【０００１】
【発明の属する技術分野】
本発明は、鉛蓄電池の製造、保存および補充電方法に関するものである。
【０００２】
【従来の技術】
鉛蓄電池の充・放電反応は、正極活物質に二酸化鉛（ＰｂＯ２、以降ＰｂＯ２という）負極活物質に鉛（Ｐｂ、以降Ｐｂという）、電解液に希硫酸を使用し、正・負極活物質は放電によって、共に希硫酸と反応して硫酸鉛（ＰｂＳＯ４、以降ＰｂＳＯ４という）に変化し、充電によってＰｂＯ２とＰｂとに戻るものである。正・負極活物質の原料はいずれも酸化鉛を主成分とする鉛粉である。
【０００３】
鉛蓄電池は、クラッド式（チューブ式）とペースト式の二種類が一般的に製造されている。
【０００４】
クラッド式鉛蓄電池の場合、正極板は、鋳造で作られた鉛合金の芯金をガラス繊維または合成繊維からなるチューブの中に通し、前記芯金と前記チューブとの隙間に鉛粉を充填したものである。負極板には通常、ペースト式極板が採用されている。この場合の極板は、鋳造等で作られた鉛合金の格子体あるいは鉛もしくは鉛合金シートを打ち抜き又はエキスパンド加工により形成した格子体に、鉛粉と所定の希硫酸とによって練り込まれたペーストを充填・乾燥したものである。
【０００５】
ペースト式鉛蓄電池は、正・負極板共に上述した方法で製造されたペースト式極板が使用されている。
【０００６】
上述した製造プロセスの時点では、各極板は発電機能を有しておらず、通常、未化成極板とよばれている。これらが発電機能を備えるには化成工程を経る必要がある。
【０００７】
該化成工程には二種類の方法がある。一つは、上記未化成正・負極板をセパレーターを介して積層した極板群（エレメント）を形成した後、該エレメントを電槽に挿入し、希硫酸を注液し、所定の電気量を供給し、電気化学的に正極に酸化、負極に還元反応を起こさせ、両極板に発電機能を付加するもので、これを電槽化成と称している。
【０００８】
もう一つは、タンク内に複数の未化成正極板および負極板をそれぞれ相対して配列し、希硫酸を注入して、所定の電気量を供給し、電槽化成と同様、両極板に発電機能を付加させるもので、これをタンク化成と称している。このようにして化成された極板は、タンクから引き上げられ、水洗および制御された環境下で乾燥を行った後に蓄電池として組み立てられる。
【０００９】
電槽化成により製作された鉛蓄電池は、未化成状態のエレメントを電槽に挿入し、化成を行うので、タンク方式で化成した極板と違って水洗・乾燥の工程が不要で製造コストが削減できるメリットを有している。また、化成後の蓄電池の極板は希硫酸で満たされており、出荷後、すぐさま使用可能である利点をも有している。その反面、該鉛蓄電池の自己放電は、常温で１日当たり定格容量の約０．２％程度進行し、保存期間が限られてしまう問題を抱えている。
【００１０】
一方、タンク化成により製作された極板を用いた蓄電池は、通常は、正・負極板が乾燥状態で電槽内に組み込まれ、出荷される。該蓄電池を乾式即用式鉛蓄電池と称している。この場合、使用時には電解液を注入しなければならない不便さがある。しかしながら、使用前までは極板が希硫酸に満たされておらず、自己放電がほとんど起こらないので保存性能が電槽化成で製作した蓄電池よりも大幅に優れた特長を有している。
【００１１】
そこで、蓄電池内に電解液が存在することが自己放電の原因であることから、電槽化成を行った蓄電池の保存期間を伸張させる方法として、電槽化成後、電解液を抜液することで自己放電速度を抑制し、その際、抜液状態で蓄電池を開放状態にすると外部から浸入した空気に負極板が晒され酸化されるので、開閉弁圧が０〜５０ｋＰａの制御弁を蓄電池に装着した湿式即用式鉛蓄電池（電解液を一部有していることから従来の電解液を保持していない乾式即用式に対してここでは湿式即用式と称する）が提案されている。この方式によって、従来の電槽化成後、電解液を保持したままの鉛蓄電池に比べて、保存性能は改善されたが、乾式即用式鉛蓄電池に比べ、まだまだ十分とはいえないのが現状で、更なる保存期間の伸張が望まれている。
【００１２】
