JPH0237672A - Manufacture of alkaline secondary battery - Google Patents

Abstract

PURPOSE:To improve discharge performance either by pouring an alkaline electrolyte into a battery case after inserting an electrode pile of specific cadmium negative poles or by reversing the sequence of pouring and insertion. CONSTITUTION:An electrode pile body comprising cadmium negative pole plates containing 40% or more by volume of cadmium oxide, positive pole plates, and separators is inserted into a battery case followed by the pouring of an alkaline electrolyte or the sequence of the insertion and pouring is reversed. As a result, the thickness of the negative pole plates increases because the cadmium negative electrode plates containing cadmium oxide come into contact with the alkaline electrolyte in the battery case. The overall thickness of the electrode pile also increases and the electrode pile body is favorable compressed and the distances between the electrodes become uniform. This makes it possible to reduce the variance in the discharge capacity and reduce the lowering of capacity during high rate discharging.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing an alkaline secondary battery equipped with a cadmium negative electrode plate.

Conventional technology and its issues At present, lead batteries and nickel-cadmium batteries are mainly used as secondary batteries, but nickel-cadmium batteries in particular have good characteristics at high rate discharge, and lead batteries Demand is rapidly increasing due to factors such as longer lifespan compared to

Sealed nickel-cadmium batteries have traditionally been cylindrical, but electronic devices have become smaller in recent years.

As a result of studies on increasing the capacity of batteries to reduce weight, rectangular sealed batteries have recently been developed.

Nickel-cadmium batteries with prismatic seals have 40% more energy density per volume than conventional cylindrical seals.
Although the above improvements have been made, it has become clear that, on the other hand, there are problems in that the capacity decreases greatly during high rate discharge and the dispersion of discharge capacity is large.

The reason is as follows. That is, in a cylindrical battery, the electrodes are made into a rotating body under pressure during assembly, and the electrodes are fixed with tape or the like, so that the distance between the electrodes is uniform and there is no loosening.

On the other hand, in flat batteries such as prismatic batteries in which flat electrodes are laminated, there is a method of using leaf springs as a means of compressing the electrode laminate, but this results in lower capacity density and higher cost. is not very large, so it is rarely used in practice.

In other words, in flat batteries, since there is no suitable method for compressing the electrode stack, the capacity decreases significantly during high rate discharge, and the dispersion of discharge capacity also increases. This tendency is remarkable in sealed batteries with a small amount of electrolyte.

Note that the tape fixing method used for cylindrical batteries cannot be applied to flat batteries.

The reason for this is that when the electrode rotating body is fixed with tape, the binding force from the tape acts equally toward the center on each part of the rotating body, whereas in the case of flat batteries, the shape of the cross section of the electrode stack This is because, since it is rectangular, the forces acting on the flat portion and the corner portion are different.

It was also found that the ratio between the thickness of the electrode laminate and the corresponding internal dimension of the battery case (hereinafter referred to as the insertion coefficient), as shown in the following equation, has the following effects on the battery performance and manufacturing process. .

Thickness of the electrode stack Insertion coefficient = Inner dimension of the battery case in the direction in which the electrodes are stacked, that is, battery performance is improved by bringing the insertion coefficient closer to 1.0, but on the other hand, when inserting the electrode stack into the battery case, This means that the defective rate due to dropout of the active material increases significantly.

Specifically, the insertion coefficient must be set to 0.98 or more in order to reduce the capacity drop and variation in discharge capacity during high-rate discharge, but on the other hand, it is necessary to lower the defective rate when inserting the electrode stack into the battery case. In order to suppress this, it is necessary to set the insertion coefficient to 0.95 or less, preferably 0.90 or less.

Therefore, with conventional manufacturing methods, it has not been possible to keep the defective rate low in the manufacturing process, and also to reduce capacity reduction and variation in discharge capacity during high rate discharge of batteries.

Means for Solving the Problems The present invention provides a method for manufacturing an alkaline secondary battery, using an electrode laminate consisting of a cadmium negative electrode plate, a positive electrode plate, and a separator in which the volume content of cadmium oxide is 40% or more; The electrode laminate is characterized in that an alkaline electrolyte is injected after the laminate is inserted into the battery container, or the electrode laminate is inserted after the alkaline electrolyte is injected into the battery container.

