Phosphorus-carbon composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sodium electric materials, in particular to a phosphorus-carbon composite material and a preparation method and application thereof. The phosphorus-carbon composite material provided by the method has a unique three-dimensional network structure with a large number of micropores and mesopores, more adsorption sites can be provided for filling of nano red phosphorus, the loading capacity of the red phosphorus is increased, the conductivity of the red phosphorus is remarkably improved, the nano pores of the carbon aerogel are uniformly filled with red phosphorus nanoparticles, and the conductivity of the red phosphorus is improved. Volume expansion of red phosphorus can be effectively buffered, and pulverization of an electrode material is avoided, so that the long-term cycling stability, specific capacity and rate capability of the phosphorus-carbon composite material are improved; besides, the method adopts a normal-temperature and normal-pressure drying method to prepare the carbon aerogel, does not need complex equipment, and also has the advantages of relatively simple operation process, greatly reduced cost and energy consumption, higher safety, more suitability for large-scale industrial production and the like.

Description

Technical Field

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

[0002] As a new type of energy storage device, sodium-ion batteries have multiple advantages in terms of cost and performance, and are expected to complement lithium-ion batteries and achieve large-scale development. At present, the development of anode materials for sodium-ion batteries mainly focuses on hard carbon, but its low sodium storage capacity (about 300 mAh / g) and energy density limit its application. Elemental phosphorus materials that store sodium based on the alloy mechanism have become anode materials for sodium-ion batteries with great practical application prospects due to their ultra-high theoretical specific capacity (2596 mAh / g), relatively safe redox potential (~0.5 V), and abundant reserves.

[0003] Among all the allotropes of elemental phosphorus, compared with black phosphorus with poor chemical stability and high price and white phosphorus that is toxic to the human body, red phosphorus has become one of the most competitive candidates for commercial anode materials for sodium-ion batteries due to its good chemical stability, low cost, and environmental harmlessness. However, the extremely low conductivity (~10-14 S cm -1 ) and huge volume expansion (the volume expansion can reach ~400% when fully sodiated) of red phosphorus will lead to its slow electrochemical reaction kinetics and rapid structural degradation and capacity decay during the cycling process, seriously hindering the development and application of red phosphorus in sodium-ion batteries.

[0004] To solve the problems of conductivity and volume expansion of the above-mentioned red phosphorus anode materials, a common and effective method is to prepare red phosphorus / carbon composite materials. Generally, red phosphorus / carbon composite materials can be divided into two categories: (1) restricting red phosphorus in the pores of porous carbon materials; (2) attaching red phosphorus to the surface or particle gaps of highly conductive carbon (including carbon black, single-walled carbon nanotubes, graphene, etc.). However, as the red phosphorus deposited on the surface of highly conductive carbon expands and contracts repeatedly during cycling, the SEI film initially formed and covering the active material ruptures, and the fresh surface is exposed to the electrolyte, consuming additional Na + to generate a new SEI film. The continuous rupture and regeneration of the SEI film will ultimately lead to rapid deterioration of battery performance. Summary of the Invention

[0005] The embodiments of the present application provide a phosphorus-carbon composite material, a preparation method thereof, and an application thereof to solve the problems of conductivity and volume expansion of phosphorus-carbon composite materials in related technologies.

[0006] In a first aspect, a preparation method of a phosphorus-carbon composite material is provided, including:

[0007] Step 1: Place the clean red phosphorus and activated carbon aerogel into the reactor without contact between them, and then seal the container under an inert atmosphere.

[0008] Step 2: Heat up and calcine the sealed reactor, then perform isothermal treatment after cooling, and finally cool it to room temperature to obtain the phosphorus-carbon composite material.

[0009] In some embodiments, the mass ratio of the red phosphorus to the activated carbon aerogel in Step 1 is (0.5 - 2):1.

