JP3238949B2 - Activation method of alkaline storage 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 activating an alkaline storage battery provided with a non-sintered nickel positive electrode to which a metal cobalt powder and a nickel oxyhydroxide powder are added.

[0002]

2. Description of the Related Art Conventionally, in an alkaline storage battery provided with a non-sintered nickel positive electrode, a cobalt compound powder or other conductive powder is added to the positive electrode for the purpose of activating the positive electrode active material. That is being done. Among them, metallic cobalt is known to have both conductivity and suitable action and effects specific to cobalt species, and is extremely effective in increasing the utilization rate of the active material (JP-A-53-51449, etc.). For this reason, metal cobalt powder has been widely added to a nickel positive electrode as an active material activator.

By the way, the above-mentioned metallic cobalt powder added for the purpose of activating the active material of the positive electrode cannot sufficiently exert the active material activating effect as long as it is added to the nickel positive electrode. That is, in order to exert the effect sufficiently, it is necessary that the metal cobalt powder in the positive electrode itself is smoothly oxidized in the battery and is in an oxidized state in which the specific effect can be sufficiently exhibited.

As a method for this purpose, a method has been proposed in which the charging current is kept low in the initial stage of charging in which anodic oxidation of cobalt occurs preferentially (JP-A 64-2186).
4). However, even if the charging current is kept low at the beginning of battery charging according to this method, the oxidation of the metal cobalt powder added to the electrode cannot be properly advanced, and the activation effect of the metal cobalt powder is sufficiently enhanced. I couldn't do that. Accordingly, the present inventors have previously proposed a method of chemically promoting the oxidation reaction of the metal cobalt powder by adding a nickel oxyhydroxide powder prepared in advance together with the metal cobalt powder to the nickel positive electrode (particularly). Kaihei 4-94058).

In the above method, nickel oxyhydroxide, which acts as an oxidizing agent on the metal cobalt powder and acts as an active material, acts as an oxidation promoter to chemically accelerate the oxidation reaction of the metal cobalt powder. It is to try to make it.

[0006]

However, even in the storage battery constructed based on the above method, the oxidation promoting effect of the nickel oxyhydroxide powder on the metal cobalt powder could not be properly exhibited, so that the cobalt The activation ability for the positive electrode active material could not be sufficiently increased.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and by appropriately applying nickel oxyhydroxide powder to metal cobalt powder added to a nickel positive electrode, the metal cobalt powder can be used. It provides a method of adjusting the active material to a state where the activation effect can be sufficiently exhibited, thereby improving the utilization rate of the positive electrode active material, and particularly improving the battery characteristics of an alkaline storage battery equipped with a non-sintered nickel positive electrode. It aims to increase battery capacity.

[0008]

In order to achieve the above object, the present invention comprises a metal cobalt powder and a nickel oxyhydroxide powder, and the content of the nickel oxyhydroxide is 60% by weight or less based on the metal cobalt powder. In an alkaline storage battery having a non-sintered nickel electrode as a positive electrode, after assembling the storage battery, the storage battery is left until the positive electrode potential reaches a potential corresponding to the equilibrium potential of Co / Co (OH) ₂ , and then the first charge / discharge is performed. It is characterized by.

[0009]

The present invention has the following effects by being configured as described above. After the storage battery is assembled, the storage battery is allowed to stand, so that the nickel oxyhydroxide added to the positive electrode can promote the oxidation of the metal cobalt powder to cobalt hydroxide. In addition, the above-mentioned leaving is performed when the potential of the positive electrode is Co / Co (O
H) By setting the potential to the potential corresponding to the equilibrium potential of ₂ , the metal cobalt powder can be preferentially subjected to electrochemical oxidation.

Therefore, according to the above configuration, the electrochemical oxidation reaction of the metal cobalt powder proceeds properly at the time of initial charging of the storage battery (at the time of initial conditioning), the utilization efficiency of the metal cobalt powder is improved, and the activation of the active material is improved. Noh is fully demonstrated. As a result, the utilization rate of nickel active material increases,
This has the effect of improving the battery characteristics of the alkaline storage battery provided with the nickel positive electrode, in particular, the battery capacity.

The above action will be described based on the oxidation reaction mechanism of metal cobalt powder and nickel oxyhydroxide shown in the following [Chemical Formula 1] and [Chemical Formula 2]. As shown in [Formula 1],
Metallic cobalt is oxidized to cobalt oxyhydroxide via cobalt hydroxide. Here, oxidation of the metal cobalt powder to cobalt hydroxide gradually proceeds from the surface of the metal cobalt powder in contact with the electrolytic solution. On the other hand, the oxidation reaction from cobalt hydroxide to cobalt oxyhydroxide is a proton diffusion reaction in the cobalt hydroxide solid phase, and therefore proceeds relatively easily once the metal cobalt is oxidized to cobalt hydroxide. Therefore, when the oxidation of the metal cobalt powder is rapidly promoted, the surface of the metal cobalt powder is oxidized to form cobalt hydroxide, and before the oxidation reaction inside the powder sufficiently proceeds, the cobalt hydroxide on the surface of the powder first becomes cobalt oxyhydroxide. Is oxidized to Therefore, a cobalt oxyhydroxide film is formed on the surface of the powder while leaving the inside of the powder,
This film acts as a barrier to prevent the contact between the metallic cobalt and the electrolyte (OH ^- ion), thereby inhibiting the further progress of the oxidation reaction. When such a so-called passivation of metallic cobalt occurs, the utilization efficiency of metallic cobalt powder added to the positive electrode decreases, and the activation effect thereof cannot be sufficiently exhibited. For this reason, it is necessary to avoid rapid oxidation during battery conditioning. On the other hand, cobalt oxyhydroxide having excellent conductivity is rapidly oxidized during the initial charge of the metallic cobalt powder (the activation ability of the cobalt oxyhydroxide is improved). (A form that can fully demonstrate).

