A molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material and its preparation method

Abstract

This invention discloses a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material and its preparation method. The preparation method includes the following steps: (1) preparing polyaniline hollow spheres using aniline, hydrogen peroxide, anhydrous ferric chloride, and phosphoric acid aqueous solution as raw materials via a hydrothermal method; (2) immersing the polyaniline hollow spheres in concentrated hydrochloric acid, drying them, and then performing a secondary hydrothermal treatment with ammonium molybdate tetrahydrate and ammonium dihydrogen phosphate to obtain a precursor; (3) further carbonizing and phosphating the precursor with sodium hypophosphite monohydrate to obtain the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material. In this composite material, molybdenum phosphide is embedded in the hard carbon wall of polyaniline hollow spheres with a diameter of 200-300 nm in the form of 2-3 nm quantum dots, accounting for approximately 20-25 wt% by mass. The composite material provided by this invention can be used as an electrode material, and the potassium-ion batteries prepared from it have high specific capacity, good cycle stability, and excellent rate performance. Furthermore, the method provided by this invention has the advantages of simple process, low cost, and large-scale production capability.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material (MoP@NPHC) and its preparation method. This material can be used as a novel anode material for high-capacity, ultra-stable potassium-ion batteries. Background Technology

[0002] Over the past few decades, lithium-ion batteries have been widely used in electric vehicles and portable electronic products due to their advantages such as high energy density, long cycle life, and high operating voltage. However, the relative scarcity and uneven distribution of lithium resources have increased the cost of manufacturing lithium-ion batteries, thus limiting their further application. Potassium-ion batteries (PIBs), on the other hand, have a similar working principle to lithium-ion batteries, and potassium ion resources are abundant and widely distributed, effectively reducing battery manufacturing costs. Furthermore, potassium has a redox potential similar to lithium, indicating that potassium-ion batteries can provide higher operating voltage and energy density. Simultaneously, potassium ions have a lower desolvation energy in solution, giving potassium-ion batteries higher rate performance. Therefore, potassium-ion batteries have received increasing attention in recent years and are considered the most promising alternative to lithium-ion batteries in large-scale energy storage. However, due to the K... + It has more than Li + Larger ionic radii typically lead to large volume expansion and slow kinetics after potassization / depotassization, resulting in poor cycling stability and low capacity.

[0003] In recent years, carbon-based materials have gained widespread favor among researchers due to their low cost, environmental friendliness, and stable cycling performance. However, their relatively large volume expansion, slow kinetics, and relatively low theoretical capacity make them difficult to meet practical daily needs. Researchers have made many attempts to improve the electrochemical performance of carbon materials, among which hollow carbon materials can effectively adapt to volume expansion and accelerate Kc. + There is a consensus that improving diffusion rate can enhance rate performance and cycling stability. Meanwhile, heteroatom doping (such as N, P, B, O, and S) has been shown to improve potassium storage performance by altering the electronic structure and increasing K storage sites.

[0004] Metal phosphides (MoP, FeP, CoP, SnP) and other conversion reaction anode materials can provide higher theoretical capacity and energy density than carbon anodes, but they also face the challenge of large volume expansion during cycling, leading to structural collapse of the active material and rapid capacity decay. Reducing the size of metal oxides to construct metal phosphide / carbon heterostructures is considered one of the most promising strategies to address this challenge, and different combination strategies have been widely applied. In 0D carbon materials, combining metal phosphides with 0D carbon to design a yolk-shell structure can mitigate volume expansion and enhance electronic conductivity. In 1D carbon materials, carbon nanotubes and carbon nanofibers can serve as effective mechanical supports while providing 1D electronic conduction pathways. In 2D carbon materials, their nanosheet structures can provide abundant anchor points, which is beneficial for the uniform dispersion of the active material. This feature helps expose more active sites and maintain continuous electrical contact between the metal phosphide and the carbon framework.

