Graphite material, method for producing the same, and use thereof

Abstract

The present application relates to the technical field of battery, in particular to a kind of graphite material and its preparation method and application.The present application provides a kind of graphite material, the graphite material includes graphite body, the graphite body has multiple through-hole structures, the hole diameter R of each through-hole structure is 0.07~1.81 μm;The particle size Dv50 of the graphite material and the hole diameter R of the through-hole structure satisfy:3.9≤Dv50 / R≤107.1.The graphite material of the present application has abundant through-hole structure, provides more channels for lithium ion deintercalation, and shortens the solid-phase diffusion path of lithium ion intercalation, so as to improve the rate performance of graphite negative electrode material, and the through-hole channel structure can improve the wettability and liquid retention of electrolyte, thereby improving the cycle performance of battery.

Description

Graphite materials, their preparation methods and applications Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a graphite material, its preparation method, and its application. Background Technology

[0002] The rapid development of new energy vehicles, energy storage power stations, and digital products has placed higher demands on long cycle life and fast charging, leading to various optimization strategies such as conductive agent coating, soft / hard carbon coating, and pore formation. Graphite materials possess advantages such as high capacity, good lithium insertion / extraction reversibility, low potential plateau, and excellent cycle performance, making them a primary anode material for 3C electronic products and widely used, with applications gradually expanding to electric vehicles (EVs) and hybrid electric vehicles (HEVs). Therefore, the development and application of high-performance electrode materials are crucial. Currently, lithium-ion batteries primarily use graphite-based materials as anode materials, but traditional graphite-based anode materials suffer from poor cycle life and rate performance during cycling.

[0003] Existing technologies involve creating pores in graphite to improve electrochemical performance. Existing technology literature:

[0004] Chinese patent CN100499215C discloses a surface-modified lithium-ion battery anode material, which is obtained by depositing metal salts on the surface of micro-powders of coke or artificial graphite, and then subjecting the micro-powders to heat treatment in an oxidizing atmosphere.

[0005] Chinese patent CN111048755A discloses a high-rate lithium-ion battery anode material and its preparation method. Potassium carbonate and nitrogen- and phosphorus-containing organic matter are mixed into a solution, which is then added to a hydrochloric acid solution. After stirring evenly, flake graphite is added and mixed evenly to prepare a graphite mixed solution. The solution is then filtered, carbonized, and modified by gas surface to obtain a graphite composite material.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a graphite material that addresses the problem of unsatisfactory rate performance and cycle performance of existing graphite materials. The graphite of this invention has a rich porous structure, providing more channels for lithium-ion insertion / extraction and shortening the solid-phase diffusion path for lithium-ion insertion, thereby improving the rate performance and cycle performance of graphite anode materials.

[0008] Another objective of this invention is to provide a method for preparing the graphite described above, which is simple and easy to implement, and can obtain a graphite material with a rich porous structure through the combination of various steps.

[0009] Another object of the present invention is to provide a negative electrode material.

[0010] Another object of the present invention is to provide a battery.

[0011] Another object of the present invention is to provide an electrical device.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] A graphite material comprising a graphite body having multiple through-hole structures, each through-hole structure having a pore diameter R of 0.07–1.81 μm; the particle size Dv50 of the graphite material and the pore diameter R of the through-hole structure satisfy the following condition: 3.9 ≤ Dv50 / R ≤ 107.1.

[0014] In one embodiment, the particle size Dv50 of the graphite material and the pore diameter R of the through-hole structure satisfy the following condition: 3.9 ≤ Dv50 / R ≤ 107.1.

[0015] In one embodiment, the particle size Dv50 of the graphite material is 6.7–17.8 μm.

[0016] In one embodiment, the particle size Dv90 of the graphite material is 14.8 to 41.4 μm; the particle size Dv90 and particle size Dv10 of the graphite material satisfy: 4 ≤ Dv90 / Dv10 ≤ 9.

[0017] In one embodiment, the specific surface area of ​​the graphite material is 3.12–4.56 m². 2 / g.

[0018] In one embodiment, the oil absorption value of the graphite material is 56-68, in mL / 100g.

[0019] In one embodiment, the graphitization degree of the graphite material is greater than or equal to 94.5%.

[0020] In one embodiment, the discharge capacity of the graphite material is 355.5–365 mAh / g.

[0021] The method for preparing the graphite material as described above includes the following steps:

[0022] A mixture of carbon source and micro / nanowire material is coked to obtain a first material; the first material is crushed to obtain a second material; the second material is graphitized; the micro / nanowire material can be gasified during the graphitization process of the second material.