[0010] In some embodiments, the heating up in Step 2 is to heat up to 450 - 550 °C at a rate of 2 - 8 °C / min; through the heating process, all the red phosphorus sublimes into phosphorus vapor.

[0011] In some embodiments, the calcination in Step 2 is carried out at a constant temperature, and the calcination time is 2 - 6 h.

[0012] In some embodiments, the cooling in Step 2 is to cool to 250 - 300 °C at a rate of 1 - 3 °C / min, and the time for isothermal treatment is 12 - 24 h; through the cooling and isothermal treatment, the white phosphorus formed after the phosphorus vapor cools is fully converted into nanoscale red phosphorus in the pores of the activated carbon aerogel.

[0013] In some embodiments, the preparation method of the activated carbon aerogel includes:

[0014] Step 1: Mix resorcinol (R), formaldehyde (F), sodium carbonate (C) and water (W) and stir to form a homogeneous solution, and let it stand at room temperature to obtain a sol.

[0015] Step 2: Heat the sol in a water bath, and after the sol gels, carry out aging to obtain a dark red wet gel mass.

[0016] Step 3: Crush the dark red wet gel mass in Step 2 to obtain an organic gel powder, and then perform solvent replacement on the organic gel powder.

[0017] Step 4: Dry the organic gel powder obtained after solvent replacement in Step 3 at normal temperature and pressure, and then carry out carbonization treatment under an inert atmosphere to obtain a carbon aerogel powder.

[0018] Step 5: Heat the carbon aerogel powder in Step 4 to 800 - 1000 °C, and carry out activation in a carbon dioxide atmosphere to obtain the activated carbon aerogel.

[0019] In some embodiments, the mass fraction of all solutes in the homogeneous solution in Step 1 is 20 - 40%.

[0020] In some embodiments, the molar ratio of resorcinol (R), formaldehyde (F), sodium carbonate (C) and water (W) in step 1 is R / F = 1:2, and R / C = 500 - 1500.

[0021] In some embodiments, the standing time in step 1 is 16 - 24 h.

[0022] In some embodiments, the temperature of water bath heating in step 2 is 40 - 60 °C, and the heating time is 16 - 24 h.

[0023] In some embodiments, the aging temperature in step 2 is 60 - 80 °C, and the aging time is 16 - 24 h.

[0024] In some embodiments, the solvent for solvent replacement in step 3 is ethanol or acetone solvent; the time for solvent replacement is 4 - 6 days, and the solvent is changed every 8 h.

[0025] In some embodiments, the drying time under normal pressure in step 4 is 3 - 5 days.

[0026] In some embodiments, the heating rate in step 5 is 2 - 5 °C / min, and the activation time is 2 - 4 h.

[0027] In some embodiments, the activation time in step 5 is 2 - 4 h.

[0028] In the second aspect, a phosphorus-carbon composite material prepared by the above method is provided.

[0029] In the third aspect, an application of the above phosphorus-carbon composite material as a negative electrode material for sodium-ion batteries is provided.

[0030] The beneficial effects brought by the technical solution provided in this application include:

[0031] (1) For the phosphorus-carbon composite material provided by the method of the present invention, on the one hand, the activated carbon aerogel framework is composed of interconnected nanoscale carbon particles, forming a unique three-dimensional network structure with a large number of micropores and mesopores. It has a higher specific surface area, a more abundant pore structure, and a higher electronic conductivity, which can not only provide more adsorption sites for the filling of nanoscale red phosphorus, but also significantly improve the conductivity of red phosphorus, thereby effectively enhancing the specific capacity and rate performance of the material; on the other hand, the red phosphorus nanoparticles are uniformly filled in the nanopores of the carbon aerogel, and the confinement structure can effectively buffer the volume expansion of red phosphorus and avoid the pulverization of the electrode material, thereby enhancing the long-term cycle stability of the material.

