JP2001085026A - Carbon electrode material assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon electrode material assembly capable of reducing the cell resistance of a redox flow battery and enhancing the energy efficiency by improving both the characteristics of carbonaceous fibers and the physical properties of non-woven fablic. SOLUTION: The carbon electrode material assembly used in a redox flow battery using aqueous solution electrolytic solution consists of a non-woven fablic of carbonaceous fibers, wherein the fiber has a pseudo-graphite crystal structure in which the size of each crystallate in the a-axis direction determined through X-ray wide-angle analysis ranges 30-80 Å, and the amount of surface acid functional radicals determined through XPS surface analysis is 0.2-1.2% of the total number of surface carbon atoms, and the non-woven fablic has a compression ratio of 10-25% according to JIS L1096 (1990) and a modulus of compression elasticity of 80% or more.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、水溶液系電解液に
よるレドックスフロー電池に使用され、炭素質繊維の不
織布よりなる炭素電極材集合体に関するものであり、特
に、バナジウム系レドックスフロー電池に有用である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redox flow battery using an aqueous electrolytic solution, and more particularly to a carbon electrode material assembly made of a nonwoven fabric of carbonaceous fibers, and is particularly useful for a vanadium redox flow battery. is there.

【０００２】[0002]

【従来の技術】従来より、電極は電池の性能を左右する
ものとして重点的に開発されている。電極には、それ自
体が活物質とならず、活物質の電気化学的反応を促進さ
せる反応場として働くタイプのものがあり、このタイプ
には導電性や耐薬品性などから炭素材料がよく用いられ
る。特に電力貯蔵用に開発が盛んなレドックスフロー電
池の電極には、耐薬品性があり、導電性を有し、かつ通
液性のある炭素質繊維の不織布等が用いられている。2. Description of the Related Art Conventionally, electrodes have been developed with emphasis on the performance of batteries. Some electrodes do not become active materials themselves, but work as a reaction field to promote the electrochemical reaction of the active material.For this type, carbon materials are often used due to their conductivity and chemical resistance. Can be In particular, a nonwoven fabric of carbon fiber having chemical resistance, conductivity, and liquid permeability is used for an electrode of a redox flow battery which is actively developed for power storage.

【０００３】レドックスフロー電池は、正極に鉄の塩酸
水溶液、負極にクロムの塩酸水溶液を用いたタイプか
ら、起電力の高いバナジウムの硫酸水溶液を両極に用い
るタイプに替わり、高エネルギー密度化されたが、最近
さらに活物質濃度を高める開発が進み、一段と高エネル
ギー密度化が進んでいる。[0003] Redox flow batteries have a higher energy density from a type using an aqueous hydrochloric acid solution of iron for the positive electrode and an aqueous solution of chromium hydrochloric acid for the negative electrode, to a type using a high-electromotive force aqueous solution of vanadium sulfuric acid for both electrodes. Recently, developments for further increasing the concentration of the active material have been advanced, and the energy density has been further increased.

【０００４】レドックスフロー型電池の主な構成は、図
１に示すように電解液を貯える外部タンク６，７と電解
槽ＥＣからなり、ポンプ８，９にて活物質を含む電解液
を外部タンク６，７から電解槽ＥＣに送りながら、電解
槽ＥＣに組み込まれた電極上で電気化学的なエネルギー
変換、すなわち充放電が行われる。The main structure of a redox flow type battery is, as shown in FIG. 1, composed of external tanks 6 and 7 for storing an electrolytic solution and an electrolytic cell EC, and pumps 8 and 9 for supplying an electrolytic solution containing an active material to the external tank. While being sent from 6, 7 to the electrolytic cell EC, electrochemical energy conversion, that is, charge / discharge is performed on the electrodes incorporated in the electrolytic cell EC.

【０００５】一般に、充放電の際には、電解液を外部タ
ンクと電解槽との間で循環させるため、電解槽は図１に
示すような液流通型構造をとる。該液流通型電解槽を単
セルと称し、これを最小単位として単独もしくは多段積
層して用いられる。液流通型電解槽における電気化学反
応は、電極表面で起こる不均一相反応であるため、一般
的には二次元的な電解反応場を伴うことになる。電解反
応場が二次元的であると、電解槽の単位体積当たりの反
応量が小さいという難点がある。In general, during charging and discharging, an electrolytic solution is circulated between an external tank and an electrolytic bath, so that the electrolytic bath has a liquid flow type structure as shown in FIG. The liquid flow type electrolytic cell is referred to as a single cell, which is used as a minimum unit and is used alone or in a multi-layered structure. Since the electrochemical reaction in the liquid flowing type electrolytic cell is a heterogeneous phase reaction occurring on the electrode surface, it generally involves a two-dimensional electrolytic reaction field. When the electrolytic reaction field is two-dimensional, there is a disadvantage that the reaction amount per unit volume of the electrolytic cell is small.

【０００６】そこで、単位面積当りの反応量、すなわち
電流密度を増すために電気化学反応場の三次元化が行わ
れるようになった。図２は、三次元電極を有する液流通
型電解槽の分解斜視図である。該電解槽では、相対する
二枚の集電板１，１間にイオン交換膜３が配設され、イ
オン交換膜３の両側にスペーサ２によって集電板１，１
の内面に沿った電解液の流路４ａ，４ｂが形成されてい
る。該流通路４ａ，４ｂの少なくとも一方には炭素質繊
維の不織布等よりなる電極材５が配設されており、この
ようにして三次元電極が構成されている。なお、集電板
１には、電解液の液流入口１０と液流出口１１とが設け
られている。In order to increase the amount of reaction per unit area, that is, the current density, three-dimensional electrochemical reaction fields have been used. FIG. 2 is an exploded perspective view of a liquid flow type electrolytic cell having three-dimensional electrodes. In the electrolytic cell, an ion exchange membrane 3 is arranged between two opposing current collector plates 1 and 1, and the current collector plates 1 and 1 are disposed on both sides of the ion exchange membrane 3 by spacers 2.
Are formed along the inner surface of the cell. At least one of the flow passages 4a, 4b is provided with an electrode material 5 made of a nonwoven fabric of carbonaceous fiber or the like, thus forming a three-dimensional electrode. The current collector 1 is provided with a liquid inlet 10 and a liquid outlet 11 for the electrolytic solution.

【０００７】正極電解液にオキシ硫酸バナジウム、負極
電解液に硫酸バナジウムの各々硫酸酸性水溶液を用いた
レドックスフロー型電池の場合、放電時には、Ｖ²⁺を含
む電解液が負極側の液流路４ａに供給され、正極側の流
路４ｂにはＶ⁵⁺（実際には酸素を含むイオン）を含む電
解液が供給される。負極側の流路４ａでは、三次元電極
５内でＶ²⁺が電子を放出しＶ³⁺に酸化される。放出され
た電子は外部回路を通って正極側の三次元電極内でＶ⁵⁺
をＶ⁴⁺（実際には酸素を含むイオン）に還元する。この
酸化還元反応に伴って負極電解液中のＳＯ₄ ^2-が不足
し、正極電解液ではＳＯ₄ ^2-が過剰になるため、イオン
交換膜３を通ってＳＯ₄ ^2-が正極側から負極側に移動し
電荷バランスが保たれる。あるいは、Ｈ⁺ がイオン交換
膜を通って負極側から正極側へ移動することによっても
電荷バランスを保つことができる。充電時には放電と逆
の反応が進行する。[0007] In the case of a redox flow battery using a sulfuric acid aqueous solution of vanadium oxysulfate as the positive electrode electrolyte and vanadium sulfate as the negative electrode electrolyte, during discharge, the electrolyte containing V ²⁺ is ^supplied to the liquid flow path 4a on the negative electrode side. And an electrolyte containing V ⁵⁺ (actually, ions containing oxygen) is supplied to the flow path 4b on the positive electrode side. In the flow path 4a on the negative electrode side, V ²⁺ emits electrons in the three-dimensional electrode 5 and is oxidized to V ³⁺ . The emitted electrons pass through an external circuit and enter V ⁵⁺ in the three-dimensional electrode on the positive electrode side.
To V ⁴⁺ (actually an ion containing oxygen). The redox reaction SO ₄ ^2-of the negative electrode electrolytic solution is insufficient with the, for SO ₄ ^2-becomes excessive in the positive electrolyte, negative electrode SO ₄ ^2-is from the positive electrode side through the ion-exchange membrane 3 Side and the charge balance is maintained. Alternatively, the charge balance can be maintained by moving H ⁺ from the negative electrode side to the positive electrode side through the ion exchange membrane. At the time of charging, a reaction reverse to that of discharging proceeds.

【０００８】バナジウム系レドックスフロー電池用電極
材の特性としては、特に以下に示す性能が要求される。As the characteristics of the electrode material for a vanadium-based redox flow battery, the following performance is particularly required.

