Metal-doped porous carbon material, metal-doped silicon-carbon composite material, preparation method and application and lithium ion battery

Abstract

This invention provides metal-doped porous carbon materials, metal-doped silicon-carbon composite materials, their preparation methods, and applications in lithium-ion batteries, belonging to the field of carbon material technology. The invention involves mixing phenolic compounds, aldehyde compounds, surfactants, alkaline reagents, metal compounds, and water. The resulting mixture is then subjected to an addition-condensation reaction to obtain a metal-doped phenolic resin. This resin is subsequently subjected to re-curing, pyrolysis, and activation treatments to obtain the metal-doped porous carbon material. The metal-doped porous carbon material prepared using this method exhibits uniform metal doping within the porous carbon material. Silicon is then deposited on this composite material to obtain a metal-doped silicon-carbon composite material. Using this metal-doped silicon-carbon composite material as a negative electrode material in lithium-ion batteries demonstrates high initial coulombic efficiency, as well as good rate performance and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of carbon materials technology, and more particularly to metal-doped porous carbon materials, metal-doped silicon-carbon composite materials, their preparation methods, and applications in lithium-ion batteries. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in electric vehicles, but their energy density remains a barrier to achieving long driving range. Porous carbon materials possess advantages such as excellent chemical stability, good electrical conductivity, and unique porosity, making them excellent anode materials for lithium-ion batteries. However, due to their low theoretical capacity and low initial coulombic efficiency, porous carbon materials cannot meet the growing demands of electric vehicles and large-scale energy storage systems. Therefore, it is necessary to develop anode materials with high capacity, long cycle stability, and high rate performance.

[0003] Carbon has a limited theoretical specific capacity, while silicon boasts an extremely high theoretical specific capacity (4200 mAh / g). However, silicon-based anode materials are prone to volume expansion during use, ultimately leading to battery capacity decay. Therefore, the preparation of silicon-carbon composite anode materials by combining silicon with porous carbon materials is currently a major development trend. Doping porous carbon materials with metal elements is beneficial for improving their performance. On one hand, the presence of metals can provide additional active sites, promoting chemical reactions. Simultaneously, metal doping may enhance the structural stability of carbon materials, improving their stability under harsh environments such as high temperatures and acid / alkali conditions. On the other hand, when silicon is deposited after incorporating metal elements into porous carbon materials, the silicon and the doped metal elements can directly contact each other, acting as interfacial doping. This facilitates smoother lithium-ion transport in the electrode, reducing energy loss and improving the charge / discharge efficiency of lithium-ion batteries. However, current metal-doped porous carbon materials still suffer from uneven metal doping, leading to poor electrochemical performance. Summary of the Invention

[0004] The purpose of this invention is to provide metal-doped porous carbon materials, metal-doped silicon-carbon composite materials, preparation methods, and applications in lithium-ion batteries. In the metal-doped porous carbon materials prepared by the method of this invention, metal is uniformly doped into the porous carbon materials. On this basis, silicon is deposited to obtain metal-doped silicon-carbon composite materials. The metal-doped silicon-carbon composite materials have excellent electrochemical performance as negative electrode materials for lithium-ion batteries, especially with high initial coulombic efficiency, good rate performance, and good cycle performance.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing metal-doped porous carbon materials, comprising the following steps:

[0007] Phenolic compounds, aldehyde compounds, surfactants, alkaline reagents, metal compounds and water are mixed, and the resulting mixture is subjected to an addition-condensation reaction to obtain metal-doped phenolic resin.

[0008] The metal-doped phenolic resin was subjected to a re-curing treatment, a pyrolysis treatment, and an activation treatment in sequence to obtain the metal-doped porous carbon material.

[0009] Preferably, the phenolic compound includes one or more of phenol, m-diphenol, and triaminophenol; the aldehyde compound includes formaldehyde and / or acetaldehyde; and the molar ratio of the phenolic compound to the aldehyde compound is 1:1.6 to 2.0.

[0010] The metal element in the metal compound includes one or more of Sn, Mg, Fe, Zn, Al, Ca, Cu, Ti, Cr and Na; the metal compound includes one or more of metal salts, metal oxides and metal sulfides; the mass of the metal compound is 0.01 to 10% of the total mass of phenolic compounds and aldehyde compounds.

