Asphalt-based hard carbon negative electrode material, preparation method thereof and sodium ion battery

Abstract

The invention relates to the technical field of sodium-ion batteries, in particular to an asphalt-based hard carbon negative electrode material, a preparation method thereof and a sodium-ion battery. The preparation method comprises the following steps: crushing asphalt, and sieving to obtain asphalt powder; the asphalt powder is subjected to a pre-oxidation cross-linking reaction, carbonization, ball milling and sieving, and asphalt-based hard carbon powder is obtained; adding the asphalt-based hard carbon powder into concentrated sulfuric acid, then adding potassium permanganate powder to carry out chemical intercalation reaction, and carrying out post-treatment to obtain modified asphalt-based hard carbon powder; and carrying out flash Joule heating on the modified asphalt-based hard carbon powder to obtain the asphalt-based hard carbon negative electrode material. According to the preparation method, the asphalt-based hard carbon negative electrode material with a microstructure in which the outside is ordered and the inside is disordered is prepared by combining chemical oxidation intercalation with a flash evaporation Joule heating technology, so that the hard carbon negative electrode material has excellent quick charging capacity and high-capacity sodium storage performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a pitch-based hard carbon negative electrode material, a preparation method thereof and a sodium ion battery. BACKGROUND

[0002] Pitch-based hard carbon is one of the most promising negative electrode materials for sodium ion batteries, although pitch-based hard carbon has broad prospects, but its research and application still faces some key challenges. The disordered structure of pitch-based hard carbon material determines its large specific surface area and rich defects on the surface, which will cause a large amount of solid-state electrolyte interface film (SEI film) to be formed in the first charge and discharge process, and the sodium ions from the positive electrode are irreversibly consumed, resulting in a low first coulombic efficiency (usually 80-85%, while graphite > 90%), which reduces the energy density of the full battery. How to improve the first coulombic efficiency and reversible capacity is the top priority of current research. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a pitch-based hard carbon negative electrode material, a preparation method thereof and a sodium ion battery, which are prepared by chemical oxidation intercalation combined with flash joule heating technology, and have an outer ordered and inner disordered microstructure, excellent fast charging capacity and high capacity sodium storage performance.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: The present application first provides a preparation method of a pitch-based hard carbon negative electrode material, which comprises the following steps: crushing pitch and sieving to obtain pitch powder; pre-oxidizing and cross-linking the pitch powder, carbonizing, ball milling and sieving to obtain pitch-based hard carbon powder; adding the pitch-based hard carbon powder into concentrated sulfuric acid, and then adding potassium permanganate powder to perform a chemical intercalation reaction, and then performing post-treatment to obtain modified pitch-based hard carbon powder; and performing flash joule heating on the modified pitch-based hard carbon powder to obtain a pitch-based hard carbon negative electrode material.

[0005] As a further improvement of the above-mentioned scheme of the present application, the pitch is at least one of petroleum pitch, coal pitch and natural pitch.

[0006] As a further improvement of the above-mentioned scheme of the present application, the crushing and sieving is performed at a rotation speed of 4000-8000 r / min and then sieved through a 200-300 mesh sieve, and the particle size of the pitch powder is 48-74 μm.

[0007] As a further improvement of the above-mentioned scheme of the present application, the pre-oxidation and cross-linking reaction is performed under an oxygen or air atmosphere, the temperature is raised to 250-350℃ at a temperature raising rate of 1-5℃ / min and the temperature is maintained for 2-10 h.

[0008] As a further improvement of the above-mentioned scheme of the present application, the carbonization is carried out under a protective atmosphere, at a temperature raising rate of 5-10℃ / min to 1000-1200℃ and for 1-4h.

[0009] As a further improvement of the above-mentioned scheme of the present application, the sieving after ball milling is carried out at a rotating speed of 500-800rpm to pass through a 300-400 mesh sieve.

