JP2021034285A - Alkaline storage battery negative electrode, production method for the same, and alkaline storage battery - Google Patents

Abstract

To provide: an alkaline storage battery negative electrode that has excellent cost stability, has high discharge capacity from an initial charge/discharge cycle, and can maintain the high discharge capacity over a long period of time; and a production method for the negative electrode; and an alkaline storage battery that includes the negative electrode.SOLUTION: A negative electrode 1 has a collector 2, a binder 3, and a powdered active material 4 that is held on the collector 2 via the binder 3. Each of particles 41 comprising the active material 4 has: a core part 412 that comprises a hydrogen storage alloy; and a surface layer 411 that contains a hydroxide of Ni and is on the surface of the core part 412. The composition of the core parts 412 is represented by Zr(1-x-y-z)TixNbyMgzNiw (where, 0.466<x<0.473, 0.009<y<0.013, 0.005<z<0.064 and 0.95≤w≤1.05 are satisfied). A hydroxide of Ni is contained in the surface layer 411.SELECTED DRAWING: Figure 1

Description

The present invention relates to a negative electrode for an alkaline storage battery, a method for manufacturing the same, and an alkaline storage battery.

For example, alkaline storage batteries such as nickel-metal hydride batteries are widely used as vehicle-mounted power sources for hybrid vehicles and fuel cell vehicles, stationary power sources for railways, and power sources for small electric devices. A hydrogen storage alloy is used as the negative electrode active material of the nickel hydrogen battery.

Hydrogen storage alloy, and affinity high A element group with hydrogen, affinity with hydrogen is constituted of an alloy of low B element group, AB ₅ type alloys, AB ₂ type alloys, and AB type alloys and the like known Has been done. _{For example, MmNi 5} , which is an alloy of mischmetal (Mm) containing a plurality of rare earth metals and nickel (Ni), has already been put into practical use as a negative electrode active material for a nickel hydrogen battery (Patent Document 1).

However, the discharge capacity of the alkaline storage battery using the hydrogen storage alloy of Patent Document 1 has already reached a value close to the theoretical capacity. Therefore, when the hydrogen storage alloy of Patent Document 1 is used, it is difficult to further increase the discharge capacity of the alkaline storage battery.

In order to further increase the discharge capacity of the alkaline storage battery, it is necessary to use a hydrogen storage alloy having a higher hydrogen storage capacity as the negative electrode active material. As such a hydrogen storage alloy, there is a ZrNi alloy having an AB type composition (Non-Patent Document 1). The hydrogen storage capacity of the ZrNi alloy is about 60% higher than that of _{the MmNi 5 alloy.} Therefore, by using the ZrNi alloy as the negative electrode active material, it can be expected that the theoretical capacity of the alkaline storage battery will be higher and the energy density will be higher.

However, the ZrNi alloy reacts with the stored hydrogen to produce hydrides such as _{ZrNiH 3 and ZrNiH.} Due to the high chemical stability of these hydrides, it is difficult to desorb hydrogen from the hydrides. Therefore, when the ZrNi alloy is used as the negative electrode active material, there is a problem that the hydrogen storage amount sharply decreases when charging and discharging are repeated, which causes a decrease in the discharge capacity.

Therefore, in order to promote the release of hydrogen from the ZrNi alloy, a quaternary hydrogen storage alloy in which a part of Zr is replaced with Ti and a part of Ni is replaced with V (vanadium) (Patent Document 2). Has been proposed.

Japanese Unexamined Patent Publication No. 2008-210809 Japanese Unexamined Patent Publication No. 5-239574

Dantzer P, Millet P, Flanagan TB. Thermodynamic characterization of Hydride Phase Gas Growth in ZrNi-H2. Metall Mater Trans A. 2001; 32A: 29-38

The hydrogen storage alloys described in Non-Patent Document 1 and Patent Document 2 have a characteristic that the discharge capacity is low at the first charge / discharge cycle and gradually increases as the cycle progresses. However, practically, a hydrogen storage alloy that has a high discharge capacity from the first charge / discharge cycle and can maintain a high discharge capacity for a long period of time when charging / discharging is repeated is desired. ing.