[0023] In one embodiment, the carbon source includes at least one of pitch and tar.

[0024] In one embodiment, the micro / nanowire material includes at least one of silicon-based micro / nanowires and metal oxide micro / nanowires.

[0025] In one embodiment, the diameter of the micro / nanowire material is 0.08–2 μm, and the length of the micro / nanowire material is 20–120 μm.

[0026] In one embodiment, the mass ratio of the micro / nanowire material to the carbon source is (0.5–5):100.

[0027] In one embodiment, the preparation method of the mixture specifically includes: preheating, settling and stirring the carbon source and the micro / nanowire material.

[0028] In one embodiment, in the preparation method of the mixture, the preheating temperature is 200-300°C; the settling time is 3-6 hours; the stirring speed is 300-600 rpm; and the stirring time is 1-3 hours.

[0029] In one embodiment, the coking temperature is 450–600°C, and the coking time is 5–10 hours.

[0030] In one embodiment, the particle size dv50 of the second material and the diameter r of the micro / nanowire material satisfy: 0.01≤r / dv50≤0.29; the particle size dv50 of the second material and the length L of the micro / nanowire material satisfy: 3≤L / dv50≤6.67.

[0031] In one embodiment, the preparation method further includes a step of crushing and grading the first material.

[0032] In one embodiment, the graphitization process includes a first heat treatment and a second heat treatment; the temperature of the first heat treatment is 1800–2100°C, and the time of the first heat treatment is 8–12 hours; the temperature of the second heat treatment is 2900–3200°C, and the time of the second heat treatment is 8–12 hours.

[0033] In one embodiment, the heating rate of the graphitization treatment is 5–15 °C / min.

[0034] A negative electrode material, comprising the aforementioned graphite material.

[0035] A battery comprising the aforementioned negative electrode material.

[0036] An electrical device, including the battery.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) The graphite material of the present invention has abundant through-pore structure, which provides more channels for lithium ion insertion and extraction and shortens the solid-phase diffusion path of lithium ion insertion, thereby improving the rate performance of graphite anode material. The through-pore structure can improve the wettability and liquid retention of electrolyte, thereby improving the cycle performance of battery.

[0039] (2) Through the coordination of each step, the present invention enables the micro-nano wire template to have a better pore-forming effect, so that the graphite material can form a rich through-pore structure. At the same time, the micro-nano wire template can promote the graphitization of graphite during the high-temperature graphitization process, so that the final graphite material has a higher degree of graphitization and capacity.

[0040] (3) The battery of the present invention has excellent cycle performance, rate performance and safety performance. Attached Figure Description

[0041] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 is a scanning electron microscope image of the graphite material in Embodiment 1 of the present invention;

[0043] Figure 2 is a schematic diagram of the structure of graphite particles in Embodiment 1 of the present invention;

[0044] Figure 3 is a scanning electron microscope image of the graphite material in Comparative Example 1 of the present invention. Detailed Implementation

[0045] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0046] According to one aspect of the present invention, the present invention relates to a graphite material comprising a graphite body having a plurality of through-hole structures, wherein the diameter R of each through-hole structure is 0.07 to 1.81 μm.

[0047] A through-hole structure refers to a single particle with two holes on its surface. These two holes form a connected channel through the internal channels of the particle. Therefore, this through-hole structure has the characteristic of allowing liquids, gases or other substances to enter from one end of the particle and exit from the other end.

[0048] The graphite material of this invention has abundant through-pores, providing more channels for lithium-ion insertion / extraction and shortening the solid-phase diffusion path for lithium-ion insertion. Furthermore, lithium-ions diffuse not only within the gaps formed by the overlapping of multiple graphite particles, but the electrolyte also diffuses through the through-pore structure in the liquid phase. Therefore, compared to conventional non-through-pore graphite structures, the number of liquid-phase diffusion channels is significantly increased, improving the rate performance of the graphite anode material. The through-pore structure also improves electrolyte wettability and liquid retention, thereby improving the battery's cycle performance. A schematic diagram of the graphite particle structure of this invention is shown in Figure 2.

[0049] In one embodiment, the diameter R of each through-hole structure is 0.07 μm, 0.09 μm, 0.1 μm, 0.5 μm, 1 μm, 1.1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, etc. The graphite material of the present invention has a through-hole structure with suitable pore diameters, thereby ensuring high capacity and improving the rate performance of the battery.

