Sodium-ion battery negative electrode material and preparation method and application thereof

Abstract

The application belongs to the technical field of battery material preparation, and particularly relates to a sodium ion battery negative electrode material and a preparation method and application thereof. The sodium ion battery negative electrode material comprises MoSe2-FeSe2-NiSe2 nanotubes and graphene sheets. The sodium ion battery negative electrode material is composed of MoSe2-FeSe2-NiSe2 nanotubes with a nanotube structure and three-dimensionally crosslinked graphene sheets, wherein the MoSe2-FeSe2-NiSe2 nanotubes are coated by the graphene sheets. The nanotube structure can relieve self expansion, improve stability, shorten the Na+ transmission path, accelerate ion transmission, and has high intrinsic conductivity. When the sodium ion battery negative electrode material is applied to a sodium ion battery, the problems of poor rate performance, poor stability, large structural expansion, and rapid capacity attenuation are overcome. + ​

Description

Technical Field

[0001] This invention belongs to the field of battery material preparation technology, specifically relating to a sodium-ion battery anode material, its preparation method, and its application. Background Technology

[0002] Currently, lithium-ion batteries (LIBs) are widely used in electric vehicles, aerospace, and grid energy storage due to their high energy density and long lifespan. However, the increasing cost of lithium-ion batteries, constrained by global lithium resource shortages, limits their large-scale application. Sodium, with its similar physicochemical properties to lithium, shares a similar energy storage principle with lithium-ion batteries. Sodium is abundant and inexpensive, making sodium-ion batteries more advantageous for large-scale energy storage devices. However, due to the difference in radii between sodium and lithium ions, graphite anode materials, which perform excellently in lithium-ion batteries, cannot exhibit similar performance in sodium-ion batteries, necessitating the development of suitable sodium-ion battery anode materials.

[0003] In recent years, transition metal selenides have been considered as one of the most promising anode materials for sodium-ion batteries, due to their affinity for Na+. + The conversion reaction has attracted widespread attention due to its advantages such as low cost, environmental friendliness, and high specific capacity. Among them, iron selenide (FeSe2) has a high theoretical capacity (500 mAh·g). -1 Iron selenide has been extensively studied. However, it has low electrical conductivity compared to Na. + The conversion reaction leads to significant volume expansion, capacity decay, and poor rate performance, severely limiting the application of iron selenide. Improving the electronic conductivity and cycle stability of selenide materials is crucial for the research of selenide-based sodium-ion battery anode materials. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of pure iron selenide material in the prior art, such as low intrinsic conductivity, poor rate performance and large structural expansion leading to rapid capacity decay when applied to sodium-ion batteries, so as to provide a sodium-ion battery anode material, its preparation method and application.

[0005] To this end, the present invention provides the following technical solution.

[0006] The first aspect of the present invention provides a sodium-ion battery anode material, the sodium-ion battery anode material comprising MoSe2-FeSe2-NiSe2 nanotubes and graphene sheets.

[0007] A second aspect of this invention provides a method for preparing a sodium-ion battery anode material, comprising the following steps:

[0008] (1) Preparation of phosphorus-doped Mo-Fe-Ni-MOF nanorods: Iron source, nickel source, phosphomolybdic acid, fumaric acid and alcohol are mixed and subjected to a first hydrothermal reaction to obtain phosphorus-doped Mo-Fe-Ni-MOF nanorods;

[0009] (2) Preparation of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes: The phosphorus-doped Mo-Fe-Ni-MOF nanorods are mixed with a selenium source and subjected to a second hydrothermal reaction and a first calcination to obtain a composite nanotube material of phosphorus-doped MoSe2-FeSe2-NiSe2 and carbon, which is referred to as phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes.

[0010] (3) Preparation of phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material: Phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene oxide are mixed, dried and then calcined to obtain a composite material of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene, which is referred to as phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material.

[0011] The temperature of the first hydrothermal reaction is 60–150°C, and the time is 6–18 hours.

[0012] The temperature of the second hydrothermal reaction is 90–200°C, and the time is 2–18 hours.

[0013] The first roasting temperature is 350–500℃, and the time is 2–12 hours;

[0014] Preferably, during the first calcination, the temperature is increased at a rate of 1 to 10 °C / min;

[0015] Preferably, the first calcination is carried out under an inert atmosphere, which is nitrogen and / or argon.

[0016] The iron source is an iron salt; preferably, the iron source is at least one of ferric chloride, ferric nitrate, and ferric sulfate.

[0017] Preferably, the nickel source is a nickel salt; preferably, the nickel source is at least one selected from nickel chloride, nickel nitrate, nickel acetate, and nickel sulfate.

