JP2004327157A - Storage battery - Google Patents
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- JP2004327157A JP2004327157A JP2003118324A JP2003118324A JP2004327157A JP 2004327157 A JP2004327157 A JP 2004327157A JP 2003118324 A JP2003118324 A JP 2003118324A JP 2003118324 A JP2003118324 A JP 2003118324A JP 2004327157 A JP2004327157 A JP 2004327157A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
Description
【０００１】
【発明の属する技術分野】
蓄電池に関する。
【０００２】
【従来の技術】
蓄電池、例えば、鉛蓄電池は、周知にように、鉛あるいは鉛合金等からなる正・負極格子に鉛酸化物を主体とする原料を希硫酸で練膏したペーストを充填し、熟成・乾燥して未化成正・負極板を作製する。該極板は、この時点では発電機能を有しておらず、化成工程を経て発電機能が付与される。充・放電に際して、該発電機能を有する正・負極活物質が電解液と接している部分から格子までの電気導電性に関しては、前記活物質自身が担っている。鉛蓄電池の正極活物質の主成分は二酸化鉛（ＰｂＯ２）、負極活物質の主成分は金属鉛（Ｐｂ）であり、いずれも前記格子までの電気導電性を十分に有している。しかし、鉛蓄電池が放電すると、（１）式に示すように、正・負極の活物質が不導体の硫酸鉛（ＰｂＳＯ４）に変化するため、活物質の反応サイトから格子までの電気導電性が悪くなり、活物質がすべて硫酸鉛に変化しないうちに放電電圧が低下してしまう。
【０００３】
Ｐｂ０２＋Ｐｂ＋２Ｈ２ＳＯ４→２ＰｂＳＯ４＋２Ｈ２Ｏ・・・・・（１）
正極活物質が放電終了までに反応した活物質量をａｐ（ｇ）、正極板に含まれる全活物質量ｂｐ（ｇ）とした時、両者の比を正極活物質の利用率と呼び、下式で示される。
【０００４】
正極活物質利用率（％）＝ａｐ／ｂｐ×１００
負極活物質についても同様にして、負極活物質が放電終了までに反応した活物質量をａｎ（ｇ）、負極板に含まれる全活物質量ｂｎ（ｇ）とした時、利用率は下式で示される。
【０００５】
負極活物質利用率（％）＝ａｎ／ｂｎ×１００
鉛蓄電池の活物質利用率は、通常は正極で４０％以下、負極で５０％以下と低い。その主原因は、上述したように、正・負極の放電生成物である硫酸鉛が不導体であるために、鉛蓄電池の内部抵抗の一部を構成する極板内の抵抗が増加し、電圧が低下するため未反応活物質が残っているにもかかわらず放電ができなくなってしまう。
【０００６】
これに対して、活物質中に蓄電池の放電反応に関与しない安定な導電性材料を添加すれば、放電が進んだ状態でもこの材料が電気導電性を担うことができ活物質の利用率を改善できると考えられる。
【０００７】
負極板に対しては、古くからカーボンがその目的で添加されており、ある程度の効果を得ている。正極板の添加剤としては、例えば、特開平４−１３７３６７に記載されているように異方性黒鉛を添加することが提案されている。これは、正極活物質の利用率を改善するという点では、効果が認められるが、容量増加の要因は、正極活物質の導電性の改善によるものというよりは、異方性黒鉛の存在により正極活物質が膨張し、正極活物質の多孔度が増加したことに起因している。また、該異方性黒鉛は正極内で分解されるので使用経過と共にその効果が低下する問題をも抱えている。
【０００８】
【発明が解決しようとする課題】
鉛蓄電池において、正・負極活物質の利用率を改善し、初期および寿命性能を改善するのに有効な添加剤が実用化され難い理由は、次によるところが大きい。
【０００９】
