JPH025362A - Cadmium negative plate and alkaline secondary battery using the same - Google Patents

Abstract

PURPOSE:To increase a substantial capacity density, and control charging with ease and make very quick charging possible with a large current flow by making a cadmium magnetic plate contain mercuric oxide at a specific rate to a total quantity of cadmium. CONSTITUTION:A charging efficiency before cadmium hydroxide is generated when a cadmium negative plate mainly composed of cadmium hydroxide or cadmium oxide and metallic cadmium as active material is charged by an electric current of 1CA on the basis of a theoretical capacity of cadmium oxide or cadmium hydroxide is approx. 93%; however, when mercuric oxide is contained at 0.25-20wt.% of a total quantity of cadmium, the charging efficiency increases to approx. 97%. If a change in potential made until generation of hydrogen at a charging time is detected as a change in a terminal voltage by use of this negative plate having a good charging efficiency, charging control is easy, and if a constant voltage is set at that point of time, a current flow becomes small in an overcharge region, so that an alkaline secondary battery capable of a quick charge and also free from loss of electrolyte is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a cadmium negative electrode plate and an alkaline secondary battery using the negative electrode plate.

Conventional technology and its issues At present, secondary batteries mainly include lead batteries and 2.1
Nickel-cadmium batteries are used, and demand for nickel-cadmium batteries in particular is rapidly increasing due to their good characteristics at high rate discharge and longer lifespan than lead batteries. On the other hand, as electronic devices have become smaller and lighter in recent years, there has been a demand for higher capacity and shorter charging time for secondary batteries.

Conventional alkaline secondary batteries using cadmium negative electrode plates have the following problems. This is related to the cadmium negative electrode plate, which contains a large amount of cadmium hydroxide that does not participate in charge/discharge reactions.

In other words, the charging efficiency of cadmium hydroxide until hydrogen gas is generated is usually about 90%, and the remaining 10% of cadmium hydroxide is of no use and occupies unnecessary volume. Furthermore, taking a nickel-cadmium battery as an example,
In order to keep the battery sealed, a so-called reserve of cadmium hydroxide of 20% or more of the capacity of the positive electrode plate was required in the negative electrode plate.

This reserve of cadmium hydroxide is 1″A of the positive electrode active material.
It is used to make the supporting metal nickel into an active material and to compensate for the space volume inside the battery, and does not contribute to the discharge capacity. The presence of these cadmium hydroxides is one of the reasons that prevents the capacity of cadmium negative electrode plates and batteries from increasing.

In addition, when conventional nickel-cadmium batteries are charged at a constant current to keep the battery sealed, the current is approximately I.
There is a problem in that it must be kept below CA. This is because when the charging current is increased to 108 or more, the negative electrode plate cannot absorb all the oxygen gas generated from the positive electrode plate in the overcharge region, and the safety valve is activated and the electrolyte This is because it causes a decrease in capacity, a decrease in capacity, and a deterioration in life characteristics. Therefore, the special application
As proposed in No. 3582 and Japanese Patent Application No. 63-13345, potential changes in the process leading to hydrogen generation in the negative electrode plate during charging are detected as changes in the charging voltage to facilitate charging control and provide rapid charging. There are attempts to make it possible, but
The charging efficiency of the negative electrode plate is insufficient.

Means for Solving the Problems The present invention relates to a cadmium negative electrode plate and an alkaline secondary battery equipped with the negative electrode plate, in which the negative electrode plate contains mercuric oxide in an amount of 0.25 to 20% relative to the total amount of cadmium. It is characterized by containing %.

As a result of studying the charging efficiency of the acting force lmium negative border plate,
It was found that charging efficiency was increased by incorporating mercuric oxide into the negative electrode active material.

For example, when a cadmium negative electrode plate whose main active materials are cadmium hydroxide or cadmium oxide and metal cadmium is charged with a current of IOA based on the theoretical capacity of cadmium oxide or cadmium hydroxide, until hydrogen gas is generated. The charging efficiency is about 93%, but when mercuric oxide is contained in an amount of 1% by weight or more based on the total amount of cadmium, the charging efficiency improves to 97% or more.

In addition, by using such a negative electrode plate with excellent charging efficiency, it is easy to control charging by detecting the potential change that leads to hydrogen generation during charging of the negative electrode plate as a change in terminal voltage, and at that point, the constant voltage If set to , the current becomes small in the overcharge region, resulting in an alkaline secondary battery that allows rapid charging and does not cause loss of electrolyte.

Example The present invention will be explained in detail below using preferred embodiments.