[0018] Preferably, the alcohol is at least one of methanol, ethanol, propanol, and isopropanol;

[0019] Preferably, the selenium source is at least one selected from selenium dioxide, sodium selenide, sodium selenide, sodium selenite, selenite, sodium selenate, and selenium powder.

[0020] The second roasting temperature is 350–600℃, and the time is 2–6 hours;

[0021] Preferably, during the second calcination, the temperature is increased at a rate of 1 to 10 °C / min;

[0022] Preferably, the second calcination is carried out under an inert atmosphere, which is nitrogen and / or argon.

[0023] In step (1), the iron source, nickel source, phosphomolybdic acid and fumaric acid are expressed in g by mass, and the alcohol is expressed in ml by volume. The ratio of the amount of iron source, nickel source, phosphomolybdic acid, fumaric acid and alcohol is (1-10):(1-10):(1-10):(1-10):(30-50).

[0024] Preferably, in step (2), the mass ratio of the phosphorus-doped Mo-Fe-Ni-MOF nanorods to the selenium source is (1-10):(1-10);

[0025] Preferably, in step (3), the mass ratio of the phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes to graphene oxide is (0.1-1):(0.1-0.5).

[0026] In step (1), before the first hydrothermal reaction is carried out, a step of adding a surfactant is also included;

[0027] Preferably, the mass ratio of the iron source to the surfactant is (1-10):(1-3);

[0028] Preferably, the surfactant is at least one selected from polyvinylpyrrolidone, polyethylene glycol, and sodium dodecylbenzenesulfonate;

[0029] Preferably, step (2), when mixing the phosphorus-doped Mo-Fe-Ni-MOF nanorods and the selenium source, further includes the step of adding a reducing agent;

[0030] Preferably, the reducing agent is hydrazine hydrate.

[0031] A third aspect of the present invention provides a sodium-ion battery, comprising the above-described sodium-ion battery anode material or a sodium-ion battery anode material prepared by the above-described preparation method.

[0032] In step (1), the raw materials are mixed at a speed of 100-800 r / min for 10-120 min.

[0033] The ratio of phosphorus-doped Mo-Fe-Ni-MOF nanorods (by mass g) to reducing agent (by volume ml) is (1-10):(1-10); in step (2), the mixing method for mixing raw materials can be, but is not limited to, ultrasonication, and the time can be, but is not limited to, 10-120 min.

[0034] In step (3), when mixing the raw materials, the mixing method may be, but is not limited to, ultrasonic mixing, and the time may be, but is not limited to, 60 to 240 minutes. In step (3), the drying method before the second calcination may be, but is not limited to, freeze drying. The specific steps of freeze drying include: quick freezing in liquid nitrogen, followed by transfer to a freeze dryer, and freeze drying for 12 hours under conditions of pressure ≤15 Pa and temperature ≤-30 °C.

[0035] The technical solution of this invention has the following advantages:

[0036] 1. The present invention provides a sodium-ion battery anode material, wherein the sodium-ion battery anode material comprises MoSe2-FeSe2-NiSe2 nanotubes and graphene sheets. This sodium-ion battery anode material is a composite of nanotube-structured MoSe2-FeSe2-NiSe2 and three-dimensionally cross-linked graphene sheets, wherein the MoSe2-FeSe2-NiSe2 nanotubes are coated with graphene sheets. The nanotube structure can, on the one hand, alleviate its own expansion and improve stability, and on the other hand, shorten the Na... + The transport path is optimized, accelerating ion transport and exhibiting high intrinsic conductivity. When applied to sodium-ion batteries, it overcomes the problems of poor rate performance, poor stability, and rapid capacity decay caused by large structural expansion inherent in existing technologies. MoSe2, in particular, has a typical layered structure with a large interlayer spacing (0.646 nm), which is beneficial for Na+ transport. + The insertion and extraction of phosphorus enhances rate performance. The high capacity and conductivity of NiSe2 improve the material's capacity and rate performance. The heterostructure combining MoSe2, FeSe2, and NiSe2 significantly improves the intrinsic conductivity, capacity, and rate performance of FeSe2. Furthermore, phosphorus doping provides more redox sites, increasing sodium storage capacity. Graphene surface coating not only effectively improves conductivity but also mitigates the impact of graphene's excellent mechanical strength on sodium absorption. + The volume expansion during the conversion reaction improves electrode stability.

[0037] Furthermore, the MoSe2-FeSe2-NiSe2 nanotubes in this sodium-ion battery anode material have a length of 200 nm-1 μm, a diameter of 100 nm-500 nm, and a specific surface area of ​​50-250 m². 2 / g, with a specific capacity of 450–650 mAh / g; the specific surface area of ​​the sodium-ion battery anode material is 50–300 m² / g. 2 / g, with a specific capacity of 400-600mAh / g.