Further, since the hydrogen storage alloy of Patent Document 2 contains V having a high uneven distribution in the producing area, the price tends to fluctuate according to changes in social conditions and the like. Therefore, the hydrogen storage alloy of Patent Document 2 has a problem that the raw material cost fluctuates relatively large.

The present invention has been made in view of this background, and is an alkali that is excellent in price stability, has a high discharge capacity from the first charge / discharge cycle, and can maintain a high discharge capacity for a long period of time. An object of the present invention is to provide a negative electrode for a storage battery, a method for manufacturing the same, and an alkaline storage battery having the negative electrode.

One aspect of the present invention is a negative electrode for an alkaline storage battery having a current collector made of a conductor, a binder, and a powdery active material held in the current collector via the binder. ,
The active material is
Composition _{Zr (1-xyz) Ti x} Nb y Mg z Ni w ( where, 0.466 <x <0.473,0.009 <y <0.013,0.005 <z <0.064,0 .95 ≦ w ≦ 1.05), and the core part made of hydrogen storage alloy
It is a negative electrode for an alkaline storage battery, which contains a hydroxide of Ni and has a surface layer existing on the surface of the core portion.

Another aspect of the present invention is an alkaline storage battery having a negative electrode for an alkaline storage battery according to the above aspect.

Yet another aspect of the present invention, the composition Zr _(1-xyz) is _{Ti x Nb y Mg z Ni w} ( where, 0.466 <x <0.473,0.009 <y <0.013,0. An ingot of a hydrogen storage alloy having 005 <z <0.064, 0.95 ≦ w ≦ 1.05) was prepared.
The ingot was crushed to prepare a powdery active material.
An electrode member is produced by holding the active material in a current collector made of a conductor via a binder.
This is a method for manufacturing a negative electrode for an alkaline storage battery, in which a surface layer containing a Ni hydroxide is formed on the surface of the active material by subjecting the electrode member to an activation treatment of boiling in a strong alkaline aqueous solution.

The negative electrode for an alkaline storage battery (hereinafter, may be appropriately referred to as a "negative electrode") has the current collector and the powdered active material held by the current collector. The active material has a core portion made of a hydrogen storage alloy having the specific composition and the surface layer containing a hydroxide of Ni. The surface layer contains a hydroxide of Ni (nickel). By applying the active material configured in this way to the negative electrode, the discharge capacity of the negative electrode can be increased from the first time of the charge / discharge cycle.

Further, by setting the specific range the composition of the core portion, in the core _{portion, Zr (1-xyz) Ti} x Nb y Mg z Ni w phase can be precipitated. Since this phase has a B33 type crystal structure similar to that of the ZrNi alloy, the hydrogen storage amount of the active material can be increased. _{Further, Zr (1-xyz) Ti} x Nb y Mg z Ni w phase, by a part of Zr in ZrNi alloy is substituted Ti, the Mg Nb and traces traces, as compared with ZrNi alloy hydrogen Can be promoted.

Thus, the active material _{Zr (1-xyz) Ti x} Nb y Mg z Ni w phase is included, the hydrogen storage amount is large, that hydrogen is easily released, properties suitable for use as a negative electrode of an alkaline storage battery have. Therefore, the negative electrode in which the active material is retained can maintain a high discharge capacity for a long period of time.

In addition, the active material does not contain a metal whose price is unstable, such as V (vanadium). Therefore, the raw material cost of the active material can be easily reduced, and the fluctuation of the raw material cost can be easily avoided. As a result, the negative electrode is excellent in price stability.

As described above, by using the active material, a negative electrode having excellent price stability, having a high discharge capacity from the first charge / discharge cycle, and being able to maintain a high discharge capacity for a long period of time can be obtained. be able to.

