JP2000277143A - Nickel-hydrogen storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel-hydrogen storage battery having a large discharge capacity and restraining a rise in internal pressure of the battery during charging. SOLUTION: This sealed nickel-hydrogen storage battery includes battery cans 1, 2, 3, a hollow negative electrode 5 disposed inside the battery cans 1, 2, 3 in such a way as to make electrical contact with the battery cans 1, 2, 3 and using a hydrogen storage alloy as negative electrode active material, a positive electrode 7 disposed inside the negative electrode 5 and using nickel hydroxide as positive electrode active material, a separator 6 positioned between the negative electrode 5 and the positive electrode 7, a positive electrode current collector 4 inserted in the positive electrode 7, and an electrolyte filling the battery cans 1, 2, 3 and impregnating the positive electrode 7, the negative electrode 5 and the separator 6. The positive electrode 7, the negative electrode 5, the separator 6, the positive electrode current collector 4, and the electrolyte account for 75 vol.% or more of volume within the battery cans 1, 2, 3. The negative electrode 5 is a solid electrode with a porosity of 15 to 45%, obtained by sintering hydrogen storage alloy powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-metal hydride storage battery, and more particularly, to a nickel-metal hydride storage battery.
It relates to a positive electrode type nickel-metal hydride storage battery.

[0002]

2. Description of the Related Art Nickel-metal hydride storage batteries have attracted attention as next-generation alkaline storage batteries because they have twice the capacity of nickel-cadmium storage batteries and are superior in environmental adaptability.

In this nickel-metal hydride storage battery, oxygen gas is generated from the positive electrode during overcharge. Therefore, in order to make the nickel-metal hydride storage battery a sealed type, a structure is adopted in which the capacity of the negative electrode is made larger than that of the positive electrode, and oxygen gas generated from the positive electrode is effectively consumed by the negative electrode. JP-A-5-22600
No. 0 proposes a nickel-hydrogen storage battery having a so-called spiral structure in which a sheet-like positive electrode and a sheet-like negative electrode are constituted by an electrode body spirally wound via a separator. In this structure, since the facing area between the positive electrode and the negative electrode is large, absorption of oxygen gas generated from the positive electrode progresses efficiently, and it is possible to suppress a rise in battery internal pressure during overcharge.

On the other hand, in order to obtain a battery structure having a high energy density, for example, a structure of an alkaline manganese battery as shown in Japanese Patent Publication No. 50-11570 is adopted. That is, an inside-out type structure (outside / positive electrode type structure) in which a hollow cylindrical positive electrode is disposed outside and a cylindrical negative electrode is disposed inside the positive electrode is adopted.
By adopting such a structure, the filling amount of the electrode active material in the battery can be increased. Therefore, compared to the battery having the spiral structure, about 150% to 180%
High energy density is obtained.

[0005]

However, in the above-described inside-out type structure, the area of the negative electrode facing the positive electrode and the volume of the space are smaller than those of the spiral structure, so that oxygen generated during overcharge is efficiently consumed. However, it was difficult to suppress an increase in battery internal pressure. Therefore, at present, nickel-hydrogen storage batteries having an inside-out type structure have not been put to practical use.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide a sealed nickel-metal hydride storage battery having a large discharge capacity and a suppressed increase in battery internal pressure during charging.

[0007]

A nickel-hydrogen storage battery according to a first aspect of the present invention comprises a battery can and a hydrogen storage alloy disposed in the battery can so as to make electrical contact with the battery can. A hollow negative electrode as a negative electrode active material, a positive electrode having nickel hydroxide as a positive electrode active material disposed inside the negative electrode, a separator disposed between the negative electrode and the positive electrode, and inserted into the positive electrode A positive electrode current collector arranged in a state, a positive electrode, a negative electrode, which is filled in a battery can, and an electrolytic solution impregnated in a separator, include a positive electrode, a negative electrode, a separator, a positive electrode current collector, and an electrolytic solution. A sealed nickel-metal hydride storage battery occupying 75% by volume or more of the volume in the battery can, wherein the porosity obtained by sintering the hydrogen storage alloy powder for the negative electrode is 15% to
It is characterized by a 45% solid electrode.

According to the first aspect of the present invention, the negative electrode is an electrode obtained by sintering a hydrogen storage alloy powder, and has a porosity of 15% to 45%, preferably 20% to 40%. . If the porosity is too low, the flow of gas such as oxygen gas generated in the positive electrode and the flow of the electrolyte may be hindered, and the rise in battery internal pressure may not be sufficiently suppressed. On the other hand, if the porosity is too high, the amount of the negative electrode active material decreases, the ability to absorb oxygen gas decreases, and the internal pressure of the battery may not be sufficiently suppressed.

