JPH10172543A - Sealed lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain charge/discharge in a lower part active material without pressing at high pressure an electrode group in the stacking direction, and gelling an electrolyte by making the mean pore size of a lower part active material layer locating in a lower part region larger than that of an upper part active material layer locating in an upper part region in the upper and lower direction of a positive plate, and adding a conducting additive to the lower part active material layer. SOLUTION: An upper part active material layer 6 is formed in the upper part in the upper and lower direction of a positive plate, and a lower part active material layer 7 is formed in the lower part. The upper part active material layer 6 and the lower part active material layer 7 are formed so as to slightly cover inner bones. The lower part active material layer 7 has a mean pore size of 0.6 micron larger than that of the upper part active material layer 6 which has a mean pore size of 0.3 micron. Carbon is dispersed in the lower part active layer 7.

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 In general, a sealed lead-acid battery has a structure in which a positive electrode plate and a negative electrode plate are arranged in a battery case, in which an electrode plate group is laminated via an electrolyte comprising a retainer containing dilute sulfuric acid (electrolytic solution). have. This type of sealed lead-acid battery is repeatedly charged and discharged by the following reaction formula.

[0003]

Embedded image As shown in the above equation, water (H ₂
O) is generated and, upon charging, sulfate ions (S
O ₄ ^2- ) is formed. As a result, when the battery is repeatedly charged and discharged, a so-called stratification phenomenon in which the specific gravity of the electrolytic solution differs in the vertical direction of the electrode plate between the electrode plate and the retainer (gap).
Occurs in When such a stratification phenomenon occurs, the lower active material layer located in the lower region in the vertical direction of the electrode plate has a lower PbSO ₄ concentration than the upper active material layer located in the upper region above the lower active material layer. The amount of generation increases. The active material is PbSO ₄
For example, the volume of the positive electrode plate expands 1.9 times, and the volume of the negative electrode plate expands 2.7 times. Therefore, in the lower active material layer of the electrode plate, the pore diameter in the active material layer becomes small, so that the electrolyte does not easily penetrate into the active material layer, and the charge / discharge reaction hardly occurs. As a result, it becomes difficult to generate a charge product, and PbSO ₄ conversion further proceeds. As a result, charge / discharge concentrates locally on the upper part of the electrode plate, or Pb with low conductivity
SO ₄ lowers the conductivity of the lower active material layer of the electrode plate,
Battery capacity is reduced and cycle life is shortened. Therefore, it has been studied to press the electrode plate group with a high pressure in the laminating direction to bring the electrode plate and the retainer into close contact with each other. Since the stratification phenomenon is likely to occur in the gap between the electrode plate and the retainer, stratification of the electrolyte can be prevented by bringing the electrode plate and the retainer into close contact with each other. It has also been studied to suppress the stratification of the electrolytic solution by gelling or solifying the electrolytic solution. When the electrolyte is gelled or solified, water (H ₂ O) or sulfate ions (SO
₄ ^2- ) The vertical movement is suppressed.

[0004]

However, in a battery in which the electrode group is pressed at a high pressure in the stacking direction, it is difficult to insert the electrode group into the battery case, and the battery assemblability is poor. Further, when the retainer is pressed at a high pressure, the retained amount of the electrolyte in the retainer decreases, and the capacity of the battery decreases. Further, when the electrolytic solution is gelled or sol, the diffusivity of ions at the time of charge and discharge is limited, so that the capacity of the battery is reduced. In addition, charge acceptability also decreases.

An object of the present invention is to maintain the charge / discharge reaction in the lower active material layer without pressing the electrode group at a high pressure in the stacking direction or gelling or solifying the electrolytic solution, and It is an object of the present invention to provide a sealed lead-acid battery capable of preventing a layer from being converted to PbSO ₄ .

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a sealed lead-acid battery in which a vertical direction in a use state is determined in advance and a fluid electrolyte is used as the electrolyte. In the present invention, at least the lower active material layer located in the lower region in the vertical direction of the positive electrode plate has a larger average pore diameter than the upper active material layer located in the upper region above it. In addition, a conductive additive is added to the lower active material layer.

