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JP4411860B2 - Storage battery - Google Patents

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Publication number
JP4411860B2
JP4411860B2 JP2003118324A JP2003118324A JP4411860B2 JP 4411860 B2 JP4411860 B2 JP 4411860B2 JP 2003118324 A JP2003118324 A JP 2003118324A JP 2003118324 A JP2003118324 A JP 2003118324A JP 4411860 B2 JP4411860 B2 JP 4411860B2
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Prior art keywords
lead
active material
storage battery
positive electrode
discharge
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JP2004327157A (en
Inventor
研 沢井
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GS Yuasa Corp
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GS Yuasa Corp
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

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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(PbO)、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(PbSO)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】
Pb0+Pb+2HSO→2PbSO+2HO・・・・・(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(PbO/PbSO)は、1.68Vであるのに対して、酸素の平衡電位(HO/1/2O+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/PbSO)は、−0.36Vであるのに対して水素の平衡電位(Pb/PbSO)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+HSO=PbSO+H・・・・・・・・・・・・(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(Pb0)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Pb0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Pb0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】
Pb0+M+HSO→PbSO+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】

Figure 0004411860
【0019】
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】
Figure 0004411860
【0022】
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】
Figure 0004411860
【0026】
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】
Figure 0004411860
【0028】
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】
Figure 0004411860
【0033】
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】
Figure 0004411860
【0038】
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。
【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]
BACKGROUND OF THE INVENTION
It relates to a storage battery.
[0002]
[Prior art]
As is well known, a storage battery, for example, a lead storage battery, is filled with a paste in which a raw material mainly composed of lead oxide is diluted with dilute sulfuric acid in a positive / negative grid made of lead or lead alloy, and is aged and dried. An unformed positive / negative electrode plate is prepared. The electrode plate does not have a power generation function at this time, and is provided with a power generation function through a chemical conversion step. When charging / discharging, 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 lattice. The main component of the positive electrode active material of the lead-acid battery is lead dioxide (PbO 2 ), and the main component of the negative electrode active material is metal lead (Pb), both of which have sufficient electrical conductivity up to the lattice. However, when the lead-acid battery is discharged, the positive and negative active materials change to non-conductive lead sulfate (PbSO 4 ), as shown in the formula (1). The discharge voltage drops before all the active material changes to lead sulfate.
[0003]
Pb0 2 + Pb + 2H 2 SO 4 → 2PbSO 4 + 2H 2 O (1)
When the amount of active material that the positive electrode active material reacted until the end of discharge is ap (g) and the total amount of active material bp (g) contained in the positive electrode plate, 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 active material reacted by the negative electrode active material until the end of discharge is an (g) and the total amount of active material bn (g) contained in the negative electrode plate, the utilization factor is Indicated by
[0005]
Negative electrode active material utilization rate (%) = an / bn × 100
The active material utilization of lead-acid batteries is usually as low as 40% or less for the positive electrode and 50% or less for the negative electrode. The main cause is that, as described above, lead sulfate, which is a positive / negative discharge product, is a non-conductor, so that the resistance in the electrode plate constituting a part of the internal resistance of the lead-acid battery increases, and the voltage As a result, the discharge becomes impossible even though 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 electrical conductivity even in the state of advanced discharge, improving the utilization rate of the active material. It is considered possible.
[0007]
Carbon has been added to the negative electrode plate for a long time, and a certain degree of 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 improving the utilization rate of the positive electrode active material, but the increase in capacity is due to the presence of anisotropic graphite rather than the improvement in conductivity of the positive electrode active material. This is because the active material expands and the porosity of the positive electrode active material increases. In addition, since the anisotropic graphite is decomposed in the positive electrode, there is a problem that the effect of the anisotropic graphite decreases with the progress of use.
