JP2017092014A - Aluminum air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum air battery capable of suppressing discharge inhibition caused by a discharge product to prolong a battery life.SOLUTION: The aluminum air battery has a structure in which aluminum or an aluminum alloy is used for a negative electrode and the negative electrode is coated with a polyanionic water-soluble polysaccharide. With the structure, it is possible to prolong the battery life by preventing discharge inhibition caused by discharge products, which is the biggest problem of aluminum air batteries.SELECTED DRAWING: Figure 2

Description

Detailed Description of the Invention

  The present invention relates to an aluminum air battery.

  Since the air battery uses oxygen that is inexhaustibly in the air as the positive electrode active material, there is no need to fill the battery container with the positive electrode active material. Therefore, it is possible to fill the negative electrode active material in most spaces in the battery container, and in principle, it has the largest energy density among chemical batteries.

  The air battery currently in practical use uses zinc as the negative electrode. By using aluminum as the negative electrode, the theoretical energy density jumps from 1300 Wh / kg of the zinc air battery to 6000-8000 Wh / kg. Increase.

  Details of the aluminum air battery are disclosed in Non-Patent Document 1. A general aluminum air battery uses an aluminum metal for the negative electrode, a liquid electrolyte for the electrolyte, and an air electrode for the positive electrode, which combines oxygen reduction at the air electrode and metal dissolution with electron emission at the metal electrode, In the air electrode and the aluminum electrode, reactions of Formulas 1 and 2 occur, respectively, and hydroxyl ions move through the liquid electrolyte to generate power.

In the air electrode and the aluminum electrode, reactions of Formulas 1 and 2 occur, respectively, and hydroxyl ions move through the liquid electrolyte to generate power. At this time, aluminum hydroxide is generated as a by-product on the negative electrode aluminum electrode, which becomes non-fluidized and inhibits battery discharge, so that the capacity and voltage are quickly deteriorated. For this reason, there are almost no examples in practical use in spite of a high volume energy density battery.

JP 2012-164636 A JP 2012-230892 A Japanese Patent Application Laid-Open No. 07-282859 JP 2012-015026 A

Journal of Power Sources 110 (2002) 110 Journal of Power Sources 193 (2009) 895 Corrosion Science 51 (2009) 658 Corrosion Science 50 (2008) 3475 Materials and Corrosion 2009, 60, No. 4

  Since the metal-air battery must take air into the battery, the performance of the battery depends on how much air (oxygen) is taken in by the positive electrode of the conventional metal-air battery. Further, in an aluminum air battery, reaction byproducts such as aluminum hydroxide and aluminum oxide are accumulated on the electrode from discharge, so that the function as the battery is hindered. In the methods described in Patent Document 1-3 and Non-Patent Documents 1 and 2, an aluminum alloy or the like is used for the negative electrode. In Patent Document 4 and Non-Patent Documents 3 and 4, a polymer or oxo acid salt is added to the electrolyte. In Non-Patent Document 5, an attempt is made to suppress the production of by-products at the electrode by using an alcohol / water mixed system in the electrolyte, but it is difficult to obtain a sufficient effect.

  The aluminum-air battery of the present invention uses aluminum or an aluminum alloy for the negative electrode, and coats the negative electrode with a polyanionic water-soluble polysaccharide, thereby preventing discharge inhibition by by-products such as aluminum hydroxide and aluminum oxide. It suppresses and raises the utilization factor of a negative electrode, The discharge obstruction byproduct by the negative electrode of the aluminum air battery by it is suppressed, It is characterized by the above-mentioned.

  According to the present invention, in an aluminum air battery using an air electrode as a positive electrode and aluminum or an aluminum alloy as a negative electrode, the negative electrode is coated with a polyanionic water-soluble polysaccharide, thereby producing aluminum hydroxide as a discharge product. In addition, it is possible to suppress discharge inhibition by by-products such as aluminum oxide and increase the utilization rate of the negative electrode. Therefore, an aluminum air battery having a long battery life can be provided.

Schematic diagram of a conventional aluminum air battery (Comparative Example 1) Schematic diagram showing an example of an aluminum air battery of the present invention (Example 1)

  FIG. 2 is a schematic view of an aluminum air battery according to an embodiment of the present invention. It has a configuration in which negative electrodes 101 and 201 made of aluminum or an aluminum alloy, and a polyanionic water-soluble polysaccharide 202 installed adjacent to the negative electrode are interposed. The electrolytic solutions 102 and 203 are sandwiched between the air electrodes 103 and 204.

