WO2018116574A1

WO2018116574A1 - Alkaline storage battery

Info

Publication number: WO2018116574A1
Application number: PCT/JP2017/035901
Authority: WO
Inventors: 徹川勝; 大山　秀明; 後藤　浩之; 宏樹竹島
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2016-12-19
Filing date: 2017-10-03
Publication date: 2018-06-28

Abstract

This alkaline storage battery is provided with: a battery case; an electrode group; a positive electrode collector plate; an alkaline electrolyte solution; and a cover plate. The electrode group comprises a positive electrode, a negative electrode and a separator that is interposed between the positive electrode and the negative electrode; and the positive electrode comprises a positive electrode core material and a positive electrode active material that is supported by the positive electrode core material. The positive electrode collector plate is connected to an end part of the positive electrode core material, while being connected to the cover plate via a lead. The positive electrode collector plate comprises: a plate that is formed from iron or an iron alloy; and a plating film that covers the plate and contains nickel. The lead is configured from a nickel metal. The negative electrode comprises a negative electrode core material and a negative electrode active material that is supported by the negative electrode core material; and the negative electrode active material contains a hydrogen storage alloy that has a hydrogen equilibrium pressure of from 0.5 atm to 3.5 atm (inclusive) at 45°C. The alkaline electrolyte solution contains at least NaOH; the alkali concentration is 6.5 mol/L or less; and the Na ion concentration is 3 mol/L or more.

Description

Alkaline storage battery

The present invention relates to an alkaline storage battery using a negative electrode active material containing a hydrogen storage alloy.

Alkaline storage batteries such as nickel metal hydride storage batteries are expected to be used in various applications due to their high capacity. In particular, in recent years, the use of alkaline storage batteries is also envisaged in applications such as the main power source of electronic devices such as portable devices or backup power sources. In such applications, it has been studied to use an alkaline storage battery as an auxiliary power source for a charged battery or as an emergency power source during a disaster. In these applications, the alkaline storage battery is required to have characteristics such as high output and durability.

Nickel metal hydride storage batteries use a hydrogen storage alloy as the negative electrode active material.

Patent Document 1 proposes using a hydrogen storage alloy having a storage hydrogen equilibrium pressure of 0.03 MPa to 0.17 MPa for a nickel metal hydride storage battery from the viewpoint of reducing self-discharge. In Patent Document 1, a 30% by mass potassium hydroxide aqueous solution is used as the electrolytic solution.

In order to increase the output, it is also important to reduce the internal resistance of the battery.

In Patent Document 2, it is proposed to increase the bonding area between the electrode group including the electrode and the current collector plate connected to the electrode group, thereby increasing the bonding strength and reducing the internal resistance to increase the output. .

JP 2009-176712 A JP 2006-221890 A

In an alkaline storage battery, metal components in the battery may be corroded or the hydrogen storage alloy may be deteriorated by the action of an alkaline electrolyte or oxygen generated in the battery. When the internal resistance increases due to corrosion of the battery components, the output of the battery (particularly, the low-temperature output characteristics) decreases. Further, when the constituent elements are corroded or the hydrogen storage alloy is deteriorated, durability (particularly, high temperature durability) is lowered. In applications such as a backup power source and an emergency power source, it is necessary to fully demonstrate the performance of the battery even when exposed to a low temperature environment or a high temperature environment.

One aspect of the present disclosure includes a bottomed battery case having an opening,
Housed in the battery case, an electrode group, a positive current collector electrically connected to the electrode group, and an alkaline electrolyte,
A sealing plate that seals the opening and is electrically connected to the positive current collector;
The electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
The positive electrode includes a positive electrode core material and a positive electrode active material supported on the positive electrode core material,
The positive current collector plate is connected to the end portion of the positive electrode core material, and is connected to the sealing plate via a lead,
The positive electrode current collector plate includes a plate formed of iron or an iron alloy, and a plating film that covers the plate and contains nickel,
The lead is made of nickel metal,
The negative electrode comprises a negative electrode core material and a negative electrode active material carried on the negative electrode core material,
The negative electrode active material includes a hydrogen storage alloy having a hydrogen equilibrium pressure at 45 ° C. of 0.5 atm to 3.5 atm,
The alkaline electrolyte contains at least NaOH,
The alkaline electrolyte has an alkaline concentration of 6.5 mol / L or less, and a sodium ion concentration of 3 mol / L or more.

According to the above aspect of the present disclosure, an alkaline storage battery having high low-temperature output characteristics and excellent high-temperature durability can be provided.

It is a longitudinal section showing an alkaline storage battery (nickel metal hydride storage battery) concerning one embodiment of the present invention roughly.

An alkaline storage battery according to an embodiment of the present invention includes a bottomed battery case having an opening, an electrode group housed in the battery case, a positive electrode current collector electrically connected to the electrode group, and alkaline electrolysis A liquid and a sealing plate that seals the opening and is electrically connected to the positive electrode current collector plate are provided. The electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode core material and a positive electrode active material supported on the positive electrode core material. The positive electrode current collector plate is connected to the end portion of the positive electrode core member and is connected to the sealing plate via a lead. The positive electrode current collector plate includes a plate formed of iron or an iron alloy, and a plating film that covers the plate and contains nickel. The lead is made of nickel metal. The negative electrode includes a negative electrode core material and a negative electrode active material supported on the negative electrode core material. The negative electrode active material includes a hydrogen storage alloy having a hydrogen equilibrium pressure at 45 ° C. of 0.5 atm to 3.5 atm. The alkaline electrolyte contains at least NaOH. In the alkaline electrolyte, the alkali concentration is 6.5 mol / L or less, and the sodium ion concentration is 3 mol / L or more.

In the alkaline storage battery, a positive electrode current collector plate or a negative electrode current collector plate may be provided at the end of the electrode group from the viewpoint of enhancing the current collecting performance from the electrode group. The positive electrode current collector plate and the negative electrode current collector plate are electrically connected to a positive electrode and a negative electrode (particularly a core material) included in the electrode group, and are also electrically connected to a battery case and a sealing plate.

