Porous carbon material as well as preparation method and application thereof

Abstract

The invention discloses a porous carbon material as well as a preparation method and application thereof, and the porous carbon material is prepared by the following steps: by taking a silicon dioxide mesoporous hollow sphere as a hard template through a hard template method, carrying out condensation reaction on phenol and formaldehyde in the hollow part of the silicon dioxide mesoporous hollow sphere to form phenolic resin; and curing, carrying out carbon activation treatment and etching to obtain the spherical phenolic resin porous carbon material. The porous carbon material prepared by the preparation method disclosed by the invention has a relatively high specific surface area and a relatively uniform pore structure, and the cycle performance of a secondary battery can be improved when the porous carbon material disclosed by the invention is used for preparing a negative pole piece and assembling the negative pole piece into the secondary battery.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly relates to a porous carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] Traditional methods for preparing porous materials pose some challenges in certain aspects, including the hard template method.

[0003] These challenges mainly include: a. High cost: Traditional hard template methods usually require expensive template materials such as metals or ceramics, as well as complex preparation and removal steps, resulting in relatively high preparation costs. b. Structure damage: The process of removing the hard template may cause partial damage or non-uniformity of the porous structure, reducing the performance of the final porous material. c. Limited controllability: The controllability of traditional methods in regulating the pore structure, pore size, and morphology is relatively limited, making it difficult to achieve precise design of porous materials. d. Limited to hard materials: The hard template method usually requires the use of hard template materials with high mechanical strength and chemical stability, restricting the range of selectable porous materials. Summary of the Invention

[0004] Embodiments of the present invention provide a porous carbon material, a preparation method thereof, and an application thereof. To overcome the limitations of traditional methods, the present invention uses silica mesoporous hollow spheres as hard templates, taking advantage of the good dispersibility, controllable pore size, and uniform pore structure of silica mesoporous hollow spheres, laying a foundation for the preparation of materials with highly controllable porous structures.

[0005] The present invention realizes the highly controllable preparation of the morphology and pore structure of spherical porous carbon materials by combining silica mesoporous hollow spheres with precursor substances such as phenolic resin and adjusting the centrifugation process. Compared with traditional methods, this innovative method is more economical, simple, and can achieve material design and preparation in a wider range.

[0006] The preparation method provided by the present invention provides a new approach for the preparation of spherical porous carbon materials used in fields such as catalysts, adsorption materials, and electrode materials. Its superior preparation method and the performance of the obtained materials will have broad application prospects in multiple fields such as environment, energy, and materials science. This innovative preparation method is expected to promote the further development and application of the porous material field.

[0007] To achieve the above object, in the first aspect, embodiments of the present invention provide a preparation method of a porous carbon material, and the preparation method includes:

[0008] Step S1, placing silica mesoporous hollow spheres, a surfactant, and deionized water in a dispersion device for dispersion treatment to uniformly disperse the silica mesoporous hollow spheres in the deionized water to obtain a dispersion liquid;

[0009] In step S2, phenol, formaldehyde, a basic catalyst, and an auxiliary additive are added to the above-mentioned dispersion. After stirring evenly, vacuum stirring is carried out to obtain a precursor solution.

[0010] In step S3, the precursor solution is placed in a centrifuge tube for centrifugal dispersion to separate the silica mesoporous hollow spheres from the liquid outside the silica mesoporous hollow spheres, and the inside of the hollow spheres is filled with phenol, formaldehyde, a basic catalyst, and an auxiliary additive, obtaining a white silica mesoporous sphere precipitate.

[0011] In step S4, the white silica mesoporous sphere precipitate is evenly dispersed in deionized water and placed in a heating device. At a certain temperature, the phenol and formaldehyde inside the hollow spheres undergo a condensation reaction to form phenolic resin. After centrifugation, a precipitate is obtained.

[0012] In step S5, the precipitate is placed in an oven to cure the phenolic resin, obtaining an intermediate material.

[0013] In step S6, the intermediate material is placed in a tube furnace for carbon activation treatment. At a certain temperature, the material is carbonized, and the auxiliary additive dispersed in the gaps of the phenolic resin decomposes and volatilizes to form pores. Additionally, activation treatment is carried out under CO2 gas to obtain a precursor material.

[0014] In step S7, the precursor material is placed in a hydrofluoric acid solution, soaked and stirred to etch away the silica mesoporous hollow spheres in the precursor material. Then, it is rinsed with deionized water at least 5 times and dried to obtain a porous carbon material.

[0015] Preferably, the particle size Dv50 of the silica mesoporous hollow spheres in step S1 is between 100 nm and 1000 nm; the pore diameter of the mesopores of the silica mesoporous hollow spheres is between 2 nm and 50 nm.

[0016] The surfactant includes one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide CTAB, and polyethylene ether PEG; the mass ratio of the surfactant to the silica mesoporous hollow spheres is 1:6.

[0017] The mass ratio of the silica mesoporous hollow spheres to deionized water is [1 - 10]:100.

[0018] The dispersion device is an ultrasonic disperser, and the dispersion treatment time is 30 min - 1 hour.

[0019] Preferably, the auxiliary additive in step S2 is a water-soluble polymer, specifically including one or more of polyethylene oxide PEO, polyacrylic acid PAA, urea, and polyethylene glycol.

[0020] The basic catalyst includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water;

[0021] The molar ratio of the phenol to the formaldehyde is 1: [1 - 10];

[0022] The mass ratio of the basic catalyst to deionized water is 1: [1 - 10];

[0023] The mass ratio of the auxiliary additive to deionized water is 1: [1 - 20];

[0024] The equipment for vacuum stirring is a vacuum mixer.