すなわち、図１に示すように、正極の平衡電位（ＰｂＯ２／ＰｂＳＯ４）は、１．６８Ｖであるのに対して、酸素の平衡電位（Ｈ２Ｏ／１／２Ｏ２＋２Ｈ＋）は１．２３Ｖで正極のそれよりも卑で、本来なら、鉛蓄電池は、開回路の状態でも酸素が発生し、鉛蓄電池として成り立たないのであるが、実際には、この酸素の発生電位は、矢印で示すように、正極の平衡電位より貴な電位でしか発生しないために、二次電池として機能している。このように理論の発生電位より高い電位でしか酸素が実際に発生しないことを酸素の過電圧が高いといっており、鉛電極の特性である。一方、負極についても同様のことが言え、図１に示すように平衡電位から言えば、鉛電極（Ｐｂ／ＰｂＳＯ４）は、−０．３６Ｖであるのに対して水素の平衡電位（Ｐｂ／ＰｂＳＯ４）は０．０Ｖと貴であり、絶えず水素が発生するはずであるが、発生しないのは、図１の矢印で示すように、鉛の平衡電位よりも卑な電位でしか水素が発生しないためである。これは鉛電極が高い水素過電圧を有していることを意味する。したがって、鉛蓄電池の添加剤として有効に機能するためには、正極の酸素発生電位以上の貴な電位特性および／あるいは負極の水素発生電位以下の卑な電位特性を有していることが必要条件である。そうでないと例え、導電性を有していても鉛蓄電池の二次的な性能劣化要因となってしまうからである。
【００１０】
すなわち、通常、充電においては、充電量が放電量のほぼ１００％になった時点から、電解液中の水の電気分解が起こり、水素、酸素が発生し始めるが、正極あるいは負極に添加剤が存在し、それらが、正極の酸素発生電位より卑な電位で酸素が発生したり、あるいは、負極の水素発生電位より貴な電位で水素が発生したりすると、充電量が１００％に到達しないうちから酸素、水素が発生することになり、充電の電気エネルギーがそちらに使用され、充電できなくなる問題が生じる。
【００１１】
さらに、特に、負極では、鉛電極の水素発生電位より低い添加剤が存在すると水素が発生し、（２）式に示すように鉛と水素と間に局部電池が形成され、自己放電量が大幅に増加する問題も生じる。
【００１２】
Ｐｂ＋Ｈ２ＳＯ４＝ＰｂＳＯ４＋Ｈ２・・・・・・・・・・・・（２）
また、蓄電池の充・放電反応は、酸化・還元反応であり、特に、正極において、放電は正極活物質（Ｐｂ０２）が還元される、すなわち、相手を酸化することであり、（３）式に示すように添加剤のような異物が存在するとＰｂ０２が対極のＰｂではなくて、添加剤と酸化・還元を行うことになり、発電反応以外にＰｂ０２が消費されることを意味し、最終的には正極としての機能を失うことになるので、添加剤としては酸化反応に対して分解されない安定した特性が要求される。
【００１３】
Ｐｂ０２＋Ｍ＋Ｈ２ＳＯ４→ＰｂＳＯ４＋ＭＯ・・・・・・・・（３）
Ｍ：添加剤（酸化される物質）
ＭＯ：酸化物
本発明は、上記のことを鑑み、なされたもので、解決しようとする課題は、導電性が優れ、放電時の蓄電池の内部抵抗の増加を抑制し、正・負極活物質の利用率および寿命性能の改善に有効で、しかも、上述したように鉛蓄電池の二次的な劣化要因、例えば、鉛蓄電池の充・放電において分解されるとか、充電に悪影響を及ぼすといったことがない添加剤を含む鉛蓄電池を提供することにある。
【００１４】
【課題を解決するための手段】
本発明の課題を解決するための手段として、請求項１によれば、蓄電池において、正極活物質中および／あるいは負極活物質中に導電性ダイヤモンドを含有させたことを特徴とするものである。
【００１５】
ダイヤモンドは、炭素の結合力が強く、化学的に非常に安定であり、蓄電池内の酸化・還元反応により分解されることがなく安定して蓄電池内に存在することができる。しかしながら、ダイヤモンドは約１０００Ωｃｍの絶縁体であり適用できないが、ダイヤモンドにホウ素や窒素をドープすることによって、条件によって違いはあるが導電率０．１〜１０Ωｃｍ以下のものが得られる。このような物質を導電性ダイヤモンドと称しており、該物質を電極に使用したときに、高い酸素・水素過電圧を有しており、蓄電池の添加剤として必要な特性を具備していることが分かった。すなわち、該導電性ダイヤモンドを蓄電池の活物質に添加すると、その導電性により、放電経過に伴う内部抵抗の増加を抑制し、正・負極活物質の利用率を改善すると共に、寿命性能をも改善する。しかも、充電特性に悪影響を与えるとか、自己放電量が増加するといった蓄電池の二次的な劣化要因にもならず、安定して存在し得る。
【００１６】
【実施例】
本発明を実施例に基づき詳細に説明する。
（実施例１）
実施例１では、鉛蓄電池の正極活物質にホウ素をドープした導電性ダイヤモンドを添加した例について説明する。
【００１７】
