Lithium-doped porous carbon materials, lithium-doped silicon-carbon composite materials, their preparation methods and applications, and lithium-ion batteries

Abstract

The present invention provides a lithium-doped porous carbon material, a lithium-doped silicon-carbon composite material, a preparation method and an application thereof, and a lithium-ion battery, belonging to the technical field of carbon materials. In the present invention, a lithium source, a first phenolic compound and a first solvent are mixed and subjected to a modification treatment to obtain a modified product liquid; the modified product liquid, an aldehyde compound, a second phenolic compound and a second solvent are mixed and subjected to an addition-polycondensation reaction to obtain a lithium-modified phenolic resin; the lithium-modified phenolic resin is successively subjected to a pyrolysis treatment and an activation treatment to obtain the lithium-doped porous carbon material. After depositing silicon on the lithium-doped porous carbon material provided by the present invention, a lithium-doped silicon-carbon composite material is obtained. Using the lithium-doped silicon-carbon composite material as the negative electrode material of a lithium-ion battery has a high initial Coulomb efficiency, good rate performance and cycling performance.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon materials, and particularly to lithium-doped porous carbon materials, lithium-doped silicon-carbon composite materials, their preparation methods, applications, and lithium-ion batteries. Background Art

[0002] With the reduction of fossil energy and the increasing demand for green energy, the development of renewable and clean energy is the core to solve the future energy crisis. Porous carbon materials usually have excellent properties such as developed pores, high specific surface area, and unique electronic conduction properties, and are widely used as anode materials for lithium batteries. However, the theoretical capacity and initial Coulomb efficiency of porous carbon materials are relatively low, far from meeting the requirements of high energy and high power density. Summary of the Invention

[0003] The purpose of the present invention is to provide lithium-doped porous carbon materials, lithium-doped silicon-carbon composite materials, their preparation methods, applications, and lithium-ion batteries. After depositing silicon on the lithium-doped porous carbon materials provided by the present invention, lithium-doped silicon-carbon composite materials are obtained. Using the lithium-doped silicon-carbon composite materials as the anode material of lithium-ion batteries has a high initial Coulomb efficiency, good rate performance, and cycling performance.

[0004] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a preparation method of lithium-doped porous carbon materials, comprising the following steps:

[0006] Mix a lithium source, a first phenolic compound, and a first solvent, and perform a modification treatment to obtain a modified product liquid;

[0007] Mix the modified product liquid, an aldehyde compound, a second phenolic compound, and a second solvent, and perform an addition-condensation reaction to obtain a lithium-modified phenolic resin;

[0008] Perform pyrolysis treatment and activation treatment on the lithium-modified phenolic resin in sequence to obtain the lithium-doped porous carbon materials.

[0009] Preferably, the lithium source is lithium hydroxide; the first phenolic compound and the second phenolic compound are independently selected from one or more of phenol, cresol, xylenol, hydroquinone, and resorcinol; the aldehyde compound includes one or more of formaldehyde, acetaldehyde, and furfural; the first solvent and the second solvent are water.

[0010] Preferably, the dosage ratio of the lithium source, the first phenolic compound, and the first solvent is 0.17 - 0.23 mol: 0.17 - 0.23 mol: 90 - 110 g; the temperature of the modification treatment is 75 - 85 °C, and the time is 22 - 26 h;

[0011] The dosage ratio of the modified product liquid, aldehyde compound and second phenolic compound is 25 - 35 mL: 0.8 - 0.9 mol: 0.17 - 0.23 mol; the addition - polycondensation reaction includes a first - stage reaction and a second - stage reaction carried out in sequence; the temperature of the first - stage reaction is 40 - 50 °C and the time is 4 - 6 h; the temperature of the second - stage reaction is 90 - 100 °C and the time is 45 - 50 h.

[0012] Preferably, the temperature of the pyrolysis treatment is 650 - 750 °C, the heat - preservation time is 1.5 - 2.5 h; the heating rate to the temperature required for the pyrolysis treatment is 8 - 12 °C / min; the pyrolysis treatment is carried out in a protective atmosphere;

[0013] The temperature of the activation treatment is 950 - 1000 °C, the heat - preservation time is 7 - 9 h; the heating rate to the temperature required for the activation treatment is 8 - 12 °C / min; the activation treatment is carried out in a CO2 atmosphere.

[0014] The present invention provides a lithium - doped porous carbon material prepared by the preparation method described in the above technical solution.

[0015] Preferably, the specific surface area of the lithium - doped porous carbon material is 1500 - 2200 m 2 / g, and the pore volume is 0.5 - 0.8 cm 3 / g; the percentage of the volume of pores with a pore diameter less than 2 nm in all pores of the lithium - doped porous carbon material is 80 - 90%, and the percentage of the volume of pores with a pore diameter of 2 - 10 nm in all pores is 6 - 11%.

