JP2001307720A - Hydrogen storage alloy electrode, secondary battery, hybrid car, and electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen storage alloy electrode, in which a high battery capacity is maintained and a discharge capacity at a low temperature can be improved. SOLUTION: A hydrogen storage alloy electrode includes a first hydrogen storage alloy having a composition represented by the following formula 1 and a second hydrogen storage alloy having a composition represented by the following formula 2. The weight ratio of the second hydrogen storage alloy to the total weight of the first and the second hydrogen storage alloys is 5% or more and less than 70%. (1) Lm(1)1-a-bMgaTbNicAd (2) Lm(2)1-a-bMgaTbNicAd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydrogen storage alloy electrode containing a rare earth-magnesium-nickel hydrogen storage alloy, and a secondary battery provided with the hydrogen storage alloy electrode.
This secondary battery is mounted on, for example, a portable electronic device, a hybrid car, or an electric vehicle.

[0002]

2. Description of the Related Art A hydrogen storage alloy is an alloy that can safely and easily store hydrogen as an energy source, and is attracting much attention as a new energy conversion and storage material. The fields of application of hydrogen storage alloys as functional materials include hydrogen storage and transport, heat storage and transport, thermo-mechanical energy conversion, hydrogen separation and purification, hydrogen isotope separation, and hydrogen as an active material. It has been widely proposed for batteries, catalysts in synthetic chemistry, temperature sensors, and the like. In particular, application and practical application to metal oxide / hydrogen secondary batteries are actively pursued, and research aimed at achieving higher capacity and longer life has been carried out.
Development is underway.

[0003] In current, CaCu ₅ type AB ₅ type rare earth such as - nickel based intermetallic compounds have been put to practical use.
However, the hydrogen storage alloy used in this practical battery has already shown a capacity of about 330 mAh / g,
It is difficult to further increase the capacity.

Incidentally, a secondary battery provided with a negative electrode containing a hydrogen storage alloy having a composition represented by the following formula (A) has been proposed.

(R _1-x Mg _x ) Ni _y A _z (A) where R is a rare earth element containing yttrium, Ca, Z
At least one element selected from r and Ti, A is Co, Mn, Fe, V, Cr, Nb, Al, Ga, Z
At least one element selected from n, Sn, Cu, Si, P and B, x, y and z are each 0 <x <1, 0
It is defined as ≦ z ≦ 1.5, 2.5 ≦ y + z <4.5.

[0006] The hydrogen storage alloy is capable of absorbing more than a hydrogen atom 1 with respect to the metal element 1, the current AB ₅ type rare earth - is expected as an alternative to nickel-based intermetallic compound. However, when this hydrogen storage alloy is selected to have a large La content as the R in order to increase the hydrogen storage capacity, the equilibrium hydrogen storage / release pressure (hydrogen equilibrium pressure) at low temperatures is lowered and the nickel-hydrogen secondary battery is reduced. This causes a problem that the low-temperature discharge characteristics are deteriorated.

In order to increase the equilibrium hydrogen storage / release pressure of the hydrogen storage alloy having a large La content, the ratio of Mg to R is increased or the value of the atomic ratio (y + z) is increased. A different phase is formed,
The reversibility of the release reaction is impaired.

[0008] As described above, it is difficult to eliminate the decrease in the equilibrium hydrogen storage / release pressure of a hydrogen storage alloy having a large La content by adjusting the alloy composition, and while taking advantage of the high hydrogen storage characteristics of this alloy, There is a long-awaited need for measures to ensure low-temperature discharge characteristics of secondary batteries.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydrogen storage alloy electrode and a secondary battery capable of improving the discharge capacity at a low temperature while securing a high battery capacity.

[0010] Another object of the present invention is to provide a hybrid car and an electric vehicle having excellent running performance.

[0011]

A hydrogen storage alloy electrode according to the present invention comprises a first electrode having a composition represented by the following formula (1).
And a second hydrogen storage alloy having a composition represented by the following formula (2), wherein the first and second hydrogen storage alloys
Wherein the weight ratio of the second hydrogen storage alloy to the total weight of the hydrogen storage alloy is 5% or more and less than 70%.

[0012] _{Lm (1) 1-ab Mg} a T b Ni c A d ... (1) where, from one or more elements Lm (1) is selected from rare earth elements (the rare earth elements include yttrium) And the La content is 70% by weight or more, and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1, 2.8
≤c + d≤3.8.

[0013] _{Lm (2) 1-ab Mg} a T b Ni c A d ... (2) where, from one or more elements selected from the Lm (2) is a rare earth element (the rare earth elements include yttrium) And the La content is less than 70% by weight, and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1, 2.8
≤c + d≤3.8.

