WO2006036077A1

WO2006036077A1 - Method for producing a non-polarisable electrode for an electrochemical capacitor

Info

Publication number: WO2006036077A1
Application number: PCT/RU2004/000326
Authority: WO
Inventors: Sergey Nikolaevich Razumov; Igor Nikolaevich Varakin; Oleg Leonidovich Goryachuk; Aleksey Borisovich Stepanov
Original assignee: Sergey Nikolaevich Razumov; Igor Nikolaevich Varakin; Oleg Leonidovich Goryachuk; Aleksey Borisovich Stepanov
Priority date: 2004-08-31
Filing date: 2004-08-31
Publication date: 2006-04-06

Abstract

The invention relates to electrotechnical engineering, more specifically to electrochemical capacitors or electric double layer capacitors and can be used for producing a non-polarisable nickel hydroxide electrode for an alkali electrolyte electrochemical capacitor. The aim of said invention is to develop a method for producing a thin nickel hydroxide electrode for a high-power electrochemical capacitor. The inventive method for producing a non-polarisable electrode for the electrochemical capacitor consists in simultaneously producing a porous current collector, in synthesising an active material, in filling the porous current collector with said active material by means of alternating anode and cathode electrochemical treatments of a base essentially consisting of nickel in a chloride ion-containing aqueous solution.

Description

A method of manufacturing a non-polarizable electrode for an electrochemical capacitor

The invention relates to the field of electrical engineering, more specifically, to electrochemical capacitors or capacitors with a double electric layer, and can be used as a method of manufacturing a non-polarizable hydroxide-nickel electrode for an electrochemical capacitor with an alkaline electrolyte. The prior art.

In such electrochemical capacitors, one electrode (polarizable) is made of carbon material, and the second electrode (non-polarizable) contains nickel hydroxide as the active material. The use of a non-polarizable hydroxide-nickel electrode can significantly increase the specific energy of these electrochemical capacitors, compared to traditional electrochemical capacitors, where both electrodes are polarizable and are made, as a rule, of activated carbon material.

Electrochemical capacitors with non-polarizable hydroxide-nickel electrodes are used, for example, in emergency power supply systems when operating in the constant and compensating charge mode, in electric vehicles for starting an internal combustion engine or as a traction battery.

A known method of manufacturing a non-polarizable hydroxide-nickel electrode for an electrochemical capacitor by pressing, in which the active material with a large content (up to 30 wt.%) of an electrically conductive additive, usually graphite, is pressed onto a current-carrying basis. [Tepth International Semípar on Dubé Lauer Saracís apd Similá Epégou Storage Dévicés. Desember, 2001, Deferred Beh, Flogida.]. The known method does not allow to obtain hydroxide-nickel electrodes with the necessary resource characteristics for operation as part of an electrochemical capacitor.

In the hydroxide-nickel electrodes of the pressed structure obtained by a known method, a decrease in performance during life tests is observed due to the oxidation of the conductive additive, in addition, the use of pressed electrodes is possible only in the structure with strong compression.

A known method of manufacturing a non-polarizable fiber hydroxide-nickel electrode for an electrochemical capacitor by pasting an active material of a current collector of nickel-plated polymer felt [patent US 6,063143, class. HOlM 10 / 04.1999].

The known method has limitations on the production of thin electrodes, which does not allow using it to obtain electrodes of an electrochemical capacitor for a number of applications, and the manufacture of nickel-plated polymer felt is a multi-stage complex process.

The closest in technical essence to the proposed solution is a method of manufacturing an non-polarizable electrode of an electrochemical capacitor, including the manufacture of a porous current collector, synthesis of the active material and filling the porous current collector with an active material, mainly nickel hydroxide. [V.V. Tenkovtsev, B.I. Center “Fundamentals of the theory and operation of sealed nickel-cadmium batteries.-L.: ENERGOATOMIZDAT, Leningrad. Ed., 1985.-26c].

The known method consists in the manufacture of a current collector by sintering in a hydrogen atmosphere at a temperature

700-900 ⁰ C mixture of carbonyl nickel with ground volatile filler deposited on a nickel tape, and then filling the pores of the sintered current collector with an active material (nickel hydroxide) by repeatedly impregnating it in solutions of nickel and alkali salts.

Sintered hydroxide-nickel electrodes, with a certain optimization of their thickness and active material content, as well as the selection of appropriate additives, fully satisfy the requirements for an non-polarizable electrode of an electrochemical capacitor, namely, they have rather high power characteristics in a wide temperature range (from -50 to +60 ⁰ C ) and a resource of more than 500,000 cycles [US patent 6,181,546, class. HOlM 10 / 04.1999].

