JP3349217B2 - Maintenance method for stationary nickel-hydrogen storage batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a maintenance method for restoring the capacity of a stationary nickel-metal hydride storage battery whose battery capacity has been reduced by repeating charge / discharge cycles.

[0002]

2. Description of the Related Art Oxygen gas is generated from a positive electrode at the end of charging of a stationary nickel-hydrogen storage battery used for a power supply of various measuring instruments such as a gas meter. If the generated oxygen gas is consumed by the reaction with the hydrogen of the negative electrode, the pressure (internal pressure) inside the battery does not increase, and the capacity balance between the positive and negative electrodes does not break.

However, a part of the oxygen gas generated during charging is consumed for oxidizing an easily oxidizable member such as a separator, so that hydrogen remains on the negative electrode. As a result, hydrogen gradually accumulates in the negative electrode during the repetition of the charge / discharge cycle, and the charge eventually becomes dominant in the negative electrode, and the battery capacity decreases. For this reason, when the battery capacity is reduced to some extent, it is necessary to periodically perform maintenance in order to recover the battery capacity.

Conventionally, as a maintenance of a stationary nickel-hydrogen storage battery provided with a negative electrode composed of a plurality of negative plates (having one positive electrode terminal and one negative electrode terminal), the present invention relates to a battery during a charge / discharge cycle. Overcharging (opening over) while releasing hydrogen accumulated in the hydrogen storage alloy of the negative electrode out of the battery system from the safety valve (check valve) provided on the top of the battery case to prevent the internal pressure from rising Charging) is being done.

FIG. 3 is an explanatory diagram of this conventional method. FIG. 3A is a diagram showing the capacity of positive and negative electrodes before maintenance.
(B) is a capacity diagram of the positive and negative electrodes after maintenance. Since hydrogen accumulates on the negative electrode due to repetition of the charge / discharge cycle, as shown in FIG.
The battery capacity which has been 1 drops to M2 before maintenance.

[0006] The maintenance is an operation performed to release the hydrogen accumulated in the negative electrode to the outside of the battery system to restore the reduced battery capacity M2 to M1. At the time of overcharging, not only hydrogen gas but also oxygen gas is removed. When a large amount is released outside the battery system,
This leads to a shortage of the electrolyte and shortens the cycle life. For this reason, it is necessary to overcharge so that a large amount of oxygen gas is not released out of the battery system. Therefore, in the conventional method, in reality, it is necessary to stop overcharging before oxygen gas is strongly generated from the positive electrode. It is for this reason that the charging depths of the positive and negative electrodes after maintenance shown in FIG. Note that hatched portions a and b in FIGS. 3A and 3B are portions where hydrogen is accumulated, respectively.

[0007] However, the above-mentioned conventional method has a problem that the battery life is short in a short cycle in a charge / discharge cycle after maintenance and also a problem that the cycle life of the storage battery is short. For this reason, development of a better maintenance method has been demanded.

The present invention has been made in order to meet such a demand, and an object of the present invention is to provide a new and useful maintenance method which does not have the above-mentioned problems by employing a divided maintenance system. is there.

[0009]

In order to achieve the above object, a maintenance method for a stationary nickel-hydrogen storage battery according to the present invention in which the negative electrode comprises a plurality of negative plates (hereinafter, referred to as the "method of the present invention"). Is divided into a plurality of negative electrode plates, connected to a plurality of negative electrode terminals for maintenance, using each of the negative electrode terminal for maintenance and the positive electrode terminal, to discharge hydrogen gas generated in the battery system outside the battery system. This is a method of sequentially performing charging and discharging operations.

As described above, the method of the present invention employs a divided maintenance system in which maintenance is performed in a plurality of times. Suitable charging capacity for maintenance is 40-7
0%. If the charge capacity is too small, the accumulated hydrogen is not sufficiently extracted from the negative electrode, so that the rate of capacity recovery is reduced and the cycle life is shortened. On the other hand, if the charge capacity in each divided maintenance is too large, oxygen gas in addition to the hydrogen gas to be released is also released to the outside of the battery system, causing a shortage of the electrolyte and shortening the cycle life.

