JP4383229B2 - Nickel metal hydride secondary battery - Google Patents

Nickel metal hydride secondary battery Download PDF

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JP4383229B2
JP4383229B2 JP2004106870A JP2004106870A JP4383229B2 JP 4383229 B2 JP4383229 B2 JP 4383229B2 JP 2004106870 A JP2004106870 A JP 2004106870A JP 2004106870 A JP2004106870 A JP 2004106870A JP 4383229 B2 JP4383229 B2 JP 4383229B2
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哲哉 山根
有紀 森川
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Sanyo Electric Co Ltd
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Description

本発明はニッケル水素二次電池に関する。   The present invention relates to a nickel metal hydride secondary battery.

ニッケル水素二次電池は密封可能な外装缶を有し、外装缶内にセパレータを介して渦巻状に巻回された正極板及び負極板がアルカリ電解液とともに収容されている。正極板は、例えば多孔質構造を有した金属の基板を有し、基板には正極活物質として水酸化ニッケル粒子が分布されている。又、負極は、例えばパンチングメタルからなる基板を有し、基板には、負極活物質としての水素を吸収及び放出可能な水素吸蔵合金粒子が分布されている。水酸化ニッケル粒子及び水素吸蔵合金粒子はその量によって、正極容量及び負極容量をそれぞれ規定するが、一般に、電池の過充電時に正極板で発生した酸素ガスを負極で還元して電池の内圧上昇を防止すべく、正極容量よりも負極容量の方が大きく設定されるので（ノイマン式の原理）、電池容量は正極容量により規定される。   The nickel metal hydride secondary battery has a sealed outer can, and a positive electrode plate and a negative electrode plate wound in a spiral shape with a separator interposed in the outer can are accommodated together with an alkaline electrolyte. The positive electrode plate has, for example, a metal substrate having a porous structure, and nickel hydroxide particles are distributed as a positive electrode active material on the substrate. The negative electrode has a substrate made of, for example, a punching metal, and hydrogen storage alloy particles capable of absorbing and releasing hydrogen as the negative electrode active material are distributed on the substrate. The nickel hydroxide particles and the hydrogen storage alloy particles define the positive electrode capacity and the negative electrode capacity, respectively, depending on their amounts. In general, the oxygen gas generated at the positive electrode plate during battery overcharge is reduced at the negative electrode to increase the internal pressure of the battery. In order to prevent this, since the negative electrode capacity is set larger than the positive electrode capacity (Neumann principle), the battery capacity is defined by the positive electrode capacity.

従って、この種の電池の体積エネルギー密度を高めるには、正極容量の増大が必要になる。例えば、特許文献１が開示する電池は、球状の水酸化ニッケル粒子と非球状の水酸化ニッケル粒子とを混合して水酸化ニッケル粒子の充填密度を高め、もって体積エネルギー密度を高めている。
特開平５−２１０６４号公報 Therefore, to increase the volume energy density of this type of battery, it is necessary to increase the positive electrode capacity. For example, in the battery disclosed in Patent Document 1, spherical nickel hydroxide particles and non-spherical nickel hydroxide particles are mixed to increase the packing density of the nickel hydroxide particles, thereby increasing the volume energy density.
Japanese Patent Laid-Open No. 5-21064

ところで、特許文献１の電池では、二次電池のサイクル特性の低下を防止すべく、水酸化ニッケル粒子がカドミウム、カルシウム、亜鉛、マグネシウム、鉄、コバルト及びマンガンのうちの少なくとも一種を含有しているものと考えられる。しかしながら、この電池にあっても、充放電を繰り返すうちに水酸化ニッケル粒子が膨張し、水酸化ニッケル粒子にアルカリ電解液が取り込まれる。ここで、体積エネルギー密度が３４０Ｗｈ／ｌ以上の場合、電池に注液されるアルカリ電解液量はもともと少量なので、セパレータが保持するアルカリ電解液が水酸化ニッケル粒子に取り込まれてしまうと、電池の内部抵抗が増大し易い。このため、特許文献１の電池を体積エネルギー密度が３４０Ｗｈ／ｌの電池に適用した場合、充放電を繰り返すうちに放電容量が低下するという問題が生じる。   By the way, in the battery of Patent Document 1, the nickel hydroxide particles contain at least one of cadmium, calcium, zinc, magnesium, iron, cobalt, and manganese in order to prevent deterioration of the cycle characteristics of the secondary battery. It is considered a thing. However, even in this battery, the nickel hydroxide particles expand as charging and discharging are repeated, and the alkaline electrolyte is taken into the nickel hydroxide particles. Here, when the volume energy density is 340 Wh / l or more, the amount of the alkaline electrolyte injected into the battery is originally small, so if the alkaline electrolyte held by the separator is taken into the nickel hydroxide particles, Internal resistance tends to increase. For this reason, when the battery of Patent Document 1 is applied to a battery having a volume energy density of 340 Wh / l, there arises a problem that the discharge capacity decreases while charging and discharging are repeated.

本発明は上述の事情に基づいてなされたものであって、その目的とするところは、体積エネルギー密度が高く且つサイクル特性に優れたニッケル水素二次電池を提供することにある。   The present invention has been made based on the above-described circumstances, and an object thereof is to provide a nickel-hydrogen secondary battery having a high volumetric energy density and excellent cycle characteristics.

上記した目的を達成するため、請求項１の発明は、円筒状の外装缶内に、アルカリ電解液と、渦巻状に巻回された正極板及び負極板並びにこれら正極板と負極板との間に挟まれたセパレータからなる電極群とが収容され、前記電極群の最外周を形成する前記負極板の部位が前記外装缶の内周壁に接しているニッケル水素二次電池において、前記電池は、３４０Ｗｈ／ｌ以上４５０Ｗｈ／ｌ以下の体積エネルギー密度を有し、前記正極板は、導電性を有する多孔質の基板と、前記基板の空孔に充填され、活物質粒子を含有した正極合剤とからなり、前記活物質粒子は、水酸化ニッケルからなるコアにコバルト化合物の被膜層を形成し、この被膜層にアルカリ熱処理した球状の第１の粒子と、水酸化ニッケルからなる非球状の第２の粒子とを含み、前記第１の粒子の全質量をＸとし、前記第２の粒子の全質量をＹとしたときに、質量比Ｙ／Ｘが０．０４以上０．１２以下の範囲にあることを特徴としている。   In order to achieve the above-mentioned object, the invention of claim 1 includes an alkaline electrolyte, a positive electrode plate and a negative electrode plate wound in a spiral shape, and a space between these positive electrode plate and negative electrode plate in a cylindrical outer can. In the nickel-metal hydride secondary battery in which the electrode group consisting of separators sandwiched between and the negative electrode plate part forming the outermost periphery of the electrode group is in contact with the inner peripheral wall of the outer can, The positive electrode plate has a volumetric energy density of 340 Wh / l or more and 450 Wh / l or less, and the positive electrode plate has a conductive porous substrate, and a positive electrode mixture containing active material particles filled in the pores of the substrate. The active material particles are formed by forming a cobalt compound coating layer on a nickel hydroxide core, and spherical first particles obtained by alkaline heat treatment on the coating layer, and nonspherical second particles of nickel hydroxide. Including particles of When the total mass of the first particles is X and the total mass of the second particles is Y, the mass ratio Y / X is in the range of 0.04 to 0.12. .

この構成によれば、正極活物質粒子が球状の第１の粒子と非球状の第２の粒子とを含み、そして、これら粒子の質量比Ｙ／Ｘを０．０４以上０．１２以下の範囲にしてあるので、基板に正極合剤を高充填密度で充填することができ、もって、３４０Ｗｈ／ｌ以上の体積エネルギー密度を達成することができる。
一方、第１の粒子において、水酸化ニッケル粒子からなるコアは、コバルト化合物からなり且つアルカリ熱処理された被覆層により覆われていることから、この被覆層の存在により、電池の充放電の際にコアの膨張が抑制される。このため、体積エネルギー密度を３４０Ｗｈ／ｌ以上にしたことにより、電池内のアルカリ電解液量が少量であっても、この構成によれば、第１の粒子のコア内へのセパレータ中のアルカリ電解液の取り込みが抑制され、この結果、充放電の繰り返しに伴なうセパレータ中のアルカリ電解液の減少が抑制される。 According to this configuration, the positive electrode active material particles include the first spherical particles and the second non-spherical particles, and the mass ratio Y / X of these particles is in the range of 0.04 to 0.12. Therefore, the positive electrode mixture can be filled at a high filling density on the substrate, and thus a volume energy density of 340 Wh / l or more can be achieved.
On the other hand, in the first particles, the core made of nickel hydroxide particles is covered with a coating layer made of a cobalt compound and subjected to an alkali heat treatment. Expansion of the core is suppressed. Therefore, by setting the volume energy density to 340 Wh / l or more, even if the amount of the alkaline electrolyte in the battery is small, according to this configuration, the alkaline electrolysis in the separator into the core of the first particles is performed. Incorporation of the liquid is suppressed, and as a result, a decrease in the alkaline electrolyte in the separator due to repeated charge and discharge is suppressed.

好適な態様として、前記基板の全空孔容積をＳとし、前記正極合剤の充填量をＭとしたときに、前記正極合剤の充填密度Ｍ／Ｓは、３．０５ｇ／ｃｍ3以上３．２５ｇ／ｃｍ3以下の範囲にある（請求項２）。
この構成では、充填密度Ｍ／Ｓの下限を３．０５ｇ／ｃｍ3にしたことにより、正極合剤の充填後に空孔内に存在する空隙の容積が小さく、この空隙に取り込まれるアルカリ電解液量を減らすことができる。このため、セパレータ中のアルカリ電解液量を相対的に増やすことができる。一方、充填密度Ｍ／Ｓの上限を３．２５ｇ／ｃｍ3にしたのは、充填密度Ｍ／Ｓが３．２５ｇ／ｃｍ3を超えると、正極板に取り込まれるアルカリ電解液量が少なくなり過ぎ、かえって内部抵抗の増大を招くからである。 As a preferred embodiment, when the total pore volume of the substrate is S and the filling amount of the positive electrode mixture is M, the filling density M / S of the positive electrode mixture is 3.05 g / cm 3 or more 3 It is in the range of 25 g / cm 3 or less (claim 2).
In this configuration, by setting the lower limit of the packing density M / S to 3.05 g / cm 3 , the volume of the voids existing in the pores after filling with the positive electrode mixture is small, and the amount of the alkaline electrolyte taken into the voids Can be reduced. For this reason, the amount of alkaline electrolyte in the separator can be relatively increased. On the other hand, was the was the 3.25 g / cm 3 the upper limit of the packing density M / S, the filling density of M / S is more than 3.25 g / cm 3, too less alkaline electrolyte amount incorporated into the positive electrode plate This is because the internal resistance is increased.

好適な態様として、前記被覆層の全質量をＧとしたときに、前記第１の粒子における前記被覆層の質量割合Ｇ／Ｘは、２．０％以上６．０％以下の範囲にある（請求項３）。
この構成では、第１の粒子における被覆層の質量割合の下限を２．０％にしたことにより、被覆層によって水酸化ニッケルのコア表面を十分に被覆することができ、充放電を繰り返した場合のコアの膨張を確実に防止することができる。一方、第１の粒子における被覆層の質量割合の上限を６．０％にしたことにより、第１の粒子における水酸化ニッケルの質量割合の低下を制限して正極容量を確保し、高い体積エネルギー密度を確実に達成することができる。 As a preferred embodiment, when the total mass of the coating layer is G, the mass ratio G / X of the coating layer in the first particles is in the range of 2.0% to 6.0% ( Claim 3).
In this configuration, when the lower limit of the mass ratio of the coating layer in the first particles is 2.0%, the core surface of nickel hydroxide can be sufficiently covered by the coating layer, and charging and discharging are repeated. The expansion of the core can be reliably prevented. On the other hand, by setting the upper limit of the mass ratio of the coating layer in the first particles to 6.0%, the decrease in the mass ratio of nickel hydroxide in the first particles is limited to ensure the positive electrode capacity, and the high volume energy. Density can be reliably achieved.

好適な態様として、前記正極合剤は、金属コバルト又はコバルト化合物からなる第３の粒子を更に含み、前記第３の粒子の全質量をＺとしたときに、前記活物質粒子に対する前記第３の粒子の質量比Ｚ／（Ｘ＋Ｙ）が０．５以上２．５以下の範囲にある（請求項４）。
この構成では、正極合剤が第３の粒子を含有することにより、第１の粒子におけるコアの膨張を一層抑制することができる。 As a preferred embodiment, the positive electrode mixture further includes third particles made of metallic cobalt or a cobalt compound, and the third mass relative to the active material particles when the total mass of the third particles is Z. The mass ratio Z / (X + Y) of the particles is in the range of 0.5 to 2.5 (claim 4).
In this configuration, the positive electrode mixture contains the third particles, whereby the expansion of the core in the first particles can be further suppressed.

好適な態様として、前記アルカリ電解液量をＶｅとし、前記電池の０．２Ｃ容量をＱとしたときに、容量液比Ｖｅ／Ｑが０．８５ｍｌ／Ａｈ以下の範囲にある（請求項５）。
この構成によれば、電池内のアルカリ電解液量を制限することで、過充電時に正極板で発生した酸素ガスを一時的に蓄えるための余剰空間を電池内に十分に確保することができ、電池内圧の上昇による安全弁の頻繁な作動が抑制される。この結果、安全弁作動時に電池外部へのアルカリ電解液の噴出が抑制され、セパレータ中のアルカリ電解液の減少を一層抑制することができる。電池内のアルカリ電解液量を制限できる理由は、本発明の構成により、正極活物質粒子内へのアルカリ電解液の取り込みが抑制されていることによる。 As a preferred embodiment, when the amount of the alkaline electrolyte is Ve and the capacity of the battery is 0.2 C, the capacity liquid ratio Ve / Q is in the range of 0.85 ml / Ah or less (Claim 5). .
According to this configuration, by limiting the amount of alkaline electrolyte in the battery, it is possible to sufficiently ensure an excess space in the battery for temporarily storing oxygen gas generated in the positive electrode plate during overcharge, Frequent operation of the safety valve due to an increase in battery internal pressure is suppressed. As a result, the discharge of the alkaline electrolyte to the outside of the battery is suppressed when the safety valve is activated, and the decrease of the alkaline electrolyte in the separator can be further suppressed. The reason why the amount of the alkaline electrolyte in the battery can be limited is that the configuration of the present invention suppresses the incorporation of the alkaline electrolyte into the positive electrode active material particles.

好適な態様として、前記負極板は、電極群の最外周を形成する部位に薄肉部を有する（請求項６）。
負極板の最外周部は、外側に正極板が配置されていないため電池反応への寄与が小さい。この構成では、このような最外周部に薄肉部を形成し、最外周部に取り込まれるアルカリ電解液量を低減したので、相対的にセパレータ中のアルカリ電解液量を増やすことができる。 As a preferred aspect, the negative electrode plate has a thin portion at a portion forming the outermost periphery of the electrode group (Claim 6).
The outermost peripheral portion of the negative electrode plate contributes little to the battery reaction because the positive electrode plate is not disposed outside. In this structure, since the thin part was formed in such an outermost periphery part and the amount of alkaline electrolyte solution taken in by the outermost periphery part was reduced, the amount of alkaline electrolyte solution in a separator can be increased relatively.

好適な態様として、前記第１の粒子は、タップ密度が２．３０ｇ／ｃｍ3以上２．４５ｇ／ｃｍ3以下の範囲にある（請求項７）。第１の粒子のタップ密度がこの範囲にあれば、充填密度Ｍ／Ｓを上述の範囲に容易にすることができる。 As a preferred embodiment, the first particles have a tap density in the range of 2.30 g / cm 3 or more and 2.45 g / cm 3 or less (Claim 7). If the tap density of the first particles is within this range, the packing density M / S can be easily made within the above range.

以上説明したように、請求項１〜７の本発明のニッケル水素二次電池は、高い体積エネルギー密度を有する一方、充放電の繰り返しに伴なうセパレータ中のアルカリ電解液の減少が抑制される。このため、この電池は、内部抵抗の増大に基づく放電容量の低下が抑制され、優れたサイクル特性も有する。
請求項２、６及び７のニッケル水素二次電池によれば、セパレータ中のアルカリ電解液量が相対的に増量され、サイクル特性が更に向上する。 As described above, the nickel metal hydride secondary battery of the present invention according to claims 1 to 7 has a high volumetric energy density, while suppressing a decrease in the alkaline electrolyte in the separator due to repeated charge and discharge. . For this reason, this battery suppresses a decrease in discharge capacity due to an increase in internal resistance and also has excellent cycle characteristics.
According to the nickel metal hydride secondary battery of claims 2, 6 and 7, the amount of the alkaline electrolyte in the separator is relatively increased, and the cycle characteristics are further improved.

請求項３及び４のニッケル水素二次電池は、第１の粒子における被覆層の質量割合及び活物質粒子に対する第３の粒子の質量比の範囲がそれぞれ制限され、高い体積エネルギー密度と優れたサイクル特性の両立に好適する。
請求項５のニッケル水素二次電池は、アルカリ電解液の外部への噴出が抑制され、サイクル特性が更に向上する。 The nickel-metal hydride secondary battery according to claim 3 and 4 has a high volume energy density and an excellent cycle in which the mass ratio of the coating layer in the first particles and the mass ratio range of the third particles to the active material particles are respectively limited. Suitable for compatibility of characteristics.
In the nickel metal hydride secondary battery according to the fifth aspect, ejection of the alkaline electrolyte to the outside is suppressed, and the cycle characteristics are further improved.

