Preparation method of asphalt-based sodium ion battery hard carbon negative electrode material

Abstract

The application discloses a preparation method of a pitch-based sodium ion battery hard carbon negative material, and comprises the following steps: S1, pretreatment: crushing and sieving pitch raw materials to obtain pitch powder; S2, raw material mixing: uniformly mixing the pitch powder, an oxygen supplier, a catalyst and a stabilizer to form a uniform raw material mixture; S3, oxidation reaction: performing oxidation reaction on the raw material mixture obtained in the step S2 to obtain oxidized pitch; S4, acid washing treatment: washing the oxidized pitch obtained in the step S3 in an acid solution, and then performing centrifugation, water washing and drying to obtain purified oxidized pitch; and S5, high-temperature sintering: performing high-temperature sintering on the purified oxidized pitch obtained in the step S4 in a protective atmosphere to obtain a high-performance hard carbon negative material. The preparation method of the pitch-based sodium ion battery hard carbon negative material is characterized by good uniformity, high sodium storage capacity and low cost.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a method for preparing a pitch-based sodium-ion battery hard carbon anode material. Background Technology

[0002] With the rapid development of the new energy storage field, sodium-ion batteries have become one of the most promising electrochemical energy storage technologies for large-scale energy storage due to their advantages such as abundant sodium resources, low cost, high safety, and excellent low-temperature performance. They have shown broad application potential in scenarios such as peak shaving in smart grids. As one of the core components of sodium-ion batteries, the structural characteristics of hard carbon anode materials, such as interlayer spacing, pore structure, and specific surface area, directly determine the electrochemical characteristics of the battery, such as energy density, rate performance, and cycle stability. These characteristics are one of the key factors restricting the large-scale application of sodium-ion batteries.

[0003] As a byproduct of petroleum or coal processing, asphalt has outstanding advantages such as high carbon content, low ash content, and low price, making it a high-quality precursor for preparing carbon-based anode materials for sodium-ion batteries.

[0004] However, using asphalt directly as a raw material for high-temperature pyrolysis and carbonization presents numerous problems. High-temperature carbonization easily leads to the formation of highly ordered graphitized structures with narrow interlayer spacing (typically <0.36 nm), resulting in high resistance to ion insertion and extraction, leading to low sodium / lithium storage capacity and poor kinetic performance. Furthermore, asphalt melts and flows during heating, easily causing agglomeration and clumping. This not only causes the raw material to stick to the equipment but also results in uneven heating and incomplete reaction during subsequent carbonization, making continuous and large-scale production difficult and significantly increasing the complexity and cost of the production process.

[0005] Currently, there are reports on the use of air oxidation to prepare pitch-based hard carbon anode materials. This method involves pre-oxidizing pitch in an air atmosphere. Through a series of reactions such as dehydrogenation condensation and oxidative crosslinking, oxygen-containing functional groups such as C=O and CO are introduced, promoting the formation of a thermosetting network structure in the pitch and effectively inhibiting the graphitization process, transforming it from an ordered soft carbon structure to a long-range disordered hard carbon structure. However, this method has significant limitations: the degree of oxidation is difficult to control precisely, often resulting in excessive surface oxidation while oxygen fails to effectively penetrate the pitch, leading to insufficient internal oxidation; simultaneously, due to the pitch's inherent difficulty in oxidation, melting and flowing phenomena are still unavoidable in subsequent processing, easily leading to agglomeration and clumping, affecting the smooth progress of subsequent processes. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a hard carbon anode material for asphalt-based sodium-ion batteries, which has the characteristics of good uniformity, high sodium storage capacity and low cost.

[0007] This invention can be achieved through the following technical solutions:

[0008] The present invention discloses a method for preparing a pitch-based sodium-ion battery hard carbon anode material, comprising the following steps:

[0009] S1. Pretreatment: The asphalt raw material is crushed and sieved to obtain asphalt powder;

[0010] S2. Raw material mixing: Mix asphalt powder, oxygen supply agent, catalyst and stabilizer evenly to form a homogeneous raw material mixture;

[0011] S3. Oxidation reaction: The raw material mixture obtained in step S2 is subjected to an oxidation reaction to obtain oxidized asphalt;

[0012] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in an acidic solution, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt;

[0013] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a protective environment to obtain a high-performance hard carbon anode material.

