A hard carbon material, a preparation method and application thereof
By controlling the combustion and condensation deposition process of heavy oil, combined with high-temperature heat treatment, the problem of structural regulation of hard carbon materials was solved, and its electrochemical performance was improved, making it suitable for sodium-ion battery anode materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA UNIV OF PETROLEUM (BEIJING)
- Filing Date
- 2026-03-05
- Publication Date
- 2026-06-05
Smart Images
Figure CN122144701A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a hard carbon material, its preparation method, and its applications. Background Technology
[0002] Lithium-ion batteries have become the primary energy source for portable electronic devices and electric vehicles. However, with the increasing scarcity of lithium resources and the continuous fluctuations in the price of battery raw materials, sodium-ion batteries, with their advantages of abundant resources, low cost, excellent rate performance, and environmental friendliness, are considered an ideal alternative to lithium-ion batteries.
[0003] In sodium-ion battery systems, hard carbon materials have attracted much attention due to their broad industrialization prospects and have been extensively studied as anode materials. Continued in-depth research is expected to further improve the energy density and cycle life of sodium-ion batteries, expanding their application prospects in energy storage and thus providing a more feasible technological path to solve resource constraints and energy security issues.
[0004] Hard carbon is an amorphous carbon material that is difficult to graphitize, and its interior is rich in defects and closed pores. Currently, various hard carbon materials have been prepared using biomass, synthetic resins, and coal-based raw materials. Heavy oil byproducts, due to their high carbon content, are considered one of the ideal precursors for hard carbon.
[0005] However, these types of oils typically exhibit high fluidity and thermoplasticity, making structural control during heat treatment difficult. Furthermore, the reaction behavior of heavy oils at high temperatures is complex, requiring precise control of process parameters such as temperature to obtain hard carbon materials with ideal structures.
[0006] Therefore, by optimizing the heat treatment process, it is hoped that the unfavorable factors in the preparation of hard carbon materials using heavy oil as a precursor can be overcome, thereby improving the structural quality and electrochemical performance of the materials. Summary of the Invention
[0007] The purpose of this invention is to provide a method for preparing hard carbon materials with excellent electrochemical properties.
[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing hard carbon materials, the method comprising: (1) In an aerobic environment, heavy oil is burned in a combustion device, and the product I obtained after combustion is condensed and deposited in a condenser to obtain a precursor; the condenser and the combustion device are positioned such that the flow distance L of the product I does not exceed 6.5 cm; L represents the distance from the outlet of the combustion device to the inlet of the condenser. (2) The precursor is heat-treated at a temperature of 1200-1300℃ in an inert atmosphere to obtain hard carbon material.
[0009] A second aspect of the present invention provides a hard carbon material prepared by the method described in the first aspect.
[0010] A third aspect of the invention provides the application of the hard carbon material described in the second aspect in sodium-ion batteries.
[0011] Compared with the prior art, the present invention has at least the following advantages: (1) The heavy oil raw material for preparing hard carbon materials by the method of the present invention is readily available and can make full use of waste heavy oil raw materials to prepare hard carbon materials with good electrochemical performance.
[0012] (2) The method of the present invention can effectively enhance the hardness and strength of hard carbon materials and improve the problem of excessive stacking of small molecule organic structures after high-temperature carbonization of oil pre-carbonization and rapid cooling collection, which leads to a reduction in capacity. Attached Figure Description
[0013] Figure 1 The charge-discharge curves of the sodium-ion battery prepared using the hard carbon material 1 in Example 1 are shown. Figure 2 The charge-discharge curves of the sodium-ion battery prepared using the hard carbon material 2 in Example 2 are shown. Figure 3 The charge-discharge curves of the sodium-ion battery prepared using the hard carbon material D2 in Comparative Example 2 are shown. Figure 4 The charge-discharge curves are those of the sodium-ion battery prepared using the hard carbon material D1 in Comparative Example 1. Figure 5 This is the nitrogen adsorption spectrum of the hard carbon material 2 prepared in Example 2; Figure 6 This is the particle size distribution spectrum of the hard carbon material 2 prepared in Example 2; Figure 7 This is a schematic diagram of the process for preparing hard carbon material 1 in Example 1; Figure 8 This is a schematic diagram of the process for preparing hard carbon material D1 in Comparative Example 1. Detailed Implementation
[0014] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0015] In this invention, the median particle size (D50) refers to the particle diameter corresponding to a cumulative distribution percentage of 50% in a particle group.
