JP4979178B2 - Hydrogen storage alloy powder for sealed alkaline storage battery and sealed alkaline storage battery using the same - Google Patents

Description

  The present invention relates to a hydrogen storage alloy powder for a sealed alkaline storage battery and a sealed alkaline storage battery using the same.

In recent years, sealed alkaline storage batteries containing hydrogen storage alloy powder have been applied to power supplies such as electric tools and household electric cleaners, but this type of alkaline storage battery includes power supplies such as communication devices and PCs (personal computers). High discharge characteristics are required as compared with the alkaline storage batteries used in the above.
In alkaline storage batteries using hydrogen storage alloys as negative electrode materials, it has been found that the influence of the negative electrode on the discharge characteristics is large, and as a method for improving the discharge performance, there has been a method of increasing the equilibrium potential or reducing the reaction overvoltage. Has been done.

The increase in the former equilibrium potential is related to the hydrogen equilibrium pressure of the hydrogen storage alloy, and the higher the hydrogen equilibrium pressure, the higher the operating voltage during discharge of the battery using this, and the higher the hydrogen equilibrium pressure 10 times. It is known that the equilibrium potential rises by about 29 mV without depending on the discharge current, and the operating voltage rises by this amount.
For example, the equilibrium potential can be increased by adjusting the components of the hydrogen storage alloy to increase the hydrogen equilibrium pressure, and adjusting the amounts of La and Mn contained as components of the hydrogen storage alloy to adjust the hydrogen equilibrium pressure to 0. It has been confirmed that when the voltage is increased from 03 MPa to 0.10 MPa, the operating voltage increases from 0.95 V to 0.97 V when discharging with a discharge current of 30 A.

On the other hand, the latter reduction in reaction overvoltage has a difference in effect depending on factors that cause overvoltage in the negative electrode, but one of the factors is the reaction area, and the hydrogen storage alloy has a reduced particle size (small particle size). it can be reduced by increasing this by reduction).
For example, it has been confirmed that when the average particle size of the hydrogen storage alloy is reduced from 60 μm to 30 μm, the operating voltage is slightly improved from 0.95 V to 0.96 V.

However, when the high rate discharge characteristics of the sealed alkaline storage battery are improved by increasing the equilibrium pressure or reducing the particle size of the hydrogen storage alloy, the following problems arise.
First, in a battery having a high hydrogen equilibrium pressure of the hydrogen storage alloy contained in the negative electrode, when the battery is charged in a high-temperature atmosphere, the internal pressure of the battery rises and the safety valve provided in the battery container is likely to operate. When the safety valve is activated, the alkaline electrolyte is jetted out of the battery together with the gas to decrease, so that there is a problem that the charge / discharge cycle life of the battery in a high temperature atmosphere is shortened.

  In addition, in a battery with a small particle size of the hydrogen storage alloy powder contained in the negative electrode, the surface area of the powder particles is large, and the particles and the alkaline electrolyte easily come into contact with each other, so that the oxidation of the hydrogen storage alloy proceeds at high temperatures. Cheap. When the alkaline electrolyte is consumed and reduced due to the oxidation of such a hydrogen storage alloy, the internal resistance of the battery increases, so that there is a problem that the charge / discharge cycle life of the battery under a high temperature atmosphere is shortened.

  The present invention has been made to solve the above-described problems, and is a hydrogen storage alloy for a sealed alkaline storage battery that can improve the high rate discharge characteristics and the charge / discharge cycle life under a high temperature atmosphere in the sealed alkaline storage battery. The object is to provide a powder and a sealed alkaline storage battery using the powder.

The inventors have made various studies to solve the problem of shortening the life of the charge / discharge cycle in a sealed alkaline storage battery in a high temperature atmosphere caused by increasing the equilibrium pressure or reducing the particle size of the hydrogen storage alloy powder. As a result, the hydrogen storage alloy powder having a predetermined composition has an average particle size of 25 μm or more and 30 μm or less, and a hydrogen equilibrium pressure at 40 ° C. when H / M = 0.5 is 0.06 MPa or more. It has been found that the high-rate discharge characteristics and the charge / discharge cycle life under high temperature atmosphere in a sealed alkaline storage battery using the same can be improved, and the hydrogen storage alloy powder for sealed alkaline storage battery of the present invention and the sealed using the same Led to the development of a type alkaline storage battery.

That is, in order to achieve the above object, according to the present invention, the A-site component occupying the A-site, sealed alkaline storage battery of hydrogen consisting of AB ₅ type hydrogen storage alloy containing a B site component occupying the B site The hydrogen-absorbing alloy powder has an average particle diameter of 25 μm or more and 30 μm or less and a hydrogen equilibrium pressure at 40 ° C. when H / M = 0.5 is 0.06 MPa or more, The site component consists only of La element, Ce element, Pr element and Nd element, the mass concentration of La element in the A site component is 30-50% by mass, and the B site component is Ni element, Mn element Co element and Al element, and the Mn element is contained in an amount of 0.2 to 0.4 mol with respect to 1 mol of the A site component, and the Co element and Al element are The A site component 1 mole hydrogen-absorbing alloy powder for sealed alkaline storage battery characterized in that it contains 0.3 to 1.0 moles in total of both elements is provided (claim 1).

According to the present invention, in a sealed alkaline storage battery in which a negative electrode and a positive electrode are accommodated together with an alkaline electrolyte in a battery can, the negative electrode contains the hydrogen storage alloy powder for an alkaline storage battery according to claim 1. A sealed alkaline storage battery is provided (claim 2).
In the configuration described above, the negative electrode liquid content, expressed as a percentage of the mass of the alkaline electrolyte that can be retained by the negative electrode divided by the dry mass of the negative electrode, is preferably 7% or more. 3).

  And in the above-mentioned structure, it is preferable that the density | concentration of the said alkaline electrolyte is 7N or more (Claim 4).

The hydrogen storage alloy powder for a sealed alkaline storage battery of the present invention has a high hydrogen equilibrium pressure and excellent corrosion resistance against an alkaline electrolyte.
In addition, the sealed alkaline storage battery using the hydrogen storage alloy powder for the sealed alkaline storage battery of the present invention has both high rate discharge characteristics and excellent charge / discharge cycle life under a high temperature atmosphere, and its industrial value is extremely large. It is.

Hereinafter, a sealed nickel-metal hydride secondary battery (hereinafter referred to as battery A) according to an embodiment of the present invention will be described in detail.
The battery A has the same configuration as that of a normal sealed alkaline storage battery except that it includes a negative electrode to be described later. In this embodiment, the battery A has a bottomed cylindrical battery container 10 having one end opened. The battery container 10 functions as a negative electrode terminal.

  A lid plate 14 is disposed in the opening of the battery container 10 via an insulating packing 12, and the lid plate 14 has a gas vent hole 15 in the center. A disc-shaped valve body 16 is disposed on the outer surface of the cover plate 14 so as to close the gas vent hole 15, and a disc-shaped spring seat 17 is also superimposed on the valve body 16. Further, a positive external terminal 18 is fixed on the outer surface of the cover plate 14 so as to surround the valve body 16 and the spring seat 17, and the spring seat 17 is interposed between the spring seat 17 and the positive external terminal 18. A coil spring 20 that presses the valve body 16 against the cover plate 14 is disposed.

  Therefore, normally, the opening of the battery container 10 is sealed by the insulating packing 12, the cover plate 14, and the valve body 16. When the gas is generated in the battery container 10 and the internal pressure is increased, the coil spring 20 is compressed through the valve body 16 and the spring seat 17, and the gas is discharged through the gas vent hole 15 of the cover plate 14. Is released. That is, the vent hole 15, the valve body 16, the spring seat 17, and the coil spring 20 form a safety valve.

