JP2003308850A - Electrode material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode material having a groove obtained by treating precursor nonwoven fablic of carbonaceous fiber nonwoven fablic at high temperatures under inactive atmosphere, which is filled in a liquid flow type electrolytic cell by compressing it to have a weight reduction rate of not more than 1% and excellent shape stability after passing it through the liquid. <P>SOLUTION: This manufacturing method is to manufacture the electrode material by applying activating treatment to the raw material of the constituent precursor nonwoven fablic having tensile strength of 18-30 kgf/mm<SP>2</SP>, breaking elongation of 20-40%, and true density of 1.30-1.45 g/cm<SP>3</SP>, when measured in accordance with JIS R7601 (1986) as a single fiber, at high temperatures and under inactive atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode material, and more particularly to an electrode material having a groove used in a liquid flow type electrolytic cell used in a redox flow type battery.

[0002]

2. Description of the Related Art In recent years, the demand for clean electric energy has been rapidly increasing, and along with this, the fields using electrolytic cells are increasing. Typical examples are various battery fields such as primary / secondary / fuel cells, electroplating, salt decomposition,
There is an electrolytic industry field such as electrolytic synthesis of organic compounds.

Conventionally, electrodes have been mainly developed as those that influence the performance of batteries. There are some types of electrodes that do not act as active materials themselves but act as a reaction field that promotes the electrochemical reaction of the active materials.This type has conductivity, is chemically stable, and is inexpensive. Because of this, carbonaceous fibers are often used. In particular, a non-woven fabric of carbonaceous fiber, which has excellent chemical resistance, conductivity, and liquid permeability, is used as an electrode material of a redox flow battery used for storing electric power.

The redox flow type battery is characterized by high charge / discharge efficiency, high energy density and long cycle life compared with conventional lead batteries and the like, and from the viewpoint of effectively securing electric energy, it is nighttime. Has been developed as a battery for electric power storage for storing excess electricity of the above and discharging it at the time of daytime demand increase to level the fluctuation of demand. It can also be applied as a power supply stabilizing device that smoothes the output of unstable natural energy such as solar power and wind power generation. It is superior to other batteries in terms of reliability and economy, and is one of the most practical batteries.

The redox flow type battery is composed of an external tank for storing an electrolytic solution and an electrolytic cell. Electrochemical energy conversion is performed on an electrode incorporated in the electrolytic cell by supplying the electrolytic solution containing an active material from the external tank to the electrolytic cell. That is, charging and discharging are performed. Generally, at the time of charging / discharging, since the electrolytic solution is circulated between the external tank and the electrolytic cell, 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 the single cell is used as a minimum unit or is used by stacking in multiple stages. The electrochemical reaction in the liquid flow type electrolytic cell is
Since it is a heterogeneous phase reaction that occurs on the electrode surface, it generally involves a two-dimensional electrolytic reaction field.

However, if the electrolytic reaction field is two-dimensional,
There is a drawback that the reaction amount per unit area of the electrolytic cell is small. Therefore, in order to increase the reaction amount per unit area, that is, the current density, three-dimensionalization of the electrochemical reaction field has been performed.

In the liquid flow type electrolytic cell having such a three-dimensional electrode, there are two current collector plates 1 facing each other, an ion exchange membrane 3 is arranged between the two, and spacers 2 on both sides of the ion exchange membrane 3 are provided.
Thus, flow paths 4a and 4b for the electrolytic solution are formed along the current collector plate 1. An electrode 5 such as a carbon fiber aggregate is arranged in at least one of the flow paths 4a and 4b, and a three-dimensional electrode is constructed in this manner. As the electrolytic solution, Fe
-Cr, VV, etc. are used.

