JP2005026134A

JP2005026134A - Lead-acid battery

Info

Publication number: JP2005026134A
Application number: JP2003191888A
Authority: JP
Inventors: Isamu Kurisawa; 栗澤　　勇
Original assignee: Japan Storage Battery Co Ltd
Current assignee: Japan Storage Battery Co Ltd
Priority date: 2003-07-04
Filing date: 2003-07-04
Publication date: 2005-01-27
Anticipated expiration: 2023-07-04
Also published as: JP4487505B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-acid battery, in which there is solved the problem that an additive is decomposed and dissolves a current collector to shorten the life, although addition of lignin having a sulfone group as a dispersant and an active material binder in a positive active material raw material is effective to solve the problem that coating (filling) of a raw material to the current collector is difficult and handling of an electrode plate is difficult when a very thin electrode plate is adopted in the lead-acid battery. <P>SOLUTION: The lead-acid battery has a positive current collector having SnO<SB>2</SB>or Ta<SB>2</SB>O<SB>5</SB>-TiO<SB>2</SB>composite oxide on the surface and a positive active material body containing 0.1-0.5 mass % lignin having the sulfone group and 0.5-4 mass % the active material binder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は鉛蓄電池に関する。
【０００２】
【従来の技術】
近年、環境対策のためにハイブリッド自動車や燃料電池自動車などの普及推進が高まる中で、これらの動力源および電源装置といったパワーソースのより小形化および低コスト化の要望が高くなっている。その対策の一つとして、急激な負荷変動によるパワー不足を負荷とパワーソースとの間でそれを補助する役目を果たす高出力性能を有する安価な二次電池のニーズがますます高まってきている。鉛蓄電池は、安価な材料からなる二次電池としてこのニーズの有力な候補の一つであるが、他の二次電池、例えばリチウムイオン電池あるいはニッケル−水素電池に比べて出力特性の劣る問題があった。
【０００３】
鉛蓄電池の出力特性を高める手段としては、極板をなるべく薄くして極板枚数を増やす、すなわち極板の見かけの表面積を大きくすることが効果的であることは既に周知であるが、薄い極板を製造するには、まず、鉛粉と硫酸および水とを練合して作製されたペースト状原料を、集電体に薄く均一に塗布（充填）する必要があり、また、極板に占める集電体の質量を極力小さくするために集電体を薄く、しかも軽くする必要がある。ところが、従来の原料は、練膏中に二次粒子が凝集して塊となりペースト状原料中に散在するために、上記の薄く湾曲しやすい集電体にペースト状原料を薄く均一に塗布（充填）することが困難であった。また、薄く湾曲しやすい集電体にペースト状原料を塗布（充填）した極板を乾燥後、持ち上げた時に湾曲して塗布（充填）された活物質が集電体から剥離し、脱落してしまうという問題をも抱えている。
【０００４】
これに対して、スルホン基を有するリグニンを分散剤として活物質に添加して、前述の二次粒子の生成を抑制することで集電体への塗布を容易にしようとする試みがこれまでにも検討されている。また、組立時の極板のハンドリング性を改善するためには、例えば変性スチレン・ブタジエン・共重合体ラテックスあるいはエチレン／アクリル酸共重合体等の活物質結着剤をペースト状原料に添加して乾燥後の集電体と活物質との密着性を高めるといったことも検討されてきた。
【０００５】
【発明が解決しようとする課題】
しかしながら、上述したこれらの解決方法を鉛蓄電池の正極板に対して採用することは困難であった。何故ならば、鉛蓄電池においては希硫酸からなる電解液中で正極板が高いアノード電位に晒されるためにリグニンや活物質結合剤等の高分子量有機物が正極活物質中に含まれているとアノード酸化を受け、分解されて酢酸などの低分子量の有機酸が生成される。前記有機酸は従来の鉛あるいは鉛合金からなる正極集電体を溶かしてしまうので、正極集電体の腐食劣化が促進し、鉛蓄電池が短寿命になる問題を抱えていた。
