JP2017010809A - Electrode for redox flow battery and redox flow battery - Google Patents

Abstract

A redox flow battery and a redox flow battery electrode having low cell resistance and excellent electrolyte flowability are provided.
A redox flow battery comprising a positive electrode, a negative electrode, and a diaphragm interposed between the positive electrode and the negative electrode, wherein one of the positive electrode and the negative electrode Is provided with a porous plate mainly composed of a continuous three-dimensional network structure formed by combining carbon, and the other electrode includes a fiber aggregate mainly composed of a plurality of carbon fibers intertwined with each other, The porous plate is a redox flow battery having an opening on at least one surface thereof and a recess through which an electrolytic solution is circulated.
[Selection] Figure 1

Description

  The present invention relates to a redox flow battery which is one of fluid flow storage batteries, and an electrode for a redox flow battery. In particular, the present invention relates to a redox flow battery having low cell resistance and excellent electrolyte flowability.

  One type of storage battery is a redox flow battery (hereinafter sometimes referred to as an RF battery) in which an electrolytic solution is supplied to an electrode to perform a battery reaction. RF battery (1) Easy to increase the capacity of megawatt class (MW class), (2) Long life, (3) Battery state of charge (SOC) can be accurately monitored It has features such as (4) battery output and battery capacity can be designed independently and has a high degree of design freedom, and is expected to be suitable for storage batteries for power system stabilization applications.

  An RF battery typically includes a battery cell including a positive electrode to which a positive electrode electrolyte is supplied, a negative electrode to which a negative electrode electrolyte is supplied, and a diaphragm interposed between both electrodes. And In large-capacity applications, a so-called cell stack configured by stacking a plurality of battery cells and tightening them to some extent is used.

  As the positive electrode and the negative electrode, a plate-like carbon material (hereinafter sometimes referred to as a fiber assembly material) in which carbon fibers such as carbon felt are aggregated is used (Patent Document 1). Patent document 1 is disclosing the electrode which provided the several linear groove | channel in parallel in the surface facing the diaphragm in a fiber assembly.

JP 2002-246035 A

  Compared to a redox flow battery, it is desired that the cell resistance is small and the flowability of the electrolyte is excellent. Moreover, an electrode capable of constructing such a redox flow battery is desired.

  When a groove is provided in a fiber aggregate such as carbon felt as described in Patent Document 1, the flowability of the electrolyte can be improved. However, since the fiber assembly is excellent in flexibility, if it is tightened like the above-mentioned cell stack, the predetermined groove may not be sufficiently maintained, for example, the groove becomes shallow due to deformation over time. . If the groove becomes shallow, it becomes difficult to obtain the effect of improving the flowability of the electrolytic solution. Therefore, a redox flow battery excellent in the flowability of the electrolyte over a long period of time is desired.

  For example, it is considered that the deformation with time can be suppressed to some extent by increasing the filling amount (weight per unit area) of the carbon fiber to form a dense fiber assembly. Moreover, if the filling amount of carbon fiber is increased, the battery reaction field is increased, the battery reactivity is increased, and the cell resistance can be reduced. However, if the fiber assembly is densified to such a degree that the above deformation can be sufficiently suppressed, the flowability of the electrolytic solution is poor.

  Accordingly, one of the objects of the present invention is to provide a redox flow battery and a redox flow battery electrode that have low cell resistance and excellent electrolyte flowability.

A redox flow battery according to one embodiment of the present invention includes a positive electrode, a negative electrode, and a diaphragm interposed between the positive electrode and the negative electrode.
Of the positive electrode and the negative electrode, one electrode includes a porous plate mainly composed of a continuous three-dimensional network structure formed by bonding carbon, and the other electrode includes a plurality of intertwined ones. A fiber assembly mainly composed of carbon fiber is provided.
The porous plate is provided with a recess that is open on at least one surface thereof and through which an electrolytic solution is circulated.

  An electrode for a redox flow battery according to an aspect of the present invention is mainly composed of a continuous three-dimensional network structure formed by bonding carbon, and includes a recess that is open at least on one surface and through which an electrolyte is distributed. A laminated body is provided in which a porous plate and a fiber assembly mainly composed of a plurality of carbon fibers that are arranged opposite to a surface of the porous plate where the concave portion is opened and intertwined with each other are laminated.

  The above redox flow battery has low cell resistance and excellent electrolyte circulation.

  The above redox flow battery electrode has a low cell resistance and can build a redox flow battery excellent in the flowability of the electrolyte.

2 is a cross-sectional explanatory view schematically showing the redox flow battery of Embodiment 1. FIG. 4 is a cross-sectional explanatory view schematically showing a redox flow battery of Embodiment 2. FIG. 6 is a cross-sectional explanatory view schematically showing a redox flow battery according to Embodiment 3. FIG. 6 is a cross-sectional explanatory view schematically showing a redox flow battery of Embodiment 4. FIG. 6 is a cross-sectional explanatory view schematically showing a redox flow battery of Embodiment 5. FIG. It is a disassembled perspective view which shows an example of the electrode for redox flow batteries of embodiment. It is explanatory drawing which shows the basic composition of a redox flow battery system provided with the redox flow battery etc. of embodiment, and a basic operating principle. It is a schematic block diagram which shows an example of the cell stack with which the redox flow battery etc. of embodiment are equipped.

[Description of Embodiment of the Present Invention]
The present inventors examined a plate-like porous material mainly composed of a continuous three-dimensional network structure formed by bonding carbon as a carbon material constituting an electrode for a redox flow battery. The porous material has a three-dimensional network structure formed by bonding the above-described carbon, and thus has a higher rigidity than the fiber aggregate in which the above-described carbon fibers are intertwined. For this reason, the porous material is difficult to be deformed, and it has been found that when the groove is provided, the flowability of the electrolytic solution is excellent. However, as shown in a test example to be described later, it has been found that when a porous material having grooves is used for both positive and negative electrodes, cell resistance is high. As a result of further investigation, it has been found that a redox flow battery having a low cell resistance can be constructed in addition to being excellent in the flowability of the electrolytic solution when both a porous material having grooves and a fiber aggregate such as carbon felt are provided. Obtained. The present invention is based on the above findings. First, the contents of the embodiment of the present invention will be listed and described.

(1) A redox flow battery (RF battery) according to an embodiment includes a positive electrode, a negative electrode, and a diaphragm interposed between the positive electrode and the negative electrode.
Of the positive electrode and the negative electrode, one electrode includes a porous plate mainly composed of a continuous three-dimensional network structure formed by bonding carbon, and the other electrode is a plurality of intertwined ones. A fiber assembly mainly composed of carbon fiber is provided.
The porous plate is provided with a recess that is open on at least one surface thereof and through which the electrolytic solution is circulated.

Examples of the recess include a groove opened on one surface of a porous plate.
The recess preferably forms a space that is sufficiently larger than the pores formed by the skeleton of the porous plate. Specifically, the surface perpendicular to the thickness direction of the porous plate is a cut surface, and the cross-sectional area of each recess in an arbitrary cut surface is sufficiently larger than the area of a circle having the average pore diameter of the porous plate Is preferred.

  The RF battery includes a porous plate having higher rigidity than the fiber assembly, and the porous plate is provided with a concave portion. Therefore, the concave portion can be maintained for a long period of time, and the electrolyte solution is excellent in circulation. In particular, since the RF battery includes a fiber assembly that is more flexible than the porous plate, the fiber assembly can function as a cushion against the porous plate, and damage such as cracking of the porous plate can be prevented. . Also from this point, it is possible to ensure good flowability due to the provision of the recesses.

