NiCo-LDH supercapacitor electrode material and preparation method thereof

Abstract

The application provides a NiCo-LDH supercapacitor electrode material and a preparation method thereof. The NiCo-LDH supercapacitor electrode material has excellent rate performance, high stability and high coulomb efficiency, and is prepared by using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors, and using tert-butyl alcohol or propylene oxide as a precipitant instead of a traditional alkali solution. + The hydrolysis of metal ions is promoted by opening a ring, and finally the NiCo-LDH supercapacitor electrode material is generated. The preparation method is simple and fast, controllable at room temperature and has strong repeatability. In the preparation process, the reaction rate can be controlled only by controlling the proportion of water in the solvent.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of supercapacitor electrode materials, and particularly relates to a NiCo-LDH supercapacitor electrode material and a preparation method thereof. BACKGROUND

[0002] Energy storage and transportation are two important issues in the field of new energy. Supercapacitors have attracted great interest in the past few decades due to their fast charge-discharge rate, high power density (1-2 orders of magnitude higher than batteries), long cycle life (2-3 orders of magnitude longer than batteries) and high reliability. So far, pure carbon-based double-layer capacitive materials (such as activated carbon) are still the mainstream materials for most commercial supercapacitors, which usually have excellent rate performance and extremely high stability, but cannot meet the relevant requirements in practical applications in terms of specific capacitance and energy density, and also cause great obstacles to the miniaturization of devices. Therefore, scientists in the relevant field are committed to finding an electrode material with excellent performance in stability, power density and energy density. Compared with pure carbon-based materials, pseudo-capacitive materials can significantly improve the specific capacitance and energy density of supercapacitors through interface reversible Faraday reaction energy storage, and also have excellent rate performance and stability, so they have attracted much attention.

[0003] Transition metal double hydroxides (LDHs) have attracted increasing interest from both academia and industry due to their wide applications in catalysis, separation, biotechnology, electrochemistry and other fields. In particular, they show great potential for application in supercapacitors. This is mainly due to their special hydrotalcite-like layered structure (the layered crystal structure is composed of a positively charged host layer, an interlayer charge-compensating anion and a solvated molecule, which can promote deep ion diffusion between electrode materials and thus efficiently utilize active centers). As a common electrode material, NiCo-LDH has been studied by many researchers due to its excellent performance. However, so far, the preparation methods of NiCo-LDH are mainly concentrated on hydrothermal method, electrodeposition and coprecipitation method with alkaline solution as precipitant. Among them, the hydrothermal method can synthesize high-quality LDH materials, but requires harsh reaction conditions of high temperature and high pressure. The electrodeposition method is efficient and fast, and the conditions are mild, but the equipment cost is high. The traditional coprecipitation method mainly uses sodium hydroxide or ammonia solution as precipitant, and the dropping rate of the precipitant has a great influence on the morphology and quality of the product, so the controllability of the method is poor. Therefore, it is of great value to find a simple process and room-temperature controllable preparation method of NiCo-LDH. SUMMARY

[0004] The application aims to provide a preparation method of a NiCo-LDH supercapacitor electrode material, which uses cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors, uses tert-butyl alcohol or propylene oxide as a precipitant instead of a traditional alkali solution, and uses a homogeneous precipitation method to prepare the NiCo-LDH supercapacitor electrode material.

[0005] Another object of the application is to provide a NiCo-LDH supercapacitor electrode material, which has excellent rate performance and higher stability and coulombic efficiency.

[0006] The application solves the technical problem by using the following technical scheme.

[0007] The application provides a preparation method of a NiCo-LDH supercapacitor electrode material, which uses cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors, and uses a homogeneous precipitation method to prepare the NiCo-LDH supercapacitor electrode material, wherein the precipitant is selected from one of tert-butyl alcohol or propylene oxide.

[0008] Further, the specific steps of using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors and using a homogeneous precipitation method to prepare the NiCo-LDH supercapacitor electrode material include:

[0009] S1, dissolving Ni(NO3)2·6H2O and Co(NO3)2·6H2O in an ethanol aqueous solution, stirring at room temperature to obtain a mixed solution;

[0010] S2, slowly adding the precipitant to the mixed solution, stirring and reacting at room temperature, centrifuging, washing, and drying to obtain the NiCo-LDH supercapacitor electrode material.