[0025] Preferably, the rotation speed of centrifugal dispersion in step S3 and the rotation speed of centrifugation in step S4 are both 1000 - 5000 revolutions per minute, and the centrifugation time is 5 - 10 minutes;

[0026] The amount of deionized water used in step S4 is 100 ml - 200 ml, and the certain temperature is 50°C - 60°C.

[0027] Preferably, the curing temperature in step S5 is 90°C - 120°C, and the curing time is 3 - 12 hours.

[0028] Preferably, the process of carbon activation treatment in step S6 is as follows: Place the intermediate material in a tubular furnace, introduce nitrogen with a flow rate of 0.1 L / min - 0.5 L / min to displace air. Under a nitrogen atmosphere, heat it at a heating rate of 3°C / min - 10°C / min to 500°C - 600°C, keep it warm for 3 - 10 hours, then heat it at a heating rate of 3°C / min - 10°C / min to 900°C. After that, introduce carbon dioxide gas with a flow rate of 0.1 L / min - 0.5 L / min to displace nitrogen, keep it warm for 3 - 18 hours, and finally naturally cool to room temperature.

[0029] Preferably, the concentration of the hydrofluoric acid solution in step S7 is 5% - 10%; the concentration of the hydrofluoric acid solution in step S7 is 5% - 10%; the soaking and stirring time is 3 - 24 hours; the drying condition is baking at 80°C for 2 - 12 hours.

[0030] Second, the embodiment of the present invention provides a porous carbon material prepared by the preparation method described in the first aspect above. The porous carbon material is a spherical phenolic resin porous carbon material;

[0031] The particle size Dv50 of the porous carbon material is between 100 nm and 1000 nm;

[0032] The pore diameter of the pores of the porous carbon material, and the specific surface area of the porous carbon material is between 400 m 2 / g - 1000 m 2 / g;

[0033] The porous carbon material is obtained by using a hard template method with a silica mesoporous hollow sphere as the hard template, causing the phenol and formaldehyde in the hollow and mesopores of the silica mesoporous hollow sphere to undergo a condensation reaction to form phenolic resin, and then through curing, carbon activation treatment, and etching.

[0034] In a third aspect, an embodiment of the present invention provides a negative electrode sheet, and the negative electrode sheet includes the porous carbon material described in the second aspect above.

[0035] In a fourth aspect, an embodiment of the present invention provides a secondary battery, and the secondary battery includes the negative electrode sheet described in the third aspect above.

[0036] An embodiment of the present invention provides a porous carbon material, its preparation method and application. By using a hard template method with a silica mesoporous hollow sphere as the hard template, the phenol and formaldehyde in the hollow of the silica mesoporous hollow sphere undergo a condensation reaction to form phenolic resin, and then a spherical phenolic resin porous carbon material is obtained through curing, carbon activation treatment, and etching.

[0037] The preparation method of the porous carbon material provided by the present invention is simple in operation. Using a silica mesoporous hollow sphere as the hard template, the silica mesoporous hollow sphere is more economically feasible compared to some traditional hard template materials, reducing the preparation cost. And the size of the synthesized spherical porous carbon material can be determined by adjusting the size of the hard template. The prepared spherical porous carbon material has a uniform pore structure, and the pore structure and pore diameter can be controlled by adjusting the type and concentration of the added materials. In addition, due to using a silica mesoporous hollow sphere as the hard template, it is more environmentally friendly compared to some traditional methods, reducing the adverse impact on the environment.

[0038] The porous carbon material obtained by the preparation method of the present invention can be used as an electrode material in a secondary battery, which can improve the cycling performance of the secondary battery. At the same time, the porous carbon material of the present invention can also be used as a catalyst, an adsorption material, etc., and has a wide range of application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The technical solutions of the embodiments of the present invention will be further described in detail below through the drawings and embodiments.

[0040] Figure 1 is a flowchart of the preparation method of the porous carbon material provided by an embodiment of the present invention.

[0041] Figure 2It is a transmission electron microscope (TEM) image of the precursor material after carbonization treatment during the preparation process of Example 4 of the present invention.

[0042] Figure 3 It is a TEM image of the precursor material after carbonization treatment during the preparation process of Example 5 of the present invention.

[0043] Figure 4 It is a scanning electron microscope (SEM) image of the phenolic resin carbon material prepared in Comparative Example 1 of the present invention. Detailed implementation manners

[0044] The present invention will be further described in detail below through the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0045] The embodiment of the present invention provides a method for preparing a porous carbon material. By using a hard template method, a silica mesoporous hollow sphere is used as a hard template, and phenol and formaldehyde in the hollow and mesopores of the silica mesoporous hollow sphere undergo a condensation reaction to form a phenolic resin, and then it is obtained after curing, carbon activation treatment and etching. The specific preparation method is as Figure 1 shown, including the following steps:

[0046] Step S1: Place the silica mesoporous hollow sphere, surfactant and deionized water in a dispersion device, perform dispersion treatment to uniformly disperse the silica mesoporous hollow sphere in deionized water to obtain a dispersion;

[0047] Among them, the particle size Dv50 of the silica mesoporous hollow sphere is between 100 nm and 1000 nm; the pore diameter of the mesopores of the silica mesoporous hollow sphere is between 2 nm and 50 nm;

[0048] The surfactant includes one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide (CTAB), and polyethylene ether (PEG); the mass ratio of the surfactant to the silica mesoporous hollow sphere is 1:6;

[0049] The mass ratio of the silica mesoporous hollow sphere to deionized water is [1-10]:100;

[0050] The dispersion device is an ultrasonic disperser, and the dispersion treatment time is 30 min - 1 hour.

