Preparation method for sodium-based modified phenolic resin hard carbon negative electrode

Abstract

The present invention belongs to the field of sodium ion batteries. Disclosed is a preparation method for a sodium-based modified phenolic resin. The method comprises: a phenolic compound and an aldehyde compound undergoing a condensation reaction under the action of an alkaline catalyst to obtain an amino phenolic resin; carrying out a neutralization reaction by using 5-amino-1,2,3-benzenetricarboxylic acid and a sodium hydroxide solution; and adding an organic solvent, the amino phenolic resin, triethylamine and glycidaldehyde diethyl acetal to carry out an addition reaction, so as to obtain the sodium-based modified phenolic resin. Also provided in the present invention is a preparation method for a sodium-based modified phenolic resin hard carbon negative electrode, comprising: carbonizing the sodium-based modified phenolic resin in an inert atmosphere, grinding same and screening same to obtain an active substance; uniformly mixing the active substance, a conductive agent and a binder, coating a copper foil with same, drying same and rolling same to obtain a sodium ion battery negative electrode sheet. The methods effectively improve the capacity and the initial coulombic efficiency of the hard carbon negative electrode, thereby effectively improving the electrochemical properties of sodium ion batteries.

Description

Preparation method of sodium-modified phenolic resin hard carbon negative electrode Technical Field

[0001] The present invention belongs to the field of sodium ion batteries, and in particular relates to a method for preparing a sodium-modified phenolic resin hard carbon negative electrode. Background Art

[0002] As an emerging electrochemical energy storage system, sodium-ion batteries (Na-ion batteries) hold enormous potential for development and are expected to replace lithium-ion batteries amid the rapid development of new energy vehicles worldwide. Compared to Li-ion batteries, Na-ion batteries offer greater reserves, higher theoretical capacity, and lower production costs.

[0003] With the rise of sodium-ion batteries, hard carbon materials have garnered widespread attention. Commercial hard carbon is widely used to improve the low-temperature fast-charging performance of lithium-ion batteries. Currently, commonly used hard carbon precursors are primarily bio-based polymers such as bamboo, coconut shells, starch, and walnut shells. Chemical raw materials such as anthracite, asphalt, and phenolic resins can also be used.

[0004] For sodium-ion batteries, the structural characteristics and preparation process of hard carbon materials have a significant impact on the battery's electrical performance. Generally speaking, hard carbon anode materials have a higher specific capacity, meaning that they can store more sodium ions for the same volume or mass, thereby improving the battery's energy density and endurance. Furthermore, hard carbon materials have a larger pore structure, which allows for more uniform expansion and contraction of the electrode during charge and discharge, enhancing the battery's cycling stability.

[0005] However, although hard carbon negative electrode materials have good stability, their cycle performance is poor, especially under high-rate charge and discharge conditions. Moreover, the first-cycle coulombic efficiency of hard carbon negative electrode materials is relatively low, and there will be large energy loss during the first charge and discharge process, affecting the overall performance of the battery.

[0006] In response to the above problems, the patent document with publication number CN117352652A (publication date 2024-01-05) discloses a preparation method and application of a high-performance hard carbon negative electrode material for sodium ion batteries, comprising the following steps: 1) asphalt crushing process: weighing asphalt, using a powder grinder to obtain asphalt particles with a particle size of 1 to 50 μm; 2) introducing a cross-linking agent process: pre-treating the asphalt particles obtained in step 1) in a tubular furnace for 2 to 30 hours to capture the cross-linking agent in the gas to obtain cross-linked asphalt; 3) carbonization process: the cross-linked asphalt obtained in step 2) is subjected to a carbonization reaction. The hard carbon material is placed in a tubular furnace under the protection of a protective gas, and then cooled to obtain a hard carbon material; 4) a hard carbon material particle size control process: the hard carbon material obtained in step 3) is used to obtain hard carbon particles with a particle size of 1 to 50 μm using a powder grinder, and then the required hard carbon particles of 8 to 10 μm are sieved using a sieve; 5) the hard carbon particles obtained in step 4) are fully mixed with a binder and conductive carbon black to obtain a mixed negative electrode material, the mixed negative electrode material is mixed with water, and stirred to obtain a mixed slurry, the mixed slurry is coated on a current collector, and dried to obtain a high-performance sodium ion battery hard carbon negative electrode material.

