JPH0513081A - Lead acid battery - Google Patents

Abstract

(57) [Summary] [Objective] It is an object of the present invention to provide a lead-acid battery excellent in energy density, cycle life, etc. by adding tin to the positive electrode active material and alkali metal ions to the electrolytic solution. [Structure] 0.01 to 5 tin or an alloy containing tin or a compound containing tin is added to an unformed active material containing tetrabasic lead sulfate.
% Addition, and an alkali metal ion in the electrolytic solution is 0.0
A battery was prepared by adding 1 to 5 mol / l. This can suppress the softening of the positive electrode active material and improve the diffusion of sulfuric acid that is the electrolytic solution. Further, it becomes possible to suppress the generation of the passive layer at the lattice interface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead storage battery, and more particularly to a lead storage battery having an improved positive electrode active material.

[0002]

2. Description of the Related Art A lead-acid battery is a battery that is relatively inexpensive and has stable performance as a secondary battery, and is a stationary power source used for backup of a portable power source for a portable device or an electric vehicle used for a cycle, a computer, etc. It is widely used as a power source. However, in recent years, there has been an increasing demand for higher performance of lead storage batteries as electronic devices have become smaller and higher in performance, and particularly long life and high energy density have become major issues.

These problems largely depend on the active material, particularly the positive electrode active material. One of the reasons why the life is short is that the binding property between the positive electrode active material particles deteriorates due to the charge / discharge cycle, so that the softening and dropping of the active material progress 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 the low utilization rate of the positive electrode active material. In the discharge reaction of the positive electrode, there is a reaction between PbO ₂ and H ₂ SO ₄ as shown in the following formula, and PbO ₂ + 4H ⁺ + 2e + SO ₄ ^2- → PbSO ₄ + 2H ₂ O SO ₄ ²⁻ is easy to move. It is important for improving the utilization rate of the positive electrode. For these reasons, improvement of charge / discharge cycle characteristics and improvement of the positive electrode active material for higher energy density are desired.

The active material of the positive electrode of a lead-acid battery is prepared by mixing lead powder as a raw material together with each additive with dilute sulfuric acid or other kneading liquid to form a paste with stirring, and filling the paste in a grid. After a predetermined aging and drying process, an unformed active material is produced, and the unformed active material becomes lead dioxide by chemical conversion.

The size and shape of the particles of this positive electrode active material are
It is greatly affected by unactivated materials. The main component of the composition of the conventional non-activated material is tribasic lead sulfate, and the crystals as primary particles have a columnar particle size of about 1 μm, and are formed from this tribasic lead sulfate 2 The secondary particles of lead dioxide are fine and have high reactivity. Therefore, the softening and dropping of the active material particles due to the charge / discharge cycle are likely to proceed,
The charge / discharge cycle life is shortened. At the same time, since a corrosion reaction at the lattice interface between the active material and the active material is likely to occur, the conductivity at the lattice interface is reduced and the capacity recovery property after long-term storage is reduced.

In order to solve this drawback, secondary particles obtained by chemical conversion of an inactive material containing tetrabasic lead sulfate whose primary particles have a larger particle shape as an aggregate of finer particles than tribasic lead sulfate. A method of improving charge / discharge cycle characteristics by using lead dioxide particles as a positive electrode active material has been adopted. The crystal size of the tetrabasic lead sulfate is 10 μm, which is larger than that of the tribasic lead sulfate, and the secondary particles of lead dioxide oxidized during the formation of the tetrabasic lead sulfate of the primary particles It becomes large lead dioxide as an aggregate of fine particles while maintaining the shape and size of the crystal. For this reason, the positive electrode active material made of tetrabasic lead sulfate has a denser array of positive electrode active materials than the positive electrode active material made of tribasic lead sulfate, and the diffusivity of the electrolytic solution is low. , Low reactivity. Therefore, the softening of the active material due to the charge / discharge cycle,
Falling off was suppressed and cycle characteristics were improved.

[0007]

In the positive electrode active material obtained by forming an unformed active material containing tetrabasic lead sulfate as described above, the secondary particles of lead dioxide are dense and agglomerated with fine particles. Since they are arranged in a row, the diffusivity of the electrolytic solution is low and the reactivity is low. For this reason, the utilization factor of the positive electrode active material is lowered, which causes a drawback that the energy density of the lead storage battery is lowered.

