A lithium-carbon nanotube-doped porous carbon, preparation method thereof and application thereof

Abstract

The present invention provides a lithium-carbon nanotube doped porous carbon, a preparation method thereof and an application thereof, belonging to the technical field of battery material preparation. The preparation method of the lithium-carbon nanotube doped porous carbon includes first uniformly doping carbon nanotubes in a resin precursor, and then preparing the carbon nanotube doped porous carbon through curing and activation. The carbon nanotubes construct an efficient conductive network in the pores and matrix of the porous carbon, which can improve the electronic conductivity of the material, and can provide structural support as a skeleton to enhance the mechanical properties and thermal stability of the material, and is beneficial to optimizing the pore structure. Then, metal lithium vapor is deposited in the pores of the porous carbon by a gas phase method, which can further reduce the defects of the porous carbon, fill the defect sites of the porous carbon, enhance the structural stability of the material, and improve the ionic conductivity of the material and the initial Coulomb efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of battery material preparation, and specifically to a lithium-carbon nanotube doped porous carbon, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its rich pore structure and good electrical conductivity, porous carbon can be used as an energy storage material and has a wide range of applications in the field of energy storage. It is commonly used in the preparation of supercapacitors, lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, etc. The parameters affecting the performance of porous carbon mainly include specific surface area, pore size, pore volume, mechanical strength, and its electronic conductivity. Currently, the commercially available porous carbon materials are mainly prepared from resin-based materials or biomass materials through processes such as pre-carbonization and activation. However, the existing porous carbon materials have disadvantages such as poor electronic conductivity, poor compressive ability, and many structural defects, resulting in low initial efficiency, which limits their performance in some applications with high requirements for electrical conductivity and initial efficiency. Porous carbon is also often used as a precursor for silicon-carbon materials. Currently, the market has increasingly high requirements for the kinetic performance and initial efficiency of new silicon-carbon materials, which requires the precursor porous carbon used in silicon-carbon materials to have high electronic conductivity and high initial efficiency.

[0003] In a Chinese patent with an application publication date of August 2, 2024, and an application publication number of CN118419892A, a metal-doped porous carbon, a silicon-carbon material, and a preparation method thereof are disclosed. In this patent, lithium is doped into the porous carbon to improve the electronic conductivity and the initial efficiency; then, through a deposition method, a solid electrolyte is deposited on the outermost layer to improve the initial Coulomb efficiency and high-temperature storage performance of the material. However, the performance improvement of this method is limited, and it will cause a decrease in the pore volume and pore size of the material, thereby reducing the ion storage capacity and transmission speed of the electrode material. Moreover, the lithium doping uniformity in its preparation method is poor, resulting in too high or too low local lithium content, which may lead to uneven current distribution and affect the charge and discharge performance of the battery. In addition, the preparation process is complex, which not only increases the production cost and time cost but also may introduce more uncertain factors, reducing the production efficiency and the stability of product quality. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention aims to provide a lithium-carbon nanotube doped porous carbon, a preparation method thereof, and an application thereof, which have high electronic conductivity, few structural defects, and can improve the rate performance and initial efficiency.

[0005] One of the purposes of the present invention is to provide a preparation method for lithium-carbon nanotube doped porous carbon, and the preparation method includes:

[0006] First, a carbon nanotube doped resin precursor is prepared by a co-precipitation method, and then a curing treatment is carried out to obtain a carbon nanotube doped resin;

[0007] Then, the carbon nanotube-doped resin is activated with carbon dioxide to obtain carbon nanotube-doped porous carbon;

[0008] Then, lithium deposition is carried out on the carbon nanotube-doped porous carbon by vacuum evaporation to obtain lithium-carbon nanotube-doped porous carbon.

[0009] Preferably, the method for preparing the carbon nanotube-doped resin precursor by coprecipitation includes:

[0010] First, an aqueous solution of a phenolic compound is added, then an aqueous solution of an aldehyde compound is added dropwise, and then carbon nanotubes, a pore-forming agent, and ammonia water are added in sequence. After mixing evenly, the mixture is reacted at 50-100 °C for 1-6 h, and then filtered to obtain the carbon nanotube-doped resin precursor.

[0011] Preferably, the mass ratio of the phenolic compound, the aldehyde compound, the carbon nanotubes, and the pore-forming agent is 100:100-200:1-5:1-5.

[0012] Preferably, the carbon nanotubes include one or more of hydroxylated carbon nanotubes, aminated carbon nanotubes, carboxylated carbon nanotubes, or nitrogen-doped carbon nanotubes.

[0013] Preferably, the phenolic compound includes one or more of m-cresol, p-cresol, o-cresol, 3,5-xylenol, or resorcinol.

[0014] Preferably, the aldehyde compound includes one or more of formaldehyde, acetaldehyde, furfural, or salicylaldehyde.

[0015] Preferably, the pore-forming agent includes one or more of polyvinyl alcohol, polyvinylpyrrolidone, or polyvinylamine.

[0016] Preferably, the concentration of the aqueous solution of the phenolic compound is 15-50 wt%.

[0017] Preferably, the concentration of the aldehyde compound is 10-40 wt%.

[0018] Preferably, the concentration of the ammonia water is 15-20 wt%, and the mass ratio of the phenolic compound to the ammonia water is 1:8-12.