さらに湿式即用式鉛蓄電池を長期間保存した場合に、電解液量が少ない、すなわち硫酸分が少なく、自己放電により該硫酸分が消費尽くされ電解液が中性状態になることがある。このような状況下では、正極格子あるいは芯金の腐食が起こり易く、寿命劣化が促進されるといった問題をも抱えている。
【００１３】
【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、電槽化成後、抜液すると共に、注液口に制御弁を装着した方式の鉛蓄電池の製造方法において、保存期間が大幅に伸張され、また、長期間保存した場合の正極格子あるいは芯金の腐食を防止し、安定した寿命性能を有する鉛蓄電池の製造方法を提供することにある。
【００１４】
【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、電槽化成後、電解液を抜き取り、制御弁を装着する鉛蓄電池の製造方法において、
前記化成後の正極活物質内に８０質量％以上の二酸化鉛（ＰｂＯ２）を存在させることを特徴とするものである。
【００１５】
電槽化成後、電解液を抜き取った湿式即用式鉛蓄電池は、電槽化成後電解液をそのまま保持した蓄電池に比べて保存性能は改善されるが、乾式即用式鉛蓄電池に比べると劣り、実用化の面で障害になっていたのに対して、本願の発明者は、電解液を抜液した湿式即用式鉛蓄電池の正・負極活物質の分析・調査を行った結果、正極活物質内に含まれる、低級酸化鉛が自己放電の大きい原因であることを見出した。
【００１６】
正極活物質のＰｂＯ２および負極活物質のＰｂは、電解液として使用される希硫酸の濃度範囲では安定で化学的にはほとんど反応しない。したがって自己放電反応は電気化学的に進行するものであるが、保存中の鉛蓄電池は無負荷であり、また、電位も低いので、該自己放電反応は緩やかに進行する。これに対して、上記低級酸化鉛は希硫酸に対して不安定で容易に反応しＰｂＳＯ４を形成する、すなわち、この反応による自己放電速度は早い。しかも、湿式即用式鉛蓄電池では、電解液量が少ないために、早期に硫酸量が低下し、保存期間が制限される結果になる。これが、湿式即用式鉛蓄電池の保存性能が乾式即用式鉛蓄電池に比べると劣る原因であることがわかった。その対策として、電槽化成終了時の電解液比重を高くすることが有効で、１．２５〜１．４０（２０℃）の希硫酸が採用されている。しかし、抜液するので絶対量が少なく、これでは十分とはいい難い。また、あまり比重を高くすると、ＰｂＯ２およびＰｂが硫酸と化学的に反応する問題が発生し、１．４０が限度である。
【００１７】
したがって、根本的には電槽化成後の低級酸化鉛の量を少なくすることが必須であり、具体的には、電槽化成後の正極活物質内のＰｂＯ２量を８０質量％以上保持させることが低級鉛酸化物を少なくすることにつながり、自己放電抑制に効果的であることがわかった。
【００１８】
請求項２によれば、前記鉛蓄電池において、保存中の開回路電圧をセル当たり１．９０Ｖ以上に保つことを特徴とするものである。
【００１９】
請求項１に示すように、正極活物質中の低級酸化鉛を低減し、ＰｂＯ２の量を８０％以上確保することによって、従来、発生した初期の自己放電の促進は抑制できるが、湿式即用式鉛蓄電池は、基本的に硫酸分が少ないので、長期間保存すれば硫酸分が消費尽くされ電解液は中性溶液になってしまう。鉛蓄電池の正極の腐食は、無負荷、すなわち開回路電圧の電位では電解液濃度が酸性溶液より中性溶液の方が腐食が進行することが知られている。しかも、このような環境下での腐食生成物は、低級酸化鉛であるといわれている。該物質は不導体であるために、格子あるいは芯金と正極活物質との界面にこのような物質が生成されると電気抵抗が大きくなって充電され難くなる。さらに、これが進行すると格子あるいは芯金と正極活物質とが剥離し、容量が取り出せなくなり早期に寿命になる問題があった。
【００２０】
本願の発明者は、電解液濃度、すなわち電解液比重と開回路電圧とに相関関係があることに着目し、保存期間中の開回路電圧を管理することによって、保存期間中の湿式即用式鉛蓄電池の電解液比重（電解液濃度）を知ることができ、自己放電が進行し過ぎて電解液が中性になり、上述したような充電できないあるいは早期に寿命になってしまうといった問題を未然に防止できることを見出した。
