In-situ deposition coated phosphorus-carbon negative electrode material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of lithium battery materials, and particularly discloses an in-situ deposition coated phosphorus-carbon negative electrode material and a preparation method and application thereof.The in-situ deposition coated phosphorus-carbon negative electrode material comprises an inner core and an in-situ deposition layer coating the inner core in an in-situ deposition mode, the inner core is porous carbon deposited with red phosphorus, and the in-situ deposition layer is coated with the in-situ deposition layer in an in-situ deposition mode. The structural formula of the in-situ deposition layer is Ag < 1-x > Cd < x > S or Zn < 1-x > Cd < x > S, wherein x is more than 0 and less than 0.3. According to the in-situ deposition coated phosphorus-carbon negative electrode material provided by the invention, Ag < 1-x > CdxS or Zn < 1-x > CdxS is used for carrying out in-situ deposition coating on the phosphorus-carbon material, and uniform coating can be realized at a relatively low temperature, so that direct contact between red phosphorus and an electrolyte is effectively avoided, the conductivity of the material can be improved, and the capacity attenuation of the phosphorus-carbon composite material in a circulating process can be inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and particularly relates to an in-situ deposited and 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, allowing red phosphorus to directly contact the electrolyte, and easily damaging the electrode structure during the lithium insertion and extraction process. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide an in-situ deposited and coated phosphorus-carbon anode material, a preparation method thereof, and an application thereof. The in-situ deposited and coated phosphorus-carbon anode material uses Ag 1-x Cd x S or Zn 1-x Cd x S to perform in-situ deposition and 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 insertion and extraction process.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention first provides an in-situ deposited and coated phosphorus-carbon anode material, which includes a core and an in-situ deposition 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 deposition layer is Ag 1-x Cd x S or Zn 1-x Cd x S, where 0 < x < 0.3.

[0006] The present invention uses Ag 1-x Cd x S or Zn 1-x Cd xIn-situ deposition coating of the phosphorus-carbon material 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 insertion and extraction process; Ag 1-x Cd x S or Zn 1-x Cd x S coating can also improve the conductivity of the phosphorus-carbon material and inhibit the capacity decay of the phosphorus-carbon material during cycling.

[0007] 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%.

[0008] 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: S1. Mix red phosphorus, porous carbon, and elemental sulfur by ball milling, and then sinter to obtain a phosphorus-carbon material; S2. Mix cadmium nitrate, thiourea, and ammonia water to obtain a growth solution; S3. Place the phosphorus-carbon material in the growth solution for growth, and then perform post-treatment to obtain a CdS-coated phosphorus-carbon anode material; S4. Add a silver source or a zinc source, urea, and deionized water to the CdS-coated phosphorus-carbon anode material, perform a hydrothermal reaction, and then perform post-treatment to obtain the in-situ deposition coated phosphorus-carbon anode material.

[0009] 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 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 back to 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.

[0010] 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.

[0011] 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 by 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.

[0012] 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.

[0013] 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).

[0014] 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.

[0015] 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.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 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, improve the electrical conductivity of the phosphorus-carbon material, and thus inhibit the capacity decay of the phosphorus-carbon material during the cycling process.

[0017] 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 electrical conductivity of the CdS coating layer, promote the rapid transmission of electrons, and thus improve the fast charging performance of the phosphorus-carbon material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the electron microscope image of the in-situ deposition-coated phosphorus-carbon negative electrode material prepared in Example 1 of the present invention; Figure 2 It is the electron microscope image of the phosphorus-carbon negative electrode material prepared in Comparative Example 1; Figure 3The first charge-discharge curve of the phosphorus-carbon negative electrode material prepared in Example 1; Figure 4 The cyclic performance comparison chart of the phosphorus-carbon negative electrode materials prepared in Example 1 and Comparative Example 1; Figure 5 The rate performance comparison chart of the phosphorus-carbon negative electrode materials prepared in Example 1 and Comparative Example 1. Specific Embodiments

[0019] 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.

[0020] 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 description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0021] Example 1 This example presents an in-situ deposited coated phosphorus-carbon negative electrode material, and its preparation method includes the following steps: S1. Red phosphorus (average particle size of 7 μm), porous carbon (average particle size of 6.5 μm) and elemental sulfur are added to 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. After uniform mixing, the average particle size of the obtained mixture 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 tubular 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; S2. Weigh 0.925 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 7.308 g of thiourea and add it to the beaker, then add 120 mL of ammonia water (concentration of 28 wt%) and 300 mL of deionized water to mix to obtain a CdS chemical bath growth solution; 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, continuously stir the reaction for 3 h during the deposition process, then perform ultrasonic treatment for 10 min, filter and dry it under vacuum at 85 °C to obtain 10.32 g of CdS-coated phosphorus-carbon negative electrode material; S4. Mix 10.32 g of the CdS-coated phosphorus-carbon anode 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 in vacuo at 85 °C to obtain 10.41 g of Ag 1-x Cd x S-coated phosphorus-carbon anode material, which is the in-situ deposited coated phosphorus-carbon anode material.

