Porous carbon material with stepped hole structure as well as preparation method and application of porous carbon material

Abstract

The invention provides a porous carbon material with a stepped hole structure as well as a preparation method and application thereof, and belongs to the technical field of carbon materials. According to the present invention, the thermal treatment temperature of the heavy hydrocarbon-containing raw material in the oxygen-containing atmosphere is regulated to regulate the polymerization degree of the hydrocarbon molecules so as to obtain the carbon components with different activities, such that the porous carbon material with the cascade pore structure is obtained; the stepped porous carbon material provided by the invention contains two-stage pore channels of micropores and mesopores, the operation process is simple, industrial amplification is facilitated, and the material has excellent rate capability when being applied to a positive electrode material of a lithium ion capacitor.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials technology, and relates to a porous carbon material and its preparation method, particularly to a porous carbon with a tiered pore structure and its preparation method. Background Technology

[0002] Against the backdrop of global carbon neutrality, the future energy landscape will shift from fossil fuel dominance to low-carbon multi-energy integration. The development and utilization of renewable energy is an important pillar for energy transformation and low-carbon economic development in countries around the world, and advanced energy storage technology is an important guarantee for achieving stable and efficient utilization of renewable energy.

[0003] Lithium-ion capacitors, as a novel energy storage device, combine the advantages of lithium-ion batteries and supercapacitors, exhibiting high energy density, power density, safety, and long-cycle stability. Electrode materials are the decisive factor in determining the performance of lithium-ion capacitors. Porous carbon materials, due to their high specific surface area, abundant pore structure, and excellent electrochemical performance, are widely used in electrochemical energy storage devices. However, traditional optimizations of porous carbon structures have mostly focused on increasing their specific surface area to improve the material's energy density and ion transport rate; reports on improving the rate performance of materials through pore structure design are relatively rare.

[0004] CN112357921A discloses a hierarchical porous carbon, its preparation method, and its application. This patent describes obtaining hierarchical porous carbon material by calcining a mixture of petroleum asphalt and bicarbonate. This hierarchical porous carbon can simultaneously serve as both the positive and negative electrode active materials in metal-ion capacitors. Both the positive and negative electrode active materials comprised of the hierarchical porous carbon exhibit good cycle stability, ideal coulombic efficiency, and high energy density.

[0005] CN106315552A discloses a hierarchical porous carbon material. This patent involves mixing and dissolving gelatin, citric acid, ferric chloride, and water to form a solution, followed by oil bath and drying to obtain a gel mixture. The gel mixture is then further carbonized to prepare the hierarchical porous carbon material. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention focuses on providing a porous carbon material with a stepped pore structure, its preparation method, and its application. The resulting carbon material has abundant mesopores, the preparation method is simple and easy to industrialize, and it can improve the rate performance of electrode materials.

[0007] The first aspect of this invention provides a method for preparing a porous carbon material with a stepped pore structure, comprising the following steps:

[0008] (1) Under contact conditions, heavy hydrocarbon-containing raw materials are mixed evenly with alkali treatment agents to obtain a mixture;

[0009] (2) Under the presence of a first atmosphere, the mixture obtained in step (1) is subjected to a first heat treatment to obtain a first product;

[0010] (3) Under the presence of a second atmosphere, the first product obtained in step (2) is subjected to a second heat treatment to obtain a second product;

[0011] (4) The second product obtained in step (3) is washed and dried to obtain a porous carbon material with a tiered pore structure.

[0012] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the heavy hydrocarbon raw material in step (1) can be selected from one or more of the following: residual oil, asphalt, wax oil, ethylene tar, catalytic slurry, etc., preferably one or more of the following: residual oil, asphalt, catalytic slurry.

[0013] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the alkali treatment agent in step (1) can be one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, lithium hydroxide, etc., preferably potassium hydroxide.

[0014] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the mixing of heavy hydrocarbon-containing raw materials and alkali treatment agents in step (1) is controlled at 60-120°C, preferably at 90-120°C.

[0015] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the mass ratio of heavy hydrocarbon raw material to alkali treatment agent in step (1) is 1:(0.5-10), preferably 1:(2-5.5).