The present invention solves the above problems by improving the utilization rate of the active material of the positive electrode active material and suppressing the formation of a passive layer at the lattice interface to recover the capacity after long-term storage. It is an object of the present invention to provide a lead storage battery having improved battery.

[0009]

In order to solve the above-mentioned problems, the lead-acid battery of the present invention comprises an unformed active material containing tin or an alloy containing tin, or a tetrabasic lead sulfate added with a compound containing tin. A positive electrode active material formed by chemical conversion is used, and an alkali metal ion is further contained in the electrolytic solution.

[0010]

With this structure, in the lead acid battery of the present invention, the number of moles of tin is 0.01 to 5 relative to the number of moles of lead in the lead powder.
%, The paste containing tin or a tin alloy or a compound containing tin is filled in a lattice to form an unformed active material positive electrode containing tetrabasic lead sulfate in which fine primary particles are densely arranged. A plate can be obtained, and by forming this positive electrode plate, the fine primary particles are aggregated while maintaining the shape and size of the densely arranged tetrabasic lead sulfate crystals of the fine primary particles. The secondary particles of lead dioxide can be formed without being allowed to do so. As a result, it is possible to increase the pores of 0.1 to 1 μm, which is optimal for the diffusion of sulfuric acid. Therefore, the softening and dropping of the active material particles due to the charge / discharge cycle is suppressed, the cycle life is improved, and
Further, by improving the diffusion of sulfuric acid, it becomes possible to improve the utilization rate of the active material. Further, by adding an alkali metal ion to the electrolytic solution, it is possible to suppress the formation of a passive state layer at the lattice interface and improve the capacity recoverability after long-term storage.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lead storage battery of an embodiment of the present invention will be described below with reference to the drawings.

(Example 1) An electrode plate of a lead storage battery was prepared by kneading a predetermined amount of lead powder while dropping water and dilute sulfuric acid according to a conventional method, filling a grid, aging, and drying. Obtain a chemical conversion plate. There are the following two methods as a method for producing tetrabasic lead sulfate in the manufacturing process of this unformed plate. The first is to raise the temperature during paste kneading, and the second is to raise the temperature and humidity during aging after the completion of kneading. In this example, the method of raising the temperature during the first kneading was performed.

In order to confirm the conditions for producing tetrabasic lead sulfate according to this kneading temperature and time, the temperature was set to 30, 60, 80 ° C.
And the kneading time was set to 5 to 30 minutes, and the composition of these pastes was confirmed by X-ray diffraction. As a result,
Tetrabasic lead sulfate did not form at 30 and 60 ° C even if the kneading time was prolonged, and if kneading was continued at 80 ° C, the tribasic lead sulfate formed during dropwise addition of sulfuric acid changed to tetrabasic lead sulfate. Then, the mixture was changed to tetrabasic lead sulfate after 20 minutes of kneading. Therefore, the conditions for kneading the tetrabasic lead sulfate paste were 80 ° C, 2
At 0 minutes, the following experiment was conducted.

According to a conventional method, a predetermined amount of lead powder was kneaded for 20 minutes at 80 ° C. while dropping water and dilute sulfuric acid to prepare a positive electrode paste containing tetrabasic lead sulfate. Pb this paste
A conventional positive electrode plate P was obtained by filling a casting grid of a Ca-based alloy, and performing aging, drying, and chemical conversion steps.

Similarly, stannous sulfate (hereinafter referred to as tin sulfate) was added to a predetermined amount of lead powder so that the number of moles of tin was 1% with respect to the number of moles of lead in the lead powder, and the mixture was stirred. . According to a conventional method, water and diluted sulfuric acid were added dropwise and kneaded at 80 ° C. for 20 minutes to prepare a positive electrode paste containing tetrabasic lead sulfate to which tin sulfate was added, and a casting grid of a Pb-Ca alloy was prepared. Filled in
The positive electrode plate A of Example 1 was obtained through the steps of aging, drying and chemical conversion under the same conditions as the positive electrode P plate.

The above-mentioned conventional positive electrode plate P and negative electrode plate are used respectively two and three, and a mat-like separator made of glass fiber is interposed between them, and they are combined and impregnated with dilute sulfuric acid as an electrolytic solution. (Time rate) A conventional battery P of 2V was obtained.