【０００６】
また、上記有機物は、最終的に炭酸ガスとなって分解されて消失してしまうが、発生時に集電体と正極活物質との密着性を低下させる傾向にある。特に薄い集電体では、従来の厚形の格子状集電体に比べて３次元的に活物質を包み込み、保持する機能が劣るために、活物質の充・放電による体積変化による応力などによって、集電体と活物質との結合が早期に維持できなくなって、両者の電気的接触が乏しくなり電気容量が取り出せなくなってしまう問題をも有している。
【０００７】
したがって、本発明が解決しようとする課題は、正極活物質にリグニンおよび活物質結着剤を含有させても上述した問題点、集電体の溶解および活物質と集電体との乖離といった問題が発生しない、超薄型極板を備えた鉛蓄電池を提供することにある。
【０００８】
【課題を解決するための手段】
課題を解決するための手段として、請求項１によれば、表面にＳｎＯ_２あるいはＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物を有する正極集電体と、スルホン基を有するリグニンを０．１〜０．５質量％、活物質結着剤を０．５〜４質量％含有する正極活物質体とを備えた正極板を有することを特徴とするものである。
【０００９】
なお、正極活物質体とは、正極活物質と、リグニンと、活物質結着剤と、必要によっては添加される短繊維等の添加剤との集合体を意味する。従って、スルホン基を有するリグニンが０．１〜０．５質量％とは、前記集合体に占めるリグニンの割合が０．１〜０．５質量％であることを意味し、活物質結着剤が０．５〜４質量％とは、前記集合体に占める活物質結着剤の割合が０．５〜４質量％であることを意味する。
【００１０】
１ｍｍ以下の超薄型正極板を製造する場合に、正極集電体へのペースト状原料の塗布（充填）を容易にするために分散剤としてスルホン基を有するリグニンを原料に添加する、あるいは正極活物質の脱落を防止するための活物質結着剤を添加すると、正極のアノード酸化により高分子量有機物からなるこれら添加剤が分解し、低分子量の有機酸、例えば酢酸を生成し、正極集電体を構成している鉛あるいは鉛合金を溶解するため正極の腐食が進行し、早期に寿命に至ったが、正極集電体表面にＳｎＯ_２あるいはＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物をコーティングすればこれらは酢酸等の有機酸に対しても安定で集電体の溶解を防止できる。
【００１１】
なお、表面のコーティングは、できるだけ集電体の全表面に行うのが好ましいが、必ずしも全表面に行わなくても相応の効果がある。
【００１２】
さらに、リグニンおよび活物質結着剤は最終的には分解して炭酸ガスを発生することがあるので正極集電体と正極活物質とを１０×１０^４〜３０×１０^４Ｐａの圧迫力で押さえることによって集電体からの正極活物質の乖離が回避でき、寿命性能の安定化という点でより好ましい。
【００１３】
以上により、１ｍｍ以下といった超薄型正極板の製造上の問題点が解決できると共に前記添加剤の存在による鉛蓄電池の二次的な性能劣化が回避でき、出力特性が優れ、しかも寿命性能の安定した鉛蓄電池が得られる。
【００１４】
【実施例】
図１は、本発明に基づく実施例の蓄電池の構造を模式的に示す要部断面図で、１は正極集電体、２は該正極集電体にコーティングしたＳｎＯ_２からなる耐食性導電剤層、３は負極集電体、４は正極活物質、５は負極活物質、６は微細ガラス繊維からなるセパレータ、７は電槽、８は電解液が漏れないためのＯリング、９は排気孔、１０は制御弁をそれぞれ示す。
【００１５】
図１において、正極集電体１は厚み２００μｍのＰｂ−２質量％Ｓｎ合金箔からなり、該集電体表面にＳｎＯ_２をスパッタリング法によって厚み３００ｎｍのコーティングがなされている。負極集電体３には、鉛メッキをした厚み４０μｍの銅箔を用いた。正極活物質４および負極活物質５には、リグニンとしてリグニンスルフォン酸ソーダ、また、活物質結着剤として、変性スチレン・ブタジエン・共重合体ラテックスが添加されている。
【００１６】
図２は、３セルが一体になったモノブロックタイプの本発明の鉛蓄電池の構造を模式的に示す要部断面図で、１１は銅板からなる端子板、１２は圧迫用プレート、１３はボルト・ナットをそれぞれ示す。他の構成部材は図１と同じ番号を付記する。
【００１７】
図２に示すように、平板状の集電体の片面に活物質を塗布した形状の極板をセパレータを介して積層して極板群を形成した場合、集電体の反対側が端子の働きをするので極板群を重ねるだけでいわゆるモノブロックタイプの鉛蓄電池が容易に構成することができる。
【００１８】
次に、本発明の効果を具体的に示すために行った試験について説明する。
（試験１）
正極板および負極板には、図１に示す実施例の構成を採用し、正極板では集電体に厚み２００μｍの正極ペースト状原料を塗布した。その際、正極集電体へのＳｎＯ_２のコーティングありなし、正極活物質へのリグニンスルホンソーダおよび変性スチレン・ブタジエン・共重合体ラテックスの添加量を変えた正極板を作製した。その内容を表１に示す。
【００１９】