【００２１】
通常、電解液比重と開回路電圧とには概ね、（１）式の関係がある。
【００２２】
開回路電圧（Ｖ）＝電解液比重＋０．８４・・・・（１）
したがって、保存期間中の開回路電圧が１．９Ｖの場合、（１）式によれば、
電解液比重＝１．９−０．８４＝１．０６
となり、電解液比重１．０６は、質量％濃度に換算すると約９質量％となり、硫酸濃度は低くなっているが酸性溶液であり、正極格子あるいは芯金の腐食が促進される状態でなく、これ以上開回路電圧が低くならなければ、上述したような問題が避けられることがわかった。
【００２３】
請求項３によれば、前記保存中の開回路電圧がセル当たり１．９０Ｖに到達した時点で、補液後、補充電を行うことを特徴とするものである。
【００２４】
請求項２に示したように、開回路電圧が１．９Ｖを維持しておれば、電解液は約９質量％の硫酸分を保持しており、正極格子あるいは芯金腐食が蓄電池の寿命に直ちに影響する段階までいっていない。しかし、安全を考慮するとこのあたりが限界で、１．９Ｖに達した時点で電槽化成後に有していた比重の電解液を注入して、補充電を行い、硫酸濃度を回復させ、再度、抜液することが該鉛蓄電池を長期間保存した後も安定して使用するために好ましい。
【００２５】
【実施例】
以下、本発明を実施例に基づいて詳細に説明する。
（実施例１）
鋳造で製作された鉛合金の芯金をガラス繊維からなるチューブの中に通し、チューブと芯金との隙間に鉛粉を充填した後、希硫酸に浸漬、熟成、乾燥してクラッド式正極板を作製した。一方、鋳造で作られた鉛合金の格子に、リグニンスルホン酸とＢａＳＯ４およびカーボンを混合した鉛粉と所定の希硫酸とを練膏して製作したペーストを充填し、熟成、乾燥してペースト式負極板を作製した。
【００２６】
上記正極板５枚と上記負極板６枚とを多孔性のポリエチレン製セパレーターを介して交互に積層しエレメントを形成し、該エレメントを電槽に挿入し、希硫酸を所定量注液して、電槽化成を行い、２Ｖ−２８０Ａｈ（１０ｈＲ）のクラッド式鉛蓄電池を製作した。電槽化成終了後、蓄電池を倒立させて電解液を抜き取った。該蓄電池に開閉弁圧が１５〜３０ｋＰａの制御弁を装着した。
【００２７】
また、化成終了時の電解液比重は１．２８（２０℃）になるように調整した。
【００２８】
このようにして製作した蓄電池について電槽化成時の条件を調整することによって電槽化成後の正極活物質内のＰｂＯ２量が９０質量％（Ａ）、８０質量％（Ｂ）、７５質量％（Ｃ）および７０質量％（Ｄ）の各蓄電池を作製した。
【００２９】
正極活物質内の低級鉛酸化物は、電槽化成の工程で極板内部の硫酸濃度あるいは化成時の電位によって生成されるもので、化成工程においてその生成はある程度避けられない。したがって、低級鉛酸化物量を少なくするためには電槽化成工程において、充電電気量を多くするのは当然であるが、充電のみを行うよりは部分的に放電工程を挿入することによって、その後の充電で低級酸化鉛が安定したＰｂＯ２に変換されるので、ＰｂＯ２量が多く、低級酸化鉛の少ない正極板が得られる。したがって、上記ＰｂＯ２量の多いサンプルを作製する際にこの処方を適用した。
【００３０】
上記Ａ，Ｂ，Ｃ，Ｄの４種類の蓄電池を４０℃雰囲気中で６ヶ月保存し、自己放電による正極活物質中のＰｂＳＯ４の蓄積量を調査した。また、比較のために電槽化成後の正極活物質内のＰｂＯ２量が８０質量％のもので、電解液を抜き取らない蓄電池（Ｅ）も併せ試験に供した。
【００３１】
保存期間と正極活物質内のＰｂＳＯ４量との関係を求めた結果を図１に示す。
【００３２】
