A method for preparing a carbon-coated zinc-cobalt metal compound having a wrinkled nanosheet shape

Abstract

The present application belongs to the field of novel clean energy material synthesis, and particularly relates to a preparation method of a zinc-cobalt metal compound with carbon-coated wrinkled nanosheet shape. The preparation method comprises the following steps: dissolving a zinc ion compound and a cobalt ion compound in water to form a metal ion solution, then adding a carbon dot solution in an oil bath for continuous stirring, and adding a sodium carbonate solution while continuously stirring, keeping for 1-50 hours to form gray flocculation, and finally centrifuging to obtain the precipitate. The method uses carbon dots as the carrier of metal ions, and uses hexadecyl trimethyl ammonium bromide or polyvinyl pyrrolidone as a surfactant, for preparing a wrinkled nanosheet-shaped Zn-Co metal compound, forming a simple and stable method for preparing a carbon-coated wrinkled nanosheet-shaped Zn-Co metal compound.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of novel clean energy material synthesis, and particularly relates to a preparation method of carbon-coated zinc-cobalt metal compound with wrinkled nanosheet shape. BACKGROUND

[0002] Rechargeable lithium ion batteries have the advantages of high efficiency, convenience, safety, no pollution, high specific capacity, no memory effect, low self-discharge, no pollution, long cycle life and the like. However, the commercial graphite carbon material as a negative electrode has a fatal defect of low theoretical specific capacity. High specific capacity metal compounds as high reversibility electrochemical lithium storage materials have shown the most potential advantages and attracted extensive attention of researchers. In the lithium storage process, the double metal compounds can play a mutual buffering role between the metals due to the different lithium storage potentials of the double metals, thereby improving the charge-discharge stability of the material. It is known that the porous metal compounds with high specific surface area have superior lithium storage electrochemical capacity and can meet the problem of volume expansion caused by lithium intercalation, thereby improving the reversible specific capacity and cycle stability of the material. In addition, carbon coating can effectively improve the cycle stability and rate performance of the material. However, it is difficult to obtain the nanosheet-shaped double metal compound with high specific surface area and form effective carbon coating at the same time. Therefore, researchers have been trying to explore a simple and feasible synthesis method for preparing carbon-coated nanosheet-shaped double metal compounds and apply them to the research in the field of energy storage electrochemistry such as lithium ion batteries. SUMMARY

[0003] The purpose of the present application is to solve the problems of the prior art and provide a preparation method of carbon-coated zinc-cobalt metal compound with wrinkled nanosheet shape. The following technical solutions are specifically adopted:

[0004] The preparation method of carbon-coated zinc-cobalt metal compound with wrinkled nanosheet shape comprises the following steps:

[0005] The zinc ion compound and the cobalt ion compound are dissolved in water to form a metal ion solution, then a carbon dot solution is added, and the mixture is continuously stirred at 30 DEG C to 80 DEG C in an oil bath for 1 h to 600 h, and a sodium carbonate solution is added while continuously stirring, and the mixture is incubated for 1 h to 50 h to form gray flocculent substances, and finally the carbon-coated zinc-cobalt metal compound with wrinkled nanosheet shape is obtained by centrifugation.

[0006] The carbon dot solution is prepared by adding a surfactant to an aqueous carbon dot solution with a pH less than 7.

[0007] In the method of the present invention, carbon dots are dispersed in water as soluble microparticles. The carbon dots possess a large number of oxygen-rich functional groups on their surface, exhibiting excellent chemical activity and capable of forming bonds with metal ions. Furthermore, the carbon dot surface functional groups form effective bonds with surfactants such as cetyltrimethylammonium bromide (CTAB) or polyvinylpyrrolidone (PVP), promoting the stable and rapid microstructural formation of the nanomaterial. This results in the preparation of carbon-coated wrinkled nanosheet-like zinc-cobalt metal compounds. Furthermore, the porous nanosheets possess a large specific surface area and pore structure, which enhances the material's reversible specific capacity and cycling stability during lithium storage electrochemical reactions. The addition of carbon coating also effectively improves the material's cycling stability and rate capability. Therefore, the carbon-coated wrinkled nanosheet-like zinc-cobalt metal compounds of the present invention hold great promise for development in lithium-ion batteries and other electrochemical energy sources.

