A pitch-based hard carbon anode material, its preparation method, and a sodium-ion battery

Abstract

This invention relates to the field of sodium-ion battery technology, and particularly to an asphalt-based hard carbon anode material, its preparation method, and a sodium-ion battery. The preparation method includes the following steps: pulverizing and sieving asphalt to obtain asphalt powder; subjecting the asphalt powder to a pre-oxidative crosslinking reaction, carbonizing, ball milling, and sieving to obtain asphalt-based hard carbon powder; adding the asphalt-based hard carbon powder to concentrated sulfuric acid, then adding potassium permanganate powder for a chemical intercalation reaction, followed by post-treatment to obtain modified asphalt-based hard carbon powder; and subjecting the modified asphalt-based hard carbon powder to flash Joule heating to obtain the asphalt-based hard carbon anode material. This invention, through chemical oxidation intercalation combined with flash Joule heating technology, prepares an asphalt-based hard carbon anode material with an externally ordered and internally disordered microstructure, giving the hard carbon anode material excellent fast-charging capability and high-capacity sodium storage performance.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to an asphalt-based hard carbon anode material, its preparation method, and a sodium-ion battery. Background Technology

[0002] Pitch-based hard carbon is one of the most commercially promising anode materials for sodium-ion batteries. Despite its promising prospects, its research and application still face several key challenges. The disordered structure of pitch-based hard carbon materials results in a large specific surface area and abundant surface defects. This leads to the formation of a large amount of solid electrolyte interphase (SEI) film during the first charge-discharge cycle, irreversibly consuming sodium ions from the cathode and causing a lower initial coulombic efficiency (typically 80-85%, compared to >90% for graphite), thus reducing the overall energy density of the battery. Improving both initial coulombic efficiency and reversible capacity is currently a top priority in research. Summary of the Invention

[0003] Based on this, the purpose of this invention is to provide an asphalt-based hard carbon anode material, its preparation method, and a sodium-ion battery. By combining chemical oxidation intercalation with flash evaporation Joule heating technology, an asphalt-based hard carbon anode material with an externally ordered and internally disordered microstructure is prepared, which has excellent fast charging capability and high-capacity sodium storage performance.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing an asphalt-based hard carbon anode material, comprising the following steps: pulverizing asphalt and sieving it to obtain asphalt powder; subjecting the asphalt powder to a pre-oxidative crosslinking reaction, carbonizing, ball milling, and sieving to obtain asphalt-based hard carbon powder; adding the asphalt-based hard carbon powder to concentrated sulfuric acid, then adding potassium permanganate powder to perform a chemical intercalation reaction, followed by post-treatment to obtain modified asphalt-based hard carbon powder; and subjecting the modified asphalt-based hard carbon powder to flash evaporation and Joule heating to obtain the asphalt-based hard carbon anode material.

[0005] As a further improvement to the above-described scheme of the present invention, the asphalt is at least one of petroleum asphalt, coal tar pitch, and natural asphalt.

[0006] As a further improvement to the above-mentioned solution of the present invention, the sieving after crushing is carried out by crushing at a speed of 4000-8000 r / min and then passing through a 200-300 mesh sieve, and the particle size of the asphalt powder is 48-74 μm.

[0007] As a further improvement to the above-mentioned scheme of the present invention, the pre-oxidative crosslinking reaction is carried out in an oxygen or air atmosphere, with a heating rate of 1-5℃ / min to 250-350℃ and held at that temperature for 2-10h.

[0008] As a further improvement to the above-mentioned solution of the present invention, the carbonization is carried out under a protective atmosphere, with the temperature increased to 1000-1200°C at a heating rate of 5-10°C / min and held for 1-4 hours.

[0009] As a further improvement to the above-mentioned solution of the present invention, the ball milling and sieving is performed by ball milling at a speed of 500-800 rpm and then passing the ball through a 300-400 mesh sieve.