Similarly, two positive electrode plates A and two negative electrode plates are used, and a mat-shaped separator made of glass fiber is interposed between them to impregnate them with dilute sulfuric acid as an electrolytic solution. A battery A of Example 1 having the same volume and weight as Example 1 was obtained.

The battery A was subjected to a charge / discharge cycle test under constant current charge / discharge conditions of 200 mA charge and 600 mA discharge to measure the capacity and charge / discharge cycle life of each battery.
The final voltage of discharge was 1.75 V, the amount of electricity charged was 120% of the amount of electricity discharged, and the charge / discharge cycle life was the number of cycles when the capacity reached 1000 mA. 40 ° C
600mA for 2 months, 4 months and 6 months
The capacity was checked by constant current discharge and the self-discharge during storage was examined.

As can be seen from FIG. 1, the battery P has a capacity of 17
Battery A is 1930 mA, while it is 50 mAh
It was h, and by adding tin sulfate to the positive electrode plate active material obtained by forming an unformed active material containing tetrabasic lead sulfate, the battery capacity was remarkably improved.

As can be seen from FIG. 2, the charge / discharge cycle life of the battery P is 430 cycles, while that of the battery A
Was 450 cycles, and it was confirmed that the charge-discharge cycle characteristics of the battery were improved by adding tin sulfate to the positive electrode active material.

In FIG. 3, the remaining capacity of the battery P is 75% when left for 2 months, while the remaining capacity of the battery A is 83%.
It was confirmed that the self-discharge can be suppressed by adding tin sulfate.

Although tin sulfate was used as the additive in the above-mentioned examples, the same effect was observed when tin, a tin-lead alloy, or stannous oxide was used. However, the number of moles of tin in the additive was set to 1% with respect to the number of moles of lead in the lead powder.

(Example 2) The characteristics were compared by changing the amount of tin sulfate added to the positive electrode plate active material obtained by forming an unformed active material containing tetrabasic lead sulfate. To a predetermined amount of lead powder, tin sulfate was added and stirred so that the number of moles of tin was each ratio shown in (Table 1) with respect to the number of moles of lead in the lead powder. While adding water and dilute sulfuric acid dropwise to this, 8
The mixture was kneaded at 0 ° C. for 20 minutes to prepare a positive electrode paste containing tetrabasic lead sulfate to which tin sulfate was added, filled in a casting grid of Pb-Ca alloy, and aged under the same conditions as the positive electrode plate P. Through the steps of drying and forming, the positive electrode plates B, C, D of Example 2
E, F and G were obtained. As in Example 1, two positive electrode plates B to G and three negative electrode plates were used respectively, and a mat-shaped separator made of glass fiber was interposed between them to combine them, and dilute sulfuric acid was impregnated as an electrolytic solution to obtain a conventional battery. Same volume as P,
Batteries B, C, D, E, F and G of Example 2 having the same weight were obtained.

[0024]

[Table 1]

For these batteries B to G, a charge of 200 m
A, charge / discharge cycle test was performed by constant current charge / discharge of 600 mA discharge, and the capacity of each battery and the charge / discharge cycle life were measured. The final voltage of discharge was 1.75 V, the amount of electricity charged was 120% of the amount of electricity discharged, and the charge / discharge cycle life was the number of cycles at which the capacity reached 1000 mA. Also,
Store in a constant temperature room at 40 ° C for 2 months, 4 months, 6 months, 60
The capacity was checked with a constant current discharge of 0 mA to examine self-discharge during storage.

It can be seen from FIG. 4 that the discharge capacity increases as the amount of tin sulfate added increases. However, at 5% or more, there is almost no difference in capacity, and 0.001%
Then, there was no difference in capacity from the conventional battery P. From FIG. 5, if the addition amount is less than 0.01%, there is no difference from the conventional battery P without addition of tin sulfate, but from 0.01 to 5% addition amount, there is no charge / discharge cycle life according to the addition amount. It was found that it was longer than the battery P of the addition. However, when the addition amount was 7%, the charge / discharge cycle life was reduced to 380 cycles, which was shorter than that of the conventional battery P.

In FIG. 6, when tin sulfate was added, the storage characteristics improved as the amount of addition increased, but at 1%, the maximum storage ratio was obtained, and at 7%, the storage characteristics were the same as those of the non-added battery P.

