JP3399265B2 - Alkaline battery with nickel positive electrode and method of activating the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an alkaline battery having a nickel positive electrode such as a nickel-cadmium battery, a nickel-zinc battery and a nickel-hydrogen battery, and a method for activating the alkaline battery. More specifically, it relates to an alkaline battery having a nickel positive electrode in which cobalt is added to an active material and having excellent capacity characteristics and high rate discharge characteristics, and a method for activating the same.

[0002]

2. Description of the Related Art Alkaline storage batteries have high reliability,
It is widely used as a power source for various portable devices and industrial use because it can be made smaller and lighter and has higher capacity. A nickel electrode having an active material mainly composed of nickel hydroxide is used for the positive electrode of the alkaline storage battery.

This nickel positive electrode is manufactured by filling an electrode base material made of a porous metal such as foamed nickel with an active material. As a method of filling the active material, for example, JP-A-5-151965 discloses a method of physically filling the porous electrode base material with an active material material mainly containing nickel hydroxide together with a binder. There is. This method
It is generally called a paste filling method.

By the way, since nickel hydroxide, which is an active material of a nickel positive electrode, does not become conductive in both charged and discharged states, a separate conductive skeleton is required. A method for filling nickel oxide powder has been developed. However, even with this, the utilization rate of the active material is still low, and it was necessary to secure the conductivity between the active material powders.

Therefore, along with the active material, metallic cobalt, cobalt oxide (CoO) or cobalt fluoride (CoF) is used.
It was found that it is desirable to include a cobalt compound such as, and the research was advanced. Due to the presence of metallic cobalt or a cobalt compound, cobalt hydroxide and CoOOH are generated when charging and discharging are repeated, and the electrical contact between the porous metal electrode substrate and the active material is improved. The utilization efficiency of the active material is improved.

That is, in the electrode containing the cobalt compound,
At the time of initial charging, the reactions of the following formulas (1) and (2) occur,
Since the reaction of the following formula (3) occurs during discharge, the generated CoOOH forms a conductive network. CoO + OH ⁻ → HCoO ₂ ⁻ (1) HCoO ₂ ⁻ + H ₂ O → Co (OH) ₂ + OH ⁻ (2) Co (OH) ₂ + OH ⁻ → CoOOH + H ₂ O + e ⁻ (3) That is, immediately after assembling the alkaline battery. , The nickel positive electrode is not activated, and the activation treatment for causing the above reaction is required before it can be used as a secondary battery.

For example, when the nickel-hydrogen battery is assembled, neither the positive electrode nor the negative electrode has been activated.
Charge about 150% with a charging current of about 0.1C, 0.2C
A general method is to activate the battery by repeating charging / discharging several times with a discharge current of about 0.9V. A method is also known in which the assembled battery is stored at high temperature and activated without being charged.

However, such an activation method has a problem that the large current discharge characteristics and the low temperature discharge characteristics of the obtained alkaline battery are not sufficient. Therefore, for example, Japanese Patent Laid-Open No. 7-
Japanese Patent No. 73902 discloses a method of activating an alkaline battery in a charged state by storing it at a high temperature for a short time. According to this method, sufficient activation can be performed in a short time, and discharge characteristics that are affected by the activation state of the battery, such as large current discharge characteristics and low temperature discharge characteristics, are improved.

[0009]

However, even in the alkaline battery treated by the conventional activation method, the large-current discharge characteristic and the low-temperature discharge characteristic are not yet sufficient, and further improvement in the characteristics is required. For example, JP-A-7-73902
The method disclosed in the publication is mainly for activating the negative electrode of a nickel-hydrogen (Ni-MH) battery, and there are almost no other documents or the like regarding activation of the positive electrode.

Also in an alkaline battery manufactured by the method of constructing a conductive network of CoOOH,
Since the generated CoOOH is highly unevenly distributed, there is a problem that the utilization efficiency is extremely low and the output is low when charging and discharging with a large current. The present invention has been made in view of such circumstances, and an object thereof is to suppress uneven distribution of CoOOH and allow CoOOH to uniformly exist in a nickel positive electrode, and further improve discharge characteristics affected by an activated state of a battery. To do.

