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

Abstract

The present invention discloses a hard carbon material, its preparation method, application and battery. The preparation method of the hard carbon material is as follows: after mixing a carbon source, a triblock copolymer and a magnesium salt, pre-carbonizing, pickling, crushing and carbonizing are carried out in sequence to obtain a hard carbon material; or, after mixing a carbon source, a triblock copolymer and a magnesium salt, solvent heat treatment is carried out to obtain a hard carbon material; wherein, the mass ratio of the magnesium salt to the triblock copolymer is 1: (0.1 to 10); the mass ratio of the magnesium salt to the carbon source is 1: (6 to 200). The hard carbon material prepared by the present invention has a controllable pore structure, and the pore size range is at the micropore level. On the premise that the sum of the sodium embedding capacity in the high and low potential regions meets the requirements of actual application, the sodium embedding capacity in the high potential region is higher, and the three-dimensional structure is stable, and the uniformity between different batches of products is high. The preparation method is simple.

Description

Technical Field

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

[0002] Graphite, a negative electrode material for lithium-ion batteries, has a theoretical specific capacity of 372 mAh / g. Currently, it has achieved an actual capacity of 360-365 mAh / g, approaching the theoretical limit. The power, energy storage, and consumer markets are placing higher demands on the fast-charging and safety performance of negative electrode materials. Furthermore, due to the low abundance of lithium in the Earth's crust, coupled with technological and market constraints, the shortage of lithium resources has become increasingly prominent in the face of surging demand.

[0003] CATL released a sodium-ion battery in July 2021 with an energy density of 160Wh / kg. The energy density of lithium-ion batteries on the market ranges from 160-300Wh / kg. Sodium-ion batteries have a lower energy density than lithium-ion batteries, making them an important supplement to the low-energy-density battery market.

[0004] Graphite anodes cannot be used as negative electrode materials for sodium-ion batteries due to limitations such as the interlayer spacing of the carbon layers. Hard carbon materials, however, have larger interlayer spacing, larger pore sizes, and richer porosity, making them suitable for use as negative electrodes in both lithium-ion and sodium-ion batteries. As an amorphous carbon, hard carbon cannot be converted into graphite even at graphitization temperatures. The fundamental reason lies in the long-range disordered arrangement of carbon layers within its structure. The presence of various heterogeneous phases and heteroatoms leads to more defects, and the accumulation of different configurations also results in a diverse pore structure. It is precisely because of these defects and pores that more space is available for the storage of lithium and sodium ions.

[0005] Theoretically, the lithium and sodium storage processes of hard carbon anode materials are primarily divided into three stages: adsorption, pore filling, and intercalation reaction. The pore filling stage provides a wider capacity range. Therefore, the pore structure of hard carbon anode materials has a significant impact on the electrochemical and kinetic performance of batteries. For hard carbon materials, how to control the appropriate pore structure to achieve excellent electrochemical and kinetic performance has become a pressing issue. Summary of the Invention

[0006] The technical problem addressed by the present invention is to overcome the drawback of prior art hard carbon materials, which suffer from the difficulty in controlling the pore structure. The present invention provides a hard carbon material, its preparation method, applications, and batteries. The hard carbon material prepared by the present invention has a controllable pore structure, with a pore size range reaching the microporous level. Furthermore, while the combined sodium insertion capacity in the high-potential region meets practical application requirements, the high-potential region exhibits a higher sodium insertion capacity. Furthermore, the material exhibits a stable three-dimensional structure, high uniformity across batches, and a simple preparation method.

[0007] The present invention provides a method for preparing a hard carbon material, which comprises the following steps:

[0008] After mixing a carbon source, a triblock copolymer and a magnesium salt, pre-carbonizing, acid washing, crushing and carbonizing are carried out in sequence to prepare the hard carbon material;

[0009] Alternatively, the carbon source, the triblock copolymer and the magnesium salt are mixed and then subjected to solvent thermal treatment to obtain the hard carbon material;

[0010] Wherein, the mass ratio of the magnesium salt to the triblock copolymer is 1:(0.1-10); the mass ratio of the magnesium salt to the carbon source is 1:(5-200).