[0007] This invention uses asphalt as a precursor of hard carbon, which can significantly reduce costs. However, this invention does not involve improvements in the microstructure of the hard carbon negative electrode material, and does not significantly improve the electrical properties of the formed sodium ion battery, such as the first-week coulombic efficiency and cycle stability.

[0008] The patent document with publication number CN117163940A (publication date is 2023-12-05) discloses a P, O co-doped sodium ion battery hard carbon negative electrode material and a preparation method thereof, the method comprising: crushing the raw material asphalt by high-energy ball milling and then sieving; acid washing / alkali washing the sieved material to remove impurities, and then washing with deionized water and drying to obtain pure asphalt powder; mixing the asphalt powder, organic phosphorus source and alcohol in a certain proportion and transferring them into a crucible and transferring them to a tubular furnace; heating at a certain heating rate, keeping warm, and cooling to room temperature at a certain cooling rate; after the tubular furnace is completely cooled, taking out the crucible, grinding the material and sieving to obtain a P, O co-doped asphalt-based carbon negative electrode material.

[0009] This invention constructs a sodium-ion battery by synthesizing P and O co-doped asphalt-based carbon negative electrode materials. However, the asphalt-based carbon negative electrode materials may introduce some defects and functional groups during the preparation process, and these defects and functional groups may undergo irreversible reactions with the electrolyte during the first charge and discharge process, resulting in battery capacity loss. In addition, the asphalt-based carbon negative electrode materials have poor conductivity, which will affect the electron transfer efficiency of the formed sodium-ion battery.

[0010] Patent document with publication number CN117117187A (publication date 2023-11-24) discloses a hard carbon negative electrode slurry for sodium ion batteries and a preparation method thereof. The hard carbon negative electrode slurry for sodium ion batteries includes the following raw materials: hard carbon, a negative electrode active material, a conductive agent, and a binder, wherein the binder is a mixture of sodium-containing acrylic acid homopolymer and sodium carboxymethyl cellulose CMC; the preparation method includes the following steps: (1) CMC and deionized water are stirred and dispersed to form a glue solution; (2) a conductive agent is added to the glue solution and stirred and dispersed to form a conductive glue; (3) a negative electrode hard carbon material is added to the conductive glue and stirred and dispersed to obtain a mixed slurry; (4) sodium-containing acrylic acid homopolymer is added to the mixed slurry and stirred and dispersed to obtain a hard carbon negative electrode slurry for sodium ion batteries.

[0011] The CMC used in this invention has good solubility and dispersibility in water. However, when it is mixed with the negative electrode hard carbon material, the surface properties of the hard carbon material are not very compatible with the polar properties of CMC, which may lead to poor dispersion uniformity of the two, thereby affecting the cycle stability of the final sodium ion battery hard carbon negative electrode slurry.

[0012] Therefore, although hard carbon is regarded as a highly promising negative electrode material for sodium-ion batteries, its low first-cycle coulombic efficiency, unstable cycle performance and poor rate performance reduce the electrical performance of sodium-ion batteries, so it is necessary to develop a new hard carbon material.

[0013] Summary of the Invention

[0014] In response to the above problems, the purpose of the present invention is to provide a method for preparing a sodium-modified phenolic resin hard carbon negative electrode, in which a sodium-modified phenolic resin is synthesized by aminophenolic resin, and the steam generated by the sodium-modified phenolic resin is used to form pores between the cross-linked phenolic resin matrix to generate a suitable closed porous structure, thereby improving the sodium storage performance of the hard carbon negative electrode, thereby improving the first-week coulombic efficiency and cycle stability of the hard carbon negative electrode.

[0015] To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0016] In a first aspect, the present invention provides a method for preparing a sodium-modified phenolic resin, comprising the following steps:

[0017] (1) Under the action of an alkaline catalyst, a phenolic compound is dissolved in a solvent and undergoes a condensation reaction with an aldehyde compound to obtain an aminophenol-formaldehyde resin;

[0018] (2) using 5-amino-1,2,3-benzenetricarboxylic acid and sodium hydroxide solution to produce a neutralization reaction;

[0019] (3) adding an organic solvent, aminophenol-formaldehyde resin, triethylamine and epoxypropionaldehyde diethyl acetal into the container where the neutralization reaction occurs to cause an addition reaction to obtain a sodium-modified phenol-formaldehyde resin.

