JP2004095512A

JP2004095512A - Zinc alloy powder for alkaline battery, its manufacturing method, and alkaline battery using it

Info

Publication number: JP2004095512A
Application number: JP2002258809A
Authority: JP
Inventors: Hikoichi Harikae; 張替　彦一; Toshiya Kitamura; 北村　利哉; Masayuki Nishina; 仁科　正行
Original assignee: Dowa Mining Co Ltd
Current assignee: Dowa Holdings Co Ltd
Priority date: 2002-09-04
Filing date: 2002-09-04
Publication date: 2004-03-25
Anticipated expiration: 2022-09-04
Also published as: JP4304317B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide zinc alloy powder for an alkaline battery of which the amount of gas generation is suppressed and heavy load pulse discharge performance is improved and its manufacturing method as well as an alkaline battery using it. <P>SOLUTION: A solid solution of the zinc alloy containing one or more kinds selected from a group of Bi 0.001 to 0.1 wt%, In 0.01 to 0.1 wt%, and 0.0001-0.1 wt% of one or more kinds of metals selected from a group of alkaline metal, alkaline earth metals, Al, and Ga, and consisting of the remaining part composed of inevitable impurities and zinc is atomized to form dispersed solid solution particles, onto which liquid is sprayed and quenched, and the dispersed crystal particles are atomized, thereby the zinc alloy powder for the alkaline battery is obtained which is substantially composed of particles of -20 mesh or less by making the crystal particles finer, and the average crystal particle numbers N are respectively 40 or more, 30 or more, 20 or more, and 5 or more in particle size distribution of respectively -200 mesh, +200 to -150 mesh, +150 to -100 mesh, and +100 to -50 mesh in 0.1 mm sq. of cross sectional powder particles. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は粉末粒子の結晶粒子サイズを微細化することにより、重負荷パルス放電性能の改善とガス発生抑制が両立したアルカリ電池用亜鉛合金粉末及びその製造方法並びにそれを用いたアルカリ電池に関するものである。
【０００２】
【従来の技術】
アルカリマンガン電池はマンガン電池が一般に使用されるものに比較して、主に高電流タイプの機器に使用されてきた。最近では、デジタルカメラ、ＰＤＡ関連などの比較的重負荷を連続的に使用する用途、あるいは高電流をパルスで使用する用途が増加しており、このような放電レートで十分放電特性を発揮できる電池の要求が高まっている。
例えば１．２Ａ程度の重負荷放電では亜鉛の利用率が３０％程度であり、電池としての性能向上のため亜鉛の利用率の向上が望まれている。
その対策として従来は、単純に亜鉛粉の表面積を増加して電解液との反応面積を増加させる目的で粒径の細かい亜鉛粉を使用することが行われてきた。
【０００３】
特許文献１では、−２００メッシュの亜鉛微粉あるいは、−３２５メッシュのダストなどの微細粉を負極活物質に含ませることにより、表面積を増加させ、連続負荷、高電流パルス試験などの放電性能が向上するとしている。
