Carbon-phosphorus composite material as well as preparation method and application thereof

Abstract

The embodiment of the invention relates to a carbon-phosphorus composite material as well as a preparation method and application thereof, and the preparation method comprises the following steps: placing porous carbon in a vapor deposition furnace at room temperature, then introducing inert gas into the vapor deposition furnace, and heating the vapor deposition furnace to a deposition temperature; first mixed gas of phosphorane and inert gas is introduced into the vapor deposition furnace, so that the phosphorane is decomposed into phosphorus nano-particles at the deposition temperature, the phosphorus nano-particles are deposited in pores of the porous carbon, and a carbon-phosphorus compound is obtained; the carbon-phosphorus compound is placed in a cladding furnace, then inert gas is introduced into the cladding furnace, and the cladding furnace is heated to the cladding temperature; and second mixed gas of inert gas and carbon source gas is introduced into the coating furnace, so that the carbon source gas performs carbon coating on the carbon-phosphorus compound at the coating temperature, and the carbon-phosphorus composite material is obtained.

Description

Technical Field

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

[0002] Energy storage technology will play a key role in the process of achieving the goals of "carbon peak and carbon neutrality". Among them, electrochemical energy storage systems are currently the focus of research and development at home and abroad. Compared with lithium-ion batteries, sodium-ion batteries have relatively low costs and are expected to be widely used in future energy storage systems. However, their practical application process is still restricted by the lack of suitable positive and negative electrode materials, especially high-performance and practical negative electrode materials.

[0003] At present, the negative electrode materials for sodium-ion batteries include carbon-based materials, alloy materials, metal oxides, metal sulfides, and metal phosphides, etc. Among them, carbon-based materials are mainly amorphous carbon, such as hard carbon, but the specific capacity of hard carbon materials is relatively low; moreover, most of the capacity of hard carbon materials is achieved in the voltage range below 0.1V, and this potential is very close to the precipitation potential of metallic sodium, which is extremely likely to cause sodium dendrites to precipitate on the electrode surface, severely restricting the capacity utilization and the improvement of the charging rate. Therefore, hard carbon materials cannot meet the requirements of high-energy density electrode materials for various application scenarios.

[0004] Phosphorus has a theoretical specific capacity as high as 2596 mAh / g, and has advantages such as a relatively high working voltage, high stability, and good safety, thus receiving extensive attention. However, during the cycling process of phosphorus-based negative electrode materials, with the insertion and extraction of lithium / sodium ions, the volume expansion rate is about 300%, resulting in poor cycling performance. In addition, the conductivity of phosphorus-based negative electrode materials is poor, resulting in poor rate performance, severely restricting the application of phosphorus-based negative electrode materials in lithium-ion / sodium-ion batteries. Summary of the Invention

[0005] The object of the present invention is to address the deficiencies existing in the prior art, and to provide a carbon-phosphorus composite material, a preparation method thereof, and an application thereof, which carbon-phosphorus composite material has good cycle stability and rate performance.

[0006] To achieve the above object, in the first aspect, the present invention provides a preparation method of a carbon-phosphorus composite material, and the preparation method includes:

[0007] Under room temperature conditions, place porous carbon in a chemical vapor deposition furnace, and then introduce an inert gas into the chemical vapor deposition furnace and heat the chemical vapor deposition furnace to a deposition temperature;

[0008] Introduce a first mixed gas of phosphine and an inert gas into the chemical vapor deposition furnace, so that phosphine decomposes into phosphorus nanoparticles at the deposition temperature and deposits in the pores of the porous carbon to obtain a carbon-phosphorus composite;

[0009] Place the carbon-phosphorus composite in a coating furnace, then introduce an inert gas into the coating furnace and heat the coating furnace to the coating temperature.

[0010] Introduce a second mixed gas of the inert gas and a carbon source gas into the coating furnace, so that the carbon source gas performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0011] Preferably, the inert gas is nitrogen and / or argon.

[0012] Preferably, the deposition temperature is 500°C - 700°C; in the first mixed gas, the volume ratio of phosphine to the inert gas is 1:6 - 3:1, and the introduction time is 0.5 - 7 hours.

[0013] Preferably, the carbon source gas is one or more of acetylene, ethylene, and methane.

