JP4517313B2 - Positive electrode mix for alkaline batteries - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、アルカリ電池の正極合剤に関するものである。
【０００２】
【従来の技術】
一般にアルカリ電池用の正極合剤活物質としては二酸化マンガンが用いられている。通常アルカリ電池用正極合剤は、この二酸化マンガン粉末に導電性向上のための黒鉛粉末を添加し、更に電解液として水酸化カリウム水溶液を適量添加し、これらを混合撹拌してできた混合物をロール状プレス等を用いて適当な圧力にて煎餅状に圧縮し、次にこの煎餅状の被圧縮物をグラニュレータにて破砕して顆粒状とすることによって得ている。
【０００３】
このようにして得られた顆粒状正極合剤を所定の圧力で中空円筒状に加圧成形する。または、正極端子を兼ねる電池缶内で、中空円筒状に加圧成形する形で高密度充填する方法もある。
使用する二酸化マンガンの粒径は、通常３００μｍ以下で、且つ平均粒径（ＭＶ）が５０〜１００μｍ程度のものが一般的である。
【０００４】
【発明が解決しようとする課題】
近年、高容量化を目的として、正極合剤中の黒鉛添加率を低減し、活物質である二酸化マンガン含有量を増加させる傾向にある。
しかし、正極合剤中に添加された黒鉛粉末は、導電剤としての機能だけではなく、中空円筒状に加圧成形する際に成形金型内において顆粒状合剤の流動性をよくして均一な密度の成形を助ける成形補助剤としての機能があり、更に金型から成形体を取り出す際の離型剤としての機能もある。このため、一般に黒鉛添加率を低くすると成形性及び離型性が悪くなる。
【０００５】
また、高容量化を目的として、正極合剤充填密度を高くする傾向にあるが、合剤を高密度充填した場合、正極合剤中へと吸液される電解液量が少なくなり、電池の放電反応における活物質の反応利用率が低下する傾向がある。すなわち、通常、電解液（例えば水酸化カリウム水溶液）は正極合剤の中空部に装着された有底円筒状のセパレータに適量注液され、この電解液はしばらく放置するとセパレータを介して正極合剤中へと吸液される。ところが、合剤を高密度充填した場合には、正極合剤中へと吸液される電解液量が少なくなる。その結果、期待通りの高容量化が実現できない。
本発明は上記問題点に対処してなされたもので、成形性及び電解液吸液性の優れたアルカリ電池用正極合剤を提供することを目的としたものである。
【０００６】
【課題を解決するための手段】
本発明は、正極合剤活物質としての二酸化マンガン粉末及び導電剤としての黒鉛粉末を含有するアルカリ電池用正極合剤において、二酸化マンガン粉末の粒径が２００μｍ以下で且つ平均粒径（ＭＶ）が２５〜５５μｍであり、黒鉛粉末の添加率（［黒鉛粉末重量］／［二酸化マンガン粉末重量＋黒鉛粉末重量］）が３〜７％であると共に、５００〜３０００ｐｐｍのステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末を添加したことを特徴とする。
【０００８】
本発明では二酸化マンガン粉末の粒径を上記の範囲に特定化したことによって、正極合剤成形体の強度が高まり、また電解液の吸液性が向上する。さらに黒鉛粉末の添加率を上記範囲にしたことによって、正極合剤の成形性を損なわない範囲で電池性能を向上させることができる。
【０００９】
また、上記正極合剤を顆粒状に造粒した後で、顆粒状合剤に対し５００〜３０００ｐｐｍのステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末を添加することによって、より成形性の優れる高性能アルカリ電池用正極合剤を得ることができる。
【００１０】
【発明の実施の形態】
以下、その実施例を詳細に説明する。
（実施例１）
まず初めに、粒径１８０μｍ以下で且つ平均粒径（ＭＶ）が５０μｍである二酸化マンガン粉末を使用し、これと黒鉛粉末を万能撹拌ミサーにて５分間ドライ撹拌する。このときの黒鉛添加率は５％とした。このようにして得られた混合粉末１００重量部に対して、濃度４０ｗｔ％の水酸化カリウム水溶液を４重量部添加して、万能撹拌ミキサーにて５分間ウェット撹拌する。
【００１１】
