar structure of the obtained graphite material can be fused, allowing the graphite material to achieve a suitable specific capacity while enabling the battery to achieve both high energy density and good cycle performance. For example, in some embodiments of the preparation method, graphite materials with a specific capacity of 340 mAh / g to 360 mAh / g can be obtained. Using this graphite material in a battery allows the battery to achieve both high energy density and good cycle performance.

[0074] It is understandable that coal washing can be performed once or multiple times. Optionally, the number of coal washing processes can be 1 to 5. For example, the number of coal washing processes can be 1, 2, 3, 4, 5, etc.

[0075] In some embodiments, the volumetric particle size distribution of the deashed anthracite is as follows: Dv10 is 2μm–8μm, Dv50 is 9μm–14μm, and Dv90 is 20μm–28μm. The tapped density of the deashed anthracite is 0.8 g / cm³. 3 ~1.6g / cm 3 It is understandable that deashed anthracite can have a suitable particle size distribution through crushing and particle size classification. Deashed anthracite has a relatively rich porous structure, and during the crushing process, the particles will break along the pore locations, which can give the graphite material a larger tap density, further promoting the improvement of battery energy density.

[0076] Optionally, in the volumetric particle size distribution of the deashed anthracite, Dv10 can be any value within the range of 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, or any two of the above values. Dv50 can be any value within the range of 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or any two of the above values. Dv90 can be any value within the range of 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, or any two of the above values. Optionally, the tap density of the deashed anthracite can be 0.8 g / cm³. 3 0.9g / cm 3 1g / cm 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 And any value within the range consisting of any two of the above values.

[0077] In some embodiments, the carbon content of the deashed anthracite is greater than or equal to 95%. Optionally, the carbon content of the deashed anthracite is greater than or equal to 96%. More preferably, the carbon content of the deashed anthracite is greater than or equal to 97%.

[0078] In some embodiments, the volatile matter content (Vdaf%) of the anthracite feedstock is 3.5% to 6.5%. The hydrogen content (Hdaf%) of the anthracite feedstock is 2% to 3%. The average maximum reflectance of the vitrinite in the anthracite feedstock is 2% to 6%. The dry ash-free higher calorific value of the anthracite feedstock is less than 34 MJ / kg to 35.1 MJ / kg. The ash content of the anthracite feedstock is greater than 10%. Optionally, the volatile matter content of the anthracite feedstock can be 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, or any value within the range of any two of the above values. The hydrogen content of anthracite feedstock can be 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any value within the range of any two of the above values. The average maximum reflectance of the vitrinite in anthracite feedstock can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or any value within the range of any two of the above values.

[0079] Understandably, the volatile matter and ash content of anthracite raw materials can be tested using the national standard GB / T30732. The hydrogen content of anthracite raw materials can be tested using the elemental furnace method specified in GB / T476-2008. The average maximum reflectance of vitrinite in anthracite raw materials can be tested using the national standard GB / T6948.

[0080] In some embodiments, the method for preparing graphite materials includes the following steps:

[0081] S101: Anthracite raw material with a volatile matter content of 3.5%–6.5%, a hydrogen content of 2%–3%, an average maximum reflectance of vitrinite of 2%–6%, and a dry ash-free high calorific value of less than 35.1 MJ / kg is selected. It is fed into a jaw crusher for coarse crushing via a vibrating feeder. The coarsely crushed material is then sieved, and the oversize material is returned to the crusher for further coarse crushing. Material with the appropriate particle size is transported via pipeline to a mechanical mill for further crushing. Finally, it undergoes initial selection using a jig, followed by further crushing to a density of 1 g / cm³. 3 ~1.5g / cm 3 The mixture of magnetite powder and water is used for two-stage isodense heavy media flotation washing of coal, followed by cyclone cleaning to obtain deashed anthracite with a carbon content ≥95% and ash content ≤2%.

[0082] S102: The deashed anthracite is crushed and classified. The particle size distribution of the classification is as follows: Dv10: 2μm~8μm, Dv50: 9μm~14μm, Dv90: 20μm~28μm. The tap density of the classified deashed anthracite is 0.8g / cm³. 3 ~1.6g / cm 3 .

