JPH10214637A - Hydride secondary battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydride secondary battery which brings about a high capacity, and sufficiently copes with downsizing of the battery in the hydride secondary battery formed by containing an electrode body which is made by spirally winding a positive electrode using paste type hydroxide as an active material and a negative electrode composed of a hydrogen storage alloy via a separator in a battery can. SOLUTION: An electrode body 4, which is made by sprially winding a positive electrode 1 using nickel hydroxide as an active material and a negative electrode 2 composed of a hydrogen storage alloy via a separator 3, is contained in a battery can 5, an electrolyte composed of alkaline aqueous solution is filled thereinto, and the same is sealed by a sealing body equipped with a reversible vent so as to form a hydride secondary battery. Therein, the nickel hydroxide is powder, its particle size is 2 to 40μm, and its average particle diameter is 8±2μm. In the powder particles of average particle diameter or more are spherical, and 95 percentage by weigh or more of the particles of less than average particle diameter are also spherical. The winding center 4a of the electrode body 4 and the center 5a of the battery can 5 are dislocated mutually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a battery can in which a positive electrode having a paste type nickel hydroxide as an active material and a negative electrode made of a hydrogen storage alloy are spirally wound through a separator to a battery can. The present invention relates to a hydride secondary battery housed therein and a method for producing the same.

[0002]

2. Description of the Related Art An electrode body in which a positive electrode and a negative electrode are spirally wound via a separator can secure a large opposing area between the positive and negative electrodes due to the wound structure, and has good load characteristics. Hydrogen storage alloy batteries, nickel-cadmium batteries,
Widely used for lithium secondary batteries and the like. Among these, the nickel-hydrogen storage alloy battery is capable of electrochemically storing and releasing a large amount of hydrogen even in an alkaline aqueous solution,
When the nickel electrode of the positive electrode is made of a so-called paste type nickel hydroxide as an active material, in which an active material slurry mainly composed of nickel hydroxide is supported on a conductive porous substrate, the capacity is increased. It is especially noted because it can be expected to have lower prices. .

[0003]

However, recently, devices using batteries have been downsized, and accordingly, batteries have been required to be downsized. In order to meet the demand for miniaturization while keeping the standard value of the current flowing per unit volume of the electrode constant, the number of turns of the electrode body decreases as the inner diameter of the battery can housing the electrode body decreases. As a result, the number of turns of the electrode body cannot be set arbitrarily, and the number of turns suitable for the current value of the equipment to be used cannot be adopted. However, there is a problem that the gap of the battery becomes large and it is impossible to achieve an improvement in battery capacity.

For example, as shown in Comparative Example 1 below,
Using a separator having a thickness of 0.15 mm, a negative electrode, and a positive electrode having an active material amount 2.1 times the volume ratio of the negative electrode, the separator and the negative electrode are wound on a winding shaft having a diameter of 2.5 mm. , A separator and a positive electrode, in order, to form an electrode body having a wound structure in which the outermost portion is wound around the negative electrode by winding the member two to three times. Next, it is assumed that the winding center and the center of the battery can are aligned and the battery can is housed in a battery can having an inner diameter of 9.4 mm. In this case, the thickness of the negative electrode is set to 0.1.
When the number of turns of the positive electrode is 2.75, the gap between the electrode body and the battery can is the smallest when the thickness of the positive electrode is 25 mm and the thickness of the positive electrode is 0.43 mm. It is difficult to increase the capacity.

[0005] If the number of turns is smaller than the above, the gap between the electrode body and the battery can becomes large, and as the electrode area decreases, the current value per unit area of the electrode increases, and the load characteristics deteriorate. If the electrode body is thinned and the number of windings is increased to improve the load characteristics, the number of separators not involved in the battery reaction increases, and the battery capacity decreases. That is, when the number of turns of the electrode body is small, there is a problem that it is difficult to set the number of turns to a value suitable for the current value of the device to be used when the electrode body is accommodated in the battery can. Also, as the number of turns of the electrode body is smaller, the cross-sectional shape of the electrode body becomes a distorted shape that deviates from a circle. This is a problem when trying to improve the quality.

In view of the above circumstances, the present invention provides a nickel-hydrogen storage alloy battery in which a positive electrode using a paste-type nickel hydroxide as an active material and a negative electrode made of a hydrogen storage alloy are interposed through a separator. To provide a hydride secondary battery in which a spirally wound electrode body is accommodated in a battery can to increase the capacity and sufficiently cope with the miniaturization of the battery. It is an object.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above objects, and as a result, have reduced the number of windings in accordance with the miniaturization of the battery, and the cross-sectional shape has shifted from a circular shape. When accommodating the distorted electrode body in the battery can, if the winding center of the electrode body and the center of the electrode can are accommodated in a displaced manner, the gap between the electrode body and the battery can is reduced, and the battery can I learned that it can greatly contribute to high capacity.