[0011]

In the method of the present invention, since a divided maintenance system is adopted in which the positive electrode terminal and a plurality of negative electrode terminals for maintenance are sequentially opened and charged and discharged, the overcharging is performed using the positive electrode terminal and the negative electrode terminal as they are. Compared to the conventional method,
An electrolyte shortage due to the release of oxygen gas outside the battery system during maintenance is unlikely to occur. In addition, since a large amount of hydrogen accumulated in the negative electrode is released outside the battery system as hydrogen gas,
The decrease in battery capacity in the charge / discharge cycle after maintenance is moderated. Hereinafter, the principle of the method of the present invention will be described.

In consideration of the subsequent accumulation of hydrogen in the negative electrode, it is preferable that the maintenance should be performed so that the depth of the negative electrode after the maintenance is as small as possible, that is, the amount of extracted hydrogen is large. Also, in order to avoid shortening the cycle life due to lack of electrolyte,
It should be preferable to discharge only the hydrogen gas to the outside of the battery system without releasing the oxygen gas. The method of the present invention has been developed based on such knowledge. That is, in the method of the present invention, a large amount of accumulated hydrogen is extracted from the negative electrode with little or no release of oxygen gas.

FIG. 1 shows a positive electrode plate and a negative electrode plate in a case where the method of the present invention is applied to maintenance of a stationary nickel-hydrogen storage battery in which three positive electrode plates and four negative electrode plates are alternately arranged to face each other. It is a wiring diagram showing an example of a connection method to a terminal or a negative electrode terminal. As shown in the figure, three positive plates P1, P
2 and P3 are all connected to the positive terminal PT, and the four negative plates N1, N2, N3 and N4 are divided into two every other plate, each connected to the maintenance negative terminals NT1 and NT2. I have.

FIG. 2 is an explanatory diagram in the case where the method of the present invention is applied to maintenance of a stationary nickel-hydrogen storage battery (unit cell) in which a positive electrode plate and a negative electrode plate are connected as shown in FIG. ) Is the positive and negative electrode capacity diagram before maintenance,
FIG. 2B shows the positive electrodes P1, P2, and P3 after the first maintenance using the positive electrode terminal PT and one of the negative electrodes NT1 for maintenance, and the negative electrode plates N1 and N1 divided and connected.
FIG. 2C shows the positive electrode plates P1, P2, and P3 after the second maintenance using the positive electrode terminal PT and the other maintenance negative electrode terminal NT2, and the separately connected negative electrode plates N2 and N4. FIG. 2D is a capacity diagram of the positive and negative electrodes after maintenance.

In the method of the present invention, the divided negative electrode plates N1, N
3 or the total capacity of the negative plates N2 and N4 is
2, N3, N4, the negative electrode plates N1, N3 or N2, N4 by charging at a shallow depth.
Thus, the accumulated hydrogen can be released outside the battery system. As a result, maintenance can be performed without releasing oxygen gas out of the battery system, and shortage of electrolyte does not easily occur (extending of cycle life).

[0016] Further, since oxygen gas is hardly generated at the end of charging for maintenance, a large amount of accumulated hydrogen can be released outside the battery system. As a result, as shown in FIG. 2D, an extra capacity S is generated in the negative electrode after maintenance,
The charge depth of the negative electrode becomes shallow. Until hydrogen is completely accumulated in the extra capacity S, charging is performed by the positive electrode, and the capacity hardly decreases during that time. Extra capacity S
After the hydrogen is completely stored, the capacity becomes lower due to simultaneous control, and eventually the charge shifts to negative electrode control.However, there is a period during which the capacity hardly decreases. Becomes slower (longer maintenance intervals).

[0017]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples, and may be carried out by appropriately changing the scope of the present invention. Is possible.