From the viewpoint of obtaining high welding strength, the positive electrode current collector plate includes a plate formed of iron or an iron alloy and a plating film containing nickel covering the plate. The positive electrode current collector plate is welded to the end portion of the positive electrode core member, and is welded to the end portion of the lead connected to the sealing plate. The positive electrode core material usually contains nickel. These welding locations (connection locations) are susceptible to corrosion by the alkaline electrolyte. In an alkaline storage battery, oxygen is generated from the electrolyte and the electrode by charging and discharging, and this oxygen reacts with hydrogen generated from the negative electrode during charging and is reduced to water. If the rate of reduction to water is slow and oxygen continues to exist in a large amount in the battery, corrosion at the connection point between the positive electrode current collector plate and the positive electrode core material and leads will be further facilitated, and a hydrogen storage alloy Is oxidized and easily deteriorates. When the connection is corroded, the resistance increases and the output decreases. If the connection location is corroded or the hydrogen storage alloy is deteriorated, the battery life is shortened and sufficient durability performance cannot be obtained. The decrease in the output of the battery is particularly noticeable at low temperatures, and the deterioration of the hydrogen storage alloy is particularly noticeable at high temperatures. In addition, in applications such as backup power supplies and emergency power supplies, alkaline storage batteries are trickle charged for a long period of time. In particular, a large amount of oxygen is generated, and the hydrogen storage alloy is easily oxidized, and deterioration is likely to proceed. Become. Oxygen generation is particularly noticeable when trickle charging is performed at high temperatures. In these applications, high durability is required even when exposed to a low temperature environment or a high temperature environment, and a high output is required when operating the battery.

In this embodiment, in an alkaline electrolyte containing at least NaOH, the sodium ion concentration is set to 3 mol / L or more, and the alkali concentration is set to 6.5 mol / L or less. Thereby, the corrosion of the connection location with the positive electrode and sealing plate of a positive electrode current collecting plate can be suppressed. Further, by using a negative electrode active material containing a hydrogen storage alloy having a hydrogen equilibrium pressure of 0.5 atm or more and 3.5 atm or less, hydrogen is easily generated from the hydrogen storage alloy. As a result, oxygen in the battery is quickly consumed, and corrosion of the connection portion between the positive electrode current collector plate and the positive electrode and the sealing plate is suppressed, and deterioration of the hydrogen storage alloy is suppressed. With these actions, the low temperature output characteristics and high temperature durability of the alkaline storage battery can be enhanced.

In general, it is considered that when the hydrogen equilibrium pressure of the hydrogen storage alloy is increased, the internal pressure is likely to increase during overcharge. The hydrogen equilibrium pressure (45 ° C.) of the hydrogen storage alloy used as the negative electrode active material in an alkaline storage battery is, for example, As in Patent Document 1, it is often adjusted to about 0.2 MPa or less. However, when overcharging is performed at a low current value as in trickle charging, an increase in internal pressure is hardly a problem.

In this specification, the hydrogen equilibrium pressure is a pressure (equilibrium dissociation pressure) when the hydrogen storage alloy releases hydrogen at 45 ° C. The hydrogen equilibrium pressure is a value measured under a condition where the atomic molar ratio of hydrogen to the metal element M (H / M ratio) in the hydrogen storage alloy is 0.4. For example, a pressure-composition isotherm is created according to JIS H 7201: 2007, and based on this isotherm, the hydrogen release pressure (hydrogen equilibrium pressure) when the H / M ratio is 0.4 at 45 ° C. Can be requested.

In general, KOH is frequently used as an alkali in an alkaline electrolyte. However, the potassium ion concentration in the alkaline electrolyte is 1.5 mol / L from the viewpoint of further enhancing the effect of suppressing corrosion at the connection point between the positive electrode current collector plate and the positive electrode or the sealing plate, and improving the high temperature charging efficiency. Or less, more preferably 1 mol / L or less. It is also preferable when the alkaline electrolyte does not substantially contain KOH (for example, when the potassium ion concentration in the alkaline electrolyte is 0.01 mol / L or less).

Hereinafter, the alkaline storage battery according to this embodiment will be described in more detail.

The alkaline storage battery has a bottomed battery case having an opening, an electrode group, a positive electrode current collector electrically connected to the electrode group, and an alkaline electrolyte, and the opening sealed in the battery case. And a sealing plate electrically connected to the positive electrode current collector plate. The electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode core material and a positive electrode active material supported on the positive electrode core material. The positive electrode current collector plate is connected to the end portion of the positive electrode core member, and is connected to the sealing plate via a lead.

The configuration of the alkaline storage battery will be described below with reference to FIG. FIG. 1 is a longitudinal sectional view schematically showing the structure of an alkaline storage battery according to an embodiment of the present invention. The alkaline storage battery includes a bottomed cylindrical battery case 1, an electrode group 2 accommodated in the battery case 1, and an alkaline electrolyte (not shown). In the electrode group 2, the positive electrode 3, the negative electrode 4, and the separator 5 interposed therebetween are wound in a spiral shape. The positive electrode 3 includes a strip-like porous positive electrode core material and a positive electrode active material filled in the positive electrode core material. The negative electrode 4 includes a strip-like porous negative electrode core material and a negative electrode active material filled in the negative electrode core material. A sealing plate 7 is disposed in the opening of the battery case 1 via an insulating gasket 6, and the opening end of the battery case 1 is caulked inward to seal the alkaline storage battery.

The alkaline storage battery further includes a negative electrode current collector plate 8 and a positive electrode current collector plate 9. The electrode group 2 is disposed on a disc-shaped negative electrode current collector plate 8 disposed on the inner bottom surface of the battery case 1, and the end surface of the electrode group 2 on the opening side of the battery case 1 is arranged in a plane direction. A disc-shaped positive current collector plate 9 having a hole in the center is disposed. On the opening side of the battery case 1, the end 3 a of the positive electrode core material in the positive electrode 3 protrudes from the end of the electrode group 2 than the ends of the negative electrode 4 and the separator 5. The protruding end 3a is welded to and electrically connected to the positive electrode current collector plate 9. The positive electrode current collector plate 9 and the bottom surface of the sealing plate 7 are connected via a lead (positive electrode lead) 10, whereby the positive electrode current collector plate 9 is electrically connected to the sealing plate 7 also serving as a positive electrode terminal. Has been. On the bottom side of the battery case 1, the end 4 a of the negative electrode core member in the negative electrode 4 protrudes from the end of the electrode group 2 than the ends of the positive electrode 3 and the separator 5. The protruding end 4a is connected to and electrically connected to the negative electrode current collector plate 8 by welding. The negative electrode current collector plate 8 is connected to the inner bottom surface of the battery case 1 serving also as a negative electrode terminal by welding, and is thereby electrically connected to the battery case 1.