[0011] The surfactant comprises gum arabic powder and / or polyvinyl alcohol; the mass of the surfactant is 2.4 to 3.5% of the total mass of phenolic and aldehyde compounds;

[0012] The alkaline reagent includes one or more of ammonia, hexamethylenetetramine, and tetramethylammonium hydroxide; the concentration of the ammonia is 25-30 wt%, and the mass of the alkaline reagent is 5.0-20% of the total mass of the phenolic and aldehyde compounds.

[0013] Preferably, the metal compound includes one or more of SnCl2, SnSO4, SnO, SnS2, MgSO4, Mg(NO3)2, MgO, FeCl3, FeSO4, Fe2O3, ZnSO4, ZnO, Al2(SO4)3, Al2O3, Al2S3, CaSO4, CaO, CuSO4, CuO, Ti(SO4)2, TiO2, Cr2(SO4)3, Cr2O3, and Na2SO4.

[0014] Preferably, the addition-condensation reaction includes sequential addition and condensation reactions; the addition reaction is carried out at a temperature of 55–70°C for 3–5 hours; the condensation reaction is carried out at a temperature of 85–95°C for 40–50 hours; and the addition-condensation reaction is carried out under stirring conditions.

[0015] The process after the polycondensation reaction further includes: solid-liquid separation of the product liquid obtained after the polycondensation reaction, drying of the obtained solid material, and obtaining the metal-doped phenolic resin; the drying temperature is 70-90℃, the holding time is 40-50h, and the drying is carried out in a protective atmosphere.

[0016] Preferably, the re-curing treatment is performed at a temperature of 180–220°C for 10–15 hours, and the re-curing treatment is carried out in a protective atmosphere.

[0017] The pyrolysis treatment is carried out at a temperature of 680–720°C for 2–4 hours, and the pyrolysis treatment is conducted in a protective atmosphere.

[0018] The activation treatment is carried out at a temperature of 950–980°C for 10–14 hours, and the activation treatment is carried out in the presence of an activating gas, which includes carbon dioxide and / or water vapor.

[0019] The re-curing process and the pyrolysis process also include a crushing process.

[0020] The present invention provides a metal-doped porous carbon material prepared by the preparation method described above, comprising a porous carbon material and metal nanoparticles dispersed inside the pores of the porous carbon material; the pores in the metal-doped porous carbon material include micropores and mesopores.

[0021] The present invention provides a metal-doped silicon-carbon composite material, comprising a metal-doped porous carbon material and silicon deposited on the surface of the metal-doped porous carbon material, wherein the metal-doped porous carbon material is the metal-doped porous carbon material described in the above technical solution.

[0022] This invention provides a method for preparing the metal-doped silicon-carbon composite material described above, comprising the following steps:

[0023] Silicon is deposited on the surface of the metal-doped porous carbon material in the presence of a gaseous silicon source and a carrier gas to obtain the metal-doped silicon-carbon composite material.

[0024] This invention provides the application of the metal-doped silicon-carbon composite material described in the above technical solution or the metal-doped silicon-carbon composite material prepared by the preparation method described in the above technical solution in the negative electrode material of lithium-ion batteries.

[0025] The present invention provides a lithium-ion battery, comprising a negative electrode, a positive electrode, an electrolyte and a separator. The negative electrode comprises a substrate and a negative electrode material loaded on the surface of the substrate. The negative electrode material comprises the metal-doped silicon-carbon composite material described in the above technical solution or the metal-doped silicon-carbon composite material prepared by the preparation method described in the above technical solution.

[0026] This invention provides a method for preparing metal-doped porous carbon materials, comprising the following steps: mixing phenolic compounds, aldehyde compounds, surfactants, alkaline reagents, metal compounds, and water; subjecting the resulting mixture to an addition-condensation reaction to obtain a metal-doped phenolic resin; and sequentially subjecting the metal-doped phenolic resin to a re-curing treatment, a pyrolysis treatment, and an activation treatment to obtain the metal-doped porous carbon material. This invention utilizes the in-situ synthesis of phenolic resin from phenolic and aldehyde compounds via an addition-condensation reaction, followed by carbonization via pyrolysis to obtain phenolic resin-based carbon materials. This invention introduces a metal compound into the reaction system, where the metal element can electrostatically interact with functional groups (such as hydroxyl groups) in the phenolic compound. Simultaneously with the addition-condensation reaction of the phenolic and aldehyde compounds, the metal element is fixed within the phenolic resin framework, achieving in-situ metal doping. The metal element enhances ion and electron transport capabilities, thereby improving the electrochemical performance of the carbon material. This invention introduces metal compounds into the reaction process... Surfactants can optimize reaction efficiency, product structure, and performance by regulating the interfacial properties, dispersion state, and phase behavior of the reaction system, which is beneficial for achieving uniform metal doping. The resulting metal-doped phenolic resin is then subjected to re-curing treatment, which allows for more stable incorporation of metal elements into the phenolic resin framework and prevents metal precipitation during pyrolysis. The cured metal-doped phenolic resin is then carbonized through pyrolysis, followed by activation treatment to create pores in the carbon material, ultimately yielding a metal-doped porous carbon material with abundant pore structure and excellent electrochemical performance. This invention further utilizes silicon deposition on the metal-doped porous carbon material to obtain a metal-doped silicon-carbon composite material. This composite material, when used as a negative electrode material in lithium-ion batteries, exhibits high initial coulombic efficiency, good rate performance, and good cycle performance. Furthermore, the method provided by this invention has low production costs and is easy to scale up for mass production. Attached Figure Description

