JP4320536B2

JP4320536B2 - Positive electrode plate for lead acid battery and lead acid battery

Info

Publication number: JP4320536B2
Application number: JP2002277681A
Authority: JP
Inventors: 勇栗澤
Original assignee: GS Yuasa Corp
Current assignee: GS Yuasa Corp
Priority date: 2002-09-24
Filing date: 2002-09-24
Publication date: 2009-08-26
Anticipated expiration: 2022-09-24
Also published as: JP2004119061A

Description

【０００１】
【発明の属する技術分野】
本発明は、鉛蓄電池に関するものである。
【０００２】
【従来の技術】
鉛蓄電池は、コスト・安全性・信頼性の面で二次電池として長く利用されてきているが、ここ数年の性能向上および普及が著しい新種電池（ニッケル水素、リチウムイオン）に比べ、エネルギー密度が低いという欠点がある。
【０００３】
鉛蓄電池は、正極活物質が二酸化鉛（ＰｂＯ_２）、負極活物質が鉛（Ｐｂ）から構成されており、集電体には正・負極いずれも鉛あるいは鉛合金が使用されている。鉛蓄電池の劣化の主要因は正極集電体の腐食である。正極集電体は、開回路の状態でも電位の高いＰｂＯ_２と常時接しているため、常に腐食される環境にある。充電時には充電過電圧が加わって、電位が高くなり、腐食がさらに加速される。集電体は、集電機能の他に活物質を保持する機能を持っているが、腐食が進めば、これらの機能が低下して蓄電池の容量を低下させることになる。したがって、寿命性能の要求を満足させるためには集電体の容積を一定以上確保する必要がある。そのことによって、正極板の厚みは自ずと厚いものになる。
【０００４】
また、正極活物質は微細構造を有する多孔性物質で多くの細孔を有しており、放電において、電解液である硫酸が関与し、極板が厚くなると、電解液の活物質細孔内への拡散が悪くなり、正極活物質の利用率が低下する。さらに、正極集電体の耐食性をよくするために、低比重電解液を用いるのが良いことは知られているが、これも電解液中の反応物として消費される硫酸根が不足して、正極活物質の利用率を下げる要因となる。活物質の利用率が低下すると、要求される電気容量を取り出すためにより多くの活物質量が必要となり、極板が重くなってエネルギー密度のさらなる低下につながる。このように正極集電体の腐食劣化が、理論エネルギー密度の低い鉛蓄電池の実用エネルギー密度を更に低くする大きな原因となっている。このような状況の中で、耐食性の優れた正極集電体の開発が望まれている。
【０００５】
鉛蓄電池の正極集電体に要求される特性は、高い導電性、硫酸への不溶性、硫酸溶液中でのＰｂＯ_２を用いることによる正極電位に対する電気化学的安定性、高い水素・酸素過電圧である。したがって、鉛以外の安価で軽量なアルミニウムやカーボンといった材料は、鉛蓄電池の電解液である硫酸中で正極電位に晒されると著しく溶解あるいは腐食してしまうために用いることはできない。そういった中で、酸素化合物や珪素化合物のようなセラミックスの中に耐食性導電材料の可能性を僅かに見出すことができる。
【０００６】
しかしながら、これらの材料は導電性に優れるとはいえ、鉛と比較すれば、比抵抗が高く、またコストも高価であり、これらの材料を集電体としてそのまま用いることは出来なかった。しかし、鉛あるいは鉛合金もしくは他の導電性の優れた集電体の表面にこの耐食性導電材層を形成し、集電体本体を被覆することで、この耐食性導電性材による電圧降下が小さく抑えられ、比抵抗の問題やコストの問題を克服し、耐食性の優れた正極集電体が得られる可能性がある。特に、近年、薄膜製法の中で、スパッタリング法やプラズマＣＶＤ法等の製法を用いれば、鉛のような低融点材料にも良質な結晶性と導電性を持ったセラミックスのような高融点の耐食性導電材を被覆することが可能になってきた。そのような方法の一例が特開平７−６５８２３に記載されている。
【０００７】
この方法によれば、鉛からなる集電体にプラズマ処理によってチタンあるいはチタン化合物層を形成するものである。
【０００８】
しかし、上述したように耐食性導電材は鉛表面に薄膜層を形成した状態であっても鉛と比較して比抵抗が高いという問題を完全に克服したわけでなく、また、従来の鉛蓄電池では、熟成工程によって集電体と活物質との化学的な結合反応により両者の密着性が確保されるのに対して、本方式では、鉛表面に耐食性導電材層が存在するので鉛と活物質との化学的な結合反応が起こり難く、基本的に集電体と活物質との密着性が弱く、充電中のガス発生や充・放電に伴う活物質の膨張・収縮あるいは外的な振動等の物理的な力によって集電体と活物質とが剥離して極板としての機能を失ってしまい易い問題点を抱えていた。
【０００９】
【発明が解決しようとする課題】
発明が解決しようとする課題は、正極集電体表面にセラミックス等からなる耐食性導電材層を形成した正極板において、導電性に問題がなく、正極活物質と集電体との密着性にも優れた正極板を備えた鉛蓄電池を提供することにある。
【００１０】
【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、正極集電体表面に耐食性導電材を形成した鉛蓄電池用正極板において、前記耐食性導電材がＴａ₂Ｏ₅−ＴｉＯ₂複合酸化物であることを特徴とし、請求項２によれば、前記正極板を備えた鉛蓄電池であって、前記正極板に４０〜２００ｋＰａの圧迫力を加えたことを特徴とするものである。
【００１１】
鉛あるいは鉛合金もしくは他の金属からなる集電体表面にセラミックスの薄膜層を形成する場合の大きな問題点は導電性の低下である。発明者は、各種チタン化合物を用いて鉛およびＴｉからなる集電体表面に薄膜層を形成させ、評価試験を行った。その結果、Ｔａ₂Ｏ₅−ＴｉＯ₂複合酸化物の薄膜層を形成した集電体は、鉛蓄電池の正極集電体として要求される特性を有し実用可能であることを見出した。
【００１２】
薄膜層の厚みに関しては、層厚みが１００ミクロン以下であれば鉛蓄電池として必要な導電性を確保できることが分かった。また、薄膜層の厚みの下限は、膜の形成方法によっても変わるが、例えば、スパッタリング法により形成された薄膜の場合は８ミクロンでも、また、ディップコーティング法により形成された薄膜の場合は１００ナノメータでも、鉛蓄電池の正極集電体として十分な耐食性を有していることがわかった。
【００１３】
さらに本発明では、前記正極板に４０〜２００ｋＰａの圧迫力を加え、活物質と集電体との電気的接触を維持することを特徴とするものである。
【００１４】
従来の鉛蓄電池では、鉛あるいは鉛合金集電体に正極活物質を当接あるいは塗布した後、上述したように熟成工程を経る。この工程により、鉛あるいは鉛合金集電体と活物質との間に化学的な結合反応が起こり両者の密着性が確保される。しかし、本発明の鉛あるいは鉛合金もしくは他の金属からなる集電体表面にＴａ₂Ｏ₅−ＴｉＯ₂複合酸化物の薄膜層を形成させた場合には、集電体の耐食性は優れているが、活物質と集電体との間に化学的な結合反応による密着性が十分に得られないので、活物質が集電体から離脱しやすい問題を抱えている。これに対して、発明者は、前記集電体に正極活物質を当接あるいは塗布した後、集電体に対して垂直方向に４０〜２００ｋＰａの圧迫力を加えることによって活物質と集電体との電気的接触が維持でき、鉛蓄電池用正極板として安定して使用可能であることを見出した。
