JP3557860B2

JP3557860B2 - Air electrode for air battery and method of manufacturing the air electrode

Info

Publication number: JP3557860B2
Application number: JP20566797A
Authority: JP
Inventors: 直子相馬; 研一仲津; 敏彦池畠
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1997-07-31
Filing date: 1997-07-31
Publication date: 2004-08-25
Anticipated expiration: 2017-07-31
Also published as: JPH1154130A

Description

【０００１】
【発明の属する技術分野】
本発明は、酸素還元触媒と集電体とからなる触媒層とガス拡散層で構成される空気極を正極ケース内部に配設する空気電池に関するものである。
【０００２】
【従来の技術】
空気電池は、電池外部の空気中の酸素を正極の活物質として利用するため負極活物質を多量に充填できることから、他の一次電池に比べ大きなエネルギー密度をもつ。また低水銀で環境にやさしく、放電電圧が放電末期まで安定であるなどの特長を有しているため、補聴器用電源を中心にその需要が多い。
【０００３】
図５は従来の空気亜鉛電池の構造を示すものである。図５に示すように、亜鉛電極１は負極ケースである封口板２に収納され、ガスケット３を介して正極ケース４を封口しており、セパレータ５が触媒を主体とする空気極６と亜鉛電極１を隔離している。７は空気中の酸素の電池内部への供給と、電解液が電池外部へ漏出することを防ぐための撥水膜であり、空気孔８を設けた正極ケース４に、拡散紙９を介して接している。シール紙１０は電池の未使用時に空気孔８を封鎖して、電池内に空気が侵入することを遮断し電池の劣化を防止するものである。
【０００４】
上記する従来の空気亜鉛電池では、空気極６中の集電体と正極ケース４との導電性は、円形に打ち抜かれた集電体の円周端面と正極ケース４の側壁内部との接触で得られる。そのため、空気極６の径が小さい場合、正極ケース４との接触が充分に得られず、電池の内部抵抗が大きくなったり、放電時に電圧が低下する放電異常が発生する。
【０００５】
【発明が解決しようとする課題】
これを防止するため、従来の空気亜鉛電池などの空気電池では、空気極を大きめにするようにしていたが、大きすぎると電池構成時の正極ケースに空気極を挿入する際に、シート状に成型された空気極の触媒が正極内壁にこすられることにより空気極の触媒部分の円周部が崩れて、電池内部に塊状の触媒が形成される。この状態で電池を構成すると塊状の触媒が電池構成部品間に異物として挟み込まれ、液密的な封口ができなくなり耐漏液性が低下する。このため、空気極を空気極の構成材料から打ち抜く径は狭い範囲で管理しなければならず、空気極の打ち抜きパンチの交換を比較的短期間で行う必要があった。
【０００６】
そこで、本発明は、触媒部分の崩れが少なく電池内部抵抗が低く、耐漏液性に優れた空気電池を供給する空気極と、その空気極の打ち抜きパンチの交換が少ない空気電池用の空気極の製造法を実現することを目的とする。
【０００７】
【課題を解決するための手段】
本発明は前記する課題を解決するために、酸素還元触媒中に集電体を偏在した触媒層とガス拡散層とで構成される空気極を正極ケース内部に配設する空気電池用空気極において、前記空気極は集電体側の直径が集電体側と反対側の触媒表面の直径より大きい円錐台形としたものである。
