Sulfur-doped porous carbon, phosphorus-carbon composite material and application thereof

Abstract

The invention discloses sulfur-doped porous carbon, a phosphorus-carbon composite material and application thereof, and belongs to the technical field of carbon material preparation. The preparation method comprises the following steps: providing a carbon source, wherein the carbon source is one or a mixture of more than two of ion exchange resin or ionic liquid; performing high-temperature pore forming on the carbon source in a CO2 / non-reaction gas mixed atmosphere; the preparation method comprises the following steps: preparing a sulfur-containing organic compound, introducing pyrolysis gas of the sulfur-containing organic compound, carrying out high-temperature vulcanization, and finally carrying out low-temperature treatment at 150-450 DEG C to form a C-S covalent bond and a stable thiophene structure. According to the preparation method, chemical combination of a carbon skeleton and sulfur is increased, uniform doping of sulfur in porous carbon is achieved, and the problems that in the prior art, sulfur doping distribution is not uniform, and combination of the carbon skeleton and sulfur is not firm are effectively solved. Moreover, the deposition efficiency of phosphorus is enhanced, the deposition uniformity of phosphorus in porous carbon is promoted, and the dynamic performance of phosphorus carbon is improved, so that the electrochemical performance of the secondary battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a sulfur-doped porous carbon and phosphorus-carbon composite material and its applications. Background Technology

[0002] To improve the energy density of lithium-ion batteries, phosphorus-carbon composite materials with red phosphorus as the active material have attracted widespread attention. The mainstream preparation route usually uses porous carbon as the phosphorus loading framework, and achieves uniform dispersion of phosphorus through physical adsorption or confined deposition. Common porous carbon precursors include glucose, phenolic resin, metal-organic framework (MOF), and biomass carbon sources. After high-temperature carbonization and activation, a carbon matrix with high specific surface area and rich pore structure is obtained. If sulfur needs to be introduced, it is usually done through post-treatment, such as impregnating the pre-synthesized porous carbon with a sulfur-containing precursor solution and then pyrolyzing it again, or introducing gaseous sulfur sources such as H2S during carbonization for co-pyrolysis.

[0003] However, current methods for sulfur doping in porous carbon materials generally suffer from uneven distribution and weak chemical bonding. On the one hand, liquid-phase impregnation methods tend to concentrate sulfur species on the outer surface or macropores of carbon materials, making it difficult for them to penetrate into the micropores and resulting in a sulfur content gradient. On the other hand, small-molecule gaseous sulfur sources such as H2S exhibit high reactivity and short residence time at high temperatures, easily escaping or generating volatile byproducts, leading to low sulfur doping efficiency and uncontrollable bonding patterns, making it difficult to form stable C–S covalent bonds and thiophene-like five-membered ring structures. Furthermore, the preparation cost of porous carbon using glucose, phenolic resin, and other carbon sources is relatively high. These defects collectively restrict the uniformity of phosphorus deposition in the carbon framework and the stability of interfacial bonding, thereby affecting the first-cycle coulombic efficiency, rate performance, and cycle life of phosphorus-carbon composite materials. Summary of the Invention

[0004] In view of this, the present invention needs to provide a method for preparing sulfur-doped porous carbon. This method uses ion exchange resin, ionic liquid, etc. as carbon sources, and sequentially performs high-temperature pore formation, high-temperature sulfidation, and low-temperature treatment to achieve uniform sulfur doping in porous carbon. This not only reduces costs, but also overcomes the problems of uneven sulfur doping distribution and weak bonding between the carbon skeleton and sulfur.

[0005] The first aspect of this application discloses a method for preparing sulfur-doped porous carbon, comprising the following steps: A carbon source is provided, wherein the carbon source is one or a mixture of two or more of ion exchange resins and ionic liquids; The carbon source is subjected to high-temperature pore formation in a mixed atmosphere of CO2 and non-reactive gas; then, pyrolysis gas containing sulfur organic compounds is introduced and sulfidation is carried out at high temperature to obtain sulfur-doped porous carbon with a large number of defects. The sulfur-doped porous carbon was placed in a non-reactive gas and subjected to low-temperature treatment at 150-450°C to form abundant CS covalent bonds and stable thiophene structures.

