JP2004281160A

JP2004281160A - Sealed nickel zinc primary battery and its manufacturing method

Info

Publication number: JP2004281160A
Application number: JP2003069247A
Authority: JP
Inventors: Natsuki Toyoda; 夏樹豊田
Original assignee: Toshiba Battery Co Ltd
Current assignee: FDK Twicell Co Ltd
Priority date: 2003-03-14
Filing date: 2003-03-14
Publication date: 2004-10-07
Anticipated expiration: 2023-03-14
Also published as: JP4357191B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed nickel zinc primary battery preventing performance drop caused by breakage of a positive electrode molding when the battery is assembled, and to provide a manufacturing method by which battery performance is enhanced and manufacturing efficiency is enhanced in the sealed nickel zinc primary battery using a nickel oxide of higher order as a positive electrode active material. <P>SOLUTION: In the sealed nickel zinc primary battery manufactured by molding a mix having the nickel oxide of higher order as the positive electrode active material in the hollow cylindrical positive electrode molding, and inserting the positive electrode molding into a cylindrical metallic can, 0.5-20 mass percent manganese dioxide is added to the positive electrode active material. The battery enhances an effect by molding the positive mix with a mold, inserting the positive electrode mold into the metallic can without applying pressure to assemble the battery. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明はニッケル高次酸化物を正極活物質とする密閉形ニッケル亜鉛一次電池及びその製造方法に関する。
【０００２】
【従来の技術】
最近、携帯電子機器の普及に伴い、電池の高容量化及び高率放電特性改善の要請が強く、アルカリ亜鉛一次電池の正極活物質については、従来より放電持続時間の向上を目的として、正極合剤中の黒鉛など、発電要素とはならない炭素系導電材の含有量を減少させて正極活物質の含有量を増加させることが検討されてきた。また、高率放電特性を改善するために、従来正極活物質として広く用いられてきた二酸化マンガンに代えて、水酸化ニッケル系化合物のようなニッケル高次酸化物を正極活物質として用いることが検討されている（特許文献１参照）。
しかしながら、この電池においては、最近の携帯電子機器に用いる際に要求される高負荷特性が十分ではなく、この点の改善が望まれている。近年、この特性を改善した電池として、ニッケル高次酸化物を正極活物質とした密閉形ニッケル亜鉛電池の開発が進められている。
【０００３】
このニッケル高次酸化物を正極活物質とする密閉形アルカリ亜鉛一次電池は、中空円筒状に成型された正極材料を、正極となる容器に収容し、正極合剤の内部にセパレータを介してゲル状負極材料を配置して電池として構成している。
【０００４】
この電池について、図１を用いて詳細に説明する。図１がいわゆるインサイドアウト構造（電池缶体が正極側、電池蓋側が負極側となっている構造）と呼ばれているＪＩＳ規格のＬＲ６形（単３形）の電池の断面図である。
図１において１は、正極端子を兼ねる有底円筒形の金属缶であり、この金属缶１の内部に、正極活物質を含有する正極合剤を、正極成形体成形用金型を用いて中空円筒状に成形された正極成形体２が金属缶１の内面に接触するように収容されている。この正極成形体２の中空内部には不織布などからなる有底円筒状のセパレータ３を介して、すでに一般に公知のゲル状亜鉛負極材料４が充填されている。そして、この負極材料４には金属棒からなる負極集電棒５が挿着され、この負極集電棒５の一端は負極材料４の表面から突出してリング状金属板７及び陰極端子を兼ねる金属封口板８に電気的に接続されている。そして、正極となる金属缶１内面と、負極集電棒５の突出部外周面には、二重環状のポリアミド樹脂からなる絶縁ガスケット６が配設され、これらは絶縁されている。また、金属缶１の開口部はかしめられて液密に封止されている。
前記正極成形体２は、通常３個を重ねて電池容器に収容されている。
【０００５】
