JP7348081B2 - liquid lead acid battery - Google Patents

Description

The present invention relates to a liquid lead acid battery.

As environmental problems have become more serious in recent years, exhaust gas regulations for automobiles and the like have become stricter worldwide. In order to comply with this regulation, automobile manufacturers have developed various environmental technologies. A known environmental technology is an idling stop system (hereinafter referred to as "ISS") that temporarily stops the engine when the vehicle is stopped. Internal combustion vehicles equipped with an ISS (hereinafter referred to as "ISS vehicles") can reduce fuel consumption due to idling when stopped at traffic lights, etc., thereby improving fuel efficiency and reducing exhaust emissions.

Lead-acid batteries for ISS vehicles are repeatedly charged and discharged in a partial state of charge (also called "PSOC"), which is not a fully charged state, because the engine frequently repeats stopping and starting. It will be done. Lead-acid batteries in ISS vehicles should be used in a partially charged state with a charging rate of 80% to 90%, because if the charging rate is higher than 90%, the receptivity to charging will decrease and the efficiency of using regenerative energy will decrease. is considered desirable.

Stratification of the electrolyte, which is one of the causes of deterioration of liquid lead-acid batteries, is a phenomenon in which there is a difference in the concentration of the electrolyte between the upper and lower parts of the battery container, and a partially charged state of 80% to 90% can be maintained. This is likely to occur when using lead-acid batteries that are controlled to In the upper part where the electrolyte concentration is low, metallic lead dendrites precipitate and grow on the surface of the negative electrode plate, making it easy for internal short circuits to occur. On the other hand, in the lower part where the concentration of the electrolytic solution is high, the high concentration of the electrolytic solution tends to cause sulfation, in which the nonconducting lead sulfate enlarges on the surface of the negative electrode plate.

When sulfation occurs, the release of sulfuric acid from the negative electrode active material is suppressed, thereby reducing the charge acceptance of the lower part of the negative electrode plate. When the charge acceptance of the lower part of the negative electrode plate decreases, the charging and discharging reactions mainly proceed in the upper part of the negative electrode plate, which may cause the positive electrode active material on the upper part of the positive electrode plate, which is opposite to the upper part of the negative electrode plate, to soften, and the current collector. Corrosion of the lead alloy substrate progresses, leading to the premature end of the lead-acid battery's life.

As for a technique for suppressing stratification of an electrolytic solution, for example, the technique described in Patent Document 1 can be mentioned.
Patent Document 1 discloses that in order to suppress stratification by more effectively utilizing the stirring action of the electrolyte caused by the gas generated during charging, an upper part of the housing space and a It is described that a communication channel communicating with the lower part is provided. As a result, during charging, an upward flow of electrolyte occurs in the storage space as the gas generated by the electrode plate group rises, and a corresponding downward flow occurs in the communication channel. Therefore, it is stated that by effectively generating convection of the electrolytic solution within the container, the stirring action of the electrolytic solution can be enhanced and stratification can be suppressed.

On the other hand, a liquid lead-acid battery includes a positive electrode plate in which a positive electrode mixture is held on a positive electrode current collector, and a negative electrode plate in which a negative electrode mixture is held in a negative electrode current collector. The positive electrode current collector and the negative electrode current collector have a rectangular lattice-shaped substrate and ears continuous with the lattice-shaped substrate, as shown in FIG. 1 of Patent Document 2, for example. The lattice-shaped substrate has an upper bone along one side of the rectangle forming the lattice-shaped substrate, and a plurality of middle bones connected to the upper bone and existing below the upper bone. The ears protrude upward from a position offset from the center of one side of the upper bone.
However, Patent Documents 1 and 2 do not describe the relationship between the potential distribution of the electrode plate during charging and discharging and the stirring action of the electrolytic solution.

Japanese Patent Application Publication No. 2015-176659 Patent No. 3452171

An object of the present invention is to provide a novel liquid lead-acid battery in which stratification of the electrolyte is suppressed due to the stirring action of gas generated during charging even when used in a partially charged state.

In order to solve the above problems, the liquid lead-acid battery according to the first embodiment of the present invention has the following configurations (1) to (4).
(1) A solution comprising an electrode plate group in which a positive electrode plate having a positive electrode current collector and a positive electrode mixture, and a negative electrode plate having a negative electrode current collector and a negative electrode mixture are alternately stacked with separators interposed therebetween. It is a type lead acid battery. The positive electrode current collector has a rectangular lattice-shaped substrate and ears continuous with the lattice-shaped substrate, and a positive electrode mixture is held on the lattice-shaped substrate. The lattice-shaped substrate has an upper bone along one side of the rectangle forming the lattice-shaped substrate, and a plurality of middle bones connected to the upper bone and existing below the upper bone. The ears protrude upward from a position offset from the center of one side of the upper bone.

