JP3397889B2 - Non-sintered nickel electrode for alkaline storage batteries - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-sintered nickel electrode for an alkaline storage battery, and more particularly to an improvement of a non-sintered nickel electrode which makes it possible to obtain an alkaline storage battery having a large battery capacity.

[0002]

BACKGROUND OF THE INVENTION A typical nickel electrode for an alkaline storage battery is a solution impregnated into pores of a sintered substrate obtained by sintering nickel powder on a perforated steel plate or the like. Sintered nickel electrode filled with an active material by the method, and an alkali-resistant metal fiber sintered body, or a porous substrate made of carbon fiber nonwoven fabric plated with a metal having excellent alkali resistance such as nickel, There is a non-sintered nickel electrode formed by filling a paste of nickel hydroxide powder.

The sintered nickel electrode has a high utilization ratio of the active material because the sintered substrate has good conductivity. However, since the bonding between the nickel particles of the sintered substrate is weak, the active material is likely to drop out of the sintered substrate when the sintered substrate having high porosity is used. Therefore, the practicable sintered substrates are limited to those having a porosity of about 80% or less. In addition, a cored bar such as a perforated steel plate for holding the nickel sintered body is required. For these reasons, the sintered nickel electrode has a problem that the packing density is low. Also, the pore size of the nickel sintered body is 10μ.
Since it is as small as m or less, when filling the active material,
It is necessary to repeat the solution impregnation operation, and there is a problem that the electrode plate production is complicated.

The non-sintered nickel electrode has been proposed to solve the above problems of the sintered nickel electrode. In this non-sintered nickel electrode, since the active material is once filled in the base material such as the alkali-resistant metal fiber sintered body having a large porosity and having no core metal, the nickel electrode having a large packing density can be obtained. Also, the production of the electrode plate is simple.

However, if the substrate is filled with only nickel hydroxide powder, the utilization factor of the active material is remarkably low due to the poor conductivity of the electrode plate, and a practical product cannot be obtained.

In an attempt to improve the utilization rate of the active material of such a non-sintered nickel electrode and put it into practical use, a cobalt hydroxide powder and a nickel hydroxide powder as a conductive agent are used.
A method has been proposed in which a substrate is filled with a slurry obtained by kneading with an aqueous solution of carboxymethyl cellulose (JP-A-61-49374).

By the way, the cobalt hydroxide powder is apt to be unevenly distributed in the paste and is difficult to be uniformly mixed and dispersed with the nickel hydroxide powder. Therefore, in order to effectively improve the utilization rate of the active material, a large amount of cobalt hydroxide powder should be used. Need to use.
However, when a large amount of cobalt hydroxide powder is used, the filling amount of nickel hydroxide powder as an active material into the substrate is inevitably reduced, so that the electrode plate capacity is reduced.

In recent years, cobalt hydroxide (α-Co (OH) ₂ or β-Co (O
There is also proposed a method in which an alkali-resistant porous body is filled with an active material powder composed of composite particles having a coating layer H) ₂ ) (Japanese Patent Laid-Open No. 234867/1987).
-237667, JP-A-62-222566, etc.).

However, although the composite particles having these coating layers have a high utilization ratio of the active material, the bulk specific gravity of the powder is extremely smaller than that of the nickel hydroxide particles not having the coating layer formed thereon. In addition, the packing density of the active material (nickel hydroxide) in the alkali-resistant porous body is lowered. Therefore, it is difficult to obtain a high capacity alkaline storage battery.

The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a high capacity alkaline storage battery with a high active material utilization rate and a high active material packing density. To provide a sintered nickel electrode.

[0011]

The non-sintered nickel electrode for an alkaline storage battery according to the present invention (hereinafter, referred to as "the electrode of the present invention") for achieving the above object is Ni (OH).
_{In a} non-sintered nickel electrode for an alkaline storage battery, which is obtained by filling an alkali resistant substrate with a powder of a solid solution containing ₂ powders or a solid solution containing Ni (OH) ₂ as a main component and a Co (OH) ₂ powder. The body powder is obtained by mixing the Ni (OH) ₂ powder or the solid solution powder with the Co (OH) ₂ powder in a weakly basic solution having a pH of 9 to 12.

The solid solution powder containing Ni (OH) ₂ as a main component includes Ni (OH) _{2 as} well as Zn (OH) ₂ ,
Co (OH) ₂ , Cd (OH) ₂ , Ca (OH) ₂ , B
Examples thereof include those obtained by co-precipitating a (OH) ₂ , Mn (OH) _{2 and the} like, or two or more of them.

