Lithium / sodium ion battery phosphorus-carbon negative electrode material and preparation method thereof

Abstract

The invention provides a lithium / sodium ion battery phosphorus-carbon negative electrode material and a preparation method thereof, the lithium / sodium ion battery phosphorus-carbon negative electrode material takes porous carbon as a matrix, red phosphorus is deposited in the porous carbon, elemental iodine is doped in the porous carbon, and a layer of titanium dioxide is coated on the surface of the phosphorus-carbon negative electrode material to form a C / P-I-coated TiO2 composite material with a core-shell structure. The volume expansion of the red phosphorus can be inhibited, and the contact area of the electrolyte and the red phosphorus is reduced, so that the cycle performance, coulombic efficiency and rate capability of the lithium / sodium ion battery are improved.

Description

Technical Field

[0001] This invention relates to the field of new energy lithium / sodium-ion batteries, and more particularly to a phosphorus-carbon anode material for lithium / sodium-ion batteries and its preparation method. Background Technology

[0002] In recent years, with the continuous growth in demand for advanced energy storage materials, phosphorus has become one of the most promising electrode materials in the field of lithium / sodium-ion batteries. Red phosphorus has a high theoretical specific capacity (2596 mAh g⁻¹). -1 The low lithium / sodium intercalation potentials (0.4V / 0.3V) effectively prevent the formation of metal dendrites. However, during lithiation / sodiumization, red phosphorus undergoes a massive volume expansion (up to 300%), leading to the pulverization of the active material. Therefore, how to suppress the volume expansion of red phosphorus and reduce the contact area between the electrolyte and red phosphorus to improve the cycle performance, coulombic efficiency, and rate performance of lithium / sodium ion batteries is a technical problem that needs to be solved. Summary of the Invention

[0003] Therefore, this invention provides a phosphorus-carbon anode material for lithium / sodium ion batteries that can suppress the volume expansion of red phosphorus and reduce the contact area between the electrolyte and red phosphorus, thereby improving the cycle performance, coulombic efficiency, and rate performance of lithium / sodium ion batteries, as well as a method for preparing the same, and a phosphorus-carbon anode for lithium / sodium ion batteries.

[0004] The aforementioned lithium / sodium ion battery phosphorus-carbon anode material uses porous carbon as a matrix, with red phosphorus deposited inside the porous carbon and iodine incorporated. A layer of titanium dioxide is coated on the surface of the phosphorus-carbon anode material to form a C / PI@TiO2 composite material with a core-shell structure.

[0005] Because the porous carbon pores of the lithium / sodium ion battery phosphorus carbon anode material of the present invention contain red phosphorus, the red phosphorus can effectively improve the specific capacity of the sodium ion battery. The titanium dioxide coating layer can suppress the volume expansion of red phosphorus and reduce the contact area between the electrolyte and red phosphorus, thereby improving the cycle performance, coulombic efficiency and rate performance of the lithium / sodium ion battery. At the same time, it can also isolate air, prevent the red phosphorus inside the pores from being oxidized, and prevent the red phosphorus material from contacting the electrolyte and generating a large amount of SEI film, which would lead to a rapid decrease in the capacity of the lithium / sodium ion battery.

[0006] Furthermore, the thickness of the titanium dioxide coating is 5~15 nm.

[0007] Furthermore, the phosphorus content deposited inside the porous carbon is 35-45 wt%.

[0008] Furthermore, the porous carbon raw material has a particle size of 5-6 μm and a pore size of 1-3 nm.

