【発明の詳細な説明】[Detailed description of the invention]
〔産業上利用する分野〕
本発明は、電解液循環型亜鉛／臭素二次電池に
おいて負極室と正極室とを区画するためのセパレ
ータに関し、更に詳しくは該二次電池のエネルギ
ー効率を高める微細多孔質膜の厚さ及び気孔率を
規定することにより、エネルギー効率を一層向上
させると共にセパレータの耐用寿命の延長を図る
ものである。
〔従来の技術〕
電解液循環型亜鉛／臭素二次電池は、第１図に
示すような基本的構成をなすものである。図中の
符号１は電池本体をなす単セル、２は正極室、３
は負極室、４はセパレータで、前記正極室２と負
極室３を区画する。５は正極、６は負極、９は正
極液貯蔵槽、１０は負極液貯蔵槽、１１，１２は
ポンプである。充電時は、ポンプ１１，１２を開
き、電解液が矢印の方向に循環し、負極６では
Zn++＋2e→Zn，正極５では2Br→Br2＋2eの反応
を生じ、正極５で生成された臭素は分子となつて
電解液中に混じり一部は溶解し、大部分は正極液
中の錯化剤によつて錯化剤となり、正極液貯蔵槽
９内に沈澱して蓄積される。放電時は、電解液が
矢印の方向に循環した状態で各電極６，５では上
記反応式と逆の反応を生じ、析出物（Zn，Br2）
が各電極６，５上で消費（酸化、還元）され、電
気エネルギーが放出される。
この場合、セパレータ４の役目即ち作用は、充
電時には亜鉛が負極６の表面に析出し、正極５で
は臭素が発生し電解液中に拡散、溶解するので、
ここで発生した臭素が負極側へ移動すると、亜鉛
と直接反応して亜鉛を溶解させてしまうことを防
止するため隔膜として設けられている。このセパ
レータ４には、価格及び耐臭素性に優れているこ
とからポリエチレン、ポリプロピレン等のポリオ
レフイン系プラスチツクと含水シリカ（SiO2・
nH2Ｏ）の混合物を主体とする多孔質の膜を用い
ている。
しかして、発明者らのグループが先に特願昭58
−5185号（特開昭59−130076号）をもつて提案し
たセパレータは、多孔質膜の膜厚を変化させるこ
とによるエネルギー効率の変動を考慮した上で、
最適の膜厚を0.4mm〜0.8mmとしたのであつた。と
ころで、その後の発明者の研究の結果から、ポリ
エチレンまたはポリプロピレンと含水シリカの混
合物を主体とした多孔質膜をセパレータとして用
いた場合、該膜内に電解液が浸透し縦横両方向に
伸びが生じることが判明した。この伸びは、第２
図ａに示す如くセパレータ４の枠７に張られた多
孔質膜８に矢印で示す撓みを生じる。実用的な電
池は単セルを複数積層し、積層長さを少くするた
め、即ち単位体積当りのエネルギー効率を大にす
るために、電極間隔を数mmにするので、多孔質膜
８が極端な場合は電極に接触して亜鉛が膜に付着
することがある。これはセパレタ４の多孔質膜８
の厚さ不足に起因するものと考えられ、薄いとよ
り撓み易いということがわかつた。
〔発明が解決しようとする問題点〕
本発明は、電解液循環型亜鉛／臭素二次電池に
おけるオレフイン系プラスチツクと含水シリカを
主体としたセパレータが、電池として充放電を繰
返す間に撓みを生じる問題に鑑みて、これを解決
するためになされたものであり、併せて電池のエ
ネルギ効率の向上とセパレータの耐用寿命の延長
を図る。
〔問題点を解決するため手段及びその作用〕
次に、上記の問題点を解決するための本発明の
概要を示せば、第１図に一例として示す如き単セ
ルを微細多孔質からなるセパレータで陰極室と正
極室に区画し、該負極室及び正極室に夫々電解液
を循環せしめるようにした電解液循環亜鉛／臭素
二次電池において、前記セパレータの実質的厚さ
を0.6mm〜1.6mm好ましくは0.6mm〜1.4mmとするこ
とを要旨としている。
また、上記セパレータの多孔範囲が5μm〜10-3
μmで、かつ最大分布孔径範囲が10-2μm〜10-1
μmで、気孔率が30〜70％であることが本発明の
効果を高める上で好ましい。
セパレータの構成を上記の通りに規制すること
により、電池内におけるセパレータの撓みは解消
し、電池のエネルギー効率の上昇、セパレータの
耐用寿命の延長が図られる。
〔発明の実施例〕
次に、本発明の実施例を示す、次の第１表は電
解液循環型亜鉛／臭素二次電池を電池として充放
電を繰返した場合のセパレータ４を構成する多孔
質膜８の撓みの発生度を示す。13.4mA／cm2の電
流密度で８時間放電を50サイクル行つた結果であ
る。
[Field of Industrial Use] The present invention relates to a separator for separating a negative electrode chamber and a positive electrode chamber in an electrolyte circulation type zinc/bromine secondary battery, and more specifically, to a separator for separating a negative electrode chamber and a positive electrode chamber in an electrolyte circulation type zinc/bromine secondary battery. By regulating the thickness and porosity of the membrane, energy efficiency is further improved and the service life of the separator is extended. [Prior Art] A circulating electrolyte type zinc/bromine secondary battery has a basic configuration as shown in FIG. In the figure, 1 is a single cell forming the battery body, 2 is a positive electrode chamber, and 3 is a positive electrode chamber.
