Lead thiophosphate composite nitrogen-doped carbon porous microsphere material as well as preparation method and application thereof

Abstract

The invention discloses a lead thiophosphate composite nitrogen-doped carbon porous microsphere material as well as a preparation method and application thereof, and belongs to the technical field of electrochemical energy storage materials. The preparation method of the lead thiophosphate composite nitrogen-doped carbon porous microsphere material comprises the following steps: dissolving a lead salt in an organic solvent, dissolving 2-methylimidazole in water, mixing the two solutions, carrying out solvothermal reaction, separating out a product, and reacting with a gas-phase sulfur source and a phosphorus source under the protection of inert gas to obtain the lead thiophosphate composite nitrogen-doped carbon porous microsphere material. The lead thiophosphate composite nitrogen-doped carbon porous microsphere composite material is obtained. According to the invention, a metal organic framework template method and a chemical vapor deposition method are ingeniously combined, and a brand new path for controllably preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material is provided. When the prepared lead thiophosphate composite nitrogen-doped carbon porous microsphere material is used as a sodium ion battery negative electrode, a porous microsphere negative electrode formed by compounding lead thiophosphate and nitrogen-doped carbon shows remarkably improved electrochemical performance.

Description

A lead thiophosphate composite nitrogen-doped carbon porous microsphere material, its preparation method and application Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials technology, specifically relating to a lead thiophosphate composite nitrogen-doped carbon porous microsphere material, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries, due to the abundance and low cost of sodium resources, are considered an important supplement and alternative to lithium-ion batteries. The performance of the anode material directly affects the energy density, cycle life, and safety performance of sodium-ion batteries. In recent years, metal phosphorus sulfides (such as lead thiophosphate, Pb2P2S6) have become promising anode material candidates due to their high theoretical specific capacity and unique layered structure. However, these materials still face the following key challenges in practical applications: Complex synthesis process: Traditional preparation methods often employ high-temperature sealed quartz tube chemical vapor transport, which has a long reaction cycle, high energy consumption, and poses a safety hazard of easy tube rupture, making it difficult to achieve large-scale production; Difficulty in morphology control: Existing methods often produce products that are irregular blocks or particles with low specific surface area, which is not conducive to the rapid insertion / extraction of sodium ions and affects rate performance; Poor intrinsic conductivity: Lead thiophosphate is a semiconductor material with low electronic conductivity, resulting in slow electrochemical reaction kinetics and severe polarization; Insufficient structural stability: During charge and discharge, the material undergoes significant volume changes, which can easily lead to the pulverization and shedding of active materials, resulting in rapid capacity decay.

[0003] To address the aforementioned issues, existing technologies often employ modification methods such as carbon coating, nano-sizing, or composite conductive polymers. However, these methods frequently suffer from uneven coating, complex processes, or weak interfacial bonding, failing to fundamentally achieve a synergistic improvement in material structural stability and conductivity. Therefore, developing a simple, cost-effective synthesis and modification method that can simultaneously optimize material morphology, conductivity, and structural stability is crucial for advancing the practical application of lead thiophosphate anodes. Summary of the Invention

[0004] The purpose of this invention is to provide a lead thiophosphate composite nitrogen-doped carbon porous microsphere material, its preparation method, and its application, in order to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solutions: One of the technical solutions of the present invention is a method for preparing a lead thiophosphate composite nitrogen-doped carbon porous microsphere material, comprising the following steps: dissolving lead salt in an organic solvent, dissolving 2-methylimidazole in water, then mixing the two solutions and carrying out a solvothermal reaction, separating the product and reacting it with a gaseous sulfur source and phosphorus source under the protection of an inert gas to obtain the lead thiophosphate composite nitrogen-doped carbon porous microsphere composite material.

[0006] Preferably, the lead salt includes at least one of lead nitrate, lead acetate, lead sulfate, and lead chloride.

[0007] Preferably, the organic solvent includes at least one of methanol, ethanol, and ethylene glycol.

[0008] Preferably, the molar ratio of 2-methylimidazole to lead ions in the lead salt is (1-20):1, more preferably (8-12):1.

[0009] Preferably, the temperature of the solvothermal reaction is 80–180°C, and the time is 6–48 h.

[0010] Preferably, the sulfur source is elemental sulfur and / or a sulfur-phosphorus compound; the phosphorus source is elemental phosphorus and / or a sulfur-phosphorus compound.

[0011] Optionally, the sulfur-phosphorus compound includes P2S5 or P4S. 10 .

[0012] Optionally, the inert gas includes argon, nitrogen, or a mixture of both.

[0013] Preferably, the reaction temperature is 400–650°C, the holding time is 1–8 h, and the heating rate to the reaction temperature is 2–10°C / min.

