JPS62287578A - Enclosed alkaline storage battery - Google Patents

Abstract

PURPOSE:To make the built-up of cell charging voltage at the time of full charging as well as to detect a voltage variation at the time of the full charging so easily and accurately, by constituting the uncharged capacity of an anode in a discharged state to be smaller that the uncharged capacity of a cathode. CONSTITUTION:The uncharged capacity of an anode at a discharged state is constituted to be smaller in substance than the uncharged capacity of a cathode, and at the time of charging, the anode is full charged earlier than the cathode. Therefore, a variation in cell charging voltage at the time of full charging is made larger by the large build-up of the anode to hydrogen generating potentional. With this constitution, such charging control as utilizing the voltage variation is made performable easily and accurately so that constant current-constant voltage charging can be done.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a sealed alkaline storage battery of a limited electrolyte amount type.

<Prior art> In alkaline storage batteries such as nickel-cadmium storage batteries, silver oxide-zinc storage batteries, or nickel-iron storage batteries,
A cathode plate containing cadmium, zinc, or iron as an active material, and an anode plate containing nickel hydroxide, silver oxide, etc. as an active material are used, and these are combined through a separator and placed in a storage can to perform alkaline electrolysis. A configuration in which liquid is injected is adopted.

In this type of alkaline storage battery, such as a nickel-cadmium storage battery, the following reactions occur during charging and discharging, and when the battery reaches full charge, oxygen gas is generated from the nickel anode and hydrogen gas is generated from the cadmium cathode.

The above M gas can be electrochemically consumed by reacting with metal cadmium, which is a charging product, at the cadmium cathode, but the hydrogen gas generated at the cadmium cathode cannot be consumed within the battery. Instead, it accumulates inside the battery container. For this reason, if the overcharge state continues for a long time, the hydrogen gas accumulation will increase and the internal pressure of the battery container will rise abnormally, causing problems such as deformation of the battery container and leakage of alkaline electrolyte to the outside due to the activation of the safety valve. The drawback is that it is very difficult to seal the battery.

In order to overcome this drawback, in current sealed alkaline storage batteries, the cathode capacity is substantially larger than the anode capacity.
During charging, a so-called anode-dominated configuration is adopted in which the anode is fully charged before the cathode. With this configuration, even if the anode is fully charged at the end of charging, the cathode will not be fully charged, and even in an overcharged state, oxygen gas will be generated from the anode with priority, so that oxygen gas will be generated from the cathode. hydrogen gas generation will be suppressed.

On the other hand, in current sealed alkaline storage batteries, in addition to the above, a configuration is used in which the amount of electrolyte is limited so that there is substantially no free electrolyte in the battery. In other words, in a type of battery in which the amount of electrolyte in the battery is increased and the electrode body is immersed in the electrolyte, even if the configuration is such that the generation of oxygen gas from the anode is prioritized first during overcharging as shown in [e] above, The aerosol gas generated at the anode cannot reach the cathode surface, which is wet with the rich electrolyte, and oxygen gas cannot be consumed within the battery by the above consumption reaction, and in the case of a sealed battery, the internal gas pressure of the battery This is because the amount will rise.

<Problems to be Solved by the Invention> However, as described above, in an anode-dominated sealed alkaline storage battery, the battery voltage change at the end of charging is small, so there is a problem that it is extremely difficult to determine the completion of charging from the voltage change. However, configuring a circuit that controls charging using such voltage changes would be extremely complex and therefore expensive. It cannot be practically applied to sealed alkaline storage batteries.

In addition, in this sealed alkaline storage battery, the cathode capacity is generally designed to be much larger than the anode capacity for safety reasons, and a considerable amount of the cathode portion, which does not substantially contribute to the battery discharge capacity, is kept inside the battery. Because we have no choice but to bring it into
There is a problem in that it is very disadvantageous in terms of volumetric efficiency.

<Means for Solving the Problems> The sealed alkaline storage battery of the present invention is of a type in which the amount of electrolyte is limited so that there is substantially no free electrolyte in the battery, and the amount of free electrolyte is limited in the battery in a discharged state. The gist is that the uncharged capacity of the cathode is substantially smaller than the uncharged capacity of the anode.