[0005] Yan et al. synthesized a composite material of molybdenum phosphide and porous carbon (MoP@PC) using a simple mixing and annealing method. In MoP@PC, a large number of MoP nanodots with an average size of approximately 4 nm were uniformly embedded in the petal-shaped porous carbon. This MoP@PC was used to prepare a potassium-ion battery anode material with a performance of 100 mA·g. -1 The reversible capacity after 100 cycles under current is 330 mAh·g. -1 , in 1A·g -1 The capacity is 240 mAh·g after 1000 cycles at current density. -1 The capacity (Journal of Energy Chemistry, 2021, 571-578); however, the synthesized porous carbon materials have many irreversible defects that lead to low initial efficiency of the battery, which seriously affects its commercial application. Yi et al. used a simple electrospinning method, combined with subsequent carbonization and phosphorylation processes, to prepare a novel flexible membrane. This flexible membrane is composed of N, P co-doped carbon nanofibers, and the surface is decorated with MoP ultrafine nanoparticles. The potassium-ion battery electrode prepared by this method achieved a capacity of 100 mA·g -1 The display shows 320mAh·g -1 High capacity, at 2A·g -1 Maintain 220mAh·g -1 The method exhibits superior electrospinning rate capability (Small, 2019, doi:10.1002 / smll.201905301); however, the electrospinning yield is low, and its low production efficiency makes it difficult to meet the needs of large-scale production. Zong et al. utilized the coordination bonds and hydrogen bonds in water-soluble polyacrylamide hydrogels to uniformly confine MoP within three-dimensional porous NC to form ultrafine nanoparticles. The potassium-ion battery material prepared exhibits excellent capacity performance (at 0.1 A·g). -1It exhibits a current density of 256.1 mAh·g -1 It exhibits high capacity and long-term cycling stability (capacity retention of 89.9% after 800 cycles) (Advanced Science, 2021, 8, 2004, 142); however, the preparation method it provides is relatively complex, and the long synthesis cycle will also limit its commercialization process.

[0006] Therefore, it is of great significance to study a simple and mass-producible method for embedding MoP quantum dots in polyaniline-derived hollow hard carbon spheres for use as a novel potassium-ion battery anode material. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material and its preparation method, which addresses the shortcomings of the prior art. The present invention synthesizes a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material by hydrothermal method and one-step phosphating and carbonization method. Using this composite material as a negative electrode material for potassium-ion batteries can improve the capacity of the electrode material and alleviate the volume expansion of molybdenum phosphide and the resulting structural collapse during electrochemical cycling. It has good electrochemical performance. Moreover, the method provided by the present invention is simple, has mild reaction conditions, and can be mass-produced.

[0008] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0009] A molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material is disclosed, wherein molybdenum phosphide is uniformly embedded in the hard carbon wall of polyaniline hollow spheres with a diameter of 200-300 nm in the form of 2-3 nm quantum dots, and the hard carbon wall thickness of the polyaniline hollow spheres is 30-40 nm, wherein the mass fraction of molybdenum phosphide accounts for 20-25% of the mass fraction of the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material.

[0010] This invention also provides a method for preparing the above-mentioned molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material, comprising the following steps:

[0011] (1) Add aniline, hydrogen peroxide and anhydrous ferric chloride to an aqueous solution of phosphoric acid, stir evenly and carry out hydrothermal reaction, filter, wash and vacuum dry to obtain polyaniline hollow spheres.

[0012] (2) The polyaniline hollow spheres obtained in step (1) are soaked in hydrochloric acid and then dried;

[0013] (3) The product obtained in step (2) and ammonium molybdate tetrahydrate and ammonium dihydrogen phosphate were stirred evenly in deionized water, and then a hydrothermal reaction was carried out. After the reaction was completed, the product was filtered, washed and vacuum dried to obtain the precursor.

[0014] (4) The precursor obtained in step (3) and sodium hypophosphite monohydrate are carbonized and phosphated in an inert atmosphere. The resulting product is molybdenum phosphide quantum dot embedded polyaniline-derived hollow sphere hard carbon composite material.

[0015] According to the above scheme, in step (1), the mass ratio of aniline, hydrogen peroxide and anhydrous ferric chloride is 1:2:(0.017-0.03); the molar concentration of the phosphoric acid aqueous solution is 0.3-0.5M; the dispersion concentration of aniline in the phosphoric acid aqueous solution is 2-5mg / mL; the stirring time is 15-30min; the stirring speed is 300-500rpm; the hydrothermal reaction temperature is 140-160℃; and the hydrothermal reaction time is 6-8h.

[0016] According to the above scheme, in step (2), the mass concentration of hydrochloric acid is 30-37%, the soaking time is 18-24h, the drying temperature is 60-80℃, and the drying time is 18-24h.

