JPH09306487A - Manufacture of positive electrode active material for alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a storage battery positive electrode material of high capacity and superior high-temperature charging efficiency from high density compound metal oxide, which is obtained by continuously reacting respective solutions of Ni salt, two kinds of dissimilar metal salts, ammonia and alkali with each other under prescribed conditions. SOLUTION: Nickel salt solution, dissimilar metal salt solution, anmonium ion solution whose adding rate is 2mol or more in relation to these metal salt 1mol, and alkali solution whose adding rate is 1.9-2.3mol in relation to these metal salt 1mol are independently and simultaneously introduced to a reaction tank. Its pH is controlled to 11-13, the temperature, 30-60 deg.C, and the mean residence time, 20-50 hours and the liquid containing compound metal oxide particles is continuously taken out as an overflow while stirring. There are two kinds in the dissimilar metal salts, one of Co, Zn, and Cd salts or more, and one of Mn, Al, V, Cr, Fe, Cu, Ge, Nb, Mo, Ag, W, Sn, Sb, Ca, Y, Ti, Sr, Bi, and rare earth metal salts or more, and the both can be independently fed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a positive electrode active material for an alkaline storage battery.

[0002]

2. Description of the Related Art In recent years, portable devices have been increasingly miniaturized, and inevitably, it has been desired to increase the energy density of small secondary batteries which are the power source thereof. In addition, since the applications of the devices are diversifying, a battery having stable performance in a wide temperature range, especially at a high temperature, is desired.

Conventionally, nickel oxide has been used as the main active material of the positive electrode for alkaline storage batteries. As a method for producing the nickel oxide powder, an aqueous nickel salt solution is caused to act on an alkaline aqueous solution such as sodium hydroxide to cause precipitation.
Then, a method of aging and crystal growth followed by crushing by a mechanical method was adopted, but there was a problem that it was difficult to obtain a high packing density because the manufacturing method was complicated and the powder shape was irregular. .

However, Japanese Patent Publication No. 4-80513 proposes a method of causing ammonia to act on a nickel salt aqueous solution to form an ammonium complex of nickel and growing nickel hydroxide in an alkaline aqueous solution. According to this method, a continuous production method is possible and the cost can be reduced, and high density packing is possible because the particle shape is close to spherical, but it is possible to charge by using high density particles grown to several tens of μm as an active material. There was a problem of reduced efficiency.

On the other hand, attempts have been made to improve it by adding Co and its divalent oxide powder, but further improvement of the positive electrode characteristics, for example, (a) utilization rate in a high temperature atmosphere. Improvement, (b) suppression of positive electrode swelling, and (c)
It is strongly desired to improve the active material itself for the purpose of increasing the energy density.

In order to solve these problems (a) and (b), Japanese Patent Publication No. 3-50384 has conventionally adopted a method of adding Cd and Co into the crystal of the active material. In view of increasing environmental awareness of battery components, a cadmium-free battery has been demanded, and a method of adding Zn or the like as an example of a metal element replacing cadmium has been proposed.

On the other hand, in order to increase the energy density of (c), an active material having a high reaction order is required. As described above, the positive electrode active material of the alkaline storage battery currently industrially used is nickel oxide, and the reaction is said to be a one-electron reaction zone, but other metal elements are contained inside the crystal of nickel oxide. It has been reported that active materials with high reaction order can be obtained by addition (Paper: C. Faure and C. De
lmas, J, Power Sources, 36 (1991) 497-506 etc.).

From the above, interest in the composite metal oxide in which a metal element other than Ni is added inside the nickel oxide crystal is increasing.

[0009]

A method for producing a composite metal oxide in which Co, Zn and Cd are added as a metal other than Ni is to mix a predetermined amount of Ni salt and each metal salt and dissolve it in water. A method has been proposed in which ammonia is allowed to act on the resulting aqueous solution to form an ammonium complex, and then an alkaline aqueous solution is added to carry out a neutralization reaction. In this case, the reagent concentration, p
Conditions such as H, temperature, and residence time were almost the same as those used in the nickel oxide production method.

However, when there are various kinds or a large amount of metals other than Ni as the metal oxide, depending on the kind of the metal salt, a salt having extremely low solubility is formed when mixed with another metal salt aqueous solution, or ammonium is formed. It was not possible to obtain high-density particles having a uniform composition, because the particles would precipitate due to pH changes when ions were made to act.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a production method capable of obtaining a high-density metal oxide.