[0009] This invention also provides a method for preparing a phosphorus-carbon anode material for lithium / sodium-ion batteries, comprising the following steps: A. By controlling a certain ball-to-material ratio, rotation speed, and ball milling time, the particle size of porous carbon can be reduced; B. Place the porous carbon matrix obtained in step A at the cold end of the tube furnace, place the raw material red phosphorus at the hot end of the tube furnace, and then dry it. After cooling, add elemental iodine to the cold end of the tube furnace. C. Vacuum the tubular furnace in step B, and then heat the hot end of the tubular furnace in the first step to cause red phosphorus to thermally decompose and generate white phosphorus vapor. A temperature gradient is built at the cold end porous carbon crucible so that the temperature of the cold end porous carbon crucible is lower than that of the surrounding environment. This allows the white phosphorus vapor to preferentially gather at the lower temperature porous carbon crucible and continuously and uniformly deposit inside the pores of the cold end porous carbon. D. Move the tubular furnace in step C to allow the cold-end porous carbon to enter the hot end, then introduce protective gas until the pressure reaches positive pressure, and then carry out the second heating step to convert the white phosphorus in the porous carbon into red phosphorus under the catalysis of iodine. After cooling, sieve to obtain C / PI composite material. E. The C / PI composite material obtained in step D, tetrabutyl titanate, and anhydrous ethanol as solvent are mixed in a certain proportion and stirred. The uniformly mixed solution is then spray-dried to obtain the C / PI@TiO2 composite material precursor. F. Place the C / PI@TiO2 composite material precursor obtained in step E into a water bath and heat it in a water bath to hydrolyze tetrabutyl titanate to generate titanium hydroxide, which is then coated on the surface of the C / PI composite material. G. Add the C / PI composite powder coated with titanium hydroxide obtained in step F into a tube furnace, introduce a protective gas, and perform heat treatment to decompose the titanium hydroxide coating layer on the surface of the C / PI composite material, thereby obtaining the final product C / PI@TiO2 composite material.

[0010] The method of the present invention distinguishes between a cold end and a hot end of a tubular furnace. A porous carbon matrix is ​​placed at the cold end, and the raw material red phosphorus is placed at the hot end. Iodine is added as a catalyst at the cold end. After evacuating the tubular furnace, the hot end is heated in the first step to thermally decompose the red phosphorus into white phosphorus vapor. A temperature gradient is created at the porous carbon crucible at the cold end, ensuring that the temperature of the porous carbon crucible is lower than the ambient temperature. This allows the white phosphorus vapor to preferentially accumulate at the lower temperature of the porous carbon crucible and continuously and uniformly deposit inside the pores of the porous carbon at the cold end. After the white phosphorus vapor has deposited inside the pores of the porous carbon at the cold end, the tubular furnace in step C is moved, allowing the porous carbon at the cold end to enter the hot end. A protective gas is then introduced until the pressure reaches positive pressure, followed by a second heating step to allow the white phosphorus within the porous carbon to... Iodine catalyzes the conversion of phosphorus into red phosphorus. After cooling, the phosphorus can be sieved to obtain a C / PI composite material. The obtained C / PI composite material, tetrabutyl titanate, and anhydrous ethanol as a solvent are then mixed and spray-dried to obtain a C / PI@TiO2 composite material precursor. The C / PI@TiO2 composite material precursor is then heated in a water bath to hydrolyze tetrabutyl titanate to generate titanium hydroxide, which coats the surface of the C / PI composite material. Subsequently, heat treatment is performed to decompose the titanium hydroxide coating layer on the surface of the C / PI composite material, yielding the final product, C / PI@TiO2 composite material. The obtained C / PI@TiO2 composite material can suppress the volume expansion of red phosphorus and reduce the contact area between the electrolyte and red phosphorus, thereby improving the cycle performance, coulombic efficiency, and rate performance of lithium / sodium ion batteries.

[0011] Furthermore, in step B, the ratio of raw materials red phosphorus, porous carbon, and elemental iodine is 45–55:15–25:2–5.

[0012] Furthermore, in step C, the vacuum degree is -0.05MPa to -0.1MPa, the first heating temperature is 400 to 700 degrees Celsius, the first heating rate is 4 to 10℃ / min, and the first heating and holding time is 5 to 8h.

[0013] Furthermore, in step C, the constructed temperature gradient ensures that the temperature at the cold end of the porous carbon crucible is 50°C to 100°C lower than the ambient temperature around the crucible.

[0014] Furthermore, in step D, the positive pressure is 0~0.1MPa, the heating temperature in the second step is 150℃~300℃, and the heating and holding time in the second step is 12~24h.