When stratification occurs in the electrolytic solution, the lower active material layer located in the lower region in the vertical direction of the electrode plate has a smaller pore size in the active material layer than the upper active material layer located in the upper region above it. Becomes smaller. Therefore, in the present invention, by increasing the average pore diameter of the lower active material layer in advance compared to the upper active material layer, even if the average pore diameter of the lower active material layer is reduced, the upper active material layer and the lower active material A large difference in pore diameter between the layer and the layer was eliminated. For this reason, the lower active material layer is also infiltrated with the electrolytic solution similarly to the upper active material layer, the charge / discharge reaction in the lower active material layer is maintained, and the lower active material layer is formed of PbSO _4.
Can be prevented from being left in the state. Then, it is possible to prevent the charge and discharge from being locally concentrated on the upper part of the electrode plate. In the present invention, although it is possible to prevent the lower club material layer Remains ₄ of PbSO, compared to the upper portion of the active material layer, the content of low conductivity PbSO ₄ is increased slightly . Therefore, the lower active material layer was made to contain a conductive additive to prevent the lower active material layer from lowering in electrical conductivity. As described above, according to the present invention, the electrode group is pressed with a high pressure in the stacking direction as in the related art, or the capacity of the battery is reduced without gelling or solifying the electrolytic solution,
Shortening of the cycle life can be efficiently suppressed. When the porosity of both the upper active material layer and the lower active material layer is increased, the charge / discharge reaction concentrates on the upper active material layer, and the cycle life is shortened. Further, when the conductive additive is added to both the active material layers, the active material filling amount is reduced, and the capacity of the battery is reduced.

As the conductive additive, graphite, acetylene black and the like can be used.

The electrode plate for a sealed lead-acid battery of the present invention can be applied to both a positive electrode plate and a negative electrode plate. However, the positive plate is
Compared with the negative electrode plate, the pores are small and the porosity of the electrode plate is low,
Since the conductivity is low, even when applied at least to the positive electrode plate, it is possible to suppress a decrease in battery capacity and a decrease in cycle life.

[0010] In the sealed lead-acid battery, the electrolyte is absorbed in the electrode group. In practice, however, the free electrolyte not absorbed in the electrode group is separated from the wall of the battery case and the electrode group. Will exist between. Therefore, when the electrode group is arranged in a battery case and an electrolytic solution (dilute sulfuric acid) is injected, the active material layer corresponding to the region of the electrode plate corresponding to the free electrolyte solution contains S in the free electrolyte solution.
The absorption of O ₄ ^2- is promoted, and the weight ratio of PbSO ₄ is increased as compared with the upper active material layer. Therefore, even if the battery is formed or charged after the injection of the electrolyte, a sufficient charge product cannot be generated (PbSO ₄ remains). Further, when the battery is repeatedly charged and discharged, PbSO ₄ conversion proceeds in a portion of the active material layer corresponding to the region of the electrode plate where the free electrolyte exists, for the following reasons. If the free electrolyte is not present, SO of charge and discharge in the electrolyte solution in the battery container lower the PbSO ₄ of advances to a certain lower club material layer stratification occurs in the electrolyte solution is repeated in the battery ₄ ^2- Is absorbed and reduced, and the specific gravity of the electrolytic solution in the lower part of the battery case decreases. for that reason,
PbSO ₄ conversion of the lower active material layer gradually decreases. However, when free electrolyte is present, S in the free electrolyte
The absorption of O ₄ ^2- continues and the conversion of the lower active material layer to PbSO ₄ proceeds without reduction.

Therefore, in a sealed lead-acid battery in which such a free electrolyte exists, the lower active material layer is formed in a region where the free electrolyte exists (height equal to or higher than the height of the free electrolyte). preferable. According to this structure, by injecting the electrolytic solution (dilute sulfuric acid), the P of the lower active material layer of the electrode plate is reduced.
Problems weight ratio of BSO ₄ is larger than the upper club material layer, a conductive additive that is added to the lower club material layer, the charge of the lower club material layer by electrodeposition container formation or charging after electrolyte injection The problem can be solved by improving the efficiency. In addition, the problem that the battery is repeatedly charged and discharged to cause stratification in the electrolytic solution and the formation of PbSO _{4 in the} lower active material layer progresses is that the average pore diameter of the lower active material layer is larger than that of the upper active material layer. The problem can be solved by both effects of containing the conductive additive in the lower active material layer.

