JP3013623B2 - Sealed lead-acid battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a cycle type sealed lead-acid battery such as an electric vehicle.

[0002]

2. Description of the Related Art Sealed lead-acid batteries are widely used because they are relatively inexpensive and have stable performance as maintenance-free secondary batteries using a trickle such as for a starter of an automobile. In recent years, it has also become widespread as a portable power supply for use in portable devices and electric vehicles, and a stationary power supply used as a backup for computers and the like.

[0003] Recently, electric vehicles have been spotlighted as non-pollution measures for vehicles, and demands for higher performance of inexpensive sealed lead-acid batteries as power sources have been increasing. However, long life and high energy density are particularly important issues for improving the performance of lead storage batteries.

[0004] These problems largely depend on the active material, particularly the positive electrode active material. One of the causes of the short life is that the charge-discharge cycle deteriorates the binding property between the positive electrode active material particles, so that the softening and falling off of the active material progresses and the conductivity between the active materials decreases. . On the other hand, one of the causes of the low energy density of the lead storage battery is a low utilization rate of the positive electrode active material. The positive electrode discharge reaction is a reaction between PbO ₂ and H ₂ SO ₄ as shown in the following equation: PbO ₂ + 4H + 2e + SO ₄ ^2- → PbSO ₄ + 2H ₂
The easiness of the movement of the O ² SO ₄ ²⁻ ion is important for improving the utilization rate of the positive electrode.

[0005] For these reasons, it is desired to improve the positive electrode active material for improving the charge / discharge cycle characteristics and increasing the energy density.

The active material of the positive electrode of the lead-acid battery is prepared by mixing a lead powder as a raw material, together with an additive, with dilute sulfuric acid or other kneading solution, stirring to form a paste, filling the paste into a grid, and filling the grid. A non-chemically activated material is produced through the steps of aging and drying, and the positive electrode active material is converted to lead dioxide (Pb
O ₂ ).

The size and shape of the particles of the positive electrode active material are as follows:
It is greatly influenced by unchemically activated materials. The main component of the composition of the conventional unformed active material is tribasic lead sulfate, the crystal particle size is about 1 μm, and the type is columnar, and it was formed from this tribasic lead sulfate. Lead dioxide has fine particles and high reactivity.

On the other hand, attempts to improve the cycle characteristics by adding a tin compound to the positive electrode active material have been made, for example, in Japanese Patent Application Laid-Open No.
This is described in JP-A-4-49538 and JP-A-54-60429.

[0009]

As described above, since the unactivated chemical active material containing tribasic lead sulfate as a main component has high reactivity, softening and falling off of active material particles due to charge / discharge cycles progress. Therefore, the corrosion reaction between the active material and the lattice interface is likely to occur at the same time, so that the conductivity of the lattice interface is reduced and the charge / discharge cycle life is shortened.

On the other hand, when a tin compound such as stannous sulfate or stannic oxide is added to the positive electrode active material, the cycle life is prolonged, but there is a disadvantage that the capacity is reduced after long-term storage.

In view of the above problems, the present invention improves the utilization rate of a positive electrode active material, suppresses the formation of a passive layer at a lattice interface, and prolongs cycle life and recovers capacity after long-term storage. It is an object of the present invention to provide an improved sealed lead-acid battery.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a sealed lead-acid battery according to the present invention comprises a stannic oxide in a positive electrode active material, in particular, an unformed active material mainly containing tetrabasic lead sulfate. (SnO ₂ ) and stannous sulfate (SnSO ₄ ) are added in a total amount of 0.01 to 5 wt% based on the total amount of the positive electrode active material, and a tin compound of stannic oxide (stannic oxide and tin oxide) is used. This is a sealed lead-acid battery using, as a positive electrode, one added in a ratio of 5 to 20 wt% relative to the total amount of stannous sulfate.

[0013]

By adding stannic oxide and stannous sulfate to the positive electrode active material, passivation can be prevented because stannic oxide, which is a conductor, is mixed in lead sulfate generated after discharge. It is possible to suppress the deterioration of the battery, extend the cycle life, and improve the recoverability after long-term storage. In addition, by using a positive electrode active material obtained by forming an unformed active material containing tetrabasic lead sulfate having a larger particle shape (secondary aggregate) than tribasic lead sulfate, secondary tetrabasic lead sulfate can be obtained. Since the crystal size of the aggregate is more than 10 μm, which is larger than that of tribasic lead sulfate, when oxidized during chemical formation, a fine 1 It becomes large lead dioxide as an aggregate of the secondary particles. For this reason, the positive electrode active material made of tetrabasic lead sulfate has a more dense arrangement of the primary particles of the positive electrode active material than the positive electrode active material made of tribasic lead sulfate. Low diffusivity and low reactivity. Therefore, softening and falling off of the active material due to charge / discharge cycles are suppressed, and cycle characteristics are improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A sealed lead-acid battery according to one embodiment of the present invention will be described below with reference to the drawings. The electrode plate of a sealed lead-acid battery has a total weight of 1 w of all tin compounds added to a predetermined amount of lead powder.
0.1 wt% of stannic oxide and 0.9 wt% of stannous sulfate were added so as to be t%, and stirred. This is kneaded at 80 ° C. for 20 minutes while dropping water and dilute sulfuric acid according to a conventional method,
A positive electrode paste mainly composed of tetrabasic lead sulfate containing stannic oxide and stannous sulfate was prepared and filled in a casting lattice of a Pb-Ca alloy to obtain a positive electrode plate.

