JPH11162459A - Nickel-hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel-hydrogen secondary battery having an equal or higher capacity and superior high-rate charging/discharging characteristics than a conventional secondary battery provided with a negative electrode containing a hydrogen storage alloy mainly constituted of magnesium, nickel and rare earth elements. SOLUTION: The negative electrode 4 of this battery contains a hydrogen storage alloy expressed by the general formula (R1-x Mgx )Niy Az (where R is at least one element selected from rare earth elements including yttrium, Ca, Zr and Ti, A is at least one element selected from Co, Mn, Fe, V, Cr, Nb, Al, Ga, Zn, Sn, Cu, Si, P and B, and (x), (y) and (z) are 0<x<1, 0<=z<=1.5, 2.5<=y+x<4.5), and conductive metal chips 0.3-20 pts.wt. added against the hydrogen storage alloy 100 pts. wt. A positive electrode Z contains nickel hydroxide as an active material, and the battery is provided with the positive electrode 2 and the negative electrode 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a nickel-metal hydride secondary battery.

[0002]

2. Description of the Related Art As a nickel-hydrogen secondary battery, CaC
a LaNi ₅ -based hydrogen storage alloy having a u ₅ type crystal as a main phase,
Alternatively, a structure having a negative electrode including a hydrogen storage alloy having a Laves phase as a main phase containing Ti, Zr, V and Ni as constituent elements has been put to practical use.

[0003] Nickel-metal hydride secondary batteries provided with a negative electrode containing a LaNi ₅ -based hydrogen storage alloy occupy most of currently produced secondary batteries and are highly versatile batteries. However, since this hydrogen storage alloy has a hydrogen storage amount of 1 hydrogen atom to 1 alloy, it is substantially difficult to store more hydrogen. When the hydrogen storage amount of the hydrogen storage alloy is converted into an electrochemical capacity, about 37
Although it corresponds to 0 mAh / g, the capacity of the current practical secondary battery has already reached about 330 mAh / g. Therefore, in order to commercialize a higher capacity secondary battery in the future, a dramatic increase cannot be expected unless a LaNi ₅ -based hydrogen storage alloy is used.

On the other hand, it is known that a hydrogen storage alloy having a Laves phase as a main phase can store one or more hydrogen atoms with respect to alloy 1, and in principle, it is possible to realize a high-capacity battery. It is possible. However, this hydrogen storage alloy forms a stable oxide film on its surface, so it cannot be used sufficiently, it takes a long time for initial activation, the charge / discharge characteristics at a high rate are inadequate, and high capacity and other batteries can be used. It has not been used as a negative electrode material because it is difficult to achieve the required characteristics.

On the other hand, newly discovered hydrogen storage alloys containing magnesium, nickel and rare earth elements as main constituent elements are higher in volume and weight than LaNi ₅ -based hydrogen storage alloys. It is characterized by its capacity, faster activation than Laves phase hydrogen storage alloys, and excellent high rate charge / discharge characteristics. For this reason, by using this negative electrode material containing a hydrogen storage alloy, a negative electrode containing a Laves phase-based hydrogen storage alloy has a higher capacity than a secondary battery having a negative electrode containing a LaNi ₅ -based hydrogen storage alloy. It is possible to manufacture a secondary battery having a higher rate rate charge / discharge characteristic than a secondary battery provided with.

[0006]

[SUMMARY OF THE INVENTION However, the magnesium, when secondary battery comprising a negative electrode containing a hydrogen storage alloy whose main constituent elements nickel and rare earth elements with a focus on high-rate charge and discharge characteristics, LaNi ₅ type There is a problem that it is not as good as a secondary battery provided with a negative electrode containing a hydrogen storage alloy.

The present invention provides a high-capacity battery having a capacity equal to or higher than that of a conventional secondary battery including a negative electrode including a hydrogen storage alloy containing magnesium, nickel and a rare earth element as main constituent elements. An object of the present invention is to provide a nickel-metal hydride secondary battery having discharge characteristics.