As described above, the negative electrode has charge / discharge characteristics suitable for alkaline storage batteries. Therefore, the alkaline storage battery having the negative electrode can have a higher discharge capacity and, by extension, a higher energy density.

The negative electrode can be manufactured, for example, by the manufacturing method of the above-described embodiment. In the production method, a powdery active material is produced by pulverizing an ingot of a hydrogen storage alloy having the specific composition. Then, after the active material is held by the current collector to prepare the electrode member, the electrode member is subjected to the activation treatment. As a result, the surface layer containing Ni hydroxide can be formed on the surface of the active material. As a result, the negative electrode having a high discharge capacity can be manufactured from the first charge / discharge cycle.

The following reasons can be considered as the reason why the charge / discharge cycle characteristics are improved by the activation treatment. After crushing the ingot, an insulating compound such as _{ZrO 2} or TiO ₂ is naturally formed on the surface of the active material. It is considered that the negative electrode using the conventional ZrNi-based alloy has caused a decrease in the discharge capacity at the first charge / discharge cycle due to the presence of this insulating compound.

On the other hand, in the production method, ZrO ₂ and TiO ₂ existing on the surface of the active material can be removed by performing the activation treatment. Further, by the activation treatment, Ni existing on the surface of the active material becomes a hydroxide. The surface layer containing Ni hydroxide can suppress the oxidation of Zr and Ti existing inside the active material. As a result of the above, it is considered that by performing the activation treatment, the _{adverse effect of the insulating compound such as ZrO 2} and TiO ₂ can be suppressed, and thus the charge / discharge cycle characteristics can be improved.

It is a partial cross-sectional view which shows the main part of the negative electrode for an alkaline storage battery in an Example. It is explanatory drawing which shows the result of the charge / discharge cycle test of the test body 1 to 4 in an Example. It is explanatory drawing which shows the result of the discharge rate characteristic evaluation of the test body 1 to 4 in an Example. It is explanatory drawing which shows the discharge curve of the test body 2 and the test body 5 in an Example.

In the negative electrode, as the current collector, for example, conductors of various aspects such as a metal foil, a punching metal, an expanded metal, and a metal mesh can be applied.

The binder has an action of retaining the active material in the current collector by interposing between the current collector and the active material. As the binder, for example, polyvinyl alcohol or the like can be used. Further, the binder may contain a known additive such as a thickener, if necessary.

If necessary, the negative electrode may contain a known conductive agent such as Cu (copper) powder or a conductive auxiliary agent. These conductive agents and conductive auxiliaries are held in the current collector via a binder, like the active material.

Each particle constituting the active material has a core portion and a surface layer existing on the surface of the core portion. The core portion is composed of an AB type hydrogen storage alloy composed of Zr, Ti, Nb and Mg as an element A having a high hydrogen affinity and Ni as an element B having a low hydrogen affinity. The composition of the hydrogen storage alloy constituting the core _{portion, Zr (1-xyz) Ti} x Nb y Mg z Ni w ( where, 0.466 <x <0.473,0.009 <y <0.013,0 .005 <z <0.064, 0.95 ≦ w ≦ 1.05). The value of x in the composition formula, the value of y, by the values and ranges of values of the particular w of z, Zr _(1-xyz) having a crystal structure of the B33 type Ti _x Nb _y Mg _z Ni _{The w} phase can be easily precipitated in the core portion.

By setting the value of x in the composition formula to the specific range, the amount of hydrogen stored in the hydrogen storage alloy can be increased, and the hydrogen stored in the hydrogen storage alloy can be released more easily. .. As a result, it is possible to increase the discharge capacity of the negative electrode and suppress a decrease in the discharge capacity due to repeated charging and discharging.

When the value of x in the composition formula is 0.466 or less, the atomic number ratio of Ti is low, so that the hydrogen stored in the hydrogen storage alloy may be difficult to be released from the hydrogen storage alloy. .. As a result, the discharge capacity may easily decrease as the number of charge / discharge cycles increases.