[0014] Preferably, the coating temperature is 500°C - 900°C; in the second mixed gas, the volume ratio of the inert gas to the carbon source gas is 1:3 - 3:2, and the introduction time is 2 hours - 6 hours.

[0015] In a second aspect, the present invention provides a carbon-phosphorus composite material, which is prepared by the preparation method according to any one of the first aspects above; the structure of the carbon-phosphorus composite material includes a shell and a core.

[0016] The core is a carbon-phosphorus composite composed of porous carbon and phosphorus nanoparticles deposited in the pores of the porous carbon.

[0017] The shell is coated on the outer surface of the core, and the shell is a carbon coating layer.

[0018] Preferably, the mass percentage of the porous carbon in the carbon-phosphorus composite is 15% - 99%; the mass percentage of the carbon-phosphorus composite in the carbon-phosphorus composite material is 85% - 99%; the mass percentage of the phosphorus nanoparticles in the carbon-phosphorus composite material is 0.1% - 85%.

[0019] Preferably, the porosity of the porous carbon is 30% - 70%, and the pore diameter is 1 nm - 300 nm.

[0020] In a third aspect, the present invention provides a negative electrode plate, which includes the carbon-phosphorus composite material according to any one of the second aspects.

[0021] In a fourth aspect, the present invention provides a secondary battery, which includes the negative electrode plate according to the third aspect.

[0022] A preparation method of a carbon-phosphorus composite material provided by an embodiment of the present invention uses porous carbon as a support body. Through chemical vapor deposition, phosphorus nanoparticles obtained by the thermal decomposition of phosphine are deposited in the pores of the porous carbon. The obtained carbon-phosphorus composite combines the excellent properties of porous carbon and phosphorus. The porous carbon can inhibit the volume expansion of phosphorus during cycling, extending the cycle life of the battery. The particle size of the phosphorus nanoparticles is small, which can reduce the ion insertion / extraction distance and improve the rate performance of the battery. A carbon coating layer is formed through a carbon coating process, which plays a protective role for the carbon-phosphorus composite, preventing the phosphorus nanoparticles from falling off due to volume expansion during charge and discharge. At the same time, it can also enhance the conductivity of the carbon-phosphorus composite and reduce the negative impact caused by the poor conductivity of phosphorus, thereby improving the rate performance of the battery. This preparation method has a simple process and is easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flowchart of the preparation method of the carbon-phosphorus composite material provided by the embodiment of the present invention;

[0024] Figure 2 It is a schematic diagram of the preparation process of the carbon-phosphorus composite material provided by the embodiment of the present invention;

[0025] Figure 3 It is the first charge-discharge curve graph of the coin-type half-cells assembled with Examples 1-6 and Comparative Example 1 of the present invention;

[0026] Figure 4 It is the capacity retention rate graph of the coin-type half-cells assembled with Examples 1-6 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0028] The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

[0029] An embodiment of the present invention provides a preparation method of a carbon-phosphorus composite material, which specifically includes the steps as Figure 1 shown below:

[0030] Step 110, at room temperature, place the porous carbon in a chemical vapor deposition furnace, then introduce an inert gas into the chemical vapor deposition furnace and heat the chemical vapor deposition furnace to the deposition temperature;

[0031] Among them, the porous carbon may specifically include one or more of activated carbon, carbon aerogel, ordered mesoporous carbon, carbide-derived carbon, zeolite-templated carbon, salt-templated carbon, and metal-organic framework (MOF)-derived carbon. The porosity of the porous carbon may specifically be 30%-70%, preferably 40%-60%, and the pore diameter may specifically be 1 nm - 300 nm, preferably 1 nm - 200 nm. Figure 2 The microstructure of the porous carbon is shown in Figure 2 . The inert gas may specifically be nitrogen and / or argon. The heating rate may specifically be 3 °C / min - 6 °C / min. The deposition temperature may specifically be 500 °C - 700 °C, preferably 500 °C - 650 °C.

[0032] Step 120: Introduce a first mixed gas of phosphine and an inert gas into the chemical vapor deposition furnace, so that the phosphine decomposes into phosphorus nanoparticles at the deposition temperature and deposits in the pores of the porous carbon to obtain a carbon-phosphorus composite.