[0038] 2. The sodium-ion battery anode material provided by this invention introduces an alcohol into the reaction system of the anode material, utilizing the esterification reaction between fumaric acid and the alcohol to reduce the hydrothermal reaction activity, thereby increasing the phosphomolybdate [PMo] ion concentration. 12 O 40 ] 3- The coordination ability in the reaction system; then, through the coordination reaction of phosphomolybdate, P and Mo are introduced into the reaction system. The layered structure of MoSe2 itself and its large interlayer spacing (0.646 nm) are conducive to Na + The insertion and extraction of phosphorus can improve rate performance. Phosphorus doping can provide more redox sites and improve sodium storage in the material. Introducing high-capacity and high-conductivity NiSe2 into FeSe2 can improve the capacity and rate performance of the material. The heterostructure of MoSe2, FeSe2 and NiSe2 can greatly improve the intrinsic conductivity, capacity and rate performance of FeSe2.

[0039] The design concept of this invention is to first dope Ni, P, and Mo into an iron-based MOF in a coordination manner, introduce an alcohol solvent, and utilize the esterification reaction between fumaric acid and the alcohol to reduce the hydrothermal reactivity and increase the phosphomolybdate [PMo] group. 12 O 40 ] 3- The coordination ability in the reaction system was improved by obtaining a phosphorus-doped MoSe2-FeSe2-NiSe2 and C composite material through selenization reaction. This not only improved the conductivity and fast-charging capability of FeSe2, but also provided more redox sites, thus improving the sodium storage capacity of the material. Further, the phosphorus-doped MoSe2-FeSe2-NiSe2 / C was combined with graphene oxide to obtain a composite anode material. In this composite material, the phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes were coated with three-dimensionally cross-linked graphene sheets, which not only mitigated the effects of MoSe2-FeSe2-NiSe2 / C on sodium storage, but also improved the overall performance of the material. 2- The expansion of FeSe2-NiSe2 can also improve its conductivity and fast charging capability.

[0040] 3. The present invention provides a method for preparing a sodium-ion battery anode material. The method first prepares phosphorus-doped Mo-Fe-Ni-MOF nanorods, in which C, O, Fe, P, Ni, and Mo are uniformly distributed. The nanorods have a length of 200 nm to 1 μm and a diameter of 100 nm to 500 nm. These nanorods are then reacted with a selenium source to obtain heterostructured nanotubes composed of MoSe2, FeSe2, and NiSe2. These heterostructured nanotubes are then reacted with graphene oxide to coat the nanotubes with graphene sheets. An alcohol solvent is introduced into the reaction system to reduce the hydrothermal reactivity by esterification of fumaric acid and alcohol, thereby increasing the phosphomolybdate [PMo] ion concentration. 12 O 40 ] 3-The coordination ability in the reaction system; then, through the coordination reaction of phosphomolybdate, P and Mo are introduced into the reaction system. The layered structure of MoSe2 itself and its large interlayer spacing (0.646 nm) are conducive to Na + The insertion and extraction of phosphorus can improve rate performance. Phosphorus doping can provide more redox sites and improve sodium storage in the material. Introducing high-capacity and high-conductivity NiSe2 into FeSe2 can improve the capacity and rate performance of the material. The heterostructure of MoSe2, FeSe2 and NiSe2 can greatly improve the intrinsic conductivity, capacity and rate performance of FeSe2.

[0041] 4. The method for preparing sodium-ion battery anode material provided by this invention optimizes the size and structure of nanorods (nanotube precursors) by controlling parameters such as the temperature and time of the hydrothermal reaction, and the temperature, time, and heating rate of the calcination process. This is a crucial factor in preparing the sodium-ion battery anode material. Furthermore, adding a surfactant during the preparation of the sodium-ion battery anode material can improve the dispersion of the raw materials, which is beneficial to the reaction. Attached Figure Description

[0042] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 This is a high-magnification transmission electron microscope image of the sodium-ion battery anode material in Embodiment 1 of the present invention. Detailed Implementation

[0044] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0045] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0046] Example 1

[0047] This embodiment provides a method for preparing a sodium-ion battery anode material, including the following steps:

[0048] (1) Add 0.5g ferric chloride hexahydrate, 0.5g nickel chloride hexahydrate, and 0.5g phosphomolybdic acid (PMo) 12 0.1 g of polyvinylpyrrolidone, 0.5 g of fumaric acid, 40 mL of deionized water, and 40 mL of ethanol were mixed and stirred at 500 r / min for 30 min to obtain a mixture. The mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 120 °C for 12 hours. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried overnight at 60 °C to obtain phosphorus-doped Mo-Fe-Ni-MOF nanorods.