The mixed powder in the present invention has a pH of 9-12.
Ni (OH) ₂ powder and Co (OH) ₂ in weakly basic solution of
It was obtained by mixing ₂ powders. This is the pH
When the ratio is less than 9, the dissolution reaction of Co (OH) ₂ ⇒ HCoO ₂ ⁻ does not proceed promptly, so that a mixture powder in which Ni (OH) ₂ particles and Co (OH) ₂ particles are uniformly mixed is obtained. When the pH exceeds 12, Co (OH)
_{This is because 2} is oxidized and a large amount of inactive CoHO ₂ (trivalent Co) is produced.

The mixture powder preferably contains Co (OH) ₂ powder in an amount of 3 to 15% by weight. Co (O
When the content of H) ₂ is less than 3% by weight, Co (O
H) ₂ powder is too small, so Co (OH) ₂ particles are Ni
It becomes difficult to obtain a highly conductive mixed powder which is uniformly present on the surface of the (OH) ₂ particles without being insufficient. On the other hand, when the content ratio exceeds 15% by weight, the active material Ni (OH) ₂ ) The packing density of the powder in the substrate decreases, leading to a decrease in the electrode plate capacity.

[0015]

When Ni (OH) ₂ powder and Co (OH) ₂ powder are mixed in a weakly basic solution of pH 9-12, Co (O) ₂
H) ₂ Part of the particles rapidly dissolves in the weakly basic solution and becomes HC
oO ₂ ⁻ (this HCoO ₂ ⁻ is deposited on the surface of the Ni (OH) ₂ particles as Co (OH) ₂ particles),
Since it mixes uniformly with the Ni (OH) ₂ particles, Co (O
H) mixing powders uneven distribution with less ₂ particles. Further, when the pH is 12 or less, inactive CoHO ₂ is hardly generated. Therefore, the mixed powder obtained by mixing in a weakly basic solution having a pH of 9 to 12 has high conductivity. Furthermore, since the dissolution / precipitation reaction of the Co (OH) ₂ particles is rapid, a dense mixture powder having a large bulk specific gravity can be obtained. In the electrode of the present invention, since the mixed powder having high conductivity and large bulk specific gravity is used, both the utilization rate of the active material and the packing density of the active material are high.

[0016]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples, and various modifications may be made without departing from the scope of the invention. Is possible.

(Preliminary Experiment) [Preliminary Experiment 1: Co for various basic pH aqueous solutions]
(OH) ₂ solubility] pH kept at 25 ° C,
Co (OH) ₂ was added to 1000 ml of 9, 10, 11, 12 or 13 ammonium chloride-sodium hydroxide aqueous solution.
After pouring 10 g of the powder and stirring and mixing for 30 minutes, the amount of Co ²⁺ in the ammonium chloride-sodium hydroxide aqueous solution was quantified by an atomic absorption method. A glass electrode pH meter equipped with an automatic temperature compensation function was used for pH measurement (the same pH meter was used in the following pH measurement). The results are shown in Fig. 1.

FIG. 1 shows the solubility of Co (OH) ₂ powder in basic aqueous solutions of various pHs, the vertical axis represents the amount of Co ²⁺ (mg / liter) in the ammonium chloride-sodium hydroxide aqueous solution, and the horizontal axis represents the solubility. 6 is a graph in which the pH of the ammonium chloride-sodium hydroxide aqueous solution is plotted on the axis, and as shown in the figure, the solubility of the Co (OH) ₂ powder decreases below pH 9. From this, Co (OH) ₂ ⇒ HC
It can be seen that it is necessary to use a basic aqueous solution having a pH of 9 or more in order to promptly carry out the dissolution reaction of oO ₂ ⁻ and form a dense conductive matrix.

[Preliminary Experiment 2: Oxidation Degree of Co (OH) ₂ Powder in Basic Aqueous Solution of Various pH] Ammonium chloride of pH 8, 9, 10, 11, 12 or 13 kept at 25 ° C. 50 ml of aqueous sodium hydroxide solution, Co
1 g of (OH) ₂ powder was immersed for 30 minutes, filtered, washed with water, and vacuum dried for each Co (OH) ₂ powder, and the degree of oxidation was determined by the following method.

<Oxidation degree of Co (OH) ₂ powder> The above Co
The amount of Co (A) in the solution obtained by dissolving a certain amount of (OH) ₂ powder in concentrated hydrochloric acid was quantified by the atomic absorption method (step 1). In this step 1, Co (OH) ₂ is also C
Since the trivalent compound is also soluble in concentrated hydrochloric acid, the Co amount (A) is the total Co amount, that is, the total amount of divalent Co and trivalent Co. Further, a solution obtained by dissolving the same amount of Co (OH) ₂ powder in concentrated nitric acid was filtered, and the amount of divalent Co (B) in the filtrate was quantified by atomic absorption spectrometry (step 2). In this step 2, Co (OH) ₂ is dissolved in concentrated nitric acid, but the Co3 valent compound is not dissolved in concentrated nitric acid and remains on the filter paper. Therefore, the oxidation degree of the Co (OH) ₂ powder was calculated from the following formula. The results are shown in Figure 2.

