Preparation method and application of petroleum coke-based hard carbon anode material

Abstract

This invention belongs to the field of electrode material technology, specifically relating to a method for preparing and applying a petroleum coke-based hard carbon anode material. The preparation method includes the following steps: mixing petroleum coke powder with an oxidant at 0-5°C and oxidizing for 12-48 hours to obtain an oxidation precursor; carbonizing the oxidation precursor under a protective atmosphere to obtain the final product. The preparation method of this invention effectively avoids the formation of a dense oxide layer on the surface by strictly suppressing the intense exothermic reaction in the initial stage, ensuring that the oxidant can slowly and fully penetrate and react from the surface inwards. The resulting petroleum coke-based hard carbon anode material exhibits excellent electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a method for preparing and applying a petroleum coke-based hard carbon anode material. Background Technology

[0002] Hard carbon materials are considered the most promising anode materials for sodium-ion batteries due to their large interlayer spacing and abundant closed-cell structure; however, they still suffer from problems such as low initial coulombic efficiency and poor rate performance. It is generally believed that a larger interlayer spacing is beneficial for improving the rate performance of hard carbon.

[0003] Petroleum coke, as a low-cost, high-carbon byproduct of petroleum refining, is an ideal carbon precursor. However, it is prone to graphitization during high-temperature carbonization, resulting in ordered carbon layers with narrow interlayer spacing (close to 0.335 nm, similar to graphite), which is not conducive to the storage and diffusion of sodium ions. Therefore, materials obtained by direct carbonization generally have poor sodium storage performance.

[0004] Existing technologies often accelerate the reaction by increasing the temperature of the acid oxidation process. However, for petroleum coke, which has a dense structure and highly ordered aromatic lamellae, high temperatures can easily lead to violent reactions on the surface of the petroleum coke particles, forming a dense oxide layer that hinders further internal oxidation. This results in a heterogeneous structure of "external oxidation-internal graphitization," making it difficult to achieve overall structural reshaping and performance improvement. In addition, high-temperature strong acid systems are highly corrosive, easily release toxic gases, require sophisticated equipment, are dangerous to operate, and have complex post-processing, resulting in a significant environmental burden. Summary of the Invention

[0005] To address the problem in existing technologies where the oxidation of petroleum coke particles at high temperatures results in a heterogeneous structure and poor overall structural stability and performance of the product, this invention provides a method for low-temperature permeation oxidation to transform the carbon structure of petroleum coke from soft carbon to hard carbon, and its application. The technical solution is as follows: A method for preparing a petroleum coke-based hard carbon anode material includes the following steps: mixing petroleum coke powder with an oxidant at 0~5℃ and oxidizing for 12~48h to obtain an oxidation precursor; carbonizing the oxidation precursor under a protective atmosphere to obtain the final product.

[0006] Furthermore, the petroleum coke is pulverized and then ball-milled at 600-1000 rpm for 2-6 hours, and then passed through a 150-250 mesh sieve to obtain petroleum coke powder.

[0007] Furthermore, the oxidant is a mixture of concentrated nitric acid and concentrated sulfuric acid.

[0008] Furthermore, the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:1~4.

[0009] Furthermore, the mass ratio of the petroleum coke powder to the oxidant is 1:10~20.

[0010] Furthermore, the heating rate of the carbonization is 5~10℃ / min; the carbonization temperature is 1200~1400℃, and the time is 1~2h.

[0011] A petroleum coke-based hard carbon anode material prepared by the above-mentioned method has an average interlayer spacing of not less than 0.37 nm.

[0012] Furthermore, the I of the negative electrode material D / I G The ratio is not less than 1.08.

[0013] A sodium-ion battery uses the above-mentioned petroleum coke-based hard carbon anode material to prepare the anode sheet.

[0014] Application of the above-mentioned petroleum coke-based hard carbon anode material in the preparation of secondary batteries.

[0015] By adopting the above scheme, the method of the present invention has the following advantages: 1. The low-temperature permeation oxidation step of the present invention can effectively suppress the orderly growth and stacking of graphite microcrystals during the subsequent high-temperature carbonization process, so that it can be successfully transformed from a highly graphitized soft carbon structure into a hard carbon structure with a moderately disordered vortex structure, which significantly improves the plateau intercalation capacity of the material.