以下に添付の図面を参照して、本発明の一実施形態のニッケル水素二次電池について詳細に説明する。
この電池はＡＡサイズの円筒型電池であり、図１に示したように、上端が開口した有底円筒形状をなす外装缶１０を備えている。外装缶１０は、１３．５ｍｍ以上１４．５ｍｍ以下の外径Ｄを有し、その底壁が導電性を有した負極端子として機能する。外装缶１０の開口内には、リング状の絶縁パッキン１２を介して導電性を有する円板形状の蓋板１４が配置され、これら蓋板１４及び絶縁パッキン１２は外装缶１０の開口縁をかしめ加工することにより外装缶１０の開口縁に固定されている。 Hereinafter, a nickel-hydrogen secondary battery according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
This battery is an AA size cylindrical battery, and includes an outer can 10 having a bottomed cylindrical shape with an open upper end as shown in FIG. The outer can 10 has an outer diameter D of 13.5 mm or more and 14.5 mm or less, and the bottom wall functions as a negative electrode terminal having conductivity. In the opening of the outer can 10, a disc-shaped cover plate 14 having conductivity is arranged via a ring-shaped insulating packing 12, and the cover plate 14 and the insulating packing 12 caulk the opening edge of the outer can 10. It is being fixed to the opening edge of the armored can 10 by processing.

蓋板１４は中央にガス抜き孔１６を有し、蓋板１４の外面上にはガス抜き孔１６を塞いでゴム製の弁体１８が配置されている。更に、蓋板１４の外面上には、弁体１８を覆うフランジ付き円筒形状の正極端子２０が固定され、正極端子２０は弁体１８を蓋板１４に押圧している。従って、通常時、外装缶１０は絶縁パッキン１２及び弁体１８を介して蓋板１４により気密に閉塞されている。一方、外装缶１０内でガスが発生し、その内圧が高まった場合には弁体１８が圧縮され、ガス抜き孔１６を通して外装缶１０からガスが放出される。つまり、蓋板１４、弁体１８及び正極端子２０は、安全弁を形成している。   The cover plate 14 has a gas vent hole 16 in the center, and a rubber valve element 18 is disposed on the outer surface of the cover plate 14 so as to close the gas vent hole 16. Further, a flanged cylindrical positive electrode terminal 20 covering the valve body 18 is fixed on the outer surface of the lid plate 14, and the positive electrode terminal 20 presses the valve body 18 against the lid plate 14. Accordingly, at the normal time, the outer can 10 is airtightly closed by the cover plate 14 via the insulating packing 12 and the valve body 18. On the other hand, when gas is generated in the outer can 10 and the internal pressure increases, the valve body 18 is compressed, and the gas is released from the outer can 10 through the gas vent hole 16. That is, the cover plate 14, the valve body 18, and the positive electrode terminal 20 form a safety valve.

ここで、正極端子２０の先端から外装缶１０の底面までの長さ、すなわち電池の高さＨは４９．２ｍｍ以上５０．５ｍｍ以下の範囲にあり、電池の体積Ｖｂは、外径Ｄ及び高さＨの円柱体の体積に等しいものとして、次式：
Ｖｂ＝π（Ｄ／２）2×Ｈ
により規定される。 Here, the length from the tip of the positive electrode terminal 20 to the bottom surface of the outer can 10, that is, the height H of the battery is in the range of 49.2 mm to 50.5 mm, and the volume Vb of the battery is the outer diameter D and the height. As equal to the volume of a cylinder of height H, the following formula:
Vb = π (D / 2) 2 × H
It is prescribed by.

外装缶１０には、電極群２２が収容されている。電極群２２は、正極板２４、負極板２６及びセパレータ２８からなり、図２に示したように、渦巻状に巻回された正極板２４と負極板２６の間にセパレータが挟まれている。即ち、セパレータ２８を介して正極板２４及び負極板２６が互い重ね合わされている。電極群２２の最外周は負極板２６の一部（最外周部）により形成され、負極板２６の最外周部が外装缶１０の内周壁と接触することで、負極板２６と外装缶１０とは互いに電気的に接続されている。   An electrode group 22 is accommodated in the outer can 10. The electrode group 22 includes a positive electrode plate 24, a negative electrode plate 26, and a separator 28. As shown in FIG. 2, the separator is sandwiched between the positive electrode plate 24 and the negative electrode plate 26 wound in a spiral shape. That is, the positive electrode plate 24 and the negative electrode plate 26 are overlapped with each other via the separator 28. The outermost periphery of the electrode group 22 is formed by a part of the negative electrode plate 26 (outermost peripheral portion), and the outermost peripheral portion of the negative electrode plate 26 is in contact with the inner peripheral wall of the outer can 10. Are electrically connected to each other.

更に、外装缶１０内には、電極群２２の一端と蓋板１４との間に、正極リード３０が配置され、正極リード３０の両端は正極板２４及び蓋板１４にそれぞれ接続されている。従って、正極端子２０と正極板２４との間は、正極リード３０及び蓋板１４を介して電気的に接続されている。なお、蓋板１４と電極群２２との間には円形の絶縁部材３２が配置され、正極リード３０は絶縁部材３２に設けられたスリットを通して延びている。また、電極群２２と外装缶１０の底部との間にも円形の絶縁部材３４が配置されている。   Further, in the outer can 10, a positive electrode lead 30 is disposed between one end of the electrode group 22 and the lid plate 14, and both ends of the positive electrode lead 30 are connected to the positive electrode plate 24 and the lid plate 14, respectively. Therefore, the positive electrode terminal 20 and the positive electrode plate 24 are electrically connected via the positive electrode lead 30 and the lid plate 14. A circular insulating member 32 is disposed between the cover plate 14 and the electrode group 22, and the positive electrode lead 30 extends through a slit provided in the insulating member 32. A circular insulating member 34 is also disposed between the electrode group 22 and the bottom of the outer can 10.

セパレータ２８の材料としては、例えば、ポリアミド繊維製不織布、ポリエチレンやポリプロピレンなどのポリオレフィン繊維製不織布に親水性官能基を付与したものをあげることができる。
負極板２６は、図３に示したように、帯状をなす導電性の負極基板４６を有し、この負極基板４６には負極合剤が保持されている。負極基板４６は、貫通孔が分布されたシート状の金属材からなり、このようなものとして、例えば、パンチングメタル、金属粉末焼結体基板、エキスパンデッドメタル及びニッケルネット等を用いることができる。とりわけ、パンチングメタルや、金属粉末を成型してから焼結した金属粉末焼結体基板は負極基板に好適する。 Examples of the material of the separator 28 include polyamide fiber nonwoven fabrics, and polyolefin fiber nonwoven fabrics such as polyethylene and polypropylene, to which hydrophilic functional groups are added.
As shown in FIG. 3, the negative electrode plate 26 has a conductive negative electrode substrate 46 having a strip shape, and the negative electrode substrate 46 holds a negative electrode mixture. The negative electrode substrate 46 is made of a sheet-like metal material in which through-holes are distributed. As such, for example, a punching metal, a metal powder sintered body substrate, an expanded metal, a nickel net, or the like can be used. . In particular, a punched metal or a metal powder sintered body substrate obtained by molding and sintering a metal powder is suitable for a negative electrode substrate.

負極合剤は、負極活物質としての水素を吸蔵及び放出可能な水素吸蔵合金粒子、導電助剤及び結着剤からなる。尚、本明細書においては、説明の便宜上、水素吸蔵合金もまた負極活物質という。
水素吸蔵合金粒子は、電池の充電時にアルカリ電解液中で電気化学的に発生させた水素を吸蔵でき、なおかつ放電時にその吸蔵水素を容易に放出できるものであればよい。このような水素吸蔵合金としては、特に限定されないが、例えば、ＬａＮｉ5やＭｍＮｉ5（Ｍｍはミッシュメタル）等のＡＢ5型系のものをあげることができる。 The negative electrode mixture includes hydrogen storage alloy particles capable of occluding and releasing hydrogen as a negative electrode active material, a conductive additive, and a binder. In the present specification, for the convenience of explanation, the hydrogen storage alloy is also referred to as a negative electrode active material.
The hydrogen storage alloy particles are not particularly limited as long as they can store hydrogen generated electrochemically in an alkaline electrolyte during battery charging and can easily release the stored hydrogen during discharge. Such a hydrogen storage alloy is not particularly limited, and examples thereof include AB 5 type alloys such as LaNi 5 and MmNi 5 (Mm is a misch metal).

また、結着剤としては親水性若しくは疎水性のポリマー等を用いることができ、導電助剤としては、カーボンブラックや黒鉛を用いることができる。
上記した負極合剤は、負極基板４６の貫通孔内に充填されるとともに、負極基板４６の両面にて層状をなしている。以下、負極基板４６の内面を被覆し且つ電極群２２の径方向内側に位置付けられる負極合剤の層を内側合金層４８といい、負極基板４６の外面を被覆し且つ電極群２２の径方向外側に位置付けられる負極合剤の層を外側合金層５０と称する。 Further, a hydrophilic or hydrophobic polymer or the like can be used as the binder, and carbon black or graphite can be used as the conductive assistant.
The negative electrode mixture described above is filled in the through hole of the negative electrode substrate 46 and is layered on both surfaces of the negative electrode substrate 46. Hereinafter, the layer of the negative electrode mixture that covers the inner surface of the negative electrode substrate 46 and is positioned on the radially inner side of the electrode group 22 is referred to as an inner alloy layer 48, covers the outer surface of the negative electrode substrate 46 and is radially outer of the electrode group 22. The layer of the negative electrode mixture that is positioned in FIG.