[0010] As a further improvement to the above-mentioned scheme of the present invention, the mass ratio of the asphalt-based hard carbon powder to concentrated sulfuric acid is 1:4-6, the mass ratio of the asphalt-based hard carbon powder to potassium permanganate powder is 1:0.2-0.5, and the chemical intercalation reaction time is 30-60 min.

[0011] As a further improvement to the above-mentioned solution of the present invention, the flash Joule heating involves transferring the modified pitch-based hard carbon powder onto carbon cloth, and heating the carbon cloth to 1500-1800°C using a Joule heating source for 3-10 seconds.

[0012] The present invention also provides an asphalt-based hard carbon anode material, which is prepared by the preparation method described above.

[0013] The present invention also provides a sodium-ion battery comprising the pitch-based hard carbon anode material as described above.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes chemical oxidation intercalation combined with flash Joule heating technology to prepare a pitch-based hard carbon anode material with an externally ordered and internally disordered microstructure. The outer layer is an ordered graphitized layer with an ultra-large spacing (≥0.40 nm), while the inner layer is a disordered morphology with abundant pores. The outer layer's ultra-large spacing ordered graphitized layer can serve as a highly efficient and reversible channel for accommodating larger-radius sodium ions, giving the hard carbon anode material excellent fast-charging capability. Furthermore, the ordered graphitized layer reduces surface defects, eliminates unstable active sites, reduces specific surface area, and minimizes side reactions, significantly improving the first-cycle coulombic efficiency and reversible capacity. Simultaneously, thanks to the multiple energy storage mechanisms of the disordered morphology with abundant pores in the inner layer, the pitch-based hard carbon anode material exhibits high-capacity sodium storage performance.

[0015] The preparation method of the present invention is simple, and the prepared pitch-based hard carbon anode material with an externally ordered and internally disordered structure has better sodium storage performance. In particular, the initial coulombic efficiency is increased from 80-85% of pitch-based hard carbon produced by existing technology to ≥87% of pitch-based hard carbon with an externally ordered and internally disordered structure. Attached Figure Description

[0016] Figure 1 Transmission electron microscopy (TEM) image of the pitch-based hard carbon anode material prepared in Example 1; Figure 2 Transmission electron microscopy image of the pitch-based hard carbon anode material prepared in Comparative Example 1; Figure 3 Transmission electron microscopy image of the pitch-based hard carbon anode material prepared in Comparative Example 2; Figure 4 The pitch-based hard carbon anode materials prepared in Example 1 and Comparative Examples 1-2 were subjected to a 0.05A g test. -1 The first charge-discharge curve at current density. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] Example 1 This embodiment proposes a pitch-based hard carbon anode material, the preparation method of which includes the following steps: (1) The petroleum asphalt was crushed in a pulverizer with a rotation speed of 5000 r / min and then passed through a sieve with a mesh size of 200 to obtain asphalt powder with a particle size of about 70 μm. (2) Pre-oxidize the asphalt powder in air atmosphere: heat up to 300℃ at a rate of 3℃ / min, and cross-link at 300℃ for 5h to obtain pre-oxidized asphalt powder; (3) Under an argon atmosphere, the pre-oxidized asphalt powder was subjected to high-temperature carbonization treatment: the temperature was increased to 1200℃ at 5℃ / min and held for 2h, and then naturally cooled to room temperature to obtain asphalt-based hard carbon. (4) Ball milling and sieving the asphalt-based hard carbon: the ball milling speed is 600 rpm, the ball milling time is 10 h, and the sieve is 300-400 mesh to obtain asphalt-based hard carbon powder; (5) Transfer the asphalt-based hard carbon powder into 400wt% concentrated sulfuric acid, and then slowly add 30wt% potassium permanganate powder of the asphalt-based hard carbon powder in batches. After reacting for 60 minutes, wash and dry the product to obtain modified asphalt-based hard carbon powder. (6) The modified pitch-based hard carbon powder is transferred onto carbon cloth and subjected to flash Joule heating. The powder is instantaneously heated to 1600 °C by a Joule heating source for 5 seconds, and then naturally cooled to obtain a pitch-based hard carbon anode material with an externally ordered and internally disordered structure.