[0020] As a further preferred embodiment of the present invention, in step (2), the following components are added, by mass: 40-60 parts of phenolic compound, 3-7 parts of 5-amino-1,2,3-benzenetricarboxylic acid, 10-20 parts of sodium hydroxide solution, 100-160 parts of aminophenol-formaldehyde resin, 2-5 parts of triethylamine, and 28-56 parts of epoxy acrolein diethyl acetal.

[0021] As a further preferred embodiment of the present invention, the solvent is an ethanol aqueous solution;

[0022] The mass percentage of the sodium hydroxide solution is 10wt%-30wt%;

[0023] The organic solvent is tetrahydrofuran.

[0024] As a further preferred embodiment of the present invention, the condensation reaction temperature is 20-25°C, the reaction time is 120-180 min, and the reaction is completed at 105-115°C.

[0025] The neutralization reaction temperature is 20-25°C and the reaction time is 50-120 minutes;

[0026] The temperature of the addition reaction is 60-80° C., and the reaction time is 50-120 min.

[0027] As a further preferred embodiment of the present invention, the phenolic compound includes: 2-aminophenol, 3-aminophenol, 4-aminophenol, resorcinol, phloroglucinol, cresol, mixed cresols, nonylphenol, octylphenol, cardanol, aralkylphenol, bisphenol A or any combination thereof;

[0028] The alkaline catalyst includes one or a mixture of any of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide, sodium isopropoxide, aqueous ammonia, magnesium oxide, ethylenediamine, tertiary amine or triethylamine;

[0029] The aldehyde compound includes one or any combination of formaldehyde, paraformaldehyde, furfural and acetaldehyde.

[0030] In a second aspect, the present invention further provides a sodium-modified phenolic resin, which is prepared according to the preparation method of the sodium-modified phenolic resin described in the first aspect.

[0031] In a third aspect, the present invention further provides a method for preparing a sodium-modified phenolic resin hard carbon negative electrode, using the sodium-modified phenolic resin described in the second aspect, comprising the following steps:

[0032] The sodium-modified phenolic resin is carbonized and ground under an inert atmosphere, and then sieved to obtain an active substance;

[0033] The active material, conductive agent and binder are mixed evenly and then coated on copper foil, dried and rolled to obtain the negative electrode sheet of the sodium ion battery.

[0034] As a further preference of the present invention, the inert atmosphere is argon;

[0035] The carbonization temperature is 1200-1400℃ and the carbonization time is 3-5h;

[0036] The grinding speed is 300-800r / min, and the grinding time is 5-10h;

[0037] The sieving adopts 200-600 mesh.

[0038] As a further preferred embodiment of the present invention, the weight ratio of the active material, the conductive agent, and the binder is (70-80):10:(20-10);

[0039] The coating thickness is 120-160 μm;

[0040] Conductive agents, including one or more of carbon black, acetylene black, vapor-deposited carbon fibers, conductive graphite, carbon nanotubes, graphene, and nitrogen-doped carbon;

[0041] The binder includes one or more of sodium alginate, sodium polyacrylate, and sodium carboxymethyl cellulose.

[0042] In a fourth aspect, the present invention further provides a sodium-modified phenolic resin hard carbon negative electrode, which is prepared according to the preparation method of the sodium-modified phenolic resin hard carbon negative electrode described in the third aspect.

[0043] The beneficial effects of the present invention are as follows:

[0044] (1) The present invention uses a resin material as the negative electrode material of the sodium ion battery. Since the resin material generally has a stable crystal structure and has higher structural stability, the formed sodium ion battery has a higher ion transmission efficiency and charge and discharge speed, which can significantly improve the first-cycle coulomb efficiency of the sodium ion battery and enhance the stability of the cycle performance;

[0045] (2) The study found that sodium-modified phenolic resin can generate steam, thereby forming pores between the cross-linked phenolic resin matrix and generating a suitable closed porous structure, which is conducive to the preparation of high-capacity hard carbon negative electrodes and improves the first-cycle coulombic efficiency and rate performance of sodium-ion batteries. The optimal hard carbon negative electrode obtained by the method of the present invention exhibits a high sodium storage capacity of about 410 mAh / g while maintaining a high first-cycle coulombic efficiency. DETAILED DESCRIPTION

[0046] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles. It should be understood that the specific embodiments described herein are only used to illustrate the present invention and do not limit the scope of protection of the present invention.