Ｐｂ−０．０８質量％Ｃａ−１．２質量％Ｓｎ合金からなる格子に、ホウ素をドープした導電性ダイヤモンドの粉末を添加した正極原料を希硫酸で練膏したペーストを充填して、熟成・乾燥を行い、厚さ２．３ｍｍの未化成正極板を作製した。負極板に関しては、正極板と同様、Ｐｂ−０．０８質量％Ｃａ−１．２質量％Ｓｎ合金からなる格子に通常のペーストを充填し、熟成・乾燥を行って厚み１．７ｍｍの未化成負極板を作製した。前記正極板１０枚と負極板１１枚とを微細ガラス繊維からなるセパレータを介して積層して、３ｈＲで６０Ａｈ（１２Ｖ）の制御弁式鉛蓄電池を作製した。比較として、従来の正極活物質に添加剤を含まない上記と同じ構成・容量の制御弁式鉛蓄電池を作製し、試験に供した。試験蓄電池の内容を表１に示す。
【００１８】
【表１】
これらの蓄電池をＪＩＳ Ｄ−５３０１による重負荷寿命試験を行った。試験条件を以下に示す。
（試験条件）
放電：２０Ａ×１時間
充電：５Ａ×５時間
試験温度：４０〜４５℃の水槽中
性能評価：２５サイクル毎に、２０Ａで１０．２Ｖまで放電を行い、ＪＩＳ Ｄ−５３０１に規定されている前記蓄電池の容量の５０％以下になった時点を寿命とした。
【００２０】
試験結果を表２に示す。初期容量は、従来品Ａの容量を１００としたときの比率で表した。また、寿命性能は、蓄電池Ａが寿命になったサイクル数を１００としたときの比率で表した。
【００２１】
【表２】
表２に示すように、初期性能では、従来品Ａに比べて、本発明の導電性ダイヤモンド０．０１質量％を添加した蓄電池Ｂは、約３０％、０．１質量％添加した蓄電池Ｃは、約４５％改善された。これは正極に添加した導電性材料が電気伝導を担うので、放電が進んでも電圧低下が抑制され、活物質の利用率が向上したためと考えられる。
【００２３】
寿命性能では、従来品Ａに対して、本発明品Ｂは、約５０％、本発明品Ｃは、８０％改善された。このように大幅に寿命性能が改善されたのは、放電可能な正極活物質量が増え、放電に対する活物質の負担が小さくなり、寿命試験中の活物質の劣化速度が抑制されたためと考えられる。
（実施例２）
実施例２では、ホウ素をドープした導電性ダイヤモンドを負極活物質に添加した例について説明する。
【００２４】
粉末状の導電性ダイヤモンドを負極活物質に対して０．０１質量％および０．１質量％添加した以外は、実施例１と同じ仕様の３ｈＲで６０Ａｈ（１２Ｖ）の制御弁式鉛蓄電池を作製した。試験蓄電池の内容を表３に示す。
【００２５】
【表３】
上記蓄電池を、実施例１と同じ条件で初期性能および寿命試験の比較を行った。その結果を表４に示す。初期性能は、従来品Ａの容量を１００としたときの比率で、また寿命試験の結果は、従来品Ａが寿命になったサイクル数を１００とした時の比率で表した。
【００２７】
【表４】
表４に示すように、初期性能では、従来品Ａに比べて、本発明の導電性ダイヤモンド０．０１質量％を添加した蓄電池Ｄは、約４％、０．１質量％を添加した蓄電池Ｅは約１２％改善された。
【００２９】
寿命性能では、従来品Ａに対して、本発明品Ｄは、約２０％、本発明品Ｅは、約３０％改善された。
【００３０】
このように、導電性ダイヤモンドを添加することにより初期および寿命性能は改善されたが、正極活物質の場合程の効果はなかった。これは、既に、負極板には、初期および寿命性能を改善するためにカーボン、リグニンスルホン酸ソーダおよび硫酸バリウムが添加され、ある程度効果があるために、本発明の添加剤の効果が正極の場合ほど顕著にならなかったと考えられる。
（実施例３）
本発明の添加剤が有効に作用することができるのは、アノード分極した場合の酸素発生電位が正極のそれと同等以上の貴な電位であると共に、カソード分極した場合の水素発生電位が負極のそれと同等以下の卑な電位であることである。そのことによって、従来の添加剤が、酸素あるいは水素が充電終了までに発生して充電が十分にできないといった充電特性に悪影響を及ぼしていたのに対して、本発明品にはそういった問題のないことを明らかにするために行った試験について説明する。
【００３１】
実施例１と同じ仕様の３ｈＲで６０Ａｈ（２Ｖ）の鉛蓄電池であるが、セパレータに多孔性ポリエチレンからなるセパレータを使用し、電解液が十分に存在する液式といわれる蓄電池を作製した。このように液式鉛蓄電池を用いたのは、制御弁式鉛蓄電池では充電中に密閉反応が伴い、各電極の電圧特性が明確にならないためである。試験蓄電池の内容を表５に示す。
【００３２】
【表５】
上記蓄電池を１８Ａの電流で終止電圧１．７Ｖまで放電を行った後、２５℃の雰囲気中で、０．１ＣＡ（６Ａ）の電流で放電量の１３０％の充電を行った。その際の端子電圧の推移を記録した。その結果を図２に示す。
【００３４】