負極板についても、集電体に通常の負極ペースト状原料を２００μｍの厚みに塗布（充填）した。その際、リグニンスルフォン酸ソーダの添加量は、０．３質量％、変性スチレン・ブタジエン・共重合体ラテックスの添加量は、０．５質量％に固定した。
【００２０】
正・負極集電体へのペースト状原料の塗布（充填）は通常のペースティングマシンを用いて行った。
【００２１】
【表１】

【００２２】
上記の正極板の充填性および組み立て性の調査を行った。その結果表２に示す。
【００２３】
【表２】

【００２４】
（充填性）
充填性の評価は、集電体表面に均一に充填できたものを○、充填はできたが表面に原料の二次粒子が残り均一に充填できなかったものを△、二次粒子が多く充填ができなかったものを×とした。
【００２５】
表２に示すように、正極活物質厚みを２００μｍに制限した場合、リグニンスルフォン酸ソーダを添加していないＮｏ．１とＮｏ．４は、ペースト状原料中に二次粒子の塊が発生して集電体に前記原料を２００μｍの厚みに均一に充填できなかった。また、リグニンスルフォン酸ソーダ量が０．０５質量％添加したＮｏ．５もその効果が十分でなく、一応、充填はできたが二次粒子が僅かに存在し均一性に欠けた。一方、リグニンスルフォン酸ソーダ量が０．８質量％のＮｏ．１５ではペースト状原料が軟らかくなり過ぎて、逆に集電体上で２００μｍの厚みを維持するのが困難であった。以上から、正極集電体に活物質を薄く塗布するためのリグニンスルフォン酸ソーダの添加量は０．１〜０．５質量％が適切であることが分かった。
（蓄電池の組み立て性）
充填性において、○および△であった極板を用いて図１に示す構造の公称電圧１２Ｖ、定格容量１．０Ａｈの制御弁式鉛蓄電池の組み立てを試みた。
【００２６】
組み立て性の評価は、組み立てができたものを○、極板の不良率は高かったが蓄電池の組み立てが一応できたものを△、ほとんど極板の活物質が脱落し組み立てが不可能であったものを×とした。
【００２７】
表２に示すように、変性スチレン・ブタジエン・共重合体ラテックスの添加量が０質量％であったＮｏ．３およびＮｏ．７の正極板は組み立て時にほとんどの正極活物質が集電体から剥離し、組み立て不可能になった。また、前記添加量が０．２質量％のＮｏ．８の正極板は活物質結着の効果が不十分で極板不良率が高かったが、一応、蓄電池の組み立てはできた。添加量が０．５質量％以上になると、活物質に対する結着効果が現れ、その量が多くなるほど正極活物質が強固になり極板の取り扱いが容易になった。
【００２８】
組み立て時の正極板に対する圧迫力は２０×１０^４Ｐａとしたが、リグニンスルフォン酸ソーダを０．３質量％、変性スチレン・ブタジエン・共重合体ラテックスを０．７質量％添加した正極板では、正極板に対する圧迫力を種々かえた蓄電池（Ｎｏ．１６〜１８）を作製した。その内容を表３に示す
【表３】。

【００２９】
上記作製された蓄電池に所定の比重の希硫酸電解液を所定量注入し、電槽内で化成を行い蓄電池を完成させた。その際、変性スチレン・ブタジエン・共重合体ラテックスを６質量％添加した正極板を用いたＮｏ．１３の蓄電池は化成が十分にできず容量がでなかったので寿命試験は行わなかった。これは結着剤の添加量が多すぎて正極活物質の表面を覆ってしまい、化成反応が十分に行われなかったためと考えられる。
【００３０】
良好に化成のできた蓄電池については、６０℃の雰囲気中で、充電電圧、１３．６５Ｖの定電圧による加速トリクル（フロート）寿命試験を行い、１カ月毎に、１ＣＡの電流（１．０Ａ）で終止電圧１．７Ｖ／セルまで放電を行った。容量が初期の５０％以下になった時点を寿命とした。その試験結果を表４に示す。
【００３１】
【表４】

【００３２】
表４に示すように、正極集電体にＳｎＯ_２のコーティングを施さなかった蓄電池Ｎｏ．２は、３カ月で寿命になった。この蓄電池を解体して調査したところ、アノード酸化により正極板に添加されているリグニンスルフォン酸ソーダおよび変性スチレン・ブタジエン・共重合体ラテックスが分解され低分子量の有機酸になったために、集電体のＰｂ−２質量％Ｓｎ合金が溶解、すなわち、腐食が急速に進行して性能が劣化したことがわかった。
【００３３】
一方、表面にＳｎＯ_２をコーティングした集電体を用いた蓄電池は、前記添加剤が分解されても集電体が腐食されることがなく安定した寿命性能を示した。しかし、正極活物質に添加されている有機物は分解され最終的には炭酸ガス（ＣＯ_２）の発生を伴い、正極活物質を集電体から脱落させる傾向にあるので、蓄電池Ｎｏ．１６のように圧迫力が５×１０^４Ｐａでは、正極活物質の保持能力が低いために若干短寿命になった。一方、圧迫力が３０×１０^４Ｐａと高いものは正極活物質の脱落を防止し長寿命であった。
【００３４】
変性スチレン・ブタジエン・共重合体ラテックスの添加量では、組み立て時に活物質の結着性に有効に作用し、しかも化成時に悪影響を及ぼさなかった０．５〜４質量％の範囲では良好な寿命性能を示した。
【００３５】
リグニンに関しては、充填が良好に行えた添加量の範囲のものは勿論、充填性に問題のあった添加量０．０５質量％を含めて０．０５〜０．５質量％の範囲で良好な寿命性能を示した。しかし、充填性をも含めた場合、０．１〜０．５質量％の範囲が好ましいことはいうまでもない。
【００３６】
以上の試験の結果から、鉛蓄電池の出力特性を改善するために、超薄型極板を採用する場合の製造上の問題点を改善するためにリグニンスルフォン酸ソーダおよび変性スチレン・ブタジエン・共重合体ラテックスを正極活物質に添加する効果および前記添加剤が鉛蓄電池性能に悪影響を及ぼすことに対するＳｎＯ_２の効果が明らかになった。
