Porous carbon material, preparation method thereof, negative electrode material and secondary battery

Abstract

This invention provides a porous carbon material, its preparation method, a negative electrode material, and a secondary battery. The preparation method includes the following steps: mixing a solid-phase activator with a liquid-phase carbon source, drying, and heat treatment to obtain the porous carbon material. The preparation method of this invention avoids the problem of a wide pore size distribution in porous carbon materials caused by the strong erosion of the carbon material framework by the activator during the activation process, and also avoids extensive contact between the activator and the equipment. Therefore, this preparation method not only yields porous carbon materials with a narrow pore size distribution, but also allows for large-scale production over long periods without causing equipment corrosion, enabling continuous large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon materials technology, and relates to a porous carbon material and its preparation method, a negative electrode material and a secondary battery. Background Technology

[0002] Ultramicroporous carbon materials typically refer to carbon-based materials with pore sizes less than 1 nm. These materials not only possess high specific surface area and abundant pore volume, but also facilitate molecular-level sieving and selective adsorption. The development of ultramicroporous carbon materials has been accompanied by advancements in porous materials science and nanotechnology. Early preparation methods for ultramicroporous carbon materials included traditional chemical activation and heat treatment processes. While these methods can provide a certain pore structure, they have limitations in terms of the precise controllability of ultramicropores.

[0003] In recent years, template-directed synthesis, polymer-induced carbonization, and interlayer exfoliation techniques have become research hotspots. These methods can achieve the formation and regulation of ultraporous structures by precisely controlling the type of raw materials and processing procedures. In addition, precursor materials designed using molecular self-assembly technology have also provided new possibilities for the synthesis of ultraporous carbon. However, these methods all suffer from high technical difficulty, high cost, and low feasibility for actual mass production.

[0004] Based on the above research, there is a need to provide a method for preparing porous carbon materials. The preparation method has a simple process, low cost, can be mass-produced continuously, and can prepare ultra-microporous porous carbon materials with uniform pore size distribution. Summary of the Invention

[0005] The purpose of this invention is to provide a porous carbon material and its preparation method, a negative electrode material, and a secondary battery. In particular, it relates to an ultramicroporous porous carbon material and its preparation method, a negative electrode material, and a secondary battery. The preparation method avoids the problem of strong erosion of the carbon material skeleton by the activator during the activation process, which would lead to a wide pore size distribution in the porous carbon material. It also avoids a large amount of contact between the activator and the equipment. Therefore, not only can a porous carbon material with a narrow pore size distribution be obtained, but it can also be produced in large quantities for a long time without causing corrosion to the equipment, thus realizing large-scale continuous production.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a porous carbon material, the method comprising the following steps:

[0008] The solid-phase activator is mixed with the liquid-phase carbon source, dried, and heat-treated to obtain the porous carbon material.

[0009] Preferably, the method for preparing the liquid-phase carbon source includes the step of mixing a solid-phase carbon source, an oxidant, and a solvent.

[0010] Preferably, the mass ratio of the oxidant to the solid carbon source is (0.2 to 1):1.

[0011] Preferably, the mass ratio of the solvent to the solid carbon source is (2-8):1.

[0012] Preferably, the solid carbon source comprises a cured thermosetting resin.

[0013] Preferably, the cured thermosetting resin includes one or more of bakelite, cured phenolic resin, cured epoxy resin, or cured polyimide resin.

[0014] Preferably, the oxidant includes H2O2.

[0015] Preferably, the solvent includes water.

[0016] Preferably, the solid-phase activator includes an alkaline activator.

[0017] Preferably, the alkaline activator includes one or more of KOH, NaOH, ZnCl2, ZnO, MgO, NaHCO3, KHCO3, zinc acetate, or magnesium citrate.

[0018] Preferably, the mass ratio of the solid-phase activator to the liquid-phase carbon source is (0.5-1):1.

[0019] Preferably, the heat treatment temperature is 500℃~700℃ and the time is 2h~4h.

[0020] Preferably, the heat treatment further includes washing and drying steps.

[0021] Preferably, the washing includes acid washing and / or water washing.

[0022] Preferably, the washing solution has a pH of 5.5-7.

