JP3316367B2 - Estimation and evaluation method of utilization rate of active material powder for non-sintered nickel electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating and evaluating the utilization rate of an active material powder for a non-sintered nickel electrode. The present invention relates to an estimation / evaluation method for easily and accurately knowing without actually assembling.

[0002]

2. Description of the Related Art
Non-sintered nickel electrodes (positive electrodes) of alkaline storage batteries such as nickel-cadmium storage batteries and nickel-hydrogen storage batteries include:
Nickel hydroxide powder has been used as the active material powder. However, due to the poor electron conductivity of the particle surface of the nickel hydroxide powder, the non-sintered nickel electrode using the same has a utilization rate (hereinafter simply referred to as “utilization rate”) of the active material. There was a problem of low.

For this reason, in recent years, in order to increase the utilization rate,
It has been proposed to coat the particle surface of the nickel hydroxide powder with a cobalt compound, thereby making it possible to increase the capacity of the non-sintered nickel electrode.

[0004] The capacity of the non-sintered nickel electrode directly connected to the battery capacity depends on the utilization factor. Conventionally, in order to know this utilization rate, a non-sintered nickel electrode had to be actually manufactured, a battery had to be assembled, and a charge / discharge test had to be performed.

[0005] However, in such a conventional method, the utilization rate cannot be known unless the battery is assembled each time, a large number of non-standard products may be generated in terms of capacity in an actual production line, and the yield is reduced.
Also, a large amount of time, labor, and cost is required for the charge / discharge test.

Accordingly, as a result of intensive studies, the present inventors have found that an active material powder composed of composite particles having a relatively high electron conductivity in which the surface of nickel hydroxide particles is coated with a cobalt compound has a specific electric conductivity. We found that there was a certain relationship between rates and utilization.

The present invention has been made based on such knowledge, and an object of the present invention is to easily and accurately determine the utilization rate of a non-sintered nickel electrode active material powder without actually assembling a battery. The purpose is to provide an estimation / evaluation method that can be known.

[0008]

In order to achieve the above object, the method for estimating and evaluating the utilization of the non-sintered nickel electrode active material powder according to the present invention (the method of the present invention) comprises the steps of: A method for estimating and evaluating the utilization rate of an active material powder for evaluation _AE composed of composite particles obtained by coating the surfaces of particles mainly composed of nickel hydroxide with a cobalt compound, comprising the steps of: Active material powders A _1, A _2, ... For preparing a plurality of calibration curves composed of composite particles obtained by coating the surfaces of particles mainly composed of nickel oxide with a cobalt compound.
Specific conductivity kappa _{1 of,} kappa _2, ... and utilization U _1, U _2, and Step (1) to a calibration curve showing the relationship between ... and specific conductivity of the evaluation active material powder A _E Step (2) for determining the rate κ _E, and the specific electric conductivity κ of the active material powder A _E for evaluation.
_E is compared with the calibration curve to obtain the active material powder A _E for evaluation.
(3) estimating and evaluating the utilization rate U _E of

Examples of the particles containing nickel hydroxide as a main component include those in which a swelling inhibitor such as cobalt, zinc, cadmium, calcium, manganese, or magnesium is dissolved in nickel hydroxide.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention is used for estimating and evaluating the utilization of an active material powder composed of nickel hydroxide particles or composite particles in which the surface of nickel hydroxide-based particles is coated with a cobalt compound. Can be widely used. However, when the cobalt compound as the coating material contains sodium, a particularly remarkable correlation is observed between the specific electric conductivity and the utilization factor, so that the present invention is particularly suitable for application in that case. Since the method of the present invention is a method of estimating and evaluating the utilization rate as an electrode material from the specific electric conductivity of the active material powder for evaluation, the specific resistance is extremely large, that is, the specific electric conductivity is numerically specified. Difficult or impossible to do,
It is not possible to simply estimate and evaluate the utilization rate of the composite particle powder obtained by coating the surface of the nickel hydroxide particles with cobalt hydroxide (Co (OH) ₂ ).

[0011]

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.

Step (1) [Preparation of active material powder for preparing calibration curve] Cobalt sulfate
100 g of nickel hydroxide powder was added to 1000 ml of an aqueous solution in which 1 g was dissolved in water, and then a 1M aqueous solution of sodium hydroxide was added dropwise with stirring until the pH of the solution reached 11, and then the stirring was continued until the pH of the solution was lowered. At the time of a slight drop, a 1M aqueous solution of sodium hydroxide was added dropwise as appropriate to adjust the pH of the solution.
Was constantly maintained at 11 and reacted for 1 hour. Monitoring of pH used a glass electrode with autofocus. Next, the precipitate was filtered off and washed with water to obtain a powder composed of composite particles obtained by coating the surfaces of nickel hydroxide particles with cobalt hydroxide. Next, 10 parts by weight of this powder was mixed with 100 parts by weight of a 30% by weight aqueous sodium hydroxide solution, and the mixture was mixed at 95 ° C. with 0.1 part by weight.
After heating for 5 hours, 1 hour, 2 hours, 5 hours, 8 hours or 12 hours, wash with water, dry at 60 ° C., and coat the surface of nickel hydroxide particles with a cobalt compound containing sodium. Active material powders a (heating time: 0.5 hour), b (heating time: 1 hour), c (heating time: 2 hours), d (heating time: 5) Time), e (heating time: 8 hours), and f (heating time: 12 hours). Incidentally, the weight ratio of cobalt in the coating layer to the total weight of each calibration curve making active material powder,
In each case, the content was 5% by weight. The weight ratio of 5% by weight of cobalt is a value confirmed by the atomic absorption method.