[0011] In the present invention, the carbon source can be any conventional one in the art, preferably one or more of phenolic resin, epoxy resin, sweet potato starch, banana peel, coconut shell, anthracite, asphalt, corn cob, rice husk, glucose, and cassava flour. The mass ratio of the magnesium salt to the carbon source is preferably 1:(5-100), more preferably 1:(6-60), for example 1:6.7, 1:15, 1:20, or 1:60.

[0012] In the present invention, the triblock copolymer can be a conventional triblock copolymer in the art that can be used as a porogen, such as a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (PEO-PPO-PEO), a polyethylene oxide-polybutylene oxide-polyethylene oxide triblock copolymer (PEO-PBO-PEO) or a polypropylene oxide-polyethylene oxide-polypropylene oxide triblock copolymer (PPO-PEO-PPO).

[0013] The number average molecular weight of the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer may be conventional in the art, for example, 10,000 to 12,000 or 5,000 to 6,000.

[0014] In the present invention, the magnesium salt may be an inorganic magnesium salt or an organic magnesium salt, preferably an organic magnesium salt. The inorganic magnesium salt is preferably magnesium nitrate and / or magnesium chloride. The organic magnesium salt is preferably one or more of magnesium ethoxide, magnesium acetate, magnesium gluconate, magnesium citrate, magnesium tert-butoxide, isopropylmagnesium chloride, and isobutylmagnesium bromide.

[0015] The mass ratio of the magnesium salt to the triblock copolymer is preferably 1:(0.1-8), such as 1:0.17, 1:0.5, 1:3 or 1:6.

[0016] In the present invention, an additive is preferably added during the mixing step. The additive can be an additive suitable for preparing hard carbon materials in the art, preferably a silicon-containing reagent, more preferably one or more of trimethylsilyl acetate, tetraethyl silicate, polysiloxane, and diphenylsilanediol. The amount of the additive can be conventional in the art, and the ratio of the mass of the magnesium salt to the volume of the additive can be 1:(0.5-25) g / mL, preferably 1:(1-20) g / mL, for example 1:1.4 g / mL, 1:5.6 g / mL, or 1:16 g / mL.

[0017] In the present invention, the mixing can be performed according to conventional material mixing methods and conditions for preparing hard carbon materials in the art.

[0018] In the mixing step, the order of mixing the materials can be arbitrary. Preferably, the triblock copolymer, magnesium salt, additive and carbon source are added in sequence, or the triblock copolymer, additive, magnesium salt and carbon source are added in sequence, or the triblock copolymer, carbon source and magnesium salt are added in sequence.

[0019] As is conventional in the art, the mixing is performed in a solvent. The solvent is preferably water or an acidic aqueous solution. The acid is preferably HCl. The concentration of the acidic aqueous solution may be 1 to 8 mol / L, preferably 1 to 3 mol / L, such as 2 mol / L.

[0020] The mixing temperature is preferably 30-80°C, more preferably 60-80°C, for example 60°C or 80°C. The heating method during the mixing process is preferably water bath heating. The mixing time is preferably 2-24 hours, more preferably 10-16 hours, for example 14 hours.

[0021] According to conventional practice in the art, the mixing is performed under stirring. The stirring speed may be 500-3000 rpm, preferably 1000-2500 rpm. Preferably, the mixing is performed by first mixing a portion of the material at 1000-2500 rpm for 1-4 hours, and then mixing with the remaining material at 400-600 rpm for 10-15 hours.

[0022] In a preferred embodiment of the present invention, the mixing is performed by first mixing part of the material at 1800 rpm for 2 hours, and then mixing with the remaining material at 500 rpm for 12 hours.

[0023] In the present invention, after the mixing is completed, cooling and drying are further performed according to the conventional art. Specifically, the mixture may be first cooled to room temperature and then freeze-dried.

[0024] In the present invention, the pre-carbonization can be carried out according to conventional pre-carbonization conditions in the art. The pre-carbonization temperature can be 250-700°C, preferably 400-550°C, such as 420°C, 450°C or 500°C. The pre-carbonization time can be 1-10 hours, preferably 1-4 hours, such as 2 hours or 3 hours. The pre-carbonization is generally carried out under a protective atmosphere that does not react with the reaction system, such as nitrogen or an inert gas.