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

[0011] As a further improvement of the above-mentioned scheme of the present application, the flash evaporation Joule heating is to transfer the modified pitch-based hard carbon powder to a carbon cloth, and heat the carbon cloth to 1500-1800℃ for 3-10s by a Joule heating source.

[0012] The present application also provides a pitch-based hard carbon negative electrode material prepared by the above-mentioned preparation method.

[0013] The present application also provides a sodium ion battery comprising the pitch-based hard carbon negative electrode material as mentioned above.

[0014] Compared with the prior art, the present application has the following beneficial effects: The present application, by means of chemical oxidation intercalation combined with flash evaporation Joule heating technology, prepares a pitch-based hard carbon negative electrode material with an outer ordered and inner disordered microstructure, the outer layer of which is an ordered graphitized layer with a super-large spacing (≥0.40nm), and the inner layer of which is a disordered form with abundant pores; the ordered graphitized layer with a super-large spacing in the outer layer can serve as a transmission channel for efficiently and reversibly accommodating sodium ions with a larger radius, so that the hard carbon negative electrode material has excellent fast charging capacity, and the ordered graphitized layer reduces surface defects, eliminates unstable active sites, reduces specific surface area, reduces side reactions, and significantly improves the first cycle coulombic efficiency and reversible capacity; at the same time, the pitch-based hard carbon negative electrode material can exhibit high capacity sodium storage performance due to the multiple energy storage mechanism of the disordered form with abundant pores in the inner layer.

[0015] The preparation method of the present application is simple, and the pitch-based hard carbon negative electrode material with an outer ordered and inner disordered structure prepared thereby has more excellent sodium storage performance, especially the first cycle coulombic efficiency is improved from 80-85% of the pitch-based hard carbon produced by the prior art to ≥87% of the pitch-based hard carbon with an outer ordered and inner disordered structure. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The transmission electron microscope image of the pitch-based hard carbon negative electrode material prepared in Example 1; Figure 2 Transmission electron microscope image of the pitch-based hard carbon negative electrode material prepared for Comparative Example 1; Figure 3 Transmission electron microscope image of the pitch-based hard carbon negative electrode material prepared for Comparative Example 2; Figure 4 Graph of the first cycle charge-discharge curve of the pitch-based hard carbon negative electrode material prepared for Example 1 and Comparative Examples 1-2 at a current density of 0.05 A g -1 DETAILED DESCRIPTION

[0017] In order to facilitate the understanding of the present application, the present application will be described more fully below in connection with specific embodiments. However, the present application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[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 application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0019] Example 1 This example proposes a pitch-based hard carbon negative electrode material, and the preparation method thereof comprises the following steps: (1) The petroleum pitch is crushed in a crusher with a rotation speed of 5000 r / min, and then passed through a sieve with a mesh size of 200 meshes to obtain pitch powder with a particle size of about 70 μm; (2) The pitch powder is subjected to pre-oxidation treatment in an air atmosphere: heated to 300 °C at a rate of 3 °C / min, and cross-linked at 300 °C for 5 h to obtain pre-oxidized pitch powder; (3) The pre-oxidized pitch powder is subjected to high-temperature carbonization treatment in an argon atmosphere: heated to 1200 °C at a rate of 5 °C / min and kept for 2 h, and naturally cooled to room temperature to obtain pitch-based hard carbon; (4) The pitch-based hard carbon is ball milled and sieved: the ball milling rotation speed is 600 rpm, the ball milling time is 10 h, and the sieve is 300-400 meshes to obtain pitch-based hard carbon powder; (5) The pitch-based hard carbon powder is transferred into 400 wt% concentrated sulfuric acid, and then 30 wt% of potassium permanganate powder based on the pitch-based hard carbon powder is slowly added batch by batch. After 60 minutes of reaction, the product is washed and dried to obtain modified pitch-based hard carbon powder; ​(6) The modified pitch-based hard carbon powder is transferred to a carbon cloth, flash Joule heating is performed, the modified pitch-based hard carbon powder is instantaneously heated to 1600 DEG C through a Joule heating source, and after 3 seconds, natural cooling is performed, to obtain a pitch-based hard carbon negative electrode material with an outer ordered and inner disordered structure.

