JPH11176449A - Sealed lead-acid battery - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent an active material from falling off and separating from the surface of a grid when an expanded grid is used as a positive grid. SOLUTION: An expanded lattice is used as a positive electrode lattice for holding an active material of a positive electrode plate, and this lattice is made of a lead-calcium-tin alloy, and an alkali metal such as Li, Na, K is 0.001 to 0.03% by weight. %, The adhesion between the oxide layer formed on the surface of the positive electrode grid and the positive electrode grid is improved to prevent the active material from falling off or peeling off, and the battery capacity is reduced during use of the battery. Suppresses abrupt deterioration and shortening of battery life.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed lead-acid battery.

[0002]

2. Description of the Related Art Conventionally, in a sealed lead-acid battery, a cast grid has been generally used as a positive grid for holding a positive electrode active material. As described above, in the sealed lead-acid battery using the cast grid as the positive grid, the life period, that is, when the battery capacity is continuously used after the period until the battery capacity decreases to a predetermined discharge capacity or less, The positive electrode plate may be elongated due to the oxidative corrosion of the positive electrode grid, and this expansion may cause a problem that the battery case is deformed or damaged. As a countermeasure to solve this problem, an alloy composition for a positive electrode grid having excellent corrosion resistance has been studied, but an alloy capable of significantly improving the corrosion resistance has not yet been developed.

Attention has been paid to the fact that the oxidative corrosion of the casting grid in the positive electrode is mainly due to intergranular corrosion of the casting grid, and a slit is formed in a lead alloy sheet produced by rolling to develop a grid. A so-called expanded lattice has been proposed. The expanded lattice has a lamellar rolled structure, and is excellent in corrosion resistance as compared with the cast lattice because the crystal grain boundaries causing corrosion are dispersed. In addition, in the expanded grid, the stress generated when the grid is expanded remains in the grid and may be corroded by the residual stress.However, the elongation force due to the corrosion is larger than that of the cast grid. Since the battery case is small and the intergranular corrosion is reduced, the battery case is hardly deformed or broken due to the expansion of the expanded grid, and is superior to the case of the cast grid.

[0004]

SUMMARY OF THE INVENTION In a conventional sealed lead-acid battery using an expanded grid as a positive grid,
Since the expansion of the expanded grid due to oxidative corrosion is smaller than that of the cast grid, there is an advantage that the battery case is less likely to be deformed or damaged by the grid expansion, but the expanded grid is larger than the cast grid. However, there is a problem in that the adhesion between the oxide and the lattice generated by oxidative corrosion is reduced, and the capacity is suddenly reduced during use of the battery due to dropping or peeling off of the active material, leading to a long life.

[0005]

In order to solve the above-mentioned problems, the present invention comprises a positive electrode plate, a negative electrode plate, and an electrode plate group comprising a separator interposed between these electrode plates and holding an electrolytic solution, The positive grid holding the active material of the positive plate,
An expanded lattice formed of a lead-calcium-tin alloy containing an alkali metal is used.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Expanded grids obtained by slitting rolled sheets of lead-calcium-tin alloy have been generally used as negative grids of sealed lead-acid batteries. When such an expanded lattice is used as the lattice of the positive electrode plate, grain boundaries in the lattice are dispersed by rolling, so that there is a property that intergranular corrosion hardly occurs.

However, on the other hand, the very surface of the grid is easily oxidized and corroded along the rolling structure parallel to the rolling direction. As a result, an oxide layer having a substantially uniform thickness is formed on the surface of the grid. The material layer easily falls off the surface of the grid,
In particular, the tendency is remarkable in a lattice formed of a lead-calcium alloy. If a gap is formed at the interface between the surface of the positive electrode grid and the oxide layer on the surface, the active material may fall off from the grid, causing a sudden drop in capacity during the use of the battery, leading to a long service life. was there.

The interface between the oxide layer formed on the surface of the positive electrode lattice formed of the rolled lead-calcium alloy and the lattice is smooth and easily peeled off, but slightly exists in the rolled structure of the lattice. If oxidative corrosion can proceed at the crystal grain boundaries, the oxide layer is formed so as to bite into the lattice surface, so that the adhesion between the lattice surface and the oxide layer is improved.

[0009] By adding a small amount of alkali metal to the lead-calcium-tin alloy forming the positive electrode lattice, the alkali metal-rich phase precipitated at the grain boundaries existing in the rolled structure is preferentially subjected to oxidative corrosion. As a result, the generated oxide layer penetrates into the crystal grain boundaries of the lattice in a wedge shape, improving the adhesion between the lattice surface and the oxide layer, preventing the active material from dropping and peeling, and improving the life characteristics of the sealed lead-acid battery. Can be improved.

[0010] There are various possible mechanisms for forming an oxide layer on the surface of the positive electrode grid. The mechanism is based on an alloy forming the grid, an active material coated on the grid, and an electrolyte. The reaction is affected by the activities of water, sulfuric acid, etc., and this reaction is affected by the activities of these reactive species. Therefore, the amount of alkali metal added, the specific gravity of the electrolyte, the weight of the positive electrode grid and the weight of the positive electrode active material Is preferably defined in an optimum range.

