JP2000012073A - Manufacture of nickel-hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a nickel hydrogen secondary battery superior in discharge characteristic at a low temperature of about -20 deg.C and positive electrode utilizing rate. SOLUTION: In the manufacture of a nickel hydrogen secondary battery provided with a positive electrode containing nickel hydroxide and a conductive agent consisting of at least one of cobalt and cobalt compound, and a negative electrode containing a hydrogen storage alloy, the battery is allowed to left standing for 1-8 hours after being assembled, and the charging quantity corresponding to 3-15% of the capacity of the negative electrode is preliminarily charged with a current exceeding 1.0C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a nickel-metal hydride secondary battery.

[0002]

2. Description of the Related Art Recent advances in electronic technology have reduced power consumption,
2. Description of the Related Art Advances in packaging technology have made portable electronic devices that could not be expected in the past. In order to make electronic devices portable, it is necessary to increase the capacity of a secondary battery as a power supply incorporated therein. Nickel-cadmium secondary batteries and nickel-hydrogen secondary batteries have been developed as secondary batteries that can meet such demands. In particular, a nickel-metal hydride secondary battery equipped with a negative electrode containing a hydrogen storage alloy can achieve about twice or more higher capacity than a nickel-cadmium secondary battery, and does not contain environmental pollutants such as cadmium. In recent years, its importance has been growing rapidly.

[0003] As a nickel-hydrogen secondary battery, a group of electrodes wound spirally with a separator interposed between a paste-type positive electrode containing nickel hydroxide and a paste-type negative electrode containing a hydrogen storage alloy is used as an alkaline electrolyte. A cylindrical sealed nickel-metal hydride rechargeable battery housed in a cylindrical container with a bottom, and an electrode group made by stacking a paste-type positive electrode and a paste-type negative electrode in a stack with a separator in A rectangular sealed nickel-metal hydride secondary battery housed in a cylindrical container is known. The positive electrode, for example, a nickel hydroxide powder, a conductive agent consisting of at least one selected from cobalt and a cobalt compound, and a binder are added, and kneaded in the presence of water to prepare a paste, The paste is prepared by filling a conductive substrate with the paste, drying and rolling. On the other hand, for the negative electrode, for example, a conductive material such as carbon black and a binder are added to a hydrogen storage alloy powder, and these are kneaded in the presence of water to prepare a paste, and the paste is applied to a conductive substrate. It is made by filling, drying and rolling.

In such nickel-metal hydride secondary batteries, in order to reduce the influence of surface oxidation of the hydrogen storage alloy in the alkaline electrolyte, the hydrogen storage alloy is subjected to surface treatment or added to the hydrogen storage alloy electrode. Researches such as adding agents have been actively conducted. According to these methods, the surface oxidation of the hydrogen storage alloy is prevented, so that the cycle characteristics and the low-temperature discharge characteristics are improved to some extent.

[0005] However, the surface treatment has a problem that the production cost is increased. On the other hand, the use of additives not only increases the manufacturing cost, but also has a problem that the capacity density of the electrode is reduced, which hinders an increase in the capacity of the secondary battery.

Meanwhile, in the initial activity of a nickel-metal hydride secondary battery, a conductive agent contained in the positive electrode dissolves in the alkaline electrolyte and is converted into a complex to promote a reaction necessary for improving the positive electrode utilization rate. Therefore, after assembling, it is left until the alkaline electrolyte permeates into the positive electrode to some extent. After that, for example, the battery is charged with a current of about 0.1 C to 0.2 C,
A charge / discharge cycle of discharging at a current of about 0.2C to 0.5C is performed.

However, such an activation method is
Since it takes too much time, various attempts have been made to reduce the time.

For example, Japanese Patent Application Laid-Open No. 9-63636 discloses that an assembled alkaline secondary battery is left at room temperature for 3 to 7 hours, and then charged at a charge rate of 0.2 to 1.0 C and a rated capacity of 10 to 10 hours.
Pre-charge until the capacity becomes 0% or less, temperature 50 ± 10
An activation method is disclosed in which the battery is left to stand at a temperature of 8 to 48 hours, charged at a charging rate of 0.2 to 0.5 C to reach 120 to 180% of the rated capacity, and then discharged.

