JPS5910544B2 - sealed storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealed storage battery, and more particularly to a sealed storage battery equipped with an auxiliary electrode for absorbing hydrogen gas and an oxidizer electrode.

Conventional sealed storage batteries, especially nickel-zinc storage batteries and nickel-cadmium storage batteries, generate hydrogen gas during charging and discharging and self-discharge, and also generate a large amount of oxygen gas during overcharging, causing an increase in internal pressure and damage to the container. There were various problems such as expansion of the battery, failure due to leakage of electrolyte, etc.

The behavior of storage batteries during charging, overcharging, and discharging will be explained using a nickel-zinc battery as an example. Generally, the electrode capacity of the cathode (Zn electrode) is about twice that of the anode (NiO0H).
Since the electrode potential of the z1 electrode is less noble than the hydrogen generation potential,
Spontaneous generation of hydrogen from the Zn electrode cannot be avoided. During charging, the potential becomes even more base, so the rate of hydrogen generation becomes even greater, and the amount of hydrogen accumulated becomes larger.
When the anode reaches about 80% charge, oxygen gas is generated,
If the battery continues to be charged and becomes overcharged, the amount of oxygen gas generated increases rapidly. This oxygen is usually chemically absorbed by the cathode through the reaction of Zn+Ko2→ZnO, so that the oxygen is eventually absorbed and used up. In the Zn electrode, the Zn regenerated during overcharging is consumed in the above reaction, so the capacity balance is not disturbed. On the other hand, since hydrogen cannot be absorbed by anything, a means is needed to absorb it and lower the battery content. Furthermore, oxygen gas generated during overcharging causes a decrease in battery capacity and the formation of andrite, which deteriorates battery performance such as a decrease in cycle life. Therefore, in order to improve battery performance, it is necessary to suppress the pressure increase inside the battery due to hydrogen gas generation during charging and discharging and self-discharge, and to detect overcharging before or at the same time as oxygen gas generation. It was hot.

Therefore, in order to prevent problems caused by hydrogen gas accumulation in sealed storage batteries, methods of absorbing hydrogen gas within the battery are being considered.For example, attempts have been made to absorb hydrogen gas within the battery using the following methods. ing.

(1) Method of chemically combining hydrogen gas and oxygen gas at a ratio of 2 x 1 using a gas phase catalyst and returning it to water (2) Method of chemically absorbing only hydrogen gas (3) Metal hydride (4) Method of electrochemically returning water using an auxiliary electrode However, in the case of (1), the consumption rate is slow and the catalyst easily gets wet with the electrolyte and produced water, resulting in a rapid loss of absorption capacity. easy to lose.

Moreover, when the amount of oxygen gas is less than the stoichiometric composition, hydrogen gas is not completely consumed and gradually accumulates in the cell. In the cases of (2) and (3), the amount of filling is limited because the space for storing the absorbent is limited. Furthermore, as hydrogen absorption progresses, the amount absorbed gradually becomes saturated and the absorption rate gradually decreases. Moreover, the amount and rate of absorption are strongly influenced by temperature. Furthermore, in the case of (4), there was a problem that the anode capacity was lost due to overcharging or polarity reversal, and the hydrogen gas absorption ability was lost when a large amount of hydrogen gas was generated.
Sealed storage batteries generate a large amount of oxygen gas when overcharged, causing various problems such as an increase in the internal pressure of the battery, expansion of the container, and failures due to electrolyte leakage.

Conventionally, in order to eliminate such a problem, the following method is known as a method for detecting overcharging after charging is completed. Known methods include (1) a battery voltage detection method, (2) a coulometer method that memorizes the amount of energization, (3) a detection method based on a rise in battery temperature or catalyst temperature, and (4) a detection method based on a change in electrolyte specific gravity. .

However, all of the above methods had large detection errors and were not practically satisfactory. For example, in a battery voltage detection method that detects overcharging by detecting the terminal voltage of a storage battery at the end of charging, it is difficult to maintain a constant terminal voltage due to changes in battery internal resistance, temperature changes due to heat generation during charging, etc. It was difficult to detect. As described above, conventionally, there has been no sealed storage battery that can obtain stable hydrogen gas absorption over many charge/discharge cycles and can accurately detect overcharging. In view of the above points, the present invention efficiently absorbs hydrogen gas, and can withstand many charge/discharge cycles without causing an increase in battery internal pressure, expansion of the battery can, or leakage of electrolyte, and is designed to absorb hydrogen gas efficiently without causing any increase in battery internal pressure, expansion of the battery can, or electrolyte leakage. An object of the present invention is to provide a sealed battery that can accurately detect overcharging without being affected by currents or the like.

