JP2019003750A - Flow battery, flow battery system, and power generation system - Google Patents

Abstract

To provide a flow battery excellent in cycle characteristics, and a flow battery system and a power generation system including the flow battery.SOLUTION: A flow battery includes: a positive electrode; a negative electrode; a positive electrode electrolyte including a positive electrode active material and supplied to the positive electrode; a positive electrode electrolyte reservoir section storing the positive electrode electrolyte; a negative electrode electrolyte including a negative electrode active material and supplied to the negative electrode; a negative electrode electrolyte reservoir section storing the negative electrode electrolyte; a barrier membrane separating the positive electrode and the negative electrode; and an insulating porous body arranged at least one of at least a part between the barrier membrane and the negative electrode and at least a part between the barrier membrane and the positive electrode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a flow battery, a flow battery system, and a power generation system.

  In recent years, as a countermeasure against global warming, the demand for renewable natural energy to replace fossil fuels has increased, and the renewable energy market is expected to grow steadily in the future. In such a background, as one of countermeasures against output fluctuation, which is a problem of power generation using natural power such as sunlight and wind power, power storage technology using a storage battery has been highlighted. Among them, the flow battery that performs charging and discharging by causing the electrolyte to flow and causing an oxidation-reduction reaction of the active material has a long charge / discharge cycle life, and output / capacity design according to the application is possible, In particular, it is attracting attention as a large-capacity storage battery.

  Other forms to which the flow battery can be applied as a large-capacity storage battery include, for example, a use on the power supply side and a use on the power demand side. The former is expected to be applied to, for example, securing power generation reserves and surplus power storage in thermal power plants, and frequency control, securing supply surplus and load leveling in substations. Also, in industrial facilities such as factories, peak cuts or time shifts for the purpose of reducing power costs, or instantaneous power outages (interruptible power supplies), uninterruptible power supplies (UPS) or emergency power supplies It is expected to be applied to other uses.

  A flow battery is composed of a positive electrode and a negative electrode, a positive electrode electrolyte and a negative electrode electrolyte, a positive electrode electrolyte reservoir and a negative electrode electrolyte reservoir, a liquid feed pump, a pipe, and the like. Charging / discharging is performed by circulating between the liquid reservoir and the negative electrode electrolyte circulating between the negative electrode and the negative electrode electrolyte reservoir. The positive electrode and the negative electrode are usually separated by a diaphragm, and mixing of the positive electrode electrolyte and the negative electrode electrolyte is prevented. Here, as the active material in the flow battery, ions whose valence changes can be candidates. Among these, vanadium (V / V) flow batteries and the like have been put into practical use from the viewpoint of safety and the like.

The electrode reaction of the V / V flow battery is shown below.
Positive: ^{VO 2+ _{(4-valent) + H 2 O⇔VO 2 + (}} 5 ^{valence) + 2H + + e - ···} (1)
Negative electrode: V ³⁺ (trivalent) + e ⁻ ⇔V ²⁺ (bivalent) (2)
Here, a reaction from left to right represents a charging reaction, and a reaction from right to left represents a discharging reaction. When the reaction from the left to the right occurs, the supplied electric power is consumed in changing the valence of V ions in the positive electrode and the negative electrode, and is stored in the electrolytic solution. Moreover, at the time of discharge, the electric power stored in electrolyte solution can be taken out by reverse reaction.

  V / V flow batteries have a long history of development, and large-scale demonstration tests are underway in Japan and overseas. On the other hand, the V / V flow battery has a problem in terms of raw material costs, and a system using an alternative material is expected. As alternative materials, cerium / zinc (Ce / Zn), zinc / bromine (Zn / Br), zinc / iodine (Zn / I), iron / chromium (Fe / Cr), and the like are known. .

Patent Document 1 and Non-Patent Document 1 disclose Zn / I-based flow batteries using iodine ions as the active material for the positive electrode electrolyte and zinc ions and zinc metal as the active material for the negative electrode electrolyte. Patent Document 2 discloses a flow battery using a halogen material such as iodine, chlorine or bromine as a positive electrode active material and zinc as a negative electrode active material.

  By the way, in the flow battery, it is preferable to use a carbon felt electrode whose surface is activated from the viewpoint of the activity of the electrode reaction, acid resistance, reaction area, and the like.

US Patent Application Publication No. 2015/0147673 U.S. Pat.No. 4,910,065

“Abipolar zinc-polyiodide electorate for a high-energy density, aqua redox flow battery”, Nature Communications 6: 6303, (2014)

Here, as shown in Patent Document 1 and Non-Patent Document 1, in a flow battery using iodine ions as a positive electrode active material and zinc ions and zinc as a negative electrode active material, I ₃ ⁻ And solid I ₂ precipitates. Therefore, during charging of the flow battery, solid I ₂ accumulates in the cell, which may cause a problem that the inside of the cell is clogged and the electrolyte cannot flow. As a result, the cycle characteristics and the like of the flow battery may be deteriorated.

  Furthermore, for example, when the metal is deposited by the reduction reaction on the positive electrode side or the reduction reaction on the negative electrode side, due to the ion migration resistance of the separator such as an ion exchange membrane that separates the positive electrode and the negative electrode, the metal is deposited on the separator side, There is a possibility that problems such as damage to the separator or short circuit may occur. As a result, the cycle characteristics and the like of the flow battery may be deteriorated.

  An object of one embodiment of the present invention is to provide a flow battery excellent in cycle characteristics, and a flow battery system and a power generation system including the flow battery.

Means for solving the above problems include the following embodiments.
<1> A positive electrode, a negative electrode, a positive electrode electrolyte containing a positive electrode active material and supplied to the positive electrode, a positive electrode electrolyte reservoir for storing the positive electrode electrolyte, a negative electrode active material, and the negative electrode A negative electrode electrolyte solution supplied to the anode, a negative electrode electrolyte storage part for storing the negative electrode electrolyte solution, a diaphragm separating the positive electrode and the negative electrode, at least a part between the diaphragm and the negative electrode, and the diaphragm An insulating porous body disposed on at least one of at least a portion between the positive electrode and the positive electrode.
<2> The insulating porous body, the bulk density was determined ^{gravimetrically,} is ^{0.03g / cm 3 ~5.00g / cm 3} , a flow cell according to <1>.
<3> The flow battery according to <1> or <2>, wherein the insulating porous body includes at least one selected from a polymer, paper, glass, ceramics, and a metal having a surface insulating coating.
<4> The flow battery according to any one of <1> to <3>, wherein the insulating porous body has a three-dimensional continuous void.
<5> When the insulating porous body is disposed in at least a part between the diaphragm and the positive electrode, the positive electrode electrolyte is disposed in the positive electrode and between the positive electrode and the diaphragm. When the insulating porous body is disposed in at least a part between the diaphragm and the negative electrode through the insulating porous body, the negative electrode electrolyte is in the negative electrode and between the negative electrode and the diaphragm. The flow battery according to any one of <1> to <4>, which circulates through the disposed insulating porous body.
<6> When the insulating porous body is disposed at least at a part between the diaphragm and the positive electrode, the insulating porous body disposed between the positive electrode and the diaphragm with respect to the thickness of the positive electrode. When the ratio of thickness is 0.002 to 0.750 and the insulating porous body is disposed at least partially between the diaphragm and the negative electrode, the negative electrode and the diaphragm with respect to the thickness of the negative electrode The flow battery according to any one of <1> to <5>, wherein a ratio of the thickness of the insulating porous body disposed between the two is between 0.002 and 0.750.
<7> The flow battery according to any one of <1> to <6>, wherein at least one of the positive electrode and the negative electrode is accompanied by precipitation of an active material during a charging reaction or a discharging reaction.
<8> The flow battery according to <7>, wherein in the positive electrode, iodine precipitates during a charging reaction.
<9> The flow battery according to <7> or <8>, wherein in the negative electrode, zinc is precipitated during a charging reaction.
<10> The flow battery according to any one of <1> to <9>, wherein the positive electrode electrolyte includes water and includes at least one of iodine ions and iodine molecules as the positive electrode active material.
<11> The flow battery according to any one of <1> to <10>, wherein the negative electrode electrolyte includes water and includes at least one of zinc ions and zinc as the negative electrode active material.
<12> Any one of <1> to <11>, wherein the insulating porous body is disposed in at least a part between the diaphragm and the negative electrode and at least a part between the diaphragm and the positive electrode. The flow battery described in 1.
<13> The flow battery according to any one of <1> to <12>, wherein the positive electrode and the negative electrode have at least one of at least two regions having different porosity and a surface flow path.
<14> The flow battery according to <13>, wherein the at least two regions having different porosity are formed in at least one of a flow direction of the electrolytic solution and a thickness direction of the electrode.
<15> The flow battery according to <13> or <14>, wherein the surface flow path is formed on at least one of the diaphragm side and the opposite side of the diaphragm so as to have a concave shape with respect to the electrode surface. .

<16> A flow battery system comprising: the flow battery according to any one of <1> to <15>; and a control unit that controls charging and discharging of the flow battery.

<17> A power generation system comprising a power generation device and the flow battery system according to <16>.

  According to one embodiment of the present invention, it is possible to provide a flow battery excellent in cycle characteristics, and a flow battery system and a power generation system including the flow battery.

