阅读说明：本技术 一种层层自组装的二维纳米复合材料的制备方法 (Preparation method of two-dimensional nanocomposite material self-assembled layer by layer ) 是由 刘建辉 李冲 李培权 张颖 颜洋 于 2020-06-03 设计创作，主要内容包括：本发明公开了一种层层自组装的二维纳米复合材料的制备方法,属于钠离子电池电极材料制备技术领域。该方法将离子液体加入基底分散液中,在分散液中引入金属源和硫源后进行水热反应,得到的材料经洗涤、真空干燥、煅烧后,得到金属硫化物/石墨烯复合材料、金属硫化物/MXene复合材料或金属硫化物/石墨烯/Mxene复合材料。离子液体起氧化石墨烯层和MXene层的稳定剂及诱导二维金属硫化物层层地自组装在石墨烯和MXene纳米大片层上的结构导向剂的作用。本发明缓解了金属硫化物作为钠离子电池负极材料大量堆聚、导电性差和体积膨胀的缺点,在电化学测试中表现出优异的性能,同时该方法简单可靠、工艺重复性好、可操作性强。(The invention discloses a preparation method of a two-dimensional nanocomposite material by layer self-assembly, belonging to the technical field of preparation of sodium-ion battery electrode materials. According to the method, ionic liquid is added into a substrate dispersion liquid, a metal source and a sulfur source are introduced into the dispersion liquid, then hydrothermal reaction is carried out, and the obtained material is washed, dried in vacuum and calcined to obtain a metal sulfide/graphene composite material, a metal sulfide/MXene composite material or a metal sulfide/graphene/Mxene composite material. The ionic liquid plays a role of a stabilizer for a graphene oxide layer and an MXene layer and a structure directing agent for inducing the layer-by-layer self-assembly of two-dimensional metal sulfide on the graphene and MXene nano large sheet layer. The method relieves the defects of large accumulation, poor conductivity and volume expansion of the metal sulfide as the negative electrode material of the sodium-ion battery, shows excellent performance in electrochemical tests, and is simple and reliable, good in process repeatability and strong in operability.)

1. A preparation method of a two-dimensional nanocomposite material self-assembled layer by layer is characterized by comprising the following steps:

1) preparing a substrate dispersion under ultrasound; adding ionic liquid into the substrate dispersion liquid, and ultrasonically homogenizing the obtained mixture to obtain a solution A; the base dispersion liquid is one or a mixture of graphene oxide dispersion liquid and MXene dispersion liquid; the concentration of the graphene oxide dispersion liquid is 13-16 mg/ml^-1The concentration of MXene dispersion is 2-8 mg/ml^-1；

2) Adding a metal source into the solution A, and performing ultrasonic homogenization to obtain a precursor solution B; adding a sulfur source into the precursor liquid B, and uniformly stirring to obtain a precursor liquid C; carrying out hydrothermal reaction on the precursor solution C at the temperature of 160-200 ℃ for 16-24 h; after the reaction is finished, washing and drying to obtain a solid product; wherein the mass ratio of the metal source to the graphene oxide or MXene is 5-8: 1, and the mass ratio of the sulfur source to the metal source is 3-5: 1;

3) and calcining the solid product in an inert atmosphere at the temperature of 300-850 ℃ for 2-3 h to obtain a metal sulfide/graphene composite material, a metal sulfide/MXene composite material or a metal sulfide/graphene/MXene composite material.

2. The preparation method of claim 1, wherein the MXene dispersion is prepared by etching using MAX phase as a raw material.

3. The production method according to claim 1 or 2, wherein the ionic liquid is one or a mixture of two or more of 1-butyl-3-methylimidazole dihydrogen phosphate, 1-butyl-3-methylimidazole hydrogensulfate, 1-butyl-3-methylimidazole hydrogensulfite, 1-butyl-3-methylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole acetate, 1-butyl-3-methylimidazole chloride, and 1-butyl-3-methylimidazole bromide.

4. The method according to claim 1 or 2, wherein the metal source is Na₂MoO₄·2H₂O、SnCl₄·5H₂O、K₂SnO₃·3H₂O、SnCl₂·2H₂O、FeCl₃·6H₂O、K₂FeO₄One or a combination of two or more of them.

5. The method according to claim 3, wherein the metal source is Na₂MoO₄·2H₂O、SnCl₄·5H₂O、K₂SnO₃·3H₂O、SnCl₂·2H₂O、FeCl₃·6H₂O、K₂FeO₄One or a combination of two or more of them.

6. The method according to claim 1, 2 or 5, wherein the sulfur source is one or more of thiourea, thioacetamide, L-cysteine, and sulfur powder.

7. The preparation method according to claim 3, wherein the sulfur source is one or more of thiourea, thioacetamide, L-cysteine, and sulfur powder.

8. The preparation method according to claim 4, wherein the sulfur source is one or more of thiourea, thioacetamide, L-cysteine and sulfur powder.