The electrode plate of the sealed lead-acid battery of the present invention is formed by filling an active material paste into a grid-like current collector, and the lower active material layer and the upper active material layer are formed by the grid of the grid-like current collector. It is preferable to form the inner bone part forming the boundary as a boundary part. With this configuration, the upper active material layer and the lower active material layer can be clearly separated from each other by the inner bone without being mixed. In addition, cracks and the like can be prevented from occurring at the boundary between the upper active material layer and the lower active material layer.

When such an electrode plate is employed on the positive electrode plate side and carbon is used as a conductive additive, the average pore diameter of the lower active material layer is set to 1.5 times the average pore diameter of the upper active material layer. ~
Preferably, the amount is 2.0 times, and the amount of carbon is 0.1 to 0.5% by weight based on lead powder, which is a main raw material of the active material layer. When the average pore diameter of the lower active material layer is smaller than 1.5 times the average pore diameter of the upper active material layer, it is sufficient to cause a large difference in the pore diameter between the upper active material layer and the lower active material layer. It cannot be eliminated. On the other hand, when the ratio exceeds 2.0 times, there is a problem that the active material is greatly shrunk and the active material is easily dropped. On the other hand, if the amount of carbon is less than 0.1% by weight based on lead powder, which is a main raw material of the active material layer, the conductivity of the lower active material layer cannot be sufficiently increased. On the other hand, when the content exceeds 0.5% by weight, a coatable active material paste cannot be obtained, and the active material particles are covered with carbon, so that the capacity of the battery decreases.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1 and Comparative Example 1) The positive electrode plate of Example 1 was manufactured as follows. First, as shown in FIG. 1A, a well-known current collector consisting of a lattice body having an ear part 1, an outer bone 2, and an inner bone 3 extending in the vertical and horizontal directions inside the outer bone 2 was prepared. In this current collector, as shown in FIG. 1B, which is a cross-sectional view taken along the line BB of FIG. 1A, the inner bone 3 has a rhombic cross section and extends in the thickness direction of the current collector. The thickness dimension is equal to the thickness dimension of the outer bone 2. In this current collector, the direction in which the ear 1 shown by the arrow U1 protrudes is upward in the vertical direction. The upper part of the central inner bone 3a extending in the direction (lateral direction) orthogonal to the vertical direction U1 at the center of the current collector forms the upper active material filling portion 4, and the lower part of the central inner bone 3a is the lower active material. The filling portion 5 is formed. The lower active material filling portion 5 corresponds to an area where a free electrolyte (electrolyte not contained in the electrode group) existing between the wall of the battery case and the electrode group of the sealed lead-acid battery to be formed later exists. doing. Next, the current collector was filled with the active material paste by the active material paste continuous filling device shown in FIG. Active material paste continuous filling equipment
It has a belt 101 and an active material paste filling machine 102. The belt 101 advances in the direction of the arrow, and a plurality of current collectors S are arranged on the belt 101 so that the vertical direction of the current collector S and the traveling direction of the belt 101 are orthogonal to each other. The active material paste filling machine 102 includes an upper active material paste filling machine unit 10.
3 and a lower active material paste filling unit 104. The upper active material paste filling unit 103 includes an upper hopper 103a, and a filling main body 103b that receives the upper active material paste from the upper hopper 103a and fills the upper active material filling unit 4 of the current collector S with the upper active material paste. It is composed of The lower active material paste filling unit 104 includes:
A lower hopper 104a, and a filling body 10 for receiving the lower active material paste from the lower hopper 104a and filling the lower active material filling machine 5 of the current collector S with the lower active material paste.
4b. An upper active material paste and a lower active material paste are sent to the upper hopper 103a and the lower hopper 104a, respectively, from an active material paste manufacturing device (not shown). The filling main body 103b and the filling main body 104b are arranged such that the upper active material paste and the lower active material filling part 5 can be filled with the upper active material paste and the lower active material paste, respectively, at the center inner bone 3a.
Adjacent to each other. The lower active material paste is an active material paste that can form a larger average pore diameter than the active material layer formed by the upper active material paste when the active material layer is formed, and further includes a conductive additive. This lower active material paste is made of lead oxide powder containing metallic lead (hereinafter, referred to as “lead metal powder”).
(Hereinafter simply referred to as lead powder) and a conductive additive composed of 0.4% by weight of carbon with respect to the lead powder dispersed and added, and then a specific gravity of 15% by weight with respect to the lead powder 1.300 (20 ° C.) Was prepared by adding 15% by weight of water to the diluted sulfuric acid and lead powder and kneading. The upper active material paste is composed of a lead oxide powder containing metallic lead (hereinafter simply referred to as lead powder), 15% by weight of lead powder, diluted sulfuric acid having a specific gravity of 1.300 (20 ° C.) and 10% of lead powder. It was made by adding and kneading water by weight. The porosity is adjusted by the water content. The porosity increases as the water content increases.

