JP3229801B2 - 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]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive agent for an alkaline storage battery used for an alkaline storage battery such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery, and a non-sintered nickel electrode using the same.

[0002]

2. Description of the Related Art Conventionally, as a nickel electrode of an alkaline storage battery such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery, a sintered substrate obtained by sintering nickel powder on a perforated steel plate or the like is impregnated with an active material (nickel hydroxide). Sintered 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%,
Therefore, the sintered nickel electrode has a problem that the amount of the active material charged is small. In addition, since the pore size of a sintered body of nickel powder is generally as small as 10 μm or less, the active material must be filled into a substrate (sintered body) by a solution impregnation method in which a complicated impregnation step is repeated several times. There is also a problem.

[0004] Under such circumstances, a non-sintered nickel electrode has recently been proposed. Non-sintered nickel electrodes are prepared by mixing a kneaded product (paste) of an active material (nickel hydroxide) and a binder solution (methylcellulose solution) with a highly porous substrate (foam metal plated with an alkali-resistant metal, etc.). It is made by directly filling the 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 easily filled into the substrate.

[0005] 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 nickel electrode. As a result, the active material utilization rate decreases.

Therefore, in order to enhance the conductivity of the non-sintered nickel electrode, cobalt hydroxide is added to the nickel hydroxide powder (see JP-A-61-74261), or graphite powder is added ( Japanese Patent Laid-Open No. 7-211316) has been proposed.

However, the present inventors have studied and found that
It has been 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.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a conductive agent for an alkaline storage battery having high conductivity and an active material using the same. An object of the present invention is to provide a non-sintered nickel electrode for an alkaline storage battery having a high utilization factor.

[0009]

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

The lithium content is expressed in terms of% by weight, that is, when the total weight of the conductive agent is 100 and the contained lithium is converted to the weight of atoms, that is, converted to atoms. In other words, it is obtained by the following equation.

Lithium content (% by weight) = (atomic weight of lithium / total weight of conductive agent) × 100 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, since the conductive agent of the present invention has extremely high conductivity, a simple mixture of a cobalt compound (such as cobalt oxyhydroxide) and lithium cannot be used. Therefore, it is presumed that the intercalation compound has a form in which lithium is incorporated in the crystal of the cobalt compound.

[0013] The heat treatment temperature for producing the conductive agent of the present invention is 50 ° C 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, for example, cobalt hydroxide is used as a starting material, the conductive agent of the present invention is considered to be synthesized by the following reaction route. However, when the heat treatment temperature is lower than 50 ° C., the reaction from CoHO ₂ to the Li-containing cobalt compound does not easily proceed sufficiently, so that a large amount of CoHO ₂ having low conductivity is generated. On the other hand, when the heat treatment temperature exceeds 200 ° C., a large amount of tricobalt tetroxide (Co ₃ O ₄ ) having low conductivity is generated. For the above reasons, the heat treatment temperature is 50 ℃ ~ 200
When the temperature is out of the range, it is considered that a conductive agent having high conductivity cannot be obtained.

[0015]

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The heat treatment time for preparing the conductive agent of the present invention varies depending on the amount and concentration of the aqueous lithium 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, nickel hydroxide 100 in this active material powder
1 part by weight to 20 parts by weight are added to parts by weight. 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, if the addition ratio of the conductive agent exceeds 20 parts by weight,
Since the filling amount of nickel hydroxide as the active material is reduced, the electrode capacity is reduced.

The particles containing nickel hydroxide as a main component include particles obtained by dissolving elements such as cobalt, zinc, cadmium, calcium, manganese, and magnesium having an action of suppressing the expansion of the nickel electrode into nickel hydroxide. Is exemplified.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. However, the present invention is not limited to the following embodiments, and the present invention is implemented by appropriately changing the scope of the invention. Is possible. (Experiment 1) [Preparation of Conductive Agent] Cobalt hydroxide and a 4% by weight aqueous solution of lithium hydroxide were mixed at a weight ratio of 1:10, and mixed at 80 ° C. for 8 hours.
Heated for hours. After the heat treatment, the film was washed with water and dried at 60 ° C. to prepare a lithium-containing cobalt compound as a conductive agent of the present invention. When the lithium content of this lithium-containing cobalt compound was analyzed by an atomic absorption method, it was 1% by weight. The value of 1% by weight is obtained by dividing the weight of lithium converted into atoms by the total weight of the conductive agent of the present invention and multiplying by 100. [Production of non-sintered nickel electrode] 100 parts by weight of nickel hydroxide as an active material, 10 parts by weight of the above-mentioned lithium-containing cobalt compound as a conductive agent, and 20 parts by weight of a 1% by weight aqueous solution of methylcellulose as a binder And the mixture was kneaded to prepare a paste. This paste is filled into a porous substrate made of nickel-plated foam metal (porosity 95%, average pore diameter 200 μm), dried, and then pressed and molded.
A non-sintered nickel electrode according to the present invention was produced. [Preparation of alkaline storage battery] The above-mentioned non-sintered nickel electrode (positive electrode), a known paste-type cadmium electrode (negative electrode) having a larger electrochemical capacity than this positive electrode, a polyamide nonwoven fabric (separator), 30% by weight potassium hydroxide An alkaline storage battery A1 was produced using an aqueous solution (alkaline electrolyte), a metal battery can, a metal battery cover, and the like.

