A polypyrrole derivative / black phosphorus carbon-based composite material, its preparation method and application

Abstract

This invention discloses a polypyrrole derivative / black phosphorus carbon-based composite material and its preparation method, relating to the field of new energy battery materials technology. The polypyrrole derivative / black phosphorus carbon-based composite material disclosed in this invention possesses stable P-C bonds, which can stabilize the structure of black phosphorus to form a phosphorus-carbon conductive network structure. Furthermore, the polypyrrole derivative coating on its surface can effectively buffer the volume expansion of black phosphorus, effectively ensuring the cycle stability of the battery. When applied to the negative electrode of lithium-ion batteries, it can enable the battery to possess both high capacity and excellent cycle performance.

Description

Technical Field

[0001] This invention relates to the field of new energy battery materials technology, and in particular to a polypyrrole derivative / black phosphorus carbon-based composite material, its preparation method and application. Background Technology

[0002] Lithium-ion batteries possess numerous advantages, including high specific energy, high operating voltage, ease of use, and low environmental pollution, and are widely used in fields such as new energy vehicles. A lithium-ion battery mainly consists of a positive electrode, a negative electrode, an electrolyte, and a separator. Among these, the negative electrode material, as a crucial component of the lithium-ion battery, is primarily composed of commercially available graphite. However, the theoretical capacity of commercially available graphite is currently approaching its theoretical limit (372 mAh / g), leaving very limited room for improvement and making it difficult to meet the ever-growing market demand.

[0003] Black phosphorus, as a novel anode material for lithium-ion batteries, possesses excellent electrical / ionic conductivity and a high theoretical capacity (up to 2596 mAh / g). Compared to traditional graphite batteries, black phosphorus batteries offer smoother charging speeds, higher energy density, and longer, more stable battery life. However, black phosphorus anodes suffer from problems such as low electronic conductivity, dissolution of process byproducts (lithium polyphosphide, LixPPs), high volume expansion, and slow interfacial reaction kinetics. Therefore, it is necessary to combine black phosphorus with other materials to construct black phosphorus-based composite materials to address the volume expansion issue during cycling. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a polypyrrole derivative / black phosphorus carbon-based composite material, its preparation method and application.

[0005] This invention proposes a method for preparing a polypyrrole derivative / black phosphorus carbon-based composite material, comprising the following steps:

[0006] S1. Add black phosphorus material and carbon material to an alcohol solvent and carry out a solvothermal reaction to obtain black phosphorus carbon-based material;

[0007] S2. The black phosphorus carbon-based material is added to deionized water and dispersed evenly. Then, pyrrole derivative monomers and initiators are added to carry out a polymerization reaction to obtain polypyrrole derivative / black phosphorus carbon-based composite material.

[0008] The pyrrole derivative monomer is selected from at least one of the compounds shown in formulas (1) to (3):

[0009]

[0010] The polypyrrole derivative / black phosphorus carbon-based composite material of this invention has stable PC bonds, which can stabilize the structure of black phosphorus and form a phosphorus-carbon conductive network structure. Compared with single carbon materials, it has higher conductivity and faster ion diffusion channels, providing a faster transport channel for ions at the interface between the electrode material and the electrolyte, exhibiting excellent electrochemical performance. The polypyrrole derivative coating on its surface acts as a flexible conductive coating, which can effectively buffer the volume expansion of black phosphorus, playing a role in maintaining the integrity of the active material and improving conductivity, effectively ensuring the cycle stability of the battery. At the same time, because this invention uses a polypyrrole derivative with a specific structure, it contains more nitrogen atoms than polypyrrole. Nitrogen atoms have a better adsorption effect on polyphosphoric compounds, which can effectively adsorb LixP, alleviate the problem of polyphosphoric compound dissolution, thereby reducing the loss of active material, improving phosphorus utilization, and further improving the cycle stability of the battery. Therefore, the polypyrrole derivative / black phosphorus carbon-based composite material, as a negative electrode, enables the battery to have both high capacity and excellent cycle performance.

[0011] Preferably, the solvothermal reaction is carried out at 80–240°C for 2–10 hours. By controlling appropriate solvothermal reaction conditions, the resulting phosphorus-carbon conductive network structure can exhibit higher uniformity and stability, further enhancing the electrochemical performance of the material.

[0012] Preferably, the mass ratio of black phosphorus material to carbon material is 1:1 to 9. By controlling the ratio of black phosphorus material to carbon material, a uniform phosphorus-carbon conductive network structure can be formed, while ensuring the amount of carbon material is sufficient, thereby forming an effective conductive channel and further improving the conductivity of the material.

[0013] Preferably, the black phosphorus material is at least one of black phosphorus micropowder, black phosphorus nanosheets, and black phosphorus quantum dots; the carbon material is at least one of graphite, carbon nanotubes, and carbon black; and the alcohol solvent is at least one of methanol, ethanol, ethylene glycol, propanol, and isopropanol.