【００１５】
本発明の他の特徴は、平板状の鉛あるいは鉛合金もしくは他の金属からなる集電体の片面に耐食性導電材層を形成し、該面に正極活物質を当接あるいは塗布し、反対面に負極活物質を当接あるいは塗布し、該正極活物質面と該負極活物質面とを電解液を保持するセパレータを介して積層したバイポーラ構造が可能であることである。
【００１６】
耐食性導電材層を形成した集電体は優れた耐食性を有しており、平板状集電体が薄くても腐食で劣化する心配がないので該集電体が正極・負極を接続する機能を備えた上記バイポーラ構造が容易に実現できる。
【００１７】
また、平板状の正極集電体の片面に正極活物質を当接あるいは塗布し、反対面は蓄電池外装、すなわち電槽と接続端子の機能を兼ね備える構造も可能である。
【００１８】
次に、鉛あるいは鉛合金もしくは他の金属からなる集電体表面に耐食性導電材層を形成した場合、鉛あるいは鉛合金のみの集電体に比べて電位的に安定でないために、化成工程ではその点での配慮が必要である。それを以下に示す。
【００１９】
蓄電池に電解液を注入後、直ちに蓄電池の電圧を１.０Ｖ以上の電圧に制御した状態で化成を行うと共に少なくとも１時間は２．０Ｖ以下に保つことが必要である。
【００２０】
集電体表面に形成させた上記耐食性導電材層は、１．０Ｖ以下の電圧になると、硫酸中に溶出することがわかった。鉛蓄電池製造中にその電位になるのは極板の化成初期で、０Ｖ〜０．５Ｖの非常に低い電圧を示す。したがって、電解液注入後、直ちに蓄電池の電圧を１．０Ｖ以上にすることが好ましい。
【００２１】
一方、高い電圧で化成すると耐食性導電材層の表面で化成中にガス発生が起こり、活物質と集電体との密着性が失われ、電池の内部抵抗が高くなる。そのため化成開始後、少なくとも１時間は、電圧を２Ｖ以下に制限することが必要である。
【００２２】
鉛蓄電池に電解液を注入した時点での電位は１．０Ｖ以下と低く、集電体表面に形成した耐食性導電材層が溶出するので、注液後直ちに通電を開始する必要がある。しかし、実際の作業において難しい面があり、発明者は耐食性導電材層の厚みと化成開始までの時間との関係を求める試験を行い、耐食性導電材層の厚みをＡ（ミクロン）、化成開始までの時間をＴ（分）とした時に
Ｔ≦１９．２ＬＯＧ₁₀Ａ
にしたがって化成を開始すればよいことを見出した。
【００２３】
【実施の形態】
以下、実施例に基づいて本発明を更に詳細に説明する。
〔実施例１〕
図１は、本発明による実施例の正極集電体を示す断面図であり、１は低融点金属である鉛からなる集電体本体、２は該集電体表面に形成されたＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物薄膜層をそれぞれ示す。
【００２４】
図１において、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物薄膜層の形成には、これと同じ組成（Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物：比率１対１）のターゲットを用いて、０．７５ＰａのＡｒガス雰囲気中でＲＦスパッタリング装置を用いて行った。薄膜層形成時の基板温度は１２０℃であり、鉛の融点３２７℃に比べ充分低く問題ない。
【００２５】
鉛集電体表面にＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物の薄膜層を上述したスパッタリング法により形成させた集電体と、被覆しない集電体とを作製し、その上にそれぞれ鉛蓄電池用のペースト状活物質を塗布し、通常の化成を行い、硫酸電解液の比重が１．２８０になるように調整した後、２０ｍＡ／ｃｍ^２の定電流でアノード酸化試験を行った。さらに、チタンの集電体にＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物の薄膜層を形成したものと被覆しないものについても試験に供した。
【００２６】
試験中の電圧推移を図２に示す。Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物の薄膜層で被覆しなかったチタン基板の集電体は基板表面が不働態化したためか、早期に著しく高い電圧を示した。すなわち高い抵抗体が形成され、正極板として機能が維持できなくなってしまった。しかし、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物層で被覆したＴｉ集電体は６００時間酸化試験を行っても全く電圧挙動に異常はなく、鉛蓄電池の集電体として十分適用可能であることが分かった。鉛の集電体に上記耐食性導電材を被覆したものも６００時間の酸化試験で異常はなかった。試験後、これらを解体調査した結果、いずれもＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物層の劣化等が見られなかった。一方、Ｐｂのみの集電体は、機能が短期間で維持できなくなるということはなかったが、被覆していないために集電体の腐食が著しかった。
【００２７】
図３に上記６００時間のアノード酸化試験後の鉛集電体の腐食量を示す。被覆ありのものは被覆なしのものに比べ、腐食量は著しく少ないことが分る。
【００２８】
図４にＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物の薄膜層ありとなしの鉛集電体を用いた正極板について、電流密度を変えた場合の放電特性を示す。被覆ありと被覆なしでは、放電性能に差はなかった。
【００２９】
また、スパッタリング法により鉛集電体表面に１０ミクロンの厚さのＴｉ_４Ｏ_７薄膜層を形成させた正極板を作製し、同様のアノード酸化試験を行った。その結果、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物で被覆した場合と同じく、ほとんど腐食せず、耐食性に著しい効果があった。
【００３０】
なお、今回の実施例ではスパッタリング法を用いたが、技術的にはプラズマＣＶＤ法を用いても同等の効果が得られることは周知である。
〔実施例２〕
スパッタリング法により０．５ｍｍ厚さの鉛シート表面に厚さ１０ミクロンのＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物薄膜層を形成した集電体の表面に、鉛蓄電池用正極ペーストを塗布し、負極には通常の鉛シート上に負極ペーストを塗布し、両極板の間に制御弁式鉛蓄電池用のガラスマットセパレータを種々の圧迫力になるように厚みを変えて挿入した。それらを定法に従い希硫酸を注液し、通電（化成）を行い、表１に示す内容の約０．２５Ａｈ容量（１０時間率）の制御弁式鉛蓄電池を作製した。該蓄電池の構造断面図を図５に示す。
【００３１】
図５において、１は正極集電体、２は耐食性導電材層（Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物）、３は正極活物質、４は負極集電体、５は負極活物質、６はセパレータ、７は排気孔、８は絶縁枠をそれぞれ示す。
【００３２】
図５に示すように、両極の集電体は外装ケースの一部をかねていると共に端子の機能も備えており、従来の鉛蓄電池のように端子が不要である。
【００３３】