[0049] (2) Take 0.5g of phosphorus-doped Mo-Fe-Ni-MOF nanorods, 1g of selenium powder, 50mL of deionized water and 5mL of hydrazine hydrate, and ultrasonically mix for 30 minutes to obtain a homogeneous mixture; transfer the mixture to a hydrothermal reactor and hydrothermally react at 180℃ for 12 hours. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor; transfer the precursor to a tube furnace and heat it to 450℃ at a rate of 3℃ / min under a nitrogen atmosphere and hold it for 6 hours. After cooling to room temperature, obtain the phosphorus-doped MoSe2-FeSe2-NiSe2 and carbon composite nanotube material, denoted as phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotube.

[0050] (3) Take 0.2g of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes, 0.2g of graphene oxide powder, and 50mL of deionized water, and ultrasonically mix them for 180 minutes to obtain a homogeneous mixture. Place the mixture in a plastic cup and freeze it in liquid nitrogen. Then transfer it to a freeze dryer and freeze dry it for more than 12 hours under the conditions of pressure ≤15Pa and temperature ≤-30℃ to obtain a blend of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene oxide. Then transfer it to a tube furnace and heat it to 500℃ at a nitrogen atmosphere at a heating rate of 2℃ / min and hold it for 3 hours. After cooling to room temperature, obtain a composite material of phosphorus-doped MoSe2-FeSe2-NiSe2 / C and graphene, which is referred to as phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material.

[0051] Example 2

[0052] This embodiment provides a method for preparing a sodium-ion battery anode material, including the following steps:

[0053] (1) Add 0.5g ferric chloride hexahydrate, 0.25g nickel chloride hexahydrate, and 0.25g phosphomolybdic acid (PMo) 120.1 g of polyvinylpyrrolidone, 0.5 g of fumaric acid, 40 mL of deionized water, and 40 mL of ethanol were mixed and stirred at 500 r / min for 30 min to obtain a mixture. The mixture was then transferred to a hydrothermal reactor and hydrothermally reacted at 120 °C for 12 hours. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried overnight at 60 °C to obtain phosphorus-doped Mo-Fe-Ni-MOF nanorods.

[0054] (2) Take 0.5g of phosphorus-doped Mo-Fe-Ni-MOF nanorods, 1g of selenium powder, 50mL of deionized water, and 5mL of hydrazine hydrate. Mix them ultrasonically for 30min to obtain a homogeneous mixture. Then transfer the mixture to a hydrothermal reactor and react it at 180℃ for 12h. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor. Then transfer the precursor to a tube furnace and heat it to 450℃ at a rate of 3℃ / min under a nitrogen atmosphere and hold it for 6h. After cooling to room temperature, obtain phosphorus-doped MoSe2-FeSe. 2- NiSe2 / C nanotubes.

[0055] (3) Take 0.2g of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes, 0.2g of graphene oxide powder, and 50mL of deionized water, and ultrasonically mix them for 180 minutes to obtain a homogeneous mixture. Place the mixture in a plastic cup and freeze it in liquid nitrogen. Then transfer it to a freeze dryer and freeze dry it for more than 12 hours under the conditions of pressure ≤15Pa and temperature ≤-30℃ to obtain a blend of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene oxide. Then transfer the product to a tube furnace and heat it to 500℃ at a nitrogen atmosphere at a heating rate of 2℃ / min and hold it for 3 hours. After cooling to room temperature, obtain a phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material.

[0056] Example 3

[0057] This embodiment provides a method for preparing a sodium-ion battery anode material, including the following steps:

[0058] (1) Add 0.5g ferric chloride hexahydrate, 0.5g nickel chloride hexahydrate, and 0.5g phosphomolybdic acid (PMo) 12 0.1 g of polyvinylpyrrolidone, 0.5 g of fumaric acid, 40 mL of deionized water, and 40 mL of ethanol were mixed and stirred at 500 r / min for 30 min to obtain a mixture. The mixture was then transferred to a hydrothermal reactor and hydrothermally reacted at 120 °C for 12 hours. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried overnight at 60 °C to obtain phosphorus-doped Mo-Fe-Ni-MOF nanorods.