In such an alkaline storage battery, the electrode group 2 is accommodated in the battery case 1, an alkaline electrolyte is injected, a sealing plate 7 is disposed in the opening of the battery case 1 via the insulating gasket 6, and the battery case It can be obtained by caulking and sealing the open end of one. At this time, the negative electrode 4 of the electrode group 2 and the battery case 1 are electrically connected via the negative electrode current collector plate 8 disposed between the electrode group 2 and the inner bottom surface of the battery case 1. Further, the positive electrode 3 of the electrode group 2 and the sealing plate 7 are electrically connected via the positive electrode current collector plate 9 and the positive electrode lead 10. The positive electrode current collector plate 9 may be electrically connected to the sealing plate 7 after being electrically connected to the positive electrode 3. The negative electrode current collector plate 8 may be electrically connected to the battery case 1 after being electrically connected to the negative electrode 4. The order of connection is not limited to these cases, and may be determined as appropriate in consideration of ease of work.

In the present embodiment, the positive electrode current collector plate 9 includes a plate formed of iron or an iron alloy and a plating film that covers the plate, and the plating film contains nickel. The positive electrode lead 10 is made of nickel metal. The positive electrode core material usually contains nickel. For the negative electrode active material layer of the negative electrode 4, a negative electrode active material containing a hydrogen storage alloy having a hydrogen equilibrium pressure at 45 ° C. of 0.5 atm or more and 3.5 atm or less is used, and an alkaline electrolyte containing at least NaOH is used. The alkali concentration in the alkaline electrolyte is 6.5 mol / L or less, and the sodium ion concentration is 3 mol / L or more.

Hereinafter, the components of the alkaline storage battery will be described more specifically.

(Electrode group)
The electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The electrode group may be a wound electrode group formed by winding a positive electrode and a negative electrode with a separator interposed therebetween, and a separator is interposed between the positive electrode and the negative electrode. A stacked electrode group in which a plurality of layers are stacked in an intervening state may be used.

(Positive electrode)
The positive electrode includes a positive electrode core material and a positive electrode active material (or a positive electrode active material layer) carried on the positive electrode core material. The positive electrode may be either a paste type positive electrode or a sintered type positive electrode. The paste type positive electrode can be formed, for example, by attaching a positive electrode paste containing at least a positive electrode active material to a positive electrode core material. More specifically, the positive electrode can be formed by applying or filling a positive electrode paste on a positive electrode core material, then drying and compressing (or rolling). The sintered positive electrode is obtained, for example, by impregnating a perforated steel sheet (positive electrode core material) in which nickel particles are sintered with a nickel nitrate aqueous solution or the like to neutralize and depositing nickel hydroxide as an active material. .

As the positive electrode core material, known materials can be used, and examples thereof include a nickel foam, and a porous substrate formed of nickel or a nickel alloy such as a sintered nickel plate.

As the positive electrode active material, for example, a nickel compound such as nickel hydroxide and / or nickel oxyhydroxide is used.

The positive electrode paste usually contains a dispersion medium, and a known component used for the positive electrode, such as a conductive agent, a binder, and / or a thickener, may be added as necessary.

As the dispersion medium, water, an organic medium, or a mixed medium in which two or more media selected from these are mixed can be used.

The conductive agent is not particularly limited as long as it is a material having electronic conductivity. For example, graphite such as natural graphite (flaky graphite etc.), artificial graphite and expanded graphite; carbon black such as acetylene black and ketjen black; conductive fibers such as carbon fiber and metal fiber; metal particles such as copper powder An organic conductive material such as a polyphenylene derivative can be exemplified. These conductive agents may be used alone or in combination of two or more. As the conductive agent, conductive cobalt oxide such as cobalt hydroxide and / or γ-type cobalt oxyhydroxide may be used.

The amount of the conductive agent is, for example, from 0.01 parts by mass to 20 parts by mass, and preferably from 0.1 parts by mass to 10 parts by mass with respect to 100 parts by mass of the active material.

The conductive agent may be added to the positive electrode paste and mixed with other components. Further, the surface of the active material particles may be previously coated with a conductive agent. The conductive agent is coated mechanically by a known method, for example, by coating the surface of the active material particles with a conductive agent, attaching a dispersion containing the conductive agent to dry, and / or a mechanochemical method. It can be carried out by coating.

As the binder, resin materials, for example, rubber-like materials such as styrene-butadiene copolymer rubber; polyolefin resins such as polyethylene and polypropylene; fluororesins such as polyvinylidene fluoride; ethylene-acrylic acid copolymers, ethylene-acrylic An acrylic resin such as an acid methyl copolymer and its Na ion crosslinked body can be exemplified. These binders can be used individually by 1 type or in combination of 2 or more types.

The amount of the binder is, for example, 7 parts by mass or less with respect to 100 parts by mass of the active material, and may be 0.01 parts by mass or more and 5 parts by mass or less.

Examples of the thickener include carboxymethyl cellulose and modified products thereof (including salts such as Na salt and ammonium salt), cellulose derivatives such as methyl cellulose; saponified polymers having vinyl acetate units such as polyvinyl alcohol; polyethylene oxide, etc. And polyalkylene oxide. These thickeners can be used singly or in combination of two or more.

The amount of the thickener is, for example, 5 parts by mass or less, and may be 0.01 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the active material.

Also, the positive electrode paste may contain, as an additive, a metal compound such as zinc oxide and / or zinc hydroxide (oxide and / or hydroxide).

(Negative electrode)
The negative electrode includes a negative electrode core material and a negative electrode active material supported on the negative electrode core material.

The negative electrode active material includes a hydrogen storage alloy having a hydrogen equilibrium pressure at 45 ° C. of 0.5 atm or more (≈0.05 MPa or more) and 3.5 atm or less (≈0.35 MPa or more). When the hydrogen equilibrium pressure at 45 ° C. is less than 0.5 atm, the low-temperature output characteristics are degraded, and when it exceeds 3.5 atm, the high-temperature durability is degraded. From the viewpoint of obtaining higher low-temperature output characteristics, the hydrogen equilibrium pressure at 45 ° C. is preferably 0.6 atm or more (≈0.06 MPa or more) and 3.5 atm or less.