[0012]

To achieve the above object, the present invention provides an aqueous solution of Ni salt, an aqueous solution containing at least one metal salt of Co, Zn and Cd, Mn and A.
l, V, Cr, Fe, Cu, Ge, Nb, Mo, Ag,
W, Sn, Sb, Ca, Y, Ti, Sr, rare earth metal,
An aqueous solution containing one or more metal salts selected from Bi, an aqueous solution containing ammonium ions, and an alkaline aqueous solution are added to a reaction system controlled to have a constant pH and temperature so that a constant concentration and a constant residence time are obtained. The mixed metal oxide is continuously stirred and simultaneously supplied to continuously obtain the composite metal oxide.

[0013]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a reaction apparatus for carrying out the present invention. In a reaction tank 1, a nickel salt aqueous solution supply line 2, a dissimilar metal salt aqueous solution supply line 3, an ammonium ion supply line 4, and an alkaline aqueous solution supply. Lines 5 and 5 are independently introduced. The alkaline aqueous solution supply line 5 is provided with a pH stat 6 to adjust the alkaline aqueous solution.

The different metal salt aqueous solution supply line 3 is provided with Co,
A line for supplying an aqueous metal salt solution of Zn and Cd, Mn,
Al, V, Cr, Fe, Cu, Ge, Nb, Mo, A
A line for supplying an aqueous solution of a metal salt of g, W, Sn, Sb, Ca, Y, Ti, Sr, Bi, or a rare earth metal may be independent.

The reaction vessel 1 is provided with a constant temperature vessel 7, and a line 8 for taking out the synthesized composite oxide particle-containing liquid is provided at the upper part so that it can be overflowed and continuously taken out. There is. A stirring blade 10 connected to a stirring device 9 is provided inside the reaction tank 1 to keep various conditions inside the reaction tank 1 constant.

[0016]

【Example】

(Example 1) 2 mol / l nickel sulfate aqueous solution, 0.
25 mol / l manganese sulfate aqueous solution, 0.1 mol / l
1 zinc sulfate aqueous solution, 0.05 mol / l cobalt sulfate aqueous solution, and 4.8 mol / l ammonia aqueous solution were prepared. Then, while maintaining these solutions at 50 ° C., they were simultaneously supplied into a 3 liter reaction tank 1 at an average rate of 0.5 ml / min, so that the temperature inside the tank was kept constant at 50 ° C. so that the solution became homogeneous quickly. 4.8 mol / l with stirring
Was added at an average of 0.5 ml / min so as to keep the pH value in the reaction tank within the range of 12.5 ± 0.2.

Here, the addition ratio of various aqueous solutions is Ni,
When the total amount of Mn, Co and Zn salts was 1 mol, the amount of each of aqueous solution sodium and ammonia was 2 mol. As a result, a composite metal oxide composed of Ni, Mn, Co, and Zn was produced, and this was overflowed from the upper part of the reaction tank and continuously taken out, and after continuously operating for 30 hours, an evaluation sample was taken.

From the result of the quantitative analysis, it was found that the molar ratio of Ni, Mn, Co and Zn in the obtained composite metal oxide powder was almost the same as the mixing ratio of the starting materials. Further, since no peak indicating the presence of impurities was observed in the X-ray diffraction pattern, it was suggested that the crystal had a uniform composition. Further, it was confirmed from the SEM photograph that the particles were spherical particles of high density and uniform in particle size.

Comparative Example 1 An evaluation sample was obtained in the same manner as in Example 1 except that the aqueous ammonia solution was not added. As a result, the obtained oxide powder formed an irregularly-shaped aggregate having a wide particle size distribution.

(Comparative Example 2) The concentration of the sodium hydroxide aqueous solution was 4.3 mol / l (about 1.8 mol of sodium hydroxide to 1 mol of metal salt), and the pH value was 10.5. A sample for evaluation was obtained in the same manner as in 1. As a result, the obtained composite metal oxide was a particle having a wide particle size distribution and being very bulky.