[0051] Step S2: Add phenol, formaldehyde, an alkaline catalyst and an auxiliary additive to the above dispersion, stir evenly, and then stir under vacuum to obtain a precursor solution;

[0052] Among them, the auxiliary additive is a water-soluble polymer, specifically including one or more of polyethylene oxide (PEO), polyacrylic acid (PAA), urea, and polyethylene glycol;

[0053] The alkaline catalyst includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water;

[0054] The molar ratio of phenol to formaldehyde is 1: [1 - 10]; the mass ratio of the alkaline catalyst to deionized water is 1: [1 - 10]; the mass ratio of the auxiliary additive to deionized water is 1: [1 - 20];

[0055] The equipment for vacuum stirring is a vacuum mixer.

[0056] In step S3, the precursor solution is placed in a centrifuge tube for centrifugal dispersion to separate the silica mesoporous hollow spheres from the liquid outside the silica mesoporous hollow spheres, and the inside of the hollow spheres is filled with phenol, formaldehyde, an alkaline catalyst, and an auxiliary additive, obtaining a white silica mesoporous sphere precipitate;

[0057] Among them, the centrifugal speed for centrifugal dispersion is 1000 - 5000 revolutions per minute, and the centrifugal time is 5 - 10 minutes.

[0058] In step S4, the white silica mesoporous sphere precipitate is evenly dispersed in deionized water and placed in a heating device. At a certain temperature, the phenol and formaldehyde inside the hollow spheres undergo a condensation reaction to form phenolic resin. After centrifugation, a precipitate is obtained;

[0059] Among them, the centrifugal speed is 1000 - 5000 revolutions per minute, and the centrifugal time is 5 - 10 minutes;

[0060] The dosage of deionized water is 100 ml - 200 ml, and the certain temperature is 50°C - 60°C.

[0061] In step S5, the precipitate is placed in an oven to cure the phenolic resin, obtaining an intermediate material;

[0062] Among them, the curing temperature is 90°C - 120°C, and the curing time is 3 - 12 hours.

[0063] In step S6, the intermediate material is placed in a tube furnace for carbon activation treatment. At a certain temperature, the material is carbonized, and the auxiliary additive dispersed in the gaps of the phenolic resin decomposes and volatilizes to form pores. Additionally, activation treatment is carried out under CO2 gas to obtain a precursor material;

[0064] Among them, the process of carbon activation treatment is as follows: Place the intermediate material in a tube furnace, introduce nitrogen with a flow rate of 0.1 L / min - 0.5 L / min to displace air. Under a nitrogen atmosphere, heat it to 500°C - 600°C at a heating rate of 3°C / min - 10°C / min, hold for 3 hours - 10 hours, then heat it to 900°C at a heating rate of 3°C / min - 10°C / min. After that, introduce carbon dioxide gas with a flow rate of 0.1 L / min - 0.5 L / min to displace nitrogen, hold for 3 hours - 18 hours, and finally naturally cool to room temperature.

[0065] Step S7: Place the precursor material in a hydrofluoric acid solution, soak and stir to etch away the silica mesoporous hollow spheres in the precursor material. Then, rinse with deionized water at least 5 times, and dry to obtain a porous carbon material.

[0066] Among them, the concentration of the hydrofluoric acid solution is 5% - 10%; the soaking and stirring time is 3 hours - 24 hours; the specific drying conditions are baking in an oven at 80°C for 2 hours - 12 hours.

[0067] In the present invention, an alkaline catalyst is used, which can promote the polycondensation reaction and accelerate the curing of the resin during the synthesis of phenolic resin. Specifically, promoting the polycondensation reaction: The alkaline catalyst can prompt the polycondensation reaction between phenol and formaldehyde to proceed more rapidly. Phenol and formaldehyde molecules are more likely to undergo an addition reaction under alkaline conditions, forming chain-like and ring-like structures, thereby promoting the formation of a cross-linked structure between resin molecules. Accelerating the resin curing: During the preparation of phenolic resin, the presence of an alkaline catalyst helps to accelerate the curing process of the resin because under alkaline conditions, the polycondensation reaction is more rapid, enabling phenol and formaldehyde to form a strong network structure more quickly.

[0068] In the present invention, the molar ratio of phenol to formaldehyde is 1:[1 - 10], which can be any ratio within this range, such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, etc. Preferably, it is 1:1.5. Using a system rich in phenol with a low formaldehyde content can form shorter polymer chains and less cross-linking, resulting in a linear structure; at a medium ratio, the polymer chain length is moderate, forming a relatively balanced cross-linked structure. This system may have better structural stability and is suitable for preparing porous materials such as porous carbon. When the molar ratio of phenol to formaldehyde is less than 1:10, the formaldehyde content is high, and a system rich in formaldehyde may lead to more cross-linking, forming a relatively dense three-dimensional network structure. This system may be more suitable for preparing materials with high hardness and higher structural stability, but it will reduce the formation of pore structures.

[0069] The porous carbon material prepared by the above preparation method in the embodiment of the present invention is a spherical phenolic resin porous carbon material; wherein, the particle size Dv50 of the porous carbon material is between 100 nm and 1000 nm, and the specific surface area is between 400 m 2 / g and 1000 m 2 / g.