Further, in the expanded grid, oxidation corrosion may be promoted by residual stress in the grid, so that even if the grid is elongated, it is necessary to minimize the stress on the battery case.
From this point as well, it is necessary to define the amount of the alkali metal added to the alloy forming the lattice, the specific gravity of the electrolytic solution, and the ratio of the weight of the positive electrode grid to the weight of the positive electrode active material in an optimum range.

From the above technical background, embodiments of the present invention are as follows. That is, a positive electrode plate and a negative electrode plate and at least a separator interposed between these electrode plates and holding an electrolytic solution, the positive electrode lattice holding the active material of the positive electrode plate is an expanded lattice, It is formed of a calcium-tin alloy.

The alkali metal precipitates a rich phase at the grain boundaries existing in the rolled structure, and the phase is preferentially subjected to oxidative corrosion, so that an oxide layer formed on the surface of the positive electrode lattice is formed. Bites into the lattice grain boundaries of the lattice,
The adhesion between the surface of the lattice and the oxide layer is improved, and the active material is prevented from falling off and peeling off, so that the life characteristics of the sealed lead-acid battery can be improved.

Further, as the alkali metal to be contained,
Lithium, sodium or potassium is efficient in terms of adhesion, and the content of alkali metal is 0.001 to
The case of 0.03% by weight is preferable because of good adhesion.

Further, the ratio of the weight of the positive electrode grid to the weight of the active material held by the positive electrode plate is set to 0.4 to 0.6. When the ratio is within this range, the discharge duration and trickle life are reduced. Is preferred.

Further, the specific gravity of the electrolyte is set to 1.
The temperature is in the range of 29 to 1.36 (20 ° C.), and the case within this range is preferable from the viewpoint of the discharge duration and the trickle life.

[0017]

Embodiments of the present invention will be described below.

First, the following test was performed on the alloy forming the expanded lattice used for the positive electrode lattice. Pb-
0.075% Ca-0.60% Sn alloy containing 0.0005 to 0.05% of Li as an alkali metal, or 0.03% of either Na or K
%, And each is cast into a plate shape.
Next, these were cold-rolled to a thickness of 1/20, slit and developed by an ordinary method to produce an expanded lattice. In addition, the content of the component in each alloy is shown by weight%.

With these expanded gratings as working poles,
The surface of the expanded grid as the working electrode is oxidized by performing a constant potential electrolysis in a dilute sulfuric acid electrolyte having a specific gravity of 1.30 at 25 ° C. using the negative grid used for the negative electrode plate of a normal sealed lead-acid battery as a counter electrode. Then, the adhesion between the oxide and the lattice was measured based on the amount of the generated oxide. In addition, the amount of the generated oxide is divided into an oxide attached to the expanded lattice (hereinafter, referred to as an attached oxide) and an oxide dropped from the lattice (hereinafter, referred to as a dropped oxide), and the amount is measured. The ratio of the attached oxide amount (A) to the dropped oxide amount (B) (A /
When B) was large, it was determined that the adhesion between the oxide and the lattice was good. The measurement results are as shown in Table 1, and the values of the attached oxide amount (A) and the dropped oxide amount (B) are shown as indices when the alloy No. 1 is set to 100.

[0020]

[Table 1]

From Table 1, it can be seen that in the case of an expanded lattice formed of a lead-calcium-tin alloy containing Li, Na or K (alloy numbers 2 to 9), the amount of deposited oxide A
Increases, the amount of oxides dropped B decreases, and A / B
It can be seen that has increased. This indicates that the adhesion between the surface of the lattice and the oxide layer formed on the lattice surface is improved, and the content of Li, Na, and K is 0.001 to 0.
It can be seen that the effect is remarkable in the range of 03%.

Next, Pb-0.075% Ca-0.60
% Sn-0.01% Li alloy (alloy No. 5 in Table 1) is rolled and slit to develop an expanded lattice, and apply a positive electrode active material paste to the expanded lattice to form a positive electrode plate. did. The amount of the positive electrode active material paste applied was such that the ratio of the weight of the positive electrode grid to the lead amount of the positive electrode plate as shown in Table 2 (positive electrode grid weight / positive electrode plate lead amount) was used. It is painted.
A sealed lead-acid battery was produced using the positive electrode plate, a negative electrode plate using a conventional expanded grid, and a group of electrodes formed of a liquid-containing separator, and was used as batteries A to J. The thickness of the separator is such that the group pressure on the electrode plate group is approximately 3
The electrolyte was selected so as to be 0 kg / dm ^2, and the specific gravity of the electrolytic solution impregnated in the separator was adjusted so that the specific gravity after the chemical conversion had a value shown in Table 2.

Also, as a comparative example, a sealed lead-acid battery K manufactured using an alloy of alloy number 1 in Table 1 as a positive electrode grid, a conventional expanded grid as a negative electrode grid, and an alloy number in Table 1 as a positive electrode grid. 5, a sealed lead-acid battery L manufactured using a conventional casting grid for the negative grid, an expanded grid of alloy No. 1 in Table 1 for the positive grid, and a conventional expanded grid for the negative grid. The manufactured sealed lead-acid battery was designated as Battery M.

