A hard carbon material, its preparation method and application, and an ion battery

Abstract

The present invention discloses a hard carbon material, a preparation method and application thereof, and an ion battery. The preparation method of the hard carbon material comprises the following steps: heat-treating a mixture of powder coke and coal coke powder to obtain the hard carbon material; the powder coke includes one or more of petroleum powder coke, needle coke powder and pitch powder; the median particle size D50 of the powder coke is 1-15 μm; the median particle size D50 of the coal coke powder is 1-20 μm; the mass ratio of the powder coke to the coal coke powder is (4-120):400; in the hard carbon material, the powder coke is filled in the pore structure of the coal coke powder. The hard carbon material prepared by the present invention has a good pore structure, a high tap density and a small specific surface area. When it is used in an ion battery, the ion battery has a high charge-discharge capacity, a high initial Coulomb efficiency and good rate performance, and is suitable for mass production.

Description

Technical Field

[0001] The present invention specifically relates to a hard carbon material, a preparation method and application thereof, and an ion battery. Background Art

[0002] With the rapid development of sodium-ion batteries, hard carbon materials have been pushed to the forefront, and the market demand has increased rapidly, especially in energy storage and low-end products. However, the current hard carbon materials have relatively high costs, rely on imports, and account for a large proportion at the raw material end, which restricts the promotion of new batteries.

[0003] In the prior art, the first charge-discharge efficiency of hard carbon materials is low, and the specific surface area of the materials is large, which is also a thorny problem in the promotion of hard carbon materials.

[0004] Chinese Patent Document (CN103066243A) uses coal tar powder as the raw material, coats the outside of high-purity coal tar powder with coal pitch to form a core-shell structure, and obtains a negative electrode material after high-temperature treatment. The material prepared by this method needs to be graphitized, which consumes a large amount of energy, has a high cost, and has a great impact on the environment. At the same time, the material prepared by this method belongs to a lamellar structure without pore structure, which affects the rapid insertion and extraction of ions, is not suitable for sodium-ion batteries, has poor fast charging performance, and the graphite market is relatively stable, so the impact on it is small.

[0005] In the prior art, generally, powder coke (generally referring to the by-product generated in the coking process with a particle diameter less than 1 mm, high volatile matter content, and high thermal expansion coefficient, which cannot be directly used for electrode preparation) is graphitized to prepare artificial graphite negative electrode materials. And there is currently no research on using powder coke to prepare hard carbon materials. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of low initial Coulomb efficiency, large specific surface area, low tap density, and high cost of raw materials when the existing coal-based hard carbon materials are used as battery negative electrode materials, and to provide a hard carbon material, a preparation method and application thereof, and an ion battery. The hard carbon material prepared by the present invention has a good pore structure, high tap density, and small specific surface area. When it is used in an ion battery, the ion battery has a high charge-discharge capacity, high initial Coulomb efficiency, and good rate performance, and is suitable for mass production.

[0007] The inventors have discovered through a series of experimental explorations that: using coal tar powder as the main raw material, through powder coke compounding and in combination with a specific preparation process, the internal structure of the hard carbon material can be modified (the powder coke fills the inside, gaps, and outer surface pores of the coal tar powder, compensating for the ineffective pore defects brought by the coal tar powder itself), while improving the added value of by-products, saving energy. When this hard carbon material is used in an ion battery, it exhibits excellent first charge-discharge efficiency, fast charging performance, and good cycle performance.

[0008] The present invention solves the above technical problems through the following technical solutions.

[0009] The present invention provides a method for preparing a hard carbon material, which comprises the following steps:

[0010] Heat-treating a mixture of pulverized coke and coal coke powder to obtain the hard carbon material;

[0011] The pulverized coke includes one or more of petroleum pulverized coke, needle coke, and pitch powder;

[0012] The median particle size D50 of the pulverized coke is 1 - 15 μm;

[0013] The median particle size D50 of the coal coke powder is 1 - 20 μm;

[0014] The mass ratio of the pulverized coke to the coal coke powder is (4 - 120):400;

[0015] In the hard carbon material, the pulverized coke is filled in the pore structure of the coal coke powder.

[0016] In the present invention, the pulverized coke generally refers to a by-product generated in the coking process with a particle diameter less than 1 mm, high volatile content, high thermal expansion coefficient, and cannot be directly used for electrode preparation, with a relatively soft carbon structure.

[0017] In the present invention, the petroleum pulverized coke generally refers to: when the coking time of petroleum raw materials is short and / or the operation during the coke pushing process is improper, coke sludge (i.e., pulverized coke) with a diameter less than 1 mm will be generated, which is a by-product of the petroleum coking process.

[0018] In the present invention, the volatile content of the petroleum pulverized coke is generally ≤15%, preferably ≤12%, for example 12.8%; the ash content of the petroleum pulverized coke can be ≤3%, for example 0.42%.

[0019] In the present invention, the needle coke generally refers to: when pulling needle coke, affected by factors such as the ventilation volume and the volatile rate of light components, an intermediate phase is formed, and the incompletely developed dust.

[0020] In the present invention, the volatile content of the needle coke is generally ≤10%, preferably ≤9%, for example 7.1%; the ash content of the needle coke can be ≤1%, for example 0.26%.

[0021] In the present invention, the pitch powder refers to the fine powder formed in processes such as pitch granulation.

[0022] In the present invention, the volatile content of the pitch powder is generally ≤40%, for example 38%; the ash content of the pitch powder can be ≤1%.

[0023] Those skilled in the art can select commercially available petroleum coke powder, needle coke powder, and pitch coke powder commonly used in the field according to actual needs based on the above conditions.

[0024] In the present invention, the coke powder is preferably petroleum coke powder or needle coke powder.

[0025] In the present invention, the coal coke powder is a by-product generated during the coking process, with a high carbon content, a well-developed pore structure required for hard carbon materials, and a relatively hard carbon structure.

[0026] In the present invention, the ash content of the coal coke powder can be ≤15%, preferably ≤10%, such as 9.8%.

[0027] In the present invention, the median particle size D50 of the coke powder is preferably 1-8 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or 7 μm.