A substantially cylindrical electrode group 21 is accommodated in the battery container 10 together with an alkaline electrolyte (not shown). More specifically, the electrode group 21 is formed by winding a plate-like positive electrode 22 and a negative electrode 24 through a separator 26, and the positive electrode 22 and the negative electrode 24 are overlapped with each other with the separator 26 interposed therebetween. Yes.
A positive electrode lead 28 is disposed between the electrode group 21 and the lid plate 14, and both ends of the positive electrode lead 28 are connected to the positive electrode 22 and the lid plate 14. Accordingly, the positive external terminal 18 and the positive electrode 22 are electrically connected via the positive electrode lead 28 and the cover plate 14.

  A disc-shaped current collecting plate 29 is disposed between the bottom of the battery container 10 and the electrode group 21, while a negative electrode core of the negative electrode 24 is formed from one end of the electrode group 21 facing the current collecting plate 29. The body 30 protrudes. Between the negative electrode core 30 and the current collector plate 29 and between the current collector plate 29 and the bottom of the battery container 10 are welded, respectively, and between the negative electrode 24 and the battery container 10 are current collectors. It is electrically connected via the plate 29.

  Examples of the separator 26 include polyamide fiber nonwoven fabrics, and polyolefin fiber nonwoven fabrics such as polyethylene and polypropylene that are provided with hydrophilic functional groups. Examples of the alkaline electrolyte include sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, potassium hydroxide aqueous solution, and an aqueous solution obtained by mixing two or more of these.

The positive electrode 22 has a positive electrode core, and a positive electrode mixture is supported on the core. For example, examples of the positive electrode core include a foamed nickel base material having a porous structure.
The positive electrode mixture is composed of, for example, a positive electrode active material, an additive, and a binder. Examples of the positive electrode active material include nickel hydroxide particles or nickel hydroxide particles in which cobalt, zinc, cadmium or the like is dissolved. Examples of the additive include a conductive agent made of a cobalt compound, and examples of the binder include a hydrophilic or hydrophobic polymer.

The negative electrode 24 has a negative electrode core 30, and a negative electrode mixture is supported on the core 30 except for the protrusions described above. Here, a normal thing can be used as the core 30 for negative electrodes, for example, a punching metal etc. can be used. In FIG. 1, the negative electrode core 30 is omitted except for the protruding portion for convenience of drawing.
The negative electrode mixture includes a hydrogen storage alloy powder capable of occluding and releasing hydrogen as a negative electrode active material and a binder, and examples of the binder include hydrophilic or hydrophobic polymers.

The hydrogen storage alloy powder of the negative electrode 24 is made of an AB ₅ type hydrogen storage alloy having a predetermined composition, is made of particles having an average particle size of 30 μm or less, and hydrogen at 40 ° C. when H / M = 0.5. The equilibrium pressure is 0.06 MPa or more.
However, after preparing a negative electrode using a hydrogen storage alloy powder having an average particle size exceeding 30 μm and assembling a battery using this negative electrode, the battery was subjected to an activation treatment to finely charge the hydrogen storage alloy powder contained in the negative electrode. The average particle size may be 30 μm or less.

  In this hydrogen storage alloy, as an A site component occupying the A site, an La (lanthanum) element and at least one element selected from the group consisting of rare earth elements other than the La element (for example, Nd, Pr, Ce) are included. Contains. Here, the ratio of the La element in the A site component, that is, the mass concentration obtained by dividing the mass of the La element contained in the hydrogen storage alloy by the total mass of the A site component is included in the range of 30 to 50% by mass. Yes.

On the other hand, the B site component occupying the B site of the hydrogen storage alloy contains at least Ni element and Mn element, and the hydrogen storage alloy is 0.2 to 0.4 relative to 1 mol of the A site component. It contains Mn element of mol.
The Ni element of the B site component is replaced with Al and Co by an appropriate amount . When a part of the Ni element is suitable amount replaced by Co element and Al elemental, while suppressing a decrease in the hydrogen absorption-desorption properties of the hydrogen storage alloy, it is possible to enhance the corrosion resistance against alkaline electrolyte preferably. Specifically, it is preferable that Co contains 0.3 to 1.0 and Al contains 0.1 to 0.5 mol with respect to 1 mol of the A site component.

