Asphalt-based hard carbon material as well as preparation method and application thereof

Abstract

The invention relates to an asphalt-based hard carbon material preparation method, which comprises: S1, mixing asphalt and a sulfur source, and carrying out vulcanization treatment in a first gas atmosphere to obtain a primary material; s2, performing oxidation treatment on the primary material obtained in the step S1 in a second gas atmosphere to obtain a secondary material; and S3, performing carbonization treatment on the secondary material obtained in the step S2 in a third gas atmosphere to obtain the asphalt-based hard carbon material, wherein in the step S1, the first gas is inert gas. The preparation method of the asphalt-based hard carbon material, provided by the invention, has the advantages of simple process flow, relatively low cost and high process adaptability, and is beneficial to realization of industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a pitch-based hard carbon material and a preparation method and application thereof. Background Art

[0002] Since the "dual carbon" goal was proposed, the low-carbon trend of global energy and industrial development has been formed. Therefore, in order to reduce CO2 emissions and achieve the goal of carbon neutrality, the use of clean energy is of great significance. Lithium-ion batteries have gradually become the focus of people's attention due to their high energy density, long cycle life, low cost and low environmental pollution. However, the small reserves and uneven distribution of lithium resources have limited the further development of lithium-ion batteries. Therefore, people have focused their research on sodium-ion batteries, which were developed at the same time as lithium-ion batteries.

[0003] Sodium ion battery is a secondary battery that uses sodium ions as metal ion carriers and has a similar working principle to lithium ion batteries. It has the advantages of abundant reserves, low price, high safety, excellent high and low temperature performance, and compatibility with existing lithium battery equipment. Since sodium ions cannot form stable intercalation compounds with graphite, people have focused on amorphous carbon materials with a low degree of graphitization.

[0004] Hard carbon materials have the advantages of large carbon layer spacing, good conductivity, and high sodium storage capacity, but their precursors are expensive and not suitable for large-scale production. Asphalt has high output, low cost, and high carbon yield, and is a high-quality precursor for preparing carbon materials for the negative electrode of sodium-ion batteries, but its carbon material exhibits soft carbon properties and has the disadvantage of low sodium storage capacity. Therefore, how to modify asphalt so that its carbon material exhibits a hard carbon structure and further improves its sodium storage capacity is an important issue worthy of study. At this stage, researchers mainly use furfural as a cross-linking agent and concentrated sulfuric acid as a catalyst to prepare asphalt-based hard carbon materials, but the preparation process is cumbersome, time-consuming, and has low safety. There are many uncontrollable factors, and it is impossible to maintain a stable material output.

[0005] Therefore, there is an urgent need for further breakthroughs, optimization of production processes, and improvement of the sodium storage capacity of asphalt-based hard carbon materials to achieve high-value utilization of asphalt and large-scale preparation of asphalt-based hard carbon materials. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a pitch-based hard carbon material and a preparation method thereof. The preparation method is not only simple and easy to implement, has high process adaptability, and is conducive to industrial production; it is also low in cost, significantly reducing the preparation cost of the pitch-based hard carbon material; and greatly improving the sodium storage capacity of the pitch-based hard carbon material.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a pitch-based hard carbon material, comprising the following steps:

[0009] S1: Mixing asphalt and a sulfur source, and performing a sulfurization treatment under a first gas atmosphere to obtain a primary material;

[0010] S2: Under a second gas atmosphere, oxidizing the primary material obtained in step S1 to obtain a secondary material;

[0011] S3: Carbonizing the secondary material obtained in step S2 under a third gas atmosphere to obtain the asphalt-based hard carbon material;

[0012] Wherein, in step S1, the first gas is an inert gas.

[0013] Preferably, in step S1, the asphalt includes at least one of coal tar asphalt, petroleum asphalt, coal liquefaction asphalt, ethylene tar asphalt, and natural asphalt.

[0014] Preferably, in step S1, the sulfur source includes at least one of elemental sulfur and thiourea.

[0015] Preferably, in step S1, the mass ratio of the asphalt to the sulfur source is (1:0.1)-(1:10).

