Red phosphorus / carbon composite based on selenium catalyst and preparation method and application thereof

Abstract

This invention discloses a red phosphorus / carbon composite material based on a selenium catalyst, its preparation method, and its application. The preparation method includes the following steps: pre-treating porous carbon and red phosphorus separately by vacuum drying; mixing the porous carbon, red phosphorus, and selenium-based catalyst, placing the mixture in a sealed container, and heat-treating it under vacuum conditions to obtain the composite product. The preparation method of this invention uses a selenium-based compound as a highly efficient and stable catalyst, solving the problem of white phosphorus residue, avoiding process contamination, and ensuring the overall performance of sodium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a red phosphorus / carbon composite material based on a selenium catalyst, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries, as a new generation of large-scale energy storage technology, have attracted widespread attention due to the advantages of abundant sodium resources and low cost. Developing anode materials with high specific capacity and long cycle stability is the core key to promoting their commercial application.

[0003] Among numerous anode material candidates, red phosphorus, with its theoretical specific capacity of up to 2596 mAh / g and suitable sodium intercalation potential, is considered one of the most promising anode materials. However, red phosphorus faces two inherent bottlenecks in practical applications: first, it undergoes approximately 300% volume expansion during charge-discharge alloying / dealloying, which easily leads to material pulverization and structural collapse, resulting in rapid degradation of cycle performance; second, its intrinsic electronic conductivity is extremely low, causing sluggish electrode reaction kinetics and poor rate performance.

[0004] In existing technologies, combining red phosphorus with porous carbon materials is an effective way to solve the above problems. Currently, the evaporation deposition method is a common method for preparing red phosphorus / carbon composite materials. This method involves heating solid red phosphorus to sublimate it into white phosphorus vapor, which then penetrates into the pores of porous carbon and is subsequently converted back into red phosphorus through appropriate temperature treatment. However, this process has significant technical drawbacks: highly toxic, flammable, and explosive white phosphorus is easily left behind during the conversion process, posing serious safety risks and greatly restricting the practical industrial application of this type of material. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one objective of this invention is to propose a red phosphorus / carbon composite material based on a selenium catalyst, its preparation method, and its application. By using a selenium-based compound as a highly efficient and stable catalyst, the problem of white phosphorus residue is solved, process contamination is avoided, and the overall performance of sodium-ion batteries can be guaranteed.

[0006] According to a first aspect of the present invention, a method for preparing a red phosphorus / carbon composite material based on a selenium catalyst includes the following steps: pre-treating porous carbon and red phosphorus by vacuum drying; mixing the porous carbon, the red phosphorus, and the selenium-based catalyst, placing the mixture in a sealed container, and heat-treating it under vacuum conditions to obtain the composite product.

[0007] Optionally, the selenium-based catalyst is elemental selenium or phosphorus pentaselenide.

[0008] Optionally, the porous carbon contains one or more of the following: micropores, mesopores, and macropores.

[0009] Optionally, the raw material weight ratio of red phosphorus and porous carbon in the mixture is (5-0.5):1.

[0010] Optionally, in the mixture, the mass of the selenium-based catalyst is 1wt%-5wt% of the mass of the red phosphorus.

[0011] Optionally, the heat treatment process is as follows: heating from room temperature (25℃) to 450℃-550℃ at a heating rate of 3℃ / min-5℃ / min, holding at that temperature for 3h-5h, then cooling down to 250℃-270℃ at a cooling rate of 3℃ / min-5℃ / min, holding at that temperature for 24h-48h, and then allowing to cool naturally.

[0012] Optionally, the pretreatment conditions are vacuum drying at 80℃-120℃ for 8-10 hours.

[0013] Optionally, when preparing the mixture, the vacuum-dried red phosphorus and the porous carbon are placed in a mortar, and the selenium-based catalyst is added, and then ground and mixed evenly.

[0014] According to a second aspect of the present invention, a red phosphorus / carbon composite material based on a selenium catalyst comprises a composite product prepared by any of the above preparation methods.

