JP2003031216A - Method of manufacturing nickel positive electrode and method of manufacuring alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a nickel positive electrode capable of reducing discharge reserve and obtaining a high active material utilization factor. SOLUTION: A layer made of cobalt hydroxide is formed on the surface of a positive active material particle. A positive electrode material is oxidized so that one part of cobalt hydroxide in the layer and one part of nickel hydroxide in a positive active material are oxidized, the positive electrode material is formed in phase, the paste is applied to a current collector to prepare a positive electrode body, the positive electrode body is arranged in an electrolyte together with a counter electrode, the positive electrode body and the counter electrode are charged, this charging process is composed of a first process and a second process, and in the first process, constant current charging is conducted at 40-80 deg.C to the specified potential in a range from -60 to 400 mV for a mercury oxide electrode, and in the second process, additional charging is conducted at 20-40 deg.C to 100-150% of the nickel hydroxide capacity in one electron reaction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a nickel positive electrode and a method for producing an alkaline storage battery having the nickel positive electrode.

[0002]

2. Description of the Related Art Nickel-hydrogen storage batteries, which are one type of alkaline storage batteries, have a higher energy density than nickel-cadmium storage batteries, and since they do not contain harmful cadmium, they are less likely to cause environmental pollution. It is widely used as a power source for portable small electronic devices such as mobile phones, small power tools, and small personal computers, and the demand for these devices has increased dramatically as they spread.

By the way, in the portable small electronic devices described above, the installation space of the power source has come to be greatly limited due to the progress of miniaturization and weight reduction. Power consumption is increasing. Therefore, in the nickel-hydrogen storage battery used for such small electronic devices, it is necessary to simultaneously achieve the contradictory issues of downsizing and high capacity.

Conventionally, nickel-metal hydride storage batteries have been said to be unsuitable for high-power applications, but by improving the high-rate discharge characteristics, they can be used in hybrid vehicles that use both electricity and gasoline as energy sources. It has also begun to be used in various applications. Against this background, development of higher performance nickel hydrogen storage batteries is expected.

A nickel-hydrogen storage battery generally has a positive electrode having a positive electrode active material containing nickel hydroxide as a main component and a negative electrode having a hydrogen storage alloy. The positive electrode active material usually has its surface coated with a low-order cobalt compound having a divalent or lower cobalt content, such as cobalt hydroxide, in order to enhance the conductivity and improve the utilization rate. This low-order cobalt compound is oxidized at the time of initial charge to change cobalt to a higher-order cobalt compound having a valence higher than 2 to form a conductive network composed of the higher-order cobalt compound, thereby utilizing the positive electrode active material. The rate is increasing. The higher cobalt compound is considered to be cobalt oxyhydroxide. Cobalt hydroxide changes into a higher cobalt compound through two paths during initial charging. One is a solid-state reaction in which cobalt hydroxide is directly oxidized to a higher cobalt compound. The other one is Co
(OH) ₂ is dissolved and HCoO ₂ ⁻ or [Co (O
H) ₄ ] ²⁻ , which is a dissolution-precipitation reaction in which CoOOH is further converted and deposited.

Various studies have so far been made on the initial charging method of the nickel-hydrogen storage battery. For example,
JP-A-5-343102, JP-A-8-153543, JP-A-9-171838, and JP-A-10-199564.
Et al. Show a method for efficiently converting cobalt hydroxide into a higher cobalt compound in initial charging.

[0007]

However, since the reaction of oxidizing the low order cobalt compound on the surface of the positive electrode active material to the high order cobalt compound by the initial charge is irreversible, the charge electricity amount required for this reaction is It is stored in the negative electrode as a potential amount of discharge electricity that cannot be discharged (hereinafter, referred to as “discharge reserve”). Therefore, when designing a battery, it is necessary to allow for a capacity equivalent to the discharge reserve on the negative electrode side.

Therefore, the nickel-metal hydride storage battery is designed so that the negative electrode capacity is set larger than the positive electrode capacity, and the charge / discharge capacity is regulated by the positive electrode capacity.
Therefore, in the nickel-metal hydride storage battery, if the capacity of the positive electrode is increased to increase the capacity of the battery, the capacity of the negative electrode also needs to be increased, which makes it difficult to reduce the size. That is,
It is difficult to achieve both miniaturization and high capacity.

Therefore, a means for reducing the discharge reserve has been proposed in order to reduce the size and increase the capacity.
For example, JP-A-7-22026 and JP-A-8-21301
In 0 and the like, a method of previously oxidizing the lower cobalt compound on the surface of the positive electrode active material is shown. According to this method, since the irreversible oxidation reaction due to the initial charge does not occur, the discharge reserve can be certainly reduced. However,
This method has the following problems. That is, when the positive electrode active material particles obtained by this method are directly filled in the current collector, the conductive network between the active material particles is only joined by physical contact, so that the active material particles easily fall off, As a result, there are cases where a sufficient utilization ratio of the active material cannot be obtained.

The present invention provides a method for producing a nickel positive electrode, which can reduce the discharge reserve and can prevent the active material particles from falling off to obtain a high utilization ratio of the active material, and such a nickel positive electrode. An object of the present invention is to provide a method for manufacturing an alkaline storage battery having a positive electrode.

[0011]

The invention according to claim 1 is
A layer of a positive electrode material in which a layer of a lower cobalt compound having a cobalt divalent or lower is formed on the surface of a positive electrode active material particle made of nickel hydroxide or a solid solution of nickel hydroxide in which a different element is solid-dissolved. In order to oxidize a portion of the lower cobalt compound and a portion of the nickel hydroxide in the positive electrode active material, an oxidizing step, an oxidizing step, and a paste forming step of the positive electrode material, a paste making step, and a paste Is applied to a current collector to produce a positive electrode body, a positive electrode body producing step, a positive electrode body is placed in an electrolytic solution together with a counter electrode, an arranging step, and the positive electrode body and the counter electrode are charged, a charging step And, the charging step includes a first step and a second step, and the first step is performed at a temperature of 40 to 80 ° C. in a range of −60 mV to 400 mV with respect to the mercury oxide electrode. With constant current charging up to a predetermined potential Ri, second step, at a temperature of 20 to 40 ° C., 100 to 150% relative to the nickel hydroxide capacity of the case of the one-electron reaction, is to add charge,
This is a method for manufacturing a nickel positive electrode.

In the manufacturing method according to the first aspect, the lower order cobalt compound is oxidized in the oxidation step, so that the cobalt becomes a higher order cobalt compound having a valence higher than 2. However, it is a part of the lower cobalt compound in the layer that is oxidized, and the unoxidized lower cobalt compound remains in the layer. The unoxidized low-order cobalt compound is entirely oxidized into a high-order cobalt compound in the first step of the charging step. In this first step, the unoxidized low order cobalt compound is dissolved and precipitated as a high order cobalt compound, so that the high order cobalt compound is obtained. Therefore, the obtained high order cobalt compound is a positive electrode active material particle. Formed over the gap. Therefore, the positive electrode active material particles are bonded to each other by the conductive network made of the higher cobalt compound obtained in the oxidation step and the first step. Since the conductive network contains the higher order cobalt compound formed between the positive electrode active material particles in the first step, the conductive network is more likely than the case where the positive electrode active material particles are joined only by physical contact. And become solid. Therefore, in the nickel positive electrode obtained by the manufacturing method according to claim 1, the positive electrode active material is prevented from falling off, and the utilization rate of the positive electrode active material is improved.

Moreover, in the nickel positive electrode obtained by the manufacturing method according to the first aspect, the discharge reserve is reduced. That is, the generation of the discharge reserve is due to the irreversible oxidation reaction due to the charge when forming the conductive network. However, according to the above manufacturing method, as described above, the conductive network is also formed by the oxidation step that does not cause the generation of the discharge reserve. Therefore, the discharge reserve is reduced by the amount of the oxidation process.

Further, the discharge reserve is also generated by the irreversible amount of electricity due to the charge oxidation of nickel hydroxide, but in the manufacturing method according to claim 1, a part of the nickel hydroxide in the positive electrode active material is subjected to the oxidation step. Is oxidized,
The amount of irreversible electricity can be suppressed. Therefore, also from this point, the discharge reserve is reduced in the nickel positive electrode obtained by the manufacturing method according to the first aspect.