[0011] Further, the total metal concentration in the mixed solution is 5.5-6.5 mol / L.

[0012] Further, the concentration of the ethanol aqueous solution is 40-60% (v / v).

[0013] Further, the volume ratio of the precipitant to the ethanol aqueous solution is 0.4-0.43:1.

[0014] Further, the stirring and reaction time is 6-12 h.

[0015] Further, the steps of centrifuging and washing include: slowly adding the precipitant to the mixed solution after reaction, collecting the precipitate by centrifugation, and washing 2-4 times with deionized water.

[0016] Further, the drying temperature is 75-85 DEG C, and the drying time is 22-26 h.

[0017] Further, in the NiCo-LDH supercapacitor electrode material, the molar ratio of nickel element and cobalt element is 1-3:1.

[0018] The application provides a NiCo-LDH supercapacitor electrode material prepared according to the preparation method.

[0019] The NiCo-LDH supercapacitor electrode material and the preparation method have the following beneficial effects:

[0020] The application uses cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors, uses tert-butyl alcohol or propylene oxide as a precipitant instead of a traditional alkali solution, and adopts a homogeneous precipitation method to prepare the NiCo-LDH supercapacitor electrode material with excellent energy storage characteristics. + The tert-butyl alcohol or propylene oxide acts as an acid scavenger in the metal ion hydrolysis process, removes H BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0022] Figure 1 XRD patterns of the NiCo-LDH supercapacitor electrode materials of the embodiments 1-3, the alpha-Ni(OH)2 powder material of the comparative example 1 and the Co2(OH)3Cl powder material of the comparative example 2;

[0023] Figure 2 GCD test comparison chart of the NiCo-LDH supercapacitor electrode materials of the embodiments 1-3, the alpha-Ni(OH)2 powder material of the comparative example 1 and the Co2(OH)3Cl powder material of the comparative example 2;

[0024] Figure 3 Rate performance chart of the Ni4Co2-LDH supercapacitor electrode material of the embodiment 1;

[0025] Figure 4 Figure for stability test of the Ni4Co2-LDH supercapacitor electrode material of embodiment 1 of the present application;

[0026] Figure 5 Flow chart for preparation of the NiCo-LDH supercapacitor electrode material of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are adopted. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0028] The NiCo-LDH supercapacitor electrode material and the preparation method thereof of the embodiments of the present application will be described in detail below.

[0029] The preparation method of the NiCo-LDH supercapacitor electrode material provided in the embodiments of the present application uses cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors and adopts a homogeneous precipitation method to prepare the NiCo-LDH supercapacitor electrode material, wherein the precipitating agent is selected from one of tert-butyl alcohol or propylene oxide. The tert-butyl alcohol or propylene oxide acts as an acid scavenger in the process of metal ion hydrolysis and removes H + In combination with ring-opening promotion of metal ion hydrolysis, the NiCo-LDH supercapacitor electrode material is finally generated.

[0030] Further, in the preferred embodiments of the present application, with reference to FIG. 1, the specific steps for preparing the NiCo-LDH supercapacitor electrode material using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors and adopting a homogeneous precipitation method include: Figure 5

[0031] S1, dissolving Ni(NO3)2·6H2O and Co(NO3)2·6H2O in an ethanol aqueous solution, stirring at room temperature to obtain a mixed solution.

[0032] Further, in the preferred embodiments of the present application, the total metal concentration in the mixed solution is 5.5-6.5 mol / L.

[0033] Further, in the preferred embodiments of the present application, the concentration of the ethanol aqueous solution is 40-60% (v / v).

[0034] S2, slowly adding the precipitating agent to the mixed solution, stirring and reacting at room temperature, centrifuging, washing and drying to obtain the NiCo-LDH supercapacitor electrode material.

[0035] ​Further, in the preferred embodiment of the present application, the volume ratio of the precipitant to the aqueous ethanol solution is 0.4-0.43:1.

[0036] Further, in the preferred embodiment of the present application, the stirring reaction time is 6-12h.

[0037] Further, in the preferred embodiment of the present application, the step of centrifugation and washing comprises: after the precipitant is slowly added to the mixed solution after reaction, the precipitate is collected by centrifugation, and washed with deionized water for 2-4 times.