[0006] High-temperature pore-forming using a CO2 / non-reactive gas mixed atmosphere enables the formation of controllable micropores and mesopores within the carbon framework, increasing the specific surface area and providing abundant attachment sites for subsequent sulfur doping. Subsequently, high-temperature sulfidation using pyrolysis gas containing sulfur-containing organic compounds achieves in-situ sulfur doping within the carbon lattice, forming numerous defect structures and enhancing the material's electrochemical activity. The final low-temperature treatment process fosters abundant CS covalent bonds and stable thiophene-like structures, increasing the chemical bonding between the carbon framework and sulfur, and achieving uniform sulfur doping within the porous carbon.

[0007] In this application, the carbon source is selected from one or a mixture of two or more ion exchange resins and ionic liquids. By selecting ion exchange resins and ionic liquids as carbon sources, the high cost problem caused by the use of chemicals such as resins, glucose, and pyridine in traditional porous carbon materials can be effectively avoided, thus realizing the efficient utilization of ion exchange resins and ionic liquids. In some specific examples, the ion exchange resin is at least one of D001 and D113, which has a high carbon content, low price, and is easy to pore-form; the ionic liquid is phenothiazine hydrogen sulfate, which can generate micropores upon pyrolysis, thereby reducing excessive dependence on activators.

[0008] In the high-temperature pore-forming step, the carbon source is placed in an atmosphere furnace, and a mixed atmosphere of CO2 and non-reactive gas is introduced. CO2 acts as an activator, reacting with the carbon to oxidize it, etching the carbon framework to form micropores and mesopores. The non-reactive gas refers to a gas that is inert to the raw material components, intermediate products, and final products, and does not react with them. It serves as a protective gas and diluent gas, used to regulate the reaction rate. Specific examples include, but are not limited to, any one of nitrogen or rare gases (such as argon or helium). The total flow rate of the mixed atmosphere can be adjusted according to the furnace volume and equipment specifications. For example, for a tubular furnace, the total flow rate can be set within the range of 0.5-1.5 L / min, such as any flow rate or a range between any two of 0.5 L / min, 0.7 L / min, 0.9 L / min, 1 L / min, 1.2 L / min, and 1.5 L / min. Furthermore, the volumetric flow rate ratio of CO2 to non-reactive gas is controlled between 1:0.5 and 1:2, for example, any ratio or range between any two ratios such as 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.7, and 1:2. For example, when the CO2 flow rate is 0.5 L / min, the flow rate of the non-reactive gas can be adjusted between 0.25 L / min and 1.0 L / min. A suitable flow rate ratio ensures sufficient CO2 concentration for adequate pore formation activation while utilizing the dilution effect of the non-reactive gas to prevent excessively vigorous activation reactions that could lead to excessive ablation of the carbon skeleton. It should be noted that the total flow rate setting must also ensure uniform atmosphere distribution within the reaction zone to avoid uneven local activation. At the same time, it should be understood that the above flow rate ratio and total flow rate range can be adjusted according to the type of carbon source, target pore structure, and equipment parameters; those skilled in the art possess this capability, and therefore there are no particular limitations.

[0009] Furthermore, the specific high-temperature pore-forming temperature and holding time need to be optimized based on the thermal stability of the carbon source, the target porosity, and the equipment performance. In some specific examples, the heating temperature for the high-temperature pore-forming step is set to 850℃~1000℃, for example, any temperature or a range between any two of 850℃, 900℃, 950℃, or 1000℃. The holding time is controlled within the range of 4~8 hours, for example, any number or a range between any two of 4h, 5h, 6h, 7h, or 8h. A suitable temperature is sufficient to activate the gasification reaction between CO2 and carbon, forming abundant micropores and mesopores. The choice of a suitable holding time directly affects the pore-forming depth: too short a holding time results in insufficient activation and limited increase in specific surface area; too long a holding time may lead to excessive etching of the carbon skeleton, reducing structural strength. In actual operation, the heating rate is usually controlled at 2-5℃ / min to avoid cracking of the carbon material or uneven atmosphere distribution due to excessively rapid heating.

[0010] After high-temperature pore formation, pyrolysis gas containing sulfur-containing organic compounds is introduced into the furnace. This pyrolysis gas is generated by the pyrolysis of sulfur-containing organic compounds in an external heating furnace and is introduced into the reaction zone along with the carrier gas. During the high-temperature sulfidation process, sulfur atoms are embedded into the lattice defects of the carbon framework through substitution or doping, forming sulfur-doped porous carbon with a large number of defects.