It is a mimetic diagram showing an example of member composition of a flow battery of this indication. It is a schematic diagram of the flow battery of this indication. It is a mimetic diagram of a flow battery of this indication showing a cell stack composition. It is a schematic diagram which shows an example of the insulating porous body applied to the flow battery of this indication. It is a schematic diagram which shows an example of the insulating porous body applied to the flow battery of this indication. In the negative electrode of the flow battery of this indication, it is a mimetic diagram which formed the field from which the porosity differs in the distribution direction of electrolyte solution. It is the schematic diagram which formed the area | region from which the porosity differs in the thickness direction in the negative electrode of the flow battery of this indication. It is the schematic diagram which formed the flow path (comb tooth structure) in the negative electrode surface of the flow battery of this indication. FIG. 6B is a schematic view in which a flow path (meandering structure) is formed on the surface of the negative electrode of the flow battery of the present invention. FIG. 6C is a schematic view in which a flow path (cross structure) is formed on the surface of the negative electrode of the flow battery of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.
In the present disclosure, the numerical ranges indicated using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical description. . Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In the present disclosure, the content of each component in the electrolytic solution is the total of the plurality of types of substances present in the electrolytic solution unless there is a specific indication when there are multiple types of substances corresponding to the respective components in the electrolytic solution. Mean content.
Further, in the present disclosure, “content ratio” represents mass% of each component when the total amount of each electrolytic solution is 100 mass% unless otherwise specified.
Moreover, it will be apparent to those skilled in the art that the present invention can be practiced without utilizing some or all of the specific details described in the present disclosure. In addition, in order to avoid obscuring aspects of the present invention, detailed descriptions or illustrations of known points may be omitted.
In the present disclosure, the positive electrode electrolyte and the negative electrode electrolyte may be referred to as an electrolyte, and the positive electrode active material and the negative electrode active material may be referred to as an active material.

[Flow battery]
The flow battery of the present disclosure includes a positive electrode, a negative electrode, a positive electrode active material, and a positive electrode electrolyte supplied to the positive electrode, a positive electrode electrolyte reservoir for storing the positive electrode electrolyte, and a negative electrode active material. And a negative electrode electrolyte supplied to the negative electrode, a negative electrode electrolyte reservoir for storing the negative electrode electrolyte, a diaphragm separating the positive electrode and the negative electrode, and at least a part between the diaphragm and the negative electrode And an insulating porous body disposed in at least one of at least a part between the diaphragm and the positive electrode. The flow battery of the present disclosure can achieve high cycle characteristics by having the above-described configuration, and can achieve high cycle characteristics even when metal or the like is deposited on the electrode surface by a charge reaction or a discharge reaction. Furthermore, it is considered that the flow battery of the present disclosure can achieve high current density and high output characteristics as well as high cycle characteristics.

For example, in a flow battery in which I ₂ and Fe are deposited on the positive electrode during the charging reaction and Zn is deposited on the negative electrode in the charging reaction, such as I / Zn flow battery and Fe / Cr flow battery, carbon felt or the like As a result of solid deposition in the electrode, the diaphragm separating the positive electrode and the negative electrode may be damaged, or clogging may occur and it may be difficult to circulate the electrolyte. There is a risk of significant reduction. In particular, such a problem can be prominent when metal deposition proceeds in an electrode such as carbon felt and dendrite growth occurs.

  For such a problem, it is preferable to dispose the positive electrode, the negative electrode, and the diaphragm so as not to be in direct contact with each other. However, particularly when carbon felt electrodes are used for the positive electrode and the negative electrode, they are often compressed after laminating the members in order to reduce the contact resistance between the electrode and the bipolar plate. As a result, the positive electrode, the negative electrode and the diaphragm are in contact with each other. Will do. For example, in the case of a positive electrode and a negative electrode having a thickness of 4 mm to 5 mm, they may be compressed to a thickness of about 2 mm to 3 mm.

  On the other hand, in the flow battery according to the present disclosure, an insulating porous body is disposed in at least one part between the diaphragm and the negative electrode and at least one part between the diaphragm and the positive electrode. Thereby, an insulating porous body is disposed as a spacer between the diaphragm and the electrode, damage to the diaphragm due to precipitation of solids can be reduced, and clogging can be suppressed. Performance degradation can be suppressed.

(Insulating porous body)
In the flow battery of the present disclosure, an insulating porous body is disposed in at least a part between the diaphragm and the negative electrode and at least a part between the diaphragm and the positive electrode in terms of cycle characteristics, current density, and output characteristics. Preferably, the entire surface perpendicular to the thickness direction of the negative electrode (the surface facing the diaphragm) is in contact with the surface perpendicular to the thickness direction of the insulating porous body (the surface opposite to the side facing the diaphragm), In addition, the entire surface perpendicular to the thickness direction of the positive electrode (the surface facing the diaphragm) is in contact with the surface perpendicular to the thickness direction of the insulating porous body (the surface opposite to the side facing the diaphragm). More preferably, they are arranged.

  In addition, in the flow battery of the present disclosure, in the case of solid deposition, particularly metal deposition, on the negative electrode side in terms of cycle characteristics, current density, and output characteristics, at least part of the gap between the diaphragm and the negative electrode is insulated porous. In the case where solid deposition, particularly metal deposition, occurs on the positive electrode side, an insulating porous body is preferably disposed at least at a part between the diaphragm and the positive electrode.

  The insulating porous body is not particularly limited as long as it is a porous insulator. The insulating porous body preferably contains at least one selected from polymers, paper, glass, ceramics and metal with a surface insulating coating from the viewpoint of cycle characteristics. Polymers, paper, glass, ceramics and surface insulating coatings are preferable. It is more preferable that it is at least one selected from metals subjected to. An insulating porous body may be used individually by 1 type, and may use 2 or more types together.

  Insulating porous materials include polyethylene resin, polyamide resin, polyester resin, cellulose resin, silicone resin, fluorine resin, acrylic resin, phenol resin, polyolefin resin, cellophane, kraft paper, vinylon mixed paper, synthetic pulp mixed paper, polyolefin Nonwoven fabrics, cupra nonwoven fabrics, polyamide nonwoven fabrics, glass fiber nonwoven fabrics; porous or honeycomb ceramics made of alumina, silicon carbide, aluminum nitride, boron nitride, sialon, and the like.

  In addition, the surface-coated metal is obtained by applying a fluororesin coating, a silicon resin coating, a rubber polymer coating, etc. to the surface of a porous metal body made of copper, aluminum, stainless steel, zinc, titanium, or the like. be able to.

The bulk density of the insulating porous body, circulation of the electrolytic solution, familiar with the diaphragm, from the viewpoint of mechanical strength ^is preferably from ^{0.03g / cm 3 ~5.00g / cm 3} , 0.04g / in cm ³ more preferably ~4.50g / cm ^3, more preferably from ^{0.05g / cm 3 ~4.00g / cm 3} , 0.05g / cm 3 ~3.00g / cm 3 particularly preferably ^in, still more preferably from ^{0.07g / cm 3 ~2.00g / cm 3} , it is even more preferably ^{0.10g / cm 3 ~1.00g / cm 3} .
The bulk density of the insulating porous body can be determined by a gravimetric method. That is, the bulk density of the insulating porous body can be obtained by dividing the weight of the insulating porous body in the air by the bulk capacity measured by a predetermined method.

  The porosity of the insulating porous body is not particularly limited, and is preferably 50.0% to 99.5%, for example, from the viewpoint of the flowability of the electrolytic solution, and is preferably 55.0% to 99.0%. It is more preferable that it is 60.0% to 98.5%.

The porosity of the insulating porous body can be calculated by cross-sectional observation or weight measurement. The method for calculating the porosity by cross-sectional observation can be suitably used for a porous body having a random structure because the area porosity and the volume porosity are equal. The porosity in cross-sectional observation can be obtained as follows.
Specifically, the insulating porous body is cut, an electron micrograph of the obtained cross section is taken, and this is taken as an observation cross section. Next, with respect to the observation cross section, in order to make it easy to compare the portion of the material constituting the insulating porous body with other portions, by performing image processing that increases the contrast ratio, for example, the material portion is a black portion, the material It is possible to obtain a cross-sectional view for evaluation in which a portion (void portion) that is not a portion is shown as a white portion. Thereafter, the void portion in the observation cross-sectional view can be the area ratio of the white portion of the evaluation cross-sectional view that has been subjected to image processing that increases the contrast ratio. The area ratio of the white portion can be calculated using image processing software such as Adobe illustrator CS6 (Adobe), Matrox Inspector 8.0 (Matrox), and ImageJ (NIH).

  When a material whose porosity changes before and after compression is used for the insulating porous body, it is preferable to calculate the porosity of the insulating porous body after compression (a state used as an insulating porous body of a flow battery). . In addition, when the relationship between the compression ratio calculated from the thickness of the insulating porous body before and after compression and the porosity is known, the porosity of the insulating porous body that is not mounted on the flow battery and is not compressed is calculated. You may measure and calculate, and you may convert into the porosity of the insulating porous body after compression.

When calculating the porosity of the insulating porous material from the weight measurement, the following equation (3) can be used.
φ = (1−V / V ′) × 100 (3)
In formula (3), φ is the porosity (%), V is the true volume (cm ³ ) of the insulating porous material, and V ′ is the apparent volume (cm ³ ) of the insulating porous material. The true volume V of the insulating porous body can be calculated by dividing the mass of the material constituting the insulating porous body by the density (g / cm ³ ) of the material.

  There is no restriction | limiting in particular as a shape of an insulating porous body, A sheet form, a mesh form, etc. are mentioned. Examples of the pattern viewed from the surface of the insulating porous material include the pattern (honeycomb structure) in FIG. 4A and the pattern (mesh structure) in FIG. 4B.

