A nano-flake selenide and its preparation method and application

Abstract

The present invention discloses a nano-flake selenide and its preparation method and application, which belongs to the field of sodium ion battery technology. First, nickel salt and cobalt salt are used to prepare a flake precursor A. Due to the agglomeration effect, the obtained nano-flake precursor A agglomerates to form a flower-like structure. The precursor A is mixed with excess selenium powder and heated. On the one hand, a selenide is obtained. On the other hand, the particle size and structure of the selenide are regulated by excess liquid selenium. Due to the effect of surface tension, the flake precursor A is gradually separated to form a flake structure with a regular morphology during the formation of the selenide. The structure is unstable and the flake selenide can be dispersed with the help of ultrasonic technology. The nano-flake selenide finally obtained has a uniform morphology and is well dispersed. The method of the present invention is simple to operate, has good controllability and repeatability, can be mass-produced, and the obtained nano-selenide can be applied to fields such as energy storage, catalysis and adsorption.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a nano-plate-shaped selenide and a preparation method and application thereof. Background Art

[0002] Energy is the material foundation for human survival and development. Lithium-ion batteries have long dominated the energy storage sector. However, the scarcity and high cost of lithium resources have severely limited their large-scale application. In contrast, sodium is abundant and inexpensive, and sodium-ion batteries offer electrochemical performance comparable to lithium-ion batteries, making them considered the most promising next-generation energy storage power source. Anode materials are key battery components. Among traditional transition metal compounds such as oxides, phosphides, and selenides, transition metal selenides offer advantages such as high theoretical specific capacity, moderate conductivity, and structural stability, holding broad application prospects in sodium storage. Selenides are prepared using methods such as hydrothermal, spinning, CVD, and electrodeposition. Beyond exploring ways to impart specialized properties to selenides by combining them with conductive or functional materials, enhancing their conductivity and catalytic activity, a key breakthrough in the energy storage field lies in more efficiently utilizing surface active sites. For example, it is well known that nano-selenides can help expose more surface active sites, and obtaining nanomaterials is a current research hotspot in selenide preparation. Traditionally, Kim et al. have used mechanical exfoliation to prepare selenide nanosheets to address the large size of selenides. While this method can remove large selenide sheets and expose surface active sites, it is inefficient. While electrospinning or electrodeposition can produce smaller selenides, these methods also present complex preparation processes and difficulties in scalable production.

[0003] In view of the problems of traditional selenides such as large size, difficulty in preparing nano-selenides and low consistency, there is an urgent need to explore a new method for preparing nano-selenides. On the one hand, it can simplify the preparation process of selenides, and on the other hand, it can improve the consistency of products and promote industrial applications. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a preparation method and application of nano-flake selenides to solve the technical problems of difficulty in preparing the nanomorphology and poor consistency of traditional nano-selenides, and to give nano-selenides excellent rate performance in sodium storage by means of the rich surface active sites of nanomaterials.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses a method for preparing nano-flake selenide, comprising the following steps:

[0007] S1. Adding nickel salt, cobalt salt and pH adjuster into deionized water and performing hydrothermal reaction to obtain precursor A;

[0008] S2, mixing the precursor A prepared in step S1 with selenium powder, and treating the mixture at low temperature under an inert atmosphere to obtain a bulk nickel-cobalt selenide;

[0009] S3. Ultrasonic dispersion treatment is performed on the bulk nickel-cobalt selenide obtained in step S2 in an ultrasonic dispersant to obtain nano-disc-shaped selenide.

[0010] Preferably, in step S1, the molar ratio of nickel salt:cobalt salt is 1:(0.5-5).

[0011] Preferably, in step S1, the temperature of the hydrothermal reaction is 80-180° C., and the time is 4-24 hours.

[0012] Preferably, in step S1, the nickel salt is nickel sulfate, nickel nitrate or nickel chloride; the cobalt salt is cobalt sulfate, cobalt nitrate or cobalt chloride; the pH adjuster is urea, ammonia water or hexamethylenetetramine; the concentration of the nickel salt and the cobalt salt dissolved in deionized water is 10 to 100 mmol / L; the concentration of the pH adjuster dissolved in deionized water is 2 to 10 mmol / L.

[0013] Preferably, in step S2, the precursor A and selenium powder are mixed in a grinding manner, and the mass ratio of the precursor A to the selenium powder is 1:(2-10).