When the upper active material paste and the lower active material paste are filled above and below the central inner bone 3a of the current collector, respectively, the upper active material paste and the lower active material paste after filling by the central inner bone 3a. Can be prevented, and furthermore, the occurrence of cracks or the like at the boundary between the upper active material paste and the lower active material paste can be prevented. Therefore, it is possible to prevent the active material from falling off, and to clearly distinguish the upper active material layer and the lower active material layer which are formed later.

Next, the undried electrode plate filled with the active material paste is subjected to ordinary aging and drying, followed by drying to obtain a height of 30 cm.
m, an unformed positive electrode plate having a width of 15 cm was prepared. Next, 20 unformed positive electrode plates and 21 known negative electrode plates having the same porosity of the upper and lower active material layers in the vertical direction and containing no conductive additive are laminated via a retainer made of glass fiber. I made a group of electrodes. Next, after placing the electrode group in the battery case, specific gravity 1.2
20 (20 ° C.) dilute sulfuric acid was injected to make a one-cell unformed battery. At this time, the free electrolyte (electrolyte not contained in the electrode group) existing between the wall of the battery case and the electrode group of the sealed lead-acid battery had half the height of the positive electrode plate. . That is, the lower active material filled portion 5 corresponds to a portion where the free electrolyte is present. Next, the unformed battery was battery-formed for 45 hours at a charging amount of 220% to complete a 2V-500Ah battery. FIG.
FIG. 3 is a plan view of a positive electrode plate arranged in the battery. As shown in the figure, an upper active material layer 6 is formed on the upper part in the vertical direction of the positive electrode plate, and a lower active material layer 7 is formed on the lower part. The upper active material layer 6 and the lower active material layer 7 are separated by a portion corresponding to the central inner bone 3a indicated by the broken line. Actually, the upper active material layer 6 and the lower active material layer 7
The inner bone 3 is formed so as to slightly cover it. FIG. 4
4A is an enlarged view of the surface of the upper active material layer 6, and FIG.
(B) is an enlarged view of the surface of the lower active material layer 7. As shown in this figure, the pores 7a of the lower active material layer 7 have an average pore diameter of 0.
It has a size of 6 μm, and is formed larger than the pores 6 a of the upper active material layer 6 having an average pore size of 0.3 μm. The lower active material layer 7 has carbon 7
b is dispersedly included. Thus, in this example, the average pore diameter of the lower active material layer was twice the average pore diameter of the upper active material layer.

Next, an active material paste similar to the upper active material paste was filled in the whole electrode plate, and the other parts were the same as in the present example to produce a positive electrode plate of Comparative Example 1 housed in a battery. That is, the positive electrode plate of Comparative Example 1 has a pore diameter smaller than the average pore diameter of the lower active material layer 7 of the positive electrode plate of the present example, and an active material layer containing no conductive additive is formed on the entire electrode plate. ing. Then, to measure the weight ratio of PbSO ₄ to the active material in the substantially central portion and substantially central portion of the plate bottom electrode plate upper part of the positive electrode plate of the present embodiment and the comparative example after completion of the container conversion. In addition,
These weight ratios are average values of 21 positive plates in the battery. Table 1 shows the measurement results.

