Carbon material, method for preparing the same, and use thereof

Abstract

This invention discloses a carbon material, its preparation method, and its applications. The carbon material is a spherical single particle with a sphericity of 0.89–0.98 and a powder compaction density of 0.85–1.2 g / cm³. 3 The interplanar spacing d of the (002) plane of the carbon material was determined by XRD. 002 The wavelength ranges from 0.3614 to 0.3722 nm. The carbon material preparation method provided by this invention employs an atomized spray spheroidizing process, forming molten asphalt during the top-down spraying process. The resulting spherical carbon materials exhibit higher tap density and powder compaction density than non-spherical carbon materials, which is beneficial for improving material processing performance and enhancing electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a carbon material, its preparation method, and its application. Background Technology

[0002] The rapid development of the new energy industry and the constant technological innovation have made it difficult for traditional natural and artificial graphite anode materials to adapt to new battery systems. For example, in sodium-ion battery systems, the formation energy of the compound formed by Na and graphite is positive, while that of other alkali metals is negative, indicating that Na-graphite compounds are thermodynamically unstable, resulting in graphite storing almost no sodium. Therefore, various novel carbon materials are gradually being used in battery anode materials.

[0003] The numerous micropores within hard carbon materials result in higher specific capacity, but this is also a key reason for the low compaction density and initial coulombic efficiency of hard carbon anode materials. Existing technologies typically use spray drying or ball milling to create pellets, achieving morphological advantages in the carbon material and improving performance in terms of powder compaction density or vibration density. However, ball milling has a detrimental effect on the material surface through mechanical damage, easily leading to excessive BET (Best Before Efficiency) and affecting the initial coulombic efficiency of the battery. Spray drying is a more commonly used pelletizing method, easily producing a high degree of sphericity. However, some existing technologies use biomass as a carbon source, requiring additional processes such as acid washing, alkali washing, and water washing, resulting in a long process route and high production safety risks. Furthermore, using dissolved carbohydrates such as starch for spray pelletizing also suffers from low carbon yield, low production efficiency, and high cost. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon material, its preparation method, and its applications. This carbon material has extremely high sphericity and high powder compaction density, which is beneficial for improving subsequent processing performance. Furthermore, this carbon material can be used as a negative electrode material in lithium-ion and sodium-ion battery systems, demonstrating strong applicability.

[0005] This invention is implemented as follows:

[0006] In a first aspect, the present invention provides a carbon material in the form of spherical single particles, wherein the sphericity of the carbon material is 0.89 to 0.98, and the powder compaction density of the carbon material is 0.85 to 1.2 g / cm³. 3 The interplanar spacing d of the (002) plane of the carbon material was determined by XRD. 002 The wavelength ranges from 0.3614 to 0.3722 nm.

[0007] Compared to existing carbon materials, the carbon material provided by this invention is a spherical single particle with a regular morphology, extremely high sphericity, and high powder compaction density, which is beneficial to improving subsequent processing performance and thus improving the electrochemical performance of batteries using this carbon material as a negative electrode material.

[0008] In an optional embodiment, the carbon material satisfies the following relationship: 1.1 ≤ (Dv50 / H + 2 / BET) ≤ 2, where H is the ratio of the intensity of the (002) peak near 26° to the intensity of the (101) peak near 43° on the XRD spectrum of the carbon material, Dv50 is the average particle size of the carbon material determined by laser diffraction in μm, and BET is the specific surface area in m². 2 / g, when calculating the relation, Dv50 and BET only take the values ​​of the corresponding units.

[0009] In an optional embodiment, the carbon material has an H value of 3.38–7.04, a Dv50 of 4–17 μm, and a BET of 1.2–3 μm. 2 / g.

[0010] In an optional embodiment, the compacted density of the carbon material powder is 0.85–1.1 g / cm³. 3 .

[0011] In an optional embodiment, the carbon material is hard carbon.

[0012] Secondly, the present invention also provides a method for preparing the above-mentioned carbon material, comprising the following steps:

[0013] Asphalt powder, dispersant and water are mixed to form a suspension;

[0014] At a first preset temperature, the suspension is sprayed, melted, and spheroidized using ultrasonic atomization, and then cooled; the first preset temperature is higher than the softening point of the asphalt powder.

[0015] The above preparation method can produce carbon materials with high sphericity and high compaction density, and the resulting carbon materials can be used in both lithium-ion and sodium-ion battery systems, demonstrating wide applicability. The preparation method provided by this invention uses only water as a solvent, making the process safe and environmentally friendly, with widely available raw materials and high carbon yield. Furthermore, it eliminates the need for graphitization, resulting in lower energy consumption and production costs, making it suitable for large-scale industrial production and possessing excellent prospects for widespread application.

