JP3187123B2 - Electrode materials and electrodes for metal-halogen secondary batteries - Google Patents

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 an electrode used for a positive electrode of a metal-halogen secondary battery, particularly a zinc-bromine secondary battery, that is, a zinc electrode.

[0002]

2. Description of the Related Art A metal-halogen secondary battery such as a zinc-bromine secondary battery discharges by reducing bromine to bromine ions at a positive electrode. In such a secondary battery, the positive electrode, i.e., a bromine electrode, is required to promptly and effectively react the bromine reduction reaction at the time of discharge, which affects the energy efficiency of the battery. Conventionally, platinum has been used as a positive electrode material, but since it is expensive, a conductive plastic plate or a carbon sintered plate obtained by heating and molding a mixture of conductive powder carbon and a resin has been used. However, in these electrodes, when the discharge progressed and the concentration of bromine, which is a positive electrode active material, decreased, the potential drop became remarkable, so that the energy efficiency of charging and discharging was low. In particular, the higher the current density, the more the potential decreased.

As a method for solving this problem, the conductive plastic plate is used as an electrode substrate in order to increase the electrode surface area and the reaction area with bromine, by joining activated carbon to the surface or kneading the electrode substrate. Used in JP-A-59-29385 proposes an example in which a woven or knitted fabric of porous carbon fibers is used by bonding it to an electrode substrate. In addition, there is an example in which fibrous activated carbon in the form of paper is used by bonding. Japanese Patent Application Laid-Open No. 59-163765 discloses that the pore volume of fibrous activated carbon, that is, the pore volume of a pore having a diameter of 30 to 1000 angstroms is 0.1 cc / cm. It has been proposed that fibrous activated carbon having a very large pore volume of not less than g is made into a paper shape and used by bonding it to an electrode substrate.

[0004]

The above-mentioned fibrous activated carbon is:
It can be applied to electrode materials as a woven fabric, knitted fabric, or paper-like material, but in particular, joining a paper-like material to an electrode substrate and using it as a positive electrode has attracted attention in recent years from the viewpoint of lowering the price of batteries. . However, at the time of discharge, when the concentration of bromine, which is a positive electrode active material, decreases, so-called polarization occurs, in which the potential drops remarkably, which lowers the energy efficiency of charging and discharging. In particular, the higher the current density, the more remarkable the polarization.

In view of such circumstances, the present inventors have conducted intensive studies on the surface of fibrous activated carbon which contributes to the reaction and the adsorbability of bromine. As a result, the polarization is low even at a low bromine concentration, and a high discharge potential is obtained even at a high current density. The present invention has provided an electrode material and an electrode for a metal-halogen secondary battery.

[0006]

According to the present invention, there is provided a fibrous material in which the number of bonded nitrogen atoms on the surface is at least 1.0% with respect to the number of carbon atoms and the amount of acidic groups per unit weight is at least 2.0 meq / g. An electrode material for a metal-halogen secondary battery comprising a sheet-shaped metal-halogen secondary battery containing activated carbon, and an electrode for a metal-halogen secondary battery, wherein the electrode material is bonded to a conductive plate.
Hereinafter, details of the present invention will be described.

The fibrous activated carbon used in the present invention is obtained by carbonizing and activating organic fibers. Organic fibers used as raw materials include cellulose, phenol novolak, polyacrylonitrile, aromatic polyamide, polyvinyl alcohol, polyvinyl chloride, petroleum or coal pitch, but can be fibrous activated carbon. If there is, it is not limited to these.
As methods for carbonization and activation, generally known methods can be used. In some cases, activation may be performed using a known activation catalyst.