図１に示すように、電解液を抜液しなかった蓄電池Ｅは、電解液が十分に存在するために保存期間中の自己放電が着実に進行し、６カ月目の正極活物質中のＰｂＳＯ４量が最も多かった。それに対して、電解液を抜液した蓄電池Ａ〜Ｄは、蓄電池内の電解液量が少ないので自己放電そのものがＥに比べて明らかに少なく、特に本発明の正極板活物質のＰｂＯ２量が９０質量％の蓄電池Ａおよび８０質量％のＢは、ＰｂＯ２量が７５質量％のＣおよび７０質量％のＤに比べて初期１カ月目のＰｂＳＯ４量が少なかった。これは、ＰｂＯ２量が多く、低級酸化鉛が少ないために初期における硫酸と低級酸化鉛との化学反応による自己放電が抑制されたためである。特に、ＰｂＯ２量が９０質量％のＤの保存期間とＰｂＳＯ４量との関係において、初期から一定の直線関係を維持して増加している。これは、低級鉛酸化物と硫酸との化学的な自己放電がほとんどなく、電気化学的な自己放電のみが進行していることを意味している。
【００３３】
このように、電槽化成後、電解液を抜液する湿式即用式鉛蓄電池において、正極活物質内のＰｂＯ２量を８０質量％以上にすることによって初期の自己放電を抑制できるために全体として自己放電量が少なくなり、保存性能が大幅に改善された。
（実施例２）
実施例２では、実施例１と同様の方法で２Ｖ−２８０Ａｈのクラッド式鉛蓄電池を作製した。
【００３４】
電槽化成後の電解液比重は、１．２８（２０℃）になるように、また、正極活物質中のＰｂＯ２量は８０質量％になるように化成条件を調整した。
【００３５】
上記蓄電池群を実施例１より厳しい温度条件の６０℃の雰囲気中で２４ヶ月保存した。保存期間中、蓄電池Ｆは開回路電圧が２Ｖ、蓄電池Ｇは１．９Ｖ、蓄電池Ｈは１．８Ｖにそれぞれ達した時点で補充電を行った。補充電は、抜液前の電解液比重と同じ１．２８の電解液を所定量注液し、５６Ａで５時間行い、補充電後に再び抜液を行った。その後、さらに保存を継続した。
【００３６】
また、比較として２４カ月間補充電を行わない蓄電池（Ｉ）も試験に供した。
【００３７】
図２に各蓄電池の６０℃雰囲気中で２４ヶ月間保存後の各蓄電池の正極芯金腐食量（質量％）を示す。
【００３８】
図２に示すように、保存期間中の開回路電圧が２Ｖあるいは１．９Ｖに達した時点で補充電を行った本発明の蓄電池ＦとＧは、２４カ月間補充電せずに保存した蓄電池Ｉに比較して、正極の芯金の腐食量が大幅に低減された。しかし、比較品の１．８Ｖに達した時点で補充電を行った蓄電池Ｈは、補充電を行わなかった蓄電池Ｉの腐食量と大差なかった。これは開回路電圧が１．８Ｖまで低下すると電解液中に硫酸分が消費尽くされ中性溶液状態になり正極芯金の腐食が進行したためと考えられる。
【００３９】
なお、実施例では、クラッド式鉛蓄電池を例にとって本発明の効果を説明したが、電槽化成後、抜液したペースト式鉛蓄電池でも、正極活物質内のＰｂＯ２量を８０質量％以上にする、また、保存期間中の開回路電圧を１．９Ｖ以上を確保し、１．９Ｖに到達した時点で補液後、補充電する方式を適用することによって、蓄電池の自己放電の改善および正極格子の腐食抑制に同様の効果が得られた。
【００４０】
【発明の効果】
以上、詳述したように、電槽化成を行った後、抜液し、制御弁を装着した即用式鉛蓄電池は、電解液量が少ないことによる自己放電の抑制効果はあるが、電槽化成後、正極活物質内に低級酸化鉛が生成されるため、初期に自己放電が多く、また、長期間保存すると電解液が少ないために硫酸分が消費されてしまい、電解液が中性状態になり、正極芯金あるいは格子の腐食が促進され、蓄電池の寿命性能に悪影響を及ぼす問題があった。これに対して本発明によれば、正極活物質内のＰｂＯ２量が８０質量％以上になるよう電槽化成条件を調整すると共に、保存期間中の開回路電圧を１．９Ｖ以上に保つと共に、１．９Ｖに到達した時点で補液後、補充電を行うことによって、実用的には製造コストが高い乾式即用蓄電池と対抗できる保存性能が得られると共に、長期放置における正極芯金あるいは格子の腐食が抑制でき、その工業的効果が極めて大である。
【図面の簡単な説明】
【図１】保存期間中の正極活物質内のＰｂＳＯ４量（質量％）の推移を示す図。
【図２】２４カ月保存後の正極芯金の腐食量（質量％）を示す図。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing, storing and supplementing a lead storage battery.
