JP2623775B2 - Sealed rectangular nickel-cadmium storage battery - Google Patents

Description

The present invention relates to a sealed nickel-cadmium storage battery,
An object of the present invention is to improve the capacity density of a battery by improving the configuration of a cathode plate in a prismatic battery.

Conventional technology Conventionally, closed nickel. Most of the cadmium storage batteries were cylindrical, with a few exceptions. This battery employs a technique in which a nickel electrode serving as an anode plate and a cadmium electrode serving as a cathode plate are wound through a separator, and the wound group is inserted into a battery can. However, there is a problem that a space that cannot be avoided in the production process is generated in the center of the winding group. Therefore, recently, a rectangular nickel cadmium storage battery capable of reducing such wasted space has been developed.

In addition, even when these batteries are combined, the rectangular nickel-cadmium storage batteries have a high capacity density, such as a clearance between the batteries can be eliminated, and are expected to be used in a wider range of applications. However, the strength of the metal case of the prismatic battery is weaker than that of the cylindrical shape, and as a result, there is a problem that deformation occurs even at a relatively low pressure of 5 to 10 kg / cm ² .

For this reason, at present, the safety valve operating pressure is set to about 5 kg / cm ² to prevent deformation of the battery case, which tends to occur during charging. If the safety valve operating pressure is set to about 5 kg / cm ² in this way, the battery case will not be deformed even if a cathode plate with poor oxygen gas absorption performance is used, but the oxygen gas will go out of the closed system. Then, the capacity balance between the anode and the cathode is lost, and the capacity is rapidly deteriorated. For this reason, at present, a sintering type is used as a cathode plate satisfying the above oxygen gas absorption performance.

However, the sintered cathode plate is made by sintering Ni powder to form a porous Ni body, in which metal cadmium or cadmium hydroxide, which is electrochemically or chemically active, is held in the pores. Yes, the proportion filled in the pores is 50-60% of the pores. Thus, the sintered cathode has a large amount of Ni current collection network and pores, and the charge capacity density is 90%.
The limit is from 0 to 1000 msh / cm ³ , whereas the paste type, which is a cathode plate mainly used for cylindrical nickel-cadmium storage batteries, that is, mainly containing cadmium oxide or cadmium hydroxide powder The paste capacity in which the powder is kneaded with an organic binder is applied to the current collector, and the filling capacity density of the dried cathode plate is significantly lower than the filling capacity density of 1400 to 1500 msh / cm ³ . When the paste method is used, the capacity density can be improved, but the paste method is inferior in oxygen gas absorption performance as compared with the sintered method, and cannot be rapidly charged.

The oxygen gas absorption reaction is a reaction in which oxygen gas generated from the anode is consumed at the cathode, and oxygen is consumed at the cathode by a chemical reaction of formula (1) or an electrochemical reaction of formula (2).

_{cd + 1 / 2O 2 + H} 2 O → cd (OH) 2 ...... (1) 1 / 2O 2 + H 2 O + 2e - → 2OH - ......... (2) is a sintered cathode plate for these reaction proceeds readily , The internal pressure of the battery is about 3k even in the weekly charging state at 1cmA charging
g / cm ² . Therefore, as described above, there is no problem even if the operating pressure of the safety valve of the battery is set to 5 kg / cm ² . However, in a cylindrical sealed nickel cadmium storage battery using a paste-type cathode plate, the battery internal pressure in the overcharged state at the time of charging 1 cmA is about 15 kg / cm ² . Since the strength of the metal case of the cylindrical storage battery is large, the operating pressure of the safety valve
And a 20 kg / cm ^2, but the safety valve does not operate if the 15 kg / cm ^2, a very high compared with the sintered type.