[0016] In an optional embodiment, ultrasonic atomization spheroidization is carried out under inert gas protection, and the first preset temperature is no more than 70°C higher than the softening point of the asphalt powder.

[0017] In an optional embodiment, cooling is achieved by dropping the spray-molten spheroidized product into a coolant. The cooling step effectively prevents particle adhesion, thereby ensuring the production of carbon material particles with high sphericity.

[0018] Preferably, the coolant is water, which avoids the introduction of impurities and helps reduce production costs.

[0019] In an optional embodiment, the mass ratio of water, asphalt powder, and dispersant in the carbon material raw material is 1:(0.4-0.5):(0.01-0.1).

[0020] In an optional embodiment, the softening point of the asphalt powder is 220–280°C.

[0021] In an optional embodiment, the average particle size of the asphalt powder is 5–18 μm.

[0022] In an optional embodiment, the dispersant includes any one or a mixture of polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol, preferably polyvinylpyrrolidone.

[0023] In an optional embodiment, the method for preparing carbon materials further includes a step of carbonization after cooling.

[0024] Preferably, the carbonization process is carried out under the protection of an inert gas.

[0025] In an optional embodiment, the method for preparing carbon materials further includes a step of stabilizing the carbon material under an oxidizing atmosphere before carbonization.

[0026] Preferably, the stabilization treatment step includes: introducing air, with the mass ratio of air to material being 0.01 to 0.03 L / g·min, heating to 120 to 140°C at a rate of 8 to 12°C / min, then heating to 300 to 360°C at a rate of 1 to 2°C / min, and holding at this temperature for 2 to 5 hours to obtain powder material.

[0027] Thirdly, the present invention also provides a negative electrode sheet comprising the aforementioned carbon material.

[0028] Fourthly, the present invention also provides a lithium-ion battery comprising the aforementioned carbon material, or comprising the aforementioned negative electrode sheet.

[0029] Fifthly, the present invention also provides a sodium-ion battery comprising the aforementioned carbon material, or comprising the aforementioned negative electrode sheet.

[0030] The present invention has the following beneficial effects:

[0031] The carbon material provided by this invention consists of spherical single particles with regular morphology, extremely high sphericity, high powder compaction density, and uniform particle size distribution. This improves subsequent processing performance and thus enhances the electrochemical performance of batteries using this carbon material as the anode material. This carbon material is highly versatile and can be used in both sodium-ion and lithium-ion battery anode materials.

[0032] The carbon material preparation method provided by this invention employs an atomized spray pelletizing process. During the top-down spraying process, molten asphalt is formed, while inert gas protection and cooling in a cooling water tank prevent particle adhesion, thus producing carbon materials with high sphericity. The spherical carbon materials prepared by this method exhibit higher tap density and powder compaction density, and lower BET than non-spherical carbon materials, which is beneficial for improving material processing performance and enhancing electrochemical performance.

[0033] The carbon material preparation method provided by this invention involves a simple production process, uses only water as a solvent, and the drying process is safe and environmentally friendly. At the same time, the raw materials are widely available and the carbon yield is high. In addition, the preparation method does not require a graphitization step, requires low energy consumption, and has low preparation cost, making it suitable for large-scale industrial production.

[0034] The carbon material provided by this invention, when applied to lithium-ion or sodium-ion batteries, can impart good initial coulombic efficiency and specific capacity to lithium-ion or sodium-ion batteries, showing promising application prospects. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 Here is a SEM image of the carbon material prepared in Example 1;

[0037] Figure 2 The XRD pattern of the carbon material prepared in Example 1 is shown below.

[0038] Figure 3 Raman characterization bar chart of the carbon material prepared in Example 1;

[0039] Figure 4 This is a charge-discharge curve of the carbon material prepared in Example 3 in a lithium-ion battery system;

[0040] Figure 5 This is a charge-discharge curve of the carbon material prepared in Example 3 in a sodium-ion battery system;

[0041] Figure 6 The XRD pattern of the carbon material prepared in Example 3;

[0042] Figure 7 The XRD pattern of the carbon material prepared in Example 8;

[0043] Figure 8The image shows the XRD pattern of the carbon material prepared in Example 9. Detailed Implementation

[0044] 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0045] The carbon materials, their preparation methods, and applications provided by this invention will be described in detail below.