[Specific Electric Conductivity κ of Active Material Powder for Making Calibration Curve] FIG. 1 shows a specific electric conductivity measuring apparatus used for obtaining the specific electric conductivity κ of the active material powders a to f for making a calibration curve. It is a fragmentary sectional view showing the important section of M. The specific electric conductivity measuring device M shown in the drawing is a ram 1 for pressing and applying pressure.
a and press substrates 1b, jigs 2 and 3, each of which is made of a conductive material, has a disk-shaped base and a disk-shaped protrusion having a diameter smaller than that of the jigs 2, 3, and an inner peripheral surface. And a resistance meter 5 and an insulating plate 6 provided with an insulating layer. The lower part of the inner peripheral surface of the cylindrical body 4 is fitted to the projecting part of the jig 3. A part of the space formed by the upper surface of the projecting portion of the jig 3 and the inner peripheral surface of the cylindrical body 4 is filled with a sample S (active material for preparing a calibration curve). A projecting part of the jig 2 is fitted to an upper part of the inner peripheral surface of the tubular body 4. Jigs 2, 3
The ram 1a and the press substrate 1b are in contact with each other from above and below, and a predetermined pressure is applied to the sample S via the jigs 2 and 3. A resistance meter 5 for measuring the electric resistance R of the sample S is connected to the jigs 2 and 3. The specific electric conductivity measuring devices M and 1 having the above configuration
g of the sample S, the electrical resistance R of the sample S when the sample S was pressed at a pressure of 400 kgf / cm ² was measured, and the specific electrical conductivity κ was calculated based on the following equation.

Specific electric conductivity κ (Ω ⁻¹ · cm ⁻¹ ) = L / (A · R) [where L is the distance between the lower surface of the jig 2 and the upper surface of the jig 3, A
Is the area of the upper surface of the protrusion of the jig 3 (= the area of the lower surface of the protrusion of the jig 2). ]

[Utilization rate of active material powder for preparing calibration curve] (Preparation of non-sintered nickel electrode) 100 parts by weight of each active material powder for preparing a calibration curve and 20 parts by weight of a 1% by weight aqueous solution of methylcellulose are kneaded. To prepare a paste, the paste is nickel-plated foam metal (porosity: 95%;
(Average pore diameter: 200 μm), dried, and press-molded to produce a non-sintered nickel electrode.

(Assembly of Nickel-Cadmium Storage Battery) An AA size nickel-cadmium storage battery was assembled using each non-sintered nickel electrode (positive electrode) and a conventionally known paste-type cadmium electrode. Note that a polyamide nonwoven fabric was used as a separator, and a 30% by weight aqueous solution of potassium hydroxide was used as an electrolyte.

For each nickel-cadmium storage battery,
After charging 160% at 0.1 ° C at 25 ° C, 25 ° C
A charge / discharge cycle test was performed in which the process of discharging to 1.0 V at 1 C was performed as one cycle, and the utilization rate of the active material powder for preparing each calibration curve at the tenth cycle defined by the following equation was determined.

Utilization rate (%) = {discharge capacity at 10th cycle (mAh) / [(weight of nickel hydroxide contained in active material powder) (g) × 288 (mAh / g)]} × 100

Table 1 shows the specific electric conductivity and utilization of the active material powders a to f for preparing the calibration curves. The utilization rate is indicated by an index with the utilization rate of the active material powder e for preparing a calibration curve as 100.

[0020]

[Table 1]

[Creation of Calibration Curve] As shown in FIG. 2, the specific electric conductivity and the utilization of the active material powders a to f for preparing the calibration curve are plotted on the vertical axis, and the specific electric conductivity is plotted on the horizontal axis. Was plotted on a scaled orthogonal coordinate graph to create a calibration curve showing the relationship between specific electrical conductivity and utilization.

Step (2) Active material powders A, B, C, D, and E for evaluation were prepared as follows. The weight ratio of cobalt in the coating layer to the total weight of each evaluation active material powder was 5% by weight. The weight ratio of 5% by weight of cobalt is a value confirmed by an atomic absorption method.

(Evaluation Active Material Powder A) When heating a mixture of a powder composed of composite particles obtained by coating the surfaces of nickel hydroxide particles with cobalt hydroxide and an aqueous sodium hydroxide solution, the heating temperature was set at 70%. An active material powder A for evaluation was prepared in the same manner as in the case of preparing the active material powders a to f for preparing a calibration curve except that the heating time was 2 hours at ° C.