[0025] In the present invention, the pickling can be carried out according to conventional conditions for pickling in the art. The acid is preferably one or more of hydrochloric acid, phosphoric acid, sulfuric acid, hydrofluoric acid, nitric acid, salicylic acid and acetic acid. The concentration of the acid can be 0.1 to 5.0 mol / L, preferably 0.5 to 2.0 mol / L, such as 1.0 mol / L. In a preferred embodiment, the acid is 1.0 mol / L hydrofluoric acid. The pickling time can be 1 to 10 hours, preferably 2 to 6 hours, for example 4 hours.

[0026] After the acid washing, washing to neutrality and drying are further performed according to the conventional method in the art.

[0027] The washing may be performed with water or alkali solution until the solution is neutral. The alkali in the alkali solution may be one or more of sodium hydroxide, ammonia, potassium hydroxide, and lithium hydroxide. The concentration of the alkali in the alkali solution may be 0.1 to 2.0 mol / L, preferably 0.5 to 1.5 mol / L, for example 1.0 mol / L.

[0028] The drying temperature may be 50-180° C., preferably 60-100° C., such as 80° C. The drying time may be 3-24 hours, preferably 8-12 hours, such as 10 hours. The drying method may be forced air drying.

[0029] In the present invention, the pulverization can be carried out according to conventional conditions in the art. The particle size of the pulverized particles can be 3 to 8 μm, for example, 5 μm. The pulverization equipment can be a jet mill.

[0030] In the present invention, the carbonization can be carried out according to the conventional conditions of pulverization in this field. The temperature of the carbonization can be 800-1600°C, preferably 900-1400°C, for example 1150°C. The time of the carbonization can be 1-12h, preferably 2-6h, for example 4h. The rate of heating to the carbonization temperature can be 0.5-10°C / min, preferably 1-5°C / min, for example 3.5°C / min. The carbonization is generally carried out under a protective atmosphere that does not react with the reaction system, such as nitrogen or inert gas. The flow rate of the protective atmosphere can be 0.5-40L / min, preferably 0.5-10L / min, for example 1L / min or 5L / min. After the carbonization is completed, the temperature is also lowered to room temperature naturally.

[0031] In the present invention, the type of solvent used in the process of the solvent thermal treatment can be conventional in the art, such as water or ethanol. The temperature of the solvent thermal treatment can be 80 to 200°C, preferably 160 to 200°C, such as 170°C, 180°C or 190°C. The time of the solvent thermal treatment can be 4 to 18 hours, preferably 6 to 10 hours, such as 7 hours, 8 hours or 9 hours. In a preferred embodiment of the present invention, the solvent thermal treatment is a hydrothermal treatment at 180°C for 8 hours.

[0032] In the present invention, screening is preferably performed after the carbonization is completed.

[0033] The present invention also provides a hard carbon material prepared by the above-mentioned preparation method of the hard carbon material.

[0034] The present invention also provides a hard carbon material, the pore size distribution range of which is micropore level, preferably 0.4-1 nm.

[0035] Preferred embodiments of the hard carbon material of the present invention also have one or more of the following parameters: particle size D 50 The particle size is 3-6 μm and the compacted density is 0.6-1.2 g / cm 3 , with a specific surface area of ​​4-20m 2 / g, the sum of the sodium insertion capacity in the high and low potential regions is 340-388 mAh.g -1 , the sodium insertion capacity in the high potential region is 58-142 mAh.g -1 , the sodium insertion capacity in the low potential region is 210-299 mAh.g -1 And the first efficacy is 82%-88%.

[0036] The present invention also provides a use of the aforementioned hard carbon material in preparing a sodium ion battery or a lithium ion battery.

[0037] The present invention also provides a battery comprising the hard carbon material as described above, wherein the battery is a sodium ion battery or a lithium ion battery.

[0038] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0039] The reagents and raw materials used in the present invention are commercially available.

[0040] The positive progress effect of the present invention is:

[0041] (1) The pore size range of the hard carbon material prepared by the present invention can be micropore level, and the pore size within this range can be continuous or discontinuous;

[0042] (2) The hard carbon material prepared by the present invention has a higher sodium embedding capacity in the high potential region, provided that the sum of the sodium embedding capacities in the high and low potential regions meets the requirements of practical applications;

[0043] (3) The hard carbon material prepared by the present invention has a controllable pore structure, a stable three-dimensional structure, and high uniformity between different batches of products;

[0044] (4) The preparation method of the hard carbon material of the present invention is simple and has low requirements on experimental equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the pore size distribution diagram of the hard carbon material prepared in Example 2.