[0011] In this application, the sulfur-containing organic compound is one or a mixture of two or more of 1,2-ethanedithiol, tert-butyl disulfide, and tert-butyl mercaptan. By selecting specific types of sulfur-containing organic compounds as sulfur sources, which have poor thermal stability and suitable pyrolysis windows, 1,2-ethanedithiol can construct carbon-sulfur cross-linked structures, tert-butyl disulfide is a low-temperature vulcanizing agent with low cost, and tert-butyl mercaptan can achieve uniform sulfur doping. Their pyrolysis gases are rich in active sulfur species, which can effectively react chemically with the carbon skeleton at high temperatures to achieve uniform sulfur doping.

[0012] In some specific embodiments, the flow rate ratio of 1,2-ethanedithiol, tert-butyl disulfide, and tert-butyl mercaptan can be controlled within the range of 1:0-2:0-2. Here, "flow rate" refers to the injection flow rate of the liquid sulfur-containing organic compound before vaporization, which can be precisely adjusted using a syringe pump or mass flow controller. It should be understood that in specific operations, the flow rate ratio and total flow rate can be adaptively adjusted according to the actual equipment conditions and the target doping amount, and therefore there are no particular limitations. In some specific examples, the mixed liquid feedstock enters the vaporization chamber for pyrolysis, and the total flow rate of the generated pyrolysis gas is controlled between 50-500 mL / min. As a specific example, the total flow rate can be any flow rate or a range between any two of the following: 50 mL / min, 100 mL / min, 150 mL / min, 200 mL / min, 250 mL / min, 300 mL / min, 350 mL / min, 400 mL / min, 450 mL / min, and 500 mL / min. If the flow rate is too low, the sulfur doping amount may be insufficient; if the flow rate is too high, the active sulfur species may be excessively deposited, clogging the pores. Therefore, by precisely controlling the flow rate ratio of sulfur-containing organic compounds and the total flow rate of pyrolysis gas, the sulfur doping concentration and doping depth can be effectively controlled, avoiding pore blockage caused by excessive sulfur source or uneven doping caused by insufficient sulfur source, thereby ensuring that the final product has a stable doped structure and excellent electrochemical activity.

[0013] The specific process of high-temperature sulfidation is as follows: maintaining the high-temperature pore-forming temperature, introducing pyrolysis gas containing sulfur-containing organic compounds, and holding at this temperature for 0.1-5 hours. Sulfidation by maintaining the high-temperature pore-forming temperature avoids increased energy consumption and time loss caused by temperature fluctuations. Simultaneously, the high-temperature conditions are conducive to the chemical bonding of sulfur-active species with carbon defect sites, forming stable covalent bonds. The flexible selection of the holding time within the range of 0.1-5 hours allows for precise control of the sulfur doping depth and amount according to actual application requirements, thereby optimizing the electrochemical performance of the material.

[0014] Furthermore, the aforementioned sulfur-doped porous carbon is subjected to low-temperature treatment under a non-reactive gas atmosphere. Here, the non-reactive gas has the same meaning as described above and will not be elaborated further. This low-temperature treatment aims to form CS covalent bonds and stable thiophene structures, increasing the chemical bonding between the carbon framework and sulfur, achieving uniform sulfur doping in the porous carbon, and effectively solving the problems of uneven sulfur doping distribution and weak bonding between the carbon framework and sulfur in existing technologies. Simultaneously, it is beneficial to enhance phosphorus deposition efficiency, promote the uniformity of phosphorus deposition in porous carbon, and improve the kinetic properties of phosphorus-carbon composite materials. In some specific examples, the process conditions for the low-temperature treatment are: the sulfur-doped porous carbon obtained after high-temperature sulfidation is heated to 150-450℃ in a non-reactive gas atmosphere and held at this temperature for 1-3 hours; the flow rate of the non-reactive gas is 0.5-1.5 L / min, and the purity is ≥99%. Specific low-temperature temperatures can be any temperature or a range between any two of 150℃, 200℃, 250℃, 300℃, 350℃, and 450℃. Simultaneously, processing in a high-purity non-reactive gas ensures the integrity and high purity of the porous carbon structure.