Examples of the different element that is solid-dissolved in nickel hydroxide include zinc and cobalt. Such a different element may be solid-solved in the crystal lattice of nickel hydroxide as a simple substance (metal), a hydroxide,
It may be dissolved in the crystal lattice of nickel hydroxide as a compound such as an oxide. Further, the content of the different element in the crystal lattice of nickel hydroxide is usually preferably set to at least 2 parts by weight or more based on the weight of nickel hydroxide in terms of the weight of the different element.

Of the layer formed on the surface of the positive electrode active material particles,
The proportion in the positive electrode material is usually preferably set to 3 to 15% by weight, and particularly preferably set to 4 to 8% by weight. If it is less than 3% by weight, the conductivity of the positive electrode active material may not be sufficiently high, and it may be difficult to improve the utilization rate. When it exceeds 15% by weight, the amount of the active material in the positive electrode material is relatively decreased, which may cause a decrease in capacity.

Examples of the lower cobalt compound include simple substance cobalt, cobalt monoxide, cobalt hydroxide and the like. Particularly, cobalt hydroxide is preferable.

Examples of the oxidizing method in the oxidizing step include a method of using an oxidizing agent in an alkaline aqueous solution or water at high temperature, or a method of heating in an oxygen atmosphere and alkaline conditions.

The oxidizing conditions in the oxidizing step are preferably set so that the average oxidation number of nickel and cobalt is 2.05 to 2.4. When the oxidation number is less than 2.05, the effect of reducing the discharge reserve becomes small. If the oxidation number exceeds 2.4, γ-NiOOH is likely to be generated, and the battery capacity may become a negative electrode restriction, resulting in reduced discharge capacity and shortened cycle life.

As an oxidant used in the above-mentioned oxidation method
Is not particularly limited, and various known ones can be used.
However, it has a large oxidizing power, so it is possible to
Those capable of chemical treatment are preferable. For example, Pell
Potassium oxodisulfate (K_TwoS _Two0₈), Peroxo
Sodium sulfate (Na_TwoS_Two0₈), Peroxodisulfate
Ammonium ((NH_Four)_TwoS_Two0₈), Sodium hypochlorite
Thorium (NaClO) and sodium chlorite (N
aClO_TwoIt is preferable to use at least one of the above).

The alkaline aqueous solution used in the above-mentioned oxidation method is not particularly limited and various known ones can be used. For example, it is preferable to use potassium hydroxide, lithium hydroxide, sodium hydroxide and the like.

The temperature of the above-mentioned or oxidation treatment is not particularly limited, but is preferably in the range of 50 ° C to 130 ° C.

The paste is prepared by adding water or water in which a thickener is dissolved to the positive electrode material, and further adding a binder if necessary.
Prepare. Examples of the thickener include polymer compounds such as polyethylene glycol and polyvinyl alcohol, carboxymethyl cellulose, and methyl cellulose. Examples of the binder include polytetrafluoroethylene and styrene-butadiene rubber.

The positive electrode body is prepared by applying the prepared paste to a current collector and drying it. It is preferable that the positive electrode material is densely filled inside the current collector by applying pressure after drying.

The current collector is not particularly limited as long as it is one normally used in the positive electrode for alkaline storage batteries, but it is made of metal and porous because it is easy to densely fill and hold the positive electrode material. It is preferable to use a body, a mesh or a perforated plate.

As the metal porous body, it is preferable to use a foamed metal porous body. The foamed metal porous body is a sponge-like metal body, and can be produced, for example, by electrolessly plating a metal on a foamed resin such as urethane foam and then heating and removing the foamed resin.

As the metal mesh body, it is preferable to use, for example, a mesh body in which metal fibers are three-dimensionally intertwined with each other, for example, a nonwoven fabric.

As the metal porous plate, for example, punching metal, expanded metal or the like can be used.

The electrolytic solution in the arranging step is not particularly limited as long as it is various alkaline aqueous solutions used in known nickel-hydrogen storage batteries, and examples thereof include potassium hydroxide, lithium hydroxide and sodium hydroxide. It is preferable to use an aqueous solution in which at least one of these is dissolved.

In the first step of the charging step, the remaining unoxidized lower cobalt compound not oxidized in the oxidation step is oxidized. In the first step, 40 ° C to 80 ° C
Charge at the temperature of. If the temperature is lower than 40 ° C, the unoxidized lower cobalt compound may not be sufficiently oxidized. 8
If the temperature is higher than 0 ° C., the electrolytic solution may leak to the outside of the battery when it is charged, and the weight of the battery may be reduced, which may shorten the cycle life.

In the first step, the mercury oxide electrode is charged with a constant current to a predetermined potential in the range of -60 mV to 400 mV. This predetermined potential needs to be determined by the temperature at which charging is performed. This is because the oxidation potential of the low order cobalt compound to the high order cobalt compound shifts to the base side with respect to the mercury oxide electrode as the temperature increases. It should be noted that there is a possibility that nickel hydroxide may be oxidized at a high temperature if it is charged over 400 mV.

For example, FIG. 1 shows the relationship between the oxidation potential of cobalt hydroxide to cobalt oxyhydroxide and the temperature. Specifically, cobalt hydroxide is oxidized in a 6.8 mol / l potassium hydroxide aqueous solution. Formula 1
Is a relational expression between temperature and oxidation potential. ^{E = -0.0988T 2 + 4.3381T + 249.79} (20~80 ℃) ... Equation 1 Note, E: potential for Hg / HgO electrode (mV),
T: Temperature (° C)

In the first step, the constant-current charging is stopped at a predetermined potential at a high temperature to prevent the oxidation reaction of nickel hydroxide in the positive electrode active material. In order to prevent such an oxidation reaction, a charging method in which the potential is fixed to the oxidation potential of the lower cobalt compound (for example, cobalt hydroxide) in the layer can be considered, but it is not preferable for the following reason. That is, when the potential is rapidly swept from the open circuit potential to the oxidation potential, a large current flows, the reaction is not uniformly performed, and a dense conductive network may not be formed. Even if the electric potential is swept stepwise, it takes a long time to complete the reaction, and the industrial value is reduced.

In the second step of the charging step, the positive electrode active material is charged. In the second step, 20 ° C to 40 ° C
Charge at a temperature of ℃. If lower than 20 ° C, γ-NiOO
The production of H may be accelerated. Above 40 ° C,
Oxygen is easily generated, and the generated oxygen may promote the corrosion and deterioration of the inactive negative electrode alloy.

In the second step, 100 to 150% of the nickel hydroxide capacity in the case of electron reaction is additionally charged. As a result, the positive electrode active material is in a charged state.

According to a second aspect of the present invention, a layer made of a lower cobalt compound having cobalt having a valence of 2 or less is formed on the surface of the positive electrode active material particles made of nickel hydroxide solid solution in which nickel hydroxide or a different element is solid-dissolved. Is formed so that all of the lower cobalt compounds in the layer and some of the nickel hydroxide in the positive electrode active material are oxidized. Next, a cobalt compound is mixed and the mixture is made into a paste, a paste preparation step, a paste is applied to a current collector to prepare a positive electrode body, a positive electrode body preparation step, and the positive electrode body together with a counter electrode in an electrolytic solution. And a charging step of charging the positive electrode body and the counter electrode. The charging step includes a first step and a second step, and the first step is 40 Mercury oxide electrode at a temperature of ~ 80 ° C 400m from -60mV for
Constant current charging to a predetermined potential in the range of V, 100 to 150% of nickel hydroxide capacity when the second step is a one-electron reaction at a temperature of 20 to 40 ° C,
A method for producing a nickel positive electrode, characterized in that the nickel positive electrode is additionally charged.

According to the second aspect of the invention, all of the lower cobalt compounds in the layer are oxidized by the oxidation step to become higher cobalt compounds. Then, the low order cobalt compound mixed in the paste making step is all oxidized in the first step of the charging step to become a high order cobalt compound. In this first step, since the high order cobalt compound is obtained by dissolving the low order cobalt compound and precipitating it as the high order cobalt compound, the obtained high order cobalt compound is spread between the positive electrode active material particles. Formed. Therefore, the positive electrode active material particles are bonded to each other by the conductive network made of the higher cobalt compound obtained in the oxidation step and the first step. Since the conductive network contains the higher order cobalt compound formed between the positive electrode active material particles in the first step,
This is stronger than the case where the positive electrode active material particles are joined by simple physical contact. Therefore, in the nickel positive electrode obtained by the manufacturing method according to claim 1, the positive electrode active material is prevented from falling off, and the utilization rate of the positive electrode active material is improved.