図２に示すように、従来品Ａの蓄電池に対して、正極活物質に導電性ダイヤモンド０．１質量％を添加したＣＣの蓄電池および負極活物質に０．１質量％添加した蓄電池ＥＥのいずれもほぼ同じ電圧推移を示した。このことは、導電性ダイヤモンドを添加した正極板をアノード分極させても、酸素の発生電位が変わらないこと、また導電性ダイヤモンドを添加した負極板をカソード分極させても水素発生電位が変わらないことを意味し、導電性ダイヤモンドを正・負極活物質に添加しても、充電特性に悪影響を及ぼさないことが明らかになった。
【００３５】
さらに、充電されたこれら蓄電池を４０℃の雰囲気中に３カ月間放置して、自己放電特性の比較を行った。その結果を表６に示す。自己放電の評価は、３カ月間放置後、充電せずに１８Ａの電流で１．７０Ｖまで放電を行った後、６０Ａｈの１．３倍の充電量で充電を行い、再度、１８Ａで１．７０Ｖまで放電した。充電せず放電した時の容量をＨ（Ａｈ）、充電後の放電容量をＩ（Ａｈ）とした時に、自己放電量（％）を次式で求めた。
【００３６】
自己放電量（％）＝（Ｉ−Ｈ）／Ｉ×１００
自己放電量の比較結果を表６に示す。自己放電率は、従来品Ａのそれを１００とした時の比率で表した。
【００３７】
【表６】
表６に示すように、従来品の蓄電池Ａに対して、導電性ダイヤモンドを０．１質量％を正極活物質に添加した蓄電池ＣＣ、および導電性ダイヤモンドを０．１質量％を負極活物質に添加した蓄電池ＥＥのいずれも、自己放電率に差が認められなかった。このことは、導電性ダイヤモンドの酸素発生電位および水素発生電位のいずれも鉛蓄電池の正極および負極のそれと同等以上であるため、放置中に、極板内で局部電池が形成され、自己放電が促進されるといったことがなく、また、鉛蓄電池の充・放電に伴う酸化・還元反応の影響を受けず安定して極板内に存在し、二次的な蓄電池の性能劣化要因にならないことが明らかになった。
【００３９】
実施例では、ダイヤモンドにホウ素をドープした導電性ダイヤモンドを適用したが、窒素をドープした導電性ダイヤモンドも同様の効果が得られた。
【００４０】
また、実施例では、粉末状の導電性ダイヤモンドを用いたが、針状、あるいはその他の形状でも同様の効果が得られた。また、添加方法についても、実施例では、乾式状態の原料に添加したが、これにこだわるものではなく、原料に希硫酸を加え、ペーストを作製する際に、該ペーストに添加してもよく、また前記希硫酸に浮遊させても同様の効果が認められた。
【００４１】
さらに、実施例では、角形の制御弁式鉛蓄電池および液式鉛蓄電池について説明したが、円筒形、バイポーラ等の他の形状を有する鉛蓄電池でも同様の効果が得られるのはいうまでもない。
【００４２】
本願発明では、鉛蓄電池を例にあげて詳細に説明してきたが、本発明の骨子とするところは、蓄電池が放電した際に放電生成物が概して不導体であるために極板内の内部抵抗が増加し、放電電圧が低下し、未反応活物質が残っているにもかかわらず容量が取り出せなくなるのを、本発明の導電性ダイヤモンド添加し、これに電気伝導性を担わせ、内部抵抗の増加を抑制し、活物質に利用率を改善することにある。したがって、鉛蓄電池に限定するものでなく、放電において同様の問題が発生する蓄電池に対して適用すれば効果があるのはいうまでもない。特に、水溶液系の電解液を用いた電池に添加剤を加えた場合、概して水素・酸素発生電位が低くなり二次的な問題が発生していたが、導電性ダイヤモンドは高い酸素過電圧および水素過電圧を有しており、水溶液系の電解液を用いた電池の添加剤として特に有効である。
【００４３】
【発明の効果】
以上、詳細に説明したように、蓄電池を放電した際の放電生成物は概して不導体であり、極板の内部抵抗が増加し電圧低下により未反応物質が残っているにもかかわらず容量が取り出せなくなる問題に対して、導電性を有する物質を添加することが有効であることは知られているが、多くの添加剤は充電特性に弊害が出たり、自己放電が大幅に多くなるといった二次的問題が発生し実用化できなかった。これに対して、導電性ダイヤモンドは、上記二次的問題が発生せず、蓄電池の活物質の利用率向上に寄与し、初期および寿命性能が大幅に改善され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】鉛蓄電池の正極および負極の平衡電位ならびに水素、酸素の理論発生電位を示す図。
【図２】本発明の導電性ダイヤモンドを正極あるいは負極活物質に添加した際の充電特性を示す図。[0001]
TECHNICAL FIELD OF THE INVENTION
Related to a storage battery.
