Pitch-based carbon materials, their preparation and use, and sodium-ion battery anode materials and sodium-ion battery anodes and use

Abstract

This invention relates to the field of electrochemical technology, and discloses a pitch-based carbon material, its preparation and application, as well as a sodium-ion battery anode material and a sodium-ion battery anode and its application. The method includes the following steps: (1) mixing pitch powder and potassium salt with a solvent to obtain a mixed slurry; (2) drying and calcining the mixed slurry at high temperature; wherein, the mass ratio of pitch powder to potassium salt in step (1) is (1-3):1. The raw materials of this method are readily available and easy to scale up industrially. The pitch-based carbon material obtained is applied in sodium-ion batteries and has high reversible capacity and first-cycle coulombic efficiency.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to a pitch-based carbon material, its preparation and application, as well as a sodium-ion battery anode material and a sodium-ion battery anode and its application. Background Technology

[0002] Existing rechargeable battery systems mainly include nickel-metal hydride batteries, lead-acid batteries, lithium-ion batteries, and polymer lithium-ion batteries. Among them, lithium-ion batteries have advantages such as high energy density, good cycle stability, and low self-discharge, and have been widely used in mobile electronics, communication equipment, electric devices, and electric vehicles. However, lithium-ion batteries still face the problem of lithium resource scarcity. Therefore, developing new high-energy-density rechargeable batteries to address resource shortages is a key research focus in the field. The application of sodium-ion batteries can not only alleviate the global lithium resource shortage and narrow the supply-demand gap, but also, the abundant sodium salt reserves and mature extraction technology together determine the lower material costs and cost fluctuation range of sodium-ion batteries.

[0003] However, the widespread application of sodium-ion batteries also faces certain challenges. Similar to lithium-ion batteries, designing and developing electrode materials capable of accommodating stable sodium ion insertion and extraction is crucial for their commercialization. In academia, various sodium-ion battery anode materials have been developed, including conversion reaction materials, alloying materials, titanium-based materials, and carbon-based materials. Carbon-based materials are abundant and widely available. Amorphous carbon-based anodes (including hard carbon and soft carbon) exhibit high reversible specific capacity and good cycle performance in sodium-ion batteries. Since their discovery, researchers have conducted extensive exploration and research on these materials. Hard carbon materials, due to their high specific capacity and low sodium storage voltage, have become the most promising anode materials for sodium-ion secondary batteries. However, the current low carbon yield of precursors for producing hard carbon leads to high costs, hindering their commercial application. Using petroleum-based products to prepare carbon-based anode materials not only offers high carbon yield and low cost but also provides a complete raw material supply chain, facilitating rapid market integration. However, the direct high-temperature carbonization of materials such as petroleum coke and asphalt yields soft carbon materials, which suffer from low specific capacity and high sodium storage voltage. Porous structure design is generally considered a reliable strategy to improve the ion transport capacity of sodium-ion batteries and increase the number of sodium storage active sites.

[0004] Therefore, the key technology is to obtain carbon-based materials with high specific capacity and low sodium storage voltage by constructing suitable pore structures. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of low specific capacity and high sodium storage voltage in existing petroleum-based carbon materials. It provides pitch-based carbon materials, their preparation and application, as well as sodium-ion battery anode materials and their applications. This method uses pitch as a carbon source, combining pitch powder with potassium salt as an activator, and employs sand milling and spray drying techniques to prepare an amorphous carbon material with a structure and properties similar to hard carbon, which is easily scaled up industrially. When the prepared pitch-based carbon material is applied to sodium-ion batteries, it exhibits high reversible capacity and first-cycle coulombic efficiency.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing pitch-based carbon materials, wherein the method includes the following steps:

[0007] (1) Mix asphalt powder and potassium salt with solvent to obtain a mixed slurry;

[0008] (2) The mixed slurry is dried and calcined at high temperature;

[0009] In step (1), the mass ratio of asphalt powder to potassium salt is (1-3):1.

