JPH027366A - Cadmium negative plate and alkaline secondary battery using this negative plate - Google Patents

Abstract

PURPOSE:To obtain a cadmium negative plate having high charging efficiency by containing a specified weight of niobium pentoxide based on the total weight of cadmium. CONSTITUTION:A negative plate contains 0.25-20wt.% niobium pentoxide based on the total weight of cadmium. Charging efficiency is increased if the content of niobium pentoxide is 0.25wt.% or more. In particular, in the content of 0.5wt.% or more, charging efficiency reaches 98% or more and inactive cadmium hydroxide is decreased. If the content of niobium pentoxide exceeds 20wt.%, the theoretical capacity density of a cadmium active material is decreased. The cadmium negative plate having high charging efficiency is obtained.

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 due to factors such as the longer discharge time 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 charge/discharge reactions.

In other words, the charging efficiency of cadmium hydroxide until hydrogen gas is generated is usually about 90χ, and the remaining approximately 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 a support for the iF, i active material, into an active material and to compensate for the space volume inside the battery. This is one of the reasons that prevents higher capacity of cadmium negative electrode plates and batteries.

In addition, when conventional nilagel-cadmium batteries are charged at a constant current to keep the battery sealed, the current is approximately 1
The problem is that it must be kept below 0.08. This is because when the charging current is increased to 1C^ 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 electrolysis occurs. This is because the liquid decreases, causing a decrease in capacity and deterioration of special characteristics. Therefore, the special application
No. 582! [As proposed in No. 1 Sho 63-13345, potential changes during the process of hydrogen generation in the negative electrode plate during charging are detected as changes in charging voltage to facilitate charging control and enable rapid charging. There are attempts to
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, wherein the negative electrode plate contains niobium pentoxide in an amount of 0.25% by weight or more based on the total amount of cadmium. 20
It is characterized by containing not more than % by weight.

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 tungsten and lithium 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 an ICA current based on the theoretical capacity of cadmium oxide or cadmium hydroxide, until hydrogen gas is generated. The charging efficiency is about 93%, but when niobium pentoxide is contained in an amount of 1% by weight based on the total amount of cadmium, the charging efficiency improves to 98% 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.

[Wo (tone example 1)] 24011g of cadmium oxide powder, 21On+g of metal cadmium powder, and niobium pentoxide with varying amounts in the range of θ to 84ng were mixed, and then pressure molded at a pressure of 230kg/cn'. , the theoretical capacity of total cadmium is 200r
It was made into aAh 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 mg of cadmium hydroxide powder, 210 Jl of metal cadmium powder, and niobium pentoxide with varying amounts in the range of 0 to 84 I1 g, tablets with a theoretical capacity of 2001 Ah were prepared in the same manner as in Example 1. It was made into a negative electrode plate. This is j
(% board 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.
1C^[1001I based on the theoretical capacity of cadmium oxide powder or cadmium hydroxide powder at the time of blending.
Charging and discharging were repeated using the current A), and the charging efficiency was determined from the following equation (1).

(%) Cadmium in discharge state? The theoretical capacity of sugar beet The results are shown in FIG. From the same figure, it is recognized that the charging efficiency is improved when the content of niobium pentoxide relative to the total amount of cadmium is 0.25% by weight or more. In particular, when the content is 0.5% by weight or more, the charging efficiency is extremely high at 98% or more, indicating that inactive cadmium hydroxide, which cannot be charged, is reduced.

On the other hand, when the content of niobium pentoxide 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 (b) that mainly used cadmium hydroxide as the active material raw material, a decrease in charging efficiency was observed when the content of dioxic pentoxide was 15% by weight or more, whereas in the negative electrode plate (b) that mainly used cadmium oxide, Almost no decrease is observed in the negative electrode plate (A). For this reason, when the content of niobium pentoxide is 15% by weight or more, it is desirable to use a material mainly composed of cadmium oxide as the active material raw material.

Although it is possible to make the content of niobium pentoxide higher than 20% by weight, the theoretical capacity density of the cadmium active material decreases significantly, so the content is preferably 20% by weight or less. Conceivable.

From the above, the content of niobium pentoxide relative to the total cadmium is suitably 0.25% by weight or more and 20% by weight or less, and it can be said that it is desirable to use cadmium oxide as the main active material raw material.