For example, in the case of a redox flow type battery using an acidic sulfuric acid aqueous solution of vanadium as the electrolytic solution, at the time of discharging, the electrolytic solution containing vanadium divalent ions V ²⁺ is supplied to the liquid flow path 4a on the negative electrode side, and the positive electrode An electrolyte containing vanadium pentavalent ions V ⁵⁺ is supplied to the side liquid flow path 4b. In the flow path 4a on the negative electrode side, V ²⁺ emits electrons in the three-dimensional electrode 5,
It is oxidized to vanadium trivalent ion V ³⁺ . The emitted electrons pass through an external circuit and reduce V ⁵⁺ to vanadium tetravalent ion V ⁴⁺ in the three-dimensional electrode on the positive electrode side. The opposite reaction proceeds during charging.

In a liquid flow type electrolytic cell comprising a three-dimensional electrode having such an electrode material, a liquid sending pump is used to supply a liquid reaction active material to the electrolytic cell during charge / discharge, but a pump. The less energy required for operation, the better, and a pump with good pump operation efficiency is used. However, when a liquid reaction active material is supplied to the electrolytic cell, liquid pressure loss is unavoidable. Here, if a fluid pressure loss occurs, it is necessary to increase the liquid feed amount of the pump in order to secure a predetermined flow rate, and the energy consumption amount for operating the pump increases. In this case, especially in a rechargeable secondary battery such as a redox flow type battery, the total energy efficiency of the battery itself is the power efficiency of charging / discharging minus the energy required for liquid transfer as a loss, and the power efficiency However, if the pump power is large, the energy loss will be large and the overall energy efficiency of the battery will decrease. Therefore, the lower the fluid pressure loss through the electrolytic cell, the better.

The fluid pressure loss in the electrolytic cell depends on whether the porous electrode material of the three-dimensional electrode is used or not (the piping of the electrolytic cell, the 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 spacer thickness reduces the flow velocity of the electrolytic solution, thereby reducing the fluid flow pressure. The loss can be reduced and the load on the pump can be reduced. However, increasing the thickness of the electrode material
This increases the amount of electrode material used, which causes a new problem of increasing the total cost of the battery.

In order to solve this problem, the present inventors invented an electrode material having a groove in Japanese Patent Laid-Open No. 8-287923. However, there is a problem in the morphological stability of the groove, and due to the pressure applied when forming the electrode,
There was a phenomenon in which the material was not damaged or destroyed, fine carbon fiber powder was generated, and when it further progressed, the grooves disappeared and the liquid permeability deteriorated over time.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has excellent morphological stability.
Minimize generation of fine powder of fibers due to fiber damage caused by pressure contact when forming the electrolytic layer, suppress reduction of grooves, pressure bonding to the inner wall surface of the battery, degree of stress applied to other materials in the battery The carbon electrode material that is excellent in energy consumption, suppresses the flow pressure loss during liquid flow without sacrificing the basic performance of the electrode material, and has excellent smoothness of the flow of the electrolyte solution and high energy efficiency. It was intended.

[0013]

[Means for Solving the Problems] That is, an electrode material having a groove made of a carbonaceous fiber nonwoven fabric obtained by treating a carbonaceous precursor nonwoven fabric at a high temperature in an inert atmosphere. The present invention provides an electrode material, which is characterized in that the material is compressed and loaded, and the weight loss rate after passing the liquid is 1% or less and the shape stability is excellent.

The present invention has a tensile strength of 60 to 100 kgf / mm ² and a breaking elongation of 5.5 to 6 in a non-woven single fiber constituting an electrode material, measured according to JIS R7601 (1986). The electrode material is characterized by being 0%.

The present invention is a method for producing an electrode material having grooves, wherein the electrode material is obtained by carbonizing a carbonaceous precursor nonwoven fabric. The method for producing a grooved electrode material according to claim 1, wherein the precursor nonwoven fabric of carbonaceous fiber nonwoven fabric contains an organic binder in an amount of ² to 15 g / m ² .