【００３７】
実施例では、耐食性導電材にＳｎＯ_２を用いたが、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物を用いても同様の効果が得られることを本願発明者は、別の試験により確認している。
【００３８】
本実施例では、正極の集電体には平板形状のＰｂ−２質量％Ｓｎ合金箔を使用したが、特にこの形状にこだわるものでなく、平板に穿孔を設けてもよく、格子形状でも同様の効果が得られるのいうまでもない。
【００３９】
また、正極集電体にはＰｂ−２質量％Ｓｎ合金箔を用いたが、チタン（Ｔｉ）を用いることも可能で、そのことによって、前記鉛合金では集電体の厚みが２００μｍ程度が限界であったのが、４０μｍのものも使用可能で、さらに薄型で軽量な極板が実現可能である。その場合、鉛合金と違い融点が高いので５００℃の雰囲気で焼成法によって耐食性導電材をディップコーティングすることも可能である。
【００４０】
また、本実施例では活物質結着剤として、変性スチレン・ブタジエン・共重合体ラテックスを用いたが、これに限定されるものでなく、非フッ素有機重合体の低密度もしくは高密度ポリエチレン、エチレン／アクリル酸共重合体等も同様の効果を有していることを本願発明者は確認している。
〔試験２〕
試験２では、本発明により可能になった超薄型極板の優れた出力性能を従来
の制御弁式鉛蓄電池と比較して示す。
【００４１】
従来品の鉛蓄電池では、鋳造方法により作製した鉛合金の集電体を用い、常法のペースト状原料を充填した正・負極板をガラス繊維からなるセパレータを介して積層した正極板５枚／負極板６枚構成の公称電圧１２Ｖ、定格容量６Ａｈ（５時間率）の制御弁式鉛蓄電池を作製した。一方、本発明品では、セルあたりの正・負極活物質量を上記の従来の蓄電池と同じにして、試験１と同じ形状の正・負極板を用いて極板群を形成した場合、正・負極板が従来品に比べて約１／４の厚さのものが可能であり、正極板２０枚／負極板２０枚構成の制御弁式鉛蓄電池を作製した。この場合、正極活物質へのリグニンスルフォン酸ソーダおよび変性スチレン・ブタジエン・共重合体ラテックスの添加量は、それぞれ０．３質量％、０．７質量％とした。また、正極板に対する圧迫力は２０×１０^４Ｐａとした。
【００４２】
これら蓄電池に所定比重の希硫酸を所定量注入して電槽内で化成を行い、蓄電池を完成させた。
【００４３】
上記制御弁式鉛蓄電池を各電流で放電を行い、その時の５秒目電圧を測定し、各放電電流と５秒目電圧との関係を求め、両蓄電池を比較した。その結果を図３に示す。放電電流は、定格容量の倍数（ＣＡ）で表示した。ここでの、Ｃは、蓄電池の定格容量、Ａは放電電流を示す。
【００４４】
図３に示すように、従来の制御弁式鉛蓄電池も通常の制御弁式鉛蓄電池に比べて薄型極板を用い、高率放電特性の優れた蓄電池であるが、それに対して、本発明品は約４倍の極板表面積を有しており、大きい電流で放電した時の５秒目電圧の低下率が大幅に改善されていることがわかる。これは、本発明の蓄電池の構成により内部抵抗が非常に小さくなっていることに起因しているといえる。
【００４５】
本発明による鉛蓄電池の正・負極板は、表面積が大きくしかも薄く軽量なため、出力密度は完全充電時において、およそ１０００Ｗ／ｋｇであり、ニッケルー水素電池のそれに匹敵する性能が得られた。しかし、この蓄電池のコストは、活物質に安価な鉛を用いているため１／３〜１／５程度である。
【００４６】
また、このように薄くて軽量な集電体を用いると、従来の鉛蓄電池では、特に高温で使われた場合に正極集電体の腐食劣化が促進し、早期に寿命に至るのに対して、本発明品では正極集電体に耐食性の優れたＳｎＯ_２をコーティングしているのでその問題が解決され、エネルギー密度を高めながらも長寿命な蓄電池が実現可能になった。
【００４７】
【発明の効果】
以上詳細に説明したように、鉛蓄電池の出力特性を改善するためには、超薄型の集電体を用いることは周知であるが、集電体へのペースト状原料の充填性および該極板のハンドリング性といった製造面に問題点がある。その対策としてペースト状原料に分散剤としてスルホン基を有するリグニンおよび活物質結着剤を正極活物質原料に添加することは有効であるが、これらの物質が鉛蓄電池の二次的な性能劣化の要因になるために実用化できなかった。それに対して、正極集電体表面に耐食性の優れたＳｎＯ_２あるいはＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物をコーティングした集電体を用いることにより上記の問題が改善され、出力特性がニッケル−水素電池と同等レベルの蓄電池をはるかに安く提供することができその工業的効果が極めて大である。
【図面の簡単な説明】
【図１】本発明の実施例のセル構造を模式的に示した要部断面図。
【図２】本発明のモノブロックタイプの構造を模式的に示した要部断面図。
【図３】本発明品と従来品の出力特性の比較を示す図。
【符号の説明】
１正極集電体
２ＳｎＯ_２のコーティング層
３鉛をメッキした銅からなる負極集電体
４正極活物質
５負極活物質
６微細ガラス繊維セパレータ
１１端子板
１２圧迫用プレート[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lead acid battery.
