JP4026257B2

JP4026257B2 - Lead acid battery

Info

Publication number: JP4026257B2
Application number: JP36265798A
Authority: JP
Inventors: 宣行高見; 雅之井出; 義文久間
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1998-12-21
Filing date: 1998-12-21
Publication date: 2007-12-26
Anticipated expiration: 2018-12-21
Also published as: JP2000188108A

Description

【０００１】
【発明の属する技術分野】
本発明は鉛蓄電池の改良に関するものである。
【０００２】
【従来の技術】
鉛蓄電池は２次電池として安価で比較的信頼性も高く、自動車のエンジン始動用電源や無停電の電源、ポータブル機器の電源として広く使用されている。
【０００３】
近年、市場の小型軽量化，高エネルギー密度の要望から極板の厚みが１ｍｍ以下の薄い極板を用い、これを円筒形に構成した電池が用いられてきている。
【０００４】
電気化学的に薄い極板を用いる利点は充放電の際の電極反応において、活物質から集電体である鉛合金基板までの電子の移動間距離が短くなる点から内部抵抗の減少が図れることと、薄い極板を用いることにより集電体と活物質の接触面積が増加でき、活物質の利用率や反応性が向上する点とである。
【０００５】
こうした薄い極板を用いる鉛蓄電池の集電体である鉛合金には特開昭５３−４７５２号公報に示されているように純鉛またはＰｂ−０．０５〜３重量％Ｓｎ合金を用い、これをエキスパンド状に加工したり、特開平５−５０３６０４号公報に示すように純鉛またはＰｂ−０．５重量％Ｓｎの集電体が用いられている。
【０００６】
しかしながら特に円筒型の鉛蓄電池においては、集電体をスパイラル状に巻回して構成することから集電体の結晶粒界に沿って亀裂が発生することがある。このような亀裂を起点として過充電により粒界腐食が進行し、これが過充電寿命劣化の要因となっていた。また特に過放電特性あるいは寿命特性を向上させることを目的として集電体中にＳｎを０．５重量％以上添加した場合、集電体の結晶粒界が顕著になることから、スパイラル状に構成するとより多く結晶粒界に亀裂が発生し易いという課題がある。また、１ｍｍ以下の厚みの薄い極板を用い円筒形に構成した電池では、集電体と活物質の接触表面積が多くなり、特に正極板のＰｂと活物質のＰｂＯ₂の界面でＰｂ＋ＰｂＯ₂→２ＰｂＯなる自己放電反応が進行し過放電状態になり易いので、過放電後の回復率を考慮して集電体中にＳｎを添加する必要性があった。
【０００７】
【発明が解決しようとする課題】
本発明は前記したような極板をスパイラル状に巻回して構成する鉛蓄電池において、集電体の結晶粒界の亀裂を抑制することにより過充電特性および寿命特性の低下を抑制するものである。また、寿命特性および耐過放電特性を考慮して集電体にＳｎを添加した構成においても上記の課題を解決しようとするものである。
【０００８】
【課題を解決するための手段】
前記の課題を解決するために、本発明は鉛合金からなる集電体の表面に活物質層を形成した正極板と負極板とをセパレータを介して渦巻状に巻回して構成した鉛蓄電池において、少なくとも前記正極板の集電体をＰｂ−Ｓｎ系合金からなる圧延箔とし、かつ前記圧延箔の圧延方向と渦巻状に巻回して構成する巻き方向とを同一方向としたものである。また本発明の構成は集電体中にＳｎを０．５〜５０重量％含有する場合において顕著に効果を得ることができる。