Nevertheless, the task of increasing the power characteristics of an electrochemical capacitor with non-polarizable hydroxide-nickel electrodes, and, first of all, reducing its internal resistance, remains relevant.

One of the ways to achieve this goal is to use ultrafine (less than 300 microns) hydroxide-nickel electrodes in an electrochemical capacitor.

Using the known method for the manufacture of thin non-polarizable hydroxide-nickel electrodes for an electrochemical capacitor leads to a significant rise in price of the product as a whole. The cost of sintered hydroxide-nickel electrodes is determined by the manufacture of the carrier of the active material and changes little with decreasing electrode thickness. Therefore, the cost of the electrochemical capacitor increases with the number of electrode plates.

In addition, obtaining sintered hydroxide-nickel electrodes with a thickness of, for example, 100 μm in a known manner is in principle difficult. Disclosure of the essence of the invention.

The objective of the invention is to provide a method of manufacturing a thin hydroxide-nickel electrode for an electrochemical capacitor of high power.

The technical result in the present invention is achieved by creating a method for manufacturing an non-polarizable electrode of an electrochemical capacitor, including manufacturing a porous current collector, synthesizing an active material and filling the porous current collector with an active material, mainly nickel hydroxide, in which, according to the invention, a porous current collector is synthesized simultaneously, the synthesis of active material and filling the porous current collector with active path material m alternating anodic and cathodic electrochemical treatment of the base, consisting essentially of nickel, in an aqueous solution containing chloride ions, and after electrochemical treatment, the electrode is treated in an aqueous solution of alkali.

The nickel base can be substantially non-porous.

To obtain electrodes in a new way, you can use Nickel rolling of different manufacturers, because the quality of the finished hydroxide-nickel electrodes does not depend on its original structure.

In alternate anodic and cathodic processes, along with the formation of a porous base, it is simultaneously filled with nickel hydroxo compounds formed during corrosion of the base metal, which during the operation of the capacitor or during special processing of the electrodes in an aqueous alkali solution are converted mainly to nickel hydroxide.

Chlorine ions during the anodic treatment of nickel have an activating effect on the metal corrosion process, while the so-called pitting or “pitting” corrosion is observed, which contributes to the development of the base surface, and the optimal frequency of changing the current direction allows obtaining the base with a regular structure with close pore sizes. The duration of the anode and cathode treatments (0, 1-300 s), as well as their ratio in one cycle, is selected so that, with the shortest time of the process, an electrode of good quality, required capacity and thickness is obtained.

The invention is also characterized in that the anodic electrochemical treatment is carried out with a current density of from 0.005 to 0.2 A / cm ² , because at a lower current value, the efficiency of the etching process decreases, and at high current densities there is a significant heating of the equipment and difficulties arise in switching the current. Conducting cathodic treatment with a current density in the range

0.001-0.2 A / cm ^{2 is} necessary, because with a larger current value, the efficiency of filling the base with basic nickel salts is reduced, and a decrease in the current value will lead to an excessive increase in the duration of the process. The invention is also characterized by the fact that the electrochemical treatment is carried out at a pH <5, and then at a pH from 5 to 11.

It should be noted that at pH greater than 11, the nickel etching process slows down. During electrochemical treatment in solutions with a pH of less than 5, a porous nickel base is obtained without an active material. The latter circumstance is used for the manufacture of a current collector for a hydroxide-nickel electrode. The most optimal is the ratio of the duration of the anodic and cathodic processes in one cycle of 8 and 2 seconds, respectively, at a current density of 0.03 A / cm ² .

With an increase in the duration of the anodic and cathodic processes in one cycle, for example, 16 and 4 seconds, electrodes of a lower quality structure are obtained, which is manifested in the formation of large grains (several microns) of the active material on the surface of the electrode. The latter circumstance may present a danger of puncture of the separator during assembly of the capacitor.

With the same anodic and cathodic periods of electrochemical treatment in one cycle, partial peeling of the active material from the current collector is observed. The electrochemical treatment is carried out in solutions of alkali metal chlorides with a concentration of 0.01-4 mol / l, the concentration range is selected based on the efficiency of the etching process and the solubility of the salts used.

The inventive method can also be obtained electrodes with various modifying additives in the active material. For this, it is necessary to introduce a certain amount of alkaline-earth ions into the solution for electrochemical treatment metals, zinc, nickel, manganese, aluminum, lanthanum, scandium, yttrium and the lanthanide family or a mixture of these ions with a total concentration of 0.001-0.1 mol / l, forming poorly soluble compounds during electrode alkalization. To better fill the current collector with active material, alkali metal carbonates with a concentration of 0.01-4 mol / l can be added to the solution for electrochemical treatment. The best results can be obtained when carrying out the process at a temperature of 60 ⁰ C or more. Modifying additives in the active material can also be introduced by processing the electrodes, after the operation of electrochemical processing, in solutions of salts of alkaline earth metals, zinc, cobalt, nickel, manganese, aluminum, lead, lanthanum, scandium, yttrium and the family of lanthanides or a mixture of these salts with a total concentration of 0.001 -0.1 mol / L, followed by treatment in alkali.