[0038] Further, in the preferred embodiment of the present application, the drying temperature is 75-85℃, and the drying time is 22-26h. Preferably, the drying temperature is 80℃, and the drying time is 24h.

[0039] Further, in the preferred embodiment of the present application, in the NiCo-LDH supercapacitor electrode material, the molar ratio of nickel element to cobalt element is 1-3:1.

[0040] The present application uses cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors, and t-butanol or propylene oxide as a precipitant instead of traditional alkali solution, and adopts homogeneous precipitation method to prepare NiCo-LDH supercapacitor electrode material with excellent energy storage characteristics. The preparation method is simple and fast, controllable at room temperature and has strong repeatability. In the preparation process, only by controlling the proportion of water in the solvent can the reaction rate be controlled.

[0041] The present application also provides a NiCo-LDH supercapacitor electrode material, which is prepared according to the above preparation method. The NiCo-LDH supercapacitor electrode material is a dark green powder material. The NiCo-LDH supercapacitor electrode material has excellent rate performance, high stability and high coulombic efficiency.

[0042] The features and properties of the present application are further described in detail below in combination with examples.

[0043] Example 1

[0044] The present application provides a NiCo-LDH supercapacitor electrode material, which is prepared according to the following method:

[0045] 0.952 g of Ni(NO3)2·6H2O and 0.476 g of Co(NO3)2·6H2O were weighed and dissolved in 10 mL (40% v / v) of ethanol aqueous solution. The solution was then stirred continuously at room temperature until a homogeneous solution was obtained. Subsequently, 4.3 mL of tert-butanol was slowly added to the solution, and stirring was continued at room temperature for 6 h. After the reaction was completed, a large amount of dark green precipitate appeared in the clear liquid. The precipitate was collected by centrifugation, washed three times with deionized water, and dried at 80 °C for 24 h to obtain Ni4Co2-LDH supercapacitor electrode material.

[0046] Example 2

[0047] This embodiment provides a NiCo-LDH supercapacitor electrode material, which is prepared according to the following method:

[0048] 1.07 g of Ni(NO3)2·6H2O and 0.357 g of Co(NO3)2·6H2O were weighed and dissolved in 10 mL of 40% v / v ethanol aqueous solution. The solution was then stirred continuously at room temperature until a homogeneous solution was obtained. Subsequently, 4.3 mL of tert-butanol was slowly added to the above solution, and stirring was continued at room temperature for 6 h. After the reaction was completed, a large amount of dark green precipitate appeared in the clear liquid. The precipitate was collected by centrifugation, washed three times with deionized water, and dried at 80 °C for 24 h to obtain Ni. 4.5 Co 1.5 -LDH supercapacitor electrode material.

[0049] Example 3

[0050] This embodiment provides a NiCo-LDH supercapacitor electrode material, which is prepared according to the following method:

[0051] 0.714 g of Ni(NO3)2·6H2O and 0.714 g of Co(NO3)2·6H2O were weighed and dissolved in 10 mL of 40% v / v ethanol aqueous solution. The solution was then stirred continuously at room temperature until a homogeneous solution was obtained. Subsequently, 4.3 mL of tert-butanol was slowly added to the above solution, and stirring was continued at room temperature for 6 h. After the reaction was completed, a large amount of dark green precipitate appeared in the clear liquid. The precipitate was collected by centrifugation, washed three times with deionized water, and dried at 80 °C for 24 h to obtain Ni3Co3-LDH supercapacitor electrode material.

[0052] Example 4

[0053] This embodiment provides a NiCo-LDH supercapacitor electrode material, which is prepared according to the following method:

[0054] 0.952 g of Ni(NO3)2·6H2O and 0.476 g of Co(NO3)2·6H2O were weighed and dissolved in 10 mL (60% v / v) of ethanol aqueous solution. The solution was then stirred continuously at room temperature until a homogeneous solution was obtained. Subsequently, 4.3 mL of propylene oxide was slowly added to the solution, and stirring was continued at room temperature for 6 h. After the reaction was completed, a large amount of dark green precipitate appeared in the clear liquid. The precipitate was collected by centrifugation, washed three times with deionized water, and dried at 80 °C for 24 h to obtain the NiCo-LDH supercapacitor electrode material.