なお、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物を形成させていない鉛シートをそのまま用いた以外は上記と同じ方法で従来型の制御弁式鉛電池も作製し、試験に供した。
【００３４】
【表１】

【００３５】
これらの蓄電池を室温で０．６ＣＡ（Ｃ：定格容量、Ａ：電流の単位）電流で１時間放電し、０．２ＣＡ電流で４．１時間充電するパターンの充・放電サイクル試験を行った。寿命試験中の放電容量の推移を図６に示す。
【００３６】
従来型鉛蓄電池は、約５００サイクルで寿命に達したが、本発明の４０〜２００ｋＰａで圧迫した蓄電池は、いずれも８００サイクルの時点でほとんど容量の低下がなかった。しかし、圧迫力が低い（２０ｋＰａ）蓄電池Ａは、１００サイクルと非常に早く容量が低下した。解体したところ、正極活物質が集電体から剥離していたので、圧迫力が低いために、サイクル中に集電体と活物質との界面の抵抗および蓄電池の内部抵抗が高くなって早期に容量が低下したものと思われる。
【００３７】
また、４００ｋＰａと最も高圧迫にして作製した蓄電池Ｅは、３００サイクルで容量が低下した。解体した結果、活物質がガラスマットの中に侵入し、短絡が起こっていた。圧迫が強すぎるために、活物質のＰｂＯ_２粒子あるいはＰｂ粒子がセパレータの小さな孔の中にまで侵入していったものと思われる。
【００３８】
以上の結果から、鉛集電体表面にＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物薄膜層を形成し、その上に活物質を塗布した正極板は、従来のＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物を被覆していない正極板に比べ集電体と活物質との密着性が良くないため圧迫力を高くする必要があること、そしてその圧迫力も高すぎると短絡が起こってしまうため、圧迫力は４０〜２００ｋＰａに制限する必要があることがわかった。
【００３９】
本実施例では、活物質を集電体に塗布した正極板を使用したが、あらかじめ別途作製した活物質のペレットを準備しておき、集電体に所定の圧力で当接しても、同じで結果が得られる。
【００４１】
本実施例では図５に示す２Ｖの蓄電池を製作したが、本発明の構造では、２Ｖの蓄電池を積層して高い電圧あるいは高容量のモジュール電池を作製することは容易である。図７は高電圧モジュールの断面図、図８は高容量のモジュールの断面図をそれぞれ示す。
【００４２】
図７において、構成部材は図５と同じ番号を付記する。
【００４３】
図８において、９は正極端子、１０は負極端子をそれぞれ示す。他の構成部材は図５と同じ番号を付記する。
【００４４】
図７および図８に示すように従来の鉛蓄電池で高電圧化の際に必要であった極板群上部での鉛あるいは鉛合金同士の溶接、もしくは蓄電池外部でリード線等による結線の手間が必要ない構造の蓄電池を容易に得ることができる。
【００４５】
また、本発明の耐食性導電材層を正極集電体表面に形成するという技術を使用すれば、基本的に集電体の腐食がないために、バイポーラ電池の実現も可能となる。図９は、バイポーラ電池の構造断面図を示すもので、１１はバイポーラ集電体を示す。他の構成部材は図５と同じ番号を付記する。
【００４６】
図９に示すように１枚の集電体の両面に正極および負極の活物質を塗布し、この極板をセパレータを介して多数枚積層することにより高電圧の蓄電池が容易に作製できる。このような１枚の極板で正極・負極活物質を有する極板を用いた蓄電池をバイポーラ電池と呼ぶ。本発明の蓄電池は集電体の腐食がほとんどないことからバイポーラ電池を作製するのに適しており、非常に安価なモジュール蓄電池が供給できる。
〔実施例３〕
これまで発明者が実験してきた結果、集電体表面に形成したＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物層は、１．０Ｖ以下の電圧になると、硫酸中に溶出することがわかった。鉛蓄電池製造中にその電位になるのは極板の化成初期である。鉛蓄電池の極板は希硫酸注液後０Ｖ〜０．５Ｖの非常に低い電圧を示す。
【００４７】
本発明では、硫酸注入後、直ちに蓄電池の電圧を１．０Ｖ以上にすることにより、集電体表面のＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物の溶出を抑制できた。
【００４８】
一方、高い電圧で化成するとＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物の表面で化成中にガス発生が起こり、活物質と集電体との密着性が失われ、電池の内部抵抗が高くなる問題がある。本発明では、化成開始後少なくとも１時間は、電圧を２Ｖ以下に制限することにより、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物と活物質との密着性を維持できることがわかった。以下、実施例にて本発明を詳細に説明する。
【００４９】
まず、スパッタリング法により厚さ０．５ｍｍの純鉛シートの表面にＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物を種々の厚さに形成した後、通常の鉛蓄電池用活物質を塗布して正極板を作製した。この極板を通常の鉛蓄電池用負極板および制御弁式鉛蓄電池用の微細ガラス繊維セパレータと組み合わせて、容量が約０．２５Ａｈの蓄電池を作製した。比較のために、鉛シート表面にＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物層を形成していない正極板を用いた従来型鉛蓄電池も作製し、試験に供した。
【００５０】
これらの蓄電池を２ステップ法により化成した。第１ステップ化成において、電解液注入後開始までの時間、化成時の電圧および時間を種々変えた。第２ステップの化成は全て、０．２ＣＡ電流で正極活物質理論容量の３５０％に達するまで行った。
【００５１】
Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物層の厚さおよび化成条件の内容を表２に示す。
【００５２】
【表２】

【００５３】
Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物層の厚さが１０ミクロンの蓄電池について、注液後直ちに第１ステップ化成を開始し、その際、化成電圧および化成時間を表２に示すように変えた。化成後、これら蓄電池の正極板中のＰｂＯ_２量を測定した。さらに、これらの蓄電池について０．０５ＣＡ電流で１２０時間アノード酸化試験を行い、試験後の腐食量を測定した。その結果を図１０および図１１にそれぞれ示す。
【００５４】
図１０に示すように、第１ステップ化成の電圧を２Ｖ以下にした場合にＰｂＯ_２量が多かった。２Ｖを超えるとＰｂＯ_２量が少なかった。これは化成初期の電圧が高すぎると、集電体表面のＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物と活物質との界面でガス発生が激しいため化成効率が低下したためと思われる。また、この第１ステップ化成の時間は、１時間以上場合にＰｂＯ_２量が多かった。
【００５５】
図１１に示すアノード酸化試験後の腐食層の厚さの測定結果から、第１ステップ化成の電圧を１Ｖよりも低くすると、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物層の溶解が起こるためか、腐食層の厚さがＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物層を集電体表面に形成させていない従来型鉛蓄電池の場合と変わらなかった。１Ｖ以上の電圧で化成すればほとんど腐食は起こっていなかった。