[0015] Furthermore, in step E, the ratio of the raw material C / PI composite material, anhydrous ethanol, and tetrabutyl titanate is 1-3:30-40:1-2, and the stirring time is 1-3 hours. Attached Figure Description

[0016] Figure 1 This is a SEM characterization image of the C / PI@TiO2 composite material in Example 1 of the present invention. Figure 2 This is an EDS characterization diagram of the C / PI@TiO2 composite material in Comparative Example 3 of the present invention. Figure 3 The image shows the TEM characterization of the C / PI composite material in Example 1 of this invention. Figure 4 The image shows the TEM characterization of the C / PI composite material in Comparative Example 2 of this invention. Figure 5 The first charge-discharge curve of the coin cell made from the C / PI@TiO2 composite material in Example 1 of this invention. Figure 6 The graph shows the cycle performance of button batteries made from the negative electrode materials in Example 1 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0018] This invention provides a phosphorus-carbon anode material for lithium / sodium ion batteries. The phosphorus-carbon anode material uses porous carbon as a matrix, in which red phosphorus is deposited and iodine is incorporated. A layer of titanium dioxide is coated on the surface of the phosphorus-carbon anode material to form a C / PI@TiO2 composite material with a core-shell structure.

[0019] Because the porous carbon pores of the lithium / sodium ion battery phosphorus carbon anode material of the present invention contain red phosphorus, the red phosphorus can effectively improve the specific capacity of the sodium ion battery. The titanium dioxide coating layer can suppress the volume expansion of red phosphorus and reduce the contact area between the electrolyte and red phosphorus, thereby improving the cycle performance, coulombic efficiency and rate performance of the lithium / sodium ion battery. At the same time, it can also isolate air, prevent the red phosphorus inside the pores from being oxidized, and prevent the red phosphorus material from contacting the electrolyte and generating a large amount of SEI film, which would lead to a rapid decrease in the capacity of the lithium / sodium ion battery.

[0020] The thickness of the titanium dioxide coating layer is 5~15nm. Setting the thickness of the titanium dioxide coating layer within this range can effectively suppress the volume expansion of red phosphorus and avoid excessive waste of coating layer material.

[0021] The phosphorus content deposited inside the porous carbon is 35-45 wt%, that is, the red phosphorus content in the C / PI composite material is 35-45 wt%. Setting the red phosphorus content in this range can effectively leverage the role of red phosphorus in improving the cycle performance, coulombic efficiency and rate performance of lithium / sodium ion batteries, without causing excessive waste of red phosphorus.

[0022] The porous carbon raw material has a particle size of 5-6 μm and a pore size of 1-3 nm. Setting the particle size of the porous carbon raw material to 5-6 μm can obtain porous carbon pores with a suitable pore size, that is, a porous carbon pore size of 1-3 nm. This porous carbon pore size is the preferred pore size. If the pore size is too small, the pores will collapse and cannot achieve adsorption of white phosphorus vapor. If the pore size is too large, the white phosphorus vapor cannot be adsorbed and will escape to the outside of the pores.

