A method for preparing a high-specific-capacity sodium-ion battery hard carbon anode material

Abstract

The application discloses a preparation method of a high-specific-capacity sodium ion battery hard carbon negative electrode material and relates to the field of sodium ion battery negative electrode materials. The boron, titanium and magnesium elements are uniformly distributed in the modified phenolic resin, and since the newly-added boron, titanium and magnesium elements are relatively large, they can increase the volume of the material, thereby improving the specific capacity of the material. Meanwhile, the uniformly dispersed boron, titanium and magnesium elements can provide more active sites, so that the material can absorb and release energy faster, thereby improving the initial efficiency.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode materials, and in particular to a method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries. Background Technology

[0002] As one of the core components of sodium-ion batteries, the negative electrode has a significant impact on the battery's energy density, rate performance, cycle performance, and initial coulombic efficiency. Generally speaking, a good sodium-ion battery negative electrode material should possess the following characteristics: high sodium storage specific capacity; minimal structural changes during sodium ion insertion / extraction; good compatibility with the electrolyte, without side reactions; high ion mobility and electronic conductivity, good chemical and thermodynamic stability; and environmental friendliness and economic efficiency.

[0003] A sodium-ion battery anode material and its preparation method based on a hard carbon precursor and a doped phase (Chinese Patent Application No.: CN202210556729.1) describes a sodium-ion battery anode material using a hard carbon precursor and a doped phase as raw materials. First, the hard carbon precursor is pretreated by heating in air. Then, the doped phase and the pretreated hard carbon precursor are mixed by simple high-energy ball milling. The resulting composite is then sintered in an inert atmosphere. After cooling, the product is acid-washed and dried to obtain a hard carbon anode material with a "graphite-like phase." The hard carbon precursor is cellulose-derived carbon; the doped phase is one or more mixtures of natural graphite, artificial graphite, modified graphite, petroleum pitch, and tar pitch. This method utilizes a low-temperature optimized doping phase strategy to reduce material costs and energy consumption. The constructed "graphite-like phase" is key to achieving a high-capacity plateau region for hard carbon anodes.

[0004] Patent application CN117303344A discloses a method for preparing high-specific-capacity hard carbon materials based on biomass. This method includes the following steps: pretreating biomass particles with a chemical dehydrating condensing agent to induce a certain degree of carbonization; obtaining black precursor particles through filtration, washing, and drying; further increasing the fixed carbon content through low-temperature pre-carbonization; and finally, obtaining a high-specific-capacity hard carbon material suitable for sodium-ion battery anodes through crushing, high-temperature sintering, and post-processing. This invention uses a chemical dehydrating condensing agent pretreatment to remove hydrogen and hydroxyl groups from cellulose-like substances in the biomass raw material, resulting in internal molecular cross-linking and rearrangement, increased molecular weight, and enhanced aromaticity, significantly fixing small-molecule organic matter and improving discharge specific capacity. However, it does not improve, and may even reduce, the first-efficiency performance.

[0005] Compared to cathode materials, the research and industrialization progress of sodium-ion battery anode materials is significantly slower, resulting in relatively higher costs. The main reason is that sodium ions have a larger radius than lithium ions, making them difficult to effectively insert and extract into graphite. Therefore, the graphite anode system used in lithium-ion batteries is difficult to apply to sodium-ion batteries.

[0006] Currently, the widely studied anode materials for sodium-ion batteries mainly include carbon-based materials (soft carbon / hard carbon, etc.), titanium-based intercalated anode materials, organic materials, and alloy materials. Among them, non-carbon-based materials exhibit problems such as volume expansion, poor stability, and poor conductivity during cycling, resulting in limited practical applications. Therefore, the preparation of carbon-based anode materials with high specific capacity and high efficiency has become a current research focus. Summary of the Invention

[0007] The main objective of this invention is to provide a method for preparing a high-specific-capacity sodium-ion battery hard carbon anode material, so as to overcome the shortcomings of the prior art.

[0008] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0009] This invention provides a method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0010] Organic carbon source is carbonized by chemical dehydration condensing agent pretreatment, then filtered, washed and dried to obtain precursor, then subjected to low-temperature pre-oxidation treatment, and then crushed, high-temperature carbonized and cooled to obtain the high specific capacity sodium-ion battery hard carbon anode material.

