High-sulfur petroleum coke derived porous carbon, method of making, electrode material, and sodium-ion battery

Abstract

The application discloses high-sulfur petroleum coke derived porous carbon, a preparation method thereof, an electrode material and a sodium ion battery. The porous carbon provided by the application is N / S doped porous carbon, and the sulfur content of the porous carbon is 1.5-5.5 wt%. The porous carbon provided by the application has the structural advantages of N / S atomic double doping, and the prepared composite material has rich active sites, a short diffusion distance and high electrical conductivity, and can be applied to sodium ion batteries as an electrode material.

Description

Technical Field

[0001] This invention relates to the field of carbon materials technology, specifically to a method for preparing and applying high-sulfur petroleum coke-derived porous carbon. Background Technology

[0002] In recent years, sodium-ion batteries have become increasingly popular due to their lower cost and higher safety performance compared to lithium-ion batteries, serving as a supplement and support for lithium-ion battery applications, such as in electric vehicles, emergency power supplies, and large-scale energy storage systems. However, compared to lithium-ion batteries... + Na + The larger radius of Na leads to + The slow kinetics during electrode material insertion / extraction hinder the commercial application of sodium-ion batteries. Notably, graphite, a commercially available anode material in lithium-ion batteries, has a theoretical capacity of only 35 mAh g⁻¹ in sodium-ion batteries. -1 This is insufficient to meet practical needs. Therefore, there is an urgent need to develop other high-performance sodium-ion battery anode materials.

[0003] Researchers have studied several promising electrochemical sodium storage anode materials, such as carbon (hard carbon, soft carbon, etc.), metals (Sn, Bi, etc.), and metal selenides (SnSe, Sb₂Se₃, etc.). Carbon materials are considered the most commercially promising anode materials due to their readily available raw materials, strong corrosion resistance, and good conductivity. Among them, hard carbon has attracted much attention due to its low sodium storage potential (below 0.1V), high capacity, and good cycle life; however, its high cost and low yield limit its industrial application. Recently, soft carbon materials other than hard carbon have attracted widespread attention due to their low cost, high yield, and outstanding performance. For example, Li et al. prepared low-cost pyrolytic anthracite soft carbon materials through direct pyrolysis, which exhibited good sodium discharge performance at 0.03A g⁻¹. -1 Capacity at current density can reach 222 mAh g -1 However, its rate performance needs further improvement. In addition, other low-cost soft carbon materials, such as petroleum coke, also require further research. In recent years, my country's oil refineries have ranked among the world's largest. Petroleum coke, a byproduct of oil refining, is abundant and inexpensive; however, it has a high sulfur content, contains many metallic impurities (vanadium, nickel, iron, etc.), and has low added value.

[0004] Therefore, in order to increase the added value of petroleum coke and develop other low-cost, high-performance carbon materials, it is necessary to develop petroleum coke-based sodium-ion battery anode materials. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a porous carbon with the structural advantages of being amorphous, porous, and doped with N / S atoms. This provides more active sites for sodium ion storage, shortens the diffusion distance of sodium ions, and buffers volume changes during cycling, thereby improving the rate performance and cycle stability of the electrode. This invention also provides a method for preparing porous carbon using petroleum coke as a raw material, increasing the added value of petroleum coke. The resulting porous carbon provides sufficient raw materials for sodium-ion battery applications, improving electrode capacity and conductivity. This invention also provides an electrode material and a sodium-ion battery.

[0006] The first aspect of the present invention provides a porous carbon, wherein the porous carbon is an N / S doped porous carbon, and the sulfur content of the porous carbon is 1.5-5.5 wt%.

[0007] According to some embodiments of the present invention, the nitrogen content of the porous carbon is 0.1-1 wt%.

[0008] According to some embodiments of the present invention, the pore volume of the porous carbon is 0.01-0.2 cm³. 3 g -1 .

[0009] According to some embodiments of the present invention, the specific surface area of ​​the porous carbon is 5-50 m². 2 g -1 .

[0010] According to some embodiments of the present invention, the metal content of the porous carbon is less than 10 mg / kg.