Function The present invention provides a cadmium negative electrode plate containing cadmium oxide, for example, a so-called paste-type cadmium negative electrode plate in which an active material paste containing cadmium oxide is applied to a current collector and dried, or an active material paste is applied to a mat of metal fibers. This is based on the discovery that when a filled cadmium negative electrode plate of the so-called metal fiber mat type is immersed in an alkaline electrolyte, the thickness of the negative electrode plate increases.Using this phenomenon, the above-mentioned problem was solved. It is something to do. That is, the present invention involves inserting an electrode stack consisting of a cadmium negative electrode plate, a positive electrode plate, and a separator containing an appropriate amount of cadmium oxide into a battery case, and then injecting an alkaline electrolyte into the battery case, or injecting an alkaline electrolyte into the battery case. After that, the electrode stack is inserted. When the cadmium negative electrode plate containing cadmium oxide comes into contact with the alkaline electrolyte in the battery case, the thickness of the negative electrode plate increases, and the thickness of the entire electrode laminated wood also increases.

In other words, the insertion coefficient of the electrode stack after contact with the alkaline electrolyte in the battery case is greater than the insertion coefficient when inserting the electrode stack into the battery case, so the compression of the electrode stack is better. , the distance between poles is also made uniform.

Therefore, according to the present invention, it is possible to reduce the insertion coefficient when inserting the electrode laminate into the battery case to keep the defective rate low, and to increase the insertion coefficient after contact with the electrolyte to enable high rate discharge of the battery. It is possible to reduce the decrease in capacity and the variation in discharge capacity.

Furthermore, when a cadmium negative electrode plate containing cadmium oxide is immersed in an alkaline electrolyte, the phenomenon in which the thickness of the negative electrode plate increases is due to an increase in the volume of the active material based on the hydration reaction shown in equation (1). considered to be a thing.

CdO+ H20→Cd(O11□) (1) Examples The present invention will be explained in detail below using preferred examples.

First, the increase in the thickness of the cadmium negative electrode plate containing cadmium oxide will be explained.

[Example 1] 100 parts by weight of cadmium oxide powder and ethylene glycol 401 were mixed to form a paste. This paste was applied to a nickel-plated perforated steel plate, then dried and pressurized to produce a negative electrode plate group with a porosity adjusted to 40 to 70%. This is called the negative electrode plate group (a). The nickel-plated perforated steel plate had a thickness of 0.1+++n and an open area ratio of 45%. Moreover, the porosity is based on equation (2).

Hole volume porosity in the electrode plate (%) = ... (2
) Volume of electrode plate - Volume of current collector [Example 2] Instead of the current collector in Example 1, that is, a nickel-plated perforated steel plate, the porosity was 90% and the thickness was 0.7n1M.
All were the same as Example 1 except that a nickel fiber mat of
In the same manner as above, a negative electrode plate group with a porosity adjusted to 40 to 70% was produced. This is called the negative electrode plate group (b).

Next, after measuring the thickness of these negative electrode plates, the specific gravity was 1.2.
50 (20°C) potassium hydroxide aqueous solution for 2 hours so that almost all of the cadmium oxide has changed to cadmium hydroxide, it is taken out from the electrolyte, the thickness of the negative electrode plate is measured again, and formula (3) and ( 4) The expansion rate was calculated from the formula.

In the case of the negative electrode plate group (a) In the case of the negative electrode plate group (b) Figure 1 shows the relationship between the porosity and expansion rate of the negative electrode plate before immersion.From the same figure, the porosity ranges from 40 to 70%. It can be seen that the thickness of the negative electrode plate is expanded by i, igs times to 1.100 times, and the smaller the porosity, the larger the expansion rate. In addition, regarding the influence of the difference in current collectors on the expansion rate, the negative electrode plate group (a) using a perforated steel plate as the current collector has a higher expansion rate than the negative electrode plate group (b) using a metal fiber mat. is large, but the difference is small.

The reason why the porosity was set to 40 to 70% is as follows.

First, the upper limit of the porosity was set to 70% because the porosity of the negative electrode plate before pressurization was 72%, so only slight irregularities on the surface of the negative electrode plate were flattened. The porosity can be increased to some extent by increasing the amount of ethylene glycol, but this is not preferable because the paste viscosity decreases and the workability of application deteriorates.

