JP2003187797A - Positive pole active material for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reform powder to powder with high fluidity and packing property without affecting a battery characteristic by a positive pole active material of Ag-Bi-(M)-O system (M is Mn, Ni or Co or the like). <P>SOLUTION: The positive pole active material for the battery is powder comprising a particle containing the crystal of a compound comprising Ag, Bi and O (oxygen) or the crystal of a compound comprising Ag, Bi and M (M represents a transition metal), wherein Bi is dispersed in the whole area of the particle, and the angle of rest of the powder is not larger than 50 degree. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode active material for alkaline batteries.

[0002]

2. Description of the Related Art Conventionally, silver oxide batteries have been widely used as alkaline batteries (commonly called button batteries) mounted on watches, measuring instruments, cameras and the like. A silver oxide battery is generally constructed by using silver oxide (Ag ₂ O) as a positive electrode active material, zinc powder as a negative electrode active material, and an alkaline solution such as an aqueous solution of KOH or NaOH as an electrolytic solution. Although silver is an expensive material, silver oxide is considered to be an indispensable positive electrode active material when high capacity is required even if it is small. For this reason, most button batteries are composed of silver oxide batteries. It is no exaggeration to say that. The positive electrode active material may be referred to as a positive electrode active material or a positive electrode active material, and similarly, the negative electrode active material may be referred to as a negative electrode active material or a negative electrode active material.

As mentioned above, silver is an expensive substance. Therefore, the inventors of the present invention, as a cost reduction measure of the positive electrode active material for a battery made of silver oxide, in Japanese Patent Application No. 2001-285788 and Japanese Patent Application No. 2001-274194 require Ag, Bi and O (oxygen). Or a crystal of a compound consisting of Ag, Bi, M (M is Ni, Co or M
The present invention has proposed a positive electrode active material for a battery, which comprises particles having a compound of O and a transition metal such as n) and having Bi dispersed throughout the particle. Even if the Ag content is 75% by weight or less, this positive electrode active material is economical because it has a discharge capacity equal to or higher than that of the conventional silver oxide.

[0004]

[Problems to be Solved by the Invention] Japanese Patent Application No. 2001-285
Although the positive electrode active material proposed in Japanese Patent Application No. 788 and Japanese Patent Application No. 2001-274194 has a small amount of Ag and is low in cost, it tends to be a powder having a small particle size (0.1 to 10 μm) due to its manufacturing history. There has been a demand for further improvement in the handleability of the body.

That is, when handling as a positive electrode active material or manufacturing a battery, it is inevitable to weigh and load the powder, but in such a case, less dust is generated and fluidity is low. Good powder characteristics such as good filling property were required.

Therefore, the present invention is based on the previously proposed Ag-
Further improving the powder characteristics of the Bi- (M) -O-based positive electrode active material for a battery, more specifically, improving the positive electrode active material having less dust generation and excellent fluidity and filling property. The purpose is to do.

[0007]

In order to solve the above-mentioned problems, the present inventors have previously proposed Ag-Bi- (M) -O.
Various granulation methods were applied to powders composed of fine particles of a series of compounds, and attempts were made to improve the powder properties without substantially changing the composition or chemical properties of the powders. .
As a result, among many granulation methods, when the spray granulation method or the crush granulation method is adopted and the average particle size is larger than 10 μm, preferably larger than 50 μm, the angle of repose becomes 50 degrees or less, and the above-mentioned problems occur. It turned out that it could be solved all at once.

That is, according to the present invention, as a positive electrode active material which generates little dust and has excellent fluidity and filling properties, a crystal of a compound composed of Ag, Bi and O (oxygen), or Ag, Bi, M ( M represents a transition metal) and a compound crystal of O and has Bi
Is a powder consisting of particles in which the angle of repose is 5
Provided is a positive electrode active material for a battery, which is made of powder having a temperature of less than 0 degree.
This powder has an average particle size of more than 10 μm, preferably more than 50 μm, 5 mm or less, preferably 1 mm or less, a bulk density of more than 1.0 to 6.3 g / cm ³ , and a tap density of more than 1.5 It is 6.3 g / cm ³ .

Here, the angle of repose is a funnel for ordinary chemical experiments having a hopper portion on which a filter paper is placed and a nozzle portion vertically descending from the center, and the hopper portion has a diameter of 60 mm.
Fix a funnel with a nozzle length of 65 mm and a nozzle inner diameter of 6 mm at a position where the tip of the nozzle is at a height of 75 mm from the horizontal stand, and add 100 g of powder to the hopper of the funnel, all of which is on the horizontal stand. The angle of repose of the deposited powder (which becomes a cone) when dropped from the horizontal is defined as the measured value.

