JPH05166540A - Method for charging secondary battery - Google Patents

Abstract

PURPOSE:To provide a safe method for charging a sealed secondary battery having a long charge and discharge cycle life whereby generation of gas during charging can be restrained together with swelling of the battery due to sealing during charging. CONSTITUTION:An aqueous solution type secondary battery having manganese- dioxide-zinc as active materials and zinc sulfate as main electrolyte is charged at a properly set charging voltage of 1.55 to 1.95V per single cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging an aqueous secondary battery using manganese dioxide as a positive electrode active material, zinc as a negative electrode active material, and an aqueous solution containing zinc sulfate as a main electrolyte as an electrolyte.

[0002]

2. Description of the Related Art Conventionally, batteries have been widely used as a power source for electronic devices and electric devices. 2. Description of the Related Art Recently, demand for secondary batteries that can be used for a long time and that is economical is rapidly increasing with miniaturization and high performance of various electronic devices and electric devices, making them portable, and personalization.

From this point of view, a manganese dioxide-zinc battery using manganese dioxide as the positive electrode active material and zinc as the negative electrode active material, which is particularly economical, has been studied as a secondary battery (Japanese Patent Laid-Open No. Sho 61-61). -248370).

However, in a secondary battery using an aqueous solution as an electrolytic solution, water present in the system is generally electrolyzed at the end of charging or overcharge, and the internal pressure of the battery sealed by the generated gas rises. However, problems such as rupture and liquid leakage occur, and various methods have been attempted for sealing the battery and preventing internal pressure rise.

That is, the method is a so-called Neumann method in which the electric capacity of the positive electrode is designed to be smaller than the electric capacity of the negative electrode, the only gas generated is oxygen from the positive electrode, and this oxygen gas is absorbed by the negative electrode.

[0006]

However, for example, as can be seen from the Ni-Cd secondary battery, the negative electrode capacity is set equal to the positive electrode capacity 2 in order to apply the Neumann method.
There is a problem that the discharge capacity of the battery cannot be designed to be large because it needs to be designed more than twice, and it has a drawback that a complicated charger is required because it is difficult to detect the end of charging. In addition, a separator that prevents an internal short circuit between the positive electrode and the negative electrode is indispensable for the battery, and that separator affects the diffusion of oxygen gas, making it difficult to absorb oxygen gas efficiently and preventing the internal pressure from rising during rapid charging. Had the drawback that it was not done enough.

Since the manganese dioxide-zinc secondary battery is also a secondary battery which uses an aqueous solution as an electrolytic solution, the above problems have occurred, but the method for solving this problem has not yet been implemented. there were.

The present invention has been made in view of the above problems, and an object thereof is an aqueous solution system using an aqueous solution containing manganese dioxide as a positive electrode active material, zinc as a negative electrode active material, and zinc sulfate as a main electrolyte as an electrolytic solution. It is an object of the present invention to provide a highly safe secondary battery charging method by preventing gas generation during charging in a secondary battery, thereby suppressing an increase in internal pressure of the battery due to charging.

[0009]

In order to solve the above problems, the present inventors have used an aqueous solution containing manganese dioxide as a positive electrode active material, zinc as a negative electrode active material, and zinc sulfate as a main electrolyte as an electrolyte. As a result of earnestly studying the method of charging the secondary battery, the inventors have found that the above problems can be solved by setting an appropriate charging voltage, and completed the present invention.

That is, the present invention relates to an aqueous secondary battery using manganese dioxide as a positive electrode active material, zinc as a negative electrode active material, and an aqueous solution containing zinc sulfate as a main electrolyte as an electrolyte.
This is a charging method in which the charging set voltage is 1.55 to 1.95 per unit cell.

The present invention will be described in more detail below.

The present invention is characterized in that when charging a manganese dioxide-zinc secondary battery, the charge set voltage range is 1.55 to 1.95 V per unit cell. If it is less than 1.55, it takes a long time to complete the charging, and if the charging set voltage exceeds 1.95V, it may exceed the electrolysis voltage of water including overvoltage and the charging efficiency of the positive electrode may decrease. . In the present invention, in order to further prevent gas generation during charging and suppress an increase in internal pressure of the battery, the charge setting voltage is 1.6 per unit cell.
It is particularly preferable that the voltage is 0 to 1.75V.

