Coal-based anode materials, their preparation methods and applications

Abstract

This invention relates to the field of carbon materials, and discloses a coal-based anode material, its preparation method, and its application. The coal-based anode material has the following characteristics: (1) the total pore volume of the coal-based anode material is ≤0.02 cm³. 3 / g, the pore volume of mesopores with a pore size of 2-50nm is ≤0.02cm³. 3 / g; the ratio of the pore volume of the mesopores to the total pore volume of the coal-based anode material is ≥68%; (2) the height ratio of the D peak and the G peak obtained by Raman spectroscopy of the coal-based anode material meets the following condition: ID / IG≤0.10; (3) the powder resistivity of the coal-based anode material is ≤400μΩ·m. The coal-based anode material has excellent conductivity, and the battery containing the coal-based anode material has high charge and discharge capacity, high initial coulombic efficiency, and excellent rate performance and cycle performance. At the same time, the preparation method of the anode material is simple and low in cost.

Description

Technical Field

[0001] This invention relates to the field of carbon materials, specifically to a coal-based anode material, its preparation method, and its application. Background Technology

[0002] The negative electrode of lithium-ion batteries is mainly composed of carbon materials, including amorphous carbon, natural graphite, and artificial graphite. Graphite has a regular layered structure and excellent conductivity, with a theoretical specific capacity of 372 mA·h / g and high efficiency, making it the mainstream negative electrode material. Currently, there are three main types of raw materials for developing artificial graphite: isotropic coke, pitch, and needle coke. Isotropic coke-based artificial graphite has low crystallinity, high isotropy, low capacity, and high power efficiency. Needle coke-based artificial graphite has high capacity but relatively lower rate capability, while pitch generally falls between the two.

[0003] CN104681786A discloses a coal-based anode material, its preparation method, and a lithium-ion battery. The coal-based anode material consists of a graphitized inner layer, a middle layer, and an outer layer distributed on the surface of the coal-based material. The preparation method includes: pulverizing the coal-based material; adding a binder, or a mixture of a binder and a modifier; and then performing molding and high-temperature graphitization to produce the finished product.

[0004] CN111232970A discloses a graphite anode material, a lithium-ion battery, a preparation method, and an application. The preparation method includes the following steps: subjecting a mixture of mesophase carbon microspheres (green pellets), anthracite powder, and a catalyst to high-temperature graphitization treatment; wherein the mass ratio of the mesophase carbon microspheres to the anthracite powder is 1:9-8:1; and the particle size D of the anthracite powder... 50 It is 10-20μm.

[0005] CN111628146A discloses a process for preparing lithium-ion battery anode materials using pitch-filled microcrystalline graphite. The process involves using microcrystalline graphite as raw material, adding medium-low temperature coal tar for kneading to obtain modified microcrystalline graphite; then transferring the modified microcrystalline graphite to a reaction vessel, adding liquid medium-temperature pitch for mixing, heating to 350-500℃, evacuating and allowing it to stand for 1-3 hours, then filling with inert gas, pressurizing and allowing it to stand for 2-5 hours, and finally depressurizing to obtain pitch-filled microcrystalline graphite; finally, the pitch-filled microcrystalline graphite is rolled, powdered, carbonized, sieved, and demagnetized to obtain the target product.

[0006] The existing technologies provide anode materials with complex structures and processes, high costs, and although the anode materials can improve the charge and discharge capacity and first coulombic efficiency of the battery, none of the above anode materials involve the powder resistivity of the anode material. The powder resistivity affects the conductivity of the anode material and the battery electrode containing the anode material, thereby affecting the electrochemical performance of the battery. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of complex structure, complicated preparation process, and high cost of existing negative electrode materials, and to provide a coal-based negative electrode material, its preparation method, and its application. This coal-based negative electrode material has excellent conductivity, and the battery containing this coal-based negative electrode material has high charge and discharge capacity, high initial coulombic efficiency, and excellent rate performance and cycle performance. At the same time, the preparation method of this negative electrode material is simple and low in cost.

