Heteroatom-doped calcined coke materials, methods of making and using the same

Abstract

The application relates to the field of material preparation, and particularly provides a heteroatom-doped calcined coke material and a preparation method and application thereof. The preparation method of the heteroatom-doped calcined coke material comprises the following steps: sequentially mixing petroleum coke, a catalyst and a binder, and performing isostatic pressing forming to obtain a blank; performing laser etching on the surface of the blank to form micro-pore channels extending to the thickness direction of the blank; then sintering at 600 DEG C-800 DEG C for 2h-12h, and then sintering at 1100 DEG C-1300 DEG C for 2h-12h to obtain cooked coke; immersing the cooked coke in an organic solution containing a heteroatom compound, and then performing spray drying; and then introducing a carbon source gas at 900 DEG C-1100 DEG C to deposit a carbon layer on the surface of the dried cooked coke. The above preparation method can significantly improve the density and conductivity of the atom-doped calcined coke material, and further improve the capacity and rate performance of the corresponding battery.

Description

Technical Field

[0001] This application relates to the field of materials preparation, specifically to a heteroatom-doped calcined coke material, its preparation method, and its application. Background Technology

[0002] With the increasing market demand for high-energy-density anode materials, high energy density and fast-charging performance are required. Anode materials are primarily prepared through pre-carbonization, graphitization, granulation, and coating of coke raw materials. Coke raw materials are divided into green coke and calcined coke. Green coke suffers from defects such as low compaction density and low specific capacity. Although pre-carbonization of green coke can remove its volatiles to form calcined coke, thereby altering the carbon arrangement and orientation, thus improving the compaction density and specific capacity of the green coke material, pre-carbonization reduces the fast-charging performance of the calcined coke material. Furthermore, the pre-carbonized calcined coke still suffers from low conductivity and low density, which can lead to lower rate performance in batteries when used as a cathode material. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for preparing heteroatom-doped calcined coke with high density and high conductivity, as well as the heteroatom-doped calcined coke material; furthermore, it is necessary to provide an application of the heteroatom-doped calcined coke material in lithium batteries.

[0004] The first aspect of this application provides a method for preparing heteroatom-doped calcined coke material, comprising the following steps: Petroleum coke, catalyst, and binder are mixed sequentially and isostatically pressed to obtain a billet. The isostatic pressing conditions include: first, increasing the pressure at a rate of 1 MPa / min to 5 MPa / min to 100 MPa, and stabilizing the pressure for 5 min to 20 min; then, depressurizing at a rate of 10 MPa / min to 20 MPa / min to 20 MPa / min to 20 MPa / min, and stabilizing the pressure for 5 min to 20 min; then, depressurizing at a rate of 20 MPa / min to 10 MPa / min to 20 MPa / min to 40 MPa, and stabilizing the pressure for 5 min to 20 min; finally, depressurizing at a rate of 5 MPa / min to 10 MPa / min to atmospheric pressure. Laser etching is performed on the surface of the billet to form micropores extending in the thickness direction of the billet; then sintering is carried out at 600℃~800℃ for 2h~12h, and then the temperature is raised to 1100℃~1300℃ for 2h~12h to obtain cooked coke; The calcined coke is impregnated in an organic solution containing heteroatom compounds and then spray-dried; a carbon source gas is then introduced at 900℃~1100℃ to deposit a carbon layer on the surface of the dried calcined coke; wherein the heteroatom compounds are organic compounds containing at least one of N atoms and S atoms.

[0005] In the above preparation method, petroleum coke, catalyst, and binder are mixed uniformly. Using isostatic pressing, the pressure is increased at a specific rate and stabilized for a specific time, which binds the dispersed raw materials together and compresses the voids in the petroleum coke, increasing the material's density. Furthermore, controlling the depressurization process using a segmented depressurization method avoids instantaneous rebound of the material, preventing a decrease in tap density. This segmented depressurization method also reduces damage to the material's morphology and structure, improving cycle performance. Next, laser etching forms micropores extending along the thickness direction on the surface and inside the billet. This facilitates the smooth removal of volatiles during two calcinations at different high temperatures, while ensuring the calcined coke has a high density. In addition, these micropores enhance lithium-ion diffusion and the material's liquid retention capacity, thereby improving the battery's cycle performance. During high-temperature sintering, two sintering processes are performed sequentially within the ranges of 600℃ to 800℃ and 1000℃ to 1300℃, respectively. These two different stages of high-temperature calcination transform the completely disordered carbon in the raw materials into an ordered state, reducing material defects and increasing specific capacity and compaction density, thereby improving the battery's initial efficiency. Furthermore, impregnating the calcined coke in an organic solution containing heteroatom compounds followed by spray drying coats the surface of the coke with a layer of heteroatom compounds, improving the electronic conductivity of the outer shell and enhancing rate performance. Introducing a carbon source gas at 900℃ to 1100℃ allows amorphous carbon to re-form on the surface of the calcined coke, further modifying the specific surface defects and improving compatibility with the electrolyte.