[0046] This invention provides a carbon material in the form of spherical single particles, wherein the sphericity of the carbon material is 0.89–0.98, and the powder compaction density of the carbon material is 0.85–1.2 g / cm³. 3 The interplanar spacing d of the (002) plane of the carbon material was determined by XRD. 002 The particle size ranges from 0.3614 to 0.3722 nm. Compared to existing secondary particles, the spherical single-particle carbon material of this invention has higher sphericity and powder compaction density, which is beneficial for improving subsequent processing performance.

[0047] For reference, the carbon material satisfies the following relationship: 1.1≤(Dv50 / H+2 / BET)≤2, where H is the ratio of the intensity of the (002) peak near 26° to the intensity of the (101) peak near 43° on the XRD spectrum of the carbon material, Dv50 is the average particle size of the carbon material determined by laser diffraction, in μm; and BET is the specific surface area, in m². 2 / g, when calculating the relationship, Dv50 and BET only take the values ​​of the corresponding units. When carbon materials satisfy the above relationship, they can be used as battery anode materials in both lithium-ion and sodium-ion batteries, and can enable the batteries to have both high capacity and high initial coulombic efficiency.

[0048] In an optional embodiment, the carbon material has an H value of 3.38–7.04, a Dv50 of 4–17 μm, and a BET of 1.2–3 μm. 2 / g. As the H value increases, the crystal structure becomes more ordered, the crystallinity increases, the number of storage sites decreases, and the battery capacity decreases with increasing H. As Dv50 decreases, the contact resistance between active materials increases, and the capacity decreases with decreasing Dv50. As BET increases, the initial coulombic efficiency decreases with increasing BET value. The H value, Dv50, and BET of the carbon material of this invention are all within an optimal parameter range, ensuring that it can impart excellent initial coulombic efficiency and capacity to the battery when used as a negative electrode material.

[0049] More preferably, the powder compaction density of the carbon material is 0.85–1.1 g / cm³. 3 Carbon materials within this compaction density range can impart better electrochemical performance to lithium-ion or sodium-ion batteries.

[0050] Furthermore, the carbon material provided by this invention is hard carbon. This invention overcomes the shortcomings of traditional hard carbon materials, such as low compaction density and low initial coulombic efficiency, and has good application prospects.

[0051] Accordingly, the present invention also provides a method for preparing the above-mentioned carbon material, comprising the following steps:

[0052] Asphalt powder, dispersant and water are mixed to form a suspension;

[0053] At a first preset temperature, the suspension is sprayed, melted, and spheroidized using ultrasonic atomization, and then cooled; the first preset temperature is higher than the softening point of the asphalt powder.

[0054] For reference, ultrasonic atomization spheroidization can be performed under inert gas protection, where the first preset temperature is no more than 70°C higher than the softening point of the asphalt powder. If the first preset temperature is too high, it will cause the asphalt to crack, resulting in irregularly shaped particles with many pores; if the first preset temperature is too low, the asphalt will not melt, also resulting in irregularly shaped particles. Poor morphological characteristics will lead to poor electrochemical performance of the battery when carbon materials are used as the negative electrode. Therefore, after repeated experiments, the first preset temperature should be set within 70°C above the softening point of the asphalt, so as to ensure that the asphalt is suspended in a molten state in the equipment cavity after melting. Due to surface tension, the molten asphalt takes on a spherical shape, and after cooling, it forms single-particle asphalt microspheres.

[0055] Furthermore, cooling can be achieved by dropping the spray-molten spheroidized product into a coolant. This cooling step effectively prevents particle agglomeration, thereby ensuring the subsequent production of highly spherical single-particle carbon material particles.

[0056] Preferably, the coolant is water, which can avoid the introduction of impurities and help reduce production costs.

[0057] Furthermore, the mass ratio of water, asphalt powder, and dispersant in the carbon material raw material is 1:(0.4~0.5):(0.01~0.1). The dispersant in the raw material participates in the final carbon material formation, playing a isolating role and effectively preventing the asphalt powder from agglomerating. Only water is used as a solvent in the raw material, eliminating the need for acid washing and other processes. The production process is safe, environmentally friendly, and low-cost, which is conducive to large-scale industrial production.

[0058] Preferably, the softening point of the asphalt powder is 220–280°C. Asphalt is widely available and inexpensive, and using it as a carbon source to prepare carbon materials has the advantages of high carbon yield and low preparation cost.

[0059] Furthermore, the average particle size of the asphalt powder is 5–18 μm. Asphalt powder can be purchased directly or obtained by crushing asphalt to a suitable particle size. Asphalt is a widely available and inexpensive primary raw material. Moreover, compared to carbohydrate carbon sources such as starch, asphalt significantly improves carbon yield when used as a carbon source for preparing carbon materials.

