JP2989877B2 - Nickel hydride rechargeable battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a nickel-metal hydride secondary battery, and more particularly to a nickel-metal hydride secondary battery in which a non-sintered nickel positive electrode is improved.

(Prior Art) Recent advances in electronic technology have led to power savings and advances in packaging technology, which have led to cordless and portable electronic devices that were not expected in the past. For this reason, a secondary battery, which is a power supply incorporated in the electronic device, is also required to have a high capacity. As such a secondary battery, an alkaline secondary battery using a negative electrode having a structure in which hydrogen storage alloy particles are fixed to a conductive core serving as a current collector has been proposed, and has begun to attract attention. The negative electrode using the hydrogen storage alloy can increase the energy density per unit weight or unit volume as compared with cadmium, which is a conventional representative negative electrode material for an alkaline secondary battery, and has a high battery capacity. In addition to being capable of reducing the risk of environmental pollution, the battery has excellent battery characteristics.

By the way, as the nickel positive electrode for determining the battery capacity in the alkaline secondary battery, a sintered positive electrode which has been used for a conventional nickel cadmium secondary battery is known. Such a sintered nickel positive electrode is formed, for example, by forming carbonyl nickel into a predetermined shape on a punched metal and sintering the porous conductive core to be immersed in an aqueous solution containing nickel ions. It is produced by generating nickel hydroxide in micropores on the surface by a typical method, and then repeating charging and discharging several times in an alkaline solution. The sintered nickel positive electrode manufactured by such a method has complicated processes, and it is not possible to reduce the manufacturing cost.In addition, since the volume of the sintered core occupying the positive electrode increases, the electric capacity density is reduced. There was a problem that it was very difficult to improve.

Therefore, non-sintered nickel positive electrodes have been developed in response to demands for higher capacity and lower cost of batteries. This non-sintered nickel positive electrode is prepared by applying nickel hydroxide powder and water to a paste with a desired binder, and applying the paste to various conductive cores having a three-dimensional structure such as foamed metal and reticulated metal fibers. After filling, it is obtained by press molding. Such a non-sintered nickel positive electrode occupies a larger amount of the active material than the sintered nickel positive electrode, so that a higher capacity can be achieved. In addition, since it does not require complicated steps such as the impregnation step and the formation step as in the case of the sintered nickel positive electrode,
Mass production and cost reduction are possible. However, in the non-sintered nickel positive electrode, the distance between the nickel particles as the active material and the metal matrix forming the conductive core as the current collector is several times to several times as compared with the sintered nickel positive electrode. Because it is ten times as long, the current collecting property is deteriorated. As a result, there is a problem that the utilization rate of nickel hydroxide is reduced to 50 to 60%, and the performance is greatly reduced as compared with the sintered nickel positive electrode.

In order to solve the above-mentioned problems, addition of a cobalt compound has been performed. Typical cobalt compounds include metallic cobalt, cobalt oxide, and cobalt hydroxide, and among them, cobalt monoxide has a very high activity, and the addition of a small amount improves the conductivity and utilization of the nickel positive electrode. A great effect can be exhibited.

However, cobalt monoxide easily reacts with oxygen in the air, oxidizes deep into the cobalt monoxide powder, and cannot exert its inherent effect. In addition, cobalt monoxide has a risk of igniting when a rapid oxidation reaction proceeds. Therefore, it is necessary to produce a non-sintered nickel positive electrode in an inert atmosphere such as nitrogen or argon. There was also a problem in point.

On the other hand, JP-A-61-183868 discloses nickel hydroxide.
85-95 mol%, cobalt hydroxide 3-8 mol% and cadmium hydroxide 2-7 mol% For eutectic active material powder mixed with cobalt monoxide (CoO) powder 5-30 wt% for alkaline storage batteries A paste-type positive electrode is disclosed. However, since such a paste-type positive electrode contains cadmium having high toxicity as one component of the active material, there is a possibility that environmental pollution will be caused when the paste-type positive electrode is disposed of.

(Problem to be Solved by the Invention) An object of the present invention is to provide a nickel-metal hydride secondary battery with an improved utilization rate of a positive electrode.

Another object of the present invention is to provide a nickel-metal hydride secondary battery having improved charge / discharge characteristics at a large current.

Still another object of the present invention is to provide a nickel-metal hydride secondary battery in which an increase in internal pressure during a charge / discharge cycle is suppressed.

Still another object of the present invention is to provide a nickel-metal hydride rechargeable battery having an improved charge / discharge cycle life by preventing a phenomenon of depletion of an alkaline electrolyte in a separator when charge / discharge is repeated. .

Still another object of the present invention is to provide a nickel-metal hydride secondary battery capable of suppressing an increase in internal pressure in an overcharged state and capable of minimizing deterioration in characteristics when overdischarge is performed over a long period of time. It is something to offer.

[Structure of the Invention] (Means for Solving the Problems) A nickel-metal hydride secondary battery according to the present invention will be described in detail with reference to FIG.

The non-sintered nickel positive electrode 1 is spirally wound between a hydrogen storage alloy negative electrode 2 containing a hydrogen storage alloy powder and a separator 3 made of a nonwoven fabric made of a synthetic resin, and has a bottomed cylindrical container 4. Is housed inside. The alkaline electrolyte is contained in the container 4. A circular sealing plate 6 having a hole 5 in the center is arranged at the upper opening of the container 4. The ring-shaped insulating gasket 7 is disposed between the peripheral edge of the sealing plate 6 and the inner surface of the upper opening of the container 4, and the sealing plate is formed on the container 4 by caulking to reduce the diameter of the upper opening inward. 6 is hermetically fixed via the gasket 7. One end of the positive electrode lead 8 is connected to the positive electrode 1, and the other end is connected to the lower surface of the sealing plate 6. A positive electrode terminal 9 having a hat shape is mounted on the sealing plate 4 so as to cover the hole 5. The rubber safety valve 10
The hole 5 is disposed in a space surrounded by the sealing plate 4 and the positive terminal 9.

The non-sintered nickel positive electrode 1 collects a mixture having a composition in which nickel hydroxide and cobalt monoxide (CoO) whose surface is covered with a higher cobalt oxide layer are used as an active material and a binder is mixed. It is configured to be formed on a conductive core body which is a body.

The high-order cobalt oxide covering the surface of cobalt monoxide blended in the mixture of the positive electrode 1 means a cobalt oxide having two or more valences, for example, Co ₂ O ₃ , Co ₃ O _{4 and the} like. be able to. Here, the coating of the higher oxide layer on the surface of cobalt monoxide means that at least a part of the surface, preferably 90% or more of the surface is covered with the higher cobalt oxide of about several atomic layers. It is. As a method for forming such a high-order cobalt oxide layer, for example, after baking the cobalt hydroxide in a non-oxidizing atmosphere to form cobalt monoxide, a small amount of oxygen is introduced into the atmosphere to remove only the surface. An oxidizing method may be employed. Also, the amount of the higher order cobalt oxide layer is desirably 0.1 to 20% by weight based on cobalt monoxide. This is for the following reason. When the amount of the higher cobalt oxide layer is less than 0.1% by weight, it is difficult to sufficiently suppress the oxidation reaction. On the other hand, if the amount of the higher cobalt oxide layer exceeds 20% by weight, the activity of cobalt monoxide may be reduced.