  In addition, the RF battery described above includes both a porous plate that is dense and excellent in conductivity and battery reactivity, and a fiber assembly that is easy to hold an electrolyte solution and excellent in battery reactivity, which will be described later. As shown in the test examples, the cell resistance is small.

  Furthermore, since the porous plate is excellent in rigidity as described above, for example, a catalyst or the like can be easily and stably attached. When the positive electrode includes a porous plate provided with a catalyst, battery reactivity can be enhanced and cell resistance can be further reduced. Therefore, the cell resistance can be further reduced particularly when the above-described RF battery includes a porous plate with a catalyst on the positive electrode.

  In addition, since the porous plate is excellent in rigidity as described above, a concave portion such as a groove can be formed easily and stably, and the manufacturability of the electrode is also excellent.

(2) As an example of the RF battery, at least one of the positive electrode and the negative electrode may include a laminated body in which the porous plate and the fiber assembly material are laminated.

  Since the above-mentioned form includes both the porous plate excellent in the flowability of the electrolytic solution and the fiber aggregate excellent in the battery reactivity due to the provision of the recesses in at least one electrode, the flowability of the electrolytic solution is excellent. Cell resistance can be further reduced. Since the electrode provided with the laminate is in contact with the porous plate with the fiber assembly material, it is easier to prevent damage such as cracking of the porous plate with this fiber assembly material. It is more excellent in nature. And since the electrode provided with a laminated body can perform battery reaction with both a porous board and a fiber assembly material, it can make cell resistance smaller.

(3) As an example of the RF battery of (2), the porous plate in the laminate may include a recess provided on the interface side with the fiber assembly.

  It can be said that the laminated body of the said form is the state by which the fiber assembly material was arrange | positioned facing the surface where the recessed part of a porous board opens, and the opening part of the recessed part was directly covered with the fiber assembly material. The electrode including such a laminate can prevent damage such as cracks in the vicinity of the recesses due to the fiber assembly material, and can easily transfer the electrolyte between the recesses and the fiber assembly material. Therefore, the said form is further excellent in the flowability of electrolyte solution. In particular, when the fiber assembly includes a laminated body disposed on the diaphragm side, the porous plate includes a recess that opens on a surface facing the diaphragm (hereinafter sometimes referred to as a diaphragm side surface) ( (Form (4) described later), the fiber assembly can perform a battery reaction in the vicinity of the diaphragm by the electrolytic solution supplied from the concave portion of the porous plate. Therefore, this form can further reduce the cell resistance.

(4) As an example of the RF battery, a form in which the porous plate provided in the one electrode includes a recess opening in a surface facing the diaphragm.

  In the above-mentioned form, for example, the fiber aggregate constituting the other electrode is arranged through the diaphragm so as to face the diaphragm side surface of the porous plate constituting one electrode. As a result, the opening of the recess formed on the side surface of the diaphragm of the porous plate is indirectly covered with the fiber assembly material, and damage such as cracks in the vicinity of the recess can be prevented. Excellent. And the said form can hold | maintain electrolyte solution to the recessed part opened on the diaphragm side surface of a porous board, and can perform battery reaction in the vicinity of a diaphragm, Therefore A cell resistance can be made smaller.

(5) As an example of the RF battery, the concave portion may include a groove group in which a plurality of linear grooves that do not communicate with the electrolyte introduction side and the discharge side are arranged in parallel.

  The porous plate provided in the above form is provided with a battery reaction field so as to cross between adjacent linear grooves, and the amount of the electrolyte flowing through the battery reaction field is a linear shape in which the introduction side and the discharge side communicate with each other. It is easy to increase as compared with the case where the groove group is provided. Therefore, the said form can anticipate activation of the battery reaction in the said battery reaction field, and can make cell resistance smaller. Moreover, the said form WHEREIN: The distribution | circulation state of the electrolyte solution in a battery reaction field tends to become uniform over the whole porous board, and it is easy to perform a battery reaction uniformly over the wide range of a porous board. Furthermore, each groove of the groove group in which the introduction side and the discharge side do not communicate with each other is linear and can be easily formed because one end is open on one side surface of the porous plate. It is excellent in manufacturability of a porous plate comprising

(6) As an example of the RF battery, the recess includes a groove, the depth of the groove is 0.3 mm to 4 mm, and the width of the opening of the groove is 0.05 mm to 5 mm. Is mentioned.

  The above-mentioned form is provided with a deep groove having a large opening, that is, a groove having a large volume as a recess, so that the flowability of the electrolytic solution is excellent, and the cell reaction field is sufficiently secured without the recess being too large.

(7) As an example of the RF battery, a form in which the positive electrode includes the porous plate can be given.

  As described above, the porous plate can easily perform the adhesion operation of the catalyst, and in the above embodiment, the positive electrode can be provided with the porous plate including the catalyst. In this case, the flowability of the electrolytic solution is excellent, and the cell resistance can be further reduced.

(8) As an example of the RF battery, a form in which the fiber assembly material includes at least one selected from carbon felt, carbon paper, and carbon cloth can be given.

  Since any of the listed fiber aggregates can be used satisfactorily as an electrode of an RF battery, the above-described form is excellent in the flowability of the electrolytic solution and has a low cell resistance. Further, all of the listed fiber aggregates are sufficiently superior in flexibility to the porous plate and function well as a cushioning material for the porous plate.

(9) The electrode for the redox flow battery (RF battery) according to the embodiment is mainly composed of a continuous three-dimensional network structure formed by bonding of carbon, and is opened at least on one side and the electrolyte is distributed. And a laminated body in which a fiber assembly mainly composed of a plurality of carbon fibers that are disposed so as to face each other and face each other is opened.

  The above-mentioned electrode for an RF battery includes both a porous plate having high rigidity as described above and a fiber assembly material having excellent flexibility, and has a recess in the porous plate. In addition to excellent fluidity, the cell resistance can be reduced. In particular, since the vicinity of the recess can be protected by the fiber assembly, the recess can be maintained for a long period of time, and the electrolyte solution can be easily exchanged between the recess and the fiber assembly. It is possible to construct an RF battery that is superior in liquid circulation. In addition, since the RF battery electrode can perform a battery reaction with both the porous plate and the fiber assembly, an RF battery having a smaller cell resistance can be constructed. In addition, when the RF battery electrode is used as a positive electrode, the catalyst can be easily attached to the porous plate and has excellent productivity.

[Details of the embodiment of the present invention]
Hereinafter, a redox flow battery (RF battery) according to an embodiment of the present invention and an electrode for an RF battery according to the embodiment will be described in detail with reference to the drawings. In the figure, the same reference numerals indicate the same names.

First, the basic configuration of the RF battery system including the RF battery 1 according to the embodiment will be described with reference to FIGS. 7 and 8, and then the RF battery according to each embodiment will be described with reference to FIGS. 1 to 6. This will be described in detail.
FIGS. 1 to 5 are cross-sectional views of battery cells 100A to 100E each including a positive electrode 10c, a diaphragm 11, and a negative electrode 10a, cut along a cross section perpendicular to the stacking direction. 10a is shown exaggerated thickly. For easy understanding, a gap is provided between the electrodes 10c and 10a and the diaphragm 11.
In FIG. 7, the ions shown in the positive electrode tank 106 and the negative electrode tank 107 are examples of ion species included in the electrolyte solution of each electrode, the solid line arrow means charging, and the broken line arrow means discharging.

(Outline of RF battery)
The RF battery 1 according to the embodiment is constructed by using an RF battery system provided with a circulation mechanism that circulates and supplies an electrolytic solution to the RF battery 1 as shown in FIG. The RF battery 1 is typically connected to a power generation unit 300 and a load 400 such as a power system or a consumer via an AC / DC converter 200, a substation facility 210, and the like. The RF battery 1 performs charging using the power generation unit 300 as a power supply source and discharging using the load 400 as a power supply target. Examples of the power generation unit 300 include a solar power generator, a wind power generator, and other general power plants.

