In-situ Deposited Coated Phosphorus-Carbon Anode Material and Its Preparation Method and Application

Abstract

The present invention relates to the technical field of lithium battery materials, and specifically discloses an in-situ deposition-coated phosphorus-carbon anode material, its preparation method and application. The in-situ deposition-coated phosphorus-carbon anode material includes a core and an in-situ deposition layer in-situ deposited and coated outside the core. The core is a porous carbon deposited with red phosphorus, and the structural formula of the in-situ deposition layer is Ag 1‑x Cd x S or Zn 1‑x Cd x S, where 0 < x < 0.3. The in-situ deposition-coated phosphorus-carbon anode material provided by the present invention uses Ag 1‑x Cd x S or Zn 1‑x Cd x S to conduct in-situ deposition and coating on the phosphorus-carbon material, which can achieve uniform coating at a lower temperature, thereby effectively avoiding direct contact between red phosphorus and the electrolyte, improving the electrical conductivity of the material, and suppressing the capacity decay during the cycling process of the phosphorus-carbon composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and particularly relates to an in-situ deposited coated phosphorus-carbon anode material, a preparation method thereof, and an application thereof. Background Art

[0002] As an important energy source for modern portable electronic devices and electric vehicles, the energy density and cycle life of lithium-ion batteries have always been the focus of research. Phosphorus-based anode materials are an effective way to improve the energy density of lithium-ion batteries due to their high theoretical specific capacity. However, elemental phosphorus is prone to volume change during charge and discharge, resulting in pulverization and shedding of the electrode material and reducing the battery cycle life. To solve this problem, researchers have tried to improve the stability and conductivity of phosphorus-based anodes through methods such as nanosizing phosphorus, composite material design, and surface coating.

[0003] Currently, phosphorus-carbon composites are mainly prepared by depositing phosphorus on porous carbon and coating amorphous carbon on the surface of the phosphorus-carbon material. The framework structure of the porous carbon is used to relieve the volume expansion of phosphorus. However, due to the low melting point and sublimation temperature of red phosphorus, this preparation method enables the amorphous carbon coating to be carried out only at a relatively low temperature, resulting in non-uniform coating of the amorphous carbon and direct contact between red phosphorus and the electrolyte, which is likely to damage the electrode structure during the lithium deintercalation process. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide an in-situ deposited coated phosphorus-carbon anode material, a preparation method thereof, and an application thereof. The in-situ deposited coated phosphorus-carbon anode material uses Ag 1-x Cd x S or Zn 1-x Cd x S to perform in-situ deposition coating on the phosphorus-carbon material, which can achieve uniform coating at a relatively low temperature, thereby effectively avoiding direct contact between red phosphorus and the electrolyte and preventing damage to the electrode structure during the lithium deintercalation process.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention first provides an in-situ deposited coated phosphorus-carbon anode material, which includes a core and an in-situ deposited layer in-situ deposited and coated outside the core. The core is porous carbon deposited with red phosphorus, and the structural formula of the in-situ deposited layer is Ag 1-x Cd x S or Zn 1-x Cd x S, where 0 < x < 0.3.

[0007] The present invention uses Ag 1-x Cd x S or Zn 1-x Cd xIn-situ deposition coating of phosphorus-carbon materials can achieve uniform coating at a relatively low temperature, thus effectively avoiding direct contact between red phosphorus and the electrolyte and preventing damage to the electrode structure during the lithium deintercalation and intercalation process; Ag 1-x Cd x S or Zn 1-x Cd x S coating can also improve the electrical conductivity of phosphorus-carbon materials and inhibit the capacity decay of phosphorus-carbon materials during cycling.

[0008] As a further improvement of the above solution of the present invention, in the in-situ deposition coated phosphorus-carbon anode material, the coating amount of the in-situ deposition layer is 1%-15%.