負極板２６において、図４に示したように、内側合金層４８の厚みＴ２は、負極巻始め端部３８から負極巻終わり端部４２に亘って一定である。一方、外側合金層５０は、負極巻始め端部３８と負極巻終わり端部４２との間で厚みが変化し、その厚みに関して、３つの領域に区分され、これら領域は負極基板４６の長手方向（負極巻始め端部３８から負極巻終わり端部４２に向う方向）でみて順に、負極本体部５２、負極境界部５４および負極薄肉部５６からなる。   As shown in FIG. 4, in the negative electrode plate 26, the thickness T <b> 2 of the inner alloy layer 48 is constant from the negative electrode winding start end portion 38 to the negative electrode winding end portion 42. On the other hand, the outer alloy layer 50 varies in thickness between the negative electrode winding start end portion 38 and the negative electrode winding end end portion 42, and is divided into three regions with respect to the thickness. As viewed in the direction from the negative electrode winding start end portion 38 toward the negative electrode winding end portion 42, the negative electrode main body portion 52, the negative electrode boundary portion 54, and the negative electrode thin portion 56 are sequentially formed.

負極本体部５２は電極群２２の径方向内側部分にて巻回され、その最内周部を除き、その両側にはセパレータ２８を介して正極板２４が配置されている。負極本体部５２における外側合金層５０の厚みは、内側合金層４８の厚みＴ２に等しく且つ一定である。
負極薄肉部５６は、電極群２２の最外周を形成すべく巻回され、外面が外装缶１０の内周壁と密接している。負極巻き終わり端部４２は、電極群２２の周方向でみて正極巻終わり端部４０を超えて延出し、その径方向内側に負極本体部５２が位置付けられている。負極薄肉部５６における外側合金層５０の厚みＴ１は、負極基板４６の長手方向でみて一定であるが、しかしながら、その内側合金層４８の厚みＴ２よりも薄い。従って、負極薄肉部５６においては、内側合金層４８の方が外側合金層５０よりも厚い。 The negative electrode main body 52 is wound around the radially inner portion of the electrode group 22, and the positive electrode plate 24 is disposed on both sides of the negative electrode main body 52 via the separators 28 except for the innermost peripheral portion. The thickness of the outer alloy layer 50 in the negative electrode main body 52 is equal to the thickness T2 of the inner alloy layer 48 and is constant.
The negative electrode thin portion 56 is wound to form the outermost periphery of the electrode group 22, and the outer surface is in close contact with the inner peripheral wall of the outer can 10. The negative electrode winding end portion 42 extends beyond the positive electrode winding end portion 40 as viewed in the circumferential direction of the electrode group 22, and the negative electrode main body portion 52 is positioned on the radially inner side. The thickness T1 of the outer alloy layer 50 in the negative electrode thin portion 56 is constant when viewed in the longitudinal direction of the negative electrode substrate 46, however, it is thinner than the thickness T2 of the inner alloy layer 48. Therefore, in the negative electrode thin portion 56, the inner alloy layer 48 is thicker than the outer alloy layer 50.

負極境界部５４は、負極本体部５２と負極薄肉部５６との間に設けられ、負極巻終わり端部４２の近傍にて、電極群２２の最外周の一部を形成している。負極境界部５４は、長さＬを有し、負極基板４６の長手方向でみて厚みが変化する。より詳しくは、負極境界部５４における外側合金層５０の厚みは、負極本体部５２から負極薄肉部５６に向かって略一定の変化率にて徐々に減少し、厚みＴ２から厚みＴ１まで変化する。   The negative electrode boundary portion 54 is provided between the negative electrode main body portion 52 and the negative electrode thin portion 56, and forms a part of the outermost periphery of the electrode group 22 in the vicinity of the negative electrode winding end portion 42. The negative electrode boundary portion 54 has a length L, and the thickness changes in the longitudinal direction of the negative electrode substrate 46. More specifically, the thickness of the outer alloy layer 50 at the negative electrode boundary portion 54 gradually decreases at a substantially constant change rate from the negative electrode main body portion 52 toward the negative electrode thin portion 56, and changes from the thickness T2 to the thickness T1.

正極板２４は、多孔質構造を有する導電性の正極基板と、この正極基板に保持された正極合剤とからなる。より詳しくは、正極基板はニッケル製の金属体であって、図１の円内に一部を模式的に示したように、３次元網目状の骨格５８と、この骨格５８によって形成された無数の空孔６０をその内部に有する。正極基板には、これらの空孔６０に所定の充填密度Ｍ／Ｓにて正極合剤が充填され、充填密度Ｍ／Ｓは好適な態様として、３．０５ｇ／ｃｍ3以上３．２５ｇ／ｃｍ3以下の範囲にある。ここで、充填密度Ｍ／Ｓは、正極基板における空孔６０の単位容積当りに充填された正極合剤の質量であり、以下のようにして求められる。 The positive electrode plate 24 includes a conductive positive electrode substrate having a porous structure and a positive electrode mixture held on the positive electrode substrate. More specifically, the positive electrode substrate is a nickel metal body. As schematically shown in part in the circle of FIG. 1, the three-dimensional network skeleton 58 and the infinite number of skeletons 58 are formed. The air holes 60 are provided therein. The positive electrode substrate is filled with the positive electrode mixture at a predetermined filling density M / S in these holes 60, and the filling density M / S is preferably 3.05 g / cm 3 or more and 3.25 g / cm. It is in the range of 3 or less. Here, the filling density M / S is the mass of the positive electrode mixture filled per unit volume of the holes 60 in the positive electrode substrate, and is obtained as follows.

まず、正極板２４の質量Ｗｐ及び体積Ｖｐを測定し、それから、正極合剤を正極基板から除去し、正極基板の質量Ｗｓを測定する。次に、正極板２４の質量Ｗｐから正極基板の質量Ｗｓを差し引いて、正極合剤の質量Ｍを求める一方、正極基板の質量Ｗｓを正極基板の材料であるニッケルの真比重ρで除して正極基板の骨格体積Ｖｓを求め、この骨格体積Ｖｓを正極板２４の体積Ｖｐから差し引いて正極基板における空孔６０の全容積Ｓを求める。そして、正極合剤の質量Ｍを全空孔容積Ｓで除して正極合剤の充填密度Ｍ／Ｓが求められる。なお、いずれの質量Ｗｐ、Ｗｓ、Ｍも乾燥質量であり、正極合剤を正極基板から除去するには、例えば、超音波洗浄器を用いて正極板２４を溶媒中で振動させればよい。   First, the mass Wp and the volume Vp of the positive electrode plate 24 are measured, and then the positive electrode mixture is removed from the positive electrode substrate, and the mass Ws of the positive electrode substrate is measured. Next, the mass Ws of the positive electrode substrate is subtracted from the mass Wp of the positive electrode plate 24 to obtain the mass M of the positive electrode mixture, while the mass Ws of the positive electrode substrate is divided by the true specific gravity ρ of nickel as the material of the positive electrode substrate. The skeleton volume Vs of the positive electrode substrate is obtained, and the skeleton volume Vs is subtracted from the volume Vp of the positive electrode plate 24 to obtain the total volume S of the holes 60 in the positive electrode substrate. Then, the packing density M / S of the positive electrode mixture is obtained by dividing the mass M of the positive electrode mixture by the total pore volume S. Note that all the masses Wp, Ws, and M are dry masses, and in order to remove the positive electrode mixture from the positive electrode substrate, for example, the positive electrode plate 24 may be vibrated in a solvent using an ultrasonic cleaner.

正極合剤は、正極活物質粒子及び結着剤６２からなり（図１）、結着剤６２は、正極活物質粒子同士を結着するとともに、これら正極活物質粒子を正極基板の骨格５８に結着している。結着剤６２としては、負極板２６の場合と同様に、疎水性及び親水性のポリマー等を用いることができる。
正極活物質粒子は、略球状の粒子６４（球状粒子）と非球状の粒子６６（非球状粒子）からなり、この電池では、球状粒子６４の全質量をＸとし、非球状粒子６８の全質量をＹとしたときに、質量比Ｙ／Ｘは０．０４以上０．１２以下の範囲にある。 The positive electrode mixture is composed of positive electrode active material particles and a binder 62 (FIG. 1). The binder 62 binds the positive electrode active material particles to each other, and the positive electrode active material particles are attached to the skeleton 58 of the positive electrode substrate. It is bound. As the binder 62, hydrophobic and hydrophilic polymers can be used as in the case of the negative electrode plate 26.
The positive electrode active material particles are composed of substantially spherical particles 64 (spherical particles) and non-spherical particles 66 (non-spherical particles). In this battery, the total mass of the spherical particles 64 is X, and the total mass of the non-spherical particles 68. Is Y, the mass ratio Y / X is in the range of 0.04 to 0.12.