[0070] The porous carbon material provided by the embodiment of the present invention can be used as a negative electrode active material to prepare a negative electrode sheet, and the negative electrode sheet can be assembled with a positive electrode sheet, an electrolyte, and a separator into a secondary battery, and the secondary battery includes a lithium ion battery or a sodium ion battery. Since the porous carbon material of the present invention has a relatively high specific surface area and a uniform pore structure, the assembled secondary battery has good electrochemical performance.

[0071] At the same time, the porous carbon material of the present invention can also be used as a catalyst, an adsorption material, etc., and has broad application prospects.

[0072] To better understand the technical solution provided by the present invention, the preparation process and characteristics of the porous carbon material of the present invention are described below with multiple specific examples. In the following examples of the present invention, liquid pure phenol with a concentration of 100 wt% commonly used in general laboratories and formaldehyde is an aqueous solution with a concentration of 37 wt% are used.

[0073] Example 1

[0074] This example provides a preparation process and performance test of a porous carbon material, and the specific process is as follows:

[0075] (1) Place 100 ml of deionized water in a three-necked flask, take 3 g of silica mesoporous hollow spheres (particle size Dv50 is 500 nm, and the pore diameter of the mesopores is 4 nm) and disperse them in deionized water, and stir at a speed of 500 rmp for 30 min. Then weigh 0.5 g of the surfactant CTAB, continue stirring for 30 min, and then perform ultrasonic dispersion treatment for 30 min using an ultrasonic disperser to obtain a dispersion liquid.

[0076] (2) Add 52.5 ml of phenol, 67.6 ml of formaldehyde, 10 ml of ammonia water and the auxiliary additive PEO to the above dispersion liquid (where the molar ratio of phenol to formaldehyde is 1:1.5), stir evenly, and then stir under vacuum for 1 hour to obtain a precursor solution.

[0077] (3) Place the precursor solution in a centrifuge tube for centrifugal dispersion, with a centrifugal speed of 1000 revolutions per minute and centrifuge for 10 min to separate the liquid and the solid. Phenol, formaldehyde, the basic catalyst ammonia water and the auxiliary additive PEO are filled into the hollow of the silica mesoporous hollow spheres to obtain a white silica mesoporous sphere precipitate.

[0078] (4) The white silica mesoporous spheres precipitate are evenly dispersed in 100 ml of deionized water, placed in a heating device, and slowly heated to 60 °C at a heating rate of 3 °C / min, so that phenol and formaldehyde in the mesopores undergo a condensation reaction to form phenolic resin. After centrifuging at a speed of 1000 revolutions per minute for 15 min, a precipitate is obtained.

[0079] (5) The precipitate is placed in an oven and baked at 90 °C for 6 hours to cure the phenolic resin, obtaining an intermediate material.

[0080] (6) The intermediate material is placed in a tubular furnace, and nitrogen with a flow rate of 0.5 L / min is introduced to displace the air. Under a nitrogen atmosphere, it is heated to 500 °C at a heating rate of 3 °C / min and held for 3 hours. Then it is heated to 900 °C at a heating rate of 3 °C / min. After that, carbon dioxide gas with a flow rate of 0.5 L / min is introduced to displace the nitrogen, and it is held for 10 hours. Finally, it is naturally cooled to room temperature to obtain a precursor material.

[0081] (7) The precursor material is placed in a 5% hydrofluoric acid solution, soaked and stirred for 24 hours to etch away the silica mesoporous hollow spheres in the precursor material. Then it is rinsed with deionized water at least 8 times and baked at 80 °C for 12 hours to obtain a porous carbon material.

[0082] The BET specific surface area measurement method is used to test the specific surface area and pore size data of the porous carbon material prepared in this example. See Table 1 for details.

[0083] The porous carbon material of this example is used to prepare an electrode sheet and assemble a battery for testing. The specific process is as follows.

[0084] The process of battery assembly is specifically as follows: The porous carbon material, conductive additive carbon black, and binder (the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber in a ratio of 1:1) are weighed according to a mass ratio of 95:2:3. At room temperature, they are placed in a pulper to prepare a slurry. The prepared slurry is evenly coated on a copper foil. After drying in a blast drying oven at 50 °C for 2 hours, it is cut into an electrode sheet of 8×8 mm and vacuum dried in a vacuum drying oven at 100 °C for 10 hours. The dried electrode sheet is immediately transferred into a glove box for standby to assemble a battery.

[0085] The assembly of the simulated battery is carried out in a glove box containing a high-purity Ar atmosphere. Metallic lithium is used as the counter electrode, a polypropylene film is used as the separator, and a solution of 1 mol / L LiPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (the volume ratio of EC to DMC is 1:1) is used as the electrolyte to assemble a half-cell.

[0086] The testing process is as follows: The constant current charge-discharge mode test is carried out using a charge-discharge instrument. The cut-off discharge voltage is 0.005 V, the cut-off charge voltage is 1.5 V, and the charge-discharge test is carried out at a current density of C / 10.

[0087] The charging specific capacity, the Coulombic efficiency of the first cycle, and the cycling capacity retention rate at 300 cycles of the half-cell are tested. The test data are shown in Table 2.

[0088] Example 2

[0089] This example provides a preparation process and performance test of a porous carbon material. The difference from Example 1 is that the molar ratio of phenol to formaldehyde in step (2) is 1:1. The specific process is as follows:

[0090] (1) Place 100 ml of deionized water in a three-necked flask. Take 3 g of silica mesoporous hollow spheres (the particle size Dv50 is 500 nm, and the pore diameter of the mesopores is 4 nm) and disperse them in deionized water. Stir at a speed of 500 rmp for 30 min. Then weigh 0.5 g of the surfactant CTAB, continue to stir for 30 min, and then perform ultrasonic dispersion treatment for 30 min using an ultrasonic disperser to obtain a dispersion.