On the other hand, the positive electrode constituting the electrode body is obtained by filling a conductive porous base material with an active material slurry mainly composed of nickel hydroxide, drying, and compression molding to obtain a sheet-like material. However, the conventional nickel hydroxide is usually several μm.
It has a particle diameter of about m to several tens of μm, has a wide particle size distribution, and a particle having a large particle diameter is spherical, while a small particle has a distorted dango-like shape. For this reason, the above-mentioned base material tends to be densely clogged at the time of the above-mentioned compression molding, and this results in impairing the impact resistance and deformation resistance against external force of the molded positive electrode.When producing an electrode body having a wound structure, It is easy to cause defects such as cracks and tears,
This problem is particularly remarkable in an electrode body having a small number of turns and easily forming an irregular cross section.

By the way, in the previous study, the present inventors added nickel hydroxide to an aqueous solution of nickel sulfate to form a precipitate of nickel hydroxide, and washed and dried it to produce nickel hydroxide powder. It has been found that by appropriately selecting various conditions such as reaction, washing, drying and pulverization, it is possible to obtain a nickel hydroxide powder having a narrow particle size distribution and a spherical shape up to a small particle diameter, which is almost spherical.

The inventors of the present invention use nickel hydroxide powder of this specific property as a nickel hydroxide for forming a positive electrode, the nickel hydroxide powder is easy to move at the time of compression molding, and the powders are spheres. Has a characteristic that it is difficult to be compressed because the contact resistance of the molded positive electrode is less than that of a dangling and distorted one. As a result, the impact resistance and deformation resistance of the molded positive electrode against external force are improved, and the production of a wound electrode body is achieved. On the other hand, it has been found that defects such as cracks and tears are less likely to occur during winding.

[0011] Further, the fact that it is difficult to be compressed is considered that the pores of the positive electrode do not decrease and this is originally disadvantageous in terms of increasing the capacity of the battery. The powder shows an excellent utilization rate compared to the conventional nickel hydroxide, which greatly contributes to increasing the capacity of the battery.As a result, the center of the electrode body and the center of the electrode can are shifted from the electrode body to the battery can. It has been found that a very high capacity hydride rechargeable battery can be manufactured in combination with the effect of reducing the gap between the battery and the battery.

A first aspect of the present invention has been completed based on the above findings, and comprises a positive electrode using nickel hydroxide as an active material and a negative electrode made of a hydrogen storage alloy, which are spirally wound through a separator. In the hydride secondary battery in which the turned electrode body is accommodated in a battery can and an electrolyte solution composed of an alkaline aqueous solution is injected and sealed with a sealing body having a reversible vent, the nickel hydroxide has a particle size of 2 to 40 μm. , Average particle size is 8 ± 2
The powder having a mean particle diameter of at least 95% by weight of particles having an average particle diameter of at least 95% by weight is spherical. A hydride secondary battery (claim 1)
To 7).

A second aspect of the present invention is that an electrode body in which a positive electrode using nickel hydroxide as an active material and a negative electrode made of a hydrogen storage alloy are spirally wound via a separator is housed in a battery can. In addition, in the method for producing a hydride secondary battery in which an electrolytic solution composed of an alkaline aqueous solution is injected and sealed with a sealed body having a reversible vent, the nickel hydroxide has a particle size of 2 to 40 μm and an average particle size of 8 ± 2 μm, particles having an average particle size or more are spherical and particles having an average particle size
Using a powder that is spherical in weight percent or more, a paste containing the nickel hydroxide powder is supported on a conductive porous substrate,
After drying, compression molding is performed to produce a positive electrode, and the electrode body obtained by spirally winding this positive electrode and a negative electrode made of a hydrogen storage alloy via a separator is placed between the winding center and the center of the battery can. The present invention relates to a method for manufacturing a hydride secondary battery, wherein the battery is housed in a battery can so that the battery is shifted.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Nickel hydroxide used in the present invention has a particle size of 2 to 2 as measured by a microtrap method.
40 μm, powder having an average particle size of 8 ± 2 μm, and this powder was observed by SEM (scanning electron microscope), where particles having an average particle size of more than 95% by weight were spherical and particles having an average particle size of not more than 95% by weight. It is spherical, that is, compared to the conventional one,
It is characterized in that it is composed of uniform particles having a narrow particle size distribution, and that not only particles having a large particle size but also particles having a small particle size are spherical.