Moreover, in the nickel positive electrode obtained by the manufacturing method according to the second aspect, the discharge reserve is reduced. That is, according to the above manufacturing method, as described above,
The conductive network is also formed by an oxidation process that does not cause the formation of a discharge reserve. Therefore,
The discharge reserve is reduced by the amount due to the oxidation process.

Further, the discharge reserve is also generated by an irreversible amount of electricity due to redox of nickel hydroxide, but in the manufacturing method according to claim 2, a part of the nickel hydroxide in the positive electrode active material is subjected to the oxidation step. Is oxidized,
The irreversible electricity quantity does not occur. Therefore, also from this point, in the nickel positive electrode obtained by the manufacturing method according to the second aspect, the discharge reserve is reduced.

Others are the same as the invention described in claim 1. In the invention of claim 1, a part of the lower cobalt compound in the layer of the positive electrode material is oxidized in the oxidation step, whereas in the invention of claim 2, the positive electrode material is oxidized in the oxidation step. All lower cobalt compounds in the layer are oxidized. This is the oxidation condition in the oxidation step,
For example, temperature, alkali type / concentration, oxidizer type /
It can be performed by setting the usage amount and the like.

According to a third aspect of the present invention, in the first or second aspect of the invention, a constant voltage charge is performed for 30 minutes or more at a predetermined potential of the first step between the first step and the second step. It has a process.

According to the first step, the unoxidized low-order cobalt compound remaining in the oxidation step is oxidized, but even if the oxidation is insufficient, the intermediate step removes the low-order cobalt compound. Assures oxidation. Therefore, according to the third aspect of the present invention, the conductive network made of the higher order cobalt compound is more reliably formed. If the charging time is shorter than 30 minutes, there is little point in adopting this intermediate step.

According to a fourth aspect of the present invention, in the paste forming step according to the first aspect of the invention, a low order cobalt compound is mixed with the positive electrode material, and the mixture is made into a paste.

In the invention according to claim 4, the low-order cobalt compound mixed at the time of preparing the paste is oxidized in the first step of the charging step like the unoxidized low-order cobalt compound in the layer after the oxidation step. And becomes a higher cobalt compound. This higher order cobalt compound is formed across the particles of the positive electrode active material. Therefore, according to the invention described in claim 4, the conductive network becomes stronger.

According to a fifth aspect of the present invention, in the second aspect of the present invention, the amount of the lower cobalt compound mixed in the paste making step is 0.5 to 8% by weight based on the positive electrode material. .

If it is less than 0.5% by weight, the effect of suppressing the falling of the positive electrode active material becomes insufficient. When it is more than 8% by weight, the quantitative ratio of the positive electrode active material is lowered, the energy density is lowered, and the discharge reserve is increased.

The invention according to claim 6 is the invention according to claim 1 or 2, wherein the charging current value in the first step is 1/10 of the nickel hydroxide capacity in the case of one-electron reaction.
The charge rate is 0 to 1/20 It (A).

If the charge rate exceeds 1/20 It (A), the unoxidized lower cobalt compound left in the oxidation step may not be sufficiently oxidized. 1/100 It
If it is smaller than the charging rate of (A), it takes a long time to charge in the first step, and the industrial value becomes low.

The invention according to claim 7 is the invention according to claim 1 or 2, wherein the charging current value in the second step is 1/2.
The charging rate is 0 to 1/3 It (A).

When the charging rate of 1/3 It (A) is exceeded,
Oxygen is easily generated, and the generated oxygen promotes the corrosion and deterioration of the inactive negative electrode alloy, and γ-NiOO
The production of H may be accelerated. 1/20 I
If it is smaller than the charging rate of t (A), the second step requires a long time and the industrial value becomes low.

The invention according to claim 8 is a layer made of a low-order cobalt compound in which cobalt is divalent or less, on the surface of positive electrode active material particles made of nickel hydroxide or a solid solution of nickel hydroxide in which a different element is solid-dissolved. Is formed so that a part of the lower cobalt compound in the layer and a part of nickel hydroxide in the positive electrode active material are oxidized, and an oxidizing step is performed. Forming a paste, a paste preparation step, a paste is applied to a current collector to prepare a positive electrode body, a positive electrode body preparation step, a positive electrode body, a negative electrode, and a separator are combined to prepare a pole group, Put in a battery case, soak it in the electrolyte, close the battery container, and assemble the battery,
It has an assembling step and a charging step of charging the battery, the charging step comprises a first step and a second step, and the first step is an oxidation at a temperature of 40 to 80 ° C. Constant-current charging is performed to a predetermined potential in the range of -60 mV to 400 mV with respect to a mercury electrode, and the second step is performed at a temperature of 20 to 40 ° C. with respect to the nickel hydroxide capacity when the one-electron reaction is performed. 100-150%, additional charging,
It is a method of manufacturing an alkaline storage battery, which is characterized by the above.

In the invention described in claim 8, since the charging step is performed after the battery is assembled in the assembly step, the alkaline storage battery provided with the nickel positive electrode according to claim 1 can be obtained. In this alkaline storage battery, good working effects based on the nickel positive electrode according to claim 1 are exhibited.

As the negative electrode, for example, in the case of a nickel-hydrogen storage battery, a negative electrode material containing a hydrogen storage alloy is usually used on a flexible collector, but the present invention is not limited thereto. Specifically, the negative electrode using the hydrogen storage alloy is manufactured as follows. That is, M
mNiAlCoMn (Mm is misch metal, L
a hydrogen-occlusion alloy powder having a particle size of 75 μm or less, which is a mixture of rare earth elements consisting of a, Ce, Pr, and Nd), and a thickener was dissolved in this powder. Water and polytetrafluoroethylene which is a binder,
Is added to prepare a paste, and the paste is applied to both surfaces of a punching metal, dried, and then pressed to adjust the thickness.

The separator is not particularly limited, and known separators can be used.

The electrolytic solution is not particularly limited, and a known one can be used. For example, potassium hydroxide,
At least one of lithium hydroxide and sodium hydroxide
An aqueous solution in which the seed is dissolved is preferred.

As the battery, for example, one having a structure as shown in FIG. 2 can be adopted. In FIG. 2, the alkaline storage battery 1 is a nickel-hydrogen storage battery, and includes a case 2, a positive electrode 3, a negative electrode 4, a separator 5, and an electrolytic solution (not shown) arranged in the case 2. The case 2 is a substantially cylindrical container having an opening 21 at the top, and the bottom surface of the case 2 is set as the negative electrode terminal. Each of the positive electrode 3, the negative electrode 4, and the separator 5 is a flexible belt-shaped member, and the positive electrode 3 and the negative electrode 4 are arranged in the case 2 in a spirally wound state with the separator 5 sandwiched therebetween. ing.
The opening portion 21 of the case 2 is liquid-tightly sealed by the sealing plate 7 with the insulating gasket 6 sandwiched in the state where the electrolytic solution is injected into the case 2. The sealing plate 7 has a positive electrode terminal 8 on the upper surface. The positive electrode terminal 8 is connected to the positive electrode 3 via a lead 9 that electrically connects the sealing plate 7 and the positive electrode 3.

In the alkaline storage battery 1, it is preferable to use, as an electrolytic solution, one obtained by adding one or both of lithium hydroxide and sodium hydroxide to an aqueous solution of potassium hydroxide and dissolving it, or an aqueous solution of potassium hydroxide. . When such an electrolytic solution is used, the production of γ-NiOOH can be suppressed in the positive electrode active material, and the oxygen overvoltage can be shifted to the noble side, so that the charging efficiency of the alkaline storage battery 1 can be increased. The amount of such an electrolyte used varies depending on the shape of the battery, but in the case of a closed cylindrical type, it is usually 0.8
It is preferably set to ~ 1.3 ml. If it is less than 0.8 ml, the charge / discharge cycle life of the alkaline storage battery 1 may be shortened. If it exceeds 1.3 ml,
Since the gas absorption capacity of the negative electrode 4 decreases, it may be difficult to suppress the increase in the internal pressure of the alkaline storage battery 1.