[0028] In the present invention, the median particle size D50 of the coal coke powder is preferably 5-20 μm, such as 8 μm, 10 μm, 12 μm, 15 μm, 16 μm, 17 μm, 18 μm, or 19 μm.

[0029] In the present invention, the mass ratio of the coke powder to the coal coke powder is preferably (6-110):400, such as 6:400, 8:400, 20:400, 40:400, 60:400, 80:400, 100:400, or 105:400.

[0030] In the present invention, during the preparation process of the mixture, the mixing temperature can be 20-350 °C, such as 80 °C, 150 °C, 200 °C, 250 °C, or 300 °C.

[0031] In the present invention, during the preparation process of the mixture, the mixing time can be 0.5-6 h, such as 1 h, 2 h, 3 h, 4 h, or 5 h.

[0032] In the present invention, the equipment for preparing the mixture can be one or more of a horizontal screw ribbon mixer, a VC mixer, a double-pot mixer, an electric heating mixer, and a vertical mixer, preferably a VC mixer.

[0033] In the present invention, the temperature of the heat treatment can be 600-1400 °C, such as 700 °C, 900 °C, 1000 °C, 1200 °C, or 1300 °C. Through the heat treatment, the hard carbon material undergoes a pyrolysis reaction, which can remove impurity elements such as nitrogen, oxygen, and metal and stabilize the material structure.

[0034] In the present invention, the time of the heat treatment can be the time of conventional heat treatment in the art, generally 3-15 h, such as 4 h, 6 h, 8 h, 10 h, 12 h, or 14 h.

[0035] In the present invention, the heat treatment is generally carried out in a reducing gas or an inert gas. The reducing gas may be one or more of ammonia gas, hydrogen gas and argon gas. The inert gas may be argon gas or nitrogen gas.

[0036] When the heat treatment is carried out in an inert gas, the flow rate of the inert gas may be 0.1 - 0.5 L / (kg·min), such as 0.2 L / (kg·min) or 0.4 L / (kg·min).

[0037] In the present invention, the heat treatment includes a first heat treatment and a second heat treatment;

[0038] Among them, the temperature of the first heat treatment may be 500 - 800 °C, such as 600 °C or 700 °C; the heating rate to the temperature of the first heat treatment may be 2 - 5 °C / min, such as 3 °C / min; the time of the first heat treatment may be 1 - 4 h, such as 2 h; the temperature of the second heat treatment may be 900 - 1500 °C, such as 1200 °C, 1300 °C or 1400 °C; the heating rate to the temperature of the second heat treatment may be 3 - 7 °C / min, such as 5 °C / min; the time of the second heat treatment may be 3 - 6 h, such as 4 h or 5 h.

[0039] In the present invention, the equipment for the heat treatment may be conventional equipment in the art, preferably a temperature-rising and heat-preserving equipment with automatic program control, such as a box furnace, a tube furnace, a roller hearth kiln, a pusher kiln or a vacuum furnace.

[0040] In the present invention, preferably, before the heat treatment, the mixture is also subjected to alkali washing and insoluble and infusible treatment.

[0041] Among them, in the alkali washing process, the alkali solution can be prepared from conventional alkaline substances in the art and a solvent. The alkaline substance can be a conventional alkaline substance in the art, generally one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide, such as lithium hydroxide. The solvent can be a conventional solvent in the art that can dissolve alkaline substances, such as deionized water.

[0042] Among them, in the alkali washing process, the concentration of the alkali solution may be 0.01 - 0.5 mol / L, such as 0.03 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L or 0.4 mol / L.

[0043] Among them, the temperature of the alkali washing can be a conventional temperature in the art, such as 50 °C.

[0044] Among them, the control method of the temperature of the alkali washing can be a conventional method in the art, such as a water bath.

[0045] Among them, the time of the caustic washing can be a conventional time in the art, such as 4 h or 6 h.

[0046] Among them, the caustic washing is generally carried out by stirring.

[0047] Among them, drying is generally included after the caustic washing. The temperature of the drying can be 80-150 °C, such as 100 °C or 150 °C. The time of the drying can be 2-24 h, such as 4 h or 10 h.

[0048] Among them, the temperature of the insoluble and infusible treatment can be 300-700 °C, such as 400 °C, 450 °C, 500 °C, 550 °C or 600 °C.

[0049] Among them, the time of the insoluble and infusible treatment can be 4-15 h, such as 6 h, 8 h, 10 h, 12 h, 13 h or 14 h.

[0050] Among them, the insoluble and infusible treatment is generally carried out in an inert gas and / or an oxidizing gas. The inert gas can be argon or nitrogen. The oxidizing gas can be air, oxygen or ozone, preferably oxygen.

[0051] Among them, during the insoluble and infusible treatment, the flow rate of the gas introduced can be 0.01-0.3 L / (kg·min), such as 0.05 L / (kg·min), 0.1 L / (kg·min), 0.15 L / (kg·min) or 0.2 L / (kg·min).

[0052] When the insoluble and infusible treatment is carried out in oxygen, the flow rate of the oxygen atmosphere can be 0.01-0.3 L / (kg·min), such as 0.05 L / (kg·min), 0.1 L / (kg·min), 0.15 L / (kg·min) or 0.2 L / (kg·min).

[0053] Among them, the insoluble and infusible treatment includes a first treatment and a second treatment;

[0054] The temperature of the first treatment can be 300-500 °C, such as 450 °C; the rate of heating up to the first treatment can be 2-5 °C / min, such as 2 °C / min; the time of the first treatment can be 1-4 h, such as 2 h or 3 h;

[0055] The temperature of the second treatment can be 500-800 °C, such as 600 °C or 700 °C; the rate of heating up to the second treatment can be 2-5 °C / min, such as 3 °C / min; the time of the second treatment can be 3-7 h, such as 4 h or 6 h.

[0056] Among them, the equipment for the insoluble and infusible treatment can be one or more of a horizontal screw ribbon mixer, a VC mixer, a double-pot mixer, an electric heating mixer, and a vertical mixer, preferably an electric heating mixer.