[0017] According to the above scheme, in step (3), the mass ratio of the partial product obtained in step (2) to ammonium molybdate tetrahydrate and ammonium dihydrogen phosphate is 2:3:7; wherein the dispersion concentration of ammonium molybdate tetrahydrate in deionized water is 3-5 mg / mL; the stirring time is 20-30 min, the stirring speed is 300-600 rpm, the hydrothermal reaction temperature is 160-180℃, and the hydrothermal reaction time is 6-8 h.

[0018] According to the above scheme, in step (4), the mass ratio of the precursor and sodium hypophosphite monohydrate is 1:4, the inert atmosphere is argon, the carbonization temperature is 750-850℃, the holding time is 4-5h, and the heating rate is 2-5℃ / min.

[0019] According to the above scheme, in steps (1) and (3), the washing and vacuum drying are performed by washing with deionized water and anhydrous ethanol 2-4 times, the vacuum drying temperature is 60-80℃, and the heat preservation time is 12-18h.

[0020] The above-mentioned molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material is used as a negative electrode material for potassium-ion batteries.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) This invention discloses a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material. Electrochemical performance testing and characterization show that molybdenum phosphide is embedded in the hard carbon wall of hollow spheres with a diameter of 200-300 nm in the form of 2-3 nm quantum dots. These quantum dots can improve the capacity of the electrode material, and at the same time, because they are embedded in the carbon wall, they can effectively alleviate the volume expansion of molybdenum phosphide during electrochemical cycling. The hollow sphere structure of this material can increase the contact area with the electrolyte and effectively alleviate the structural collapse caused by the volume expansion during potassium insertion / depotassium removal. The successful doping of hard carbon with N and P in this material can improve the wettability of the material to the electrolyte.

[0023] (2) A potassium-ion half-cell prepared using the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material disclosed in this invention was tested at 100 mA·g. -1 The electrode material exhibits a current of 319 mAh·g -1 High reversible capacity, still retaining 251mAh·g after 300 cycles. -1 The specific capacitance has a capacity retention of 88.3%, and when the current density increases from 50 mA·g... -1 Gradually increase to 100, 200, 500, 1000, 2000, and then back to 100 mA·g -1 At that time, their specific capacities were 298, 274, 246, 194, 146, 100, and 264 mAh·g, respectively. -1 This indicates that the prepared electrode material has excellent rate performance and good stability.

[0024] (3) The preparation method of the molybdenum phosphide quantum dot embedded polyaniline-derived hollow sphere hard carbon composite material provided by the present invention is simple and efficient, with mild reaction conditions and low cost, suitable for industrial production, and has broad application prospects and huge market potential in potassium-ion batteries. Attached Figure Description

[0025] Figure 1 This is the XRD pattern of the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material of Example 1 of the present invention.

[0026] Figure 2 This is a transmission electron microscope (TEM) image of the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material of Example 1 of the present invention.

[0027] Figure 3 This is the EDS diagram of the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material of Example 1 of the present invention.

[0028] Figure 4 This is a thermogravimetric image of the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material of Example 1 of the present invention.

[0029] Figure 5 The half-cell assembled from molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material and potassium metal in Example 1 of this invention operates at 100 mA·g. -1 Performance diagram after 300 cycles at current density.

[0030] Figure 6 The graph shows the rate performance of a half-cell assembled with a potassium metal and molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material in Example 1 of this invention at different current densities.

[0031] Figure 7 The half-cell assembled from molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material and potassium metal in Example 1 of this invention operates at 1000 mA·g. -1 Capacity cycling diagram after 1000 cycles at high current density. Detailed Implementation

[0032] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments. The following, in conjunction with preferred embodiments, details the specific implementation methods, steps, features, and effects of a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material and its preparation method according to the present invention:

[0033] A molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material (MoP@NPHC) is disclosed, wherein molybdenum phosphide is uniformly embedded in the hard carbon wall of polyaniline hollow spheres with a diameter of 200-300 nm in the form of 2-3 nm quantum dots, and the hard carbon wall thickness of the polyaniline hollow spheres is 30-40 nm, wherein the mass of molybdenum phosphide accounts for 20-25% of the mass fraction of the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material.

[0034] Example 1

[0035] A method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material (MoP@NPHC) includes the following steps:

[0036] (1) Dissolve 2g aniline, 4g hydrogen peroxide and 0.06g anhydrous ferric chloride in 800mL of 0.4M phosphoric acid aqueous solution, and then stir at 300rpm for 20 minutes with an electromagnetic stirrer. Then, put the mixed solution into a reaction vessel and react at 140℃ in a drying oven for 6 hours. After the reaction is completed, cool to room temperature, filter by vacuum filtration device and wash three times with deionized water and anhydrous ethanol. Then place the obtained product in a vacuum drying oven and dry at 80℃ for 12 hours to obtain polyaniline hollow spheres for later use.