[0011] The organic carbon source is a modified phenolic resin.

[0012] The specific steps of the preparation method are as follows:

[0013] Step 1: Dehydration Condensation

[0014] Weigh 80-120 parts of modified phenolic resin according to the mass ratio, add it to 500-1000 parts of dehydrating condensing agent and soak for 2-6 hours, then filter, wash repeatedly with deionized water until neutral, and dry to obtain the precursor.

[0015] Step 2: Pre-oxidation

[0016] The precursor material obtained in step one is transferred to an air furnace, heated to 400-600℃ for pre-oxidation, and then naturally cooled to room temperature and pulverized into powder by airflow.

[0017] Step 3: High-temperature carbonization

[0018] The powder from step two is transferred to a tube furnace and slowly heated to 1150-1650℃ under a nitrogen atmosphere for high-temperature carbonization. After carbonization, the temperature is maintained for 1-2 hours, and then slowly cooled to room temperature to obtain hard carbon anode material.

[0019] Preferably, the modification method of the modified phenolic resin includes the following steps:

[0020] 3-(2-Carboxyvinyl)phenylboronic acid and titanium tetranitrate undergo a coordination reaction under an inert gas atmosphere at a first temperature to obtain a reaction solution. Phenolic resin containing silane bonds and a cassiterite catalyst are then added to the reaction solution. After a second temperature heat treatment, magnesium dimethacrylate is added, followed by a second temperature heat treatment to obtain a modified phenolic resin.

[0021] The modification method of the modified phenolic resin specifically includes the following steps:

[0022] M1: Add 0.05-0.2 parts of 3-(2-carboxyvinyl)phenylboronic acid, 0.05-0.5 parts of titanium tetranitrate, and 500-1000 parts of ethanol to a reaction vessel by mass, purge with nitrogen gas, heat to 40℃-50℃ and stir for 20-50 minutes to obtain a reaction solution.

[0023] M2: Add 100-160 parts of phenolic resin containing silane bonds and 0.01-0.4 parts of caster catalyst to the reaction solution of step M1, stir and react at 60℃-70℃ for 30-50 minutes, then add 0.5-2.4 parts of magnesium dimethacrylate, stir and react at 60℃-70℃ for 10-30 minutes. After the reaction is completed, distill off the ethanol to obtain the modified phenolic resin.

[0024] The method for preparing the phenolic resin containing silane bonds includes the following steps:

[0025] The phenolic resin was placed in a plasma device, and bis(dimethylamino)silane vapor was introduced at a flow rate of 10-17 ml / min. Plasma modification was carried out in this atmosphere for 100-120 min to obtain the phenolic resin containing silane bonds.

[0026] The plasma modification conditions are as follows: the plasma radio frequency device frequency is 200-500kHz and the output power is 100-200W.

[0027] Boron atoms form new carbon-boron bonds. Due to the small size and unique electronic structure of boron atoms, they can form multiple bonds, ensuring the uniform distribution of boron in phenolic resin. Titanium atoms add to the unsaturated bonds in phenolic resin, forming stable titanium-carbon bonds. Due to titanium's coordination ability, it can react with multiple functional groups, ensuring the uniform dispersion of titanium in the resin. The addition reaction of magnesium is similar to that of boron and titanium, forming stable magnesium-carbon bonds. Due to magnesium's reactive nature, it also ensures the uniform distribution of magnesium in the resin.

[0028] Modified phenolic resin can effectively improve the first reversible capacity and first efficiency of sodium-ion batteries. The first reversible capacity can reach up to 322.7 mAh / g, and the first efficiency is increased from 75.5% to 90.4%, representing a 31.5% improvement in first reversible capacity compared to the existing technology (first reversible capacity of 245.4 mAh / g).

[0029] Furthermore, the dehydrating condensing agent is at least one of concentrated sulfuric acid, fuming sulfuric acid, and fuming nitric acid, and the mass percentage concentration of the dehydrating condensing agent is 98%-105%.

[0030] The pre-oxidation involves holding the dried precursor at 400-600℃ for 0.5-3 hours. During this process, volatile substances vaporize and escape, while macromolecules and benzene compounds undergo dehydrogenation and carbonization.

[0031] The pulverization is airflow crushing, and the airflow crushes the particles to a particle size D. 50 It is 6-18μm.

