JPH02155165A - Cadmium negative plate and alkaline secondary battery using this negative plate - Google Patents

Abstract

PURPOSE:To enhance charging efficiency by containing a specified ratio of dinickel trioxide based on the amount of total cadmium. CONSTITUTION:0.25-20wt.% dinickel trioxide (Ni2O3) based on the weight of total cadmium is contained in a negative plate of an alkaline secondary battery. By containing dinickel trioxide in the negative active material, charging efficiency is enhanced. For example, when a cadmium negative plate mainly comprising cadmium hydroxide or cadmium oxide and metallic cadmium is charged at 1cA on the basis of the theoretical capacity of cadmium oxide or cadmium hydroxide, charging efficiency until hydrogen evolution starts is about 93%. If 2wt.% dinickel trioxide based on the weight of total cadmium is contained, charging efficiency exceeds 93%.

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, 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 Demand is rapidly increasing for reasons such as their long lifespan compared to batteries. On the other hand, as electronic devices have become smaller and lighter in recent years, secondary batteries are required to have higher capacity and shorter charging time.

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 the charging and discharging Th reaction.

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 cadmium hydroxide is used to make the metal nickel, which is the support for the positive electrode active material, into an active material and to compensate for the space volume inside the battery, and does not contribute to the discharge capacity. This is one of the reasons that prevents higher capacity of cadmium negative electrode plates and batteries.

In addition, when conventional nickel-cadmium batteries are charged at a constant current to keep the battery sealed, the current is approximately 1
There is a problem in that it must be kept below CA. This is because when the charging current is increased to 1 CA or more, the negative electrode plate cannot absorb all the oxygen gas generated from the positive electrode plate in the overcharging region, and the safety valve is activated and the electrolyte is dissolved. This is because it causes a decrease in capacity and a deterioration in wealth. Therefore, the special application
As proposed in No. 582 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. Although there are attempts to make this possible, they are insufficient in terms of charging efficiency of the negative electrode plate.

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, the negative electrode plate containing nickel sesquioxide (Ni, O,) relative to the total amount of cadmium. 0.
It is characterized by containing 25% by weight or more and 20% by weight or less.

As a result of investigating the charging efficiency of a cadmium negative electrode plate, it was found that the charging efficiency was increased by incorporating nickel sesquioxide 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 1 CA, based on the theoretical capacity of cadmium oxide or cadmium hydroxide, until hydrogen gas is generated. The charging efficiency is about 93''g, but when nickel sesquioxide is contained, for example, 2% by weight based on the total amount of cadmium, the charging efficiency improves to 99% 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 plate9 [Example 1] After mixing cadmium oxide powder 240+1 (l), 210 ng of metal cadmium powder, and nickel oxide in a blending amount of 0 to b, the mixture was heated at a pressure of 230 kv/cn''. Pressure molded, total theoretical capacity of cadmium is 200
It was made into iAh 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] After mixing 273 ng of cadmium hydroxide powder, 210 u of metal cadmium powder, and nickel sesquioxide with varying amounts in the range of 0 to 8419, tablets with a theoretical capacity of 200 nAh were prepared in the same manner as in Example 1. It was made into a negative electrode plate.

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 1.250 (20°C), using two nickel flat plates as counter electrodes, and ICAt1OOn based on the theoretical capacity of the cadmium oxide powder or cadmium hydroxide powder at the time of compounding.
Charging and discharging were repeated using the current A), and the charging efficiency was determined from the following equation (1).

The results are shown in Figure 1. From the figure, no difference was observed due to the use of cadmium oxide or cadmium hydroxide as the raw material for the active material, and the content of nickel sesquioxide relative to the total amount of cadmium was 0.25% by weight or more. An improvement in charging efficiency is observed within the range of .

In particular, when the content is in the range from 1% by weight to 20% by weight, the charging efficiency is extremely high at 98X or more, indicating that inactive cadmium hydroxide, which cannot be charged, is reduced.

