Modified artificial graphite materials, their preparation methods, applications, and secondary batteries

Abstract

This invention provides a modified artificial graphite material, its preparation method, applications, and secondary batteries. The modified artificial graphite material comprises a graphite crystal matrix and a functionalized carbon composite layer encapsulating the graphite crystal matrix. The functionalized carbon composite layer contains amorphous carbon, carbon surface defects, and oxygen-containing functional groups. Raman spectroscopy reveals the presence of Ig in the spectrum. D / I G The peak area ratio is 0.30–0.60, I D The representative is located at 1350cm ‑1 peak D at location I G The representative is located at 1580cm ‑1 The G peak at [location]. In the Raman spectrum, I [value missing]. D / I G A peak area ratio of 0.30–0.60 indicates that the disorder of amorphous carbon is within a certain range. A certain degree of amorphous carbon can provide more lithium-ion diffusion channels, thus improving fast charge / discharge performance, and can also avoid excessive disorder affecting graphite performance. Carbon surface defects can increase specific surface area to improve material capacity. A functionalized carbon composite layer containing amorphous carbon, carbon surface defects, and oxygen-containing functional groups, encapsulating the surface of the graphite crystalline matrix, can reduce the rebound rate and increase the compaction density.

Description

Technical Field

[0001] This invention relates to the field of carbon material preparation technology, and in particular to a modified artificial graphite material, its preparation method, applications, and secondary batteries. Background Technology

[0002] With the widespread adoption of new energy vehicles, electric vehicles replacing gasoline-powered vehicles has become an inevitable trend in the industry. As a core component of electric vehicles, the energy density and rate performance of the power battery determine the vehicle's range and fast-charging capabilities. Therefore, the market is placing increasingly higher demands on the capacity, compaction density, and fast charging / discharging performance of power batteries.

[0003] Graphite, as the most widely used negative electrode material, is one of the important factors affecting battery performance and has a significant impact on battery performance. Graphite is generally divided into artificial graphite and natural graphite. Because natural graphite is relatively soft and easily deforms when compacted, the industry uses artificial graphite more often.

[0004] To improve the specific capacity, compaction density, and fast-charging performance of artificial graphite, current commercial products typically employ optimized raw materials, improved aggregate particle size, and coating. Specifically, the capacity and compaction density of the final material are increased by selecting easily graphitized petroleum coke, needle coke, or natural graphite; or surface coating is used to enhance the material's fast-charging performance. While these methods can produce artificial graphite materials with high capacity, high compaction, or fast-charging performance, none can simultaneously achieve all three.

[0005] Therefore, how to improve the compaction density and capacity of artificial graphite while simultaneously enhancing its fast-charging performance is a pressing technical problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a modified artificial graphite material, its preparation method, applications, and secondary batteries. This modified artificial graphite material exhibits high specific capacity and compaction density, excellent fast-charging performance, a simple preparation process, and can be mass-produced, meeting market requirements for the capacity, compaction density, and fast charge / discharge performance of power batteries.

[0007] To achieve the above objectives, a first aspect of the present invention provides a modified artificial graphite material, comprising a graphite crystal matrix and a functionalized carbon composite layer encapsulating the graphite crystal matrix, wherein the functionalized carbon composite layer contains amorphous carbon, carbon surface defects, and oxygen-containing functional groups, and, according to Raman spectroscopy, exhibits Ig in its spectrum. D / I G The peak area ratio is 0.30–0.60, I D The representative is located at 1350cm -1 peak D at location I GThe representative is located at 1580cm -1 The G peak at that location.

[0008] In the technical solution adopted in this invention, the modified artificial graphite material includes a graphite crystal matrix and a functionalized carbon composite layer encapsulating the graphite crystal matrix, wherein the functionalized carbon composite layer contains amorphous carbon, carbon surface defects, and oxygen-containing functional groups. In Raman spectroscopy, I... D / I G A peak area ratio of 0.30–0.60 indicates that the disorder of amorphous carbon is within a certain range. A certain degree of amorphous carbon can provide more lithium-ion diffusion channels, thus improving fast charge / discharge performance, and can also avoid excessive disorder affecting graphite performance. Carbon surface defects can increase specific surface area to improve material capacity. A functionalized carbon composite layer containing amorphous carbon, carbon surface defects, and oxygen-containing functional groups, encapsulating the surface of the graphite crystalline matrix, can reduce the rebound rate and increase the compaction density.

