JP3234491B2 - Conductive agent for alkaline storage battery and non-sintered nickel electrode for alkaline storage battery using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conductive agent for an alkaline storage battery and a non-sintered nickel electrode for an alkaline storage battery using the same.

[0002]

2. Description of the Related Art
As a nickel electrode of an alkaline storage battery such as a nickel-cadmium storage battery and a nickel-hydrogen storage battery, a sintering method in which an active material (nickel hydroxide) is impregnated into a sintered substrate obtained by sintering nickel powder on a perforated steel plate or the like. Nickel electrodes are well known.

[0003] In order to increase the packing density of the active material in the sintered nickel electrode, it is necessary to use a sintered substrate having a high porosity. However, the bond between the nickel particles due to sintering is weak, and if the porosity of the sintered substrate is increased, the nickel powder tends to fall off the sintered substrate. Therefore, in practice, the porosity of the sintered substrate cannot be made larger than 80%, and the sintered nickel electrode has a problem that the packing density of the active material is small. Further, since the pore diameter of the sintered body of nickel powder is generally as small as 10 μm or less, the active material must be filled into the substrate (sintered body) by a solution impregnation method which requires a complicated impregnation step to be repeated several times. There is also the problem that it must be done.

[0004] Under such circumstances, a non-sintered nickel electrode has recently been newly proposed. Non-sintered nickel electrodes are prepared by directly mixing a kneaded material (paste) of an active material (nickel hydroxide) and a binder solution (methylcellulose aqueous solution) onto a substrate with high porosity (such as foamed metal plated with an alkali-resistant metal). It is made by filling. In the non-sintered nickel electrode, a substrate having a high porosity can be used (a substrate having a porosity of 95% or more can be used), so that the packing density of the active material can be increased and Can be once filled into the substrate.

However, when a non-sintered nickel electrode having a large porosity is used to increase the packing density of the active material, the current collecting capability of the substrate is lower than that of the sintered substrate used in the sintered nickel electrode. As a result, the conductivity becomes worse as compared with the sintered nickel electrode, and the active material utilization decreases.

Therefore, in order to increase the conductivity of the non-sintered nickel electrode, cobalt hydroxide powder is added to nickel hydroxide powder (see JP-A-61-74261).
It has been proposed to add graphite powder (see JP-A-7-212316).

However, the present inventors have studied and found that it is difficult to obtain a non-sintered nickel electrode having a sufficiently high active material utilization rate even if cobalt hydroxide powder or graphite powder is added. Was.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conductive agent for an alkaline storage battery having a high conductivity and a non-conductive agent for an alkaline storage battery having a high utilization rate of an active material using the same. To provide a sintered nickel electrode.

[0009]

In order to achieve the above object, a conductive agent for an alkaline storage battery according to the present invention (conductive agent of the present invention) is prepared by adding cobalt or a cobalt compound to an aqueous solution of sodium hydroxide. , 50-200 ° C., and sodium content of 0.1.
It contains 1 to 10% by weight. If the sodium content is out of this range, a conductive agent having sufficiently high conductivity cannot be obtained.

Examples of the cobalt compound include cobalt hydroxide and cobalt oxide.

Although the chemical structure of the conductive agent of the present invention is not known at present, the conductive agent of the present invention has an extremely high conductivity, and is not a simple mixture of a cobalt compound (such as cobalt oxyhydroxide) and sodium. It is presumed that the intercalation compound is a form in which sodium is incorporated in the crystal of the cobalt compound.

The heat treatment temperature for producing the conductive agent of the present invention is 50 to 200 ° C. If the heat treatment temperature is out of this range, a conductive agent having high conductivity cannot be obtained.

That is, when the conductive agent of the present invention uses, for example, cobalt hydroxide as a starting material, it is considered that it is synthesized by the following reaction route. However, if the heat treatment temperature is 50
When the temperature is lower than ° C, the reaction of CoHO ₂ ⇒Na-containing cobalt compound becomes difficult to proceed sufficiently, so that a large amount of CoHO ₂ having low electric conductivity is generated. On the other hand, when the heat treatment temperature is 20
When the temperature exceeds 0 ° C., a large amount of tricobalt tetroxide (Co ₃ O ₄ ) having low conductivity is generated. For the above reasons, it is considered that when the heat treatment temperature is out of the range of 50 to 200 ° C., a conductive agent having high conductivity cannot be obtained.