[0015] Another aspect of this application discloses a sulfur-doped porous carbon, prepared using the method described above. The sulfur-doped porous carbon prepared by this method possesses a high specific surface area, abundant microporous / mesoporous structures, and a high content of stable chemically doped sulfur. This not only reduces raw material costs but, more importantly, improves the uniformity of sulfur doping distribution and its strong bonding with carbon. This is more conducive to increasing the subsequent phosphorus deposition efficiency, promoting the uniformity of phosphorus deposition in porous carbon, and improving the kinetic properties of phosphorus-carbon composite materials. Another aspect of this application discloses a phosphorus-carbon composite material comprising a porous carbon support on which phosphorus is deposited, wherein the porous carbon support is the sulfur-doped porous carbon described above. The phosphorus-carbon composite material should at least include the sulfur-doped porous carbon described in this application. Using sulfur-doped porous carbon as the phosphorus support, its high specific surface area, abundant pore structure, and polar sites introduced by sulfur doping enable efficient loading and uniform dispersion of phosphorus. The synergistic effect between sulfur and phosphorus can also suppress the volume expansion and shuttle effect of phosphorus during cycling, significantly improving the cycle stability and rate performance of the phosphorus-carbon composite material in energy storage fields (such as lithium-ion battery anodes).

[0016] Furthermore, it is understood that the phosphorus-carbon composite material can be further improved by introducing a coating layer as needed. The specific preparation of the phosphorus-carbon composite material can be carried out using methods known in the art or independently developed, which will not be elaborated here.

[0017] In some specific embodiments, the method of phosphorus deposition is not specifically limited, including but not limited to vapor phase deposition, melt diffusion, or solution impregnation-thermal conversion. As a specific example, vapor phase deposition can be used: the sulfur-doped porous carbon is placed at one end of the reactor, and red or white phosphorus is placed in the upstream low-temperature zone of the reactor. Heating under an inert atmosphere causes the phosphorus to sublimate, and the phosphorus vapor enters the pores of the porous carbon with the carrier gas, condensing or chemically adsorbing at a suitable temperature to achieve phosphorus deposition. The sulfur atoms in the sulfur-doped porous carbon can act as phosphorophilic sites, enhancing the interaction between phosphorus and the carbon matrix and improving the uniformity and stability of phosphorus loading. It should be understood that the phosphorus deposition process parameters (such as temperature, time, and phosphorus source dosage) can be adjusted according to the target loading, which will not be specifically elaborated here.

[0018] In some specific examples, the mass percentage of phosphorus deposition in the phosphorus-carbon composite material is 35% to 55%. For example, it can be any value or a range of any two values ​​from 35%, 40%, 45%, 50%, or 55%. Thanks to the performance advantages of the sulfur-doped porous carbon in this application, uniform distribution and stable loading of phosphorus in the sulfur-doped porous carbon support can be ensured, improving phosphorus deposition efficiency and the kinetic properties of the phosphorus-carbon composite material.

[0019] The present invention has at least the following beneficial effects: Using one or a mixture of ion exchange resins and ionic liquids as carbon sources and sulfur-containing organic compounds as sulfur sources, sulfurization is carried out at high temperature under a mixture of carbon dioxide and non-reactive gases to prepare sulfur-doped porous carbon with a large number of defects. This avoids the high cost problem caused by the use of chemicals such as resins, glucose, and pyridine in traditional porous carbon materials, and realizes the effective utilization of ion exchange resins and ionic liquids.

[0020] By employing low-temperature treatment in a non-reactive atmosphere, CS covalent bonds and stable thiophene-like structures are formed in porous carbon, increasing the chemical bonding between the carbon framework and sulfur. This achieves uniform sulfur doping in porous carbon, effectively solving the problems of uneven sulfur doping distribution and weak bonding between the carbon framework and sulfur in existing technologies. Furthermore, these abundant CS covalent bonds and stable thiophene-like structures enhance phosphorus deposition efficiency, promote the uniformity of phosphorus deposition in porous carbon, and improve the kinetic properties of phosphorus-carbon composites. Attached Figure Description

[0021] Figure 1This is a scanning electron microscope (SEM) image of the sulfur-doped porous carbon product in Example 2.