[0020] Example 2 This embodiment proposes a pitch-based hard carbon anode material, the preparation method of which includes the following steps: (1) The petroleum asphalt was crushed in a pulverizer with a rotation speed of 5000 r / min and then passed through a sieve with a mesh size of 200 to obtain asphalt powder with a particle size of about 70 μm. (2) Pre-oxidize the asphalt powder in air atmosphere: heat up to 250°C at a rate of 3°C / min, and cross-link at 250°C for 10h to obtain pre-oxidized asphalt powder. (3) Under an argon atmosphere, the pre-oxidized asphalt powder is subjected to high-temperature carbonization treatment: the temperature is increased to 1000℃ at 5℃ / min and kept at 4h, and then naturally cooled to room temperature to obtain asphalt-based hard carbon. (4) Ball milling and sieving of pitch-based hard carbon: the ball milling speed is 600 rpm, the ball milling time is 10 h, and the sieve is 300-400 mesh to obtain pitch-based hard carbon powder; (5) Transfer the asphalt-based hard carbon powder into 500wt% concentrated sulfuric acid, and slowly add 40wt% potassium permanganate powder of the asphalt-based hard carbon powder in batches. After reacting for 60 minutes, wash and dry the product to obtain modified asphalt-based hard carbon powder. (6) The modified pitch-based hard carbon powder is transferred onto carbon cloth and subjected to flash Joule heating. The powder is instantaneously heated to 1600 °C by a Joule heating source for 3 seconds, and then naturally cooled to obtain an externally ordered and internally disordered pitch-based hard carbon anode material.

[0021] Example 3 This embodiment proposes a pitch-based hard carbon anode material, the preparation method of which includes the following steps: (1) The petroleum asphalt was crushed in a pulverizer with a rotation speed of 5000 r / min and then passed through a sieve with a mesh size of 200 to obtain asphalt powder with a particle size of about 70 μm. (2) Pre-oxidize the asphalt powder in air atmosphere: heat up to 350℃ at a rate of 3℃ / min, and cross-link at 350℃ for 2h to obtain pre-oxidized asphalt powder; (3) Under an argon atmosphere, the pre-oxidized asphalt powder is subjected to high-temperature carbonization treatment: the temperature is increased to 1100℃ at 5℃ / min and kept at 3h, and then naturally cooled to room temperature to obtain asphalt-based hard carbon. (4) Ball milling and sieving of pitch-based hard carbon: the ball milling speed is 600 rpm, the ball milling time is 10 h, and the sieve is 300-400 mesh to obtain pitch-based hard carbon powder; (5) Transfer the asphalt-based hard carbon powder into 600wt% concentrated sulfuric acid, and slowly add 50wt% potassium permanganate powder of the asphalt-based hard carbon powder in batches. After reacting for 60 minutes, wash and dry the product to obtain modified asphalt-based hard carbon powder. (6) The modified pitch-based hard carbon powder is transferred onto carbon cloth and subjected to flash Joule heating. The powder is instantaneously heated to 1600 °C by a Joule heating source for 10 seconds, and then naturally cooled to obtain an externally ordered and internally disordered pitch-based hard carbon anode material.

[0022] Comparative Example 1 The difference between this comparative example and Example 1 is that step (6) was not performed in this comparative example.

[0023] Comparative Example 2 The difference between this comparative example and Example 1 is that step (5) was not performed in this comparative example.