[0083] S103: The graded, deashed anthracite is kept at 1800℃~2000℃ for 10h~15h, and then kept at 2800℃~3000℃ for 10h~50h. The heat preservation treatment can be carried out in an internal furnace.

[0084] S104: After heat preservation treatment, the graphite material is sieved to obtain the target graphite material.

[0085] Another embodiment of this application provides a secondary battery. The secondary battery includes a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, wherein the negative electrode active material of the negative electrode active layer includes the aforementioned graphite material.

[0086] Another embodiment of this application provides an electrical device. The electrical device includes the aforementioned secondary battery.

[0087] The secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0088] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0089] Positive electrode sheet

[0090] The positive electrode includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer including a positive active material.

[0091] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0092] In some embodiments, 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 substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0093] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional 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 include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as: NCM) 333 LiNi 0.5 Co0.2 Mn 0.3 O2 (abbreviated as: NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as: NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as: NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as: NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0094] In some embodiments, the positive electrode active layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0095] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0096] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector.

[0097] Negative electrode sheet

[0098] The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, wherein the negative active layer includes a negative active material. The negative active material includes graphite material according to any of the above embodiments.

[0099] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0100] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0101] In some embodiments, the negative electrode active material may also include other negative electrode active materials known in the art for use in batteries. As a non-limiting example, other negative electrode active materials may include one or more of the following: carbon-based materials other than the graphite material of this application, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used.

[0102] In some embodiments, the negative electrode active layer may optionally include a binder. The binder may include one or more 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).

[0103] In some embodiments, the negative electrode active layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0104] In some embodiments, the negative electrode active layer may also optionally include other additives, such as thickeners. Thickeners may include sodium carboxymethyl cellulose (CMC-Na) and the like.

[0105] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent to form a negative electrode slurry. A non-limiting example of the solvent is deionized water. The negative electrode slurry is coated onto at least one surface of the negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector.

[0106] electrolytes

[0107] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0108] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0109] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0110] In some embodiments, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0111] 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 may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0112] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and trifluoromethyl ethylene carbonate (TFPC).

[0113] Separating membrane

[0114] In some embodiments, the secondary battery also includes a separator. 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.

[0115] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0116] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0117] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0118] In some embodiments, the outer packaging of the secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0119] 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. For example, Figure 1 shows a square-structured secondary battery 1 as an example.

[0120] In some embodiments, referring to FIG2, the outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The secondary battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to actual needs.

[0121] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0122] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0123] Figure 3 shows an example of an electrical device 2. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0124] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0125] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0126] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0127] Example 1

[0128] The method for preparing graphite material in this embodiment includes:

[0129] S101: Anthracite raw material with a volatile matter content of 4.5%, a hydrogen content of 2.4%, an average maximum reflectance of vitrinite of 3.5%, and a dry ash-free high calorific value of less than 34 MJ / kg is selected. It is fed into a crusher for coarse crushing via a vibrating feeder. The coarsely crushed material is then sieved, and the oversize material is sent back to a jaw crusher for further coarse crushing. Material with the appropriate particle size is transported via pipeline to a mechanical mill for further crushing. Finally, it undergoes initial selection using a jig, followed by further crushing to a density of 1 g / cm³. 3 The mixture of magnetite powder and water is subjected to two stages of equal-density heavy medium flotation washing, followed by cyclone cleaning to obtain de-ashed anthracite with a carbon content ≥95% and an ash content ≤2%.

[0130] S102: The deashed anthracite is crushed and classified. The particle size distribution of the classification is Dv10 = 5.9 μm, Dv50 = 11.6 μm, and Dv90 = 22.5 μm. The tap density of the classified deashed anthracite is 0.79 g / cm³. 3 .

[0131] S103: The graded, deashed anthracite is held at 1800℃ for 12 hours, and then held at a graphitization temperature of 3000℃ for 12 hours. The holding treatment is carried out in an inner furnace.

[0132] S104: After heat preservation treatment, the graphite material is sieved using a 325-mesh sieve to obtain graphite material with a particle size of 12.4μm.