【００５６】
以上の結果より、第１ステップ化成の電圧は１Ｖ以上にすべきこと、さらにＰｂＯ_２量を向上させるには電圧を２Ｖ以下にした化成を１時間以上すべきであることがわかった。
【００５７】
次に、第１ステップ化成を１Ｖ×５ｈに固定し、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物薄膜層の厚さおよび注液から化成開始までの時間を表２に示すように変えたときのアノード酸化の腐食に及ぼす影響について調べた。その結果を図１２に示す。
【００５８】
図１２に示すように、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物層を厚くして、注液後化成開始までの時間を短くしたものは、酸化試験において腐食はほとんど起こっていなかった。一方、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物層が薄い場合や注液後化成開始までの時間が長い場合には、酸化試験後の腐食量が多くなった。
【００５９】
腐食量が少なくなる条件を明らかにするために、腐食の少ない限界の化成開始時間とＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物薄膜の厚さとの関係を図１３にプロットし直した。この図から、化成中にＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物薄膜の溶解を抑制して耐食性能を向上させるには、Ｔａ_２Ｏ_５−ＴｉＯ_２複合酸化物の薄膜層厚さをＡ（ミクロン）とし、電解液を注液後、化成開始までの時間をＴ（分）とした時に、以下の式にしたがって化成すればよいことがわかった。
【００６０】
Ｔ＜１９．２ＬＯＧ₁₀Ａ
【効果】
以上説明したように、鉛あるいは鉛合金もしくは他の金属からなる集電体表面に耐食性導電材層を形成した正極板を用いた鉛蓄電池においては、集電体の導電性に問題があったり、集電体と活物質との密着性が悪く電気が取り出せなくなったりする等の問題点を抱えていたが、本発明によれば、そのような問題点を解決し、耐食性に優れた軽くて薄い鉛蓄電池用正極集電体が得られ、そのことによって長寿命でエネルギー密度が高く、しかも信頼性の高い鉛蓄電池を安価で提供できその工業的な価値は極めて大きい。
【図面の簡単な説明】
【図１】本発明による正極集電体の実施例の構造を示す要部模式断面図
【図２】アノード酸化試験中の端子電圧の推移を示す特性図
【図３】アノード酸化試験後の鉛集電体の腐食量を示す特性図
【図４】放電特性を示す図
【図５】耐食性導電材層を形成した正極板を用いた鉛蓄電池の構造の一例を示す模式断面図
【図６】サイクル寿命試験中の放電容量の推移を示す特性図
【図７】耐食性導電材層を形成した正極板を用いた鉛蓄電池の高電圧化の一例を示す模式断面図
【図８】耐食性導電材層を形成した正極板を用いた鉛蓄電池の高容量化の一例を示す模式断面図
【図９】耐食性導電材層を形成した正極板によるバイポーラ鉛蓄電池の構造を示す模式断面図
【図１０】第１ステップ化成時の電圧および化成時間と化成後のＰｂＯ_２量との関係を示す特性図
【図１１】第１ステップ化成時の電圧および化成時間とアノード酸化試験後の腐食層厚さとの関係を示す特性図
【図１２】注液後、化成開始までの時間およびＴａ_２Ｏ_５−ＴｉＯ_２複合酸化物の薄膜厚さと腐食層厚さとの関係を示す特性図
【図１３】Ｔａ_２Ｏ_５−ＴｉＯ_２薄膜層の溶解が鉛蓄電池の性能に影響しない限界厚さと化成開始までの時間との関係を示す特性図
【符号の説明】
１正極集電体
２耐食性導電材層
３正極活物質
４負極集電体
５負極活物質
６セパレータ
７排気孔
８絶縁枠
９正極端子
１０負極端子
１１バイポーラ集電体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lead-acid battery.
[0002]
[Prior art]
Lead storage batteries have long been used as secondary batteries in terms of cost, safety, and reliability, but compared to new types of batteries (nickel metal hydride and lithium ion), which have seen remarkable improvements in performance and popularity over the past few years, energy density Has the disadvantage of being low.
[0003]
In the lead storage battery, the positive electrode active material is composed of lead dioxide (PbO ₂ ) and the negative electrode active material is composed of lead (Pb). Both the positive and negative electrodes are made of lead or lead alloy. The main cause of deterioration of the lead acid battery is corrosion of the positive electrode current collector. Since the positive electrode current collector is always in contact with PbO ₂ having a high potential even in an open circuit state, the positive electrode current collector is always corroded. During charging, a charging overvoltage is applied to increase the potential and further accelerate corrosion. The current collector has a function of holding the active material in addition to the current collecting function. However, when corrosion progresses, these functions are reduced and the capacity of the storage battery is reduced. Therefore, in order to satisfy the life performance requirement, it is necessary to secure a certain volume of the current collector. This naturally increases the thickness of the positive electrode plate.