[0019] Preferably, the method for curing the carbon nanotube-doped resin precursor includes:

[0020] The carbon nanotube-doped resin precursor is cured at 500-800 °C for 1-6 h to obtain the carbon nanotube-doped resin.

[0021] Preferably, the method for activating the carbon nanotube-doped resin includes:

[0022] After heating the carbon nanotube-doped resin to 1100 - 1400 °C, carbon dioxide is introduced for activation treatment for 30 - 300 min to obtain carbon nanotube-doped porous carbon.

[0023] Preferably, the flow rate of carbon dioxide for activation treatment is 100 - 500 ml / min.

[0024] Preferably, the method for lithium deposition on the carbon nanotube-doped porous carbon using vacuum evaporation includes:

[0025] Lithium deposition is carried out under vacuum conditions. Using a high-energy laser beam irradiation, lithium is vaporized and then deposited into the pores and on the surface of the carbon nanotube-doped porous carbon. The evaporation time is 5 - 15 min, and then carbon dioxide is introduced for passivation treatment.

[0026] Preferably, the mass ratio of carbon nanotube-doped porous carbon to lithium is 100:1 - 5.

[0027] Preferably, the wavelength of the laser beam is 900 - 1090 nm, the pulse width is 0.5 ms - 4 ms, and the laser power is 100 W - 600 W.

[0028] Preferably, the flow rate of carbon dioxide for passivation treatment is 100 - 500 ml / min.

[0029] Preferably, the time for passivation treatment is 30 - 300 min.

[0030] The second object of the present invention is to provide a lithium-carbon nanotube-doped porous carbon, which comprises 1 - 5 wt% carbon nanotubes, 1 - 5 wt% lithium carbonate, and 90 - 98 wt% porous carbon.

[0031] The third object of the present invention is to provide an application of the lithium-carbon nanotube-doped porous carbon in the preparation of secondary batteries.

[0032] The beneficial effects of the present invention include:

[0033] The present invention first uniformly dopes carbon nanotubes in a resin precursor, and then prepares carbon nanotube-doped porous carbon through curing and activation. The carbon nanotubes construct an efficient conductive network in the pores and matrix of the porous carbon, which can improve the electronic conductivity of the material, and can provide structural support as a skeleton to enhance the mechanical properties and thermal stability of the material, and is beneficial to optimizing the pore structure. Then, metal lithium vapor is deposited in the pores of the porous carbon by a gas-phase method, which can further reduce the defects of the porous carbon, fill the defect sites of the porous carbon, enhance the structural stability of the material, and improve the ionic conductivity of the material and the initial Coulomb efficiency. Description of the Drawings

[0034] Figure 1 SEM image of the lithium-carbon nanotube doped porous carbon prepared in Example 1. Detailed implementation manners

[0035] In the following description, certain specific details are included to provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the relevant art will recognize that the embodiments can be implemented without one or more of these specific details, and by using other methods, components, materials, etc.

[0036] Unless otherwise required in the present invention, the words "comprising" and "including" shall be construed in an open, inclusive sense, i.e., "including but not limited to".

[0037] The phrase "in one embodiment" or "in an embodiment" or "in a preferred embodiment" or "in certain embodiments" mentioned throughout this specification means that at least one embodiment includes the specific reference elements, structures, or features related to those described in that embodiment. Thus, the phrases "in one embodiment", "in an embodiment", "in a preferred embodiment", or "in certain embodiments" that appear at different positions throughout the specification do not necessarily all refer to the same embodiment. In addition, the specific elements, structures, or features can be combined in any suitable manner in one or more embodiments.

[0038] According to a first aspect of the present invention, there is provided a method for preparing lithium-carbon nanotube doped porous carbon, the preparation method comprising:

[0039] First, a carbon nanotube doped resin precursor is prepared by a co-precipitation method, and then a curing treatment is carried out to obtain a carbon nanotube doped resin;

[0040] Then, the carbon nanotube doped resin is activated with carbon dioxide to obtain carbon nanotube doped porous carbon;

[0041] Then, lithium deposition is carried out on the carbon nanotube doped porous carbon by a vacuum evaporation method to obtain lithium-carbon nanotube doped porous carbon.

[0042] In the present invention, during the reaction process before preparing the resin, carbon nanotubes are doped by the co-precipitation method. Carbon nanotubes have a unique tubular structure and certain rigidity. During the polymerization reaction process, the surrounding carbonaceous materials will deposit and polymerize around the carbon nanotubes, and the carbon nanotubes can interact with monomer molecules. On the one hand, during the polymerization process, the carbon nanotubes are gradually embedded into the resin structure, which is beneficial to achieving more uniform doping and can better participate in the resin formation process; on the second hand, the functional groups on the surface of the carbon nanotubes may form strong interactions with the active groups in the resin molecules, making the carbon nanotubes less likely to fall off during subsequent processing and being beneficial to maintaining the structural stability of the material; on the third hand, the carbon nanotubes can act as a structural template to guide the polymerization direction, and the structure formed around the carbon nanotubes will be retained during the subsequent activation treatment process, so that the pores of the porous carbon exhibit shape and distribution characteristics related to the carbon nanotubes, forming a more ordered pore structure; on the fourth hand, the carbon nanotubes can also act as a skeleton to provide structural support and enhance the mechanical properties and thermal stability of the material.