[0032] Preferably, the conditions for high-temperature carbonization are: high-temperature carbonization is carried out by heating to 1150-1650°C under a nitrogen atmosphere, and the nitrogen flow rate is 15-45cc / min.

[0033] The heating steps are as follows: heating to 800-1000℃ at a heating rate of 3-6℃ / min; heating to 1150-1650℃ at a heating rate of 3-5℃ / min.

[0034] The cooling steps are as follows: cool down to 400-600℃ at a cooling rate of 3-5℃ / min; cool down to room temperature at a cooling rate of 4-8℃ / min.

[0035] High-temperature carbonization, stepped heating and stepped cooling: During high-temperature carbonization, the structure of hard carbon changes. As the temperature rises, the disordered carbon in hard carbon gradually transforms into ordered carbon, forming a more stable graphitized structure. This structural change affects the physical and chemical properties of hard carbon.

[0036] During the stepped heating and cooling processes, the pore structure of hard carbon is also affected. During heating, some pores in hard carbon may expand or connect, increasing the specific surface area and pore volume of hard carbon. During cooling, the pore structure may shrink or close, affecting the adsorption and ion transport properties of hard carbon.

[0037] Technical effects of the present invention:

[0038] This invention modifies phenolic resin by uniformly distributing boron, titanium, and magnesium elements within it. Because the newly added boron, titanium, and magnesium elements are relatively large, they may increase the material's volume, thereby improving its specific volume. Simultaneously, the uniformly dispersed boron, titanium, and magnesium elements can provide more active sites, enabling the material to absorb and release energy more quickly, thus improving its first-efficiency. Detailed Implementation

[0039] Example 1

[0040] A modified phenolic resin, the modification method of which is as follows:

[0041] M1: Add 0.05g of 3-(2-carboxyvinyl)phenylboronic acid, 0.05g of titanium tetranitrate, and 500g of ethanol to the reaction vessel, purge with nitrogen, raise the temperature, and stir the reaction at 40°C for 20 minutes.

[0042] M2: Continue to add 100g of phenolic resin with silane bonds and 0.1g of caster catalyst (CAS: 81032-58-8), stir and react at 60℃ for 30 minutes, then add 0.5g of magnesium dimethacrylate, stir and react at 60℃ for 10 minutes. After the reaction is completed, distill to remove ethanol to obtain modified phenolic resin.

[0043] The preparation method of the phenolic resin with silane-hydrogen bonds is as follows:

[0044] 120g of phenolic resin was placed in a plasma device, and bis(dimethylamino)silane vapor was introduced at a flow rate of 10ml / min. Plasma modification was carried out in this atmosphere for 100min to obtain phenolic resin with silane-hydrogen bonds. The plasma modification conditions were: the plasma radio frequency device frequency was 200kHz and the output power was 100W.

[0045] A method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0046] Step 1: Dehydration Condensation

[0047] Weigh 80g of modified phenolic resin, add it to 500g of concentrated sulfuric acid with a mass percentage concentration of 98% and soak for 2 hours. Then filter, wash repeatedly with deionized water until neutral, and dry to obtain the precursor.

[0048] Step 2: Pre-oxidation

[0049] The precursor material obtained in step one was transferred to an air furnace and heated to 400°C for pre-oxidation for 0.5 h. Then it was naturally cooled to room temperature and pulverized into powder with a D50 range of 12±6 μm.

[0050] Step 3: High-temperature carbonization

[0051] The powder from step two was transferred to a tube furnace, and nitrogen gas was introduced at a flow rate of 15 cc / min. Under the nitrogen atmosphere, the temperature was increased to 1000℃ at a heating rate of 6℃ / min; then increased to 1650℃ at a heating rate of 5℃ / min for high-temperature carbonization. After carbonization, the temperature was maintained for 1 hour, and then decreased to 600℃ at a cooling rate of 5℃ / min; finally, the temperature was decreased to room temperature at a cooling rate of 8℃ / min to obtain the hard carbon anode material.

[0052] Example 2

[0053] A modified phenolic resin, the modification method of which is as follows:

[0054] M1: Add 0.1g of 3-(2-carboxyvinyl)phenylboronic acid, 0.25g of titanium tetranitrate, and 750g of ethanol to the reaction vessel, purge with nitrogen, raise the temperature, and stir the reaction at 45°C for 30 minutes.