According to the present invention, the single fiber as a raw material constituting the above-mentioned carbonaceous precursor nonwoven fabric is JIS R7601 (198).
The tensile strength measured according to 6) is 18 to 30 kgf / m.
The electrode material having a groove according to claim 1, wherein m ^{2 is} a breaking elongation of 20 to 40%, and the true density of the raw material is 1.30 to 1.45 g / cm ^3. Is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The grooved electrode material of the present invention is required to be a grooved electrode material made of a carbonaceous fiber nonwoven fabric. Mainly for liquid flow type electrolytic cell, that is, the electrode material is present in at least one of both electrodes through a diaphragm, and is a three-dimensional electrode configured by pressure contact with a current collector plate, especially for suitable application to redox flow type batteries. is there. In addition, in the present invention, a groove refers to a groove in which a concave state is continuously formed in a cross section of a nonwoven fabric to form a flow path (FIG. 3).

The grooved electrode material of the present invention is an electrode material having a groove made of a carbonaceous fiber nonwoven fabric obtained by treating a carbonaceous precursor nonwoven fabric at a high temperature in an inert atmosphere. It is necessary that the electrode material is compressed and loaded, and the weight loss rate after passing the liquid is 1% or less, and the shape stability is excellent. If the weight loss rate after passing through the liquid exceeds 1%, damage or destruction of the material occurs due to the pressure applied particularly when the electrode is formed, which is not preferable because fine powder of carbon fiber is easily generated. Further, the grooves disappear, liquid permeability deteriorates, and energy efficiency further decreases. As a condition for realizing this, it is important that the weight loss rate after water flow is 1% or less.

The manufacturing method of the electrode material having the groove of the present invention is as follows.
² to 15 g / m ^{2 of} organic binder, preferably 5 to
It is necessary to heat-press and mold the carbonized flameproof fiber nonwoven fabric containing 10 g / m ² to form the grooves, and then to perform high temperature treatment in an inert atmosphere.

The above-mentioned non-woven fabric which can be treated at a high temperature in an inert atmosphere is not particularly limited, and examples thereof include precursor fibers of isotropic pitch or meso-face pitch, cellulose fibers, cured novolac fibers, polyvinyl alcohol fibers, There are aromatic polyamide fibers, poly-p-phenylenebenzoxazole fibers, and the like, but it is particularly preferable to use flame-resistant fibers obtained by flame-proofing polyacrylonitrile fibers by a known method as a raw material. In this case, it is particularly preferable that the tensile strength of the single fiber as the raw material measured by the method according to JIS R7601 (1986) is 18 to 30 kgf / mm ² and the elongation at break is 20 to 40%.

The method for making the carbonizable material into a non-woven fabric is not particularly limited, and for example, a method in which a multi-layered web is made into a non-woven fabric by needle punching after opening with a card is suitable. Used. Further, in order to facilitate the formation of the grooves, nonwoven fabrics of different fiber materials may be laminated in multiple layers, or different fiber materials may be mixed to form a nonwoven fabric.

The method of adding a groove to the above-mentioned non-woven fabric
2 to 15 g / m of organic binder ²After containing
The mold with the specified mountain width, mountain interval, and height is specified above
Place it on a non-woven fabric and heat it at a temperature of 100-250 ℃ for 0.1-hours.
5 minutes, pressure 1 to 500 kgf / cm²With heat and pressure molding
You can get it. Especially the amount of binder is preferable
Is 5 to 10 g / m²Is. 15 g / m²If the above
Grooves tend to crack during compression and become powdered, and the weight loss rate after liquid passage
This is unfavorable because it makes it hard. 2 g / m²If:
No effective groove is formed during compression, and liquid permeability deteriorates.

The above organic binder is an acrylic type,
Cellulose type, polyvinyl alcohol type, epoxy type,
There are vinyl acetate type and phenol resin type, but it is particularly preferable to use a phenol resin type which forms a stable groove after firing by heating and curing and carbonization. The method of including the binder in the nonwoven fabric includes a method of mixing the powdery material at the time of opening the raw cotton, a method of impregnating the nonwoven material with the liquid material, and a method of directly dispersing the powdery material on the nonwoven fabric, but the method is not particularly limited. Not a thing.