[0046] Figure 2 This is the pore size distribution diagram of the hard carbon material prepared in Example 3.

[0047] Figure 3 This is the pore size distribution diagram of the hard carbon material prepared in Example 5.

[0048] Figure 4 This is the pore size distribution diagram of the hard carbon material prepared in Example 6.

[0049] Figure 5 This is the pore size distribution diagram of the hard carbon material prepared in Example 11. DETAILED DESCRIPTION

[0050] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0051] In the following examples, Pluronic P123 refers to a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer with a number average molecular weight of 5000-6000, purchased from Sinopharm Reagent, product model XW90031165; F127 has a number average molecular weight of 10000-12000, purchased from Sinopharm Reagent, product model XW90031161.

[0052] Example 1

[0053] (1) Mixing: Add 100 g of the triblock copolymer Pluronic P123 and 200 g of magnesium salt MgNO3 (the mass ratio of magnesium salt to triblock copolymer is 1:0.5) to a 2.0 M aqueous solution of HCl. Maintain the water bath at 60°C and add 280 mL of trimethylsilyl acetate (the mass ratio of magnesium salt to volume of additive is 1:1.4 g / mL). Keep rotating at 1800 rpm. After 2 h, add 3 kg of the carbon source glucose solution (the mass ratio of magnesium salt to carbon source is 1:15) to the above solution. Then reduce the speed to 500 rpm and keep stirring for 12 h. After removing the heating equipment, cool to room temperature and then freeze-dry.

[0054] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0055] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0056] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0057] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0058] Example 2

[0059] (1) Mixing: Add 100 g of Pluronic P123 to a 2.0 M HCl aqueous solution, maintain the water bath at 60°C, add 280 mL of tetraethyl silicate (the mass ratio of magnesium salt to volume of additive is 1:1.4 g / mL), and after 12 hours, add 200 g of MgNO3 (the mass ratio of magnesium salt to triblock copolymer is 1:0.5). Keep rotating at 1800 rpm. After 2 hours, add 3 kg of glucose solution (the mass ratio of magnesium salt to carbon source is 1:15) to the above solution, then reduce the speed to 500 rpm and keep stirring for 12 hours. After removing the heating equipment, let it cool to room temperature and then freeze-dry.

[0060] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0061] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0062] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0063] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0064] Example 3

[0065] (1) Mixing: Add 300 g of Pluronic P123 to a 2.0 M HCl aqueous solution, maintain the water bath at 60°C, add 280 mL of tetraethyl silicate (the mass ratio of magnesium salt to volume of additive is 1:5.6 g / mL), and after 12 hours, add 50 g of magnesium ethoxide (the mass ratio of magnesium salt to triblock copolymer is 1:6). Keep rotating at 1800 rpm. After 2 hours, add 3 kg of glucose solution (the mass ratio of magnesium salt to carbon source is 1:60) to the above solution, then reduce the speed to 500 rpm and keep stirring for 12 hours. After removing the heating equipment, cool to room temperature naturally and then freeze-dry.

[0066] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0067] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0068] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0069] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0070] Example 4

[0071] (1) Mixing: Add 300 g of Pluronic P123 to a 2.0 M HCl aqueous solution. Maintain the water bath at 60°C, add 280 mL of tetraethyl silicate (the mass ratio of magnesium salt to volume of additive is 1:5.6 g / mL). After 12 hours, add 50 g of MgNO3 (the mass ratio of magnesium salt to triblock copolymer is 1:6). Keep rotating at 1800 rpm. After 2 hours, add 3 kg of glucose solution (the mass ratio of magnesium salt to carbon source is 1:60) to the above solution. Then reduce the speed to 500 rpm and keep stirring for 12 hours. Remove the heating equipment, let it cool to room temperature, and then freeze-dry.

[0072] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0073] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0074] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0075] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0076] Example 5

[0077] (1) Mixing: Add 30 g of Pluronic P123 to a 2.0 M HCl aqueous solution. Maintain the water bath at 60°C. Add 80 mL of tetraethyl silicate (the ratio of the mass of the magnesium salt to the volume of the additive is 1:16 g / mL). After 12 hours, add 5 g of MgNO3 (the mass ratio of the magnesium salt to the triblock copolymer is 1:6). Maintain rotation at 1800 rpm. After 2 hours, add 300 g of glucose (the mass ratio of the magnesium salt to the carbon source is 1:60) to the above solution. Then reduce the speed to 500 rpm and continue stirring for 12 hours.