[0016] The present invention provides a lithium - doped silicon - carbon composite material, including a lithium - doped porous carbon material and silicon deposited on the lithium - doped porous carbon material, and the lithium - doped porous carbon material is the lithium - doped porous carbon material described in the above technical solution.

[0017] The present invention provides a preparation method of the lithium - doped silicon - carbon composite material described in the above technical solution, including the following steps:

[0018] Under the conditions of the presence of a gaseous silicon source and a carrier gas, silicon deposition is carried out on the surface of the lithium - doped porous carbon material to obtain the lithium - doped silicon - carbon composite material.

[0019] The present invention provides the application of the lithium - doped silicon - carbon composite material described in the above technical solution or the lithium - doped silicon - carbon composite material prepared by the preparation method described in the above technical solution in the negative electrode material of a lithium - ion battery.

[0020] The present invention provides a lithium-ion battery, which includes a negative electrode, a positive electrode, an electrolyte, and a separator. The negative electrode includes a substrate and a negative electrode material loaded on the surface of the substrate. The negative electrode material includes the lithium-doped silicon-carbon composite material described in the above technical solution or the lithium-doped silicon-carbon composite material prepared by the preparation method described in the above technical solution.

[0021] Beneficial effects: The present invention provides a preparation method of a lithium-doped porous carbon material, which includes the following steps: mixing a lithium source, a first phenolic compound, and a first solvent, and performing a modification treatment to obtain a modified product liquid; mixing the modified product liquid, an aldehyde compound, a second phenolic compound, and a second solvent, and performing an addition-condensation reaction to obtain a lithium-modified phenolic resin; sequentially performing a pyrolysis treatment and an activation treatment on the lithium-modified phenolic resin to obtain the lithium-doped porous carbon material. The present invention uses lithium element as a doping element, and realizes the in-situ doping of lithium element by in-situ polymerization and condensing it into the phenolic resin structure, thereby preparing a lithium-modified phenolic resin. On this basis, a lithium-doped porous carbon material is prepared by pyrolysis treatment and activation treatment. The lithium-doped porous carbon material prepared by the present invention has developed pores and a large specific surface area. After depositing silicon on the lithium-doped porous carbon material provided by the present invention, a lithium-doped silicon-carbon composite material is obtained. Using the lithium-doped silicon-carbon composite material as the negative electrode material of a lithium-ion battery has excellent electrochemical performance, a relatively high initial Coulomb efficiency, and good rate performance and cycling performance. Description of the Drawings

[0022] Figure 1 SEM image of the lithium-doped porous carbon material prepared in Example 1;

[0023] Figure 2 SEM image of the porous carbon material prepared in Comparative Example 1;

[0024] Figure 3 First-cycle charge-discharge voltage curve of the lithium-ion battery assembled with the silicon-carbon composite material prepared from the porous carbon material in Example 1. Detailed Embodiments

[0025] The present invention provides a preparation method of a lithium-doped porous carbon material, which includes the following steps:

[0026] Mix a lithium source, a first phenolic compound, and a first solvent, and perform a modification treatment to obtain a modified product liquid;

[0027] Mix the modified product liquid, an aldehyde compound, a second phenolic compound, and a second solvent, and perform an addition-condensation reaction to obtain a lithium-modified phenolic resin;

[0028] Sequentially perform a pyrolysis treatment and an activation treatment on the lithium-modified phenolic resin to obtain the lithium-doped porous carbon material.

