JP2014165123A - Alkali storage battery - Google Patents

Alkali storage battery Download PDF

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JP2014165123A
JP2014165123A JP2013037298A JP2013037298A JP2014165123A JP 2014165123 A JP2014165123 A JP 2014165123A JP 2013037298 A JP2013037298 A JP 2013037298A JP 2013037298 A JP2013037298 A JP 2013037298A JP 2014165123 A JP2014165123 A JP 2014165123A
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battery
electrode
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basis weight
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Hidefumi Isaji
秀文 伊佐治
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FDK Twicell Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Abstract

PROBLEM TO BE SOLVED: To provide an alkali storage battery the cycle life characteristics of which can be enhanced, by minimizing local deterioration of a battery reaction material to be involved in the battery reaction within the battery.SOLUTION: An alkali storage battery includes an outer can 10, and an electrode group 22 housed in the outer can 10 together with an alkaline electrolyte. The electrode group 22 is formed by winding a positive electrode 24 and a negative electrode 26 while sandwiching a separator 28. The positive electrode 24 includes a nickel form, and a positive electrode active material held by the nickel form. The nickel form includes a first outer peripheral region located on the outer periphery of the electrode group 22, and a region of higher weight than the first outer peripheral region located on the inside of the outer periphery of the electrode group 22.

Description

本発明は、アルカリ蓄電池に関する。   The present invention relates to an alkaline storage battery.

アルカリ蓄電池の一つとして、ニッケル水素蓄電池が知られている。ニッケル水素蓄電池は、正極に正極活物質としての水酸化ニッケルを含み、負極に負極活物質としての水素を吸蔵放出可能な水素吸蔵合金を含んでいる。このようなニッケル水素蓄電池は、充電効率が高く、しかも、安定した充放電が可能であり、充放電特性に優れることから、各種のポータブル機器やハイブリッド電気自動車等、さまざまな用途に使用されるようになっている。このように、さまざまな用途が見出されたことによりニッケル水素蓄電池に対しては、より長い期間、安定して使用できるように、寿命特性の向上が望まれている。   As one of alkaline storage batteries, a nickel metal hydride storage battery is known. The nickel-metal hydride storage battery includes nickel hydroxide as a positive electrode active material in a positive electrode, and a hydrogen storage alloy capable of occluding and releasing hydrogen as a negative electrode active material in a negative electrode. Such nickel-metal hydride storage batteries have high charging efficiency, can be stably charged and discharged, and are excellent in charge and discharge characteristics. Therefore, they are used in various applications such as various portable devices and hybrid electric vehicles. It has become. As described above, since various uses are found, it is desired to improve the life characteristics of the nickel-metal hydride storage battery so that it can be used stably for a longer period of time.

ここで、ニッケル水素蓄電池の寿命は、電池の充放電を繰り返すサイクル用途の場合、充放電を繰り返したサイクル数で表され、一般的に電池容量が定格容量の６０％以下まで低下した状態をもって寿命が尽きたものとされている。これをサイクル寿命という。   Here, the life of a nickel metal hydride storage battery is represented by the number of cycles in which charging / discharging is repeated in the case of cycle applications in which charging / discharging of the battery is repeated. Generally, the life of the battery is reduced to 60% or less of the rated capacity. It is said that was exhausted. This is called cycle life.

ニッケル水素蓄電池の寿命に影響を与える因子の一つとしては、正極活物質及び水素吸蔵合金といった電池反応に関与する電池反応材料が高温にさらされることによる劣化が挙げられる。例えば、電池の充放電に際し、電池の各部の構成部材が電気的な抵抗となって発熱することにより、電池内部は高温となり、その結果、電池反応材料の劣化が進行してしまう。このように電池反応材料が劣化すると、電池反応を良好に進行させることが困難となり、電池容量が低下して電池の寿命が尽きてしまう。   One of the factors affecting the life of a nickel metal hydride storage battery is deterioration due to exposure of battery reaction materials involved in the battery reaction, such as positive electrode active materials and hydrogen storage alloys, to high temperatures. For example, when the battery is charged and discharged, the constituent members of each part of the battery generate electric resistance and generate heat, so that the temperature inside the battery becomes high, and as a result, deterioration of the battery reaction material proceeds. When the battery reaction material is deteriorated in this way, it is difficult to make the battery reaction proceed well, and the battery capacity is reduced and the battery life is exhausted.

ところで、一般的な電池は、正極及び負極の間にセパレータを介在させてこれらを巻回して形成した円柱状の電極群を、負極端子を兼ねる導電性を有した外装缶内に収容し、電解液を注入したのち、外装缶の上端開口を封口体で封口することにより製造されている。この封口体は、正極端子を含んでおり、外装缶との絶縁性を確保した状態で外装缶の開口縁に固定されている。ここで、正極は、帯状の正極タブを介して正極端子と電気的に接続されている。一方、負極は、電極群の最外周部に露出しており、この最外周部が外装缶の内周壁と接触させられることにより、負極端子（外装缶）と電気的に接続されている。   By the way, in a general battery, a cylindrical electrode group formed by winding a separator between a positive electrode and a negative electrode is housed in a conductive outer can also serving as a negative electrode terminal, and electrolysis is performed. After injecting the liquid, it is manufactured by sealing the upper end opening of the outer can with a sealing body. The sealing body includes a positive electrode terminal, and is fixed to the opening edge of the outer can in a state in which insulation with the outer can is secured. Here, the positive electrode is electrically connected to the positive electrode terminal via a strip-shaped positive electrode tab. On the other hand, the negative electrode is exposed at the outermost peripheral portion of the electrode group, and the outermost peripheral portion is brought into contact with the inner peripheral wall of the outer can so as to be electrically connected to the negative electrode terminal (external can).

このような円柱状の電池においては、充放電にともない熱が発生すると、電池の中心部は熱がこもり易いので比較的高温となり、一方、電池の外周側は外部へ熱を放散させ易いのであまり高温とはならない。したがって、電池の外周部に比べ電池の中心部においては電池反応材料の劣化が進行し易くなっている。このように、電池の中心部の電池反応材料が劣化して電池反応の進行が困難となると、電池の外周部の電池反応材料が未だ電池反応を進行させることが十分できる状態であっても、電池全体としては容量が低下し、寿命が尽きた状態となってしまう。つまり、電池内の電池反応材料を十分に活用できないといった問題が生じることがある。   In such a cylindrical battery, when heat is generated due to charging / discharging, the center part of the battery is relatively hot because it tends to accumulate heat, while the outer peripheral side of the battery tends to dissipate heat to the outside. It will not be hot. Therefore, the deterioration of the battery reaction material is more likely to proceed at the center of the battery than at the outer periphery of the battery. Thus, when the battery reaction material at the center of the battery deteriorates and the progress of the battery reaction becomes difficult, the battery reaction material at the outer periphery of the battery is still in a state where the battery reaction can still sufficiently proceed, As a whole battery, the capacity decreases and the life is exhausted. That is, the problem that the battery reaction material in a battery cannot fully be utilized may arise.

そこで、電池の発熱をなるべく抑えることができるとともに放熱をなるべく均等にできる構造の電池の開発が種々試みられている。かかる構造の電池としては、例えば、金属板からなる集電体を用いる構造の電池が挙げられる。このような集電体としては、例えば、特許文献１に示されるような円板状の集電体が用いられる。詳しくは、セパレータを介して正極及び負極を巻回する際に、正極の一部をセパレータの上端縁から突出させるとともに、負極の一部をセパレータの下端縁から突出させるようにして電極群を形成する。これにより、電極群の上端から正極の端部が渦巻き状に突出し、電極群の下端から負極の端部が渦巻き状に突出することになる。そして、金属製の円板からなる正極用集電体及び負極用集電体を準備し、正極用集電体を電極群における正極の突出端部に、負極用集電体を電極群における負極の突出端部にそれぞれ溶接する。これら正極用集電体及び負極用集電体には、それぞれリード部が一体的に形成されているので、電極群を外装缶内に挿入したのち、各リードを、それぞれ、正極端子及び負極端子に電気的に接続する。   Accordingly, various attempts have been made to develop a battery having a structure that can suppress heat generation of the battery as much as possible and can make heat dissipation as even as possible. Examples of such a battery include a battery having a structure using a current collector made of a metal plate. As such a current collector, for example, a disk-shaped current collector as shown in Patent Document 1 is used. Specifically, when winding the positive electrode and the negative electrode through the separator, an electrode group is formed so that a part of the positive electrode protrudes from the upper edge of the separator and a part of the negative electrode protrudes from the lower edge of the separator. To do. As a result, the end of the positive electrode protrudes spirally from the upper end of the electrode group, and the end of the negative electrode protrudes spirally from the lower end of the electrode group. Then, a positive electrode current collector and a negative electrode current collector made of a metal disc are prepared, the positive electrode current collector is provided at the protruding end of the positive electrode in the electrode group, and the negative electrode current collector is provided in the negative electrode in the electrode group. Weld to the protruding end of each. Each of the positive electrode current collector and the negative electrode current collector is integrally formed with a lead portion. Therefore, after inserting the electrode group into the outer can, each lead is connected to the positive electrode terminal and the negative electrode terminal, respectively. Electrically connect to

このように、正極用集電体及び負極用集電体は、比較的広い範囲で正極及び負極と接続されているので、電池内の電気抵抗が低くなり、電気的な抵抗にともなう発熱がより抑制される。また、正極用集電体及び負極用集電体は、電極群の上端及び下端を覆っており、電池の中心部から外周部にかけての伝熱経路となり得るため、電池内の温度的な偏りの抑制にも寄与する。   As described above, since the positive electrode current collector and the negative electrode current collector are connected to the positive electrode and the negative electrode in a relatively wide range, the electric resistance in the battery is lowered, and more heat is generated due to the electric resistance. It is suppressed. Further, the positive electrode current collector and the negative electrode current collector cover the upper and lower ends of the electrode group, and can serve as a heat transfer path from the center to the outer periphery of the battery. Contributes to suppression.