[0033] Specifically, in the first mixed gas, the volume ratio of phosphine to the inert gas is specifically 1:6 - 3:1, preferably 1:5 - 1:1. The introduction time of the first mixed gas is 0.5 hour - 7 hours, preferably 1 hour - 6 hours. The chemical equation for the thermal decomposition of phosphine is as follows:

[0034] 2PH→2P + 3H 2

[0035] The phosphine thermally decomposes into phosphorus nanoparticles with a size of 0.5 nm - 50 nm. In this way, the ion deintercalation distance is reduced, and the rate performance of the battery can be improved. Then, the phosphorus nanoparticles are deposited in the pores of the porous carbon by chemical vapor deposition, as shown in Figure 2 . The porous carbon as a support can inhibit the volume expansion of phosphorus during cycling and extend the battery cycle life. At the same time, it can also provide good electronic conductivity, which helps to improve the rate performance of the battery. Figure 2

[0036] Step 130: Place the carbon-phosphorus composite in a coating furnace, then introduce an inert gas into the coating furnace and heat the coating furnace to the coating temperature.

[0037] Specifically, the coating temperature may specifically be 500 °C - 900 °C; preferably 550 °C - 600 °C. The inert gas may specifically be nitrogen and / or argon. The heating rate may specifically be 3 °C / min - 6 °C / min.

[0038] Step 140: Introduce a second mixed gas of an inert gas and a carbon source gas into the coating furnace, so that the carbon source gas performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0039] ​Specifically, in the second mixed gas, the volume ratio of the inert gas to the carbon source gas is specifically 1:3 - 3:2, preferably 1:2 - 1:1. The introduction time of the second mixed gas can be 2 hours - 6 hours, preferably 3 hours - 5 hours. The carbon source gas can specifically be one or more of ethylene, acetylene, and methane.

[0040] It can be seen from Figure 2 that a carbon coating layer is formed through carbon coating. The carbon coating layer plays a protective role for the carbon-phosphorus composite, preventing the volume expansion of phosphorus nanoparticles from causing shedding during charge and discharge. At the same time, it can enhance the conductivity of the carbon-phosphorus composite material, reduce the negative impact brought by the poor conductivity of phosphorus, and improve the rate performance of the battery.

[0041] In summary, the preparation method of a carbon-phosphorus composite material provided by the embodiments of the present invention uses porous carbon as a support, and through chemical vapor deposition, the phosphorus nanoparticles obtained by the thermal decomposition of phosphine are deposited in the pores of the porous carbon. The obtained carbon-phosphorus composite has the excellent properties of both porous carbon and phosphorus. The porous carbon can inhibit the volume expansion of phosphorus during cycling, extending the cycle life of the battery. The particle size of the phosphorus nanoparticles is relatively small, which can reduce the ion deintercalation distance and improve the rate performance of the battery. Through the carbon coating process, a carbon coating layer is formed, which plays a protective role for the carbon-phosphorus composite, preventing the phosphorus nanoparticles from falling off due to volume expansion during charge and discharge. At the same time, it can also enhance the conductivity of the carbon-phosphorus composite material, reduce the negative impact brought by the poor conductivity of phosphorus, thereby improving the rate performance of the battery. This preparation method has a simple process and is easy to operate.

[0042] Combined with Figure 2 as shown, a carbon-phosphorus composite material prepared by the above preparation method provided by the embodiments of the present invention has a structure including a core and a shell. Among them, the core is specifically a carbon-phosphorus composite. The carbon-phosphorus composite is composed of porous carbon and phosphorus nanoparticles deposited in the pores of the porous carbon. The shell is specifically a carbon coating layer. The shell coats the outer surface of the core.

[0043] The porous carbon can specifically include one or more of activated carbon, carbon aerogel, ordered mesoporous carbon, carbide-derived carbon, zeolite-templated carbon, salt-templated carbon, and metal-organic framework (MOF)-derived carbon. The porosity of the porous carbon can specifically be 30% - 70%, preferably 40% - 60%, and the pore diameter can specifically be 1 nm - 300 nm, preferably 1 nm - 200 nm. The particle size of the phosphorus nanoparticles is 0.5 nm - 50 nm.