[0009] As one technical solution of the present invention, the specific surface area of ​​the modified artificial graphite material is ≥1.20 m². 2 / g.

[0010] As one technical solution of the present invention, the Dv50 of the modified artificial graphite material is 8.0 to 16.0 μm.

[0011] As a technical solution of the present invention, the compaction density of the graphite crystal matrix under 50000N pressure is D1, the compaction density of the modified artificial graphite material under 50000N pressure is D2, and the compaction change rate of the modified artificial graphite is D, wherein D=D2-D1≥0.05g / cm³ 3 .

[0012] As a technical solution of the present invention, the rebound rate of the modified artificial graphite material is ρ, where ρ is 10.0–50.0%, and ρ = (P 5t -P 20N ) / P 5t *100, where ρ is the rebound rate, P 5t To determine the compaction density under a pressure of 50,000 N, P 20N This is to retain only the compaction density under 20N pressure after unloading the pressure.

[0013] As a technical solution of the present invention, the modified artificial graphite material has a specific capacity ≥350.0mAh / g and a 3C / 1C charging capacity retention rate ≥82.0%.

[0014] A second aspect of this invention provides a method for preparing a modified artificial graphite material, comprising the steps of:

[0015] ① The carbon source precursor is graphitized to obtain the first intermediate;

[0016] ② The first intermediate is mechanically pulverized to obtain the second intermediate;

[0017] ③ The second intermediate is acid-etched to obtain a mixed solution containing the third intermediate;

[0018] ④ After adding an oxidant to the mixed solution for oxidation treatment, wash and dry.

[0019] In the preparation method of this invention, the first intermediate is mechanically pulverized to create numerous defects on the graphite surface, thereby increasing the specific surface area of ​​the material. Then, acid etching is used to etch the defects in the second intermediate and the graphite edges, thereby disrupting the long-range ordered crystal structure of the graphite surface and forming a disordered amorphous carbon layer. Further oxidation with an oxidant is used to further promote the ordered growth of the amorphous carbon layer and simultaneously promote the adhesion of oxygen-containing functional groups to the material surface, forming a functionalized carbon composite layer containing amorphous carbon, carbon surface defects, and oxygen-containing functional groups. Oxidation following acid etching is to avoid the oxidant's enhanced oxidizing properties in acid, which could lead to an excessively rapid reaction, making it difficult to control the growth of the amorphous carbon layer, affecting the performance of the graphite crystal matrix itself, and potentially producing excessive metal residues. Therefore, this invention, through mechanical pulverization, acid activation, and subsequent oxidation, forms an artificial functionalized carbon composite layer interface on the graphite surface, improving both compaction density and capacity while also enhancing fast-charging performance.

[0020] As a technical solution of the present invention, the carbon source precursor is obtained by crushing, classifying and shaping graphitized raw materials, wherein the graphitized raw materials include at least one of petroleum coke, needle coke and coal tar pitch.

[0021] As one technical solution of the present invention, the graphitization temperature is 2700~3200℃.

[0022] As a technical solution of the present invention, heat treatment is performed simultaneously with the mechanical crushing, and the temperature of the heat treatment is 40-120°C.

[0023] As a technical solution of the present invention, the mechanical pulverization is carried out in an atmosphere, which includes one or more of air, nitrogen and carbon dioxide.

[0024] As one technical solution of the present invention, the processing time of the mechanical crushing is 5 to 120 minutes.

[0025] As a technical solution of the present invention, the equipment used for mechanical crushing includes one or more of the following: crusher, horizontal kettle, fusion machine, impact mill, rod mill, vertical kettle and ball mill.

[0026] As one technical solution of the present invention, the mechanical crushing equipment is a crusher, and the main unit frequency is 5-50Hz.

[0027] As one technical solution of the present invention, the mechanical crushing equipment is an impact mill, and the main unit frequency is 5-50Hz.

[0028] As a technical solution of the present invention, the mechanical crushing equipment is a vertical kettle, and the main unit frequency is 5-40Hz.