[0008] To achieve the above objectives, the first aspect of the present invention provides a coal-based anode material, characterized in that the coal-based anode material has the following features:

[0009] (1) The total pore volume of the coal-based anode material is ≤0.02 cm³. 3 / g, the pore volume of mesopores with a pore size of 2-50nm is ≤0.02cm³. 3 / g; The ratio of the pore volume of the mesopores to the total pore volume of the coal-based anode material is ≥68%;

[0010] (2) The height ratio of the D peak and the G peak obtained by Raman spectroscopy of the coal-based anode material satisfies the following condition: ID / IG≤0.10;

[0011] (3) The specific resistivity of the coal-based negative electrode material is ≤400μΩ·m.

[0012] A second aspect of the present invention provides a method for preparing a coal-based anode material, wherein the method includes the following steps:

[0013] (1) The coal is crushed to obtain coal particles;

[0014] (2) The coal particles are mixed with a modifier and extruded to obtain an extruded material;

[0015] (3) The extruded material is pre-carbonized and granulated to obtain pre-carbonized particles;

[0016] (4) The pre-carbonized particles are graphitized to obtain the coal-based anode material.

[0017] A third aspect of the present invention provides a coal-based anode material prepared by the above method.

[0018] The fourth aspect of this invention provides the application of the above-mentioned coal-based anode material in lithium-ion batteries.

[0019] Through the above technical solutions, the coal-based anode material, its preparation method, and its application provided by the present invention achieve the following beneficial effects:

[0020] (1) The coal-based anode material provided by the present invention has a dense structure and a small total pore volume. Furthermore, the coal-based anode material has a suitable degree of crystallinity, a small grain size, and a low powder resistivity, which makes the coal-based anode material have excellent conductivity. Consequently, the battery containing the coal-based anode material has high charge and discharge capacity, high initial coulombic efficiency, and excellent rate performance and cycle performance.

[0021] (2) The coal-based anode material provided by this invention has excellent electrical conductivity. Specifically, the powder resistivity of the coal-based anode material is ≤300 μΩ·m. Furthermore, the battery containing this coal-based anode material has high charge / discharge capacity, initial coulombic efficiency, and excellent rate performance. Specifically, the charge / discharge capacity of the coal-based anode material is ≥345 mAh / g, the initial coulombic efficiency is ≥94%, the 2C / 0.2C capacity retention is ≥47%, and the capacity retention after 100 cycles at 0.1C is ≥96%.

[0022] (3) In the preparation method provided by the present invention, after the modifier and coal particles are mixed and extruded, the modifier can be fully filled into the pores of the coal particles to reduce the pore volume of the coal particles. This can significantly reduce the pore volume in the obtained coal-based anode material. In particular, the modifier can also modify the surface of the coal particles, making the structure of the obtained coal-based anode material more compact and having a small grain size. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of this invention provides a coal-based anode material, characterized in that the coal-based anode material has the following features:

[0025] (1) The total pore volume of the coal-based anode material is ≤0.02 cm³. 3 / g, the pore volume of mesopores with a pore size of 2-50nm is ≤0.02cm³. 3 / g; The ratio of the pore volume of the mesopores to the total pore volume is ≥68%;

[0026] (2) The height ratio of the D peak and the G peak obtained by Raman spectroscopy of the coal-based anode material satisfies the following condition: ID / IG≤0.10;

[0027] (3) The specific resistivity of the coal-based negative electrode material is ≤400μΩ·m.

[0028] In this invention, the coal-based anode material has a dense structure and a small total pore volume. Furthermore, the coal-based anode material has suitable crystallinity, small grain size, and low powder resistivity, which gives it excellent conductivity. Consequently, the battery containing the coal-based anode material has high charge and discharge capacity, high initial coulombic efficiency, and excellent cycle performance and rate performance.

[0029] In this invention, the total pore volume and mesopore volume of the coal-based anode material are measured using the nitrogen adsorption specific surface area method.