On the other hand, the reason why the lower limit of porosity was set to 40% is that it requires an extremely large pressing force (ioo) to further reduce the porosity.

kg/- or more) is required.

Above, we have explained the case where only cadmium oxide is used as an active material raw material, but it is usually used in a mixed system of cadmium oxide and metal cadmium, or in a mixed system that also contains cadmium hydroxide. The expansion rate of a negative electrode plate using a mixed active material will be explained.

[Example 3] An appropriate amount of ethylene glycol was added to and mixed with cadmium oxide powder and metal cadmium powder at different mixing ratios to form a paste. This paste is applied to a nickel-plated perforated steel plate and then dried.

Negative electrode plate groups with porosity of 40% and 70% were manufactured by applying pressure. Those with a porosity of 40% are designated as a negative electrode plate group (c), and those with a porosity of 70% are designated as a negative electrode plate group (d).

[Example 4] A negative electrode plate group with a porosity of 40% and 70χ was manufactured in the same manner as in Example 3, except that cadmium hydroxide powder was used instead of the metal cadmium strength wood in Example 3. Those with a porosity of 40'A are referred to as a negative electrode plate group (E), and those with a porosity of 70% are referred to as a negative electrode plate group (E).

Next, these negative electrode plate groups (c), (d), (e) and (
The expansion coefficient of the electrode thickness was measured in the same manner as in the previous example.

The results for the negative electrode plate groups (c) and (d) of Example 3 are shown in FIG. 2, and the results for the negative electrode plate groups (e) and (f) of Example 4 are shown in FIG.

Note that the volume content of cadmium oxide on the horizontal axis in the figure was determined from equation (5) for the negative electrode plate before immersion.

Volume content of cadmium oxide (%) From FIG. 2, it can be seen that the higher the volume content of cadmium oxide, the higher the expansion coefficient. Further, it can be seen that the expansion coefficient is particularly high when the volume content of cadmium oxide is 40% or more.

The same thing as in FIG. 2 can be said from FIG. Note that the expansion coefficient of the electrode plate made of 100% cadmium hydroxide shown in FIG. 3 could not be measured because the active material fell off significantly when immersed in the electrolytic solution.

From the above, it can be seen that the effects of the present invention can be obtained by using a paste-type or metal fiber matte-type cadmium negative electrode plate containing cadmium oxide. In particular, it is desirable that the volume content of cadmium oxide is 40% or more. Although the embodiments have been described using a perforated plate and a metal fiber mat as the current collector, the same effect can be obtained when a metal foam is used in addition to these.

Next, an example using a battery will be described.

[Example 5] 70 parts by weight of cadmium oxide powder and 3 parts of metal cadmium powder
0 parts by weight and length 1 nn short polypropylene fibers 0
．． 1 part by weight and 1.0% by weight of polyvinyl alcohol 3
Mix with 01m+ to form a paste. This paste was applied to a nickel-plated perforated steel plate, then dried and pressed to a length of 52n+11. The width is 141111,
A negative electrode plate was manufactured with a thickness of 0.8 nn, a porosity of 65%, and a volume content of cadmium oxide of 71%.

The theoretical capacities of cadmium oxide and metal cadmium per negative electrode plate are 450 nAh and 220 IIAh, respectively, assuming that charging and discharging of cadmium is a two-electron reaction.

The thickness of the nickel-plated perforated steel plate is 0.1nl.
1, and the opening rate was 45%.

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

A sintered nickel substrate with a porosity of about 80 circles was coated with an aqueous solution of cobalt nitrate and nickel nitrate containing 8% of the total nickel and cobalt content [Ph=2, specific gravity 1.50].
(20℃)] Specific gravity 1.200f20℃)
Soak in aqueous sodium hydroxide solution and wash with hot water.

dry. Repeat this operation until the theoretical capacity of nickel hydroxide is 310+1Ah and the dimensions are 0.86x 14x 5
21 nm) positive electrode plate was manufactured. Note that the theoretical capacity of nickel hydroxide is calculated assuming that charging and discharging of hydroxide di/gel is a one-electron reaction.