(2) Among the divided bodies produced by cutting the positive electrode current collector along the diagonal line passing through the corner of one side of the rectangle forming the grid-like substrate, the divided body in which the ears are present is connected to the upper bone of the ear. It is divided into a first part and a second part by a reference line K passing through the center point P on the boundary line and perpendicular to the upper bone, and the first part has a larger area than the second part.

(3) On a coordinate plane where both the x-axis and the y-axis are linear scales, each resistance value Rn between each cutting surface Cn of the plurality of backbones in the first part and the center point P is expressed as the y-coordinate, All the plots made with each distance Xn between the center point of each cut plane Cn and the center point P as the x coordinate can be approximated to two straight lines with different slopes with x=H as the intersection point, and each of the plots where x<H The ratio A/B between the average value A of each resistance value Rn at distance Xn and the average value B of each resistance value Rn at each distance Xn where x≧H is 0.35 or more and 0.55 or less. be.
In addition, the above-mentioned "can be approximated to a straight line" means that the absolute value |ρ| of the correlation coefficient ρ is 0.90 or more when a plurality of plots are subjected to linear regression using the least squares method. Moreover, "two straight lines with different slopes" means that the ratio (a1/a2) of the slopes a1 and a2 (a1>a2) of the two straight lines is 1.3 or more.

(4) The separator has a film-like base portion, and the base portion has a porosity of 45 to 70% as measured by mercury porosimetry.

According to the present invention, it is possible to provide a novel liquid lead-acid battery in which stratification of the electrolytic solution is suppressed by the stirring action of gas generated during charging even when used in a partially charged state.

It is a front view showing the positive electrode current collector which constitutes the positive electrode plate which the liquid lead acid battery of the first embodiment has. FIG. 2 is a front view showing a divided body in which ears are formed by cutting the positive electrode current collector of FIG. 1 along a diagonal line passing through one corner of a rectangle forming a lattice-like substrate. It is a front view which shows the positive electrode collector which comprises the positive electrode plate which the liquid lead-acid battery of 2nd embodiment has. FIG. 3 is a front view showing a divided body in which ears are formed by cutting the positive electrode current collector of FIG. 2 along a diagonal line passing through one corner of a rectangle forming a lattice-like substrate. Each resistance value Rn between each cut surface Cn of the plurality of backbones and the center point P of the ear in the first part of the positive electrode current collector obtained for sample No. 1 prepared in the example , is a graph showing the relationship between each distance Xn between the center point of each cut plane Cn and the center point P of the ear. Each resistance value Rn between each cut surface Cn of the plurality of backbones and the center point P of the ear in the first part of the positive electrode current collector obtained for sample No. 2 prepared in the example , is a graph showing the relationship between each distance Xn between the center point of each cut plane Cn and the center point P of the ear. Each resistance value Rn between each cut surface Cn of the plurality of backbones and the center point P of the ear in the first part of the positive electrode current collector obtained for sample No. 3 prepared in the example , is a graph showing the relationship between each distance Xn between the center point of each cut plane Cn and the center point P of the ear. Each resistance value Rn between each cut surface Cn of the plurality of backbones and the center point P of the ear in the first part of the positive electrode current collector obtained for sample No. 4 prepared in the example , is a graph showing the relationship between each distance Xn between the center point of each cut plane Cn and the center point P of the ear. Each resistance value Rn between each cut surface Cn of the plurality of backbones and the center point P of the ear in the first part of the positive electrode current collector obtained for sample No. 5 prepared in the example , is a graph showing the relationship between each distance Xn between the center point of each cut plane Cn and the center point P of the ear. Each resistance value Rn between each cut surface Cn of the plurality of backbones and the center point P of the ear in the first part of the positive electrode current collector obtained for sample No. 6 prepared in the example , is a graph showing the relationship between each distance Xn between the center point of each cut plane Cn and the center point P of the ear. Each resistance value Rn between each cut surface Cn of the plurality of backbones and the center point P of the ear in the first part of the positive electrode current collector obtained for sample No. 7 prepared in the example , is a graph showing the relationship between each distance Xn between the center point of each cut plane Cn and the center point P of the ear. It is a graph showing the charging/discharging pattern of one cycle of the life test conducted in the example.

Embodiments of the present invention will be described below, but the present invention is not limited to the embodiments shown below. In the embodiments shown below, technically preferable limitations are made for carrying out the present invention, but these limitations are not essential to the present invention.