[0008] As a further preferred embodiment, the preparation process of the aqueous carbon dot solution is as follows:

[0009] After glucose is dissolved in water, it is placed at 130℃~220℃ for carbonization reaction for 10h~30h, and then it is repeatedly centrifuged with ethanol and water, filtered, and separated; or lithium hydroxide or sodium hydroxide is dissolved in water, an appropriate amount of ethanol is added, and it is obtained by platinum metal electrolysis and repeated centrifugation and filtration.

[0010] As a further preferred embodiment, the concentration of the zinc ion compound and the cobalt ion compound is 0.1 M to 2 M. The zinc ion compound is any one of zinc chloride, zinc sulfate, zinc nitrate and zinc acetate; the cobalt ion compound is any one of cobalt chloride, cobalt sulfate, cobalt nitrate and cobalt acetate;

[0011] As a further preferred embodiment, in the step of preparing the carbon dot solution, the acid used to adjust the pH value of the aqueous carbon dot solution is at least one of hydrochloric acid, acetic acid, nitric acid, and sulfuric acid.

[0012] As a further preferred embodiment, the surfactant is polyvinyl pyrrolidone or cetyltrimethylammonium bromide; wherein the concentration of the surfactant is 0.05 g / L to 20 g / L. Excessively high or low concentrations of the surfactant will affect the stable molding of the material.

[0013] As a further preferred embodiment, the molar mass ratio of the metal ions to sodium carbonate is 1:1 to 1:30. If the mass ratio is too low, the material cannot be co-precipitated, and if the mass ratio is too high, it cannot be dissolved in water.

[0014] As a further preferred embodiment, the concentration of the carbon dot solution is 0.1 g / L to 30 g / L.

[0015] The present application has the advantages that the present application provides a simple and stable synthesis method for preparing carbon-coated wrinkle nanosheet-like Zn-Co metal compound, and the Zn-Co metal compound can be applied in the field of electrochemical energy sources such as lithium ion battery negative electrode materials. The method uses carbon dots as a carrier of metal ions, and hexadecyl trimethyl ammonium bromide (CTAB) or polyvinylpyrrolidone (PVP) as a surfactant, to form a simple and stable method for preparing carbon-coated wrinkle nanosheet-like Zn-Co metal compound, for preparing carbon-coated wrinkle nanosheet-like Zn-Co metal compound. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The figure shows the digital camera photo and transmission electron microscope (TEM) of the aqueous solution of the soluble carbon dots prepared by using the aqueous solution of glucose through high-temperature and high-pressure hydrothermal in Example 1;

[0017] Figure 2 The figure shows the digital camera photo and TEM of the aqueous solution of the soluble carbon dots prepared by using the LiOH alkaline solution in Example 3;

[0018] Figure 3 The figure shows the scanning electron microscope (SEM), X-ray energy spectrum element analysis (EDS) and digital camera photo of the carbon-coated wrinkle nanosheet-like structure zinc-cobalt metal compound obtained in Example 1;

[0019] Figure 4 The figure shows the SEM and EDS of the carbon-coated wrinkle nanosheet-like structure zinc-cobalt metal compound obtained in Example 2;

[0020] Figure 5 The figure shows the SEM of the carbon-coated wrinkle nanosheet-like structure zinc-cobalt metal compound obtained in Example 3;

[0021] Figure 6 The figure shows the SEM and digital camera photo of the nanosheet-like structure zinc-cobalt metal compound obtained in Comparative Example 1. DETAILED DESCRIPTION

[0022] The concept, specific structure and generated technical effects of the present application will be described clearly and completely in combination with the embodiments and the drawings, so as to fully understand the purpose, scheme and effects of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0023] Example 1

[0024] A preparation method of carbon-coated wrinkle nanosheet-like zinc-cobalt metal compound, which specifically comprises the following steps:

[0025] Take 6 g of glucose dissolved in 60 mL of deionized water to form an aqueous solution, hydrothermal at 200 ℃ for 20 h, and separate the brown-red transparent water-soluble carbon dot solution by repeated high-speed centrifugation and filtration with 60 mL of water and 240 mL of ethanol in 5 times, as shown in Figure 1 (A, B); TEM images are shown in Figure 1 (C).