The composition of the above hydrogen storage alloy has the general formula:
La _x (M1) _1-x Ni _yzw Mn _z (M2) _w (1)
(However, M1 represents at least one element selected from the group consisting of rare earth elements other than La elements, M2 represents the elemental Al and Co, x is the mass concentration of La element in the A site component Y, z and w are 4.8 ≦ y ≦ 5.4, 0.2 ≦ z ≦ 0.4, and 0.3 ≦, respectively, which are numbers selected to be 30 to 50% by mass. It is a number that satisfies the relationship of w ≦ 1.0)
Can be expressed as

The battery A having the above-described configuration has an excellent charge / discharge cycle life in a high-temperature atmosphere and also has excellent high rate discharge characteristics.
The reason why the high rate discharge characteristic is improved is as follows. That is, when the hydrogen storage pressure is increased when the average particle size of the hydrogen storage alloy is small and the reaction area is large, the hydrogen concentration on the surface of the hydrogen storage alloy increases and the discharge reaction is effectively promoted. This is considered to be because the reaction overvoltage at the time of discharge is reduced.

Meanwhile, it is contemplated that the following reasons for the charge-discharge cycle life characteristics under a high temperature atmosphere is above improvement. That is, when increasing the average particle size is small reaction area is hydrogen equilibrium pressure is greater of the hydrogen storage alloy, the surface area of the hydrogen storage alloy by particle size reduction is increased, the hydrogen from the surface thereof during charge dissociate Is suppressed, and the hydrogen concentration on the surface of the hydrogen storage alloy is increased by increasing the hydrogen equilibrium pressure. This is considered to be because the promotion of oxidation due to the reduction in particle size is suppressed.

As described above, increasing the equilibrium pressure and reducing the particle size of the hydrogen storage alloy is effective as a method for improving the high rate discharge characteristics. However, when applied independently, charging and discharging in a high temperature atmosphere. It has been known so far that it is a factor that deteriorates cycle life characteristics. Thus hydrogen effects of the present invention described above, dare performed simultaneously further plurality of operations has been recognized as a disadvantage for the charge-discharge cycle life characteristics under a high temperature atmosphere, yet which is optimized to the composition of the very limited range It can be said that this is a specific effect in that the effect is found only when the above operation is applied to the storage alloy.

In addition, when the average particle diameter of the hydrogen storage alloy powder is less than 10 μm, the corrosion resistance is lowered, so that the average particle diameter is preferably 10 μm or more.
Moreover, it is preferable that the density | concentration of the alkaline electrolyte of the battery A is 7-9N. Since the hydrogen storage alloy described above exhibits excellent corrosion resistance, it is possible to use a high-concentration alkaline electrolyte in the range of 7 to 9 N in the battery A, and further increase the electrical conductivity of the electrolyte. The rate discharge characteristic can be improved.

Moreover, in the negative electrode (hydrogen storage alloy negative electrode) of the battery A described above, the negative electrode liquid content expressed as a percentage obtained by dividing the mass of the alkaline electrolyte that can be retained by the negative electrode itself by the dry mass of the negative electrode. Is preferably 7% or more.
The liquid content was measured by a method in which the negative electrode was taken out from the battery, and the wet mass of the negative electrode containing the electrolyte solution and the dry mass of the negative electrode after washing and drying were measured. At this time, the value obtained by subtracting the dry mass from the wet mass of the negative electrode was defined as the amount of electrolyte contained in the negative electrode, the amount of the electrolyte was divided by the dry mass of the negative electrode, and the value expressed as a percentage was defined as the negative electrode liquid content. .

