Single-particle artificial graphite material, preparation method thereof, negative electrode material, and negative electrode sheet

Abstract

This application relates to a single-particle artificial graphite material and its preparation method, a negative electrode material, and a negative electrode sheet. The preparation method includes the following steps: preparing graphite sheets from a carbon source via chemical vapor deposition; heat-treating the graphite sheets at 1300℃~2800℃ to prepare artificial graphite; and pulverizing and sieving the artificial graphite to prepare the single-particle artificial graphite material. This preparation method, by preparing graphite sheets through vapor deposition and then heat-treating them to graphitize them, prepares the single-particle artificial graphite material. The graphite sheets prepared by vapor deposition have a layered structure. Compared with traditional artificial graphite, the single-particle artificial graphite material prepared by the above method has higher conductivity and better electrochemical stability, exhibiting superior rate performance in secondary batteries.

Description

Technical Field

[0001] This application relates to the field of secondary battery anode material technology, specifically to a single-particle artificial graphite material and its preparation method, anode material, and anode sheet. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries that primarily function by the movement of lithium ions between the positive and negative electrodes. Due to their high energy density, lack of memory effect, and long cycle life, lithium-ion batteries are widely used in various fields, including small electronic devices such as mobile phones, portable computers, camcorders, and cameras, as well as large equipment such as electric vehicles and energy storage systems.

[0003] Negative electrode materials for lithium-ion batteries include carbon-based, silicon-based, and tin-based materials. Among them, carbon-based materials, such as natural graphite, artificial graphite, coke, soft carbon, and hard carbon, are the most commonly used negative electrode materials for lithium-ion batteries. Artificial graphite is a graphite material obtained through organic carbonization followed by high-temperature graphitization; its degree of graphitization can be controlled through synthesis methods. However, the conductivity and rate performance of artificial graphite materials are not ideal, limiting their widespread application in negative electrode materials. Summary of the Invention

[0004] Therefore, it is necessary to provide a single-particle artificial graphite material with good electrical conductivity and excellent rate performance, and its preparation method.

[0005] In addition, negative electrode materials and negative electrode sheets containing the above-mentioned single-particle artificial graphite materials are also provided.

[0006] One aspect of this application provides a method for preparing a single-particle artificial graphite material, comprising the following steps:

[0007] Graphite sheets were prepared from carbon sources via chemical vapor deposition.

[0008] The graphite sheets are heat-treated at 1300℃~2800℃ to prepare artificial graphite;

[0009] The artificial graphite is pulverized and sieved to prepare the single-particle artificial graphite material.

[0010] In some embodiments, prior to the heat treatment, a metal-based coating is prepared on the surface of the graphite sheet;

[0011] The steps for preparing the metal-based coating include:

[0012] The graphite sheet was immersed in a metal-organic solution;

[0013] The graphite sheet immersed in the metal-organic solution is removed and dried to prepare the metal-based coating.

[0014] In some embodiments, the organometallic compound includes at least one of organometallic compounds of iron, nickel, copper, and chromium.

[0015] In some embodiments, prior to the heat treatment, the process further includes grafting a graphite sheet having the metal-based coating on its surface.

[0016] In some embodiments, the step of grafting graphite sheets with a metal-based coating on their surface includes:

[0017] The graphite sheet with a metal-based coating on its surface is immersed in a grafting compound solution;

[0018] The graphite sheet impregnated with the grafting compound solution is heated at 100°C to 150°C.

[0019] The grafting compound includes at least one of aminosilane, hydroxysilane, and isocyanate.

[0020] In some embodiments, the chemical vapor deposition temperature is 800°C to 1200°C;

[0021] And / or, the thickness of the graphite sheet is 5nm to 100nm;

[0022] And / or, the heat treatment time is 1 hour to 5 hours.

[0023] Secondly, this application also provides a single-particle artificial graphite material, which is prepared by the method for preparing single-particle artificial graphite material described in the first aspect above.

[0024] In some embodiments, the particle size D10 of the single-particle artificial graphite material is 4 μm to 7 μm; the particle size D50 of the single-particle artificial graphite material is 9 μm to 12 μm; and the particle size D90 of the single-particle artificial graphite material is 18 μm to 25 μm.

[0025] Thirdly, this application also provides a negative electrode material, including the single-particle artificial graphite material described in the second aspect above.

[0026] Fourthly, this application also provides a negative electrode sheet, comprising the negative electrode material described in the third aspect above.

