JPH027368A - 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 potassium titanate based on the total weight of cadmium. CONSTITUTION:A negative plate contains 0.25-20wt.% potassium titanate based on the total weight of cadmium. In particular, in a content range of 0.5-15wt.%, charging efficiency reaches 97% or more and inactive cadmium hydroxide is decreased. If the content of potassium titanate 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 for reasons such as the longer sealing time compared to batteries. On the other hand, as electronic appliances 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 90%, and the remaining approximately 10π 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 about I.
There is a problem in that it must be kept below CA. 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 the electrolyte solution is 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. 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, wherein the negative electrode plate contains potassium titanate in an amount of 0.25% by weight or more based on the total amount of cadmium. It is characterized by containing 20% by weight or less.

As a result of investigating the charging efficiency of a functional cadmium negative electrode plate, it was found that the charging efficiency was increased by including potassium titanate in the negative electrode active material.

For example, hydrogen gas is generated 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 C^ based on the theoretical capacity of cadmium oxide or cadmium hydroxide. The charging efficiency is about 93%, but when potassium titanate is contained in an amount of 1% by weight 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 mg and metal cadmium powder 2
After mixing 10u and potassium titanate with varying amounts in the range of 0 to 84mg, the mixture was press-molded at a pressure of 230kg/cn', resulting in a total theoretical capacity of cadmium of 20fli.
It was made into a tablet of Ah. Furthermore, this tablet was wrapped in a nickel mesh of 20 meshes to form a negative electrode plate. This is the negative electrode plate group (a)
shall be.

[Example 2] After mixing 273 mg of cadmium hydroxide powder, 21,011 g of metal cadmium powder, and potassium titanate with varying amounts in the range of 0 to 841 g, tablets with a theoretical capacity of 200 IIAh 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.
ICA (100iA) based on the theoretical capacity of cadmium oxide powder or cadmium hydroxide powder at the time of compounding.
) Charging and discharging were repeated with the @ flow, and the charging efficiency was determined from the following formula (1).

(%) The theoretical capacity of the cadmium active material in the discharge state is 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 total amount of cadmium When the content of potassium titanate is 0.25% by weight or more, charging efficiency is improved. In particular, the content is 0.5% by weight or more1
In the range of 5% by weight or less, the charging efficiency is extremely high at 97% or more, indicating that inactive cadmium hydroxide, which cannot be charged, is reduced.

Although it is possible to make the content of potassium titanate higher than 20% by weight, the content is preferably 20% by weight or less because the theoretical capacity density of the cadmium active material decreases significantly. it is conceivable that.

From the above, it can be said that the content of potassium titanate 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 hydroxide powder with an average particle diameter of 1 μm produced by the atomization method Metallic cadmium powder obtained by immersing the above cadmium oxide powder in purified water to hydrate it Electrochemical substitution method Average particle size 2μm manufactured by
Monokoku Potassium Titanate> 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-dimensional S-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] Cadmium oxide powder 60f! Quantity parts, 40 parts by weight of metallurgical dominium powder, 2 parts by weight of potassium titanate, and length 111I
0.1 part by weight of short polypropylene fiber of B 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 nickel-plated (5 μn+) perforated steel plate, then dried and pressurized to reach a theoretical capacity of cadmium oxide of 960.
A negative electrode plate with nAh dimensions of 2.9x14x52 (IIn) 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. After impregnating 1 with a specific gravity of 1.50 (20°C), the specific gravity of 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 400nA.
A positive electrode plate with dimensions of 1.4 x 14 x 521111 was manufactured.

Next, one negative electrode plate was wrapped in a polyamide non-woven fabric with a thickness of 0.211 nm, sandwiched between two positive electrode plates, and a potassium hydroxide aqueous solution with a specific gravity of 1°250 (20°C) was used as the electrolyte. A nickel-cadmium battery (^) using a synthetic resin battery case with a nominal capacity of 700 mAh was manufactured using All. External dimensions are 67x 16.5x 8 (+ua
) and is equipped with a safety valve that operates at 0.1 kg/am2.

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 potassium titanate, and length 11
0.1 part by weight of I+1 short polypropylene fibers and 1
．． Mix with ethylene glycol 301 containing 5% by weight of polyvinyl alcohol to form a paste. This paste was applied to a perforated copper plate plated with copper (5μII), then dried and pressurized to give a cadmium hydroxide plate (customer 1) of 96%.
A negative electrode plate of 0 nAh, size 2.9 x 14 x 52 (ml) 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 (5μ11
) A prismatic nickel-cadmium battery (C) with a nominal capacity of 700 ah 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 70
A 0 nAh prismatic nickel-cadmium battery (0) was manufactured.