In the case of a nickel-hydrogen storage battery, the final voltage for charging in the first step depends on the charging temperature, the composition of the positive electrode active material, and the composition and type of the hydrogen storage alloy, but is 0.8 to 1.3 V.
Is preferred.

According to a ninth aspect of the present invention, a layer made of a low-order cobalt compound in which cobalt is divalent or lower is formed on the surface of positive electrode active material particles made of nickel hydroxide or a solid solution of nickel hydroxide in which a different element is solid-dissolved. Is formed so that all of the lower cobalt compounds in the layer and some of the nickel hydroxide in the positive electrode active material are oxidized. Next, the following cobalt compound is mixed and the mixture is made into a paste, a paste making step, a paste is applied to a current collector to make a positive electrode body, a positive electrode body making step, a positive electrode body, a negative electrode and a separator are combined. To prepare a group of electrodes, put the group of electrodes in a battery case, immerse the battery in an electrolytic solution, seal the battery container, and assemble a battery, and have an assembly process and a charging process of charging the battery. And the charging process is the same as the first process Consists of a 2 step, the first step is at a temperature of 40 to 80 ° C., with respect to mercury oxide electrode -
Constant-current charging is performed to a predetermined potential in the range of 60 mV to 400 mV, and the second step is 100 to 150% with respect to the nickel hydroxide capacity when the one-electron reaction is performed at a temperature of 20 to 40 ° C. A method of manufacturing an alkaline storage battery, which is characterized in that the battery is additionally charged.

According to the ninth aspect of the invention, since the battery is assembled in the assembling step and the charging step is performed, the alkaline storage battery having the nickel positive electrode of the second aspect can be obtained. In this alkaline storage battery, good working effects based on the nickel positive electrode according to claim 2 are exhibited. Others are the same as the alkaline storage battery according to claim 8.

The invention according to claim 10 is the invention according to claim 8 or 9.
In the invention described in, between the first step and the second step,
It has an intermediate step of performing constant voltage charging for 30 minutes or more at the predetermined potential of the first step.

According to this alkaline storage battery,
Good effects based on the described nickel positive electrode are exhibited.

According to an eleventh aspect of the present invention, in the invention according to the eighth aspect, a low order cobalt compound is mixed with the positive electrode material in the paste making step, and the mixture is made into a paste.

According to the alkaline storage battery of claim 4,
Good effects based on the described nickel positive electrode are exhibited.

According to a twelfth aspect of the present invention, in the invention according to the ninth aspect, the amount of the lower cobalt compound mixed in the paste producing step is 0.5 to 8% by weight based on the positive electrode material. .

According to this alkaline storage battery,
Good effects based on the described nickel positive electrode are exhibited.

The invention according to claim 13 is the invention according to claim 8 or 9.
In the invention described in 1), the charging current value in the first step is 1/1 with respect to the nickel hydroxide capacity in the case of one-electron reaction.
The charging rate is from 00 to 1/20 It (A).

In the alkaline storage battery according to claim 6,
Good effects based on the described nickel positive electrode are exhibited.

The invention according to claim 14 is the invention according to claim 8 or 9.
In the invention described in, the charging current value in the second step is 1 /
The charging rate is 20 to 1/3 It (A).

In the alkaline storage battery according to claim 7,
Good effects based on the described nickel positive electrode are exhibited.

[0071]

BEST MODE FOR CARRYING OUT THE INVENTION {Production of nickel positive electrode} Example 1
9 relates to the invention according to claim 1. In particular,
Embodiments 7 to 9 relate to the invention described in claim 3.

Example 1 (1) Oxidation Step First, the positive electrode material was oxidized. As the positive electrode material, there was used one in which a layer made of β-cobalt hydroxide was formed on the surface of positive electrode active material particles made of a nickel hydroxide solid solution in which zinc and cobalt were solid-dissolved. The contents of dissolved zinc and cobalt were 4 parts by weight and 5 parts by weight, respectively, in terms of metal ratio. The content of the layer made of β-cobalt hydroxide is
It was 6% by weight with respect to the positive electrode material. Oxidation is 90 ℃, 5
% Sodium hydroxide aqueous solution, oxidizer NaC
This was done by treating with 10 for 2 hours. Na
The amount of ClO used was 5 ml per 10 g of the positive electrode material. The average oxidation number of nickel and cobalt after the oxidation step was 2.15.

Cyclic voltammetry was performed on the positive electrode material after the oxidation step. The measurement conditions are as follows. That is, the working electrode is a foam substrate having a size of 1 × 1 cm filled with a positive electrode material. The counter electrode is a nickel plate. The reference electrode is Hg / HgO. The electrolyte is a 6.5N potassium hydroxide aqueous solution. A potential scan was performed at 20 ° C. The potential scanning speed is 1 mV / min, and the potential scanning range is 0 to 350 mV. FIG. 3 shows a cyclic voltammogram of the positive electrode material after the oxidation step.

As can be seen from FIG. 3, an oxidation peak from cobalt hydroxide to cobalt oxyhydroxide is observed near 350 mV. From this, it can be seen that unoxidized cobalt hydroxide is present in the surface layer of the positive electrode material after the oxidation step.

(2) Paste Preparation Step 80 parts by weight of the positive electrode material after the oxidation step and 20 parts by weight of an aqueous solution of carboxymethyl cellulose as a thickener were mixed to prepare a paste.

(3) Step of Producing Positive Electrode Body The above paste was uniformly applied to a current collector and dried. Then, the current collector was pressed and then cut into 4 × 6 cm ² .
A nickel porous substrate was used as the current collector. As a result, a positive electrode body having a capacity of 1000 mAh was obtained.

(4) Arrangement Step Using the above positive electrode body, an open type test battery was prepared together with a negative electrode and the like. The negative electrode was manufactured as follows. That is, CaCu
MmNi _3.5 Co _0.8 Mn _0.4 having a _5- type structure
Al _0.3 composition (Mm is misch metal, La,
A paste was prepared by adding an aqueous solution of carboxymethyl cellulose, which is a thickener, to a powder of a hydrogen storage alloy represented by (a mixture of rare earth elements consisting of Ce, Pr, and Nd). Next, this paste was applied to both surfaces of a perforated steel plate which is a current collector and dried. Then, the perforated steel sheet was pressed and then cut into 4 × 6 cm ² . The capacity of the negative electrode was set to 4 times the capacity of the positive electrode body. The open-type test battery was manufactured as follows. That is, the positive electrode body and the negative electrode were laminated with a separator made of non-woven fabric interposed therebetween. Then, a pressure of 0.5 MPa was applied to this laminate to form an open-type test battery with excess electrolyte. The non-woven fabric is formed by using polyolefin resin fibers. As the electrolytic solution, a 6.8 mol / l potassium hydroxide aqueous solution was used. An Hg / HgO electrode was used as the reference electrode.

(5) Charging Step The open type test battery was charged by the following first step and second step. In the first step, 1/40 at 40 ° C
At a charging rate of 50 It (A), the positive electrode potential is Hg /
Constant current charging was performed up to +350 mV with respect to the HgO reference electrode. In the second step, 0.1 It (A) at 20 ° C.
The charging rate of current is 120 against the nickel hydroxide capacity.
% Additional charging was performed.

Through the above steps, a nickel positive electrode was obtained.

(Example 2) A nickel positive electrode was obtained in the same manner as in Example 1 except that the first step of the charging step was different. In this first step, 1/50 It at 60 ° C.
Constant current charging was performed until the positive electrode potential was +280 mV with respect to the Hg / HgO reference electrode with the current having the charging rate of (A).

(Example 3) A nickel positive electrode was obtained in the same manner as in Example 1, except that the first step of the charging step was different. In this first step, 1/50 It at 80 ° C.
Constant current charging was performed at a charge rate of (A) at a positive electrode potential of +250 mV with respect to the Hg / HgO reference electrode.

Example 4 A nickel positive electrode was obtained in the same manner as in Example 1 except that the first step of the charging step was different. In this first step, 1/50 It at 40 ° C.
Constant current charging was performed at a charge rate of (A) at a positive electrode potential of +320 mV with respect to the Hg / HgO reference electrode.