JIS of the raw material monofilament constituting the non-woven fabric
The tensile strength measured by the method according to R7601 (1986) is 18 to 30 kgf / mm ² , and the breaking elongation is 20 to 40.
% Is desirable. JIS R7601 (198
The tensile strength measured by the method according to 6) is 18 kgf / m.
If it is less than m ^2, the processability in producing the raw material nonwoven fabric is lowered and the tensile strength of the raw material nonwoven fabric is lowered, which is not preferable. Further, the tensile strength of the electrode material having the grooves made of the carbonaceous fiber nonwoven fabric obtained by the high temperature treatment in the inert atmosphere is lowered. When the elongation at break is less than 20%, the workability in producing the raw material nonwoven fabric decreases.

The true density of the raw material is 1.30 to 1.45 g / c
m ³ is preferred. When the true density of the raw material exceeds 1.45 g / cm ³ , the tensile strength and the breaking elongation of the raw material itself decrease,
When this is used, the processability when carbonizing the raw material nonwoven fabric decreases.

The true density method used in the present invention is measured according to JIS R7603 (1999) D method: specific gravity bottle method (pycnometer method). The specific gravity bottle used had a capacity of about 50 ml. Further, ethanol was used as the immersion liquid.

The basis weight of the electrode material used in the present invention,
The thickness, groove thickness, liquid passing pressure loss, and weight reduction rate after the liquid passing test are measured in the following manner.

(1) Sample 10 cm square (dimensions:
a [m]) is dried at 100 ° C. for 1 hour, allowed to cool in a desiccator, and then weighed with an electronic balance (weight: w [g]). Further, the basis weight is calculated by the following formula. Basis weight [g / m ² ] = W / a ²

(2) Thickness (t) A total of 5 points of the four corners of the sample 10 cm square and the central part used for the measurement of the liquid pressure loss are aligned with the bank portion of the sample at the center of the probe, and are digital by Ozaki Manufacturing Co., Ltd. Measure with a linear gauge D10 (maximum load 100 g-f) using a 32 mmφ probe, read and average up to two digits after the decimal point, and round off the minimum. The unit used is millimeters (Fig. 3).

(3) Groove Thickness (tm) Six pieces of 10 cm square groove thickness of the sample used for measuring the fluid pressure loss were contacted with a dial thickness gauge (model G: maximum load 180 g-f) manufactured by Ozaki Seisakusho KK Surface dimension 1
Measure in mm x 10 mm, read to the second decimal place and average, round off the lowest position. The unit used is millimeters (Fig. 3).

(4) Liquid flow pressure loss 20 in the liquid flow direction with the same shape as the liquid flow type electrolytic cell shown in FIG.
cm, width direction (flow channel width) 10 cm, 2 / thickness of electrode material
A liquid flow type electrolytic cell formed by the spacer (2) having a thickness of 3 is prepared, and the prepared electrode material is cut into 10 cm squares and loaded. Ion-exchanged water having a liquid volume of 10 liters / hour is circulated, and the liquid pressure loss at the inlet and outlet of the electrolytic cell is measured. The same measurement is performed in a system in which no electrode material is installed as a blank, and the difference between the measured value and the blank measured value is defined as the fluid pressure loss of the electrode material.

