JP2010092635A - Storage battery - Google Patents

Abstract

An inexpensive and safe storage battery is provided by using all iron as a metal involved in a battery reaction.
A storage battery includes a positive electrode, a positive electrode cell that holds an electrolyte solution in contact with the positive electrode, a negative electrode, a negative electrode cell that holds an electrolyte solution in contact with the negative electrode, a positive electrode cell, and a negative electrode cell. The positive electrode cell 3 charges and discharges charges by the reaction of divalent and trivalent iron ions, and the negative electrode cell 4 charges and discharges by the reaction of divalent iron ions and iron. Since the oxidation-reduction reaction of the battery is performed with metallic iron and its ions, a storage battery with significantly reduced raw material costs can be realized.
[Selection] Figure 1

Description

  The present invention relates to a secondary battery that can be repeatedly charged and discharged, and more particularly to a storage battery that uses only the valence change of iron ions in an electrolyte solution as a battery reaction.

  Conventionally, there is a redox flow type battery in which only a valence change of a metal ion in an electrolyte of this type is used as a battery reaction, and there is a vanadium type redox flow battery using a single metal (for example, a patent) Reference 1).

  FIG. 2 is a cross-sectional view of the redox flow battery described in Patent Document 1. In the battery, a positive electrode 25 and a negative electrode 26 are inserted into a positive electrode cell 23 and a negative electrode cell 24, respectively, from which a battery reaction cell 21 is separated by a separation membrane 22, and an electrolyte pumps a positive electrode liquid tank 27 and a negative electrode liquid tank 28. 29 is configured to be circulated. The positive electrode cell 23 and the positive electrode liquid tank 27 store tetravalent and pentavalent vanadium ions, and the negative electrode cell 24 and the negative electrode liquid tank 28 store divalent and trivalent vanadium ions.

In the vanadium redox flow battery, pentavalent and tetravalent vanadium ions stored in the positive electrode liquid tank 27 at the time of charging are sent to the positive electrode cell 23 by the pump 29 to receive and reduce electrons from the external circuit 30. In addition, divalent and trivalent vanadium ions stored in the negative electrode liquid tank 28 are sent to the negative electrode cell 24 by the pump 29, discharge electrons to the external circuit 30, and are oxidized to trivalent. At the time of discharging, electrons are extracted from the positive electrode liquid tank 27 and the negative electrode liquid tank 28 by a reaction opposite to that at the time of charging.
Japanese Patent No. 2724817

  However, although a vanadium-based redox flow battery uses only one type of metal, vanadium is highly ubiquitous as a resource, its supply tends to be unstable, and is expensive.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an inexpensive and safe storage battery.

  In order to achieve the above object, the storage battery of the present invention comprises a positive electrode, a positive electrode cell holding an electrolyte solution in contact with the positive electrode, a negative electrode, a negative electrode cell holding an electrolyte solution in contact with the negative electrode, and the positive electrode cell. A separation membrane for separating the negative electrode cell, wherein the positive electrode cell charges and discharges charges by a reaction of divalent and trivalent iron ions, and the negative electrode cell performs a reaction of divalent iron ions and iron. It is what.

  Thereby, since the oxidation-reduction reaction of the battery is performed with metallic iron and ions thereof, a storage battery with a significantly reduced raw material cost can be realized.

  The storage battery according to the present invention is inexpensive by charging and discharging the charge by the reaction of divalent and trivalent iron ions in the positive electrode cell and the reaction of divalent iron ions and iron in the negative electrode cell across the separation membrane. A storage battery can be realized using simple iron.

  The first invention includes a positive electrode, a positive electrode cell holding an electrolyte solution in contact with the positive electrode, a negative electrode, a negative electrode cell holding an electrolyte solution in contact with the negative electrode, and a separation membrane separating the positive electrode cell and the negative electrode cell. In the positive electrode cell, charge and discharge are performed by reaction of divalent and trivalent iron ions, and in the negative electrode cell, reaction of divalent iron ions and iron is performed.

  Iron is a low-cost material that has a large reserve and is easy to recycle. In the present invention, only iron and iron ions are used for the battery reaction, so that the constituent materials can be manufactured at low cost.

  The second invention is particularly characterized in that the electrolytic solution of the first invention is mixed with fine carbon powder. By adding conductive carbon to the electrolytic solution, the internal resistance can be reduced, and therefore the reduction in the ratio of the discharge charge amount to the charge amount can be suppressed.

  In the third invention, the pH of the electrolytic solutions of the first and second inventions is less than 2. Metal ions are deposited as iron oxide in a high pH region. The generation of iron oxide adversely affects the charging and discharging performance. Here, since the oxidation-reduction potential of iron of this configuration is about 1.21 V, precipitation of iron oxide can be suppressed by setting the pH of the electrolytic solution to less than 2.