[0091] (2) Add 52.5 ml of phenol, 45.1 ml of formaldehyde, 10 ml of ammonia water, and the auxiliary additive PEO to the above dispersion. After stirring evenly, vacuum stir for 1 hour to obtain a precursor solution.

[0092] (3) Place the precursor solution in a centrifuge tube for centrifugal dispersion. The centrifugal speed is 1000 revolutions per minute, and centrifuge for 10 min to separate the liquid and the solid. Phenol, formaldehyde, the alkaline catalyst ammonia water, and the auxiliary additive PEO are filled into the hollow of the silica mesoporous hollow spheres to obtain a white silica mesoporous sphere precipitate.

[0093] (4) Uniformly disperse the white silica mesoporous sphere precipitate in 100 ml of deionized water, place it in a heating device, and slowly heat it to 60 °C at a heating rate of 3 °C / min to cause the phenol and formaldehyde in the mesopores to undergo a condensation reaction to form phenolic resin. After centrifuging at a speed of 1000 revolutions per minute for 15 min, a precipitate is obtained.

[0094] (5) Place the precipitate in an oven and bake it at 90 °C for 6 hours to cure the phenolic resin and obtain an intermediate material.

[0095] (6) Place the intermediate material in a tubular furnace, introduce nitrogen with a flow rate of 0.5 L / min to displace air. Under a nitrogen atmosphere, heat it at a heating rate of 3 °C / min to 500 °C, hold for 3 hours, then heat it at a heating rate of 3 °C / min to 900 °C. After that, introduce carbon dioxide gas with a flow rate of 0.5 L / min to displace nitrogen, hold for 10 hours, and finally let it cool to room temperature naturally to obtain the precursor material.

[0096] (7) Place the precursor material in a 5% hydrofluoric acid solution, soak and stir for 24 hours to etch away the silica mesoporous hollow spheres in the precursor material. Then rinse with deionized water at least 8 times and bake at 80 °C for 12 hours to obtain the porous carbon material.

[0097] Test the specific surface area and pore size data of the porous carbon material prepared in this example. See Table 1 for details.

[0098] Use the porous carbon material of this example to prepare an electrode sheet and assemble a battery for testing. The specific process is the same as that in Example 1. The test data are shown in Table 2.

[0099] Example 3

[0100] This example provides a preparation process and performance test of a porous carbon material. The difference from Example 1 is that the molar ratio of phenol to formaldehyde in step (2) is 1:5. The specific process is as follows:

[0101] (1) Place 100 ml of deionized water in a three-necked flask, take 3 g of silica mesoporous hollow spheres (with a particle size Dv50 of 500 nm and a mesopore diameter of 4 nm) and disperse them in deionized water, stir at a speed of 500 rmp for 30 min. Then weigh 0.5 g of the surfactant CTAB, continue to stir for 30 min, and then perform ultrasonic dispersion treatment for 30 min using an ultrasonic disperser to obtain a dispersion.

[0102] (2) Add 52.5 ml of phenol, 225.7 ml of formaldehyde, 10 ml of ammonia water, and the auxiliary additive PEO to the above dispersion. After stirring evenly, evacuate and stir for 1 hour to obtain a precursor solution.

[0103] (3) Place the precursor solution in a centrifuge tube for centrifugal dispersion at a centrifugal speed of 1000 revolutions per minute for 10 min to separate the liquid and solid. Phenol, formaldehyde, the alkaline catalyst ammonia water, and the auxiliary additive PEO are filled into the hollow of the silica mesoporous hollow spheres to obtain a white silica mesoporous sphere precipitate.

[0104] (4) The white silica mesoporous spheres are evenly dispersed in 100 ml of deionized water, placed in a heating device, and slowly heated to 60 °C at a heating rate of 3 °C / min to cause the condensation reaction of phenol and formaldehyde in the mesopores to form phenolic resin. After centrifuging at 1000 revolutions per minute for 15 minutes, a precipitate is obtained.

[0105] (5) The precipitate is placed in an oven and baked at 90 °C for 6 hours to cure the phenolic resin and obtain an intermediate material.

[0106] (6) The intermediate material is placed in a tube furnace, and nitrogen with a flow rate of 0.5 L / min is introduced to displace the air. Under a nitrogen atmosphere, it is heated to 500 °C at a heating rate of 3 °C / min and held for 3 hours. Then, it is heated to 900 °C at a heating rate of 3 °C / min. After that, carbon dioxide gas with a flow rate of 0.5 L / min is introduced to displace the nitrogen, and it is held for 10 hours. Finally, it is naturally cooled to room temperature to obtain a precursor material.

[0107] (7) The precursor material is placed in a 5% hydrofluoric acid solution, soaked and stirred for 24 hours to etch away the silica mesoporous hollow spheres in the precursor material. Then, it is rinsed with deionized water at least 8 times and baked at 80 °C for 12 hours to obtain a porous carbon material.

[0108] The specific surface area and pore size data of the porous carbon material prepared in this example are shown in Table 1.

[0109] The porous carbon material of this example is used to prepare an electrode sheet and assemble a battery for testing. The specific process is the same as that of Example 1, and the test data are shown in Table 2.