[0027] Figure 1 EDS image of the metal-doped porous carbon material prepared in Example 1;

[0028] Figure 2 The images show the XRD patterns of the metal-doped porous carbon materials prepared in Example 1 and Comparative Example 1.

[0029] Figure 3 The first charge-discharge curve of the lithium-ion battery assembled using the metal-doped silicon-carbon composite material prepared in Example 1 is shown under a 0.1C rate condition. Detailed Implementation

[0030] This invention provides a method for preparing metal-doped porous carbon materials, comprising the following steps:

[0031] Phenolic compounds, aldehyde compounds, surfactants, alkaline reagents, metal compounds and water are mixed, and the resulting mixture is subjected to an addition-condensation reaction to obtain metal-doped phenolic resin.

[0032] The metal-doped phenolic resin was subjected to a re-curing treatment, a pyrolysis treatment, and an activation treatment in sequence to obtain the metal-doped porous carbon material.

[0033] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0034] This invention involves mixing phenolic compounds, aldehyde compounds, surfactants, alkaline reagents, metal compounds, and water to obtain a mixed solution. In one embodiment, the phenolic compound may include one or more of phenol, m-diphenol, and triaminophenol, specifically phenol, m-diphenol, or triaminophenol; the aldehyde compound may include formaldehyde and / or acetaldehyde, specifically formaldehyde or acetaldehyde; the molar ratio of the phenolic compound to the aldehyde compound may be 1:1.6–2.0, specifically 1:1.8; the formaldehyde is preferably used in the form of an aqueous formaldehyde solution, with a concentration of 35–37 wt%; this invention does not specifically limit the content of the phenolic compound in the mixed solution, as long as the reaction proceeds smoothly. In embodiments of this invention, the content of the phenolic compound in the mixed solution may be 5–20 wt%, more preferably 10–15 wt%, and even more preferably 11–12 wt%. This invention synthesizes phenolic resin in situ from phenolic and aldehyde compounds. Phenolic resin has a large molecular weight, diverse molecular structure, and abundant functional groups, making it easy to prepare in large quantities. This invention also carbonizes phenolic resin by pyrolysis to obtain carbon materials. After carbonization, the original morphology of the phenolic resin is maintained (i.e., the morphology of the phenolic resin does not change during the carbonization process), resulting in good structural stability and a high yield.

[0035] In one embodiment of the present invention, the metal element in the metal compound may include one or more of Sn, Mg, Fe, Zn, Al, Ca, Cu, Ti, Cr, and Na, specifically Sn, Mg, Fe, Zn, Al, Ca, Cu, Ti, Cr, or Na, preferably Sn or Mg; the metal compound may include one or more of metal salt compounds, metal oxides, and metal sulfides, specifically metal salt compounds, metal oxides, or metal sulfides. In another embodiment of the present invention, the metal compound may include one or more of SnCl2, SnSO4, SnO, SnS2, MgSO4, Mg(NO3)2, MgO, FeCl3, FeSO4, Fe2O3, ZnSO4, ZnO, Al2(SO4)3, Al2O3, Al2S3, CaSO4, CaO, CuSO4, CuO, Ti(SO4)2, TiO2, Cr2(SO4)3, Cr2O3, and Na2SO4, specifically Sn or Mg. The metal doping agents used in this invention are: nCl2, SnSO4, SnO, SnS2, MgSO4, Mg(NO3)2, MgO, FeCl3, FeSO4, Fe2O3, ZnSO4, ZnO, Al2(SO4)3, Al2O3, Al2S3, CaSO4, CaO, CuSO4, CuO, Ti(SO4)2, TiO2, Cr2(SO4)3, Cr2O3, or Na2SO4, preferably SnCl2 or SnSO4; in the embodiments of this invention, SnCl2 or SnSO4 is preferred. The use of metal doping in this invention is beneficial for improving the electrochemical performance of carbon materials, especially the use of SnCl2 or SnSO4, which can optimize electron transport capabilities and significantly improve electrochemical performance. In one embodiment of the present invention, the mass of the metal compound is 0.01% to 10% of the total mass of the phenolic and aldehyde compounds, specifically 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.4%, 2.7%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.3%, 4.5%, 5%, 5.5%, 6%, 7%, 8%, 9%, or 10%.