[0043] Furthermore, during lithium deposition, on the one hand, a more stable and ordered pore structure is beneficial to the uniform deposition of lithium, and the doping of carbon nanotubes also provides more active sites for lithium deposition; on the second hand, the deposition of lithium can fill some defect sites in the porous carbon, reduce the defects in the material, and make the material structure more complete and stable; on the third hand, metallic lithium has high ionic conductivity. After depositing it in the porous carbon, it provides more channels and active sites for ion transport, and lithium ions can migrate more rapidly at the interface between lithium and the porous carbon, thus significantly improving the ionic conductivity of the material; at the same time, the structure of carbon nanotube-doped porous carbon provides good support and restraint for the deposition of lithium, and can prevent the aggregation and volume change of lithium during charge and discharge.

[0044] In a preferred embodiment of the present invention, the method for preparing a carbon nanotube-doped resin precursor using the co-precipitation method includes:

[0045] First, add an aqueous solution of a phenolic compound, then dropwise add an aqueous solution of an aldehyde compound, and then successively add carbon nanotubes, a pore-forming agent, and ammonia water. After mixing evenly, react at 50 - 100 °C for 1 - 6 h, and then filter to obtain the carbon nanotube-doped resin precursor.

[0046] In the present invention, after adding the phenolic compound, the aldehyde compound, the carbon nanotubes, the pore-forming agent, and ammonia water, the phenolic compound and the aldehyde compound react to form a phenolic resin precursor, and the pore-forming agent is used to promote the formation of pores. During the reaction process, the carbon nanotubes are uniformly doped in the phenolic resin precursor.

[0047] In the present invention, the reaction temperature is, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, and the point values between any two of the above. The reaction time is, for example, 1 h, 2 h, 3 h, 4 h, 5 h or 6 h, and the point values between any two of the above.

[0048] In the present invention, if the temperature is lower than 50°C, on the one hand, the polycondensation reaction of the aldehyde resin proceeds very slowly, which may lead to a significant extension of the reaction time and affect the production efficiency; on the second hand, the dispersion effect of the carbon nanotubes in the system may deteriorate because the fluidity of the system weakens at a lower temperature, which is not conducive to the uniform dispersion of the carbon nanotubes in the resin precursor, and agglomeration may occur, thus affecting the performance of the material; on the third hand, it is also difficult to form an ideal pore structure, resulting in a lower specific surface area and porosity of the material, affecting its adsorption performance and ion transport ability, etc.

[0049] In the present invention, if the temperature is higher than 100°C, on the one hand, side reactions may be triggered, and it can cause over-crosslinking of the phenolic resin and even side reactions such as thermal decomposition, damaging the structure of the resin and reducing the performance and stability of the material; on the second hand, it may be difficult to control the size and distribution of the pores at too high a temperature, and even the pore structure may collapse, affecting the pore characteristics of the material; on the third hand, it consumes a large amount of energy, increases the production cost, and also places higher requirements on the production equipment. More complex heating and temperature control equipment may be required to ensure the stability of the temperature, increasing the difficulty and risk of production.

[0050] In a preferred embodiment of the present invention, the mass ratio of the phenolic compound, aldehyde compound, carbon nanotubes and pore-forming agent is 100:100 - 200:1 - 5:1 - 5. Taking the mass of the phenolic compound as 100 parts as an example, the mass of the aldehyde compound is, for example, 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts or 200 parts, the mass of the carbon nanotubes is, for example, 1 part, 2 parts, 3 parts, 4 parts or 5 parts, and the mass of the pore-forming agent is, for example, 1 part, 2 parts, 3 parts, 4 parts or 5 parts, and the point values between any two of the above.

[0051] In a preferred embodiment of the present invention, the carbon nanotubes include one or more of hydroxylated carbon nanotubes, aminated carbon nanotubes, carboxylated carbon nanotubes or nitrogen-doped carbon nanotubes.

[0052] In the present invention, hydroxylated carbon nanotubes, aminated carbon nanotubes, carboxylated carbon nanotubes and nitrogen-doped carbon nanotubes can interact with the active groups in the phenolic resin, thereby enhancing the interfacial bonding force between the carbon nanotubes and the phenolic resin, and also facilitating the uniform dispersion of the carbon nanotubes in the phenolic resin.

[0053] In the present invention, the carbon nanotubes are, for example, hydroxylated carbon nanotubes, aminated carbon nanotubes, amino-functionalized carbon nanotubes, nitrogen-doped carbon nanotubes, hydroxylated carbon nanotubes and aminated carbon nanotubes, hydroxylated carbon nanotubes and carboxylated carbon nanotubes, carboxylated carbon nanotubes and nitrogen-doped carbon nanotubes, or a combination of carboxylated carbon nanotubes, hydroxylated carbon nanotubes and nitrogen-doped carbon nanotubes.

[0054] Preferably, the carbon nanotubes are carboxylated carbon nanotubes. The presence of carboxyl groups endows the carbon nanotubes with good hydrophilicity and enables them to disperse well in an aqueous phase system, which is very advantageous for the co-precipitation method, a preparation method usually carried out in a liquid phase environment. The carboxylated carbon nanotubes can undergo chemical reactions such as esterification reactions with phenolic hydroxyl groups in phenolic resins, enhancing the compatibility and binding force between the two.