[0009] The present invention also provides a method for preparing the in-situ deposition coated phosphorus-carbon anode material as described above, which includes the following steps:

[0010] S1. Mix red phosphorus, porous carbon, and elemental sulfur by ball milling, and then sinter to obtain phosphorus-carbon materials;

[0011] S2. Mix cadmium nitrate, thiourea, and ammonia water to obtain a growth solution;

[0012] S3. Place the phosphorus-carbon materials in the growth solution for growth, and then perform post-treatment to obtain CdS-coated phosphorus-carbon anode materials;

[0013] S4. Add a silver source or a zinc source, urea, and deionized water to the CdS-coated phosphorus-carbon anode materials and mix them, perform a hydrothermal reaction, and then perform post-treatment to obtain the in-situ deposition coated phosphorus-carbon anode materials.

[0014] As a further improvement of the above solution of the present invention, in step S1, the mass ratio of red phosphorus, porous carbon, and elemental sulfur is (30-55):(40-65):(1-5); the rotation speed of the ball milling mixture is 80-130 r / min, and the time is 4-12 h; the sintering is to keep the temperature at 500-700 °C for 3-5 h first, and then keep the temperature at 250-300 °C for 12-20 h. During the sintering process, red phosphorus first sublimes to form white phosphorus, and the gaseous white phosphorus is then converted into red phosphorus and deposited in the porous carbon. In this process, elemental sulfur can inhibit the generation of white phosphorus during the deposition process, improve the deposition rate of red phosphorus, and facilitate the conversion of white phosphorus to red phosphorus.

[0015] As a further improvement of the above solution of the present invention, in step S2, the mass ratio of cadmium nitrate, thiourea, and ammonia water is (1-2):(7-16):(100-250); the mixing is ultrasonic mixing for 5-15 min.

[0016] As a further improvement of the above solution of the present invention, in step S3, the mass ratio of the phosphorus-carbon material to the growth solution is 1:50 - 60; the growth is carried out under water bath heating at 60 - 75 °C for 1 - 6 h; the post-treatment sequentially includes ultrasonic treatment for 5 - 15 min, filtration, and vacuum drying at 85 °C.

[0017] As a further improvement of the above solution of the present invention, in step S4, the silver source is at least one of silver nitrate, silver acetate, and silver oxalate, and the zinc source is at least one of zinc nitrate and zinc acetate.

[0018] As a further improvement of the above solution of the present invention, in step S4, the mass ratio of the CdS-coated phosphorus-carbon negative electrode material, the silver source or the zinc source, urea, and deionized water is (10 - 12):(0.8 - 2):(0.3 - 1):(20 - 50).

[0019] As a further improvement of the above solution of the present invention, in step S4, the hydrothermal reaction is carried out at 110 - 160 °C for 1 - 10 h, and the post-treatment sequentially includes filtration, washing, and vacuum drying at 85 °C.

[0020] The present invention also provides an application of the in-situ deposition-coated phosphorus-carbon negative electrode material as described above as a negative electrode material for a lithium battery.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses Ag 1-x Cd x S or Zn 1-x Cd x S to carry out in-situ deposition coating on the phosphorus-carbon material, which can achieve uniform coating at a relatively low temperature (60 - 75 °C), thereby effectively avoiding direct contact between red phosphorus and the electrolyte and preventing the destruction of the electrode structure during the lithium insertion and extraction process; Ag 1-x Cd x S or Zn 1-x Cd x S coating can also inhibit the expansion of the phosphorus-carbon material and improve the conductivity of the phosphorus-carbon material, thereby inhibiting the capacity decay of the phosphorus-carbon material during the cycling process.

[0023] The present invention first in-situ deposits and coats CdS on the surface of the phosphorus-carbon material, which can effectively reduce the specific surface area and resistivity of the phosphorus-carbon material, reduce the occurrence of side reactions on the surface of the phosphorus-carbon material, improve the cycling stability of the phosphorus-carbon material, and thus effectively inhibit the capacity decay of the phosphorus-carbon material during the cycling process; then doping the CdS coating layer with nano silver or nano zinc can further improve the conductivity of the CdS coating layer and promote the rapid transmission of electrons, thereby improving the fast charging performance of the phosphorus-carbon material. Description of the Drawings