ところで、ニッケル高次酸化物を正極活物質とする合剤を中空円筒形状の正極成形体に成形し、筒状の正極となる金属缶に挿入すると、ニッケル高次酸化物を正極活物質とする正極合剤は、正極成形体の成形時に金型への合剤の付着が多く、成形体の寸法変動が大きい。その為、密閉形ニッケル亜鉛一次電池においては、筒型金属缶内の所定の位置に成形体を収める為、金属缶と成形体の密着性を高めるために、筒型金属缶に成形体を挿入後、再加圧工程を必要としている。挿入後の再加圧工程では、成形体の中空部にコア棒を挿入後、上杵で成形体を高さ方向に圧縮している。結果として成形体は径方向に膨張するので、正極缶内壁およびコア棒に密着する。その後上杵およびコア棒を引き抜き所定寸法としている。
【０００６】
この工程で、かかる密閉形ニッケル亜鉛一次電池においては、成形高さの変動により再加圧前の高さ寸法が高くなる、すなわち再加圧時の高さ方向の圧縮量が大きくなると、合剤の高さ方向での粗密差が大きくなり、コア棒引き抜き時の金型への食いつきが大きくなる。それによって、再加圧後の合剤に亀裂が入りやすくなり、最悪の場合、合剤の欠損が生じる。合剤の欠損が生じると、合剤重量が狙い値よりも小さくなる為、電解液量および負極容量とのバランスが崩れるため、電池性能低下を引き起こす原因となっていた。
【０００７】
【特許文献１】特開２０００−０４８８２７号公報
【０００８】
【発明が解決しようとする課題】
本発明は、前記ニッケル高次酸化物を正極活物質とする密閉形ニッケル亜鉛一次電池において、電池組み立て時の正極成形体の破損に基づく電池性能の低下を防止することのできる密閉形ニッケル亜鉛一次電池、および、電池性能に優れ、かつ、製造効率に優れた製造方法を実現するものである。
【０００９】
【課題を解決するための手段】
第１の本発明は、ニッケル高次酸化物を正極活物質とする合剤を中空円筒形状の正極成形体に成形し、筒状の金属缶に挿入した密閉型ニッケル亜鉛一次電池において、
前記正極活物質に対し、０．５〜２０質量％の二酸化マンガンを添加したことを特徴とする密閉型ニッケル亜鉛一次電池である。
【００１０】
第２の本発明は、ニッケル高次酸化物を正極活物質とする合剤を中空円筒形状の正極成形体に成形し、筒状の金属缶に挿入する密閉型ニッケル亜鉛一次電池の製造方法において、
ニッケル高次酸化物、および前記ニッケル高次酸化物に対して０．５〜２０質量％の割合で二酸化マンガンを含む合剤を正極成形体成形金型に充填し、加圧成形して中空円筒状の正極成形体を製作する工程、
前記正極成形体を前記金属缶内部に挿入し、加圧することなく、正極成形体を前記容器内に配置させる工程、
および、前記正極成形体の中空内部にセパレータ、及びゲル状負極を充填し、負極集電棒を前記ゲル状負極に挿入して電池を組み立てる工程を少なくとも備えたことを特徴とする密閉型ニッケル亜鉛一次電池の製造方法である。
【００１１】
【発明の実施の形態】
以下本発明の実施の形態について詳細に説明する。
本発明の密閉形ニッケル亜鉛一次電池において、正極として用いられる正極合剤は、オキシ水酸化ニッケル系化合物あるいは表面にコバルト系化合物を被着したオキシ水酸化ニッケル系化合物粒子に、二酸化マンガン粒子および必要に応じて炭素粒子のような導電剤、バインダー、潤滑剤等の添加成分を配合したものであり、これを金型を用いて加圧して中空円筒状の正極成形体に成形する。
この際にニッケル高次酸化物からなる正極活物質に二酸化マンガン粒子を添加することにより、正極成形体の製造時に成形寸法の変動を抑止することができる。これは正極合剤を金型に充填し、加圧成形した場合、ニッケル高次酸化物を含有する正極合剤が加圧によって金型内面に付着して、正極成形体を金型から取り出した後、金型内部に残留する現象が発生するが、二酸化マンガン粒子を添加すると、金型に付着した正極合剤がこの二酸化マンガン粒子によって削り取られ、その結果、金型内部に正極合剤が付着残留する現象が防止される為と考えられる。
【００１２】
このように、二酸化マンガン粒子を配合した正極合剤を用いて成形した正極成形体は、成形時の材料減耗が少なく、成形寸法の変動が少ないため、この正極成形体を金属缶に収容し再加圧した場合の圧縮率変動も小さくなり、再加圧後の合剤の高さ方向での粗密差が減少し、その結果、正極成形体の破損率が減少する。上記正極合剤の減耗防止には、ニッケル高次酸化物に対して、二酸化マンガン粒子を少なくとも０．５質量％配合することが必要であり、３質量％以上添加することがさらに好ましい。
一方、二酸化マンガンを添加することによって、ニッケル高次酸化物を正極活物質とした密閉型ニッケル亜鉛一次電池の特徴であるハイレートパルス特性が低下することも確認している。具体的には１２００ｍＡの電流を３秒間放電させた後７秒間開放する過程を開路電圧が０．９Ｖに低下するまでのパルス放電持続時間で比較すると、２０％以上添加したもので、４％以上の性能ダウンが認められる。従って、二酸化マンガン粒子の正極合剤への添加量は、２０質量％以下、より好ましくは、７質量％以下である。
【００１３】
以上に説明したように、本発明においては、ニッケル高次酸化物を含有する正極活物質に、０．５〜２０質量％の二酸化マンガン粒子を配合することにより、正極成形体の破損を効果的に防止するものである。
【００１４】
また、本発明において、正極活物質に二酸化マンガン粒子を添加することにより、成形寸法の変動が小さくなり成形工程での寸法管理が容易になる為、あらかじめ金属缶に適合するように合剤寸法に成形し、筒型の金属缶に挿入するだけで金属缶と正極成形体とが十分接触し狙った電池特性を得ることが出来る。これによって前記金属缶に収容した正極成形体の再加圧成形工程が不要となり、製造設備の設置スペースの縮小、消費電力削減、管理工数の削減が可能となる．さらに再成形後の合剤の欠損は事実上皆無となり、製造した電池の電池性能不良を低減できる。
【００１５】
以下、本発明を適用した電池の実施の形態について、図面を参照しながら詳細に説明する。
（正極合剤及び正極成形体）
本発明の正極成形体は、ニッケル高次酸化物からなる正極活物質、二酸化マンガン粒子、及び必要に応じて導電性付与剤としての炭素系導電材、ポリオレフィン等のバインダー、及びその他の添加剤成分からなる正極合剤材料を顆粒状に成形し、その表面に必要に応じて潤滑剤を被覆し、所要形状に成形したものである。
【００１６】