[0002]
[Prior art]
In recent years, as the promotion of the spread of hybrid vehicles, fuel cell vehicles, and the like for environmental measures is increasing, there is a growing demand for smaller and lower cost power sources such as these power sources and power supply devices. As one of the countermeasures, there is an increasing need for an inexpensive secondary battery having high output performance that serves to assist a power shortage due to a rapid load fluctuation between the load and the power source. A lead-acid battery is one of the strong candidates for this need as a secondary battery made of an inexpensive material. However, there is a problem that output characteristics are inferior to other secondary batteries such as lithium ion batteries or nickel-hydrogen batteries. there were.
[0003]
As a means for improving the output characteristics of a lead-acid battery, it is already well known that it is effective to increase the number of plates by making the plates as thin as possible, that is, to increase the apparent surface area of the plates. In order to produce a plate, it is necessary to apply (fill) a paste-like raw material prepared by kneading lead powder, sulfuric acid and water to a current collector thinly and uniformly. In order to minimize the mass of the current collector, it is necessary to make the current collector thinner and lighter. However, since the conventional raw material aggregates secondary particles in the paste to form a lump and is dispersed in the paste-like raw material, the paste-like raw material is thinly and uniformly applied (filled) to the thin and easily bent current collector. ) Was difficult to do. Also, after drying the electrode plate that is coated (filled) with a paste-like raw material on a thin and easy-to-curve current collector, the active material that is curved and applied (filled) peels off from the current collector when it is lifted and falls off It also has the problem of end.
[0004]
On the other hand, attempts have been made so far to facilitate application to the current collector by adding lignin having a sulfone group to the active material as a dispersant and suppressing the formation of the secondary particles described above. Has also been considered. In order to improve the handling of the electrode plate during assembly, an active material binder such as modified styrene / butadiene / copolymer latex or ethylene / acrylic acid copolymer is added to the pasty raw material. It has been studied to improve the adhesion between the current collector after drying and the active material.
[0005]
[Problems to be solved by the invention]
However, it has been difficult to employ these solutions described above for the positive electrode plate of a lead storage battery. This is because, in a lead-acid battery, the positive electrode plate is exposed to a high anode potential in an electrolyte solution composed of dilute sulfuric acid, so that the anode active material contains high molecular weight organic substances such as lignin and an active material binder. Oxidized and decomposed to produce low molecular weight organic acids such as acetic acid. Since the organic acid dissolves a conventional positive electrode current collector made of lead or a lead alloy, corrosion deterioration of the positive electrode current collector is accelerated, and the lead storage battery has a problem of shortening its life.
[0006]
Moreover, although the said organic substance is decomposed | disassembled and lose | disappeared finally in a carbon dioxide gas, it exists in the tendency to reduce the adhesiveness of a collector and a positive electrode active material at the time of generation | occurrence | production. In particular, a thin current collector is inferior in function to wrap and hold an active material three-dimensionally compared to a conventional thick grid-like current collector. Also, there is a problem that the coupling between the current collector and the active material cannot be maintained at an early stage, the electrical contact between the two becomes poor, and the electric capacity cannot be taken out.
[0007]
Therefore, the problem to be solved by the present invention is that the above-mentioned problems even when the positive electrode active material contains lignin and an active material binder, problems such as dissolution of the current collector and separation between the active material and the current collector. An object of the present invention is to provide a lead-acid battery having an ultra-thin electrode plate that does not generate any problem.
[0008]
[Means for Solving the Problems]
As means for solving the problems, according to claim 1, 0.1 to 0 of a positive electrode current collector having SnO ₂ or Ta ₂ O ₅ —TiO ₂ composite oxide on the surface and a lignin having a sulfone group is used. It has a positive electrode plate provided with a positive electrode active material body containing 0.5% by mass and an active material binder of 0.5 to 4% by mass.
[0009]
The positive electrode active material body means an aggregate of a positive electrode active material, lignin, an active material binder, and additives such as short fibers that are added as necessary. Therefore, 0.1 to 0.5% by mass of the lignin having a sulfone group means that the proportion of lignin in the aggregate is 0.1 to 0.5% by mass, and the active material binder. 0.5-4 mass% means that the proportion of the active material binder in the aggregate is 0.5-4 mass%.
