JP3225129B2 - Manufacturing method of alkaline secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an alkaline secondary battery having an improved initial charging step.

[0002]

2. Description of the Related Art For example, an alkaline secondary battery such as a nickel hydride secondary battery is manufactured by the following method. First, a paste containing nickel hydroxide (Ni (OH) ₂ ) and cobalt monoxide (CoO) as main components is prepared.
This paste is filled in a current collector, dried, and then pressed with a roller to produce a positive electrode. Subsequently, a paste containing a hydrogen storage alloy as a main component is prepared, the paste is filled in a current collector, dried, and then pressed with a roller to produce a negative electrode. Subsequently, the electrode group spirally wound between the positive electrode and the negative electrode via a separator is housed together with the electrolytic solution in a bottomed cylindrical container and sealed. Next, the secondary battery is manufactured by performing initial charging with a constant current to activate the positive electrode and the negative electrode.

[0003] According to such a manufacturing method, the CoO in the positive electrode is converted into CoOOH by the initial charge and functions as a conductive auxiliary in the positive electrode, so that the utilization rate of the positive electrode is improved. Can be. The first charge is
The CoOOH conversion potential of the CoO is Ni (OH) ₂
Is lower than the oxidation potential of CoOO.
After conversion to H, the voltage is further increased to increase the Ni (O
H) It is performed by a voltage change that oxidizes ₂ .

However, as described above, when the initial charge is performed at a constant current, the voltage applied to the secondary battery varies depending on the battery because the internal resistance of the secondary battery varies depending on manufacturing conditions. Therefore, depending on the magnitude of the internal resistance, the voltage at the time of initial charging of the secondary battery becomes higher than the voltage capable of converting the CoO to the CoOOH,
Since all of O remains without being converted to the CoOOH and the amount of CoOOH generated decreases, there is a problem that the utilization rate of the positive electrode decreases.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a method of manufacturing an alkaline secondary battery capable of improving the utilization of a paste-type nickel positive electrode. Is what you do.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an electrode group formed by sandwiching a separator between a paste-type nickel positive electrode containing Ni (OH) ₂ and CoO as active materials and a negative electrode, and an alkaline electrolyte. Wherein the initial charging is performed at a voltage of 0.9 V to 1.3 V and a constant voltage of a current value of 1/2 CA or less, and all of the CoO is converted to CoOOH. This is a method for manufacturing an alkaline secondary battery.

The reason why the voltage of the first charge is limited to the above range is as follows. The voltage is 0.9
If it is less than V, the conversion of the CoO to CoOOH becomes difficult to progress, so that it becomes difficult to sufficiently convert the CoO to the CoOOH. On the other hand, when the voltage is 1.
Exceeds 3V, the prior oxidation of the Ni (OH) ₂ is advanced the CoO and is simultaneously oxidized Ni (OH) ₂
Is oxidized and a good conductive path cannot be obtained.

The reason for limiting the initial charging current to the above range is as follows. The current is ２
When the current exceeds CA, a large current flows before a sufficient conductive path is generated in the electrode, so that the current density is unevenly distributed in the electrode and a partial peroxide is generated, so that good CoOOH cannot be obtained. . The first charge is desirably performed within a range of 10 hours to 30 hours from the viewpoint of suppressing the generation of the peroxide of CoO.

It is desirable that the initial charging is performed in a temperature range of 0 ° C. to 30 ° C. When the temperature is lower than 0 ° C., the CoO may not be sufficiently converted to the CoOOH. When the temperature exceeds 30 ° C., the CoO has little effect as a conductive auxiliary such as Co ₃ O ₄ or Co ₂ O _3.
May be converted to The alkaline secondary battery manufactured by the method of the present invention, for example, a nickel hydride secondary battery has a structure shown in FIG. 1 described below.