The present invention includes a cathode, an anode, a separator interposed between the cathode and the anode, a waterproofed auxiliary electrode for absorbing hydrogen gas, and a connection to the auxiliary electrode via a nonlinear resistor and a fixed resistor. an oxidizing agent electrode made of a positive electrode active material; a container in which the cathode, anode, separator, auxiliary electrode, and oxidizing agent electrode are sealed; an anode terminal connected to the anode and led out of the container; A cathode terminal that is connected and led out of the container, and an oxidizer electrode terminal that is connected to the oxidizer electrode and is electrically conductive with the anode terminal during charging, and is not electrically conductive with the anode terminal during discharge. The battery is a sealed storage battery having an auxiliary electrode terminal connected to the auxiliary electrode and led out of the container. This is a method for detecting overcharge of a sealed storage battery, in which overcharging is detected by detecting a voltage change between an auxiliary electrode terminal and an oxidizer electrode terminal of the sealed storage battery. In the above, the nonlinear resistor is something like a diode that blocks reverse current, and the fixed resistor is one that makes it easy to detect the voltage between the oxidizer electrode terminal and the auxiliary electrode terminal, and that there is enough hydrogen gas in the auxiliary electrode. It is preferable to set the resistance value within the range through which the absorption current flows, for example, about 10 to 2000 Ω.

Furthermore, it is practically preferable to use a fixed resistor of 100 to 500 Ω for single, double AA, and AA types used as small general-purpose batteries. Further, the anode terminal and the cathode terminal can also be used as a lid, a container, etc., respectively.

In other words, in the sealed storage battery according to the present invention as described above, by making the anode terminal and the oxidizer electrode electrically non-conductive during discharging, even if the battery capacity of the anode is exhausted, the capacity of the oxidizer electrode is is retained and hydrogen gas absorption is not interrupted.

In addition, when hydrogen gas is generated from the cathode during overcharging or from the anode reversed due to overdischarge, it is possible to prevent loss of capacity of the oxidizer electrode and drop in electrode potential, allowing continuous absorption of hydrogen gas. . On the other hand, in those without an oxidizer electrode, when the anode and auxiliary electrode are connected through a nonlinear resistor, if the hot water electrode capacity is exhausted, hydrogen gas generated due to overcharging or polarity reversal is absorbed. I couldn't do that. Furthermore, during charging, by making the anode terminal and the oxidizer electrode terminal electrically conductive, the oxidizer auxiliary electrode is charged at the same time as the anode, thereby reducing the capacity of the oxidizer electrode caused by hydrogen gas absorption and self-discharge. It will recover and become able to absorb hydrogen gas again. As long as such an oxidant electrode has a capacity, hydrogen gas absorption will occur regardless of whether or not there is electrical continuity between the anode and the oxidant electrode.

For example, when a nickel compound is used as an anode, the reaction occurs as follows. Furthermore, by interposing a diode and a fixed resistor as nonlinear resistors between the oxidizer electrode and the auxiliary electrode, the auxiliary electrode potential is maintained in a potential range approximately 0.6 base lower than the oxidizer electrode potential. , hydrogen gas is efficiently ionized.

This prevents the auxiliary electrode potential from shifting to the oxygen gas generation potential, thereby preventing deterioration of the auxiliary electrode performance. Additionally, by measuring the voltage between the oxidizer electrode terminal and the hydrogen gas absorption auxiliary electrode terminal during charging and overcharging, the generation of oxygen gas at the end of charging can be confirmed, which makes it possible to detect the end of charging. It is.

