【発明の詳細な説明】[Detailed description of the invention]
本発明はペースト式鉛蓄電池の改良に関するも
ので、その目的とするところは初期性能に優れ、
かつ寿命性能も良好な鉛蓄電池を提供することで
ある。
一般に鉛蓄電池は正極板の劣化によつて寿命が
尽きる場合が多く、この寿命性能を改良するため
に、正極板の厚みを大きくしたり、ペースト密度
を高くする方法がとられる。ところがこのように
すると鉛蓄電池の初期性能は悪くなつてしまうの
で、初期性能，寿命性能とともに良好な鉛蓄電池
を得ることは困難であつた。本発明は極板厚みお
よびペースト密度が大なる正極板に異方性の大き
い黒鉛を添加することによつて初期性能の向上を
図り、優れた寿命性能はそのまゝ維持しようとす
るものである。
更に本発明はゲル状電解液を用いるか又は極板
やセパレータに電解液を保持することにより無漏
液化した密閉式鉛蓄電池の改良に係るもので、そ
の目的とするところは性能の優れた密閉式鉛蓄電
池を提供することである。
密閉式鉛蓄電池は無漏液構造であるためにどの
ような姿勢でも使用が可能であり、かつ無保守で
ある等の優れた特徴を有する為に、コードレス時
代を反映してその需要が拡大しつつある。ところ
が密閉式鉛蓄電池では無漏液構造をとることから
くる欠点があり、一般の電解液が豊富な湿式鉛蓄
電池に比べて電解液によつて性能が制限されやす
い。この放電性能を向上させるには活物質にでき
るだけ多くの電解液を保持することが望ましく、
そのためには軟質ペーストを用いて活物質の多孔
度を上げればよいが、一方、軟質ペーストは寿命
性能に劣るというように一長一短があつた。
本発明は放電性能にも優れ、また寿命性能も良
好な密閉式鉛蓄電池を提供するもので、その骨子
とするところは正極ペーストに異方性の大なる黒
鉛を添加することである。
これまでも初期性能を改善するために、正極活
物質に炭素繊維や黒鉛を添加することが提案され
ている。これは電池の放電に伴なう活物質の電気
抵抗の増加を比較的導電性に優れた炭素や黒鉛を
添加することで抑制し、初期性能の改善を図ろう
とするものであると思われる。
そこでこの従来の提案をペースト密度が大なる
正極板に適用してみたが性能改善の効果はわずか
であつた。ペースト密度の大なる正極板では化成
後の活物質が硬質で多孔性に乏しく、これが正極
板の放電性能を大きく支配している為に、黒鉛や
炭素を添加して活物質の導電性を改良するだけで
は、大巾な性能の向上は期待できない。
本発明は異方性の大なる黒鉛は陽極酸化を受け
ると結晶のＣ軸方向に膨張するという特性を利用
するものであり、正極ペーストに異方性の大なる
黒鉛を添加することによつてペースト密度が大き
い正極板でも多孔度が増加し、初期性能が著しく
向上することがわかつたことに基づくものであ
る。黒鉛は炭素原子の正六角平面網が層状に積重
なつた構造の結晶で、層平面内は共有結合によつ
て強力に結合されているが、層平面間はフアンデ
ルワールス力により結合されているだけで弱く、
黒鉛の結晶内で層間化合物が生成すると層平面間
隔が拡がつて結晶はＣ軸方向（層平面に垂直方
向）に膨張する。ここで黒鉛が等方性の場合は膨
張する方向が一定でない為に、層間化合物が生成
するにつれて損傷しやがて崩壊するに至るが、異
方性の黒鉛では一定方向にのみ膨張するのでこの
ようなことは起らない。また黒鉛を硫酸中で陽極
酸化すると層間化合物が生成することは古くから
知られている。正極活物質に異方性の大なる黒鉛
を添加した正極板を用いれば、電池の充電によつ
て黒鉛は損傷を受けることなく膨張し、周囲の活
物質に作用して活物質の多孔度が増すものと考え
られる。次に本発明の一実施例につき詳述する。
市販の天然黒鉛を2000℃で加熱処理して異方性
の大きい黒鉛とし、粒度を32〜48メツシユにそろ
えた。ついで金属鉛約30wt％残部酸化鉛よりな
る鉛粉に該黒鉛を1wt％添加して良く混合し、公
知の方法によりペースト密度約4.6ｇ／cm3の正極
ペーストを調製した。これを厚み３mmの鉛合金格
子に充填し、熟成、化成の各工程を経て活物質が
硬質の正極板を作製した。比較の為に黒鉛を添加
しない場合、等方性黒鉛を添加した場合およびペ
ースト密度が約3.7ｇ／cm3の低密度ペーストを充
填して化成後の活物質を軟質とした場合について
も同様にして正極板を作製した。
第１表はこれらの正極板を用いて組立てた公称
容量50Ahの電池を5hR放電して得た結果である。
The present invention relates to the improvement of paste type lead-acid batteries, and its purpose is to have excellent initial performance,
Another object of the present invention is to provide a lead-acid battery that also has good life performance. Generally, the life of a lead-acid battery often ends due to deterioration of the positive electrode plate, and in order to improve this life performance, methods are used to increase the thickness of the positive electrode plate or increase the paste density. However, if this is done, the initial performance of the lead-acid battery deteriorates, so it has been difficult to obtain a lead-acid battery that has good initial performance and lifetime performance. The present invention aims to improve the initial performance by adding highly anisotropic graphite to the positive electrode plate, which has a large electrode plate thickness and paste density, while maintaining the excellent lifetime performance. . Furthermore, the present invention relates to an improvement in a sealed lead-acid battery that is leak-free by using a gel electrolyte or by retaining the electrolyte in electrode plates or separators, and its purpose is to provide a sealed lead-acid battery with excellent performance. The main purpose of the company is to provide lead-acid batteries. Sealed lead-acid batteries have