【０００９】
【発明の実施の形態】
本発明の一実施形態による鉛蓄電池は正極板の集電体としてＰｂ−Ｓｎ系合金から鋳造により得た２０ｍｍ厚みのスラブを１００μｍに１０段階圧延して得た帯状の圧延箔を用いた。この集電体の表面上に正極活物質層を形成させて本発明による正極板を得る。そしてこの正極板と負極板とをセパレータを介してスパイラル状に巻回して構成する。圧延箔は結晶粒界が顕著に形成されず、微細なために巻回しても粒界に沿った亀裂の発生を著しく抑制することができる。また、特に圧延箔において結晶粒子は圧延方向を長手方向としており、粒界は主として圧延方向に沿って形成されている。よって圧延方向と巻回方向とを一致させる方が好ましい。なぜならば圧延方向と巻回方向とを直角とした場合には圧延方向に沿って形成した結晶粒界を引き離すような応力がかかり微少な亀裂が発生することがあるためである。
【００１０】
また、上記のような本発明の構成は、集電体として０．５〜５０重量％のＳｎを含有することが好ましい。このような組成の合金は一般に結晶粒界が極めて顕著に形成されるため、集電体を巻回した構成においては粒界に沿った亀裂が顕著に発生して性能劣化を引き起こす場合があった。本発明の圧延箔を用いる構成によればこのような粒界の形成を抑制できることから過放電後の回復性あるいは寿命特性を考慮して集電体中にＳｎを一定以上含有する構成においても集電体の亀裂の発生とこれによる過充電寿命の低下を抑制することができる。よって、本来のＳｎの効果である過放電特性の向上効果と過充電寿命特性の向上効果とを両立して得ることができる。
【００１１】
【実施例】
（第１の実施例）
以下本発明の第１の実施例について、図面を参照しながら説明する。
【００１２】
まず、Ｐｂ−１重量％Ｓｎ合金を連続鋳造により２０ｍｍの厚みの鋳造スラブを作製した。この鋳造スラブを１０段の連続圧延機により１００μｍの厚みにまで冷間圧延して圧延箔を得た。この圧延箔をトリミングして幅３２ｍｍ，長さ２００ｍｍの帯状の集電体を作製した。ここで集電体の長さ方向を圧延方向と一致させたものを集電体Ａ、集電体の幅方向を圧延方向と一致させたものを集電体Ｂとした。次にＰｂ−１重量％Ｓｎ合金を連続鋳造により厚みが１００μｍの合金箔を作製した。この合金箔は前記と同様、幅３２ｍｍ，長さ２００ｍｍの帯状の集電体とした。この鋳造による集電体を集電体Ｃとした。
【００１３】
これらの集電体Ａ，ＢおよびＣの表面上に正極活物質層を形成させた正極板とした後に帯状の負極板，セパレータと組み合わせ、スパイラル状に巻回して極板群を形成した。ここで正極活物質としては一酸化鉛，鉛丹および金属鉛の混合粉体を水と希硫酸とで混練したものを用いた。負極板と純鉛の合金箔表面に一酸化鉛と金属鉛との混合粉体を水と硫酸を混練して得た活物質ペーストを充填後熟成乾燥したものを用いた。これらの極板群を円筒形の電槽に収納して２Ｖ２Ａｈの密閉形鉛蓄電池を作製した。これらの電池をそれぞれ電池Ａ，電池Ｂ，電池Ｃとし、これらの電池の過充電寿命試験を行った。試験条件は４０℃気相中において２．３Ｖ定電圧充電を１週間、放電は１Ａ定電流で終止電圧１．６Ｖとし、この充放電を繰り返して行い、放電持続時間が初期の５０％以下となった時点で寿命終了とした。これらの結果を表１に示す。なお、寿命としては集電体Ｃを用いた従来の電池の寿命を１００とした指数で示した。
【００１４】
【表１】