次に、得られた混合物をロール状プレスにて煎餅状に圧縮する。このときのプレス圧は２００〜３００ｋｇ／ｃｍ2 程度が望ましい。続いてこの煎餅状の被圧縮物をグラニュレータにて破砕し、続いて、２２〜１００メッシュの自動篩分機にて分級して、粒径１５０〜７１０μｍ程度の顆粒状合剤を得た。
【００１２】
（実施例２）
実施例１の顆粒状合剤１００重量部に対して、０．１重量部のステアリン酸亜鉛粉末を添加してアルカリ電池用正極合剤を得た。
【００１３】
（実施例３）
粒径１００μｍ以下で且つ平均粒径（ＭＶ）が３０μｍである二酸化マンガン粉末を使用した以外は実施例２の場合と同様にしてアルカリ電池用正極合剤を得た。
【００１４】
（比較例１）
粒径２５０μｍ以下で且つ平均粒径（ＭＶ）が７０μｍである二酸化マンガン粉末を使用した以外は実施例１の場合と同様にしてアルカリ電池用正極合剤を得た。
【００１５】
（比較例２）
粒径２５０μｍ以下で且つ平均粒径（ＭＶ）が７０μｍである二酸化マンガン粉末を使用した以外は実施例２の場合と同様にしてアルカリ電池用正極合剤を得た。
【００１６】
（比較例３）
粒径６０μｍ以下で且つ平均粒径（ＭＶ）が２０μｍである二酸化マンガン粉末を使用した以外は実施例２の場合と同様にしてアルカリ電池用正極合剤を得た。
【００１７】
（比較例４）
黒鉛添加率を１０％としたこと以外は、比較例１の場合と同様にしてアルカリ電池用正極合剤を得た。
【００１８】
以上のようにして得られた７種類の顆粒状合剤をそれぞれＪＩＳ規格ＬＲ６形（単３形）用サイズの中空円筒状に加圧成形した。成形密度は３．２０ｇ／ｃｍ3 とした。
【００１９】
成形性のバロメータとして、これらの成形体の強度を比較するため、（株）サン科学 レオメーターＣＲ−２００Ｄを使用して成形体の圧潰強度を測定した（ｎ＝１００）。その測定結果を以下に記す（ｎ＝１００の平均値）。
【００２０】
実施例１：６６０ｇｆ
実施例２：６８３ｇｆ
実施例３：７０２ｇｆ
比較例１：５６３ｇｆ
比較例２：５９１ｇｆ
比較例３：７４７ｇｆ
比較例４：６８７ｇｆ
【００２１】
上記試験において、実施例１と比較例１を比較すると、黒鉛添加率が同じ５％でも使用した二酸化マンガンの粒径が小さく且つ平均粒径が小さい実施例１の方が成形体の強度が高いことがわかる。
【００２２】
実施例２〜３と比較例２〜３を比較すると、黒鉛添加率が５％でステアリン酸亜鉛添加量が１０００ｐｐｍの同一条件において、使用した二酸化マンガンの粒径が小さく且つ平均粒径が小さいものの方が成形体の強度が高いことがわかる。
【００２３】
一般に黒鉛は導電剤としての機能以外にも成形金型内での顆粒状合剤の流動性を良くして均一な密度の成形を助けるための成形補助剤としての機能、更に金型から成形体を取り出す際の離型剤としての機能を兼ね備えており、黒鉛添加率を低くした場合には当然ながら成形性及び離型性が悪くなる。
【００２４】
そこで上記実施例では、粒径が小さく且つ平均粒径が小さい二酸化マンガンを使用することに加えて、ステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末を添加して、黒鉛添加率を低くした場合の成形性及び離型性を向上させている。ステアリン酸亜鉛粉末を添加していない実施例１とステアリン酸亜鉛粉末を顆粒合剤に対して１０００ｐｐｍ添加した実施例２を比較すると成形体の強度が向上していることがわかる。過去の種々の実験結果によれば、比較例４のように黒鉛添加率１０％程度ではステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末添加の効果は確認できなかったが、黒鉛添加率を８％以下にすると成形性及び離型性が向上することがわかっている。特に黒鉛添加率７％以下ではステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末添加の効果は顕著である。
【００２５】
ステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末の添加量は顆粒状合剤に対して５００〜３０００ｐｐｍが好ましく、更に好ましくは１０００〜２０００ｐｐｍが良い。５００ｐｐｍより少ない添加量では成形性及び離型性の向上はあまりないことがわかっている。また、ステアリン酸亜鉛及びステアリン酸カルシウムはアルカリ乾電池としての放電反応に全く関係がない有機化合物であり、添加量が多すぎると電池特性を妨害することとなるため、またコスト面から考えても、３０００ｐｐｍより多い添加は好ましくない。
【００２６】
また、ステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末の顆粒状合剤への添加は単独でも併用でも良く、併用の場合の添加量は、添加するステアリン酸亜鉛粉末重量とステアリン酸カルシウム粉末重量の合計が、顆粒状合剤に対して５００〜３０００ｐｍが好ましく、更に好ましくは１０００〜２０００ｐｐｍが良い。
【００２７】
次に、上記５種類の顆粒状合剤をそれぞれＪＩＳ規格ＬＲ６形（単３形）用サイズの中空円筒状に加圧成形して成形密度３．２０ｇ／ｃｍ3 にした成形体を、正極端子を兼ねる電池缶内に挿入した後、この電池缶内で中空円筒状に再加圧して正極合剤の充填密度を３．４０ｇ／ｃｍ3 とした。充填された合剤の中空部に有底円筒状にセパレータを装着し、セパレータ内に電解液として濃度４０ｗｔ％の水酸化カリウム水溶液を約２．５ｇ注液し、３０分間放置した後、セパレータ及び正極合剤中へ吸液された以外の余剰の電解液を除去して、セパレータ及び正極合剤中へ吸液された電解液の重量を測定した。その結果を以下に記す（ｎ＝１００の平均値）。
【００２８】
実施例１：１．５８ｇ
実施例２：１．５７ｇ
実施例３：１．６２ｇ
比較例１：１．４８ｇ
比較例２：１．４８ｇ
比較例３：１．７０ｇ
比較例４：１．３８ｇ
【００２９】
この電解液吸液実験における実施例２〜３と比較例２〜３の測定結果を比較すると、黒鉛添加率が５％でステアリン酸亜鉛添加量が１０００ｐｐｍという同一条件において、二酸化マンガンの粒径が小さく且つ平均粒径が小さい場合の方が、より多量の電解液を吸液できることがわかる。実際の電池設計上の観点からは、電解液吸液量が多ければ多いほど活物質の反応利用率向上が期待できる。
【００３０】
上記電解液吸液実験では、あらかじめ中空円筒状に成形密度３．２０ｇ／ｃｍ3 で加圧成形した成形体を、正極端子を兼ねる電池缶内に挿入した後、この電池缶内で中空円筒状に再加圧して正極合剤の充填密度を３．４０ｇ／ｃｍ3 としたものを使用したが、あらかじめの成形を省略して電池缶内ではじめから中空円筒状に充填密度３．４０ｇ／ｃｍ3 で合剤充填したものでも同等の結果になることを確認済みである。
【００３１】
次に、上記電解液吸液実験に使用したセルを用いて、それぞれＪＩＳ規格ＬＲ６形（単３形）のアルカリマンガン電池を各１００個作成した。作成した電池をそれぞれ５０個ずつ１．５Ａ定電流放電試験を行った。また、それぞれ５０個ずつを６０℃ＤＲＹに設定された恒温恒湿槽に１ヶ月貯蔵後、取り出してから２４時間常温にて放置し（電池温度を常温に戻すため）、１．５Ａ定電流放電試験を行った。いずれの場合も放電試験環境は２０℃，６５％ＲＨとした。初度及び６０℃１ヶ月貯蔵後の、終止電圧０．９Ｖまでの接続時間測定結果と初度を１００％としたときの６０℃１ヶ月貯蔵維持率を表１に記す（各ｎ＝５０の平均値）。
【００３２】
【表１】
これによれば、初度の接続時間は上記吸液実験結果との相関が見られ、吸液量の多いものほど接続時間が長い。ところが、上記吸液実験で吸液量が一番多かった比較例３は６０℃１ヶ月貯蔵すると性能劣化がかなり激しく、貯蔵維持率は６５％以下であった。以上の結果から粒径６０μｍ以下で且つ平均粒径（ＭＶ）が２０μｍであるような極端に微細な二酸化マンガンを使用すると高温貯蔵特性が良くないことがわかった。この理由については詳細は定かではないが、極端に微細な二酸化マンガン粉末自体が劣化しやすいと考えられる。１．５Ａ定電流放電というのはＬＲ６形（単３形）サイズのアルカリマンガン電池にとっては、かなり負荷の大きい大電流放電であるが、上記実施例１〜３は、初度及び６０℃１ヶ月貯蔵後においても、かなり優秀な性能となった。
【００３４】
同じ粒径で且つ同じ平均粒径の二酸化マンガンを使用した比較例２と比較例４を比較すると、黒鉛添加率の違いによって活物質量が多い比較例２は比較例４よりも性能が優れていることが分かる。しかし比較例２でも実施例１〜３に比べると電池性能は十分ではなく、二酸化マンガンの粒径が電池性能に大きく関わっていることが分かる。