[0078] (2) Solvothermal treatment: The solution was transferred to a 500 mL hydrothermal reactor and heated to 180°C at atmospheric pressure for 8 h. The reactor was opened after natural cooling to room temperature. The product obtained after sedimentation and centrifugation was immersed in a 1.0 M HF solution, stirred for 4 h, and then washed with a 1 mol / L ammonia solution and filtered until neutral. The filtered product was dried at 80°C for 10 h, cooled to room temperature, and then collected and sieved.

[0079] Example 6

[0080] (1) Mixing: Add 30 g of F127 to a 2.0 M HCl aqueous solution. Maintain the water bath at 60°C. Add 80 mL of tetraethyl silicate (the ratio of the mass of the magnesium salt to the volume of the additive is 1:16 g / mL). After 12 hours, add 5 g of MgNO3 (the mass ratio of the magnesium salt to the triblock copolymer is 1:6). Maintain rotation at 1800 rpm. After 2 hours, add 300 g of glucose (the mass ratio of the magnesium salt to the carbon source is 1:60) to the above solution. Then reduce the speed to 500 rpm and continue stirring for 12 hours.

[0081] (2) Solvothermal treatment: The solution was transferred to a 500 mL hydrothermal reactor and heated to 180°C at atmospheric pressure for 8 h. The reactor was opened after natural cooling to room temperature. The product obtained after sedimentation and centrifugation was immersed in a 1.0 M HF solution, stirred for 4 h, and then washed with a 1 mol / L ammonia solution and filtered until neutral. The filtered product was dried at 80°C for 10 h, cooled to room temperature, and then collected and sieved.

[0082] Example 7

[0083] (1) Mixing: Add 300 g of F127 to deionized water and keep the water bath environment at 60 °C, add 2 kg of glucose, stir at 1800 rpm for 2 h, then add 100 g of magnesium acetate (the mass ratio of magnesium salt to triblock copolymer is 1:3, and the mass ratio of magnesium salt to carbon source is 1:20), then reduce the speed to 500 rpm and keep stirring for 12 h, remove the heating equipment, and cool naturally to room temperature before freeze-drying.

[0084] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0085] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0086] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0087] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0088] Example 8

[0089] (1) Mixing: Add 300 g of F127 to deionized water and keep the water bath environment at 60 °C, add 2 kg of glucose, stir at 1800 rpm for 2 h, then add 100 g of magnesium gluconate (the mass ratio of magnesium salt to triblock copolymer is 1:3, and the mass ratio of magnesium salt to carbon source is 1:20), then reduce the speed to 500 rpm and keep stirring for 12 h, remove the heating equipment, and cool naturally to room temperature before freeze-drying.

[0090] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0091] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0092] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0093] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0094] Example 9

[0095] (1) Mixing: Add 300 g of F127 to deionized water and keep the water bath environment at 60 °C, add 2 kg of glucose, stir at 1800 rpm for 2 h, then add 100 g of magnesium ethanolate (the mass ratio of magnesium salt to triblock copolymer is 1:3, and the mass ratio of magnesium salt to carbon source is 1:20), then reduce the speed to 500 rpm and keep stirring for 12 h, remove the heating equipment, and cool naturally to room temperature before freeze-drying.

[0096] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0097] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0098] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0099] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0100] Example 10

[0101] (1) Mixing: Add 300 g of F127 to deionized water and keep the water bath environment at 80 °C, add 2 kg of water-soluble phenolic resin, stir at 1800 rpm for 2 h, then add 100 g of magnesium gluconate (the mass ratio of magnesium salt to triblock copolymer is 1:3, and the mass ratio of magnesium salt to carbon source is 1:20), then reduce the speed to 500 rpm and keep stirring for 12 h, remove the heating equipment, and cool naturally to room temperature before freeze-drying.

[0102] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0103] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0104] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0105] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0106] Example 11

[0107] (1) Mixing: Add 50 g of F127 to deionized water and keep the water bath environment at 80 °C, add 2 kg of water-soluble phenolic resin, stir at 1800 rpm for 2 h, then add 300 g of magnesium citrate (the mass ratio of magnesium salt to triblock copolymer is 1:0.17, and the mass ratio of magnesium salt to carbon source is 1:6.7), then reduce the speed to 500 rpm and keep stirring for 12 h, remove the heating equipment, and cool naturally to room temperature before freeze-drying.