[0057] In the present invention, before the coal char powder is mixed with the fine coke powder, the coal char powder is generally pre-treated first.

[0058] Among them, the pre-treatment method can be a conventional pre-treatment method in the art, for example, generally including drying, pulverizing, pickling, and suction filtration. After pickling the coal char powder, the ash content can be reduced, the purity can be improved, and the influence on the electrochemical performance can be reduced.

[0059] The temperature of the drying can be 100 - 150 °C. The time of the drying can be 1 - 5 h.

[0060] The equipment for the pulverizing can be a jet mill, a mechanical mill, a roller press mill, or a ball mill.

[0061] The acid solution used for the pickling can be prepared from conventional acidic substances and solvents in the art. The acidic substances can be conventional acidic substances in the art, generally one or more of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid, such as hydrochloric acid and hydrofluoric acid. The solvents can be conventional solvents for diluting acidic substances in the art, such as deionized water.

[0062] The concentration of the acid solution used for the pickling can be 0.1 - 2 mol / L, such as 1 mol / L.

[0063] The temperature of the pickling can be 10 - 80 °C, such as 50 °C.

[0064] The control method of the temperature of the pickling can be a conventional method in the art, such as a water bath.

[0065] The time of the pickling can be 0.5 - 6 h, such as 4 h.

[0066] The number of washing times of the pickling can be 1 - 6 times, such as 4 times.

[0067] In an embodiment of the present invention, the steps of the pickling are as follows: First, 2 kg of coal char powder with an ash content of 9.8% is placed in 1000 mL of a 1 mol / L hydrofluoric acid solution, water-bathed at 50 °C, stirred for 2 hours, washed 2 times, and then the above coal char powder is placed in 1000 mL of a 1 mol / L hydrochloric acid solution, water-bathed at 50 °C, stirred for 2 hours, and washed 2 times.

[0068] In a preferred embodiment of the present invention, the preparation method of the hard carbon material includes the following steps:

[0069] 1. Take 2 kg of coal char powder with an ash content of 9.8%, dry it at 120 °C for 5 hours using a drying oven, and use a ball mill to pulverize it to D50 of 10 μm;

[0070] 2. Prepare a 1 mol / L acid solution of 1000 mL by mixing hydrofluoric acid and hydrochloric acid in a mass ratio of 5:1. Place it in a water bath at 50 °C. Add 500 g of pulverized coal char powder to the solution and stir continuously for 4 hours for full reaction. Then, perform vacuum filtration and washing 4 times repeatedly to obtain low-ash coal char powder.

[0071] 3. Feed 60 g of pulverized coke with D50 of 2 μm and 400 g of the low-ash coal char powder obtained in the above step 1 into a VC mixer. Heat the equipment to 80 °C and mix at 100 revolutions per minute for 3 hours. Protect the whole process with nitrogen, and the flow rate is 0.05 L / (kg·min).

[0072] 4. Take 400 g of the discharged material from the mixer and place it in 1000 mL of a 0.01 mol / L lithium hydroxide alkaline solution. Place it in a water bath at 50 °C and stir continuously for 4 hours for full reaction. After vacuum filtration, place it in a drying oven and dry at 100 °C for 4 hours to obtain a weakly basic complex.

[0073] 5. Transfer the weakly basic complex to an electrically heated mixer. Heat it to 450 °C at a rate of 2 °C / min, keep it warm for 2 hours, then heat it to 700 °C at a rate of 3 °C / h and keep it at a constant temperature for 4 hours. The linear velocity of the whole process of the material running in the mixer is 0.8 m / s. Select an oxygen atmosphere with a flow rate of 0.05 L / (kg·min). After cooling to room temperature, discharge the material to obtain a modified hard carbon precursor.

[0074] 6. Place the modified hard carbon precursor in a tube furnace for high-temperature heat treatment. The nitrogen atmosphere flow rate is 0.1 L / (kg min). Heat it to 600 °C at a rate of 3 °C / min, keep it warm for 2 hours, then heat it to 1200 °C at a rate of 5 °C / min and keep it warm for 6 hours to end. After cooling to room temperature, discharge the material to obtain a stable hard carbon material.

[0075] The present invention also provides a hard carbon material prepared by the preparation method of the hard carbon material as described above.

[0076] In the present invention, the particle size D50 of the hard carbon material can be 10 - 21 μm, such as 10.6 μm, 10.8 μm, 11.0 μm, 11.2 μm, 11.1 μm, 11.3 μm, 11.5 μm, 11.6 μm, 12.0 μm, 13.3 μm, 15.2 μm, 16.0 μm, 17.0 μm, 19.0 μm or 20.4 μm.

[0077] In the present invention, the BET specific surface area of the hard carbon material can be ≤ 3.2 m 2 / g, such as 2.39 m 2 / g, 2.53 m 2 / g, 2.55 m 2 / g, 2.56 m 2 / g, 2.60 m 2 / g, 2.63 m 2 / g, 2.64 m 2 / g, 2.65 m 2 / g, 2.68 m 2 / g, 2.74 m 2 / g, 2.77 m 2 / g, 2.83 m 2 / g, 2.84 m 2 / g, 2.87 m 2 / g, 2.96 m 2 / g or 3.11 m 2 / g.

[0078] In the present invention, the tap density of the hard carbon material can be 0.96 - 1.1 g / cm 3 , such as 0.98 g / cm 3 , 0.99 g / cm 3 , 1.01 g / cm 3 , 1.02 g / cm 3 , 1.03 g / cm 3 , 1.04 g / cm 3 , 1.05 g / cm 3 , 1.06 g / cm 3 , 1.07 or 1.08 g / cm 3 .

[0079] The present invention also provides an ion battery, which includes the hard carbon material as described above.

[0080] In the present invention, the ion battery is preferably a lithium ion battery or a sodium ion battery.

[0081] The present invention also provides an application of the hard carbon material as described above as an electrode material in an ion battery.

[0082] In the present invention, preferably, the application is an application of the hard carbon material as described above as a negative electrode material in a lithium ion battery or a sodium ion battery.