[0014] Further, in step S2, the oxygen-supplying agent is one or more of the following: Na2O2, CaO2, BaO2, ZnO2, KClO3, Ba(ClO3)2, KMnO4, NaMnO4, Ca(ClO)2, and NaClO; the mass ratio of the oxygen-supplying agent to the asphalt powder is 0.05-0.6:1; its function is to decompose upon heating during the oxidation reaction, releasing oxygen in situ within the bulk phase of the reaction system, allowing simultaneous oxidation of the material's interior and exterior, thus avoiding external over-oxidation and insufficient internal oxidation. The amount of oxygen-supplying agent added affects the effectiveness of this invention: too much or too little will lead to internal over-oxidation or insufficient oxidation of the asphalt.

[0015] Further, in step S2, the catalyst is one or more of the following: KOH, K2CO3, NaOH, Na2CO3, NaHCO3, Ca(OH)2, CaCO3, MgO, Mg(OH)2, MgCl2, Li2CO3, and LiCl. The mass ratio of the catalyst to the asphalt powder is 0.01-0.3:1. This catalyst is an alkali or / and the corresponding alkaline earth metal alkali and its salt, possessing both catalytic oxidation and pore-forming activation functions: metal ions can significantly reduce the activation energy of the oxidation reaction and accelerate the oxidation rate, specifically by promoting the breaking of CH bonds to form free radicals, which then rapidly react with oxygen to form cross-linked structures, laying the foundation for the subsequent formation of a rich porous structure. In addition, metal ions can break down long-chain organic components in the asphalt, generating small-molecule volatiles. After the small molecules escape, they leave vacancies and volatile pathways, thereby forming a porous structure. The catalyst has a dual function of catalytic oxidation and activation pore formation. Its addition amount needs to be strictly controlled. If the addition amount is insufficient, the oxidation reaction cannot be effectively catalyzed. If the addition amount is too large, it is easy to over-activate and destroy the carbonized skeleton structure of the pitch, affecting the performance of subsequent hard carbon materials.

[0016] Further, in step S2, the stabilizer consists of one or more of the following: carbon black, graphite powder, graphene powder, carbon nanotubes, biomass charcoal powder, and anthracite powder. All stabilizers are carbon powder, and the mass ratio of stabilizer to asphalt powder is 0.02-0.2:1. Insufficient addition will not achieve the goal of stabilizing the system; excessive addition of carbon powder additives with low sodium storage capacity will affect the final capacity of the hard carbon material. Carbon powder acts as a stabilizer in the system to suppress melting, agglomeration, and wall adhesion during the heating and oxidation of asphalt. Carbon powder itself has excellent thermal stability, does not melt or soften during heating, and can form a rigid physical barrier and three-dimensional skeleton structure between asphalt particles, spatially restricting the flow, deformation, and particle adhesion of asphalt after heating, thereby avoiding agglomeration and wall adhesion. Simultaneously, carbon powder has a high specific surface area, which can adsorb lightweight components in asphalt and stably bind them to the particle surface, reducing the free-flowing phase in the system and further improving the asphalt's resistance to melting. In addition, carbon-based materials have a significantly higher thermal conductivity than asphalt, which can quickly conduct and disperse heat, making the temperature distribution of the system more uniform and avoiding excessive melting, wall sticking and uneven oxidation caused by local overheating.