[0002]
[Prior art]
The charge / discharge reaction of a lead-acid battery uses lead dioxide (PbO 2 , hereinafter referred to as PbO 2 ) as a positive electrode active material, lead (Pb, hereinafter Pb) as a negative electrode active material, and dilute sulfuric acid as an electrolytic solution. The substance reacts with dilute sulfuric acid by discharge to change to lead sulfate (PbSO 4 , hereinafter referred to as PbSO 4 ), and returns to PbO 2 and Pb by charging. Both raw materials of the positive and negative electrode active materials are lead powders mainly composed of lead oxide.
[0003]
Lead storage batteries are generally manufactured in two types, a clad type (tube type) and a paste type.
[0004]
In the case of a clad-type lead storage battery, the positive electrode plate is made by passing a lead alloy core metal made by casting into a tube made of glass fiber or synthetic fiber, and filling a gap between the core metal and the tube with lead powder. Things. Usually, a paste-type electrode plate is adopted as the negative electrode plate. In this case, the electrode plate is a paste kneaded with lead powder and a predetermined diluted sulfuric acid into a grid of lead alloy made by casting or the like or a grid formed by punching or expanding a lead or lead alloy sheet. Is filled and dried.
[0005]
The paste-type lead storage battery uses a paste-type electrode plate manufactured by the above-described method for both the positive and negative electrode plates.
[0006]
At the time of the above-described manufacturing process, each electrode plate does not have a power generation function, and is usually called an unformed electrode plate. In order for these to have a power generation function, they need to go through a chemical conversion process.
[0007]
There are two kinds of methods in the chemical conversion step. One is to form an electrode group (element) in which the above-mentioned unformed positive / negative plates are laminated via a separator, then insert the element into a battery case, inject diluted sulfuric acid, and discharge a predetermined amount of electricity. It is supplied and electrochemically oxidizes the positive electrode and causes the negative electrode to undergo a reduction reaction, thereby adding a power generation function to both electrode plates. This is called battery case formation.
[0008]
The other is to arrange a plurality of non-formed positive and negative electrode plates in a tank facing each other, inject dilute sulfuric acid, supply a predetermined amount of electricity, and generate power on both plates in the same manner as in battery case formation. It adds functions and is called tank formation. The electrode plate thus formed is pulled out of the tank, washed with water and dried in a controlled environment, and then assembled as a storage battery.
[0009]
Since lead-acid batteries manufactured by battery case formation insert elements in a non-formation state into the battery case and perform formation, unlike the electrode plate formed by the tank method, there is no need for a washing and drying process and the manufacturing cost is reduced. It has the merit that can be done. Further, the electrode plate of the storage battery after formation is filled with dilute sulfuric acid, and has an advantage that it can be used immediately after shipment. On the other hand, the self-discharge of the lead storage battery progresses at about 0.2% of the rated capacity per day at room temperature, and there is a problem that the storage period is limited.
[0010]
On the other hand, a storage battery using an electrode plate manufactured by tank formation is usually shipped with the positive and negative electrode plates assembled in a battery case in a dry state. This storage battery is referred to as a dry-type immediate-use lead storage battery. In this case, there is an inconvenience that the electrolyte must be injected at the time of use. However, before use, the electrode plate is not filled with dilute sulfuric acid and self-discharge hardly occurs, so that the storage performance is significantly superior to that of a storage battery manufactured by a battery case.
[0011]
Therefore, since the presence of the electrolyte in the storage battery is a cause of self-discharge, as a method of extending the storage period of the storage battery that has been subjected to battery formation, the electrolyte is drained after the formation of the battery. Suppressing the self-discharge rate. At this time, if the storage battery is opened in the drained state, the negative electrode plate is exposed to air that has entered from the outside and oxidized, so a control valve with an on-off valve pressure of 0 to 50 kPa is attached to the storage battery. There has been proposed a wet-type ready-to-use lead-acid battery (hereinafter referred to as a wet-type ready-to-use type, which has a part of the electrolytic solution and thus has a dry-type immediate type which does not hold a conventional electrolytic solution). With this method, storage performance has been improved compared to a conventional lead-acid battery that retains electrolyte after battery formation, but it is still not enough compared to a dry-type immediate lead-acid battery. Therefore, further extension of the storage period is desired.
[0012]
Furthermore, when the wet-type ready-to-use lead storage battery is stored for a long period of time, the amount of the electrolytic solution is small, that is, the sulfuric acid content is small, and the sulfuric acid content is consumed by self-discharge, and the electrolytic solution may be in a neutral state. Under such circumstances, there is a problem that corrosion of the positive electrode grid or the core metal is apt to occur, and deterioration of life is promoted.