Comparative Example 3 The concentration of the aqueous sodium hydroxide solution was 6.0 mol / l (about 2.5 mol of sodium hydroxide to 1 mol of metal salt), and the pH value was 13.5. A sample for evaluation was obtained in the same manner as in 1. As a result, the obtained composite metal oxide formed an aggregate of fine particles.

Comparative Example 4 A sample for evaluation was obtained in the same manner as in Example 1, except that the concentration of the aqueous ammonia solution was 4.3 mol / l (about 1.8 mol of ammonium ion to 1 mol of metal salt). It was As a result, the obtained composite metal oxide particles were bulky particles having an irregular shape.

Comparative Example 5 An evaluation sample was obtained in the same manner as in Example 1 except that the temperature inside the bath was 20 ° C. As a result, the obtained composite metal oxide particles were spherical particles having a uniform particle size, but were very bulky with many voids.

(Comparative Example 6) An evaluation sample was obtained in the same manner as in Example 1 except that the temperature inside the bath was 80 ° C. As a result, the obtained composite metal oxide was an aggregate of fine particles.

Comparative Example 7 An evaluation sample was obtained in the same manner as in Example 1, except that the supply amount was controlled so that the residence time was 15 hours. As a result, the obtained oxide particles had a small particle size as a whole, and the surface was mainly composed of a curved surface and had a roundness as a whole, but was not spherical.

Example 1 and Comparative Examples 1, 2, 3, 4,
The characteristics of the composite oxide powders obtained in Nos. 5, 6 and 7 are shown in (Table 1). As is clear from this result, Ni-Mn of the example
The -Zn-Co mixed metal oxide powder had a higher tap density than the mixed metal oxide powder of the comparative example.

[0027]

[Table 1]

(Example 2) Ni-Mn shown in Example 1
Using a method similar to that of the —Zn—Co mixed metal oxide production method, (a) Mn, (b) Al, (c) V,
(D) Cr, (e) Fe, (f) Cu, (g) Ge,
(H) Nb, (i) Mo, (j) Ag, (k) W,
(L) Sn, (m) Sb, (n) Ca, (o) Y,
(P) Ti, (q) Sr, (r) La and (s) Bi were added to obtain a composite metal oxide. As a result, it was confirmed that the obtained composite metal oxide was spherical particles having a uniform composition and a high density, as in Example 1.

The tap density and average particle diameter of the obtained composite metal oxide are summarized in (Table 2). From these results, all showed high tap density of 1.9 g / cm ³ or more.

[0030]

[Table 2]

Example 3 First, 3 l of a 4.8 mol / l ammonia aqueous solution and 3 l of a 2 mol / l nickel sulfate aqueous solution were mixed, and then this mixed aqueous solution and 0.25 were mixed.
3 mol / l manganese sulphate, 0.1 mol / l zinc sulphate aqueous solution, 0.05 mol / l cobalt sulphate aqueous solution at a rate of 0.5 ml / min on average while keeping at 50 ° C.
The reaction mixture was independently and simultaneously supplied to a reaction tank of 1 l, and while the temperature inside the tank was kept constant at 50 ° C, while stirring the solution so as to be rapidly uniform, a 4.8 mol / l sodium hydroxide aqueous solution was added. The average pH of 0.5 ml / min was added so that the pH value in the reaction vessel was kept within the range of 12.5 ± 0.2. Here, the addition ratio of various aqueous solutions is Ni, Mn, C
When the total amount of o and Zn salts was 1 mol, sodium hydroxide and ammonia were each adjusted to 2 mol.

As a result, a composite metal oxide composed of Ni, Mn, Co and Zn is produced, which is continuously taken out by overflowing it from the upper part of the reaction tank and continuously operated for 30 hours, and then a sample for evaluation is taken. did. Example 1
Similarly to the above, it was confirmed that the obtained composite metal oxide was a spherical particle having a uniform composition and high density and uniform size.

(Comparative Example 8) First, 2 mol / l of nickel sulfate was added to 1 liter of a 4.8 mol / l aqueous ammonia solution.
0.25 mol / l manganese sulfate, 0.1 mol / l
1 zinc sulphate aqueous solution and 0.05 mol / l cobalt sulphate aqueous solution were added respectively, and then this mixed aqueous solution was supplied to a 3 liter reaction tank at an average rate of 0.5 ml / min while maintaining at 50 ° C. While keeping the internal temperature constant at 50 ℃, stir it quickly and evenly.
An aqueous solution of 4.8 mol / l sodium hydroxide was added on average to 0.
The pH value in the reaction tank was 12.5 ± at a rate of 5 ml / min.
It was added so as to keep in the range of 0.2.