4 is a negative electrode chamber, and 4 is a separator that partitions the positive electrode chamber 2 and the negative electrode chamber 3. 5 is a positive electrode, 6 is a negative electrode, 9 is a positive electrode liquid storage tank, 10 is a negative electrode liquid storage tank, and 11 and 12 are pumps. During charging, the pumps 11 and 12 are opened, the electrolyte circulates in the direction of the arrow, and the negative electrode 6
A reaction of Zn ++ +2e→Zn and 2Br→Br 2 +2e occurs at the positive electrode 5, and the bromine generated at the positive electrode 5 becomes molecules and mixes in the electrolyte, some of which dissolves, and most of the bromine in the positive electrode. The complexing agent becomes a complexing agent, and is precipitated and accumulated in the positive electrode liquid storage tank 9. During discharge, with the electrolyte circulating in the direction of the arrow, a reaction opposite to the above reaction formula occurs at each electrode 6, 5, and precipitates (Zn, Br 2 )
is consumed (oxidized, reduced) on each electrode 6, 5, and electrical energy is released. In this case, the role or action of the separator 4 is that during charging, zinc is deposited on the surface of the negative electrode 6, and bromine is generated at the positive electrode 5 and diffused and dissolved into the electrolyte.
A diaphragm is provided to prevent the bromine generated here from directly reacting with zinc and dissolving the zinc when it moves to the negative electrode side. This separator 4 is made of polyolefin plastics such as polyethylene and polypropylene and hydrated silica (SiO 2 /
A porous membrane mainly composed of a mixture of nH 2 O) is used. However, a group of inventors first applied for a patent in 1982.
The separator proposed in No.-5185 (Japanese Unexamined Patent Publication No. 59-130076) takes into consideration the fluctuation in energy efficiency caused by changing the thickness of the porous membrane.
The optimum film thickness was set at 0.4 mm to 0.8 mm. By the way, the results of the inventor's subsequent research revealed that when a porous membrane mainly made of a mixture of polyethylene or polypropylene and hydrated silica is used as a separator, the electrolyte permeates into the membrane, causing elongation in both the vertical and horizontal directions. There was found. This growth is the second
As shown in Figure a, the porous membrane 8 stretched over the frame 7 of the separator 4 is bent as shown by the arrow. Practical batteries are made by stacking multiple single cells, and in order to reduce the stacking length, that is, to increase the energy efficiency per unit volume, the electrode spacing is set to several mm, so the porous membrane 8 is extremely In some cases, zinc may adhere to the membrane due to contact with the electrode. This is the porous membrane 8 of separator 4.
This is thought to be due to the lack of thickness, and it was found that the thinner the material, the easier it is to bend. [Problems to be Solved by the Invention] The present invention solves the problem in which a separator mainly composed of olefin plastic and hydrated silica in an electrolyte circulation type zinc/bromine secondary battery warps during repeated charging and discharging as a battery. This was done in order to solve this problem, and also aims to improve the energy efficiency of the battery and extend the service life of the separator. [Means for Solving the Problems and Their Effects] Next, the outline of the present invention for solving the above-mentioned problems will be described. As an example, a single cell as shown in FIG. In an electrolyte circulation zinc/bromine secondary battery which is divided into a cathode chamber and a cathode chamber, and an electrolyte is circulated through the anode chamber and the cathode chamber, respectively, the substantial thickness of the separator is preferably 0.6 mm to 1.6 mm. The gist is that it should be between 0.6mm and 1.4mm. In addition, the porosity range of the separator above is 5 μm to 10 -3
μm, and the maximum distribution pore size range is 10 -2 μm to 10 -1
In order to enhance the effect of the present invention, it is preferable that the porosity is 30 to 70% in μm. By regulating the structure of the separator as described above, the deflection of the separator within the battery is eliminated, thereby increasing the energy efficiency of the battery and extending the service life of the separator. [Embodiments of the Invention] Next, Table 1 below, which shows Examples of the present invention, shows the porous material constituting the separator 4 when an electrolyte circulation type zinc/bromine secondary battery is repeatedly charged and discharged. The degree of occurrence of deflection of the membrane 8 is shown. These are the results of 50 cycles of 8-hour discharge at a current density of 13.4 mA/cm 2 .
〔発明の効果〕〔Effect of the invention〕
以上説明したように、本発明によれば次の効果
が得られる。
(1) 高いエネルギー効率を得ることができる。
(2) セパレータの多孔質膜の撓みが一ケ所へ集中
せず、セパレータの耐用寿命を延長させること
ができる。
As explained above, according to the present invention, the following effects can be obtained. (1) High energy efficiency can be obtained. (2) Deflection of the porous membrane of the separator is not concentrated in one place, and the service life of the separator can be extended.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は電解液循環型亜鉛／臭素二次電池の模
式的縦断面図、第２図はセパレータの模式的横断
面図で、ａは膜厚0.4mm以下のもの、ｂは膜厚0.6
mm以上のもの、第３図はセパレータの膜厚と電池
効率の関係を示すグラフである。
１……単セル、２……正極室、３……負極室、
４……セパレータ、５……正極、６……負極、７
……セパレータの枠、８……セパレータの多孔質
膜、９……正極液貯蔵槽、１０……負極液貯蔵
槽、１１，１２……ポンプ。
Figure 1 is a schematic vertical cross-sectional view of an electrolyte circulation type zinc/bromine secondary battery, and Figure 2 is a schematic cross-sectional view of a separator, where a is a film thickness of 0.4 mm or less, and b is a film thickness of 0.6 mm.
mm or more, FIG. 3 is a graph showing the relationship between separator film thickness and battery efficiency. 1...Single cell, 2...Positive electrode chamber, 3...Negative electrode chamber,
4...Separator, 5...Positive electrode, 6...Negative electrode, 7
... Separator frame, 8 ... Porous membrane of separator, 9 ... Positive electrode liquid storage tank, 10 ... Negative electrode liquid storage tank, 11, 12 ... Pump.