  The insulating porous body preferably has a three-dimensional continuous void. Thereby, electrolyte solution distribute | circulates suitably through an insulating porous body, and exists in the tendency for the distribution | circulation property of the electrolyte solution in a cell to be excellent. From the point of being excellent in the flowability of the negative electrode electrolyte, when the insulating porous body is disposed at least partly between the diaphragm and the negative electrode, the negative electrode electrolyte has a structure that flows through both the negative electrode and the insulating porous body. Preferably there is. In addition, from the viewpoint of excellent flowability of the positive electrode electrolyte, when the insulating porous body is disposed at least partly between the diaphragm and the positive electrode, the positive electrode electrolyte flows through both the positive electrode and the insulating porous body. A structure is preferred.

Further, the insulating porous body on the positive electrode side preferably has a structure having a three-dimensional continuous void, and the positive electrode electrolyte solution flows through both the positive electrode and the insulating porous body on the positive electrode side. The porous body preferably has a three-dimensional continuous void portion and has a structure in which the negative electrode electrolyte flows in both the negative electrode and the insulating porous body on the negative electrode side. With these configurations, the burden on the diaphragm due to the precipitation of a solid such as a metal can be suppressed, and the dendrite growth of Zn or the like tends to be suppressed. The reason can be considered as follows, for example. When the zinc ion (Zn ²⁺ ) reaches the electrode surface (especially the negative electrode surface) during the charging reaction of the flow battery and forms a Zn cluster by an electrochemical reaction, and Zn dendrite grows from it, a one-dimensional semi-infinite The thickness (δ) of the diffusion layer in the Cottrell equation relating to diffusion can be expressed as a function of the flow rate (v) of the electrolytic solution containing Zn ²⁺ . At this time, when v = 0, δ = (πDt) ^1/2 , but the diffusion layer thickness (δ) decreases as the flow velocity (v) on the electrode surface increases. Here, D is a diffusion coefficient of Zn ²⁺ ions in the electrolytic solution, and t is time. That is, in order to suppress the burden on the diaphragm due to the precipitation of solids such as metals, and to suppress the growth of Zn dendrite on the diaphragm side, the electrolyte flows along the surface of the electrode on the electrode surface on the diaphragm side, It is preferable that a decrease in the flow rate of the electrolyte is suppressed. Therefore, in the flow battery of the present disclosure, the electrolyte solution is also applied to the inside of the insulating porous body in that the burden on the diaphragm due to the precipitation of a solid such as metal is suppressed and the growth of Zn dendrite on the diaphragm side is suppressed. For this purpose, the insulating porous body preferably has a three-dimensional continuous void portion.

Furthermore, in the flow battery according to the present disclosure, the positive electrode electrolyte is supplied to the surface of the positive electrode on the diaphragm side, because the positive electrode electrolyte flows through both the positive electrode and the insulating porous body on the positive electrode side. There is a tendency to further suppress dendrite growth.
Further, in the flow battery of the present disclosure, the negative electrode electrolyte is supplied to the surface of the negative electrode on the diaphragm side by the negative electrode electrolyte flowing through both the negative electrode and the insulating porous body on the negative electrode side. There is a tendency to further suppress dendrite growth.

In the flow battery according to the present disclosure, by disposing an insulating porous body at least at a part between the diaphragm and the positive electrode, for example, I ₂ is generated as shown in the following formula (7), and the generated I ₂ is When it remains in the positive electrode as a solid, damage to the diaphragm tends to be suppressed. When the insulating porous body is not disposed between the diaphragm and the positive electrode, the flow path blocking property, reaction non-uniformity, and the like are increased, and the cycle characteristics, the characteristics of the battery itself, and the like may be deteriorated. This is because the solubility of I ₂ in water is as low as about 10 mM.

  Physical properties such as the material, dimensions, density, etc. of the insulating porous material disposed on the positive electrode side can be appropriately selected according to other members, the electric liquid composition, etc., and the material, dimensions, Physical properties such as density can be appropriately selected according to other members, the composition of the electric liquid, and the like.

(Positive electrode and negative electrode)
As a positive electrode and a negative electrode, what is used for a conventionally well-known secondary battery, especially a conventionally well-known flow battery can be used. Specific examples include metals such as aluminum, copper and zinc, and carbon such as graphite. In addition, conductive materials such as InSnO ₂ , SnO ₂ , ZnO, In ₂ O ₂ , fluorine-doped tin oxide (SnO ₂ : F), antimony-doped tin oxide (SnO ₂ : Sb), tin-doped indium oxide (In ₂ O _3). : Sn), Al-doped zinc oxide (ZnO: Al), Ga-doped zinc oxide (ZnO: Ga) and other conductive materials doped with impurities such as single layer or multiple layers were formed on glass or polymer. Things. Examples of the shape of the positive electrode and the negative electrode include a plate shape and a mesh shape.

  At least one of the positive electrode and the negative electrode preferably contains carbon fiber from the viewpoint of increasing a reaction field as an exchange of electrons with the active material, that is, an electrode area.

  When at least one of the positive electrode and the negative electrode contains carbon fiber, it is preferably a porous body made of carbon fiber from the viewpoints of handling, workability, manufacturability, and surface area. Specifically, examples of the porous body made of carbon fibers include carbon felt, carbon cloth, and carbon paper. Among them, it is preferable to use carbon felt from the viewpoint of reaction activity and surface area during charge / discharge.

  Examples of the carbon fiber raw material fiber include carbonizable fibers, and specific examples include cellulose-based, acrylic-based, rayon-based, phenol-based, aromatic polyamide-based, pitch-based fiber, and polyacrylonitrile-based fiber.

  As a method for producing carbon felt, raw fibers before firing are laminated and spread into a sheet shape, and then a web is formed. Then, a gap between fibers is appropriately determined by a known method such as a needle punch method, a thermal bond method, or a stitch bond method. There is a method of bonding, finishing in a felt shape, and finally performing a heat treatment.

  The heat treatment conditions are not particularly limited, and include, for example, a step (carbonization treatment) of heat treating a felt material made of raw material fibers at a temperature of 800 ° C. to 2000 ° C. in an inert gas. Further, if necessary, a step of heat treatment at a temperature of 100 ° C. to 500 ° C. before the carbonization treatment (flame resistance) and a step of heat treatment at a temperature of 2000 ° C. to 3000 ° C. after the carbonization treatment (graphitization treatment) are included. You may go out. By performing the graphitization treatment, the carbonized raw material fibers are further graphitized, the crystal structure as graphite becomes regular, and excess functional groups on the surface of the carbon fibers are removed, so that the electrode physical properties such as conductivity are improved. There is a tendency.

  As other conditions of heat processing, the process (activation process) which heat-processes the felt material which consists of raw material fibers at the temperature of 800 to 2000 degreeC in water vapor | steam atmosphere, for example is included. Thereby, the carbonized raw material fibers become porous and become activated carbon fibers, and the adsorption efficiency of the active material onto the fiber surface tends to be increased.

  Carbon cloth and carbon paper can also be suitably manufactured by performing heat treatment after finishing the raw material fibers into a cloth shape or a paper shape by a known method.

  The fiber diameter of the carbon fiber is preferably 1.0 μm to 30.0 μm, preferably 1.5 μm to 25 μm, from the viewpoints of physical properties as a carbon felt, production method, efficiency of electron transfer reaction with the electrolyte active material, and the like. It is more preferably 0.0 μm, and further preferably 2.0 μm to 20.0 μm.

  As shown in FIGS. 2 and 3, the positive electrode and the negative electrode are preferably compressed in the thickness direction when mounted (filled) in the flow battery. Thereby, the electrical conductivity of the material which comprises a positive electrode and a negative electrode (in the case of carbon felt, carbon fiber) and a bipolar plate improves, and it exists in the tendency which can reduce cell resistance.

  When the positive electrode and the negative electrode are used after being compressed, the ratio of the thickness before and after compression (thickness before compression / thickness after compression) is preferably 1.1 to 4.0, and preferably 1.2 to 3 Is more preferably 0.8, and still more preferably 1.3 to 3.6.

  When the insulating porous body is disposed at least partially between the diaphragm and the positive electrode, the ratio of the thickness of the insulating porous body disposed between the positive electrode and the diaphragm to the thickness of the positive electrode is 0.002 to 0. .750, preferably 0.003 to 0.500, and more preferably 0.004 to 0.400. When the thickness ratio is 0.002 or more, the flow of the positive electrode electrolyte in the insulating porous body can be suitably secured, and when the dendrite grows on the positive electrode surface, the dendrite comes into contact with the diaphragm, There is a tendency that clogging of the liquid can be effectively suppressed. In addition, when the thickness ratio is 0.750 or less, the resistance (liquid resistance) of the positive electrode electrolyte according to the distance between the positive electrode and the diaphragm tends to be kept low.

  When the insulating porous body is disposed at least partly between the diaphragm and the negative electrode, the ratio of the thickness of the insulating porous body disposed between the negative electrode and the diaphragm to the thickness of the negative electrode is 0.002 to 0 .750, preferably 0.003 to 0.500, and more preferably 0.004 to 0.400. When the thickness ratio is 0.002 or more, the flow of the negative electrode electrolyte in the insulating porous body can be suitably secured, and when the dendrite grows on the negative electrode surface, the dendrite comes into contact with the diaphragm, and the negative electrode electrolysis There is a tendency that clogging of the liquid can be effectively suppressed. Further, when the thickness ratio is 0.750 or less, the resistance (liquid resistance) of the negative electrode electrolyte according to the distance between the negative electrode and the diaphragm tends to be kept low.

  In the flow battery of the present disclosure, at least one of the positive electrode and the negative electrode, preferably the positive electrode and the negative electrode may have at least one of at least two regions having different porosity and a surface flow path. When the electrode has at least one of two regions having different porosity and a surface flow path, pressure loss and power loss of the liquid feed pump tend to be suppressed even when there is a solid precipitation reaction such as metal. . This can be considered, for example, as follows.

