JP3370071B2 - Hydrogen storage alloy electrode and nickel-metal hydride storage battery using this electrode - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage alloy electrode capable of reversibly electrochemically storing and releasing hydrogen, and a nickel-hydrogen storage battery using the hydrogen storage alloy electrode.

[0002]

2. Description of the Related Art In recent years, in order to obtain an alkaline storage battery having a high energy density, a nickel-metal alloy using a hydrogen storage alloy electrode is used.
Hydrogen storage batteries have been attracting attention and have come into practical use. Examples of hydrogen storage alloys used in this nickel-hydrogen storage battery include AB ₅ type rare earth-based LaNi ₅ -based hydrogen storage alloys,
An MmNi ₅ -based hydrogen storage alloy based on Mm (Misch metal), which is cheaper than La, is known. Also,
AB ₂ type zirconium based ZrNi ₂ based hydrogen storage alloys and TiNi based alloys are known.

As a hydrogen storage alloy used for such a hydrogen storage alloy electrode, a crushed alloy obtained by mechanically or electrochemically crushing an alloy lump (ingot), flakes or spherical powder, or an atomizing method, rotation Spherical or similar-shaped powder (hereinafter simply referred to as a spheroidal alloy) produced by a disc method, a rotating nozzle method, a single roll powder, or a twin roll method is used.

By the way, in the hydrogen storage alloy electrode using the crushed alloy alone, the contact between the alloy particles is mainly a surface contact, which has an advantage that the electrical contact resistance is small, but the drawback is that the packing density is low. was there. On the other hand, in the hydrogen storage alloy electrode using the substantially spherical alloy alone,
While it has the advantage of high packing density, it has a drawback that the electrical contact resistance is large because the contact between alloy particles is mainly point contact. By the way, when a hydrogen storage alloy having a low packing density is used for a hydrogen storage alloy electrode, the low rate discharge characteristics are deteriorated, and when a hydrogen storage alloy having a large contact resistance between alloy particles is used for the hydrogen storage alloy electrode, a high rate discharge characteristic is obtained. Is reduced.

Further, since the substantially spherical alloy has an oxide film mainly containing rare earth oxides on the surface of the alloy and has not been crushed at the same time, the substantially spherical alloy is cracked at the time of charging in the initial step of the charge / discharge cycle. It is difficult to form a new active hydrogen storage surface. Therefore, hydrogen is likely to be generated during charging and the internal pressure of the battery is increased, which causes a problem that the charge / discharge cycle life is shortened due to leakage of the electrolyte solution and depletion of the electrolyte solution resulting from the leak.

[0006]

Therefore, in order to bring out the advantages of both the crushed alloy and the substantially spherical alloy, it is preferable to use the crushed alloy and the substantially spherical alloy in a mixture.
It was proposed in Japanese Patent No. 105943. In the one proposed in Japanese Patent Laid-Open No. 7-105943, a low-rate discharge and a high rate are achieved by using a mixed powder in which a crushed alloy and a substantially spherical alloy are mixed in a specific ratio for a hydrogen storage alloy electrode. That is, it is possible to obtain a hydrogen storage alloy electrode that exhibits excellent discharge characteristics regardless of discharge.

However, the above-mentioned Japanese Patent Laid-Open No. 7-105.
In the hydrogen storage alloy electrode proposed in Japanese Patent Publication No. 943, since the crushed alloy and the substantially spherical alloy have the same alloy composition, a difference occurs in the crackability of the alloy due to charge and discharge in the activation step and the like. Here, the substantially spherical hydrogen storage alloy has a large amount of rare earth components distributed on the surface and a large amount of nickel components inside, so the crackability of the alloy due to charge and discharge is poor. If the alloy has poor cracking properties, the number of active surfaces does not increase, so the hydrogen storage property is poor at the beginning of charging, and hydrogen gas is easily generated by charging. Therefore, the pressure in the battery rises, the electrolyte leaks, the electrolyte decreases, the charge / discharge cycle decreases, and the charge / discharge cycle life decreases due to electrolyte depletion. .

