【発明の詳細な説明】[Detailed description of the invention]
産業上の利用分野
本発明は、電解液にアルカリ水溶液、負極活物
質として亜鉛を用い、正極活物質に二酸化マンガ
ン、酸化銀、酸化水銀、酸素などを用いる亜鉛ア
ルカリ一次電池の負極の改良に係るものである。
従来例の構成とその問題点
上記の亜鉛アルカリ一次電池の共通した問題点
として、保存中の負極亜鉛の電解液中での腐食が
拳げられる。従来、亜鉛に５〜10％程度の水銀を
添加した汞化亜鉛粉末を用いて水素過電圧を高
め、実用的に問題のない程度に腐食を抑制するこ
とが工業的な手段として採用されている。しかし
近年、低公害化のため電池内の含有水銀量を低減
させることが社会的ニーズとして高まつてきてい
る。その対策として種々の提案がなされている
が、決定的な解決手段はないのが現状である。す
なわち、例えば、亜鉛中に鉛，カドミウム，イン
ジウムなど添加して水素過電圧を高めた合金粉末
を用いて耐食性を向上させ、汞化率を低減させる
方法が提案されている。この方法は多少の効果は
あつても汞化率を３％程度にまで低減するのが限
度と考えられる。又、インジウム，タリウムなど
水銀との大きい元素を亜鉛粉末の表面に付着させ
て汞化し、表面の水銀濃度を高めて中心部の濃度
を低くした状態で耐食性を増し、平均的な汞化率
を低減させる方法も提案されているが、上記の付
着元素の水銀捕博力のみでは経時変化により水銀
が中心部に拡散して表面の水銀濃度が低下するの
を抑止し切れないため所期の防食効果が得られ
ず、汞化率を低減した電池を長期保存すると水素
ガスの発生による漏液や電池の膨張及び放電性能
の劣化をさけることができない。
発明の目的
本発明は亜鉛アルカリ一次電池の貯蔵性，耐漏
液性を劣化させることなく、負極亜鉛の汞化率を
飛躍的に低減させることを目的とする。
発明の構成
本発明による亜鉛アルカリ一次電池は、少くと
も銀を含み、さらにインジウム、ガリウム、タリ
ウムよりなる郡から選ばれた一種以上の元素が共
存する均一な被覆層を形成せしめ、その被覆層を
水銀量２％以下で汞化した亜鉛合金粉末を負極活
物質に用いたことを特徴とするものである。さら
に付言すれば、上記の表面層の付着元素は亜鉛と
のイオン化傾向の差による置換メツキにより亜鉛
粉末の表面に付着させたもので、インジウム塩、
ガリウム塩、タリウム塩の一種以上と銀塩とを溶
解させた水溶液又は分解液中に亜鉛を投入して亜
鉛の溶解と対応した付着元素の析出反応を行わせ
て亜鉛粉末の表面にこれら元素の均一な被覆層を
形成させればよい。従来、この種の金属元素を亜
鉛粉末の表面に置換メツキにより析出させること
により負極用亜鉛を防食する提案は多くあり、例
えば、ガリウム、インジウム、タリウムのように
水素過電圧が大きく、水銀との親和性も大きい元
素を表面に付着させた後汞化し、亜鉛粉末の表面
に水銀を担持させ、亜鉛粒子の内部への水銀の拡
散を抑制し、水量の水銀で亜鉛表面の水銀濃度を
高く維持し、さらに付着元素の本来の水素過電圧
が大きい性質に期待して、低汞化率で防食性のす
ぐれた亜鉛負極を得る方法がある。しかし上記の
方法では、付着元素すなわち、ガリウム、インジ
ウム、タリウムと亜鉛とのイオン傾向の差が比較
的小さいため、析出した元素の付着力が弱かつた
り、均一な付着層が得られなかつたり、付着層を
形成するのに長時間を要するなどの問題があつ
た。そのため、亜鉛粉末の表面層は付着元素の付
着量の不足やバラツキを生じたり、或いは部分的
な付着層のみしか得られず、亜鉛粉末表面が十分
に付着元素で被覆されることなく亜鉛な露出部分
が多く存在せざるを得ないので、これらの亜鉛粉
を汞化する場合、付着元素とともに表面に露出し
た亜鉛が汞化されて順次、亜鉛粉末の内部に水銀
が拡散して移行するため、汞化亜鉛粉の表面の水
銀濃度は経時的な低下が進行する。
そのため、汞化亜鉛粉末の表面の水素過電圧が
経時的に小さくなり、十分な防食効果が得られな
いのが問題とされている。一方、均一で強固な付
着層を得る方法としては、亜鉛よりはるかにイオ
ン化傾向が小さく、水銀との親和性も大きい銀を
付着元素とすることも考えられるが、銀自体が水
素過電圧が非常に小さいため、表面に付着した銀
を汞化するのみでは防食に十分な水素過電圧とす
ることはできず、十分な防食性が得られない。本
発明は上記の二例の方法の欠点を補い、双方の長
所を生して達成した発明であつて、付着元素とし
ての銀の役割は、水銀の亜鉛粉末の内部への拡散
を抑制し、表面の水銀濃度を高めるに足る均一な
被覆層を形成させることに主眼をおき、この表面
汞化層の水素過電圧を一層大きくするため、ガリ
ウム、インジウム、タリウムからなる群のうち一
種以上の元素を表面被覆層に共存させるもので、
これにより小量の水銀で、水素過電圧の大きい亜
鉛粉末表面を経時変化なく維持することができ、
長期間の防食性が確保され、アルカリ亜鉛一次電
池の負極汞化率を格段することができる。
実施例の説明
純度、99.997％の亜鉛地金を約500℃で溶融し
て圧縮空気により噴射して粉末化し、50〜150メ
ツシユの粒度範囲にフイル別けした。次いで、硫
酸銀の所定量と、ガリウム、インジウム、タリウ
ムの酸化物又は、硫酸塩又はその混合物の所定量
とを３％濃度の塩化アンモニウム溶液中に溶解又
は分散させ、前期の亜鉛粉を撹拌しながら添加
し、置換反応により亜鉛粉末の表面に前記の各金
属元素を析出させ均一な被覆層を形成させた。次
いで、所定量の水銀を撹拌しながら添加して、表
面被覆層から汞化した。その後水洗し、アセトン
で置換して乾燥し、汞化亜鉛粉を作成した。さら
に比較例として、付着元素のないもの、或いは単
体の付着元素のみを付着させたものについても同
様の方式で試料を作成した。
これらの各汞化粉末を用い、図に示すボタン形
酸化銀電池を製作した。図において、１はステン
レススチール製の封口板であり、内面には銅メツ
キ１′が施されている。２は40％濃度のか性カリ
水溶液に酸化亜鉛を飽和させた電解液をカルボキ
シルメチルセルロースによりゲル化し、このゲル
中に汞化粉末を分散させた亜鉛負極、３はセルロ
ース系の保液材、４は多孔性ポリプロピレン製の
セパレータ、５は酸化銀に黒鉛を混合して加圧成
型した正極、５′は鉄にニツケルメツキ施した正
極リング、６はステンレススチール製の正極缶
で、ニツケルメツキ６′が施されている。７はポ
リプロピレン製のガスケツトで、正極缶の折り曲
げにより密封している。試作した電池は直11.6
mm、高さ5.4mmであり、負極の汞化粉末の重量を
193mgに統一した。試作した電池の内訳は60℃で
１カ月保存した後の放電試験（20℃、5.1KΩ、
0.9V終止、ｎ＝３の平均値）、漏液発生率（ｎ＝
100）、及び電池総高の変化量（ｎ＝20の平均値）
の各測定結果を次表に示す。なお水銀の添加量
（汞化率）は表面処理後の亜鉛粉末に対して2wt
％とした。
