JP4599832B2 - Grooved electrode material and electrode for liquid flow type electrolytic cell - Google Patents

Description

  The present invention relates to an electrode material, and more particularly to a grooved electrode material used in a liquid flow type electrolytic cell used for a redox flow battery and an electrode using the same.

  In recent years, the demand for clean electrical energy has increased rapidly, and the fields using electrolytic cells are increasing accordingly. Typical examples include various batteries such as primary, secondary, and fuel cells, and electrolysis industries such as electroplating, salt electrolysis, and electrosynthesis of organic compounds. The electrodes used in these electrolytic cells include an electrode itself that is often found in batteries such as lead-acid batteries as an active material, and a reaction field that promotes the electrochemical reaction of the active material. There are things that work and the electrode itself does not change. The latter electrode is mainly applied to new secondary batteries and the electrolysis industry.

  Among the new type secondary batteries, the redox flow type battery is composed of an external tank and an electrolytic cell for storing an electrolytic solution, and an electrolytic solution containing an active material is supplied from the external tank to the electrolytic cell and is mounted on the electrode incorporated in the electrolytic cell. Electrochemical energy conversion, that is, charge / discharge is performed. In general, in charging and discharging, the electrolytic solution is circulated between the external tank and the electrolytic cell, so that the electrolytic cell has a liquid flow type structure as shown in FIG. The liquid flow type electrolytic cell is referred to as a single cell, and this is used as a minimum unit alone or in multiple layers. Since the electrochemical reaction in the liquid flow type electrolytic cell is a heterogeneous phase reaction that occurs on the electrode surface, it generally involves a two-dimensional electrolytic reaction field. If the electrolytic reaction field is two-dimensional, there is a drawback that the reaction amount per unit volume of the electrolytic cell is small. Therefore, the electrochemical reaction field has been three-dimensionalized in order to increase the reaction amount per unit area, that is, the current density. FIG. 2 is a schematic view of a liquid flow type electrolytic cell having a three-dimensional electrode.

  In the electrolytic cell, there are two opposing current collector plates 1, an ion exchange membrane 3 is disposed between the current collector plates 1, and along the current collector plate 1 by spacers 2 on both sides of the ion exchange membrane 3. The electrolyte flow paths 4a and 4b are formed. At least one of the flow passages 4a and 4b is provided with a porous electrode material 5 such as a carbon fiber aggregate to form a three-dimensional electrode.

  In a liquid flow type electrolytic cell composed of a three-dimensional electrode having such an electrode material, a liquid feed pump is used to supply a liquid reaction active material to the electrolytic cell when charging / discharging. Less energy is required, and a pump with good pump power efficiency is used. However, when a liquid reaction active material is supplied to the electrolytic cell, a liquid passing pressure loss inevitably occurs. In this case, when a loss of liquid flow pressure occurs, it is necessary to increase the pumping amount in order to secure a predetermined flow rate, and the energy consumption for operating the pump increases. In this case, especially in a rechargeable secondary battery such as a redox flow battery, the total energy efficiency of the battery itself is obtained by subtracting the energy required for liquid transfer from the power efficiency of charge / discharge as a loss. At best, if the pump power is large, the energy loss is large and the overall energy efficiency of the battery is lowered. Therefore, the lower the fluid pressure loss due to the electrolytic cell, the better.

  The electrolytic bath pressure loss depends on the porous electrode material of the three-dimensional electrode and others (electrolyzer piping, manifold, etc.). Here, when the porous electrode material having the three-dimensional electrode has the same density, increasing the thickness of the porous electrode material forming the three-dimensional electrode and increasing the thickness of the spacer can reduce the flow rate of the electrolyte. Liquid pressure loss can be reduced, and the load on the pump can be reduced. However, increasing the thickness of the three-dimensional electrode increases the amount of the electrode material used, resulting in a new problem of increasing the total cost of the battery.