[0023] Preferably, after washing and drying, a secondary heat treatment step is also included.

[0024] Preferably, the temperature of the secondary heat treatment is higher than the temperature of the heat treatment described above;

[0025] Preferably, the temperature of the secondary heat treatment is not lower than 850°C, and the time is 2h to 4h.

[0026] In a second aspect, the present invention provides a porous carbon material, which is prepared by means of the preparation method described in the first aspect.

[0027] Preferably, the porous carbon material comprises ultramicropores with a pore size distribution in the range of 0.33 nm to 0.53 nm.

[0028] Preferably, the porosity of the micropores in the porous carbon material is 30%-70%.

[0029] Thirdly, the present invention provides a negative electrode material, which is obtained by carbon coating with a porous carbon material as described in the second aspect.

[0030] Fourthly, the present invention provides a secondary battery comprising the negative electrode material as described in the third aspect.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention does not pre-carbonize the carbon source, but instead pre-embeds the activator in the carbon source, avoiding direct contact between the activator and the carbonized carbon skeleton. This avoids the problem of excessively large pore size distribution in porous carbon materials caused by the activator eroding the carbon skeleton, thus obtaining ultra-microporous porous carbon materials with pore size distribution of 0.33nm-0.53nm. The porous carbon material can also be used as a negative electrode active material for lithium-ion batteries after carbon coating, effectively improving the electrochemical performance of lithium-ion batteries. Detailed Implementation

[0033] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0034] In a first specific embodiment, the present invention provides a method for preparing porous carbon materials, the method comprising the following steps:

[0035] The solid-phase activator is mixed with the liquid-phase carbon source, dried, and heat-treated to obtain the porous carbon material.

[0036] This invention first mixes a solid-phase activator with a liquid-phase carbon source and dries the mixture, embedding the solid-phase activator within the carbon source before heat treatment activation. This differs from carbonizing the carbon source before mixing it with the activator. On one hand, this avoids the strong erosion of the carbon material framework by the activator during activation, which could lead to a wider pore size distribution, resulting in porous carbon materials with a narrower pore size distribution. On the other hand, because the activator is embedded within the carbon source, direct and extensive contact between the equipment and the activator is avoided during activation, preventing corrosion of the equipment. This means that even after long-term, large-scale production, the equipment shows no signs of corrosion, thus enabling the continuous, large-scale production of porous carbon materials.

[0037] In some embodiments, the method for preparing the liquid-phase carbon source includes the step of mixing a solid-phase carbon source, an oxidant, and a solvent.

[0038] In some embodiments, the mass ratio of the oxidant to the solid carbon source is (0.2 to 1):1, for example, it can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] In this invention, the mass ratio of oxidant to solid carbon source is controlled within the above-mentioned range, so that the solid activator is uniformly embedded in the carbon source, which is beneficial to the control of the pore size of porous carbon.

[0040] In some embodiments, the mass ratio of the solvent to the solid carbon source is (2-8):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In this invention, controlling the mass ratio of solvent to solid carbon source within the above-mentioned range is beneficial to the dispersion of carbon source.

[0042] In some embodiments, the solid carbon source comprises a cured thermosetting resin.

[0043] In some embodiments, the cured thermosetting resin includes one or more of bakelite, cured phenolic resin, cured epoxy resin, or cured polyimide resin.

[0044] In some embodiments, the solid carbon source includes bakelite waste containing thermosetting resin.

[0045] The bakelite described in this invention is a phenolic resin with wood flour as filler. The preparation of bakelite typically involves mixing phenolic resin and wood flour (or other fillers) in a certain proportion, followed by pressing, drying, and other processes. When bakelite is used to make molds, it needs to be cut, which generates a large amount of bakelite scrap waste. This invention utilizes bakelite waste as a carbon source, thus significantly reducing preparation costs.

[0046] In some embodiments, the bakelite waste is first crushed and sieved to prepare powder before use.

[0047] In order to ensure that the solid-phase activator is fully embedded in the carbon source, the cut bakelite waste needs to be crushed and sieved to obtain powder before use.

[0048] In some embodiments, the oxidant includes H2O2.