[0023] This invention also provides a method for preparing a phosphorus-carbon anode material for lithium / sodium-ion batteries, comprising the following steps: A. By controlling a certain ball-to-material ratio, rotation speed, and ball milling time, the particle size of porous carbon can be reduced; B. Place the porous carbon matrix obtained in step A at the cold end of the tube furnace, place the raw material red phosphorus at the hot end of the tube furnace, and then dry it. After cooling, add elemental iodine to the cold end of the tube furnace. C. Vacuum the tubular furnace described in step B, and then heat the hot end of the tubular furnace in the first step to cause red phosphorus to thermally decompose and generate white phosphorus vapor. A temperature gradient is built at the cold end porous carbon crucible so that the temperature of the cold end porous carbon crucible is lower than that of the surrounding environment. This allows the white phosphorus vapor to preferentially gather at the lower temperature porous carbon crucible and continuously and uniformly deposit inside the pores of the cold end porous carbon. D. Move the tubular furnace in step C to allow the cold-end porous carbon to enter the hot end, then introduce protective gas until the pressure reaches positive pressure, and then carry out the second heating step to convert the white phosphorus in the porous carbon into red phosphorus under the catalysis of iodine. After cooling, sieve to obtain C / PI composite material. E. The C / PI composite material obtained in step D, tetrabutyl titanate, and anhydrous ethanol as solvent are mixed in a certain proportion and stirred. The uniformly mixed solution is then spray-dried to obtain the C / PI@TiO2 composite material precursor. F. Place the C / PI@TiO2 composite material precursor obtained in step E into a water bath and heat it in a water bath to hydrolyze tetrabutyl titanate to generate titanium hydroxide, which is then coated on the surface of the C / PI composite material. G. Add the C / PI composite powder coated with titanium hydroxide obtained in step F into a tube furnace, introduce a protective gas, and perform heat treatment to decompose the titanium hydroxide coating layer on the surface of the C / PI composite material, thereby obtaining the final product C / PI@TiO2 composite material.

[0024] The method of the present invention distinguishes between a cold end and a hot end of a tubular furnace. A porous carbon matrix is ​​placed at the cold end, and the raw material red phosphorus is placed at the hot end. Iodine is added as a catalyst at the cold end. After evacuating the tubular furnace, the hot end is heated in the first step to thermally decompose the red phosphorus into white phosphorus vapor. A temperature gradient is created at the porous carbon crucible at the cold end, ensuring that the temperature of the porous carbon crucible is lower than the ambient temperature. This allows the white phosphorus vapor to preferentially accumulate at the lower temperature of the porous carbon crucible and continuously and uniformly deposit inside the pores of the porous carbon at the cold end. After the white phosphorus vapor has deposited inside the pores of the porous carbon at the cold end, the tubular furnace in step C is moved, allowing the porous carbon at the cold end to enter the hot end. A protective gas is then introduced until the pressure reaches positive pressure, followed by a second heating step to allow the white phosphorus within the porous carbon to... Iodine catalyzes the conversion of phosphorus into red phosphorus. After cooling, the phosphorus can be sieved to obtain a C / PI composite material. The obtained C / PI composite material, tetrabutyl titanate, and anhydrous ethanol as a solvent are then mixed and spray-dried to obtain a C / PI@TiO2 composite material precursor. The C / PI@TiO2 composite material precursor is then heated in a water bath to hydrolyze tetrabutyl titanate to generate titanium hydroxide, which coats the surface of the C / PI composite material. Subsequently, heat treatment is performed to decompose the titanium hydroxide coating layer on the surface of the C / PI composite material, yielding the final product, C / PI@TiO2 composite material. The obtained C / PI@TiO2 composite material can suppress the volume expansion of red phosphorus and reduce the contact area between the electrolyte and red phosphorus, thereby improving the cycle performance, coulombic efficiency, and rate performance of lithium / sodium ion batteries.

[0025] Furthermore, in step A, the ball-to-material ratio is 3~5:1~2, the ball mill speed is 400rpm~800rpm, and the ball milling time is 3~5h, so that a porous carbon raw material with a suitable particle size of 5-6um can be obtained.

[0026] Furthermore, in step B, the ratio of the raw material red phosphorus, porous carbon and elemental iodine is 45-55:15-25:2-5, which can control the phosphorus content deposited inside the porous carbon to be 35-45 wt%.

[0027] Furthermore, in step B, the drying temperature is 100~300℃ and the drying time is 2~5h, so that the porous carbon matrix and raw material red phosphorus in the tube furnace can be dried in terms of composition and the moisture inside can be evaporated.

[0028] Further, in step C, the vacuum degree is -0.05MPa to -0.1MPa. Vacuuming the tubular furnace described in step B prevents the red phosphorus at the hot end of the furnace from burning. The first heating step is designed to thermally decompose the red phosphorus, and the preferred first heating temperature is 400-700 degrees Celsius. The first heating holding time is designed to allow for complete thermal decomposition of the red phosphorus, and the preferred first heating holding time is 5-8 hours. The first heating rate is designed to ensure uniform thermal decomposition of the red phosphorus, and the preferred first heating rate is 4-10℃ / min.