9. The method of claim 1, 2, 5, 7 or 8, wherein the inert atmosphere is N₂Atmosphere or Ar atmosphere.

10. The preparation method according to claim 1, 2, 5, 7 or 8, wherein the ultrasonic process in the step 1) is performed for 1.5-3 hours at 23-30 ℃; the ultrasound in the step 2) is performed for 0.5-1 h at 23-30 ℃, and the stirring is performed for 0.25-1 h at 23-30 ℃ in the stirring process.

Technical Field

The invention belongs to the technical field of preparation of sodium-ion battery electrode materials, and particularly relates to a preparation method of a two-dimensional nanocomposite material by layer self-assembly.

Background

With the gradual depletion of global traditional fossil energy and the problem of environmental pollution caused by use, the development of renewable clean energy mainly based on solar energy and wind energy has become a global inevitable trend; however, these new energy sources have the characteristics of intermittency, space and time, and are difficult to be effectively utilized, and the advanced large-scale energy storage system is the key to solve the problem. Among various energy storage systems, electrochemical energy storage becomes the mainstream of people for developing energy storage technology due to the characteristics of high efficiency and flexibility, wherein a lithium ion battery has the advantages of high energy density, high conversion efficiency and the like and is one of the most concerned electric energy storage devices; however, the characteristics of the global demand and price of lithium resources are continuously increased year by year and the regional distribution is uneven, which fundamentally limits the development of the lithium ion battery in the large-scale energy storage industry. And the sodium element in the same main group with the lithium element has the physical and chemical properties similar to the lithium element, and the sodium resource is rich, widely distributed and low in price, so that the sodium-ion battery is very reasonable and extremely feasible to replace a lithium-ion battery in a large-scale energy storage system, and is widely concerned by people.

The two-dimensional material is a single atomic layer or severalThe layered material of the atomic layer mainly comprises metal sulfide, graphene, MXene and the like, and the carrier migration and the heat diffusion of the layered material are limited in a two-dimensional plane, so that the layered material has the characteristics of high electric conduction and heat conduction performance, large specific surface area and the like, and is widely applied to various fields. Metal sulfides (MoS)₂、SnS₂、SnS、FeS₂Etc.) also serve as a type of sodium ion battery cathode material, and two reactions can occur in the electrochemical reaction process: the conversion reaction and the alloying reaction can transfer more electrons in the reaction process, and the high theoretical specific capacity is realized. However, the low electron/ion conductivity of the metal sulfide itself and the serious volume expansion problem in the sodium intercalation process, and at the same time, the van der waals force between layers greatly promotes the massive accumulation of the material, which may cause a great amount of side reactions during the reaction process, resulting in irreversible capacity loss and poor cycle stability. Therefore, in order to further improve the sodium storage performance of the metal sulfide, the published literature designs various metal sulfide and carbon material (such as graphene, carbon nanotube and the like) nano composite materials through strategies such as structure design, size control, composite material synthesis and the like, and the problems existing in the metal sulfide are relieved by utilizing the high conductivity and porous structure of the carbon material.

The ionic liquid is a salt which is composed of organic cations and anions and is liquid at room temperature or near room temperature, has the characteristics of non-volatility and no pollution, is called as a green solvent, and is applied to various fields due to the advantages of excellent thermal stability, chemical stability, structural designability and the like; meanwhile, the ionic liquid has good affinity with the surfaces of inorganic materials and carbon materials, and the ionic liquid has a very wide prospect in the field of nano composite materials.

Disclosure of Invention

In order to solve the problem of poor cycling stability and specific capacity caused by the characteristics of a metal sulfide layer when the metal sulfide is used as a sodium ion battery cathode material, the invention provides a preparation method of a layer-by-layer self-assembled two-dimensional nanocomposite.

The invention is realized by the following technical scheme:

a preparation method of a two-dimensional nanocomposite material self-assembled layer by layer comprises the following steps:

1) preparing a substrate dispersion under ultrasound; adding ionic liquid into the substrate dispersion liquid, and uniformly mixing the obtained mixture under ultrasonic waves to obtain a solution A.

The substrate dispersion liquid is one or a mixture of Graphene Oxide (GO) dispersion liquid and MXene dispersion liquid; the Graphene Oxide (GO) dispersion liquid is prepared by using natural graphite powder as a raw material through an improved Hummers method, and the concentration of the Graphene Oxide (GO) dispersion liquid is 13-16 mg/ml^-1The dosage is less than 5 ml; MXene dispersion is in MAX phase (Ti)₂AlC、Ti₃AlC₂、V₂AlC、Nb₂AlC, etc.) as raw materials, and is prepared by an etching method, wherein the Mxene comprises Ti₂C、Ti₃C₂、V₂C or Nb₂C, etc., wherein the concentration of MXene dispersion is 2-8 mg/ml^-1The dosage is below 25 ml.

The concentration of the ionic liquid is 2-5 mg/ml^-1The dosage is less than 3 ml.

