CN102709058B - Method for preparing manganese dioxide-nickel hydroxide composite electrode materials of super capacitors - Google Patents

Abstract

The present invention relates to the preparation method of composite electrode material of electrochemical supercapacitor, particularly a kind of method of preparation supercapacitor manganese dioxide-nickel hydroxide composite electrode material, is to use foamed nickel, nickel sheet or titanium sheet as pole plate in high manganese Cathodic electrochemical deposition is carried out in the mixed aqueous solution electrolyte of potassium nitrate and nickel nitrate, and the surface of the plate after deposition is cleaned with deionized water and dried to obtain foamed nickel, nickel sheet or titanium sheet as the substrate, and the surface layer has manganese dioxide - Composite electrode material of nickel hydroxide composite film. The manganese dioxide and nickel hydroxide composite electrode material prepared by the method has excellent cycle stability and high specific capacity. The electrode preparation process is simple and convenient, and easy to industrialize.

Description

Method for preparing supercapacitor manganese dioxide-nickel hydroxide composite electrode material

technical field

The invention relates to a preparation method of an electrochemical supercapacitor composite electrode material, in particular to a method for preparing a supercapacitor manganese dioxide-nickel hydroxide composite electrode material.

Background technique

Supercapacitors have the advantages of high power density, fast response time, long life, and simple maintenance. They can be widely used in the fields of information, electronics, energy, environment, transportation, and military industry. Electrochemical capacitor electrode materials with excellent instantaneous charge and discharge performance and good cycle performance are imminent.

According to the electrode materials used, supercapacitors can be divided into the following two categories: electric double layer supercapacitors with carbon materials such as activated carbon as electrodes and pseudocapacitive supercapacitors with metal oxides or conductive polymers as electrode materials, or "supercapacitors". Faraday quasicapacitor". Carbon materials are used as electrodes, which have high conductivity and high specific power, but have limited power storage capacity in the form of an electric double layer, and low capacitance and specific energy. The pseudocapacitive supercapacitor is accompanied by the adsorption capacitance of H ⁺ or OH ^- intercalation and desorption during the charging and discharging process, or the capacitance caused by the electrochemical redox reaction, which can realize two-dimensional or quasi-two-dimensional bulk phase electricity storage, greatly increasing the power storage capacity. Among them, ruthenium oxide has high specific capacity, good conductivity, and is very stable in the electrolyte. It is currently the most excellent supercapacitor electrode material. However, because ruthenium is a rare and precious metal, its resources are limited, its price is too high, and it pollutes the environment. Large-scale production in a short period of time and finding alternative materials with low cost and high performance are current research hotspots. Studies have found that transition metal oxides such as cobalt, manganese, and nickel have similar properties to RuO ₂ , and are expected to replace RuO ₂ as electrode materials for supercapacitors that are more suitable for commercialization. Manganese dioxide is widely used as a battery electrode material and catalyst material due to the advantages of extensive resources, low price, environmental friendliness, multiple oxidation valence states, and rich structures. The research on the use of manganese dioxide as an electrode material for supercapacitors has only been developed in recent years. It shows good capacitance characteristics in neutral electrolytes and has a wide potential window. It is considered to be a kind of electrode with great development potential. electrode material. However, due to the poor conductivity and compact structure of the bulk manganese dioxide prepared by the traditional method, it is not conducive to the diffusion of electrolyte ions and the transport of electrons, and the specific capacitance value of the prepared electrode is far lower than its theoretical specific capacitance (1370F/ g). Recently, the development of manganese dioxide nanoparticles or films with nanostructures for supercapacitor electrodes has attracted attention. Based on the characteristics of the nanostructure, manganese dioxide can have a high specific surface area, which is beneficial to maximize the infiltration of the electrolyte, shorten the ion diffusion path, and promote the oxidation-reduction reaction on the electrode surface, thereby improving the charge-discharge rate characteristics and specific capacitance. However, there is a fatal problem in the nanostructure, that is, the structure is prone to collapse during the cycle, which greatly reduces the cycle specific capacitance of the electrode. Nickel hydroxide is an attractive class of pseudocapacitive materials due to its good electrochemical redox activity, low cost, and high theoretical specific capacitive properties. However, due to the weak combination between the electrode material and the current collector, phase transition, and grain growth during the redox process, the cycle stability of nickel hydroxide with high specific capacitance is often poor. At present, people have prepared a compound of manganese dioxide and nickel hydroxide by chemical methods. When the mass percentage of manganese dioxide is 35.5%, the specific capacitance in alkaline electrolyte reaches 487.4F/g.