[0026] Half of the above prepared brown-red transparent water-soluble carbon dot solution (150 mL) was dissolved in 100 mL of deionized water, 4 mL of glacial acetic acid was added to make the whole system in a weak acid state, 1.8 g of cetyltrimethylammonium bromide (CTAB) was added as a surfactant to form a weak acid state carbon dot aqueous solution; 2.491 g (10 mmol) of cobalt acetate tetrahydrate and 1.0997 g (5 mmol) of zinc acetate dihydrate were weighed and dissolved in the above carbon dot water-ethanol solution; then 100 mL of 1 M sodium carbonate aqueous solution was gradually added to the above solution under the condition of 40 ℃ oil bath and continuous stirring, and the stirring was continued for 15 h to form a stable brown-black Zn-Co metal compound precipitate, finally, the precipitate was repeatedly washed by centrifugation until the pH value was neutral, and finally a carbon-coated wrinkled nanosheet-shaped zinc-cobalt metal compound was obtained.

[0027] The obtained suspension-Zn-Co metal compound was centrifuged and dried, and microanalysis by scanning electron microscope showed that the material was a wrinkled nanosheet structure, as shown in Figure 3 (A, B).

[0028] X-ray energy spectrum analysis of the obtained suspension-Zn-Co metal compound showed that the material contained elements such as cobalt, zinc and oxygen, and the molar ratio of zinc and cobalt was close to 1:2, as shown in Figure 3 C. The sample color was brown-black, as shown in Figure 3 D.

[0029] Example 2

[0030] A method for preparing a carbon-coated wrinkled nanosheet-shaped zinc-cobalt metal compound, which specifically comprises the following steps:

[0031] Take 6 g of glucose dissolved in 60 mL of deionized water to form an aqueous solution, hydrothermal at 200 ℃ for 20 h, and separate the brown-red transparent water-soluble carbon dot solution by repeated high-speed centrifugation and filtration with 60 mL of water and 240 mL of ethanol in 5 times, as shown in Figure 1 (A, B); TEM images are shown in Figure 1 (C).

[0032] Half of the prepared brown-red transparent water-soluble carbon dot solution (150 mL) was dissolved in 100 mL of deionized water, 2 mL of hydrochloric acid was added to make the whole system acidic, 0.5 g of cetyltrimethylammonium bromide (CTAB) was added as a surfactant to form a weakly acidic carbon dot aqueous solution; 10 mmol of cobalt chloride and 5 mmol of zinc nitrate were weighed and dissolved in the above carbon dot water-ethanol solution; then 300 mL of 0.15 M sodium carbonate aqueous solution was gradually added dropwise to the above solution under oil bath at 30 ℃ under continuous stirring, and the stirring was continued for 1 h to form a stable brown-black Zn-Co metal compound precipitate. Finally, repeated centrifugal washing was performed until the pH value was neutral, and finally a carbon-coated wrinkled nanosheet-shaped zinc-cobalt metal compound was obtained.

[0033] The obtained suspension of Zn-Co metal compound was centrifugally dried, and microanalysis by scanning electron microscope showed that the material was a wrinkled nanosheet structure, as shown in Figure 4 A.

[0034] X-ray energy spectrum analysis of the obtained suspension of Zn-Co metal compound showed that the material contained elements such as cobalt, zinc and oxygen, as shown in Figure 4 B.

[0035] Example 3

[0036] 2.5172 g of lithium hydroxide monohydrate was weighed and dissolved in 60 mL of deionized water to form a 1 M LiOH aqueous solution, then 15 mL of ethanol was added, and a brown-red transparent water-soluble carbon dot solution was separated by high-speed centrifugation and filtration under a voltage of 15 V, as shown in Figure 2 (A). TEM is shown in Figure 2 (B).

[0037] The above prepared brown-red transparent water-soluble carbon dot solution was dissolved in 100 mL of deionized water and 90 mL of ethanol, 2 mL of acetic acid was added to make the whole system weakly acidic, and 1.5 g of polyvinylpyrrolidone (PVP, molecular weight 54000) was added as a surfactant. 10 mmol of cobalt chloride and 5 mmol of zinc sulfate were weighed and dissolved in the above water-ethanol solution; then 2000 mL of 1.5 M sodium carbonate aqueous solution was gradually added dropwise to the above solution under oil bath at 80 ℃ under continuous stirring, and the stirring was continued for 120 h to form a stable Zn-Co metal compound precipitate. Finally, repeated centrifugal washing was performed until the pH value was neutral.