[0011]

Activation of an alkaline battery having a nickel positive electrode according to claim 1 for solving the above-mentioned problems .
The characteristic of the method is that metallic cobalt (Co) powder and cobalt monoxide are used.
Nickel containing at least one of the alloys (CoO) powder
Inject the electrolyte into a non-active alkaline battery with a pole at 40 ° C
A maturing step of maintaining a temperature of less than a predetermined time for 40 to 60
20 mA or less per 1 g of the positive electrode active material at a temperature of ℃
The amount of charge will be 100 to 110% of the rated capacity based on the amount of current.
The charging process for initial charging and
is there. The Arca with nickel positive electrode according to claim 2
The rechargeable battery is characterized by the method for activating a base material according to claim 1.
The formed amorphous CoOOH should be included in the nickel positive electrode.
And in.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the activation method of the present invention, by containing at least one of Co and CoO, it is considered that the reaction of the following formula (1) occurs at the time when they come into contact with the electrolytic solution in the aging step. . CoO (Co) + OH ⁻ → HCoO ₂ ⁻ (1) That is, at least one of Co and CoO is dissolved in the electrolytic solution by the reaction of the formula (1) to become HCoO ₂ ⁻ ion.
The HCoO ₂ ⁻ ions diffuse in the electrolytic solution and uniformly cover the surface of the active material. At this point, the HCoO ₂ ⁻ ions are in the equilibrium state of the formula (2).

HCoO ₂ ⁻ + H ₂ O = Co (OH) ₂ + OH ⁻ (2) It is desirable that the reaction of the formulas (1) and (2) is performed at a temperature of less than 40 ° C. When the temperature rises above 40 ° C, an oxidation reaction of at least one of Co and CoO occurs and Co ₃ O ₄
Is generated and is hardly dissolved in the electrolytic solution and is present as an impurity in the active material, so that the production amount of HCoO ₂ ⁻ ions and the production amount of CoOOH are reduced and the discharge characteristics of the alkaline battery are deteriorated.

The time of this aging step is determined according to the aging temperature, and the lower the aging temperature, the longer the aging time. For example, if the aging temperature is room temperature of about 20 ° C., the aging time will be about 10 hours or more. Then, in the charging step, at a temperature of 40 to 60 ° C., with a current amount of 20 mA per 1 g of the positive electrode active material (which corresponds to a charging current of 0.07 C) or less, the charged amount becomes 100 to 110% of the rated capacity. (This is 300 to 32 per 1 g of the positive electrode active material.
By carrying out the initial charging (corresponding to the total amount of electricity of 0 mAh), the competitive reaction of the following equations (3) and (4) occurs.

Co (OH) ₂ + OH ⁻ → CoOOH + H ₂ O + e ⁻ (3) Ni (OH) ₂ + OH ⁻ → NiOOH + H ₂ O + e ⁻ (4) Since the equilibrium reaction of the formula (2) shifts to the right slowly, In that case, the reaction of formula (3) also proceeds slowly. As a result, extremely fine amorphous CoOO is formed on the surface of the active material.
H is uniformly formed, and conductivity between the active materials is secured.

If the temperature in the charging step is lower than 40 ° C., the reaction of the formula (3) is less likely to occur, and as a result, at least one of Co and CoO remains and adversely affects the discharge characteristics. If it exceeds 60 ° C., the negative electrode may be oxidized and deteriorated. Further, when the amount of current exceeds 20 mA per 1 g of the positive electrode active material, the reaction of the formula (3) rapidly progresses, and crystalline CoOOH having large particles is nonuniformly deposited, resulting in nonuniform conductivity between the active materials. It is considered that the discharge characteristics deteriorate.

The lower limit of the amount of current is not particularly limited, but the smaller the amount of current is, the longer the charging time is and the lower the productivity is. Therefore, the lower limit is preferably 5 mA or more. When the charge amount is less than 100% of the rated capacity, the reaction of the formula (3) does not proceed sufficiently and the production of CoOOH is small.
When it exceeds, the reaction of the formula (3) rapidly progresses and crystalline CoOOH having large particles is nonuniformly deposited, so that it is considered that the conductivity between the active materials becomes nonuniform, and the discharge characteristics are deteriorated. The range of 103 to 110% of the rated capacity is particularly preferable.

Therefore, in the alkaline battery activated by the activation method of the present invention, since the surface of the active material of the nickel positive electrode is uniformly covered with fine particles of amorphous CoOOH, a dense conductive network is formed. Shows high discharge characteristics. The particle diameters of Co and CoO that are the starting materials are preferably as small as possible in consideration of the solubility in the electrolytic solution. For example, the average particle size of Co is preferably 10 μm or less, and the average particle size of CoO is preferably 8 μm or less. If the particle size is larger than this, dissolution in the electrolytic solution becomes difficult, and at least one of Co and CoO remains in the electrolytic solution as Co ₃ O ₄ , which may adversely affect the discharge characteristics.