[0015] According to a third aspect of the present invention, a method for preparing a red phosphorus / carbon composite material based on a selenium catalyst is applied in the preparation of a sodium-ion battery. The composite product prepared by any of the above-described methods is used in the sodium-ion battery.

[0016] According to the present invention, a method for preparing red phosphorus / carbon composite materials based on selenium catalysts involves heat-treating porous carbon with a porous structure, red phosphorus, and a selenium-based catalyst under a closed vacuum environment to produce high-performance red phosphorus / carbon composite materials, i.e., composite products. By employing a selenium-based catalyst, the technical bottlenecks of traditional catalysts in terms of process contamination and electrochemical compatibility are successfully overcome, providing reliable technical support for the industrial production and practical application of red phosphorus / carbon composite materials.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a diagram showing the ignition state of the product in air atmosphere corresponding to Example 2; Figure 2 This is a diagram showing the ignition state of the product in air atmosphere corresponding to Comparative Example 1. Figure 3 This is the XRD pattern corresponding to the product of Example 2; Figure 4 This is the first-week charge-discharge curve of the product from Example 2; Figure 5 This is a graph showing the capacity retention rate change after 10 cycles at 0.1C in Example 2. Detailed Implementation

[0019] The negative electrode slurry according to an embodiment of the present invention will be described in detail below.

[0020] The preparation method of red phosphorus / carbon composite material based on selenium catalyst according to embodiments of the present invention includes the following steps: Porous carbon and red phosphorus were pretreated by vacuum drying.

[0021] After mixing porous carbon, red phosphorus and selenium-based catalyst, the mixture is placed in a sealed container, which can be corrosion resistant.

[0022] Subsequently, heat treatment was performed under vacuum conditions to obtain the composite product.

[0023] First, selenium-based catalysts, through their unique electronic structure characteristics, significantly promote the conversion of white phosphorus to red phosphorus, completely eliminating white phosphorus residue and fundamentally solving the risk of spontaneous combustion during the preparation, storage, and use of materials, thus ensuring the inherent safety of production processes and product applications.

[0024] Secondly, compared to iodine catalysts, which are prone to sublimation, and sulfur catalysts, which are prone to initiating side reactions, the selenium and its compounds (such as phosphorus pentaselenide) used in the embodiments of this invention have extremely low vapor pressures at the process temperature, resulting in no sublimation loss or equipment contamination issues. Simultaneously, selenium exhibits chemical stability in the battery operating environment, avoiding side effects such as electrolyte decomposition and electrode interface deterioration caused by sulfur catalysts, demonstrating excellent environmental compatibility.

[0025] Furthermore, based on the unique advantages of selenium catalysts, the composite product prepared in this embodiment of the invention achieves a breakthrough in electrochemical performance. The composite product exhibits high specific capacity and excellent cycle stability, and can be applied as a high-performance anode material for sodium-ion batteries.

[0026] In this embodiment, a high-performance red phosphorus / carbon composite material, i.e., the composite product, can be prepared by heat-treating porous carbon with a porous structure, red phosphorus, and a selenium-based catalyst under a closed vacuum environment. By using a selenium-based catalyst, the technical bottlenecks of traditional catalysts in terms of process pollution and electrochemical compatibility are successfully solved, providing reliable technical support for the industrial production and practical application of red phosphorus / carbon composite materials.

[0027] According to one embodiment of the present invention, the selenium-based catalyst is elemental selenium (Se) or phosphorus pentaselenide (P2Se5). It is understood that selenium and related selenium-phosphorus compounds have low vapor pressures at the process temperature and are difficult to sublimate, thus enabling them to exert a continuous and stable catalytic effect, ensuring complete conversion of white phosphorus, fundamentally eliminating white phosphorus residue in the product, and achieving inherent safety in the preparation process.

[0028] In some specific embodiments of the present invention, porous carbon contains one or more of micropores, mesopores, and macropores. For example, microporous carbon or mesoporous carbon can be used. Its high specific surface area and adjustable pore structure can be utilized to penetrate into the pores of porous carbon after solid red phosphorus sublimates into white phosphorus vapor.