However, when ammonia was allowed to act on the aqueous metal salt solution, zinc oxide and manganese oxide were precipitated, and the pump was clogged, making subsequent operations difficult. In addition, this method cannot control the composition of the target oxide of a plurality of metal elements. As mentioned above,
Since the stable pH range varies depending on the type of metal ion,
It is inappropriate to apply ammonia to the aqueous solution of metal salt other than Ni salt in advance.

Comparative Example 9 First, a 2 mol / l nickel sulfate aqueous solution, a 0.25 mol / l calcium nitrate aqueous solution, a 0.1 mol / l zinc sulfate aqueous solution, 0.05 m
1 liter each of ol / l cobalt sulfate aqueous solution was mixed, and then the mixed aqueous solution and 4.8 mol / l ammonia aqueous solution were kept at 50 ° C. to give an average of 0.5 ml / m.
It is supplied at a rate of in into the reaction vessel 1 of 3 liters, and the temperature in the vessel is set to 5
While keeping the temperature constant at 0 ° C., the pH value in the reaction tank was adjusted to 1 at an average of 0.5 ml / min with a 4.8 mol / l sodium hydroxide aqueous solution while stirring quickly and uniformly.
It was added so as to keep it within the range of 2.5 ± 0.2. However, when each metal salt aqueous solution was mixed, CaSO
₄ was precipitated and the target Ni-Ca-Zn-Co mixed metal oxide could not be obtained. As mentioned above,
The solubility and reaction rate differ depending on the type of metal salt, and premixing is inappropriate. Therefore, in order to obtain a composite metal oxide having a uniform composition, it is preferable to independently supply the respective metal salt aqueous solutions so that the concentration is always constant in the reaction system.

Next, among the composite metal oxides obtained in Examples 1 and 2, (a) Mn, (b) Al,
(L) Sn, (m) Sb, (n) Ca, (o) Y,
The results of examining the utilization rate as an electrode active material and the oxygen generation overvoltage by forming a positive electrode using (p) Ti and (q) Sr are shown below.

The positive electrode is composed of the respective composite metal oxides 100.
8 g of metallic cobalt was mixed with g, and water was added to form a paste. A substrate made of foam metal (thickness: 1.3 m
m, porosity of about 95%), dried and press-pressed under a fixed condition to obtain a metal foam positive electrode. Using these positive electrodes, a hydrogen storage alloy electrode having a large excess capacity than the positive electrode was used as the negative electrode, and an aqueous potassium hydroxide solution having a concentration of 30 wt% was used as the electrolytic solution to assemble an open model cell.

After charging the model cells with a current equivalent to 0.1 C for 15 hours, 0.9 V was applied at a current equivalent to 0.2 C.
Then, the discharge capacity was measured, and the respective utilization factors were calculated from the calculated discharge capacity and the theoretical electric capacity obtained from the nickel hydroxide in the active material and the equivalent amount of the different metals. The overvoltage of oxygen generation was measured by measuring the potential with respect to the negative electrode after charging for 13 hours with a current equivalent to 0.1 C, and the evaluation was compared with the potential of the nickel hydroxide electrode. 2 obtained as above
The utilization rate and oxygen overvoltage at 0 ° C. and 40 ° C. are summarized in (Table 3).

[0039]

[Table 3]

As shown in (Table 3), all of the multi-metal oxides obtained by the production method of the present invention showed a high utilization rate, but especially when Mn, Al, Sn, and Sb were added, 100% was obtained.
The usage rate was over%. In addition, Ca, Y, Ti, Sr
With the addition of, a high value was obtained in the utilization factor at high temperature.
This is due to their high oxygen evolution overvoltage, as shown in Table 3.

In the present embodiment, the amount of the alkaline aqueous solution used is preferably proportionally supplied so as to be 1.9 to 2.3 mol with respect to 1 mol of the Ni salt and the metal salt other than the Ni salt. It is preferable that the amount of the aqueous solution containing is used in proportion to 2 mol or more per 1 mol of the nickel salt and the different metal salt. PH of reaction system is 1
1 to 13 are preferable, and the temperature of the reaction system is preferably 30 to 60 ° C. The residence time is preferably 20 to 50 hours.