Therefore, from the above results, the addition amount is 0.01
Must be in the range of ~ 5%. Although tin sulfate was used as the additive in the above examples, the same effect was observed when tin, a lead alloy containing tin, or stannous oxide was used. However, as described above, the number of moles of tin added must be 0.01 to 5% with respect to the number of moles of lead in the positive electrode active material.

(Example 3) Tin sulfate was added to a positive electrode active material obtained by forming an unformed active material containing tetrabasic lead sulfate, and an alkali metal ion was added to dilute sulfuric acid as an electrolytic solution and added. The characteristics were compared by changing the amount.

In the same manner as in Example 1, a battery was prepared by adding tin sulfate to a predetermined amount of lead powder so that the number of moles of tin was 1% with respect to the number of moles of lead in the lead powder. A battery H of this example using an electrolytic solution in which ions were added to dilute sulfuric acid at 1 mol / l and a battery A using an electrolytic solution without addition of alkali metal ions were prepared. These batteries were stored in a constant temperature room at 40 ° C. for 2 months, 4 months, and 6 months, and the capacity was checked by a constant current discharge of 600 mA to examine self-discharge during storage.

In FIG. 7, the residual capacity ratio after leaving for 2 months is 84% in the battery A in which the alkali metal ion is not added, whereas it is 94 in the battery H in which the alkali metal ion is added as the electrolytic solution in the dilute sulfuric acid. The capacity remaining rate was%.

Although not shown, if the amount of alkali metal ion added is less than 0.01 mol / l, the effect is similar to the case of no addition, and if it exceeds 5 mol / l, long-term storage characteristics are deteriorated. The amount of metal ions added must be 0.01 to 5 mol / l.

[0033]

As is apparent from the above description of the embodiments, according to the lead-acid battery of the present invention, by adding tin or an alloy containing tin or a compound containing tin to the positive electrode active material, the positive electrode plate The secondary particles of lead dioxide are the individual forms of tetrabasic lead sulfate crystals in which fine primary particles are densely arranged.
Form lead dioxide while retaining its size. Therefore, it is possible to improve the cycle rate of the active material by suppressing the softening and dropping of the active material particles in the charge / discharge cycle, and further improve the diffusion rate of sulfuric acid and the reactivity to improve the utilization rate of the active material. It was In addition, the addition of alkali metal ions into the electrolytic solution suppresses the formation of the passive state layer at the lattice interface, so that the capacity recovery property after long-term storage is further enhanced.

[Brief description of drawings]

FIG. 1 is a graph showing a comparison of discharge capacities of a battery in which tin is added to the positive electrode active material of Example 1 of the present invention and a conventional battery.

FIG. 2 is a graph showing a comparison of the same charge / discharge cycle characteristics.

FIG. 3 is a graph showing a comparison of discharge capacities after storage for 2 months, 4 months, and 6 months in the same 40 ° C. high temperature room.

FIG. 4 is a graph showing the relationship between the amount of tin added to the positive electrode active material of the battery of Example 2 of the present invention and the discharge capacity.

FIG. 5 is a graph showing the relationship between the amount of tin added and the charge / discharge cycle life.

FIG. 6 is a graph showing the relationship between the amount of tin added and the residual capacity rate after storage for 2 months in a high temperature room at 40 ° C.

FIG. 7: After storage for 2 months, 4 months, 6 months in a high temperature room at 40 ° C. of a battery in which an alkali metal ion was added to the electrolytic solution of Example 3 of the present invention and a conventional battery in which an alkali metal ion was not added. Graph showing capacity comparisons

Claims (5)

[Claims] 1. A lead storage battery in which tin, an alloy containing tin, or a compound containing tin is added to an unformed active material containing tetrabasic lead sulfate. 2. The lead-acid battery according to claim 1, wherein the alloy containing tin is a tin-lead alloy, and the compound containing tin is stannous oxide or stannous sulfate. 3. The tin element or the tin-containing alloy or the tin-containing compound in which the number of moles of tin element is 0.01 to 5% with respect to the number of moles of lead in the positive electrode active material. Lead acid battery. 4. The lead storage battery according to claim 1, wherein the electrolytic solution contains an alkali metal ion. 5. The lead storage battery according to claim 4, wherein the alkali metal ion concentration in the electrolytic solution is 0.01 to 5 mol / l.