[0110] Example 4

[0111] This example provides a preparation process and performance test of a porous carbon material. The difference from Example 1 is that the addition amount of silica mesoporous hollow spheres in step (1) is different, which is greater than that in Example 1. The specific process is as follows:

[0112] (1) 100 ml of deionized water is placed in a three-necked flask. 20 g of silica mesoporous hollow spheres (with a particle size Dv50 of 500 nm and a mesopore diameter of 4 nm) are dispersed in the deionized water and stirred at a speed of 500 rmp for 30 min. Then, 0.5 g of surfactant CTAB is weighed and stirring is continued for 30 min. Then, ultrasonic dispersion treatment is carried out for 30 min using an ultrasonic disperser to obtain a dispersion liquid.

[0113] (2) 52.5 ml of phenol, 67.6 ml of formaldehyde, 10 ml of ammonia water, and auxiliary additive PEO are added to the above dispersion liquid. After stirring evenly, it is vacuum stirred for 1 hour to obtain a precursor solution.

[0114] (3) Place the precursor solution in a centrifuge tube for centrifugal dispersion at a centrifugal speed of 1000 revolutions per minute for 10 minutes to separate the liquid and solid. Phenol, formaldehyde, the alkaline catalyst ammonia water, and the auxiliary additive PEO are filled into the hollow of the silica mesoporous hollow sphere to obtain a white silica mesoporous sphere precipitate.

[0115] (4) Uniformly disperse the white silica mesoporous sphere precipitate in 100 ml of deionized water, place it in a heating device, and slowly heat it to 60 °C at a heating rate of 3 °C / min to cause the condensation reaction of phenol and formaldehyde in the mesopores to generate phenolic resin. After centrifuging at a speed of 1000 revolutions per minute for 15 minutes, a precipitate is obtained.

[0116] (5) Place the precipitate in an oven and bake it at 90 °C for 6 hours to cure the phenolic resin and obtain an intermediate material.

[0117] (6) Place the intermediate material in a tubular furnace, introduce nitrogen with a flow rate of 0.5 L / min to displace the air. Under a nitrogen atmosphere, heat it to 500 °C at a heating rate of 3 °C / min and hold for 3 hours. Then heat it to 900 °C at a heating rate of 3 °C / min. After that, introduce carbon dioxide gas with a flow rate of 0.5 L / min to displace the nitrogen and hold for 10 hours. Finally, naturally cool it to room temperature to obtain a precursor material.

[0118] The TEM image of the precursor material after carbonization treatment in this example is as Figure 2 shown. It can be seen that when the addition amount of the silica mesoporous hollow sphere is relatively large, there will be silica mesoporous hollow spheres with an empty center that are not filled with phenolic resin.

[0119] (7) Place the precursor material in a 5% hydrofluoric acid solution, soak and stir for 24 hours to etch away the silica mesoporous hollow spheres in the precursor material. Then rinse it with deionized water at least 8 times and bake it at 80 °C for 12 hours to obtain a porous carbon material.

[0120] Test the specific surface area and pore size data of the porous carbon material prepared in this example. See Table 1 for details.

[0121] Use the porous carbon material of this example to prepare an electrode sheet and assemble a battery for testing. The specific process is the same as that in Example 1. The test data are shown in Table 2.

[0122] Example 5

[0123] This example provides a preparation process and performance test of a porous carbon material. It is different from Example 1 in that the addition amount of the silica mesoporous hollow sphere in step (1) is different and less than that in Example 1. The specific process is as follows:

[0124] (1) Place 100 ml of deionized water in a three-necked flask. Take 0.5 g of silica mesoporous hollow spheres (with a particle size Dv50 of 500 nm and a mesopore diameter of 4 nm) and disperse them in deionized water. Stir at a speed of 500 rmp for 30 min. Then weigh 0.5 g of the surfactant CTAB, continue stirring for 30 min, and then perform ultrasonic dispersion treatment for 30 min using an ultrasonic disperser to obtain a dispersion.

[0125] (2) Add 52.5 ml of phenol, 67.6 ml of formaldehyde, 10 ml of ammonia water, and the auxiliary additive PEO to the above dispersion. After stirring evenly, evacuate and stir for 1 hour to obtain a precursor solution.

[0126] (3) Place the precursor solution in a centrifuge tube for centrifugal dispersion at a centrifugal speed of 1000 revolutions per minute for 10 min to separate the liquid and solid. Phenol, formaldehyde, the basic catalyst ammonia water, and the auxiliary additive PEO are filled into the hollow of the silica mesoporous hollow spheres to obtain a white silica mesoporous sphere precipitate.

[0127] (4) Uniformly disperse the white silica mesoporous sphere precipitate in 100 ml of deionized water, place it in a heating device, and slowly heat it to 60 °C at a heating rate of 3 °C / min to cause the phenol and formaldehyde in the mesopores to undergo a condensation reaction to form phenolic resin. After centrifuging at a speed of 1000 revolutions per minute for 15 min, a precipitate is obtained.

[0128] (5) Place the precipitate in an oven and bake it at 90 °C for 6 hours to cure the phenolic resin and obtain an intermediate material.

[0129] (6) Place the intermediate material in a tubular furnace, introduce nitrogen with a flow rate of 0.5 L / min to displace the air. Under a nitrogen atmosphere, heat it to 500 °C at a heating rate of 3 °C / min and hold for 3 hours. Then heat it to 900 °C at a heating rate of 3 °C / min. After that, introduce carbon dioxide gas with a flow rate of 0.5 L / min to displace the nitrogen and hold for 10 hours. Finally, let it cool naturally to room temperature to obtain a precursor material.

