JP2919544B2 - Hydrogen storage electrode - Google Patents

Description

Description: (a) Industrial application field The present invention relates to a hydrogen storage electrode for an alkaline storage battery using a hydrogen storage alloy capable of storing and releasing hydrogen as a negative electrode material.

(B) Conventional technology Conventionally used storage batteries include nickel-cadmium storage batteries and lead storage batteries. In recent years, there is a possibility that these batteries are lighter, have higher capacity, and have higher energy density than these batteries. Therefore, a nickel-hydrogen alkaline storage battery provided with a hydrogen storage electrode using a hydrogen storage alloy as a negative electrode material has attracted attention.

The hydrogen storage alloy electrode used for the negative electrode of this alkaline storage battery is generally, as shown in JP-A-61-66366,
A binder is prepared by kneading a binder such as polytetrafluoroethylene or polyethylene oxide and a hydrogen storage alloy powder to prepare a paste, and the paste is applied to both surfaces of a core body such as a punching metal or expanded metal, and dried to produce a paste. You. The hydrogen storage electrode manufactured in this manner is housed in a battery outer can in a spirally wound state with a separator interposed between the sintered nickel positive electrode used in the nickel-cadmium storage battery and the battery. Is configured.

As described above, when the hydrogen storage electrode mainly composed of the hydrogen storage alloy powder and the binder is used for the negative electrode, the performance of the negative electrode largely depends on the performance of the hydrogen storage alloy powder. In view of this point, JP-A-62-154562 discloses that
By configuring the electrode by regulating the particle size of the hydrogen storage alloy to 20 to 149 μm, it is possible to provide a battery having a long cycle life due to repeated charge and discharge and high performance.

However, as disclosed in JP-A-62-154562, if the hydrogen storage alloy is classified in advance to a prescribed particle size and used without particles having a particle size outside the range, the discharge capacity of the negative electrode may be reduced. Although the performance can be improved, the oxygen gas consuming capacity of the negative electrode has not been able to be sufficiently increased yet.

(C) Problems to be Solved by the Invention The present invention is to solve the above-mentioned problems, and is to provide a hydrogen storage electrode having an improved electrode capacity and an improved oxygen gas consuming capacity in a negative electrode. It is.

(D) Means for Solving the Problems The hydrogen storage electrode of the present invention has a mean particle diameter of 50 to 100 μm and a particle diameter of 1 as a hydrogen storage alloy used for a negative electrode material.
An alloy containing an alloy of 50 μm or more in an amount of 3 wt% or more of the total amount of the alloy is used.

(E) Action When a hydrogen storage alloy having a large particle diameter is used as a negative electrode material, the packing density of the alloy in the negative electrode decreases,
The energy density of the negative electrode decreases. Furthermore, compared with the case where the alloy has a small particle size, the number of contact points between the alloys filled in the negative electrode is reduced, and the current collecting property is reduced.

However, conversely, if an alloy having a large particle size is mixed in the alloy powder, the oxygen gas consuming capacity of the negative electrode is greatly improved.

Generally, it is necessary to maintain high activity of the alloy surface in order to improve the oxygen gas consumption capacity of the negative electrode,
This facilitates the reaction between oxygen and hydrogen on the alloy surface.

On the other hand, a hydrogen storage alloy as a negative electrode material is an active alloy by nature, but its surface is easily oxidized in the presence of oxygen, and the alloy becomes inactive. In the case of an alloy whose surface has been made inert in this way, if the alloy has a large particle size,
When hydrogen is absorbed and released by charging and discharging, cracks occur in the oxide film on the alloy surface, and active parts inside the alloy become
Exposed on the surface of the alloy, the reactivity is improved. However, when the particle size of the hydrogen storage alloy is small, cracks are less likely to be generated on the surface of the alloy, so that an active alloy is less likely to be generated on the surface. For this reason, by using an alloy having a large particle size, it is possible to easily expose an active portion inside on the alloy surface, so that a reaction between oxygen and hydrogen on the alloy surface can be facilitated and oxygen gas consumption ability can be improved. It is considered possible.

In the present invention, by adjusting the average particle size of the hydrogen storage alloy as a negative electrode material to an appropriate particle size of 50 to 100 μm,
In addition to improving the capacity of the negative electrode, it is possible to improve the oxygen gas consumption ability by mixing a hydrogen storage alloy having a large particle size of 150 μm or more, which easily causes cracks on the surface of the alloy, into the alloy powder.

(F) Examples Examples of the present invention are shown below, and reference is made to comparison with comparative examples.