[0002]
[Prior art]
Storage batteries, for example, lead storage batteries are, as is well known, filled with a paste obtained by pulverizing a raw material mainly composed of lead oxide with dilute sulfuric acid into a positive / negative grid made of lead or a lead alloy, and then aging and drying. An unformed positive / negative plate is produced. At this time, the electrode plate does not have a power generation function, and is provided with a power generation function through a chemical conversion step. During charge / discharge, the active material itself is responsible for the electrical conductivity from the portion where the positive and negative electrode active materials having the power generation function are in contact with the electrolyte to the grid. The main component of the positive electrode active material of the lead storage battery is lead dioxide (PbO 2 ), and the main component of the negative electrode active material is metallic lead (Pb), and both have sufficient electric conductivity up to the lattice. However, when the lead storage battery discharges, the positive and negative electrode active materials change to non-conductive lead sulfate (PbSO 4 ) as shown in equation (1), so that the electrical conductivity from the active material reaction site to the lattice is changed. And the discharge voltage is reduced before all the active material is changed to lead sulfate.
[0003]
Pb0 2 + Pb + 2H 2 SO 4 → 2PbSO 4 + 2H 2 O (1)
When the amount of the active material reacted until the end of the discharge of the positive electrode active material is ap (g) and the total amount of the active material contained in the positive electrode plate is bp (g), the ratio between the two is called the utilization rate of the positive electrode active material. It is shown by the formula.
[0004]
Positive electrode active material utilization rate (%) = ap / bp × 100
Similarly, for the negative electrode active material, when the amount of the active material reacted until the discharge of the negative electrode active material is an (g) and the total amount of the active material bn (g) contained in the negative electrode plate is expressed by the following formula: Indicated by
[0005]
Negative electrode active material utilization rate (%) = an / bn × 100
The active material utilization of a lead storage battery is usually as low as 40% or less for a positive electrode and 50% or less for a negative electrode. The main cause is that, as described above, since lead sulfate, which is a discharge product of the positive and negative electrodes, is a nonconductor, the resistance in the electrode plate, which constitutes a part of the internal resistance of the lead-acid battery, increases, and the voltage increases. , The discharge becomes impossible even though the unreacted active material remains.
[0006]
On the other hand, if a stable conductive material that does not participate in the discharge reaction of the storage battery is added to the active material, this material can take on the electrical conductivity even after the discharge has progressed, improving the utilization rate of the active material. It is considered possible.
[0007]
For a long time, carbon has been added to the negative electrode plate for that purpose, and a certain effect has been obtained. As an additive for the positive electrode plate, for example, it has been proposed to add anisotropic graphite as described in JP-A-4-137367. This is effective in terms of improving the utilization rate of the positive electrode active material, but the cause of the increase in capacity is not due to the improvement in conductivity of the positive electrode active material but to the positive electrode due to the presence of anisotropic graphite. This is because the active material expanded and the porosity of the positive electrode active material increased. In addition, since the anisotropic graphite is decomposed in the positive electrode, there is a problem that its effect is reduced with use.
[0008]
[Problems to be solved by the invention]
The reasons why it is difficult for a lead storage battery to practically use an additive effective for improving the utilization rate of the positive / negative electrode active material and improving the initial and lifetime performance are as follows.
[0009]
That is, as shown in FIG. 1, the equilibrium potential of the positive electrode (PbO 2 / PbSO 4 ) is 1.68 V, whereas the equilibrium potential of oxygen (H 2 O / １ ／ O 2 + 2H + ) is 1 .23 V, which is lower than that of the positive electrode. Normally, a lead-acid battery generates oxygen even in an open circuit state and does not work as a lead-acid battery. As shown in the figure, since it is generated only at a potential noble than the equilibrium potential of the positive electrode, it functions as a secondary battery. The fact that oxygen is actually generated only at a potential higher than the theoretical generation potential is referred to as a high oxygen overvoltage, which is a characteristic of a lead electrode. On the other hand, the same can be said for the negative electrode. As shown in FIG. 1, in terms of the equilibrium potential, the lead electrode (Pb / PbSO 4 ) has a potential of −0.36 V, whereas the equilibrium potential of hydrogen (Pb / Pb / PbSO 4 ). PbSO 4 ) is as precious as 0.0 V, and hydrogen should be generated continuously. However, hydrogen is generated only at a potential lower than the equilibrium potential of lead, as indicated by the arrow in FIG. This is because they do not. This means that the lead electrode has a high hydrogen overvoltage. Therefore, in order to function effectively as an additive for a lead storage battery, it is necessary that the additive has a noble potential characteristic equal to or higher than the oxygen generation potential of the positive electrode and / or a noble potential characteristic equal to or lower than the hydrogen generation potential of the negative electrode. It is. Otherwise, even if it has conductivity, it will be a secondary performance deterioration factor of the lead storage battery.
