Asphalt-based sodium ion battery negative electrode material and preparation method thereof

Abstract

The invention provides an asphalt-based sodium ion battery negative electrode material and a preparation method thereof, and belongs to the technical field of sodium ion batteries. The asphalt-based sodium ion battery negative electrode material has a pseudo graphite layer structure and a disordered structural domain at the same time. The preparation method of the asphalt-based sodium ion battery negative electrode material comprises the following steps: S1, crushing and screening an asphalt raw material to obtain asphalt precursor powder; s2, performing combined pretreatment on the asphalt precursor powder obtained in the S1 by using air and water vapor at the same time; s3, carrying out post-treatment on the combined pre-treatment product obtained in the S2; and S4, carbonizing the post-treatment product in S3 in an inert atmosphere, and cooling to obtain the asphalt-based sodium-ion battery negative electrode material. The asphalt-based sodium ion battery negative electrode material provided by the invention combines the advantages of soft carbon and hard carbon, and has excellent sodium storage reversible capacity, high rate capability and high initial coulombic efficiency. The preparation method is simple, has controllable conditions, has no special requirements on equipment, and is suitable for industrial large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and particularly relates to a pitch-based sodium ion battery negative electrode material and a preparation method thereof. Background Art

[0002] Due to the abundant sodium resources in the earth's crust and the low cost, sodium ion batteries have become the most promising alkali metal ion batteries for commercialization after lithium ion batteries. Non-graphitized carbon materials (hard carbon, soft carbon) have a relatively ordered internal microcrystalline structure, and the layer spacing is larger than that of graphite (0.34 nm). They are the most widely studied sodium storage negative electrodes at present. Hard carbon has a lower sodium storage potential, a larger layer spacing (0.38 nm), and defects and pore structures, showing a relatively high reversible sodium storage capacity. It has become the sodium ion battery negative electrode material with the most promising application prospects. However, the sodium storage in the hard carbon plateau corresponds to the sodium ion intercalation reaction and closed pore filling. Due to the slow ion diffusion kinetics and intercalation reaction kinetics, the rate performance is poor, resulting in a lower power density of the battery and not meeting the requirements of fast charging and discharging of power batteries. Compared with hard carbon, soft carbon has graphite microcrystals and carbon layer spacing similar to those of graphite, with higher conductivity and rate performance, and is suitable for charge and discharge at high current density. However, during the preparation process of soft carbon, the π-π interaction between aromatic molecules makes the material tend to form a smaller carbon layer spacing, which limits the sodium storage capacity of soft carbon. At present, there is still a lack of negative electrode materials with excellent comprehensive performance to improve the capacity and rate performance of sodium ion batteries.

[0003] The reported anode material precursors for sodium-ion batteries mainly include biomass, resins, and minerals. However, biomass and resin precursors often have low carbon yields, high impurity contents, and difficulty in controlling batch consistency. The preparation process requires impurity removal, washing, or curing processes, which are relatively complex and restrict their large-scale application. Pitch is inexpensive, with a carbon content of approximately 82%-88%. The resulting carbon material has a high carbon yield and good conductivity, making it an excellent carbon precursor. After direct carbonization of pitch, typical soft carbon materials are obtained, which have a very low capacity (about 100 mAh / g) when used as anodes for sodium-ion batteries. To address this issue, researchers have proposed some modification methods. For example, by regulating the microstructure of the material and increasing the active sodium storage sites to improve the reversible sodium storage capacity of pitch-based soft carbon. Patent CN114430030A proposes uniformly embedding highly conductive nanomaterials inside the soft carbon to create a large number of interconnected interfacial structures between the soft carbon matrices, providing channels for the rapid diffusion of ions and electrons inside, and improving the reversible capacity and rate performance of the material. Bin Cao et al. published a paper reporting the regulation of the microstructure of mesophase pitch materials through a templating method to obtain pitch-based soft carbon with an interconnected mesoporous structure of 40-50 nm, effectively shortening the sodium ion diffusion path, facilitating the rapid transport of sodium ions at the electrode and electrolyte interface, and the interconnected porous structure inside is more conducive to the full immersion of the electrolyte. The material shows a sodium storage capacity of 331 mAh / g at a current density of 30 mA / g. When the current density increases to 500 mA / g, there is still a sodium storage capacity of 103 mAh / g. However, due to the porous structure and large specific surface area of the material, the initial Coulombic efficiency is only 45%.