[0006] In this application, atmospheric pressure refers to 0.1 MPa.

[0007] In some embodiments, the process parameters for laser etching include: a carbon dioxide laser source, an output power of 50W to 150W, laser etching performed in a nitrogen atmosphere, an output wavelength of 150nm to 1500nm, and a laser scanning rate of 0.1cm / s to 100cm / s. It can be understood that under the above laser etching conditions, microchannels with a certain depth and diameter extending in the thickness direction of the blank can be formed on the surface of the blank.

[0008] In some embodiments, the laser etching time is 60s to 300s. By controlling the laser etching time, the channel depth on the surface of the blank can be controlled, preventing insufficient laser etching from resulting in insufficient channel depth and a small increase in the lithium ion insertion / extraction rate during charging and discharging; at the same time, it also prevents excessively long laser etching time from causing structural damage to the material and reducing the compaction density of the material.

[0009] In some embodiments, the diameter of the microchannel is 10 nm to 100 nm, and the depth of the microchannel is 1 μm to 5 μm. The depth of the microchannel is the depth extending from the surface of the billet in the thickness direction of the billet.

[0010] In some embodiments, the carbonization process includes: sintering at 600°C to 800°C for 2 to 12 hours, and then sintering at 1100°C to 1300°C for 2 to 12 hours.

[0011] In some embodiments, the heteroatom compound is selected from imidazole, pyrazole, thiophene, pyrrole, and quinoline.

[0012] In some embodiments, the adhesive is selected from petroleum asphalt, coal tar pitch, phenolic resin, and epoxy resin.

[0013] In some embodiments, the organic solvent in the organic solution is selected from chloroform, N-methylpyrrolidone, cyclohexane, and diethyl ether.

[0014] In some embodiments, the catalyst is selected from ferric chloride, tin chloride, boron chloride, and cobalt chloride.

[0015] In some embodiments, the carbon source gas is selected from methane, ethane, ethylene, and acetylene.

[0016] The second aspect of this application provides a heteroatom-doped calcined coke material, which is prepared according to the preparation method provided in the first aspect.

[0017] The third aspect of this application provides the application of heteroatom-doped calcined coke material obtained according to the preparation method provided in the first aspect of this application in lithium-ion batteries.

[0018] In some embodiments, in lithium-ion battery applications, heteroatom-doped calcined coke material is graphitized and used as the active material of the negative electrode. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0020] Figure 1 The image shows a SEM image of the heteroatom-doped calcined coke material prepared in Example 1.

[0021] Figure 2 This is a SEM image of the heteroatom-doped calcined coke material prepared in Example 1 at another magnification. Detailed Implementation

[0022] The embodiments described in this specification are merely for explaining this application and are not intended to limit this application.

[0023] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit, combined with any other point or individual value, or combined with other lower or upper limits to form an unspecified range.

[0024] The present application is further illustrated below with reference to embodiments. It should be understood that these embodiments are merely illustrative, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized using conventional methods and can be used directly without further processing, as are the instruments used in the embodiments. In particular, the raw materials and their information used in the various embodiments and comparative examples of this application are as follows: Example 1

[0025] Preparation of cooked caramel: Raw material mixing: Mix 100g of petroleum coke, 3g of ferric chloride and 8g of petroleum pitch evenly to obtain a mixture.