In the present invention, the charge setting voltage is 1.5.
The power supply for charging may be any of a constant voltage power supply, a constant current power supply, and a constant power power supply as long as it is in the range of 5 to 1.95 V, and the charging method is a constant voltage charging method. ,
Either a constant current charging method or a charging method composed of a combination thereof may be used. In addition, in order to charge efficiently in a short time, a charging method in which constant current charging is performed up to a set voltage and switching to constant voltage charging after reaching the set voltage is particularly preferable.

The electrolytic solution of the secondary battery of the present invention uses zinc sulfate as the main electrolyte, and its concentration is such that the ionic conductivity is large and the reversibility is maintained without impairing the utilization factor of the positive electrode. 0.5 to 2 mol / l of zinc sulfate for the reason
An aqueous solution containing it is desirable.

Further, the zinc used as the negative electrode active material of the secondary battery of the present invention is not particularly limited, and for example, zinc plate, zinc powder, or an electrode substrate composed of other materials may be plated or plated. Examples thereof include zinc formed by a method such as pressure bonding. Further, a binder used when forming the electrode with zinc powder, for example, a paste-like substance such as sodium polyacrylate may be contained.

Further, as the manganese dioxide used as the positive electrode active material of the secondary battery of the present invention, natural manganese dioxide, chemical manganese dioxide, electrolytic manganese dioxide and the like are used. It is preferred to use high electrolytic manganese dioxide. Also,
These manganese dioxides can be used as they are, but it is preferable to use a mixture of conductive carbon powder such as acetylene black because the conductivity can be improved and the electrolyte retaining property can be improved. Further, such a positive electrode active material is press-molded on a net-shaped current collecting substrate to form a positive electrode, or a thin film is formed by a method such as screen printing,
In order to obtain a positive electrode having an arbitrary shape, a binder or the like may be mixed with these positive electrode active materials and molded.

[0017]

EXAMPLES In order to explain the present invention in more detail, examples will be given below, but the present invention is not limited thereto.

Example 1 SUS430 having a surface area of 12 cm ² and a thickness of 0.3 mm was washed with water and degreased with acetone, then placed in a 2 mol / l zinc sulfate electrolytic bath, and a zinc plate having a purity of 99.9% was used as a counter electrode.
Electrolysis was carried out for 15 hours at a constant current of 0 mA, and zinc was electrodeposited on the SUS430 electrode substrate to give a negative electrode for the battery. When the weight change before and after electrolysis was measured and the zinc electrodeposition efficiency was calculated, it was confirmed that zinc was electrodeposited almost quantitatively. A separator made of glass fiber filter paper and a positive electrode mixture made of 1 g of electrolytic manganese dioxide and 0.3 g of acetylene plaque were placed on the negative electrode, and 3 ml of
A mol / l zinc sulfate aqueous solution was dropped and impregnated. further,
These were placed in an acrylic resin airtight container equipped with a pressure sensor to obtain a sealed battery for measuring internal pressure change during charging. It was confirmed that the electromotive force of this battery was 1.55 V and the internal pressure before the start of measurement was 0 kgf / cm ² .

After discharging this battery at a constant current of 50 mA to a discharge end voltage of 0.3 V, constant voltage charging was performed at a set voltage of 1.6 V for 10 hours, and changes in the internal pressure of the battery and changes in the charging current were measured. Further, after the end of charging, the battery was discharged at a constant current of 50 mA to a discharge end voltage of 0.3 V, the discharge capacity after charging was measured, and the charging efficiency was obtained. At the end of charging, the internal pressure of the battery was 0 kgf / cm ² , and the charging efficiency at this time was 95 kgf / cm ^2.
%Met. Since the internal pressure of the battery did not rise and the charging efficiency was high, it is considered that forced gas generation due to charging did not occur by using the charging method of the present invention.

Example 2 Using a battery manufactured in the same manner as in Example 1, 50 mA was used.
After discharging at a constant current to a discharge end voltage of 0.3 V, constant voltage charging was performed at a set voltage of 1.75 V for 10 hours, and changes in the internal pressure of the battery and changes in the charging current were measured. Further, after the end of charging, the battery was discharged at a constant current of 50 mA to a discharge end voltage of 0.3 V, the discharge capacity after charging was measured, and the charging efficiency was obtained. The internal pressure of the battery at the end of charging was 0 kgf / cm ² , and the charging efficiency at this time was 97%. Since the internal pressure of the battery did not rise and the charging efficiency was high, it is considered that forced gas generation due to charging did not occur by using the charging method of the present invention.