[0016] The particle size refers to the diameter of the particle. The particle can be regular or irregular in shape; the particle diameter refers to the straight-line distance between the two farthest ends.
[0017] In this invention, the flow distance refers to the total length of the path along which the combusted medium flows from the outlet of the combustion device to the inlet of the condenser, rather than the straight-line distance.
[0018] As previously described, a first aspect of the present invention provides a method for preparing hard carbon materials, the method comprising: (1) In an aerobic environment, heavy oil is burned in a combustion device, and the product I obtained after combustion is condensed and deposited in a condenser to obtain a precursor; the condenser and the combustion device are positioned such that the flow distance L of the product I does not exceed 6.5 cm; L represents the distance from the outlet of the combustion device to the inlet of the condenser. (2) The precursor is heat-treated at a temperature of 1200-1300℃ in an inert atmosphere to obtain hard carbon material.
[0019] This invention obtains high-quality hard carbon materials through steps such as combustion, oxidation, condensation deposition, and heat treatment. The intermediate products are collected after combustion deposition. These hard carbon material precursors are mostly small molecular polymers with chain-like or saturated structures. Such structures are conducive to further processing. The intermediate material structure is relatively simple, which is conducive to the accumulation of graphite-like microcrystals in the hard carbon material during carbonization, thereby improving the hardness and strength of the hard carbon material.
[0020] Furthermore, by subjecting the collected precursors to high-temperature carbonization through heat treatment, the release of volatiles and internal carbon pyrolysis can promote the formation of pores in the hard carbon material, increase the microporous structure of the material, give it more sodium storage sites, and increase its sodium storage capacity.
[0021] The present invention does not impose any particular requirements on the combustion device, and those skilled in the art can select one based on known techniques. For example, the heavy oil raw material can be fixed or ignited using a mold, such as an alcohol lamp, into which it can be inserted and ignited for an extended period.
[0022] In a preferred embodiment, in step (1), the combustion conditions include a temperature of 400-600°C and a time of 10-300 min, preferably 80-100 min.
[0023] Preferably, in step (1), the conditions for condensation deposition include: a temperature of -20°C to 0°C and a time of 10-300 min.
[0024] More preferably, the condensation deposition conditions include a temperature of -20°C to -10°C and a time of 80-100 min. The inventors have discovered that under these preferred conditions, the condensation deposition temperature has a high thermal energy difference with the combustion temperature, allowing incompletely combusted carbon to condense and be fixed on the condenser quickly, thereby further improving the electrochemical performance of hard carbon materials.
[0025] According to a preferred embodiment, in step (1), the flow distance L is 4-6 cm. The inventors have found that under this preferred condition, the yield of the precursor can be further improved.
[0026] According to another preferred embodiment, in step (2), the conditions of the heat treatment include: a heating rate of 10-20℃ / min, preferably 15-20℃ / min, and a holding time of 1-180min.
[0027] The present invention does not have any special requirements for the inert gas in the inert atmosphere, and those skilled in the art can choose according to their needs, for example, nitrogen.
[0028] In a preferred embodiment, the heavy oil contains the following components by mass percentage: 50-60 wt% aromatic hydrocarbons, 10-20 wt% saturated hydrocarbons, 10-15 wt% gums, and 5-15 wt% asphaltenes.
[0029] Preferably, the heavy oil contains 90-95 wt% carbon. The inventors have discovered that under these preferred conditions, the electrochemical performance of hard carbon materials can be further improved.
