JP2990725B2 - Sealed nickel-cadmium battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sealed nickel-cadmium battery capable of quick charging.

2. Description of the Related Art Conventionally, secondary batteries commonly used at present are mainly lead batteries and nickel-cadmium batteries. In particular, nickel-cadmium batteries are widely used because of their superior high-rate discharge performance and long life compared to lead batteries. However, on the other hand, with the recent miniaturization of electronic devices, it is desired to increase the capacity density of batteries and to shorten the charging time. However, the improvement of these properties in conventional nickel-cadmium batteries has already been limited.

Recently, as a solution to the above problems, for example, Japanese Patent Application Nos. 62-83582, 63-13345, and 1-39.
No. 513 and the like propose a new sealed nickel-cadmium battery provided with a cadmium negative electrode plate having little cadmium hydroxide for reserve and having excellent charging performance. This battery can control charging by detecting a potential change leading to hydrogen generation during charging of a cadmium negative electrode plate as a change in battery voltage, and can be charged in a short time without requiring temperature compensation. .

However, this battery has a problem that the life in cycle use is short when a metal battery case generally used in a sealed nickel-cadmium battery having cadmium hydroxide for a conventional reserve is used. I was

 The reason is as follows.

As already mentioned, the characteristics of the charging characteristics of this battery are:
At the end of charging, an extremely large change in battery voltage is caused based on a change in potential that leads to the generation of hydrogen on the negative electrode plate. However, it was found that when a metal battery case was applied to this battery, the change in battery voltage at the end of charging was greatly reduced.

This is because, in general, iron plated with nickel having a property of low hydrogen overvoltage is used as the material of the metal battery case. In other words, the magnitude of the voltage change at the end of charging is primarily based on the magnitude of the polarization of hydrogen generation of the cadmium negative electrode plate, but when a metal battery case is used, nickel on the inner surface of the battery case is Significantly reduced by the generation of hydrogen. Further, this also causes a decrease in oxygen gas absorption performance due to accumulation of hydrogen gas, that is, a significant decrease in the amount of electrolyte.

Note that such a problem does not occur in the conventional sealed nickel-cadmium battery because the cadmium negative electrode plate does not polarize to the potential of hydrogen generation of nickel by having cadmium hydroxide for so-called reserve. It is.

As can be seen from the above, the application of a metal container should be avoided for a battery that controls charging by detecting a potential change leading to hydrogen generation on the negative electrode plate as a change in battery voltage,
A battery case made of synthetic resin was used.

However, a synthetic resin battery case has a lower mechanical strength than a metal battery case, and therefore it is necessary to maintain the strength by increasing the thickness of the battery case wall. That is, it is known that a battery provided with a battery case made of a synthetic resin has a smaller capacity density per volume than a battery using a metal battery case. In addition, the battery provided with the battery case made of synthetic resin also has a problem that the phenomenon that the alkaline electrolyte leaks at the electrode terminal portion and the phenomenon that water vapor permeates through the battery case wall are not sufficiently suppressed.

Means for Solving the Problems The present invention relates to the aforementioned Japanese Patent Application Nos. 62-83582 and 63-133.
No. 45 and Japanese Patent Application No. 1-39513, related to a sealed nickel-cadmium battery in which the weight of cadmium hydroxide in the negative electrode plate is 0.95 times or less the weight of nickel hydroxide in the positive electrode plate. And is characterized by the following structure. That is, the present invention is characterized in that a synthetic resin layer is provided between an electrode plate group including a positive electrode plate, a negative electrode plate, a separator, and the like, and a metal container containing the electrode plate group.

Action The present invention has an effect of suppressing generation of hydrogen on the inner surface of the metal battery case by having a synthetic resin layer between the electrode group and the metal battery case.

That is, in a battery having no structure including a synthetic resin film, a current flows between the element and the metal case via the electrolytic solution, so that hydrogen is generated from the inner surface of the metal container at the end of charging. On the other hand, in a battery having a structure provided with a synthetic resin film, the passage of electricity through the electrolytic solution is cut off, so that generation of hydrogen from the inner surface of the metal container can be prevented. That is, the battery having the structure of the present invention provided with the synthetic resin film has a long life with almost no decrease in the electrolytic solution due to repeated use.

Further, the change in potential of the negative electrode plate of the battery of the present invention leading to the generation of hydrogen is larger than that of the battery having no synthetic resin film due to almost no generation of hydrogen from the nickel surface. That is, the battery of the present invention provided with the synthetic resin film shows a larger change in battery voltage at the end of charging than the battery which does not.

Therefore, the battery of the present invention can perform charge control at a higher voltage than a battery having no synthetic resin film, and it can be said that the charge control has high reliability. This means that the influence of the ambient temperature during charging on the discharge capacity when the battery is charged by the constant voltage charging method without temperature compensation is small, for example.