[0029] The present invention uses phenolic resin as a carbon source to prepare lithium-doped porous carbon materials. Phenolic resin is a polymer material obtained by the polycondensation reaction of phenolic compounds and aldehyde compounds. Pyrolysis treatment is carried out on it to achieve carbonization, and then pore formation is carried out through activation treatment, and then phenolic resin-based porous carbon materials can be obtained. Both phenolic compounds and aldehyde compounds widely exist in nature, are relatively easy to obtain and have low prices, which is convenient for realizing the large-scale production of carbon materials. Phenolic resin has excellent thermal stability, and its original morphology can be maintained after carbonization, with good structural stability and rich functional groups, and metal ions can be introduced through electrostatic adsorption. In addition, phenolic resin also has an extremely high carbon residue content, and the carbonized sample has a high yield. The lithium-doped porous carbon material prepared based on phenolic resin in the present invention is deposited with silicon to obtain a lithium-doped silicon-carbon composite material. Using the lithium-doped silicon-carbon composite material as the negative electrode material of a lithium-ion battery has excellent electrochemical performance. On the one hand, the lithium-doped silicon-carbon composite material can greatly improve the rate performance and cycling performance of the lithium-ion battery. Specifically, due to the high specific surface area of the porous carbon material and the additional active sites brought by lithium doping, more lithium ions can be combined. On the other hand, the lithium-doped silicon-carbon composite material can reduce the AC impedance value of the lithium-ion battery. Specifically, good conductivity makes the transmission of ions in the electrode smoother, which can reduce energy loss, thereby being beneficial to improving the charge-discharge efficiency of the lithium-ion battery. The carbon-based material not only acts as a buffer to adapt to volume expansion, but also can prevent the aggregation of doped particles. Therefore, the present invention successfully incorporates lithium elements into the porous carbon material to prepare a lithium-doped porous carbon material. On this basis, silicon is deposited to obtain a lithium-doped silicon-carbon composite material. Using the lithium-doped silicon-carbon composite material as the negative electrode material in a lithium-ion battery has excellent electrochemical performance, with a relatively high initial Coulomb efficiency and good rate performance and cycling performance. The method of the present invention will be described in detail below.

[0030] In the present invention, unless otherwise specified, the raw materials used are commercially available products well-known to those skilled in the art or are prepared by methods well-known to those skilled in the art.

[0031] The present invention mixes a lithium source, a first phenolic compound and a first solvent, and carries out modification treatment to obtain a modified product liquid. As an implementation manner of the present invention, the lithium source can be lithium hydroxide, specifically lithium hydroxide monohydrate; the first phenolic compound can be selected from one or more of phenol, cresol, xylenol, hydroquinone and resorcinol, specifically phenol, cresol, xylenol, hydroquinone or resorcinol; the first solvent can be water; the dosage ratio of the lithium source, the first phenolic compound and the first solvent can be 0.17~0.23 mol: 0.17~0.23 mol: 90~110 g, specifically 0.19~0.20 mol: 0.19~0.20 mol: 100 g.

[0032] As an embodiment of the present invention, the temperature of the modification treatment can be 75 - 85 °C, further can be 78 - 82 °C, and specifically can be 80 °C; the time can be 22 - 26 h, further can be 23 - 25 h, and specifically can be 24 h; the modification treatment can be carried out under stirring conditions, and the present invention has no special limitation on the stirring rate, as long as the modification treatment can proceed smoothly. In the examples of the present invention, during the modification treatment, the lithium source reacts with the first phenolic compound in the first solvent. Taking phenol as an example, after the hydroxyl group in phenol removes a hydrogen atom, it forms a monovalent negative group with a negative charge, which combines with a lithium ion with a positive charge to form lithium phenoxide, facilitating subsequent in-situ doping of lithium through an addition - polycondensation reaction to prepare a lithium-modified phenolic resin.

[0033] After obtaining the modified product liquid, the present invention mixes the modified product liquid, aldehyde compound, second phenolic compound and second solvent to carry out an addition - polycondensation reaction to obtain a lithium-modified phenolic resin. As an embodiment of the present invention, the aldehyde compound can include one or more of formaldehyde, acetaldehyde and furfural, specifically can be formaldehyde, acetaldehyde or furfural; the second phenolic compound can be selected from one or more of phenol, cresol, xylenol, hydroquinone and resorcinol, specifically can be phenol, cresol, xylenol, hydroquinone or resorcinol, and the second phenolic compound is preferably the same as the first phenolic compound; the second solvent can be water; the dosage ratio of the modified product liquid, aldehyde compound and second phenolic compound can be 25 - 35 mL: 0.8 - 0.9 mol: 0.17 - 0.23 mol; specifically can be 30 mL: 0.84 - 0.85 mol: 0.19 - 0.20 mol; the dosage ratio of the second phenolic compound and the second solvent can be 0.17 - 0.23 mol: 200 - 220 g, specifically can be 0.19 - 0.20 mol: 208 - 210 g.