特開平１１−１９１４１０号公報JP 11-191410 A

しかしながら、上記したような集電体を用いた電池においては、以下のような問題がある。まず、電池の製造に際し、かかる集電体を電極群に溶接する作業が必要であり、製造工数の増加を招くため、製造効率が従来の電池に比べて低くなるといった問題がある。また、部品点数が増えるので、製造コストも嵩んでしまう。   However, a battery using a current collector as described above has the following problems. First, when manufacturing the battery, an operation of welding the current collector to the electrode group is necessary, which causes an increase in the number of manufacturing steps, resulting in a problem that the manufacturing efficiency is lower than that of a conventional battery. Moreover, since the number of parts increases, manufacturing cost also increases.

このため、より簡便な構造で電池内の温度の偏りを抑え、もって電池のサイクル寿命を向上させることができる電池の開発が望まれている。   For this reason, development of the battery which can suppress the bias | inclination of the temperature in a battery with a simpler structure and can improve the cycle life of a battery is desired.

本発明は、上記の事情に基づいてなされたものであり、その目的とするところは、電池内の電池反応材料が熱により局部的に劣化することを抑え、電池のサイクル寿命特性の向上を図ることができるアルカリ蓄電池を提供することにある。   The present invention has been made on the basis of the above-described circumstances, and an object of the present invention is to suppress local deterioration of the battery reaction material in the battery due to heat and to improve the cycle life characteristics of the battery. An object of the present invention is to provide an alkaline storage battery.

上記目的を達成するために、本発明によれば、容器と、前記容器内にアルカリ電解液とともに密閉状態で収容された電極群とを備え、前記電極群は、互いに異なる極性を示す第１電極と第２電極とがセパレータを間に挟んだ状態で巻回されてなり、前記第１電極は、帯状の金属多孔体からなる第１電極芯体と、前記第１電極芯体に保持されており、電池反応に関与する第１電池反応材料とを含み、前記第１電極芯体は、前記電極群の外周部に位置付けられる第１外周領域と、前記電極群の外周部より内側に位置付けられ、前記第１外周領域より目付が高い領域と、を含むことを特徴とするアルカリ蓄電池が提供される。   In order to achieve the above object, according to the present invention, a container and an electrode group housed in an airtight state together with an alkaline electrolyte in the container are provided, and the electrode group is a first electrode having different polarities. And the second electrode are wound with a separator interposed therebetween, and the first electrode is held by the first electrode core body made of a band-shaped metal porous body and the first electrode core body. A first battery reaction material involved in a battery reaction, wherein the first electrode core is positioned inside a first outer peripheral region positioned at an outer peripheral portion of the electrode group and an outer peripheral portion of the electrode group. And an area having a higher weight per unit area than the first outer peripheral area.

好ましくは、前記第２電極は、帯状の金属多孔体からなる第２電極芯体と、前記第２電極芯体に保持されており、電池反応に関与する第２電池反応材料とを含み、前記第２電極芯体は、前記電極群の外周部に位置付けられる第２外周領域と、前記電極群の外周部より内側に位置付けられ、前記第２外周領域より目付が高い領域と、を含む構成とする。   Preferably, the second electrode includes a second electrode core body made of a band-shaped metal porous body, and a second battery reaction material held in the second electrode core body and involved in a battery reaction, The second electrode core includes a second outer peripheral region positioned at the outer peripheral portion of the electrode group, and a region positioned inside the outer peripheral portion of the electrode group and having a higher basis weight than the second outer peripheral region; To do.

本発明に係るアルカリ蓄電池は、第１電極と第２電極とを有し、第１電極は、帯状の金属多孔体からなる第１電極芯体と、前記第１電極芯体に保持されており、電池反応に関与する第１電池反応材料とを含み、前記第１電極芯体は、前記電極群の外周部に位置付けられる第１外周領域と、前記電極群の外周部より内側に位置付けられ、前記第１外周領域より目付が高い領域と、を含んでいる。このため、電極群の外周部より内側に位置付けられる電極芯体の電気抵抗が下がり、電池の中心部における発熱を抑えることができる。その結果、電池の中心部の電池反応材料は、高温にさらされることを抑制され、劣化を防ぐことができる。よって、電池のサイクル寿命特性が向上する。つまり、本発明によれば、集電体などの別部材を用いることなく、第１電極芯体において、電極群の外周部に位置付けられる第１外周領域と、電極群の外周部よりも内側に位置付けられ、第１外周領域よりも目付が高い領域とを含む構成にすることでサイクル寿命特性に優れたアルカリ蓄電池を得ることができる。   The alkaline storage battery according to the present invention has a first electrode and a second electrode, and the first electrode is held by a first electrode core body made of a strip-shaped metal porous body and the first electrode core body. A first battery reaction material involved in a battery reaction, wherein the first electrode core is positioned on the outer periphery of the electrode group and on the inner side of the outer periphery of the electrode group, And an area having a higher basis weight than the first outer peripheral area. For this reason, the electrical resistance of the electrode core located inside the outer peripheral part of an electrode group falls, and it can suppress the heat_generation | fever in the center part of a battery. As a result, the battery reaction material at the center of the battery can be prevented from being exposed to high temperatures and can be prevented from deteriorating. Therefore, the cycle life characteristics of the battery are improved. That is, according to the present invention, without using a separate member such as a current collector, in the first electrode core, the first outer peripheral region positioned on the outer peripheral portion of the electrode group and the inner side of the outer peripheral portion of the electrode group. An alkaline storage battery having excellent cycle life characteristics can be obtained by including a region that is positioned and has a higher basis weight than the first outer peripheral region.

本発明の一実施形態に係るニッケル水素蓄電池を部分的に破断して示した斜視図である。It is the perspective view which fractured | ruptured and showed the nickel hydride storage battery which concerns on one Embodiment of this invention. 本発明の一実施形態に係るニッケル水素蓄電池の横断面図である。1 is a cross-sectional view of a nickel metal hydride storage battery according to an embodiment of the present invention. 本発明の一実施形態に係る正極芯体を示す平面図である。It is a top view which shows the positive electrode core which concerns on one Embodiment of this invention. 本発明の一実施形態に係る負極芯体を示す平面図である。It is a top view which shows the negative electrode core which concerns on one Embodiment of this invention.

以下、本発明に係るニッケル水素蓄電池（以下、単に電池と称する）２を、図面を参照して説明する。
電池２は、例えば、図１に示すＡＡサイズの円筒型電池である。 Hereinafter, a nickel metal hydride storage battery (hereinafter simply referred to as a battery) 2 according to the present invention will be described with reference to the drawings.
The battery 2 is, for example, an AA size cylindrical battery shown in FIG.

図１に示すように、電池２は、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は導電性を有し、その底壁３５は負極端子として機能する。外装缶１０の開口内には、導電性を有する円板形状の蓋板１４及びこの蓋板１４を囲むリング形状の絶縁パッキン１２が配置され、絶縁パッキン１２は外装缶１０の開口縁３７をかしめ加工することにより外装缶１０の開口縁３７に固定されている。即ち、蓋板１４及び絶縁パッキン１２は互いに協働して外装缶１０の開口を気密に閉塞している。   As shown in FIG. 1, the battery 2 includes an outer can 10 having a bottomed cylindrical shape with an open upper end. The outer can 10 has conductivity, and its bottom wall 35 functions as a negative electrode terminal. In the opening of the outer can 10, a disc-shaped cover plate 14 having conductivity and a ring-shaped insulating packing 12 surrounding the cover plate 14 are arranged. The insulating packing 12 caulks the opening edge 37 of the outer can 10. It is fixed to the opening edge 37 of the outer can 10 by processing. That is, the lid plate 14 and the insulating packing 12 cooperate with each other to airtightly close the opening of the outer can 10.

ここで、蓋板１４は中央に中央貫通孔１６を有し、そして、蓋板１４の外面上には中央貫通孔１６を塞ぐゴム製の弁体１８が配置されている。更に、蓋板１４の外面上には、弁体１８を覆うようにして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に向けて押圧している。なお、この正極端子２０には、図示しないガス抜き孔が開口されている。   Here, the cover plate 14 has a central through hole 16 in the center, and a rubber valve body 18 that closes the central through hole 16 is disposed on the outer surface of the cover plate 14. Further, a flanged cylindrical positive terminal 20 is fixed on the outer surface of the cover plate 14 so as to cover the valve body 18, and the positive terminal 20 presses the valve body 18 toward the cover plate 14. The positive electrode terminal 20 has a gas vent hole (not shown).

通常時、中央貫通孔１６は弁体１８によって気密に閉じられている。一方、外装缶１０内にガスが発生し、その内圧が高まれば、弁体１８は内圧によって圧縮され、中央貫通孔１６を開き、この結果、外装缶１０内から中央貫通孔１６及び正極端子２０のガス抜き孔を介して外部にガスが放出される。つまり、中央貫通孔１６、弁体１８及び正極端子２０は電池のための安全弁を形成している。   Normally, the central through hole 16 is hermetically closed by the valve body 18. On the other hand, if gas is generated in the outer can 10 and its internal pressure increases, the valve body 18 is compressed by the internal pressure and opens the central through hole 16. As a result, the central through hole 16 and the positive electrode terminal 20 are opened from the outer can 10. Gas is released to the outside through the vent holes. That is, the central through hole 16, the valve body 18, and the positive electrode terminal 20 form a safety valve for the battery.