[0024]

[Table 2]

For the batteries A to M shown in Table 2, 3CA
The discharge duration during discharge was measured, and the test conditions were a discharge current value of 3 CA, an end voltage of 1.60 V / cell, and a test temperature of 25 ° C. A trickle life test was performed on these batteries A to M. The test conditions were 40 ° C.
The battery was charged at a constant voltage of 2.28 V / cell for 3 months in an atmosphere, and then a final voltage of 1.60 with a discharge current of 3 CA.
1 cycle of charge / discharge to discharge to V / cell, 3CA
, The number of cycles until the discharge duration was reduced to 5 minutes. These measurement results are as shown in Table 3.

[0026]

[Table 3]

From Table 3, it can be seen that the discharge duration decreases when the ratio of the weight of the positive electrode grid to the lead amount of the positive electrode plate exceeds 0.6, and the trickle life decreases when the ratio is less than 0.4. . That is, in a sealed lead-acid battery using an expanded grid as the positive grid, the condition that both the discharge duration and the trickle life are equal to or more than that of the conventional sealed lead-acid battery (battery K) is determined by the amount of the positive grid with respect to the lead amount of the positive plate. It can be seen that the weight ratio is in the range of 0.4 to 0.6.

The decrease in the discharge duration when the ratio of the weight of the positive electrode grid to the lead amount of the positive electrode plate exceeds 0.6 is due to the decrease in the amount of the positive electrode active material, and is constant at 0.6 or less. This is because the discharge duration is limited by the amount of the electrolyte.

Regarding the trickle life, when the ratio of the weight of the positive electrode grid to the lead amount of the positive electrode plate is 0.4 or less, a sharp decrease in the life is observed because the trickle charging current flowing through the positive electrode grid during trickle charging. Since the positive electrode active material increases in proportion to the positive electrode active material, in the case of a configuration in which the amount of the positive electrode active material is increased with respect to the weight of the positive electrode grid, the positive electrode grid is strongly subjected to an oxidative corrosion reaction caused by trickle charging current. It is considered something.

Next, regarding the relationship between the specific gravity of the electrolytic solution, the duration of discharge and the trickle life characteristic, when the specific gravity of the electrolytic solution is 1.29 or less, the duration of discharge is limited by the amount of sulfuric acid and decreases. When the liquid specific gravity exceeds 1.36, the trickle life is sharply reduced. This is considered to be because sulfuric acid itself acts as an oxidizing agent and the concentration as an electrolyte increases, so that the trickle charge current increases and the positive electrode grid undergoes severe oxidative corrosion. Therefore, in order to make the discharge duration time and the trickle life compatible, it is desirable that the specific gravity of the electrolytic solution be in the range of 1.29 to 1.36 at 20 ° C.

Next, a life test was further continued for each of the batteries (A to M) having reached the end of their life. The test conditions were the same as those described above, the test period was the same as the life period of the battery, and each battery was subjected to a life test corresponding to twice the original life period. After the test of these batteries (A to M), the expansion rate of the width of the battery case and the breakage rate of the battery case were examined. The results are as shown in Table 4.

[0032]

[Table 4]

As shown in Table 4, the battery (A
To J), it was confirmed that the expansion rate of the width of the battery case, that is, the deformation of the battery case was smaller than that of the batteries K and L using the conventional cast grid as the positive electrode grid, and the battery case could be prevented from being damaged. Was.

[0034]

As described above, in the sealed lead-acid battery according to the present invention, the expansion of the positive electrode grid is achieved by using an expanded lattice formed of a lead-calcium-tin alloy containing an alkali metal for the positive electrode plate. In addition to preventing the battery case from being deformed and damaged by the force of the above, there is an effect that it is possible to suppress the deterioration of the service life in which the capacity is suddenly reduced during use of the battery due to the falling off or peeling of the active material.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiro Inoue 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A positive electrode plate, a negative electrode plate, and at least a separator interposed between these electrode plates and holding an electrolytic solution, wherein a positive electrode lattice holding an active material of the positive electrode plate is an expanded lattice and contains an alkali metal. Sealed lead-acid battery formed of a lead-calcium-tin alloy. 2. The sealed lead-acid battery according to claim 1, wherein the alkali metal contained in the lead-calcium-tin alloy is at least one selected from the group consisting of lithium, sodium and potassium. 3. A lead-calcium-tin alloy containing 0.005
2. The composition according to claim 1, which contains 1 to 0.03% by weight of an alkali metal.
Or a sealed lead-acid battery according to 2. 4. The sealed lead-acid battery according to claim 1, wherein the ratio of the weight of the positive electrode grid to the weight of the active material held by the positive electrode plate is 0.4 to 0.6. 5. The electrolyte has a specific gravity of 1.29 to less in a charged state.
The sealed lead-acid battery according to any one of claims 1 to 4, which has a ratio of 1.36.