CN1300812C - Manufacture of high-capacity electrochemical capacitor - Google Patents

Abstract

The present invention relates to a manufacture method of an electrochemical super capacitor with high capacity, which belongs to the field of an electrochemical capacitor. The present invention is characterized in that materials formed by compounding oxides or hydroxides of ruthenium and activated carbon with high specific surface area serve as a positive electrode and a negative electrode of the electrochemical capacitor or the compounded materials serving as the positive electrode and the negative electrode are made of porous carbon materials with high specific surface area. Two composing modes of the positive electrode and the negative electrode both take aqueous alkali or acid solution as electrolytes. Insulated polymer is taken as a diaphragm between the positive electrode and the negative electrode to assemble electrochemical capacitors with different shapes and purposes. The manufacture method provided by the present invention is simple, the price of the present invention is cheaper than that of an electrochemical capacitor made of the oxides of the ruthenium, and the capacity is far larger than that of an electrochemical capacitor made of pure activated carbon materials.

Description

A kind of manufacturing method of high-capacity electrochemical capacitor

technical field

The present invention relates to a kind of preparation method of high-capacity electrochemical capacitor, more specifically relate to its composite material formed by the oxide or hydroxide of ruthenium and porous activated carbon as electrode in electrochemical capacitor to prepare a kind of high-capacity electrochemical capacitor The invention discloses a method for preparing a capacitor, which belongs to the field of electrochemical capacitors.

Background technique

Electrochemical capacitors have been widely recognized in the electronics industry for their outstanding functions and advantages. Compared with traditional capacitors, electrochemical capacitors have extremely high capacitance values, limited frequency response, high equivalent series resistance (ESR), voltage-dependent capacitance, and voltage-dependent self-discharge rate. Electrochemical capacitors were originally used to provide high excitation energy for high-energy lasers. The new electrochemical capacitor can also replace nickel-cadmium batteries and lithium batteries as an uninterruptible power supply (UPS) for computers and communication systems. Large electrochemical capacitors are used in electric vehicles to provide high-current discharge during starting and braking, which effectively solves the problem of high-power charging and discharging of batteries and prolongs the working life of batteries. Therefore, electrochemical capacitors are widely used in many fields.

Unlike conventional capacitors, the high capacity of electrochemical capacitors is achieved by employing large-area porous electrodes and storing energy between diffused double layers. Such bilayers, which can naturally form at the electrode-electrolyte interface when a voltage is applied between the electrodes, are typically as thick as one water molecule's diameter, thereby creating minimal effective "plate separation." In addition, in many cases, the stored energy is substantially increased by the so-called "quasicapacitance" or "pseudocapacitance", which also occurs at the electrode-electrolyte interface. The capacitance of the electric double layer is generally 16-40 microfarads/cm2, while the capacitance formed by "quasicapacitance" can reach up to 100 microfarads/cm2. This capacity can be further increased when adsorption-desorption or fast electrochemical redox reactions occur at or near the electrodes (there is no significant phase change in the active species). This increased capacitance is called "quasicapacitance", and the resulting device is colloquially known as "ultracapacitor" or "ultracapacitor", which is a pseudocapacitor reflecting Faraday's signal and has a higher capacitance than pure electric double layer capacitance. specific capacity.

Double-layer capacitors are based on the high-surface-area electrode material activated carbon, which provides a high surface area, A, and an "effective double-layer" thickness, d, that is reduced to the atomic diameter scale, thus resulting in high capacitance. Beck first published the first patents on electric double layer capacitors in the 1960s. However, the real rise of electrochemical capacitor research came after it was widely used as a computer uninterruptible power supply and after the US Department of Energy proposed a huge plan to apply electrochemical capacitors to electric vehicles in the early 1990s.

The energy stored in a general chemical power source is equal to the charge associated with the electrochemical redox change multiplied by the potential difference between the battery electrodes. The process of charge-discharge reaction often involves the change of active material phase. Thus, although the energy density is relatively high, the charge-discharge reaction rate is relatively slow compared with electrochemical capacitors. Compared with batteries, electrochemical capacitors have the advantages of no maintenance, longer cycle life, safe use, and no memory effect. More importantly, electrochemical capacitors have high-power and high-current continuous charge and discharge performance that batteries do not have, which promotes the development of such high-power devices and products. Therefore, electrochemical capacitors are an attractive energy storage device.