[0034] As an embodiment of the present invention, specifically, the aldehyde compound, the second phenolic compound and the second solvent are mixed, and then the modified product liquid is added to carry out an addition-condensation reaction. As an embodiment of the present invention, the addition-condensation reaction includes a first-stage reaction and a second-stage reaction carried out in sequence. As an embodiment of the present invention, the temperature of the first-stage reaction can be 40-50 °C, specifically 45 °C; the time can be 4-6 h, specifically 5 h; the first-stage reaction can be carried out under stirring conditions, and the present invention has no special limitation on the stirring rate, as long as the first-stage reaction proceeds smoothly. As an embodiment of the present invention, the temperature of the second-stage reaction can be 90-100 °C, specifically 95 °C; the time can be 45-50 h, specifically 48 h; the second-stage reaction can be carried out under stirring conditions, and the present invention has no special limitation on the stirring rate, as long as the second-stage reaction proceeds smoothly. In the examples of the present invention, taking the synthesis of lithium-modified phenolic resin using phenol, lithium phenoxide and formaldehyde as an example, first, phenol and formaldehyde carry out a first-stage reaction under low-temperature conditions. In this process, phenol and formaldehyde undergo an addition reaction to form various hydroxymethyl phenols, that is, the product is a mixture of monophenol alcohols and polyphenol alcohols. When the temperature rises (such as above 60 °C), a second-stage reaction is carried out. In this process, the addition reaction and the condensation reaction occur simultaneously. The lithium phenoxide generated by the modification treatment and the monophenol alcohol and polyphenol alcohol continuously carry out a condensation reaction during the reaction, increasing the molecular weight of the resin continuously, and finally obtaining lithium-modified phenolic resin.

[0035] As an embodiment of the present invention, after the addition-condensation reaction, specifically, the precipitate generated in the system is collected and dried and pulverized in sequence to obtain a lithium-modified phenolic resin powder. Then, the lithium-modified phenolic resin powder is pyrolyzed and activated in sequence to obtain the lithium-doped porous carbon material. The present invention has no special limitation on the conditions of drying and pulverization, and the conditions well-known to those skilled in the art can be adopted.

[0036] As an embodiment of the present invention, the temperature of the pyrolysis treatment can be 650-750 °C, further 680-720 °C, specifically 700 °C; the heat preservation time can be 1.5-2.5 h, specifically 2 h; the heating rate to the temperature required for the pyrolysis treatment can be 8-12 °C / min, specifically 10 °C / min; the pyrolysis treatment can be carried out in a protective atmosphere, and the protective atmosphere can specifically be argon, and the flow rate of the argon can be 8-12 mL / min, specifically 10 mL / min. As an embodiment of the present invention, the pyrolysis treatment can specifically be carried out in a tubular furnace. In the examples of the present invention, during the pyrolysis treatment process, the lithium-modified phenolic resin undergoes carbonization to form pyrolytic carbon.

[0037] As an embodiment of the present invention, the temperature of the activation treatment can be 950 - 1000 °C, further can be 970 - 980 °C, and specifically can be 975 °C; the heat preservation time can be 7 - 9 h, further can be 7.5 - 8.5 h, and specifically can be 8 h; the heating rate for heating to the temperature required for the activation treatment can be 8 - 12 °C / min, and specifically can be 10 °C / min. As an embodiment of the present invention, the activation treatment can be carried out in a CO₂ atmosphere. Based on the mass of the pyrolytic carbon, the flow rate of the CO₂ can be 4 - 5 mL / min / g, and specifically can be 4.51 mL / min / g; in the examples of the present invention, taking 6 g of pyrolytic carbon as an example, the flow rate of the CO₂ can be 27.06 mL / min. As an embodiment of the present invention, the activation treatment can specifically be carried out in a tubular furnace. In the examples of the present invention, the CO₂ activation method is adopted. By introducing CO₂ to react with the pyrolytic carbon under high temperature conditions, pores are formed in the pyrolytic carbon, which can effectively regulate the pore structure and specific surface area of the lithium-doped porous carbon material, and a lithium-doped porous carbon material with a rich pore structure and excellent electrochemical performance is prepared.

[0038] The present invention provides a lithium-doped porous carbon material prepared by the preparation method of the above technical solution. As an embodiment of the present invention, the specific surface area of the lithium-doped porous carbon material can be 1500 - 2200 m 2 / g, further can be 1520 - 2150 m 2 / g, and specifically can be 1530.6774, 1762.3424 m 2 / g, 1811.9925 m 2 / g, 1918.8347 m 2 / g, 2026.5146 m 2 / g or 2130.1523 m 2 / g; the pore volume can be 0.5 - 0.8 cm 3 / g, and specifically can be 0.5485 m 2 / g, 0.6414 m 2 / g, 0.6621 m 2 / g, 0.7325 m 2 / g, 0.7750 m 2 / g or 0.7972 m 2 / g; The percentage of pores with a pore diameter less than 2 nm in the lithium-doped porous carbon material can account for 80-90% of the volume of all pores, specifically, it can be 83.78%, 84.56%, 85.86%, 85.95%, 88.19% or 89.76%; the percentage of pores with a pore diameter of 2-10 nm can account for 6-11% of the volume of all pores, specifically, it can be 6.03%, 6.94%, 8.28%, 8.66%, 8.96% or 10.52%; the lithium-doped porous carbon material also has remaining pores with a pore diameter greater than 10 nm.

