JPH10199563A - Electrode for lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a lead-acid battery by suppressing generation of a short-circuit or the like caused by grid corrosion without generating a decrease in electric capacity due to an increase in the weight of an electrode grid or a decrease in active material amount. SOLUTION: This lead-acid battery electrode consisting of an electrode grid 1 constituted of a mesh grid skeleton part, and an active material 2 retained in a space to the grid skeleton part and the end surface 1a of the grid skeleton part is characterized by the electrode grid 1 being formed so that its thickness may be increased gradually as it goes from its upper part to its lower part. The lower part of the electrode grid 1 whose corrosion is easy to generate is formed so as to be thick, therefore, many grid parts exist without corrosion being increased at the lower part of the electrode grid 1. As a result, elongation of the whole electrode grid 1 caused by corrosion is suppressed more than in such a case it is formed without being thickened, thus it is possible to effectively-suppress generation of a short-circuit caused by volume expansion of the electrode grid 1 due to corrosion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a lead-acid battery, and more particularly to an electrode for a lead-acid battery which has improved durability by improving the shape of an electrode grid.

[0002]

2. Description of the Related Art A lead storage battery includes a battery case having a liquid stopper and a plurality of cells, an electrolyte (dilute sulfuric acid) injected into each cell,
Each cell is composed of a positive electrode plate, a negative electrode plate, and an electrode plate group in which a required number of separators are combined. The positive electrode plate or the negative electrode plate is formed by filling an active material (PbO _{2 for} the positive electrode and Pb for the negative electrode) into an electrode grid made of a lead alloy.
An electrode group is configured with a separator made of a glass mat or the like interposed between the two electrode plates.

In this lead-acid battery, a positive electrode active material (Pb
O ₂ ) and the negative electrode active material (Pb) are discharged by lead sulfate (Pb).
bSO ₄ ), and almost returns to the original state by charging, so that charging and discharging can be repeated many times. Such a lead storage battery is generally manufactured as follows. First, an electrode grid is cast from a lead alloy made of pure lead, calcium, antimony or the like. Alternatively, a lead grid is manufactured by processing the lead alloy substrate by an expanding method. On the other hand, a paste is prepared by mixing a lead powder mainly composed of PbO produced from pure lead and sulfuric acid. And, filling the paste between the electrode grids with the paste,
After the paste is applied to both end portions of the electrode plate grid, the paste is aged by leaving it at room temperature or in an atmosphere at 40 to 50 ° C. for about 2 days, and cut into a predetermined shape. This allows
An unformed positive / negative electrode plate using PbO as an active material is obtained. The required number of unformed positive / negative electrode plates and separators thus obtained are combined, and the lugs of each electrode plate are welded to a lead alloy strap to produce an electrode plate group. A plurality of manufactured electrode groups are inserted into each cell of the battery case, and the straps of the adjacent electrode groups are welded to each other. Then, an electrolytic solution is injected into each cell, and the lid and the liquid port plug are heated. The lead storage battery is assembled by welding. The unformed lead storage battery thus obtained is subjected to a chemical conversion treatment by being energized, is brought into an initial charged state, and is a charged lead storage battery.

[0004]

Here, one of the causes of deterioration of the lead storage battery is corrosion in the electrode grid constituting the electrodes. In particular, when corrosion occurs in the electrode grid of the positive electrode, Pb changes to PbO or PbSO ₄ , and the volume of the electrode grid expands. Due to this volume expansion, when the positive electrode grid extends vertically and projects upward from the upper end of the separator partitioning the positive and negative electrodes, the positive electrode grid and the lugs of the negative electrode grid and the negative electrode strap are separated. Contact may cause a short circuit. When such a short circuit occurs, the discharge voltage of the lead-acid battery gradually decreases, and the life of the lead-acid battery is reduced. Therefore, in order to improve the durability of the lead storage battery, it is necessary to solve the problem of grid corrosion.

