JPH0917429A - Nickel hydroxide for non-sintered nickel positive electrode of alkaline storage battery - Google Patents

Abstract

PURPOSE: To make a tap density as high as possible without degrading a discharging property and a life characteristics, by causing powder particles of nickel hydroxide including Co or Cd dissolved therein to have a spherical or spheroidal shape of specific properties. CONSTITUTION: Powder particles of nickel hydroxide for a non-sintered nickel positive electrode of an alkaline storage battery are caused to have a spherical or spheroidal shape and to include Co or Cd dissolved therein, the specific surface area thereof being 5 to 10m<2> /g, the averaged particle diameter thereof being 1 to 30μm, and the half-power band width thereof being 0.9 to 1.3 deg.. Preferably, content quantity of the above-mentioned Co is 0.5 to 2wt.%, and content quantity of Cd is 1.5 to 5%. This nickel hydroxide powder can realize a tap density more than 2.1g/ml.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to nickel hydroxide suitable for use in a non-sintered nickel positive electrode of an alkaline storage battery.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller and more portable, the alkaline storage batteries mounted therein have been required to be smaller and lighter. Therefore, the capacity of alkaline storage batteries is rapidly increasing. As one of the technologies for increasing the capacity, a non-sintered nickel positive electrode in which a porous nickel substrate is filled with nickel hydroxide as an active material has been put into practical use (see Japanese Patent Publication No. 60-40667). . This non-sintered nickel positive electrode can hold nickel hydroxide, which is an active material, in the electrode plate at a higher density than the conventional sintered nickel positive electrode. As characteristics of nickel hydroxide, which is an active material of a non-sintered nickel positive electrode, it is said that (1) tap density is sufficiently high and (2) crystallinity is low. The above (1) is required
(A) The filling amount of nickel hydroxide and the energy density of the non-sintered nickel positive electrode have a positive correlation, and (b) the filling amount of nickel hydroxide is the porosity of the porous nickel substrate and the nickel hydroxide. This is because the porosity of the porous nickel substrate (c), which is proportional to the tap density of, has an upper limit. Further, the above (2) is required because in the positive electrode prepared by using nickel hydroxide having too high crystallinity, the movement of protons, which is indispensable for the discharge reaction, is restricted, and the current density increases during charging. This is because a large amount of high-order oxide γ-NiOOH, which causes deterioration of discharge characteristics and life characteristics, is generated. Conventionally, various studies have been made on nickel hydroxide satisfying the above (1) and (2), and for example, nickel hydroxide described in Japanese Patent Publication No. 4-68249 is known. That is, this nickel hydroxide is a powder composed of spherical or ellipsoidal particles, having a specific surface area of 10 to 30 m ² / g and an average particle diameter of 2 to 5
0 μm, tap density is 1.8 to 2.02 g / ml. However, when the above nickel hydroxide is used as the active material of the non-sintered nickel positive electrode, the energy density of the non-sintered nickel positive electrode in (1) above is not satisfactory.

[0003]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to non-burn an alkaline storage battery in which the tap density is as high as possible without deteriorating the discharge characteristics and life characteristics in (2) above. (EN) Provided is nickel hydroxide for a bonded nickel positive electrode.

[0004]

The present invention achieves the above object, and is a powder comprising spherical or elliptic spherical particles containing cobalt and / or cadmium as a solid solution, and having a specific surface area of 5 to 5. 10 m ² / g, average particle size is 1
The nickel hydroxide for a non-sintered nickel positive electrode of an alkaline storage battery having a half-value width of a diffraction peak of (101) plane measured by X-ray diffraction of ˜30 μm and 0.9-1.3 °.
The content of cobalt contained in the nickel hydroxide for a non-sintered nickel positive electrode of the alkaline storage battery of the present invention is 0.5
~ 2 wt%, cadmium content is 1.5-5 wt%
It is preferred that The nickel hydroxide powder for non-sintered nickel positive electrode of the alkaline storage battery of the present invention has a specific surface area of 5 to 10 m ² / g, and therefore has a tap density of 2.
1g / ml or more.