When a fluid flows through a space, it is subject to resistance due to friction with the material it contacts. This is the basic cause of pressure loss. The pressure loss in the laminar flow can be obtained by the so-called Hagen-Poiseille equation.
There is a clear relationship between the reaction rate of the electrochemical reaction between the positive electrode and the negative electrode, which is the basic constituent reaction of the battery reaction, and the pressure loss. When the pressure loss changes, it means that the flow velocity changes in the space in which the electrolyte for evaluating it flows. Regarding the relationship between the rate of the electrochemical reaction and the flow rate of the reaction field, the reaction rate is higher in the high flow rate field than in the low flow rate field. This is because the mass flow layer at the electrode interface is thinner in the high flow field than in the low flow field, and the flux (mol / (cm ² · sec)), which is the supply speed of the active material, is increased.
Therefore, when the potential of the reaction field is controlled to be constant, the reaction rate on the side into which the electrolyte solution flows becomes faster than the side on which the electrolyte solution in which pressure loss has occurred. In the case of constant current control, that is, when the reaction rate of the reaction field is made constant by external control, there is a change in the difference in the reaction overvoltage of the battery reaction due to pressure loss between the electrolyte inflow side and the electrolyte outflow side. Arise. That is, the rate of increase of the overvoltage of the electrochemical reaction on the side where the electrolyte flows in, which is a place where the flow rate of the electrolyte is fast, can be suppressed lower than the rate of increase of the overvoltage of the electrochemical reaction on the side where the electrolyte flows. . Thus, pressure loss and battery reaction characteristics are closely related.

When a deposition reaction of metal or the like is accompanied by charging / discharging, the influence on the reaction of the flow battery due to the pressure loss becomes more obvious. For example, when the deposition of metal or the like occurs in the negative electrode due to a charging reaction, the pressure loss is further amplified. The reason for this is that the reaction rate is fast on the side where the negative electrode electrolyte flows, so that the flow path area on the side where the negative electrode electrolyte flows becomes smaller with the charging time due to the deposited metal or the like. When the flow path area decreases with the charging time, the region where the negative electrode electrolyte flows in is covered with the solid produced by the charging reaction, and the negative electrode electrolyte may not flow. When the negative electrode electrolyte stops flowing, it is no longer a flow battery, and the battery function stops.
As described above, a reaction system involving a precipitation reaction of a metal or the like is greatly different from a normal ion / ion reaction system not involving a precipitation reaction of a metal or the like with respect to a pressure loss phenomenon. That is, in the case of a flow battery with a precipitation reaction, the pressure loss phenomenon is amplified, and depending on how it is used, a situation may occur in which the electrolyte cannot flow.

  In the flow battery, when the active material is precipitated in the charge / discharge reaction, a large amount of metal or the like tends to be deposited on the counter electrode side where the battery reaction actively occurs. This is because, in principle, a position closer to the counter electrode has a small absolute value of ohmic loss and is an advantageous position in terms of potential as an electrochemical reaction field. For example, when the porosity is uniform in the negative electrode or the porosity is small on the positive electrode side that is the counter electrode, and deposition of a metal or the like of the negative electrode active material occurs in the charge / discharge reaction, the deposition of metal or the like on the side closer to the positive electrode It tends to occur and the gap is easily closed. As a result, on the side closer to the positive electrode, the flow of the negative electrode electrolyte is hindered and pressure loss increases, ion conductivity through the negative electrode electrolyte is impaired, and the battery reaction is less likely to proceed. As a result, the power loss of the liquid feed pump increases, and the output such as current density and discharge capacity decreases. Therefore, it is preferable to prevent the negative electrode electrolyte from being inhibited from flowing on the side closer to the positive electrode and to allow the battery reaction to proceed appropriately.

  In the flow battery of the present disclosure, at least one of the positive electrode and the negative electrode has at least two regions having different porosity. Thereby, when it accompanies precipitation reaction of a metal etc., it exists in the tendency which can suppress a pressure loss and can maintain the characteristic of a flow battery for a long period of time. When a solid such as a metal is deposited by the charge / discharge reaction, for example, when solid iodine molecules are deposited in the positive electrode by a charging reaction or zinc is deposited in the negative electrode by a charging reaction, the reaction rate is first high. The channel area decreases from the inflow side of the electrolyte. In order to suppress this, the porosity of the positive electrode and the porosity of the negative electrode on the electrolyte inflow side are made larger than the porosity of the positive electrode and the negative electrode on the electrolyte outflow side, and a wide flow path is secured. It is preferable to do. Thereby, it is in the tendency which can suppress the obstruction | occlusion of the electrode by solid precipitation, such as a metal, during charge / discharge of a battery, and can balance and optimize a flow battery function.

  As the electrode having at least two regions having different porosity, the electrode having at least two regions having different porosity in the flowing direction of the electrolyte as described above, and at least two regions having different porosity in the thickness direction. An electrode having

  As an electrode having at least two regions having different porosity in the thickness direction, an electrode having a larger porosity on the diaphragm side than the porosity on the opposite side is preferable. As a result, blockage of the gap on the diaphragm side is suppressed, and an increase in the ionic conduction resistance of the electrolytic solution is suppressed, so that a flow battery function having a high current density and a high output can be maintained for a long time. is there.

  In the flow battery, when providing at least two regions having different porosity in the electrode, for example, as shown in FIG. 5A, the porosity of the electrode 1 on the electrolyte inflow side is It is preferable that the porosity of the electrode 1 on the outflow side is higher. Further, as shown in FIG. 5B, in the thickness direction, the porosity of the electrode 1 on the diaphragm 2 side is preferably higher than the porosity on the opposite side. In FIG. 5B, illustration of the insulating porous body is omitted.

The porosity of the electrode can be calculated by cross-sectional observation or weight measurement. The method of calculating the porosity by cross-sectional observation can be suitably used for porous bodies having a random structure such as carbon felt because the area porosity and volume porosity are equal. The porosity in cross-sectional observation can be obtained as follows.
Specifically, the electrode is cut with a cutter or the like, an electron micrograph of the obtained cross section is taken, and this is taken as an observation cross-sectional view. Next, with respect to the observation cross section, in order to make it easier to compare the portion constituting the electrode portion with other portions, for example, the electrode portion is a black portion, a portion that is not the electrode portion by increasing the contrast ratio. A cross-sectional view for evaluation showing (void portion) as a white portion can be obtained. Thereafter, the void portion in the observation cross-sectional view can be the area ratio of the white portion of the evaluation cross-sectional view that has been subjected to image processing that increases the contrast ratio. The area ratio of the white portion can be calculated using image processing software such as Adobe illustrator CS6 (Adobe), Matrox Inspector 8.0 (Matrox), and ImageJ (NIH).

  When a material whose porosity changes before and after compression is used for the electrode, it is preferable to calculate the porosity of the electrode after compression (a state used as an electrode of a flow battery). In addition, when the relationship between the compression ratio calculated from the thickness of the electrode before and after compression and the porosity is known, the measurement is performed to calculate the porosity of the uncompressed state that is not mounted on the flow battery, and the compression is performed. You may convert into the porosity of a later electrode.

When calculating the porosity of an electrode from weight measurement, the following (3) 'formula can be used.
φ = (1−V / V ′) × 100 (3) ′
In formula (3) ′, φ is the porosity (%), V is the true volume (cm ³ ) of the electrode, and V ′ is the apparent volume (cm ³ ) of the electrode. The true volume V of the electrode can be calculated by dividing the mass of the material constituting the electrode by the density (g / cm ³ ) of the material.

  Furthermore, at least one of the positive electrode and the negative electrode may have a porosity gradient. At this time, the porosity gradient may be provided in a partial region of the electrode, and the porosity gradient may not be provided in the remaining region.

  In the flow battery of the present disclosure, at least one of the positive electrode and the negative electrode may have a surface flow path. As a result, as in the case of using an electrode having at least two regions having different porosity, when accompanied by a precipitation reaction of metal or the like, the pressure loss tends to be suppressed and the characteristics of the flow battery can be maintained for a long time. is there. More specifically, by providing a surface flow path, clogging of the electrode due to deposition of metal or the like on the inflow side in the electrolyte flow direction and the diaphragm side of the electrode is suppressed, and the electrolyte can be distributed efficiently. There is a tendency to be able to.

  The surface channel may be provided on at least one of the diaphragm side and the opposite side of the electrode. Moreover, the insulating porous body arrange | positioned at the diaphragm side may bear the function of a surface flow path. By disposing the surface flow channel on the diaphragm side, there is a tendency that pressure loss can be suitably suppressed when accompanied by a precipitation reaction of metal or the like. By arranging the surface flow channel on the opposite side of the diaphragm, the electrode and the insulating porous The body tends to be able to control the flow rate of the electrolyte almost uniformly.

  The surface flow path is preferably formed on at least one of the diaphragm side and the opposite side so as to have a concave shape with respect to the electrode surface.

  There are no particular restrictions on the flow path pattern when the surface flow paths are provided on the positive electrode and the negative electrode. Examples of the flow path pattern include a comb-tooth structure as shown in FIG. 6A, a meander structure as shown in FIG. 6B, and a surface flow path 17 having a cross structure (preferably an orthogonal structure) as shown in FIG. 6C. It is done.

(diaphragm)
The flow battery may further include a diaphragm between the positive electrode and the negative electrode. The diaphragm is not particularly limited as long as it can withstand the usage conditions of the flow battery. Examples of the diaphragm include an ion conductive polymer film capable of conducting ions, an ion conductive solid electrolyte film, a polyolefin porous film, and a cellulose porous film.