[0050] In one embodiment, the particle size Dv50 of the graphite material and the pore diameter R of the through-hole structure satisfy the following condition: 3.9 ≤ Dv50 / R ≤ 107.1. The value of Dv50 / R includes, but is not limited to, 3.9, 4, 5, 10, 15, 20, 30, 50, 60, 70, 80, 90, 100, and 107. The through-hole structure of this invention exists on the particle surface and inside, penetrating the entire particle. If the ratio is too large, it is not conducive to ensuring the formation of the through-hole structure and to improving the liquid retention capacity; if the ratio is too small, it is not conducive to the mechanical strength of the through-hole graphite particles themselves, easily leading to particle breakage during post-processing and affecting electrochemical performance. By limiting Dv50 / R within a suitable range, it is more beneficial to improve the electrochemical performance of graphite.

[0051] In one embodiment, the preferred particle size Dv50 of the graphite material and the pore diameter R of the through-hole structure satisfy: 3.9≤Dv50 / R≤30. Within this range, Dv50 / R has a larger pore diameter while also taking into account the strength of the graphite particles themselves, which is beneficial to improving the liquid retention capacity and thus improving the rate performance.

[0052] In one embodiment, the particle size Dv50 of the graphite material is 6.7–17.8 μm, such as 6.7 μm, 7 μm, 8 μm, 10 μm, 11 μm, 12 μm, 13 μm, 15 μm, 17 μm, etc.; and the particle size Dv90 is 14.8–41.4 μm, such as 14.8 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 41 μm, etc.

[0053] In one embodiment, the particle sizes Dv90 and Dv10 of the graphite material satisfy: 4 ≤ Dv90 / Dv10 ≤ 9, for example, 4, 4.5, 5, 5.5, 6, 6.5, 7, 8, 9, etc. This invention, by employing a suitable particle size distribution combined with a porous structure, is more conducive to ensuring the electrochemical performance of the graphite material and improving the overall performance of the battery.

[0054] In one embodiment, the specific surface area of ​​the graphite material is 3.12–4.56 m². 2 / g, including but not limited to 3.12m 2 / g、3.3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.1m 2 / g, 4.56m 2 / g etc. The graphite material of the present invention has a large pore size and a suitable specific surface area, which is beneficial to preventing the deterioration of the high first-efficiency characteristics of the graphite material.

[0055] In one embodiment, the oil absorption value of the graphite material is 56-68, for example, 56, 57, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, etc., in mL / 100g. The oil absorption value of the graphite material of the present invention is within the above-mentioned suitable range, thereby ensuring its excellent dispersibility, avoiding excessive consumption of dispersants and binders, and contributing to improved electrochemical performance of the battery.

[0056] In one embodiment, the graphitization degree of the graphite material is greater than or equal to 94.5%. The graphite of the present invention has a high degree of graphitization and high structural regularity of carbon materials, which can improve the electrolyte wetting performance of the negative electrode sheet and is beneficial to improving the cycle performance of the battery.

[0057] In one embodiment, the discharge capacity of the graphite material is 355.5–365 mAh / g. The graphite material of this invention exhibits excellent discharge capacity, which is beneficial for improving the electrochemical performance of the battery.

[0058] According to another aspect of the present invention, the present invention also relates to a method for preparing the graphite material as described above, comprising the following steps:

[0059] A mixture of carbon source and micro / nanowire material is coked to obtain a first material; the first material is crushed to obtain a second material; and the second material is graphitized.

[0060] The micro / nanowire material can be vaporized during the graphitization process of the second material.

[0061] This invention, through the coordination of various steps, enables micro- and nanowire materials to have better pore-forming effects, thereby enabling graphite materials to form rich through-pore structures. At the same time, the micro- and nanowire material template can promote the graphitization of carbon during the high-temperature graphitization process and before gasification removal, resulting in graphite materials with higher graphitization degree and capacity.

[0062] In one embodiment, the carbon source includes at least one of bitumen and tar. The softening point of the bitumen is determined according to the method described in ASTM D3104-99 (R2005).

[0063] In one embodiment, the micro / nanowire material includes at least one of silicon-based micro / nanowires and metal oxide micro / nanowires; the silicon-based micro / nanowires include silicon micro / nanowires and silicon dioxide micro / nanowires; the metal oxide micro / nanowires include tin oxide micro / nanowires, titanium oxide micro / nanowires, etc. The diameter of the micro / nanowire material is 0.08–2 μm, including but not limited to 0.08 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, etc. The length of the micro / nanowire material is 20–120 μm, including but not limited to 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, etc. This invention uses micro-nanowire material templates with suitable diameter and length, which is more conducive to forming through-hole structures. If the diameter of the micro-nanowire material is too low or the length is too short, the small hole structure is prone to shrinkage during the preparation process, leading to hole closure.

