JP2771584B2 - Manufacturing method of non-sintering type sealed alkaline storage battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a non-sintered sealed alkaline storage battery having a non-sintered nickel anode to which at least metal cobalt is added and a cadmium cathode.

2. Description of the Related Art In recent years, as a method for manufacturing a nickel anode used for an alkaline storage battery, a so-called non-sintered anode using a three-dimensional porous body of metal such as sponge-like nickel or nickel fibrous sintered body as an active material holding body has been proposed. Manufacturing methods have been proposed. Compared to the sintering method, this manufacturing method has the advantages that the steps can be shortened and simplified, and that a high-porosity holding member is used, so that a high energy density can be achieved. A specific method for manufacturing such an electrode plate is a method in which an active material powder mainly composed of nickel hydroxide is formed into a paste using an aqueous dispersion medium on a three-dimensional porous body (hereinafter, referred to as a substrate) made of the above metal. And then a binder is added. Next, the paste is dried and then pressed and compressed.

However, the battery manufactured by the above manufacturing method has a problem that the electrochemical utilization of the active material is low. In addition, in the case of a closed battery, the closed charge capacity ratio ([cathode capacity] / (cathode capacity) /
[Anode capacity] is desirably set to one or more as high as possible. For this reason, conventionally, pre-charging was performed before assembling the cathode, or by adding a metal cadmium having electrochemical activity. However, in the former case, a new process of pre-charging is required, so that the manufacturing cost of the battery rises. On the other hand, in the latter case, metal cadmium is expensive and lacks chemical stability, so the battery cost is high and the battery performance is degraded. Had the problem of doing so.

Therefore, as disclosed in JP-A-58-206055, a proposal has been made to add a metal cobalt powder to an active material paste. When manufactured in this way, when the metal cobalt powder is made into a paste or when the electrolytic solution is injected into the battery, the metal cobalt is once dissolved in the dispersion medium, and then the nickel hydroxide particles as the main active material To form a solid solution in the crystal lattice of the surface layer and re-extract metallic cobalt. Thereby, the charging potential of the nickel hydroxide shifts toward the base side (that is, the charging becomes easier), and the electrochemical utilization of the active material can be improved.

However, the above manufacturing method has the following problems.

The effect of improving the electrochemical utilization rate of the active material varies greatly.

This is considered to be caused by the fact that the re-extrusion of the metal cobalt is not performed uniformly, so that a defective portion is formed in the solid solution film, and that the amount of dissolved metal cobalt differs due to environmental changes such as temperature.

This leads to an increase in battery manufacturing cost or a decrease in battery energy density.

As disclosed in JP-A-63-4568, the addition of metallic cobalt to the anode makes it possible to increase the sealed charge capacity ratio of the sealed battery. Because, when metallic cobalt is added to the anode, metallic cobalt has a much lower potential than nickel hydroxide, so it is anodized in preference to nickel hydroxide during charging, and its product, CoOOH
Little contributes to the discharge, so that the charging efficiency of the anode as a whole becomes very low. Therefore, this is due to the fact that the difference in charging efficiency from the cathode becomes large. By the way, the charging efficiency of the initial charge in the open system single electrode of the anode to which 5 wt% of metallic cobalt is added and the anode consisting of nickel hydroxide alone are about 60% and 70%, respectively, while the cadmium oxide is the main component. The charging efficiency of the cathode is about 80%. Therefore, even when 5 wt% of metallic cobalt is added, the sealed charge capacity ratio is about 1.2. Therefore, the amount of metallic cobalt to be added to the anode becomes very large in order to secure a desirable closed charge capacity ratio (1.3 or more) as a battery. However, metallic cobalt is several times more expensive than nickel hydroxide, which increases battery manufacturing costs. In addition, the occupancy ratio of cobalt in the electrode plate that does not contribute to charging and discharging increases, so that the energy density of the battery decreases.

The charge efficiency of the anode in the second and subsequent cycles is stable at a high level of 90% or more because the metal cobalt once anodized does not participate in charge and discharge.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, the present invention seeks to stabilize the active material utilization rate while increasing the effect of increasing the active material utilization rate by adding metal cobalt, and only adds a small amount of metal cobalt. It is an object of the present invention to provide a method of manufacturing a non-sintered sealed alkaline storage battery capable of ensuring a sufficient sealed charge capacity ratio at a low temperature.

Means for Solving the Problems The present invention, in order to achieve the above object, a non-sintered nickel anode to which at least metal cobalt is added, and a method of manufacturing a non-sintered sealed alkaline storage battery having a cadmium cathode, After winding the anode and cathode through a separator, a first step of inserting this into a battery can, and after injecting an electrolyte into the battery can, a second step of sealing the battery can, A third step of performing an initial discharge until the terminal voltage becomes less than 0 V.