[0049] An oxidant is added to this invention to promote the dispersion and dissolution of the carbon source in the solvent, thereby promoting the mixing of the solid-phase activator and the carbon source.

[0050] In some embodiments, the solvent includes water.

[0051] In some embodiments, the mixing step of the solid carbon source, oxidant and solvent includes first mixing the solid carbon source and solvent to obtain a first suspension, and then mixing the first suspension with the oxidant to obtain a liquid carbon source.

[0052] In some embodiments, the mixing time of the carbon source and solvent is not limited.

[0053] In some embodiments, the time for mixing the first suspension with the oxidant is 2h to 4h, for example, it can be 2h, 3h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] In some embodiments, the solid-phase activator includes an alkaline activator.

[0055] The activator described in this invention is alkaline and has a certain degree of corrosiveness. By pre-embedding the activator, this invention can avoid its corrosion of the carbon skeleton and equipment. Therefore, the preparation method described in this invention is a novel activation method that avoids the drawbacks of traditional alkaline activation methods.

[0056] In some embodiments, the alkaline activator includes one or more of KOH, NaOH, ZnCl2, ZnO, MgO, NaHCO3, KHCO3, zinc acetate, or magnesium citrate.

[0057] In some embodiments, the mass ratio of the solid-phase activator to the liquid-phase carbon source is (0.5 to 1):1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] This invention controls the mass ratio of solid-phase activator to liquid-phase carbon source within the above-mentioned range, which can ensure the full activation of carbon materials and prepare ultra-microporous carbon materials with pore size distribution of 0.33nm-0.53nm.

[0059] In some embodiments, the solid-phase activator is mixed with the liquid-phase carbon source for more than 4 hours, for example, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours or 16 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 4 hours to 12 hours.

[0060] In some embodiments, the drying temperature after mixing the solid-phase activator with the liquid-phase carbon source is 90-120°C, for example, 90°C, 100°C, 110°C or 120°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, the dried material is further crushed into 5-10 mesh particles before undergoing the heat treatment.

[0062] In some embodiments, the temperature of the heat treatment is 500℃ to 700℃, for example, 500℃, 600℃ or 700℃, and the time is 2h to 4h, for example, 2h, 3h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] In this invention, the temperature of the heat treatment is controlled within the above-mentioned range, which enables the carbon material to react fully with the solid-phase activator and ensures the activation effect.

[0064] In some embodiments, the heat treatment may further include washing and drying steps.

[0065] In some embodiments, the washing includes acid washing and / or water washing.

[0066] In some embodiments, the washing is performed until the pH of the washing solution is 5.5 to 7, for example, it can be 5.5, 6, 6.5 or 7, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0067] In some embodiments, after heat treatment, pickling can be performed first to remove residual activator, followed by water washing to remove residual acid from the pickling process.

[0068] In some embodiments, the temperature for drying after washing is 90 to 120°C, for example, 90°C, 100°C, 110°C or 120°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, after washing and drying, a secondary heat treatment step is further included.

[0070] The present invention further includes a secondary heat treatment after washing and drying, which serves to passivate the porous carbon material, reduce the content of surface active groups in the porous carbon material, and improve the stability of the porous carbon material.

[0071] In some embodiments, the temperature of the secondary heat treatment is higher than the temperature of the heat treatment described above.

[0072] The present invention performs passivation at a higher temperature to significantly reduce the content of active groups on the surface of porous carbon materials.

[0073] In some embodiments, the temperature of the secondary heat treatment is not lower than 850°C, for example, it can be 850°C, 900°C, 950°C or 1050°C, and the time is 2h to 4h, for example, it can be 2h, 3h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] In some embodiments, the heat treatment is performed in a protective gas.

[0075] In some embodiments, the secondary heat treatment is performed in a protective gas.

[0076] In some embodiments, the protective gas includes nitrogen and / or argon.

[0077] In a second embodiment, the present invention provides a porous carbon material, which is prepared by the preparation method described in the first embodiment.