[0044] Among them, the mass percentage of the porous carbon in the carbon-phosphorus composite can be 15%-99%; the mass percentage of the carbon-phosphorus composite in the carbon-phosphorus composite material can be 85%-99%; the mass percentage of the phosphorus nanoparticles in the carbon-phosphorus composite material can be 0.1%-85%, preferably 1%-60%.

[0045] In the core-shell structure of the carbon-phosphorus composite material, the porous carbon as the support can inhibit the volume expansion of the phosphorus nanoparticles during the battery cycling process, and the carbon coating layer as the shell can prevent the phosphorus nanoparticles from falling off due to volume expansion, overcoming the disadvantage of poor stability of traditional phosphorus-based materials and extending the battery life. Moreover, the porous carbon and the carbon coating layer can increase the conductivity. The particle size of the phosphorus nanoparticles is small, which can reduce the distance of ion deintercalation and improve the rate performance of the battery.

[0046] The carbon-phosphorus composite material provided by the embodiments of the present invention can be applied to the electrode materials of secondary batteries such as lithium-ion batteries and sodium-ion batteries. When the carbon-phosphorus composite material is applied in a lithium-ion battery / sodium-ion battery, since the working voltage of phosphorus is higher than the lithium / sodium deposition voltage, it is ensured that the lithium / sodium intercalation is completed before the lithium / sodium deposition, and the lithium-ion battery / sodium-ion battery can be charged at a higher rate, so that the lithium-ion battery / sodium-ion battery has a higher charge-discharge specific capacity.

[0047] To better understand the technical solutions provided by the present invention, the following uses multiple specific examples to separately illustrate the specific process of preparing the carbon-phosphorus composite material by using the method provided by the above embodiments of the present invention, and the electrochemical characteristics of the prepared carbon-phosphorus composite material.

[0048] Example 1

[0049] First step, at room temperature, take 1 kg of ordered mesoporous carbon and place it in a chemical vapor deposition furnace, then introduce nitrogen into the chemical vapor deposition furnace to discharge the air in the deposition furnace, and then heat the chemical vapor deposition furnace to 550 °C at a heating rate of 5 °C / min. Among them, the porosity of the ordered mesoporous carbon is 40%, and the pore diameter is 1 nm - 10 nm.

[0050] Second step, close the introduction of nitrogen, introduce a first mixed gas of phosphine and nitrogen with a volume ratio of 1:1 into the chemical vapor deposition furnace for 1 hour, so that the phosphine decomposes into phosphorus nanoparticles at 550 °C and deposits in the pores of the ordered mesoporous carbon to obtain a carbon-phosphorus composite.

[0051] Third step, take 1 kg of the carbon-phosphorus composite and place it in a coating furnace, then introduce nitrogen into the coating furnace to discharge the air, and then heat the coating furnace to 550 °C at a heating rate of 5 °C / min.

[0052] Fourthly, turn off the nitrogen supply, and introduce a second mixed gas of argon and acetylene with a volume ratio of 1:1.5 into the coating furnace for 3 hours, so that acetylene carbon-coats the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0053] After that, use the prepared carbon-phosphorus composite material as the electrode of the sodium-ion battery, and assemble a coin-type half-cell for testing, which is specifically as follows:

[0054] First, add the carbon-phosphorus composite material, acetylene black, and binder into deionized water in a mass ratio of 90:5:5 and mix evenly. Among them, the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber, and the mass ratio of the two is 1:1. Prepare a slurry with a pulper, coat it on an aluminum foil to obtain an electrode, and dry it at 80 °C for 12 hours.

[0055] Secondly, cut the dried electrode into 12-mm round pieces, and the loading of the active material on each round piece is 6 mg / cm 2 .

[0056] Then, assemble the above electrode into a CR2032 coin-type half-cell in an argon-filled glove box. Among them, the electrolyte of the CR2032 coin-type half-cell is 1 mol / L sodium hexafluorophosphate NaPF 6 , the solvent of the electrolyte is ethylene carbonate (EC) and dimethyl carbonate (DMC), and the volume ratio of EC and DMC is 1:1. The counter electrode is a sodium sheet.

[0057] Finally, let the CR2032 coin-type half-cell stand for 8 hours, and perform charge-discharge tests on a Blue Electric Battery Test System (CT2001A) at room temperature. The test conditions are as follows: test the initial Coulomb efficiency at a 0.1C rate, the charging cut-off voltage is 3V, the discharging cut-off voltage is 0V, and then perform charge-discharge cycle tests at a 0.2C rate.