The total amount of at least one of Co and CoO, if both are added, is 15 times the amount of the positive electrode active material.
It is preferable to set the content to be not more than weight%. If it is mixed in an amount of more than 15% by weight, the battery capacity will relatively decrease, which is not preferable. Note that at least one of Co and CoO may be included as a starting material, but it is preferable to include both Co and CoO. Due to this, the mechanism is unknown, but Co
_Since the formation of ₃ O ₄ is suppressed, Co and CoO smoothly become HCoO ₂ ⁻ ions, and the reaction of the formula (3) is promoted. As a result, a large amount of amorphous CoOOH is formed with a small amount of Co and CoO. . Therefore, Co added compared to the conventional
The amount of the nickel positive electrode can be reduced to obtain a nickel positive electrode having the same performance as the conventional one, the cost can be reduced, and the battery capacity is increased by the relative increase in the amount of the active material.

The present invention can be applied to various alkaline batteries such as nickel-hydrogen (Ni-MH) batteries, nickel-cadmium batteries and nickel-zinc batteries, and is particularly suitable for activating nickel-hydrogen batteries. For example, nickel monoxide (Ni
O), nickel oxide such as nickel dioxide (NiO ₂ ), nickel hydroxide such as nickel hydroxide [Ni (OH) ₂ ] and the like are used as the active material. Further, as this nickel positive electrode, one prepared by either a sintering method or a paste method can be used.

In addition, a negative electrode active material for a nickel-hydrogen battery
For example, AB₂System, AB_FiveSystem, AB system, A₂B series
Hydrogen storage alloys such as A is T
i, Zr, Mn, V, etc., and B is V, Ni, Cr,
Co, Fe, Mn, etc., and as the hydrogen storage alloy,
For example Ti₁₆Zr₁₆V_{twenty two}Ni₃₉Cr₇, Ti₁₆Zr₁₆V
_{twenty two}Ni₃₂Cr₇Co₇, Ti₁₅Zr₁₅V_20.6Ni₃₀Cr
_6.6Co_6.6Mn_3.6Al_2.7, Ti₁₅Zr₁₅V_{twenty one}Ni
₃₁Cr₆Co₆Fe₆, Ti₁₅Zr_{twenty one}V₁₅Ni ₃₁Cr₆
Co₆Fe₆Are exemplified.

An alkaline aqueous solution is used as the electrolytic solution of the nickel-hydrogen battery, and for example, an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide or the like can be used.

[0023]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. (Example 1) <Assembly of Ni-MH battery> 1.6 wt% Zn and Co
Containing 1.5% by weight and having an average particle size of 10 μm and a maximum particle size of 30 μ
100 parts by weight of nickel hydroxide powder with an average particle size of 8
2 parts by weight of metallic cobalt powder having an average particle diameter of 5.3 μm
5 parts by weight of CoO powder of m in terms of metallic Co, 1.5 parts by weight of CMC (carboxymethyl cellulose) as a binder, and an appropriate amount of pure water are mixed, and further mixed by a ball mill.
The paste was prepared by dispersing for 8 hours.

Next, a foamed nickel electrode substrate having a three-dimensional network structure (“Celmet” manufactured by Sumitomo Electric Industries, Ltd., thickness 1.
6 mm, porosity 95%) was prepared and the above paste was filled using a spatula. The filling amount of the paste is 0.75 g per 1 cm ³ of the foamed nickel electrode substrate. And 60
After being heated to -80 ° C. and sufficiently dried, it was rolled and cut into a predetermined size to prepare a positive electrode plate.

On the other hand, Mm Ni _3.55 Co _0.75 Mn _0.4 Al
_0.3 hydrogen storage alloy is mechanically crushed, sieved with a micro sieve, average particle size 55μm, maximum particle size 75μ
m MH powder was prepared. 100 parts by weight of this MH powder, 0.5 parts by weight of CMC, 0.5 parts by weight of carbon powder having an average particle diameter of 2 μm as a conductive additive, and an appropriate amount of ethanol and water are mixed, and further mixed with a ball mill. The paste was prepared by dispersing for time. Then, a foamed nickel electrode base material was filled in the same manner as the positive electrode, and similarly dried, rolled and cut to prepare a negative electrode plate.

The positive electrode plate and the negative electrode plate thus obtained were wound around a separator of polypropylene / polyethylene non-woven fabric which had been hydrophilized, and this was housed in a cylindrical battery can, and then KOH: NaOH = 7: A predetermined amount of an alkaline electrolyte prepared to a concentration of 6 mol / L at a ratio of 3 was injected, a battery lid was provided, and a 1200 mAh cylindrical sealed Ni-MH of AA type.
I assembled the battery. This battery has a negative electrode capacity regulation
The positive electrode was 1.2, and the rated capacity per 1 g of the positive electrode active material was 289 mA / g.