[0013]
[Problems to be solved by the invention]
The problem to be solved by the invention is that, in a method of manufacturing a lead storage battery in which a battery is drained after formation of a battery case and a control valve is attached to a filling port, the storage period is greatly extended, and the storage period is long. An object of the present invention is to provide a method for manufacturing a lead storage battery having stable life performance by preventing corrosion of a positive electrode grid or a cored bar in such a case.
[0014]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a method of manufacturing a lead storage battery in which an electrolytic solution is extracted after a battery case is formed, and a control valve is mounted.
The positive electrode active material after the formation contains at least 80% by mass of lead dioxide (PbO 2 ).
[0015]
The wet-ready immediate-use lead-acid battery, from which the electrolyte has been removed after battery formation, has improved storage performance compared to a storage battery that retains the electrolyte as-is after battery formation, but is inferior to the dry-ready lead-acid battery. In contrast, the inventors of the present application analyzed and investigated the positive and negative electrode active materials of a wet-type immediate lead-acid battery from which the electrolyte was drained. It has been found that lower lead oxide contained in the active material is a major cause of self-discharge.
[0016]
PbO 2 of the positive electrode active material and Pb of the negative electrode active material are stable and hardly chemically reacted in the concentration range of dilute sulfuric acid used as the electrolytic solution. Accordingly, the self-discharge reaction proceeds electrochemically, but the self-discharge reaction proceeds slowly since the lead storage battery during storage is unloaded and has a low potential. On the other hand, the lower lead oxide is unstable to dilute sulfuric acid and easily reacts to form PbSO 4 , that is, the self-discharge rate by this reaction is high. In addition, in the wet-type immediate lead-acid battery, since the amount of the electrolytic solution is small, the amount of sulfuric acid is rapidly reduced, and the storage period is limited. It has been found that this is the reason why the storage performance of the wet-type immediate storage battery is inferior to that of the dry-type immediate storage battery. As a countermeasure, it is effective to increase the specific gravity of the electrolytic solution at the end of formation of the battery case, and dilute sulfuric acid of 1.25 to 1.40 (20 ° C.) is employed. However, since the liquid is drained, the absolute amount is small, and it is difficult to say that this is sufficient. If the specific gravity is too high, a problem occurs in that PbO 2 and Pb chemically react with sulfuric acid, and the limit is 1.40.
[0017]
Therefore, it is fundamentally necessary to reduce the amount of the lower lead oxide after the battery case formation. Specifically, the PbO 2 amount in the positive electrode active material after the battery case formation is maintained at 80% by mass or more. This leads to a reduction in lower lead oxides, and is effective in suppressing self-discharge.
[0018]
According to a second aspect of the present invention, in the lead storage battery, the open circuit voltage during storage is maintained at 1.90 V or more per cell.
[0019]
As described in claim 1, by lowering the amount of lower lead oxide in the positive electrode active material and securing the amount of PbO 2 at 80% or more, the promotion of the initial self-discharge that has conventionally occurred can be suppressed. Since a lead-acid battery for use basically has a small amount of sulfuric acid, if stored for a long time, the sulfuric acid is consumed and the electrolyte becomes a neutral solution. It is known that the corrosion of a positive electrode of a lead storage battery is progressed with a neutral solution having no electrolytic solution concentration than an acidic solution with no load, that is, at the potential of the open circuit voltage. Moreover, it is said that the corrosion product under such an environment is lower lead oxide. Since such a substance is a non-conductor, if such a substance is generated at the interface between the grid or the core metal and the positive electrode active material, the electric resistance increases and charging becomes difficult. Further, when this progresses, the grid or the core metal and the positive electrode active material are separated, and there is a problem that the capacity cannot be taken out and the life is shortened at an early stage.
[0020]
The inventors of the present application have noted that there is a correlation between the electrolytic solution concentration, that is, the specific gravity of the electrolytic solution and the open circuit voltage, and by managing the open circuit voltage during the storage period, the wet immediate use type during the storage period It is possible to know the electrolyte specific gravity (electrolyte concentration) of the lead-acid battery, and the self-discharge proceeds too much to make the electrolyte neutral, so that the above-mentioned problems such as the inability to charge or the end of life will occur beforehand. Found that it can be prevented.
[0021]
Normally, the specific gravity of the electrolyte and the open circuit voltage generally have a relationship represented by the expression (1).