[0017] Furthermore, in step S3, the oxidation reaction atmosphere is air and / or oxygen, the oxidation reaction temperature is 200-400℃, and the oxidation reaction time is 1-5 hours. During the oxidation reaction, reasonable control of the oxidation temperature and time can achieve controllable oxidation of asphalt, avoiding excessive oxidation that leads to excessive breakage of the asphalt molecular chains and a decrease in carbon yield. During the oxidation reaction, under the action of a catalyst, the alkyl side chains in the asphalt molecules undergo oxidation, introducing oxygen-containing functional groups (C=O, CO, etc.), promoting the oxidative cross-linking of aromatic rings in the asphalt molecules, breaking the original ordered structure of the asphalt molecules, inhibiting graphitization, and transforming it from a long-range ordered soft carbon structure into a long-range disordered hard carbon structure.

[0018] Furthermore, in step S5, the protective atmosphere is nitrogen and / or argon, and the high-temperature sintering is carried out in two stages using a staged heating mode.

[0019] Furthermore, this phase of warming pattern includes phase one and phase two.

[0020] The heating rate of stage one is 0.5-10℃ / min, the holding time is 1-6h, and the holding temperature is 400-800℃. Stage one mainly removes residual volatiles and a small amount of water from the purified oxidized asphalt to achieve the initial formation of the carbon skeleton and avoid the collapse of hard carbon pores due to the rapid escape of volatiles during subsequent high-temperature sintering.

[0021] The heating rate in stage two is 0.5-5℃ / min, the holding time is 1-6h, and the holding temperature is 1100-1300℃. Stage two further graphitizes the carbonization precursor to form a disordered hard carbon structure, while regulating the graphite crystallite size, carbon interlayer spacing (0.37-0.40 nm), and pore distribution of the hard carbon, thereby improving the sodium storage performance of the hard carbon.

[0022] Further, in step S4, the acidic solution is one or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and hydrofluoric acid, with a concentration of 0.05-2.0 mol / L and an acid washing temperature of 25-80℃. In this step, the acidic solution reacts chemically with impurity molecules in the asphalt (ash in the asphalt, metal ions in the catalyst, etc.) to convert them into soluble salts, which are then thoroughly removed by centrifugation and washing with water.

[0023] Furthermore, in step S2, the mixing method is one or more of the following: ball mill mixer, high-speed mixer, double-spiral conical mixer, plow mixer, V-type mixer, and ribbon mixer. The purpose of mixing is to ensure that the components are uniformly dispersed and that there is no local clumping.

[0024] Furthermore, in step S1, the asphalt raw material is coal tar pitch and / or petroleum asphalt. The softening point of the asphalt is ≥80℃. High softening point asphalt is used because it has high aromaticity and high carbon yield, making it more suitable for preparing high-performance hard carbon materials. The sieve mesh size is ≥80 mesh to avoid excessively large particle size, which could lead to uneven mixing and insufficient oxidation, affecting process stability.

[0025] Asphalt, a typical precursor to soft carbon, directly pyrolyzes into soft carbon, which suffers from narrow interlayer spacing and low sodium storage capacity. Furthermore, during pyrolysis, it melts, agglomerates, and adheres to equipment, making continuous and large-scale production difficult. To address this problem, this invention uses...

[0026] This invention discloses a method for preparing a pitch-based sodium-ion battery hard carbon anode material, which has the following beneficial effects:

[0027] First, it exhibits excellent oxidation uniformity. By employing a self-decomposition mechanism of the oxygen-supplying agent, oxygen is released in situ within the bulk phase of the reaction system, achieving simultaneous oxidation both inside and outside the material. This effectively avoids the problems of external over-oxidation and insufficient internal oxidation, significantly improving oxidation uniformity and laying the foundation for stable subsequent performance of the material.

[0028] Secondly, it exhibits high sodium storage capacity. This invention utilizes the synergistic effect of oxidation and catalytic activation to construct a rich microporous structure in pitch-based hard carbon, providing ample space for ion storage and directly enhancing the material's sodium storage capacity. Specifically, the oxygen-supplying agent ensures sufficient oxidation within the hard carbon, preventing capacity loss due to incomplete internal oxidation; the catalyst plays a dual role: on one hand, metal ions significantly reduce the activation energy of the oxidation reaction, accelerating the oxidation rate and promoting rapid reaction between the material and oxygen to form a cross-linked structure, laying the foundation for subsequent rich pore formation; on the other hand, metal ions can break down long-chain organic components in the pitch, generating small-molecule volatiles. These small molecules, after escaping, leave vacancies and volatilization channels, further improving the pore structure.