【００３５】
以上の実験で示したように、二酸化マンガンの粒径を２００μｍ以下で且つ平均粒径（ＭＶ）が２５〜５５μｍとなるようにし、黒鉛粉末の添加率を３〜８％とすることによって、高性能で、大電流特性に優れ、且つ、高温貯蔵特性に優れる、高性能な高容量アルカリ電池を得ることができる。
【００３６】
以上の例では黒鉛添加率５％の場合を中心に説明をしてきたが、更に低黒鉛添加率の場合でも実用上は問題なく、放電性能を踏まえた電池仕様設計上の観点や、大量生産のための生産設備での機械的な観点から言及すれば、黒鉛添加率３％までが本発明の有効な範囲である。
【００３７】
なお、上記においてはアルカリマンガン電池として特に円筒形のアルカリマンガン電池を想定して、中空円筒状の正極合剤成形体について説明したが、本発明の正極合剤はボタン形電池及びコイン形電池についても適用可能であり、したがって成形体の形状としては中空円筒状に限らず、これらの各電池に内填するための円盤ペレット状の成形体等いずれも適用可能である。
【００３８】
【発明の効果】
以上説明したように、本発明の正極合剤は、活物質である二酸化マンガン粉末の粒径を規定し、且つ導電剤として添加する黒鉛粉末の添加率を規定したことによって、成形性及び電解液吸液性の優れたものとなり、本合剤を使用することにより優れた性能のアルカリ電池を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a positive electrode mixture for an alkaline battery.
[0002]
[Prior art]
In general, manganese dioxide is used as a positive electrode mixture active material for alkaline batteries. Usually, the positive electrode mixture for alkaline batteries is obtained by adding graphite powder for improving conductivity to this manganese dioxide powder, adding an appropriate amount of an aqueous potassium hydroxide solution as an electrolytic solution, and mixing and stirring the mixture. It is obtained by compressing it into a rice cracker shape at a suitable pressure using a glass-like press, etc., and then crushing the rice cracker-like object to be compressed into granules by a granulator.
[0003]
The granular positive electrode mixture thus obtained is pressure-molded into a hollow cylinder at a predetermined pressure. Alternatively, there is a method of high-density filling in the form of pressure forming into a hollow cylinder in a battery can also serving as a positive electrode terminal.
The particle size of manganese dioxide to be used is generally 300 μm or less and the average particle size (MV) is generally about 50 to 100 μm.