A secondary battery according to the present invention is a secondary battery including a positive electrode, a negative electrode, and an alkaline electrolyte, wherein the negative electrode has a first composition having a composition represented by the above formula (1).
And a second hydrogen storage alloy having a composition represented by the formula (2), wherein the first and second hydrogen storage alloys
Wherein the weight ratio of the second hydrogen storage alloy to the total weight of the hydrogen storage alloy is 5% or more and less than 70%.

[0015] A hybrid car according to the present invention includes an electric drive means and a power supply for the electric drive means, and the power supply includes a secondary battery including a positive electrode, a negative electrode, and an alkaline electrolyte. The negative electrode includes a first hydrogen storage alloy having a composition represented by the formula (1) and a second hydrogen storage alloy having a composition represented by the formula (2);
The weight ratio of the second hydrogen storage alloy to the total weight of the first and second hydrogen storage alloys is 5% or more and less than 70%.

The electric vehicle according to the present invention includes a secondary battery as a driving power source, the secondary battery includes a positive electrode, a negative electrode, and an alkaline electrolyte.
A first hydrogen storage alloy having a composition represented by the formula (2) and a second hydrogen storage alloy having a composition represented by the formula (2), wherein the total weight of the first and second hydrogen storage alloys is The weight ratio of the second hydrogen storage alloy occupying is not less than 5% and less than 70%.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a hydrogen storage alloy electrode according to the present invention will be described.

This hydrogen storage alloy electrode includes a first hydrogen storage alloy having a composition represented by the following formula (1) and a second hydrogen storage alloy having a composition represented by the following formula (2). The weight ratio of the second hydrogen storage alloy to the total weight of the first and second hydrogen storage alloys is 5% or more and less than 70%.

[0019] _{Lm (1) 1-ab Mg} a T b Ni c A d ... (1) where, Lm (1) from one or more elements selected from rare earth elements (the rare earth elements include yttrium) And the La content is 70% by weight or more, and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1.0,
2.8 ≦ c + d ≦ 3.8.

[0020] _{Lm (2) 1-ab Mg} a T b Ni c A d ... (2) where, from one or more elements selected from the Lm (2) is a rare earth element (the rare earth elements include yttrium) And the La content is less than 70% by weight, and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1.0,
2.8 ≦ c + d ≦ 3.8.

(1) First Hydrogen Storage Alloy Lm (1) may be formed only from La, but from the viewpoint of reducing the cost of the hydrogen storage alloy electrode, La and C
It is preferable to use at least one element selected from e, Pr, Nd and Y. Among them, it is more preferable to use misch metal which is a mixture of rare earth elements.

The La content in the Lm (1) is 70% by weight.
With the above, the hydrogen storage amount of the first hydrogen storage alloy can be increased, and the discharge capacity of the secondary battery can be improved. A more preferable range of the La content is:
It is 72% by weight or more, and a more preferable range is 75% by weight or more.

As the Lm (1), La, Ce, P
When using at least one element selected from r, Nd and Y, it is desirable that the Ce content in Lm (1) be 20% by weight or less (including 0% by weight). Ce amount is 2
If it exceeds 0% by weight, a phase other than the target phase (for example, CaCu
₍ Type ₅ phase) may precipitate in large quantities, and the hydrogen storage capacity may decrease. The preferred range of Ce content is less than 18% by weight,
A more preferred range is less than 16% by weight.

A more preferred range of the atomic ratio a is 0.18
≦ a ≦ 0.32.

A more preferred range of the atomic ratio b is 0.01
≦ b ≦ 0.18.

A more preferable range of the atomic ratio d of the element A is 0.05 ≦ d ≦ 0.95. As the A,
Among them, Co, Mn, and Al are preferable.

A more preferable range of the sum of the atomic ratio c and the atomic ratio d (c + d) is 2.85 ≦ c + d ≦ 3.75.

The first hydrogen storage alloy has a first phase group having a hexagonal crystal system (excluding a phase having a CaCu ₅ type structure) and a second phase group having a rhombohedral crystal system. At least one phase selected from the group consisting of

The first phase group includes a phase having a Ce ₂ Ni ₇ type structure, a phase having a CeNi ₃ type structure, and a phase having a Ce ₂ Ni ₇ type structure.
Desirably, the phase comprises a phase structure or a phase having a crystal structure similar to the CeNi ₃ type structure. On the other hand, the second phase group includes a phase having a Gd ₂ Co ₇ type structure, a phase having a PuNi ₃ type structure, and a phase having a Gd ₂ Co ₇ type structure or PuNi.
It preferably comprises a phase having a crystal structure similar to the type ₃ structure. Here, a phase having a crystal structure similar to the Ce ₂ Ni ₇ type structure, CeNi ₃ type structure, Gd ₂ Co ₇ type structure or PuNi ₃ type structure (hereinafter referred to as a similar crystal phase)
Means a phase that satisfies the condition (a) or (b) described below.