[0010] The second aspect of the present invention provides a pitch-based carbon material prepared by the preparation method described in the first aspect.

[0011] The third aspect of this invention provides an application of the pitch-based carbon material described in the second aspect in a sodium-ion battery.

[0012] A fourth aspect of the present invention provides a sodium-ion battery anode material comprising the pitch-based carbon material and binder described in the second aspect.

[0013] The fifth aspect of the present invention provides a sodium-ion battery negative electrode, the negative electrode comprising a current collector and a negative electrode material coated and / or filled on the current collector, wherein the negative electrode material is the negative electrode material described in the fourth aspect of the present invention.

[0014] The sixth aspect of this invention provides the application of the sodium-ion battery negative electrode described in the fifth aspect in a sodium-ion battery.

[0015] The beneficial effects achieved through the above technical solution are as follows:

[0016] (1) In this invention, asphalt raw material is used as carbon source and potassium salt is introduced as pore-forming activator to prepare amorphous carbon material with similar structure and properties to hard carbon. The asphalt-based carbon material is applied in sodium-ion batteries and has high reversible capacity and first-cycle coulombic efficiency.

[0017] (2) In this invention, the cost of asphalt raw materials is low, the introduced potassium salt can be recycled and reused, the raw material cost is low, and the use of sand milling and spray drying technology makes it easy to scale up industrially and suitable for industrial production. Attached Figure Description

[0018] Figure 1 This is the XRD pattern of the pitch-based carbon material prepared in Example 1;

[0019] Figure 2 This is a SEM image of the pitch-based carbon material prepared in Example 1. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of this invention provides a method for preparing pitch-based carbon materials, wherein the method includes the following steps:

[0022] (1) Mix asphalt powder and potassium salt with solvent to obtain a mixed slurry;

[0023] (2) The mixed slurry is dried and calcined at high temperature;

[0024] In step (1), the mass ratio of asphalt powder to potassium salt is (1-3):1.

[0025] In this invention, asphalt raw material is used as carbon source, and potassium salt is introduced as pore-forming activator to prepare an amorphous carbon material with a structure and properties similar to hard carbon. This material is then used as the negative electrode active material in sodium-ion batteries, exhibiting high reversible capacity and first-cycle coulombic efficiency.

[0026] In this invention, the term "asphalt" has the conventional definition in the art and can be petroleum asphalt and / or coal tar pitch.

[0027] According to the present invention, preferably, the mass ratio of asphalt powder to potassium salt in step (1) is (1-3):1, for example 1:1, 1.25:1, 1.5:1, 1.75:1, 2:1, 2.25:1, 2.5:1, 3:1, or any range between the two, preferably (1.5-2.5):1. Asphalt powder and potassium salt are mixed according to the above ratio, and the potassium salt acts as a pore-forming activator combined with the asphalt raw material to prepare an asphalt-based carbon material with high reversible capacity and first-cycle coulombic efficiency. Excessive addition of potassium salt reduces the first-cycle coulombic efficiency; insufficient addition limits the activation effect.

[0028] According to the present invention, the average particle size of the asphalt powder is not particularly limited, and it is sufficient to be a powder with a uniform particle size distribution. Preferably, the average particle size of the asphalt powder is 5-15 micrometers, more preferably 8-12 micrometers. Asphalt powder with an average particle size not within the above range can be obtained by grinding and sieving to achieve an average particle size within the above range, wherein the grinding and sieving methods are conventional methods in the art. The average particle size of the asphalt powder is measured by a laser particle size analyzer.

[0029] According to the present invention, preferably, the softening point of the asphalt powder is 100-300℃, more preferably 200-300℃. In this invention, the method for testing the softening point of the asphalt is to place the asphalt raw material in a specially made test tube, heat it at a stable heating rate under a nitrogen atmosphere, and continuously probe the asphalt with a steel needle rod with a diameter of 1mm during the process. When the asphalt becomes soft and begins to adhere to the steel needle, the temperature at this point is recorded, which is the softening point of the asphalt.