[0004]
[Problems to be solved by the invention]
In recent years, for the purpose of increasing the capacity, the graphite addition rate in the positive electrode mixture tends to be reduced and the content of manganese dioxide as an active material tends to be increased.
However, the graphite powder added to the positive electrode mixture not only functions as a conductive agent, but also improves the fluidity of the granular mixture in the molding die when it is pressed into a hollow cylinder. It functions as a molding aid that helps molding with a high density, and also functions as a mold release agent when the molded body is taken out from the mold. For this reason, generally, when the graphite addition rate is lowered, the moldability and the mold release property become worse.
[0005]
In addition, for the purpose of increasing the capacity, the positive electrode mixture filling density tends to be increased. However, when the mixture is filled at a high density, the amount of the electrolyte absorbed into the positive electrode mixture is reduced, and the battery There exists a tendency for the reaction utilization factor of the active material in a discharge reaction to fall. That is, usually, an appropriate amount of electrolyte (for example, potassium hydroxide aqueous solution) is poured into a bottomed cylindrical separator attached to the hollow portion of the positive electrode mixture. It is sucked in. However, when the mixture is filled at a high density, the amount of electrolyte solution absorbed into the positive electrode mixture is reduced. As a result, the expected increase in capacity cannot be realized.
The present invention has been made in response to the above problems, and an object of the present invention is to provide a positive electrode mixture for an alkaline battery excellent in moldability and electrolyte solution absorption.
[0006]
[Means for Solving the Problems]
The present invention provides a positive electrode mixture for an alkaline battery containing manganese dioxide powder as a positive electrode mixture active material and graphite powder as a conductive agent, wherein the manganese dioxide powder has a particle size of 200 μm or less and an average particle size (MV). It is 25 to 55 μm, and the addition rate of graphite powder ([graphite powder weight] / [manganese dioxide powder weight + graphite powder weight]) is 3 to 7%, and 500 to 3000 ppm of zinc stearate powder or calcium stearate powder Is added .
[0008]
In the present invention, by specifying the particle diameter of the manganese dioxide powder in the above range, the strength of the positive electrode mixture molded body is increased, and the liquid absorbency of the electrolytic solution is improved. Furthermore, by making the addition rate of graphite powder into the said range, battery performance can be improved in the range which does not impair the moldability of a positive electrode mixture.
[0009]
In addition, after granulating the positive electrode mixture into granules, by adding 500 to 3000 ppm of zinc stearate powder or calcium stearate powder to the granule mixture, the moldability is further improved for high performance alkaline batteries. A positive electrode mixture can be obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the embodiment will be described in detail.
Example 1
First, manganese dioxide powder having a particle size of 180 μm or less and an average particle size (MV) of 50 μm is used, and this and graphite powder are dry-stirred in a universal stirring mass for 5 minutes. The graphite addition rate at this time was 5%. 4 parts by weight of a 40 wt% potassium hydroxide aqueous solution is added to 100 parts by weight of the mixed powder thus obtained, and wet-stirred for 5 minutes with a universal stirring mixer.
[0011]
Next, the obtained mixture is compressed into a rice cracker shape with a roll-shaped press. The press pressure at this time is preferably about 200 to 300 kg / cm 2 . Subsequently, this rice cracker-like object to be compressed was crushed with a granulator, and then classified with an automatic sieving machine of 22 to 100 mesh to obtain a granular mixture having a particle size of about 150 to 710 μm.
[0012]
(Example 2)
0.1 parts by weight of zinc stearate powder was added to 100 parts by weight of the granular mixture of Example 1 to obtain a positive electrode mixture for an alkaline battery.
[0013]
(Example 3)
A positive electrode mixture for an alkaline battery was obtained in the same manner as in Example 2 except that manganese dioxide powder having a particle size of 100 μm or less and an average particle size (MV) of 30 μm was used.
[0014]
(Comparative Example 1)
A positive electrode mixture for an alkaline battery was obtained in the same manner as in Example 1 except that manganese dioxide powder having a particle size of 250 μm or less and an average particle size (MV) of 70 μm was used.