(Evaluation Active Material Powder B) When heating a mixture of a powder composed of composite particles obtained by coating the surfaces of nickel hydroxide particles with cobalt hydroxide and an aqueous sodium hydroxide solution, the heating temperature was set at 70%. An active material powder B for evaluation was prepared in the same manner as in the case of preparing the active material powders a to f for preparing calibration curves except that the heating time was 5 hours at ° C.

(Evaluation Active Material Powder C) When heating a mixture of a powder composed of composite particles obtained by coating the surfaces of nickel hydroxide particles with cobalt hydroxide and an aqueous sodium hydroxide solution, the heating temperature was set at 70%. An active material powder C for evaluation was prepared in the same manner as in the case of preparing the active material powders a to f for the preparation of the calibration curves except that the heating time was 8 hours at ° C.

(Evaluation Active Material Powder D) When heating a mixture of a powder composed of composite particles obtained by coating the surfaces of nickel hydroxide particles with cobalt hydroxide and an aqueous sodium hydroxide solution, the heating temperature was set at 70%. An active material powder D for evaluation was prepared in the same manner as in the case of preparing the active material powders a to f for the calibration curve except that the heating time was set to 10 hours at ° C.

(Evaluation Active Material Powder E) When heating a mixture of a powder composed of composite particles obtained by coating the surfaces of nickel hydroxide particles with cobalt hydroxide and an aqueous sodium hydroxide solution, the heating temperature was set at 70%. An active material powder E for evaluation was prepared in the same manner as in the case of preparing the active material powders a to f for the calibration curve except that the heating time was 12 hours at ° C.

Next, the specific electric conductivity of these evaluation active material powders was determined using the specific electric conductivity measuring device M described above. Table 2 shows the specific electrical conductivity of the active material powders A to E for evaluation.

[0029]

[Table 2]

Step (3) The specific utilization of each of the active material powders for evaluation was compared with the previously prepared calibration curve to obtain an estimated utilization factor. The estimated utilization rate of each active material powder for evaluation was determined by obtaining the value of the specific electric conductivity (horizontal axis coordinate) of each active material powder for evaluation on a calibration curve, and reading the value of the vertical axis coordinate at that point. Table 2 shows the estimated utilization rates of the active material powders A to E for evaluation.

Reliability of the Method of the Present Invention Nickel was prepared in the same manner as above except that active material powders A to E for evaluation were used instead of active material powders a to f for preparing calibration curves.
Cadmium storage batteries were assembled and subjected to a charge / discharge cycle test under the same conditions as described above, and the utilization rates (actual utilization rates) of the evaluation active material powders A to E to be used were determined. Table 2 shows the measured utilization rates of the active material powders A to E for evaluation.
Shown in FIG. 3 is a graph in which the respective measured utilization rates of the active material powders for evaluation A to E are plotted on the graph of FIG.

As shown in Table 2 and FIG. 3, the estimated utilization rates of the active material powders for evaluation A to E are substantially equal to the actually measured utilization rates, respectively. From this fact, it can be seen that the method of the present invention is an extremely reliable method for estimating and evaluating the utilization of the non-sintered nickel electrode active material powder.

[0033]

According to the method of the present invention, the utilization of the non-sintered nickel active material powder can be easily and accurately determined without actually assembling the battery.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a main part of a specific electric conductivity measuring device used in an example.

FIG. 2 is a graph showing a calibration curve representing the relationship between the specific electric conductivity and the utilization rate of the active material powder for preparing a calibration curve.

FIG. 3 is a graph in which the measured utilization rate of the active material powder for evaluation is plotted on the graph of FIG. 2;

──────────────────────────────────────────────────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 Pref. Sanyo Electric Co., Ltd. (72) Inventor, Teruhiko Imoto 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (56) References JP-A-62-80590 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/00-27/24 H01M 4 / 52

Claims (2)

(57) [Claims] 1. A method for estimating and evaluating the utilization rate of an active material powder for evaluation _AE comprising nickel hydroxide particles or composite particles obtained by coating the surfaces of nickel hydroxide-based particles with a cobalt compound. The ratio of a plurality of active material powders A _1, A _2, ... For preparing a calibration curve comprising nickel hydroxide particles or composite particles obtained by coating the surfaces of nickel hydroxide-based particles with a cobalt compound. Step (1) of preparing a calibration curve showing the relationship between the electric conductivity κ _1, κ _2, ... And the utilization rate U _1, U ₂ ,, and the specific electric conductivity κ of the evaluation active material powder _AE.
Step (2) for obtaining _E , and the evaluation active material powder A
The specific conductivity kappa _E of _E against the above calibration curve, non-sintered, characterized in that a step (3) to estimate and evaluate the utilization U _E of the evaluation active material powder A _E Method for estimating and evaluating the utilization rate of the active material powder for the formula nickel electrode. 2. The method according to claim 1, wherein the cobalt compound is a sodium-containing cobalt compound.