外装缶１０には、電極群２２が収容されている。電極群２２は、互いに異なる極性を示す第１電極と第２電極とが電気的に絶縁された状態で渦巻き状に巻回されて形成され、全体として円柱状をなしている。ここで、第１電極には、帯状の金属多孔体からなる第１電極芯体と、この第１電極芯体に保持されており、電池反応に関与する第１電池反応材料とが含まれている。本発明においては、第１電極芯体は、電極群２２の外周部に位置付けられる第１外周領域と、電極群２２の外周部より内側に位置付けられ、第１外周領域より目付（単位面積当たりの質量）が高い領域とを含んでいる。これにより、電極群２２の外周部よりも内側の部分、すなわち、電極群２２の中心部を含む部分の電気抵抗が低くなり、発熱が抑えられる。その結果、電極群の中心部の電池反応材料は高温にさらされることが抑制される。   An electrode group 22 is accommodated in the outer can 10. The electrode group 22 is formed by spirally winding a first electrode and a second electrode having different polarities from each other, and has a cylindrical shape as a whole. Here, the first electrode includes a first electrode core body made of a band-shaped metal porous body, and a first battery reaction material held in the first electrode core body and involved in the battery reaction. Yes. In the present invention, the first electrode core is positioned on the inner side of the outer peripheral portion of the electrode group 22 and the first outer peripheral region positioned on the outer peripheral portion of the electrode group 22, and has a basis weight (per unit area). And a region having a high mass). Thereby, the electrical resistance of the part inside the outer peripheral part of the electrode group 22, ie, the part including the center part of the electrode group 22, becomes low, and heat generation is suppressed. As a result, the battery reaction material at the center of the electrode group is suppressed from being exposed to high temperatures.

更に、本発明においては、第２電極の第２電極芯体も電極群２２の外周部に位置付けられる第２外周領域と、電極群２２の外周部より内側に位置付けられ、第２外周領域より目付（単位面積当たりの質量）が高い領域とを含んでいる態様とすることが好ましい。これにより、電極群２２の中心部の発熱をより抑えることができる。   Furthermore, in the present invention, the second electrode core of the second electrode is also positioned on the outer peripheral portion of the electrode group 22 and on the inner side of the outer peripheral portion of the electrode group 22, and has a weight per unit area of the second outer peripheral region. It is preferable to include an embodiment including a region having a high (mass per unit area). Thereby, the heat_generation | fever of the center part of the electrode group 22 can be suppressed more.

つまり、外周領域とこの外周領域より内側の領域とで目付に差をつけることを第１電極芯体のみで行っても電極群２２の中心部の発熱を抑える効果を得ることができる。そして、第２電極芯体についても併せて目付に差を設けると、上記した効果はより大きくなる。   That is, the effect of suppressing the heat generation at the center of the electrode group 22 can be obtained even if the basis weight is made different between the outer peripheral region and the inner region from the outer peripheral region only by the first electrode core. If the difference in basis weight is also provided for the second electrode core, the above-described effect is further increased.

以下、電極群２２のより具体的な構成につき詳しく説明する。
まず、極性の異なる電極とは、正極２４及び負極２６である。つまり、第１電極とは、正極２４及び負極２６のうちの一方であり、第２電極とは、正極２４及び負極２６のうちの他方である。本実施形態においては、第１電極を正極２４とし、第２電極を負極２６として説明する。これら正極２４及び負極２６の絶縁性を確保する部材は、セパレータ２８である。 Hereinafter, a more specific configuration of the electrode group 22 will be described in detail.
First, the electrodes having different polarities are the positive electrode 24 and the negative electrode 26. That is, the first electrode is one of the positive electrode 24 and the negative electrode 26, and the second electrode is the other of the positive electrode 24 and the negative electrode 26. In the present embodiment, the first electrode is described as a positive electrode 24 and the second electrode is described as a negative electrode 26. A member that ensures the insulation of the positive electrode 24 and the negative electrode 26 is a separator 28.

電極群２２は、それぞれ帯状の正極２４、負極２６及びセパレータ２８からなり、これらは正極２４と負極２６との間にセパレータ２８が挟み込まれた状態で渦巻状に巻回されている。即ち、電極群２２は、図２に示すように、正極２４及び負極２６が、セパレータ２８を間に挟んだ状態で電極群２２の径方向でみて交互に重ね合わされた状態となる。電極群２２の外周面は負極２６の一部により形成され、外装缶１０の内周壁と接触している。これにより、負極２６と外装缶１０とは互いに電気的に接続されている。   The electrode group 22 includes a strip-like positive electrode 24, a negative electrode 26, and a separator 28, which are wound in a spiral shape with the separator 28 sandwiched between the positive electrode 24 and the negative electrode 26. That is, as shown in FIG. 2, the electrode group 22 is in a state where the positive electrode 24 and the negative electrode 26 are alternately overlapped when viewed in the radial direction of the electrode group 22 with the separator 28 interposed therebetween. The outer peripheral surface of the electrode group 22 is formed by a part of the negative electrode 26 and is in contact with the inner peripheral wall of the outer can 10. Accordingly, the negative electrode 26 and the outer can 10 are electrically connected to each other.

ここで、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用いることができる。具体的には、スルホン化処理が施されてスルホン基が付与されたポリオレフィン繊維を主体とする不織布を用いることが好ましい。   Here, as a material of the separator 28, for example, a polyamide fiber nonwoven fabric or a polyolefin fiber nonwoven fabric such as polyethylene or polypropylene provided with a hydrophilic functional group can be used. Specifically, it is preferable to use a non-woven fabric mainly composed of polyolefin fibers that have been subjected to sulfonation treatment and are provided with sulfone groups.

正極２４は、非焼結式のニッケル極であり、導電性の金属多孔体からなる正極芯体と、この正極芯体に保持された正極合剤とを含んでいる。
正極合剤は、電池反応材料としての正極活物質粒子と、正極の特性を改善するための種々の添加剤粒子と、これら正極活物質粒子及び添加剤粒子の混合粒子を正極芯体に結着するための結着剤とからなる。 The positive electrode 24 is a non-sintered nickel electrode, and includes a positive electrode core body made of a conductive metal porous body, and a positive electrode mixture held on the positive electrode core body.
The positive electrode mixture is a positive electrode active material particle as a battery reaction material, various additive particles for improving the characteristics of the positive electrode, and a mixed particle of these positive electrode active material particles and additive particles bound to the positive electrode core. And a binder for the purpose.

正極活物質粒子は、水酸化ニッケル粒子又は高次水酸化ニッケル粒子である。なお、これら水酸化ニッケル粒子は、コバルト、亜鉛、カドミウム等を固溶していてもよく、あるいは表面がコバルト化合物で被覆されていてもよい。   The positive electrode active material particles are nickel hydroxide particles or higher order nickel hydroxide particles. In addition, these nickel hydroxide particles may be dissolved in cobalt, zinc, cadmium or the like, or the surface may be coated with a cobalt compound.

添加剤としては、特に限定されることはないが、酸化イットリウムが好適に用いられる。また、酸化イットリウムの他に、酸化コバルト、金属コバルト、水酸化コバルト等のコバルト化合物、金属亜鉛、酸化亜鉛、水酸化亜鉛等の亜鉛化合物、酸化エルビウム等の希土類化合物等を用いることもできる。   The additive is not particularly limited, but yttrium oxide is preferably used. In addition to yttrium oxide, cobalt compounds such as cobalt oxide, metal cobalt and cobalt hydroxide, zinc compounds such as metal zinc, zinc oxide and zinc hydroxide, and rare earth compounds such as erbium oxide can also be used.

結着剤としては、例えば、カルボキシメチルセルロース、メチルセルロース、ＰＴＦＥ（ポリテトラフルオロエチレン）ディスパージョン、ＨＰＣ（ヒドロキシプロピルセルロース）ディスパージョンなどを用いることができる。   As the binder, for example, carboxymethylcellulose, methylcellulose, PTFE (polytetrafluoroethylene) dispersion, HPC (hydroxypropylcellulose) dispersion, and the like can be used.

正極芯体３６はニッケル製であり、図３に展開して概略的に示したように、シート状をなしている。この正極芯体３６は、図３中の円Ａ，Ｂに拡大して示すように、三次元網目状の構造を有し、相互に連通した無数の空孔を有する。詳しくは、無数の金属骨格３８と、金属骨格３８が相互に交差する節部４０とからなり、これら金属骨格３８及び節部４０が無数の空孔４２を形成している。正極２４において、正極合剤はこれらの空孔４２内に充填された状態にて保持される。   The positive electrode core 36 is made of nickel and has a sheet shape as schematically shown in FIG. The positive electrode core 36 has a three-dimensional network structure and has innumerable holes communicating with each other, as shown enlarged in circles A and B in FIG. Specifically, the metal skeleton 38 and the nodes 40 where the metal skeletons 38 cross each other are formed, and the metal skeletons 38 and the nodes 40 form an infinite number of holes 42. In the positive electrode 24, the positive electrode mixture is held in a state filled in these holes 42.

正極芯体３６は、電極群２２の形成に際して巻回されたときに、電極群２２の外周部４８に位置付けられる第１外周領域と、電極群２２の外周部４８よりも内側に位置付けられ、第１外周領域よりも目付が高い領域とを備えている。つまり、正極芯体３６において、電極群２２の外周部４８よりも内側に位置付けられる部分の少なくとも一部に、第１外周領域の目付よりも高い目付の領域が存在している。ここで、正極芯体３６における第１外周領域は、図３において、正極芯体３６の一方の端部である最外端部５４側の所定範囲に位置付けられる。また、正極芯体３６における最外端部５４とは反対側の他方の端部には、最内端部５２が存在し、この最内端部５２は、電極群２２の中心部４４に位置付けられる。
本発明の好ましい態様としては、正極芯体３６の最内端部５２の目付を正極芯体３６の最外端部５４の目付よりも高く設定する。 The positive electrode core 36 is positioned on the inner side of the outer peripheral portion 48 of the electrode group 22 and the first outer peripheral region positioned on the outer peripheral portion 48 of the electrode group 22 when the electrode group 22 is wound. And an area having a higher basis weight than that of one outer peripheral area. That is, in the positive electrode core 36, a weight area higher than the weight of the first outer peripheral area exists in at least a part of the portion positioned inside the outer peripheral portion 48 of the electrode group 22. Here, the first outer peripheral region of the positive electrode core 36 is positioned in a predetermined range on the outermost end 54 side which is one end of the positive electrode core 36 in FIG. 3. An innermost end 52 exists at the other end of the positive electrode core 36 opposite to the outermost end 54, and the innermost end 52 is positioned at the center 44 of the electrode group 22. It is done.
As a preferred aspect of the present invention, the basis weight of the innermost end 52 of the positive electrode core 36 is set higher than the basis weight of the outermost end 54 of the positive electrode core 36.