[0058] Example 2

[0059] First step, at room temperature, take 1 kg of ordered mesoporous carbon and place it in a chemical vapor deposition furnace. Then, introduce nitrogen into the chemical vapor deposition furnace to discharge the air in the deposition furnace, and then heat the chemical vapor deposition furnace to 600 °C at a heating rate of 5 °C / min. Among them, the porosity of the ordered mesoporous carbon is 50%, and the pore diameter is 2 nm - 20 nm.

[0060] Second step, turn off the nitrogen supply, and introduce a first mixed gas of phosphine and nitrogen with a volume ratio of 2:1 into the chemical vapor deposition furnace for 2 hours, so that phosphine decomposes into phosphorus nanoparticles at 600 °C and deposits in the pores of the ordered mesoporous carbon to obtain a carbon-phosphorus composite.

[0061] In the third step, take 1 kg of the carbon-phosphorus composite and place it in the coating furnace. Then, introduce nitrogen into the coating furnace to expel the air. After that, heat the coating furnace to 600 °C at a heating rate of 5 °C / min.

[0062] In the fourth step, close the introduction of nitrogen, and introduce a second mixed gas of argon and acetylene with a volume ratio of 1:1.5 into the coating furnace for 3 hours, so that acetylene performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0063] The assembly process of the coin-type half-cell and the electrochemical test process are the same as those in Example 1.

[0064] Example 3

[0065] In the first step, at room temperature, take 1 kg of activated carbon and place it in the chemical vapor deposition furnace. Then, introduce nitrogen into the chemical vapor deposition furnace to expel the air in the deposition furnace. After that, heat the chemical vapor deposition furnace to 600 °C at a heating rate of 5 °C / min. Among them, the porosity of the activated carbon is 60%, and the pore diameter is 2 nm - 20 nm.

[0066] In the second step, close the introduction of nitrogen, and introduce a first mixed gas of phosphine and nitrogen with a volume ratio of 3:1 into the chemical vapor deposition furnace for 2 hours, so that phosphine decomposes into phosphorus nanoparticles at 600 °C and deposits in the pores of the activated carbon to obtain a carbon-phosphorus composite.

[0067] In the third step, take 1 kg of the carbon-phosphorus composite and place it in the coating furnace. Then, introduce nitrogen into the coating furnace to expel the air. After that, heat the coating furnace to 600 °C at a heating rate of 5 °C / min.

[0068] In the fourth step, close the introduction of nitrogen, and introduce a second mixed gas of argon and acetylene with a volume ratio of 1:1.5 into the coating furnace for 4 hours, so that acetylene performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0069] The assembly process of the coin-type half-cell and the electrochemical test process are the same as those in Example 1.

[0070] Example 4

[0071] In the first step, at room temperature, take 1 kg of activated carbon and place it in the chemical vapor deposition furnace. Then, introduce nitrogen into the chemical vapor deposition furnace to expel the air in the deposition furnace. After that, heat the chemical vapor deposition furnace to 650 °C at a heating rate of 5 °C / min. Among them, the porosity of the activated carbon is 50%, and the pore diameter is 3 nm - 300 nm.

[0072] In the second step, the introduction of nitrogen is closed, and a first mixed gas of phosphine and nitrogen with a volume ratio of 1:4 is introduced into the chemical vapor deposition furnace for 3 hours, so that the phosphine decomposes into phosphorus nanoparticles at 650 °C and deposits in the pores of the activated carbon to obtain a carbon-phosphorus composite.

[0073] In the third step, 1 kg of the carbon-phosphorus composite is placed in the coating furnace, and then nitrogen is introduced into the coating furnace to expel the air. After that, the coating furnace is heated to 600 °C at a heating rate of 5 °C / min.

[0074] In the fourth step, the introduction of nitrogen is closed, and a second mixed gas of argon and acetylene with a volume ratio of 1:1.5 is introduced into the coating furnace for 4 hours, so that acetylene performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0075] The assembly process of the coin-type half-cell and the electrochemical test process are the same as those in Example 1.