[0011] In this invention, the metal in porous carbon refers to vanadium, nickel, iron, etc. According to some embodiments of the invention, the porous carbon is in the form of irregular granules.

[0012] According to some embodiments of the present invention, the porous carbon has a microstructure that is short-range ordered and long-range disordered.

[0013] As can be seen from the microstructure, the porous carbon obtained by this invention has an amorphous structure.

[0014] A second aspect of the present invention provides a method for preparing the porous carbon described in the first aspect, comprising the following steps:

[0015] S1. Preparation of porous petroleum coke: obtain powdered petroleum coke, and then contact the petroleum coke with an acid solution to obtain porous petroleum coke;

[0016] S2. Preparation of porous carbon: Porous carbon is obtained by calcining the porous petroleum coke prepared in step S1.

[0017] According to some embodiments of the present invention, the petroleum coke is high-sulfur petroleum coke. In the present invention, high sulfur means that the sulfur content in the petroleum coke is 1.5 wt% or more.

[0018] According to some embodiments of the present invention, the sulfur content of the petroleum coke is 1.5-5.5 wt%.

[0019] According to some embodiments of the present invention, the sulfur content of the petroleum coke is 1.7-4.5 wt%.

[0020] According to some embodiments of the present invention, the petroleum coke has a sulfur content of 2.1-4.2 wt%.

[0021] According to some embodiments of the present invention, the sulfur content of the petroleum coke is 2.8-3.2 wt%.

[0022] According to some embodiments of the present invention, the sulfur content of the petroleum coke is 3 wt%.

[0023] According to some embodiments of the present invention, the raw materials for the production of petroleum coke include petroleum residue oil, petroleum asphalt, or heavy oil.

[0024] According to some embodiments of the present invention, the nitrogen content of the petroleum coke is 0.1-2 wt%.

[0025] According to some embodiments of the present invention, the petroleum coke is selected from raw coke and cooked coke.

[0026] The raw coke is obtained from the coke tower of the delayed coking unit, and the cooked coke is obtained from the raw coke through calcination.

[0027] According to some embodiments of the present invention, the petroleum coke is raw coke.

[0028] According to some embodiments of the present invention, the particle size of the petroleum coke powder is less than 5 μm.

[0029] According to some embodiments of the present invention, the particle size of the petroleum coke powder is 0.5-1.5 μm.

[0030] According to some embodiments of the present invention, the particle size of the petroleum coke powder is 1 μm.

[0031] According to some embodiments of the present invention, in step S1, the method for obtaining powdered petroleum coke includes the step of ball milling the petroleum coke.

[0032] According to some embodiments of the present invention, the calcination conditions in step S2 include: a calcination temperature of 800-1800°C.

[0033] According to some embodiments of the present invention, the calcination conditions in step S2 include: a calcination temperature of 1000-1600°C.

[0034] According to some embodiments of the present invention, the calcination conditions in step S2 include: a calcination temperature of 1300°C.

[0035] According to some embodiments of the present invention, the calcination conditions in step S2 include: calcination time of 1-10 hours.

[0036] According to some embodiments of the present invention, the calcination conditions in step S2 include: calcination time of 2-5 hours.

[0037] According to some embodiments of the present invention, the calcination conditions in step S2 include a heating rate of 1-10°C / min.

[0038] According to some embodiments of the present invention, the calcination conditions in step S2 include a heating rate of 4-6°C / min.

[0039] According to some embodiments of the present invention, the calcination is carried out in an inactive atmosphere.

[0040] According to some embodiments of the present invention, the calcination is carried out in a nitrogen and / or argon atmosphere.

[0041] According to some embodiments of the present invention, the calcination is carried out in a tubular furnace.

[0042] According to some embodiments of the present invention, in step S1, the petroleum coke is contacted with an excess of acid solution to obtain porous petroleum coke.

[0043] According to some embodiments of the present invention, the concentration of the acid solution is 1-10 mol / L.

[0044] According to some embodiments of the present invention, the concentration of the acid solution is 2-4 mol / L.

[0045] According to some embodiments of the present invention, the acid solution is at least one of hydrochloric acid and nitric acid.