[0036] In one embodiment of the present invention, the surfactant may include gum arabic powder and / or polyvinyl alcohol, specifically gum arabic powder or polyvinyl alcohol; the mass of the surfactant may be 2.4% to 3.5% of the total mass of phenolic and aldehyde compounds, specifically 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, or 3.5%. The present invention utilizes surfactants to optimize reaction efficiency, product structure, and performance by controlling the interfacial properties, dispersion state, and phase behavior of the reaction system, which is beneficial for achieving uniform metal doping.

[0037] In one embodiment of the present invention, the alkaline reagent may include one or more of ammonia, hexamethylenetetramine, and tetramethylammonium hydroxide, specifically ammonia; the concentration of the ammonia may be 25-30 wt%, specifically 30 wt% in the examples; the mass of the alkaline reagent may be 5.0-20% of the total mass of the phenolic and aldehyde compounds, more specifically 10-15 wt%, and even more specifically 11-12 wt%. The use of an alkaline reagent in this invention can adjust the pH value of the reaction system, which is beneficial for accelerating the reaction.

[0038] In one embodiment of the present invention, the water may be softened water.

[0039] In one embodiment of the present invention, the mixing of phenolic compounds, aldehyde compounds, surfactants, alkaline reagents, metal compounds and water can be carried out under heating and stirring conditions; the heating temperature can be 45-55°C, specifically 50°C; the stirring time can be 1.5-2.5 hours, specifically 2 hours; the present invention does not have a special limitation on the stirring speed.

[0040] After obtaining the mixed liquid, the present invention subjectes the mixed liquid to an addition-condensation reaction to obtain a metal-doped phenolic resin. In one embodiment of the present invention, the addition-condensation reaction includes sequential addition and condensation reactions; the temperature of the addition reaction can be 55–70°C, specifically 60°C or 65°C, and the time can be 3–5 hours, specifically 4 hours; the temperature of the condensation reaction can be 85–95°C, specifically 90–95°C, and the time can be 40–50 hours, specifically 45–48 hours; the addition-condensation reaction is preferably carried out under stirring conditions, and the present invention does not specifically limit the stirring rate. In the present invention, taking phenol and formaldehyde as an example, during the addition reaction, phenol and formaldehyde generate hydroxymethylphenol; during the condensation reaction, hydroxymethylphenol or hydroxymethylphenol and phenol lose water molecules to form a phenolic resin with a three-dimensional network structure.

[0041] In one embodiment of the present invention, the polycondensation reaction preferably further includes: solid-liquid separation of the product liquid obtained after the polycondensation reaction, drying the obtained solid material, and obtaining the metal-doped phenolic resin. In one embodiment of the present invention, the solid-liquid separation can be performed by centrifugation, which may include sequentially performing a first centrifugation and a second centrifugation; the rotation speed of the first centrifugation can be 400–600 r / min, specifically 500 r / min, and the time can be 20–40 min, specifically 30 min; the rotation speed of the second centrifugation can be 1500–1700 r / min, specifically 1600 r / min, and the time can be 10–30 min, specifically 20 min; preferably, the supernatant obtained from the first centrifugation is removed, the remaining material is subjected to the second centrifugation, then the supernatant obtained from the second centrifugation is removed, and the obtained solid material is dried. In one embodiment of the present invention, the drying temperature can be 75–85°C, specifically 80°C; the holding time can be 45–50 h, specifically 48 h; the drying is preferably carried out in a protective atmosphere, preferably nitrogen.