[0016] Preferably, in step S1, the inert gas includes at least one of argon, helium and nitrogen.

[0017] Preferably, in step S1, the temperature of the vulcanization treatment is 100°C-500°C, and the holding time is 0.5h-24h.

[0018] Preferably, in step S1, the temperature rise rate of the vulcanization treatment is 0.1°C / min-10°C / min.

[0019] Preferably, in step S2, the second gas includes air.

[0020] Preferably, in step S2, the temperature of the oxidation treatment is 200°C-600°C, and the holding time is 0.5h-24h.

[0021] Preferably, in step S2, the heating rate of the oxidation treatment is 0.1°C / min-10°C / min.

[0022] Preferably, in step S3, the third gas is an inert gas, and the inert gas includes at least one of argon, helium and nitrogen.

[0023] Preferably, in step S3, the temperature of the carbonization treatment is 1200° C.-1800° C., and the holding time is 0.5 h-24 h.

[0024] Preferably, in step S3, the heating rate of the carbonization treatment is 0.1°C / min-10°C / min.

[0025] Preferably, in step S1, the mixing further includes crushing and grinding.

[0026] Preferably, the step S2 further comprises crushing and grinding the primary material.

[0027] Preferably, the step S3 further comprises crushing and grinding the secondary material.

[0028] Preferably, step S1 is performed under closed conditions.

[0029] In a second aspect, the present invention provides a pitch-based hard carbon material, which is prepared by the method for preparing a pitch-based hard carbon material provided by the first aspect of the present invention.

[0030] In a third aspect, the present invention provides a negative electrode plate, wherein the negative electrode plate comprises the asphalt-based hard carbon material provided in the second aspect of the present invention.

[0031] In a fourth aspect, the present invention provides a sodium ion battery, comprising the negative electrode sheet provided in the third aspect of the present invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The preparation method of the asphalt-based hard carbon material provided by the present invention has a simple process flow, low cost, and high process adaptability, which is conducive to industrial production.

[0034] (2) The present invention provides a method for preparing asphalt-based hard carbon materials. By optimizing asphalt precursors, sulfur sources, sulfurization / oxidation / carbonization heating rates, sulfurization / oxidation / carbonization temperatures, sulfurization / oxidation / carbonization times, and the ratio of asphalt precursors to sulfur sources, and coordinating pre- and post-treatments, asphalt-based hard carbon materials are obtained. When used as negative electrodes for sodium ion batteries, the reversible specific capacity and rate performance are significantly improved when charged and discharged between 0-2.5V compared to untreated asphalt-based hard carbon materials. In a specific embodiment, a reversible specific capacity of more than 320mAh / g can be obtained, which exhibits excellent sodium storage capacity and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a rate performance test chart of the asphalt-based hard carbon material prepared in Examples 1-6 and the carbon material prepared in Comparative Examples 1-2. DETAILED DESCRIPTION

[0036] In order to make the technical solutions and beneficial effects of the present invention more clearly understandable, the following is a detailed description by listing specific embodiments. The drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of the local features; unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which the present invention belongs.

[0037] In the following description, a large number of specific details are given to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described; that is, all features of actual embodiments are not described here, and well-known functions and steps are not described in detail.

[0038] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0039] In order to fully understand the present invention, detailed steps and detailed structures will be proposed in the following description to illustrate the technical solution of the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0040] Unless otherwise defined, technical and scientific terms used herein have the same meanings as those in the technical field to which the invention belongs.

[0041] If no specific techniques or conditions are specified in the following examples, the conventional techniques or conditions described in the literature in the art, or the conditions recommended by the product instructions and the manufacturer are generally used. The numerical ranges in the following examples all include the endpoint values.

[0042] [Method for preparing pitch-based hard carbon material]

[0043] In a first aspect, the present invention provides a method for preparing a pitch-based hard carbon material, comprising the following steps:

[0044] S1: Mixing asphalt and a sulfur source, and performing a sulfurization treatment under a first gas atmosphere to obtain a primary material;

[0045] S2: Under a second gas atmosphere, oxidizing the primary material obtained in step S1 to obtain a secondary material;

[0046] S3: Carbonizing the secondary material obtained in step S2 under a third gas atmosphere to obtain the asphalt-based hard carbon material;

[0047] Wherein, in step S1, the first gas is an inert gas.