Note that although it is possible to make the content of nickel sesquioxide higher than 20% by weight, it is desirable that the content is 20% by weight or less because the decrease in the theoretical capacity density of the cadmium active material will be large. Conceivable.

From the above, it can be said that the content of nickel sesquioxide relative to the total cadmium is preferably 0.25% by weight or more and 20% by weight or less.

The properties of each raw material used in the examples are shown below.

<Cadmium oxide powder> Cadmium hydroxide powder with an average particle size of 1 μl produced by the atomization method> Metallic cadmium powder obtained by immersing the above cadmium oxide powder in purified water and hydrating it> Electrochemical substitution method Average particle size 2μm manufactured by
Monokuku Nickel Sesquioxide> Commercially available reagent 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 with 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 examples, a battery 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 most commonly used active material 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, it is a nickel, copper, or cadmium net, an expanded metal, a perforated plate, or a three-dimensionally structured metal foam or metal fiber mat that serves both as a current collector and an active material holder.

Further, iron plated with nickel, iron or nickel plated with copper, and iron, nickel or copper plated with cadmium can also be used.

[Example 3] 60 parts by weight of cadmium oxide powder and 4 parts by weight of metal cadmium powder
0 parts by weight of nickel sesquioxide, 2 parts by weight of nickel sesquioxide, and 0.1 parts by weight of short polypropylene fibers having a length of 11 m, and ethylene glycol 3 containing 1.5% by weight of polyvinyl alcohol.
Mix with 01 to make a paste. Nickelmets this paste? The theoretical capacity of cadmium oxide is 960 nA by coating it on a perforated steel plate with a diameter of 5 μm and then drying and pressurizing it.
A negative electrode plate with dimensions of 2.9 x 14 x 52 (nn) was manufactured in h.

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)].
Immerse in aqueous sodium hydroxide solution at 2QO (20°C),
Wash with hot water and dry. This operation was repeated to produce a positive electrode plate having a total theoretical capacity of nickel hydroxide and cobalt hydroxide of 400 nAh and dimensions of 1.4 x 14 x 52 mm.

Next, one negative electrode plate was wrapped in a polyamide nonwoven fabric with a thickness of 0.2 nn, and then sandwiched between two positive electrode plates, and the electrolyte was prepared using potassium hydroxide aqueous solution I2 with a specific gravity of 1.250 (20°C).
．． A nickel-cadmium battery (A) using a synthetic resin battery case with a nominal capacity of 700 nAh was manufactured using 4nl. The external dimensions are 67 x 16.5 x 8 [in], and it is equipped with a safety valve that operates at 0.1 kg/cn'.

In addition, since the cadmium oxide in the negative electrode plate of this battery consumes water by the reaction shown in the following equation (2) when an electrolytic solution is added, an extra amount of water corresponding to the consumed amount was injected.

CdO+H, 0-Cd (OH), ... (2) [
Example 4] 68.5 parts by weight of cadmium hydroxide powder, 40 parts by weight of metal cadmium powder, 2 parts by weight of nickel sesquioxide, and 1 part by weight of nickel sesquioxide
0.1 part by weight of short polypropylene fibers of 1IIIl are mixed with ethylene glycol 301 containing 1.5% by weight of polyvinyl alcohol to form a paste. This paste was applied to a copper-plated (5μr#) perforated steel plate, then dried and pressurized to reach a theoretical capacity of 96%.
A negative electrode plate of 0 mAh, size 2.9 x 14 x 52 (nl) was manufactured.

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

[Example 5] Instead of the current collector of the negative electrode plate in Example 3, that is, the nickel-plated perforated steel plate, cadmium
A prismatic nickel-cadmium battery (C) with a nominal capacity of 700 IIAh was manufactured in the same manner as in Example 3 except that the perforated steel plate prepared in s) was used.

[Comparison Example 1] The same procedure as in Example 3 was made except that nickel sesquioxide was removed from the formulation of the negative electrode plate in Example 3, with a nominal capacity of 70.
Make a 0iAh square nickel-cadmium battery (0).