[0029] According to one embodiment of the present invention, the weight ratio of red phosphorus to porous carbon in the mixture is (5-0.5):1. For example, the weight ratio of red phosphorus to porous carbon in the mixture is 0.5:1, 1:1, 2:1, 3:1, 4:1, or 5:1, etc. By adopting the above-mentioned weight ratio, not only can the red phosphorus be deposited in the pores of the porous carbon, but the overall performance of the battery can also be guaranteed.

[0030] In some specific embodiments of the present invention, the mass of the selenium-based catalyst in the mixture is 1wt%-5wt% of the mass of red phosphorus. For example, the mass of the selenium-based catalyst in the mixture is 1wt%, 2wt%, 3wt%, 4wt%, or 5wt% of the mass of red phosphorus. In this embodiment, by limiting the above mass ratio, while ensuring efficient catalysis and improving reaction kinetics, excess inactive components can be avoided, thereby balancing the capacity, rate capability, and cycle stability of the sodium-ion battery.

[0031] According to one embodiment of the present invention, the heat treatment process is as follows: the temperature is increased from room temperature (25°C) to 450°C-550°C at a heating rate of 3°C / min-5°C / min, held for 3-5 hours, then decreased to 250°C-270°C at a cooling rate of 3°C / min-5°C / min, held for 24-48 hours, and then allowed to cool naturally. The above numerical ranges include the endpoints. Preferably, the temperature is increased to 500°C at a heating rate of 3°C / min, held for 3 hours, then decreased to 260°C at a cooling rate of 3°C / min, held for 24 hours, and then allowed to cool naturally. By employing the above heat treatment process, advantages such as a moderate red phosphorus sublimation rate and a short deposition time of white phosphorus vapor within the porous carbon pores are achieved.

[0032] In some specific embodiments of the present invention, the pretreatment conditions are vacuum drying at 80℃-120℃ for 8-10 hours, and the above-mentioned numerical range includes the endpoints. Preferably, the pretreatment conditions are vacuum drying at 100℃ for 8 hours. By adopting the above pretreatment process, the advantages of high water removal efficiency and short time are achieved.

[0033] In some specific embodiments of the present invention, when preparing the mixture, vacuum-dried red phosphorus and porous carbon are placed in a mortar, and a selenium-based catalyst is added. The mixture is then ground and mixed evenly, which can improve the uniformity of dispersion and enhance the catalytic effect.

[0034] This invention also discloses a red phosphorus / carbon composite material based on a selenium catalyst, including the composite product prepared by the preparation method of any of the above embodiments, which can meet the dual needs of red phosphorus / carbon composite materials in industrial production and electrochemical applications.

[0035] This invention also discloses the application of a method for preparing red phosphorus / carbon composite material based on selenium catalyst in the preparation of sodium-ion batteries. The composite product prepared by the method of any of the above embodiments can be used in sodium-ion batteries to avoid pollution problems in the process and compatibility defects of red phosphorus / carbon composite material in sodium-ion batteries, which is beneficial to ensuring the overall performance of the battery.

[0036] The following detailed description of the red phosphorus / carbon composite material based on selenium catalyst of the present invention, its preparation method, and its application are illustrated with specific embodiments.

[0037] Example 1 First, porous carbon and red phosphorus were vacuum dried at 100°C for 8 hours.

[0038] Next, the dried raw materials were weighed at a mass ratio of red phosphorus to porous carbon of 3:1, placed in a mortar, and 2 wt% (by weight of red phosphorus) of elemental selenium powder was added and ground until homogeneous. The mixture was transferred to a stainless steel high-pressure reactor, evacuated, and then subjected to programmed heat treatment: the temperature was increased from room temperature (25°C) to 500°C at a rate of 3°C / min and held for 3 hours; then the temperature was decreased to 260°C at a rate of 3°C / min and held for 24 hours; followed by natural cooling. The sample was removed, and the product was obtained, denoted as Se-PC-1.

[0039] Example 2 The difference between this embodiment and Example 1 is that the mass ratio of red phosphorus to porous carbon is adjusted to 2:1, while the other steps and parameters are exactly the same. The resulting product is denoted as Se-PC-2.

