Asphalt-based carbon negative electrode material and two-step pre-oxidation synthesis preparation method and application thereof

Abstract

The application provides a pitch-based carbon negative electrode material and a two-step pre-oxidation synthesis preparation method and application thereof. The two-step pre-oxidation synthesis preparation method of the pitch-based carbon negative electrode material comprises the following steps: uniformly grinding and mixing a pitch precursor and an initiator to obtain a mixed precursor; performing heat treatment on the mixed precursor in an oxidizing atmosphere, cooling and cooling down to obtain a pre-oxidized precursor I; mixing the pre-oxidized precursor I with an oxidizing agent in a liquid phase to perform secondary oxidation to obtain a pre-oxidized precursor II; performing calcination on the pre-oxidized precursor II in an inert gas atmosphere, cooling, grinding, washing and drying to obtain the pitch-based carbon negative electrode material. The pitch-based carbon negative electrode material comprises a product prepared by the above method. The method provided by the application introduces oxygen functional groups into the pitch precursor through two-step pre-oxidation, crosslinks with pitch molecules, hinders carbon layer rearrangement, reduces the graphitization degree after carbonization, improves the sodium storage capacity, enhances the surface capacitance contribution and improves the rate capability.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode material technology, specifically to pitch-based carbon anode materials and their two-step pre-oxidation synthesis preparation method and application. Background Technology

[0002] The gradual depletion of traditional energy sources and related environmental problems have driven technological advancements towards clean energy sources such as solar, wind, and geothermal energy. However, due to the intermittent nature of these energy sources, the demand for energy storage has increased significantly, leading to a rapid increase in lithium resource usage. Besides uneven geographical distribution, this has also raised concerns about the rapid depletion of lithium resources, ultimately increasing the price of lithium raw materials and hindering the commercial production of lithium-ion batteries. Sodium-ion batteries, with their advantages of abundant resources, low cost, long lifespan, and good safety performance, can not only supplement lithium-ion batteries but also alleviate lithium resource shortages to some extent, ensuring national energy security and sustainable social development. Based on these advantages, sodium-ion batteries are considered the next generation of energy storage devices suitable for large-scale development.

[0003] However, the commercial application of sodium-ion batteries still lacks low-cost anode materials, and achieving high-performance and low-cost sodium-ion batteries remains a significant challenge. Therefore, it is necessary to find or develop more suitable electrodes to meet the requirements of high energy density and high cycle stability in the most economical and efficient way. Pitch pitch is a typical soft carbon precursor with advantages of wide availability and low cost, and it holds promise for large-scale production and industrial application. However, pitch-derived soft carbon has a relatively ordered microstructure and small interlayer distances, resulting in poor electrochemical sodium storage performance. + Storage capacity is limited. Therefore, providing pitch-based carbon anode materials and their two-step pre-oxidation synthesis preparation method and applications is of great significance. Summary of the Invention

[0004] The purpose of this invention is to address at least one of the aforementioned shortcomings of the prior art. For example, one objective of this invention is to provide a low-cost and simple two-step pre-oxidation synthesis method for preparing pitch-based carbon anode materials. Another objective of this invention is to provide a Na... + Pitch-based carbon anode materials with good storage capacity, meeting the requirements of high energy density and high cycle stability.

[0005] To achieve the above objectives, the present invention provides a two-step pre-oxidation synthesis method for preparing asphalt-based carbon anode materials. The method may include: uniformly grinding and mixing an asphalt-based precursor and an initiator to obtain a mixed precursor; heat-treating the mixed precursor under an oxidizing atmosphere and cooling it to obtain a pre-oxidized precursor I; mixing the pre-oxidized precursor I with an oxidant in liquid phase for secondary oxidation to obtain a pre-oxidized precursor II; calcining the pre-oxidized precursor II under an inert gas atmosphere, cooling, grinding, washing, and drying to obtain the asphalt-based carbon anode material.

