JP2000106191A - Electrode for alkaline storage battery and the alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep high discharge capacity and high operating voltage, even at high- current discharge, and to prevent running down earlier with the capacity remaining, by limiting the three-dimensional nickel porous body density and the number of vacancies within a unit distance in an electrode formed by filling an active material into a base of the three-dimensional nickel porous body, within the specific ranges. SOLUTION: This battery with a positive electrode plate having a three-dimensional nickel porous body density of 1.25 g/cc or more maintains the battery voltage of more 1 V, even at the discharge depth of 80%. Consequently, the porous body density is set to more than 1.25 g/cc, in order to secure the capacity of more 80% of nominal capacity of high-current discharge. As the density rises, the voltage rises also, and when rising beyond a certain point, the battery weight is enlarged for maintaining the discharge capacity, and the battery output energy density is lowered. Also, filling of an active material becomes difficult, and from the order beyond the density of 1.8 g/cc, cracks and exfoliation, etc., occur in the electrode plate. Consequently, the density is set at 1.75 g/cc. Furthermore, the number of vacancies within unit distance indicating fineness of grain of the vacancies is set at 45-55 pieces/inch, to prevent cracks, exfoliation, and lowering of the capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an alkaline storage battery suitable for applications requiring large current discharge, such as electric power tools and electric vehicles.

[0002]

2. Description of the Related Art As an electrode used in an alkaline storage battery, a porous substrate formed by sintering nickel powder on a core body such as a punching metal is impregnated with an active material, for example, an active material made of nickel hydroxide by impregnation. There is a so-called sintered nickel electrode, and a so-called non-sintered nickel electrode in which a nickel hydroxide powder as a positive electrode active material is directly filled in a base made of a three-dimensional nickel porous body.

[0003] The former sintered nickel electrode has a feature of being excellent in high-rate discharge characteristics, but has a low energy density.
It is necessary to repeat the step of filling the active material many times, and there has been a problem that the production step is complicated.

On the other hand, the latter non-sintered nickel electrode uses a three-dimensional metal porous body such as foamed nickel which has a higher porosity of the substrate than a sintered substrate, and therefore has a high energy density and a high active density. The material filling process also has the advantage that the production process can be simplified by directly filling the nickel hydroxide powder,
There was a drawback that the high-rate discharge characteristics were inferior due to the low density of the substrate that took charge of conductivity.

[0005] In particular, as the area of the electrode plate increases with an increase in the size of the battery, the distance between the active material and the current collector for connection to the positive electrode terminal disposed at the end of the electrode plate is increased. Polarization increases, and the battery voltage decreases. Furthermore, in large batteries used in electric vehicles and the like, large current discharge is required, so that the above-described polarization in the electrode plate becomes remarkable,
There is a problem that the voltage drop as a battery is remarkable.

As a result, when control is performed so as to end discharge at a constant voltage, the discharge end voltage is reached before the discharge is sufficiently completed, and the discharge ends in a so-called premature cutoff. . Further, in the case of discharging with a constant power, for example, the current value is increased as much as the voltage decreases, and a vicious circle occurs in which the battery voltage further decreases as the current value increases.

[0007] Further, the fact that the polarization in the electrode plate is large means that the active material of the electrode plate near the current collector receives a deeper discharge than the active material of the electrode plate far from the current collector. Deterioration progresses geographically.

For example, when used as a large power source for an electric vehicle or the like, a large current of about several hundred A flows. In such a case, it is necessary to allow a current of about several hundreds A to flow at a discharge depth of 80%, which is a measure of the end of battery discharge.

Generally, in the case of a nickel-metal hydride storage battery or a nickel cadmium storage battery, the discharge end control of the battery is completed when each cell reaches 1 V or less. If it is less than this, there is a risk of overdischarging.

From the above, it is desirable that a large-sized battery used for power supply has a battery voltage of 1 V or more even when a large current of several hundred A is applied at a discharge depth of 80%.

Conventionally, the density occupied by the three-dimensional porous nickel material in the non-sintered nickel positive electrode plate has a density of about 0.6 to 1.2 g / cc as disclosed in JP-A-61-133563. Was.