[0078] In some embodiments, the porous carbon material includes ultramicropores with a pore size distribution in the range of 0.33 nm to 0.53 nm, for example, 0.33 nm, 0.43 nm or 0.53 nm, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0079] The porous carbon material obtained by the preparation method of the present invention is an ultraporous carbon material, and the pore size can be distributed in a narrow range of 0.33nm-0.53nm.

[0080] In some embodiments, the porosity of the micropores of the porous carbon material is in the range of 30%-70%, for example, it can be 30%, 40%, 50%, 60% or 70%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0081] In a third embodiment, the present invention provides a negative electrode material, which is obtained by carbon coating with a porous carbon material as described in the second embodiment.

[0082] The porous carbon material described in this invention, after being coated with carbon, can be used as a lithium-ion battery anode material. Because the porous carbon material, after being coated with carbon, has a large number of closed pores with a pore size in the range of 0.33nm-0.53nm, it can serve as lithium storage sites for the anode material, thereby improving the capacity of the lithium-ion battery.

[0083] In some embodiments, the carbon coating method includes one or more of liquid phase coating, solid phase coating, and CVD (chemical vapor deposition).

[0084] In a fourth embodiment, the present invention provides a secondary battery comprising the negative electrode material as described in the third embodiment.

[0085] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0086] Example 1

[0087] This embodiment provides a method for preparing porous carbon materials, the method comprising the following steps:

[0088] (1) Take the scraps generated during the cutting of bakelite materials, crush them and pass them through a 325-mesh sieve. Collect the powder under the sieve as a solid carbon source. Mix the solid carbon source with water to obtain a first suspension. Add H2O2 to the first suspension and stir continuously for 3 hours to obtain a liquid carbon source. Add KOH to the liquid carbon source and stir continuously for 8 hours until a dark brown paste is obtained.

[0089] The mass ratio of H₂O₂ to the solid carbon source is 1:1, the mass ratio of water to the solid carbon source is 2:1, and the mass ratio of KOH to the liquid carbon source is 0.5:1.

[0090] (2) Pour the dark brown paste from step (1) into a tray and dry it completely in an oven at 100°C. Crush the dried material into particles that pass through a 5-mesh sieve but not a 10-mesh sieve. Then place it in a converter and heat it to 600°C at a heating rate of 5°C / min under N2 protection with a flow rate of 5L / min. Hold it for 3 hours for heat treatment. Then allow it to cool naturally to room temperature to obtain the heat-treated material.

[0091] (3) The heat-treated material described in step (2) is impregnated and stirred with hydrochloric acid, and then repeatedly washed with distilled water until the pH of the washing effluent is 6. Then it is placed in an oven at 100°C and dried completely. The dried material is placed in a converter and heated to 950°C at a heating rate of 5°C / min under N2 protection with a flow rate of 5L / min. It is then held for 3 hours for secondary heat treatment and then cooled naturally to obtain the porous carbon material.

[0092] This embodiment also provides a method for preparing a negative electrode material, the method comprising the following steps:

[0093] Using a 10% methane mixture (methane + argon) as a coating agent, the porous carbon material obtained in this embodiment was placed in a CVD furnace and heated to 900°C at a heating rate of 3°C / min under a N2 atmosphere. After reaching the target temperature, the nitrogen gas was turned off, and a 10% methane mixture was introduced at a flow rate of 1.5 L / min. The mixture was kept at this temperature for 6 hours. After cooling, the target sample was removed to obtain the negative electrode material.

[0094] Example 2

[0095] This embodiment provides a method for preparing porous carbon materials, the method comprising the following steps:

[0096] (1) Take the scraps generated during the cutting of bakelite materials, crush them and pass them through a 325-mesh sieve. Collect the powder under the sieve as a solid carbon source. Mix the solid carbon source with water to obtain a first suspension. Add H2O2 to the first suspension and stir continuously for 2 hours to obtain a liquid carbon source. Add NaOH to the liquid carbon source and stir continuously for 12 hours until a dark brown paste is obtained.

[0097] The mass ratio of H₂O₂ to the solid carbon source is 0.5:1, the mass ratio of water to the solid carbon source is 2:1, and the mass ratio of NaOH to the liquid carbon source is 1:1.