[0060] The dispersant includes one or more of polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol. In a preferred embodiment, the dispersant is polyvinylpyrrolidone (PVP). Although the dispersant participates in the final carbon material formation, the amount added is much smaller than that of asphalt, and the yield is also much lower. Its main function is to prevent the agglomeration of asphalt powder, and its impact on the performance of the carbon material is minimal.

[0061] Furthermore, the preparation method of carbon materials also includes a step of carbonization after cooling.

[0062] Typically, carbonization is carried out under inert gas protection. Specific steps may include: heating to 1400℃ at a rate of 5℃ / min, holding at that temperature for 2 hours, and then introducing an inert gas (nitrogen, argon, etc.) for protection.

[0063] Furthermore, the preparation method of carbon materials also includes a stabilization treatment under an oxidizing atmosphere before carbonization. The stabilization treatment can transform thermoplastic pitch microspheres into thermosetting materials, thereby ensuring that the basic morphology of the pitch microspheres remains unchanged after carbonization, and finally preparing carbon materials with good sphericity.

[0064] Preferably, the stabilization treatment step includes: introducing air at a mass ratio of air to material of 0.01–0.03 L / g·min, heating to 120–140°C at a rate of 8–12°C / min, then heating to 300–360°C at a rate of 1–2°C / min, and holding at this temperature for 2–5 hours to obtain a powder material. The specific parameters in the stabilization treatment step can be adjusted according to actual conditions, as long as it ensures that the thermoplastic asphalt microspheres are transformed into a thermosetting material.

[0065] Accordingly, the present invention also provides a negative electrode sheet comprising the aforementioned carbon material. The excellent sphericity and compaction density of the aforementioned carbon material can bring excellent electrochemical performance to the negative electrode sheet, which is beneficial for its application in batteries.

[0066] Accordingly, the present invention also provides a lithium-ion battery comprising the aforementioned carbon material, or comprising the aforementioned negative electrode sheet. This lithium-ion battery exhibits good initial coulombic efficiency and specific capacity.

[0067] Accordingly, the present invention also provides a sodium-ion battery comprising the aforementioned carbon material, or comprising the aforementioned negative electrode sheet. This sodium-ion battery exhibits good initial coulombic efficiency and specific capacity.

[0068] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0069] Example 1

[0070] This embodiment provides a carbon material, which is prepared by the following steps:

[0071] (1) The asphalt with a softening point of 220℃ is crushed into asphalt powder with a Dv50 of 12μm. Then, water, asphalt powder and dispersant PVP are mechanically stirred in a mass ratio of 1:0.4:0.08 at a stirring speed of 600rpm for 1h to obtain a uniformly dispersed suspension A.

[0072] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 260°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0073] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 300℃ at 1℃ / min, and holding for 2 hours to obtain powder material C.

[0074] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1400℃ at 5℃ / min and kept for 2 hours. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0075] Example 2

[0076] This embodiment provides a carbon material, which is prepared by the following steps:

[0077] (1) The asphalt with a softening point of 260℃ is crushed into asphalt powder with a Dv50 of 5μm. Then, water, asphalt powder and dispersant PVP are mechanically stirred in a mass ratio of 1:0.5:0.09 at a stirring speed of 600rpm for 3h to obtain a uniformly dispersed suspension A.

[0078] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 320°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0079] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 340℃ at 1℃ / min, and holding for 5 hours to obtain powder material C.

[0080] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1400℃ at 5℃ / min and kept at the temperature for 2 hours. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0081] Example 3

[0082] This embodiment provides a carbon material, which is prepared by the following steps:

[0083] (1) The asphalt with a softening point of 240℃ is crushed into asphalt powder with a Dv50 of 18μm. Then, water, asphalt powder and dispersant PVP are mechanically stirred in a mass ratio of 1:0.4:0.1 at a stirring speed of 800rpm for 3h to obtain a uniformly dispersed suspension A.

[0084] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 280°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0085] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 320℃ at 2℃ / min, and holding for 3h to obtain powder material C.

[0086] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1200℃ at 5℃ / min, and the temperature is held for 2 hours. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0087] Example 4

[0088] This embodiment provides a carbon material, which is prepared by the following steps:

[0089] (1) The asphalt with a softening point of 280℃ is crushed into asphalt powder with a Dv50 of 15μm. Then, water, asphalt powder and dispersant PVA (polyvinyl alcohol) are mechanically stirred in a mass ratio of 1:0.4:0.09 at a stirring speed of 800rpm for 2h to obtain a uniformly dispersed suspension A.