[0030] In this invention, the heavy oil may further include 1-3 wt% of other impurities; the other impurities refer to substances other than aromatic hydrocarbons, saturated hydrocarbons, gums, and asphaltenes. For example, the other impurities include metal elements, sulfur elements, nitrogen elements, etc.
[0031] Preferably, the method further includes distilling the heavy oil at 240-320°C.
[0032] Preferably, the method further includes: sieving and grinding the intermediate product obtained from the condensation deposition to obtain an intermediate with a median particle size of 6-9 µm. The inventors have found that under these preferred conditions, uniformly sized intermediates can be obtained, facilitating the subsequent preparation of hard carbon materials.
[0033] The present invention does not have any special requirements for the sieving and grinding process, as long as an intermediate with a median particle size of 6-9µm can be obtained. The present invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of the present invention.
[0034] The method of the present invention may further include using commonly known post-processing methods in the art to post-process the intermediate after sieving and grinding. For example, the intermediate is washed with water and dried in sequence to obtain the precursor.
[0035] According to a particularly preferred embodiment, the preparation process of the hard carbon material is as follows: Figure 7 As shown, specifically: (1) In the air atmosphere (i.e. Figure 7 Under conditions of oxidation upon contact with air, heavy oil is ignited using an alcohol lamp. A condenser plate is placed above the flame, with the distance L between the top of the flame and the inlet of the condenser plate not exceeding 6.5 cm. The condenser plate is connected to a refrigeration pump, and the pump temperature is set to -20℃ to 0℃ to ensure that the black products volatilized during flame combustion can be cooled and condensed into a black powder solid after passing through the condenser. The material has a distinct granular texture. The flame temperature during combustion is 400-600℃, maintained for 10-300 minutes, meaning the time for collecting the condensed black powder solid is 10-300 minutes, yielding the precursor (i.e., Figure 7 (incomplete combustion precursors in) (2) Under an inert atmosphere, the precursor is heat-treated in a tube furnace: the temperature is raised to 1200-1300℃ at a rate of 10-20℃ / min and held for 1-180min. After cooling, the precursor is collected to obtain hard carbon material.
[0036] As previously stated, a second aspect of the present invention provides a hard carbon material prepared by the method described in the first aspect.
[0037] Preferably, the hard carbon material has a median particle size of 4-6 μm, an interlayer spacing of 3.5-4.0 Å, and a specific surface area of 8-25 m². 2 / g.
[0038] Preferably, the reversible specific capacity of the hard carbon material is ≥230mAh / g, and the capacity retention rate after 2000 cycles is ≥80%.
[0039] As previously stated, a third aspect of the present invention provides the application of the hard carbon material described in the second aspect in sodium-ion batteries.
[0040] The present invention will be described in detail below through examples. Unless otherwise specified, specific experimental steps or conditions in the following examples can be performed according to known experimental steps or conditions described in the literature in this field. Unless otherwise specified, the raw materials or instruments used are commercially available. Unless otherwise specified, the reaction temperature in the following examples is at room temperature, which refers to 25±2℃.
[0041] Heavy crude oil: carbon content is 94 wt%; composition: 58.4 wt% aromatic hydrocarbons, 15.3 wt% saturated hydrocarbons, 13.6 wt% gums, 11.4 wt% asphaltenes, and 1.3 wt% other impurities.
[0042] Heavy oil 1: obtained by distillation of heavy crude oil at 280℃.
[0043] Heavy oil 2: obtained by distillation of heavy crude oil at 320℃.
[0044] Example 1 (1) In an air atmosphere, heavy oil 1 was ignited with an alcohol lamp. A condenser plate was placed above the flame. The distance L between the top of the flame and the inlet of the condenser plate was 5 cm. The condenser plate was connected to a refrigeration pump. The temperature of the refrigeration pump was set to -10℃ to ensure that the black product volatilized by the flame could be cooled and condensed into a black powder solid after passing through the condenser plate. The material had obvious particle texture. The flame temperature was 430℃ during combustion and was maintained for 90 min. That is, the time for collecting the condensed black powder solid was 90 min. After the combustion was stopped, the material collected by the condenser plate was removed and sieved and ground to obtain an intermediate with a D50 of 6µm. After washing with water, it was dried at 80℃ for 90 min to obtain the precursor. (2) The precursor was heat-treated in a nitrogen atmosphere: the temperature was raised to 1200℃ at a rate of 20℃ / min and held for 5 min. After cooling, it was collected to obtain hard carbon material 1.
