Asphalt resin-based hard carbon negative electrode material and preparation method thereof

Abstract

The application provides a pitch resin-based hard carbon negative material and a preparation method thereof, and belongs to the technical field of sodium ion battery negative materials. First, naphthalene, p-xylene glycol and p-methyl benzene sulfonic acid are mixed and subjected to a condensation reaction to obtain pitch resin; then, the pitch resin is sequentially subjected to a curing reaction, ball milling treatment and carbonization treatment to obtain a carbonized precursor; finally, the carbonized precursor and pitch are mixed and subjected to calcination treatment to obtain the pitch resin-based hard carbon negative material. The pitch resin-based hard carbon negative material prepared by the application has excellent electrochemical performance, the initial reversible specific capacity is greater than or equal to 320 mAh / g, the initial coulombic efficiency is greater than or equal to 92%, the discharge capacity is high, and the low-voltage platform capacity accounts for more than 75% of the total discharge capacity.

Description

Technical Field

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

[0002] Hard carbon anodes possess advantages such as low voltage plateau, high capacity, good cycle stability, and abundant raw material sources, attracting significant attention from researchers and industry. However, hard carbon anode materials also suffer from a series of problems, including low plateau capacity, poor rate performance, and low initial coulombic efficiency, which restrict their large-scale application.

[0003] In recent years, the sodium storage mechanism of hard carbon has been explored in greater depth. Extensive research has demonstrated that the capacity of hard carbon consists of a ramp capacity and a low-voltage plateau capacity. The ramp capacity corresponds to the adsorption of sodium ions by carbon layer defects and surface functional groups. The plateau capacity is mainly related to the adsorption of sodium ions by Na+. + The insertion and extraction between graphitic carbon layers are related to (i.e., adsorption-deintercalation mechanism) and Na. + The issue relates to the filling of closed pores. Closed pores are complex amorphous structures, consisting of porous structures surrounded by bent, stacked carbon layers. An effective way to increase the operating voltage and energy density of sodium-ion full cells is to enhance the low-plateau capacity of hard carbon, i.e., to increase the number of closed pores.

[0004] Currently, there are limited methods for controlling the closed-pore structure because excessively high temperatures can easily lead to the formation of too many graphite-like structures within the carbon material. These graphite-like structures lack closed-pore structure and are not conducive to sodium storage. Conversely, excessively low sintering temperatures make it difficult to form sufficient graphite-like microcrystals to constitute the pore walls of the closed pores. Therefore, how to control the closed-pore structure to improve sodium storage capacity, especially the plateau region capacity, is a hot topic in hard carbon anode material research. Summary of the Invention

[0005] The purpose of this invention is to provide an asphalt resin-based hard carbon anode material and its preparation method, so as to solve the problems of low number of closed pores and low plateau capacity in existing hard carbon anode materials.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing an asphalt resin-based hard carbon anode material, comprising the following steps:

[0008] (1) Naphthalene, terephthalic acid and p-toluenesulfonic acid are mixed and then subjected to a condensation reaction to obtain asphalt resin;

[0009] (2) The asphalt resin is subjected to curing reaction, ball milling and carbonization in sequence to obtain carbonized precursor;

[0010] (3) The carbonized precursor and asphalt are mixed and then calcined to obtain asphalt resin-based hard carbon anode material.

[0011] Preferably, in step (1), the molar ratio of naphthalene to terephthalic acid is 1:0.5 to 2; and the amount of p-toluenesulfonic acid added accounts for 2 to 7% of the total mass of naphthalene and terephthalic acid.

[0012] Preferably, in step (1), the temperature of the condensation reaction is 120-170°C, and the condensation reaction ends when the rod-like phenomenon occurs.

[0013] Preferably, in step (2), the curing reaction includes a first curing reaction and a second curing reaction, wherein the temperature of the first curing reaction is 110-130°C and the time of the first curing reaction is 15-20h, the temperature of the second curing reaction is 180-220°C and the time of the second curing reaction is 1-5h.