[0064] In one embodiment, the mass ratio of the micro / nanowire material to the carbon source is (0.5–5):100, including but not limited to 0.5:100, 0.8:100, 1:100, 1.5:100, 2:100, 3:100, 4:100, or 5:100. This invention employs a suitable mass ratio of micro / nanowire material to carbon source to ensure that the graphite material possesses a rich porous structure while maintaining its mechanical properties, thus guaranteeing excellent overall performance.

[0065] In one embodiment, the method for preparing the mixture specifically includes: preheating, settling, and stirring the carbon source and the micro / nanowire material; softening the carbon source through preheating and settling; the preheating temperature is 200–300°C, including but not limited to 200°C, 220°C, 250°C, etc.; the settling time is 3–6 hours, such as 3 hours, 4 hours, 5 hours, etc.; the stirring speed is 300–600 rpm, such as 300 rpm, 400 rpm, 500 rpm, 600 rpm, etc.; and the stirring time is 1–3 hours, such as 1 hour, 2 hours, or 3 hours, etc. By using the above treatment conditions, the micro / nanowire material and the carbon source are mixed uniformly.

[0066] In one embodiment, the coking temperature is 450–600°C, including but not limited to 450°C, 480°C, 500°C, 520°C, 55°C, 580°C, and 600°C. The coking time is 5–10 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, or 10 hours. By employing suitable coking conditions, high graphitization and high capacity of the graphite material are ensured.

[0067] In one embodiment, the particle size dv50 of the second material and the diameter r of the micro / nanowire material satisfy the following: 0.01 ≤ r / dv50 ≤ 0.29, where r / dv50 includes, but is not limited to, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, 0.15, 0.2, or 0.29; the particle size dv50 of the second material and the length L of the micro / nanowire material satisfy the following: 3 ≤ L / dv50 ≤ 6.67, where L / dv50 includes, but is not limited to, 3, 3.2, 3.5, 3.8, 4, 4.5, 5, 5.5, 6, 6.5, or 6.67. By limiting r / dv50 and L / dv50 to suitable ranges, this invention is more conducive to graphitization and obtaining graphite materials with suitable particle size distributions, thereby ensuring the electrochemical performance of the graphite materials.

[0068] In one embodiment, the preparation method further includes a step of crushing and grading the first material.

[0069] In one embodiment, the graphitization process includes a first heat treatment and a second heat treatment; the temperature of the first heat treatment is 1800–2100°C, including but not limited to 1800°C, 1850°C, 1900°C, 1950°C, 2000°C, 2100°C, etc.; the duration of the first heat treatment is 8–12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours; the temperature of the second heat treatment is 2900–3200°C, for example, 2900°C, 2950°C, 3000°C, 3100°C, 3200°C, etc.; the duration of the second heat treatment is 8–12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours; the heating rate of the graphitization process is 5–15°C / min, for example, 5°C / min, 10°C / min, 15°C / min, etc. By employing appropriate graphitization treatment conditions, micro- and nanowire materials can be removed, ensuring that the final graphite material has a high degree of graphitization.

[0070] According to another aspect of the invention, the invention also relates to a negative electrode material, comprising the aforementioned graphite material.

[0071] The graphite material of this invention, when used as a negative electrode material, can improve the rate performance and cycle performance of the battery.

[0072] According to another aspect of the invention, the invention also relates to a negative electrode sheet comprising the graphite material. In one embodiment, the negative electrode sheet comprises a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector; the negative electrode material layer comprises the aforementioned graphite material, a binder, and a conductive agent.

[0073] According to another aspect of the invention, the invention also relates to a battery comprising the aforementioned negative electrode material. The battery of the present invention exhibits excellent rate performance, cycle performance, and safety performance.

[0074] A battery is a single physical module comprising one or more individual cells to provide a predetermined voltage and capacity. The individual cell is the basic unit of a battery, and can be classified according to its packaging method, such as cylindrical cells, prismatic cells, and pouch cells. An individual cell includes the aforementioned negative electrode, as well as the positive electrode, electrolyte, and separator.

[0075] According to another aspect of the invention, the invention also relates to an electrical device including the aforementioned battery. The electrical device of the invention includes, but is not limited to, ships, automobiles, trains, etc.