(Examples 1 to 21) A stationary nickel-hydrogen storage battery cell in which three positive electrode plates and four negative electrode plates are alternately arranged to face each other (rated capacity: 100 Ah; safety valve opening pressure: 3 atm). After charging for 1 hour at 1C,
A charge / discharge cycle test was performed in which the process of discharging to a discharge end voltage of 1 V was one cycle, and after 300 or 1000 cycles, three positive plates and four negative electrodes were used as shown in FIG. Each plate is a positive terminal PT
And the negative terminals NT1 and NT2, and the positive terminal P
T and charge / discharge while releasing hydrogen gas from the safety valve using the negative electrode terminal NT1 for maintenance.
Using T and the negative electrode terminal for maintenance NT2, charging and discharging were performed in the same manner to perform maintenance. Tables 1 and 2 show the charging capacity (Ah), the timing of performing the maintenance (cycle), the battery capacity (Ah) before and after the maintenance, and the internal pressure (atmospheric pressure) in each maintenance. In addition, the internal pressure before and after the maintenance in both tables is the internal pressure after charging until the internal pressure reaches 3 atm at 0.1 C and leaving it to stand for 1 hour. The battery capacity before and after maintenance in both tables is 0.1 C
Is the battery capacity when the battery is charged to a charge end pressure of 3 atm and then discharged at 0.1 C to a discharge end voltage of 1 V.

[0019]

[Table 1]

[0020]

[Table 2]

As shown in Table 1, Examples 1 to 1 in which maintenance by the method of the present invention was performed after 300 cycles had elapsed.
0, the amount of stored hydrogen was small because maintenance was performed early, and the battery capacity did not decrease at all before maintenance. However, in Examples 4 to 10 in which the charging capacity was 40 Ah (40%) or more, Before and after, the internal pressure drops from 1.5 atm to 1.1 or 1.0 atm. This indicates that when the charging capacity is increased to 40 Ah (40%) or more, the amount of extracted hydrogen is significantly increased.

On the other hand, as shown in Table 2, in Examples 11 to 21 in which the maintenance according to the method of the present invention was carried out after the lapse of 1000 or 1500 cycles, a considerable amount of hydrogen was accumulated on the negative electrode, and thus the battery capacity was reduced to 80 before the maintenance.
Ah or 60 Ah. However, in Examples 14 to 21 in which the charge capacity was 40 Ah (40%) or more,
Since the amount of accumulated hydrogen has been significantly reduced due to the maintenance, the internal pressure has largely decreased from 2.0 atm to 1.3 to 1.1 atm before and after the maintenance, and the battery capacity has recovered to 90% or more of the initial level. I have. From these results, it is understood that the charging capacity during maintenance in the method of the present invention is preferably set to 40% or more.

(Comparative Examples 1 to 18) A charge / discharge cycle test was performed under the same conditions as in Examples 1 to 21, and the maintenance negative electrode terminal N1 and the maintenance negative electrode terminal N2 were short-circuited to form one negative electrode terminal. The maintenance was performed in the same manner as in Examples 1 to 21 except that charging and discharging were performed only once using the negative electrode terminal and the positive electrode terminal PT. Tables 3 and 4 show the charge capacity at the time of maintenance, the timing of the maintenance, the battery capacity before and after the maintenance, and the battery internal pressure. The battery internal pressure and the battery capacity before and after the maintenance were measured in the same manner as above.

[0024]

[Table 3]

[0025]

[Table 4]

As shown in Table 3, in Comparative Examples 1 to 9 in which the maintenance by the conventional method was performed after 300 cycles, the battery capacity did not decrease at all before the maintenance because the maintenance was performed early. 120-
In Comparative Examples 6 to 9 as large as 180 Ah, the internal pressure increased from 1.5 atm to 1.7 to 2.0 atm before and after maintenance. This is because oxygen gas is generated from the positive electrode due to large-capacity charging with little hydrogen stored in the negative electrode, and corresponding hydrogen is stored in the negative electrode, increasing the hydrogen concentration in the battery system. This is because the.

On the other hand, as shown in Table 4, in Comparative Examples 10 to 18 in which maintenance by the conventional method was performed after 1000 or 1500 cycles, the battery capacity was 80 Ah before maintenance due to accumulation of hydrogen in the negative electrode. Has declined. In Comparative Examples 10 to 13 in which the charge capacity is as small as 60 Ah, there is no change in the battery capacity and the internal pressure before and after the maintenance. Since part of the battery was released outside the battery system, the internal pressure after charging after maintenance was reduced, and the battery capacity was recovered to 95% of the initial value.