[0055] Preferably, the phenolic compounds include one or more of m-cresol, p-cresol, o-cresol, 3,5-xylenol or resorcinol. The phenolic compounds are, for example, the phenolic compounds including m-cresol, p-cresol, o-cresol, 3,5-xylenol, resorcinol, m-cresol and p-cresol, m-cresol and o-cresol, m-cresol and 3,5-xylenol, m-cresol and resorcinol, m-cresol, p-cresol and o-cresol, or a combination of m-cresol, p-cresol, o-cresol and 3,5-xylenol.

[0056] Preferably, the aldehyde compounds include one or more of formaldehyde, acetaldehyde, furfural or salicylaldehyde. The aldehyde compounds are, for example, formaldehyde, acetaldehyde, furfural, salicylaldehyde, formaldehyde and acetaldehyde, formaldehyde and furfural, formaldehyde and salicylaldehyde, formaldehyde, acetaldehyde and furfural, formaldehyde, acetaldehyde and salicylaldehyde, or a combination of formaldehyde, acetaldehyde, furfural and salicylaldehyde.

[0057] Preferably, the pore-forming agent includes one or more of polyvinyl alcohol, polyvinylpyrrolidone or polyvinylamine. The pore-forming agent is, for example, polyvinyl alcohol, polyvinylpyrrolidone, polyvinylamine, polyvinyl alcohol and polyvinylpyrrolidone, polyvinyl alcohol and polyvinylamine, or a combination of polyvinyl alcohol, polyvinylpyrrolidone and polyvinylamine.

[0058] Preferably, the concentration of the aqueous solution of the phenolic compound is 15 - 50 wt%, for example, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 40 wt% or 50 wt%, and the point values between any two of the above.

[0059] Preferably, the concentration of the aldehyde compound is 10 wt - 40 wt%, for example, 10 wt%, 20 wt%, 30 wt% or 40 wt%, and the point values between any two of the above.

[0060] Preferably, the concentration of the ammonia water is 15-20 wt%, such as 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%; the mass ratio of the phenolic compound to the ammonia water is 1:8-12, such as 1:8, 1:9, 1:10, 1:11 or 1:12.

[0061] In a preferred embodiment of the present invention, the method for curing the carbon nanotube-doped resin precursor includes:

[0062] Curing the carbon nanotube-doped resin precursor at 500-800 °C for 1-6 h to obtain a carbon nanotube-doped resin.

[0063] In the present invention, the temperature of the curing treatment is, for example, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C or 800 °C.

[0064] Specifically, the curing treatment is carried out in an inert atmosphere. During the curing treatment at 500-800 °C, cross-linking reaction and preliminary carbonization reaction occur in the carbon nanotube-doped resin precursor, forming a three-dimensional network structure and a basic pore structure. At the same time, the interfacial bonding force between the carbon nanotubes and the phenolic resin is further enhanced during the curing process. At the same time, due to the skeleton support effect of the carbon nanotubes, the volume shrinkage of the material during the cross-linking process can be restricted, and the stability of the pore structure can be maintained. When the temperature is lower than 500 °C, it may be difficult for the phenolic resin to be fully cross-linked; when the temperature is higher than 800 °C, it may cause resin decomposition or other side reactions.

[0065] In the present invention, the time of the curing treatment is, for example, 1 h, 2 h, 3 h, 4 h, 5 h or 6 h.

[0066] As the curing treatment time is prolonged, the cross-linking reaction of the phenolic resin is more sufficient, and the performance of the material gradually tends to be stable; if the curing time is too short, the resin may not be fully cross-linked, resulting in insufficient performance of the material; while if the curing time is too long, it may waste energy and may cause excessive changes in the material performance or side reactions.

[0067] Preferably, the heating rate of the curing treatment is 1-10 °C / min, such as 1 °C / min, 2 °C / min, 4 °C / min, 6 °C / min, 8 °C / min or 10 °C / min.

[0068] In a preferred embodiment of the present invention, the method for activating the carbon nanotube-doped resin includes:

[0069] After heating the carbon nanotube-doped resin to 1100 - 1400 °C, carbon dioxide is introduced and activation treatment is carried out for 30 - 300 min to obtain carbon nanotube-doped porous carbon.

[0070] In the present invention, during the activation treatment, carbon dioxide etches the porous carbon material, further optimizing the pore structure, increasing the specific surface area and porosity of the material, forming more active sites. By controlling the activation temperature, time, and carbon dioxide flow rate, the size, distribution, and shape of the pores can be adjusted. During the activation process, the high-temperature treatment makes the contact between the carbon nanotubes and the porous carbon closer, which is more conducive to electron transport and forms a stronger structural support. The presence of carbon nanotubes can also prevent structural collapse.

[0071] In the present invention, the temperature of the activation treatment is, for example, 1100 °C, 1150 °C, 1200 °C, 1250 °C, 1300 °C, 1350 °C, or 1400 °C. Too high an activation temperature may cause structural damage or performance degradation of the material.

[0072] In the present invention, the time of the activation treatment is, for example, 30 min, 50 min, 100 min, 150 min, 200 min, 250 min, or 300 min. Too short an activation time may not sufficiently etch the carbon material, resulting in insufficient porosity and specific surface area, while too long an activation time may over-etch the material, making the structure too loose and reducing the mechanical strength of the material.