[0008]
[Problems to be solved by the invention]
In lead-acid batteries, the reason why it is difficult to put into practical use an additive that improves the utilization rate of positive and negative electrode active materials and improves the initial performance and life performance is largely 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 / 2O 2 + 2H + ) is 1 .23V, which is more basic than that of the positive electrode. Originally, a lead-acid battery generates oxygen even in an open circuit state, and does not hold as a lead-acid battery. As shown, since it is generated only at a potential nobler 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 theoretically generated potential is said to be high oxygen overvoltage and is a characteristic of the lead electrode. On the other hand, the same can be said for the negative electrode. From the viewpoint of the equilibrium potential as shown in FIG. 1, the lead electrode (Pb / PbSO 4 ) is −0.36 V, whereas the hydrogen equilibrium potential (Pb / Pb / Pb / PbSO 4 ) is −0.36 V. PbSO 4 ) is noble at 0.0V, and hydrogen should be generated constantly, but it is not generated as shown by the arrows in FIG. 1 that hydrogen is generated only at a base potential lower than the equilibrium potential of lead. It is because it does not. This means that the lead electrode has a high hydrogen overvoltage. Therefore, in order to function effectively as an additive for a lead-acid battery, it is necessary to have a noble potential characteristic higher than the oxygen generation potential of the positive electrode and / or a lower potential characteristic lower than the hydrogen generation potential of the negative electrode. It is. Otherwise, even if it has conductivity, it becomes a secondary performance deterioration factor of the lead storage battery.
[0010]
That is, normally, in charging, the electrolysis of water in the electrolytic solution starts from the time when the charged amount becomes almost 100% of the discharged amount, and hydrogen and oxygen begin to be generated. If the oxygen is generated at a potential lower than the oxygen generation potential of the positive electrode or the hydrogen is generated at a potential nobler than the hydrogen generation potential of the negative electrode, the charge amount may not reach 100%. Oxygen and hydrogen are generated from the gas, and the electric energy for charging is used there, causing a problem that charging cannot be performed.
[0011]
Furthermore, particularly in the negative electrode, hydrogen is generated when an additive lower than the hydrogen generation potential of the lead electrode is present, and a local battery is formed between lead and hydrogen as shown in the formula (2), and the self-discharge amount is greatly increased. There is also an increasing problem.
[0012]
Pb + H 2 SO 4 = PbSO 4 + H 2 (2)
The charge / discharge reaction of the storage battery is an oxidation / reduction reaction. In particular, in the positive electrode, the discharge is the reduction of the positive electrode active material (Pb0 2 ), that is, the other party is oxidized. 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, it means that the Pb0 2 is consumed in addition to the power generation reaction, Since the function as the positive electrode is eventually lost, the additive is required to have stable characteristics that are not decomposed by the oxidation reaction.
[0013]
Pb0 2 + M + H 2 SO 4 → PbSO 4 + MO (3)
M: Additive (substance to be oxidized)
MO: Oxide The present invention has been made in view of the above, and the problem to be solved is that the conductivity is excellent, the increase in the internal resistance of the storage battery during discharge is suppressed, and the positive and negative electrode active materials Effective in improving utilization and lifetime performance, and as described above, there is no secondary deterioration factor of the lead storage battery, such as being decomposed in charging / discharging of the lead storage battery or adversely affecting charging. It is providing the lead acid battery containing an additive.
[0014]
[Means for Solving the Problems]
As a means for solving the problems of the present invention, according to claim 1, in the lead- acid battery, conductive diamond is contained in the positive electrode active material and / or the negative electrode active material. .
[0015]
Diamond has a strong bonding force of carbon are chemically very stable, can be present in the lead-acid battery stably without being degraded by oxidation and reduction reactions in the lead-acid battery. However, diamond is an insulator of about 1000 Ωcm and cannot be applied. However, 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 material is referred to as conductive diamond, and when the material is used for an electrode, it has a high oxygen / hydrogen overvoltage and has characteristics necessary as an additive for a lead storage battery. I understood. That is, when the conductive diamond is added to the active material of the lead storage battery, the conductivity suppresses an increase in internal resistance with the progress of discharge, improves the utilization rate of the positive and negative electrode active materials, and improves the life performance. Improve. Moreover, it does not become a secondary deterioration factor of the lead- acid battery, which adversely affects the charging characteristics or increases the self-discharge amount, and can exist stably.
[0016]
【Example】
The present invention will be described in detail based on examples.
Example 1
In Example 1, an example in which conductive diamond doped with boron is added to the positive electrode active material of a lead-acid battery will be described.