The amount of cobalt monoxide mixed in the mixture of the positive electrode 1 is preferably in the range of 2 to 20% by weight based on the nickel hydroxide. This is for the following reason. If the amount of the cobalt monoxide is less than 2% by weight, the utilization of the non-sintered nickel positive electrode may not be improved. On the other hand, the compounding amount of the cobalt monoxide is 20
If the content is more than 10% by weight, the amount of nickel hydroxide occupying in the positive electrode decreases, resulting in a decrease in capacity. Moreover, in the practical current region, the amount of electricity required for the oxidation of the cobalt monoxide, which is an irreversible reaction, increases, so the reserve amount of charge of the negative electrode of the hydrogen storage alloy becomes too small. There is a possibility that the capacity (hydrogen storage capacity) of the negative electrode is reduced and the internal pressure is increased.

Examples of the binder mixed in the mixture of the positive electrode 1 include polyacrylates such as sodium polyacrylate and potassium polyacrylate, and carboxymethyl cellulose (CMC). It is desirable that the compounding ratio of such a binder be in the range of 0.1 to 2% by weight based on nickel hydroxide.

Examples of the conductive core of the positive electrode 1 include those having a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those having a three-dimensional structure such as foamed metal and reticulated metal fiber.

The positive electrode 1 is prepared by kneading the nickel hydroxide and cobalt monoxide, the surface of which is covered with a higher oxide layer, together with the binder in the presence of water to prepare a paste. It is manufactured by applying to a body, drying, and then performing a roller press.

The hydrogen storage alloy negative electrode 2 has a configuration in which a mixture of a composition obtained by mixing a hydrogen storage alloy powder, a conductive material powder, and a binder is formed on a conductive core serving as a current collector.

The hydrogen storage alloy blended in the mixture of the negative electrode 2 is not particularly limited, and can store electrochemically generated hydrogen in an electrolytic solution, and easily store the stored hydrogen during discharge. Anything that can be released can be used. For example, the general formula XY _5-a Z _a (provided that the rare earth element X including La, Y is N
i and Z are at least one element selected from Co, Mn, Al, V, Cu, and B, and a represents 0 ≦ a <2.0). Specifically, LaNi ₅ , MmNi ₅ , LmNi ₅ (L
m; lanthanum-enriched misch metal) and their Ni
Is a multi-element-based material in which part of is replaced by an element such as Al, Mn, Fe, Co, Ti, Cu, Zn, Zr, Cr, and B.

Examples of the conductive material powder mixed in the mixture of the negative electrode 2 include carbon black, graphite, and acetylene black. In particular, from the viewpoint of improving the hydrogen absorption and desorption characteristics of the hydrogen storage alloy powder contained in the negative electrode and suppressing the voltage drop of the negative electrode when current is applied, the specific surface area is preferably 700 m ² / g or more, more preferably It is preferable to use carbon black having a specific surface area of 800 m ² / g or more. Examples of such carbon black include furnace black and Ketjen black. The reason for limiting the specific surface area of the carbon black is that when the specific surface area is less than 700 m ² / g, it is possible to sufficiently improve the hydrogen absorption / desorption characteristics and the voltage drop of the hydrogen storage alloy powder contained in the negative electrode. This is because it becomes difficult. As the carbon black, those having a three-dimensional chain structure in which carbon particles (primary particles) of about 10 to 30 nm are secondarily aggregated are more preferable.

The amount of the conductive material powder mixed in the mixture of the negative electrode 2 is as follows:
It is desirable that the amount be 0.1 to 4 parts by weight based on 100 parts by weight of the hydrogen storage alloy powder. This is for the following reason. When the amount of the conductive material powder is less than 0.1 part by weight, the electrical connection between the hydrogen storage alloy powder and the electrical connection between the hydrogen storage alloy powder and the conductive core, which is an effect of adding the conductive powder, is sufficiently improved. It becomes difficult. On the other hand, if the amount of the conductive powder exceeds 4 parts by weight, the amount of the hydrogen-absorbing alloy powder per unit volume of the negative electrode may decrease, and a large capacity may not be obtained. A more preferable mixing ratio of the conductive powder is in the range of 0.1 to 2 parts by weight based on 100 parts by weight of the hydrogen storage alloy.

Examples of the binder mixed in the mixture of the negative electrode 2 include polyacrylates such as sodium polyacrylate and potassium polyacrylate, fluorine-based resins such as polytetrafluoroethylene (PTFE), and carboxymethyl cellulose. (CMC) and the like. The mixing ratio of the binder is 100 parts by weight of the hydrogen storage alloy.
It is desirable to add 0.1 to 5 parts by weight.

Examples of the conductive core of the negative electrode 2 include those having a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those having a three-dimensional structure such as foamed metal and reticulated metal fiber.

The negative electrode 2 was prepared by kneading the hydrogen storage alloy powder and the conductive material powder together with the binder in the presence of water to prepare a paste, applying the paste to the conductive core, drying the paste, and then pressing the paste with a roller press. It is manufactured by performing.

The negative electrode 2 has a capacity in the range of 1.0 to 2.5 times the sum of the capacity of nickel hydroxide of the non-sintered nickel positive electrode 1 and the quantity of electricity required for oxidizing cobalt monoxide. this is,
This is for the following reasons. If the capacity of the negative electrode is less than 1.0 times that of the positive electrode, the hydrogen storage capacity at the beginning of the charge / discharge cycle becomes insufficient, and the internal pressure of the battery during charging increases. On the other hand, if the capacity of the negative electrode exceeds 2.5 times that of the positive electrode, the volume of the non-sintered nickel positive electrode that can be stored in a container of a fixed volume is reduced due to the increase in the volume of the negative electrode. In addition to alienation, the use of a large amount of expensive hydrogen-absorbing alloy causes an increase in cost.

Examples of the synthetic resin nonwoven fabric from which the separator 3 is made include a polypropylene nonwoven fabric, a polyamide nonwoven fabric,
A nonwoven fabric in which polypropylene fibers and polyamide fibers are mixed can be used. In particular, the basis weight (fiber weight per unit area) is 50 to 100 g / m ² and the thickness is 0.1 to 0.25
It is desirable to use a mm separator. The reason for limiting the basis weight of the separator is as follows. When the basis weight of the separator to less than 50 g / m ^2, the amount of the alkaline electrolyte, wherein the separator can hold is small fence, liquid withered phenomenon of the electrolyte solution is generated with the progress of charge-discharge cycles, charge and discharge cycles Life may be shortened. On the other hand, the basis weight of the separator is 100 g / m ²
When the ratio exceeds, the volume of the fibers occupying in the separator increases, so that the space for holding the alkaline electrolyte becomes too small, and there is a possibility that a liquid withering phenomenon may occur from the beginning of the charge / discharge cycle. The reason for limiting the thickness of the separator is as follows. If the thickness of the separator is less than 0.1 mm, the occurrence rate of internal short circuit may increase. On the other hand, when the thickness of the separator exceeds 0.25 mm, the volume occupied by the separator in the container is increased, and the volume occupied by the positive electrode and the negative electrode is reduced, which may hinder high capacity.

Examples of the alkaline electrolyte include a mixture of potassium hydroxide (KOH) and lithium hydroxide (LiOH), a mixture of sodium hydroxide (NaOH) and LiOH, or a mixture of NaOH, KOH and LOH.
A mixed solution of iOH and the like can be used. In particular, NaOH and LiO
It is preferable to use a mixture of H as the alkaline electrolyte.