[0030] In this invention, the resistivity of the coal-based anode material powder is tested according to JB-T8537-2010, wherein the particle size is based on the particle size of the product of this invention.

[0031] Furthermore, when the total pore volume of the coal-based anode material is 0.0001-0.01 cm³... 3 / g, the pore volume of mesopores with a pore size of 2-50nm is 0.0001-0.01cm³. 3 At / g, the conductivity of the coal-based anode material is further improved, thereby further improving the charge-discharge capacity, initial coulombic efficiency, rate performance, and cycle performance of the battery containing the coal-based anode material.

[0032] Furthermore, when the total pore volume of the coal-based anode material is 0.0001-0.01 cm³... 3 / g, the pore volume of mesopores with a pore size of 2-50nm is 0.0002-0.0079cm³. 3 At / g, the conductivity of the coal-based anode material is further improved, thereby further improving the charge-discharge capacity, initial coulombic efficiency, rate performance, and cycle performance of the battery containing the coal-based anode material.

[0033] Furthermore, when the height ratio of the D peak and the G peak obtained by Raman spectroscopy of the negative electrode material satisfies the following condition: 0.02≤ID / IG≤0.10, more preferably 0.04≤ID / IG≤0.099, the conductivity of the coal-based negative electrode material is further improved, thereby further improving the charge-discharge capacity, initial coulombic efficiency, rate performance, and cycle performance of the battery containing the coal-based negative electrode material.

[0034] Furthermore, when the ratio of the pore volume of the mesopores to the total pore volume of the coal-based anode material is 69-90%, preferably 70-80%, the conductivity of the coal-based anode material is further improved, thereby further improving the charge-discharge capacity, initial coulombic efficiency, rate performance, and cycle performance of the battery containing the coal-based anode material.

[0035] Furthermore, the powder resistivity of the coal-based anode material is ≤380μΩ·m, preferably ≤350μΩ·m.

[0036] In this invention, the minimum pore size of the coal-based anode material is ≥2 nm. Preferably, the minimum pore size of the coal-based anode material is 2-10 nm.

[0037] According to the present invention, the specific surface area of ​​the coal-based anode material is ≤10m². 2 / g, preferably 1-5m 2 / g is more preferably 1-3.5m 2 / g.

[0038] In this invention, the specific surface area of ​​the coal-based anode material is measured using the nitrogen adsorption specific surface area method.

[0039] According to the present invention, the coal-based anode material comprises a first phase of graphite carbon formed by graphitization of coal and a second phase of graphite carbon formed by graphitization of a modifier.

[0040] The surface of the first phase graphite carbon is partially or entirely coated with the second phase graphite carbon;

[0041] Alternatively, the second phase of graphitic carbon is dispersed in the first phase of graphitic carbon.

[0042] According to the present invention, the content of the first phase graphite carbon is 60-99.9 wt% and the content of the second phase graphite carbon is 0.1-40 wt% based on the total weight of the coal-based anode material.

[0043] In this invention, the content of the first phase graphite carbon and the second phase graphite carbon in the negative electrode material is calculated based on the amount of raw materials fed and the residual carbon rate.

[0044] According to the present invention, the content of the first phase graphite carbon is 80-99.5 wt% and the content of the second phase graphite carbon is 0.5-20 wt% based on the total weight of the coal-based anode material.

[0045] In this invention, the crystallite size L along the c-axis of the graphite anode material is obtained by XRD. c Crystallite size L along the a-axis direction a The following conditions must be met:

[0046] 30nm≤L c ≤70nm, preferably 30nm≤L c ≤40nm;

[0047] 50nm≤L a ≤120nm, preferably 60nm≤L a ≤100nm;

[0048] The degree of graphitization of the graphite anode material satisfies the following condition: 85 ≤ degree of graphitization ≤ 93.

[0049] In this invention, the coal-based anode material with the above-mentioned microstructural characteristics has high isotropy and small grain size, thereby further improving the charge-discharge capacity, initial coulombic efficiency, rate performance and cycle performance of the battery containing the coal-based anode material.