Contents of the invention

The object of the present invention is to propose an improved method for preparing supercapacitors in order to overcome the defects of low product specific capacity, poor stability, poor dispersion, poor conductivity, and complicated preparation process in the preparation of manganese dioxide-doped composite electrode materials by current chemical methods. A method for manganese dioxide-nickel hydroxide composite electrode material, the manganese dioxide and nickel hydroxide composite electrode material prepared by the method has excellent cycle stability and high specific capacity. The electrode preparation process is simple and convenient, and easy to industrialize.

The method for preparing the manganese dioxide-nickel hydroxide composite electrode material of the supercapacitor in the present invention is to carry out cathodic electrochemical deposition in the mixed aqueous solution electrolyte of potassium permanganate and nickel nitrate with nickel foam, nickel sheet or titanium sheet as the pole plate, The surface of the electrode plate after deposition is washed with deionized water and dried to obtain a composite electrode material with nickel foam, nickel sheet or titanium sheet as the base and manganese dioxide-nickel hydroxide composite film on the surface.

In the mixed aqueous solution of potassium permanganate and nickel nitrate, the concentration of potassium permanganate is 0.005mol/L-0.05mol/L, and the concentration of nickel nitrate is 0.004mol/L-0.12mol/L. Preferably, the concentration of potassium permanganate is 0.01mol/L-0.04mol/L, and the concentration of nickel nitrate is 0.014mol/L-0.12mol/L.

The working temperature of the electrolyte is 20°C to 30°C.

The cathode constant potential electrochemical deposition potential is -0.7V～-0.95V. A preferred deposition potential is -0.8V.

The present invention uses a simple and easy-to-operate electrochemical deposition method to dope or compound manganese dioxide, and the prepared manganese dioxide-nickel hydroxide composite electrode material has a relatively high specific capacity and can be used in a 1mol/L KOH electrolyte Among them, when the current density is 5A/g, the specific volume can reach up to 2334F/g; the instantaneous charge and discharge performance is excellent, and it can be charged and discharged rapidly under the condition of a large current density of 20A/g; the cycle stability is good, and the current density is 20A. Under the condition of /g, the specific capacity can still maintain more than 82.8% after 500 charge and discharge cycles. The compound of manganese dioxide-nickel hydroxide prepared by chemical method, when the mass percentage of manganese dioxide is 35.5%, the specific capacitance only reaches 487.4F/g in 1mol/L KOH electrolyte. The method of the invention has the advantages of simple and convenient operation, low manufacturing cost and easy industrialization. Moreover, while the electrode has a high specific capacitance, it can maintain a specific capacitance value of more than 80% under hundreds of high current density charging and discharging conditions, and can be widely used in fields such as hybrid power sources.

Description of drawings

Fig. 1 (a, b, c, d) is the scanning electron micrograph (SEM) of the electrochemical deposition layer of the manganese dioxide-nickel hydroxide composite electrode material that embodiment 1 to 4 prepares;

Figure 2 (a, b, c) is the X-ray photoelectron spectrum (XPS) of the manganese dioxide-nickel hydroxide composite electrode material prepared in Examples 1 to 3.