[0108] (2) Pre-carbonization: The obtained product was heat treated at 420 °C in a nitrogen atmosphere for 2 h and then cooled to room temperature naturally.

[0109] (3) Acid washing and cleaning: The product was immersed in 1.0 M HF solution, stirred for 4 h, and then washed with 1 mol / L ammonia solution and filtered until neutral.

[0110] (4) Drying and pulverizing: The product obtained by filtration was dried at 80°C for 10 h, and then pulverized into a particle size of D using a jet mill. 50 5μm.

[0111] (5) Carbonization: The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a heating rate of 3.5°C / min under a nitrogen atmosphere for 4 h. During the heating and natural cooling process, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0112] Comparative Example 1

[0113] 3 kg of glucose was placed in a box furnace and heat treated at 450 ° C in a nitrogen atmosphere for 2 hours. After the temperature naturally dropped to room temperature, the product was crushed into particles of size D using a jet mill. 50 The pulverized product was transferred to a box furnace and heated from room temperature to 1150°C at a rate of 3.5°C / min under a nitrogen atmosphere for 4 hours. During the holding period and natural cooling, the nitrogen flow rate was maintained at 1 L / min. After cooling to room temperature, the product was removed and sieved.

[0114] Effect embodiment

[0115] 1. Test Method

[0116] 1. Aperture test:

[0117] For the hard carbon materials prepared in Examples 1-11 and the comparative example, when testing their pore size distribution, the analyzer model used was the fully automatic specific surface area and pore analyzer ASAP 2460, the test conditions were carbon dioxide as the adsorption and desorption medium, the powder degassing temperature was 300°C, and the relative pressure range P / P0 of the test was 0-1.

[0118] 2. Electrochemical performance test

[0119] The hard carbon materials prepared in Examples 1-11 and the comparative example were used to prepare a slurry, wherein the weight ratio of hard carbon material: binder: conductive carbon black was 95:2.5:2.5. The prepared slurry was then scraped onto a copper foil with a scraping thickness of 250-300 μm. The dried electrode was assembled into a button cell using a CR2430 battery shell, with the counter electrode being a Na sheet, in a glove box environment with an oxygen and water content of <0.1 ppm. The electrolyte used was 1.0 M NaPF6 (EC:DMC=1:1). After assembly, the cells were first kept overnight for 8 hours, and then the capacity of Na intercalation and deintercalation was tested at a rate of C / 20. The intercalation capacity is the specific capacity of the first Na intercalation. The first efficiency is the percentage of the removal capacity to the total intercalation capacity.

[0120] 2. Test Results

[0121] 1. Pore size distribution

[0122] Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 The pore size distributions of Examples 2, 3, 5, 6 and 11 are shown. As shown in the figure, the pore size distributions of Examples 2, 3, 5, 6 and 11 of the present invention are between 0.4 and 1 nm, which are continuous or discontinuous distributions.

[0123] 2. Particle size, compacted density, specific surface area, cumulative pore volume, and electrochemical properties

[0124] Table 1 shows the physicochemical parameters and electrochemical performance parameters of the hard carbon materials prepared in Examples 1-11 and Comparative Examples.

[0125] Table 1 Physicochemical parameters and electrochemical performance parameters of the products in Examples 1-11

[0126]

[0127]

[0128] It can be seen from Table 1 that the particle size D of the hard carbon materials prepared in Examples 1-11 is 50 The particle size is 3.0-6.0 μm and the compacted density is 0.70-1.1 g.cm -3 Specific surface area is 4.5-18.0m 2 .g -1 The sum of the sodium insertion capacity in the high and low potential regions is 340-388 mAh.g -1 , the sodium insertion capacity in the high potential region is 58-142 mAh.g -1, the sodium insertion capacity in the low potential region is 210-299 mAh.g -1 , the initial effect is 82%-88%.

[0129] In practical applications, the hard carbon material prepared in this application can not only ensure that the sum of the sodium embedding capacity in the high and low potential regions meets the requirements of actual use, but also ensure that the sodium embedding capacity in the high potential region is higher.