[0004] In addition, researchers have proposed to polymerize and crosslink asphalt to bridge asphalt molecules and form a three-dimensional structure, thereby preventing the growth of sheet-like polycyclic aromatic molecules and preparing an asphalt-based hard carbon anode material. Zhou Ying et al. published a paper reporting that a large number of oxygen-containing functional groups were introduced into petroleum asphalt through air oxidation, triggering dehydrogenation condensation and oxidative crosslinking reactions, converting petroleum asphalt from thermoplastic to thermosetting, effectively inhibiting the inherent graphitization tendency of asphalt during high-temperature carbonization, and increasing the sodium storage capacity from 99.7 mAh / g to 276.8 mAh / g (New Carbon Materials, 2021, 36(6): 1074-1080). Raphael Janot et al. published a paper reporting the mechanism of action of asphalt pre-oxidation and pointing out the important influence of parameters such as atmosphere and pre-oxidation time on the electrochemical performance of the material (ACS Applied Energy Materials, 2020, 3, 6501-6510). Patent (CN106099109A) and patent (CN115259134A) reported the preparation of hard carbon materials by chemical crosslinking at a certain temperature using asphalt as a precursor and terephthalyl alcohol and ion exchange resin as crosslinking agents, which can be applied to sodium-ion batteries. Patent (CN116040602A) proposed using asphalt as a precursor and reacting with liquid bromine under the protection of an inert atmosphere to obtain modified asphalt, effectively preventing the orderly arrangement of asphalt molecules at high temperatures, thereby obtaining hard carbon materials. However, most of the above studies use treatment steps such as using crosslinking agents or pre-oxidation methods to hinder the growth of graphite microcrystals during the high-temperature pyrolysis of asphalt, preparing asphalt-based hard carbon to improve the sodium storage capacity, but losing the high-rate performance of soft carbon. How to improve the sodium storage reversible capacity and the first Coulomb efficiency while maintaining the high-rate performance of asphalt is an urgent problem to be solved at present.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide an asphalt-based anode material for sodium-ion batteries and a preparation method thereof to solve the above problems.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solutions:

[0008] The present invention provides an asphalt-based anode material for sodium-ion batteries, and the material simultaneously has a pseudo-graphite layer structure and a disordered domain; preferably, the material is between soft carbon and hard carbon, and its interlayer spacing is 0.35-0.38 nm.

[0009] Preferably, the material has an irregular morphology, and there are closed pores at the edges; the diameter of the closed pores is 1-5 nm; the specific surface area of the material is 1-20 m 2 / g.

[0010] Further preferably, the particle size of the material is 1 - 10 μm; the ash content is 0.01% - 0.2%, and the tap density is 1.1 - 1.3 g / cm 3 .

[0011] The pitch-based carbon material provided by the present invention combines the structural advantages of soft carbon and hard carbon, with an interlayer spacing of 0.35 nm < d 002 < 0.38 nm, between soft carbon and hard carbon, and contains a rich closed pore structure with a size of 1 - 5 nm. For use as the anode material of a sodium-ion battery, it can not only provide a plateau sodium storage capacity, but also has high conductivity and a suitable interlayer spacing to accelerate electron transport, improve the rate performance of the material, and give full play to the structural advantages of the combination of soft carbon and hard carbon to maximize the comprehensive electrochemical performance of the sodium-ion battery.

[0012] The present invention also provides a preparation method of the pitch-based sodium-ion battery anode material described above, which includes the following steps:

[0013] S1: Crushing and screening the pitch raw material to obtain pitch precursor powder;

[0014] The pitch raw material includes one or more of coal tar pitch, petroleum pitch, modified pitch, and coated pitch;

[0015] Preferably, the ash content of the pitch raw material is less than 0.1%, the sulfur content is less than 0.5%, and the softening point is 150 - 350 °C;

[0016] Further preferably, the particle size of the pitch precursor powder is 10 - 80 μm;

[0017] S2: Simultaneously using air and water vapor to perform a combined pretreatment on the pitch precursor powder obtained in S1; the combined pretreatment includes placing the pitch precursor powder in a rotary kiln and simultaneously introducing air and water vapor, and raising the temperature in the kiln from room temperature to 200 - 350 °C at a heating rate of 1 - 10 °C / min and holding for 1 - 5 h;

[0018] Preferably, based on the unit mass of the pitch precursor powder, the air flow rate used in the combined pretreatment is 5 - 50 L / h;

