A phosphorus-doped coal-tar pitch-based hard carbon material, its preparation method and application

Abstract

The present invention belongs to the technical field of sodium-ion batteries, and particularly relates to a phosphorus-doped coal-tar pitch-based hard carbon material, a preparation method thereof, and an application thereof. The preparation method of the hard carbon material comprises the following steps: mixing coal-tar pitch with yeast, grinding, and performing carbonization to obtain the phosphorus-doped coal-tar pitch-based hard carbon material. The preparation method has the characteristics of simplicity, economy, and environmental friendliness. In the present invention, yeast is used as a phosphorus source, and in-situ phosphidation by yeast is utilized to inhibit graphitization during the carbonization of coal-tar pitch. At the same time, uniform doping of phosphorus is achieved during the carbonization of yeast, inhibiting the growth of coal-tar pitch carbon microcrystals during high-temperature carbonization. In addition, phosphorus atoms improve the surface defects and oxygen functional groups of the material, which can effectively improve the sodium storage capacity and cycle stability, expand the interlayer spacing, and promote the rapid and efficient transfer of sodium ions. The phosphorus-doped coal-tar pitch-based hard carbon material can be used for preparing sodium-ion batteries and has important application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium-ion batteries, and particularly relates to a phosphorus-doped coal-tar pitch-based hard carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] Disclosing the information of this background art section is intended to enhance the understanding of the overall background of the present invention, and it is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] With the growth of the world's population and the development of the economy, the demand for energy in today's society is increasing day by day, and the excessive consumption and exploitation of fossil fuels have caused the continuous deterioration of the ecological environment. Countries around the world have been increasing the development and utilization of renewable energy such as solar energy and wind energy. However, due to the intermittency and instability of renewable energy, it has become increasingly urgent to develop an efficient and economical energy storage and conversion system. Lithium-ion batteries with graphite as the negative electrode material have been widely used in various fields of people's lives, especially in the field of portable electronic devices, due to their high energy density and long cycle life. However, the rapid development of electronic devices and electric vehicles has further increased the social energy demand and also put forward higher requirements for the energy storage system. Lithium-ion batteries are about to reach the limit of their energy density. Therefore, sodium-ion batteries with a mechanism similar to that of lithium-ion batteries but relatively richer lithium source reserves are expected to become one of the most promising next-generation electrochemical energy storage systems.

[0004] The lack of high-capacity negative electrode materials has hindered the further development of sodium-ion batteries. Commercial graphite is used as the commercial negative electrode material for lithium-ion batteries, but it is difficult to form sodium-graphite intercalation compounds for sodium-ion batteries. Substances such as coal-tar pitch and polycyclic aromatic hydrocarbons are good carbon material precursors due to their high carbon yield induced by benzene rings. However, coal-tar pitch is prone to graphitization during the heat treatment process, and the prepared carbon materials exhibit the bottleneck problem of low sodium storage specific capacity. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the first object of the present invention is to provide a preparation method of a phosphorus-doped coal-tar pitch-based hard carbon material. The present invention uses yeast in-situ phosphorization to achieve uniform doping of phosphorus during the carbonization process, and inhibits the growth of coal-tar pitch carbon microcrystals during the high-temperature carbonization process. The preparation method has the characteristics of simplicity, economy, and environmental protection.

[0006] The second object of the present invention is to provide the phosphorus-doped coal-tar pitch-based hard carbon material prepared by the above method. The phosphorus-doped coal-tar pitch-based hard carbon material has a high specific capacity and good cycle stability.

[0007] The third object of the present invention is to provide an application of the above-mentioned phosphorus-doped coal-tar pitch-based hard carbon material. The phosphorus-doped coal-tar pitch-based hard carbon material has good electrochemical properties and can be used for preparing sodium-ion batteries.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A preparation method of a phosphorus-doped coal-tar pitch-based hard carbon material, the preparation method comprising the following steps: mixing coal-tar pitch with yeast, grinding, and performing carbonization to obtain the phosphorus-doped coal-tar pitch-based hard carbon material.

[0010] Further, the preparation method of the yeast comprises the following steps: adding dry yeast powder into deionized water, culturing, and centrifuging to obtain the yeast.

[0011] Further, the Angel high-activity dry yeast powder is purchased from a supermarket.