[0016] 2. The method of this invention employs a low-temperature oxidation strategy of 0-5℃ to suppress the initial reaction intensity, promote deep penetration of the oxidant, and achieve deep and homogeneous oxidation of petroleum coke particles from the surface to the interior. This effectively prevents the particle surface from being rapidly oxidized or even "ablated," forming a dense, highly cross-linked oxide shell that hinders the oxidant from further penetrating and diffusing into the particle interior. This achieves homogeneous oxidation of petroleum coke from the surface to the interior.

[0017] 3. The oil coke-based hard carbon anode of this invention exhibits excellent electrochemical performance, specifically: a 132.4 mAh g increase in reversible capacity during the first cycle. -1 The first-cycle coulombic efficiency is improved by 11.9%. At a current density of 1C, the capacity retention rate is as high as 93.5% after 400 cycles, and at a current density of 5C, it can still maintain a high reversible specific capacity.

[0018] 4. The oxidation process of the method of the present invention is carried out at low temperature only, without any high temperature treatment, resulting in low production cost. Attached Figure Description

[0019] Figure 1 Scanning electron microscope (SEM) images of the negative electrode materials of Examples 1, 2, and Comparative Examples 1 and 2; Figure 2The images are projection electron microscope (TEM) images of the petroleum coke-based carbon anode materials of Example 2 and Comparative Example 1. Figure 3 These are the Fourier transform infrared (FTIR) spectra of the oxidized precursors of Examples 1, 2, and Comparative Examples 1 and 2; Figure 4 These are the X-ray diffraction (XRD) patterns of the petroleum coke-based carbon anode materials of Examples 1, 2, 1, and 2. Figure 5 These are the Raman spectra of petroleum coke-based carbon anode materials from Examples 1, 2, 1, and 2; Figure 6 These are the electrochemical performance test results of the petroleum coke-based carbon anode materials in Example 2 and Comparative Examples 1 and 2. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: (1) The blocky petroleum coke was crushed and ball-milled at a speed of 600 rpm for 6 hours. After passing through a 200-mesh sieve, petroleum coke powder was obtained. (2) Mix concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 to prepare an oxidant. Take 50 mL of the oxidant to oxidize 3.0 g of petroleum coke powder. Stir the reaction in an ice-water bath at 0°C for 1 day, then pour it into deionized water to stop the oxidation reaction. Let it stand until the solid is completely precipitated at the bottom. Pour off the supernatant and repeatedly centrifuge and wash the lower liquid until it is neutral. Dry the obtained solid at 80°C for 12 h. (3) Place the oxidized petroleum coke powder in a tube furnace and heat it to 1400℃ in a nitrogen environment and keep it at that temperature for 2 hours. After the equipment cools down to room temperature, take out the mold and collect the powder to obtain the petroleum coke-based carbon anode material (referred to as PC-P1-S).

[0022] Example 2: The difference from Example 1 is as follows: (2) Mix concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 to prepare an oxidant. Take 90 mL of the oxidant to oxidize 5.0 g of petroleum coke powder. Stir the reaction in an ice-water bath at 0°C for 2 days, then pour it into deionized water to stop the oxidation reaction. Let it stand until the solid is completely precipitated at the bottom. Pour off the supernatant and repeatedly centrifuge and wash the lower liquid until it is neutral. Dry the obtained solid at 80°C for 12 h.

[0023] The resulting petroleum coke-based carbon anode material is designated PC-P2-S.

[0024] Comparative Example 1: (1) The blocky petroleum coke was crushed and ball-milled at a speed of 600 rpm for 6 hours and then sieved to obtain petroleum coke powder. (2) Place the oxidized petroleum coke powder in a tube furnace and heat it to 1400℃ in a nitrogen environment and keep it at that temperature for 2 hours. After the equipment cools down to room temperature, take out the mold and collect the powder to obtain the petroleum coke-based carbon anode material (referred to as PC-S).