本実施の形態において用いる二酸化マンガン粒子としては、例えば電解によって製造された電解二酸化マンガンを破砕して得られる二酸化マンガン粒子を用いることができる。この二酸化マンガンとしては、粒径範囲が、１０〜８０μｍの範囲のものが適切である。この粒径範囲が上記範囲を下回った場合、正極成形体成形時の金型への原料残留を防止することが困難になり、成形体破損の可能性が大きくなる。一方、粒径範囲が上記範囲を上回った場合、金型への原料残留防止に必要な添加量が増加し性能低下の問題が発生して好ましくない、
【００１７】
本発明において用いられる前記正極活物質であるニッケル高次酸化物としては、水酸化ニッケル系化合物、すなわち、水酸化ニッケル、およびオキシ水酸化ニッケルがあげられる。これらの内、オキシ水酸化ニッケルが高濃度である程、電池電圧が高く、放電容量も増すという点で望ましい。
【００１８】
さらに、正極活物質である水酸化ニッケル系化合物自体が、亜鉛もしくはコバルト単独あるいはその両方と共晶しているものであることが、低電解液比率でも安定した放電が行えることから好ましい。水酸化ニッケル系化合物に共晶させる亜鉛もしくはコバルトの量としては、４．０〜１２．０％の範囲が好ましい。亜鉛の量がこの範囲を下回ると、利用率低下の問題が発生し、またこの範囲を上回ると、比重低下により容量密度が低下する問題があるからである。
【００１９】
また、かかる水酸化ニッケル系化合物粒子の表面には、オキシ水酸化コバルト、三酸化二コバルト、一酸化コバルト、水酸化コバルト、金属ニッケル、金属コバルトより選ばれる少なくとも一つの物質により被覆されていることが望ましい。電気伝導度の高い物質によりオキシ水酸化ニッケルの表面が被覆されることで、正極全体の電気伝導性が高まり、放電容量、高率放電特性が向上するので好ましい。これらの物質の内でも、オキシ水酸化コバルト、金属ニッケル、金属コバルトを用いることが、より導電性が高いという理由で好ましい。
【００２０】
かかる被覆層の量は、正極活物質に対して、２．０〜６．０質量％の範囲が望ましい。被覆層の量がこの範囲を上回ると、コスト高の問題が生じ、またこの範囲を下回ると、集電性低下の問題が生じて好ましくない。
【００２１】
また、上記水酸化ニッケル系化合物からなる正極活物質に、Ｙ、Ｅｒ、Ｙｂ、Ｃａの化合物を添加することにより、貯蔵時の容量維持率を改善することができる。本発明において用いられる上記化合物としては、例えばＹ_２Ｏ_３、Ｅｒ_２Ｏ_３、Ｙｂ_２Ｏ_３、などの金属酸化物、およびＣａＦ_２などの金属フッ化物があげられる。これらの金属酸化物および金属フッ化物は、正極活物質であるニッケル水酸化物に対して、０．１〜２質量％の範囲で用いることができる。金属酸化物もしくは金属フッ化物の配合量が上記範囲を下回った場合、貯蔵特性の改善効果が得られず、一方配合量が上記範囲を上回った場合、相対的に正極活物質の量が減るので高容量化に適さなくなるため好ましくない。
【００２２】
上記本発明で用いる水酸化ニッケル系化合物の製造方法は、本出願人の出願である特願２００１−３１０３２３号に詳細に説明されており、本発明においても、この出願に記載されている水酸化ニッケル系化合物を用いることが好ましい。
【００２３】
また、本発明において用いられる炭素系導電材としては、黒鉛、カーボンブラックなど公知の電池用炭素系導電材を用いることができるが、特に黒鉛が好ましい。
さらに、本発明において用いるバインダーとしては、電池の正極合剤用バインダーとして公知の物質を用いることができるが、そのうちでポリオレフィンが好ましい。本発明において、ポリオレフィンを添加する理由は、正極合剤において黒鉛を減量した場合、正極合剤の結着性が低下し、正極合剤の保形性が低下するのを防止するものであり、黒鉛より少量で正極合剤成分を結着することができる。本発明においては、ポリオレフィンとして、ポリエチレン及びポリプロピレンが挙げられる。これらのポリオレフィンは、正極合剤に粒子状で添加される。その平均粒径は、およそ５〜５００μｍの範囲が好ましい。
また、正極合剤には、正極合剤成型時に電解液を混合することにより成形性及び導電性を改善することができる。
【００２４】
上記正極合剤において用いられる正極合剤材料の成分の配合比率は、正極合剤：炭素系導電材：バインダーが、質量比にして１００：３〜１２：０．０５〜０．５の範囲が好ましい。
炭素系導電材の量がこの範囲を下回った場合、放電容量は向上するが、正極活物質の導電性が低下し、起電力が低下するとともに重負荷放電特性が低下する。一方、上記範囲を上回った場合、成形性、成形作業性は良好となるが、正極活物質の量が制限されるため、放電容量が低下する。
また、バインダーの量がこの範囲を下回った場合、成形体の強度が低く電池制作時に歩留まりが低下する。一方、バインダーの量がこの範囲を上回った場合、正極活物質の量が制限されるため、放電容量が低下する。
【００２５】
（正極合剤の製造）
以下、本発明の正極合剤の製造について、そのプロセスを示す図２を用いて、より詳細に説明する。
図１中、２１ないし２４が、本発明において用いる原材料であり、Ｓ２１ないしＳ２７が製造過程の工程であり、２５が得られる正極合剤である。以下これらの工程を順次説明する。
【００２６】
（Ｓ２１：ドライ攪拌）
正極活物質であるニッケル高次酸化物に、二酸化マンガン粒子及び炭素系導電材粉末を加え万能攪拌ミキサーにてドライ攪拌する。
【００２７】
（Ｓ２２：ウェット攪拌）
上記ドライ攪拌によって得られた混合粉末１００質量部に対し、電解液を添加して万能攪拌ミキサーにてウェット攪拌する。この工程により、上記ドライ攪拌で混合した正極合剤成分粉末が、相互に凝着し成形可能となる。この工程において用いる電解液の量は、正極合剤成分１００質量部に対して、２〜７質量部程度である。
【００２８】
（Ｓ２３：圧縮）
上記工程において配合された正極合剤は、次いで、ローラコンパクタと呼ばれるロール状プレス機によって圧縮加圧され、造粒のために充填密度を高められる。このローラコンパクタは、双ロール間に正極合剤を供給し、加圧して充填密度を高めるものであり、圧縮応力は、印加力をローラ幅で割った０．５×１０４〜５×１０４Ｎ／ｃｍの範囲のものが好ましく、１．５×１０４〜３．５×１０４Ｎ／ｃｍの範囲がより好ましい。これによって、１ｍｍ以下の厚さの板状の被圧縮物が得られる。