In other words, during charging, the gas absorption auxiliary electrode is polarized in the base direction with respect to the oxidizer electrode potential, and the hydrogen gas generated by charging and discharging and self-discharge is electrochemically oxidized and the hydrogen absorption current H
2+20H→2H20+2e flows. However, during overcharging, the catalyst on the gas absorption auxiliary electrode is chemically oxidized due to the generation of oxygen gas, and the hydrogen gas absorption reaction that has been taking place thus far is stopped, and the hydrogen pressure begins to rise. Due to the oxidation of the catalyst, the potential of the gas absorption auxiliary electrode increases, and the voltage between the anode and the gas absorption auxiliary electrode rapidly decreases. Note that when charging is interrupted, most of the oxygen gas is absorbed by the cathode, and the potential of the gas absorption auxiliary electrode rapidly recovers. Therefore, by measuring the voltage between the oxidizer electrode and the gas absorption auxiliary electrode, a sudden voltage drop due to the generation of oxygen gas during overcharging can be detected, thereby making it possible to detect the end of charging.

Next, a nickel-zinc storage battery will be cited as an example of the sealed storage battery according to the invention, and the invention will be described in detail with reference to FIG.

, the above-mentioned sealed storage battery is configured as follows, for example.

In this power generation section, a sintered anode 1 mainly composed of a nickel compound and a cathode 2 mainly composed of a zinc compound are laminated with a separator 3 (also serving as an electrolyte holding layer) interposed therebetween. It has a spiral structure. This power generation section is housed, for example, in a metal container 7, which is open at one end and also serves as a cathode terminal, via a heat-shrinkable tube 9 having electrical insulation. The anode lead 4 is connected to a lid 6 which also serves as an anode terminal, and the cathode lead 5 is connected to a metal container 7 which also serves as a cathode terminal. The lid, which also serves as the anode terminal 6, is sealed and attached to the opening of the metal container 7, which also serves as the cathode terminal, via an electrical insulating material 8. In addition, an oxidizer electrode 11 and a waterproof auxiliary electrode 10 for absorbing hydrogen gas are provided in the air core through a separator 3, and a silicon diode as a nonlinear resistor 12 and a fixed resistor 13 are for absorbing hydrogen gas. The auxiliary electrode 10 and the oxidizer electrode 11 are connected in series. Note that the oxidizer electrode lead 14 is connected to the lid 6 which also serves as an anode terminal.
It is connected to an oxidizer electrode terminal 15 provided through an electrolyte-resistant insulating resin layer. In addition, the auxiliary pole lead 16
is connected to an auxiliary electrode terminal 17 provided on the lid body 6 which also serves as an anode terminal via an electrolyte-resistant insulating resin layer. In the case of a single-type nickel-zinc storage battery, the gas absorption auxiliary electrode 10 has an apparent surface area of 5cr11 and a thickness of Q. 3llI
A porous nickel sintered body of T was used, impregnated with platinum as a hydrogen gas absorption catalyst, and bound with polytetrafluoroethylene for waterproofing. The oxidizer electrode 11 is a sintered nickel electrode with the same composition as the nickel anode, with a thickness of 0.7 m and an apparent surface area of 4 C! It(2
I used one from Recruit x 2. Further, the silicon diode fixed resistor 13 as the nonlinear resistor 12, the oxidizing agent electrode lead 14, and the auxiliary electrode lead 16 are each coated with an electrically insulating and electrolyte-resistant resin, such as an epoxy resin. . Figure 2 shows the charging current of 300 mA for 15 hours in the above-mentioned nickel-zinc storage battery.

5Ah], a discharge current of 600mA, and a discharge stop of 1V were measured at intervals of 2 hours.
The solid line indicates the pressure inside the battery (open circuit) during charge/discharge cycles.

Note that the oxidizer electrode terminal 15 and the anode terminal 6 were electrically conductive during charging, and were non-conductive during discharging and opening. In this embodiment, as the fixed resistor 13, 10
A 0Ω resistor was used. Furthermore, in order to clarify the effects of the present invention, the inside of the battery when charging and discharging was performed under the same conditions as above while keeping the oxidizer electrode terminal 15 and the anode terminal 6 electrically non-conducting. The pressure at is shown by the dashed line. As is clear from FIG. 2, the hydrogen gas absorption effect in the battery of the present invention is as follows:
When charging and discharging are repeated many times (after 100 cycles in this example), compared to the case where charging and discharging are performed while the oxidizer electrode terminal 15 and the anode terminal 6 are electrically disconnected, The effect is remarkable.

That is, in the present invention, the oxidizer electrode is charged every time it is charged and the oxidizer electrode recovers its capacity, so that hydrogen gas absorption is efficiently performed.