[0024] Figure 1 This is the electron microscopy image of the in-situ deposited and coated phosphorus-carbon anode material prepared in Example 1 of the present invention;

[0025] Figure 2 This is the electron microscopy image of the phosphorus-carbon anode material prepared in Comparative Example 1;

[0026] Figure 3 This is the first charge-discharge curve of the phosphorus-carbon anode material prepared in Example 1;

[0027] Figure 4 This is the comparison chart of the cycling performance of the phosphorus-carbon anode materials prepared in Example 1 and Comparative Example 1;

[0028] Figure 5 This is the comparison chart of the rate performance of the phosphorus-carbon anode materials prepared in Example 1 and Comparative Example 1. Detailed Embodiments

[0029] For the convenience of understanding the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0031] Example 1

[0032] This example provides an in-situ deposited and coated phosphorus-carbon anode material, and its preparation method includes the following steps:

[0033] S1. Red phosphorus (average particle size of 7 μm), porous carbon (average particle size of 6.5 μm) and elemental sulfur are added into a nylon tube according to a mass ratio of 45:54:1, and ball milled at a rotation speed of 110 r / min (ball-to-material ratio of 5:1) for 6 h. The average particle size of the mixture obtained after uniform mixing is 6.8 μm, and the proportion of red phosphorus is 45%; the mixture is subjected to vacuum tube sealing treatment, and then placed in a tube furnace and kept at 660 °C for 4 h to sublime red phosphorus to form white phosphorus, and then cooled to 260 °C and kept for 18 h to convert gaseous white phosphorus into red phosphorus and deposit it in the porous carbon. After cooling to room temperature, a phosphorus-carbon material is obtained;

[0034] S2. Weigh 0.925 g of cadmium nitrate and place it in a 1000 mL beaker. Add 200 mL of deionized water and stir ultrasonically for 6 min until completely dissolved to obtain a cadmium nitrate solution. Weigh 7.308 g of thiourea and add it to the beaker. Then add 120 mL of ammonia water (concentration 28 wt%) and 300 mL of deionized water and mix to obtain a CdS chemical bath growth solution.

[0035] S3. Put 10 g of the phosphorus-carbon material obtained in step S1 into 550 g of the CdS chemical bath growth solution obtained in step S2, deposit it in a 65 °C water bath, continuously stir and react for 3 h during the deposition process, then perform ultrasonic treatment for 10 min, filter and dry it in vacuo at 85 °C to obtain 10.32 g of a CdS-coated phosphorus-carbon negative electrode material.

[0036] S4. Mix 10.32 g of the CdS-coated phosphorus-carbon negative electrode material obtained in step S3, 1.7 g of silver nitrate and 0.6 g of urea, add 50 mL of deionized water, stir evenly, react in a reaction kettle at 150 °C for 2 h, filter, wash three times with deionized water, and dry it in vacuo at 85 °C to obtain 10.41 g of an Ag 1-x Cd x S-coated phosphorus-carbon negative electrode material, which is the in-situ deposited coated phosphorus-carbon negative electrode material.

[0037] In this example, the material before coating (phosphorus-carbon material) is 10 g, and the material after coating (Ag 1-x Cd x S-coated phosphorus-carbon negative electrode material) is 10.41 g, and the content of the Ag 1-x Cd x S coating layer is about 4%.

[0038] Example 2

[0039] The difference between this example and Example 1 is as follows: In step S1 of this example, the mass ratio of red phosphorus, porous carbon and elemental sulfur is 30:65:5; in step S1, the mixture is kept at 500 °C for 5 h in a tube furnace first, and then cooled to 250 °C and kept for 20 h; in step S3, put 10 g of the phosphorus-carbon material obtained in step S1 into 550 g of the CdS chemical bath growth solution obtained in step S2, deposit it in a 65 °C water bath, and continuously stir and react for 1 h during the deposition process; 10.13 g of a CdS-coated phosphorus-carbon negative electrode material is finally obtained in step S3; 10.18 g of an in-situ deposited coated phosphorus-carbon negative electrode material is finally obtained in step S4.