[0012] Further, the mass-volume ratio of the dry yeast powder to the deionized water is 5 g:(50 - 100) mL.

[0013] Further, the temperature of the culturing is (25 - 35)°C, and the time is (12 - 24) h.

[0014] Further, the volume ratio of the coal-tar pitch to the yeast is 1:(1 - 5).

[0015] Preferably, the volume ratio of the coal-tar pitch to the yeast is 1:(2 - 5).

[0016] Further, the source of the coal-tar pitch is lignite, bituminous coal, anthracite, etc.

[0017] Further, the carbonization is carried out in an inert atmosphere, the temperature is (900 - 1500)°C, the time is (1 - 4) h, and the heating rate is (3 - 10)°C / min.

[0018] Preferably, the temperature is (900 - 1200)°C, the time is 2 h, and the heating rate is 5°C / min.

[0019] Further, the inert atmosphere is nitrogen.

[0020] The present invention provides a preparation method of a phosphorus-doped coal-tar pitch-based hard carbon material. The present invention utilizes in-situ phosphorization of yeast to achieve uniform doping of phosphorus during the carbonization process. By introducing heteroatoms, the development of coal-tar pitch carbon microcrystals during the high-temperature carbonization process is inhibited. When applied to the negative electrode of a sodium-ion battery, it has a high specific capacity and has the characteristics of simplicity, economy, and environmental protection.

[0021] The phosphorus-doped coal tar pitch-based hard carbon material prepared by the above method, wherein the phosphorus doping uses the phosphorus source provided by yeast. The phosphorus-doped coal tar pitch-based hard carbon material is a composite, which includes coal tar pitch-based hard carbon and yeast biomass carbon. Among them, in-situ phosphating occurs on the yeast matrix, and phosphorus in the phosphorus-doped coal tar pitch matrix forms a bond with the matrix in the form of P-C.

[0022] Application of the above phosphorus-doped coal tar pitch-based hard carbon material, the phosphorus-doped coal tar pitch-based hard carbon material can be used to prepare a sodium-ion battery, and the negative electrode of the sodium-ion battery includes the above phosphorus-doped coal tar pitch-based hard carbon material.

[0023] Further, the preparation method of the negative electrode adopts the following steps:

[0024] ①. Mix the phosphorus-doped coal tar pitch-based hard carbon material, a conductive agent and a binder, add a solvent to obtain a slurry;

[0025] ②. Coat the slurry obtained in step ① on a metal foil and perform vacuum drying to obtain the negative electrode.

[0026] Further, in step ①, the mass ratio of the phosphorus-doped coal tar pitch-based hard carbon material, the conductive agent and the binder is (7-8):(0.5-1.5):(0.5-1.5).

[0027] Preferably, the mass ratio of the phosphorus-doped coal tar pitch-based hard carbon material, the conductive agent and the binder is 8:1:1.

[0028] Further, the conductive agent is carbon black, conductive graphite, carbon nanotube, graphene, Ketjen black, acetylene black or Super P, etc.

[0029] Further, the conductive agent is acetylene black.

[0030] Further, the binder is polyvinylidene fluoride (PVDF), styrene-butadiene rubber latex (SBR) or carboxymethyl cellulose (CMC), etc.

[0031] Further, the binder is PVDF.

[0032] Further, the solvent is 1-methyl-2-pyrrolidone solution or water, etc.

[0033] Further, the solvent is 1-methyl-2-pyrrolidone solution.

[0034] Further, in step ②, the metal foil is copper foil or aluminum foil, etc.;

[0035] The temperature of the vacuum drying is (50 - 60) °C, and the time is (6 - 24) h. In this step, the solvent in the slurry is removed by vacuum drying, thereby forming an electrode sheet containing phosphorus-doped coal tar pitch-based hard carbon material on the copper foil surface.

[0036] Preferably, the temperature of the vacuum drying is 60 °C, and the time is 6 h.

[0037] Furthermore, the sodium-ion battery further includes a separator, a positive electrode, and an electrolyte.

[0038] Furthermore, the separator is a glass fiber or a polypropylene microporous membrane, etc.

[0039] Preferably, the separator is a glass fiber.

[0040] Furthermore, the electrolyte is a sodium hexafluorophosphate (NaPF 6 ) solution or a sodium perchlorate solution, etc.

[0041] Preferably, the electrolyte is a sodium hexafluorophosphate solution.