[0098] (2) Pour the dark brown paste from step (1) into a tray and dry it completely in an oven at 120°C. Crush the dried material into particles that pass through a 5-mesh sieve but not a 10-mesh sieve. Then place it in a converter and heat it to 700°C at a heating rate of 5°C / min under N2 protection with a flow rate of 5L / min. Hold it for 2 hours for heat treatment. Then allow it to cool naturally to room temperature to obtain the heat-treated material.

[0099] (3) The heat-treated material described in step (2) is impregnated and stirred with hydrochloric acid, and then repeatedly washed with distilled water until the pH of the washing effluent is 7. Then it is placed in an oven at 120°C and dried completely. The dried material is placed in a converter and heated to 850°C at a heating rate of 5°C / min under N2 protection with a flow rate of 5L / min. It is then held for 4 hours for secondary heat treatment and then cooled naturally to obtain the porous carbon material.

[0100] This embodiment also provides a method for preparing a negative electrode material, the method comprising the following steps:

[0101] Using a 10% methane mixture (methane + argon) as a coating agent, the porous carbon material obtained in this embodiment was placed in a CVD furnace and heated to 900°C at a heating rate of 3°C / min under a N2 atmosphere. After reaching the target temperature, the nitrogen gas was turned off, and a 10% methane mixture was introduced at a flow rate of 1.5 L / min. The mixture was kept at this temperature for 6 hours. After cooling, the target sample was removed to obtain the negative electrode material.

[0102] Example 3

[0103] This embodiment provides a method for preparing porous carbon materials, the method comprising the following steps:

[0104] (1) Take the scraps generated during the cutting of bakelite materials, crush them and pass them through a 325-mesh sieve. Collect the powder under the sieve as a solid carbon source. Mix the solid carbon source with water to obtain a first suspension. Add H2O2 to the first suspension and stir continuously for 4 hours to obtain a liquid carbon source. Add KOH to the liquid carbon source and stir continuously for 4 hours until a dark brown paste is obtained.

[0105] The mass ratio of H2O2 to the solid carbon source is 0.2:1, the mass ratio of water to the solid carbon source is 4:1, and the mass ratio of KOH to the liquid carbon source is 0.8:1.

[0106] (2) Pour the dark brown paste from step (1) into a tray and dry it completely in an oven at 90°C. Crush the dried material into particles that pass through a 5-mesh sieve but not a 10-mesh sieve. Then place it in a converter and heat it to 500°C at a heating rate of 5°C / min under N2 protection with a flow rate of 5L / min. Hold it for 4 hours for heat treatment. Then allow it to cool naturally to room temperature to obtain the heat-treated material.

[0107] (3) The heat-treated material described in step (2) is impregnated and stirred with hydrochloric acid, and then repeatedly washed with distilled water until the pH of the washing effluent is 5.5. Then it is placed in an oven at 90°C and dried completely. The dried material is placed in a converter and heated to 900°C at a heating rate of 5°C / min under N2 protection with a flow rate of 5L / min. It is then held for 2 hours for secondary heat treatment and then cooled naturally to obtain the porous carbon material.

[0108] This embodiment also provides a method for preparing a negative electrode material, the method comprising the following steps:

[0109] Using a 10% methane mixture (methane + argon) as a coating agent, the porous carbon material obtained in this embodiment was placed in a CVD furnace and heated to 900°C at a heating rate of 3°C / min under a N2 atmosphere. After reaching the target temperature, the nitrogen gas was turned off, and a 10% methane mixture was introduced at a flow rate of 1.5 L / min. The mixture was kept at this temperature for 6 hours. After cooling, the target sample was removed to obtain the negative electrode material.

[0110] Example 4

[0111] This embodiment provides a method for preparing porous carbon materials. Except for step (1), in which H2O2 is not added and KOH is directly added to the first suspension for continuous stirring, the preparation method is the same as in Example 1.

[0112] This embodiment also provides a method for preparing a negative electrode material. Except for using the porous carbon material obtained in this embodiment, the method for preparing the negative electrode material is the same as in Example 1.

[0113] Example 5

[0114] This embodiment provides a method for preparing porous carbon materials. The preparation method is the same as in Example 1, except that the bakelite material in step (1) is replaced by thermosetting phenolic resin in equal mass and thermosetting phenolic resin is used as the solid carbon source.