[0014] Preferably, in step (2), the ball-to-material ratio for ball milling is 3 to 5:1, and the ball milling time is 20 to 50 hours.

[0015] Preferably, in step (2), the heating rate of the carbonization treatment is 1 to 5 °C / min, the temperature of the carbonization treatment is 1200 to 1600 °C, and the carbonization treatment time is 2 to 10 h.

[0016] Preferably, in step (3), the mass ratio of carbonized precursor to asphalt is 100:1 to 5; the asphalt is high softening point asphalt or medium temperature asphalt.

[0017] Preferably, in step (3), the heating rate of the calcination treatment is 1-5℃ / min, the calcination temperature is 900-1100℃, and the calcination time is 2-5h.

[0018] The present invention also provides a pitch resin-based hard carbon anode material prepared by the above preparation method, wherein the pitch resin-based hard carbon anode material has a D50 of 5-10 μm and a specific surface area of ​​≤10 m². 2 / g.

[0019] Preferably, the pitch resin-based hard carbon anode material has an initial reversible specific capacity ≥320mAh / g and an initial coulombic efficiency ≥92%.

[0020] The beneficial effects of this invention are:

[0021] (1) This invention uses naphthalene, a polycyclic aromatic hydrocarbon, as a carbon source precursor and terephthalic acid as a crosslinking agent. Under the catalysis of p-toluenesulfonic acid, a condensation reaction is carried out to obtain a three-dimensional network structure of condensed polycyclic aromatic hydrocarbons, namely pitch resin. The pitch resin undergoes a ring-closing reaction after carbonization treatment, and the occurrence of the ring-closing reaction can be controlled by adjusting the mass ratio of naphthalene and the crosslinking agent terephthalic acid.

[0022] (2) Asphalt resin has the characteristics of resin. During the curing reaction and carbonization process, small molecule compounds will volatilize. This process will also form more open pores. After being coated with solid carbon, the open pores can be transformed into a certain number of closed pores, which will also improve the low voltage platform capacity of hard carbon anode materials.

[0023] (3) The asphalt resin-based hard carbon anode material prepared by the present invention has excellent electrochemical performance, with an initial reversible specific capacity ≥320mAh / g, an initial coulombic efficiency ≥92%, a high discharge capacity, and a low voltage plateau capacity accounting for more than 75% of the total discharge capacity. Attached Figure Description

[0024] Figure 1 The image shows the XRD pattern of the pitch resin-based hard carbon anode material prepared in Example 1.

[0025] Figure 2 The image shows the charge-discharge curves of the asphalt resin-based hard carbon anode material prepared in Example 1. Detailed Implementation

[0026] This invention provides a method for preparing an asphalt resin-based hard carbon anode material, comprising the following steps:

[0027] (1) Naphthalene, terephthalic acid and p-toluenesulfonic acid are mixed and then subjected to a condensation reaction to obtain asphalt resin;

[0028] (2) The asphalt resin is subjected to curing reaction, ball milling and carbonization in sequence to obtain carbonized precursor;

[0029] (3) The carbonized precursor and asphalt are mixed and then calcined to obtain asphalt resin-based hard carbon anode material.

[0030] In this invention, in step (1), the molar ratio of naphthalene to terephthalic acid is 1:0.5 to 2, preferably 1:0.8 to 1.8, and more preferably 1:1 to 1.5; the amount of p-toluenesulfonic acid added accounts for 2 to 7% of the total mass of naphthalene and terephthalic acid, preferably 3 to 6%, and more preferably 4 to 5%.

[0031] In this invention, in step (1), the condensation reaction is carried out in an inert atmosphere, preferably in a nitrogen atmosphere.

[0032] In this invention, in step (1), the temperature of the condensation reaction is 120-170°C, preferably 130-160°C, and more preferably 140-150°C. The condensation reaction ends when the rod entanglement phenomenon occurs.