[0014] Preferably, in step S2, the temperature of the low-temperature treatment is 300-500° C., and the time is 2-8 hours.

[0015] Preferably, in step S3, the ultrasonic dispersant is NMP, DMSO, ethanol or methanol.

[0016] Preferably, in step S3, the concentration of the bulk nickel cobalt selenide in the ultrasonic dispersant is 500-5000 mg / L, the ultrasonic machine power is 250-1800 W, and the ultrasonic time is 30-120 min.

[0017] The invention also discloses a nano-plate-shaped selenide prepared by the preparation method. The nano-plate-shaped selenide consists of nickel-cobalt selenide and has a plate-shaped structure with a diameter less than 100 nm and a thickness of 9 to 11 nm.

[0018] The invention also discloses the use of the nano-plate-shaped selenide in preparing negative electrode materials for sodium ion batteries.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention discloses a method for preparing nano-disc-shaped selenides. First, a flaky precursor A is prepared using nickel salt and cobalt salt by a solution method. Under normal circumstances, due to the agglomeration effect, the obtained nano-disc-shaped precursor A agglomerates to form a flower-like structure, presenting a flower-like structure composed of countless nano-sheets with large size and relatively stable structure. In the later low-temperature selenization process, an excess of selenium powder is used. After melting, it can provide a liquid selenium environment to promote the progress of selenization. The liquid selenium interacts with the flower-like structure to regulate the particle size and structure of the selenide. Not only can the precursor A be induced to transform into a selenide, but the selenization process in the liquid phase can also disrupt the original morphology of the lamellar structure, causing it to form countless tiny nano-discs. Due to the effect of surface tension, the flaky precursor A is gradually separated to form a flaky structure with a regular morphology during the selenide formation process. The structure is unstable and can be dispersed by ultrasonic technology. The nano-disc-shaped selenide finally obtained has a uniform morphology and is well dispersed. During the experiment, it was found that the nanosheet size of the nano-disc-shaped selenide was concentrated around 100 nm, which showed a significant nano-scale trend compared to the micron-sized flower-like structure. Its structural stability was relatively low, and it could be fully separated and dispersed by ultrasound alone to form nano-disc-shaped selenides. The present invention combines the selenization process with ultrasonic stripping to obtain a nano-disc-shaped selenide with good rate performance, and avoids the problems of uncontrollable morphology and easy agglomeration in the preparation process of traditional nanomaterials. The invention has the characteristics of simple preparation method, good material consistency, and can be produced on a large scale. The obtained nano-disc-shaped selenide can not only be applied to sodium ion batteries to enhance the rate performance of materials, but also has good application prospects in fields such as energy storage, catalysis and adsorption.

[0021] The present invention also discloses a nano-flake selenide obtained by the above-mentioned preparation method. The nano-flake selenide is composed of nickel cobalt selenide. On the one hand, the structural advantage of the double metal hydroxide can be used to obtain a sheet structure precursor. On the other hand, the synergistic effect of the double metal selenide can be used to improve the sodium storage performance in the later sodium storage process. The nano-flake selenide presents a flake-like morphology with a diameter of less than 100 nm and a thickness of 9 to 11 nm. Compared with the micron-scale flower-like structure, it has an obvious nano-scale trend. This structural stability is relatively low, and it can be fully separated and dispersed by ultrasonic means to form a nano-flake selenide, which solves the problems of traditional selenide materials such as large size, unstable and uncontrollable structure, and low rate performance.

[0022] The present invention also discloses the use of the nano-plate-shaped selenide in preparing the negative electrode material of sodium ion battery. The nano-plate-shaped selenide is used as the negative electrode of sodium ion battery, even at a current density of up to 30A g -1 When it is still possible to present 400mAh g -1The specific capacity is about 20000 tons; it has excellent rate performance in sodium ion batteries and has potential advantages in the application of high-power electrical appliances. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the flower-shaped nickel-cobalt compound precursor A prepared in Example 1 of the present invention;

[0024] Figure 2 This is an SEM image of the nano-flake selenide prepared in Example 1 of the present invention;

[0025] Figure 3 This is a diagram showing the rate performance of the nano-disc-shaped selenide prepared in Example 1 of the present invention in a sodium ion battery. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] The present invention is described in further detail below with reference to the accompanying drawings:

[0029] In response to the problems of large size and insufficient rate performance of traditional selenides, the present invention combines a method of combining low-temperature selenization treatment and ultrasonic stripping to prepare flaky nano-selenides, which not only effectively exposes its surface active sites and improves the sodium storage rate performance of the material, but also has good consistency in the preparation process, which is conducive to large-scale preparation. First, nickel salt and cobalt salt are used to prepare a flaky precursor A. Due to the agglomeration effect, the obtained nano-flaky precursor A agglomerates to form a flower-like structure. The precursor A is mixed and heated with excess selenium powder to obtain a selenide on the one hand, and on the other hand, the particle size and structure of the selenide are regulated by excess liquid selenium. Due to the effect of surface tension, the flaky precursor A is gradually separated to form a flaky structure with a regular morphology during the formation of the selenide. The structure is unstable and the flaky selenide can be dispersed by ultrasonic technology. The nano-flaky selenide finally obtained has a uniform morphology and is well dispersed. The method of the present invention is simple to operate, has good controllability and repeatability, can be mass-produced, and the obtained nano-selenide can be applied to fields such as energy storage, catalysis and adsorption.

[0030] The present invention discloses a method for preparing a nano-disc-shaped selenide, comprising the following steps:

[0031] S1. Adding nickel salt, cobalt salt and pH adjuster to deionized water to perform hydrothermal reaction to obtain precursor A;

[0032] S2, mixing the precursor A prepared in step S1 with selenium powder, and performing low-temperature treatment under an inert atmosphere to obtain a bulk nickel-cobalt selenide;

[0033] S3, ultrasonically dispersing the bulk nickel-cobalt selenide obtained in step S2 into an ultrasonic dispersant, and ultrasonically treating the resultant to obtain a target product, nano-disc-shaped selenide;

[0034] In step S1, the metal salt is introduced in the form of sulfate, nitrate, chloride or carbonate, the molar ratio of nickel salt to cobalt salt is 1:(0.5-5), and the ion concentration is 10-100 mmol / L;

[0035] In step S1, the hydrothermal temperature is 80-180° C., and the hydrothermal time is 4-24 hours; the pH adjuster is urea, ammonia water, or hexamethylenetetramine, and its concentration is 2-10 mmol / L;

[0036] In step S2, the precursor A and selenium powder are mixed in a ground form at a mass ratio of 1:(2-10), the heating temperature of the low temperature treatment is 300-500° C., and the heating time is 2-8 hours;

[0037] In step S3, the ultrasonic dispersant is NMP, DMSO, ethanol or methanol;

[0038] In step S3, the concentration of the bulk nickel cobalt selenide in the dispersant is 500-5000 mg / L, the ultrasonic machine power is 250-1800 W, and the ultrasonic time is 30-120 min.

[0039] The nano-plate-shaped selenide prepared by the above method disclosed in the present invention can ultimately be applied to the fields of energy storage, catalysis, adsorption, etc.

[0040] Example 1

[0041] A method for preparing nano-flake selenide comprises the following steps:

[0042] S1. Dissolve 7 mmol of nickel nitrate hexahydrate, 3.5 mmol of cobalt nitrate hexahydrate, and 2 mmol of urea in 1 L of deionized water, hydroheat at 80°C for 24 h, cool, wash, and dry to obtain precursor A.

[0043] S2. Precursor A prepared in step S1 and selenium powder were weighed in a mass ratio of 1:2, mixed evenly, and then selenized under argon at 300° C. for 8 h to obtain bulk nickel-cobalt selenide;

[0044] S3. Disperse the bulk nickel cobalt selenide obtained in step S2 in an NMP solution with a concentration of 500 mg / L, and use an ultrasonic instrument with a power of 250 W for 120 minutes to obtain nano-disc-shaped selenide.

[0045] The obtained nano-flake selenide, conductive carbon black and PVDF were mixed in a mass ratio of 8:1:1, and evenly coated on copper foil using NMP as solvent. The mixture was placed in a vacuum drying oven at 110°C for 12 hours, and then cut into 12mm discs. The sodium sheet was used as the negative electrode to assemble a sodium ion battery for performance testing.