[0046] According to some embodiments of the present invention, the petroleum coke is washed 3-5 times with an acid solution.

[0047] According to some embodiments of the present invention, after washing with an acid solution, the petroleum coke is washed with water 3-5 times.

[0048] According to some embodiments of the present invention, the washed petroleum coke is dried for 8-12 hours to obtain porous petroleum coke.

[0049] A third aspect of the present invention provides an electrode material comprising the porous carbon described in the first aspect or the porous carbon prepared by the preparation method described in the second aspect.

[0050] According to some embodiments of the present invention, a copper foil and a mixed material coated on the copper foil are included, the mixed material comprising a conductive agent, a thickener and the porous carbon.

[0051] According to some embodiments of the present invention, the coating amount of the mixed material is 0.1-20 mg / cm². 2 .

[0052] According to some embodiments of the present invention, the coating amount of the mixed material is 1-5 mg / cm². 2 .

[0053] According to some embodiments of the present invention, the mass ratio of porous carbon, conductive agent and thickener is (7-9):(0.8-1.2):(0.8-1.2).

[0054] According to some embodiments of the present invention, the mass ratio of porous carbon, conductive agent and thickener is 8:1:1.

[0055] According to some embodiments of the present invention, the thickener is selected from at least one of sodium carboxymethyl cellulose and polyvinylidene fluoride (PVDF).

[0056] According to some embodiments of the present invention, the conductive agent is selected from at least one of acetylene black and Ketjen black.

[0057] According to some embodiments of the present invention, the preparation method of the electrode material includes: mixing the active material, namely the porous carbon, with acetylene black and sodium carboxymethyl cellulose powder, coating it on a copper foil, and then drying it to obtain the electrode material.

[0058] According to some embodiments of the present invention, electrode materials are obtained by vacuum drying at 40-100°C for 10-12 hours.

[0059] A fourth aspect of the present invention provides a sodium-ion battery, wherein the electrode material described in the third aspect is used as the negative electrode material.

[0060] According to some embodiments of the present invention, the electrode material serves as the working electrode, and the sodium sheet serves as the counter electrode and / or reference electrode; the electrolyte comprises sodium perchlorate.

[0061] According to some embodiments of the present invention, the electrode material has a capacity of 70-99 mAh / g at a current density of 1 A / g.

[0062] According to some embodiments of the present invention, the electrode material has a capacity of 80-99 mAh / g at a current density of 1 A / g.

[0063] According to some embodiments of the present invention, the electrode material has a capacity of 210-250 mAh / g after 100 cycles at a current density of 0.1 A / g.

[0064] According to some embodiments of the present invention, the electrode material has a capacity of 230-250 mAh / g after 100 cycles at a current density of 0.1 A / g.

[0065] According to some embodiments of the present invention, the electrode material has a capacity of 60-70.5 mAh / g after 1000 cycles at a current density of 1 A / g.

[0066] According to some embodiments of the present invention, the electrode material has a capacity of 65-70.5 mAh / g after 1000 cycles at a current density of 1 A / g.

[0067] According to some embodiments of the present invention, the separator of the sodium-ion battery is made of glass fiber.

[0068] According to some embodiments of the present invention, the electrolyte of the sodium-ion battery is a mixture of sodium perchlorate, ethylene carbonate, diethyl carbonate and fluoroethylene carbonate.

[0069] According to some embodiments of the present invention, the electrolyte of the sodium-ion battery is a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate.

[0070] According to some embodiments of the present invention, the volume ratio of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate is (0.8-1.2):(0.8-1.2):(0.8-1.2).

[0071] According to some embodiments of the present invention, the volume ratio of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate is 1:1:1.

[0072] According to some embodiments of the present invention, the method for preparing the sodium-ion battery includes assembling the working electrode, counter electrode, reference electrode, separator, and electrolyte into a button cell.

[0073] According to some embodiments of the present invention, the button battery is a CR2025 type button battery.

[0074] According to some embodiments of the invention, the assembly is carried out in a glove box.

[0075] According to some embodiments of the present invention, the glove box is filled with argon gas.