Commercially available misch metal (Mm, a mixture of rare earth elements), nickel, cobalt, aluminum, and manganese as elemental metals for hydrogen storage alloys, with an elemental ratio of 1.0: 3.2: 1.0: 0.2:
After weighing to 0.6, it is melted and cast in a high frequency induction furnace. Thus, an alloy having a composition of MmNi _3.2 CoAl _0.2 Mn _0.6 is obtained. Next, the pulverization conditions were variously changed, and the alloy ingot was pulverized mechanically to have an average particle size of 30, 40, 50, 75, 10, 1.
Powders of 10 and 120 μm were made.

Further, 1 wt% of polyethylene oxide and water as a dispersing medium were added to each of these powders to form a slurry, and a slurry was prepared. The slurry was applied to the surface of a conductive support made of punched metal, and then dried and dried. Pressurization was performed to obtain a hydrogen storage electrode.

Then, each of these electrodes was filled with 30% KOH 5
The charge / discharge test was performed in an atm pressurized container. The charge and discharge conditions at that time were as follows: after charging for 8 hours at a current value of 50 mA / g,
It discharges at a current value of g and stops when the electrode potential reaches -0.7 V vs Hg / HgO.

The result is shown in FIG. As is clear from FIG. 1, the average particle size of the alloy used for the electrode is 50 μm to 100 μm.
It can be seen that in the case of (1), the discharge capacity increases. On the other hand, when the average particle size is smaller than 50 μm and when the average particle size is larger than 100 μm, the discharge capacity is low.

Furthermore, in the same manner as described above, alloy ingots were produced, and various conditions of pulverization were changed to produce powders a to c having the particle sizes shown in Table 1,
Using this powder, a hydrogen storage electrode was obtained in the same manner.

The electrode thus fabricated was used as a negative electrode, a sintered nickel electrode was used as a positive electrode, and a spiral electrode body was obtained by winding the positive and negative electrodes through a separator made of a nonwoven fabric. Then, insert this spiral electrode body into the battery outer can.
A 30% by weight aqueous solution of potassium hydroxide was injected as an electrolytic solution, which was then sealed and sealed with a nominal capacity of 1000 mAh.
A hydrogen battery was assembled. The batteries assembled in this manner were used as batteries A to C according to the reference number of the hydrogen storage alloy used for the negative electrode.
And

The batteries thus fabricated were charged at a current of 100 mA for 16 hours, then discharged at a current of 200 mA, and a discharge / charge cycle test was performed under a cycle condition in which the discharge was stopped when the battery voltage reached 1.0 V. The life was measured. In this cycle test, the point at which the capacity became 50% or less of the initial capacity was defined as the cycle life.

After the same battery was used and the above-described charge / discharge cycle was performed for 5 cycles, a hole was provided in the bottom of the battery outer can, and a pressure sensor for measuring the internal pressure was attached to the hole. 1000 batteries
The battery was charged with a current of mA, and after the battery voltage reached a peak value, the charging was stopped when the battery voltage dropped by 10 mV from the peak value, and the negative battery internal pressure was measured. Table 2 shows the results. However, the battery internal pressure is shown as the maximum value during the charging.

As shown in Table 2, it can be seen that batteries A and B have a long cycle life and a small increase in battery internal pressure. In contrast, battery C has a short cycle life and a large increase in internal pressure.

Since the battery C does not contain particles of 150 μm or more, the oxygen gas consumption capacity of the alloy is low, causing an increase in the internal pressure of the battery. Release the gas inside. Then, along with the gas release, the electrolyte is simultaneously discharged to the outside of the battery, and the amount of the electrolyte in the battery becomes insufficient, resulting in a decrease in cycle life. On the other hand, in the batteries A and B, the gas consumption capacity of the negative electrode is high, the rise in the battery internal pressure is small, and the cycle life is accordingly improved.

(G) Effect The hydrogen storage electrode of the present invention has a hydrogen storage alloy as a negative electrode material having an average particle size of 50 to 100 μm and a particle size of 150 μm.
m or more containing 3 wt% or more of the total amount of the alloy, it is possible to sufficiently bring out the performance of the alloy, to improve the capacity of the negative electrode, and to improve the oxygen gas consumption capacity. be able to. In addition, a battery using the electrode of the present invention as a negative electrode has an effect of improving the cycle life as the oxygen gas consuming ability is improved.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the average particle size of the hydrogen storage alloy and the discharge capacity.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kenji Inoue 2--18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Yoshikazu Ishikura 2--18 Keihanhondori, Moriguchi-shi, Osaka (56) References JP-A-1-1766 (JP, A) JP-A-2-65058 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04M 4 / 38 H04M 4/24-4/26

Claims (1)

(57) [Claims] 1. A hydrogen storage electrode using a hydrogen storage alloy as a negative electrode material, wherein the hydrogen storage alloy has an average particle size of 50 to 50.
A hydrogen storage electrode comprising an alloy having a particle size of 100 μm and a particle size of 150 μm or more, 3 wt% or more of the total amount of the alloy.