[0055] Comparative Example 1

[0056] This comparative example provides an α-Ni(OH)₂ powder material, which is prepared according to the following method:

[0057] 1.43 g of Ni(NO3)2·6H2O was weighed and dissolved in 10 mL of 40% v / v ethanol aqueous solution. The solution was then stirred continuously at room temperature until a homogeneous solution was obtained. Subsequently, 4.3 mL of tert-butanol was slowly added to the above solution, and stirring was continued at room temperature for 6 h. After the reaction was completed, a large amount of dark green precipitate appeared in the clear liquid. The precipitate was collected by centrifugation, washed three times with deionized water, and dried at 80 °C for 24 h to obtain α-Ni(OH)2 powder material.

[0058] Comparative Example 2

[0059] This comparative example provides a Co2(OH)3Cl powder material, which is prepared according to the following method:

[0060] 1.428 g of Co(NO3)2·6H2O was weighed and dissolved in 10 mL of 40% v / v ethanol aqueous solution. The solution was then stirred continuously at room temperature until a homogeneous solution was obtained. Subsequently, 4.3 mL of tert-butanol was slowly added to the above solution, and stirring was continued at room temperature for 6 h. After the reaction was completed, a large amount of pink precipitate appeared in the clear liquid. The precipitate was collected by centrifugation, washed three times with deionized water, and dried at 80 °C for 24 h to obtain Co2(OH)3Cl powder material.

[0061] Experimental Example 1

[0062] In this experiment, X-ray diffraction patterns of the NiCo-LDH supercapacitor electrode materials of Examples 1-3, the α-Ni(OH)2 powder material of Comparative Example 1, and the Co2(OH)3Cl powder material of Comparative Example 2 were analyzed.

[0063] like Figure 1The figures shown are XRD patterns of the NiCo-LDH supercapacitor electrode materials of Examples 1-3 of the present invention, the α-Ni(OH)₂ powder material of Comparative Example 1, and the Co₂(OH)₃Cl powder material of Comparative Example 2. From... Figure 1 It can be seen that when the cobalt-nickel feed ratio is between 1:3 and 1:1, the resulting product is NiCo-LDH supercapacitor electrode material. When only nickel salt or cobalt salt is used, the products are α-Ni(OH)2 and Co2(OH)3Cl, respectively. The shift of α-Ni(OH)2 at the (015) crystal plane may be due to incomplete hydrolysis of the material and the large amount of chloride ion intercalation. All peaks of the NiCo-LDH supercapacitor electrode material belong to PDF#38-0715, with no impurity peaks, proving the successful synthesis of the material.

[0064] Experimental Example 2

[0065] This experimental example performs GCD tests on the NiCo-LDH supercapacitor electrode materials of Examples 1-3, the α-Ni(OH)2 powder material of Comparative Example 1, and the Co2(OH)3Cl powder material of Comparative Example 2, including the following steps:

[0066] Electrode preparation: The NiCo-LDH supercapacitor electrode materials of Examples 1-3, the α-Ni(OH)2 powder material of Comparative Example 1, and the Co2(OH)3Cl powder material of Comparative Example 2 were ground and mixed evenly with PVDF and conductive carbon black (mixing mass ratio of 8:1:1). NMP was added to form a uniform slurry, which was then coated to an area of ​​1 cm². 2 The electrode was vacuum dried overnight at 70°C on nickel foam and then pressed for 1 minute under 10 MPa pressure to obtain the test electrode, with the active material loading controlled at 2-3 mg.

[0067] Test Method: The test equipment was the Donghua multi-channel electrochemical workstation. The three-electrode performance was tested using the test electrode as the working electrode, the Hg / HgO electrode as the reference electrode, and the platinum electrode as the counter electrode. The test method selected was custom charge / discharge, with a charge / discharge current density of 1 Ag. -1 The energy storage capacity of the relevant electrodes was tested. Before testing, the electrodes were activated by cyclic voltammetry in the electrolyte for 20 cycles at a scan rate of 50 mV / s. -1 .

[0068] like Figure 2 The figures shown are the NiCo-LDH supercapacitor electrode materials of Examples 1-3 of the present invention, the α-Ni(OH)2 powder material of Comparative Example 1, and the Co2(OH)3Cl powder material of Comparative Example 2, in 1Ag. -1 Comparison of GCD test results under current density. From Figure 2It can be seen that the NiCo-LDH supercapacitor electrode material with a nickel-cobalt ratio of 2:1 has the best performance.