【００１５】
表１に示した結果から本発明の構成によれば過充電での寿命特性を向上させる効果が得られることがわかる。また、特に集電体の巻き方向と圧延方向を一致させることによってより顕著な効果を得ることができる。これらの電池を寿命試験終了後、分解調査したところ、本発明の電池ＡおよびＢについては集電体表面が均一に腐食され二酸化鉛に酸化していた。その中でも集電体Ｂについては一部に腐食により微細な孔が発生していた。従来例の電池Ｃについては集電体が激しく腐食されていてほとんど元の形状を維持していなかった。また、その一部を断面観察したところ、結晶粒界に沿って腐食が進行していた。また、腐食の進行はスパイラル状に巻いた外側からがほとんどであった。これは図１に模式的に示したように集電体１を巻くことにより巻きの外側の粒界２が広げられ、亀裂３が発生し、これを起点として腐食が進行したと考えられる。一方、本発明の構成においては結晶粒界が顕著に形成されないため従来例で見られた亀裂の発生を抑制できたと考えられる。また本発明例の中でも特に圧延方向と巻き方向を一致させた方が好ましいが、これは圧延組織でも結晶粒界は微少ながら形成されるものの結晶粒界は主に圧延方向に沿って形成されることから、圧延方向と巻き方向を一致させた場合にはこの結晶粒界が広げられる方向とならないことによると考えられる。
【００１６】
（第２の実施例）
第１の実施例で示した電池Ａ，Ｂおよび従来例電池Ｃについて正極の集電体中のＳｎの濃度を変化させて電池を作製した。これらの電池において第１の実施例と同じ条件での過充電寿命試験と過放電試験を行った。過放電試験条件としては電池を１Ａ放電（終止電圧１．６Ｖ）し放電持続時間を測定する。その後、４０℃で１００ｍΩの定抵抗負荷での過放電を連続３ヵ月行った。その後２．６Ｖ定電圧充電（最大電流２．５Ａ）を５時間、回復充電を行った。この回復充電後に１Ａ（０．５Ｃ放電電流）で１．６Ｖまで放電し、その時の放電持続時間を測定した。ここで回復充電後の放電持続時間の過放電前の放電持続時間に対する比率として過放電後の回復率をもとめた。図２はＳｎの濃度別の過放電後の回復率と過充電寿命とを示す図である。図２から従来例および本発明例ともにＳｎの濃度を０．５〜５０重量％の範囲で良好な回復率を示していることがわかる。Ｓｎの濃度が６０重量％では従来例、本発明例ともに正負極間にＳｎのデンドライト結晶が成長し短絡が発生していたため、回復率が極端に低下した。過充電寿命に関しては本発明例ではＳｎの濃度を高くするにつれて寿命が伸びる一方で、従来例では０．２５重量％を上限としてそれ以上の濃度領域で寿命の著しい低下が認められた。この従来例の電池について分解調査したところ、Ｓｎの濃度が０．２５重量％では集電体の粒界腐食はそれほど顕著ではないが０．５重量％では激しく粒界腐食を受けていた。
【００１７】
これらの結果によれば、従来例の構成では過放電後の回復性と過充電寿命とを両立させることができなかった。しかし本発明の構成によればＳｎの濃度を０．５〜５０重量％とすることにより過放電後の回復性と過充電寿命とを両立して、より良好にできることが明らかとなった。
【００１８】
【発明の効果】
以上説明したように本発明の構成によれば、極板をスパイラル状に巻回した構成の鉛蓄電池における正極板の集電体の亀裂の発生と、それによる過充電寿命特性の低下を抑制するとともに良好な過放電後の回復性を得ることができ、工業上極めて有効なものである。
【図面の簡単な説明】
【図１】従来例の電池における集電体の亀裂発生と腐食状態を示す模式図
【図２】本発明例および従来例の電池の過放電後の回復率と過充電寿命を示す図
【符号の説明】
１集電体
２粒界
３亀裂[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a lead storage battery.
[0002]
[Prior art]
Lead-acid batteries are inexpensive and relatively reliable as secondary batteries, and are widely used as power sources for starting automobile engines, uninterruptible power sources, and portable devices.
[0003]
In recent years, in order to reduce the size and weight and demand for high energy density in the market, a thin plate having a thickness of 1 mm or less is used, and a battery having a cylindrical shape is used.
[0004]
The advantage of using an electrochemically thin electrode plate is that the internal resistance can be reduced because the distance between the movement of electrons from the active material to the lead alloy substrate that is the current collector is shortened in the electrode reaction during charging and discharging. In addition, by using a thin electrode plate, the contact area between the current collector and the active material can be increased, and the utilization factor and reactivity of the active material are improved.
[0005]
As a lead alloy which is a current collector of a lead storage battery using such a thin electrode plate, pure lead or a Pb-0.05 to 3 wt% Sn alloy is used as disclosed in JP-A-53-4752. This is processed into an expanded shape, or a collector of pure lead or Pb-0.5 wt% Sn is used as disclosed in JP-A-5-503604.
[0006]
However, particularly in a cylindrical lead-acid battery, since the current collector is wound in a spiral shape, cracks may occur along the crystal grain boundaries of the current collector. Starting from such cracks, intergranular corrosion has progressed due to overcharging, which has been a cause of deterioration in overcharge life. In addition, when Sn is added to the current collector in an amount of 0.5% by weight or more for the purpose of improving overdischarge characteristics or life characteristics, the grain boundary of the current collector becomes prominent. Then, there is a problem that more cracks are likely to occur in the grain boundaries. In addition, in a battery configured in a cylindrical shape using a thin electrode plate having a thickness of 1 mm or less, the contact surface area between the current collector and the active material increases, and in particular, at the interface between Pb of the positive electrode plate and PbO ₂ of the active material, Pb + PbO ₂ → Since the self-discharge reaction of 2PbO proceeds and tends to be in an overdischarge state, it was necessary to add Sn to the current collector in consideration of the recovery rate after overdischarge.
[0007]
[Problems to be solved by the invention]
The present invention suppresses deterioration of overcharge characteristics and life characteristics by suppressing cracks in the crystal grain boundaries of the current collector in a lead storage battery configured by winding the electrode plate as described above in a spiral shape. . In addition, the above-described problems are also solved in a configuration in which Sn is added to a current collector in consideration of life characteristics and overdischarge resistance characteristics.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is in a lead-acid battery formed by winding spirally with a separator and a positive electrode plate and negative electrode plate with an active material layer formed on a surface of a current collector made of lead alloy At least the current collector of the positive electrode plate is a rolled foil made of a Pb—Sn alloy , and the rolling direction of the rolled foil is the same as the winding direction formed by winding in a spiral shape. Moreover, the structure of this invention can acquire an effect notably when Sn contains 0.5 to 50weight% in a collector.