【０００９】1)目的とする反応以外の副反応を起こさな
いこと（反応選択性が高いこと）、具体的には電流効率
（η_I ）が高いこと。 2)電極反応活性が高いこと、具体的にはセル抵抗（Ｒ）
が小さいこと。すなわち電圧効率（η_V ）が高いこと。 3)上記1)、2)に関連する電池エネルギー効率（η_E ）が
高いこと。 η_E ＝η_I ×η_V 4)くりかえし使用に対する劣化が小さいこと（高寿
命）、具体的には電池エネルギー効率（η_E ）の低下量
が小さいこと。1) No side reaction other than the intended reaction should occur (high reaction selectivity), specifically, high current efficiency (η _I ). 2) High electrode reaction activity, specifically cell resistance (R)
Is small. That is, the voltage efficiency (η _V ) is high. 3) High battery energy efficiency (η _E ) related to 1) and 2) above. η _E = η _I × η _V 4) Deterioration due to repeated use is small (long life), and specifically, the amount of decrease in battery energy efficiency (η _E ) is small.

【００１０】例えば、特開昭６０−２３２６６９号公報
には、Ｘ線広角解析より求めた＜００２＞面間隔が、平
均３．７０Å以下であり、またｃ軸方向の結晶子の大き
さが平均９．０Å以上の擬黒鉛微結晶を有し、かつ全酸
性官能基量が少なくとも０．０１ｍｅｑ／ｇである炭素
質材料をレドックスフロー電池の電解槽用電極材として
用いることが提案されている。For example, Japanese Patent Application Laid-Open No. 60-232669 discloses that the <002> plane spacing determined by X-ray wide angle analysis is 3.70 ° or less on average, and the crystallite size in the c-axis direction is It has been proposed to use a carbonaceous material having pseudographite crystallites of 9.0 ° or more and having a total acidic functional group content of at least 0.01 meq / g as an electrode material for an electrolytic cell of a redox flow battery.

【００１１】また、特開平５−２３４６１２号公報に
は、ポリアクリロニトリル系繊維を原料とする炭素質繊
維で、Ｘ線広角解析より求めた＜００２＞面間隔が３．
５０〜３．６０Åの擬黒鉛結晶構造を有し、炭素質材料
表面の結合酸素原子数が炭素原子数の１０〜２５％とな
るような炭素質材料をレドックスフロー電池の電解槽用
電極材として用いることが提案されている。Japanese Unexamined Patent Publication (Kokai) No. 5-234612 discloses a carbonaceous fiber made of polyacrylonitrile-based fiber having a <002> plane spacing of 3.0 obtained by X-ray wide-angle analysis.
A carbonaceous material having a pseudo-graphite crystal structure of 50 to 3.60 ° and having a number of bonded oxygen atoms of 10 to 25% of the number of carbon atoms on the surface of the carbonaceous material is used as an electrode material for an electrolytic cell of a redox flow battery. It has been proposed to use.

【００１２】[0012]

【発明が解決しようとする課題】しかしながら、特開昭
６０−２３２６６９号公報、特開平５−２３４６１２号
公報では、炭素質材料表面と電解液との間に有効な濡れ
性を発現させるために、全酸性官能基量が０．０１ｍｅ
ｑ／ｇ以上か、あるいはＸ線広角解析より求めた＜００
２＞面間隔が３．５０Å以上、かつ炭素質材料表面の結
合酸素原子数が炭素原子数の１０％以上必要であったの
で、この条件を満たすために低い温度での炭素化を行わ
ざるを得ず、そのため炭素の導電性を高められないとい
う問題点があった。さらに炭素質材料表面と集電板との
接触抵抗も官能基が多すぎるため高くなり、その結果セ
ル抵抗が高くなり、高いエネルギー効率を得られないこ
とも問題となった。However, JP-A-60-232669 and JP-A-5-234612 disclose that in order to exhibit effective wettability between the carbonaceous material surface and the electrolyte, Total acidic functional group content is 0.01me
q / g or more, or determined by X-ray wide-angle analysis <00
2> Since the plane spacing was 3.50 ° or more and the number of bonded oxygen atoms on the surface of the carbonaceous material was required to be 10% or more of the number of carbon atoms, carbonization at a low temperature had to be performed to satisfy this condition. Thus, there was a problem that the conductivity of carbon could not be increased. Further, the contact resistance between the surface of the carbonaceous material and the current collector plate is increased due to too many functional groups. As a result, the cell resistance is increased, and a problem that high energy efficiency cannot be obtained is also a problem.

【００１３】一方、炭素質材料表面と集電板との接触抵
抗は、炭素質材料で構成される不織布（集合体）の物性
によっても変化するため、炭素質材料の特性の改善だけ
では、接触抵抗を十分小さくするのが容易ではなかっ
た。また、当該不織布の物性は炭素質材料の製法や物
性、及び不織布の製法等により変化するため、炭素質材
料の物性等に応じて不織布の製法を最適化する必要があ
った。On the other hand, the contact resistance between the surface of the carbonaceous material and the current collector plate varies depending on the physical properties of the nonwoven fabric (aggregate) made of the carbonaceous material. It was not easy to reduce the resistance sufficiently. In addition, since the physical properties of the nonwoven fabric change depending on the manufacturing method and physical properties of the carbonaceous material, the manufacturing method of the nonwoven fabric, and the like, it is necessary to optimize the manufacturing method of the nonwoven fabric according to the physical properties of the carbonaceous material.

【００１４】そこで、本発明の目的は、かかる事情に鑑
み、炭素質繊維の特性と不織布の物性を共に改善するこ
とで、レドックスフロー電池のセル抵抗を低減してエネ
ルギー効率を高めることができる炭素電極材集合体を提
供することにある。In view of the foregoing, an object of the present invention is to improve the properties of carbonaceous fibers and the properties of non-woven fabrics, thereby reducing the cell resistance of a redox flow battery and improving energy efficiency. An object of the present invention is to provide an electrode material assembly.

【００１５】[0015]

【課題を解決するための手段】本発明者らは、上記目的
を達成すべく鋭意研究したところ、ａ軸方向の結晶子の
大きさを特定の範囲に制御しつつ、その表面酸性官能基
量を従来より低く抑えた炭素質繊維にて不織布を構成
し、その圧縮率と圧縮弾性率とを特定の範囲とすること
で、上記目的を達成できることを見出し、本発明を完成
するに至った。Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and found that while controlling the crystallite size in the a-axis direction to a specific range, the surface acidic functional group It has been found that the above object can be achieved by forming a non-woven fabric using carbonaceous fibers having a lower compression ratio than before and setting the compression ratio and compression elastic modulus in specific ranges, thereby completing the present invention.

【００１６】即ち、本発明の炭素電極材集合体は、水溶
液系電解液によるレドックスフロー電池に使用され、炭
素質繊維の不織布よりなる炭素電極材集合体において、
前記炭素質繊維は、Ｘ線広角解析より求めたａ軸方向の
結晶子の大きさが３０〜８０Åである擬黒鉛結晶構造を
有し、ＸＰＳ表面分析より求めた表面酸性官能基量が全
表面炭素原子数の０．２％以上１．２％以下であると共
に、前記不織布は、ＪＩＳ Ｌ１０９６（１９９０）に
準ずる圧縮率が１０〜２５％、圧縮弾性率が８０％以上
であることを特徴とする。That is, the carbon electrode material assembly of the present invention is used in a redox flow battery using an aqueous electrolyte solution, and in a carbon electrode material assembly made of a nonwoven fabric of carbonaceous fibers,
The carbonaceous fiber has a pseudo-graphite crystal structure in which the crystallite size in the a-axis direction determined by X-ray wide-angle analysis is 30 to 80 °, and the amount of surface acidic functional groups determined by XPS surface analysis is equal to the total surface area. The number of carbon atoms is 0.2% or more and 1.2% or less, and the nonwoven fabric has a compression rate of 10 to 25% and a compression elastic modulus of 80% or more according to JIS L1096 (1990). I do.

【００１７】本発明によると、炭素の結晶子が適度な大
きさとなり、炭素質繊維の導電性が向上すると共に、結
晶子の周囲のエッジ面への表面酸性官能基の良好な賦与
が可能となる。また、表面酸性官能基量が適量であるた
め、電極材表面の接触抵抗を低く抑えながら、水溶液系
電解液との濡れ性を適度に付与することができる。更
に、不織布の圧縮率と圧縮弾性率を上記範囲にすること
で、集電板との接触性を良好にして、接触抵抗を小さく
することができる。その結果、レドックスフロー電池の
セル抵抗を低減してエネルギー効率を高めることができ
る。According to the present invention, the carbon crystallite has an appropriate size, the conductivity of the carbonaceous fiber is improved, and the surface acidic functional group can be favorably applied to the edge surface around the crystallite. Become. In addition, since the amount of the surface acidic functional group is appropriate, the wettability with the aqueous electrolyte solution can be appropriately given while the contact resistance on the electrode material surface is kept low. Further, by setting the compression ratio and the compression elastic modulus of the nonwoven fabric in the above ranges, the contact property with the current collector plate can be improved, and the contact resistance can be reduced. As a result, the cell resistance of the redox flow battery can be reduced and the energy efficiency can be increased.