Example 5 A nickel positive electrode was obtained in the same manner as in Example 1 except that the first step of the charging step was different. In this first step, 1/50 It at 40 ° C.
Constant current charging was performed at a charge rate of (A) at a positive electrode potential of +300 mV with respect to the Hg / HgO reference electrode.

(Example 6) A nickel positive electrode was obtained in the same manner as in Example 1 except that the first step of the charging step was different. In this first step, 1/50 It at 40 ° C.
Constant current charging was performed until the positive electrode potential was +270 mV with respect to the Hg / HgO reference electrode with the current having the charging rate of (A).

(Comparative Example 1) A nickel positive electrode was obtained in the same manner as in Example 1, except that the first step of the charging step was different. In this first step, 1/50 It at 20 ° C.
Constant current charging was performed at a charging rate of (A) at a positive electrode potential of +400 mV with respect to the Hg / HgO reference electrode.

Comparative Example 2 A nickel positive electrode was obtained in the same manner as in Example 1, except that the oxidation step was not performed and the charging step was performed as follows. In this charging process, at 20 ℃, 1
After charging for 12 hours at a charge rate of / 50 It (A), it was charged for 10 hours at a charge rate of 0.1 It (A).

Table 1 shows the conditions of the charging process in Examples 1 to 6 and Comparative Example 1.

[0088]

[Table 1]

After the charging step, the test batteries of Examples 1 to 6 and Comparative Examples 1 and 2 were discharged to 0 mV with respect to the Hg / HgO reference electrode with a current having a discharge rate of 0.2 It (A). did. The charge / discharge cycle was repeated 5 times until the discharge capacity became stable. The cycle is 0.1 It
Charged at constant current for 15 hours at a charging rate of (A), 0.2 It
0 mV against Hg / HgO reference electrode at discharge rate of (A)
It is a constant current discharge until. After the discharge capacities were stabilized, the nickel positive electrodes of Examples 1 to 6 and Comparative Examples 1 and 2 were subjected to the following tests (a), (b), (d) and (e).
The test (c) was conducted after the test (b).

(A) Utilization rate of active material As shown in Equation 2, 0.2 It with respect to theoretical capacity
The ratio of the discharge rate capacity of (A) was defined as the utilization rate (%). Utilization rate = ((0.2 It (A) discharge rate capacity) / (theoretical capacity)) × 100 Equation 2

(B) High Rate Discharge Characteristics High rate discharge was performed as follows. That is, 0.1 It
After carrying out constant current charging for 15 hours at the charging rate of (A), 5.0
It was discharged at a constant current with a discharge rate of It (A) until it reached 0 mV with respect to the Hg / HgO reference electrode. As shown in Expression 3, the ratio of the discharge rate capacity of 5.0 It (A) to the theoretical capacity was defined as the high rate discharge characteristic (%). High rate discharge characteristic = ((5.0 It (A) discharge rate capacity) / (theoretical capacity)) × 100 ... Equation 3

(C) Active material retention rate After constant current discharge with a discharge rate of 5.0 It (A) in the measurement of high rate discharge characteristics was completed, 0.2 It was further added.
Constant-current discharge was performed at the discharge rate of (A). Then, the test battery was disassembled and the nickel positive electrode was taken out. The nickel positive electrode taken out was thoroughly washed with ion-exchanged water, and then 10
It was dried at 0 ° C. overnight, and its weight was measured. This weight is referred to as front weight A. Next, the nickel positive electrode after the weight measurement was put into a beaker, and ultrasonic vibration was applied for 10 minutes. afterwards,
The nickel positive electrode was taken out of the beaker, dried overnight at 100 ° C., and weighed. This weight is the rear weight B
And Then, as shown in Expression 4, from the weight difference before and after applying the ultrasonic vibration, the degree of the positive electrode active material falling off in the nickel positive electrode was determined as the active material retention rate (%). Active material retention rate = (B / A) × 100 ... Equation 4

(D) Leaving recovery rate A high temperature standing test was conducted. That is, after leaving it at 60 ° C. for 30 days, it is charged 150% at a charge rate of 0.1 It (A),
It was discharged at a discharge rate of 0.2 It (A) until it reached 0 mV with respect to the Hg / HgO reference electrode. As shown in Equation 5,
The ratio of the discharge capacity after standing to the discharge capacity before standing was defined as the standing recovery rate (%). Recovery rate after leaving = ((Discharge capacity after leaving) / (Discharge capacity before leaving)) x 100 ... Equation 5

(E) Overdischarge recovery rate An overdischarge test was conducted. That is, after short-circuiting with a 6Ω resistance for 72 hours, it is charged 150% at a charge rate of 0.1 It (A), and becomes 0 mV to a Hg / HgO reference electrode at a discharge rate of 0.2 It (A). Discharged up to. As shown in Expression 6, the ratio of the discharge capacity after the short circuit to the discharge capacity before the short circuit was defined as the overdischarge recovery rate (%). Over discharge recovery rate = ((discharge capacity after short circuit) / (discharge capacity before short circuit)) × 100 ... Equation 6

The results of the above tests (a) to (e) are shown in Table 2.

[0096]

[Table 2]

As can be seen from Table 2, the nickel positive electrodes of Examples 1 to 6 are higher than the nickel positive electrodes of Comparative Examples 1 and 2.
The active material utilization rate, high rate discharge characteristics, active material retention rate, leaving recovery rate, and overdischarge recovery rate were all excellent. this is,
The unoxidized cobalt hydroxide left on the surface layer of the positive electrode material is charged or oxidized at a temperature of 40 to 80 ° C. in the first step of the charging step, so that a stronger conductive network is formed. It is thought that it is because it was done.

Further, as can be seen by comparing Examples 4 to 6, the high rate discharge characteristics and the active material retention rate are changed depending on the current cut potential. From this, it can be said that there is utility in defining the current cut potential.

Example 7 A nickel positive electrode was obtained in the same manner as in Example 1 except that the charging step had an intermediate step. This charging step has an intermediate step between the first step and the second step, and in the intermediate step, the cut potential of the first step is held for 2 hours.

Example 8 A nickel positive electrode was obtained in the same manner as in Example 2, except that the charging step had an intermediate step. This charging step has an intermediate step between the first step and the second step, and in the intermediate step, the cut potential of the first step is held for 2 hours.

Example 9 A nickel positive electrode was obtained in the same manner as in Example 3, except that the charging step had an intermediate step. This charging step has an intermediate step between the first step and the second step, and in the intermediate step, the cut potential of the first step was held for 2 hours.

Comparative Example 3 A nickel positive electrode was obtained in the same manner as in Example 1 except that the charging process was different. This charging step includes a first step, an intermediate step, and a second step. In the first step, 1/50 It at 20 ° C.
Constant current charging was performed at a charging rate of (A) at a positive electrode potential of +350 mV with respect to the Hg / HgO reference electrode. In the intermediate step, the cut potential of the first step was maintained for 2 hours. In the second step, 120% additional charging was performed at 20 ° C. with a current having a charging rate of 0.1 It (A) with respect to the nickel hydroxide capacity.

Table 3 shows the conditions of the charging process in Examples 7 to 9 and Comparative Example 3.

[0104]

[Table 3]

After the discharge capacity was stabilized in the same manner as described above, the same tests as described above were conducted on the nickel positive electrodes of Examples 7 to 9 and Comparative Example 3. The results are shown in Table 4.

[0106]

[Table 4]

As can be seen from Table 4, the nickel positive electrodes of Examples 7 to 9 are higher than the nickel positive electrodes of Examples 1 to 3.
Performance is improved. From this, it is considered that by performing the intermediate step in the charging step, the unoxidized cobalt hydroxide in the layer of the positive electrode material after the oxidation step was sufficiently oxidized and the conductive network was further strengthened.

Examples 10 to 18 relate to the invention described in claim 2. In particular, Examples 16 to 18 are claimed in Claim 3.
The present invention relates to the described invention.