A nickel-hydrogen storage battery according to a second aspect of the present invention comprises a battery can, and a hollow having a hydrogen storage alloy as a negative electrode active material, which is disposed in the battery can so as to be in electrical contact with the battery can. -Shaped negative electrode, a positive electrode using nickel hydroxide as a positive electrode active material, disposed inside the negative electrode, a separator disposed between the negative electrode and the positive electrode, and a positive electrode disposed in a state inserted in the positive electrode A current collector and a positive electrode, a negative electrode, and an electrolytic solution that are filled in the battery can and are impregnated in the separator.The positive electrode, the negative electrode, the separator, the positive electrode current collector, and the electrolytic solution have a volume of A sealed nickel-metal hydride storage battery occupying 75% by volume or more, characterized in that the negative electrode is a solid electrode obtained by sintering a hydrogen storage alloy powder, and communication holes or cuts are formed on the surface of the negative electrode. And

According to the second aspect of the present invention, a communication hole or cut is formed in the surface of the negative electrode. The communication hole spatially connects the surface of the negative electrode and the void inside the negative electrode. The communication hole may be formed so as to communicate from the surface of the negative electrode to the inside of the negative electrode, or may be formed so as to penetrate from one surface of the negative electrode to the other surface of the negative electrode. Is also good. For example, in the case of a hollow cylindrical negative electrode, the negative electrode may be formed inward from the outer peripheral surface of the negative electrode, or may be formed outward from the inner peripheral surface of the negative electrode. Further, the anode may be formed from the upper surface or the lower surface to the other surface. When the negative electrode is a hollow cylindrical negative electrode, the cut may be formed on any part of the outer peripheral surface, inner peripheral surface, upper surface, or lower surface of the negative electrode.

In the second aspect of the present invention, since the communication holes or cuts are formed on the surface of the negative electrode, the holes form a passage for the electrolytic solution into the voids inside the negative electrode. And the utilization of the negative electrode active material can be improved. In addition, since these communication holes and cuts also function as gas flow passages, the ability of the negative electrode to absorb gas can be increased, and an increase in battery internal pressure can be suppressed.

[0012] The communication hole and the cut in the second aspect of the present invention may be formed in the negative electrode in the first aspect of the present invention. In this case, in addition to the effect of defining the porosity within a predetermined range, the effect of forming the above-described communication hole or notch is exhibited, and the effect of suppressing an increase in battery internal pressure can be enhanced.

Since the negative electrode used in the first and second aspects of the present invention is a solid electrode obtained by sintering a hydrogen storage alloy powder, tightly packed hydrogen storage alloy particles are strongly bonded. It has the following structure. For this reason, the gap is hardly closed, and it has a sufficient function for the circulation of the electrolyte and the gas. In addition, since the sintered body has high mechanical strength, pulverization of the alloy powder due to charging and discharging of the battery is suppressed. Therefore, a decrease in the discharge capacity after the charge / discharge cycle is suppressed.

[0014] Nickel hydroxide of the positive electrode active material of the negative electrode used in the first and second aspects of the present invention includes:
At least one selected from manganese (Mn), aluminum (Al), cobalt (Co), zinc (Zn), magnesium (Mg), bismuth (Bi), and a rare earth element
The seed element may be dissolved. By dissolving these elements, the oxygen overvoltage of the positive electrode can be increased, and the generation of oxygen gas can be suppressed. Further, by dissolving these elements, swelling of the positive electrode during charging can be suppressed, and cycle characteristics can be improved. The addition amount of these elements to nickel hydroxide is preferably about 1 to 20% by weight. If the addition amount is smaller than this, the effect of suppressing expansion during charging and the like may not be sufficiently exhibited. On the other hand, when the addition amount is larger than this, the amount of the positive electrode active material is relatively reduced, so that the discharge capacity may be reduced.

In the nickel-metal hydride storage battery according to the first and second aspects of the present invention, the positive electrode, the negative electrode, the separator, the positive electrode current collector, and the electrolytic solution account for 75% by volume or more of the volume in the battery can. is occupying. Therefore, the active material can be filled in the battery can at a high density, the battery can have a high energy density, and the discharge capacity can be increased.

Further, in the nickel-metal hydride storage battery of the present invention, the negative electrode is disposed outside the inside of the battery can, and the positive electrode is disposed inside the battery can. By arranging the negative electrode around the positive electrode in this way, oxygen gas generated from the positive electrode can be efficiently absorbed. When the inside / positive electrode structure of the present invention is reverse to the inside / positive electrode structure, the outer peripheral portion of the positive electrode, that is, oxygen gas generated near the inner wall of the battery can,
It is hardly absorbed by the negative electrode, which may cause an increase in battery internal pressure.