  Examples of the negative electrode include aluminum or an aluminum alloy. As the aluminum alloy, Li, Mg, Sn, Zn, In, Mn, Ga, Bi, Fe, or the like is individually or two or more types alloyed with aluminum. An aluminum alloy is mentioned. Aluminum alloys such as Al—Li, Al—Mg, Al—Sn, and Al—Zn are particularly preferable because they give a high battery voltage.

As the positive electrode, that is, the air electrode catalyst material, any substance that receives electrons generated at the negative electrode and reduces oxygen can be used. The positive electrode includes activated carbon, carbon, carbon materials such as carbon nanotubes, and lanthanum manganite represented by La (1-x) AxMnO ₃ (0.05 <x <0.95; A = Ca, Sr, Ba). An electrode that is at least one selected from perovskite-type composite oxides such as manganese lower oxides such as Mn ₂ O ₃ and Mn ₃ O ₄ , or conductive polymers such as polyacetylene and polythiophenes.

(Polyanionic water-soluble polysaccharide)
The polyanionic water-soluble polysaccharide for coating the electrode is alginate, more specifically, sodium alginate, potassium alginate, or ammonium alginate. The coated electrode may be freeze-dried.

  The content of the polyanionic water-soluble polysaccharide is preferably 0.1 to 10% by weight, and more preferably 0.1 to 3% by weight. Further, in the dry weight obtained by drying the gel composition, the content of the polyanionic water-soluble polysaccharide is preferably 50 to 100% by weight, more preferably 80 to 100% by weight.

  Calcium ions can also be added to promote the gelation of the alginate.

(Method for manufacturing electrode)
In the method for producing an electrode of the present invention, a conductive material connected to a positive electrode is immersed in a solution containing a polyanionic water-soluble polysaccharide and electrolyzed, whereby the polyanionic water-soluble polysaccharide is added to the conductive material connected to the positive electrode. Deposit. The deposited polyanionic water-soluble polysaccharide is gelled by ionic bonds and hydrogen bonds. Further, gelation may be promoted by adding calcium ions.

  Since the electrolysis time for electrolysis increases, the amount of polyanionic water-soluble polysaccharide deposited increases, so that the electrolysis time can be appropriately adjusted in order to obtain the desired amount of deposition. For example, it is usually 10 seconds to 60 minutes, preferably 60 seconds to 10 minutes.

Moreover, since the deposition amount of the polyanionic water-soluble polysaccharide is increased by increasing the current density of electrolysis, the current density can be appropriately adjusted in order to obtain the target deposition amount. For example, it is 0.1-100 mA / cm < ² > normally, Preferably it is 0.1-20 mA / cm < ² >. The thickness of the polyanionic water-soluble polysaccharide deposit is preferably 0.05 mm to 5 cm, more preferably 0.1 mm to 1 cm, and most preferably 0.2 mm to 5 mm.

  The electrolyte may be neutral or alkaline, and examples include sodium chloride aqueous solution, sodium hydrogen carbonate aqueous solution, hydrogen peroxide, magnesium chloride aqueous solution, seawater, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution and the like. However, the present invention is not limited to this, and any ion conductivity can be used. Moreover, it is also possible to add a polymer, a moisturizing polymer, water glass, etc. to this. Further, an organic solvent or an ionic liquid may be used as the electrolytic solution.

(Comparative Example 1)
An aluminum-air battery whose schematic cross-sectional view is shown in FIG. 1 was assembled. The configuration of the test battery is as follows.

<Battery configuration>
Negative electrode: A commercially available metal aluminum plate having a thickness of 1 mm was used after being processed into 25 mm × 35 mm.
Electrolytic solution: 2 mol / NaCl aqueous solution.
Air electrode: Manganese oxide + activated carbon + nickel mesh Here, the air electrode weighed commercially available manganese oxide, activated carbon and polytetrafluoroethylene (Teflon) at a weight ratio of 4: 4: 1, and mixed thoroughly using ethanol as a solvent. Thereafter, a sheet made of Teflon resin was applied together with a nickel mesh serving as a current collector, dried at 120 ° C. for 1 h, and then processed into φ15 mm.
The negative electrode is fitted into one side of a fluororesin mold having an inner diameter of 25 mm and a length of 15 mm, and 3.0 ml of the electrolytic solution is injected into the fluororesin mold with the negative electrode serving as the bottom of the cylinder, and sealed with the air electrode so that no air bubbles enter. An aluminum air battery was constructed.

Example 1
An aluminum-air battery whose schematic cross-sectional view is shown in FIG. 2 was assembled. The configuration of the test battery is as follows.