<Condition (a)> A phase in which the main peak appearing in the X-ray diffraction pattern is similar to the main peak appearing in the X-ray diffraction pattern having the normal structure. Such similar crystal phases include, for example, Ce ₂ Ni ₇ type structure, CeNi ₃ type structure, G
Examples thereof include a phase having a crystal structure that can be defined by a d ₂ Co ₇ type structure or a PuNi ₃ type surface index (Miller index). In particular, the similar crystal phase preferably has a crystal structure described in the following (1) or (2).

(1) In X-ray diffraction using CuKα ray, the peak having the highest intensity appears in the range of 2θ of 42.1 ± 1 °, and the intensity ratio represented by the following formula (I) is 80% or less. Crystal structure that satisfies.

I ₃ / I ₄ (I) where I ₄ is the intensity of the peak having the highest intensity in X-ray diffraction using CuKα ray, and I ₃ is that the 2θ in the X-ray diffraction is 31 to 34 °. Is the intensity of the peak appearing in the range. Is the Bragg angle.

(2) 2 in X-ray diffraction using CuKα ray
A crystal structure in which a peak having the highest intensity appears in the range of θ of 42.1 ± 1 °, and a plurality of peaks appearing in the range of 2θ of 31 to 34 ° appear.

<Condition (b)> In the electron beam diffraction pattern photographed by the transmission electron microscope, the basic lattice reflection point (00
L) and a phase where a regular lattice reflection point exists at 5n equal points of the distance | G _00L | between the origin (000). Here, L and n are natural numbers.

The aforementioned distance | G _00L | is 0.385 n
It is desirable to be within the range of m ^{-1 to} 0.413 nm ^-1 . The most preferred value is 0.4 nm ^-1 .

For example, when n is 1, the distance | G _00L | between the basic grid reflection point (00L) and the origin (000) is set to 5
There are regular grid reflection points at equally dividing positions.

A hydrogen storage alloy having a Ce ₂ Ni ₇ type crystal structure or a Gd ₂ Co ₇ type crystal structure has a basic lattice reflection point (00 L) in the electron diffraction pattern.
A regular lattice reflection point exists at a position that equally divides the distance | G _00L | On the other hand, a hydrogen storage alloy having a CeNi ₃ type crystal structure or a PuNi ₃ type crystal structure has a distance | G _00L between the basic lattice reflection point (00L) and the origin (000) in the electron diffraction pattern.
A regular lattice reflection point exists at a position that bisects |.

Among the similar crystal phases, the aforementioned (a)
Those satisfying both conditions (b) and (b) are preferable.

Here, the “main phase” means that at least one phase selected from the group consisting of the first phase and the second phase occupies the largest volume in the hydrogen storage alloy, or It means that it occupies the largest area in the cross section of the storage alloy. In particular, it is preferable that the volume ratio of the at least one phase selected from the group consisting of the first phase and the second phase in the hydrogen storage alloy is 50% by volume or more. A more preferred range of the volume ratio is 60% by volume or more, further preferably 70% by volume or more.

(2) Second Hydrogen Storage Alloy As the Lm (2), an alloy comprising La and one or more other rare earth elements can be used.
Among them, it is preferable to use La and at least one element selected from Ce, Pr, Nd and Y.
In particular, it is more preferable to use a misch metal which is a mixture of rare earth elements.

The La content in the Lm (2) is 70% by weight.
By making the value less than the above value, the equilibrium hydrogen storage / release pressure at a low temperature of the second hydrogen storage alloy can be increased. A more preferred range for the La content is 68% by weight or less, and a still more preferred range is 65% by weight or less. Lm
As the La content in (2) is reduced, the equilibrium pressure can be increased, but the hydrogen storage amount may be significantly reduced, and the pulverization tends to occur due to the repetition of the hydrogen storage / release cycle. Therefore, the lower limit of the La content is preferably set to 5% by weight. A more preferred lower limit is 10% by weight.

As Lm (2), La, Ce, P
When at least one element selected from r, Nd and Y is used, it is desirable that the Ce content in Lm (2) be 20% by weight or less (including 0% by weight). Ce amount is 2
If it exceeds 0% by weight, a phase other than the target phase (for example, CaCu
₍ Type ₅ phase) may precipitate in large quantities, and the hydrogen storage capacity may decrease. The preferred range of Ce content is less than 18% by weight,
A more preferred range is less than 16% by weight.

A more preferable range of the atomic ratio a is 0.18
≦ a ≦ 0.32.

A more preferred range of the atomic ratio b is 0.01
≦ b ≦ 0.18.