[0083] On the basis of conforming to common general knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention. It should be noted that due to technological development, the best embodiment may have performance beyond the test results of the present invention.

[0084] The reagents and raw materials used in the present invention are all commercially available.

[0085] The positive and progressive effects of the present invention are as follows:

[0086] 1. The hard carbon material obtained by the present invention has a good pore structure, high tap density, and small specific surface area. When used in ion batteries, the ion batteries have high initial charge-discharge specific capacity, relatively high initial efficiency, and strong cycling ability.

[0087] 2. The present invention uses by-products of coking (powder coke and coal coke powder) as raw materials. The raw materials have a wide source, low price, good processability, high yield, easy industrial production, stable quality, and high added value. Recycling these waste materials can reduce solid waste production and is environmentally friendly.

[0088] 3. The preparation method of the present invention has simple process, good processing performance, safety and reliability, and is suitable for industrial production. It is beneficial to promote the commercial use of lithium-ion and sodium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 It is the pore size distribution diagram of the hard carbon material obtained in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0090] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0091] In the present invention, unless otherwise specified, the raw materials and reagents used in the specific examples and comparative examples are commercially available.

[0092] Example 1

[0093] 1. Take 2 kg of coal coke powder with an ash content of 9.8%, dry it in an oven at 120 °C for 5 hours, and use a ball mill to crush it to D50 of 10 μm.

[0094] 2. Prepare a 1000 mL acid solution with a concentration of 1 mol / L by mixing hydrofluoric acid and hydrochloric acid in a mass ratio of 5:1, place it in a water bath at 50 °C, add 500 g of the crushed coal coke powder to the solution, stir continuously for 4 hours, fully react, and repeatedly vacuum filter and wash 4 times to obtain low-ash coal coke powder.

[0095] 3. Put 60 g of needle-shaped coke powder crushed to D50 of 2 μm and 400 g of the low-ash coal coke powder obtained in the above step 1 into a VC mixer, heat the equipment to 80 °C, and mix at 100 revolutions per minute for 3 hours. Protect with nitrogen throughout the process, with a flow rate of 0.05 L / (kg·min).

[0096] 4. Take 400 g of the material discharged from the mixing machine and place it in 1000 mL of a lithium hydroxide alkaline solution with a concentration of 0.01 mol / L. Put it in a water bath at 50 °C and stir continuously for 4 hours to fully react. After vacuum filtration, place it in a drying oven and dry at 100 °C for 4 hours to obtain a weakly alkaline composite.

[0097] 5. Transfer the weakly alkaline composite into an electrically heated mixing machine. Heat it to 450 °C at a rate of 2 °C / min, hold for 2 hours, then heat it to 700 °C at a rate of 3 °C / h and keep it at a constant temperature for 4 hours. The linear velocity of the material running in the mixing machine throughout the process is 0.8 m / s. Select an oxygen atmosphere with a flow rate of 0.05 L / (kg·min), and discharge the material after cooling to room temperature to obtain a modified hard carbon precursor.

[0098] 6. Place the modified hard carbon precursor in a tube furnace for high-temperature heat treatment. The nitrogen atmosphere flow rate is 0.1 L / (kg min). Heat it to 600 °C at a rate of 3 °C / min, hold for 2 hours, then heat it to 1200 °C at a rate of 5 °C / min and hold for 6 hours to end. Discharge the material after cooling to room temperature to obtain a stable hard carbon material.

[0099] Example 2

[0100] 1. Use the same operation as in step 1 of Example 1 to prepare coal coke powder crushed to D50 of 10 μm.

[0101] 2. Prepare 1000 mL of an acid solution with a concentration of 1 mol / L by mixing hydrofluoric acid and hydrochloric acid in a mass ratio of 5:3. Place it in a water bath at 50 °C. Take 500 g of the crushed coal coke powder and add it to the solution. Stir continuously for 4 hours to fully react. Conduct vacuum filtration and wash once to obtain low-ash coal coke powder.

[0102] 3. Feed 110 g of needle-like coke powder crushed to D50 of 3 μm and 400 g of the low-ash coal coke powder obtained in the above step 1 into a VC mixing machine, and the mixing parameters are the same as in Example 1.

[0103] 4. Take 400 g of the material discharged from the mixing machine and place it in 1000 mL of a lithium hydroxide alkaline solution with a concentration of 0.05 mol / L. Put it in a water bath at 50 °C and stir continuously for 6 hours to fully react. After vacuum filtration, place it in a drying oven and dry at 150 °C for 4 hours to obtain a weakly alkaline composite.

[0104] 5. Transfer the weakly alkaline composite into an electrically heated mixing machine. Heat it to 400 °C at a rate of 2 °C / min, hold for 1 hour, then heat it to 600 °C at a rate of 3 °C / h and keep it at a constant temperature for 6 hours. The linear velocity of the material running in the mixing machine throughout the process is 2 m / s. Select an oxygen atmosphere with a flow rate of 0.01 L / (kg·min), and discharge the material after cooling to room temperature to obtain a modified hard carbon precursor.

[0105] 6. Place the modified hard carbon precursor in a box furnace for high-temperature heat treatment. The flow rate of the nitrogen atmosphere is 0.1 L / (kg min). Heat it up to 1400 °C at a rate of 5 °C / min and hold for 4 hours to complete. Wait until it cools down to room temperature and then discharge to obtain a stable hard carbon material.

[0106] Example 3

[0107] 1. The same as step 1 of Example 1.

[0108] 2. The same as step 2 of Example 1.

[0109] 3. Take 20 g of needle coke powder with a D50 of 2 μm pulverized to the above and 400 g of low-ash coal char powder obtained in step 1 above and feed them into a VC mixer. Heat the equipment to 300 °C and mix at 100 revolutions per minute for 2 hours. Protect with nitrogen throughout the process, with a flow rate of 0.05 L / (kg·min).