(Examples 22 to 28 and Comparative Examples 19 to 2)
4) For the same type of stationary nickel-hydrogen storage battery, the charge / discharge cycle was repeated under the same conditions as above,
Maintenance was performed for each cycle using the method of the present invention or the conventional method, and the cycle life was examined. For comparison,
The cycle life when no maintenance was performed was also examined. Only the cycle life when the charge capacity was set to 40 Ah (40%) or more as in Examples 22 to 28 was examined. When the charge capacity was set to less than 40 Ah from the results of Examples 1 to 3, the capacity recovery was performed. Was found to be almost difficult. The cycle life is 50
The battery capacity was measured at every cycle, and indicated by the total number of cycles until the battery capacity decreased to 50% of the initial capacity.
Table 5 shows the results.

[0029]

[Table 5]

As shown in Table 5, in Examples 22 to 28 where maintenance was performed by the method of the present invention, Comparative Examples 19 to 23 where maintenance was performed by the conventional method and Comparative Example 24 where maintenance was not performed, The cycle life of the storage battery is generally long. This is because the capacity was recovered with almost no shortage of the electrolyte caused by the release of oxygen gas outside the battery system during charging. Further, even in the case of the method of the present invention, as shown in Examples 26 to 28, if the charging capacity is too large, the amount of released oxygen gas becomes large, so that the electrolyte becomes insufficient and the cycle life becomes short. , The charging capacity is preferably 70 Ah (70%) or less. Considering this and the fact that the charging capacity of 40% or more is preferable in terms of the capacity recovery described above, it can be seen that the charging capacity in maintenance is preferably 40 to 70%.

In the above embodiment, a stationary nickel-hydrogen storage battery having three positive electrode plates and four negative electrode plates has been described as an example, but a plurality of negative electrode plates are used as a plurality of maintenance negative electrode terminals. The number of the electrode plates is not particularly limited as long as it is a structure that can be divided and connected to perform the divided maintenance method. In the above embodiment, the case where the method of the present invention is applied to the maintenance of a unit cell is described as an example.However, the method of the present invention is applied to the maintenance of an assembled battery in which a plurality of pairs of positive electrodes and negative electrodes are connected in series. Is also applicable.

[0032]

According to the method of the present invention, the capacity decrease after the maintenance is gradual, and the maintenance interval can be lengthened. In addition, by setting the charging capacity at the time of maintenance to a size that hardly releases oxygen gas, maintenance can be performed without shortening the cycle life due to insufficient electrolyte.

[Brief description of the drawings]

FIG. 1 is a wiring diagram showing an example of a method of connecting a positive electrode plate and a negative electrode plate to each terminal when carrying out the method of the present invention.

FIGS. 2A and 2B are explanatory diagrams of the method of the present invention, wherein FIG. 2A is a diagram showing the capacity of positive and negative electrodes before maintenance, and FIG. 2B is a diagram after the first maintenance using a positive terminal and one maintenance negative terminal. The capacity diagram of the positive electrode and the divided negative electrode, (C) is a capacity diagram of the positive electrode and the divided negative electrode after the second maintenance using the positive terminal and the other maintenance negative terminal, and (D) is after the maintenance. FIG. 4 is a capacity diagram of positive and negative electrodes of FIG.

3A and 3B are explanatory diagrams of a conventional method, in which FIG. 3A is a capacity diagram of positive and negative electrodes before maintenance, and FIG. 3B is a capacity diagram of positive and negative electrodes after maintenance.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-36442 (JP, A) JP-A-61-49384 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/00-10/48

Claims (2)

(57) [Claims] 1. A maintenance method for a stationary nickel-hydrogen storage battery in which a negative electrode comprises a plurality of negative plates, wherein the plurality of negative plates are divided and connected to a plurality of negative terminals for maintenance. A maintenance method for a stationary nickel-hydrogen storage battery, comprising sequentially performing charging and discharging operations while discharging hydrogen gas generated in the battery system to the outside of the battery system using the negative electrode terminal and the positive electrode terminal. 2. The charging capacity in said operation is 40 to 70%.
The maintenance method for a stationary nickel-hydrogen storage battery according to claim 1, wherein