Further, in addition to this configuration, a total dielectric material or a metal compound having a larger hydrogen overvoltage than the cathode 1* active material may be added to and contained in the cathode.

<Function> Figure 5 shows the change in charging voltage (V) with respect to the amount of charge (%) when charging with a constant current using a conventional sealed nickel-cadmium storage battery with anode-dominated type and limited electrolyte volume. It was shown to. It is clear from the figure that the change in charging voltage at full charge (near 100% charge) is extremely small.

Figure 6 shows the electrode potential (VVS HCJ/Hg0) of the nickel anode (II>) and the cadmium cathode (I>), and the cadmium cathode ■ has a large voltage rise (hydrogen generation) when fully charged. The reason why the above conventional sealed nickel-cadmium storage battery does not show a large voltage rise when fully charged is that, as mentioned above, the anode is closer to the anode than the cathode. Since the battery is configured so that it is fully charged first, when the anode becomes fully charged and begins to generate liquid gas, the oxygen gas consumption reaction occurs at the cathode and the electrode, and charging no longer progresses. This is because the cathode is apparently groove-charged, so the potential rise shown in FIG. 6 does not occur.

Since the sealed alkaline storage battery of the present invention is constructed as described above, the cathode becomes fully charged before the anode during charging, so the battery charging voltage at full charge is reduced due to a large rise in the hydrogen generation potential of the cathode. The voltage change can be increased.

In addition, by adding a metal or metal compound with a higher hydrogen overvoltage than the cathode active material to the cathode, the cathode exhibits a larger voltage rise when fully charged, as shown by the dotted line ■ in Figure 6, and therefore the above The change in battery charging voltage can be made larger.

As described above, since the voltage change during full charging can be increased, charging can be easily controlled using this voltage change, making it practical to apply the constant current constant voltage charging method described above. It becomes possible. However, in that case, since the hydrogen generation potential of the cathode changes depending on the environmental temperature, it may be difficult to use the same potential over a wide temperature range as the limiting potential when transitioning from constant current charging to constant voltage charging, but as mentioned above, This can be improved by adding a metal or metal compound (for example, In or Zn in the case of a cadmium cathode) that has a higher hydrogen overvoltage than the cathode active material, making it possible to use the same limiting potential over a wide temperature range. It becomes possible. FIG. 1 shows typical changes in charging current when the sealed storage battery of the present invention is charged with constant current and constant voltage.

Furthermore, the cathode capacity that does not substantially contribute to the battery discharge capacity can be significantly reduced, and the anode capacity and the cathode portion that contribute to the battery discharge capacity can be increased by that amount, so that the volumetric efficiency of the battery can be greatly improved.

<Example> An example in which the present invention is applied to a nickel-cadmium storage battery will be described below.

A sintered nickel anode with an actual damage f of 41,800 mAH and a sintered cadmium cathode with an actual capacity of 1,500 mAH were combined in a discharge state via a separator, and then wound together to form an electrode body. This electrode body is placed in a battery outer can, and 5cc of 25% by weight potassium hydroxide aqueous solution is injected as an alkaline electrolyte.Then, the opening of the outer can is sealed and the electrolyte amount is limited to a sealed nickel-cadmium storage battery. Invention battery A (nominal capacity: 1500 mAH) was produced.

The plate capacities of the cadmium cathode and nickel anode used in this battery are schematically shown in FIG. 3(A).

FIG. 3(B) is a schematic diagram of the capacity of each plate of a cadmium cathode and a nickel anode used in a conventional sealed nickel-cadmium storage battery (conventional battery B) configured in the same manner. In the figure, the shaded area indicates the capacity in the charged state, and the white area indicates the capacity in the discharged state.

This battery has a nominal capacity of 1200mAH.
The battery of the present invention was able to have a nominal capacity of 125% of that of the conventional battery.

In addition, as shown in Figure 4, the actual capacity is 1800mAH.
A sealed nickel-cadmium storage battery with a limited amount of electrolyte (invention battery C: nominal capacity) is constructed using a sintered nickel anode of 1500
mAH> was produced.

The volumetric efficiencies (mAH/cc) of these three batteries are shown in Table 1.