[0048] The preparation method of the asphalt-based hard carbon material provided by the present invention can prepare an asphalt-based hard carbon material with excellent electrochemical properties by controlling the gas atmosphere and reaction conditions of the three steps of vulcanization treatment, oxidation treatment and carbonization treatment. In the vulcanization treatment step, by introducing a sulfur source, it is embedded in the material structure in the form of a sulfur-containing functional group; in terms of electrical properties, the introduction of the sulfur source can increase the sodium storage capacity and improve the rate of the material; in terms of materials, vulcanization can promote the cross-linking reaction between asphalt molecules, making it less likely to rearrange the carbon layer and easier to form a hard carbon structure. In the oxidation treatment step, by controlling the degree of oxidation, the surface functional groups and oxidation state of the material can be adjusted to further optimize the electrochemical activity of the material. The carbonization treatment step is the key to forming a hard carbon material. Through high-temperature carbonization treatment, a hard carbon material with a high specific surface area and good sodium storage performance can be obtained.

[0049] In certain embodiments, in step S1, the asphalt includes at least one of coal tar asphalt, petroleum asphalt, coal liquefaction asphalt, ethylene tar asphalt, and natural asphalt.

[0050] In certain embodiments, in step S1, the sulfur source includes at least one of elemental sulfur and thiourea.

[0051] In certain embodiments, in step S1, the mass ratio of the asphalt to the sulfur source is (1:0.1)-(1:10).

[0052] In certain embodiments, in step S1, the mass ratio of the asphalt to the sulfur source is (1:0.5)-(1:8), for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.5, 1:2.0, 1:2.5, 1:3.0, 1:3.01, 1:3.02, 1:3.03, 1:3.04, 1:3.05, 1:3.55, 1:4.0, 1:5.0, 1:6.0, 1:7.0 or 1:8.0, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] In certain embodiments, in step S1, the inert gas includes at least one of argon, helium, and nitrogen.

[0054] In certain embodiments, in step S1, the temperature of the sulfurization treatment is 100°C-500°C, and the holding time is 0.5h-24h.

[0055] In certain embodiments, in step S2, the temperature of the oxidation treatment is 200°C-500°C, for example, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, or 500°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; the holding time of the oxidation treatment is 4h-18h, for example, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h or 18h, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0056] In certain embodiments, in step S1, the temperature rise rate of the vulcanization treatment is 0.1°C / min-10°C / min.

[0057] In certain embodiments, in step S1, the heating rate of the vulcanization treatment is 0.5°C / min-5°C / min, for example, 0.5°C / min, 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] In some embodiments, in step S2, the second gas includes air.

[0059] In certain embodiments, in step S2, the oxidation treatment is carried out at a temperature of 200°C-600°C and a holding time of 0.5h-24h.

[0060] In certain embodiments, in step S2, the temperature of the oxidation treatment is 200°C-500°C, for example, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, or 500°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; the holding time of the oxidation treatment is 2h-10h, for example, 2h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] In certain embodiments, in step S2, the heating rate of the oxidation treatment is 0.1°C / min-10°C / min.

[0062] In certain embodiments, in step S2, the heating rate of the oxidation treatment is 1°C / min-7°C / min, for example, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min or 7°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] In some embodiments, in step S3, the third gas is an inert gas, and the inert gas includes at least one of argon, helium, and nitrogen.

[0064] In certain embodiments, in step S3, the temperature of the carbonization treatment is 1200° C.-1800° C., and the holding time is 0.5 h-24 h.

[0065] In certain embodiments, in step S3, the temperature of the carbonization treatment is 1200°C-1700°C, for example, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C or 1700°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; the holding time of the carbonization treatment is 3h-18h, for example, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h or 18h, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0066] In certain embodiments, in step S3, the heating rate of the carbonization treatment is 0.1°C / min-10°C / min.

