JP2792913B2 - Non-sintered cadmium negative electrode plate for alkaline storage batteries - Google Patents

Description

Description: (a) Industrial application field The present invention relates to a non-sintered cadmium negative electrode plate used for an alkaline storage battery such as a nickel-cadmium storage battery.

(B) Conventional technology As a cadmium negative electrode plate used for a nickel-cadmium storage battery or the like, a non-sintering type cadmium electrode plate whose manufacturing process is simple and whose manufacturing cost is low is widely used industrially. This type of cadmium electrode plate is formed by applying a paste formed by kneading an active material such as cadmium oxide powder or cadmium hydroxide powder together with a paste liquid to a core body such as a punching metal or a porous body such as nickel foam. It is manufactured after filling and drying.

In such a non-sintering type cadmium negative electrode plate, a pre-charging product is added to the paste containing the cadmium oxide or the like for the purpose of omitting a chemical conversion step performed for imparting a pre-charging amount and further simplifying a manufacturing process. Of cadmium metal is used as a mixture. However,
In general, metal cadmium has a low utilization rate. In order to improve the reactivity of this metal cadmium, for example, JP-A-62-24
No. 3254 proposes to use metal cadmium containing indium.

Further, in the case of a non-sintered cadmium negative electrode plate, in order to improve the absorption performance of oxygen gas generated from the positive electrode at the time of filling, as proposed in JP-A-60-216449, nickel or carbon A conductive layer made of an alkali-resistant conductive material is formed to increase the conductivity of the electrode plate surface to promote the production of metal cadmium on the electrode plate surface.

However, when a conductive layer made of nickel is formed on the surface of the electrode plate, hydrogen gas is generated during charging, and furthermore, indium is contained in metal cadmium in order to improve the utilization rate of the active material. Then, hydrogen gas is more easily generated. On the other hand, merely forming a conductive layer made of carbon powder on the surface of the electrode plate has not yet sufficiently improved the oxygen gas absorption performance.

(C) Problems to be Solved by the Invention The present invention is intended to provide a non-sintered cadmium negative electrode plate which can suppress generation of hydrogen gas, and have improved utilization rate of active material and oxygen gas absorption performance. is there.

(D) Means for Solving the Problems The non-sintered cadmium negative electrode plate for an alkaline storage battery according to the present invention comprises a carbon powder on a surface of an electrode plate mainly composed of cadmium oxide powder and metal cadmium powder containing indium. And a nickel powder, the amount of the indium with respect to the total amount of the active material is defined as y weight%, and the surface area of the nickel per 1 g of the active material is defined as xm ² , x ≧ 0.001 y ≧ 0.002 y ≦ −0.4x + 0.02.

(E) Function When the conductive layer disposed on the surface of the non-sintering type cadmium negative electrode plate is formed of carbon powder, the charging of the active material existing in the portion in contact with the conductive layer during charging is promoted to become metal cadmium, Oxygen gas absorption performance is improved. But,
The formation of metal cadmium cannot be promoted in and on the surface of the conductive layer where the oxygen gas absorption reaction is most likely to occur.

On the other hand, when the conductive layer is formed of nickel powder, the nickel powder can serve as a nucleus of metal cadmium generation during charging, so that metal cadmium is generated in the conductive layer and on the surface thereof. Therefore, the oxygen gas absorbing ability is further improved as compared with the case where the conductive layer is formed of carbon powder. However, nickel has a smaller hydrogen overpotential than the cadmium compound of the active material and lowers the hydrogen generation potential of the electrode plate. Therefore, excessive addition of nickel to cover the electrode plate surface with nickel powder causes hydrogen gas generation, which is not preferable.

Therefore, when a mixture layer of carbon powder and nickel powder is used as the conductive layer on the surface of the electrode plate, it is possible to find the optimum conditions for suppressing the generation of hydrogen gas and improving the oxygen gas absorption performance.

However, the optimum conditions are closely related to the amount of indium added to the metal cadmium for the purpose of improving the utilization factor. This is because when the amount of indium increases, the negative electrode charge potential becomes a lower potential. In other words, the addition of indium reduces the difference between the hydrogen gas generation potential and the active material charge level, so it is necessary to consider the conditions for forming the conductive layer on the electrode plate surface that affect the hydrogen gas generation.

The present inventors have considered the above-described effects, and have found that a cadmium negative electrode plate capable of improving oxygen gas absorption performance, improving the utilization rate of an active material, and suppressing hydrogen gas generation is obtained. It was completed.

In other words, regarding the oxygen gas absorption performance, the surface area of nickel mixed with the carbon powder in the conductive layer on the electrode plate surface is as follows:
By setting the content to 0.001 m ² or more per 1 g of the active material, it is possible to increase the effect as compared with the case where the conductive layer made of the carbon powder alone is used. This gives a surface area of nickel of 0.001m
^{When the number is 2} or more, the generation of metal cadmium in or on the surface of the conductive layer described above can be sufficiently promoted, and the charge of the active material in a portion in contact with the conductive layer that the conductive layer originally has is added thereto. This is because the effect of acceleration is added and the oxygen gas absorption performance is improved. Regarding the utilization rate of the active material, indium was added to the metal cadmium, and the amount of indium relative to the total amount of the active material was 0.002.
Greater improvements can be obtained by setting the content by weight or more. Furthermore,
Hydrogen gas generation is affected by the addition of any of nickel and indium as described above, but when the surface area of nickel per 1 g of the active material is xm ² and the ratio of indium to the total amount of the active material is y wt%, Especially y ≦ −0.4x
By making the relationship of +0.02, it is possible to suppress the generation of hydrogen gas even under the condition that large-current charging at low temperature is likely to generate hydrogen gas.

