Preparation method and application of secondary ball-milled sulfur-doped phosphorus-carbon negative electrode material

Abstract

The invention relates to a preparation method of a secondary ball-milled sulfur-doped phosphorus-carbon negative electrode material and application of the secondary ball-milled sulfur-doped phosphorus-carbon negative electrode material in a sodium-ion battery. The preparation method comprises the following steps: respectively weighing a proper amount of phosphorus source, carbon source and sulfur source according to a certain ball-to-material ratio; the phosphorus source can be selected from red phosphorus or black phosphorus, and the carbon source can be a carbon material with good conductivity and structural stability, such as graphite, carbon nanotubes, conductive carbon black and the like; the sulfur source may be a mixture of an inorganic sulfur source and a sulfur-containing biological agent. The primary ball-milling comprises the following steps: adding a phosphorus source and a carbon source into a ball-milling tank according to a certain proportion, and carrying out ball-milling treatment at a certain rotating speed for a certain time under the protection of inert gas, so that the phosphorus source and the carbon source are fully hybridized to form a phosphorus-carbon bond; and mixing the phosphorus-carbon material obtained by primary ball milling with a sulfur source, uniformly adding the mixture into the ball milling tank, carrying out secondary ball milling treatment at a certain rotating speed for a certain time under the protection of inert gas, and gradually dispersing and doping the sulfur source into the phosphorus-carbon system in the process to form the sulfur-doped phosphorus-carbon negative electrode material.

Description

Technical Field

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

[0002] Against the backdrop of the booming global new energy revolution, phosphorus-carbon anode materials, as a key area of ​​cutting-edge exploration, are gradually emerging. Compared with traditional graphite / hard carbon anode materials, phosphorus-carbon anode materials have a high theoretical specific capacity of 2596 mA h / g, which can greatly improve the energy density of batteries. At the same time, phosphorus-carbon anodes also have high safe reaction potentials (the lithiation reaction potential of phosphorus is 0.7V / sodium deposition reaction potential is 0.4V, which is much higher than the lithium / sodium deposition potential of 0V, effectively avoiding the formation of dendrites in lithium / sodium deposition). However, phosphorus-carbon anodes still face a severe challenge in practical applications, namely the volume expansion problem caused by the alloying reaction mechanism of the lithium / sodium intercalation process. This will seriously affect the cycle stability of the material and pose a major obstacle to its widespread application. Here, combining phosphorus and carbon sources through high-energy ball milling can form stable PC bonds and reduce the particle size of phosphorus sources. This helps to reduce the volume expansion effect during the alloying process. However, in this process, the phosphorus source cannot be completely covered by the carbon source, and a small amount of phosphorus source will still be exposed, which will adversely affect the stability of the material. To address the aforementioned issues, a sulfur source is added through a secondary ball milling process. The resulting PSC bond crosslinking network effectively alleviates volume expansion. Furthermore, the introduction of sulfur can passivate carbon surface defect sites, reduce excessive SEI film formation, and improve the first-efficiency of the phosphorus-carbon anode material. Summary of the Invention

[0003] The purpose of this invention is to obtain a sulfur-doped phosphorus-carbon anode material with high specific capacity and long cycle stability by forming PC and PS bonds between a phosphorus source and a carbon source and a sulfur source in sequence through secondary ball milling.

[0004] To achieve the above objectives, the experimental method employed in this invention is as follows: Appropriate amounts of phosphorus source, carbon source, and sulfur source are weighed according to a specific ball-to-material ratio. The phosphorus source can be red phosphorus or black phosphorus; the carbon source can be carbon materials with good conductivity and structural stability, such as graphite, carbon nanotubes, or conductive carbon black; and the sulfur source can be a mixture of inorganic sulfur source and sulfur-containing biological agents. The first ball milling involves adding the phosphorus source and carbon source to a ball milling jar in a specific ratio and, under the protection of an inert gas, performing ball milling at a specific speed and for a specific time, allowing the phosphorus source and carbon source to fully hybridize and form phosphorus-carbon bonds. The phosphorus-carbon anode material obtained from the first ball milling is then mixed with the sulfur source and uniformly added to the ball milling jar. Under the protection of an inert gas, a second ball milling process is performed at a specific speed and for a specific time. During this process, the sulfur source gradually disperses and incorporates into the phosphorus-carbon system, forming a sulfur-doped phosphorus-carbon anode material.

[0005] The phosphorus source is selected from red phosphorus or black phosphorus, and the carbon source is selected from one or more of the following substances, including but not limited to: acetylene black, Super P, Ketjen black, supercapacitor carbon, graphite, and carbon nanotubes. Preferably, it is one or more of acetylene black, graphite, and carbon nanotubes, and most preferably, it is graphite and carbon nanotubes (mass ratio of 1-5:0.5-2).