[0022]
Open circuit voltage (V) = specific gravity of electrolyte solution + 0.84 (1)
Therefore, when the open circuit voltage during the storage period is 1.9 V, according to equation (1),
Electrolyte specific gravity = 1.9-0.84 = 1.06
The specific gravity of the electrolytic solution, 1.06, becomes about 9% by mass in terms of the concentration by mass, and although the sulfuric acid concentration is low, it is an acidic solution, and the corrosion of the positive electrode grid or the core metal is not promoted. It has been found that the problem described above can be avoided if the open circuit voltage is not lowered any more.
[0023]
According to the third aspect, when the open circuit voltage during storage reaches 1.90 V per cell, the supplementary charge is performed after the replacement.
[0024]
As described in claim 2, when the open circuit voltage is maintained at 1.9 V, the electrolytic solution holds about 9% by mass of sulfuric acid, and the corrosion of the positive electrode grid or the core metal affects the life of the storage battery. It has not yet reached the stage where it will have an immediate effect. However, considering the safety, this is the limit, and when it reaches 1.9 V, the electrolyte of the specific gravity that was possessed after the formation of the battery case is injected, supplementary charging is performed, the sulfuric acid concentration is recovered, and again, It is preferable to drain the liquid so that the lead storage battery can be used stably even after being stored for a long time.
[0025]
【Example】
Hereinafter, the present invention will be described in detail based on examples.
(Example 1)
A lead alloy core made by casting is passed through a tube made of glass fiber, and the gap between the tube and the core is filled with lead powder, immersed in dilute sulfuric acid, aged, dried, and clad positive electrode plate Was prepared. On the other hand, a paste made by plastering a lead powder obtained by mixing lignin sulfonic acid, BaSO 4 and carbon and a predetermined dilute sulfuric acid into a lattice of a lead alloy produced by casting, filling, maturing and drying is used to form a paste. A negative electrode plate was prepared.
[0026]
The five positive electrode plates and the six negative electrode plates are alternately laminated via a porous polyethylene separator to form an element, the element is inserted into a battery case, and a predetermined amount of dilute sulfuric acid is injected. The battery case was formed to produce a 2V-280Ah (10hR) clad type lead storage battery. After the battery case formation was completed, the storage battery was inverted and the electrolytic solution was extracted. A control valve having an on-off valve pressure of 15 to 30 kPa was mounted on the storage battery.
[0027]
The specific gravity of the electrolyte at the end of the formation was adjusted to 1.28 (20 ° C.).
[0028]
By adjusting the conditions at the time of battery case formation for the storage battery thus manufactured, the amount of PbO 2 in the positive electrode active material after the battery case formation was 90% by mass (A), 80% by mass (B), and 75% by mass. (C) and 70 mass% (D) of the respective storage batteries were produced.
[0029]
The lower lead oxide in the positive electrode active material is generated by the concentration of sulfuric acid in the electrode plate or the potential at the time of formation during the battery forming step, and its formation is unavoidable to some extent in the formation step. Therefore, in order to reduce the amount of low-grade lead oxide, in the battery case formation step, it is natural to increase the amount of charge electricity, but by inserting a discharge step partially rather than performing only charge, Since the lower lead oxide is converted into stable PbO 2 by the charging of PbO 2 , a positive electrode plate having a larger amount of PbO 2 and a lower amount of lower lead oxide can be obtained. Therefore, this formulation was applied when preparing a sample having a large amount of PbO 2 .
[0030]
The four types of storage batteries A, B, C and D were stored in a 40 ° C. atmosphere for 6 months, and the amount of PbSO 4 accumulated in the positive electrode active material due to self-discharge was investigated. For comparison, a storage battery (E) in which the amount of PbO 2 in the positive electrode active material after battery formation was 80% by mass and from which the electrolyte was not extracted was also subjected to the test.
[0031]
FIG. 1 shows the result of determining the relationship between the storage period and the amount of PbSO 4 in the positive electrode active material.