[0033] In this invention, step (2) includes a first curing reaction and a second curing reaction. The temperature of the first curing reaction is 110-130°C, preferably 115-125°C, and more preferably 120°C. The time of the first curing reaction is 15-20 hours, preferably 16-19 hours, and more preferably 17-18 hours. The temperature of the second curing reaction is 180-220°C, preferably 190-210°C, and more preferably 200°C. The time of the second curing reaction is 1-5 hours, preferably 2-4 hours, and more preferably 3 hours.

[0034] In this invention, the product of the curing reaction is cured asphalt resin, and preferably, the cured asphalt resin is coarsely ground before being ball-milled. During the ball-milling process, anhydrous ethanol dispersant is preferably added to the cured asphalt resin, wherein the mass ratio of cured asphalt resin to anhydrous ethanol is 5–13:20, preferably 7–12:20, and more preferably 8–11:20.

[0035] In this invention, in step (2), the ball-to-material ratio of the ball milling process is 3 to 5:1, preferably 4:1; the ball milling time is 20 to 50 hours, preferably 25 to 45 hours, and more preferably 30 to 40 hours.

[0036] In this invention, after ball milling, a powdered cured asphalt resin is obtained. The D50 of the powdered cured asphalt resin is 6.8 to 9.8 μm, preferably 7.0 to 9.0 μm, and more preferably 7.5 to 8.5 μm.

[0037] In this invention, in step (2), the carbonization process is carried out in an inert atmosphere, preferably in a nitrogen atmosphere.

[0038] In this invention, in step (2), the heating rate of the carbonization treatment is 1-5℃ / min, preferably 2-4℃ / min, and more preferably 3℃ / min; the temperature of the carbonization treatment is 1200-1600℃, preferably 1300-1500℃, and more preferably 1400℃; the carbonization treatment time is 2-10h, preferably 3-9h, and more preferably 4-8h.

[0039] In this invention, in step (3), the mass ratio of carbonization precursor to asphalt is 100:1 to 5, preferably 100:2 to 4, and more preferably 100:3; the asphalt is high softening point asphalt or medium temperature asphalt, preferably high softening point asphalt.

[0040] The asphalt used in this invention has no special requirements; any asphalt known in the art can be used. Both the high softening point asphalt and the medium-temperature asphalt used in this invention were purchased from Rixin (Dalian) New Material Technology Co., Ltd., with the high softening point asphalt being MQ-250 and the medium-temperature asphalt being MQ-180.

[0041] In this invention, in step (3), the calcination treatment is carried out in an inert atmosphere, preferably in a nitrogen atmosphere or an argon atmosphere.

[0042] In this invention, in step (3), the heating rate of the calcination treatment is 1-5℃ / min, preferably 2-4℃ / min, and more preferably 3℃ / min; the calcination temperature is 900-1100℃, preferably 920-1050℃, and more preferably 950-1000℃; and the calcination time is 2-5h, preferably 3-4h, and more preferably 3.5h.

[0043] This invention also provides a pitch resin-based hard carbon anode material prepared by the above-described method, wherein the D50 of the pitch resin-based hard carbon anode material is 5–10 μm, preferably 6–9 μm, and more preferably 7–8 μm; and the specific surface area is ≤10 m². 2 / g, preferably 2-8m 2 / g, more preferably 3-7m 2 / g.

[0044] In this invention, the initial reversible specific capacity of the pitch resin-based hard carbon anode material is ≥320mAh / g, and the initial coulombic efficiency is ≥92%.

[0045] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] Naphthalene and terephthalic acid were added to a three-necked flask at a molar ratio of 1:1, followed by the addition of p-toluenesulfonic acid (5% of the total mass of naphthalene and terephthalic acid). The mixture was stirred thoroughly under a nitrogen atmosphere and then subjected to a condensation reaction at 140°C until the reaction product exhibited a rod-like phenomenon, at which point the reaction was terminated, yielding asphalt resin.