a non-leakage structure, so they can be used in any position, and they require no maintenance, so demand for them is expanding as a result of the cordless era. It's coming. However, sealed lead-acid batteries have a drawback due to their non-leakage structure, and their performance is more likely to be limited by the electrolyte compared to wet lead-acid batteries, which are generally rich in electrolyte. In order to improve this discharge performance, it is desirable to retain as much electrolyte as possible in the active material.
To achieve this, it is possible to increase the porosity of the active material by using a soft paste, but on the other hand, soft pastes have both advantages and disadvantages, such as inferior longevity performance. The present invention provides a sealed lead-acid battery with excellent discharge performance and good life performance, and the key point thereof is to add highly anisotropic graphite to the positive electrode paste. Up to now, it has been proposed to add carbon fiber or graphite to positive electrode active materials in order to improve initial performance. This seems to be an attempt to improve the initial performance by suppressing the increase in electrical resistance of the active material as the battery discharges by adding carbon or graphite, which have relatively excellent conductivity. Therefore, we applied this conventional proposal to a positive electrode plate with a large paste density, but the effect of improving performance was small. In positive electrode plates with high paste density, the active material after chemical formation is hard and has little porosity, and this greatly controls the discharge performance of the positive electrode plate, so graphite and carbon are added to improve the conductivity of the active material. You cannot expect a significant performance improvement just by doing so. The present invention utilizes the property that highly anisotropic graphite expands in the C-axis direction of the crystal when subjected to anodic oxidation, and by adding highly anisotropic graphite to the positive electrode paste. This is based on the fact that even with a positive electrode plate having a high paste density, the porosity increases and the initial performance is significantly improved. Graphite is a crystal with a structure in which a regular hexagonal planar network of carbon atoms is stacked in layers, and the layer planes are strongly bonded by covalent bonds, but the layers are bonded by van der Waals forces. Just being there makes me feel weak,
When an intercalation compound is generated within a graphite crystal, the interlayer spacing increases and the crystal expands in the C-axis direction (perpendicular to the layer plane). If graphite is isotropic, the direction of expansion is not constant, so as intercalation compounds are formed, it will be damaged and eventually collapse, but with anisotropic graphite, it expands only in one direction. Nothing happens. Furthermore, it has been known for a long time that intercalation compounds are generated when graphite is anodized in sulfuric acid. If a positive electrode plate containing highly anisotropic graphite added to the positive electrode active material is used, the graphite expands without being damaged when the