Abstract: A cell that includes a positive electrode, a negative electrode and a membrane interposed between the electrodes, and that is used in a redox flow battery, wherein the membrane includes an ion permeable portion that is permeable to hydrogen ions, at least at a center of the membrane in a plan view, planar areas of the positive electrode and the negative electrode are both 250 cm2 or more, and a planar area of the ion permeable portion is smaller than each of the planar areas of the positive electrode and the negative electrode, and, in the ion permeable portion, a planar area of a facing portion that actually faces the positive electrode and the negative electrode is 50% or more and 99.9% or less of a smaller of the planar areas of the positive electrode and the negative electrode.

Abstract: A cell that includes a positive electrode, a negative electrode and a membrane interposed between the electrodes, and that is used in a redox flow battery, wherein the membrane includes an ion permeable portion that is permeable to hydrogen ions, at least at a center of the membrane in a plan view, planar areas of the positive electrode and the negative electrode are both 250 cm2 or more, and a planar area of the ion permeable portion is smaller than each of the planar areas of the positive electrode and the negative electrode, and, in the ion permeable portion, a planar area of a facing portion that actually faces the positive electrode and the negative electrode is 50% or more and 99.9% or less of a smaller of the planar areas of the positive electrode and the negative electrode.

Abstract: An object of the present invention is to provide a redox flow secondary battery being low in the electric resistance and excellent in the current efficiency as well, and further having the durability. The present invention relates to an electrolyte membrane for a redox flow secondary battery, the electrolyte membrane containing an ion-exchange resin composition containing a fluorine-based polyelectrolyte polymer, and having an ion cluster diameter of 1.00 to 2.95 nm as measured in water at 25° C. by a small angle X-ray method, and to a redox flow secondary battery using the electrolyte membrane.

Abstract: Provided is an electrolyte for a redox flow battery, the electrolyte allowing suppression of generation of precipitate during a battery reaction. In the electrolyte for a redox flow battery, the total concentration of impurity element ions contributing to generation of precipitate during a battery reaction is 220 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include metal element ions, the total concentration of the metal element ions may be 195 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include non-metal element ions, the total concentration of the non-metal element ions may be 21 mass ppm or less.

Abstract: Provided is an electrolyte for a redox flow battery, the electrolyte allowing suppression of generation of precipitate during a battery reaction. In the electrolyte for a redox flow battery, the total concentration of impurity element ions contributing to generation of precipitate during a battery reaction is 220 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include metal element ions, the total concentration of the metal element ions may be 195 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include non-metal element ions, the total concentration of the non-metal element ions may be 21 mass ppm or less.

Abstract: Provided are an electrolyte for a redox flow battery, the electrolyte allowing suppression of generation of hydrogen during a battery reaction; and a redox flow battery including the electrolyte. In the electrolyte for a redox flow battery, the total concentration of platinum-group element ions is 4.5 mass ppm or less. The platinum-group element ions may satisfy in terms of concentration at least one of those described below: the concentration of rhodium ions is 1 mass ppm or less, the concentration of palladium ions is 1 mass ppm or less, the concentration of iridium ions is 1 mass ppm or less, and the concentration of platinum ions is 1 mass ppm or less.

Abstract: Provided are an electrolyte for a redox flow battery, the electrolyte allowing suppression of generation of precipitate and suppression of generation of hydrogen during a battery reaction; and a redox flow battery including the electrolyte. In the electrolyte for a redox flow battery, the total concentration of impurity element ions contributing to generation of precipitate during a battery reaction is 220 mass ppm or less, and the total concentration of platinum-group element ions is 4.5 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include metal element ions, the total concentration of the metal element ions may be 195 mass ppm or less.

Abstract: Provided are an electrolyte for a redox flow battery, the electrolyte allowing suppression of generation of precipitate and suppression of generation of hydrogen during a battery reaction; and a redox flow battery including the electrolyte. In the electrolyte for a redox flow battery, the total concentration of impurity element ions contributing to generation of precipitate during a battery reaction is 220 mass ppm or less, and the total concentration of platinum-group element ions is 4.5 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include metal element ions, the total concentration of the metal element ions may be 195 mass ppm or less.

Abstract: Provided are a redox flow battery (RF battery) in which a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode, a negative electrode, and a membrane, to charge and discharge the battery, and a method of operating the RF battery. The positive electrode electrolyte contains a manganese ion, or both of a manganese ion and a titanium ion. The negative electrode electrolyte contains at least one type of metal ion selected from a titanium ion, a vanadium ion, a chromium ion, a zinc ion, and a tin ion. The RF battery can have a high electromotive force and can suppress generation of a precipitation of MnO2 by containing a titanium ion in the positive electrode electrolyte, or by being operated such that the positive electrode electrolyte has an SOC of not more than 90%.

Abstract: Provided are an electrolyte for a redox flow battery, the electrolyte allowing suppression of generation of hydrogen during a battery reaction; and a redox flow battery including the electrolyte. In the electrolyte for a redox flow battery, the total concentration of platinum-group element ions is 4.5 mass ppm or less. The platinum-group element ions may satisfy in terms of concentration at least one of those described below: the concentration of rhodium ions is 1 mass ppm or less, the concentration of palladium ions is 1 mass ppm or less, the concentration of iridium ions is 1 mass ppm or less, and the concentration of platinum ions is 1 mass ppm or less.