Further according to the present invention, a crystal of a compound consisting of Ag, Bi and O (oxygen), or Ag, Bi,
A powder comprising particles of a compound comprising M (M represents a transition metal) and O and having Bi dispersed throughout the particle, and having a specific surface area measured by the BET method of 0.1.
Provided is a positive electrode active material for a battery, which comprises ^{1 to} 30 m ² / g of powder.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the present invention is directed to Japanese Patent Application No.
01-285788 and Japanese Patent Application No. 2001-27419.
It is intended to impart to the positive electrode active material powder composed of the particles of the Ag-Bi- (M) -O-based compound proposed in No. 4 the property that dust is unlikely to be generated and the fluidity and the filling property are excellent. To do. Therefore, Japanese Patent Application No. 2001-28
The description of the composition, properties, manufacturing method, etc. of the powder described in the respective specifications and drawings of Japanese Patent No. 5788 and Japanese Patent Application No. 2001-274194 can be directly incorporated as the description of the powder targeted by the present invention.

That is, the powder for the positive electrode active material for alkaline batteries used in the present invention is basically composed of Ag, Bi,
The particles are composed of the four elements (M) and O, and are characterized in that compound crystals are contained in the particles and Bi is dispersed throughout the particles. M is one or more elements selected from transition elements, and is added for the purpose of keeping the open circuit voltage, which is a battery characteristic, low. For example, Ni, Co, Mn.
Is mentioned. M may not be added depending on the case.

The compound crystals in the particles are Ag-Bi-
It is a (M) -O-based compound, and is preferably characterized in that it does not have crystals of Ag ₂ O or AgO compounds in the particles, and even if it does, it only has impurities. This particle powder has a composition in which the molar ratio Ag / (Bi + M) is 1 or more and 7 or less, preferably 2 or more and 5 or less and the oxygen content is 5% by weight or more. Ag content is 80% by weight or less, preferably 75% by weight or less, more preferably 70% by weight or less.
It can be less than or equal to 60% by weight, in some cases less than or equal to 60% by weight. The preferred composition range is, in% by weight, A
g: 45 to 75%, Bi: 10 to 40%, M: 0 to 10
%, O (oxygen): 5 to 15%, the balance: inevitable impurities. The average particle size of the particles is in the range of 0.1 to 10 μm.

Such a positive electrode active material can be manufactured by the following steps. (1) A step of reacting each salt of silver, bismuth, and transition metal with an alkali in water to obtain a neutralized precipitate (referred to as a neutralization step),
(2) a step of adding an oxidizing agent to the obtained suspension of neutralized starch to oxidize the starch (oxidation step), (3) solid-liquid separation of the suspension of the oxidized starch, Process for collecting things (separation process), (4)
A step of washing and drying the recovered oxidized starch, (5) a step of crushing the obtained dried material into a powder. Each step will be described below.

[Neutralization Step] As a salt of silver, bismuth or a transition metal, silver nitrate, bismuth nitrate, nickel nitrate or the like can be typically used. A strong alkali (eg, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.) is used as the alkali. For the neutralization treatment, a method of adding an aqueous solution of a salt of silver, bismuth or a transition metal to an alkaline aqueous solution can be applied. The higher the alkalinity, the easier the reaction proceeds. The reaction temperature is preferably in the range of room temperature to 110 ° C., and stirring is preferably such that the neutralization reaction proceeds uniformly.

[Oxidation Step] Although the neutralization step can be performed simultaneously, it is preferable to perform the neutralization step and the oxidation step separately, and it is preferable to insert a temperature raising step between these steps. As the oxidant, an ordinary oxidant (eg KMnO) is used.
₄ , NaOCl, H ₂ O ₂ , K ₂ S ₂ O _8, Na ₂ S ₂ O ₈ ,
Ozone etc.) can be used. For the oxidation treatment, it is preferable that the temperature of the liquid is 50 ° C. or higher, preferably 70 ° C. or higher and the oxidizing agent is added under stirring. If the liquid temperature becomes too high, the decomposition of the oxidant proceeds, so the liquid temperature is preferably 110 ° C. or lower.
The amount of the oxidizing agent added may be an amount sufficient to increase the valences of silver, bismuth, and a transition metal, and is equivalent to or more than this change in valence, preferably about twice the equivalent.