[0022] Figure 2 The image shows a cross-sectional electron microscope (CP) image and corresponding elemental distribution (EDS) of the sulfur-doped porous carbon product after phosphorus deposition in Example 2. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, unless otherwise specified, methods not specifically describing conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0025] Example 1 1.1 Sulfur-doped porous carbon (1) Mix 50g of ion exchange resin D113 and 50g of ionic liquid phenothiazine hydrogen sulfate evenly and put them into a crucible. Place the crucible into a tube furnace and then, under the atmosphere of nitrogen and carbon dioxide, control the flow rate at 1L / min and the flow ratio of the two gases at 1:1. Gradually raise the temperature to 950℃ at 5℃ / min and hold for 5h. Then, under the atmosphere, introduce a pyrolysis mixture of 1,2-ethylenedithiol, tert-butyl disulfide and tert-butyl mercaptan at a flow ratio of 1:1:1 and control the flow rate at 100mL / min. Hold for 2h and cool to room temperature to obtain sulfur-doped porous carbon.

[0026] (2) The sulfur-doped porous carbon obtained in step (1) is placed in a sagger, and the sagger is placed in a tube furnace. Under a nitrogen atmosphere, the flow rate is controlled at 1 L / min, and the temperature is gradually increased to 250℃ at 5℃ / min and held for 2 hours to form abundant CS covalent bonds and stable thiophene structures in the sulfur-doped porous carbon.

[0027] 1.2 Phosphorus-carbon composite materials (1) Add 4.5g of red phosphorus, 5.4g of sulfur-doped porous carbon and 0.1g of elemental sulfur into a nylon tube and grind it at a speed of 110r / min (ball-to-material ratio of 5:1) for 6h. The mixture obtained after uniform mixing has a red phosphorus content of 45%. The mixture is vacuum sealed and then placed in a tube furnace and kept at 660℃ for 4h to allow the red phosphorus to sublimate into white phosphorus. Then, the temperature is lowered to 260℃ and kept for 18h to allow the gaseous white phosphorus to be converted into red phosphorus and deposited in the sulfur-doped porous carbon. After cooling to room temperature, phosphorus-carbon material is obtained.

[0028] (2) Weigh 0.925g of cadmium nitrate and place it in a 500mL beaker. Add 200mL of deionized water and sonicate for 6min until completely dissolved to obtain a cadmium nitrate solution. Weigh 7.308g of thiourea and add it to a beaker. Then add 120mL of ammonia (concentration of 28 wt%) and 200mL of deionized water and mix to obtain a CdS chemical bath growth solution.

[0029] (3) Place 10g of the phosphorus-carbon material obtained in step (1) into the CdS chemical bath growth solution obtained in step (2), and deposit it in a water bath at 65°C. After stirring continuously for 3 hours during the deposition process, it is ultrasonically treated for 10 minutes, filtered, and dried under vacuum at 85°C to obtain the CdS-coated phosphorus-carbon anode material.

[0030] (4) The CdS-coated phosphorus-carbon anode material obtained in step (3), 1.7 g of silver nitrate and 0.6 g of urea were mixed, 50 mL of deionized water was added, and the mixture was stirred evenly. The mixture was then reacted in a reactor at 150 °C for 2 h, filtered, and dried under vacuum at 85 °C to obtain 10.41 g of Ag. 1-x Cd x S-coated phosphorus-carbon anode material is an in-situ deposited phosphorus-carbon anode material.

[0031] The porous carbon has a specific surface area of ​​1531 m². 2 / g, pore volume is 0.697cm³ 3 / g, D50 is 8.04μm; sulfur doping is 1% by mass, and phosphorus deposition is 45%.

[0032] Example 2 2.1 Sulfur-doped porous carbon (1) Mix 50g of ion exchange resin D113 and 50g of ionic liquid phenothiazine hydrogen sulfate evenly and put them into a crucible. Place the crucible into a tube furnace and then, under the atmosphere of nitrogen and carbon dioxide, control the flow rate at 1L / min and the flow ratio of the two gases at 1:1. Gradually raise the temperature to 950℃ at 5℃ / min and hold for 5h. Then, under the atmosphere, introduce a pyrolysis mixture of 1,2-ethylenedithiol, tert-butyl disulfide and tert-butyl mercaptan at a flow ratio of 1:1:1 and control the flow rate at 300mL / min. Hold for 2h and cool to room temperature to obtain sulfur-doped porous carbon.

[0033] (2) The sulfur-doped porous carbon obtained in step (1) is placed in a sagger, and the sagger is placed in a tube furnace. Under a nitrogen atmosphere, the flow rate is controlled at 1 L / min, and the temperature is gradually increased to 250℃ at 5℃ / min and held for 2 hours to form abundant CS covalent bonds and stable thiophene structures in the sulfur-doped porous carbon.

[0034] 2.2 Phosphorus-carbon composite materials The preparation process is the same as that of the phosphorus-carbon composite material in Example 1.