[0076] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0077] Example 1

[0078] A method for preparing graphite material includes the following steps:

[0079] (1) A silicon wire with a diameter of 1 μm and a length of 36 μm and asphalt with a softening point of 150℃ were added to a mixing vessel at a temperature of 200℃ at a mass ratio of 1:100. After standing for 5 hours (waiting for the asphalt to heat up and soften), the mixing was started at a speed of 500 rpm for 2 hours to obtain a mixture.

[0080] (2) The mixture above is heated to 500°C in a reactor and kept at that temperature for 10 hours for coking to obtain the first material.

[0081] (3) The first material is crushed and classified to obtain the second material with dv10 = 5μm, dv50 = 9μm, and dv90 = 30μm.

[0082] (4) The second material above is subjected to heat treatment. The temperature is increased from room temperature to 2000℃ at 10℃ / min and held for 10h. Then the temperature is increased to 3000℃ at 10℃ / min and held for 10h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0083] The scanning electron microscope image of the graphite material in this embodiment is shown in Figure 1. It can be seen that the graphite material obtained by the method of the present invention has a rich porous structure.

[0084] Example 2

[0085] A method for preparing graphite material includes the following steps:

[0086] (1) Add silicon wire with a diameter of 1μm and a length of 36μm and asphalt with a softening point of 150℃ to a mixing vessel at a mass ratio of 0.5:100. After standing for 3 hours (waiting for the asphalt to heat up and soften), start stirring at a speed of 200rpm for 3 hours to obtain a mixture.

[0087] (2) The mixture above is heated to 500°C in a reactor and kept at that temperature for 10 hours for coking to obtain the first material.

[0088] (3) The first material is crushed and classified to obtain the second material with dv10 = 5μm, dv50 = 9μm, and dv90 = 30μm.

[0089] (4) The second material above is subjected to heat treatment. The temperature is increased from room temperature to 2000℃ at 5℃ / min and held for 10h. Then the temperature is increased to 3000℃ at 5℃ / min and held for 10h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0090] Example 3

[0091] A method for preparing graphite material includes the following steps:

[0092] (1) A silicon wire with a diameter of 1 μm and a length of 36 μm and asphalt with a softening point of 150℃ were added to a mixing vessel at a temperature of 200℃ at a mass ratio of 3:100. After standing for 3 hours (waiting for the asphalt to heat up and soften), the mixing was started at a speed of 400 rpm for 5 hours to obtain a mixture.

[0093] (2) The mixture above is heated to 500°C in a reactor and kept at that temperature for 10 hours for coking to obtain the first material.

[0094] (3) The first material is crushed and classified to obtain the second material with dv50 = 9μm and dv90 = 30μm.

[0095] (4) The second material is heat-treated by raising the temperature from room temperature to 2000℃ at 50℃ / min and holding it for 5 hours. Then, the temperature is raised to 3000℃ at 50℃ / min and held for 1 hour to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0096] Example 4

[0097] A method for preparing graphite material includes the following steps:

[0098] A silica wire with a diameter of 1 μm and a length of 36 μm was added to asphalt with a softening point of 150℃ at a mass ratio of 1:100 into a mixing vessel at a temperature of 200℃. After standing for 2 hours (waiting for the asphalt to heat up and soften), the mixing was started at a speed of 600 rpm for 5 hours to obtain a mixture.

[0099] (2) The mixture above is heated to 500°C in a reactor and kept at that temperature for 10 hours for coking to obtain the first material.

[0100] (3) The first material is crushed and graded to obtain the second material with dv10 = 5μm, dv50 = 12μm, and dv90 = 30μm.

[0101] (4) The second material is heat-treated by raising the temperature from room temperature to 2000℃ at 50℃ / min and holding it for 5 hours. Then, the temperature is raised to 3000℃ at 50℃ / min and held for 2 hours to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0102] Example 5

[0103] A method for preparing graphite material includes the following steps:

[0104] (1) A silica wire with a diameter of 1 μm and a length of 21 μm and asphalt with a softening point of 150℃ are added to a mixing vessel at a temperature of 200℃ at a mass ratio of 1.5:100. After standing for 2 hours (waiting for the asphalt to heat up and soften), the mixing is started at a speed of 200 rpm for 3 hours to obtain a mixture.

[0105] (2) The mixture above is heated to 550°C in a reactor and kept at that temperature for 5 hours to coke, thereby obtaining the first material.

[0106] (3) The first material is crushed and graded to obtain the second raw material with dv10 = 4μm, dv50 = 7μm, and dv90 = 16μm.