[0030] According to the present invention, preferably, the mass percentage of ash in the asphalt powder is 0-0.5 wt%, more preferably 0-0.1 wt%. In the present invention, ash has the conventional meaning in the art, referring to the inorganic substances remaining after asphalt is burned or calcined. In the present invention, the mass percentage of ash in the asphalt powder is determined by the calcination method: (1) record the initial mass of the asphalt sample; (2) place the asphalt sample in a drying oven and dry it to constant weight at a constant temperature of 110℃-115℃; (3) take out the sample, place it in a calciner, bake it at a low temperature for 30 minutes, and then calcin it to constant weight at 815℃; (4) take out the sample, place it in an air cooler to cool it, and weigh the difference in mass of the sample, which is the ash content. The ratio of the ash content to the mass of the asphalt sample is recorded as the mass percentage of ash.

[0031] In this invention, asphalt-based carbon materials are prepared using asphalt powder that meets the above conditions in terms of softening point and ash content. The high softening point and low ash content of the asphalt are beneficial for improving carbon production rate and the selection of pretreatment processes.

[0032] In this invention, the source of the asphalt powder is not particularly limited; it can be commercially purchased or prepared by existing methods, as long as the asphalt powder meets the above-mentioned conditions.

[0033] According to the present invention, the type of potassium salt is not particularly limited, and it is a conventional potassium salt in the art. Preferably, the potassium salt is selected from at least one of potassium hydroxide, potassium carbonate, and potassium bicarbonate, and more preferably potassium hydroxide and / or potassium bicarbonate. In the present invention, the potassium salt can be reused through subsequent washing and recycling, achieving environmental protection and cost reduction.

[0034] According to the present invention, there is no particular limitation on the type of solvent. Those skilled in the art can choose conventional volatile organic solvents and / or inorganic solvents, as long as they can mix the asphalt powder and potassium salt evenly and can be volatilized and removed. Preferably, the solvent is ethanol and / or water. Adding the above solvent to prepare a mixed slurry allows for more uniform mixing of the asphalt powder and potassium salt during subsequent sand milling.

[0035] According to the present invention, the amount of solvent added is not particularly limited. According to a preferred embodiment of the present invention, the total mass ratio of the solvent to the asphalt powder and potassium salt is 2-30:1, for example 2:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, or any range between the two, preferably 5-15:1.

[0036] According to the present invention, preferably, step (1) further includes milling the mixed slurry, wherein the milling conditions include:

[0037] The grinding time is 2-12 hours, preferably 3-8 hours; the grinding speed is 1500-2500 r / min, preferably 1800-2200 r / min. In this invention, the grinding equipment is not particularly limited, as long as it can grind the mixed slurry uniformly; those skilled in the art can choose conventional grinding equipment.

[0038] According to the present invention, preferably, in step (2), the drying conditions include: spray drying under a protective atmosphere, with a spray pressure of 0.1-0.4 MPa, preferably 0.2-0.3 MPa, and a temperature of 100-220°C, preferably 150-200°C. In the present invention, preferably, spray drying of the mixed slurry under the above conditions can ensure the morphology of the mixed material while evaporating the solvent, preventing agglomeration, improving dispersibility, and ensuring the cycle stability of the prepared pitch-based carbon material.

[0039] In this invention, the type of protective atmosphere is not particularly limited. Those skilled in the art can choose a conventional, stable protective atmosphere, preferably selected from at least one of nitrogen, helium, argon, and neon.

[0040] According to the present invention, preferably, the conditions for high-temperature calcination include: under a protective atmosphere, a reaction temperature of 1000-1500℃, preferably 1200-1400℃, a heating rate of 2-10℃ / min, preferably 3-8℃ / min, and a reaction time of 0.5-4 hours, preferably 1-3 hours.

[0041] In this invention, the equipment used for spray drying and high-temperature calcination is not particularly limited, and those skilled in the art can make appropriate selections. According to a specific embodiment of this invention, the high-temperature calcination is carried out in a tube furnace.