[0005]

The nickel hydroxide for the non-sintered nickel positive electrode of the alkaline storage battery of the present invention must be a powder composed of spherical or elliptic spherical particles containing cobalt and / or cadmium as a solid solution. Cobalt and / or cadmium is solid-dissolved in nickel hydroxide particles, unless cobalt and / or cadmium is solid-dissolved, (1) nickel positive electrode swells due to repeated charge / discharge cycles, (2) nickel hydroxide Does not have an appropriately low crystallinity, the movement of protons, which is indispensable for the discharge reaction, is restricted, and the current density increases during charging.
Since a large amount of OOH is generated, cobalt and / or cadmium is contained to prevent the deterioration of the above discharge characteristics and life characteristics. When only cobalt is contained, the content is 0.5 to 2% by weight, when only cadmium is contained, the content is 1.5 to 5% by weight, and when cobalt and cadmium are contained, the respective contents are Is preferably 2 to 7% by weight. Below the respective lower limits, the action of cobalt and / or cadmium is not sufficient, while above the respective upper limits,
The Ni content is reduced and the energy density of the nickel positive electrode is reduced. Further, the shape of the nickel hydroxide particles of the present invention needs to be spherical or elliptic spherical, and if the shape is other than this, such as angular shape, a sufficiently high tap density cannot be obtained.

The nickel hydroxide powder for the non-sintered nickel positive electrode of the alkaline storage battery of the present invention has a specific surface area of 5 to 10 m.
² / g, the average particle size is 1 to 30 μm, and the half width of the diffraction peak of the (101) plane measured by X-ray diffraction is 0.9 to 1.
It is also important that it is 3 °. If the specific surface area is less than 5 m ² / g, the space volume inside the nickel hydroxide particles formed by agglomeration of primary particles (crystallites), that is, the pore volume becomes too small, and the transfer of protons necessary for the battery reaction However, if it exceeds 10 m ² / g, a sufficiently high tap density cannot be obtained. If the average particle size is less than 1 μm, nickel hydroxide will fall off from the porous nickel substrate, and the energy density of the nickel positive electrode will tend to decrease. On the other hand, if it exceeds 30 μm, a sufficiently high tap density will not be obtained. . Further, when the half width of the diffraction peak of the (101) plane measured by X-ray diffraction is less than 0.9 °, the movement of protons necessary for the battery reaction is likely to be blocked, while when it exceeds 1.3 °. However, it is impossible to obtain a sufficiently high tap density. The nickel hydroxide powder as described above has a tap density of 2.1 g / ml or more, and usually 2.
It is 3 g / ml or less.

The non-sintered nickel hydroxide powder for a non-sintered nickel positive electrode of an alkaline storage battery of the present invention differs from the conventional nickel hydroxide powder for a non-sintered nickel positive electrode of an alkaline storage battery in the following points. That is, when the conventional nickel hydroxide powder reduces the specific surface area to 10 m ² / g or less in an attempt to increase the tap density to 2.1 g / ml or more, X
The half-value width of the diffraction peak of the (101) plane measured by line diffraction is less than 0.9 °, whereas the nickel hydroxide powder of the present invention reduces the specific surface area to 10 m ² / g or less. However, there is the above difference in that the full width at half maximum of the diffraction peak of the (101) plane measured by X-ray diffraction can be maintained at 0.9 ° or more. The reason is not clear, but in the nickel hydroxide particles of the present invention, compared to conventional nickel hydroxide particles,
It is inferred that this is because the size of the primary particles (crystallites) that aggregate to form the particles was significantly reduced.

Next, a method for producing the nickel hydroxide powder for the non-sintered nickel positive electrode of the alkaline storage battery of the present invention will be described. Aqueous solution containing nickel, cobalt and /
Alternatively, an aqueous solution containing cadmium, an aqueous alkali hydroxide solution, and aqueous ammonia are simultaneously and continuously supplied, and reacted with vigorous stirring to produce them. The reaction conditions at that time are: (1) nickel ion concentration in the reaction liquid: 1 to 20 mg / l, (2) reaction liquid temperature: 40 to
Constant temperature within the range of 70 ° C., (3) Discharge head and discharge flow rate of impeller of stirrer (per 1 m ^{3 of} reaction tank volume): 15 to ³⁰ m ² / s ² , 0.2 m ³ / s, respectively
As described above, (4) residence time of the produced powder in the reaction tank is 8 hours or more.

[0009]

【Example】

Example 1 A mixed aqueous solution of nickel sulfate and cadmium sulfate having a molar ratio of Ni: Cd = 1.6: 0.04, 22
A nickel hydroxide powder in which cadmium was solid-dissolved was continuously produced while vigorously stirring using a weight% sodium hydroxide aqueous solution (for pH adjustment) and 25 weight% ammonia water. The reaction conditions at this time were as follows. Addition rate of mixed aqueous solution of nickel sulfate and cadmium sulfate 27.6 liter / hr Addition rate of ammonia water 2.0 liter / hr Nickel ion concentration in reaction solution 10-20 mg / l Reaction solution temperature 50 ° C Reaction solution pH 12.4 Discharge head of impeller of stirrer 16.3 m ² / s ² Discharge flow rate of impeller of stirrer (per reaction tank volume of 1 m ³ ) 0.23 m ³ / s Residence time of generated powder in reaction tank 11 After continuously taking out the generated nickel hydroxide powder,
It was filtered, washed with water and dried. The obtained powder was analyzed for cadmium content, and the particle shape, tap density, specific surface area, average particle diameter, and half-value width of the diffraction peak of the (101) plane measured by X-ray diffraction were measured. The average particle size is based on Coulter Counter TA-II type, and the X-ray diffractometer used is Rigaku Rotaflex RU.
-200B type, tube voltage 50kV, tube current 5
0 mA and the target material was Cu. Then, the full width at half maximum of the diffraction peak at 2θ = 37 to 39 ° was obtained from the obtained diffraction chart. Table 1 shows the obtained results.