However, when a current of about several hundred A is applied to such a positive electrode plate, a battery voltage of 1 V or more cannot be maintained over a discharge depth of 0 to 80%, and the battery is quickly cut off while retaining the capacity. It became a state.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a high discharge capacity and an operating voltage even when discharged with a large current, so that the capacity is quickly cut off. It is an object of the present invention to provide an electrode for an alkaline storage battery which is unlikely to be in a state of the above and an alkaline storage battery provided with the electrode.

[0014]

An electrode for an alkaline storage battery according to the present invention is an electrode in which a base made of a three-dimensional porous nickel material is filled with an active material, wherein the density of the three-dimensional porous nickel material in the electrode is 1.25. 1.71.75 g / cc, and the number of vacancies within a unit distance of the three-dimensional nickel porous body is 45 to 55
K / inch.

Further, the electrode for an alkaline storage battery of the present invention comprises:
An electrode for an alkaline storage battery in which an active material is filled in a substrate made of a three-dimensional nickel porous body,
The density of the one-dimensional nickel porous body is 1.40 to 1.60 g / cc,
The number of vacancies within a unit distance of the three-dimensional nickel porous body is
It is 45-60 pieces / inch.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Experiment 1] A thickness of 1.5 mm, a weight per unit area of 1200 g / m ² and a pore density of 50 / in.
The three-dimensional nickel porous body of ch was filled with a nickel hydroxide active material, dried, and then rolled to produce a positive electrode plate a having a thickness of 0.63 mm and a three-dimensional nickel porous body density of 1.90 g / cc. Similarly, the basis weight indicating the weight per unit area at a thickness of 1.5 mm is 1100 g / m ² ,
900g / m ² , 800g / m ² , 700g / m ² , 600g / m ² each three-dimensional nickel porous material is filled with nickel hydroxide active material, dried,
Rolled to a thickness of 0.63mm, 3D nickel porous material density 1.75g / cc, 1.43g / cc, 1.26g / cc, 1.11g / cc, 0.91g / c
Each positive electrode plate b, c, d, e, and f, which was c, was produced.

The positive electrodes a to f produced as described above are 100 × 1
Cut to a size of 20 mm, current collector tabs were welded by resistance welding, and 20 sheets of a hydrogen storage alloy negative electrode produced by applying a hydrogen storage alloy to a current collector made of punching metal of the same size After laminating via a polyolefin nonwoven fabric, inserting it into a plastic case, injecting 150 g of 31% by weight potassium hydroxide electrolyte, sealing it, and producing prototype nickel-metal hydride storage batteries A to F having a nominal capacity of 85 Ah.

At this time, the weight of the battery A is 1.63 kg, the weight of the battery B is 1.57 kg, the weight of the battery C is 1.53 kg, and the weight of the battery D is
1.52kg, Battery E weighs 1.51kg, Battery F weighs 1.49kg
Met.

Each of the prismatic nickel-metal hydride storage batteries produced as described above was charged at 8.5 A for 16 hours, and after a one-hour pause, 28.
The activation process was performed by repeating 10 cycles of discharging at 3 A until the battery voltage reached 0.8 V.

Next, the battery after the activation treatment is charged at 8.5 A for 12 hours in an atmosphere of 25 ° C., and after a pause of 1 hour, a discharge depth of 0% to 90% for 30 seconds every 10%. The battery voltage at 10 seconds after discharging at 255 A was measured.

FIG. 1 shows the results.

As is apparent from FIG. 1, the battery F provided with the positive electrode plate f having a three-dimensional nickel porous material density of 0.91 g / cc uses the positive electrode plate e having a discharge depth of about 65% and 1.11 g / cc. The battery voltage falls below 1 V at a discharge depth of about 75%.
This means that these batteries have a nominal capacity of 85 Ah, but in practice they can only be used up to about 65% or 75% of them, which is a so-called premature battery shutdown.

On the other hand, the three-dimensional nickel porous body density is 1.25 g /
Batteries A to D with a positive electrode plate of cc or more have a discharge depth of 80%
However, it can be seen that the battery voltage is maintained at 1.0 V or more.

Therefore, in order to secure a capacity of 80% or more of the nominal capacity when a large current is discharged, it is necessary to make the three-dimensional nickel porous body density 1.25 g / cc or more.