[0019] More preferably, based on the unit mass of the pitch precursor powder, the water vapor flow rate used in the combined pretreatment is 0.1 - 10 L / h;

[0020] S3: Performing a post-treatment on the combined pretreatment product obtained in S2; the post-treatment includes, after the combined pretreatment is completed, stopping the introduction of air and only introducing water vapor;

[0021] Preferably, based on the unit mass of the pitch precursor powder, the flow rate of the water vapor is 0.1 - 10 L / h;

[0022] Furthermore, the post-treatment further includes: heating the system temperature to 400 - 800 °C at a rate of 5 - 10 °C / min and holding for 0.1 - 3 h. The post-treatment temperature is relatively low and the reaction time is short, preventing the sample from continuously expanding pores during the reaction until the pore channels collapse;

[0023] S4: Carbonize and cool the post-treatment product of S3 under an inert atmosphere to obtain the anode material for the sodium-ion battery based on pitch. The carbonization includes: heating to 800 - 1500 °C at a rate of 1 - 10 °C / min under an inert atmosphere and holding for carbonization for 1 - 10 h;

[0024] Preferably, the inert atmosphere for the carbonization is N2 and / or Ar; the flow rate of the inert atmosphere gas is 5 - 50 L / h.

[0025] The present invention creatively adopts a combined pretreatment of air oxidation and water vapor treatment. Its mechanism of action is that first, during the air oxidation process, an appropriate amount of oxygen-containing functional groups are introduced into the pitch matrix. While appropriately increasing the cross-linking degree of the pitch, the water vapor treatment etches and creates pores on the pitch surface to form soft and hard carbon precursors. This reaction introduces a small amount of oxygen-containing functional groups into the material, effectively preventing the growth of graphite microcrystals during subsequent high-temperature carbonization, increasing the disorder degree of the material, and appropriately expanding the layer spacing of the material; furthermore, the water vapor post-treatment at a relatively low temperature makes the pore diameter of the material further larger but does not collapse. Therefore, during subsequent high-temperature carbonization, the pore structure shrinks into closed pores, providing active sodium storage sites and increasing the sodium storage capacity of the plateau. And the specific surface area of the material after carbonization is controlled within 20 m 2 / g, which is beneficial to improving the first Coulombic efficiency of the battery.

[0026] The importance of the combined pretreatment process of air oxidation combined with water vapor is that if the pitch is not subjected to the combined pretreatment but directly subjected to high-temperature carbonization, the obtained is a soft carbon material of pitch. When it is applied to the anode material of the sodium-ion battery, the sodium storage capacity is low and the first Coulombic efficiency is low; if the pitch is only subjected to air oxidation without combining with water vapor treatment, its reaction rate is low, and it is necessary to oxidize at a low temperature for a long time to make oxygen diffuse uniformly into the material interior. After high-temperature carbonization, a hard carbon based on pitch is obtained. When it is applied to the anode material of the sodium-ion battery, the sodium storage capacity is limitedly increased, but the rate performance is not good. Therefore, the combined treatment of air oxidation combined with water vapor adopted in the present invention is the key to preparing an anode material for the sodium-ion battery with excellent comprehensive properties of both soft and hard carbon.

[0027] Advantages of the present invention:

[0028] The anode material of the asphalt-based sodium-ion battery provided by the present invention, due to its special structure between soft and hard carbons, gives full play to the structural advantages of the combination of soft and hard carbons. When used as the anode material of a sodium-ion battery, the battery shows a reversible capacity of up to 280 mAh / g at a current density of 0.2C, and a reversible capacity of higher than 160 mAh / g at a large current density of 2C. In addition, due to the smaller specific surface area and fewer defects of the material, it shows an excellent first Coulombic efficiency of higher than 80%.

[0029] In the preparation process of the asphalt-based soft and hard carbon anode material of the present invention, there are no special requirements for equipment, and ordinary rotary furnace equipment can be used. The preparation conditions are simple and the efficiency is high. Using soft carbon precursor asphalt as the carbon source, without adding other chemical substances such as cross-linking agents, the construction of the comprehensive structure of asphalt soft and hard carbons is realized. The prepared carbon material has the advantages of both soft and hard carbons. The synthesis method is simple, the preparation process has excellent controllability, the production cost is low, and it is easy to realize large-scale production. Description of the Drawings