[0042] After obtaining the metal-doped phenolic resin, the present invention sequentially subjects the metal-doped phenolic resin to a re-curing treatment, a pyrolysis treatment, and an activation treatment to obtain the metal-doped porous carbon material. In one embodiment of the present invention, the temperature of the re-curing treatment can be 180–220°C, specifically 190°C, 200°C, or 210°C; the holding time can be 10–15 hours, specifically 11 hours, 12 hours, 13 hours, or 14 hours; the re-curing treatment is preferably carried out in a protective atmosphere, preferably nitrogen. In the embodiments of the present invention, the re-curing treatment under the above conditions can prolong the cross-linking strengthening of the polycondensation reaction, forming a highly cross-linked three-dimensional network structure, which is beneficial for the more stable incorporation of dopant elements into the resin skeleton and reduces precipitation problems during carbonization.

[0043] As one embodiment of the present invention, the re-curing treatment preferably further includes: crushing the obtained cured metal-doped phenolic resin, and then pyrolyzing the obtained powder material; the particle size of the powder material can be 100-300 μm.

[0044] In one embodiment of the present invention, the temperature of the pyrolysis treatment can be 680–720°C, specifically 690°C, 700°C, or 710°C; the holding time can be 2–4 hours, specifically 3 hours; the heating rate to the pyrolysis treatment temperature can be 2–4°C / min, specifically 3°C / min; the pyrolysis treatment is preferably carried out in a protective atmosphere, preferably nitrogen, and the nitrogen flow rate can be 50–70 L / min, specifically 55 L / min, 60 L / min, or 65 L / min. In this embodiment of the present invention, pyrolysis treatment under the above conditions can break the chemical bonds of the phenolic resin, which is beneficial to the formation of porous carbon materials. Specifically, in this embodiment of the present invention, the pyrolysis treatment is carried out in a rotary kiln.

[0045] In one embodiment of the present invention, the activation treatment temperature can be 950–980°C, specifically 960 or 970°C; the holding time can be 10–14 h, specifically 11 h, 12 h, or 13 h; the heating rate to the activation treatment temperature can be 4–6°C / min, specifically 5°C / min; the activation treatment is carried out in the presence of an activating gas, which may include carbon dioxide and / or water vapor, specifically carbon dioxide; the flow rate of the carbon dioxide can be 70–90 L / min, specifically 80 L / min. In this embodiment of the present invention, the activation treatment under the above conditions can regulate the microstructure of the porous carbon material, which is beneficial to increasing porosity and specific surface area, improving the adsorption capacity and the number of catalytic active sites of the material, and ultimately ensuring the acquisition of a metal-doped porous carbon material with excellent electrochemical performance. Specifically, in this embodiment of the present invention, the activation treatment is carried out in a rotary kiln.

[0046] This invention provides a metal-doped porous carbon material prepared by the preparation method described above, comprising a porous carbon material and metal nanoparticles dispersed within the pores of the porous carbon material (i.e., the metal exists in an elemental state in the metal-doped porous carbon material); the pores in the metal-doped porous carbon material include micropores and mesopores. In one embodiment of this invention, the particle size of the metal nanoparticles can be 50–600 nm. In another embodiment of this invention, the specific surface area of ​​the metal-doped porous carbon material can be 2553–3066 m². 2 / g, which can further be 2615~3041m 2 / g, and even further, it can be 2870~2971m. 2 / g; pore volume can be 0.4~1.2cm³ 3 / g, and can be further reduced to 0.8–1.1cm. 3 / g, and even further, it can be 0.9–1.0cm. 3 / g; the volume percentage of pores with a diameter less than 2nm in the metal-doped porous carbon material can be 80-89%, specifically 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88% or 89%; the volume percentage of pores with a diameter of 2-10nm in the metal-doped porous carbon material can be 8-18%, specifically 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17% or 18%; the metal-doped porous carbon material also has remaining pores with a diameter greater than 10nm.

[0047] This invention provides a metal-doped silicon-carbon composite material, comprising a metal-doped porous carbon material and silicon deposited on the surface of the metal-doped porous carbon material, wherein the metal-doped porous carbon material is the same as described in the above-mentioned technical solution. As one embodiment of this invention, the mass content of silicon in the metal-doped silicon-carbon composite material can be 20-90%, more preferably 30-80%, specifically 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%; the median particle size of the metal-doped silicon-carbon composite material can be 1-30 μm, more preferably 2-20 μm.

[0048] This invention provides a method for preparing the metal-doped silicon-carbon composite material described above, comprising the following steps:

[0049] Silicon is deposited on the surface of the metal-doped porous carbon material in the presence of a gaseous silicon source and a carrier gas to obtain the metal-doped silicon-carbon composite material.