[0029] As a technical solution of the present invention, the mechanical crushing equipment is a horizontal kettle, and the main unit frequency is 5-50Hz.

[0030] As a technical solution of the present invention, the mechanical crushing equipment is a fusion machine with a rotation speed of 100 to 1000 rpm.

[0031] As a technical solution of the present invention, the acid solution used in the acid etching includes one or more of nitric acid, hydrochloric acid and sulfuric acid.

[0032] As a technical solution of the present invention, the concentration of the acid solution used in the acid etching is 1 to 10 mol / L.

[0033] As one technical solution of the present invention, the acid etching temperature is 40-100℃.

[0034] As one technical solution of the present invention, the acid etching time is 5 to 20 minutes.

[0035] As a technical solution of the present invention, the solid-liquid ratio of the second intermediate and the acid solution used in the acid etching is 3-300:6-600 kg / L.

[0036] As one technical solution of the present invention, the oxidation treatment is carried out under heating conditions, and the heating temperature is 60-80°C.

[0037] As one technical solution of the present invention, the oxidant includes one or more of potassium dichromate, potassium ferrate, sodium ferrate, potassium permanganate, and sodium periodate.

[0038] As a technical solution of the present invention, the mass ratio of the third intermediate to the oxidant is 3-300:1-100.

[0039] As one technical solution of the present invention, the oxidation treatment time is 0.5 to 2.0 hours.

[0040] A third aspect of the present invention provides the application of the modified artificial graphite material prepared according to the aforementioned modified artificial graphite material or the aforementioned method for preparing the modified artificial graphite material in a negative electrode material.

[0041] A fourth aspect of the present invention provides a secondary battery comprising a positive electrode material, a negative electrode material and an electrolyte, wherein the negative electrode material is the aforementioned modified artificial graphite material, or a modified artificial graphite material prepared by the aforementioned method for preparing modified artificial graphite material. Attached Figure Description

[0042] Figure 1 The Raman curves are for Example 1 and Comparative Examples 1, 3-4. Detailed Implementation

[0043] The modified artificial graphite material of this invention was tested by Raman spectroscopy, and the spectrum contained I... D / I G The peak area ratio is 0.30–0.60, where I D The representative is located at 1350cm -1 peak D at location I G The representative is located at 1580cm -1 The G peak at that location. As an example, I... D / I G The peak area ratio can be, but is not limited to, 0.30, 0.40, 0.50, or 0.60. D / I G A moderate peak area ratio indicates that the disorder of the modified artificial graphite material is within a certain range. A certain degree of amorphous carbon can provide more lithium-ion diffusion channels to improve fast charge and discharge performance, and can also avoid excessive disorder from affecting the performance of graphite.

[0044] The specific capacity of the modified artificial graphite material is ≥350.0 mAh / g, and for example, it may be, but is not limited to, ≥350.0 mAh / g, ≥355.0 mAh / g, ≥360.0 mAh / g, ≥365.0 mAh / g, ≥370.0 mAh / g, ≥375.0 mAh / g, ≥380.0 mAh / g, ≥385.0 mAh / g, or ≥390.0 mAh / g. The 3C / 1C charging capacity retention rate of the modified artificial graphite material is ≥82.0%, and for example, it may be, but is not limited to, ≥82.0%, ≥83.0%, ≥84.0%, ≥85.0%, ≥86.0%, ≥87.0%, ≥88.0%, ≥89.0%, ≥90.0%, ≥91.0%, ≥92.0%, ≥93.0%, ≥94.0%, or ≥95.0%. The specific surface area of ​​the modified artificial graphite material is ≥1.20 m². 2 / g, in one embodiment, the specific surface area of ​​the modified artificial graphite material is ≥1.50m². 2 / g. As an example, the specific surface area can be, but is not limited to, ≥1.20m². 2 / g, ≥1.25m 2 / g, ≥1.30m 2 / g, ≥1.40m 2 / g, ≥1.50m 2 / g, ≥1.60m 2 / g, ≥1.70m 2 / g, ≥1.80m 2 / g, ≥1.90m 2 / g, ≥2.00m 2 / g, ≥2.10m 2 / g, ≥2.20m 2 / g, ≥2.30m 2 / g, ≥2.40m 2 / g, ≥2.50m 2 / g. The Dv50 of the modified artificial graphite material is 8.0–16.0 μm, and as an example, it can be, but is not limited to, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, and 16.0 μm. The compaction density of the graphite crystal matrix under 50,000 N pressure is D1, the compaction density of the modified artificial graphite material under 50,000 N pressure is D2, and the compaction change rate of the modified artificial graphite is D, where D = D2 - D1 ≥ 0.05 g / cm³. 3 The rebound rate of the modified artificial graphite material is ρ, which ranges from 10.0% to 50.0%, and ρ = (P... 5t -P 20N ) / P 5t *100, as an example, ρ can be, but is not limited to, 10.0%, 15.0%, 20.0%, 25.0%, 30.0%, 35.0%, 40.0%, 45.0%, and 50.0%. Where ρ is the rebound rate, and P... 5t To determine the compaction density under a pressure of 50,000 N, P 20N This is to retain only the compaction density under 20N pressure after unloading the pressure.

