JP2010092636A - Storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a storage battery with improved charge and discharge characteristics through reduction of battery inner resistance by having electrolyte contain carbon materials. <P>SOLUTION: The storage battery includes a cathode 5, a cathode electrolyte 3 containing carbon materials in contact with the cathode 5, an anode 6, an anode electrolyte 4 containing carbon materials in contact with the anode 6, and a separating film 2 separating the cathode electrolyte 3 and the anode electrolyte 4. Charging and discharging of a load is carried out by reaction of bivalent and trivalent iron ions at the cathode electrolyte 3, and by reaction of bivalent iron ions and iron at the anode electrolyte 4. The electrolyte solution is enhanced in conductivity by mixing carbon materials with different average particle diameters, so that a storage battery with inner resistance reduced is realized. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 a change in the valence of iron ions in an electrolyte 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 electrolyte 23 and a negative electrode electrolyte 24, respectively, in which a battery reaction cell 21 is separated by a separation membrane 22, and the electrolyte pumps a positive electrode liquid tank 27 and a negative electrode liquid tank 28. 29 is configured to be circulated. The positive electrode electrolyte 23 and the positive electrode liquid tank 27 store tetravalent and pentavalent vanadium ions, and the negative electrode electrolyte 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 cathode solution tank 27 at the time of charging are sent to the cathode electrolyte 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 electrolyte 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.

In addition, graphite, carbon, carbon fiber, carbon cloth, and the like are used as electrodes.
Japanese Patent No. 2724817

  However, in the conventional redox flow battery, there is a problem that the conductivity is insufficient when graphite, carbon or the like is used as an electrode.

  This invention solves the said conventional subject, and it aims at providing the storage battery which reduced battery internal resistance and improved the charging / discharging characteristic.

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

  Thereby, since internal resistance of a battery can be reduced, charging / discharging efficiency can be improved.

  The storage battery of the present invention contains a carbon material when charge / discharge is performed by the reaction of divalent and trivalent iron ions in the positive electrode electrolyte and the reaction of divalent iron ions and iron in the negative electrode electrolyte across the separation membrane. By using the electrolyte, a storage battery with improved charge / discharge efficiency can be realized.

  The first invention includes a positive electrode, a positive electrode electrolyte holding an electrolyte containing a carbon material in contact with the positive electrode, a negative electrode, a negative electrode electrolyte holding an electrolyte containing a carbon material in contact with the negative electrode, and the positive electrode electrolyte. And a separation membrane that separates the negative electrode electrolyte. The positive electrode electrolyte charges and discharges by a reaction of divalent and trivalent iron ions, and the negative electrode electrolyte charges and discharges by a reaction of divalent iron ions and iron. .

  By adding conductive carbon to the electrolyte, 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 second invention, the carbon material of the first invention is a mixture of a plurality of types of graphite having different average particle diameters.

  The conductivity of the electrolyte can be improved as a whole by increasing the conductivity by graphite having a large average particle diameter and connecting the graphite and the graphite by a small graphite.

  In the third invention, in particular, the ratio of the average particle diameters of the two types of graphite of the second invention is 10 times or more.

  Thereby, the electroconductivity of electrolyte can be improved as a whole and internal resistance can be reduced.

  In a fourth invention, the carbon material of the first invention is a mixture of carbon black and graphite.

  Although carbon black has a smaller conductivity than graphite, it has no directionality in the conduction direction, but graphite has a larger conductivity than carbon black, but has a directionality in the conduction direction. This is a feature that depends on the crystal structure of the carbon material. By combining the carbon black and graphite, the conductivity of the electrolyte can be stably improved, and the internal resistance can be reduced.

  The fifth invention is particularly characterized in that the average particle diameter of graphite is 50 times or more larger than the average particle diameter of the carbon black of the fourth invention.

  By increasing the conductivity by graphite having a large average particle diameter and connecting the graphite and graphite by a small carbon black, the conductivity of the electrolyte as a whole can be improved.

  The sixth invention is the first to sixth inventions, and in particular, the volume ratio of the positive electrode electrolyte to the negative electrode electrolyte is 2: 1.

  In the negative electrode electrolyte, one divalent iron ion receives two electrons and deposits as metallic iron, while in the positive electrode electrolyte, one divalent iron ion emits one electron and trivalent iron ions. It becomes. That is, the molar ratio of the divalent iron ions involved in the charging reaction is 2 to 1 between the positive electrode and the negative electrode, and ions in either cell remain unreacted at other molar ratios.

  Therefore, according to the present invention, since the volume of the negative electrode can be reduced, the internal resistance of the battery can be reduced.

Hereinafter, embodiments of the storage battery of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.
(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 electrolyte 3 and a negative electrode electrolyte 4 separated from a battery reaction cell 1 by a separation membrane 2. 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 positive electrode electrolyte 3 and the negative electrode electrolyte 4 are prepared by dissolving ferrous chloride having a molar fraction of 0.17 and ammonium chloride having a molar ratio of 0.17 in water, and further adding a carbon material to one tenth of the total weight. I let you. The volume ratio between the positive electrode electrolyte 3 and the negative electrode electrolyte 4 was 2: 1.

  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 embodiment, when carbon material is mixed with graphite having an average particle diameter of 0.5 μm and graphite having a particle diameter of 10 μm at a weight ratio of 1: 1, carbon black having an average particle diameter of 20 nm and graphite having a particle diameter of 1 μm are mixed. About the case where it mixed by the ratio of 1: 1 by weight ratio, the magnitude | size of the value of charging / discharging efficiency was measured about the case where the volume ratio of a positive electrode electrolyte and a negative electrode electrolyte is set to 1: 1, and 2: 1. Compared with the case where only this value is mixed with carbon black having an average particle diameter of 20 nm, in all cases, the storage battery having the configuration of the present embodiment has higher charging efficiency and is more stable even during repeated charging and discharging. It turns out to gain efficiency.

  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 electrolyte 4 Negative electrode electrolyte 5 Positive electrode 6 Negative electrode

Claims (6)

A positive electrode, a positive electrode electrolyte containing a carbon material in contact with the positive electrode, a negative electrode, a negative electrode electrolyte containing a carbon material in contact with the negative electrode, and a separation membrane separating the positive electrode electrolyte and the negative electrode electrolyte, A storage battery characterized in that charge is charged and discharged by reaction of divalent and trivalent iron ions in the positive electrode electrolyte, and reaction of divalent iron ions and iron in the negative electrode electrolyte. The storage battery according to claim 1, wherein the carbon material is a mixture of a plurality of types of graphite having different average particle diameters. The storage battery according to claim 2, wherein the ratio of the average particle diameter of the two types of graphite is 10 times or more. The storage battery according to claim 1, wherein the carbon material is a mixture of carbon black and graphite. The storage battery according to claim 4, wherein the average particle diameter of graphite is 50 times or more larger than the average particle diameter of carbon black. The storage battery according to any one of claims 1 to 5, wherein the volume ratio of the positive electrode electrolyte to the negative electrode electrolyte is 2 to 1.

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