CN103227057B - A kind of method preparing manganese dioxide electrode of super capacitor - Google Patents

Abstract

A preparation method of a manganese dioxide supercapacitor electrode. It is characterized in that the preparation process of the electrode includes the following steps: first, a layer of manganese alloy coating is electrochemically co-deposited on the surface of the electrode current collector; and then the obtained electrode with the manganese alloy coating is subjected to anodic oxidation treatment to obtain a manganese dioxide electrode. The present invention realizes the uniform distribution of alloy elements in the prepared electrode through electrochemical co-deposition, so as to improve its electronic conductivity in the process of anodic oxidation and charging and discharging; on the one hand, through anodic oxidation, the manganese in the alloy layer is converted into The chemically active manganese dioxide material can also construct a pore structure on the surface and inside of the prepared electrode, thereby improving the solid-phase mass transfer characteristics and electrochemical reactivity of the material, and obtaining an electrode with high specific capacitance characteristics.

Description

A kind of method for preparing manganese dioxide supercapacitor electrode

technical field

The invention belongs to the technical field of electrochemistry, and in particular relates to a method for preparing manganese dioxide supercapacitor electrodes.

technical background

Supercapacitor is a new concept energy storage device between batteries and traditional electrostatic capacitors. Compared with traditional electrostatic capacitors such as aluminum electrolytic capacitors, supercapacitors have higher specific capacitance, and the energy density that can be stored is traditional electrostatic capacitors Compared with batteries, supercapacitors have greater power density, and have the characteristics of high charge and discharge efficiency and long cycle life. Due to the many advantages above, the development of supercapacitor technology has been widely valued by academia, industry and military departments, and it is gradually being used as a backup power supply for electronic instruments, rockets, missiles, artificial satellites, spacecraft space stations, etc. The power supply has been applied, and the ultra-high power capacitor used for ignition can provide MW-level extra large starting power.

With the world's climate change and the continuous depletion of fossil resources, mankind's enthusiasm for the development and utilization of renewable energy continues to rise. Great progress has been made in the development of solar energy and wind energy. At the same time, in order to save limited oil resources, zero emissions can be achieved. And the development of low-emission electric vehicles and hybrid electric vehicle technology has also received much attention. Since electricity generated by sunlight and wind is intermittent, and our demand for electricity is always, energy storage systems will play an important role in the production and life of human beings in the future. As a typical electrical energy storage system, the development of high-performance batteries and supercapacitors with high power, high energy density and low cost will be one of the key links to realize the effective utilization of renewable energy.

The main problem faced by supercapacitors is their relatively low energy density compared to batteries. In order to improve the performance of supercapacitors, that is, to increase the specific energy while maintaining its advantages such as high specific power, research around transition metal oxide electrodes with electric double layer capacitance and faradaic pseudocapacitive behavior has attracted much attention. At present, RuO ₂ is widely studied as the electrode material. It can not only realize high-power charging and discharging, but also has a relatively high mass specific energy. It is a type of electrode material that has made breakthroughs in material processing and application so far. However, the key problem facing this material is the high cost of materials, so it is difficult to obtain commercial promotion in the civilian industry. In order to seek cheap supercapacitor electrode materials, research on the preparation and electrochemical performance of transition metal oxide materials such as NiO, Co ₃ O ₄ , V ₂ O ₅ , and MnO ₂ has been carried out. However, most of the research is to first prepare the above-mentioned transition metal oxides into powder granular materials, and then mix these powder materials with binders and coat them on the current collector to prepare electrodes, which is easy to cause electrode active materials. Poor contact with the current collector affects the charge and discharge performance of the electrode. In addition, since the internal structure of the electrode material and its interface characteristics with the electrolyte play a crucial role in the performance of the capacitor, it is difficult to prepare the powder electrode material by chemical precipitation method, hydrothermal method, etc. It is difficult to obtain electrode materials with high power density and high energy density through effective design of structure; it is difficult to do element doping for electrode materials prepared by conventional electrolytic manganese dioxide production methods, and the specific capacitance of prepared electrode materials can only reach 200F.g ^-1 or so. The invention adopts an electrochemical method to prepare manganese dioxide supercapacitor electrodes, realizes active material components and internal structure design through electrochemical construction, and simultaneously improves the contact between the electrode active material and the current collector, so that it has high specific capacity characteristics.