<Battery configuration>
Polyanionic water-soluble polysaccharide: 1% sodium alginate aqueous solution is used.
Negative electrode: Sodium alginate (manufactured by Wako Pure Chemical Industries, Ltd., viscosity 80 to 120 mPa · s) was dissolved in purified water to prepare a 1% aqueous solution. Next, 20 mL of the prepared sodium alginate aqueous solution was added to a polystyrene container. In order to perform electrolysis, the same metal aluminum plate as Comparative Example 1 was set on the anode and the cathode. The distance between the electrodes was 10 mm, and a DC stabilized power supply (ACHEX 305D, manufactured by ATEX Co., Ltd.) was used as the power supply. The current density was set to 2.0 mA / cm ² and each was energized for 120 seconds. The anode-side electrode on which alginic acid containing oxygen bubbles after energization was deposited was washed with water to complete the anode.
Electrolytic solution: The same one as in Comparative Example 1 was used.
Air electrode: The same one as in Comparative Example 1 was used.
The negative electrode is fitted into one side of a fluororesin mold having an inner diameter of 25 mm and a length of 15 mm, and 3.0 ml of the electrolytic solution is injected into the fluororesin mold with the negative electrode serving as the bottom of the cylinder, and sealed with the air electrode so that no air bubbles enter. An aluminum air battery was constructed.

(Evaluation 1)
The aluminum air batteries obtained in Example 1 and Comparative Example 1 were discharged at a current density of 5 mA / cm ² , and the discharge times were compared using 0.3 times the initial voltage as the discharge end voltage. The results are shown in Table 1 as relative values with the discharge time of Comparative Example 1 as 1.

From Table 1, the discharge time of the aluminum air battery of Example 1 is clearly longer than that of the aluminum air battery of Comparative Example 1. Alginic acid between the negative electrode and the electrolytic solution, and between the electrolytic solution and the positive electrode (air electrode) prevents the adhesion of reaction byproducts such as aluminum hydroxide, and oxygen trapped in the alginate exists in the structure. It has been found that there is an effect on extending the life of the aluminum-air battery by not inconveniencing the incorporation of the battery.

(Evaluation 2)
The aluminum air batteries obtained in Example 1 and Comparative Example 1 were charged / discharged at a current density of ± 5 mA / cm ² , and the charge / discharge time was compared using 0.1 times the initial voltage as the charge / discharge end voltage. The results are shown in Table 2.

From Table 2, the examples clearly have longer charge / discharge times than the comparative aluminum air battery. It was found that it was effective in extending the life of the aluminum air battery.

  According to the present invention, the utilization rate of the metal or alloy used as the negative electrode is increased, and the longevity of the battery is extended by preventing discharge inhibition due to the discharge product, which is the biggest problem of all types of metal-air batteries. can do. An aluminum air battery and an aluminum air battery having a long battery life can be provided at low cost. For this reason, the operation time of the portable device can be improved, and it can be suitably used for an electric vehicle, a portable device, a robot, and the like.

101 Negative electrode 102 Electrolyte 103 Positive electrode (air electrode)
201 Negative electrode 202 Alginic acid film 203 Electrolytic solution 204 Positive electrode (air electrode)

Claims (4)

A negative electrode and a positive electrode (air electrode) are one-chamber batteries arranged in an electrolytic cell,
(1) As a negative electrode, aluminum or an aluminum alloy conductor is immersed in a solution containing a polyanionic water-soluble polysaccharide and electrolyzed, whereby the aluminum or aluminum alloy conductor connected to the positive electrode is converted into a polyanion. Consisting of a negative electrode on which water-soluble polysaccharides are deposited,
(2) As a positive electrode (air electrode), activated carbon, carbon, carbon materials such as carbon nanotubes, La (1-x) AxMnO ₃ (0.05 <x <0.95; A = Ca, Sr, Ba) A positive electrode which is at least one selected from perovskite complex oxides such as lanthanum manganite, manganese lower oxides such as Mn ₂ O ₃ and Mn ₃ O ₄ , or conductive polymers such as polyacetylene and polythiophenes Consists of
(3) consisting of electrolyte solution,
Aluminum air battery.   The aluminum air battery, wherein the polyanionic water-soluble polysaccharide is an alginate.   An aluminum air battery, wherein the alginate is sodium alginate, potassium alginate, or ammonium alginate.   The electrolytic solution according to claim 1 is at least one selected from the group consisting of an aqueous solution of sodium chloride, an aqueous solution of sodium bicarbonate, hydrogen peroxide, an aqueous solution of magnesium chloride, seawater, an aqueous solution of sodium hydroxide, and an aqueous solution of potassium hydroxide. battery.

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