[0110] 4. Take 400 g of the discharged material from the mixer and place it in 1000 mL of a lithium hydroxide alkaline solution with a concentration of 0.1 mol / L. Place it in a water bath at 50 °C and stir continuously for 6 hours to fully react. After vacuum filtration, place it in a drying oven and dry at 100 °C for 10 hours to obtain a weakly alkaline complex.

[0111] 5. Transfer the weakly alkaline complex to an electrically heated mixer. Heat it up to 300 °C at a rate of 2 °C / min, hold for 4 hours, then heat it up to 700 °C at a rate of 3 °C / h and keep it at a constant temperature for 6 hours. The mixer and atmosphere are the same as in Example 1. Wait until it cools down to room temperature and then discharge to obtain a modified hard carbon precursor.

[0112] 6. Place the modified hard carbon precursor in a tube furnace for high-temperature heat treatment. The flow rate of the nitrogen atmosphere is 0.1 L / (kg min). Heat it up to 700 °C at a rate of 3 °C / min, hold for 1 hour, then heat it up to 1300 °C at a rate of 5 °C / min and hold for 2 hours to complete. Wait until it cools down to room temperature and then discharge to obtain a stable hard carbon material.

[0113] Example 4

[0114] 1. Perform the same operation as in step 1 of Example 1 to prepare coal char powder with a D50 of 15 μm pulverized.

[0115] 2. The same as step 2 of Example 1.

[0116] 3. Take 6 g of needle coke powder with a D50 of 4 μm pulverized and 400 g of low-ash coal char powder obtained in step 1 above and feed them into a VC mixer. Heat the equipment to 200 °C and mix at 100 revolutions per minute for 2 hours. Protect with nitrogen throughout the process, with a flow rate of 0.5 L / (kg·min).

[0117] 4. The same as step 4 of Example 1.

[0118] 5. Transfer the weak alkaline complex into an electrically heated mixer, heat it up to 700 °C at a rate of 2 °C / min, and keep it at a constant temperature for 6 hours. The mixer and the atmosphere are the same as in Example 1. After cooling to room temperature, discharge the material to obtain a modified hard carbon precursor.

[0119] 6. Put the modified hard carbon precursor into a tubular furnace for high-temperature heat treatment. The flow rate of the nitrogen atmosphere is 0.1 L / (kg·min), heat it up to 1200 °C at a rate of 3 °C / min, and keep it at a constant temperature for 6 hours to end. After cooling to room temperature, discharge the material to obtain a stable hard carbon material.

[0120] Example 5

[0121] In step 3 of Example 5: Take 60 g of petroleum coke powder crushed to D50 of 2 μm and 400 g of low-ash coal char powder and feed them into a VC mixer. The conditions of the remaining steps are the same as in Example 1.

[0122] Example 6

[0123] In step 3 of Example 6: Take 60 g of acicular coke powder crushed to D50 of 3 μm and 400 g of the low-ash coal char powder obtained in step 1 and feed them into a VC mixer. The conditions of the remaining steps are the same as in Example 1.

[0124] Example 7

[0125] In Example 7, use the same step 1 as in Example 1, take 2 kg of coal char powder with an ash content of 9.8%, and crush it to D50 of 12 μm. The conditions of the remaining steps are the same as in Example 1.

[0126] Example 8

[0127] In step 4 of Example 8: Take 400 g of the discharged material from the mixer and place it in 1000 mL of lithium hydroxide alkaline solution with a concentration of 0.03 mol / L. The conditions of the remaining steps are the same as in Example 1.

[0128] Example 9

[0129] In step 5 of Example 9: Transfer the weak alkaline complex into an electrically heated mixer, heat it up to 450 °C at a rate of 2 °C / min, keep it at a constant temperature for 2 hours, then heat it up to 600 °C at a rate of 3 °C / h, and keep it at a constant temperature for 4 hours. The conditions of the remaining steps are the same as in Example 1.

[0130] Example 10

[0131] In step 5 of Example 10: The linear velocity of the whole material running in the mixer is 0.8 m / s. Select an oxygen atmosphere with a flow rate of 0.2 L / (kg·min). The conditions of the remaining steps are the same as in Example 1.

[0132] Example 11

[0133] Example 11, compared with Example 1, does not include steps 4-5, and the conditions of the remaining steps are the same as those in Example 1.

[0134] Example 12

[0135] Example 12, compared with Example 1, does not include step 4, and the conditions of the remaining steps are the same as those in Example 1.

[0136] Example 13

[0137] Example 13, compared with Example 1, does not include step 5, and the conditions of the remaining steps are the same as those in Example 1.

[0138] Example 14

[0139] 1. The same as step 1 of Example 1.

[0140] 2. Prepare a 1 mol / L acid solution of 1000 mL of hydrofluoric acid, place it in a water bath at 50 °C, add 500 g of pulverized coal char powder to the solution, stir continuously for 2 hours, fully react, wash it by repeated vacuum filtration 2 times, then use 1000 mL of 1 mol / L hydrochloric acid solution, place it in a water bath at 50 °C, stir continuously for 2 hours, fully react, and wash it by repeated vacuum filtration 2 times to obtain low-ash coal char powder.

[0141] 3. The same as step 3 of Example 1.

[0142] 4. Transfer the discharge of the VC mixer to an electrically heated mixer, heat it to 400 °C at a rate of 2 °C / min, keep it at this temperature for 1 hour, then heat it to 600 °C at a rate of 3 °C / h, and keep it at a constant temperature for 6 hours. The linear velocity of the material running in the mixer throughout the process is 0.5 m / s. Select a nitrogen atmosphere with a flow rate of 0.05 L / (kg·min), and discharge it after cooling to room temperature to obtain a modified hard carbon precursor.

[0143] 5. The same as step 6 of Example 1.

[0144] Example 15

[0145] In Example 15, the same step 1 as in Example 1 is adopted, and 2 kg of coal char powder with an ash content of 9.8% is taken and pulverized to D50 of 20 μm. The conditions of the remaining steps are the same as those in Example 1.

[0146] Comparative Example 1

[0147] 1. The same as step 1 of Example 1.

[0148] 2. The same as step 2 of Example 1.