In the present invention, the acidic group means a hydroxyl group (-OH) or a carboxyl group (-COO) on the surface of the fibrous activated carbon.
H), a hydroxyamino group (-NH-OH), and a hydroxyimino group (= N-OH). The amount of the acidic group of the fibrous activated carbon used in the present invention is 2.0 meq / g or more per unit weight of the fibrous activated carbon, and preferably 2.
Those having a content of 5 meq / g or more and 5.0 meq / g or less are preferable. Thereby, the wettability between the fibrous activated carbon and the electrolytic solution is improved, and the surface of the fibrous activated carbon is effectively used. However, when less than 2.0 meq / g of fibrous activated carbon per unit weight is used, the wettability between the fibrous activated carbon and the electrolyte deteriorates,
Since the area for the reaction is substantially reduced, bromine cannot be effectively adsorbed, and the polarization increases.

In the present invention, the number of surface-bound nitrogen atoms means the amount of nitrogen on the surface of the fibrous activated carbon detected by ESCA surface analysis (analysis method will be described later). Expressed as a ratio (%, hereinafter referred to as N / C ratio). Unpaired electrons are formed on the surface by the introduction of nitrogen atoms on the surface of fibrous activated carbon,
The reactivity with bromine having a strong electron affinity is increased by the unpaired electrons. Therefore, by using a fibrous activated carbon having an N / C ratio of 1.0% or more, desirably 1.5% or more and 15% or less, the reactivity of the fibrous activated carbon used for the electrode reaction with bromine is improved, and the low concentration In order to make bromine react efficiently, polarization can be suppressed. But 1.5%
If it is less than 10, the reactivity with bromine rapidly deteriorates, and it becomes difficult to adsorb bromine, so that polarization increases.

[0010] As described above, the fibrous activated carbon having a large amount of acidic group used in the present invention is obtained by carbonizing and activating the above-mentioned organic fibers, and then obtaining a weight yield under an oxygen atmosphere having an oxygen partial pressure of 0.01 torr or more. By oxidizing to a range of 30 to 99%. 30% weight yield
If it is less than this, etching of the surface proceeds, which leads to an increase in contact resistance, which is not preferable. Other methods of oxidizing fibrous activated carbon include oxidation in a nitric acid aqueous solution and oxidation in a plasma by generating plasma using high frequency in an atmosphere containing oxygen. In these methods, a predetermined acidic group can be obtained, and these methods may be used in combination.

Further, as a method for introducing nitrogen into fibrous activated carbon, in particular, a raw material containing a nitrogen atom, for example, an organic fiber such as a polyacrylonitrile type or an aromatic polyamide type is carbonized by itself or in a state of being mixed with other organic fibers. It is desirable to obtain it by activation in consideration of the production cost. However, as described above, a fibrous activated carbon obtained from a raw material that does not contain a nitrogen atom introduces an amino group into the surface by hydrazine treatment after dry oxidation, or acid chlorides with thionyl chloride, and then uses various amines. A nitrogen atom may be introduced into the surface by chemical treatment such as introduction of an amide group. Further, the raw material may be carbonized or activated in an ammonia atmosphere.

The specific surface area of the fibrous activated carbon thus selected is not particularly limited, but may be 500 to 2000 m ² / g obtained by a known production method.

The fibrous activated carbon prepared as described above is formed into a sheet. The sheet shape is a woven, knitted or paper-like material. In particular, in forming a paper layer, the basis weight is 25 g / g together with at least one other organic or inorganic material to obtain a certain strength.
Paper is made to have a thickness of at least m ² and a thickness of at least 0.15 mm.
It should be noted that the present invention is not limited to this as long as strength is not particularly required. The content of the fibrous activated carbon in the paper-like material is not particularly limited, but is preferably 60% by weight or more.