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

Cadmium hydroxide powder with an average particle diameter of 1 μm produced by the atomization method Metallic cadmium powder prepared by immersing the above cadmium oxide powder in vI water and hydrating it Electrochemical Average particle size 2μm produced by substitution method
Commercially available reagentsNext, 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, 1 part of niobium pentoxide double, and 0.12I of short polypropylene fibers with a length of 1raIm! parts and ethylene glycol 3011 containing 1.5% by weight of polyvinyl alcohol to form a paste.

This paste was applied to a nickel-plated (5 μn) 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 (
nl) 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.
Mixed aqueous solution of cobalt nitrate and nickel nitrate (P11
= 2, specific gravity 1.50 (20℃)], specific gravity 1.
．． The sample was immersed in a sodium hydroxide aqueous solution at 200°C (20°C), washed with hot water, and dried. Repeat this operation until the total theoretical capacity of nickel hydroxide and cobalt hydroxide is 400n.
A positive electrode plate with dimensions of 1.4 x 14 x 521 Fin was manufactured using Ah.

Next, one negative electrode plate was wrapped in a polyamide non-woven fabric with a thickness of 0.21 inches, and then sandwiched between two positive electrode plates, and the electrolyte was prepared using 2 parts potassium hydroxide aqueous solution with a ratio fm of 1.250 (20°C).
．． Using No. 41, a nickel-cadmium battery (^) with a nominal capacity of 700+1 Ah and a synthetic resin battery case was manufactured. The external dimensions are 67x1G, 5x81us), and it is equipped with a safety valve that operates at 0.1kg/c+a'.

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+H20→Cd(OH)2...(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 niobium pentoxide, and length 1111
Short L made of polypropylene! 0.1 part by weight of fiber and 1.5 parts by weight
Mix with ethylene glycol 301 containing % by weight of polyvinyl alcohol to form a paste.

This paste was applied to a copper-plated perforated steel plate (5 μl), then dried and pressurized to form a plate with a theoretical capacity of cadmium hydroxide of 96011 Ah and dimensions of 2.9 x 14 x 52 (
rua) negative electrode plate 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 mAh was manufactured.

[Example 5] Cadmium plating (5 μn) was used instead of the current collector of the negative electrode plate in Example 3, that is, the nickel-plated perforated copper plate.
A prismatic nickel-cadmium battery TC) with a nominal capacity Ji of 700 iAh was manufactured in the same manner as in Example 3 except that a perforated steel plate was used.

[Comparative Example 1] A nominal capacity of 700 was obtained in the same manner as in Example 3 except that niobium pentoxide was removed from the formulation of the negative electrode plate in Example 3L.
A nAh prismatic nickel-cadmium battery (D) was manufactured.

Batteries (A), (B), (
C) and (D) were charged at a constant voltage of 1°90V for 30 minutes at a current of maximum type: a3cA at 20°C, and then
．． A charge/discharge cycle of discharging to 0.5V with a current of 2C^ 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
Although not shown in the figure, it can be seen from the figure that the batteries (A), (B), and (C) of the present invention clearly have a higher capacity retention rate than the comparative battery (0). 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 there is almost no decrease in efficiency during the cycle.

The content of cadmium hydroxide in the negative electrode plates of batteries (^), (B), (C) and (D) is approximately 0.95 times the weight ratio of nickel hydroxide in the positive electrode [2,73( g/^h
) /2.88 (g/Ah)], and the properties of the raw materials such as cadmium oxide used to manufacture 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 a constant voltage charging method that regulated the maximum current, but this method does not reduce the charging voltage due to gas absorption after charging with the constant current used in conventional nickel-cadmium batteries. One of the features of the present invention is that it does not require a complicated charging system, such as a method that detects gas absorption and terminates charging, or a method that detects heat generation due to gas absorption and terminates charging. The constant voltage charging method, which has been difficult to apply, can now be easily implemented. 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 low at 2001V, constant voltage charging method could not be applied, but in the case of the battery according to the present invention, the difference is 0.
．． Since the current reaches 40011 V or more with a current of 2 C^ 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 nAh was charged at a constant voltage of 1.9 V for 30 minutes at a maximum current of 3 C^, 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 1.9V.

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 metal foams and metals that serve as current collectors and active material holders. fiber mat etc.
Furthermore, 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. I can do it.

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] Short fibers made of polypropylene containing 100 parts by weight of metal cadmium powder, 2 parts by weight of niobium pentoxide, and a length of 11111111! I
IO, 1 part by weight is mixed with ethylene glycol 301 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 IIAh and dimensions of 2.9 x 14 x 52 (n
A negative electrode plate of n) was manufactured.