[0016] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the first atmosphere in step (2) includes a mixture of an inert atmosphere and an oxygen-containing atmosphere; the volume percentage of the inert atmosphere in the mixture is 50% to 95%, preferably 80% to 95%; the volume percentage of the oxygen-containing atmosphere is 5% to 50%, preferably 5% to 20%; wherein the oxygen-containing atmosphere can be one or more of carbon dioxide gas, water vapor, ethanol gas, methanol gas, etc., preferably carbon dioxide gas; the inert atmosphere can be one or more of nitrogen gas, argon gas, helium gas, etc., preferably nitrogen gas.

[0017] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the first heat treatment temperature in step (2) is 470-550°C, preferably 470-490°C; the first heat treatment time is 6-48h, preferably 6-12h.

[0018] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the second atmosphere in step (3) is an inert atmosphere, which can be nitrogen and / or an inert gas, preferably nitrogen; the inert gas can be one or more of helium, neon, argon, krypton, and xenon.

[0019] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the second heat treatment temperature in step (3) is 600-1400℃, preferably 800-1000℃; the second heat treatment time is 1-12h, preferably 1-6h.

[0020] Furthermore, in the above-mentioned method for preparing porous carbon materials with a stepped pore structure, as a specific embodiment, the second heat treatment temperature is 150-850°C higher than the first heat treatment temperature, preferably 350-500°C higher.

[0021] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the washing in step (4) involves first washing with water several times, and then washing with hydrochloric acid with a mass concentration of 1% to 10%, and washing several times until the filtrate is neutral.

[0022] Furthermore, in the above-mentioned method for preparing porous carbon materials with a tiered pore structure, as a specific embodiment, the drying temperature in step (4) is 60-120°C, preferably 80-100°C; the drying time is 6-48h, preferably 12-48h.

[0023] The second aspect of the present invention provides a porous carbon material with a stepped pore structure obtained by the preparation method described in the first aspect.

[0024] Furthermore, in the aforementioned porous carbon material with a stepped pore structure, the porous carbon material with a stepped pore structure includes two levels of channels: a first-level channel and a second-level channel. The pore diameter of the first-level channel is less than 2 nm, and the pore diameter of the second-level channel is 2–15 nm. The pore volume of the second-level channel accounts for 5%–30% of the total pore volume of the stepped pore porous carbon material, preferably 9%–20%.

[0025] Furthermore, in the aforementioned porous carbon material with a stepped pore structure, the total pore volume of the stepped pore porous carbon material is 0.80–1.93 cm³. 3 / g.

[0026] Furthermore, in the aforementioned porous carbon material with a stepped pore structure, the specific surface area of ​​the stepped pore porous carbon material is 1000–2200 m². 2 / g.

[0027] The third aspect of this invention provides the application of the porous carbon material with a stepped pore structure prepared above as a positive electrode material in lithium-ion capacitors.

[0028] It is particularly important to emphasize that the porous carbon material with a stepped pore structure provided by this invention can be used not only as a cathode material for lithium-ion capacitors, but also as a widely applicable electrode material for other capacitors, batteries, or driving devices.

[0029] Compared with existing technologies, the beneficial effects of the porous carbon material with a stepped pore structure and its preparation method provided by this invention are mainly reflected in the following aspects:

[0030] 1. The present invention firstly provides a porous carbon material prepared directly from heavy hydrocarbon compounds as raw materials. The obtained porous carbon material has two levels of channels: micropores and mesopores. In particular, the increase in the proportion of mesopore channels is beneficial to accelerating electrolyte transfer, shortening ion transport paths, and improving the rate performance of electrode materials.

[0031] 2. In the preparation method of porous carbon material with a stepped pore structure provided by the present invention, a mixture of heavy hydrocarbon raw material and alkali treatment agent is heat-treated under an oxygen-containing atmosphere. Under the combined effect of comprehensive regulation and control of operating conditions, the degree of polymerization of hydrocarbon molecules can be controlled to obtain matrix units with different activities. At the same time, treatment under an oxygen-containing atmosphere can promote the dispersion of inorganic substances such as activators in organic hydrocarbons, thereby obtaining porous carbon with a stepped pore distribution. As a positive electrode material for lithium-ion capacitors, it has high rate capability and can also improve the activation effect.