[0029] Furthermore, in step C, the constructed temperature gradient makes the temperature at the cold end of the porous carbon crucible 50°C to 100°C lower than the ambient temperature around the crucible. By designing this temperature gradient, white phosphorus vapor will preferentially gather at the lower temperature of the porous carbon crucible and continuously and uniformly deposit inside the pores of the cold end porous carbon.

[0030] Further, in step D, the positive pressure is 0~0.1 MPa. The protective gas introduced in step D serves two purposes: first, to prevent the combustion of white phosphorus and red phosphorus, and second, to inhibit the sublimation of white phosphorus. The heating temperature in the second step is designed to rapidly convert white phosphorus into red phosphorus under the catalysis of iodine; preferably, this heating temperature is 150℃~300℃. The heating and holding time in the second step is designed to ensure that white phosphorus is fully converted into red phosphorus under the catalysis of iodine; preferably, this heating and holding time is 12~24 hours.

[0031] Furthermore, in step D, the sieving process involves passing the material through a 200-400 mesh sieve. This allows for the acquisition of C / PI composite materials with suitable particle size.

[0032] Furthermore, in step E, the ratio of the raw material C / PI composite material, anhydrous ethanol, and tetrabutyl titanate is 1–3:30–40:1–2, and the stirring time is 1–3 hours. This allows for the acquisition of a titanium dioxide coating layer of suitable thickness (5–15 nm), and the 1–3 hour stirring time ensures thorough mixing.

[0033] Furthermore, in step E, the inlet air temperature for spray drying is 120℃~150℃, the feed rate for spray drying is 5~15ml / min, and the needle frequency for spray drying is 5~15s / cycle. This allows for better drying of the C / PI composite material, anhydrous ethanol, and tetrabutyl titanate mixture, resulting in a high-quality C / PI@TiO2 composite material precursor.

[0034] Further, in step G, the heating rate of the heat treatment is 2~5℃ / min, the heat treatment temperature is 300℃~400℃, and the holding time is 3~6h. A heat treatment temperature of 300℃~400℃ allows the titanium hydroxide coating on the surface of the C / PI composite material to decompose. A holding time of 3~6h allows for sufficient decomposition of the titanium hydroxide coating on the surface of the C / PI composite material. The heating rate should not be too fast or too slow. If it is too fast, the titanium hydroxide coating will be heated unevenly, resulting in an uneven titanium dioxide coating. If it is too slow, it will increase the time cost; a rate of 2~5℃ / min is preferable.

[0035] The following is an embodiment of the method for preparing the phosphorus-carbon anode material for lithium / sodium ion batteries according to the present invention. Example 1

[0036] A method for preparing a phosphorus-carbon anode material for lithium / sodium-ion batteries includes the following steps: S1. Place porous carbon (average particle size 6.5 μm) into a ball mill jar, place the ball mill jar in a ball mill and ball mill at 600 rpm (ball-to-material ratio 4:1) for 4 hours. The average particle size of the porous carbon after ball milling is 5.3 μm. Then weigh 4 g of porous carbon and 10 g of red phosphorus, put the red phosphorus into a crucible, place the crucible in the hot end of the tube furnace, put the porous carbon into another crucible and place it in the cold end of the tube furnace, introduce argon gas, and heat to 200°C at a heating rate of 5°C / min, hold at that temperature for 2 hours to dry the tube furnace, and then cool naturally to room temperature.

[0037] S2. Weigh 0.6g of elemental iodine, open the tube furnace, place the elemental iodine inside the cold-end porous carbon crucible, and evacuate the tube furnace until the pressure inside the tube reaches -0.1MPa. Then heat the hot end of the tube furnace to 450℃ and hold for 6 hours to perform the first heating of the hot end of the tube furnace and build a temperature gradient at the cold-end porous carbon crucible so that the temperature at the cold-end porous carbon crucible is 60℃ lower than the ambient temperature. During this period, the red phosphorus at the hot end of the tube furnace thermally decomposes to generate white phosphorus vapor, which is continuously and uniformly deposited inside the porous carbon pores.