[0005] Therefore, a means for improving the alloy composition of the electrode grid or increasing the thickness of the electrode grid so as to contribute to the improvement of corrosion resistance can be considered. However, the effect of improving the corrosion resistance by improving the alloy composition is not sufficient. On the other hand, when the electrode grid is made thicker, the portion of the grid that remains without being corroded increases by the increased thickness, so that the elongation due to corrosion of the entire electrode grid is larger than when the thickness is not increased. Is suppressed. However, when the thickness of the electrode grid is increased, there is a problem that the grid weight increases. In addition, since the space in the lead-acid battery is limited, the thickness of the electrode grid is increased, so that the amount of active material applied to the end face portion of the electrode grid is reduced, and there is a problem that the electric capacity is reduced. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and aims to solve the problem of an increase in the weight of an electrode plate grid and the problem of a decrease in electric capacity due to a decrease in the amount of active material. An object of the present invention is to provide a lead-acid battery electrode that can contribute to improving the durability of a lead-acid battery by suppressing generation thereof.

[0007]

Means for Solving the Problems In order to solve the above problems,
The present inventor has observed the electrode grid in detail for a lead-acid battery whose life has been shortened due to grid corrosion.As a result, the cross-sectional area of the remaining electrode grid is larger in the upper part than in the lower part, and the lattice corrosion is lower in the lower part. It was found that it was easy to proceed. This is thought to be because the temperature and the sulfuric acid concentration of the electrolytic solution tend to be higher in the lower part than in the upper part, so that the corrosion easily proceeds in the lower part of the electrode plate grid due to this effect.

[0008] The present invention has been completed based on the above findings. An electrode for a lead-acid battery according to the present invention comprises an electrode grid formed of a mesh-like lattice skeleton, a space between the lattice skeletons, and the lattice skeleton. In the electrode for a lead storage battery comprising the active material held on the end face of the above, the thickness of the electrode grid is increased from the upper part to the lower part. Here, the upper and lower portions of the electrode plate grid are defined as the upper surface of the electrode plate lattice when the electrode plate lattice is incorporated in a cell to constitute a lead-acid battery, and the deepest side of the electrolyte is the electrode surface. It means below the plate grid.

In a preferred embodiment of the electrode for a lead-acid battery according to the present invention, the active material held on the end face of the grid frame constituting the electrode grid is made thicker from the lower part to the upper part. And the active material together have a substantially constant thickness from the top to the bottom.

[0010]

Embodiments of the present invention will be described below. The lead-acid battery electrode of the present invention is composed of an electrode plate grid composed of a mesh-like lattice skeleton, a space between the lattice skeletons, and an active material held on an end face of the lattice skeleton. The material and mesh shape of the electrode grid are not particularly limited. As the material, generally used lead or lead alloy can be used. However, from the viewpoint of improving the corrosion resistance of the electrode plate grid, it is preferable to use a lead alloy having good corrosion resistance as much as possible. Further, in order to reduce the weight, it is also possible to use a synthetic resin plate and a lead or lead alloy thin plate which are layered and integrated.

A characteristic configuration of the lead storage battery of the present invention is that the thickness of the electrode plate grid is increased from the upper part to the lower part. As a mode in which the thickness of the electrode grid is increased from the upper portion to the lower portion, even in a mode in which the thickness continuously changes from the upper portion to the lower portion,
Alternatively, the thickness may be changed stepwise from the upper part to the lower part. From the viewpoint of making the potential distribution more uniform, it is preferable to change the thickness continuously rather than changing the thickness stepwise. When the thickness is continuously changed, the thickness may be changed from the upper end to the lower end of the electrode plate grid, or a portion near the upper end and / or lower end of the electrode plate grid may be formed. May be constant, and the thickness of the remaining portion may be continuously changed.

Further, the thickness of the electrode grid is made thicker from the upper part to the lower part. The center of the electrode grid in the up-down direction is made to have the same thickness as that of the conventional electrode grid. In contrast, the thickness of the upper part of the electrode grid is 10 to 20%.
It is preferable that the thickness be reduced and the thickness of the lower part of the electrode grid be increased by 10 to 20%. If the degree of increasing the thickness of the lower part of the electrode grid is too small, the effect of increasing the thickness becomes insufficient. On the other hand, if the thickness of the lower part of the electrode grid is made too thick, there arises a problem of space in the cells of the lead storage battery and a problem of a decrease in the amount of active material that can be applied. In addition, the thickness of the upper part of the electrode grid is made thinner than the thickness of the conventional electrode grid, because the thinner part can hold more active material on the end face of the grid frame constituting the electrode grid. This is advantageous in increasing the electric capacity. However, if the thickness is too small, the strength required for the electrode plate grid cannot be secured. The thickness of the upper part of the electrode grid may be made equal to the thickness of the conventional electrode grid, and the thickness of the lower part may be increased by a predetermined ratio with respect to the upper part.