  Examples of the ion conductive polymer membrane include a cation exchange membrane and an anion exchange membrane, and more specifically, Seleion APS (registered trademark) (AGC), Nafion (registered trademark) (DuPont) and Neoceptor. (Registered trademark) (Astom).

(Electrolyte)
The flow battery includes a positive electrode electrolyte that includes a positive electrode active material and is supplied to the positive electrode, and a negative electrode electrolyte that includes a negative electrode active material and is supplied to the negative electrode.
The electrolytic solution may contain a liquid medium in which the active material is dispersed or dissolved.

The active material in the electrolytic solution preferably contains ions whose valence changes, and known materials can be used.
Specifically, the active material in the electrolytic solution is an oxidant / reductant satisfying the following reaction formula (4) or the reaction formula (5) (hereinafter sometimes referred to as a redox pair). May be included.
A ^{n +} + xe ⁻ ⇔A ^{(n−x) +} (4)
A ⁿ⁻ + xe ⁻ ⇔A ^{(n + x) −} (5)
In the general formula (4), n and x are integers and n ≧ x, and in the general formula (5), n and x are positive integers.

Examples of the redox pair satisfying the general formula (4) or (5) include Fe ³⁺ / Fe ²⁺ , Cr ³⁺ / Cr ²⁺ , Ga ³⁺ / Ga ²⁺ , Ti ³⁺ / Ti ²⁺ , Co ³⁺ / Co ²⁺ , Cu ^{2 +} / Cu ⁺ , V ³⁺ / V ²⁺ , V ⁵⁺ / V ⁴⁺ , Ce ⁴⁺ / Ce ³⁺ , Cl ⁻ / Cl ³⁻ , Br ⁻ / Br ³⁻ , Zn ²⁺ / Zn, Pb ²⁺ / Pb, Fe ²⁺ / Fe, Cr ²⁺ / Cr, Ga ²⁺ / Ga, Ti ²⁺ / Ti, Mn ²⁺ / Mn, Mg ²⁺ / Mg, Mg ⁺ / Mg, Ag ⁺ / Ag, Cd ²⁺ / Cd, Co ²⁺ / Co, Cu ²⁺ / Cu, Cu ⁺ / Cu, Hg ²⁺ / Hg, and the like.
Examples of the redox _couple other than the redox _couple satisfying the general formula (4) or the general formula (5) include I ₃ ⁻ / I ⁻ and S ₄ ²⁻ / S ₂ ²⁻ .

  In the flow battery of the present disclosure, it is preferable that at least one of the positive electrode and the negative electrode is accompanied by precipitation of an active material during a charge reaction or a discharge reaction. More preferably, the precipitate contains a metal. By depositing the active material in the electrolytic solution in the charge reaction or the discharge reaction, for example, the movement of ions from the positive electrode side to the negative electrode side through the diaphragm is suppressed, and the increase in ionic conduction resistance is suppressed. It tends to be a flow battery with high current density and high output.

An oxidation-reduction pair that accompanies deposition of metal or the like on at least one of the positive electrode and the negative electrode during charge reaction or discharge reaction, preferably as an oxidation-reduction pair that accompanies deposition of metal or the like on the negative electrode during charge reaction, For example, Zn ²⁺ / Zn, Pb ²⁺ / Pb, Fe ²⁺ / Fe, Cr ²⁺ / Cr, Ga ²⁺ / Ga, Ti ²⁺ / Ti, Mn ²⁺ / Mn, Mg ²⁺ / Mg, Mg ⁺ / Mg, Ag ⁺ / Ag, Cd ²⁺ / Cd, Co ²⁺ / Co, Cu ²⁺ / Cu, Cu ⁺ / Cu, Hg ²⁺ / Hg, and the like.

  Further, in the positive electrode, it is preferable that iodine precipitates during the charging reaction, and in the negative electrode, it is preferable that metal precipitates during the charging reaction, and it is more preferable that zinc precipitates.

  In addition, you may use the positive electrode electrolyte solution which contains these redox couples as a positive electrode active material, and the negative electrode electrolyte solution which contains these redox couples as a negative electrode active material. At this time, a combination of the positive electrode active material and the negative electrode active material may be selected so that the standard redox potential of the negative electrode is lower than the standard redox potential of the positive electrode.

The deposit preferably contains a metal, more preferably a metal. Further, the volume resistivity of the metal is preferably 1.0 × 10 ⁻⁵ Ωcm or less. When the deposit is a metal and the volume resistivity of the metal is 1.0 × 10 ⁻⁵ Ωcm or less, the metal or the like deposited on the electrode becomes a new current collector during charge and discharge, It tends to be able to suppress a decrease in the efficiency of electron transfer reaction during charging and discharging.

  The positive electrode electrolyte preferably contains water and contains at least one of iodine ions and iodine molecules as the positive electrode active material. When the positive electrode electrolyte contains water, the viscosity of the positive electrode electrolyte can be lowered, and particularly when the positive electrode electrolyte is flowed, the flow battery tends to have a higher output. In addition, by including at least one of iodine ions and iodine molecules as the positive electrode active material, a flow battery having excellent safety, low environmental load, and high energy density can be realized. At least one of iodine ions and iodine molecules is preferably used in a state of being dispersed or dissolved in a liquid medium.

Examples of iodine ions include I ⁻ , I ₃ ⁻ , I ₅ ^{− and the} like. Therefore, when the positive electrode electrolyte solution containing at least one iodine ion and iodine molecule as a positive electrode active material, for _{^{example, I -, I 3 -,}} I 5 - or if it contains and at least one I _2.

Further, positive electrode electrolyte may contain an iodine compound, the iodine _{compound, CuI, ZnI 2, NaI,} KI, HI, LiI, NH 4 I, BaI 2, CaI 2, MgI 2, SrI 2, CI ₄ , AgI, NI ₃ , tetraalkylammonium iodide, pyridinium iodide, pyrrolidinium iodide, sulfonium iodide and the like can be mentioned. The iodine compound may be ionized in the positive electrode electrolyte.

Iodine ions are preferably dissolved in the positive electrode electrolyte. When water is used as the liquid medium, the iodine compound is preferably at least one of NaI, KI and NH ₄ I. Since NaI, KI and NH ₄ I have high solubility in water, the energy density of the flow battery can be further improved by using at least one of NaI, KI and NH ₄ I.

When the positive electrode electrolyte contains at least one of iodine ions and iodine molecules as the positive electrode active material, the main redox pair in the charge / discharge reaction is I ⁻ / I ₃ ⁻ , and the reaction formula of the following formula (6) Happens.
3I ⁻ ⇔I ₃ ⁻ + 2e ⁻ (6)
In the reaction of the formula (6), precipitation of iodine molecules does not occur, and high current density and high output characteristics can be realized in the flow battery.

When the positive electrode electrolyte contains at least one of iodine ions and iodine molecules as the positive electrode active material, in addition to the reaction of the formula (6), a reaction such as the following formula (7) is involved depending on charge / discharge conditions and the like. Sometimes.
2I ⁻ ⇔I ₂ + 2e ⁻ (7)
In the reaction of the formula (7), it means that the I ⁻ ion is oxidized during the charging to generate I ₂ . When I ₂ is generated, I ₂ is deposited on the electrode surface as a solid, which may reduce the porosity of the electrode and increase the pressure loss. Therefore, when at least one of iodine ions and iodine molecules is used as the positive electrode active material, at least two regions with different porosity are provided in the positive electrode in the flow direction of the positive electrode electrolyte from the viewpoint of suppressing an increase in pressure loss. It is preferable that the porosity of the positive electrode is higher on the inflow side of the positive electrode electrolyte than the outflow side of the positive electrode electrolyte, or the porosity on the diaphragm side of the positive electrode is on the opposite side in the thickness direction. It is more preferable that the porosity is higher.

In the positive electrode electrolyte, the total content of iodine compounds and iodine molecules is preferably 1% by mass to 80% by mass, more preferably 3% by mass to 70% by mass, and 5% by mass to 50% by mass. % Is more preferable. By setting the total content of the iodine compound and iodine molecules to 1% by mass or more, a flow battery suitable for practical use with a high capacity tends to be obtained. Moreover, it exists in the tendency for the solubility or dispersibility in a liquid medium to become favorable because the total content rate of an iodine compound and an iodine molecule shall be 80 mass% or less. In addition, the content rate of an iodine compound and an iodine molecule represents the total content rate of the ion derived from an iodine compound and an iodine molecule in a positive electrode electrolyte, and the ion derived from the iodine compound in a positive electrode electrolyte (for example, I ⁻ , I ₃ ⁻ , I ₅ ⁻ and their counter ions) and the total content of iodine molecules (I ₂ ).

The negative electrode electrolyte preferably contains water and preferably contains at least one of zinc ions (Zn ²⁺ ), zinc (Zn) and polysulfide as a negative electrode active material, and contains water and zinc ions (Zn) as a negative electrode active material. More preferably, it includes at least one of ( ²⁺ ) and zinc (Zn). When the negative electrode electrolyte contains water, the viscosity of the negative electrode electrolyte can be reduced, and particularly when the negative electrode electrolyte is flowed, the flow battery tends to have a higher output. In addition, by including at least one of zinc ions and zinc as the negative electrode active material, a flow battery having excellent safety, low environmental load, and high energy density can be realized. The zinc ion may be derived from a compound containing zinc. The compounds containing zinc include zinc iodide, zinc acetate, zinc nitrate, zinc terephthalate, zinc sulfate, zinc chloride, zinc bromide, zinc oxide, zinc peroxide, zinc selenide, zinc diphosphate, acrylic acid Examples thereof include zinc, zinc hydroxide carbonate, zinc stearate, zinc propionate, zinc fluoride, and zinc citrate. Of these, zinc chloride and zinc sulfate are preferable.