Oxidation degree (%) of Co (OH) ₂ powder = {total Co amount (A) -2 valent Co amount (B)} × 100 / total Co amount (A)

FIG. 2 shows the oxidation degree of Co (OH) ₂ powder in basic aqueous solutions of various pHs, and the vertical axis shows the oxidation degree (%).
Is a graph showing the pH of the ammonium chloride-sodium hydroxide aqueous solution on the abscissa. As shown in the figure, when the pH exceeds 12, the Co (OH) ₂ powder is rapidly oxidized and the oxidation degree is increased. Soar. From this, it is understood that it is necessary to use a basic aqueous solution having a pH of 12 or less in order to obtain a mixed powder having a small content of inert trivalent cobalt (CoHO ₂ ) and excellent conductivity.

(Examples and Comparative Examples) [Preparation of Active Material Powder] pH of 8 at 25 ° C.
Ni (OH) ₂ was added to 1000 ml of 9, 10, 11, 12 or 13 ammonium chloride-sodium hydroxide aqueous solution.
90 g of powder and 10 g of Co (OH) ₂ powder were added,
After stirring and mixing for 60 minutes, the mixture was filtered and vacuum dried to prepare mixture powders (active material powders) A, B, C, D, E and F in order. This manufacturing method is called a manufacturing method.

Further, 27.0 g of cobalt sulfate was added to water (25
Nitrogen to 1000 ml of cobalt aqueous solution
90 g of (OH) ₂ powder was added, and a 1 mol / liter sodium hydroxide aqueous solution was added to adjust the pH of the liquid to 8, 9, 10, and 1.
Add dropwise while stirring and mixing until 1, 12 or 13.
After stirring and mixing for 60 minutes, the mixture is filtered, washed with water, dried in vacuum, and coated powder (active material powder) P, Q, R, S, T, in order.
U was made. This manufacturing method is called a manufacturing method. This production method is a production method according to the method disclosed in JP-A-62-234867.

The bulk specific gravity of each active material powder is determined according to JIS K-51.
The bulk specific gravity of the active material powder and the bulk specific gravity of the nickel hydroxide powder (raw powder) used as a raw material (1.6
The value of the ratio to (0) (bulk specific gravity ratio) was calculated by the following formula. The results are shown in Fig. 3.

Bulk specific gravity ratio of active material powder = bulk specific gravity of mixture powder or coating powder / bulk specific gravity of nickel hydroxide powder (1.6
0)

In FIG. 3, the bulk specific gravity ratio of each active material powder, the vertical axis represents the bulk specific gravity ratio, and the horizontal axis represents ammonium chloride used.
It is a graph showing the pH of an aqueous sodium hydroxide solution or an aqueous sodium hydroxide solution, and from the figure, regardless of the pH, the active material powder having a bulk specific gravity ratio of 0.8 or more can always be obtained according to the production method. In contrast, it is difficult to obtain an active material powder having a bulk specific gravity ratio of 0.8 or more by the production method.

[Preparation of Nickel Electrode] 80 parts by weight of each active material powder and 20 parts by weight of a 1% by weight methylcellulose aqueous solution were kneaded to prepare a paste, and this paste was nickel-plated metal foam (porosity 95%; average). Particle size 200μ
m) was filled in a porous body (alkali resistant substrate), dried and molded to prepare a nickel electrode.

[Assembly of Alkaline Storage Battery] Each nickel electrode is used as a positive electrode, a known paste type cadmium electrode having a sufficiently large electrochemical capacity with respect to each nickel electrode is used as a negative electrode, a polyamide nonwoven fabric is used as a separator, and water is used as an electrolytic solution. AA-sized nickel-cadmium storage batteries A, B and C were prepared by using strong alkaline aqueous solutions (specific gravity = 1.285) containing potassium oxide, sodium hydroxide and lithium hydroxide in a weight ratio of 8: 1: 1. , D, E, F
And P, Q, R, S, T, U (theoretical capacity: 700 mA
h) was assembled. The sign of each storage battery represents the sign of the active material powder used.

[Charge / Discharge Cycle Test] Each nickel-cadmium storage battery was subjected to a charge / discharge cycle test in which one cycle includes a process of charging to a depth of 160% at 0.1C and then discharging to 1.0V at 1C. The battery capacity at the cycle was calculated. The results are shown in Fig. 4.