[0038] S3. Move the cold-end porous carbon to the hot-end position and introduce protective gas until the pressure reaches positive pressure. Then, reduce the temperature of the hot end of the tubular furnace to 260℃ and keep it at that temperature for 24 hours. Then, carry out the second heating step, so that the white phosphorus inside the pores of the porous carbon is converted into red phosphorus under the catalysis of iodine. After cooling, sieve to obtain 7.33g of C / PI composite material.

[0039] S4. Take a 100ml beaker, pour 40ml of anhydrous ethanol into it, slowly add 0.5ml of tetrabutyl titanate dropwise into the beaker, then place it in a magnetic stirrer and stir for 1h (200rpm). Add 2g of the C / PI composite material obtained in S3 into the beaker and continue stirring for 2h (200rpm). Add the resulting mixed solution into a spray dryer, control the spray drying air volume to 95%, the air temperature to 130℃, the feed rate to 10ml / min, and the needle frequency to 7s / time to obtain the C / PI@TiO2 composite material precursor.

[0040] S5. Take the C / PI@TiO2 composite material precursor from S4 and place it in a water bath. Heat it to 70°C to evaporate the anhydrous ethanol. At the same time, the tetrabutyl titanate on the surface of the C / PI@TiO2 composite material precursor comes into contact with a trace amount of water vapor and undergoes hydrolysis to generate titanium hydroxide, which coats the surface of the C / PI composite material.

[0041] S6. Subsequently, the C / PI composite powder coated with titanium hydroxide obtained in S5 was added to a tube furnace, and argon gas was introduced as a protective gas. Then, it was heated to 380°C at a heating rate of 2°C / min and held for 3 hours for heat treatment to decompose the titanium hydroxide coating layer on the surface of the C / PI composite material. After cooling to room temperature, 2.37g of C / PI@TiO2 composite material was obtained.

[0042] In this embodiment, the red phosphorus content in the C / PI composite material is about 40%, and the TiO2 coating content in the C / PI@TiO2 composite material is about 4%.

[0043] Comparative Example 1 The difference between this comparative example and Example 1 is that no elemental iodine was added in step S2 of this comparative example. The final C / P composite material obtained in this comparative example is 5.35g, of which red phosphorus accounts for about 25% by mass.

[0044] Comparative Example 2 The difference between this comparative example and Example 1 is that in this comparative example, step S2 did not involve constructing a temperature gradient for the cold-end porous carbon crucible. This comparative example ultimately yielded approximately 4.51g of C / PI composite material, with red phosphorus comprising approximately 5% of the total mass.

[0045] Comparative Example 3 The difference between this comparative example and Example 1 is that the heating rate in step S6 of this comparative example is 5℃ / min, and the TiO2 coating on the surface of the C / PI@TiO2 composite material obtained in this comparative example is uneven under scanning electron microscopy.

[0046] Comparative Example 4 The difference between this comparative example and Example 1 is that steps S4-S6 in Example 1 were not performed in this comparative example, and 7.24g of C / PI composite material was finally obtained.

[0047] The C / PI@TiO2 composite materials prepared in Example 1 and Comparative Example 3 were characterized using scanning electron microscopy, and the results were obtained. Figure 1 and Figure 2 .from Figure 1 and Figure 2 The comparison shows that the TiO2 coating layer obtained in Example 1 is uniform, while the TiO2 coating layer obtained in Comparative Example 3 is uneven and exhibits surface agglomeration. This is because the heating rate in step S6 of Comparative Example 3 is 5℃ / min, which is higher than the heating rate of 2℃ / min in step S6 of Example 1. The excessively rapid heating rate of the heat treatment leads to uneven heating of the titanium hydroxide powder, resulting in an uneven TiO2 coating layer obtained from the decomposition of the titanium hydroxide powder.