[0018]

[Table 1] In this table, the reason why the weight ratio of PbSO ₄ at the lower part of the positive electrode plate of the comparative example is larger than that at the upper part is that the lower part of the positive electrode plate is free electrolyte solution during the start of battery formation after the injection of the electrolyte solution. This is because a large amount of SO ₄ ^2- was absorbed.
In the positive electrode plate of this embodiment, since the lower active material layer 7 contains the conductive additive, the formation efficiency of the battery formation is improved, and the weight ratio of PbSO ₄ can be reduced.

Next, the battery using the positive electrode plate of this embodiment and the battery using the positive electrode plate of the comparative example were discharged at 0.2 C (0.2 C10) for 3.5 hours with respect to the 10 hour rate capacity, and then discharged for 10 hours. And charging at 0.2 C (0.2 C 10) for 4.5 hours was repeated. Then, Example 1 and Comparative Example 1 in 50 cycles and 100 cycles
Approximately the center of the upper part of the positive electrode plate (the center of the upper active material layer) and the lower part of the electrode plate (the center of the lower active material layer)
, The weight ratio of PbSO _{4 to} the active material was measured. Table 2 shows the measurement results.

[0020]

[Table 2] In this table, the weight ratio of PbSO ₄ at the lower part of the positive electrode plate of the comparative example is larger than that at the upper part, and the difference becomes larger as the number of cycles increases, because the stratification of the electrolytic solution proceeds more than the charge and discharge of the battery. is there. In the positive electrode plate of this example, the PbSO 4 of the lower active material layer was formed by both increasing the average pore diameter of the lower active material layer as compared with the upper active material layer and by containing a conductive additive in the lower active material layer. _It can be seen that the weight ratio of ₄ can be reduced.

Next, the water content of the lower active material paste was changed to change the size of the average pore diameter of the lower active material layer with respect to the average pore diameter of the upper active material layer. A battery was prepared in which positive electrode plates having different ratios of the average pore diameter of the lower active material layer to the average pore diameter of the upper active material layer (average pore diameter ratio) were arranged. Then, after 50 cycles, the ratio of the weight ratio of PbSO _{4 to} the active material at the lower part of the electrode plate relative to the weight ratio of PbSO _{4 to} the active material at the upper part of the electrode plate, and the shrinkage ratio of the lower active material layer were measured. FIG. 5 shows the measurement results. According to this figure, the average pore diameter of the lower active material layer is 1.5 to 2.0 times the average pore diameter of the upper active material layer.
It can be seen that it is preferably set to 0 times. When the average pore diameter of the lower active material layer is smaller than 1.5 times the average pore diameter of the upper active material layer, it is sufficient to cause a large difference in the pore diameter between the upper active material layer and the lower active material layer. can not be eliminated, PbSO ₄ weight ratio of the lower club material layer to the PbSO ₄ weight ratio of the upper club material layer is significantly increased. On the other hand, when the ratio exceeds 2.0 times, the contraction of the lower active material layer is large, and the battery life is shortened.

Next, a battery in which positive electrodes having different amounts of carbon were arranged inside was manufactured in the same manner as in the present embodiment except that the amount of carbon (conductive additive) was changed with respect to the lead powder as the raw material of the active material layer. Was. And a ratio of the weight ratio of PbSO _{4 to} the active material at the lower portion of the electrode plate with respect to the weight ratio of PbSO _{4 to} the active material at the upper portion of the electrode plate after completion of the battery case formation;
The discharge capacity ratio of the battery was measured. FIG. 6 shows the measurement results. From the figure, without greatly reducing the discharge capacity to the amount of carbon (conductive additive) to 0.1 to 0.5 wt% with respect to lead powder, it can reduce the weight ratio of PbSO ₄ of the electrode plate lower I understand.