[0025] Comparative Example 2: The difference from Example 1 is that: (2) Mix concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 to prepare an oxidant. Take 50 mL of the oxidant to oxidize 3.0 g of petroleum coke powder. Stir the reaction in an ice-water bath at 60 °C for 1 day, then pour it into deionized water to stop the oxidation reaction. Let it stand until the solid is completely precipitated at the bottom. Pour off the supernatant and repeatedly centrifuge and wash the lower liquid until it is neutral. Dry the obtained solid at 80 °C for 12 h.

[0026] The resulting petroleum coke-based carbon anode material is designated PC-HP-S.

[0027] Example sample morphology characterization: Figure 1 SEM images of petroleum coke-derived carbon are shown. Both the directly carbonized Comparative Example 1 sample PC-S and the non-low-temperature oxidized Comparative Example 2 sample PC-HP-S exhibit irregular blocky morphologies with relatively smooth surfaces and only a small number of fine particles attached. In contrast, the samples PC-P1-S and PC-P2-S from Examples 1 and 2, which underwent low-temperature oxidation treatment, showed rough surfaces, blurred edge contours, and numerous wrinkled structures, with the blocky particles being eroded into rich pores.

[0028] Figure 2 The images shown are high-resolution transmission electron microscopy (HRTEM) images of PC-S in Comparative Example 1 and PC-P2-S in Example 2. PC-S in Comparative Example 1 exhibits higher order, primarily composed of thick and numerous long-range ordered graphite domains, while PC-P2-S in Example 2 displays a vortex structure composed of short-range, thin, and locally distorted, more disordered graphite domains, exhibiting a typical hard carbon structure. Furthermore, the interlayer spacing (d) of PC-S in Comparative Example 1 was measured from the HRTEM images. 002 The interlayer spacing of PC-P2-S in Example 2 is 0.391 nm, while that of PC-P2-S in Example 2 is 0.355 nm. This more disordered, curved structure with a larger interlayer spacing is beneficial for Na + The insertion and extraction of [the material] were studied. The results showed that under low-temperature oxidation, its overall structure changed, transforming from a highly graphitized soft carbon structure to a moderately disordered hard carbon structure.

[0029] Table 1. Structural analysis of carbon derived from petroleum coke: Table 1 shows the structural analysis of petroleum coke-derived carbon. The d... (The sentence is incomplete and requires further context to be fully translated.) 002 The values ​​are consistent with the HRTEM structure, and the interlayer spacing is increased after low-temperature oxidation treatment. Raman spectroscopy was used to further analyze the structure and defects of the sample. The intensity ratio of the D band (ID) to the G band (IG) is typically used to examine the degree of disorder in carbon materials, and the results are as follows: Figure 5 As shown, the ID / IG ratios of PC-S, PC-HP-S, PC-P1-S, and PC-P2-S are 0.87, 1.05, 1.12, and 1.10, respectively. The larger the ratio, the more disordered the structure. Figure 5 This also indicates that the material structure is more disordered after low-temperature permeation oxidation treatment.

[0030] Figure 3 The image shows the FTIR spectrum of petroleum coke before carbonization. The oxidized sample is at 3430 cm⁻¹. -1 (-OH) and 1720cm -1 The vibration peak at (C=O) is significantly enhanced, and it reaches 1530 cm⁻¹. -1 and 1350cm -1 A characteristic double peak belonging to -NO2 appeared. Among them, the intensity of each characteristic peak of PC-HP-S in Comparative Example 2 (non-low-temperature oxidation) was significantly weaker than that of PC-P1-S in Example 1 and PC-P2-S in Example 2 (low-temperature oxidation), indicating that non-low-temperature oxidation was insufficient and incomplete, while low-temperature oxidation achieved deep and uniform functionalization.

[0031] Figure 4 XRD patterns of petroleum coke-derived carbons are shown. Comparative Example 1, PC-S, exhibits a sharp (002) diffraction peak at approximately 26°, indicating a highly ordered graphitic microcrystalline structure and a high degree of graphitization. Comparative Example 2, PC-HP-S, shows a slightly weakened (002) peak intensity but still maintains a high degree of graphitization. In contrast, after low-temperature permeation oxidation treatment, the (002) diffraction peaks of the samples in all examples shift significantly to lower angles, while the peak intensity decreases significantly and the peak shape broadens. Low-temperature permeation oxidation effectively increases the carbon interlayer spacing d. 002 This reduces the stacking order of graphite microcrystals.