[0042] In this invention, preferably, the product is allowed to cool naturally after high-temperature calcination, which helps to obtain stable pitch-based carbon materials and avoids the danger of operating the calcination equipment at high temperatures.

[0043] According to the present invention, preferably, the method further includes pulverizing, washing, and drying the product calcined at high temperature. In the present invention, the conditions for pulverizing, washing, and drying are not particularly limited, and those skilled in the art can adjust them accordingly. According to a preferred embodiment of the present invention, the product calcined at high temperature is washed with deionized water until neutral. Washing the product calcined at high temperature removes potassium salts from the product. Concentrating and drying the resulting solution allows for the recovery of potassium salts added in step (1), enabling the reuse of potassium salts.

[0044] The second aspect of the present invention provides a pitch-based carbon material prepared by the preparation method described in the first aspect.

[0045] According to the present invention, preferably, the interlayer spacing of the pitch-based carbon material is 0.36-0.4 nm, more preferably 0.36-0.38 nm. This preferred embodiment is more advantageous for improving the sodium storage capacity of the pitch-based carbon material. The interlayer spacing is the carbon interlayer spacing of the pitch-based carbon material, calculated using the Bragg equation.

[0046] Specifically, in this invention, the X-ray diffraction pattern of the pitch-based carbon material was obtained using an XRD-6000 X-ray powder diffractometer (Shimadzu, Japan). The XRD testing conditions were: Cu target, Kα rays (wavelength λ = 0.154 nm), tube voltage 40 kV, tube current 200 mA, and scanning speed 10°(2θ) / min. (Reference) Figure 1The X-ray diffraction pattern of the pitch-based carbon material shows a diffraction peak at a 2θ angle of 22.3 ± 0.5°, which corresponds to the (002) diffraction peak of the hard carbon material, proving that hard carbon material was generated in the pitch-based carbon material.

[0047] The third aspect of this invention provides an application of the pitch-based carbon material described in the second aspect in a sodium-ion battery.

[0048] According to the present invention, preferably, the application of the pitch-based carbon material in the anode material of sodium-ion batteries.

[0049] A fourth aspect of the present invention provides a sodium-ion battery anode material comprising the pitch-based carbon material and binder described in the second aspect.

[0050] In this invention, the negative electrode material made from the above-mentioned pitch-based carbon material is used in sodium-ion batteries and has high reversible capacity and first-cycle coulombic efficiency.

[0051] In this invention, the amount and type of binder for the electrode material can be selected within a wide range, and can be chosen according to conventional techniques in the art. According to a preferred embodiment of the invention, the binder is sodium alginate, which can be provided in the form of an aqueous solution. The amount of binder used is sufficient to prepare the anode material from the pitch-based carbon material; those skilled in the art can adjust this appropriately.

[0052] The fifth aspect of the present invention provides a sodium-ion battery negative electrode, the negative electrode comprising a current collector and a negative electrode material coated and / or filled on the current collector, wherein the negative electrode material is the negative electrode material described in the fourth aspect of the present invention.

[0053] The sixth aspect of this invention provides the application of the sodium-ion battery negative electrode described in the fifth aspect in a sodium-ion battery.

[0054] According to the present invention, preferably, the sodium-ion battery includes an electrode assembly and a non-aqueous electrolyte, the electrode assembly and the non-aqueous electrolyte being sealed within a battery casing, the electrode assembly including a positive electrode, a negative electrode and a separator, the separator being located between the positive electrode and the negative electrode, and the negative electrode being the negative electrode of the sodium-ion battery as described in the fifth aspect.

[0055] In this invention, the non-aqueous electrolyte refers to an electrolyte solution whose solvent is not water. Those skilled in the art can select a suitable non-aqueous electrolyte based on the composition of the sodium-ion battery, and no limitation is made here.