ここで、目付に差を付ける手段としては、例えば、図３に示すように、金属骨格３８の太さを調整することにより目付に差を付ける。つまり、最内端部５２側の金属骨格３８の太さを最外端部５４側の金属骨格３８の太さよりも太くする。具体的には、目付の異なる正極芯体の半製品を複数準備し、これら半製品を繋げる方法、または、正極芯体を製造する過程で、ベースとなる発泡ウレタン（ウレタンフォーム）に析出させるニッケルめっきの量を電流を制御することにより最外端部５４側と最内端部５２側で変化させる方法により、最外端部５４側の目付と最内端部５２側の目付とに差を付ける。   Here, as a means for giving a difference in basis weight, for example, as shown in FIG. 3, the basis weight is made different by adjusting the thickness of the metal skeleton 38. That is, the thickness of the metal skeleton 38 on the innermost end 52 side is made thicker than the thickness of the metal skeleton 38 on the outermost end 54 side. Specifically, nickel that is deposited on foamed urethane (urethane foam) as a base in the process of preparing a plurality of semifinished products of positive electrode cores with different basis weights and connecting these semifinished products, or in the process of manufacturing positive electrode cores By changing the amount of plating between the outermost end portion 54 side and the innermost end portion 52 side by controlling the current, the difference between the basis weight on the outermost end portion 54 side and the basis weight on the innermost end portion 52 side is made. wear.

正極芯体３６において、目付は、最内端部５２から最外端部５４へ向かって漸減していく態様が好ましい。しかしながら、この態様の場合、製造に手間がかかるため、目付量は段階的に変化させる態様でも構わない。また、図３の参照符号５６で示される中央線を境に最内端部５２側と最外端部５４側とで２段階に目付量を変化させる態様でもよい。   In the positive electrode core 36, it is preferable that the basis weight gradually decreases from the innermost end portion 52 toward the outermost end portion 54. However, in the case of this aspect, since manufacturing takes time, the aspect weight may be changed stepwise. Alternatively, the basis weight may be changed in two steps on the innermost end 52 side and the outermost end 54 side with respect to the center line indicated by reference numeral 56 in FIG.

次に、負極２６について説明する。
負極２６は、帯状をなす導電性の負極芯体６０を有し、この負極芯体６０に負極合剤が保持されている。 Next, the negative electrode 26 will be described.
The negative electrode 26 has a conductive negative electrode core 60 having a strip shape, and a negative electrode mixture is held in the negative electrode core 60.

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であって、電池反応材料としての水素吸蔵合金粒子と、導電材と、結着剤とを含む。この結着剤は水素吸蔵合金粒子及び導電材を互いに結着させると同時に負極合剤を負極芯体に結着させる働きをなす。ここで、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、導電材としては、カーボンブラックや黒鉛を用いることができる。   The negative electrode mixture is hydrogen storage alloy particles capable of occluding and releasing hydrogen as a negative electrode active material, and includes hydrogen storage alloy particles as a battery reaction material, a conductive material, and a binder. This binder serves to bind the hydrogen storage alloy particles and the conductive material to each other and at the same time bind the negative electrode mixture to the negative electrode core. Here, 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 material.

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、希土類−Ｎｉ系水素吸蔵合金、希土類−Ｍｇ−Ｎｉ系水素吸蔵合金等を用いることができる。   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. For example, a rare earth-Ni-based hydrogen storage alloy, a rare-earth-Mg-Ni-based hydrogen storage alloy, or the like can be used.

負極芯体は、貫通孔が分布されたシート状の金属材からなり、例えば、金属製の孔あき板（パンチングメタルシート）や、金属粉末を型成形して焼結した焼結基板を用いることができる。負極合剤は、負極芯体の貫通孔内に充填されるばかりでなく、負極芯体の両面上にも層状にして保持されている。   The negative electrode core is made of a sheet-like metal material in which through holes are distributed. For example, a metal perforated plate (punched metal sheet) or a sintered substrate obtained by molding and sintering metal powder is used. Can do. The negative electrode mixture is not only filled in the through hole of the negative electrode core, but also held in layers on both surfaces of the negative electrode core.

負極芯体６０は、電極群２２の形成に際して巻回されたときに、電極群２２の外周部４８に位置付けられる第２外周領域と、電極群２２の外周部４８よりも内側に位置付けられ、第２外周領域よりも目付が高い領域とを備えている。つまり、負極芯体６０において、電極群２２の外周部４８よりも内側に位置付けられる部分の少なくとも一部に、第２外周領域の目付よりも高い目付の領域が存在している。ここで、負極芯体６０における第２外周領域は、図４において、負極芯体６０の一方の端部である最外端部６８側の所定範囲に位置付けられる。また、負極芯体６０における最外端部６８とは反対側の他方の端部には、最内端部６６が存在し、この最内端部６６は、電極群２２の中心部４４に位置付けられる。
本発明の好ましい態様としては、負極芯体６０の最内端部６６の目付を負極芯体６０の最外端部６８の目付よりも高く設定する。 When the negative electrode core body 60 is wound when the electrode group 22 is formed, the negative electrode core body 60 is positioned inside the second outer peripheral region positioned on the outer peripheral portion 48 of the electrode group 22 and the outer peripheral portion 48 of the electrode group 22. 2 and an area having a higher basis weight than the outer peripheral area. That is, in the negative electrode core body 60, a weight area higher than the weight of the second outer peripheral area exists in at least a part of the portion positioned inside the outer peripheral part 48 of the electrode group 22. Here, the second outer peripheral region of the negative electrode core 60 is positioned in a predetermined range on the outermost end 68 side which is one end of the negative electrode core 60 in FIG. Further, an innermost end 66 is present at the other end of the negative electrode core 60 opposite to the outermost end 68, and the innermost end 66 is positioned at the center 44 of the electrode group 22. It is done.
As a preferred embodiment of the present invention, the basis weight of the innermost end 66 of the negative electrode core 60 is set higher than the basis weight of the outermost end 68 of the negative electrode core 60.

ここで、目付に差を付ける手段としては、例えば、図４に示すように、貫通孔７０，７２の孔径を調整することにより目付に差を付ける。つまり、最内端部６６側の貫通孔７０の孔径を最外端部６８側の貫通孔７２の孔径よりも小さくする。具体的には、目付の異なる負極芯体の半製品を複数準備し、これら半製品を繋げる方法、最内端部６６側と最外端部６８側で厚さが異なる芯体を用いる方法、または、負極芯体６０を製造する過程で貫通孔７０，７２の大きさや数量を制御する方法により、最外端部６８側の目付と最内端部６６側の目付とに差を付ける。   Here, as means for giving a difference in basis weight, for example, as shown in FIG. 4, the basis weight is made different by adjusting the hole diameters of the through holes 70 and 72. That is, the diameter of the through hole 70 on the innermost end 66 side is made smaller than the diameter of the through hole 72 on the outermost end 68 side. Specifically, preparing a plurality of semi-finished negative electrode cores with different basis weights, connecting these semi-finished products, using the cores having different thicknesses on the innermost end 66 side and the outermost end 68 side, Alternatively, the basis weight on the outermost end 68 side and the basis weight on the innermost end 66 side are made different by a method of controlling the size and quantity of the through holes 70 and 72 in the process of manufacturing the negative electrode core 60.

負極芯体６０において、目付は、最内端部６６から最外端部６８へ向かって漸減していく態様が好ましい。しかしながら、この態様の場合、製造に手間がかかるため、目付量は段階的に変化させる態様でも構わない。また、図４の参照符号７４で示される中央線を境に最内端部６６側と最外端部６８側とで２段階に目付量を変化させる態様でもよい。   In the negative electrode core 60, it is preferable that the basis weight gradually decreases from the innermost end portion 66 toward the outermost end portion 68. However, in the case of this aspect, since manufacturing takes time, the aspect weight may be changed stepwise. Further, the basis weight may be changed in two steps on the innermost end 66 side and the outermost end 68 side with respect to the center line indicated by reference numeral 74 in FIG.

ついで、外装缶１０内の他の部分について説明する。
外装缶１０内には、図１に示すように、電極群２２の一端と蓋板１４との間に正極リード３０が配置されている。詳しくは、正極リード３０は、その一端が正極２４に接続され、その他端が蓋板１４に接続されている。従って、正極端子２０と正極２４とは、正極リード３０及び蓋板１４を介して互いに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３９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。 Next, other parts in the outer can 10 will be described.
In the outer can 10, as shown in FIG. 1, a positive electrode lead 30 is disposed between one end of the electrode group 22 and the lid plate 14. Specifically, the positive electrode lead 30 has one end connected to the positive electrode 24 and the other end connected to the lid plate 14. Therefore, the positive electrode terminal 20 and the positive electrode 24 are electrically connected to each other via the positive electrode lead 30 and the cover 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 39 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.

更に、外装缶１０内には、所定量のアルカリ電解液（図示せず）が注入されており、このアルカリ電解液は正極２４、負極２６及びセパレータ２８に含浸され、正極２４と負極２６との間での充放電反応を進行させる。なお、アルカリ電解液の種類としては、特に限定されないが、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、適当な充放電反応を進行させることができる濃度であれば特には限定されない。   Further, a predetermined amount of alkaline electrolyte (not shown) is injected into the outer can 10, and the alkaline electrolyte is impregnated in the positive electrode 24, the negative electrode 26, and the separator 28. The charge / discharge reaction between them is advanced. The type of the alkaline electrolyte is not particularly limited, and examples thereof include an aqueous sodium hydroxide solution, an aqueous lithium hydroxide solution, an aqueous potassium hydroxide solution, and an aqueous solution obtained by mixing two or more of these, Further, the concentration of the alkaline electrolyte is not particularly limited as long as it is a concentration capable of causing an appropriate charge / discharge reaction to proceed.