[0035] The porous carbon has a specific surface area of ​​1582 m². 2 / g, pore volume is 0.709cm³ 3 / g, D50 is 8.13μm; sulfur doping ratio is 2.7%, phosphorus deposition is 49%.

[0036] Example 3 3.1 Sulfur-doped porous carbon (1) Mix 50g of ion exchange resin D113 and 50g of ionic liquid phenothiazine hydrogen sulfate evenly and put them into a crucible. Place the crucible into a tube furnace and then, under the atmosphere of nitrogen and carbon dioxide, control the flow rate at 1L / min and the flow ratio of the two gases at 1:1. Gradually raise the temperature to 950℃ at 5℃ / min and hold for 5h. Then, under the atmosphere, introduce a pyrolysis mixture of 1,2-ethylenedithiol, tert-butyl disulfide and tert-butyl mercaptan at a flow ratio of 1:1:1 and control the flow rate at 500mL / min. Hold for 2h and cool to room temperature to obtain sulfur-doped porous carbon.

[0037] (2) The sulfur-doped porous carbon obtained in step (1) is placed in a sagger, and the sagger is placed in a tube furnace. Under a nitrogen atmosphere, the flow rate is controlled at 1 L / min, and the temperature is gradually increased to 250℃ at 5℃ / min and held for 2 hours to form abundant CS covalent bonds and stable thiophene structures in the sulfur-doped porous carbon.

[0038] 3.2 Phosphorus-carbon composite materials The preparation process is the same as that of the phosphorus-carbon composite material in Example 1.

[0039] The porous carbon has a specific surface area of ​​1648 m². 2 / g, pore volume is 0.717cm³ 3 / g, D50 is 8.06μm; sulfur doping ratio is 4.8%, phosphorus deposition is 46%.

[0040] Example 4 4.1 Sulfur-doped porous carbon (1) Mix 50g of ion exchange resin D113 and 50g of ionic liquid phenothiazine hydrogen sulfate evenly and put them into a crucible. Place the crucible into a tube furnace and then, under the atmosphere of nitrogen and carbon dioxide, control the flow rate at 1L / min and the flow ratio of the two gases at 1:1. Gradually raise the temperature to 950℃ at 5℃ / min and hold for 5h. Then, under the atmosphere, introduce a pyrolysis mixture of 1,2-ethylenedithiol, tert-butyl disulfide and tert-butyl mercaptan at a flow ratio of 1:1:1 and control the flow rate at 300mL / min. Hold for 2h and cool to room temperature to obtain sulfur-doped porous carbon.

[0041] (2) The sulfur-doped porous carbon obtained in step (1) is placed in a sagger, and the sagger is placed in a tube furnace. Under a nitrogen atmosphere, the flow rate is controlled at 1L / min, and the temperature is gradually increased to 150℃ at 5℃ / min and held for 2h. Abundant CS covalent bonds and stable thiophene structures are formed in the sulfur-doped porous carbon.

[0042] 4.2 Phosphorus-carbon composite materials The preparation process is the same as that of the phosphorus-carbon composite material in Example 1.

[0043] The porous carbon has a specific surface area of ​​1543 m². 2 / g, pore volume is 0.704cm³ 3 / g, D50 is 8.14μm; sulfur doping ratio is 1.6%, phosphorus deposition is 44%.

[0044] Example 5 5.1 Sulfur-doped porous carbon (1) Mix 50g of ion exchange resin D113 and 50g of ionic liquid phenothiazine hydrogen sulfate evenly and put them into a crucible. Place the crucible into a tube furnace and then, under the atmosphere of nitrogen and carbon dioxide, control the flow rate at 1L / min and the flow ratio of the two gases at 1:1. Gradually raise the temperature to 950℃ at 5℃ / min and hold for 5h. Then, under the atmosphere, introduce a pyrolysis mixture of 1,2-ethylenedithiol, tert-butyl disulfide and tert-butyl mercaptan at a flow ratio of 1:1:1 and control the flow rate at 300mL / min. Hold for 2h and cool to room temperature to obtain sulfur-doped porous carbon.

[0045] (2) The porous carbon obtained in step (1) is placed in a sagger, and the sagger is placed in a tube furnace. Under a nitrogen atmosphere, the flow rate is controlled at 1L / min, and the temperature is gradually increased to 450℃ at 5℃ / min and held for 2h. Abundant CS covalent bonds and stable thiophene structures are formed in the sulfur-doped porous carbon.