The hydrogen storage alloy has a metallic bond and includes a combination of an element having a high hydrogen affinity and an element having a low hydrogen affinity. An element with high hydrogen affinity is likely to be located at the A site, and an element with low hydrogen affinity is likely to be located at the B site. The crystal structure of the hydrogen storage alloy is not particularly limited, for example, AB ₂ type (e.g., MgCu ₂ type), AB ₃ type (e.g., CeNi ₃ type), AB ₅ type (e.g., CaCu ₅ type), A ₂ B Any of ₇ types (for example, Ce ₂ Ni ₇ type) may be used. A plurality of hydrogen storage alloys having different crystal structures may be used in combination. The crystalline structure of the hydrogen storage alloy, in addition to the above, is also known _19-A ₅ B. The hydrogen storage alloy having the AB ₅ type crystal structure has a higher value of the enthalpy of the hydrogen dissociation reaction than the other crystal structures, particularly the hydrogen storage alloy having the AB ₃ type or A ₅ B ₁₉ type crystal structure. . This suppresses the collapse of the alloy crystal structure, which is one of the deteriorations of battery characteristics at high temperatures. Therefore, in the case of using a hydrogen storage alloy having a crystal structure of the ₅ type AB, it is particularly advantageous since it is possible to ensure the high temperature durability. The ratio of the hydrogen storage alloy having AB ₅ type crystal structure occupying in the negative electrode active material is preferably 80 mass% or more, preferably 90 mass% or more.

Depending on the type of crystal structure, the elements located at the A site include Group 2 to 4 elements of the periodic table, and other elements are likely to be located at the B site. As the element located at the A site, for example, at least one selected from the group consisting of a lanthanoid element, an actinoid element, an alkaline earth metal element, Sc, Y, Ti, Zr, and Hf is preferable. From the viewpoint of easily obtaining a high capacity, the element located at the A site preferably contains at least a lanthanoid element, and includes lanthanoid elements, actinoid elements, alkaline earth metal elements, Sc, Y, Ti, Zr, and Hf. And at least one selected from the group consisting of:

Lanthanoid elements include La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Examples of actinoid elements include Ac, Th, Pa, Np, and the like. Examples of the alkaline earth metal element include Mg, Ca, Sr, Ba, and the like. From the viewpoint of easily ensuring high high temperature durability, the ratio of an alkaline earth metal element such as Mg to the element located at the A site is preferably small, and more preferably, for example, 1 mol% or less. In particular, (not including or Mg) ratio is small Mg hydrogen storage alloy having AB ₅ type crystal structure, an alkali electrolyte solution containing sodium ion, a high corrosion resistance. Therefore, such a hydrogen storage alloy is particularly suitable for use in combination with an alkaline electrolyte having a high sodium ion concentration, like the alkaline storage battery according to this embodiment.

From the viewpoint of easily increasing the hydrogen storage amount and forming a hydrogen-rich state on the surface of the hydrogen storage alloy, the element located at the A site preferably contains La and / or Ce among lanthanoid elements, and at least La is contained. It is further preferable to include it. The hydrogen equilibrium pressure can be increased by increasing the ratio of La and Ce. The ratio of La in the elements located at the A site is preferably 50% by mass or more, and may be 55% by mass or more or 60% by mass or more. When the La ratio is within such a range, the effect of promoting the reduction reaction of oxygen by hydrogen is further enhanced. Therefore, the effect of suppressing the oxidation of the hydrogen storage alloy can be further enhanced, and the effect of suppressing the corrosion of the connection portion between the positive electrode current collector plate and the positive electrode core material or the positive electrode lead can be further enhanced. The hydrogen storage alloy may contain Group 4 elements of the periodic table such as Zr in addition to La and / or Ce.

The element located at the B site is selected from the group consisting of transition metal elements of Group 5 to Group 11 of the periodic table, Group 12 elements, and elements of Groups 3 to 14 of Groups 3 to 14 At least one of the above is preferred. Elements located at the B site include transition metal elements such as V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Pd, Cu, and Ag; Group 12 elements such as Zn; Al Group 13 elements such as Si, Ge and Sn; and Group 14 elements such as Si, Ge and Sn are preferred. Among them, the element located at the B site is composed of V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, Al, Ga, In, Si, Ge, and Sn. It is preferably at least one selected from the group. The element located at the B site preferably contains Mn, but from the viewpoint of increasing the hydrogen equilibrium pressure, a smaller Mn ratio is preferred. The hydrogen storage alloy preferably contains Mn, Co, and Ni. When the hydrogen storage alloy contains Mn and Co, even if the crystal of the hydrogen storage alloy expands and contracts, the crystal structure can be prevented from being disturbed, and the pulverization of the hydrogen storage alloy particles can be suppressed. In addition, when the hydrogen storage alloy contains Ni, high capacity can be secured and low temperature characteristics can be improved. From the viewpoint of further increasing the capacity and low temperature characteristics, it is preferable that the Ni ratio is large. However, as the Ni ratio increases, the displacement of the crystal lattice position of the atoms accompanying expansion and contraction becomes larger, resulting in fine powder due to structural destruction. It tends to occur more easily. When the hydrogen storage alloy contains Mn and Co in addition to Ni, the effect of suppressing pulverization by these elements will be more effectively exhibited.

Further, from the viewpoint of obtaining high durability, the hydrogen storage alloy preferably contains Al, and more preferably contains Al and Mn. When Al and Mn are contained, the pulverization of the hydrogen storage alloy particles can be suppressed by the synergistic effect of these elements. The molar ratio of Al to the element located at the A site is preferably 0.25 or more, more preferably more than 0.3. When the molar ratio of Al is within such a range, durability can be further enhanced. From the viewpoint of easily obtaining a synergistic effect with Mn, the molar ratio of Al to the element located at the A site is preferably 0.5 or less.

Specific examples of the hydrogen storage alloy include La _0.849 Ce _0.151 Ni _4.304 Co _0.418 Mn _0.240 Al _0.310 , La _0.836 Ce _0.142 Ni _4.456 Co _0.147 Mn _0.252 Al _0.401 Zr _0.022 , La _0.625 Ce _0.375 Ni _4.287 Co _0.448 Mn _0.099 Al _0.304, etc. Is mentioned.

One kind of hydrogen storage alloy may be used alone, or two or more kinds may be used in combination.

The hydrogen equilibrium pressure can be adjusted, for example, by adjusting the type and / or ratio of the constituent elements of the hydrogen storage alloy. For example, as described above, the hydrogen equilibrium pressure can be increased by using a large amount of La and Ce or using a small amount of Mn, but the present invention is not limited to these cases.