[0012]

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Therefore, in consideration of the oxidation reaction characteristics of the metal cobalt powder in the battery as described above, the oxidation of the metal cobalt powder to cobalt hydroxide is appropriately advanced in advance, and then the electrochemical oxidation is performed by the first charge. It is desirable to proceed. Therefore, in the activation method of the present invention, the nickel oxyhydroxide powder added to the positive electrode is allowed to act on the metal cobalt powder by leaving the battery after assembling the storage battery (after injecting the electrolytic solution), thereby obtaining the metal cobalt powder. To promote the oxidation of

The nickel oxyhydroxide powder added to the positive electrode serves as an oxidizing agent, and is mixed in a sufficiently mixed state with the metal cobalt powder. The powder can be chemically oxidized. Therefore, unlike the case where electrochemical oxidation is promoted, the oxidation reaction can be uniformly promoted throughout the positive electrode without being affected by the conductivity of each part in the positive electrode. Even if the oxidation is promoted, if the oxidation is not properly performed, the subsequent electrochemical oxidation cannot be properly advanced. Therefore, in the activation method of the present invention, the content ratio of the nickel oxyhydroxide powder to the metal cobalt powder is regulated to 60% by weight or less,
This is until the potential of the positive electrode reaches a potential corresponding to the equilibrium potential of Co / Co (OH) ₂ . Thereby, the metal cobalt powder is preferentially adjusted to be easily susceptible to electrochemical oxidation, and the oxidation reaction of the metal cobalt powder can be efficiently promoted by the first charge after being left.

[0015]

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The phrase "leave the storage battery until the positive electrode has a potential corresponding to the equilibrium potential of Co / Co (OH) ₂ " means that the electrode potential of the positive electrode is mainly represented by the following reaction formula (3): It means that the storage battery is left until the equilibrium electrode potential represented by the formula, but the electrode potential of the positive electrode depends on other than the one based on the following reaction formula, and since it appears as a mixed potential, its exact value is It is difficult to determine. Therefore, the battery voltage should be approximately equivalent to the value of the equilibrium potential.

[0017]

Embedded image As described above, the activation method of the present invention is configured to perform so-called chemical oxidation treatment and electrochemical oxidation treatment in a storage battery. It is possible to improve the utilization efficiency of the compound and sufficiently exert its activating effect. And
This can activate the nickel active material, nickel positive
This has the effect of significantly improving the battery characteristics of the alkaline storage battery having the poles, especially the battery capacity.

[0018]

〔Example〕

[Production of nickel oxyhydroxide powder] Nickel hydroxide powder (Fisher sub-sieve sizer FSS: 9.0
2 μl of a 10% by weight aqueous solution of sodium hypochlorite was added to 100 g of μm), and the mixture was stirred at room temperature for about 3 hours to oxidize the nickel hydroxide powder. And
The treated powder was sufficiently washed and then dried to produce a nickel oxyhydroxide powder. The treated powder was confirmed to be a nickel oxyhydroxide powder by X-ray diffraction analysis.

[Preparation of Nickel Hydroxide Positive Plate] Nickel hydroxide powder (FSS: 9.0 μm) and nickel oxyhydroxide powder (prepared above) were mixed at a predetermined ratio, and the mixed powder was further reduced to 90% by weight. Metallic cobalt powder (FSS:
1.0 μm) 10% by weight was added and mixed to prepare an active material powder for a positive electrode. Next, 50% by weight of a 1% by weight aqueous solution of methylcellulose is added to the powder and kneaded to form a slurry. This slurry was filled in a nickel foam substrate, dried and molded to produce a nickel hydroxide positive electrode plate.

Here, the "predetermined ratio" means that the compounding amount of the nickel oxyhydroxide powder is set in several steps (5, 2
0, 30, 40, 50, 60, 90, 120% by weight), which means that the amount of the nickel hydroxide powder was changed correspondingly (see FIG. 1). [Production of Nickel Cadmium Storage Battery] The nickel hydroxide positive electrode plate produced above and the non-sintered cadmium negative electrode plate produced by the following method were made of polypropylene.
Hoisting the electrode body via a woven fabric separator, 30 wt%
An aqueous potassium hydroxide solution was injected and sealed, to produce a sealed nickel-cadmium storage battery (JIS. KR-A size, nominal capacity: 1.2 AH).