Other materials used simultaneously with the fibrous activated carbon as the paper-like material include pulp and aggregate, and if necessary, a binder such as starch and polyvinyl alcohol, as well as a tackifier, a surfactant, and a release agent. Various additives such as an agent, an antifoaming agent, and a flocculant may be added. The pulp used is water resistant,
A synthetic pulp of polyethylene or polypropylene which is excellent in chemical resistance is desirable, but natural pulp may be used in addition to regenerated cellulose, acrylic or polyamide pulp. As the aggregate, chopped fibers of polyethylene and polypropylene, which are excellent in water resistance and chemical resistance, and layered fibers thereof (sea core fiber) are preferable, but linear and / or aromatic polyamide-based, polyester, phenol novolak, and polyacrylonitrile-based fibers are preferable. In addition to organic fibers, various inorganic fibers such as glass fiber, asbestos, quartz, and alumina can be used. These pulp and aggregate are not limited to the materials described above, as long as they have a certain strength after the formation of the paper layer.

The conductive plate referred to in the present invention is an electrode substrate formed by heating and molding a mixture of conductive fine powdered carbon and a resin. The bonding between the electrode substrate and the electrode material is performed using carbon black or carbon fiber. A conductive substance mainly composed of carbon is uniformly mixed with a polyethylene resin powder so as to have a concentration of 30% by weight or more, and laid so as to have a constant thickness on the bottom of a mold set at a temperature higher by 10 ° C. than the resin softening point. Then, it is press-bonded under heat and pressure to a conductive electrode base material having a thickness of 1.0 mm and a size of 10 cm square by hot pressing.

Next, a method for measuring the amount of the acidic group, the specific surface area, the N / C ratio, and the polarization value of the electrode used in the present invention will be described. (1) Amount of acidic group: fibrous activated carbon containing acidic group is thoroughly washed with water, dried, and about 1 g is collected.
Vacuum dried for 2 hours, weighed, 60 ml of 1 / 10N N
It was immersed in an aOH aqueous solution and shaken at 25 ° C. for 10 hours.
This solution was filtered with a glass filter, 25 ml of the filtrate was accurately collected, and back-titrated with a 1 / 10N HCl standard solution. In titration, phenolphthalein was used as an indicator. The blank test was performed in the same manner, and the amount of acidic groups per unit weight of the fibrous activated carbon was determined by Equation 1.

[0017] In the formula, D is the amount (ml) obtained by subtracting the titer in the blank test from the titer of the 1 / 10N HCl standard solution, and K is 1 / 10N HC.
The normality of the standard solution, W, is the weight (g) of the fibrous activated carbon.

(2) Specific surface area: about 0.1 g of fibrous activated carbon
The sample was collected, dried at 120 ° C. for 12 hours and weighed, and the amount of nitrogen gas adsorbed at the boiling point of liquid nitrogen (−195.8 ° C.) was measured while gradually increasing the relative pressure in the range of 0.0 to 0.2. Point measurement; E. FIG. The specific surface area per unit weight (m ² / g) was determined by T plot.

(3) N / C ratio: ESCA or XPS
The N / C ratio of the sufficiently dried fibrous activated carbon surface is measured by X-ray photoelectron spectroscopy, which is abbreviated as "A". The measuring device was Shimadzu ESCA750, and the analysis was ESCAPAC76.
0 was used. The electrode material was cut into 6 mmφ, attached to a heated sample table with a conductive paste, and vacuum-degassed for more than 3 hours while heating the sample at 120 ° C., followed by measurement. An MgKα ray (1253.6 eV) was used as a radiation source, and the surface of the sample was analyzed under the condition that the degree of vacuum in the apparatus was 10 −7 torr. The surface here means a depth region from the outermost layer of the sample to several tens of angstroms. The measurement is C1S,
This is performed on the N1S peak, and the area of each peak is determined using ESCAPAC760. The obtained area is referred to as "J. H. Sco
1.0 for C1S based on the correction method by field
For 0 and N1S, the surface (nitrogen / carbon) atomic ratio was directly calculated as a percentage from the value obtained by dividing by a relative intensity of 1.77.

(4) Electrode polarization value: The electrode of the present invention described above was used as a positive electrode, that is, a bromine electrode of a zinc-bromine battery, and the discharge potential was evaluated using the apparatus shown in FIG. The electrolytic solution was obtained by dissolving bromine in a 3 mol / l zinc bromide solution, and the current density at the time of discharge was measured at 60 mA / square cm, and the bromine concentration was measured at 0.1 mol / l. The current density is based on the geometric area of the electrode. A 99.99% rolled zinc plate was used as a counter electrode, the measurement temperature was 25 ° C., and a saturated calomel electrode was used as a reference electrode. The open circuit potential of the halogen electrode at a predetermined bromine concentration was Vopen, the potential of the halogen electrode when a current of a predetermined density was passed was Vi, and the difference between Vopen and Vi was the polarization value. The smaller the polarization value is, the better the halogen electrode of the metal-halogen secondary battery is.

[0021]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. (Example 1) Polyacrylonitrile fiber having a single fiber thickness of 2.0 d and a length of 54 mm was used as a raw material, and was heated at 260 ° C in air for 30 minutes.
After heating for minutes and flame resistance, a nonwoven fabric with a basis weight of 400 g / m ² was produced. Subsequently, the temperature was raised to 1000 ° C. over about 90 minutes under a nitrogen stream, and carbonized by maintaining the temperature at 1000 ° C. for 60 minutes. After the temperature was further lowered to 850 ° C., a steam activation treatment was carried out for 60 minutes, and then allowed to cool.
Heat treated at 10 ° C. for 10 minutes. The fibrous activated carbon thus obtained had an acidic group content of 2.9 meq / g and an N / C ratio of 13.1.
%, And the specific surface area was 763 m ² / g. After the fibrous activated carbon was pulverized by a cutter mill, it was collected in a dry weight of 80% by weight, to which 12% by weight of a polypropylene single fiber chopped fiber, 6% by weight of a synthetic pulp made of polyethylene and 2% by weight. By adding a polyvinyl alcohol binder, a paper having a basis weight of 38 g / m ² and a thickness of 0.21 mm was prepared.

Further, the conductive carbon powder is uniformly mixed with the polyethylene resin powder so as to have a concentration of 30% by weight, and a predetermined thickness is set on the bottom of a mold set at 10 ° C. higher than the resin softening point. After that, a conductive electrode substrate mainly composed of carbon and having a thickness of 1.0 mm and a size of 10 cm square was prepared by hot pressing. The above-mentioned paper-like material was press-bonded to the electrode substrate under pressure and heat to obtain an electrode of a metal-halogen secondary battery. The polarization value of the electrode thus obtained was 83 mV.

(Example 2) Single fiber thickness 2.0 d, length 5
4mm polyacrylonitrile fiber as raw material, 2 in air
After heating at 60 ° C. for 30 minutes for flame resistance, a nonwoven fabric with a basis weight of 400 g / m ² was produced. Subsequently, the temperature was raised to 1100 ° C. over about 90 minutes under a nitrogen stream, and the carbonization was performed by maintaining the temperature at 1100 ° C. for 60 minutes. After the temperature was further lowered to 850 ° C., a steam activation treatment was performed for 90 minutes, then the mixture was allowed to cool, and further heat-treated in air at 500 ° C. for 10 minutes. The amount of acidic groups in the fibrous activated carbon thus obtained was 2.7 meq / g, N / C
The ratio was 7.0%, and the specific surface area was 592 m ² / g. After the fibrous activated carbon was pulverized by a cutter mill, it was collected in a dry weight of 80% by weight, to which 12% by weight of a polypropylene single fiber chopped fiber, 6% by weight of a synthetic pulp made of polyethylene and 2% by weight. By adding a binder of polyvinyl alcohol, a paper having a basis weight of 41 g / m ² and a thickness of 0.24 mm was prepared. Further, a mixture of the conductive carbon powder and the polyethylene resin powder uniformly mixed so as to be 30% by weight was spread on the bottom of a mold set at a temperature higher by 10 ° C. than the resin softening point so as to have a constant thickness. rear,
A conductive electrode substrate mainly composed of carbon and having a thickness of 1.0 mm and a size of 10 cm square was prepared by hot pressing. The above-mentioned paper-like material was press-bonded to the electrode substrate under pressure and heat to obtain an electrode of a metal-halogen secondary battery. The polarization value of the electrode thus obtained was 75 mV.

(Example 3) Single fiber thickness 2.0 d, length 5
4mm polyacrylonitrile fiber as raw material, 2 in air
After heating at 60 ° C. for 30 minutes for flame resistance, a nonwoven fabric with a basis weight of 400 g / m ² was produced. Subsequently, the temperature was raised to 1200 ° C. over about 90 minutes under a nitrogen stream, and the carbonization was performed by maintaining the temperature at 1200 ° C. for 60 minutes. After the temperature was further lowered to 950 ° C., a steam activation treatment was performed for 90 minutes, then the mixture was allowed to cool, and further heat-treated in air at 600 ° C. for 10 minutes. The fibrous activated carbon thus obtained has an acidic group content of 2.8 meq / g and N / C
The ratio was 3.6% and the specific surface area was 544 m ² / g. After the fibrous activated carbon was pulverized by a cutter mill, it was collected in a dry weight of 80% by weight, to which 12% by weight of a polypropylene single fiber chopped fiber, 6% by weight of a synthetic pulp made of polyethylene and 2% by weight. By adding a binder of polyvinyl alcohol, a paper having a basis weight of 43 g / m ² and a thickness of 0.26 mm was prepared. Further, a mixture of the conductive carbon powder and the polyethylene resin powder uniformly mixed so as to be 30% by weight was spread on the bottom of a mold set at a temperature higher by 10 ° C. than the resin softening point so as to have a constant thickness. rear,
A conductive electrode substrate mainly composed of carbon and having a thickness of 1.0 mm and a size of 10 cm square was prepared by hot pressing. The above-mentioned paper-like material was press-bonded to the electrode substrate under pressure and heat to obtain an electrode of a metal-halogen secondary battery. The polarization value of the electrode thus obtained was 92 mV.

(Example 4) Single fiber thickness 5.5d, length 7
Using a regenerated cellulose fiber of 6 mm as a raw material, a nonwoven fabric having a basis weight of 600 g / m ² was produced, and an aqueous solution of diammonium phosphate was immersed in these nonwoven fabrics, squeezed, and then dried. % Impregnation. Further, this is heated in an inert gas at 270 ° C. for 30 minutes, then heated from 270 ° C. to 850 ° C. over about 90 minutes, and subjected to a steam activation treatment at 800 ° C. for 60 minutes. Heat treated for 9 minutes. Further, this was added to 9% aqueous solution of hydroxylamine dihydrochloride in 9% by weight.
After treating at 5 ° C. for 1 hour, it was washed with water and dried. The amount of acidic groups in the fibrous activated carbon thus obtained was 2.7 meq / g, N /
The C ratio was 6.3%, and the specific surface area was 966 m ² / g. After the fibrous activated carbon was pulverized by a cutter mill, it was collected in a dry weight of 80% by weight, and 12% by weight of a polypropylene single fiber chopped fiber, 6% by weight.
Was added, and a binder of 2% by weight of polyvinyl alcohol was added to prepare a paper having a basis weight of 39 g / m ² and a thickness of 0.22 mm. Further, a mixture of the conductive carbon powder and the polyethylene resin powder uniformly mixed so as to have a concentration of 30% by weight was spread on the bottom of a mold set at a temperature higher by 10 ° C. than the resin softening point so as to have a constant thickness. rear,
A conductive electrode substrate mainly composed of carbon and having a thickness of 1.0 mm and a size of 10 cm square was prepared by hot pressing. The above-mentioned paper-like material was press-bonded to the electrode substrate under pressure and heat to obtain an electrode of a metal-halogen secondary battery. The polarization value of the electrode thus obtained was 96 mV.