[0045] The present invention provides an exemplary schematic diagram of the process for preparing hard carbon material 1 in Example 1.
[0046] Example 2 (1) In an air atmosphere, heavy oil 1 was ignited with an alcohol lamp. A condenser plate was placed above the flame. The distance L between the top of the flame and the inlet of the condenser plate was 4 cm. The condenser plate was connected to a refrigeration pump. The temperature of the refrigeration pump was set to -20℃ to ensure that the black product volatilized by the flame could be cooled and condensed into a black powder solid after passing through the condenser plate. The material had obvious granular texture. The flame temperature was 420℃ during combustion and was maintained for 80 min. That is, the time for collecting the condensed black powder solid was 80 min. After the combustion was stopped, the material collected by the condenser plate was removed and sieved and ground to obtain an intermediate with a D50 of 6µm. After washing with water, it was dried at 80℃ for 90 min to obtain the precursor. (2) The precursor was heat-treated in a nitrogen atmosphere: the temperature was raised to 1300℃ at a rate of 20℃ / min and held for 5 min. After cooling, it was collected to obtain hard carbon material 2.
[0047] Example 3 (1) In an air atmosphere, heavy oil 2 was ignited with an alcohol lamp. A condenser plate was placed above the flame. The distance L between the top of the flame and the inlet of the condenser plate was 6 cm. The condenser plate was connected to a refrigeration pump. The temperature of the refrigeration pump was set to -10℃ to ensure that the black product volatilized by the flame could be cooled and condensed into a black powder solid after passing through the condenser plate. The material had obvious particle texture. The flame temperature was 600℃ during combustion and was maintained for 100 min. That is, the time for collecting the condensed black powder solid was 100 min. After the combustion was stopped, the material collected by the condenser plate was removed and sieved and ground to obtain an intermediate with a D50 of 6µm. After washing with water, it was dried at 80℃ for 90 min to obtain the precursor. (2) The precursor was heat-treated in a nitrogen atmosphere: the temperature was raised to 1200℃ at a rate of 20℃ / min and held for 180min. After cooling, it was collected to obtain hard carbon material 3.
[0048] Example 4 The same method as in Example 1 was used, except that the distance L in step (1) was adjusted to 6.5 cm to obtain hard carbon material 4.
[0049] Example 5 The same method as in Example 1 was used, except that the distance L in step (1) was adjusted to 3 cm to obtain hard carbon material 5.
[0050] Comparative Example 1 (1) Use a flask to place heavy oil 1 and assemble it into a rotary evaporator. Connect the condenser to the refrigeration pump and loop it. Set the temperature of the refrigeration pump to -10℃, the rotation speed of the rotary evaporator to 100rpm, and the oil bath temperature to 240℃. Collect its condensate in a collector. The sample is a dark brown liquid fluid. After cooling, it becomes a smooth black hard solid. (2) After the material is simply crushed, it is carbonized in a tube furnace. The temperature is maintained at 1300℃ for 5 minutes and the heating rate is 20℃ / min. After the material is cooled, the material is collected and the resulting product is washed with water and dried at 80℃ for 90 minutes to obtain hard carbon material D1.
[0051] The present invention provides, by way of example, a schematic diagram of the process for preparing hard carbon material D1 in Comparative Example 1, as follows: Figure 8 As shown, from Figure 8 As can be seen, a flask is used to place heavy oil and it is assembled into a rotary evaporator. The condenser is connected to the refrigeration pump and circulated. The temperature of the refrigeration pump is set to -10℃, the rotation speed of the rotary evaporator is set to 100rpm, and the oil bath temperature is set to 240℃. The condensate is collected in a collector and is a dark brown liquid fluid.