Next, an electrode laminate consisting of three negative electrode plates, two positive electrode plates, and a polypropylene group separator with a thickness of 0.2 m1N was inserted into the battery case, and then a potassium hydroxide aqueous solution I1 with a specific gravity of 1.280 (20°C) was inserted. After injecting .4i1, seal it and
A prismatic sealed nickel-cadmium battery (A) with a nominal capacity of 55 (llIAh) was manufactured.The internal dimensions of the battery case were 5.211 mm in the stacking direction of the electrodes.

When an electrolytic solution is added to the cadmium oxide in the negative electrode plate of this battery, it is hydrated and changed into cadmium hydroxide by the reaction shown in equation (1). At this time, since water was consumed, an extra amount of water was injected to cover the amount of water consumed. 0.1 part by weight of short fibers of the above group are mixed with ethylene glycol 3011 containing 0.1% by weight of polyvinyl alcohol to form a paste. This paste was applied to a nickel-plated perforated steel plate, then dried and pressurized, and the length was 52n.
A negative electrode plate having a width of 141 nm, a thickness of 0.81111, and a porosity of 42% was manufactured.

The theoretical capacities of cadmium hydroxide and metal cadmium per negative electrode plate are 45QIIAh and 220nAh, respectively, assuming that charging and discharging of cadmium is a two-electron reaction. The difference from the negative electrode plate used in Example 5 is whether the main active material raw material is cadmium oxide or cadmium hydroxide.

Next, using the same positive electrode as used in Example 5, a prismatic sealed nickel-cadmium battery (B) having a nominal capacity of 5501'lAh was manufactured in the same manner as in Example 5.

100 cells each of the batteries (A) and (B) manufactured as described above were prepared, and the average, maximum, and minimum values of capacity when discharged at various rates are shown in FIG.

From the same figure, it can be seen that the discharge rate dependence of the discharge capacity of the battery (A) produced by the manufacturing method of the present invention is better than that of the Hisame battery (B), and the discharge capacity is particularly large at IOA or higher.

Furthermore, battery (A) had little variation in discharge capacity, indicating stable performance. The reason for this difference is as follows. That is, 24 hours after electrolyte injection.
When the batteries fA) and FB) were disassembled after the lapse of time and the thickness of the negative electrode plate was measured, the thickness of the negative electrode plate of battery TA) had increased from 0.80111 to 0.881'In. On the other hand, no increase in thickness was observed in the negative electrode plate of battery +8).

In other words, the insertion coefficient when inserting the battery (^) and FB) tiger electrode stack into the battery case was 0.95, but after the electrolyte was injected, the insertion coefficient of battery (A) was 0.99. This is because the pressure of the electrode stack has improved and the distance between the electrodes has become uniform.

In the above embodiments, a prismatic sealed Nylagel-Cadmium battery using a paste-type cadmium negative electrode plate was explained as an example. The same effect can be obtained when a metal foam or metal foam is used, and the shape of the battery is similar to that of a flat sealed battery using a flat electrode, such as a coin-shaped battery. Furthermore, it goes without saying that similar effects can be obtained when manganese dioxide or silver oxide is used in place of nickel hydroxide as the main positive electrode active material.

Effects of the Invention As described above, an alkaline secondary battery with excellent discharge performance can be obtained by the manufacturing method of the present invention.

It is also possible to lower the defective rate during battery assembly.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are diagrams showing the expansion rate of the negative electrode plate thickness when a cadmium negative electrode plate containing cadmium oxide is immersed in an alkaline electrolyte. FIG. 4 is a diagram showing the discharge performance of a prismatic double-cadmium battery and a battery for comparison according to the manufacturing method of the present invention. Tsuke 1 10 da, QOJ da 0 I7 ordinary torture /7- ton z (71 ° to) Sushi tl-mi 7 Musuba Sensama 4fli / Zo・Q 6 ° 1 o. 1 sosu 013 k mi bum - banyu54 shoulder ki /
Bu・

Claims (1)

[Claims] Either inserting an electrode stack using a cadmium negative electrode plate having a volume content of cadmium oxide of 40% or more into a battery case and then injecting an alkaline electrolyte, or injecting an alkaline electrolyte into the battery case and then stacking the electrode. A method for producing an alkaline secondary battery, which comprises inserting a battery into the battery.