Energy storage systems used in electric vehicles require high energy density to provide sufficient driving range. It must have a high power density to meet the acceleration performance requirements of electric vehicles. It must have a long enough charge and discharge life and must have a price that users can afford. The many advantages of the electrochemical capacitive energy storage system make it have the potential to be applied in the fields of electric vehicle power supply and so on. Electrochemical capacitors are necessary in the composite power supply of hybrid electric vehicles. Electrochemical capacitors can provide the power increment required for rapid acceleration and heavy load operation of electric vehicles, thus solving the biggest problem that electric vehicle batteries cannot be discharged with high power. Commercial technical problems. The battery and the capacitor form a parallel circuit, and the battery is still powered by the battery when the car is roaming. The capacitor starts to work under relatively harsh conditions such as starting, accelerating, climbing and braking. The use of the capacitor effectively solves the problem of the battery. The problem of large current discharge, and it is much more cost-effective than designing a battery with the same effect.

At present, the electrochemical double-layer capacitor with porous activated carbon as the electrode material is more mature (that is, the positive and negative electrodes of the capacitor are both composed of activated carbon-like symmetrical capacitors). However, according to the determination of the surface area and the dipole The theoretical capacitance of the material obtained by calculating the thickness of the layer is generally difficult to achieve in practice. The larger the surface area of the material, the greater the gap between the theoretical calculation and the actual measured capacity. Pores", people cannot make full use of the surface area of activated carbon. Therefore, there is little room for increasing the material capacity by increasing the surface area of the material. The contact resistance between activated carbon particles limits the electric double layer capacitance output at higher power densities. The direction of efforts to promote the development of electrochemical capacitor energy storage should be on how to make full use of the "quasi-capacitance" of materials to greatly improve the capacity characteristics of materials.

Materials with higher Faraday "quasi-capacitance" are more researched on transition metal oxide materials such as ruthenium oxide (RuO ₂ xH ₂ O) such as U.S5621609A, which discloses that both the positive and negative electrodes are oxidized by moisture It is composed of ruthenium and carbon black or carbon fiber with excellent porous water permeability, and sulfuric acid solutions of various concentrations are used as electrolytes. Although RuO ₂ ·xH ₂ O has a satisfactory capacity (hundreds of Farads/g active material), its high price limits its further commercial application.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings in the prior art: porous activated carbon is used as electrode material, its surface area cannot be fully utilized, and the energy intensity of the material cannot be greatly improved, while ruthenium oxide has a satisfactory capacity but is expensive. Thereby, a high-capacity electrochemical capacitor is provided while reducing the cost of the capacitor.

The present invention is implemented by the following two schemes, one is to use the composite material of the oxide or hydroxide of ruthenium and the active carbon material of high specific surface area as the positive and negative electrodes of the electrochemical capacitor to improve the energy of the electrochemical capacitor Density; Another solution is to use porous high specific surface area carbon material as the negative electrode, and use the composite material of ruthenium oxide or hydroxide and high specific surface area activated carbon material as the positive electrode to improve the operating voltage of the electrochemical capacitor thereby increasing its energy density. In the two schemes, alkaline solution or acid solution is used as the electrolyte of the electrochemical capacitor, and an insulating polymer that can pass ions is between the positive electrode and the negative electrode, and finally assembled into electrochemical capacitors of different shapes and different uses.

Discuss them separately below

plan 1

(1) Choose 100 milliliters of aqueous solution of 0.05-0.5M ruthenium halide salt or sulfate, add 2g activated carbon, nano-scale carbon fiber, carbon nanotube, carbon aerosol or the mixture of any two compositions between them, mixture The mass ratio of the two components is 1:1, and the specific surface area is 900-2000m ² /g. Stir thoroughly for 3-5 hours, then add 0.3M KOH or NaOH solution drop by drop and continue stirring. When the pH of the solution reaches 7 , stop adding the alkali solution, and continue to stir for 5 hours, filter the mixture, wash and filter with distilled water, dry at 80°C, dehydrate below 150°C, and grind for 10 minutes in an agate grinder;

(2) Weigh part of the material prepared according to the above method, add graphite, carbon black, nickel powder accounting for 10-30wt% of the total weight as the conductive agent, add 5-10wt% of the total weight as the binder, such as Polytetrafluoroethylene and polytetrafluoroethylene are coated on nickel foam, punched nickel-plated steel plate, aluminum foil, and copper foil as current collectors, and are processed by pressing, drying, and slicing to make positive and negative capacitors. negative electrode.

(3) Dissolve strongly alkaline substances (such as LiOH, KOH, NaOH, etc.) or strongly acidic substances (such as H ₂ SO ₄ , etc.) in ionic solvents (such as water) or nonionic solvents (such as ethanol, propylene carbonate, etc.) ) as the electrolyte. Select an insulating material with ion conductivity as the diaphragm (such as glass fiber paper, polymer film, etc.). The positive electrode, negative electrode, electrolyte, and separator are assembled into electrochemical capacitors with different shapes and uses.