[0048] The C / PI composite materials prepared in Example 1 and Comparative Example 2 were characterized using a transmission electron microscope, and the results were obtained. Figure 3 and Figure 4 .from Figure 3 and Figure 4 The comparison shows that, Figure 3 The red phosphorus with a deeper contrast contains a higher amount and is more evenly distributed. Figure 4 The red phosphorus with deeper contrast has a lower content and is unevenly distributed. That is, in Example 1, the red phosphorus deposition is uniform, while in Comparative Example 2, the red phosphorus distribution is low and it is not deposited. This is because Example 1 distinguishes between the cold and hot ends of the tubular furnace. The hot end of the tubular furnace is heated in the first step to thermally decompose the red phosphorus into white phosphorus vapor, and a temperature gradient is created at the porous carbon crucible at the cold end, so that the temperature of the porous carbon crucible at the cold end is lower than that of the surrounding environment. This allows the white phosphorus vapor to preferentially gather at the lower temperature of the porous carbon crucible and continuously and uniformly deposit inside the pores of the porous carbon at the cold end, thereby obtaining a higher content and more uniformly distributed red phosphorus inside the porous carbon pores.

[0049] Button batteries were fabricated using the C / PI@TiO2 composite material from Example 1, the C / P composite material from Comparative Example 1, the C / PI composite material from Comparative Example 2, the C / PI@TiO2 composite material from Comparative Example 3, and the C / PI composite material from Comparative Example 4. Specifically, a slurry was prepared by mixing the composite material, sodium carboxymethyl cellulose (CMC), carbon-based conductive agent Super-P, and styrene-butadiene rubber in a mass ratio of 92:2:3:3. The slurry was uniformly coated onto a copper foil current collector and dried in a vacuum oven at 85°C for 12 hours to obtain the negative electrode. A lithium metal sheet was used as the counter electrode, polypropylene (PP) as the separator, and LiPF6 solution (a mixed solution of 1 mol / L lithium hexafluorophosphate in ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate = 1:1:1) as the electrolyte. The batteries were assembled into button batteries in an argon-protected glove box.

[0050] The prepared button cells were subjected to constant current charge-discharge tests at a current density of 300 mA / g and a charge-discharge voltage range of 0.005–1.5 V. The results are as follows: Figures 5-6 As shown.

[0051] from Figure 5 As can be seen, the button cell made using the C / PI@TiO2 composite material in Example 1 has a specific capacity of 1472.03 mAh / g after the first discharge; the button cell made using the C / PI@TiO2 composite material in Example 1 has a specific capacity of 1198.23 mAh / g after the first charge. The initial efficiency is 81.4%. This button cell exhibits good cycle performance, coulombic efficiency, and rate performance.

[0052] from Figure 6 As can be seen, the discharge specific capacity of Example 1 and Comparative Examples 1-4 decreases with increasing cycle number, but under the premise of the same cycle number, the discharge specific capacity of Example 1 is always higher than that of Comparative Examples 1-4. Furthermore, the coulombic efficiency of Example 1 and Comparative Examples 1-4 decreases slightly with increasing cycle number, but under the premise of the same cycle number, the coulombic efficiency of Example 1 is always higher than that of Comparative Examples 1-4. This also demonstrates that the phosphorus-carbon anode material prepared by this invention can suppress the volume expansion of red phosphorus and reduce the contact area between the electrolyte and red phosphorus, thereby improving the cycle performance, coulombic efficiency, and rate performance of lithium / sodium ion batteries.

[0053] Furthermore, the present invention also provides a lithium / sodium ion battery phosphorus-carbon anode, comprising a lithium / sodium ion battery phosphorus-carbon anode material, wherein the phosphorus-carbon anode material is prepared by the preparation method described above.

[0054] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A phosphorus-carbon anode material for lithium / sodium-ion batteries, characterized in that, The phosphorus-carbon anode material uses porous carbon as a matrix, in which red phosphorus is deposited and iodine is incorporated. A layer of titanium dioxide is coated on the surface of the phosphorus-carbon anode material to form a C / PI@TiO2 composite material with a core-shell structure.