Therefore, the present invention has been made to solve the above problems, and optimizes the molar ratio of the constituent metals of the crushed alloy and the substantially spherical alloy to obtain the gas absorption performance during charge and discharge and the low temperature. An object is to obtain a hydrogen storage electrode having excellent discharge characteristics and excellent cycle characteristics.

[0009]

Means for Solving the Problem and Its Action / Effect To achieve the above object, the hydrogen storage alloy electrode of the present invention comprises:
AB _X type (where A is La,
Rm is a rare earth element such as Mm, B is Ni and a plurality of other metal elements such as Co and Mn, Al in which Ni is partially replaced), and is a substantially spherical AB _X type substantially spherical alloy. The hydrogen storage alloy is mixed, and the value of _X in AB _X of the substantially spherical hydrogen storage alloy is made smaller than the value of _X in AB _X of the ground hydrogen storage alloy.

When the value of _X in AB _X of the substantially spherical hydrogen storage alloy is set to be smaller than that of the ground hydrogen storage alloy in this way, distortion is likely to occur in the crystals of the substantially spherical hydrogen storage alloy, so that the activation step It becomes easily cracked by charging and discharging. As a result, the substantially spherical hydrogen-storing alloy, which is poorly cracked, is easily cracked, so that the number of active surfaces of the hydrogen-storing alloy electrode increases. As a result, the hydrogen storage property at the initial stage of charge and discharge is improved, and the generation of hydrogen gas is reduced even during charging, so that the pressure inside the battery does not rise and the decrease in the electrolyte solution can be prevented. The discharge cycle is improved. In this case, it is preferable to optimize the value of _X in AB _X of the substantially spherical hydrogen storage alloy to be smaller than the value of _X in AB _X of the ground hydrogen storage alloy by 0.05 to 0.30.

Further, in order to achieve the above object, the hydrogen storage alloy electrode of the present invention is made of AB _X produced through a crushing process.
Type (however, A is a rare earth element such as La or Mm, B is N
A substantially spherical AB is added to a pulverized hydrogen storage alloy of Co and a plurality of other metal elements such as Mn and Al in which a part of i and Ni are replaced.
_{The X-} shaped substantially spherical hydrogen storage alloy is mixed, and the cobalt component of the substantially spherical hydrogen storage alloy is smaller than that of the ground hydrogen storage alloy.

When the cobalt component of the substantially spherical hydrogen storage alloy is made smaller than that of the crushed hydrogen storage alloy in this way, the substantially spherical hydrogen storage alloy has a large volume change rate during hydrogen storage, so that the substantially spherical hydrogen storage alloy has a substantially spherical shape. The crackability of the hydrogen storage alloy is improved. As a result, the substantially spherical hydrogen-storing alloy, which is poorly cracked, is easily cracked, so that the number of active surfaces of the hydrogen-storing alloy electrode increases. As a result,
Since the hydrogen storage property at the beginning of charge and discharge is improved and the generation of hydrogen gas is reduced even during charging, the pressure inside the battery does not rise, the decrease of the electrolyte can be prevented, and the charge and discharge cycle can be improved. improves.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention when the hydrogen storage alloy electrode of the present invention is applied to a nickel-hydrogen storage battery will be described below. 1. Production of Hydrogen Storage Alloy (1) Ground Hydrogen Storage Alloy MmNi _3.20 Co _1.00 Mn _0.60 Al _0.20 Commercially available metal elements Mm, Ni, so as to be a hydrogen storage alloy represented by
Co, Al, and Mn were weighed and mixed, and then charged into a high-frequency melting furnace to be melted and cooled to prepare a hydrogen storage alloy ingot (ingot). 1 liter of water was added to 1 kg of this hydrogen storage alloy lump, and the mixture was put into a ball mill.
It was crushed so that the average particle size was 50 μm. The hydrogen storage alloy having an average particle size of 50 μm thus obtained was designated as crushed alloy α.

[0014] (2) On the other hand substantially spherical hydrogen absorbing alloy in the hydrogen storage alloy represented by _{Mm a Ni b Co c Mn d} Al e, so that the alloy compositions as shown in Table 1 below, a commercially available Each metal element Mm, Ni, Co, A
l and Mn were weighed and mixed to prepare a substantially spherical hydrogen storage alloy having an average particle size of 50 μm by a gas atomizing method. The hydrogen storage alloy produced in this manner is replaced by a substantially spherical hydrogen storage alloy β, γ, δ, ε, ζ, η, θ, ι,
κ, λ, ν. In Table 1 below, the molar ratio of the rare earth component (Mm) is A, and the total molar ratio of the other components (Ni component, Co component, Mn component, Al component) is B (= b + c + d + e), and A The ratio of: B is a stoichiometric ratio (hereinafter, this is referred to as AB, for example, A: B =
1: expressed 5 as a an AB _5).

[0015]

[Table 1]

2. Surface Treatment of Hydrogen Storage Alloy Next, each hydrogen storage alloy α obtained as described above
ν is put in a 30 mass% aqueous solution of potassium hydroxide (KOH), heated to 100 ° C. and stirred to immerse each hydrogen storage alloy. After performing this immersion treatment for about 1 hour, it was cooled and washed. Then, each of them was heat-treated in a hydrogen gas atmosphere (1 atm) at a temperature of 800 ° C. for 10 hours.

3. Production of Hydrogen Storage Alloy Negative Electrode Plate (1) Example 1 Hydrogen storage alloy α produced as described above (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) in 50 mass% and the hydrogen storage alloy β (substantially spherical alloy: AB _4.97 ) produced as described above.
Of 50% by weight and polyethylene oxide (PEO) as a binder of 0.5% by weight with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. The core was coated on a nickel current collector made of punching metal with Ni plating to prepare a hydrogen storage alloy negative electrode plate a of Example 1.

(2) Example 2 Hydrogen storage alloy α (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) in 50 mass% and the hydrogen storage alloy γ (substantially spherical alloy: AB _4.95 ) produced as described above.
Of 50% by weight and polyethylene oxide (PEO) as a binder of 0.5% by weight with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. The core was coated on a nickel current collector made of punching metal with Ni plating to prepare a hydrogen storage alloy negative electrode plate b of Example 2.

(3) Example 3 Hydrogen storage alloy α (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) and 50 mass% of the hydrogen storage alloy δ (substantially spherical alloy: AB _4.80 ) produced as described above.
Of 50% by weight and polyethylene oxide (PEO) as a binder of 0.5% by weight with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. The core was coated on a nickel current collector made of punching metal with Ni plating, to prepare a hydrogen storage alloy negative electrode plate c of Example 3.

(4) Example 4 Hydrogen storage alloy α (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) and 50 mass% of the hydrogen storage alloy ε (substantially spherical alloy: AB _4.70 ) produced as described above.
Of 50% by weight and polyethylene oxide (PEO) as a binder of 0.5% by weight with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. The core was coated on a nickel current collector made of punching metal with Ni plating to prepare a hydrogen storage alloy negative electrode plate d of Example 4.

(5) Example 5 Hydrogen storage alloy α (ground alloy:
Co ₁ . ₀₀ , AB _5.00 ) in an amount of 50% by mass, and the hydrogen storage alloy ζ (substantially spherical alloy: AB _4.65 ) produced as described above.
Of 50% by weight and polyethylene oxide (PEO) as a binder of 0.5% by weight with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. A core of the hydrogen storage alloy negative electrode plate e of Example 5 was prepared by coating the core on a nickel current collector made of punching metal.

(6) Example 6 Hydrogen storage alloy α (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) in an amount of 50% by mass, and the hydrogen storage alloy η (substantially spherical alloy: Co _0.98 , Co _0.98 ,
AB _4.89 ) and 50% by mass of polyethylene oxide (PEO) as a binder with respect to the total amount of the hydrogen storage alloy and 0.5% by mass of water, and kneading with water to prepare a hydrogen storage alloy slurry. A hydrogen storage alloy negative electrode plate f of Example 6 was produced by coating a nickel current collector made of a punched metal obtained by plating an iron core with Ni.

(7) Example 7 Hydrogen storage alloy α (ground alloy:
Co ₁ . ₀₀ , AB _5.00 ) in an amount of 50 mass% and the hydrogen storage alloy θ (substantially spherical alloy: Co _0.96 ,
AB _4.79 ) and 50% by mass of polyethylene oxide (PEO) as a binder with respect to the total amount of the hydrogen storage alloy and 0.5% by mass of water, and kneading with water to prepare a hydrogen storage alloy slurry. A hydrogen storage alloy negative electrode plate g of Example 7 was prepared by coating a nickel current collector made of a punching metal obtained by plating an iron core with Ni.

(8) Example 8 Hydrogen storage alloy α (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) in an amount of 50 mass% and the hydrogen storage alloy ι (substantially spherical alloy: Co _0.90 , Co _0.90 ,
50% by mass of AB _5.00 ), 0.5% by mass of polyethylene oxide (PEO) as a binder with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. A hydrogen storage alloy negative electrode plate h of Example 8 was produced by coating a nickel current collector made of a punching metal obtained by plating an iron core with Ni.

(9) Example 9 Hydrogen storage alloy α (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) in an amount of 50% by mass, and the hydrogen storage alloy κ (substantially spherical alloy: Co _0.85 , produced as described above).
50% by mass of AB _5.00 ), 0.5% by mass of polyethylene oxide (PEO) as a binder with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. A hydrogen storage alloy negative electrode plate i of Example 9 was prepared by coating a nickel current collector made of a punching metal obtained by plating an iron core with Ni.

(10) Example 10 Hydrogen storage alloy α (crushed alloy:
Co ₁ . ₀₀ , AB _5.00 ) in an amount of 50% by mass, and the hydrogen storage alloy λ (substantially spherical alloy: Co _0.80 , Co _0.80 ,
50% by mass of AB _5.00 ), 0.5% by mass of polyethylene oxide (PEO) as a binder with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a hydrogen storage alloy slurry. Example 10: Application to a nickel current collector made of punching metal obtained by plating an iron core with Ni
A hydrogen storage alloy negative electrode plate j of was prepared.

(6) Comparative Example 1 Hydrogen storage alloy α (ground alloy:
Co ₁ . ₀₀ , AB _5.00 ) and 100% by weight of polyethylene oxide (PEO) as a binder with respect to the hydrogen storage alloy, and 0.5% by weight of water, and kneading with water to prepare a hydrogen storage alloy slurry. A hydrogen storage alloy negative electrode plate x of Comparative Example 1 was prepared by coating an iron core on a nickel current collector made of a punched metal plated with Ni.

(7) Comparative Example 2 Hydrogen storage alloy α (ground alloy:
Co ₁ . ₀₀ , AB _5.00 ) in an amount of 50 mass% and the hydrogen storage alloy ν (substantially spherical alloy: Co _1.00 , Co _1.00 ,
50% by mass of AB _5.00 ), 0.5% by mass of polyethylene oxide (PEO) as a binder with respect to the total amount of the hydrogen storage alloy, and water are added and kneaded to prepare a slurry. A core of the hydrogen storage alloy negative electrode plate y of Comparative Example 2 was produced by coating a nickel current collector made of punched metal with Ni plating on the core.

Then, the hydrogen storage alloy negative electrode plates a to j of Examples 1 to 10 and the hydrogen storage alloy negative electrode plates x and y of Comparative Examples 1 and 2 produced as described above were each rolled to 100 tons. The weight was applied, and the packing density of the active material was measured from the thickness of each negative electrode plate at that time, and the measurement results are shown in Table 2 below. Here, as the packing density of the active material is higher, a negative electrode plate having a higher packing density can be manufactured, and a nickel-hydrogen storage battery having a high capacity and a long life can be obtained. Also, even if the thickness of the negative electrode plate is adjusted to the same, if the negative electrode plate is capable of high packing density, the strength of the negative electrode plate is improved and the quality of the negative electrode plate is improved. By being able to prevent the negative electrode active material from peeling off,
Handleability is improved.

4. Preparation of Nickel-Hydrogen Storage Batteries Each of the hydrogen storage alloy negative electrode plates a to j of Examples 1 to 10 and each of the hydrogen storage alloy negative electrode plates x and y of Comparative Examples 1 and 2 manufactured as described above were 115 mm in length and width, respectively. After being adjusted to have a size of 42 mm and a thickness of 0.4 mm, each of these hydrogen storage alloy negative electrode plates and a well-known sintered nickel positive electrode plate are wound with a separator made of an alkali resistant nylon non-woven fabric interposed therebetween. . At this time, the negative electrode plate of the hydrogen storage alloy was wound in a spiral shape to prepare a spiral electrode plate group.

Each of the spirally wound electrode plates thus prepared was inserted into an AA-sized bottomed cylindrical metal outer can, and then potassium hydroxide (KO) was placed in each metal outer can.
H), lithium hydroxide (LiOH), and sodium hydroxide (NaOH), each of which is 2.1 g, and is sealed to give a nominal capacity of 1000 mAh.
AA size nickel-hydrogen storage batteries were manufactured. Here, the one using the hydrogen storage alloy negative electrode plate a is referred to as a battery A, the one using the hydrogen storage alloy negative electrode plate b is referred to as a battery B, and the one using the hydrogen storage alloy negative electrode plate c is referred to as a battery C,
A battery using the hydrogen storage alloy negative electrode plate d was designated as battery D, and a product using the hydrogen storage alloy negative electrode plate e was designated as battery E. Also,
A battery using a hydrogen storage alloy negative electrode plate f, a battery G using a hydrogen storage alloy negative electrode plate g, a battery H using a hydrogen storage alloy negative electrode plate h, and a hydrogen storage alloy negative electrode plate. A battery using i was used as a battery I, and a battery using a hydrogen storage alloy negative electrode plate j was used as a battery J. Further, a battery using the hydrogen storage alloy negative electrode plate x was designated as a battery X, and a product using the hydrogen storage alloy negative electrode plate y was designated as a battery Y.

5. Battery Characteristic Test Each of the nickel-hydrogen storage batteries A to J and X and Y produced as described above was measured at 100 mA (0.1 It: It (A) is a numerical value represented by rated capacity (Ah) / 1 h (hour)). After charging for 16 hours with a rechargeable stream, let it rest for 1 hour. Then, it is discharged by a discharge current of 1000 mA (1 It) until the final voltage becomes 1.0 V, and then left for 1 hour.
This charging / discharging was repeated at room temperature for 2 cycles to activate each nickel-hydrogen storage battery.

(1) Low temperature discharge rate Each nickel-hydrogen storage battery A activated as described above.
~ J and X, Y are charged for 16 hours at a charging current of 100 mA (0.1 It) and then rested for 1 hour. afterwards,
1000 mA (1
It was discharged by a discharge current of (It) until the final voltage became 1.0 V, and the discharge capacity at 0 ° C. and the discharge capacity at 25 ° C. were measured from the discharge time. At this time, (discharge capacity at 0 ° C.) / (Discharge capacity at 25 ° C.) × 100 (%) was obtained as a low temperature discharge rate, and the result is shown in Table 2 below. The higher the low-temperature discharge rate, the higher the dischargeability, and the excellent characteristics are exhibited even at the high-rate discharge.

(2) Cycle life Each of the nickel-hydrogen storage batteries A to J and X, Y activated as described above is 100 m at room temperature (25 ° C.).
After charging for 16 hours with a charge current of A (0.1 It), 1
Pause for a time. Then, the charge and discharge cycle of discharging with a discharge current of 1000 mA (1 It) until the final voltage reaches 1.0 V was repeated, and the battery capacity was 500.
A cycle life test in which the number of cycles when reaching mAh (50% of the battery capacity) or less was determined as the cycle life resulted in the results shown in Table 2 below.

(3) Battery internal pressure Further, as described above, each nickel-hydrogen storage battery A to
After producing J, X, and Y, they were left for 24 hours or more, and after punching holes in the bottom of each of these battery cans, 1000 mA
Charging was performed by passing a charging current of (1 It). At this time, the gas generated from the bottom of each battery can is captured, and the gas pressures of these gases are measured.
When the time required to reach Mpa (15 kgf / cm ² ) (arrival time) was measured, the results shown in Table 2 below were obtained. The gas pressure was measured using a pressure transmitter.