In this specification, the time when the storage battery is completed is referred to as "after the storage battery is assembled". The non-sintered cadmium negative electrode plate was manufactured by the following method. A predetermined amount of cadmium oxide powder and metal cadmium powder are mixed with a known paste liquid to form a paste, and this paste is applied to a punching metal, followed by drying and rolling. The plate is then applied to the nominal capacity (1.2 AH) with a current of 0.2C for 2 hours.
The battery was formed by charging to 40%, forming a chemical by discharging with a current of 0.2 C, washing with water and drying.

[Activation of Battery] The sealed nickel-cadmium storage battery prepared above was
After being left at room temperature until the potential corresponding to the equilibrium potential of Co / Co (OH) ₂ (about 0.1 V as the battery voltage),
200 0.1C rate to the nominal capacity (1.2 A H)
% And discharged at a rate of 1.0 C to produce an activated nickel-cadmium sealed battery.

The method for treating in this manner is hereinafter referred to as the activation method of the present invention, and the storage battery that has been activated by the activation method of the present invention is referred to as the battery (A) of the present invention. [Comparative Example] A sealed nickel-cadmium storage battery similar to that used in the above embodiment was left to stand before reaching a potential corresponding to the equilibrium potential of Co / Co (OH) ₂ (battery voltage: about 0.1 V). The charge and discharge were performed under the same conditions as in the case of the activation method of the present invention.

The method for treating in this manner is hereinafter referred to as Comparative Example Method, and the storage battery treated in this manner is referred to as Comparative Example Battery (X). [Experiment] Various storage batteries manufactured by the manufacturing method of the above embodiment in which the blending amount of the nickel oxyhydroxide powder was changed to multiple levels were respectively processed using the two storage battery processing methods described above, and the batteries of the storage batteries were processed. The capacity was measured.

FIG. 1 shows the result. In FIG. 1, the battery capacity of a storage battery containing no nickel oxyhydroxide powder is set to 100, and the values are shown based on this. As is clear from FIG. 1, the storage battery (A) (○-○) treated by the activation method of the present invention is the storage battery (X) treated by the comparative example method.
The battery capacity is significantly higher than (●-●).
However, the activation method of the present invention could not be applied to a storage battery containing nickel oxyhydroxide powder in an amount of 60% by weight or more based on the metal cobalt powder. This is based on the following reasons.

In a storage battery containing nickel oxyhydroxide powder in an amount of 60% by weight or more based on the metal cobalt powder, the potential attributable to the nickel oxyhydroxide powder itself becomes dominant. .1V
Therefore, the storage battery cannot have a potential corresponding to the equilibrium potential of Co / Co (OH) ₂ . From the above experimental results, the activation method of the present invention provides a non-sintered nickel hydroxide electrode comprising a metal cobalt powder and a nickel oxyhydroxide powder, wherein the nickel oxyhydroxide powder is 60% by weight or less based on the metal cobalt powder. It can be seen that, in an alkaline storage battery having a plate as a positive electrode, the nickel positive electrode active material can be activated to significantly improve the battery capacity of the storage battery.

In the above embodiment, a nickel-cadmium storage battery was used as an alkaline storage battery. However, the present invention is not limited to this. For example, a nickel-hydrogen storage battery, a nickel-iron storage battery, a nickel-zinc storage battery And so on. Co / Co of these storage batteries
The electrode voltage corresponding to the equilibrium potential of (OH) ₂ is roughly as shown in the table below.

[0028]

[Table 1]

[0029]

According to the present invention as described above,
It is possible to activate an alkaline storage battery using a non-sintered nickel electrode plate to which metal cobalt powder and nickel oxyhydroxide are added as a positive electrode, and to increase the battery capacity of the storage battery.

[Brief description of the drawings]

In the invention, FIG activation method, the addition ratio and the nickel positive electrode of the nickel oxyhydroxide powder of the nickel positive electrode
4 is a graph showing a relationship between a battery capacity of a provided alkaline storage battery.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaki Higuchi 2-18-18 Keihanhondori Moriguchi City Sanyo Electric Co., Ltd. (72) Inventor Kenji Arisawa 2-18-18 Keihanhondori Moriguchi City Sanyo Electric Co., Ltd. ( 56) References JP-A-61-138454 (JP, A) JP-A-60-254564 (JP, A) JP-A-59-51463 (JP, A) JP-A-3-105856 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) H01M 4/24-4/34 H01M 4/52

Claims (1)

(57) [Claims] 1. An alkaline storage battery comprising a non-sintered nickel electrode containing a metal cobalt powder and nickel oxyhydroxide and having a nickel oxyhydroxide content of 60% by weight or less based on the metal cobalt powder as a positive electrode. A method for activating an alkaline storage battery, comprising: after the storage battery is left standing until the positive electrode potential becomes a potential corresponding to the equilibrium potential of Co / Co (OH) ₂ , and then performing initial charge and discharge.