Using this method, it is possible to obtain thin electrodes (for example, 50-200 μm) with a developed surface of the bases and a layer of active material of optimal thickness. The inventive method of manufacturing a hydroxide-nickel electrode compares favorably with the known simple technological scheme, low material and labor costs, as well as high productivity.

The proposed method of manufacturing a non-polarizable electrode for an electrochemical capacitor contains a small number of technological operations: electrochemical processing, processing in an aqueous alkali solution, washing in water and drying.

The proposed method does not require large energy consumption, in contrast, for example, from the technology of production of sintered electrodes, which includes sintering in a hydrogen atmosphere at temperatures above 900 ⁰ C.

The proposed method of manufacturing a non-polarizable electrode for an electrochemical capacitor can be largely mechanized and automated, since all technological operations can be performed continuously in the tape.

The materials used for the manufacture of electrodes by the proposed method are available and do not require special development from the manufacturer, and the resulting waste is simple in chemical composition, easily disposed of. All of the above advantages of the method of manufacturing a non-polarizable electrode for an electrochemical capacitor will reduce the cost of hydroxide-nickel electrodes, reduce the cost of the capacitor and improve its basic characteristics. When conducting patent research, no solutions were found that are identical to the claimed, and, therefore, this invention meets the criterion of "novelty."

The invention does not follow explicitly from the known solutions, and, therefore, the proposed solution meets the criterion of "inventive step".

A brief description of the graphs presented. The essence of the invention is illustrated by the following examples and graphs, where graph 1 shows the dependence of the specific energy of the element with new electrodes on its specific power in the voltage window l, 5-0.75B -27 ° C in comparison with EC with sintered hydroxide-nickel electrodes having the same overall dimensions with an experimental element. on the graph 2. Dependences of the specific energy of the capacitors on the ^ specific power per unit volume at + 20C. Examples of the proposed method. Example 1. Hydroxide-nickel electrodes were obtained by electrochemical treatment of a nickel tape (nickel rolled) with a thickness of 100 μm in a solution of sodium chloride with a concentration of 2 mol / l, with a periodic change in direction of current with a density of 0.03 A / cm. The duration of the anodic and cathodic process during each cycle was 8 and 2 seconds, respectively, and i _{Q the} duration of the process as a whole was 40 minutes.

Then the tape was treated in a solution of potassium hydroxide with a concentration of 6 mol / L, washed in distilled water, dried and the electrodes were cut out of it. The electrodes had a thickness of 120 μm and a capacity of 0.15 A h / cm ³ .

2 ^ Example 2. In contrast to example 1, the electrochemical treatment was carried out in a solution of nickel chloride with a concentration of 1 mol / L. In this case, electrodes were obtained with the same capacity as in Example 1, but of a greater thickness due to the layer of adhering base salt. When cycling the electrodes, a partial lag ø of this layer from the substrate was found.

Example 3. In contrast to example 1, the electrochemical treatment was carried out with the addition of calcium chloride with a concentration in the solution of 0.05 mol / L. The result was electrodes with a slightly lower capacity (0.14 A h / cm ³ ), but c mechanically more durable. Chemical analysis showed the presence of calcium in the composition of AM.

Similar results were obtained when zinc, aluminum, manganese, magnesium, and lanthanum chlorides were added to the solution. Example 4. In contrast to example 1, the electrochemical treatment was carried out with the addition of potassium carbonate with a concentration in the solution of 0.7 mol / L. At the same time, electrodes similar to Example 2 were obtained. Example 5. In contrast to example 4, the electrochemical treatment was carried out at a temperature of 60 ⁰ C for 30 minutes.

Received electrodes with the same characteristics as in example 1.

Example In contrast to example 1, after electrochemical processing, the treatment was carried out in a solution of cobalt chloride with a concentration of 2 mol / l and then in example 1. Received electrodes with the characteristics as in example 1. Chemical analysis showed the presence of cobalt in the composition of AM electrodes. Similar results were obtained with a similar treatment in solutions of salts of calcium, lead, manganese, lanthanum. An experimental electrochemical capacitor was made of 35 non-polarizable hydroxide-nickel electrodes made according to Example 1 and 36 polarizable electrodes. The polarizable electrode consisted of a 50 µm thick copper collector and 150 µm thick cards attached to it on both sides, made of activated carbon powder. Hydroxide-nickel electrodes were wrapped in two layers of a 50 μm separator. A potassium hydroxide solution with a concentration of 6 mol / L with the addition of lithium hydroxide with a concentration of 0.6 mol / L was used as an electrolyte.