Fig. 3 is the X-ray energy spectrum (EDS) of the manganese dioxide-nickel hydroxide composite electrode material prepared by implementing 3;

Fig. 4 is the transmission electron micrograph (TEM) of the manganese dioxide-nickel hydroxide composite electrode material that embodiment 3 prepares, and illustration is the selected area electron diffraction pattern (SAED) of sample;

Fig. 5 is the discharge curve under the current density of 5A/g of the manganese dioxide-nickel hydroxide composite electrode material that embodiment 5 to 8 prepares;

Fig. 6 is the electrochemical performance test figure of the manganese dioxide-nickel hydroxide composite electrode material prepared in embodiment 3; (a) is successively the cyclic voltammogram under different scanning speeds, (b) the charge of current density 5A/g Discharge diagram, (c) discharge curves under different current densities (d) specific volume changes after 500 cycles at a current density of 20A/g.

Detailed ways

The method of the present invention is further described in detail through the following examples.

The cathodic electrochemical deposition is carried out in the mixed aqueous electrolyte of potassium permanganate and nickel nitrate with foamed nickel, nickel sheet or titanium sheet as the electrode plate, and the surface of the electrode plate after deposition is cleaned with deionized water and dried to obtain the following Foam nickel, nickel sheet or titanium sheet is a composite electrode material with manganese dioxide-nickel hydroxide composite thin film on the surface.

Understand by following examples, adopt the product characteristic obtained under different process conditions:

Example 1

The electrolytic cell filled with the mixed aqueous electrolyte of potassium permanganate and nickel nitrate is heated through a constant temperature water bath so that the working temperature of the electrolyte is 20°C to 30°C;

The concentration of potassium permanganate in the electrolyte is 0.02mol/L, and the concentration of nickel nitrate is 0.004mol/L

The deposition potential was adjusted to -0.8V; the deposition time was 6 min, and the thickness of the obtained deposition layer was about 150 nm.

The obtained composite film electrode adopts a three-electrode system (Pt is a counter electrode, a saturated calomel electrode SCE is a reference electrode, and the prepared electrode is a working electrode) to carry out electrochemical performance tests, including cyclic voltammetry tests and galvanostatic charge-discharge tests. The electrolyte is 1mol/L KOH, the charging and discharging voltage is -0.1V～0.5V, the current density is 5A/g, and the measured specific volume of the composite electrode material is 515F/g.

The appearance of the composite thin film electrode material deposition layer is shown in Figure 1 (a) scanning electron microscope (SEM). It can be seen from the figure that the spherical particles are piled up, and the surface of the particles is covered with nanofibers, showing a three-dimensional network internal connection structure.

Example 2

The concentration of potassium permanganate in the electrolyte is 0.02mol/L, and the concentration of nickel nitrate is 0.014mol/L;

Other conditions, practice are with embodiment 1.

The resulting deposited layer was approximately 180 nm thick.

The measured specific volume of the composite electrode material can reach 1125F/g.

The appearance of the composite film electrode material deposition layer is shown in the accompanying drawing 1 (b) scanning electron microscope (SEM). It can be seen from the figure that the nanofibers covered on the surface of the stacked spherical particles become thick and dense.

Example 3

The concentration of potassium permanganate in the electrolyte is 0.02mol/L, and the concentration of nickel nitrate is 0.05mol/L;

Other conditions, practice are with embodiment 1. The resulting deposited layer was approximately 200 nm thick.

The appearance of the composite thin film electrode material deposition layer is shown in the accompanying drawing 1 (c) scanning electron microscope (SEM). It can be seen from the figure that there is no spherical particle shape, which is completely interwoven with loose nanofibers, and the pore structure is evenly distributed and obvious.

See Figure 2 for the X-ray photoelectron spectroscopy (XPS) of the composite thin film electrode material.

The X-ray energy spectrum (EDS) of the composite electrode material is shown in Fig. 3 .

The transmission electron microscope image (TEM) of the composite electrode material is shown in Fig. 4 . By XPS analysis, combined with EDS and TEM, it can be determined that manganese dioxide and nickel hydroxide exist in the composite, that is, a composite of manganese dioxide-nickel hydroxide has been prepared.

The electrochemical performance of the composite electrode material is shown in Figure 6. The specific volume of the electrode material is high (the specific volume can reach 2334F/g (under the condition of 5A/g), 2120F/g (under the condition of 10A/g), 1933F/g (under the condition of 20A/g), 1567F/g (under the condition of 40A/g) g condition), 1292F/g (50A/g condition), high cycle stability (500 cycles at a current density of 20A/g and the specific volume still maintains more than 82.8%).