[0014] Preferably, the mass ratio of the product to the total mass of the sulfur source and phosphorus source is 1:(1-5), more preferably 1:(1-3).

[0015] Preferably, the molar ratio of sulfur in the sulfur source to phosphorus in the phosphorus source is (2-5):1.

[0016] Optionally, the product reacts with the gaseous sulfur and phosphorus sources under the protection of an inert gas as follows: the sulfur and phosphorus sources are placed upstream of the constant temperature zone of the tubular furnace, and the product is placed downstream. The inert gas is used as a carrier gas (the gas flow rate is preferably 20-100 sccm) to carry the vapors of the sulfur and phosphorus sources sublimated by heating to the downstream of the constant temperature zone of the tubular furnace to react with the product.

[0017] The second technical solution of the present invention provides a lead thiophosphate composite nitrogen-doped carbon porous microsphere material prepared according to the above-mentioned preparation method of lead thiophosphate composite nitrogen-doped carbon porous microsphere material.

[0018] The third technical solution of the present invention provides an application of the above-mentioned lead thiophosphate composite nitrogen-doped carbon porous microsphere material in the preparation of battery anode materials.

[0019] The beneficial technical effects of this invention are as follows: This invention ingeniously combines the metal-organic framework template method and chemical vapor deposition method, providing a novel route for the controllable preparation of lead thiophosphate composite nitrogen-doped carbon porous microspheres. The solvothermal product (Pb-ZIF precursor) in the preparation method provided by this invention has a regular structure, laying the foundation for the subsequent generation of highly crystalline and uniformly morphologically consistent lead thiophosphate composite nitrogen-doped carbon porous microspheres.

[0020] When the lead thiophosphate composite nitrogen-doped carbon porous microsphere material prepared in this invention is used as the anode of sodium-ion batteries, thanks to the porous nitrogen-doped carbon framework structure derived from the Pb-ZIF precursor, the porous microsphere anode formed by the composite of lead thiophosphate and nitrogen-doped carbon exhibits significantly improved electrochemical performance, specifically manifested as higher reversible specific capacity, excellent rate performance and outstanding long-cycle stability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 shows the XRD pattern of the nitrogen-doped carbon porous microsphere material of lead thiophosphate prepared in Example 1 and the standard XRD card of lead thiophosphate.

[0023] Figure 2 shows the SEM images of the nitrogen-doped carbon porous microspheres made of lead thiophosphate composite prepared in Example 1, where (a) and (b) are different magnifications.

[0024] Figure 3 shows the energy spectrum of the nitrogen-doped carbon porous microsphere material composed of lead thiophosphate prepared in Example 1. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0026] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0027] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] Example 1: Preparation method of lead thiophosphate composite nitrogen-doped carbon porous microspheres. The specific steps are as follows: 2.0 g (6 mmol) of lead nitrate was dissolved in 50 mL of methanol to obtain solution A; 4.0 g (48.7 mmol) of 2-methylimidazole was dissolved in 50 mL of deionized water to obtain solution B. Solution B was quickly poured into solution A, stirred for 10 min, and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 120 ℃ for 12 h. After centrifugation and washing, the mixture was vacuum dried at 70 ℃ to obtain a grayish-white precursor. 0.5 g of the ground grayish-white precursor was placed in a ceramic boat downstream of the isothermal zone of a tube furnace. 0.1 g of red phosphorus and 0.4 g of sulfur powder were mixed and placed in a ceramic boat upstream of the isothermal zone of the tube furnace. Under argon (50 sccm) protection, the temperature was increased to 500 ℃ at 5 ℃ / min and held for 2 h. After cooling, a yellowish-brown powder was obtained, which is the lead thiophosphate composite nitrogen-doped carbon porous microsphere material.

[0031] Example 2: Preparation method of lead thiophosphate composite nitrogen-doped carbon porous microspheres. The specific steps are as follows: 1.8 g (5.4 mmol) of lead acetate was weighed and dissolved in 40 mL of ethanol to obtain solution A; 8.0 g (97.4 mmol) of 2-methylimidazole was weighed and dissolved in 40 mL of deionized water to obtain solution B. Solution B was quickly poured into solution A, stirred for 10 min, and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 100 ℃ for 24 h, followed by centrifugation, washing, and vacuum drying at 70 ℃ to obtain a grayish-white precursor. 0.5 g of the ground grayish-white precursor and 0.6 g of P2S5 powder were placed in ceramic boats downstream and upstream of the isothermal zone of a tube furnace, respectively. Under nitrogen (30 sccm) protection, the temperature was increased to 450 ℃ at 3 ℃ / min and held for 4 h. After cooling, a yellowish-brown powder was obtained, which is the lead thiophosphate composite nitrogen-doped carbon porous microsphere material.