Contents of the invention

The purpose of the present invention is to propose a method for preparing manganese dioxide supercapacitor electrodes, focusing on building the internal pore structure of the material by electrochemical methods and carrying out component design to improve the internal mass transfer characteristics and electronic conductivity of the material, thereby A supercapacitor electrode with high specific capacity characteristics is obtained.

The present invention proposes a kind of method for preparing manganese dioxide supercapacitor electrode, comprises the following steps:

Step 1: Electrochemical co-deposition of manganese alloy coating

Soluble manganese salts, soluble alloy component salts, supporting electrolyte salts, and additives are dissolved in water in proportion to prepare a mixed aqueous solution as an electroplating solution. The current collector material after surface polishing and cleaning is used as the cathode, and the inert anode is used as the anode. Electrochemical co-deposition of alloys to obtain manganese alloy plated electrodes;

The second step: anodic oxidation of manganese alloy coating

Using the manganese alloy plated electrode obtained in the first step as the anode, the stainless steel sheet, graphite sheet or peptide sheet and other inert electrodes as the cathode, and using a solution containing a soluble halogen salt as the electrolyte to carry out anodic oxidation treatment to obtain a porous manganese oxide electrode;

Step Three: Electrode Formation

The porous manganese oxide electrode obtained in the second step is used as the working electrode, the inert electrode such as stainless steel or graphite sheet is used as the auxiliary electrode, and the commonly used supercapacitor electrolyte is used as the electrolyte. The two-electrode system is assembled and charged and discharged several times with a small current to make the porous manganese oxide The manganese in the electrode is completely oxidized to manganese dioxide.

The invention relates to a preparation method of a manganese dioxide electrode, wherein the manganese alloy coating is obtained through electrochemical co-deposition.

A kind of preparation method of manganese dioxide supercapacitor electrode, the soluble manganese salt described in the first step is manganese sulfate, manganese nitrate, manganese chloride or manganese acetate; The alloy element in the described soluble alloy composition salt comprises Ni, One or more of Co, Mo, Fe, Cu, W, Ag, Ru, Au, Pt; soluble alloy component salts include Ni, Co, Mo, Fe, Cu, W, Ag, Ru, Au, Pt One or more of sulfate, nitrate, hydrochloride, cyanate or thiocyanate.

A kind of preparation method of manganese dioxide supercapacitor electrode, in the first step, supporting electrolyte is ammonium sulfate, ammonium chloride, alkali metal sulfate or chloride, and additive comprises pH buffering agent, complexing agent, wherein pH buffering The agent is one or more of boric acid, sodium citrate, and ammonia, and the complexing agent includes one or more of soluble ethylenediamine tetraacetate, citrate, thiourea, thiocyanate, and cyanide. A substance that can effectively complex the desired alloying elements. Materials used as current collectors include conductive metals and conductive non-metals.

A method for preparing a manganese dioxide electrode. In the first step, the concentration of manganese ions in the electroplating solution is 0.1 to 0.8 mol/L, the concentration of the supporting electrolyte is 0.7 to 1.2 mol/L, and the manganese ions and alloy element ions The molar concentration ratio is 20-50, the molar ratio of the complexing agent to the alloy element is 1-10, and the pH value range of the electroplating solution is 4-7.

A method for preparing a manganese dioxide electrode, in the first step, the material used as a current collector includes conductive metal and conductive non-metal.

A method for preparing a manganese dioxide electrode. In the first step, when performing electrochemical co-deposition, pulse, constant voltage or constant current co-deposition can be used.

A method for preparing a manganese dioxide electrode, wherein the electrolyte used in the second step is an electrolyte containing halogen ions such as F ^- or Cl ^- , and the mass concentration of the halogen ions ranges from 0.1 to 0.5%.

A method for preparing a manganese dioxide electrode, wherein the solvent in the electrolyte solution used in the second step is water, alcohols or a mixture thereof.

The invention relates to a preparation method of a manganese dioxide electrode. In the second step, pulse, constant current or constant voltage oxidation can be performed during anodic oxidation, and a porous manganese oxide electrode is finally obtained.

A method for preparing a manganese dioxide electrode. In the second step, constant-current or constant-voltage oxidation can be carried out during anodic oxidation. The current density of constant-current oxidation ranges from 0.1 to 10mA/cm ² . The voltage range is 5-80V.