[0067] In certain embodiments, in step S3, the heating rate of the carbonization treatment is 1°C / min-9°C / min, for example, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min or 9°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] In certain embodiments, in step S1, the mixing further comprises crushing and grinding.

[0069] In certain embodiments, the step S2 further includes crushing and grinding the primary material.

[0070] In some embodiments, the step S3 further includes crushing and grinding the secondary material.

[0071] In certain embodiments, step S1 is performed under closed conditions.

[0072] [Pitch-based hard carbon materials]

[0073] In a second aspect, the present invention provides a pitch-based hard carbon material, which is prepared by the method for preparing a pitch-based hard carbon material provided by the first aspect of the present invention.

[0074] It should be understood that since the asphalt-based hard carbon material provided by the present invention is prepared according to the preparation method of the asphalt-based hard carbon material provided by the first aspect of the present invention, the beneficial effects of preparing the asphalt-based hard carbon material in any of the above-mentioned embodiments are applicable to the asphalt-based hard carbon material.

[0075] [Negative electrode]

[0076] In a third aspect, the present invention provides a negative electrode plate, wherein the negative electrode plate comprises the asphalt-based hard carbon material provided in the second aspect of the present invention.

[0077] The negative electrode plate of the present invention may also include a conductive agent and a binder. There is no particular restriction on the types of the conductive agent and the binder in the negative electrode plate, as long as the purpose of the present invention can be achieved. For example, the binder may include but is not limited to polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin or nylon. For example, the conductive agent may include but is not limited to: conductive carbon black, acetylene black, Ketjen black, carbon fiber or any combination thereof.

[0078] There is no particular limitation on the method for preparing the negative electrode sheet in the present invention, and any preparation method known in the art may be used as long as the purpose of the present invention can be achieved.

[0079] It should be understood that since the negative electrode plate provided by the present invention includes the asphalt-based hard carbon material described in the second aspect of the present invention, the beneficial effects of preparing the asphalt-based hard carbon material described in any of the above embodiments are applicable to the negative electrode plate.

[0080] [Sodium-ion battery]

[0081] In a fourth aspect, the present invention provides a sodium ion battery, comprising the negative electrode sheet provided in the third aspect of the present invention.

[0082] The battery structure of the present invention may also include but is not limited to button batteries, soft-pack batteries, cylindrical batteries, etc.

[0083] The sodium ion battery of the present invention may also include a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. There is no particular restriction on the positive electrode sheet, the separator and the electrolyte in the sodium ion battery, and those skilled in the art can select according to actual needs, as long as the purpose of the present invention can be achieved. For example, the separator is a polypropylene separator (PP), a polyethylene separator (PE), a polypropylene / polyethylene double-layer composite film (PP / PE), a polypropylene / polyethylene / polypropylene three-layer composite film (PP / PE / PP), a polyimide electrospinning separator (PI), a cellulose non-woven separator, a polyethylene terephthalate non-woven separator (PET) and a separator with a ceramic coating.

[0084] The reagents, instruments or materials used in the present invention can be obtained through commercial channels.

[0085] The method of the present invention is described below by means of specific examples. It should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in routine experiments.

[0086] Example 1

[0087] (1) Weigh 3 g of coal tar pitch and petroleum pitch mixed powder and 10 g of elemental sulfur powder, grind and mix them evenly. In a nitrogen atmosphere, put the mixed materials into a stainless steel sealed kettle, heat it to 350°C at 4°C / min, and keep it at this temperature for 5 hours to obtain a primary material.

[0088] (2) The primary material is crushed and ground, and the temperature is increased to 400° C. at a rate of 2° C. / min in an air atmosphere, and maintained at the constant temperature for 6 h to obtain a secondary material.

[0089] (3) The secondary material was crushed and ground, and the temperature was increased to 1600°C at 7°C / min under an argon atmosphere and kept at the constant temperature for 18 hours to obtain a pitch-based hard carbon material.