[0009]

However, according to such a method, there is a problem that the utilization rate of the positive electrode decreases.

An object of the present invention is to provide a method for manufacturing a nickel-metal hydride secondary battery having both excellent discharge characteristics at a low temperature of about −20 ° C. and a positive electrode utilization factor.

[0011]

According to the present invention, there is provided a method for manufacturing a nickel-metal hydride secondary battery, comprising: a positive electrode containing nickel hydroxide and a conductive agent comprising at least one selected from cobalt and a cobalt compound; In a method for manufacturing a nickel-metal hydride secondary battery comprising: a negative electrode comprising:
Is preliminarily charged with a current exceeding 1.0C.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a nickel-metal hydride secondary battery according to the present invention will be described.

(First step) A nickel-hydrogen secondary battery is prepared by forming an electrode group with a separator interposed between a positive electrode and a negative electrode, storing the electrode group and an alkaline electrolyte in a container, and sealing the container. Assemble.

The positive electrode, negative electrode, separator and alkaline electrolyte will be described.

1) Positive electrode This positive electrode contains nickel hydroxide and a conductive agent comprising at least one selected from cobalt and a cobalt compound.

This positive electrode can be produced, for example, by the method (a) or (b) described below.

(A) One or more powders selected from metallic cobalt and a cobalt compound, a binder and water are added to the nickel hydroxide powder and kneaded to prepare a paste, and the paste is used as a current collector. The positive electrode is manufactured by filling, drying, and pressing.

(B) At least a portion of the surface of the nickel hydroxide powder is coated with at least one selected from metallic cobalt and a cobalt compound to produce a composite nickel hydroxide powder. The composite nickel hydroxide powder, the binder and water are kneaded to prepare a paste, and the paste is filled in a current collector, which is dried and pressed to produce the positive electrode.

As the nickel hydroxide powder, for example, a powder composed of nickel hydroxide, or zinc and / or zinc
Alternatively, nickel hydroxide powder in which cobalt is eutectic can be used.

The nickel hydroxide has a peak half-value width of the (101) plane determined by an X-ray powder diffraction method of 0.8 ° / 2θ (C
u-Kα) or more. More preferred nickel hydroxide particles have a peak half width of 0.9 to 1.0 ° /
2θ (Cu-Kα).

Examples of the cobalt compound include dicobalt trioxide (Co ₂ O ₃ ) and cobalt monoxide (Co ₂ O ₃ ).
O), cobalt hydroxide {Co (OH) ₂ } and the like. As the cobalt compound, one or more kinds selected from the above-mentioned kinds can be used.

Examples of the binder include a hydrophobic polymer such as polytetrafluoroethylene (PTF).
E) fluoropolymers, polyethylene, polypropylene, rubber-based polymers (eg, styrene butadiene rubber (SBR) latex, acrylonitrile butadiene rubber (NBR) latex, ethylene propylene diene monomer (EPDM) latex), hydrophilicity Polymers such as carboxymethylcellulose (CM
C), hydroxypropyl methylcellulose (HPM
C), methylcellulose (MC), polyacrylate (for example, sodium polyacrylate (SPA)), polyvinyl alcohol (PVA), polyethylene oxide, copolymer of vinyl alcohol with a monomer having at least one COOX group ( However, X is one or more elements selected from hydrogen, an alkali metal, and an alkaline earth metal). As the binder, one or more kinds selected from the above-mentioned polymers can be used. In particular, it is preferable to use a mixed polymer composed of the hydrophobic polymer and the hydrophilic polymer. Among these mixed polymers, PTFE, CM
Those composed of C, HPMC and polyacrylate are preferred. In addition, polyethylene, polypropylene and PTF
E can be used in the form of a dispersion.

Examples of the current collector include those having a sponge-like, fibrous, felt-like, or net-like porous structure made of a metal such as nickel or stainless steel, or a nickel-plated resin. it can.

2) Negative electrode This negative electrode contains a hydrogen storage alloy.

This negative electrode comprises a hydrogen storage alloy powder, a conductive material,
The paste is prepared by kneading with a binder and water to prepare a paste, filling the paste into a conductive substrate, drying and molding.