(Basic configuration of RF battery)
The RF battery 1 includes a positive electrode 10c to which a positive electrode electrolyte is supplied, a negative electrode 10a to which a negative electrode electrolyte is supplied, and a diaphragm 11 interposed between the positive electrode 10c and the negative electrode 10a. 100 is the main component. The RF battery 1 typically includes a plurality of battery cells 100 and a bipolar plate 150 (FIG. 8) between adjacent battery cells 100 and 100.

The electrodes 10c and 10a of each electrode are reaction fields where the active material ions contained in the supplied electrolyte solution perform a battery reaction, and are made of a porous body so that the electrolyte solution can flow.
The diaphragm 11 is a positive / negative separation member that separates the positive electrode 10c and the negative electrode 10a and transmits predetermined ions.

  The bipolar plate 150 is a conductive member which is sandwiched between the electrodes 10c and 10a of both electrodes and allows current to flow but does not allow electrolyte to pass through. Typically, it is used in the state of a frame assembly 15 including a frame 151 formed on the outer periphery of the bipolar plate 150 as shown in FIG. The frame 151 has openings on the front and back surfaces thereof, and liquid supply holes 152 c and 152 a for supplying an electrolytic solution to the electrode 10 disposed on the bipolar plate 150 and drainage holes 154 c and 154 a for discharging the electrolytic solution.

  The plurality of battery cells 100 are stacked and used in a form called a cell stack. As shown in FIG. 8, the cell stack is configured by repeatedly laminating a bipolar plate 150 of one frame assembly 15, a positive electrode 10c, a diaphragm 11, a negative electrode 10a, a bipolar plate 150 of another frame assembly 15, and so on. The A current collector plate (not shown) is disposed in place of the bipolar plate 150 on the electrodes 10 positioned at both ends of the battery cell 100 in the stacking direction of the cell stack. End plates 170 are typically disposed at both ends of the battery cell 100 in the cell stack in the cell stack, and the pair of end plates 170 and 170 are connected and integrated by a connecting member 172 such as a long bolt.

(Outline of RF battery system)
The RF battery system includes the RF battery 1 and the following positive electrode circulation path and negative electrode circulation path, and circulates and supplies the positive electrode electrolyte to the positive electrode 10c and circulates and supplies the negative electrode electrolyte to the negative electrode 10a. By this circulation supply, the RF battery 1 performs charging / discharging in accordance with the valence change reaction of ions serving as active materials in the electrolyte solution of each electrode.
The positive electrode circulation path is provided in the positive electrode tank 106 that stores the positive electrode electrolyte supplied to the positive electrode 10c, the pipes 108 and 110 that connect the positive electrode tank 106 and the RF battery 1, and the supply-side pipe 108. And a pump 112.
The negative electrode circulation path is provided in the negative electrode tank 107 that stores the negative electrode electrolyte supplied to the negative electrode 10 a, the pipes 109 and 111 that connect the negative electrode tank 107 and the RF battery 1, and the supply-side pipe 109. And a pump 113.
By laminating the plurality of frame assemblies 15, the liquid supply holes 152 c and 152 a and the drain holes 154 c and 154 a constitute a flow path for the electrolytic solution, and the pipes 108 to 111 are connected to the pipe lines. As the basic configuration of the RF battery system, a known configuration can be used as appropriate.

(Main features of RF battery)
One of the features of the RF battery 1 of the embodiment is that a plurality of different carbon materials are provided in one battery cell 100, and an electrode is constituted by these carbon materials. Specifically, one electrode includes a porous plate mainly composed of a continuous three-dimensional network structure formed by bonding carbon, and the other electrode mainly includes a plurality of carbon fibers intertwined with each other. A fiber assembly material is provided. In addition, the RF battery 1 according to the embodiment is characterized in that the porous plate is provided with a recess that is open on at least one surface thereof and through which the electrolytic solution is circulated. The RF battery 1 according to the embodiment includes both a porous plate having relatively high rigidity as an electrode and a fiber assembly material having relatively excellent flexibility, and has a concave portion in the porous plate, so that the electrolyte solution has a good quality. Ensures flowability and reduces cell resistance.

  Hereinafter, the RF battery of each embodiment will be described, and then the porous plate and the fiber assembly will be described in detail. In each embodiment, since the arrangement state of the porous plate and the fiber assembly provided in the battery cell 100 is different, description will be made mainly on the arrangement state, and detailed description of overlapping configurations and effects will be omitted.

[Embodiment 1]
The RF battery of Embodiment 1 includes a battery cell 100A shown in FIG. In the battery cell 100A, both the positive electrode 10c and the negative electrode 10a include a laminate in which a porous plate 101 and a fiber assembly material 102 are laminated. The porous plate 101 includes a recess 101g that opens on one surface thereof. In this example, the porous plate 101 in the laminate includes a recess 101g that opens on the interface side with the fiber assembly 102, and the fiber assembly 102 is on the surface on the interface side where the recess 101g in the porous plate 101 opens. Opposed to each other. This laminate is an example of the RF battery electrode of the embodiment.

  In FIG. 1, a plurality of linear grooves in which concave portions 101g are arranged in parallel are provided, and each groove opens on the surface on the interface side of the porous plate 101 provided in each laminate, here on the side surface of the diaphragm facing the diaphragm 11. An example is shown (this is the same in FIGS. 2 to 5 described later). The fiber assembly 102 in each laminate covers the opening of the recess 101g (groove), and also covers one surface of the porous plate 101 (here, the diaphragm in which the recess 101g is open) so as to contact the ridge that exists between adjacent grooves. (This is the same in the embodiments 3 and 5 described later).

  In the battery cell 100A, the above-described laminate constituting the positive electrode 10c and the above-described laminate constituting the negative electrode 10a are arranged symmetrically with the diaphragm 11 interposed therebetween. That is, the concave portion forming surface of the porous plate 101 provided in the positive electrode 10c and the concave portion forming surface of the porous plate 101 provided in the negative electrode 10a are arranged to face each other, and the bipolar fibers 101, 101 are disposed between the bipolar plates 101, 101. The aggregates 102 and 102 and the diaphragm 11 are interposed.

The RF battery of Embodiment 1 has the following effects.
Since each electrode 10c, 10a includes both the porous plate 101 having higher rigidity than the fiber assembly 102 and the fiber assembly 102 having excellent flexibility, the porous plate 101 includes the recess 101g. The porous plate 101 itself is not easily deformed, and the concave portion 101g can be maintained for a long time by the cushion function of the fiber assembly 102. In addition, the electrodes 10c and 10a of each electrode can perform a battery reaction with both the porous plate 101 and the fiber assembly 102, and are excellent in battery reactivity. Therefore, the RF battery of Embodiment 1 is excellent in the flowability of the electrolyte and has a low cell resistance. This effect will be specifically described in a test example described later.

In particular, the RF battery of this example can reduce the cell resistance in the following points.
(Α) The electrolyte flowing through the recess 101g can be easily introduced into the fiber assembly 102 from the opening of the recess 101g, so that the battery reaction of the fiber assembly 102 can be performed satisfactorily.
(Β) Since the recess 101g is open on the side surface of the diaphragm of the porous plate 101, the electrolyte can be stored in the vicinity of the diaphragm 11, and the battery reaction can be performed in the vicinity of the diaphragm 11 (in this example, the fiber aggregate 102 in particular) ( This also applies to the RF batteries of Embodiments 2 to 6 described later).