[0040] In this example, the material before coating (phosphorus-carbon material) is 10 g, and the material after coating (Ag 1-x Cd x S-coated phosphorus-carbon negative electrode material) is 10.18 g, and the Ag 1-x Cd xThe content of the S coating layer is about 2%.

[0041] Example 3

[0042] The difference between this example and Example 1 is as follows: In step S1 of this example, the mass ratio of red phosphorus, porous carbon and elemental sulfur is 55:40:5; in step S1, the mixture is kept at 700 °C in a tubular furnace for 3 h and then cooled to 300 °C and kept for 12 h; in step S3, 10 g of the phosphorus-carbon material obtained in step S1 is put into 550 g of the CdS chemical bath growth solution obtained in step S2, and deposited in a water bath at 65 °C, and the deposition process is continuously stirred and reacted for 5 h; finally, 11.15 g of the CdS-coated phosphorus-carbon negative electrode material is obtained in step S3; and 11.32 g of the in-situ deposited and coated phosphorus-carbon negative electrode material is obtained in step S4.

[0043] In this example, the material before coating is 10 g, and the material after coating is 11.32 g, Ag 1-x Cd x The content of the S coating layer is about 13%.

[0044] Example 4

[0045] The difference between this example and Example 1 is as follows:

[0046] Step S2 of this example is as follows: Weigh 2 g of cadmium nitrate and place it in a 1000 mL beaker, add 200 mL of deionized water, and ultrasonically stir for 6 min until completely dissolved to obtain a cadmium nitrate solution; weigh 16 g of thiourea and add it to the beaker, then add 278 mL of ammonia water (concentration 28 wt%) and 300 mL of deionized water and mix to obtain a CdS chemical bath growth solution;

[0047] In step S3 of this example, 10 g of the phosphorus-carbon material obtained in step S1 is put into 600 g of the CdS chemical bath growth solution obtained in step S2, and deposited in a water bath at 60 °C, and the deposition process is continuously stirred and reacted for 3 h; finally, 11.32 g of the CdS-coated phosphorus-carbon negative electrode material is obtained in step S3;

[0048] Step S4 of this example is as follows: Mix 11.32 g of the CdS-coated phosphorus-carbon negative electrode material obtained in step S3, 2 g of silver nitrate and 1 g of urea, add 50 mL of deionized water, stir evenly, react in a reaction kettle at 160 °C for 1 h, filter, wash three times with deionized water, and dry in vacuum at 85 °C to obtain 11.48 g of the in-situ deposited and coated phosphorus-carbon negative electrode material.

[0049] In this example, the material before coating is 10 g, and the material after coating is 11.48 g, Ag 1-x Cd x The content of the S coating layer is about 14.8%.

[0050] Example 5

[0051] The difference between this example and Example 1 is that:

[0052] In step S2 of this example: Weigh 1.5 g of cadmium nitrate and place it in a 1000 mL beaker, add 200 mL of deionized water, and ultrasonically stir for 6 min until completely dissolved to obtain a cadmium nitrate solution; Weigh 11.5 g of thiourea and add it to the beaker, then add 200 mL of ammonia water (concentration 28 wt%) and 300 mL of deionized water and mix to obtain a CdS chemical bath growth solution;

[0053] In step S3 of this example, put 10 g of the phosphorus-carbon material obtained in step S1 into 500 g of the CdS chemical bath growth solution obtained in step S2, deposit it in a water bath at 75 °C, and continuously stir and react during the deposition process for 3 h; Finally, 10.67 g of the phosphorus-carbon negative electrode material coated with CdS is obtained in step S3;

[0054] In step S4 of this example: Mix 10.67 g of the phosphorus-carbon negative electrode material coated with CdS obtained in step S3, 0.8 g of silver nitrate, and 0.3 g of urea, add 20 mL of deionized water, stir evenly, react in a reaction kettle at 160 °C for 3 h, filter, wash three times with deionized water, and dry in vacuo at 85 °C to obtain 10.81 g of the phosphorus-carbon negative electrode material with in-situ deposited coating.