[0015] Nickel hydroxide powder in which small particles are not spherical and dango-shaped as in the prior art has low crystallinity, so that the efficiency of the electrochemical reaction is reduced and the utilization rate of the positive electrode is reduced. Become. On the other hand, the nickel hydroxide powder of the present invention has high crystallinity, improves the efficiency of the electrochemical reaction, improves the utilization rate of the positive electrode, and has a narrow particle size distribution. It is likely to occur uniformly, which is also considered to have contributed to the improvement of the utilization rate and the extension of the service life.

The nickel hydroxide powder of the present invention can be prepared as follows. First, a solution obtained by mixing a sulfuric acid solution obtained by dissolving cobalt or zinc in an aqueous solution containing nickel, an alkaline aqueous solution and an ammonium ion donor are simultaneously and continuously supplied so that a nickel ion concentration of 40 mg / liter or less is obtained. The solution is maintained at 5 to 20 ° C., and the pH is adjusted to 9 to 12 by adding sodium hydroxide. The mixture is aged for 12 hours or more with stirring, and the pH is maintained at 9 to 12 during the aging. Next, the nickel hydroxide precipitate is filtered by suction, washed with water and dried at 80 to 120 ° C. to obtain the nickel hydroxide powder of the present invention. This method is significantly different from the conventional preparation method in that nickel hydroxide is prepared at a low temperature (5 to 20 ° C.).

The nickel hydroxide powder thus prepared has a pore radius measured by the BET adsorption method of 7 to 8 ° which is the same as that of the conventional nickel hydroxide powder, and is in the range of 5 to 6 °. Also, it has a peculiar property that it has a peak, and usually, the ratio (la :) of the peak intensity (la) of 7 to 8 mm to the peak intensity (lb) of 5 to 6 mm described above.
lb) is 100: 50 or more.

Usually, the specific surface area measured by the BET adsorption method is 5 to ²⁰ m ² / g, the pore volume measured by the BET adsorption method is 0.015 to 0.030 cc / g, and the average pore radius is Is in the range of 25 to 50 °. BET
The specific surface area measured by the adsorption method is a value measured on the adsorption side in a nitrogen adsorption method (Yuasa Ionics, Otosop 1) at 1 to 100 ° C, 1 g of sample, 127 minutes of measurement time.

In the present invention, the positive electrode is prepared by kneading the above-mentioned nickel hydroxide powder with a binder such as carboxymethyl cellulose or polytetrafluoroethylene.
It is produced by supporting a strike on a conductive porous base material such as a nickel foam, drying, and compression molding. At that time, the paste has a mean particle size of 1.5 as a conductive aid.
μm or less of cobalt powder may be included. In this case,
It is desirable to add a step of dipping in an aqueous alkali solution after compression molding. In addition to the cobalt powder, other conductive aids such as nickel powder and a cobalt compound may be included.

A negative electrode made of a hydrogen-absorbing alloy is used for the positive electrode made of the paste-type nickel hydroxide as an active material, and the positive and negative electrodes are spirally wound through a separator such as a nonwoven fabric of nylon. To form a wound electrode body. At this time, the thickness of the positive electrode and the number of windings thereof are selected in accordance with the miniaturization of the battery. However, there is no particular concern that the positive electrode will have a defect such as cracking or tearing when producing such an electrode body.

In the present invention, the wound electrode body is accommodated in a battery can so that the center of the wound and the center of the battery can are displaced from each other. The desired hydride secondary battery can be obtained by injecting an alkaline aqueous solution in which an electrolyte such as LiOH is dissolved into an aqueous solution of, and hermetically sealing with a sealing body having a reversible vent according to a conventional method. .

In the present invention, the offset distance between the winding center of the electrode body and the center of the battery can is preferably at least 4% of the inner diameter of the battery can. When such a shift distance is set, even if the cross-sectional shape of the electrode body is deviated from the circular shape due to a small number of windings or the like, this shift is easily absorbed, and the gap between the electrode body and the battery can is small. It will be.
However, if the deviation distance is too large,
Since the gap between the electrode body and the battery can tends to be rather large, the deviation distance is set to 4% of the inner diameter of the battery can.
It is desirable that the above is 9% or less.

Further, in the present invention, in order to suppress the cross-sectional shape of the electrode body from being deviated from a circle as much as possible, the direction in which the cross-sectional diameter of the electrode body becomes the largest, that is, the winding end portion of the electrode body It is preferred that the ratio of the shortest diameter to the longest diameter of the electrode body be close to 1 by reducing the diameter of the direction in which is present as much as possible, so that the cross-sectional shape of the electrode body is as circular as possible.