[0050] In one embodiment of the present invention, the gaseous silicon source can be silane, specifically methanesilane; the carrier gas can be helium. In another embodiment, the silicon deposition can be performed in a CVD furnace, where the furnace rotation speed is 15–25 rpm, specifically 20 rpm; based on a mass of 50 g of the metal-doped silicon-carbon composite material, the carrier gas flow rate is 3–8 L / min, specifically 5 L / min; and the gaseous silicon source flow rate is 0.1–0.3 L / min, specifically 0.2 L / min. In yet another embodiment, the silicon deposition conditions include: a deposition temperature of 500–700 °C, specifically 550 °C, 600 °C, or 650 °C; and a deposition time of 1–3 h, specifically 1.5 h, 2 h, or 2.5 h. In an embodiment of the present invention, the metal-doped porous carbon material is placed in a CVD furnace and its rotation speed is set to 15–25 rpm. A carrier gas is introduced at a flow rate of 3–8 L / min. The temperature is raised to the temperature required for silicon deposition in the carrier gas environment. The carrier gas flow rate is maintained, and a gaseous silicon source is introduced at a flow rate of 0.1–0.3 L / min for silicon deposition. The present invention utilizes chemical vapor deposition to decompose silane and deposit it onto the metal-doped porous carbon material.

[0051] This invention provides the application of the metal-doped silicon-carbon composite material described in the above technical solution or the metal-doped silicon-carbon composite material prepared by the preparation method described in the above technical solution in the negative electrode material of lithium-ion batteries.

[0052] The present invention provides a lithium-ion battery, comprising a negative electrode, a positive electrode, an electrolyte and a separator. The negative electrode comprises a substrate and a negative electrode material loaded on the surface of the substrate. The negative electrode material comprises the metal-doped silicon-carbon composite material described in the above technical solution or the metal-doped silicon-carbon composite material prepared by the preparation method described in the above technical solution.

[0053] In one 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 may be a copper foil; the raw materials for preparing the negative electrode material may include a metal-doped silicon-carbon composite material, carbon black, and a binder, wherein the mass ratio of the metal-doped silicon-carbon composite material, carbon black, and binder may be 75-85:8-12:8-12, specifically 80:10:10; the binder is a carboxymethyl cellulose and styrene-butadiene rubber composite binder. In a specific embodiment of the present invention, the metal-doped silicon-carbon composite material, carbon black, and binder are mixed, the resulting mixture is coated on the surface of the substrate, and the negative electrode is obtained after drying.

[0054] In one embodiment of the present invention, the positive electrode is specifically a lithium metal sheet.

[0055] In one 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.

[0056] The present invention does not have any particular limitation on the diaphragm, and any diaphragm known to those skilled in the art can be used.

[0057] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0058] Example 1

[0059] 27 kg of phenol, 40.8 kg of formaldehyde aqueous solution (concentration 37 wt%), 8 kg of ammonia water (concentration 30 wt%), 2.2 kg of gum arabic powder, 2.6 kg of stannous chloride, and 150 kg of softened water were added to a reactor. The mixture was stirred and heated to 50°C for 2 hours to fully dissolve the added materials. Then, the temperature was raised to 65°C and an addition reaction was carried out under stirring for 4 hours. After that, the temperature was raised to 95°C and a polycondensation reaction was carried out under stirring for 48 hours. After the reaction was completed, the resulting product system was poured into a centrifuge and centrifuged at 500 r / min for 30 minutes. The supernatant was removed. The remaining material was centrifuged at 1600 r / min for 20 minutes and the supernatant was removed. The resulting solid material was placed in an oven and dried at 80°C under nitrogen protection for 48 hours. Then, it was re-cured at 200°C for 12 hours. The resulting material was pulverized to a particle size of 100-300 μm to obtain the cured metal-doped resin (i.e., cured tin-doped phenolic resin).

[0060] The cured metal-doped resin was placed in a rotary furnace and heated from room temperature (25°C) to 700°C at a rate of 3°C / min under an argon flow rate of 60 L / min, and held at that temperature for 3 h for pyrolysis treatment to obtain metal-doped carbon material; the pyrolyzed carbon material was placed in a rotary furnace and heated from room temperature (25°C) to 960°C at a rate of 5°C / min under a CO2 flow rate of 80 L / min, and held at that temperature for activation treatment to obtain metal-doped porous carbon material (the particle size of the metal nanoparticles is 50-600 nm);

[0061] 50g of metal-doped porous carbon material was placed in a CVD furnace at a rotation speed of 20rpm. Helium gas was introduced at a flow rate of 5L / min, and the temperature was raised to 600℃ in the helium atmosphere. The helium flow rate was maintained, and silane was introduced at a flow rate of 0.2L / min for silicon deposition for 2h to obtain a metal-doped silicon-carbon composite material with a silicon content of 50wt%.