[0024] Test case (1) The pitch-based hard carbon anode materials prepared in Example 1 and Comparative Examples 1-2 were characterized respectively, and the results were as follows: Figure 1-3 The transmission electron microscope image shown is from... Figure 1 It can be clearly seen that in Example 1, a crystalline ordered layer forms on the surface of the pitch-based hard carbon modified by oxidation intercalation treatment and flash Joule heating. The interlayer spacing is relatively large, reaching 0.41 nm. This ordered layer can both ensure the insertion and extraction of sodium ions and serve as a protective layer; while Figure 2 No ordered layer was observed in Comparative Example 1, which was modified by flash joule heating; Figure 3 Although a small number of tiny ordered regions appeared on the surface of the comparative example 2 without chemical oxidation intercalation modification due to flash Joule heating treatment, they were relatively dispersed and had small interlayer spacing, so they could not provide protection and were not conducive to sodium ion intercalation / deintercalation.

[0025] (2) The asphalt-based hard carbon negative electrode material prepared in Example 1 and Comparative Examples 1-2 was used to prepare a sodium-ion battery: The asphalt-based hard carbon prepared in Example 1 and Comparative Examples 1-2 was used as the active material of the negative electrode. It was mixed with conductive carbon black and sodium carboxymethyl cellulose binder at a mass ratio of 8:1:1 and coated to prepare a negative electrode sheet. Sodium metal sheet was used as the positive electrode. Diethylene glycol dimethyl ether (Diglyme) containing 1M NaPF6 was used as the electrolyte. Glass fiber was used as the separator to assemble a sodium-ion button battery.

[0026] The prepared sodium-ion battery was subjected to performance testing, and the results were as follows: Figure 4 The first charge-discharge curve shown is from... Figure 4As can be seen, the first-cycle coulombic efficiency and reversible capacity of the pitch-based hard carbon modified by oxidation intercalation treatment + flash Joule heating in Example 1 were greatly improved compared with Comparative Example 1 (without flash Joule heating modification) and Comparative Example 2 (without chemical oxidation intercalation modification). This is attributed to the fact that oxidation intercalation treatment + flash Joule heating modification can form an ordered layer on the surface of pitch-based hard carbon. The external ordered layer can reduce surface defects, eliminate unstable active sites, and reduce specific surface area, thereby improving the low first-cycle coulombic efficiency and reversible capacity caused by side reactions with electrolyte.

[0027] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0028] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an asphalt-based hard carbon anode material, characterized in that, It includes the following steps: Asphalt is pulverized and sieved to obtain asphalt powder; the asphalt powder is subjected to a pre-oxidation crosslinking reaction, carbonized, ball-milled, and sieved to obtain asphalt-based hard carbon powder; the asphalt-based hard carbon powder is added to concentrated sulfuric acid, and then potassium permanganate powder is added to carry out a chemical intercalation reaction, followed by post-treatment to obtain modified asphalt-based hard carbon powder; the modified asphalt-based hard carbon powder is subjected to flash evaporation and Joule heating to obtain asphalt-based hard carbon anode material. The mass ratio of the asphalt-based hard carbon powder to concentrated sulfuric acid is 1:4-6, the mass ratio of the asphalt-based hard carbon powder to potassium permanganate powder is 1:0.2-0.5, and the chemical intercalation reaction time is 30-60 min; the flash Joule heating involves transferring the modified asphalt-based hard carbon powder onto carbon cloth, and heating the carbon cloth to 1500-1800℃ using a Joule heating source for 3-10 s.

2. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The asphalt is at least one of petroleum asphalt, coal tar pitch, and natural asphalt.

3. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The sieving after crushing involves crushing the material at a speed of 4000-8000 r / min and then passing it through a 200-300 mesh sieve. The particle size of the asphalt powder is 48-74 μm.

4. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The pre-oxidative crosslinking reaction is carried out in an oxygen or air atmosphere, with the temperature increased to 250-350°C at a heating rate of 1-5°C / min and held for 2-10 hours.

5. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The carbonization process involves heating to 1000-1200℃ at a rate of 5-10℃ / min under a protective atmosphere and holding at that temperature for 1-4 hours.

6. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The ball milling and sieving process involves passing the ball through a 300-400 mesh sieve at a speed of 500-800 rpm.

7. A pitch-based hard carbon anode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

8. A sodium-ion battery, characterized in that, It includes the pitch-based hard carbon anode material as described in claim 7.

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