特許文献２、特許文献３、特許文献４ではそれぞれ−７５μｍ程度の亜鉛微粉を使用することにより、高率放電特性の向上、利用率の向上及び低温時の放電特性が向上するとしている。
しかし、表面積が増えて反応面積が増加した結果、重負荷放電特性は向上するが、ガスの発生が増大するといった問題が生じていた。ガスの増加は電池の液漏れ、破裂の原因となり電池の重要特性のひとつである安全性を損なってしまう。
【０００４】
【特許文献１】
特表２００１−５１２２８４号公報
【特許文献２】
特開昭５３−１２０１４３号公報
【特許文献３】
特開昭５７−１８２９７２号公報
【特許文献４】
特開昭５９−２２８３６３号公報
【０００５】
【発明が解決しようとする課題】
従って本発明の目的は従来技術に代わる新たな構成を採用することによってガス発生を抑制して重負荷パルス放電性能を向上させた亜鉛粉末及びその製造方法並びにそれを用いた電池を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者等は鋭意研究の結果、亜鉛合金粉末の結晶粒子を微細化することにより、ガス発生を抑制しつつ重負荷パルス放電性能を向上できることを見出したものである。
【０００７】
すなわち、本発明は第１に、２００メッシュのフルイ目の開きサイズ（すなわち、７４μｍ）より小径（−２００メッシュという。）、２００メッシュのフルイ目の開きサイズより大径でかつ１５０メッシュのフルイ目の開きサイズ（すなわち、１０４μｍ）より小径（＋２００〜−１５０メッシュという。）、１５０メッシュのフルイ目の開きサイズより大径でかつ１００メッシュのフルイ目の開きサイズ（すなわち、１４７μｍ）より小径（＋１５０〜−１００メッシュという。）及び１００メッシュのフルイ目の開きサイズより大径でかつ５０メッシュのフルイ目の開きサイズ（すなわち、２９５μｍ）より小径（＋１００〜−５０メッシュという。）の各粒度における粉末粒子断面における縦、横の長さがいずれも０．１ｍｍの正方形（０．１ｍｍ平方という。）中の平均の結晶粒子数Ｎが、それぞれ２００メッシュ、１５０メッシュ、１００メッシュ及び５０メッシュのフルイ目の開きサイズ（各メッシュのサイズという。）ｘμｍに関して、Ｎ＞−２０．５Ｌｎ（ｘ）＋１２６．９であることを特徴とするアルカリ電池用亜鉛合金粉末；第２に、−２００メッシュ、＋２００〜−１５０メッシュ、＋１５０〜−１００メッシュ及び＋１００〜−５０メッシュの各粒度における粉末粒子断面の０．１ｍｍ平方中の平均の結晶粒子数Ｎが、それぞれ２００メッシュ、１５０メッシュ、１００メッシュ及び５０メッシュのサイズｘμｍに関して、Ｎ≧−３６．２Ｌｎ（ｘ）＋２１８．６であることを特徴とするアルカリ電池用亜鉛合金粉末；第３に、前記粉末が実質的に２０メッシュのフルイ目の開きサイズ（すなわち、８３３μｍ）より小径（−２０メッシュという。）の粒子からなる、第１または第２に記載のアルカリ電池用亜鉛合金粉末；第４に、実質的に−２０メッシュの粒子からなり、−２００メッシュ、＋２００〜−１５０メッシュ、＋１５０〜−１００メッシュ及び＋１００〜−５０メッシュの各粒度における粉末粒子断面の０．１ｍｍ平方中の平均の結晶粒子数Ｎが、それぞれ４０個以上、３０個以上、２０個以上及び５個以上であることを特徴とするアルカリ電池用亜鉛合金粉末；第５に、前記亜鉛合金がＢｉ　０．００１〜０．１重量％及びＩｎ　０．０１〜０．１重量％からなる群から選ばれる１種以上と、アルカリ金属、アルカリ土類金属、Ａｌ及びＧａからなる群から選ばれる１種以上の金属を０．０００１〜０．１重量％とを含有し、残部が不可避不純物と亜鉛からなる亜鉛合金である、第１〜４のいずれかに記載のアルカリ電池用亜鉛合金粉末；第６に、前記亜鉛合金の溶体がアトマイズされて生じた分散溶体粒子に液体を吹きつけることによって急冷し前記結晶粒子を微細化することを特徴とする、第１〜５のいずれかに記載のアルカリ電池用亜鉛合金粉末の製造方法；第７に、前記液体が室温において液相または気相の物質である、第６記載の製造方法；第８に、第１〜５のいずれかに記載の亜鉛合金粉末が負極活物質として含有されていることを特徴とするアルカリ電池を提供するものである。
【０００８】
【発明の実施の形態】
本発明における電池特性への効果としては以下のように推測される。粒子内の結晶粒界が放電反応の起点となり、反応開始点が増加することによって放電性能が改善されることが考えられる。結晶粒界を増加させるためには、金属の凝固時に急冷する方法が一般的に知られている。発明者等はこれを金属粉製造に応用した。すなわち、分散媒体によって分散された溶体粒子が凝固時に吹きつけられた液体または気体によって急冷処理されることにより結晶粒界が増加する。
亜鉛合金粉末の製法としては電解法あるいは蒸留法などで作製した亜鉛地金を溶融し、電池を作製した場合の使用に耐えうるような耐食性を得るため、Ｂｉ　０．００１〜０．１重量％及びＩｎ　０．０１〜０．１重量％からなる群から選ばれる１種以上と、アルカリ金属、アルカリ土類金属、Ａｌ及びＧａからなる群から選ばれる１種以上の金属を０．０００１〜０．１重量％とを添加する。
【０００９】
本発明に係る亜鉛合金の組成は特に限定されるものではないが、上記の見地からＡｌ、Ｂｉ及びＩｎを含有する亜鉛合金が好ましく、Ａｌを０．０００１〜０．１重量％、Ｂｉを０．００１〜０．１重量％及びＩｎを０．０１〜０．１重量％含有し残部が不可避不純物と亜鉛からなる亜鉛合金がさらに好ましい。