[Experiment 2] Under the same experimental conditions as in Experiment 1,
That is, at a discharge depth of 80% for each battery, the battery voltage at 10 seconds after discharge at 255 A for 30 seconds and the output energy density obtained by multiplying the battery voltage by the current value of 255 A and dividing by the battery weight are plotted. The result is shown in FIG.

As is apparent from FIG. 2, as the density of the nickel porous body increases, the voltage increases, but when the density exceeds a certain level, the battery weight increases to maintain the same discharge capacity. As a result, the output energy density of the battery decreases. Also, it becomes difficult to fill the active material, and when the density of the nickel porous body exceeds 1.8 g / cc, defects such as cracking and peeling of the electrode plate in the manufacturing process occur.

From the above, the nickel porous body density was 1.
It is preferably 75 g / cc or less.

[Experiment 3] In this experiment, an electrode plate was prepared in which the number of holes in the unit distance of the three-dimensional porous nickel body and the density of the three-dimensional porous body in the electrode plate were variously changed, and the electrode plate was manufactured. Was rolled to a predetermined value, and the cracks and peeling of the electrode plate and the active material utilization were measured. The result is shown in FIG.

As is apparent from FIG. 3, when the three-dimensional nickel porous material density is about 1.8 g / cc or less and the number of holes in a unit distance, which is a value indicating the fineness of the holes, is 55. /
It can be seen that the electrode plate provided with nickel foam of about inch or less does not cause problems such as manufacturing defects such as cracking, peeling and capacity reduction. Further, from the viewpoint of the active material utilization rate, that is, in order to make the active material utilization rate 70% or more, it is preferable that the number of holes in a unit distance is 45 holes / inch or more.

According to FIG. 2 in Experiment 2, the most preferable range of the nickel porous body density of the output energy density is 1.4 g / cc to 1.6 g / cc. From FIG. 3 in Experiment 3, it is necessary that the number of holes within a unit distance of the three-dimensional nickel porous body be 45 to 60 holes / inch in order to prevent production defects such as a reduction in capacity.

[0031]

According to the present invention, an electrode in which a base made of a three-dimensional nickel porous body is filled with an active material and the density of the three-dimensional nickel porous body in the electrode is 1.25 to 1.75 g / cc, the The path is enlarged, polarization can be suppressed, and the operating voltage of the battery can be increased.

As a result, it is possible to prevent the battery voltage from dropping to a voltage of 1 V or less even at the time of discharging a large current of several hundred amperes, thereby preventing the discharge from being terminated immediately without leaving the actual discharge capacity. Can be.

The number of vacancies within a unit distance is 45 to
By setting to 55 pieces / inch, the density of the three-dimensional nickel porous body in the electrode is within a range of 1.25 to 1.75 g / cc,
Without reducing the discharge capacity, it is possible to suppress the occurrence of cracking, peeling, and the like of the electrode plate during production, and its industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 shows that a battery provided with an electrode manufactured by varying the density of a three-dimensional nickel porous material has a 255
10 is a plot of the battery voltage after 10 seconds when discharging at A for 30 seconds.

FIG. 2 is a diagram showing a relationship between a battery voltage and an output energy density at a discharge depth of 80% for each battery manufactured by changing the three-dimensional nickel porous body density in various ways.

FIG. 3 is a diagram showing ranges of a non-defective area and a defective area of an electrode manufactured by variously changing the electrode plate density of a three-dimensional nickel porous body and the number of holes (porosity) within a unit distance.

Continued on the front page F-term (reference)

Claims (3)

[Claims] 1. An electrode for an alkaline storage battery in which an active material is filled in a base made of a three-dimensional nickel porous body, wherein the density of the three-dimensional nickel porous body in the electrode is 1.25 to 1.75.
An electrode for an alkaline storage battery, wherein the number of pores per unit distance of the three-dimensional porous nickel body is 45 to 55 / g in g / cc. 2. An electrode for an alkaline storage battery in which a base made of a three-dimensional porous nickel body is filled with an active material, wherein the density of the three-dimensional porous nickel body in the electrode is 1.40 to 1.60.
g / cc, wherein the number of pores per unit distance of the three-dimensional porous nickel body is 45 to 60 pores / inch. 3. An alkaline storage battery comprising the electrode for an alkaline storage battery according to claim 1.