[0056] According to a particularly preferred embodiment of the present invention, a method for preparing an asphalt-based carbon material includes the following steps:

[0057] (1) Mix asphalt powder and potassium salt with solvent to obtain a mixed slurry;

[0058] (2) The mixed slurry is subjected to spray drying and high-temperature calcination;

[0059] In step (1), the mass ratio of asphalt powder to potassium salt is (1.5-2.5):1;

[0060] The softening point of the asphalt powder is 200-300℃;

[0061] The mass percentage of ash in the asphalt powder is 0-0.1 wt%.

[0062] The potassium salt is selected from at least one of potassium hydroxide, potassium carbonate, and potassium bicarbonate.

[0063] The total mass ratio of solvent to asphalt powder and potassium salt is 5-15:1.

[0064] The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, the room temperature is 25°C; unless otherwise specified, all reagents used are commercially available.

[0065] The microstructure of pitch-based carbon materials was observed using a scanning electron microscope.

[0066] Example 1

[0067] (1) The asphalt (high temperature petroleum asphalt, the softening point of the asphalt is 278℃, and the ash content is 0.05wt%) is crushed and sieved to obtain asphalt powder with an average particle size of 10 micrometers. The asphalt powder and KOH are mixed in a mass ratio of 2:1 and dissolved in ethanol solvent. The mass ratio of ethanol solvent to asphalt powder and KOH is 10:1. The mixture is sand-milled for 6 hours at a sand-milling speed of 2200r / min.

[0068] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 180°C.

[0069] The spray-dried product was placed in a tube furnace and heated to 1300°C at a rate of 5°C / min under a nitrogen atmosphere and held for 2 hours, then allowed to cool naturally.

[0070] (3) The material obtained in step (2) is crushed, washed with deionized water until neutral, and finally dried to obtain pitch-based carbon material.

[0071] Figure 1 The X-ray diffraction (XRD) pattern of the prepared pitch-based carbon material was obtained from... Figure 1 As can be seen, there is a broadened (002) diffraction peak at a 2θ angle of 24.0°, indicating that it has high amorphousness and large interlayer spacing, exhibiting the characteristics of hard carbon.

[0072] Figure 2 SEM images of the prepared pitch-based carbon materials, from Figure 2 As can be seen, the alkali activation treatment destroyed the original lamellar structure of the asphalt, and the sample surface became rough with obvious pores.

[0073] Example 2

[0074] (1) The asphalt (high temperature petroleum asphalt, the softening point of the asphalt is 278℃, and the ash content is 0.05wt%) is crushed and sieved to obtain asphalt powder with an average particle size of 10 micrometers. The asphalt powder and KOH are mixed in a mass ratio of 1:1 and dissolved in ethanol solvent. The mass ratio of ethanol solvent to asphalt powder and KOH is 10:1. The mixture is sand-milled for 6 hours at a sand-milling speed of 2200r / min.

[0075] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 180°C.

[0076] The spray-dried product was placed in a tube furnace and heated to 1300°C at a rate of 5°C / min under a nitrogen atmosphere and held for 2 hours, then allowed to cool naturally.

[0077] (3) The material obtained in step (2) is crushed, washed with deionized water until neutral, and finally dried to obtain pitch-based carbon material.

[0078] Example 3

[0079] (1) The asphalt (high temperature petroleum asphalt, the softening point of the asphalt is 278℃, and the ash content is 0.05wt%) was crushed and sieved to obtain asphalt powder with an average particle size of 10 micrometers. The asphalt powder and KOH were mixed in a mass ratio of 3:1 and dissolved in ethanol solvent. The mass ratio of ethanol solvent to asphalt powder and KOH was 10:1. The mixture was sand-milled for 6 hours at a sand-milling speed of 2200r / min.

[0080] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 180°C.

[0081] The spray-dried product was placed in a tube furnace and heated to 1300°C at a rate of 5°C / min under a nitrogen atmosphere and held for 2 hours, then allowed to cool naturally.

[0082] (3) The material obtained in step (2) is crushed, washed with deionized water until neutral, and finally dried to obtain pitch-based carbon material.