【００１０】
この亜鉛合金溶体を細い溶湯流として、ガスまたは回転ディスクなどのアトマイズによりせん断力を与えて分散して粉状とする。ガスの場合の分散媒はエアー及び窒素、アルゴンなどの不活性ガスを使用することができる。粉末の粒度分布は放電性能、ガス発生のバランスを考慮して実質的に−２０メッシュの粒子からなる粉末が好ましい。
結晶粒を効率良く微細化するためには亜鉛粉末の分散、凝固時に急冷が必要である。この亜鉛合金溶湯流を分散する際に冷却媒体を吹き付けることによって急冷することができる。冷却媒体としては直接冷風を吹き付ける方法、液体状物質を吹き付けて蒸発時の潜熱を利用する方法が考えられるが、分散溶体粒子に液体を吹き付けて蒸発の潜熱を利用する場合の方が結晶粒の微細化のための冷却効果がはるかに大きい。また、用いられる液体としては蒸留水などの純水でよいが、室温で気相であって液化できかつ凝固点の低い液体、例えば液体窒素などがより好ましい。
【００１１】
結晶粒の大きさの定量的な評価としては単位面積あたりの結晶粒数を測定する方法が一般的に知られている。また、粉末粒子の凝固速度はその粒径に依存する。すなわち、粉末粒子の粒径が小さいほど結晶粒の粒径は小さくなる。従って粉末粒子の粒径毎に結晶粒の大きさを規定する必要があるので、篩い分けを行い粉末粒子の粒径毎に結晶粒の大きさを測定した。具体的には亜鉛合金の粉末粒子の断面を研磨し、例えば酸、アルカリなどで腐食すると腐食度差により結晶粒が観察され、液体吹きつけにより冷却処理していないこと以外は全て同じ条件の亜鉛合金粉末に比較すると本発明に係る亜鉛合金粉末の結晶粒が微細になっていることが観察できる。亜鉛合金粉末粒子の断面全体の結晶粒数をカウントし、単位面積あたりの平均の個数を算出する。これらは市販のパソコンソフトで容易に処理できる。
【００１２】
上記のように、液体吹きつけにより冷却処理をした亜鉛合金粉末と液体吹きつけの冷却処理をしないこと以外は全て同じ条件の亜鉛合金粉末の両者について、−２００メッシュ、＋２００〜−１５０メッシュ、＋１５０〜−１００メッシュ及び＋１００〜−５０メッシュの各粒度で粉末粒子１０個ずつ０．１ｍｍ平方中の結晶粒子数を測定した。各粒度毎の１０個の粉末粒子の平均の結晶粒子数Ｎと、それぞれ２００メッシュ、１５０メッシュ、１００メッシュ及び５０メッシュのサイズｘμｍとの関係を近似式で表すと、液体吹きつけの冷却処理をしないこと以外は全て本発明と同じ条件の亜鉛合金粉末については図３に示す次式（Ａ）が求められた。すなわち、
Ｎ＝−２０．５Ｌｎ（ｘ）＋１２６．９　　　（Ａ）
であり、本発明に係る亜鉛合金粉末においては次式を充足することが好ましい。すなわち、
Ｎ＞−２０．５Ｌｎ（ｘ）＋１２６．９
である。また、液体吹きつけにより冷却処理をした本発明に係る亜鉛合金粉末について上記と同様に統計的に処理して近似式で表すと、図３に示す次式（Ｂ）が求められた。すなわち、
Ｎ＝−３６．２Ｌｎ（ｘ）＋２１８．６　　　（Ｂ）
であり、本発明に係る亜鉛合金粉末においては次式を充足することがより好ましい。すなわち、
Ｎ≧−３６．２Ｌｎ（ｘ）＋２１８．６
である。
【００１３】
また、便法として、放電特性を向上させるための結晶粒子の微細化については、実質的に−２０メッシュの粒子からなり、−２００メッシュ、＋２００〜−１５０メッシュ、＋１５０〜−１００メッシュ及び＋１００〜−５０メッシュの各粒度における粉末粒子断面の０．１ｍｍ平方中の平均の結晶粒子数Ｎが、それぞれ４０個以上、３０個以上、２０個以上及び５個以上であることが好ましく、さらに好ましくはそれぞれ５０個以上、４０個以上、３０個以上及び１５個以上であり、パルス放電特性向上効果が奏される。
負極活物質はこれらの亜鉛合金粉末、ゲル化剤、電解液で構成される。ゲル化剤としてはポリアクリル酸などの公知の材料を用いることができる。また、アルカリ電解液は酸化亜鉛を溶解したものを用い、セパレーターを介して、正極に二酸化マンガンなどを用いて電池を構成する。
【００１４】
【実施例】
以下に実施例によって本発明をさらに詳細に説明するが、本発明の技術的範囲はこれらの記載によって限定されるものではない。
【００１５】
〔実施例１〕　Ａｌ：０．００３重量％、Ｂｉ：０．０１５重量％、Ｉｎ：０．０５重量％、残部が実質的に亜鉛からなる亜鉛合金の溶体を純水（蒸留水）を吹き付けながら空気でアトマイズして粉末化した。純水の添加量は結露しない量とする。この亜鉛合金粉末を篩い分けして−２０メッシュの粉末を得た。この粉末を５ｇとり、４０％ＫＯＨ水溶液に３重量％の酸化亜鉛を溶解した液に浸し、図１に示す装置を用いて６０℃で３日間保持して発生したガス量から、ガス発生速度（μｌ／ｇ・ｄａｙ）を求めた。
【００１６】
結晶粒の評価としては、−２００メッシュ、＋２００〜−１５０メッシュ、＋１５０〜−１００メッシュ及び＋１００〜−５０メッシュの各粒度範囲の亜鉛合金粉末を各々樹脂埋めして研磨し、亜鉛合金粉末粒子の断面を塩酸５０％の水溶液で２０秒間腐食して結晶粒を金属顕微鏡で観察し、亜鉛粉末粒子断面０．１ｍｍ平方中の平均の結晶粒の個数Ｎを測定した。測定は各粒度で粉末粒子１０個ずつ行い、その平均値を示した。その結果を表１に示す。
【００１７】
【表１】