[0040] Example 3 The difference between this embodiment and Example 1 is that the mass ratio of red phosphorus to porous carbon is adjusted to 1:1, while all other steps and parameters are exactly the same. The resulting product is denoted as Se-PC-3.

[0041] Example 4 The catalyst was changed from elemental selenium to an equal mass of phosphorus pentaselenide (P2Se5), and all other steps were exactly the same as in Example 2. The resulting product was designated P2Se5-PC.

[0042] Comparative Example 1 The steps were exactly the same as in Example 2, except that no catalyst was added. The resulting product was denoted as PC.

[0043] The parameters of each embodiment and comparative example, as well as the ignition situation of air atmosphere discharge, were statistically analyzed and summarized in Table 1 below.

[0044] Table 1 According to Table 1 and Figure 1 As shown, when the product was discharged in an air atmosphere, none of the examples with added selenium-based catalysts experienced spontaneous combustion, while Comparative Example 1, without added selenium-based catalysts, ignited immediately. This phenomenon originates from the white phosphorus remaining during the preparation of phosphorus-carbon materials by the evaporation deposition method. Without the addition of selenium-based catalysts, the residual white phosphorus in the product spontaneously combusts upon contact with air. However, with the addition of selenium-based catalysts, elemental selenium can react with gaseous white phosphorus (P4) during heat treatment to generate active intermediates such as phosphorus pentaselenide (P2Se5), significantly reducing the activation energy required for the polymerization of white phosphorus into red phosphorus and greatly accelerating the reaction process. Simultaneously, because selenium and related selenium-phosphorus compounds have low vapor pressures at the process temperature and are difficult to sublimate, they can continuously and stably exert a catalytic effect, ensuring complete conversion of white phosphorus and fundamentally eliminating residual white phosphorus in the product, thus achieving inherent safety in the preparation process.

[0045] XRD analysis was performed on the Se-PC-2 phosphorus carbon sample from Example 2, and the results were obtained. Figure 3 The XRD pattern shown reveals a characteristic peak combination of red phosphorus and porous carbon. Specifically, the characteristic peaks at 15° and 32° correspond to red phosphorus, while the peaks at 25° and 43° belong to porous carbon. Furthermore, no diffraction peaks related to elemental selenium were observed in the pattern, primarily due to the extremely low addition amount of the selenium-based catalyst. These results demonstrate that the selenium-based catalyst successfully promoted the composite of red phosphorus and porous carbon.

[0046] Furthermore, the phosphorus-carbon anode materials obtained in each embodiment were assembled into coin cells and their electrochemical performance was tested. The working electrode consisted of 70 wt% phosphorus-carbon anode material, 15 wt% Super P conductive agent, and 15 wt% binder (carboxymethyl cellulose CMC and styrene-butadiene rubber SBR), uniformly coated onto an aluminum foil current collector. The counter electrode was a sodium metal sheet, the separator was glass fiber, and the electrolyte was a mixture of 1 M NaPF6 dissolved in a 1:1 volume ratio of EC and DMC.

[0047] The specific surface area and electrochemical data of each embodiment are summarized in Table 2 below.

[0048] Table 2 Based on the structure of Table 2 and Figure 4 The first-week charge-discharge curves of Se-PC-2 show an extremely high first-cycle coulombic efficiency (90.02%) and a reversible specific capacity of 1248.91 mAh / g, significantly higher than the typical capacity of current hard carbon anode materials (300–400 mAh / g). Figure 5 As can be seen, after 10 cycles at an active substance loading of 2 mg / cm² and 0.1C (1C=600 mA / g), the material still retains 83.98% of its capacity, demonstrating good cycling stability.

[0049] Compared to Example 2, the mass ratio of red phosphorus to porous carbon in Example 1 was higher, resulting in the mixing of more excess red phosphorus powder during discharge. This portion of red phosphorus has low conductivity and lacks the buffering effect of the carbon matrix, thus reducing electrochemical performance, with the 10-cycle capacity retention rate decreasing to 63.42%.