The invention relates to a method for preparing a manganese dioxide electrode. In the third step, the charging and discharging current density used during electrode formation is 0.1-10 mA/cm ² .

The present invention adopts the above method. Firstly, the soluble manganese salt and the soluble alloy component salt are weighed according to the molar ratio of manganese and alloy elements being 20-50, respectively dissolved in water, and respectively prepared into aqueous solutions. Adding the complexing agent whose molar ratio is 1-10 according to the alloying element and the complexing agent into the alloy component salt solution, and fully stirring to make it dissolve to form a uniform and transparent solution. Mix the prepared manganese salt solution and the alloy component salt solution, and add a supporting electrolyte to the mixed solution, so that the concentration of the supporting electrolyte reaches 0.7-1.2mol/L, and finally add a pH buffer and other additives, add water Stir for at least 30 minutes to obtain the desired electroplating solution. The concentration of manganese ions in the electroplating solution is 0.1-0.8mol/L, the concentration of supporting electrolyte is 0.7-1.2mol/L, the molar concentration ratio of manganese ions to alloy element ions is 20-50, and the ratio of complexing agent to alloy element The molar ratio is 1-10, which is determined by the coordination number of complex ions formed by the complexing agent and alloy element ions, and the pH value range of the electroplating solution is 4-7. The alloy component salt used here includes one or more of soluble salts of Ni, Co, Mo, Fe, Cu, W, Ag, Ru, Au, and Pt. The electrolyte is one or more of ammonium sulfate, ammonium chloride and alkali metal sulfate or chloride, and the pH buffer is one or more of boric acid, sodium citrate, and ammonia water. The complexing agent includes one or more of soluble ethylenediaminetetraacetic acid salt, citrate, thiourea, thiocyanate, cyanide, etc., which can effectively complex the required alloy elements.

The current collector used for supercapacitors is surface treated by conventional electroplating parts surface treatment methods, such as surface polishing, cleaning, etc., and then used as the cathode (working electrode), and the inert anode such as titanium and graphite is used as the anode. Electrodeposition is carried out in the electroplating tank of the electroplating solution prepared above to prepare a manganese alloy coating electrode. For electrodeposition, pulse, constant voltage or constant current co-deposition can be used, but the pulse cathode potential or constant voltage cathode potential is not higher than -1.2V (relative to the hydrogen standard electrode).

The above-mentioned manganese alloy coating electrode is used as the anode, and the stainless steel sheet or other metal sheet is used as the cathode, and the solution containing halogen ions with a mass concentration of 0.1 to 0.5% is used as the electrolyte to anodize the manganese alloy coating to obtain a porous manganese oxide electrode. . In order to improve the conductivity of the electrolyte during anodic oxidation, other supporting electrolytes, such as sodium sulfate, can be added to the halogen salt solution.

Since the manganese in the porous manganese oxide electrode formed during anodic oxidation cannot be completely oxidized to +4-valent manganese, which affects the electrochemical performance of the electrode, the porous manganese oxide electrode must be chemically treated at last to convert the manganese into manganese with Electrochemically active +4-valent manganese. The formation method is the same as the formation process of other energy storage devices such as lead-acid batteries. For example, put the electrode in 0.5mol/L sodium sulfate aqueous solution and charge and discharge several times with a current of 0.5mA/ ^cm2 , and finally obtain super manganese dioxide capacitor electrodes. The advantages of the present invention are: 1) In the preparation process of the electrode sheet, there is no need for active material slurry preparation, smearing and other processes, and the process is simple; 2) Manganese alloy is prepared by alloy co-deposition, which is an alloy group with a positive corrosion potential than manganese It can overcome the shortcoming of pure manganese coating being relatively brittle and improve the processing performance of the coating. In the process of electrode oxidation and chemical formation, manganese is converted into +4 valent manganese; 3) The alloy components with positive corrosion potential are difficult to Corrosion, which can provide sufficient electron channels for the electrochemical reaction of the electrode polarization and charge and discharge process, and reduce the ohmic polarization; 4) Through electrochemical oxidation, while the metal manganese is oxidized, part of the metal manganese or low-valence state is oxidized Manganese is etched by the H ⁺ produced by the decomposition of water during this oxidation process, thereby forming a porous structure that provides a large electrode/solution interface for electrochemical reactions and electric double layer capacitance, making the electrodes characteristic of high specific volume.