[0036]

[Table 2]

The following can be seen from the results of Table 2 above. That is, the battery X using the negative electrode plate x having only the crushed hydrogen storage alloy α produced by ingot crushing, the hydrogen storage alloy α and the substantially spherical hydrogen storage alloy ν produced by the atomization method are mixed (α and ν And a battery Y using a negative electrode plate y having the same alloy composition and the same amount),
It can be seen that the negative electrode plate x is superior to the negative electrode plate y in low temperature discharge rate and battery life, but inferior in packing density. This means that the packing density is improved by using the substantially spherical hydrogen storage alloy produced by the atomization method.

A sphere having the same alloy composition as the crushed alloy α
A battery Y using a negative electrode plate y in which a granular alloy ν is mixed, and crushed
AB rather than alloy α_XThe value of X at is small, AB_4.97
Negative electrode plates a and A prepared by mixing substantially spherical alloy β and crushed alloy α
B_4.95Negative electrode plate obtained by mixing substantially spherical alloy γ and crushed alloy α
b, AB_4.80Approximately spherical alloy δ and crushed alloy α were mixed
Negative electrode plate c, AB_4.70Of approximately spherical alloy ε and crushed alloy α
Combined negative plate d, AB _4.65Approximately spherical alloy ζ and crushed alloy α
And negative electrode plate e, AB_4.89Approximately spherical alloy η and crushed
Negative electrode plate f mixed with alloy α, and AB_4.79Almost spherical
For each negative electrode plate g in which alloy θ and crushed alloy α are mixed
Comparing the batteries A, B, C, D, E, F, G
Both the negative electrode plate y and the negative electrode plates a, b, c, d, e, f, g are packed and packed.
Although the degrees are almost the same, batteries A, B, C, D, E,
F and G have better low temperature discharge rate and battery life than battery Y
I understand that.

This is because when the value of _X in AB _X of the substantially spherical alloy is smaller than that of the pulverized alloy, the crystals of the substantially spherical alloy are likely to be distorted, so that they are easily cracked during charge / discharge during the activation step or the like. As a result, the substantially spherical hydrogen-storing alloy, which is poorly cracked, is easily cracked, so that the number of active surfaces of the hydrogen-storing alloy electrode increases. As a result, the hydrogen storage property at the initial stage of charge and discharge is improved, and the generation of hydrogen gas is reduced even when charging is performed, so that the pressure inside the battery does not rise and the decrease of the electrolyte solution can be prevented. It seems that the charge / discharge cycle has improved. In this case, the value of _X in AB _X of the substantially spherical hydrogen storage alloy is optimized so as to be smaller by 0.05 to 0.30 than the value of _X in AB _X of the hydrogen storage alloy produced through the crushing process. It is preferable.

Further, a battery Y using a negative electrode plate y in which a pulverized alloy α and a substantially spherical alloy ν having the same alloy composition are mixed, and a substantially spherical alloy of AB _5.00 in which the X values of the pulverized alloy α and AB _X are equal. negative electrode plate h mixed with ι (cobalt component Co _0.90 ), negative spherical plate κ mixed with substantially spherical alloy κ (cobalt component Co _0.85 ), and substantially spherical alloy λ (cobalt component Co _0.80) (Compared with the batteries H, I, and J) using the negative electrode plates j mixed with each other.
It can be seen that the negative electrodes h, i, and j have almost the same packing density, but the batteries H, I, and J have better low-temperature discharge rate and battery life than the battery Y.

Further, a battery Y using a negative electrode plate y in which the crushed alloy α and a substantially spherical alloy ν having the same alloy composition are mixed, and a substantially spherical alloy of AB _4.89 in which the values of _X in the crushed alloy α and AB _X are small. Battery F using a negative electrode plate f in which η (cobalt component is Co _0.98 ) and crushed alloy α are mixed, and AB
_4.79 almost spherical alloy θ (cobalt component is Co _0.96 )
Comparing the battery G using the negative electrode plate g in which the powder and the crushed alloy α are mixed, the packing densities of the negative electrode plate y and the negative electrode plates f and g are almost the same, but the batteries F and G are lower in temperature than the battery Y. It can be seen that the discharge rate and the battery life are excellent.