[0133] The method for preparing the secondary battery in this embodiment includes:

[0134] (1) Preparation of positive electrode sheet

[0135] Lithium iron phosphate (LiFePO4), a positive electrode active material, Super P, and PVDF, a binder, were mixed in a weight ratio of 97%:1%:2% and dissolved in N-methylpyrrolidone to prepare a positive electrode slurry. The positive electrode slurry was then coated onto an aluminum current collector foil, dried, and subjected to cold pressing, edge trimming, cutting, and slitting to obtain the positive electrode sheet.

[0136] (2) Preparation of negative electrode sheet

[0137] A negative electrode slurry is prepared by mixing graphite (the negative electrode active material), carbon black (the conductive agent), sodium carboxymethyl cellulose (the thickener), and styrene-butadiene rubber (the binder) in a weight ratio of 96%:1%:1.2%:1.8% and dissolving them in deionized water. The slurry is then coated onto copper foil (the current collector), dried, and subjected to cold pressing, edge trimming, cutting, and slitting to obtain the negative electrode sheet.

[0138] (3) Separating membrane

[0139] Polypropylene film is used as the separator.

[0140] (4) Preparation of electrolyte

[0141] In an argon-atmospheric glove box with a water content of <10 ppm, diethyl carbonate, methyl ethyl carbonate, and ethylene carbonate were mixed in a weight ratio of 1:1:1 to obtain an organic solvent. LiPF6 was then dissolved in the organic solvent at a concentration of 1.0 mol / L, followed by the addition of vinylene carbonate, with a vitamin C content of 2% of the total electrolyte mass.

[0142] (5) Preparation of secondary batteries

[0143] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrodes are then wound to form an electrode assembly. The electrode assembly is placed in outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0144] The different parameters of the preparation process of Examples 2-4 and Comparative Examples 1-2 compared with Example 1 are shown in Table 1. The La, Lc, pore volume, degree of graphitization, and specific capacity of the graphite materials in Examples 1-4 and Comparative Examples 1-2 are shown in Table 2.

[0145] Table 1

[0146] Comparative Example 3

[0147] The petroleum coke feedstock was crushed to obtain intermediate 1 with an average particle size Dv50 of 13.8 μm;

[0148] Intermediate 1 is shaped and then graded to adjust the particle size distribution of the raw materials, thus obtaining intermediate 2.

[0149] Intermediate 2 was placed in a graphitization furnace for high-temperature graphitization at 3000℃ to obtain intermediate 3;

[0150] Intermediate 3 is sieved and demagnetized to obtain the final graphite material.

[0151] The SEM images of the graphite materials in Example 1 and Comparative Example 3 are shown in Figures 4 and 5, respectively. As can be seen from Figures 4 and 5, the graphite particles in Example 1 have a more abundant porous structure, while the graphite particles in Comparative Example 3 have virtually no pores. This unique porous structure of the graphite material in Example 1 effectively mitigates volume expansion during charge-discharge cycles, resulting in better battery cycle performance.

[0152] Test case

[0153] (1) The specific capacity of the graphite materials in Examples 1-4 and Comparative Examples 1-2 was tested. The test method was as follows: the graphite material sample was thoroughly mixed with conductive carbon black and polyvinylidene fluoride in an appropriate amount of solvent NMP at a mass ratio of 91.6%:1.8%:6.6% to form a uniform negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of the negative electrode current collector copper foil and dried and cold pressed. Then, using a lithium metal sheet as the counter electrode and a polypropylene film as the separator, a CR2430 coin cell was assembled in an argon-protected glove box. The electrolyte in Example 1 was used. At 25°C, the coin cell was first discharged at a constant current of 0.05 coulombs (C) to 0.005 volts (V), and then discharged at a constant current of 10 microamps (μA) to 0.005 V. After standing for 5 minutes (min), the first discharge capacity of the coin cell was recorded. The coin cell was then charged to 2.0V at a constant current of 0.1C, and the charging capacity was recorded. The ratio of the charging capacity of the coin cell to the mass of the graphite sample is the specific capacity of the graphite material. The specific capacity results are shown in Table 2.