次に、本発明の電池２の製造方法について説明する。
まず、電極群２２を製造するために、正極２４及び負極２６を製造する。
正極２４は、例えば、以下のようにして製造することができる。
まず、正極活物質粒子からなる正極活物質粉末、導電材、正極添加剤、水及び結着剤を含む正極合剤ペーストを調製する。得られた正極合剤ペーストは、上記のようにして準備された最内端部５２側と最外端部５４側とで目付の異なるニッケルフォーム（正極芯体）３６に充填され、乾燥させられる。乾燥後、水酸化ニッケル粒子等が充填されたニッケルフォーム３６は、ロール圧延されてから裁断される。これにより、正極合剤を保持した正極２４が作製される。 Next, the manufacturing method of the battery 2 of the present invention will be described.
First, in order to manufacture the electrode group 22, the positive electrode 24 and the negative electrode 26 are manufactured.
The positive electrode 24 can be manufactured as follows, for example.
First, a positive electrode mixture paste including a positive electrode active material powder composed of positive electrode active material particles, a conductive material, a positive electrode additive, water, and a binder is prepared. The obtained positive electrode mixture paste is filled in a nickel foam (positive electrode core) 36 having a different basis weight between the innermost end 52 side and the outermost end 54 side prepared as described above, and is dried. . After drying, the nickel foam 36 filled with nickel hydroxide particles and the like is rolled and then cut. Thereby, the positive electrode 24 holding the positive electrode mixture is produced.

次に、負極２６は、例えば、以下のようにして製造することができる。
まず、水素吸蔵合金粒子からなる水素吸蔵合金粉末、導電材、結着剤及び水を混練して負極合剤ペーストを調製する。得られた負極合剤ペーストは、上記のようにして準備された最内端部６６側と最外端部６８とで目付の異なる金属製孔あき板（負極芯体）６０に塗着され、乾燥させられる。乾燥後、水素吸蔵合金粒子等が付着した金属製孔あき板６０はロール圧延及び裁断が施され、これにより負極２６が作製される。 Next, the negative electrode 26 can be manufactured as follows, for example.
First, a negative electrode mixture paste is prepared by kneading a hydrogen storage alloy powder composed of hydrogen storage alloy particles, a conductive material, a binder and water. The obtained negative electrode mixture paste was applied to a metal perforated plate (negative electrode core) 60 having a different basis weight between the innermost end 66 side and the outermost end 68 prepared as described above. Dried. After drying, the metal perforated plate 60 to which the hydrogen storage alloy particles and the like are attached is rolled and cut, whereby the negative electrode 26 is produced.

以上のようにして作製された正極２４及び負極２６は、セパレータ２８を介在させた状態で、渦巻き状に巻回され、電極群２２に形成される。   The positive electrode 24 and the negative electrode 26 manufactured as described above are spirally wound with the separator 28 interposed therebetween, and are formed in the electrode group 22.

このようにして得られた電極群２２は、外装缶１０内に収容される。引き続き、当該外装缶１０内にはアルカリ電解液が所定量注入される。その後、電極群２２及びアルカリ電解液を収容した外装缶１０は、正極端子２０を備えた蓋板１４により封口され、本発明に係る電池２が得られる。   The electrode group 22 thus obtained is accommodated in the outer can 10. Subsequently, a predetermined amount of alkaline electrolyte is injected into the outer can 10. Thereafter, the outer can 10 containing the electrode group 22 and the alkaline electrolyte is sealed by the cover plate 14 provided with the positive electrode terminal 20, and the battery 2 according to the present invention is obtained.

本発明に係る電池２は、電極群２２内の電極芯体（正極芯体３６、負極芯体６０）において、電極群２２の中心部４４、即ち、電極群２２の径方向内側に位置付けられる最内端部５２，６６の目付が、電極群２２の外周部４８、即ち、電極群２２の径方向外側に位置付けられる最外端部５４，６８の目付よりも高い値に設定されている。つまり、電極芯体は、電極群２２の外周部４８に位置付けられる外周領域と、電極群２２の外周部４８より内側に位置付けられ、外周領域より目付が高い領域とを含む構成となっている。このため、電極群２２の中心部４４の電気抵抗が電極群２２の外周部４８の電気抵抗よりも低くなり、電極群２２の中心部４４での発熱が抑えられる。その結果、電極群２２の中心部４４の電池反応材料（正極活物質、水素吸蔵合金）の劣化が抑制され、電池２内における電池反応材料の劣化の度合いの偏りが抑制されるため、電池２のサイクル寿命特性を向上させることができる。   The battery 2 according to the present invention is positioned at the central portion 44 of the electrode group 22, that is, the radially inner side of the electrode group 22 in the electrode core body (the positive electrode core body 36 and the negative electrode core body 60) in the electrode group 22. The basis weights of the inner end portions 52 and 66 are set to be higher than the outer perimeter portion 48 of the electrode group 22, that is, the basis weight of the outermost end portions 54 and 68 positioned on the radially outer side of the electrode group 22. That is, the electrode core is configured to include an outer peripheral region positioned on the outer peripheral portion 48 of the electrode group 22 and an area positioned on the inner side of the outer peripheral portion 48 of the electrode group 22 and having a higher basis weight than the outer peripheral region. For this reason, the electrical resistance of the central portion 44 of the electrode group 22 is lower than the electrical resistance of the outer peripheral portion 48 of the electrode group 22, and heat generation at the central portion 44 of the electrode group 22 is suppressed. As a result, the deterioration of the battery reaction material (positive electrode active material, hydrogen storage alloy) in the central portion 44 of the electrode group 22 is suppressed, and the unevenness of the degree of deterioration of the battery reaction material in the battery 2 is suppressed. Cycle life characteristics can be improved.

また、本発明によれば、従来のように外装缶１０内に集電体を配置する必要がない。このため、電池２内において電池反応に直接関与しない部材の占める容積の割合を低減でき、相対的に電池反応に直接関与する正極活物質及び水素吸蔵合金の量を増やすことができる。その結果、本発明の電池は、サイクル寿命に優れ、しかも、従来の電池よりも高容量化を図ることが可能である。   Further, according to the present invention, it is not necessary to arrange a current collector in the outer can 10 as in the prior art. For this reason, the ratio of the volume which the member which does not directly participate in the battery reaction in the battery 2 occupies can be reduced, and the amount of the positive electrode active material and the hydrogen storage alloy which are directly involved in the battery reaction can be relatively increased. As a result, the battery of the present invention has an excellent cycle life and can have a higher capacity than conventional batteries.

１．電池の製造
実施例１
（１）正極の作製
目付が４５０ｇ／ｃｍ2の第１ニッケルフォーム及び目付が３５０ｇ／ｃｍ2の第２ニッケルフォームを準備した。そして、第１ニッケルフォームと第２ニッケルフォームとを繋げることにより、図３に示すような目付が２段階で異なる正極芯体としてのニッケルフォーム３６を形成した。つまり、このニッケルフォーム３６は、最内端部５２側の目付が４５０ｇ／ｃｍ2であり、最外端部５４側の目付が３５０ｇ／ｃｍ2である。なお、ニッケルフォーム３６の厚さは約２ｍｍである。 1. Production of Battery Example 1
(1) Positive Preparation basis weight first nickel foam and the basis weight of 450 g / cm 2 was prepared second nickel foam of 350 g / cm 2. Then, by connecting the first nickel foam and the second nickel foam, a nickel foam 36 as a positive electrode core body having different basis weights in two stages as shown in FIG. 3 was formed. That is, the nickel foam 36 has a basis weight on the innermost end 52 side of 450 g / cm 2 and a basis weight on the outermost end 54 side of 350 g / cm 2 . The thickness of the nickel foam 36 is about 2 mm.

ついで、表面が高次コバルト酸化物で被覆された水酸化ニッケル粒子からなるニッケル正極活物質粉末、酸化亜鉛粉末及び水酸化コバルト粉末を準備した。そして、これらの粉末が、ニッケル正極活物質粉末９５質量％、酸化亜鉛３質量％、水酸化コバルト２質量％となるように混合して混合粉末を得た。その後、かかる混合粉末に、結着剤としての０．２質量％ヒドロキシプロピルセルロース水溶液を混合粉末の質量に対して５０質量％となるように添加して、正極合剤スラリーを作製した。   Next, nickel positive electrode active material powder, zinc oxide powder and cobalt hydroxide powder comprising nickel hydroxide particles whose surfaces were coated with higher cobalt oxide were prepared. And these powders were mixed so that it might become nickel positive electrode active material powder 95 mass%, zinc oxide 3 mass%, and cobalt hydroxide 2 mass%, and mixed powder was obtained. Thereafter, a 0.2% by mass hydroxypropylcellulose aqueous solution as a binder was added to the mixed powder so as to be 50% by mass with respect to the mass of the mixed powder to prepare a positive electrode mixture slurry.

そして、得られた正極合剤スラリーを上記したニッケルフォーム３６に充填した。正極合剤が充填されたニッケルフォーム３６を乾燥後、ロール圧延した。圧延加工された正極合剤が付着したニッケルフォーム３６は、所定形状に裁断され、ＡＡサイズ用の正極２４に形成された。この正極２４は、正極容量が２０００ｍＡｈとなるように正極合剤を担持している。   The obtained positive electrode mixture slurry was filled in the nickel foam 36 described above. The nickel foam 36 filled with the positive electrode mixture was dried and rolled. The nickel foam 36 to which the rolled positive electrode mixture was adhered was cut into a predetermined shape and formed on the positive electrode 24 for AA size. The positive electrode 24 carries a positive electrode mixture so that the positive electrode capacity is 2000 mAh.

（２）負極の作製
負極芯体として、目付が３００ｇ／ｃｍ2の鉄製の孔あき板６０を準備した。詳しくは、この孔あき板は、全体に同じ孔径の貫通孔が無数に穿設されており、目付は全体として一定である。また、この孔あき板は、厚さが６０μｍであり、表面にニッケルめっきが施してある。 (2) Production of Negative Electrode An iron perforated plate 60 with a basis weight of 300 g / cm 2 was prepared as a negative electrode core. Specifically, the perforated plate has an infinite number of through-holes having the same hole diameter as a whole, and the basis weight is constant as a whole. The perforated plate has a thickness of 60 μm and has a nickel plating on the surface.