The hydrogen storage alloy is not particularly limited and may be any alloy that can store hydrogen electrochemically generated in an electrolyte and easily release the stored hydrogen during discharge. For example, LaNi ₅ , MmNi
₅ (Mm is misch metal), LmNi ₅ (Lm is La
At least one element selected from the group consisting of rare earth elements containing Al), Mn, Co, Ti, Cu,
Examples thereof include a multi-element-based material substituted with an element such as Zn, Zr, Cr, and B, a TiNi-based material, and a TiFe-based material. In particular, the general formula LmNi _w Co _x Mn _y A
l _z (where Lm is a rare earth element, atomic ratio w, x, y,
(The total value of z is 5.00 ≦ w + x + y + z ≦ 5.50.) A hydrogen storage alloy having a composition represented by the following formula: It is. In the general formula, the atomic ratios w, x, y, and z are respectively 3.30 ≦ w ≦ 4.50,
0.50 ≦ x ≦ 1.10, 0.20 ≦ y ≦ 0.50,
0.05 ≦ z ≦ 0.20 and the total value is 4.90
It is preferred that ≦ w + x + y + z ≦ 5.50. More preferable values of the atomic ratio w, x, y, z are 3.80 ≦ w ≦ 4.20, 0.70 ≦ x ≦ 0.90, respectively.
0.30 ≦ y ≦ 0.40, 0.08 ≦ z ≦ 0.13,
And the total value is 5.00 ≦ w + x + y + z ≦ 5.20
It is.

Examples of the conductive material include carbon black, graphite and the like.

As the binder, one or more selected from the same polymers as those described for the positive electrode can be used. Among them, PTFE, CMC,
It is preferable to use PVA or polyacrylate.

Examples of the conductive substrate include a two-dimensional substrate such as a punched metal, an expanded metal, a perforated rigid plate, and a nickel net; a felt-like metal porous body;
Examples include a three-dimensional substrate such as a sponge-like porous metal body.

3) Separator Examples of the separator include a nonwoven fabric made of a polyamide fiber and a nonwoven fabric made of a polyolefin fiber such as polyethylene and polypropylene provided with a hydrophilic functional group.

4) Alkaline Electrolyte As the alkaline electrolyte, for example, an aqueous solution of sodium hydroxide (NaOH), lithium hydroxide (LiOH)
Aqueous solution, potassium hydroxide (KOH) aqueous solution, NaO
H and LiOH mixed solution, KOH and LiOH mixed solution, K
A mixed solution of OH, LiOH, and NaOH can be used.

(Second Step) The secondary battery is left for 1 to 8 hours.

The reason why the above-mentioned leaving time is specified in the above-mentioned range is as follows. If the leaving time is less than 1 hour, it is difficult to charge the battery because the alkaline electrolyte hardly permeates the positive electrode and the negative electrode.
On the other hand, if the standing time exceeds 8 hours, the surface oxidation of the hydrogen storage alloy contained in the negative electrode proceeds, so that the discharge capacity at low temperatures decreases. A more preferable range of the standing time is 1 to 5 hours.

The leaving is performed without heating the secondary battery. This is because, when the secondary battery is heated during standing, the surface oxidation of the hydrogen storage alloy is promoted, and the low-temperature discharge characteristics deteriorate. The leaving is preferably performed at room temperature.

(Third Step) Preliminary charging of the secondary battery with a current exceeding 1.0 C is performed until the secondary battery reaches a charge amount corresponding to 3 to 15% of the capacity of the negative electrode.

When the charging current for the pre-charging is set to 1.0 C or less, the utilization rate of the positive electrode is reduced, so that the initial capacity and the cycle life are reduced. That is, in the precharging, both the charging reaction of nickel hydroxide and the oxidation reaction of the conductive agent occur. When the charging current is 1.0 C or less, an oxidation reaction of the conductive agent occurs preferentially. Since the standing time before the pre-charging is short, the degree of penetration of the alkaline electrolyte into the positive electrode during the pre-charging is low, and when the oxidation reaction of the conductive agent occurs in such a state, the utilization rate of the positive electrode decreases. I do. Also,
The charging current is preferably set to 3.0 C or less. If the charging current exceeds 3.0 C, the initial capacity may decrease. The more preferable range of the charging current is as follows.
3 to 2.0C.