[0073] Preferably, the heating rate of the activation treatment is 1 - 10 °C / min, for example, 1 °C / min, 2 °C / min, 4 °C / min, 6 °C / min, 8 °C / min, or 10 °C / min.

[0074] Preferably, the flow rate of carbon dioxide for the activation treatment is 100 - 500 ml / min, for example, 100 ml / min, 200 ml / min, 300 ml / min, 400 ml / min, or 500 ml / min.

[0075] In a preferred embodiment of the present invention, the method for lithium deposition on the carbon nanotube-doped porous carbon includes:

[0076] Lithium deposition is carried out under vacuum conditions. Using a high-energy laser beam to irradiate, lithium is vaporized and then deposited into the pores and on the surface of the carbon nanotube-doped porous carbon. The evaporation coating time is 5 - 15 min, and then carbon dioxide is introduced for passivation treatment.

[0077] In the present invention, a high-energy laser beam irradiates a lithium source, causing the lithium to rapidly heat up and vaporize. The vaporized lithium atoms have high activity and mobility, and can more easily diffuse and deposit into the pores and on the surface of carbon nanotube-doped porous carbon. The presence of carbon nanotubes in the porous carbon can provide more deposition sites, and also helps to enhance the interaction between lithium and the carbon material. This interaction can strengthen the binding force between lithium and the carbon material, improving the stability and electrochemical performance of the material. Lithium deposits into the pores of the porous carbon. On the one hand, it can increase the energy storage capacity of the material. The pore structure can also limit the volume change of lithium, reduce the stress during charge and discharge, and improve the cycle stability of the material.

[0078] The evaporation deposition time is, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min. If the evaporation deposition time is too short, it may result in insufficient lithium deposition and the lithium cannot fully play its role; while if the evaporation deposition time is too long, it may lead to excessive lithium deposition, making the structure of the material unstable, and may even block the pores, affecting ion transport.

[0079] After introducing carbon dioxide, carbon dioxide reacts with lithium to form a lithium carbonate passivation layer on the surface of lithium. This passivation layer can prevent lithium from further reacting with oxygen and moisture in the air, improving the stability and safety of the material.

[0080] Preferably, the mass ratio of carbon nanotube-doped porous carbon to lithium is 100:1 - 5, for example, 100:1, 100:2, 100:3, 100:4 or 100:5.

[0081] If the mass ratio of carbon nanotube-doped porous carbon to lithium is too large, the content of lithium is relatively too small, and the effect on improving the energy storage capacity and conductivity is not obvious; if the mass ratio of carbon nanotube-doped porous carbon to lithium is too small, too much lithium deposits on the carbon nanotube-doped porous carbon. During charge and discharge, the repeated insertion and extraction of lithium will cause a large volume change, which may lead to the destruction of the material structure and reduce the cycle stability of the material. When the lithium content is too high, lithium agglomeration is also likely to occur in the material, affecting the uniform distribution of lithium in the material, and further affecting the consistency and reliability of the battery performance. The range of the mass ratio of 100:1 - 5 can achieve a good synergistic effect between carbon nanotube-doped porous carbon and lithium. Within this ratio range, the carbon material can provide sufficient structural support and active sites, and at the same time, the content of lithium can also meet the requirements of energy storage and conductivity.

[0082] Specifically, the carbon nanotube-doped porous carbon is placed in a vacuum chamber and evacuated to a vacuum (≤1 torr). A lithium block is placed in the evaporation chamber. A high-energy laser beam is emitted by a laser and focused onto the coating material through a focusing lens. The temperature is raised to 300 - 400 °C, causing it to be heated and vaporized. The vaporized lithium vapor deposits on the pores and surface of the carbon nanotube-doped porous carbon, obtaining lithium-carbon nanotube-doped porous carbon.

[0083] Preferably, the wavelength of the laser beam is 900 - 1090 nm, such as 900 nm, 930 nm, 960 nm, 1000 nm, 1030 nm, 1060 nm, or 1090 nm; the pulse width is 0.5 ms - 4 ms, such as 0.5 ms, 1 ms, 1.5 ms, 2 ms, 2.5 ms, 3 ms, 3.5 ms, 4 ms, 4.5 ms, or 5 ms; and the laser power is 100 W - 600 W, such as 100 W, 200 W, 300 W, 400 W, 500 W, or 600 W.

[0084] Preferably, the flow rate of carbon dioxide for passivation treatment is 100 - 500 ml / min, such as 100 ml / min, 200 ml / min, 300 ml / min, 400 ml / min, or 500 ml / min.

[0085] Preferably, the time for passivation treatment is 30 - 300 min, such as 30 min, 50 min, 100 min, 150 min, 200 min, 250 min, or 300 min.