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 SEM image of the asphalt-based sodium-ion battery anode material prepared in Example 1, Figure 1 The magnification of the left figure is 100,000 times, Figure 1 The magnification of the right figure is 5,000 times;

[0032] Figure 2 TEM image of the asphalt-based sodium-ion battery anode material prepared in Example 2;

[0033] Figure 3 Specific surface area measurement diagram of the asphalt-based sodium-ion battery anode material and intermediate products prepared in Example 4;

[0034] Figure 4 Charge and discharge curve diagram of the asphalt-based sodium-ion battery anode material prepared in Example 5 at a current density of 0.2C;

[0035] Figure 5 Rate diagram of the asphalt-based sodium-ion battery anode material prepared in Example 5 at different current densities. Specific Embodiments

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0037] Example 1

[0038] In this embodiment, a negative electrode material for an asphalt-based sodium-ion battery was prepared, and the specific steps are as follows:

[0039] S1: Select petroleum asphalt with an ash content of less than 0.1%, a sulfur content of less than 0.5%, and a softening point of 180°C, crush and screen it to obtain asphalt precursor powder with a particle size of 10 - 80 μm, and weigh 1 kg of the asphalt precursor powder and put it into a crucible for standby;

[0040] S2: Transfer the crucible to a rotary furnace, and simultaneously introduce air and steam. The air flow rate is 10 L / h, and the steam flow rate is 1 L / h. Heat from room temperature to 200°C at a heating rate of 5°C / min and keep it warm for 1 h;

[0041] S3: After the reaction in S2 is completed, stop introducing air and only introduce steam with a flow rate of 1 L / h. Heat from 200°C to 500°C at a heating rate of 5°C / min and keep it warm for 1 h;

[0042] S4: After the reaction in S3 is completed, stop introducing steam and change to introducing an argon atmosphere with a gas flow rate of 10 L / h. Heat from 500°C to 1500°C at a rate of 5°C / min, keep it warm for 3 h, cool to room temperature and take out the material to obtain the negative electrode material for the asphalt-based sodium-ion battery.

[0043] Figure 1 is the SEM image of the negative electrode material for the asphalt-based sodium-ion battery prepared in this embodiment, where Figure 1 The magnification of the left figure is 100,000 times, Figure 1 The magnification of the right figure is 5,000 times; It can be seen from Figure 1 that the negative electrode material for the asphalt-based sodium-ion battery prepared in this embodiment is in the form of irregular blocks with a particle size range of 2 - 10 nm. The interlayer spacing of the asphalt-based hard and soft carbon material prepared in Example 1 is 0.371 nm, the ash content is 0.01%, and the tap density is 1.20 g / cm 3 .

[0044] Example 2

[0045] In this embodiment, a negative electrode material for an asphalt-based sodium-ion battery was prepared, and the specific steps are as follows:

[0046] S1: Select a modified asphalt with an ash content of less than 0.1%, a sulfur content of less than 0.5%, and a softening point of 230 °C. Crush and screen it to obtain an asphalt precursor powder with a particle size of 10 - 80 μm. Weigh 1 kg of the asphalt precursor powder and put it into a crucible for standby;

[0047] S2: Transfer the crucible to a rotary kiln, and simultaneously introduce air and steam. The air flow rate is 30 L / h, and the steam flow rate is 0.5 L / h. Heat from room temperature to 240 °C at a heating rate of 10 °C / min, and keep it warm for 2 h;

[0048] S3: After the reaction in S2 is completed, stop introducing air and only introduce steam with a flow rate of 0.5 L / h. Heat from 200 °C to 600 °C at a heating rate of 10 °C / min, and keep it warm for 2 h;

[0049] S4: After the reaction in S3 is completed, stop introducing steam and change to introduce an argon atmosphere with a gas flow rate of 30 L / h. Heat from 600 °C to 1300 °C at a rate of 5 °C / min, keep it warm for 3 h, cool to room temperature and take out the material to obtain an anode material for an asphalt-based sodium-ion battery.

[0050] Figure 2 The TEM image of the anode material for the asphalt-based sodium-ion battery prepared in this example shows that Figure 2 it can be seen that the structure of the anode material for the asphalt-based sodium-ion battery prepared in this example includes a pseudo-graphite layer structure and an amorphous domain, indicating that the obtained material is between soft carbon and hard carbon, and there are abundant closed pores at the edge of the material with a pore size of 3 - 5 nm. The particle size range of the asphalt-based soft and hard carbon material prepared in Example 2 is 5 - 10 nm, the interlayer spacing is 0.373 nm, the ash content is 0.01%, and the compaction density is 1.12 g / cm 3 .