[0010]
When manufacturing an ultra-thin positive electrode plate of 1 mm or less, a lignin having a sulfone group is added to the raw material as a dispersant to facilitate the application (filling) of the paste-like raw material to the positive electrode current collector, or the positive electrode When an active material binder for preventing the active material from falling off is added, these additives composed of high molecular weight organic substances are decomposed by anodic oxidation of the positive electrode to produce a low molecular weight organic acid, for example, acetic acid. Corrosion of the positive electrode progressed because the lead or lead alloy constituting the body was dissolved, and the life was reached early, but the surface of the positive electrode current collector was coated with SnO ₂ or Ta ₂ O ₅ —TiO ₂ composite oxide Then, they are stable against organic acids such as acetic acid and can prevent the current collector from dissolving.
[0011]
The surface coating is preferably performed on the entire surface of the current collector as much as possible, but there is a corresponding effect even if it is not necessarily performed on the entire surface.
[0012]
Furthermore, since the lignin and the active material binder may eventually decompose to generate carbon dioxide gas, the positive electrode current collector and the positive electrode active material are pressed with a pressure of 10 × 10 ⁴ to 30 × 10 ⁴ Pa. By holding down, the detachment of the positive electrode active material from the current collector can be avoided, which is more preferable in terms of stabilizing the life performance.
[0013]
As described above, the manufacturing problems of ultra-thin positive electrode plates of 1 mm or less can be solved, secondary performance deterioration of the lead storage battery due to the presence of the additive can be avoided, output characteristics are excellent, and life performance is stable. Lead acid battery is obtained.
[0014]
【Example】
FIG. 1 is a cross-sectional view schematically showing the structure of a storage battery according to an embodiment of the present invention. 1 is a positive electrode current collector, 2 is a corrosion-resistant conductive agent layer made of SnO ₂ coated on the positive electrode current collector. 3 is a negative electrode current collector, 4 is a positive electrode active material, 5 is a negative electrode active material, 6 is a separator made of fine glass fiber, 7 is a battery case, 8 is an O-ring for preventing electrolyte from leaking, and 9 is an exhaust hole. Reference numerals 10 denote control valves.
[0015]
In FIG. 1, a positive electrode current collector 1 is made of a Pb-2 mass% Sn alloy foil having a thickness of 200 μm, and SnO ₂ is coated on the surface of the current collector with a thickness of 300 nm by sputtering. For the negative electrode current collector 3, a lead-plated copper foil having a thickness of 40 μm was used. To the positive electrode active material 4 and the negative electrode active material 5, lignin sodium sulfonate is added as lignin, and modified styrene / butadiene / copolymer latex is added as an active material binder.
[0016]
FIG. 2 is a cross-sectional view schematically showing the structure of a monoblock type lead-acid battery according to the present invention in which three cells are integrated. 11 is a terminal plate made of a copper plate, 12 is a compression plate, and 13 is a bolt. -Each nut is shown. The other components are given the same numbers as in FIG.
[0017]
As shown in FIG. 2, when the electrode plate group is formed by laminating the electrode plate having the shape in which the active material is applied on one side of the flat plate current collector through the separator, the terminal on the opposite side of the current collector functions as a terminal. Therefore, a so-called monoblock type lead-acid battery can be easily configured by simply stacking the electrode plates.
[0018]
Next, a test conducted to specifically show the effect of the present invention will be described.
(Test 1)
The configuration of the example shown in FIG. 1 was adopted for the positive electrode plate and the negative electrode plate, and in the positive electrode plate, a positive electrode paste material having a thickness of 200 μm was applied to the current collector. At that time, a positive electrode plate was produced in which the positive electrode current collector was not coated with SnO ₂ and the addition amount of lignin sulfosoda and modified styrene / butadiene / copolymer latex to the positive electrode active material was changed. The contents are shown in Table 1.
[0019]
Also for the negative electrode plate, a normal negative electrode paste-like raw material was applied (filled) to a thickness of 200 μm on the current collector. At that time, the addition amount of sodium lignin sulfonate was fixed at 0.3% by mass, and the addition amount of the modified styrene / butadiene / copolymer latex was fixed at 0.5% by mass.
[0020]
Application (filling) of the pasty raw material to the positive and negative electrode current collectors was performed using a normal pasting machine.
[0021]
[Table 1]

[0022]
The filling property and assembling property of the positive electrode plate were investigated. The results are shown in Table 2.
[0023]
[Table 2]

[0024]
(Fillability)
Evaluation of filling performance was ○ when the current collector surface was evenly filled, △ when the surface was filled but the secondary particles of the raw material could not be uniformly filled, and many secondary particles were filled Those that could not be marked as x.
[0025]
As shown in Table 2, when the positive electrode active material thickness was limited to 200 μm, No. lignin sulfonate was not added. 1 and No. In No. 4, a lump of secondary particles was generated in the pasty raw material, and the current collector could not be uniformly filled to a thickness of 200 μm in the current collector. In addition, No. 1 containing 0.05% by mass of sodium lignin sulfonate was added. No. 5 also had an insufficient effect, and although it could be filled, there were a few secondary particles and it was not uniform. On the other hand, No. 1 in which the amount of sodium lignin sulfonate was 0.8% by mass. In No. 15, the pasty raw material became too soft, and conversely, it was difficult to maintain a thickness of 200 μm on the current collector. From the above, it was found that 0.1 to 0.5% by mass of sodium lignin sulfonate for applying the active material thinly on the positive electrode current collector was appropriate.