[0006] According to one or more exemplary embodiments of one aspect of the present invention, the initiator may include one or more of boric acid, boron oxide, tetraphenylboronic acid, sodium tetraphenylborate, phosphoric acid, phosphorus pentoxide, and phosphorus trioxide.

[0007] According to one or more exemplary embodiments of one aspect of the present invention, the bitumen precursor may include one or more of coal tar pitch, petroleum pitch, natural pitch and mesophase pitch.

[0008] According to one or more exemplary embodiments of one aspect of the present invention, the asphalt precursor and the initiator may be uniformly ground and mixed in a mass ratio of 1:0.5 to 5.

[0009] According to one or more exemplary embodiments of one aspect of the present invention, the heat treatment may include: heating to 250-450°C at a heating rate of 2-5°C / min and holding at that temperature for 2-5 hours; the calcination may include: heating to 700-1400°C at a heating rate of 3-10°C / min and holding at that temperature for 2-4 hours.

[0010] According to one or more exemplary embodiments of one aspect of the present invention, the oxidant may include one or more of hydrogen peroxide, ferric nitrate, sodium nitrate, potassium nitrate, zinc nitrate, and potassium permanganate; the liquid phase may include deionized water; the pre-oxidation precursor I and the oxidant may be mixed in a liquid phase at a molar ratio of 1:0.5 to 3.

[0011] According to one or more exemplary embodiments of one aspect of the present invention, the mixed secondary oxidation may include: stirring for 3 to 5 hours in a water bath at 60 to 90°C, and then evaporating to dryness to obtain pre-oxidized asphalt precursor II.

[0012] According to one or more exemplary embodiments of one aspect of the present invention, the washing may include: dispersing the obtained material after grinding in deionized water, stirring, filtering, washing until the washing liquid is neutral, stirring for 25 to 35 minutes, and sonicating for 5 to 15 minutes.

[0013] According to one or more exemplary embodiments of one aspect of the present invention, the oxidizing atmosphere may include one or more of air, oxygen and ozone; the inert gas may include one or more of argon, nitrogen, helium and argon-hydrogen mixture.

[0014] According to one or more exemplary embodiments of one aspect of the present invention, the equipment used for the heat treatment and the calcination may include carbonization equipment, which includes tubular carbonization furnaces, box-type carbonization furnaces, roller kilns and pusher kilns.

[0015] Another aspect of the present invention provides a pitch-based carbon anode material, which may include products prepared by the two-step pre-oxidation synthesis preparation method of the pitch-based carbon anode material described above.

[0016] Another aspect of the present invention provides the application of the asphalt-based carbon anode material as described above in sodium-ion battery anode materials.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0018] (1) The preparation method proposed in this invention introduces oxygen functional groups into the asphalt precursor through two-step pre-oxidation, which cross-links with the asphalt molecules, hinders carbon layer rearrangement, reduces the degree of graphitization after carbonization, improves sodium storage capacity, enhances surface capacitance contribution, and improves rate capability.

[0019] (2) The preparation method proposed in this invention utilizes widely available and inexpensive raw materials, and the overall process is simple and environmentally friendly. The preparation operation is simple, the process is controllable, and it is suitable for large-scale production.

[0020] (3) The electrochemical performance of the pitch-based carbon anode material proposed in this invention can meet the requirements of industrial batteries. Attached Figure Description

[0021] The above and other objects and features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1 The XRD comparison diagrams of the pitch-based carbon anode material of Example 1 and the material obtained by direct carbonization of pitch are shown;

[0023] Figure 2A The first three charge-discharge curves of the pitch-based carbon anode material in Example 1 are shown.

[0024] Figure 2B for Figure 2A grayscale image;

[0025] Figure 3 The rate factor plots of the pitch-based carbon anode material of Example 1 at different current densities are shown.