[0010]

[Table 1] Additive element-containing particles Tap dense specific surface area Average particle size (101) surface content (% by weight) Form factor (g / ml) (m ² / g) (μm) half width (°) Example 1 Cd: 2.5 spherical 2.22 8.6 7.7 1.07 Example 2 Cd: 2.7 spherical 2.20 5.8 6.9 0.97 Example 3 Cd: 3.1 spherical 2 .18 9.4 12.2 0.98 Example 4 Cd: 3.2 Spherical 2.12 9.7 10.0 1.17 Example 5 Cd: 3.0 Co: 1.5 Spherical 2.157 7.8 7.3 1.00 Comparative Example 1 Cd: 3.2 Spherical 2.08 20.7 9.6 0.96 Comparative Example 2 Zn: 3.1 Co: 1.5 Spherical 2.05 15.08 .2 0.96 Conventional Example 1 No addition spherical 2.04 25.8 17.7 0.99 Conventional Example 2 no addition spherical 2.08 15.6 13.2 1.01 Conventional 3 no addition spherical 1.90 21.2 16.4 1.1 1 Conventional Example 4 No addition, spherical 1.79 31.9 18.9 1.23

Next, using the nickel hydroxide powder obtained above as an electrode active material, a non-sintered nickel electrode was prepared as follows. That is, 90 parts by weight of the nickel hydroxide powder obtained above, 8 parts by weight of nickel powder, 2 parts by weight of cobalt powder and a paste containing carboxymethyl cellulose as a thickening agent are prepared, and then the paste is made porous. A non-sintered nickel electrode was prepared by filling an alkali-resistant nickel substrate and further drying and compressing the nickel substrate. Then, this nickel electrode was used as a positive electrode, a cadmium electrode having a large excess capacity as compared with the positive electrode was used as a negative electrode, and a 30 wt% potassium hydroxide aqueous solution was used as an electrolytic solution, and a glass bipolar electrolytic cell partitioned by a glass filter was used. Was used to assemble an open model cell. Using this model cell, the utilization rate of the electrode active material was measured as follows. That is, after charging this model cell with a current equivalent to 0.1 C for 12 hours, it is charged with a current equivalent to 0.5 C to 1
The discharge capacity is measured by discharging to 0V. From the discharge capacity and the theoretical electric capacity of the nickel hydroxide powder used, the initial utilization rate (first cycle) was determined. In addition, the utilization rate at the 100th cycle was calculated by repeating 100 cycles with the charge / discharge cycle as one cycle.
Table 2 shows the obtained results.

[0012]

Table 2 Active material at 1st cycle Active material at 100th cycle (%) Utilization rate (%) Example 1 94 93 Example 2 97 95 Example 3 95 92 Example 4 93 92 Example 5 95 93 Comparative Example 1 92 87 Comparative Example 2 94 89 Conventional Example 1 83 52 Conventional Example 2 88 64 Conventional Example 3 81 46 Conventional Example 4 91 59

Examples 2 to 4 The reaction conditions for continuously producing nickel hydroxide powder were as follows: reaction liquid temperature 55 ° C.
Discharge head 20.9 m ² / s ² of impeller of stirrer, discharge flow rate of impeller of stirrer (per 1 m ^{3 of} reaction tank volume)
The test was performed in the same manner as in Example 1 except that the amount was 0.26 m ³ / s. The obtained results are shown in Tables 1 and 2.

Example 5 Instead of a mixed aqueous solution of nickel sulfate and cadmium sulfate, a molar ratio of Ni: Cd: Co =
The test was performed in the same manner as in Example 1 except that a mixed aqueous solution of nickel sulfate, cadmium sulfate, and cobalt sulfate having a ratio of 1.6: 0.04: 0.04 was used. The obtained results are shown in Tables 1 and 2.