[0047] Example 1

[0048] Example 1 provides a method for preparing a sodium-modified phenolic resin hard carbon negative electrode, comprising the following steps:

[0049] Step 1: 40 g of 2-aminophenol and 40 ml of a 25 wt % sodium hydroxide solution are dissolved in 2500 ml of a 33 vol % ethanol aqueous solution to form an alkaline solution; 140 ml of 37 wt % formaldehyde is injected into the alkaline solution under mechanical stirring at room temperature, followed by further reaction for 120 min, centrifugation and washing, and drying at 105° C. overnight to obtain an aminophenol-formaldehyde resin.

[0050] Step 2: Add 3 grams of 5-amino-1,2,3-benzenetricarboxylic acid and 10 grams of 10 wt% sodium hydroxide solution to a reactor, stir at room temperature for 50 minutes, then add 100 grams of aminophenol-formaldehyde resin, 500 grams of tetrahydrofuran, 2 grams of triethylamine, and 28 grams of epoxy acrolein diethyl acetal, stir and react at 60°C for 50 minutes. After the reaction is completed, distill off the tetrahydrofuran to obtain a sodium-modified phenolic resin.

[0051] Step 3: 10 g of sodium-modified phenolic resin was carbonized at 1200° C. for 3 h in a tube furnace under an argon atmosphere, ball-milled at 300 rpm for 5 h in a ball mill, and then passed through a 200-mesh sieve to obtain an active substance.

[0052] Step 4: Using N-methylpyrrolidone as a solvent, the active material, conductive agent (carbon black), and binder (sodium alginate) are mixed evenly in a weight ratio of 70:10:20 and then coated on a copper foil with a coating thickness of 120 μm. The mixture is vacuum dried at 60°C for 10 hours and then rolled to a thickness of 75 μm to obtain a sodium ion battery negative electrode sheet.

[0053] Example 2

[0054] Example 2 provides a method for preparing a sodium-modified phenolic resin hard carbon negative electrode, comprising the following steps:

[0055] Step 1: dissolving 50 g of 3-aminophenol and 50 ml of a 25 wt% ammonium hydroxide solution in 3000 ml of a 33 vol% ethanol aqueous solution to form an alkaline solution; injecting 160 ml of 37 wt% acetaldehyde into the alkaline solution under mechanical stirring at room temperature, followed by further reacting for 160 minutes, washing by centrifugation, and drying at 110° C. overnight to obtain an aminophenol-formaldehyde resin;

[0056] Step 2: Add 5 g of 5-amino-1,2,3-benzenetricarboxylic acid and 15 g of a 20 wt% sodium hydroxide solution to a reactor, stir at room temperature for 85 min, then add 130 g of aminophenol-formaldehyde resin, 750 g of tetrahydrofuran, 3.5 g of triethylamine, and 42 g of epoxy acrolein diethyl acetal, stir at 70° C. for 85 min, and after the reaction is completed, distill off the tetrahydrofuran to obtain a sodium-modified phenolic resin;

[0057] Step 3: 15 g of sodium-modified phenolic resin was carbonized at 1300° C. for 4 h in a tube furnace under an argon atmosphere, ball-milled at 600 / min for 8 h in a ball mill, and then passed through a 400-mesh sieve to obtain the active material.

[0058] Step 4: Using N-methylpyrrolidone as a solvent, the active material, conductive agent (acetylene black), and binder (sodium polyacrylate) are mixed evenly in a weight ratio of 75:10:15 and then coated on a copper foil with a coating thickness of 140 μm. The mixture is vacuum dried at 70°C for 15 hours and then rolled to a thickness of 110 μm to obtain a sodium ion battery negative electrode sheet.