Conventionally, a knitted fabric-like fabric (Patent Document 1) has been used as a three-dimensional electrode. However, in order to solve this problem, a thick yarn of 5th or higher is crossed with this. A carbonaceous electrode material of a knitted fabric composed of a thread thinner than this has been proposed (Patent Document 2). However, with this electrode material, the thick and / or thin threads that make up the electrode material fall off or misalign, and the shape is not stable when cut to a predetermined size, and the handling is poor, such as being unable to cut accurately. Problem has occurred. Therefore, the present inventors have proposed a carbonaceous nonwoven fabric (Patent Document 3) having a groove with a predetermined dimension. However, in this invention, when an ion exchange membrane is sandwiched between electrode materials and a three-dimensional electrode is formed by pressure contact with a pair of current collector plates, grooves are reduced by the pressure of the pressure contact, and the expected fluid pressure loss is obtained. The problem of not having occurred. Then, the electrode material with a groove | channel (patent document 4) which the retention rate of the said groove depth when compressing the thickness of a nonwoven fabric to 2/3 was 50% or more was proposed. Although the present invention has made it possible to distribute the electrolytic solution to the three-dimensional electrode at a higher flow rate, a problem has newly occurred that causes unevenness in the distribution of the electrolytic solution. This unevenness is a flow velocity difference in the width direction of the three-dimensional electrode, and indicates that the electrolytic solution concentrates and circulates in the central portion of the electrode. In addition, there is an example in which a carbon fiber nonwoven fabric having embossed shapes such as a circle, a square, and a hexagon is used as an electrode (Patent Document 5). However, in these concavo-convex electrode materials, in the center portion where the electrolyte solution concentrates in the liquid flow type electrode, the geometrical effective area where the electrolyte solution flows and reacts only in the groove and its vicinity is reduced, while the flow of the electrolyte solution is small. In part, stagnation occurs and excessive reaction proceeds. This phenomenon generally requires a reduction in the geometric utilization rate of the electrode, which leads to an increase in resistance due to an increase in current density, a corresponding decrease in effective use of the electrolyte, and a decrease in the life of the electrode. is there.
JP 59-119680 A Japanese Patent Laid-Open No. Sho 63-200467 JP 08-287923 A JP-A-11-273691 JP 2003-64566 A

  The present invention has been made in view of such circumstances, and it is intended to reduce flow unevenness to the three-dimensional electrode of the electrolyte when the electrolyte is passed through the three-dimensional electrode at a high flow rate, in particular, flow unevenness in the width direction of the electrode. The purpose of this is to provide an electrode material and an electrode that increase the efficiency of use of the electrolyte while maintaining the loss of fluid flow pressure and reduce the electrical resistance and improve the life of the electrolytic cell. It is.

That is, the present invention is an electrode material comprising a nonwoven fabric mainly composed of carbonaceous fibers, and having a plurality of grooves and a plurality of wrinkles formed by the grooves on a surface layer portion of the nonwoven fabric. Is a grooved electrode material characterized in that at least the grooves continuous in the longitudinal direction of the electrode material and the widths of the plurality of ridges divided by the groove are different in the width direction of the electrode material.
Further, the grooved electrode material is characterized in that the width of the ridge of the electrode material is wider at the center portion than at both ends in the width direction of the electrode material.

Furthermore, it is preferable that the grooved electrode material of the present invention sets the ridge having the maximum ridge width as a starting point, and the ridge width (y) with respect to the number (x) of grooves from the starting point is calculated by the following formula. .
(X ² / a ² ) + (y ² / b ² ) = 1
(Where a and b are coefficients, a> 0, b ≠ 0, x is an integer, and y> 0.)

  The grooved electrode material of the present invention preferably has a retention rate of the groove depth of 50% or more when the thickness of the nonwoven fabric is compressed to 2/3.

In the grooved electrode material of the present invention, the basis weight of the nonwoven fabric is preferably 100 g / m ² or more, and the bulk density of the nonwoven fabric is preferably 0.05 to 0.15 g / cc.

  In the grooved electrode material of the present invention, the groove width is preferably 1 to 5 mm, and the groove depth is preferably 20% or more of the thickness of the nonwoven fabric.

  Furthermore, in the electrode of the present invention, a diaphragm is disposed between a pair of current collector plates arranged to face each other with a gap therebetween, and the electrolyte solution formed between the current collector plate and the diaphragm is circulated. In the electrode for a liquid flow type electrolytic cell in which a grooved electrode material is disposed on at least one of the paths, the groove of the electrode material is formed in parallel to the flow path of the electrolytic solution, and is formed by the groove of the electrode material. The width of the ridge is characterized in that the central portion is wider than both ends in the width direction of the electrode material.