[0050] In this invention, the degree of graphitization G of the negative electrode material is calculated according to the following formula:

[0051] G = (0.344 - d) 002 ) / (0.344-0.3354), where d 002 It was calculated using the Bragg equation.

[0052] A second aspect of the present invention provides a method for preparing a coal-based anode material, wherein the method includes the following steps:

[0053] (1) The coal is crushed to obtain coal particles;

[0054] (2) The coal particles are mixed with a modifier and extruded to obtain an extruded material;

[0055] (3) The extruded material is pre-carbonized and granulated to obtain pre-carbonized particles;

[0056] (4) The pre-carbonized particles are graphitized to obtain the coal-based anode material.

[0057] In this invention, during the preparation of graphite anode material, the pulverized coal particles are mixed with a modifier and extruded, which allows the coal particles and modifier to be fully and uniformly mixed, and the modifier to fully fill the defect positions of the coal. This significantly improves the uniformity and structural density of the anode material, enhances its conductivity, and consequently significantly improves the charge-discharge capacity, initial coulombic efficiency, rate performance, and cycle performance of the battery containing this anode material.

[0058] Furthermore, by pre-carbonizing and granulating the extruded material to obtain pre-carbonized particles, and then graphitizing it, the surface defects of the extruded material can be further reduced, resulting in uniform anode material particles with a more compact structure. This can further improve the conductivity of the anode material and, consequently, the electrochemical performance of the battery containing the anode material.

[0059] Furthermore, this invention uses coal as a raw material, and when preparing anode materials using the above method, it can not only significantly reduce the preparation cost of anode materials, but also achieve high-value-added utilization and clean and efficient conversion of coal.

[0060] According to the present invention, the coal meets the following conditions: vitrinite reflectance ≥2; volatile matter ≤10wt%; ash content ≤15wt%.

[0061] In this invention, coal that meets the above conditions is selected as a raw material to prepare graphite anode material, which can obtain graphite anode material with moderate crystallinity, small grain size and high isotropy, so that the graphite anode material has low powder resistivity, thereby further improving the rate performance of the battery containing the graphite anode material.

[0062] In this invention, the vitrinite reflectance of the coal was measured using the national standard GB / T 6948 method, and the volatile matter content and ash content of the coal were measured using the national standard GB / T30732 method.

[0063] In this invention, conventional equipment in the art, such as an air jet mill, can be used to pulverize coal.

[0064] In this invention, the particle size D of the coal particles 50 The size is 1-100μm, preferably 2-50μm.

[0065] According to the present invention, the modifier is at least one of coal tar pitch, petroleum asphalt, oxidized asphalt, and resin.

[0066] In this invention, the use of the aforementioned specific modifier to modify coal particles can significantly improve the density of the coal particles, thereby significantly improving the structural density of the coal-based anode material and giving the coal-based anode material a low powder resistivity, which in turn further improves the cycle performance of the battery containing the graphite anode material.

[0067] According to the present invention, the ratio of the coal particles to the modifier is 1-99:1.

[0068] In this invention, when the amounts of coal particles and modifiers meet the above-mentioned range, the structural density of the prepared coal-based anode material can be significantly improved, thereby significantly improving the electrochemical performance of the battery containing the coal-based anode material.

[0069] Furthermore, the ratio of the coal particles to the modifier is 2-80:1, preferably 3-50:1.

[0070] In this invention, preferably, the modifier is a composite modifier consisting of oxidized asphalt as the first modifier and at least one selected from coal tar pitch, petroleum asphalt, and resins as the second modifier.

[0071] In this invention, during the graphitization process, on the one hand, the modifier can fill the pores on the surface of coal-based graphite, and on the other hand, the light components of the modifier itself will escape to form pores. Compared with a single type of modifier, the above-mentioned composite modifier can exert a synergistic effect, significantly reduce the pore volume and increase the graphitization degree of the material, so that the graphite anode material has a low powder resistivity, thereby enabling the battery containing the graphite anode material to have high charge and discharge capacity and initial coulombic efficiency, and significantly improve cycle life and cycle rate.