[0014] Preferably, the mass ratio of the black phosphorus carbon-based material, pyrrole derivative monomer, and initiator is 10:2 to 30:2 to 25. By controlling the ratio of the black phosphorus carbon-based material, pyrrole derivative monomer, and initiator, the polypyrrole derivative coating layer on the material surface can have a suitable thickness and uniformity, which is beneficial to further improving the cycle stability of the battery.

[0015] Preferably, the initiator is a ferric salt, ammonium persulfate, or a combination thereof.

[0016] Preferably, in step S2, the polymerization reaction temperature is 0–25°C, and the reaction time is 1–12 h. By controlling appropriate polymerization reaction conditions, the polypyrrole derivative coating layer on the material surface can have suitable thickness and uniformity, which is beneficial for further improving the cycle stability of the battery.

[0017] The present invention also proposes a polypyrrole derivative / black phosphorus carbon-based composite material, which is prepared by the aforementioned preparation method.

[0018] The present invention also proposes the use of the aforementioned polypyrrole derivative / black phosphorus carbon-based composite material as a negative electrode active material for lithium-ion batteries.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The polypyrrole derivative / black phosphorus carbon-based composite material of the present invention has stable PC bonds, which can stabilize the structure of black phosphorus to form a phosphorus-carbon conductive network structure. It has higher conductivity and faster ion diffusion channels than single carbon materials, and can provide faster transport channels for ions at the interface between electrode materials and electrolyte, exhibiting excellent electrochemical performance. The polypyrrole derivative coating on its surface acts as a flexible conductive coating, which can effectively buffer the volume expansion of black phosphorus, playing a role in maintaining the integrity of active materials and improving conductivity, and effectively ensuring the cycle stability of the battery. At the same time, since the present invention selects a polypyrrole derivative with a specific structure, it contains more N atoms than polypyrrole. N atoms have a better adsorption effect on polyphosphoric compounds, which can effectively adsorb LixP, alleviate the problem of polyphosphoric compound dissolution, thereby reducing the loss of active materials, improving phosphorus utilization, and further improving the cycle stability of the battery. Therefore, the polypyrrole derivative / black phosphorus carbon-based composite material of the present invention, as a negative electrode, can enable the battery to have both high capacity and excellent cycle performance.

[0021] (2) The preparation process of the polypyrrole derivative / black phosphorus carbon-based composite material of the present invention adopts a two-step method. First, black phosphorus carbon-based material is prepared by solvothermal method, and then a polypyrrole derivative coating layer is constructed on the surface of the composite material by in-situ polymerization method. It has the advantages of mild reaction conditions, simple operation and simple equipment. Detailed Implementation

[0022] The technical solution of the present invention will now be described in detail through specific embodiments.

[0023] Example 1

[0024] Preparation of polypyrrole derivative / black phosphorus carbon-based composite materials:

[0025] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes to 40mL of ethanol solvent and stir to disperse evenly. Then transfer to 50mL of reaction vessel and keep at 180℃ for 5h. After cooling, centrifuge, wash and dry to obtain black phosphorus carbon-based material.

[0026] S2. Add 0.4g of black phosphorus carbon-based material to deionized water and disperse it evenly. Then add 0.08g of pyrrole derivative monomer and 0.08g of ferric chloride. Stir and react at 15℃ for 12h. Then centrifuge, wash and dry to obtain polypyrrole derivative / black phosphorus carbon-based composite material.

[0027] The structural formulas of pyrrole derivative monomers are as follows:

[0028]

[0029] Example 2

[0030] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes to 40mL of ethanol solvent and stir to disperse evenly. Then transfer to 50mL of reaction vessel and keep warm at 100℃ for 4h. After cooling, centrifuge, wash and dry to obtain black phosphorus carbon-based material.

[0031] S2. Add 0.4g of black phosphorus carbon-based material to deionized water and disperse it evenly. Then add 0.08g of pyrrole derivative monomer and 0.08g of ferric chloride. Stir and react at 15℃ for 12h. Then centrifuge, wash and dry to obtain polypyrrole derivative / black phosphorus carbon-based composite material.

[0032] The structural formulas of pyrrole derivative monomers are as follows:

[0033]

[0034] Example 3

[0035] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes to 40mL of ethanol solvent and stir to disperse evenly. Then transfer to 50mL of reaction vessel and keep at 180℃ for 5h. After cooling, centrifuge, wash and dry to obtain black phosphorus carbon-based material.

[0036] S2. Add 0.4g of black phosphorus carbon-based material to deionized water and disperse it evenly. Then add 1g of pyrrole derivative monomer and 1g of ferric chloride. Stir and react at 15℃ for 12h. Then centrifuge, wash and dry to obtain polypyrrole derivative / black phosphorus carbon-based composite material.

[0037] The structural formulas of pyrrole derivative monomers are as follows:

[0038]

[0039] Comparative Example 1

[0040] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes to 40mL of ethanol solvent and stir to disperse evenly. Then transfer to a 50mL reactor and keep it at 180℃ for 5h. After cooling, centrifuge, wash and dry to obtain black phosphorus carbon-based material.