The method for manufacturing an electrode for a nickel-metal hydride storage battery according to the present invention is a method for manufacturing a negative electrode for the nickel-metal hydride storage battery according to the present invention, wherein a hydrogen storage alloy powder having an average particle size of 5 μm to 50 μm is added in a hollow shape. The method is characterized in that a compact is formed by pressing, and the compact is sintered at a temperature of 600 ° C. to 1000 ° C.

By using a hydrogen storage alloy powder having an average particle size of 5 μm to 50 μm, the porosity of the present invention can be increased by 15%.
To 45% and a solid electrode having sufficient mechanical strength can be easily obtained. The average particle size of the hydrogen storage alloy powder can be measured by, for example, a laser diffraction type particle size distribution analyzer. Further, by performing sintering of the negative electrode within the range of 600 to 1000 ° C., a nickel-hydrogen storage battery having better discharge characteristics and cycle characteristics can be obtained.

As a method of manufacturing the negative electrode of the nickel-metal hydride storage battery according to the second aspect of the present invention, a method of forming a communication hole or a cut in the surface of the sintered body obtained by the above-described manufacturing method may be mentioned. .

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail along with comparative examples. However, the present invention is not limited to the following embodiments, and may be appropriately changed within the scope of the present invention. Can be implemented.

(Experiment 1) In Experiment 1, the characteristics of a spiral-type nickel-metal hydride storage battery having a conventional battery structure and the characteristics of an inside / positive-type nickel-metal hydride storage battery having a battery structure of the present invention were compared. . Further, the influence of the porosity of the hydrogen storage alloy electrode used in the nickel-hydrogen storage battery of the present invention was also examined.

[Inside / Positive Nickel of the Invention
Production of hydrogen storage battery] A mixed solution of 10% ammonia and 10% sodium hydroxide is added to nickel nitrate at pH 11.
It was added to be 5 ± 0.2. The precipitate formed at this time was filtered, further stored in a 20% aqueous KOH solution at room temperature for one week, and then washed and filtered to obtain a positive electrode active material. 10 parts by weight of graphite was added to 90 parts by weight of the obtained positive electrode active material, and pressed into a columnar shape having a diameter of 8.3 mm and a height of 36 mm to prepare a positive electrode. A metal positive electrode current collector rod (positive electrode current collector) having a diameter of 1.4 mm and a length of 30 mm was attached to the center of the obtained positive electrode.

Mm (La 25%, Ce 50%, Pr6
%, Nd 19% mixture), Ni, Co, Al, and M
n (each 99.9% pure metal) in a molar ratio of 1.0: 3.1: 0.8: 0.4: 0.7, and arc melting in an argon atmosphere After melting in a furnace, the mixture is allowed to cool naturally, and the composition formula is MmNi _3.1 Co _0.8 A
A hydrogen storage alloy represented by l _0.4 Mn _0.7 was produced. The obtained hydrogen storage alloy ingot was mechanically pulverized in air to obtain a hydrogen storage alloy powder having an average particle diameter of 30 μm.

The obtained hydrogen-absorbing alloy powder has an outer diameter of 13.
After being pressure-formed into a hollow cylindrical shape (doughnut type) having a size of 3 mm, an inner diameter of 10.3 mm and a height of 12 mm, it was heat-treated at 800 ° C. for 2 hours and sintered to produce a negative electrode body. The porosity of the obtained negative electrode body was 30%. The porosity was calculated from the volume calculated from the dimensions of the negative electrode body, the weight, and the specific gravity of the hydrogen storage alloy powder.

The above three negative electrode bodies were inserted into an AA type battery can to form a negative electrode. A separator having double nylon nonwoven fabric was placed inside the negative electrode, and the above-mentioned separator was placed inside the negative electrode through this separator. Of the positive electrode was inserted. Next, 30% by weight
After 3.5 g of a KOH aqueous solution was injected as an electrolytic solution, the nickel-hydrogen storage battery of the present invention was manufactured by closing the opening. The obtained nickel-hydrogen storage battery was used as sample A.

FIG. 1 is a schematic sectional view showing the inside / positive electrode type nickel-metal hydride storage battery of sample A. As shown in FIG. 1, the nickel-hydrogen storage battery of the present embodiment has a cylindrical bottomed negative electrode can (negative electrode external terminal) 1, a positive electrode cover (positive electrode external terminal) 2, an insulating packing 3, a positive electrode current collector 4, It is composed of a hollow cylindrical negative electrode 5, a separator 6, a positive electrode 7, and the like. The outer peripheral surface of the negative electrode 5 is housed in the negative electrode can 1 so as to be in contact with the inner peripheral surface of the negative electrode can 1. The negative electrode 5 is configured by stacking three negative electrode bodies as described above. Inside the negative electrode 5, a cylindrical positive electrode 7 is housed via a separator 6. In the center of the positive electrode 7,
The positive electrode current collector 4 is inserted. The upper end of the positive electrode current collector 4 is supported by the insulating packing 3. The insulating packing 3 is attached to electrically insulate the negative electrode can 1 and the positive electrode lid 2 from each other. The battery can includes a negative electrode can 1, a positive electrode lid 2, and an insulating packing 3, and the volume inside the battery can is defined by a space closed by the negative electrode can 1 and the insulating packing 3. An electrolytic solution composed of an aqueous solution of potassium hydroxide is filled in such a battery can, and is impregnated in the positive electrode 7, the negative electrode 5, and the separator 6. In the present embodiment, the positive electrode 7, the negative electrode 5, the separator 6, the positive electrode current collector 4, and the electrolyte are configured to occupy 85% by volume of the volume inside the battery can.