[0045] The modified artificial graphite material comprises a graphite crystal matrix and a functionalized carbon composite layer encapsulating the graphite crystal matrix. The functionalized carbon composite layer contains amorphous carbon, carbon surface defects, and oxygen-containing functional groups. The amorphous carbon is obtained through acid etching and oxidation treatment, the carbon surface defects are obtained through mechanical crushing, and the oxygen-containing functional groups are attached to the surface layer by oxidizing the edges and surface defects of the graphite crystal matrix with an oxidizing agent.

[0046] The method for preparing the modified artificial graphite material of the present invention includes the following steps: ① graphitizing a carbon source precursor to obtain a first intermediate; ② mechanically pulverizing the first intermediate to obtain a second intermediate; ③ acid etching the second intermediate to obtain a mixed solution containing a third intermediate; ④ adding an oxidant to the mixed solution for oxidation treatment, followed by washing and drying.

[0047] In step ①, the carbon source precursor is obtained by crushing, classifying, and shaping graphitized raw materials. The graphitized raw materials include at least one of petroleum coke, needle coke, and coal tar pitch. The graphitization temperature is 2700–3200℃. As an example, the temperature may be, but is not limited to, 2700℃, 2800℃, 2900℃, 3000℃, 3100℃, and 3200℃.

[0048] In step ②, heat treatment is performed simultaneously with mechanical pulverization. The heat treatment temperature is 40–120°C, and in one embodiment, the heat treatment temperature is 60–80°C. As examples, the temperature may be, but is not limited to, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 1000°C, 110°C, or 120°C. Mechanical pulverization is carried out under an atmosphere, which may include one or more of air, nitrogen, and carbon dioxide. The processing time for mechanical pulverization is 5–120 min, and in one embodiment, the processing time is 20–60 min. As examples, the processing time for mechanical pulverization may be, but is not limited to, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min.

[0049] Mechanical pulverization equipment includes one or more of the following: pulverizers, horizontal kettles, fusion machines, impact mills, rod mills, vertical kettles, and ball mills. For example, if the mechanical pulverization equipment is a pulverizer with a main unit frequency of 5–50 Hz, in one technical solution, the main unit frequency is 15–20 Hz. If the mechanical pulverization equipment is an impact mill with a main unit frequency of 5–50 Hz, in one technical solution, the main unit frequency is 20–30 Hz. If the mechanical pulverization equipment is a vertical kettle with a main unit frequency of 5–40 Hz, in one technical solution, the main unit frequency is 10–20 Hz. If the mechanical pulverization equipment is a horizontal kettle with a main unit frequency of 5–50 Hz, in one technical solution, the main unit frequency is 10–20 Hz. If the mechanical pulverization equipment is a fusion machine with a rotation speed of 100–1000 rpm, in one technical solution, the rotation speed is 500–800 rpm.