The hydrogen storage alloy negative electrode 1 is spirally wound with a separator 3 interposed between the negative electrode 1 and the nickel positive electrode 2 and housed in a bottomed cylindrical container 4. The negative electrode 1, which is the outermost periphery of the manufactured electrode group, is brought into contact with the container 4 to collect current. The alkaline electrolyte is contained in the container 4. A circular sealing plate 6 having a hole 5 in the center
Are arranged in the upper opening of the container 4. The ring-shaped insulating gasket 7 is arranged between the peripheral edge of the sealing plate 6 and the inner surface of the upper opening of the container 4, and is formed by caulking to reduce the diameter of the upper opening of the container 4 to the inside. The sealing plate 6 is hermetically fixed via the gasket 7. One end of the positive electrode lead 8 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 6. The hat-shaped positive electrode terminal 9 is provided with the hole 5 on the sealing plate 6.
It is attached to cover. Rubber safety valve 10
Is disposed so as to close the hole 5 in a space surrounded by the sealing plate 6 and the positive electrode terminal 9.

[0011]

According to the present invention, the initial charging is performed at a voltage of 0.9 V to 1.
The utilization of the positive electrode can be improved by performing the operation at a constant voltage of 3 V and a current value of 1/2 CA or less and converting all of the CoO in the paste-type nickel positive electrode to CoOOH. Also, by converting all of the CoO into the CoOOH, the CoOOH is discharged during the discharge.
Since it is hard to be reduced to O, the CoOOH, which becomes the discharge reserve amount of the positive electrode, can be present in the positive electrode as it is. As a result, the discharge reserve amount is reduced at the time of overdischarge, so that it is possible to prevent decomposition of the electrolytic solution and generation of gas.

Furthermore, since the CoO has a higher solubility in the alkaline electrolyte than the metallic cobalt, the utilization of the positive electrode can be improved. That is, the CoO
, The precipitated in the from paste in the re-Ni dissolved in the electrolyte (OH) ₂ surface Co (OH) ₂ in the state when the initial charge, said the precipitates by initial charging CoO
Converted to OH. Therefore, it is possible to precipitate the Co (OH) _{2 down} to the details of the Ni (OH) ₂ ,
In addition, since the CoOOH can be generated in more detail, the current density of the Ni (OH) ₂ can be made uniform and the utilization rate of the positive electrode can be improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to FIGS. Example 1

[0014] First, a mixed powder consisting of Ni (OH) ₂ powder 90 weight part and CoO10 parts, Ni (OH) ₂
3% by weight of carboxymethylcellulose and 5% by weight of polytetrafluoroethylene, and 45% by weight of pure water with respect to Ni (OH) ₂ were added thereto and kneaded to prepare a paste. . Subsequently, the paste was applied to a nickel net serving as a current collector, dried, and roller-pressed to produce a positive electrode.

Next, 0.5 parts by weight of sodium polyacrylate, 0.5 parts by weight of carboxymethylcellulose, 3 parts by weight of polytetrafluoroethylene dispersion, 1 part by weight of carbon black, and 100 parts by weight of hydrogen storage alloy powder A paste was prepared by kneading 50 parts by weight, the paste was applied to a nickel net as a current collector, dried, and roller pressed to produce a negative electrode.

Next, the negative electrode, the separator made of polypropylene, and the positive electrode were laminated in this order, and spirally wound to form an electrode group. Such an electrode group and 7N
An electrolytic solution comprising KOH and 1N LiOH was stored in a cylindrical container having a bottom, and an AA-size cylindrical nickel-metal hydride secondary battery having a capacity of 1000 mAh and having the structure shown in FIG. 1 was assembled.

Five of the obtained secondary batteries were prepared, the current value of each of the secondary batteries was set at 25 ° C., the current value was １ ／ CA or less, and the voltages were 0.5 V, 0.75 V, 1.0 V,
After performing initial charging for 20 hours at 1.25 V and 1.5 V, activation was performed by performing 100% charging at 0.3 C. Subsequently, each secondary battery was discharged at 1 C, and the utilization rate of the positive electrode was obtained from the discharge capacity obtained until the voltage reached 1 V. The result is shown in FIG.

As is apparent from FIG. 2, the current value is reduced to 1/3.
It can be seen that the utilization rate of the secondary battery, which was initially charged at a voltage of 1.0 V or less and 1.25 V or less, is extremely high at 95% or more. On the other hand, even if the current value is 1/3 CA or less,
A battery that has been initially charged with voltages of 0.5 V, 0.75 V, and 1.5 V has a utilization factor of 75% or less.