[0008]

The nickel-hydrogen secondary battery according to the present invention has a general formula (R _1-x Mg _x ) Ni _{y AZ}
(Where R is a rare earth element containing yttrium, Ca,
At least one element selected from Zr and Ti, A
Are Co, Mn, Fe, V, Cr, Nb, Al, Ga, Z
n, Sn, Cu, Si, P, and at least one element selected from B and x, y, and z are each 0 <x <
1, 0 ≦ z ≦ 1.5, 2.5 ≦ y + z <4.5. ) And the hydrogen storage alloy 1
A negative electrode containing 0.3 to 20 parts by weight of a conductive metal piece added to 00 parts by weight; and a positive electrode containing nickel hydroxide as an active material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a nickel-metal hydride secondary battery according to the present invention will be described in detail by taking a cylindrical nickel-metal hydride secondary battery shown in FIG. 1 as an example. As shown in FIG. 1, an electrode group 5 produced by stacking a positive electrode 2, a separator 3, and a negative electrode 4 and winding them spirally is accommodated in a bottomed cylindrical container 1. The negative electrode 4 includes the electrode group 5
And is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. A circular first sealing plate 7 having a hole 6 in the center is arranged at the upper opening of the container 1. The ring-shaped insulating gasket 8 is disposed between the peripheral edge of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the sealing plate is formed on the container 1 by caulking to reduce the diameter of the upper opening inward. 7
Are hermetically fixed via the gasket 8. One end of the positive electrode lead 9 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is attached on the sealing plate 7 so as to cover the hole 6. A rubber safety valve 11 is disposed so as to close the hole 6 in a space surrounded by the sealing plate 7 and the positive electrode terminal 10. A circular holding plate 12 made of an insulating material having a hole in the center is arranged on the positive electrode terminal 10 such that a protrusion of the positive electrode terminal 10 projects from the hole of the holding plate 12. The outer tube 13 covers the periphery of the holding plate 12, the side surface of the container 1, and the periphery of the bottom of the container 1.

Next, the positive electrode 2, the negative electrode 4, the separator 3
And the electrolyte will be described. 1) Positive electrode 2 This positive electrode 2 contains nickel hydroxide powder as an active material.

The positive electrode is prepared by adding a conductive material to, for example, nickel hydroxide powder as an active material, kneading the mixture with a polymer binder and water to prepare a paste, filling the paste into a conductive substrate, and drying the paste. After that, it is produced by molding.

Examples of the conductive material include cobalt oxide, cobalt hydroxide, metallic cobalt, metallic nickel, and carbon. Examples of the polymer binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, and polytetrafluoroethylene.

Examples of the conductive substrate include a mesh-like, sponge-like, fibrous, or felt-like porous metal body made of nickel, stainless steel, or nickel-plated metal.

2) Negative Electrode 4 The negative electrode 4 has the general formula (R _1-x Mg _x ) Ni _{y AZ}
(Where R is a rare earth element containing yttrium, Ca,
At least one element selected from Zr and Ti, A
Are Co, Mn, Fe, V, Cr, Nb, Al, Ga, Z
n, Sn, Cu, Si, P, and at least one element selected from B and x, y, and z are each 0 <x <
1, 0 ≦ z ≦ 1.5, 2.5 ≦ y + z <4.5. ) And the hydrogen storage alloy 1
And 0.3 to 20 parts by weight of conductive metal pieces added to 00 parts by weight.

The hydrogen storage alloy represented by the above general formula is L
aNi exhibit large hydrogen storage capacity of about 120% per volume compared to the ₅ system hydrogen absorbing alloy. R contained in the hydrogen storage alloy is preferably a rare earth element containing yttrium. Thus, when a rare earth element is used as R,
In consideration of the cost reduction of the hydrogen storage electrode, La, Ce, P
It is preferable to use at least one rare earth element selected from r, Nd and Y. An example of this is Ce
And Mm metal of a rare earth mixture such as Mm rich in La and Lm rich La.