An object of the present invention is to obtain a cadmium negative electrode plate with excellent charging efficiency, and to apply it to batteries. Therefore, first we will discuss the cadmium negative electrode plate.

[Example 1] Cadmium oxide powder 240 ng and metal cadmium powder 2
1019 and mercuric oxide with varying amounts in the range of 0 to 841 g, and then pressure molded at a pressure of 230 kg/ci'' to obtain a total theoretical capacity of cadmium of 200 iAh.
It was made into tablets. Furthermore, this tablet was wrapped in a nickel mesh of 20 meshes to form a negative electrode plate. This is called the negative electrode plate group (a).

[Example 2] Cadmium hydroxide powder 273u and metal cadmium powder 2
After mixing 10 ng of mercuric oxide with varying amounts in the range of 0 to 84 B, a tablet-shaped negative electrode plate with a theoretical capacity of 2001^h was prepared in the same manner as in Example 1. This is called the negative electrode plate group (b).

Note that the total amount of cadmium is the total amount of Cd atoms contained in the cadmium negative electrode plate.

These negative electrode plates were placed in a potassium hydroxide aqueous solution with a specific gravity of 1.25 of 20°C, using two nickel flat plates as counter electrodes, and ICA (1001
Charging and discharging were repeated using the current A), and the charging efficiency was determined from the following equation (1).

Amount of electricity charged until generation of hydrogen scum is observed Charging efficiency = (χ) Theoretical capacity of cadmium active material in a discharged state X 100 (1) The results are shown in FIG. From the same figure, it is recognized that the charging efficiency is improved when the content of mercuric oxide relative to the total amount of cadmium is 0.25% by weight or more. In particular, the content is 0.5% by weight.
The above shows that the charging efficiency is extremely high at 97% or more, and that inactive cadmium hydroxide, which cannot be charged, is reduced.

On the other hand, when the content of mercuric oxide is 15% by weight or more, differences in charging efficiency are observed depending on the active material raw materials. That is, in the negative electrode plate (a) using cadmium oxide as the active material raw material, a decrease in charging efficiency was observed when the content of mercuric oxide was 15% by weight or more, whereas in the negative electrode plate using cadmium hydroxide (B) is hardly recognized. Therefore, when the content of mercuric oxide is 15% by weight or more, it is desirable to use a material containing mainly cadmium hydroxide as the active material raw material.

Although it is possible to make the content of mercuric oxide higher than 20% by weight, the decrease in the theoretical capacity density of the cadmium active material will be large, so the content should not be lower than 20% by weight. considered desirable.

From the above, the content of mercuric oxide relative to the total cadmium is preferably 0.25% by weight or more and 20% by weight or less, and if it is 15% by weight or more, it is desirable to use cadmium hydroxide as the main active material raw material. It can be said.

The properties of each raw material used in the examples are shown below. Cadmium oxide powder〉 Cadmium hydroxide powder with an average particle diameter of 1 μm manufactured by the atomization method〉 The above cadmium oxide powder was immersed in purified water. Hydrated metal cadmium powder> Average particle size 2μm produced by electrochemical substitution method
Commercially available reagents Next, a battery using the cadmium negative electrode plate of the present invention having extremely high charging efficiency as described in the above examples was evaluated.

The cadmium negative electrode plate of the present invention can be used in conventional nickel-cadmium batteries that require cadmium hydroxide as a reserve, and also has cadmium hydroxide as a reserve, which enables higher capacity and shorter charging time. The effect is more obvious when used on batteries that do not. This is due to the excellent charging efficiency of the cadmium negative electrode plate of the present invention. Therefore, in the following embodiments, a battery with and without cadmium hydroxide as a reserve will be described as an example.

Positive electrode active materials that can be used in the alkaline battery of the present invention are nickel hydroxide, manganese dioxide and silver oxide. Among these, the active material that is often used in the membrane is nickel hydroxide, so the explanation will focus on nickel-cadmium batteries.

The cadmium negative electrode plate used in the present invention can basically be manufactured using the current collector shown below.

That is, metal foam or metal fiber mats of Ni-Nokel, steel or cadmium nets, expanded metal, perforated plates, or three-dimensional supplements that serve as current collectors and active material holders.

Additionally, nickel-plated steel, copper-plated iron or nickel, and cadmium-plated iron, nickel, or copper can also be used.

[Example 3] 60 parts by weight of cadmium oxide powder and 4 parts by weight of metal cadmium powder
Ethylene glycol 301 containing 0 parts by weight of mercuric oxide, 2 parts by weight of mercuric oxide, and 0.1 parts by weight of staple fibers made of polypropylene having a length of 111 cm and containing 1.5% by weight of polyvinyl alcohol.
Mix in Step 11 to make a paste.