[0039] The present invention provides a lithium-doped silicon-carbon composite material, comprising a lithium-doped porous carbon material and silicon deposited on the lithium-doped porous carbon material, and the lithium-doped porous carbon material is the lithium-doped porous carbon material described in the above technical solution.

[0040] As an implementation mode of the present invention, the content of silicon in the lithium-doped silicon-carbon composite material can be 40-60 wt%, specifically, it can be 40 wt%, 45 wt%, 48 wt%, 50 wt%, 52 wt%, 55 wt% or 60 wt%.

[0041] The present invention provides a preparation method of the lithium-doped silicon-carbon composite material described in the above technical solution, comprising the following steps:

[0042] Under the conditions of the presence of a gaseous silicon source and a carrier gas, silicon deposition is carried out on the surface of the lithium-doped porous carbon material to obtain the lithium-doped silicon-carbon composite material.

[0043] As an embodiment of the present invention, the gaseous silicon source may be silane, specifically silane; the carrier gas may specifically be helium. As an embodiment of the present invention, the silicon deposition may specifically be carried out in a CVD furnace. During the silicon deposition process, the rotation speed of the CVD furnace may be 15 - 25 rpm, specifically 20 rpm; based on the mass of the lithium-doped porous carbon material being 25 g, the flow rate of the carrier gas may be 4.5 - 5.5 L / min, specifically 5 L / min; the flow rate of the silane may be 0.08 - 0.12 L / min, specifically 0.1 L / min. As an embodiment of the present invention, the conditions for silicon deposition include: the deposition temperature may be 500 - 600 °C, specifically 500 °C, 530 °C, 550 °C, 580 °C or 600 °C; the deposition time may be 1 - 9 h, specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h or 9 h. In the embodiments of the present invention, specifically, the lithium-doped porous carbon material may be placed in a CVD furnace and its rotation speed may be set to 15 - 25 rpm, the carrier gas may be introduced at a flow rate of 4.5 - 5.5 L / min, and the temperature may be raised to the required temperature for silicon deposition in the carrier gas environment. While maintaining the carrier gas flow rate, the gaseous silicon source may be introduced at a flow rate of 0.08 - 0.12 L / min for silicon deposition. As an embodiment of the present invention, after the silicon deposition, it may further include: stopping the introduction of the gaseous silicon source, maintaining the carrier gas flow rate to remove the excess gaseous silicon source, and then introducing acetylene gas at a flow rate of 0.18 - 0.22 L / min (specifically 0.2 L / min) for deposition. As an embodiment of the present invention, the conditions for deposition using acetylene gas include: the deposition temperature may be 500 - 600 °C, specifically 500 °C, 530 °C, 550 °C, 580 °C or 600 °C; the deposition time may be 1 - 5 h, specifically 1 h, 2 h, 3 h, 4 h or 5 h.

[0044] The present invention provides the use of the lithium-doped silicon-carbon composite material described in the above technical solution or the lithium-doped silicon-carbon composite material prepared by the preparation method described in the above technical solution in the negative electrode material of a lithium-ion battery.

[0045] The present invention provides a lithium-ion battery, including a negative electrode, a positive electrode, an electrolyte and a separator. The negative electrode includes a substrate and a negative electrode material loaded on the surface of the substrate. The negative electrode material includes the lithium-doped silicon-carbon composite material described in the above technical solution or the lithium-doped silicon-carbon composite material prepared by the preparation method described in the above technical solution.

[0046] As an embodiment of the present invention, the negative electrode includes a substrate and a negative electrode material loaded on the surface of the substrate; the substrate in the negative electrode can be a copper foil; the raw materials for preparing the negative electrode material can include a lithium-doped silicon-carbon composite material, Super P, carbon nanotubes, carboxymethyl cellulose, and a styrene-butadiene rubber composite binder. The present invention does not have special limitations on the dosages of the raw materials for preparing the negative electrode material, and the dosages well-known to those skilled in the art can be adopted. In the embodiments of the present invention, specifically, the silicon-carbon composite material is mixed with Super P, carbon nanotubes, carboxymethyl cellulose, and a styrene-butadiene rubber composite binder, and the obtained mixed material is coated on the surface of the substrate, and after drying, the negative electrode is obtained.

[0047] As an embodiment of the present invention, the positive electrode is specifically a lithium metal sheet.