[0029] Third, the production cost is low. This invention uses asphalt as the carbon source, which is widely available, has a high yield, and is inexpensive. This achieves high-value utilization of industrial by-products and aligns with the green and low-carbon development concept, possessing excellent economic and environmental benefits. Simultaneously, an oxygen-supplying agent fully oxidizes the asphalt, ensuring uniform penetration of the oxidation reaction into the asphalt interior. Combined with a stabilizer, a three-dimensional skeletal structure is formed between asphalt particles. This stabilizer also adsorbs lightweight components in the asphalt and stably binds them to the particle surface, reducing the free-flowing phase within the system and further enhancing the asphalt's resistance to melting. The synergistic effect of the oxygen-supplying agent and stabilizer effectively inhibits asphalt melting, preventing adhesion between asphalt particles and between asphalt and equipment, providing a strong guarantee for the smooth progress of continuous and large-scale production. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0031] The present invention discloses a method for preparing a pitch-based sodium-ion battery hard carbon anode material, comprising the following steps:

[0032] S1. Pretreatment: The asphalt raw material is crushed and sieved to obtain asphalt powder;

[0033] S2. Raw material mixing: Mix asphalt powder, oxygen supply agent, catalyst and stabilizer evenly to form a homogeneous raw material mixture;

[0034] S3. Oxidation reaction: The raw material mixture obtained in step S2 is subjected to an oxidation reaction to obtain oxidized asphalt;

[0035] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in an acidic solution, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt;

[0036] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a protective environment to obtain a high-performance hard carbon anode material.

[0037] Further, in step S2, the oxygen supply agent is one or more of Na2O2, CaO2, BaO2, ZnO2, KClO3, Ba(ClO3)2, KMnO4, NaMnO4, Ca(ClO)2, and NaClO; the mass ratio of the oxygen supply agent to the asphalt powder is 0.05-0.6:1.

[0038] Further, in step S2, the catalyst is one or more of KOH, K2CO3, NaOH, Na2CO3, NaHCO3, Ca(OH)2, CaCO3, MgO, Mg(OH)2, MgCl2, Li2CO3, and LiCl, and the mass ratio of the catalyst to the asphalt powder is 0.01-0.3:1.

[0039] Further, in step S2, the stabilizer is one or more of the following: carbon black, graphite powder, graphene powder, carbon nanotubes, biomass charcoal powder, and anthracite powder, and the mass ratio of the stabilizer to the asphalt powder is 0.02-0.2:1.

[0040] Furthermore, in step S3, the atmosphere for the oxidation reaction is air and / or oxygen, the temperature for the oxidation reaction is 200-400℃, and the time for the oxidation reaction is 1-5h.

[0041] Furthermore, in step S5, the protective atmosphere is nitrogen and / or argon, and the high-temperature sintering is carried out in two stages using a staged heating mode.

[0042] Furthermore, this phase of warming pattern includes phase one and phase two.

[0043] The heating rate in stage one is 0.5-10℃ / min, the holding time is 1-6h, and the holding temperature is 400-800℃.

[0044] The heating rate in stage two is 0.5-5℃ / min, the holding time is 1-6h, and the holding temperature is 1100-1300℃.

[0045] Further, in step S4, the acidic solution is one or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and hydrofluoric acid, the concentration of the acidic solution is 0.05-2.0 mol / L, and the acid washing temperature is 25-80℃.

[0046] Further, in step S2, the mixing method is one or more of the following: ball mill mixer, high-speed mixer, double spiral conical mixer, plow mixer, V-type mixer, and ribbon mixer.

[0047] Furthermore, in step S1, the asphalt raw material is coal tar pitch and / or petroleum asphalt; the sieve mesh size is ≥80 mesh.