As the hydrogen storage alloy, a commercially available one may be used, or one manufactured by a known manufacturing method may be used. The hydrogen storage alloy is, for example, a process A in which an alloy is formed from a single element constituting the hydrogen storage alloy, a process B in which the alloy obtained in the process A is granulated, and a granular material obtained in the process B is activated. It can be obtained through Step C, etc. Each step can be performed according to a known method.

As the negative electrode core material, known materials can be used, and examples thereof include a porous or non-porous substrate formed of an iron alloy (such as stainless steel), nickel or an alloy thereof. The negative electrode core material may be subjected to a plating treatment such as nickel plating. When the support is a porous substrate, the active material may be filled in the pores of the support.

The negative electrode can be formed by attaching a negative electrode paste containing at least a negative electrode active material to the negative electrode core material. Specifically, the negative electrode can be formed by applying or filling a negative electrode paste on a support, drying, and compressing in the thickness direction according to the case of the positive electrode.

The negative electrode paste may contain known components used for the negative electrode, for example, a conductive agent, a binder, a thickener, and the like, if necessary. The dispersion medium, conductive agent, binder and thickener, and their amounts can be selected from the same or range as in the case of the positive electrode paste. As the conductive agent, artificial graphite, ketjen black, carbon fiber and the like are preferable.

The negative electrode is electrically connected to the battery case, but the positive electrode and the battery case may be electrically connected via a lead. However, as in the case of the positive electrode, the negative electrode It is preferable to electrically connect the battery case. By using the negative electrode current collector plate, the output is easily increased. The negative electrode current collector plate will be described later.

(Separator)
As a separator, the well-known thing used for an alkaline storage battery, for example, a microporous film, a nonwoven fabric, these laminated bodies, etc. can be used. Examples of the material for the microporous membrane and the nonwoven fabric include polyolefin resins such as polyethylene and polypropylene; fluororesins; polyamide resins and the like. From the viewpoint of high decomposition resistance to an alkaline electrolyte, it is preferable to use a separator made of polyolefin resin.

It is preferable to introduce a hydrophilic group into a separator formed of a highly hydrophobic material such as a polyolefin resin by a hydrophilic treatment. Examples of the hydrophilic treatment include corona discharge treatment, plasma treatment, and sulfonation treatment. Among these, it is particularly preferable to use a sulfonated separator, that is, a separator having a sulfonic acid group (such as a polyolefin separator).

(Positive electrode current collector)
The positive electrode current collector plate is connected to the end portion of the positive electrode core material of the positive electrode included in the electrode group, and is thereby electrically connected to the electrode group (specifically, the positive electrode). At the end of the electrode group on the positive electrode current collector plate side, the end of the positive electrode core material (specifically, the end in the width direction of the core material) protrudes beyond the end of the separator or negative electrode. The positive electrode current collector plate (specifically, the main surface on the electrode group side of the positive electrode current collector plate) is connected to the end of the positive electrode core material. A high current collecting property can be ensured by directly connecting the end of the positive electrode core member and the positive electrode current collector plate. Moreover, the positive electrode current collector plate is connected to the sealing plate via a lead. Thereby, the positive electrode current collector plate is electrically connected to the sealing plate.

The positive electrode current collector plate includes a plate formed of iron or an iron alloy, and a plating film that covers the plate and contains nickel. By using such a positive electrode current collector plate, it is possible to ensure high welding strength with a positive electrode core material formed of a nickel-containing material such as nickel or a nickel alloy, and nickel for connecting to a sealing plate High weld strength with a lead made of metal can be secured. However, since iron or iron alloy is contained in the plate, the iron element is diffused by welding at the connection point between the positive electrode current collector plate and the positive electrode core material or the lead (the crack of the plating film containing nickel). Is likely to be corroded by the alkaline electrolyte. In the present embodiment, the alkali concentration and sodium ion concentration in the alkaline electrolyte are controlled, and the hydrogen equilibrium pressure of the hydrogen storage alloy of the negative electrode active material is controlled, so that the positive electrode current collector plate, the positive electrode core material, and the lead Corrosion at the connection point can be suppressed.

¡Stainless steel can be used as the iron alloy that composes the plate. The nickel plating may be either electroless plating or electrolytic plating. The plating film preferably covers the entire surface of the positive electrode current collector plate.

The thickness of the positive electrode current collector plate is, for example, 0.2 mm or more and 0.5 mm or less.

The shape of the positive electrode current collector plate is selected according to the shape of the battery. For example, a cylindrical battery has a disk shape as shown in FIG. 1, and a rectangular battery has a square (or a shape close to a square) plate shape. The positive electrode current collector plate usually has a hole in the center in the surface direction in order to insert a welding electrode rod when the negative electrode current collector plate (or the negative electrode) is connected to the inner bottom surface of the battery case.

(Positive lead)
Leads connected to both the positive electrode current collector plate and the sealing plate (hereinafter also referred to as positive electrode leads) are made of nickel metal. Therefore, corrosion to the alkaline electrolyte is suppressed, and an increase in resistance due to corrosion is suppressed, so that a high output can be secured. Moreover, it is easy to increase the bonding strength with the nickel-plated positive electrode current collector plate.

The nickel metal constituting the positive electrode lead may contain impurities other than nickel. The content of impurities in the nickel metal is preferably smaller, for example, 1% by mass or less, and more preferably 0.5% by mass or less.

From the viewpoint of easily obtaining a high output, it is preferable that the positive electrode lead is connected to the positive electrode current collector plate and the sealing plate using a tab-like lead that can easily obtain a larger cross-sectional area than the lead wire. The width of the tab-like lead is determined according to the battery size. The thickness of the tab-like lead is also selected according to the battery size, and is, for example, not less than 0.3 mm and not more than 0.6 mm.

(Negative electrode current collector plate)
When the alkaline storage battery includes a negative electrode current collector plate, the negative electrode current collector plate may be any material as long as it can electrically connect the negative electrode and the battery case, and known materials and shapes can be employed. As in the case of the positive electrode current collector plate, a negative electrode current collector plate provided with a plate formed of iron or an iron alloy, and a plating film covering the plate and containing nickel may be used. For the negative electrode current collector plate, the description of the positive electrode current collector plate can be referred to. In order to weld the negative electrode current collector plate and the inner bottom surface of the battery case, it is desirable that the negative electrode current collector plate has no hole in the center portion in the surface direction.