[0015]
(Comparative Example 2)
A positive electrode mixture for alkaline batteries was obtained in the same manner as in Example 2 except that manganese dioxide powder having a particle size of 250 μm or less and an average particle size (MV) of 70 μm was used.
[0016]
(Comparative Example 3)
A positive electrode mixture for alkaline batteries was obtained in the same manner as in Example 2 except that manganese dioxide powder having a particle size of 60 μm or less and an average particle size (MV) of 20 μm was used.
[0017]
(Comparative Example 4)
A positive electrode material mixture for alkaline batteries was obtained in the same manner as in Comparative Example 1 except that the graphite addition rate was 10%.
[0018]
The seven types of granular mixture obtained as described above were each pressure-molded into a hollow cylindrical shape having a size for JIS standard LR6 type (AA size). The molding density was 3.20 g / cm 3 .
[0019]
In order to compare the strength of these molded bodies as a barometer of moldability, the crushing strength of the molded bodies was measured using Sun Scientific Rheometer CR-200D (n = 100). The measurement results are shown below (average value of n = 100).
[0020]
Example 1: 660 gf
Example 2: 683 gf
Example 3: 702 gf
Comparative Example 1: 563 gf
Comparative Example 2: 591 gf
Comparative Example 3: 747 gf
Comparative Example 4: 687 gf
[0021]
In the above test, when Example 1 and Comparative Example 1 are compared, the strength of the molded body is higher in Example 1 where the particle size of manganese dioxide used is smaller and the average particle size is smaller even when the graphite addition rate is 5%. I understand that.
[0022]
When Examples 2-3 and Comparative Examples 2-3 were compared, under the same conditions where the graphite addition rate was 5% and the zinc stearate addition amount was 1000 ppm, the manganese dioxide used had a small particle size and a small average particle size. It can be seen that the strength of the molded body is higher.
[0023]
In general, graphite functions not only as a conductive agent, but also as a molding aid for improving the fluidity of the granular mixture in the molding die and assisting the molding of uniform density. It also has a function as a mold release agent when taking out the resin. When the graphite addition rate is lowered, the moldability and mold release property are naturally deteriorated.
[0024]
Therefore, in the above embodiment, in addition to using manganese dioxide having a small particle size and a small average particle size, the formability when the graphite addition rate is lowered by adding zinc stearate powder or calcium stearate powder and Improves releasability. Comparing Example 1 in which no zinc stearate powder was added and Example 2 in which 1000 ppm of zinc stearate powder was added to the granule mixture, it was found that the strength of the molded body was improved. According to various past experimental results, the effect of adding zinc stearate powder or calcium stearate powder could not be confirmed at a graphite addition rate of about 10% as in Comparative Example 4, but when the graphite addition rate was made 8% or less. It has been found that moldability and mold release are improved. In particular, when the graphite addition rate is 7% or less, the effect of adding zinc stearate powder or calcium stearate powder is remarkable.
[0025]
The amount of zinc stearate powder or calcium stearate powder added is preferably 500 to 3000 ppm, more preferably 1000 to 2000 ppm based on the granular mixture. It has been found that when the addition amount is less than 500 ppm, there is not much improvement in moldability and releasability. In addition, zinc stearate and calcium stearate are organic compounds that have nothing to do with the discharge reaction as an alkaline battery, and if the amount added is too large, battery characteristics will be hindered. More addition is not preferred.
[0026]
In addition, the addition of zinc stearate powder or calcium stearate powder to the granular mixture may be performed alone or in combination. In the case of combined use, the total amount of zinc stearate powder and calcium stearate powder added is 500 to 3000 pm is preferable with respect to the mixture, and more preferably 1000 to 2000 ppm.
[0027]
Next, the above-mentioned five types of granular mixture were pressure-molded into hollow cylinders each having a size for JIS standard LR6 type (AA type) to form a molded body having a molding density of 3.20 g / cm 3 , as a positive terminal After being inserted into a battery can that also serves as a positive electrode mixture, the packing density of the positive electrode mixture was 3.40 g / cm 3 . A separator with a bottomed cylindrical shape is mounted in the filled hollow portion of the mixture, and about 2.5 g of a 40 wt% potassium hydroxide aqueous solution is injected into the separator as an electrolyte, and left for 30 minutes. Excess electrolyte solution other than that absorbed into the positive electrode mixture was removed, and the weight of the electrolyte solution absorbed into the separator and the positive electrode mixture was measured. The results are described below (average value of n = 100).
[0028]
Example 1: 1.58 g
Example 2: 1.57g
Example 3: 1.62 g
Comparative Example 1: 1.48 g
Comparative Example 2: 1.48 g
Comparative Example 3: 1.70 g
Comparative Example 4: 1.38 g
[0029]
Comparing the measurement results of Examples 2-3 and Comparative Examples 2-3 in this electrolyte solution absorption experiment, the particle size of manganese dioxide is the same under the same conditions that the graphite addition rate is 5% and the zinc stearate addition amount is 1000 ppm. It can be seen that a larger amount of electrolyte can be absorbed when the average particle size is smaller. From the viewpoint of actual battery design, the larger the amount of electrolyte solution absorbed, the better the reaction utilization rate of the active material can be expected.
[0030]
In the above electrolyte solution absorption experiment, a molded body that was previously press-formed into a hollow cylindrical shape at a molding density of 3.20 g / cm 3 was inserted into a battery can that also serves as a positive electrode terminal, and then the hollow cylindrical shape was formed in the battery can. The positive electrode mixture was packed at a packing density of 3.40 g / cm 3 , but the pre-molding was omitted and the packing density was 3.40 g / cm in the form of a hollow cylinder from the beginning in the battery can. It has been confirmed that even when the mixture is filled in step 3 , the same result is obtained.
[0031]
Next, 100 JIS standard LR6 type (AA type) alkaline manganese batteries were prepared for each of the cells used in the electrolyte solution absorption experiment. A 1.5 A constant current discharge test was performed for each of the prepared batteries by 50 pieces. In addition, 50 pieces each were stored in a constant temperature and humidity chamber set at 60 ° C. DRY for 1 month, then taken out and left at room temperature for 24 hours (to return the battery temperature to room temperature), and 1.5 A constant current discharge. A test was conducted. In either case, the discharge test environment was 20 ° C. and 65% RH. Table 1 shows the connection time measurement results up to a final voltage of 0.9V after storage for the first time and 60 ° C for one month, and the storage retention rate for 60 ° C for one month when the initial value is 100% (each n = 50 average value) ).
[0032]
[Table 1]
According to this, the initial connection time is correlated with the liquid absorption experiment result, and the connection time is longer as the liquid absorption amount is larger. However, Comparative Example 3, which had the largest amount of liquid absorption in the above liquid absorption experiment, had a considerably severe performance deterioration when stored at 60 ° C. for one month, and the storage maintenance rate was 65% or less. From the above results, it was found that when extremely fine manganese dioxide having a particle size of 60 μm or less and an average particle size (MV) of 20 μm is used, the high-temperature storage characteristics are not good. Although the details are not clear for this reason, it is considered that the extremely fine manganese dioxide powder itself tends to deteriorate. The 1.5 A constant current discharge is a large current discharge with a considerably large load for the LR6 type (AA type) size alkaline manganese battery, but the above Examples 1 to 3 are the first time and stored at 60 ° C. for one month. Even later, the performance was quite excellent.
[0034]
Comparing Comparative Example 2 and Comparative Example 4 using manganese dioxide having the same particle diameter and the same average particle diameter, Comparative Example 2 having a larger amount of active material is superior to Comparative Example 4 due to the difference in the graphite addition rate. I understand that. However, it can be seen that the battery performance in Comparative Example 2 is not sufficient as compared with Examples 1 to 3, and the particle size of manganese dioxide is greatly related to the battery performance.
[0035]
As shown in the above experiment, the particle size of manganese dioxide is 200 μm or less, the average particle size (MV) is 25 to 55 μm, and the addition rate of graphite powder is 3 to 8%. It is possible to obtain a high-performance high-capacity alkaline battery that is superior in performance, large current characteristics and high-temperature storage characteristics.