This paste was applied to a nickel-plated (5 μm) perforated steel plate, then dried and pressurized to form a plate with a theoretical capacity of cadmium oxide of 960 nAh and dimensions of 2.9 x 14 x 52 (
nn+) negative electrode plate was manufactured.

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

A sintered nickel substrate with a porosity of approximately 80%, and a cobalt content of 8 mol% based on the total of nickel and cobalt.
A mixed aqueous solution of cobalt nitrate and nickel nitrate (PH=
2, specific gravity 1.50 (20°C)], specific gravity 1.50 (20°C)]
．． 200°C (20°C) aqueous sodium hydroxide solution, washed with hot water, and dried. Repeat this operation until the total theoretical capacity of nickel hydroxide and cobalt hydroxide is 400.
A positive electrode plate with dimensions of 1.4×14×52IIIm was manufactured using nAh.

Next, one negative electrode plate was wrapped in a polyamide non-woven fabric with a thickness of 0.2 In, and then sandwiched between two positive electrode plates, and the electrolyte was prepared using a potassium hydroxide aqueous solution with a specific gravity of 1.250 (20°C).
A nickel-cadmium battery (^) with a nominal capacity of 700 mAh and a synthetic resin container was manufactured using 2.4 nl. External dimensions are 67x 16.5x 8 (nn)
It is equipped with a safety valve that operates at 0.1 kg/c12.

Also, the cadmium oxide in the negative electrode plate of this battery is electrolyzed 7α
When water is added, water is consumed by the reaction shown in equation (2) below, so extra water corresponding to the amount consumed was injected.

Cd O+ H20-Cd (OH) 2...(
2) [Example 4] Cadmium hydroxide powder 68.51! parts by weight, 40 parts by weight of metal cadmium powder, 2 parts by weight of mercuric oxide, and 1 inch in length.
and 0.1 part by weight of short polypropylene fibers are mixed with ethylene glycol 3011 containing 1.5% by weight of polyvinyl alcohol to form a paste.

This paste was applied to a separately plated perforated steel plate, then dried and pressurized until the theoretical capacity of cadmium hydroxide was 960.
nAh and dimensions are 2.9 x 14 x 52 (n+n+)
A negative electrode plate was manufactured.

On the other hand, the Seiko board was manufactured using the following method.

Next, using the above negative electrode plate and the same positive electrode plate as used in Example 3, the nominal capacity of the same configuration as Example 3 was 700 +
A prismatic nickel-cadmium battery (B) of a A h was manufactured.

[Example 5] Cadmium, Men, 8 (5 μm
A prismatic nickel-cadmium battery (C) having a nominal capacity of Jt 7001 IAh was manufactured in the same manner as in Example 3 except that the perforated steel plate (C) was used.

[Reference Example 11 The same procedure as in Example 3 was made except that mercuric oxide was removed from the formulation of the negative electrode plate in Example 3, with a nominal capacity of 7001.
An Ah prismatic nickel-cadmium battery (D) was manufactured.

Batteries (A), (B), (
C) and (0) were charged at a constant voltage of 1°90V for 30 minutes at a maximum current of 3CA at 20°C, and then
．． A charge/discharge cycle of discharging to 0.5V at a current of 20^ was performed 250 times. The discharge capacity of the first cycle is 1
The capacity retention rate in each cycle when set to 00 is the second
As shown in the figure. From the figure, it can be seen that the batteries (^), (B), and (C) of the present invention have clearly higher capacity retention rates than the comparative battery fD). The reason for this is that the charging efficiency of the negative electrode active material of the battery of the present invention is extremely high.
Even if it is a, there is a negative gi at the end of charging! This is because the amount of electricity charged until the potential rises is large, and there is almost no decrease in charging efficiency during the cycle.

The content of cadmium hydroxide in the negative electrode plates of batteries (8), f8), fc) and (D) was approximately 0.95 times that of nickel hydroxide in the positive electrode by weight [2,73 fq/Ah].
) /2.88 (g/^h)]. Further, the properties of the raw materials such as cadmium oxide used for manufacturing the negative electrode plate are the same as those used in the previous embodiment of the tablet-shaped negative electrode plate.

As described above, the battery of the present invention can be charged very quickly using a simple charging method called constant voltage control.