[0032] Electrochemical performance testing: Petroleum coke-based carbon anode materials, CMC, and SP from Examples 2, Comparative Examples 1, and 2 were mixed and ground in a mass ratio of 8:1:1 and then uniformly coated onto a circular carbon-coated copper foil with a diameter of 1.2 cm as the working electrode. Metallic sodium was used as the counter electrode, and the electrolyte was 1M NaPF6 dissolved in DIGLYME. Battery assembly was carried out entirely in a glove box under argon protection (oxygen and moisture content were both below 0.01 ppm).

[0033] The results are as follows Figure 6 As shown, where, Figure 6 a shows that at 0.1C, the reversible capacity and initial coulombic efficiency of PC-S in Comparative Example 1 and PC-HP-S in Comparative Example 2 are 147.1 mAh g, respectively. -1 66.3% and 171.5mAh g -1 The electrochemical performance of Comparative Example 2, which underwent low-temperature oxidation, was 65.4%. However, the PC-P2-S from Example 2, after low-temperature oxidation, exhibited 274.1 mAh g⁻¹ and 78.2%. This demonstrates that, compared to low-temperature oxidation, Comparative Example 2, oxidized at a higher temperature, showed significantly poorer electrochemical performance. Figure 6 In Example 2 of b, the platform capacity was significantly improved, accounting for 49.6%. This significant improvement in platform capacity is mainly attributed to the overall significant expansion of the interlayer spacing of petroleum coke caused by the low-temperature permeation oxidation process. Figure 6 The long-cycle performance test results show that the PC-P2-S in Example 2 can achieve a retention rate of 93.5% after 400 cycles at 1C. Cycling test results at different current densities (0.1, 0.2, 0.5, 1, 2, 3, 5C) are as follows: Figure 6 As shown in d, the specific capacitance of PC-P2-S in Example 2 is significantly higher than that of PC-S in Comparative Example 1. In particular, when the current density gradually increases from 0.1C to 5C, the capacitance of PC-P2-S in Example 2 can still reach nearly twice that of PC-S in Comparative Example 1.

[0034] For those skilled in the art, various other corresponding changes and modifications can be made based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this invention.

Claims

1. A method for preparing a petroleum coke-based hard carbon negative electrode material, characterized by, Includes the following steps: Petroleum coke powder is mixed with an oxidant at 0~5℃ and oxidized for 12~48h to obtain an oxidation precursor; the oxidation precursor is then carbonized under a protective atmosphere to obtain the final product.

2. The method for preparing petroleum coke-based hard carbon anode material according to claim 1, characterized in that, The petroleum coke is crushed and then ball-milled at 600-1000 rpm for 2-6 hours. The powder is then passed through a 150-250 mesh sieve to obtain petroleum coke powder.

3. The method for preparing petroleum coke-based hard carbon anode material according to claim 1, characterized in that, The oxidant is a mixture of concentrated nitric acid and concentrated sulfuric acid.

4. The method for preparing petroleum coke-based hard carbon anode material according to claim 3, characterized in that, The volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:1~4.

5. The method for preparing petroleum coke-based hard carbon anode material according to claim 1, characterized in that, The mass ratio of petroleum coke powder to oxidant is 1:10~20.

6. The method for preparing petroleum coke-based hard carbon anode material according to claim 1, characterized in that, The carbonization heating rate is 5~10℃ / min; the carbonization temperature is 1200~1400℃, and the time is 1~2h.

7. A petroleum coke-based hard carbon anode material prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The average interlayer spacing is not less than 0.37 nm.

8. The petroleum coke-based hard carbon anode material according to claim 7, characterized in that, The negative electrode material has I D / I G The ratio is not less than 1.

08.

9. A sodium-ion battery, characterized in that, Anode sheets are prepared using the petroleum coke-based hard carbon anode material as described in claim 7.

10. The application of the petroleum coke-based hard carbon anode material as described in claim 7 in the preparation of secondary batteries.

Images