[0022] 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 anode material) is 10.41 g, and the content of the Ag 1-x Cd x S coating layer is about 4%.

[0023] Example 2 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 in a water bath at 65 °C, and continuously stir and react for 1 h during the deposition process; finally, 10.13 g of CdS-coated phosphorus-carbon anode material is obtained in step S3; finally, 10.18 g of in-situ deposited coated phosphorus-carbon anode material is obtained in step S4.

[0024] 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 anode material) is 10.18 g, and the content of the Ag 1-x Cd x S coating layer is about 2%.

[0025] Example 3 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 for 3 h in a tube furnace first, and then cooled to 300 °C and kept for 12 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 in a water bath at 65 °C, and continuously stir and react for 5 h during the deposition process; finally, 11.15 g of CdS-coated phosphorus-carbon anode material is obtained in step S3; finally, 11.32 g of in-situ deposited coated phosphorus-carbon anode material is obtained in step S4.

[0026] In this embodiment, 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%.

[0027] Example 4 The difference between this embodiment and Example 1 is that: In step S2 of this embodiment: 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; In step S3 of this embodiment, put 10 g of the phosphorus-carbon material obtained in step S1 into 600 g of the CdS chemical bath growth solution obtained in step S2, deposit it in a water bath at 60 °C, and continuously stir and react for 3 h during the deposition process; Finally, 11.32 g of the CdS-coated phosphorus-carbon negative electrode material is obtained in step S3; In step S4 of this embodiment: 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.

[0028] In this embodiment, 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%.

[0029] Example 5 The difference between this embodiment and Example 1 is that: In step S2 of this embodiment: 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; In step S3 of this embodiment, 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 for 3 h during the deposition process; Finally, 10.67 g of the CdS-coated phosphorus-carbon negative electrode material is obtained in step S3; Step S4 of this embodiment is as follows: Mix 10.67 g of the CdS-coated phosphorus-carbon anode material 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 under vacuum at 85 °C to obtain 10.81 g of the in-situ deposited and coated phosphorus-carbon anode material.

[0030] In this embodiment, the mass of the material before coating is 10 g, and the mass of the material after coating is 10.81 g. The content of the Ag 1-x Cd x S coating layer is about 8%.

[0031] Example 6 The difference between this embodiment and Example 1 is as follows: In step S1 of this embodiment, 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 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 CdS-coated phosphorus-carbon anode material is obtained in step S3; finally, 11.13 g of the in-situ deposited and coated phosphorus-carbon anode material is obtained in step S4.

[0032] In this embodiment, the mass of the material before coating is 10 g, and the mass of the material after coating is 11.13 g. The content of the Ag 1-x Cd x S coating layer is about 11%.

[0033] Example 7 The difference between this embodiment and Example 1 is as follows: In step S4 of this embodiment, use 1.61 g of zinc nitrate to replace 1.7 g of silver nitrate, and finally obtain 10.52 g of the in-situ deposited and coated phosphorus-carbon anode material.

[0034] In this embodiment, the mass of the material before coating is 10 g, and the mass of the material after coating is 10.52 g. The content of the Zn 1-x Cd x S coating layer is about 5%.

[0035] Example 8 The difference between this embodiment and Example 7 is as follows: In step S3 of this embodiment, 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 in a water bath at 65 °C, and continuously stir and react during the deposition process for 1 h; finally, 10.16 g of the CdS-coated phosphorus-carbon anode material is obtained in step S3; finally, 10.23 g of the in-situ deposited and coated phosphorus-carbon anode material is obtained in step S4.

[0036] In this embodiment, the material before coating is 10 g, and the material after coating is 10.23 g, with Zn 1-x Cd x The content of the S coating layer is about 2%.

[0037] Example 9 The difference between this embodiment and Example 5 is 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 deposition coated phosphorus-carbon anode material is obtained.

[0038] In this embodiment, the material before coating is 10 g, and the material after coating is 10.82 g, with Zn 1-x Cd x The content of the S coating layer is about 8%.

[0039] Comparative Example 1 This comparative example presents 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-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, and cooled to room temperature to obtain the phosphorus-carbon anode material.