[0014] _{Co (OH) 2 ⇔ HCoO 2} - ⇔ Co
HO ₂ ⇒Na-containing cobalt compound (conductive agent of the present invention)

The heat treatment time for preparing the conductive agent of the present invention varies depending on the amount and concentration of the aqueous sodium hydroxide solution, the heat treatment temperature and the like, but is generally 0.5 to 10 hours.

The non-sintered nickel electrode for an alkaline storage battery according to the present invention (the electrode of the present invention) uses the above-described conductive agent of the present invention having a high conductivity as the conductive agent of the non-sintered nickel electrode. Yes, the conductive agent of the present invention, the active material powder consisting of nickel hydroxide particles or particles containing nickel hydroxide as a main component, 100 parts by weight of nickel hydroxide in the active material powder, 1 to 20 parts by weight It has been added.
When the addition ratio of the conductive agent is less than 1 part by weight, a non-sintered nickel electrode having a sufficiently high active material utilization rate cannot be obtained. on the other hand,
When the proportion of the conductive agent exceeds 20 parts by weight, the filling amount of nickel hydroxide, which is an active material, decreases, so that the electrode capacity decreases.

The particles containing nickel hydroxide as a main component include those obtained by dissolving an element having a function of suppressing swelling of the nickel electrode, such as cobalt, zinc, cadmium, calcium, manganese, and magnesium, in nickel hydroxide. Is exemplified.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and the present invention may be practiced by appropriately changing the gist of the invention. Is possible.

(Experiment 1) [Preparation of Conductive Agent] Cobalt hydroxide and a 25% by weight aqueous solution of sodium hydroxide were mixed at a weight ratio of 1:10, and mixed.
Heat treatment was performed at 0 ° C. for 8 hours. After heat treatment, wash with water, 6
After drying at 0 ° C., a sodium-containing cobalt compound as a conductive agent of the present invention was prepared. When the sodium content of this sodium-containing cobalt compound was analyzed by atomic absorption spectrometry, it was 1% by weight.

[Preparation of Non-Sintered Nickel Electrode] 100 parts by weight of nickel hydroxide as an active material, 10 parts by weight of the above sodium-containing cobalt compound as a conductive agent, and a 1% by weight aqueous solution of methylcellulose as a binder 20 parts by weight to prepare a paste, and the paste is nickel-plated foam metal (porosity 95%; average pore diameter 2).
A non-sintered nickel electrode according to the present invention was prepared by filling a porous substrate of (00 μm), drying and pressing.

[Preparation of Alkaline Storage Battery] The above-mentioned non-sintered nickel electrode (positive electrode), a known paste cadmium electrode (negative electrode) having a larger electrochemical capacity than this positive electrode, a polyamide nonwoven fabric (separator), 30% by weight An alkaline storage battery A1 was produced using a potassium hydroxide aqueous solution (alkaline electrolyte), a metal battery can, a metal battery cover, and the like.

Separately, in the preparation of the non-sintered nickel electrode, a sodium-containing cobalt compound 1 was used as a conductive agent.
10 parts by weight of cobalt hydroxide or graphite 1 instead of 0 parts by weight
Except that 0 parts by weight were used, alkaline storage batteries A2 and A3 were produced in the same manner.

<Active Material Utilization> The above alkaline storage battery A
For 1 to A3, charge / discharge was performed 10 times at 25 ° C. at a rate of 0.1 C at 160 ° C. and then discharged at 25 ° C. to 1.0 V at 1 C as 10 cycles. The active material utilization rate of the positive electrode at the defined 10th cycle was determined. Table 1 shows the results. The active material utilization rate in Table 1 is
This is an index when the active material utilization rate of the alkaline storage battery A1 is set to 100.

Active material utilization rate (%) = ｛discharge capacity at the 10th cycle (mAh) / (amount of nickel hydroxide (g) × 2)
88 (mAh / g)｝ × 100

[0025]

[Table 1]

As shown in Table 1, the alkaline storage batteries A2,
The active material utilization of the positive electrode of A3 is lower at 95 and 87 , respectively, than that of the alkaline storage battery A1. From these results, it can be seen that the conductive agent (sodium-containing cobalt compound) according to the present invention has significantly higher conductivity than cobalt hydroxide and graphite. In Example 1, cobalt hydroxide was used as a cobalt raw material when synthesizing a sodium-containing cobalt compound. However, when cobalt metal, cobalt oxide, or the like was used, the conductivity was the same as when cobalt hydroxide was used. It has been confirmed that a high-content sodium-containing cobalt compound can be obtained.

(Experiment 2) In preparing a sodium-containing cobalt compound, 5% by weight, 10% by weight, 15% by weight, 35% by weight, 40% by weight, 45% by weight or Except that a 50% by weight aqueous sodium hydroxide solution was used,
Sodium-containing cobalt compounds having different sodium contents were prepared. When the sodium content of these sodium-containing cobalt compounds was analyzed by atomic absorption spectroscopy, they were sequentially 0.05% by weight, 0.1% by weight, 0.5% by weight, 5% by weight, 10% by weight, 12% by weight, It was 15% by weight. Next, alkaline storage batteries A4 to A10 were prepared in the same manner as in Experiment 1, except that each of these sodium-containing cobalt compounds was used.

For these alkaline storage batteries A4 to A10, 10 cycles of charge / discharge under the same conditions as in Experiment 1 were performed to determine the active material utilization of the positive electrode at the 10th cycle, and the sodium content of the sodium-containing cobalt compound and the active material were determined. The relationship of utilization rate was investigated. The results are shown in FIG. FIG. 1 shows the relationship between the sodium content of the sodium-containing cobalt compound and the active material utilization, the active material utilization on the vertical axis, and the sodium content (% by weight) of the sodium-containing cobalt compound on the horizontal axis. FIG. In FIG. 1,
The results for the alkaline storage battery A1 produced in Experiment 1 above are also shown. The active material utilization rate on the vertical axis in FIG.
This is an index when the active material utilization rate of the alkaline storage battery A1 is set to 100.

As shown in FIG. 1, the alkaline storage batteries A1, A
Since the active material utilization ratio of 5-A8 is extremely high, it is understood that the sodium-containing cobalt compound (the conductive agent of the present invention) having a sodium content of 0.1 to 10% by weight has an extremely high electric conductivity.

(Experiment 3) In the preparation of a non-sintered nickel electrode, the amount of the sodium-containing cobalt compound added was 0.5 parts by weight, 1 part by weight, 5 parts by weight, and 15 parts by weight based on 100 parts by weight of nickel hydroxide. , 20 parts by weight, 22.5 parts by weight, or 25 parts by weight in the same manner as in Experiment 1, to produce non-sintered nickel electrodes having different addition amounts of the sodium-containing cobalt compound (conductive agent). However, as the sodium-containing cobalt compound, the sodium content is 1
% By weight. Next, alkaline storage batteries A11 to A17 were manufactured in the same manner as in Experiment 1, except that each of these non-sintered nickel electrodes was used.

With respect to these alkaline storage batteries A11 to A17, 10 cycles of charge / discharge under the same conditions as in Experiment 1 were performed to determine the active material utilization rate of the positive electrode at the 10th cycle. The relationship between the rates was examined. Table 2 shows the results. Table 2 shows that the previous experiment 1
Also shown are the results for the alkaline storage battery A1 manufactured in the above.

[0032]

[Table 2]

From Table 2, it can be seen that when 1 part by weight or more of the sodium-containing cobalt compound is added to 100 parts by weight of nickel hydroxide, a non-sintered nickel electrode having a high active material utilization rate can be obtained.

FIG. 2 shows the relationship between the added amount of the sodium-containing cobalt compound and the battery capacity, the vertical axis represents the battery capacity, and the horizontal axis represents the added amount of the sodium-containing cobalt compound (parts by weight based on 100 parts by weight of nickel hydroxide). FIG. FIG. 2 also shows the result of the alkaline storage battery A1 manufactured in the above-described experiment 1. The battery capacity on the vertical axis in FIG. 2 is an index when the battery capacity of the alkaline storage battery A1 is set to 100.