[0032] Example 3: Preparation method of lead thiophosphate composite nitrogen-doped carbon porous microspheres. The specific steps are as follows: 1.5 g (5.4 mmol) of lead chloride was weighed and dissolved in 30 mL of a mixed solvent of ethylene glycol and methanol (1:1 volume ratio) to obtain solution A; 5.0 g (61.0 mmol) of 2-methylimidazole was weighed and dissolved in 30 mL of deionized water to obtain solution B. Solution B was quickly poured into solution A, stirred for 10 min, and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 140 ℃ for 6 h, followed by centrifugation, washing, and vacuum drying at 70 ℃ to obtain a grayish-white precursor. 0.5 g of the ground grayish-white precursor, 0.16 g of red phosphorus, and 0.32 g of sulfur powder were placed in ceramic boats downstream and upstream of the isothermal zone of a tube furnace, respectively. Under argon (80 sccm) protection, the temperature was increased to 550 ℃ at 8 ℃ / min and held for 1.5 h. After cooling, a yellowish-brown powder was obtained, which is the lead thiophosphate composite nitrogen-doped carbon porous microsphere material.

[0033] Example 4: Preparation method of lead thiophosphate composite nitrogen-doped carbon porous microspheres. The specific steps are as follows: Weigh 2.5 g (7.5 mmol) of lead nitrate and dissolve it in 60 mL of methanol to obtain solution A; weigh 3.0 g (36.5 mmol) of 2-methylimidazole and dissolve it in 60 mL of deionized water to obtain solution B. Quickly pour solution B into solution A, stir for 10 min, and then transfer to a polytetrafluoroethylene reactor. React at 80 ℃ for 48 h, centrifuge and wash, and then vacuum dry at 70 ℃ to obtain a grayish-white precursor. Take 0.5 g of the ground grayish-white precursor and P4S... 10 0.8 g of powder was placed in ceramic boats downstream and upstream of the isothermal zone of a tube furnace. Under argon protection (40 sccm), the temperature was first increased to 400 ℃ at 2 ℃ / min and held for 1 h, then increased to 600 ℃ at 5 ℃ / min and held for 2 h. After cooling, a yellow-brown powder was obtained, which is the lead thiophosphate composite nitrogen-doped carbon porous microsphere material.

[0034] Example 5: Preparation method of lead thiophosphate composite nitrogen-doped carbon porous microspheres, the specific steps are as follows: Weigh 2.0 g (6 mmol) of lead acetate and dissolve it in 50 mL of ethanol to obtain solution A; weigh 7.39 g (90 mmol) of 2-methylimidazole, imidazole and Pb 2+Solution B was obtained by dissolving lead thiophosphate (15:1 molar ratio) in 50 mL of deionized water. Solution B was quickly poured into solution A, stirred for 10 min, and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 180 °C for 8 h. After centrifugation and washing, the solution was dried under vacuum at 70 °C to obtain a grayish-white precursor. 0.5 g of the ground grayish-white precursor, 0.09 g of red phosphorus, and 0.45 g of sulfur powder were placed in ceramic boats at the downstream and upstream of the constant temperature zone of a tube furnace, respectively. Under argon protection (100 sccm), the temperature was increased to 650 °C at 10 °C / min and held for 1 h. After cooling, a yellowish-brown powder was obtained, which is the lead thiophosphate composite nitrogen-doped carbon porous microsphere material.

[0035] Example 6: Preparation method of lead thiophosphate composite nitrogen-doped carbon porous microspheres. The specific steps are as follows: Weigh 1.0 g each of lead sulfate and lead acetate (3.3 mmol and 3 mmol respectively), dissolve in 50 mL of methanol to obtain solution A; weigh 6.0 g (73.1 mmol) of 2-methylimidazole and dissolve in 50 mL of deionized water to obtain solution B. Quickly pour solution B into solution A, stir for 10 min, and then transfer to a polytetrafluoroethylene reactor. React at 160 ℃ for 18 h, centrifuge, wash, and vacuum dry at 70 ℃ to obtain a grayish-white precursor. Take 0.5 g of the ground grayish-white precursor, 0.12 g of red phosphorus, and 0.48 g of sulfur powder, and place them respectively in ceramic boats downstream and upstream of the constant temperature zone of a tubular furnace. Under the protection of an argon / nitrogen mixture (Ar:N2=1:1, total flow rate 60 sccm), the temperature was increased to 480 ℃ at 4℃ / min and held for 6 h. After cooling, a yellow-brown powder was obtained, which is the lead thiophosphate composite nitrogen-doped carbon porous microsphere material.