[0026] Figure 4 Example 1 shows a pitch-based carbon anode material at a current density of 1 Ag. -1 Long-term cycle curve graph. Detailed Implementation

[0027] The pitch-based carbon anode material of the present invention, its two-step pre-oxidation synthesis preparation method, and its application will be described in detail below with reference to the accompanying drawings and exemplary embodiments.

[0028] It should be noted that "Ⅰ", "Ⅱ", etc., are merely for ease of description and distinction, and should not be construed as indicating or implying relative importance. In the description of this invention, unless otherwise stated, "multiple" means two or more. The terms "S1", "S2", "S3", "S4", "S41", "S42", etc., used in this invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0029] Exemplary Example 1

[0030] This exemplary embodiment provides a two-step pre-oxidation synthesis preparation method for pitch-based carbon anode materials.

[0031] The two-step pre-oxidation synthesis method for preparing pitch-based carbon anode materials may include the following steps:

[0032] S1. Grind and mix the asphalt precursor and initiator evenly to obtain a mixed precursor.

[0033] S2. The mixed precursors are heat-treated in an oxidizing atmosphere and then cooled to obtain pre-oxidized precursor I.

[0034] S3. Pre-oxidized precursor I is mixed with oxidant in liquid phase and oxidized twice to obtain pre-oxidized precursor II.

[0035] S4. The pre-oxidized precursor II is calcined, cooled, ground, washed, and dried in an inert gas atmosphere to obtain the pitch-based carbon anode material.

[0036] In this exemplary embodiment, in step S1, the asphalt-based precursor and the initiator are uniformly ground and mixed in a mass ratio of 1:0.5 to 5, for example, 1:0.6, 1:3, or 1:5. Here, a ratio that is too low will result in insufficient introduction of oxygen-containing functional groups during the pre-oxidation process, failing to effectively reduce the graphitization degree of the material; a ratio that is too high may lead to excessive introduction of defects, which is detrimental to Na… +The reversible intercalation / deintercalation and initial coulombic efficiency are observed. Asphalt precursors may include one or more of coal tar pitch, petroleum pitch, natural pitch, and mesophase pitch. Initiators may include one or more of boric acid, boron oxide, tetraphenylboronic acid, sodium tetraphenylborate, phosphoric acid, phosphorus pentoxide, and phosphorus trioxide.

[0037] In this exemplary embodiment, in step S2, the oxidizing atmosphere may include one or more of air, oxygen, and ozone. The heat treatment may include heating to 250–450°C at a heating rate of 2–5°C / min and holding at that temperature for 2–5 hours. The equipment used for the heat treatment may include carbonization equipment, such as tubular carbonization furnaces, box-type carbonization furnaces, roller kilns, and pusher kilns.

[0038] In this exemplary embodiment, in step S3, the pre-oxidation precursor I and the oxidant can be mixed in a liquid phase at a molar ratio of 1:0.5 to 3, for example, 1:0.5, 1:1.3, 1:2.6, or 1:3.

[0039] In this exemplary embodiment, in step S3, the oxidant may include one or more of hydrogen peroxide, ferric nitrate, sodium nitrate, potassium nitrate, zinc nitrate, and potassium permanganate.

[0040] In this exemplary embodiment, in step S3, the liquid phase may include deionized water.

[0041] In this exemplary embodiment, in step S3, the secondary oxidation may include: stirring and mixing for 3 to 5 hours in a water bath at 60 to 90°C, and then evaporating to dryness to obtain pre-oxidized asphalt precursor II.

[0042] In this exemplary embodiment, in step S4, the inert gas may include one or more of argon, nitrogen, helium, and an argon-hydrogen mixture. Calcination may include heating to 700–1400°C at a heating rate of 3–10°C / min and holding at that temperature for 2–4 hours. The equipment used for calcination may include carbonization equipment, such as tubular carbonization furnaces, box-type carbonization furnaces, roller kilns, and pusher kilns.