[0032] 3. The preparation method of porous carbon material with a stepped pore structure provided by the present invention is simple and easy to scale up. Attached Figure Description

[0033] Figure 1 The graphs show the rate performance of the lithium-ion capacitor cathode materials obtained in Examples 1-3 of this invention at different current densities. Detailed Implementation

[0034] To further illustrate the present invention, the following describes in detail a method for preparing porous carbon with a stepped pore structure provided by the present invention in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0035] In the context of this specification, the pore structure and specific surface area of ​​the material were measured using a low-temperature nitrogen physical adsorption method. The instrument used was a Micromeritics ASAP2460 physical adsorption instrument. Test conditions included: sample treatment under vacuum at 200°C for 5 hours, and testing at liquid nitrogen temperature (-196°C). Adsorption-desorption isotherms were obtained using the static method. The specific surface area was calculated using the BET (Brunauer-Emmett-Teller) equation, and the pore size distribution was calculated using the NLDFT method.

[0036] In the context of this specification, the electrochemical testing method for the positive electrode material of the lithium-ion capacitor is as follows: Stepwise porous carbon, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed uniformly at a mass ratio of 8:1:1, and then... (The sentence is incomplete and requires more context to translate accurately.) 2 The loading amount was uniformly coated onto aluminum foil, and after drying, the electrode material was obtained. The voltage window was 2–4.2 V, and the electrolyte concentration was 1.0 mol·L⁻¹. -1 The electrochemical performance of LiPF6 / EC-DMC-EMC with a lithium metal counter electrode was tested using a Newway battery tester (model BTS-5V50mA).

[0037] Example 1

[0038] A catalytic slurry with a mass ratio of 1:5 and potassium hydroxide were mixed uniformly at 90°C to obtain a mixture. The distillation range of the catalytic slurry was above 350°C. Under a mixed atmosphere of carbon dioxide and nitrogen (10% carbon dioxide), the mixture was heated to 470°C at a heating rate of 10°C / h for 6 hours to obtain a first product. Under a nitrogen atmosphere, the first product was heated to 600°C at a heating rate of 10°C / h for 2 hours to obtain a second product. The product was then removed and subjected to several water washes and hydrochloric acid washes (5% hydrochloric acid mass concentration) until neutral. After being dried at a constant temperature of 80°C for 48 hours, a porous carbon material with a stepped pore structure was obtained. The stepped pore porous carbon material comprises two levels of channels, wherein the pore diameter of the first level channels is less than 2 nm, and the pore diameter of the second level channels is 2–12 nm; the pore volume of the second level channels accounts for 16% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 1.24 cm³.3 / g, specific surface area is 1301m² 2 / g.

[0039] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 170 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 97 F·g -1 The capacitance retention rate reached 57.06%.

[0040] Example 2

[0041] A catalytic slurry with a mass ratio of 1:3 and potassium hydroxide are mixed uniformly at 100°C to obtain a mixture. The distillation range of the catalytic slurry is above 350°C. Under a mixed atmosphere of carbon dioxide and nitrogen (10% carbon dioxide), the mixture is heated to 470°C at a heating rate of 10°C / h for 6 hours to obtain a first product. Under a nitrogen atmosphere, the first product is heated to 800°C at a heating rate of 10°C / h for 6 hours to obtain a second product. The product is then removed and subjected to several water washes and hydrochloric acid washes (5% hydrochloric acid mass concentration) until neutral. After being dried at 80°C for 48 hours, a porous carbon material with a stepped pore structure is obtained. The stepped pore porous carbon material comprises two levels of channels, wherein the pore size of the first level channels is less than 2 nm, and the pore size of the second level channels is 2–15 nm; the pore volume of the second level channels accounts for 12% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 1.51 cm³. 3 / g, specific surface area is 2107m² 2 / g.

[0042] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 198 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 122 F·g -1 The capacitance retention rate reached 61.61%.