We determined the power electrical characteristics of the element at temperatures of +20 ⁰ C and -27 ° C.

In an electrochemical capacitor with sintered electrodes, hydroxide-nickel electrodes had a thickness of 300 μm and a capacity of 0.25 g / cm ³ , the negative electrodes consisted of a copper collector 50 μm thick and 300 μm of carbon activated carbon tape cloths on both sides of the collector. Sintered hydroxide-nickel electrodes are wrapped in two layers of a separator with a thickness of 50 μm. The electrolyte is a solution of potassium hydroxide with a concentration of 6 mol / L with the addition of lithium hydroxide with a concentration of 0.6 mol / L. The electrode pair count in this EC was 20.

From graphs 1 and 2 it can be seen that, despite the lower capacitance, an element with non-polarizable electrodes made by the proposed method, in comparison with ECs with non-polarizable sintered hydroxide-nickel electrodes, had higher characteristics at high current densities, especially at low temperatures.

This will allow the successful use of an electrochemical capacitor with a non-polarizable electrode manufactured by the proposed method for pulsed applications with short charge and discharge times and reduce the cost of the capacitor as a whole.

Life tests of the element were conducted in the mode:

- charge at an average power of 200 W / kg to a voltage of 1.6 V;

- pause 20 seconds; - discharge at an average power of 300 W / kg to a voltage of 0.9 V;

- pause 20 seconds

During the tests for 120,000 cycles, the specific energy and internal resistance of the capacitor remained practically unchanged. The average energy efficiency was 90%.

Claims

Claim.

1. A method of manufacturing a non-polarizable electrode of an electrochemical capacitor, including the manufacture of a porous current collector, synthesis of the active material and filling the porous current collector with an active material, mainly nickel hydroxide, characterized in that the porous current collector is produced simultaneously, the active material is synthesized and the porous current collector is filled with active material by alternating anodic and cathodic electrochemical processing of the base, consisting of about the essence of Nickel, in an aqueous solution containing chloride ions, and after electrochemical treatment, the electrode is treated in an aqueous solution of alkali.

2. A method of manufacturing a non-polarizable electrode of an electrochemical capacitor according to claim 1, characterized in that the duration of the anode and cathode treatments in one cycle is 0.1 to 300 seconds.

3. A method of manufacturing a non-polarizable electrode of an electrochemical capacitor according to claim 1, characterized in that the anodic electrochemical treatment is carried out with a current density of from 0.005 to 0.2 A / cm ² .

4 A method of manufacturing a non-polarizable electrode of an electrochemical capacitor according to claim 1, characterized in that the cathodic electrochemical treatment is carried out with a current density of from 0.001 to 0.2 A / cm ² .

5. A method of manufacturing a non-polarizable electrode of an electrochemical capacitor according to claim 1, characterized in that the electrochemical treatment is carried out in chloride solutions alkali metals with a concentration of 0.01 to 4 mol / l.

6. A method of manufacturing a non-polarizable electrode of an electrochemical capacitor according to claim 1, characterized in that the electrochemical treatment is carried out in the presence of ions

5 alkaline earth metals and / or zinc and / or nickel and / or manganese and / or aluminum and / or lanthanum and / or scandium and / or yttrium and / or the lanthanide family and / or a mixture of the following ions with a total concentration of 0.001 mol / L -0.1 mol / L.

7. A method of manufacturing a non-polarizable electrode U of an electrochemical capacitor according to claim 1, characterized in that the electrochemical treatment is carried out in the presence of alkali metal carbonates or hydrogen carbonates with a concentration of 0.01 mol / l. - 4 mol / l.

8. A method of manufacturing a non-polarizable electrode 15 of an electrochemical capacitor according to claim I n, characterized in that the electrochemical treatment is carried out at pH <5, and then at pH from 5 to 11.

9. A method of manufacturing a non-polarizable electrode of an electrochemical capacitor according to claim l, characterized in that 0 electrochemical treatment is carried out in solutions with a pH value of from 5 to 11.

10. A method of manufacturing a non-polarizable electrode of an electrochemical capacitor according to claim 1, characterized in that after the electrochemical treatment, the electrode is treated with a 5 solution of alkaline earth metal salts and / or zinc and / or cobalt and / or nickel, manganese and / or aluminum, and / or lead and / or lanthanum and / or scandium and / or yttrium and / or elements from the family of lanthanides and / or a mixture of these salts with a total concentration of 0.001 mol / L - 0.1 mol / L.