[0083] Example 4

[0084] (1) The asphalt (high temperature petroleum asphalt, the softening point of the asphalt is 278℃, and the ash content is 0.05wt%) is crushed and sieved to obtain asphalt powder with an average particle size of 10 micrometers. The asphalt powder and potassium carbonate are mixed in a ratio of 2:1 and dissolved in ethanol solvent. The mass ratio of ethanol solvent to asphalt powder and potassium carbonate is 10:1. The mixture is sand-milled for 6 hours at a sand-milling speed of 2200r / min.

[0085] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 180°C.

[0086] The spray-dried product was placed in a tube furnace and heated to 1300°C at a rate of 5°C / min under a nitrogen atmosphere and held for 2 hours, then allowed to cool naturally.

[0087] (3) The material obtained in step (2) is crushed, then washed with deionized water until neutral, and finally dried to obtain pitch-based carbon material.

[0088] Example 5

[0089] Following the method of Example 1, except that the softening point of the asphalt powder was 200°C and the ash content was 0.2 wt%, and other conditions were the same as in Example 1, asphalt-based carbon materials were obtained.

[0090] Example 6

[0091] The method of Example 1 is different except that in step (2), the spray-dried product is placed in a tube furnace, heated to 1500°C at a heating rate of 5°C / min under a nitrogen atmosphere and held for 2 hours, and then cooled naturally. Other conditions are the same as in Example 1 to obtain pitch-based carbon material.

[0092] Example 7

[0093] The method of Example 1 is different except that step (2) is dried by baking at a temperature of 180°C to obtain pitch-based carbon material.

[0094] Comparative Example 1

[0095] (1) The asphalt (high temperature petroleum asphalt, the softening point of the asphalt is 278℃, and the ash content is 0.05wt%) is crushed and sieved to obtain asphalt powder with an average particle size of 10 micrometers. The asphalt powder and KOH are mixed in a ratio of 2:1. The mixed powder is placed in a ball mill jar and dry-milled for 6 hours.

[0096] (2) Place the product obtained in step (1) in a tube furnace, heat it to 1300°C at a heating rate of 5°C / min under a nitrogen atmosphere and hold it for 2 hours, then let it cool naturally.

[0097] (3) The material obtained in step (1) is crushed, washed with deionized water until neutral, and finally dried to obtain pitch-based carbon material.

[0098] Comparative Example 2

[0099] (1) The asphalt (high temperature petroleum asphalt, the softening point of the asphalt is 278℃, and the ash content is 0.05wt%) is crushed and sieved to obtain asphalt powder with an average particle size of 10 micrometers.

[0100] (2) Place the asphalt powder in a tube furnace, heat it to 1300°C at a heating rate of 5°C / min under a nitrogen atmosphere and keep it at that temperature for 2 hours, and then let it cool naturally to obtain asphalt-based carbon material.

[0101] Test case

[0102] The pitch-based carbon materials obtained in the examples and comparative examples were used to prepare sodium-ion battery negative electrode sheets and assembled into batteries.

[0103] 1) Preparation of the negative electrode sheet:

[0104] The dried asphalt-based carbon materials prepared in the above examples and comparative examples were mixed with an aqueous solution of sodium alginate (adhesive, sodium alginate mass fraction of 2%) at a mass ratio of 9:1 and stirred on a magnetic stirrer for 6 hours to obtain a paste-like slurry. The obtained paste-like slurry was uniformly coated on the current collector copper foil and then dried in a vacuum drying oven at 100°C for 20 hours for later use.

[0105] 2) Battery assembly:

[0106] The dried negative electrode sheet was formed into a circular sheet with a diameter of 12 mm; and held under a pressure of 8 MPa for 30-180 seconds to obtain the negative electrode of the sodium-ion battery. Using a metallic sodium sheet as the counter electrode, glass fiber as the separator, and 1 mol / L sodium hexafluorophosphate as the electrolyte, with a solvent volume ratio of EC (ethylene carbonate):DEC (diethyl carbonate) = 1:1, a CR2032 coin cell was assembled. The entire battery assembly was completed in a glove box, thus obtaining the sodium-ion battery.