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The lead-acid battery according to one embodiment of the present invention used a strip-shaped rolled foil obtained by rolling a 20 mm-thick slab obtained by casting from a Pb—Sn-based alloy to 100 μm for 10 steps as a current collector of a positive electrode plate. A positive electrode active material layer is formed on the surface of the current collector to obtain a positive electrode plate according to the present invention. Then, the positive electrode plate and the negative electrode plate are spirally wound via a separator. In the rolled foil , crystal grain boundaries are not formed remarkably, and since it is fine, the occurrence of cracks along the grain boundaries can be remarkably suppressed even if it is wound. In particular, in the rolled foil , the crystal grains have the rolling direction as the longitudinal direction, and the grain boundaries are mainly formed along the rolling direction. Therefore, it is preferable to match the rolling direction with the winding direction. This is because when the rolling direction and the winding direction are perpendicular, a stress that separates the crystal grain boundaries formed along the rolling direction is applied and a minute crack may occur.
[0010]
Moreover, it is preferable that the structure of this invention as mentioned above contains 0.5 to 50 weight% Sn as a collector. In general, an alloy having such a composition has crystal grain boundaries that are extremely prominent. Therefore, in a configuration in which a current collector is wound, cracks along the grain boundaries may occur remarkably, leading to performance deterioration. . According to the configuration using the rolled foil of the present invention, the formation of such grain boundaries can be suppressed. Therefore, even in a configuration in which Sn is contained in the current collector in a certain amount or more in consideration of recoverability after overdischarge or life characteristics. Generation | occurrence | production of the crack of an electric body and the fall of the overcharge lifetime by this can be suppressed. Therefore, the improvement effect of the overdischarge characteristic which is the original effect of Sn and the improvement effect of the overcharge life characteristic can be obtained at the same time.
[0011]
【Example】
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0012]
First, a cast slab having a thickness of 20 mm was produced by continuous casting of a Pb-1 wt% Sn alloy. This cast slab was cold-rolled to a thickness of 100 μm with a 10-stage continuous rolling mill to obtain a rolled foil. The rolled foil was trimmed to produce a strip-shaped current collector having a width of 32 mm and a length of 200 mm. Here, a current collector A in which the length direction of the current collector was matched with the rolling direction was designated as current collector A, and a current collector B in which the width direction of the current collector was matched with the rolling direction. Next, an alloy foil having a thickness of 100 μm was produced by continuous casting of a Pb-1 wt% Sn alloy. This alloy foil was a strip-shaped current collector having a width of 32 mm and a length of 200 mm as described above. The current collector obtained by casting was designated as current collector C.
[0013]
A positive electrode plate having a positive electrode active material layer formed on the surfaces of the current collectors A, B, and C was formed, and then combined with a strip-shaped negative electrode plate and a separator, and wound in a spiral shape to form an electrode plate group. Here, as the positive electrode active material, a mixture powder of lead monoxide, red lead and metallic lead kneaded with water and dilute sulfuric acid was used. A mixed powder of lead monoxide and lead metal was filled on the negative electrode plate and pure lead alloy foil surface with an active material paste obtained by kneading water and sulfuric acid, and then aged and dried. These electrode plate groups were housed in a cylindrical battery case to produce a sealed lead-acid battery of 2V2Ah. These batteries were designated as battery A, battery B, and battery C, respectively, and an overcharge life test of these batteries was performed. The test conditions were 2.3V constant voltage charging in a gas phase at 40 ° C. for 1 week, and discharging was performed at 1A constant current with a final voltage of 1.6V. This charging and discharging was repeated, and the discharge duration was 50% or less of the initial value. At that time, the life was finished. These results are shown in Table 1. In addition, as a lifetime, it showed with the index | exponent which set the lifetime of the conventional battery using the collector C to 100.
[0014]
[Table 1]