(5) Weight reduction rate after liquid permeation test The electrode material was cut into 10 cm squares and the weight (m1) was measured in advance, and the electrode material was formed with a spacer having a thickness of ⅔ of the thickness of the electrode material. The electrode material is compressed and loaded in a liquid flow type electrolytic cell, ion-exchanged water is circulated for 1 hour at a flow rate of 10 L / hour, and then the electrode material is washed with water and ultrasonically washed to generate fibers during this period. After completely removing the fine powder of the fiber due to the damage of No. 1, it is dried and the weight (m2) is measured, and the weight reduction rate [%] is calculated from the following formula. Weight reduction rate [%] = (m1−m2) / m2 ×
100

[0033]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. (Example 1) A true density obtained by crimping a polyacrylonitrile fiber having an average fiber diameter of 14 μm in air at 200 to 300 ° C. and then performing a crimping treatment, 1.40 g / cm ³ ,
600 g / m basis weight by making it felt using a staple fiber with a tensile strength of 25 kgf / mm ² and an elongation of 32%.
A flameproof fiber nonwoven fabric of No. ² was produced. Powdered novolac resin (BRP534A manufactured by Showa Highpolymer Co., Ltd.) was evenly dispersed on the non-woven fabric at a rate of 5 g / m ² , and a linear velocity of 2.6 was applied from below.
A binder-containing flame-retardant non-woven fabric was obtained by suctioning with a suction of m / sec to fix the binder in the non-woven fabric. Further, the non-woven fabric is cut into 30 cm squares, and the mountain width is 2 mm, the mountain height is 10 mm, the mountain length is 300 mm, and the distance between the mountains is 13 mm.
Aluminum mold with convex peaks of mm 30 cm
The corners are piled up so that the pile faces the nonwoven fabric, and the temperature is 180 ℃
It was set in a heat press machine having 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 with grooves was heated to 1500 ° C. in an inert gas at a temperature rising rate of 10 ° C./min, held at this temperature for 1 hour to perform carbonization, and then cooled to obtain a carbide. The carbide has a weight yield of 9 at 700 ° C. in air.
Oxidation treatment was performed until it reached 3% to obtain an electrode material having grooves.
Unit weight of the electrode material, thickness, groove thickness, tensile strength of single fiber,
Table 1 shows the single fiber elongation, the weight reduction rate after the liquid passing test, the initial liquid passing pressure loss, and the liquid passing pressure loss after the liquid passing test.

COMPARATIVE EXAMPLE 1 Polyacrylonitrile fiber having an average fiber diameter of 14 μm was subjected to flameproofing treatment in air at 200 to 300 ° C. and then crimped to obtain a true density of 1.53.
g / cm ³ , tensile strength 18 kgf / mm ² , elongation 15%
Using a staple fiber of No. 6
A flameproof fiber nonwoven fabric of 50 g / m ² was prepared. Powdered novolac resin (BRP5 manufactured by Showa Highpolymer Co., Ltd.) on the non-woven fabric.
34A) was uniformly sprayed at a rate of 5 g / m ² , and suctioned from below with a suction at a linear velocity of 2.6 m / sec to obtain a binder-containing flame-resistant nonwoven fabric in which the binder was fixed in the nonwoven fabric. Further, the non-woven fabric is cut into 30 cm squares, and a non-woven fabric is formed on the aluminum mold 30 cm square having convex ridges having a mountain width of 2 mm, a mountain height of 10 mm, a mountain length of 300 mm, and a mountain interval of 13 mm. Were set so as to face each other and set in a heat press device 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 grooved flame-resistant fiber non-woven fabric was heated in an inert gas at a temperature rising rate of 10 ° C./min for 15
The temperature was raised to 00 ° C., and the temperature was maintained for 1 hour to carry out carbonization and then cooling to obtain a carbide. The carbide was oxidized in air at 700 ° C. until the weight yield was 93% to obtain a grooved electrode material. Table showing the areal weight of the electrode material, the thickness, the groove thickness, the tensile strength of the single fiber, the single fiber elongation, the weight reduction rate after the liquid passing test, the initial liquid passing pressure loss, and the liquid passing pressure loss after the liquid passing test. 1
Shown in.

