JP4556250B2

JP4556250B2 - Lead acid battery

Info

Publication number: JP4556250B2
Application number: JP28875798A
Authority: JP
Inventors: 孝夫大前; 山中　　健司; 義臣藤原
Original assignee: GS Yuasa International Ltd
Current assignee: GS Yuasa International Ltd
Priority date: 1998-09-25
Filing date: 1998-09-25
Publication date: 2010-10-06
Anticipated expiration: 2018-09-25
Also published as: JP2000100468A

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。
【０００２】
【従来の技術】
従来の鉛電池の負極活物質量は正極活物質量とほぼ同等かそれ以上になるように設計されていた。これは負極活物質に余裕を持たせることで、正極板が寿命の制限因子となるようにするためであった。最近では電池のエネルギー密度の向上要求が大きくなってきたため、負極活物質量を減らしその分正極活物質量を増量した電池が多くなってきた。負極活物質の利用率は正極活物質に比べて大きいため、正極活物質が容量制限因子となるためである。
【０００３】
しかしこのような電池では正極と負極とのバランスがとれていないために定電流−定電圧充電を行う充放電サイクルを行った際には、正極の充電が十分に行われず早期に容量が低下してしまうことがある。
【０００４】
図１は放電充電１サイクル分の電流、端子電圧および正負極単極電位の推移を示したものである。定電流−定電圧充電では最初に一定の電流で充電し、端子電圧が規定の電圧に達すると電圧を一定に保つ。定電圧領域に達すると電流は徐々に垂下してゆく。
【０００５】
鉛電池の正極の充電特性は、活物質の充電反応と酸素発生反応が同時に進行するために、充電の進行と共に直線的に電位が上昇してゆく。それに対し負極では、活物質の充電反応が先に起こり、充電がほぼ１００％に達した後に急激に水素発生反応が起こる。そのため電位は最初はほとんど変化せず、水素発生と共に分極が急激に上昇する。負極活物質量が多い電池では負極の分極開始が遅いために定電流領域が長くなり、正極の充電を十分に行うことができる。しかし負極活物質量の少ない電池では負極の分極開始が早いために早期に定電圧領域に達し、正極の充電が十分に行えないまま充電電流が垂下してしまう。そしてこのサイクルを繰り返していくと正極への充電不足の蓄積により早期に容量低下がおこってしまう。
【０００６】
【発明が解決しようとする課題】
このように負極活物質量の少ない電池であっても、定電流−定電圧充電サイクル性能を向上させることが本発明の課題である。
【０００７】
【課題を解決するための手段】
本発明は上述した問題を解決するものであり、その要旨は、鉛蓄電池において、電解液硫酸にＮａイオンが４〜１０ｇ／ｌかつＦｅイオンが０．００１〜０．０２ｇ／ｌ含まれ、正極活物質に対する負極活物質の重量比が０．５〜１．０であることを特徴とするものである。
【０００８】
本発明に係る鉛蓄電池では、電解液にＮａイオンを４〜１０ｇ／ｌかつＦｅイオンを０．００１〜０．０２ｇ／ｌ含ませ、正極活物質に対する負極活物質の重量比を０．５〜１．０とする。このようにすることにより、定電流−定電圧サイクルで使用した際の寿命性能を向上させることができる。
【０００９】
【実施例】
上述した問題点の解決のためには次の２つの方法が考えられる。
【００１０】
ａ．正極活物質の充電効率を上げ、少ない電気量でも充電反応が十分に起こるようにする。
【００１１】
ｂ．負極活物質の水素発生による分極開始を遅くすることで定電流領域を長くし、正極が十分に充電されるようにする。
【００１２】
（実験１）
まず、正極活物質の充電効率改善のための実験を行った。特許第１２６３７３５号には電解液中にアルカリ金属イオンを存在させることにより過放電後の充電回復性が向上することが記載されている。この中では充電効率改善については述べられていないが、ここではその効果を調べた。
【００１３】
通常の鉛電池に用いられている正極板１枚と負極板２枚とを組み合わせて実験用のセルを組み立てた。正極板を評価するために負極板が過剰な構造となっている。電解液硫酸は比重１．２８０とし、硫酸ナトリウムを添加することで電解液中のＮａイオン量を０から２０ｇ／ｌの間で変化させ、Ｎａイオン量の影響を調べた。このセルの硫酸ナトリウム添加なしの場合の５時間率放電容量は約１０Ａｈであった。放電容量はＮａイオン量が１０ｇ／ｌ以下の場合にはほぼ１０Ａｈで変化がなかったが、１０ｇ／ｌを超えると急激に容量が低下した。