(Embodiment 10) (1) Oxidation process First, the positive electrode material was oxidized. As the positive electrode material, zinc and
And nickel cobalt solid solution with cobalt and cobalt
Layer made of β-cobalt hydroxide on the surface of positive electrode active material particles
Was used. Zinc and Cobal dissolved
The content of g is 4 parts by weight and 5 parts by weight in terms of metal ratio, respectively.
Part and The content of the layer made of β-cobalt hydroxide is
It was 6% by weight with respect to the positive electrode material. Oxidation is 90 ℃, 3
K which is an oxidant in 0% sodium hydroxide aqueous solution_Two
S _TwoO₈Was carried out for 2 hours.
K_TwoS_TwoO₈The amount of use of 2. is based on 10 g of the positive electrode material.
It was 5 g. Average of nickel and cobalt after oxidation process
The oxidation number was 2.15.

When the cyclic voltammetry of the positive electrode material after the oxidation step was performed in the same manner as in Example 1, no oxidation peak from cobalt hydroxide to cobalt oxyhydroxide was observed. This shows that unoxidized cobalt hydroxide does not exist in the layer on the surface of the positive electrode material after the oxidation step.

(2) Paste Preparation Step 98 parts by weight of the positive electrode material after the oxidation step and 2 parts by weight of cobalt hydroxide were mixed, and 80 parts by weight of the mixture and 20 parts by weight of an aqueous solution of carboxymethyl cellulose as a thickener were mixed. , And mixed to prepare a paste.

(3) Step of Manufacturing Positive Electrode Body The same process as in Example 1 was carried out. A positive electrode body having a capacity of 1000 mAh was obtained.

(4) Arrangement process The same procedure as in Example 1 was performed.

(5) Charging Step The open type test battery was charged by the following first step and second step. In the first step, 1/40 at 40 ° C
At a charging rate of 50 It (A), the positive electrode potential is Hg /
Constant current charging was performed up to +350 mV with respect to the HgO reference electrode. In the second step, 0.1 It (A) at 20 ° C.
The charging rate of current is 120 against the nickel hydroxide capacity.
% Additional charging was performed.

Through the above steps, a nickel positive electrode was obtained.

(Example 11) A nickel positive electrode was obtained in the same manner as in Example 10, except that the first step of the charging step was different. In this first step, at 60 ° C., 1/50 I
Constant current charging was performed until the positive electrode potential was +280 mV with respect to the Hg / HgO reference electrode with a current having a charging rate of t (A).

(Example 12) A nickel positive electrode was obtained in the same manner as in Example 10 except that the first step of the charging step was different. In this first step, 1/50 I at 80 ° C
Constant current charging was performed at a charge rate of t (A) until the positive electrode potential reached +250 mV with respect to the Hg / HgO reference electrode.

(Example 13) A nickel positive electrode was obtained in the same manner as in Example 10, except that the first step of the charging step was different. In this first step, 1/50 I at 40 ° C
Constant current charging was performed at a charge rate of t (A) until the positive electrode potential was +320 mV with respect to the Hg / HgO reference electrode.

(Example 14) A nickel positive electrode was obtained in the same manner as in Example 10, except that the first step of the charging step was different. In this first step, 1/50 I at 40 ° C
Constant current charging was performed at a charge rate of t (A) until the positive electrode potential was +300 mV with respect to the Hg / HgO reference electrode.

(Example 15) A nickel positive electrode was obtained in the same manner as in Example 10 except that the first step of the charging step was different. In this first step, 1/50 I at 40 ° C
Constant current charging was performed until the positive electrode potential was +270 mV with respect to the Hg / HgO reference electrode with a current having a charging rate of t (A).

(Comparative Example 4) A nickel positive electrode was obtained in the same manner as in Example 10 except that the first step of the charging step was different. In this first step, 1/50 It at 20 ° C.
Constant current charging was performed at a charging rate of (A) at a positive electrode potential of +400 mV with respect to the Hg / HgO reference electrode.

(Comparative Example 5) A nickel positive electrode was obtained in the same manner as in Example 10 except that cobalt hydroxide was not mixed in the paste making step and the charging step was carried out as follows. In this charging process, 1/50 It at 20 ° C.
0.1 It after charging for 12 hours at the charging rate of (A)
The battery was charged at the charge rate of (A) for 10 hours.

Table 5 shows the conditions of the charging process in Examples 10 to 15 and Comparative Example 4.

[0124]

[Table 5]

After the charging step, the test batteries of Examples 10 to 15 and Comparative Examples 4 and 5 were subjected to a discharge rate of 0.2 It (A) at a current of up to 0 mV with respect to the Hg / HgO reference electrode. Discharged. The charge / discharge cycle was repeated 5 times until the discharge capacity became stable. The cycle is 0.1 I
Charged with constant current for 15 hours at a charging rate of t (A), 0.2 I
0m with respect to Hg / HgO reference electrode at a discharge rate of t (A)
A constant current discharge is performed until the voltage reaches V. After the discharge capacity was stabilized, the nickel positive electrodes of Examples 10 to 15 and Comparative Examples 4 and 5 were subjected to the same tests (a) to (e) as described above. The test results are shown in Table 6.

[0126]

[Table 6]

As can be seen from Table 6, Examples 10 to 15
The nickel positive electrode of No. 4 was superior to the nickel positive electrodes of Comparative Examples 4 and 5 in all of the active material utilization rate, high rate discharge characteristics, active material retention rate, leaving recovery rate, and overdischarge recovery rate. This is because the cobalt hydroxide mixed in the paste making process
It is considered that in the first step of the charging step, a strong conductive network was formed by being charged or oxidized at a temperature of 40 to 80 ° C.

Further, as can be seen by comparing Examples 13 to 15, the high rate discharge characteristics and the active material retention rate are changed depending on the current cut potential. From this, it can be said that there is utility in defining the current cut potential.

(Example 16) A nickel positive electrode was obtained in the same manner as in Example 10 except that the charging step had an intermediate step. This charging step has an intermediate step between the first step and the second step, and in the intermediate step, the cut potential of the first step is held for 2 hours.

Example 17 A nickel positive electrode was obtained in the same manner as in Example 11 except that the charging step had an intermediate step. This charging step has an intermediate step between the first step and the second step, and in the intermediate step, the cut potential of the first step is held for 2 hours.

Example 18 A nickel positive electrode was obtained in the same manner as in Example 12 except that the charging step had an intermediate step. This charging step has an intermediate step between the first step and the second step, and in the intermediate step, the cut potential of the first step was held for 2 hours.

Comparative Example 6 A nickel positive electrode was obtained in the same manner as in Example 10 except that the charging process was different. This charging step includes a first step, an intermediate step, and a second step. In the first step, 1/50 It at 20 ° C.
Constant current charging was performed at a charging rate of (A) at a positive electrode potential of +350 mV with respect to the Hg / HgO reference electrode. In the intermediate step, the cut potential of the first step was maintained for 2 hours. In the second step, 120% additional charging was performed at 20 ° C. with a current having a charging rate of 0.1 It (A) with respect to the nickel hydroxide capacity.

Table 7 shows the conditions of the charging process in Examples 16 to 18 and Comparative Example 6.

[0134]

[Table 7]

After the discharge capacity was stabilized in the same manner as described above, the nickel positive electrodes of Examples 16 to 18 and Comparative Example 6 were
The same tests (a) to (e) as described above were performed. The test results are shown in Table 8.

[0136]

[Table 8]

As can be seen from Table 8, Examples 16-18
The nickel positive electrode of No. 1 has improved performance as compared with the nickel positive electrodes of Examples 10 to 12. From this, by performing the intermediate step in the charging step, the cobalt hydroxide mixed in the paste making step is sufficiently oxidized,
It is considered that the conductive network was further strengthened.

{Manufacture of Alkaline Storage Battery} Example 19 relates to the invention described in claim 8, and Example 20 relates to the invention described in claim 9.

Example 19 A positive electrode body was manufactured in the same manner as in the oxidizing step, paste manufacturing step, and positive electrode body manufacturing step of Example 1. However, the positive electrode body was for AAA size, and the capacity was 750 mAh.