  As the electrolytic solution, a combination of a positive electrode electrolytic solution containing at least one of iodine molecules and iodine ions as a positive electrode active material and a negative electrode electrolytic solution containing a redox pair that accompanies deposition of metal or the like as a negative electrode active material, A combination of a positive electrode electrolyte containing at least one of iodine molecules and iodine ions as the positive electrode active material and a negative electrode electrolyte containing at least one of zinc and zinc ions as the negative electrode active material is more preferable.

  There is no restriction | limiting in particular in the content rate of the positive electrode active material in positive electrode electrolyte solution, From the point of the activity of charging / discharging reaction, it is preferable that it is 0.1 mass%-80.0 mass%, for example, 0.5 mass%. It is more preferably ˜75.0% by mass, and further preferably 1.0% by mass to 70.0% by mass.

  There is no restriction | limiting in particular in the content rate of the negative electrode active material in negative electrode electrolyte solution, From the point of the activity of charging / discharging reaction, it is preferable that it is 0.1 mass%-80.0 mass%, for example, 0.5 mass% It is more preferably ˜75.0% by mass, and further preferably 1.0% by mass to 70.0% by mass.

<Liquid medium>
The electrolytic solution is preferably one in which at least one active material is dissolved or dispersed in a liquid medium. A liquid medium means a medium in a liquid state at room temperature (25 ° C.).

  Liquid media include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl isopropyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-pentyl ketone, methyl-n-hexyl ketone, diethyl ketone, dipropyl ketone , Ketone solvents such as diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl ether, Tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di -N-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n-butyl ether, triethylene glycol Ethylene glycol Ru-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene glycol methyl n- Hexyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol di-n-butyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl ether, dipropylene glycol Methyl-n-butyl ether, dipropylene glycol Cold di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl-n -Butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl-n-butyl ether, tetra Propylene glycol di-n-butyl ether, tetrapropylene Ether solvents such as ethylene glycol methyl-n-hexyl ether; carbonate solvents such as propylene carbonate, ethylene carbonate, diethyl carbonate; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, Sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, acetic acid Cyclohexyl, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate Dipropylene glycol ethyl ether, glycol diacetate, methoxytriethylene glycol acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, lactic acid n-butyl, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene Ester solvents such as glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; acetonitrile, N-methyl Aprotic polarities such as rupyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide Solvent: methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, t-pentanol , 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-oct Tanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2- Alcohol solvents such as propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether Diethylene glycol mono-n-hexyl ether, triethylene glycol monoethyl ether, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, etc. And terpene solvents such as α-terpinene, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, oximene, and ferrandrene; water and the like. A liquid medium may be used individually by 1 type, and may use 2 or more types together.

<Polymer>
When the electrolytic solution (particularly, the positive electrode electrolytic solution) contains at least one of iodine molecules and iodine ions, it may contain a polymer that forms a complex with iodine ions. When the electrolytic solution contains a polymer that forms a complex with iodine ions, precipitation of iodine molecules that may occur during the oxidation-reduction reaction of iodine ions is suppressed, and the flow battery tends to have high output. Polymers that form complexes with iodine ions include nylon 6, polytetrahydrofuran, polyvinyl alcohol, polyacrylonitrile, poly-4-vinylpyridine, polyvinylpyrrolidone, polymethyl (meth) acrylate, polytetramethylene ether glycol, polyacrylamide, polypropylene glycol , Polyethylene glycol, polyethylene oxide and the like. These polymers may be used individually by 1 type, and may use 2 or more types together.

<Good solvent for iodine molecules>
Moreover, when electrolyte solution (especially positive electrode electrolyte solution) contains at least one of an iodine molecule and an iodine ion, it is preferable to contain the good solvent with respect to an iodine molecule other than water. When the electrolytic solution contains a good solvent for iodine molecules, the iodine film formed on the electrode during the charge / discharge reaction is thinned and the inhibition of the charge / discharge reaction by the film tends to be suppressed. Good solvents for iodine molecules include amides such as dimethylformamide, diethylformamide, acetamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, ketones such as acetone and methylethylketone, methyl acetate, ethyl acetate, and methyl nicotinate. Examples thereof include esters, sulfoxides such as dimethyl sulfoxide, alcohols such as ethanol and ethylene glycol, ethers such as diethyl ether, pyridine derivatives such as nicotinamide and cyanopyridine. As a good solvent for iodine molecules, one kind may be used alone, or two or more kinds may be used in combination.

<Supporting electrolyte>
The positive electrode electrolyte and the negative electrode electrolyte may further contain a supporting electrolyte. When the electrolytic solution contains the supporting electrolyte, the ionic conductivity in the electrolytic solution can be increased, and the internal resistance of the flow battery tends to be reduced.

Examples of the supporting electrolyte include HCl, HNO ₃ , H ₂ SO ₄ , HClO ₄ , NaCl, Na ₂ SO ₄ , NaClO ₄ , KCl, K ₂ SO ₄ , KClO ₄ , NaOH, LiOH, KOH, alkylammonium salt, Examples include alkyl imidazolium salts, alkyl piperidinium salts, and alkyl pyrrolidinium salts. A supporting electrolyte may be used individually by 1 type, or may use 2 or more types together.

  The positive electrode electrolyte and the negative electrode electrolyte may further contain a pH buffer. Examples of the pH buffer include an acetate buffer, a phosphate buffer, a citrate buffer, a borate buffer, a tartar buffer, and a Tris buffer.

(Bipolar plate)
The flow battery includes a pair of bipolar plates that are provided on the side opposite to the side facing the negative electrode in the positive electrode and on the side opposite to the side facing the positive electrode in the negative electrode, and each exchange electrons with the positive electrode and the negative electrode. Is preferred. Examples of the bipolar plate include a carbon material system and a metal material system, and it is preferable to use a carbon material system from the viewpoints of cost and corrosion resistance against an electrolytic solution. The bipolar plate is preferably a plate-like bipolar plate obtained by subjecting a composite material obtained by kneading graphite powder, a binder or the like to molding such as pressing or injection. In addition, in the case of a single cell structure having one positive electrode and one negative electrode as shown in FIG. 2 described later, there is no need for a bipolar plate, and the corrosion of the current collector plate due to the current collector plate coming into contact with the electrolyte is suppressed. A bipolar plate may be provided from the point.

(Reference electrode)
The flow battery may include a positive electrode reference electrode for measuring the positive electrode potential, or may include a negative electrode reference electrode for measuring the negative electrode potential. In the flow battery, the reference electrode for the positive electrode and the reference electrode for the negative electrode are not indispensable components, and the positive electrode reference electrode and the negative electrode reference electrode are used as necessary to measure the positive electrode potential and the negative electrode potential. May be.

Examples of the reference electrode include an Ag / AgCl reference electrode, an Ag / AgI reference electrode, an Ag / AgBr reference electrode, and a Zn / Zn ²⁺ reference electrode.

(Cathode electrolyte reservoir and anode electrolyte reservoir)
The flow battery includes a positive electrode electrolyte storage part that stores a positive electrode electrolyte containing a positive electrode active material and a negative electrode electrolyte storage part that stores a negative electrode electrolyte containing a negative electrode active material. As a positive electrode electrolyte storage part and a negative electrode electrolyte storage part, an electrolyte storage tank is mentioned, for example.

(Liquid feeding part)
The flow battery preferably includes a liquid feeding part that circulates the positive electrode electrolyte between the positive electrode and the positive electrode electrolyte reservoir and circulates the negative electrode electrolyte between the negative electrode and the negative electrode electrolyte reservoir. The positive electrode electrolyte stored in the positive electrode electrolyte reservoir is supplied to the positive electrode chamber where the positive electrode is disposed through the liquid delivery unit, and the negative electrode electrolyte stored in the negative electrode electrolyte reservoir is disposed through the liquid feeder. Supplied to the negative electrode chamber.

  In the flow battery, for example, the liquid supply unit circulates the positive electrode electrolyte between the positive electrode chamber and the positive electrode electrolyte storage unit and circulates the negative electrode electrolyte between the negative electrode chamber and the negative electrode electrolyte storage unit. And a liquid feed pump.

  The amount of the positive electrode electrolyte to be circulated between the positive electrode chamber and the positive electrode electrolyte reservoir and the amount of the negative electrode electrolyte to be circulated between the negative electrode chamber and the negative electrode electrolyte reservoir are appropriately adjusted using a liquid feed pump, respectively. What is necessary is just to set suitably according to a battery scale, for example.

(Charge / discharge characteristics of flow battery)
As the charge / discharge characteristics of the flow battery, in addition to the battery capacity, current efficiency (CE), voltage efficiency (VE), and power efficiency (EE) are listed.
The current efficiency CE is a ratio between the amount of electricity obtained by discharging and the amount of electricity required for charging. The voltage efficiency VE is a ratio of the average voltage during discharging and the average voltage during charging. The power efficiency EE is a ratio between the discharged electric energy and the charged electric energy.

  FIG. 1 is a schematic diagram illustrating an example of a member configuration of a flow battery according to the present disclosure. The positive electrode 1 a and the negative electrode 1 b are separated by a diaphragm 2, and the insulating porous body 16 is disposed between the positive electrode 1 a and the diaphragm 2 and between the negative electrode 1 b and the diaphragm 2. During the charge / discharge reaction, electrons are exchanged between each electrode and the bipolar plate 5. The bipolar plate 5 may be used as the bipolar plate frame 6. The bipolar plate frame 6 has a structure in which the outer peripheral portion is surrounded by the sealing material 3 or the like in a state where the bipolar plate 5 having the same area as each electrode is exposed. Further, the bipolar plate 5 is in contact with the current collector plate 9 and is connected to an external terminal for charging and discharging. Moreover, the sealing material 3 and the liquid separation plate 4 are arrange | positioned in the outer peripheral part of each electrode, The slit (a groove | channel, not shown) is formed in the liquid separation plate 4, and electrolyte solution (not shown) is each shown. It can be distributed in the electrode.