The charge amount of the pre-charge is defined in the above range for the following reason. When the charge amount is less than 3% of the capacity of the negative electrode, it becomes difficult to suppress the surface oxidation of the hydrogen storage alloy, so that the discharge capacity at a low temperature decreases. On the other hand, when the charged amount corresponds to an amount exceeding 15% of the capacity of the negative electrode, the amount of the conductive agent that is oxidized in a state where the distribution of the electrolyte in the positive electrode is biased increases, and the positive electrode utilization rate decreases. . The charge amount is preferably set to an amount corresponding to 5 to 10% of the capacity of the negative electrode.

The preliminary charging is performed without heating the secondary battery. This is because, when the secondary battery is heated at the time of preliminary charging, surface oxidation of the hydrogen storage alloy is promoted, and the low-temperature discharge characteristics deteriorate. Preferably, the preliminary charging is performed at normal temperature.

(Fourth Step) After leaving the secondary battery,
Apply the first charge.

It is preferable that the initial charging be performed 24 hours or more after the secondary battery is assembled. If the time from assembling to starting the first charge is less than 24 hours,
The degree of penetration of the alkaline electrolyte into the positive electrode may be insufficient. If initial charging is performed in a state where the distribution of the alkaline electrolyte in the positive electrode is biased, it becomes difficult to form a sufficient conductive path in the positive electrode, and the utilization rate of the positive electrode decreases.

The leaving is performed without heating the secondary battery. This is because, when the secondary battery is heated during standing, the surface oxidation of the hydrogen storage alloy is promoted, and the low-temperature discharge characteristics deteriorate. The leaving is preferably performed at room temperature.

A nickel-hydrogen secondary battery is manufactured by the method including the first to fourth steps described above. A method for producing a nickel-metal hydride secondary battery according to the present invention provides a nickel-metal hydride secondary battery comprising: a positive electrode including nickel hydroxide and a conductive agent comprising at least one selected from cobalt and a cobalt compound; a negative electrode including a hydrogen storage alloy. The method of manufacturing a secondary battery is characterized in that the battery is left for 1 to 8 hours after assembling, and is preliminarily charged with a charge amount corresponding to 3 to 15% of the capacity of the negative electrode with a current exceeding 1.0 C. . According to such a manufacturing method, the utilization rate of the positive electrode can be improved, and a decrease in discharge capacity at a low temperature can be suppressed.

That is, an electrode group is formed with a separator interposed between the positive electrode and the negative electrode, and the electrode group and the alkaline electrolyte are accommodated in a container, and when sealed, the components of the hydrogen storage alloy of the negative electrode are removed. Some elute in the alkaline electrolyte. For example, in the case of the hydrogen storage alloy having a composition represented by _{LmNi w Co x Mn y Al z} , is the earliest elution into alkaline electrolyte potentially Al and Mn. The surface of the hydrogen storage alloy that has been eluted into the alkaline electrolyte is susceptible to oxidation. When the surface of the hydrogen storage alloy is oxidized, the discharge capacity, particularly the discharge capacity at a low temperature, is reduced.

After pre-charging under the above-described conditions after the assembly is left for 1 to 8 hours as in the present invention,
The hydrogen storage alloy can be charged relatively early after assembly, and the hydrogen storage alloy can be stabilized in potential. As a result, elution from the surface of the hydrogen storage alloy is less likely to occur, and the surface oxidation of the hydrogen storage alloy can be suppressed due to the anodic anticorrosive action.

Incidentally, the preliminary charging is not preferable for the positive electrode. If the charging is performed before the alkaline electrolyte is sufficiently permeated into the positive electrode, the conductive agent in the positive electrode is not oxidized well, so that a conductive path is not uniformly formed in the positive electrode, which causes a decrease in the positive electrode utilization rate. .