[0026] Isostatic pressing is used: First, the mixture is loaded into the mold, compacted, and vacuumed. Then, it is fed into the isostatic press. The pressure is first increased to 100 MPa at a rate of 3 MPa / min and stabilized for 10 min. Then, the pressure is released to 35 MPa at a rate of 15 MPa / min and stabilized for 10 min. Then, the pressure is released to 30 MPa at a rate of 15 MPa / min and stabilized for 10 min. Finally, the pressure is released to atmospheric pressure at a rate of 8 MPa / min to obtain the billet.

[0027] Laser etching is employed: Laser etching equipment (manufacturer: Suzhou Delong Laser Co., Ltd.; model: ALS05) is used to perform laser etching on the surface of the blank; wherein, the laser source is a carbon dioxide laser source with an output power of 100W, the laser atmosphere is nitrogen, the wavelength of the light is 500nm, the laser scanning rate is 10cm / s, and the etching time is 120s.

[0028] Sintering: Sinter at 700℃ for 6 hours, then raise the temperature to 1200℃ for a second sintering for 6 hours to obtain cooked coke.

[0029] Preparation of heteroatom-doped calcined coke materials: 3g of imidazole was added to 500g of chloroform organic solvent and dispersed evenly, and 100g of calcined coke was added and dispersed evenly; then spray drying was carried out (inlet temperature 220℃, outlet temperature 80℃, flow rate 0.5kg / h, drying time 5h); then the temperature was raised to 1000℃, and methane gas was introduced at a flow rate of 30mL / min for 150min to obtain heteroatom-doped calcined coke material.

[0030] Example 2

[0031] Preparation of cooked caramel: Raw material mixing: Mix 100g of petroleum coke, 1g of tin chloride and 5g of coal tar pitch evenly to obtain a mixture.

[0032] Isostatic pressing: First, the mixture is loaded into the mold, compacted, and vacuumed. Then, it is fed into an isostatic press. The pressure is increased to 100 MPa at a rate of 1 MPa / min and held for 5 minutes. Then, the pressure is released to 50 MPa at a rate of 10 MPa / min and held for 5 minutes. Next, the pressure is released to 20 MPa at a rate of 1 MPa / min and held for 5 minutes. Finally, the pressure is released to atmospheric pressure at a rate of 5 MPa / min to obtain the billet.

[0033] Laser etching: Laser etching is performed on the surface of the blank using a laser etching equipment (manufacturer: Suzhou Delong Laser Co., Ltd.; model: ALS05); wherein the laser source is a carbon dioxide laser source with an output power of 50W, the laser atmosphere is nitrogen, the wavelength of the light is 150nm, the laser scanning rate is 0.1 cm / s, and the etching time is 300s.

[0034] Sintering: Sinter at 600℃ for 12 hours, then raise the temperature to 1100℃ for a second sintering for 12 hours to obtain cooked coke.

[0035] Preparation of heteroatom-doped calcined coke materials: 1g of pyrazole was added to 100g of N-methylpyrrolidone and dispersed evenly, followed by the addition of 100g of calcined coke and dispersed evenly. Then, spray drying was performed (inlet temperature 220℃, outlet temperature 80℃, flow rate 0.5kg / h, time 5h). After that, the temperature was raised to 900℃, and methane gas was introduced at a flow rate of 10mL / min for 300min to obtain heteroatom-doped calcined coke material.

[0036] Example 3

[0037] Preparation of cooked caramel: Raw material mixing: Mix 100g of petroleum coke, 5g of boron chloride and 10g of phenolic resin evenly to obtain a mixture.

[0038] Isostatic pressing: First, the mixture is loaded into the mold, compacted, and vacuumed. Then, it is fed into an isostatic press. The pressure is increased to 100 MPa at a rate of 5 MPa / min and held for 20 minutes. Then, the pressure is released to 40 MPa at a rate of 20 MPa / min and held for 20 minutes. Then, the pressure is released to 20 MPa at a rate of 20 MPa / min and held for 20 minutes. Finally, the pressure is released to atmospheric pressure at a rate of 10 MPa / min to obtain the billet.

[0039] Laser etching: Laser etching is performed on the surface of the blank using a laser etching equipment (manufacturer: Suzhou Delong Laser Co., Ltd.; model: ALS05); wherein the laser source is a carbon dioxide laser source with an output power of 150W, the laser atmosphere is nitrogen, the wavelength of the light is 1500nm, the laser scanning rate is 100cm / s, and the etching time is 60s.