[0072] Furthermore, the ratio of the first modifier to the second modifier is 1-10:10-1, preferably 1-5:5-1.

[0073] According to the present invention, the extrusion conditions include an extrusion temperature of 100-500°C.

[0074] In this invention, under the above conditions, extruding the mixture of coal particles and modifier can reduce the pore volume in the coal-based anode material, improve the structural density and overall uniformity of the coal-based anode material, so that the obtained anode material has a low powder resistivity, thereby further improving the electrochemical performance of the battery containing the anode material.

[0075] Furthermore, the extrusion conditions include an extrusion temperature of 200-420°C.

[0076] According to the present invention, the pre-carbonization conditions include: a pre-carbonization temperature of 400-1200°C and a pre-carbonization time of 1-20 h.

[0077] Furthermore, the pre-carbonization conditions include: a pre-carbonization temperature of 500-1000℃ and a pre-carbonization time of 1-10h.

[0078] According to the present invention, the graphitization conditions include: a graphitization temperature of 2800°C or higher and a graphitization time of 0.5-100 h.

[0079] According to the present invention, the graphitization conditions include: a graphitization temperature of 3000-3500℃ and a graphitization time of 1-50h.

[0080] A third aspect of the present invention provides a coal-based anode material prepared by the above-described preparation method.

[0081] The fourth aspect of this invention provides the application of the above-mentioned coal-based anode material in lithium-ion batteries.

[0082] In this invention, the coal-based anode material has a low powder resistivity; specifically, the powder resistivity of the coal-based anode material is ≤400 μΩ·m.

[0083] Furthermore, in this invention, the battery comprising the coal-based graphite anode material exhibits excellent electrochemical performance. Specifically, the battery comprising the coal-based graphite anode material has a charge / discharge capacity ≥346mAh / g, an initial coulombic efficiency ≥94%, a 2C / 0.2C capacity retention ≥45%, and a capacity retention ≥96% after 100 cycles at 0.1C.

[0084] The present invention will be described in detail below through embodiments.

[0085] (1) Particle size (D) 50 )

[0086] The D50 was obtained through testing using a Malvern Mastersizer 2000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0087] (2) BET and pore volume

[0088] Pore ​​volume was determined using a Micron 3flex N2 adsorption-desorption instrument. The test method followed the national standard GB / T19587. Sample pretreatment conditions were: treatment temperature 350℃, treatment time 6 hours. The DFT model was used to calculate the pore volume.

[0089] (3) ID / IG

[0090] The height ratio of the D and G peaks of coal-based anode materials obtained by Raman spectroscopy was determined using an NGSLabspec Raman spectrometer with a scanning range of 700-2100 cm⁻¹. -1 .

[0091] (4) Powder resistivity is tested in accordance with JB-T8537-2010, wherein the particle size is based on the particle size of the product of this invention.

[0092] (5) The vitrinite reflectance of coal was measured using the national standard GB / T 6948 method, and the volatile matter content and ash content of coal were measured using the national standard GB / T30732 method.

[0093] (6) Softening point of the modifier

[0094] The softening point of asphalt was tested using the Mettler titration method.

[0095] (7) Battery performance

[0096] The battery's charge / discharge capacity, initial coulombic efficiency, and rate performance were tested using the CT2001A battery tester from Wuhan Landian Electronics Co., Ltd., with a current of 0.1C (1C = 350mAh / g) and a voltage range of 0-3V.

[0097] Example 1

[0098] (1) Coal (vitrinite reflectance 2.445; volatile matter 7.7wt%; ash 2.6wt%) was pulverized by Raymond mill to obtain coal particles with D50 = 10μm;

[0099] (2) Mix 85 parts of coal particles with 15 parts of modifier and extrude them in an extruder at 320°C to obtain extruded material, wherein the mass ratio of coal particles to modifier is 5.67:1; wherein the modifier includes oxidized asphalt (softening point of 260°C) and petroleum asphalt (softening point of 240°C) in a mass ratio of 7:8.