Next, an assembly process was performed instead of the arrangement process of Example 1. In the assembling step, a positive electrode body, a negative electrode, and a separator were combined to prepare a pole group, the pole group was placed in a battery case, immersed in an electrolytic solution, and the battery container was sealed to assemble a battery.
The negative electrode was produced in the same manner as the negative electrode in the arrangement process of Example 1. However, the negative electrode was for AAA size, and the capacity was set to 1.6 times the capacity of the positive electrode body. As the separator, a polypropylene resin-based non-woven fabric graft-polymerized with acrylic acid was used. The pole group was produced by winding the positive electrode body and the negative electrode with the separator interposed therebetween. A cylindrical case was used as the battery case. As the electrolyte,
6.8 mol / l potassium hydroxide aqueous solution and 0.5 mo
A mixed solution with a 1 / l lithium hydroxide aqueous solution was used. Thus, a cylindrical AAA size sealed alkaline storage battery (nickel hydrogen storage battery) having a capacity of 750 mAh was manufactured. The electrolytic solution was injected in an amount of 0.9 ml per 1 Ah of the positive electrode capacity.

Then, the charging process was performed. This charging step includes a first step, an intermediate step, and a second step.
In the first step, constant current charging was performed at 60 ° C. with a current having a charging rate of 1/50 It (A) until the terminal voltage was 1150 mV. In the intermediate step, the cut potential of the first step is set to 2
Held for hours. In the second step, 0.1 It at 20 ° C.
With the current having the charging rate of (A), the nickel hydroxide capacity was additionally charged for 12 hours.

An alkaline storage battery was obtained through the above steps.

(Comparative Example 7) The oxidation step was not carried out, and the charging step was carried out as follows.
An alkaline storage battery was obtained. In this charging step, constant-current charging was performed at 20 ° C. at a charging rate of 1/50 It (A) for 12 hours, and then at 20 ° C. at a charging rate of 0.1 It (A) for 10 hours.

Example 20 A positive electrode body was manufactured in the same manner as in the oxidizing step, paste manufacturing step, and positive electrode body manufacturing step of Example 10. However, the positive electrode body was for AAA size, and the capacity was 750 mAh.

Next, the same assembling process as in Example 19 was performed.

Then, the same charging process as in Example 19 was performed.

An alkaline storage battery was obtained through the above steps.

(Comparative Example 8) The oxidation step was not performed, and the charging step was performed as follows, except that the same procedure as in Example 20 was carried out.
An alkaline storage battery was obtained. In this charging step, constant-current charging was performed at 20 ° C. at a charging rate of 1/50 It (A) for 12 hours, and then at 20 ° C. at a charging rate of 0.1 It (A) for 10 hours.

The alkaline storage batteries of Examples 19 and 20 and Comparative Examples 7 and 8 were treated with 0.2 It (A) after the charging step.
The voltage between the terminals was discharged to 1.0 V with the current having the discharge rate of. The charge / discharge cycle was repeated 5 times until the discharge capacity became stable. The cycle is 0.1 It (A)
Charged at constant current for 15 hours at a charging rate of 0.2 It (A)
At constant discharge rate, constant current discharge is performed until the voltage between terminals becomes 1.0V. After the discharge capacity became stable, Example 1
Regarding the alkaline storage batteries of 9, 20 and Comparative Examples 7 and 8,
The following tests (a), (d), (e) and (f) were conducted.

(A) Utilization rate of active material As shown in the above equation 2, 0.2 It with respect to the theoretical capacity
The ratio of the discharge rate capacity of (A) was defined as the utilization rate (%).

(D) Leaving recovery rate A high temperature standing test was conducted. That is, after leaving it at 60 ° C. for 30 days, it is charged 150% at a charge rate of 0.1 It (A),
It was discharged at a discharge rate of 0.2 It (A) until the voltage between terminals became 1.0V. As shown in the above formula 5, the ratio of the discharge capacity after standing to the discharge capacity before standing was defined as the standing recovery rate (%).

(E) Over-discharge recovery rate An over-discharge test was conducted. That is, after short-circuiting with a 6Ω resistor for 72 hours, the battery is charged at 150% at a charge rate of 0.1 It (A) and the terminal voltage is 1.0 at a discharge rate of 0.2 It (A).
It was discharged to V. As shown in the above formula 6, the ratio of the discharge capacity after the short circuit to the discharge capacity before the short circuit was defined as the overdischarge recovery rate (%).

(F) Guideline for Discharge Reserve The battery at the end of discharge was disassembled, the negative electrode was taken out, and the amount of hydrogen gas contained in the negative electrode was measured. The measuring method is as follows. That is, first, the taken out negative electrode was put into an Erlenmeyer flask filled with distilled water and sealed with a silicone rubber stopper. In order to take out the hydrogen gas generated from the negative electrode, a tube was passed through the center of the rubber stopper and the hydrogen gas was guided to the graduated cylinder by the water replacement method. At this time, the Erlenmeyer flask containing the negative electrode was heated, the hydrogen gas contained in the negative electrode was generated by Formula 7, and the amount of generated hydrogen gas was measured. The amount of collected hydrogen gas is 1 mol of hydrogen gas according to the formula 8.
= 22400 ml per 2 Faraday consumed, and converted into electrochemical capacity.

[0154] That is, (negative) MH → M + 1/2 H 2 ... Equation _{7 H 2 → 2H + 2e -} ... Equation 8 1F (Faraday) = 96500C (coulomb) 1C = 1A · sec. Is. Therefore, (reference for discharge reserve) [Ah] = (amount of hydrogen gas)
[Ml] x (2 x 96500) / (22400 x 360
0)

The results of the above tests are shown in Table 9.

[0156]

[Table 9]

As can be seen from Table 9, Examples 19 and 20
The alkaline storage battery of 1 is superior in leaving recovery rate and over-discharge recovery rate to the alkaline storage batteries of Comparative Examples 7 and 8. Further, the discharge reserve amount of the alkaline storage batteries of Examples 19 and 20 is considerably smaller than that of the alkaline storage batteries of Comparative Examples 7 and 8. Therefore, in the alkaline storage batteries of Examples 19 and 20, the substantial charge / discharge capacity on the negative electrode side can be increased,
Therefore, high capacity can be achieved while achieving miniaturization.

(Other Example) In Example 1, cobalt hydroxide may be mixed with the positive electrode material in the paste preparation step. According to this, the mixed cobalt hydroxide is precipitated as a higher cobalt compound across the positive electrode active material particles in the first step of the charging step together with the unoxidized cobalt hydroxide in the layer of the positive electrode material, Form a strong conductive network. Therefore, the same effect as that of the first embodiment is obtained. However, the effect of reducing the discharge reserve is reduced as compared with Example 1 by the amount of the mixed cobalt hydroxide.

As the method for producing an alkaline storage battery, two examples 19 and 20 are given. The method for producing nickel positive electrodes of Examples 1 to 18 is the same as Example 1.
It goes without saying that the alkaline storage battery can be obtained by appropriately changing the manufacturing method as described in 9, 20.

[0160]

According to the invention described in claim 1 or 2,
It is possible to obtain a nickel positive electrode that can reduce the discharge reserve and improve the utilization rate of the active material.

According to the invention described in claim 3 or 4, it is possible to obtain a nickel positive electrode which can more reliably improve the utilization rate of the active material.

According to the invention described in claim 5, it is possible to obtain a nickel positive electrode which can reduce the discharge reserve to a satisfactory level and can improve the active material utilization rate to a satisfactory level.

According to the invention described in claim 6, a nickel positive electrode which can more reliably improve the utilization rate of the active material can be obtained in a practically relatively short time.

According to the invention described in claim 7, the nickel positive electrode can be obtained in a practically relatively short time without causing deterioration of the negative electrode or swelling of the positive electrode.

According to the invention described in claim 8, it is possible to obtain an alkaline storage battery based on the nickel positive electrode described in claim 1 and capable of exhibiting good effects.

According to the invention described in claim 9, it is possible to obtain an alkaline storage battery based on the nickel positive electrode according to claim 2, which can exhibit good effects.

According to the invention of claim 10, claim 3
It is possible to obtain an alkaline storage battery that can exert good effects based on the described nickel positive electrode.

According to the invention of claim 11, claim 4
It is possible to obtain an alkaline storage battery that can exert good effects based on the described nickel positive electrode.

According to the invention of claim 12, claim 5
It is possible to obtain an alkaline storage battery that can exert good effects based on the described nickel positive electrode.

According to the invention described in claim 13, claim 6
It is possible to obtain an alkaline storage battery that can exert good effects based on the described nickel positive electrode.