The charging method used was a constant voltage charging method that regulated the maximum current. However, this method does not reduce the charging voltage due to gas absorption after charging at the constant current used in conventional nickel-cadmium batteries. It is not a complicated charging system, such as a method that detects the occurrence of heat generation due to gas absorption and aborts charging. Furthermore, one of the features of the present invention is that constant voltage charging method, which was difficult to apply with conventional nickel-cadmium batteries, can be easily performed.
That is. In other words, in conventional nickel-cadmium batteries, the difference between the voltage during the charging process and the voltage at the end of charging is at most 150
Since the voltage was as low as ~200 nV, a constant voltage charging method could not be applied, but in the case of the battery according to the present invention, the difference reaches 400 mV or more at a current of 0.2 CA or more, so it is possible to detect changes in charging voltage. is easy. In this case, the battery may be charged with a constant current and the current may be lowered after detecting an increase in the charging voltage, or the battery may be charged with a constant voltage. Note that the nominal capacity using conventional sintered electrode plates is 700IIAh.
When a cylindrical nickel-cadmium battery (^^ size) was charged at a constant voltage of 1.9V with a maximum current of 3C^ for 30 minutes, the safety valve was activated and an ia 1f7f leak occurred. This is because the battery was overcharged because the charging voltage of the conventional battery did not reach 1.9V.

As described above, in the battery of the present invention, it is advantageous to increase the potential change of the negative electrode plate at the end of charging, and the surface of the current collector is
Basically copper or cadmium with a large overvoltage for hydrogen generation, such as copper or cadmium nets, expanded metals, perforated plates, or three-dimensional horizontal metal foams that double as current collectors and active material holders. Suitable materials include metal fiber mats, iron or nickel, or cadmium plated. However, even with a nickel current collector that has a small overvoltage for hydrogen generation,
1. Of course, use nickel powder, etc., which has low hydrogen overvoltage.
By reducing the amount, for example, to 5% by weight or less, it can be used as a current collector.

In the above embodiments of the present invention, nickel hydroxide was used as the positive electrode active material, or even if mankane dioxide was used as the active material, the same effects as in the nickel-cadmium battery can be obtained. Hereinafter, a case where the present invention is applied to a mankane dioxide-cadmium battery will be explained using preferred embodiments.

[Example 6] 100 parts by weight of metal cadmium powder, 2 parts by weight of mercuric oxide, and 0.1 part by weight of polypropylene short fibers having a length of 11'lIm were mixed into ethylene containing 1.5% by weight of polyvinyl alcohol. Mix base 1 with glycol 3011
make into ~ shape. This paste was applied to another expanded metal, then dried and pressurized to obtain a metal cadmium with a capacity of 8001^h and dimensions of 2.9x 14x52 (nn).
A negative electrode plate was manufactured.

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

After kneading 80 parts by weight of manganese dioxide (γ-M n O2) and 10 parts by weight of graphite with 60% by weight polytetrafluoroethylene aqueous dispersion 301, the mixture was formed into a sheet using a roller and formed into a 20-mesh nickel mesh. Further pressure is applied from both sides to increase the theoretical capacity to 200 mA.
h. Prepare a positive electrode plate with dimensions of 1.4 x 14 x 52 (mn).

Next, one negative electrode plate was wrapped in a non-woven fabric made of polyvinyl alcohol with a thickness of 0.2 nn, and then sandwiched between two positive electrode plates, and potassium hydroxide with a specific gravity of 1.350 (20°C) was used as the electrolyte. Using 2.711 aqueous solution, the nominal capacity is 240
A prismatic manganese dioxide-cadmium battery (E) using a synthetic resin container was manufactured using nAh. This battery has outer diameter dimensions of 67 x 16.5 x 8 (nun) and is 0.1k.
It has a safety valve that operates at "g/cn+".

[Comparative Example 2] A prismatic diacid (himancan-cadmium battery (F)) of a comparative example was manufactured in the same manner as in Example 6 except that mercuric oxide was omitted from the formulation of the negative electrode plate of Example 6.

The battery manufactured as above ([) and fF) is 0
．． FIG. 3 shows the results of the change in capacity when charging and discharging were performed under the conditions of discharging 100 nAh with a current of 2 CA, and then charging to 1.6 V with the same current.

As can be seen from Figure 3, the battery of the present invention ([) with a negative electrode plate has excellent charging efficiency and almost no decrease in charging efficiency during cycles, and the capacity decrease is clearly smaller than that of the Hi-Same battery (F). It can be seen that the capacity hardly decreases even after the cycle.

Note that these batteries contain almost no reserve cadmium hydroxide.

In other words, the content of cadmium hydroxide contained in the negative electrode plate is always about 0.84 of the manganese dioxide of the positive electrode active material in terms of weight ratio.
times [2,73((1/^h)/2.34 f(1/^h
)].

Although the above description has been made using a nickel-cadmium battery and a manganese dioxide-cadmium battery as examples, a silver oxide-cadmium battery with easy charge control can be obtained even if silver oxide is used as the positive electrode active material.