More specifically, a thin portion is provided in a part of the positive electrode or the negative electrode, and the thin portion is arranged somewhere in the direction in which the winding end portion of the electrode body exists. The ratio between the shortest diameter and the longest diameter of the cross section can be made closer to 1. In order to provide a thin portion in a part of the positive electrode or the negative electrode, a part of the base material used for forming each electrode may be thinned so that the active material is not filled therein. In addition, by not matching the direction in which the diameter of the cross section of the cavity at the center of the electrode body becomes the longest and the direction in which the winding end portion of the electrode body exists, the ratio between the shortest diameter and the longest diameter of the cross section of the electrode body is reduced. You may make it approach 1.

The hydrogen storage alloy used for the negative electrode is Mm
(La, Ce, Nd, Pr) -Ni-based, Ti-Ni-based,
_{Ti-NiZr (Ti 2-x} Zr x V 4-y Ni y) 1-z C
r _z system (x = 0 to 1.5, y = 0.6 to 3.5, z =
0.2 or less), various alloys such as Ti-Mn-based and Zr-Mn-based alloys. These hydrogen storage alloys are usually
The paste is kneaded with a binder such as carboxymethyl rose or polytetrafluoroethylene to form a paste. The paste is supported on a nickel foam base material, dried, and then compression-molded to form a sheet. Molded.

[0026]

Next, an embodiment of the present invention will be described in more detail. In the following, “parts” means “parts by weight”. The nickel hydroxide powders of types A and B used in Examples 1 and 2 were obtained in Synthesis Examples 1 and 2 below.

<Synthesis Example 1> 10 kg of an aqueous solution containing 50% by weight of nickel sulfate, 5 kg of a sulfuric acid solution in which 2 g of cobalt and 4 g of zinc were dissolved, an aqueous solution of 25% by weight of sodium hydroxide, and an aqueous solution of 7% by weight of ammonia At the same time and continuously to reduce the nickel ion concentration in the reaction solution to 4
Adjusted to 0 mg / litre or less. This mixed solution is
It was kept at 15 ° C. and adjusted to pH 9-12.
The obtained nickel hydroxide precipitate is filtered by suction, washed with water, and dried at 90 to 95 ° C. to obtain a nickel hydroxide powder (type A) in which cobalt and zinc are uniformly dissolved in the nickel hydroxide. Obtained.

This type A nickel hydroxide powder is
CP method (emission spectroscopy, Nippon Jarrell Atsushi I
CP727, single mode), the cobalt content was 1% by weight and the zinc content was 2% by weight. This nickel hydroxide powder was subjected to SEM (magnification: 1,000
The result of observation by (0 ×) is as shown in FIG. 1, where particles having an average particle size or more were spherical and 95% by weight or more of the particles having an average particle size or less were spherical.

FIG. 4 shows the result of examining the particle size distribution by the microtrap method. The particle size was 2 to 40 μm, and the average particle size was 9.2 μm. Further, the result of the measurement of the pore radius by the BET adsorption method is as shown by a curve -7a in FIG. 7, and in addition to the peak at 7 to 8 °, the peak also exists at 5 to 6 °. , 7-8 peak intensity (la) and 5-6 peak intensity (l)
The ratio (la: lb) of b) was 100: 83. The specific surface area by the BET adsorption method was 5 m ² / g, the pore volume was 0.015 cc / g, and the average pore radius was 25 °.

<Synthesis Example 2> 2 g of cobalt and 10 g of zinc
A nickel hydroxide powder (type B) was obtained in the same manner as in Synthesis Example 1 except that g was used. The cobalt content was 1% by weight and the zinc content was 5% by weight as determined by ICP method. The result of observation of the nickel hydroxide powder by SEM (1,000-fold magnification) is as shown in FIG. 2, where 95% by weight of the particles having an average particle size or more are spherical and the particles having an average particle size or less are spherical. The above was also spherical.

The result of examining the particle size distribution by the microtrap method is as shown in FIG. 5, and the particle size was 2 to 40 μm and the average particle size was 7.2 μm. Further, the result of measuring the pore radius by the BET adsorption method is as shown by a curve -7b in FIG. 7, and in addition to the peak at 7 to 8 °, the peak also exists at 5 to 6 °. , 7-8 peak intensity (la) and 5-6 peak intensity (l)
The ratio (la: lb) of b) was 100: 70. Further, the specific surface area by the BET adsorption method was 20 m ² / g, the pore volume was 0.030 cc / g, and the average pore radius was 50 °.