[0050] In step ③, the acid solution used for etching includes one or more of nitric acid, hydrochloric acid, and sulfuric acid. The concentration of the acid solution used for etching is 1–10 mol / L. In one technical solution, the concentration is 3–6 mol / L. As an example, the concentration of the acid solution can be, but is not limited to, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L. Acid etching is carried out under heating conditions at a temperature of 40–100°C. In one technical solution, the heating temperature is 60–80°C. As an example, the heating temperature can be, but is not limited to, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C. The etching time is 5–20 min. As an example, the time can be, but is not limited to, 5 min, 8 min, 10 min, 13 min, 15 min, 17 min, 19 min, or 20 min. The solid-liquid ratio of the second intermediate and the acid solution used in the etching process is 3-300:6-600 kg / L. For example, the solid-liquid ratio can be, but is not limited to, 3:6 kg / L, 3:50 kg / L, 3:100 kg / L, 3:500 kg / L, 100:6 kg / L, 100:50 kg / L, 100:100 kg / L, or 100:500 kg / L.

[0051] In step ④, the oxidation treatment is carried out under heating conditions at a temperature of 60–80°C. For example, the heating temperature may be, but is not limited to, 60°C, 65°C, 70°C, 75°C, or 80°C. The oxidant includes one or more of potassium dichromate, potassium ferrate, sodium ferrate, potassium permanganate, and sodium periodate. The mass ratio of the third intermediate to the oxidant is 3–300:1–100. For example, the solid-liquid ratio may be, but is not limited to, 3:1 kg / L, 3:5 kg / L, 3:50 kg / L, 3:100 kg / L, 100:1 kg / L, 100:5 kg / L, or 100:50 kg / L. The oxidation treatment time is 0.5–2.0 h. For example, the time may be, but is not limited to, 0.5 h, 0.8 h, 1.0 h, 1.2 h, 1.5 h, 1.8 h, or 2.0 h.

[0052] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0053] Example 1

[0054] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0055] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0056] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 15 Hz to obtain the second intermediate.

[0057] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0058] ④ Add 5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0059] Example 2

[0060] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0061] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0062] ② Place 10 kg of the first intermediate into an impact mill, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main machine frequency of 15 Hz to obtain the second intermediate.

[0063] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0064] ④ Add 5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0065] Example 3

[0066] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0067] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0068] ② Place 10 kg of the first intermediate into a fusion machine, heat it to 70°C in an air atmosphere, and mechanically pulverize it at 800 rpm for 30 minutes to obtain the second intermediate.

[0069] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0070] ④ Add 5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0071] Example 4

[0072] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0073] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3200℃ to obtain a Dv50 of approximately 15μm and a specific surface area ≥0.90m². 2 / g's first intermediate.

[0074] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 15 Hz to obtain the second intermediate.

[0075] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0076] ④ Add 5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0077] Example 5

[0078] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0079] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0080] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 15 Hz to obtain the second intermediate.

[0081] ③ Mix 8 kg of the second intermediate with 10 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0082] ④ Add 2.5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0083] Example 6

[0084] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0085] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0086] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 15 Hz to obtain the second intermediate.

[0087] ③ Mix 8 kg of the second intermediate with 40 L of nitric acid solution with a concentration of 4 mol / L, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0088] ④ Add 10 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0089] Example 7

[0090] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0091] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0092] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 5 Hz to obtain the second intermediate.

[0093] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0094] ④ Add 5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0095] Example 8

[0096] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0097] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0098] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 25 Hz to obtain the second intermediate.

[0099] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0100] ④ Add 5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0101] Example 9

[0102] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0103] ① The coal tar pitch is crushed, graded, and shaped to produce a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0104] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 60°C under a carbon dioxide atmosphere, and mechanically pulverize it for 50 min at a main frequency of 15 Hz to obtain the second intermediate.

[0105] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min to obtain a mixed solution containing the third intermediate.

[0106] ④ Add 5 kg of potassium ferrate to the mixed solution, while maintaining the temperature at 80°C, and continue to stir the reaction evenly for 1.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0107] Example 10

[0108] This embodiment describes a method for preparing a modified artificial graphite material, comprising the following steps.

[0109] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0110] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 80°C in an air atmosphere, and mechanically pulverize it for 25 min at a main unit frequency of 15 Hz to obtain the second intermediate.

[0111] ③ Mix 8 kg of the second intermediate with 20 L of 2 mol / L hydrochloric acid solution, place in a water bath and heat to 60 °C, while stirring evenly for 20 min to obtain a mixed solution containing the third intermediate.