[0017]
Pb-0.08 mass% Ca-1.2 mass% Sn lattice filled with a paste prepared by kneading a positive electrode material added with conductive diamond powder doped with boron 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, as in the positive electrode plate, a normal paste is filled in a lattice made of a Pb-0.08 mass% Ca-1.2 mass% Sn alloy, and aging and drying are performed. A negative electrode plate was produced. The 10 positive electrode plates and 11 negative electrode plates were laminated through a separator made of fine glass fibers to produce a 60 Ah (12 V) control valve type lead storage battery at 3 hR. As a comparison, a control valve type lead storage battery having the same configuration and capacity as described above, which does not contain an additive in the conventional positive electrode active material, was prepared and used for the test. Table 1 shows the contents of the test storage battery.
[0018]
[Table 1]
Figure 0004411860
[0019]
These storage batteries were subjected to a heavy load life test according to JIS D-5301. Test conditions are shown below.
(Test conditions)
Discharge: 20 A × 1 hour Charge: 5 A × 5 hour Test temperature: 40 to 45 ° C. Performance evaluation in water tank: Discharge up to 10.2 V at 20 A every 25 cycles, and as defined in JIS D-5301 The time when the capacity of the storage battery became 50% or less was defined as the life.
[0020]
The test results are shown in Table 2. The initial capacity is expressed as a ratio when the capacity of the conventional product A is 100. The life performance was expressed as a ratio when the number of cycles in which the storage battery A reached the end of life was taken as 100.
[0021]
[Table 2]
Figure 0004411860
[0022]
As shown in Table 2, in the initial performance, compared to the conventional product A, the storage battery B to which 0.01% by mass of the conductive diamond of the present invention was added was about 30%, 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 is responsible for electrical conduction, so that the voltage drop is suppressed even when the discharge proceeds and the utilization factor 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 by 80% compared to the conventional product A. The reason why the life performance is greatly improved in this way is thought to be that the amount of positive electrode active material that can be discharged is increased, the burden of the active material on the discharge is reduced, and the deterioration rate of the active material during the life test is suppressed. .
(Example 2)
In Example 2, an example in which conductive diamond doped with boron is added to the negative electrode active material will be described.
[0024]
A control valve type lead acid battery of 60 Ah (12 V) of 3 hR having 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 was produced. did. Table 3 shows the contents of the test storage battery.
[0025]
[Table 3]
Figure 0004411860
[0026]
The storage battery was compared for initial performance and life test under the same conditions as in Example 1. The results are shown in Table 4. The initial performance is expressed as a ratio when the capacity of the conventional product A is 100, and the result of the life test is expressed as a ratio when the number of cycles when the conventional product A reaches the end of life is 100.
[0027]
[Table 4]
Figure 0004411860
[0028]
As shown in Table 4, in the initial performance, the storage battery D to which 0.01% by mass of the conductive diamond of the present invention was added compared to the conventional product A was about 4%, and the storage battery E to which 0.1% by mass was added. 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 by about 30% compared to the conventional product A.
[0030]
Thus, although the initial and lifetime performance was improved by adding conductive diamond, it was not as effective as in the case of the positive electrode active material. This is because the negative electrode plate is already added with carbon, sodium lignin sulfonate and barium sulfate in order to improve the initial and life performance, and is effective to some extent. It seems that it was not so noticeable.
(Example 3)
The additive of the present invention can act effectively when the oxygen generation potential when the anode is polarized is a noble potential equal to or higher than that of the positive electrode, and the hydrogen generation potential when the cathode is polarized is different from that of the negative electrode. The base potential is equivalent or less. As a result, the conventional additive had an adverse effect on the charging characteristics such that oxygen or hydrogen was generated by the end of charging and could not be fully charged, whereas the product of the present invention had no such problem. A test conducted to clarify the above will be described.
[0031]
A lead storage battery of 3 hR and 60 Ah (2 V) having the same specifications as in Example 1 was used, but a separator made of porous polyethylene was used as a separator, and a storage battery called a liquid type in which an electrolyte was sufficiently present was produced. The reason why the liquid type lead storage battery is used in this way is that the control valve type lead storage battery involves a sealing 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]
Figure 0004411860
[0033]
The storage battery was discharged with a current of 18 A to a final voltage of 1.7 V, and then charged in an atmosphere of 25 ° C. with a current of 0.1 CA (6 A) at 130% of the discharge amount. The transition of the terminal voltage at that time was recorded. The result is shown in FIG.