[0013] The electrode grid having such a configuration can be manufactured by casting or expanding as in the past. The active material is held in a space between lattice skeletons constituting an electrode lattice and an end face of the lattice skeleton. Here, the thickness of the active material held on the end face of the lattice skeleton may be substantially constant from the upper part to the lower part of the lattice electrode plate. However, assuming that the thickness of the active material is constant from the upper part to the lower part, the thickness of the electrode grid is reduced in the lower part where the thickness of the electrode grid is increased due to the restriction on the space in the cell. It cannot be made sufficiently thick, and problems of passivation and sulfation are likely to occur as described later. Therefore, the thickness of the active material held on the end face of the lattice skeleton is made thicker from the lower part to the upper part, and the combined thickness of the electrode grid and the active material is made substantially constant from the upper part to the lower part. Is preferred. In this case, the thickness of the active material held in the space between the lattice skeletons should be substantially the same as the combined thickness of the electrode grid and the active material held on the end face of the electrode grid. Can be.

The specific size of the thickness of the active material held on the end faces of the electrode grid and the grid bone is, for example, that the thickness is continuously changed from the upper end to the lower end of the electrode grid. In the case, the thickness of the central part of the electrode grid in the vertical direction is 1.3 to 1.5 mm, the thickness of the upper end part of the electrode grid is 1.0 to 1.4 mm, and the thickness of the lower end part of the electrode grid is The thickness is preferably 1.4 to 1.8 mm, and the combined thickness of the electrode grid and the active material held on the end face of the grid frame is substantially constant from the upper part to the lower part, and is 1.5. It is preferable to set it to 2.0 mm.

[0015] The type and filling method of the active material are not particularly limited, and can be the same as in the prior art. For example, a paste is prepared by kneading a lead powder mainly composed of PbO made from pure lead and sulfuric acid, and applying this paste to the space between the grid bones of the electrode plate grid and the end face of the grid bone, After drying, the electrode material is left to stand in an atmosphere at room temperature or an atmosphere of 40 to 50 ° C. for about 2 days to ripen, whereby the active material can be filled and held in the electrode grid. Then, it is cut into a predetermined shape, and PbO
Can be obtained as an active material.

The unformed positive / negative plates obtained in this manner are welded to a strap by combining a plurality of them while sandwiching a separator, such as a synthetic resin separator or a glass mat, according to a conventional method. can do. Then, a plurality of electrode groups are inserted into each cell of the battery case, and after the straps of the adjacent electrode groups are welded to each other, an electrolytic solution is injected into each cell, and a lid and a liquid port stopper are attached. By heat welding, a lead storage battery can be assembled.

The unformed lead storage battery thus obtained is subjected to a chemical conversion treatment by being energized, and becomes an initial charged state.
It can be a charged lead storage battery. In the lead-acid battery electrode of the present invention, the lower part of the electrode grid where corrosion is apt to proceed is thickened, so that even after grid corrosion has progressed to some extent, the lower part of the electrode grid is not corroded. The number of remaining lattice parts increases. If the number of remaining grid portions increases, the force for suppressing the elongation of the grid electrode plate increases, so the elongation due to corrosion of the entire electrode plate grid is suppressed as compared with the case where the thickness is not increased. . Therefore,
It is possible to effectively suppress occurrence of a short circuit caused by volume expansion of the electrode plate grid due to corrosion.