[0154] (2) The cycle performance of the secondary batteries in Examples 1-4 and Comparative Examples 1-3 was tested. The test method was as follows: at 60°C, the secondary batteries in Examples 1-4 and Comparative Examples 1-3 were charged at a constant current of 1C to a voltage of 3.65V, then charged at a constant voltage of 3.65V until the current ≤0.05C, and then discharged at a constant current of 1C to a voltage of 2.5V. This constituted one charge-discharge cycle, and the discharge capacity C1 of the first cycle was recorded. This charge-discharge cycle was repeated until the battery capacity decayed to 80% of the initial capacity C1, at which point the test was stopped, and the number of test cycles was recorded. The results of the cycle performance of the secondary batteries are shown in Table 2.

[0155] Table 2

[0156] As can be seen from Table 2, when the La of graphite material is in the range of 135nm to 150nm, it can effectively improve the cycle performance of the battery while maintaining a high specific capacity.

[0157] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A graphite material, wherein the crystallite size La along the a-axis of the graphite material is 135 nm to 150 nm.

2. The graphite material according to claim 1, wherein, La has a wavelength of 140 nm to 148 nm.

3. The graphite material according to claim 1 or 2, wherein, The crystallite size Lc along the c-axis of the graphite material is 20 nm to 40 nm.

4. The graphite material according to any one of claims 1 to 3, wherein, The graphite material particles have a porous structure inside.

5. The graphite material according to claim 4, wherein, The volume percentage of the pore structure in the graphite material is 8% to 15%.

6. The graphite material according to claim 4 or 5, wherein, The pore volume of the graphite material is 0.006 cm³. 3 / g~0.015cm 3 / g.

7. The graphite material according to any one of claims 1 to 6, wherein, The graphitization degree of the graphite material is 91% to 95%.

8. The graphite material according to any one of claims 1 to 7, wherein, The true density of the graphite material is 2.2 g / cm³. 3 ~2.3g / cm 3 .

9. The graphite material according to any one of claims 1 to 8, wherein, The tap density of the graphite material is 1.1 g / cm³. 3 ~1.4g / cm 3 .

10. The graphite material according to any one of claims 1 to 9, wherein, The specific capacity of the graphite material is 340mAh / g to 360mAh / g.

11. The graphite material according to any one of claims 1 to 10, wherein, The graphite material I D / I G It is 0.01-0.13; where, I D This indicates that the Raman spectrum of the material is at 1350±50 cm⁻¹. -1 The intensity of peak D at I G This indicates that the Raman spectrum of the material is at 1580±50 cm⁻¹. -1 The intensity of the G peak at that location.

12. The graphite material according to any one of claims 1 to 11, wherein, The particle size of the graphite material satisfies one or more of the following (1) to (4): (1) The volume distribution particle size Dv50 of the graphite material is 8μm to 18μm; (2) The volume distribution particle size Dv90 of the graphite material is 20μm~35μm; (3) The volume distribution particle size Dv10 of the graphite material is 2μm to 8μm; (4) The particle size distribution (Dv90-Dv10) / Dv50 of the graphite material is 1.0 to 1.

8.

13. A method for preparing the graphite material according to any one of claims 1 to 12, comprising the following steps: Anthracite raw material is washed to obtain deashed anthracite, wherein the ash content of the deashed anthracite is less than or equal to 2%; The deashed anthracite is kept at 1800℃~2000℃ for 10h~15h, and then kept at 2800℃~3000℃ for 10h~50h.

14. The preparation method according to claim 13, wherein, The anthracite raw material has one or more of the following (1) to (5): (1) Ash content greater than 10%; (2) The volatile content is 3.5% to 6.5%; (3) The hydrogen content is 2% to 3%; (4) The average maximum reflectance of vitrinite is 2% to 6%; (5) Dry, ash-free, high calorific value is less than 34 MJ / kg to 35.1 MJ / kg.

15. A secondary battery, comprising a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material comprising the graphite material according to any one of claims 1 to 12.

16. An electrical device comprising the secondary battery of claim 15.

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