[0076] According to some embodiments of the present invention, the water oxygen values ​​of the glove box are [H2O]<1ppm and [O2]<1ppm, respectively.

[0077] This invention discloses a method for preparing high-sulfur petroleum coke-derived porous carbon (PC), which involves acid etching and calcination of high-sulfur petroleum coke to obtain PC. Specifically, hydrochloric acid reacts with metallic impurities in the petroleum coke, such as vanadium, nickel, and iron, to generate corresponding metal salts, thus removing these impurities. After washing with water, a porous structure is formed. It is noteworthy that if the metallic impurities in the petroleum coke are not removed, their use in sodium-ion batteries can lead to reduced battery capacity and electrolyte decomposition. Furthermore, the petroleum coke undergoes thermal decomposition during calcination, forming a porous structure. This porous structure increases the contact area between the PC and the electrolyte, mitigating volume expansion during cycling and reducing the transport distance of sodium ions. In addition, the N and S impurity atoms inherited from the petroleum coke in the PC not only provide more active sites for sodium ion insertion but also accelerate electron transfer.

[0078] Compared with the prior art, the present invention has the following beneficial effects:

[0079] (1) The porous carbon provided by the present invention has the structural advantage of N / S atom doping. The composite material prepared by using the porous carbon of the present invention has abundant active sites, short diffusion distance and high electrical conductivity, and can also effectively release the stress generated by volume change during charge and discharge cycle.

[0080] (2) The method for preparing porous carbon provided by the present invention uses petroleum coke as raw material, and the prepared porous carbon has the characteristics of N / S atom dual doping, porous and uniform particle dispersion.

[0081] (3) The electrode material and sodium-ion battery provided by the present invention have excellent rate performance and cycle stability. Attached Figure Description

[0082] Figure 1 The image shows the Raman spectrum of the porous carbon (PC) material prepared in Example 1 of this invention. Detailed Implementation

[0083] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0084] In this invention, cyclic voltammetry and electrochemical impedance spectroscopy are performed using a DH7000 electrochemical workstation.

[0085] Battery performance testing was performed using the LAND CT2001A battery testing system.

[0086] In this invention, the high-sulfur petroleum coke was purchased from the Maoming branch of China Petroleum & Chemical Corporation.

[0087] Acetylene black was purchased from Tianjin Yiborui Company, CAS number 1333-86-4;

[0088] Sodium carboxymethyl cellulose powder was purchased from Sinopharm Reagent Company, CAS No. 9004-32-4, with a weight-average molecular weight of 263.2;

[0089] The fiberglass diaphragm was purchased from Whatman, product model MA-EN-SE-04;

[0090] Ethylene carbonate was purchased from Sigma-Aldriich, CAS No. 362049-63-6;

[0091] Diethyl carbonate was purchased from Sigma-Aldriich, CAS number 105-58-8;

[0092] Fluoroethylene carbonate was purchased from Sigma-Aldriich, CAS number 114435-02-8.

[0093] Example 1

[0094] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0095] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 3wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), then washed 4 times each with excess 3mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0096] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at a nitrogen atmosphere at a rate of 5℃ / min. After cooling, high-sulfur petroleum coke-derived porous carbon (PC) material was obtained.

[0097] Morphological and structural characterization of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0098] Porous carbon is in the form of irregular granules, exhibiting a microstructure of short-range order and long-range disorder. The metal content of porous carbon is 5 mg / kg. Figure 1 The image shows the Raman spectrum of PC, where the two characteristic peaks belonging to carbon materials are located at 1353.0 (D band) and 1604.5 cm⁻¹, respectively. -1(G band). The intensity ratio of these two characteristic peaks is approximately 0.84, indicating that PC still contains a large number of defects after calcination, which is beneficial for sodium ion storage. Furthermore, X-ray photoelectron spectroscopy (XPS) was used for testing (the testing method is described in the literature "Rational design of porous Sn nanospheres / Ndoped carbon nanofibers as an ultra-stable potassium-ion battery anode material"). The N and S contents of the porous carbon were 0.42 wt% and 3.1 wt%, respectively, with a pore volume of 0.15 cm³. 3 g -1 Its specific surface area is 10.3 m². 2 g -1 .