[0038] The obtained suspension of Zn-Co metal compound was centrifugally dried, and microscopic analysis by scanning electron microscope showed that the material was a wrinkled nanosheet structure, as shown in Figs. 1 (A, B). The material was pink in color, as shown in Fig. 1 (C). Figure 5

[0039] Comparative Example 1

[0040] 120 mL of ethanol and 130 mL of deionized water were measured, 4 mL of glacial acetic acid was added to make the whole system weakly acidic, and 1.8 g of cetyltrimethylammonium bromide (CTAB) was added as a surfactant. 2.491 g (10 mmol) of cobalt acetate tetrahydrate and 1.0997 g (5 mmol) of zinc acetate dihydrate were weighed and dissolved in the above water-ethanol solution; then 100 mL of 1 M sodium carbonate aqueous solution was gradually added dropwise to the above solution under the condition of an oil bath at 40 °C with continuous stirring, and the stirring was continued for 15 h to form a stable Zn-Co metal compound precipitate. Finally, repeated centrifugal washing was performed until the pH value was neutral.

[0041] The obtained suspension of Zn-Co metal compound was centrifugally dried, and microscopic analysis by scanning electron microscope showed that the material was a wrinkled nanosheet structure, as shown in Figs. 1 (A, B). The material was pink in color, as shown in Fig. 1 (C). Figure 6 Figure 6

[0042] Although the description of the present application has been quite detailed and particularly described with respect to several described embodiments, it is not intended to be limited to any of these details or embodiments or any special embodiment, but should be considered to provide a broad interpretation of the possibility of the appended claims in view of the prior art, so as to effectively cover the intended scope of the present application. In addition, the present application is described above in embodiments that the inventors can foresee, and the purpose is to provide a useful description, and non-essential modifications to the present application that have not yet been foreseen can still represent equivalent modifications of the present application.​​​

Claims

1. A method for preparing a carbon-coated zinc-cobalt metal compound having a wrinkled nanosheet shape, characterized by, The method comprises the following steps: The zinc ion compound and the cobalt ion compound are dissolved in water to form a metal ion solution, then the carbon dot solution is added, and the mixture is continuously stirred at 30-80 DEG C in an oil bath for 1-600 h, while continuously stirring, the sodium carbonate solution is added, and the mixture is incubated for 1-50 h to form gray flocculent precipitate, and finally the precipitate is centrifuged to obtain the carbon-coated zinc-cobalt metal compound with wrinkled nanosheet structure; The carbon dot solution is prepared by adding a surfactant to an aqueous carbon dot solution with a pH less than 7; The aqueous carbon dot solution is prepared as follows: After glucose is dissolved in water, the mixture is carbonized at 130-220 DEG C for 10-30 h, then the mixture is repeatedly centrifuged and filtered with ethanol and water, and the carbon dot solution is obtained by separation; or lithium hydroxide or sodium hydroxide is dissolved in water, and an appropriate amount of ethanol is added, then the mixture is electrolyzed by platinum metal, and the carbon dot solution is obtained by repeatedly centrifuging and filtering; The molar mass ratio of the metal ion to sodium carbonate is 1:1-1:

30.

2. The production method according to claim 1, characterized by, The concentration of the zinc ion compound and the cobalt ion compound is 0.1-2 M; the zinc ion compound is any one of zinc chloride, zinc sulfate, zinc nitrate and zinc acetate; and the cobalt ion compound is any one of cobalt chloride, cobalt sulfate, cobalt nitrate and cobalt acetate.

3. The preparation method according to claim 1, characterized in that In the step of preparing the carbon dot solution, the acid used for adjusting the pH of the aqueous carbon dot solution is at least one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid.

4. The method of claim 1, wherein, The surfactant is polyvinylpyrrolidone or cetyltrimethylammonium bromide; and the concentration of the surfactant is 0.05-20 g / L.

5. The preparation method according to claim 1, characterized in that The concentration of the carbon dot solution is 0.1-30 g / L.

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