[0055] In this example, the material before coating is 10 g, the material after coating is 10.81 g, and the content of the Ag 1-x Cd x CdS coating layer is about 8%.

[0056] Example 6

[0057] The difference between this example and Example 1 is that: In step S1 of this example, the mass ratio of red phosphorus, porous carbon, and elemental sulfur is 40:57:3; In step S3, put 10 g of the phosphorus-carbon material obtained in step S1 into 550 g of the CdS chemical bath growth solution obtained in step S2, deposit it in a water bath at 65 °C, and continuously stir and react during the deposition process for 4 h; Finally, 10.92 g of the phosphorus-carbon negative electrode material coated with CdS is obtained in step S3; Finally, 11.13 g of the phosphorus-carbon negative electrode material with in-situ deposited coating is obtained in step S4.

[0058] In this example, the material before coating is 10 g, the material after coating is 11.13 g, and the content of the Ag 1-x Cd x CdS coating layer is about 11%.

[0059] Example 7

[0060] The difference between this embodiment and Embodiment 1 lies in that in step S4 of this embodiment, 1.61 g of zinc nitrate is used to replace 1.7 g of silver nitrate, and finally 10.52 g of the in-situ deposited and coated phosphorus-carbon anode material is obtained.

[0061] In this embodiment, the material before coating is 10 g, and the material after coating is 10.52 g. The content of the Zn 1-x Cd x S coating layer is about 5%.

[0062] Embodiment 8

[0063] The difference between this embodiment and Embodiment 7 lies in that in step S3 of this embodiment, 10 g of the phosphorus-carbon material obtained in step S1 is put into 550 g of the CdS chemical bath growth solution obtained in step S2, and deposition is carried out in a water bath at 65°C with continuous stirring during the deposition process for 1 h; finally, 10.16 g of the CdS-coated phosphorus-carbon anode material is obtained in step S3; and finally, 10.23 g of the in-situ deposited and coated phosphorus-carbon anode material is obtained in step S4.

[0064] In this embodiment, the material before coating is 10 g, and the material after coating is 10.23 g. The content of the Zn 1-x Cd x S coating layer is about 2%.

[0065] Embodiment 9

[0066] The difference between this embodiment and Embodiment 5 lies in that in step S4 of this embodiment, 1.61 g of zinc nitrate is used to replace 1.7 g of silver nitrate, and finally 10.82 g of the in-situ deposited and coated phosphorus-carbon anode material is obtained.

[0067] In this embodiment, the material before coating is 10 g, and the material after coating is 10.82 g. The content of the Zn 1-x Cd x S coating layer is about 8%.

[0068] Comparative Example 1

[0069] This comparative example proposes a phosphorus-carbon anode material, and its preparation method includes the following steps: Red phosphorus (average particle size of 7 μm), porous carbon (average particle size of 6.5 μm) and elemental sulfur are added into a nylon tube according to a mass ratio of 45:54:1, and ball milling is carried out at a rotation speed of 110 r / min (ball-to-material ratio of 5:1) for 6 h. The average particle size of the mixture obtained after uniform mixing is 6.8 μm, and the proportion of red phosphorus is 45%; the mixture is subjected to vacuum tube sealing treatment, and then placed in a tube furnace and kept at 660°C for 4 h to sublime red phosphorus to form white phosphorus, and then cooled to 260°C and kept for 18 h to convert gaseous white phosphorus into red phosphorus and deposit it in the porous carbon, and cooled to room temperature to obtain the phosphorus-carbon anode material.

[0070] In the phosphorus-carbon negative electrode material prepared in this comparative example, the content of phosphorus is 45%, the content of carbon material is 54%, and the content of sulfur is 1%.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 1 is that step S4 was not carried out in this comparative example, and finally 10.32 g of CdS-coated phosphorus-carbon negative electrode material was obtained.

[0073] In this comparative example, the material before coating was 10 g, the material after coating was 10.32 g, and the content of the CdS coating layer was about 3%.