【００１４】
試験は、放電を２Ａで４時間（放電深さ８０％）、充電を２Ａで３．８時間（放電量に対し９５％の充電電気量）の充放電サイクルを１０回繰り返し、試験後の容量の初期容量に対する低下度合いを調べた。理論的には初期の５０％にまで容量が低下するはずである。試験結果を図２に示す。
【００１５】
硫酸ナトリウムを添加しないものでは容量は初期比０．１５にまで低下した。Ｎａイオン量が増えるほど低下度合いは少なくなり、４ｇ／ｌ以上では約０．４で飽和に達した。このことはＮａイオンを電解液に添加することで同一の充電電気量であっても充電効率が向上することを示している。しかしＮａイオン量が１０ｇ／ｌを超えると絶対容量が低下するために、Ｎａイオン添加量は４から１０ｇ／ｌとするのが望ましい。
【００１６】
Ｎａイオン添加により充電効率が向上する明確な理由は不明であるが、極板内部での溶液の電気伝導性が向上するためで、添加量が多くなると容量が低下するのはＰｂの溶解度が低下することがその一因と考えられる。
【００１７】
（実験２）
次に負極板の分極特性改善のための実験を行った。通常の鉛電池に用いられている正極板２枚と負極板１枚とを組み合わせて実験用のセルを組み立てた。負極板を評価するために正極板が過剰な構造となっている。電解液硫酸は比重１．２８０とし、各種金属を硫酸塩で添加し負極板の放電後の充電特性を調べた。その中でＦｅイオンを添加したもので分極特性の変化が見られたため、定量的な評価を行った。
【００１８】
ＦｅイオンはＦｅ₂（ＳＯ₄）₃により添加し、電解液中のＦｅイオン量が０〜０．０５ｇ／ｌとした。放電は２Ａで４時間、充電は２Ａで５時間行ない充電時の負極電位の変化を調べた。試験結果を図３に示す。
【００１９】
Ｆｅイオンを添加することで分極開始は遅くなった。しかし添加量が多くなると水素発生電位の貴な方向へのシフトがみられた。これは水素過電圧の低下を意味しており、自己放電や電池の減液が多くなってしまう。従ってＦｅイオンの添加量は０．００１〜０．０２ｇ／ｌが適当である。
【００２０】
Ｆｅイオンの添加により水素発生分極が遅くなった明確な理由は不明であるが、Ｆｅイオンが正負極間で次の酸化還元反応
Ｆｅ²⁺←→Ｆｅ³⁺＋ｅ
を繰り返すことにより水素発生に必要な電子を奪ったことが一因と考えられる。
【００２１】
（実験３）
次に本発明の効果を電池に適用して確認した。
【００２２】
電池としては自動車用電池（５５Ｄ２３，１２Ｖ，４８Ａｈ／５ｈＲ）を作製し、試験を行った。この電池は正極格子、負極格子ともＰｂ−Ｃａ−Ｓｎ系合金からなるエキスパンド格子を用いている。正極のエキスパンド格子に用いる鉛合金圧延シートの合金組成は、Ｐｂ−０．０６ｗｔ％Ｃａ−１．５ｗｔ％Ｓｎ、負極用のシートの合金組成はＰｂ−０．０６ｗｔ％Ｃａ−０．５ｗｔ％Ｓｎである。いずれも冷間圧延法により作製し、その厚みは正極用で１．１ｍｍ、負極用で０．７ｍｍとした。
【００２３】
これらの圧延シートは、ロータリー方式によるエキスパンド機により展開・切断を行い格子を作製した。このエキスパンド格子に自動車用鉛蓄電池用の一般的なペーストを充填し、通常の方法で熟成を行ない正極板を作製した。負極板についても一般的なものを用いた。正極活物質に対する負極活物質の比は０．７を標準として０．４〜１．２のものを作製した。
【００２４】
次に正極板を、袋状の微孔性ポリエチレンセパレータに入れた。正極板に当接する面である内側にはリブが形成されている。セパレータはポリエチレンシートを２つ折りにし、両サイドを一対の歯車により圧着することにより作製した。今回は正極板を袋状セパレータに入れたが、負極板を入れてもよくその際にはリブが外側にくるようにする。
【００２５】
セパレータに入れた正極板５枚、負極板６枚を交互に重ね合わせエレメントを作製し、６個のエレメントを電槽に挿入後セル間接続を行い、ふたを溶着して電池とした。
【００２６】
この電池に電解液として硫酸を注入し、電槽化成を行った。化成の方法は、最初低比重（１．１前後）の電解液を入れて通電しその後換液して所定の比重とする方法（低比重化成）、および最初比較的高比重（１．２前後）の電解液をいれて通電しそのまま所定の比重とする方法（高比重化成）の２種類を行った。電解液添加剤は低比重化成では換液する電解液に、高比重化成では最初の電解液にそれぞれ添加した。本試験では低比重化成を標準とした。電槽化成終了後の電解液比重は１．２８０とした。これらの電池の内容を表１に示す。
【００２７】
【表１】