  In the electrode of the present invention, it is preferable that the difference in the width in the width direction of the electrode is such that the width at the center is within 8 times the width at both ends.

  By using the electrode material of the present invention, in the field of using various electrolytic cells, it is possible to increase the utilization efficiency of the electrolytic solution while maintaining a low liquid passing pressure loss, and to reduce the electrical resistance and improve the life of the electrolytic cell. . Thereby, the total energy efficiency as a battery can be improved and the lifetime can be extended. These are particularly effective for redox flow batteries.

  The grooved electrode material in the present invention needs to be a grooved electrode material made of a nonwoven fabric containing carbon fiber as a main component (at least 50% by mass). Mainly because it is suitable for use in a liquid flow electrolytic cell, that is, a three-dimensional electrode in which an electrode material is present on at least one of both electrodes through a diaphragm and is pressed by a current collector, particularly a redox flow battery. .

The groove in the grooved electrode material of the present invention refers to a groove formed continuously on the nonwoven fabric surface to form a flow path, and a plurality of grooves are formed on the nonwoven fabric in the longitudinal direction of the nonwoven fabric (electrolytic solution). It is preferable that they are formed in parallel with each other in the flow direction and at least in the longitudinal direction, and the ridges divided by the grooves are arranged with different widths. In particular, the wrinkle width (y) with respect to the number of wrinkles from the starting point (x) is expressed by the following formula 1.
(X ² / a ² ) + (y ² / b ² ) = 1 (Formula 1)
(Where a and b are coefficients, a> 0, b ≠ 0, x is an integer, y> 0)
It is desirable that the heel width is smaller than the heel width of the starting point as the distance from the starting point increases. In this case, the coefficients a and b are arbitrarily set according to the conditions of the electrode to be created, the liquid flow rate, and the like.
For example, in the grooved electrode material shown in FIG. 3 and FIG. 4, when the width of the arbitrarily set starting point (0) is Y0, it exists continuously (1), (2), (3) ... (n-1), (n) groove-to-groove spacings Y1, Y2, Y3, Y (n-1), Yn have a width according to the notation. The heel width decreases as the value of n in Yn increases. The electrode material in which the groove-to-groove interval (gutter width) is continuously changed according to such a constant law is intended to prevent uneven flow of electrolyte in the three-dimensional electrode in the electrolytic cell, especially in the width direction. Particularly important, since the inside of the electrode is used effectively, the resistance value is reduced, and the electrolyte utilization factor is increased.

  Moreover, the groove | channel should just be continued at least in the longitudinal direction, and may be continued also in the width direction. An example of the shape of the groove is a shape as shown in FIG. When viewed from the side of the ridge, the shape of the ridge is an island shape, and is dotted with a large number of islands such as an ellipse, an egg shape, and a rhombus. It is preferable that such ridges also satisfy the above arrangement and width (see FIGS. 7, 8, and 9).

  Furthermore, the grooved electrode material of the present invention preferably has a groove depth retention of 50% or more when the thickness of the nonwoven fabric is compressed to 2/3, more preferably 55% or more. This is because, when the retention rate is less than 50%, the groove disappears due to the pressure applied when forming the electrode even when the deep groove is formed, and the liquid permeability deteriorates. In the present application, the thickness of the nonwoven fabric is compressed to 2/3. This is the case when the thickness is compressed to 2/3 as a value that is considered optimal when the electrode material is pressure-welded at the time of electrode preparation. It is set.

Moreover the weight per unit area of the nonwoven fabric constituting the grooved electrode material of the present invention is at least 100 g / m ^2, more preferably if 100 to 800 g / m ^2. When the basis weight is less than 100 g / m ² , the reaction field as a three-dimensional electrode material is insufficient and the internal resistance of the electrolytic layer increases. The bulk density is preferably 0.05 to 0.15 g / cc, more preferably 0.06 to 0.14 g / cc. When the bulk density is less than 0.05 g / cc, the contact property with the current collector plate is low and the contact resistance of the electrolytic cell is increased. On the contrary, when the bulk density exceeds 0.15 g / cc, electrolysis is performed. The liquid tends to concentrate in the groove and circulate, so that the liquid does not diffuse uniformly into the electrode material, and the utilization factor of the electrode material decreases. In the present invention, it is preferable that the range of the weight per unit area and the density is satisfied, and that the thickness of the electrode material is larger than the thickness of the spacer 2 of FIG. More preferable.