[0040] In the phosphorus-carbon anode material prepared in this comparative example, the content of phosphorus is 45%, the content of the carbon material is 54%, and the content of sulfur is 1%.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that in this comparative example, step S4 is not carried out, and finally 10.32 g of the CdS-coated phosphorus-carbon anode material is obtained.

[0042] In this comparative example, the material before coating is 10 g, and the material after coating is 10.32 g, and the content of the CdS coating layer is about 3%.

[0043] Test Example (1) The phosphorus-carbon anode 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 anode material particles prepared in Example 1 is smooth, and Ag 1-x Cd xS is uniformly coated on the surface of the phosphorus-carbon material.

[0044] (2) Nitrogen adsorption and desorption tests were carried out on the phosphorus-carbon anode 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 anode material, and the results are shown in Table 1.

[0045] Table 1 Specific surface area data

[0046] (3) Powder resistance tests were carried out on the phosphorus-carbon anode 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 anode material is measured using an ST2722-SZ powder resistance meter. The results are shown in Table 2.

[0047] Table 2 Powder resistivity data

[0048] It can be seen from the results of Table 1 and Table 2 that: Compared with Comparative Example 1: In Example 1 and Example 7, a relatively thin Ag 1-x Cd x S coating layer (coating amount of 4%) and Zn 1-x Cd x S coating layer (coating amount of 5%) are uniformly coated on the surface of the phosphorus-carbon material respectively. The specific surface area of the phosphorus-carbon anode 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 anode material and improve the electrical conductivity, thereby reducing the generation of side reactions during the lithium intercalation process of the phosphorus-carbon anode material and improving the initial Coulomb efficiency; reducing the repeated rupture and reconstruction of the SEI film and improving the cycle stability; Compared with Example 1: When the deposition time of the phosphorus-carbon material in the CdS chemical bath growth solution in Example 2 was reduced to 1 h, the specific surface area of the in-situ deposited and coated phosphorus-carbon anode material increased slightly, and the resistivity increased. This may be because the CdS deposition time was short, resulting in non-uniform coating, and some porous carbon materials were exposed on the surface, thus slightly increasing the specific surface area and resistivity of the phosphorus-carbon anode material; when the deposition time of the phosphorus-carbon material in the CdS chemical bath growth solution in Example 3 and Example 6 was extended to 5 h and 4 h respectively, the specific surface area of the in-situ deposited and coated phosphorus-carbon anode material increased significantly and the resistivity increased slightly. This may be because the CdS deposition time was too long, resulting in a too thick 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; Compared with Example 1, when the concentration of the CdS chemical bath growth solution was increased in Example 4 and Example 5, the CdS coating layer was too thick, making the surface of the red phosphorus-carbon material relatively rough, thus increasing the specific surface area and slightly increasing the resistivity; Compared with Comparative Example 1, in Comparative Example 2, a CdS material was coated on the surface of the phosphorus-carbon material, resulting in a significant decrease in the specific surface area and a decrease in the resistivity; this is because the CdS was uniformly coated and the coating layer was thin, resulting in a significant decrease in the specific surface area and a decrease in the resistivity, indicating that the CdS coating layer can effectively reduce the specific surface area of the phosphorus-carbon anode material and reduce the resistivity of the material, reduce the generation of side reactions of the phosphorus-carbon anode material, avoid direct contact between red phosphorus and the electrolyte, inhibit the expansion of the phosphorus-carbon anode material, and improve the electrical properties of the phosphorus-carbon anode material.

[0049] Application Example The phosphorus-carbon anode materials prepared by using Examples 1-9 and Comparative Examples 1-2 were respectively made into button cells: the phosphorus-carbon anode material, 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, and the slurry was uniformly coated on the copper foil current collector and dried in a vacuum oven at 85 °C for 12 h to obtain the negative electrode sheet; a metal lithium sheet was used as the counter electrode, glass fiber was used as the separator, and NaClO 4 solution (concentration 1 mol / L, solvent composed of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) was used as the electrolyte, and button cells were assembled in a glove box under argon protection.

[0050] 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.