[0115] This embodiment also provides a method for preparing a negative electrode material. Except for using the porous carbon material obtained in this embodiment, the method for preparing the negative electrode material is the same as in Example 1.

[0116] Example 6

[0117] This embodiment provides a method for preparing porous carbon materials. The preparation method is the same as that in Example 1, except that step (2) is not subjected to secondary heat treatment.

[0118] This embodiment also provides a method for preparing a negative electrode material. Except for using the porous carbon material obtained in this embodiment, the method for preparing the negative electrode material is the same as in Example 1.

[0119] Comparative Example 1

[0120] This comparative example provides a method for preparing a porous carbon material, the method comprising the following steps:

[0121] (1) Take the scrap material generated during the cutting of bakelite material, crush it and pass it through a 325-mesh sieve. Collect the powder under the sieve as a carbon source. Carbonize the carbon source at 500°C for 2 hours under N2 protection at 5L / min to obtain the precursor material.

[0122] (2) The precursor material described in step (1) is mixed with KOH for 8 hours, and then heated to 600°C for 3 hours under N2 protection with a flow rate of 5 L / min and held at the temperature for 5°C / min for heat treatment. After that, it is naturally cooled to room temperature to obtain the heat-treated material.

[0123] (3) The heat-treated material described in step (2) is impregnated and stirred with hydrochloric acid, and then repeatedly washed with distilled water until the pH of the washing effluent is 6. Then it is placed in an oven at 100°C and dried completely. The dried material is placed in a converter and heated to 950°C at a heating rate of 5°C / min under N2 protection with a flow rate of 5L / min. It is then held for 3 hours for secondary heat treatment and then cooled naturally to obtain the porous carbon material.

[0124] This comparative example also provides a method for preparing a negative electrode material, the method comprising the following steps:

[0125] Using a 10% methane mixture (methane + argon) as a coating agent, the porous carbon material obtained in this comparative example was placed in a CVD furnace and heated to 900℃ at a heating rate of 3℃ / min under a N2 atmosphere. After reaching the target temperature, the nitrogen gas was turned off, and a 10% methane mixture was introduced at a flow rate of 1.5L / min. The mixture was held at this temperature for 6 hours, and after cooling, the target sample was removed to obtain the negative electrode material.

[0126] The porous carbon materials provided in Examples 1-6 and Comparative Example 1 were tested for pore volume and BET specific surface area.

[0127] Material pore structure testing:

[0128] Pore ​​volume and BET specific surface area tests: The adsorption and desorption properties of porous carbon materials were tested according to GB / T 19587-2004, with CO2 as the adsorption medium. The results are recorded in Table 1.

[0129] Table 1

[0130]

[0131]

[0132] Batteries were prepared using the negative electrode materials provided in Examples 1-6 and Comparative Example 1, and their performance was tested.

[0133] Battery preparation: The negative electrode materials provided in Examples 1-6 and Comparative Example 1 were used as negative electrode active materials. The negative electrode active material, binder polyvinylidene fluoride (PVDF) and conductive acetylene black were mixed in a mass ratio of 80:5:15. 1-Methyl-2-pyrrolidone (NMP) was added and stirred evenly to form a slurry. The slurry was then uniformly coated on the surface of copper foil. The electrode sheet was then dried at 80°C for 12 hours. The electrode sheet was pressed by a roller press and then placed in a vacuum oven to dry at 90°C for 8 hours. The electrode sheet was then slit to prepare the negative electrode sheet for lithium-ion batteries.

[0134] The prepared negative electrode sheet was assembled into a lithium-ion half-cell, in which a lithium metal sheet was used as the counter electrode; the electrolyte was DEC (diethyl carbonate) + EC (ethylene carbonate) containing 1 mol / L LiPF6 (volume ratio DEC:EC = 7:3); the separator was made of polypropylene Celgard 2300; the battery assembly was completed in a dry glove box with a relative humidity of less than 1%.