[0059] Example 3

[0060] Example 3 provides a method for preparing a sodium-modified phenolic resin hard carbon negative electrode, comprising the following steps:

[0061] Step 1: dissolving 60 g of 4-aminophenol and 60 ml of a 25 wt% potassium hydroxide solution in 3500 ml of a 33 vol% ethanol aqueous solution to form an alkaline solution; injecting 180 ml of a 37 wt% furfural solution into the alkaline solution under mechanical stirring at room temperature, followed by further reacting for 180 minutes, washing by centrifugation, and drying at 115° C. overnight to obtain an aminophenol-formaldehyde resin;

[0062] Step 2: Add 7 grams of 5-amino-1,2,3-benzenetricarboxylic acid and 20 grams of a 30 wt% sodium hydroxide solution to a reactor, stir at room temperature for 120 minutes, then add 160 grams of aminophenol-formaldehyde resin, 1000 grams of tetrahydrofuran, 5 grams of triethylamine, and 56 grams of epoxy acrolein diethyl acetal, stir and react at 80° C. for 120 minutes. After the reaction is completed, distill off the tetrahydrofuran to obtain a sodium-modified phenolic resin;

[0063] Step 3: 20 g of sodium-modified phenolic resin was carbonized at 1400° C. for 5 h in a tube furnace under an argon atmosphere, ball-milled at 800 rpm for 10 h in a ball mill, and then passed through a 600-mesh sieve to obtain the active material.

[0064] Step 4: Using N-methylpyrrolidone as a solvent, the active material, conductive agent (carbon nanotubes), and binder (sodium carboxymethyl cellulose) are mixed evenly in a weight ratio of 80:10:10 and then coated on a copper foil with a coating thickness of 160 μm. The mixture is vacuum dried at 80°C for 20 hours and then rolled to a thickness of 150 μm to obtain a sodium ion battery negative electrode sheet.

[0065] Comparative Example 1

[0066] In Comparative Example 1, step 2 is deleted, that is, the step of synthesizing the sodium-modified phenolic resin is omitted, and the rest of the technical scheme is the same as in Example 1. The details are as follows:

[0067] Step 1: 40 g of 2-aminophenol and 40 ml of a 25 wt % sodium hydroxide solution are dissolved in 2500 ml of a 33 vol % ethanol aqueous solution to form an alkaline solution; 140 ml of 37 wt % formaldehyde is injected into the alkaline solution under mechanical stirring at room temperature, followed by further reaction for 120 min, centrifugation and washing, and drying at 105° C. overnight to obtain an aminophenol-formaldehyde resin;

[0068] Step 2: 10 g of aminophenol-formaldehyde resin was carbonized at 1200° C. for 3 h in a tube furnace under an argon atmosphere, and ball-milled at 300 rpm for 5 h in a ball mill, and then passed through a 200-mesh sieve to obtain an active substance.

[0069] Step 3: Using N-methylpyrrolidone as a solvent, the active material, carbon black, and sodium alginate are mixed evenly in a weight ratio of 70:10:20 and then coated on a copper foil with a coating thickness of 120 μm. The mixture is vacuum dried at 60°C for 10 hours and then rolled to a thickness of 75 μm to obtain a sodium ion battery negative electrode sheet.

[0070] Comparative Example 2

[0071] In Comparative Example 2, 5-amino-1,2,3-benzenetricarboxylic acid was not added in Step 2, and the rest of the technical scheme was the same as in Example 1.

[0072] Comparative Example 3

[0073] In Comparative Example 3, epoxy acrolein diethyl acetal was not added in step 2, and the rest of the technical solutions were the same as in Example 1.

[0074] Test Example 1

[0075] Electrochemical performance test of the above examples and comparative examples:

[0076] The method for assembling the hard carbon negative electrode materials prepared in each embodiment 1-3 and each comparative example 1-3 into a battery is as follows: the battery is assembled in a high-purity argon atmosphere glove box, and the positive electrode shell - electrode sheet - electrolyte - diaphragm - electrolyte - sodium sheet - negative electrode shell are assembled in sequence, wherein a CR2032 button battery shell is used, the electrolyte is: EC:DMC=1:1 (volume ratio) electrolyte containing 1.0M NaPF6, and the diaphragm is a glass fiber diaphragm.

[0077] The constant current charge / discharge test was carried out on the battery testing system with a voltage range of 0.01 to 3 V and a cycle current density of 1C. The test results are shown in Table 1.