[0074] Test Example

[0075] (1) The phosphorus-carbon negative electrode materials prepared in Example 1 and Comparative Example 1 were characterized by scanning electron microscopy to obtain Figure 1 and Figure 2 , Figure 1 、 Figure 2 By comparison, it can be seen that the surface of the in-situ deposition-coated phosphorus-carbon negative electrode material prepared in Example 1 is smooth, and Ag 1-x Cd x S is uniformly coated on the surface of the phosphorus-carbon material.

[0076] (2) Nitrogen adsorption and desorption tests were carried out on the phosphorus-carbon negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-2: degassing at 140 °C for 6 h to obtain the specific surface area of each phosphorus-carbon negative electrode material, and the results are shown in Table 1.

[0077] Table 1 Specific surface area data

[0078]

[0079] (3) Powder resistance tests were carried out on the phosphorus-carbon negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-2: Weigh 1 g of the powder of the sample to be tested and place it in a special mold. The test pressure is 15 Mpa, and the resistivity of each phosphorus-carbon negative electrode material is measured using an ST2722-SZ powder resistance meter. The results are shown in Table 2.

[0080] Table 2 Powder resistivity data

[0081]

[0082] According to the results of Table 1 and Table 2, it can be known that:

[0083] Compared with Comparative Example 1: In Example 1 and Example 7, a relatively thin Ag 1-x Cd x S coating layer (coating amount is 4%) and Zn 1-x Cd xWhen the S coating layer (coating amount is 5%), the specific surface area of the phosphorus-carbon negative electrode material can be reduced from 53.2 m 2 / g to 2.3 m 2 / g and 5.3 m 2 / g respectively, and the resistivity is reduced from 118.7 Ω·cm to 0.3 Ω·cm and 0.8 Ω·cm respectively. This shows that the Ag 1-x Cd x S coating layer and Zn 1-x Cd x S coating layer can reduce the specific surface area of the phosphorus-carbon negative electrode material and improve the electrical conductivity, thereby reducing the generation of side reactions during the lithium insertion process of the phosphorus-carbon negative electrode material and improving the initial Coulomb efficiency; reducing the repeated rupture and reconstruction of the SEI film and improving the cycle stability;

[0084] Compared with Example 1: When the deposition time of the phosphorus-carbon material in the CdS chemical bath growth solution is reduced to 1 h in Example 2, the specific surface area of the in-situ deposited coated phosphorus-carbon negative electrode material prepared is slightly increased and the resistivity is increased. This may be due to the short deposition time of CdS, resulting in non-uniform coating and partial exposure of the porous carbon material on the surface, thus slightly increasing the specific surface area and resistivity of the phosphorus-carbon negative electrode material; When the deposition time of the phosphorus-carbon material in the CdS chemical bath growth solution is extended to 5 h and 4 h in Example 3 and Example 6 respectively, the specific surface area of the in-situ deposited coated phosphorus-carbon negative electrode material prepared is significantly increased and the resistivity is slightly increased. This may be due to the too long deposition time of CdS resulting in too thick a coating layer and preferential growth of some CdS, resulting in a rough coating layer surface and a decrease in the silver doping amount, thus resulting in a significant increase in the specific surface area and a significant increase in the resistivity;

[0085] Compared with Example 1, when the concentration of the CdS chemical bath growth solution is increased in Example 4 and Example 5, the CdS coating layer is too thick, making the surface of the red phosphorus-carbon material relatively rough, thus increasing the specific surface area and slightly increasing the resistivity;

[0086] Compared with Comparative Example 1, in Comparative Example 2, a CdS material is coated on the surface of the phosphorus-carbon material, resulting in a significant reduction in the specific surface area and resistivity; This is because the CdS is uniformly coated and the coating layer is relatively thin, resulting in a significant reduction in the specific surface area and resistivity, indicating that the CdS coating layer can effectively reduce the specific surface area of the phosphorus-carbon negative electrode material and the resistivity of the material, reduce the generation of side reactions of the phosphorus-carbon negative electrode material, avoid direct contact between red phosphorus and the electrolyte, inhibit the expansion of the phosphorus-carbon negative electrode material, and improve the electrical properties of the phosphorus-carbon negative electrode material.