As described above, the present invention provides a sealed alkaline secondary battery that has a long life and can be charged quickly with high reliability of charge control.

In addition, the battery of the structure of the present invention can be manufactured by a method in which the electrode group is housed in a metal battery case coated with a synthetic resin on the inner surface, and after the electrode group is housed in a synthetic resin bag, It can also be manufactured by inserting it into a battery case. In particular, a method of using a so-called heat-shrinkable tube as a bag made of a synthetic resin is a method in which the electrode group is formed of a plurality of flat electrode plates, that is, the stacked electrodes are used when the battery has a rectangular shape. This has the effect of correcting the positional deviation between the plates and the effect of preventing breakage in handling the electrode plate group. Also, when inserting the electrode group with the heat-shrinkable tube into a square metal battery case, the thickness of the electrode plate at the tip of the electrode group is made thinner than the thickness of the other parts. The occurrence rate of defects in the step of inserting the battery into the battery case is significantly reduced. These effects are based on the action of shrinking the tube of the synthetic resin film, which is more advantageous than using a normal tube that does not shrink. The thickness of the shrink tube is desirably 0.1 mm or less from the viewpoint of energy density.

FIGS. 1, 2 and 3 show examples of the structure of the present invention described above.

FIG. 1 is a cross-sectional view of a rectangular sealed battery using a metal battery case whose inner surface is coated with a synthetic resin, while FIGS. 2 and 3 show a metal battery case equipped with heat-shrinkable tubes. FIG. 4 is a cross-sectional view of a prismatic sealed battery manufactured by being housed in a battery. In particular, the battery having the structure shown in FIG. 3 is easy to assemble for the following reasons.

That is, one of the problems in the process of assembling the prismatic battery is the method of injecting the electrolytic solution. In the case of the structure shown in FIG.
A battery can be easily manufactured by housing a flexible resin plate, an electrolytic solution, and an electrode plate group equipped with a heat-shrinkable tube in a metal battery case in this order. At this time, the size of the resin plate is
It is desirable that one of the length or the width is slightly larger than the inner size of the bottom portion of the metal container. The reason for this is that when the length and width of the resin plate are smaller than the size of the inner bottom surface of the battery case, the resin plate rises due to a difference in specific gravity when the electrolyte is injected.

The purpose of providing the synthetic resin layer in the present invention is to suppress the flow of current between the electrode group and the metal battery case via the electrolytic solution as described above. Therefore, the synthetic resin layer needs to be impermeable to the electrolytic solution. The material of the synthetic resin film is desirably a material having both oxidation resistance and alkali resistance, such as a polyolefin resin, a fluorine resin, a polyvinyl chloride resin or a polysulfone resin. The reason for this is that the deterioration or deformation of the synthetic resin film, such as an increase in the number of carbonates, contributes to the performance degradation of the battery.

Note that a battery structure similar to the present invention has already
No. -22223. However, the present invention clearly differs from this proposal in the following points. That is, the use of a bag made of synthetic resin in the proposal of Japanese Utility Model Publication No. 1-222223 requires the use of a common metal container for electrode groups having different capacities, that is, several electrode groups having different thicknesses in the stacking direction. The purpose is to insert a spacing plate of an appropriate size between the electrode plate group and the metal battery case. The reason for this is that this proposal makes it possible to use a battery container of a fixed size regardless of the size of the storage element in terms of cost reduction, so that the storage element is smaller than the inner size of the container. This is because smaller spacers require more spacing plates. In other words, when a bag made of synthetic resin is not provided, the larger the number of spacing plates, the more the electrolytic solution to be held by the electricity storage element is located between the spacing plate and the other spacing plate and between the spacing plate and the battery case. Since a large amount of stagnation occurs in the space between the two, the power storage element is likely to be in a state of lack of electrolyte. In other words, it can be said that the use of the synthetic resin bag in this proposal is not necessary unless a spacing plate is used.

On the other hand, the present invention is based on the premise that a spacing plate is not used, and the purpose is to provide a particularly effective structure for a battery which controls charging by detecting a potential change leading to hydrogen generation of a cadmium negative electrode plate. Things. Further, the present invention has an effect on simplification of a manufacturing process such as use of a heat-shrinkable tube and reduction of a defect occurrence rate. Thus, the present invention is different from the conventional proposal.

Examples Hereinafter, the present invention will be described using preferred examples.