[0027] The method for preparing single-particle artificial graphite material provided in this application involves preparing graphite sheets via vapor deposition, followed by heat treatment of the graphite sheets at 1300℃ to 2800℃ to graphitize them, thereby preparing single-particle artificial graphite. The graphite sheets prepared by vapor deposition have a layered structure. Compared to traditional artificial graphite, the single-particle artificial graphite material prepared by the above method exhibits higher conductivity and better electrochemical stability, resulting in superior rate performance in secondary batteries. Detailed Implementation

[0028] To facilitate understanding of this application, a more complete description will be provided below. 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 more thorough and complete understanding of the disclosure of this application.

[0029] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0030] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0031] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 800–850nm means that the units for the left endpoint “800” and the right endpoint “850” are both nm (nanometers).

[0032] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0033] Unless otherwise specified, the temperature parameters in this document can be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0034] In this document, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the invention, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates 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.

[0037] 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.

[0038] One aspect of this application provides a method for preparing a single-particle artificial graphite material, comprising the following steps S100 to S300.

[0039] Step S100: Graphite sheets are prepared from carbon source by chemical vapor deposition (CVD).

[0040] In some embodiments, the carbon source includes, but is not limited to, carbon-containing materials such as petroleum coke, coal coke, and natural gas. The carbon source can decompose at high temperatures, releasing carbon atoms to provide a carbon source for the CVD reaction.

[0041] In some embodiments, the carbon source is grafted. Grafted carbon sources exhibit better overall uniformity when used to prepare single-particle artificial graphite materials.

[0042] In some embodiments, the chemical vapor deposition temperature is 800°C to 1200°C. Optionally, the chemical vapor deposition temperature is within the range of 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, or any combination thereof. Further, the chemical vapor deposition temperature is 900°C to 1000°C. Controlling the chemical vapor deposition temperature within the range of 900°C to 1000°C results in higher chemical vapor deposition efficiency.

[0043] In some embodiments, the CVD reaction in step S100 further includes a carrier gas to ensure gas flow. In some embodiments, the carrier gas is hydrogen. Hydrogen helps to remove impurities from the CVD reaction chamber and improve CVD reaction efficiency.

[0044] During the CVD reaction, the carbon source decomposes at high temperature, releasing carbon atoms, which then deposit to form graphite sheets. In some embodiments, the thickness of the graphite sheets is 5 nm to 100 nm. Optionally, the thickness of the graphite sheets is within the range of 5 nm, 10 nm, 20 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, or any combination thereof.

[0045] In some embodiments, prior to the heat treatment in step S200, a step S110 is included: preparing a metal-based coating on the surface of the graphite sheet. By preparing a metal-based coating on the surface of the graphite sheet, the electrochemical activity of the graphite sheet can be improved, thereby improving the conductivity of the obtained single-particle artificial graphite material.

[0046] In some embodiments, step S110 includes:

[0047] Step S112: Immerse the graphite sheet in a metal-organic solution.

[0048] In some embodiments, the organometallic compound includes at least one of organoferric compounds, organonickel compounds, organocopper compounds, and organochromium compounds.

[0049] In some of these embodiments, the organoiron compound includes, but is not limited to, iron pentacarbonyl.

[0050] In some embodiments, the organonickel compounds include, but are not limited to, nickel carbene complexes and nickel cyclopentadiene complexes.

[0051] In some of these embodiments, the copper organochemical compounds include, but are not limited to, copper cyclopentadiene complexes.

[0052] In some of these embodiments, the chromium organic compound includes, but is not limited to, chromium carbonylate.

[0053] In some embodiments, the organometallic solution is a 0.05M iron pentacarbonyl solution, and the solvent is n-hexane.

[0054] Step S114: Remove the graphite sheet immersed in the metal-organic solution and dry it to prepare a metal-based coating.

[0055] In some embodiments, prior to the heat treatment in step S200, a step S120 is included: grafting a graphite sheet with a metal-based coating onto its surface. By grafting the graphite sheet with the metal-based coating, the surface properties of the graphite sheet can be altered, improving the compatibility of the resulting single-particle artificial graphite material with the electrolyte.

[0056] In some embodiments, step S120 includes:

[0057] Step S122: Immerse the graphite sheet with a metal-based coating on its surface in a grafting compound solution.

[0058] Step S124: Heat the graphite sheet impregnated with the grafting compound solution at 100°C to 150°C. This heat treatment allows the grafting compound to be stably grafted onto the surface of the graphite sheet. Optionally, the heating temperature is within the range of 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or any combination thereof.

[0059] In some embodiments, the grafting compound includes at least one of aminosilane, hydroxysilane, and isocyanate.

[0060] In some embodiments, the grafting compound includes at least one of vinyltrichlorosilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, triethoxysilane, propylene cyanate, and methyltrichlorosilane.