[0006] The sulfur source includes a mixture of inorganic sulfur source and sulfur-containing biological agent; The inorganic sulfur source is selected from any one of Fe2S3, Fe3S4 or Fe7S8; The sulfur-containing biological agent is selected from any one of cysteine, methionine, glutathione, and keratin; The mass ratio of inorganic sulfur source to sulfur-containing biological agent is 1-5:0.1-0.5; The mass ratio of the phosphorus-carbon composite material to the sulfur source is from 90:10 to 97.5:2.5.

[0007] The mass ratio of the phosphorus source, graphite, and carbon nanotubes is 5-10:1-5:0.5-2, preferably 5-7:2-4:0.5-1, and most preferably 6:3:1.

[0008] The ball-to-material ratio is 60-120:1, preferably 80-100:1.

[0009] The first ball milling operation was performed at a speed of 500-700 rpm for 12-36 hours, and the second ball milling operation was performed at a speed of 500-700 rpm for 12-36 hours.

[0010] The ratio of the phosphorus-carbon anode material obtained by ball milling to sublimated sulfur is 90-97.5:2.5-10, preferably 95-97.5:2.5-5.

[0011] Application of any of the above-mentioned sulfur-doped phosphorus-carbon anode materials obtained by secondary ball milling in sodium-ion batteries.

[0012] The above applications, using any of the sulfur-doped phosphorus-carbon anode materials for sodium-ion batteries as the anode, should also include binders and conductive agents.

[0013] The beneficial effects of this invention are as follows: This invention provides a secondary ball-milled sulfur-doped phosphorus-carbon anode material for use in sodium-ion batteries. Compared with the phosphorus-carbon anode material obtained by primary ball milling, the addition of sulfur in the secondary ball milling process can form a PSC crosslinking structure with the phosphorus-carbon anode material through chemical bonds, effectively suppressing the volume expansion of phosphorus during charging and discharging. In addition, the introduction of sulfur can passivate the defect sites on the carbon surface, reduce the excessive formation of SEI film, and improve the first-stage efficiency of the anode material. Attached Figure Description

[0014] Figure 1 These are the capacity-voltage curves of sodium-ion half-cells assembled from the P / C anode materials and P / C@S anode materials prepared in Examples 1 and 3.

[0015] Figure 2 This is a comparison of the discharge capacity and coulombic efficiency of button batteries assembled with P / C anode materials and P / C@S anode materials prepared in Examples 1 and 3 after 55 cycles at 0.5C. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0017] To better understand the present invention, the following description, in conjunction with embodiments and related drawings, further illustrates the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0018] Example 1 According to the ball-to-material ratio of 80:1, red phosphorus, graphite and carbon nanotubes were weighed into a ball mill jar in a ratio of 6:3:1. Under the protection of inert gas, the mixture was ball-milled at 600 rpm for 24 h to fully hybridize the phosphorus source and carbon source, form PC bonds, and obtain P / C anode material.

[0019] Using P / C negative electrode material as the active material, a slurry was prepared by mixing the active material, conductive agent SP, and binder PAA in a ratio of 8:1:1. The slurry was coated onto copper foil, and the negative electrode sheet was obtained after drying, rolling, and slicing. A button cell was assembled using a sodium sheet as the counter electrode, glass fiber as the separator, and NaPF6 / EC+DEC+EMC as the electrolyte. Electrochemical performance was tested on the Xinwei battery testing system, with a voltage range of 0.001-2 V and a rate of 0.5 C. The battery test results are listed in Table 1.

[0020] Example 2 According to the ball-to-material ratio of 80:1, red phosphorus, graphite and carbon nanotubes were weighed into a ball mill jar in a ratio of 7:2:1. Under the protection of inert gas, the mixture was ball-milled at 600 rpm for 24 h to fully hybridize the phosphorus source and carbon source, forming PC bonds, thus obtaining the P / C anode material.

[0021] The testing method was the same as in Example 1, and the battery test results are listed in Table 1.

[0022] Example 3 The P / C anode material obtained by ball milling in Example 1 was mixed with a sulfur source (Fe2S3 and cysteine ​​in a mass ratio of 1:0.5) at a ratio of 95:5 and then added to a ball mill jar. Under inert gas protection, the mixture was ball milled at 600 rpm for 24 h. During this process, the sulfur source gradually dispersed and was incorporated into the phosphorus-carbon system, resulting in the P / C@S anode material.

[0023] Using P / C@C anode material as the active material, the testing method was the same as in Experiment 1, and the battery test results are listed in Table 1.

[0024] Example 4 The P / C anode material obtained by ball milling in Example 1 was mixed with a sulfur source (Fe7S8 and glutathione at a mass ratio of 1:0.5) at a ratio of 97.5:2.5 and then added to a ball mill jar. Under inert gas protection, the mixture was ball milled at 600 rpm for 24 h. During this process, the sulfur source gradually dispersed and was incorporated into the phosphorus-carbon system, resulting in the P / C@S anode material.

[0025] Using P / C@C anode material as the active material, the testing method was the same as in Experiment 1, and the battery test results are listed in Table 1.