The following two are considered as reasons why the oxygen gas absorption performance of the paste type cathode plate is inferior. That is, in the paste method, the active material is charged from the vicinity of the current collector, so that the oxygen gas is difficult to diffuse to the metal cadmium generated by charging, that is, the reaction of the formula (1) decreases, and
This is because there is no catalytic nickel on the surface, that is, the reaction of the formula (2) decreases. The method of improving the oxygen gas absorption of the paste-type cathode plate used in the cylindrical battery is, in particular, as a means of improving the oxygen gas absorption performance according to the formula (1), by applying a conductive material to the surface of the cathode plate. How to facilitate the production of metal cadmium in the
As means for improving the oxygen gas absorption performance according to the formula (2), application of carbon and provision of water repellency, which is considered to be a factor assisting the reactions of the formulas (1) and (2), are considered. According to these methods, the internal pressure at the time of overcharging is indeed 5 times less than that of a conventional paste-type cathode plate battery of 15 kg / cm ^2.
Can be reduced to to 10 kg / cm ^2, it is effective. In the case of a cylindrical battery, the operating pressure of the safety valve is high as described above, and there is no problem in practical use at this level of oxygen gas absorption performance. However, in the case of a prismatic battery, as described above, the pressure resistance of the metal case is small, so the safety valve operating pressure must be 5 kg / cm ² . With the current operating pressure, it must be said that it is very difficult to act as a cathode plate of a prismatic battery even if a conventional paste-type or an improved paste-type cathode plate as described above is used. . To solve this problem, it is conceivable to increase the pressure resistance of the metal case and at the same time increase the operating pressure of the safety valve. Specifically, thickening the thickness of the metal case, attaching ribs to the metal case, etc., are not much different from the sintered type cathode plate because these methods reduce the volume of the electrode plate that can be contained. That was the current situation.

Problems to be Solved by the Invention In order to increase the capacity of a prismatic battery, the capacity of the sintered cathode plate is increased from the aspect of the active material filling capacity density, and that of the paste type cathode plate is increased from the aspect of oxygen gas absorption performance. Was impossible.

Means for Solving the Problems In order to essentially solve the above problems, it is necessary to improve the oxygen gas absorbing performance of the paste type cathode plate. However, providing a paste type cathode plate with oxygen gas absorption performance equivalent to that of a sintered type is an essential problem, and it can be said that it is almost impossible. Therefore, a sintered type and a paste type are used for the cathode plate.

The effect of this is that the oxygen gas absorption capacity of the paste type cathode plate is improved, and the capacity density of the prismatic battery can be improved.

EXAMPLES Example 1 A sealed rectangular nickel-cadmium storage battery having a battery having two electrode plates and three cathode plates was prepared. The anode plate is a sintered type produced by a usual method. The thickness is 0.6mm and the capacity is 300mAh. The sintered cathode plate was also prepared by a usual method. 0.5mm and 1.0 thickness
mm, and the theoretical capacity of discharge was 420 mAh and 800 mAh, respectively. The active material of the paste-type cathode was composed of 100 parts by weight of cadmium oxide powder, 1 part by weight of carbon powder, 20 parts by weight of metal cadmium powder, and 3 parts by weight of polytetrafluoroethylene. The current collector was nickel-plated. Uses iron punching metal. If the logic capacity of this paste type cathode plate is the same as that of the sintered type, the thickness will be
0.37mm and 0.7mm. The discharge utilization rate was the same for both the paste type and the sintered type. Separator 0.20 thick
A nylon nonwoven fabric having a thickness of 0.15 mm (when the electrode plate group was formed, but with a pressure of 0.15 mm) was used. When the electrode group was formed using only the sintering method for the cathode plate, the thickness was 3.8 mm (referred to as “battery A”). When only the paste type is used for the cathode plate, the thickness of 0 (referred to as “battery B”) is 3.24 mm, and when the paste type is disposed at the center and the sintered type is disposed outside,
The thickness was 3.5 mm (referred to as “battery C”). These electrode plates were placed in a 4.0 mm wide metal case inside a rectangular metal case. Since the electrode plate group was thinner than the metal case, a combination of 0.05 mm, 0.1 mm, and 0.2 mm nickel plates was used as a spacer when inserting the group. In this way, the electrode group was placed in the metal case, and this was brought into electrical contact with the anode and cathode terminals by a usual method, and sealed to obtain a battery. FIG. 1 shows a battery internal pressure curve at the time of charging 1 cmA of these batteries, that is, at the time of charging 600 mA. In battery B, the safety valve operating pressure reached 5 kg · f / cm ² 70 minutes after the start of charging. On the other hand, the values for the batteries A and C were 3 to 3.5 kg · f / cm ² even after 90 minutes. As described above, the oxygen gas absorption performance was improved by using the sintering method and the paste method for the cathode plate. FIG. 2 is a discharge voltage curve when discharging at 1 cmA. Battery B shows a paste type only, battery A shows a sintered type only, and battery C shows a paste type at the center and a sintered type at the outside. Battery B is 1c better than batteries A and B
The mA discharge duration was short, presumably because charging was stopped because the safety valve was activated before the anode active was fully charged. Since the anode plate capacity was the same, Battery A and Battery B were almost the same in both capacity and voltage characteristics.
As described above, there is no problem in charge and discharge characteristics even when the paste type is used in the center and the sintered type is used in the outside as the cathode plate.
By the way, this battery has a nickel plate spacer in an extra space as described above. The actual thickness of the electrode plate group is 3.80 mm for the sintered type, 3.50 mm for the sintered type and the space type, and 3.24 mm for the paste type.By adopting the paste type at the center, The thickness of the electrode group can be reduced by about 9% as compared with the case of using only the sintering method, and there is no difference in charge / discharge characteristics between the two as described above. By optimizing the thickness of the anode plate and the cathode plate according to the method of the metal case, it is possible to increase the energy density by 9%.