[0107] Routine battery performance testing: The LAND CT2001A charge / discharge tester from Wuhan Lanbo Electronics Co., Ltd. was used to conduct charge / discharge tests on the batteries. The charge / discharge voltage range was 0V to 2.5V. The specific capacity of the assembled sodium-ion batteries was tested at a 0.1C rate.

[0108] The performance test results of the sodium-ion batteries prepared in the examples and comparative examples are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] As can be seen from the results in Table 1, the present invention uses low-cost asphalt and potassium salt as precursor carbon sources to prepare hard carbon materials. When these materials are used as asphalt-based carbon materials in sodium-ion batteries, they exhibit high reversible capacity and first-cycle coulombic efficiency.

[0113] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a pitch-based carbon material, characterized in that, The method includes the following steps: (1) Mix asphalt powder and potassium salt with solvent to obtain a mixed slurry; (2) The mixed slurry is dried and calcined at high temperature; In step (1), the mass ratio of asphalt powder to potassium salt is (1.5-2.5):1; The softening point of the asphalt powder is 200-300℃; The ash content in the asphalt powder is 0-0.1 wt% by mass; In step (2), the drying conditions include: spray drying under a protective atmosphere, with a spray pressure of 0.2-0.3 MPa and a temperature of 150-200℃; The conditions for high-temperature calcination include: under a protective atmosphere, a reaction temperature of 1200-1400℃, a heating rate of 3-8℃ / min, and a reaction time of 1-3 hours; the average particle size of the asphalt powder is 5-15 micrometers. The total mass ratio of the solvent to the asphalt powder and potassium salt is 2-30:1; Step (1) also includes sand milling the mixed slurry.

2. The preparation method according to claim 1, wherein, The average particle size of the asphalt powder is 8-12 micrometers.

3. The preparation method according to claim 1, wherein, The potassium salt is selected from at least one of potassium hydroxide, potassium carbonate, and potassium bicarbonate.

4. The preparation method according to claim 1, wherein, The solvent is ethanol and / or water.

5. The preparation method according to claim 1, wherein, The total mass ratio of the solvent to the asphalt powder and potassium salt is 5-15:

1.

6. The preparation method according to claim 1, wherein, The protective atmosphere is selected from at least one of nitrogen, helium, argon and neon.

7. The preparation method according to claim 1, wherein, The grinding conditions include: The grinding time is 2-12 hours; the grinding speed is 1500-2500 r / min.

8. The preparation method according to claim 7, wherein, The grinding conditions include: The grinding time is 3-8 hours; the grinding speed is 1800-2200 r / min.

9. The preparation method according to claim 1, wherein, The method also includes pulverizing, washing, and drying the product calcined at high temperature.

10. A pitch-based carbon material prepared by the preparation method according to any one of claims 1-9.

11. The pitch-based carbon material according to claim 10, wherein, The interlayer spacing of the pitch-based carbon material is 0.36-0.4 nm.

12. The pitch-based carbon material according to claim 11, wherein, The interlayer spacing of the asphalt-based carbon material is 0.36-0.38 nm.

13. The application of the pitch-based carbon material according to any one of claims 10-12 in sodium-ion batteries.

14. The application according to claim 13, wherein, The application of the pitch-based carbon material in sodium-ion battery anode materials.

15. A sodium-ion battery anode material, said anode material comprising the pitch-based carbon material and binder as described in any one of claims 10-12.

16. A sodium-ion battery negative electrode, characterized in that, The negative electrode includes a current collector and a negative electrode material coated and / or filled on the current collector, wherein the negative electrode material is the negative electrode material as described in claim 15.

17. The application of the sodium-ion battery negative electrode according to claim 16 in a sodium-ion battery.

18. The application according to claim 17, wherein the sodium-ion battery comprises an electrode assembly and a non-aqueous electrolyte, the electrode assembly and the non-aqueous electrolyte being sealed within a battery casing, the electrode assembly comprising a positive electrode, a negative electrode and a separator, the separator being located between the positive electrode and the negative electrode.

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