[0046] 5.2 Phosphorus-carbon composite materials The preparation process is the same as that of the phosphorus-carbon composite material in Example 1.

[0047] The porous carbon has a specific surface area of ​​1597 m². 2 / g, pore volume is 0.711cm³ 3 / g, D50 is 8.09μm; sulfur doping ratio is 4.2%, phosphorus deposition is 52%.

[0048] Comparative Example 1 The only difference between this comparative example and Example 2 is that the carbon source used is phenolic resin.

[0049] The specific steps for preparing sulfur-doped porous carbon are as follows: (1) 100g of phenolic resin was evenly placed into a sagger, and the sagger was placed in a tube furnace. Then, under the atmosphere of nitrogen and carbon dioxide mixture, the flow rate was controlled at 1L / min and the flow ratio of the two gases was 1:1. The temperature was gradually increased to 950℃ at 5℃ / min and held for 5h. Then, under the atmosphere, pyrolysis mixture of 1,2-ethylenedithiol, tert-butyl disulfide and tert-butyl mercaptan in a flow ratio of 1:1:1 was introduced and the flow rate was controlled at 300mL / min. The temperature was held for 2h and then cooled to room temperature to obtain sulfur-doped porous carbon.

[0050] (2) The porous carbon obtained in step (1) is placed in a sagger, and the sagger is placed in a tube furnace. Under a nitrogen atmosphere, the flow rate is controlled at 1L / min, and the temperature is gradually increased to 250℃ at 5℃ / min and held for 2h. Abundant CS covalent bonds and stable thiophene structures are formed in the sulfur-doped porous carbon.

[0051] The preparation process of the phosphorus-carbon composite material is the same as that of the phosphorus-carbon composite material in Example 1.

[0052] The porous carbon has a specific surface area of ​​1464 m². 2 / g, pore volume is 0.681cm³ 3 / g, D50 is 8.21μm; sulfur doping ratio is 1.5%, phosphorus deposition is 42%.

[0053] Comparative Example 2 The only difference between this comparative example and Example 2 is that sulfur doping is not performed.

[0054] The specific steps for preparing porous carbon are as follows: (1) Mix 50g of ion exchange resin D113 and 50g of ionic liquid phenothiazine hydrogen sulfate evenly and put them into a crucible. Place the crucible into a tube furnace and then, under the atmosphere of nitrogen and carbon dioxide mixture, control the flow rate at 1L / min and the flow ratio of the two gases at 1:1, gradually raise the temperature to 950℃ at 5℃ / min and keep it at that temperature for 5h.

[0055] (2) Place the porous carbon obtained in step (1) into a sagger, place the sagger into a tube furnace, and under a nitrogen atmosphere, control the flow rate at 1L / min, gradually increase the temperature to 250℃ at 5℃ / min and keep it at that temperature for 2h to obtain porous carbon.

[0056] The preparation process of the phosphorus-carbon composite material is the same as that of the phosphorus-carbon composite material in Example 1.

[0057] The porous carbon has a specific surface area of ​​1527 m². 2 / g, pore volume is 0.701cm³ 3 / g, D50 is 8.11μm; sulfur doping ratio is 0%, phosphorus deposition is 37%.

[0058] Comparative Example 3 The only difference between this comparative example and Example 2 is that no low-temperature treatment was performed.

[0059] The specific steps for preparing sulfur-doped porous carbon are as follows: (1) Mix 50g of ion exchange resin D113 and 50g of ionic liquid phenothiazine hydrogen sulfate evenly and put them into a crucible. Place the crucible into a tube furnace and then, under the atmosphere of nitrogen and carbon dioxide, control the flow rate at 1L / min and the flow ratio of the two gases at 1:1. Gradually raise the temperature to 950℃ at 5℃ / min and hold for 5h. Then, under the atmosphere, introduce a pyrolysis mixture of 1,2-ethylenedithiol, tert-butyl disulfide and tert-butyl mercaptan at a flow ratio of 1:1:1 and control the flow rate at 300mL / min. Hold for 2h and cool to room temperature to obtain porous carbon products.

[0060] The preparation process of the phosphorus-carbon composite material is the same as that of the phosphorus-carbon composite material in Example 1.