【００１８】また、本発明の炭素電極材は、バナジウム
系レドックスフロー電池に用いられることが好ましい。
バナジウム系のレドックスフロー電池では、上記の電解
液との濡れ性が比較的良好になるため、上記の如き作用
効果がより顕著になる。また、当該電池では電極材を構
成する繊維間や集電板に対する電極材表面の接触抵抗が
特に問題になり易いため、上記作用効果を有する本発明
の炭素電極材が特に有用なものとなる。Further, the carbon electrode material of the present invention is preferably used for a vanadium redox flow battery.
In a vanadium-based redox flow battery, the wettability with the above-mentioned electrolyte is relatively good, so that the above-described effects are more remarkable. Further, in the battery, since the contact resistance between the fibers constituting the electrode material and the surface of the electrode material with respect to the current collector plate tends to be particularly problematic, the carbon electrode material of the present invention having the above-mentioned effects is particularly useful.

【００１９】[0019]

【発明の実施の形態】本発明の炭素電極材集合体は炭素
質繊維からなり、取扱いや加工性、製造性等の点から炭
素質繊維の不織布が使用される。当該不織布は、焼成
（炭化）前の不融化あるいは耐炎化された短繊維を開繊
し、カードにかけ、幾層かに重ねられたレイヤーからな
るウェブをまず作成し、さらにニードルパンチ加工機に
かけることで、好適に作製される。BEST MODE FOR CARRYING OUT THE INVENTION The carbon electrode material aggregate of the present invention is made of carbonaceous fiber, and a nonwoven fabric of carbonaceous fiber is used from the viewpoint of handling, workability, manufacturability and the like. The non-woven fabric is obtained by opening infusible or flame-resistant short fibers before firing (carbonization), applying them to a card, first creating a web composed of several layers, and then applying the web to a needle punching machine. Thereby, it is suitably manufactured.

【００２０】不織布の目付量は、隔膜と集電板に挟まれ
た充填状態の厚みを２〜３ｍｍで使用する場合、１００
〜１０００ｇ／ｍ² が好ましく、特に２００〜６００ｇ
／ｍ ² が望ましい。また片面に凹溝加工が施された不織
布が通液性の点から好んで用いられる。その場合の溝
幅、溝深さは少なくとも０．３ｍｍ、特に０．５ｍｍ以
上が望ましい。該炭素質繊維不織布の厚みは、上記充填
状態の厚みより少なくとも大きいこと、好ましくは充填
状態の厚みの１．５倍程度である。しかしながら、厚み
が厚すぎると圧縮応力で膜を突き破ってしまうので、圧
縮応力を１ｋｇｆ／ｃｍ² 以下に設計するのが好まし
い。[0020] The basis weight of the non-woven fabric is sandwiched between the diaphragm and the current collector.
When the thickness of the filled state is 2-3 mm, 100
~ 1000g / m^Two Is preferred, especially 200 to 600 g
/ M ^Two Is desirable. Non-woven fabric with a groove on one side
A cloth is preferably used from the viewpoint of liquid permeability. Groove in that case
Width and groove depth should be at least 0.3mm, especially 0.5mm or less
Above is desirable. The thickness of the carbonaceous fiber nonwoven fabric is
At least greater than the thickness of the state, preferably filling
It is about 1.5 times the thickness of the state. However, the thickness
If it is too thick, it will break through the membrane with compressive stress.
Shrinkage stress of 1kgf / cm^Two It is preferable to design
No.

【００２１】なお、上記の炭素質繊維の平均繊維径は５
〜２０μｍ程度が好ましく、平均長さは３０〜１００ｍ
ｍ程度が好ましい。The average fiber diameter of the carbonaceous fibers is 5
About 20 μm is preferable, and the average length is 30 to 100 m.
m is preferable.

【００２２】炭素質繊維不織布は、電池の中に圧接され
て組み込まれ、その薄い隙間を粘度の高い電解液が流れ
るため、脱落を防止して形態保持するためには引張強度
を０．１ｋｇ／ｃｍ以上にすることが望ましい。また集
電板との接触抵抗を良くするために、隔膜、集電板に挟
まれた充填層の密度を０．０５ｇ／ｃｍ³ 以上に、電極
面に対する反発力を０．１ｋｇｆ／ｃｍ² 以上にするこ
とが好ましい。The carbonaceous fiber non-woven fabric is assembled by being pressed into a battery, and a high-viscosity electrolytic solution flows through the thin gap. cm or more. Also, in order to improve the contact resistance with the current collector, the density of the diaphragm and the packed layer sandwiched between the current collectors is set to 0.05 g / cm ³ or more, and the repulsive force to the electrode surface is set to 0.1 kgf / cm ² or more. Is preferable.

【００２３】さらに本発明の炭素繊維は、電極材として
の本来必要な導電性と圧接型電解層における接触性を両
立するために、Ｘ線広角解析より求めたａ軸方向の結晶
子の大きさ（Ｌａ）が３０〜８０Åで、かつＸＰＳ表面
分析より求めた表面酸性官能基量が全表面炭素原子数の
０．２％以上１．２％以下に調整される。好ましくはＬ
ａが３５〜８０Åで、かつ表面酸性官能基量が０．２〜
１．１％であり、より好ましくはＬａが４０〜７９Å
で、かつ表面酸性官能基量が０．３〜１．０％である。Further, the carbon fiber of the present invention has a crystallite size in the a-axis direction determined by X-ray wide-angle analysis in order to achieve both the originally required conductivity as an electrode material and the contact property in the pressure-contact type electrolytic layer. (La) is 30 to 80 °, and the amount of surface acidic functional groups determined by XPS surface analysis is adjusted to 0.2% or more and 1.2% or less of the total number of surface carbon atoms. Preferably L
a is 35 to 80 ° and the amount of surface acidic functional groups is 0.2 to
1.1%, more preferably La is 40 to 79 °.
And the amount of surface acidic functional groups is 0.3 to 1.0%.

【００２４】ａ軸方向の結晶子の大きさとは、炭素の結
晶子における網面の広がりを意味し、ａ軸方向の結晶子
の大きさが３０Å未満である場合、電池内部抵抗（セル
抵抗）の内の電極材導電抵抗成分が無視できないように
なり、その結果セル抵抗が増加し（電圧効率が低下
し）、エネルギー効率が低下する。反面８０Åより大き
いと電解液の濡れ性を左右する親水基の賦与ができなく
なり、活物質の反応性が著しく低下するため、電池の内
部抵抗が高くなる。なおａ軸方向の結晶子の大きさはＸ
線広角解析にて得られる＜１０＞面回折ピークの半値幅
より算出される。The crystallite size in the a-axis direction means the spread of the net plane in carbon crystallites. When the crystallite size in the a-axis direction is less than 30 °, the internal resistance of the battery (cell resistance) Of the electrode material cannot be ignored, as a result, the cell resistance increases (voltage efficiency decreases) and energy efficiency decreases. On the other hand, if it is larger than 80 °, it becomes impossible to provide a hydrophilic group which affects the wettability of the electrolytic solution, and the reactivity of the active material is significantly reduced, so that the internal resistance of the battery is increased. The size of the crystallite in the a-axis direction is X
It is calculated from the half width of the <10> plane diffraction peak obtained by line wide angle analysis.

【００２５】また表面酸性官能基量は０．２％未満の場
合には、電解液の濡れ性が悪く、セル抵抗が著しく増加
する。これは、炭素原子そのものは疎水性であるため、
親水基の酸性官能基が少ない場合には水をはじきやすい
ためと考えられる。１．２％以上の場合、官能基の存在
が大きく影響し、電極材の繊維間接触および繊維−集電
板間の導電性が阻害され好ましくない。なお、上記の表
面酸性官能基量とは、含酸素官能基のうち硝酸銀処理に
よって銀イオン置換されうる水酸基やカルボキシル基の
量を意味し、ＸＰＳ表面分析によって検出される表面銀
イオン量の表面炭素原子数に対する割合（百分率）とし
て表す。When the amount of surface acidic functional groups is less than 0.2%, the wettability of the electrolytic solution is poor and the cell resistance is significantly increased. This is because the carbon atoms themselves are hydrophobic,
It is considered that when the number of the acidic functional groups of the hydrophilic group is small, water is easily repelled. When the content is 1.2% or more, the presence of the functional group greatly affects the contact between the fibers of the electrode material and the conductivity between the fibers and the current collector plate, which is not preferable. The above-mentioned surface acidic functional group amount refers to the amount of hydroxyl groups or carboxyl groups that can be replaced with silver ions by silver nitrate treatment among the oxygen-containing functional groups, and indicates the surface carbon ion amount of the surface carbon ions detected by XPS surface analysis. Expressed as a ratio (percentage) to the number of atoms.