[0100] (3) Under inert gas, the extruded material is carbonized at 700°C for 3 hours and then granulated to obtain pre-carbonized particles;

[0101] (4) The pre-carbonized particles were graphitized at 3000℃ for 16h; the coal-based anode material A1 was obtained by sieving.

[0102] In the coal-based anode material A1, the content of the first phase graphite carbon is 91.2 wt%, and the content of the second phase graphite carbon is 8.8 wt%.

[0103] Example 2

[0104] (1) Coal (vitrinite reflectance 2.445; volatile matter 7.7wt%; ash 2.6wt%) was pulverized by Raymond mill to obtain coal particles with D50 = 10μm;

[0105] (2) Mix 85 parts of coal particles with 15 parts of modifier and extrude them in an extruder at 320°C to obtain extruded material. The mass ratio of the coal particles to the modifier is 5.67:1. The modifier is petroleum asphalt (softening point is 240°C).

[0106] (3) Under inert gas, the extruded material is carbonized at 700°C for 3 hours and then granulated to obtain pre-carbonized particles;

[0107] (4) The pre-carbonized particles were graphitized at 3000℃ for 16h; the coal-based anode material A2 was obtained by sieving.

[0108] In the coal-based anode material A2, the content of the first phase graphite carbon is 91.9 wt%, and the content of the second phase graphite carbon is 8.1 wt%.

[0109] Example 3

[0110] (1) Coal (vitrinite reflectance 2.445; volatile matter 7.7wt%; ash 2.6wt%) was pulverized by Raymond mill to obtain coal particles with D50 = 10μm;

[0111] (2) Mix 85 parts of coal particles with 15 parts of modifier and extrude them in an extruder at 320°C to obtain extruded material, wherein the mass ratio of coal particles to modifier is 5.67:1, and the modifier is oxidized asphalt (softening point is 260°C).

[0112] (3) Under inert gas, the extruded material is carbonized at 700°C for 3 hours and then granulated to obtain pre-carbonized particles;

[0113] (4) The pre-carbonized particles were graphitized at 3000℃ for 16h; the coal-based anode material A3 was obtained by sieving.

[0114] In the coal-based anode material A3, the content of the first phase graphite carbon is 90.4 wt%, and the content of the second phase graphite carbon is 9.6 wt%.

[0115] Example 4

[0116] Anode material A4 was prepared according to the method in Example 1, except that the amount of coal particles was 95 parts, the amount of modifier was 5 parts, and the mass ratio of the two was 19:1. Among the modifiers, the mass ratio of oxidized asphalt to petroleum asphalt was 2:3. Coal-based anode material A4 was thus obtained.

[0117] In the coal-based anode material A4, the content of the first phase graphite carbon is 97.2 wt%, and the content of the second phase graphite carbon is 2.8 wt%.

[0118] Example 5

[0119] The negative electrode material A5 was prepared according to the method of Example 1, except that the amount of coal particles was 70 parts, the amount of modifier was 30 parts, and the mass ratio of the two was 2.33:1. Among the modifiers, the mass ratio of oxidized asphalt to petroleum asphalt was 1:1. Coal-based negative electrode material A5 was thus obtained.

[0120] In the coal-based anode material A5, the content of the first phase graphite carbon is 80.9 wt%, and the content of the second phase graphite carbon is 19.1 wt%.

[0121] Example 6

[0122] The negative electrode material A6 was prepared according to the method of Example 2, except that petroleum asphalt with a softening point of 100°C was used instead of petroleum asphalt with a softening point of 250°C to obtain coal-based negative electrode material A6.

[0123] In the coal-based anode material A6, the content of the first phase graphite carbon is 93.4 wt%, and the content of the second phase graphite carbon is 6.6 wt%.