  In the fourth invention, in particular, the electrolytic solution of the third invention contains ascorbic acid. Ascorbic acid is highly acidic due to the action of the hydroxy group and the carbonyl group, and has been confirmed to be safe as a food additive. Therefore, the pH can be reduced to less than 2 by adding an appropriate amount of ascorbic acid.

  In the fifth invention, in particular, the volume ratio of the positive electrode cell to the negative electrode cell is 2: 1. In the negative electrode cell, one divalent iron ion receives two electrons and precipitates as metallic iron, whereas in the positive electrode cell, one divalent iron ion emits one electron to become a trivalent iron ion. . That is, the molar ratio of the divalent iron ions involved in the charging reaction is 2 to 1 in the positive electrode cell and the negative electrode cell, and in other molar ratios, ions in either cell remain unreacted. End up. Therefore, according to the present invention, unreacted divalent iron ions can be minimized, and the energy density per volume and weight can be increased.

Hereinafter, embodiments of the storage battery of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the fundus by this embodiment.
(Embodiment 1)
FIG. 1 is a cross-sectional view of a storage battery according to the first embodiment of the present invention.

  The storage battery is composed of a positive electrode cell 3 and a negative electrode cell 4 in which a battery reaction cell 1 is separated by a separation membrane 2, and a positive electrode 5 and a negative electrode 6 are arranged on the wall of each cell and fixed by an outer frame 7. Yes. Each pole is electrically connected to the power supply 8 and the load 9.

  The separation membrane 2 is a microporous resin membrane having a pore diameter of 0.1 μm and a thickness of 5 μm, the positive electrode 5 and the negative electrode 6 are 2 mm thick resin-impregnated graphite materials, and the outer frame 7 is a 2 mm thick titanium plate. The power source 8 and the load 9 are electrically connected to the electrodes via lead frames 7 by means of lead wires. Here, the distance between the positive electrode 5 and the separation membrane 3 is 3 mm, and the distance between the negative electrode 6 and the separation membrane 3 is 1.5 mm.

  The electrolytic solution was prepared by dissolving ferrous chloride having a molar fraction of 0.17, ammonium chloride having a molar fraction of 0.17, and ascorbic acid having a molar fraction of 0.002 in water, and further having a primary particle diameter of several tens of nm. Carbon black is added to 1/10 of the total weight and mixed. In this state, it was confirmed that the acid was a strong acid having a pH of about 1 by litmus paper.

  A method for evaluating the efficiency of charging and discharging in the storage battery configured as described above will be described.

  First, a voltage is applied for 10 minutes by the power source 8 so that the current becomes a constant value of 50 mA. The power supply 8 is short-circuited and held for 2 minutes. Thereafter, it is connected to a load 9 having a resistance of 50Ω and discharged. The current flowing at this time is measured. The charge transferred by charging and discharging can be estimated from the current value. Here, the ratio of the discharged charge amount to the charged charge amount is defined as charge / discharge efficiency.

  In this evaluation method, the case where carbon is mixed with the electrolytic solution, the case where the pH of the electrolytic solution is less than 2, and the case where the pH is 2 or more, and the volume ratio of the positive electrode cell to the negative electrode cell is 1: 1. And 2 to 1, the magnitude of the charge / discharge efficiency value and the stability of repeated charge / discharge were compared. As a result, in any case, the storage battery having the configuration of the present embodiment has higher charging efficiency, and stable efficiency can be obtained even in repeated charging and discharging.

  The storage battery according to the present invention is a low-cost storage battery. This storage battery can be used not only as a large-capacity battery for installation in a substation or factory, but also because of its high safety, it can be applied to a battery for home use, for example, a storage battery for storing nighttime power and using it in the daytime.

Sectional drawing of the storage battery in Embodiment 1 of this invention Cross-sectional view of a conventional storage battery

Explanation of symbols

2 Separation membrane 3 Positive electrode cell 4 Negative electrode cell 5 Positive electrode 6 Negative electrode

Claims (5)

A positive electrode, a positive electrode cell that holds an electrolyte solution in contact with the positive electrode, a negative electrode, a negative electrode cell that holds an electrolyte solution in contact with the negative electrode, and a separation membrane that separates the positive electrode cell and the negative electrode cell; The battery is charged and discharged by a reaction of divalent and trivalent iron ions in the cell, and by a reaction of divalent iron ions and iron in the negative electrode cell. The storage battery according to claim 1, wherein the electrolytic solution is a mixture of fine carbon powder. The storage battery according to claim 1 or 2, wherein the pH of the electrolytic solution is less than 2. The storage battery according to claim 3, wherein the electrolytic solution contains ascorbic acid. The storage battery according to claim 1 or 2, wherein the volume ratio of the positive electrode cell to the negative electrode cell is 2 to 1.

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