The metal cobalt powder added to the anode is anodic oxidized to CoOOH during the first charge. At this time, according to the investigation by the present inventor, it was found that 30 to 50% of the metal cobalt was subjected to anodic oxidation. The structure of the metal cobalt that has undergone the anodic oxidation has been estimated from electrochemical measurements to indicate that an oxide film is formed on the surface of the metal cobalt particles, and that the interior of the particles will be kept as a metal. You.

By the way, the above-mentioned oxide film of cobalt is stable and usually kept in its form. However, a deep discharge takes place, the anode is completely discharged, and the potential of the cathode (i.e., -0.
9V ( _VS Hg / HgO)], the oxide film is reduced, the film is broken, and the internal metal cobalt is exposed. For this reason, metallic cobalt is dissolved in an alkaline solution and nickel-
A cobalt solid solution forming reaction occurs, and the defective portion of the solid solution film that was incomplete is newly covered with the reaction. As a result, the utilization rate of the active material is improved and stabilized.

Further, if the initial discharge is performed until the terminal voltage becomes less than 0 V, the metal cobalt is exposed and the charging efficiency of the anode is reduced again. On the other hand, since the cathode also releases a part of the surplus capacity once secured, the remaining capacity of the cathode at the end of discharge decreases. However, if the cathode is charged and discharged for one cycle, the charging efficiency from the second cycle is improved. For this reason, the difference in the charging efficiency between the anode and the cathode increases, and as a result, the sealed charging capacity ratio increases. For example, using a battery with a combination of an anode containing 5 to 10% of metallic cobalt and a cathode containing cadmium oxide as a main component, a terminal voltage of less than 0 V in the first discharge and an overdischarge of 10% of the anode capacity Do. After the end of the overdischarge, the cathode has only a remaining capacity corresponding to 5 to 7% of the anode capacity. However, the charging efficiency of the anode and the cathode in this state is 75 and 95%, respectively, so that the closed charging capacity ratio can reach the level of 1.25 to 1.30 in the charging of the second cycle.

Example [Example I] First, an active material composed of 7.5 parts by weight of metal cobalt powder and 92.5 parts by weight of nickel hydroxide powder was kneaded with a paste liquid to prepare a paste, and then the paste was converted into sponge-like nickel. Fill. Next, a PTFE (polytetrafluoroethylene) dispersion serving as a binder is added to the paste, and the paste is dried, followed by pressure rolling to produce a positive electrode. Next, by combining the above positive electrode and a non-sintered cathode using cadmium oxide as an active material, to produce a sealed Ni-Cd battery of a normal SC size, the initial charge and discharge of this sealed Ni-Cd battery was performed. went. The charging / discharging condition at this time is the charging power
After charging for 16 hours at 0.1 CmA, the battery was discharged for 6 minutes after the terminal voltage was divided by 0 V by the discharge current of 1 CmA.

The battery fabricated in this manner is hereinafter referred to as (A ₁ ) battery.

(Examples II to VII)

As shown in Table 1 below, a battery was produced in the same manner as in Example I except that the amount of metallic cobalt added to the positive electrode and the initial charge / discharge conditions were changed.

The battery fabricated in this manner is referred to as a battery (A ₂ ) below.
(A ₇ )

Comparative Examples I and II As shown in Table 1 above, batteries were produced in the same manner as in Example I except that the amount of metal cobalt added to the positive electrode and the initial charge / discharge conditions were changed.

The battery fabricated in this manner is hereinafter referred to as (B ₁ ) battery,
(B ₂ ) called a battery.

[Experiment]

(A ₁ ) battery prepared by the method of the present invention to (A ₇ )
(B ₁ ) battery produced by the method of the battery and the comparative example,
(B ₂ ) The sealed charging capacity ratio of the battery, the battery capacity and its variation were examined, and the results are shown in Table 2 below.

The charging and discharging conditions were as follows: after charging for 16 hours at a charging current of 0.1 CmA, discharging was performed at a discharging current of 1 cmA until the terminal voltage became 1.0 V. The time required for the terminal voltage to reach 1.0 V was defined as the battery capacity.

As is evident from Table 1 above, when the (A ₂ ) to (A ₄ ) batteries of the present invention and the (B ₁ ) battery of the comparative example in which the addition amount of metallic cobalt is the same (5 wt%) are compared, (A ₂₎ battery -
It can be seen that the (A ₄ ) battery has a sealed charge capacity ratio of 1.23 to 1.28, whereas the (B ₁ ) battery has only 1.15. Furthermore, the battery capacity in the second cycle is (A ₂ )
(A ₄ ) For batteries, 63.0-63.5 (minutes),
(B ₁ ) It is recognized that the battery has only 61.2 (minutes).
Furthermore, the variation in the battery capacity is (A ₂ ) battery to (A ₄ )
It is recognized that the battery (B ₁ ) has 6.0 (min) while the battery has 3.0 to 4.5 (min). Similarly, the (A ₁ ) battery and the (B ₂ ) battery both containing 7.5 wt% of metallic cobalt were added.
It can be seen that the same result was obtained with the battery.