[0086] In a preferred embodiment of the present invention, the preparation method includes:

[0087] (1) First, an aqueous solution of a phenolic compound is added, and then an aqueous solution of an aldehyde compound is added dropwise. Subsequently, carbon nanotubes, a pore-forming agent, and ammonia water are added. After mixing evenly, the mixture is reacted at 50 - 100 °C for 1 - 6 h, and then filtered to obtain a carbon nanotube-doped resin precursor. Under an inert atmosphere, the carbon nanotube-doped resin precursor is cured at 500 - 800 °C for 1 - 6 h to obtain a carbon nanotube-doped resin;

[0088] (2) After heating the carbon nanotube-doped resin to 1100 - 1400 °C, carbon dioxide is introduced for activation treatment for 30 - 300 min to obtain carbon nanotube-doped porous carbon;

[0089] (3) According to the mass ratio of carbon nanotube-doped porous carbon: lithium metal = 100:1 - 5, put the carbon nanotube-doped porous carbon into a vacuum chamber and evacuate it to a vacuum (≤1 torr). Put the lithium block into the evaporation chamber. Use a laser to emit a high-energy laser beam, which is focused and irradiated onto the coating material. The temperature is raised to 300 - 400 °C to make it vaporize by heating. The vaporized lithium vapor deposits in the pores and on the surface of the carbon nanotube-doped porous carbon. The evaporation time is 5 - 15 min. Then, introduce carbon dioxide at normal pressure and introduce it at a flow rate of 100 - 500 ml / min for 30 - 300 min to obtain lithium carbon nanotube-doped porous carbon.

[0090] According to the second aspect of the present invention, there is provided a lithium carbon nanotube-doped porous carbon obtained by using the preparation method as described in the first aspect. The lithium carbon nanotube-doped porous carbon comprises 1 - 5 wt% carbon nanotubes, 1 - 5 wt% lithium carbonate, and 90 - 98 wt% porous carbon.

[0091] The lithium carbon nanotube-doped porous carbon has a high specific surface area and a good pore structure, and has good electrical properties, energy storage capacity, and rate performance. At the same time, the stability and cycle life of the material are also greatly improved.

[0092] According to the third aspect of the present invention, there is provided an application of the lithium carbon nanotube-doped porous carbon in the preparation of secondary batteries.

[0093] Preferably, the secondary battery includes a sodium battery or a lithium battery.

[0094] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0095] Examples

[0096] The following further elaborates on the present invention in conjunction with examples. It can be understood that the specific examples described herein are only used to explain the relevant invention, rather than limiting the invention. It should be noted that, without conflict, the examples in the present invention and the features in the examples can be combined with each other.

[0097] In the following examples, unless otherwise specified, each raw material component is a commercially available product.

[0098] Example 1

[0099] A preparation method of lithium carbon nanotube-doped porous carbon, comprising the following steps:

[0100] (1) Add 100 g of m-cresol to 300 g of deionized water and disperse evenly. Then, dropwise add 450 g of formaldehyde (30 wt%) solution, and successively add 3 g of carboxylated carbon nanotubes, 3 g of polyvinyl alcohol, and 1000 g of 17% ammonia water. After mixing evenly, react at 80 °C for 3 h and filter;

[0101] (2) The obtained filter residue is heated to 650 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and cured for 3 h. Then, it is heated to 1250 °C at a heating rate of 5 °C / min, and carbon dioxide gas is introduced at a flow rate of 300 ml / min for activation treatment for 150 min to obtain carbon nanotube-doped porous carbon;

[0102] (3) Place 100 g of carbon nanotube-doped porous carbon into a vacuum chamber and evacuate it to a vacuum (≤1 torr). Place 3 g of lithium block into the evaporation chamber. Use a laser to emit a high-energy laser beam, which is focused and irradiated onto the coating material. The temperature rises to 350 °C to make it vaporize by heating. The vaporized lithium vapor deposits on the pores and surface of the carbon nanotube-doped porous carbon, and the evaporation time is 10 min. Then, pass carbon dioxide for passivation treatment at a flow rate of 300 ml / min under normal pressure for 150 min to obtain lithium-carbon nanotube-doped porous carbon.

[0103] Example 2

[0104] A preparation method of lithium-carbon nanotube-doped porous carbon, comprising the following steps:

[0105] (1) Add 100 g of p-cresol to 100 g of deionized water and disperse evenly. Then, dropwise add 1000 g of acetaldehyde (10 wt%) solution, and successively add 1 g of carboxylated carbon nanotubes, 1 g of polyvinylpyrrolidone, and 1000 g of 17 wt% ammonia water. After mixing evenly, react at 50 °C for 6 h and filter;

[0106] (2) The obtained filter residue is heated to 500 °C at a heating rate of 1 °C / min and cured for 6 h. Then, it is heated to 1100 °C at a heating rate of 1 °C / min, and carbon dioxide gas is introduced at a flow rate of 100 ml / min for activation treatment for 300 min to obtain carbon nanotube-doped porous carbon;

[0107] (3) Place 100 g of carbon nanotube-doped porous carbon into a vacuum chamber and evacuate it to a vacuum (≤1 torr). Place 1 g of lithium block into the evaporation chamber. Use a laser to emit a high-energy laser beam, which is focused and irradiated onto the coating material. The temperature rises to 300 °C to make it vaporize by heating. The vaporized lithium vapor deposits on the pores and surface of the carbon nanotube-doped porous carbon, and the evaporation time is 5 min. Then, pass carbon dioxide for passivation treatment at a flow rate of 100 ml / min under normal pressure for 300 min to obtain lithium-carbon nanotube-doped porous carbon.