Moreover, the RF battery of this example has the following effects.
(Γ) The positive electrode 10c includes the porous plate 101 having excellent rigidity as described above. For example, since the catalyst can be easily attached, the positive electrode 10c including the porous plate 101 including the catalyst can be obtained. it can. In this case, further reduction in cell resistance can be expected.
(Δ) The porous plate 101 and the fiber assembly material 102 have substantially the same plane area (see FIG. 6), and the entire surface of the diaphragm side surface of the porous plate 101 is covered with the fiber assembly material 102, It is easier to prevent damage to the porous plate 101 (this also applies to the RF batteries of Embodiments 2 to 6 described later).

  As a modification of the RF battery of the first embodiment, the stacking order of the stacked body provided in at least one of the electrodes can be changed (this modification is the same in the third and fifth embodiments described later). For example, one electrode can include a laminate in which the porous plate 101 is disposed on the diaphragm 11 side and the fiber assembly 102 is disposed on the bipolar plate side (see the positive electrode 10c in FIG. 4).

[Embodiment 2]
The RF battery of Embodiment 2 includes a battery cell 100B shown in FIG. The battery cell 100B includes the porous plate 101 on one electrode (the positive electrode 10c in FIG. 2) and does not include the fiber assembly 102, and the fiber assembly on the other electrode (the negative electrode 10a in FIG. 2). 102, the porous plate 101 is not provided, and the electrodes 10c and 10a of both electrodes are made of different carbon materials. The porous plate 101 includes a recess 101g that opens on one surface thereof. In this example, the porous plate 101 included in one electrode includes a recess 101 g that opens on the side surface of the diaphragm facing the diaphragm 11. Therefore, the opening part of the recessed part 101g provided in the diaphragm side surface of this porous board 101 is covered with the fiber assembly material 102 through the diaphragm 11.

The RF battery of Embodiment 2 has the following effects.
Since one electrode includes the porous plate 101 having higher rigidity than the fiber assembly 102 and the other electrode includes the fiber assembly 102 having excellent flexibility, and the porous plate 101 includes the recess 101g, the porous plate 101 101 itself is not easily deformed, and the recess 101g formed in the porous plate 101 provided in one electrode can be maintained for a long time by the cushion function of the fiber assembly 102 provided in the other electrode. Moreover, both the porous plate 101 which is excellent in conductivity and battery reactivity due to being dense, and the fiber assembly material 102 which is easy to hold an electrolytic solution and excellent in battery reactivity are provided. Therefore, the RF battery of Embodiment 2 has excellent electrolyte flowability and low cell resistance. This effect will be specifically described in a test example described later.

  The RF battery of this example includes the porous plate 101 having excellent rigidity as described above on the positive electrode 10c. For example, since the catalyst can be easily attached, the positive electrode 10c including the catalyst can be obtained. . In this case, further reduction in cell resistance can be expected. This also applies to the RF batteries of Embodiments 3 to 5 described later.

  As a modification of the RF battery of Embodiment 2, the positive electrode 10c includes the fiber assembly 102 and does not include the porous plate 101, and the negative electrode 10a includes the porous plate 101 and includes the fiber assembly 102. There can be no configuration.

[Embodiment 3]
The RF battery of Embodiment 3 includes a battery cell 100C shown in FIG. The battery cell 100C includes a laminate in which a porous plate 101 having a recess 101g formed on one electrode (positive electrode 10c in FIG. 3) and a fiber assembly 102 are laminated, and the other electrode (negative electrode in FIG. 3). The electrode 10a) is provided with a fiber assembly 102 and is not provided with a porous plate 101. The battery cell 100C includes the porous plate 101 only in one electrode (here, positive electrode 10c, hereinafter the same in this embodiment), and the fiber aggregate 102 in both electrodes 10c and 10a.

  The battery cell 100C is common to the first embodiment in that one electrode is provided with the above laminate and the concave portion 101g of the porous plate 101 in this laminate is open on the interface side with the fiber assembly 102. One electrode is provided with a porous plate 101, the other electrode (here, negative electrode 10 a) is provided with a fiber assembly 102, and the porous plate 101 provided on one electrode is opened on the side of the diaphragm facing the diaphragm 11. It is common with Embodiment 2 by the point provided with 101g.

  Since the RF battery of the third embodiment has the same configuration as that of the first and second embodiments as described above, the effects of both the first and second embodiments described above are achieved, and the flowability of the electrolyte is improved. In addition to being excellent, the cell resistance is small.

  In the RF battery of this example, the porous plate 101 provided in one electrode is provided with the fiber assembly material 102 serving as a cushion in the electrodes 10c and 10a of both electrodes, so that the porous plate 101 is sufficiently mechanically protected. Expected to be able to. In particular, since the plurality of fiber aggregates 102 are arranged so as to face the surface of the porous plate 101 where the concave portion 101g opens, it is expected that the concave portion 101g is more easily maintained.

  As a modification of the RF battery according to Embodiment 3, the positive electrode 10c includes the fiber assembly 102, and does not include the porous plate 101, and the negative electrode 10a can include the above-described laminate.

[Embodiment 4]
The RF battery of Embodiment 4 includes a battery cell 100D shown in FIG. As with the RF battery of the third embodiment, the battery cell 100D is a laminate in which a porous plate 101 having a recess 101g formed in one electrode (the positive electrode 10c in FIG. 4) and a fiber assembly 102 are laminated. Provided, the other electrode (the negative electrode 10a in FIG. 4) is provided with the fiber assembly 102, and the porous plate 101 is not provided. In the RF battery of Embodiment 4, the stacking order of the laminate is different from that of Embodiment 3, and the porous plate 101 is provided on the diaphragm 11 side and the fiber assembly 102 is provided on the bipolar plate 150 (FIG. 8) side. In this way, the stacking order of the porous plate 101 and the fiber assembly 102 constituting the laminate can be changed.

  Since the RF battery of the fourth embodiment has the same configuration as that of the first and second embodiments similarly to the third embodiment, the effects of both the first and second embodiments described above can be achieved, and the electrolyte can be circulated. In addition to excellent properties, the cell resistance is small.

  In particular, the RF battery of Embodiment 4 is excellent in the flowability of the electrolytic solution by changing the flowability of the electrolytic solution in accordance with the electrolytic solution characteristics of the electrodes 10c and 10a of each electrode. In the RF battery according to the fourth embodiment, the porous plate 101 included in one electrode is sandwiched between the fiber aggregates 102 and 102, and thus the porous plate 101 is more easily protected mechanically. In addition, in the RF battery of this example, since the porous plate 101 provided in one of the electrodes is provided with the concave portion 101g opened in the side surface of the diaphragm, the battery reaction is easily performed in the vicinity of the diaphragm 11, and the cell resistance is easily reduced.

  As a modification of the RF battery of Embodiment 4, a laminate in which the positive electrode 10c is provided with the fiber assembly 102, the porous plate 101 is not provided, and the negative electrode 10a is provided with the porous plate 101 on the above-described diaphragm 11 side. The body can be provided.

[Embodiment 5]
The RF battery of Embodiment 5 includes a battery cell 100E shown in FIG. The battery cell 100E is common to the first and third embodiments in that the battery cell 100E includes a laminate in which a porous plate 101 having a recess 101g formed in one electrode (positive electrode 10c in FIG. 5) and a fiber assembly 102 are laminated. However, this embodiment is different from the third embodiment in that the other plate (the negative electrode 10a in FIG. 5) includes the porous plate 101 in which the concave portion 101g is formed and the fiber assembly material 102 is not provided. The battery cell 100E includes the fiber aggregate 102 only on one electrode (here, the positive electrode 10c, hereinafter the same in this embodiment), and includes the porous plate 101 on both electrodes 10c and 10a. In this example, both of the porous plates 101, 101 provided in the electrodes 10 c, 10 a of both electrodes include a recess 101 g that opens on the side surface of the diaphragm facing the diaphragm 11.