Example 5 A commercially available nonwoven fabric of pitch-based fibrous activated carbon (type A-1 manufactured by Unitika Ltd.)
0) was heat-treated in air at 500 ° C. for 10 minutes. This was further treated in a 10% by weight aqueous solution of hydroxylamine dihydrochloride at 95 ° C. for 3 hours, washed with water and dried. The amount of acidic groups in the fibrous activated carbon thus obtained is 2.6 meq / g,
The N / C ratio was 2.0%, and the specific surface area was 1078 m ² / g. After crushing this fibrous activated carbon with a cutter mill,
This was collected as a dry weight in an amount of 80% by weight.
Wt% polypropylene single fiber chopped fiber,
6% by weight of synthetic pulp made of polyethylene and a binder of 2% by weight of polyvinyl alcohol were added thereto to obtain a basis weight of 39 g /
A paper having an m ² and a thickness of 0.25 mm was prepared. Further, a mixture of the conductive carbon powder and the polyethylene resin powder uniformly mixed so as to be 30% by weight is 10% from the resin softening point.
After laying it on the bottom of a mold set at a higher temperature by a predetermined degree, it was hot-pressed to prepare a conductive electrode substrate mainly composed of carbon and having a thickness of 1.0 mm and a size of 10 cm square. The above-described paper-like material is press-bonded to the electrode substrate under pressure and heat to form a metal sheet.
An electrode of a halogen secondary battery was obtained. The polarization value of the electrode thus obtained was 118 mV.

(Example 6) Single fiber thickness 2.0 d, length 6
2g phenol novolak fiber as raw material, 300g
/ M ² to produce a nonwoven fabric with a basis weight, and the nonwoven fabric in an inert gas,
The temperature was raised to 850 ° C over about 90 minutes and carbonized, and 800
A steam activation treatment was performed at 60 ° C. for 60 minutes, and after cooling, a heat treatment was performed at 500 ° C. for 10 minutes in air. This was further treated in a 10% by weight aqueous solution of hydroxylamine dihydrochloride at 95 ° C. for 2 hours, washed with water and dried. The fibrous activated carbon thus obtained had an acidic group content of 2.8 meq / g, an N / C ratio of 2.5%, and a specific surface area of 889 m ² / g. After the fibrous activated carbon was pulverized by a cutter mill, it was collected in a dry weight of 80% by weight, to which 12% by weight of a polypropylene single fiber chopped fiber, 6% by weight of a synthetic pulp made of polyethylene and 2% by weight. By adding a binder of polyvinyl alcohol, the basis weight was 42 g / m ² and the thickness was 0.1 g / m ² .
A 22 mm paper was made. Further, a mixture of the conductive carbon powder and the polyethylene resin powder uniformly mixed so as to be 30% by weight was spread on the bottom of a mold set at a temperature higher by 10 ° C. than the resin softening point so as to have a constant thickness. Thereafter, the resultant was subjected to hot pressing to prepare a conductive electrode substrate mainly composed of carbon and having a thickness of 1.0 mm and a size of 10 cm square. The above-mentioned paper-like material was press-bonded to the electrode substrate under pressure and heat to obtain an electrode of a metal-halogen secondary battery. The polarization value of the electrode thus obtained was 91 mV.