[0149] 3. Charge 400 g of the low-ash coal char powder obtained in the above step 1 into a VC mixer, heat the equipment to 80 °C, and mix at 100 revolutions per minute for 3 hours. Protect the whole process with nitrogen, and the flow rate is 0.05 L / (kg·min).

[0150] 4. The same as step 4 of Example 1.

[0151] 5. Transfer the weak alkaline complex to an electrically heated mixer, heat it to 700 °C at a rate of 2 °C / min, and keep it at a constant temperature for 4 hours. The linear velocity of the material running in the mixer throughout the process is 1.5 m / s. Select an oxygen atmosphere with a flow rate of 0.01 L / (kg·min), and discharge the material after cooling to room temperature to obtain a modified hard carbon precursor.

[0152] 6. Place the modified hard carbon precursor in a tubular furnace for high-temperature heat treatment. The nitrogen atmosphere flow rate is 0.1 L / (kg min), heat it to 1400 °C at a rate of 5 °C / min, and keep it at a constant temperature for 4 hours to end. Discharge the material after cooling to room temperature to obtain a stable hard carbon material.

[0153] Comparative Example 2

[0154] In step 3 of Comparative Example 2: Charge 60 g of lime powder with a D50 of 2 μm and 400 g of the low-ash coal char powder obtained in step 1 into a VC mixer, and the conditions of the remaining steps are the same as those of Example 1.

[0155] Comparative Example 3

[0156] In step 3 of Comparative Example 3: Charge 400 g of acicular coke powder with a D50 of 2 μm and 400 g of the low-ash coal char powder obtained in step 1 into a VC mixer, and the conditions of the remaining steps are the same as those of Example 1.

[0157] The main condition parameters involved in the above examples and comparative examples are shown in Tables 1-1 and 1-2 below:

[0158] Table 1-1

[0159]

[0160]

[0161]

[0162] Table 1-2

[0163]

[0164]

[0165]

[0166] Note: In Table 1-2, " / " indicates that this parameter is not set in this example or comparative example.

[0167] Effect Example

[0168] 1. Median particle size D50, tapped density, BET test

[0169] Test object: Hard carbon materials prepared in Examples 1-15 and Comparative Examples 1-3.

[0170] Test methods and conditions:

[0171] (1) Test method, standard or instrument model for median particle size D50: The particle size D50 is measured by a Mastersize 2000 laser particle size analyzer for particle size distribution. The test method can be a conventional method for measuring the median particle size D50 in this field.

[0172] (2) Test method, standard or instrument model for tapped density: The tapped density is tested by Yisite ST-ZS100D powder tapped density tester. The test method can be a conventional method for measuring the tapped density in this field.

[0173] (3) Test method, standard or instrument model for BET specific surface area: The BET test is carried out by Belsd 3H-2000. The test method can be a conventional method for measuring the BET specific surface area in this field.

[0174] Test results: As Figure 1 shown, the pore distribution of the hard carbon material prepared in Example 1 is uniform. Due to the addition of coke powder, the pore diameter has a blue shift (i.e., the pore diameter becomes smaller), enabling more pores to participate in sodium storage.

[0175] 2. Electrochemical performance test

[0176] Test object: Sodium-ion batteries assembled with the hard carbon materials prepared in Examples 1-15 and Comparative Examples 1-3.

[0177] Test methods and conditions:

[0178] (1) Preparation of electrodes

[0179] At room temperature, the carbon negative electrode materials obtained in Examples 1-15 and Comparative Examples 1-3, acetylene black conductive agent and PVDF binder are mixed in a mass ratio of 8:1:1, and NMP is used as the solvent to prepare a uniform slurry. The slurry is uniformly coated on the copper foil, and the coating surface density is about 6 mg / cm 2 , and then the copper foil is placed in a vacuum drying oven and dried at 80 °C for 12 h. The dried copper foil is cut into circular pieces with an area of 2 cm 2 to make working electrodes.

[0180] (2) Assembly of button cells

[0181] Assembly of sodium-ion button battery: At room temperature, using a sodium metal sheet as the negative electrode and counter electrode, the product obtained in step (1) as the working electrode, a GE-Whatman fiberglass separator as the separator, and a 1 mol / L NaPF6 / EC:DMC (volume ratio 1:1) solution as the electrolyte, assemble a CR-2032 type button battery in a vacuum glove box and seal it tightly mechanically.

[0182] (3) Specific capacity and capacity retention rate test of sodium-ion button battery: After standing the assembled battery at room temperature for 24 h, start the electrochemical test. On an Arbin battery test system, according to the mass of the active material, a current of 100 mA / g is used in the first week, the first discharge is to 0 V, and the charging voltage range is 0 V to 2 V. After charging or discharging is completed, leave it for 5 min before proceeding to the next step. After 1000 cycles, the capacity retention rate is charged and discharged in a constant current of 1C.

[0183] Test results: See Table 2.

[0184] Table 2 Performance test results of hard carbon anode materials

[0185]

[0186] Note: First Coulombic efficiency = first discharge capacity / first charge capacity.

[0187] The tap density of the existing hard carbon materials is difficult to reach 1.0 g / cm 3 or more, the BET specific surface area is difficult to control within 3 m 2 / g, the first Coulombic efficiency is lower than 80%, and the capacity retention rate is lower than 80% after 1000 cycles under 1C charge and discharge conditions.

[0188] From the test results in Table 2 above, it can be seen that the hard carbon material prepared by the preparation method of the present invention finally obtains a hard carbon material with a good pore structure, reduces the specific surface area of the hard carbon material, increases the tap density, and uses it as the negative electrode material for sodium-ion batteries, with a high capacity retention rate after 1000 cycles.

[0189] Among them:

[0190] Compared with Example 1, in Example 11, alkali washing and insoluble and infusible treatment were not carried out. The tap density of the prepared hard carbon material is basically the same as that of Example 1, the specific surface area is smaller, and when it is used in a sodium-ion battery, the first Coulombic efficiency of the sodium-ion battery is basically the same as that of Example 1, but the first charge capacity and the capacity retention rate after 1000 cycles under 1C charge and discharge conditions are lower.