[0051] Example 3

[0052] An anode material for an asphalt-based sodium-ion battery was prepared in this example, and the specific steps are as follows:

[0053] S1: Select mesophase asphalt with an ash content of less than 0.1%, a sulfur content of less than 0.5%, and softening points of 270 °C, 300 °C, and 350 °C. Mix them evenly according to a mass ratio of 1:1:1, and then crush and screen to obtain a mixed asphalt precursor powder with a particle size of 10 - 80 μm. Weigh 1 kg of the mixed asphalt precursor powder and put it into a crucible for standby;

[0054] S2: Transfer the crucible to a rotary kiln, and simultaneously introduce air and steam. The air flow rate is 20 L / h, and the steam flow rate is 1.5 L / h. Heat from room temperature to 350 °C at a heating rate of 10 °C / min, and keep it warm for 4 h;

[0055] S3: After the reaction in S2 is completed, stop introducing air and only introduce steam at a flow rate of 1.5 L / h. Heat from 350 °C to 700 °C at a heating rate of 10 °C / min and keep the temperature for 0.5 h.

[0056] S4: After the reaction in S3 is completed, stop introducing steam and change to introduce a nitrogen atmosphere with a gas flow rate of 20 L / h. Heat from 700 °C to 1100 °C at a rate of 3 °C / min, keep the temperature for 3 h, cool to room temperature and take out the material to obtain the anode material for sodium-ion batteries based on pitch.

[0057] The particle size range of the pitch-based hard and soft carbon material prepared in Example 3 is 4 - 10 nm, the interlayer spacing is 0.369 nm, the ash content is 0.01%, and the tap density is 1.11 g / cm 3 。

[0058] Example 4

[0059] In this example, an anode material for sodium-ion batteries based on pitch was prepared, and the specific steps are as follows:

[0060] S1: Select coal pitch with an ash content of less than 0.1%, a sulfur content of less than 0.5%, and a softening point of 250 °C, crush and screen it to obtain pitch precursor powder with a particle size of 10 - 80 μm, and weigh 1 kg of pitch precursor powder and put it into a crucible for standby.

[0061] S2: Transfer the crucible to a rotary kiln, and introduce air and steam at the same time. The air flow rate is 8 L / h and the steam flow rate is 5 L / h. Heat from room temperature to 300 °C at a heating rate of 10 °C / min and keep the temperature for 3 h.

[0062] S3: After the reaction in S2 is completed, stop introducing air and only introduce steam at a flow rate of 5 L / h. Heat from 300 °C to 800 °C at a heating rate of 10 °C / min and keep the temperature for 0.5 h.

[0063] S4: After the reaction in S3 is completed, stop introducing steam and change to introduce an argon atmosphere with a gas flow rate of 8 L / h. Heat from 800 °C to 900 °C at a rate of 1 °C / min, keep the temperature for 5 h, cool to room temperature and take out the material to obtain the anode material for sodium-ion batteries based on pitch.

[0064] Figure 3 This is the specific surface area measurement chart of the anode material for sodium-ion batteries based on pitch and its intermediate products prepared in this example. As Figure 3 can be seen, the specific surface area of the intermediate product obtained after treating the pitch precursor powder with air oxidation and steam in step S3 of this example is 238 m 2 / g, the pore size is 2.1 nm, and the specific surface area of the anode material for sodium-ion batteries based on pitch prepared after carbonization in step S4 is reduced to 1 m 2 / g. The particle size range of the asphalt-based hard and soft carbon materials prepared in Example 4 is 1-10 nm, the interlayer spacing is 0.363 nm, the ash content is 0.01%, and the compaction density is 1.15 g / cm 3 .