[0037] (2) Add the polyaniline hollow spheres obtained in step (1) to 3 mL of hydrochloric acid (mass fraction 37%), let stand for 24 h, and then put them into a magnetic heating stirrer to dry at 80 °C for 24 h for later use.

[0038] (3) Weigh 200 mg of the product obtained in step (2) and add it to 70 mL of deionized water. Then add 300 mg of ammonium molybdate tetrahydrate and 700 mg of ammonium dihydrogen phosphate to the solution in sequence. Stir the mixture at 500 rpm for 30 minutes using an electromagnetic stirrer and transfer it to a 100 mL reactor. React the mixture in a drying oven at 180 °C for 6 hours. After the reaction is completed, cool the mixture to room temperature. Then filter the mixture using a vacuum filter and wash it three times with deionized water and anhydrous ethanol. Place the separated and washed product in a vacuum drying oven and dry it at 80 °C for 12 hours to obtain the precursor.

[0039] (4) Weigh 100 mg and 400 mg of the precursor obtained in step (3) and place them into two ceramic boats respectively. Place the ceramic boat containing sodium hypophosphite monohydrate at the upwind end, and then heat it to 800°C at a rate of 5°C / min under an argon atmosphere and keep it at that temperature for 4 hours to obtain the product molybdenum phosphide quantum dot embedded polyaniline-derived hollow sphere hard carbon composite material. Treat the tail gas with saturated copper sulfate solution.

[0040] Taking the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material prepared in this embodiment as an example, such as Figure 1 As shown, the XRD images indicate that MoP is well bonded to the hollow spheres of hard carbon, and that MoP possesses a good crystal structure corresponding to PDF card 24-0771. Figure 2 As shown, the scanning electron microscope images indicate that the prepared MoP@NPHC hollow spheres have a diameter of 200-300 nm and a wall thickness of 30-40 nm. Figure 3 The image shows an EDS image of the MoP@NPHC product. The HAADF image indicates that MoP is uniformly embedded in the wall of hard carbon spheres as 2-3 nm quantum dots, and the uniform distribution of N, P, and Mo elements indicates successful N and P doping. This also helps improve the wettability of the electrode material with the electrolyte. Figure 4 The thermogravimetric image shown indicates that after heating to 800°C in air, only 37.39 wt% of MoOPO4 remains. Based on this, the content of molybdenum phosphide quantum dots is calculated to be 23.76% of the total mass of the material.

[0041] Molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material as an anode active material for potassium-ion batteries:

[0042] The prepared molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material, conductive carbon black SuperP, sodium carboxymethyl cellulose, and styrene-butadiene rubber were mixed and ground in a mass ratio of 70:20:5:5. The mixture was then dispersed in an appropriate amount of deionized water using a magnetic stirrer and stirred for 12 hours to form a uniform slurry. This slurry was then uniformly coated onto copper foil and finally dried in a vacuum oven at 120℃ for 12 hours to obtain the negative electrode material. The electrode sheet was fabricated by cutting the copper foil into circular pieces with a diameter of 10 mm. The active material mass loading of the cut electrode sheet was 1.0 mg·cm³. -2 Using potassium metal as the negative electrode and 12 mm diameter glass fiber (GF / D) as the battery separator, the electrolyte was a 5 M potassium bis(fluorosulfonyl)imide (KFSI) dissolved in a mixed solution of ethylene glycol dipotassium ether (DME). The cells were assembled into a 2016 type coin cell in an argon-atmosphere glove box, and the electrochemical performance of the cells was tested (0.01-3V).