Example 1 Commercially available Mm (La, Ce, Nd, Pr), Ni, Co,
Each sample of Mn, Al, and Mo (all with a purity of 99.9% by weight or more) was subjected to Mm (La: 0.32 atomic%, Ce:
0.48 atomic%, Nd: 0.15 atomic%, Pr: 0.0
4 atomic%), Ni: 3.55 atomic%, Co: 0.75 atomic%, Mn: 0.4 atomic%, Al: 0.3 atomic%, M
o: The composition was heated and melted in a high-frequency melting furnace so as to have a composition of 0.04 atomic% to obtain a hydrogen storage alloy. This alloy is evacuated to 10 ⁻⁴ Torr in a pressure vessel, purged with argon gas three times, and then subjected to a hydrogen pressure of 14 kg / g.
cm ² for 24 hours, evacuated hydrogen, and further heated to 400 ° C.
To release hydrogen completely, so that 20 to 1
A powder of 00 μm was obtained.

To 100 parts of this alloy powder, 50 parts of a 3% by weight aqueous solution of carboxymethyl cellulose, 5 parts of a 60% by weight polytetrafluoroethylene (hereinafter referred to as PTFE) dispersant solution, and 10 parts of carbonyl nickel powder are mixed. Then, a paste was prepared. The paste was filled and supported on a nickel foam base material, dried, and compression molded. Thereafter, the sheet was cut into a predetermined size to obtain a negative electrode sheet having a thickness of 0.295 mm.

Separately, 100 parts of nickel hydroxide hydroxide powder of type A, 10 parts of nickel powder, and 1 part of cobalt powder
0 parts, 2% by weight carboxymethyl cellulose aqueous solution 5
And a 60% by weight PTFE dispersant solution were mixed to give a paste. The paste was filled and supported on a partially crushed nickel foam base material, dried at 80 ° C. for 2 hours, and compression-molded at 1 ton / cm ² to form a sheet. The coating material on the partially crushed substrate was washed away. This was immersed in an alkaline aqueous solution at 80 ° C for 2 hours,
After washing with warm water for 2 hours and drying at 80 ° C for 1 hour,
Compression molded, cut to size, thickness 0.53mm
Positive electrode sheet.

The above-mentioned negative electrode sheet and positive electrode sheet are spirally wound via a separator made of a non-woven polyamide fabric having a thickness of 0.15 mm. In this way, the outermost peripheral portion was wound around the negative electrode, whereby an electrode body having a wound structure was produced. In the production of this electrode body, a rod having a circular cross section with a diameter of 2.5 mm was used as a winding shaft around which a member consisting of a positive electrode, a negative electrode and a separator was wound. Was extracted from the electrode body.

The electrode body manufactured in this manner was accommodated in a battery can having a size of AAA and having an inner diameter of 9.4 mm. FIG. 8 shows a cross section of the electrode body in this state. In the figure, 1 is a positive electrode, 2 is a negative electrode, and 3 is a separator. Reference numeral 4 denotes an electrode body having a wound structure formed by spirally winding the positive electrode 1 and the negative electrode 2 via a separator 3, and reference numeral 4 a denotes a winding center of the electrode body 4. 5 is a battery can and 5a is a center of the battery can 5.
However, only the inner peripheral surface of the battery can 5 is shown by a thin line.

The electrode body 4 uses a positive electrode whose thickness is locally reduced without forming an active material layer on a part of the base material as described above. The longest diameter of the cross section of the electrode body 4 was reduced by arranging in the direction in which the diameter of the electrode body becomes the longest, that is, the direction in which the winding end portion exists, and the ratio of the shortest diameter to the longest diameter was 1: 1.05. . Incidentally, the ratio of the shortest diameter to the longest diameter of the cross section of the electrode body when the thickness of the positive electrode was not partially reduced was 1: 1.10. When the electrode body 4 having the above configuration is accommodated in the battery can 5, the winding center 4 a of the electrode body 4 is aligned with the center 5 of the electrode can 5.
a was shifted by a distance corresponding to 6.8% of the inner diameter of the battery can 5 from the container a.

Although the present invention is characterized in that the gap between the electrode body 4 and the battery can 5 is reduced, the gap between the electrode body 4 and the battery can 5 is shown in FIG. Are shown with a fairly large void. However, this is because the members such as the positive electrode 1, the negative electrode 2 and the separator 3, which constitute the electrode body 4, are actually shown in FIG. 8 in order to schematically show the positional relationship between the electrode body 4 and the battery can 5. This is because the thickness of each of the above members is actually much smaller than this, so that a large gap does not actually occur as shown in the drawing.