非球状粒子６６は、例えば球状の水酸化ニッケル粒子を粉砕することにより得られ、１．０μｍ以上３．０μｍ以下の平均粒径を有する。質量比Ｙ／Ｘが上述の範囲にあり、且つ、球状粒子６４よりも小さいことから、球状粒子６４間に形成される隙間を埋めるような状態で正極合剤中に分布される。
一方、球状粒子６４は、例えば平均粒径が１０μｍ以上２０μｍ以下の範囲にあり、好適な態様として、タップ密度が２．３０ｇ／ｃｍ3以上２．４５ｇ／ｃｍ3以下の範囲にある。タップ密度とは、ＪＩＳ Ｋ ５１０１に規定されたタップ法による見掛け密度のことをいう。より詳しくは、タップ密度は、任意量の球状粒子６４を入れて栓をしたメスシリンダーを一定の高さから所定回数落下させ、球状粒子６４の体積を測定し、メスシリンダー内の球状粒子６４の質量を得られた体積で除して求められる。従って、同じ質量で比べた場合、タップ密度が高い粒子は、タップ密度が低い粒子に比べて体積が小さくなる。 The non-spherical particles 66 are obtained, for example, by pulverizing spherical nickel hydroxide particles, and have an average particle diameter of 1.0 μm or more and 3.0 μm or less. Since the mass ratio Y / X is in the above-described range and is smaller than the spherical particles 64, the mass ratio Y / X is distributed in the positive electrode mixture in a state in which gaps formed between the spherical particles 64 are filled.
On the other hand, the spherical particles 64 have, for example, an average particle diameter in the range of 10 μm or more and 20 μm or less, and in a preferred embodiment, the tap density is in the range of 2.30 g / cm 3 or more and 2.45 g / cm 3 or less. The tap density means an apparent density according to a tap method defined in JIS K 5101. More specifically, the tap density is determined by dropping a graduated cylinder filled with an arbitrary amount of spherical particles 64 from a certain height a predetermined number of times, measuring the volume of the spherical particles 64, and measuring the spherical particles 64 in the graduated cylinder. It is determined by dividing the mass by the volume obtained. Therefore, when compared with the same mass, particles having a high tap density have a smaller volume than particles having a low tap density.

上述の球状粒子６４は、水酸化ニッケルからなる略球状のコア６８と、コア６８の表面に形成された後述する被覆層７０とからなり、一方、非球状の粒子６６は、水酸化ニッケルからなる。従って、球状粒子６４のコア６８及び非球状粒子６６として正極板２４に含まれる水酸化ニッケルの総量により正極容量が規定され、ひいては体積エネルギー密度が規定される。この電池では、正極板２４に含まれる水酸化ニッケルの総量は、体積エネルギー密度が３４０Ｗｈ／ｌ以上４５０Ｗｈ／ｌ以下の範囲に入るように設定されている。電池の体積エネルギー密度とは、電池の０．２Ｃ容量に作動電圧として１．２Ｖを乗じた値を、上述した電池の体積Ｖｂで除して求められる値である。電池の０．２Ｃ容量は、ＪＩＳ Ｃ ８７０８−１９９７に規定され、周囲温度２０±５℃にて、まず、電池を０．１Ｃ相当の電流量で１６時間充電してから、１〜４時間休止した後、０．２Ｃ相当の電流量で１．０Ｖの放電終止電圧まで放電させたときの容量のことをいう。   The spherical particles 64 are composed of a substantially spherical core 68 made of nickel hydroxide and a coating layer 70 described later formed on the surface of the core 68, while the non-spherical particles 66 are made of nickel hydroxide. . Therefore, the positive electrode capacity is defined by the total amount of nickel hydroxide contained in the positive electrode plate 24 as the cores 68 and the non-spherical particles 66 of the spherical particles 64, and thus the volume energy density is defined. In this battery, the total amount of nickel hydroxide contained in the positive electrode plate 24 is set so that the volume energy density falls within the range of 340 Wh / l to 450 Wh / l. The volume energy density of a battery is a value obtained by dividing the value obtained by multiplying the 0.2 C capacity of the battery by 1.2 V as the operating voltage by the volume Vb of the battery described above. The 0.2 C capacity of the battery is defined in JIS C 8708-1997. At an ambient temperature of 20 ± 5 ° C., the battery is first charged with a current amount equivalent to 0.1 C for 16 hours and then suspended for 1 to 4 hours. After that, the capacity when discharged to a discharge end voltage of 1.0 V with a current amount equivalent to 0.2 C.

なお、球状粒子６４のコア６８及び非球状粒子６６の水酸化ニッケルは、実質的に純粋な水酸化ニッケルの他、亜鉛及びコバルトの何れか一方若しくは両方が共沈された水酸化ニッケルであってもよい。
球状粒子６４の被覆層７０は、略均一な厚みでコア６８の表面を覆っている。被覆層７０は、アルカリ酸化処理（アルカリ熱処理）されたコバルト化合物からなり、良好な導電性を有する。より詳しくは、この被覆層７０は、コア６８の表面に三酸化二コバルト（Ｃｏ2Ｏ3）、一酸化コバルト（ＣｏＯ）及び水酸化コバルト（Ｃｏ（ＯＨ）2）等のコバルト化合物又は金属コバルト（Ｃｏ）を析出させた後に、この金属コバルト又はコバルト化合物の析出物をアルカリ液と酸素の共存下で加熱処理して形成することができる。従って、アルカリ酸化処理によって、この被覆層７０は、コバルト化合物の結晶構造が乱され、且つ、その表面から内部に亘り、例えばＮａ+等のアルカリカチオンが分布されている。 The core 68 of the spherical particles 64 and the nickel hydroxide of the non-spherical particles 66 are nickel hydroxides in which either one or both of zinc and cobalt are coprecipitated in addition to substantially pure nickel hydroxide. Also good.
The covering layer 70 of the spherical particles 64 covers the surface of the core 68 with a substantially uniform thickness. The coating layer 70 is made of a cobalt compound that has been subjected to alkali oxidation treatment (alkali heat treatment), and has good conductivity. More specifically, the coating layer 70 is formed on the surface of the core 68 with a cobalt compound such as dicobalt trioxide (Co 2 O 3 ), cobalt monoxide (CoO), and cobalt hydroxide (Co (OH) 2 ), or metallic cobalt. After depositing (Co), this metal cobalt or cobalt compound precipitate can be formed by heat treatment in the presence of an alkali solution and oxygen. Accordingly, the coating layer 70 is disturbed in the crystal structure of the cobalt compound by the alkali oxidation treatment, and alkali cations such as Na + are distributed from the surface to the inside.

また更に、外装缶１０内には、所定量のアルカリ電解液（図示せず）が注液され、セパレータ２８に含まれたアルカリ電解液を介して正極板２４と負極板２６との間での充放電反応（電池反応）が進行する。この電池では、容量液比が０．８５ｍｌ／Ａｈ以下の範囲で、アルカリ電解液が外装缶１０に注液されているのが好適な態様である。容量液比は、上述の０．２Ｃ容量に対するアルカリ電解液の体積の比であり、アルカリ電解液の体積をＶｅとし、上述した０．２Ｃ容量をＱとしたときに、Ｖｅ／Ｑで示される。   Furthermore, a predetermined amount of alkaline electrolyte (not shown) is injected into the outer can 10, and between the positive electrode plate 24 and the negative electrode plate 26 via the alkaline electrolyte contained in the separator 28. Charge / discharge reaction (battery reaction) proceeds. In this battery, it is preferable that the alkaline electrolyte is injected into the outer can 10 in a capacity liquid ratio range of 0.85 ml / Ah or less. The capacity liquid ratio is the ratio of the volume of the alkaline electrolyte to the above-mentioned 0.2 C capacity, and is represented by Ve / Q, where Ve is the volume of the alkaline electrolyte and Q is the above-mentioned 0.2 C capacity. .