  Since the RF battery of the fifth embodiment has the same configuration as that of the first and third embodiments, the same effects as those of the first and third embodiments described above can be obtained, the electrolytic solution is excellent in flowability, and the cell resistance is small. In particular, the RF battery of Embodiment 5 is superior in the flowability of the electrolytic solution because it includes the porous plate 101 in which the recesses 101g are formed in the electrodes 10c and 10a of both electrodes. In addition, in the RF battery of this example, since the porous plates 101 and 101 provided in the bipolar electrodes 10c and 10a each include the concave portion 101g opened on the side surface of the diaphragm, the battery reaction is easily performed in the vicinity of the diaphragm 11, and the cell resistance It is easy to make small.

  As a modification of the RF battery of Embodiment 5, the positive electrode 10c is provided with the porous plate 101 in which the concave portion 101g is formed, the fiber aggregate 102 is not provided, and the negative electrode 10a can be provided with the above-described laminate. .

[Embodiment 6]
Embodiment 1 etc. demonstrated the example provided with the porous board 101 and the fiber assembly material 102 each as a laminated body with which one electrode is equipped. The laminate provided for at least one electrode can include a plurality of at least one of the porous plate 101 and the fiber assembly 102. For example, the laminated body (not shown) provided with a pair of fiber aggregate 102,102 so that both surfaces of the porous board 101 may be pinched | interposed. This laminate is another example of the RF battery electrode of the embodiment.

  The RF battery of the sixth embodiment provided with the above-described laminate is excellent in the flowability of the electrolytic solution as in the first embodiment and has a low cell resistance. In particular, the RF battery of Embodiment 6 is more excellent in the flowability of the electrolytic solution when the number of laminated porous plates 101 in the laminate is large.

[Embodiment 7]
In the case of an RF battery including a plurality of battery cells, each battery cell has the same specification, for example, all of the plurality of battery cells are configured by the battery cell 100A, and in Embodiments 1 to 6 A combination of at least two or more selected from the battery cells 100A to 100E described above can be provided.

(Porous plate)
The porous plate 101 has a plate-like porous structure in which carbons are at least physically bonded to each other, and a skeleton that forms a continuous three-dimensional network by the bonding and a plurality of open pores formed by the network. Carbon material.

Ingredients The porous plate 101 is substantially composed of carbon except for pores, and is mainly composed of the above-described network-like skeleton. “Mainly composed of the main body” means that the ratio of the main body in the porous plate 101 is more than 30% by mass. It is allowed to contain carbon fiber or the like in the range of 50% by mass or less. For example, a density measurement method can be used for the measurement of the mass ratio.

-Porosity The porosity (porosity) of the porous plate 101 is, for example, about 30% to 90% by volume. In addition, the porosity of the porous plate 101 is lower than the porosity of the fiber assembly material 102 (typically about 50 volume% or more and 95 volume% or less).
The average pore diameter of the porous plate 101 is, for example, about 0.01 μm or more and 5 μm or less. The larger the pore size, the easier the electrolyte penetrates, and the smaller the pore size, the more carbon per unit volume (the higher the density), the better the conductivity, and the larger the cell reaction field (this is the fiber The same applies to the aggregate material 102).

-Other components It is preferable that the porous plate 101 contains oxygen (or an oxide) on the surface because of excellent wettability with the electrolytic solution. Examples of the oxygen content include a surface oxygen element ratio of about 3% to about 15% in terms of the number ratio by analysis by photoelectron spectroscopy. When an oxidation treatment described later is performed, the porous plate 101 containing oxygen can be obtained.

-Rigidity The porous board 101 preferably has higher rigidity than the fiber assembly 102. This is because even when the cell stack is provided and maintained in a predetermined tightening state for a long period of time, it is difficult to deform, and the recess 101g can be maintained for a long period of time. Moreover, it is because formation of the recessed part 101g, adhesion of a catalyst, etc. can be performed easily and it is excellent in the productivity of the porous board with a groove | channel and the porous board with a catalyst.

  Qualitatively, it is preferable that the porous plate 101 has such rigidity that a change in thickness over time is small or a change in thickness does not substantially occur when a predetermined stress is applied. Quantitatively, for example, in terms of compression modulus, if the fiber assembly 102 is carbon felt, about 1 kgf / 2 mm, if carbon paper is about 1 kgf / 0.05 mm, if carbon cloth, 1 kgf / 0.1 mm. On the other hand, in the porous plate 101, it is about (1 kgf / 0.03 mm) or more (1 kgf≈10 N). A tensile tester can be used to measure the compression modulus. If the compression elastic modulus of the fiber aggregate 102 is not more than (1 kgf / 0.05 mm) and the compression elastic modulus of the porous plate 101 is not less than about (1 kgf / 0.03 mm), the porous plate 101 is a fiber assembly. It can be said that the rigidity is higher than that of the material 102.

-Shape and size The porous plate 101 is typically a rectangular flat plate as shown in FIG. Other planar shapes can be various shapes such as a circular shape, an elliptical shape, and a polygonal shape.
The size of the porous plate 101 when viewed in plan, for example, the width and length if the planar shape is rectangular, the diameter if the planar shape is circular, and the planar area, etc., are determined by the RF battery 1 satisfying a desired capacity. What is necessary is just to select so that it can form.

As the thickness t ₁₀₁ of the porous plate 101 is thicker, the battery reaction field can be increased, and the thinner the thin plate RF battery 1 is, the better. Specific thickness _t101 is 0.5 mm or more and 5 mm or less. In particular, when at least one of the electrodes is a laminated body including the porous plate 101 and the fiber assembly material 102 (such as Embodiment 1), the thickness t ₁₀₁ may be thin. For example, the thickness t ₁₀₁ may be It can be 1.5 mm or less. A more preferable thickness t ₁₀₁ in the case of the laminated body is about 0.5 mm or more and 1.5 mm or less. The thickness t _{101 in} the case other than the laminated body (Embodiment 2 or the like) is about 0.5 mm or more and 5 mm or less.

-Concave part The porous plate 101 includes a diaphragm side surface disposed opposite to the diaphragm 11 and a bipolar plate side surface opposed to the diaphragm side surface and disposed parallel to the bipolar plate 150 (FIG. 8) as shown in FIG. . The porous plate 101 includes a recess 101g that opens on at least one of the diaphragm side surface and the bipolar side surface. The porous plate 101 has a relatively small porosity and is dense as described above, but is excellent in the flowability of the electrolyte because it includes the recess 101g. And since the recessed part 101g is provided in the porous board 101 excellent in rigidity as mentioned above, it is easy to maintain the recessed part 101g over a long period of time, and the favorable distribution | circulation property of electrolyte solution can be ensured. Further, as shown in Test Example 2 to be described later, the cell resistance can be easily reduced by adjusting the size of the recess 101g and the like.

..Type of concave portion The concave portion 101g includes at least one of a groove that opens only on the side surface of the diaphragm and a groove that opens only on the side surface of the bipolar plate. Each of the recesses 101g shown in FIGS. 1 to 6 is a groove opened only on the side surface of the diaphragm.
When the concave portion 101g includes a groove, the electrolytic solution can easily flow along the longitudinal direction of the groove, and the flowability of the electrolytic solution is excellent. Further, the groove can be easily formed by a cutting tool, and the productivity of the porous plate 101 having the recess 101g is excellent. In particular, as shown in FIG. 6, it is easier to form the groove if the groove reaches the periphery of the porous plate 101 and opens on the side surface.