【０００８】
従って、直径の寸法が大きい集電体の側面が正極ケースの内壁面に接触して良導通を図り、強度の弱い触媒層の側面が正極ケースの内壁に電池構成時にこすられることが少なく、従って触媒の周縁部が脱落することがない。
【０００９】
また、本発明は先端に突段部を有する空気極打ち抜きパンチにより、集電体を酸素還元触媒中に偏在させた触媒層を前記集電体側より撓ませて打ち抜くことにより、集電体側の径が集電体側と反対側の触媒表面の直径より大きい円錐台形とする空気電池用空気極の製造法としたものである。
【００１０】
そして、本発明法により空気極において、集電体側の直径が集電体側と反対側の触媒表面の直径より大きい空気極を簡単に製造することができる。
【００１１】
【発明の実施の形態】
本発明は、請求項に記載の形態で実施できるものであり、
請求項１記載のように、酸素還元触媒中に集電体を偏在した触媒層とガス拡散層とで構成される空気極を正極ケース内部に配設する空気電池用空気極において、前記空気極は集電体側の直径が集電体側と反対側の触媒表面の直径より大きくした円錐台形の空気極を用いることにより、正極ケースの内壁には直径の大きい集電体側が接触し、集電体が存在していない触媒層の周縁は電池構成時に正極ケースの内壁によりこすられることが少なく、従って触媒の周縁部が脱落することがない。
【００１２】
また、請求項２記載のように、先端に突段部を有する空気極打ち抜きパンチにより、集電体を酸素還元触媒中に偏在させた触媒層を前記集電体側より撓ませて打ち抜くことにより、集電体側の径が集電体側と反対側の触媒表面の直径より大きい円錐台形の空気極を製造することが容易に可能となる。
【００１３】
すなわち、空気極をシート状のガス拡散層を片面に有する触媒材料より打ち抜いて製造する時に、パンチの先端に径を少し小さくした突段部が空気極の中央部を打ち上げ、撓めた状態で打ち抜くため、作製される空気極は図１に示すようにパンチに近い集電体１１側の径が集電体１１側と反対側の触媒面１２部分の径より大きい円錐台形となる。なお、図１中の１３はガス拡散層である。
【００１４】
そして、請求項３記載のように、空気極の厚みをａとし、空気極に当接する面の突段部の高さをｈとした場合、０．０２ａ≦ｈ≦０．５０ａとした打ち抜きパンチを用いることにより、請求項２に記載した製造法は容易に実施できるものである。
【００１５】
【実施例】
以下、本発明の実施例を図面を参照しながら説明する。
【００１６】
まず実際に、空気極の打ち抜きパンチを作製した。作製したパンチは、直径が正極ケース底部内径と等しいＰＲ５３６（直径５．８ｍｍ、高さ３．６ｍｍ）用で、図２に示すように空気極の厚みａに対しパンチ１４の先端に設けた突段部１５の高さｈが０．０１ａ〜２．００ａにわたる８種類のパンチと、図３に示す空気極当接面がフラット面１６の１種類のパンチの合計９種類とした。そして、前記した９種類のパンチでそれぞれ打ち抜いた空気極を用いて電池を作製し、封口部と空気孔からの耐漏液性能を評価した。なお、図２に示す例では底部１７より若干径の小さい頂面１８がある円錐台形となり、図３に示す従来では底部１７と頂面とは同じ径で図４に断面を示すように集電体１１ａ，触媒面１２ａならびにガス拡散層１３ａの各径は同じである。
【００１７】
封口部からの耐漏液性能試験は、未放電の電池をシールを貼った状態で４５℃９２％Ｒ．Ｈ．の高温多湿条件下に保存した後、室温でクレゾールレッドを噴霧して呈色させることにより、正極ケースとガスケットの間、あるいはガスケットと封口板といった部品の隙間からのアルカリ電解液の漏出を確認した。４週間保存後の結果を表１に示す。
【００１８】
【表１】