[0048] The asphalt resin was placed in a forced-air drying oven for curing. The first stage of curing was carried out at 120℃ for 15 hours, and the second stage at 200℃ for 2 hours, yielding cured asphalt resin. The cured asphalt resin was coarsely ground and dispersed in anhydrous ethanol (mass ratio of cured asphalt resin to anhydrous ethanol: 9:20). This was then ball-milled in a ball mill jar using zirconia balls at a ball-to-material ratio of 4:1 for 30 hours. The mixture was then dried at 80℃ for 12 hours to obtain powdered cured asphalt resin with a D50 of 8.8 μm. The powdered cured asphalt resin was placed in a tube furnace and carbonized at 1400℃ for 3.5 hours under a nitrogen atmosphere at a heating rate of 3℃ / min, followed by natural cooling to room temperature to obtain the carbonized precursor.

[0049] The carbonized precursor and high-temperature softening point asphalt (MQ-250) were mixed at a mass ratio of 100:3, and then calcined at 950℃ for 3 hours under a nitrogen atmosphere at a heating rate of 4℃ / min. The mixture was then naturally cooled to room temperature to obtain an asphalt resin-based hard carbon anode material. The asphalt resin-based hard carbon anode material had a D50 of 8.6 μm and a specific surface area of ​​4.8 m². 2 / g.

[0050] The performance of the pitch resin-based hard carbon anode material prepared in Example 1 was characterized by Cu-Kα X-ray diffraction analysis, and the test results are as follows: Figure 1 As shown, from Figure 1 It can be seen that the prepared pitch resin-based hard carbon anode material has an amorphous carbon material structure with an interlayer spacing d002 of 0.388 nm.

[0051] The asphalt resin-based hard carbon anode material prepared in Example 1 was used as the electrode, and a sodium sheet was used as the counter electrode. The first charge-discharge test was conducted in a sodium-ion coin cell, and the test results are as follows: Figure 2 As shown, from Figure 2 It can be seen that at a current of 0.1C, the measured initial discharge capacity is 320.8mAh / g, the initial coulombic efficiency is 92.45%, and the low voltage plateau capacity is also relatively high, accounting for 78% of the total discharge capacity.

[0052] Example 2

[0053] Naphthalene and terephthalic acid were added to a three-necked flask at a molar ratio of 1:1.2, followed by the addition of p-toluenesulfonic acid (2% of the total mass of naphthalene and terephthalic acid). The mixture was stirred thoroughly under a nitrogen atmosphere and then subjected to a condensation reaction at 170°C until the reaction product exhibited a rod-like phenomenon, at which point the reaction was complete, yielding asphalt resin.

[0054] The asphalt resin was placed in a forced-air drying oven for curing. The first stage of curing was carried out at 110℃ for 18 hours, and the second stage at 180℃ for 5 hours, yielding cured asphalt resin. The cured asphalt resin was coarsely ground and dispersed in anhydrous ethanol (mass ratio of cured asphalt resin to anhydrous ethanol was 8:20). This was then ball-milled in a ball mill jar using zirconia balls at a ball-to-material ratio of 5:1 for 50 hours. The mixture was then dried at 80℃ for 12 hours to obtain powdered cured asphalt resin with a D50 of 6.8 μm. The powdered cured asphalt resin was placed in a tube furnace and carbonized at 1600℃ for 2 hours under a nitrogen atmosphere at a heating rate of 5℃ / min. Afterward, it was naturally cooled to room temperature to obtain the carbonized precursor.

[0055] The carbonized precursor and medium-temperature pitch (MQ-18) were mixed at a mass ratio of 100:5, and then calcined at 1100℃ for 2 hours in an argon atmosphere at a heating rate of 1℃ / min. The mixture was then naturally cooled to room temperature to obtain a pitch resin-based hard carbon anode material. The pitch resin-based hard carbon anode material had a D50 of 6.2 μm and a specific surface area of ​​5.8 m². 2 / g.