  The groove width of the grooved electrode material of the present invention is preferably 1 to 5 mm, and the groove depth is preferably 20% or more with respect to the thickness of the nonwoven fabric. When the groove width is less than 1 mm, or when the groove depth is less than 20% of the thickness, the groove disappears when the electrode material is pressure-contacted at the time of making the electrolytic cell, and the liquid pressure loss increases. There are things to do. When the groove width exceeds 5 mm, the groove may disappear when the electrode material is pressed. Further, the width of the ridge is preferably larger than the groove width. When the interval between the grooves is smaller than the groove width, the bondability between the electrode material and the current collector plate is lowered, and the contact resistance may be increased. In the grooved nonwoven fabric of the present invention, the groove direction may be provided so as to face the ion exchange membrane in the center of the electrolytic cell, or may be provided so as to face the current collector plate.

The manufacturing method of the electrode material with a groove | channel of this invention is 100-200 degreeC for 0.1 to 5 minutes at the pressure of 1-500 kg / cm < ² > at the carbonizable nonwoven fabric containing 0.1-10 mass% of organic binders. It is preferable to carbonize after forming the groove by heat and pressure molding. The carbonizable non-woven fabric is not particularly limited. For example, isotropic pitch or mesoface pitch precursor fiber, cellulose fiber, cured novolac fiber, polyvinyl alcohol fiber, aromatic polyamide fiber, poly-p-phenylene. Although there are benzoxazole fibers and the like, it is particularly preferable to use as a raw material a flame resistant fiber obtained by making a polyacrylonitrile fiber flame resistant by a known method.

  The method for making the carbonizable material into a nonwoven fabric is not particularly limited, but, for example, a method of defibrating with a card and making a multilayered web with a needle punch is suitably used. . In order to facilitate the formation of the grooves, non-woven fabrics of different fiber materials may be laminated in multiple layers, or non-woven fabrics may be created by mixing different fiber materials.

In addition, the method of providing the groove is a mold having a width that can be produced by taking into account that the above-mentioned nonwoven fabric has a predetermined peak width, height, and shrinkage by firing calculated by the above formula. It puts on the said nonwoven fabric, and heat-press-molds by the pressure of 1-500 kg / cm < ² > for 0.1 to 5 minutes at the temperature of 100-200 degreeC, and obtains a grooved nonwoven fabric. Here, in order to form a groove having excellent groove depth retention ratio, it is preferable to add 0.1 to 10% by mass of an organic binder to the non-woven material, and groove the groove in the above range. If it can form, it will not be limited to this method. In addition, the said pressure has employ | adopted the value which remove | divided the load (= cylinder sectional area of a press machine x gauge pressure) divided by the area of the nonwoven fabric to be pressed.

  The above organic binders include acrylic, cellulose, polyvinyl alcohol, epoxy resin, vinyl acetate, and phenol resin, but especially phenol resin that forms stable grooves even after firing by heat curing and carbonization. System is desirable. The method of containing the binder in the nonwoven fabric includes a method of mixing the powdery material when the raw cotton is opened, a method of impregnating the liquid material into the nonwoven fabric, and a method of spraying the powdered material directly on the nonwoven fabric, but are particularly limited is not. However, in order to increase the retention ratio of the groove depth during compression, when the powder binder is sprayed on the surface, the binder is fixed inside the nonwoven fabric by spraying from the top and sucking with suction from below after spraying. Things are desirable. Moreover, about the nonwoven fabric in which provision of a groove | channel is difficult, you may bond and integrate with the nonwoven fabric which formed the groove | channel previously.

  The grooved nonwoven fabric thus obtained is carbonized at 800 to 2500 ° C. in an inert atmosphere for imparting conductivity. Furthermore, after carbonization, in order to improve wettability with the electrolytic solution, surface oxidation is performed in air at 500 to 1000 ° C. to obtain a carbonaceous electrode material. The carbonization method and the oxidation method may be known methods, but the crystal plane spacing of carbon is 3.7 angstroms or less, and the number of surface oxygen atoms by ESCA surface analysis is at least 7% or more of the number of carbon atoms. It is preferable to be manufactured.