[0062] Example 2

[0063] The procedure is the same as in Example 1, except that stannous chloride is replaced with stannous sulfate, and the amount of stannous sulfate used is 2.94 kg.

[0064] Example 3

[0065] The procedure is the same as in Example 1, except that stannous chloride is replaced with stannous oxide and the amount of stannous oxide used is 1.85 kg.

[0066] Example 4

[0067] The procedure is the same as in Example 1, except that stannous chloride is replaced with tin disulfide and the amount of tin disulfide used is 2.51 kg.

[0068] Example 5

[0069] The procedure is the same as in Example 1, except that stannous chloride is replaced with magnesium sulfate and the amount of magnesium sulfate used is 1.65 kg.

[0070] Example 6

[0071] The procedure is the same as in Example 1, except that stannous chloride is replaced with magnesium oxide and the amount of magnesium oxide used is 0.56 kg.

[0072] Example 7

[0073] The procedure is the same as in Example 1, except that stannous chloride is replaced with zinc sulfate and the amount of zinc sulfate used is 2.21 kg.

[0074] Example 8

[0075] The procedure is the same as in Example 1, except that stannous chloride is replaced with aluminum sulfate and the amount of aluminum sulfate used is 4.69 kg.

[0076] Example 9

[0077] The procedure is the same as in Example 1, except that stannous chloride is replaced with calcium sulfate and the amount of calcium sulfate used is 1.87 kg.

[0078] Example 10

[0079] The procedure is the same as in Example 1, except that stannous chloride is replaced with copper sulfate, and the amount of copper sulfate used is 2.19 kg.

[0080] Comparative Example 1

[0081] The procedure is the same as in Example 1, except that stannous chloride is omitted. Specifically, 27 kg of phenol, 40.8 kg of formaldehyde aqueous solution, 8 kg of ammonia, 2.2 kg of gum arabic powder and 150 kg of softened water are added to the reaction vessel and dissolved before the reaction is carried out.

[0082] Comparative Example 2

[0083] The procedure is the same as in Example 1, except that the gum arabic powder is omitted. Specifically, 27 kg of phenol, 40.8 kg of formaldehyde aqueous solution, 8 kg of ammonia (concentration of 30 wt%), 2.6 kg of stannous chloride and 150 kg of softened water are added to the reaction vessel and dissolved before the reaction is carried out.

[0084] Comparative Example 3

[0085] The procedure is the same as in Example 1, except that the re-curing step is omitted. Specifically, the dried material is crushed to a particle size of 100-300 μm and then directly added to a rotary kiln for pyrolysis.

[0086] Test Example 1

[0087] Figure 1 The image shows the EDS diagram of the metal-doped porous carbon material prepared in Example 1, with the upper part showing the morphology of the metal-doped porous carbon material prepared in Example 1 and the lower part showing the corresponding elemental distribution. The results show that Sn is uniformly distributed in the metal-doped porous carbon material.

[0088] Figure 2 The XRD patterns of the metal-doped porous carbon materials prepared in Example 1 and Comparative Example 1 show that Sn doping in Example 1 is doped in the metal-doped porous carbon material in the form of an element.

[0089] The performance of the metal-doped porous carbon materials prepared in the examples and comparative examples was tested, and the specific results are shown in Table 1. Table 1 shows that the incorporation of metal elements reduces the pore volume of the metal-doped porous carbon materials.

[0090] Table 1. Performance test results of metal-doped porous carbon materials in the examples and comparative examples.

[0091]

[0092]

[0093] Test Example 2

[0094] The metal-doped silicon-carbon composite materials prepared in the examples and comparative examples were mixed with carbon black and a binder (specifically, a composite binder of carboxymethyl cellulose and styrene-butadiene rubber) in a mass ratio of 80:10:10. The resulting mixture 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 1 mol / L LiPF6 solution was used as the electrolyte (the solvents were diethyl carbonate, dimethyl carbonate, and ethylene carbonate, with a volume ratio of 1:1:1). The electrolyte, along with the separator, the negative electrode, and the positive electrode, was assembled to obtain a lithium-ion battery. The lithium-ion battery was then tested on a LAND charge-discharge tester under conditions of a current density of 0.1C and a voltage range of 0.005V to 1.5V.