これらの電池は容量試験（５時間率放電、９．６Ａ放電）を行ったあと、定電流−定電圧サイクル寿命試験に供した。試験温度は４０℃、放電は９．６Ａで２時間、充電は２５Ａ−１４．８Ｖで４時間とした。放電中の電圧が６Ｖを切った時点で寿命とし、そのときのサイクル数を寿命サイクル数とした。試験結果を表２に示す。
【００２８】
【表２】

Ｎａイオン量が２０ｇ／ｌと多いもの（電池Ｎｏ．６），活物質比が０．４と小さいもの（電池Ｎｏ．１１），活物質比が１．２と多いもの（電池Ｎｏ．１４）は他の電池に比べて容量が劣った。
【００２９】
寿命性能は，ＮａイオンとＦｅイオンが同時に添加されているもので優れており，それぞれ単独では効果が小さいことがわかった。正極の充電効率向上と負極の分極特性の改善を同時に行うことで、それらの相乗効果により正極の充電不足が抑制され寿命性能が改善されたものである。
【００３０】
Ｆｅイオンの量が０．０３ｇ／ｌと多い電池（電池Ｎｏ．１０）は寿命性能は優れていたものの、減液量が多く実用には不適と思われた。化成方法は、低比重、高比重いずれでも容量や寿命性能に大きな差はないことがわかった（電池Ｎｏ．１、２）。
【００３１】
【発明の効果】
以上、詳述したように本発明によれば負極活物質量の少ない電池であっても、定電流−定電圧充電サイクル性能に優れる電池を得ることができる。
【図面の簡単な説明】
【図１】放電−充電特性図
【図２】電解液中のＮａイオン量と試験後の容量低下率との関係を示した図
【図３】Ｆｅイオンの添加による負極板の充電特性を比較した図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a lead-acid battery.
[0002]
[Prior art]
The amount of the negative electrode active material of the conventional lead battery is designed to be almost equal to or more than the amount of the positive electrode active material. This was to allow the positive electrode plate to be a limiting factor for the life by providing a margin for the negative electrode active material. Recently, demands for improving the energy density of batteries have increased, and the number of batteries in which the amount of negative electrode active material is reduced and the amount of positive electrode active material is increased accordingly. This is because the utilization factor of the negative electrode active material is larger than that of the positive electrode active material, so that the positive electrode active material becomes a capacity limiting factor.
[0003]
However, in such a battery, since the positive electrode and the negative electrode are not balanced, when the charge / discharge cycle in which constant current-constant voltage charging is performed is performed, the positive electrode is not sufficiently charged and the capacity is quickly reduced. May end up.
[0004]
FIG. 1 shows changes in current, terminal voltage, and positive / negative single electrode potential for one cycle of discharge charging. In constant current-constant voltage charging, charging is initially performed at a constant current, and the voltage is kept constant when the terminal voltage reaches a specified voltage. When reaching the constant voltage range, the current gradually drops.
[0005]
Regarding the charging characteristics of the positive electrode of the lead battery, since the charging reaction of the active material and the oxygen generation reaction proceed simultaneously, the potential increases linearly with the progress of charging. On the other hand, in the negative electrode, the charge reaction of the active material occurs first, and the hydrogen generation reaction occurs rapidly after the charge reaches almost 100%. Therefore, the potential hardly changes at first, and the polarization rapidly increases as hydrogen is generated. In a battery having a large amount of negative electrode active material, the negative electrode starts slowly, so that the constant current region becomes long, and the positive electrode can be sufficiently charged. However, in a battery having a small amount of negative electrode active material, the negative electrode starts to polarize quickly, so that it reaches the constant voltage region at an early stage, and the charging current drops while the positive electrode cannot be charged sufficiently. When this cycle is repeated, the capacity is quickly reduced due to the accumulation of insufficient charge on the positive electrode.
[0006]
[Problems to be solved by the invention]
Thus, it is an object of the present invention to improve the constant current-constant voltage charging cycle performance even in a battery having a small amount of negative electrode active material.
[0007]
[Means for Solving the Problems]
The present invention solves the above-described problems, and the gist of the present invention is that, in a lead-acid battery, the electrolytic solution sulfuric acid contains 4 to 10 g / l of Na ions and 0.001 to 0.02 g / l of Fe ions. The weight ratio of the negative electrode active material to the active material is 0.5 to 1.0.
[0008]
In the lead storage battery according to the present invention, the electrolyte contains Na ions of 4 to 10 g / l and Fe ions of 0.001 to 0.02 g / l, and the weight ratio of the negative electrode active material to the positive electrode active material is 0.5 to 1.0. By doing in this way, the lifetime performance at the time of using it by a constant current-constant voltage cycle can be improved.
[0009]
【Example】
The following two methods are conceivable for solving the above-mentioned problems.
[0010]
a. The charging efficiency of the positive electrode active material is increased so that the charging reaction can occur sufficiently even with a small amount of electricity.
[0011]
b. The constant current region is lengthened by delaying the start of polarization due to hydrogen generation of the negative electrode active material so that the positive electrode is sufficiently charged.
[0012]
(Experiment 1)
First, an experiment for improving the charging efficiency of the positive electrode active material was performed. Japanese Patent No. 1263735 describes that the charge recovery after overdischarge is improved by the presence of alkali metal ions in the electrolyte. Although charging efficiency improvement is not described in this, the effect was investigated here.
[0013]
An experimental cell was assembled by combining one positive electrode plate and two negative electrode plates used in an ordinary lead battery. In order to evaluate the positive electrode plate, the negative electrode plate has an excessive structure. The electrolyte solution sulfuric acid had a specific gravity of 1.280, and the sodium ion amount in the electrolyte solution was changed between 0 and 20 g / l by adding sodium sulfate, and the influence of the Na ion amount was examined. The 5-hour rate discharge capacity of this cell without addition of sodium sulfate was about 10 Ah. The discharge capacity was almost 10 Ah when the amount of Na ions was 10 g / l or less, but the capacity rapidly decreased when it exceeded 10 g / l.