【００１８】
この亜鉛合金粉末、ポリアクリル酸１重量％、酸化亜鉛を３重量％溶解させた４０％ＫＯＨ水溶液を混合してゲル状負極活物質とした。正極を二酸化マンガンとして図２に示すＬＲ６型試作電池を作製した。この試作電池の重負荷パルス放電性能を１．２Ａ３秒間放電、７秒間休止で測定した。この電池を１．６　Ｖからスタートさせて１．０　Ｖ、０．９　Ｖまでの持続時間を測定した。なお、上記組成、粒度分布が同一であって純水吹きつけで冷却処理していない亜鉛合金粉末（比較例１）の持続時間を１００％として相対値％で表した。その測定結果を表１に示す。
【００１９】
〔実施例２〕　亜鉛合金組成をＡｌ：０．０００５重量％、Ｂｉ：０．０３重量％、Ｉｎ：０．０５重量％とした以外は実施例１と同様にして試作評価した結果を表１に示す。
【００２０】
〔実施例３〕　組成をＡｌ：０．０００５重量％、Ｂｉ：０．０３重量％、Ｉｎ：０．０５重量％とし、冷却媒体として液体窒素を液体の状態で亜鉛粉の分散時に吹き付けたこと以外は実施例１と同様に試作評価した結果を表１に示す。
【００２１】
〔比較例１〕　組成をＡｌ：０．００３重量％、Ｂｉ：０．０１５重量％、Ｉｎ：０．０５重量％とし、噴霧時に液体の冷却媒を吹き付けない以外は実施例１と同様に試作評価した結果を表１に示す。
【００２２】
〔比較例２〕　組成をＡｌ：０．０００５重量％、Ｂｉ：０．０３重量％、Ｉｎ：０．０５重量％とし、噴霧直後に粉末粒子を液体窒素に浸した。それ以外は実施例１と同様に試作評価した結果を表１に示す。
【００２３】
〔比較例３〕　組成をＡｌ：０．００３重量％、Ｂｉ：０．０１５重量％、Ｉｎ：０．０５重量％とし、液体吹きつけの冷却処理をしないで作製した亜鉛合金粉を２００℃で２時間熱処理したこと以外は実施例１と同様に試作評価した結果を表１に示す。
【００２４】
これらの結果から本発明に係る亜鉛合金粉末は、ガス発生量を抑制し、かつ、液体吹きつけの冷却処理をしない以外は同様の比較例に係る亜鉛合金粉末よりもパルス放電性能を向上させていることが明らかである。
【００２５】
【発明の効果】
本発明に係るアルカリ電池用亜鉛合金粉末は、亜鉛合金粉の結晶粒子を微細化することにより、重負荷パルス放電性能の改善とガス発生抑制が両立されたものであり、さらに、その製造にあたっては液体を吹き付ける部分を追加することにより亜鉛合金溶体をアトマイズして粉末を作製する従来の粉末製造装置を実質的にそのまま使用でき低コストで効率的に製造できるという製造上の効果も奏する。
【図面の簡単な説明】
【図１】ガス発生測定装置の縦断面図。
【図２】試作電池の縦断面図。
【図３】粉末粒子の粒径と結晶粒子数との関係図。
【符号の説明】
１　亜鉛合金粉末
２　電解液
３　流動パラフィン
４　シリコン栓
５　メスピペット
６　正極缶
７　正極活物質
８　セパレータ
９　負極活物質
１０　負極集電棒
１１　ゴムパッキン
１２　キャップ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a zinc alloy powder for an alkaline battery, in which the improvement in heavy load pulse discharge performance and the suppression of gas generation are achieved by reducing the crystal particle size of the powder particles, a method for producing the same, and an alkaline battery using the same. is there.
[0002]
[Prior art]
Alkaline manganese batteries have been mainly used for high current type devices as compared with those generally used for manganese batteries. Recently, applications that use relatively heavy loads continuously, such as digital cameras and PDAs, or applications that use high current in pulses are increasing, and batteries that can exhibit sufficient discharge characteristics at such a discharge rate are increasing. The demand for is increasing.
For example, in a heavy load discharge of about 1.2 A, the utilization rate of zinc is about 30%, and it is desired to improve the utilization rate of zinc in order to improve the performance as a battery.
Conventionally, as a countermeasure, zinc powder having a small particle size has been used for the purpose of simply increasing the surface area of the zinc powder and increasing the reaction area with the electrolytic solution.
[0003]
In Patent Document 1, by including fine powder such as -200 mesh zinc fine powder or -325 mesh dust in the negative electrode active material, the surface area is increased, and the discharge performance such as continuous load and high current pulse test is improved. I have to.