[0048] Example 1

[0049] This embodiment relates to a method for preparing pitch-based sodium-ion battery hard carbon anode material, including the following steps:

[0050] S1. Pretreatment: The asphalt raw material is crushed and sieved to obtain asphalt powder. Specifically, the asphalt raw material is coal tar pitch and petroleum asphalt. The sieve mesh size is ≥80 mesh.

[0051] S2. Raw Material Mixing: The asphalt powder, oxygen supply agent, catalyst, and stabilizer are uniformly mixed to form a homogeneous raw material mixture. Specifically, the oxygen supply agent is Na2O2, CaO2, or BaO2, with a mass ratio of oxygen supply agent to asphalt powder of 0.6:1; the catalyst is KOH, K2CO3, or NaOH, with a mass ratio of catalyst to asphalt powder of 0.12:1; the stabilizer is carbon black, graphite powder, graphene powder, carbon nanotubes, or biochar powder, with a mass ratio of stabilizer to asphalt powder of 0.02:1; the mixing method is ball milling, high-speed mixing, or double-spiral conical mixing.

[0052] S3. Oxidation reaction: The raw material mixture obtained in step S2 is subjected to an oxidation reaction to obtain oxidized asphalt. Specifically, the atmosphere for the oxidation reaction is air and oxygen, the temperature for the oxidation reaction is 400℃, and the time for the oxidation reaction is 3 hours.

[0053] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in an acidic solution, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt; specifically, the acidic solution is hydrochloric acid, nitric acid, and phosphoric acid, the concentration of the acidic solution is 2.0 mol / L, and the acid washing temperature is 50℃.

[0054] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a protective atmosphere to obtain a high-performance hard carbon anode material. Specifically, the protective atmosphere is nitrogen and argon, and the high-temperature sintering is carried out in two stages using a staged heating mode. This staged heating mode includes stage one and stage two: the heating rate of stage one is 10℃ / min, the holding time is 3h, and the holding temperature is 400℃; the heating rate of stage two is 5℃ / min, the holding time is 3h, and the holding temperature is 1100℃.

[0055] Example 2

[0056] This embodiment relates to a method for preparing pitch-based sodium-ion battery hard carbon anode material, including the following steps:

[0057] S1. Pretreatment: The asphalt raw material is crushed and sieved to obtain asphalt powder. Specifically, the asphalt raw material is coal tar pitch, and the sieve mesh size is ≥80 mesh.

[0058] S2. Raw Material Mixing: The asphalt powder, oxygen supply agent, catalyst, and stabilizer are uniformly mixed to form a homogeneous raw material mixture. Specifically, the oxygen supply agent is ZnO2, KClO3, Ba(ClO3)2, Ca(ClO)2, or NaClO, with a mass ratio of oxygen supply agent to asphalt powder of 0.2:1; the catalyst is NaHCO3, Ca(OH)2, CaCO3, MgO, or Mg(OH)2, with a mass ratio of catalyst to asphalt powder of 0.01:1; the stabilizer is carbon nanotubes, biochar powder, or anthracite powder, with a mass ratio of stabilizer to asphalt powder of 0.2:1; the mixing method is V-type mixer or ribbon mixer.

[0059] S3. Oxidation reaction: The raw material mixture obtained in step S2 is subjected to an oxidation reaction to obtain oxidized asphalt. Specifically, the oxidation reaction atmosphere is air, the oxidation reaction temperature is 300℃, and the oxidation reaction time is 1 hour.

[0060] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in an acidic solution, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt; specifically, the acidic solution is phosphoric acid and sulfuric acid, the concentration of the acidic solution is 1.0 mol / L, and the acid washing temperature is 25℃.

[0061] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a protective atmosphere to obtain a high-performance hard carbon anode material. Specifically, the protective atmosphere is nitrogen, and the high-temperature sintering is carried out in two stages using a staged heating mode, which includes stage one and stage two: the heating rate of stage one is 5℃ / min, the holding time is 1h, and the holding temperature is 800℃; the heating rate of stage two is 3℃ / min, the holding time is 1h, and the holding temperature is 1300℃.