[0042] Furthermore, the positive electrode material is sodium metal, etc.

[0043] Furthermore, the voltage window range of the sodium-ion battery is (0.01–3) V.

[0044] Beneficial effects: (1) The present invention provides a preparation method of a phosphorus-doped coal tar pitch-based hard carbon material. The present invention uses yeast for in-situ phosphorization to achieve uniform doping of phosphorus during the carbonization process. By introducing heteroatoms, the development of coal tar pitch carbon microcrystals during high-temperature carbonization is inhibited, and it has a high specific capacity when applied to the negative electrode of a sodium-ion battery. The phosphorus source for preparing the phosphorus-doped coal tar pitch-based hard carbon material in the present invention is yeast, which is a cheap, abundant, and easy-to-culture microorganism, with the characteristics of simplicity, economy, and environmental protection.

[0045] (2) For the phosphorus-doped coal tar pitch-based hard carbon material prepared by the present invention, phosphorus forms a bond with the matrix in the form of P-C. Phosphorus doping can improve defects and oxygen functional groups, increase the sodium storage capacity, enhance the cycle stability, and can also increase the interlayer spacing and promote fast and efficient electron transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings.

[0047] Figure 1 XRD pattern of the phosphorus-doped coal tar pitch-based hard carbon material prepared in Example 1;

[0048] Figure 2 SEM image of the phosphorus-doped coal tar pitch-based hard carbon material prepared in Example 1;

[0049] Figure 3 Cycling capacity diagrams of the batteries prepared in Example 1, Example 3 and Comparative Example 1. Specific embodiments

[0051] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0052] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be obtained through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in the conventional manner in the art or according to the product instructions. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described in the present invention are only for demonstration purposes. The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0053] Example 1

[0054] 1. Preparation of phosphorus-doped coal tar pitch-based hard carbon material:

[0055] (1) Cultivation of yeast: 5 g of Angel high-activity dry yeast powder was added to 100 mL of deionized water in a petri dish and cultured at 35 °C for 24 h. The yeast was centrifuged and dried for later use;

[0056] (2) Preparation of phosphorus-doped coal tar pitch-based hard carbon material: The coal tar pitch was mixed with the yeast cultured in step (1) at a volume ratio of 1:2, ground with alcohol for 1 h, and then the mixed solid powder was placed in a porcelain boat and placed in a tubular furnace. Carbonization was carried out at 1200 °C under a nitrogen atmosphere protection, and kept at this temperature for 2 h, and the heating rate was 5 °C / min to obtain the phosphorus-doped coal tar pitch-based hard carbon material. The coal tar pitch used was sourced from anthracite.

[0057] 2. Preparation of sodium-ion battery:

[0058] (1) The phosphorus-doped coal tar pitch-based hard carbon material prepared in step 1, acetylene black and the binder PVDF were put into a mortar and ground at a mass ratio of 8:1:1. Subsequently, 1-methyl-2-pyrrolidone solution was added until the powder became a black viscous slurry for later use;

[0059] (2) Use a 100-μm doctor blade to evenly coat the slurry obtained in step (1) on a copper foil, then vacuum dry the copper foil at 60 °C for 6 h, and finally stamp it into a circular electrode sheet with a diameter of 12 mm. The electrode sheet is the negative electrode of the sodium-ion battery.

[0060] (3) Use the electrode sheet obtained in step (2) as the negative electrode, sodium metal as the positive electrode, glass fiber as the separator, and 1 mol / L NaPF 6 solution as the electrolyte, with a voltage range of (0.01 - 3) V to prepare a sodium-ion battery.

[0061] Example 2

[0062] 1. Preparation of phosphorus-doped coal-tar pitch-based hard carbon material:

[0063] (1) Cultivation of yeast: The same as step (1) in step 1 of Example 1;

[0064] (2) Preparation of phosphorus-doped coal-tar pitch-based hard carbon material: Mix coal-tar pitch with the yeast cultured in step 1 at a volume ratio of 1:5, grind with alcohol for 1 h, then place the mixed solid powder in a porcelain boat, put it in a tube furnace, and carry out carbonization at 1200 °C under the protection of a nitrogen atmosphere, hold at this temperature for 2 h, and its heating rate is 5 °C / min to obtain the phosphorus-doped coal-tar pitch-based hard carbon material. The coal-tar pitch used is sourced from anthracite.