Example 4

The concentration of potassium permanganate in the electrolyte is 0.02mol/L, and the concentration of nickel nitrate is 0.12mol/L;

Other conditions, practice are with embodiment 1.

The thickness of the resulting deposited layer is about 300 nm.

It is measured that the specific volume of the obtained composite electrode material can reach 1368F/g.

The appearance of the composite film electrode material deposition layer is shown in the accompanying drawing 1 (d) scanning electron microscope (SEM). It can be seen from the figure that the denser nanofibers present a spherical aggregation distribution.

Example 5

The working temperature of the electrolyte is 20°C to 30°C;

The concentration of potassium permanganate in the electrolyte is 0.02mol/L, and the concentration of nickel nitrate is 0.05mol/L;

The deposition potential was adjusted to -0.7V; the accumulated charge of deposition was 0.11mAh, and the thickness was about 200nm.

Other conditions, practice are with embodiment 1.

The obtained composite film electrode adopts a three-electrode system (Pt is a counter electrode, a saturated calomel electrode SCE is a reference electrode, and the prepared electrode is a working electrode) to carry out electrochemical performance tests, including cyclic voltammetry tests and galvanostatic charge-discharge tests. The electrolyte is 1mol/L KOH, the charging and discharging voltage is -0.1V～0.45V, and the current density is 5A/g.

The discharge characteristics of the obtained composite electrode material at a current density of 5 A/g are shown in FIG. 5 . The measured specific volume of the composite electrode material is 745.5F/g.

Example 6

The deposition potential was adjusted to -0.75V; other conditions and methods were the same as in Example 5. The deposition thickness is about 200nm.

The discharge characteristics of the obtained composite electrode material at a current density of 5 A/g are shown in FIG. 5 . It is measured that the specific volume of the composite thin film electrode can reach 766F/g.

Example 7

The deposition potential was adjusted to -0.8V; other conditions and methods were the same as in Example 5. The deposition thickness is about 200nm.

The discharge characteristics of the obtained composite electrode material at a current density of 5 A/g are shown in FIG. 5 . It is measured that the specific volume of the composite thin film electrode can reach 845F/g.

Example 8

The deposition potential was adjusted to -0.95V; other conditions and methods were the same as in Example 5. The deposition thickness is about 200nm.

The discharge characteristics of the obtained composite electrode material at a current density of 5 A/g are shown in FIG. 5 . It is measured that the specific volume of the composite thin film electrode can reach 737F/g.

Example 9

The working temperature of the electrolyte is 20°C to 30°C;

The concentration of potassium permanganate in the electrolyte is 0.005mol/L, and the concentration of nickel nitrate is 0.05mol/L;

The deposition potential was adjusted to -0.8V; the cumulative electric charge of deposition was 0.11mAh, and the deposition thickness was about 150nm.

Other conditions, practice are with embodiment 1.

The obtained composite film electrode adopts a three-electrode system (Pt is a counter electrode, a saturated calomel electrode SCE is a reference electrode, and the prepared electrode is a working electrode) to carry out electrochemical performance tests, including cyclic voltammetry tests and galvanostatic charge-discharge tests. The electrolyte is 1mol/L KOH, the charging and discharging voltage is -0.1V～0.45V, the current density is 10mA/cm ² , and the measured specific volume of the composite electrode material is 1196F/g.

Example 10

The concentration of potassium permanganate in the electrolyte is 0.01mol/L, and the concentration of nickel nitrate is 0.05mol/L;

Other conditions, practice are the same as embodiment 9. The deposition thickness is about 180nm.

It is measured that the specific volume of the obtained composite thin film electrode can reach 1784F/g.

Example 11

The concentration of potassium permanganate in the electrolyte is 0.02mol/L, and the concentration of nickel nitrate is 0.05mol/L;

Other conditions, practice are the same as embodiment 9. The deposition thickness is about 200nm.

It is measured that the specific volume of the obtained composite thin film electrode can reach 1920F/g.