[0032]
As shown in FIG. 1, in the storage battery E from which the electrolyte was not drained, the self-discharge during the storage period proceeded steadily due to the sufficient presence of the electrolyte, and the PbSO 4 4 was the most. On the other hand, in the storage batteries A to D from which the electrolyte was drained, the self-discharge itself was clearly smaller than that of E because the amount of the electrolyte in the storage batteries was small, and particularly, the PbO 2 amount of the positive electrode plate active material of the present invention was low. 90 wt% of the storage batteries a and 80 wt% of B is, PbO 2 weight were less PbSO 4 of initial 1 month compared to 75 wt% of C and 70% by weight of D. This is because the amount of PbO 2 is large and the amount of lower lead oxide is small, so that self-discharge due to a chemical reaction between sulfuric acid and lower lead oxide in the initial stage is suppressed. In particular, the relationship between the storage period of D in which the amount of PbO 2 is 90% by mass and the amount of PbSO 4 increases while maintaining a constant linear relationship from the beginning. This means that there is almost no chemical self-discharge between the lower lead oxide and sulfuric acid, and only electrochemical self-discharge is progressing.
[0033]
As described above, in a wet-type immediate lead-acid battery in which the electrolyte is drained after the battery case formation, the initial self-discharge can be suppressed by setting the amount of PbO 2 in the positive electrode active material to 80% by mass or more. As a result, the self-discharge amount was reduced, and the storage performance was greatly improved.
(Example 2)
In Example 2, a 2V-280Ah clad lead storage battery was manufactured in the same manner as in Example 1.
[0034]
The formation conditions were adjusted so that the specific gravity of the electrolytic solution after the battery case formation was 1.28 (20 ° C.), and the amount of PbO 2 in the positive electrode active material was 80% by mass.
[0035]
The storage battery group was stored for 24 months in an atmosphere of 60 ° C. under more severe temperature conditions than in Example 1. During the storage period, when the open circuit voltage of the storage battery F reached 2 V, the storage battery G reached 1.9 V, and the storage battery H reached 1.8 V, auxiliary charging was performed. The supplementary charge was performed by injecting a predetermined amount of an electrolytic solution having the same specific gravity as that of the electrolytic solution before the drainage, at 56 A, for 5 hours, and after the supplementary charge, draining again. Thereafter, the preservation was further continued.
[0036]
For comparison, a storage battery (I) which was not subjected to supplementary charging for 24 months was also subjected to the test.
[0037]
FIG. 2 shows the positive electrode core metal corrosion amount (% by mass) of each storage battery after storage in a 60 ° C. atmosphere for 24 months.
[0038]
As shown in FIG. 2, the storage batteries F and G of the present invention, which were supplementarily charged when the open circuit voltage during the storage period reached 2 V or 1.9 V, were stored without supplementary charging for 24 months. Compared with I, the amount of corrosion of the core metal of the positive electrode was significantly reduced. However, the storage battery H that was supplementarily charged when the voltage reached 1.8 V of the comparative product was not much different from the corrosion amount of the storage battery I that was not supplementarily charged. This is considered to be because when the open circuit voltage was reduced to 1.8 V, the sulfuric acid content was consumed in the electrolyte and the electrolyte became a neutral solution state, and the corrosion of the positive electrode core proceeded.
[0039]
In the examples, the effect of the present invention was explained by taking a clad type lead storage battery as an example. However, even in a paste type lead storage battery drained after battery formation, the amount of PbO 2 in the positive electrode active material was increased to 80% by mass or more. In addition, by improving the open-circuit voltage of the storage battery to 1.9 V or more during the storage period and applying a replenishing solution after reaching 1.9 V, the self-discharge of the storage battery can be improved and the positive electrode grid can be improved. A similar effect was obtained in inhibiting corrosion of steel.
[0040]
【The invention's effect】
As described in detail above, the immediate-use lead-acid battery, which has been drained after performing battery case formation and then equipped with a control valve, has an effect of suppressing self-discharge due to a small amount of electrolyte solution. After chemical formation, low-grade lead oxide is generated in the positive electrode active material, causing a large amount of self-discharge at the initial stage. And the corrosion of the positive electrode core bar or the grid is accelerated, which has a problem of adversely affecting the life performance of the storage battery. On the other hand, according to the present invention, the battery forming conditions are adjusted so that the amount of PbO 2 in the positive electrode active material becomes 80% by mass or more, and the open circuit voltage during the storage period is kept at 1.9V or more. By performing supplementary charge after reaching 1.9 V, supplementary charge is performed, so that practically high storage cost can be obtained, which is comparable to that of a dry-type immediate storage battery that has a high production cost. Corrosion can be suppressed, and the industrial effect is extremely large.
[Brief description of the drawings]
FIG. 1 is a graph showing a change in the amount (% by mass) of PbSO 4 in a positive electrode active material during a storage period.
FIG. 2 is a graph showing the corrosion amount (% by mass) of a positive electrode core after storage for 24 months.