Description of drawings

Accompanying drawing 1 is the cyclic voltammetry curve of the manganese dioxide supercapacitor electrode prepared in Example 1 of the present invention.

From the cyclic voltammetry curve of accompanying drawing 1, the specific capacitance of the electrode active material prepared in Example 1 is calculated to be 413 F/g.

specific embodiment

Embodiment one

Prepare MnSO ₄ .H ₂ O and NiSO ₄ .7H ₂ O aqueous solutions respectively, and add disodium edetate to the NiSO ₄ solution according to the molar ratio of nickel to disodium edetate at 1:1 and carry out sufficient Stir to form a homogeneous clear solution. Mix the prepared two solutions containing manganese salt and nickel salt, add ammonium sulfate and sodium lauryl sulfate to the mixed solution after mixing, and dissolve after adding water; the concentration of each component is: the concentration of manganese ions is 0.5mol/L, ammonium sulfate concentration is 1.2mol/L, nickel ion concentration is 0.025mol/L. Adjust the pH value of the solution to 5 with ammonia water, continue to stir for 60 minutes and set aside.

The 304 stainless steel foil was cut into a stainless steel strip with an area of ⁴ ×1cm2 as a current collector, and the current collector was ultrasonically washed with 10% sulfuric acid aqueous solution and acetone, and finally rinsed with water and dried. Use 4×4cm as the titanium mesh electrode, the above-mentioned solution containing nickel and manganese as the electroplating solution, and the current collector after cleaning the surface as the cathode (the working area is 1×1cm ² ), conduct constant current manganese-nickel alloy electrodeposition, and the current density 300mA/cm ² , the electrodeposition time is 8 minutes, and a manganese-nickel alloy coating is obtained. The nickel content in the alloy was found to be 8% by ICP analysis.

The manganese alloy plated electrode obtained above is used as the anode, and the stainless steel sheet (area 4×4cm ² ) is used as the cathode, and the ethylene glycol solution containing NH ₄ F0.25% and water 5% is used as the electrolyte for anodic oxidation treatment. The cell voltage is 20V, and the time is 7 minutes to obtain a porous manganese oxide electrode. Use 0.5mol/L sodium sulfate aqueous solution as electrolyte, porous manganese oxide electrode as anode, and platinum electrode with an area of ⁴ ×4cm2 as cathode to assemble a simulated capacitor, and charge and discharge at a constant current for 10 times with a current of 1mA/ ^cm2 . Finally, the manganese dioxide supercapacitor electrode is obtained after washing with water and drying. Use 0.5mol/L sodium sulfate aqueous solution as the electrolyte, the manganese oxide electrode prepared above as the working electrode, and the platinum electrode with an area of ⁴ × 4cm2 as the auxiliary electrode to assemble a three-electrode system, and perform cyclic voltammetry test. The test potential range is 0 ~0.8 V (vs. silver-silver chloride electrode) with a scan rate of 10 mV/s. According to the cyclic voltammetry curve, the specific capacitance of the electrode active material is 413F/g.

Embodiment two

The operation process is the same as in Example 1, except that the concentration of manganese sulfate used is 0.8mol/L, the soluble alloy component salt is CoSO ₄ .7H ₂ O, the complexing agent is sodium citrate, and the molar ratio of cobalt to sodium citrate is 1 : 5, the ammonium sulfate concentration is 0.9mol/L, and the cobalt ion concentration is 0.016mol/L. Adjust the pH of the solution to 7 with ammonia. Use the ethylene glycol solution containing NH ₄ F0.1%, water 5% as the electrolyte to carry out anodic oxidation treatment, the voltage of the constant pressure oxidation tank is 80V, the cobalt content in the alloy coating is 11%, and the specific capacitance of the electrode active material It is 381F/g.

Embodiment three

The operation process is the same as in Example 1, except that the concentration of manganese sulfate used is 0.8mol/L, the soluble alloy component salt is AgNO ₃ , the complexing agent is NaCN, the molar ratio of silver to NaCN is 1:10, and the Ag ⁺ The concentration is 0.02mol/L. Adjust the pH of the solution to 7 with ammonia. Use ethylene glycol solution containing 0.5% NH ₄ CL and 5% water as the electrolyte for anodic oxidation treatment. The voltage of the constant voltage oxidation tank is 5V, and the current of 0.1mA/cm ² is used for constant current charge and discharge for 10 times. The silver content in the obtained alloy coating is 4%, and the specific capacitance of the electrode active material is 437F/g.