【００２９】
（Ｓ２４：破砕）
上記工程によって処理された正極合剤は、圧縮塊状となっている。これを用いて成形体を作製するためには一旦粒状に造粒する必要がある。そのためにロール表面に互いに嵌合する突起を有する双ロールを用いたグラニュレータによる破砕処理を行う。圧縮塊状に成形された正極合剤はこのグラニュレータに通すことによって、粒状に破砕される。
【００３０】
（Ｓ２５：篩い分け）
次に、１４〜６０メッシュの自動篩分機にて分級して、粒径２５０〜１１８０μｍ程度の顆粒状正極合剤を選別し分級する。
【００３１】
（Ｓ２６：混合攪拌）
上記工程によって得られた顆粒状合剤に、所望に応じてエチレンビス飽和脂肪族アミド粉末のような潤滑剤を所定量添加し、混合攪拌する。これまでの工程によって、エチレンビス飽和脂肪酸アミド粉末を顆粒状正極合剤表面に付着させた顆粒状合剤が製造される。
【００３２】
（Ｓ２７：成形）
上記工程で造粒された顆粒状正極合剤粒子は、次いで、金型を用いて正極合剤に成形される。
インサイドアウト型電池の正極合剤は、中空円筒状をしており、中央のマンドレルを有し、所要の体積を有する円筒形状の金型中に上記正極合剤粒子を充填して、雄型を圧入することにより成形が行われる。このときの成形圧力は、０．５×１０８〜９．８×１０８Ｐａの圧力が好ましい。成形圧力が上記範囲を下回った場合、必要な正極合剤の充填密度が得られず、また、粒子同士の接触も確保しにくくなるので、電池とした場合、所定の放電容量が得られない。一方、成形圧力が上記範囲を上回った場合、正極合剤中に電解液が浸透しにくくなり、その利用率を下げてしまう。
【００３３】
（Ｓ２８：電池組み立て工程）
次いで、上記工程までで得られた正極成形体を用いて、密閉形電池を製造する。まず、金属缶に正極成形体を収納する。この際、正極成形体に圧力を加えて、正極缶と正極成形体との密着性を高めてもよいが、上記工程で製造された正極成形体は、寸法精度が向上しているため、強いて加圧することなく金属缶に挿着しても、金属缶と正極成形体とが十分密着し、必要な電気的接続が得られる。さらに、この加圧によって、正極成形体の破損が生じる可能性が高まり、かえって加圧によって電池性能が低下することが考えれられるので、正極成形体を金属缶に収容する際に加圧する必要はない。
次いで、図１に見られるように、正極成形体の中央の空所に、有底円筒状のセパレータ紙を配置し、その内部にゲル状負極を充填する。そして、このゲル状負極内部に負極集電棒を挿着し、以降、リング状金属板、金属封口板、絶縁ガスケット等を所定の位置に配置し、金属缶の開口端部をかしめ封口して電池を組み立てることができる。
【００３４】
【実施例】
（試験例１）
まず、ニッケル高次酸化物であるオキシ水酸化ニッケルに対して、表１に示す量の二酸化マンガン粒子及び７質量％の黒鉛を配合し、顆粒状合剤を造粒した。これをＪＩＳ規格ＬＲ６形（単３形）用のサイズの円筒状の成形型に充填し、加圧成形して正極成形体を得た。この工程を複数回繰り返し、得られる正極成形体の高さを測定し、成型工程の実施回数と正極成形体の高さの関係を調べた。その結果を図３に示す。
【００３５】
図３の結果から、二酸化マンガン粒子を０．５質量％以上添加した正極合剤を使用した正極成形体においては、成形体高さの変化率が顕著に低下していることが明かとなった。
【００３６】
また、正極端子を兼ねるＪＩＳ規格ＬＲ６形（単３形）用の有底円筒形の金属缶１内に上述した正極成形体を収納して、正極成形体の中空部にコア棒を挿入し、上杵によって加圧して正極成形体を金属缶１の缶壁に密着させて正極成形合剤２とした。更に正極成形合剤２の中空部にアセタール化ポリビニルアルコール繊維の不織布からなる有底円筒状セパレータ３を挿入した。このセパレータ３内にゲル状負極を充填し、図１に示したＪＩＳ規格ＬＲ６形（単３形）アルカリ電池を組み立てた。
【００３７】
上記工程によって得られた電池について、正極成形体の欠損の発生率を調査した。その結果を表１に併せて示す。
【００３８】
【表１】

【００３９】
表１の結果から、正極活物質に二酸化マンガンを０．５質量％添加した正極成形合剤の欠損発生率が、低下し、実用的であることが明かとなった。
【００４０】
（試験例２）
上記試験例１の電池の組み立て方法において、正極成形体を金属缶に収容する際に加圧せずに行ったこと以外試験例１と同様にして、電池を作成した。試験例１及び試験例２によって得られた電池について、１２００ｍＡの電流を３秒間放電させた後７秒間開放する過程を開路電圧が０．９Ｖに低下するまでのパルス放電持続時間を調べた。その結果を表２に示す。
【００４１】
【表２】

【００４２】
表２に見られるように、二酸化マンガン粒子を５０．０質量％添加した正極合剤を用いた電池においては、高負荷パルス放電特性が悪化していることが判明した。
【００４３】
【発明の効果】
以上に説明した本発明の密閉形ニッケル亜鉛一次電池によれば、電池組み立て時の正極成形体の破損に基づく電池性能の低下を防止することができる。
また、本発明の密閉形ニッケル亜鉛一次電池の製造方法によれば、電池性能に優れ、かつ、製造効率の改善された方法を実現することができる。
【図面の簡単な説明】
【図１】本発明により製造された密閉形アルカリ亜鉛一次電池をＪＩＳ規格ＬＲ６形（単３形）に応用した電池の断面図。
【図２】本発明の正極成形体の製造工程を示すプロセスフロー図。
【図３】本発明の製造方法の効果を示すグラフ。
【符号の説明】
１・・・正極缶
２・・・正極合剤
３・・・セパレータ
４・・・ゲル状亜鉛負極
５・・・負極集電棒
６・・・絶縁ガスケット
７・・・リング状金属板
８・・・金属封口板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sealed nickel-zinc primary battery using a nickel higher oxide as a positive electrode active material and a method for producing the same.