[0043] Example 3

[0044] A catalytic slurry with a mass ratio of 1:2 and sodium hydroxide were mixed uniformly at 120°C to obtain a mixture. The distillation range of the catalytic slurry was above 350°C. Under a mixed atmosphere of carbon dioxide and nitrogen (5% carbon dioxide), the mixture was heated to 550°C at a heating rate of 10°C / h for 48 hours to obtain a first product. Then, under a nitrogen atmosphere, the first product was heated to 800°C at a heating rate of 10°C / h for 2 hours to obtain a second product. The product was removed and subjected to several water washes and hydrochloric acid washes (5% hydrochloric acid mass concentration) until neutral. After being dried at 80°C for 24 hours, a porous carbon material with a stepped pore structure was obtained. The stepped pore porous carbon material includes two levels of channels, wherein the pore size of the first level channels is less than 2 nm, and the pore size of the second level channels is 2–6 nm; the pore volume of the second level channels accounts for 9% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 0.89 cm³. 3 / g, specific surface area is 1155m² 2 / g.

[0045] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 155 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 76 F·g -1 The capacitance retention rate reached 49.03%.

[0046] Example 4

[0047] A catalytic slurry with a mass ratio of 1:3 and potassium hydroxide were mixed uniformly at 120°C to obtain a mixture. The distillation range of the catalytic slurry was above 350°C. Under a mixed atmosphere of carbon dioxide and nitrogen (20% carbon dioxide), the mixture was heated to 470°C at a heating rate of 10°C / h for 12 hours to obtain a first product. Under a nitrogen atmosphere, the first product was heated to 800°C at a heating rate of 10°C / h for 2 hours to obtain a second product. The product was then subjected to several water washes and hydrochloric acid washes (5% hydrochloric acid mass concentration) until neutral. After being dried at a constant temperature of 100°C for 12 hours, a porous carbon material with a stepped pore structure was obtained. The stepped pore porous carbon material comprises two levels of channels, wherein the pore diameter of the first level channels is less than 2 nm, and the pore diameter of the second level channels is 2–15 nm; the pore volume of the second level channels accounts for 12% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 1.76 cm³. 3 / g, specific surface area is 1622m²2 / g.

[0048] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 163 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 106 F·g -1 The capacitance retention rate reached 65.03%.

[0049] Example 5

[0050] Asphalt and potassium hydroxide at a mass ratio of 1:2 were mixed uniformly at 60°C to obtain a mixture. The softening point of the asphalt was approximately 220°C. Under a mixed atmosphere of carbon dioxide and nitrogen (5% carbon dioxide), the mixture was heated to 490°C at a heating rate of 10°C / h for 6 hours to obtain a first product. Then, under a nitrogen atmosphere, the first product was heated to 1400°C at a heating rate of 10°C / h for 6 hours to obtain a second product. The product was then subjected to several water washes and hydrochloric acid washes (5% hydrochloric acid mass concentration) until neutral. After being dried at a constant temperature of 80°C for 24 hours, a porous carbon material with a stepped pore structure was obtained. The stepped pore porous carbon material comprises two levels of channels, wherein the pore diameter of the first level of channels is less than 2 nm, and the pore diameter of the second level of channels is 2–10 nm; the pore volume of the second level of channels accounts for 15% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 1.17 cm³. 3 / g, specific surface area is 1091m² 2 / g.

[0051] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 121 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 64 F·g -1 The capacitance retention rate reached 52.89%.

[0052] Example 6

[0053] Asphalt and sodium hydroxide at a mass ratio of 1:2 were mixed uniformly at 100°C to obtain a mixture. The softening point of the asphalt was approximately 220°C. Under a mixed atmosphere of methanol and nitrogen (10% methanol), the mixture was heated to 470°C at a heating rate of 10°C / h for 12 hours to obtain a first product. Then, under a nitrogen atmosphere, the first product was heated to 1000°C at a heating rate of 10°C / h for 1 hour to obtain a second product. The product was then subjected to several water washes and hydrochloric acid washes (10% hydrochloric acid mass concentration) until neutral. After being dried at a constant temperature of 100°C for 12 hours, a porous carbon material with a stepped pore structure was obtained. The stepped pore porous carbon material comprises two levels of channels, wherein the pore size of the first level channels is less than 2 nm, and the pore size of the second level channels is 2–10 nm; the pore volume of the second level channels accounts for 14% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 1.22 cm³. 3 / g, specific surface area is 1128m² 2 / g.