On the other hand, if charging and discharging are repeated with the oxidizer electrode terminal 15 and the anode terminal 6 electrically disconnected, the oxidizer electrode capacity gradually decreases due to hydrogen gas absorption and self-discharge, and the point at which the capacity is lost is reached. At this point, hydrogen gas absorption stops and hydrogen gas gradually accumulates inside the battery.

In this example, it is clearly shown that the hydrogen gas absorption ability stops after 100 cycles due to loss of oxidant electrode capacity. Next, hydrogen gas enters the battery during overdischarge or polarity reversal.
When the atmospheric pressure had accumulated, the circuit was opened and the internal pressure of the battery was measured. The results are shown in Figure 3.

The solid line shows the case where the sealed zinc-alkaline secondary battery according to the present invention is used, and the broken line shows the case where the oxidizer electrode terminal 15 and the anode terminal 6 remain electrically connected during the charge/discharge cycle. This is the result.

In the present invention, since the oxidizing agent electrode is electrically independent from the anode, even if the anode is over-discharged or polarized, the oxidizing agent electrode will not be over-discharged or polarized.

That is, since the oxidizer electrode capacity is maintained, the generated hydrogen gas (,) is continuously absorbed. When discharged or polarized, the oxidizer electrode is also over-discharged or reversed along with the anode, so when the anode capacity is lost, the oxidizer electrode capacity is also lost and its electrode potential drops.For this reason, hydrogen gas is effectively That is, the present invention allows the oxidant electrode terminal 15 and the anode terminal 6 to be connected each time charging is performed.
Since the oxidizer electrode can be charged by electrically conducting the
No cessation of hydrogen gas absorption occurs.

Furthermore, by making the oxidizing agent electrode terminal 15 and the anode terminal 6 electrically non-conductive when the circuit is opened during discharge, overdischarge or polarity reversal of the oxidizing agent electrode does not occur, so that the generated hydrogen gas continues. and is absorbed. As described above, in order to absorb hydrogen gas, a hydrogen absorption auxiliary electrode and an oxidizing agent electrode are provided, the auxiliary electrode is electrically connected to the nonlinear resistor and the fixed resistor, and furthermore, the anode and the oxidizing agent electrode are provided. The present invention is intended to be electrically conductive (short-circuited) only when charging, and electrically non-conductive when discharging or opening. It is generally applicable.

In the above embodiment, conduction and disconnection between the oxidizer electrode and the anode during charging and discharging was performed using a switch, but it goes without saying that the configuration can be changed as appropriate if the desired effect is obtained. Furthermore, when applying the present invention to other storage batteries, it is desirable that the anode and oxidizer electrode of the storage battery have the same composition.

For example, in the case of a lead-acid battery, a lead dioxide oxidizer electrode is used, and in the case of a silver-zinc oxide battery, a silver oxide oxidizer electrode is used. By making the oxidizer electrode composition the same as the anode composition in this manner, gas generation from either electrode can be prevented during charging, and both electrodes can be brought into a similar charged state.

Next, an overcharge detection method characterized by detecting oxygen gas generated during overcharge will be described using examples.

First, Figure 4 shows the anode-to-cathode voltage El2 (Figure 4-1a), the oxidizer electrode-auxiliary electrode voltage E,3 (Figure 4-b), and the battery internal voltage with respect to the charging time when charging at 300 mA. The change in pressure (Fig. 4-c) is shown.

In Fig. 4-a, A1 to A2 show changes in E,2 during charging, and during this time hydrogen gas is generated, but due to the good hydrogen gas absorption of the gas absorption auxiliary electrode, Fig. 4-C (7) C1
As shown in C2, almost no change in the internal pressure of the battery was observed. Further, the voltage increase of A2 to A3 indicates the progress of overcharging. At A3, most of the charging current is used for oxygen gas generation, and at this time, oxygen gas generation from the anode rapidly increases, as shown in Figure 4-
As shown in CO)C3, the pressure inside the battery rises rapidly.
Further, in FIG. 4-b showing El3, a rapid voltage drop is seen from B2. This is because the potential of the gas absorption auxiliary electrode is polarized in the noble direction at the same time as oxygen gas is generated. In Naori 4, most of the oxygen gas is absorbed by the cathode, and El3 rapidly recovers again. FIG. 5 shows E, 2 and El3 with respect to charging time when the environmental temperature is changed.