なお、アルカリ電解液の種類としては、特に限定されないけれども、例えば、水酸化ナトリウム水溶液、水酸化リチウム水溶液、水酸化カリウム水溶液、及びこれらのうち２つ以上を混合した水溶液等をあげることができ、またアルカリ電解液の濃度についても特には限定されず、例えば７Ｎのものを用いることができる。
上述した構成を有する電池は、球状粒子６４が空孔６０内に高密度に分布され、更に、これら球状粒子６４間の隙間に非球状粒子６６が分布されていることにより、正極板２４中の水酸化ニッケル量の増量が確保されている。このため、３４０Ｗｈ／ｌ以上の高い体積エネルギー密度を達成することができる。なお、体積エネルギー密度の上限を４５０Ｗｈ／ｌにしたのは、４５０Ｗｈ／ｌを超えると、サイクル特性の低下を抑制するのが困難だからである。 In addition, although it does not specifically limit as a kind of alkaline electrolyte, For example, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, potassium hydroxide aqueous solution, the aqueous solution which mixed 2 or more of these, etc. can be mention | raise | lifted, Also, the concentration of the alkaline electrolyte is not particularly limited, and for example, a 7N solution can be used.
In the battery having the above-described configuration, the spherical particles 64 are distributed at high density in the pores 60, and the non-spherical particles 66 are distributed in the gaps between the spherical particles 64. An increase in the amount of nickel hydroxide is secured. For this reason, a high volume energy density of 340 Wh / l or more can be achieved. The reason why the upper limit of the volume energy density is set to 450 Wh / l is that when it exceeds 450 Wh / l, it is difficult to suppress the deterioration of the cycle characteristics.

一方、この電池は、球状粒子６４が被覆層７０を有するので、メカニズムは明らかではないけれども、充放電を繰り返しても水酸化ニッケルからなるコア６８の膨張が抑制される。このため、コア６８内へのセパレータ２８中のアルカリ電解液の取り込みが抑制され、内部抵抗の増大に基づく放電容量の低下が防止される。それ故、この電池は、高い体積エネルギー密度を有するとともに、優れたサイクル特性も有する。   On the other hand, in this battery, since the spherical particles 64 have the coating layer 70, the mechanism is not clear, but the expansion of the core 68 made of nickel hydroxide is suppressed even if charging and discharging are repeated. For this reason, uptake of the alkaline electrolyte in the separator 28 into the core 68 is suppressed, and a decrease in discharge capacity due to an increase in internal resistance is prevented. Therefore, this battery has a high volumetric energy density and excellent cycle characteristics.

そして、この電池では、好適な態様として、正極合剤の充填密度Ｍ／Ｓの下限を３．０５ｇ／ｃｍ3にしたので、正極合剤の充填後に正極基板の空孔６０内に存在する空隙の容積が小さく、この空隙に取り込まれるアルカリ電解液量をも減らすことができる。このため、セパレータ２８中のアルカリ電解液量が相対的に増量されることになり、内部抵抗の増大を更に抑制することができる。一方、充填密度Ｍ／Ｓの上限を３．２５ｇ／ｃｍ3にするのが好ましいのは、充填密度Ｍ／Ｓが３．２５ｇ／ｃｍ3を超えると、正極板２４内に取り込まれるアルカリ電解液量が少なくなり過ぎ、反応律速となりかえって内部抵抗の増大を招くからである。 And in this battery, since the lower limit of the packing density M / S of the positive electrode mixture was set to 3.05 g / cm 3 as a preferred embodiment, voids existing in the holes 60 of the positive electrode substrate after filling the positive electrode mixture. The volume of the alkaline electrolyte is small, and the amount of the alkaline electrolyte taken into the gap can also be reduced. For this reason, the amount of the alkaline electrolyte in the separator 28 is relatively increased, and an increase in internal resistance can be further suppressed. On the other hand, it is preferable to set the upper limit of the packing density M / S to 3.25 g / cm 3. When the packing density M / S exceeds 3.25 g / cm 3 , the alkaline electrolyte is taken into the positive electrode plate 24. This is because the amount becomes too small, and the reaction rate is limited, which increases the internal resistance.

なお、球状粒子６４のタップ密度が２．３０ｇ／ｃｍ3以上２．４５ｇ／ｃｍ3以下の範囲にあれば、充填密度Ｍ／Ｓを上述の範囲に容易にすることができる。
また、この電池では、好適な態様として、球状粒子６４における被覆層７０の質量割合の下限を２．０％にしたことにより、被覆層７０によって水酸化ニッケルからなるコア６８の表面を十分に被覆することができ、充放電を繰り返した場合でもコア６８の膨張を確実に抑制することができる。一方、球状粒子６４における被覆層７０の質量割合の上限を６．０％にするのが好ましいのは、球状粒子６４における水酸化ニッケルの質量割合の低下を制限するためである。これにより、正極容量が確保され、高い体積エネルギー密度を確実に達成することができる。 In addition, if the tap density of the spherical particles 64 is in the range of 2.30 g / cm 3 or more and 2.45 g / cm 3 or less, the packing density M / S can be easily adjusted to the above range.
In this battery, as a preferred embodiment, the lower limit of the mass ratio of the coating layer 70 in the spherical particles 64 is set to 2.0%, so that the surface of the core 68 made of nickel hydroxide is sufficiently covered by the coating layer 70. The expansion of the core 68 can be reliably suppressed even when charging and discharging are repeated. On the other hand, the reason why the upper limit of the mass ratio of the coating layer 70 in the spherical particles 64 is preferably 6.0% is to limit the decrease in the mass ratio of nickel hydroxide in the spherical particles 64. Thereby, a positive electrode capacity | capacitance is ensured and a high volume energy density can be achieved reliably.

更に、この電池では、好適な態様として、容量液比Ｖｅ／Ｑの上限を０．８５ｍｌ／Ａｈにしたことにより、電池内のアルカリ電解液量が制限されている。このため、過充電時に正極板２４で発生した酸素ガスを一時的に蓄える余剰空間が電池内に十分に確保され、電池内圧の上昇に伴う安全弁の頻繁な作動が抑制される。この結果、安全弁作動時に電池外部へのアルカリ電解液の噴出が抑制され、セパレータ２８中のアルカリ電解液の減少を一層抑制することができる。ここで、容量液比Ｖｅ／Ｑの範囲を０．８５ｍｌ／Ａｈ以下にできる理由は、この電池の場合、球状粒子６４のコア６８によるアルカリ電解液の取り込みが抑制されているからである。なお、容量液比Ｖｅ／Ｑの下限は、０．６０ｍｌ／Ａｈにするのが好ましい。   Furthermore, in this battery, as a preferred embodiment, the amount of the alkaline electrolyte in the battery is limited by setting the upper limit of the capacity liquid ratio Ve / Q to 0.85 ml / Ah. For this reason, a surplus space for temporarily storing oxygen gas generated in the positive electrode plate 24 at the time of overcharge is sufficiently secured in the battery, and frequent operation of the safety valve accompanying an increase in the battery internal pressure is suppressed. As a result, the discharge of the alkaline electrolyte to the outside of the battery is suppressed during the operation of the safety valve, and the decrease of the alkaline electrolyte in the separator 28 can be further suppressed. Here, the reason why the range of the capacity liquid ratio Ve / Q can be 0.85 ml / Ah or less is that in the case of this battery, the uptake of the alkaline electrolyte by the core 68 of the spherical particles 64 is suppressed. The lower limit of the volume liquid ratio Ve / Q is preferably 0.60 ml / Ah.

上述の電池は、通常の方法により製造することができるけれども、以下では正極板２４の作製方法の一例について説明する。
まず、水酸化ニッケル粒子は、硫酸ニッケル水溶液とアンモニア水とを反応容器内の水に加え、液のｐＨをアルカリ水溶液を添加して調整した後、所定時間攪拌混合することにより沈殿物として得ることができる。なお、亜鉛及びコバルトを共沈するには、硫酸亜鉛水溶液及び硫酸コバルト水溶液を更に液に添加すればよい。 Although the above-described battery can be manufactured by a normal method, an example of a method for manufacturing the positive electrode plate 24 will be described below.
First, nickel hydroxide particles are obtained as a precipitate by adding an aqueous nickel sulfate solution and aqueous ammonia to the water in the reaction vessel, adjusting the pH of the solution by adding an alkaline aqueous solution, and then stirring and mixing for a predetermined time. Can do. In order to coprecipitate zinc and cobalt, an aqueous zinc sulfate solution and an aqueous cobalt sulfate solution may be further added to the solution.

次に、得られた水酸化ニッケル粉末と水酸化コバルト粉末とを混合し、これにアルカリ水溶液を添加した後、酸化雰囲気下にて加熱処理する。このアルカリ酸化熱処理により、水酸化ニッケル粒子の表面にアルカリ酸化処理されたコバルト化合物からなる被覆層７０が形成され、球状粒子６４を得ることができる。なお、被覆層７０の形成の際、水酸化コバルト粉末に代えて、一酸化コバルト粉末又は金属コバルト粉末を用いてもよい。   Next, the obtained nickel hydroxide powder and cobalt hydroxide powder are mixed, and an alkaline aqueous solution is added thereto, followed by heat treatment in an oxidizing atmosphere. By this alkali oxidation heat treatment, a coating layer 70 made of a cobalt compound subjected to alkali oxidation treatment is formed on the surface of the nickel hydroxide particles, and spherical particles 64 can be obtained. In forming the coating layer 70, cobalt monoxide powder or metal cobalt powder may be used instead of the cobalt hydroxide powder.