[0032] (2) Compared with the solid large-sized carbon aerogels produced by the backend crushing process in the prior art, the carbon aerogel powder with smaller particle sizes is produced by the frontend crushing process in the method of the present invention. When contacting with CO2 for activation, a larger contact area with CO2 can be achieved, resulting in better CO2 activation effect. The specific surface area of the carbon aerogel material after activation is significantly increased, and the micropores and small mesopores less than 10 nm are significantly increased, which is beneficial to loading a larger amount of red phosphorus nanoparticles;

[0033] (3) Compared with the complex operation, high cost and high danger of the traditional supercritical drying method, the carbon aerogel is prepared by the normal temperature and normal pressure drying method in the method of the present invention. It does not require complex equipment, the operation process is relatively simple, the cost and energy consumption are greatly reduced, and it is very safe, which is more suitable for large-scale industrial production. Description of the Drawings

[0034] Figure 1 It is the pore size distribution diagram of the activated carbon aerogel in Example 1 and Comparative Example 1;

[0035] Figure 2 It is the pore size distribution diagram of the activated carbon aerogel in Example 2 and Comparative Example 2;

[0036] Figure 3 It is the conductivity of the activated carbon aerogel or carbon aerogel in Example 1 and Comparative Example 4 under different pressures. Detailed Embodiments

[0037] The technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0038] Example 1

[0039] I. Preparation of the phosphorus-carbon composite material:

[0040] Step 1: Remove the oxides and impurities on the surface of red phosphorus, wash and dry it. In the glove box, put the pretreated red phosphorus and the activated carbon aerogel into both ends of the quartz tube according to the mass ratio of 1:1, and then seal the open end of the quartz tube with a flange in the glove box;

[0041] Step 2: Then take out the sealed quartz tube from the glove box and place it on the horizontal tube furnace for calcination. First, heat it to 500 °C at a rate of 5 °C / min, and then keep it at a constant temperature for 4 hours; then cool it to 280 °C at a rate of 1 °C / min and keep it at a constant temperature for 24 h; finally, let the device cool naturally to room temperature to obtain the phosphorus-carbon composite material.

[0042] II. Preparation of Activated Carbon Aerogel:

[0043] Step 1: Mix resorcinol (R), formaldehyde (F), sodium carbonate (C) and water (W) according to the molar ratio of R / F = 1:2 and R / C = 500, stir to form a homogeneous solution with a solute mass fraction of 30%, inject it into a cylindrical mold, and let it stand at room temperature for 20 h to obtain a sol;

[0044] Step 2: Heat the sol in a water bath at 50 °C for 24 h. After the sol gels, age it at 75 °C for 24 h to obtain a dark red wet gel block;

[0045] Step 3: Crush the organic wet gel block in Step 2 to obtain organic gel powder, soak the obtained organic gel powder in acetone solvent for 5 days, and change the solvent every 8 h;

[0046] Step 4: Dry the organic gel powder after solvent replacement in Step 3 at normal temperature and pressure for 4 days to obtain RF organic aerogel powder. Then, carbonize the obtained RF organic aerogel powder under an inert atmosphere, control the temperature to rise to 1000 °C at a rate of 3 °C / min, and then hold for 3 h to obtain carbon aerogel powder;

[0047] Step 5: Heat up and activate the carbon aerogel powder in Step 4 at 950 °C in a carbon dioxide atmosphere for 4 h to obtain activated carbon aerogel.

[0048] Example 2

[0049] I. Preparation of Phosphorus-Carbon Composite Material:

[0050] The preparation process in this example is the same as that in Example 1.