[0041] Comparative Example 2

[0042] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes to 40mL of ethanol solvent and stir to disperse evenly. Then transfer to 50mL of reaction vessel and keep at 180℃ for 5h. After cooling, centrifuge, wash and dry to obtain black phosphorus carbon-based material.

[0043] S2. Add 0.4g of black phosphorus carbon-based material to deionized water and disperse it evenly. Then add 0.08g of pyrrole monomer and 0.08g of ferric chloride. Stir and react at 15℃ for 12h. Then centrifuge, wash and dry to obtain polypyrrole / black phosphorus carbon-based composite material.

[0044] The structural formula of pyrrole monomer is as follows:

[0045]

[0046] Test case

[0047] The materials obtained in the above examples and comparative examples were mixed with conductive agent (conductive carbon black SP) and binder (polyvinylidene fluoride PVDF, solid content 10%) at a mass ratio of 90:2:8 to form a slurry. The slurry was then uniformly coated on a copper foil with a thickness of 6 μm, pressed into a sheet, punched into an electrode sheet with a diameter of 14 mm, and dried in a vacuum drying oven at 120°C for 10 h to form the electrode sheet.

[0048] Using the electrode sheet prepared above as the working electrode, the lithium metal sheet as the auxiliary electrode and reference electrode, and a 1 mol / L LiPF6 solution (the solvent is composed of EC, DMC and EMC in a volume ratio of 1:1:1), a CR2430 coin cell was assembled in a glove box.

[0049] The electrochemical performance of the prepared coin cells was tested. Test conditions: constant current charge-discharge experiment was conducted at a current density of 0.5C, with a voltage range of 0.005V-2.5V. The initial charge-discharge capacity and initial coulombic efficiency of the material were measured. Cyclic test was conducted at 25℃ under a constant current charge-discharge system of 0.5C / 0.5C, with 100 cycles.

[0050] The test results are shown in Table 1.

[0051] Table 1

[0052]

[0053] As can be seen from the examples, the polypyrrole derivative / black phosphorus carbon-based composite material prepared by the preparation method provided by the present invention has excellent electrochemical performance. The discharge capacity of the prepared batteries is all greater than 1500 mAh·g⁻¹, the initial efficiency is all greater than 90%, and the capacity retention rate after 100 cycles is all greater than 90%.

[0054] As shown in the table above, the capacity retention of the polypyrrole derivative / black phosphorus carbon-based composite material prepared in the examples after 100 cycles is significantly better than that of Comparative Examples 1 and 2. Specifically, the uncoated black phosphorus carbon-based material in Comparative Example 1 exhibits extremely unstable cycling performance, with a capacity retention of only 28.6% after 100 cycles. The cycling performance of the polypyrrole-coated black phosphorus carbon-based composite material in Comparative Example 2 is also significantly lower than that of the polypyrrole derivative / black phosphorus carbon-based composite material prepared in this invention. This is because the present invention uses a polypyrrole derivative with a specific structure for coating, which contains more nitrogen atoms than polypyrrole, effectively alleviating the problem of polyphosphorus leaching and thus reducing the loss of active materials. Therefore, the black phosphorus carbon composite material coated with polypyrrole derivative in the examples can more effectively ensure the cycle stability of the battery, thus enabling the battery to have both high capacity and excellent cycle performance.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a polypyrrole derivative / black phosphorus carbon-based composite material, characterized in that, Includes the following steps: S1. Add black phosphorus material and carbon material to an alcohol solvent and carry out a solvothermal reaction to obtain black phosphorus carbon-based material; S2. The black phosphorus carbon-based material is added to deionized water and dispersed evenly. Then, pyrrole derivative monomers and initiators are added to carry out a polymerization reaction to obtain a polypyrrole derivative / black phosphorus carbon-based composite material. The pyrrole derivative monomers are selected from at least one of the compounds shown in formulas (1) to (3). ； Equation (1) Equation (2) Equation (3).

2. The method for preparing the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 1, characterized in that, The conditions for the solvothermal reaction are: reaction at 80~240℃ for 2~10h.

3. The method for preparing the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 1, characterized in that, The mass ratio of black phosphorus material to carbon material is 1:1~9.

4. The method for preparing the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 1, characterized in that, The black phosphorus material is at least one of black phosphorus micro powder, black phosphorus nanosheets, and black phosphorus quantum dots; the carbon material is at least one of graphite, carbon nanotubes, and carbon black; and the alcohol solvent is at least one of methanol, ethanol, ethylene glycol, propanol, and isopropanol.

5. The method for preparing the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 1, characterized in that, The mass ratio of the black phosphorus carbon-based material, pyrrole derivative monomer, and initiator is 10:2~30:2~25.

6. The method for preparing the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 1, characterized in that, The initiator is a ferric salt, ammonium persulfate, or a combination thereof.

7. The method for preparing the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 1, characterized in that, In S2, the polymerization temperature is 0~25℃ and the reaction time is 1~12h.

8. A polypyrrole derivative / black phosphorus carbon-based composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The use of the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 8 as a negative electrode active material for lithium-ion batteries.

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