[0112] ④ Add 10 kg of potassium permanganate to the mixed solution, while maintaining the temperature at 60°C, and continue to stir the reaction evenly for 2.0 h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0113] Comparative Example 1

[0114] This comparative example illustrates a method for preparing an artificial graphite material, comprising the following steps: crushing, classifying, and shaping petroleum coke into a carbon source precursor; and graphitizing the carbon source precursor at 3000℃ to obtain a Dv50 of approximately 10 μm and a specific surface area ≥1.20 m². 2 / g of artificial graphite.

[0115] Comparative Example 2

[0116] This comparative example illustrates a method for preparing an artificial graphite material, comprising the following steps: crushing, classifying, and shaping petroleum coke into a carbon source precursor; and graphitizing the carbon source precursor at 3200℃ to obtain a Dv50 of approximately 15 μm and a specific surface area ≥0.90 m². 2 / g of artificial graphite.

[0117] Comparative Example 3

[0118] This comparative example illustrates a method for preparing a modified artificial graphite material, comprising the following steps.

[0119] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0120] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a host frequency of 15 Hz to obtain artificial graphite.

[0121] Comparative Example 4

[0122] This comparative example illustrates a method for preparing a modified artificial graphite material, comprising the following steps.

[0123] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0124] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 15 Hz to obtain the second intermediate.

[0125] ③ Mix 8 kg of the second intermediate with 20 L of 4 mol / L nitric acid solution, place in a water bath and heat to 80 °C, while stirring evenly for 10 min. Wash with deionized water and dry to obtain the modified artificial graphite material.

[0126] Comparative Example 5

[0127] This comparative example illustrates a method for preparing a modified artificial graphite material, comprising the following steps.

[0128] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0129] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 30 Hz to obtain the second intermediate.

[0130] ③ Add 20L of deionized water and 5kg of potassium ferrate to the second intermediate, and keep the water bath at 80℃ while stirring the reaction uniformly for 1.0h; then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0131] Comparative Example 6

[0132] This comparative example illustrates a method for preparing a modified artificial graphite material, comprising the following steps.

[0133] ① The petroleum coke is crushed, graded, and shaped into a carbon source precursor. The carbon source precursor is then graphitized at 3000℃ to obtain a Dv50 of approximately 10μm and a specific surface area ≥1.20m². 2 / g's first intermediate.

[0134] ② Place 10 kg of the first intermediate into a pulverizer, heat it to 70°C in an air atmosphere, and mechanically pulverize it for 30 min at a main unit frequency of 30 Hz to obtain the second intermediate.

[0135] ③ Add 20L of 4mol / L nitric acid solution and 5kg of potassium ferrate to 8kg of the second intermediate, mix, place in a water bath and heat to 80℃, stir evenly for 1.0h, then wash and dry the product with deionized water to obtain the modified artificial graphite material.

[0136] The modified artificial graphite materials or artificial graphite prepared in Examples 1-10 and Comparative Examples 1-6 were subjected to various performance tests. The test results are shown in Table 1, and the test methods are as follows.

[0137] Raman testing: The test is performed using a Raman spectrometer, and the spectrum is as follows. Figure 1 As shown, I D / I G The values ​​can be obtained through the software on the instrument.

[0138] Particle size Dv50 test: Tested using Malvern MS2000 laser particle size analyzer.

[0139] Specific surface area test: Measured using a Konta NOVA2000e specific surface area meter.

[0140] Compacted density test: The compacted density of battery powder was determined using a UTM7305 battery powder compaction density tester.

[0141] Half-cell electrical performance testing: A polyvinylidene fluoride (PVDF) solution with a mass fraction of 6-7% was prepared using N-methylpyrrolidone as a solvent. Modified artificial graphite materials or artificial graphite, PVDF, and conductive carbon black prepared in Examples 1-10 and Comparative Examples 1-6 were mixed uniformly at a mass ratio of 91:7:2 and coated onto copper foil. The coated electrode was then placed in a vacuum drying oven at 105°C and vacuum dried for 4 hours for later use. It was then punched into small discs with a diameter of 14 mm. The discs were then transferred to an argon-filled glove box and assembled into 2430 coin cells. A three-component mixed solvent of 1 mol / L LiPF6 with a volume ratio of EC:DMC:EMC = 1:1:1 was used as the electrolyte. A lithium metal sheet was used as the counter electrode, and a 16 μm thick separator was used as the separator. The electrochemical performance of the assembled half-cells was tested on an electrochemical detection system. The charge and discharge voltage range was 0 V to 2.0 V. The charge and discharge specific capacity and the 3C / 1C charge capacity retention rate were obtained.