[0124] Example 7

[0125] The negative electrode material A7 was prepared according to the method of Example 1, except that in step (2), the extrusion temperature was 400°C. Coal-based negative electrode material A7 was obtained.

[0126] In the coal-based anode material A7, the content of the first phase graphite carbon is 91.2 wt%, and the content of the second phase graphite carbon is 8.8 wt%.

[0127] Example 8

[0128] Anode material A8 was prepared according to the method of Example 1, except that the extrusion temperature in step (2) was 260°C. Coal-based anode material A7 was obtained.

[0129] In the coal-based anode material A8, the content of the first phase graphite carbon is 91.2 wt%, and the content of the second phase graphite carbon is 8.8 wt%.

[0130] Comparative Example 1

[0131] The negative electrode material was prepared according to the method of Example 1, except that steps (2) and (3) were not performed, and coal-based negative electrode material D1 was obtained.

[0132] In the coal-based anode material D1, the content of the first phase graphite carbon is 100 wt%, and the content of the second phase graphite carbon is 0 wt%.

[0133] Comparative Example 2

[0134] The negative electrode material was prepared according to the method of Example 1, except that extrusion was not performed in step (2). Coal-based negative electrode material D2 was obtained.

[0135] In the coal-based anode material D2, the content of the first phase graphite carbon is 91.2 wt%, and the content of the second phase graphite carbon is 8.8 wt%.

[0136] Comparative Example 3

[0137] The negative electrode material was prepared according to the method of Example 1, except that step (3) was not performed. Coal-based negative electrode material D3 was obtained.

[0138] In the coal-based anode material D3, the content of the first phase graphite carbon is 91.2 wt%, and the content of the second phase graphite carbon is 8.8 wt%.

[0139] The coal-based anode materials obtained in the examples and comparative examples were characterized, and the results are shown in Table 1.

[0140] Table 1

[0141]

[0142]

[0143] V1 refers to the total pore volume of the negative electrode material; V2 refers to the mesopore volume of the negative electrode material.

[0144] Test case

[0145] The negative electrode materials prepared in the examples and comparative examples were mixed uniformly with conductive carbon black Super P and binder polyvinylidene fluoride (PVDF) at a mass ratio of 92:3:5. N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred to form a uniform negative electrode slurry. The slurry was then uniformly coated onto aluminum foil using a scraper, dried, and the resulting negative electrode sheet was cut and transferred to an MBraun 2000 glove box (Ar atmosphere, H2O and O2 concentrations less than 0.1 × 10⁻⁶). -6 The lithium metal sheet (volume percentage) was used as a reference electrode to assemble a coin cell. The charge / discharge capacity, initial coulombic efficiency, and rate performance of the coin cell were tested, and the test results are shown in Table 2.

[0146] Table 2

[0147]

[0148]

[0149] As can be seen from the results in Tables 1 and 2, the coal-based anode material provided by the embodiments of the present invention has a dense structure and a small total pore volume. Furthermore, the coal-based anode material has suitable crystallinity, small grain size, and low powder resistivity, which gives it excellent conductivity. Consequently, the battery containing the coal-based anode material has high charge and discharge capacity, high initial coulombic efficiency, excellent rate performance, and long cycle life.

[0150] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A coal-based anode material, characterized in that, The coal-based anode material has the following characteristics: (1) The total pore volume of the coal-based negative electrode material is 0.006791-0.01 cm³. 3 / g, the pore volume of mesopores with a pore size of 2-50nm is 0.0002-0.0079cm³. 3 / g; the ratio of the pore volume of the mesopores to the total pore volume of the coal-based anode material is ≥68%; (2) The height ratio of the D peak and the G peak obtained by Raman spectroscopy of the coal-based anode material satisfies the following condition: ID / IG≤0.10; (3) The powder resistivity of the coal-based negative electrode material is ≤380μΩ·m; The specific surface area of ​​the coal-based anode material is ≤10m². 2 / g; The coal-based anode material comprises a first phase of graphite carbon formed by graphitization of coal and a second phase of graphite carbon formed by graphitization of a modifier. The surface of the first phase graphite carbon is partially or entirely coated with the second phase graphite carbon; Alternatively, the second phase of graphitic carbon is dispersed in the first phase of graphitic carbon; Specifically, based on the total weight of the coal-based anode material, the content of graphite carbon in the first phase is 60-99.9 wt%, and the content of graphite carbon in the second phase is 0.1-40 wt%. The c-axis crystallite size L of the coal-based anode material was obtained by XRD. c The following condition must be met: 30nm≤L c ≤40nm; The modifier is selected from at least one of coal tar pitch, petroleum asphalt, oxidized asphalt, and resins.