Example 12

The concentration of potassium permanganate in the electrolyte is 0.04mol/L, and the concentration of nickel nitrate is 0.05mol/L;

Other conditions, practice are the same as embodiment 9. The deposition thickness is about 250nm.

It is measured that the specific volume of the obtained composite thin film electrode can reach 1580F/g.

Example 13

The concentration of potassium permanganate in the electrolyte is 0.05mol/L, and the concentration of nickel nitrate is 0.05mol/L;

Other conditions, practice are the same as embodiment 9. The deposition thickness is about 300nm.

It is measured that the specific volume of the obtained composite thin film electrode can reach 920F/g.

Can find out by above-mentioned embodiment:

1) The electrode material prepared by the above method is observed by scanning electron microscope, and it can be seen that the electrode material obtained by adding the concentration of nickel nitrate in the electrolyte presents different shapes, and wherein, Example 3 presents a uniform, loose The pore structure is conducive to obtaining a large specific surface area to facilitate the entry and exit of the electrolyte, ensuring the excellent electrochemical performance of the electrode material.

2) XPS analysis was carried out on the samples prepared above, combined with EDS and SADE, it was confirmed that manganese dioxide and nickel hydroxide existed in the composite, that is, a composite electrode material of manganese dioxide-nickel hydroxide was prepared by this method.

3) Examples 5 to 8 optimize the deposition potential conditions of Examples 1 to 4, and it is obtained that the specific capacitance of the electrode material prepared in Example 7 is the highest, that is, -0.8V is the best deposition potential.

4) Example 9 to 13 is to explore the concentration range of potassium permanganate, the specific capacitance of the electrode material prepared by example 9 and example 13 is not high, and the specific capacitance of the electrode material obtained from example 10 to example 12 is all at 1500F/g From the above, it can be concluded that 0.01mol/L～0.04mol/L is the optimum concentration range.

5) The electrode material obtained under the conditions of Example 3 has a higher specific volume (the specific volume can reach 2334F/g at a charge-discharge current density of 5A/g), good power characteristics, and high cycle stability (at a current density of 20A/g). 500 cycles of specific volume still maintain more than 82.8%). Thus providing favorable technical support for fields such as hybrid power energy.

Claims (6)

1. A method for preparing supercapacitor manganese dioxide-nickel hydroxide composite electrode material is characterized in that, taking foam nickel, nickel sheet or titanium sheet as pole plate in potassium permanganate and nickel nitrate mixed aqueous solution electrolyte Carry out cathodic electrochemical deposition, wash the surface of the plate after deposition with deionized water, and dry it to obtain a composite electrode material with nickel foam, nickel sheet or titanium sheet as the base and a manganese dioxide-nickel hydroxide composite film on the surface . 2. the method for preparing supercapacitor manganese dioxide-nickel hydroxide composite electrode material according to claim 1 is characterized in that, described potassium permanganate and nickel nitrate mixed aqueous solution electrolyte, wherein, potassium permanganate The concentration of nickel nitrate is 0.005mol/L～0.05mol/L, and the concentration of nickel nitrate is 0.004mol/L～0.12mol/L. 3. the method for preparing supercapacitor manganese dioxide-nickel hydroxide composite electrode material according to claim 1, is characterized in that, described potassium permanganate and nickel nitrate mixed aqueous electrolyte, wherein, potassium permanganate The concentration of nickel nitrate is 0.01mol/L～0.04mol/L, and the concentration of nickel nitrate is 0.014mol/L～0.12mol/L. 4. The method for preparing a manganese dioxide-nickel hydroxide composite electrode material for a supercapacitor according to claim 1, wherein the operating temperature of the electrolyte is 20°C to 30°C. 5. The method for preparing a manganese dioxide-nickel hydroxide composite electrode material for a supercapacitor according to claim 1, wherein the electrochemical deposition potential is -0.7～-0.95V. 6. the method for preparing supercapacitor manganese dioxide-nickel hydroxide composite electrode material according to claim 1, is characterized in that, electrochemical deposition potential is-0.8V.