Examples 1-5, Comparative Examples 1-10
1. Preparation of positive electrode 50 parts by weight of a 0.2 wt% aqueous HPC (hydroxypropylcellulose) solution was added to a mixed powder comprising 90 parts by weight of nickel hydroxide powder, 10 parts by weight of cobalt hydroxide powder, and 3 parts by weight of zinc oxide powder. Addition and kneading were performed to obtain a positive electrode active material slurry. This active material slurry is filled and dried in a foamed nickel base material having a basis weight of about 600 g / m ² and a porosity of 95%, and then the foamed nickel substrate is rolled and then cut. A band-shaped non-sintered positive electrode was produced for a nickel metal hydride secondary battery.

2. Production of Negative Electrode A raw material powder obtained by weighing and mixing metal powder such as Mm (Misch Metal) so as to have a predetermined composition ratio was melted in a high-frequency melting furnace to cast a hydrogen storage alloy ingot. Next, the ingot was subjected to a heat treatment at a temperature of 1000 ° C. for 10 hours, and then the ingot was mechanically pulverized and sieved to obtain a plurality of hydrogen storage alloy powders having the compositions and average particle sizes shown in Table 1, respectively. Was made.

Then, with respect to 99 parts by weight of each alloy powder, 0.5 parts by weight of PVP (polyvinylpyrrolidone) and 0.5 parts by weight of PEO (polyethylene oxide) are added together with an appropriate amount of water and kneaded to prepare a negative electrode active material slurry. Produced. And after apply | coating and drying this negative electrode active material slurry on both surfaces of the punching metal board | substrate as a negative electrode core, this punching metal board | substrate was roll-rolled and cut | judged to the strip | belt shape of a predetermined dimension. Next, the negative electrode mixture on one side edge of the cut punching metal substrate is scraped off to form a protruding portion (lead portion) of the negative electrode core, for a 4/5 SC size nickel-hydrogen secondary battery, The hydrogen storage alloy negative electrodes of Examples 1 to 5 and Comparative Examples 1 to 10 were produced.

3. Assembly and activation of nickel-metal hydride secondary battery A positive electrode produced as described above, and any one negative electrode of Examples 1 to 5 and Comparative Examples 1 to 10 , and a polyolefin mainly composed of polypropylene and polyethylene The electrode group was produced by winding it through a separator made of a non-woven fabric, and the electrode group was housed in a battery container and subjected to a predetermined attachment process. Thereafter, a 7N alkaline aqueous solution mainly composed of potassium hydroxide is injected into the battery container as an electrolytic solution, and then the battery container is sealed with a lid plate or the like, so that the capacity is 4/5 SC size with a nominal capacity of 2000 mAh. The nickel hydride secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 10 were produced.

The nickel hydride secondary batteries obtained in Examples 1 to 5 and Comparative Examples 1 to 10 were charged with a current of 200 mA for 16 hours, rested for 1 hour, and then terminated with a current of 400 mA. The activation process which performs the charge / discharge cycle which discharges to 0V 3 times was performed.
4). Hydrogen Storage Alloy and Battery Evaluation Test (1) For each of the obtained hydrogen storage alloy powders of Examples 1 to 5 and Comparative Examples 1 to 10, the hydrogen storage amount (H / M) is 40 ° C. in an atmosphere. The dissociation pressure at 0.5 was measured as the hydrogen equilibrium pressure, and the results are shown in Table 1.

The hydrogen equilibrium pressure of each hydrogen storage alloy powder was measured based on JIS H7201 (1991) “Method of measuring pressure-composition isotherm (PTC line) of hydrogen storage alloy”. The measurement temperature was 40 ° C., which is an average value of the actual use temperature exhibited by the battery in a general use environment.
Moreover, the following evaluation tests were done about each nickel hydride secondary battery of Examples 1-5 and Comparative Examples 1-10, and these results were shown in Table 1. And the test results (1) and (2) of Examples 1 to 3 and Comparative Examples 1 to 8 are collectively shown in FIG. 2, and the test results (1) and (3) are also shown in FIG. It was.