The negative electrode current collector plate is preferably disposed at the bottom of the battery case, and the electrode group is disposed on the negative electrode current collector plate. The negative electrode current collector plate may be electrically connected to the inner bottom surface of the battery case, for example. The negative electrode current collector plate and the battery case may be connected via a lead (negative electrode lead), but in many cases, they are directly connected by welding.

The negative electrode current collector plate may be electrically connected to the negative electrode, and an exposed portion of the negative electrode core material may be provided on the negative electrode, and the exposed portion and the negative electrode current collector plate may be connected via a lead. From the viewpoint of easily obtaining a high output, the negative electrode current collector plate is preferably connected to the end of the negative electrode core material in the same manner as the positive electrode current collector plate. From the viewpoint of suppressing internal short circuit, the end of the negative electrode core material (specifically, the end in the width direction of the negative electrode core material) is the end of the separator or positive electrode at the end of the electrode group on the bottom side of the battery case. It is preferable that the end portion of the negative electrode core material and the negative electrode current collector plate be directly connected to each other.

(Alkaline electrolyte)
As the alkaline electrolyte, an aqueous solution containing alkali as a solute is used. In the present embodiment, the alkaline electrolyte only needs to contain at least NaOH, may contain only NaOH, or may contain NaOH and an alkali other than NaOH. Examples of the alkali other than NaOH include KOH and / or LiOH. By using an alkaline electrolyte containing at least NaOH, high temperature durability can be obtained.

In the alkaline electrolyte, the alkali concentration is 6.5 mol / L or less, preferably 6.2 mol / L or less, and more preferably 6 mol / L or less. If the alkali concentration exceeds 6.5 mol / L, the effect of inhibiting corrosion at the connection point between the positive electrode current collector plate and the positive electrode core material or the positive electrode lead is reduced, and the high-temperature durability is greatly reduced.

In the alkaline electrolyte, the sodium ion concentration is 3 mol / L or more. When the sodium ion concentration is less than 3 mol / L, the high-temperature durability decreases. From the viewpoint of obtaining higher temperature durability, the sodium ion concentration in the alkaline electrolyte is preferably 3.5 mol / L or more, more preferably 3.8 mol / L or more, or 4 mol / L or more. preferable. The sodium ion concentration is 6.5 mol / L or less, preferably 6 mol / L or less. When the upper limit of the sodium ion concentration is such a value, corrosion of the joint portion between the positive electrode current collector plate and the positive electrode core material or the positive electrode lead, particularly at a high temperature, can be more effectively suppressed. These lower limit values and upper limit values can be arbitrarily combined. Sodium ion concentration is 3 mol / L or more and 6.5 mol / L or less, for example, 3 mol / L or more and 6 mol / L or less, 3.5 mol / L or more and 6.5 mol / L or less, 3.5 mol / L or more and 6 mol / L or less. L or less, 3.8 mol / L or more and 6 mol / L or less, or 4 mol / L or more and 6 mol / L or less may be sufficient.

The potassium ion concentration in the alkaline electrolyte is, for example, 3 mol / L or less, and preferably 2 mol / L or less. When the potassium ion concentration is in such a range, corrosion of the connection portion between the positive electrode core plate and the positive electrode lead of the positive electrode current collector plate and deterioration of the hydrogen storage alloy are likely to proceed. However, in this embodiment, in order to control the alkali concentration and sodium ion concentration of the electrolytic solution and the hydrogen equilibrium pressure of the hydrogen storage alloy, even if the potassium ion concentration is in such a range, the corrosion of the connection site and the hydrogen storage alloy Deterioration can be suppressed. From the viewpoint of ensuring high high-temperature charging efficiency, the potassium ion concentration in the alkaline electrolyte is preferably 1.5 mol / L or less, more preferably 1.2 mol / L or less or 1 mol / L or less. .

(Other)
The battery case only needs to be able to accommodate at least the electrode group, the positive electrode current collector plate, and the alkaline electrolyte, and a known case used for alkaline storage batteries is used. The shape of the battery case is not particularly limited, and examples thereof include a cylindrical shape, an elliptical cylindrical shape, and a rectangular shape.

Examples of the battery case material include iron and iron alloys (stainless steel, etc.). The battery case is usually subjected to a plating treatment such as nickel plating.

The sealing plate is not particularly limited as long as it can be electrically connected to the positive electrode current collecting plate and seal the opening of the battery case, and a known structure can be adopted.

Examples of the material of the sealing plate (at least the material connected to the positive electrode lead (such as the bottom surface of the sealing plate)) include iron and iron alloys (stainless steel, etc.). The sealing plate (at least a portion connected to the positive electrode lead (such as the bottom surface of the sealing plate)) is usually subjected to a plating treatment such as nickel plating.

As the insulating gasket for insulating between the sealing plate and the battery case at the peripheral edge of the sealing plate, a known one is used without any particular limitation.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
According to the following procedure, an alkaline storage battery (nickel metal hydride storage battery) as shown in FIG. 1 was produced and evaluated.

(1) Production of positive electrode A positive electrode paste was prepared by mixing nickel oxide particles and a predetermined amount of water.

The positive electrode paste was filled in a foamed nickel porous body (porosity 95%, surface density 300 g / cm ² ) as a core material and dried. The dried product was compressed in the thickness direction, and then cut into predetermined dimensions (thickness: 0.4 mm, length: 80 mm, width: 40 mm) to produce a positive electrode. When the theoretical capacity of the positive electrode is one-electron reaction by charge / discharge of nickel oxide, the filling amount of the positive electrode paste was adjusted so as to be 800 mAh. One end of the positive electrode in the width direction was not filled with the positive electrode paste, and only the positive electrode core material was in a protruding state.

(2) Production of negative electrode As a hydrogen storage alloy, La _0.849 Ce _0.151 Ni _4.304 Co _0.418 Mn _0.240 Al _0.310 (hydrogen equilibrium pressure at 45 ° C. = 3.0 atm) 100 parts by mass, carboxymethyl cellulose 0.15 as a thickener By mixing 0.3 parts by mass of carbon black as a conductive agent and 0.7 parts by mass of a styrene butadiene copolymer as a binder, adding water to the resulting mixture and further mixing, A negative electrode paste was prepared.