ついで、組成が、Ｎｄ0.36Ｓｍ0.54Ｍｇ0.10Ｎｉ3.33Ａｌ0.17である水素吸蔵合金の粉末を準備した。そして、この水素吸蔵合金の粉末１００質量部に対し、ポリアクリル酸ナトリウム０．２質量部、カルボキシメチルセルロース０．２質量部、スチレンブタジエン共重合ゴム（ＳＢＲ）のディスバージョン(固形分５０質量％)０．５質量部(固形分換算)、ケッチェンブラック０．５質量部、水５０質量部を添加して混練し、負極合剤スラリーを調製した。 Next, a powder of a hydrogen storage alloy having a composition of Nd 0.36 Sm 0.54 Mg 0.10 Ni 3.33 Al 0.17 was prepared. And, with respect to 100 parts by mass of the hydrogen storage alloy powder, 0.2 parts by mass of sodium polyacrylate, 0.2 parts by mass of carboxymethyl cellulose, and a styrene butadiene copolymer rubber (SBR) disversion (solid content 50% by mass) 0.5 parts by mass (in terms of solid content), 0.5 parts by mass of ketjen black, and 50 parts by mass of water were added and kneaded to prepare a negative electrode mixture slurry.

この負極合剤スラリーを、準備した負極芯体としての孔あき板の両面に均等、且つ、厚さが一定となるように塗布した。スラリーの乾燥後、水素吸蔵合金の粉末が付着した孔あき板を更にロール圧延したのち裁断し、ＡＡサイズ用の負極２６を作成した。   This negative electrode mixture slurry was applied to both surfaces of the prepared perforated plate as the negative electrode core so that the thickness was uniform and constant. After the slurry was dried, the perforated plate to which the hydrogen storage alloy powder was adhered was further rolled and then cut to prepare an AA size negative electrode 26.

（３）ニッケル水素蓄電池の組み立て
得られた正極２４及び負極２６をこれらの間にセパレータ２８を挟んだ状態で渦巻状に巻回し、電極群２２を作製した。ここでの電極群２２の作製に使用したセパレータ２８はスルホン基を有するポリプロピレン繊維製不織布から成り、その厚みは０．１ｍｍ(目付は４０ｇ／ｍ2)であった。 (3) Assembly of Nickel Metal Hydride Battery The obtained positive electrode 24 and negative electrode 26 were spirally wound with a separator 28 sandwiched therebetween, and an electrode group 22 was produced. The separator 28 used for production of the electrode group 22 here was made of a nonwoven fabric made of polypropylene fiber having a sulfone group, and its thickness was 0.1 mm (weight is 40 g / m 2 ).

得られた電極群２２を有底円筒形状の外装缶１０内に収納するとともに、３０質量％の水酸化ナトリウム水溶液からなるアルカリ電解液を２．２ｇ注入した。この後、蓋板１４等で外装缶１０の開口を塞ぎ、公称容量が２０００ｍＡｈのＡＡサイズの密閉型ニッケル水素蓄電池２を組み立てた。このニッケル水素蓄電池を電池ａと称する。   The obtained electrode group 22 was housed in a bottomed cylindrical outer can 10 and 2.2 g of an alkaline electrolyte composed of a 30% by mass sodium hydroxide aqueous solution was injected. After that, the opening of the outer can 10 was closed with a cover plate 14 or the like, and an AA size sealed nickel-metal hydride storage battery 2 having a nominal capacity of 2000 mAh was assembled. This nickel metal hydride storage battery is referred to as battery a.

（４）初期活性化処理
電池ａに対し、温度２５℃の環境下にて、２００ｍＡの充電電流で１６時間の充電を行った後に、４００ｍＡの放電電流で電池電圧が０．５Ｖになるまで放電させる初期活性化処理を２回繰り返した。このようにして、電池ａを使用可能状態とした。 (4) Initial activation treatment After charging the battery a for 16 hours at a charging current of 200 mA in an environment of a temperature of 25 ° C., discharging until the battery voltage reaches 0.5 V with a discharging current of 400 mA. The initial activation treatment was repeated twice. In this way, the battery a was made usable.

実施例２
正極芯体として、目付が４００ｇ／ｃｍ2で全体的に一定であるニッケルフォームを用いたこと、負極芯体として、目付が３５０ｇ／ｃｍ2の第１孔あき板及び目付が２５０ｇ／ｃｍ2の第２孔あき板を準備し、これら第１孔あき板及び第２孔あき板を繋げることにより形成した、目付が２段階で異なる孔あき板（最内端部６６側の目付が３５０ｇ／ｃｍ2であり、最外端部６８側の目付が２５０ｇ／ｃｍ2である。）６０を用いたこと以外は、実施例１の電池ａと同様なニッケル水素蓄電池（電池ｂ）を製造した。 Example 2
Nickel foam having a basis weight of 400 g / cm 2 and a constant overall weight was used as the positive electrode core, and a first perforated plate having a basis weight of 350 g / cm 2 and a basis weight of 250 g / cm 2 was used as the negative electrode core. A perforated plate prepared by preparing a second perforated plate and connecting the first perforated plate and the second perforated plate with different weights in two stages (the weight on the innermost end 66 side is 350 g / cm) 2 and the basis weight on the outermost end 68 side is 250 g / cm 2. ) A nickel-metal hydride storage battery (battery b) similar to the battery a of Example 1 was manufactured except that 60 was used.

実施例３
負極芯体として、目付が３５０ｇ／ｃｍ2の第１孔あき板及び目付が２５０ｇ／ｃｍ2の第２孔あき板を準備し、これら第１孔あき板及び第２孔あき板を繋げることにより形成した、目付が２段階で異なる孔あき板（最内端部６６側の目付が３５０ｇ／ｃｍ2であり、最外端部６８側の目付が２５０ｇ／ｃｍ2である。）６０を用いたこと以外は、実施例１の電池ａと同様なニッケル水素蓄電池（電池ｃ）を製造した。 Example 3
By preparing a first perforated plate with a basis weight of 350 g / cm 2 and a second perforated plate with a basis weight of 250 g / cm 2 as the negative electrode core, and connecting the first perforated plate and the second perforated plate The formed perforated plates 60 having different basis weights (the basis weight on the innermost end 66 side is 350 g / cm 2 and the basis weight on the outermost end 68 side is 250 g / cm 2 ) 60 were used. Except for this, a nickel-metal hydride storage battery (battery c) similar to the battery a of Example 1 was produced.

比較例１
正極芯体として、目付が４００ｇ／ｃｍ2で全体的に一定であるニッケルフォームを用いたこと以外は、実施例１の電池ａと同様なニッケル水素蓄電池（電池ｄ）を製造した。 Comparative Example 1
A nickel-metal hydride storage battery (battery d) similar to the battery a of Example 1 was manufactured except that nickel foam having a basis weight of 400 g / cm 2 and a constant overall weight was used as the positive electrode core.

比較例２
正極芯体として、目付が５００ｇ／ｃｍ2で全体的に一定であるニッケルフォームを用いたこと、負極芯体として、目付が４００ｇ／ｃｍ2で全体的に一定である孔あき板を用いたこと以外は、実施例１の電池ａと同様なニッケル水素蓄電池（電池ｅ）を製造した。 Comparative Example 2
Nickel foam with a basis weight of 500 g / cm 2 and an overall constant weight was used as the positive electrode core, and a perforated plate with a basis weight of 400 g / cm 2 and an overall constant was used as the negative electrode core. Except for the above, a nickel metal hydride storage battery (battery e) similar to the battery a of Example 1 was produced.

２．ニッケル水素蓄電池の評価
（１）２００サイクル後の極板の単位容量比
初期活性化処理済みの電池ａ〜電池ｅに対し、２５℃の環境下にて、２０００ｍＡの充電電流で電池電圧が最大値に達した後、１０ｍＶ低下するまで充電するいわゆる−ΔＶ制御での充電（以下、単に−ΔＶ充電という）を行い、その後、１時間放置した。ついで、同一の環境下にて２０００ｍＡの放電電流で電池電圧が１．０Ｖになるまで放電した後、１時間放置した。この充放電のサイクルを１サイクルとして、各電池につきサイクル試験を行った。 2. Evaluation of Nickel Metal Hydride Battery (1) Unit Capacity Ratio of Electrode Plate after 200 Cycles The battery voltage is the maximum value at a charging current of 2000 mA in the environment of 25 ° C. with respect to the batteries a to e after the initial activation treatment. The battery was charged by so-called -ΔV control (hereinafter, simply referred to as -ΔV charge) for charging until the voltage decreased by 10 mV, and then left for 1 hour. Next, the battery was discharged at a discharge current of 2000 mA under the same environment until the battery voltage became 1.0 V, and then left for 1 hour. The cycle test was performed for each battery with this charge / discharge cycle as one cycle.

このサイクル試験において、サイクル数が２００サイクルとなったときの電池に対して、正極及び負極の単位容量を測定した。このとき、正極及び負極において、電池の中心部に位置付けられる最内端部及び電池の外周部に位置付けられる最外端部の単位容量をそれぞれ測定した。そして、比較例１の最外端部における測定値を１００としたきの各部分の測定値の比を求め、その結果を２００サイクル後の極板の単位容量比として表１に示した。この単位容量比の値が高いほど電池容量が高く、正極活物質及び水素吸蔵合金の熱による劣化が抑制されていることを示す。ここで、各部分の単位容量の測定方法を以下に示す。   In this cycle test, the unit capacities of the positive electrode and the negative electrode were measured for the battery when the number of cycles was 200. At this time, in the positive electrode and the negative electrode, the unit capacities of the innermost end portion positioned at the center of the battery and the outermost end portion positioned at the outer peripheral portion of the battery were measured. And the ratio of the measured value of each part when the measured value in the outermost edge part of the comparative example 1 was set to 100 was calculated | required, and the result was shown in Table 1 as unit capacity ratio of the electrode plate after 200 cycles. The higher the unit capacity ratio, the higher the battery capacity, indicating that the positive electrode active material and the hydrogen storage alloy are prevented from being deteriorated by heat. Here, the measuring method of the unit capacity of each part is shown below.