【００１９】
表１において、漏液は従来例および突段部１５の高さｈが０．０１ａのパンチで打ち抜いた空気極を用いた電池で漏液が発生し、かつ、分解観察により塊状の触媒が電池内部で観察されたことから、パンチの突段部１５の高さｈが０．０２ａ以上のものについて有効であることがわかる。
【００２０】
一方、空気孔からの耐漏液性能試験は４５℃７０％Ｒ．Ｈ．の高温多湿条件下で、３．０ｋΩの定抵抗で放電を行い、放電中および過放電状態での空気孔からの電解液の漏出を観察した。３週間過放電後の漏液の発生数を表２に示す。
【００２１】
【表２】

【００２２】
空気亜鉛電池は放電による負極亜鉛の酸化にともなう体積膨張により、放電後の電池内部の圧力が上昇し、電解液が電池外へ空気孔を通って押し出され空気孔からの漏液が発生することがある。表２において、突段部１５の高さｈが１．００ａ以上のパンチで打ち抜いた空気極を用いた電池について分解観察をしたところ、ガス拡散層にパンチの突段部による円形の跡が付きここから漏液が発生していることから、空気極打ち抜き時の圧力でガス拡散層が傷つけられ、放電後の電池内部の圧力上昇に耐えられなくなったものである。
【００２３】
【発明の効果】
以上のように本発明によれば、先端に突段部を有する打ち抜きパンチを用いて得られる集電体側がその反対側の径より大きい円錐台形状の触媒層の空気極を用いることにより、電気的に安定で、かつ、触媒層の崩落と挟み込みを防止し、液密性に優れた耐漏液性の高い電池を簡単な構成と製造法により安定して得られる。
【図面の簡単な説明】
【図１】本発明の空気極打ち抜きパンチにより打ち抜かれた空気極を示す図
【図２】本発明の空気極打ち抜きパンチの要部拡大模式図
【図３】従来例の空気極打ち抜きパンチの要部拡大模式図
【図４】従来例の空気極打ち抜きパンチにより打ち抜かれた空気極を示す図
【図５】従来の空気亜鉛電池の半截側断面図
【符号の説明】
１１，１１ａ集電体
１２，１２ａ触媒面
１３，１３ａガス拡散層
１４パンチ
１５突段部
１７底部
１８頂面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an air battery in which an air electrode composed of a catalyst layer including an oxygen reduction catalyst and a current collector and a gas diffusion layer is disposed inside a positive electrode case.
[0002]
[Prior art]
An air battery uses oxygen in the air outside the battery as an active material for the positive electrode and thus can be filled with a large amount of the negative electrode active material, and thus has a higher energy density than other primary batteries. In addition, it has features such as low mercury, environmental friendliness, and stable discharge voltage until the end of discharge.
[0003]
FIG. 5 shows the structure of a conventional zinc-air battery. As shown in FIG. 5, the zinc electrode 1 is housed in a sealing plate 2 which is a negative electrode case, seals the positive electrode case 4 via a gasket 3, and a separator 5 is composed of an air electrode 6 mainly composed of a catalyst and a zinc electrode. Isolate one. Reference numeral 7 denotes a water-repellent film for supplying oxygen in the air to the inside of the battery and preventing the electrolyte from leaking out of the battery. In contact. The seal paper 10 seals the air hole 8 when the battery is not used, blocks air from entering the battery, and prevents deterioration of the battery.
[0004]
In the above-described conventional zinc-air battery, the conductivity between the current collector in the air electrode 6 and the positive electrode case 4 is determined by the contact between the circumferential end face of the circularly punched current collector and the inside of the side wall of the positive electrode case 4. can get. Therefore, when the diameter of the air electrode 6 is small, sufficient contact with the positive electrode case 4 cannot be obtained, and the internal resistance of the battery increases, or a discharge abnormality occurs in which the voltage decreases during discharge.
[0005]
[Problems to be solved by the invention]
In order to prevent this, in the case of conventional air batteries such as zinc-air batteries, the air electrode was made large.However, if it is too large, when the air electrode is inserted into the positive electrode case at the time of battery construction, it is formed into a sheet. When the molded catalyst of the air electrode is rubbed against the inner wall of the positive electrode, the circumferential portion of the catalyst portion of the air electrode collapses, and a massive catalyst is formed inside the battery. When a battery is formed in this state, a massive catalyst is sandwiched between the battery components as a foreign substance, so that liquid-tight sealing cannot be performed and the liquid leakage resistance decreases. For this reason, the diameter at which the air electrode is punched out of the constituent material of the air electrode must be controlled in a narrow range, and it is necessary to exchange the punch for punching the air electrode in a relatively short time.
[0006]
Therefore, the present invention provides an air electrode for supplying an air cell with low collapse of the catalyst portion and low internal resistance of the battery, and excellent in liquid leakage resistance, and an air electrode for the air cell with a small exchange of punching punches of the air electrode. The purpose is to realize the manufacturing method.
[0007]
[Means for Solving the Problems]
The present invention provides an air battery air electrode in which an air electrode composed of a catalyst layer and a gas diffusion layer in which a current collector is unevenly distributed in an oxygen reduction catalyst is disposed inside a positive electrode case in order to solve the above-described problem. The air electrode has a truncated cone shape in which the diameter on the current collector side is larger than the diameter of the catalyst surface on the side opposite to the current collector side.
[0008]