Example 2 A sealed rectangular nickel-cadmium storage battery having a battery with two electrode plates and three cathode plates was prepared. The same anode plate as in Example 1 was used. The sintered cathode plate has a thickness of 1.0 mm used in Example 1, and the paste cathode plate has a thickness of 0.37 mm. The arrangement of the cathode plate is different from that of the battery C of Example 1, and the sintering type was disposed at the center and the paste type was disposed on both sides. This electrode group was referred to as “battery D”. The thickness of the electrode group was 3.45 mm, and the electrode group was inserted into the metal case used in Example 1 and a spacer was inserted. This was sealed by an ordinary method to obtain a battery. In this battery, the paste having a large resistance is in contact with the entire surface of the metal case, and the cathode plate at the center is of a sintered type, so that the internal resistance is almost the same as that of the sintered type alone. For this reason, the voltage characteristics at the time of discharge are not different from the sintering type. The capacity did not change with the discharge current of 1 cmA or less as compared with the battery C of Example 1, but with the discharge current of 3 cmA, the discharge time of the battery D was longer by about 2 minutes as shown in FIG. This is considered to be the effect of the internal resistance as described above. Since the battery D has a larger electrode group thickness than the battery C, the battery C has a larger discharge capacity per unit volume at a discharge current of 0.2 cmA and 1 cmA. Therefore, the battery C and the battery D become more effective when used properly according to the purpose of use. The internal pressure of the batteries during charging was unchanged for both batteries C and D.

Example 3 A sealed rectangular nickel-cadmium storage battery having a battery having five anode plates and six cathode plates was prepared. The same anode plate as in Example 1 was used. As for the batteries, when the paste type and the sintering type are alternately arranged as shown in FIG. 4 (referred to as “battery E”), as shown in FIG. (Referred to as “battery F”). FIG. 6 shows battery internal pressure curves when these batteries were charged at 1 cmA (3 A) for 90 minutes. Battery E had a battery internal pressure of 3.5 kg · f / cm ² at the end of charging. On the other hand, the battery F exceeds 5 kg · f / cm ² after 80 minutes and 10 kg after 90 minutes.
・ It has reached f / cm ² . When the thickness of the metal case was measured after charging, the thickness increased by 0.1 mm and deformation was observed. Such batteries cannot be used in practice. The capacity at the time of discharge of 0.2 cmA was the same as in the case of the battery E, the battery F and the case where the sintering method was used for the cathode plate (battery G). Since the thicknesses of the electrode groups were 8.77 mm, 8.77 mm, and 9.50 mm, respectively, the discharge capacity per unit volume was improved by about 80% when using the paste type and the sintered type.

Example 4 A thin nickel-cadmium storage battery comprising one anode plate and one cathode plate was prepared. The metal case used in Example 1 was used, and a spacer was inserted in the gap. As shown in FIG. 7, the cathode plate was made of a sintered type for 60% of the total surface area and a paste type for 40% of the total surface area. The active substance packing density of this sintered plate was increased by 20% as compared with the sintering method alone. This battery is referred to as “battery H”. The capacity per unit of the electrode group of this thin battery was increased by 10%. The internal pressure of the battery at the time of charging was completely the same as that of the battery H in the case of only the sintering type, and it was found that the present invention product had no problem.