[0034]
As shown in FIG. 2, either a CC storage battery in which 0.1% by mass of conductive diamond is added to the positive electrode active material or a storage battery EE in which 0.1% by mass is added to the negative electrode active material with respect to the storage battery of the conventional product A Also showed almost the same voltage transition. This means that even if the positive electrode plate to which conductive diamond is added is anodically polarized, the generation potential of oxygen does not change, and even if the negative electrode plate to which conductive diamond is added is cathode-polarized, the hydrogen generation potential does not change. It was clarified that even when conductive diamond was added to the positive and negative electrode active materials, the charging characteristics were not adversely affected.
[0035]
Further, these charged storage batteries were left in an atmosphere of 40 ° C. for 3 months to compare self-discharge characteristics. The results are shown in Table 6. The self-discharge was evaluated by leaving the battery for 3 months, discharging it to 1.70 V at a current of 18 A without charging, charging it with a charge amount 1.3 times that of 60 Ah, and then recharging it at 18 A for 1. The battery was discharged to 70V. The self-discharge amount (%) was determined by the following equation, where H (Ah) is the capacity when discharged without charging, and I (Ah) is the discharge 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 is expressed as a ratio when the value of the conventional product A is 100.
[0037]
[Table 6]
Figure 0004411860
[0038]
As shown in Table 6, with respect to the conventional storage battery A, the storage battery CC obtained by adding 0.1% by mass of conductive diamond to the positive electrode active material, and 0.1% by mass of conductive diamond as the negative electrode active material None of the added storage batteries EE showed a difference in self-discharge rate. This is because both 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 negative electrode of the lead storage battery, so that a local battery is formed in the electrode plate during standing, and self-discharge is promoted. It is clear that it is not affected by the oxidation / reduction reactions associated with charging / discharging of lead-acid batteries and is stably present in the electrode plate, and does not cause secondary battery deterioration. Became.
[0039]
In the examples, conductive diamond obtained by doping boron into diamond was applied, but the same effect was obtained with conductive diamond doped with nitrogen.
[0040]
In the examples, powdered conductive diamond was used, but the same effect was obtained with needles or other shapes. As for the addition method, in the examples, it was added to the raw material in a dry state, but this is not particular, but when adding dilute sulfuric acid to the raw material to prepare a paste, it may be added to the paste, The same effect was observed even when suspended in the dilute sulfuric acid.
[0041]
Further, in the embodiments, the rectangular control valve type lead acid battery and the liquid type lead acid battery have been described, but it goes without saying that the same effect can be obtained even in a lead acid battery having other shapes such as a cylindrical shape and a bipolar type.
[0042]
The main point of the present invention is that when the lead storage battery is discharged, the discharge product is generally non-conductive, so the internal resistance in the electrode plate increases, the discharge voltage decreases, and the unreacted active material remains. The reason why the capacity cannot be taken out in spite of this is that the conductive diamond of the present invention is added, which is responsible for electric conductivity, suppresses an increase in internal resistance, and improves the utilization factor of the active material .
[0043]
【The invention's effect】
As described above in detail, the discharge product when the lead acid battery is discharged is generally non-conductive, and the capacity increases despite the fact that the internal resistance of the electrode plate increases and unreacted substances remain due to voltage drop. It is known that the addition of a conductive substance is effective for the problem of being unable to be removed, but many additives have a negative effect on the charging characteristics and the self-discharge is greatly increased. The following problem occurred and it could not be put into practical use. In contrast, conductive diamond does not cause the secondary problem described above, contributes to improving the utilization rate of the active material of the lead storage battery, greatly improves the initial and life performance, and has an extremely large industrial effect. is there.
[Brief description of the drawings]
FIG. 1 is a diagram showing equilibrium potentials of positive and negative electrodes of a lead-acid battery and theoretically generated potentials of hydrogen and oxygen.
FIG. 2 is a graph 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)

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蓄電池。In lead-acid batteries, lead-acid battery, characterized in that it contained conductive diamond in the positive electrode active material during and / or negative electrode active material.
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