Table 1 Also, when batteries A and C of the present invention were charged at a current of 10 hours (0, IC), a sharp rise in charging voltage, which was not observed in conventional battery B, was observed when fully charged. It was seen.

Further, the two batteries A and C were subjected to constant current and constant voltage charging tests at environmental temperatures of 0'C, 20'C, and 50C under the conditions shown in Table 2, respectively.

The test results in Table 2 are as shown in FIG. 2, and at 20'C, normal charging was performed in which the charging current decreased from the time of full charge, as indicated by the solid line a in the figure. Also, the temperature is 50
In 'C, as shown by the dashed-dotted line, the charging current decreases once from full charge, but increases again and eventually becomes overcharged. This is because the battery temperature further rises due to electrolysis caused by the charging current that flows after full charge, and the battery charging voltage after full charge decreases due to the temperature rise, becoming below the limit voltage and returning to constant voltage charging. This is thought to be because the degree of voltage rise during full charge is somewhat small. On the other hand, at a temperature of 0° C., as shown by the dotted line C, the charging current decreased from the initial stage of charging, resulting in insufficient charging. This is because the battery charging voltage had reached the limiting potential from the beginning of charging, resulting in constant voltage charging from the beginning.

In addition, cadmium oxide is used as an active material, and 0.5 to 1% indium oxide is added to cadmium oxide, and an active material paste made by kneading these with a glue is applied to the current collector. A sealed nickel-cadmium storage battery (Battery D of the present invention) similar to Battery A of the present invention was made except that the cadmium cathode of the PACE 1~ type prepared by the above method was used.

Furthermore, a sealed nickel-cadmium storage battery (Battery E of the present invention) similar to the battery of the present invention was prepared except that 0.2 to 5% by weight of zinc oxide was added to the cadmium oxide instead of indium oxide.

These two batteries each have 10 Ri! Space rate (0
, IC>, the rise of the battery charging voltage at full charge increased by 200 to 250 mV compared to the case where no indium oxide or zinc oxide was added.

Next, these batteries, E, and the above battery A under the conditions shown in Table 3.
As in the case of , C, constant current constant voltage charging tests 1 to 1 were conducted.

As a result of the test, the charging current showed the change shown by the solid line C in FIG. 2 at all temperatures of 0° C., 20° C., and 50° C., and normal charging was possible in all cases.

<Effects of the Invention> According to the alkaline storage battery of the present invention configured as described above, since the rise of the battery charging voltage at full charge can be increased, voltage changes at full charge can be easily and reliably detected, which is different from conventional Constant-current, constant-voltage charging, which is practically impossible with batteries, can be performed. Further, by adding a metal or a metal compound having a higher hydrogen overvoltage than the cathode active material to the cathode, constant current and constant voltage charging becomes possible over a wide temperature range.

Furthermore, since the actual capacity of the cathode can be significantly reduced compared to conventional batteries, it is possible to increase the battery charging voltage and provide a battery with good volumetric efficiency.

[Brief explanation of drawings]

Figure 1 is a graph showing typical changes in charging current when the battery of the present invention is charged with constant current and voltage, and Figure 2 is a graph showing changes in charging current when the environmental temperature during charging is changed. The graphs shown in Figures 3 (^), (B) and Figure 4 are schematic diagrams of the electrode plate bodies of the battery of the present invention and the conventional battery, and Figure 5 is a graph showing changes in charging voltage of the conventional battery. FIG. 6 is a graph similarly showing changes in electrode potential. Fig. 1 Fig. 2 Amount of electricity (%) Fig. 3 Fig. 4 Fig. 5 1111%) Amount of electricity (%)

Claims (1)

[Scope of Claims] 1. An electrolyte amount-limiting type battery in which the amount of electrolyte is limited so that there is substantially no free electrolyte in the battery, and the uncharged capacity of the cathode in a discharged state is equal to the uncharged capacity of the anode. A sealed alkaline storage battery characterized by being configured to be substantially smaller than its capacity. 2. The sealed alkaline storage battery according to claim 1, wherein a metal or a metal compound having a higher hydrogen overvoltage than the cathode active material is added to and contained in the cathode.