[Preparation of Conventional Spiral-Type Nickel-Hydrogen Storage Battery] A positive electrode for a spiral-type storage battery was prepared using a positive electrode active material obtained in the same manner as in the above-mentioned inside / positive-type storage battery. 100 parts by weight of a positive electrode active material and a 1% by weight aqueous solution of methylcellulose as a binder 2
And 0 parts by weight to prepare a paste. This paste is mixed with a nickel foam (95% porosity, 200 μm average pore diameter).
m), filled into the pores, dried, and then press-molded.

The negative electrode was composed of 100 parts by weight of a hydrogen-absorbing alloy powder having an average particle size of 30 μm, obtained in the same manner as in the case of the inside / positive-type storage battery, and PE as a binder.
A paste is prepared by mixing 20 parts by weight of an aqueous solution of 5% by weight of O (polyethylene oxide), and the paste is applied to both sides of a core made of a punched metal plated with nickel and dried at room temperature. , And was cut to predetermined dimensions.

After winding the obtained negative electrode one turn around the innermost circumference,
The end of the positive electrode was inserted into the outer periphery thereof, with the positive electrode placed via a separator, wound in a spiral shape, and housed in an AA battery can. The manufactured spiral nickel-hydrogen storage battery was used as Sample X.

FIG. 2 is a schematic sectional view showing a spiral storage battery of Comparative Sample X. As shown in FIG. 2, the spiral-type storage battery of this comparative example includes a negative electrode can (negative electrode external terminal) 8, a positive electrode external terminal 9, an insulating packing 10, and a negative electrode 1.
1, a separator 12, a positive electrode 13, a negative electrode lead 14, a positive electrode lead 15, a sealing lid 16 and the like. The negative electrode 11 and the positive electrode 13 are housed in the negative electrode can 8 in a state of being spirally wound via the separator 12. The positive electrode 13 is connected to the sealing lid 16 via the positive electrode lead 15,
The negative electrode 11 is connected to the negative electrode can 8 via a negative electrode lead 14. An insulating packing 10 is attached to the joint between the negative electrode can 8 and the sealing lid 16, thereby sealing the inside of the battery. The battery can is filled with an electrolytic solution composed of an alkaline aqueous solution.

[Test conditions] In the following tests, ten experimental cells (batteries) were prepared, and evaluation was performed using the average value of the characteristics.

(Evaluation Method of Battery Internal Pressure Characteristics) The battery was charged at 25 ° C. at a current of 0.2 C for 6 hours, and then discharged at 0.2 C to 1.0 V. Thereafter, the battery was charged at the same temperature at 0.2 C, and the battery internal pressure at that time was measured.
The charging time until reaching gf / cm ² was measured.

(Evaluation method for battery weight loss) After charging at 5 ° C. and a current of 0.2 C for 6 hours, discharging was performed at 0.2 C for 1.0 hour.
The charge / discharge test performed up to V is defined as one cycle,
The cycle was repeated 00 times, and the reduction in battery weight from the time of fabrication was determined.

(Evaluation Method of Discharge Characteristics) After charging at 25 ° C. at a current of 0.2 C for 6 hours, discharging was performed at 0.2 C for 1.0 hour.
The charge / discharge test performed up to 5 V was regarded as one cycle, and the charge / discharge test was performed for 5 cycles.
The cycle was performed, and the discharge capacity at the fifth cycle was measured. Table 1 shows the measurement results of the discharge capacity.

[0035]

[Table 1]

As is apparent from Table 1, it is understood that the battery A of the present invention, which has the inside / positive electrode structure, has a larger discharge capacity than the spiral sample X, which is a comparative battery. This is due to the difference in the active material filling amount in the battery. Note that, during the charging time until the battery internal pressure reached 10 kgf / cm ² , no substantial difference was observed between Sample A and Sample X. In addition, in each of Samples A and X, no decrease in the battery weight was observed after 100 cycles, indicating that there was no leakage of the electrolyte.