[0040] Sintering: Sinter at 800℃ for 2 hours, then raise the temperature to 1300℃ for a second sintering for 2 hours to obtain cooked coke.

[0041] Preparation of heteroatom-doped calcined coke materials: 5g of thiophene was added to 500g of cyclohexane and dispersed evenly, followed by the addition of 100g of calcined coke and dispersed evenly. Then, spray drying was performed (inlet temperature 220℃, outlet temperature 80℃, flow rate 0.5kg / h, drying time 5h). Afterward, the temperature was raised to 1100℃, and methane gas was introduced at a flow rate of 50mL / min for 30min to obtain heteroatom-doped calcined coke material.

[0042] Comparative Example 1 The preparation method of this comparative example is basically the same as that of Example 1, except that the mixture in this comparative example is not subjected to isostatic pressing and laser etching, but is directly sintered. Other steps and parameters are the same as those in Example 1.

[0043] Comparative Example 2 The preparation method of this comparative example is basically the same as that of Example 1. The only difference is that this comparative example does not coat the surface of the calcined coke with heteroatom compounds. Instead, the calcined coke is directly heated to 1000°C and methane gas is introduced at a flow rate of 30 mL / min for 150 min to obtain the calcined coke material.

[0044] Comparative Example 3 The preparation method of this comparative example is basically the same as that of Example 1, except that the isostatic pressing conditions are different. Specifically, the isostatic pressing steps of this comparative example are as follows: first, the mixture is loaded into the mold, compacted and vacuumed, and then sent into the isostatic press. The pressure is first increased to 100 MPa at a rate of 3 MPa / min and stabilized for 20 min; finally, the pressure is released to atmospheric pressure at a rate of 15 MPa / min to obtain the billet.

[0045] Comparative Example 4 The preparation method of this comparative example is basically the same as that of Example 1, except that the blank was not laser-etched in this comparative example. The blank after isostatic pressing was directly sintered.

[0046] Comparative Example 5 The preparation method of this comparative example is basically the same as that of Example 1, except that the sintering procedure in the preparation of the calcined coke is different. Specifically, in this comparative example 5, the sintering step in the preparation of the calcined coke is to perform a secondary sintering at 1200℃ for 8 hours to obtain the calcined coke. The process parameters of other steps are the same as those in Example 1.

[0047] Performance testing: (1) Performance testing of calcined coke materials SEM testing: The heteroatom-doped calcined coke material prepared in Example 1 was subjected to SEM testing, and the results are as follows: Figure 1 and Figure 2 As shown in the figure, the heteroatom-doped calcined coke material exhibits a streamlined structure with a length of 10 μm to 50 μm.

[0048] Physicochemical performance testing: The ash content, sulfur content, volatile matter, true density, specific surface area, coefficient of thermal expansion, electrical conductivity, and powder compaction density of the calcined coke material were tested according to GB / T 37308-2019 "Oil-based Needle Coke" and GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The specific test results are shown in Table 1.

[0049]

[0050] As shown in Table 1, the calcined coke materials prepared by the method of this application in Examples 1-3 have high true density and tap density, which is beneficial for preparing anode materials with high tap density. Furthermore, the calcined coke materials have low volatile matter and ash content, which is beneficial for improving the specific capacity and tap density of the corresponding anode materials. Moreover, the calcined coke materials prepared by the method of this application have high conductivity, which is beneficial for improving the rate performance of the corresponding batteries. The main reason for the increased density and conductivity of the calcined coke materials is that the heteroatoms doped in the materials increase the active sites and thus improve conductivity; the stepped heat treatment can fully volatilize the impurities inside the materials, reducing defects and thus contributing to the increase in density.

[0051] (2) Preparation of negative electrode materials and testing of lithium-ion batteries The heteroatom-doped calcined coke materials of Examples 1-3 and Comparative Examples 1-5 were graphitized at 3000℃ for 12 hours, pulverized to 10µm, and coated with amorphous carbon with a residual carbon content of 2% to prepare anode materials, which were labeled as A1, A2, A3, B1, B2, B3, B4, and B5, respectively.