[0130] The TEM image of the precursor material after carbonization treatment in this example is as Figure 3 shown. It can be seen that when the addition amount of silica mesoporous hollow spheres is small, although the inside of each silica mesoporous hollow sphere is filled with phenolic resin, excessive other raw materials are washed away, resulting in waste.

[0131] (7) Place the precursor material in a 5% hydrofluoric acid solution, soak and stir for 24 hours to etch away the silica mesoporous hollow spheres in the precursor material. Then rinse with deionized water at least 8 times and bake at 80 °C for 12 hours to obtain a porous carbon material.

[0132] The specific surface area and pore size data of the porous carbon material prepared in this example were tested, as shown in Table 1 for details.

[0133] The electrode sheet was prepared using the porous carbon material of this example and the battery was assembled for testing. The specific process was the same as that of Example 1, and the test data are shown in Table 2.

[0134] Example 6

[0135] This example provides a preparation process and performance test of a porous carbon material. Different from Example 1, the alkaline catalyst used was potassium hydroxide and the auxiliary additive was PAA. Other preparation processes were the same as those of Example 1.

[0136] Example 7

[0137] This example provides a preparation process and performance test of a porous carbon material. Different from Example 1, the alkaline catalyst used was sodium hydroxide and the auxiliary additive was polyethylene glycol. Other preparation processes were the same as those of Example 1.

[0138] Example 8

[0139] This example provides a preparation process and performance test of a porous carbon material. Different from Example 1, the alkaline catalyst used was sodium carbonate and the auxiliary additive was urea. Other preparation processes were the same as those of Example 1.

[0140] To better illustrate the effects of the embodiments of the present invention, Comparative Examples 1-2 were compared with the above embodiments.

[0141] Comparative Example 1

[0142] This comparative example provides a preparation process of a phenolic resin carbon material. Different from Example 1, silica mesoporous hollow spheres were not used as the hard template. The specific preparation process was as follows:

[0143] (1) Add 52.5 ml of phenol, 67.6 ml of formaldehyde (molar ratio of phenol to formaldehyde 1:1.5), 10 ml of ammonia water, and 5 g of polyethylene oxide to a beaker, and stir for 1 hour to obtain a mixed solution.

[0144] (2) Disperse the mixed solution evenly in 100 ml of deionized water, place it in a heating device, and slowly heat it to 60 °C at a heating rate of 3 °C / min to cause the condensation reaction of phenol and formaldehyde to form phenolic resin. After centrifuging at a speed of 1000 revolutions per minute for 15 minutes, a precipitate was obtained.

[0145] (3) Place the precipitate in an oven and bake it at 90 °C for 6 hours to cure the phenolic resin and obtain the cured material.

[0146] (4) The cured material was placed in a tubular furnace, and nitrogen gas was introduced at a flow rate of 0.5 L / min to replace the air. In a nitrogen atmosphere, the temperature was increased to 500°C at a heating rate of 3°C / min, and the temperature was kept at this temperature for 3 hours. The temperature was then increased to 900°C at a heating rate of 3°C / min. Carbon dioxide gas was then introduced at a flow rate of 0.5 L / min to replace the nitrogen, and the temperature was kept at this temperature for 10 hours. Finally, the temperature was naturally cooled to room temperature to obtain a phenolic resin carbon material.

[0147] The SEM image of the phenolic resin carbon material prepared in this comparative example is as follows: Figure 4 As shown, it can be seen that the phenolic resin carbon material prepared in this comparative example is not spherical, but blocky. This is because in the preparation process of this comparative example, the silicon dioxide mesoporous hollow spheres were not used as hard templates, and the large resin flakes formed were cross-linked together and did not form a sphere, making it difficult to activate. Therefore, the obtained material has fewer pores and a smaller specific surface area.

[0148] The specific surface area and pore diameter data of the phenolic resin carbon material of this comparative example are tested, as shown in Table 1.

[0149] The phenolic resin carbon material of this comparative example was used to prepare pole pieces and assemble batteries for testing. The specific process was the same as that of Example 1. The test data is shown in Table 2.

[0150] Comparative Example 2

[0151] This comparative example provides a preparation process and performance test of a phenolic resin porous carbon material, which is different from Example 1 in that no auxiliary additive PEO is added during the synthesis process, and the other preparation processes are the same as Example 1.

[0152] The specific surface area and pore diameter data of the phenolic resin carbon material of this comparative example are tested, as shown in Table 1.

[0153] The phenolic resin porous carbon material of this comparative example was used to prepare pole pieces and assemble batteries for testing. The specific process was the same as that of Example 1. The test data is shown in Table 2.

[0154] Table 1 summarizes the specific surface area and pore size data of the materials prepared in Examples 1-10 and Comparative Example 1.

[0155]

[0156]

[0157] Table 1

[0158] From the comparison of the test data in Table 1, it can be seen that the specific surface areas of the porous carbon materials prepared in Examples 1-5 are all larger than those of the materials in Comparative Example 1 and Comparative Example 2. This is because the porous carbon materials in Examples 1-5 are synthesized by adjusting the size of the hard template to determine the size of the spherical porous carbon materials, and the prepared spherical porous carbon materials have a large specific surface area and a uniform pore structure.

[0159] Table 2 summarizes the test data of the electrochemical performance of the batteries assembled in Examples 1-10 and Comparative Example 1.