[0051] II. Preparation of Activated Carbon Aerogel:

[0052] Step 1: Mix resorcinol (R), formaldehyde (F), sodium carbonate (C) and water (W) according to the molar ratio of R / F = 1:2 and R / C = 1500, stir to form a homogeneous solution with a solute mass fraction of 30%, inject it into a cylindrical mold, and let it stand at room temperature for 20 h to obtain a sol;

[0053] Step 2: Heat the sol in a water bath at 50 °C for 24 h. After the sol gels, age it at 75 °C for 24 h to obtain a dark red wet gel block;

[0054] Step 3: Crush the organic wet gel block in Step 2 to obtain organic gel powder, soak the obtained organic gel powder in acetone solvent for 5 days, and change the solvent every 8 h;

[0055] Step 4: Dry the organic gel powder after solvent replacement in Step 3 at normal temperature and pressure for 4 days to obtain RF organic aerogel powder. Then, perform carbonization treatment on the obtained RF organic aerogel powder under an inert atmosphere, controlling the temperature to rise to 1000 °C at a rate of 3 °C / min, and then hold for 3 h to obtain carbon aerogel powder;

[0056] Step 5: Raise the temperature and activate the carbon aerogel powder in Step 4 in a carbon dioxide atmosphere at 950 °C for 4 h to obtain activated carbon aerogel.

[0057] Comparative Example 1

[0058] I. Preparation of phosphorus-carbon composite material:

[0059] The preparation process in this comparative example is the same as that in Example 1.

[0060] II. Preparation of activated carbon aerogel:

[0061] Step 1: Mix resorcinol (R), formaldehyde (F), sodium carbonate (C), and water (W) at a molar ratio of R / F = 1:2 and R / C = 500, and stir to form a homogeneous solution with a solute mass fraction of 30%. Inject it into a cylindrical mold and let it stand at room temperature for 20 h to obtain a sol;

[0062] Step 2: Perform water bath heating on the sol at 50 °C for 24 h. After the sol gels, age it at 75 °C for 24 h to obtain a dark red wet gel block;

[0063] Step 3: Immerse the organic wet gel block obtained in Step 2 in acetone solvent for 5 days, and change the solvent every 8 h;

[0064] Step 4: Dry the organic wet gel block after solvent replacement in Step 3 at normal temperature and pressure for 4 days to obtain RF organic aerogel block. Perform carbonization treatment on the obtained RF organic aerogel block under an inert atmosphere, controlling the temperature to rise to 1000 °C at a rate of 3 °C / min, and then hold for 3 h to obtain carbon aerogel block;

[0065] Step 5: Activate the carbon aerogel block obtained in Step 4 in a carbon dioxide atmosphere at 950 °C for 4 h to obtain an activated carbon aerogel block, and then crush the activated carbon aerogel block to obtain activated carbon aerogel.

[0066] Comparative Example 2

[0067] I. Preparation of phosphorus-carbon composite material:

[0068] The preparation process in this comparative example is the same as that in Example 2.

[0069] II. Preparation of activated carbon aerogel:

[0070] Step 1: Mix resorcinol (R), formaldehyde (F), sodium carbonate (C) and water (W) at a molar ratio of R / F = 1:2 and R / C = 1500, and stir to form a homogeneous solution with a solute mass fraction of 30%. Inject it into a cylindrical mold and let it stand at room temperature for 20 h to obtain a sol.

[0071] Step 2: Heat the sol in a water bath at 50 °C for 24 h. After the sol gels, age it at 75 °C for 24 h to obtain a dark red wet gel block.

[0072] Step 3: Immerse the organic wet gel block obtained in Step 2 in an acetone solvent for 5 days, and change the solvent every 8 h.

[0073] Step 4: Dry the organic wet gel block after solvent replacement in Step 3 at room temperature and normal pressure for 4 days to obtain an RF organic aerogel block. Carbonize the obtained RF organic aerogel block under an inert atmosphere, control the temperature to rise to 900 °C at a rate of 3 °C / min, and then hold for 3 h to obtain a carbon aerogel block.

[0074] Step 5: Activate the carbon aerogel block obtained in Step 4 in a carbon dioxide atmosphere at 950 °C for 4 h to obtain an activated carbon aerogel block, and then crush the activated carbon aerogel block to obtain activated carbon aerogel.