[0061] In some embodiments, the grafting compound is vinyltrichlorosilane. The concentration of the grafting compound solution is 0.1 M, and the solvent is acetone.

[0062] Step S200: The graphite sheet is heat-treated at 1300℃~2800℃ to prepare artificial graphite. Optionally, the heat treatment temperature is within the range of 1300℃, 1500℃, 2000℃, 2200℃, 2400℃, 2500℃, 2800℃ or any combination thereof.

[0063] In some embodiments, the heat treatment includes:

[0064] Step S210: Starting from room temperature, increase the temperature to 500°C at a rate of 10°C / min and hold for 1 hour.

[0065] Step S220: Increase the temperature from 500℃ to 1500℃ at a rate of 5℃ / min and hold for 2 hours.

[0066] Step S230: Heat from 1500℃ to 2600℃ at a rate of 2℃ / min and hold for 3 hours.

[0067] Step S240: Lower the temperature from 2600℃ to 2300℃ and keep it at that temperature for 1 hour, then raise the temperature back to 2600℃ and keep it at that temperature for 2 hours. Repeat this cycle 3 times.

[0068] Step S250: Cool from 2600°C to 500°C at a rate of 10°C / min; then cool to room temperature at a rate of 5°C / min.

[0069] Through the heat treatment methods described in steps S210 to S250, the crystallization of graphite sheets can be made more uniform, and internal stress of the graphite sheets can be avoided.

[0070] Step S300: Crush and sieve the artificial graphite to prepare single-particle artificial graphite material.

[0071] In some embodiments, a ball mill or grinding mill is used to pulverize the artificial graphite.

[0072] Secondly, this application also provides a single-particle artificial graphite material, which is prepared by the method for preparing single-particle artificial graphite material described in the first aspect above.

[0073] In some embodiments, the particle size D10 of the single-particle artificial graphite material is 4 μm to 7 μm; the particle size D50 of the single-particle artificial graphite material is 9 μm to 12 μm; and the particle size D90 of the single-particle artificial graphite material is 18 μm to 25 μm.

[0074] In some embodiments, the tap density of a single-particle artificial graphite material is ≥1.0 g / cm³. 3 .

[0075] In some embodiments, the specific surface area of ​​a single particle of artificial graphite material is ≤2.0 m². 2 / g.

[0076] Thirdly, this application also provides a negative electrode material, including the single-particle artificial graphite material described in the second aspect above.

[0077] Fourthly, this application also provides a negative electrode sheet, comprising the negative electrode material described in the third aspect above.

[0078] Fifthly, this application also provides a secondary battery, including the negative electrode sheet described in the fourth aspect above.

[0079] To make the objectives, technical solutions, and advantages of this application clearer and more concise, the following specific embodiments are used for illustration, but this application is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of this application and can be used to describe this application, but should not be construed as limiting the scope of this application. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

[0080] Example 1

[0081] The method for preparing single-particle artificial graphite in this embodiment includes the following steps:

[0082] (1) Petroleum coke and hydrogen are introduced into the CVD reaction chamber and CVD reaction is carried out at 950℃ to deposit carbon atoms to form graphite sheets.

[0083] (2) Prepare a 0.5M hexane solution of iron pentacarbonyl; immerse the graphite sheet obtained in step (1) in the solution and stir for 2 hours to ensure full contact between the solution and the graphite sheet. Then remove the graphite sheet, dry it, and obtain a graphite sheet with a metal-based coating on its surface.

[0084] (3) Prepare an acetone solution of vinyltrichlorosilane with a concentration of 0.1M; immerse the graphite sheet obtained in step (2) in the solution and stir for 3 hours to ensure that the solution and graphite sheet are in full contact. Then remove the graphite sheet and heat it at 150°C to obtain a surface-grafted graphite sheet.

[0085] (4) Place the graphite sheet prepared in step (3) in a heating furnace and heat it from room temperature to 500°C at a rate of 10°C / min and hold for 1 hour. Then, starting from 500°C, heat it to 1500°C at a rate of 5°C / min and hold for 2 hours. Starting from 1500°C, heat it to 2600°C at a rate of 2°C / min and hold for 3 hours. Cool it down from 2600°C to 2300°C and hold for 1 hour, then heat it up to 2600°C and hold for 2 hours. Repeat this cycle 3 times. Then, cool it down from 2600°C to 500°C at a rate of 10°C / min, and then cool it down to room temperature at a rate of 5°C / min. Remove the prepared artificial graphite.