<Aging Step> The obtained inactive sealed battery was first allowed to stand at room temperature (25 ° C.) for 10 to 24 hours,
The electrolytic solution was sufficiently permeated into the positive electrode and the negative electrode. <Charging process> After that, the temperature is 60 ° C and the charging current is 0.07C.
(20 mA per 1 g of positive electrode active material), with a rated capacity of 10
The battery was charged to 3% (298 mA / g of positive electrode active material) and discharged at 1 / 5C.

<Test> The activated battery was charged at 1 / 5C for 5.5 hours and then discharged at 1 / 5C, 1C,
The discharge capacities when discharged at 3C and 6C were measured, and the results are shown in Table 1. As can be seen from Table 1, this battery shows stable discharge characteristics regardless of the magnitude of discharge current.

When the battery after activation was disassembled and the surface of the positive electrode was observed with a microscope, it was observed that fine particles of several nm to several tens nm were uniformly attached to the surface of the positive electrode active material. When the surface of this positive electrode was analyzed by infrared spectroscopy, the presence of CoOOH and Co ₃ O ₄ was confirmed. When particles on the surface of the positive electrode active material were analyzed by X-ray diffraction, a Co ₃ O ₄ peak was observed as shown in FIG. 1, but a CoOOH peak was not observed at all. That is, crystalline CoOOH is not contained in the particles uniformly attached to the surface of the positive electrode active material, and CoOOH is present as amorphous.

(Example 2) The same inactive battery as in Example 1 was used, and the temperature in the charging step was 40 ° C.
And a charging current of 0.06 C (17 g / g of positive electrode active material)
mA) was activated in the same manner as in Example 1. Then, the discharge capacity and the morphology of CoOOH were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 A positive electrode plate manufactured in the same manner as in Example 1 was used except that the amount of Co powder added was 4 parts by weight and the amount of CoO powder added was 10 parts by weight. An inactive battery was prepared in the same manner. The charging current was set to 0.05 C (14 mA / g of positive electrode active material), and 105% of the rated capacity (3 / g of positive electrode active material).
(Corresponding to 03 mA), activation was performed in the same manner as in Example 1 except that charging was performed so that discharge capacity and CoOO
The results of measuring the morphology of H are shown in Table 1.

(Example 4) The procedure of Example 1 was repeated except that the amount of Co powder added was 10 parts by weight, and the amount of CoO powder having an average particle size of 8 μm was 4 parts by weight. An inactive battery was produced in the same manner as in Example 1 using the positive electrode plate. The charging current was set to 0.05 C (14 mA per 1 g of the positive electrode active material), and the rated capacity was 10
Table 1 shows the results of measuring the discharge capacity and the morphology of CoOOH in the same manner as in Example 1 except that the battery was charged to 5% (corresponding to 303 mA per 1 g of the positive electrode active material).

Example 5 Example 1 was carried out without using Co powder.
An inactive battery was produced in the same manner as in Example 1 except that the positive electrode plate produced in the same manner as in Example 1 was used except that 7 parts by weight of the CoO powder used in 2) was added. Then, activation was performed in the same manner as in Example 1 except that the temperature in the charging step was set to 50 ° C., and the discharge capacity and the morphology of CoOOH were similarly measured.

Example 6 In place of Co powder and CoO powder, 8 parts by weight of commercially available cobalt oxide having an average particle diameter of 3.8 μm (main component is CoO and some metal Co is contained) was added. An inactive battery was produced in the same manner as in Example 1, except that the positive electrode plate produced in the same manner as in Example 1 was used except for the above.
Then, activation was performed in the same manner as in Example 1 except that the temperature in the charging step was set to 50 ° C., and the discharge capacity and CoOOH were similarly activated.
Table 1 shows the results of measuring the morphology.

Example 7 A positive electrode plate manufactured in the same manner as in Example 1 was used except that the amount of Co powder added was 3 parts by weight and the amount of CoO powder added was 6 parts by weight. An inactive battery was prepared in the same manner as in. The charging current was set to 0.01 C (3 mA per 1 g of the positive electrode active material), and 110% of the rated capacity (3 per 1 g of the positive electrode active material).
(Equivalent to 18 mA) was activated in the same manner as in Example 1 except that the battery was charged to a discharge capacity and CoOO.
The results of measuring the morphology of H are shown in Table 1.