On the other hand, when the value of x in the composition formula is 0.473 or more, a phase having a crystal structure other than B33 type _{, such as a TiNi phase or a Zr 9} Ni _{11 phase, is likely to precipitate in the core portion.} Become. These _{phases, Zr (1-xyz) Ti} x Nb y Mg z Ni w -phase hydrogen storage capacity is lower than the. Therefore, when the value of x is 0.473 or more, the hydrogen storage amount may decrease, which may lead to a decrease in the discharge capacity.

By setting the value of y in the composition formula to the specific range, the amount of Ti substituted can be increased while suppressing the precipitation of a phase having a crystal structure other than B33 type. When the value of y in the composition formula is 0.009 or less, a phase having a crystal structure other than B33 type is likely to be precipitated in the core portion, which may lead to a decrease in discharge capacity. On the other hand, when the value of y in the composition formula is 0.013 or more, a phase having a crystal structure other than B33 type is likely to be precipitated in the core portion, which may lead to a decrease in the hydrogen storage amount. is there.

By setting the value of z in the composition formula to the specific range, Mg having a relatively low hydrogen affinity as the element A can be appropriately present in the hydrogen storage alloy. As a result, the hydrogen stored in the hydrogen storage alloy can be more easily released from the hydrogen storage alloy while maintaining a high hydrogen storage amount. As a result, it is possible to increase the discharge capacity of the negative electrode and suppress a decrease in the discharge capacity due to repeated charging and discharging.

Further, by setting the value of z in the composition formula within the specific range, the potential of the negative electrode at the time of discharge can be further lowered. Therefore, by combining the negative electrode containing the active material having the core portion with the positive electrode, the discharge voltage of the alkaline storage battery, that is, the potential difference between the potential of the positive electrode and the potential of the negative electrode at the time of discharge can be further increased.

Further, by setting the value of z in the composition formula to the specific range, the discharge capacity of the negative electrode is further increased, and the discharge rate, that is, the decrease in the discharge capacity when the current density at the time of discharge is increased is reduced. It can be suppressed. Therefore, the active material whose z value is within the specific range can be suitably used for the negative electrode of an alkaline storage battery, which is required to perform high rate discharge.

The effect of increasing the discharge capacity of the negative electrode, the effect of suppressing the decrease in discharge capacity due to repeated charging and discharging, the effect of lowering the potential of the negative electrode during discharge, and the effect of suppressing the decrease in discharge capacity when the discharge rate is increased. From the viewpoint of further enhancing the effect of the discharge, the value of z in the composition formula is preferably 0.006 <z <0.050, more preferably 0.010 <z <0.040. It is more preferable that 0.015 <z <0.035.

When the value of z in the composition formula is 0.005 or less, the atomic number ratio of Mg contained in the core portion is low, so that the hydrogen stored in the hydrogen storage alloy is difficult to be released from the hydrogen storage alloy. There is a risk of becoming. As a result, the discharge capacity may easily decrease as the number of charge / discharge cycles increases. On the other hand, when the value of z in the composition formula is 0.064 or more, a phase having a crystal structure other than B33 type is likely to be precipitated in the core portion, which may lead to a decrease in the hydrogen storage amount. .. As a result, the discharge capacity may decrease.

Further, by setting the value of w in the composition formula, that is, the ratio of the number of atoms of Ni to the total of Zr, Ti, Nb and Mg within the specific range, Zr _(1-xyz) Ti _x Nb in the core portion. _y Mg _z N _w phase can be easily precipitated. When the value of w is outside the specific range, a phase having a crystal structure other than B33 type is likely to be precipitated. As a result, the hydrogen storage amount of the active material becomes low, which may lead to a decrease in the discharge capacity.
The above-mentioned "B33 type crystal structure" is the same as the CrB type structure clarified in, for example, "Metal vol.80 (2010) No.7, page 32".