Separately, except that 10 parts by weight of cobalt hydroxide or 10 parts by weight of graphite were used instead of 10 parts by weight of the lithium-containing cobalt compound as the conductive agent in the preparation of the non-sintered nickel electrode. For comparison, alkaline storage batteries A2 and A3 were produced, respectively. <Active Material Utilization> The above alkaline storage batteries A1 to A3 were charged 160% at 25 ° C. at 0.1 C, and then charged at 1 ° C. at 25 ° C.
Charge and discharge with one cycle of discharging to 1.0 V
After 0 cycles, the active material utilization of the positive electrode at the tenth cycle defined by the following equation was determined.

Active material utilization rate (%) = ｛discharge capacity at 10th cycle (mAh) / (amount of nickel hydroxide (g) × 288 (mAh /
g))｝ × 100 The results are shown in Table 1. The active material utilization rate in Table 1 is a relative index when the active material utilization rate of the alkaline storage battery A1 is set to 100.

[0022]

[Table 1]

As shown in Table 1, the alkaline storage batteries A2,
The active material utilization of the positive electrode of A3 is 96 and 88, respectively, lower than that of the alkaline storage battery A1. From these results, the conductive agent (lithium-containing cobalt compound) according to the present invention is:
It can be seen that it has a significantly higher conductivity than cobalt hydroxide and graphite.

In Example 1, cobalt hydroxide was used as a cobalt raw material for synthesizing a lithium-containing cobalt compound. However, when cobalt metal, cobalt oxide, or the like was used, cobalt hydroxide was used. It has been confirmed that a lithium-containing cobalt compound having high electrical conductivity can be obtained in the same manner as described above. (Experiment 2) In preparing a lithium-containing cobalt compound, 1% by weight, 2% by weight, 3% by weight, 5% by weight, 6% by weight, 7% by weight or 8% by weight instead of 4% by weight aqueous lithium hydroxide solution Lithium-containing cobalt compounds having different lithium contents were produced in the same manner as in Experiment 1 except that a lithium hydroxide aqueous solution was used. When the lithium content of these lithium-containing cobalt compounds was analyzed by the atomic absorption method, they were 0.05% by weight, 0.1% by weight, 0.5% by weight, 5% by weight, 10% by weight, 12% by weight, and 15% by weight, respectively. . Next, alkaline storage batteries A4 to A10 were prepared in the same manner as in Experiment 1 except that each of these lithium-containing cobalt compounds was used.

The alkaline storage batteries A4 to A10 were charged and discharged under the same conditions as in Experiment 1 for 10 cycles.
The active material utilization of the positive electrode at the cycle was determined, and the relationship between the lithium content of the lithium-containing cobalt compound and the active material utilization was examined. The result is shown in FIG. FIG. 1 is a diagram showing the relationship between the lithium content of a lithium-containing cobalt compound and the active material utilization. In FIG. 1, the vertical axis plots the active material utilization rate, and the horizontal axis plots the lithium content (% by weight) of the lithium-containing cobalt compound. FIG.
Also shows the results for the alkaline storage battery A1 produced in Experiment 1 on the left. The active material utilization rate shown on the vertical axis of FIG.
This is a relative index when 0 is set.

As shown in FIG. 1, the alkaline storage batteries A1,
Since the active material utilization of A5 to A8 is extremely high, it can be seen that the lithium-containing cobalt compound (the conductive agent of the present invention) having a lithium content of 0.1% by weight to 10% by weight has an extremely high electrical conductivity. (Experiment 3) In the production of a non-sintered nickel electrode, the addition amount of the lithium-containing cobalt compound to 100 parts by weight of nickel hydroxide was 0.5 parts by weight, 1 part by weight, 5 parts by weight, 15 parts by weight, 20 parts by weight, Except that the amount was 22.5 parts by weight or 25 parts by weight, a non-sintered nickel electrode having a different addition amount of the lithium-containing cobalt compound (conductive agent) was produced in the same manner as in Experiment 1. However, a lithium-containing cobalt compound having a lithium content of 1% by weight was used. Next, in the same manner as in Experiment 1, except that these non-sintered nickel electrodes were used, the alkaline storage batteries A11 to A11 were sequentially used.
A17 was produced.