(2) High-rate discharge test After charging for 16 hours at a current of 200 mA, after resting for 1 hour, it was discharged to a final voltage of 0.6 V with a current of 30 A, and the change over time in the discharge voltage was measured. And based on this measurement result, the discharge voltage (discharge intermediate voltage) at the time of discharging about half of the discharge capacity was determined as the operating voltage of the battery.

(3) High-temperature charge / discharge cycle life test In an atmosphere at a temperature of 40 ° C., the battery was charged to full charge with a current of 2 A by a −ΔV control method, paused for 1 hour, and then terminated at 0 A with a current of 15 A. Repeat the battery capacity measurement to discharge to 6 V with a one-hour pause between measurements until the measured battery capacity is 60% or less of the initially measured battery capacity. Counted as discharge cycle life.

From Table 1, FIG. 2 and FIG. 3, the following is clear.
The amount of La is 30 to 50% by mass ratio, the amount of Mn is 0.50 to 0.20 by mole ratio so that the hydrogen equilibrium pressure of the hydrogen storage alloy is 0.03 to 0.10 MPa, and the average particle size is In Comparative Examples 1 to 5 using a 60 μm hydrogen storage alloy, all of the high-rate discharge characteristics (operating voltage) showed a slight increasing tendency as the hydrogen equilibrium pressure increased, but all were less than 1.000 V. The charge cycle life characteristics were also 300 cycles or less. In particular, Comparative Examples 3 to 5 using a hydrogen storage alloy having a high hydrogen equilibrium pressure caused a significant decrease in charge / discharge cycle life. The following are known as the cause of this. That is, by repeatedly charging and discharging the battery at a high temperature, the higher the hydrogen equilibrium pressure of the alloy, the easier the hydrogen dissociates from the negative electrode during charging, leading to an increase in the internal pressure of the battery, and the electrolyte leaks out of the battery. As a result, it was found that the internal resistance was increased by the depletion.

  Next, Comparative Examples 6 and 7 using the hydrogen storage alloy used in Comparative Example 1 with the average particle size reduced to 40 μm and 30 μm, respectively, have high rate discharge characteristics of less than 1.000 V, There has been no significant improvement due to diameter. Moreover, the charge / discharge cycle life characteristics were less than 280 cycles, which was lower than that of Comparative Example 1. Here, after completion of the charge / discharge cycle test, the battery was disassembled, the hydrogen storage alloy was taken out of the negative electrode, and the oxygen concentration contained therein was measured. The smaller the average particle size, the higher the oxygen concentration. I understood. That is, it was found that the smaller the average particle size of the hydrogen storage alloy, the more the electrolyte was consumed due to the oxidation of the hydrogen storage alloy, and the depletion progressed, leading to a decrease in high-temperature cycle life characteristics.

Next, while the Comparative Examples 7 and 8 is less than the high-rate discharge characteristics is 1.000V, La amount mass ratio of 30-50%, the molar ratio of Mn content 0.20 to 0.40, hydrogen In Examples 1 to 4 using a hydrogen storage alloy having an equilibrium pressure of 0.06 MPa or more and an average particle size of 30 μm or less, the high rate discharge characteristics greatly exceeded 1.000V. This is because the hydrogen concentration on the surface of the hydrogen storage alloy increases with the increase of the hydrogen equilibrium pressure, and the reaction area increases as a result of the reduction in particle size. . Moreover, as for the charge / discharge cycle life characteristics, Comparative Examples 7 and 8 have less than 250 cycles, whereas Examples 1 to 4 all have 340 cycles or more. This is presumably because, even when the hydrogen storage alloy was made smaller in size, an atmosphere in which more hydrogen was present was formed on the alloy surface due to the increased hydrogen equilibrium pressure, and the alloy oxidation was suppressed.