[0055] M2: Continue to add 120g of phenolic resin with silane bonds and 0.25g of caster catalyst (CAS: 81032-58-8), stir and react at 65℃ for 40 minutes, then add 1.2g of magnesium dimethacrylate, stir and react at 65℃ for 20 minutes. After the reaction is completed, distill to remove ethanol to obtain modified phenolic resin.

[0056] The preparation method of the phenolic resin with silane-hydrogen bonds is as follows:

[0057] 135g of phenolic resin was placed in a plasma device, and bis(dimethylamino)silane vapor was introduced at a flow rate of 12ml / min. Plasma modification was carried out in this atmosphere for 110min to obtain phenolic resin with silane-hydrogen bonds. The plasma modification conditions were: the plasma radio frequency device frequency was 300kHz and the output power was 150W.

[0058] A method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0059] Step 1: Dehydration Condensation

[0060] Weigh 100g of modified phenolic resin, add it to 750g of fuming sulfuric acid with a mass percentage concentration of 105% and soak for 3h. Then filter, wash repeatedly with deionized water until neutral, and dry to obtain the precursor.

[0061] Step 2: Pre-oxidation

[0062] The precursor material obtained in step one was transferred to an air furnace and heated to 500°C for pre-oxidation for 1.5 hours. Then it was naturally cooled to room temperature and pulverized into powder with a D50 range of 12±6μm.

[0063] Step 3: High-temperature carbonization

[0064] The powder from step two was transferred to a tube furnace, and nitrogen gas was introduced at a flow rate of 25 cc / min. Under the nitrogen atmosphere, the temperature was increased to 900°C at a heating rate of 5°C / min; then increased to 1450°C at a heating rate of 4°C / min for high-temperature carbonization. After carbonization, the temperature was maintained for 1 hour, and then decreased to 500°C at a cooling rate of 4°C / min; finally, the temperature was decreased to room temperature at a cooling rate of 6°C / min to obtain the hard carbon anode material.

[0065] Example 3

[0066] A modified phenolic resin, the modification method of which is as follows:

[0067] M1: Add 0.15g of 3-(2-carboxyvinyl)phenylboronic acid, 0.4g of titanium tetranitrate, and 750g of ethanol to the reaction vessel, purge with nitrogen, raise the temperature, and stir the reaction at 45°C for 40 minutes.

[0068] M2: Continue to add 140g of phenolic resin with silane bonds and 0.3g of caster catalyst (CAS: 81032-58-8), stir and react at 65℃ for 40 minutes, then add 1.8g of magnesium dimethacrylate, stir and react at 65℃ for 20 minutes. After the reaction is completed, distill to remove ethanol to obtain modified phenolic resin.

[0069] The preparation method of the phenolic resin with silane-hydrogen bonds is as follows:

[0070] 145g of phenolic resin was placed in a plasma device, and bis(dimethylamino)silane vapor was introduced at a flow rate of 15ml / min. Plasma modification was carried out in this atmosphere for 110min to obtain phenolic resin with silane-hydrogen bonds. The plasma modification conditions were: the plasma radio frequency device frequency was 400kHz and the output power was 150W.

[0071] A method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0072] Step 1: Dehydration Condensation

[0073] Weigh 100g of modified phenolic resin, add it to 750g of fuming nitric acid with a mass percentage concentration of 98% and soak for 4 hours. Then filter, wash repeatedly with deionized water until neutral, and dry to obtain the precursor.

[0074] Step 2: Pre-oxidation

[0075] The precursor material obtained in step one was transferred to an air furnace and heated to 500°C for pre-oxidation for 2.5 hours. Then it was naturally cooled to room temperature and pulverized into powder with a D50 range of 12±6μm.

[0076] Step 3: High-temperature carbonization

[0077] The powder from step two was transferred to a tube furnace, and nitrogen gas was introduced at a flow rate of 35 cc / min. The temperature was increased to 900°C at a heating rate of 4°C / min under nitrogen atmosphere. The temperature was then increased to 1300°C at a heating rate of 4°C / min for high-temperature carbonization. After carbonization, the temperature was maintained for 2 hours. The temperature was then decreased to 500°C at a cooling rate of 4°C / min. Finally, the temperature was decreased to room temperature at a cooling rate of 6°C / min to obtain the hard carbon anode material.