A more preferable range of the atomic ratio d of the element A is 0.05 ≦ d ≦ 0.95. As the A,
Among them, Co, Al, and Mn are preferable.

The more preferable range of the sum of the atomic ratio c and the atomic ratio d (c + d) is 2.85 ≦ c + d ≦ 3.75.

The second hydrogen storage alloy has a first phase group having a hexagonal crystal system (excluding a phase having a CaCu ₅ type structure) and a second phase group having a rhombohedral crystal system. At least one phase selected from the group consisting of Examples of the first phase group and the second phase group include those similar to those described in the first hydrogen storage alloy.

The weight ratio of the second hydrogen storage alloy to the total weight of the first hydrogen storage alloy and the second hydrogen storage alloy is defined in the above range for the following reason. .

That is, the first hydrogen storage alloy is L
Since the La content in m (1) is 70% by weight or more, a high hydrogen storage amount can be obtained, but the hydrogen equilibrium pressure at low temperatures is low. On the other hand, the second hydrogen storage alloy has a lower hydrogen storage amount than the first alloy because the La content in Lm (2) is less than 70% by weight, but has a higher hydrogen equilibrium pressure at low temperatures. When a secondary battery having an electrode containing the first hydrogen storage alloy and the second hydrogen storage alloy as a negative electrode is discharged at a low temperature, the second hydrogen storage alloy having a high hydrogen equilibrium pressure at a low temperature first discharges. To contribute. When the temperature of the electrode rises due to the heat generated by the discharge, the discharge of the first hydrogen storage alloy tends to occur. When the weight ratio of the second hydrogen storage alloy to the total weight of the first and second hydrogen storage alloys is less than 5%, the electrode temperature is sufficiently increased by the heat generated by the discharge of the second hydrogen storage alloy, and Since it is difficult to increase the height uniformly, the first hydrogen storage alloy hardly contributes to the discharge, so that high-temperature discharge characteristics cannot be obtained. On the other hand, when the weight ratio of the second hydrogen storage alloy is 70% or more, the discharge characteristics of the secondary battery gradually approach the discharge characteristics of the second hydrogen storage alloy, and a high battery capacity cannot be obtained.

As in the present invention, by setting the weight ratio of the second hydrogen storage alloy to the total weight of the first and second hydrogen storage alloys to be 5% or more and less than 70%, a low-temperature environment can be obtained. When the discharge is performed, the electrode temperature can be raised as a whole by the heat generated by the discharge of the second hydrogen storage alloy, so that the first hydrogen storage alloy having a high hydrogen storage amount can sufficiently contribute to the discharge. As a result, the discharge capacity of the secondary battery at a low temperature can be improved. Further, since the discharge characteristics of the first hydrogen storage alloy can be sufficiently reflected in the discharge characteristics of the secondary battery, a high battery capacity can be obtained. A more preferred range of the weight ratio is 7% or more and 65% or less, and a still more preferred range is 10% or more and 60% or less.

The first hydrogen storage alloy and the second hydrogen storage alloy each have an average particle size of 10 to 150 μm.
It is preferable to be within the range. When the average particle size is less than 10 μm, the surface area of the hydrogen storage alloy increases, so that corrosion of the alloy surface due to the electrolytic solution may increase and the cycle life may be reduced. On the other hand, if the average particle diameter exceeds 150 μm, the electrode reactivity is significantly reduced due to the decrease in the surface area of the hydrogen storage alloy, and high-temperature discharge characteristics may not be obtained. A more desirable range of the average particle size is 40 to 130.
μm. Note that the average particle diameter of the first hydrogen storage alloy and the second hydrogen storage alloy may be the same or different from each other.

In the hydrogen storage alloy electrode according to the present invention, for example, a conductive material is added to the powder of the first and second hydrogen storage alloys described above, and the mixture is kneaded with a binder and water to prepare a paste. The paste is filled in a conductive substrate, dried, and then formed by pressure molding.

Examples of the binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, and polytetrafluoroethylene.

Examples of the conductive material include carbon black.

Examples of the conductive substrate include a two-dimensional substrate such as a punched metal, an expanded metal, and a nickel net, and a three-dimensional substrate such as a felt-like metal porous body and a sponge-like metal substrate. it can.

In the hydrogen storage alloy electrode according to the present invention,
Composition and crystal structure of the second hydrogen storage alloy, first and second hydrogen storage alloys
Is measured by the method described below.

(I) Compositions and Crystal Structures of First and Second Hydrogen Storage Alloys The compositions of the first and second hydrogen storage alloys can be determined, for example, by a wavelength-dispersive X-ray microanalyzer of a scanning electron microscope.

The crystal structure of the main phase of the first and second hydrogen storage alloys can be determined from an X-ray diffraction pattern using Cu-Kα radiation as an X-ray source.