As a result, the rate of change in El2 during overcharging is significantly affected by the environmental temperature, and the higher the temperature is, the smaller the change (voltage rise) becomes, making it difficult to detect overcharge. However, the rate of change of E,3 is not affected by changes in environmental temperature and shows a rapid change (voltage drop) during overcharging, allowing accurate detection of overcharging. Figure 6 shows when the charging current is changed,
Further, FIG. 7 shows El2 and E,3 with respect to charging time when the number of charging/discharging cycles is changed.

As a result, El2 is significantly affected by the lowest battery capacity due to changes in charge current and number of charge/discharge cycles, increase in internal resistance, etc., making it difficult to detect overcharge. On the other hand, El3 shows a sudden change (voltage drop) during overcharging, and overcharging can be reliably detected. As described above, the change in the voltage E,2 between the anode and cathode terminals is affected by the environmental temperature, charging current, number of charging/discharging cycles, etc., and it has been difficult to detect overcharging.

On the other hand, by measuring the voltage between the auxiliary electrode terminal, which is the third electrode provided according to the present invention, and the oxidizer electrode, overcharging can be easily detected without being affected by the above conditions. Next, the change in battery capacity when a sealed storage battery as shown in Fig. 1 is repeatedly charged and discharged to prevent overcharging (curve a in Fig. 8), charging at 300 mA for 5 hours, discharging at 600 mA,
Battery capacity when constant current constant time charging and discharging are repeated with 2 hour intervals between each cycle of discharge stop (8th
A comparison with curve b) is shown in FIG.

In other words, when the sealed storage battery according to the present invention was used, there was less deterioration in battery capacity and the cycle life was significantly improved compared to the conventional constant current constant time battery. As described above, by using the sealed storage battery according to the present invention, hydrogen gas can be efficiently absorbed, and even after many charge/discharge cycles, there will be no increase in internal pressure of the battery, expansion of the battery can, leakage of electrolyte, etc. Moreover, overcharging can be accurately detected without being affected by environmental temperature, charging current, etc.

As the charging circuit used in the present invention, for example, one shown in a schematic diagram as shown in FIG. 9 is used. That is, anode terminal 6
and a voltage recorder 1 between the metal container 7 which also serves as a cathode terminal.
8 and a charging source 19, and a voltage recorder 20 is connected between the anode terminal 6 and the auxiliary electrode terminal 7. Furthermore, a switch 2 is connected between the anode terminal 6 and the oxidizer electrode terminal 15.
1 is provided, and this switch 21 is made conductive during charging and non-conductive during discharging. As a result, the voltage change between the oxidizer electrode terminal 15 and the auxiliary electrode terminal 7 during charging is measured by the voltmeter 20. However, the 9th
The figure shows an example of a charging circuit, and it goes without saying that any circuit having the required functions can be used in the present invention.

[Brief explanation of the drawing]

1 and 9 are explanatory diagrams showing configuration examples of a sealed storage battery and its overcharge detection device according to the present invention, and FIGS. 2 to 8 are curve diagrams showing various characteristics of the embodiment according to the present invention. . In the figure, 1... Anode, 2...
・Cathode, 3... Separator, G... Anode terminal (also serves as lid) 7... Container (also serves as cathode terminal), 10... Auxiliary electrode , 11... Oxidizer electrode, 12... Nonlinear resistor, 13...
... Fixed resistor, 15 ... Oxidizer electrode terminal, 1
7...Auxiliary pole terminal.

Claims (1)

[Claims] 1 a cathode, an anode, a separator interposed between the cathode and the anode, a waterproofed auxiliary electrode for absorbing hydrogen gas, and the auxiliary electrode connected to the auxiliary electrode via a nonlinear resistor and a fixed resistor. an oxidizing agent electrode made of an anode active material constituting an anode; a container in which the cathode, anode, separator, auxiliary electrode, and oxidizing agent electrode are hermetically sealed; a cathode terminal connected to the cathode and led out of the container; An anode terminal connected to the anode and led out of the container, and an anode terminal connected to the oxidizing agent electrode to be electrically conductive with the anode terminal during charging and non-conductive with the anode terminal during discharge. What is claimed is: 1. A sealed storage battery comprising: an oxidizing agent electrode terminal; and an auxiliary electrode terminal connected to the auxiliary electrode and led out of the container.