[0056] Using the asphalt resin-based hard carbon anode material prepared in Example 2 as the electrode and the sodium sheet as the counter electrode, the first charge-discharge test was carried out in a sodium-ion coin cell. At a current of 0.1C, the first discharge capacity was measured to be 322.9 mAh / g, the first coulombic efficiency was 92.3%, and the low voltage plateau capacity was also relatively high, accounting for 76.9% of the total discharge capacity.

[0057] Example 3

[0058] Naphthalene and terephthalic acid were added to a three-necked flask at a molar ratio of 1:2, followed by the addition of p-toluenesulfonic acid (7% of the total mass of naphthalene and terephthalic acid). The mixture was stirred thoroughly under a nitrogen atmosphere and then subjected to a condensation reaction at 120°C until the reaction product exhibited a rod-like phenomenon, at which point the reaction was complete, yielding asphalt resin.

[0059] The asphalt resin was placed in a forced-air drying oven for curing. The first stage of curing was carried out at 130℃ for 20 hours, and the second stage at 220℃ for 1 hour, yielding cured asphalt resin. The cured asphalt resin was coarsely ground and dispersed in anhydrous ethanol (mass ratio of cured asphalt resin to anhydrous ethanol was 11:20). This was then ball-milled in a ball mill jar using zirconia balls at a ball-to-material ratio of 3:1 for 20 hours. The mixture was then dried at 80℃ for 12 hours to obtain powdered cured asphalt resin with a D50 of 9.8 μm. The powdered cured asphalt resin was placed in a tube furnace and carbonized at 1200℃ for 10 hours under a nitrogen atmosphere at a heating rate of 1℃ / min, followed by natural cooling to room temperature to obtain the carbonized precursor.

[0060] A carbonized precursor and medium-temperature pitch (MQ-18) were mixed at a mass ratio of 100:1 and calcined at 900℃ for 5 hours under an argon atmosphere at a heating rate of 5℃ / min. The mixture was then naturally cooled to room temperature to obtain a pitch resin-based hard carbon anode material. The pitch resin-based hard carbon anode material had a D50 of 9.1 μm and a specific surface area of ​​8.9 m². 2 / g.

[0061] Using the asphalt resin-based hard carbon anode material prepared in Example 3 as the electrode and the sodium sheet as the counter electrode, the first charge-discharge test was carried out in a sodium-ion coin cell. At a current of 0.1C, the first discharge capacity was measured to be 321.1 mAh / g, the first coulombic efficiency was 92.1%, and the low voltage plateau capacity was also relatively high, accounting for 76.0% of the total discharge capacity.

[0062] Example 4

[0063] Naphthalene and terephthalic acid were added to a three-necked flask at a molar ratio of 1:0.5, followed by the addition of p-toluenesulfonic acid (3% of the total mass of naphthalene and terephthalic acid). The mixture was stirred thoroughly under a nitrogen atmosphere and then subjected to a condensation reaction at 130°C until the reaction product exhibited a rod-like phenomenon, at which point the reaction was complete, yielding asphalt resin.

[0064] The asphalt resin was placed in a forced-air drying oven for curing. The first stage of curing was carried out at 115℃ for 16 hours, and the second stage at 190℃ for 4 hours, yielding cured asphalt resin. The cured asphalt resin was coarsely ground and dispersed in anhydrous ethanol (mass ratio of cured asphalt resin to anhydrous ethanol was 12:20). This was then ball-milled in a ball mill jar using zirconia balls at a ball-to-material ratio of 4:1 for 50 hours. The mixture was then dried at 80℃ for 12 hours to obtain powdered cured asphalt resin with a D50 of 7.5 μm. The powdered cured asphalt resin was placed in a tube furnace and carbonized at 1500℃ for 3 hours under a nitrogen atmosphere at a heating rate of 1℃ / min, followed by natural cooling to room temperature to obtain the carbonized precursor.