[0043] In this exemplary embodiment, in step S4, washing may include: dispersing the obtained material after grinding in deionized water, stirring, filtering, and washing until the washing liquid is neutral, stirring for 25 to 35 minutes, and ultrasonic treatment for 5 to 15 minutes.

[0044] Exemplary Example 2

[0045] This exemplary embodiment provides an asphalt-based carbon anode material.

[0046] The pitch-based carbon anode material may include the product prepared by the two-step pre-oxidation synthesis preparation method of the pitch-based carbon anode material described in Exemplary Example 1 above.

[0047] To better understand the above exemplary embodiment 2 of the present invention, it will be further described below with reference to specific examples.

[0048] Example 1

[0049] S1. Weigh 2g of coal tar pitch powder (coal tar pitch) and 3g of boric acid in a ratio of 1:1.5, grind and mix them evenly in a mortar to obtain a mixed precursor.

[0050] S2. The mixed precursors are placed in a tube furnace (tube carbonization furnace) and heated in an air atmosphere at 2°C for 1 minute. -1 The temperature was increased to 300℃ for 3 hours, and then naturally cooled to room temperature to obtain pre-oxidized asphalt precursor I.

[0051] S3. Disperse the pre-oxidized asphalt precursor I uniformly in deionized water, add 60 mL of 5% hydrogen peroxide solution, heat in a water bath at 80°C and stir for 4 h, and then evaporate to dryness to obtain the pre-oxidized asphalt precursor II.

[0052] S41. Transfer the pre-oxidized asphalt precursor II to a tube furnace, then heat it to 800℃ at a heating rate of 5℃ / min under N2 atmosphere and hold it for 2 hours. Then cool it naturally to room temperature and grind and mix it evenly in a mortar.

[0053] S42. Disperse the sample obtained in step S41 in 80ml of deionized water and stir for 30min, sonicate for 10min, then filter and wash until the filtrate is neutral, and finally dry the sample at 80℃ for 12h to obtain the asphalt-based carbon anode material.

[0054] The pitch-based carbon anode material in this example is a pitch-based carbon anode material that has undergone dual pre-oxidation. The phase characterization of the pitch-based carbon anode material prepared in this example was performed. Figure 1 A comparison of the XRD results of the asphalt-based carbon anode material prepared in this example and the material obtained by direct carbonization of asphalt without any treatment is presented. The XRD pattern shows typical amorphous carbon, with two peaks representing the (002) crystal plane and the (100) crystal plane, respectively. It can be seen that the (002) crystal plane diffraction peak of the asphalt-based carbon anode material in this example has a significantly lower peak intensity and broader peak compared to the directly carbonized sample. This indicates that the two-step pre-oxidation of this invention can effectively suppress the graphitization of asphalt during the carbonization process. Furthermore, the peak position shifts to the left, indicating an increase in interlayer spacing, which is more favorable for Na… + migrate.

[0055] Example 2

[0056] S1. Weigh 2g of coal tar pitch powder and 3g of boric acid in a mortar and grind them evenly in a mortar to obtain a mixed precursor.

[0057] S2. The mixed precursors are placed in a tube furnace and heated at 2°C for 1 minute in an air atmosphere. -1 The temperature was increased to 300℃ for 3 hours, and then naturally cooled to room temperature to obtain pre-oxidized asphalt precursor I.

[0058] S3. Disperse the pre-oxidized asphalt precursor I uniformly in deionized water, add 60 mL of 10% hydrogen peroxide solution, heat in a water bath at 80°C and stir for 4 h, and then evaporate to dryness to obtain the pre-oxidized asphalt precursor II.

[0059] S41. Transfer the pre-oxidized asphalt precursor II to a tube furnace, then heat it to 800℃ at a heating rate of 5℃ / min under N2 atmosphere and hold it for 2 hours. Then cool it naturally to room temperature and grind and mix it evenly in a mortar.