[0036] The preparation method of lead thiophosphate in Comparative Example 1 is as follows: 0.5 g (1.5 mmol) of lead nitrate was ground and placed in a ceramic boat in the downstream section of the constant temperature zone of a tube furnace. Separately, 0.1 g of red phosphorus and 0.4 g of sulfur powder were mixed and placed in a ceramic boat in the upstream section of the constant temperature zone of the tube furnace. Under argon (50 sccm) protection, the temperature was increased to 500 °C at 5 °C / min and held for 2 h. After cooling, a yellowish-brown powder was obtained, which is lead thiophosphate.

[0037] The composite materials prepared in the above examples and comparative examples were characterized and tested: Figure 1 shows the XRD pattern of the lead thiophosphate composite nitrogen-doped carbon porous microsphere material prepared in Example 1 and the standard XRD card of lead thiophosphate.

[0038] Figure 2 shows the SEM images of the nitrogen-doped carbon porous microspheres made of lead thiophosphate composite prepared in Example 1, where (a) and (b) are different magnifications.

[0039] Figure 3 shows the energy spectrum of the nitrogen-doped carbon porous microsphere material composed of lead thiophosphate prepared in Example 1.

[0040] XRD results showed that characteristic diffraction peaks of lead thiophosphate were observed in the final products of all examples and comparative examples, indicating that the method provided by this invention can successfully synthesize lead thiophosphate-containing composite materials. SEM results showed that the composite materials prepared in the examples were all porous microspheres. Energy dispersive spectroscopy further showed that Pb, P, S, N, and C elements were uniformly distributed in the porous microspheres.

[0041] Electrochemical performance testing: The composite material was used as the negative electrode material for sodium-ion batteries to assemble half-cells for testing. The products obtained in the examples and comparative examples were used as active materials, mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 7:2:1, and N-methylpyrrolidone was added to form a uniform slurry. This slurry was then coated onto copper foil, vacuum dried, and cut into 9mm diameter disc electrodes. Batteries were assembled in a glove box with moisture and oxygen content below 0.1 ppm: the prepared disc electrodes were used as working electrodes, sodium foil as the counter / reference electrode, Whatman GF / D glass fiber as the separator, and a 1M NaPF6 diethylene glycol dimethyl ether solution as the electrolyte. After encapsulation, the batteries were allowed to stand for 12 hours to ensure full wetting of the active materials. The assembled batteries were subjected to constant current charge-discharge (GCD) testing using a Neware battery testing system, with the voltage window set from 0.01 to 3.0 V. The electrochemical performance data of Examples 1-6 and Comparative Example 1 at a current density of 0.1 A / g are shown in Table 1.

[0042] Table 1 As shown in Table 1, the nitrogen-doped carbon-modified lead thiophosphate composite material prepared using a metal-organic framework as a template exhibits significantly improved cycle stability as an anode material compared to pure lead thiophosphate. Example 1 (Pb2P2S6 / NC) demonstrates the highest reversible specific capacity (approximately 648.3 mAh / g) and excellent cycle stability (capacity retention >86% after 200 cycles) at a current density of 0.1 A / g, significantly outperforming the pure lead thiophosphate material without nitrogen doping.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a lead thiophosphate composite nitrogen-doped carbon porous microsphere material, characterized in that, The process includes the following steps: dissolving lead salt in an organic solvent, dissolving 2-methylimidazole in water, then mixing the two solutions and carrying out a solvothermal reaction, separating the product and reacting it with a gaseous sulfur source and phosphorus source under the protection of an inert gas to obtain the lead thiophosphate composite nitrogen-doped carbon porous microsphere composite material.

2. The method for preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 1, characterized in that, The lead salt includes at least one of lead nitrate, lead acetate, lead sulfate, and lead chloride; and / or, the organic solvent includes at least one of methanol, ethanol, and ethylene glycol.

3. The method for preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 1, characterized in that, The molar ratio of 2-methylimidazole to lead ions in the lead salt is (1-20):

1.

4. The method for preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 1, characterized in that, The solvothermal reaction is carried out at a temperature of 80–180°C for a duration of 6–48 h.

5. The method for preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 1, characterized in that, The sulfur source is elemental sulfur and / or sulfur-phosphorus compounds; the phosphorus source is elemental phosphorus and / or sulfur-phosphorus compounds.

6. The method for preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 1, characterized in that, The reaction temperature is 400–650℃, the holding time is 1–8h, and the heating rate to the reaction temperature is 2–10℃ / min.

7. The method for preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 1, characterized in that, The mass ratio of the product to the total mass of the sulfur and phosphorus sources is 1:(1-5).

8. The method for preparing the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 1, characterized in that, The molar ratio of sulfur in the sulfur source to phosphorus in the phosphorus source is (2-5):

1.

9. A lead thiophosphate composite nitrogen-doped carbon porous microsphere material prepared by the preparation method of the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to any one of claims 1 to 8.

10. The application of the lead thiophosphate composite nitrogen-doped carbon porous microsphere material according to claim 9 in the preparation of battery anode materials.

Images