The gist of the present invention is to suppress the flow of current through an electrolyte between an electrode group and a metal battery case in a battery that controls charging by detecting a potential change leading to hydrogen generation of a cadmium negative electrode plate. By doing so, the generation of hydrogen on the inner surface of the metal battery case is suppressed. As a result, the voltage change at the end of charging of the battery becomes large based on the amount of change in potential inherent in the cadmium negative electrode plate, which leads to hydrogen generation. Therefore, in the following examples, a comparison was made between the battery having a synthetic resin layer between the electrode group and the metal battery case and the battery having no such layer, and the life in a cycle test. Another object of the present invention is to increase the voltage change at the end of charging of a battery. Therefore, the performance of batteries using nickel and copper as the current collector of the cadmium negative electrode plate was also compared.

[Example 1] 100 parts by weight of cadmium oxide powder and metal cadmium powder 3
0 parts by weight and 0.1 part by weight of a polypropylene rectangular fiber having a length of 1 mm were mixed with 45 parts by weight of ethylene glycol containing 0.4 parts by weight of hydroxyethyl cellulose to form a paste. This paste is applied to a nickel-plated perforated steel sheet, and then dried and pressed to obtain a theoretical capacity of cadmium oxide of 400 mAh and 220 mAh and dimensions of 0.68 × 15 × 53, respectively.
(Mm) and 0.40 × 15 × 53 (mm), two kinds of cadmium negative electrode plates were produced.

 On the other hand, the positive electrode plate was manufactured by the following method.

A sintered nickel substrate with a porosity of about 80% contains 8 mol% and 3.5 mol% of cobalt and cadmium, respectively.
Impregnated with a mixed aqueous solution consisting of nickel nitrate, cobalt nitrate and cadmium nitrate [pH = 2, specific gravity 1.50 (20 ° C.)], immersed in a sodium hydroxide aqueous solution having a specific gravity 1.20 (20 ° C.), and then washed with hot water And drying. This operation was repeated to produce a nickel hydroxide positive electrode plate having a theoretical capacity of 350 mAh and dimensions of 0.92 × 15 × 53 (mm).

 The battery was manufactured by the following method.

After wrapping the positive electrode plate with a polysaliphone nonwoven fabric separator having a thickness of 0.17 mm, a thickness of 0.68
mm negative electrode plate, and both sides are 0.40 mm thick.
By sandwiching between two negative electrode plates having a thickness of 2 mm, an electrode plate group having a structure in which the negative electrode plates and the positive electrode plates were alternately laminated via a separator was manufactured. Next, after wrapping this electrode plate group in a tubular heat-shrinkable tube made of polyvinyl chloride (trade name: Hishilex, thickness: about 30 μm) having upper and lower ends opened in the same manner as shown in FIG. The tube was shrunk by heating. Further, the positive electrode plate and the negative electrode plate of this electrode plate group were connected to respective terminal portions formed on a nickel-plated iron lid. After inserting a 100-μm-thick polyvinyl chloride plate into the bottom of the square metal battery case with the top opening, the battery is injected with the electrolyte and the electrode plates are inserted. It was manufactured by joining the lid and the lid by laser welding. The electrolytic solution used was 1.4 ml of a mixed aqueous solution of a specific gravity 1.33 (20 ° C.) aqueous potassium hydroxide solution and a specific gravity 1.25 (20 ° C.) aqueous sodium hydroxide solution having a volume ratio of 85:15. Battery outer diameter is 4.8
× 16.5 × 64 (mm) with a nominal capacity of 650 mAh. The battery also has a safety valve that operates with a pressure difference of 0.5 kg / cm ² . This is called battery A.

[Example 2] Except that a nickel-plated perforated steel plate was used in place of the nickel-plated perforated steel plate in the negative electrode plate of Example 1, and that
A sealed rectangular nickel-cadmium battery having a nominal capacity of 650 mAh was manufactured in the same manner as in Example 1. This is called battery B.

Comparative Example 1 A sealed prismatic nickel-cadmium battery having a nominal capacity of 650 mAh was manufactured in the same manner as in Example 1 except that the heat-shrinkable tube and the resin plate on the inner bottom surface of the battery case were not used. This is called battery C.

The negative plates of these batteries have almost no cadmium hydroxide for reserve. In other words, the weight of cadmium hydroxide in the negative electrode plate is about 0.95 times the weight of nickel hydroxide in the positive and negative electrode plates [2.73 (g / Ah) /2.88 (g / Ah)]
It is. Therefore, the terminal voltage at the end of charging of the battery sharply increases based on a potential change leading to hydrogen generation on the negative electrode plate.

 Next, the charging characteristics of each manufactured battery will be described.