Industrial Application Field The present invention relates to the improvement of the negative electrode of a zinc-alkaline primary battery, which uses an aqueous alkaline solution as an electrolyte, zinc as a negative electrode active material, and manganese dioxide, silver oxide, mercury oxide, oxygen, etc. as a positive electrode active material. It is something. Structure of conventional example and its problems A common problem with the above-mentioned zinc-alkaline primary batteries is corrosion of the negative electrode zinc in the electrolyte during storage. Conventionally, it has been adopted as an industrial means to increase the hydrogen overvoltage by using zinc chloride powder containing about 5 to 10% mercury added to zinc, and to suppress corrosion to a level that causes no practical problems. However, in recent years, there has been an increasing social need to reduce the amount of mercury contained in batteries in order to reduce pollution. Although various proposals have been made as countermeasures, there is currently no definitive solution. That is, for example, a method has been proposed in which the corrosion resistance is improved and the corrosion rate is reduced by using an alloy powder in which lead, cadmium, indium, etc. are added to zinc to increase the hydrogen overvoltage. Although this method has some effect, it is considered that the limit is a reduction in the filtration rate to about 3%. In addition, elements that are similar to mercury, such as indium and thallium, are attached to the surface of zinc powder and converted into mercury, increasing the mercury concentration on the surface and lowering the concentration in the center, increasing corrosion resistance and reducing the average rate of mercury formation. Methods to reduce the amount of mercury have been proposed, but the mercury trapping ability of the above-mentioned attached elements alone cannot prevent mercury from diffusing into the center due to changes over time and decreasing the mercury concentration on the surface, so it is difficult to achieve the desired corrosion protection. If a battery is stored for a long time with no effect and a reduced rate of oxidation, leakage due to generation of hydrogen gas, expansion of the battery, and deterioration of discharge performance cannot be avoided. OBJECTS OF THE INVENTION An object of the present invention is to dramatically reduce the filtration rate of negative electrode zinc without deteriorating the storage performance and leakage resistance of zinc-alkaline primary batteries. Structure of the Invention The zinc-alkaline primary battery according to the present invention forms a uniform coating layer containing at least silver and in which one or more elements selected from the group consisting of indium, gallium, and thallium coexist. The present invention is characterized in that a zinc alloy powder containing mercury of 2% or less is used as the negative electrode active material. In addition, the elements attached to the surface layer mentioned above are those attached to the surface of zinc powder by substitution plating due to the difference in ionization tendency with zinc; indium salt,