[0059] (2) Take 0.5g of phosphorus-doped Mo-Fe-Ni-MOF nanorods, 0.5g of selenium powder, 50mL of deionized water and 5mL of hydrazine hydrate, and ultrasonically mix for 30 minutes to obtain a homogeneous mixture; transfer the above mixture to a hydrothermal reactor and hydrothermally react at 180℃ for 12 hours. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor; transfer the precursor to a tube furnace and heat it to 450℃ at a rate of 3℃ / min under a nitrogen atmosphere and hold for 6 hours. After cooling to room temperature, obtain phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes.

[0060] (3) Take 0.2g of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes, 0.4g of graphene oxide powder, and 50mL of deionized water, and ultrasonically mix them for 180 minutes to obtain a homogeneous mixture. Place the mixture in a plastic cup and freeze it in liquid nitrogen. Then transfer it to a freeze dryer and freeze dry it for more than 12 hours under the conditions of pressure ≤15Pa and temperature ≤-30℃ to obtain a blend of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene oxide. Transfer the product to a tube furnace and heat it to 500℃ at a rate of 2℃ / min under a nitrogen atmosphere and hold it for 3 hours. After cooling to room temperature, obtain a phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material.

[0061] Example 4

[0062] This embodiment provides a method for preparing a sodium-ion battery anode material, including the following steps:

[0063] (1) Add 0.5g ferric chloride hexahydrate, 0.5g nickel chloride hexahydrate, and 0.5g phosphomolybdic acid (PMo) 12 0.1 g of polyvinylpyrrolidone, 0.5 g of fumaric acid, 40 mL of deionized water, and 40 mL of ethanol were mixed and stirred at 500 r / min for 30 min to obtain a mixture. The mixture was then transferred to a hydrothermal reactor and hydrothermally reacted at 120 °C for 12 hours. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried overnight at 60 °C to obtain phosphorus-doped Mo-Fe-Ni-MOF nanorods.

[0064] (2) Take 0.5g of phosphorus-doped Mo-Fe-Ni-MOF nanorods, 1g of selenium source, 50mL of deionized water and 5mL of hydrazine hydrate, and ultrasonically mix for 30 minutes to obtain a homogeneous mixture; transfer the above mixture to a hydrothermal reactor and hydrothermally react at 180℃ for 12 hours. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor; transfer the precursor to a tube furnace and heat it to 450℃ at a rate of 3℃ / min under a nitrogen atmosphere and hold it for 6 hours. After cooling to room temperature, obtain phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes.

[0065] (3) Take 0.2g of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes, 0.6g of graphene oxide powder, and 50mL of deionized water, and ultrasonically mix them for 180 minutes to obtain a homogeneous mixture. Place the mixture in a plastic cup and freeze it in liquid nitrogen. Then transfer it to a freeze dryer and freeze dry it for more than 12 hours under the conditions of pressure ≤15Pa and temperature ≤-30℃ to obtain a blend of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene oxide. Transfer the product to a tube furnace and heat it to 500℃ at a rate of 2℃ / min under a nitrogen atmosphere and hold it for 3 hours. After cooling to room temperature, obtain a phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material.

[0066] Example 5

[0067] This embodiment provides a method for preparing a sodium-ion battery anode material, including the following steps:

[0068] (1) Add 0.8g ferric nitrate, 0.2g nickel acetate, and 0.8g phosphomolybdic acid (PMo) 12 0.2 g polyethylene glycol, 0.5 g fumaric acid, 40 mL deionized water, and 40 mL methanol were mixed and stirred at 500 r / min for 30 min to obtain a mixture. The mixture was then transferred to a hydrothermal reactor and hydrothermally reacted at 80 °C for 10 hours. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried overnight at 60 °C to obtain phosphorus-doped Mo-Fe-Ni-MOF nanorods.

[0069] (2) Take 0.2g of phosphorus-doped Mo-Fe-Ni-MOF nanorods, 0.6g of selenium powder, 50mL of deionized water and 5mL of hydrazine hydrate, and ultrasonically mix for 30 minutes to obtain a homogeneous mixture; transfer the mixture to a hydrothermal reactor and hydrothermally react at 100℃ for 6 hours. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor; transfer the precursor to a tube furnace and heat it to 380℃ at a rate of 7℃ / min under a nitrogen atmosphere and hold it for 10 hours. After cooling to room temperature, obtain a composite material of phosphorus-doped MoSe2-FeSe2-NiSe2 and carbon, which is denoted as phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes.