Further, the occupancy of the main phase of the first and second hydrogen storage alloys is measured by the method described below. That is, scanning electron micrographs of five arbitrary visual fields are taken, and for each micrograph, the area ratio of the main phase to the alloy area in the visual field (this alloy area is taken as 100%) is determined. The average value of the obtained area ratios is calculated, and this is defined as the volume ratio of the main phase in the hydrogen storage alloy. However, when the hydrogen storage alloy is produced by quenching the molten metal, the crystal grain size becomes as small as about 1 μm or less, so that it may be difficult to observe the main phase with a scanning electron microscope. In this case, a transmission electron microscope is used instead of the scanning electron microscope.

(II) Mixing Ratio The mixing ratio of the first and second hydrogen storage alloys can be determined by, for example, combining wet analysis such as titration analysis and ICP analysis with the method (I). The composition formulas of the first and second hydrogen storage alloys are represented by the following formulas (3) and (4), respectively, and the mixing ratio of the first and second hydrogen storage alloys is k:
(1-k), the total weight of each element Lm _total , Mg
_total , T _total , Ni _total , A _total are the following (5)-
Equation (9) is obtained.

Lm _1-a1-b1 Mg _a1 T _b1 Ni _c1 A _d1 (3) Lm _1-a2-b2 Mg _a2 T _b2 Ni _c2 A _d2 (4) Lm _total = k (1-a1-b1) + (1−k) (1−a2−b2) (5) Mg _total = k × a1 + (1−k) × a2 (6) T _total = k × b1 + (1−k) × b2 (7) Ni _total = k × c1 + (1-k) × c2 (8) A _total = k × d1 + (1-k) × d2 (9) By the way, the (I) first and second hydrogen storage alloys According to the method described in the composition and crystal structure of
_{total, Mg total, T total,} Ni total and A _{tota l} is because it is known, the mixing ratio k: (1-k) can be obtained. Further, the La concentration in Lm of the first and second hydrogen storage alloys can be calculated from Lm _total and the mixing ratio k: (1-k).

Next, a secondary battery provided with the hydrogen storage alloy electrode according to the present invention will be described.

This secondary battery has an electrode group including a positive electrode, the above-described hydrogen storage alloy electrode as a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an alkali impregnated in the electrode group. An electrolyte is provided.

Hereinafter, the positive electrode, the negative electrode, the separator, and the electrolyte will be described.

1) Positive electrode This positive electrode is prepared, for example, by adding a conductive material to nickel hydroxide powder as an active material, kneading the mixture with a polymer binder and water to prepare a paste, and applying the paste to a conductive substrate. It is produced by filling, drying, and then molding.

The above-mentioned nickel hydroxide powder contains zinc oxide,
It may contain at least one compound selected from the group consisting of cobalt oxide, zinc hydroxide and cobalt hydroxide.

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, fiber-like, or felt-like porous metal body made of nickel, stainless steel, or nickel-plated metal.

2) Separator Examples of the separator include a polymer nonwoven fabric such as a polypropylene nonwoven fabric, a nylon nonwoven fabric, and a nonwoven fabric in which polypropylene fibers and nylon fibers are mixed. In particular, a polypropylene nonwoven fabric whose surface has been hydrophilized is suitable as a separator.

3) Alkaline Electrolyte Examples of the alkaline electrolyte include an aqueous solution of sodium hydroxide (NaOH), an aqueous solution of lithium hydroxide (LiOH), an aqueous solution of potassium hydroxide (KOH), and a mixed solution of NaOH and LiOH. , A mixed solution of KOH and LiOH, a mixed solution of KOH, LiOH and NaOH, and the like.

FIG. 1 shows a cylindrical alkaline secondary battery which is an example of the secondary battery according to the present invention.

As shown in FIG. 1, an electrode group 5 produced by laminating a positive electrode 2, a separator 3, and a negative electrode 4 and spirally winding them is housed in a bottomed cylindrical container 1. ing. The negative electrode 4 is arranged at the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. Hole 6 in the center
Is disposed in 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 attached to the container 1 by caulking to reduce the diameter of the upper opening inward. 7 is 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 provided with the sealing plate 7.
It is attached so as to cover the hole 6 above. 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.
Circular holding plate 12 made of an insulating material having a hole in the center
Are arranged on the positive electrode terminal 10 such that the projections of the positive electrode terminal 10 protrude from the holes of the holding plate 12. The outer tube 13 is provided on the periphery of the holding plate 12,
The side surface of the container 1 and the periphery of the bottom of the container 1 are covered.