[0010]
That is, in charging, usually, when the charged amount becomes almost 100% of the discharged amount, electrolysis of water in the electrolytic solution occurs, and hydrogen and oxygen start to be generated, but the additive is added to the positive electrode or the negative electrode. When oxygen is generated at a potential lower than the oxygen generation potential of the positive electrode or hydrogen is generated at a potential noble than the hydrogen generation potential of the negative electrode, the charge amount may not reach 100%. Then, oxygen and hydrogen are generated, and the electric energy for charging is used there, causing a problem that charging cannot be performed.
[0011]
Furthermore, especially in the case of the negative electrode, when an additive having a potential lower than the hydrogen generation potential of the lead electrode is present, hydrogen is generated, and a local battery is formed between lead and hydrogen as shown in equation (2), and the self-discharge amount is significantly increased. There is also a problem that increases.
[0012]
Pb + H 2 SO 4 = PbSO 4 + H 2 (2)
Further, the charge / discharge reaction of the storage battery is an oxidation / reduction reaction. In particular, in the positive electrode, the discharge is to reduce the positive electrode active material (PbO 2 ), that is, to oxidize the other party. to a foreign substance is present Pb0 2 as additives as shown is not the Pb of the counter electrode, will be performing oxidation-reduction and additives, means that the Pb0 2 is consumed in addition to the power generation reaction, Eventually, the function of the positive electrode is lost, so that the additive is required to have stable characteristics that are not decomposed by the oxidation reaction.
[0013]
PbO 2 + M + H 2 SO 4 → PbSO 4 + MO (3)
M: additive (oxidized substance)
MO: Oxide The present invention has been made in view of the above, and the problem to be solved is to have excellent conductivity, to suppress an increase in the internal resistance of the storage battery at the time of discharging, and to improve the positive and negative electrode active materials. Effective for improving the utilization factor and life performance, and as described above, there is no secondary deterioration factor of the lead storage battery, such as being decomposed in charging / discharging the lead storage battery or adversely affecting charging. It is to provide a lead storage battery containing an additive.
[0014]
[Means for Solving the Problems]
According to a first aspect of the present invention, a rechargeable battery is characterized in that conductive diamond is contained in a positive electrode active material and / or a negative electrode active material.
[0015]
Diamond has a strong carbon bonding force, is chemically very stable, and can be stably present in a storage battery without being decomposed by oxidation / reduction reactions in the storage battery. However, although diamond is an insulator of about 1000 Ωcm and cannot be applied, by doping diamond with boron or nitrogen, a conductivity of 0.1 to 10 Ωcm or less can be obtained depending on conditions. Such a substance is called a conductive diamond, and when the substance is used for an electrode, it has a high oxygen-hydrogen overvoltage, and has been found to have the characteristics required as an additive for a storage battery. Was. That is, when the conductive diamond is added to the active material of the storage battery, the conductivity suppresses an increase in internal resistance due to the discharge process, improves the utilization rate of the positive and negative electrode active materials, and also improves the life performance. I do. In addition, the battery can be stably present without adversely affecting the charging characteristics or causing secondary deterioration of the storage battery such as an increase in the amount of self-discharge.
[0016]
【Example】
The present invention will be described in detail based on examples.
(Example 1)
Example 1 describes an example in which conductive diamond doped with boron is added to the positive electrode active material of a lead storage battery.
[0017]
A grid made of Pb-0.08% by mass Ca-1.2% by mass Sn alloy is filled with a paste obtained by pulverizing a cathode material obtained by adding boron-doped conductive diamond powder with dilute sulfuric acid. Drying was performed to produce an unformed positive electrode plate having a thickness of 2.3 mm. As for the negative electrode plate, similarly to the positive electrode plate, a grid made of a Pb-0.08% by mass Ca-1.2% by mass Sn alloy is filled with a normal paste, aged and dried to form a 1.7 mm-thick unchemically-formed. A negative electrode plate was produced. The 10 positive electrode plates and 11 negative electrode plates were laminated with a separator made of fine glass fibers interposed therebetween, to produce a 3 hR, 60 Ah (12 V) control valve type lead-acid battery. As a comparison, a control valve-type lead-acid battery having the same configuration and capacity as described above, in which no additive was added to the conventional positive electrode active material, was prepared and subjected to tests. Table 1 shows the contents of the test storage battery.
[0018]
[Table 1]
These storage batteries were subjected to a heavy load life test according to JIS D-5301. The test conditions are shown below.
(Test condition)
Discharge: 20 A × 1 hour Charge: 5 A × 5 hours Test temperature: Performance in a water tank at 40 to 45 ° C .: Discharge to 20 V at 10.2 V at every 25 cycles, and the discharge is performed as specified in JIS D-5301. The point in time when the capacity of the storage battery became 50% or less was defined as the life.