Batteries manufactured as above (, A), (8),
After charging (C) and (D) at a constant voltage of 1°90V for 30 minutes at a maximum current of 3CA at 20°C,
．． Do 250 charge/discharge cycles of discharging to 0.5V with a current of 2CA. 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 (A), f8), and (C) of the present invention have clearly higher capacity retention rates than the comparative battery (D). 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.
This is because the amount of electricity charged until the negative electrode potential rises at the end of charging is large even when current is applied, and there is almost no decrease in charging efficiency during the cycle.

The content of cadmium hydroxide in the negative electrode plates of batteries (A), (B), (C) and TO) is about 0.95 times [2,73 (9 /^h
) /2.88((]/Ah)], and the properties of the raw materials such as cadmium oxide powder used to manufacture the negative electrode plate are the same as those used in the previous example of the tablet-shaped negative electrode plate. be.

As described above, the battery of the present invention can be charged extremely rapidly using a simple charging method of constant voltage control, and has an excellent capacity retention rate.

The charging method used a constant voltage charging method that regulated the maximum current, but this method is similar to that used in conventional nickel-cadmium batteries, where after charging with a constant current, the charging voltage changes due to gas absorption. One of the features of the present invention is that it does not require a complicated charging system, such as a method that stops charging by detecting a drop in battery voltage or a method that stops charging by detecting heat generation due to gas absorption. The constant voltage charging method, which has been difficult to apply, can be easily performed. 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 ~
However, in the case of the battery according to the present invention, the difference was reduced to 0.
．． Since the current reaches 400 Ilv or more with a current of 2 CA or more, it is easy to detect changes in charging voltage. In this case, you can charge with a constant current and then lower the current after detecting an increase in the charging voltage, or you can charge with a constant voltage. When a cylindrical nickel-cadmium battery (AA size) with a capacity of 700 mAh was charged at a constant voltage of 1.9 V for 30 minutes at a maximum current of 3 CA, the safety valve was activated and leakage occurred. This is because the battery was overcharged because the charging voltage of the conventional battery did not reach 1.9μ.

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 metal foams and metals that serve as current collectors and active material holders. fiber mat etc.
Further, suitable materials include iron or nickel plated with copper or cadmium. However, even if a nickel current collector has a small hydrogen overvoltage, it can still be used as a current collector by reducing the amount of a substance with a small hydrogen overvoltage, such as nickel powder, in the active material, for example to 5% by weight or less. Can be done.

Although the above embodiments of the present invention have been described using nickel hydroxide as the positive electrode active material, the same effects as those of the nickel-cadmium battery can be obtained even when manganese dioxide is used as the active material. Below, the case where the present invention is applied to a manganese dioxide-cadmium battery will be explained using preferred embodiments.

[Example 6] 100 parts by weight of metal cadmium powder, 2 parts by weight of nickel sesquioxide, and 0 short fibers made of polypropylene with a length of inn.
．． 1 part by weight and ethylene glycol 3011 containing 1.5% by weight of polyvinyl alcohol to form a paste. This paste was applied to copper expanded metal, then dried and pressurized to form a metal cadmium with a capacity of 800 iAh and dimensions of 2°9 x 14 x 52 (nr
A negative electrode plate of m) was manufactured.

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

80 parts by weight of manganese dioxide (γ-MnO2) and 10f of graphite! After kneading the following parts with 60% by weight of polytetrafluoroethylene aqueous dispersion 301,
It was formed into a sheet using a roller and further pressed from both sides against a 20-mesh nickel mesh to produce a positive electrode plate with a theoretical capacity of 2001 mAh and dimensions of 1.4 x 14 x 52 (ll).

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 an aqueous potassium hydroxide solution with a specific gravity of 1.350 (20°C) was used as the electrolyte. 2.71, the nominal capacity is 240iA
A prismatic manganese dioxide-cadmium battery (E) using a synthetic resin battery case was manufactured in 1.h. This battery has an outer diameter of 67
x 16.5X 8 (+111) and 0.1kg/
It has a safety valve that operates at c12.