[0065] Example 5

[0066] In this example, a negative electrode material for an asphalt-based sodium-ion battery was prepared. The specific steps are as follows:

[0067] S1: Select modified asphalt with an ash content of less than 0.1%, a sulfur content of less than 0.5%, and a softening point of 270 °C, crush and screen it to obtain asphalt precursor powder with a particle size of 10-80 μm, and weigh 1 kg of asphalt precursor powder and put it into a crucible for standby;

[0068] S2: Transfer the crucible to a rotary kiln, and simultaneously introduce air and steam. The air flow rate is 35 L / h, the steam flow rate is 3 L / h, and it is heated from room temperature to 300 °C at a heating rate of 6 °C / min and held for 3.5 h;

[0069] S3: After the reaction in S2 is completed, stop introducing air and only introduce steam with a flow rate of 3 L / h, and heat from 300 °C to 600 °C at a heating rate of 6 °C / min and hold for 3.5 h;

[0070] S4: After the reaction in S3 is completed, stop introducing steam and change to an argon atmosphere with a gas flow rate of 35 L / h, heat from 600 °C to 1000 °C at a rate of 5 °C / min, hold for 3.5 h, cool to room temperature and take out the material to obtain a negative electrode material for an asphalt-based sodium-ion battery.

[0071] Figure 4 is the charge-discharge curve of the negative electrode material for the asphalt-based sodium-ion battery prepared in this example at a current density of 0.2C. From Figure 4 it can be seen that the material prepared in this example shows a reversible capacity of 280 mAh / g when applied as a negative electrode material for a sodium-ion battery, and the first Coulomb efficiency reaches 85%.

[0072] Figure 5 is the rate performance diagram of the negative electrode material for the asphalt-based sodium-ion battery prepared in this example at different current densities. Figure 5 It shows the rate performance diagrams at current densities of 0.05C, 0.1C, 0.2C, 0.5C, 0.8C, 1C, 1.2C, 1.5C, and 2C respectively. From Figure 5 it can be obtained that the negative electrode material for the asphalt-based sodium-ion battery provided in this example has excellent rate performance and cycle stability. At 2C, there is still a reversible capacity of 170 mAh / g. After the material is tested by charge and discharge at a high current density, it is tested again at a current density of 0.1C, and it can still maintain a high sodium storage capacity.

[0073] The particle size range of the asphalt-based soft and hard carbon materials prepared in Example 5 is 3 - 10 nm, the interlayer spacing is 0.375 nm, the ash content is 0.01%, and the compacted density is 1.25 g / cm 3 .

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing an asphalt-based soft carbon material. The main difference from the examples of the present invention is that no combined pretreatment of air and water vapor is carried out, and high-temperature carbonization is directly carried out. The other steps are basically the same as those of the examples of the present invention. The specific steps are as follows:

[0076] S1: Select modified asphalt with an ash content of less than 0.1%, a sulfur content of less than 0.5%, and a softening point of 270°C, crush and screen it to obtain asphalt precursor powder with a particle size of 10 - 80 μm, weigh 1 kg of asphalt precursor powder and put it into a crucible for standby;

[0077] S2: Transfer the crucible to a rotary kiln, introduce argon, with a gas flow rate of 40 L / h, heat from room temperature to 900°C at a heating rate of 2°C / min, hold for 5 h, cool to room temperature and take out the material to obtain the asphalt-based soft carbon material.

[0078] The particle size range of the asphalt-based soft carbon material prepared in Comparative Example 1 is 1 - 6 nm, the interlayer spacing is 0.343 nm, the ash content is 0.01%, and the compacted density is 0.8 g / cm 3 .

[0079] Comparative Example 2

[0080] This comparative example provides a method for preparing an asphalt-based hard carbon material. The main difference from the examples of the present invention is that a sufficient pre-oxidation reaction is carried out in an air atmosphere and then obtained through high-temperature carbonization. The other steps are basically the same as those of the examples of the present invention. The specific steps are as follows:

[0081] S1: Select coal tar pitch with an ash content of less than 0.1%, a sulfur content of less than 0.5%, and a softening point of 230°C, crush and screen it to obtain asphalt precursor powder with a particle size of 10 - 80 μm, weigh 1 kg of asphalt precursor powder and put it into a crucible for standby;

[0082] S2: Transfer the crucible to a rotary kiln, introduce air, with a gas flow rate of 50 L / h, heat from room temperature to 250°C at a heating rate of 1°C / min, and hold for 20 h;

[0083] S3: After the reaction in S2 is completed, stop introducing air and change to introducing argon, with a gas flow rate of 50 L / h, heat from 250°C to 1500°C at a heating rate of 5°C / min, hold for 5 h, cool to room temperature and take out the material to obtain the asphalt-based hard carbon material.