[Comparative Example 1] The reaction conditions for continuously producing nickel hydroxide powder were as follows: discharge head 11.7 m ² / s ² of impeller of stirrer, discharge flow rate of impeller of stirrer (reaction tank volume except that the 1 m ³ per) 0.19 m ³ / s were tested as in example 1. The obtained results are shown in Tables 1 and 2.

[Comparative Example 2] Instead of a mixed aqueous solution of nickel sulfate and cadmium sulfate, a molar ratio of Ni: Zn: Co =
A test was performed in the same manner as in Example 1 except that a mixed aqueous solution of nickel sulfate, zinc sulfate, and cobalt sulfate having a ratio of 1.6: 0.07: 0.04 was used. The obtained results are shown in Table 1 and Table 2.
Shown in

[Conventional Examples 1 to 4] 42 wt% nickel sulfate aqueous solution, 22 wt% sodium hydroxide aqueous solution (pH
Nickel hydroxide powder was continuously produced using (for adjustment) and 25% by weight of aqueous ammonia. Further, after taking out the produced nickel hydroxide powder, the same test as in Example 1 was conducted. The obtained results are shown in Tables 1 and 2.

Of the results shown in Table 1, Examples 1-5,
FIG. 1 shows the relationship between the tap density and the specific surface area in Comparative Examples 1 and 2 and Conventional Examples 1 to 4, and shows the relationship between the specific surface area and the half width of the diffraction peak of the (101) plane measured by X-ray diffraction. ,
FIG. 2 shows the example and the conventional example in layers. From FIG.
(1) The tap density increases as the specific surface area decreases,
(2) The nickel hydroxide powder containing 2.5 to 3.2 wt% of Cd in Examples 1 to 4 and the nickel hydroxide powder containing 4.5 wt% of Cd and Co in Example 5 It can be seen that the tap density shows a high value of 2.1 g / ml or more. Further, the following can be seen from FIG. That is, it was measured by specific surface area and X-ray diffraction (10
1) The relationship with the half width of the diffraction peak of the plane is different between the case of the example containing the additive element and the case of the conventional example not containing the additive element. In the case of the conventional example, the half width of the (101) plane is 0.99
Even if the crystallinity is appropriately low at 1.23 °, nickel hydroxide powder particles having a specific surface area of 10 m ² / g or less that achieves a tap density of 2.1 g / ml or more cannot be obtained.
In the case of the examples, the half value width of the (101) plane shows a value of 0.9 to 1.3 ° even if the specific surface area is 10 m ² / g or less, and the degree of crystallinity is moderately low as usual. Nickel powder particles are obtained. Furthermore, the following can be seen from Tables 1 and 2. That is, the nickel hydroxide of the example,
Because the tap density is high enough and the crystallinity is low,
While excellent energy density, discharge characteristics and life characteristics are exhibited, the nickel hydroxides of Comparative Example and Conventional Example have various characteristics in Table 1 that do not necessarily match the requirements of the present invention. It is hard to say that all of the energy density, the discharge characteristics and the life characteristics other than the above energy density are excellent.

[0019]

As is apparent from the above, according to the present invention, (1) since the tap density is 2.1 g / ml or more, the energy density of the nickel positive electrode is increased, and (2) it is measured by X-ray diffraction ( The full width at half maximum of the diffraction peak of the (101) plane is 0.
Since the crystallinity is appropriately low at 9 to 1.3 °, it is possible to provide nickel hydroxide for a non-sintered nickel positive electrode for alkaline storage batteries, which has excellent discharge characteristics and life characteristics.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between tap density and specific surface area in Examples, Comparative Examples and Conventional Examples.

FIG. 2 is a graph showing the relationship between the specific surface area and the half-value width of the diffraction peak of the (101) plane measured by X-ray diffraction, stratified into Examples and Conventional Examples.

Claims (4)

[Claims] 1. A powder comprising spherical or elliptic spherical particles containing cobalt and / or cadmium in a solid solution, having a specific surface area of 5 to 10 m ² / g and an average particle diameter of 1 to 3.
Nickel hydroxide for a non-sintered nickel positive electrode of an alkaline storage battery in which the half-value width of the diffraction peak of the (101) plane measured by 0 μm and X-ray diffraction is 0.9 to 1.3 °. 2. The cobalt content is 0.5 to 2% by weight.
The nickel hydroxide for a non-sintered nickel positive electrode of an alkaline storage battery according to claim 1. 3. The nickel hydroxide for a non-sintered nickel positive electrode of an alkaline storage battery according to claim 1, wherein the content of cadmium is 1.5 to 5% by weight. 4. The nickel hydroxide for a non-sintered nickel positive electrode of an alkaline storage battery according to claim 1, wherein the powder has a tap density of 2.1 g / ml or more.