The negative electrode paste was applied to both surfaces of nickel-plated iron punching metal (thickness 30 μm) as a negative electrode core material to form a coating film. After the obtained coating film was dried, it was pressed together with the core material and cut into a predetermined size (thickness: 0.3 mm, length: 120 mm, width: 40 mm) to produce a hydrogen storage alloy negative electrode. The capacity of the negative electrode was adjusted to 1600 mAh. In addition, only the negative electrode core material was made to protrude in one end part of the width direction of a negative electrode core material, without forming the coating film of negative electrode paste.

(3) Production of alkaline storage battery Using the positive electrode obtained in (1) and the negative electrode obtained in (2), a nickel hydride storage battery having the structure shown in FIG. 1 was produced.

First, with the separator 5 interposed between the positive electrode 3 and the negative electrode 4, these were overlapped and wound into a spiral shape to form the electrode group 2. At this time, the positive electrode 3 and the negative electrode 4 were overlapped so that the end portion 3 a of the positive electrode core material of the positive electrode 3 and the end portion 4 a of the negative electrode core material of the negative electrode 4 were positioned opposite to each other. As the separator 5, a sulfonated polypropylene separator was used.

The end portion 3 a of the positive electrode core member protruding from one end portion in the width direction of the positive electrode 3 was welded to the positive electrode current collector plate 9. The end 4a of the negative electrode core member protruding to the side opposite to the end 3a of the positive electrode core member was welded to the negative electrode current collector plate 8. Along with the positive electrode current collector plate 9 and the negative electrode current collector plate 8, the electrode group 2 is accommodated in a bottomed cylindrical battery case 1, and a welding electrode rod is inserted into the central cavity of the electrode group 2, thereby The electric plate 8 and the inner bottom surface of the battery case 1 were spot welded. As the positive electrode current collector plate 9, a nickel plate plated square plate having a hole in the center was used. The size of the positive electrode current collector plate 9 was 11 mm long × 11 mm wide × 1 mm thick, and the hole in the center was circular with a diameter of 3 mm. As the negative electrode current collector plate 8, a disk-shaped plate plated with nickel was used. The size of the negative electrode current collector plate 8 was 11 mm in diameter × 1 in thickness. The positive electrode current collector plate 9 and the sealing plate 7 use nickel-made (Ni purity: 99.9%) tab-shaped leads (width 5 mm, thickness 1 mm) as the positive electrode leads 10. Each part was connected by welding.

The outer periphery in the vicinity of the opening of the battery case 1 was recessed to provide a groove, and an alkaline electrolyte was injected into the battery case 1. As the alkaline electrolyte, an aqueous sodium hydroxide solution having a concentration of 6 mol / L was used.

Next, a sealing plate 7 was attached to the opening of the battery case 1 through the insulating gasket 6. AA-size alkaline storage battery (sealed nickel-metal hydride storage battery) having a theoretical capacity of 800 mAh in which the opening capacity of the battery case 1 is caulked toward the gasket 6 and the battery case 1 is sealed to regulate the battery capacity with the positive electrode. Produced. The alkaline storage battery was activated by charging / discharging (temperature: 20 ° C., charging condition: 80 mA for 16 hours, discharging condition: 160 mA for 5 hours), and then subjected to evaluation (4).

(4) Evaluation The following evaluation was performed using the alkaline storage battery obtained in (3) above.

(A) Initial internal resistance (low temperature output characteristics)
Discharging and charging tests were performed by discharging at a current of 160 mA in a 20 ° C. atmosphere until the voltage reached 1.0 V, and then charging for 16 hours at a current of 80 mA.

Thereafter, pulse charge / discharge was performed under the following conditions (i) to (iv) in an atmosphere of 0 ° C., and the internal resistance was calculated from the voltage drop after 10 seconds of discharge.
(I) Discharge: Pulse discharge for 20 seconds at a current of 400 mA, and rest for 5 minutes. Charging: Pulse charging for 20 seconds at a current of 400 mA, and charging is stopped for 5 minutes.
(Ii) Discharge: Pulse discharge at a current of 800 mA for 20 seconds, and stop the discharge for 5 minutes. Charging: Pulsed for 20 seconds at a current of 800 mA and rested for 4 minutes.
(Iii) Discharge: Discharge for 20 seconds at a current of 1600 mA and pause the discharge for 5 minutes. Charging: Charged for 20 seconds at a current of 1600 mA and paused for 5 minutes.
(Iv) Discharge: Discharge for 20 seconds at a current of 2400 mA and pause for 5 minutes. Charging: Charging for 20 seconds at a current of 2400 mA and stopping charging for 5 minutes.
The internal resistance was calculated from these four current values and the voltage drop after 10 seconds of discharge.

For other examples and comparative examples described later, the initial internal resistance of Example 1 was evaluated as 100.

(B) Trickle durability test (high temperature durability)
In a 70 ° C. atmosphere, trickle charging was performed under the following conditions, and then discharging was performed.
Trickle charge: Charge for 60 days at a current of 40 mA.
Discharge: Discharge until the voltage reaches 1.0 V at a current of 160 mA.
This trickle charge and discharge were repeated three times to obtain a trickle durability test.

Thereafter, an internal resistance test was performed under the same conditions as in (a) above to obtain an internal resistance after the trickle durability test.

For other examples and comparative examples described later, the internal resistance after the trickle durability test of Example 1 was evaluated as 100.

(C) High temperature charge / discharge efficiency The room temperature charge / discharge test and the high temperature charge test shown below were performed, and the ratio of the discharge capacity of the high temperature charge test to the discharge capacity of the room temperature charge / discharge test was defined as the high temperature charge efficiency.

(Normal temperature charge / discharge test)
Charge and discharge were performed under the following conditions in an atmosphere of 20 ° C.
Charging: Charged at 80 mA current for 16 hours in an atmosphere of 20 ° C., then left for 1 hour.
Discharge: Discharge in a 20 ° C. atmosphere at a current of 160 mA until the voltage reaches 1.0V.

(High temperature charge test)
Charging: Charged at a current of 80 mA for 16 hours in a 60 ° C. atmosphere, and then left for 3 hours in a 20 ° C. atmosphere.
Discharge: Discharge in a 20 ° C. atmosphere at a current of 160 mA until the voltage reaches 1.0V.

For other examples and comparative examples described later, evaluation was made with values when the high-temperature charge / discharge efficiency of Example 1 was 100.