[0099] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0100] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0101] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0102] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0103] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0104] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0105] As an anode material for sodium-ion batteries, PC exhibits excellent rate performance (capacity of 98.2 mAh / g at a current density of 1 A / g) and cycle stability (capacity of up to 250 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 70.5 mAh / g after 1000 cycles at a current density of 1 A / g).

[0106] Example 2

[0107] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0108] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 4.2wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), then washed 4 times each with excess 3mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0109] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at 5℃ / min under an argon atmosphere, and then cooled to obtain PC.

[0110] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0111] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0112] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0113] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0114] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0115] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0116] As an anode material for sodium-ion batteries, PC exhibits excellent rate performance (capacity of 70.3 mAh / g at a current density of 1 A / g) and cycle stability (capacity of up to 233 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 60.3 mAh / g after 1000 cycles at a current density of 1 A / g).

[0117] Example 3

[0118] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0119] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 2.1wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), then washed 4 times each with excess 3mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0120] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at a rate of 5℃ / min under a nitrogen atmosphere, and then cooled to obtain PC.

[0121] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0122] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0123] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0124] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0125] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0126] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0127] As an anode material for sodium-ion batteries, PC exhibits good rate performance (capacity of 92.5 mAh / g at a current density of 1 A / g) and cycle stability (capacity as high as 241.3 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 67.2 mAh / g after 1000 cycles at a current density of 1 A / g).

[0128] Example 4

[0129] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0130] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 3wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), then washed 4 times each with excess 3mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0131] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke is heated to 1000℃ for 2h at a rate of 5℃ / min under a nitrogen atmosphere, and then cooled to obtain PC.

[0132] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0133] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0134] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0135] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0136] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0137] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0138] As an anode material for sodium-ion batteries, PC exhibits good rate performance (capacity of 80.2 mAh / g at a current density of 1 A / g) and cycle stability (capacity of up to 220.3 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 63.2 mAh / g after 1000 cycles at a current density of 1 A / g).

[0139] Example 5

[0140] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0141] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 3wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), then washed 4 times each with excess 3mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0142] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1600℃ for 2h at a nitrogen atmosphere at a rate of 5℃ / min, and then cooled to obtain PC.

[0143] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0144] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0145] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0146] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0147] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0148] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0149] As a negative electrode material for sodium-ion batteries, PC exhibits good rate performance (capacity of 82.3 mAh / g at a current density of 1 A / g) and cycle stability (capacity of up to 230.1 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 65.1 mAh / g after 1000 cycles at a current density of 1 A / g). Furthermore, PC exhibits a lower degree of graphitization compared to the PC in Example 1.

[0150] Example 6

[0151] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0152] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 3wt%) was ball-milled into petroleum coke powder (particle size of about 2μm), then washed 4 times each with excess 3mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0153] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at a rate of 5℃ / min under a nitrogen atmosphere, and then cooled to obtain PC.

[0154] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0155] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0156] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0157] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0158] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0159] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0160] As an anode material for sodium-ion batteries, PC exhibits good rate performance (capacity of 79.2 mAh / g at a current density of 1 A / g) and cycle stability (capacity of up to 210.5 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 61.5 mAh / g after 1000 cycles at a current density of 1 A / g).

[0161] Example 7

[0162] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0163] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 3wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), and then washed 4 times each with excess 10mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0164] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at a rate of 5℃ / min under a nitrogen atmosphere, and then cooled to obtain PC.

[0165] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0166] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0167] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0168] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0169] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0170] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0171] Morphological and structural characterization of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0172] As an anode material for sodium-ion batteries, PC exhibits good rate performance (capacity of 87.3 mAh / g at a current density of 1 A / g) and cycle stability (capacity of 237.2 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 62.3 mAh / g after 1000 cycles at a current density of 1 A / g).

[0173] Example 8

[0174] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0175] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 3wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), then washed 4 times each with excess 1mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0176] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at a rate of 5℃ / min under a nitrogen atmosphere, and then cooled to obtain PC.