battery is charged, and acts on the surrounding active material, reducing the porosity of the active material. It is thought that this will increase. Next, one embodiment of the present invention will be described in detail. Commercially available natural graphite was heat-treated at 2000℃ to produce highly anisotropic graphite, and the particle size was adjusted to 32 to 48 mesh. Next, 1 wt % of the graphite was added to lead powder consisting of about 30 wt % metallic lead and the balance was lead oxide, and the mixture was thoroughly mixed to prepare a positive electrode paste having a paste density of about 4.6 g/cm 3 by a known method. This was filled into a lead alloy grid with a thickness of 3 mm, and a positive electrode plate with a hard active material was produced through aging and chemical formation steps. For comparison, the same procedure was carried out for cases in which no graphite was added, cases in which isotropic graphite was added, and cases in which a low-density paste with a paste density of approximately 3.7 g/cm 3 was filled to make the active material soft after chemical formation. A positive electrode plate was prepared. Table 1 shows the results obtained by discharging a battery with a nominal capacity of 50 Ah, assembled using these positive electrode plates, for 5 hours.
【表】【table】
【表】
この結果から明らかなように本発明品ＡはＢや
Ｃに比べて優れ、低密度ペーストを充填したＤに
匹敵する性能を示した。なお、正極既化活物質の
多孔度を測定したところＡは53.2％，Ｂ，Ｃは共
に50.2％Ｄは58.1％であつた。次にこれらの４種
類の電池をJISに規定されている方法に準じて寿
命試験を行なつた結果を第１図に示す。本発明品
Ａは寿命試験中高い放電容量を維持し、等方性黒
鉛を添加したＢや黒鉛添加なしのＣ及び低密度ペ
ーストのＤに比べ明らかに優れていた。本発明品
が優れた寿命性能を示したのは正極ペーストに添
加した異方性大の黒鉛が寿命サイクル中に膨張
し、それに伴なつて正極活物質も膨張した為に、
極板群が自然に圧迫されて正極活物質の脱落を防
ぐと共に、活物質粒子間の接触も良好になつたこ
とによると思われる。
次に密閉式鉛蓄電池における本発明の一実施例
を詳述する。正極板の作製は前記実施例の場合と
同様とした。第２表はこれらの正極板を用いて組
立てた公称容量4Ahの密閉式鉛蓄電池を5hR放電
して得た結果である。[Table] As is clear from the results, product A of the present invention was superior to products B and C, and exhibited performance comparable to product D filled with low-density paste. When the porosity of the positive active material was measured, it was 53.2% for A, 50.2% for both B and C, and 58.1% for D. Next, these four types of batteries were subjected to a life test according to the method prescribed by JIS, and the results are shown in FIG. Product A of the present invention maintained a high discharge capacity during the life test and was clearly superior to B with added isotropic graphite, C with no graphite added, and D with low density paste. The reason why the product of the present invention showed excellent life performance is that the highly anisotropic graphite added to the positive electrode paste expanded during the life cycle, and the positive electrode active material also expanded accordingly.
This seems to be due to the fact that the electrode plate group was naturally compressed to prevent the positive electrode active material from falling off, and the contact between the active material particles was also improved. Next, an embodiment of the present invention in a sealed lead-acid battery will be described in detail. The production of the positive electrode plate was the same as in the previous example. Table 2 shows the results obtained by discharging a sealed lead-acid battery with a nominal capacity of 4 Ah for 5 hours using these positive electrode plates.