Scenario 2

(1) choose 0.05M-0.5M ruthenium halide salt or the aqueous solution 100 milliliters of vitriol, add activated carbon, nanoscale carbon fiber, carbon nanotube, carbon aerosol or the mixture that any two forms between them, two in the mixture The mass ratio of the two components is 1:1, and the specific surface area is 900-2000m ² /g. Stir thoroughly for 3-5 hours, add 0.3M KOH or NaOH solution dropwise and continue stirring. When the pH of the solution reaches 7, stop Add alkali solution and continue to stir for 5 hours, filter the mixture, wash the filter cake, and dry the filter cake at 80°C, dehydrate it below 150°C, grind it in an agate mortar for 10 minutes, and then weigh part According to the material prepared by the above method, add graphite, carbon black, nickel powder accounting for 10-30wt% of the total weight as a conductive agent, and add polytetrafluoroethylene and polytetrafluoroethylene as a binder accounting for 5-10wt% of the total weight Vinyl fluoride, coated on nickel foam, punched nickel-plated steel plate, aluminum foil, and copper foil as a current collector, after pressing, drying, and slicing processes, it is made into the positive electrode of the capacitor;

(2) choose its specific surface area as 900-2000m ² /g activated carbon, nano-scale carbon fiber, carbon nanotube, carbon aerosol or the mixture of any two compositions between them, the mass ratio of two kinds of compositions in the mixture is 1: 1. Add 10-30wt% of the total weight of graphite, carbon black, and nickel powder as a conductive agent to add 5-10wt% of the total weight as polytetrafluoroethylene and polytetrafluoroethylene as a binder, and coat On the nickel foam, punched nickel-plated steel plate, aluminum foil, and copper foil as the current collector, the negative electrode of the capacitor is made through pressing, drying, and slicing processes.

(3) Select strong alkaline substances, such as LiOH, KOH, NaOH, etc., or strongly acidic substances (such as H ₂ SO ₄ , etc.) dissolved in ionic solvents (such as water) or non-ionic solvents, such as ethanol, propylene carbonate, etc. , as an electrolyte. Select an insulating material with ion conductivity as the diaphragm, such as glass fiber paper, polymer film, etc., and assemble the positive electrode, negative electrode, electrolyte, and diaphragm into electrochemical capacitors with different shapes and uses.

The electrochemical capacitor prepared according to the method provided by the invention has a simple preparation process, is cheaper than an electrochemical capacitor using ruthenium oxide as an electrode, and has a capacitance far greater than that of an electrochemical capacitor composed of pure activated carbon materials.

Detailed ways

The substantive features and remarkable progress of the present invention will be further described below according to the above scheme, but the present invention is by no means limited to the embodiments.

Example 1

Select 100 ml of aqueous solution of ruthenium chloride with a concentration of 0.1M, add 2 g of porous activated carbon with a large specific surface area, and its specific surface area is 1500 m ² /g, stir thoroughly for more than 4 hours, add 0.3 M KOH solution drop by drop and continue stirring , when the acidity pH of the solution reaches 7, stop adding the alkali solution and continue to stir for 5 hours, filter the mixed solution, wash the filter cake, and dry the filter cake at 80°C, dehydrate it below 150°C, and grind it in agate Grind in a bowl for 10 minutes.

Weigh part of the material prepared according to the above method, add 20Wt% graphite conductive agent, add 8% polytetrafluoroethylene adhesive, press to form an electrode diaphragm, and through the processes of pressing, drying, slicing, etc., the capacitor is made Positive and negative electrodes.

Place two electrode membranes with exactly the same composition above on both sides of the ion-conducting glass fiber paper to form a sandwich structure, after pressing, slicing and other processes, cut into different shapes as required. Select strong alkaline substances, such as LiOH dissolved in water ionic solvent as electrolyte. The prepared electrodes and electrolytes are assembled into capacitors of different shapes and purposes.

Example 2

Select several milliliters of an aqueous solution of 0.25M ruthenium sulfate at a certain concentration, and add 2 g of a mixture of porous large specific surface area with a specific surface area of 1000 m ² /g and 1800 m ² /g nanoscale carbon fiber and carbon aerosol, and the mass ratio of the two is 1 : 1. Stir fully for more than 5 hours, add 0.3M NaOH solution drop by drop and continue stirring. When the acidity pH of the solution reaches 7, stop adding alkali solution and continue stirring for 5 hours, filter the mixed solution, wash the filter cake, and put the filter cake in Dry at 80°C, dehydrate at below 150°C, and grind in an agate mortar for 10 minutes.