[0062] Example 3

[0063] This embodiment relates to a method for preparing pitch-based sodium-ion battery hard carbon anode material, including the following steps:

[0064] S1. Pretreatment: The asphalt raw material is crushed and sieved to obtain asphalt powder. Specifically, the asphalt raw material is petroleum asphalt, and the sieve mesh size is ≥80 mesh.

[0065] S2. Raw Material Mixing: The asphalt powder, oxygen supply agent, catalyst, and stabilizer are uniformly mixed to form a homogeneous raw material mixture. Specifically, the oxygen supply agent is Na2O2, CaO2, BaO2, KMnO4, NaMnO4, or NaClO, with a mass ratio of oxygen supply agent to asphalt powder of 0.05:1; the catalyst is KOH, K2CO3, NaOH, MgO, Mg(OH)2, MgCl2, Li2CO3, or LiCl, with a mass ratio of catalyst to asphalt powder of 0.3:1; the stabilizer is carbon black or graphite powder, with a mass ratio of stabilizer to asphalt powder of 0.1:1; the mixing method is ball mill mixing.

[0066] S3. Oxidation reaction: The raw material mixture obtained in step S2 is subjected to an oxidation reaction to obtain oxidized asphalt. Specifically, the atmosphere for the oxidation reaction is oxygen, the temperature for the oxidation reaction is 200℃, and the time for the oxidation reaction is 5 hours.

[0067] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in an acidic solution, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt; specifically, the acidic solution is hydrochloric acid and phosphoric acid, the concentration of the acidic solution is 0.05 mol / L, and the acid washing temperature is 80℃.

[0068] S5. High-Temperature Sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a protective atmosphere to obtain a high-performance hard carbon anode material. Specifically, the protective atmosphere is nitrogen and / or argon. The high-temperature sintering is carried out in two stages using a staged heating mode, which includes stage one and stage two: the heating rate of stage one is 0.5℃ / min, the holding time is 6h, and the holding temperature is 600℃; the heating rate of stage two is 0.5℃ / min, the holding time is 6h, and the holding temperature is 1200℃.

[0069] Example 4

[0070] This embodiment relates to a method for preparing pitch-based sodium-ion battery hard carbon anode material, including the following steps:

[0071] S1. Pretreatment: The asphalt raw materials are crushed and sieved to obtain asphalt powder. Specifically, the asphalt raw materials are coal tar pitch and petroleum asphalt, and the sieve mesh size is ≥80 mesh.

[0072] S2. Raw Material Mixing: The asphalt powder, oxygen supply agent, catalyst, and stabilizer are uniformly mixed to form a homogeneous raw material mixture. Specifically, the oxygen supply agent is Na2O2, CaO2, or BaO2, with a mass ratio of oxygen supply agent to asphalt powder of 0.1:1; the catalyst is KOH, K2CO3, NaOH, or Na2CO3, with a mass ratio of catalyst to asphalt powder of 0.1:1; the stabilizer is carbon black, graphite powder, or graphene powder, with a mass ratio of stabilizer to asphalt powder of 0.1:1; the mixing method is ball mill mixing.

[0073] S3. Oxidation reaction: The raw material mixture obtained in step S2 is subjected to an oxidation reaction to obtain oxidized asphalt. Specifically, the atmosphere for the oxidation reaction is air and / or oxygen, the temperature for the oxidation reaction is 300℃, and the time for the oxidation reaction is 3 hours.

[0074] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in an acidic solution, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt; specifically, the acidic solution is phosphoric acid and sulfuric acid, the concentration of the acidic solution is 0.5 mol / L, and the acid washing temperature is 60℃.