Example 2 and Comparative Example 2 FIG. 7 is a plan view of a positive electrode plate of Example 2. FIG. The positive electrode plate of this example uses the same current collector as that shown in FIG. 1, and sets a direction perpendicular to the direction in which the ear 11 protrudes as a vertical direction, and the direction indicated by an arrow U2 where the ear 11 is located. Is a positive electrode plate with the upper side in the vertical direction. In this positive electrode plate, the upper active material layer 16 is formed above a central inner bone extending in a direction (horizontal direction) perpendicular to the vertical direction at the center of the current collector, and the lower active material layer 1 is formed below the central inner bone.
7 are formed. The upper active material layer 16 and the lower active material layer 17 are formed of the same active material as the upper active material layer 6 and the lower active material layer 7 of the positive electrode plate shown in FIG. That is, the pores of the lower active material layer 17 are formed larger (twice) than the pores of the upper active material layer 16. Further, carbon is dispersed in the lower active material layer 17. These positive electrode plates were completed in a state where they were arranged in the battery by battery case formation similarly to the positive electrode plate shown in FIG. Specifically, as shown in FIG. 8, a positive electrode plate 21 and a known negative electrode plate 22 having the same porosity in the upper and lower active material layers in the vertical direction and containing no conductive additive are laminated via a retainer 23. The assembled electrode group is arranged in a battery case. In this drawing, reference numeral 21a denotes a positive electrode terminal extending from a strap connecting each positive electrode ear, and 22a denotes a negative electrode terminal extending from a strap connecting each negative electrode ear.

Next, an active material paste similar to the upper active material paste was filled in the entire electrode plate, and the other conditions were the same as in Example 2 to prepare a positive electrode plate of Comparative Example 2 housed in the battery. Then, the same charge / discharge as described above was repeated for each battery, and the PbSO 4 with respect to the active material at approximately the center of the upper part of the positive electrode plate and the substantially central part of the lower part of the electrode plate of the present example and the comparative example at 50 cycles and 100 cycles, Table 3 in which the weight ratio of ₄ was measured shows the measurement results.

[0025]

[Table 3] Also in this example, the PbSO 4 under the positive electrode plate of Comparative Example 2 was used.
_The reason that the weight ratio of No. ₄ is higher than that of the upper portion and the difference increases as the number of cycles increases is because the stratification of the electrolyte proceeds more than the charging and discharging of the battery. Similarly to the positive electrode plate of Example 1, the positive electrode plate of Example 2 has an average pore diameter of the lower active material layer larger than that of the upper active material layer and contains a conductive additive in the lower active material layer. It can be seen that both of these facts make it possible to reduce the weight ratio of PbSO _{4 in} the lower active material layer.

In each of the above embodiments, the present invention is applied to a positive electrode plate. However, even if the present invention is applied to a negative electrode plate,
Needless to say, the weight ratio of PbSO _{4 in} the lower active material layer can be reduced.

Hereinafter, the configuration of the present invention described in the specification will be described.

(1) An active material paste is provided on the upper active material filled portion and the lower active material filled portion of the current collector formed of a lattice in which the upper active material filled portion and the lower active material filled portion are separated by a bone. And filling the active material layer to form an electrode plate for a sealed lead-acid battery in which the vertical direction is determined. The lower active material-filled portion includes the upper active material layer when the active material layer is formed. A method of manufacturing an electrode plate for a sealed type lead-acid battery, characterized in that an average pore diameter can be formed larger than an active material layer formed in a material filling portion, and an active material paste containing a conductive additive is filled. .

(2) An active material paste is provided on the upper active material filled portion and the lower active material filled portion of the current collector formed of a lattice in which the upper active material filled portion and the lower active material filled portion are separated by a bone. After filling an active material paste from a filling machine, a method for producing an active material layer and forming an electrode plate for a sealed lead-acid battery in which the top and bottom are defined, wherein the active material paste filling machine includes the upper active material A lower active material paste filling unit having an upper active material paste filling unit for filling an upper active material paste in a filling unit and a lower active material paste filling unit for filling a lower active material paste in the lower active material filling unit; As the paste, an active material paste that can be formed to have a larger average pore diameter than the active material layer formed in the upper active material filling portion at the time of forming the active material layer and that contains a conductive additive is used. Method for producing a sealed lead acid battery electrode plate, characterized in that.