[0177] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0178] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0179] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0180] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0181] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0182] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0183] Morphological and structural characterization of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0184] As an anode material for sodium-ion batteries, PC exhibits good rate performance (capacity of 85.6 mAh / g at a current density of 1 A / g) and cycle stability (capacity of 225.3 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 61.7 mAh / g after 1000 cycles at a current density of 1 A / g).

[0185] Example 9

[0186] Preparation of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0187] (1) Preparation of porous petroleum coke: 5g of high-sulfur petroleum coke (sulfur content of about 3wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), washed with water 4 times, and then dried for 10h to obtain porous petroleum coke.

[0188] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at a rate of 5℃ / min under a nitrogen atmosphere, and then cooled to obtain PC.

[0189] The high-sulfur petroleum coke-derived porous carbon (PC) material obtained by the above preparation method is used as an electrode material for electrochemical testing, including the following steps:

[0190] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0191] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0192] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0193] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0194] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0195] Morphological and structural characterization of high-sulfur petroleum coke-derived porous carbon (PC) materials:

[0196] The metal content of porous carbon is 165 mg / kg. As an anode material for sodium-ion batteries, PC exhibits excellent rate performance (capacity of 62.3 mAh / g at a current density of 1 A / g) and cycle stability (capacity of up to 169.2 mAh / g after 100 cycles at a current density of 0.1 A / g; and capacity of 58.3 mAh / g after 1000 cycles at a current density of 1 A / g).

[0197] Comparative Example 1

[0198] Preparation of low-sulfur petroleum coke-derived porous carbon (PC) materials:

[0199] (1) Preparation of porous petroleum coke: 5g of low-sulfur petroleum coke (sulfur content of about 0.5wt%) was ball-milled into petroleum coke powder (particle size of about 1μm), then washed 4 times each with excess 3mol / L hydrochloric acid solution and water, and then dried for 10h to obtain porous petroleum coke;

[0200] (2) Preparation of PC: In a tube furnace, the prepared porous petroleum coke was heated to 1300℃ for 2h at a rate of 5℃ / min under a nitrogen atmosphere, and then cooled to obtain PC.

[0201] The prepared low-sulfur petroleum coke-derived porous carbon material (PC) was used as an electrode material for electrochemical testing, including the following steps:

[0202] a. Preparation of electrode materials: First, the active material, i.e. PC material, is mixed evenly with acetylene black and sodium carboxymethyl cellulose powder in water at a mass ratio of 8:1:1 and then coated onto copper foil. Then, it is vacuum dried at 70°C for 11 hours.

[0203] b. Sodium-ion battery assembly: Under room temperature conditions, the electrode material prepared in step a was used as the working electrode, the sodium sheet was used as the counter electrode / reference electrode, the separator was made of glass fiber, and the electrolyte was a mixture of 1 mol / L sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1. The CR2025 button battery was assembled in an argon-filled glove box. The water oxygen values ​​in the glove box were [H2O] < 1 ppm and [O2] < 1 ppm, respectively.

[0204] c. Cyclic voltammetry tests were performed using an electrochemical workstation at a scan rate of 0.1 mV / s and a voltage range of 0.01-2.0 V.

[0205] d. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.01-2.0V;

[0206] e. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 MHz.

[0207] Morphological and structural characterization of low-sulfur petroleum coke-derived porous carbon (PC) materials:

[0208] As an anode material for sodium-ion batteries, PC exhibits poor rate performance (capacity of 82.5 mAh / g at a current density of 1 A / g) and cycle stability (capacity of 217.3 mAh / g after 100 cycles at a current density of 0.1 A / g; capacity of 60.9 mAh / g after 1000 cycles at a current density of 1 A / g).

[0209] In summary, the porous carbon provided by this invention can be used as an electrode material in sodium-ion batteries, and the sodium-ion batteries prepared from it have good rate performance and cycle stability.