[0020] Example 2 The embodiment provides a pitch-based hard carbon negative electrode material, and a preparation method thereof includes the following steps. (1) Petroleum pitch is crushed in a crusher at a rotation speed of 5000 r / min, and then passed through a sieve with a mesh size of 200 meshes, to obtain pitch powder with a particle size of about 70 μm; (2) The pitch powder is pre-oxidized in an air atmosphere: the temperature is raised to 250 DEG C at a rate of 3 DEG C / min, and cross-linking reaction is performed at 250 DEG C for 10 h, to obtain pre-oxidized pitch powder; (3) The pre-oxidized pitch powder is high-temperature carbonized in an argon atmosphere: the temperature is raised to 1000 DEG C at a rate of 5 DEG C / min and kept for 4 h, and natural cooling is performed to room temperature, to obtain pitch-based hard carbon; (4) The pitch-based hard carbon is ball milled and sieved: the ball milling rotation speed is 600 rpm, the ball milling time is 10 h, and the sieve is 300-400 meshes, to obtain pitch-based hard carbon powder; (5) The pitch-based hard carbon powder is transferred into 500 wt% concentrated sulfuric acid, and 40 wt% of potassium permanganate powder based on the pitch-based hard carbon powder is slowly added in batches, and after 60 minutes of reaction, the product is washed and dried, to obtain modified pitch-based hard carbon powder; (6) The modified pitch-based hard carbon powder is transferred to a carbon cloth, flash Joule heating is performed, the modified pitch-based hard carbon powder is instantaneously heated to 1600 DEG C through a Joule heating source, and after 3 seconds, natural cooling is performed, to obtain a pitch-based hard carbon negative electrode material with an outer ordered and inner disordered structure.

[0021] Example 3 The embodiment provides a pitch-based hard carbon negative electrode material, and a preparation method thereof includes the following steps. (1) Petroleum pitch is crushed in a crusher at a rotation speed of 5000 r / min, and then passed through a sieve with a mesh size of 200 meshes, to obtain pitch powder with a particle size of about 70 μm; (2) The pitch powder is pre-oxidized in an air atmosphere: the temperature is raised to 350 DEG C at a rate of 3 DEG C / min, and cross-linking reaction is performed at 350 DEG C for 2 h, to obtain pre-oxidized pitch powder; (3) The pre-oxidized pitch powder is high-temperature carbonized in an argon atmosphere: the temperature is raised to 1100 DEG C at a rate of 5 DEG C / min and kept for 3 h, and natural cooling is performed to room temperature, to obtain pitch-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: Figures 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 4It can be seen that the first circle coulomb efficiency and reversible capacity of the pitch-based hard carbon modified by the oxidation intercalation treatment + flash joule heating in Example 1 are greatly improved compared with Comparative Example 1 (not flash joule heating modified) and Comparative Example 2 (not chemically oxidation intercalation modified), which is attributed to the fact that the oxidation intercalation treatment + flash joule heating modification can form ordered layers on the surface of the pitch-based hard carbon, the external ordered layers can reduce surface defects, eliminate unstable active sites, and reduce the specific surface area, thereby improving the low first circle coulomb efficiency and reversible capacity caused by the side reaction with the electrolyte.

[0027] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are described, however, as long as the combinations of the technical features do not contradict each other, they should be considered to be within the scope of the present disclosure.

[0028] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to 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.

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. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, 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.

8. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The flash Joule heating involves transferring the modified pitch-based hard carbon powder onto carbon cloth, and then heating the carbon cloth to 1500-1800°C using a Joule heating source for 3-10 seconds.

9. A pitch-based hard carbon anode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. A sodium-ion battery, characterized in that, It includes the pitch-based hard carbon anode material as described in claim 9.

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