[0052] Comparative Example 2 The process was carried out using a method similar to that in Example 1, except that the temperature of the heat treatment in step (2) was adjusted to 1400°C to obtain hard carbon material D2.
[0053] Comparative Example 3 The same method as in Example 1 was used, except that the distance L in step (1) was adjusted to 7 cm to obtain hard carbon material D3.
[0054] Comparative Example 4 (1) Place heavy oil 1 in a muffle furnace and pre-oxidize it at 300°C for 90 min to obtain a pre-oxidized precursor; (2) Under a nitrogen atmosphere, the pre-oxidized precursor was heat-treated: the temperature was raised to 1200℃ at a rate of 20℃ / min and held for 5 min. After cooling, it was collected to obtain hard carbon material D4.
[0055] Test Example 1 The hard carbon materials prepared in the examples and comparative examples were used as anode materials for sodium-ion batteries to assemble half-cells, and the following performance tests were conducted. The specific steps are as follows: (1) Hard carbon material, conductive carbon black and polyvinylidene fluoride (molecular weight 4000, purchased from Duoduo Reagent Network) are mixed in a mass ratio of 90:5:5, dissolved in N-methylpyrrolidone solvent, and ground thoroughly to obtain a viscous slurry. The slurry is then coated onto copper foil using a scraping method and dried at room temperature. The coated electrode sheet is then placed in a vacuum oven at 60°C and dried for 12 hours to serve as the negative electrode sheet. (2) Take out the dried negative electrode sheet, weigh and calculate the mass of the coated active material, use sodium sheet as reference electrode, and use 1 mol / L NaClO4 EC / DEC mixed solution as electrolyte (where the volume ratio of EC and DEC is 1:1; EC is ethylene carbonate and DEC is diethyl carbonate). Assemble the button cell under the condition that the mass content of water and oxygen is less than 0.01 ppm. Use polypropylene microporous membrane (Celgard 2400) as separator, seal the assembled battery with button cell sealing machine, and then use LAND charge and discharge tester to perform charge and discharge test on it. Obtain the charge and discharge curve of the first three cycles at a current density of 0.05 A / g, and read the reversible specific capacity and the first coulombic efficiency.
[0056] This invention provides, by way of example, the charge-discharge curves of a sodium-ion battery prepared using the hard carbon material 1 in Example 1, such as... Figure 1 As shown. By Figure 1 It is known that the obtained hard carbon material 1 has a reversible specific capacity of 306 mAh / g and an initial coulombic efficiency of 78%. This is because, under the preparation process of pre-carbonization rapid cooling and carbonization rapid heating, the raw materials are partially converted into smaller particles after thermal decomposition and float upwards. After cooling and deposition, the long-chain organic matter in the oil can be converted into a short-chain structure, which helps to form the hard carbon material structure in the subsequent carbonization process, thus solving the procedural dilemma of preparing hard carbon materials from oil.
[0057] This invention provides, by way of example, the charge-discharge curves of a sodium-ion battery prepared using the hard carbon material 2 in Example 2, such as... Figure 2 As shown. By Figure 2 It can be seen that the hard carbon material 2 has a reversible specific capacity of 317 mAh / g and an initial coulombic efficiency of 79.5%, indicating that good electrochemical performance can be obtained by selecting an appropriate carbonization temperature during the high-temperature rapid carbonization stage.
[0058] This invention provides, by way of example, the charge-discharge curves of a sodium-ion battery prepared using the hard carbon material D2 in Comparative Example 2, such as... Figure 3 As shown. By Figure 3 It can be seen that the performance of hard carbon material D2 is poor, with a reversible specific capacity of only 132 mAh / g and a first coulombic efficiency of 57.8%. This indicates that if the carbonization temperature is too high, it is easy to form a hard carbon structure with a higher graphitization structure, resulting in a sharp decrease in sodium storage sites.