[0090] Example 2

[0091] (1) Weigh 2 g of a mixed powder of ethylene tar pitch and coal liquefaction pitch and 14 g of thiourea powder, grind and evenly mix the two. In an argon atmosphere, place the mixed materials in a stainless steel sealed kettle, heat the mixture to 250°C at a rate of 2°C / min, and maintain the temperature for 8 hours to obtain a primary material.

[0092] (2) The primary material is crushed and ground, and the temperature is increased to 450° C. at a rate of 7° C. / min in an air atmosphere, and maintained at the temperature for 10 h to obtain a secondary material.

[0093] (3) The secondary material was crushed and ground, and the temperature was increased to 1200°C at 2°C / min under a nitrogen atmosphere and kept constant for 4 hours to obtain a pitch-based hard carbon material.

[0094] Example 3

[0095] (1) Weigh 10 g of natural asphalt powder, 8 g of thiourea and elemental sulfur powder, grind and mix them evenly. In a helium atmosphere, put the mixed materials into a stainless steel sealed kettle, heat it to 500°C at a rate of 0.5°C / min, and keep the temperature constant for 18 hours to obtain a primary material.

[0096] (2) The primary material is crushed and ground, and the temperature is increased to 500° C. at a rate of 6° C. / min in an air atmosphere, and maintained at the constant temperature for 4 h to obtain a secondary material.

[0097] (3) The secondary material is crushed and ground, and the temperature is increased to 1700°C at a rate of 5°C / min in a helium atmosphere and maintained at this temperature for 15 hours to obtain a pitch-based hard carbon material.

[0098] Example 4

[0099] (1) Weigh 5 g of a mixed powder of petroleum asphalt and ethylene tar asphalt and 4 g of elemental sulfur powder, grind and evenly mix the two. In a nitrogen atmosphere, place the mixed materials in a stainless steel sealed kettle, heat the kettle at 2°C / min to 400°C, and keep the temperature constant for 10 hours to obtain a primary material.

[0100] (2) The primary material is crushed and ground, and the temperature is increased to 300° C. at a rate of 4° C. / min in an air atmosphere, and maintained at the constant temperature for 6 h to obtain a secondary material.

[0101] (3) The secondary material was crushed and ground, and the temperature was increased to 1500°C at a rate of 9°C / min under an argon atmosphere and kept constant for 3 hours to obtain a pitch-based hard carbon material.

[0102] Example 5

[0103] (1) Weigh 3 g of natural asphalt and coal liquefaction asphalt mixed powder and 3 g of elemental sulfur powder, grind and evenly mix the two. Under argon atmosphere, put the mixed materials into a stainless steel sealed kettle, heat it to 200°C at 3°C / min, and keep it at this temperature for 4 hours to obtain the primary material.

[0104] (2) The primary material is crushed and ground, and the temperature is increased to 250° C. at a rate of 6° C. / min in an air atmosphere, and maintained at the temperature for 2 h to obtain a secondary material.

[0105] (3) The secondary material is heated to 1400°C at a rate of 3°C / min in a nitrogen atmosphere and maintained at this temperature for 6 hours to obtain a pitch-based hard carbon material.

[0106] Example 6

[0107] (1) Weigh 4 g of coal tar pitch and coal liquefaction pitch mixed powder and 30 g of elemental sulfur and thiourea powder, grind and evenly mix the two. Under nitrogen atmosphere, put the mixed materials into a stainless steel sealed kettle, heat it to 350°C at 5°C / min, and keep it at this temperature for 9 hours to obtain the primary material.

[0108] (2) The primary material is crushed and ground, and the temperature is increased to 300° C. at a rate of 5° C. / min in an air atmosphere, and maintained at the constant temperature for 5 h to obtain a secondary material.

[0109] (3) The secondary material was heated to 1600°C at a rate of 7°C / min under an argon atmosphere and kept at this temperature for 7 hours to obtain a pitch-based hard carbon material.

[0110] Comparative Example 1

[0111] 2 g of the mixed powder of ethylene tar pitch and coal liquefaction pitch was weighed and ground, and then heated to 1200° C. at 2° C. / min in a nitrogen atmosphere and kept at the constant temperature for 4 h to obtain a carbon material.