[0076] Example 5

[0077] In the first step, at room temperature, 1 kg of carbon aerogel is placed in the chemical vapor deposition furnace, and then nitrogen is introduced into the chemical vapor deposition furnace to expel the air in the deposition furnace. After that, the chemical vapor deposition furnace is heated to 500 °C at a heating rate of 5 °C / min. Among them, the porosity of the carbon aerogel is 60%, and the pore diameter is 10 nm - 100 nm.

[0078] In the second step, the introduction of nitrogen is closed, and a first mixed gas of phosphine and nitrogen with a volume ratio of 1:5 is introduced into the chemical vapor deposition furnace for 5 hours, so that the phosphine decomposes into phosphorus nanoparticles at 500 °C and deposits in the pores of the carbon aerogel to obtain a carbon-phosphorus composite.

[0079] In the third step, 1 kg of the carbon-phosphorus composite is placed in the coating furnace, and then nitrogen is introduced into the coating furnace to expel the air. After that, the coating furnace is heated to 600 °C at a heating rate of 5 °C / min.

[0080] In the fourth step, the introduction of nitrogen is closed, and a second mixed gas of argon and acetylene with a volume ratio of 1:1.5 is introduced into the coating furnace for 4 hours, so that acetylene performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0081] The assembly process of the coin-type half-cell and the electrochemical test process are the same as those in Example 1.

[0082] Example 6

[0083] First step, at room temperature, take 1 kg of carbon aerogel and place it in a chemical vapor deposition furnace. Then, introduce nitrogen gas into the chemical vapor deposition furnace to expel the air inside the deposition furnace. After that, heat the chemical vapor deposition furnace at a heating rate of 5 °C / min to 650 °C. Among them, the porosity of the carbon aerogel is 50%, and the pore diameter is 30 nm - 200 nm.

[0084] Second step, close the introduction of nitrogen gas, and introduce a first mixed gas of phosphine and nitrogen with a volume ratio of 1:5 into the chemical vapor deposition furnace for 6 hours, so that the phosphine decomposes into phosphorus nanoparticles at 650 °C and deposits in the pores of the carbon aerogel to obtain a carbon-phosphorus composite.

[0085] Third step, take 1 kg of the carbon-phosphorus composite and place it in a coating furnace. Then, introduce nitrogen gas into the coating furnace to expel the air. After that, heat the coating furnace at a heating rate of 5 °C / min to 600 °C.

[0086] Fourth step, close the introduction of nitrogen gas, and introduce a second mixed gas of argon and acetylene with a volume ratio of 1:1.5 into the coating furnace for 5 hours, so that acetylene carbon-coats the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0087] The assembly process of the coin-type half-cell and the electrochemical test process are the same as those in Example 1.

[0088] Comparative Example 1

[0089] Directly use carbon aerogel to assemble a coin-type half-cell, and its assembly process and electrochemical test process are the same as those in Example 1.

[0090] Table 1 shows the electrochemical performance test data of the coin-type half-cells of Examples 1 - 6 and Comparative Example 1.

[0091]

[0092] Table 1

[0093] From Table 1 and Figure 3 it can be seen that compared with Comparative Example 1, after the carbon-phosphorus composite material prepared by the present invention is used as the negative electrode material of a sodium-ion battery, the first-cycle charge and discharge specific capacity of the sodium-ion battery can be improved, and the first-cycle Coulomb efficiency of the battery can be improved. This is because phosphorus itself has a relatively high specific capacity, and the doping of phosphorus greatly improves the specific capacity of the carbon-phosphorus composite material.

[0094] In addition, the carbon-phosphorus composite material of the present application adopts a core-shell structure, thus effectively suppressing the volume expansion of phosphorus during the battery cycling process, and the capacity retention rate of the battery is very good, solving the problem of poor stability of phosphorus-based materials.

[0095] Such as Figure 4As shown, the capacity retention rate of the assembled coin-type half-cell of this application remains at a relatively high level after 100 cycles. This is because the support of the porous carbon and the protection of the carbon coating layer inhibit the expansion of phosphorus during the cycling process, ensuring the stability of the carbon-phosphorus composite material.