Next, a novel electrode for a liquid flow type electrolytic cell using the electrode material of the present invention will be described.
In the electrode of the present invention, a plurality of grooves of the electrode material of the present invention are provided in parallel to the flow path of the electrolyte solution, and the gap between the grooves of the electrode material (groove width) is the center in the width direction of the electrode. The feature is that the part is wider than both ends. In a general three-dimensional electrode, the flow of the liquid tends to flow more easily in the center portion than in the both end portions in the width direction of the electrode. In particular, when using an electrode material having a groove, the electrode material groove is made parallel to the electrolyte flow path in order to reduce the fluid pressure loss. The flow rate of the end portion is reduced, and the geometrically effective use of the entire electrode is hindered. Therefore, the electrode material in the electrode according to the present invention is prepared such that the maximum width portion of the electrode material is the center in the width direction of the electrode, and the width of the electrode material is gradually reduced toward both end portions. Is desirable.
For example, in the grooved electrode material shown in FIGS. 4 and 5, when the maximum ridge width is Y0 at the central portion 0 in the width direction of the electrode, (1), (2), (3) .. (n-1), (n), (-1), (-2), (-3) ... (-(n-1)), (-n) in the right direction It is desirable that the widths Y1, Y2, Y3, Y (n-1), Yn, Y-1, Y-2, Y-3, Y- (n-1), and Y-n conform to the following formula 1.
(X ² / a ² ) + (y ² / b ² ) = 1 (Formula 1)
(Where a and b are coefficients, a> 0, b ≠ 0, x is an integer, y> 0)

  However, at this time, the difference between the collar width (Y0) at the center and the collar width (minimum value) (Yn) at both ends is preferably within 8 times, more preferably within 7 times. More preferably, it is within 6 times. When the difference between the maximum value of the width of the ridge and the minimum value of the width of the edge is greater than 8 times, the ratio of the electrolyte flowing preferentially to the edge and flowing to the center becomes high. Is not preferable because there is a possibility that the battery charge rate may deteriorate. Further, the lower limit of the difference between the collar width (Y0) at the center and the collar width (minimum value) (Yn) at both ends is preferably 1.2 times or more, more preferably 1.3 times, and even more preferably. 1.5 times or more. If it is less than 1.2 times, there is no difference in the charging rate from the case where the heel widths are arranged at equal intervals, which is not preferable.

  Further, in the present invention, a groove having a linear shape as illustrated in FIG. 4 can be used effectively, but the ridges between the grooves as illustrated in FIGS. 7 to 9 are elliptical. It is also possible to use those arranged in the form of In the case of the grooved electrode material having such an elliptical ridge, the ratio (A / B) of the longer diameter (A) to the shorter diameter (B) of the elliptical ridge is 1.2 to 5.0. It is preferable that the longer diameter of the ellipse is arranged in parallel with the liquid flow passage (FIG. 8). FIG. 9 is a schematic cross-sectional view of an example of such a grooved electrode material.

Constants a and b that determine the basis weight, thickness, bulk density, groove thickness, groove width, groove depth retention ratio, liquid passage pressure loss and ridge width and ridge width of the electrode material employed in the present invention are as follows. Measured in
(1) Weight per unit (W)
A 10 cm square (size: a) sample is taken, dried at 100 # C for 1 hour, allowed to cool with a desiccator, and weighed with an electronic balance (mass: w ′). Further, the basis weight is calculated by dividing w ′ by the square of the dimension a. (Unit: g / m ² )

(2) Thickness (t)
A sample used for the measurement of fluid pressure loss is 5 points of the 50 cm square and the center part, the bank part of the sample is aligned with the center of the probe, and the digital linear gauge D10 (maximum load 100 g-f) manufactured by Ozaki Mfg. Co., Ltd. Measure using a 32 mmΦ probe, read to 2 digits after the decimal point, and round to the minimum. The unit used is millimeter.
(3) Bulk density Calculated by dividing the basis weight by the electrode material thickness (unit: g / cc).

(4) Groove thickness (tm)
Measure 6 points of thickness of the 10cm square groove part of the sample used for the measurement of fluid pressure loss on a dial thickness gauge (model G: maximum load 180g-f) manufactured by Ozaki Mfg. Co., Ltd. with a contact surface size of 1mm x 10mm. Read and average up to 2 digits and round off to the nearest decimal place. The unit used is millimeter.
(5) Groove depth (tM)
The difference between the value of the groove thickness in (4) and the value of the electrode material thickness in (2) is defined as the groove depth (unit: millimeter).