[0108] Example 3

[0109] A preparation method of lithium-carbon nanotube-doped porous carbon, comprising the following steps:

[0110] (1) Add 100 g of 3,5-xylenol to 500 g of deionized water and disperse evenly. After that, add 500 g of furfural (40 wt%) solution dropwise, and then add 5 g of carboxylated carbon nanotubes, 5 g of polyvinylamine and 1000 g of 17 wt% ammonia water in sequence and mix evenly. React at 100 °C for 1 h, and filter;

[0111] (2) Heat the obtained filter residue to 800 °C at a heating rate of 10 °C / min for solidification treatment for 1 h, and then heat it to 1400 °C at a heating rate of 10 °C / min. Pass carbon dioxide gas at a flow rate of 500 ml / min for activation treatment for 30 min to obtain carbon nanotube-doped porous carbon;

[0112] (3) Put 100 g of carbon nanotube-doped porous carbon into a vacuum chamber and evacuate it to a vacuum (≤1 torr). Put 5 g of lithium blocks into the evaporation chamber. Use a high-energy laser beam emitted by a laser, focus it on the plating material, and raise the temperature to 400 °C to make it vaporize by heating. The vaporized lithium vapor deposits in the pores and on the surface of the carbon nanotube-doped porous carbon, and the evaporation time is 15 min; then pass carbon dioxide for passivation treatment at a flow rate of 500 ml / min under normal pressure for 30 min to obtain lithium-carbon nanotube-doped porous carbon.

[0113] Example 4

[0114] The difference from Example 1 is that 0.5 g of carboxylated carbon nanotubes is used in step (1), and the others are the same as in Example 1.

[0115] Example 5

[0116] The difference from Example 1 is that 1 g of carboxylated carbon nanotubes is used in step (1), and the others are the same as in Example 1.

[0117] Example 6

[0118] The difference from Example 1 is that 5 g of carboxylated carbon nanotubes is used in step (1), and the others are the same as in Example 1.

[0119] Example 7

[0120] The difference from Example 1 is that 6 g of carboxylated carbon nanotubes is used in step (1), and the others are the same as in Example 1.

[0121] Example 8

[0122] Different from Example 1, 0.5 g of polyvinyl alcohol was used in step (1), and the others were the same as in Example 1.

[0123] Example 9

[0124] Different from Example 1, 1 g of polyvinyl alcohol was used in step (1), and the others were the same as in Example 1.

[0125] Example 10

[0126] Different from Example 1, 5 g of polyvinyl alcohol was used in step (1), and the others were the same as in Example 1.

[0127] Example 11

[0128] Different from Example 1, 6 g of polyvinyl alcohol was used in step (1), and the others were the same as in Example 1.

[0129] Example 12

[0130] Different from Example 1, the reaction was carried out at 50 °C for 6 h in step (1), and the others were the same as in Example 1.

[0131] Example 13

[0132] Different from Example 1, the reaction was carried out at 150 °C for 1 h in step (1), and the others were the same as in Example 1.

[0133] Example 14

[0134] Different from Example 1, the curing treatment was carried out at 500 °C for 8 h in step (2), and the others were the same as in Example 1.

[0135] Example 15

[0136] Different from Example 1, the curing treatment was carried out at 800 °C for 1 h in step (2), and the others were the same as in Example 1.

[0137] Example 16

[0138] Different from Example 1, the activation treatment was carried out at 1100 °C for 300 min in step (2), and the others were the same as in Example 1.

[0139] Example 17

[0140] Different from Example 1, the activation treatment was carried out at 1400 °C for 30 min in step (2), and the others were the same as in Example 1.

[0141] Example 18

[0142] Different from Example 1, in step (3), the temperature of lithium deposition was 300 °C and the evaporation time was 5 min, and the others were the same as in Example 1.

[0143] Example 19

[0144] Different from Example 1, in step (3), the temperature of lithium deposition is 400 °C, and the evaporation coating time is 25 min. Others are the same as in Example 1.

[0145] Example 20

[0146] Different from Example 1, in step (3), the amount of lithium used is 0.5 g. Others are the same as in Example 1.

[0147] Example 21

[0148] Different from Example 1, in step (3), the amount of lithium used is 1 g. Others are the same as in Example 1.

[0149] Example 22

[0150] Different from Example 1, in step (3), the amount of lithium used is 5 g. Others are the same as in Example 1.

[0151] Example 23

[0152] Different from Example 1, in step (3), the amount of lithium used is 6 g. Others are the same as in Example 1.

[0153] Comparative Example 1

[0154] Different from Example 1, in step (1), carboxylated carbon nanotubes and polyvinyl alcohol are not added. Others are the same as in Example 1.

[0155] Comparative Example 2

[0156] Different from Example 1, the operation of step (3) is not carried out, that is, the carbon nanotube-doped porous carbon in step (2) is used as the negative electrode material.

[0157] Performance Test

[0158] 1. Scanning electron microscope (SEM) test:

[0159] Figure 1 The SEM image of the lithium-carbon nanotube-doped porous carbon prepared in Example 1, from Figure 1 it can be seen that the material presents a small particle size spherical structure, with a uniform size distribution, and there are a small number of carbon nanotubes winding around. The particle size of the material is between 5 - 15 μm.