2) Adding a metal source into the solution A, and uniformly mixing under ultrasonic to obtain a precursor solution B; adding a sulfur source into the precursor liquid B, and uniformly stirring and mixing to obtain a precursor liquid C; transferring the precursor liquid C into a stainless steel reaction kettle with a polytetrafluoroethylene lining for hydrothermal reaction at the temperature of 160-200 ℃ for 16-24 h; and after the reaction is finished, washing and drying to obtain a solid product. Wherein the mass ratio of the metal source to the GO or MXene is 5-8: 1, and the mass ratio of the sulfur source to the metal source is 3-5: 1.

3) Calcining the dried solid product in a tubular furnace under an inert atmosphere at the calcining temperature of 300-850 ℃ for 2-3 h to obtain a product: the composite material comprises a metal sulfide/graphene composite material, a metal sulfide/MXene composite material or a metal sulfide/graphene/MXene composite material.

In the step 1), the ionic liquid is 1-butyl-3-methylimidazole dihydrogen phosphate ([ BMIM)][H₂PO₄]) 1-butyl-3-methylimidazolium hydrogen sulfate ([ BMIM ]][HSO₄]) 1-butyl-3-methylimidazolium bisulfite ([ BMIM)][HSO₃]) 1-butyl-3-methylimidazolium tetrafluoroborate ([ BMIM ]][BF₄]) 1-butyl-3-methylimidazolium acetate ([ BMIM ]][Ac]) 1-butyl-3-methylimidazolium chloride ([ BMIM)]Cl), 1-butyl-3-methylimidazolium bromide ([ BMIM)]Br) or a mixture of two or more thereof; 1-butyl-3-methylimidazole dihydrogenphosphate ([ BMIM ] is preferred][H₂PO₄])。

In the step 1), the ultrasonic cleaner for ultrasound has the parameter conditions that: carrying out ultrasonic treatment at the temperature of 23-30 ℃ for 1.5-3 h.

In the step 2), the metal source is Na₂MoO₄·2H₂O、SnCl₄·5H₂O、K₂SnO₃·3H₂O、SnCl₂·2H₂O、FeCl₃·6H₂O、K₂FeO₄One or a combination of two or more of them; the sulfur source is one or the combination of more than two of thiourea, thioacetamide, L-cysteine and sulfur powder.

In the step 2), the ultrasonic cleaner is used in the ultrasonic process, and the parameter conditions are as follows: carrying out ultrasonic treatment for 0.5-1 h at the temperature of 23-30 ℃; the stirring is carried out by using a magnetic heating stirrer, and the parameter conditions are as follows: stirring for 0.25-1 h at 23-30 ℃ to obtain a precursor which is uniformly mixed.

In the step 2), the washing process is as follows: washing with deionized water and absolute ethyl alcohol for two times respectively in sequence to obtain wet solid products; the drying process comprises the following steps: and (3) putting the wet solid product into a vacuum drying oven, and drying for 8-12 h at the temperature of 60 ℃.

In the step 3), the inert atmosphere is N₂Atmosphere or Ar atmosphere.

The invention has the beneficial effects that: the invention provides a preparation method of a layer-by-layer self-assembled two-dimensional nanocomposite, which takes Ionic Liquid (IL) as a solvent additive, wherein the electrostatic interaction between the cations of the ionic liquid and Graphene Oxide (GO) and MXene can stabilize the structures of the GO and the MXene, and induce the layer-by-layer self-assembly of metal sulfides, so that the metal sulfides can uniformly grow on the GO and the MXene. Meanwhile, anions of the ionic liquid can promote the release of sulfur ions in the metal sulfide. The composite material prepared and synthesized by the method has excellent performance as a cathode material of a sodium-ion battery, and meanwhile, the method is simple and reliable, good in process repeatability and strong in operability.

Drawings

FIG. 1 is the MoS prepared in example 1₂XRD pattern of/graphene composite material.

FIG. 2 is the MoS prepared in example 1₂TEM image of/graphene composite.

FIG. 3 is the MoS prepared in example 1₂The graphene composite material is 1 A.g^-1And a cycle performance chart under 100 circles.

FIG. 4 shows MoS prepared in example 1₂The content of the graphene composite material is 0.1-12.8 A.g^-1Graph of rate performance at current density.

FIG. 5 is the MoS prepared in example 1₂Nyquist plot for the/graphene composite.

FIG. 6 is the MoS prepared in example 4₂/Ti₃C₂XRD pattern of the composite.

FIG. 7 is the MoS prepared in example 4₂/Ti₃C₂SEM image of the composite material.

FIG. 8 is the MoS prepared in example 4₂/Ti₃C₂Cycle performance profile of the composite.

FIG. 9 is the MoS prepared in example 4₂/Ti₃C₂The composite material is in the range of 0.1-10 A.g^-1Graph of rate performance at current density.

FIG. 10 is the MoS prepared in example 4₂/Ti₃C₂Nyquist plot for composite material.

Detailed Description

The present invention will now be described in further detail by way of the following description of specific embodiments and the accompanying drawings, which are illustrative of the invention and not limiting.