[0004]
In addition, the positive electrode active material is a porous material having a fine structure and has many pores. In the discharge, sulfuric acid, which is an electrolytic solution, is involved. The diffusion to the negative electrode worsens, and the utilization factor of the positive electrode active material decreases. Furthermore, in order to improve the corrosion resistance of the positive electrode current collector, it is known that it is good to use a low specific gravity electrolyte, but this also lacks the sulfate radical consumed as a reactant in the electrolyte, It becomes a factor which reduces the utilization factor of a positive electrode active material. When the utilization factor of the active material decreases, a larger amount of active material is required to extract the required electric capacity, and the electrode plate becomes heavy, leading to a further decrease in energy density. Thus, the corrosion deterioration of the positive electrode current collector is a major cause of further lowering the practical energy density of the lead storage battery having a low theoretical energy density. Under such circumstances, development of a positive electrode current collector excellent in corrosion resistance is desired.
[0005]
The characteristics required for the positive electrode current collector of the lead-acid battery are high conductivity, insolubility in sulfuric acid, electrochemical stability with respect to the positive electrode potential by using PbO ₂ in sulfuric acid solution, and high hydrogen / oxygen overvoltage. . Therefore, inexpensive and lightweight materials such as aluminum and carbon other than lead cannot be used because they are significantly dissolved or corroded when exposed to the positive electrode potential in sulfuric acid, which is an electrolyte for lead-acid batteries. Under such circumstances, the possibility of a corrosion-resistant conductive material can be slightly found in ceramics such as oxygen compounds and silicon compounds.
[0006]
However, although these materials are excellent in electrical conductivity, they are higher in specific resistance and expensive than lead, and these materials cannot be used as a current collector as they are. However, by forming this corrosion-resistant conductive material layer on the surface of lead, lead alloy or other highly conductive current collector and covering the current collector body, the voltage drop due to this corrosion-resistant conductive material can be kept small. Therefore, there is a possibility that a positive electrode current collector having excellent corrosion resistance can be obtained by overcoming the problems of specific resistance and cost. In particular, in recent years, high-melting-point corrosion resistance such as ceramics with good crystallinity and conductivity can be applied to low-melting-point materials such as lead by using methods such as sputtering and plasma CVD in thin film manufacturing methods. It has become possible to coat a conductive material. An example of such a method is described in JP-A-7-65823.
[0007]
According to this method, a titanium or titanium compound layer is formed on a current collector made of lead by plasma treatment.
[0008]
However, as described above, the corrosion-resistant conductive material does not completely overcome the problem that the specific resistance is higher than that of lead even in a state where a thin film layer is formed on the lead surface. In this method, the chemical bonding reaction between the current collector and the active material ensures the adhesion between the current collector and the active material, whereas in this method there is a corrosion-resistant conductive material layer on the lead surface. Is difficult to occur, basically the adhesion between the current collector and the active material is weak, gas generation during charging, expansion / contraction of the active material due to charging / discharging, external vibration, etc. However, the current force of the current collector and the active material peeled off, and the function as an electrode plate was easily lost.
[0009]
[Problems to be solved by the invention]
The problem to be solved by the present invention is that there is no problem in conductivity in the positive electrode plate in which a corrosion-resistant conductive material layer made of ceramics or the like is formed on the surface of the positive electrode current collector, and also the adhesion between the positive electrode active material and the current collector. It is providing the lead acid battery provided with the outstanding positive electrode plate.
[0010]
[Means for Solving the Problems]
As a means for solving the problem, according to claim 1, in the positive electrode plate for a lead storage battery in which a corrosion-resistant conductive material is formed on the surface of the positive electrode current collector, the corrosion-resistant conductive material is a Ta ₂ O ₅ —TiO ₂ composite oxide. According to a second aspect of the present invention, the lead storage battery includes the positive electrode plate, and a pressing force of 40 to 200 kPa is applied to the positive electrode plate.
[0011]
A major problem in forming a ceramic thin film layer on the surface of a current collector made of lead, a lead alloy or other metal is a decrease in conductivity. The inventor formed a thin film layer on the surface of a current collector made of lead and Ti using various titanium compounds, and performed an evaluation test. As a result, it has been found that a current collector formed with a thin film layer of Ta ₂ O ₅ —TiO ₂ composite oxide has characteristics required as a positive electrode current collector of a lead storage battery and is practical.
[0012]
Regarding the thickness of the thin film layer, it was found that if the layer thickness is 100 microns or less, the conductivity required for a lead storage battery can be secured. The lower limit of the thickness of the thin film layer also varies depending on the film formation method. For example, the thickness of the thin film formed by the sputtering method is 8 microns, or the thin film formed by the dip coating method is 100 nanometers. However, it turned out that it has sufficient corrosion resistance as a positive electrode electrical power collector of lead acid battery.
[0013]
Furthermore, the present invention is characterized in that a pressing force of 40 to 200 kPa is applied to the positive electrode plate to maintain electrical contact between the active material and the current collector.
[0014]
In a conventional lead-acid battery, a positive electrode active material is brought into contact with or applied to a lead or lead alloy current collector and then subjected to an aging process as described above. By this step, a chemical bonding reaction occurs between the lead or lead alloy current collector and the active material, and adhesion between the two is ensured. However, if the lead or the current collector surface consisting of lead alloy or other metals of the present invention to form a thin layer of Ta _₂ O ₅ -TiO ₂ composite oxide is excellent in corrosion resistance of the current collector However, since sufficient adhesion due to a chemical bonding reaction cannot be obtained between the active material and the current collector, there is a problem that the active material is easily detached from the current collector. In contrast, the inventor applied or applied a positive electrode active material to the current collector, and then applied a pressing force of 40 to 200 kPa in the vertical direction to the current collector to thereby collect the active material and the current collector. It was found that the electrical contact with the battery can be maintained and can be used stably as a positive electrode plate for a lead storage battery.
[0015]
Another feature of the present invention is that a corrosion-resistant conductive material layer is formed on one side of a current collector made of flat lead, lead alloy, or other metal, and a positive electrode active material is contacted or applied to the side, and the opposite side A bipolar structure is possible in which a negative electrode active material is brought into contact with or applied to the substrate, and the positive electrode active material surface and the negative electrode active material surface are laminated via a separator for holding an electrolytic solution.