[0065] 2. Preparation of sodium-ion battery: The same as step 2 of Example 1.

[0066] Example 3

[0067] 1. Preparation of phosphorus-doped coal-tar pitch-based hard carbon material:

[0068] (1) Cultivation of yeast: The same as step (1) in step 1 of Example 1;

[0069] (2) Preparation of phosphorus-doped coal-tar pitch-based hard carbon material: Mix coal-tar pitch with the yeast cultured in step (1) at a volume ratio of 1:2, grind with alcohol for 1 h, then place the mixed solid powder in a porcelain boat, put it in a tube furnace, and carry out carbonization at 900 °C under the protection of a nitrogen atmosphere, hold at this temperature for 2 h, and its heating rate is 5 °C / min to obtain the phosphorus-doped coal-tar pitch-based hard carbon material. The coal-tar pitch used is sourced from anthracite.

[0070] 2. Preparation of sodium-ion battery: The same as step 2 of Example 1.

[0071] Example 4

[0072] 1. Preparation of phosphorus-doped coal-tar pitch-based hard carbon material:

[0073] (1) Cultivation of yeast: same as step (1) in step 1 of Example 1;

[0074] (2) Preparation of phosphorus-doped coal-tar pitch-based hard carbon material: Mix coal-tar pitch with the yeast cultivated in step (1) at a volume ratio of 1:2, grind with alcohol for 1 h, then place the mixed solid powder in a porcelain boat, put it in a tubular furnace, and carry out carbonization at 1000 °C under the protection of nitrogen atmosphere, keep the temperature for 2 h at this temperature, and its heating rate is 5 °C / min, thus obtaining the phosphorus-doped coal-tar pitch-based hard carbon material. The coal-tar pitch used is sourced from anthracite.

[0075] 2. Preparation of sodium-ion battery: same as step 2 of Example 1.

[0076] Example 5

[0077] 1. Preparation of phosphorus-doped coal-tar pitch-based hard carbon material:

[0078] (1) Cultivation of yeast: Add 5 g of Angel high-activity dry yeast powder to 50 mL of deionized water in a petri dish, cultivate at 35 °C for 24 h, and centrifuge and purify the yeast for standby;

[0079] (2) Preparation of phosphorus-doped coal-tar pitch-based hard carbon material: same as step (2) in step 1 of Example 1.

[0080] 2. Preparation of sodium-ion battery: same as step 2 of Example 1.

[0081] Example 6

[0082] 1. Preparation of phosphorus-doped coal-tar pitch-based hard carbon material:

[0083] (1) Cultivation of yeast: Add 5 g of Angel high-activity dry yeast powder to 50 mL of deionized water in a petri dish, cultivate at 25 °C for 24 h, and centrifuge and purify the yeast for standby;

[0084] (2) Preparation of phosphorus-doped coal-tar pitch-based hard carbon material: same as step (2) in step 1 of Example 1.

[0085] 2. Preparation of sodium-ion battery: same as step 2 of Example 1.

[0086] Example 7

[0087] 1. Preparation of phosphorus-doped coal-tar pitch-based hard carbon material:

[0088] (1) Cultivation of yeast: Add 5 g of Angel high-activity dry yeast powder to 100 mL of deionized water in a petri dish, cultivate at 35 °C for 12 h, and centrifuge and purify the yeast for standby;

[0089] (2) Preparation of phosphorus-doped coal-tar pitch-based hard carbon material: same as step (2) in step 1 of Example 1.

[0090] 2. Preparation of sodium-ion battery: same as step 2 of Example 1.

[0091] Comparative Example 1

[0092] 1. Preparation of coal-tar pitch-based carbon material: Untreated coal-tar pitch is carbonized at 1200 °C under nitrogen gas, held at this condition for 2 h, and its heating rate is 5 °C / min, thus obtaining the coal-tar pitch-based carbon material.