[0142] Table 1 Performance test results of Examples 1-10 and Comparative Examples 1-6

[0143]

[0144]

[0145] As shown in Table 1, the modified artificial graphite materials in Examples 1-10, comprising a functionalized carbon composite layer containing amorphous carbon, carbon surface defects, and oxygen-containing functional groups, exhibit high specific capacity and compaction density, as well as superior rate performance. This is because the presence of the functionalized carbon composite layer reduces the compaction rebound rate of graphite and provides more lithium-ion diffusion channels and reactive sites, resulting in higher compaction density and specific capacity in their artificial graphite anode materials, along with superior rate performance. In contrast, Comparative Examples 1-2 merely graphitized the carbon source precursor to obtain artificial graphite, which lacks disordered amorphous carbon and surface defects, thus exhibiting poor performance, especially low 3C / 1C charging capacity retention. Although mechanical pulverization in Comparative Example 3 introduced surface defects in the graphite material, it did not promote the formation of disordered amorphous carbon; therefore, although the specific surface area increased, the rate performance remained poor. Comparative Examples 4 and 5 involved only acid etching or oxidation, which, while promoting the formation of disordered amorphous carbon, resulted in a limited amount of amorphous carbon, thus their performance was still inferior to Example 1. In Comparative Example 6, acid etching and oxidation were performed simultaneously, resulting in modified artificial graphite with a higher I... D / I G The large peak area is due to the enhanced oxidizing power of the oxidant in acid. The simultaneous oxidation and acid etching can lead to an excessively fast reaction, making it difficult to control the orderly growth of the amorphous carbon layer. The Raman ID / IG ratio is greater than 0.60, and more metal residues may be generated, thus affecting the electrochemical performance of the battery.

[0146] As can be seen from the comparison of Examples 1 to 3, the modified artificial graphite obtained by using a pulverizer during mechanical crushing has a larger specific surface area and compaction density, smaller particle size and rebound rate, higher disorder of amorphous carbon, and better electrochemical performance. This may be because the pulverizer can obtain a more perfect interface.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A modified artificial graphite material, characterized in that, The system comprises a graphite crystal matrix and a functionalized carbon composite layer encapsulating the graphite crystal matrix. The functionalized carbon composite layer contains amorphous carbon, carbon surface defects, and oxygen-containing functional groups. Raman spectroscopy reveals that the ionization index (I) in the composite layer is... D / I G The peak area ratio is 0.30~0.60, I D The representative is located at 1350cm -1 peak D at location I G The representative is located at 1580cm -1 The method for preparing the modified artificial graphite material includes the following steps: (G peak at the location) ① The carbon source precursor is graphitized to obtain the first intermediate; ② The first intermediate is mechanically pulverized to obtain the second intermediate; ③ The second intermediate is acid-etched to obtain a mixed solution containing the third intermediate. The acid etching temperature is 40~100℃, and the solid-liquid ratio of the second intermediate and the acid solution used in the acid etching is 3~300:6~600kg / L. ④ After adding an oxidant to the mixed solution for oxidation treatment, wash and dry. The oxidation treatment is carried out under heating conditions, and the heating temperature is 60~80℃. The mass ratio of the third intermediate to the oxidant is 3~300:1~100.

2. The modified artificial graphite material according to claim 1, characterized in that, The specific surface area of ​​the modified artificial graphite material is ≥1.20 m². 2 / g.

3. The modified artificial graphite material according to claim 1, characterized in that, The Dv50 of the modified artificial graphite material is 8.0~16.0μm.