[0070] (3) Take 0.8g of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes, 0.2g of graphene oxide powder, and 50mL of deionized water, and ultrasonically mix them for 180 minutes to obtain a homogeneous mixture. Place the mixture in a plastic cup and freeze it in liquid nitrogen. Then transfer it to a freeze dryer and freeze dry it for more than 12 hours under the conditions of pressure ≤15Pa and temperature ≤-30℃ to obtain a blend of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene oxide. Then transfer it to a tube furnace and heat it to 400℃ at a nitrogen atmosphere at a heating rate of 8℃ / min and hold it for 5 hours. After cooling to room temperature, obtain a composite material of phosphorus-doped MoSe2-FeSe2-NiSe2 / C and graphene, which is referred to as phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material.

[0071] Comparative Example 1

[0072] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0073] (1) Mix 0.5g ferric chloride hexahydrate, 0.1g polyvinylpyrrolidone, 0.5g fumaric acid, 40mL deionized water and 40mL ethanol solution, and stir at 500r / min for 30min to obtain a mixture; transfer the above mixture to a hydrothermal reactor, and hydrothermally react at 120℃ for 12 hours. After cooling to room temperature, wash the precipitate alternately with deionized water and ethanol and dry it overnight at 60℃ to obtain iron-based MOF nanorods.

[0074] (2) Take 0.5g of iron-based MOF nanorods, 1g of selenium source, 50mL of deionized water and 5mL of hydrazine hydrate, and ultrasonically mix for 30 minutes to obtain a homogeneous mixture; transfer the above mixture to a hydrothermal reactor and hydrothermally react at 180℃ for 12 hours. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor; transfer the precursor to a tube furnace and heat it to 450℃ at a heating rate of 3℃ / min under an inert atmosphere and hold it for 6 hours. After cooling to room temperature, pure FeSe2 / C nanotubes are obtained.

[0075] Comparative Example 2

[0076] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0077] (1) Add 0.5g ferric chloride hexahydrate, 0.5g nickel chloride hexahydrate, and 0.5g phosphomolybdic acid (PMo) 12 0.1 g of polyvinylpyrrolidone, 0.5 g of fumaric acid, and 40 mL of deionized water were mixed and stirred at 500 r / min for 30 min to obtain a mixture. The mixture was then transferred to a hydrothermal reactor and hydrothermally reacted at 120 °C for 12 hours. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried overnight at 60 °C to obtain Fe-Ni-MOF nanorods.

[0078] (2) Take 0.5g of Fe-Ni-MOF nanorods, 1g of selenium powder, 50mL of deionized water and 5mL of hydrazine hydrate, and ultrasonically mix for 30 minutes to obtain a homogeneous mixture; transfer the mixture to a hydrothermal reactor and hydrothermally react at 180℃ for 12 hours. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor; transfer the precursor to a tube furnace and heat it to 450℃ at a heating rate of 3℃ / min under an inert atmosphere and hold it for 6 hours. After cooling to room temperature, FeSe2-NiSe2 / C nanotubes are obtained.

[0079] (3) Take 0.2g of FeSe2-NiSe2 / C nanotubes, 0.2g of graphene oxide powder, and 50mL of deionized water, and ultrasonically mix them for 180 minutes to obtain a homogeneous mixture. Place the mixture in a plastic cup and freeze it in liquid nitrogen. Then transfer it to a freeze dryer and freeze dry it for more than 12 hours under the conditions of pressure ≤15Pa and temperature ≤-30℃ to obtain FeSe2-NiSe2 / C / GO. Then transfer it to a tube furnace and heat it to 500℃ at a heating rate of 2℃ / min under an inert atmosphere and hold it for 3 hours. After cooling to room temperature, obtain FeSe2-NiSe2 / C / graphene composite anode material.

[0080] Comparative Example 3

[0081] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0082] (1) Mix 0.5g ferric chloride hexahydrate, 0.5g fumaric acid, 40mL deionized water and 40mL ethanol, and stir at 500r / min for 30min to obtain a mixture; transfer the mixture to a hydrothermal reactor and hydrothermally react at 120℃ for 12 hours. After cooling to room temperature, wash the precipitate alternately with deionized water and ethanol and dry it overnight at 60℃ to obtain Fe-MOF nanorods.

[0083] (2) Take 0.5g Fe-MOF nanorods, 1g selenium powder, 50mL deionized water and 5mL hydrazine hydrate, and ultrasonically mix for 30 minutes to obtain a homogeneous mixture; transfer the mixture to a hydrothermal reactor and hydrothermally react at 180℃ for 12 hours. After cooling to room temperature, wash the precipitate with deionized water and dry it overnight at 60℃ to obtain the precursor; transfer the precursor to a tube furnace and heat it to 450℃ at a heating rate of 3℃ / min under an inert atmosphere and hold for 6 hours. After cooling to room temperature, FeSe2 / C nanotubes are obtained.