[0087] Application Example

[0088] The phosphorus-carbon anode materials prepared using Examples 1-9 and Comparative Examples 1-2 were respectively made into button cells: The phosphorus-carbon anode materials, polyacrylic acid PAA, carbon-based conductive agent Super-P, and styrene-butadiene rubber SBR were prepared into a slurry at a mass ratio of 80:10:7:3. The slurry was evenly coated on a copper foil current collector and dried in a vacuum oven at 85°C for 12 h to obtain the negative electrode sheet; a lithium metal sheet was used as the counter electrode, a glass fiber was used as the separator, and an NaClO4 solution (concentration of 1 mol / L, and the solvent was a 1:1 volume ratio mixture of ethylene carbonate and dimethyl carbonate) was used as the electrolyte, and button cells were assembled in a glove box under argon protection.

[0089] The prepared button cells were subjected to constant current charge and discharge tests: The current density was 300 mA / g, and the charge and discharge voltage range was 0.005-2.0 V. The results are shown in Table 3 and Figures 3 - 5 as follows.

[0090] Table 3 Electrical properties

[0091]

[0092] According to Table 3, Figure 3 , Figure 4 , Figure 5 it can be seen from the results that:

[0093] In Example 1, when the deposition time of the phosphorus-carbon material in the CdS chemical bath growth solution was 3 h and the silver-doped hydrothermal reaction time was 2 h, the specific capacity and initial Coulombic efficiency of the obtained phosphorus-carbon anode material were optimal, being 1326 mAh / g and 88.14% respectively. After 100 cycles, the specific capacity retention rate reached 92%, and the charge and discharge performance at different current densities was significantly improved, and the rate performance was significantly improved; this was because when the CdS deposition time was 3 h and the silver-doped hydrothermal reaction time was 2 h, the Ag x Cd 1-x S coating layer uniformly coated the phosphorus-carbon material and the coating layer was relatively thin, with a coating amount of 4%. The specific surface area decreased from 53.2 m 2 / g to 2.3 m 2 / g, reducing the generation of side reactions of the phosphorus-carbon anode material, improving its conductivity, avoiding direct contact between red phosphorus and the electrolyte, suppressing the expansion of the phosphorus-carbon material, improving the electrical properties of the phosphorus-carbon material, and improving its cycle stability and rate performance;

[0094] Compared with Example 1: In Example 2, the addition amount of red phosphorus is reduced, resulting in a significant decrease in specific capacity. However, some exposed red phosphorus directly contacts the electrolyte and expands and pulverizes, leading to a significant decrease in the initial Coulombic efficiency. In Example 3, the increase in the addition amounts of red phosphorus and elemental sulfur improves the specific capacity, but the increase in specific surface area and resistivity results in more side reactions and a decrease in the initial Coulombic efficiency. In Example 6, the growth time is extended, resulting in an overly thick CdS coating layer, which affects the specific capacity and the initial Coulombic efficiency.

[0095] Compared with Example 1, in Examples 4 and 5, due to the overly thick CdS coating layer, the relative proportion of red phosphorus decreases, thus reducing the specific capacity. The increase in specific surface area and resistivity also makes the transmission channel longer, resulting in a decrease in the initial Coulombic efficiency.

[0096] Compared with Comparative Example 1, in Comparative Example 2, a CdS material is coated on the surface of the phosphorus-carbon material, resulting in a significant improvement in specific capacity and initial Coulombic efficiency. This shows that the CdS coating layer can reduce the specific surface area, isolate the direct contact between red phosphorus and the electrolyte, inhibit the expansion of the phosphorus-carbon material, improve the electrical properties of the phosphorus-carbon material, and enhance its cycle stability.