Further, R may be a rare earth element and at least one element selected from Ca, Zr and Ti. In this case, the latter element is preferably replaced with the former rare earth element in an amount of 0.3 atomic% or less.

In the hydrogen storage alloy, by setting x, which is the substitution amount of Mg to R, in the above range, the problem that hydrogen is hardly released can be improved, and a large discharge capacity can be realized. In particular, the substitution amount x is set to 0.1.
It is preferable that 1 ≦ x ≦ 0.6. If the substitution amount x is less than 0.1, the problem of difficulty in releasing hydrogen may not be improved, and it may be difficult to obtain a secondary battery having a large discharge capacity. On the other hand, if the substitution amount x exceeds 0.6, the amount of reversible hydrogen storage and release decreases, and it may be difficult to obtain a secondary battery having a large discharge capacity. Further, the preferable substitution amount x is:
0.15 ≦ x ≦ 0.45.

In the hydrogen storage alloy, the amount of A (z)
Is within the above range, the hydrogen storage / release characteristics such as the hydrogen storage / release speed of the alloy can be improved, and the cycle characteristics of the nickel-metal hydride secondary battery can be dramatically improved. If the amount (z) of A exceeds 1.5, the discharge capacity decreases. A more preferable range of the amount (z) of A is 0.1 ≦ z ≦ 1.0. In particular, A is preferably Co or Mn. An alkaline secondary battery provided with such a negative electrode containing a hydrogen storage alloy containing the element A has improved cycle characteristics, and particularly when Co is used, has improved discharge capacity.

When the content (y + z) of Ni and A in the hydrogen storage alloy is 2.5 or more, the hydrogen storage / release characteristics such as the hydrogen storage / release speed of the hydrogen storage alloy are remarkably improved, and a large discharge capacity is obtained. And cycle characteristics are improved. However, (y + z) is 4.5
By doing so, the number of hydrogen sites in the alloy is reduced, the hydrogen storage amount is reduced, and the discharge capacity is reduced. More preferred (y +
z) is 3.0 ≦ (y + z) ≦ 3.8.

The conductive metal piece is a hydrogen storage alloy 10
By adding 0.3 to 20 parts by weight with respect to 0 parts by weight, the discharge capacity at a relatively small current such as 100 mA can be increased, and the discharge capacity at a large current of 1 A or more can be improved. If the amount of the conductive metal pieces exceeds 20 parts by weight, it becomes difficult to improve the discharge capacity at a relatively small current such as 100 mA. A more preferable addition amount of the conductive metal piece is 0.5 to 15 parts by weight based on 100 parts by weight of the hydrogen storage alloy.

As the conductive metal, any metal can be used as long as the metal state is stable at the potential of the hydrogen electrode (negative electrode). For example, various conductive metals such as Ni and Cu can be used. In particular, Ni can improve the discharge capacity at a relatively small current such as 100 mA.

The conductive metal pieces are used, for example, in the form of particles or flakes having an average particle size of 1 to 100 μm. The negative electrode is prepared, for example, by adding the conductive metal piece conductive material to a powder of a hydrogen storage alloy represented by the general formula, kneading the mixture with a polymer binder and water to prepare a paste, and forming the paste into a conductive material. It is produced by filling a substrate, drying and molding.

Examples of the polymer binder include those similar to those used for the positive electrode 2. The paste allows a conductive material such as carbon black to be separately added.

Examples of the conductive substrate include a two-dimensional substrate such as a punched metal, an expanded metal, a perforated rigid plate, and a nickel net, and a three-dimensional substrate such as a felt-like metal porous body and a sponge-like metal substrate. Can be mentioned.

3) Separator 3 The separator 3 is made of a polymer non-woven fabric such as a non-woven fabric made of, for example, polypropylene fiber or nylon fiber, or a non-woven fabric in which polypropylene fiber and nylon fiber are mixed. In particular, a nonwoven fabric of a polyolefin fiber such as polypropylene whose surface is subjected to a hydrophilic treatment is suitable as a separator.