On the other hand, in the lead-acid battery electrode of the present invention, the thickness of the electrode grid is not increased uniformly but is increased from the upper part to the lower part of the electrode grid. Therefore, an increase in the weight of the electrode plate grid can be suppressed as compared with the case where the thickness is increased uniformly from the upper portion to the lower portion.
Also, in the upper part of the plate grid which is not thickened,
Since the active material can be sufficiently applied to the electrode grid portion, the amount of the active material applied to the end face portion of the electrode grid and, consequently, the electric power can be reduced as compared with the case where the thickness is uniformly increased from the upper portion to the lower portion. A decrease in capacity can be suppressed.

Further, in the lead storage battery electrode of the present invention, the thickness is increased toward the lower part of the grid where the grid resistance increases as the distance from the ear formed integrally with the upper end of the electrode plate grid increases. It is possible to suppress an increase in the lattice resistance due to being farther from the ears by the thickness. As a result, the in-plane resistance distribution of the electrode grid can be made uniform as compared with the case where the thickness of the electrode grid is uniform from the upper part to the lower part, thereby improving the reaction efficiency of the active material and, consequently, the capacity and the efficiency discharge. This is advantageous for improving the output at the time.

Further, since the resistance at the lower part of the lattice is reduced and the reaction efficiency of the active material is improved, it is advantageous in suppressing the passivation and sulfation described later. Then, the thickness of the active material held on the end face of the lattice skeleton constituting the electrode grid is increased from the lower portion to the upper portion, and the thickness of the electrode grid and the active material is substantially increased from the upper portion to the lower portion. When it is constant, the following operation and effect can be further obtained.

That is, in the positive electrode, a passivation film is more likely to be formed at the interface between the grid and the active material at the lower portion of the electrode plate grid during discharge, but it is said that the cause is an unreacted surplus active material. In this regard, if the thickness of the active material is smaller at the lower part of the electrode grid, the amount of the unreacted surplus active material that causes the passivation also decreases. For this reason, it is possible to suppress a decrease in output and capacity due to passivation.

In the negative electrode, sulfation is more likely to occur in the lower part of the electrode plate grid during discharge, but one of the causes is said to be an unreacted surplus active material. Note that sulfation refers to a phenomenon in which PbO ₂ changes to PbSO ₄ and causes no battery reaction. In this regard,
If the thickness of the active material is smaller at the lower part of the electrode grid, the unreacted surplus active material that causes sulfation is also reduced. Therefore, it is possible to suppress a decrease in output and capacity due to sulfation.

Further, if the combined thickness of the electrode grid and the active material is substantially constant from the upper part to the lower part, it is advantageous in securing a space for the electrode group in the cell.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the lead storage battery electrode according to the present invention will be specifically described below. An electrode grid 1 consisting of a grid bone was cast from a molten metal of a lead alloy (1.0% Sn-0.08% Ca-Pb) consisting of pure lead, tin and calcium. The center of the electrode grid 1 in the vertical direction has a thickness of 1.4 mm equivalent to the thickness of the conventional electrode grid, the upper end of the electrode grid 1 has a thickness of 1.25 mm, and the lower end of the electrode grid 1 The thickness of the part is 1.55 mm. The thickness of the upper and lower ends of the electrode grid 1 is changed by 10% with respect to the thickness of the conventional electrode grid, that is, the thickness of the central part of the electrode grid 1.

Then, a paste made by kneading lead powder or lead oxide powder with diluted sulfuric acid is filled in the space between the lattice skeletons of the electrode plate lattice 1 and applied to both end surfaces of the lattice skeleton, and dried. The electrode grid 1 is filled with the active material 2 by aging at room temperature or in an atmosphere of 40 to 50 ° C. for 2 days,
Was held. And it cut | disconnected in the predetermined shape, and obtained the unformed positive / negative electrode plate which uses PbO as an active material. The combined thickness of the electrode grid 1 and the active material 2 held on the end surface 1a of the grid frame of the electrode grid 1 is substantially constant over the upper end and the lower end of the electrode grid 1. , Its thickness is 1.7m
m. Also, the thickness of the active material held in the space between the lattice skeletons of the electrode grid 1 is the sum of the electrode grid 1 and the active material 2 held on the end surface 1a of the electrode grid 1 lattice skeleton. It is substantially the same as the thickness.