[0160] 2. Physical and chemical properties and button battery test:

[0161] 2.1 Physical and chemical property test:

[0162] The pore volume and pore diameter of the porous carbon obtained from Test Examples 1-11 and Comparative Examples 1-2 were tested with reference to the national standard GB / T-38949-2020 "Standard Particle Method for Measuring the Pore Size of Porous Membranes"; and its specific surface area and tapped density were tested in accordance with the national standard GB / T-24533-2019 "Graphite for Lithium-Ion Battery Anode Materials - Graphite"; and the powder conductivity of each porous carbon material was tested using a four-probe tester; the test results are shown in Table 1 below.

[0163] 2.2 Coin cell performance test:

[0164] The coin cells were prepared using the corresponding porous carbon of Examples 1-23 and Comparative Examples 1-2 as the anode material for lithium-ion batteries according to the following method:

[0165] A binder, a conductive agent and a solvent were added to each corresponding porous carbon composite, stirred to make a slurry, coated on a copper foil, and dried and rolled to obtain a negative electrode sheet; the binder used was LA132, the conductive agent was SP (conductive carbon black), and the solvent was NMP (N-methylpyrrolidone), and the dosage ratios of the composite material, SP, LA132, and NMP were 80 g:15 g:15 g:300 mL; the electrolyte was a solution with LiPF 6 as the electrolyte, with a concentration of 1 mol / L. Among them, the solvent used was a mixture of EC and DEC with a volume ratio of 1:1; the metal lithium sheet was used as the counter electrode, and the separator was a polypropylene (PP) membrane.

[0166] Each coin cell was assembled in a glove box filled with argon gas, and then the following performance tests were carried out:

[0167] Electrochemical performance test: Specifically, the electrochemical performance was carried out on a Wuhan Blue Electric CT2001A battery tester. The charge-discharge voltage range was 0.005 V to 2.0 V, and the charge-discharge rate was 0.1 C. The discharge specific capacity and its first efficiency of the corresponding coin cell were tested. At the same time, the rate performance (1 C / 0.1 C) and the cycle performance test (0.1 C / 0.1 C, 100 cycles) of the corresponding coin cell were tested;

[0168] The test results are shown in Table 1.

[0169] Table 1 Test Results of Examples 1-23 and Comparative Examples 1-2

[0170]

[0171] The applicant declares that the process method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing lithium carbon nanotube-doped porous carbon, characterized in that: The preparation method comprises: Firstly, a carbon nanotube-doped resin precursor is prepared by a coprecipitation method, and then a curing treatment is performed to obtain a carbon nanotube-doped resin; The method for preparing a carbon nanotube-doped resin precursor by coprecipitation method comprises: First, add an aqueous solution of a phenolic compound, then drop an aqueous solution of an aldehyde compound, and then sequentially add carbon nanotubes, a pore-forming agent, and ammonia water, mix well, react at 50-100° C. for 1-6 hours, and filter to obtain a carbon nanotube-doped resin precursor; The mass ratio of the phenolic compound, the aldehyde compound, the carbon nanotubes and the pore-forming agent is 100:100-200:1-5:1-5; The curing method comprises: Curing the carbon nanotube-doped resin precursor at 500-800° C. for 1-6 hours; Then, the carbon nanotube-doped resin is activated by using carbon dioxide to obtain carbon nanotube-doped porous carbon; Then, lithium is deposited on the carbon nanotube-doped porous carbon by vacuum evaporation to obtain lithium carbon nanotube-doped porous carbon; The mass ratio of carbon nanotube-doped porous carbon to lithium is 100:1-5.

2. The preparation method according to claim 1, characterized in that: The carbon nanotubes include one or more of hydroxylated carbon nanotubes, aminated carbon nanotubes, carboxylated carbon nanotubes or nitrogen-doped carbon nanotubes; The phenolic compound includes one or more of m-cresol, p-cresol, o-cresol, 3,5-dimethylphenol or resorcinol; The aldehyde compound includes one or more of formaldehyde, acetaldehyde, furfural or salicylaldehyde; The pore-forming agent includes one or more of polyvinyl alcohol, polyvinyl pyrrolidone or polyvinyl amine.

3. The preparation method according to claim 1, characterized in that: The method for activating the carbon nanotube-doped resin comprises: After heating the carbon nanotube-doped resin to 1100-1400° C., introducing carbon dioxide and performing activation treatment for 30-300 minutes to obtain carbon nanotube-doped porous carbon; The flow rate of carbon dioxide for activation treatment is 100-500 ml / min.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The method for depositing lithium on the carbon nanotube-doped porous carbon using a vacuum evaporation method comprises: Lithium deposition is carried out under vacuum conditions. First, a high-energy laser beam is used to irradiate the lithium, which is then vaporized and deposited into the pores and surface of the carbon nanotube-doped porous carbon. The evaporation time is 5-15 minutes, and then carbon dioxide is introduced for passivation treatment.

5. The preparation method according to claim 4, characterized in that: The wavelength of the laser beam is 900-1090nm, the pulse width is 0.5ms-4ms, and the laser power is 100W-600W; The flow rate of carbon dioxide for passivation treatment is 100-500ml / min; The passivation treatment time is 30-300min.

6. A lithium carbon nanotube-doped porous carbon obtained by the preparation method according to any one of claims 1 to 5, characterized in that: The lithium carbon nanotube-doped porous carbon comprises 1-5wt% carbon nanotubes, 1-5wt% lithium carbonate and 90-98wt% porous carbon.

7. Use of the lithium carbon nanotube-doped porous carbon as claimed in claim 6 in preparing a secondary battery.

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