[0060] S42. Disperse the sample obtained in step S41 in 80ml of deionized water and stir for 30min, sonicate for 10min, then filter and wash until the filtrate is neutral, and finally dry the sample at 80℃ for 12h to obtain the asphalt-based carbon anode material.

[0061] Example 3

[0062] S1. Weigh 2g of coal tar pitch powder and 3g of boric acid in a mortar and grind them evenly in a mortar to obtain a mixed precursor.

[0063] S2. The mixed precursors are placed in a tube furnace and heated at 2°C for 1 minute in an air atmosphere. -1 The temperature was increased to 300℃ for 3 hours, and then naturally cooled to room temperature to obtain pre-oxidized asphalt precursor I.

[0064] S3. Disperse the pre-oxidized asphalt precursor I uniformly in deionized water, add 60 mL of 5% hydrogen peroxide solution, heat in a water bath at 60°C and stir for 4 h, and then evaporate to dryness to obtain the pre-oxidized asphalt precursor II.

[0065] S41. Transfer the pre-oxidized asphalt precursor II to a tube furnace, then heat it to 800℃ at a heating rate of 5℃ / min under N2 atmosphere and hold it for 2 hours. Then cool it naturally to room temperature and grind and mix it evenly in a mortar.

[0066] S42. Disperse the sample obtained in step S41 in 80ml of deionized water and stir for 30min, sonicate for 10min, then filter and wash until the filtrate is neutral, and finally dry the sample at 80℃ for 12h to obtain the asphalt-based carbon anode material.

[0067] Example 4

[0068] S1. Weigh 2g of coal tar pitch powder and 3g of boric acid in a mortar and grind them evenly in a mortar to obtain a mixed precursor.

[0069] S2. The mixed precursors are placed in a tube furnace and heated at 2°C for 1 minute in an air atmosphere. -1 The temperature was increased to 300℃ for 3 hours, and then naturally cooled to room temperature to obtain pre-oxidized asphalt precursor I.

[0070] S3. Disperse the pre-oxidized asphalt precursor I uniformly in deionized water, add 60 mL of 5% hydrogen peroxide solution, heat in a water bath at 80°C and stir for 4 h, and then evaporate to dryness to obtain the pre-oxidized asphalt precursor II.

[0071] S41. Transfer the pre-oxidized asphalt precursor II to a tube furnace, then heat it to 1000℃ at a heating rate of 5℃ / min under N2 atmosphere and hold it for 2 hours. Then cool it naturally to room temperature and grind and mix it evenly in a mortar.

[0072] S42. Disperse the sample obtained in step S41 in 80ml of deionized water and stir for 30min, sonicate for 10min, then filter and wash until the filtrate is neutral, and finally dry the sample at 80℃ for 12h to obtain the asphalt-based carbon anode material.

[0073] Exemplary Example 3

[0074] Another aspect of the present invention provides the application of the asphalt-based carbon anode material as described above in sodium-ion battery anode materials.

[0075] The pitch-based carbon anode materials obtained in Examples 1-4 above can be used to prepare coin cells. Specific steps may include: mixing the pitch-based carbon anode material with a conductive agent (acetylene black) and a binder (PVDF) in a mass ratio of 8:1:1, and adding N-methylpyrrolidone to form a slurry. The slurry is uniformly coated onto a Cu foil (50 μm thick) and vacuum dried at 80°C for 12 hours. A circular electrode sheet with a diameter of 14 mm is then stamped using a stamping machine to serve as the working electrode. A sodium metal sheet is used as the counter electrode, 1 mol L⁻¹ NaPF₆ in DME is used as the electrolyte, and glass microfiber is used as the separator to assemble a CR2032 type coin cell. Constant current charge-discharge tests are performed at room temperature, with a voltage range of 0.01–3 V.