As described above, by adopting the inside / positive electrode type structure of the present invention in which the hollow cylindrical sintered body of the hydrogen storage alloy is used for the negative electrode and the positive electrode is disposed inside the negative electrode, the conventional spiral-type storage battery is provided. It shows the same charge / discharge cycle characteristics as those of
It has been clarified that a nickel-metal hydride storage battery having a larger discharge capacity than a conventional spiral storage battery can be obtained.

Next, the influence of the porosity of the negative electrode (negative electrode body) used on the inside / positive electrode type nickel-metal hydride storage battery of the present invention was examined. In the same manner as in the above experiment, a hydrogen storage alloy powder having an average particle size of 30 μm was press-formed into a hollow cylindrical shape. This was sintered at 800 ° C. for an arbitrary time to produce hydrogen storage alloy electrodes having porosity of 10%, 20%, 30%, 40%, and 50%. Using these hydrogen-absorbing alloy electrodes, inside / positive-type nickel-hydrogen storage batteries were produced, and these were designated as Samples B1 to B5, respectively.

Table 2 shows the measurement results of the charging time (internal pressure rise time) until the internal pressure of the battery reaches 10 kgf / cm ² , the decrease in the weight of the battery (reduced weight) after 100 cycles, and the discharge capacity. Table 2 also shows data of the sample A used in the above experiment, that is, the data of the sample B3.

[0040]

[Table 2]

As is clear from Table 2, samples B2 to B4
In this example, the battery internal pressure was kept relatively low, and the battery weight did not decrease even after 100 cycles. on the other hand,
In sample B1 and sample B5, a decrease in battery weight was confirmed after 100 cycles. This is for sample B1
Since the porosity was 10%, it was considered that the gas flow in the negative electrode was hindered and the internal pressure of the battery increased. On the other hand, in sample B5, since the porosity was 50%, the amount of the filled negative electrode active material was relatively small, the gas absorption rate was reduced, and the battery internal pressure was thought to have increased.

From the results shown in Table 2, the porosity needs to be in the range of 15% to 45%, and preferably in the range of 20% to 40%, in order to suppress the rise in the internal pressure of the battery. It can be seen that it is.

(Experiment 2) In this experiment 2, the inside
The effect of the average particle size of the hydrogen storage alloy used and the effect of the sintering temperature when sintering the compact on the positive electrode type nickel-metal hydride battery were studied.

[Preparation of Inside / Positive Electrode Type Nickel-Hydrogen Storage Battery]
3 μm, 5 μm, 10 μm, 30 μm, 50 μm, 60
A μm hydrogen storage alloy powder was produced. These were formed into a hollow cylinder under various pressures and sintered at 800 ° C. for 2 hours to produce negative electrodes a1 to a6. The porosity of all the obtained negative electrode bodies was 30%. Using these negative electrodes, inside / positive nickel-metal hydride storage batteries were prepared, and as shown in Table 3, samples C1 to C6 were obtained.

[0045]

[Table 3]

[Test conditions] In the same manner as in Example 1, the battery internal pressure characteristics, battery weight reduction, and discharge characteristics were evaluated.
The evaluation of the cycle characteristics was performed as follows.

(Evaluation of cycle characteristics) After charging at 25 ° C at a current of 0.2 C for 6 hours, discharging was performed at 0.2 C for 1.0 hour.
A charge / discharge test was performed with charging / discharging performed up to V as one cycle, and the number of cycles when the discharge capacity became 70% or less of the discharge capacity in the first cycle was recorded.

Table 4 shows the measurement results of the charging time (internal pressure rise time), the discharge capacity, and the number of cycles until the internal pressure of the battery reaches 10 kgf / cm ² . Table 4 also shows data of the sample A used in the above experiment 1, that is, the sample C4.

[0049]

[Table 4]

As is clear from Table 4, in the samples C2 to C5, the rise time of the internal pressure of the battery is longer and the discharge characteristics and the cycle characteristics are improved as compared with the samples C1 and C6. I understand.

In sample C1 using an alloy powder having an average particle size of 3 μm, the filling rate of the alloy powder was too high, so it was necessary to lower the pressure during pressure molding to 30% porosity.
For this reason, in Sample C1, sufficient electrical contact between the alloy particles was not obtained, and it is considered that the utilization rate of the negative electrode was reduced. In sample C6 using a hydrogen storage alloy powder having an average particle diameter of 60 μm, it was necessary to increase the pressing pressure to secure sufficient mechanical strength for the sintered body. For this reason, it is considered that the gap between the alloy particles was closed, and the permeability of the electrolytic solution was reduced.

In each of the samples, no decrease in battery weight after 100 cycles was observed. Therefore, no leakage of the electrolyte was observed. From the results shown in Table 4, the average particle size of the hydrogen storage alloy powder used was as follows:
It turns out that 5 micrometers-50 micrometers are especially preferable.