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

80 parts by weight of manganese dioxide (γ-M n O2) and 10 parts by weight of graphite were added to GOfi fi% aqueous dispersion of polytetrafluoroethylene 30111.
After kneading with a roller, it was made into a sheet with a roller, and further pressure was applied from both sides to a 20-mesh nickel mesh until the theoretical capacity was 20.
0 nAh, dimensions 1.4 x 14 x 521 nIN
) was manufactured.

Next, one negative electrode plate was wrapped in a polyvinyl alcohol nonwoven fabric with a thickness of 0.2 ni, 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 2.71 aqueous solution, the nominal capacity is 2401^
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 (nm) and 0.1kg/am
It has a safety valve that operates at 2.

[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 niobium pentoxide 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 capacity change when charging and discharging were performed under the condition that 100 IIAb was discharged at a current of 20 V and then charged to 1.6 V at 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 comparative battery ([), and can last 1 ooo cycle. There was almost no decrease in capacity over time.

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(Ill/^h)/2.34 ((1/A
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.

[Example 7] 100 parts by weight of metal cadmium powder and 271 parts by weight of niobium pentoxide
! Polypropylene short fibers with weight and length iln 0.1
Parts by weight are mixed with ethylene glycol 301 containing 1.5% by weight of polyvinyl alcohol to form a base. This base plate was applied to expanded copper metal plated with cadmium (5 μl), 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 (ralm).

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

Silver oxide powder as an active material and expanded silver metal as a current collector are pressurized and sintered by a conventional method, and then electrolytically oxidized in an aqueous potassium hydroxide solution, washed with water, and dried to have a theoretical capacity of 500 mAh. The dimensions are 1゜3 x 14x 5
A positive electrode plate of 2 (nm) was manufactured.

Next, wrap one negative electrode plate with 0.0211n thick cellophane for 42r! A prismatic silver oxide-cadmium battery (G) with a nominal capacity of 5,001 liters was fabricated using an aqueous potassium hydroxide solution with a specific gravity of 1.250 (120°C) as the electrolyte. . Outer diameter size is 67x
The size of the battery was 16.5 x 8 (n+n), and the container was made of synthetic resin. It is also equipped with a safety valve that operates at a pressure of 0.5 kQ/ClI2.

[Comparative Example 3] A prismatic silver oxide-cadmium battery (11) was manufactured in the same manner as in Example 7 except that niobium pentoxide 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 (Q/Ah) 2.01 (g/^h)
].

Figure 4 shows the charging voltage characteristics when batteries (G) and (11) manufactured as described above were discharged at 20°C with a current of 0.2C^ for 300IIAh and then charged with the same current. It was shown to.

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 (11), and its charging efficiency is approximately 100χ. This 2
The timing of voltage rise of the two batteries is different based on the charging efficiency of the II 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 current collector of the cadmium negative electrode plate of the present invention has a nickel surface.

Copper or cadmium may be used. In other words, in addition to nickel, copper, and cadmium, these materials include those that have a layer of nickel, copper, or cadmium on the surface of iron, 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.

Its shape is expanded metal.

Netting, perforated foam or fiber mats can be used.

Effects of the Invention As described above, the cadmium negative electrode 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 control is easy by adjusting the ratio of the amount of carbon to the negative electrode active material, and ultra-rapid charging is possible with a large current of IOA or more.

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 niobium pentoxide content and charging efficiency in the cadmium negative electrode plate of the present invention;
Figure 2 is a diagram showing the capacity retention rate during charge/discharge cycles between the nickel-hydrogen J-battery of the present invention and a comparative battery, and Figure 3 is a diagram showing the capacity retention rate of the manganese dioxide-cadmium battery of the present invention and a comparative battery. FIG. 3 is a diagram showing the capacity retention rate during charge/discharge cycles with the battery. FIG. 4 is a diagram showing the charging characteristics of the silver oxide-cadmium battery of the present invention and a battery for comparison. ■ ■ 30 0O 4o. 6o. oD Bonsei t-'i Ihurusha/Decoy ivy 21 birds O 1riO Lsp L fragrance-1i 71shih/+eye Figure 4 Water Ishik- Sakima/Tori.

Claims (1)

[Scope of Claims] 1. A cadmium negative electrode plate containing niobium pentoxide in an amount of 0.25% by weight or more and 20% by weight or less 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.