[0090] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 320°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0091] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 360℃ at 1℃ / min, and holding for 5 hours to obtain powder material C.

[0092] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1400℃ at 5℃ / min and kept at that temperature for 5h. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0093] Example 5

[0094] This embodiment provides a carbon material, which is prepared by the following steps:

[0095] (1) The asphalt with a softening point of 240℃ is crushed into asphalt powder with a Dv50 of 14μm. Then, water, asphalt powder and dispersant PEG (polyethylene glycol) are mechanically stirred in a mass ratio of 1:0.4:0.08 at a stirring speed of 600rpm for 1h to obtain a uniformly dispersed suspension A.

[0096] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 280°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0097] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 350℃ at 2℃ / min, and holding for 2 hours to obtain powder material C.

[0098] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1200℃ at 5℃ / min, and the temperature is held for 2 hours. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0099] Example 6

[0100] This embodiment provides a carbon material, which is prepared by the following steps:

[0101] (1) The asphalt with a softening point of 260℃ is crushed into asphalt powder with a Dv50 of 17μm. Then, water, asphalt powder and dispersant PVP are mechanically stirred in a mass ratio of 1:0.4:0.4 at a stirring speed of 800rpm for 3h to obtain a uniformly dispersed suspension A.

[0102] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 300°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0103] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 350℃ at 1℃ / min, and holding for 3 hours to obtain powder material C.

[0104] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1400℃ at 5℃ / min and kept for 2 hours. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0105] Example 7

[0106] This embodiment provides a carbon material, which is prepared by the following steps:

[0107] (1) The asphalt with a softening point of 220℃ is crushed into asphalt powder with a Dv50 of 11μm. Then, water, asphalt powder and dispersant PVP are mechanically stirred in a mass ratio of 1:0.4:0.01 at a stirring speed of 600rpm for 1h to obtain a uniformly dispersed suspension A.

[0108] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 260°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0109] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 300℃ at 1℃ / min, and holding for 2 hours to obtain powder material C.

[0110] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1200℃ at 5℃ / min, and the temperature is held for 2 hours. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0111] Example 8

[0112] This embodiment provides a carbon material, which is prepared by the following steps:

[0113] (1) The asphalt with a softening point of 240℃ is crushed into asphalt powder with a Dv50 of 13μm. Then, water, asphalt powder and dispersant PVP are mechanically stirred in a mass ratio of 1:0.4:0.09 at a stirring speed of 800rpm for 2h to obtain a uniformly dispersed suspension A.

[0114] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 280°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0115] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 320℃ at 1℃ / min, and holding for 3h to obtain powder material C.

[0116] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1500℃ at 5℃ / min and kept at the temperature for 2 hours. Inert gas (nitrogen, argon, etc.) is introduced for protection. After the material is cooled, carbon material is obtained.

[0117] Example 9

[0118] This embodiment provides a carbon material, which is prepared by the following steps:

[0119] (1) The asphalt with a softening point of 280℃ is crushed into asphalt powder with a Dv50 of 15μm. Then, water, asphalt powder and dispersant PVP are mechanically stirred in a mass ratio of 1:0.4:0.08 at a stirring speed of 800rpm for 3h to obtain a uniformly dispersed suspension A.

[0120] (2) The above suspension A is loaded into an ultrasonic atomizing device for spray melting and spheroidizing. The melting temperature is set to 320°C. Inert gas protection is used. The liquid is sprayed from top to bottom and melted in the air to form a spherical shape. It falls into the cooling water pool at the bottom to cool and dry, and then powder material B is obtained.

[0121] (3) Stabilize the above powder material B by introducing air, with the mass ratio of air to material being 0.02 L / g·min, heating to 130℃ at 10℃ / min, then heating to 360℃ at 1℃ / min, and holding for 4 hours to obtain powder material C.

[0122] (4) The material C is subjected to high-temperature carbonization treatment. The temperature is increased to 1000℃ at 5℃ / min and kept at the temperature for 2 hours. Inert gas is introduced for protection. After the material cools down, carbon material is obtained.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 1 is that in this comparative example, step 1, after crushing the asphalt into powder, does not involve preparing a suspension, and step 2 is omitted. The remaining preparation methods and parameters are consistent with those of Example 1.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 8 is that in this comparative example, after crushing the asphalt into powder in step 1, a suspension is not prepared, and in step 2, the powder is spheroidized using a spheroidizing machine. The remaining preparation methods and parameters are the same as in Example 8.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 1 is that the final stabilization temperature in step 3 of this comparative example is 240°C, while the rest of the preparation methods are the same as in Example 1.