The atomic number ratio Nb / Mg of Nb to Mg in the core portion is preferably 0.15 or more and 2.00 or less. In this case, it is possible to increase the discharge capacity of the negative electrode and more effectively suppress the decrease in the discharge capacity when the discharge rate is increased. Further, in this case, the potential of the negative electrode at the time of discharging can be further lowered. From the viewpoint of further enhancing these effects, the atomic number ratio Nb / Mg of Nb to Mg is more preferably 0.40 or more and 1.50 or less.

A surface layer containing a Ni hydroxide is present on the surface of the core portion. In addition to the hydroxide of Ni, the surface layer may contain an oxide of Ni and an insulating compound such as _{ZrO 2} and TiO _{2 remaining after the activation treatment.} Further, the surface layer may be composed of fine particles containing Ni hydroxide.

The negative electrode can be manufactured, for example, by the following method. First, a hydrogen storage alloy having the specific composition is cast. By the composition during casting and the specific range, it is possible to precipitate _{Zr (1-xyz) Ti x} Nb y Mg z Ni w phase in the ingot. Next, the obtained ingot is crushed to prepare a powdery active material. At this time, by heating the ingot in an inert gas atmosphere before crushing the ingot, it is possible to remove dislocations and defects generated in the solidification process while maintaining the specific crystal structure. .. Then, by producing a negative electrode using a hydrogen storage alloy from which dislocations and the like have been removed, the discharge capacity of the negative electrode can be further increased.

Next, the electrode member is produced by causing the current collector to hold the active material via the binder. Then, the electrode member is subjected to an activation treatment of boiling in a strong alkaline aqueous solution. Thereby, the surface layer can be formed on the surface of each particle constituting the active material. As the strong alkaline aqueous solution, for example, an aqueous solution having a temperature of 105 ° C. or higher and a pH of 14 or higher can be used.

Examples of the negative electrode and the method for manufacturing the same will be described with reference to the drawings. As shown in FIG. 1, the negative electrode 1 of this example is a powdery active material 4 held by a current collector 2 made of a conductor, a binder 3, and a current collector 2 via the binder 3. And is configured as a negative electrode for alkaline storage batteries. The individual particles 41 constituting the active material 4 have a core portion 412 made of a hydrogen storage alloy and a surface layer 411 containing a hydroxide of Ni and existing on the surface of the core portion 412. As shown in Table 1, the composition of the core portion _{412 Zr (1-xyz) Ti} x Nb y Mg z Ni w ( where, 0.466 <x <0.473,0.009 <y <0.013, 0.005 <z <0.064, 0.95 ≦ w ≦ 1.05).

In this example, first, the active material 4 in the form of powder was prepared by variously changing the composition as shown in Table 1. Next, an electrode member was produced by holding the active material 4 in a separately prepared current collector 2 via a binder 3. Then, the electrode member was subjected to an activation treatment under the treatment conditions shown in Table 1 to form a surface layer 411 on the surface of the individual particles 41 constituting the active material 4. From the above, the negative electrode 1 (test bodies 1 to 3) was prepared. The manufacturing method of the negative electrode 1 will be described in more detail below.

[Preparation of active material]
Using an arc melting furnace, Zr (manufactured by High Purity Chemical Laboratory Co., Ltd., wire-cut product, purity 98.0%), Ti (manufactured by High Purity Chemical Laboratory Co., Ltd., powder, purity 99.0%), Nb (Made by High Purity Chemical Laboratory Co., Ltd., powder, purity 99.0%), Mg (manufactured by High Purity Chemical Laboratory Co., Ltd., granular, purity 99.9%) and Ni (manufactured by High Purity Chemical Laboratory Co., Ltd. The powder (purity 99.9%) was melted to prepare an ingot of a hydrogen storage alloy having the composition shown in Table 1. The ingot was heated to 400-480 ° C. in an argon atmosphere to reduce dislocations and defects in the ingot.

The ingot obtained by using a wet cutting machine was divided into two equal parts, and the specific gravity was measured and the structure was observed using one of the ingots. Further, the other ingot was coarsely pulverized by a disc mill, finely pulverized by a tungsten carbide mortar, and sieved to prepare a powdery active material 4. The diameter of the individual particles 41 constituting the active material was 20 to 40 μm.