.. Existence of recesses It is preferable to provide a plurality of recesses 101g in one porous plate 101 because of excellent fluidity of the electrolyte solution. Moreover, when providing the several recessed part 101g in one porous board 101, the form provided with both a groove | channel and a through-hole other than the form (FIGS. 1-6) provided with the groove | channel opened on the surface of the same side, It is possible to adopt a configuration including both a groove opening on the diaphragm side surface and a groove opening on the bipolar plate side surface (a configuration including grooves on both the diaphragm side surface and the bipolar plate side surface). The form provided with the groove that opens only on one surface of one porous plate 101 is easy to form the groove, and is excellent in the productivity of the porous plate 101 provided with the recess 101g. In particular, a configuration in which grooves having uniform shapes, sizes, and intervals are provided on one surface of the porous plate 101 can easily make the distribution state of the electrolyte solution in one porous plate 101 uniform.

.. Groove When the recess 101g includes a groove, it is preferable to include a groove formed from the electrolyte supply side to the discharge side. For example, when the cell stack shown in FIG. 8 is constructed and the electrolytic solution is supplied from the lower side to the upper side in FIG. 8, it is preferable to provide vertical grooves along the vertical direction. The cross-sectional shape of the groove can be selected as appropriate. In addition to a rectangular cross section as shown in FIG. 1 and the like, a V shape, a U shape (semi-arc shape), and the like can be given. The planar shape of the groove may be a linear shape such as a rectangular shape. For example, the form provided with the several linear groove | channel arranged in parallel is mentioned. At this time, if each groove opens to one side surface of the porous plate 101 as described above and continues from one side surface (periphery), (1) the electrolyte solution extends from the periphery along the longitudinal direction of the groove. Easy to introduce and excellent in the flowability of the electrolyte. (2) A battery reaction field (saddle) is provided so as to cross between adjacent linear grooves, and the battery reaction can be performed well. (3) Parallel straight lines Various effects can be achieved, such as the ability to easily form a groove and excellent manufacturability of the porous plate 101 having the recess 101g.

A plurality of linear grooves in which the recesses 101g are arranged in parallel, and a groove group in which a plurality of linear grooves in which the electrolyte introduction side and the discharge side do not communicate with each other as shown in FIG. preferable. Compared to the case where a linear groove communicated from the introduction side to the discharge side, that is, a groove group communicated from one side surface of the porous plate to the other side surface opposed to each other, is introduced into the flange portion. This is because the amount of the electrolyte can be increased and activation of the battery reaction can be expected. As a result, a decrease in cell resistance can be expected.
In particular, as shown in FIG. 6, one end of each groove is open to the side surface of the porous plate 101, the other end is a groove reaching the middle of the porous plate 101, and one end of the groove is open to one side surface. Further activation of the battery reaction can be expected by providing a groove group in which the groove on the side and the groove on the discharge side opened on the other side surface where one end of the groove faces one side surface are alternately arranged. Such a groove group can be easily formed, and the productivity of the porous plate 101 including the groove group is excellent.
Although FIG. 6 shows a form in which the introduction-side grooves and the discharge-side grooves are alternately arranged one by one, a form in which a plurality of grooves are arranged alternately and the like can be adopted.
In addition, the introduction-side groove and the discharge-side groove are comb-like grooves each having a lateral groove and a plurality of parallel longitudinal grooves extending from the transverse groove, and the introduction-side longitudinal groove and the discharge-side longitudinal groove are It can be set as the form provided with the opposing comb tooth groove arrange | positioned so that it may mesh | engage.

  When the recess 101g includes a plurality of grooves, the larger the depth d of each groove, the width w of the opening, and the length l, the larger the volume of the groove. It is preferable that the width w is large because of excellent flowability of the electrolytic solution. If the volume of the groove is too large, the battery reaction field in the porous plate 101 may be narrowed. Further, if the size of each groove is substantially the same, it is easy to form the groove, and the flow of the electrolytic solution in the porous plate 101 is easily made uniform. However, the groove | channels from which a magnitude | size differs among some groove | channels can be included.

The depth d (maximum depth) of the groove is, for example, 0.3 mm or more and 4 mm or less. Although depending on the thickness t ₁₀₁ , width w, and length l of the porous plate 101, the depth d can be set to, for example, 0.3 mm to 3 mm, and further 0.5 mm to 2 mm. Depth d, 20% to 80% of the thickness _{t 101} of the porous plate 101 or less, may be further 40% to 70%.

The width w of the groove opening is, for example, 0.05 mm or more and 5 mm or less. Although depending on the thickness t ₁₀₁ , depth d, and length l of the porous plate 101, the width w can be set to, for example, 0.1 mm to 4 mm, and further 0.4 mm to 1 mm.

  The length l of the groove can be, for example, 80% to 99% of the length of the porous plate 101, and further 90% to 98%.

  When the recess 101g includes a groove group in which the above-described introduction-side groove and the discharge-side groove are arranged in parallel, the overlapping length ll of adjacent grooves is, for example, 70% or more and 95% of the length of the porous plate 101. Hereinafter, 80% or more and 90% or less are mentioned.

  When the recess 101g includes a plurality of grooves in parallel, the adjacent groove interval cg is, for example, 0.5 mm or more and 20 mm or less, and further 1 mm or more and 5 mm or less. The groove interval cg can be set to the same level as the width w of the opening.

-Manufacturing method etc. The porous board 101 can utilize a well-known thing. For example, what is marketed as a porous carbon material and what was manufactured by the well-known manufacturing method can be utilized. As an example of the production method, a molded body containing carbon powder (preferably containing activated carbon), a fiber containing carbon element, and a resin is fired and carbonized. Further, graphitization by high temperature treatment may be performed.

Since carbon is generally highly hydrophobic, heat treatment (oxidation treatment) for enhancing hydrophilicity can be further performed. Examples of heat treatment conditions (heating temperature, atmosphere, holding time) are shown below. The porous plate 101 that has been subjected to the heat treatment has oxygen or oxide on the surface thereof, and has improved wettability with the electrolytic solution, so that the electrochemical reaction can be favorably performed on the surface.
Heating temperature 400 ° C. to 700 ° C. Atmosphere An atmosphere containing oxygen such as air. As for oxygen content, 10 volume% or more and about 30 volume% or less are mentioned.
Retention time 5 minutes or more and 30 minutes or less.
In addition, plasma treatment or the like can be performed to increase hydrophilicity.

(Fiber aggregate)
The fiber aggregate 102 is a sheet-like carbon material including a mesh-like main body formed by intertwining a plurality of carbon fibers and a plurality of open pores formed between the carbon fibers. The fiber assembly material 102 is more flexible than the porous plate 101 described above, and functions as a cushion material for the porous plate 101 in this respect as described above. In addition, the fiber assembly material 102 is easier to hold the electrolytic solution than the porous plate 101 and is excellent in battery reactivity in this respect.

-Component The fiber assembly 102 is substantially composed of carbon except for pores, and is mainly composed of the carbon fiber. “Mainly composed of carbon fibers” means that the proportion of carbon fibers in the fiber aggregate 102 is 85% by mass or more.

In addition to carbon fibers, binder carbon can be included. The fiber aggregate 102 containing the binder carbon has effects such as improvement in conductivity (particularly carbon felt) and improvement in strength (particularly carbon paper).
As for the magnitude | size (fiber diameter) of carbon fiber, 1 micrometer or more and about 15 micrometers or less are mentioned, for example.