(Assemblyability of storage battery)
An attempt was made to assemble a control valve type lead-acid battery having a nominal voltage of 12 V and a rated capacity of 1.0 Ah having the structure shown in FIG.
[0026]
Evaluation of assemblability was ○ when the assembly was completed, the defective rate of the electrode plate was high, but △ when the assembly of the storage battery was able to be completed, and the active material of the electrode plate almost dropped and assembly was impossible The thing was made into x.
[0027]
As shown in Table 2, the modified styrene / butadiene / copolymer latex was added in an amount of 0% by mass. 3 and no. In the positive electrode plate 7, most of the positive electrode active material was peeled off from the current collector during assembly, making it impossible to assemble. In addition, the addition amount is 0.2 mass% No. The positive electrode plate 8 had an insufficient active material binding effect and had a high electrode plate defect rate, but the battery could be assembled. When the amount added was 0.5% by mass or more, a binding effect on the active material appeared, and as the amount increased, the positive electrode active material became stronger and handling of the electrode plate became easier.
[0028]
The pressing force against the positive electrode plate during assembly was 20 × 10 ⁴ Pa, but in the positive electrode plate added with 0.3% by mass of lignin sulfonate sodium and 0.7% by mass of modified styrene / butadiene / copolymer latex, Storage batteries (Nos. 16 to 18) with various pressing forces on the positive electrode plate were produced. The contents are shown in Table 3 [Table 3].

[0029]
A predetermined amount of dilute sulfuric acid electrolyte solution having a specific gravity was injected into the produced storage battery, and chemical conversion was performed in the battery case to complete the storage battery. At that time, No. 1 using a positive electrode plate to which 6% by mass of a modified styrene / butadiene / copolymer latex was added. The battery of No. 13 was not fully formed and did not have a capacity, so a life test was not performed. This is presumably because the amount of the binder added was too large to cover the surface of the positive electrode active material and the chemical conversion reaction was not sufficiently performed.
[0030]
Accelerated trickle (float) life tests were conducted on a storage battery that had been successfully formed in a 60 ° C atmosphere at a charging voltage and a constant voltage of 13.65 V. At a current of 1 CA (1.0 A) every month. Discharge was performed to a final voltage of 1.7 V / cell. The time when the capacity became 50% or less of the initial value was defined as the life. The test results are shown in Table 4.
[0031]
[Table 4]

[0032]
As shown in Table 4, when the positive electrode current collector was not coated with SnO ₂ , the storage battery No. 2 reached the end of its life in 3 months. When the storage battery was disassembled and investigated, the lignin sulfonate and modified styrene / butadiene / copolymer latex added to the positive electrode plate by anodic oxidation were decomposed into low molecular weight organic acids. It was found that the Pb-2 mass% Sn alloy was dissolved, that is, the corrosion progressed rapidly and the performance deteriorated.
[0033]
On the other hand, a storage battery using a current collector coated with SnO ₂ on the surface showed stable life performance without corrosion of the current collector even when the additive was decomposed. However, since the organic matter added to the positive electrode active material is decomposed and finally accompanied by generation of carbon dioxide (CO ₂ ), the positive electrode active material tends to fall off from the current collector. When the pressing force was 5 × 10 ⁴ Pa as in No. 16, the life of the positive electrode active material was low and the life was slightly shortened. On the other hand, when the pressing force was as high as 30 × 10 ⁴ Pa, the positive electrode active material was prevented from falling off and the life was long.
[0034]
When the amount of the modified styrene / butadiene / copolymer latex is added, it effectively acts on the binding property of the active material at the time of assembly, and in the range of 0.5 to 4% by mass, which has no adverse effect at the time of chemical conversion, good life performance. showed that.
[0035]
Regarding the lignin, not only in the range of the addition amount in which the filling could be performed satisfactorily, but also in the range of 0.05 to 0.5% by mass including the addition amount of 0.05% by mass having a problem in the filling property. Lifetime performance is shown. However, it is needless to say that the range of 0.1 to 0.5% by mass is preferable when the filling property is included.
[0036]
From the results of the above tests, in order to improve the output characteristics of lead-acid batteries, to improve manufacturing problems when using ultra-thin electrode plates, sodium lignin sulfonate and modified styrene / butadiene / copolymer are used. The effect of adding the combined latex to the positive electrode active material and the effect of SnO ₂ on the adverse effect of the additive on the performance of the lead-acid battery were revealed.
[0037]
In the examples, SnO ₂ was used as the corrosion-resistant conductive material, but the present inventor has confirmed by another test that the same effect can be obtained even if Ta ₂ O ₅ —TiO ₂ composite oxide is used. .
[0038]
In this example, a Pb-2 mass% Sn alloy foil having a flat plate shape was used as the positive electrode current collector. However, this shape is not particularly limited, and the plate may be provided with perforations, and the lattice shape is the same. Needless to say, the effect is obtained.