[0084] (3) Take 0.2g of FeSe2 / C nanotubes, 0.2g of graphene oxide powder, and 50mL of deionized water, and ultrasonically mix them for 180 minutes to obtain a homogeneous mixture. Place the mixture in a plastic cup and freeze it in liquid nitrogen. Then transfer it to a freeze dryer and freeze dry it for more than 12 hours under the conditions of pressure ≤15Pa and temperature ≤-30℃ to obtain FeSe2 / C / GO. Then transfer it to a tube furnace and heat it to 500℃ at a heating rate of 2℃ / min under an inert atmosphere and hold it for 3 hours. After cooling to room temperature, obtain FeSe2 / C / graphene composite anode material.

[0085] Comparative Example 4

[0086] This comparative example provides a method for preparing a negative electrode material. The difference from Example 1 is that terephthalic acid is used instead of fumaric acid. The rest is the same as in Example 1. During the preparation process, ferric chloride hexahydrate, nickel chloride hexahydrate, phosphomolybdic acid, polyvinylpyrrolidone, terephthalic acid and ethanol cannot react to form a precipitate. No product is obtained in step (1) and the reaction cannot proceed. This shows that a negative electrode material cannot be prepared by using terephthalic acid.

[0087] Test case

[0088] This experimental example provides the performance test results of the anode materials prepared in the embodiments and comparative examples, specifically:

[0089] (1) Figure 1 This is a high-magnification transmission electron microscope (TEM) image of the sodium-ion battery anode material from Example 1. Figure 1As can be seen from the data, the anode material of this sodium-ion battery has a hollow nanotube structure. The nanotubes are wrapped in graphene sheets. The nanotubes are about 800 nm long, about 400 nm in diameter, and about 50 nm thick.

[0090] (2) Assembly and performance testing of CR2032 button sodium-ion batteries mainly include the following steps:

[0091] A mixture of negative electrode material, conductive agent Ketjen black, and binder polyvinylidene fluoride was prepared at a mass ratio of 8:1:1. This mixture was then combined with N-methylpyrrolidone at a mass ratio of 25:75 and stirred until homogeneous to obtain a slurry. The slurry was then coated onto copper foil, dried, and rolled to obtain a sodium-ion battery electrode sheet with a thickness of 10–24 μm. Using the sodium-ion battery electrode sheet as the negative electrode and a sodium sheet as the positive electrode, a glass fiber separator was used. The electrolyte was preferably a diethylene glycol dimethyl ether solution containing 1 M NaCF3SO3. The cells were assembled into a CR2032 coin cell sodium-ion battery in an argon-filled glove box. The negative electrode material was derived from various examples and comparative examples.

[0092] The CR2032 coin cell sodium-ion battery underwent charge-discharge cycle testing at different current densities within a voltage range of 0–2V; at 200 mA·g -1 The capacity and capacity retention rate obtained from the first and 500th cycles of charge-discharge testing at different current densities are shown in Table 1. The average charging capacity after 10 charge-discharge cycles at different current densities is shown in Table 2.

[0093] Table 1 Charge / Discharge Capacity and Capacity Retention Rate

[0094]

[0095] Table 2 Average Charging Capacity

[0096]

[0097]

[0098] Note: 0.2' is the result of the rate test after high-rate charge and discharge.

[0099] As can be seen from Table 1, the negative electrode material prepared according to the present invention, when applied to a sodium-ion battery, achieves a performance of 200 mA·g⁻¹. -1 After 500 cycles at the current density, the charging capacity is 420mAh·g. -1 The above-mentioned capacity retention rate is ≥96%, with high energy density and excellent cycle stability.

[0100] As shown in Table 2, the anode material prepared by this invention exhibits excellent rate performance, maintaining a high capacity even at a current density of 3 A / g, indicating excellent fast-charging capability. Furthermore, the test results at 0.2° in Table 2 demonstrate that the sodium-ion battery obtained from the anode material of this invention exhibits good reversibility and excellent rate performance.

[0101] In Comparative Example 2, no alcohol was added during the preparation of the sodium-ion battery anode material. The coordination ability of phosphomolybdic acid was insufficient, preventing the introduction of P and Mo into the reaction system. Specifically, Mo could not be introduced into the nanotubes to form the MoSe2 structure, thus failing to improve the material's rate performance and capacity. Comparative Example 3, without introducing Mo and Ni into the anode material, resulted in a FeSe2 structure that did not significantly improve the material's rate performance and capacity. Comparative Example 4, using terephthalic acid instead of fumaric acid, failed to yield the desired anode material. Therefore, the experimental results show that this invention introduces alcohol into the system, utilizing the esterification reaction between fumaric acid and alcohol to reduce hydrothermal reactivity, thereby increasing the phosphomolybdate [PMo] group. 12 O 40 ] 3- The coordination ability in the reaction system; then, through the coordination reaction of phosphomolybdate, P and Mo are introduced into the reaction system. The layered structure of MoSe2 itself and its large interlayer spacing (0.646 nm) are conducive to Na + The insertion and extraction of phosphorus can improve rate performance. Phosphorus doping can provide more redox sites and improve sodium storage in the material. Introducing high-capacity and high-conductivity NiSe2 into FeSe2 can improve the capacity and rate performance of the material. The heterostructure of MoSe2, FeSe2 and NiSe2 can greatly improve the intrinsic conductivity, capacity and rate performance of FeSe2.