Weigh part of the material prepared according to the above method, add 15wt% nickel powder conductive agent, add 5wt% polytetrafluoroethylene adhesive, coat on the foamed nickel current collector, go through processes such as pressing, drying, and slicing, Make the positive and negative poles of the capacitor.

Select a strong alkaline substance, such as NaOH dissolved in ethanol as the electrolyte. The polymer film is selected as the diaphragm, and the positive electrode, the negative electrode, the electrolyte, and the diaphragm are assembled into electrochemical capacitors with different shapes and uses.

Example 3

Select activated carbon with a specific surface area of 2000m ² /g, add 12wt% carbon black as a conductive agent, add 8%wt% polytetrafluoroethylene as an adhesive, and coat it on a copper foil current collector, after pressing and baking Drying, slicing and other processes to make the negative electrode of the capacitor.

The positive electrode, electrolyte and diaphragm of the capacitor are all the same as in Example 2, and the negative electrode made in this embodiment constitutes a high-capacity electrochemical capacitor.

Claims (2)

1, a kind of manufacture method of high-capacity electrochemical capacitor, it is characterized in that with the oxide or hydroxide of ruthenium and the activated carbon composite material of high specific area as the positive and negative electrode of electrochemical capacitor, with alkaline solution or acid The solution is used as the electrolyte, and the insulating polymer is used as the diaphragm between the positive and negative electrodes to assemble electrochemical capacitors of different shapes and uses. The specific preparation method of the positive and negative electrodes is (1) Choose 100 milliliters of aqueous solution of 0.05-0.5 M ruthenium halide salt or sulfate, add 2 g of activated carbon, nano-scale carbon fiber, carbon tube nanometer, carbon aerosol or any two mixtures between them, the mixture The mass ratio of the two components is 1:1 and the specific surface area is 900-2000m ² /g. After fully stirring for 3-5 hours, add 0.3M KOH or NaOH solution dropwise and continue stirring; when the pH value of the solution is equal to At 7 o'clock, stop adding the alkali solution, and continue to stir for 5 hours, filter the mixed solution, wash and filter with distilled water, dry at 80°C, dehydrate below 150°C, and grind in an agate grinder for 10 minutes; (2) Weighing part of the material prepared according to the above method, adding graphite, carbon black or nickel powder accounting for 10-30% of the total weight as a conductive agent and adding 5-10% of the total weight as a binder of polytetrafluoroethylene Vinyl fluoride or polytetrafluoroethylene is coated on nickel foam, punched nickel-plated steel plate, aluminum foil or copper foil as a current collector, and is made into the positive and negative electrodes of the capacitor after pressing, drying and slicing processes. 2, a kind of manufacture method of high-capacity electrochemical capacitor, it is characterized in that with the active carbon material composite material of ruthenium halide salt or sulfate and high specific surface area as the positive electrode of electrochemical capacitor, with porous large specific surface area carbon material as Negative electrode; alkaline solution or acid solution is used as the electrolyte; the positive and negative electrodes are assembled into electrochemical capacitors of different shapes and uses through an insulating polymer as a diaphragm. The specific preparation method of the positive and negative electrodes is (1) choose 0.05M-0.5M ruthenium halide salt or the aqueous solution 100 milliliters of vitriol, add activated carbon, nanoscale carbon fiber, carbon nanotube, carbon aerosol or the mixture that any two forms between them, two in the mixture The mass ratio of the two components is 1:1. After fully stirring for 3-5 hours, add 0.3M KOH or NaOH solution dropwise and continue stirring. When the pH value of the solution is equal to 7, stop adding the alkali solution and continue stirring for 5 hour, filter the mixture, wash the filter cake, and dry the filter cake at 80°C, dehydrate it below 150°C, and grind it in an agate mortar for 10 minutes, then weigh part of the materials prepared according to the above method, Add 10-30% of the total weight of graphite, carbon black or nickel powder as a conductive agent and add 5-10 wt% of the total weight as a binder of polytetrafluoroethylene or polytetrafluoroethylene, coated on as Nickel foam on the current collector, punched nickel-plated steel plate, aluminum foil, and copper foil are pressed, dried, and sliced to make the positive electrode of the capacitor; (2) choose its specific surface area as 900-2000m ² /g activated carbon, nano-scale carbon fiber, carbon nanotube, carbon aerosol or the mixture of any two compositions between them, the mass ratio of two kinds of compositions in the mixture is 1: 1. Add 10-30% of the total weight of graphite, carbon black or nickel powder as a conductive agent, add 5-10% of the total weight of polytetrafluoroethylene or polytetrafluoroethylene as a binder, and coat On the nickel foam, punched nickel-plated steel plate, aluminum foil, and copper foil as the current collector, the negative electrode of the capacitor is made through pressing, drying, and slicing processes.