[0052] Button cell battery testing: The negative electrode materials prepared by the above method are assembled into coin cells according to the following methods: A1–A3 and B1–B5 were used as negative electrodes and assembled into coin cells with lithium foil, electrolyte, and separator in a glove box with argon and water content both below 0.1 ppm. The separator was Celegard 2400; the electrolyte was a LiPF6 solution with a LiPF6 concentration of 1 mol / L, and the solvent was a mixture of ethylene carbonate (EC) and diethyl carbonate (DMC) in a 1:1 weight ratio.

[0053] The fabricated coin cells were tested using a blue electrode tester. The test conditions were: 0.1C charge-discharge rate, voltage range of 0.05–2V, 3 cycles, followed by testing the discharge capacity at 1C. The 1C / 0.1C rate performance and cycle performance (25±3℃, 0.2C / 0.2C, 100 cycles) were calculated. The test results are shown in Table 2.

[0054]

[0055] As can be seen from Table 2, the anode materials prepared in Examples 1-3 are significantly better than those in Comparative Examples 1-5 in terms of specific capacity, initial efficiency, rate capability, and cycle performance. This may be because the materials in the examples have high conductivity, resulting in anode materials with low impedance, which reduces polarization and improves the specific capacity and rate capability of the materials. At the same time, the materials in the examples have low coefficients of expansion, which reduces the expansion of the anode materials and improves cycle performance.

[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing heteroatom-doped calcined coke material, characterized in that, The steps include the following: Petroleum coke, catalyst, and binder are mixed sequentially and isostatically pressed to obtain a billet. The isostatic pressing conditions include: first, increasing the pressure at a rate of 1 MPa / min to 5 MPa / min to 100 MPa, and stabilizing the pressure for 5 min to 20 min; then, depressurizing at a rate of 10 MPa / min to 20 MPa / min to 20 MPa / min to 20 MPa / min, and stabilizing the pressure for 5 min to 20 min; then, depressurizing at a rate of 20 MPa / min to 10 MPa / min to 20 MPa / min to 40 MPa, and stabilizing the pressure for 5 min to 20 min; finally, depressurizing at a rate of 5 MPa / min to 10 MPa / min to atmospheric pressure. Laser etching is performed on the surface of the blank to form microchannels extending in the thickness direction of the blank; then sintering is carried out at 600℃~800℃ for 2h~12h, followed by sintering at 1100℃~1300℃ for 2h~12h to obtain coke; the process parameters of the laser etching include: the laser source is carbon dioxide, the output power of the laser source is 50W~150W, the laser etching is carried out in a nitrogen atmosphere, the output wavelength of the laser is 150nm~1500nm, the laser scanning rate is 0.1cm / s~100cm / s; the laser etching time is 60s~300s; the diameter of the microchannel is 10nm~100nm, and the depth of the microchannel is 1μm~5μm; The calcined coke is immersed in an organic solution containing a heteroatom compound and then spray-dried; a carbon source gas is then introduced at 900℃~1100℃ to deposit a carbon layer on the surface of the dried calcined coke; the heteroatom compound is an organic compound containing at least one of N atoms and S atoms.

2. The preparation method according to claim 1, characterized in that, The heteroatom compound is selected from one of imidazole, pyrazole, thiophene, pyrrole, and quinoline.

3. The preparation method according to claim 1, characterized in that, When the char is immersed in an organic solution containing heteroatom compounds, the mass ratio of the char to the heteroatom compounds is 100:(1-5).

4. The preparation method according to claim 1, characterized in that, The mass ratio of the petroleum coke, the catalyst, and the binder is 100:(1-5):(5-10).

5. The preparation method according to claim 1, characterized in that, The catalyst is selected from one of ferric chloride, tin chloride, boron chloride, and cobalt chloride; The adhesive is selected from one of petroleum asphalt, coal tar pitch, phenolic resin and epoxy resin; The organic solvent in the organic solution is one of chloroform, N-methylpyrrolidone, cyclohexane, and diethyl ether; The carbon source gas is selected from one of methane, ethane, ethylene, and acetylene.

6. A heteroatom-doped calcined coke material, characterized in that, It is prepared according to any one of claims 1 to 5.

7. The application of heteroatom-doped calcined coke material obtained by the preparation method according to any one of claims 1 to 5 in lithium-ion batteries.

Images