Polypyrrole derivative / black phosphorus carbon-based composite material as well as preparation method and application thereof

Abstract

The invention discloses a polypyrrole derivative / black phosphorus carbon-based composite material and a preparation method thereof, and relates to the technical field of new energy battery materials. The polypyrrole derivative / black phosphorus carbon-based composite material disclosed by the invention has stable P-C bonds, the structure of black phosphorus can be stabilized to form a phosphorus-carbon conductive network structure, the polypyrrole derivative coated on the surface of the composite material can effectively buffer the volume expansion of black phosphorus, the cycling stability of a battery is effectively ensured, and the composite material can be applied to a negative electrode of a lithium ion battery, so that the service life of the battery is prolonged. And the battery has high capacity and excellent cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy battery materials, and in particular to a polypyrrole derivative / black phosphorus carbon-based composite material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have many advantages such as high specific energy, high operating voltage, convenient use, and low environmental pollution, and are widely used in new energy vehicles and other fields. Lithium-ion batteries are mainly composed of positive electrodes, negative electrodes, electrolytes, and separators. Among them, the negative electrode material, as an important component of lithium-ion batteries, is mainly composed of commercial graphite. However, the theoretical capacity of commercial graphite is currently close to its theoretical limit (372mAh / g), and there is very limited room for improvement, making it difficult to meet the growing market demand.

[0003] As a new type of negative electrode material for lithium-ion batteries, black phosphorus has excellent electrical / ionic conductivity and high theoretical capacity (up to 2596 mAh / g). Compared with traditional graphite batteries, black phosphorus batteries charge more smoothly, have a higher energy density, and have a longer and more stable battery life. However, black phosphorus negative electrodes have problems such as low electronic conductivity, dissolution of process products lithium polyphosphide (LixPPs), high volume expansion rate, and slow interfacial reaction kinetics. Therefore, it is necessary to combine black phosphorus with other materials to construct black phosphorus-based composite materials to solve the volume expansion problem during the cycle. 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 and a preparation method and application thereof.

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

[0006] S1, adding a black phosphorus material and a carbon material into an alcohol solvent to perform a solvothermal reaction to obtain a black phosphorus carbon-based material;

[0007] S2, adding the black phosphorus carbon-based material into deionized water to disperse it evenly, then adding a pyrrole derivative monomer and an initiator to carry out a polymerization reaction to obtain a polypyrrole derivative / black phosphorus carbon-based composite material;

[0008] The pyrrole derivative monomer is selected from at least one of the compounds represented by formula (1) to formula (3):

[0009]

[0010] The polypyrrole derivative / black phosphorus carbon-based composite material of the present invention has a stable PC bond, which can stabilize the structure of black phosphorus to form a phosphorus-carbon conductive network structure, has higher conductivity and faster ion diffusion channels than single carbon materials, can provide faster transmission channels for ions at the interface between electrode materials and electrolytes, and exhibits excellent electrochemical performance; the polypyrrole derivative coated on its surface as a flexible conductive coating can effectively buffer the volume expansion of black phosphorus, play a role in maintaining the integrity of active materials and improving conductivity, and effectively ensure the cycle stability of the battery; at the same time, because the present invention selects polypyrrole derivatives with a specific structure, it contains more abundant N atoms than polypyrrole, and N atoms have a relatively excellent adsorption effect on polyphosphides, can effectively adsorb LixP, alleviate the problem of polyphosphide dissolution, thereby reducing the loss of active substances, improving the utilization rate of phosphorus, and further improving the cycle stability of the battery; therefore, the polypyrrole derivative / black phosphorus carbon-based composite material as a negative electrode can enable the battery to have both high capacity and excellent cycle performance.

[0011] Preferably, the solvothermal reaction conditions are: reacting at 80-240° C. for 2-10 hours. By controlling appropriate solvothermal reaction conditions, the formed phosphorus-carbon conductive network structure can have higher uniformity and stability, further improving the electrochemical performance of the material.

[0012] Preferably, the mass ratio of the black phosphorus material to the carbon material is 1: 1 to 9. By controlling the ratio of the black phosphorus material to the carbon material, a uniform phosphorus-carbon conductive network structure can be formed while ensuring the amount of carbon material, 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 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.

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

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

[0016] Preferably, in S2, the polymerization temperature is 0-25°C and the reaction time is 1-12 hours. By controlling the appropriate polymerization conditions, the polypyrrole derivative coating layer on the surface of the material can have an appropriate thickness and uniformity, which is beneficial to further improve the cycle stability of the battery.

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

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

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

[0020] (1) The polypyrrole derivative / black phosphorus carbon-based composite material of the present invention has a stable PC bond, which can stabilize the structure of black phosphorus to form a phosphorus-carbon conductive network structure, has higher conductivity and faster ion diffusion channel than single carbon material, can provide a faster transmission channel for ions at the interface between electrode material and electrolyte, and exhibits excellent electrochemical performance; the polypyrrole derivative coated on its surface as a flexible conductive coating can effectively buffer the volume expansion of black phosphorus, play a role in maintaining the integrity of active materials and improving conductivity, and effectively ensure the cycle stability of the battery; at the same time, since the present invention uses a polypyrrole derivative with a specific structure, it contains more N atoms than polypyrrole, and N atoms have a better adsorption effect on polyphosphides, can effectively adsorb LixP, alleviate the problem of polyphosphide dissolution, thereby reducing the loss of active substances, improving the utilization rate of phosphorus, 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, the black phosphorus carbon-based material is prepared by a solvent thermal method, and then a layer of polypyrrole derivative coating is constructed on the surface of the composite material by an in situ polymerization method. It has the advantages of mild reaction conditions, simple operation, and simple equipment. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is described in detail below 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 into 40mL of ethanol solvent and stir to disperse them evenly, then transfer them into a 50mL reactor, keep the reaction at 180°C for 5h, cool, centrifuge, wash and dry to obtain a black phosphorus carbon-based material;