  Next, Comparative Examples 9 and 10 using a hydrogen storage alloy having a molar ratio of Mn of 0.50 have a high rate discharge characteristic of less than 1.000 V, and a charge cycle life characteristic of about 200 cycles and a short life. is there. Further, even when the hydrogen equilibrium pressure was increased with Al, these characteristics were not improved. On the other hand, Example 5 using a hydrogen storage alloy in which the molar ratio of the amount of Mn was reduced to 0.40 and the average particle size was 30 μm had a high rate discharge characteristic of 1.000 V or more and a charge cycle life characteristic. Good results of 300 cycles or more were obtained. This is because, when the amount of Mn is as large as 0.50, corrosion due to dissolution and oxidation of Mn in the electrolytic solution is remarkable, so even if the hydrogen equilibrium pressure is increased, corrosion is not suppressed. It is considered that this did not occur when the amount of Mn was reduced to 0.40.

As described above, the hydrogen equilibrium pressure is set at 0. 0 in the range of La content in the A site component of 30 to 50% by mass and Mn content in the B site component of 0.20 to 0.40 in molar ratio. It can be said that the composition of the hydrogen storage alloy is selected so as to be 06 MPa, and the average particle size is preferably 30 μm or less.
Further, when the negative electrode liquid content was evaluated for each of Comparative Example 5 and Example 3, both were about 7%, but in comparison with Comparative Example 5, the negative electrode liquid content was about 8%. When the amount of electrolyte injected into the battery was increased, the leakage due to the increase in internal pressure increased, and the charge / discharge cycle life decreased by about 30 cycles. On the other hand, when the amount of the negative electrode liquid content was increased to 8% with respect to Example 3, the life was improved by about 20 cycles.

Further, for Comparative Example 5 and Example 3, when the concentration of the electrolyte injected into the battery was increased from 7N to 8N, a tendency similar to the above was observed, and in Comparative Example 5, the life decreased by about 20 cycles, About Example 3, it improved about 20 cycles. Therefore, it is desirable that the negative electrode liquid content is 7% or more and the electrolyte concentration is 7N or more.
The present invention is not limited to the above-described embodiment and examples, and various modifications are possible. For example, the structure of the battery container, the safety valve, etc. is not particularly limited, Instead of providing the core protrusion on the negative electrode, the outermost peripheral surface of the negative electrode and the inner peripheral wall of the battery container may be brought into direct contact.

The perspective view which showed the nickel hydride secondary battery of one embodiment of this invention in the partial cross section. It is the graph which showed the relationship between hydrogen equilibrium pressure and high temperature charge / discharge cycle life. It is the graph which showed the relationship between hydrogen equilibrium pressure and a high rate discharge characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Battery container 21 Electrode group 22 Positive electrode 24 Negative electrode 26 Separator

Claims (4)

A hydrogen storage alloy powder for a sealed alkaline storage battery comprising an AB ₅ type hydrogen storage alloy containing an A site component occupying an A site and a B site component occupying a B site,
The hydrogen storage alloy has an average particle diameter of 25 μm or more and 30 μm or less and a hydrogen equilibrium pressure at 40 ° C. when H / M = 0.5 is 0.06 MPa or more,
The A site component consists of only La element, Ce element, Pr element and Nd element, and the mass concentration of the La element in the A site component is 30 to 50% by mass,
The B site component consists of only Ni element, Mn element, Co element and Al element, and the Mn element is contained in an amount of 0.2 to 0.4 mol per mol of the A site component,
The hydrogen storage alloy powder for a sealed alkaline storage battery, wherein the Co element and the Al element are contained in an amount of 0.3 to 1.0 mol in total with respect to 1 mol of the A site component. In a sealed alkaline storage battery in which a negative electrode and a positive electrode are housed together with an alkaline electrolyte in a battery can,
The said negative electrode contains the hydrogen storage alloy powder for alkaline storage batteries of Claim 1, The sealed alkaline storage battery characterized by the above-mentioned.   3. The hermetically sealed structure according to claim 2, wherein the negative electrode liquid content, expressed as a percentage of the mass of the alkaline electrolyte that can be retained by the negative electrode divided by the dry mass of the negative electrode, is 7% or more. Type alkaline storage battery.   4. The sealed alkaline storage battery according to claim 2, wherein the concentration of the alkaline electrolyte is 7N or more.

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