[0102] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a sodium-ion battery anode material, characterized in that, Includes the following steps: (1) Preparation of phosphorus-doped Mo-Fe-Ni-MOF nanorods: Iron source, nickel source, phosphomolybdic acid, fumaric acid and alcohol are mixed and subjected to a first hydrothermal reaction to obtain phosphorus-doped Mo-Fe-Ni-MOF nanorods; (2) Preparation of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes: The phosphorus-doped Mo-Fe-Ni-MOF nanorods are mixed with a selenium source and subjected to a second hydrothermal reaction and a first calcination to obtain a composite nanotube material of phosphorus-doped MoSe2-FeSe2-NiSe2 and carbon, which is referred to as phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes; (3) Preparation of phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material: Phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene oxide are mixed, dried and then calcined to obtain a composite material of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes and graphene, which is referred to as phosphorus-doped MoSe2-FeSe2-NiSe2 / C / graphene composite anode material; The temperature of the first hydrothermal reaction is 60~150℃, and the time is 6~18h; The temperature of the second hydrothermal reaction is 90~200℃, and the time is 2~18h; The first roasting temperature is 350~500℃, and the time is 2~12h; During the first calcination, the temperature is increased at a rate of 1~10℃ / min; The first calcination was carried out under an inert atmosphere; The second roasting temperature is 350~600℃, and the time is 2~6h; During the second calcination, the temperature is increased at a rate of 1~10℃ / min; The second calcination is carried out under an inert atmosphere.

2. The preparation method according to claim 1, characterized in that, The iron source is an iron salt.

3. The preparation method according to claim 2, characterized in that, The iron source is at least one of ferric chloride, ferric nitrate, and ferric sulfate.

4. The preparation method according to claim 2, characterized in that, The nickel source is a nickel salt.

5. The preparation method according to claim 4, characterized in that, The nickel source is at least one of nickel chloride, nickel nitrate, nickel acetate, and nickel sulfate.

6. The preparation method according to claim 2, characterized in that, The alcohol is at least one of methanol, ethanol, propanol, and isopropanol.

7. The preparation method according to claim 2, characterized in that, The selenium source is at least one of selenium dioxide, sodium selenide, sodium selenide, sodium selenite, selenite, sodium selenate, and selenium powder.

8. The preparation method according to claim 1, characterized in that, In step (1), the iron source, nickel source, phosphomolybdic acid and fumaric acid are expressed in g by mass, and the alcohol is expressed in ml by volume. The ratio of the amount of iron source, nickel source, phosphomolybdic acid, fumaric acid and alcohol is (1~10):(1~10):(1~10):(1~10):(30~50).

9. The preparation method according to claim 8, characterized in that, In step (2), the mass ratio of the phosphorus-doped Mo-Fe-Ni-MOF nanorod to the selenium source is (1~10):(1~10).

10. The preparation method according to claim 8, characterized in that, In step (3), the mass ratio of phosphorus-doped MoSe2-FeSe2-NiSe2 / C nanotubes to graphene oxide is (0.1~1):(0.1~0.5).

11. The preparation method according to claim 1, characterized in that, In step (1), before the first hydrothermal reaction is carried out, a step of adding a surfactant is also included.

12. The preparation method according to claim 11, characterized in that, The mass ratio of the iron source to the surfactant is (1~10):(1~3).

13. The preparation method according to claim 11, characterized in that, The surfactant is at least one of polyvinylpyrrolidone, polyethylene glycol, and sodium dodecylbenzenesulfonate.

14. The preparation method according to claim 11, characterized in that, Step (2) further includes adding a reducing agent when the phosphorus-doped Mo-Fe-Ni-MOF nanorods and selenium source are mixed.

15. The preparation method according to claim 14, characterized in that, The reducing agent is hydrazine hydrate.

16. A sodium-ion battery, characterized in that, Including sodium-ion battery anode materials prepared by the preparation method according to any one of claims 1-15.

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