[0075] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a protective atmosphere to obtain a high-performance hard carbon anode material. Specifically, the protective atmosphere is nitrogen and argon, and the high-temperature sintering is carried out in two stages using a staged heating mode. This staged heating mode includes stage one and stage two: the heating rate of stage one is 5℃ / min, the holding time is 3h, and the holding temperature is 600℃; the heating rate of stage two is 2℃ / min, the holding time is 3h, and the holding temperature is 1200℃.

[0076] Application Example 1

[0077] This embodiment relates to a pitch-based sodium-ion battery hard carbon anode material, the preparation method of which includes the following steps:

[0078] S1. Pretreatment: Petroleum asphalt with a softening point of 150℃ is crushed and passed through a 100-mesh sieve to obtain asphalt powder of a certain fineness.

[0079] S2. Mixing: Use a ball mill to uniformly mix asphalt powder, KMnO4, NaOH, and carbon nanotubes to form a homogeneous mixture. The mass ratio of KMnO4, NaOH, carbon nanotubes to asphalt powder is 0.1:0.15:0.05:1.

[0080] S3. Oxidation reaction: The mixture obtained in step S2 is placed in a reaction vessel and oxidized at 300°C for 2 hours in an air atmosphere to obtain oxidized asphalt.

[0081] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in a 1.0 mol / L hydrochloric acid solution at 70°C, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt.

[0082] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a nitrogen atmosphere. First, the temperature is increased to 600°C at a rate of 5°C / min and held for 2 hours; then the temperature is increased to 1300°C at a rate of 2°C / min and held for 3 hours to obtain the hard carbon anode material of Application Example 1.

[0083] Comparative Example 1

[0084] This embodiment relates to a pitch-based sodium-ion battery hard carbon anode material, the preparation method of which includes the following steps:

[0085] S1. Pretreatment: Petroleum asphalt with a softening point of 150℃ is crushed and passed through a 100-mesh sieve to obtain asphalt powder of a certain fineness.

[0086] S2. Mixing: Use a ball mill to uniformly mix asphalt powder, NaOH, and carbon nanotubes to form a homogeneous mixture. The mass ratio of NaOH, carbon nanotubes, and asphalt powder is 0.1:0.05:1.

[0087] S3. Oxidation reaction: The mixture obtained in step S2 is placed in a reaction vessel and oxidized at 300°C for 2 hours in an air atmosphere to obtain oxidized asphalt.

[0088] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in a 1.0 mol / L hydrochloric acid solution at 70°C, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt.

[0089] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a nitrogen atmosphere. First, the temperature is increased to 600℃ at 5℃ / min and held for 2h; then the temperature is increased to 1300℃ at 2℃ / min and held for 3h to obtain the hard carbon anode material of Comparative Example 1.

[0090] Comparative Example 2

[0091] This embodiment relates to a pitch-based sodium-ion battery hard carbon anode material, the preparation method of which includes the following steps:

[0092] S1. Pretreatment: Petroleum asphalt with a softening point of 150℃ is crushed and passed through a 100-mesh sieve to obtain asphalt powder of a certain fineness.

[0093] S2. Mixing: The asphalt powder, KMnO4, and carbon nanotubes are uniformly mixed using a ball mill to form a homogeneous mixture. The mass ratio of KMnO4, carbon nanotubes, and asphalt powder is 0.1:0.15:1.

[0094] S3. Oxidation reaction: The mixture obtained in step S2 is placed in a reaction vessel and oxidized at 300°C for 2 hours in an air atmosphere to obtain oxidized asphalt.

[0095] S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in a 1.0 mol / L hydrochloric acid solution at 70°C, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt.

[0096] S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a nitrogen atmosphere. First, the temperature is increased to 600℃ at 5℃ / min and held for 2h; then the temperature is increased to 1300℃ at 2℃ / min and held for 3h to obtain the hard carbon anode material of Comparative Example 2.

[0097] During the oxidation process, it was observed that after oxidation, the products of Example 1, Comparative Example 1 and Comparative Example 2 all maintained a good powder structure and did not exhibit melting or adhesion. This indicates that carbon nanotubes can effectively inhibit melting, agglomeration and adhesion during the heating and oxidation of asphalt.