[0130] By comparing Examples 1-6 with Examples 7-11, it can be found that after adding the additive, the sodium insertion capacity in the high potential region is higher and the sodium insertion capacity in the low potential region is lower.

[0131] By comparing Example 3 and Example 4, it can be seen that when the magnesium source used is an organic magnesium salt, the sum of the sodium insertion capacity in the high and low potential regions of the prepared hard carbon material is higher, the sodium insertion capacity in the high potential region is higher, and the electrochemical performance is better.

Claims

1. A method for preparing a hard carbon material, characterized in that: It includes the following steps: Scheme 1: After mixing a carbon source, a triblock copolymer and a magnesium salt, pre-carbonizing, acid washing, crushing and carbonizing are carried out in sequence to obtain the hard carbon material; an additive is also added during the mixing step; the additive is a silicon-containing reagent, and the silicon-containing reagent is selected from one or more of trimethylsilyl acetate, tetraethyl silicate, polysiloxane and diphenylsilanediol; the ratio of the mass of the magnesium salt to the volume of the additive is 1: (5.6-25) g / mL; the mass ratio of the magnesium salt to the carbon source is 1: (60-200); the mass ratio of the magnesium salt to the triblock copolymer is 1: (3-10); the carbon source is glucose; Alternatively, Option 2: A carbon source, a triblock copolymer and a magnesium salt are mixed and then subjected to solvent thermal treatment to obtain the hard carbon material; an additive is also added during the mixing step; the additive is a silicon-containing reagent, and the silicon-containing reagent is selected from one or more of trimethylsilyl acetate, tetraethyl silicate, polysiloxane and diphenylsilanediol, and the ratio of the mass of the magnesium salt to the volume of the additive is 1: (0.5~25) g / mL; the mass ratio of the magnesium salt to the carbon source is 1: (5~200); the mass ratio of the magnesium salt to the triblock copolymer is 1: (0.1~10).

2. The method for preparing a hard carbon material according to claim 1, wherein: The preparation method satisfies one or more of the following conditions: (1) In the second embodiment, the carbon source is one or more of phenolic resin, epoxy resin, sweet potato starch, banana peel, coconut shell, anthracite, asphalt, corn cob, rice husk, glucose and cassava flour; (2) In the second embodiment, the mass ratio of the magnesium salt to the carbon source is 1:(5-100); (3) In the first or second embodiment, the triblock copolymer is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, a polyethylene oxide-polybutylene oxide-polyethylene oxide triblock copolymer, or a polypropylene oxide-polyethylene oxide-polypropylene oxide triblock copolymer; (4) In the first or second embodiment, the magnesium salt is an inorganic magnesium salt or an organic magnesium salt; and (5) In the second embodiment, the mass ratio of the magnesium salt to the triblock copolymer is 1:(0.1-8).

3. The method for preparing a hard carbon material according to claim 2, wherein: The preparation method satisfies one or both of the following conditions: (1) In the second embodiment, the mass ratio of the magnesium salt to the carbon source is 1:(6-60); (2) In the second embodiment, the mass ratio of the magnesium salt to the triblock copolymer is 1:0.17, 1:0.5, 1:3 or 1:

6.

4. The method for preparing a hard carbon material according to claim 3, wherein: In the second scheme, the mass ratio of the magnesium salt to the carbon source is 1:6.7, 1:15, 1:20 or 1:

60.

5. The method for preparing a hard carbon material according to claim 2, wherein: The inorganic magnesium salt is magnesium nitrate and / or magnesium chloride.

6. The method for preparing a hard carbon material according to claim 2, wherein: The organic magnesium salt is one or more of magnesium ethoxide, magnesium acetate, magnesium gluconate, magnesium citrate, magnesium tert-butoxide, isopropylmagnesium chloride and isobutylmagnesium bromide.

7. The method for preparing a hard carbon material according to claim 1, wherein: In the first embodiment, the ratio of the mass of the magnesium salt to the volume of the additive is 1:5.6 g / mL or 1:16 g / mL.

8. The method for preparing a hard carbon material according to claim 1, wherein: In the first embodiment, the mass ratio of the magnesium salt to the triblock copolymer is 1:3 or 1:

6.

9. The method for preparing a hard carbon material according to claim 8, wherein: In the second solution, the ratio of the mass of the magnesium salt to the volume of the additive is 1: (1-20) g / mL.