Next, the influence of the sintering temperature when sintering the hydrogen-absorbing alloy powder on the inside / positive electrode type nickel-hydrogen storage battery was examined. In the same manner as in the above experiment, a hydrogen storage alloy powder having an average particle diameter of 30 μm was pressed into a hollow cylinder and sintered at the temperatures shown in Table 5 to obtain a negative electrode body having a porosity of 30%. b1 to b5 were prepared. Using these anode bodies, inside / cathode type nickel-metal hydride storage batteries were prepared, and as shown in Table 5, samples D1 to D5 were obtained.

[0054]

[Table 5]

Next, the internal pressure rise time, the discharge capacity and the number of cycles were measured in the same manner as described above. Table 6 shows the measurement results. Table 6 also shows the data of Sample A used in Experiment 1 above, that is, the data of Sample D3.

[0056]

[Table 6]

As shown in Table 6, it can be seen that in Samples D2 to D4, the internal pressure rise time is longer and the discharge characteristics and cycle characteristics are improved as compared with Samples D1 and D5. Note that no reduction in the battery weight after 100 cycles was observed in any of the samples. Therefore,
No leakage of the electrolyte was observed. From the above results, the sintering temperature of the hydrogen storage alloy used was 600 ° C. to 1 ° C.
It turns out that 000 ° C. is particularly preferred.

(Experiment 3) In Experiment 3, the inside
The effect of forming communication holes or cuts in the surface of the negative electrode of the positive electrode nickel-metal hydride battery was examined.

[Preparation of Inside / Positive Electrode Nickel / Hydrogen Storage Battery] In the same manner as in Experiment 1, the hydrogen-absorbing alloy powder was pressed into a hollow cylinder and sintered at 800 ° C. for 2 hours to obtain a porosity of 30%. Was produced. Next, a communication hole was formed from the outer peripheral surface of the cylindrical negative electrode body toward the center using a metal needle having a diameter of 1.0 mm.

FIG. 3 is a perspective view for explaining the communication hole formed in this way. Negative electrode body 5a shown in FIG.
Is one of the three negative electrodes constituting the negative electrode 5 shown in FIG. As shown in FIG. 3, the outer peripheral surface 5 of the negative electrode body 5a
A communication hole 20 is formed in b. The communication hole 20 is formed to extend from the outer peripheral surface 5b toward the center and penetrate to the inner peripheral surface 5c. In addition, the through hole 20 shown in FIG. 3 is shown to be considerably larger than the actual size.

The through-holes 20 were formed such that the number of the through-holes 20 was substantially constant per unit surface area of the outer peripheral surface 5b of the negative electrode body 5a. Number of through holes from 10 to 2
The ratio (W / W ₀ ) of the weight W of the negative electrode body after processing to the weight W ₀ of the negative electrode body before processing is changed to about 50.
Negative electrode bodies c2 to c7 having values as shown in Table 7 were produced. Using these anode bodies, inside / cathode type nickel-metal hydride batteries were produced, and as shown in Table 7, each was designated as Samples E2 to E7.

For each sample, the internal pressure rise time, the discharge capacity, and the number of cycles were measured in the same manner as described above. Table 7 shows the measurement results. Table 7 also shows data of the sample A used in the above experiment 1, that is, the sample E1.

[0063]

[Table 7]

As is clear from Table 7, W / W ₀ × 10
Particularly preferable results are obtained when the value of 0 is in the range of 99.0 to 95.0%. Therefore, when forming the communication hole on the surface of the negative electrode in the present invention, the weight of the negative electrode after forming the communication hole is 99.0 to 95.0% of the weight of the negative electrode before formation.
It can be seen that it is preferable to form the communication hole so as to fall within the range. In addition, when forming a communication hole, it is preferable that the diameter of a hole is about 30 micrometers-3.0 mm.

FIG. 4 is a perspective view showing a state in which a cut 21 is formed on the outer peripheral surface 5b of the negative electrode body 5a. In the present invention, even when such a cut 21 is formed, the same effect as when the communication hole 20 shown in FIG. 3 is formed can be obtained. That is, such communication holes and cuts serve as passages for the electrolyte, so that the electrolyte can easily penetrate into the negative electrode, and the utilization rate of the negative electrode active material can be improved. In addition, since it can also function as a gas distribution channel, it is possible to enhance the absorption of oxygen gas in the negative electrode,
The increase in battery internal pressure can be further suppressed.

When forming the notch 21 as shown in FIG. 4, the width of the notch 21 is preferably about 30 μm to 3.0 mm. Further, it is preferable that the depth of the notch when such a notch is formed is substantially equal to the width of the notch. Therefore, the depth of the cut 21 is preferably about 30 μm to 3.0 mm depending on the width of the cut.