[0097] Compared with Comparative Example 2, in Example 1 and Example 7, silver nanoparticles and zinc nanoparticles are doped in the CdS coating layer respectively, and both the specific capacity and the initial Coulombic efficiency are significantly improved. This shows that doping silver nanoparticles or zinc nanoparticles in the CdS coating layer can improve the conductivity of the CdS coating layer, promote the rapid transmission of electrons, and thus improve the fast charging performance of the phosphorus-carbon material.

[0098] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0099] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A preparation method of an in-situ deposited and coated phosphorus-carbon anode material, characterized in that, It includes the following steps: S1. After grinding and mixing red phosphorus, porous carbon, and elemental sulfur in a jar mill, sintering is carried out to obtain a phosphorus-carbon material; S2. Cadmium nitrate, thiourea, and ammonia water are mixed to obtain a growth solution; S3. The phosphorus-carbon material is placed in the growth solution for growth, and after-treatment is carried out to obtain a CdS-coated phosphorus-carbon negative electrode material; S4. A silver source or a zinc source, urea, and deionized water are added to the CdS-coated phosphorus-carbon negative electrode material and mixed, and a hydrothermal reaction and after-treatment are carried out to obtain an in-situ deposited and coated phosphorus-carbon negative electrode material.

2. The preparation method of the in-situ deposition-coated phosphorus-carbon anode material according to claim 1, characterized in that The in-situ deposited and coated phosphorus-carbon anode material includes a core and an in-situ deposited layer in-situ deposited and coated outside the core. The core is porous carbon deposited with red phosphorus, and the structural formula of the in-situ deposited layer is Ag 1-x Cd x S or Zn 1-x Cd x S, where 0 < x < 0.

3.

3. The preparation method of the in-situ deposition-coated phosphorus-carbon anode material according to claim 2, characterized in that, In the in-situ deposited and coated phosphorus-carbon negative electrode material, the coating amount of the in-situ deposited layer is 1% - 15%.

4. The preparation method of the in-situ deposition-coated phosphorus-carbon anode material according to claim 1, characterized in that, In step S1, the mass ratio of red phosphorus, porous carbon, and elemental sulfur is (30 - 55):(40 - 65):(1 - 5); the rotation speed of the jar mill mixing is 80 - 130 r / min, and the time is 4 - 12 h; The sintering is to keep the temperature at 500 - 700 °C for 3 - 5 h first, and then keep the temperature at 250 - 300 °C for 12 - 20 h.

5. The preparation method of the in-situ deposition-coated phosphorus-carbon anode material according to claim 1, wherein, In step S2, the mass ratio of cadmium nitrate, thiourea, and ammonia water is (1 - 2):(7 - 16):(100 - 250); the mixing is ultrasonic mixing for 5 - 15 min.

6. The preparation method of the in-situ deposited and coated phosphorus-carbon anode material according to claim 1, wherein, In step S3, the mass ratio of the phosphorus-carbon material to the growth solution is 1:50 - 60; the growth is carried out by water bath heating at 60 - 75 °C for 1 - 6 h; the after-treatment sequentially includes ultrasonic treatment for 5 - 15 min, filtration, and vacuum drying at 85 °C.

7. The preparation method of the in-situ deposition-coated phosphorus-carbon anode material according to claim 1, characterized in that In step S4, the silver source is at least one of silver nitrate, silver acetate, and silver oxalate, and the zinc source is at least one of zinc nitrate and zinc acetate.

8. The preparation method of the in-situ deposition-coated phosphorus-carbon anode material according to claim 1, characterized in that, In step S4, the mass ratio of the CdS-coated phosphorus-carbon negative electrode material, the silver source or the zinc source, urea, and deionized water is (10 - 12):(0.8 - 2):(0.3 - 1):(20 - 50).

9. The preparation method of the in-situ deposition-coated phosphorus-carbon anode material according to claim 1, wherein, In step S4, the hydrothermal reaction is carried out at 110 - 160 °C for 1 - 10 h, and the after-treatment sequentially includes filtration, washing, and vacuum drying at 85 °C.

10. Application of an in-situ deposited and coated phosphorus-carbon negative electrode material prepared by the preparation method according to any one of claims 1 - 9 as a negative electrode material for a lithium battery.

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