The above two positive electrode plates and three negative electrode plates are combined with a mat-shaped separator made of glass fiber interposed therebetween, and impregnated with dilute sulfuric acid as an electrolyte to have a nominal capacity of 2 Ah (10 hour rate). A 2V battery was produced.

The battery was charged at 200 mA and discharged at 6 mA.
A charge / discharge cycle test was performed with a constant current charge / discharge of 00 mA.
The battery capacity and charge / discharge cycle life were measured. The discharge end voltage was 1.75 V, the amount of charged electricity was 120% of the amount of discharged electricity, and the charge / discharge cycle life was 1 Ah.
Was reached. Further, the battery of this example and various batteries produced under the above-mentioned conditions while keeping the weight of the active material of the positive electrode shown in Table 1 constant were stored in a constant temperature room at 40 ° C. for 2 months.
The capacity was checked at a constant current discharge of 00 mA, and after storage, the battery characteristics were examined.

[0017]

[Table 1]

The initial capacity of the conventional battery (having tribasic lead sulfate as a main component and not containing a tin compound) was 1.75 Ah, but in this embodiment, the capacity was improved to 2.00 Ah. Stannic oxide (SnO ₂ ) or stannous sulfate (SnS)
The effect of adding only O ₄ ) to the positive electrode active material at 1 wt% was also observed, but was not sufficient. In this example, the cycle life was 520 cycles, and the residual capacity after discharge was 86%, both of which were superior to the conventional battery and the battery containing only the tin compound.
Also, a mixture of 0.1 wt% of stannic oxide and 0.9 wt% of stannous sulfate mixed with a positive electrode active material obtained by chemical conversion of an unchemical conversion material containing tribasic lead sulfate as a main component (Table 1) As is clear, it was found to be superior to the conventional battery. As an improvement factor, passivation due to lead sulfate (PbSO ₄ ) generated at the time of discharge by adding stannic oxide and stannous sulfate to the positive electrode active material is mixed with stannic oxide, which is a conductor. It is considered that self-discharge was further suppressed.

FIG. 1 shows the amounts of stannic oxide and stannous sulfate to be added to the positive electrode active material obtained by forming an unformed active material containing tetrabasic lead sulfate as a main component. The battery characteristics when the weight ratio of stannous sulfate is fixed at 1: 9) are shown.

A charge / discharge cycle test was performed on these batteries at a constant current charge / discharge of 200 mA for charging and 600 mA for discharging, and the capacity of each battery and the charge / discharge cycle life were measured.
The discharge end voltage is 1.75 V, the amount of charge is 120% of the amount of discharge, and the cycle life is 1 Ah.
Was reached. In a constant temperature room at 40 ° C, 2
After storage for a month, the capacity was checked by discharging at a constant current of 600 mA, and the self-discharge during storage was examined.

FIG. 1 shows that the discharge capacity increases as the addition amount of the tin compound increases. However, when the addition amount was 5 wt% or more, almost no difference in capacity was observed, and even when the addition amount was 0.01 wt% or less, there was no difference in capacity from the conventional battery. Further, the addition amount is 0.01 to 5 in the cycle life.
It was found that the range of wt% was longer than that of the conventional battery without tin compound added. However, when the addition amount was 6 wt%, the charge / discharge cycle life was 380 cycles, which was shorter than that of the conventional battery. Further, when the tin compound was added, the storage characteristics were improved as the amount of addition increased, but the storage rate was the highest at 1 wt%, and was equivalent to that of the conventional battery with no addition at 7 wt%. Therefore, it was found that the best addition amount was in the range of 0.01 to 5 wt%.

On the other hand, FIG. 2 shows cycle life characteristics when the total amount of stannic oxide and stannous sulfate is fixed at 2 wt% and the mixing ratio of stannic oxide and stannous sulfate is changed. From this result, there is a region where the ratio of stannic oxide to the total tin compound (stannic oxide and stannous sulfate) is 5 to 20 wt% and the cycle characteristics are improved as compared with the case where each tin compound is added alone. I understand. The reason for this is that by mixing a small amount of stannic oxide, which is a conductor, into stannous sulfate, passivation due to the formation of lead sulfate can be prevented from the beginning of the reaction, and the crystal size of lead sulfate can be suppressed to a small value. It is considered that the cycle characteristics are extended.

[0023]

As described above, according to the structure of the present invention, the initial capacity is improved, the cycle life is extended, and the capacity deterioration after standing is small. Furthermore, it was effective in suppressing the influence on the cycle life due to the charge / discharge conditions.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of a tin compound in a positive electrode active material and battery characteristics.

FIG. 2 is a diagram showing the relationship between the mixing ratio of stannic oxide and stannous sulfate and cycle life characteristics.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Miyuki Toyoda 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-54-50839 (JP, A) JP-A-51- 47233 (JP, A) JP-A-59-167959 (JP, A) JP-A-4-14758 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/14, 4 / 57,4 / 62

Claims (2)

(57) [Claims] 1. A sealed lead-acid battery characterized in that stannic oxide and stannous sulfate are added to a positive electrode active material. 2. The total amount of stannic oxide and stannous sulfate added to an unformed active material containing tetrabasic lead sulfate as a main component is 0.01 to 0.01% based on the total amount of the positive electrode active material. 5 wt%,
The ratio of stannic oxide to the total amount of tin compound added is 5 to 20.
The sealed lead-acid battery according to claim 1, wherein the content is wt%.