[0020]
Table 2 shows the test results. The initial capacity was represented by a ratio when the capacity of the conventional product A was set to 100. The life performance is represented by a ratio when the number of cycles at which the storage battery A reaches the end of life is 100.
[0021]
[Table 2]
As shown in Table 2, in the initial performance, the storage battery B to which 0.01% by mass of the conductive diamond of the present invention was added was about 30% compared to the conventional product A, and the storage battery C to which 0.1% by mass was added was , About 45% improvement. This is presumably because the conductive material added to the positive electrode plays a role of electric conduction, so that even if the discharge proceeds, the voltage drop is suppressed and the utilization rate of the active material is improved.
[0023]
In the life performance, the product B of the present invention was improved by about 50% and the product C of the present invention was improved by 80% compared with the conventional product A. The reason why the life performance was greatly improved in this way is considered to be that the amount of the positive electrode active material that can be discharged increased, the load of the active material on discharge became smaller, and the deterioration rate of the active material during the life test was suppressed. .
(Example 2)
Example 2 describes an example in which conductive diamond doped with boron is added to a negative electrode active material.
[0024]
A control valve type lead-acid battery of 60 Ah (12 V) was manufactured at 3 hR with the same specifications as in Example 1 except that 0.01% by mass and 0.1% by mass of powdered conductive diamond were added to the negative electrode active material. did. Table 3 shows the contents of the test storage battery.
[0025]
[Table 3]
The initial performance and the life test of the storage battery were compared under the same conditions as in Example 1. Table 4 shows the results. The initial performance was expressed as a ratio when the capacity of the conventional product A was set to 100, and the result of the life test was expressed as a ratio when the number of cycles at which the life of the conventional product A reached 100 was set.
[0027]
[Table 4]
As shown in Table 4, in the initial performance, as compared with the conventional product A, the storage battery D containing 0.01% by mass of the conductive diamond of the present invention showed a storage battery E containing approximately 4% and 0.1% by mass. Was improved by about 12%.
[0029]
In the life performance, the product D of the present invention was improved by about 20% and the product E of the present invention was improved by about 30% compared with the conventional product A.
[0030]
As described above, the addition of the conductive diamond improved the initial and life performances, but was not as effective as in the case of the positive electrode active material. This is because carbon, sodium ligninsulfonate and barium sulfate are already added to the negative electrode plate to improve the initial and life performance, and the effect of the additive of the present invention is positive when the effect of the additive of the present invention is positive. Probably not as noticeable.
(Example 3)
The additive of the present invention can work effectively because the oxygen generation potential when anodic polarized is a noble potential equal to or higher than that of the positive electrode, and the hydrogen generation potential when cathodically polarized is different from that of the negative electrode. That is, the potential is lower than the equivalent. As a result, the conventional additives had an adverse effect on charging characteristics such as insufficient charging due to the generation of oxygen or hydrogen before the end of charging, whereas the present invention does not have such a problem. The test performed to clarify is described.
[0031]
A 3hR, 60Ah (2V) lead-acid battery having the same specifications as in Example 1 was used, but a separator made of porous polyethylene was used as the separator to produce a storage battery called a liquid type in which an electrolyte was sufficiently present. The reason why the liquid-type lead-acid battery is used is that the control valve-type lead-acid battery involves a hermetic reaction during charging, and the voltage characteristics of each electrode are not clear. Table 5 shows the contents of the test storage battery.
[0032]
[Table 5]
After discharging the storage battery to a final voltage of 1.7 V with a current of 18 A, the battery was charged in a 25 ° C. atmosphere with a current of 0.1 CA (6 A) at a discharge amount of 130%. The transition of the terminal voltage at that time was recorded. The result is shown in FIG.
[0034]
As shown in FIG. 2, the storage battery of the conventional product A is different from the storage battery of CC in which 0.1% by mass of conductive diamond is added to the positive electrode active material and the storage battery EE in which 0.1% by mass is added to the negative electrode active material. Also showed almost the same voltage transition. This means that the generation potential of oxygen does not change even if the positive electrode plate to which conductive diamond is added is anodically polarized, and the hydrogen generation potential does not change even if the negative electrode plate to which conductive diamond is added is cathodically polarized. This means that addition of the conductive diamond to the positive and negative electrode active materials does not adversely affect the charging characteristics.
[0035]
Further, these charged storage batteries were left in an atmosphere at 40 ° C. for 3 months, and the self-discharge characteristics were compared. Table 6 shows the results. The self-discharge evaluation was performed after leaving the battery for 3 months, discharging the battery to a current of 18 A to 1.70 V without charging the battery, charging the battery at 1.3 times the charge amount of 60 Ah, and again charging the battery at 18 A. Discharged to 70V. The self-discharge amount (%) was determined by the following equation, where H (Ah) is the capacity when discharging without charging and I (Ah) is the discharging capacity after charging.