FIG. 5 is a perspective view showing a communication hole 22 formed in the upper surface 5d of the negative electrode body 5a. Negative electrode body 5a shown in FIG.
In FIG. 5, a communication hole 20 penetrating from the outer peripheral surface 5b to the inner peripheral surface 5c is formed. However, the communication hole in the present invention is not limited to this, and for example, the communication hole 22 shown in FIG. The communication hole may extend from the upper surface 5d to the lower surface 5e and penetrate therethrough. Even such a communication hole serves as a passage for the electrolyte and a gas passage. Therefore, similarly to the communication hole and the cut, the utilization rate of the negative electrode active material is improved, and the internal pressure of the battery due to gas generation is increased. Can be suppressed.

The diameter of the communication hole 22 shown in FIG. 5 is preferably about 30 μm to 3.0 mm. The cut 21 shown in FIG. 4 and the communication hole 22 shown in FIG. 5 also have a weight of the negative electrode body after processing of 99.0 to 95.0% before processing, similarly to the communication hole 20 shown in FIG. Preferably, it is processed to be inside.

(Experiment 4) In this experiment 4, the inside
In the positive electrode nickel-metal hydride battery, the effect of using nickel hydroxide in which various elements are dissolved as a positive electrode active material was examined.

[Preparation of Inside / Positive Electrode Nickel / Hydrogen Storage Battery] Sulfates of elements other than Ni shown in Table 8 and nickel sulfate were mixed in the molar ratio shown in Table 8, and the same procedure as in Experiment 1 was carried out. Thus, a positive electrode active material was prepared, and a positive electrode was prepared using the positive electrode active material. The obtained positive electrodes were used as positive electrodes d1 to d6 as shown in Table 8.

[0071]

[Table 8]

Using the positive electrodes d1 to d6, an inside / positive nickel-metal hydride storage battery was produced in the same manner as in Experiment 1. The obtained storage batteries were designated as Sample F1 to Sample F6, respectively. In Samples F1 to F6, a cylindrical negative electrode having the same porosity of 30% as the negative electrode used in Experiment 1 was used.

[Test conditions] In the same manner as in Experiments 1 and 2,
The internal pressure rise time, battery weight reduction, discharge characteristics and cycle characteristics were evaluated. Table 9 shows the measurement results of the internal pressure rise time, the discharge capacity, and the number of cycles. Table 9 also shows the data of the sample A used in the above experiment 1, that is, the sample F1.

[0074]

[Table 9]

As is clear from Table 9, samples F2 to F6
In the example, the internal pressure rise time or the discharge characteristics and the cycle characteristics are improved as compared with the sample F1. It is considered that the reason why the internal pressure rise time was long and the internal pressure characteristics of the battery were improved was that oxygen overvoltage at the positive electrode was increased by dissolving various metals in nickel hydroxide. on the other hand,
It is considered that the discharge characteristics were improved due to an increase in discharge voltage due to the solid solution component. The improvement in cycle characteristics is particularly remarkable, which is considered to be due to suppression of expansion of the positive electrode by the solid solution component.

As is clear from the results of Sample F6, the above-mentioned characteristics can be further improved by dissolving a plurality of metals in nickel hydroxide.
In this case, the solid solution of the metal is not limited to manganese, cobalt, zinc and magnesium, and it has been confirmed that the above properties are improved even when aluminum, bismuth (Bi) and a rare earth element are dissolved. Note that no reduction in the battery weight after 100 cycles was observed in any of the samples. Therefore, no leakage of the electrolyte from the battery was observed.

In each of the above experiments, the hydrogen storage alloy powder produced by the arc melting method was used as the hydrogen storage alloy powder. However, the present invention is not limited to this. A hydrogen storage alloy powder produced by a quenching method may be used.

[0078]

According to the present invention, since the inside / positive electrode type structure is used, the negative electrode is arranged around the positive electrode, and the oxygen gas generated from the positive electrode is easily absorbed by the negative electrode. Further, since a larger amount of active material can be filled in the battery can than in the conventional spiral structure, the energy density can be increased and the discharge capacity can be increased.

Further, according to the first aspect of the present invention, since the solid electrode having a porosity of 15% to 45% is used, the electrolyte easily penetrates the negative electrode, and the utilization rate of the negative electrode active material is improved. At the same time, oxygen gas generated from the positive electrode can be effectively consumed at the negative electrode.

In the second aspect of the present invention, communication holes or cuts are formed in the surface of the negative electrode, and these communication holes or cuts serve as a flow path for the electrolyte and also as a flow path for the gas. Therefore, the utilization rate of the negative electrode active material is improved, and an increase in battery internal pressure due to gas generation can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an inside / positive-type nickel-metal hydride storage battery of the present invention.