[0096] Example 7

[0097] First step, at room temperature, take 1 kg of carbide-derived carbon and place it in a chemical vapor deposition furnace. Then, introduce argon into the chemical vapor deposition furnace to expel the air in the deposition furnace. After that, heat the chemical vapor deposition furnace at a heating rate of 3 °C / min to 700 °C. Among them, the porosity of the carbide-derived carbon is 60%, and the pore diameter is 20 nm - 200 nm.

[0098] Second step, close the introduction of argon, and introduce a first mixed gas of phosphine and argon with a volume ratio of 1:6 into the chemical vapor deposition furnace for 0.5 hours, so that the phosphine decomposes into phosphorus nanoparticles at 700 °C and deposits in the pores of the carbide-derived carbon to obtain a carbon-phosphorus composite.

[0099] Third step, take 1 kg of the carbon-phosphorus composite and place it in a coating furnace. Then, introduce argon into the coating furnace to expel the air. After that, heat the coating furnace at a heating rate of 3 °C / min to 500 °C.

[0100] Fourth step, close the introduction of argon, and introduce a second mixed gas of argon and ethylene with a volume ratio of 1:2 into the coating furnace for 6 hours, so that ethylene carbon-coats the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0101] After that, use the prepared carbon-phosphorus composite material as the electrode of a lithium-ion battery, and assemble a coin-type half-cell for testing, as follows:

[0102] First, add the carbon-phosphorus composite material, conductive carbon black, and binder to deionized water in a mass ratio of 90:5:5 and mix well. Among them, the binder is polyacrylic acid (PAA) and carboxymethyl cellulose (CMC), and the mass ratio of PAA to CMC is 1:1. Use a beater to prepare a slurry, coat it on a copper foil current collector, and dry it in a vacuum oven at 80 °C for 12 hours.

[0103] Second, cut the dried electrode into 12 mm circular pieces, and the loading of the active material on each circular piece is 6 mg / cm 2 .

[0104] Then, use the above electrode to assemble a coin-type half-cell in a glove box. Among them, the aqueous electrolyte of the assembled lithium-ion half-cell is 1 mol / L lithium hexafluorophosphate (LiPF 6), The solvent of the electrolyte is ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC), and the volume ratio of EC, DMC and DEC is 1:1:1. The counter electrode is a lithium sheet.

[0105] Example 8

[0106] First step, at room temperature, take 1 kg of zeolite template carbon and place it in a chemical vapor deposition furnace. Then, introduce argon into the chemical vapor deposition furnace to expel the air in the deposition furnace. After that, heat the chemical vapor deposition furnace to 700 °C at a heating rate of 6 °C / min. Among them, the porosity of the zeolite template carbon is 50%, and the pore diameter is 80 nm - 300 nm.

[0107] Second step, close the introduction of argon, and introduce a first mixed gas of phosphine and argon with a volume ratio of 1:3 into the chemical vapor deposition furnace for 0.8 hours, so that phosphine decomposes into phosphorus nanoparticles at 700 °C and deposits in the pores of the zeolite template carbon to obtain a carbon-phosphorus composite.

[0108] Third step, take 1 kg of the carbon-phosphorus composite and place it in a coating furnace. Then, introduce argon into the coating furnace to expel the air. After that, heat the coating furnace to 700 °C at a heating rate of 6 °C / min.

[0109] Fourth step, close the introduction of argon, and introduce a second mixed gas of argon and ethylene with a volume ratio of 1:1 into the coating furnace for 3 hours, so that ethylene performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0110] Example 9

[0111] First step, at room temperature, take 1 kg of salt template carbon and place it in a chemical vapor deposition furnace. Then, introduce nitrogen into the chemical vapor deposition furnace to expel the air in the deposition furnace. After that, heat the chemical vapor deposition furnace to 650 °C at a heating rate of 6 °C / min. Among them, the porosity of the salt template carbon is 30%, and the pore diameter is 1 nm - 10 nm.

[0112] Second step, close the introduction of nitrogen, and introduce a first mixed gas of phosphine and nitrogen with a volume ratio of 1:6 into the chemical vapor deposition furnace for 4 hours, so that phosphine decomposes into phosphorus nanoparticles at 650 °C and deposits in the pores of the salt template carbon to obtain a carbon-phosphorus composite.

[0113] Third step, take 1 kg of the carbon-phosphorus composite and place it in a coating furnace. Then, introduce nitrogen into the coating furnace to expel the air. After that, heat the coating furnace to 800 °C at a heating rate of 6 °C / min.