Patent Documents

2, 3, and 4 disclose that the use of zinc fine powder of about -75 μm improves the high-rate discharge characteristics, the utilization factor, and the discharge characteristics at low temperatures.
However, as a result of an increase in the reaction area due to an increase in the surface area, the heavy-load discharge characteristics are improved, but a problem such as an increase in gas generation occurs. The increase in gas causes leakage and rupture of the battery, and impairs safety, which is one of the important characteristics of the battery.
[0004]
[Patent Document 1]
JP-T-2001-512284 [Patent Document 2]
JP-A-53-120143 [Patent Document 3]
JP-A-57-182972 [Patent Document 4]
JP-A-59-228363.
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a zinc powder having improved heavy-load pulse discharge performance by suppressing gas generation by adopting a new configuration replacing the prior art, a method of manufacturing the same, and a battery using the same. is there.
[0006]
[Means for Solving the Problems]
The present inventors have assiduously studied and, as a result, have found that, by making the crystal particles of the zinc alloy powder finer, it is possible to improve the heavy-load pulse discharge performance while suppressing gas generation.
[0007]
That is, the present invention firstly provides a screen having a smaller diameter (referred to as -200 mesh) than the opening size of a 200-mesh screen (that is, 74 μm), a larger diameter than the opening size of a 200-mesh screen, and a 150-mesh screen. Smaller than the opening size (ie, 104 μm) (+200 to −150 mesh), larger than the opening size of the 150 mesh screen and smaller than the opening size of the 100 mesh screen (ie, 147 μm) (+150 mesh).という 100 mesh) and a powder having a diameter larger than the mesh opening size of 100 mesh and smaller than the mesh opening size of 50 mesh (that is, 295 μm) (+100 to -50 mesh). A square with a vertical and horizontal length of 0.1 mm in the particle cross section The average number N of crystal grains in a 0.1 mm square is 200> 150 mesh, 100 mesh, and 50 mesh, and the mesh opening size (each mesh size) x μm is N> −20. 0.5 Ln (x) +126.9; zinc alloy powder for an alkaline battery; secondly, each particle size of -200 mesh, +200 to -150 mesh, +150 to -100 mesh, and +100 to -50 mesh The average number N of crystal grains in a 0.1 mm square of the cross section of the powder particles in the above is N ≧ −36.2 Ln (x) +218.6 with respect to the sizes xμm of 200 mesh, 150 mesh, 100 mesh and 50 mesh, respectively. Thirdly, the zinc alloy powder for an alkaline battery; The zinc alloy powder for an alkaline battery according to the first or second aspect, comprising particles having a smaller diameter (referred to as -20 mesh) than the opening size (i.e., 833 µm) of the screen; fourth, substantially -20. The average number N of crystal grains in a 0.1 mm square of the cross section of the powder particles at each particle size of -200 mesh, +200 to -150 mesh, +150 to -100 mesh and +100 to -50 mesh is respectively 40 or more, 30 or more, 20 or more, and 5 or more zinc alloy powder for an alkaline battery; fifthly, the zinc alloy contains 0.001 to 0.1% by weight of Bi and In 0 One or more metals selected from the group consisting of 0.11 to 0.1% by weight and one or more metals selected from the group consisting of alkali metals, alkaline earth metals, Al and Ga The zinc alloy powder for an alkaline battery according to any one of the first to fourth aspects, wherein the zinc alloy powder comprises 0.000001 to 0.1% by weight, and the balance is a zinc alloy comprising unavoidable impurities and zinc; sixth, the zinc alloy The method according to any one of claims 1 to 5, characterized in that the solution is rapidly cooled by spraying a liquid onto the dispersed solution particles generated by atomizing the solution to refine the crystal particles. 7. The manufacturing method according to the sixth aspect, wherein the liquid is a substance in a liquid or gaseous phase at room temperature; eighth, the zinc alloy powder according to any one of the first to fifth aspects is a negative electrode active material. It is intended to provide an alkaline battery characterized by being contained as:
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The effects on the battery characteristics in the present invention are presumed as follows. It is conceivable that the crystal grain boundaries in the particles become the starting point of the discharge reaction, and the discharge performance is improved by increasing the reaction start point. In order to increase the crystal grain boundaries, a method of rapidly cooling the metal during solidification is generally known. The inventors applied this to the production of metal powder. That is, the crystal grains are increased by quenching the solution particles dispersed by the dispersion medium with the liquid or gas sprayed during solidification.
As a method for producing a zinc alloy powder, 0.001 to 0.1% by weight of Bi is used in order to obtain a corrosion resistance that can withstand use when a battery is produced by melting zinc ingot produced by an electrolytic method or a distillation method. And In at least one selected from the group consisting of 0.01 to 0.1% by weight and one or more metals selected from the group consisting of alkali metals, alkaline earth metals, Al and Ga in the range of 0.0001 to 0. .1% by weight.
[0009]
Although the composition of the zinc alloy according to the present invention is not particularly limited, a zinc alloy containing Al, Bi and In is preferable from the above viewpoint, and 0.0001 to 0.1% by weight of Al and 0% of Bi More preferably, a zinc alloy containing 0.001 to 0.1% by weight and 0.01 to 0.1% by weight of In, with the balance being unavoidable impurities and zinc.
[0010]
This zinc alloy solution is dispersed as a thin molten metal stream by applying a shearing force by atomizing gas or a rotating disk or the like to powder. In the case of gas, air and an inert gas such as nitrogen and argon can be used as the dispersion medium. The particle size distribution of the powder is preferably a powder substantially consisting of particles of −20 mesh in consideration of the balance between discharge performance and gas generation.