COMPARATIVE EXAMPLE 2 Polyacrylonitrile fiber having an average fiber diameter of 14 μm was subjected to flameproofing treatment in air at 200 to 300 ° C. and then crimped to obtain a true density of 1.40.
g / cm ³ , tensile strength 25 kgf / mm ² , elongation 32%
Using a staple fiber of No. 6
A flameproof fiber nonwoven fabric of 00 g / m ² was prepared. Powdered novolac resin (BRP5 manufactured by Showa Highpolymer Co., Ltd.) on the non-woven fabric.
34A) was uniformly sprayed at a rate of 25 g / m ² , and suctioned from below with a suction at a linear velocity of 2.6 m / sec to obtain a binder-containing flame-resistant nonwoven fabric in which the binder was fixed in the nonwoven fabric. Further, the non-woven fabric is cut into 30 cm squares, and a non-woven fabric is formed on the aluminum mold 30 cm square having convex ridges having a mountain width of 2 mm, a mountain height of 10 mm, a mountain length of 300 mm, and a mountain interval of 13 mm. Were set so as to face each other and set in a heat press device 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 grooved flame-resistant fiber non-woven fabric was heated in an inert gas at a temperature rising rate of 10 ° C./min for 15
The temperature was raised to 00 ° C., and the temperature was maintained for 1 hour to carry out carbonization and then cooling to obtain a carbide. The carbide was oxidized in air at 700 ° C. until the weight yield was 93% to obtain a grooved electrode material. Table showing the areal weight of the electrode material, the thickness, the groove thickness, the tensile strength of the single fiber, the single fiber elongation, the weight reduction rate after the liquid passing test, the initial liquid passing pressure loss, and the liquid passing pressure loss after the liquid passing test. 1
Shown in.

[0036]

[Table 1]

[0037]

EFFECTS OF THE INVENTION By using the electrode material of the present invention, it is possible to reduce the fluid pressure loss in the field where various electrolytic cells are used, and to reduce the load of the liquid feed pump, thereby saving energy for pump operation. It can reduce consumption. As a result, the total energy efficiency of the battery can be increased. These are particularly effective for redox flow type batteries.

[Brief description of drawings]

FIG. 1 shows a schematic view of a battery using a flow-through type electrolytic cell such as a redox flow type battery having a three-dimensional electrode.

FIG. 2 is an exploded perspective schematic view of a liquid flow type electrolytic cell having an electrode material showing an embodiment of the present invention.

FIG. 3 is a perspective schematic view of an electrode material showing an embodiment of the present invention.

[Explanation of symbols]

1 ... current collector, 2 ... spacer, 3 ... Ion exchange membrane, 4a, b ... liquid passage, 5 ... electrode, 6 ... Positive electrode liquid tank, 7 ... Anode liquid tank, 8, 9 ... Liquid feed pump, 10 ... Liquid inlet, 11 ... Liquid outlet

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Claims (5)

[Claims] 1. An electrode material having a groove made of carbonaceous fiber non-woven fabric, wherein the electrode material is compressed and loaded in a liquid flow type electrolytic cell, and the weight reduction rate after passing the liquid is 1% or less. Characteristic electrode material. 2. JIS R for single fiber of carbonaceous fiber non-woven fabric
The tensile strength measured according to 7601 (1986) is 60.
~100kgf / mm ² and elongation at break 5.5-6.
It is 0%, The electrode material of Claim 1 characterized by the above-mentioned. 3. The method for producing an electrode material according to claim 1, which is obtained by subjecting a precursor nonwoven fabric of carbonaceous fiber nonwoven fabric to high temperature carbonization treatment in an inert atmosphere. 4. A precursor of a carbonaceous fiber non-woven fabric. A single fiber as a raw material constituting a non-woven fabric has a tensile strength of 18 to 30 kgf / mm ² measured according to JIS R7601 (1986) and a breaking elongation of 20%. 40% and a manufacturing method of an electrode material according to any one of claims 1 to 3 true density of the material is characterized in that it is 1.30~1.45g / cm ^3. 5. The method for producing an electrode material according to claim 1, wherein the precursor nonwoven fabric of carbonaceous fiber nonwoven fabric contains an organic binder in an amount of ² to 15 g / m ² .