FIG. 2 is a schematic sectional view showing an example of a conventional spiral nickel-metal hydride storage battery.

FIG. 3 is a perspective view showing a negative electrode body used in one embodiment of the present invention in which a communication hole is formed on the surface of the negative electrode.

FIG. 4 is a perspective view showing a negative electrode body used in another embodiment of the present invention in which a cut is formed on the surface of the negative electrode.

FIG. 5 is a perspective view showing a negative electrode body having a communication hole formed on a surface of a negative electrode and used in still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Negative electrode can (negative electrode external terminal) 2 ... Positive electrode cover (positive electrode external terminal) 3 ... Insulating packing 4 ... Positive electrode collector 5 ... Negative electrode 6 ... Separator 7 ... Positive electrode 5a ... Negative electrode body 5b ... Outer peripheral surface of negative electrode body 5c ... Inner peripheral surface of negative electrode body 5d: upper surface of negative electrode body 5e: lower surface of negative electrode body 20: communication hole 21: cut 22: communication hole

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/28 B22F 5/00 101G (72) Inventor Kikuko Kato 2-5-5 Keihanhondori, Moriguchi-shi, Osaka 5 No. 5 Sanyo Electric Co., Ltd. (72) Nobuyuki Higashiyama 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Mamoru Kimoto 2 Keihanhondori, Moriguchi-shi, Osaka 5-5-5 Sanyo Electric Co., Ltd. (72) Inventor Yasuhiko Ito 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio Keihanmoto, Moriguchi, Osaka 2-5-5 Sanyo Electric Co., Ltd. F term (reference) 4K018 AA07 BD07 CA11 DA00 HA03 KA37 5H003 AA02 BA01 BA05 BB02 BB04 BC04 BD01 BD02 BD03 5H016 AA02 BB01 BB05 EE01 EE05 HH02 HH11 H H13 5H028 AA02 AA06 AA07 BB04 BB05 CC07 CC17 EE01 EE05 HH01 HH02 HH05 HH08

Claims (6)

[Claims] 1. A battery can, a hollow negative electrode made of a hydrogen storage alloy as a negative electrode active material, which is disposed inside the battery can so as to be in electrical contact with the battery can, and disposed inside the negative electrode. A positive electrode using nickel hydroxide as a positive electrode active material, a separator disposed between the negative electrode and the positive electrode, and a positive electrode current collector disposed while being inserted into the positive electrode,
Filled in the battery can, comprising the positive electrode, the negative electrode, and an electrolytic solution impregnated in the separator, the positive electrode, the negative electrode, the separator, the positive electrode current collector, and the electrolytic solution, A sealed nickel-metal hydride storage battery occupying 75% by volume or more of the volume in a battery can, wherein the negative electrode is a solid electrode having a porosity of 15% to 45% obtained by sintering a hydrogen storage alloy powder. A nickel-metal hydride storage battery. 2. The nickel-metal hydride storage battery according to claim 1, wherein a communication hole or a cut is formed in a surface of the negative electrode. 3. The manganese (Mn), aluminum (Al), cobalt (C)
3. Nickel / hydrogen according to claim 1, wherein at least one element selected from the group consisting of o), zinc (Zn), magnesium (Mg), bismuth (Bi), and a rare earth element is dissolved. Storage battery. 4. A battery can, a hollow negative electrode made of a hydrogen storage alloy as a negative electrode active material, which is disposed in the battery can so as to be in electrical contact with the battery can, and disposed inside the negative electrode. A positive electrode using nickel hydroxide as a positive electrode active material, a separator disposed between the negative electrode and the positive electrode, and a positive electrode current collector disposed while being inserted into the positive electrode,
Filled in the battery can, comprising the positive electrode, the negative electrode, and an electrolytic solution impregnated in the separator, the positive electrode, the negative electrode, the separator, the positive electrode current collector, and the electrolytic solution, A sealed nickel-metal hydride storage battery occupying 75% by volume or more of the volume in a battery can, wherein the negative electrode is a solid electrode obtained by sintering a hydrogen storage alloy powder, and a communication hole or a hole is formed on the surface of the negative electrode. A nickel-metal hydride storage battery, wherein a notch is formed. 5. A method for producing a negative electrode of a nickel-metal hydride storage battery according to claim 1, wherein the hydrogen storage alloy powder having an average particle size of 5 μm to 50 μm is pressure-formed into a hollow shape. To form a molded body, and the molded body is heated to 600 ° C. to 10 ° C.
A method for producing an electrode for a nickel-metal hydride storage battery, comprising sintering at 00 ° C. 6. A method for producing a negative electrode of a nickel-metal hydride storage battery according to claim 2 or 4, wherein communication holes or cuts are formed on the surface of the sintered body obtained according to the method according to claim 5. A method for producing an electrode for a nickel-metal hydride storage battery.