The alkaline storage batteries A11 to A17 were charged and discharged under the same conditions as in Experiment 1 for 10 cycles, and
The active material utilization of the positive electrode at the cycle was determined, and the relationship between the added amount of the lithium-containing cobalt compound and the active material utilization was examined. Table 2 shows the results. Table 2 also shows the results for the alkaline storage battery A1 produced in the above Experiment 1.

[0028]

[Table 2]

Table 2 shows that when 1 part by weight or more of the lithium-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 is a diagram showing the relationship between the amount of lithium-containing cobalt compound added and the battery capacity. In FIG. 2, the abscissa plots the added amount of the lithium-containing cobalt compound (parts by weight based on 100 parts by weight of nickel hydroxide), and the ordinate plots the battery capacity. FIG. 2 also shows the result of the alkaline storage battery A1 produced in the above-mentioned experiment 1. The battery capacity on the vertical axis in FIG.
An index when the battery capacity of the alkaline storage battery A1 is set to 100, which is relatively expressed.

As shown in FIG. 2, the alkaline storage batteries A1, A
It can be understood that the battery capacities of 12 to A15 are extremely high. Because of the large battery capacity, nickel hydroxide 10
It is understood that the non-sintered nickel electrode (the electrode of the present invention) in which the addition amount of the lithium-containing cobalt compound is 1 part by weight to 20 parts by weight with respect to 0 part by weight has an extremely high electrode capacity. (Experiment 4) In the preparation of the lithium-containing cobalt compound, the heat treatment temperature was set at 45 ° C, 50 ° C, 60 ° C, 100 ° C, 150 ° C.
Experiment 1 except that the temperature was 200 ℃, 220 ℃, or 250 ℃
In the same manner as in the above, a lithium-containing cobalt compound was produced.
The lithium content of these lithium-containing cobalt compounds was analyzed by atomic absorption spectroscopy.
5%), 1% by weight (50 ° C), 1% by weight (60 ° C), 1% by weight (100%
° C), 1% by weight (150 ° C), 1% by weight (200 ° C), 0.05% by weight
(220 ° C.) and 0.02% by weight (250 ° C.). Then, in the same manner as in Experiment 1, except that each of these lithium-containing cobalt compounds was used, the alkaline storage batteries A18 to A18 were sequentially formed.
25 were produced.

The alkaline storage batteries A18 to A25 were subjected to 10 cycles of charge / discharge under the same conditions as in Experiment 1 to obtain the active material utilization of the positive electrode at the 10th cycle. Investigated the relationship.

FIG. 3 shows the result. FIG. 3 shows the relationship between the heat treatment temperature and the active material utilization when synthesizing a lithium-containing cobalt compound. In FIG.
The abscissa plots the heat treatment temperature (° C.), and the ordinate plots the active material utilization rate. FIG. 3 also shows the results for 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 a relative index when the active material utilization rate of the alkaline storage battery A1 is 100.

As shown in FIG. 3, the alkaline storage batteries A1,
Since the active material utilization rate of A19-23 is extremely high, 50-20
It can be seen that the lithium-containing cobalt compound (the conductive agent of the present invention) produced by heat treatment at 0 ° C. has an extremely high electrical conductivity.

In the above embodiment, nickel hydroxide was used as the active material. However, the present invention is also applicable to a case in which nickel, cobalt, 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.

[0036]

As described above, since the conductive agent of the present invention contains lithium, it has high conductivity. Further, since the electrode of the present invention has a conductive agent having a high conductivity added to the active material, the active material utilization rate is high, and the industrial value is extremely large.

[Brief description of the drawings]

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

FIG. 2 is a graph showing the relationship between the amount of a lithium-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 lithium-containing cobalt compound.

──────────────────────────────────────────────────続 き Continued on the front page (72) Kozo Nogami 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Ikuo Yonezu 2-5-2 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-60-211767 (JP, A) JP-A Hei 4-109557 (JP, A) JP-A-9-129224 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/24-4/62 H01M 10/24-10 / 34

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein cobalt or a cobalt compound is added with an aqueous solution of lithium hydroxide at 50 ° C. to 200 ° C.
A conductive agent for an alkaline storage battery, wherein the conductive agent is obtained by heat-treating with 0.1% by weight and contains 0.1% by weight to 10% by weight of lithium. 2. The method according to claim 1, wherein the conductive agent for an alkaline storage battery comprises nickel hydroxide particles or an active material powder comprising 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 is added to the nickel electrode.