[0016]
The current collector formed with the corrosion-resistant conductive material layer has excellent corrosion resistance, and even if the flat plate current collector is thin, there is no fear of deterioration due to corrosion, so the current collector has a function of connecting the positive electrode and the negative electrode. The bipolar structure provided can be easily realized.
[0017]
Further, a structure in which a positive electrode active material is brought into contact with or coated on one surface of a plate-shaped positive electrode current collector, and the opposite surface has a function of a storage battery, that is, a battery case and a connection terminal is also possible.
[0018]
Next, when a corrosion-resistant conductive material layer is formed on the surface of a current collector made of lead, lead alloy, or other metal, it is not stable in terms of potential compared to a current collector made of only lead or lead alloy. Consideration in that respect is necessary. This is shown below.
[0019]
Immediately after injecting the electrolytic solution into the storage battery, it is necessary to carry out the conversion while keeping the voltage of the storage battery at a voltage of 1.0 V or higher and to keep it at 2.0 V or lower for at least one hour.
[0020]
It was found that the corrosion-resistant conductive material layer formed on the current collector surface was eluted in sulfuric acid when the voltage was 1.0 V or less. It becomes the electric potential at the initial stage of the formation of the electrode plate during the production of the lead acid battery, and shows a very low voltage of 0V to 0.5V. Therefore, it is preferable to set the voltage of the storage battery to 1.0 V or more immediately after the electrolyte injection.
[0021]
On the other hand, when chemical conversion is performed at a high voltage, gas is generated during chemical conversion on the surface of the corrosion-resistant conductive material layer, the adhesion between the active material and the current collector is lost, and the internal resistance of the battery increases. Therefore, it is necessary to limit the voltage to 2 V or less for at least one hour after the start of conversion.
[0022]
Since the potential at the time of injecting the electrolyte into the lead storage battery is as low as 1.0 V or less and the corrosion-resistant conductive material layer formed on the surface of the current collector is eluted, it is necessary to start energization immediately after the injection. However, there is a difficult aspect in the actual work, the inventor conducted a test to determine the relationship between the thickness of the corrosion-resistant conductive material layer and the time until the start of chemical conversion, the thickness of the corrosion-resistant conductive material layer A (micron), until the start of chemical conversion T ≦ 19.2 LOG ₁₀ A when the time of T is T (minutes)
It was found that chemical formation should be started according to
[0023]
Embodiment
Hereinafter, the present invention will be described in more detail based on examples.
[Example 1]
FIG. 1 is a cross-sectional view showing a positive electrode current collector according to an embodiment of the present invention. 1 is a current collector body made of lead which is a low melting point metal, and 2 is Ta ₂ O formed on the surface of the current collector. ₅ shows a _5- TiO ₂ composite oxide thin film layer.
[0024]
In FIG. 1, a Ta ₂ O ₅ —TiO ₂ composite oxide thin film layer is formed by using a target having the same composition (Ta ₂ O ₅ —TiO ₂ composite oxide: ratio of 1: 1), and using a target of 0.02%. An RF sputtering apparatus was used in an Ar gas atmosphere of 75 Pa. The substrate temperature at the time of forming the thin film layer is 120 ° C., which is sufficiently lower than the melting point of lead 327 ° C.
[0025]
A current collector in which a thin film layer of Ta ₂ O ₅ —TiO ₂ composite oxide is formed on the surface of the lead current collector by the above-described sputtering method and a current collector that is not covered are prepared, and each of them is used for a lead storage battery. The paste-form active material was applied, subjected to normal chemical conversion, and adjusted so that the specific gravity of the sulfuric acid electrolyte was 1.280, and then an anodic oxidation test was performed at a constant current of 20 mA / cm ² . Further, a titanium current collector formed with a Ta ₂ O ₅ —TiO ₂ composite oxide thin film layer and a non-coated titanium current collector were also subjected to the test.
[0026]
The voltage transition during the test is shown in FIG. The current collector of the titanium substrate that was not coated with the Ta ₂ O ₅ —TiO ₂ composite oxide thin film layer showed a significantly high voltage at an early stage because the substrate surface was passivated. That is, a high resistor was formed, and the function as a positive electrode plate could not be maintained. However, the Ti current collector coated with the Ta ₂ O ₅ —TiO ₂ composite oxide layer has no abnormality in voltage behavior even when subjected to an oxidation test for 600 hours, and is sufficiently applicable as a current collector for a lead storage battery. I understood. A lead current collector coated with the above corrosion-resistant conductive material also showed no abnormality in the 600-hour oxidation test. After the test, we dismantled survey result, any deterioration of the _Ta ₂ _O 5 -TiO 2 composite oxide layer was observed. On the other hand, the Pb-only current collector did not lose its function in a short period of time, but the current collector was markedly corroded because it was not coated.
[0027]
FIG. 3 shows the corrosion amount of the lead current collector after the anodic oxidation test for 600 hours. It can be seen that the amount of corrosion is significantly less with the coating than with the coating.
[0028]
FIG. 4 shows the discharge characteristics when the current density is changed for a positive electrode plate using a lead current collector with and without a thin film layer of Ta ₂ O ₅ —TiO ₂ composite oxide. There was no difference in discharge performance with and without coating.
[0029]
Further, a positive electrode plate in which a Ti ₄ O ₇ thin film layer having a thickness of 10 microns was formed on the surface of the lead current collector by a sputtering method was prepared, and the same anodic oxidation test was performed. As a result, as in the case of coating with Ta ₂ O ₅ —TiO ₂ composite oxide, there was almost no corrosion and a significant effect on the corrosion resistance.
[0030]
Although the sputtering method is used in this example, it is well known that the same effect can be obtained from the technical point of view by using the plasma CVD method.
[Example 2]
A positive electrode paste for a lead storage battery is applied to the surface of a current collector in which a Ta ₂ O ₅ —TiO ₂ composite oxide thin film layer having a thickness of 10 μm is formed on the surface of a 0.5 mm-thick lead sheet by sputtering. A negative electrode paste was applied onto a normal lead sheet, and a glass mat separator for a control valve type lead-acid battery was inserted between the electrode plates with varying thicknesses so as to have various pressing forces. In accordance with an ordinary method, dilute sulfuric acid was injected and energization (chemical conversion) was performed to produce a control valve type lead-acid battery having the contents shown in Table 1 and having a capacity of about 0.25 Ah (10 hour rate). A structural sectional view of the storage battery is shown in FIG.