Therefore, the side surface of the current collector having a large diameter dimension contacts the inner wall surface of the positive electrode case to achieve good conduction, and the side surface of the weak catalyst layer is less rubbed against the inner wall of the positive electrode case during battery construction. The periphery of the catalyst does not fall off.
[0009]
Also, the present invention provides a cathode having a projecting step at the tip thereof, and punches the catalyst layer in which the current collector is unevenly distributed in the oxygen reduction catalyst by bending the current collector side from the current collector side, thereby obtaining a diameter on the current collector side. Is a method for manufacturing an air electrode for an air battery having a truncated cone shape larger than the diameter of the catalyst surface opposite to the current collector.
[0010]
Then, according to the method of the present invention, it is possible to easily manufacture an air electrode in which the diameter on the current collector side is larger than the diameter of the catalyst surface on the side opposite to the current collector side.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention can be implemented in the form described in the claims.
The air electrode for an air battery according to claim 1, wherein an air electrode composed of a catalyst layer in which a current collector is unevenly distributed in an oxygen reduction catalyst and a gas diffusion layer is disposed inside a positive electrode case. By using a truncated conical air electrode whose diameter on the current collector side is larger than the diameter of the catalyst surface on the side opposite to the current collector side, the current collector side with a large diameter contacts the inner wall of the positive electrode case, The peripheral edge of the catalyst layer where no is present is less likely to be rubbed by the inner wall of the positive electrode case when the battery is constructed, so that the peripheral edge of the catalyst does not fall off.
[0012]
Further, as described in claim 2, the air electrode punching punch having a projecting step at the tip, the catalyst layer in which the current collector is unevenly distributed in the oxygen reduction catalyst is bent from the current collector side and punched out. It is possible to easily produce a truncated conical air electrode having a diameter on the current collector side larger than the diameter of the catalyst surface on the side opposite to the current collector side.
[0013]
In other words, when the air electrode is manufactured by punching out a catalyst material having a sheet-shaped gas diffusion layer on one surface, a projecting step with a slightly smaller diameter at the tip of the punch launches the center of the air electrode and is bent. As shown in FIG. 1, the air electrode to be formed has a truncated conical shape in which the diameter on the side of the current collector 11 close to the punch is larger than the diameter of the catalyst surface 12 on the side opposite to the side of the current collector 11 as shown in FIG. Note that 13 in FIG. 1 is a gas diffusion layer.
[0014]
In the case where the thickness of the air electrode is a and the height of the protruding step on the surface in contact with the air electrode is h, the punching punch is set to 0.02a ≦ h ≦ 0.50a. The production method described in claim 2 can be easily implemented by using.
[0015]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
First, an air electrode punch was actually manufactured. The produced punch is for a PR536 (diameter 5.8 mm, height 3.6 mm) having a diameter equal to the inner diameter of the bottom of the positive electrode case. As shown in FIG. The height h of the step portion 15 is eight types of punches ranging from 0.01a to 2.00a, and the air electrode contact surface shown in FIG. Then, batteries were manufactured using the air electrodes punched by the nine types of punches described above, and the resistance to liquid leakage from the sealing portion and the air holes was evaluated. In the example shown in FIG. 2, a truncated cone having a top surface 18 slightly smaller in diameter than the bottom portion 17 is formed. In the conventional case shown in FIG. 3, the bottom portion 17 and the top surface have the same diameter and the current is collected as shown in the cross section in FIG. The diameters of the body 11a, the catalyst surface 12a, and the gas diffusion layer 13a are the same.
[0017]
The liquid leakage resistance test from the sealing portion was performed at 45 ° C. and 92% R.F. H. After storing under high temperature and high humidity conditions, cresol red was sprayed at room temperature to develop color, and leakage of the alkaline electrolyte from the gap between the positive electrode case and the gasket or the gap between the gasket and the sealing plate was confirmed. . Table 1 shows the results after storage for 4 weeks.
[0018]
[Table 1]