[0026] Example 5 The P / C anode material obtained by ball milling in Example 1 was mixed with a sulfur source (Fe3S4 and keratin mixed at a mass ratio of 1:0.5) at a ratio of 92.5:7.5 and then added to a ball milling jar. Under inert gas protection, the mixture was ball milled at 600 rpm for 24 h. During this process, the sulfur source gradually dispersed and was incorporated into the phosphorus-carbon system, resulting in the P / C@S anode material.

[0027] Using P / C@C anode material as the active material, the testing method was the same as in Experiment 1. The material particle size and battery test results are listed in Table 1.

[0028] Table 1. Performance Test Results of Phosphorus-Carbon Anode Materials

[0029] The comparison of material particle size D50 in Table 1 shows that secondary ball milling is beneficial for reducing material particle size. Lower particle size helps to mitigate the volume change of red phosphorus during cycling, thereby achieving better electrochemical performance. With the introduction of sulfur source, the material D50 gradually decreases, reaching its lowest value when the sulfur addition is 5%. At the same time, the comparison of battery performance shows that the material's initial efficiency and cycle stability are significantly positively correlated with particle size. Furthermore, increasing the carbon source ratio in primary ball milling helps to improve the material's cycle stability, and the introduction of sulfur in secondary ball milling can improve the initial efficiency and cycle stability of the anode material.

[0030] Figure 1 The figures show the capacity-voltage curves of sodium-ion half-cells assembled from the P / C anode material and the P / C@S anode material prepared in Examples 1 and 3. The first-stage efficiency of the P / C anode material battery is 85.85%, and that of the P / C@S anode material battery is 88.63%. The introduction of sulfur through secondary ball milling improved the first-stage efficiency by 2.78%. This is because the introduction of sulfur passivates the defect sites on the surface of the P / C anode material, reduces the excessive formation of the SEI film, and thus improves the first-stage efficiency of the anode material.

[0031] Figure 2 The discharge capacity and coulombic efficiency of the button cells assembled with the P / C anode material and P / C@S anode material prepared in Examples 1 and 3 after 100 cycles at 0.5C are compared. The capacity retention rate is obtained by dividing the discharge capacity of the 100th cycle by the discharge capacity of the 2nd cycle. The capacity retention rate of the P / C anode material battery is 56.34%, while the capacity retention rate of the P / C@S anode material battery is close to 100%. This is due to the cross-linking effect of PSC bonds, which suppresses the volume expansion of phosphorus during cycling.

[0032] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations; therefore, any obvious variations or modifications derived therefrom remain within the scope of protection of this invention.

Claims

1. A method for preparing a sulfur-doped phosphorus-carbon anode material, characterized in that, The method comprises the following steps: mixing the phosphorus source and the carbon source in a certain proportion, and then performing a first ball milling treatment to obtain a phosphorus-carbon composite material; mixing the phosphorus-carbon composite material and a sulfur source in a certain proportion, and then performing a second ball milling treatment to obtain a sulfur-doped phosphorus-carbon negative electrode material.

2. The production method according to claim 1, characterized by, The phosphorus source comprises at least one of red phosphorus and black phosphorus, and the carbon source comprises at least one of graphite, carbon nanotubes, acetylene black, Super P, Ketjen black and supercapacitor carbon.

3. The production method according to claim 2, characterized by, When the carbon source is graphite and / or carbon nanotubes, the mass ratio of graphite and / or carbon nanotubes is 1-5:0.5-2.

4. The production method according to claim 1, characterized by, The mass ratio of the phosphorus source, graphite and carbon nanotubes is 5-10:1-5:0.5-2.

5. The preparation method according to claim 1, characterized in that, The sulfur source comprises a mixture of an inorganic sulfur source and a sulfur-containing biological agent. The inorganic sulfur source is selected from any one of Fe2S3, Fe3S4 or Fe7S8. The sulfur-containing biological agent is selected from any one of cysteine, methionine, glutathione or keratin. The mass ratio of the inorganic sulfur source and the sulfur-containing biological agent is 1-5:0.1-0.

5. The mass ratio of the phosphorus-carbon composite material and the sulfur source is 90:10 to 97.5:2.

5.

6. The method of claim 1, wherein, The ball-to-material ratio of the first ball milling and / or the second ball milling is 60:1 to 120:

1.

7. The preparation method according to claim 1, characterized in that, The rotation speed of the first ball milling is 500-700 rpm, and the time is 12-36 hours; the rotation speed of the second ball milling is 500-700 rpm, and the time is 12-36 hours.

8. A sulfur-doped phosphorus-carbon anode material, characterized in that, The sulfur-doped phosphorus-carbon negative electrode material is prepared by the method of any one of claims 1-7.

9. An electrode sheet characterized by The sulfur-doped phosphorus-carbon negative electrode material of claim 8.

10. A sodium-ion battery or lithium-ion battery, characterized in that, The electrode sheet of claim 9.

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