[0043] In this example, the MoP@NPHC electrode material prepared was assembled with a pure potassium electrode to create a 100mA coin cell. -1 Cyclic performance under current such as Figure 5 As shown, the electrode material exhibits a capacity of 319 mAh·g. -1 High reversible capacity, still retaining 251mAh·g after 300 cycles. -1 The specific capacity has a capacity retention rate of 88.29% (the capacity retention rate is the capacity after 300 cycles divided by the capacity after the third cycle, which is automatically calculated by the software). Figure 6 Demonstrating the rate performance of MoP@NPHC electrode material at different current densities, from 50 mA·g -1 Gradually increase to 100, 200, 500, 1000, 2000, and then back to 100 mA·g -1 At those times, their specific capacities were 298, 274, 246, 194, 146, 100, and 264 mAh·g, respectively. -1 This indicates that the prepared electrode material has excellent rate performance and good stability. Figure 7 MoP@NPHC electrode material at 1000 mA·g -1 A schematic diagram of the long-cycle performance under high current density is shown in the figure. It can be seen that the electrode material exhibits high cycling performance at 1000 mA·g. -1 It still retains 150mAh·g after 1000 cycles at high current density. -1 The specific capacity demonstrates that the MoP@NPHC electrode material prepared in this embodiment has excellent high-current long-cycle performance.

[0044] Example 2

[0045] A method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material (MoP@NPHC) includes the following steps:

[0046] (1) Dissolve 2.5g aniline, 5g hydrogen peroxide and 0.065g anhydrous ferric chloride in 700mL of 0.3M phosphoric acid aqueous solution, and then stir at 400rpm for 25 minutes with an electromagnetic stirrer. Then, put the mixed solution into a reaction vessel and react at 150℃ in a drying oven for 6 hours. After the reaction is completed, cool to room temperature, filter by vacuum filtration device and wash three times with deionized water and anhydrous ethanol. Then place the obtained product in a vacuum drying oven and dry at 70℃ for 14 hours to obtain polyaniline hollow spheres for later use.

[0047] (2) Add the polyaniline hollow spheres obtained in step (1) to 3 mL of hydrochloric acid (mass fraction 37%), let stand for 20 h, and then put them into a magnetic heating stirrer to dry at 70 °C for 20 h for later use.

[0048] (3) Weigh 200 mg of the product obtained in step (2) and add it to 80 mL of deionized water. Then add 300 mg of ammonium molybdate tetrahydrate and 700 mg of ammonium dihydrogen phosphate to the solution in sequence. Stir the mixture at 400 rpm for 30 minutes using an electromagnetic stirrer and transfer it to a 100 mL reactor. React the mixture in a drying oven at 170 °C for 8 hours. After the reaction is completed, cool the mixture to room temperature. Then filter the mixture using a vacuum filter and wash it three times with deionized water and anhydrous ethanol. Place the separated and washed product in a vacuum drying oven and dry it at 70 °C for 14 hours to obtain the precursor.

[0049] (4) Weigh 100 mg and 400 mg of the precursor obtained in step (3) and place them into two ceramic boats respectively. Place the ceramic boat containing sodium hypophosphite monohydrate at the upwind end, and then heat it to 850°C at a rate of 4°C / min under an argon atmosphere and keep it at that temperature for 4 hours to obtain the product molybdenum phosphide quantum dot embedded polyaniline-derived hollow sphere hard carbon composite material. Treat the tail gas with saturated copper sulfate solution.

[0050] Molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material as an anode active material for potassium-ion batteries:

[0051] The prepared molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material, conductive carbon black SuperP, sodium carboxymethyl cellulose, and styrene-butadiene rubber were mixed and ground in a mass ratio of 70:20:5:5. The mixture was then dispersed in an appropriate amount of deionized water using a magnetic stirrer and stirred for 12 hours to form a uniform slurry. This slurry was then uniformly coated onto copper foil and finally dried in a vacuum oven at 120℃ for 12 hours to obtain the negative electrode material. The electrode sheet was fabricated by cutting the copper foil into circular pieces with a diameter of 10 mm. The active material mass loading of the cut electrode sheet was 1.0 mg·cm³.-2 Using potassium metal as the negative electrode and 12 mm diameter glass fiber (GF / D) as the battery separator, the electrolyte was a 5 M potassium bis(fluorosulfonyl)imide (KFSI) dissolved in a mixed solution of ethylene glycol dipotassium ether (DME). The cells were assembled into a 2016 type coin cell in an argon-atmosphere glove box, and the electrochemical performance of the cells was tested (0.01-3V).