[0039]
Moreover, although the Pb-2 mass% Sn alloy foil was used for the positive electrode current collector, titanium (Ti) can also be used, and as a result, the lead alloy has a limit of about 200 μm. However, a 40 μm plate can be used, and a thinner and lighter electrode plate can be realized. In that case, unlike the lead alloy, the melting point is high, so that the corrosion-resistant conductive material can be dip-coated by a firing method in an atmosphere of 500 ° C.
[0040]
In this example, modified styrene / butadiene / copolymer latex was used as the active material binder. However, the present invention is not limited to this, and non-fluorine organic polymer low density or high density polyethylene, ethylene The inventor of the present application has confirmed that the / acrylic acid copolymer has the same effect.
[Test 2]
Test 2 shows the superior output performance of the ultra-thin electrode plate made possible by the present invention compared to a conventional control valve type lead acid battery.
[0041]
In a conventional lead-acid battery, a positive-electrode negative electrode plate filled with conventional paste-like raw materials is laminated using glass fiber separators using a lead alloy current collector produced by a casting method. A control valve type lead storage battery having a nominal voltage of 12 V and a rated capacity of 6 Ah (5-hour rate) was prepared. On the other hand, in the product of the present invention, when the positive / negative electrode active material amount per cell is the same as that of the above-described conventional storage battery and the positive / negative electrode plates having the same shape as in Test 1 are used, The negative electrode plate can be about 1/4 of the thickness of the conventional product, and a control valve type lead-acid battery having a structure of 20 positive plates / 20 negative plates was produced. In this case, the addition amounts of sodium lignin sulfonate and modified styrene / butadiene / copolymer latex to the positive electrode active material were 0.3 mass% and 0.7 mass%, respectively. The pressing force against the positive electrode plate was 20 × 10 ⁴ Pa.
[0042]
A predetermined amount of dilute sulfuric acid having a specific gravity was injected into these storage batteries, and chemical conversion was performed in the battery case to complete the storage batteries.
[0043]
The control valve type lead-acid battery was discharged with each current, the voltage at the 5th second at that time was measured, the relationship between each discharge current and the voltage at the 5th second was determined, and both batteries were compared. The result is shown in FIG. The discharge current was expressed as a multiple of the rated capacity (CA). Here, C is the rated capacity of the storage battery, and A is the discharge current.
[0044]
As shown in FIG. 3, the conventional control valve type lead storage battery is a storage battery that uses a thin electrode plate and has excellent high rate discharge characteristics as compared with a normal control valve type lead storage battery. Has an electrode plate surface area of about 4 times, and it can be seen that the rate of decrease in the voltage at the 5th second when discharging with a large current is greatly improved. It can be said that this is because the internal resistance is very small due to the configuration of the storage battery of the present invention.
[0045]
Since the positive and negative plates of the lead storage battery according to the present invention have a large surface area and are thin and lightweight, the output density is about 1000 W / kg when fully charged, and performance comparable to that of a nickel-hydrogen battery is obtained. However, the cost of this storage battery is about 1/3 to 1/5 because inexpensive lead is used for the active material.
[0046]
In addition, when such a thin and lightweight current collector is used, the corrosion of the positive electrode current collector is accelerated especially when used at high temperatures, and the life is shortened early. In the product of the present invention, since the positive electrode current collector is coated with SnO ₂ having excellent corrosion resistance, the problem is solved, and a long-life storage battery can be realized while increasing the energy density.
[0047]
【The invention's effect】
As described above in detail, in order to improve the output characteristics of the lead-acid battery, it is well known to use an ultra-thin current collector. There are problems in manufacturing such as handling of the plate. As countermeasures, it is effective to add a lignin having a sulfone group as a dispersant and an active material binder as a dispersant to the positive electrode active material, but these materials may cause secondary performance deterioration of the lead storage battery. It could not be put into practical use because it would be a factor. On the other hand, by using a current collector coated with SnO ₂ or Ta ₂ O ₅ —TiO ₂ composite oxide having excellent corrosion resistance on the surface of the positive electrode current collector, the above problem is improved, and the output characteristics are nickel-hydrogen. A storage battery of the same level as the battery can be provided at a much lower price, and its industrial effect is extremely great.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a cell structure of an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an essential part schematically showing a monoblock type structure of the present invention.
FIG. 3 is a diagram showing a comparison of output characteristics between the product of the present invention and a conventional product.
[Explanation of symbols]
1 the positive electrode current collector 2 SnO ₂ anode current collector 4 a positive electrode active material 5 the anode active material 6 fine glass fiber separator 11 terminal plate 12 for pressurizing plate of the coating layer 3 of lead from plated copper

Claims

A positive electrode current collector having SnO ₂ or Ta ₂ O ₅ —TiO ₂ composite oxide on the surface, 0.1 to 0.5% by mass of lignin having a sulfone group, and 0.5 to 0.5% of an active material binder A lead-acid battery comprising a positive electrode plate including a positive electrode active material body containing 4% by mass.