[0107] (4) The second raw material is subjected to heat treatment. The temperature is increased from room temperature to 2200℃ at 10℃ / min and held for 10h. Then the temperature is increased to 3000℃ at 10℃ / min and held for 5h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0108] Example 6

[0109] A method for preparing graphite material includes the following steps:

[0110] (1) A silica wire with a diameter of 2μm and a length of 21μm and asphalt with a softening point of 200℃ are added to a mixing vessel at a temperature of 300℃ at a mass ratio of 1.5:100. After standing for 2 hours (waiting for the asphalt to heat up and soften), the mixing is started at a speed of 200rpm for 3 hours to obtain a mixture.

[0111] (2) The mixture above is heated to 550°C in a reactor and kept at that temperature for 5 hours to coke, thereby obtaining the first material.

[0112] (3) The first material is crushed and classified to obtain the second material with dv10 = 4μm, dv50 = 7μm, and dv90 = 16μm.

[0113] (4) The second material above is subjected to heat treatment. The temperature is increased from room temperature to 2200℃ at 10℃ / min and held for 10h. Then the temperature is increased to 3000℃ at 10℃ / min and held for 5h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0114] Example 7

[0115] A method for preparing graphite material includes the following steps:

[0116] (1) A silica wire with a diameter of 2μm and a length of 100μm and asphalt with a softening point of 200℃ are added to a mixing vessel at a temperature of 300℃ at a mass ratio of 1.5:100. After standing for 2 hours (waiting for the asphalt to heat up and soften), the mixing is started at a speed of 200rpm for 3 hours to obtain a mixture.

[0117] (2) The mixture above is heated to 550°C in a reactor and kept at that temperature for 5 hours for coking to obtain the first raw material.

[0118] (3) The first material is crushed and graded to obtain the second raw material with dv10 = 6μm, dv50 = 15μm, and dv90 = 36μm.

[0119] (4) The second material above is subjected to heat treatment. The temperature is increased from room temperature to 2400℃ at 10℃ / min and held for 10h. Then the temperature is increased to 3000℃ at 10℃ / min and held for 5h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0120] Example 8

[0121] A method for preparing graphite material includes the following steps:

[0122] (1) A silica wire with a diameter of 0.5 μm and a length of 100 μm and asphalt with a softening point of 200℃ are added to a mixing vessel at a temperature of 300℃ at a mass ratio of 1.5:100. After standing for 2 hours (waiting for the asphalt to heat up and soften), the mixing is started at a speed of 600 rpm for 5 hours to obtain a mixture.

[0123] (2) The mixture was heated to 480°C in a reactor and kept at that temperature for 15 hours to coke, thus obtaining the first material.

[0124] (3) The first material is crushed and classified to obtain the second material with dv10 = 5μm, dv50 = 20μm, and dv90 = 45μm.

[0125] (4) The second material above is subjected to heat treatment. The temperature is increased from room temperature to 2200℃ at 10℃ / min and held for 10h. Then the temperature is increased to 3000℃ at 10℃ / min and held for 5h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0126] Example 9

[0127] A method for preparing graphite material includes the following steps:

[0128] (1) Titanium dioxide fibers with a diameter of 0.2 μm and a length of 32 μm and asphalt with a softening point of 105℃ were added to a mixing vessel at a temperature of 200℃ at a mass ratio of 1.5:100. After standing for 2 hours (waiting for the asphalt to heat up and soften), the mixing was started at a speed of 600 rpm for 5 hours to obtain a mixture.

[0129] (2) The mixture above is heated to 480°C in a reactor and kept at that temperature for 15 hours for coking to obtain the first material.

[0130] (3) The first material is crushed and classified to obtain the second material with dv10 = 4μm, dv50 = 8μm, and dv90 = 28μm.

[0131] (4) The second material above is subjected to heat treatment. The temperature is increased from room temperature to 2200℃ at 10℃ / min and held for 10h. Then the temperature is increased to 2900℃ at 10℃ / min and held for 5h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0132] Example 10

[0133] A method for preparing graphite material includes the following steps:

[0134] (1) A silicon wire with a diameter of 0.08 μm and a length of 32 μm and tar with a softening point of 25 °C were added to a stirring vessel at a temperature of 200 °C at a mass ratio of 1.5:100. After standing for 2 hours (waiting for the asphalt to heat up and soften), stirring was started at a speed of 600 rpm for 5 hours to obtain a mixture.

[0135] (2) The mixture above is heated to 480°C in a reactor and kept at that temperature for 15 hours for coking to obtain the first material.