[0014]
In the test, the charge / discharge cycle of discharge at 2A for 4 hours (discharge depth 80%) and charge at 3.8 hours at 2A (95% of charge electricity) was repeated 10 times, and the capacity after the test The degree of decrease in the initial capacity was investigated. Theoretically, the capacity should drop to 50% of the initial value. The test results are shown in FIG.
[0015]
In the case where sodium sulfate was not added, the capacity decreased to an initial ratio of 0.15. As the amount of Na ions increased, the degree of decrease decreased, and at 4 g / l or more, saturation was reached at about 0.4. This indicates that charging efficiency is improved by adding Na ions to the electrolyte even with the same amount of charge. However, if the amount of Na ions exceeds 10 g / l, the absolute capacity decreases, so the amount of Na ions added is preferably 4 to 10 g / l.
[0016]
The clear reason why the charging efficiency is improved by the addition of Na ions is unclear, but because the electrical conductivity of the solution inside the electrode plate is improved, the capacity decreases when the added amount increases, the solubility of Pb decreases. It is considered that one of the reasons.
[0017]
(Experiment 2)
Next, an experiment for improving the polarization characteristics of the negative electrode plate was performed. An experimental cell was assembled by combining two positive electrode plates and one negative electrode plate used in an ordinary lead battery. In order to evaluate the negative electrode plate, the positive electrode plate has an excessive structure. The electrolyte solution sulfuric acid had a specific gravity of 1.280, various metals were added as sulfates, and the charge characteristics after discharge of the negative electrode plate were examined. Among them, a change in polarization characteristics was observed with the addition of Fe ions, and therefore quantitative evaluation was performed.
[0018]
Fe ions were added by Fe ₂ (SO ₄ ) _{3 so} that the amount of Fe ions in the electrolyte was 0 to 0.05 g / l. Discharging was performed at 2 A for 4 hours, and charging was performed at 2 A for 5 hours, and changes in the negative electrode potential during charging were examined. The test results are shown in FIG.
[0019]
The onset of polarization was delayed by adding Fe ions. However, as the amount added increased, the hydrogen generation potential shifted in a noble direction. This means a decrease in hydrogen overvoltage, and self-discharge and battery liquid reduction increase. Accordingly, the addition amount of Fe ions is suitably 0.001 to 0.02 g / l.
[0020]
Although the clear reason why the hydrogen generation polarization was slowed by the addition of Fe ions is unknown, the next redox reaction Fe ²⁺ ← → Fe ³⁺ + e occurs between the positive and negative electrodes.
This is thought to be due to the deprivation of electrons necessary for hydrogen generation by repeating the above.
[0021]
(Experiment 3)
Next, the effect of the present invention was confirmed by applying it to a battery.
[0022]
As a battery, an automobile battery (55D23, 12V, 48Ah / 5hR) was produced and tested. This battery uses an expanded lattice made of a Pb—Ca—Sn alloy for both the positive electrode lattice and the negative electrode lattice. The alloy composition of the lead alloy rolled sheet used for the positive grid of the positive electrode is Pb-0.06 wt% Ca-1.5 wt% Sn, and the alloy composition of the negative electrode sheet is Pb-0.06 wt% Ca-0.5 wt% Sn. It is. All were produced by the cold rolling method, and the thickness was 1.1 mm for the positive electrode and 0.7 mm for the negative electrode.
[0023]
These rolled sheets were developed and cut by a rotary type expanding machine to produce a lattice. The expanded grid was filled with a general paste for a lead-acid battery for automobiles and aged by a normal method to produce a positive electrode plate. A general negative electrode plate was also used. The ratio of the negative electrode active material to the positive electrode active material was 0.4 to 1.2 with 0.7 as a standard.
[0024]
Next, the positive electrode plate was put into a bag-like microporous polyethylene separator. A rib is formed on the inner side which is a surface in contact with the positive electrode plate. The separator was produced by folding a polyethylene sheet in two and crimping both sides with a pair of gears. Although the positive electrode plate was put in a bag-shaped separator this time, the negative electrode plate may be put in that case so that the rib comes outside.
[0025]
Five positive electrode plates and six negative electrode plates placed in a separator were alternately stacked to produce an element. After inserting the six elements into a battery case, the cells were connected to each other, and a lid was welded to obtain a battery.
[0026]
Sulfuric acid was injected into the battery as an electrolytic solution, and a battery case was formed. The chemical conversion method includes a method in which an electrolyte solution having a low specific gravity (around 1.1) is first charged and energized, and then the liquid is changed to a predetermined specific gravity (low specific gravity conversion), and a relatively high specific gravity (around 1.2) at first. 2) (the high specific gravity chemical conversion) was carried out. The electrolyte solution additive was added to the electrolyte solution to be replaced in the low specific gravity chemical conversion, and to the first electrolyte solution in the high specific gravity chemical conversion. In this test, low specific gravity conversion was standard. The electrolyte specific gravity after the completion of battery case formation was 1.280. Table 1 shows the contents of these batteries.
[0027]
[Table 1]