[0054] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 133 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 73 F·g -1 The capacitance retention rate reached 54.89%.

[0055] Comparative Example 1

[0056] A catalytic oil slurry with a mass ratio of 1:3 and potassium hydroxide are mixed uniformly at 100°C to obtain a mixture. The distillation range of the catalytic oil slurry is above 350°C. Under a nitrogen atmosphere, the mixture is heated to 470°C at a heating rate of 10°C / h for 6 hours to obtain a first product. Then, under a nitrogen atmosphere, the first product is heated to 800°C at a heating rate of 10°C / h for 6 hours to obtain a second product. The product is removed and subjected to several water washings and hydrochloric acid washings (5% hydrochloric acid mass concentration) until neutral. After being dried at a constant temperature of 80°C for 48 hours, a porous carbon material with a stepped pore structure is obtained. The stepped pore porous carbon material includes two levels of channels, wherein the pore diameter of the first level channel is less than 2 nm, and the pore diameter of the second level channel is 2–4 nm; wherein the pore volume of the second level channel accounts for 7% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 1.61 cm³. 3 / g, specific surface area is 1733m² 2 / g.

[0057] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 182 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 76 F·g -1 The capacitance retention rate reached 41.76%.

[0058] Comparative Example 2

[0059] The catalytic oil slurry was heated to 470°C in a reactor at a heating rate of 10°C / h for 6 hours to obtain the first product. The distillation range of the catalytic oil slurry was above 350°C. Under a nitrogen atmosphere, the first product was mixed with potassium hydroxide at a mass ratio of 1:5 and heated to 800°C at a heating rate of 10°C / h for 2 hours to obtain the second product. The product was then removed and subjected to several water washes and hydrochloric acid washes (5% hydrochloric acid mass concentration) until neutral. After being dried at 80°C for 48 hours, a porous carbon material with a stepped pore structure was obtained. The stepped pore porous carbon material comprises two levels of channels, wherein the pore diameter of the first level channels is less than 2 nm, and the pore diameter of the second level channels is 2–5 nm; the pore volume of the second level channels accounts for 2% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped pore porous carbon material is 1.93 cm³. 3 / g, specific surface area is 2845m² 2 / g.

[0060] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 160 F·g -1 , in 15A·g -1 The specific capacitance at the current density is 53 F·g -1 The capacitance retention rate is only 33%.

[0061] Comparative Example 3

[0062] A catalytic slurry with a mass ratio of 1:3 and potassium hydroxide were mixed uniformly at 140°C to obtain a mixture. The distillation range of the catalytic slurry was above 350°C. Under a mixed atmosphere of carbon dioxide and nitrogen (20% carbon dioxide), the mixture was heated to 470°C at a heating rate of 10°C / h for 12 hours to obtain a first product. Under a nitrogen atmosphere, the first product was heated to 800°C at a heating rate of 10°C / h for 2 hours to obtain a second product. The product was then subjected to several water washes and hydrochloric acid washes (5% hydrochloric acid mass concentration) until neutral. After being dried at a constant temperature of 100°C for 12 hours, a porous carbon material with a stepped pore structure was obtained. The stepped pore porous carbon material comprises two levels of channels, wherein the pore diameter of the first level channels is less than 2 nm, and the pore diameter of the second level channels is 2–4 nm; the pore volume of the second level channels accounts for 5% of the total pore volume of the stepped pore porous carbon material. The total pore volume of the stepped porous carbon material is 1.55 cm³. 3 / g, specific surface area is 1600m² 2 / g.

[0063] The obtained stepped-pore porous carbon material was subjected to electrochemical testing according to the above-mentioned electrochemical testing method for lithium-ion capacitor cathode materials. The test results showed that the stepped-pore structure of the porous carbon material was 0.5 A·g -1 The specific capacitance at the current density is 147 F·g -1 , in 15A·g -1 The specific capacitance at the given current density is 73.6 F·g. -1 The capacitance retention rate reached 50.07%.