[0136] (3) The first material is crushed and classified to obtain the second material with dv10 = 4μm, dv50 = 8μm, and dv90 = 28μm.

[0137] (4) The second material above is subjected to heat treatment. The temperature is increased from room temperature to 2200℃ at 10℃ / min and held for 10h. Then the temperature is increased to 2900℃ at 10℃ / min and held for 5h to perform high-temperature graphitization and remove impurities. After the material is cooled, a graphite material with a through-hole structure is obtained.

[0138] Comparative Example 1

[0139] The preparation method of graphite material is the same as in Example 1, except that silicon wires are not added in step (1).

[0140] The scanning electron microscope image of the graphite material in this comparative example is shown in Figure 3.

[0141] Comparative Example 2

[0142] The preparation method of graphite material is the same as in Example 1, except that the diameter of the silicon wire in step (1) is 1 μm and the length is 5 μm.

[0143] Experimental Example

[0144] I. Particle size and pore size testing of the second material and graphite material

[0145] The morphology and pore structure of the graphite samples were observed using scanning electron microscopy, and the pore diameter R was measured. The diameter r and length L of the micro / nanowire additives were also measured. The particle size of the samples was measured using a Malvern laser particle size analyzer (MS3000) with an opacity of 8%–12% and water as the test medium. This yielded the particle sizes dv10, dv50, and dv90 of the second material, and the particle sizes Dv10, Dv50, and Dv90 of the graphite material. Dv90 / Dv10, r / dv50, L / dv50, and Dv50 / R were calculated.

[0146] The test results are shown in Table 1.

[0147] Table 1 Structural Performance Tests of Graphite Materials

[0148]

[0149] II. Specific surface area, oil absorption value, graphitization degree, and ash content testing of graphite materials

[0150] The degree of graphitization was determined according to the method described in GB / T 24533-2019.

[0151] Specific surface area (BET) was determined in accordance with the provisions of GB / T 19587.

[0152] The ash content was determined according to the method described in YS / T 63.19-2012.

[0153] Oil absorption value test: The ASAHI S500 was used as the testing instrument, flaxseed oil was used as the test liquid medium, the sample addition amount was 25±0.05g, the flaxseed oil dripping rate was 4mL / min, and the Peak Mode was used for testing. The minimum oil absorption amount corresponding to 70% of the highest peak was selected as the oil absorption value.

[0154] The test results of the specific surface area, oil absorption value, graphitization degree and ash content of the graphite material are shown in Table 2.

[0155] Table 2. Test results of specific surface area, oil absorption value, graphitization degree, and ash content of graphite materials.

[0156]

[0157] III. Electrochemical Performance Testing of the Battery

[0158] A negative electrode sheet was prepared by slurry preparation of CMC:SBR in a ratio of 95.5:1.5:3, followed by coating, drying, and rolling to obtain the negative electrode sheet. This process was then used to fabricate a CR2430 coin cell, with a lithium metal sheet as the counter electrode. The electrolyte composition was 1.1M LiPF6, EC:DMC = 1:2 (volume ratio), 1% VC (ethylene carbonate by mass), and 1% FEC (fluoroethylene carbonate by mass). The separator was Celgard 2320, 23 mm in diameter and 20 μm thick. The initial delithiation capacity, initial coulombic efficiency, and rate performance of the graphite negative electrode material were tested. A coin cell was discharged to 0.005V at 0.1C, allowed to stand for 10 minutes, then discharged to 0.005V at 0.01C, allowed to stand for 10 minutes, and then charged to 2V at 0.1C. This yielded the lithium insertion and extraction capacities, respectively. The ratio of lithium extraction capacity to lithium insertion capacity is the first-efficiency characteristic. The lithium insertion capacity was obtained by discharging to 0.01V at 0.2C, followed by constant-voltage discharge to 0.01C at 0.01V, and allowed to stand for 10 seconds; then charging to 1.5V at 0.2C, allowed to stand for 10 seconds, followed by discharge to 0.01V at 2C, constant-voltage discharge to 0.01C at 0.01V, and charging to 1.5V at 2C. This yielded the lithium insertion capacity under 0.2C and 2C conditions, respectively.

[0159] The battery performance test results are shown in Table 3.

[0160] Table 3 Battery performance test results

[0161]

[0162] As can be seen from the above, the addition of micro / nanowire templates not only creates pores but also promotes graphitization under high-temperature heat treatment. Therefore, the graphite material obtained in this invention has a higher degree of graphitization and capacity. Furthermore, graphite materials with through-pore structures exhibit superior rate performance. Due to the addition of micro / nanowire templates, although the raw coke contains a large amount of non-carbon substances, the ash content of the graphite material obtained after high-temperature graphitization is very low, meeting the requirements for lithium-ion battery applications. The oil absorption value data shows that the graphite sample obtained in this invention has a stronger adsorption capacity for liquids.