[0059] This invention provides, by way of example, the charge-discharge curves of a sodium-ion battery prepared using the hard carbon material D1 in Comparative Example 1, such as... Figure 4 As shown. By Figure 4It can be seen that the hard carbon material D1 has poor electrochemical performance, with a reversible specific capacity of only 159 mAh / g and an initial coulombic efficiency of 49.4%. Moreover, the capacity in the ramp region of the charge-discharge curve is greater than that in the plateau region, exhibiting the characteristics of a soft carbon sodium storage curve. This indicates that the material prepared from unburned heavy oil materials is not sufficiently disordered, and the lack of microporous structure results in a smaller capacity in the plateau region and poor electrochemical performance.
[0060] Capacity retention rate of hard carbon material after 2000 cycles = reversible specific capacity after 2000 cycles / reversible specific capacity after the first cycle × 100%.
[0061] Test Example 2 The hard carbon materials prepared in the above embodiments and comparative examples were subjected to the following tests: 1. Nitrogen adsorption spectroscopy was obtained by using a nitrogen adsorption-desorption apparatus.
[0062] The present invention provides, by way of example, the nitrogen adsorption spectrum of the hard carbon material 2 prepared in Example 2, such as... Figure 5 As shown. By Figure 5 It can be seen that the specific surface area of hard carbon material 2 is 8.9 m². 2 / g.
[0063] 2. The particle size distribution spectrum was obtained by using a laser particle size analyzer.
[0064] The present invention provides, by way of example, a particle size distribution map of the hard carbon material 2 prepared in Example 2, as shown below. Figure 6 As shown. By Figure 6 It can be seen that the D50 of hard carbon material 2 is 5.9µm.
[0065] 3. Test method for interlayer spacing of hard carbon materials: The interlayer spacing of the (002) crystal plane is calculated by X-ray diffraction (XRD) combined with Bragg equation.
[0066] The test results are shown in Table 1.
[0067] Table 1
[0068] As can be seen from the results in Table 1, the method of the present invention, which utilizes combustion deposition and rapid carbonization processes, can effectively transform oil feedstocks into hard carbon materials and improve the electrochemical performance of hard carbon materials.
[0069] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing hard carbon materials, characterized in that, The method includes: (1) In an aerobic environment, heavy oil is burned in a combustion device, and the product I obtained after combustion is condensed and deposited in a condenser to obtain a precursor; the condenser and the combustion device are positioned such that the flow distance L of the product I does not exceed 6.5 cm; L represents the distance from the outlet of the combustion device to the inlet of the condenser. (2) The precursor is heat-treated at a temperature of 1200-1300℃ in an inert atmosphere to obtain hard carbon material.
2. The method according to claim 1, characterized in that, In step (1), the combustion conditions include a temperature of 400-600℃ and a time of 10-300min.
3. The method according to claim 1 or 2, characterized in that, In step (1), the conditions for the condensation deposition include: a temperature of -20°C to 0°C and a time of 10-300 min.
4. The method according to claim 1 or 2, characterized in that, In step (1), the flow distance L is 4-6 cm.
5. The method according to claim 1 or 2, characterized in that, In step (2), the heat treatment conditions include: a heating rate of 10-20℃ / min and a holding time of 1-180min.
6. The method according to claim 1 or 2, characterized in that, The heavy oil contains the following components by mass percentage: 50-60 wt% aromatic hydrocarbons, 10-20 wt% saturated hydrocarbons, 10-15 wt% gums, and 5-15 wt% asphaltenes. And / or, the carbon content in the heavy oil is 90-95 wt%.
7. The hard carbon material prepared by the method according to any one of claims 1-6.
8. The hard carbon material according to claim 7, characterized in that, The hard carbon material has a median particle size of 4-6 μm, an interlayer spacing of 3.5-4.0 Å, and a specific surface area of 8-25 m². 2 / g.
9. The hard carbon material according to claim 7 or 8, characterized in that, The reversible specific capacity of the hard carbon material is ≥230mAh / g, and the capacity retention rate after 2000 cycles is ≥80%.
10. The application of the hard carbon material according to any one of claims 7-9 in sodium-ion batteries.