4) Alkaline Electrolyte Examples of the alkaline electrolyte include an aqueous solution of sodium hydroxide (NaOH), lithium hydroxide (LiOH)
Aqueous solution, potassium hydroxide (KOH) aqueous solution, NaO
H and LiOH mixed solution, KOH and LiOH mixed solution, K
A mixed solution of OH, LiOH, and NaOH can be used.

In FIG. 1 described above, the separator is interposed between the positive electrode and the negative electrode and spirally wound and accommodated in the cylindrical container 1 having a bottom. It is not limited to such a structure, for example, a separator is interposed between the positive electrode and the negative electrode, and a stack of a plurality of these is housed in a bottomed rectangular cylindrical container, and a square nickel-metal hydride secondary battery is also used. The same applies.

The nickel-hydrogen secondary battery according to the present invention described above has the general formula (R _1-x Mg _x ) Ni _y A _z (where R is a rare earth element containing yttrium, Ca, Zr
And at least one element selected from Ti and A is C
o, Mn, Fe, V, Cr, Nb, Al, Ga, Zn,
At least one element selected from Sn, Cu, Si, P and B, wherein x, y and z are each 0 <x <1,
0 ≦ z ≦ 1.5, 2.5 ≦ y + z <4.5. ), And a negative electrode comprising a conductive metal piece added in an amount of 0.3 to 20 parts by weight based on 100 parts by weight of the hydrogen storage alloy.

The hydrogen storage alloy represented by the above general formula is L
while indicating approximately 20% greater hydrogen storage capacity per volume compared to the ANI ₅ system hydrogen absorbing alloy, the secondary battery comprising a negative electrode containing this hydrogen-absorbing alloy comprising a negative electrode containing a LaNi ₅ type hydrogen absorbing alloy two As compared with the secondary battery, the discharge capacity is significantly reduced with an increase in the discharge current. For this reason, by adding a predetermined amount of conductive metal pieces to the negative electrode together with the hydrogen storage alloy, the polarization that occurs during charging or discharging is significantly reduced, and the LaNi ₅ -based hydrogen storage alloy has a high rate charge / discharge characteristic. A nickel-hydrogen secondary battery having a capacity higher than that of the case of using a negative electrode containing

That is, the negative electrode containing the LaNi ₅ hydrogen storage alloy is selectively corroded by an electrochemically low component such as lanthanum in an alkaline electrolyte, so that a surface layer containing a large amount of metallic nickel is formed. . Since this surface layer exhibits high activity in the reaction of the hydrogen electrode (negative electrode), it is considered that good characteristics can be maintained without causing a large voltage drop even in high-rate discharge.

On the other hand, the negative electrode containing the hydrogen storage alloy represented by the above general formula has a large capacity in low-rate discharge, but has a large voltage drop in high-rate discharge, and has a large LaNi ₅ content.
The capacity is considerably lower than that of a negative electrode containing a system hydrogen storage alloy. This is presumably because the hydrogen storage alloy of the above general formula has a lower nickel content than the LaNi ₅ -based hydrogen storage alloy, and magnesium contained as a constituent element easily forms a stable oxide film. In other words, both the lack of catalytic ability for the hydrogen electrode reaction on the surface of the hydrogen storage alloy particles and the decrease in conductivity between the negative electrode current collector and the hydrogen storage alloy particles caused by the coating on the surface of the hydrogen storage alloy during high-rate discharge. It is presumed to work as a large voltage drop.