[0135] Performance testing:

[0136] Capacity and initial efficiency: The obtained batteries were subjected to constant current charge-discharge tests using a Blue Electric testing device at 25±2℃. The discharge cutoff voltage was 0.01V, and the charge cutoff voltage was 2.5V. The first week of charge-discharge testing was conducted at a current density of 0.1C, and the corresponding charge specific capacity and initial coulombic efficiency were recorded. Initial coulombic efficiency = initial charge capacity / initial discharge capacity × 100%. The results are recorded in Table 2.

[0137] Table 2

[0138]

[0139]

[0140] As shown in Table 1: According to Example 1 and Comparative Example 1, the preparation method of the present invention, compared with the traditional activation method, can obtain porous carbon materials with smaller pore sizes and narrower pore size distribution ranges. Furthermore, the porous carbon materials obtained, when used to prepare lithium-ion battery anode materials, can improve the electrochemical performance of lithium-ion batteries. According to Examples 1 and 4, the present invention preferably also adds an oxidant, which can promote the uniform pre-embedding of the solid-phase activator in the carbon source, thereby regulating the pore size distribution range of the porous carbon material and improving the performance of the lithium-ion battery. According to Examples 1 and 5, the present invention can use bakelite waste as a carbon source, reducing preparation costs. According to Examples 1 and 6, the secondary heat treatment of the present invention can improve the stability of the porous carbon material, thereby improving the performance of the lithium-ion battery.

[0141] In summary, this invention provides a porous carbon material and its preparation method, a negative electrode material, and a secondary battery. The preparation method avoids the problem of strong erosion of the carbon material skeleton by the activator during the activation process, which would otherwise lead to a wide pore size distribution in the porous carbon material. It also avoids excessive contact between the activator and the equipment. Therefore, not only can porous carbon materials with a narrow pore size distribution be obtained, but they can also be produced in large quantities for a long time without causing corrosion to the equipment, thus achieving large-scale continuous production.

[0142] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing porous carbon materials, characterized in that, The preparation method includes the following steps: The solid-phase activator is mixed with the liquid-phase carbon source, dried, and heat-treated to obtain the porous carbon material.

2. The preparation method according to claim 1, characterized in that, The method for preparing the liquid-phase carbon source includes the step of mixing a solid-phase carbon source, an oxidant, and a solvent. Preferably, the mass ratio of the oxidant to the solid carbon source is (0.2-1):1; Preferably, the mass ratio of the solvent to the solid carbon source is (2-8):1; Preferably, the solid carbon source comprises a cured thermosetting resin; Preferably, the cured thermosetting resin includes one or more of bakelite, cured phenolic resin, cured epoxy resin, or cured polyimide resin. Preferably, the oxidant includes H2O2; Preferably, the solvent includes water.

3. The preparation method according to claim 1, characterized in that, The solid-phase activator includes an alkaline activator; Preferably, the alkaline activator includes one or more of KOH, NaOH, ZnCl2, ZnO, MgO, NaHCO3, KHCO3, zinc acetate, or magnesium citrate.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the solid-phase activator to the liquid-phase carbon source is (0.5-1):

1.

5. The preparation method according to claim 1, characterized in that, The heat treatment temperature is 500℃~700℃, and the time is 2h~4h.

6. The preparation method according to claim 1, characterized in that, The heat treatment process also includes washing and drying steps; Preferably, the washing includes acid washing and / or water washing; Preferably, the pH of the washing solution is 5.5 to 7.

7. The preparation method according to claim 6, characterized in that, After washing and drying, a secondary heat treatment step is also included; Preferably, the temperature of the secondary heat treatment is higher than the temperature of the heat treatment according to claim 1; Preferably, the temperature of the secondary heat treatment is not lower than 850°C, and the time is 2h to 4h.

8. A porous carbon material, characterized in that, The porous carbon material is obtained by the preparation method described in any one of claims 1-7. Preferably, the porous carbon material comprises ultramicropores with a pore size distribution in the range of 0.33 nm to 0.53 nm; Preferably, the porosity of the micropores in the porous carbon material is 30%-70%.

9. A negative electrode material, characterized in that, The negative electrode material is obtained by carbon coating of the porous carbon material as described in claim 8.

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

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