[0129] Comparative Example 4

[0130] The difference between this comparative example and Example 1 is that the final stabilization temperature in step 3 of this comparative example is 380°C, while the rest of the preparation methods are the same as in Example 1.

[0131] Comparative Example 5

[0132] The difference between this comparative example and Example 1 is that the melting temperature in step 2 of this comparative example is 220°C, while the rest of the preparation method is the same as that in Example 1.

[0133] Comparative Example 6

[0134] The difference between this comparative example and Example 1 is that the melting temperature in step 2 of this comparative example is 360°C, while the rest of the preparation method is the same as that in Example 1.

[0135] Performance testing

[0136] The carbon materials prepared in Examples 1-9 and Comparative Examples 1-6 were subjected to the following tests:

[0137] (1) The particle size of the material was determined using a Malvern 3000 laser particle size analyzer;

[0138] (2) The specific surface area (BET) of the sample shall be determined in accordance with the provisions of GB / T 19587;

[0139] (3) The tap density was determined in accordance with the provisions of GB / T 24533-2019;

[0140] (4) The compacted density of the powder shall be determined in accordance with the provisions of GB / T 24533-2019;

[0141] (5) Perform sphericity statistical calculation on the samples. Randomly select no less than 20 particle samples for each sample. Use the ratio of the particle's minor axis a to its major axis b to characterize the sphericity of the sample. Sphericity Swl = a / b, Swl ≤ 1.

[0142] (6) XRD patterns of carbon material samples were scanned using a copper target X-ray diffractometer with a wavelength of 0.154056 nm and a scanning speed of approximately 4° / min. Spectral information, such as the corresponding left half-width and right half-width, was obtained using HighScore Plus analysis software. The full width at half maximum (FWHM) value was then calculated: FWHM = (left half-width + right half-width) / 2. The interlayer spacing (d) corresponding to the (002) peak was then obtained. 002 The ratio of the intensity of peak (002) to that of peak (101) near 43° is H1 / H2.

[0143] (7) The surface morphology of the carbon material sample was observed by scanning electron microscopy (SEM);

[0144] (8) Electrochemical performance tests were conducted on the lithium-ion battery system. A negative electrode sheet was prepared by slurry preparation of carbon material: conductive carbon: SBR: CMC = 93.5:2:3:1.5, followed by coating, drying, and rolling. This process was then used to prepare a CR2430 coin cell, with a lithium metal sheet as the counter electrode. The carbon material underwent initial delithiation capacity and initial coulombic efficiency tests. The coin cell was discharged to 0V at 0.05C, allowed to stand for 10 minutes, discharged to 0.005C with CV, allowed to stand for 10 minutes, and then charged to 2.5V at 0.05C to obtain the reversible specific capacity and initial coulombic efficiency.

[0145] (9) Electrochemical performance tests were conducted on the sodium-ion battery system. A negative electrode sheet was prepared by slurry preparation of carbon material: conductive carbon: CMC: SBR = 93:2.5:1.5:3, followed by coating, drying, and rolling. This process was then used to prepare a CR2430 coin cell, with a sodium metal sheet as the counter electrode. The carbon material underwent initial sodium removal capacity and initial coulombic efficiency tests. The coin cell was discharged at 0.1C to 0.005V, then discharged at 0.01C to 0V, allowed to stand for 5 minutes, and then charged at 0.1C to 2.5V to obtain the reversible specific capacity and initial coulombic efficiency.

[0146] (10) Adhering to the principle of not damaging or ablating the sample, Raman detection was performed using a laser Raman spectrometer coupled with a laser wavelength of 532 nm for micro-area analysis of carbon materials. The obtained Raman spectra were analyzed, with R = I. D / I G I D I represents the peak intensity value of peak D. G The peak intensity of peak G is given, and the Raman shift of peak D is at 1350 cm⁻¹. -1 Nearby, the Raman shift of peak G is at 1580 cm⁻¹. -1 The sample was scanned nearby, and the scanning result consisted of 400 single-point Raman spectra. The R value of the above 400 single-point laser Raman spectra was calculated by the instrument's built-in function, and the average value of the R value was obtained by statistical calculation.

[0147] The test and calculation results are shown in Tables 1, 2 and 3.

[0148] Table 1. Test data of carbon materials prepared in the examples and comparative examples.

[0149]

[0150] Table 2. Performance test data of lithium-ion and sodium-ion batteries made from carbon materials obtained in application examples and comparative examples.