The secondary battery according to the present invention includes, in addition to the cylindrical alkaline secondary battery as shown in FIG. 1 described above, an electrode group having a structure in which a positive electrode and a negative electrode are alternately laminated with a separator interposed therebetween. The present invention can be similarly applied to a rectangular alkaline secondary battery having a structure in which an electrolytic solution is contained in a bottomed rectangular cylindrical container.

Next, a hybrid car and an electric vehicle according to the present invention will be described.

The hybrid car according to the present invention includes an external combustion engine or an internal combustion engine, an electric driving means such as a motor, and a power supply for the electric driving means. The power supply includes a secondary battery including a positive electrode, a negative electrode, and an alkaline electrolyte. The hydrogen storage alloy electrode according to the present invention is used for the negative electrode.

The “hybrid car” referred to here includes an external combustion engine or an internal combustion engine that drives a generator, and an electric drive unit that drives wheels by electric power generated and electric power from the secondary battery. The one that drives the wheels by selectively using the driving force of both the fuel engine or the internal combustion engine and the electric driving means is included.

The electric vehicle according to the present invention includes a secondary battery as a driving power supply. The secondary battery includes a positive electrode, a negative electrode, and an alkaline electrolyte. The hydrogen storage alloy electrode according to the present invention is used for the negative electrode.

According to the hybrid car and the electric vehicle equipped with the secondary battery having the hydrogen storage alloy electrode according to the present invention as a negative electrode, the running performance such as fuel efficiency can be improved.

[0080]

Embodiments of the present invention will be described below in detail.

(Examples 1 to 5 and Comparative Examples 1 to 3) << Preparation of Negative Electrode >> (Preparation of First Hydrogen Storage Alloy) Misch metal Lm (1) containing 96% lanthanum as a main component, magnesium, nickel , Cobalt, manganese, and aluminum were mixed, and an alloy ingot was prepared using a high-frequency induction furnace. This alloy ingot was heat-treated at 900 ° C. for 10 hours in an argon atmosphere, and the composition was Lm (1) _0.82 Mg _0.18 Ni _2.9 C
A hydrogen storage alloy ingot represented by o _0.4 Mn _0.2 Al _0.08 was obtained.

When the crystal structure of the hydrogen storage alloy was observed from an X-ray diffraction pattern using Cu-Kα radiation as an X-ray source, the crystal structure of the main phase was Ce ₂ Ni ₇ type.

Further, with respect to this hydrogen storage alloy, scanning electron micrographs of five arbitrary visual fields were taken. For each micrograph, the area ratio of the main phase to the alloy area in the visual field was determined. Next, the volume ratio of the main phase in the hydrogen storage alloy was obtained by calculating the average value of the area ratio, and the volume ratio was 70% by volume.

Subsequently, the hydrogen-absorbing alloy was mechanically pulverized in an inert atmosphere, and sieved to select an alloy powder having a size of not less than 20 μm and not more than 150 μm. When the particle size distribution was measured by a laser diffraction / scattering type particle size distribution analyzer, the average particle size corresponding to 50% by weight was 100 μm.

(Preparation of second hydrogen storage alloy) 48% lanthanum, 35% neodymium, 4% cerium and 1%
Misch metal Lm containing 0% praseodymium as a main component
(2), magnesium, nickel, cobalt, manganese,
Aluminum was mixed and an alloy ingot was prepared using a high frequency induction furnace. This alloy ingot was subjected to a heat treatment at 900 ° C. for 10 hours in an argon atmosphere to obtain a hydrogen storage alloy ingot having a composition shown in Table 1 below.

When the crystal structure of the hydrogen storage alloy was observed from an X-ray diffraction pattern using Cu-Kα radiation as an X-ray source, the crystal structure of the main phase was Ce ₂ Ni ₇ type.

Further, with respect to this hydrogen storage alloy, scanning electron micrographs of five arbitrary visual fields were taken. For each micrograph, the area ratio of the main phase to the alloy area in the visual field was determined. Next, the volume ratio of the main phase in the hydrogen storage alloy was obtained by calculating the average value of the area ratio, and the volume ratio was 70% by volume.

Subsequently, this hydrogen storage alloy was mechanically pulverized in an inert atmosphere, and an alloy powder having a size of 20 μm or more and 150 μm or less was selected by sieving. When the average particle size was determined in the same manner as described for the first hydrogen storage alloy, it was 100 μm.

The weight ratio of the second hydrogen storage alloy powder to the total weight of the obtained first hydrogen storage alloy powder and the second hydrogen storage alloy powder is set to the value shown in Table 1 below. The mixture was mixed to obtain a hydrogen storage alloy mixed powder for an electrode. 0.4 parts by weight of sodium polyacrylate and 0.1 parts by weight of carboxymethyl cellulose were added to 100 parts by weight of the alloy powder.
Parts by weight of a polytetrafluoroethylene dispersion (dispersion medium:
2.5 parts by weight of water and a solid content of 60% by weight) are added and kneaded,
It was evenly applied to both sides of a substrate made of a nickel-plated iron perforated plate having a thickness of 60 μm. Subsequently, after drying, pressing, and cutting, a negative electrode was produced.