(Comparative Example 1) Activation was performed in the same manner as in Example 1 except that the same inactive battery as in Example 1 was used and the temperature in the charging step was 20 ° C. And Example 1
The discharge capacity and the morphology of CoOOH were measured in the same manner as in, and the results are shown in Table 1. (Comparative Example 2) The same operation as in Example 1 was performed, except that the temperature in the charging step was 40 ° C and the charging current was 0.1 C (29 mA per 1 g of the positive electrode active material). Activation was carried out as in Example 1. Then, the discharge capacity and the morphology of CoOOH were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 3 Instead of Co powder and CoO powder, cobalt hydroxide (Co (OH)) having an average particle size of 6 μm was used.
An inactive battery was produced in the same manner as in Example 1 except that 8 parts by weight of ₂ ) was added and the positive electrode plate produced in the same manner as in Example 1 was used. Then, activation was performed in the same manner as in Example 1, and similarly, the discharge capacity and the form of CoOOH were measured, and the results are shown in Table 1.

Reference Example A positive electrode plate manufactured in the same manner as in Example 1 was used except that Co powder having an average particle size of 15 μm and CoO powder having an average particle size of 10 μm were used. An active battery was made. Then, activation was performed in the same manner as in Example 1 except that the temperature in the charging step was 40 ° C., and the discharge capacity and the morphology of CoOOH were measured in the same manner.

(Evaluation)

[0040]

[Table 1]

As is clear from Table 1, Ni of each Example
It can be seen that the -MH battery exhibits a stable discharge capacity even when the discharge current fluctuates greatly, and has extremely excellent discharge characteristics. However, in each of the comparative examples, the discharge capacity is greatly reduced as the discharge current is increased, and the discharge characteristics are inferior. FIG. 2 shows an X-ray diffraction chart of particles attached to the surface of the positive electrode active material of Comparative Example 3. This particle contains crystalline CoOOH, which is completely different from the chart of the embodiment shown in FIG. In other words, the difference between the example and the comparative example in terms of phenomenon is that CoO
Due to the difference in whether OH is amorphous or crystalline and the difference in distribution of CoOOH being uniform or non-uniform, it is possible that amorphous CoOOH is uniformly distributed as in the example. It is clear that it gives favorable results.

In Comparative Example 1, the temperature in the charging step was as low as 20 ° C., in Comparative Example 2, the charging current in the charging step was 0.1 C (29 mA per 1 g of the positive electrode active material), which was large. The substance is cobalt hydroxide, which is different from the examples, and it is clear that when it is out of the constitution of the present invention, amorphous CoOOH is not formed and the discharge characteristic is deteriorated.

Further, as shown in the reference example, when the particle size of the starting material is as large as 10 to 15 μm, there is an insoluble portion in the electrolytic solution during the aging step, which becomes Co ₃ O _4. It exists as non-uniform crystalline particles. This does not have a favorable effect on the characteristics, but rather deteriorates the discharge characteristics. Therefore, it is desirable to make the particle diameter as fine as 10 μm or less as shown in each example.

[0044]

In other words, according to the alkaline battery having the nickel positive electrode of the present invention, a uniform conductive network is formed by amorphous CoOOH, so that a stable discharge capacity is exhibited even when the discharge current is large, and the discharge characteristics are improved. Is excellent. Further, since the utilization rate of the active material is improved, the output and the capacity are high.

According to the activation method of the present invention, it is possible to easily and surely form the alkaline battery having the above-mentioned excellent characteristics. Furthermore, when the battery was activated by the conventional method, it took several days for the aging / aging period to disperse the cobalt compound as cobalt hydroxide after adding the electrolytic solution, but this period can be shortened. With improved productivity, cobalt to CoO
Since the efficiency of forming OH is improved, the amount of cobalt used can be reduced and the cost can be reduced.
Further, since the amount of active material is relatively increased, the battery capacity is increased.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction chart of particles attached to a surface of an active material of an alkaline battery positive electrode of Example 1.

2 is an X-ray diffraction chart of particles adhering to the surface of the active material of the alkaline battery positive electrode of Comparative Example 3. FIG.

Claims (2)

(57) [Claims] 1. An electrolytic solution is injected into an inactive alkaline battery having a nickel positive electrode containing at least one of metallic cobalt (Co) powder and cobalt monoxide (CoO) powder, and 40 ° C.
And a aging step of maintaining the temperature for less than a predetermined time, and 20 at a temperature of 40 to 60 ° C. per 1 g of positive electrode active material.
A method of activating an alkaline battery having a nickel positive electrode, which comprises performing a charging step of performing initial charging so that a charged amount is 100 to 110% of a rated capacity at a current amount of mA or less. 2. Formed by the activation method according to claim 1.
Including formed amorphous CoOOH in nickel positive electrode
Alkaline battery with a nickel positive electrode.