[0095] Figure 3 The table shows the first charge-discharge curves of the lithium-ion battery assembled using the metal-doped silicon-carbon composite material prepared in Example 1 at a rate of 0.1C. Table 2 shows the performance test results of the lithium-ion batteries assembled using the metal-doped silicon-carbon composite materials from each example and comparative example. As can be seen from Table 2, the incorporation of metal elements can significantly improve the electrochemical performance of lithium-ion batteries. Adding surfactants and adding a re-curing treatment step also improve the electrochemical performance of lithium-ion batteries.

[0096] Table 2 Performance test results of lithium-ion batteries assembled using metal-doped silicon-carbon composite materials

[0097]

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a metal-doped porous carbon material, comprising the following steps: A phenolic compound, an aldehyde compound, a surfactant, an alkaline reagent, a metal compound, and water are mixed, and the resulting mixture is subjected to an addition-condensation reaction to obtain a metal-doped phenolic resin; the surfactant is gum arabic powder and / or polyvinyl alcohol; the metal compound contains one or more of the metal elements Sn and Mg. The metal-doped phenolic resin was subjected to a re-curing treatment, a pyrolysis treatment and an activation treatment in sequence to obtain the metal-doped porous carbon material. The re-curing treatment is performed at a temperature of 180~200℃ for 10~15 hours. The activation process is carried out in the presence of an activating gas.

2. The preparation method according to claim 1, characterized in that, The phenolic compounds include one or more of phenol, m-diphenol, and triaminophenol; the aldehyde compounds include formaldehyde and / or acetaldehyde; the molar ratio of the phenolic compounds to the aldehyde compounds is 1:1.6~2.0; The metal compound includes one or more of metal salts, metal oxides, and metal sulfides; the mass of the metal compound is 0.01-10% of the total mass of the phenolic and aldehyde compounds. The surfactant accounts for 2.4-3.5% of the total mass of the phenolic and aldehyde compounds. The alkaline reagent includes one or more of ammonia, hexamethylenetetramine, and tetramethylammonium hydroxide; the concentration of the ammonia is 25-30 wt%, and the mass of the alkaline reagent is 5.0-20% of the total mass of the phenolic and aldehyde compounds.

3. The preparation method according to claim 2, characterized in that, The metal compound includes one or more of SnCl2, SnSO4, SnO, SnS2, MgSO4, Mg(NO3)2 and MgO.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The addition-condensation reaction includes sequential addition and condensation reactions; the addition reaction is carried out at a temperature of 55-70°C for 3-5 hours; the condensation reaction is carried out at a temperature of 85-95°C for 40-50 hours; the addition-condensation reaction is carried out under stirring conditions. The process after the polycondensation reaction further includes: solid-liquid separation of the product liquid obtained after the polycondensation reaction, drying of the obtained solid material, and obtaining the metal-doped phenolic resin; the drying temperature is 70~90℃, the holding time is 40~50h, and the drying is carried out in a protective atmosphere.

5. The preparation method according to claim 4, characterized in that, The re-curing process is carried out in a protective atmosphere; The pyrolysis treatment is carried out at a temperature of 680~720℃ and a holding time of 2~4h in a protective atmosphere. The activation treatment is performed at a temperature of 950~980℃ for 10~14h, and the activation gas includes carbon dioxide and / or water vapor. The re-curing process and the pyrolysis process also include a crushing process.

6. The metal-doped porous carbon material prepared by the preparation method according to any one of claims 1 to 5 comprises a porous carbon material and metal nanoparticles dispersed inside the pores of the porous carbon material; the pores in the metal-doped porous carbon material include micropores and mesopores.

7. A metal-doped silicon-carbon composite material, comprising a metal-doped porous carbon material and silicon deposited on the surface of the metal-doped porous carbon material, wherein the metal-doped porous carbon material is the metal-doped porous carbon material of claim 6.

8. The method for preparing the metal-doped silicon-carbon composite material according to claim 7, comprising the following steps: Silicon is deposited on the surface of the metal-doped porous carbon material in the presence of a gaseous silicon source and a carrier gas to obtain the metal-doped silicon-carbon composite material.

9. The application of the metal-doped silicon-carbon composite material of claim 7 or the metal-doped silicon-carbon composite material prepared by the preparation method of claim 8 in lithium-ion battery anode materials.

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

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