[0002]
[Prior art]
Recently, with the spread of portable electronic devices, there has been a strong demand for higher capacity and higher rate discharge characteristics of batteries. For positive electrode active materials of alkaline zinc primary batteries, a positive electrode active material has been used for the purpose of improving the discharge duration. It has been studied to increase the content of the positive electrode active material by reducing the content of a carbon-based conductive material that does not become a power generation element, such as graphite in the agent. In addition, in order to improve the high-rate discharge characteristics, a study is being made to use a nickel higher oxide such as a nickel hydroxide-based compound as the positive electrode active material instead of manganese dioxide, which has been widely used as the conventional positive electrode active material. (See Patent Document 1).
However, this battery does not have sufficient high load characteristics required for use in recent portable electronic devices, and it is desired to improve this point. In recent years, as a battery with improved characteristics, a sealed nickel-zinc battery using a nickel higher oxide as a positive electrode active material has been developed.
[0003]
The sealed alkaline zinc primary battery using the nickel higher oxide as a positive electrode active material contains a positive electrode material molded into a hollow cylindrical shape in a container serving as a positive electrode, and a gel inside the positive electrode mixture via a separator. A negative electrode material is arranged to form a battery.
[0004]
This battery will be described in detail with reference to FIG. FIG. 1 is a cross-sectional view of a JIS standard LR6 type (AA) battery called a so-called inside-out structure (a structure in which a battery can body is a positive electrode side and a battery lid side is a negative electrode side).
In FIG. 1, reference numeral 1 denotes a bottomed cylindrical metal can also serving as a positive electrode terminal. Inside the metal can 1, a positive electrode mixture containing a positive electrode active material is hollowed by using a positive electrode molded body molding die. A positive electrode molded body 2 formed into a cylindrical shape is accommodated in contact with the inner surface of the metal can 1. A generally known gelled zinc negative electrode material 4 is filled in the hollow interior of the positive electrode molded body 2 via a bottomed cylindrical separator 3 made of nonwoven fabric or the like. A negative electrode current collector 5 made of a metal bar is inserted into the negative electrode material 4, and one end of the negative electrode current collector 5 protrudes from the surface of the negative electrode material 4 and a ring-shaped metal plate 7 and a metal sealing plate also serving as a cathode terminal. 8 is electrically connected. An insulating gasket 6 made of a double annular polyamide resin is disposed on the inner surface of the metal can 1 serving as the positive electrode and on the outer peripheral surface of the protruding portion of the negative electrode current collecting rod 5, and these are insulated. The opening of the metal can 1 is caulked and sealed in a liquid-tight manner.
The positive electrode molded body 2 is usually housed in a battery container in a stack of three.
[0005]
By the way, when a mixture containing nickel higher oxide as a positive electrode active material is molded into a hollow cylindrical positive electrode molded body and inserted into a metal can to be a cylindrical positive electrode, the nickel higher oxide becomes a positive electrode active material. In the positive electrode mixture, a large amount of the mixture adheres to a mold during molding of the positive electrode molded body, and the dimensional variation of the molded body is large. Therefore, in a sealed nickel-zinc primary battery, the compact is inserted into a cylindrical metal can in order to increase the adhesion between the metal can and the compact in order to store the compact in a predetermined position in the cylindrical metal can. Later, a repressurization step is required. In the re-pressurizing step after insertion, after the core rod is inserted into the hollow portion of the molded body, the molded body is compressed in the height direction by the upper punch. As a result, the molded body expands in the radial direction, and thus closely adheres to the inner wall of the positive electrode can and the core rod. Thereafter, the upper punch and the core bar are pulled out to a predetermined size.
[0006]
In this step, in such a sealed nickel-zinc primary battery, when the height dimension before re-pressing is increased due to a change in molding height, that is, when the amount of compression in the height direction during re-pressing is increased, The difference in density in the height direction becomes large, and the bite into the mold when the core rod is pulled out increases. As a result, the mixture after re-pressurization tends to crack, and in the worst case, the mixture is deficient. When the mixture is deficient, the weight of the mixture becomes smaller than the target value, and thus the balance between the amount of the electrolyte and the capacity of the negative electrode is lost, thereby causing a decrease in battery performance.
[0007]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-048827
[Problems to be solved by the invention]
The present invention relates to a sealed nickel-zinc primary battery using the nickel higher oxide as a positive electrode active material, wherein a sealed nickel-zinc primary battery capable of preventing a decrease in battery performance due to breakage of a positive electrode molded body during battery assembly can be prevented. It is intended to realize a battery and a manufacturing method which is excellent in battery performance and excellent in manufacturing efficiency.
[0009]
[Means for Solving the Problems]
A first aspect of the present invention is a sealed nickel-zinc primary battery in which a mixture containing a nickel higher oxide as a positive electrode active material is formed into a hollow cylindrical positive electrode molded body and inserted into a cylindrical metal can.
A sealed nickel zinc primary battery, wherein 0.5 to 20% by mass of manganese dioxide is added to the positive electrode active material.
[0010]
The second present invention relates to a method for producing a sealed nickel-zinc primary battery in which a mixture containing nickel higher oxide as a positive electrode active material is formed into a hollow cylindrical positive electrode molded body and inserted into a cylindrical metal can. ,
A positive mold is filled with a nickel high-order oxide and a mixture containing manganese dioxide at a ratio of 0.5 to 20% by mass based on the nickel high-order oxide, and the mixture is pressed and molded to form a hollow cylinder. Manufacturing a positive electrode shaped body,
Inserting the positive electrode molded body inside the metal can, without pressurizing, disposing the positive electrode molded body in the container,
A sealed nickel zinc primary comprising at least a step of filling a separator and a gelled negative electrode in the hollow interior of the positive electrode molded body, and assembling a battery by inserting a negative electrode current collector into the gelled negative electrode. This is a method for manufacturing a battery.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
In the sealed nickel-zinc primary battery of the present invention, the positive electrode mixture used as the positive electrode includes nickel oxyhydroxide-based compound or nickel oxyhydroxide-based compound particles having a cobalt-based compound adhered on the surface, manganese dioxide particles and According to the above, an additive component such as a conductive agent such as carbon particles, a binder, or a lubricant is blended, and the mixture is pressurized using a mold to form a hollow cylindrical positive electrode molded body.