4. The modified artificial graphite material according to claim 1, characterized in that, The compaction density of the graphite crystal matrix under 50,000 N pressure is D1, the compaction density of the modified artificial graphite material under 50,000 N pressure is D2, and the compaction change rate of the modified artificial graphite is D, where D = D2 - D1 ≥ 0.05 g / cm³. 3 .

5. The modified artificial graphite material according to claim 1, characterized in that, The rebound rate of the modified artificial graphite material is ρ, where ρ is 10.0~50.0%, and ρ=(P 5t -P 20N ) / P 5t *100, where ρ is the rebound rate, P 5t To determine the compaction density under a pressure of 50,000 N, P 20N This is to retain only the compaction density under 20N pressure after unloading the pressure.

6. The modified artificial graphite material according to claim 1, characterized in that, The modified artificial graphite material has a specific capacity ≥350.0 mAh / g and a 3C / 1C charging capacity retention rate ≥82.0%.

7. A method for preparing a modified artificial graphite material, characterized in that, The modified artificial graphite material comprises a graphite crystal matrix and a functionalized carbon composite layer encapsulating the graphite crystal matrix. The functionalized carbon composite layer contains amorphous carbon, carbon surface defects, and oxygen-containing functional groups. Raman spectroscopy reveals that the Ig group in the spectrum... D / I G The peak area ratio is 0.30~0.60, I D The representative is located at 1350cm -1 peak D at location I G The representative is located at 1580cm -1 Peak G at the location includes the following steps: ① The carbon source precursor is graphitized to obtain the first intermediate; ② The first intermediate is mechanically pulverized to obtain the second intermediate; ③ The second intermediate is acid-etched to obtain a mixed solution containing the third intermediate. The acid etching temperature is 40~100℃, and the solid-liquid ratio of the second intermediate and the acid solution used in the acid etching is 3~300:6~600kg / L. ④ After adding an oxidant to the mixed solution for oxidation treatment, wash and dry. The oxidation treatment is carried out under heating conditions, and the heating temperature is 60~80℃. The mass ratio of the third intermediate to the oxidant is 3~300:1~100.

8. The method for preparing the modified artificial graphite material according to claim 7, characterized in that, Includes at least one of the following features (1) to (16): (1) The carbon source precursor is obtained by crushing, classifying and shaping graphitized raw materials, wherein the graphitized raw materials include at least one of petroleum coke, needle coke and coal tar pitch. (2) The graphitization temperature is 2700~3200℃; (3) The mechanical crushing is carried out simultaneously with the heat treatment, and the temperature of the heat treatment is 40~120℃; (4) The mechanical crushing is carried out in an atmosphere, which includes one or more of air, nitrogen and carbon dioxide; (5) The processing time for the mechanical crushing is 5~120 min; (6) The equipment used for mechanical crushing includes one or more of the following: crusher, horizontal kettle, fusion machine, impact mill, rod mill, vertical kettle and ball mill; (7) The equipment used for mechanical crushing is a crusher, and the main unit frequency is 5~50Hz; (8) The mechanical crushing equipment used is an impact mill, and the main frequency is 5~50Hz; (9) The mechanical crushing equipment used is a vertical kettle, and the main unit frequency is 5~40Hz; (10) The mechanical crushing equipment used is a horizontal kettle, and the main unit frequency is 5~50Hz; (11) The mechanical crushing equipment used is a fusion machine with a rotation speed of 100~1000 rpm; (12) The acid solution used in the acid etching includes one or more of nitric acid, hydrochloric acid and sulfuric acid; (13) The concentration of the acid solution used in the acid etching is 1~10 mol / L; (14) The acid etching time is 5~20 min; (15) The oxidizing agent includes one or more of potassium dichromate, potassium ferrate, sodium ferrate, potassium permanganate and sodium periodate; (16) The oxidation treatment time is 0.5~2.0h.

9. The application of the modified artificial graphite material according to any one of claims 1 to 6, or the modified artificial graphite material prepared by the preparation method according to any one of claims 7 to 8, in a negative electrode material.

10. A secondary battery, comprising a positive electrode material, a negative electrode material, and an electrolyte, characterized in that, The negative electrode material is the modified artificial graphite material according to any one of claims 1 to 6, or the modified artificial graphite material prepared by the preparation method of the modified artificial graphite material according to any one of claims 7 to 8.

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