[0078] Example 4

[0079] A modified phenolic resin, the modification method of which is as follows:

[0080] M1: Add 0.2g of 3-(2-carboxyvinyl)phenylboronic acid, 0.5g of titanium tetranitrate, and 1000g of ethanol to the reaction vessel, purge with nitrogen, raise the temperature, and stir at 50°C for 50 minutes.

[0081] M2: Continue to add 160g of phenolic resin with silane bonds and 0.4g of caster catalyst (CAS: 81032-58-8), stir and react at 70℃ for 50 minutes, then add 2.4g of magnesium dimethacrylate, stir and react at 70℃ for 30 minutes. After the reaction is completed, distill to remove ethanol to obtain modified phenolic resin.

[0082] The preparation method of the phenolic resin with silane-hydrogen bonds is as follows:

[0083] 165g of phenolic resin was placed in a plasma device, and bis(dimethylamino)silane vapor was introduced at a flow rate of 17ml / min. Plasma modification was carried out in this atmosphere for 120min to obtain phenolic resin with silane-hydrogen bonds. The plasma modification conditions were: the plasma radio frequency device frequency was 500kHz and the output power was 200W.

[0084] A method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0085] Step 1: Dehydration Condensation

[0086] Weigh 120g of phenolic resin and soak it in 1000g of concentrated sulfuric acid with a mass percentage concentration of 100% for 6 hours. Then filter it, wash it repeatedly with deionized water until neutral, and dry it to obtain the precursor.

[0087] Step 2: Pre-oxidation

[0088] The precursor material obtained in step one was transferred to an air furnace and heated to 600℃ for pre-oxidation for 3 hours. Then it was naturally cooled to room temperature and pulverized into powder with a D50 range of 12±6μm.

[0089] Step 3: High-temperature carbonization

[0090] The powder from step two was transferred to a tube furnace, and nitrogen gas was introduced at a flow rate of 45 cc / min. The temperature was increased to 800°C at a heating rate of 3°C / min under nitrogen atmosphere. The temperature was then increased to 1150°C at a heating rate of 3°C / min for high-temperature carbonization. After carbonization, the temperature was maintained for 2 hours. The temperature was then decreased to 600°C at a cooling rate of 3°C / min. Finally, the temperature was decreased to room temperature at a cooling rate of 4°C / min to obtain the hard carbon anode material.

[0091] Comparative Example 1

[0092] A method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0093] Step 1: Dehydration Condensation

[0094] Weigh 80g of phenolic resin and soak it in 500g of concentrated sulfuric acid with a mass percentage concentration of 98% for 2 hours. Then filter it, wash it repeatedly with deionized water until neutral, and dry it to obtain the precursor.

[0095] Step 2: Pre-oxidation

[0096] The precursor material obtained in step one was transferred to an air furnace and heated to 400°C for pre-oxidation for 0.5 h. Then it was naturally cooled to room temperature and pulverized into powder with a D50 range of 12±6 μm.

[0097] Step 3: High-temperature carbonization

[0098] The powder from step two was transferred to a tube furnace, and nitrogen gas was introduced at a flow rate of 15 cc / min. Under the nitrogen atmosphere, the temperature was increased to 1000℃ at a heating rate of 6℃ / min; then increased to 1650℃ at a heating rate of 5℃ / min for high-temperature carbonization. After carbonization, the temperature was maintained for 1 hour, and then decreased to 600℃ at a cooling rate of 5℃ / min; finally, the temperature was decreased to room temperature at a cooling rate of 8℃ / min to obtain the hard carbon anode material.

[0099] Comparative Example 2

[0100] A modified phenolic resin, the modification method of which is as follows:

[0101] M1: Add 0.05g of 3-(2-carboxyvinyl)phenylboronic acid, 0.05g of titanium tetranitrate, and 500g of ethanol to the reaction vessel, purge with nitrogen, raise the temperature, and stir the reaction at 40°C for 20 minutes.

[0102] M2: Continue to add 100g of phenolic resin and 0.1g of caster catalyst (CAS: 81032-58-8), stir and react at 60℃ for 30 minutes, then add 0.5g of magnesium dimethacrylate, stir and react at 60℃ for 10 minutes. After the reaction is completed, distill to remove ethanol to obtain modified phenolic resin.