[0015]
From the results shown in Table 1, it can be seen that according to the configuration of the present invention, the effect of improving the life characteristics in overcharging can be obtained. In particular, a more remarkable effect can be obtained by matching the winding direction of the current collector with the rolling direction. When these batteries were disassembled after completion of the life test, the surfaces of the current collector were uniformly corroded and oxidized to lead dioxide in the batteries A and B of the present invention. Among them, the current collector B partially had fine holes due to corrosion. Regarding the battery C of the conventional example, the current collector was severely corroded, and the original shape was hardly maintained. Further, when a part of the cross-section was observed, corrosion progressed along the crystal grain boundary. The progress of corrosion was mostly from the outside wound in a spiral. As schematically shown in FIG. 1, it is considered that when the current collector 1 is wound, the grain boundary 2 outside the winding is expanded, cracks 3 are generated, and corrosion starts from this. On the other hand, in the structure of this invention, since the crystal grain boundary is not formed notably, it is thought that generation | occurrence | production of the crack seen in the prior art example was able to be suppressed. Further, among the examples of the present invention, it is particularly preferable to match the rolling direction with the winding direction. This is because the grain boundary is formed along the rolling direction, although the grain boundary is formed in the rolled structure although it is small. From this, it is considered that when the rolling direction and the winding direction are made coincident with each other, the crystal grain boundary is not expanded.
[0016]
(Second embodiment)
The batteries A and B shown in the first example and the conventional battery C were manufactured by changing the Sn concentration in the positive electrode current collector. These batteries were subjected to an overcharge life test and an overdischarge test under the same conditions as in the first example. As overdischarge test conditions, the battery is discharged at 1 A (end voltage 1.6 V) and the discharge duration is measured. Thereafter, overdischarge with a constant resistance load of 100 mΩ at 40 ° C. was performed continuously for 3 months. Thereafter, 2.6 V constant voltage charging (maximum current 2.5 A) was performed for 5 hours for recovery charging. After this recovery charge, the battery was discharged at 1 A (0.5 C discharge current) to 1.6 V, and the discharge duration at that time was measured. Here, the recovery rate after overdischarge was obtained as the ratio of the discharge duration after recovery charge to the discharge duration before overdischarge. FIG. 2 is a graph showing the recovery rate after overdischarge and the overcharge life for each Sn concentration. It can be seen from FIG. 2 that both the conventional example and the inventive example show a good recovery rate when the Sn concentration is in the range of 0.5 to 50% by weight. When the Sn concentration was 60% by weight, since the dendrite crystal of Sn grew between the positive and negative electrodes and a short circuit occurred in both the conventional example and the present invention example, the recovery rate was extremely lowered. With respect to the overcharge life, in the present invention example, the life increased as the Sn concentration was increased, whereas in the conventional example, a significant decrease in the life was observed in a concentration region beyond the upper limit of 0.25% by weight. When the battery of this conventional example was disassembled and investigated, when the Sn concentration was 0.25% by weight, the intergranular corrosion of the current collector was not so remarkable, but at 0.5% by weight, it was severely subjected to intergranular corrosion.
[0017]
According to these results, the configuration of the conventional example cannot achieve both recoverability after overdischarge and overcharge life. However, according to the configuration of the present invention, it has been clarified that by making the Sn concentration 0.5 to 50% by weight, both the recoverability after overdischarge and the overcharge life can be achieved.
[0018]
【The invention's effect】
As described above, according to the configuration of the present invention, the occurrence of cracks in the current collector of the positive electrode plate in the lead storage battery having the configuration in which the electrode plate is wound in a spiral shape, and the deterioration of the overcharge life characteristic due to the crack are suppressed. In addition, good recoverability after overdischarge can be obtained, which is extremely effective industrially.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the occurrence of cracks and corrosion of a current collector in a battery of a conventional example. FIG. 2 is a diagram showing the recovery rate and overcharge life after overdischarge of the battery of the present invention and the conventional example. Explanation of]
1 Current collector 2 Grain boundary 3 Crack

Claims

A lead-acid battery in which a positive electrode plate and a negative electrode plate , each having an active material layer formed on the surface of a current collector made of a lead alloy , are spirally arranged via a separator, and at least the current collector of the positive electrode plate is a Pb-Sn alloy. and rolled foil made of, and lead-acid battery, characterized in that the winding direction constituting wound in the rolling direction and spiral the rolled foil was same direction.

The lead-acid battery according to claim 1, wherein the rolled foil is a Pb-Sn alloy containing 0.5 to 50 wt% of Sn.