After accommodating the electrode body in the battery can, an alkaline aqueous solution in which 17 g of LiOH was dissolved in 1 liter of a 30% by weight aqueous potassium hydroxide solution was used as an electrolytic solution, and 0.85 milliliter of this electrolytic solution was injected. After that, various steps for battery fabrication were carried out according to a conventional method. Finally, the battery was hermetically sealed with a sealing body having a reversible vent to form a AAA-type nickel-hydrogen storage alloy alkaline secondary battery. did. This was stored at 60 ° C. for 17 hours, and 0.1 C (50
(mA) for 15 hours, and discharged to 1.0 V at 0.2 C (100 mA). This cycle was repeated until the discharge capacity became constant, to produce a hydride secondary battery having the structure shown in FIG.

FIG. 9 schematically shows each member for easy understanding. The positional relationship and dimensions of each member are slightly different from those of FIG. 9, reference numeral 1 denotes a positive electrode, 2 denotes a negative electrode, 3 denotes a separator, 4 denotes a wound electrode body, 5 denotes a battery can, 6 denotes an annular gasket, 7 denotes a battery lid, 8 denotes a terminal plate, and 9 denotes a terminal plate. Sealing plate, 10 is a metal spring, 11
Is a valve body, 12 is a positive electrode terminal plate, and 13 and 14 are insulators.

The positive electrode 1 is composed of a paste-type nickel electrode as described above, and the negative electrode 2 is composed of a paste-type hydrogen storage alloy electrode as described above. The separator 3 is made of a polyamide non-woven fabric as described above, and the positive electrode 1 and the negative electrode 2 are spirally wound via the separator 3 to form a battery can 4 as a wound electrode body 4. 5, and an insulator 14 is arranged on the upper part.

The annular gasket 6 is made of nylon 66, the battery lid 7 is composed of a terminal plate 8 and a sealing plate 9, and the opening of the battery can 5 is sealed with the battery lid 7 and the annular gasket 6 described above. Have been. That is, after inserting the wound electrode body 4 and the insulator 14 into the battery can 5, the battery can 5
Annular groove 5 whose bottom portion protrudes inward in the vicinity of the open end
b, the lower portion of the annular gasket 6 is supported by the inner peripheral side protruding portion of the groove 5b, and the annular gasket 6 and the battery lid 7 are supported.
Are placed in the opening of the battery can 5, the portion of the battery can 5 beyond the groove 5 b is tightened inward, and the opening of the battery can 5 is sealed with the battery lid 7 and the annular gasket 6.

The terminal plate 8 constituting the battery cover 7 is provided with a gas discharge hole 8a, the sealing plate 9 is provided with a gas detection hole 9a, and a metal spring 10 is provided between the terminal plate 8 and the sealing plate 9.
And the valve body 11 are arranged, and the outer peripheral portion of the sealing plate 9 is bent to sandwich the outer peripheral portion of the terminal plate 8 to fix the terminal plate 8 and the sealing plate 9 together.

This battery is a metal spring 1 under normal circumstances.
Since the valve body 11 closes the gas detection hole 9a by the pressing force of 0, the inside of the battery is kept in a sealed state. However, when gas is generated inside the battery and the battery internal pressure rises abnormally, The metal spring 10 contracts and the valve body 11 and the gas detection hole 9a
A gap is created between the gas detection hole 9a and the gas inside the battery.
And is discharged outside the battery through the gas discharge hole 8a,
It is configured to prevent battery rupture. That is,
This battery is hermetically sealed by a sealing body having a reversible vent as described above.

In this battery, the positive electrode lead 1
One end of the positive electrode 2 is spot-welded to a current collector (tab) made of a nickel ribbon spot-welded to the end of the positive electrode 2, and the other end is spot-welded to the lower end of the sealing plate 9. The terminal plate 8 functions as a positive electrode terminal by contact with the sealing plate 9. Further, as described above, the outermost peripheral portion of the wound electrode body 4 is constituted by the negative electrode 2.
A metal base (not shown) is exposed on the outer peripheral side of the outermost peripheral portion of the battery can 5, and this base comes into contact with the inner wall of the battery can 5, whereby the battery can 5 functions as a negative electrode terminal.

Example 2 A hydride secondary battery was produced in the same manner as in Example 1 except that nickel hydroxide powder of type B was used as the nickel hydroxide powder of the positive electrode.

COMPARATIVE EXAMPLE 1 A commercially available nickel hydroxide powder was used as the nickel hydroxide powder for the positive electrode, and a paste was filled without crushing a part of the base material during the preparation of the positive electrode sheet. A positive electrode sheet having a thickness of 0.43 mm was produced in the same manner as in Example 1 except that the immersion treatment in the aqueous alkali solution was not performed. Also, a negative electrode sheet was produced in the same manner as in Example 1 except that the thickness became 0.25 mm.