[0103] A method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0104] Step 1: Dehydration Condensation

[0105] Weigh 80g of modified phenolic resin, add it to 500g of concentrated sulfuric acid with a mass percentage concentration of 98% and soak for 2 hours. Then filter, wash repeatedly with deionized water until neutral, and dry to obtain the precursor.

[0106] Step 2: Pre-oxidation

[0107] The precursor material obtained in step one was transferred to an air furnace and heated to 400°C for pre-oxidation for 0.5 h. Then it was naturally cooled to room temperature and pulverized into powder with a D50 range of 12±6 μm.

[0108] Step 3: High-temperature carbonization

[0109] The powder from step two was transferred to a tube furnace, and nitrogen gas was introduced at a flow rate of 15 cc / min. Under the nitrogen atmosphere, the temperature was increased to 1000℃ at a heating rate of 6℃ / min; then increased to 1650℃ at a heating rate of 5℃ / min for high-temperature carbonization. After carbonization, the temperature was maintained for 1 hour, and then decreased to 600℃ at a cooling rate of 5℃ / min; finally, the temperature was decreased to room temperature at a cooling rate of 8℃ / min to obtain the hard carbon anode material.

[0110] Comparative Example 3

[0111] A modified phenolic resin, the modification method of which is as follows:

[0112] M1: Add 0.05g of titanium tetranitrate and 500g of ethanol to the reaction vessel, purge with nitrogen, heat to 40°C and stir for 20 minutes.

[0113] M2: Continue to add 100g of phenolic resin with silane bonds and 0.1g of caster catalyst (CAS: 81032-58-8), stir and react at 60℃ for 30 minutes, then add 0.5g of magnesium dimethacrylate, stir and react at 60℃ for 10 minutes. After the reaction is completed, distill to remove ethanol to obtain modified phenolic resin.

[0114] The preparation method of the phenolic resin with silane-hydrogen bonds is as follows:

[0115] 120g of phenolic resin was placed in a plasma device, and bis(dimethylamino)silane vapor was introduced at a flow rate of 10ml / min. Plasma modification was carried out in this atmosphere for 100min to obtain phenolic resin with silane-hydrogen bonds. The plasma modification conditions were: the plasma radio frequency device frequency was 200kHz and the output power was 100W.

[0116] A method for preparing a high-specific-capacity hard carbon anode material for sodium-ion batteries, comprising the following steps:

[0117] Step 1: Dehydration Condensation

[0118] Weigh 80g of modified phenolic resin, add it to 500g of concentrated sulfuric acid with a mass percentage concentration of 98% and soak for 2 hours. Then filter, wash repeatedly with deionized water until neutral, and dry to obtain the precursor.

[0119] Step 2: Pre-oxidation

[0120] The precursor material obtained in step one was transferred to an air furnace and heated to 400°C for pre-oxidation for 0.5 h. Then it was naturally cooled to room temperature and pulverized into powder with a D50 range of 12±6 μm.

[0121] Step 3: High-temperature carbonization

[0122] The powder from step two was transferred to a tube furnace, and nitrogen gas was introduced at a flow rate of 15 cc / min. Under the nitrogen atmosphere, the temperature was increased to 1000℃ at a heating rate of 6℃ / min; then increased to 1650℃ at a heating rate of 5℃ / min for high-temperature carbonization. After carbonization, the temperature was maintained for 1 hour, and then decreased to 600℃ at a cooling rate of 5℃ / min; finally, the temperature was decreased to room temperature at a cooling rate of 8℃ / min to obtain the hard carbon anode material.

[0123] Test Example 1

[0124] In a dry room with humidity less than 10%, the hard carbon materials, conductive carbon black, and binder obtained in Examples 1-4 and Comparative Examples 1-3 were mixed in NMP at a mass ratio of 90:5:5, homogenized, and the solid content was controlled at 45%. The mixture was then coated onto an aluminum foil current collector, vacuum-baked at 110°C for 4 hours, pressed into shape, and then die-cut to prepare a sodium negative electrode sheet. A coin cell was assembled in an argon-filled glove box. The counter electrode was a metallic sodium sheet, the separator was PE, and the electrolyte was 1 mol / L NaPF6 with an EC / DMCVol ratio of 1:1. Charge-discharge tests were performed on the coin cells using the following procedure: 0.1C CC 4.0V, 4.0V CV 0.03C, 0.1CDC 2V. The first reversible capacity and efficiency of the sodium negative electrode materials in the examples and comparative examples were measured. The test results are shown in Table 1.