[0191] Compared with Example 1, in Example 12, the insolubilization and infusibilization treatment was not carried out. The tapped density of the prepared hard carbon material was basically the same as that of Example 1, but the specific surface area was larger. When it was used in a sodium-ion battery, the initial charge capacity, initial Coulombic efficiency, and capacity retention rate after 1000 cycles under 1C charge and discharge conditions of the sodium-ion battery were all low.

[0192] Compared with Example 1, in Example 13, alkali washing was not carried out. The tapped density of the prepared hard carbon material was basically the same as that of Example 1, but the specific surface area was larger. When it was used in a sodium-ion battery, the initial charge capacity, initial Coulombic efficiency, and capacity retention rate after 1000 cycles under 1C charge and discharge conditions of the sodium-ion battery were all low.

[0193] Compared with Example 1, in Example 15, the particle size of the coal char powder used was relatively large. The tapped density of the prepared hard carbon material was small, and the specific surface area was large. When it was used in a sodium-ion battery, the initial charge capacity, initial Coulombic efficiency, and capacity retention rate after 1000 cycles under 1C charge and discharge conditions of the sodium-ion battery were all low.

[0194] Based on the comparison of the above test phenomena, the inventor inferred that the alkali washing in the present invention can modify the pore structure of the mixture to a certain extent; the insolubilization and infusibilization treatment may play a role in further adjusting the pore defects and removing volatile components, so as to make the pore structure distribution of the hard carbon material more uniform.

[0195] Compared with Example 1, in Comparative Example 1, no powdered coke was added. The tapped density of the prepared hard carbon material was small, and the specific surface area was large. When it was used in a sodium-ion battery, the initial charge capacity, initial Coulombic efficiency, and capacity retention rate after 1000 cycles under 1C charge and discharge conditions of the sodium-ion battery were all low.

[0196] Compared with Example 1, in Comparative Example 2, the powdered coke was replaced with lime powder. The tapped density of the prepared hard carbon material was small, and the specific surface area was large. When it was used in a sodium-ion battery, the initial charge capacity, initial Coulombic efficiency, and capacity retention rate after 1000 cycles under 1C charge and discharge conditions of the sodium-ion battery were all low.

[0197] Compared with Example 1, in Comparative Example 3, the mass ratio of the powdered coke and the coal char powder was relatively large. The tapped density of the prepared hard carbon material was small, and the specific surface area was large. When it was used in a sodium-ion battery, the initial charge capacity, initial Coulombic efficiency, and capacity retention rate after 1000 cycles under 1C charge and discharge conditions of the sodium-ion battery were all low.

Claims

1. A method for preparing a hard carbon material, characterized in that, It includes the following steps: heat-treating a mixture of pulverized coke and pulverized coal coke to obtain the hard carbon material; The pulverized coke includes one or both of petroleum pulverized coke and needle coke; The median particle size D50 of the pulverized coke is 1-7 μm; The median particle size D50 of the pulverized coal coke is 8-19 μm; The mass ratio of the pulverized coke to the pulverized coal coke is (4-120):400; In the hard carbon material, the pulverized coke is filled in the gaps and outer surface pores of the pulverized coal coke; Before the heat treatment, it also includes alkali washing and insoluble and infusible treatment of the mixture; The temperature of the heat treatment is 600-1400 °C; The temperature of the insoluble and infusible treatment is 300-700 °C; The atmosphere of the insoluble and infusible treatment is an oxidizing gas.

2. The preparation method of the hard carbon material according to claim 1, characterized in that, It satisfies one or more of the following conditions a-c; a. The volatile content of the petroleum pulverized coke ≤ 15%; the ash content of the petroleum pulverized coke ≤ 3%; b. The volatile content of the needle coke ≤ 10%; the ash content of the needle coke ≤ 1%; c. The pulverized coke is petroleum pulverized coke or needle coke.

3. The preparation method of the hard carbon material according to claim 2, characterized in that, The volatile content of the petroleum pulverized coke ≤ 12%.

4. The method for preparing the hard carbon material according to claim 2, wherein, The volatile content of the petroleum pulverized coke is 12.8%.

5. The preparation method of the hard carbon material according to claim 2, wherein, The ash content of the petroleum pulverized coke is 0.42%.

6. The method for preparing the hard carbon material according to claim 2, characterized in that, The volatile content of the needle coke ≤ 9%.

7. The preparation method of the hard carbon material according to claim 6, characterized in that, The volatile content of the needle coke is 7.1%.

8. The preparation method of the hard carbon material according to claim 2, wherein, The ash content of the needle coke is 0.26%.

9. The preparation method of the hard carbon material according to claim 1, characterized in that, The temperature of the heat treatment is 700 °C, 900 °C, 1000 °C, 1200 °C or 1300 °C.

10. The preparation method of the hard carbon material according to claim 1, characterized in that, It satisfies one or two of the following conditions a-b; a. The ash content of the pulverized coal coke ≤ 15%; b. The mass ratio of the pulverized coke to the pulverized coal coke is (6-110):

400.

11. The preparation method of the hard carbon material according to claim 10, characterized in that, The preparation method of the hard carbon material simultaneously satisfies the above conditions a-b.

12. The preparation method of the hard carbon material according to claim 1, wherein, It satisfies one or more of the following conditions a-d; a. The ash content of the pulverized coal coke ≤ 10%; b. The median particle size D50 of the pulverized coke is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm or 7 μm; c. The median particle size D50 of the pulverized coal coke is 8 μm, 10 μm, 12 μm, 15 μm, 16 μm, 17 μm, 18 μm or 19 μm; d. The mass ratio of the pulverized coke to the pulverized coal coke is 6:400, 8:400, 20:400, 40:400, 60:400, 80:400, 100:400 or 105:

400.

13. The preparation method of the hard carbon material according to claim 12, wherein, The preparation method of the hard carbon material simultaneously satisfies the above conditions a-d.

14. The method for preparing the hard carbon material according to claim 12, wherein, The ash content of the pulverized coal coke is 9.8%.