[0048] As an embodiment of the present invention, the electrolyte can be a LiPF6 solution, the concentration of LiPF6 in the LiPF6 solution can be 1 mol / L, the solvent in the LiPF6 solution can be diethyl carbonate, dimethyl carbonate, and ethylene carbonate, and the volume ratio of diethyl carbonate, dimethyl carbonate, and ethylene carbonate can be 1:1:1.

[0049] The present invention does not have special limitations on the separator, and a separator well-known to those skilled in the art can be adopted.

[0050] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] Example 1

[0052] 18 g of phenol, 8.04 g of lithium hydroxide monohydrate, and 100 g of water are mixed, and modification treatment is carried out at 80 °C under stirring conditions for 24 h to obtain a modified product liquid;

[0053] 18 g of phenol, 25.29 g of formaldehyde, and 208.71 g of water are mixed, then 30 mL of the modified product liquid is added, and a first-stage reaction is carried out at 45 °C under stirring conditions for 5 h, and then the temperature is raised, and a second-stage reaction is carried out at 95 °C under stirring conditions for 48 h; after the second-stage reaction is completed, the precipitate generated in the system is collected as a lithium-modified phenolic resin;

[0054] The lithium-modified phenolic resin is dried and then pulverized to obtain a lithium-modified phenolic resin powder. Subsequently, under the condition that the argon gas flow rate is 10 mL / min and the heating rate is 10 °C / min, the lithium-modified phenolic resin powder is heated from room temperature to 700 °C and kept warm for 2 h for pyrolysis treatment to obtain pyrolytic carbon;

[0055] Take 6 g of the pyrolytic carbon, and under the condition that the CO2 gas flow rate is 27.06 mL / min and the heating rate is 10 °C / min, heat the pyrolytic carbon from room temperature to 975 °C and keep warm for 8 h for activation treatment to obtain a lithium-doped porous carbon material.

[0056] Example 2

[0057] Mix 21.06 g of resorcinol, 8.04 g of lithium hydroxide monohydrate and 100 g of water, and carry out modification treatment for 24 h at 80 °C under stirring conditions to obtain a modified product liquid;

[0058] Mix 21.06 g of resorcinol, 25.29 g of formaldehyde and 208.71 g of water, then add 30 mL of the modified product liquid, carry out the first-stage reaction for 5 h at 45 °C under stirring conditions, and then raise the temperature, and carry out the second-stage reaction for 48 h at 95 °C under stirring conditions to obtain a lithium-modified phenolic resin;

[0059] Refer to the method of Example 1 to carry out pyrolysis treatment and activation treatment on the lithium-modified phenolic resin in sequence to obtain a lithium-doped porous carbon material.

[0060] Example 3

[0061] Mix 23.36 g of xylenol, 8.04 g of lithium hydroxide monohydrate and 100 g of water, and carry out modification treatment for 24 h at 80 °C under stirring conditions to obtain a modified product liquid;

[0062] Mix 23.36 g of xylenol, 25.29 g of formaldehyde and 208.71 g of water, then add 30 mL of the modified product liquid, carry out the first-stage reaction for 5 h at 45 °C under stirring conditions, and then raise the temperature, and carry out the second-stage reaction for 48 h at 95 °C under stirring conditions to obtain a lithium-modified phenolic resin;

[0063] Refer to the method of Example 1 to carry out pyrolysis treatment and activation treatment on the lithium-modified phenolic resin in sequence to obtain a lithium-doped porous carbon material.

[0064] Example 4

[0065] Mix 21.06 g of resorcinol, 8.04 g of lithium hydroxide monohydrate and 100 g of water, and carry out modification treatment for 24 h at 80 °C under stirring conditions to obtain a modified product liquid;

[0066] Mix 21.06 g of resorcinol, 37.10 g of acetaldehyde and 208.71 g of water, then add 30 mL of the modified product solution, and carry out the first-stage reaction at 45 °C with stirring for 5 h. After that, raise the temperature and carry out the second-stage reaction at 95 °C with stirring for 48 h to obtain lithium-modified phenolic resin;

[0067] Refer to the method of Example 1 to pyrolyze and activate the lithium-modified phenolic resin in sequence to obtain lithium-doped porous carbon material.

[0068] Example 5

[0069] Mix 18 g of phenol, 8.04 g of lithium hydroxide monohydrate and 100 g of water, and carry out the modification treatment at 80 °C with stirring for 24 h to obtain the modified product solution;

[0070] Mix 18 g of phenol, 37.10 g of acetaldehyde and 208.71 g of water, then add 30 mL of the modified product solution, and carry out the first-stage reaction at 45 °C with stirring for 5 h. After that, raise the temperature and carry out the second-stage reaction at 95 °C with stirring for 48 h to obtain lithium-modified phenolic resin;

[0071] Refer to the method of Example 1 to pyrolyze and activate the lithium-modified phenolic resin in sequence to obtain lithium-doped porous carbon material.