This is because when the cobalt component of the substantially spherical alloy is set to be smaller than that of the crushed alloy, the substantially spherical hydrogen storage alloy has a large volume change rate during hydrogen storage, so that the crackability of the substantially spherical alloy is improved. As a result, the substantially spherical hydrogen-storing alloy, which is poorly cracked, is easily cracked, so that the number of active surfaces of the hydrogen-storing alloy electrode increases. As a result, the hydrogen storage property at the beginning of charge and discharge is improved,
It is considered that since the generation of hydrogen gas is reduced even when the battery is charged, the pressure in the battery does not rise, the decrease in the electrolytic solution can be prevented, and the charge / discharge cycle is improved.

As described above, in the present invention, the value of _X in AB _X of the substantially spherical hydrogen storage alloy is optimized so as to be smaller than the value of _X in AB _X of the ground hydrogen storage alloy, or the Since the cobalt component of the spherical hydrogen storage alloy is optimized to be smaller than that of the ground hydrogen storage alloy, the packing density of the active material is improved, and the gas absorption performance during charge and discharge and the discharge characteristics at low temperature are improved. An improved hydrogen storage alloy electrode can be obtained. As a result, it is possible to obtain a nickel-hydrogen storage battery having a high capacity and excellent low-temperature discharge characteristics and cycle characteristics.

[0044] In the embodiment described above, using _{Mm a Ni b Co c Mn d} Al a part of Ni is represented by _e Co, Mn, hydrogen storage alloy obtained by substituting Al as a hydrogen absorbing alloy Example I explained about a part of Ni
Alternatively, a hydrogen storage alloy substituted with Cu, Fe, Cr, Si, Mo or the like may be used. Also, Mm _a Ni _b C
o _c Mn _d Al _e expressed other than hydrogen absorbing alloys in AB ₅
-Type rare earth-based hydrogen storage alloy, for example, LaNi ₅ system with N
A hydrogen storage alloy in which a part of i is replaced with Co and Al, W or the like may be used.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-138659 (JP, A) JP-A-10-53801 (JP, A) JP-A-10-172546 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01M 4/24-4/26 H01M 4/38

Claims (4)

(57) [Claims] 1. A hydrogen storage alloy electrode comprising a hydrogen storage alloy capable of reversibly electrochemically storing and releasing hydrogen, wherein the hydrogen storage alloy electrode is manufactured through a crushing process. A
B _X type (where A is a rare earth element, B is nickel, cobalt in which a part of nickel is replaced, and a plurality of other metal elements) is a pulverized hydrogen storage alloy, and a substantially spherical form of the AB _X type is used. A hydrogen storage alloy electrode in which a spherical hydrogen storage alloy is mixed, and a value of _X in AB _X of the substantially spherical hydrogen storage alloy is smaller than a value of _X in AB _X of the ground hydrogen storage alloy. . 2. The value of _X in AB _X of the substantially spherical hydrogen storage alloy is smaller than the value of _X in AB _X of the ground hydrogen storage alloy by 0.05 to 0.30. Item 2. The hydrogen storage alloy electrode according to item 1. 3. A hydrogen storage alloy electrode comprising a hydrogen storage alloy capable of reversibly electrochemically storing and releasing hydrogen, wherein the hydrogen storage alloy electrode is produced through a crushing process. A
B _X type (where A is a rare earth element, B is nickel, cobalt in which a part of nickel is replaced, and a plurality of other metal elements) is a pulverized hydrogen storage alloy, and a substantially spherical form of the AB _X type is used. A hydrogen storage alloy electrode, wherein a spherical hydrogen storage alloy is mixed, and a cobalt component of the substantially spherical hydrogen storage alloy is smaller than a cobalt component of the ground hydrogen storage alloy. 4. A negative electrode made of a hydrogen storage alloy capable of reversibly electrochemically storing and releasing hydrogen, a positive electrode, a separator separating the negative electrode and the positive electrode, and an alkaline electrolyte. A nickel-hydrogen storage battery provided with the hydrogen-storage alloy electrode according to any one of claims 1 to 3 as a negative electrode.