[0061] The porous carbon has a specific surface area of ​​1532 m². 2 / g, pore volume is 0.702cm³ 3 / g, D50 is 8.12μm; sulfur doping ratio is 0.5%, phosphorus deposition is 38%.

[0062] Material characterization and performance testing (1) Figure 1 This is a scanning electron microscope (SEM) image of the sulfur-doped porous carbon in Example 2. Figure 2 The images shown are cross-sectional electron microscope images and corresponding elemental distributions of sulfur-doped porous carbon after phosphorus deposition in Example 2. Combined with the test results in Table 1, uniform sulfur doping enhances the amount of phosphorus deposited and improves the uniformity of phosphorus deposition.

[0063] (2) Using the phosphorus-carbon composite materials obtained in Examples 1-5 and Comparative Examples 1-3 as negative electrode active materials, button batteries were prepared respectively: The phosphorus-carbon composite material, polyacrylic acid PAA, carbon-based conductive agent Super-P and styrene-butadiene rubber SBR were prepared into a slurry in a mass ratio of 80:10:7:3. The slurry was uniformly coated on a copper foil current collector and dried in a vacuum oven at 85°C for 12 hours to obtain a negative electrode sheet. A lithium metal sheet was used as the counter electrode, glass fiber was used as the separator, and NaClO4 solution (concentration of 1 mol / L, solvent is ethylene carbonate and dimethyl carbonate mixed in a volume ratio of 1:1) was used as the electrolyte. The button batteries were assembled in an argon-protected glove box.

[0064] The prepared button cells were subjected to constant current charge-discharge tests: the current density was 300 mA / g, and the charge-discharge voltage range was 0.005 to 2.0 V. The results are shown in Table 1.

[0065] Table 1. Performance test results of button batteries

[0066] As can be seen from the table, the preparation method of this application uniformly dops sulfur into porous carbon materials, thereby enhancing the deposition efficiency of phosphorus, promoting the uniformity of phosphorus deposition in porous carbon, and improving the kinetic properties of phosphorus-carbon.

[0067] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing sulfur-doped porous carbon, characterized in that, Includes the following steps: Provide a carbon source, wherein the carbon source is one or a mixture of two or more of ion exchange resins or ion liquids; The carbon source is subjected to high-temperature pore formation in a mixed atmosphere of CO2 and non-reactive gas; then, pyrolysis gas containing sulfur organic compounds is introduced and sulfidation is carried out at high temperature to obtain sulfur-doped porous carbon with a large number of defects. The sulfur-doped porous carbon was placed in a non-reactive atmosphere and subjected to low-temperature treatment at 150-450°C to form CS covalent bonds and stable thiophene structures.

2. The preparation method according to claim 1, characterized in that, The sulfur-containing organic compound is one or a mixture of two or more of 1,2-ethanedithiol, tert-butyl disulfide, and tert-butyl mercaptan.

3. The preparation method according to claim 2, characterized in that, The flow rate ratio of 1,2-ethanedithiol, tert-butyl disulfide, and tert-butyl mercaptan is 1:0-2:0-2; the total flow rate of the sulfur-containing organic compound pyrolysis gas is 50-500 mL / min.

4. The preparation method according to claim 1, characterized in that, In the mixed atmosphere, the volumetric flow rate ratio of CO2 to non-reactive gas is 1:0.5-2, and the total flow rate is 0.5-1.5 L / min.

5. The preparation method according to claim 1, characterized in that, The high-temperature pore-forming temperature is 850-1000℃, and the temperature is maintained at this temperature for 4-8 hours.

6. The preparation method according to claim 1, characterized in that, The specific process of the high-temperature vulcanization is as follows: maintain the temperature of the high-temperature pore-forming process, introduce the pyrolysis gas containing sulfur organic compounds, and keep it at the temperature for 0.1-5 hours.

7. The preparation method according to claim 1, characterized in that, The process conditions for the low-temperature treatment are as follows: heating to 150-450℃ in a non-reactive gas and holding at this temperature for 1-3 hours; the flow rate of the non-reactive gas is 0.5-1.5L / min, and the purity is ≥99%.

8. A sulfur-doped porous carbon, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. A phosphorus-carbon composite material, characterized in that, It includes a porous carbon support deposited with phosphorus, wherein the porous carbon support is the sulfur-doped porous carbon as described in claim 8.

10. The phosphorus-carbon composite material as described in claim 9, characterized in that, In the phosphorus-carbon composite material, the phosphorus deposition content is 35-55%.

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