[After Separation Step] Next, solid-liquid separation of the oxidized starch is performed. Before that, it is preferable to insert a step of aging the oxidized starch. This aging process
This is a treatment in which the suspension after the oxidation treatment is held at that temperature for about 10 to 120 minutes, and thereby it is possible to make the oxidized starch uniform. After filtering off the starch, it is washed with water and dried to obtain a black starch. The drying is preferably performed at a temperature of 50 to 200 ° C. If the temperature exceeds 200 ° C, the produced compound may decompose. The obtained dried product is crushed with a crusher to obtain a powder.

The powder thus obtained generally has a small average particle size of 0.1 to 10 μm as described above, and does not necessarily have good flowability and filling property. In order to improve this, in the present invention, this powder is treated by spray granulation or crush granulation.

In spray granulation, a slurry in which a powder is dispersed in a liquid medium such as water is sprayed in a high temperature air stream, and the slurry droplets come into contact with hot air, whereby the liquid in the slurry droplets is instantly evaporated. At the same time, the particles agglomerate and are granulated, and the disk method and nozzle method are known depending on the shape of the spray nozzle. A as the subject of the present invention
For powders composed of g-Bi- (M) -O compounds,
It has been found to be good to apply spray granulation by the disc method.

In the crushing and granulating method, a powder raw material is compression-molded at a high pressure to obtain a high-density powder compacting resistance, and the molded product is mechanically crushed and crushed, and then sized to a predetermined size. This is a method for obtaining granules of Sasa. The powder of Ag-Bi- (M) -O compound, which is the object of the present invention, tends to be a dense molded product when compression-molded at high pressure. It was found that if the particles were sized, a powder with different dimensions and properties from the raw powder could be obtained.

Therefore, by subjecting the powder to secondary treatment by spray granulation or crush granulation, the composition and morphology of the compound crystals of the original powder are maintained as they are and Bi is dispersed throughout the particle. A powder consisting of the granulated particles is obtained. The average particle size of the powder formed from the particles thus granulated is preferably more than 10 μm and 5 mm or less, and the angle of repose is less than 50 degrees. The lower the angle of repose, the better the fluidity of the powder. However, the Ag-Bi- (M) -O-based positive electrode active material according to the present invention has a repose angle of less than 50 degrees, and even 45 degrees or less, depending on the case. 40
Since it is less than 100 degrees, it is possible to perform precise weighing and cell filling, which are indispensable for battery manufacturing, with good workability.

Further, the bulk density of the granulated powder exceeds 1.0 to 6.3 g / cm ³ , and the tap density exceeds 1.5 to 6.
It can be set to ³ g / cm ³ , which contributes to high filling of the cell and the specific surface area can be set to 30 m ² / g or less by the BET method. This means that the content of fine powder is very low, which reduces the generation of dust.

Therefore, according to the present invention, a positive electrode active material composed of an Ag-Bi- (M) -O type compound having good workability and good filling property can be obtained, and the positive electrode active material, the negative electrode active material and the electrolyte can be obtained. Thus, an inexpensive and high-performance alkaline battery can be constructed.

[0024]

[Example] [Example 1] In the neutralization step described above, A
g / (Bi + Ni) molar ratio = 3, Bi / Ni molar ratio = 1, so that silver nitrate (AgNO ₃ ) and bismuth nitrate [Bi (NO
₃ ) ₃ ] and nickel nitrate [Ni (NO ₃ ) ₂ .6 H ₂ O] were weighed and dissolved to obtain an aqueous solution at a temperature of 50 ° C. (Ag + Bi + N
The mixture was added to an aqueous solution in which a molar ratio of sodium hydroxide was 10 times that of i) was dissolved under stirring to obtain a neutralized precipitate. The temperature of the suspension of the neutralized precipitate was raised to 90 ° C., and sodium peroxodisulfate (Na ₂ S ₂ O ₈ ) was added as an oxidant (Ag ⁺ , Bi
³⁺ , Ni ²⁺ ) was added to the suspension in an amount twice as much as the change in valence, and the suspension was oxidized. After the oxidation process is completed, the temperature is raised to 90 ° C for 30
After aging for holding for 1 minute, the precipitate was filtered off, washed with water and dried at 100 ° C, and the dried product was pulverized with a crusher to obtain a powder. This powder is called [intermediate powder].

A sample for measurement was sampled from the obtained intermediate powder, and its bulk density, tap density, angle of repose, particle size and specific surface area were measured, and the results are shown in Table 1. The fluidity of the intermediate powder, the degree of dust generation, and the packing property were evaluated, and the results are also shown in Table 1. These measurements were performed as follows.