From the above, by adding a small conductive metal piece to the negative electrode, electrical contact between the hydrogen storage alloy particles is promoted, and the metal state can be stably present at the negative electrode potential. In addition, since the conductive metal pieces also function as a catalyst for the negative electrode reaction, they have an effect of reducing the reaction resistance of the negative electrode. Therefore, due to the synergistic effect of the two and the high capacity characteristics of the hydrogen storage alloy of the above general formula, it is inferior in the high capacity and high rate discharge characteristics as compared with the secondary battery including the negative electrode including the LaNi ₅ -based hydrogen storage alloy. A nickel-metal hydride secondary battery can be obtained.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. (Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-3) <Preparation of Negative Electrode> La _0.7 Mg was obtained by melting La, Mg, Ni and Co in a high-frequency melting furnace.
_A hydrogen storage alloy having a composition of _0.3 Ni _2.5 Co _0.5 was produced. This alloy was heat-treated in an argon atmosphere to homogenize the alloy composition. Subsequently, the hydrogen storage alloy was mechanically pulverized in an inert atmosphere and sieved to obtain a particle size of 4%.
The alloy powder in the range of 00 to 200 mesh was selected. 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, 1.0 parts by weight, 3.0 parts by weight, 5 parts by weight of nickel powder obtained by a commercially available carbonyl method were added to 100 parts by weight of this alloy. .
After adding and mixing 0 parts by weight, 20 parts by weight, and 30 parts by weight, 11 parts of pastes were prepared by adding 25 parts by weight of a 4% by weight aqueous solution of polyvinyl alcohol to 100 parts by weight of the mixture. Subsequently, these pastes were filled in a foamed nickel substrate (three-dimensional substrate) and press-molded to produce 11 types of negative electrodes. At this time, the filling amount of the hydrogen storage alloy per unit volume is MmNi ₅ based M
The initial filling amount and press pressure were adjusted so that the volume ratio was reduced by 20% as compared with the negative electrode containing m _1.0 Ni _4.0 Co _0.4 Mn _0.3 Al _0.3 (Reference Example 1). Among the obtained negative electrodes, the negative electrode to which nickel powder was added in an amount of 20 parts by weight or less was thinner than the negative electrode containing MmNi ₅ -based alloy, and the negative electrode to which 30 parts by weight of nickel powder was added was thicker than the negative electrode containing MmNi ₅ -based alloy. Was.

<Preparation of Paste-Type Positive Electrode> To a mixed powder consisting of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder, 1 part by weight of polytetrafluoroethylene and 0.2 parts by weight of carboxymethyl cellulose were added. A paste was prepared by adding 60 parts by weight of pure water to these and kneading them. Subsequently, the paste was filled in a nickel-plated fiber substrate, dried, and then rolled by roller pressing to produce a paste-type positive electrode.

Next, a separator made of a nonwoven fabric made of a polypropylene fiber subjected to a hydrophilic treatment was interposed between each of the negative electrode and the positive electrode, and spirally wound to produce eleven kinds of electrode groups. After each of such electrode groups is housed in a cylindrical container having a bottom, an electrolytic solution made of potassium hydroxide is injected into the container, and the container is sealed and the like, whereby the positive electrode capacity regulation having the structure shown in FIG. AA size cylindrical nickel-metal hydride secondary battery was assembled. The diameter of the electrode group was made constant by adjusting the change in the thickness of the negative electrode by changing the thickness of the positive electrode. Thus, higher capacity than the battery comprising the negative electrode capacity of the battery is obtained by adding nickel powder 20 parts by weight or less, including a MmNi ₅ system alloy, is obtained by adding 30 parts by weight of nickel powder a negative electrode containing a MmNi ₅ system alloy The capacity is lower than the battery provided.

Each of the obtained secondary batteries is activated according to the existing nickel-metal hydride secondary battery processing method, and
After charging for 18 hours at a current of 00 mA and resting for 30 minutes, a charge / discharge cycle of discharging at a current of 100 mA until the voltage dropped to 1 V was repeated 10 times. After this, 10
After charging for 18 hours at 0 mA and resting for 30 minutes,
The discharge capacity was measured until the voltage dropped to 1 V at a discharge current of mA. After charging and pausing under the same conditions,
The discharge capacity until the voltage dropped to 1 V with the discharge current of A was measured. Furthermore, after collecting and suspending power under the same conditions,
The discharge capacity until the voltage dropped to 1 V with the discharge current of A was measured. The results are shown in Table 1 below. Incidentally, the negative electrode in the following Table 1 was added 1 part by weight relative to Mm _1.0 Ni _4.0 Co _0.4 Mn _0.3 see secondary battery comprising a negative electrode containing Al _0.3 Example 1, the alloys and the nickel powder same alloy 100 parts by weight The secondary battery provided with is also described as Reference Example 2.