As in the present invention, the pre-charging is performed at a high current value exceeding 1.0 C, and the charge amount is set to 3 to 1 of the negative electrode capacity.
By making the amount equivalent to 5%, the charging reaction of nickel hydroxide can be preferentially caused, and
It is possible to suppress the conductive agent from being oxidized by the precharge. Thereafter, after the alkaline electrolyte is sufficiently infiltrated into the positive electrode by leaving to stand, the initial charge is performed, whereby the discharge characteristics at a low temperature can be improved without impairing the utilization rate of the positive electrode.

Therefore, according to the present invention, it is possible to manufacture a nickel-hydrogen secondary battery in which the utilization rate of the positive electrode is high and the decrease in the discharge capacity at a low temperature is suppressed at a low cost.

Further, by carrying out the initial charge at least 24 hours after assembling, the alkaline electrolyte can sufficiently penetrate into the positive electrode, so that the utilization rate of the positive electrode can be further improved. .

[0049]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Examples 1 to 5 and Comparative Examples 1 and 2) <Preparation of positive electrode> Carboxymethyl cellulose was added to a mixed powder comprising 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder as a conductive agent. 3 parts by weight and 0.5 parts by weight of polytetrafluoroethylene are added,
Further, 45 parts by weight of water was added to the mixture and kneaded to prepare a paste. The paste was filled in a sintered fiber substrate as a current collector, dried, and then roll-pressed to form a positive electrode.

<Preparation of Negative Electrode> Commercially available lanthanum-enriched misch metals Lm, Ni, Co, Mn and Al were used in a high frequency furnace to produce LmNi _4.0 Co _0.4 Mn _0.3 Al.
_A hydrogen storage alloy having a composition of _0.3 was prepared. The hydrogen storage alloy was mechanically pulverized and passed through a 200-mesh sieve. 0.5 part by weight of sodium polyacrylate, 0.125 part by weight of carboxymethylcellulose, and a dispersion of polytetrafluoroethylene (specific gravity 1.5, solid content 60% by weight) based on 100 parts by weight of the obtained hydrogen storage alloy powder. A paste was prepared by adding 2.5 parts by weight and 1 part by weight of carbon powder and mixing with 50 parts by weight of water. Apply this paste to punched metal,
After drying, a hydrogen storage alloy negative electrode was prepared by press molding.

Next, a separator made of a polypropylene nonwoven fabric on which an acrylic acid monomer was graft-copolymerized was interposed between the positive electrode and the negative electrode, and spirally wound to form an electrode group. The obtained electrode group and an alkaline electrolyte comprising 7N KOH and 1N LiOH were housed in a bottomed cylindrical container to assemble a cylindrical nickel-metal hydride secondary battery.

After the assembled secondary battery was allowed to stand at 25 ° C. for the time shown in Table 1 below, it was heated at 25 ° C. for 1.1 hours.
Preliminary charge was performed at a current of C and a charge amount corresponding to 5% of the capacity of the negative electrode (theoretical capacity of the negative electrode), and then left again at 25 ° C. After 24 hours from the assembly, the initial charge is performed in an atmosphere of 25 ° C. at 0.2 C for 6 hours to obtain an AA-size (theoretical capacity; 1200 mAh) cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. A battery was manufactured.

That is, in the bottomed cylindrical container 1, an electrode group 5 produced by stacking the positive electrode 2, the separator 3, and the negative electrode 4 and winding them in a spiral shape is accommodated. The negative electrode 4 is arranged at the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. A circular first sealing plate 7 having a hole 6 in the center is arranged at the upper opening of the container 1. The ring-shaped insulating gasket 8 is disposed between the peripheral edge of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the sealing plate is formed on the container 1 by caulking to reduce the diameter of the upper opening inward. 7 is hermetically fixed via the gasket 8. One end of the positive electrode lead 9 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is provided with the sealing plate 7.
It is attached so as to cover the hole 6 above. A rubber safety valve 11 is disposed so as to close the hole 6 in a space surrounded by the sealing plate 7 and the positive electrode terminal 10.
Circular holding plate 12 made of an insulating material having a hole in the center
Are arranged on the positive electrode terminal 10 such that the protrusions of the positive electrode terminal 10 protrude from the holes of the holding plate 12. The outer tube 13 is provided on the periphery of the holding plate 12,
The side surface of the container 1 and the periphery of the bottom of the container 1 are covered.