[0163] Within a suitable range, the more micro / nanowire templates added, the higher the BET value of the resulting sample. The graphite material of this invention has a rich porous structure on its surface, which is beneficial for improving the rate performance of the graphite material. Furthermore, the graphite material of this invention has a relatively large pore size, resulting in a lower BET value, which helps prevent the deterioration of the high first-efficiency characteristics of the graphite material.

[0164] No micro / nanowire template was added in Comparative Example 1, and the length of the micro / nanowire template in Comparative Example 2 was relatively small. Neither Comparative Example 1 nor Comparative Example 2 could obtain graphite material with a through-pore structure. The specific surface area of ​​the graphite obtained in Comparative Examples 1 and 2 was relatively low, and the rate performance of the prepared batteries was poor.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A graphite material, characterized in that, The graphite material includes a graphite body having multiple through-hole structures, each through-hole structure having a pore diameter R of 0.07~1.81μm; the particle size Dv50 of the graphite material and the pore diameter R of the through-hole structure satisfy: 3.9≤Dv50 / R≤107.

1.

2. The graphite material according to claim 1, characterized in that, The material comprises at least one of the following features (1) to (7): (1) the particle size Dv50 of the graphite material and the pore diameter R of the through-hole structure satisfy: 3.9 ≤ Dv50 / R ≤ 30; (2) the particle size Dv50 of the graphite material is 6.7~17.8 μm; (3) the particle size Dv90 of the graphite material is 14.8~41.4 μm; the particle size Dv90 and particle size Dv10 of the graphite material satisfy: 4 ≤ Dv90 / Dv10 ≤ 9; (4) the specific surface area of ​​the graphite material is 3.12~4.56 m². 2 / g; (5) The oil absorption value of the graphite material is 56~68, and the unit is mL / 100g; (6) The graphitization degree of the graphite material is greater than or equal to 94.5%; (7) The discharge capacity of the graphite material is 355.5~365mAh / g.

3. The method for preparing the graphite material according to any one of claims 1 to 2, characterized in that, Includes the following steps: A mixture of carbon source and micro / nanowire material is coked to obtain a first material; the first material is crushed to obtain a second material; and the second material is graphitized. The micro-nanowire material vaporizes during the graphitization process of the second material. The diameter of the micro-nanowire material is 0.08~2μm, and the length of the micro-nanowire material is 20~120μm.

4. The method for preparing graphite material according to claim 3, characterized in that, The mixture comprises at least one of the following features (1) to (6): (1) the carbon source includes at least one of pitch and tar; (2) the micro-nanowire material includes at least one of silicon-based micro-nanowires and metal oxide micro-nanowires; (3) the mass ratio of the micro-nanowire material to the carbon source is (0.5~5):100; (4) the preparation method of the mixture specifically includes: preheating the carbon source and the micro-nanowire material, settling, and stirring; in the preparation method of the mixture, the preheating temperature is 200~300℃; the settling time is 3~6h; the stirring speed is 300~600rpm, and the stirring time is 1~3h.

5. The method for preparing graphite material according to claim 3, characterized in that, The coking temperature is 450~600℃, and the coking time is 5~10h.

6. The method for preparing graphite material according to claim 3, characterized in that, The material contains at least one of the following features (1) to (3): (1) the particle size dv50 of the second material and the diameter r of the micro / nanowire material satisfy: 0.01≤r / dv50≤0.29; (2) the particle size dv50 of the second material and the length L of the micro / nanowire material satisfy: 3≤L / dv50≤6.67; (3) the preparation method further includes a step of crushing the first material and then classifying it.

7. The method for preparing graphite material according to claim 3, characterized in that, It includes at least one of the following features (1) to (2): (1) the graphitization process includes a first heat treatment and a second heat treatment; the temperature of the first heat treatment is 1800~2100℃ and the time of the first heat treatment is 8~12h; the temperature of the second heat treatment is 2900~3200℃ and the time of the second heat treatment is 8~12h; (2) the heating rate of the graphitization process is 5~15℃ / min.

8. A negative electrode material, characterized in that, The graphite material included in any one of claims 1 to 2.

9. A battery, characterized in that, Includes the negative electrode material as described in claim 8.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.

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