As shown in FIG. 2, the alkaline storage batteries A1, A
Since the battery capacity of 12 to A15 is extremely high, the non-sintered nickel electrode (the electrode of the present invention) in which the addition amount of the sodium-containing cobalt compound is 1 to 20 parts by weight based on 100 parts by weight of nickel hydroxide is extremely high. It can be seen that it has a capacity.

(Experiment 4) In the preparation of the sodium-containing cobalt compound, the heat treatment temperature was set to 45 ° C. and 50 ° C.
C, 60 ° C, 100 ° C, 150 ° C, 200 ° C,
A sodium-containing cobalt compound was prepared in the same manner as in Experiment 1 except that the temperature was 220 ° C. or 250 ° C.
The sodium content of these sodium-containing cobalt compounds was analyzed by atomic absorption spectroscopy.
% By weight, 1% by weight, 1% by weight, 1% by weight, 1% by weight, 1%
%, 0.05% and 0.02% by weight. Next, alkaline storage batteries A18 to A25 were produced in the same manner as in Experiment 1, except that each of these sodium-containing cobalt compounds was used.

For these alkaline storage batteries A18 to A25, 10 cycles of charge / discharge under the same conditions as in Experiment 1 were performed to determine the active material utilization of the positive electrode at the 10th cycle, and the relationship between the heat treatment temperature and the active material utilization was determined. Examined. The results are shown in FIG. FIG. 3 shows the relationship between the heat treatment temperature and the active material utilization rate when synthesizing the sodium-containing cobalt compound, the vertical axis represents the active material utilization rate, and the horizontal axis represents the heat treatment temperature (° C.). It is a graph. FIG. 3 also shows the result of the alkaline storage battery A1 produced in the above-mentioned experiment 1. The active material utilization rate on the vertical axis in FIG. 3 is an index when the active material utilization rate of the alkaline storage battery A1 is set to 100.

As shown in FIG. 3, the alkaline storage batteries A1, A
Since the active material utilization rate of 19 to A23 is extremely high, 5
It can be seen that the sodium-containing cobalt compound (the conductive agent of the present invention) produced by heat treatment at 0 to 200 ° C. has an extremely high conductivity.

In the above embodiment, nickel hydroxide was used as an active material. However, the present invention is also applicable to a case where cobalt hydroxide, zinc, cadmium, calcium, manganese, magnesium or the like is dissolved in nickel hydroxide. It has been confirmed that a non-sintered nickel electrode having a high active material utilization rate can be obtained by adding a predetermined amount of the inventive conductive agent.

[0040]

According to the present invention, since the conductive agent contains sodium, it has high conductivity. Further, the electrode of the present invention has a high active material utilization rate because a conductive agent having high conductivity is added to the active material.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the sodium content of a sodium-containing cobalt compound and the active material utilization rate.

FIG. 2 is a graph showing the relationship between the amount of sodium-containing cobalt compound added and the battery capacity.

FIG. 3 is a graph showing the relationship between the heat treatment temperature and the active material utilization when synthesizing a sodium-containing cobalt compound.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Masao Inoue 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Hiroshi Watanabe 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Reizou Maeda 2-5-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Ikuo Yonezu 2-chome, Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-4-109557 (JP, A) Kaihei 7-22027 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01M 4/24-4/62 H01M 10/24-10/34

Claims (2)

(57) [Claims] (1) Cobalt or a cobalt compound, to which an aqueous solution of sodium hydroxide is added, is added at 50 to 200 ° C.
A conductive agent for an alkaline storage battery obtained by heat treatment with C and containing 0.1 to 10% by weight of sodium. 2. The method according to claim 1, wherein the conductive agent for an alkaline storage battery comprises nickel hydroxide particles or particles containing nickel hydroxide as a main component, and 100 parts by weight of nickel hydroxide in the active material powder. A non-sintered nickel electrode for an alkaline storage battery, wherein 1 to 20 parts by weight of the nickel electrode is added.