(6) Groove width (DM)
The groove width is measured with a Digimatic caliper (Series 500) manufactured by Mitutoyo Corp., read to two digits after the decimal point, and rounded off to the nearest decimal place.

(7) Groove depth retention rate The distance between the base of the compression tester and the probe (dimension 25 mm x 80 mm) is adjusted to the electrode material thickness, and the sample (dimension 25 mm x 50 mm) is observed so that the cross section of the groove can be observed. Insert between the base of the compression tester and the probe. The groove depth observed at this time is measured with a Digimatic caliper (series 500) manufactured by Mitutoyo Corporation, and is read to two digits after the decimal point to obtain the groove depth (tM [1]). After that, it is compressed to 2/3 of the original nonwoven fabric thickness using a compression tester, and the groove depth observed at this time is measured with the above-mentioned Digimatic Caliper (Series 500) manufactured by Mitutoyo Corporation. The reading groove depth is 2/3 to the second decimal place (tM [2/3]). From these data, the retention ratio of the groove depth is obtained by Equation 2. Note that the groove depth reading was enlarged by applying a linen tester to the measurement part.
Retention rate of groove depth (%) = tM [2/3] / tM [1] × 100 (Formula 2)

(8) Liquid-flowing pressure loss Liquid-flowing electrolytic layer having the same shape as the liquid-flowing electrolytic layer shown in FIG. 2 and formed by a spacer (2) having a thickness of 30 cm in the liquid-flowing direction, a width direction (channel width) of 50 cm, and a predetermined thickness. Prepare. Manifolds are installed on the lower left and upper right of the electrolytic cell. The prepared electrode material is cut into 20 cm × 50 cm and installed. Ion exchange water with a liquid volume of 50 liters / hour is circulated from the lower side, and the liquid passage pressure loss is measured. It measures similarly by the system which does not install an electrode material as a blank, and makes the difference of a measured value and a blank measured value the liquid pressure loss of an electrode material.

(9) 畝 width (Y) and constants a and b values Measure the width of 畝 with a Digimatic caliper (Series 500) manufactured by Mitutoyo Corp., read to two digits after the decimal point, and round off to the minimum. The width of the post-processed portion of the portion that defines the width of the position that is the maximum width when creating the original fabric groove as Y′0 (equal to the b ′ value) is assumed to be Y0 (equal to the b value). The order (n) of the width at the end of the electrode configuration and the width of the intermediate point (n / 2) are measured, a is calculated from Equation 1, and the average is taken.

(10) Electrode characteristics A small cell having an electrode area of 1000 cm ² having an electrode area of 20 cm in the vertical direction (liquid passing direction) and 50 cm in the width direction is formed, and charging and discharging are performed at a constant current density to test the electrode performance. A 3 mol / l sulfuric acid aqueous solution of 2 mol / l vanadium oxysulfate was used for the positive electrode electrolyte, and a 3 mol / l sulfuric acid aqueous solution of 2 mol / l vanadium sulfate was used for the negative electrode electrolyte. The amount of the electrolytic solution was excessively large with respect to the cells and piping. The liquid flow rate was 50 liters / hour, and the measurement was performed at 30 ° C.

(A) Current efficiency: η _I
In a one-cycle test starting with charging and ending with discharging, the current density is 40 mA / cm ² (400 mA) per electrode geometric area, and the amount of electricity required for charging up to 1.7 V is Q ₁ coulomb and up to 1.0 V. Let Q ₂ and Q ₃ coulomb be the amounts of electricity taken out by constant current discharge and the subsequent constant voltage discharge at 1.2 V, respectively, and the current efficiency ηI is obtained by Equation 3.

(B) Cell resistance: R
The ratio of the amount of electricity taken out by discharge to the theoretical amount of electricity Q _th required to completely reduce V ³⁺ in the negative electrode solution to V ²⁺ is taken as the charging rate, and the charging rate is obtained by Equation 4.

The charging voltage V _C50 and the discharging voltage V _D50 corresponding to the amount of electricity when the charging rate is 50% are obtained from the amount of electricity-voltage curve, and the cell resistance R (Ω · cm ² ) with respect to the electrode geometric area is obtained from Equation 5. .