[0125] Table 1

[0126] First reversible capacity mAh / g First-time efficiency % Example 1 312.2 88.3 Example 2 316.9 89.2 Example 3 321.5 90.1 Example 4 322.7 90.4 Comparative Example 1 245.4 75.5 Comparative Example 2 271.0 81.6 Comparative Example 3 284.6 84.8

[0127] The test data from the examples and comparative examples in Table 1 above clearly show that the hard carbon anode material prepared by the modified phenolic resin in this method effectively improves the first reversible capacity and first efficiency of sodium-ion batteries.

[0128] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high specific capacity sodium-ion battery hard carbon anode material, characterized in that, The method comprises the following steps: The organic carbon source is carbonized by pretreatment with a dehydration condensation agent by a chemical method, and then filtered, washed, and dried to obtain a precursor, which is then subjected to low-temperature pre-oxidation, crushing, high-temperature carbonization, and cooling to obtain the hard-carbon negative electrode material for sodium-ion batteries with high specific capacity; The organic carbon source is modified phenolic resin. The modification method of the modified phenolic resin comprises the following steps: 3-(2-carboxyvinyl)phenylboronic acid and titanium tetranitrate are subjected to a coordination reaction at a first temperature under an inert gas to obtain a reaction solution, and then a phenolic resin containing a silicon-hydrogen bond and a Karstedt catalyst are added to the reaction solution, and the mixture is subjected to a second temperature heat treatment, and then dimethyl magnesium acrylate is added and subjected to a second temperature heat treatment to obtain the modified phenolic resin; The preparation method of the phenolic resin containing a silicon-hydrogen bond comprises the following steps: The phenolic resin is placed in a plasma device, and di(dimethylamino)silane vapor is introduced at a flow rate of 10-17 ml / min; and the plasma modification is performed in the atmosphere to obtain the phenolic resin containing a silicon-hydrogen bond, wherein the modification time is 100-120 min; The plasma modification conditions are as follows: the frequency of the plasma radio frequency device is 200-500 kHz, and the output power is 100-200 W; The high-temperature carbonization conditions are as follows: The high-temperature carbonization is performed at 1150-1650℃ under a nitrogen atmosphere, and the nitrogen flow rate is 15-45 cc / min; The temperature rising step is as follows: the temperature is raised to 800-1000℃ at a temperature rising rate of 3-6℃ / min; and the temperature is raised to 1150-1650℃ at a temperature rising rate of 3-5℃ / min; The temperature lowering step is as follows: the temperature is lowered to 400-600℃ at a temperature lowering rate of 3-5℃ / min; and the temperature is lowered to room temperature at a temperature lowering rate of 4-8℃ / min.

2. The method of claim 1, wherein the method is characterized by: The modification method of the modified phenolic resin comprises the following steps: M1: 0.05-0.2 parts of 3-(2-carboxyvinyl)phenylboronic acid, 0.05-0.5 parts of titanium tetranitrate, and 500-1000 parts of ethanol are added to a reaction kettle, nitrogen is introduced, the temperature is raised to 40-50℃, and the mixture is stirred for 20-50 min to obtain a reaction solution; M2: 100-160 parts of the phenolic resin containing a silicon-hydrogen bond and 0.01-0.4 parts of a Karstedt catalyst are continuously added to the reaction solution of step M1, the mixture is stirred at 60-70℃ for 30-50 min, 0.5-2.4 parts of dimethyl magnesium acrylate is added, the mixture is stirred at 60-70℃ for 10-30 min, and then the ethanol is removed by distillation to obtain the modified phenolic resin. 3.The method of claim 1, wherein the method further comprises the step of: The dehydration condensation agent is at least one of concentrated sulfuric acid, fuming sulfuric acid, and fuming nitric acid. ​ 4.The method of claim 1, wherein the method further comprises the step of: The pre-oxidation is that the dried precursor is subjected to heat preservation at 400-600℃ for 0.5-3 h. ​ 5. The method of claim 1, wherein the method is characterized by: The comminution is air-jet fragmentation, the air-jet fragmentation being to a particle size D 50 of 6-18 μm.