[0019]
In Table 1, the leakage occurred in the conventional example and in a battery using an air electrode punched with a punch having a height h of 0.01 a of the protruding step portion 15. From the observation inside, it can be seen that the punch is effective when the height h of the projecting step 15 is 0.02a or more.
[0020]
On the other hand, the leak resistance test from the air hole was performed at 45 ° C. and 70% H. Was discharged at a constant resistance of 3.0 kΩ under the conditions of high temperature and high humidity, and leakage of the electrolyte solution from the air holes during the discharge and in the overdischarged state was observed. Table 2 shows the number of liquid leaks after overdischarge for 3 weeks.
[0021]
[Table 2]

[0022]
In a zinc-air battery, the internal pressure of the battery after discharge increases due to volume expansion accompanying oxidation of the negative electrode zinc due to discharge, and the electrolyte is pushed out of the battery through the air holes, causing leakage from the air holes. There is. In Table 2, when a battery using an air electrode punched with a punch having a height h of the protrusion 15 of 1.00 a or more was disassembled and observed, a circular mark due to the protrusion of the punch was found on the gas diffusion layer. Since the liquid leakage occurred from this, the gas diffusion layer was damaged by the pressure at the time of punching the air electrode, and could not withstand the pressure increase inside the battery after the discharge.
[0023]
【The invention's effect】
As described above, according to the present invention, the current collector side obtained by using a punch having a protruding step at the tip uses the air electrode of the catalyst layer having a truncated cone shape that is larger than the diameter on the opposite side. It is possible to stably obtain a battery which is stable in terms of stability, prevents collapse and pinching of the catalyst layer, and has excellent liquid tightness and high liquid leakage resistance by a simple structure and a manufacturing method.
[Brief description of the drawings]
FIG. 1 is a diagram showing an air electrode punched by an air electrode punching punch of the present invention; FIG. 2 is an enlarged schematic view of a main part of the air electrode punching punch of the present invention; FIG. FIG. 4 is an enlarged schematic view of a part. FIG. 4 is a view showing an air electrode punched by a conventional air electrode punch. FIG. 5 is a half sectional side view of a conventional air zinc battery.
11, 11a

Current collector

12,

12a Catalyst surface

13, 13a Gas diffusion layer 14 Punch 15 Protrusion 17 Bottom 18 Top

Claims

In an air electrode for an air battery in which an air electrode composed of a catalyst layer in which a current collector is unevenly distributed in an oxygen reduction catalyst and a gas diffusion layer is disposed inside a positive electrode case, the air electrode has a current collector side diameter. An air electrode for an air battery, wherein the air electrode has a truncated cone shape larger than the diameter of the catalyst surface on the side opposite to the conductor.

By the air electrode punch having a projecting step at the tip, the catalyst layer in which the current collector is unevenly distributed in the oxygen reduction catalyst is bent from the current collector side and punched out, so that the diameter of the current collector side is the same as that of the current collector side. A method of manufacturing an air electrode for an air battery having a truncated conical shape larger than the diameter of the opposite catalyst surface.

The air electrode is punched out using an air electrode punching punch having a relationship of 0.02a ≦ h ≦ 0.50a, where a is the thickness of the air electrode and h is the height of the projecting step. Manufacturing method of air electrode for air battery.