FIG. 4 is a graph showing the battery capacity at the 10th cycle of each nickel-cadmium storage battery, with the vertical axis representing the battery capacity and the horizontal axis representing the pH during active material powder preparation. The battery capacity on the vertical axis is p when the active material powder was produced.
It is shown by an index with the battery capacity of the nickel-cadmium storage battery C in which H is 10 as 100. From the figure,
To obtain a high capacity nickel-cadmium battery,
It can be seen that the pH of the basic aqueous solution used when mixing the Ni (OH) ₂ powder and the Co (OH) ₂ powder needs to be 9 to 12.

[Relationship between Co (OH) ₂ powder content of mixed powder and battery capacity] In the manufacturing method, the mixing ratio of Co (OH) ₂ powder in the mixed powder was 0, 1, 2, 3,
Co (OH) was obtained in the same manner as in the previous example except that the content was changed to 4, 6, 8, 10, 12, 14, 15, 16% by weight.
Active material powders having different content ratios of the _two powders were produced.

Next, a nickel-cadmium storage battery was prepared in the same manner as in the previous example except that these active material powders were used, and a charge / discharge cycle test was conducted under the same conditions as above, and the 10th cycle of each storage battery was performed. The battery capacity of
The relationship between the content ratio of the o (OH) ₂ powder and the battery capacity was investigated. Results are shown in FIG.

In FIG. 5, the vertical axis represents battery capacity and the horizontal axis represents C.
It is the graph which took and showed the content rate (weight%) of o (OH) ₂ powder. The battery capacity on the vertical axis is Co (OH)
₂ The battery capacity is 10 when the content of powder is 10% by weight.
It is shown by an index of 0. From the figure, in order to obtain a high capacity alkaline storage battery, Co (O
It can be seen that the H) ₂ powder content is preferably 3 to 15% by weight.

In the above embodiment, Ni (OH) ₂ powder and C
The case of using a mixed powder of o (OH) ₂ powder has been described as an example, but a mixed powder of a solid solution powder containing Ni (OH) ₂ as a main component and Co (OH) ₂ powder is used. It was confirmed that the same excellent effect was exhibited by applying the present invention in the above.

[0036]

In the non-sintered nickel electrode according to the present invention, since the mixed powder having high conductivity and large bulk specific gravity is used as the active material powder, the active material utilization rate and the active material packing density are high. Are both high. Therefore, by using the electrode of the present invention as the positive electrode, it is possible to obtain an alkaline storage battery having a large battery capacity.

[Brief description of drawings]

FIG. 1 shows Co (O 2) for basic aqueous solutions of various pH.
3 is a graph showing the solubility of H) ₂ powder.

FIG. 2 Co (OH) in basic aqueous solutions of various pH
₂ is a graph showing the degree of oxidation of _two powders.

FIG. 3 is a graph showing the bulk specific gravity ratios of the active material powders (mixture powder and coating powder) produced in the examples.

FIG. 4 is a graph showing the relationship between pH and battery capacity during production of active material powder.

FIG. 5 is a graph showing the relationship between the content ratio of Co (OH) ₂ powder in the mixed powder and the battery capacity.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuhiko Niiyama 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Koji Nishio 2-5 Keihan Hondori, Moriguchi City, Osaka Prefecture No. 5 In Sanyo Electric Co., Ltd. (72) Inventor Toshihiko Saito 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (56) Reference JP-A-61-49374 (JP, A) JP Flat 2-103859 (JP, A) Special Table Flat 5-500730 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01M 4/32 H01M 4/26 H01M 4/52

Claims (4)

(57) [Claims] 1. A non-alkaline battery for non-alkaline batteries, which is prepared by filling an alkali resistant substrate with Ni (OH) ₂ powder or a mixed powder of solid solution powder containing Ni (OH) ₂ as a main component and Co (OH) ₂ powder. In the sintered nickel electrode, the mixture powder is Ni (OH) in a weakly basic solution of pH 9-12.
_A non-sintered nickel electrode for an alkaline storage battery, which is obtained by mixing ₂ powders or the solid solution powder and the Co (OH) ₂ powder. 2. The non-sintered nickel electrode for an alkaline storage battery according to claim 1, wherein the mixed powder contains 3 to 15 wt% of the Co (OH) ₂ powder. 3. In a weakly basic solution having a pH of 9 to 12, Ni
An active material for an alkaline storage battery, comprising a mixture powder obtained by mixing a solid solution powder containing (OH) ₂ powder or Ni (OH) ₂ as a main component and Co (OH) ₂ powder. 4. The active material for an alkaline storage battery according to claim 3, wherein the mixed powder contains 3 to 15% by weight of the Co (OH) ₂ powder.