【００２６】こうした結晶性と表面特性を有する炭素質
材料は、緊張下２００〜３００℃の初期空気酸化（耐炎
化）を経たポリアクリロニトリル、等方性ピッチ、メソ
フェーズピッチ、セルロースやフェノール、ポリパラフ
ェニレンベンゾビスオキサゾール（ＰＢＯ）などを原料
として用いて製造される。中でも、特にポリアクリロニ
トリルの重量平均分子量（Ｍｗ）を２００００〜５００
０００に調整されたものが耐炎化の原料として好まし
い。分子量が大きくなった場合、より低い焼成（炭化）
温度でも所定のＬａを得ることができるが、同時に結晶
子の配向性が相対的に高くなる傾向にあり、単繊維の曲
げ弾性率が高くなってセル接合時の圧縮弾性率が低下
し、反面分子量が小さくなると焼成時に単繊維の結晶化
が進まず、乱層構造が発達し導電性が向上しない傾向が
ある。こうした所定の分子量を有するポリアクリロニト
リル繊維は公知の方法で耐炎化される。Carbonaceous materials having such crystallinity and surface characteristics include polyacrylonitrile, isotropic pitch, mesophase pitch, cellulose, phenol, and polyparaphenylene that have been subjected to initial air oxidation (flame resistance) at 200 to 300 ° C. under tension. It is manufactured using benzobisoxazole (PBO) or the like as a raw material. Among them, particularly, the weight average molecular weight (Mw) of polyacrylonitrile is set to 20000 to 500.
Those adjusted to 000 are preferred as raw materials for flame resistance. Lower firing (carbonization) for higher molecular weights
Although a predetermined La can be obtained even at a temperature, the orientation of crystallites tends to be relatively high at the same time, the bending elastic modulus of the single fiber increases, the compressive elastic modulus at the time of cell joining decreases, and When the molecular weight is small, crystallization of the single fiber does not proceed during firing, and a turbostratic structure tends to develop and the conductivity does not tend to improve. Such polyacrylonitrile fibers having a predetermined molecular weight are flame-resistant by a known method.

【００２７】耐炎化された原料は不活性雰囲気下１００
０〜１８００℃で焼成され、擬黒鉛結晶構造を有する炭
素材料となる。炭化温度は原料やその分子量によって結
晶性が異なるので、温度には特に限定されず、原料に応
じた炭化温度の最適化が必要である。つまり、Ｌａは、
原料の分子量と炭化温度の兼ね合い等により制御するこ
とができる。The flame-resistant raw material is 100
It is fired at 0 to 1800 ° C. to become a carbon material having a pseudo-graphite crystal structure. Since the crystallinity differs depending on the raw material and its molecular weight, the carbonization temperature is not particularly limited to the temperature, and it is necessary to optimize the carbonization temperature according to the raw material. That is, La is
It can be controlled by a balance between the molecular weight of the raw material and the carbonization temperature.

【００２８】さらに所定の酸素濃度で乾式酸化処理し、
必要があれば水素ガス存在下によって官能基を一部還元
してもよい。乾式酸化については公知の方法が採用でき
るが、電極材に適度の表面酸性官能基量を得るために
は、酸化処理後の重量収率にて９０〜９６％に調整する
ことが望ましい。Further, dry oxidation treatment is performed at a predetermined oxygen concentration,
If necessary, the functional groups may be partially reduced in the presence of hydrogen gas. For the dry oxidation, a known method can be adopted, but in order to obtain an appropriate amount of surface acidic functional groups in the electrode material, it is desirable to adjust the weight yield after the oxidation treatment to 90 to 96%.

【００２９】本発明の炭素質繊維不織布は、圧縮率が１
０〜２５％で、圧縮弾性率が８０％以上であるが、好ま
しくは、圧縮率１０〜２０％で、圧縮弾性率８２％以上
である。圧縮率が１０％未満の場合、繊維間の絡みが得
られず、炭素質繊維不織布としての形態を保持すること
ができない。一方、圧縮率が２５％を越えるか、圧縮弾
性率か８０％未満の場合は、電池の中に圧接させて組み
込まれた際の集電板との接触抵抗が高くなり、その結
果、セル抵抗が増加し（電圧効率が低下し）、エネルギ
ー効率が低下する。The carbon fiber nonwoven fabric of the present invention has a compression ratio of 1
The compression elastic modulus is 0% to 25% and the compression elastic modulus is 80% or more, but preferably the compression ratio is 10 to 20% and the compression elastic modulus is 82% or more. When the compression ratio is less than 10%, entanglement between fibers cannot be obtained, and the form as a carbonaceous fiber nonwoven fabric cannot be maintained. On the other hand, when the compression ratio exceeds 25% or the compression elasticity is less than 80%, the contact resistance with the current collector when the battery is pressed into the battery and assembled is increased, and as a result, the cell resistance is increased. Increase (voltage efficiency decreases) and energy efficiency decreases.

【００３０】このような炭素質繊維不織布の圧縮特性
は、上述した炭素の結晶構造と表面酸性官能基を持つこ
とが前提となるが、前段階のニードルパンチの条件を制
御することによって得られる。すなわち、柔軟性があ
り、繊維の脱落のない不織布形態を保ちつつ、なおかつ
圧接した際の集電板との接触性（接触面と接触力）が向
上するように、ニードルパンチの密度を１５０〜３００
本／ｃｍ² 、好ましくは、２００〜３００本／ｃｍ² に
し、ニードルパンチの針を不融化繊維あるいは耐炎化繊
維が交互に絡みやすいもの、例えばＳＢ＃３６やＳＢ＃
４０（ＦｏｓｔｅｒＮｅｅｄｌｅ社）にすることが好ま
しい。The compression characteristics of such a carbonaceous fiber nonwoven fabric are premised on having the above-mentioned carbon crystal structure and surface acidic functional groups, but can be obtained by controlling the conditions of the needle punch in the preceding stage. That is, the density of the needle punch is set to 150 to 100% so as to maintain the nonwoven fabric form that is flexible and does not cause the fibers to fall off, and that the contact property (contact surface and contact force) with the current collector plate when pressed is improved. 300
Needles / cm ² , preferably 200 to 300 needles / cm ² , and the needle of the needle punch is made of an infusible fiber or an oxidized fiber which is easily entangled alternately, for example, SB # 36 or SB #
40 (Foster Needle).

【００３１】また、不織布の圧縮率と圧縮弾性率とを上
記範囲に制御する上で、乾式酸化処理を、０．０１ｋｇ
ｆ／ｃｍ幅以上のテンション下で行うのが好ましい。In order to control the compression ratio and the compression elastic modulus of the nonwoven fabric within the above ranges, the dry oxidation treatment is performed at 0.01 kg.
It is preferable to carry out under a tension of f / cm width or more.

【００３２】次に、本発明において採用されるａ軸方向
の結晶子の大きさ（Ｌａ）、ＸＰＳ表面分析、不織布の
圧縮率及び圧縮弾性率、集電板との接触抵抗、電極性能
の各測定法について説明する。Next, the crystallite size (La) in the a-axis direction employed in the present invention, XPS surface analysis, compression ratio and compression elastic modulus of the nonwoven fabric, contact resistance with the current collector, and electrode performance The measurement method will be described.

【００３３】１．ａ軸方向の結晶子の大きさ（Ｌａ） 電極材料をメノウ乳鉢で、粒径１０μｍ程度になるまで
粉砕し、試料に対して約５重量％のＸ線標準用高純度シ
リコン粉末を内部標準物質として混合し、試料セルに詰
め、ＣｕＫα線を線源として、ディフラクトメーター法
によって広角Ｘ線を測定する。1. Crystallite size in the a-axis direction (La) The electrode material is pulverized in an agate mortar to a particle size of about 10 μm, and about 5% by weight of the sample, high purity silicon powder for X-ray standard is used as an internal standard material. , And packed in a sample cell, and a wide angle X-ray is measured by a diffractometer method using CuKα radiation as a radiation source.

【００３４】曲線の補正には、いわゆるローレンツ因
子、偏光因子、吸収因子、原子散乱因子等に関する補正
を行わず、次の簡便法を用いる。即ち、＜１０＞回折に
相当するピークのべースラインからの実質強度をプロッ
トし直して＜１０＞補正強度曲線を得る。この曲線のピ
ーク高さの１／２の高さに引いた角度軸に平行な線が補
正強度曲線と交わる線分の長さ（半値幅β）から数式１
によって結晶子の大きさを求める。For the correction of the curve, the following simple method is used without correcting the so-called Lorentz factor, polarization factor, absorption factor, atomic scattering factor and the like. That is, the actual intensity from the base line of the peak corresponding to the <10> diffraction is plotted again to obtain the <10> corrected intensity curve. A line parallel to the angle axis drawn to half the peak height of this curve is expressed by the following equation (1) from the length of the line segment (half width β) that intersects the corrected intensity curve.
To determine the size of the crystallite.