[0036]
Self-discharge amount (%) = (I−H) / I × 100
Table 6 shows a comparison result of the self-discharge amount. The self-discharge rate was represented by a ratio when the value of the conventional product A was set to 100.
[0037]
[Table 6]
As shown in Table 6, with respect to the conventional storage battery A, the storage battery CC in which 0.1% by mass of conductive diamond was added to the positive electrode active material, and 0.1% by mass of conductive diamond in the negative electrode active material were used. No difference was found in the self-discharge rate of any of the added storage batteries EE. This means that the oxygen generation potential and the hydrogen generation potential of the conductive diamond are equal to or higher than those of the positive electrode and the negative electrode of the lead-acid battery, so that a local battery is formed in the electrode plate during standing and self-discharge is promoted. It does not appear to be affected by oxidation / reduction reactions associated with charge / discharge of lead-acid batteries. Became.
[0039]
In the embodiment, the conductive diamond in which boron is doped into diamond is applied. However, the same effect can be obtained by the conductive diamond in which nitrogen is doped.
[0040]
Further, in the examples, powdery conductive diamond was used, but the same effect was obtained with needle-like or other shapes. In addition, as for the addition method, in the examples, it was added to the raw material in a dry state, but it is not limited to this, and diluted sulfuric acid may be added to the raw material, and when the paste is produced, it may be added to the paste. Similar effects were also observed when suspended in dilute sulfuric acid.
[0041]
Further, in the embodiment, the rectangular control valve type lead storage battery and the liquid type lead storage battery have been described. However, it goes without saying that the same effect can be obtained by a lead storage battery having another shape such as a cylindrical shape and a bipolar shape.
[0042]
Although the present invention has been described in detail by taking a lead storage battery as an example, the gist of the present invention is that when the storage battery is discharged, the internal resistance in the electrode plate is reduced because the discharge product is generally non-conductive. Increases, the discharge voltage decreases, and the capacity cannot be taken out even though the unreacted active material remains. The conductive diamond of the present invention is added, and the conductive diamond is added to the conductive diamond. The purpose is to suppress the increase and improve the utilization rate of the active material. Therefore, it is needless to say that the present invention is not limited to a lead storage battery, but is effective when applied to a storage battery in which a similar problem occurs in discharging. In particular, when an additive was added to a battery using an aqueous electrolyte solution, the hydrogen / oxygen generation potential generally became low, causing secondary problems.However, conductive diamond has high oxygen overvoltage and hydrogen overvoltage. Which is particularly effective as an additive for a battery using an aqueous electrolyte solution.
[0043]
【The invention's effect】
As described in detail above, the discharge product when the storage battery is discharged is generally non-conductive, and the capacity cannot be taken out despite the unreacted substance remaining due to the increase in the internal resistance of the electrode plate and the voltage drop. It is known that it is effective to add a conductive substance to solve the problem of disappearance.However, many additives have adverse effects on the charging characteristics and self-discharge greatly increase. Problems occurred and could not be put to practical use. On the other hand, the conductive diamond does not cause the above-mentioned secondary problem and contributes to the improvement of the utilization rate of the active material of the storage battery, and the initial and life performances are greatly improved and the industrial effect is extremely large. .
[Brief description of the drawings]
FIG. 1 is a diagram showing equilibrium potentials of a positive electrode and a negative electrode of a lead storage battery, and theoretical potentials of hydrogen and oxygen.
FIG. 2 is a diagram showing charging characteristics when the conductive diamond of the present invention is added to a positive electrode or a negative electrode active material.
Claims (1)
正極活物質中および／あるいは負極活物質中に導電性ダイヤモンドを含有させたことを特徴とする蓄電池。In storage batteries,
A storage battery comprising conductive diamond contained in a positive electrode active material and / or a negative electrode active material.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102790220A (en) * | 2012-08-27 | 2012-11-21 | 优科能源(漳州)有限公司 | Manufacturing method of diamond-shaped conductive additive for improving liquid absorbing performance of pole piece of lithium ion battery |
| EP3016182A1 (en) * | 2014-11-03 | 2016-05-04 | Centurion Bipolair B.V. | A bipolar plate for a bipolar lead acid battery and a method of manufacturing a substrate for a bipolar plate |
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| CN102790220A (en) * | 2012-08-27 | 2012-11-21 | 优科能源(漳州)有限公司 | Manufacturing method of diamond-shaped conductive additive for improving liquid absorbing performance of pole piece of lithium ion battery |
| EP3016182A1 (en) * | 2014-11-03 | 2016-05-04 | Centurion Bipolair B.V. | A bipolar plate for a bipolar lead acid battery and a method of manufacturing a substrate for a bipolar plate |
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| JP4411860B2 (en) | 2010-02-10 |
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