With respect to the obtained secondary batteries of Examples 1 to 5 and Comparative Examples 1 and 2, a current of 1.0 C at 25 ° C.
After charging for 2 minutes, the discharge capacity at the time of discharging to 1.0 V at a current of 1.0 C at −20 ° C. was measured, and the ratio of the obtained discharge capacity to the nominal capacity was obtained. The results are shown in FIG. .

[0056]

[Table 1]

As is apparent from FIG. 2, Example 1 obtained by the method in which the standing time before the preliminary charge is 1 to 8 hours.
The secondary batteries of Nos. 1 to 5 were -20 compared to the secondary battery of Comparative Example 1 and the secondary battery of Comparative Example 2 in which the leaving time was 10 hours, which was obtained by a method of performing pre-charging without leaving. It is understood that the discharge capacity at a low temperature of ° C. is high.

(Examples 6 to 10 and Comparative Examples 3 to 7) A nickel-metal hydride secondary battery was assembled in the same manner as described in Examples 1 to 5 and then left at 25 ° C. for 1 hour.
Preliminary charging was performed at 5 ° C. with a current shown in Table 2 below and a charge amount corresponding to 5% of the capacity of the negative electrode (negative electrode theoretical capacity), and then left again at 25 ° C. 2 from assembly
After four hours, the first charge is performed under the same conditions as those described in the above-described Examples 1 to 5, so that the AA size (theoretical capacity; 1200) having the structure shown in FIG.
mAh) was manufactured.

The obtained Examples 6 to 10 and Comparative Examples 3 to 7
Was charged at 25 ° C. with a current of 1.0 C for 72 minutes, and then discharged at 25 ° C. with a current of 1.0 C to 1.0 V, and the discharge capacity was measured. The ratio to the nominal capacity was determined, and the results are shown in FIG. FIG. 3 also shows the results of Example 1 described above.

[0060]

[Table 2]

As is apparent from FIG. 3, the secondary batteries of Examples 1, 6 to 10 obtained by the method in which the pre-charge rate exceeds 1.0 C have the above-mentioned charge rate of 1.0 C.
It can be seen that the initial capacity is higher than the secondary batteries of Comparative Examples 3 to 7 below.

(Examples 11 to 15 and Comparative Examples 8 to 11)
After assembling the nickel-metal hydride secondary battery in the same manner as described in Examples 1 to 5, the battery was left at 25 ° C. for 1 hour, charged at 1.1 ° C. at 25 ° C., and charged as shown in Table 3 below. Preliminary charge was performed in the amount (ratio to the theoretical capacity of the negative electrode), and then left at 25 ° C. again. 2 from assembly
After four hours, the first charge is performed under the same conditions as those described in the above-described Examples 1 to 5, so that the AA size (theoretical capacity; 1200) having the structure shown in FIG.
mAh) was manufactured.

The obtained Examples 11 to 15 and Comparative Examples 8 to
The low-temperature discharge capacity and the initial capacity of the secondary battery of No. 11 were measured in the same manner as described above, and the results are shown in FIGS. 4 and 5 also show the results of Example 1 described above.

[0064]

[Table 3]

As is apparent from FIG. 4, the secondary batteries of Examples 1, 11 to 15 obtained by the method in which the amount of precharge corresponds to 3 to 15% of the negative electrode capacity were obtained by the method without precharge. It can be seen that the low-temperature discharge capacity is higher than the obtained secondary battery of Comparative Example 8 and the secondary battery of Comparative Example 9 in which the preliminary charge amount is 2% of the negative electrode capacity.

As is apparent from FIG. 5, the secondary batteries of Examples 1 and 11 to 15 have a precharge amount of 17, 20% of the negative electrode capacity compared to the secondary batteries of Comparative Examples 10 and 11. This shows that the initial capacity is high.