一方、得られた水酸化ニッケル粉末の一部を粉砕機で粉砕することにより非球状粒子６６が得られる。
この後、得られた球状粒子６４、非球状粒子６６及び結着剤６２に水を加えて混合したペーストを用意し、このペーストを正極基板となる多孔質構造のニッケル板に充填してから乾燥させ、そして、このニッケル板を圧延・裁断して正極板２４を作製することができる。 On the other hand, non-spherical particles 66 are obtained by pulverizing a part of the obtained nickel hydroxide powder with a pulverizer.
Thereafter, a paste is prepared by adding water to the obtained spherical particles 64, non-spherical particles 66 and binder 62 and mixing them. The paste is filled in a porous nickel plate serving as a positive electrode substrate and then dried. Then, the nickel plate can be rolled and cut to produce the positive electrode plate 24.

本発明は、上記した一実施形態に限定されることはなく、種々変形が可能であり、例えば、ＡＡＡサイズであってもよいが、この電池はＡＡサイズの円筒型ニッケル水素二次電池に好適する。
また、上記した一実施形態において、正極合剤は、正極活物質粒子及び結着剤６２からなるが、好適な態様として、金属コバルト又はコバルト化合物からなるコバルト系粒子を更に含んでいてもよく、この場合、コバルト系粒子の全質量をＺとしたときに、正極活物質粒子に対するコバルト系粒子の質量比Ｚ／（Ｘ＋Ｙ）は０．５以上２．５以下の範囲にある。この変形例によれば、コバルト系粒子の存在により、充放電を繰り返したときのコア６８の膨張を一層抑制することができる。なお、コバルト化合物としては、三酸化二コバルト（Ｃｏ2Ｏ3）、一酸化コバルト（ＣｏＯ）及び水酸化コバルト（Ｃｏ（ＯＨ）2）等を用いることができる。 The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, an AAA size may be used, but this battery is suitable for an AA size cylindrical nickel-hydrogen secondary battery. To do.
Further, in the above-described embodiment, the positive electrode mixture includes the positive electrode active material particles and the binder 62. However, as a preferable aspect, the positive electrode mixture may further include cobalt-based particles including metal cobalt or a cobalt compound. In this case, when the total mass of the cobalt-based particles is Z, the mass ratio Z / (X + Y) of the cobalt-based particles to the positive electrode active material particles is in the range of 0.5 to 2.5. According to this modification, the expansion of the core 68 when charging / discharging is repeated can be further suppressed due to the presence of the cobalt-based particles. As the cobalt compound, dicobalt trioxide (Co 2 O 3 ), cobalt monoxide (CoO), cobalt hydroxide (Co (OH) 2 ), or the like can be used.

そして、上記した一実施形態において、負極板２６の最外周部には、負極薄肉部５６が形成されていたが、厚み一定の負極板を用いても良い。ただし、負極板２６の最外周部は、径方向外側に正極板２４が配置されていないため、正極板２４との電池反応への寄与が低い。そこで、負極薄肉部５６を形成することにより、負極板２６の最外周部にて外側合金層５０に取り込まれるアルカリ電解液量を減らし、相対的にセパレータ２８中のアルカリ電解液量を増やせば、内部抵抗の増大を一層抑制することができるので好ましい。   In the above-described embodiment, the negative electrode thin portion 56 is formed on the outermost peripheral portion of the negative electrode plate 26. However, a negative electrode plate having a constant thickness may be used. However, the outermost peripheral portion of the negative electrode plate 26 has no contribution to the battery reaction with the positive electrode plate 24 because the positive electrode plate 24 is not disposed on the radially outer side. Therefore, by forming the negative electrode thin portion 56, if the amount of alkaline electrolyte taken into the outer alloy layer 50 at the outermost peripheral portion of the negative electrode plate 26 is reduced and the amount of alkaline electrolyte in the separator 28 is relatively increased, This is preferable because an increase in internal resistance can be further suppressed.

また、上記した一実施形態において、正極合剤は、体積エネルギー密度及びサイクル特性が低下しない範囲で、上述した以外の金属元素又は化合物を更に含有していてもよい。   In the above-described embodiment, the positive electrode mixture may further contain a metal element or compound other than those described above as long as the volume energy density and the cycle characteristics are not deteriorated.

１．電池の組み立て
（１）実施例１
実施例１として、図１〜４に示した構成を有するＡＡサイズの円筒型ニッケル水素二次電池を組立てた。この電池の仕様を表１に示す。 1. Battery assembly (1) Example 1
As Example 1, an AA-sized cylindrical nickel-metal hydride secondary battery having the configuration shown in FIGS. Table 1 shows the specifications of this battery.

Figure 0004383229
Figure 0004383229

（２）実施例２〜１２、比較例１〜４
実施例２〜１２及び比較例１〜４として、表２に示したように、球状粒子に対する非球状粒子の質量比Ｙ／Ｘ、正極合剤の充填密度Ｍ／Ｓ、球状粒子のタップ密度、及び、被覆層の質量割合Ｇ／Ｘを変えて、体積エネルギー密度を変化させた以外は実施例１の場合と同様にしてニッケル水素二次電池を組立てた。 (2) Examples 2 to 12 and Comparative Examples 1 to 4
As Examples 2 to 12 and Comparative Examples 1 to 4, as shown in Table 2, the mass ratio Y / X of the non-spherical particles to the spherical particles, the packing density M / S of the positive electrode mixture, the tap density of the spherical particles, And the nickel hydride secondary battery was assembled like the case of Example 1 except having changed the mass ratio G / X of the coating layer, and changing volume energy density.

（３）比較例５〜７
比較例５〜７として、表３に示したように、球状粒子の表面に被覆層を形成しなかった以外は実施例１〜３の場合と同様にしてニッケル水素二次電池を組立てた。
（４）実施例１３
実施例１３として、表３に示したように、厚み一定の負極板を用いたこと以外は実施例１の場合と同様にしてニッケル水素二次電池を組立てた。 (3) Comparative Examples 5-7
As Comparative Examples 5 to 7, as shown in Table 3, nickel hydride secondary batteries were assembled in the same manner as in Examples 1 to 3 except that the coating layer was not formed on the surface of the spherical particles.
(4) Example 13
As Example 13, as shown in Table 3, a nickel metal hydride secondary battery was assembled in the same manner as in Example 1 except that a constant thickness negative electrode plate was used.

（５）実施例１４〜１７
実施例１４〜１７として、表３に示したように、容量液比Ｖｅ／Ｑを変化させたこと以外は実施例１の場合と同様にしてニッケル水素二次電池を組立てた。
（６）実施例１８〜２０
実施例１８〜２０として、表４に示したように、正極合剤にコバルト系粒子として金属コバルト粒子を更に含ませたこと以外は実施例１の場合と同様にしてニッケル水素二次電池を組立てた。 (5) Examples 14-17
As Examples 14 to 17, as shown in Table 3, nickel-hydrogen secondary batteries were assembled in the same manner as in Example 1 except that the capacity liquid ratio Ve / Q was changed.
(6) Examples 18-20
As Examples 18 to 20, as shown in Table 4, a nickel metal hydride secondary battery was assembled in the same manner as in Example 1 except that the positive electrode mixture further contained metallic cobalt particles as cobalt-based particles. It was.

２．電池のサイクル特性評価試験
得られた実施例及び比較例の各電池にまず初充放電を施した。次に、これらの電池に、１ＩｔでのΔＶ充電工程、１時間の休止工程及び１Ｉｔでの終止電圧１．０Ｖまでの放電工程を１サイクルとする充放電サイクルを繰り返し行った。この充放電サイクルの間、１サイクル毎に各電池の放電容量を測定し、放電容量が初期の放電容量の６０％となったときのサイクル数を数えた。この結果を表１〜４に示した。 2. Battery Cycle Characteristic Evaluation Test Each battery of the obtained Examples and Comparative Examples was first charged and discharged. Next, a charge / discharge cycle in which a ΔV charging step at 1 It, a resting step for 1 hour, and a discharging step up to a final voltage of 1.0 V at 1 It were performed on these batteries was repeated. During this charge / discharge cycle, the discharge capacity of each battery was measured every cycle, and the number of cycles when the discharge capacity reached 60% of the initial discharge capacity was counted. The results are shown in Tables 1-4.

Figure 0004383229
Figure 0004383229

Figure 0004383229
Figure 0004383229

Figure 0004383229
Figure 0004383229

表２から以下のことが明らかである。
（１）球状粒子に対する非球状粒子の質量割合Ｙ／Ｘが０．０４以上０．１２以下の範囲にある実施例１〜８は、範囲外の比較例1〜４に比べて体積エネルギー密度が高い。
（２）特に、球状粒子のタップ密度が２．３０ｇ／ｃｍ3以上２．４５ｇ／ｃｍ3以下の範囲にあり、充填密度Ｍ／Ｓが３．０５ｇ／ｃｍ3以上３．２５ｇ／ｃｍ3以下の範囲にある実施例１〜４は、体積エネルギー密度が高い。 From Table 2, it is clear that:
(1) Examples 1-8 in which mass ratio Y / X of non-spherical particles to spherical particles is in the range of 0.04 or more and 0.12 or less have a volume energy density as compared with Comparative Examples 1 to 4 outside the range. high.
(2) In particular, the tap density of the spherical particles is in the range of 2.30 g / cm 3 or more 2.45 g / cm 3 or less, the packing density M / S is 3.05 g / cm 3 or more 3.25 g / cm 3 or less In Examples 1 to 4, the volume energy density is high.