(Comparative Example 1) Single fiber thickness 5.5d, length 7
Using a regenerated cellulose fiber of 6 mm as a raw material, a nonwoven fabric having a basis weight of 600 g / m ² was produced, and an aqueous solution of diammonium phosphate was immersed in these nonwoven fabrics, squeezed, and then dried. % Impregnation. Further, this is heated in an inert gas at 270 ° C. for 30 minutes, then heated from 270 ° C. to 850 ° C. over about 90 minutes, and subjected to a steam activation treatment at 800 ° C. for 60 minutes. Heat treated for 10 minutes. The amount of acidic groups in the fibrous activated carbon thus obtained was 2.9 meq / g,
The N / C ratio was 0.5% and the specific surface area was 1020 m ² / g. After the fibrous activated carbon was pulverized by a cutter mill, the dry activated carbon was collected in an amount of 80% by weight, and 12% by weight of chopped polypropylene single fiber, 6% by weight.
Weight of synthetic pulp made of polyethylene, and a binder of 2 weight% of polyvinyl alcohol was added thereto, and a basis weight of 40 g /
A paper having an m ² and a thickness of 0.25 mm was prepared. Further, a mixture of the conductive carbon powder and the polyethylene resin powder uniformly mixed so as to be 30% by weight is 10% from the resin softening point.
After laying it on the bottom of the mold set at a higher temperature of ℃ so as to have a certain thickness, it was hot pressed to prepare a conductive electrode substrate mainly composed of carbon having a thickness of 1.0 mm and a size of 10 m ² square. . The above-described paper-like material is press-bonded to the electrode substrate under pressure and heat to form a metal sheet.
An electrode of a halogen secondary battery was obtained. The polarization value of the electrode thus obtained was 150 mV.

(Comparative Example 2) Single fiber thickness 2.0 d, length 5
4mm polyacrylonitrile fiber as raw material, 2 in air
After heating at 60 ° C. for 30 minutes for flame resistance, a nonwoven fabric with a basis weight of 400 g / m ² was produced. Subsequently, the temperature was raised to 1100 ° C. over about 90 minutes under a nitrogen stream, and the carbonization was performed by maintaining the temperature at 1100 ° C. for 60 minutes. After the temperature was further lowered to 850 ° C., a steam activation treatment was performed for 90 minutes, and then the mixture was allowed to cool. The amount of acidic groups in the fibrous activated carbon thus obtained was 0.2 meq /
g, the N / C ratio was 7.0%, and the specific surface area was 584 m ² / g. After crushing this fibrous activated carbon with a cutter mill,
This was collected as a dry weight in an amount of 80% by weight.
Wt% polypropylene single fiber chopped fiber,
6% by weight of synthetic pulp made of polyethylene, and a binder of 2% by weight of polyvinyl alcohol were added thereto to add a basis weight of 41 g /
A paper having an m ² and a thickness of 0.25 mm was prepared. Further, a mixture of the conductive carbon powder and the polyethylene resin powder uniformly mixed so as to be 30% by weight is 10% from the resin softening point.
After laying it on the bottom of a mold set at a higher temperature by a predetermined degree, it was hot-pressed to prepare a conductive electrode substrate mainly composed of carbon and having a thickness of 1.0 mm and a size of 10 cm square. The above-described paper-like material is press-bonded to the electrode substrate under pressure and heat to form a metal sheet.
An electrode of a halogen secondary battery was obtained. The polarization value of the electrode thus obtained was 325 mV.

[0030]

As described above, the electrode material of the present invention improves the contact with the electrolytic solution by providing a large amount of acidic group per unit weight of the fibrous activated carbon used,
Furthermore, by introducing nitrogen atoms on the surface of the fibrous activated carbon, affinity with bromine as an active material is improved, and bromine is effectively adsorbed, so that an electrode having low bromine concentration and low polarization even at high current density can be provided. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used for polarization characteristics of an electrode. 1 in 1: halogen electrode 2: Zinc plate counter electrode 3: alginic capillary 4: voltmeter 5: Power 6: ammeters 7: electrolyte 8: KCl aqueous solution _{9: Hg 2 Cl 2 -Hg 10} : Hg

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the number of nitrogen atoms on the surface is at least 1.0% based on the number of carbon atoms, and the amount of acidic groups per unit weight is 2.0%.
An electrode material for a sheet-shaped metal-halogen secondary battery containing fibrous activated carbon of not less than meq / g. 2. An electrode for a metal-halogen secondary battery, wherein the electrode material according to claim 1 is joined to a conductive plate.