The amount contained in the nickel oxide powder is preferably 0.5 to 20.0% by weight. That is,
If it is less than 0.5% by weight, the effect of improving the properties is not sufficient, and if it is more than 20.0% by weight, it becomes difficult to obtain a powder having a uniform composition even under the above conditions, which is not preferable.

Under these conditions of reagent concentration ratio, pH, temperature, residence time, etc., oxide powders of a plurality of metal elements having a tap density of 1.9 g / cm ³ or more can be obtained, and electrodes are formed. In this case, it is possible to achieve the same packing density as that of the positive electrode using the current nickel oxide as the active material.

Metals other than Ni include Zn, Cd, and C.
o, at least one or more metals, and Ca, Y, and Ti, which are mainly expected to have an effect of improving high-temperature charging efficiency.
Sr, rare earth metal, Bi, or Mn, Al, V, Cr, Fe, Cu, Ge, which is expected mainly to improve the reaction order,
It is preferable to select one or more selected from Nb, Mo, Ag, W, Sn, and Sb.

[0045]

As described above, according to the present invention, the nickel salt aqueous solution, the dissimilar metal salt aqueous solution, the ammonium ion-containing aqueous solution, and the alkali metal hydroxide aqueous solution having a predetermined concentration ratio are kept constant at a predetermined pH and temperature. High-density composite metal oxides can be obtained by simultaneously supplying to a reaction system controlled at 1, while stirring so as to have a predetermined residence time. When these are used as the positive electrode material for alkaline storage batteries, it is possible to improve the characteristics such as high capacity or high temperature charging efficiency.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a reaction apparatus used in one embodiment of the present invention.

[Explanation of symbols]

 1 Reaction Tank 2 Nickel Salt Aqueous Solution Supply Line 3 Dissimilar Metal Salt Aqueous Solution Supply Line 4 Ammonium Ion Supply Line 5 Alkaline Aqueous Solution Supply Line 6 pH Stat 7 Constant Temperature Tank 8 Complex Oxide Particle-Containing Liquid Extraction Line 9 Stirrer 10 Stirrer

Claims (4)

[Claims] 1. A first aqueous solution which is an aqueous solution of Ni salt, and C
a second aqueous solution containing a salt of at least one metal selected from o, Zn and Cd, and Mn, Al, V, Cr, Fe and C
u, Ge, Nb, Mo, Ag, W, Sn, Sb, Ca,
Composite metal using a third aqueous solution containing a salt of one or more metals selected from Y, Ti, Sr, rare earth metals and Bi, a fourth aqueous solution which is an alkaline aqueous solution and a fifth aqueous solution containing ammonium ions In the method for producing an oxide, the amount of the alkali metal in the fourth aqueous solution is 1.9 with respect to 1 mol of the total amount of metal ions in the first, second and third aqueous solutions.
~ 2.3 mol, each ammonium ion in the fifth aqueous solution is adjusted to 2 mol or more with respect to the total amount of 1 mol of metal ions in the first, second and third aqueous solutions, The pH is 11 to 13 and the temperature is 30 to 60 ° C., and the mixture is simultaneously supplied to a reaction tank controlled to be constant, and the grown particles are taken out while stirring so that the average residence time is 20 to 50 hours. A method for producing a positive electrode active material for an alkaline storage battery, which comprises continuously obtaining a composite metal oxide. 2. The method for producing a positive electrode active material for an alkaline storage battery according to claim 1, wherein all the aqueous solutions are independently adjusted and then simultaneously supplied to the reaction tank. 3. A mixed aqueous solution of a first aqueous solution and a fifth aqueous solution, a mixed aqueous solution of a second aqueous solution and a third aqueous solution, and a fourth aqueous solution.
The method for producing a positive electrode active material for an alkaline storage battery according to claim 1, wherein the aqueous solution and the aqueous solution are each independently adjusted and then simultaneously supplied to the reaction tank. 4. The method for producing a positive electrode active material for an alkaline storage battery according to claim 1, wherein the composite metal oxide is an oxide in a eutectic state and / or a solid solution state of each metal.