Embodiment four

The operation process is the same as in Example 1, except that the concentration of manganese sulfate used is 0.1mol/L, the soluble alloy component salt is CoSO ₄ .7H ₂ O, the complexing agent is sodium citrate, and the molar ratio of cobalt to sodium citrate is 1 : 5, the ammonium sulfate concentration is 0.7mol/L, and the cobalt ion concentration is 0.003mol/L. The pH value of the solution was adjusted to 4 with ammonia water, and a constant current charge and discharge was performed 10 times with a current of 10mA/cm ² . The cobalt content in the alloy coating was measured to be 5%, and the specific capacitance of the electrode active material was 341F/g.

Claims (7)

1. prepare a method for manganese dioxide electrode of super capacitor, comprise the steps:

The first step: electrochemical co-deposition manganese alloy coating

Soluble manganese salt, soluble alloy component salt, supporting electrolyte salt, additive are dissolved in water in proportion and are mixed with mixed aqueous solution as electroplate liquid, with being negative electrode through surface finish and cleaned current collector material, inert anode is that anode carries out manganese alloy electrochemical co-deposition, obtains manganese alloy coating electrode;

In electroplate liquid, the concentration of manganese ion is 0.1 ~ 0.8mol/L, and electrolytical concentration is 0.7 ~ 1.2mol/L, and manganese ion is 20 ~ 50 with the ratio of alloying element ion molar concentration, and the mol ratio of complexing agent and alloying element is 1 ~ 10, and the pH value range of electroplate liquid is 4 ~ 7;

Second step: the anodic oxidation of manganese alloy coating

Using the manganese alloy coating electrode of first step gained as anode, inert electrode is cathode, is that electrolyte carries out anodized, obtains porous oxidation manganese electrode with the solution containing solubility haloid;

3rd step: electrode changes into

The porous oxidation manganese electrode obtained by second step is anode, and inert electrode is as negative electrode, and conventional electrolytic solution for super capacitor is electrolyte, assembles two electrode systems and carries out small area analysis discharge and recharge for several times, make the manganese in porous oxidation manganese electrode be completely oxidized to manganese dioxide.

2. the preparation method of manganese dioxide electrode of super capacitor according to claim 1, is characterized in that: the soluble manganese salt described in the first step is manganese sulfate, manganese nitrate, manganese chloride or manganese acetate; The alloying element of described soluble alloy component salt comprises one or more in Ni, Co, Mo, Fe, Cu, W, Ag, Ru, Au, Pt; Soluble alloy component salt comprises one or more in the sulfate of Ni, Co, Mo, Fe, Cu, W, Ag, Ru, Au, Pt, nitrate, hydrochloride, cyanate or rhodanate.

3. the preparation method of manganese dioxide electrode of super capacitor according to claim 1 and 2, it is characterized in that: supporting electrolyte salt comprises ammonium sulfate, ammonium chloride or alkali-metal sulfate or chloride, additive comprises pH buffer, complexing agent, wherein pH buffer comprises one or more in boric acid, natrium citricum, ammoniacal liquor, complexing agent comprises one or more in solubility edetate, citrate, sulphur urine, rhodanate, cyanide, and inert anode is titanium or graphite.

4. the preparation method of manganese dioxide electrode of super capacitor according to claim 1, is characterized in that: in the described first step, when carrying out electrochemical co-deposition, adopts pulse, constant voltage or constant current codeposition.

5. the preparation method of manganese dioxide electrode of super capacitor according to claim 1, it is characterized in that: the electrolyte used in second step is the solution of solubility haloid, the mass concentration scope of halide ion is 0.1 ~ 0.5%, and the solvent in this electrolyte is water, alcohols or its mixture.

6. the preparation method of manganese dioxide electrode of super capacitor according to claim 1 or 5, is characterized in that: carry out pulse, constant current or constant voltage oxidation in second step when carrying out anodic oxidation, the current density range of constant current oxidation is 0.1 ~ 10mA/cm ², the tank voltage scope of constant voltage oxidation is 0 ~ 200V.

7. the preparation method of manganese dioxide electrode of super capacitor according to claim 6, is characterized in that: the charging and discharging currents density used when carrying out electrode and changing in the 3rd step is at 0.1 ~ 10mA/cm ².