Next, the obtained active material 4, Ni powder, PVA (polyvinyl alcohol) and CMC (carboxymethyl cellulose) as the binder 3 were added to the active material 4: Ni powder: PVA: CMC = 79: 19: 0.5. A paste-like negative electrode mixture was prepared by mixing at a mass ratio of: 1.5. This negative electrode mixture was filled in a Ni mesh as a separately prepared current collector 2. Then, the Ni mesh was rolled using a roll press, and the negative electrode mixture was brought into close contact with the Ni mesh. From the above, the electrode member was manufactured.

Then, the electrode member was subjected to an activation treatment of boiling in a 6 mol / L potassium hydroxide aqueous solution for 3 to 4 hours to form a surface layer 411 on the surface of each particle 41 constituting the active material 4. From the above, test bodies 1 to 3 were obtained. The temperature of the potassium hydroxide aqueous solution was 105 ° C.

In this example, for comparison with the test bodies 1 to 3, the test body 4 having an active material whose core composition is outside the specific range and the test body 5 having an active material containing no Mg are used. Got ready. The test body 4 is a test body prepared by the same procedure as the test bodies 1 to 3 except that the composition of the hydrogen storage alloy is changed as shown in Table 1. The test body 5 is a test body prepared by the same procedure as the test bodies 1 to 3 except that the composition of the hydrogen storage alloy is Zr _0.536 Ti _0.468 Nb _0.013 Ni _0.983.

The negative electrode (test specimens 1 to 5) obtained as described above _{is combined with a commercially available Ni (OH) 2} / NiOOH positive electrode and an Hg / HgO reference electrode to obtain 6 mol / L potassium hydroxide and 1 mol / L lithium hydroxide. A tripolar battery cell was constructed using the containing electrolyte. The charge / discharge cycle characteristics, discharge rate characteristics, and discharge potential were evaluated by measuring the charge / discharge and discharge capacities of the battery cells using a potentiostat (VMP3 manufactured by Bio-Logic).

[Charge / discharge cycle characteristics]
A charge / discharge cycle test in which charging / discharging was repeated at a temperature of 30 ° C. was performed using the test bodies 1 to 4, and the discharge capacity in each charging / discharging cycle was measured. One charge / discharge cycle consists of a step of charging for 5 hours at a current density of 100 mA / g, a step of resting for 10 minutes to stabilize the potential, and a step of stabilizing the potential at a current density of 25 mA / g with reference to the potential of Hg / HgO. It consists of a step of discharging to a potential of 0.5 V. FIG. 2 shows the measurement results of the discharge capacity in each charge / discharge cycle. The vertical axis of FIG. 2 is the discharge capacity (mAh / g), and the horizontal axis is the number of cycles (times).

After repeating the charge / discharge cycle consisting of the above three steps 10 times, the capacity retention rate was calculated by dividing the discharge capacity after 10 cycles by the initial discharge capacity. Table 1 shows the initial discharge capacity, the discharge capacity after 10 cycles, and the capacity retention rate.

[Discharge rate characteristics]
Using the test bodies 1 to 4, the discharge capacity when the current density at the time of discharge was changed to various values was measured. Specifically, the battery was charged for 5 hours under the conditions of a temperature of 30 ° C. and a current density of 100 mA / g, and then paused for 10 minutes to stabilize the potential. Next, the discharge capacity when discharged to a potential of −0.5 V with reference to the potential of Hg / HgO was measured at a current density of 25 mA / g, 50 mA / g, 100 mA / g, 250 mA / g or 500 mA / g. ..

Tables 2 and 3 show the discharge capacities when discharging is performed at each of the current densities. The vertical axis of FIG. 3 is the ratio of the discharge capacity at each current density to the discharge capacity at a current density of 25 mA / g as a percentage (%), and the horizontal axis is the current density at the time of discharge (mA / g). ). Further, in the "High rate discharge characteristics" column of Table 2, the value obtained by expressing the ratio of the discharge capacity at the current density of 500 mA / g to the discharge capacity at the current density of 25 mA / g as a percentage (%) is described.