According to the invention of claim 14, claim 7
It is possible to obtain an alkaline storage battery that can exert good effects based on the described nickel positive electrode.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the oxidation potential of cobalt hydroxide to cobalt oxyhydroxide and temperature.

FIG. 2 is a cutaway perspective view showing an embodiment of the alkaline storage battery of the present invention.

FIG. 3 is a diagram showing a cyclic voltammogram of the positive electrode material after the oxidation step of Example 1.

[Explanation of symbols]

1 alkaline storage battery 2 cases 3 positive electrode 4 Negative electrode 5 separator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Seijiro Ochiai             2-32 Kosobe-cho, Takatsuki City, Osaka Prefecture Stock             Ceremony company Yuasa Corporation (72) Inventor Kengo Furukawa             2-32 Kosobe-cho, Takatsuki City, Osaka Prefecture Stock             Ceremony company Yuasa Corporation (72) Inventor Minoru Kuzuhara             2-32 Kosobe-cho, Takatsuki City, Osaka Prefecture Stock             Ceremony company Yuasa Corporation (72) Inventor, Shoji Watada             2-32 Kosobe-cho, Takatsuki City, Osaka Prefecture Stock             Ceremony company Yuasa Corporation (72) Inventor Masahiko Oshiya             2-32 Kosobe-cho, Takatsuki City, Osaka Prefecture Stock             Ceremony company Yuasa Corporation F term (reference) 5H028 AA05 AA07 BB01 BB03 BB06                       BB10 EE05 FF02 HH00 HH01                       HH08 HH10                 5H050 AA02 AA08 BA11 CA03 CB16                       GA10 GA13 GA15 GA18 GA22                       HA14 HA18 HA19 HA20

Claims (14)

[Claims] 1. A layer made of a low-order cobalt compound having cobalt having a valence of 2 or less is formed on the surface of positive electrode active material particles made of nickel hydroxide solid solution in which nickel hydroxide or a different element is solid-dissolved. An oxidizing step of oxidizing the positive electrode material so that a part of the lower cobalt compound in the layer and a part of the nickel hydroxide in the positive electrode active material are oxidized, and a step of forming the positive electrode material into a paste, a paste Manufacturing process, applying the paste to the current collector to manufacture the positive electrode body, positive electrode body manufacturing process, arranging the positive electrode body in the electrolytic solution together with the counter electrode, charging the positive electrode body and the counter electrode The charging step includes a first step and a second step, and the first step is performed at a temperature of 40 to 80 ° C. to a mercury oxide electrode of −60 mV. To a predetermined potential in the range from 1 to 400 mV Flow charging, and the second step is 100 to 150 relative to the nickel hydroxide capacity when the one-electron reaction is performed at a temperature of 20 to 40 ° C.
%, Additional charging is performed, the method for producing a nickel positive electrode. 2. A layer made of a lower cobalt compound having a divalent or lower cobalt is formed on the surface of positive electrode active material particles made of nickel hydroxide solid solution in which nickel hydroxide or a different element is solid-dissolved. The positive electrode material is oxidized so that all of the lower cobalt compounds in the layer and some of the nickel hydroxide in the positive electrode active material are oxidized, and an oxidizing step is performed, and the lower material cobalt compound is mixed with the positive electrode material. A step of making the mixture into a paste, a step of making a paste, a step of applying a paste to a current collector to make a positive electrode body, a step of making a positive electrode body, and a step of placing the positive electrode body together with a counter electrode in an electrolytic solution And a charging step of charging the positive electrode body and the counter electrode. The charging step includes a first step and a second step, and the first step is performed at a temperature of 40 to 80 ° C. -60 mV against mercury oxide electrode To constant current charging to a predetermined potential in the range of 400 to 400 mV, and the second step is 100 to 150 with respect to the nickel hydroxide capacity when the one-electron reaction is performed at a temperature of 20 to 40 ° C.
%, Additional charging is performed, the method for producing a nickel positive electrode. 3. The nickel positive electrode according to claim 1, further comprising an intermediate step between the first step and the second step, in which constant voltage charging is performed for 30 minutes or more at a predetermined potential of the first step. Manufacturing method. 4. The method for producing a nickel positive electrode according to claim 1, wherein a low order cobalt compound is mixed with the positive electrode material in the paste preparation step to make the mixture into a paste. 5. The method for producing a nickel positive electrode according to claim 2, wherein the amount of the lower cobalt compound mixed in the paste preparation step is 0.5 to 8% by weight based on the positive electrode material. 6. The charging current value in the first step is 1/100 to 1 with respect to the nickel hydroxide capacity in the case of one-electron reaction.
The method for producing a nickel positive electrode according to claim 1 or 2, wherein the charge rate is / 20 It (A). 7. The charging current value in the second step is 1/20 to 1
The method for producing a nickel positive electrode according to claim 1 or 2, wherein the charging rate is / 3 It (A). 8. A layer made of a lower cobalt compound having a divalent or lower cobalt is formed on the surface of positive electrode active material particles made of nickel hydroxide solid solution in which nickel hydroxide or a different element is solid-dissolved. An oxidizing step of oxidizing the positive electrode material so that a part of the lower cobalt compound in the layer and a part of the nickel hydroxide in the positive electrode active material are oxidized, and a step of forming the positive electrode material into a paste, a paste Manufacturing process, applying a paste to a current collector to manufacture a positive electrode body, a positive electrode body manufacturing process, combining a positive electrode body, a negative electrode and a separator to prepare a pole group, and putting the pole group in a battery case. It has an assembling process of assembling a battery by closing the battery case with an electrolytic solution, a charging process of charging the battery, and a charging process. The charging process includes the first process and the second process. The first step is at a temperature of 40 to 80 ° C. Constant-current charging is performed to a predetermined potential in the range of -60 mV to 400 mV with respect to the mercury oxide electrode, and the nickel hydroxide capacity when the second step is a one-electron reaction at a temperature of 20 to 40 ° C. To 100-150
%, Additional charging is performed, and a method of manufacturing an alkaline storage battery. 9. A layer made of a lower cobalt compound having a cobalt valence of 2 or less is formed on the surface of positive electrode active material particles made of nickel hydroxide or a solid solution of nickel hydroxide in which a different element is solid-dissolved. The positive electrode material is oxidized so that all of the lower cobalt compounds in the layer and some of the nickel hydroxide in the positive electrode active material are oxidized, and an oxidizing step is performed, and the lower material cobalt compound is mixed with the positive electrode material. A step of forming the mixture into a paste, a step of producing a paste, a step of applying the paste to a current collector to produce a positive electrode body, a step of producing a positive electrode body, a combination of a positive electrode body, a negative electrode and a separator to produce a pole group , The electrode group is placed in a battery case, immersed in an electrolytic solution, the battery container is sealed, and a battery is assembled, and an assembly process and a charging process of charging the battery are included. , Consisting of the first step and the second step The first step is to charge the mercury oxide electrode with a constant current to a predetermined potential in the range of −60 mV to 400 mV at a temperature of 40 to 80 ° C., and the second step is to a temperature of 20 to 40 ° C. 100 to 150 relative to the nickel hydroxide capacity in the case of one-electron reaction
%, Additional charging is performed, and a method of manufacturing an alkaline storage battery. 10. The alkaline storage battery according to claim 8, further comprising an intermediate step between the first step and the second step, which performs constant voltage charging for 30 minutes or more at a predetermined potential of the first step. Manufacturing method. 11. The method of manufacturing an alkaline storage battery according to claim 8, wherein a low order cobalt compound is mixed with the positive electrode material in the paste preparation step to make the mixture into a paste. 12. The amount of the lower cobalt compound mixed in the paste preparation step is 0.5 to 8% by weight with respect to the positive electrode material.
The method for manufacturing an alkaline storage battery according to claim 9, wherein 13. The charging current value in the first step is 1/100 to the nickel hydroxide capacity in the case of one-electron reaction.
The charging rate is 1/20 It (A), and the charging rate is 8 or 9.
The method for manufacturing an alkaline storage battery according to. 14. The charging current value in the second step is 1/20 to 20.
The method for manufacturing an alkaline storage battery according to claim 8 or 9, wherein the charging rate is 1/3 It (A).