Examples 2 to 9 and Comparative Examples 1 to 3
An alkaline electrolyte containing sodium ions and potassium ions at concentrations shown in Tables 1 and 2 was used. As an alkaline electrolyte containing both sodium ions and potassium ions, an aqueous solution containing NaOH and KOH was used. As the hydrogen storage alloy, those having the hydrogen equilibrium pressure (45 ° C.) shown in Tables 1 and 2 were used. Except for these, alkaline storage batteries were produced and evaluated in the same manner as in Example 1.

The compositions of the hydrogen storage alloys used in the examples and comparative examples are as follows.
(I) Composition: La _0.849 Ce _0.151 Ni _4.304 Co _0.418 Mn _0.240 Al _0.310 , hydrogen equilibrium pressure: 3.0 atm (≈0.3 MPa)
(Ii) _{_{_{Composition: La 0.836 Ce 0.142 Ni 4.456 Co}}} 0.147 Mn 0.252 Al 0.401 Zr 0.022,
Hydrogen equilibrium pressure: 0.6 atm (≒ 0.06 MPa)
(Iii) Composition: La _0.895 Ce _0.081 Ni _4.395 Co _0.146 Mn _0.250 Al _0.397 Zr _0.024 ,
Hydrogen equilibrium pressure: 0.5atm (≒ 0.05MPa)
(Iv) Composition: La _0.625 Ce _0.375 Ni _4.287 Co _0.448 Mn _0.099 Al _0.304 , hydrogen equilibrium pressure: 3.5 atm (≈0.35 MPa)
(V) Composition: La _0.672 Ce _0.327 Ni _3.632 Co _0.721 Mn _0.387 Al _0.315 , hydrogen equilibrium pressure: 0.2 atm (≈0.02 MPa)
(Vi) Composition: La _0.622 Ce _0.378 Ni _4.226 Co _0.516 Mn _0.111 Al _0.290 , hydrogen equilibrium pressure: 3.6 atm (≈0.36 MPa)
Comparative Example 4
A stainless steel tab-shaped lead plated with nickel was used as the positive electrode lead 10 connected to the positive electrode current collector plate 9. Except for this, an alkaline storage battery was produced and evaluated in the same manner as in Example 1.

Comparative Example 5
The positive electrode current collector plate 9 is not provided, and one end portion of the same positive electrode lead as in Example 1 is welded to the end portion 3a of the positive electrode core material, and the other end portion is welded to the bottom surface of the sealing plate 7, thereby The positive electrode 3 and the sealing plate 7 were electrically connected to each other. Except for this, an alkaline storage battery was produced and evaluated in the same manner as in Example 1.

Tables 1 and 2 show the results of Examples and Comparative Examples. A1 to A9 are Examples 1 to 9, and B1 to B5 are Comparative Examples 1 to 5.

As shown in Table 1, in the batteries of the examples, the initial internal resistance at 0 ° C. was low, and high low-temperature output characteristics were obtained. In the examples, the internal resistance after the trickle durability test was kept low at a high temperature, and a high temperature durability was obtained. On the other hand, as shown in Table 2, in the comparative example, the high temperature durability was remarkably reduced as compared with the example. In Comparative Example 7 in which the positive electrode and the sealing plate were connected by the lead, the low-temperature output characteristics were extremely low.

From the viewpoint of further improving the low temperature output characteristics, the hydrogen equilibrium pressure of the hydrogen storage alloy at 45 ° C. is preferably 0.6 atm or more. Further, from the viewpoint of further enhancing the high temperature durability and ensuring high high temperature charging efficiency, the sodium ion concentration is preferably a concentration exceeding 3 mol / L, and more preferably 4 mol / L or more. It is also advantageous to make the potassium ion concentration less than 2 mol / L (preferably 1 mol / L or less) in order to further enhance the high-temperature durability or increase the high-temperature charging efficiency.

Since the alkaline storage battery according to the embodiment of the present invention has high low-temperature output characteristics and high-temperature durability, it can be used for applications exposed to low and high temperatures. The alkaline storage battery is suitable for use as an auxiliary power source for backup, an emergency power source, a standby power source for a fire alarm, a power source for emergency broadcasting, and the like. The alkaline storage battery can also be used as a power source for various electronic devices, transportation devices, power storage devices, and the like.

DESCRIPTION OF SYMBOLS 1: Battery case 2: Electrode group 3: Positive electrode 3a: End part 4 of positive electrode core material: Negative electrode 4a: End part of negative electrode core material 5: Separator 6: Insulating gasket 7: Sealing plate 8: Negative electrode collector plate 9: Positive electrode Current collector plate 10: positive electrode lead

Claims

A bottomed battery case having an opening;
Housed in the battery case, an electrode group, a positive current collector electrically connected to the electrode group, and an alkaline electrolyte,
A sealing plate that seals the opening and is electrically connected to the positive current collector;
The electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
The positive electrode includes a positive electrode core material and a positive electrode active material supported on the positive electrode core material,
The positive current collector plate is connected to the end portion of the positive electrode core material, and is connected to the sealing plate via a lead,
The positive electrode current collector plate includes a plate formed of iron or an iron alloy, and a plating film that covers the plate and contains nickel,
The lead is made of nickel metal,
The negative electrode comprises a negative electrode core material and a negative electrode active material carried on the negative electrode core material,
The negative electrode active material includes a hydrogen storage alloy having a hydrogen equilibrium pressure at 45 ° C. of 0.5 atm to 3.5 atm,
The alkaline electrolyte contains at least NaOH,
The alkaline storage battery in which the alkali concentration in the alkaline electrolyte is 6.5 mol / L or less and the sodium ion concentration is 3 mol / L or more.
The alkaline storage battery according to claim 1, wherein the hydrogen equilibrium pressure of the hydrogen storage alloy is 0.6 atm or more and 3.5 atm or less.
The alkaline storage battery according to claim 1 or 2, wherein a potassium ion concentration in the alkaline electrolyte is 1.5 mol / L or less.
The alkaline storage battery according to any one of claims 1 to 3, wherein the sodium ion concentration in the alkaline electrolyte is 3.5 mol / L or more.
The alkaline storage battery according to any one of claims 1 to 4, wherein a concentration of the alkali in the alkaline electrolyte is 6 mol / L or less.
Furthermore, a negative electrode current collector plate is provided,
The alkaline storage battery according to any one of claims 1 to 5, wherein the negative electrode current collector plate is connected to an end portion of the negative electrode core member and to an inner bottom surface of the battery case.