Zinc is added to an aqueous solution or decomposition solution in which one or more of gallium salts and thallium salts and silver salt are dissolved, and a reaction of dissolving the zinc and precipitation of the attached elements corresponding to the dissolution of the zinc takes place, so that these elements are deposited on the surface of the zinc powder. It is sufficient to form a uniform coating layer. Conventionally, there have been many proposals to prevent corrosion of zinc for negative electrodes by precipitating this type of metal element on the surface of zinc powder by substitution plating. After attaching a highly reactive element to the surface, it turns into a starch, supporting mercury on the surface of the zinc powder, suppressing the diffusion of mercury into the interior of the zinc particles, and maintaining a high mercury concentration on the zinc surface with the amount of mercury. Furthermore, there is a method of obtaining a zinc negative electrode with a low hydrogenation rate and excellent corrosion resistance, based on the inherent high hydrogen overvoltage of the attached element. However, in the above method, because the difference in ionic tendency between the adhering elements, that is, gallium, indium, thallium, and zinc is relatively small, the adhesion force of the precipitated elements is weak, and a uniform adhesion layer cannot be obtained. There were problems such as it took a long time to form the adhesion layer. As a result, the surface layer of the zinc powder may have insufficient or uneven adhesion amount of the adhering element, or only a partial adhesion layer can be obtained, and the surface of the zinc powder may not be sufficiently covered with the adhering element and the zinc may be exposed. Therefore, when these zinc powders are made into a liquid, the zinc exposed on the surface is made into a liquid along with the adhering elements, and mercury diffuses and migrates into the zinc powder. The mercury concentration on the surface of the zinc chloride powder decreases over time. Therefore, the problem is that the hydrogen overvoltage on the surface of the zinc chloride powder decreases over time, making it impossible to obtain a sufficient anticorrosion effect. On the other hand, one possible way to obtain a uniform and strong adhesion layer is to use silver, which has a much lower ionization tendency than zinc and has a greater affinity for mercury, as the adhesion element, but silver itself has a very high hydrogen overvoltage. Because of the small size, it is not possible to create a sufficient hydrogen overvoltage for corrosion protection by simply converting the silver attached to the surface into hydrogen, and sufficient corrosion protection cannot be obtained. The present invention has been achieved by compensating for the drawbacks of the above two methods and taking advantage of the advantages of both methods.The role of silver as an adhesion element is to suppress the diffusion of mercury into the zinc powder, The main focus was on forming a uniform coating layer sufficient to increase the mercury concentration on the surface, and in order to further increase the hydrogen overvoltage of this surface mercury layer, one or more elements from the group consisting of gallium, indium, and thallium were added. It is made to coexist with the surface coating layer,