[0069] Experimental Example 3

[0070] This experimental example measures the rate performance of the Ni4Co2-LDH prepared in Example 1, specifically including the following steps:

[0071] Electrode preparation: Ni4Co2-LDH, PVDF, and conductive carbon black were ground and mixed evenly (mixing mass ratio of 8:1:1), and NMP was added to form a uniform slurry, which was then coated to an area of ​​1 cm². 2 On nickel foam, the material was vacuum dried overnight at 70°C and pressed for 1 min under 10 MPa pressure to obtain Ni4Co2-LDH electrode sheets, with the active material loading controlled at 2-3 mg.

[0072] Test Method: The test equipment was the Donghua multi-channel electrochemical workstation. Three-electrode performance tests were performed using a Ni4Co2-LDH electrode as the working electrode, a Hg / HgO electrode as the reference electrode, and a platinum electrode as the counter electrode. The test method selected was a custom charge-discharge test, with charge-discharge current densities of 1, 3, 5, 8, and 10 A g. -1 Under these conditions, the capacity change of the Ni4Co2-LDH electrode was tested at different current densities. Before testing, the electrode was activated by cyclic voltammetry in the electrolyte for 20 cycles at a scan rate of 50 mV / s. -1 .

[0073] like Figure 3 The figure shows the rate performance of the Ni4Co2-LDH supercapacitor electrode material in Example 1 of this invention. Figure 3 It can be seen that the Ni4Co2-LDH supercapacitor electrode material has excellent rate performance.

[0074] Test Example 4

[0075] This experimental example measures the Ni4Co2-LDH supercapacitor electrode material prepared in Example 1 at 10Ag. -1 The stability of the system under a current density of 1000 charge-discharge cycles. For example... Figure 4 The figure shown is a stability test diagram of the Ni4Co2-LDH supercapacitor electrode material of Embodiment 1 of the present invention. From... Figure 4 It can be seen that the NiCo-LDH supercapacitor electrode material prepared by the preparation method of the present invention has high stability and coulombic efficiency.

[0076] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing NiCo-LDH supercapacitor electrode material, characterized in that, NiCo-LDH supercapacitor electrode materials were prepared by homogeneous precipitation using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors, wherein the precipitant was selected from tert-butanol. The specific steps for preparing NiCo-LDH supercapacitor electrode materials by homogeneous precipitation using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as precursors include: S1. Dissolve Ni(NO3)2·6H2O and Co(NO3)2·6H2O in an aqueous ethanol solution and stir at room temperature to obtain a mixed solution. The concentration of the aqueous ethanol solution is 40~60% v / v. S2. The precipitant is slowly added to the mixed solution, and after stirring and reacting at room temperature, the mixture is centrifuged, washed, and dried to obtain the NiCo-LDH supercapacitor electrode material.

2. The method for preparing the NiCo-LDH supercapacitor electrode material according to claim 1, characterized in that, In step S1, the total metal concentration in the mixed solution is 5.5~6.5 mol / L.

3. The method for preparing the NiCo-LDH supercapacitor electrode material according to claim 1, characterized in that, The volume ratio of the precipitant to the aqueous ethanol solution is 0.4~0.43:

1.

4. The method for preparing the NiCo-LDH supercapacitor electrode material according to claim 1, characterized in that, In step S2, the stirring reaction time is 6~12 h.

5. The method for preparing the NiCo-LDH supercapacitor electrode material according to claim 1, characterized in that, In step S2, the centrifugation and washing steps include: slowly adding the precipitant to the mixed solution to react, collecting the precipitate by centrifugation, and washing it with deionized water 2 to 4 times.

6. The method for preparing the NiCo-LDH supercapacitor electrode material according to claim 1, characterized in that, In step S2, the drying temperature is 75~85 ºC and the drying time is 22~26 h.

7. The method for preparing the NiCo-LDH supercapacitor electrode material according to claim 1, characterized in that, In the NiCo-LDH supercapacitor electrode material, the molar ratio of nickel to cobalt is 1~3:

1.

8. A NiCo-LDH supercapacitor electrode material, characterized in that, The NiCo-LDH supercapacitor electrode material is prepared by the preparation method according to any one of claims 1 to 7 and is a dark green powder material.

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