[0151]

[0152] Table 3 shows the test data and calculated data of the carbon materials used in the formulas.

[0153]

[0154]

[0155] The test results of the samples obtained in Examples 1-9 and Comparative Examples 1-6 show that the H value increases with increasing carbonization temperature. When the H value increases, the crystal structure becomes more ordered, the crystallinity increases, the storage sites decrease, and the capacity decreases with increasing H. When Dv50 decreases, the contact resistance between active materials increases, and the capacity decreases with decreasing Dv50. When BET increases, the initial coulombic efficiency decreases with increasing BET value. The capacity and initial coulombic efficiency of carbon materials are affected by the combined effects of H, Dv50, and BET. When the carbon material satisfies 1.1 ≤ (Dv50 / H + 2 / BET) ≤ 2, the carbon material as a negative electrode material can be used in both lithium-ion and sodium-ion batteries, exhibiting both high capacity and high initial coulombic efficiency. The data results from Examples 1-9 show that this invention provides a carbon material with a large interlayer spacing, which can be used as a negative electrode material in both lithium-ion and sodium-ion batteries. The carbon material is a spherical single particle with high sphericity and small BET. Batteries made using this carbon material as the negative electrode material have high initial coulombic efficiency.

[0156] Please also refer to Figures 1-8 The test results of the samples obtained in Examples 1, 3, and 8-9 show that the ratio of the peak intensity of the (002) crystal plane diffraction peak to that of the (004) crystal plane diffraction peak increases with increasing carbonization temperature, indicating a more ordered crystal structure. This is beneficial for electron and ion transport, improves electrochemical reaction activity, and increases the first coulombic efficiency. The FWHM gradually decreases from 7.73° to 6.15°, the peak spacing of the (002) crystal plane diffraction peaks decreases, the half-peak width decreases, and the crystallite size of the carbon material (including La and Lc, where La represents the crystallite width or diameter spacing along the a-axis, and Lc represents the crystallite width or diameter spacing along the c-axis) increases, leading to increased crystallinity. A more regular crystal structure and higher crystallinity provide more active reaction sites, thereby improving the charge and discharge efficiency of the battery. 002 The wavelength decreased from 0.3722 nm to 0.3614 nm, which is greater than that of graphite materials. 002 (0.3354nm), the interlayer spacing is reduced, the R value is reduced from 1.154 to 0.851, the defects of carbon materials are reduced, the electron transport performance is improved, the charge transport resistance is reduced, the structural stability is improved, the capacity decay of the battery can be reduced, and the first coulombic efficiency can be improved.

[0157] By comparing the particle size data of each embodiment, it can be seen that the particle size range of Dv50 is 4.0 to 16.8 μm, while the particle size range of the raw material asphalt powder is 5 to 17 μm. It can be seen that the difference between the particle size of the raw material and the particle size of the final product is small. This shows that the preparation method has strong controllability over the particle size of the product, which is beneficial for the large-scale production of carbon materials with the required particle size.

[0158] Comparing the test results of the samples obtained in Examples 1 and 4-5, it can be seen that the choice of dispersant type has little impact on product performance, such as battery specific capacity and initial coulombic efficiency.

[0159] Comparing the test results of the samples obtained in Examples 1 and 6-7, it can be seen that the addition of a high proportion of dispersant prevents the asphalt powder from agglomerating during the asphalt melting process, thus playing an isolating role. The powder compaction density and vibration density are increased, which helps to reduce the defects generated during the asphalt melting process and reduces the specific surface area of ​​the carbon material.

[0160] Comparing the data results of Example 1 with Comparative Examples 1 and 2, it can be seen that the absence of a pelletizing process results in irregular morphology of the carbon material particles, poor sphericity, and lower powder compaction density and tap density compared to the test data of Example 1. The BET value is also higher than that of the sample in Example 1, leading to a decrease in both battery capacity and initial coulombic efficiency. Mechanical pelletizing mainly involves spheroidizing the particle surface and grinding the edges of the broken particles. The sphericity of the treated particles is worse than that of Example 1, resulting in lower powder compaction density and tap density performance compared to the test data of Example 1. Furthermore, the mechanical grinding method creates defects on the particle surface, leading to an increase in the BET value of the material. This requires more lithium ions to form the SEI film, making the material more prone to volume changes, resulting in peeling and cracking, thus reducing the initial coulombic efficiency of the battery.