In order to efficiently refine the crystal grains, it is necessary to quench the zinc powder during dispersion and solidification. When the zinc alloy melt flow is dispersed, it can be rapidly cooled by spraying a cooling medium. As a cooling medium, a method in which cold air is directly blown or a method in which a liquid substance is sprayed and latent heat during evaporation is used are considered. The cooling effect for miniaturization is much greater. The liquid used may be pure water such as distilled water, but more preferably a liquid which is in a gas phase at room temperature and can be liquefied and has a low freezing point, for example, liquid nitrogen.
[0011]
As a quantitative evaluation of the crystal grain size, a method of measuring the number of crystal grains per unit area is generally known. The solidification rate of the powder particles depends on the particle size. That is, the smaller the particle size of the powder particles, the smaller the particle size of the crystal grains. Therefore, since it is necessary to define the size of the crystal grains for each particle size of the powder particles, sieving was performed to measure the size of the crystal particles for each particle size of the powder particles. Specifically, when the cross section of the powder particles of the zinc alloy is polished, and is corroded with, for example, an acid or an alkali, crystal grains are observed due to a difference in the degree of corrosion. Compared with the alloy powder, it can be observed that the crystal grains of the zinc alloy powder according to the present invention are fine. The number of crystal grains in the entire cross section of the zinc alloy powder particles is counted, and the average number per unit area is calculated. These can be easily processed with commercially available personal computer software.
[0012]
As described above, both the zinc alloy powder subjected to the cooling treatment by the liquid spraying and the zinc alloy powder under the same conditions except that the cooling treatment by the liquid spraying is not performed are both -200 mesh, +200 to -150 mesh, +150 mesh. The number of crystal particles in 0.1 mm square was measured by 10 powder particles at each particle size of -100 mesh and +100 to -50 mesh. When the relationship between the average number of crystal particles N of 10 powder particles for each particle size and the size x μm of 200 mesh, 150 mesh, 100 mesh and 50 mesh, respectively, is expressed by an approximate expression, the cooling process of liquid spraying is performed. The following formula (A) shown in FIG. 3 was obtained for the zinc alloy powder under the same conditions as those of the present invention except that it was not performed. That is,
N = -20.5Ln (x) +126.9 (A)
Therefore, the zinc alloy powder according to the present invention preferably satisfies the following expression. That is,
N> -20.5Ln (x) +126.9
It is. Further, the following formula (B) shown in FIG. 3 was obtained by statistically treating the zinc alloy powder according to the present invention, which had been cooled by spraying with a liquid, in the same manner as described above and expressing the approximate expression. That is,
N = -36.2Ln (x) +218.6 (B)
It is more preferable that the zinc alloy powder according to the present invention satisfies the following expression. That is,
N ≧ -36.2Ln (x) +218.6
It is.
[0013]
Further, as a convenient method, regarding the refinement of the crystal particles for improving the discharge characteristics, the particles substantially consist of particles of −20 mesh, −200 mesh, +200 to −150 mesh, +150 to −100 mesh, and +100 to −100 mesh. The average number of crystal particles N in a 0.1 mm square of the powder particle cross section at each particle size of −50 mesh is preferably 40 or more, 30 or more, 20 or more, and 5 or more, more preferably The number is 50 or more, 40 or more, 30 or more, and 15 or more, respectively, and an effect of improving pulse discharge characteristics is exhibited.
The negative electrode active material is composed of the zinc alloy powder, the gelling agent, and the electrolyte. Known materials such as polyacrylic acid can be used as the gelling agent. In addition, a battery is formed using an alkaline electrolyte solution in which zinc oxide is dissolved, and using manganese dioxide or the like as a positive electrode through a separator.
[0014]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the technical scope of the present invention is not limited by these descriptions.
[0015]
[Example 1] A solution of a zinc alloy consisting of 0.003% by weight of Al, 0.015% by weight of Bi, 0.05% by weight of In and the balance substantially consisting of zinc was sprayed with pure water (distilled water). While atomizing with air, powder was obtained. The amount of pure water added is such that it does not condense. The zinc alloy powder was sieved to obtain a -20 mesh powder. 5 g of this powder was immersed in a solution in which 3% by weight of zinc oxide was dissolved in a 40% KOH aqueous solution, and was held at 60 ° C. for 3 days using the apparatus shown in FIG. μl / g · day) was determined.
[0016]
As the evaluation of the crystal grains, zinc alloy powders in each particle size range of -200 mesh, +200 to -150 mesh, +150 to -100 mesh and +100 to -50 mesh were respectively filled with resin and polished, and the zinc alloy powder particles were polished. The cross section was corroded with an aqueous solution of 50% hydrochloric acid for 20 seconds and the crystal grains were observed with a metallographic microscope, and the average number N of crystal grains in a 0.1 mm square cross section of the zinc powder particles was measured. The measurement was performed for 10 powder particles for each particle size, and the average value was shown. Table 1 shows the results.
[0017]
[Table 1]