The thus prepared negative and positive electrode sheets
In the same manner as in Example 1, using a rod having a circular cross section with a diameter of 2.5 mm as a winding axis, a spiral winding is performed through a separator made of a nonwoven polyamide fabric having a thickness of 0.15 mm.
The number of turns of the positive electrode was set to 2.75, and an electrode body having a wound structure in which the outermost peripheral portion was wound around the negative electrode was manufactured. When the number of turns of the positive electrode is 2.75, the thickness of the positive electrode is 1.7 times that of the negative electrode, and the number of turns of the positive electrode is two to three times, and the center of the electrode body is not shifted from the center of the battery can. Under the condition of being inserted into the battery can, the number of turns of the positive electrode at which the battery capacity is maximized.

After the winding body of the electrode body thus manufactured is taken out, the winding center of the electrode body and the center of the battery can coincide with the size of the AAA-size battery can having an inner diameter of 9.4 mm. So housed. A cross section of the electrode body in this state is schematically shown in FIG. In FIG. 10, 1 is a positive electrode, 2 is a negative electrode, 3 is a separator, 4 is an electrode body having a wound structure, and 5 is a battery can. In the same figure, since the center of the winding of the electrode body 4 and the center of the battery can 5 coincide, each center is not shown. In the state where the number of turns of the positive electrode is set to 2.75 and the center of the electrode body 4 and the center of the battery can 5 are aligned, the thickness of the positive electrode 1 and the negative electrode 2 is made larger than the above. I can't do it. Except for this, in the same manner as in Example 1,
A hydride secondary battery was manufactured.

The results obtained by observing the commercially available nickel hydroxide powder by SEM (1,000-fold magnification) are as shown in FIG. 3, and particles having an average particle diameter or more were spherical. The particles having an average particle size or less had a dango-like and irregular shape. The result of examining the particle size distribution by the micro trap method is as shown in FIG. 6, where the particle size is 0.4 to 96 μm, the average particle size is 12 μm,
The particle size distribution was wide. Further, the result of measuring the pore radius by the BET adsorption method is as shown by a curve -7c in FIG. 7, where a peak was observed at 7 to 8 °, but a peak was observed at 5 to 6 °. It wasn't. In addition, BET
Specific surface area by adsorption method is 20 m ² / g, pore volume is 0.0
30 cc / g and the average pore radius was 35 °.

Comparative Example 2 A hydride secondary battery was produced in the same manner as in Example 1 except that the commercially available nickel hydroxide powder used in Comparative Example 1 was used as the nickel hydroxide powder for the positive electrode.

Each of the hydride secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 2 was manufactured at the time of manufacturing the electrode body (at the time of winding).
The crack occurrence rate, the utilization rate of the positive electrode, the charging capacity and the battery capacity were examined. The results are shown in Table 1.

[0053]

From the above results, as shown in Table 1, the hydride secondary batteries of Examples 1 and 2 of the present invention have different cross-sectional shapes by shifting the center of the electrode body and the center of the battery can. The gap between the rounded electrode body and the battery can with round cross section is reduced, and the specific nickel hydroxide powder is used to suppress cracking during winding and to increase the utilization rate of the positive electrode. 1
By increasing the value by about 0%, the battery capacity is increased by about 30% or more as compared with the hydride secondary battery of Comparative Example 1 using the conventional nickel hydroxide powder.

On the other hand, although the winding center of the electrode body is shifted from the center of the battery can, in the hydride secondary battery of Comparative Example 2 using the conventional nickel hydroxide powder, cracking occurs during winding. Since the efficiency is high and the utilization rate of the positive electrode is low, the effect of improving the battery capacity is recognized as compared with Comparative Example 1, but the battery capacity of Examples 1 and 2 is not obtained.

[0056]

As described above, the present invention provides a structure in which nickel hydroxide powder having specific properties is used and the winding center of the wound electrode body is shifted from the center of the battery can. Further, it is possible to provide a hydride secondary battery having a higher capacity than the conventional one and capable of sufficiently coping with the miniaturization of the battery, and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a scanning electron microscope (1,000 magnification) showing the particle structure of a nickel hydroxide powder of type A used in Example 1.
Photo).

FIG. 2 is a scanning electron microscope (1,000 magnification) showing a particle structure of a nickel hydroxide powder of type B used in Example 2.
Photo).

FIG. 3 is a scanning electron microscope (1,000 times magnification) showing the particle structure of a commercially available nickel hydroxide powder used in Comparative Example 1.
It is a photograph.

FIG. 4 is a particle size distribution diagram of a nickel hydroxide powder of type A used in Example 1.