[0084] The particle size range of the pitch-based hard carbon material prepared in Comparative Example 2 is 2 - 10 nm, the interlayer spacing is 0.381 nm, the ash content is 0.01%, and the tap density is 0.8 g / cm 3 。

[0085] The pitch-based carbon materials prepared in Examples 1 - 5 and Comparative Examples 1 - 2 were assembled into half-cells of sodium-ion batteries, and the preparation was carried out according to the following steps:

[0086] The pitch-based carbon material was mixed with carbon black, carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 92:3:2.5:2.5 to form a slurry. Then, the slurry was evenly scraped onto the current collector copper foil. After drying, the electrode was obtained by rolling and cutting. The battery was assembled in a glove box under an argon atmosphere, using metallic sodium as the counter electrode and a 1M NaPF6 (ethylene carbonate: dimethyl carbonate volume ratio of 1:1) solution as the electrolyte, and assembled into a CR2025 coin cell. After standing for 12 h, electrochemical tests were carried out. The results are shown in Table 1 below:

[0087] Table 1 Performance test results of sodium-ion batteries assembled with carbon materials provided in Examples and Comparative Examples

[0088]

[0089]

[0090] As can be seen from Table 1, compared with the comparative examples, when the carbon materials provided in the examples of the present invention are used as the negative electrode materials of sodium-ion batteries, the initial Coulombic efficiency of the batteries at 0.1C is all 80% or more, the reversible specific capacity at 0.1C is all 200 mAh / g or more, and the reversible specific capacity at 2C can be as high as 170 mAh / g, which is significantly improved compared with the comparative examples, showing better electrical properties.

[0091] Please note that the technical features of the above examples can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. The above examples only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An anode material for an asphalt-based sodium-ion battery, characterized in that, The material simultaneously has a pseudo-graphite layer structure and a disordered domain structure.

2. The material according to claim 1, characterized in that, The material is between soft carbon and hard carbon, and its interlayer spacing is 0.35 - 0.38 nm.

3. The material according to claim 1, characterized in that, The material has an irregular morphology, and there are closed pores at the edges; Preferably, the diameter of the closed pores is 1 - 5 nm; Preferably, the specific surface area of the material is 1-20 m 2 / g.

4. A method for preparing the anode material of an asphalt-based sodium-ion battery as described in claims 1-3, characterized in that, It includes the following steps: S1: Crush and screen the asphalt raw material to obtain an asphalt precursor powder; S2: Simultaneously use air and steam to perform a combined pretreatment on the asphalt precursor powder obtained in S1; S3: Perform a post-treatment on the combined pretreatment product obtained in S2; S4: Carbonize and cool the post-treatment product in S3 under an inert atmosphere to obtain the anode material for the asphalt-based sodium-ion battery.

5. The preparation method according to claim 4, characterized in that, Step S1 satisfies one or more of the following conditions: The asphalt raw material includes one or more of coal tar pitch, petroleum pitch, modified pitch, and coated pitch; The ash content of the asphalt raw material is less than 0.1%, the sulfur content is less than 0.5%, and the softening point is 150 - 350 °C; The particle size of the asphalt precursor powder is 10 - 80 μm.

6. The preparation method according to claim 4, wherein Step S2 satisfies one or more of the following conditions: The combined pretreatment includes placing the asphalt precursor powder in a rotary kiln and simultaneously introducing air and steam, and raising the temperature in the kiln from room temperature to 200 - 350 °C at a heating rate of 1 - 10 °C / min and holding for 1 - 5 h; Based on the amount of the asphalt precursor powder as the unit mass, the air flow rate used in the combined pretreatment is 5 - 50 L / h; Based on the amount of the asphalt precursor powder as the unit mass, the steam flow rate used in the combined pretreatment is 0.1 - 10 L / h.

7. The preparation method according to claim 4, characterized in that, The post-treatment includes, after the combined pretreatment is completed, stopping the introduction of air and only introducing steam; Based on the amount of the asphalt precursor powder as the unit mass, the flow rate of the steam is 0.1 - 10 L / h.

8. The preparation method according to claim 7, characterized in that, The post-treatment further includes: raising the system temperature to 400 - 800 °C at a rate of 5 - 10 °C / min and holding for 0.1 - 3 h.

9. The preparation method according to any one of claims 4-8, characterized in that, The carbonization includes: raising the temperature to 800 - 1500 °C at a rate of 1 - 10 °C / min in an inert atmosphere and holding for carbonization for 1 - 10 h.

10. The preparation method according to claim 9, characterized in that, The inert atmosphere for the carbonization is N2 and / or Ar; Preferably, the flow rate of the inert atmosphere gas is 5 - 50 L / h.

Images