[0037]

[Table 1]

(Examples 2-1 to 2-8 and Comparative Example 2-
1-2-3) La _0.7 Mg _0.3 Ni as hydrogen storage alloy
An AA-size cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except that the one having a composition of _3.0 was used.

For each of the obtained secondary batteries, 100 mA
, A discharge current of 1 A, and a discharge capacity at a discharge current of 2 A, respectively. The results are shown in Table 2 below.
Shown in

[0040]

[Table 2]

(Examples 3-1 to 3-8 and Comparative Example 3-
1-3-3) 1 μm thick and 1 long diameter as conductive metal pieces
An AA-size cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except that flake nickel of 0 μm was desired to be used.

For each of the obtained secondary batteries, a discharge current of 100 mA, a discharge current of 1 A,
The discharge capacity at the discharge current of A was measured. The results are shown in Table 3 below.

[0043]

[Table 3]

(Examples 4-1 to 4-8 and Comparative Example 4-
1-4-4) 1 μm thick, major axis 1 as conductive metal pieces
An AA-size cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1, except that 0 μm flake copper was desired to be used.

For each of the obtained secondary batteries, a discharge current of 100 mA, a discharge current of 1 A,
The discharge capacity at the discharge current of A was measured. The results are shown in Table 4 below.

[0046]

[Table 4]

(Examples 5-1 to 5-8 and Comparative Example 5-
1-5-3) <Preparation of Negative Electrode> Dispersion of sodium polyacrylate 0.4 part by weight, carboxymethyl cellulose (CMC) 0.1 part by weight, and polytetrafluoroethylene in 100 parts by weight of the same mixture as in Example 1 (Specific gravity 1.5, solid content 60% by weight) 2.5 parts by weight were added and kneaded to prepare 11 kinds of pastes. Subsequently, these pastes were applied to a perforated substrate made of nickel-plated iron having a thickness of 60 μm and having different thicknesses so that both surfaces became uniform, and press-molded to produce 11 types of negative electrodes. At this time,
Filling amount of the hydrogen storage alloy per unit volume _{Mm 1.0 Ni 4.0 Co 0.4 Mn 0.3} Al 0.3 to containing negative electrode (see Example 1) at a volume ratio versus initial to be reduced by 20 percent in a ₅ system MmNi The coating amount and press pressure were adjusted. Among the obtained negative electrodes, the negative electrode to which nickel powder was added in an amount of 20 parts by weight or less was thinner than the negative electrode containing MmNi ₅ -based alloy, and the negative electrode to which 30 parts by weight of nickel powder was added was thicker than the negative electrode containing MmNi ₅ -based alloy. Was.

Next, a separator made of a nonwoven fabric made of a polypropylene fiber subjected to a hydrophilic treatment was interposed between each of the negative electrodes and the positive electrode similar to that in Example 1, and spirally wound to form a nonwoven fabric.
One kind of electrode group was produced. After each of such electrode groups is housed in a cylindrical container having a bottom, an electrolytic solution made of potassium hydroxide is injected into the container, and the container is sealed and the like, whereby the positive electrode capacity regulation having the structure shown in FIG. AA size cylindrical nickel-metal hydride secondary battery was assembled. The diameter of the electrode group was made constant by adjusting the change in the thickness of the negative electrode by changing the thickness of the positive electrode. Therefore, the capacity of the battery is higher than that of the battery including the negative electrode containing the MmNi ₅ -based alloy when the nickel powder is added in an amount of 20 parts by weight or less, and the capacity of the battery is equal to or less than 30% by weight.
It became lower capacity than the battery comprising a negative electrode containing i ₅ alloy.