(F) Example (Example) A cadmium salt solution containing a predetermined amount of indium is reacted with zinc powder, and is composed of 20% by weight of metal cadmium powder containing indium generated by substitution and 80% by weight of cadmium oxide powder. The active material powder, a methylcellulose solution, a nylon fiber, and the like were kneaded to form a paste, and the paste was applied to a conductive core made of punching metal and dried to obtain a base electrode plate.

Next, a predetermined amount of nickel powder having a specific surface area of 5 m ² / g by BET method and acetylene black were mixed, and methyl cellulose was added to obtain a slurry. This slurry was applied to the base electrode plate by a roller transfer method and dried to prepare a cadmium negative electrode plate having a conductive layer on the surface.

Further, the cadmium negative electrode plate and the sintered nickel positive electrode plate are wound with a separator interposed therebetween to obtain a spiral electrode body, and a sealed nickel-cadmium storage battery (SCA having a nominal capacity of 1.3 Ah).
Size).

(Test 1) Using the cadmium negative electrode plate used in the battery, the relationship between the amount of indium (% by weight) based on the total amount of the active material powder and the electrode plate utilization was examined. The test conditions at this time were as follows: in an excessive amount of 25% by weight aqueous potassium hydroxide solution, using a metal nickel plate as a counter electrode, charging 0.3% of the electrode plate capacity with a current of 0.3A, and then charging with a current of 0.5A It discharges to -1.0V.

The result is shown in FIG. In FIG. 1, ○ indicates that the surface area of nickel in the conductive layer on the surface of the cadmium negative electrode plate was 0 m ² per 1 g of the active material powder, ● indicates that the surface area was 0.01 m ² per 1 g of the active material, Indicates similarly that the amount was set to 0.05 m ² per 1 g of the active material.

FIG. 1 shows that even if the surface area of nickel in the conductive layer is different, when the amount of indium in the metal cadmium is 0.002% by weight or more with respect to the total amount of the active material, the electrode plate utilization rate is greatly improved. .

(Test 2) Next, using the batteries prepared in the examples, the relationship between the surface area of nickel in the conductive layer per 1 g of the active material in the cadmium negative electrode plate and the battery internal pressure was examined. The test conditions at this time are such that charging is performed at room temperature with a current of 1.3 A, and the pressure is measured in a state where the internal pressure of the battery is balanced.

The result is shown in FIG. In FIG. 2, ○ indicates that the amount of indium in the cadmium negative electrode plate was 0 with respect to the total amount of the active material.
% Is the same as the weight%.
Weight percent, Similarly, the values of 0.03% by weight with respect to the total amount of the active materials are shown. Under the above test conditions, no hydrogen gas was generated, and the generated gas was only oxygen gas.

As is clear from FIG. 2, when the surface area of nickel in the conductive layer of the cadmium negative electrode plate becomes 0.001 m ² or more per 1 g of the active material, the battery internal pressure becomes low, and the oxygen gas absorption performance is improved. Recognize.

(Test 3) Similarly, the surface area of nickel in the conductive layer per 1 g of the active material in the cadmium negative electrode plate and the hydrogen partial pressure in the battery of the battery manufactured in the example were examined. The test condition at this time is to charge 160% of the battery capacity at 10 ° C. with a current of 2.6 A.

FIG. 3 shows the results. Further, in FIG. 3, the indium content with respect to the total active material content in the cadmium negative electrode plate is indicated by using symbols as shown in the following table.

FIG. 3 shows that the upper limit of the amount of nickel that can prevent generation of hydrogen gas differs depending on the amount of indium, and that the upper limit of the amount of nickel decreases as the amount of indium increases.

Next, the results of Tests 1 to 3 are summarized in FIG. 4, and the optimum values of the amount of indium and the surface area of nickel in the cadmium negative electrode plate are shown by oblique lines. In FIG. 4, x indicates the surface area (m ² ) of nickel per 1 g of the active material, and y indicates the amount of indium (% by weight) relative to the total amount of the active material. Further, black circles (●) plot the upper limit of the nickel addition amount for each indium amount shown in FIG. From FIG. 4, by determining the surface area and the amount of indium of the nickel so as to enter a region satisfying x ≧ 0.001, y ≧ 0.002, y ≦ −0.4x + 0.02, the utilization rate of the electrode plate and the oxygen gas absorption performance It can be understood that the cadmium negative electrode plate with improved hydrogen gas generation and no generation of hydrogen gas can be obtained.

(G) Effects of the Invention According to the present invention, it is possible to improve oxygen gas absorption performance and electrode plate utilization while suppressing generation of hydrogen gas during charging in a non-sintered cadmium negative electrode plate. The value is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of indium with respect to the total amount of the active material and the electrode plate utilization factor. FIG. 2 is a diagram showing the relationship between the surface area of nickel per 1 g of the active material and the internal pressure of the battery. The figure shows the relationship between the surface area of nickel per gram of active material and the hydrogen partial pressure in the battery, and FIG. 4 shows the optimum values of the amount of indium and the surface area of nickel.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-16554 (JP, A) JP-A-63-158746 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/24-4 / 26,4 / 44

Claims (1)

(57) [Claims] 1. An electrode plate comprising a cadmium oxide powder and a metal cadmium powder containing indium as main components, having on the surface thereof a conductive layer in which carbon powder and nickel powder are mixed, wherein The amount of indium is y
Weight%, and the surface area of the nickel per 1 g of the active material is defined as
A non-sintered cadmium negative electrode plate for an alkaline storage battery, wherein x ≧ 0.001, y ≧ 0.002, and y ≦ −0.4x + 0.02, where xm ² .