[0072] Example 6

[0073] Mix 18 g of phenol, 8.04 g of lithium hydroxide monohydrate and 100 g of water, and carry out the modification treatment at 80 °C with stirring for 24 h to obtain the modified product solution;

[0074] Mix 18 g of phenol, 80.92 g of furfural and 208.71 g of water, then add 30 mL of the modified product solution, and carry out the first-stage reaction at 45 °C with stirring for 5 h. After that, raise the temperature and carry out the second-stage reaction at 95 °C with stirring for 48 h to obtain lithium-modified phenolic resin;

[0075] Refer to the method of Example 1 to pyrolyze and activate the lithium-modified phenolic resin in sequence to obtain lithium-doped porous carbon material.

[0076] Comparative Example 1

[0077] Mix 18 g of phenol, 25.29 g of formaldehyde and 208.71 g of water, and carry out the first-stage reaction at 45 °C with stirring for 5 h. After that, raise the temperature and carry out the second-stage reaction at 95 °C with stirring for 48 h to obtain phenolic resin; then refer to the method of Example 1 to pyrolyze and activate the phenolic resin in sequence to obtain porous carbon material.

[0078] Comparative Example 2

[0079] 21.06 g of resorcinol, 25.29 g of formaldehyde and 208.71 g of water were mixed, and the first-stage reaction was carried out at 45 °C with stirring for 5 h. Then the temperature was raised, and the second-stage reaction was carried out at 95 °C with stirring for 48 h to obtain a phenolic resin. Then, the phenolic resin was successively pyrolyzed and activated according to the method of Example 1 to obtain a porous carbon material.

[0080] Comparative Example 3

[0081] 23.36 g of xylenol, 25.29 g of formaldehyde and 208.71 g of water were mixed, and the first-stage reaction was carried out at 45 °C with stirring for 5 h. Then the temperature was raised, and the second-stage reaction was carried out at 95 °C with stirring for 48 h to obtain a phenolic resin. Then, the phenolic resin was successively pyrolyzed and activated according to the method of Example 1 to obtain a porous carbon material.

[0082] Test Example 1

[0083] Figure 1 It is the SEM image of the lithium-doped porous carbon material prepared in Example 1. The results show that there are no obvious holes on the surface of the lithium-doped porous carbon material prepared in Example 1, but there are relatively many pits, which is caused by the doping of lithium element.

[0084] Figure 2 It is the SEM image of the porous carbon material prepared in Comparative Example 1. The results show that the surface of the porous carbon material prepared in Comparative Example 1 is basically dense and smooth, and no large holes and pits are found.

[0085] The porous carbon materials prepared in the examples and comparative examples were subjected to performance tests, and the specific results are shown in Table 1. It can be seen from Table 1 that among the lithium-doped porous carbon materials prepared in Examples 1 to 6, due to the embedding of lithium element in the carbon skeleton, the specific surface area and pore volume of the porous carbon material will be slightly reduced.

[0086] Table 1 Performance test results of porous carbon materials in examples and comparative examples

[0087]

[0088] Test Example 2

[0089] The porous carbon materials prepared in each example and comparative example were respectively subjected to silicon deposition to obtain silicon-carbon composite materials. The specific steps are as follows: Place 25 g of the porous carbon material in a CVD furnace with a rotation speed of 20 rpm. Introduce helium gas at a flow rate of 5 L / min, heat up to 600 °C in a helium atmosphere, maintain the helium gas flow rate and introduce silane gas at a flow rate of 0.1 L / min for chemical vapor deposition for 1 h. After the deposition is completed, continue to introduce helium gas at a flow rate of 5 L / min to remove excess silane gas, and then introduce acetylene gas at a flow rate of 0.2 L / min for vapor deposition at 600 °C for 1 h to obtain the silicon-carbon composite material, and the silicon content in the silicon-carbon composite material is 50 wt%.

[0090] The silicon-carbon composite materials were respectively mixed with Super P, carbon nanotubes, carboxymethyl cellulose and styrene-butadiene rubber composite binder. The obtained mixed material was coated on the surface of a copper foil and dried to obtain a negative electrode; a lithium metal sheet was used as the positive electrode; a LiPF6 solution with a concentration of 1 mol / L was used as the electrolyte (the solvent was diethyl carbonate, dimethyl carbonate and ethylene carbonate, and the volume ratio of the three was 1:1:1); the separator and the negative electrode, positive electrode, and electrolyte were assembled together to obtain a lithium-ion battery. Using a LAND charge-discharge tester, the lithium-ion battery was subjected to charge-discharge tests under the conditions of a current density of 0.1 C and a voltage range of 0.005~1.5 V. The specific results are as Figure 3 shown in Table 2.