[0046] The results show that at a current density of 1A g -1 When the battery capacity is 500mAh g -1 The current density can be further increased to 30A g -1 When the battery capacity is maintained at 370mAh g -1 It has a capacity retention rate of about 74% and has broad application prospects in power batteries.

[0047] See also Figure 1 This is an SEM image of the flower-shaped nickel-cobalt compound precursor A prepared in Example 1 of the present invention. As can be seen, Precursor A is composed of a large number of stacked nanosheets forming a nanoflower-like structure. The structure is relatively large, approaching 5μm in size. This step faithfully displays the precursor morphology, allowing for comparison with the subsequent nanosheets, highlighting the advantages of our further ultrasonic dispersion method for obtaining nanoselenide.

[0048] See also Figure 2 This is an SEM image of the nano-flake selenide prepared in Example 1 of the present invention; as can be seen from the figure, after the two steps of selenization and ultrasonication, a nano-flake selenide with a relatively uniform morphology can be obtained, the size of which is basically maintained at about 100nm and the thickness is about 10nm. The nano-flake selenide has good dispersibility, which helps to expose more active sites for sodium storage reaction and improve the material rate performance.

[0049] See also Figure 3 This is a rate performance diagram of the nano-platelet-shaped selenide prepared in Example 1 of the present invention in a sodium ion battery; as can be seen from the figure, the nano-platelet-shaped selenide has a current density of 1A g -1 When the battery capacity is 500mAh g -1 Around, increase the current density to 30A g -1 Still showing up to 370mAh g -1 The specific capacity is about 1.5 Å, indicating that the prepared nano-flake selenide has good rate performance.

[0050] Example 2

[0051] A method for preparing nano-flake selenide comprises the following steps:

[0052] S1. Dissolve 10 mmol of nickel nitrate hexahydrate, 50 mmol of cobalt nitrate hexahydrate, and 10 mmol of ammonia water in 1 L of deionized water, hydroheat at 180°C for 4 h, cool, wash, and dry to obtain precursor A.

[0053] S2. Precursor A prepared in step S1 and selenium powder were weighed in a mass ratio of 1:10, mixed evenly, and then selenized at 500° C. under nitrogen for 2 h to obtain bulk nickel-cobalt selenide;

[0054] S3. Disperse the bulk nickel cobalt selenide obtained in step S2 in a DMSO solution at a concentration of 5000 mg / L, and use an ultrasonic instrument with a power of 1800 W to perform ultrasonic dispersion for 60 minutes to obtain nano-disc-shaped selenide.

[0055] Example 3

[0056] A method for preparing nano-flake selenide comprises the following steps:

[0057] S1. Dissolve 16 mmol of nickel nitrate hexahydrate, 80 mmol of cobalt nitrate hexahydrate, and 5 mmol of hexamethylenetetramine in 1 L of deionized water, hydroheat at 180°C for 4 h, cool, wash, and dry to obtain precursor A.

[0058] S2. Precursor A prepared in step S1 and selenium powder were weighed in a mass ratio of 1:5, mixed evenly, and then selenized at 400° C. under argon for 2 h to obtain bulk nickel-cobalt selenide;

[0059] S3. Disperse the bulk nickel cobalt selenide obtained in step S2 in a methanol solution with a concentration of 500 mg / L, and use an ultrasonic instrument with a power of 500 W to perform ultrasonic dispersion for 30 minutes to obtain nano-disc-shaped selenide.

[0060] Example 4

[0061] A method for preparing nano-flake selenide comprises the following steps:

[0062] S1. Dissolve 50 mmol of nickel nitrate hexahydrate, 50 mmol of cobalt nitrate hexahydrate, and 10 mmol of urea in 1 L of deionized water, hydroheat at 100°C for 12 h, cool, wash, and dry to obtain precursor A.

[0063] S2. Precursor A prepared in step S1 and selenium powder were weighed in a mass ratio of 1:10, mixed evenly, and then selenized at 300° C. under argon for 8 h to obtain bulk nickel-cobalt selenide;

[0064] S3. Disperse the bulk nickel cobalt selenide obtained in step S2 in an ethanol solution with a concentration of 2000 mg / L, and use an ultrasonic instrument with a power of 1000 W to perform ultrasonic dispersion for 120 minutes to obtain nano-disc-shaped selenide.

