JPH06283195A - Nickel-hydrogen secondary battery - Google Patents

Abstract

PURPOSE:To improve rapid discharging characteristic and life expectancy by forming a nickel-hydrogen secondary battery of a positive electrode filled with an active material paste consisting of a porous conductive base material and Ni(OH)2, CoO and ZnO, for each of which the wt.% is specified, a negative electrode consisting of hydrogen absorption alloy, and of an electrolyte consisting of KOH and LiOH. CONSTITUTION:For a porous conductive base material, an Ni sponge having 95-97% of communicating holes is used. For an active paste, a required component consisting of Ni(OH)2, CoO and ZnO is used. The Ni(OH)2 is activated as a positive electrode active material, and the compound ratio thereof in the active material paste is 85-98wt.%. CoO is used to improve the utilization efficiency of the active material, while it is a component for degrading rapid discharging characteristic. The compound ratio of CoO is thus 1-7wt.%. ZnO is a component for restricting the reduction in the cycle life, and the compound ratio is also 1-7wt.%. An electrolyte consisting of KOH and LiOH is a component for maintaining the high level of utilization factor of the active material, and the compound ratio is 36-41wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-hydrogen secondary battery, and more specifically, it has a long cycle life, a high utilization rate of an active material, a good rapid discharge characteristic, and can be used in a wide temperature range. Nickel-hydrogen secondary battery.

[0002]

2. Description of the Related Art With the progress of miniaturization, weight reduction and cordlessness of various electric / electronic devices, there is an increasing demand for miniaturization, weight reduction and high capacity of batteries used as their power sources. As a high-capacity battery that meets this demand, nickel-hydrogen secondary batteries have recently attracted attention.

This nickel-hydrogen secondary battery operates by using hydrogen as a negative electrode active material, and its power generating element is
A negative electrode formed by supporting a hydrogen storage alloy capable of reversibly absorbing and releasing hydrogen on a conductive base material, and a positive electrode formed by supporting Ni (OH) ₂ which normally operates as a positive electrode active material on the conductive base material. And are placed in an alkaline electrolyte.

As the shape of this battery, there are a cylindrical type and a square type, and generally, a closed cylindrical type is being studied. This sealed cylindrical battery usually has a structure as shown in FIG. That is, the insulating plate 2 is arranged on the bottom of the cylindrical container which also serves as the negative electrode terminal, and the sheet-shaped positive electrode 3 and the sheet-shaped negative electrode 4 are provided on the insulating plate 2 via the separator made of electrically insulating mat-shaped synthetic resin. An electrode plate group that is superposed and wound in a spiral shape is accommodated. Then, after injecting a predetermined alkaline electrolyte into the container, the insulating plate 2 is placed on the electrode plate group, and the plate is closed with the sealing plate 6, and the whole lid 7 also serving as the positive electrode terminal is used.
Are sealed via an insulating gasket 8.

As the above-mentioned sheet-shaped positive electrode 3, a porous conductive sheet is used for Ni (O) which functions as a positive electrode active material.
H) ₂ which is mainly filled with an active material paste is used, and the sheet-shaped negative electrode 4 is formed by mixing a powder of a hydrogen storage alloy with a binder and sheet-forming the same. A porous conductive sheet carrying a slurry of a hydrogen storage alloy and a binder is widely used. Furthermore, as the alkaline electrolyte, KOH having a predetermined concentration is used.
Aqueous solutions are commonly used.

[0006]

By the way, the positive electrode of the nickel-hydrogen secondary battery described above has a long cycle life, a high utilization rate of the active material, and can sufficiently cope with rapid discharge. There is a demand for properties such as having characteristics and being able to be used in a wide temperature range regardless of the temperature of the environment in which it is used.

However, at present, a nickel-hydrogen secondary battery satisfying all of these four properties, especially the properties up to, has not been developed. An object of the present invention is to solve the above-mentioned problems, to provide a nickel-hydrogen secondary battery which has a long cycle life, a high utilization rate of an active material, excellent rapid discharge characteristics, and can be used in a wide temperature range. To do.

[0008]

Means for Solving the Problems By the way, the positive electrode active material N
The battery reaction for i (OH) ₂ is:

[0009]

[Equation 1]

[0010] That is, Ni (OH) ₂ becomes NiOOH during the charging process and is restored to Ni (OH) ₂ during the discharging process. At this time, as NiOOH, β-NiOOH in which the valence of Ni is trivalent and γ-NiOOH in which the valence of Ni is 3.4 are generated. Especially when the active material utilization rate is 100% or higher, which indicates a high utilization rate,
During charging, most of the active material Ni (OH) ₂ is γ-N.
means converted to iOOH.

When the battery is discharged when Ni (OH) ₂ is converted to γ-NiOOH, Ni having a valence of 3.4 is used.
Is reduced to Ni having a valence of 2, the discharge capacity obtained as a battery is from β-NiOOH (valence 3 of Ni) to Ni.
Greater than in the case of reduction to (OH) ₂ . That is, for the manufacture of batteries with high discharge capacity, during charging,
It is preferable that Ni (OH) ₂ which is the positive electrode active material is converted into γ-NiOOH.

However, γ-NiOOH is β-Ni
Higher volume than OOH. Therefore, when charging, γ-N
When iOOH is generated, the positive electrode expands and absorbs the alkaline electrolyte retained in the separator to increase the internal resistance of the battery, which causes a problem that the cycle life of the battery is shortened. That is, γ-NiO
The generation of OH realizes higher capacity of the battery, but on the other hand, it has an effect of shortening the cycle life of the battery, and as a result, lowers the utilization rate of the active material.

In order to achieve the above-mentioned object based on the above findings, the present inventor has conducted diligent research on the composition of the active material paste used for the positive electrode and the composition of the alkaline electrolyte, and as a result, A battery that combines an active material paste and an alkaline electrolyte with the composition and concentration described below achieves high utilization of the active material (higher battery capacity) and longer cycle life, and at the same time has excellent rapid discharge characteristics. The present invention has led to the development of the nickel-hydrogen secondary battery of the present invention by finding the fact that it can be used even in a wide temperature range.

That is, in the nickel-hydrogen secondary battery of the present invention, Ni (OH) ₂ : 85-9 is formed on the porous conductive substrate.
A positive electrode formed by filling an active material paste, which essentially contains 8% by weight, CoO: 1 to 7% by weight, ZnO: 1 to 7% by weight,
It is characterized in that a negative electrode made of a hydrogen storage alloy and an alkaline electrolyte having KOH and LiOH as essential electrolytes and an electric electrolyte concentration of 36 to 41% by weight are used as power generating elements.

The battery of the present invention is charged by the means described below.
Ni (OH) which is the active material when electricity is applied ₂As much as γ−
Converted to NiOOH to ensure high capacity of the battery, and at the same time
In addition, the above-mentioned inconvenience associated with the production of γ-NiOOH is eliminated.
It was done. One of the power generation elements in the battery of the present invention
The positive electrode is an active material based on the above-mentioned components.
Are filled in a porous conductive base material.

The porous conductive base material is not particularly limited as long as it is conventionally used, but, for example, it is possible to increase the filling amount of the active material paste. A Ni sponge having a porosity of 95 to 97% and having communication holes can be mentioned as a preferable example. Such a Ni sponge is usually formed by subjecting a plastic foam having a desired porosity and communicating holes, for example, a polyurethane or polyethylene foam to known electroless Ni plating or Ni vapor deposition to form a skeleton portion of the foam. The surface is N
After being coated with i, the whole is fired in air at a temperature higher than the thermal decomposition temperature of the foam to thermally decompose and remove the plastic skeleton, and a sponge having a Ni skeleton having the same network structure as the plastic skeleton. Manufactured as.

The active material paste of the present invention is Ni (OH)
₂ , CoO and ZnO are essential components. Of these,
Ni (OH) ₂ acts as the positive electrode active material. The blending ratio of Ni (OH) ₂ in the active material paste is 85 to 9
It is set to 8% by weight. When the blending ratio is less than 85% by weight, the positive electrode capacity that predominantly defines the battery capacity becomes low, which is inconvenient for increasing the capacity of the battery.
On the other hand, if it is more than 98% by weight, the blending ratio of other components becomes small, and the desired effect cannot be obtained. A preferred blending ratio is 90 to 95% by weight.

CoO is a component that contributes to improving the utilization rate of the active material. However, on the other hand, it is also a component that deteriorates the rapid discharge characteristics of the battery. The latter function is that CoO dissolves in an alkaline electrolyte to form a complex ion, which covers the surface of Ni (OH) ₂ which is an active material, and the complex ion is oxidized and converted to CoOOH during charging. Is the result of doing. That is, the above-mentioned CoOOH covering the surface of Ni (OH) ₂ has a low discharge potential, so that the polarization of the positive electrode during rapid discharge is increased.

Taking this into consideration, the blending ratio of CoO is set to 1 to 7% by weight. 1% by weight
If it is less than the above, the effect of improving the utilization rate of the active material is not exhibited, and if it exceeds 7% by weight, it is meaningless for the effect of improving the utilization rate of the active material and, conversely, rapid discharge occurs. This is because the characteristics deteriorate and the capacity of the battery decreases. A preferred blending ratio is 2 to 5% by weight.

Zn which is another essential component of the active material paste
O has a function of suppressing a decrease in the cycle life of the active material due to the production of γ-NiOOH described above. At the same time, it is considered that it dissolves in the alkaline electrolyte as zincate ions to prevent the above-mentioned CoO complex ions from covering the surface of Ni (OH) ₂ , thus contributing to the improvement of the utilization rate of the active material.

The compounding ratio of this ZnO is set to 1 to 7% by weight. When the blending ratio is less than 1% by weight, the effect of prolonging the cycle life of the active material is not exhibited, and when it exceeds 7% by weight, not only is it meaningless to the effect of improving the cycle life, but conversely This is because the capacity of the battery is reduced. The preferred blending ratio is 2-5
% By weight.

This active material paste is prepared with the above-mentioned three components as essential components, but Ni powder may be further compounded if necessary. This Ni powder functions as a conductive material, improves the electrical connection between the active material paste and the porous conductive base material in which the active material paste is filled, and thus contributes to improving the utilization rate of the active material. The mixing ratio of this Ni powder is 7% by weight or less.
If it is mixed in a larger amount than this, the blending ratio of other essential components is decreased, leading to a decrease in the utilization rate of the active material.
This is because the blending ratio of H) ₂ decreases and the capacity decreases.

Next, the negative electrode of the battery of the present invention may be any one conventionally used, and is not particularly limited. In particular, a punched nickel sheet is coated with a known hydrogen-absorbing alloy powder, an alloy slurry prepared with a thickening agent such as methylcellulose and ion-exchanged water, dried, and then rolled at a predetermined pressure to obtain a uniform thickness. What is supported as the alloy layer of is preferable.

Here, as the punching nickel sheet, for example, a nickel sheet having a predetermined thickness and a plurality of small holes having a predetermined diameter, or a plurality of small holes having a predetermined diameter, for example, are punched. At least the surface of which is formed of nickel, such as a porous sheet of other material plated or vapor-deposited with nickel, is used. As the electrolytic solution of the battery of the present invention, a solution containing KOH and LiOH as essential electrolytes is used.

In this electrolytic solution, the electrolyte that mainly contributes to the battery reaction is KOH, and LiOH is blended in order to keep the utilization rate of the active material at a high level even when the battery is used in a high temperature range. It is a component that is used. The proportion of the electrolyte in the electrolytic solution is set to 36 to 41% by weight as a whole. When the proportion of the electrolyte is less than 36% by weight, the active material Ni (OH) ₂ is not converted to γ-NiOOH sufficiently, so that the utilization rate of the active material is reduced and the cycle life is shortened. When the content is more than 41% by weight, even when the active material paste is adjusted to the above-mentioned composition, the same problems as the utilization rate of the active material and the cycle life are shortened. As the electrolyte,
An electrolytic solution having an electrolyte concentration of 37 to 40% by weight is suitable.

The mixing ratio of KOH and LiOH in this electrolytic solution is KOH: LiOH 20 to 40: 1 by weight.
Is preferred. If you use too much LiOH,
LiOH precipitation occurs due to low solubility, and as a result,
This is because the concentration of the whole electrolyte cannot be increased to 36% by weight or more. In addition, this electrolyte further contains Cs
You may mix | blend OH or / and RbOH. CsO
Both H and RbOH have a function of maintaining the utilization rate of the active material at a high level even when the operating temperature of the battery is in the low temperature range. Furthermore, since NaOH can maintain the utilization rate of the active material at a high level in a high temperature range,
It is also possible to add aOH.

If the amount of these CsOH, RbOH, and NaOH is too small, the above-mentioned characteristics of each cannot be utilized, and if the amount is too large, the function of KOH, which is the main electrolyte, is diminished. Because it will
Usually, 2 to 2 for 100 total amount of KOH and LiOH
It is preferably about 0.

[0028]

Examples of the invention

(1) Composition of active material paste and battery characteristics A sponge-like nickel sheet is manufactured by applying electroless nickel plating to a foamed polyurethane sheet with a porosity of 96% and a thickness of 1.6 mm, and then firing in a reducing atmosphere at 700 ° C. Then
This was prepared as a positive electrode conductive base material.

Then, the solid component having the composition shown in Table 1 was added to 1.
The above sponge-like nickel sheet was filled with a paste obtained by adding a 2% aqueous solution of carboxymethyl cellulose, dried at 80 ° C. for 2 hours, and then rolled at a pressure of ² ton / cm ² to produce various sheet-like positive electrodes. In each of the positive electrodes, the filling amount of Ni (OH) _{2 as} the active material was 4.0 g in all cases.

Next, by the arc melting method, the composition: MmN
After producing a hydrogen storage alloy represented by i _3.3 Co _1.0 Mn _0.4 Al _0.3 (Mm is misch metal), the hydrogen storage alloy was pulverized to obtain an alloy powder under 150 mesh (Tyler sieve). Then, an alloy slurry comprising 400 parts by weight of the alloy powder and 1 part by weight of carboxymethyl cellulose was prepared with respect to 100 parts by weight of ion-exchanged water, and a punching nickel sheet having a thickness of 0.07 mm and a porosity of 38% was prepared. After soaking, pull up, dry in air, 2ton /
Rolling was performed at a pressure of cm ² to produce a sheet-shaped negative electrode having a total thickness of 0.4 mm.

A nylon separator having a thickness of 0.18 mm and a porosity of 65% was arranged between the sheet-shaped positive electrode and the sheet-shaped negative electrode, and the whole was spirally wound to form a plate group having a diameter of 13 mm. Next, the above-mentioned power generating element is housed in a bottomed cylindrical container having an inner diameter of 13.2 mm, which is made by plating nickel on steel, and an electrolytic solution in which KOH: 36 wt% and LiOH: 1 wt% are dissolved therein is placed therein. After injection, the container was sealed with a lid to obtain a sealed cylindrical battery.

With respect to these batteries, a charge / discharge cycle test was conducted under the conditions of temperature: 20 ° C., charge: 1 C, -ΔV control, discharge: 1 C, 1.0 V, and the number of cycles until reaching 80% of the rating. I checked. In addition, the temperature of each battery is 20
After charging under conditions of ℃, 0.2C, 7.5 hours, temperature is 20 ℃
Then, the discharge capacity was measured by discharging at a temperature of 20 ° C. and 0.2 C, and the utilization rate (%) of the positive electrode active material at the time of low rate discharge was calculated from the value.

Further, each battery has a temperature of 20 ° C. and 0.2
After charging under the conditions of C, 7.5 hours, left at 20 ° C. for 16 hours, and then discharged at 20 ° C., 3 C to measure the discharge capacity. The utilization rate (%) was calculated. The above results are collectively shown in Table 1.

[0034]

[Table 1]

As is clear from the results shown in Table 1, by using the active material paste having the composition defined in the present invention, the cycle life of the battery is extended to 700 times or more, and at the same time, the positive electrode activity at the time of low rate discharge is also increased. 100% utilization of substances
As described above, the utilization factor of the positive electrode active material during high-rate discharge is 80%, and a high utilization factor is obtained in any discharge. That is, higher capacity of the battery has been realized. (2) Effect of Electrolyte Concentration As the active material paste, the composition of Example 6 shown in Table 1 was used, and as the electrolyte, the electrolyte was KOH, LiO.
Various batteries were manufactured by using H and CsOH, each having a constant weight ratio of 35: 1: 1 but varying the concentration of the electrolyte as a whole.

With respect to these batteries, a charge / discharge cycle test was conducted under the conditions of temperature: 20 ° C., charge: 1 C, -ΔV control, discharge: 1 C, 1.0 V, and the number of cycles until reaching 80% of the rating. I checked. The results are shown in FIG. 2 as a relationship diagram with the electrolyte concentration. Furthermore, each battery has a temperature of 2
After charging under conditions of 0 ℃, 0.2C, 7.5 hours, temperature 20
After leaving it at 16 ° C. for 16 hours, the battery was discharged at a temperature of 20 ° C. and 3 C, the discharge capacity was measured, and the utilization rate (%) of the positive electrode active material at the time of high rate discharge was calculated from the value. The results are shown in FIG. 3 as a relational diagram with the concentration of the electrolytic solution.

As is apparent from FIG. 3, the electrolyte concentration is 3
When it is in the range of 6 to 41% by weight, the utilization rate of the active material is 80% or more. At that time, the cycle life is 950
It is secured more than once. (3) Effect of type of electrolytic solution First, an electrolytic solution having the composition shown in Table 2 was prepared.

[0038]

[Table 2] Next, as the active material paste, Example 6 shown in Table 1 was used.
6 types of batteries were manufactured by using each of the electrolyte solutions of A to F shown in Table 2 as the electrolytic solution.

For these batteries, the temperature was 20 ° C. and the temperature was 0.2.
Charge at C for 7.5 hours, then 16 at each discharge temperature
After leaving it for an hour, it is 1.0 at 0.5C at that temperature.
After discharging to V, the discharge capacity was measured, and the utilization rate (%) of the positive electrode active material was calculated from the value. The result is
FIG. 4 shows the relationship with the discharge temperature. In the figure, ○ indicates electrolyte A, Δ indicates electrolyte B, □ indicates electrolyte C, ◇ indicates electrolyte D, × indicates electrolyte E, and ▽ marks. Represents the case of the electrolytic solution F, respectively.

As is apparent from FIG. 4, in the battery using the electrolytic solution containing only KOH (D, ⋄), the utilization factor of the active material in the low temperature region is extremely low, and the utilization factor in the high temperature region is low. Is also low. When the electrolytic solution (B, Δ) containing LiOH is further used as the electrolytic solution D, the utilization factor in the low temperature region is slightly improved, but the utilization factor in the high temperature region is greatly improved. From this, it can be seen that LiOH contributes to the improvement of the utilization factor in the low temperature region, but is basically an electrolyte effective in improving the utilization factor in the high temperature region.

When the electrolytic solution (C, □ mark) containing CsOH is used as the electrolytic solution D, the utilization factor in the low temperature region is remarkably improved, but the utilization factor in the high temperature region is not improved. From this, CsOH (or Rb
It can be seen that OH) is an electrolyte effective for improving the utilization rate in the low temperature range. From the above, in the battery of the present invention, if an electrolytic solution containing CsOH (or RbOH), that is, an electrolytic solution composed of KOH, LiOH, and CsOH is used, the active material in a low temperature region and a high temperature region is increased. The utilization rate of the battery will be improved, and the operating temperature range of the battery will be expanded.

[0042]

As is apparent from the above description, the battery of the present invention has a long cycle life, a high utilization rate of the active material,
It has good rapid discharge characteristics, can be used in a wide temperature range, and satisfies a great demand for nickel-hydrogen secondary batteries, and its industrial value is great.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing the internal structure of a sealed cylindrical battery.

FIG. 2 is a graph showing the relationship between electrolyte temperature and battery cycle life.

FIG. 3 is a graph showing a relationship between an electrolytic solution temperature and a utilization rate of a positive electrode active material.

FIG. 4 is a graph showing the relationship between the discharge temperature and the utilization rate of the positive electrode active material when various electrolytic solutions are used.

[Explanation of symbols]

 1 Cylindrical container 2 Insulation plate 3 Sheet-shaped positive electrode 4 Sheet-shaped negative electrode 5 Separator 6 Sealing plate 7 Lid 8 Insulation gasket

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 23, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

That is, in the nickel-hydrogen secondary battery of the present invention, Ni (OH) ₂ : 85-9 is formed on the porous conductive substrate.
A positive electrode formed by filling an active material paste, which essentially contains 8% by weight, CoO: 1 to 7% by weight, ZnO: 1 to 7% by weight,
A negative electrode comprising a hydrogen storage alloy, the KOH and LiOH as essential electrolytes, the concentration of the electrolyte, characterized in that the power generating elements and an alkaline electrolyte is a 36-41 wt%.

Claims (4)

[Claims] 1. A porous conductive substrate is provided with Ni (OH) ₂ :
85-98% by weight, CoO: 1-7% by weight, ZnO: 1
A positive electrode formed by filling an active material paste containing 7 to 7% by weight, a negative electrode formed of a hydrogen storage alloy, and KOH and L
iOH is used as an essential electrolyte, and the concentration of the electrolyte is 36-
A nickel-hydrogen secondary battery comprising an alkaline electrolyte of 41% by weight as a power generating element. 2. The active material paste further contains Ni.
The nickel-hydrogen secondary battery according to claim 1, wherein the nickel-hydrogen secondary battery contains less than or equal to wt% (excluding 0). 3. The alkaline electrolyte further contains CsO.
The nickel-hydrogen secondary battery according to claim 1 or 2, which contains H or / and RbOH. 4. The alkaline electrolyte further contains NaO.
The nickel-hydrogen secondary battery according to any one of claims 1 to 3, which contains H.