15. The preparation method of the hard carbon material according to claim 1, wherein, It satisfies one or more of the following conditions a-c; a. During the preparation process of the mixture, the mixing temperature is 20-350 °C; b. During the preparation process of the mixture, the mixing time is 0.5-6 h; c. The time of the heat treatment is 3-15 h.

16. The preparation method of the hard carbon material according to claim 15, characterized in that, The preparation method of the hard carbon material simultaneously satisfies the above conditions a-c.

17. The preparation method of the hard carbon material according to claim 15, characterized in that, It satisfies one or more of the following conditions a-c; a. During the preparation process of the mixture, the mixing temperature is 80 °C, 150 °C, 200 °C, 250 °C or 300 °C; b. During the preparation process of the mixture, the mixing time is 1 h, 2 h, 3 h, 4 h, or 5 h; c. The time of the heat treatment is 4 h, 6 h, 8 h, 10 h, 12 h, or 14 h.

18. The preparation method of the hard carbon material according to claim 17, wherein, The preparation method of the hard carbon material simultaneously satisfies the above conditions a - c.

19. The preparation method of the hard carbon material according to claim 1, characterized in that, It satisfies one or both of the following conditions a - b; a. The heat treatment includes a first heat treatment and a second heat treatment; the temperature of the first heat treatment is 500 - 800 °C; the heating rate to the temperature of the first heat treatment is 2 - 5 °C / min; the time of the first heat treatment is 1 - 4 h; the temperature of the second heat treatment is 900 - 1500 °C; the heating rate to the temperature of the second heat treatment is 3 - 7 °C / min; the time of the second heat treatment is 3 - 6 h; b. Before the coal char powder is mixed with the coke fines, the coal char powder is first pretreated, and the pretreatment includes drying, pulverizing, pickling, and suction filtration.

20. The method for preparing the hard carbon material according to claim 19, wherein, The preparation method of the hard carbon material simultaneously satisfies the above conditions a - b.

21. The method for preparing the hard carbon material according to claim 19, wherein, The temperature of the first heat treatment is 600 °C or 700 °C.

22. The method for preparing the hard carbon material according to claim 19, wherein The heating rate to the temperature of the first heat treatment is 3 °C / min.

23. The method for preparing the hard carbon material according to claim 19, wherein, The time of the first heat treatment is 2 h.

24. The preparation method of the hard carbon material according to claim 19, wherein, The temperature of the second heat treatment is 1200 °C, 1300 °C, or 1400 °C.

25. The method for preparing the hard carbon material according to claim 19, characterized in that, The heating rate to the temperature of the second heat treatment is 5 °C / min.

26. The method for preparing the hard carbon material according to claim 19, characterized in that, The time of the second heat treatment is 4 h or 5 h.

27. The preparation method of the hard carbon material according to claim 1, characterized in that, It satisfies one or more of the following conditions a - d; a. During the alkali washing process, the alkaline substance in the alkali solution is one or more of sodium hydroxide, lithium hydroxide, and potassium hydroxide; b. During the alkali washing process, the concentration of the alkali solution is 0.01 - 0.5 mol / L; c. The temperature of the alkali washing is 50 °C; d. The time of the alkali washing is 4 h or 6 h.

28. The method for preparing the hard carbon material according to claim 27, wherein, It simultaneously satisfies the above conditions a - d.

29. The method for preparing the hard carbon material according to claim 27, wherein, It satisfies one or both of the following conditions a - b: a. During the alkali washing process, the alkaline substance in the alkali solution is lithium hydroxide; b. During the alkali washing process, the concentration of the alkali solution is 0.03 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, or 0.4 mol / L.

30. The preparation method of the hard carbon material according to claim 29, characterized in that, It simultaneously satisfies the above conditions a - b.

31. The preparation method of the hard carbon material according to claim 1, characterized in that The time of the insoluble and infusible treatment is 4 - 15 h.

32. The method for preparing the hard carbon material according to claim 1, characterized in that, The insoluble and infusible treatment includes a first treatment and a second treatment; The temperature of the first treatment is 300 - 500 °C; the heating rate to the temperature of the first treatment is 2 - 5 °C / min; the time of the first treatment is 1 - 4 h; The temperature of the second treatment is 500 - 800 °C; the heating rate to the temperature of the second treatment is 2 - 5 °C / min; the time of the second treatment is 3 - 7 h.

33. The preparation method of the hard carbon material according to claim 1, characterized in that, The temperature of the insoluble and infusible treatment is 400 °C, 450 °C, 500 °C, 550 °C, or 600 °C.

34. The preparation method of the hard carbon material according to claim 31, characterized in that, The time of the insoluble and infusible treatment is 6 h, 8 h, 10 h, 12 h, 13 h, or 14 h.

35. The method for preparing the hard carbon material according to claim 32, wherein The temperature of the first treatment is 450 °C.

36. The method for preparing the hard carbon material according to claim 32, wherein, The heating rate to the temperature of the first treatment is 2 °C / min.

37. The method for preparing the hard carbon material according to claim 32, wherein The time of the first treatment is 2 h or 3 h.

38. The method for preparing the hard carbon material according to claim 32, characterized in that, The temperature of the second treatment is 600 °C or 700 °C.

39. The method for preparing the hard carbon material according to claim 32, wherein, The rate of heating up to the second treatment temperature is 3 °C / min.

40. The preparation method of the hard carbon material according to claim 32, characterized in that, The time of the second treatment is 4 h or 6 h.

41. The preparation method of the hard carbon material according to claim 1, characterized in that, The oxidizing gas is air, oxygen or ozone.

42. The method for preparing the hard carbon material according to claim 41, wherein, The oxidizing gas is oxygen.

43. A hard carbon material prepared by the preparation method of the hard carbon material according to any one of claims 1-42.

44. An ion battery, characterized in that, It includes the hard carbon material according to claim 43.

45. An application of the hard carbon material according to claim 43 as an electrode material in an ion battery.

46. Use of the hard carbon material as described in claim 45 as an electrode material in an ion battery, characterized in that, The ion battery is a lithium ion battery or a sodium ion battery.

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