Measurement of bulk density: diameter 15 mm, height 160
A mm test tube was filled with the powder, and it was determined from the measured values of the filling weight and the filling volume. Measurement of tap density: Powder was filled in the same test tube used for the measurement of bulk density, and the filling weight and the filling volume after tapping the filled powder 1000 times were determined. Measurement of angle of repose: Funnel for chemistry experiment, caliber 60m
m, nozzle length 65 mm, nozzle part inner diameter 6 mm,
The tip of the nozzle was fixed at a height of 75 mm from the horizontal table, and 100 g of powder was put into the hopper of the funnel.
The angle from the horizontal of the deposit was measured when all of them were deposited in a conical shape on the horizontal table. Measurement of particle size: by a laser diffraction method (particle size measuring device manufactured by Shimadzu Corporation). Measurement of specific surface area: BET method (manufactured by Kantachrome Co., Ltd.) was used.

Evaluation of fluidity: Fluidity is good when the angle of repose is 40 degrees or less (marked by ◯), acceptable when the angle of repose is more than 40 degrees and less than 50 degrees (△), and is not acceptable when it is greater than 50 degrees (marked x) ) Was evaluated in three stages. Evaluation of dust generation: Powder 2 in 100CC transparent plastic container
Put 5 g, shake 10 times, and visually observe the particles floating in the upper part of the container when left standing for 10 seconds. If no floating material is observed, it is good (marked with ○), and it becomes cloudy with floating material Those that were found to be defective (marked with x) and those that were slightly floating were recognized, but those that were not noticeable were evaluated as acceptable (marked with), and three-level evaluation was performed. Evaluation of packing property: Good packing property of bulk density of 2.0 g / cm ³ or more (circle), exceeding 1.0 g / cm ³ to 2.0 g / cm ³
Less than 1 is acceptable for packing (marked with Δ), and those with 1.0 g / cm ³ or less are considered for poor packing (marked with x), and three-level evaluation was performed.

As can be seen from the results in Table 1, the evaluation of the fluidity of the intermediate powder and the generation of dust was not always good.

Next, the intermediate powder was heated to a hot air temperature of 2 using a spray dryer FOC-16 manufactured by Okawara Kakoki Co., Ltd.
Spray granulation was performed at 00 ° C. The obtained granulated product is called [granulated powder]. Observation of the granulated powder by an electron microscope (SEM image) showed that most of them consisted of spherical particles of about 65 μm. A sample for measurement was sampled from the granulated powder, and its bulk density, tap density, angle of repose, particle size and specific surface area were measured, and the fluidity of the granulated powder, the degree of dust generation, and the packing property were evaluated. The results are also shown in Table 1.

As can be seen from the results shown in Table 1, the granulated powder has a high bulk density and a low angle of repose and has a good fluidity, and no dust is generated.

Example 2 Example 1 was carried out until an intermediate powder was obtained.
Was repeated. The obtained intermediate powder was compacted by using a roller compactor of WP160 manufactured by Turbo Industry Co., Ltd., and this molded product was manufactured by Nippon Granulator Co., Ltd. GR.
The granulated powder was obtained by crushing with N-1531. Here, the molding pressure of the roller compactor was set to 1.0 t / cm. The crushing with a granulator is performed in three stages, and the groove pitch of the first stage of the roll is 2 mm (roll clearance
0.35 mm), the groove pitch of the second stage of the roll is 1.2 mm
(Roll clearance 0.11 mm), The groove pitch of the third roll is 0.6 mm (Roll clearance 0.11 mm)
And

A sample for measurement was sampled from this granulated powder, the bulk density, tap density, angle of repose, particle size and specific surface area were measured, and the fluidity of the granulated powder, the degree of dust generation, and the packing property were evaluated. . The results are also shown in Table 1.

Further, the granulated powder was removed from particles having a size of 50 μm or less by using a sieve having an opening of 50 μm. A sample for measurement is sampled from the obtained powder on the sieve (referred to as sized powder 1),
The bulk density, tap density, angle of repose, particle size and specific surface area were measured, and the fluidity of the sized powder, the degree of dust generation, and the packing property were evaluated. The results are also shown in Table 1.

As is clear from the results shown in Table 1, also in this example, as in the case of Example 1, a positive electrode active material excellent in evaluation of fluidity, dust generation and packing property was obtained.

Then, the granulated powder was removed from particles having a size of 100 μm or less by using a sieve having a mesh size of 100 μm. A sample for measurement is sampled from the obtained powder on the sieve (referred to as sized powder 2), and its bulk density, tap density, angle of repose, particle size and specific surface area are measured, and the fluidity of the sized powder, Degree of dust generation,
The packing property was evaluated. The results are also shown in Table 1.