(Assembly of Battery) An electrode group was manufactured by spirally winding the negative electrode and a non-sintered nickel positive electrode prepared by a known technique via a separator. The obtained electrode group was inserted into a battery can, and 6 mol /
L KOH, 1 mol / L NaOH and 0.5 mol
/ L LiOH mixed aqueous solution was injected, and then sealed to obtain a capacity of 1400 mAh.
Thus, an AA size nickel-metal hydride secondary battery was assembled.

(Examples 6 to 11 and Comparative Examples 4 and 5) The composition of the second hydrogen storage alloy was changed to the composition shown in Table 2 below, and the second hydrogen storage alloy and the first hydrogen storage alloy described above were used. The negative electrode was prepared in the same manner as described in Example 1 except that the alloy was mixed with the alloy so that the weight ratio of the second hydrogen storage alloy to the total weight thereof became the value shown in Table 2 below. Was prepared. Next, a nickel-hydrogen secondary battery was assembled in the same manner as described in Example 1 except that this negative electrode was used.

(Examples 12 to 17 and Comparative Examples 6 and 7)
The composition of the second hydrogen storage alloy was changed to the composition shown in Table 3 below, and the second hydrogen storage alloy and the first hydrogen storage alloy described above accounted for the total weight of the second hydrogen storage alloy. A negative electrode was prepared in the same manner as described in Example 1 above, except that the weight ratio was mixed as shown in Table 3 below. Next, a nickel-hydrogen secondary battery was assembled in the same manner as described in Example 1 except that this negative electrode was used.

(Examples 18 to 24 and Comparative Examples 8 to 1)
4) Composition of second hydrogen storage alloy and Lm of this alloy
The weight ratio of La in (2) is as shown in Table 4 below, and the second hydrogen storage alloy occupies the total weight of the second hydrogen storage alloy and the first hydrogen storage alloy. A negative electrode was produced in the same manner as described in Example 1 except that the weight ratio was mixed as shown in Table 4 below. Then, except using this negative electrode,
A nickel-metal hydride secondary battery was assembled in the same manner as described in Example 1 described above.

The obtained Examples 1 to 24 and Comparative Examples 1 to 1
After charging the secondary battery of No. 4 at room temperature with a current of 140 mA for 13 hours, the battery was subjected to five charge / discharge cycles of discharging at a current of 140 mA until the battery voltage dropped to 1.0 V. Next, after charging for 13 hours with a current of 140 mA, the secondary battery was cooled to −20 ° C.
Was discharged until the battery voltage dropped to 1.0 V, and the discharge capacity at this time was measured. 2 obtained in this way
The discharge capacities at 0 ° C. and −20 ° C. are represented by relative values when the discharge capacity of the secondary battery of Comparative Example 1 is 1.00, and the results are also shown in Tables 1 to 4 below.

[0095]

[Table 1]

[0096]

[Table 2]

[0097]

[Table 3]

[0098]

[Table 4]

As is clear from Table 1, the above (1)
Including a first hydrogen storage alloy having a composition represented by the formula and a second hydrogen storage alloy having a composition represented by the above formula (2), wherein the weight ratio of the second alloy is 5% or more and 70% or more.
It can be seen that the secondary batteries of Examples 1 to 5 provided with a hydrogen storage alloy electrode of less than 20 ° C. can improve the discharge capacity at a low temperature without substantially impairing the discharge capacity at 20 ° C. (battery capacity).

On the other hand, the secondary battery of Comparative Example 2 in which the weight ratio of the second hydrogen storage alloy is less than 5% has a high discharge capacity at 20 ° C. (battery capacity), but has improved low-temperature discharge characteristics. It turns out that you can't. Further, it can be seen that the secondary battery of Comparative Example 3 in which the weight ratio of the second hydrogen storage alloy is 70% or more is inferior in both battery capacity and low-temperature discharge characteristics.

Further, from Tables 2 and 3, even when the composition of the second hydrogen storage alloy was changed, the weight ratio of the second alloy was 5%.
% To less than 70%, the discharge capacity at low temperatures can be improved while securing a high battery capacity.