まず、電池を解体して正極を取り出して１０ｍｍ×１０ｍｍの寸法に切り取った。切り取った正極は、セパレータに包み、対極に負極で挟むように固定した。これを電解液に浸漬し、参照極としてＨｇ／ＨｇＯを用いて正極容量を測定した。詳しくは、０．１Ｉｔ×１６０％の充電後に０．２Ｉｔで０Ｖに到達するまでの放電容量を測定した。その後、この正極の活物質量を測定し、活物質量当たりの放電容量を正極の単位容量（ｍＡｈ／ｇ）とした。負極の単位容量は、以下のようにして測定した。まず、負極を１０ｍｍ×１０ｍｍの寸法に切り取り、切り取った負極をセパレータに包み、対極に正極で挟むように固定した。これを電解液に浸漬し、参照極としてＨｇ／ＨｇＯを用いて負極容量を測定した。詳しくは、０．１Ｉｔ×１６０％の充電後に０．２Ｉｔで−０．６Ｖに到達するまでの放電容量を測定した。その後、この負極の活物質量を測定し、活物質量当たりの放電容量を負極の単位容量（ｍＡｈ／ｇ）とした。   First, the battery was disassembled and the positive electrode was taken out and cut to a size of 10 mm × 10 mm. The cut positive electrode was wrapped in a separator and fixed so as to be sandwiched between the negative electrode and the counter electrode. This was immersed in an electrolytic solution, and the positive electrode capacity was measured using Hg / HgO as a reference electrode. Specifically, the discharge capacity until reaching 0 V at 0.2 It after charging 0.1 It × 160% was measured. Thereafter, the amount of the active material of the positive electrode was measured, and the discharge capacity per active material amount was defined as the unit capacity (mAh / g) of the positive electrode. The unit capacity of the negative electrode was measured as follows. First, the negative electrode was cut to a size of 10 mm × 10 mm, and the cut negative electrode was wrapped in a separator and fixed so as to be sandwiched between the positive electrode and the counter electrode. This was immersed in an electrolytic solution, and the negative electrode capacity was measured using Hg / HgO as a reference electrode. Specifically, the discharge capacity until reaching -0.6 V at 0.2 It after charging 0.1 It × 160% was measured. Thereafter, the amount of the active material of the negative electrode was measured, and the discharge capacity per active material amount was defined as the unit capacity (mAh / g) of the negative electrode.

（２）サイクル寿命特性比
上記した充放電のサイクルを、各電池の放電容量が２０００ｍＡｈから１２００ｍＡｈに低下するまで繰り返し、放電容量が１２００ｍＡｈに至ったときのサイクル数をサイクル寿命とした。ここで、比較例１の電池ｄがサイクル寿命に至ったときのサイクル数を１００として、各電池のサイクル寿命との比を求め、その結果をサイクル寿命特性比として表１に示した。このサイクル寿命特性比の値が高いほどサイクル寿命が長く、サイクル寿命特性に優れていることを示す。 (2) Cycle life characteristic ratio The above charge / discharge cycle was repeated until the discharge capacity of each battery decreased from 2000 mAh to 1200 mAh, and the cycle number when the discharge capacity reached 1200 mAh was defined as the cycle life. Here, assuming that the number of cycles when the battery d of Comparative Example 1 reached the cycle life was 100, the ratio to the cycle life of each battery was determined, and the results are shown in Table 1 as the cycle life characteristic ratio. The higher the cycle life characteristic ratio, the longer the cycle life and the better the cycle life characteristics.

Figure 2014165123
Figure 2014165123

（３）考察
（i）比較例１の電池ｄは、一般的な電池であり、正極及び負極の芯体として、最内端部の目付と最外端部の目付との間に差を設けていない、全体の目付が一様な芯体を用いている。この電池ｄの場合、充放電を２００サイクル繰り返した後、正極の単位容量比は、最外端部が１００であるのに対し、最内端部が８８であり、最外端部側よりも最内端部側の単位容量が低下している。これは、電池の中心部が高温となり、この部分の正極活物質が劣化したためである。一方、負極の単位容量についても、最外端部が１００であるのに対し、最内端部が８５であり、最外端部側よりも最内端部側の単位容量が低下している。これも、電池の中心部が高温となったことにともない、この部分の水素吸蔵合金が劣化したためである。このように、電池内において、電池中心部の正極活物質または水素吸蔵合金の劣化の進行により、電池全体としての電池容量が減り、早期に寿命が尽きる。 (3) Consideration (i) The battery d of Comparative Example 1 is a general battery, and provides a difference between the basis weight of the innermost end and the basis weight of the outermost end as the positive and negative electrode cores. A core body with a uniform basis weight is used. In the case of this battery d, after 200 cycles of charge / discharge, the unit capacity ratio of the positive electrode is 100 at the outermost end, but 88 at the innermost end, which is more than the outermost end side. The unit capacity on the innermost end side is reduced. This is because the central portion of the battery is at a high temperature and the positive electrode active material in this portion is deteriorated. On the other hand, regarding the unit capacity of the negative electrode, the outermost end is 100, whereas the innermost end is 85, and the unit capacity on the innermost end side is lower than the outermost end side. . This is also because the hydrogen storage alloy in this part deteriorated as the center of the battery became hot. As described above, in the battery, the battery capacity of the whole battery is reduced due to the progress of the deterioration of the positive electrode active material or the hydrogen storage alloy in the center of the battery, and the life is exhausted at an early stage.

（ii）実施例１の電池ａは、正極芯体において、最内端部の目付を最外端部の目付よりも高くしている。具体的には、最内端部の目付を４５０ｇ／ｃｍ2とし、最外端部の目付を３５０ｇ／ｃｍ2としている。この電池ａの場合、充放電を２００サイクル繰り返した後、正極の単位容量比は、最外端部が９７であるのに対し、最内端部が９２であった。つまり、最内端部の正極活物質の劣化が抑えられ、最内端部と最外端部とで、正極活物質の劣化の進行の偏りの度合いが電池ｄよりも低減されている。これは、正極芯体の最内端部の目付を高めたことにより、正極芯体の最内端部側の電気抵抗が低くなり、電池中心部の発熱を抑えることができたからである。このように、正極の最内端部と最外端部とで正極活物質の劣化の偏りの度合いを小さくすると、電池内で、正極活物質をより均等に近い状態で利用することができ電池のサイクル寿命も延びる。 (Ii) In the battery a of Example 1, in the positive electrode core body, the basis weight of the innermost end portion is made higher than the basis weight of the outermost end portion. Specifically, the basis weight of the innermost end is 450 g / cm 2 and the basis weight of the outermost end is 350 g / cm 2 . In the case of the battery a, after 200 cycles of charge and discharge, the unit capacity ratio of the positive electrode was 97 at the outermost end and 92 at the innermost end. That is, the deterioration of the positive electrode active material at the innermost end portion is suppressed, and the degree of bias of the deterioration of the positive electrode active material at the innermost end portion and the outermost end portion is reduced as compared with the battery d. This is because by increasing the basis weight of the innermost end portion of the positive electrode core body, the electric resistance on the innermost end portion side of the positive electrode core body is reduced, and heat generation at the battery center portion can be suppressed. As described above, when the degree of bias of deterioration of the positive electrode active material is reduced between the innermost end portion and the outermost end portion of the positive electrode, the positive electrode active material can be used in a state that is closer to the inside of the battery. This also extends the cycle life.

（iii）実施例２の電池ｂは、負極芯体において、最内端部の目付を最外端部の目付よりも高くしている。具体的には、最内端部の目付を３５０ｇ／ｃｍ2とし、最外端部の目付を２５０ｇ／ｃｍ2としている。この電池ｂの場合、充放電を２００サイクル繰り返した後、負極の単位容量比は、最外端部が９７であるのに対し、最内端部が８９であった。つまり、最内端部の水素吸蔵合金の劣化が抑えられ、最内端部と最外端部とで、水素吸蔵合金の劣化の進行の偏りの度合いが電池ｄよりも低減されている。これは、負極芯体の最内端部の目付を高めたことにより、負極芯体の最内端部側の電気抵抗が低くなり、電池中心部の発熱を抑えることができたからである。このように、負極の最内端部と最外端部とで水素吸蔵合金の劣化の偏りの度合いを小さくすると、電池内で、水素吸蔵合金をより均等に近い状態で利用することができ電池のサイクル寿命も延びる。 (Iii) In the battery b of Example 2, in the negative electrode core, the basis weight of the innermost end is made higher than the basis weight of the outermost end. Specifically, the basis weight of the innermost end portion is 350 g / cm 2 and the basis weight of the outermost end portion is 250 g / cm 2 . In the case of this battery b, after 200 cycles of charge and discharge were repeated, the unit capacity ratio of the negative electrode was 97 at the outermost end and 89 at the innermost end. That is, the deterioration of the hydrogen storage alloy at the innermost end portion is suppressed, and the degree of bias in the deterioration of the hydrogen storage alloy at the innermost end portion and the outermost end portion is reduced as compared with the battery d. This is because by increasing the basis weight of the innermost end of the negative electrode core, the electric resistance on the innermost end side of the negative electrode core is reduced, and heat generation at the center of the battery can be suppressed. In this way, when the degree of deterioration of the hydrogen storage alloy is reduced at the innermost end and the outermost end of the negative electrode, the battery can be used in a state that is closer to the hydrogen storage alloy in the battery. This also extends the cycle life.