[0091] Figure 3 Fig. 9 is the first-cycle charge-discharge voltage curve of the lithium-ion battery assembled with the silicon-carbon composite material prepared from the porous carbon material in Example 1. The relevant data are specifically listed in Table 2. As can be seen from Table 2, compared with the silicon-carbon composite materials prepared from the porous carbon materials in Comparative Examples 1 to 3, the lithium-doped silicon-carbon composite materials prepared from the lithium-doped porous carbon materials in Examples 1 to 6 have excellent electrochemical performance, with relatively high reversible specific capacity, first efficiency and 100-cycle capacity retention rate.

[0092] Table 2 Performance test results of lithium-ion batteries assembled with various silicon-carbon composite materials

[0093]

[0094] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a lithium-doped porous carbon material is carried out according to the following steps: Mix a lithium source, a first phenolic compound and a first solvent, and carry out a modification treatment to obtain a modified product liquid; the first phenolic compound is phenol; the lithium source is lithium hydroxide; the temperature of the modification treatment is 75-85 °C, and the time is 22-26 h; Mix the modified product liquid, an aldehyde compound, a second phenolic compound and a second solvent, and carry out an addition-polycondensation reaction. Then collect the precipitate generated in the system and perform drying and crushing in sequence to obtain a lithium-modified phenolic resin; the aldehyde compound is formaldehyde or furfural, and the second phenolic compound is phenol; Carry out pyrolysis treatment and activation treatment on the lithium-modified phenolic resin in sequence to obtain the lithium-doped porous carbon material.

2. The preparation method according to claim 1, characterized in that, The first solvent and the second solvent are water.

3. The preparation method according to claim 1 or 2, characterized in that, The dosage ratio of the lithium source, the first phenolic compound and the first solvent is 0.17-0.23 mol: 0.17-0.23 mol: 90-110 g; The dosage ratio of the modified product liquid, the aldehyde compound and the second phenolic compound is 25-35 mL: 0.8-0.9 mol: 0.17-0.23 mol; the addition-polycondensation reaction includes a first-stage reaction and a second-stage reaction carried out in sequence; the temperature of the first-stage reaction is 40-50 °C, and the time is 4-6 h; the temperature of the second-stage reaction is 90-100 °C, and the time is 45-50 h.

4. The preparation method according to claim 1 or 2, characterized in that, The temperature of the pyrolysis treatment is 650-750 °C, and the heat preservation time is 1.5-2.5 h; the heating rate for rising to the temperature required for the pyrolysis treatment is 8-12 °C / min; the pyrolysis treatment is carried out in a protective atmosphere; The temperature of the activation treatment is 950-1000 °C, and the heat preservation time is 7-9 h; the heating rate for rising to the temperature required for the activation treatment is 8-12 °C / min; the activation treatment is carried out in a CO2 atmosphere.

5. The lithium-doped porous carbon material prepared by the preparation method according to any one of claims 1-4.

6. The lithium-doped porous carbon material according to claim 5, wherein The specific surface area of the lithium-doped porous carbon material is 1500-2200 m 2 / g, and the pore volume is 0.5-0.8 cm 3 / g; the percentage of the pores with a pore diameter less than 2 nm in the total pore volume of the lithium-doped porous carbon material is 80-90%, and the percentage of the pores with a pore diameter of 2-10 nm in the total pore volume of all pores is 6-11%.

7. A lithium-doped silicon-carbon composite material, including a lithium-doped porous carbon material and silicon deposited on the lithium-doped porous carbon material, and the lithium-doped porous carbon material is the lithium-doped porous carbon material according to claim 5 or 6.

8. A preparation method of the lithium-doped silicon-carbon composite material according to claim 7, including the following steps: Under the conditions of the presence of a gaseous silicon source and a carrier gas, carry out silicon deposition on the surface of the lithium-doped porous carbon material to obtain the lithium-doped silicon-carbon composite material.

9. The application of the lithium-doped silicon-carbon composite material according to claim 7 or the lithium-doped silicon-carbon composite material prepared by the preparation method according to claim 8 in the negative electrode material of a lithium-ion battery.

10. A lithium-ion battery, including a negative electrode, a positive electrode, an electrolyte and a separator, the negative electrode includes a substrate and a negative electrode material loaded on the surface of the substrate, and the negative electrode material includes the lithium-doped silicon-carbon composite material according to claim 7 or the lithium-doped silicon-carbon composite material prepared by the preparation method according to claim 8.

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