[0114] Step 4: Stop introducing nitrogen, and introduce a second mixed gas of nitrogen and methane with a volume ratio of 1:3 into the coating furnace for 2.5 hours, so that methane performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0115] Example 10

[0116] Step 1: At room temperature, place 1 kg of MOFs-derived carbon in a chemical vapor deposition furnace, then introduce argon into the chemical vapor deposition furnace to discharge the air in the deposition furnace, and then heat the chemical vapor deposition furnace to 550 °C at a heating rate of 4 °C / min. Among them, the porosity of the MOFs-derived carbon is 70%, and the pore diameter is 50 nm - 150 nm.

[0117] Step 2: Stop introducing argon, and introduce a first mixed gas of phosphine and argon with a volume ratio of 1:4 into the chemical vapor deposition furnace for 7 hours, so that phosphine decomposes into phosphorus nanoparticles at 550 °C and deposits in the pores of the MOFs-derived carbon to obtain a carbon-phosphorus composite.

[0118] Step 3: Place 1 kg of the carbon-phosphorus composite in a coating furnace, then introduce argon into the coating furnace to discharge the air, and then heat the coating furnace to 900 °C at a heating rate of 4 °C / min.

[0119] Step 4: Stop introducing argon, and introduce a second mixed gas of nitrogen and methane with a volume ratio of 3:2 into the coating furnace for 2 hours, so that methane performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

[0120] The above specific embodiments have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a carbon-phosphorus composite material, It is characterized in that The preparation method comprises: Under room temperature, placing porous carbon in a vapor deposition furnace, then introducing inert gas into the vapor deposition furnace and heating the vapor deposition furnace to a deposition temperature; Passing a first mixed gas of phosphine and an inert gas into the vapor deposition furnace, so that the phosphine is decomposed into phosphorus nanoparticles at the deposition temperature and deposited in the pores of the porous carbon to obtain a carbon-phosphorus composite; Placing the carbon-phosphorus composite in a coating furnace, then introducing an inert gas into the coating furnace and heating the coating furnace to a coating temperature; A second mixed gas of the inert gas and the carbon source gas is introduced into the coating furnace, so that the carbon source gas performs carbon coating on the carbon-phosphorus composite at the coating temperature to obtain a carbon-phosphorus composite material.

2. The preparation method according to claim 1, It is characterized in that The inert gas is nitrogen and / or argon.

3. The preparation method according to claim 1, It is characterized in that The deposition temperature is 500° C.-700° C.; in the first mixed gas, the volume ratio of phosphine to inert gas is 1:6-3:1, and the introduction time is 0.5-7 hours.

4. The preparation method according to claim 1, It is characterized in that The carbon source gas is one or more of acetylene, ethylene and methane.

5. The preparation method according to claim 1, It is characterized in that The coating temperature is 500° C.-900° C.; in the second mixed gas, the volume ratio of the inert gas to the carbon source gas is 1:3-3:2, and the introduction time is 2 hours-6 hours.

6. A carbon-phosphorus composite material, It is characterized in that The carbon-phosphorus composite material is prepared by the preparation method described in any one of claims 1 to 5 above; the structure of the carbon-phosphorus composite material includes a core and an outer shell; The core is a carbon-phosphorus composite composed of porous carbon and phosphorus nanoparticles deposited in the pores of the porous carbon; The shell is coated on the outer surface of the inner core, and the shell is a carbon coating layer.

7. The carbon-phosphorus composite material according to claim 1, It is characterized in that The porous carbon accounts for 15%-99% of the carbon-phosphorus composite material by mass; the carbon-phosphorus composite material accounts for 85%-99% of the carbon-phosphorus composite material by mass; and the phosphorus nanoparticles account for 0.1%-85% of the carbon-phosphorus composite material by mass.

8. The carbon-phosphorus composite material according to claim 1, It is characterized in that The porosity of the porous carbon is 30%-70%, and the pore diameter is 1nm-300nm.

9. A negative electrode sheet, It is characterized in that The negative electrode plate comprises the carbon-phosphorus composite material according to any one of claims 6-8.

10. A secondary battery, It is characterized in that The secondary battery comprises the negative electrode sheet according to claim 9.

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