Batteries manufactured as above (^), (B), T
C) and (D) were charged at a constant voltage of 1°90V for 30 minutes at a maximum current of 3CA at 20°C, and then 0.
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 10
FIG. 2 shows the capacity retention rate in each cycle when it is set to 0. From the figure, it can be seen 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, and even with a large current such as 3C^, the amount of electricity charged until the negative electrode potential rises at the end of charging is large, and the charging efficiency is also high. This is because there is almost no decline during the cycle.

The content of cadmium hydroxide in the negative electrode plates of batteries (^), (B), (C) and (D) is approximately 0°95 times [2,73( g/Ah
) /2.88 (9/^h)], 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 example 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 as low as 200 nV, the constant voltage charging method could not be applied, but in the case of the battery according to the present invention, the difference was 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, 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. In addition, when a cylindrical nickel-cadmium battery (AA size) with a nominal capacity of 700 nAb using conventional sintered electrode plates 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 a fluid 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 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. 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] 100 parts by weight of metal cadmium powder, 2 parts by weight of potassium titanate, and 0 short fibers made of polypropylene with a length of inn.
．． 1 part by weight and ethylene glycol 301 containing 1.5% by weight of polyvinyl alcohol to form a paste. This paste is applied to copper expanded metal, then dried and pressurized to reduce the capacity of the metal cadmium to 80%.
A negative electrode plate with dimensions of 2.9×14×52 (11n) was manufactured using 0nAt+.

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

After kneading 1 part by weight of 80 manganese dioxide (γ-M n 02 ) 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 was coated with a 20-mesh nickel mesh. Further pressure is applied from both sides to increase the theoretical capacity to 200 nA.
h, a positive electrode plate with dimensions of 1.4 x 14 x 52 (nn) was manufactured.

Next, wrap one negative electrode plate in a polyvinyl alcohol nonwoven fabric with a thickness of 0.21, and then sandwich it between two positive electrode plates.
Ratio as an electrolyte! [! 1.350 (20°C) potassium hydroxide aqueous solution was used at 2.71, and the nominal capacity was 240n.
A prismatic manganese dioxide-cadmium battery (E) using a synthetic resin container was manufactured using Ah. This battery has an outer diameter of 6
7X 1G, Sx & (nn), G, IJ/Cf
It has a safety valve that operates at 1".

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

The batteries ([) and ([) produced as above are 0
．． FIG. 3 shows the results of the capacity change when charging and discharging were performed under the conditions of discharging 100 nAh at a current of 20 ns 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 comparative battery (F), and can survive 1000 cycles. 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 I2.73 (9/Ah)/2.34 (IJ/Ah)]
It becomes.

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 co-metal cadmium powder and 2 parts by weight of potassium titanate
Knowledge tf made of polypropylene with weight part and length 11I11
1 part of o, i g are mixed with ethylene glycol 301 containing 1.5% by weight of polyvinyl alcohol to form a paste. This paste was applied to expanded copper metal coated with cadmium (15 μm), then dried.
By applying pressure, a negative electrode plate having a theoretical capacity of 1000 nAh of metal cadmium and dimensions of 3 x 14 x 52 (u) was fabricated.

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 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 nAh. The dimensions are 1゜3 x 14x 5
2 (nn) positive electrode plates were manufactured.

Next, one negative electrode plate was wrapped four times in cellophane with a thickness of 0.02I11, and then sandwiched between two positive electrode plates, and a potassium hydroxide aqueous solution with a specific gravity of 1.250 (20'C) 31 A prismatic silver oxide-cadmium battery (G) with a nominal capacity of 500 IIAh was manufactured using the following method. Outer diameter size is 67x
It is 1B, 5x8 (nn), and the battery case is made of synthetic resin and is equipped with a safety valve that operates at pressures of 0, 5 kg/cm2.

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

Figure 4 shows the charging voltage characteristics when the batteries (G) and (11) manufactured as described above were discharged for 300nA with a current of 0.20A at 20°C and then charged with the same current. Indicated.

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 voltage rise of these two batteries is based on the charging efficiency of the Pt 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.

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, 5F1, 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 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 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]

Figure 1 shows the relationship between potassium titanate content 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 comparative battery. FIG. 3 is a diagram showing the capacity retention rate during charge/discharge cycles of the manganese dioxide-cadmium battery of the present invention and a battery for comparison. FIG. 4 is a diagram showing the charging characteristics of the silver oxide-cadmium battery of the present invention and a battery for comparison. Atsushi 1st rho, y r IJ 3 +5 QD 1o. 3o. oo0 Nine Mosquito Densui 2I Shimaki/Tagoz'fiJ O ea Ir. 2o. 2nd year Ojc Kintsu Iful Atsushi / 1st night light night clear / I can't do it.

Claims (1)

[Scope of Claims] 1. A cadmium negative electrode plate containing potassium titanate 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.