[0052] In this example, the MoP@NPHC electrode material prepared in this study was assembled into a coin cell with a pure potassium electrode sheet, and the cell was tested at 100 mA g. -1 Under current cycling, the electrode material exhibits a capacity of 312 mAh·g. -1 High reversible capacity, still retaining 231mAh·g after 300 cycles. -1 The specific capacity was 84.11%. Rate performance of MoP@NPHC electrode material at different current densities: when the current density increases from 50 mA·g... -1 Gradually increase to 100, 200, 500, 1000, 2000, and then back to 100 mA·g -1 At those times, their specific capacities were 290, 261, 230, 185, 135, 95, and 255 mAh·g, respectively. -1 This indicates that the prepared electrode material possesses excellent rate performance and superior stability. The MoP@NPHC electrode material exhibits excellent rate performance and stability at 1000 mA·g. -1 It still retains 140mAh·g after 1000 cycles at high current density. -1 The specific capacity demonstrates that the MoP@NPHC electrode material prepared in this embodiment has excellent high-current long-cycle performance.

[0053] Example 3

[0054] A method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material (MoP@NPHC) includes the following steps:

[0055] (1) Dissolve 3g aniline, 6g hydrogen peroxide and 0.06g anhydrous ferric chloride in 600mL of 0.4M phosphoric acid aqueous solution, and then stir at 500rpm for 30 minutes with an electromagnetic stirrer. Then, put the mixed solution into a reaction vessel and react at 160℃ in a drying oven for 8 hours. After the reaction is completed, cool to room temperature, filter by vacuum filtration device and wash three times with deionized water and anhydrous ethanol. Then place the obtained product in a vacuum drying oven and dry at 60℃ for 18 hours to obtain polyaniline hollow spheres for later use.

[0056] (2) Add the polyaniline hollow spheres obtained in step (1) to 3 mL of hydrochloric acid (mass fraction 37%), let stand for 18 h, and then put them into a magnetic heating stirrer to dry at 60 °C for 24 h for later use.

[0057] (3) Weigh 200 mg of the product obtained in step (2) and add it to 90 mL of deionized water. Then add 300 mg of ammonium molybdate tetrahydrate and 700 mg of ammonium dihydrogen phosphate to the solution in sequence. Stir the mixture at 600 rpm for 20 minutes using an electromagnetic stirrer and transfer it to a 100 mL reactor. React the mixture in a drying oven at 180 °C for 6 hours. After the reaction is completed, cool the mixture to room temperature. Then filter the mixture using a vacuum filter and wash it three times with deionized water and anhydrous ethanol. Place the separated and washed product in a vacuum drying oven and dry it at 60 °C for 18 hours to obtain the precursor.

[0058] (4) Weigh 100 mg and 400 mg of the precursor obtained in step (3) and place them into two ceramic boats respectively. Place the ceramic boat containing sodium hypophosphite monohydrate at the upwind end, and then heat it to 800°C at a rate of 3°C / min under an argon atmosphere and keep it at that temperature for 5 hours to obtain the product molybdenum phosphide quantum dot embedded polyaniline-derived hollow sphere hard carbon composite material. Treat the tail gas with saturated copper sulfate solution.

[0059] Molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material as an anode active material for potassium-ion batteries:

[0060] The prepared molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material, conductive carbon black SuperP, sodium carboxymethyl cellulose, and styrene-butadiene rubber were mixed and ground in a mass ratio of 70:20:5:5. The mixture was then dispersed in an appropriate amount of deionized water using a magnetic stirrer and stirred for 12 hours to form a uniform slurry. This slurry was then uniformly coated onto copper foil and finally dried in a vacuum oven at 120℃ for 12 hours to obtain the negative electrode material. The electrode sheet was fabricated by cutting the copper foil into circular pieces with a diameter of 10 mm. The active material mass loading of the cut electrode sheet was 1.0 mg·cm³. -2 Using potassium metal as the negative electrode and 12 mm diameter glass fiber (GF / D) as the battery separator, the electrolyte was a 5 M potassium bis(fluorosulfonyl)imide (KFSI) dissolved in a mixed solution of ethylene glycol dipotassium ether (DME). The cells were assembled into a 2016 type coin cell in an argon-atmosphere glove box, and the electrochemical performance of the cells was tested (0.01-3V).