【００３５】[0035]

【数１】 ここで、波長λ＝１．５４１８Å、構造係数ｋ２＝１．
８４、θは＜１０＞回折角を、βは＜１０＞回折ピーク
の半値幅を示す。(Equation 1) Here, the wavelength λ = 1.5418 °, the structure coefficient k2 = 1.
84 and θ indicate the <10> diffraction angle, and β indicates the half value width of the <10> diffraction peak.

【００３６】２．ＸＰＳ表面分析 ＥＳＣＡあるいはＸＰＳと略称されているＸ線光電子分
光法の測定に用いる装置は島津ＥＳＣＡ７５０で、解析
にはＥＳＣＡＰＡＣ７６０を用いる。2. XPS Surface Analysis A device used for measurement of X-ray photoelectron spectroscopy, which is abbreviated as ESCA or XPS, is Shimadzu ESCA750, and ESCAPAC760 is used for analysis.

【００３７】各試料を硝酸銀のアセトン溶液に浸漬し、
酸性官能基のプロトンを完全に銀置換し、アセトン及び
水でそれぞれ洗浄後、６ｍｍ径に打ち抜き、導電性ペー
ストにより加熱式試料台に貼り付け、分析に供する。予
め、測定前に試料を１２Ｏ℃に加熱し、３時間以上真空
脱気する。線源にはＭｇＫα線（１２５３．６ｅＶ）を
用い、装置内真空度は１０^-7ｔｏｒｒとする。Each sample was immersed in an acetone solution of silver nitrate,
The proton of the acidic functional group is completely replaced with silver, washed with acetone and water, punched out to a diameter of 6 mm, attached to a heated sample stand with a conductive paste, and subjected to analysis. Before the measurement, the sample is heated to 120 ° C. and vacuum degassed for 3 hours or more. MgKα radiation (1253.6 eV) is used as the radiation source, and the degree of vacuum in the apparatus is set to 10 ⁻⁷ torr.

【００３８】測定はＣｌｓ，Ａｇ３ｄピークに対して行
い、各ピークをＥＳＣＡＰＡＣ７６０（Ｊ．Ｈ．Ｓｃｏ
ｆｉｅｌｄによる補正法に基づく）を用いて補正解析
し、各ピーク面積を求める。得られた面積にＣｌｓにつ
いては１．００、Ａｇ３ｄについては１０．６８の相対
強度を乗じたものの比が原子数比であり、全表面炭素原
子数に対する表面酸性官能基量は（表面銀原子数／表面
炭素原子数）比を百分率（％）で算出する。The measurement was carried out on the Cls and Ag3d peaks, and each peak was taken as ESCAPAC760 (JH Sco
(based on the field correction method) to determine the respective peak areas. The ratio of the obtained area multiplied by the relative intensity of 1.00 for Cls and 10.68 for Ag3d is the atomic number ratio, and the amount of surface acidic functional groups to the total number of surface carbon atoms is (the number of surface silver atoms) / Number of surface carbon atoms) is calculated as a percentage (%).

【００３９】３．不織布の圧縮率及び圧縮弾性率 ＪＩＳ Ｌ１０９６（１９９０）に記載の「６．１８圧
縮率及び圧縮弾性率」に準じ、約５×約５ｃｍの試験片
を５枚採取し、１枚の試験片を初荷重０．４９ｋＰａの
下で、厚さ（ｍｍ）を測り、次に荷重を２４．５ｋＰａ
の下で１分間放置して厚さ（ｍｍ）を計る。次に荷重を
除き１分間放置した後、再び初荷重の下で厚さ（ｍｍ）
を測り、それぞれの厚さより圧縮率及び圧縮弾性率を求
め、５回の平均値で表す（整数位まで）。3. Compressibility and Compressive Modulus of Nonwoven Fabric According to “6.18 Compressibility and Compressive Modulus” described in JIS L1096 (1990), five test pieces of about 5 × about 5 cm are sampled, and one test piece is taken. Measure the thickness (mm) under the initial load of 0.49 kPa, and then apply the load of 24.5 kPa.
And leave it for 1 minute under a jar to measure the thickness (mm). Next, remove the load and leave it for 1 minute, then again under initial load thickness (mm)
Is measured, and the compressibility and the compressive elastic modulus are obtained from the respective thicknesses, and are represented by an average value of five times (up to an integer).

【００４０】４．集電板との接触抵抗 ２枚の集電板を用い、その間に幅１ｃｍ、長さ１０ｃｍ
の炭素質繊維不織布の試料を挟んで２ｍｍ厚みに圧接し
た時の抵抗をデジタルマルチメータで簡易的に測定し、
単位面積あたりの抵抗を求める。集電板には固有抵抗
０．０５Ω・ｃｍの樹脂結合質黒鉛板（厚み３ｍｍ）を
用い、集電板同士をそのまま圧接した時の抵抗は不織布
との接触抵抗に対して無視できるものである。4. Contact resistance with current collector plate Two current collector plates were used, with a width of 1 cm and a length of 10 cm between them.
The resistance when pressed to a thickness of 2 mm across the carbonaceous fiber nonwoven fabric sample is simply measured with a digital multimeter,
Find the resistance per unit area. A resin-bonded graphite plate (thickness: 3 mm) having a specific resistance of 0.05 Ω · cm is used as the current collector, and the resistance when the current collectors are pressed against each other as is is negligible with respect to the contact resistance with the nonwoven fabric. .

【００４１】５．電極性能 上下方向（通液方向）に１０ｃｍ、幅方向に１ｃｍの電
極面積１０ｃｍ² を有する小型のセルを作り、定電流密
度で充放電を繰り返し、電極性能のテストを行う。正極
電解液には２ｍｏｌ／ｌのオキシ硫酸バナジウムの３ｍ
ｏｌ／ｌ硫酸水溶液を用い、負極電解液には２ｍｏｌ／
ｌの硫酸バナジウムの３ｍｏｌ／ｌ硫酸溶液を用いる。
電解液量はセル、配管に対して大過剰とした．液流量は
毎分６．２ｍｌとし、３０℃で測定を行う。5. Electrode Performance A small cell having an electrode area of 10 cm ² of 10 cm in the vertical direction (liquid flow direction) and 1 cm in the width direction is made, and charge / discharge is repeated at a constant current density to perform a test of the electrode performance. 3 m of 2 mol / l vanadium oxysulfate was used for the positive electrode electrolyte.
ol / l sulfuric acid aqueous solution, and 2 mol / l
A 3 mol / l sulfuric acid solution of 1 vanadium sulfate is used.
The amount of electrolyte was set to a large excess with respect to the cells and piping. The liquid flow rate is 6.2 ml per minute, and the measurement is performed at 30 ° C.

【００４２】（ａ）電流効率：η_I 充電に始まり、放電で終わる１サイクルのテストにおい
て、電流密度を電極幾何面積当たり４０ｍＡ／ｃｍ²
（４００ｍＡ）として、１．７Ｖまでの充電に要した電
気量をＱ₁ クーロン、１．０Ｖまでの定電流放電、およ
びこれに続く１．２Ｖでの定電圧放電で取りだした電気
量をそれぞれＱ₂ 、Ｑ₃ クーロンとし、数式２で電流効
率η_I を求める。(A) Current efficiency: η _{I In a} one-cycle test starting from charging and ending with discharging, the current density was set to 40 mA / cm ² per electrode geometrical area.
(400 mA), the quantity of electricity required for charging up to 1.7 V is Q ₁ coulomb, the quantity of electricity taken out by constant current discharge up to 1.0 V, and the subsequent quantity of electricity taken out by constant voltage discharge at 1.2 V are Q ₂ , Q ₃ coulombs, and the current efficiency η _I is obtained by equation (2).

【００４３】[0043]

【数２】 （ｂ）セル抵抗：Ｒ 負極液中のＶ³⁺をＶ²⁺に完全に還元するのに必要な理論
電気量Ｑ_thに対して、放電により取りだした電気量の比
を充電率とし、数式３で充電率を求める。(Equation 2) (B) Cell resistance: R The ratio of the amount of electricity taken out by discharging to the theoretical amount of electricity Q _th required to completely reduce V ³⁺ in the negative electrode solution to V ²⁺ is defined as a charging rate. The charging rate is determined in step 3.

【００４４】[0044]

【数３】 充電率が５０％のときの電気量に対応する充電電圧Ｖ
_C50 、放電電圧Ｖ_D50 を電気量−電圧曲線からそれぞれ
求め、数式４より電極幾何面積に対するセル抵抗Ｒ（Ω
・ｃｍ² ）を求める。(Equation 3) Charging voltage V corresponding to the amount of electricity when the charging rate is 50%
_C50 and discharge voltage V _D50 are obtained from the electric quantity-voltage curve, respectively.
・ Calculate cm ² ).

【００４５】[0045]

【数４】 ここで、Ｉは定電流充放電における電流値０．４Ａであ
る。(Equation 4) Here, I is a current value of 0.4 A in constant current charging and discharging.

【００４６】（ｃ）電圧効率：η_V 上記の方法で求めたセル抵抗Ｒを用いて数式５の簡便法
により電圧効率η_V を求める。(C) Voltage efficiency: η _V Using the cell resistance R obtained by the above method, the voltage efficiency η _V is obtained by a simple method of Expression 5.

【００４７】[0047]

【数５】 ここで、Ｅは充電率５０％のときのセル開回路電圧１．
４３２Ｖ（実測値）、Ｉは定電流充放電における電流値
０．４Ａである。(Equation 5) Here, E is the cell open circuit voltage when the charging rate is 50%.
432 V (actual measurement value), and I is a current value of 0.4 A in constant current charging and discharging.

【００４８】（ｄ）エネルギー効率：η_E 前述の電流効率η_I と電圧効率η_V を用いて、数式６に
よりエネルギー効率η _E を求める。(D) Energy efficiency: η_E Current efficiency η described above_I And voltage efficiency η_V And using equation 6
More energy efficiency η _E Ask for.

【００４９】[0049]

【数６】 電流効率、電圧効率が高くなる程、エネルギー効率は高
くなり、従つて充放電におけるエネルギーロスが小さ
く、優れた電極であると判断される。(Equation 6) The higher the current efficiency and the voltage efficiency, the higher the energy efficiency. Therefore, the energy loss in charging and discharging is small, and it is determined that the electrode is an excellent electrode.

【００５０】本発明の炭素電極材集合体は、水溶液系電
解液を使用するレドックスフロー電池に用いられるもの
である。当該レドックスフロー電池は、前述のように、
例えば間隙を介した状態で対向して配設された一対の集
電板間に隔膜が配設され、該集電板と隔膜との間に少な
くとも一方に電極材が配設され、電極材は活物質を含ん
だ水溶液からなる電解液を含んだ構造を有する電解槽を
備える。The carbon electrode material assembly of the present invention is used for a redox flow battery using an aqueous electrolyte. The redox flow battery, as described above,
For example, a diaphragm is provided between a pair of current collectors disposed facing each other with a gap therebetween, and an electrode material is provided on at least one of the current collectors and the diaphragm, and the electrode material is An electrolytic cell having a structure containing an electrolytic solution composed of an aqueous solution containing an active material is provided.

【００５１】水溶液系電解液としては、前述の如きバナ
ジウム系電解液の他、鉄−クロム系、チタン−マンガン
系、マンガン−クロム系、クロム−クロム系、鉄−チタ
ン系などが挙げられるが、バナジウム系電解液が好まし
い。本発明の炭素電極材は、特に、粘度が２５℃にて
０．００５Ｐａ・ｓ以上であるバナジウム系電解液、あ
るいは１．５ｍｏｌ／ｌ以上のバナジウムイオンを含む
バナジウム系電解液を使用するレドックスフロー電池に
用いるのが有用である。Examples of the aqueous electrolytic solution include iron-chromium-based, titanium-manganese-based, manganese-chromium-based, chromium-chromium-based, iron-titanium-based, and the like, in addition to the vanadium-based electrolyte described above. Vanadium-based electrolytes are preferred. In particular, the carbon electrode material of the present invention is a redox flow using a vanadium-based electrolyte having a viscosity of at least 0.005 Pa · s at 25 ° C. or a vanadium-based electrolyte containing 1.5 mol / l or more of vanadium ions. Useful for batteries.

【００５２】[0052]

【実施例】以下、本発明の構成及び効果を具体的に示
す、実施例等について説明する。EXAMPLES Examples and the like that specifically show the structure and effects of the present invention will be described below.

【００５３】（実施例１）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量７５０００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎化繊維の短繊維（長さ約８０ｍｍ）を用いて
フェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度２５０本／ｃｍ² でフェルト化し
て目付量６００ｇ／ｍ² 、厚み５．０ｍｍの不織布を作
成した。該不織布にアルゴンガスを絶えず６００ｃｃ／
ｍｉｎ／ｍ² 吹き付けた状態で１００゜Ｃ／分の昇温速
度で１４００℃まで昇温し、この温度で１時間保持し炭
化を行って冷却し、続いて空気中７００℃で重量収率９
３％になるまで０．１ｋｇｆ／ｃｍ幅のテンションで引
っ張って処理し炭素質繊維不織布を得た。Example 1 Acrylonitrile 98 mol%
-Polyacrylonitrile fibers having a weight average molecular weight of 75,000 and an average fiber diameter of 16 [mu] m composed of 2 mol% of methyl methacrylate are oxidized in air at 200 to 300 [deg.] C., and then short fibers of the oxidized fibers (about 80 mm in length) Needle # 36 (Foster Needle)
Co., Ltd., and felted at a punching density of 250 pieces / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 5.0 mm. Argon gas is constantly added to the nonwoven fabric at 600 cc /
The temperature was raised to 1400 ° C. at a temperature rising rate of 100 ° C./min while spraying min / m ² , kept at this temperature for 1 hour, carbonized and cooled, and subsequently, in air at 700 ° C. and a weight yield of 9
The carbonaceous fiber nonwoven fabric was obtained by pulling with a tension of 0.1 kgf / cm width until the content became 3%.

【００５４】（実施例２）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量７５０００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎繊維の短繊維（長さ約８０ｍｍ）を用いてフ
ェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度２５０本／ｃｍ² でフェルト化し
て目付量６００ｇ／ｍ² 、厚み５．０ｍｍの不織布を作
成した。該不織布にアルゴンガスを絶えず６００ｃｃ／
ｍｉｎ／ｍ ² 吹き付けた状態で１００℃／分の昇温速度
で1 ４００℃まで昇温し、この温度で１時間保持し炭化
を行って冷却し、続いて空気中７００℃で重量収率９０
％になるまで０．１ｋｇｆ／ｃｍ幅のテンションで引っ
張って処理し炭素質繊維不織布を得た。Example 2 98 mol% of acrylonitrile
-Weight average composed of 2 mol% methyl methacrylate
Polyacrylo with a molecular weight of 75,000 and an average fiber diameter of 16 µm
Nitrile fiber was flame resistant at 200-300 ° C in air
Then, using the short fiber (length of about 80 mm) of the flame resistant fiber,
Gel Needle SB # 36 (Foster Needle
Company), punching density 250 / cm^Two Felt with
600g / m^Two , Make a 5.0mm thick non-woven fabric
Done. Argon gas is constantly added to the nonwoven fabric at 600 cc /
min / m ^Two 100 ° C / min heating rate with sprayed
Temperature to 1400 ° C, hold at this temperature for 1 hour and carbonize
And then cooled in air at 700 ° C. at a weight yield of 90
% With a tension of 0.1 kgf / cm width
It was stretched and processed to obtain a carbonaceous fiber nonwoven fabric.

【００５５】（実施例３）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量７５０００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎化繊維の短繊維（長さ約８０ｍｍ）を用いて
フェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度２５０本／ｃｍ² でフェルト化し
て目付量６００ｇ／ｍ² 、厚み５．０ｍｍの不織布を作
成した。該不織布にアルゴンガスを絶えず６００ｃｃ／
ｍｉｎ／ｍ² 吹き付けた状態で１００℃／分の昇温速度
で1 ６００℃まで昇温し、この温度で１時間保持し炭化
を行って冷却し、続いて空気中７００℃で重量収率９３
％になるまで０．１ｋｇｆ／ｃｍ幅のテンションで引っ
張って処理し炭素質繊維不織布を得た。Example 3 98 mol% of acrylonitrile
-Polyacrylonitrile fibers having a weight average molecular weight of 75,000 and an average fiber diameter of 16 [mu] m composed of 2 mol% of methyl methacrylate are oxidized in air at 200 to 300 [deg.] C., and then short fibers of the oxidized fibers (about 80 mm in length) Needle # 36 (Foster Needle)
Co., Ltd., and felted at a punching density of 250 pieces / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 5.0 mm. Argon gas is constantly added to the nonwoven fabric at 600 cc /
The temperature was raised to 1600 ° C. at a rate of 100 ° C./min while spraying min / m ² , kept at this temperature for 1 hour, carbonized and cooled, and subsequently in air at 700 ° C. for a weight yield of 93
% To give a carbonaceous fiber nonwoven fabric.