As described above, the sealed square nickel. By using the sintering method and the paste method for the electrode plate of the cadmium storage battery, the oxygen gas absorption performance in the case of only the sintering method can be made exactly the same. When the paste method and the sintering method are used, the reaction mainly proceeds on the sintered type cathode plate having good oxygen gas absorption performance, but the oxygen gas absorption capacity is completely the same as shown in Examples 1 to 4 simply by this alone. It is not expected to be. This is probably because the presence of the sintering method and the paste method slightly changed the amount of electrolyte retained between the electrode plates, and also improved the oxygen gas absorption performance on the paste-type cathode plate. It is presumed that sealing can be achieved in the prismatic battery in this way. Since the paste type, which has a higher active substance packing density than the sintered type, is used at the same time for the cathode plate, it is possible to increase the capacity by about 10%, although it varies slightly depending on the electrode plate configuration, and to further reduce the battery thickness. It has become possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a battery internal pressure curve when charged at 1 cmA, and FIG.
The figure shows a discharge battery voltage curve at 1 cmA, FIG. 3 shows a discharge duration curve at 3 cmA, and FIG. 4 shows a battery having an electrode group consisting of five anode plates and six cathode plates, in which the cathode plate is a paste. FIG. 5 is an explanatory view in the case where the formula and the sintering formula are alternately provided.
FIG. 7 is an explanatory view of a battery of a group of six cathode plates, in which there are three paste plates and three sintering cathode plates, FIG. 6 is a battery internal pressure curve diagram when charged at 1 cmA, and FIG. , The area of the cathode plate
It is an explanatory view in the case where 60% is a sintering type and 40% is a paste type. Battery C is composed of two anode plates and three cathode plates, a battery in which the central cathode plate is of a paste type and both cathode plates are of a sintered type, and battery D is two anode plates and three cathode plates. A battery in which the cathode plate at the center is of a sintered type and a cathode plate on both sides is of a paste type, a battery E is a battery having the electrode plate configuration of FIG. 4, and a battery F is a battery of FIG. Battery having the electrode plate configuration of

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Mitsuru Koseki Examiner, Shin Kobe Electric Co., Ltd. Michiko Sakai 2-1-1 Nishi Shinjuku, Shinjuku-ku, Tokyo

Claims (9)

(57) [Claims] 1. A sealed rectangular nickel-cadmium storage battery comprising an anode plate and a cathode plate via a separator, wherein the cathode plate comprises a sintered cathode plate and a paste cathode plate. 2. The method according to claim 2, wherein the number of the cathode plates is three or more at the time of stacking the electrode plates,
2. A sealed square nickel alloy according to claim 1, wherein both ends are made of a paste type cathode plate and the inside is made of a sintered type cathode plate.
Cadmium storage battery. 3. The method according to claim 1, wherein the number of the cathode plates is three or more at the time of laminating the plates.
2. A sealed square nickel alloy according to claim 1, wherein both ends are sintered cathode plates and the inside is a paste cathode plate.
Cadmium storage battery. 4. The sealed rectangular nickel-cadmium storage battery according to claim 1, wherein sintered cathode plates and paste cathode plates are alternately arranged when the electrode plates are laminated. 5. The sealed rectangular nickel-cadmium storage battery according to claim 1, wherein the binder of the paste-type cathode plate is polytetrafluoroethylene. 6. A sealed rectangular nickel-cadmium storage battery according to claim 1, wherein carbon is applied to the paste-type cathode plate. 7. A sealed rectangular nickel-cadmium storage battery according to claim 1, wherein the cathode plate has a paste-type cathode plate portion and a sintered-type cathode plate portion. . 8. The sealed rectangular nickel-cadmium storage battery according to claim 7, wherein the binder of the paste type cathode plate is made of polytetrafluoroethylene. 9. The sealed rectangular nickel-cadmium storage battery according to claim 7, wherein carbon is applied to a portion of the paste type cathode plate.