[0078] Table 1 Constant current charge / discharge test results

[0079] It can be seen from the test results in Table 1 that the sodium-modified phenolic resin hard carbon material prepared by the present invention has excellent electrochemical performance, significantly improved capacity, improved coulombic efficiency and cycle stability, and provides ideas and possibilities for the industrial application of sodium ion batteries.

[0080] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the implementation process of the present invention is described in detail above, it is still possible for those familiar with the art to modify the technical solutions described in the above examples or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a sodium-modified phenolic resin, characterized in that: The following steps are involved: (1) Under the action of an alkaline catalyst, a phenolic compound is dissolved in a solvent and undergoes a condensation reaction with an aldehyde compound to obtain an aminophenol-formaldehyde resin; (2) using 5-amino-1,2,3-benzenetricarboxylic acid and sodium hydroxide solution to produce a neutralization reaction; (3) adding an organic solvent, aminophenol-formaldehyde resin, triethylamine and epoxypropionaldehyde diethyl acetal into the container where the neutralization reaction occurs to cause an addition reaction to obtain a sodium-modified phenol-formaldehyde resin.

2. The preparation method of sodium-modified phenolic resin according to claim 1, wherein In step (2), according to the mass parts, 3-7 parts of 5-amino-1,2,3-benzenetricarboxylic acid, 10-20 parts of sodium hydroxide solution, 100-160 parts of aminophenol-formaldehyde resin, 2-5 parts of triethylamine, and 28-56 parts of epoxy acrolein diethyl acetal are added.

3. The preparation method of sodium-modified phenolic resin according to claim 1, wherein The solvent is an ethanol aqueous solution; The mass percentage of the sodium hydroxide solution is 10wt%-30wt%; The organic solvent is tetrahydrofuran.

4. The preparation method of sodium-modified phenolic resin according to claim 1, wherein The condensation reaction temperature is 20-25°C, the reaction time is 120-180 minutes, and the reaction is dried at 105-115°C after completion of the reaction; The neutralization reaction temperature is 20-25°C and the reaction time is 50-120 minutes; The temperature of the addition reaction is 60-80° C., and the reaction time is 50-120 min.

5. The preparation method of sodium-modified phenolic resin according to claim 1, wherein The phenolic compound includes: 2-aminophenol, 3-aminophenol, 4-aminophenol, resorcinol, phloroglucinol, cresol, mixed cresols, nonylphenol, octylphenol, cardanol, aralkylphenol, bisphenol A or any combination thereof; The alkaline catalyst includes one or a mixture of any of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide, sodium isopropoxide, aqueous ammonia, magnesium oxide, ethylenediamine, tertiary amine or triethylamine; The aldehyde compound includes one or any combination of formaldehyde, paraformaldehyde, furfural and acetaldehyde.

6. The sodium-modified phenolic resin prepared by the arbitrary preparation method of claim 1-5.

7. A method for preparing a sodium-modified phenolic resin hard carbon negative electrode, characterized in that: Using the sodium-modified phenolic resin according to claim 6 comprises the following steps: The sodium-modified phenolic resin is carbonized and ground under an inert atmosphere, and then sieved to obtain an active substance; The active material, conductive agent and binder are mixed evenly and then coated on copper foil, dried and rolled to obtain the negative electrode sheet of the sodium ion battery.

8. The method for preparing a sodium-modified phenolic resin hard carbon negative electrode according to claim 7, characterized in that: The content of sodium-modified phenolic resin is 10-20g; The inert atmosphere used was argon; The carbonization temperature is 1200-1400℃ and the carbonization time is 3-5h; The grinding speed is 300-800r / min, and the grinding time is 5-10h; The sieving adopts 200-600 mesh.

9. The method for preparing a sodium-modified phenolic resin hard carbon negative electrode according to claim 7, characterized in that: The weight ratio of the active material, the conductive agent, and the binder is (70-80):10:(20-10); The coating thickness is 120-160 μm; Conductive agents, including: carbon black, acetylene black, vapor deposited carbon fiber, conductive graphite, carbon nanotubes one or more of nanotubes, graphene, and nitrogen-doped carbon; The binder includes one or more of sodium alginate, sodium polyacrylate, and sodium carboxymethyl cellulose.

10. A sodium-modified phenolic resin hard carbon negative electrode prepared by the preparation method according to any one of claims 7 to 9.

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