At this time, by adding manganese dioxide particles to the positive electrode active material composed of a nickel higher oxide, it is possible to suppress fluctuations in the molding dimensions during the production of the positive electrode molded body. This is because when the positive electrode mixture is filled in a mold and pressed, the positive electrode mixture containing a nickel higher oxide adheres to the inner surface of the mold by pressure, and the positive electrode molded body is taken out from the mold. Later, the phenomenon that remains in the mold occurs, but when manganese dioxide particles are added, the positive electrode mixture adhering to the mold is scraped off by the manganese dioxide particles, and as a result, the positive electrode mixture adheres inside the mold. It is considered that the residual phenomenon is prevented.
[0012]
As described above, since the positive electrode molded article formed using the positive electrode mixture containing manganese dioxide particles has a small amount of material consumption during molding and a small variation in molding dimensions, the positive electrode molded article is accommodated in a metal can and re-used. The variation in the compression ratio when pressurizing is also reduced, and the difference in density in the height direction of the mixture after re-pressing is reduced. As a result, the breakage rate of the positive electrode molded body is reduced. In order to prevent the positive electrode mixture from being worn down, it is necessary to mix at least 0.5% by mass of manganese dioxide particles with respect to the nickel higher oxide, and it is more preferable to add 3% by mass or more.
On the other hand, it has also been confirmed that the addition of manganese dioxide lowers the high-rate pulse characteristics that are characteristic of a sealed nickel-zinc primary battery using a nickel higher oxide as a positive electrode active material. Specifically, comparing the process of discharging a current of 1200 mA for 3 seconds and then opening for 7 seconds with the pulse discharge duration until the open-circuit voltage drops to 0.9 V, 20% or more is added, and 4% or more is added. Of the performance is recognized. Therefore, the amount of the manganese dioxide particles added to the positive electrode mixture is 20% by mass or less, more preferably 7% by mass or less.
[0013]
As described above, in the present invention, by mixing 0.5 to 20% by mass of manganese dioxide particles with the positive electrode active material containing a nickel higher oxide, damage to the positive electrode molded body can be effectively prevented. It is to prevent.
[0014]
In addition, in the present invention, by adding manganese dioxide particles to the positive electrode active material, fluctuations in molding dimensions are reduced, and dimensional control in the molding process is facilitated. By simply molding and inserting the battery into a cylindrical metal can, the metal can and the positive electrode molded body are sufficiently in contact with each other, and the intended battery characteristics can be obtained. This eliminates the need for a step of re-pressing the positive electrode molded body accommodated in the metal can, thereby reducing the installation space of manufacturing equipment, reducing power consumption, and reducing man-hours required for management. Furthermore, there is virtually no loss of the mixture after reshaping, and the battery performance of the manufactured battery can be reduced.
[0015]
Hereinafter, embodiments of a battery to which the present invention is applied will be described in detail with reference to the drawings.
(Positive electrode mixture and positive electrode molded body)
The positive electrode molded body of the present invention is a positive electrode active material composed of a nickel higher oxide, manganese dioxide particles, and, if necessary, a carbon-based conductive material as a conductivity-imparting agent, a binder such as polyolefin, and other additive components. The positive electrode mixture material is formed into granules, and the surface thereof is coated with a lubricant, if necessary, and formed into a required shape.
[0016]
As the manganese dioxide particles used in the present embodiment, for example, manganese dioxide particles obtained by crushing electrolytic manganese dioxide produced by electrolysis can be used. As this manganese dioxide, one having a particle size range of 10 to 80 μm is suitable. When the particle size range is below the above range, it is difficult to prevent the raw material from remaining in the mold at the time of molding the positive electrode molded body, and the possibility of breakage of the molded body increases. On the other hand, if the particle size range exceeds the above range, the amount of addition necessary to prevent the raw material remaining in the mold is increased, and the problem of performance deterioration occurs, which is not preferable.
[0017]
Examples of the nickel higher oxide as the positive electrode active material used in the present invention include nickel hydroxide-based compounds, that is, nickel hydroxide and nickel oxyhydroxide. Of these, the higher the concentration of nickel oxyhydroxide, the higher the battery voltage and the more desirable the discharge capacity.
[0018]
Further, it is preferable that the nickel hydroxide-based compound itself, which is a positive electrode active material, is eutectic with zinc or cobalt alone or both, since a stable discharge can be performed even at a low electrolyte solution ratio. The amount of zinc or cobalt to be co-crystallized with the nickel hydroxide compound is preferably in the range of 4.0 to 12.0%. If the amount of zinc is below this range, the problem of a decrease in utilization occurs, and if it exceeds this range, there is a problem that the capacity density decreases due to a decrease in specific gravity.
[0019]
Further, the surface of the nickel hydroxide-based compound particles is coated with at least one substance selected from cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, cobalt hydroxide, metallic nickel, and metallic cobalt. Is desirable. It is preferable that the surface of the nickel oxyhydroxide is coated with a substance having a high electric conductivity because the electric conductivity of the entire positive electrode is increased, and the discharge capacity and the high-rate discharge characteristics are improved. Among these substances, it is preferable to use cobalt oxyhydroxide, metallic nickel, and metallic cobalt because they have higher conductivity.
[0020]
The amount of the coating layer is desirably in the range of 2.0 to 6.0% by mass based on the positive electrode active material. If the amount of the coating layer exceeds this range, a problem of high cost arises, and if it is less than this range, a problem of a decrease in current collecting property occurs, which is not preferable.