This makes it possible to maintain the zinc powder surface, which has a large hydrogen overvoltage, without any change over time with a small amount of mercury.
Long-term corrosion protection is ensured, and the negative electrode conversion rate of alkaline zinc primary batteries can be significantly improved. Description of Examples Zinc ingots with a purity of 99.997% were melted at about 500°C, pulverized by spraying with compressed air, and divided into films into particle size ranges of 50 to 150 meshes. Next, a predetermined amount of silver sulfate and a predetermined amount of an oxide or sulfate of gallium, indium, thallium, or a mixture thereof are dissolved or dispersed in a 3% ammonium chloride solution, and the zinc powder from the previous stage is stirred. The above metal elements were precipitated on the surface of the zinc powder by a substitution reaction to form a uniform coating layer. Next, a predetermined amount of mercury was added while stirring to form a liquid from the surface coating layer. Thereafter, it was washed with water, replaced with acetone, and dried to produce a zinc chloride powder. Furthermore, as comparative examples, samples were prepared in the same manner with no attached element or with only a single attached element attached. The button-shaped silver oxide battery shown in the figure was manufactured using each of these oxidized powders. In the figure, 1 is a sealing plate made of stainless steel, the inner surface of which is plated with copper 1'. 2 is a zinc negative electrode made by gelling an electrolyte made of a 40% concentration caustic potassium aqueous solution saturated with zinc oxide with carboxymethyl cellulose, and dispersing gelatinized powder in this gel; 3 is a cellulose-based liquid retaining material; 4 is a A separator made of porous polypropylene, 5 a positive electrode made of a mixture of silver oxide and graphite and pressure molded, 5' a positive electrode ring made of iron with nickel plating, and 6 a positive electrode can made of stainless steel with nickel plating 6' applied. ing. 7 is a gasket made of polypropylene, which is sealed by bending the positive electrode can. The prototype battery has a straight line of 11.6
mm, height 5.4 mm, and the weight of the anode powder is
The dosage has been standardized to 193mg. The breakdown of the prototype battery was the discharge test after storing it at 60℃ for one month (20℃, 5.1KΩ,
0.9V end, average value of n=3), leakage rate (n=
100), and the amount of change in total battery height (average value of n = 20)
The results of each measurement are shown in the table below. The amount of mercury added (concentration rate) is 2wt relative to the zinc powder after surface treatment.
%.