（iv）実施例３の電池ｃは、正極芯体において、最内端部の目付を最外端部の目付よりも高くしており、また、負極芯体において、最内端部の目付を最外端部の目付よりも高くしている。具体的には、正極芯体における最内端部の目付を４５０ｇ／ｃｍ2、最外端部の目付を３５０ｇ／ｃｍ2とし、負極芯体における最内端部の目付を３５０ｇ／ｃｍ2、最外端部の目付を２５０ｇ／ｃｍ2としている。この電池ｃの場合、充放電を２００サイクル繰り返した後、正極の単位容量比は、最外端部が９８、最内端部が９４であり、負極の単位容量比は、最外端部が９８、最内端部が９２であった。つまり、最内端部の正極活物質及び水素吸蔵合金の劣化が抑えられ、最内端部と最外端部とで、正極活物質及び水素吸蔵合金の劣化の進行の偏りの度合いが電池ｄよりも低減されている。これは、正極芯体及び負極芯体の最内端部の目付を高めたことにより、正極芯体及び負極芯体の最内端部の電気抵抗が低くなり、電池中心部の発熱を抑えることができたからである。このように、正極及び負極の最内端部と最外端部とで正極活物質及び水素吸蔵合金の劣化の偏りの度合いを小さくすると、電池内で、正極活物質及び水素吸蔵合金をより均等に近い状態で利用することができ電池のサイクル寿命も延びる。 (Iv) In the battery c of Example 3, the basis weight of the innermost end portion is higher than the basis weight of the outermost end portion in the positive electrode core body, and the basis weight of the innermost end portion is increased in the negative electrode core body. It is higher than the basis weight of the outermost end. Specifically, the basis weight of the innermost end in the positive electrode core is 450 g / cm 2 , the basis weight of the outermost end is 350 g / cm 2, and the basis weight of the innermost end in the negative electrode core is 350 g / cm 2 , The basis weight of the outermost end is 250 g / cm 2 . In the case of this battery c, after repeating 200 cycles of charge and discharge, the unit capacity ratio of the positive electrode is 98 at the outermost end and 94 at the innermost end, and the unit capacity ratio of the negative electrode is at the outermost end. 98, the innermost end was 92. That is, the deterioration of the positive electrode active material and the hydrogen storage alloy at the innermost end portion is suppressed, and the degree of progress of the deterioration of the positive electrode active material and the hydrogen storage alloy at the innermost end portion and the outermost end portion is determined by the battery d. Has been reduced. This increases the basis weight of the innermost ends of the positive electrode core and the negative electrode core, thereby lowering the electrical resistance of the innermost ends of the positive electrode core and the negative electrode core and suppressing the heat generation at the center of the battery. It was because it was made. Thus, when the degree of deterioration of the positive electrode active material and the hydrogen storage alloy is reduced at the innermost end and the outermost end of the positive electrode and the negative electrode, the positive electrode active material and the hydrogen storage alloy are more evenly distributed in the battery. It can be used in a state close to that, and the cycle life of the battery is also extended.

（v）比較例２の電池ｅは、正極及び負極の芯体として、最内端部の目付と最外端部の目付との間に差を設けていない、全体の目付が一様な芯体であって、比較例１の電池ｄの正極及び負極の芯体よりも目付が高い芯体を用いている。この電池ｅの場合、充放電を２００サイクル繰り返した後の正極及び負極の単位容量比は、最内端部及び最外端部ともに電池ｄのものよりも優れている。これは、芯体の目付が高くなったことにより、正極芯体及び負極芯体の電気抵抗が低くなり、電池における発熱を全体的に抑えることができ、正極活物質及び水素吸蔵合金の劣化を抑制できたためである。 (V) The battery e of Comparative Example 2 is a core having a uniform overall weight, with no difference between the weight of the innermost end and the weight of the outermost end, as the positive and negative electrode cores. A core body having a higher basis weight than that of the positive electrode and negative electrode cores of the battery d of Comparative Example 1 is used. In the case of this battery e, the unit capacity ratio between the positive electrode and the negative electrode after 200 cycles of charging / discharging is superior to that of the battery d at both the innermost end and the outermost end. This is because the electrical resistance of the positive electrode core body and the negative electrode core body is lowered due to the increased basis weight of the core body, and heat generation in the battery can be suppressed as a whole, and the deterioration of the positive electrode active material and the hydrogen storage alloy can be prevented. This is because it could be suppressed.

しかしながら、電池ｅでは、電池ｄよりもサイクル寿命特性が低下しているが、これは、漏液したためでる。電池に対しサイクル試験を行うと、電池内のアルカリ電解液の水成分の一部がガス化する。このガスは、電池内の空間に予備的に保持される。しかしながら、正極芯体及び負極芯体の目付を高くした場合、電池内の空間がより小さくなるので、かかるガスを保持しておく空間の大きさが十分ではなくなる。このため、電池内圧が上昇し易くなり安全弁が作動し、漏液したと考えられる。その結果、電解液量が減りサイクル寿命が短くなった。   However, in the battery e, the cycle life characteristics are lower than in the battery d, but this is because the liquid leaked. When the cycle test is performed on the battery, a part of the water component of the alkaline electrolyte in the battery is gasified. This gas is preliminarily held in a space in the battery. However, when the basis weight of the positive electrode core and the negative electrode core is increased, the space in the battery becomes smaller, so that the size of the space for holding such gas is not sufficient. For this reason, it is considered that the battery internal pressure easily rises, the safety valve is activated, and the liquid leaks. As a result, the amount of the electrolyte decreased and the cycle life was shortened.

（vi）以上より、電極芯体において、最内端部の目付を最外端部の目付よりも高くすることは、電池中心部の電池反応材料（正極活物質又は水素吸蔵合金）の劣化を抑え、サイクル寿命の向上を図ることができるといった優れた効果を奏するといえる。このような効果は、実施例１及び２から明らかなように、正極芯体及び負極芯体のうちのどちらか一方についてのみ、最内端部の目付を最外端部の目付よりも高くする態様としても得ることができる。そして、実施例３から明らかなように、正極芯体及び負極芯体の両方について最内端部の目付を最外端部の目付よりも高くする態様とすると、より優れた効果を得ることができる。 (Vi) From the above, in the electrode core body, making the basis weight of the innermost end part higher than the basis weight of the outermost end part causes deterioration of the battery reaction material (positive electrode active material or hydrogen storage alloy) in the battery center part. It can be said that there is an excellent effect of suppressing the cycle life and improving the cycle life. As is apparent from Examples 1 and 2, such an effect is achieved by making the basis weight of the innermost end portion higher than the basis weight of the outermost end portion of only one of the positive electrode core body and the negative electrode core body. It can also be obtained as an embodiment. As is apparent from Example 3, when both the positive electrode core and the negative electrode core have a basis weight at the innermost end higher than that of the outermost end, a more excellent effect can be obtained. it can.

また、比較例２から明らかなように、正極芯体及び負極芯体の目付を、最内周部と最外周部とで差を付けずに一様に高めただけでは、容量は上がるもののサイクル寿命が短くなる不具合が発生する。このことからも、正極芯体及び負極芯体において、最内端部の目付を最外端部の目付よりも高くすることが有効であるといえる。   Further, as is clear from Comparative Example 2, the capacity increases only by increasing the basis weight of the positive electrode core and the negative electrode core uniformly without making a difference between the innermost and outermost peripheral parts. A problem occurs that shortens the service life. From this, it can be said that it is effective to make the basis weight of the innermost end portion higher than the basis weight of the outermost end portion in the positive electrode core body and the negative electrode core body.

なお、本発明は、上記した実施形態及び実施例に限定されるものではなく、種々の変形が可能であり、例えば、ニッケル水素蓄電池の他、ニッケルカドミウム蓄電池等の他のアルカリ蓄電池にも適用することができる。   In addition, this invention is not limited to above-described embodiment and Example, A various deformation | transformation is possible, For example, it applies to other alkaline storage batteries, such as a nickel cadmium storage battery other than a nickel hydride storage battery. be able to.

２ ニッケル水素蓄電池
１０ 外装缶
１２ 絶縁パッキン
１４ 蓋板
２０ 正極端子
２２ 電極群
２４ 正極
２６ 負極
２８ セパレータ
３６ 正極芯体
６０ 負極芯体
５２，６６ 最内端部
５４，６８ 最外端部 2 Nickel Metal Hydride Battery 10 Exterior Can 12 Insulating Packing 14 Lid Plate 20 Positive Electrode 22 Electrode Group 24 Positive Electrode 26 Negative Electrode 28 Separator 36 Positive Electrode Core 60 Negative Electrode Core 52, 66 Innermost Ends 54, 68 Outermost End

Claims (2)

容器と、前記容器内にアルカリ電解液とともに密閉状態で収容された電極群とを備え、
前記電極群は、互いに異なる極性を示す第１電極と第２電極とがセパレータを間に挟んだ状態で巻回されてなり、
前記第１電極は、帯状の金属多孔体からなる第１電極芯体と、前記第１電極芯体に保持されており、電池反応に関与する第１電池反応材料とを含み、
前記第１電極芯体は、前記電極群の外周部に位置付けられる第１外周領域と、前記電極群の外周部より内側に位置付けられ、前記第１外周領域より目付が高い領域と、を含むことを特徴とするアルカリ蓄電池。 A container, and an electrode group housed in an airtight state together with an alkaline electrolyte in the container,
The electrode group is wound with a first electrode and a second electrode having different polarities sandwiched between separators,
The first electrode includes a first electrode core made of a band-shaped metal porous body, and a first battery reaction material that is held by the first electrode core and is involved in a battery reaction,
The first electrode core includes a first outer peripheral region positioned on the outer peripheral portion of the electrode group, and a region positioned on the inner side of the outer peripheral portion of the electrode group and having a higher basis weight than the first outer peripheral region. An alkaline storage battery. 前記第２電極は、帯状の金属多孔体からなる第２電極芯体と、前記第２電極芯体に保持されており、電池反応に関与する第２電池反応材料とを含み、
前記第２電極芯体は、前記電極群の外周部に位置付けられる第２外周領域と、前記電極群の外周部より内側に位置付けられ、前記第２外周領域より目付が高い領域と、を含むことを特徴とする請求項１に記載のアルカリ蓄電池。 The second electrode includes a second electrode core made of a band-shaped metal porous body, and a second battery reaction material that is held by the second electrode core and participates in a battery reaction,
The second electrode core includes a second outer peripheral region positioned on the outer peripheral portion of the electrode group, and a region positioned inside the outer peripheral portion of the electrode group and having a higher basis weight than the second outer peripheral region. The alkaline storage battery according to claim 1.
JP2013037298A 2013-02-27 2013-02-27 Alkali storage battery Pending JP2014165123A (en)

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