Hereinafter, the present invention will be described with reference to examples and comparative examples.
Examples 1 to 3, Comparative Example 2
A polyacrylonitrile (PAN) fiber having an average fiber diameter of 16 μm is made flame resistant at 250 ° C. in the air, and then made into a felt by using the short fiber of the flame resistant fiber to form a nonwoven fabric having a basis weight of 900 g / m ² and a thickness of 6.1 mm. Obtained. A powder novolak resin (BRP534A manufactured by Showa Polymer Co., Ltd.) is uniformly sprayed on the nonwoven fabric at a rate of 18.9 g / m ² and sucked from below with a suction of a linear speed of 3.0 m / sec to remove the binder from the nonwoven fabric. Immobilized on top to obtain a flame retardant nonwoven fabric containing binder.
As shown in FIG. 5, the width of the indentation at the center (Y′0), the number of indentations (2n + 1) 51, the peak width 2.0 mm, the peak height 10 mm, and the peak length 300 mm, the width of each recess portion is A die having a total width of 560 mm in which the peaks are arranged in parallel with the indentation width derived by substituting constants a ′ and b ′ according to (Formula 1) (X: position from the center, Y ′: calculated width) And piled so that the mountain side faces the nonwoven fabric, set in a heat press apparatus having a temperature of 180 ° C. and a cylinder diameter of 160 mm, and pressed at a pressure of 50 kg / cm ² for 1 minute to obtain a flame-resistant nonwoven fabric with grooves. . The constants a ′ and b ′ of the heel obtained in Table 1 and the heel width (Y′n) of the endmost portion are shown in Table 1 assuming that the continuity of the ridge width obtained in the mold is equal to the continuity of the depression of the mold. Show.
The flame-resistant fiber nonwoven fabric was heated to 1500 ° C. at a rate of temperature increase of 10 ° C./min in an inert gas, kept at this temperature for 1 hour for carbonization, and then cooled to obtain a carbide. The carbide was further oxidized in air at 700 ° C. to a mass yield of 93% to obtain a grooved carbonaceous fiber nonwoven fabric. A rectangle having a width of 500 mm and a length of 200 mm was cut out from the ridge having the maximum width as a center, and used as an electrode. The basis weight, thickness, groove portion thickness, groove depth, groove width, groove depth retention rate, groove center width (Y0; b value), endmost portion of the grooved carbon fiber nonwoven fabric thus obtained Table 2 shows the heel width (Yn) and the constant a value calculated from Equation 1. Further, Table 3 shows liquid passage pressure loss and electrode performance when the spacer thickness is 2.5 mm.

Comparative Example 1
Polyacrylonitrile (PAN) fibers having an average fiber diameter of 16 μm are made flame resistant at 250 ° C. in the air, and then made into felt using the short fibers of the flame resistant fibers to obtain a nonwoven fabric having a basis weight of 900 g / m ² and a thickness of 6.1 mm. It was. A powdered novolak resin (BRP534A manufactured by Showa Polymer Co., Ltd.) is uniformly sprayed on the nonwoven fabric at a rate of 18.9 g / m ² and sucked from below with a suction of a linear speed of 3.0 m / sec to remove the binder from the nonwoven fabric. A binder-containing flameproof nonwoven fabric was obtained by immobilization on the top. An aluminum mold having a total width of 560 mm in which the nonwoven fabric is cut into a 700 mm square, and a mountain width of 2.0 mm, a mountain height of 10 mm, a mountain length of 300 mm, and a crest having a width of 15.13 mm are arranged in parallel. The piles were stacked so that the piles faced the nonwoven fabric, and set in a heat press apparatus having a temperature of 180 ° C. and a cylinder diameter of 160 mm, and pressed at a pressure of 20 kg / cm ² for 1 minute to obtain a grooved flame-resistant fiber nonwoven fabric.
The flame resistant fiber nonwoven fabric was heated to 1500 ° C. at a temperature rising rate of 10 ° C./min in an inert gas, kept at this temperature for 1 hour, carbonized, and then cooled to obtain a carbide. The carbide was further oxidized in air at 700 ° C. to a mass yield of 93% to obtain a grooved carbonaceous fiber nonwoven fabric. The basis weight, thickness, density, groove portion thickness, groove depth, groove width, groove depth retention rate, and ridge width (in this case, equal interval: Y0) of the obtained grooved carbon fiber nonwoven fabric are shown. It is shown in 2. Further, Table 3 shows liquid passage pressure loss and electrode performance when the spacer thickness is 2.5 mm.