[0112] Comparative Example 2

[0113] 10 g of natural asphalt powder was weighed and ground, and then heated to 1700° C. at 5° C. / min in a helium atmosphere and kept at this temperature for 15 h to obtain a carbon material.

[0114] Performance Test:

[0115] The asphalt-based hard carbon materials provided in Examples 1 to 6 of the present invention and the carbon materials provided in Comparative Examples 1-2 were used as active material materials for negative electrode plates of sodium ion batteries and assembled into button batteries for rate performance testing.

[0116] The rate performance test method is as follows: 1) first stand for 5 minutes; 2) first discharge at a current density of 25mA / g, discharge to 0V; 3) jump to start charging, charge to 2.5V, this is one circle, and cycle 10 times; 4) stand for 5 minutes; 5) the same process is changed to different current densities of 50mA / g, 125mA / g, 0.25A / g, 0.5A / g, 1.25A / g, 2.5A / g, 25mA / g; 6) finally, after the test is completed with a current density of 25mA / g, the test process ends.

[0117] The results are shown in Table 1.

[0118] Table 1 Rate performance test results

[0119]

[0120]

[0121] As can be seen from Table 1, Examples 1-6 show good sodium storage capacity, rate performance and cycle stability compared to Comparative Examples 1-2. Among them, the result of Example 6 shows the best sodium storage capacity, rate performance and cycle stability.

[0122] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes may be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present invention and do not limit the scope of protection of the patent of the present invention.

Claims

1. A method for preparing a pitch-based hard carbon material, characterized in that: The following steps are involved: S1: Mixing asphalt and a sulfur source, and performing a sulfurization treatment under a first gas atmosphere to obtain a primary material; S2: Under a second gas atmosphere, oxidizing the primary material obtained in step S1 to obtain a secondary material; S3: Carbonizing the secondary material obtained in step S2 under a third gas atmosphere to obtain the asphalt-based hard carbon material; Wherein, in step S1, the first gas is an inert gas.

2. The method for preparing a pitch-based hard carbon material according to claim 1, characterized in that: In the step S1, the asphalt includes at least one of coal tar asphalt, petroleum asphalt, coal liquefaction asphalt, ethylene tar asphalt, and natural asphalt; the sulfur source includes at least one of elemental sulfur and thiourea; and the mass ratio of the asphalt to the sulfur source is (1:0.1)-(1:10).

3. The method for preparing a pitch-based hard carbon material according to claim 1, characterized in that: In the step S1, the inert gas includes at least one of argon, helium and nitrogen; the temperature of the vulcanization treatment is 100°C-500°C, and the holding time is 0.5h-24h; the heating rate of the vulcanization treatment is 0.1°C / min-10°C / min.

4. The method for preparing a pitch-based hard carbon material according to claim 1, characterized in that: In step S2, the second gas includes air; the temperature of the oxidation treatment is 200°C-600°C, and the holding time is 0.5h-24h; the heating rate of the oxidation treatment is 0.1°C / min-10°C / min.

5. The method for preparing a pitch-based hard carbon material according to claim 1, characterized in that: In step S3, the third gas is an inert gas, and the inert gas includes at least one of argon, helium, and nitrogen; the temperature of the carbonization treatment is 1200°C-1800°C, and the insulation time is 0.5h-24h; the heating rate of the carbonization treatment is 0.1°C / min-10°C / min.

6. The method for preparing a pitch-based hard carbon material according to claim 1, characterized in that: In the step S1, the mixing further comprises crushing and grinding; The step S2 further includes crushing and grinding the primary material; The step S3 also includes crushing and grinding the secondary material.

7. The method for preparing a pitch-based hard carbon material according to claim 1, characterized in that: The step S1 is performed under closed conditions.

8. A pitch-based hard carbon material, characterized in that: The asphalt-based hard carbon material is prepared by the method for preparing the asphalt-based hard carbon material according to any one of claims 1 to 7.

9. A negative electrode plate, characterized in that: The negative electrode plate includes the pitch-based hard carbon material according to claim 8.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the negative electrode sheet according to claim 9.

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