2. The lithium / sodium ion battery phosphorus-carbon anode material as described in claim 1, characterized in that, The thickness of the titanium dioxide coating is 5~15nm.

3. The lithium / sodium ion battery phosphorus-carbon anode material as described in claim 1, characterized in that, The porous carbon contains 35-45 wt% phosphorus deposited inside.

4. The lithium / sodium ion battery phosphorus-carbon anode material as described in claim 1, characterized in that, The porous carbon raw material has a particle size of 5-6 μm and a pore size of 1-3 nm.

5. A method for preparing a phosphorus-carbon anode material for lithium / sodium-ion batteries, characterized in that, Includes the following steps: A. By controlling a certain ball-to-material ratio, rotation speed, and ball milling time, the particle size of porous carbon can be reduced; B. Place the porous carbon matrix obtained in step A at the cold end of the tube furnace, place the raw material red phosphorus at the hot end of the tube furnace, and then dry it. After cooling, add elemental iodine to the cold end of the tube furnace. C. Vacuum the tubular furnace described in step B, and then heat the hot end of the tubular furnace in the first step to cause red phosphorus to thermally decompose and generate white phosphorus vapor. A temperature gradient is built at the cold end porous carbon crucible so that the temperature of the cold end porous carbon crucible is lower than that of the surrounding environment. This allows the white phosphorus vapor to preferentially gather at the lower temperature porous carbon crucible and continuously and uniformly deposit inside the pores of the cold end porous carbon. D. Move the tubular furnace in step C to allow the cold-end porous carbon to enter the hot end, then introduce protective gas until the pressure reaches positive pressure, and then carry out the second heating step to convert the white phosphorus in the porous carbon into red phosphorus under the catalysis of iodine. After cooling, sieve to obtain C / PI composite material. E. The C / PI composite material obtained in step D, tetrabutyl titanate, and anhydrous ethanol as solvent are mixed in a certain proportion and stirred. The uniformly mixed solution is then spray-dried to obtain the C / PI@TiO2 composite material precursor. F. Place the C / PI@TiO2 composite material precursor obtained in step E into a water bath and heat it in a water bath to hydrolyze tetrabutyl titanate to generate titanium hydroxide, which is then coated on the surface of the C / PI composite material. G. Add the C / PI composite powder coated with titanium hydroxide obtained in step F into a tube furnace, introduce a protective gas, and perform heat treatment to decompose the titanium hydroxide coating layer on the surface of the C / PI composite material, thereby obtaining the final product C / PI@TiO2 composite material.

6. The method for preparing the phosphorus-carbon anode material for lithium / sodium ion batteries as described in claim 5, characterized in that, In step B, the ratio of the raw materials red phosphorus, porous carbon, and elemental iodine is 45-55:15-25:2-5.

7. The method for preparing the phosphorus-carbon anode material for lithium / sodium ion batteries as described in claim 5, characterized in that, In step C, the vacuum degree is -0.05MPa to -0.1MPa, the first heating temperature is 400 to 700 degrees Celsius, the first heating rate is 4 to 10℃ / min, and the first heating and holding time is 5 to 8 hours.

8. The method for preparing the phosphorus-carbon anode material for lithium / sodium ion batteries as described in claim 5, characterized in that, In step C, the constructed temperature gradient ensures that the temperature at the cold end of the porous carbon crucible is 50°C to 100°C lower than the ambient temperature around the crucible.

9. The method for preparing the phosphorus-carbon anode material for lithium / sodium ion batteries as described in claim 5, characterized in that, In step D, the positive pressure is 0~0.1MPa, the heating temperature in the second step is 150℃~300℃, and the heating and holding time in the second step is 12~24h.

10. The method for preparing the phosphorus-carbon anode material for lithium / sodium ion batteries as described in claim 5, characterized in that, In step E, the ratio of the raw material C / PI composite material, anhydrous ethanol and tetrabutyl titanate is 1-3:30-40:1-2, and the stirring time is 1-3 hours.

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