-Pore Since the fiber assembly 102 is formed by entangled carbon fibers, the porosity (porosity) tends to be larger than that of the porous plate 101. Examples of the porosity of the fiber aggregate 102 include about 50% by volume to 95% by volume.
The average pore diameter of the fiber aggregate 102 is, for example, about 1 μm or more and 30 μm or less.

Specific examples The specific fiber assembly material 102 is selected from carbon felt, carbon paper (all of which are not woven with fibers), and carbon cloth (what is woven of fibers or woven of twisted fibers). At least one kind. As the listed fiber assembly 102, commercially available products or those manufactured by a known manufacturing method can be used. One electrode may be provided with only one type of fiber aggregate listed, or may be provided with two or more types of fiber aggregate stacked, for example, a form including carbon felt and carbon cloth. it can.

When carbon felt is used, (1) when an aqueous solution is used as the electrolytic solution, oxygen gas is hardly generated even when the oxygen generation potential is reached during charging, and (2) there is an advantage in that there is an excellent flowability of the electrolytic solution. Can be expected.
When carbon paper is used, effects such as (1) excellent electronic conductivity, (2) excellent strength, and (3) easy thinning of the electrode can be expected.
When carbon cloth is used, there is flexibility and the electrode can be made thin.

-Shape, size, etc. The fiber aggregate 102 is typically a rectangular flat plate as shown in FIG. Other planar shapes can be various shapes such as a circular shape, an elliptical shape, and a polygonal shape. As shown in FIG. 6, the planar shape of the fiber assembly 102 and the planar shape of the porous plate 101 can be equalized, and both can be made different.

  The size of the fiber assembly 102 when viewed in plan, for example, the width and length if the planar shape is rectangular, the diameter if the planar shape is circular, and the planar area, etc., are determined by the RF battery 1 satisfying a desired capacity. What is necessary is just to select so that it can form. As shown in FIG. 6, in addition to making the size of the fiber assembly 102 viewed in plan and the size of the porous plate 101 viewed in plan, they can be made different.

  In order for the fiber aggregate 102 to function satisfactorily as a cushioning material for the porous plate 101, one side of the fiber aggregate 102 and one side of the porous plate 101 have substantially the same planar shape and size when viewed in plan. Preferably equal.

As the thickness t102 of the fiber assembly ₁₀₂ is thicker, the battery reaction field can be increased and the cushioning property can be enhanced, and the thinner the tatter ₁₀₂ is, the thinner the RF battery 1 can be constructed. Specific thicknesses _{t 102} include the extent to 1mm 0.05 mm. If containing laminate of the porous plate 101 and a fiber assemblage 102 on at least one of the electrodes can be made thin (for example, Embodiment 1), the thickness _{t 102,} for example 0.5mm or less, and further 0.3mm or less can do. The preferred thickness _{t 102} of the fiber aggregate member 102 provided on the laminate include extent than 0.8mm or less 0.1 mm. The preferred thickness _{t 102} of the fiber aggregate member 102 in the case of non-laminate (Embodiment 2,5) include the extent to 1mm 0.3 mm.

In addition, the fiber aggregate 102 has a tendency to increase the battery reaction field as the basis weight increases and to improve the cushioning property, and to decrease the pump loss as it decreases. Specific weight per unit area is about 30 g / m ² or more and 300 g / m ² or less.

(Other RF battery components)
Frame assembly The bipolar plate 150 is a conductive material having a low electrical resistance, does not react with the electrolyte, and has resistance to the electrolyte (chemical resistance, acid resistance, etc.), for example, carbon materials and organic materials Can be used. More specifically, it is possible to use a conductive plastic material including a conductive inorganic material such as graphite (powder or fiber) and an organic material such as a polyolefin-based organic compound or a chlorinated organic compound formed into a plate shape.
The frame 151 is made of a resin having excellent resistance to an electrolytic solution and excellent electrical insulation.

-Diaphragm Examples of the diaphragm 11 include an ion exchange membrane such as a cation exchange membrane or an anion exchange membrane. The ion exchange membrane has characteristics such as (1) excellent isolation between positive electrode active material ions and negative electrode active material ions, and (2) excellent H ⁺ ion permeability as a charge carrier in the battery cell 100. It can be suitably used for the diaphragm 11. A known diaphragm can be used.

(Electrolyte)
The electrolytic solution used for the RF battery 1 includes active material ions such as metal ions and non-metal ions. For example, the positive electrode active material and the negative electrode active material include vanadium-based electrolytes containing vanadium ions (FIG. 7) having different valences. In addition, an iron-chromium-based electrolyte containing iron (Fe) ions as a positive electrode active material, chromium (Cr) ions as a negative electrode active material, manganese (Mn) ions as a positive electrode active material, and titanium (Ti) ions as a negative electrode active material Examples thereof include a manganese-titanium electrolyte solution. As the electrolytic solution, in addition to the active material, an aqueous solution containing at least one acid or acid salt selected from sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid can be used.

[Test Example 1]
RF batteries including various carbon materials as a positive electrode and a negative electrode were produced, and the flow state of the electrolyte and the cell resistance were measured.

In this test and Test Example 2 described later, as a carbon material used for the electrodes, a rectangular porous plate having a length of 30 mm × width of 30 mm × thickness of 1 mm, and a rectangular shape of length of 30 mm × width of 30 mm × thickness of 0.2 mm. Carbon paper (an example of a fiber assembly) and a rectangular carbon cloth (an example of a fiber assembly) having a length of 30 mm × width of 30 mm × thickness of 0.3 mm were prepared. Both are commercially available products.
The porous plate has a porosity of about 40% by volume and carbon fiber in the range of 1% by mass or less, and the remainder is bonded with carbon to form a continuous three-dimensional network structure. The porous plate of each sample was oxidized in an air atmosphere at 550 ° C. for 1 hour.
The porosity of carbon paper is about 70% by volume, the porosity of carbon cloth is about 60% by volume, and the porosity is larger than that of the porous plate.

A plurality of linear grooves arranged in parallel on one surface of the porous plate, the introduction side and the discharge side are not in communication, and one end of the groove is open on one side of the porous plate; A groove group (refer to FIG. 6) in which one end of the groove is alternately arranged with a groove on the discharge side opened on the other side opposite to one side of the porous plate is formed by a cutting tool, and a porous plate with a groove is also prepared. did.
The groove width w is 0.7 mm, the depth d is 0.7 mm, the groove interval cg is 1 mm, the groove length l is 28 mm, and the overlap length ll is 25 mm. Each linear groove is provided so that its longitudinal direction is along the flow direction of the electrolyte (in this case, the vertical direction), and as described above, the groove is formed on the opposite peripheral edge so as to open on the side surface of the porous plate. It provided so that one end might be located.

Sample No. Each of the positive electrode and the negative electrode 1-101 includes a porous plate that does not form the groove, and does not include a fiber assembly.
Sample No. Each of the positive electrode and the negative electrode 1-102 includes a grooved porous plate and does not include a fiber assembly. In this test, the porous plate of the electrode of each electrode was disposed so that the opening of the groove was located on the side surface of the diaphragm of the porous plate.
Sample No. The positive electrode of 1-1 is provided with a grooved porous plate, and the negative electrode is provided with carbon paper. In this test, the porous plate of the positive electrode was arranged so that the opening of the groove was located on the side surface of the diaphragm of the porous plate.
Sample No. Each of the positive electrode and the negative electrode of 1-2 includes a laminate in which a grooved porous plate and a carbon cloth are laminated. In this test, the laminated body was disposed so that the interface side of the porous plate with the fiber assembly was the diaphragm side, the opening of the groove was located on the side of the diaphragm, and the opening was covered with carbon cloth.