10. The method for preparing a hard carbon material according to claim 9, wherein: In the second scheme, the ratio of the mass of the magnesium salt to the volume of the additive is 1:1.4 g / mL, 1:5.6 g / mL or 1:16 g / mL.

11. The method for preparing a hard carbon material according to claim 1, wherein: The preparation method satisfies one or more of the following conditions: (1) The pre-carbonization temperature is 250-700°C; (2) The pre-carbonization time is 1 to 10 hours; (3) The acid used for pickling is one or more of hydrochloric acid, phosphoric acid, sulfuric acid, hydrofluoric acid, nitric acid, salicylic acid and acetic acid; (4) the concentration of the acid used in the pickling is 0.1 to 5.0 mol / L; and (5) The pickling time is 1 to 10 hours.

12. The method for preparing a hard carbon material according to claim 11, wherein: The preparation method satisfies one or more of the following conditions: (1) The pre-carbonization temperature is 400-550°C; (2) The pre-carbonization time is 1 to 4 hours; (3) the concentration of the acid used in the pickling is 0.5 to 2.0 mol / L; and (4) The pickling time is 2 to 6 hours.

13. The method for preparing a hard carbon material according to claim 12, wherein: The preparation method satisfies one or more of the following conditions: (1) The pre-carbonization temperature is 420°C, 450°C or 500°C; (2) The pre-carbonization time is 2h or 3h; (3) the concentration of the acid used in the pickling is 1.0 mol / L; and (5) The pickling time is 4 hours.

14. The method for preparing a hard carbon material according to claim 1, wherein: The preparation method satisfies one or more of the following conditions: (1) The particle size of the crushed product is 3 to 8 μm; (2) The carbonization temperature is 800-1600° C.; (3) the carbonization time is 1 to 12 hours; and (4) The rate of heating to the carbonization temperature is 0.5 to 10° C. / min.

15. The method for preparing a hard carbon material according to claim 14, wherein: The preparation method satisfies one or more of the following conditions: (1) The crushed particle size is 5 μm; (2) The carbonization temperature is 900-1400° C.; (3) The carbonization time is 2 to 6 hours; and (4) The rate of heating to the carbonization temperature is 1 to 5°C / min.

16. The method for preparing a hard carbon material according to claim 15, wherein: The preparation method satisfies one or more of the following conditions: (1) The carbonization temperature is 1150°C; (2) the carbonization time is 4 hours; and (3) The rate of heating to the carbonization temperature is 3.5°C / min.

17. The method for preparing a hard carbon material according to claim 16, wherein: The preparation method satisfies one or more of the following conditions: (1) The solvent used in the solvent thermal treatment process is water or ethanol; (2) the temperature of the solvent heat treatment is 160 to 200° C.; and (3) The solvent heat treatment time is 4 to 18 hours.

18. The method for preparing a hard carbon material according to claim 17, wherein: The preparation method satisfies one or more of the following conditions: (1) the temperature of the solvent thermal treatment is 170°C, 180°C or 190°C; and (2) The solvent heat treatment time is 6 to 10 hours.

19. The method for preparing a hard carbon material according to claim 18, wherein: The solvent thermal treatment time is 7h, 8h or 9h.

20. A hard carbon material, characterized in that The hard carbon material is prepared by the method for preparing the hard carbon material according to any one of claims 1 to 19.

21. The hard carbon material according to claim 20, wherein Its pore size distribution range is micropore level.

22. The hard carbon material according to claim 21, wherein The pore size distribution range is 0.4-1nm.

23. The hard carbon material according to claim 20, wherein The hard carbon material has one or more of the following parameters: particle size D 50 The particle size is 3-6 μm and the compacted density is 0.6-1.2 g / cm 3 , with a specific surface area of ​​4-20m 2 / g, the sum of the sodium insertion capacity in the high and low potential regions is 340-388 mAh.g -1 , the sodium insertion capacity in the high potential region is 58-142 mAh.g -1 , the sodium insertion capacity in the low potential region is 210-299 mAh.g -1 And the first efficacy is 82%-88%.

24. Use of the hard carbon material according to any one of claims 20 to 23 in preparing a sodium ion battery or a lithium ion battery.

25. A battery, characterized in that: It comprises the hard carbon material according to any one of claims 20 to 23, and the battery is a sodium ion battery or a lithium ion battery.

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