For each of the obtained secondary batteries, a discharge current of 100 mA, a discharge current of 1 A,
The discharge capacity at the discharge current of A was measured. The results are shown in Table 5 below.

[0050]

[Table 5]

As is clear from Tables 1 to 5, a hydrogen storage alloy having a specific composition, and a conductive metal piece added in a ratio of 0.3 to 20 parts by weight with respect to 100 parts by weight of the hydrogen storage alloy, The secondary battery of each of the examples provided with the negative electrode containing Ni was compared with the secondary battery of Reference Example 1 provided with the negative electrode containing the MmNi ₅ -based alloy in addition to increasing the capacity by discharging with a relatively small current of 100 mA. This shows that a high capacity can be obtained in both the 1A discharge and the 2A discharge.

On the other hand, Comparative Example 1 provided with a negative electrode containing a hydrogen storage alloy and a conductive metal piece added in a ratio exceeding 20 parts by weight with respect to 100 parts by weight of the hydrogen storage alloy
The secondary batteries of -3 to 5-3 have lower capacities in discharging with a relatively small current of 100 mA than those of the secondary battery of Reference Example 1 including the negative electrode including the MmNi ₅ -based alloy, and have an advantage of higher capacity. Is found to be impaired.

Further, it can be seen from the above examples that the same high discharge capacity is exhibited without being influenced by the shape of the conductive metal piece added. However, in the case of Examples 3-1 to 3-8 using nickel as the conductive metal piece, the case of Example 3-1 to 3-8 using copper as the conductive metal piece was 100 times smaller.
It turns out that the capacity at the time of mA discharge becomes high.

As is clear from comparison between the secondary batteries of Reference Example 1 provided with a negative electrode containing an MmNi ₅ -based alloy and Reference Example 2 provided with a negative electrode obtained by adding nickel powder to the same alloy, this alloy-based It can be seen that the presence or absence of nickel powder has little effect on the large current discharge characteristics of the secondary battery containing.

[0055]

As described above in detail, according to the present invention, the capacity of the secondary battery is smaller than that of a conventional secondary battery having a negative electrode containing a hydrogen storage alloy containing magnesium, nickel and a rare earth element as main constituent elements. It is possible to provide a nickel-metal hydride secondary battery that is equal to or higher and has excellent high-rate charge / discharge characteristics.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a cylindrical nickel-metal hydride secondary battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 4 ... Negative electrode, 5 ... Electrode group, 7 ... Sealing plate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shusuke Inada 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Kawasaki Office (72) Inventor Isao Sakai 72-Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Pref. Inside the Toshiba Kawasaki Plant (72) Inventor Ryuko Kono 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Kawasaki Plant (72) Inventor Hideki Yoshida 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Co., Ltd. Inside Toshiba Kawasaki Office (72) Takamichi Inaba Inventor 72, Horikawacho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Inside Toshiba Kawasaki Office (72) Inventor Motoi Kanda 72, Horikawacho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Toshiba Kawasaki Corporation In business office

Claims (2)

[Claims] 1. A compound of the general formula (R _1-x Mg _x ) Ni _y A _z
(Where R is a rare earth element containing yttrium, Ca,
At least one element selected from Zr and Ti, A
Are Co, Mn, Fe, V, Cr, Nb, Al, Ga, Z
n, Sn, Cu, Si, P, and at least one element selected from B and x, y, and z are each 0 <x <
1, 0 ≦ z ≦ 1.5, 2.5 ≦ y + z <4.5. ) And the hydrogen storage alloy 1
A nickel-hydrogen secondary battery, comprising: a negative electrode including a conductive metal piece added in an amount of 0.3 to 20 parts by weight with respect to 00 parts by weight; and a positive electrode including nickel hydroxide as an active material. 2. The nickel-metal hydride secondary battery according to claim 1, wherein the conductive metal pieces are nickel.