Further, in the nickel-metal hydride secondary battery having the above-described configuration, from the viewpoint of suppressing the internal pressure rise in an overcharged state and improving the discharge / overdischarge characteristics of a large current, the monoxide of the positive electrode is started from the start of the first charge step. It is desirable that the current value during a period when an amount of electricity equal to or more than 1.5 times the amount of electricity in which cobalt is oxidized to cobalt oxyhydroxide be in the range of 0.05 to 1 CmA. Here, 1 CmA means a current value (mA) that can charge or discharge the nominal capacity of the secondary battery in one hour. For example, 0.05 CmA means that the nominal capacity of the secondary battery is charged or discharged in 20 hours. It is a current value that can be discharged.

The reason for limiting the current value in the initial charging step of the secondary battery is as follows. If the current value in the initial charging step is less than 0.05 CmA, the amount of electricity consumed by gas generation, which is a competitive reaction during charging, increases. As a result, the oxidation of cobalt monoxide contained in the non-sintered nickel positive electrode to cobalt oxyhydroxide becomes insufficient, and it becomes difficult to leave a part of the charged part in the hydrogen storage alloy negative electrode. The effect of improving current discharge / overdischarge characteristics cannot be expected. On the other hand, if the current value in the first charging step exceeds 1 CmA, oxidation of cobalt monoxide and nickel hydroxide occur simultaneously with oxidation of cobalt monoxide, so that the efficiency of oxidation of cobalt monoxide to cobalt oxyhydroxide decreases (the hydrogen storage (A part of the charged portion of the alloy negative electrode is reduced), and it is difficult to improve the activity of the negative electrode. As a result, the reduction reaction for rapidly returning oxygen gas generated from the positive electrode to water in the overcharge region becomes insufficient, which may cause an increase in internal pressure.

The reason for limiting the period in the initial charging step of the secondary battery is that if the period is shorter than the period, the oxidation of cobalt monoxide contained in the positive electrode to cobalt oxyhydroxide is insufficient, and the negative electrode is partially charged. This is because it is difficult to leave the portion.

In FIG. 1 described above, the separator 3 is interposed between the non-sintered nickel positive electrode 1 and the hydrogen storage alloy negative electrode 2 and spirally wound and accommodated in the bottomed cylindrical container 4. A separator may be interposed between the non-sintered nickel positive electrode and the plurality of hydrogen storage alloy negative electrodes to form a laminate, and the laminate may be housed in a bottomed cylindrical container.

(Operation) The nickel-hydrogen secondary battery according to the present invention has various excellent characteristics listed below.

. By providing a non-sintered nickel positive electrode having a structure in which a mixture containing nickel hydroxide and cobalt monoxide whose surface is covered with a higher cobalt oxide layer is formed on a conductive core, the positive electrode before the first charge is provided. Can be suppressed in the air by the higher-order cobalt oxide layer to suppress the natural oxidation reaction of cobalt monoxide contained in the positive electrode. Moreover, cobalt monoxide whose surface is covered with a higher cobalt oxide layer can improve storage characteristics as compared with pure cobalt monoxide. Accordingly, the utilization rate of the positive electrode, which is a characteristic inherent to cobalt monoxide, is improved, and a nickel-hydrogen secondary battery having a long charge-discharge cycle life can be obtained.

Further, the cobalt monoxide covered with the higher cobalt oxide layer can avoid the danger of ignition accompanying the rapid progress of the oxidation reaction, and has stable characteristics even in air,
Without special gas atmosphere such as argon, nitrogen, etc.
A positive electrode can be manufactured under a normal atmosphere.

Furthermore, if a non-sintered nickel positive electrode containing 5 to 20% by weight of cobalt monoxide covered with the higher cobalt oxide layer with respect to nickel hydroxide is used, the effect of the cobalt monoxide can be obtained. Is sufficiently achieved, and a sufficient amount of hydrogen (preliminary discharge) remaining in the hydrogen-absorbing alloy negative electrode at the end of discharge can be maintained. Discharge characteristics)
A nickel-metal hydride secondary battery with improved properties can be obtained.

. The capacity of the hydrogen storage alloy negative electrode in which the mixture containing the hydrogen storage alloy powder and the conductive material powder is formed in the conductive core is changed to the non-sintering in which the mixture containing nickel hydroxide and cobalt monoxide is formed in the conductive core. By setting the range of 1.0 to 2.5 times the sum of the capacity of the nickel hydroxide and the amount of electricity required for the oxidation of the cobalt monoxide in the formula nickel positive electrode, the internal pressure rise at a relatively early stage of the charge / discharge cycle can be reduced. A suppressed nickel-hydrogen secondary battery can be obtained.

That is, at the time of charging a nickel-metal hydride secondary battery, a reaction occurs in which nickel hydroxide contained therein is oxidized to nickel oxyhydroxide on the non-sintered nickel positive electrode side, and an alkaline electrolyte solution is formed on the hydrogen storage alloy negative electrode side. Since the reaction that absorbs the hydrogen generated by the electrolysis occurs, the internal pressure does not increase. At the time of discharging the secondary battery, the nickel oxyhydroxide therein is reduced to nickel hydroxide on the positive electrode side, and the absorbed hydrogen is oxidized on the negative electrode side,
Similarly, no internal pressure rise occurs. In order for the charge and discharge to be performed smoothly without such an increase in the internal pressure, the capacity of the hydrogen storage alloy negative electrode must be large enough to absorb the entire amount of hydrogen generated by electrolysis of the alkaline electrolyte during charging. It is necessary to have.

By the way, in a normal nickel-metal hydride secondary battery, the capacity of the hydrogen storage alloy negative electrode was set to be equal to the capacity of nickel hydroxide in the non-sintered nickel positive electrode. However, at the time of charging, a part of the cobalt monoxide is oxidized together with the nickel hydroxide in the positive electrode to become cobalt oxyhydroxide. When the cobalt monoxide is oxidized, electrolysis of the alkaline electrolyte in the container containing the positive electrode and the negative electrode occurs, generating hydrogen in an amount corresponding to the amount of electricity required for the oxidation and absorbing the hydrogen in the negative electrode. Is done. Moreover, once the cobalt monoxide is oxidized to cobalt oxyhydroxide, it is hardly reduced at the time of discharge, so that it is generated at the relatively early stage of charging and discharging as the cobalt monoxide is oxidized to cobalt oxyhydroxide. The absorbed hydrogen remains absorbed by the negative electrode. That is, at a relatively early stage of charging and discharging, the hydrogen storage capacity of the negative electrode decreases by the amount of hydrogen generated by the oxidation of the cobalt monoxide. As a result, when the capacity of the negative electrode is set in accordance with the amount of hydrogen generated due to the oxidation of nickel hydroxide in the positive electrode,
At the time of charging, the negative electrode cannot absorb a part of hydrogen generated as the nickel hydroxide is oxidized, and remains in the container. Therefore, a significant increase in the internal pressure occurs at a relatively early stage of charging and discharging.

For this reason, the capacity of the hydrogen storage alloy negative electrode is within a range of 1.0 to 2.5 times the sum of the capacity of nickel hydroxide of the non-sintered nickel positive electrode and the quantity of electricity required for oxidizing cobalt monoxide. That is, assuming that the negative electrode has a capacity that also accounts for the amount of hydrogen generated along with the oxidation of cobalt monoxide,
A nickel-metal hydride secondary battery in which an increase in internal pressure at a relatively early stage of a charge / discharge cycle is suppressed can be obtained.

. In the hydrogen-absorbing alloy negative electrode, if carbon black having a specific surface area of 700 m ² / g or more is used as the conductive material powder, the carbon black causes the hydrogen-absorbing alloy powder or the hydrogen-absorbing alloy powder to have a conductive core that is a current collector. Since the electrical contact point with the body can be increased, the electric resistance of the negative electrode can be reduced, a large current can be taken out, and a nickel-hydrogen secondary battery having excellent charge / discharge characteristics at a large current can be obtained. it can.

Further, as the carbon black, particularly about 10 to 30 nm
If a fine carbon particle (primary particle) having a texture in which secondary carbon particles (primary particles) are secondary aggregated and the three-dimensional chain structure is well developed is used,
Since the number of particles at the same weight increases and more carbon molecules can be dispersed in the negative electrode, the electrical contact points between the hydrogen storage alloy powder and between the hydrogen storage alloy powder and the conductive core can be further increased. In addition, since the three-dimensional chain structure is well developed, the electrical contacts between the hydrogen-absorbing alloy powders or the hydrogen-absorbing alloy powder and the conductive core are in a matrix. As a result, the electric resistance of the negative electrode can be significantly reduced, so that a large current can be taken out and a nickel-hydrogen secondary battery having significantly improved charge / discharge characteristics at a large current can be obtained.

The hydrogen storage alloy powder contained in the negative electrode can be electrically and efficiently used by the action of the carbon black described above, so that the surface area of the hydrogen storage alloy involved in the battery reaction (oxidation / reduction reaction) can be increased, and the charge / discharge time can be increased. Can reduce the polarization in the hydrogen storage alloy, and can improve not only the large current characteristics but also the gas reaction rate. In addition, since the carbon black in the negative electrode causes an electrochemical reaction also on the surface thereof, the reaction on the carbon black also contributes to the improvement of the gas reaction rate during overcharging and discharging. Therefore, overcharging,
It is possible to obtain a nickel-metal hydride secondary battery having a long charge-discharge cycle life in which the reactivity of oxygen gas and hydrogen gas during overdischarge is increased and the internal pressure is suppressed from rising.

. In non-basis weight between sintered nickel positive electrode, the hydrogen storage alloy negative electrode is 50 to 100 g / m ^2, when brought into interposed separator thickness formed of a synthetic resin nonwoven fabric of 0.1 to 0.25 mm, in the separator A secondary battery can be obtained from a nickel-metal hydride battery having a long charge-discharge cycle life by preventing the alkaline electrolyte from withering.

That is, in a normal nickel-hydrogen secondary battery, as the charge / discharge cycle progresses, the positive electrode housed in the container expands and presses the separator, and the amount of the alkaline electrolyte in the separator decreases and the electrolyte dies. The phenomenon occurs. For this reason, if a separator having the specific weight and the thickness specified in the above ranges is used, a sufficient amount of the alkaline electrolyte can be held in the separator. As a result, even if the positive electrode expands and presses the separator with the progress of the charge / discharge cycle, it is possible to prevent the alkaline electrolyte in the separator from withering. You can get a battery.

. A hydrogen storage alloy negative electrode in which a mixture containing a hydrogen storage alloy powder and a conductive material powder is formed on a conductive core, and a mixture containing nickel hydroxide and cobalt monoxide whose surface is covered with a higher cobalt oxide layer. A separator is interposed between the non-sintered nickel positive electrode formed on the conductive core body, and this is stored in a container.The nickel-hydrogen secondary battery having a configuration in which an alkaline electrolyte is further stored in the container is 0.05 to 1 CmA. When the battery is charged for the first time with the above current value, cobalt monoxide in the positive electrode is oxidized to cobalt oxyhydroxide, and then the nickel hydroxide is oxidized to generate nickel oxyhydroxide. Cobalt oxyhydroxide generated at the time of the first charge is hardly reduced even after discharging, and is maintained in a stable state. Further, since the amount of electricity consumed during the oxidation directly acts on the generation of hydrogen at the negative electrode, a charged portion corresponding to the amount of electricity remains on the negative electrode. If the initial charge at such a current value is performed during a period in which an amount of electricity of 1.5 times or more the amount of electricity that the cobalt monoxide is oxidized to cobalt oxyhydroxide is applied, the cobalt monoxide in the positive electrode is almost completely charged. All can be converted to cobalt oxyhydroxide. As a result, the utilization rate of the positive electrode is improved, so that a high-capacity nickel-metal hydride secondary battery can be obtained. On the other hand, since a part of the charged portion remains in the negative electrode, it is possible to obtain a highly reliable nickel-metal hydride secondary battery in which gas generation due to large current discharge is prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Examples 1 to 3 First, 90 parts by weight of nickel hydroxide and 10% by weight of Co ₃ O ₄
10 parts by weight of cobalt monoxide, the surface of which is covered with a higher oxide layer, is dry-mixed with polytetrafluoroethylene (PTFE) and carboxymethylcellulose (CMC), and then pure water is added and kneaded to form a paste. Was prepared. Subsequently, this paste is filled into a nickel sintered fiber core,
Drying, pressing and cutting were performed to produce a non-sintered nickel positive electrode.

In addition, the composition of LmNi _4.2 Co _0.2 Mn _0.3 Al _0.3 (Lm indicates La-enriched misch metal) and 100 parts by weight of hydrogen storage alloy powder with 200 mesh pass and specific surface area of 700 m ² / g, 800 m ² / g, 1200 m
One part by weight of ² / g furnace black was added to sodium polyacrylate, CMC and PTFE, and kneaded with a mixer in the presence of pure water to prepare three types of pastes. These pastes were applied to punched metal, dried, pressed, and cut to produce three types of hydrogen storage alloy negative electrodes.

Next, a test cell shown in FIG. 2 was assembled using the positive electrode and the negative electrodes. In FIG. 2, an alkaline electrolyte 12 composed of an 8N-KOH solution is accommodated in a bottomed rectangular cylindrical container 11. On both sides of the hydrogen storage alloy negative electrode 13, non-sintered nickel positive electrodes 14 are respectively arranged. Separators 15 made of polypropylene nonwoven fabric are interposed between both sides of the negative electrode 13 and the positive electrode, respectively. The negative electrode 13, the positive electrode 14, and the separator 15 are housed in the container 11. Pressing plates 16 made of two insulating materials are disposed on both sides of the two positive electrodes 14,
And a separator 15. The reference electrode 17 is housed in the container 11.

A test cell having a capacity of 1000 mAh and an AA size as shown in FIG. 3 was assembled using the positive electrode and the negative electrodes. Third
In the figure, a space having the same inner diameter and height as the AA size metal container is provided near the center of the acrylic resin cell body 21.
22 are formed. Cap 23 acts as sealing plate
Is attached to the opening of the cell body 21. An electrode group 24 in which a non-sintered nickel positive electrode and a hydrogen storage alloy negative electrode were wound via a separator made of a polyamide nonwoven fabric,
It is housed in the space 22 of the cell body 21. The pressure detector 25 for monitoring the pressure in the cell is provided with the cap
Attached to 23. The cell body 21 and the cap
23 is an 8N-KO in the space 22 in which the electrode group 24 is housed.
After injecting 2.4 ml of an alkaline electrolyte composed of an H solution, the assembly is assembled with the rubber sheet 26 and the O-ring 27 interposed between the cell main body 21 and the cap 23, and sealed with bolts 28 and nuts 29. The lead 30 for the nickel positive electrode is connected to the positive electrode of the electrode group 24, the lead 31 for the hydrogen storage alloy negative electrode is connected to the negative electrode of the electrode group 24, and the leads 30, 31 are connected to the rubber sheet 26 and O Each extends outside through between the rings 27.

Comparative Example 1 100 parts by weight of the hydrogen storage alloy powder as in Example 1 and 1 part by weight of acetylene black having a specific surface area of 80 m ² / g were added to sodium polyacrylate, CMC and PTFE, and the mixture was mixed in the presence of pure water. To prepare a paste. This paste is applied to punched metal, dried and pressed,
By cutting, a hydrogen storage alloy negative electrode was produced. A test cell having the structure shown in FIG. 2 described above was assembled using the prepared negative electrode and the same positive electrode as in Example 1.

In addition, an AA-size test cell having the structure shown in FIG. 3 described above was assembled using the negative electrode and the same positive electrode as in Example 1.

Comparative Example 2 100 parts by weight of the same hydrogen storage alloy powder as in Example 1 and 1 part by weight of graphite having a specific surface area of 5 m ² / g were added to sodium polyacrylate, CMC and PTFE, and mixed with a mixer in the presence of pure water. A paste was prepared by kneading. This paste was applied to punched metal, dried, pressed, and cut to produce a hydrogen storage alloy negative electrode. A test cell having the structure shown in FIG. 2 described above was assembled using the prepared negative electrode and the same positive electrode as in Example 1.

In addition, an AA-size test cell having the structure shown in FIG. 3 described above was assembled using the negative electrode and the same positive electrode as in Example 1.

The test cells having the structure shown in FIG. 2 in Examples 1 to 3 and Comparative Examples 1 and 2 were repeatedly charged and discharged at a current of 150 mA per 1 g of the hydrogen storage alloy contained in the hydrogen storage alloy negative electrode.
The voltage of the hydrogen-absorbing alloy negative electrode with respect to the reference electrode during the discharge in the cycle was measured. The results are shown in FIG.

As is clear from FIG. 4, a non-sintered nickel positive electrode containing cobalt monoxide whose surface is covered with a higher cobalt oxide layer and a hydrogen storage alloy negative electrode containing furnace black having a specific surface area of 700 m ² / g or more are provided. The test cells of Examples 1 to 3
It can be seen that the potential characteristics and the capacity of the negative electrode are superior to those of the test cell of Comparative Example 1 including the hydrogen storage alloy negative electrode containing acetylene black and Comparative Example 2 including the hydrogen storage alloy negative electrode including graphite. .

Further, with respect to the test cells having the structure shown in FIG.
First charge for 1 hour, discharge to 0.8V at 1A, then 1.5A at 1A
Charge and discharge for 1 hour and discharge to 0.8 V at 1 A,
An overdischarge test was performed at the 30th cycle, and a change in pressure in the battery with respect to elapsed time was measured using a pressure detector incorporated in the cell. The results are shown in FIG.

As is clear from FIG. 5, the test cells having the AA size of Examples 1 to 3 had a specific surface area of 700 m ² / g incorporated in the cell body.
It can be seen that the hydrogen storage alloy negative electrode containing furnace black described above has a higher reactivity of hydrogen gas during overdischarge than the negative electrodes incorporated in the test cells of Comparative Examples 1 and 2, and the internal pressure rise can be significantly suppressed.

Examples 4 to 9 100 parts by weight of the hydrogen storage alloy powder as in Example 1 and 0.05 parts by weight, 0.1 part by weight, 1 part by weight, 2 parts by weight, 4 parts by weight, and 5 parts by weight of furnace black having a specific surface area of 800 m ² / g. Parts by weight were added to sodium polyacrylate, CMC and PTFE, and kneaded with a mixer in the presence of pure water to prepare six types of pastes. These pastes were applied to punched metal, dried, pressed, and cut to produce six types of hydrogen storage alloy negative electrodes. Each negative electrode produced, the same positive electrode as in Example 1, a polypropylene separator,
Six types of nickel having a structure shown in FIG. 1 having a theoretical capacity of 1000 mAh calculated from the amount of nickel hydroxide using a bottomed cylindrical container and an alkaline electrolyte composed of a mixed solution of 7N-KOH and 1N-LiOH. A hydrogen secondary battery was assembled.

The secondary batteries of Examples 4 to 9 were initially charged at 100 mA for 15 hours, discharged at 1 A to 0.8 V, then charged at 1 A for 1.5 hours, and discharged and discharged at 1 A to 0.8 V 30 times. , 30
The discharge characteristics at 5 A in the cycle were examined. The results are shown in FIG. An open state of 30 minutes was provided between the charge and discharge and between the discharge and charge as a pause time.

As can be seen from FIG. 6, a non-sintered nickel positive electrode containing cobalt monoxide whose surface is covered with a higher cobalt oxide layer and a furnace black having a specific surface area of 700 m ² / g or more were 0.1%.
Examples 5 to 8 provided with a hydrogen storage alloy negative electrode containing not less than parts by weight
It can be seen that the secondary battery of can further improve the discharge characteristics. However, in Example 9 including the hydrogen storage alloy negative electrode containing more than 4 parts by weight of the furnace black, the amount of hydrogen storage alloy per unit volume was reduced, indicating that the capacity was reduced.

Examples 10-12, Comparative Examples 3 and 4 Cobalt monoxide (CoO) whose surface was covered with nickel hydroxide [Ni (OH) ₂ ] and a higher cobalt oxide layer of 10% by weight.
To sodium polyacrylate, CMC and PTFE,
Five kinds of pastes were prepared by kneading in the presence of pure water. Subsequently, these pastes were applied to a nickel sintered fiber core, dried, pressed, and cut to produce five types of non-sintered nickel positive electrodes having the capacity shown in Table 1 below.

Further, five kinds of pastes were prepared by kneading the same hydrogen storage alloy powder and carbon black as in Example 1 together with sodium polyacrylate, CMC, and PTFE by a mixer in the presence of pure water. These pastes are applied to punched metal, dried, pressed, and cut to obtain the first
Five types of hydrogen storage alloy negative electrodes having the capacities shown in the table were produced. In Table 1 below, the capacity ratio of the negative electrode / the positive electrode is also shown.

Next, the theoretical capacity calculated from the amount of nickel hydroxide using the positive electrode and the negative electrode, the same separator as in Example 1, the bottomed cylindrical container, and the alkaline electrolyte was 1000 mA.
h, five types of nickel-metal hydride secondary batteries having the structure shown in FIG. 1 were assembled.

The nickel-hydrogen secondary batteries of Examples 10 to 12 and Comparative Examples 3 and 4 were repeatedly charged and discharged (0.3 CmA 150% charge, 1 CmA discharge), and the discharge capacity was measured until the discharge voltage became 1 V or less during this discharge. Then, the number of cycles when the discharge capacity was reduced to 80% or less of the charge / discharge in the second cycle was examined. The results are shown in Table 1.

As apparent from Table 1 above, Examples 10 to 10 provided with a hydrogen storage alloy negative electrode having a capacity of 1.0 to 2.5 times the sum of the capacity of nickel hydroxide of the positive electrode and the quantity of electricity required for oxidation of cobalt monoxide. It can be seen that the nickel-metal hydride secondary battery of No. 12 exceeds 500 cycles, which is a practically sufficient life, and the secondary batteries of Examples 11 and 12 particularly have an excellent charge-discharge cycle life of more than 800 cycles. In the nickel-metal hydride secondary batteries of Comparative Examples 3 and 4, in which the capacity ratio of the negative electrode / positive electrode is less than 1.0, the discharge capacity is reduced from the beginning of the charge / discharge cycle, and the electrolyte is provided around the safety valve provided on the sealing plate and the positive electrode terminal. Leakage was confirmed. It is considered that the decrease in the discharge capacity of the nickel-metal hydride secondary batteries of Comparative Examples 3 and 4 was caused by the liquid withering due to the leakage of the electrolytic solution due to the increase in the battery internal pressure.

Examples 13 to 17 and Reference Examples Cobalt monoxide (CoO) coated with nickel hydroxide [Ni (OH) ₂ ] and a high-order cobalt oxide layer of 10% by weight.
To sodium polyacrylate, CMC and PTFE,
Six kinds of pastes were prepared by kneading in the presence of pure water. Subsequently, these pastes were applied to a nickel sintered fiber core, dried, pressed, and cut to produce six types of non-sintered nickel positive electrodes having the capacity shown in Table 2 below.

In addition, the same hydrogen storage alloy powder and carbon black as in Example 1 were kneaded together with PTFE by a mixer in the presence of pure water to prepare six types of pastes. These pastes were applied to punched metal, dried, pressed, and cut to produce six types of hydrogen storage alloy negative electrodes having the capacity shown in Table 2 below. In Table 2 below, the capacity ratio of the negative electrode / the positive electrode and the content of CoO in the positive electrode are shown together.

Next, the theoretical capacity calculated from the amount of nickel hydroxide using the positive electrode and the negative electrode, the same separator as in Example 1, the bottomed cylindrical container, and the alkaline electrolyte was 1000 mA.
h, six types of nickel-metal hydride secondary batteries having the structure shown in FIG. 1 were assembled.

For the nickel-metal hydride secondary batteries of Examples 13 to 17 and Reference Example, after performing a 20-cycle break-in charge and discharge, a discharge capacity until the discharge voltage becomes 1 V or less at 1 CmA discharge, and 5 CmA
During discharge, the discharge capacity until the discharge voltage became 1 V or less was measured. Table 2 also shows the ratio of the 5 CmA discharge capacity to the 1 CmA discharge capacity.

As is clear from Table 2 above, the secondary battery of the reference example is:
The discharge capacity at 5 CmA discharge is low. This is because the amount of cobalt monoxide added was small and the large-current discharge characteristics of the non-sintered nickel positive electrode deteriorated, and the amount of hydrogen occlusion in the hydrogen storage alloy negative electrode was too small at the end of discharge. It is considered that the regulation was a result of mutual influence. On the other hand, the secondary batteries of Examples 13 to 17 were 5 m
There was no problem due to a decrease in discharge capacity during AC discharge, and the device operated well. Although the discharge capacity of the secondary battery of Example 13 at 5 CmA discharge tended to be slightly unstable, it can be seen that the secondary batteries of Examples 14 to 17 have sufficient large current discharge characteristics.

Example 18 First, 90 parts by weight of nickel hydroxide and 10 parts by weight of cobalt monoxide whose surface was covered with a 10% by weight high-order cobalt oxide layer were dry-mixed with sodium polyacrylate and CMC. PTFE and pure water were added and kneaded to prepare a paste. Subsequently, this paste was filled in a nickel sintered fiber core, dried, pressed, and cut to produce a non-sintered nickel positive electrode.

Further, a hydrogen storage alloy powder having the same composition as in Example 1 and 200 mesh pass and carbon black were added to sodium polyacrylate, PTFE and CMC, and kneaded in the presence of pure water to prepare a paste. This paste was applied to punched metal, dried, pressed, and cut to produce a hydrogen storage alloy negative electrode.

Further, the basis weight is 25 g / m ² , 50 g / m ² , 75 g / m ² , 100 g / m ²
m ^2, at ^{125g / m 2, 150g / m} 2, 0.05mm thickness, 0.10 mm, 0.15
Separators made of 42 types of polypropylene fiber nonwoven fabric of mm, 0.20 mm, 0.25 mm, 0.30 mm, and 0.35 mm were prepared.

Next, the separator made of each of the polypropylene nonwoven fabrics is spirally wound between the non-sintered nickel positive electrode and the hydrogen storage alloy negative electrode, and these are housed in a mild steel bottomed cylindrical container, and further the container Within 7N-KOH and 1N-L
Forty-two types of nickel-metal hydride rechargeable batteries having the structure shown in Fig. 1 and containing an alkaline electrolyte consisting of a mixture of iOH and having a theoretical capacity of 1000 mAh calculated from the amount of nickel hydroxide were assembled.

For each nickel-metal hydride secondary battery of Example 18, the battery was charged to 150% of the battery capacity at 1 CmA, and the discharge voltage was 0.8 V at 1 CmA.
Charge / discharge was repeated until the discharge capacity decreased to less than 50% of the initial discharge capacity, and the number of cycles was determined. The results are shown in Table 3 below.

As is evident from Table 3 above, a non-sintered nickel positive electrode containing cobalt monoxide whose surface was covered with a high-order cobalt oxide layer, a basis weight of 50 to 100 g / m ² and a thickness of 0.1 ~
A secondary battery provided with a separator made of 0.25 mm polypropylene nonwoven fabric has a sufficient charge / discharge cycle life, exceeding the battery life of a typical nickel-cadmium secondary battery of 500 cycles. In contrast, the thickness is 0.05mm
In, since the basis weight secondary batteries having a separator made of ^{25g / m 2, 50g / m} 2, 75g / m 2 polypropylene non-woven fabric is already internal short when wound in the positive and negative electrodes sandwiching the separator, The charge / discharge cycle test could not be performed. Further, in a secondary battery provided with a separator made of a 0.3-mm-thick polypropylene fiber nonwoven fabric, an alkaline electrolyte leaked from a safety valve disposed between a positive electrode terminal and a sealing plate, and the discharge voltage was reduced. It is considered that the reason for this is that the gas permeability was reduced due to the thick separator, and the internal pressure was increased.

Example 19 First, 90 parts by weight of nickel hydroxide and 10 parts by weight of cobalt monoxide whose surface was covered with a higher-order cobalt oxide layer were dry-mixed with sodium polyacrylate, PTFE and CMC, and then purified water was added. Was added and kneaded to prepare a paste.
Subsequently, this paste was filled in a nickel sintered fiber core, dried, pressed, and cut to produce a non-sintered nickel positive electrode. In the positive electrode thus manufactured, the theoretical capacity of nickel hydroxide was 980 to 2020 mAh, and the amount of electricity required for oxidation of cobalt monoxide was 121 to 126 mAh.

Further, a hydrogen storage alloy powder having the same composition as that of Example 1 and 200 mesh pass and carbon black were added to sodium polyacrylate, PTFE and CMC, and kneaded in the presence of water to prepare a paste. This paste was applied to punched metal, dried, pressed, and cut to produce a hydrogen storage alloy negative electrode. The negative electrode manufactured in this manner has a capacity of 1650 to 1750 mAh, and has a capacity of 1.7 times the sum of the capacity of nickel hydroxide and the quantity of electricity required for oxidation of cobalt monoxide of the positive electrode. Met.

Next, using the non-sintered nickel positive electrode and the hydrogen storage alloy negative electrode, the theoretical capacity of 1000 mAh shown in FIG.
An A-size test cell was assembled.

After the obtained test cell (theoretical capacity: 1000 mAh) was allowed to stand at 45 ° C. for 24 hours and stored, it was initially charged to 150% of the battery capacity at various current values shown in Table 4 below. For the test cell after such initial charge, the internal pressure behavior during initial charge,
The residual capacity, cycle life, and internal pressure behavior during overdischarge of the hydrogen storage alloy negative electrode were examined. The results are also shown in Table 4.

In addition, the residual capacity of the negative electrode is for the battery after the first charge.
The battery discharged to 0.8 V at a current value of 1 CmA was disassembled, and the amount of electricity in a partially charged state remaining without being discharged to the negative electrode (residual amount), that is, remaining without being discharged to the negative electrode with respect to the total capacity of the negative electrode It was measured from the ratio of the amount of electricity in a partially charged state.

The cycle life is 150% of the battery capacity at 1 CmA.
It was measured by repeating charge / discharge of charging up to 0.8 V at 1 CmA. However, an open state of 30 minutes was provided between the charge and the discharge and between the discharge and the charge as a pause time.

Further, the internal pressure behavior at the time of the overdischarge is such that charge and discharge under the above conditions are repeated for each of 100 test cells, the discharge is continued at 0.2 CmA at the 30th cycle, and after a point crossing 0 V (complete discharge). Evaluation was made based on the pressure change in the overdischarge process of forcibly discharging 100% of the battery capacity.

In the internal pressure behavior at the time of the first charge in Table 4 below, “good” means that the pressure of the test cell is 15 kgf /
Failure to reach cm ² means that the pressure in the test cell reached 15 kgf / cm ² corresponding to the operating pressure of the safety valve, respectively. Further, that the pressure of the well and all 100 test cells in the inner pressure behavior during the over-discharge is not reached 15 kgf / cm ^2, which corresponds to the operating pressure of the safety valve, half in 100 pieces somewhat good test the pressure of the cell reached 15 kgf / cm ^2, which corresponds to the operating pressure of the safety valve, the failure 1
It means that the pressure of all the test cells reached 15 kgf / cm ² corresponding to the operating pressure of the safety valve.

As is clear from Table 4 above, No. 2, No. 3, No. 4, N
In the test cell of o.5, cobalt monoxide in the positive electrode was sufficiently oxidized in the initial charging step, and the utilization rate of the positive electrode was improved. In addition, since the charged portion is generated in the hydrogen storage alloy negative electrode in the first charging step, the overdischarge characteristics are improved. In contrast,
In test cells No. 1 and No. 8, cobalt monoxide in the positive electrode was not sufficiently oxidized in the initial charging step, and the utilization rate of the positive electrode was low. In addition, since the charged portion generated in the negative electrode of the hydrogen storage alloy in the initial charging step is small, the internal pressure rises during overdischarge. Also,
In the test cell No. 7, the overdischarge characteristics were slightly improved, but the battery characteristics were not practically satisfactory.

Example 20 A test cell having the same structure and structure as in Example 19 (theoretical capacity: 1000
mAh) was allowed to stand at a temperature of 45 ° C. for 24 hours, stored, and then initially charged under the conditions shown in Table 5 below. 1C after such initial charge
The residual capacity of the negative electrode after complete discharge at mA was measured. The results are shown in Table 5 above. The residual capacity of the cobalt monoxide contained in the positive electrodes of these test cells is 10% when the entire amount is oxidized and converted into cobalt oxyhydroxide.

As is clear from Table 5 above, in the test cells No. 9 and No. 10, the initial charge amount was small (the initial charge period was short), so that the oxidation of cobalt monoxide in the positive electrode was not sufficiently performed, and It can be seen that the amount of the remaining capacity portion of the occlusion alloy negative electrode is also reduced. Therefore, similarly to the test cell No. 1 in Table 4 described above, the cycle life is short, and the overdischarge characteristics are deteriorated. On the other hand, in the test cells No. 11 to No. 13, cobalt monoxide in the positive electrode is sufficiently oxidized in the initial charging step, and at the same time, the amount of the remaining capacity portion of the hydrogen storage alloy negative electrode increases. Therefore, the cycle life and overdischarge characteristics were good. Based on the characteristics of these test cells, the initial charge amount should be 15% or more of the battery capacity (period in which the amount of electricity is at least 1.5 times the amount of electricity consumed by cobalt monoxide to oxidize cobalt oxyhydroxide).
It can be seen that there is no problem in characteristics. No.14
As in the test cell above, if the current value during the initial charge is changed halfway to reduce the initial charge process and the battery is charged to a total of 150%, the cobalt monoxide in the positive electrode is sufficiently oxidized as described above. At the same time, the amount of remaining capacity of the hydrogen storage alloy negative electrode is sufficient. However, when the period is equivalent to the period consumed for oxidizing cobalt monoxide to cobalt oxyhydroxide as in the test cell of No. 10, the oxidation reaction of cobalt monoxide to cobalt oxyhydroxide is performed. Since a part of the amount of electricity is consumed in a reaction in which nickel hydroxide in the positive electrode is oxidized to nickel oxyhydroxide, which is a competitive reaction of the positive electrode, the oxidation reaction of the cobalt monoxide cannot be completely performed, and the use of the positive electrode Rate etc. decrease.

Example 21 First, 90 parts by weight of nickel hydroxide and 10 parts by weight of cobalt monoxide whose surface was covered with a 10% by weight high-order cobalt oxide layer were dry-mixed together with PTFE and CMC, and then pure water was added. In addition, the mixture was kneaded to prepare a paste. Subsequently, this paste was filled in a nickel sintered fiber core, dried, pressed, and cut to produce a non-sintered nickel positive electrode. In the positive electrode thus manufactured, the theoretical capacity of nickel hydroxide was 1051 mAh, and the amount of electricity required for oxidation of cobalt monoxide was 117.0 mAh.

Further, 100 parts by weight of the same hydrogen storage alloy powder as in Example 1 and 1 part by weight of furnace black having a specific surface area of 800 m ² / g were added to sodium polyacrylate, CMC and PTFE,
A paste was prepared by kneading with a mixer in the presence of pure water. This paste was applied to punched metal, dried, pressed, and cut to produce a hydrogen storage alloy negative electrode. The negative electrode manufactured in this manner has a capacity of 29
At 29 mAh, it had a capacity of 2.50 times the sum of the capacity of nickel hydroxide of the positive electrode and the quantity of electricity required for oxidation of cobalt monoxide.

Next, the basis weight is 75 g / m ² between the non-sintered nickel positive electrode and the hydrogen storage alloy negative electrode, and a separator made of a polypropylene nonwoven fabric having a thickness of 0.15 mm is sandwiched and spirally wound. The above-described first container having a theoretical capacity of 1051 mAh calculated from the amount of nickel hydroxide by storing an alkaline electrolyte composed of a mixture of 7N-KOH and 1N-LiOH in the bottomed cylindrical container, A nickel hydrogen secondary battery having the structure shown in the figure was assembled.

About the obtained nickel-hydrogen secondary battery of Example 21,
The alkaline electrolyte contained in the container was allowed to sufficiently permeate the separator by being left at room temperature for 24 hours. Thereafter, the battery was charged at 0.2 CmA to 150% of the theoretical capacity of the positive electrode, and completely charged at 0.2 CmA. The utilization after 10 cycles of discharging was measured. As a result, it has a 95% utilization rate,
High capacity has been achieved.

Further, for the nickel-metal hydride secondary battery, after performing break-in charge and discharge of 20 cycles, the discharge capacity until the discharge voltage becomes 1 V or less at 1 CmA discharge, and the discharge capacity until the discharge voltage becomes 1 V or less at 5 CmA discharge. The capacity was measured, and the ratio of the 5 CmA discharge capacity to the 1 CmA discharge capacity was examined. as a result,
It was about 80%, and there was no problem due to the decrease in discharge capacity at 5 CmA discharge, and it operated well.

Further, the nickel-hydrogen secondary battery was repeatedly charged and discharged at 1 CmA to 150% of the battery capacity, and discharged at 1 CmA to a discharge voltage of 0.8 V, and the discharge capacity was reduced to less than 50% of the initial discharge capacity. The number of cycles at the time was determined. As a result, the battery had a sufficiently good charge / discharge cycle life, exceeding 1452 cycles, which is 500 cycles, which is the life of a general nickel cadmium secondary battery.

Example 22 A test cell having the structure shown in FIG. 2 described above was assembled using the same non-sintered nickel positive electrode, hydrogen-absorbing alloy negative electrode, and separator made of polypropylene nonwoven fabric as in Example 21.

For the test cell obtained in Example 22, the charge and discharge were repeated at a current of 150 mA per 1 g of the hydrogen storage alloy contained in the hydrogen storage alloy negative electrode, and the voltage of the hydrogen storage alloy negative electrode with respect to the reference electrode at the time of the discharge in the 10th cycle was measured. . as a result,
As in Example 3 described above, it has excellent potential characteristics, and a high capacity is realized.

Example 23 Using the same non-sintered nickel positive electrode, hydrogen-absorbing alloy negative electrode and a separator made of polypropylene non-woven fabric as in Example 21, the A of the structure shown in FIG.
An A-size test cell was assembled.

About the obtained AA size test cell of Example 23, 10
First charge for 15 hours at 0 mA, discharge to 0.8 V at 1 A, then
Repeat charging and discharging by charging at 1.5 A for 1.5 hours and discharging at 0.8 V at 1 A. Perform an overdischarge test at the 30th cycle, and measure the change in battery pressure over time using a pressure detector built into the cell. did. As a result, since the negative electrode incorporated in the test cell had excellent oxygen gas reactivity during overcharge and hydrogen gas reactivity during overdischarge, almost no increase in internal pressure was observed.

Example 24 Using the same non-sintered nickel positive electrode, hydrogen-absorbing alloy negative electrode, and separator made of polypropylene non-woven fabric as in Example 21, an A having a theoretical capacity of 1000 mAh and a structure shown in FIG.
An A-size test cell was assembled. Subsequently, the battery was left standing at a temperature of 45 ° C. for 24 hours and stored, and then initially charged at a current value of 0.5 CmA to 150% of the battery capacity.

For the test cell after the first charge, as in Example 19,
The internal pressure behavior during the initial charge, the residual capacity of the hydrogen storage alloy negative electrode, the cycle life, and the internal pressure behavior during overdischarge were investigated. As a result, the internal pressure behavior during the initial charge and the internal pressure behavior during the overdischarge did not both reach 15 kgf / cm ² corresponding to the operating pressure of the safety valve, and the internal pressure rise was successfully suppressed. The residual capacity of the hydrogen storage alloy negative electrode can be partially charged to 10%,
Moreover, it had a cycle life of 500 times or more. This is because cobalt monoxide in the positive electrode was sufficiently oxidized in the initial charging step to improve the utilization rate of the positive electrode, and at the same time, the amount of the partially charged portion of the hydrogen storage alloy negative electrode increased.

[Effects of the Invention] As described above in detail, according to the present invention, the utilization rate of the positive electrode is high, the charge / discharge characteristics at a large current are improved, and the increase in the internal pressure during the charge / discharge cycle is suppressed. A nickel-hydrogen secondary battery with an improved life can be provided.

[Brief description of the drawings]

1 is a partially exploded perspective view showing a nickel-metal hydride secondary battery according to the present invention, FIG. 2 is a sectional view showing a test cell used in an embodiment of the present invention, and FIG. FIG. 4 is a cross-sectional view showing a test cell of AA size, FIG. 4 is a characteristic diagram showing a relationship between a negative electrode capacity and a negative electrode potential measured in the test cells in Examples 1 to 3 and Comparative Examples 1 and 2, and FIG. 1
FIG. 6 is a characteristic diagram showing the relationship between the internal discharge pressure and the overdischarge time measured in the AA size test cells in Comparative Examples 1 and 2, and FIG. 6 shows the discharge time in the nickel-metal hydride secondary batteries of Examples 4 to 9. FIG. 6 is a characteristic diagram showing a relationship between a battery voltage and a power voltage. 1, 14 ... non-sintered nickel positive electrode, 2, 13 ... hydrogen storage alloy negative electrode, 3, 15 ... separator, 4, 11 ... container, 6
... sealing plate, 7 ... insulating gasket, 12 ... electrolyte, 17
…… Reference electrode, 21 …… Cell body, 23 …… Cap, 25…
... pressure detector, 24 ... electrode group.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoshi Kiyasu 1st Toshiba-cho, Komukai-ku, Kawasaki-shi, Kanagawa Prefecture Inside Toshiba Research Institute, Inc. No. 1 Toshiba Research Institute, Inc. (72) Inventor Hiroyuki Takahashi 3-4-10, Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation (72) Inventor Hirotaka Hayashida Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa No. 1 Toshiba Research Institute, Inc. (72) Inventor Ichiro Saruwatari 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd. (72) Koji Isawa 3-4-4 Minamishinagawa, Shinagawa-ku, Tokyo No. 10 Toshiba Battery Co., Ltd. (72) Katsuyuki Hata 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd. (72) Kazuhiro Yoshida Tokyo Metropolitan Product 3-4-10 Minamishinagawa-ku, Toshiba Battery Co., Ltd. (72) Kunihiko Sasaki, Inventor Toshiba Research Laboratories, Komukai Toshiba-cho, Koyuki-ku, Kawasaki-shi, Kanagawa Prefecture, Japan (58) Field surveyed (Int.Cl . ^6, DB name) H01M 4/32 H01M 4/24 H01M 10/34 H01M 4/52

Claims (4)

(57) [Claims] 1. A non-sintered nickel positive electrode, which is contained in a container and has a conductive core coated with a mixture containing nickel hydroxide and cobalt monoxide whose surface is covered with a higher cobalt oxide layer; It has a structure in which a mixture containing a hydrogen storage alloy powder and a conductive material powder is formed in a conductive core body, and is required for the capacity of nickel hydroxide of the positive electrode and the oxidation of the cobalt monoxide. A hydrogen storage alloy negative electrode having a capacity in the range of 1.0 to 2.5 times the sum of various electric quantities, a separator made of a synthetic resin nonwoven fabric interposed between the positive electrode and the negative electrode, and an alkali contained in the container. A nickel-hydrogen secondary battery, comprising: an electrolytic solution. 2. The nickel-hydrogen secondary battery according to claim 1, wherein the conductive material powder is carbon black having a specific surface area of 700 m ² / g or more. 3. The separator has a basis weight of 50 to 100 g / m ^2.
3. The nickel-metal hydride secondary battery according to claim 1, wherein the secondary battery is made of a synthetic resin nonwoven fabric having a thickness of 0.1 to 0.25 mm. 4. The method according to claim 1, wherein the amount of electricity that the positive electrode cobalt monoxide is oxidized to cobalt oxyhydroxide from the start of the initial charging step is 1.
The current value during the period when 5 times or more electricity is supplied is 0.05 to 1 cm
The nickel-metal hydride secondary battery according to claim 1, wherein the range is A. 5.