[0018]
This zinc alloy powder, 1% by weight of polyacrylic acid, and a 40% KOH aqueous solution in which 3% by weight of zinc oxide were dissolved were mixed to obtain a gelled negative electrode active material. An LR6 type prototype battery shown in FIG. 2 was prepared using manganese dioxide as the positive electrode. The heavy-load pulse discharge performance of this prototype battery was measured by discharging 1.2 A for 3 seconds and resting for 7 seconds. The battery was started at 1.6 V and the duration of time from 1.0 V to 0.9 V was measured. In addition, the duration of a zinc alloy powder (Comparative Example 1) having the same composition and particle size distribution and not subjected to cooling treatment by spraying with pure water was expressed as a relative value% assuming 100%. Table 1 shows the measurement results.
[0019]
[Example 2] Table 1 shows the results of trial manufacture and evaluation in the same manner as in Example 1 except that the composition of the zinc alloy was 0.0005% by weight of Al, 0.03% by weight of Bi, and 0.05% by weight of In. Shown in
[0020]
Example 3 The composition was set to 0.0005% by weight of Al, 0.03% by weight of Bi, and 0.05% by weight of In, and liquid nitrogen was sprayed in a liquid state as a cooling medium during dispersion of zinc powder. Except for the above, the results of the trial production evaluation in the same manner as in Example 1 are shown in Table 1.
[0021]
Comparative Example 1 A prototype was produced in the same manner as in Example 1, except that the composition was set to 0.003% by weight of Al, 0.015% by weight of Bi, and 0.05% by weight of In, and the liquid cooling medium was not sprayed during spraying. Table 1 shows the results of the evaluation.
[0022]
Comparative Example 2 The composition was set to 0.0005% by weight of Al, 0.03% by weight of Bi, and 0.05% by weight of In, and the powder particles were immersed in liquid nitrogen immediately after spraying. Other than that, the result of the trial production evaluation in the same manner as in Example 1 is shown in Table 1.
[0023]
[Comparative Example 3] A zinc alloy powder having a composition of 0.003% by weight of Al, 0.015% by weight of Bi, and 0.05% by weight of In was prepared at 200 ° C without cooling treatment by spraying liquid. Table 1 shows the results of the prototype evaluation in the same manner as in Example 1 except that the heat treatment was performed for 2 hours.
[0024]
From these results, the zinc alloy powder according to the present invention suppresses the amount of generated gas, and improves the pulse discharge performance over the zinc alloy powder according to the same comparative example except that the cooling treatment of liquid spraying is not performed. It is clear that there is.
[0025]
【The invention's effect】
The zinc alloy powder for an alkaline battery according to the present invention has both improved heavy-load pulse discharge performance and reduced gas generation by miniaturizing the crystal grains of the zinc alloy powder. By adding a part to which the liquid is sprayed, a conventional powder production apparatus for producing a powder by atomizing a zinc alloy solution can be used substantially as it is, and a production effect that the production can be efficiently performed at low cost is also achieved.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a gas generation measuring device.
FIG. 2 is a longitudinal sectional view of a prototype battery.
FIG. 3 is a graph showing the relationship between the particle size of powder particles and the number of crystal particles.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 zinc alloy powder 2 electrolyte 3 liquid paraffin 4 silicon stopper 5 female pipette 6 positive electrode can 7 positive electrode active material 8 separator 9 negative electrode active material 10 negative electrode current collector rod 11 rubber packing 12 cap