These batteries were subjected to a capacity test (5-hour rate discharge, 9.6 A discharge) and then subjected to a constant current-constant voltage cycle life test. The test temperature was 40 ° C., the discharge was 9.6 A for 2 hours, and the charge was 25 A-14.8 V for 4 hours. The life was determined when the voltage during discharging was less than 6 V, and the number of cycles at that time was defined as the number of life cycles. The test results are shown in Table 2.
[0028]
[Table 2]

One having a large amount of Na ions of 20 g / l (battery No. 6), one having a small active material ratio of 0.4 (battery No. 11), and one having a large active material ratio of 1.2 (battery No. 14) Has inferior capacity compared to other batteries.
[0029]
The lifetime performance was excellent when Na ions and Fe ions were added simultaneously, and it was found that the effects were small when used alone. By simultaneously improving the charging efficiency of the positive electrode and the polarization characteristics of the negative electrode, a shortage of charging of the positive electrode is suppressed by the synergistic effect thereof, and the life performance is improved.
[0030]
Although the battery (battery No. 10) with a large amount of Fe ions of 0.03 g / l was excellent in life performance, it was considered unsuitable for practical use because of its large amount of liquid reduction. It was found that the chemical conversion method has no significant difference in capacity and life performance regardless of whether the specific gravity is low or high (battery Nos. 1 and 2).
[0031]
【The invention's effect】
As described above, according to the present invention, a battery having excellent constant current-constant voltage charging cycle performance can be obtained even with a battery having a small amount of negative electrode active material.
[Brief description of the drawings]
[Fig. 1] Discharge-charge characteristics diagram [Fig. 2] Diagram showing the relationship between the amount of Na ions in the electrolyte and the rate of decrease in capacity after the test [Fig. 3] Comparison of the charge characteristics of the negative electrode plate by addition of Fe ions Figure

Claims

The electrolyte solution sulfuric acid contains 4 to 10 g / l Na ions and 0.001 to 0.02 g / l Fe ions, and the weight ratio of the negative electrode active material to the positive electrode active material is 0.5 to 1.0. Lead-acid battery characterized.