  The electrode material of the present invention reduces the unevenness of the electrolyte solution in the width direction of the three-dimensional electrode, and allows the electrolyte solution to be uniformly supplied into the electrode. The current distribution due to is reduced, and the battery system can be operated efficiently. As a result, it can contribute to higher output of liquid flow type batteries, and can be used for conventional power storage battery applications, peak output applications requiring high output and high efficiency, and emergency backup battery applications. .

It is the schematic which shows the battery using flow-type electrolytic cells, such as a redox flow type battery. It is a disassembled perspective schematic diagram which shows an example of the liquid circulation type electrolytic cell which has the electrode material of this invention. It is a cross-sectional schematic diagram which shows the measurement position of the thickness of a grooved electrode material, groove part thickness, groove depth, groove width, and ridge width. It is a perspective schematic diagram which shows an example of the electrode material of this invention. It is a cross-sectional schematic diagram which shows an example of the electrode material of this invention. It is a cross-sectional schematic diagram which shows an example of the metal mold | die for manufacturing the electrode material of this invention. It is an upper surface schematic diagram which shows an example of the electrode material of this invention. It is a figure which shows the dimension of the elliptical ridge of the electrode material of this invention. It is a cross-sectional schematic diagram which shows an example of the electrode material which has the elliptical ridge of this invention.

Explanation of symbols

1: current collector plate, 2: spacer, 3: ion exchange membrane, 4a and 4b: liquid flow path,
5: Electrode, 6: Cathode solution tank, 7: Anode solution tank, 8 and 9: Liquid feed pump,
10: liquid inlet, 11: liquid outlet,
t: thickness of electrode material, tm: thickness of groove portion of electrode material, tM: groove depth of electrode material,
Y: width of electrode material, DM: groove width of electrode material,
A: The major axis of the ellipse ridge of the electrode material, B: The minor axis of the ellipse ridge of the electrode material,

Claims (6)

An electrode material comprising a nonwoven fabric mainly composed of carbonaceous fibers, and having a plurality of grooves and a plurality of ridges formed by the grooves in a surface layer portion of the nonwoven fabric, wherein the plurality of grooves of the electrode material is at least the length of the electrode material It is a groove that is continuous in the direction, and the width of a plurality of ridges divided by the groove is used in a liquid flow-type electrolytic cell characterized in that the central part is wider than both ends in the width direction of the electrode material. grooved electrode material that. The wrinkle width (y) with respect to the cumulative number of wrinkles (x) is calculated from the starting point at a wrinkle having the maximum wrinkle width of the electrode material, according to the following formula: A grooved electrode material used in the liquid-flowing electrolytic cell as described.
(X ² / a ² ) + (y ² / b ² ) = 1 (Formula 1)
(Where a and b are coefficients, a> 0, b ≠ 0, x is an integer, and y> 0.) The groove used in the liquid-flowing electrolytic cell according to claim 1 or 2, wherein a retention rate of the groove depth when the thickness of the electrode material is compressed to 2/3 is 50% or more. With electrode material. The basis weight of the electrode material is 100 g / m ² or more, and the bulk density of the electrode material is 0.05 to 0.15 g / cc. Grooved electrode material used in the liquid flow type electrolytic cell . The groove width is 1 to 5 mm, and the groove depth is 20% or more of the thickness of the electrode material , used in the liquid flow-type electrolytic cell according to any one of claims 1 to 3. grooved electrode material that.   A diaphragm is disposed between a pair of current collector plates disposed opposite to each other with a gap therebetween, and a groove is provided in at least one of the electrolyte flow paths formed between the current collector plates and the diaphragm. An electrode for a liquid flow type electrolytic cell provided with an electrode material, wherein the groove of the electrode material is arranged in parallel with the flow direction of the electrolyte solution, and the width of the ridge formed by the groove of the electrode material is: An electrode for a liquid flow-type electrolytic cell, characterized in that the width of the center portion in the width direction of the electrode material is 1.2 times or more and within 8 times the width of the width of both end portions.