[0160]

[0161] Table 2

[0162] From the comparison of the test data in Table 2, it can be seen that the specific capacity, the first-cycle Coulombic efficiency, and the cycling performance of the half-cells assembled in Examples 1-5 are all better than those of the batteries in Comparative Example 1 and Comparative Example 2. It is precisely because the porous carbon materials in Examples 1-5 have a high specific surface area and a uniform pore structure that the assembled batteries have good electrochemical performance.

[0163] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a porous carbon material, characterized in that, The preparation method includes: Step S1: Put the silica mesoporous hollow spheres, surfactant and deionized water into a dispersion device for dispersion treatment, so that the silica mesoporous hollow spheres are uniformly dispersed in the deionized water to obtain a dispersion; Step S2: Add phenol, formaldehyde, alkaline catalyst and auxiliary additive to the above dispersion, stir evenly, and then stir under vacuum to obtain a precursor solution; Step S3: Place the precursor solution in a centrifuge tube for centrifugal dispersion to separate the silica mesoporous hollow spheres from the liquid outside the silica mesoporous hollow spheres, and the inside of the hollow spheres is filled with phenol, formaldehyde, alkaline catalyst and auxiliary additive to obtain a white silica mesoporous sphere precipitate; Step S4: Uniformly disperse the white silica mesoporous sphere precipitate in deionized water, place it in a heating device, and at a certain temperature, cause the phenol and formaldehyde inside the hollow spheres to undergo a condensation reaction to form phenolic resin. After centrifugation, a precipitate is obtained; Step S5: Place the precipitate in an oven to cure the phenolic resin to obtain an intermediate material; Step S6: Place the intermediate material in a tubular furnace for carbon activation treatment. At a certain temperature, carbonize the material and decompose and volatilize the auxiliary additive dispersed in the gaps of the phenolic resin to form pores. In addition, carry out activation treatment under CO2 gas to obtain a precursor material; Step S7: Place the precursor material in a hydrofluoric acid solution, soak and stir to etch away the silica mesoporous hollow spheres in the precursor material, and then rinse with deionized water at least 5 times. After drying, a porous carbon material is obtained.

2. The preparation method according to claim 1, characterized in that, The particle size Dv50 of the silica mesoporous hollow spheres in Step S1 is between 100 nm and 1000 nm; the pore diameter of the mesopores of the silica mesoporous hollow spheres is between 2 nm and 50 nm; The surfactant includes one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide CTAB, and polyethylene ether PEG; the mass ratio of the surfactant to the silica mesoporous hollow spheres is 1:6; The mass ratio of the silica mesoporous hollow spheres to deionized water is [1-10]:100; The dispersion device is an ultrasonic disperser, and the dispersion treatment time is 30 min - 1 hour.

3. The preparation method according to claim 1, characterized in that, The auxiliary additive in Step S2 is a water-soluble polymer, specifically including one or more of polyethylene oxide PEO, polyacrylic acid PAA, urea, and polyethylene glycol; The alkaline catalyst includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water; The molar ratio of phenol to formaldehyde is 1:[1-10]; The mass ratio of the alkaline catalyst to deionized water is 1:[1-10]; The mass ratio of the auxiliary additive to deionized water is 1:[1-20]; The device for stirring under vacuum is a vacuum stirrer.

4. The preparation method according to claim 1, wherein The rotation speed of centrifugal dispersion in Step S3 and the rotation speed of centrifugation in Step S4 are both 1000 revolutions per minute - 5000 revolutions per minute, and the centrifugation time is 5 minutes - 10 minutes; The amount of deionized water used in Step S4 is 100 ml - 200 ml, and the certain temperature is 50 °C - 60 °C.

5. The preparation method according to claim 1, characterized in that, The curing temperature in step S5 is 90°C - 120°C, and the curing time is 3 hours - 12 hours.

6. The preparation method according to claim 1, wherein The process of carbon activation treatment in step S6 is as follows: Place the intermediate material in a tubular furnace, introduce nitrogen with a flow rate of 0.1 L / min - 0.5 L / min to displace air. Under a nitrogen atmosphere, heat it at a heating rate of 3°C / min - 10°C / min to 500°C - 600°C, keep it warm for 3 hours - 10 hours, then heat it at a heating rate of 3°C / min - 10°C / min to 900°C. After that, introduce carbon dioxide gas with a flow rate of 0.1 L / min - 0.5 L / min to displace nitrogen, keep it warm for 3 hours - 18 hours, and finally let it cool naturally to room temperature.

7. The preparation method according to claim 1, wherein The concentration of the hydrofluoric acid solution in step S7 is 5% - 10%; the soaking and stirring time is 3 hours - 24 hours; the drying condition is baking at 80°C for 2 hours - 12 hours.

8. A porous carbon material prepared by the preparation method according to any one of claims 1-7 above, characterized in that, The porous carbon material is a spherical phenolic resin porous carbon material; The particle size Dv50 of the porous carbon material is between 100 nm and 1000 nm; The pore diameter of the pores of the porous carbon material, and the specific surface area of the porous carbon material is between 400 m 2 / g - 1000 m 2 / g; The porous carbon material is obtained by using a hard template method with a silica mesoporous hollow sphere as the hard template, causing the phenol and formaldehyde in the hollow and mesopores of the silica mesoporous hollow sphere to undergo a condensation reaction to form phenolic resin, and then through curing, carbon activation treatment, and etching.

9. A negative electrode plate, characterized in that, The negative electrode sheet includes the porous carbon material described in claim 8 above.

10. A secondary battery, characterized in that, The secondary battery includes the negative electrode sheet described in claim 9 above.

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