[0093] 2. Preparation of sodium-ion battery:

[0094] (1) The coal-tar pitch-based carbon material obtained in step 1, acetylene black, and binder PVDF are put into a mortar and ground in a mass ratio of 8:1:1. Subsequently, 1-methyl-2-pyrrolidone solution is added until the powder becomes a black viscous slurry, and it is reserved for use;

[0095] (2) The slurry obtained in step (1) is evenly coated on a copper foil using a 100 μm scraper, and then the copper foil is dried at 60 °C for 6 h. Finally, it is stamped into a circular electrode sheet with a diameter of 12 mm, and the electrode sheet is the negative electrode of the sodium-ion battery;

[0096] (3) Using the electrode sheet obtained in step (2) as the negative electrode, sodium metal as the positive electrode, glass fiber as the separator, and 1 mol / L NaPF 6 solution as the electrolyte, with a voltage range of (0.01 - 3) V, a sodium-ion battery is prepared.

[0097] Performance Test

[0098] Figure 1 The XRD pattern of the phosphorus-doped coal-tar pitch-based hard carbon material prepared in Example 1 is shown. It can be seen that the XRD spectrum of the phosphorus-doped coal-tar pitch-based hard carbon material has two broad diffraction peaks at 25° and 43°, which are typical diffraction peaks of hard carbon in the (002) and (100) crystal planes.

[0099] Figure 2 The SEM image of the phosphorus-doped coal-tar pitch-based hard carbon material prepared in Example 1 is shown. It can be seen that the phosphorus-doped coal-tar pitch-based hard carbon material includes an irregular-shaped coal-tar pitch matrix and nitrogen-doped carbon microspheres in-situ grown on the surface of the matrix.

[0100] Electrochemical performance tests are carried out in the voltage range of (0.01–3) V. Figure 3Cycling capacity diagrams of the batteries prepared in Example 1, Example 3 and Comparative Example 1 at 0.1 A / g in the first cycle. The results show that compared with the coal tar pitch-based carbon material without yeast mixture (Comparative Example 1), the phosphorus-doped coal tar pitch-based hard carbon materials prepared at different carbonization temperatures (Example 1 and Example 3), the phosphorus-doped coal tar pitch-based hard carbon materials prepared in Example 1 and Example 3 can significantly improve the capacity of sodium-ion batteries.

[0101] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a phosphorus-doped coal-tar pitch-based hard carbon material, characterized in that: The preparation method comprises the following steps: mixing coal tar and yeast, grinding, and carbonizing to obtain the phosphorus-doped coal tar-based hard carbon material; The preparation method of the yeast comprises the following steps: adding deionized water to dry yeast powder, culturing, and centrifuging to obtain the yeast; The mass volume ratio of the dry yeast powder and deionized water is 5g: (50-100) mL; the culture temperature is (25-35) °C, and the culture time is (12-24) h; The volume ratio of the coal tar and the yeast is 1:(1-5).

2. The preparation method according to claim 1, characterized in that: The coal tar pitch is sourced from lignite, bituminous coal or anthracite; the carbonization is carried out in a nitrogen atmosphere at a temperature of (900-1500)°C, a time of (1-4) hours, and a heating rate of (3-10)°C / min.

3. Phosphorus-doped coal tar pitch-based hard carbon material prepared by the method described in any one of claims 1-2.

4. The use of the phosphorus-doped coal-tar pitch-based hard carbon material according to claim 3, characterized in that: The phosphorus-doped coal tar pitch-based hard carbon material is used for preparing sodium ion batteries.

5. The use according to claim 4, characterized in that: The negative electrode of the sodium ion battery comprises the phosphorus-doped coal tar pitch-based hard carbon material according to claim 3.

6. The use according to claim 5, characterized in that: The preparation method of the negative electrode adopts the following steps: ①, mixing the phosphorus-doped coal tar pitch-based hard carbon material, the conductive agent and the binder, adding a solvent to obtain a slurry; ②. Coat the slurry obtained in step ① on a metal foil and perform vacuum drying to obtain the negative electrode.

7. The use according to claim 6, characterized in that: In step ①, the mass ratio of the phosphorus-doped coal tar-based hard carbon material, the conductive agent and the binder is (7-8): (0.5-1.5): (0.5-1.5); in step ②, the metal foil is copper foil or aluminum foil; the vacuum drying temperature is (50-60)°C and the time is (6-24) h.

8. The use according to claim 7, characterized in that The conductive agent is carbon black, conductive graphite, carbon tube, graphene, Ketjen black, acetylene black or SuperP; the binder is polyvinylidene fluoride, styrene butadiene rubber latex or carboxymethyl cellulose; the solvent is 1-methyl-2-pyrrolidone solution or water.

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