[0021]
Further, by adding a compound of Y, Er, Yb, and Ca to the positive electrode active material composed of the nickel hydroxide-based compound, the capacity retention rate during storage can be improved. Examples of the compound used in the present invention include metal oxides such as Y ₂ O ₃ , Er ₂ O ₃ , and Yb ₂ O ₃ , and metal fluorides such as CaF ₂ . These metal oxides and metal fluorides can be used in the range of 0.1 to 2% by mass based on nickel hydroxide as the positive electrode active material. When the amount of the metal oxide or the metal fluoride falls below the above range, the effect of improving the storage characteristics cannot be obtained.On the other hand, when the amount of the metal oxide or the metal fluoride exceeds the above range, the amount of the positive electrode active material decreases relatively. It is not preferable because it is not suitable for increasing the capacity.
[0022]
The method for producing the nickel hydroxide-based compound used in the present invention is described in detail in Japanese Patent Application No. 2001-310323 filed by the present applicant, and in the present invention, the hydroxide described in this application is also described. It is preferable to use a nickel compound.
[0023]
As the carbon-based conductive material used in the present invention, known carbon-based conductive materials for batteries such as graphite and carbon black can be used, and graphite is particularly preferable.
Further, as the binder used in the present invention, a substance known as a binder for a positive electrode mixture of a battery can be used, and among them, polyolefin is preferable. In the present invention, the reason for adding the polyolefin is that when graphite is reduced in the positive electrode mixture, the binding property of the positive electrode mixture is reduced, and the shape retention of the positive electrode mixture is prevented from being reduced, The positive electrode mixture component can be bound in a smaller amount than graphite. In the present invention, the polyolefin includes polyethylene and polypropylene. These polyolefins are added to the positive electrode mixture in the form of particles. The average particle size is preferably in the range of about 5 to 500 μm.
In addition, moldability and conductivity can be improved by mixing the positive electrode mixture with an electrolytic solution at the time of molding the positive electrode mixture.
[0024]
The compounding ratio of the components of the positive electrode mixture material used in the positive electrode mixture is such that the mass ratio of the positive electrode mixture: the carbon-based conductive material: the binder is 100: 3 to 12: 0.05 to 0.5. preferable.
When the amount of the carbon-based conductive material falls below this range, the discharge capacity is improved, but the conductivity of the positive electrode active material is reduced, the electromotive force is reduced, and the heavy load discharge characteristics are reduced. On the other hand, when the ratio exceeds the above range, the moldability and the molding workability are improved, but the discharge capacity is reduced because the amount of the positive electrode active material is limited.
On the other hand, when the amount of the binder is less than the above range, the strength of the molded body is low, and the yield during battery production decreases. On the other hand, when the amount of the binder exceeds this range, the amount of the positive electrode active material is limited, so that the discharge capacity decreases.
[0025]
(Manufacture of positive electrode mixture)
Hereinafter, the production of the positive electrode mixture of the present invention will be described in more detail with reference to FIG. 2 showing the process.
In FIG. 1, 21 to 24 are raw materials used in the present invention, S21 to S27 are steps in the production process, and 25 is a positive electrode mixture obtained. Hereinafter, these steps will be sequentially described.
[0026]
(S21: dry stirring)
Manganese dioxide particles and a carbon-based conductive material powder are added to nickel higher oxide, which is a positive electrode active material, and dry-stirred with a universal stirring mixer.
[0027]
(S22: wet stirring)
An electrolytic solution is added to 100 parts by mass of the mixed powder obtained by the dry stirring, and the mixture is wet-stirred with a universal stirring mixer. By this step, the positive electrode mixture component powders mixed by the above-mentioned dry stirring adhere to each other and can be formed. The amount of the electrolytic solution used in this step is about 2 to 7 parts by mass based on 100 parts by mass of the positive electrode mixture component.
[0028]
(S23: compression)
Next, the positive electrode mixture compounded in the above step is compressed and pressed by a roll press machine called a roller compactor to increase the packing density for granulation. This roller compactor supplies a positive electrode mixture between twin rolls and increases the packing density by applying pressure. The compressive stress is 0.5 × 104 to 5 × 104 N / cm obtained by dividing the applied force by the roller width. Is preferable, and the range of 1.5 × 104 to 3.5 × 104 N / cm is more preferable. Thereby, a plate-shaped object to be compressed having a thickness of 1 mm or less is obtained.
[0029]
(S24: crush)
The positive electrode mixture treated in the above steps is in a compressed mass. In order to produce a molded body using this, it is necessary to granulate once into granules. For this purpose, a crushing process is performed by a granulator using a twin roll having projections fitted to each other on the roll surface. The positive electrode mixture formed into a compressed mass is crushed into granules by passing through the granulator.
[0030]
(S25: sieving)
Next, the particles are classified by an automatic sieve of 14 to 60 mesh to select and classify a granular positive electrode mixture having a particle size of about 250 to 1180 μm.
[0031]
(S26: mixing and stirring)
A predetermined amount of a lubricant such as ethylenebissaturated aliphatic amide powder is added to the granular mixture obtained in the above step, if desired, and mixed and stirred. By the steps described above, a granular mixture in which the ethylene bis-saturated fatty acid amide powder is adhered to the surface of the granular positive electrode mixture is produced.
[0032]
(S27: molding)
The granular positive electrode mixture particles granulated in the above step are then formed into a positive electrode mixture using a mold.
The positive electrode mixture of the inside-out type battery has a hollow cylindrical shape, has a central mandrel, and is filled with the positive electrode mixture particles in a cylindrical mold having a required volume to form a male mold. The molding is performed by press-fitting. The molding pressure at this time is preferably 0.5 × 108 to 9.8 × 108 Pa. If the molding pressure is lower than the above range, the required filling density of the positive electrode mixture cannot be obtained, and it is difficult to secure the contact between the particles. Therefore, when the battery is used, a predetermined discharge capacity cannot be obtained. On the other hand, when the molding pressure exceeds the above range, the electrolyte does not easily penetrate into the positive electrode mixture, and the utilization rate decreases.