【００５６】（実施例４）アクリロニトリル９７モル％
−酢酸ビニル３モル％から構成される重量平均分子量２
０００００の平均繊維径１６μｍのポリアクリロニトリ
ル繊維を空気中２００〜３００℃で耐炎化した後、該耐
炎化繊維の短繊維（長さ約８０ｍｍ）を用いてフェルト
針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ社）、パン
チング密度２５０本／ｃｍ² でフェルト化して目付量６
００ｇ／ｍ² 、厚み５．０ｍｍの不織布を作成した。該
不織布にアルゴンガスを絶えず６００ｃｃ／ｍｉｎ／ｍ
² 吹き付けた状態で１００℃／分の昇温速度で1 ４００
℃まで昇温しこの温度で１時間保持し炭化を行って冷却
し、続いて空気中７００℃で重量収率９３％になるまで
０．１ｋｇｆ／ｃｍ幅のテンションで引っ張って処理し
炭素質繊維不織布を得た。Example 4 97 mol% of acrylonitrile
Weight average molecular weight 2 composed of 3 mol% of vinyl acetate
After oxidizing polyacrylonitrile fibers having an average fiber diameter of 16 μm in air at 200 to 300 ° C. in air, felt needles SB # 36 (Foster Needle) using short fibers (about 80 mm in length) of the oxidized fibers, Felt at a punching density of 250 pieces / cm ² and a basis weight of 6
00g / m ^2, created a thickness 5.0mm nonwoven. Argon gas is continuously applied to the nonwoven fabric at 600 cc / min / m.
^{2 While} spraying, 1 400 at a heating rate of 100 ° C / min.
℃, held at this temperature for 1 hour, carbonized and cooled, and then stretched in air at 700 ℃ with a tension of 0.1 kgf / cm width until the weight yield became 93%. A non-woven fabric was obtained.

【００５７】（実施例５）アクリロニトリル９７モル％
−酢酸ビニル３モル％から構成される重量平均分子量２
０００００の平繊維径１６μｍのポリアクリロニトリル
繊維を空気中２００〜３００℃で耐炎化した後、該耐炎
化繊維の短繊維（長さ約８０ｍｍ）を用いてフェルト針
ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ社）、パンチ
ング密度２５０本／ｃｍ² でフェルト化して目付量６０
０ｇ／ｍ² 、厚み５．０ｍｍの不織布を作成した。該不
織布にアルゴンガスを絶えず６００ｃｃ／ｍｉｎ／ｍ²
吹き付けた状態で１００℃／分の昇温速度で1 ６００℃
まで昇温し、この温度で１時間保持し炭化を行って冷却
し、続いて空気中７００℃で重量収率９５％になるまで
０．０５ｋｇｆ／ｃｍ幅のテンションで引っ張って処理
し炭素質繊維不織布を得た。Example 5 97 mol% of acrylonitrile
Weight average molecular weight 2 composed of 3 mol% of vinyl acetate
After oxidizing polyacrylonitrile fibers having a flat fiber diameter of 16 μm in air at 200 to 300 ° C. in air, felt needles SB # 36 (Foster Needle) using short fibers (about 80 mm in length) of the oxidized fibers, Felt at a punching density of 250 pieces / cm ² and a basis weight of 60
A nonwoven fabric having a thickness of 0 g / m ² and a thickness of 5.0 mm was prepared. Argon gas is continuously applied to the nonwoven fabric at 600 cc / min / m ^2.
1600 ° C at a heating rate of 100 ° C / min while spraying
Temperature, held at this temperature for 1 hour, carbonized, cooled, and then stretched at 700 ° C. in air with a tension of 0.05 kgf / cm width until a weight yield of 95% was obtained. A non-woven fabric was obtained.

【００５８】（比較例１）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量１００００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎化繊維の短繊維（長さ約８０ｍｍ）を用いて
フェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度２５０本／ｃｍ² でフェルト化し
て目付量６００ｇ／ｍ² 、厚み５．０ｍｍの不織布を作
成した。該不織布にアルゴンガスを絶えず６００ｃｃ／
ｍｉｎ／ｍ² 吹き付けた状態で１００℃／分の昇温速度
で1 ６００℃まで昇温し、この温度で１時間保持し炭化
を行って冷却し、続いて空気中７００℃で重量収率９３
％になるまで０．１５ｋｇｆ／ｃｍ幅のテンションで引
っ張って処理し炭素質繊維不織布を得た。Comparative Example 1 98 mol% of acrylonitrile
After oxidizing polyacrylonitrile fiber having a weight average molecular weight of 10000 and having an average fiber diameter of 16 μm composed of 2 mol% of methyl methacrylate in air at 200 to 300 ° C. in air, short fibers of the oxidized fiber (about 80 mm in length) Needle # 36 (Foster Needle)
Co., Ltd., and felted at a punching density of 250 pieces / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 5.0 mm. Argon gas is constantly added to the nonwoven fabric at 600 cc /
The temperature was raised to 1600 ° C. at a rate of 100 ° C./min while spraying min / m ² , kept at this temperature for 1 hour, carbonized and cooled, and subsequently in air at 700 ° C. for a weight yield of 93
% To obtain a carbonaceous fiber nonwoven fabric.

【００５９】（比較例２）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量１００００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎化繊維の短繊維（長さ約８０ｍｍ）を用いて
フェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度２５０本／ｃｍ² でフェルト化し
て目付量６００ｇ／ｍ² 、厚み５．０ｍｍの不織布を作
成した。該不織布にアルゴンガスを絶えず６００ｃｃ／
ｍｉｎ／ｍ² 吹き付けた状態で１００℃／分の昇温速度
で１４００℃まで昇温し、この温度で１時間保持し炭化
を行って冷却し、続いて空気中７００℃で重量収率９７
％になるまで０．１ｋｇｆ／ｃｍ幅のテンションで引っ
張って処理し炭素質繊維不織布を得た。Comparative Example 2 98 mol% of acrylonitrile
After oxidizing polyacrylonitrile fiber having a weight average molecular weight of 10000 and having an average fiber diameter of 16 μm composed of 2 mol% of methyl methacrylate in air at 200 to 300 ° C. in air, short fibers of the oxidized fiber (about 80 mm in length) Needle # 36 (Foster Needle)
Co., Ltd., and felted at a punching density of 250 pieces / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 5.0 mm. Argon gas is constantly added to the nonwoven fabric at 600 cc /
The temperature was raised to 1400 ° C. at a rate of 100 ° C./min while spraying min / m ² , the temperature was maintained for 1 hour, carbonization was performed, and cooling was performed.
% To give a carbonaceous fiber nonwoven fabric.

【００６０】（比較例３）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量１００００００の平均繊維径１６μｍのポリアク
リロニトリル繊維を空気中２００〜３００℃で耐炎化し
た後、該耐炎化繊維の短繊維（長さ約８０ｍｍ）を用い
てフェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度２５０本／ｃｍ² でフェルト化し
て目付量６００ｇ／ｍ² 、厚み５．０ｍｍの不織布を作
成した。該不織布にアルゴンガスを絶えず６００ｃｃ／
ｍｉｎ／ｍ² 吹き付けた状態で１００℃／分の昇温速度
で１４００℃まで昇温し、この温度で１時間保持し炭化
を行って冷却し、続いて空気中７００℃で重量収率９３
％になるまで０．０５ｋｇｆ／ｃｍ幅のテンションで引
っ張って処理し炭素質繊維不織布を得た。Comparative Example 3 98 mol% of acrylonitrile
After oxidizing polyacrylonitrile fibers having a weight average molecular weight of 1,000,000 and having an average fiber diameter of 16 μm, which is composed of 2 mol% of methyl methacrylate, at 200 to 300 ° C. in air, short fibers of the oxidized fibers (about 80 mm in length) Needle # 36 (Foster Needle)
Co., Ltd., and felted at a punching density of 250 pieces / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 5.0 mm. Argon gas is constantly added to the nonwoven fabric at 600 cc /
The temperature was raised to 1400 ° C. at a rate of 100 ° C./min while spraying min / m ² , the temperature was maintained for 1 hour, carbonization was performed, and cooling was performed.
% To give a carbonaceous fiber nonwoven fabric.

【００６１】（比較例４）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量７５０００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎繊維の短繊維（長さ約８０ｍｍ）を用いてフ
ェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度１５０本／ｃｍ² でフェルト化し
て化して目付量６００ｇ／ｍ² 、厚み５．２ｍｍの不織
布を作成した。該不織布にアルゴンガスを絶えず６００
ｃｃ／ｍｉｎ／ｍ² 吹き付けた状態で１００℃／分の昇
温速度で１４００℃まで昇温し、この温度で１時間保持
し炭化を行って冷却し、続いて空気中７００℃で重量収
率９３％になるまで０．１ｋｇｆ／ｃｍ幅のテンション
で引っ張って処理し炭素質繊維不織布を得た。Comparative Example 4 98% by mole of acrylonitrile
-Polyacrylonitrile fibers having a weight average molecular weight of 75,000 and an average fiber diameter of 16 μm composed of 2 mol% of methyl methacrylate are flame-resistant in air at 200 to 300 ° C., and then the short fibers (length: about 80 mm) of the flame-resistant fibers are removed. Needle SB # 36 (Foster Needle)
Co., Ltd.) and felted at a punching density of 150 / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 5.2 mm. Argon gas is continuously applied to the nonwoven fabric for 600 hours.
The temperature was raised to 1400 ° C. at a temperature rising rate of 100 ° C./min while spraying cc / min / m ² , kept at this temperature for 1 hour, carbonized and cooled, and subsequently weighed at 700 ° C. in air. The carbon fiber nonwoven fabric was obtained by pulling with a tension of 0.1 kgf / cm width to 93% to obtain a nonwoven fabric.