Claims

1. A method for preparing a porous carbon material with hierarchical pore structure, comprising the following steps: (1) mixing a heavy hydrocarbon-containing raw material with an alkali treatment agent under contact conditions to obtain a mixture; (2) performing a first heat treatment on the mixture obtained in step (1) in the presence of a first atmosphere to obtain a first product; the first atmosphere comprises a mixture of an inert atmosphere and an oxygen-containing atmosphere; (3) performing a second heat treatment on the first product obtained in step (2) in the presence of a second atmosphere to obtain a second product; the second atmosphere is an inert atmosphere; (4) washing and drying the second product obtained in step (3) to obtain a porous carbon material with hierarchical pore structure.

2. The method for producing the porous carbon material having a hierarchical pore structure according to claim 1, characterized by: The heavy hydrocarbon-containing raw material in step (1) is selected from one or more of residual oil, pitch, wax oil, ethylene tar, and catalytic oil slurry.

3. The method of claim 1, wherein the method further comprises: The alkali treatment agent in step (1) is one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, and lithium hydroxide, and is preferably potassium hydroxide. ​ 4. The method of claim 1, wherein: The mixing of the heavy hydrocarbon-containing raw material and the alkali treatment agent in step (1) is controlled at 60-120°C, and is preferably performed at 90-120°C.

5. The method of claim 1, wherein: The mass ratio of the heavy hydrocarbon-containing raw material to the alkali treatment agent in step (1) is 1:(0.5-10), and the mass ratio is preferably 1:(2-5.5).

6. The method of claim 1, wherein: The volume ratio of the inert atmosphere in the mixture gas in step (2) is 50%-95%, and is preferably 80%-95%; the volume ratio of the oxygen-containing atmosphere is 5%-50%, and is preferably 5%-20%; the oxygen-containing atmosphere is one or more of carbon dioxide gas, water vapor, ethanol gas, and methanol gas, and is preferably carbon dioxide gas; the inert atmosphere is one or more of nitrogen, argon, and helium, and is preferably nitrogen.

7. The method of claim 1, wherein the method further comprises: The first heat treatment temperature in step (2) is 470-550°C, and the first heat treatment temperature is preferably 470-490°C; the first heat treatment time is 6-48h, and the first heat treatment time is preferably 6-12h.

8. The method of claim 1, wherein: The inert atmosphere in step (3) is nitrogen and / or an inert gas, and is preferably nitrogen; the inert gas is one or more of helium, neon, argon, krypton, and xenon.

9. The method of claim 1, wherein: The second heat treatment temperature in step (3) is 600-1400°C, and the second heat treatment temperature is preferably 800-1000°C; the second heat treatment time is 1-12h, and the second heat treatment time is preferably 1-6h.

10. The method of claim 1, wherein: The second heat treatment temperature is 150-850°C higher than the first heat treatment temperature, and is preferably 350-500°C higher.

11. The method of claim 1, wherein: The washing in step (4) is washing with water followed by washing with hydrochloric acid; the mass concentration of the hydrochloric acid is 1%-10%, and the washing is performed until the filtrate is neutral.

12. The method of claim 1, wherein: The drying temperature in step (4) is 60-120°C, and the drying temperature is preferably 80-100°C; the drying time is 6-48h, and the drying time is preferably 12-48h.

13. A porous carbon material with hierarchical pore structure obtained by the method of any one of claims 1-12.

14. The porous carbon material having a hierarchical pore structure according to claim 13, characterized in that: The porous carbon material with the hierarchical pore structure comprises two levels of pores, i.e. a first level of pores with a pore size less than 2 nm and a second level of pores with a pore size of 2-15 nm; wherein the pore volume of the second level of pores accounts for 5%-30%, preferably 9%-20% of the total pore volume of the hierarchical porous carbon material.

15. The porous carbon material having a hierarchical pore structure according to claim 13, wherein: The total pore volume of the hierarchical porous carbon material is 0.80-1.93 cm 3 / g.

16. The porous carbon material having a hierarchical pore structure according to claim 13, wherein: The specific surface area of the gradient-pore porous carbon material is 1000-2200 m 2 / g.

17. Use of the porous carbon material with the hierarchical pore structure according to any one of claims 13-16 as a positive electrode material in a lithium ion capacitor.

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