[0102]

As described above in detail, according to the hydrogen storage alloy electrode and the secondary battery according to the present invention, it is possible to improve the low-temperature discharge capacity while securing a high battery capacity. It works. Further, according to the hybrid car and the electric vehicle according to the present invention, remarkable effects such as improvement in running performance such as fuel efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a cylindrical alkaline secondary battery as an example of a secondary battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 5 ... Electrode group, 7 ... Sealing plate, 8 ... Insulating gasket.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/30 B60K 9/00 C (72) Inventor Isao Sakai 8 Shinsugita-cho Isogo-ku, Yokohama-shi, Kanagawa Inside the Toshiba Yokohama Office (72) Inventor Takamichi Inaba, 8-8 Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa Prefecture Inside the Toshiba Yokohama Office (72) Inventor Jun-ichi Takabayashi 8th, Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa Toshiba Yokohama Office (72) Inventor Masaaki Yamamoto 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Yokohama Office (72) Inventor Hideharu Suzuki 3-4-1-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Stock In-company (72) Inventor Shuichiro Irie 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation (72) Inventor Takeno Wada 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo F-term in Toshiba Battery Corporation (reference) 3D035 AA00 5H028 EE01 EE05 HH01 HH05 5H050 AA06 AA08 BA14 CA03 CB16 CB29 FA19 HA01 HA02 HA05

Claims (9)

[Claims] A first hydrogen storage alloy having a composition represented by the following formula (1) and a second hydrogen storage alloy having a composition represented by the following formula (2); A hydrogen storage alloy electrode, wherein the weight ratio of the second hydrogen storage alloy to the total weight of the second hydrogen storage alloy is 5% or more and less than 70%. _{Lm (1) 1-ab Mg} a T b Ni c A d ... (1) where, Lm (1) together with consists of one or more elements selected from rare earth elements (the rare earth elements include yttrium), La content is 70% by weight or more, and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1, 2.8
≤c + d≤3.8. _{Lm (2) 1-ab Mg} a T b Ni c A d ... (2) However, Lm (2) together with consists of one or more elements selected from rare earth elements (the rare earth elements include yttrium), La content is less than 70% by weight and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1, 2.8
≤c + d≤3.8. 2. The first hydrogen storage alloy and the second hydrogen storage alloy are composed of a first phase group having a hexagonal crystal system (excluding a phase having a CaCu ₅ type structure) and a crystal system. 2. The hydrogen storage alloy electrode according to claim 1, wherein each of the main phases includes at least one type of phase selected from the group consisting of a second phase group that is a rhombohedral. 3. The average particle diameter of each of the first hydrogen storage alloy and the second hydrogen storage alloy is 10 to 150 μm.
2. The hydrogen storage alloy electrode according to claim 1, wherein m is within a range of m. 4. The Lm (2) has a La content of 5 to 68.
2. The hydrogen storage alloy electrode according to claim 1, wherein the content of Ce is 20% by weight (including 0% by weight) or less within a range of 2% by weight. 5. A secondary battery comprising a positive electrode, a negative electrode, and an alkaline electrolyte, wherein the negative electrode comprises: a first hydrogen storage alloy having a composition represented by the following formula (1); A second hydrogen storage alloy having a composition represented by the following formula: wherein the weight ratio of the second hydrogen storage alloy to the total weight of the first and second hydrogen storage alloys is 5% or more and less than 70% A secondary battery characterized by the following. _{Lm (1) 1-ab Mg} a T b Ni c A d ... (1) where, Lm (1) together with consists of one or more elements selected from rare earth elements (the rare earth elements include yttrium), La content is 70% by weight or more, and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1, 2.8
≤c + d≤3.8. _{Lm (2) 1-ab Mg} a T b Ni c A d ... (2) However, Lm (2) together with consists of one or more elements selected from rare earth elements (the rare earth elements include yttrium), La content is less than 70% by weight and T is Ca
And at least one element selected from the group consisting of Ti and A, where A is Co, Al, Mn, Fe, Cr, Cu, Sn,
At least one element selected from the group consisting of Zn, Ga, Si and B, and the atomic ratios a, b, c and d are 0.15
≦ a ≦ 0.35, 0 ≦ b ≦ 0.2, 0 ≦ d ≦ 1, 2.8
≤c + d≤3.8. 6. The average particle diameter of each of the first hydrogen storage alloy and the second hydrogen storage alloy is 10 to 150 μm.
The secondary battery according to claim 5, wherein m is within a range of m. 7. The Lm (2) has a La content of 5 to 68.
6. The secondary battery according to claim 5, wherein the content of Ce is 20% by weight or less (including 0% by weight) within a range of 10% by weight. 8. A hybrid car comprising an electric drive means and a power supply for the electric drive means, wherein the power supply is a positive electrode, a negative electrode comprising the hydrogen storage alloy electrode according to claim 1, and an alkaline electrolyte. A hybrid car comprising a secondary battery comprising: 9. An electric vehicle including a secondary battery as a driving power source, wherein the secondary battery includes a positive electrode, a negative electrode including the hydrogen storage alloy electrode according to claim 1, and an alkaline electrolyte. And an electric car.