The unformed positive / negative electrode plates thus obtained are combined with each other while sandwiching a separator such as a synthetic resin separator or a glass mat, and welded to a strap according to a conventional method. did. Then, a plurality of electrode groups are inserted into each cell of the battery case so that the upper part of each electrode grid 1 is located upward, and the straps of the adjacent electrode groups are welded to each other. A lead-acid battery was assembled by pouring dilute sulfuric acid as an electrolytic solution into the inside, and thermally welding the lid and the liquid port stopper. The number of cells is 6, and the amount of electrolyte is 0.55 liter per cell.

The unformed lead-acid battery thus obtained was subjected to a chemical conversion treatment by applying a current of 1 A at room temperature for 200 hours to produce a lead-acid battery in an initial charged state. The lead storage battery is of the battery type 95D31. (Evaluation) For the lead storage battery obtained in the above example, 85
The durability was examined by a JIS light load life test at ℃. The JIS light load life test is a charge / discharge cycle test defined in JIS D5301.

As a result, the life was improved by about 20% as compared with the conventional lead storage battery. In addition, the life was determined when the discharge voltage fell below 7.2V. (Relationship between Life and Life of Degree of Thickness of Electrode Grid from Top to Bottom)
Were changed by 20%, 5%, and 25% with respect to the thickness of the conventional electrode grid, that is, the thickness of the central part of the electrode grid 1, In each case, the durability was examined in the same manner as described above. For comparison, the durability of a conventional product in which the thickness of the electrode plate grid 1 was uniform from the upper end to the lower end was also examined in the same manner as described above. FIG. 3 shows these results together with the results of the above example.
Shown in

In FIG. 3, A is a 10% change in the first embodiment, B is a 20% change, C
Indicates the result of 5% change, D indicates the result of 25% change, and E indicates the result of the conventional product. As is clear from FIG.
In the case of A in which the thicknesses of the upper end and the lower end of the electrode grid 1 were changed by 20% with respect to the thickness of the conventional electrode grid, the life was improved by about 40% as compared with the conventional product E.

On the other hand, in the case of C in which the thickness of the upper end and the lower end of the electrode grid 1 is changed by only 5% with respect to the thickness of the conventional electrode grid, and in the case of D in which the thickness is changed by 25%. ,
The life was almost the same as that of the conventional product E. In the case of C, the thickness of the lower part of the electrode grid 1 was too small to be increased.
It is considered that the effect of increasing the thickness was not sufficiently exhibited. In the case of D, it is considered that the voltage was reduced early because the current collection efficiency from the active material was reduced because the thickness of the upper part of the electrode plate grid 1 was too thin.

[0031]

As described above in detail, in the lead-acid battery electrode of the present invention, by increasing the thickness of the electrode grid from the upper part to the lower part, the weight of the electrode grid increases and the amount of active material decreases. , While effectively suppressing the occurrence of a short circuit due to the corrosion of the electrode plate grid, thereby contributing to an improvement in the life of the lead storage battery.

Further, the thickness of the active material held on the end face of the grid frame constituting the electrode grid is increased from the lower portion to the upper portion, and the total thickness of the electrode grid and the active material is increased from the upper portion to the lower portion. When it is substantially constant, a decrease in output and capacity due to passivation or sulfation can be further suppressed.

[Brief description of the drawings]

FIG. 1 is a plan view of an electrode for a lead storage battery of the present embodiment.

2 is a cross-sectional view of the lead-acid battery electrode of the present embodiment, which is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing the relationship between the degree of increasing the thickness of the electrode grid from the upper part to the lower part and the service life.

[Explanation of symbols]

 1 is an electrode grid, and 2 is an active material.

Claims (2)

[Claims] An electrode plate grid comprising a mesh-like grid frame,
In a lead-acid battery electrode comprising a space between the lattice skeletons and an active material held on an end face of the lattice skeleton, the electrode plate lattice is characterized in that the thickness is increased from the upper part to the lower part. For lead-acid batteries. 2. The thickness of the active material held on the end face of the lattice frame constituting the electrode grid increases from the lower part to the upper part, and the total thickness of the electrode grid and the active material increases from the upper part to the lower part. 2. The electrode for a lead storage battery according to claim 1, wherein the electrode is substantially constant over the entire length.