(Embodiments 16 and 19)
After assembling the nickel-metal hydride secondary battery in the same manner as described in 5 above, the battery was allowed to stand at 25 ° C. for 1 hour. Preliminary charge is performed with the corresponding charge amount, and then 25
It was left at ℃ again. At the time when the time shown in the following Table 4 has elapsed from the assembling, the initial charging is performed under the same conditions as those described in the above-described Examples 1 to 5, so that the AA size (theoretical capacity; 1200 mAh)
Was manufactured.

The initial capacities of the obtained secondary batteries of Examples 16 to 19 were measured in the same manner as described above, and the results are shown in FIG. FIG. 6 also shows the results of Example 1 described above.

[0069]

[Table 4]

As is apparent from FIG. 6, the secondary batteries of Examples 1, 18, and 19 obtained by the method in which the time from assembly to the start of the first charge was 24 hours or more were obtained from the assembly to the start of the first charge. It can be seen that the initial capacity is higher than the secondary battery of Example 16 obtained by the method in which the time is 6, 12 hours.

(Embodiments 20 and 21)
After assembling the nickel-metal hydride secondary battery in the same manner as described in 5 above, the battery was allowed to stand at 25 ° C. for 1 hour. Preliminary charging was performed with a corresponding amount of charge, and then the device was left again at a temperature shown in Table 5 below. At 24 hours after the assembly, the first charge is performed under the same conditions as described in the first to fifth embodiments, so that the AA size (theoretical capacity: 1200 mA) having the structure shown in FIG.
h) A cylindrical nickel-metal hydride secondary battery was manufactured.

The low-temperature discharge capacities of the obtained secondary batteries of Examples 20 and 21 were measured in the same manner as described above.
Table 5 shows the results. Table 5 also shows the results of Example 1 described above.

[0073]

[Table 5]

As is clear from Table 5, Examples 1 and 20
It can be understood that the secondary battery of No. has a higher discharge capacity at a low temperature than the secondary battery of Example 21.

[0075]

As described above in detail, according to the method for manufacturing a nickel-metal hydride secondary battery according to the present invention, the surface of the hydrogen storage alloy is reformed to suppress the elution of the hydrogen storage alloy into the alkaline electrolyte. Thus, the low temperature discharge characteristics can be improved, the utilization rate of the positive electrode can be improved, and a relatively low cost, high capacity, and a long life can be realized.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a nickel-metal hydride secondary battery of an embodiment.

FIG. 2 is a characteristic diagram showing a relationship between a standing time before preliminary charging and a low-temperature discharge capacity in the nickel-hydrogen secondary batteries of Examples 1 to 5 and Comparative Examples 1 and 2.

FIG. 3 is a characteristic diagram showing a relationship between a charge rate of precharge and an initial capacity in the nickel-metal hydride secondary batteries of Examples 1, 6 to 10, and Comparative Examples 3 to 7.

FIG. 4 is a characteristic diagram showing a relationship between a charge amount of precharge and a low-temperature discharge capacity in the nickel-metal hydride secondary batteries of Examples 1, 11 to 15, and Comparative Examples 8 to 11.

FIG. 5 is a characteristic diagram showing the relationship between the amount of pre-charged battery and the initial capacity in the nickel-metal hydride secondary batteries of Examples 1, 11 to 15, and Comparative Examples 8 to 11.

FIG. 6 is a characteristic diagram showing the relationship between the time from assembly to the start of initial charging and the initial capacity in the nickel-hydrogen secondary batteries of Examples 1 and 16 to 20.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 7 ... Sealing plate.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Taguchi, Inventor 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation F-term (reference) 5H028 AA05 BB10 BB15 EE01 EE05 HH00 HH10 5H030 AA01 AS11 BB01

Claims (2)

[Claims] 1. A method for manufacturing a nickel-metal hydride secondary battery comprising: a positive electrode comprising nickel hydroxide and a conductive agent comprising at least one selected from cobalt and a cobalt compound; a negative electrode comprising a hydrogen storage alloy; , And left for 1 to 8 hours, and 3 to 3
A method for manufacturing a nickel-metal hydride secondary battery, comprising precharging a charge amount corresponding to 15% with a current exceeding 1.0 C. 2. The method for manufacturing a nickel-metal hydride secondary battery according to claim 1, wherein the initial charging is performed at least 24 hours after the assembly.