  Specifically, the positive electrode electrolyte injected from the positive electrode electrolyte electrode chamber inlet 8a reaches the positive electrode separator 4 and flows into the positive electrode 1a through the slit. Here, the flow direction of the positive electrode electrolyte in FIG. 1 is from the bottom to the top. Next, through the slit formed in the positive electrode separator plate 4 from the upper end of the positive electrode 1a, the ends of the positive electrode seal material 3, the diaphragm 2, the negative electrode seal material 3, the negative electrode separator plate 4, and the negative electrode bipolar plate frame 6 are provided. It flows out from the positive electrode electrolyte electrode chamber outlet 8b through the positive electrode electrolyte flow path (sometimes called a manifold) formed in the section.

  Moreover, the negative electrode electrolyte injected from the negative electrode electrolyte electrode chamber inlet 8c reaches the liquid separator 4 of the negative electrode, and circulates in the negative electrode 1b via the slit. Here, the flow direction of the negative electrode electrolyte in FIG. 1 is from the bottom to the top. Next, through the slit formed in the negative electrode separation plate 4 from the upper end of the negative electrode 1b, the ends of the negative electrode sealing material 3, the diaphragm 2, the positive electrode sealing material 3, the positive electrode liquid separation plate 4, and the positive electrode bipolar plate frame 6 It flows out from the negative electrode electrolyte electrode chamber outlet 8d through a negative electrode electrolyte flow path (sometimes called a manifold) formed in the section.

  FIG. 2 is a schematic diagram of a flow battery. That is, the positive electrode electrolyte solution 10a flowing out from the positive electrode electrolyte electrode chamber outlet 8b passes through the pipe (circulation path) 13 and is stored in the positive electrode electrolyte storage part 11a. Further, the negative electrode electrolyte 10b flowing out from the negative electrode electrolyte electrode chamber outlet 8d passes through the pipe (circulation path) 13 and is stored in the negative electrode electrolyte storage part 11b. Thus, during charging and discharging, the positive electrode electrolyte 10a and the negative electrode electrolyte 10b are circulated in the positive electrode 1a and the negative electrode 1b, respectively, by operating the liquid feed pump 12, and the positive electrode electrolyte reservoir 11a and The cycle of returning to the negative electrode electrolyte storage part 11b again is repeated. Electrical control when charging / discharging is performed using the power supply 14 and the external load 15. Further, in FIG. 2, insulating porous bodies 16 are disposed between the positive electrode 1 a and the diaphragm 2 and between the negative electrode 1 b and the diaphragm 2, respectively.

  FIG. 3 is a schematic view of a flow battery in a state where a combination of positive electrode and negative electrode members (also referred to as cells) shown in FIG. 2 is electrically connected in series to form a stack structure. By increasing the number of cells and forming a stack structure, the output voltage of the flow battery can be increased. Here, the positive electrode 1a and the negative electrode 1b of the adjacent cells are electrically connected via the bipolar plate 5, and can exchange electrons during charging and discharging. Moreover, the positive electrode electrolyte solution 10a and the negative electrode electrolyte solution 10b are the same as FIG. 2 except having changed the structure of the piping (circulation path) 13 so that it can distribute | circulate in parallel with each electrode arrange | positioned in series. In the flow battery in a stack structure, the side where the positive electrode and the negative electrode face each other is the side where the bipolar plate is not provided between the positive electrode and the negative electrode, and in FIG. 3, the positive electrode 1a and the negative electrode 1b. The side where the diaphragm 2 exists is indicated. Also in FIG. 3, in each cell, an insulating porous body 16 is disposed between the positive electrode 1 a and the diaphragm 2 and between the negative electrode 1 b and the diaphragm 2.

[Flow battery system]
The flow battery system of the present disclosure includes the above-described flow battery of the present disclosure and a control unit that controls charging / discharging of the flow battery. The flow battery system of the present disclosure may be a flow battery system in which the flow battery is a flow battery, and the control unit may be configured to control charge / discharge of the flow battery.

(Control part)
The flow battery system includes a control unit that controls charging and discharging of the flow battery. For example, the control unit may be configured to control the charging voltage in the flow battery system, the charging potential of the positive electrode and the negative electrode, and the like.
The charging voltage indicates a potential difference between the negative electrode and the positive electrode, and the charging potential indicates a potential difference with respect to a reference electrode (reference electrode) having a constant reference potential.

[Power generation system]
A power generation system of the present disclosure includes a power generation device and the flow battery system of the present disclosure described above. The power generation system of the present disclosure can level and stabilize power fluctuations or stabilize power supply and demand by combining a flow battery system and a power generation device.

  The power generation system includes a power generation device. The power generation device is not particularly limited, and examples thereof include a power generation device that generates power using renewable energy, a hydroelectric power generation device, a thermal power generation device, and a nuclear power generation device. Among them, a power generation device that generates power using renewable energy is preferable. .

  The amount of power generated by power generators using renewable energy varies greatly depending on weather conditions, etc., but when combined with a flow battery system, the generated power can be leveled and supplied to the power system. .

  Examples of the renewable energy include wind power, sunlight, wave power, tidal power, running water, tide, geothermal heat, etc., preferably wind power or sunlight.

  In some cases, generated power generated using renewable energy such as wind power and sunlight is supplied to a high-voltage power system. In general, wind power generation and solar power generation are affected by weather such as wind direction, wind power, and weather, and thus generated power is not constant and tends to fluctuate greatly. If the generated power that is not constant is supplied to the high-voltage power system as it is, it is not preferable because it promotes instability of the power system. For example, the power generation system of the present embodiment can level the generated power waveform to the target power fluctuation level by superimposing the charge / discharge waveform of the flow battery system on the generated power waveform.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these Examples.

<Example 1>
(A) Configuration of electrodes (positive electrode and negative electrode) A carbon felt electrode (AAF304ZS, Toyobo Co., Ltd.) was used as the electrode. The thickness of the electrode as a product is 4.3 mm, and the density is 0.08 g / cm ³ . When attached to the flow battery, the electrode was compressed to a thickness of 2.5 mm. The area of the surface of the electrode perpendicular to the thickness direction was 150 mm × 100 mm. In addition, the porosity of the electrode after compression was 94.1%.

(B) Preparation of Electrolyte Solution An aqueous positive electrode electrolyte solution containing 6.0 mol / L sodium iodide (NaI) was prepared. Also, an aqueous negative electrode electrolyte solution containing 2.0 mol / L zinc chloride (ZnCl ₂ ) and _2.5 mol / L ammonium chloride (NH ₄ Cl) as a pH adjuster was prepared.

(C) Configuration of Flow Battery In addition to the electrode prepared above and the electrolyte, a cation exchange membrane “Nafion 117” was used as a diaphragm. Further, a net-like insulating porous body made of polyethylene having the pattern shown in FIG. 4A was disposed between the positive electrode and the diaphragm and between the negative electrode and the diaphragm. The area of the surface of the insulating porous material perpendicular to the thickness direction was the same size as the electrode, and the thickness of the insulating porous material was 0.3 mm. The bulk density determined by gravimetric method was 0.14 g / cm ³ .
In addition, a bipolar plate (Showa Denko Co., Ltd.) made of highly conductive graphite fine powder as a bipolar plate, an ethylene propylene rubber sheet as a sealing material, and a copper (Cu) plate plated with nickel (Ni) as a current collector plate Also, a single cell type flow battery as shown in FIGS. 1 and 2 was produced using a PVC tank, piping and a circulation pump (Iwaki Pump Co., Ltd.). Note that, as described above, the member in the portion sandwiched between the current collector plates was appropriately compressed so that the attached positive electrode and negative electrode had a thickness of 2.5 mm. At this time, it was confirmed that there were no gaps and steps at the boundary between the compression-filled electrodes.

(D) Evaluation of flow battery characteristics Pressure sensors (HPS-24-F, Surpass Industries Co., Ltd.) were attached to the inflow side and outflow side piping sections of the positive electrode electrolyte and the negative electrode electrolyte of the produced flow battery. Next, 0.50 L each of the positive electrode electrolyte and the negative electrode electrolyte prepared above are stored in the positive electrode electrolyte reservoir and the negative electrode electrolyte reservoir, and the flow rates of the positive electrode electrolyte and the negative electrode electrolyte are adjusted using a liquid feed pump. The positive electrode electrolyte and the negative electrode electrolyte were circulated through the positive electrode and the negative electrode, respectively, while adjusting the output of the liquid feed pump so as to be 0.20 L per minute.
Thereafter, after confirming that the flow rates of the positive electrode electrolyte and the negative electrode electrolyte were constant, a charge / discharge experiment was performed at a current density of 50 mA / cm ² . Specifically, the current density is made constant, the battery is charged until the cell voltage reaches 1.5V, and then discharged at the same current density until the cut-off voltage becomes 0.7V, and the electric capacity (Ah) of the battery is obtained. It was.
The capacity retention rate was calculated using the following equation after measuring the discharge capacity (Ah) at the first cycle and the discharge capacity (Ah) at the 100th cycle.
Capacity retention rate (%) = (discharge capacity at the 100th cycle / discharge capacity at the first cycle) × 100
When evaluating the characteristics of the flow battery, the temperature was kept at 25 ° C.