A single-cell battery cell was prepared using the positive electrode and negative electrode described above and the diaphragm, and the electrolyte solution was supplied to examine the flow state of the electrolyte solution. Further, the following charge / discharge test was conducted to examine the cell resistivity (Ω · cm ² ). The same battery cell components such as a diaphragm in each sample were used.

  A vanadium-based electrolyte was prepared as the electrolyte, and a cell resistivity was determined by conducting a charge / discharge test with a constant current and a constant voltage for a plurality of cycles. The test conditions were: discharge end voltage: 1V, charge end voltage: 1.6V, current: 600mA. For the cell resistivity, a charge / discharge curve was created based on the charge / discharge test, and the cell resistivity at the third cycle was examined from this charge / discharge curve.

As a result of this test, Sample No. No. 2 was provided with a porous plate on both electrodes and no fiber assembly. In 1-101, the flow of the electrolyte was insufficient, and it was difficult to repeatedly charge and discharge.
Sample No. provided with a porous plate with grooves in both electrodes and no fiber assembly. In 1-102, the electrolyte flowed and charge / discharge could be repeated, but the cell resistivity was 2.5 Ω · cm ² and the cell resistance was large.

Sample No. provided with a porous plate on one electrode and a fiber assembly on the other electrode. In 1-1, the electrolyte solution flowed satisfactorily and charge / discharge could be repeated, and the cell resistivity was 1.1 Ω · cm ² and the cell resistance was small. In this test, sample no. The cell resistivity of 1-1 is the sample No. Less than half of 1-102.
Furthermore, No. 1 provided with a laminate of a porous plate and a fiber assembly on both electrodes. In 1-2, on the electrolyte has repeatedly performed satisfactorily flow discharge, is a cell resistivity of 0.87Ω · cm ^2, the cell resistance is even smaller, less than 1Ω · cm ^2.

  From this test result, it was shown that an RF battery including a porous plate having a recess formed as a material for an electrode and a fiber assembly material has excellent electrolyte flowability and low cell resistance. Moreover, it was shown that the cell resistance can be further reduced by providing a laminate of a porous plate and a fiber assembly on at least one electrode.

[Test Example 2]
An RF battery including a porous plate as one electrode and a fiber assembly as the other electrode was produced, and the flow state of the electrolytic solution and the cell resistance were measured.

  In this test, a positive electrode was formed by forming a groove group (see FIG. 6) in which introduction-side grooves and discharge-side grooves were alternately arranged in parallel on one surface of the porous plate described in Test Example 1. A single-cell RF battery comprising a laminate obtained by laminating the carbon paper and the carbon cloth described in 1 as a negative electrode was produced. The porous plate of the positive electrode was arranged so that the groove opening was positioned on the side surface of the diaphragm of the porous plate. In particular, in this test, a plurality of grooved porous plates having different thicknesses and groove sizes were prepared and used for the positive electrode. Table 1 shows the thickness t (mm), groove width w (mm), depth d (mm), and groove interval cg (mm) of the porous plate of each sample. The porous plate prepared in Test Example 2 is different in thickness from the porous plate used in Test Example 1.

  The same charge / discharge test as in Test Example 1 was performed, and the cell resistivity was examined in the same manner as in Test Example 1. The results are shown in Table 1.

In addition, the current efficiency (%) was examined. The results are shown in Table 1. In this test, the current efficiency η is defined as the amount of electricity Q ₁ required for charging up to a charging end voltage: 1.6 V, the amount of electricity Q ₂ taken out by constant current discharging up to a discharging end voltage: 1.0 V, and 1 Using the quantity of electricity Q ₃ extracted by constant voltage discharge at 0.0 V, η = [(Q ₂ + Q ₃ ) / Q ₁ ] × 100.

As shown in Table 1, in constructing an RF battery comprising a grooved porous plate and a fiber assembly as the electrode material, the cell resistance can be further increased by adjusting the thickness of the porous plate and the size of the groove. It can be seen that the current efficiency can be further reduced. In this test, each sample has a cell resistivity of 1.2 Ω · cm ² or less and a low cell resistance. In this test, there are many samples having a cell resistivity of 1 Ω · cm ² or less and a current efficiency of 97% or more.

  From this test result, as an electrode material, an RF battery including a porous plate with a concave portion and a fiber assembly is excellent in the flowability of the electrolyte, and has a low cell resistance. It was shown that the cell resistance can be further reduced by the thickness of the substrate and the size of the groove.

  The present invention is not limited to these exemplifications, but is defined by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. For example, the electrode specifications (material, size, stacking order, recess size, shape, etc.) in Test Examples 1 and 2 and the type of electrolyte can be changed.

  The redox flow battery of the present invention is a storage battery for the purpose of stabilizing fluctuations in power generation output, storing electricity when surplus generated power, load leveling, etc., for power generation of natural energy such as solar power generation and wind power generation. Available. In addition, the redox flow battery of the present invention can be used as a storage battery that is installed in a general power plant and is used for the purpose of instantaneous voltage drop / power failure countermeasures and load leveling. In particular, the redox flow battery of the present invention can be suitably used for a large-capacity storage battery for the aforementioned purpose. The electrode for redox flow batteries of the present invention can be used as a constituent member of a redox flow battery.

1 Redox flow battery (RF battery)
100, 100A, 100B, 100C, 100D, 100E Battery cell 10 Electrode 10c Positive electrode 10a Negative electrode 11 Diaphragm 101 Porous plate 101g Recess 102 Fiber assembly 15 Frame assembly 150 Bipolar plate 151 Frame body 152c, 152a Supply hole 154c, 154a Drainage hole 170 End plate 172 Connecting member 106 Positive electrode tank 107 Negative electrode tank 108-111 Piping 112, 113 Pump 200 AC / DC converter 210 Substation equipment 300 Power generation unit 400 Load

Claims (9)

A redox flow battery comprising a positive electrode, a negative electrode, and a diaphragm interposed between the positive electrode and the negative electrode,
Of the positive electrode and the negative electrode,
One electrode includes a porous plate mainly composed of a continuous three-dimensional network structure formed by bonding carbon,
The other electrode includes a fiber assembly mainly composed of a plurality of carbon fibers intertwined with each other,
The porous plate is a redox flow battery having an opening on at least one surface thereof and a recess through which an electrolytic solution is circulated.   2. The redox flow battery according to claim 1, wherein at least one of the positive electrode and the negative electrode includes a laminate in which the porous plate and the fiber assembly are laminated.   The redox flow battery according to claim 2, wherein the porous plate in the laminate includes a concave portion that opens to an interface side with the fiber assembly.   The redox flow battery according to any one of claims 1 to 3, wherein the porous plate included in the one electrode includes a recess that opens to a surface facing the diaphragm.   5. The redox flow battery according to claim 1, wherein the concave portion includes a groove group in which a plurality of linear grooves in which the electrolyte introduction side and the discharge side do not communicate with each other are arranged in parallel.   The said recessed part is provided with a groove | channel, The depth of the said groove | channel is 0.3 mm or more and 4 mm or less, The width | variety of the opening part of the said groove | channel is 0.05 mm or more and 5 mm or less, The any one of Claims 1-5. Redox flow battery according to 1.   The redox flow battery according to claim 1, wherein the positive electrode includes the porous plate.   The redox flow battery according to any one of claims 1 to 7, wherein the fiber assembly includes at least one selected from carbon felt, carbon paper, and carbon cloth. A porous plate mainly comprising a continuous three-dimensional network structure formed by bonding carbon, and having a recess that is open at least on one surface and through which an electrolyte flows;
An electrode for a redox flow battery, comprising a laminate in which a plurality of carbon fibers mainly composed of carbon fibers are disposed so as to face a surface of the porous plate where the concave portion is open and are intertwined with each other.

Images