[0026] S2, adding 0.4 g of black phosphorus carbon-based material into deionized water and dispersing it evenly, then adding 0.08 g of pyrrole derivative monomer and 0.08 g of ferric chloride, stirring and reacting at 15° C. for 12 h, then centrifuging, washing, and drying to obtain a polypyrrole derivative / black phosphorus carbon-based composite material;

[0027] The structural formula of the pyrrole derivative monomer is as follows:

[0028]

[0029] Example 2

[0030] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes into 40mL of ethanol solvent and stir to disperse them evenly, then transfer them into a 50mL reactor, keep them at 100°C for 4h, cool them, centrifuge, wash and dry them to obtain black phosphorus carbon-based materials;

[0031] S2, adding 0.4 g of black phosphorus carbon-based material into deionized water and dispersing it evenly, then adding 0.08 g of pyrrole derivative monomer and 0.08 g of ferric chloride, stirring and reacting at 15° C. for 12 h, then centrifuging, washing, and drying to obtain a polypyrrole derivative / black phosphorus carbon-based composite material;

[0032] The structural formula of the pyrrole derivative monomer is as follows:

[0033]

[0034] Example 3

[0035] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes into 40mL of ethanol solvent and stir to disperse them evenly, then transfer them into a 50mL reactor, keep the reaction at 180°C for 5h, cool, centrifuge, wash and dry to obtain a black phosphorus carbon-based material;

[0036] S2, adding 0.4 g of black phosphorus carbon-based material into deionized water and dispersing it evenly, then adding 1 g of pyrrole derivative monomer and 1 g of ferric chloride, stirring and reacting at 15° C. for 12 h, then centrifuging, washing, and drying to obtain a polypyrrole derivative / black phosphorus carbon-based composite material;

[0037] The structural formula of the pyrrole derivative monomer is as follows:

[0038]

[0039] Comparative Example 1

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

[0041] Comparative Example 2

[0042] S1. Add 1g of black phosphorus nanosheets and 1g of carbon nanotubes into 40mL of ethanol solvent and stir to disperse them evenly, then transfer them into a 50mL reactor, keep the reaction at 180°C for 5h, cool, centrifuge, wash and dry to obtain a black phosphorus carbon-based material;

[0043] S2, adding 0.4 g of black phosphorus carbon-based material into deionized water and dispersing it evenly, then adding 0.08 g of pyrrole monomer and 0.08 g of ferric chloride, stirring and reacting at 15° C. for 12 h, then centrifuging, washing, and drying to obtain a polypyrrole / black phosphorus carbon-based composite material;

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

[0045]

[0046] Test example

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

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

[0049] The prepared button cell was subjected to electrochemical performance test. Test conditions: constant current charge and discharge experiment was carried out at 0.5C current density, voltage range was 0.005V-2.5V, the first charge and discharge capacity and first coulomb efficiency of the material were measured, and cycle test was carried out at 25℃, 0.5C / 0.5C constant current charge and discharge mode, and the number of cycles was 100.

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

[0051] Table 1

[0052]

[0053] It can be seen from the examples that the polypyrrole derivative / black phosphorus carbon-based composite material prepared by the preparation method provided by the present invention has excellent electrochemical properties, the discharge capacity of the prepared batteries is more than 1500mAh.g-1, the first efficiency is more than 90%, and the capacity retention rate after 100 cycles is more than 90%.

[0054] As can be seen from the above table, the capacity retention rate of the polypyrrole derivative / black phosphorus carbon-based composite material prepared in the embodiment after 100 cycles is much better than that of Comparative Example 1 and Comparative Example 2. Among them, the uncoated black phosphorus carbon-based material in Comparative Example 1 exhibits extremely unstable cycle performance, and the capacity retention rate after 100 cycles is only 28.6%. The cycle performance of the black phosphorus carbon-based composite material coated with polypyrrole in Comparative Example 2 is also significantly lower than that of the polypyrrole derivative / black phosphorus carbon-based composite material prepared in the present invention. This is because the present invention uses a polypyrrole derivative with a specific structure for coating, which contains more N atoms than polypyrrole, and can effectively alleviate the problem of polyphosphide dissolution, thereby reducing the loss of active substances. Therefore, the black phosphorus carbon composite material coated with a polypyrrole derivative in the embodiment can more effectively ensure the cycle stability of the battery, so that the battery has both high capacity and excellent cycle performance.

[0055] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a polypyrrole derivative / black phosphorus carbon-based composite material, characterized in that: The following steps are involved: S1, adding a black phosphorus material and a carbon material into an alcohol solvent to perform a solvothermal reaction to obtain a black phosphorus carbon-based material; S2. Add the black phosphorus carbon-based material into deionized water and disperse it evenly, then add a pyrrole derivative monomer and an initiator to carry out a polymerization reaction to obtain a polypyrrole derivative / black phosphorus carbon-based composite material; the pyrrole derivative monomer is selected from at least one of the compounds represented by formula (1) to formula (3):

2. The method for preparing the polypyrrole derivative / black phosphorus carbon-based composite material according to claim 1, characterized in that: The solvent thermal reaction conditions are: reacting at 80-240° C. for 2-10 hours.

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 the black phosphorus material to the 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 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, the pyrrole derivative monomer and the 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 trivalent iron 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 reaction temperature is 0 to 25°C, and the reaction time is 1 to 12 hours.

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

9. 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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