[0161] A comparison of the data results from Example 1 and Comparative Example 3 shows that the stabilization treatment temperature was too low, resulting in incomplete stabilization. The spherical particles after pelletizing and melting did not completely transform from thermoplastic to thermosetting materials. During the subsequent high-temperature carbonization process, the particles adhered to each other, and the particle morphology was irregular, resulting in low sphericity of the carbon material. Furthermore, the tap density and powder compaction density were reduced, ultimately leading to poor electrochemical performance of the battery.

[0162] A comparison of the data results from Example 1 and Comparative Example 4 shows that the stabilization treatment temperature was too high, resulting in excessive oxidation and cross-linking. During the high-temperature carbonization process, excessive oxygen was released in the form of carbon monoxide and carbon dioxide, resulting in excessive carbon loss and causing more defects in the sample. The material had a high BET, and therefore the first coulombic efficiency of the obtained battery sample was low.

[0163] A comparison of the data results from Example 1 and Comparative Example 5 shows that when the set melting temperature is too low, the asphalt cannot melt and the asphalt powder cannot be melted into spherical shapes, which leads to poor sphericity of the carbon material particles. This results in low sample tap density and powder compaction density, ultimately leading to poor electrochemical performance of the battery.

[0164] The data results from Example 1 and Comparative Example 6 show that when the set melting temperature is too high, the light components of asphalt evaporate rapidly at high temperatures, the asphalt foams, and the particles produce more defects, resulting in poor sphericity. This leads to lower sample tap density and powder compaction density, as well as poor electrochemical performance.

[0165] In summary, this invention employs an atomized spray spheroidizing process to prepare carbon materials with high sphericity, which can be applied to anode materials for sodium-ion and lithium-ion batteries. The spherical carbon materials prepared by this invention exhibit higher tap density and powder compaction density, and lower specific surface area than existing carbon materials, which is beneficial for improving material processing performance and enhancing the electrochemical performance of batteries.

[0166] The production process involved in this invention is simple, using only water as a solvent. The drying process is safe and environmentally friendly, the raw materials are widely available, the carbon yield is high, graphitization is not required, the energy consumption is low, and the cost is low, making it suitable for large-scale industrial production.

[0167] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon material, characterized by, The carbon material is in the form of spherical single particles, with a sphericity of 0.89~0.98 and a powder compaction density of 0.85~1.2 g / cm³. 3 The interplanar spacing d of the (002) plane of the carbon material was determined by XRD. 002 The wavelength range is 0.3614~0.3722 nm, and the H value of the carbon material is 3.38~7.

04. H is the ratio of the intensity of the (002) peak near 26° to the intensity of the (101) peak near 43° on the XRD spectrum. The preparation method of the carbon material includes the following steps: mixing asphalt powder, dispersant and water to form a suspension; spraying and melting the suspension using ultrasonic atomization at a first preset temperature, and then cooling it; the first preset temperature is higher than the softening point of the asphalt powder; The ultrasonic atomization is carried out under inert gas protection, and the first preset temperature is no more than 70°C higher than the softening point of the asphalt powder; the cooling is achieved by dropping the sprayed molten spheroidized product into a coolant; the coolant is water; The mass ratio of water, asphalt powder, and dispersant is 1:(0.4~0.5):(0.01~0.1); the softening point of the asphalt powder is 220~280℃; the average particle size of the asphalt powder is 5~18μm; the dispersant includes any one or a mixture of polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol. The step of carbonization after cooling; The step of stabilizing the carbonized material under an oxidizing atmosphere; The stabilization process includes: introducing air at a volume-to-mass ratio of 0.01 to 0.03 L / g·min, heating to 120 to 140°C at a rate of 8 to 12°C / min, then heating to 300 to 360°C at a rate of 1 to 2°C / min, and holding at that temperature for 2 to 5 hours to obtain powdered material.

2. The carbon material of claim 1, wherein, The carbon material has a Dv50 of 4~17μm and a BET of 1.2~3μm. 2 / g, where Dv50 is the average particle size of the carbon material determined by laser diffraction, in μm; BET is the specific surface area, in m². 2 / g.

3. The carbon material according to any one of claims 1 to 2, wherein The compacted density of the carbon material powder is 0.85~1.1 g / cm³. 3 ; and / or the powder tap density of the carbon material is 0.89 to 0.98 g / cm3 3 ; And / or, the carbon material is hard carbon.

4. The carbon material of claim 1, wherein The dispersant is polyvinylpyrrolidone.

5. A negative electrode sheet characterized by comprising: Includes the carbon materials as described in any one of claims 1 to 4.

6. A battery, which is a lithium ion battery or a sodium ion battery, characterized by, The battery comprises the carbon material as described in any one of claims 1 to 4 or the negative electrode sheet as described in claim 5.

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