[0076] Example 1: The first three charge-discharge test results of the pitch-based carbon anode material are as follows: Figure 2A or Figure 2B As shown, the initial charge specific capacity is 195 (mAh g). -1 The discharge specific capacity is 251.8 (mAh g). -1 The initial coulomb efficiency was 77.5%. Rate performance was as follows: Figure 3 As shown, 5A g -1 The discharge specific capacity is 145 (mAh g). -1 ). In 1A g -1 Long-cycle testing was performed at current density, and the results are as follows: Figure 4 As shown. After 1000 cycles, the discharge specific capacity is 138.9 (mAh g). -1 It has a capacity retention rate of 95.8% and excellent long-cycle performance.

[0077] In summary, the advantages proposed by this invention include at least one of the following:

[0078] (1) The preparation method proposed in this invention has the advantages of low cost, simple process, high carbon yield and suitability for large-scale production.

[0079] (2) The preparation method proposed in this invention introduces a large number of oxygen-containing functional groups into the asphalt precursor through initiator-assisted pre-oxidation and oxidant-assisted secondary pre-oxidation. These functional groups cross-link with asphalt molecules, hindering carbon layer rearrangement and reducing the degree of graphitization after carbonization. The oxygen-containing functional groups retained after carbonization can also provide additional Na through redox reactions. + Adsorption sites.

[0080] (3) The Na-based carbon anode material proposed in this invention + It has good storage performance, high initial coulomb efficiency, good rate performance, and excellent long-cycle performance.

[0081] Although the invention has been described above in conjunction with exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the exemplary embodiments of the invention without departing from the spirit and scope defined by the claims.

Claims

1. A two-step pre-oxidation synthesis method for preparing pitch-based carbon anode materials, characterized in that, The method includes: A mixed precursor is obtained by uniformly grinding and mixing an asphalt-based precursor and an initiator; the initiator includes one or more of boric acid, boron oxide, tetraphenylboronic acid, and sodium tetraphenylborate. The mixed precursors are heat-treated in an oxidizing atmosphere and then cooled to obtain pre-oxidized precursor I; the heat treatment includes heating to 250-450°C at a heating rate of 2-5°C / min and holding at that temperature for 2-5 hours. Pre-oxidized precursor I is mixed with an oxidant in liquid phase and then oxidized to obtain pre-oxidized precursor II; the oxidant is hydrogen peroxide; the mixed secondary oxidation includes: stirring for 3-5 hours in a water bath at 60-90℃, and then evaporating to dryness to obtain pre-oxidized asphalt precursor II. The pre-oxidized precursor II was calcined, cooled, ground, washed, and dried in an inert gas atmosphere to obtain a pitch-based carbon anode material; the calcination included heating to 700-1400℃ at a heating rate of 3-10℃ / min and holding at that temperature for 2-4 hours.

2. The two-step pre-oxidation synthesis method for preparing pitch-based carbon anode material according to claim 1, characterized in that, The asphalt precursors include one or more of coal tar pitch, petroleum pitch, natural pitch, and mesophase pitch.

3. The two-step pre-oxidation synthesis method for preparing pitch-based carbon anode material according to claim 1, characterized in that, The asphalt precursor and the initiator are uniformly ground and mixed at a mass ratio of 1:0.5~5.

4. The two-step pre-oxidation synthesis method for preparing pitch-based carbon anode material according to claim 1, characterized in that, The liquid phase includes deionized water; the pre-oxidation precursor I and the oxidant are mixed in a liquid phase at a molar ratio of 1:0.5~3.

5. The two-step pre-oxidation synthesis method for preparing pitch-based carbon anode material according to claim 1, characterized in that, The washing process includes: dispersing the ground material in deionized water, stirring, filtering, washing until the washing solution is neutral, stirring for 25-35 minutes, and sonicating for 5-15 minutes.

6. A pitch-based carbon anode material, characterized in that, The pitch-based carbon anode material is prepared by the two-step pre-oxidation synthesis preparation method for pitch-based carbon anode materials as described in any one of claims 1 to 5.

7. The application of the pitch-based carbon anode material as described in claim 6 in sodium-ion battery anode materials.

Images