From these facts, it can be seen that the battery manufactured by the manufacturing method of the present invention has significantly improved battery performance as compared with the battery manufactured by the manufacturing method of the comparative example.

Here, an appropriate range of the addition amount of metallic cobalt is examined. As shown in Table 2 above, it is recognized that the battery capacity changes depending on the amount of metallic cobalt added. For example, batteries for 6 minutes after the initial charge / discharge conditions are all below 0V [(A ₁ ) battery, (A ₃ ) battery, (A ₅ ) battery, (A ₆ ) battery,
(A ₇₎ Examining the batteries]. Batteries containing 5 to 10% of metallic cobalt [(A ₁ ) batteries, (A ₃ ) batteries, (A ₅ )
Battery] is 63.5 to 64.2 (min), whereas the amount of metallic cobalt added is 15% or more [(A ₆ ) battery, (A ₇ )
Battery] is only 59.5 to 60.8 (minutes). Further, although not shown in Table 2, it was confirmed that the battery capacity was 56 (minutes) for the battery in which the addition amount of metallic cobalt was 2.5%. For these reasons, it is desirable that the addition amount of metallic cobalt is 5 to 10%. It should be noted that if the added amount of metallic cobalt is increased, the sealed charge capacity ratio becomes 1.3 or more. However, if the amount is excessively increased as described above, the battery capacity decreases. Therefore, it is not preferable to add more than 10%.

Next, an appropriate range of the time of the first discharge is examined. As shown in Table 2 above, it is recognized that the battery capacity changes depending on the time of the first discharge. For example, batteries containing 5 wt% of metallic cobalt [(A ₂ ) batteries, (A ₃ ) batteries,
(A ₄₎ Examining the batteries]. Initial discharge time is 0V
63.0 minutes for a battery [(A ₂ ) battery] for 3 minutes after cracking
However, after the time of the first discharge is less than 0V, 6
And 10-minute batteries ((A ₃ ) and (A ₄ ) batteries)
3.5 (minutes). Moreover, whereas the variation in (A ₂₎ cells of the battery capacity is 4.5 (minutes), (A ₃₎ batteries, 3.0 (min) in (A ₄₎ batteries, 4.0 (min)
It is admitted that there is only one. Therefore, from the viewpoint of battery capacity, it is preferable that the time of the first discharge is long. However, from the viewpoint of the sealed charge capacity ratio, (A ₃ )
It is recognized that there are only 1.23 in the (A ₄ ) battery, while it is 28. This is because if the discharge time after dividing 0 V is too long, the surplus charge amount of the cathode secured in the first charge will be completely consumed, so the difference between the positive and negative charge efficiency in the second cycle will be different. It is considered that the reason is that even if the charge is expanded beyond the initial charge, the difference is not enough to make up for the consumption. From these facts, it can be said that it is preferable that the time of the first discharge is less than 6 minutes after dividing 0V (that is, about 10% of the anode capacity is excessively discharged).

In the above embodiment, cadmium oxide is used as a cathode active material as a main component. However, the same effect as described above can be obtained by using cadmium hydroxide or a mixture of cadmium oxide and cadmium hydroxide. Have confirmed.

Advantageous Effects of the Invention As described above, in the present invention, the stabilization of the active material utilization rate can be achieved while increasing the effect of improving the utilization rate of the active material by adding metal cobalt without significantly changing the process. Therefore, the battery capacity can be improved and the variation in the battery capacity can be reduced. In addition, a sufficient closed charge capacity ratio can be ensured without adding expensive cadmium metal lacking chemical stability or performing pre-charge treatment. From these facts, there is an effect that the battery performance can be drastically improved without increasing the manufacturing cost of the battery.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takuya Tamagawa 2-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-63-4568 (JP, A) (58) Surveyed fields (Int.Cl. ⁶ , DB name) H01M 10/24-10/34

Claims (1)

(57) [Claims] 1. A method for producing a non-sintered sealed alkaline storage battery having a non-sintered nickel anode to which at least metal cobalt is added and a cadmium cathode, wherein the anode and the cathode are wound via a separator. Then, a first step of inserting the battery can into the battery can, a second step of injecting the electrolytic solution into the battery can and then sealing the battery can, and performing an initial discharge until the terminal voltage becomes less than 0V. 3. A method for producing a non-sintered sealed alkaline storage battery, comprising: