JPH0917427A - Non-sintered nickel hydroxide positive electrode plate for alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-sintered nickel hydroxide positive electrode plate having high energy density and a long cycle life, by maintaining a coefficient of utilization of a plate at a high level as well as restraining the plate from swelling steadily. SOLUTION: Nickel hydroxide powder is stipulated as that half-power band width of a peak appearing in the proximity of 2γ=38.5 deg. in X-ray diffraction using CuK α rays is 0.8 to 1.2deg and 5 specific surface area of a Ni active material is 5 to 25m<2> /g (BET method), in the case of a non-sintered nickel hydroxide positive electrode plate comprizing Ni-active material powder composed of nickel hydroxide powder and a compound layer of II group elements formed on the surfaces thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-sintered nickel hydroxide positive electrode plate used in alkaline storage batteries such as nickel-cadmium storage batteries and nickel-hydrogen storage batteries.

[0002]

2. Description of the Related Art Non-sintered nickel hydroxide positive electrode plates for alkaline storage batteries are widely used in high capacity type alkaline storage batteries because they have higher productivity and higher energy density than sintered nickel hydroxide positive electrode plates. It is used. However, the non-sintered nickel positive electrode plate has a greater degree of swelling of the electrode plate with charge / discharge cycles than the sintered positive electrode plate. The expansion of the electrode plate pushes out and depletes the electrolytic solution in the separator, which deteriorates the discharge performance, and this expansion is a factor that governs the battery life.

Therefore, in non-sintered nickel positive electrode plates, suppression of electrode plate swelling has been an important issue in the past. As a method of suppressing swelling, for example, a group II element is solid-dissolved in nickel hydroxide powder. Method (JP-A-1-18266)
2), a method of mixing and using nickel hydroxide powder and a group II element compound powder (JP-A-59-33758), and a method of forming a layer of the group II element compound on the surface of the nickel hydroxide powder (JP-A-3). -274666) and the like have been proposed.
Among them, the technique described in JP-A-3-274666 can suppress expansion of the electrode plate most effectively.

However, as will be described in detail later, in the non-sintered nickel hydroxide positive electrode plate for alkaline storage batteries, there is a technically contradictory relationship between the improvement of the electrode plate utilization rate and the suppression of electrode plate swelling. For this reason, it is not easy to sufficiently extend the battery life without impairing the feature of high energy density. Therefore, the above-mentioned technique (Japanese Patent Laid-Open No. 3-274666)
However, it is still not sufficient, and further improvement in energy density and cycle life is required.

[0005]

DISCLOSURE OF THE INVENTION The present invention is an improvement of the above-mentioned technique (Japanese Patent Laid-Open No. 3-274666), which favorably balances two contradictory factors, namely, improvement of electrode plate utilization rate and suppression of electrode plate swelling. Another object of the present invention is to provide a nickel hydroxide positive electrode plate for alkaline storage batteries having a longer life and a higher energy density.

[0006]

In order to achieve the above object, the present invention is configured as follows. The invention of claim 1 provides a non-sintered nickel hydroxide positive electrode plate for alkaline storage batteries, which comprises a Ni active material powder having a group II compound layer formed on the surface of the nickel hydroxide powder. X-ray diffraction using CuKα ray
The half value width of the peak appearing near θ = 38.5 ° is 0.8.
~ 1.2 deg. The above nickel hydroxide powder is used.

According to a second aspect of the present invention, in the non-sintered nickel hydroxide positive electrode plate for alkaline storage batteries according to the first aspect, N is
The specific surface area of the i active material powder is specified to be 5 to 25 m ² / g.

According to a third aspect of the present invention, in the non-sintered nickel hydroxide positive electrode plate for an alkaline storage battery according to the first aspect, the group II element is selected from the group consisting of Cd, Zn and Mg. It is characterized by

According to a fourth aspect of the present invention, in the non-sintered nickel hydroxide positive electrode plate for alkaline storage batteries according to the second aspect, II
The group element is selected from the group consisting of Cd, Zn and Mg.

[0010]

The operation of the present invention will be described, taking into consideration the cause of the expansion of the electrode plate. The nickel hydroxide in the electrode plate changes to β-type nickel oxyhydroxide by charging, and this β-type nickel oxyhydroxide takes in the metal and water in the alkaline electrolyte by overcharging and forms γ-type nickel oxyhydroxide. Changes to. When this γ-type nickel oxyhydroxide is produced, the electrode plate swells, so that it physically presses the separator and acts to push out the electrolytic solution in the separator. In addition, this may cause the active material to fall off or cause an internal short circuit. Therefore, the expansion of the electrode plate hinders a smooth electrode reaction, but since the non-sintered electrode plate is weaker in strength than the sintered electrode plate, this expansion determines battery performance and battery life. It becomes a factor.

However, the above-mentioned technique ((Japanese Laid-Open Patent Publication No. 3-2746)
According to 66), when the Ni active material powder in which the compound layer of the group II element is formed on the surface of the nickel hydroxide powder is used as the positive electrode active material, the group II element compound layer present on the surface of the Ni active material powder is Prevents alkali metal and water from penetrating into crystals during overcharge, and consequently suppresses the formation of γ-type nickel oxyhydroxide. Here, since the group II element compound layer does not directly contribute to power generation, increasing the amount of addition thereof lowers the energy density of the electrode plate, but in the above technique, a small amount of group II element arranged on the surface of the nickel hydroxide powder is used. Since the compound layer effectively suppresses swelling, the decrease in energy density is small.

However, as a result of various examinations of the above-mentioned techniques by the present inventors, a difference was found in the energy density and cycle life of the electrode plate depending on the properties of the nickel hydroxide powder as the active material body. Also, depending on the properties of the Ni active material powder,
Differences were observed in the energy density and cycle life of the electrode plates.

Therefore, the present inventors have paid attention to the crystallinity of the nickel hydroxide powder as the main body of the active material and the specific surface area of the Ni active material powder, and examined the relationship between these factors and the expansion rate and utilization rate of the electrode plate. However, when the crystallinity of the nickel hydroxide powder, which is the active material main body (nucleus), is increased, the electrode plate utilization rate decreases, but the electrode plate swelling is suppressed, and the Ni active material powder (group II element compound on the surface It was found that when the specific surface area of (having a layer) is increased, the electrode plate swelling tends to increase, but the electrode plate utilization rate increases. The present invention has been completed based on this finding.

That is, according to the present invention, X using CuKα rays is used.
The half width of the peak appearing in the vicinity of 2θ = 38.5 ° of the line diffraction is used as an index showing the crystallinity of nickel hydroxide, and the half width is 0.8 to 1.2 deg. The nickel hydroxide powder in the range of is used as the main body (core) of the Ni active material powder. Further, the present invention has a half width of 0.8 to 1.2.
deg. The nickel hydroxide powder is used as the active material body (nucleus), and the specific surface area of the Ni active material powder formed by forming the group II compound layer on the surface of the nickel hydroxide powder is 5 to 25 m ^2.
It is specified in the range of / g.

When the crystallinity of the nickel hydroxide powder is in the above range, both the electrode plate utilization rate and the electrode plate swelling rate can be balanced within a suitable range. Further, if the specific surface area of the Ni active material powder is within the above range, a negative factor resulting from the action of the group II element compound layer to limit the contact between nickel hydroxide and the alkaline electrolyte (alkali metal or water) Rate drop) can be eliminated. As a result, a nickel positive electrode plate for alkaline storage batteries having a high energy density and a long life can be obtained.

Further, in the present invention, when the group II element compound layer is composed of a compound of an element selected from the group consisting of Cd, Zn and Mg, a nickel hydroxide positive electrode plate having further excellent energy density and cycle life. Is obtained.
The reason for this is not well understood.

[0017]

The contents of the present invention will be clarified below based on Experiments 1 to 3. [Experiment 1] In Experiment 1, five kinds of nickel hydroxide powders having different crystallinity were prepared, Ni active material powder was prepared by using the nickel hydroxide powder as a core, and the crystallinity of the nickel hydroxide powder as the active material body was measured. The effect of the difference on the electrode utilization rate and electrode swelling rate was investigated. The following is a sequential description according to the experimental procedure.

(Preparation of Various Nickel Hydroxide Powders) While adjusting the pH with 15 wt% ammonia water, 3 mol% aqueous sodium hydroxide solution was gradually added to 3 mol% nickel nitrate aqueous solution with stirring to react. A nickel hydroxide precipitate was obtained. During this precipitation reaction, the pH value of the reaction solution was variably adjusted within the range of 9 to 12, and the reaction temperature was variably adjusted within the range of 20 ° C to 60 ° C. Further, the stirring speed of the reaction solution was set to a half width of 1.0 deg. When the stirring speed at the time of producing the nickel hydroxide powder of
It was variably adjusted in the range of 40 to 500. By changing each condition within the above range, 5 kinds of nickel hydroxide precipitates were obtained, which were washed with water and dried to obtain the Fisher Sub-sieve Sizer.
Nickel hydroxide powder having a size (hereinafter referred to as FSSS) of 10 μm was prepared.

With respect to these nickel hydroxide powders, diffraction line: CuKα (λ = 1.5418Å), tube voltage: 30k
V, tube current; 12.5 mA, scanning speed; 5 deg / mi
X-ray diffraction analysis was performed under the condition of n, and the half width of the peak at 2θ = about 38.5 ° was measured.
g. , 0.8 deg. , 1.0 deg. , 1.2de
g. , 1.4 deg. Met.

(Preparation of Various Ni Active Material Powders) The above-mentioned five kinds of nickel hydroxide powders were used, and a cadmium hydroxide layer (group II compound layer) was formed on the surface of each powder.
The manufacturing method is as follows. About 1 part of nickel hydroxide powder
Mix and disperse in 0 times the amount of ion-exchanged water, and in this mixed dispersion, while stirring, 3 mol% sodium hydroxide aqueous solution and
Cadmium nitrate aqueous solution was added while adjusting the liquid amounts of both solutions so that the pH of the mixed dispersion liquid was maintained at a predetermined value (within a range of PH 9 to 12). Thereby, a cadmium hydroxide layer is formed on the surface of the nickel hydroxide powder, washed with water and dried to prepare five kinds of Ni active material powders having different crystallinity of the nickel hydroxide powder as the active material body. did.

When the nickel hydroxide and the cadmium hydroxide of the Ni active material powder produced as described above were quantified, a cadmium hydroxide layer of 5% by weight based on the nickel hydroxide powder was formed in each case. Further, when the specific surface area of each Ni active material powder was measured by the BET method using a mixed gas of nitrogen gas and helium gas (He: N ₂ = 70: 30) as an adsorbed gas, both were 10 m ² / g. there were.

(Preparation of non-sintered nickel electrode plate) 90% by weight of the above various Ni active material powders and cobalt hydroxide powder (F
(SSS: 1 μm) 10% by weight and 1% by weight aqueous solution of methylcellulose were mixed in appropriate amounts to prepare an active material slurry. The active material slurry was filled in nickel foam having a porosity of 95%, dried, and then roll-molded. As a result, five types of non-sintered nickel positive electrode plates differing only in the crystallinity of the nickel hydroxide powder were produced.

(Measurement of Utilization Rate of Electrode Plate) Using each of the non-sintered nickel positive electrode plates as a positive electrode, a sintered cadmium negative electrode plate as a counter electrode, and an aqueous potassium hydroxide solution as an alkaline electrolyte, the positive electrode is controlled by a known method. Open cell (theoretical capacity 60
0 mAh) was prepared in 5 ways. 60 for these cells
After charging to 150% of theoretical capacity with mA current, 20
The discharge capacity was measured by discharging at a current of 0 mA until the battery voltage reached 0.8V. The electrode plate utilization rate was calculated according to Equation 1.

[0024]

## EQU00001 ## Electrode plate utilization rate = [discharge capacity / theoretical capacity] × 100 ...

(Measurement of Swelling Ratio of Electrode Plate) Using the non-sintered nickel positive electrode plate (5 ways), the sintered cadmium negative electrode plate, and an electrolytic solution containing an aqueous solution of potassium hydroxide, a nominal capacity was measured by a known method. A 1200 mAh cylindrical closed nickel-cadmium storage battery (JIS type: KR-A size) was produced. For these storage batteries, an operation (1 cycle) of charging the storage battery at a current of 1200 mA to 150% of the nominal capacity and then discharging the battery at a current of 1200 mA until the battery voltage became 0.8 V was performed 500 cycles. The electrode plate swelling ratio was calculated according to equation 2.

[0026]

## EQU00002 ## Electrode plate swelling ratio = [thickness of positive electrode plate after 500 cycles / thickness of positive electrode plate before start of cycle] × 100 ...

(Experimental Results) Table 1 shows the utilization rate and expansion rate of each positive electrode plate. In addition, each numerical value of Table 1 has an X-ray half width of 1.0 deg. The case of is shown as the reference (100). As is clear from Table 1, the electrode plate utilization rate tends to decrease as the half-value width of the nickel hydroxide powder decreases, and the electrode plate utilization rate decreases significantly particularly when the half-value width is less than 0.8. On the other hand, the swelling ratio of the electrode plate after 500 cycles tends to increase as the half width of the nickel hydroxide powder increases, and the swelling ratio of the electrode plate has a half width of 1.2 deg. It increased remarkably beyond. From these results, the active material body (nucleus)
X-ray half-value width of 0.8
~ 1.2 deg. It is understood that the non-sintered nickel hydroxide positive electrode plate for an alkaline storage battery, which has good electrode plate utilization rate and electrode plate swelling rate, can be obtained by preparing the above.

[0028]

[Table 1]

[Experiment 2] In Experiment 2, Ni active material powders having different specific surface areas were prepared by the following method, and the Ni active material powder was used to measure Ni active material powder by the same measurement method as in Experiment 1.
The influence of the difference in the specific surface area of the active material powder on the electrode utilization rate and electrode plate swelling rate was investigated. (Preparation of Ni Active Material Powder with Different Specific Surface Area) As the nickel hydroxide powder, the X-ray half width of 1.0 prepared in Experiment 1 was used.
deg. , FSSS 10 μm nickel hydroxide powder was used. In addition, the stirring speed when forming the cadmium hydroxide layer on the surface of the nickel hydroxide powder is such that the specific surface area is 10 m ²
When the stirring speed at the time of producing the Ni active material powder of / g was 100 (reference speed), it was changed in the range of 40 to 300. Other conditions were the same as in Experiment 1.
As a result, 6 kinds of Ni active material powders having different specific surface areas were produced. The items other than the above were the same as in Experiment 1.

For each of the above Ni active material powders, the BE
When the specific surface area was measured by the T method, it was 3 m ²
/ G, 5m ² / g, 10m ² / g, 18m ² / g, 25
It was m ² / g and 28 m ² / g. (Experimental Results) Table 2 shows the results of Experiment 2. From Table 2, the electrode plate utilization rate decreased significantly when the specific surface area was less than 5 m ² / g. On the other hand, the swelling ratio of the electrode plate is such that the specific surface area is 25 m ² /
It became larger when it exceeded g. From these results, when Ni active material powder having a specific surface area of 5 to 25 m ² / g is used, a non-sintered nickel hydroxide positive electrode plate with less expansion of the electrode plate and high utilization rate can be obtained. I understand.

[0031]

[Table 2]

[Experiment 3] In Experiment 3, Ni active material powder (specific surface area: 10 m ² / g) in which the kind of layer formed on the surface of nickel hydroxide powder was changed was prepared, and II was prepared in the same manner as in Experiment 1. The relationship between the kinds of group element compounds and the electrode plate utilization rate and electrode plate swelling ratio was investigated. The layer of the group II element compound was prepared as follows. X-ray half width of 1.0 de produced in Experiment 1
g. , FSSS 10 μm nickel hydroxide powder was used, and a layer consisting of cadmium hydroxide, zinc oxide, magnesium hydroxide, calcium hydroxide and barium hydroxide was formed on the surface of the nickel hydroxide powder in the same manner as in Experiment 1. Formed. The preparation method of the surface layer and other matters were the same as in Experiment 1. (Experimental Results) Table 3 shows the results of Experiment 3. In addition, each numerical value in Table 3 is represented with 100 (reference) in the case of the Ni active material powder having Cd (OH) ₂ as the surface layer.

[0033]

[Table 3]

From Table 3, the electrode plate utilization ratio is Cd (OH)
₂ , ZnO, Mg (OH) ₂ , Ca (OH) ₂ , Ba
There is no great difference in any of (OH) ₂ . On the other hand, the swelling rate of the electrode plate is larger in the case of Ca (OH) ₂ and Ba (OH) _{2 than in} the case of Cd (OH) ₂ , ZnO and Mg (OH) ₂ . From this, when considering both the electrode plate utilization rate and the expansion, Cd (OH) ₂ , ZnO, Mg (O
It has been found that it is preferable to form the surface layer of nickel hydroxide powder with a compound selected from H) ₂ . [Other Matters] In the above embodiment, the group II element compound is 1
Although the type is used, the type is not limited to this, and two or more types may be used in combination. In addition, although the group II element compound layer is one layer in the above-mentioned embodiment similarly to the above, it may be two or more layers. Furthermore, although a sintered cadmium negative electrode is used as the counter electrode in the above embodiment, it is of course that the same effect can be obtained even if the counter electrode is a hydrogen storage alloy electrode.

[0035]

According to the present invention, swelling of the electrode plate can be reliably suppressed without reducing the electrode plate utilization rate. Therefore, according to the present invention, a non-sintered nickel hydroxide positive electrode plate for alkaline storage batteries having a high energy density and a long cycle life can be obtained.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Kenji Arisawa 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (4)

[Claims] 1. A non-sintered nickel hydroxide positive electrode plate for an alkaline storage battery, which comprises a Ni active material powder having a group II compound layer formed on the surface of a nickel hydroxide powder, wherein the nickel hydroxide powder is: The half-value width of the peak appearing in the vicinity of 2θ = 38.5 ° of X-ray diffraction using CuKα ray is 0.8 to 1.2 deg. A non-sintered nickel hydroxide positive electrode plate for an alkaline storage battery, characterized in that 2. The specific surface area of the Ni active material powder is 5 to 5.
The non-sintered nickel hydroxide positive electrode plate for an alkaline storage battery according to claim 1, wherein the positive electrode plate has a thickness of 25 m ² / g. 3. The non-sintered nickel hydroxide positive electrode plate for an alkaline storage battery according to claim 1, wherein the Group II element is selected from the group consisting of Cd, Zn and Mg. 4. The non-sintered nickel hydroxide positive electrode plate for an alkaline storage battery according to claim 2, wherein the Group II element is selected from the group consisting of Cd, Zn and Mg.