Example 3 A battery manufactured in the same manner as in Example 1 was used to obtain 50 mA.
After discharging at a constant current to a discharge end voltage of 0.3 V, constant voltage charging was performed at a set voltage of 1.9 V for 10 hours, and changes in the internal pressure of the battery and changes in the charging current were measured. Furthermore, after the end of charging, the discharge end voltage was 0. The discharge efficiency after charging was measured by discharging to V. The internal pressure of the battery at the end of charging was 0.5 kgf / cm ² , and the charging efficiency at this time was 81%.

The change in the current value during charging gradually decreased with the passage of the charging time and once approached 0, but the current value slightly increased at the end of charging and showed a steady current. In addition, since the rise in the internal pressure of the battery was observed at the end of charging, forced gas generation did not occur by using this charging method, and the internal pressure of the battery increased due to steady oxygen generation only at the end of charging. Thought to be a thing.

Example 4 A battery manufactured in the same manner as in Example 1 was used to obtain 50 mA.
After discharging at a constant current to a discharge end voltage of 0.3V, charge at 50mA constant current until the battery voltage reaches 1.75V, and then charge at 1.75V constant voltage for 2 hours after the battery voltage reaches 1.75V. The charging / discharging cycle test was performed by the charging method of performing. The charging efficiency with this charging method is 98%,
The internal pressure of the battery at the end of charging was 0 kgf / cm ² . The change in discharge capacity in the charge / discharge cycle test is shown in FIG.
As a result, the battery capacity and charge efficiency were not decreased even after the 200th charge / discharge cycle, and the internal pressure of the battery was hardly increased.

Comparative Example 1 A battery manufactured in the same manner as in Example 1 was used to obtain 50 mA.
After discharging at a constant current to a discharge end voltage of 0.3 V, constant voltage charging was performed at a set voltage of 2.1 V for 10 hours, and changes in the internal pressure of the battery and changes in the charging current were measured. Further, after completion of charging, the battery was discharged at a constant current of 50 mA to a discharge end voltage of 0.3 V, the discharge capacity after charging was measured, and the charging efficiency was obtained.
The internal pressure of the battery at the end of charging was 4.8 kgf / cm ² , and the charging efficiency at this time was 32%. It is considered that the battery internal pressure increased remarkably from the beginning of charging, and most of the charging current was consumed for electrolysis of the electrolytic solution.

Comparative Example 2 Using a battery prepared in the same manner as in Example 1, 50 mA was used.
Discharge end voltage is 0 at constant current. -50 after discharging to V
A charge / discharge cycle test was performed in which the same amount of electricity as the initial amount of electricity discharged was charged at a constant current of mA. The battery voltage at the end of charging reached 2.3V. At the end of charging, the internal pressure of the battery was 0.6 kgf / cm ² , and the charging efficiency was 74%. The internal pressure of the battery accumulated and increased each time the charge / discharge cycle was repeated, and exceeded 10 kgf / cm ² at the 18th cycle.

[0026]

As described above, according to the charging method of the present invention, it is considered that the increase of the internal pressure of the battery can be suppressed because the electrolysis of water does not substantially occur inside the battery. As described above, the manganese dioxide-zinc secondary battery suppresses gas generation at the time of charging by setting an appropriate charging voltage and charging, and suppresses the bulge at the time of charging due to the sealing of the battery. In addition, it has an effect that it can be used as a sealed secondary battery which is safe and has a long charge / discharge cycle life.

[Brief description of drawings]

FIG. 1 is a diagram showing changes in discharge capacity and charge efficiency in a charging / discharging cycle in Example 4.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shintaro Suzuki, 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Co., Ltd.

Claims (1)

[Claims] 1. An aqueous secondary battery using manganese dioxide as a positive electrode active material, zinc as a negative electrode active material, and an aqueous solution containing zinc sulfate as a main electrolyte as an electrolyte has a charge set voltage of 1.55 to 1 per unit cell. A charging method for a secondary battery, wherein the charging method is 0.95.