[0031]
In FIG. 5, 1 is a positive electrode current collector, 2 is a corrosion-resistant conductive material layer (Ta ₂ O ₅ —TiO ₂ composite oxide), 3 is a positive electrode active material, 4 is a negative electrode current collector, 5 is a negative electrode active material, 6 Denotes a separator, 7 denotes an exhaust hole, and 8 denotes an insulating frame.
[0032]
As shown in FIG. 5, the current collector of both electrodes serves as a part of the outer case and also has a function of a terminal, and no terminal is required unlike a conventional lead-acid battery.
[0033]
A conventional control valve type lead battery was also produced by the same method as described above except that the lead sheet on which the Ta ₂ O ₅ —TiO ₂ composite oxide was not formed was used as it was, and used for the test.
[0034]
[Table 1]

[0035]
These storage batteries were subjected to a charge / discharge cycle test in which the battery was discharged at 0.6 CA (C: rated capacity, A: unit of current) at room temperature for 1 hour and charged at 0.2 CA for 4.1 hours. The transition of the discharge capacity during the life test is shown in FIG.
[0036]
The conventional lead-acid battery has reached the end of its life in about 500 cycles, but the storage batteries pressed at 40 to 200 kPa according to the present invention have almost no decrease in capacity at the time of 800 cycles. However, the capacity of the storage battery A having a low compression force (20 kPa) was very quickly reduced to 100 cycles. When the battery was disassembled, the positive electrode active material was peeled off the current collector, and because of the low compression force, the resistance at the interface between the current collector and the active material and the internal resistance of the storage battery increased early during the cycle. The capacity seems to have decreased.
[0037]
Moreover, the capacity of the storage battery E produced with the highest pressure of 400 kPa decreased in 300 cycles. As a result of dismantling, the active material entered the glass mat and a short circuit occurred. It seems that PbO ₂ particles or Pb particles of the active material have penetrated into the small holes of the separator because the pressure is too strong.
[0038]
From the above results, the positive electrode plate in which the Ta ₂ O ₅ —TiO ₂ composite oxide thin film layer is formed on the surface of the lead current collector and the active material is applied thereon is a conventional Ta ₂ O ₅ —TiO ₂ composite oxide. Compared to the positive electrode plate that does not cover the object, the adhesion between the current collector and the active material is not good, so it is necessary to increase the compression force, and if the compression force is too high, a short circuit will occur. Was found to be limited to 40-200 kPa.
[0039]
In this example, a positive electrode plate in which an active material was applied to a current collector was used. However, it is the same even if an active material pellet prepared separately is prepared in advance and brought into contact with the current collector at a predetermined pressure. Results are obtained.
[0041]
In this embodiment, the 2V storage battery shown in FIG. 5 is manufactured. However, in the structure of the present invention, it is easy to stack a 2V storage battery to produce a high voltage or high capacity module battery. FIG. 7 is a sectional view of a high voltage module, and FIG. 8 is a sectional view of a high capacity module.
[0042]
In FIG. 7, the same reference numerals as those in FIG.
[0043]
In FIG. 8, 9 indicates a positive terminal and 10 indicates a negative terminal. The other components are given the same numbers as in FIG.
[0044]
As shown in FIG. 7 and FIG. 8, it is necessary to weld lead or lead alloys at the upper part of the electrode plate group, which has been necessary for high voltage in the conventional lead storage battery, or to connect the lead wire etc. outside the storage battery. A storage battery having an unnecessary structure can be easily obtained.
[0045]
Further, if the technique of forming the corrosion-resistant conductive material layer of the present invention on the surface of the positive electrode current collector is used, a bipolar battery can be realized because the current collector is basically not corroded. FIG. 9 is a sectional view of the structure of the bipolar battery, and 11 is a bipolar current collector. The other components are given the same numbers as in FIG.
[0046]
As shown in FIG. 9, a high-voltage storage battery can be easily produced by applying positive and negative electrode active materials on both surfaces of a current collector and laminating a large number of this electrode plate via a separator. A storage battery using such a single electrode plate having a positive electrode / negative electrode active material is called a bipolar battery. Since the storage battery of the present invention hardly corrodes the current collector, it is suitable for producing a bipolar battery, and a very inexpensive module storage battery can be supplied.
Example 3
As a result of experiments conducted by the inventors so far, it was found that the Ta ₂ O ₅ —TiO ₂ composite oxide layer formed on the current collector surface elutes in sulfuric acid when the voltage is 1.0 V or less. It is at the initial stage of formation of the electrode plate that the potential is reached during the production of the lead-acid battery. The electrode plate of the lead storage battery shows a very low voltage of 0 V to 0.5 V after the dilute sulfuric acid injection.
[0047]
In the present invention, after the injection sulfate, immediately by the voltage of the battery above 1.0 V, it is possible to suppress the elution of _Ta ₂ _O 5 -TiO 2 composite oxide of the collector surface.
[0048]
On the other hand, when the conversion is performed at a high voltage, gas is generated during the formation on the surface of the Ta ₂ O ₅ —TiO ₂ composite oxide, the adhesion between the active material and the current collector is lost, and the internal resistance of the battery is increased. There is. In the present invention, it was found that the adhesion between the Ta ₂ O ₅ —TiO ₂ composite oxide and the active material can be maintained by limiting the voltage to 2 V or less for at least 1 hour after the start of chemical conversion. Hereinafter, the present invention will be described in detail with reference to examples.
[0049]
First, after forming Ta ₂ O ₅ —TiO ₂ composite oxide in various thicknesses on the surface of a pure lead sheet having a thickness of 0.5 mm by a sputtering method, a normal active material for a lead storage battery is applied, and a positive electrode plate Was made. This electrode plate was combined with a normal negative electrode plate for a lead storage battery and a fine glass fiber separator for a control valve type lead storage battery to produce a storage battery having a capacity of about 0.25 Ah. For comparison, a conventional lead storage battery using a positive electrode plate in which a Ta ₂ O ₅ —TiO ₂ composite oxide layer was not formed on the surface of the lead sheet was also prepared and used for the test.
[0050]
These storage batteries were formed by a two-step method. In the first step formation, the time from the start of the electrolyte injection to the start, the voltage and time during the formation were variously changed. All the chemical conversions in the second step were performed at 0.2 CA current until 350% of the theoretical capacity of the positive electrode active material was reached.