Claims

The average number N of crystal grains in a 0.1 mm square of the cross section of the powder particles at each particle size of −200 mesh, +200 to −150 mesh, +150 to −100 mesh, and +100 to −50 mesh is 200 mesh, 150 mesh, respectively. A zinc alloy powder for an alkaline battery, wherein N> −20.5 Ln (x) +126.9 with respect to a size x μm of 100 mesh and 50 mesh.

The average number N of crystal grains in a 0.1 mm square of the cross section of the powder particles at each particle size of −200 mesh, +200 to −150 mesh, +150 to −100 mesh, and +100 to −50 mesh is 200 mesh, 150 mesh, respectively. A zinc alloy powder for an alkaline battery, wherein N ≧ −36.2 Ln (x) +218.6 with respect to a size x μm of 100 mesh and 50 mesh.

The zinc alloy powder for an alkaline battery according to claim 1, wherein the powder substantially comprises particles of −20 mesh.

Consisting essentially of particles of -20 mesh, average crystal particles in 0.1 mm square of the cross section of the powder particles at each particle size of -200 mesh, +200 to -150 mesh, +150 to -100 mesh and +100 to -50 mesh A zinc alloy powder for an alkaline battery, wherein the number N is 40 or more, 30 or more, 20 or more, and 5 or more, respectively.

The zinc alloy is at least one selected from the group consisting of BiＢ0.001 to 0.1% by weight and In 0.01 to 0.1% by weight, and a group consisting of an alkali metal, an alkaline earth metal, Al and Ga. The alkaline battery according to claim 1, wherein the zinc alloy contains 0.0001 to 0.1% by weight of at least one metal selected from the group consisting of: Zinc alloy powder.

The alkaline zinc battery according to any one of claims 1 to 5, wherein the zinc alloy solution is rapidly cooled by spraying a liquid onto dispersed solution particles generated by atomizing the solution of the zinc alloy to refine the crystal particles. Manufacturing method of zinc alloy powder.

The method according to claim 6, wherein the liquid is a substance in a liquid phase or a gas phase at room temperature.

An alkaline battery comprising the zinc alloy powder according to claim 1 as a negative electrode active material.