【表】
質的には放電前後で総高が低くなる
ことは考えられないが、実測変
化値として示した。
この表に見られる如く、本発明を適用した場合
（ｆ〜ｏ）はいずれも、従来法（ａ〜ｅ）に対し
てガス発生による電池膨張と漏液発生率が少く、
貯蔵後の放電性能も良好である。従来例のうち、
(a)は亜鉛表面に水銀親和性の付着金属が存在せ
ず、水銀が容易に亜鉛粒子内部に移行して表面濃
度を下げるため最も負極が腐食し易く、次いで
（ｂ〜ｅ）のように単一元素のみを付着させた場
合は(a)より防食性は良いとはいえ、前述の理由に
より、十分な負極の耐食性を備えているとはいえ
ない。本発明のうちでも、付着元素の量によつて
効果に差が認められ、Agは0.02％以上、これに
Ga、In、Tlのうち一種を0.02％以上共存して付
着させたｇ，ｈ，ｉ及びｋ，ｌ，ｎ，ｏが比較的
良好である、以上のように、本発明による銀を含
む複合付着層の防食効果は著しく大きく、低汞化
率で性能のすぐれた負極を構成するに極めて有用
で、この負極を用い得るアルカリ亜鉛一次電池の
低公害化を実現する上で有効な手段であることが
実証されている。
発明の効果
前述したとおり本発明は亜鉛アルカリ一次電池
中の負極亜鉛の低汞化を化を果す上で極めて効果
的である。また、実施例では被覆元素を付着した
後に汞化する方法で本発明を説明したが、被覆元
素を付着させると同時に、汞化する方法、亜鉛合
金表面を汞化した直後に被覆元素を付着させる方
法のいづれを採つても本発明に基づいた同様の効
果が得られる。[Table] Qualitatively, it is unlikely that the total height will decrease before and after discharge, but the actual measured change
It is shown as a value.
As seen in this table, in all cases where the present invention is applied (f to o), the battery expansion due to gas generation and the rate of leakage are lower than in the conventional methods (a to e).
The discharge performance after storage is also good. Among the conventional examples,
In (a), there is no attached metal with mercury affinity on the zinc surface, and mercury easily moves inside the zinc particles to lower the surface concentration, so the negative electrode is the most likely to corrode, followed by (b to e). Although the corrosion resistance is better than (a) when only a single element is attached, it cannot be said to have sufficient corrosion resistance of the negative electrode for the reasons mentioned above. Even in the present invention, differences in effectiveness were observed depending on the amount of attached elements, with Ag being 0.02% or more,
As described above, the silver-containing composite according to the present invention is relatively good in g, h, i and k, l, n, o, in which 0.02% or more of one of Ga, In, and Tl is coexisting and deposited. The corrosion-preventing effect of the adhesion layer is extremely large, and it is extremely useful for constructing a negative electrode with a low rate of change in moisture and excellent performance, and is an effective means for achieving low pollution in alkaline zinc primary batteries that can use this negative electrode. This has been proven. Effects of the Invention As described above, the present invention is extremely effective in reducing the flux of negative electrode zinc in zinc-alkaline primary batteries. In addition, in the examples, the present invention was explained using a method in which the coating element is applied and then made into a layer, but there is also a method in which the coating element is attached and made into a layer at the same time, and a method in which the coating element is attached immediately after the surface of the zinc alloy is made into a layer. Regardless of which method is adopted, the same effects based on the present invention can be obtained.
【図面の簡単な説明】[Brief explanation of drawings]
図は本発明の効果を検討するため製作したボタ
ン形酸化銀電池の断面図ある。
１……封口板、２……亜鉛負極、３……保液
材、４……セパレータ、５……酸化銀正極、６…
…正極缶、７……ガスケツト。
The figure is a cross-sectional view of a button-shaped silver oxide battery manufactured to examine the effects of the present invention. DESCRIPTION OF SYMBOLS 1... Sealing plate, 2... Zinc negative electrode, 3... Liquid retaining material, 4... Separator, 5... Silver oxide positive electrode, 6...
...Positive electrode can, 7...Gasket.