[0098] The true density of Application Example 1, Comparative Example 1, and Comparative Example 2 was characterized using a He gas true density test, and the pore volume of their internal pores was then calculated. The measured true densities of Application Example 1, Comparative Example 1, and Comparative Example 2 were 1.80, 1.95, and 1.92 cm³, respectively. 3 / g. The lower true density of Application Example 1 indicates a larger internal pore volume, suggesting that the activation of the catalyst and the uniform oxidation of the oxidant can significantly increase the internal pore volume of the resulting pitch-based hard carbon, thereby increasing its sodium storage space sites.

[0099] The first-cycle charge specific capacities of Application Example 1, Comparative Example 1, and Comparative Example 2 at a 0.1C rate, measured by constant current testing, were 302, 226, and 245 mAh / g, respectively, with first-cycle charge-discharge efficiencies of 91.3%, 71.5%, and 76.4%, respectively. The higher reversible capacity of Application Example 1 is attributed to its larger pore volume, which provides more sodium-storing active sites.

[0100] The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A method for preparing a pitch-based sodium-ion battery hard carbon anode material, characterized in that... Includes the following steps: S1. Pretreatment: The asphalt raw material is crushed and sieved to obtain asphalt powder; S2. Raw material mixing: Mix asphalt powder, oxygen supply agent, catalyst and stabilizer evenly to form a homogeneous raw material mixture; S3. Oxidation reaction: The raw material mixture obtained in step S2 is subjected to an oxidation reaction to obtain oxidized asphalt; S4. Acid washing treatment: The oxidized asphalt obtained in step S3 is washed in an acidic solution, followed by centrifugation, water washing, and drying to obtain purified oxidized asphalt; S5. High-temperature sintering: The purified oxidized asphalt obtained in step S4 is sintered at high temperature in a protective environment to obtain a high-performance hard carbon anode material.

2. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S2, the oxygen supply agent is one or more of the following: Na2O2, CaO2, BaO2, ZnO2, KClO3, Ba(ClO3)2, KMnO4, NaMnO4, Ca(ClO)2, and NaClO; the mass ratio of the oxygen supply agent to the asphalt powder is 0.05-0.6:

1.

3. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S2, the catalyst is one or more of KOH, K2CO3, NaOH, Na2CO3, NaHCO3, Ca(OH)2, CaCO3, MgO, Mg(OH)2, MgCl2, Li2CO3, and LiCl, and the mass ratio of the catalyst to the asphalt powder is 0.01-0.3:

1.

4. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S2, the stabilizer is one or more of the following: carbon black, graphite powder, graphene powder, carbon nanotubes, biomass charcoal powder, and anthracite powder. The mass ratio of the stabilizer to the asphalt powder is 0.02-0.2:

1.

5. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S3, the atmosphere for the oxidation reaction is air and / or oxygen, the temperature for the oxidation reaction is 200-400℃, and the time for the oxidation reaction is 1-5h.

6. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S5, the protective atmosphere is nitrogen and / or argon, and the high-temperature sintering is carried out in two stages using a staged heating mode.

7. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 6, characterized in that: This phase of warming includes two stages: Phase 1 and Phase 2. The heating rate in stage one is 0.5-10℃ / min, the holding time is 1-6h, and the holding temperature is 400-800℃. The heating rate in stage two is 0.5-5℃ / min, the holding time is 1-6h, and the holding temperature is 1100-1300℃.

8. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S4, the acidic solution is one or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and hydrofluoric acid, the concentration of the acidic solution is 0.05-2.0 mol / L, and the acid washing temperature is 25-80℃.

9. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S2, the mixing method is one or more of the following: ball mill mixer, high-speed mixer, double spiral conical mixer, plow mixer, V-type mixer, and ribbon mixer.

10. The method for preparing the pitch-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S1, the asphalt raw material is coal tar pitch and / or petroleum asphalt, and the sieve mesh size is ≥80 mesh.