Also, three secondary batteries are prepared, and the voltage of the secondary batteries is set to 1.2 V at 25 ° C., and the current values are set to 1/10 CA or less, 1/2 CA or less, and 1 CA, respectively.
After performing the initial charge for 20 hours in the following manner,
Activation was performed by performing 0% charging. Then,
Each secondary battery was discharged at 1 C, and the utilization rate of the positive electrode was determined from the discharge capacity obtained until the voltage reached 1 V. The result is shown in FIG.

As is apparent from FIG.
It can be seen that the utilization rate of the secondary battery, which was initially charged at V and a current value of 1/10 CA or less and 1/2 CA or less, is extremely high at 95% or more. On the other hand, even if the voltage is 1.2 V,
A secondary battery that has been initially charged with a current value of 1 CA or less is
It can be seen that the utilization drops to 78%.

Therefore, as in the present invention, a voltage of 0.9 V to
It is understood that the initial charge is performed under the conditions of a constant voltage of 1.3 V and a current value of 1/2 CA or less, whereby the utilization rate of the positive electrode can be significantly improved.

Further, four secondary batteries were prepared, and the secondary batteries were initially charged at 25 ° C. at a voltage of 1.2 V and a current value of 1/3 CA or less for 10 hours and 2 hours, respectively.
After 0 hours, 30 hours and 40 hours, 0.3C for 10 hours
Activation was performed by performing 0% charging. Then,
Each secondary battery was discharged at 1 C, and the utilization rate of the positive electrode was determined from the discharge capacity obtained until the voltage reached 1 V. The result is shown in FIG.

As is apparent from FIG. 4, the secondary battery having been subjected to the initial charge for 10 hours, 20 hours, and 30 hours has an availability of 8 hours.
It turns out that it is as high as 0% or more. On the other hand, it can be seen that the utilization rate of the secondary battery that has been initially charged for 40 hours is reduced to 75%.

Further, seven secondary batteries were prepared, and for these secondary batteries, -10.degree. C., 0.degree. C., 10.degree.
Activated by performing initial charging for 20 hours at 0 ° C, 30 ° C, 40 ° C, and 60 ° C with a voltage of 1.2 V and a current value of 1/3 CA or less, and then performing 100% charging at 0.3C. Was done. Subsequently, each secondary battery was discharged at 1 C, and the utilization rate of the positive electrode was determined from the discharge capacity obtained until the voltage reached 1 V. The result is shown in FIG.

As apparent from FIG. 5, 0 ° C., 10 ° C.,
A secondary battery that has been initially charged at 20, 30 and 40 ° C.
It can be seen that the utilization is as high as 85% or more. On the other hand, -10
The secondary battery that was initially charged at 60 ° C and 60 ° C had a utilization rate of 75%.
%. Although the first embodiment has been described by applying the present invention to a nickel-metal hydride secondary battery, the present invention can be similarly applied to a nickel-cadmium secondary battery.

[0026]

As described above in detail, according to the present invention, it is possible to provide a method of manufacturing an alkaline secondary battery capable of improving the utilization of a paste-type nickel positive electrode.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a nickel-metal hydride secondary battery manufactured by the method of the present invention.

FIG. 2 is a diagram showing a utilization rate of a positive electrode when a voltage is changed.

FIG. 3 is a diagram showing a utilization rate of a positive electrode when a current value is changed.

FIG. 4 is a diagram showing a utilization rate of a positive electrode when a time of an initial charge is changed.

FIG. 5 is a diagram showing a utilization rate of a positive electrode when a temperature of an initial charge is changed.

[Explanation of symbols]

 1. Positive electrode, 2: Negative electrode, 3 ... Separator.

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01M 10/00-10/34 H01M 4/24-4/34 H01M 10/42-10/48

Claims (1)

(57) [Claims] 1. An alkaline secondary battery comprising an electrode group produced by sandwiching a separator between a paste-type nickel positive electrode containing nickel hydroxide and cobalt monoxide as active materials and a negative electrode, and an alkaline electrolyte. In the manufacturing method, the initial charge is performed at a voltage of 0.9 V to 1.3 V and a constant voltage having a current value of 1/2 CA or less.
A method for producing an alkaline secondary battery, comprising converting to OOH.