After the batteries A, B and C were subjected to formation charge / discharge at an ambient temperature of 20 ° C., they were charged at a current of 5 C, that is, 3.25 A, at an ambient temperature of 40 ° C. to an overcharge region. Fig. 4 shows the characteristics of 5C charging. It can be seen from the figure that the batteries A and B of the present invention have a larger voltage change at the end of charging than the battery C of the comparative example. The reason for this is that in the batteries A and B, the potential change leading to hydrogen generation on the cadmium negative electrode plate is hardly affected by the generation of hydrogen on the nickel surface inside the battery case. That is, the batteries A and B of the present invention can control charging in a wider voltage range than the battery C of the comparative example. This indicates that charging without temperature compensation is possible over a wide temperature range. The reason why the ambient temperature during the test was set to 40 ° C. is that the charging of the nickel-cadmium battery is usually performed in the range of 0 ° C. to 40 ° C., and that the higher the ambient temperature, the higher the hydrogen generation of the cadmium negative electrode plate. This is because the amount of potential change is reduced. That is, the voltage that reaches the end of charging of the battery becomes lowest at the highest ambient temperature of 40 ° C. Therefore, for example, the control voltage when charging the battery in a range of 0 ° C. to 40 ° C. and without temperature compensation needs to be set to a value that the battery can reach by charging at 40 ° C. As described above, the charge control conditions should be set in consideration of the charge characteristics of the battery when the ambient temperature is the highest.

Next, the cycle life of the battery will be described. Battery A,
After performing chemical conversion charge and discharge of B and C at 20 ° C., a cycle test was performed under the following conditions. That is, a cycle of performing a constant voltage charge of 1.5 to 2.0 V at a maximum current of 5 C at 40 ° C. for 15 minutes and then discharging the battery to 1 V at a constant current of 0.2 C was repeatedly performed. FIG. 5 shows the influence of the constant voltage set value during charging on the cycle life and the discharge capacity at the first cycle.
The cycle life of the battery was exhausted when the discharge capacity during the test was reduced to 60% or less in the first cycle.
As can be seen from the figure, the batteries A and B of the present invention have a longer life than the battery C of the comparative example. In particular, the battery B has a long life in a wide constant voltage setting range because the surface of the negative electrode current collector is copper. You can see that there is.

On the other hand, looking at the effect of the constant voltage set value on the discharge capacity, it can be seen that the discharge capacity is stably large when the constant voltage set value is 1.65 V or more. Constant voltage setting value is 1.65
The reason why the discharge capacity is small when charged under a condition lower than V is insufficient charging due to control of the charging current by the battery voltage in the charging process.

It is considered that the reason why the discharge capacity of the battery C of the comparative example is larger than that of the other batteries is that the current value flowing in the constant voltage charging region due to the generation of hydrogen from the inner surface of the battery case is large. In addition, when the range of the constant voltage setting suitable for charging each battery is determined from the figure, the range of 1.65 V to 1.85 V for the battery A according to the present invention, while the range of 1.65 V to 2.0 for the battery B of the present invention. Range is considered suitable.
On the other hand, in the battery C of the comparative example, a constant voltage set value range suitable for obtaining a stable discharge capacity and cycle life is not recognized. As described above, the battery of the present invention has a long life in a wide range of constant voltage setting values.

In the examples of the present invention, a battery using a heat-shrinkable tube made of polyvinyl chloride was described as the simplest and most practical method. In this case, the same effect was obtained. The gist of the present invention is to prevent a current from flowing between the electrode group and the metal battery case via the electrolytic solution. Therefore, the effects of the present invention can also be obtained by using a metal battery case whose inner surface is coated with a synthetic resin, or by storing the electrode plate group in a synthetic resin bag.

Effect of the Invention As described above, the present invention relates to a battery that has little cadmium hydroxide for reserve and detects a potential change leading to hydrogen generation on the negative electrode plate as a change in charging voltage, and controls charging by using a metal battery. This has the effect of improving the cycle life of the battery when the tank is provided. The present invention is also effective in simplifying the battery manufacturing process and reducing the rate of occurrence of defects.

[Brief description of the drawings]

1, 2 and 3 are sectional views of a battery according to an embodiment of the present invention. FIG. 4 is a diagram comparing the charging voltage characteristics of the battery of the present invention and the battery of the comparative example. FIG. 5 is a diagram showing the influence of a constant voltage set value during charging on the cycle life and discharge capacity of the battery of the present invention and the battery of the comparative example. 2 ... Synthetic resin coating 3 ... Heat shrink tube 4 ... Synthetic resin plate, 5 ... Cadmium negative electrode plate

Claims (1)

(57) [Claims] A cadmium negative electrode plate, a nickel hydroxide positive electrode plate, and a metal container serving also as a negative electrode terminal, wherein the weight of cadmium hydroxide in the negative electrode plate is 0.95 times the weight of nickel hydroxide in the positive electrode plate. The sealed nickel-cadmium battery according to claim 1, further comprising a synthetic resin tank that covers a side surface and a bottom surface of the electrode group between the metal battery case and the electrode group.