[0030]

According to the present invention, as in the case of the upper active material layer, the electrolytic solution permeates the lower active material layer, the charge / discharge reaction in the lower active material layer is maintained, and the lower active material layer is converted to PbSO ₄ . It can be prevented from being left. Then, it is possible to prevent the charge and discharge from being locally concentrated on the upper part of the electrode plate. In the present invention, although it is possible to prevent the lower club material layer Remains ₄ of PbSO, compared to the upper portion of the active material layer, the content of low conductivity PbSO ₄ is increased slightly . Therefore, the lower active material layer was made to contain a conductive additive to prevent the lower active material layer from lowering in electrical conductivity. As described above, according to the present invention, the capacity of the battery is reduced and the cycle life is shorter than in the conventional case where the electrode group is pressed with a high pressure in the stacking direction or the electrolyte is gelled or solated. Can be efficiently suppressed from becoming shorter.

[Brief description of the drawings]

FIG. 1A is a plan view of a current collector used for a positive electrode plate used in a sealed lead-acid battery of the present embodiment, and FIG. 1B is a cross-sectional view taken along line BB of FIG. 1A. It is.

FIG. 2 is a schematic view of an active material paste continuous filling apparatus used for manufacturing a positive electrode plate of the present embodiment.

FIG. 3 is a plan view of a positive electrode plate used in the sealed lead-acid battery of the present embodiment.

FIG. 4A is an enlarged view of an upper active material layer of a positive electrode plate used in the sealed lead-acid battery of the present embodiment, and FIG. 4B is a view of the positive electrode plate used in the sealed lead-acid battery of the present embodiment. It is an enlarged view of a lower active material layer.

FIG. 5 shows the ratio of the average pore diameter of the lower active material layer to the average pore diameter of the upper active material layer, and the P for the active material at the upper part of the electrode plate.
P for the active material below the plate to the weight ratio of bSO ₄
FIG. ₄ is a diagram showing the relationship between the weight ratio of bSO ₄ and the shrinkage rate of the lower active material layer.

FIG. 6 shows the amount of carbon with respect to the lead powder in the lower active material layer,
It is a diagram showing the relationship between the PbSO ₄ weight ratio and discharge capacity ratio of the battery of to the active material of the electrode plate bottom to weight ratio of PbSO ₄ to the active material of the electrode plate top.

FIG. 7 is a plan view of a positive electrode plate used in a sealed lead-acid battery according to another embodiment of the present invention.

FIG. 8 is a perspective view of a battery in which a positive electrode plate used in a sealed lead-acid battery according to another embodiment of the present invention is disposed.

[Explanation of symbols]

 Reference Signs List 3 inner bone 3a central inner bone 4 upper active material filling part 5 lower active material filling part 6,16 upper active material layer 7,17 lower active material layer 102 active material paste filling machine 103 upper active material paste filling machine part 104 lower active Material paste filling machine

Claims (4)

[Claims] 1. A sealed lead-acid battery in which a vertical direction in a use state is determined in advance and a fluid electrolyte is used as an electrolyte, wherein a lower active material is located at least in a lower region of the positive electrode plate in the vertical direction. The layer has a larger average pore diameter than the upper active material layer located in the upper region above it, and the lower active material layer has a conductive additive added thereto. . 2. The sealed lead-acid battery according to claim 1, wherein the lower region is a region where a free electrolyte is present. 3. The at least positive electrode plate is formed by filling a grid-like current collector with an active material paste, and the lower active material layer and the upper active material layer are formed of the grid-like current collector. 2. The sealed lead-acid battery according to claim 1, wherein the inner bone part forming the lattice is formed as a boundary part. 4. An average pore diameter of the lower active material layer of the positive electrode plate is 1.5 to 2.0 times an average pore diameter of the upper active material layer.
0 times, wherein the conductive additive is carbon, and the amount of the carbon is 0.1 to 0.5% by weight based on lead powder which is a main raw material of the active material layer. The sealed lead-acid battery according to claim 2.