FIG. 5 is a particle size distribution diagram of type B nickel hydroxide powder used in Example 2.

FIG. 6 is a particle size distribution diagram of a commercially available nickel hydroxide powder used in Comparative Example 1.

FIG. 7 is a characteristic diagram showing pore radii of nickel hydroxide powders of types A and B used in Examples 1 and 2 and a commercially available nickel hydroxide powder used in Comparative Example 1.

FIG. 8 is a cross-sectional view schematically showing a state in which an electrode body having a wound structure in a hydride secondary battery of Example 1 is accommodated in a battery can.

FIG. 9 is a cross-sectional view schematically showing a hydride secondary battery of Example 1.

FIG. 10 is a cross-sectional view schematically showing a state in which an electrode body having a wound structure in a hydride secondary battery of Comparative Example 1 is housed in a battery can.

[Explanation of symbols]

 Reference Signs List 1 positive electrode 2 negative electrode 3 separator 4 electrode body 4a winding center of electrode body 5 battery can 5a center of battery can 7a type A nickel hydroxide powder of type A used in example 1 7b type B used in example 2 Nickel hydroxide powder 7c Commercial nickel hydroxide powder used in Comparative Example 1

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ryu Nagai 1-1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell Co., Ltd.

Claims (9)

[Claims] 1. An electrolyte comprising an alkaline aqueous solution containing an electrode body obtained by spirally winding a positive electrode comprising nickel hydroxide as an active material and a negative electrode comprising a hydrogen storage alloy via a separator in a battery can. And the nickel hydroxide is a powder having a particle size of 2 to 40 μm and an average particle size of 8 ± 2 μm in the hydride secondary battery sealed with a sealed body having a reversible vent. The above hydride is characterized in that the above particles are spherical and at least 95% by weight of the particles having an average particle size or less are spherical, and the winding center of the electrode body and the center of the battery can are shifted. Next battery. 2. The nickel hydroxide powder has a peak having a pore radius of at least 7 to 8 ° and a peak of 5 to 6 °, and has a peak intensity (la) of 7 to 8 ° and 5 to 5 °. The ratio (la: lb) to the peak intensity (lb) of 6 ° is 100:
The hydride secondary battery according to claim 1, which is 50 or more. 3. Nickel hydroxide powder has a specific surface area of 5 to ²⁰ m ² / g and a pore volume of 0.015 by a BET adsorption method.
The hydride secondary battery according to claim 1, wherein the hydride secondary battery has an average pore radius of 25 to 50 °. 4. The hydride secondary battery according to claim 1, wherein the positive electrode contains cobalt powder as a conductive additive. 5. The hydride secondary battery according to claim 1, wherein the distance between the center of the electrode body and the center of the battery can is 4% or more of the inner diameter of the battery can. 6. A cross section of an electrode body by providing a thin part in a part of a positive electrode or a negative electrode and arranging the thin part somewhere in a direction in which a winding end part of the electrode body exists. The hydride secondary battery according to any one of claims 1 to 5, wherein the ratio of the shortest diameter to the longest diameter is set to be close to 1. 7. The shortest diameter and the longest diameter of the cross section of the electrode body are not matched by making the direction in which the diameter of the cross section of the hollow portion at the center of the electrode body becomes the longest coincide with the direction in which the winding end portion of the electrode body exists. 2. The configuration of claim 1, wherein the ratio of
6. The hydride secondary battery according to any one of claims 1 to 5. 8. An electrolytic solution comprising an electrode body in which a positive electrode comprising nickel hydroxide as an active material and a negative electrode comprising a hydrogen storage alloy are spirally wound via a separator to be contained in a battery can, and comprising an alkaline aqueous solution. In the hydride secondary battery sealed with a sealed body having a reversible vent, the nickel hydroxide has a particle size of 2 to 40 μm, an average particle size of 8 ± 2 μm, Particles having a diameter of at least 95% by weight of particles having an average particle diameter or less are spherical, and a paste containing the nickel hydroxide powder is supported on a conductive porous substrate and dried. After that, compression molding is performed to produce a positive electrode, and an electrode body in which this positive electrode and a negative electrode made of a hydrogen storage alloy are spirally wound via a separator,
A method for manufacturing a hydride secondary battery, wherein the winding center and the center of the battery can are accommodated in the battery can so as to be displaced from each other. 9. The method according to claim 8, wherein a step of adding a cobalt powder having an average particle diameter of 1.5 μm or less to the paste of the nickel hydroxide powder and immersing the paste in an aqueous alkali solution after compression molding is performed. A method for producing the hydride secondary battery according to the above.