[0050] In Example 3, the red phosphorus to porous carbon mass ratio was too low, resulting in insufficient phosphorus loading on the carbon and a large number of unfilled pores remaining in the porous carbon, thus leading to a large specific surface area (10.255 m² / g). The high specific surface area and low phosphorus loading together resulted in low initial efficiency (84.65%) and reversible specific capacity (1094.04 mAh / g).

[0051] Example 4 simply replaced elemental selenium with phosphorus pentaselenide. Its overall performance was similar to that of Example 2, with a low specific surface area (1.892 m² / g) and excellent electrochemical performance, with an initial efficiency of 90.33% and a reversible specific capacity of 1289.83 mAh / g.

[0052] The above embodiments and test results demonstrate that, in these embodiments of the invention, the use of selenium-based catalysts, particularly elemental selenium, enables the efficient and safe catalytic preparation of red phosphorus / carbon composite materials. This method not only completely eliminates white phosphorus residue but also overcomes the drawbacks of iodine catalysts (easily sublimating and causing contamination) and sulfur catalysts (easily initiating electrochemical side reactions). The composite material prepared by the method of these embodiments of the invention, when used as a negative electrode in sodium-ion batteries, exhibits high specific capacity and excellent cycle stability, demonstrating significant potential for industrial applications.

[0053] In summary, this invention addresses the aforementioned problems of the vapor deposition method by providing a method for preparing red phosphorus / carbon composite materials. By employing a selenium-based catalyst, the conversion of white phosphorus to red phosphorus can be promoted, effectively avoiding the spontaneous combustion safety issues caused by residual white phosphorus and solving the problem of volatile pollution. In other words, by selecting a selenium-based catalyst, the technical bottlenecks of traditional catalysts in terms of process pollution and electrochemical compatibility are successfully overcome, providing reliable technical support for the industrial production and practical application of red phosphorus / carbon composite materials.

[0054] Other configurations and operations of the sodium-ion battery according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0055] In the description of this invention, it should be understood that the terms "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "inner", "outer", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0056] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0057] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0058] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a red phosphorus / carbon composite material based on a selenium catalyst, characterized in that, Includes the following steps: Porous carbon and red phosphorus were pretreated by vacuum drying. After mixing the porous carbon, the red phosphorus, and the selenium-based catalyst, the mixture is placed in a sealed container and heat-treated under vacuum conditions to obtain the composite product.

2. The preparation method according to claim 1, characterized in that, The selenium-based catalyst is elemental selenium or phosphorus pentaselenide.

3. The preparation method according to claim 1, characterized in that, The porous carbon contains one or more of the following: micropores, mesopores, and macropores.

4. The preparation method according to claim 1, characterized in that, In the mixture, the raw material weight ratio of red phosphorus and porous carbon is (5-0.5):

1.

5. The preparation method according to claim 1, characterized in that, In the mixture, the mass of the selenium-based catalyst is 1wt%-5wt% of the mass of the red phosphorus.

6. The preparation method according to claim 1, characterized in that, The heat treatment process is as follows: the temperature is increased from room temperature (25℃) to 450℃-550℃ at a heating rate of 3℃ / min-5℃ / min, held for 3h-5h, then cooled to 250℃-270℃ at a cooling rate of 3℃ / min-5℃ / min, held for 24h-48h, and then allowed to cool naturally.

7. The preparation method according to claim 1, characterized in that, The pretreatment conditions are vacuum drying at 80℃-120℃ for 8-10 hours.

8. The preparation method according to claim 1, characterized in that, In preparing the mixture, the vacuum-dried red phosphorus and the porous carbon are placed in a mortar, and the selenium-based catalyst is added and ground and mixed evenly.

9. A red phosphorus / carbon composite material based on a selenium catalyst, characterized in that, This includes composite products prepared by any of the preparation methods according to claims 1-8.

10. The application of a method for preparing a red phosphorus / carbon composite material based on a selenium catalyst in the preparation of sodium-ion batteries, characterized in that, The composite product prepared by the preparation method according to any one of claims 1-8 is used in the sodium-ion battery.

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