<Example 2>
In Example 1, filter paper (Whatman Corp., thickness: 0.21 mm) was used in place of the net-like insulating porous body made of polyethylene, and the flow path having the pattern shown in FIG. 6A was formed. The width of the flow path was 1.5 mm, and the depth of the flow path in each electrode after compression was 1.0 mm. Except for these, a flow battery was produced in the same manner as in Example 1, and the characteristics were evaluated.

<Example 3>
In Example 1, instead of the net-like insulating porous body made of polyethylene, a polyolefin porous film (Celgard Co., Ltd., product number: 3501, hydrophilized) was used to form a flow path having the pattern shown in FIG. 6A. The width of the flow path was 1.5 mm, and the depth of the flow path in each electrode after compression was 1.0 mm. Except for these, a flow battery was produced in the same manner as in Example 1, and the characteristics were evaluated.

<Example 4>
In the positive electrode and the negative electrode, two regions having different porosity were formed in the electrolyte flow direction. Specifically, the carbon felt electrode used in Example 1 and another carbon felt electrode (AAF153ZS, Toyobo Co., Ltd., thickness is 3.0 mm, density is 0.05 g / cm ³ ) are shown in Table 1. Combined with the dimensions shown. The porosity of the carbon felt electrode (AAF153ZS) mounted on the flow battery was 97.3%. Other than that was carried out similarly to Example 1, and produced the flow battery and evaluated the characteristic.

<Example 5>
In Example 1, channels were formed on the surfaces of the positive electrode and the negative electrode. Specifically, a flow path having a pattern shown in FIG. 6A was formed on the bipolar plate side of each electrode. The width of the flow path was 1.5 mm, and the depth of the flow path in each electrode after compression was 1.0 mm. Other than that was carried out similarly to Example 1, and produced the flow battery and evaluated the characteristic.

<Example 6>
In Example 5, the specification of the insulating porous material was changed as shown in Table 1. Specifically, an insulating porous body made of a cupra nonwoven fabric shown in FIG. 4B was used. The area of the surface of the insulating porous body perpendicular to the thickness direction was the same size as the electrode, and the thickness was 0.4 mm. Further, the bulk density determined by a gravimetric method was 0.35 g / cm ³ . Other than that was carried out similarly to Example 5, produced the flow battery, and evaluated the characteristic.

<Example 7>
In Example 5, the specification of the insulating porous material was changed as shown in Table 1. Specifically, an insulating porous body made of a glass nonwoven fabric shown in FIG. 4B was used. The area of the surface of the insulating porous material perpendicular to the thickness direction was the same size as the electrode, and the thickness was 0.3 mm. The bulk density determined by gravimetric method was 0.55 g / cm ³ . Other than that was carried out similarly to Example 5, produced the flow battery, and evaluated the characteristic.

<Example 8>
In Example 5, a flow battery was produced in the same manner as in Example 5 except that the flow rate of the electrolytic solution for evaluating the characteristics of the flow battery was changed from 0.20 L / min to 0.35 L / min. The characteristics were evaluated.

<Example 9>
In Example 5, except that the current density at the time of evaluating the characteristics of the flow battery was changed from 50 mA / cm ² to 100 mA / cm ² , a flow battery was produced and the characteristics were evaluated in the same manner as in Example 5. did.

<Example 10>
In Example 5, the specification of the insulating porous material was changed as shown in Table 1. Specifically, an insulating porous body made of a glass nonwoven fabric shown in FIG. 4B was used. The area of the surface of the insulating porous body perpendicular to the thickness direction was the same size as the electrode, and the thickness was 0.5 mm. The bulk density determined by gravimetric method was 3.85 g / cm3. Other than that was carried out similarly to Example 5, produced the flow battery, and evaluated the characteristic.

<Comparative Example 1>
In Example 1, a flow battery was prepared and the characteristics were evaluated in the same manner as in Example 1 except that the insulating porous material was not disposed between the positive electrode and the diaphragm and between the negative electrode and the diaphragm.

<Comparative Example 2>
In Example 5, a flow battery was prepared and the characteristics were evaluated in the same manner as in Example 5 except that the insulating porous material was not disposed between the positive electrode and the diaphragm and between the negative electrode and the diaphragm.

  About the flow battery of each Example and each comparative example, a structure and a characteristic are shown in Tables 1-3.

As shown in Table 3, it was confirmed that the flow batteries produced in Examples 1 to 10 exhibited a high capacity retention rate even after 100 cycles. In particular, when Example 1 and Examples 4, 5, 8, and 9 using an insulating porous material made of the same material are compared, two regions or surface channels having different porosity are provided in the positive electrode and the negative electrode. It was confirmed that those having a higher capacity retention rate were observed.
On the other hand, the capacity retention rates in Comparative Example 1 and Comparative Example 2 were greatly reduced. This is probably because the insulating porous material is not disposed between the negative electrode and the diaphragm, and therefore, the Zn dendrite formed on the surface of the negative electrode during charging / discharging penetrates the diaphragm, and so on. .
In addition, the capacity retention rate of Example 10 was better than that of Comparative Example 1 and Comparative Example 2, while the capacity retention rate was lower than that of Examples 1-9. This is thought to be because the bulk density of the disposed insulating porous body was large and the porosity was reduced, so that the electrolyte flowing through the insulating porous body was reduced and Zn dendrite was easily formed on the negative electrode surface. .

  DESCRIPTION OF SYMBOLS 1 ... Electrode, 1a ... Positive electrode, 1b ... Negative electrode, 2 ... Diaphragm, 3 ... Sealing material, 4 ... Separation plate, 5 ... Bipolar plate, 6 ... Dipolar plate frame, 7 ... Polar chamber, 8a ... Positive electrode cathode chamber Inlet, 8b ... Positive electrode electrolyte electrode chamber outlet, 8c ... Negative electrode electrolyte electrode chamber inlet, 8d ... Negative electrode electrolyte electrode chamber outlet, 9 ... Current collector plate, 10a ... Positive electrode electrolyte, 10b ... Negative electrode electrolyte, 11a ... Positive electrode Electrolyte storage part, 11b ... Negative electrode electrolyte storage part, 12 ... Liquid feed pump, 13 ... Pipe (circulation path), 14 ... Power source, 15 ... External load, 16 ... Insulating porous body, 17 ... Surface flow path

Claims (17)

  A positive electrode, a negative electrode, a positive electrode electrolyte containing a positive electrode active material and supplied to the positive electrode, a positive electrode electrolyte reservoir for storing the positive electrode electrolyte, a negative electrode active material, and supplied to the negative electrode A negative electrode electrolyte solution, a negative electrode electrolyte storage part for storing the negative electrode electrolyte solution, a diaphragm separating the positive electrode and the negative electrode, at least a part between the diaphragm and the negative electrode, and the diaphragm and the positive electrode An insulating porous body disposed on at least one of at least a part of the flow battery. The insulating porous body, the bulk density was determined ^{gravimetrically,} is ^{0.03g / cm 3 ~5.00g / cm 3} , a flow cell according to claim 1.   The flow battery according to claim 1 or 2, wherein the insulating porous body includes at least one selected from a polymer, paper, glass, ceramics, and a metal having a surface insulating coating.   The flow battery according to any one of claims 1 to 3, wherein the insulating porous body has a three-dimensional continuous void portion. In the case where the insulating porous body is disposed at least partially between the diaphragm and the positive electrode, the positive electrode electrolyte is contained in the insulating porous body disposed in the positive electrode and between the positive electrode and the diaphragm. Circulate
When the insulating porous body is disposed at least at a part between the diaphragm and the negative electrode, the negative electrode electrolyte is contained in the insulating porous body disposed in the negative electrode and between the negative electrode and the diaphragm. The flow battery according to any one of claims 1 to 4, wherein the battery is distributed. When the insulating porous body is disposed at least partially between the diaphragm and the positive electrode, the thickness of the insulating porous body disposed between the positive electrode and the diaphragm with respect to the thickness of the positive electrode The ratio is 0.002 to 0.750,
When the insulating porous body is disposed at least partly between the diaphragm and the negative electrode, the thickness of the insulating porous body disposed between the negative electrode and the diaphragm with respect to the thickness of the negative electrode The flow battery according to any one of claims 1 to 5, wherein the ratio is 0.002 to 0.750.   The flow battery according to claim 1, wherein at least one of the positive electrode and the negative electrode is accompanied by precipitation of an active material during a charge reaction or a discharge reaction.   The flow battery according to claim 7, wherein iodine is deposited in the positive electrode during a charging reaction.   The flow battery according to claim 7 or 8, wherein zinc is deposited during the charging reaction in the negative electrode.   The flow battery according to any one of claims 1 to 9, wherein the positive electrode electrolyte includes water and includes at least one of iodine ions and iodine molecules as the positive electrode active material.   11. The flow battery according to claim 1, wherein the negative electrode electrolyte contains water and contains at least one of zinc ions and zinc as the negative electrode active material.   The insulating porous body according to any one of claims 1 to 11, wherein the insulating porous body is disposed in at least a part between the diaphragm and the negative electrode and at least a part between the diaphragm and the positive electrode. Flow battery.   The flow battery according to any one of claims 1 to 12, wherein the positive electrode and the negative electrode have at least one of at least two regions having different porosity and a surface flow path.   The flow battery according to claim 13, wherein the at least two regions having different porosity are formed in at least one of a flowing direction of the electrolytic solution and a thickness direction of the electrode.   The flow battery according to claim 13 or 14, wherein the surface flow path is formed on at least one of the diaphragm side and the opposite side of the diaphragm so as to be concave with respect to the electrode surface. The flow battery according to any one of claims 1 to 15,
A control unit for controlling charging and discharging of the flow battery;
A flow battery system comprising: A power generator,
A power generation system comprising: the flow battery system according to claim 16.