[0065] The carbonized precursor and medium-temperature pitch (MQ-18) were mixed at a mass ratio of 100:5, and then calcined at 1000℃ for 3.5 h in an argon atmosphere at a heating rate of 2℃ / min. After natural cooling to room temperature, pitch resin-based hard carbon anode material was obtained. The pitch resin-based hard carbon anode material had a D50 of 7.6 μm and a specific surface area of ​​7.2 m². 2 / g.

[0066] Using the asphalt resin-based hard carbon anode material prepared in Example 4 as the electrode and the sodium sheet as the counter electrode, the first charge-discharge test was carried out in a sodium-ion coin cell. At a current of 0.1C, the first discharge capacity was measured to be 322.5 mAh / g, the first coulombic efficiency was 92.8%, and the low voltage plateau capacity was also relatively high, accounting for 75.9% of the total discharge capacity.

[0067] As can be seen from the above embodiments, the present invention provides an asphalt resin-based hard carbon anode material and its preparation method. First, naphthalene, terephthalic acid, and p-toluenesulfonic acid are mixed and subjected to a condensation reaction to obtain asphalt resin. Then, the asphalt resin is sequentially subjected to a curing reaction, ball milling, and carbonization to obtain a carbonization precursor. Finally, the carbonization precursor and asphalt are mixed and calcined to obtain the asphalt resin-based hard carbon anode material. The asphalt resin-based hard carbon anode material prepared by the present invention exhibits excellent electrochemical performance, with an initial reversible specific capacity ≥320 mAh / g, an initial coulombic efficiency ≥92%, a high discharge capacity, and a low-voltage plateau capacity accounting for more than 75% of the total discharge capacity.

[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an asphalt resin-based hard carbon anode material, characterized in that, The steps include the following: (1) Naphthalene, terephthalic acid and p-toluenesulfonic acid are mixed and then subjected to a condensation reaction to obtain asphalt resin; (2) The asphalt resin is subjected to curing reaction, ball milling and carbonization in sequence to obtain carbonized precursor; (3) The carbonized precursor and asphalt are mixed and then calcined to obtain asphalt resin-based hard carbon anode material. In step (1), the molar ratio of naphthalene to terephthalic acid is 1:0.5-2; the amount of p-toluenesulfonic acid added accounts for 2-7% of the total mass of naphthalene and terephthalic acid. In step (1), the temperature of the condensation reaction is 120-170°C, and the condensation reaction ends when the rod-like phenomenon occurs. In step (2), the curing reaction includes a first curing reaction and a second curing reaction, wherein the temperature of the first curing reaction is 110-130℃ and the time of the first curing reaction is 15-20h, and the temperature of the second curing reaction is 180-220℃ and the time of the second curing reaction is 1-5h. In step (2), the heating rate of the carbonization treatment is 1-5℃ / min, the carbonization temperature is 1200-1600℃, and the carbonization time is 2-10h. In step (3), the heating rate of the calcination treatment is 1-5℃ / min, the calcination temperature is 900-1100℃, and the calcination time is 2-5h.

2. The preparation method according to claim 1, characterized in that, In step (2), the ball-to-material ratio for ball milling is 3 to 5:1, and the ball milling time is 20 to 50 hours.

3. The preparation method according to claim 1 or 2, characterized in that, In step (3), the mass ratio of carbonized precursor to asphalt is 100:1 to 5; the asphalt is high softening point asphalt or medium temperature asphalt.

4. A pitch resin-based hard carbon anode material prepared by the preparation method according to any one of claims 1 to 3, characterized in that, The asphalt resin-based hard carbon anode material has a D50 of 5–10 μm and a specific surface area of ​​≤10 m². 2 / g.

5. The pitch resin-based hard carbon anode material according to claim 4, characterized in that, The first reversible specific capacity of the pitch resin-based hard carbon anode material is ≥320mAh / g, and the first coulombic efficiency is ≥92%.

Images