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

The batteries (E) and ([) produced as above are 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 FIG. 3, the battery (E) of the present invention, which has a negative electrode plate with excellent charging efficiency and almost no decrease in charging efficiency during cycles, has a clearly smaller capacity decrease than the Hikyo battery (F), and has a 1ooo cycle. There was almost no decrease in capacity even after 30 days.

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(q/Ah)/2.34 ((1/Ah)
].

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.

[Example 7] 100 parts by weight of metal cadmium powder and 2 parts of nickel sesquioxide
Short fibers made of polypropylene with weight part and length 111 0.1
parts by weight and mixed with 30 ml of ethylene glycol containing 1.5% by weight of polyvinyl alcohol to form a paste. This paste was applied to expanded copper metal plated with cadmium (5 μm), then dried and pressurized to produce a negative electrode plate with a theoretical capacity of 1000 nAh and dimensions of 3 x 14 x 52 (Ill).

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 an aggregate are sintered under pressure using a conventional method, electrolytically oxidized in an aqueous potassium hydroxide solution, washed with water, and dried to have a theoretical capacity of 500 iAh. The dimensions are 1゜3 x 14x 5
A positive electrode plate of 2(nIl) was manufactured.

Next, one negative electrode plate was wrapped four times in cellophane with a thickness of 0.02n11, then sandwiched between two positive electrode plates, and a potassium hydroxide aqueous solution 31 with a specific gravity of 1.250 (20°C) was added as an electrolyte. Using this method, a prismatic silver oxide-cadmium battery (G) with a nominal capacity of 500 mAh was manufactured. Outer diameter size is 67x1
The size was 6.5 x 8 (ill), and the container was made of synthetic resin. Additionally, a safety valve is installed that operates at a pressure of 0.5kg/cm''.

[Comparative Example 3] A prismatic silver oxide-cadmium battery (H) was manufactured in the same manner as in Example 7 except that nickel sesquioxide 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 the silver of the positive electrode active material.
4 times [2,73((J/^h)/2.01((1/^h)
h)].

Batteries (G) and (H) manufactured as described above are
After discharging 300nA with a current of 0.2CA at 0°C,
Figure 4 shows the charging voltage characteristics when charging with the same current is repeated.

From FIG. 4, the voltage rise at the end of charging of the silver oxide-cadmium battery (G) of the present invention occurs later than that of the comparative battery [H), and its charging efficiency is approximately 100%. The difference in the timing of the 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 an excellent 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.

Any material such as copper or cadmium is sufficient; in other words, in addition to nickel, copper, and cadmium, the material is one that has a layer of nickel, @, or cadmium on the surface of iron, or one that has a layer of copper or cadmium on the surface of nickel. , which also has a cadmium layer on the copper surface.

Its shape is expanded metal.

Netting, perforated foam or fiber mats can be used.

Effects of the Invention As stated above, the cadmium negative electrode plate of the present invention has extremely high charging efficiency, so it contains almost no inert cadmium hydroxide, and therefore has a substantial capacity compared to conventional cadmium negative electrode plates. Density increases.

In addition, in an alkaline secondary battery using this, charging control is easy by adjusting the ratio of the positive and negative electrode active materials, and ultra-rapid charging is possible with a large current higher than ICA.

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

[Brief explanation of the drawing]

Figure 1 shows the relationship between the content of nickel sesquioxide and charging efficiency in the cadmium negative electrode plate of the present invention, and Figure 2 shows the relationship between the nickel-cadmium battery of the present invention and a battery for comparison. Figure 3 shows the capacity retention rate during charge/discharge cycles of the manganese dioxide-cadmium battery of the present invention and a comparative battery; Figure 4 shows the capacity retention rate during charge/discharge cycles of the manganese dioxide-cadmium battery of the present invention. FIG. 3 is a diagram showing the charging characteristics of a silver oxide-cadmium battery and a battery for comparison.力r r almost 已I [道Iiifuru number / Tadai L (Medo / D. rv λ!: O erate 1r ii 2 1I-sha / (n Ta Denzaki Jun / k.

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 nickel sesquioxide 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.