Abstract: Provided is an electrolyte for a redox flow battery, the electrolyte allowing suppression of generation of precipitate during a battery reaction. In the electrolyte for a redox flow battery, the total concentration of impurity element ions contributing to generation of precipitate during a battery reaction is 220 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include metal element ions, the total concentration of the metal element ions may be 195 mass ppm or less. In a case where the impurity element ions contributing to generation of precipitate include non-metal element ions, the total concentration of the non-metal element ions may be 21 mass ppm or less.

Abstract: An object of the present invention is to provide a redox flow secondary battery being low in the electric resistance and excellent in the current efficiency as well, and further having the durability. The present invention relates to an electrolyte membrane for a redox flow secondary battery, the electrolyte membrane containing an ion-exchange resin composition containing a fluorine-based polyelectrolyte polymer, and having an ion cluster diameter of 1.00 to 2.95 nm as measured in water at 25° C. by a small angle X-ray method, and to a redox flow secondary battery using the electrolyte membrane.

Abstract: Provided are a redox flow battery (RF battery) in which a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode, a negative electrode, and a membrane, to charge and discharge the battery, and a method of operating the RF battery. The positive electrode electrolyte contains a manganese ion, or both of a manganese ion and a titanium ion. The negative electrode electrolyte contains at least one type of metal ion selected from a titanium ion, a vanadium ion, a chromium ion, a zinc ion, and a tin ion. The RF battery can have a high electromotive force and can suppress generation of a precipitation of MnO2 by containing a titanium ion in the positive electrode electrolyte, or by being operated such that the positive electrode electrolyte has an SOC of not more than 90%.

Abstract: A redox flow battery having a high electromotive force and capable of suppressing generation of a precipitation is provided. In a redox flow battery 100, a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode 104, a negative electrode 105, and a membrane 101 interposed between the electrodes 104 and 105, to charge and discharge the battery. The positive electrode electrolyte contains a manganese ion, or both of a manganese ion and a titanium ion. The negative electrode electrolyte contains at least one type of metal ion selected from a titanium ion, a vanadium ion, a chromium ion, a zinc ion, and a tin ion. The redox flow battery 100 can suppress generation of a precipitation of MnO2, and can be charged and discharged well by containing a titanium ion in the positive electrode electrolyte, or by being operated such that the positive electrode electrolyte has an SOC of not more than 90%.

Abstract: A redox flow battery having a high electromotive force and capable of suppressing generation of a precipitation is provided. In a redox flow battery 100, a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode 104, a negative electrode 105, and a membrane 101 interposed between the electrodes 104 and 105, to charge and discharge the battery. The positive electrode electrolyte contains a manganese ion, or both of a manganese ion and a titanium ion. The negative electrode electrolyte contains at least one type of metal ion selected from a titanium ion, a vanadium ion, a chromium ion, a zinc ion, and a tin ion. The redox flow battery 100 can suppress generation of a precipitation of MnO2, and can be charged and discharged well by containing a titanium ion in the positive electrode electrolyte, or by being operated such that the positive electrode electrolyte has an SOC of not more than 90%.

Abstract: The present invention provides electrolyte that can suppress reduction of battery efficiencies and capacities with increased cycles of charge/discharge of the battery, a method for producing the same, and a redox flow battery using the same electrolyte. The redox flow battery uses the electrolyte having a NH4 content of not more than 20 ppm and a relation of Si concentration (ppm)×electrolyte quantity (m3)/electrode area (m2) of less than 5 ppm·m3/m2. By limiting a quantity of contaminants in the electrolyte, a clogging of carbon electrodes to cause reduction of the battery performances with increased charge/discharge operations can be suppressed.

Abstract: A modified vanadium compound characterized in that vanadium sulfate (III), or a mixed vanadium compound of vanadium sulfate (III) and vanadyl sulfate (IV) contains excessive sulfuric acid other than sulfate group composing the vanadium sulfate (III) or the vanadyl sulfate (IV), and when the modified vanadium compound is used, a redox flow battery electrolyte can be prepared easily.

Abstract: The present invention provides electrolyte that can suppress reduction of battery efficiencies and capacities with increased cycles of charge/discharge of the battery, a method for producing the same, and a redox flow battery using the same electrolyte. The redox flow battery uses the electrolyte having a NH4 content of not more than 20 ppm and a relation of Si concentration (ppm)×electrolyte quantity (m3)/electrode area (m2) of less than 5 ppm·m3/m2. By limiting a quantity of contaminants in the electrolyte, a clogging of carbon electrodes to cause reduction of the battery performances with increased charge/discharge operations can be suppressed.

Abstract: The present invention provides method of producing a trivalent and tetravalent mixed vanadium compound having excellent solubility with sulfuric acid directly from a tetravalent or pentavalent vanadium compound by using a reducing agent,and a method of producing a vanadium electrolyte. For example, a vanadium compound mainly containing a pentavalent vanadium compound; sulfur and concentrated sulfuric acid in molar ratios with respect to (one mol of vanadium atom in the pentavalent vanadium compound) 0.35 to 0.4:1.2 to 1.9 are kneaded into paste form, and the paste-form mixture is calcined at a temperature of not less than 150° C. to less than 440° C. so that a trivalent and tetravalent mixed vanadium compound is obtained, and a redox flow battery-use vanadium electrolyte is obtained by dissolving the trivalent and tetravalent mixed vanadium compound in a sulfuric acid solution.

Abstract: A modified vanadium compound of the present invention in such that vanadium sulfate (III) or a mixed vanadium compound of vanadium sulfate (III) and vanadyl sulfate (IV) contains excessive sulfuric acid other than sulfate group composing the vanadium sulfate (III) or the vanadyl sulfate (IV), and when the modified vanadium compound is used, a redox flow battery electrolyte can be prepared easily.