[0086] (5) The artificial graphite obtained in step (4) is ball-milled, sieved, and the single-particle artificial graphite material of this embodiment is obtained. The particle size of the obtained single-particle artificial graphite is D10 of 4.5 μm, D50 of 10.6 μm, and D90 of 20.3 μm.

[0087] Comparative Example 1

[0088] This comparative example uses commercially available artificial graphite as the negative electrode material.

[0089] Test example:

[0090] Working electrode preparation: A slurry was prepared by mixing the negative electrode active material, conductive agent SuperP, and binder PVDF in the above-described examples or comparative examples at a mass ratio of 92:3:5. The slurry was then coated onto copper foil to prepare the working electrode.

[0091] Battery fabrication: Lithium foil was used as the counter electrode; the electrolyte contained 1M LiPF6, and its solvent was a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1. The electrolyte also contained 1wt% of the additive vinylene carbonate (VC). The working electrode, separator, and counter electrode were stacked to prepare the battery cell, and then the electrolyte was injected to prepare the battery to be tested.

[0092] The prepared test cells were subjected to electrochemical tests using the methods described below. The test results are recorded in Table 1.

[0093] Conductivity testing method: Conductivity was tested using a resistivity meter. The artificial graphite materials from Example 1 and Comparative Example 1 were mounted on the testing instrument, ensuring good contact between the test electrodes and the sample surface. The current and voltage difference passing through the sample were then measured to calculate the conductivity. The resistivity was calculated using Ohm's law based on the voltage and current values, and then the conductivity was calculated from the resistivity.

[0094] Cycle stability (capacity retention after 500 cycles) test method: The battery is subjected to 500 charge-discharge cycles, and the discharge capacity after the 500th cycle is compared with the initial discharge capacity. Capacity retention rate = (discharge capacity after 300 cycles / initial discharge capacity) * 100%.

[0095] Rate performance (2C, 5C discharge capacity) test method: The discharge capacity of the battery under test is tested at different discharge rates (2C, 5C).

[0096] Table 1

[0097]

[0098] As can be seen from the data in Table 1, the single-particle artificial graphite material prepared by the method of this application in Example 1 has high electrical conductivity and high capacity retention after 500 cycles; the discharge capacity at 2C and 5C rates is 350mAh / g and 320mAh / g, respectively, which shows good rate performance.

[0099] 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.

[0100] The embodiments described above merely illustrate several implementation methods of this application to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection 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 scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a single-particle artificial graphite material, characterized in that, Includes the following steps: Graphite sheets were prepared from carbon sources via chemical vapor deposition. The graphite sheets are heat-treated at 1300℃~2800℃ to prepare artificial graphite; The artificial graphite is pulverized and sieved to prepare the single-particle artificial graphite material; Prior to the heat treatment, the preparation method further includes preparing a metal-based coating on the surface of the graphite sheet; The steps for preparing the metal-based coating include: immersing the graphite sheet in a metal-organic solution; removing the graphite sheet immersed in the metal-organic solution and drying it to prepare the metal-based coating; Prior to the heat treatment, the preparation method further includes: grafting a graphite sheet with the metal-based coating on its surface; the step of grafting a graphite sheet with the metal-based coating on its surface includes: immersing the graphite sheet with the metal-based coating on its surface in a grafting compound solution; heating the graphite sheet immersed in the grafting compound solution at 100°C to 150°C; wherein the grafting compound includes at least one of aminosilane, hydroxysilane, and isocyanate.

2. The method for preparing single-particle artificial graphite material according to claim 1, characterized in that, The organometallic compounds include at least one of organometallic compounds of iron, organometallic compounds of nickel, organometallic compounds of copper, and organometallic compounds of chromium.

3. The method for preparing single-particle artificial graphite material according to claim 1, characterized in that, The temperature for chemical vapor deposition is 800℃~1200℃; And / or, the thickness of the graphite sheet is 5 nm to 100 nm; And / or, the heat treatment time is 1 hour to 5 hours.

4. A single-particle artificial graphite material, characterized in that, The single-particle artificial graphite material was prepared using the preparation method described in any one of claims 1 to 3.

5. The single-particle artificial graphite material according to claim 4, characterized in that, The particle size D10 of the single-particle artificial graphite material is 4 μm to 7 μm; the particle size D50 of the single-particle artificial graphite material is 9 μm to 12 μm; and the particle size D90 of the single-particle artificial graphite material is 18 μm to 25 μm.

6. A negative electrode material, characterized in that, Includes the single-particle artificial graphite material as described in claim 4 or 5.

7. A negative electrode sheet, characterized in that, Includes the negative electrode material as described in claim 6.

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