表２及び表３から以下のことが明らかである。
（３）球状粒子のコアに被覆層を形成した実施例1〜３は、形成しなかった比較例５〜７に比べてサイクル特性が優れている。
（４）特に、球状粒子における被覆層の質量割合Ｇ／Ｘが２.０％以上６.０％以下の範囲にある実施例１，９，１０は実施例１１，１２に比べ体積エネルギー密度が高く且つサイクル特性が優れている。 From Tables 2 and 3, the following is clear.
(3) Examples 1 to 3 in which the coating layer is formed on the core of the spherical particles are superior in cycle characteristics to Comparative Examples 5 to 7 in which the coating layer was not formed.
(4) In particular, Examples 1, 9, and 10 in which the mass ratio G / X of the coating layer in the spherical particles is in the range of 2.0% to 6.0% have a volume energy density as compared with Examples 11 and 12. High and excellent cycle characteristics.

（５）最外周部に薄肉部を有する実施例１〜３は、実施例１と同様の正極板を使用し薄肉部を形成しなかった実施例１３に比べてサイクル特性が優れている。
（６）容量液比Ｖｅ／Ｑが０．８５ｍｌ／Ａｈ以下の範囲にある実施例１，１４，１６は、０．８５ｍｌ／Ａｈを超えている実施例１５に比べてサイクル特性が優れている。 (5) Examples 1-3 which have a thin part in an outermost periphery part are excellent in cycling characteristics compared with Example 13 which used the positive electrode plate similar to Example 1, and did not form a thin part.
(6) Examples 1, 14, and 16 in which the volumetric liquid ratio Ve / Q is in the range of 0.85 ml / Ah or less have better cycle characteristics than Example 15 that exceeds 0.85 ml / Ah. .

表４から以下のことが明らかである。
（７）正極活物質粒子に対するコバルト系粒子の質量比Ｚ／（Ｘ＋Ｙ）が０．５以上２．５以下の範囲にある実施例１８〜２０は、コバルト系粒子を含まない実施例１に比べてサイクル特性が優れている。 From Table 4, the following is clear.
(7) Examples 18 to 20 in which the mass ratio Z / (X + Y) of the cobalt-based particles to the positive electrode active material particles is in the range of 0.5 to 2.5 are compared with Example 1 that does not include cobalt-based particles. Excellent cycle characteristics.

本発明の実施形態に係るニッケル水素二次電池の部分切欠き斜視図であり、円内に正極板２４の一部を拡大して模式的に示した。1 is a partially cutaway perspective view of a nickel metal hydride secondary battery according to an embodiment of the present invention, and schematically shows an enlarged part of a positive electrode plate 24 in a circle. 図１の電池の横断面図である。It is a cross-sectional view of the battery of FIG. 図１の電池の負極板を展開して示した斜視図である。It is the perspective view which expanded and showed the negative electrode plate of the battery of FIG. 図３の側面図である。FIG. 4 is a side view of FIG. 3.

符号の説明Explanation of symbols

１０ 外装缶
２２ 電極群
２４ 正極板
２６ 負極板
２８ セパレータ
６０ 正極基板の空孔
６２ 結着剤
６４ 球状粒子（第１の粒子）
６６ 非球状粒子（第２の粒子）
６８ コア
７０ 被覆層 DESCRIPTION OF SYMBOLS 10 Exterior can 22 Electrode group 24 Positive electrode plate 26 Negative electrode plate 28 Separator 60 Hole of positive electrode substrate 62 Binder 64 Spherical particle (first particle)
66 Non-spherical particles (second particles)
68 Core 70 Coating layer

Claims (7)

円筒状の外装缶内に、アルカリ電解液と、渦巻状に巻回された正極板及び負極板並びにこれら正極板と負極板との間に挟まれたセパレータからなる電極群とが収容され、前記電極群の最外周を形成する前記負極板の部位が前記外装缶の内周壁に接しているニッケル水素二次電池において、
前記電池は、３４０Ｗｈ／ｌ以上４５０Ｗｈ／ｌ以下の体積エネルギー密度を有し、
前記正極板は、
導電性を有する多孔質の基板と、
前記基板の空孔に充填され、活物質粒子を含有した正極合剤とからなり、
前記活物質粒子は、
水酸化ニッケルからなるコアにコバルト化合物の被膜層を形成し、この被膜層にアルカリ熱処理した球状の第１の粒子と、
水酸化ニッケルからなる非球状の第２の粒子とを含み、
前記第１の粒子の全質量をＸとし、前記第２の粒子の全質量をＹとしたときに、質量比Ｙ／Ｘが０．０４以上０．１２以下の範囲にある
ことを特徴とするニッケル水素二次電池。 A cylindrical outer can contains an alkaline electrolyte, a positive electrode plate and a negative electrode plate wound in a spiral shape, and an electrode group composed of a separator sandwiched between the positive electrode plate and the negative electrode plate, In the nickel metal hydride secondary battery in which the portion of the negative electrode plate forming the outermost periphery of the electrode group is in contact with the inner peripheral wall of the outer can,
The battery has a volume energy density of 340 Wh / l or more and 450 Wh / l or less,
The positive electrode plate is
A porous substrate having electrical conductivity;
Filled in the vacancies of the substrate, consisting of a positive electrode mixture containing active material particles,
The active material particles are
A cobalt compound coating layer is formed on a nickel hydroxide core, and the coating layer is subjected to alkaline heat treatment, and spherical first particles;
Non-spherical second particles made of nickel hydroxide,
When the total mass of the first particles is X and the total mass of the second particles is Y, the mass ratio Y / X is in the range of 0.04 to 0.12. Nickel metal hydride secondary battery. 前記基板の全空孔容積をＳとし、前記正極合剤の充填量をＭとしたときに、前記正極合剤の充填密度Ｍ／Ｓは、３．０５ｇ／ｃｍ3以上３．２５ｇ／ｃｍ3以下の範囲にあることを特徴とする請求項１に記載のニッケル水素二次電池。 The total pore volume of the substrate and S, the filling amount of the positive electrode mixture is taken as M, the packing density M / S of the positive electrode mixture, 3.05 g / cm 3 or more 3.25 g / cm 3 The nickel hydride secondary battery according to claim 1, wherein the nickel hydride secondary battery is in the following range. 前記被覆層の全質量をＧとしたときに、前記第１の粒子における前記被覆層の質量割合Ｇ／Ｘは、２．０％以上６．０％以下の範囲にあることを特徴とする請求項１又は２記載のニッケル水素二次電池。   The mass ratio G / X of the coating layer in the first particles is in the range of 2.0% to 6.0%, where G is the total mass of the coating layer. Item 3. A nickel metal hydride secondary battery according to item 1 or 2. 前記正極合剤は、金属コバルト又はコバルト化合物からなる第３の粒子を更に含み、
前記第３の粒子の全質量をＺとしたときに、前記活物質粒子に対する前記第３の粒子の質量比Ｚ／（Ｘ＋Ｙ）は、０．５以上２．５以下の範囲にあることを特徴とする請求項１乃至３の何れかに記載のニッケル水素二次電池。 The positive electrode mixture further includes third particles made of metallic cobalt or a cobalt compound,
When the total mass of the third particles is Z, the mass ratio Z / (X + Y) of the third particles to the active material particles is in the range of 0.5 to 2.5. The nickel metal hydride secondary battery according to any one of claims 1 to 3. 前記アルカリ電解液量をＶｅとし、前記電池の０．２Ｃ容量をＱとしたときに、容量液比Ｖｅ／Ｑは、０．８５ｍｌ／Ａｈ以下の範囲にあることを特徴とする請求項１乃至４の何れかに記載のニッケル水素二次電池。   The capacity liquid ratio Ve / Q is in a range of 0.85 ml / Ah or less, where Ve is the amount of the alkaline electrolyte and Q is the 0.2 C capacity of the battery. 4. The nickel metal hydride secondary battery according to any one of 4 above. 前記負極板は、前記部位に薄肉部を有することを特徴とする請求項１乃至５の何れかに記載のニッケル水素二次電池。   The nickel metal hydride secondary battery according to claim 1, wherein the negative electrode plate has a thin portion at the portion. 前記第１の粒子は、タップ密度が２．３０ｇ／ｃｍ3以上２．４５ｇ／ｃｍ3以下の範囲にあることを特徴とする請求項１乃至６の何れかに記載のニッケル水素二次電池。 The nickel-hydrogen secondary battery according to claim 1, wherein the first particles have a tap density in a range of 2.30 g / cm 3 to 2.45 g / cm 3 .
JP2004106870A 2004-03-31 2004-03-31 Nickel metal hydride secondary battery Expired - Fee Related JP4383229B2 (en)

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