As can be seen from the results shown in Table 1, the sized powder has a higher bulk density and tap density, a lower specific surface area, and has a good evaluation of fluidity, dust generation and packing property. Was given.

[Comparative Example] In the neutralization step described above, A
g / (Bi + Ni) molar ratio = 3, Bi / Ni molar ratio = 0.5 so that silver nitrate (AgNO ₃ ) and bismuth nitrate [Bi
An aqueous solution in which (NO ₃ ) ₃ ] and nickel nitrate [Ni (NO ₃ ) ₂ .6 H ₂ O] were weighed and dissolved at a liquid temperature of 50 ° C (Ag + Bi
+ Ni) was added to an aqueous solution in which a molar ratio of 10 times the amount of sodium hydroxide was dissolved under stirring to obtain a neutralized precipitate.
The temperature of the suspension of the neutralized precipitate was raised to 90 ° C., and sodium peroxodisulfate (Na ₂ S ₂ O ₈ ) was added as an oxidant (Ag ⁺ ,
Bi ³⁺ , Ni ²⁺ ) was added to the suspension in an amount twice as much as the change in valence, and an oxidation treatment was performed. After completion of the oxidation treatment, aging was carried out by keeping the temperature at 90 ° C for 30 minutes, then the precipitate was filtered off, washed with water and dried at 100 ° C, and the dried product was pulverized with a crusher to obtain a powder. It was

A sample for measurement was sampled from this powder, and the bulk density, tap density, angle of repose, particle size and specific surface area were measured, and the results are shown in Table 1. The fluidity of the powder, the degree of dust generation, and the packing property were evaluated, and the results are also shown in Table 1.

[0039]

[Table 1]

As shown in Table 1, Japanese Patent Application No. 2001-2
The Ag-Bi- (M) -O-based positive electrode active material proposed in Japanese Patent Application No. 85788 and Japanese Patent Application No. 2001-274194 can be converted into a powder that is easy to handle by spray granulation or crush granulation. Since this positive electrode active material contains expensive Ag, it is required to be handled with a good yield before being incorporated into a battery product, and it can be seen that this requirement was sufficiently satisfied by spray granulation or crush granulation.

[0041]

As described above, according to the present invention,
A that has the same battery characteristics as silver oxide even if the amount of Ag is reduced
With respect to the g-Bi- (M) -O-based positive electrode active material, it is possible to improve the powder to an easy-to-handle powder without affecting the battery characteristics. It can contribute to the improvement of the yield.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshikazu Omoto             1-8-2 Marunouchi, Chiyoda-ku, Tokyo             Within Wa Mining Co., Ltd. (72) Inventor Masayuki Nishina             1-8-2 Marunouchi, Chiyoda-ku, Tokyo             Within Wa Mining Co., Ltd. F-term (reference) 5H024 AA01 AA04 CC03 HH00 HH01                       HH08 HH13                 5H050 AA19 BA04 CA07 CB13 FA17                       FA19 HA00 HA02 HA05 HA07                       HA08

Claims (8)

[Claims] 1. A crystal of a compound consisting of Ag, Bi and O (oxygen), or a crystal of a compound consisting of Ag, Bi, M (M represents a transition metal) and O, and Bi is distributed throughout the particle. A positive electrode active material for a battery, which is a powder composed of dispersed particles and has a repose angle of less than 50 degrees. 2. The positive electrode active material for a battery according to claim 1, which has an average particle size of more than 10 μm and 5 mm or less. 3. The positive electrode active material for a battery according to claim 1, which has a bulk density of more than 1.0 to 6.3 g / cm ³ and a tap density of more than 1.5 to 6.3 g / cm ³ . 4. A crystal of a compound consisting of Ag, Bi and O (oxygen), or a crystal of a compound consisting of Ag, Bi, M (M represents a transition metal) and O, and Bi is distributed throughout the particle. A powder consisting of dispersed particles, B
A positive electrode active material for a battery, which comprises a powder having a specific surface area of 0.1 to 30 m ² / g measured by the ET method. 5. The positive electrode active material for a battery according to claim 1, which does not have Ag ₂ O or AgO crystals in the particles or has only an impurity level. 6. The positive electrode active material for a battery according to claim 1, wherein the particles have a composition in which the molar ratio Ag / (Bi + M) is 1 or more and 7 or less and the oxygen content is 5% by weight or more. material. 7. The positive electrode active material for a battery according to claim 1, wherein the Ag content in the particles is 75% by weight or less. 8. An alkaline battery comprising a negative electrode active material, a positive electrode active material and an electrolyte, wherein the positive electrode active material according to any one of claims 1 to 7 is used as the positive electrode active material.