[0061] In this example, the MoP@NPHC electrode material prepared in this study was assembled into a coin cell with a pure potassium electrode sheet, and the cell was tested at 100 mA g. -1 Under current cycling, the electrode material exhibits a capacity of 309 mAh·g. -1 High reversible capacity, still retaining 228mAh·g after 300 cycles. -1 The specific capacity was 86.12%. Rate performance of MoP@NPHC electrode material at different current densities: when the current density increases from 50 mA·g... -1Gradually increase to 100, 200, 500, 1000, 2000, and then back to 100 mA·g -1 At those times, their specific capacities were 292, 265, 238, 188, 139, 96, and 258 mAh·g, respectively. -1 This indicates that the prepared electrode material possesses excellent rate performance and superior stability. The MoP@NPHC electrode material exhibits excellent rate performance and stability at 1000 mA·g. -1 It still retains 142mAh·g after 1000 cycles at high current density. -1 The specific capacity demonstrates that the MoP@NPHC electrode material prepared in this embodiment has excellent high-current long-cycle performance.

[0062] In summary, the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material provided by this invention has the characteristics of high specific capacity, good cycle stability, and excellent rate performance, making it a potential application material for high-rate, long-life potassium-ion batteries.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material for use as a negative electrode material in potassium-ion batteries, characterized in that, Includes the following steps: (1) Add aniline, hydrogen peroxide and anhydrous ferric chloride to an aqueous solution of phosphoric acid, stir evenly and carry out hydrothermal reaction, filter, wash and vacuum dry to obtain polyaniline hollow spheres; (2) The polyaniline hollow spheres obtained in step (1) are soaked in hydrochloric acid and then dried; (3) The product obtained in step (2) and ammonium molybdate tetrahydrate and ammonium dihydrogen phosphate are stirred evenly in deionized water, and then a hydrothermal reaction is carried out. After the reaction is completed, the product is filtered, washed and vacuum dried to obtain the precursor. (4) The precursor obtained in step (3) and sodium hypophosphite monohydrate are carbonized and phosphated in an inert atmosphere. The resulting product is a molybdenum phosphide quantum dot embedded polyaniline-derived hollow sphere hard carbon composite material used in potassium-ion battery anode materials. In the aforementioned molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material used as a negative electrode material for potassium-ion batteries, molybdenum phosphide is uniformly embedded in the hard carbon wall of polyaniline hollow spheres with a diameter of 200-300 nm in the form of 2-3 nm quantum dots. The hard carbon wall thickness of the polyaniline hollow spheres is 30-40 nm, and the mass fraction of molybdenum phosphide in the molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material is 20-25%.

2. The method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material for use as a negative electrode material in potassium-ion batteries according to claim 1, characterized in that... In step (1), the mass ratio of aniline, hydrogen peroxide and anhydrous ferric chloride is 1:2:(0.017-0.03); the molar concentration of the phosphoric acid aqueous solution is 0.3-0.5M; the dispersion concentration of aniline in the phosphoric acid aqueous solution is 2-5mg / mL; the stirring time is 15-30min; the stirring speed is 300-500rpm; the hydrothermal reaction temperature is 140-160℃; and the hydrothermal reaction time is 6-8h.

3. The method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material for use as a negative electrode material in potassium-ion batteries according to claim 1, characterized in that... In step (2), the hydrochloric acid mass concentration is 30-37%, the soaking time is 18-24h, the drying temperature is 60-80℃, and the drying time is 18-24h.

4. The method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material for use as a negative electrode material in potassium-ion batteries according to claim 1, characterized in that... In step (3), the mass ratio of the partial product obtained in step (2) to ammonium molybdate tetrahydrate and ammonium dihydrogen phosphate is 2:3:7; wherein the dispersion concentration of ammonium molybdate tetrahydrate in deionized water is 3-5 mg / mL; the stirring time is 20-30 min, the stirring speed is 300-600 rpm, the hydrothermal reaction temperature is 160-180℃, and the hydrothermal reaction time is 6-8 h.

5. The method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material for use as a negative electrode material in potassium-ion batteries according to claim 1, characterized in that... In step (4), the mass ratio of the precursor to sodium hypophosphite monohydrate is 1:4, the inert atmosphere is argon, the carbonization temperature is 750-850℃, the holding time is 4-5h, and the heating rate is 2-5℃ / min.

6. The method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material for use as a negative electrode material in potassium-ion batteries according to claim 1, characterized in that, In steps (1) and (3), the washing and vacuum drying are performed by washing with deionized water and anhydrous ethanol 2-4 times, with a vacuum drying temperature of 60-80℃ and a holding time of 12-18h.

7. The method for preparing a molybdenum phosphide quantum dot-embedded polyaniline-derived hollow sphere hard carbon composite material for use as a potassium-ion battery anode material, as described in claim 1, provides the application of this material as a potassium-ion battery anode material.

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