[0210] The above description is merely a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, based on the technical teachings provided by the present invention and as common knowledge in the field, other equivalent modifications and improvements can be made, and these should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing porous carbon, characterized in that, Includes the following steps: S1. Preparation of porous petroleum coke: Powdered petroleum coke is obtained, and then the petroleum coke is contacted with an acid solution to obtain porous petroleum coke. The petroleum coke has a sulfur content of 2.1-3.2 wt%, a particle size of 0.5-1.5 μm, and a nitrogen content of 0.1-2 wt%. S2. Preparation of porous carbon: Porous carbon is obtained by calcining the porous petroleum coke prepared in step S1, wherein the calcination temperature is 1300-1600℃. The porous carbon is an N / S doped porous carbon, and the sulfur content of the porous carbon is 1.5-3.1 wt%.

2. The preparation method according to claim 1, characterized in that, The petroleum coke is selected from raw coke and cooked coke; And / or, in step S1, the method for obtaining powdered petroleum coke includes the step of ball milling the petroleum coke.

3. The preparation method according to claim 1 or 2, characterized in that, The calcination conditions in step S2 include: calcination time of 1-10 h; And / or, the heating rate is 1-10 ℃ / min; And / or, the calcination is carried out in a non-reactive atmosphere.

4. The preparation method according to claim 3, characterized in that, The calcination time is 2-5 hours; And / or, the heating rate is 4-6 ℃ / min; And / or, the inactive atmosphere is nitrogen and / or argon.

5. The preparation method according to claim 1 or 2, characterized in that, In step S1, the petroleum coke is contacted with an excess of acid solution to obtain porous petroleum coke.

6. The preparation method according to claim 5, characterized in that, The concentration of the acid solution is 1-10 mol / L; The acid solution is at least one of hydrochloric acid and nitric acid.

7. The preparation method according to claim 1, characterized in that, The nitrogen content of the porous carbon is 0.1-1 wt%; And / or, the porous carbon has a pore volume of 0.01-0.2 cm³. 3 g -1 Specific surface area is 5-50 m² 2 g -1 ; And / or, the metal content of the porous carbon is less than 10 mg / kg; And / or, the porous carbon is in the form of irregular granules; And / or, the porous carbon has a microstructure that is short-range ordered and long-range disordered.

8. An electrode material, characterized in that, Porous carbon prepared by any one of claims 1-7.

9. The electrode material according to claim 8, characterized in that, It includes copper foil and a mixed material coated on the surface of the copper foil, the mixed material including a conductive agent, a thickener and the porous carbon.

10. The electrode material according to claim 9, characterized in that, The coating amount of the mixed material is 0.1-20 mg / cm³. 2 ; The mass ratio of porous carbon, conductive agent, and thickener is (7-9):(0.8-1.2):(0.8-1.2); The thickener is selected from at least one of sodium carboxymethyl cellulose and polyvinylidene fluoride; The conductive agent is selected from at least one of acetylene black and Ketjen black.

11. A sodium-ion battery, characterized in that, The electrode material according to any one of claims 8-10 is used as the negative electrode material.

12. The sodium-ion battery according to claim 11, characterized in that, The electrode material serves as the working electrode, and the sodium sheet serves as the counter electrode and / or reference electrode; the electrolyte includes sodium perchlorate. The electrode material has a capacity of 70-99 mAh / g at a current density of 1 A / g; The electrode material has a capacity of 210-250 mAh / g after 100 cycles at a current density of 0.1 A / g; The electrode material has a capacity of 60-70.5 mAh / g after 1000 cycles at a current density of 1 A / g.

13. The sodium-ion battery according to claim 11 or 12, characterized in that, The separator of the sodium-ion battery is made of glass fiber; And / or, the electrolyte of the sodium-ion battery is a mixture of sodium perchlorate, ethylene carbonate, diethyl carbonate and fluoroethylene carbonate.

14. The sodium-ion battery according to claim 13, characterized in that, The electrolyte of the sodium-ion battery is a mixture of sodium perchlorate dissolved in ethylene carbonate, diethyl carbonate and fluoroethylene carbonate. The concentration of sodium perchlorate is 0.8-1.2 mol / L; The volume ratio of ethylene carbonate, diethyl carbonate, and fluoroethylene carbonate is (0.8-1.2): (0.8-1.2): (0.8-1.2).

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