[0051]
Table 2 shows the thickness of the Ta ₂ O ₅ —TiO ₂ composite oxide layer and the contents of chemical conversion conditions.
[0052]
[Table 2]

[0053]
For a storage battery having a Ta ₂ O ₅ —TiO ₂ composite oxide layer thickness of 10 microns, the first step formation was started immediately after the injection, and the formation voltage and formation time were changed as shown in Table 2. . After the formation, the amount of PbO _{2 in} the positive plates of these storage batteries was measured. Further, these storage batteries were subjected to an anodic oxidation test at 0.05 CA current for 120 hours, and the amount of corrosion after the test was measured. The results are shown in FIGS. 10 and 11, respectively.
[0054]
As shown in FIG. 10, the amount of PbO ₂ was large when the voltage of the first step formation was 2 V or less. When it exceeded 2 V, the amount of PbO ₂ was small. This is probably because if the voltage at the initial stage of conversion is too high, gas generation is intense at the interface between the Ta ₂ O ₅ —TiO ₂ composite oxide and the active material on the surface of the current collector, resulting in a decrease in conversion efficiency. Further, the amount of PbO ₂ was large when the time for the first step formation was 1 hour or longer.
[0055]
From the measurement result of the thickness of the corrosion layer after the anodic oxidation test shown in FIG. 11, if the voltage of the first step formation is lower than 1 V, the dissolution of the Ta ₂ O ₅ —TiO ₂ composite oxide layer may occur. The thickness of the corrosion layer was not different from that of the conventional lead storage battery in which the Ta ₂ O ₅ —TiO ₂ composite oxide layer was not formed on the current collector surface. If it was formed at a voltage of 1 V or higher, almost no corrosion occurred.
[0056]
From the above result, the voltage of the first step conversion it should be more than 1V, it was found that in order to further improve the PbO ₂ amount should the chemical conversion in which the voltage below 2V over 1 hour.
[0057]
Next, the first step chemical conversion was fixed at 1 V × 5 h, and the thickness of the Ta ₂ O ₅ —TiO ₂ composite oxide thin film layer and the time from the injection to the start of chemical conversion were changed as shown in Table 2. The effect of anodic oxidation on corrosion was investigated. The result is shown in FIG.
[0058]
As shown in FIG. 12, when the Ta ₂ O ₅ —TiO ₂ composite oxide layer was thickened and the time from the start of injection to the start of chemical conversion was shortened, corrosion hardly occurred in the oxidation test. On the other hand, when the Ta ₂ O ₅ —TiO ₂ composite oxide layer was thin or when the time from the start of injection to the start of chemical conversion was long, the amount of corrosion after the oxidation test increased.
[0059]
In order to clarify the conditions for reducing the amount of corrosion, the relationship between the formation start time at the limit of low corrosion and the thickness of the Ta ₂ O ₅ —TiO ₂ composite oxide thin film was re-plotted in FIG. From this figure, in order to suppress the dissolution of the Ta ₂ O ₅ —TiO ₂ composite oxide thin film during the chemical conversion and improve the corrosion resistance, the thin film layer thickness of the Ta ₂ O ₅ —TiO ₂ composite oxide is defined as A ( It was found that the chemical conversion may be performed according to the following formula when the time from the injection of the electrolytic solution to the start of chemical conversion is T (minutes).
[0060]
T <19.2 LOG ₁₀ A
【effect】
As explained above, in a lead storage battery using a positive electrode plate in which a corrosion-resistant conductive material layer is formed on the surface of a current collector made of lead, a lead alloy or other metal, there is a problem in the conductivity of the current collector, Although there were problems such as poor adhesion between the current collector and the active material and the inability to take out electricity, the present invention solved such problems and was light and thin with excellent corrosion resistance. A positive electrode current collector for a lead storage battery can be obtained, which makes it possible to provide a lead storage battery with a long life, high energy density, and high reliability at low cost, and its industrial value is extremely high.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an essential part showing the structure of an embodiment of a positive electrode current collector according to the present invention. FIG. 2 is a characteristic diagram showing a transition of terminal voltage during an anodic oxidation test. Fig. 4 is a characteristic diagram showing the amount of corrosion of the current collector. Fig. 4 is a diagram showing the discharge characteristics. Fig. 5 is a schematic cross-sectional view showing an example of the structure of a lead-acid battery using a positive electrode plate on which a corrosion-resistant conductive material layer is formed. Characteristic diagram showing transition of discharge capacity during cycle life test [Fig. 7] Schematic cross-sectional view showing an example of high voltage of a lead-acid battery using a positive electrode plate on which a corrosion-resistant conductive material layer is formed [Fig. 8] Corrosion-resistant conductive material layer FIG. 9 is a schematic cross-sectional view showing an example of increasing the capacity of a lead-acid battery using a positive electrode plate on which a lead is formed. FIG. 9 is a schematic cross-sectional view showing the structure of a bipolar lead-acid battery using a positive electrode plate on which a corrosion-resistant conductive material layer is formed. Relationship between voltage and formation time during one-step formation and the amount of PbO ₂ after formation FIG. 11 is a characteristic diagram showing the relationship between the voltage and the formation time during the first step formation and the corrosion layer thickness after the anodic oxidation test. FIG. 12 is the time from the injection to the start of formation and Ta _2. O ₅ -TiO ₂ composite characteristic diagram showing the relationship between the film thickness and the corrosion layer thickness of the oxide 13 Ta _₂ O ₅ -TiO ₂ dissolution limit thickness and chemical initiator that does not affect the performance of lead-acid battery of the thin film layer Characteristic diagram showing the relationship with time until
DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Corrosion-resistant electrically conductive material layer 3 Positive electrode active material 4 Negative electrode current collector 5 Negative electrode active material 6 Separator 7 Exhaust hole 8 Insulation frame 9 Positive electrode terminal 10 Negative electrode terminal 11 Bipolar current collector

Claims

A positive electrode plate for a lead storage battery in which a corrosion-resistant conductive material layer is formed on the surface of the positive electrode current collector, wherein the corrosion-resistant conductive material is a Ta ₂ O ₅ —TiO ₂ composite oxide .

A lead storage battery comprising the positive electrode plate according to claim 1, wherein a pressing force of 40 to 200 kPa is applied to the positive electrode plate.