[0051] Table 3 Electrical Properties

[0052] According to Table 3, Figure 3 , Figure 4 , Figure 5 it can be seen from the results that: In Example 1, when the deposition time of the phosphorus-carbon material in the CdS chemical bath growth solution is 3 h and the silver-doped hydrothermal reaction time is 2 h, the specific capacity and the first Coulombic efficiency of the obtained phosphorus-carbon negative electrode material are optimal, which are 1326 mAh / g and 88.14% respectively. After 100 cycles, the specific capacity retention rate reaches 92%, and the charge-discharge performance at different current densities is significantly improved, and the rate performance is significantly improved. This is because when the CdS deposition time is 3 h and the silver-doped hydrothermal reaction time is 2 h, Ag x Cd 1-x S coating layer uniformly coats the phosphorus-carbon material and the coating layer is thinner, the coating amount is 4%, and the specific surface area decreases from 53.2 m 2 / g to 2.3 m 2 / g, reducing the generation of side reactions of the phosphorus-carbon negative electrode material, improving its conductivity, avoiding direct contact between red phosphorus and the electrolyte, inhibiting the expansion of the phosphorus-carbon material, improving the electrical properties of the phosphorus-carbon material, and improving its cycle stability and rate performance; Compared with Example 1: In Example 2, the addition amount of red phosphorus is reduced, resulting in a significant decrease in the specific capacity, but part of the exposed red phosphorus directly contacts the electrolyte and expands and pulverizes, resulting in a significant decrease in the first Coulombic efficiency; while in Example 3, the increase in the addition amounts of red phosphorus and elemental sulfur improves the specific capacity, but the increase in the specific surface area and resistivity leads to an increase in side reactions and a decrease in the first 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 first Coulombic efficiency; Compared with Example 1, in Examples 4 and 5, due to the overly thick CdS coating layer, the relative proportion of red phosphorus decreases, resulting in a reduction in the specific capacity. The increase in the specific surface area and resistivity also makes the transmission channel longer, resulting in a decrease in the first Coulombic efficiency; 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 the specific capacity and the first Coulombic efficiency, indicating 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 improve its cycle stability; Compared with Comparative Example 2, in Example 1 and Example 7, nano-silver and nano-zinc are doped in the CdS coating layer respectively, and the specific capacity and the first Coulombic efficiency are both significantly improved, indicating that doping nano-silver or nano-zinc 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.

[0053] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise 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 the scope recorded in this specification.

[0054] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on 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 shall be subject to the appended claims.

Claims

1. An in-situ deposited phosphorus-carbon negative electrode material, characterized in that: The invention comprises an inner core and an in-situ deposited layer in-situ deposited and coated outside the inner core, wherein the inner 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.

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

3. A method for preparing an in-situ deposited coated phosphorus-carbon negative electrode material as described in any one of claims 1 to 2, characterized in that: It includes the following steps: S1. Grind and mix red phosphorus, porous carbon and elemental sulfur, and sinter to obtain a phosphorus-carbon material; S2. mixing cadmium nitrate, thiourea and ammonia water to obtain a growth solution; S3. growing the phosphorus-carbon material in the growth solution, and post-treating the material to obtain a CdS-coated phosphorus-carbon negative electrode material; S4. Add a silver source or a zinc source, urea, and deionized water to the CdS-coated phosphorus-carbon negative electrode material, mix them, perform a hydrothermal reaction, and perform post-treatment to obtain an in-situ deposited phosphorus-carbon negative electrode material.

4. The method for preparing an in-situ deposited coated phosphorus-carbon negative electrode material according to claim 3, characterized in that: In step S1, the mass ratio of the red phosphorus, porous carbon and elemental sulfur is (30-55): (40-65): (1-5); the rotation speed of the pot mill mixing is 80-130 r / min, and the time is 4-12 h; The sintering is firstly carried out at 500-700°C for 3-5 hours and then at 250-300°C for 12-20 hours.

5. The method for preparing an in-situ deposited coated phosphorus-carbon negative electrode material according to claim 3, characterized in that: In step S2, the mass ratio of cadmium nitrate, thiourea and aqueous ammonia is (1-2):(7-16):(100-250); and the mixing is ultrasonic mixing for 5-15 minutes.

6. The method for preparing an in-situ deposited coated phosphorus-carbon negative electrode material according to claim 3, characterized in that: In step S3, the mass ratio of the phosphorus-carbon material to the growth liquid is 1:50-60; the growth is carried out under 60-75°C water bath heating for 1-6 hours; and the post-treatment includes ultrasonic treatment for 5-15 minutes, filtration, and vacuum drying at 85°C in sequence.

7. The method for preparing an in-situ deposited coated phosphorus-carbon negative electrode material according to claim 3, 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 method for preparing an in-situ deposited coated phosphorus-carbon negative electrode material according to claim 3, 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, the urea, and the deionized water is (10-12): (0.8-2): (0.3-1): (20-50).

9. The method for preparing an in-situ deposited coated phosphorus-carbon negative electrode material according to claim 3, characterized in that: In step S4, the hydrothermal reaction is carried out at 110-160° C. for 1-10 h, and the post-treatment includes filtration, washing, and vacuum drying at 85° C. in sequence.

10. Use of the in-situ deposited and coated phosphorus-carbon negative electrode material as claimed in any one of claims 1 to 2 as a negative electrode material for a lithium battery.

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