[Discharge potential]
The discharge curve when the test body 3 and the test body 5 were discharged at a temperature of 30 ° C. was measured. Specifically, the battery was charged for 5 hours under the conditions of a temperature of 30 ° C. and a current density of 100 mA / g, and then paused for 10 minutes to stabilize the potential. Next, the discharge curve when discharged to a potential of −0.5 V with reference to the potential of Hg / HgO at a current density of 25 mA / g was measured. FIG. 4 shows the discharge curves of the test body 3 and the test body 5. The vertical axis of FIG. 4 is the potential of the test piece (V vs Hg / HgO) based on the potential of Hg / HgO, and the horizontal axis is the value of the potential of the test piece on the vertical axis from the start of discharge. It is the capacity (mAh / g) discharged by the time when becomes.

As shown in Table 1 and FIG. 2, the test bodies 1 to 3 in which the composition of the core portion is within the specific range are charged and discharged as compared with the test body 4 in which the composition of the core portion is out of the specific range. It had a high discharge capacity from the first time of the cycle and was able to maintain a high discharge capacity for a long period of time. From these results, it can be understood that the negative electrode 1 having excellent charge / discharge cycle characteristics can be obtained by setting the composition of the core portion 412 to the above-mentioned specific range.

Further, as shown in Table 2 and FIG. 3, the test bodies 1 to 3 were able to suppress a decrease in the discharge capacity when the current density at the time of discharge was increased as compared with the test body 4. Therefore, it can be understood that by applying an active material having a core composition in the specific range to the negative electrode, a negative electrode 1 suitable for an alkaline storage battery, which is required to perform high rate discharge, can be obtained.

Further, as shown in FIG. 4, the test body 3 provided with the core portion containing Mg was able to lower the potential in the flat portion of the discharge curve by about 0.2 V as compared with the test body 5 containing no Mg. .. From these results, it can be understood that the potential difference between the anode and the negative electrode at the time of discharge, that is, the discharge potential can be further increased by incorporating the negative electrode having the core portion containing Mg into the alkaline storage battery.

1 Negative electrode for alkaline storage battery 2 Current collector 3 Binder 4 Active material 41 Particle 411 Surface layer 412 Core part

Claims (5)

A negative electrode for an alkaline storage battery having a current collector made of a conductor, a binder, and a powdery active material held in the current collector via the binder.
The active material is
Composition _{Zr (1-xyz) Ti x} Nb y Mg z Ni w ( where, 0.466 <x <0.473,0.009 <y <0.013,0.005 <z <0.064,0 .95 ≦ w ≦ 1.05), and the core part made of hydrogen storage alloy
A negative electrode for an alkaline storage battery, which contains a hydroxide of Ni and has a surface layer existing on the surface of the core portion. The negative electrode for an alkaline storage battery according to claim 1, wherein the atomic number ratio Nb / Mg of Nb to Mg in the core portion is 0.15 or more and 2.00 or less. The negative electrode for an alkaline storage battery according to claim 1 or 2, wherein the surface layer is composed of fine particles containing a hydroxide of Ni. An alkaline storage battery having a negative electrode for an alkaline storage battery according to any one of claims 1 to 3. Composition _{Zr (1-xyz) Ti x} Nb y Mg z Ni w ( where, 0.466 <x <0.473,0.009 <y <0.013,0.005 <z <0.064,0 Prepare an ingot of hydrogen storage alloy with .95 ≦ w ≦ 1.05).
The ingot was crushed to prepare a powdery active material.
An electrode member is produced by holding the active material in a current collector made of a conductor via a binder.
A method for producing a negative electrode for an alkaline storage battery, which forms a surface layer containing a Ni hydroxide on the surface of the active material by subjecting the electrode member to an activation treatment of boiling in a strong alkaline aqueous solution.

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