[0065] Example 5

[0066] A method for preparing nano-flake selenide comprises the following steps:

[0067] S1. Dissolve 5 mmol of nickel nitrate hexahydrate, 5 mmol of cobalt nitrate hexahydrate, and 2 mmol of urea in 1 L of deionized water, hydroheat at 120°C for 12 h, cool, wash, and dry to obtain precursor A.

[0068] S2. Precursor A and selenium powder prepared in step S1 were weighed in a mass ratio of 1:8, mixed evenly, and then selenized at 500° C. under argon for 5 h to obtain bulk nickel-cobalt selenide;

[0069] S3. Disperse the bulk nickel cobalt selenide obtained in step S2 in an NMP solution with a concentration of 3000 mg / L, and use an ultrasonic instrument with a power of 500 W to perform ultrasonic dispersion for 60 minutes to obtain nano-disc-shaped selenide.

[0070] The uniqueness of the present invention lies in the use of a slightly excessive amount of selenium powder, the melting point of selenium is 220 ° C, and the selenium is melted in the heated state to become liquid selenium. At this time, the precursor A prepared in step S1 is selenized. In the early exploration process, we explored two selenization methods: mixing precursor A with selenium powder and heating it, and placing precursor A and selenium powder in different areas for heating. It was found that mixed heating can not only selenize, but also induce large-scale precursor A to nano-nization, but it still presents the morphology of precursor A on the surface. In fact, it can be dispersed after high-power ultrasonic treatment to obtain nano-disc-shaped selenide. Therefore, the present invention provides a unique nano-selenide preparation technology, that is, a large-scale precursor is mixed with selenium powder for selenization, and then further ultrasonic treatment is used to obtain nano-disc-shaped selenide. Compared with the traditional selenization method by regulating the morphology of the precursor, it is simpler and there is almost no need to consider the dispersibility of the nanomaterial, because the selenide can be effectively dispersed in step S3.

[0071] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing nano-flake selenide, characterized in that: The following steps are involved: S1. Add nickel salt, cobalt salt, and pH adjuster to deionized water and perform hydrothermal reaction to obtain precursor A; the molar ratio of nickel salt:cobalt salt is 1:(0.5-1) or 1:5; the hydrothermal reaction temperature is 80-100°C or 180°C, and the reaction time is 4-12 hours; S2. Precursor A prepared in step S1 is mixed with selenium powder, and subjected to low-temperature treatment under an inert atmosphere to obtain a bulk nickel-cobalt selenide; the precursor A and selenium powder are mixed in a ground form, and the mass ratio of the precursor A to the selenium powder is 1:(2-10); the low-temperature treatment temperature is 400-500° C., and the time is 5-8 hours; an excess of selenium powder is used, and the melted selenium powder can provide an environment for liquid selenium; S3. Ultrasonic dispersion treatment of the bulk nickel cobalt selenide obtained in step S2 in an ultrasonic dispersant to obtain nano-disc selenide; the concentration of the bulk nickel cobalt selenide in the ultrasonic dispersant is 500-5000 mg / L, the ultrasonic machine power is 250-1800 W, and the ultrasonic time is 30-120 min; The nano-disc-shaped selenide exhibits a disc-like morphology with a diameter of less than 100 nm and a thickness of 9-11 nm. The current density is 30 A g -1 When the battery capacity is 370 mAh g -1 Specific capacity.

2. The method for preparing nano-disc-shaped selenide according to claim 1, wherein: In step S1, the nickel salt is nickel sulfate, nickel nitrate or nickel chloride; the cobalt salt is cobalt sulfate, cobalt nitrate or cobalt chloride; the pH adjuster is urea, ammonia water or hexamethylenetetramine; the nickel salt and cobalt salt are dissolved in deionized water at a concentration of 10 to 100 mmol / L; and the pH adjuster is dissolved in deionized water at a concentration of 2 to 10 mmol / L.

3. The method for preparing nano-disc-shaped selenide according to claim 1, wherein: In step S3, the ultrasonic dispersant is NMP, DMSO, ethanol or methanol.

4. The nano-plate-shaped selenide prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The nano-disc-shaped selenide is composed of nickel-cobalt selenide and presents a disc-shaped structure with a diameter of less than 100 nm and a thickness of 9-11 nm.

5. Use of the nano-disc-shaped selenide according to claim 4 in preparing a negative electrode material for sodium ion batteries.

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