【表】
この結果から明らかなように、本発明品A′は
活物質が硬質であるにもかかわらず、低密度ペー
ストを充填したD′と匹適する初期性能を示し、
等方性黒鉛を添加したB′や黒鉛添加なしのC′より
も優れていた。既化活物質の多孔度を測定した結
果はA′が53.6％B′とC′は共に50.3％，D′は57.9％
であつた。A′の活物質多孔度はD′ほど高くはな
つてはいなかつたが、黒鉛添加の効果と多孔度の
増加と相乗効果によつて良好な結果を得ることが
できた。次にこれら４種類の電池をJISに規定さ
れている方法に従つて寿命試験を行つた結果を第
２図に示した。本発明品A′は寿命試験中高い容
量を維持し等方性黒鉛を添加したＢや黒鉛添加な
しのC′及び低密度ペーストを使用したD′よりも明
らかに優れていた。本発明品A′が優れた寿命性
能を示したのは、正極ペーストに添加した異方性
大の黒鉛が寿命サイクル中に陽極酸化を操り返し
受けて膨張し、それに伴なつて正極活物質も膨張
した為に電解液の保持量が十分確保されると共
に、極板群が自然に圧迫されて活物質粒子間及び
活物質と格子との接触が良好となつたことによる
と思われる。
なお、これらの実施例では黒鉛の加熱処理を
2000℃で行なつた場合を示したが2000〜3000℃で
よい。添加量については0.1wt％以下ではあまり
効果なく2wt％以上添加しても1wt％添加と同程
度の効果であつたことから、0.3〜1.5wt％の範囲
が適当である。粒径はあまり細かいと膨張の程度
が小さく15〜100メツシシユの粒度で良好な結果
を得た。
以上詳述したように本発明によれば初期性能，
寿命性能とも優れた鉛蓄電池が得られ工業的価値
は大である。[Table] As is clear from the results, although the active material is hard, the product A′ of the present invention showed an initial performance comparable to D′ filled with a low-density paste.
It was superior to B' with the addition of isotropic graphite and C' without the addition of graphite. The results of measuring the porosity of the activated active material are: A' is 53.6%, B' and C' are both 50.3%, and D' is 57.9%.
It was hot. Although the active material porosity of A' was not as high as D', good results could be obtained due to the effect of graphite addition, the increase in porosity, and the synergistic effect. Next, these four types of batteries were subjected to a life test according to the method prescribed by JIS, and the results are shown in Figure 2. Product A' of the present invention maintained a high capacity during the life test and was clearly superior to B with added isotropic graphite, C' without graphite addition, and D' with low density paste. Inventive product A' showed excellent life performance because the highly anisotropic graphite added to the positive electrode paste undergoes anodic oxidation and expands during the life cycle, and the positive electrode active material also expands. This seems to be because the expansion ensured a sufficient amount of electrolyte to be retained, and the electrode plate group was naturally compressed, resulting in good contact between the active material particles and between the active material and the grid. In addition, in these examples, the heat treatment of graphite was
Although the case where the test was carried out at 2000°C is shown, the temperature may be 2000 to 3000°C. As for the amount added, a range of 0.3 to 1.5 wt% is appropriate, since it is not very effective when added at 0.1 wt% or less, and even when added at 2 wt% or more, the effect is comparable to that of 1 wt% addition. If the particle size is too small, the degree of expansion will be small, and good results were obtained with a particle size of 15 to 100 mesh. As detailed above, according to the present invention, initial performance,
A lead-acid battery with excellent longevity and performance can be obtained, and is of great industrial value.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は本発明品と従来品の寿命性能を示す。
第２図は密閉式鉛蓄電池における本発明品と従来
品の寿命性能を示す。
Ａ，A′……本発明品、Ｂ，B′，Ｃ，C′，Ｄ，
D′……従来品。
Figure 1 shows the life performance of the product of the present invention and the conventional product.
FIG. 2 shows the life performance of the product of the present invention and the conventional product in sealed lead-acid batteries. A, A'...Invention product, B, B', C, C', D,
D'...Conventional product.