【００６２】（比較例５）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量７５０００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎繊維の短繊維（長さ約８０ｍｍ）を用いてフ
ェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度３５０本／ｃｍ² でフェルト化し
て化して目付量６００ｇ／ｍ² 、厚み４．７ｍｍの不織
布を作成した。該不織布にアルゴンガスを絶えず６００
ｃｃ／ｍｉｎ／ｍ² 吹き付けた状態で１００℃／分の昇
温速度で１４００℃まで昇温し、この温度で１時間保持
し炭化を行って冷却し、続いて空気中７００℃で重量収
率９３％になるまで０．１ｋｇｆ／ｃｍ幅のテンション
で引っ張って処理し炭素質繊維不織布を得た。Comparative Example 5 98 mol% of acrylonitrile
-Polyacrylonitrile fibers having a weight average molecular weight of 75,000 and an average fiber diameter of 16 μm composed of 2 mol% of methyl methacrylate are flame-resistant in air at 200 to 300 ° C., and then the short fibers (length: about 80 mm) of the flame-resistant fibers are removed. Needle SB # 36 (Foster Needle)
Co., Ltd.), and formed into a felt at a punching density of 350 / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 4.7 mm. Argon gas is continuously applied to the nonwoven fabric for 600 hours.
The temperature was raised to 1400 ° C. at a temperature rising rate of 100 ° C./min while spraying cc / min / m ² , kept at this temperature for 1 hour, carbonized and cooled, and subsequently weighed at 700 ° C. in air. The carbon fiber nonwoven fabric was obtained by pulling with a tension of 0.1 kgf / cm width to 93% to obtain a nonwoven fabric.

【００６３】（比較例６）アクリロニトリル９８モル％
−メタクリル酸メチル２モル％から構成される重量平均
分子量７５０００の平均繊維径１６μｍのポリアクリロ
ニトリル繊維を空気中２００〜３００℃で耐炎化した
後、該耐炎繊維の短繊維（長さ約８０ｍｍ）を用いてフ
ェルト針ＳＢ＃３６（Ｆｏｓｔｅｒ Ｎｅｅｄｌｅ
社）、パンチング密度２５０本／ｃｍ² でフェルト化し
て化して目付量６００ｇ／ｍ² 、厚み５．０ｍｍの不織
布を作成した。該不織布にアルゴンガスを絶えず６００
ｃｃ／ｍｉｎ／ｍ² 吹き付けた状態で１００℃／分の昇
温速度で１４００℃まで昇温し、この温度で１時間保持
し炭化を行って冷却し、続いて空気中７００℃で重量収
率９３％になるまでテンションをかけずに処理し炭素質
繊維不織布を得た。Comparative Example 6 98 mol% of acrylonitrile
-Polyacrylonitrile fibers having a weight average molecular weight of 75,000 and an average fiber diameter of 16 μm composed of 2 mol% of methyl methacrylate are flame-resistant in air at 200 to 300 ° C., and then the short fibers (length: about 80 mm) of the flame-resistant fibers are removed. Needle SB # 36 (Foster Needle)
Co., Ltd., and felted at a punching density of 250 / cm ² to prepare a nonwoven fabric having a basis weight of 600 g / m ² and a thickness of 5.0 mm. Argon gas is continuously applied to the nonwoven fabric for 600 hours.
The temperature was raised to 1400 ° C. at a rate of 100 ° C./min while spraying cc / min / m ² , kept at this temperature for 1 hour, carbonized and cooled, and subsequently weighed at 700 ° C. in air. The treatment was carried out without applying tension to 93% to obtain a carbonaceous fiber nonwoven fabric.

【００６４】以上で実施例、比較例で得られた炭素質繊
維不織布のａ軸方向の結晶子の大きさ（Ｌａ）、ＸＰＳ
表面分析、不織布の圧縮率及び圧縮弾性率、集電板との
接触抵抗、電極性能を、製造条件と共に表１に示す。The crystallite size (La) in the a-axis direction of the carbonaceous fiber nonwoven fabrics obtained in Examples and Comparative Examples above, XPS
Table 1 shows the surface analysis, the compression ratio and compression modulus of the nonwoven fabric, the contact resistance with the current collector, and the electrode performance together with the production conditions.

【００６５】[0065]

【表１】 表１の結果から明らかなように、実施例１〜５の炭素質
繊維不織布は、集電板との接触抵抗が小さく、電圧効率
が高く、エネルギー効率に優れていた。これに対し、炭
素質繊維の特性が適当でない比較例１〜３では、電圧効
率とエネルギー効率が共に不十分となり、また、不織布
の物性が適当でない比較例４〜６では、集電板との接触
抵抗が大きくなり、電圧効率とエネルギー効率が共に更
に劣化していた。[Table 1] As is clear from the results in Table 1, the carbonaceous fiber nonwoven fabrics of Examples 1 to 5 had low contact resistance with the current collector, high voltage efficiency, and excellent energy efficiency. On the other hand, in Comparative Examples 1 to 3 in which the characteristics of the carbonaceous fiber are not appropriate, both the voltage efficiency and the energy efficiency are insufficient, and in Comparative Examples 4 to 6 in which the physical properties of the nonwoven fabric are not appropriate, The contact resistance was increased, and both the voltage efficiency and the energy efficiency were further deteriorated.

【図面の簡単な説明】[Brief description of the drawings]

【図１】バナジウム系レドックスフロー電池の概略図FIG. 1 is a schematic diagram of a vanadium-based redox flow battery.

【図２】三次元電極を有するバナジウム系レドックスフ
ロー電池の電解槽の分解斜図FIG. 2 is an exploded perspective view of an electrolytic cell of a vanadium-based redox flow battery having a three-dimensional electrode.

【符号の説明】[Explanation of symbols]

１ 集電板 ２ スペーサ ３ イオン交換膜 ４ａ，４ｂ 通液路 ５ 電極材 ６ 外部液タンク（正極側） ７ 外部液タンク（負極側） ８，９ ポンプ １０ 液流入口 １１ 液流出口 DESCRIPTION OF SYMBOLS 1 Current collection plate 2 Spacer 3 Ion exchange membrane 4a, 4b Liquid passage 5 Electrode material 6 External liquid tank (positive electrode side) 7 External liquid tank (negative electrode side) 8, 9 Pump 10 Liquid inlet 11 Liquid outlet

───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 5H018 AA08 AS07 CC06 DD06 EE05 HH03 HH05 HH09 5H026 AA10 CC01 CX03 EE05 HH03 HH05 HH09 RR01  ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H018 AA08 AS07 CC06 DD06 EE05 HH03 HH05 HH09 5H026 AA10 CC01 CX03 EE05 HH03 HH05 HH09 RR01

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】 水溶液系電解液によるレドックスフロー
電池に使用され、炭素質繊維の不織布よりなる炭素電極
材集合体において、 前記炭素質繊維は、Ｘ線広角解析より求めたａ軸方向の
結晶子の大きさが３０〜８０Åである擬黒鉛結晶構造を
有し、ＸＰＳ表面分析より求めた表面酸性官能基量が全
表面炭素原子数の０．２％以上１．２％以下であると共
に、 前記不織布は、ＪＩＳ Ｌ１０９６（１９９０）に準ず
る圧縮率が１０〜２５％、圧縮弾性率が８０％以上であ
ることを特徴とする炭素電極材集合体。 1. A carbon electrode material assembly comprising a nonwoven fabric of carbonaceous fibers used in a redox flow battery using an aqueous electrolyte solution, wherein the carbonaceous fibers are crystallites in the a-axis direction obtained by X-ray wide-angle analysis. Has a pseudo-graphite crystal structure with a size of 30 to 80 °, and the amount of surface acidic functional groups determined by XPS surface analysis is 0.2% or more and 1.2% or less of the total number of surface carbon atoms. A carbon electrode material aggregate, wherein the nonwoven fabric has a compression ratio according to JIS L1096 (1990) of 10 to 25% and a compression elastic modulus of 80% or more . 【請求項２】 バナジウム系レドックスフロー電池に使
用される請求項１記載の炭素電極材集合体。2. The carbon electrode material assembly according to claim 1, which is used for a vanadium redox flow battery.