[0075] Comparative Example 3

[0076] I. Preparation of phosphorus-carbon composite material:

[0077] The difference from Example 1 is that the activated carbon aerogel is replaced with the carbon aerogel prepared as follows.

[0078] II. Preparation of carbon aerogel:

[0079] Step 1: Mix resorcinol (R), formaldehyde (F), sodium carbonate (C) and water (W) at a molar ratio of R / F = 1:2 and R / C = 500, and stir to form a homogeneous solution with a solute mass fraction of 30%. Inject it into a cylindrical mold and let it stand at room temperature for 20 h to obtain a sol.

[0080] Step 2: Heat the sol in a water bath at 50 °C for 24 h. After the sol gels, age it at 75 °C for 24 h to obtain a dark red wet gel block.

[0081] Step 3: Crush the organic wet gel block in Step 2 to obtain organic gel powder, and immerse the obtained organic gel powder in an acetone solvent for 5 days, and change the solvent every 8 h.

[0082] Step 4: Dry the organic gel powder after solvent replacement in Step 3 at normal temperature and pressure for 4 days to obtain RF organic aerogel powder. Then, carbonize the obtained RF organic aerogel powder under an inert atmosphere, controlling the temperature to rise to 1000 °C at a rate of 3 °C / min and then holding for 3 h to obtain carbon aerogel.

[0083] Comparative Example 4

[0084] Preparation of phosphorus-carbon composite material:

[0085] The difference from Example 1 is that the activated carbon aerogel is replaced with commercial activated carbon. The manufacturer of the commercial activated carbon is Kureha Corporation, Japan, and the model is YP-50F.

[0086] Performance test

[0087] Test the performance of the activated carbon aerogel and phosphorus-carbon composite material prepared in the examples and comparative examples. The test results are shown in Table 1.

[0088] Among them, the specific surface area (S BET ) and pore size distribution (V t、 V meso、 V micro、 D pore ) were tested using a TriStar 3000 specific surface area and pore size distribution tester from Micromeritics, USA. When testing, after loading a certain mass (~150 mg) of the sample into the sample tube, first degas at 200 °C under vacuum for 4 hours, and then transfer it to a cold trap cup filled with liquid nitrogen for testing.

[0089] Table 1 Performance test results of the activated carbon aerogel and phosphorus-carbon composite material prepared in the examples and comparative examples

[0090] Types of carbon substrates <![CDATA[S BET (m 2 / g)]]> <![CDATA[V t (cm 3 / g)]]> <![CDATA[V meso (cm 3 / g)]]> <![CDATA[V micro (cm 3 / g)]]> <![CDATA[D pore (nm)]]> Example 1 2803 2.13 1.72 0.78 3.05 Example 2 2721 4.41 3.86 0.98 6.48 Comparative Example 1 1641 1.20 0.74 0.51 2.94 Comparative Example 2 2021 3.47 2.87 0.69 6.86 Comparative Example 3 490 0.49 0.37 0.12 3.97 Comparative Example 4 1645 0.76 0.13 0.63 1.86

[0091] From Table 1 and Figure 1 、 Figure 2 、 Figure 3 it can be seen that compared with the back-end crushing process of Comparative Examples 1-2, the activated carbon aerogel prepared by the front-end crushing process in Examples 1-2 of the present invention method has a higher specific surface area (>2700 m 2 / g) and more micropores (<2 nm) and small-sized mesopores (2-10 nm) structures; in addition, compared with the commercial activated carbon substrate in Comparative Example 4, the activated carbon aerogel substrate in Example 1 of the present invention method has more excellent powder conductivity (8 S / cm @ 30 MPa).