[0033]
(S28: Battery assembly process)
Next, a sealed battery is manufactured using the positive electrode molded body obtained through the above steps. First, the positive electrode molded body is stored in a metal can. At this time, pressure may be applied to the positive electrode molded body to increase the adhesion between the positive electrode can and the positive electrode molded body. However, since the dimensional accuracy of the positive electrode molded body manufactured in the above process is improved, it is strongly required. Even if the metal can is inserted into the metal can without pressing, the metal can and the positive electrode molded body are sufficiently adhered to each other, and necessary electric connection can be obtained. Furthermore, the pressurization increases the possibility that the positive electrode molded article may be damaged, and it is considered that the pressurization may lower the battery performance. Therefore, it is not necessary to pressurize the positive electrode molded article in the metal can. .
Next, as shown in FIG. 1, a bottomed cylindrical separator paper is arranged in a central space of the positive electrode molded body, and the inside thereof is filled with a gelled negative electrode. Then, a negative electrode current collector rod is inserted into the inside of the gelled negative electrode, and thereafter, a ring-shaped metal plate, a metal sealing plate, an insulating gasket and the like are arranged at predetermined positions, and the open end of the metal can is swaged to seal the battery. Can be assembled.
[0034]
【Example】
(Test Example 1)
First, manganese dioxide particles in the amounts shown in Table 1 and 7% by mass of graphite were mixed with nickel oxyhydroxide, which is a nickel higher oxide, to granulate a granular mixture. This was filled into a cylindrical mold having a size for JIS standard LR6 type (AA type), and was subjected to pressure molding to obtain a positive electrode molded body. This step was repeated plural times, the height of the obtained positive electrode molded body was measured, and the relationship between the number of times of performing the molding step and the height of the positive electrode molded body was examined. The result is shown in FIG.
[0035]
From the results in FIG. 3, it was clarified that the rate of change in the height of the positive electrode molded article using the positive electrode mixture containing 0.5% by mass or more of manganese dioxide particles was significantly reduced.
[0036]
Further, the above-described positive electrode molded body is housed in a bottomed cylindrical metal can 1 for JIS standard LR6 type (AA type) also serving as a positive electrode terminal, and a core rod is inserted into a hollow portion of the positive electrode molded body. The positive electrode was pressed with an upper punch to bring the positive electrode molded body into close contact with the can wall of the metal can 1 to obtain a positive electrode molding mixture 2. Further, a bottomed cylindrical separator 3 made of a non-woven fabric of acetalized polyvinyl alcohol fiber was inserted into the hollow portion of the positive electrode molding mixture 2. The separator 3 was filled with a gelled negative electrode to assemble the LR6 (AA) alkaline battery according to JIS shown in FIG.
[0037]
With respect to the battery obtained by the above-described process, the incidence of defects in the positive electrode molded body was investigated. The results are shown in Table 1.
[0038]
[Table 1]

[0039]
From the results shown in Table 1, it was clarified that the defect generation rate of the positive electrode molding mixture obtained by adding 0.5% by mass of manganese dioxide to the positive electrode active material was reduced and was practical.
[0040]
(Test Example 2)
A battery was prepared in the same manner as in Test Example 1 except that the positive electrode formed body was placed in a metal can without applying pressure in the battery assembling method of Test Example 1 described above. With respect to the batteries obtained in Test Example 1 and Test Example 2, the process of discharging a current of 1200 mA for 3 seconds and then opening for 7 seconds was examined for the pulse discharge duration until the open circuit voltage was reduced to 0.9 V. Table 2 shows the results.
[0041]
[Table 2]

[0042]
As can be seen from Table 2, it was found that in the battery using the positive electrode mixture containing 50.0% by mass of manganese dioxide particles, the high-load pulse discharge characteristics were deteriorated.
[0043]
【The invention's effect】
According to the above-described sealed nickel-zinc primary battery of the present invention, it is possible to prevent a decrease in battery performance due to breakage of the positive electrode molded body during battery assembly.
Further, according to the method for manufacturing a sealed nickel-zinc primary battery of the present invention, it is possible to realize a method that is excellent in battery performance and has improved manufacturing efficiency.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a battery in which a sealed alkaline zinc primary battery manufactured according to the present invention is applied to a LR6 (AA) type JIS standard.
FIG. 2 is a process flow chart showing a manufacturing process of the positive electrode molded body of the present invention.
FIG. 3 is a graph showing the effect of the manufacturing method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Positive electrode can 2 ... Positive electrode mixture 3 ... Separator 4 ... Gel zinc negative electrode 5 ... Negative electrode current collecting rod 6 ... Insulating gasket 7 ... Ring-shaped metal plate 8 ...・ Metal sealing plate

Claims

In a sealed nickel zinc primary battery in which a mixture containing nickel higher oxide as a positive electrode active material is formed into a hollow cylindrical positive electrode molded body and inserted into a cylindrical metal can,
A sealed nickel-zinc primary battery, wherein 0.5 to 20% by mass of manganese dioxide is added to the positive electrode active material.

The sealed nickel zinc primary battery according to claim 1, wherein the manganese dioxide is added in an amount of 3 to 7% by mass based on the positive electrode active material.

In a method for producing a sealed nickel-zinc primary battery in which a mixture containing nickel higher oxide as a positive electrode active material is formed into a hollow cylindrical positive electrode molded body and inserted into a cylindrical metal can,
A positive mold is filled with a nickel high-order oxide and a mixture containing manganese dioxide at a ratio of 0.5 to 20% by mass based on the nickel high-order oxide, and the mixture is pressed and molded to form a hollow cylinder. Manufacturing a positive electrode shaped body,
Inserting the positive electrode molded body inside the metal can, without pressurizing, disposing the positive electrode molded body in the container,
A sealed nickel zinc primary comprising at least a step of filling a separator and a gelled negative electrode in the hollow interior of the positive electrode molded body, and assembling a battery by inserting a negative electrode current collector into the gelled negative electrode. Battery manufacturing method.

4. The method according to claim 3, wherein a ratio of the manganese dioxide to the nickel higher oxide is 3 to 7% by mass. 5.