[0036]
In the above example, the explanation has been made mainly on the case where the graphite addition rate is 5%. However, even in the case where the graphite addition rate is lower, there is no practical problem. From the viewpoint of the battery specification design based on the discharge performance and the mass production. From the mechanical point of view in the production equipment, the effective range of the present invention is a graphite addition rate of up to 3%.
[0037]
In the above description, a hollow cylindrical positive electrode mixture molded body has been described assuming an especially cylindrical alkaline manganese battery as the alkaline manganese battery. Therefore, the shape of the molded body is not limited to a hollow cylindrical shape, and any of a disk pellet-shaped molded body to be embedded in each of these batteries can be applied.
[0038]
【The invention's effect】
As described above, the positive electrode mixture of the present invention defines the particle size of the manganese dioxide powder, which is the active material, and also regulates the addition rate of the graphite powder added as a conductive agent. An alkaline battery having excellent performance can be provided by using this mixture because of excellent liquid absorption.
Claims (1)
二酸化マンガン粉末の粒径が２００μｍ以下で且つ平均粒径（ＭＶ）が２５〜５５μｍであり、黒鉛粉末の添加率（［黒鉛粉末重量］／［二酸化マンガン粉末重量＋黒鉛粉末重量］）が３〜７％であると共に、５００〜３０００ｐｐｍのステアリン酸亜鉛粉末またはステアリン酸カルシウム粉末を添加したことを特徴とするアルカリ電池用正極合剤。In the positive electrode mixture for alkaline batteries containing manganese dioxide powder as a positive electrode mixture active material and graphite powder as a conductive agent,
The particle size of the manganese dioxide powder is 200 μm or less and the average particle size (MV) is 25 to 55 μm, and the addition rate of graphite powder ([graphite powder weight] / [manganese dioxide powder weight + graphite powder weight]) is 3 to 3. A positive electrode mixture for an alkaline battery , which is 7% and has 500 to 3000 ppm of zinc stearate powder or calcium stearate powder added thereto.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13186098A JP4517313B2 (en) | 1998-05-14 | 1998-05-14 | Positive electrode mix for alkaline batteries |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13186098A JP4517313B2 (en) | 1998-05-14 | 1998-05-14 | Positive electrode mix for alkaline batteries |
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| Publication Number | Publication Date |
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| JPH11329419A JPH11329419A (en) | 1999-11-30 |
| JP4517313B2 true JP4517313B2 (en) | 2010-08-04 |
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| JP13186098A Expired - Fee Related JP4517313B2 (en) | 1998-05-14 | 1998-05-14 | Positive electrode mix for alkaline batteries |
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| JP4739493B2 (en) * | 2000-08-31 | 2011-08-03 | Ｆｄｋ株式会社 | Positive electrode mixture molded body and battery |
| US7754386B2 (en) * | 2005-11-28 | 2010-07-13 | Pure Energy Visions Corporation | Rechargeable alkaline manganese cell having reduced capacity fade and improved cycle life |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57185674A (en) * | 1981-05-11 | 1982-11-15 | Matsushita Electric Ind Co Ltd | Alkaline manganess battery |
| JPH0736332B2 (en) * | 1987-01-28 | 1995-04-19 | 松下電器産業株式会社 | Battery |
| JPH1083810A (en) * | 1996-09-11 | 1998-03-31 | Toshiba Battery Co Ltd | Positive cathode mix for zinc alkaline battery |
-
1998
- 1998-05-14 JP JP13186098A patent/JP4517313B2/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57185674A (en) * | 1981-05-11 | 1982-11-15 | Matsushita Electric Ind Co Ltd | Alkaline manganess battery |
| JPH0736332B2 (en) * | 1987-01-28 | 1995-04-19 | 松下電器産業株式会社 | Battery |
| JPH1083810A (en) * | 1996-09-11 | 1998-03-31 | Toshiba Battery Co Ltd | Positive cathode mix for zinc alkaline battery |
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| JPH11329419A (en) | 1999-11-30 |
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