3 Example 7] 100 parts by weight of metal cadmium powder, 2 parts by weight of mercuric oxide, and 0.1 part of short polypropylene fiber having a length of 1 M11
Parts by weight are mixed with ethylene glycol 3011 containing 1.5% by weight of polyvinyl alcohol to form a paste. This paste was applied to expanded metal plated with cadmium (5 μn), then dried and pressurized to produce a negative electrode plate with dimensions of 3 x 14 x 52 (IIllM) and the theoretical capacity of metal cadmium of 1000 nAh.

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

Silver oxide powder as an active material and expanded silver metal as a mass are sintered under pressure using a conventional method, and then electrolytically oxidized in a 7B potassium hydroxide solution, washed with water, and dried to obtain the theoretical capacity. is 5001^h and the dimensions are 1゜3 x 14x
A positive electrode plate of 52 (nn) was manufactured.

Next, wrap one negative electrode plate four times in cellophane with a thickness of 0.0211, sandwich it between two positive electrode plates, and use a potassium hydroxide aqueous solution with a specific gravity of 1.250 (20″C) as the electrolyte. A prismatic silver oxide-cadmium battery (G) with a nominal capacity of 500 mAh was manufactured using
The size was 6.5×8 (nn), and the container was made of synthetic resin. It also houses a safety valve that operates at a pressure of 0.5 kg/cI12.

[Comparative Example 3] A prismatic silver oxide-cadmium battery (11) was manufactured in the same manner as in Example 7 except that mercuric oxide was omitted from the formulation of the negative electrode plate in Example 7.

In addition, the cadmium hydroxide for the reserve of these batteries is
The content of cadmium hydroxide contained in the negative electrode plate is always about 1.0% by weight of silver, which is a positive active material.
4 times [2,73℃g/Ah)/2.01℃g/^11
)].

The charging voltage characteristics when batteries (G) and (11) manufactured as described above were discharged at 20°C with a current of 0.2 CA for 3001^h and then charged with the same current were repeated. Shown in the figure.

From Figure 71, the silver oxide battery (G) of the present invention
The voltage rise at the end of charging occurred later than in the comparative battery (H), and the charging efficiency was approximately 100%. The difference in the timing of voltage rise of these two batteries is based on the charging efficiency of the negative electrode plate, and it is clear that the battery of the present invention has a collapsed capacity retention rate.

The characteristics of the cadmium negative electrode plate and battery of the present invention have been explained in the above examples.

As explained in each example, the surface of the current collector of the cadmium negative electrode plate of the present invention is nickel.

It may be different or cadmium. In other words, the materials include those that have a layer of nickel, 5Fl, or cadmium on the iron surface, those that have a layer of copper or cadmium on the surface of nickel, and those that have a layer of cadmium on the surface of copper. It has layers.

As for its shape, expanded metal netting, perforated foam, or fiber mat can be used.

Effects of the Invention As described above, the cadmium negative 5 plate of the present invention has extremely high charging efficiency and therefore contains almost no inactive cadmium hydroxide. Therefore, the actual capacity density is higher than that of the conventional cadmium negative electrode plate.

In addition, in an alkaline secondary battery using this, charging can be easily controlled by adjusting the ratio of the positive and negative electrode active materials, and ultra-rapid charging with a large current of 1 C^ or more is possible.

Moreover, this battery requires almost no cadmium hydroxide for reserve, so it is possible to increase the capacity.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the content of mercuric oxide and charging efficiency in the cadmium negative electrode plate of the present invention. FIG. 2 is a diagram showing the capacity retention rates of the nickel-cadmium battery of the present invention and a comparative battery during charge/discharge cycles. FIG. 3 is a diagram showing the capacity retention rate of the manganese dioxide-cadmium battery of the present invention and a comparative battery during charge/discharge cycles. FIG. 4 is a diagram showing the charging characteristics of the silver oxide-cadmium battery of the present invention and the battery for the shark. ¥, 1 diagram ρri "'l, 3 + sword 4o. 6D. 9a. (OCa light release t-ti 7I release 7 times - 42 + eyes O / CO FD OO λr0 older brother release 47 ・shio / times Ryo 41 eyes / h,.

Claims (1)

[Scope of Claims] 1. A cadmium negative electrode plate containing 0.25% by weight or more and 20% by weight or less of mercuric oxide based on the total amount of cadmium. 2. An alkaline secondary battery comprising a positive electrode plate whose active material is either nickel hydroxide, manganese dioxide or silver oxide, and a cadmium negative electrode plate according to claim 1.