[0092] Table 2 Comparison of the electrochemical performance of the phosphorus-carbon composite material

[0093]

[0094] As can be seen from the data in Table 2, since the activated carbon aerogel substrate prepared by the method of the present invention has a higher specific surface area, a richer pore structure and more excellent electrical conductivity, it can effectively deposit a larger amount of red phosphorus nanoparticles, enabling the phosphorus-carbon composites in Examples 1-2 to exhibit ultra-high specific capacity and excellent rate performance. In addition, the red phosphorus nanoparticles are uniformly filled in the nano-pores of the carbon aerogel, and the confinement structure can better inhibit the volume expansion of red phosphorus, and the prepared phosphorus-carbon composite has good cycle stability.

[0095] In Comparative Examples 1-3, due to the relatively low specific surface area of the carbon aerogel substrate and the underdeveloped pore structure (especially the unactivated carbon aerogel in Comparative Example 3), the amount of loaded nano red phosphorus is limited, resulting in a low specific capacity of the prepared phosphorus-carbon composite; in Comparative Example 4, due to the low specific surface area, mesopore content and electrical conductivity of the commercial activated carbon substrate, the prepared phosphorus-carbon composite has a low specific capacity and poor rate performance and cycle stability.

[0096] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a phosphorus-carbon composite material, characterized in that: include: Step 1, placing clean red phosphorus and activated carbon aerogel into a reactor without contacting each other, and then sealing the container under an inert atmosphere; Step 2: The sealed reactor is heated and calcined, then cooled and kept at a constant temperature, and finally cooled to room temperature to obtain the phosphorus-carbon composite material.

2. The method for preparing the phosphorus-carbon composite material according to claim 1, characterized in that: The mass ratio of red phosphorus to activated carbon aerogel in step 1 is (0.5-2):

1.

3. The method for preparing the phosphorus-carbon composite material according to claim 1, characterized in that: In step 2, the temperature is increased to 450-550° C. at a rate of 2-8° C. / min; the temperature is reduced by 250-300° C., and the constant temperature treatment time is 12-24 hours.

4. The method for preparing the phosphorus-carbon composite material according to claim 1, characterized in that: The preparation method of the activated carbon aerogel comprises: Step 1, resorcinol, formaldehyde, sodium carbonate and water are mixed and stirred to form a uniform solution, and the solution is allowed to stand at room temperature to obtain a sol; Step 2, heating the sol in a water bath, aging the sol after it is gelled, and obtaining a dark red wet gel block; Step 3, crushing the dark red wet gel block in step 2 to obtain an organogel powder, and then performing solvent replacement on the organogel powder; Step 4, drying the organic gel powder obtained after the solvent replacement in step 3 at room temperature and pressure, and then carbonizing it under an inert atmosphere to obtain a carbon aerogel powder; Step 5: The carbon aerogel powder in step 4 is heated to 800-1000° C. and activated in a carbon dioxide atmosphere to obtain activated carbon aerogel.

5. The method for preparing the phosphorus-carbon composite material according to claim 4, characterized in that: The mass fraction of all solutes in the homogeneous solution in step 1 is 20-40%.

6. The method for preparing the phosphorus-carbon composite material according to claim 4, characterized in that: The molar ratio of resorcinol, formaldehyde, sodium carbonate and water in step 1 is: R / F=1:2, R / C=500-1500; wherein R represents resorcinol, F represents formaldehyde, and C represents sodium carbonate.

7. The method for preparing the phosphorus-carbon composite material according to claim 4, characterized in that: The temperature increase in step 5 is controlled at a rate of 2 to 5° C. / min, and the activation time is 2 to 4 hours.

8. The method for preparing the phosphorus-carbon composite material according to claim 4, characterized in that: The water bath heating temperature in step 2 is 40-60° C., and the time is 16-24 h; the aging temperature is 60-80° C., and the aging time is 16-24 h.

9. A phosphorus-carbon composite material, characterized in that: Prepared by the method according to any one of claims 1 to 8.

10. Use of the phosphorus-carbon composite material according to claim 9 as a negative electrode material for sodium ion batteries.

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