2. The coal-based anode material according to claim 1, wherein, The height ratio of the D peak and G peak obtained by Raman spectroscopy of the negative electrode material satisfies the following condition: 0.02≤ID / IG≤0.

10.

3. The coal-based anode material according to claim 1 or 2, wherein, The height ratio of the D peak and G peak obtained by Raman spectroscopy of the negative electrode material satisfies the following condition: 0.04≤ID / IG≤0.

099.

4. The coal-based anode material according to claim 1 or 2, wherein, The ratio of the pore volume of the mesopores to the total pore volume of the coal-based anode material is 69-90%.

5. The coal-based anode material according to claim 4, wherein, The ratio of the pore volume of the mesopores to the total pore volume of the coal-based anode material is 70-80%.

6. The coal-based anode material according to claim 1 or 2, wherein, The powder resistivity of the coal-based anode material is ≤350μΩ·m.

7. The coal-based anode material according to claim 1 or 2, wherein, The specific surface area of ​​the coal-based anode material is 1-5m². 2 / g.

8. The coal-based anode material according to claim 7, wherein, The specific surface area of ​​the coal-based anode material is 1-3.5 m². 2 / g.

9. The coal-based anode material according to claim 1, wherein, Based on the total weight of the coal-based anode material, the content of the first phase graphite carbon is 80-99.5 wt%, and the content of the second phase graphite carbon is 0.5-20 wt%.

10. A method for preparing the coal-based anode material according to any one of claims 1-9, wherein, The method includes the following steps: (1) The coal is crushed to obtain coal particles; (2) The coal particles are mixed with the modifier and extruded to obtain the extruded material; (3) The extruded material is pre-carbonized and granulated to obtain pre-carbonized particles; (4) The pre-carbonized particles are graphitized to obtain the coal-based anode material; The mass ratio of the coal particles to the modifier is 1-99:1; The modifier is selected from at least one of coal tar pitch, petroleum asphalt, oxidized asphalt, and resins.

11. The preparation method according to claim 10, wherein, The coal must meet the following conditions: vitrinite reflectance ≥2; volatile matter ≤10wt%; ash content ≤15wt%.

12. The preparation method according to claim 10, wherein, The mass ratio of the coal particles to the modifier is 2-80:

1.

13. The preparation method according to claim 12, wherein, The mass ratio of the coal particles to the modifier is 3-50:

1.

14. The preparation method according to claim 10, wherein, The extrusion conditions include an extrusion temperature of 100-500℃.

15. The preparation method according to claim 14, wherein, The extrusion conditions include an extrusion temperature of 200-420℃.

16. The preparation method according to claim 10, wherein, The pre-carbonization conditions include: a pre-carbonization temperature of 400-1200℃ and a pre-carbonization time of 1-20h.

17. The preparation method according to claim 16, wherein, The pre-carbonization conditions include: pre-carbonization temperature of 500-1000℃ and pre-carbonization time of 1-10h.

18. The preparation method according to claim 10, wherein, The graphitization conditions include: a graphitization temperature of 2800℃ or higher and a graphitization time of 0.5-100h.

19. The preparation method according to claim 18, wherein, The graphitization conditions include: a graphitization temperature of 3000-3500℃ and a graphitization time of 1-50h.

20. The application of the coal-based anode material according to any one of claims 1-9 in lithium-ion batteries.

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