[Configuration of liquid lead acid battery of first embodiment and second embodiment]
The liquid lead-acid batteries of the first embodiment and the second embodiment have a monoblock type battery case, a lid, and six electrode plate groups. The battery case is divided into six cell chambers by partition walls. The six cell chambers are arranged along the longitudinal direction of the battery case. One electrode plate group is arranged in each cell chamber. Electrolyte is injected into each cell chamber.
Each electrode plate group has a laminate including a plurality of positive electrode plates and negative electrode plates arranged alternately, and a separator arranged between the positive electrode plates and the negative electrode plates.

The positive electrode plate has a positive electrode current collector and a positive electrode mixture (a mixture containing a positive electrode active material). The positive electrode current collector has a rectangular lattice-shaped substrate and ears continuous with the lattice-shaped substrate, and a positive electrode mixture is held on the lattice-shaped substrate. The negative electrode plate includes a negative electrode current collector and a negative electrode mixture (a mixture containing a negative electrode active material). The negative electrode current collector has a rectangular lattice-shaped substrate and ears continuous with the lattice-shaped substrate, and a negative electrode mixture is held on the lattice-shaped substrate. The plurality of positive electrode plates and negative electrode plates are arranged alternately with separators interposed therebetween. The number M _n of negative electrode plates constituting the laminate is one more than the number M _p of positive electrode plates.

The negative electrode plate is housed within a bag-shaped separator. Then, by alternately stacking the bag-shaped separators containing the negative electrode plates and the positive electrode plates, the separator is placed between the positive electrode plate and the negative electrode plate. Note that the positive electrode plates may be housed in a bag-like separator and stacked alternately with the negative electrode plates.
The separator has at least a film-like base portion. The base portion has a porosity of 45 to 70% by mercury intrusion method. Note that the shape of the separator is not particularly limited, and may be a bag-like shape that can accommodate the positive or negative electrode plate, or a film-like material may be bent into a U-shape to sandwich the positive or negative electrode plate. It may also be in the form of a film that allows for

In addition, each electrode plate group includes a positive electrode strap and a negative electrode strap that connect the plurality of positive electrode plates and negative electrode plates that constitute the laminate at different positions in the width direction, and a positive electrode intermediate pole that rises from the positive electrode strap and the negative electrode strap, respectively. and a negative intermediate pole, and a positive pole and a negative pole serving as external terminals.
The positive electrode strap and the negative electrode strap connect and fix the ears of a plurality of positive electrode plates and negative electrode plates, respectively. The positive intermediate poles and the negative intermediate poles of adjacent cell chambers are resistance welded to electrically connect the adjacent cells in series.
The positive pole pole and the negative pole pole are formed on the positive pole strap and the negative pole strap, which are arranged in the cell chambers at both ends in the cell arrangement direction, with small pieces interposed therebetween.

[Positive electrode current collector of first embodiment]
As shown in FIG. 1, the positive electrode current collector 1 of the first embodiment has a rectangular grid-like substrate 11 and ears 12 continuous to the grid-like substrate 11, and the positive electrode mixture is held on the grid-like substrate 11. has been done. The lattice-shaped substrate 11 has an upper bone 111 along one side of the rectangle forming the lattice-shaped substrate 11, and a plurality of middle ribs 112 connected to the upper bone 111 and existing below the upper bone 111. The ear 12 protrudes upward from a position shifted to one side (to the right in FIG. 1) from the center of one side of the upper bone 111.

Among the divided bodies produced by cutting the positive electrode current collector 1 along the diagonal line T passing through the right (one side) corner of the rectangle forming the grid-like substrate 11, the divided body in which the ears are present is shown in FIG. show. This divided body 2 is divided into a first part 21 and a second part 22 by a reference line K that passes through a center point P on a boundary line L between the ear 12 and the upper bone 111 and is perpendicular to the upper bone 111. The first portion 21 has a larger area than the second portion 22.

The first portion 21 has a cut surface of 13 midribs 112. On a coordinate plane where both the x-axis and y-axis are linear scales, each resistance value R1 to R13 between each of the 13 cutting planes C1 to C13 and the center point P is expressed as the y coordinate, and the center of each cutting plane C1 to C13. When each distance X1 to X13 between a point and the center point P is plotted as an x coordinate, all plots can be approximated to two straight lines with different slopes with x=H as the intersection. The ratio A/B of the average value A of each resistance value Rn at each distance Xn where x<H and the average value B of each resistance value Rn at each distance Xn where x≧H is 0.35. It is 0.55 or less.

For example, if the dimension S1 = 115.0 mm, the dimension S2 = 110.0 mm, the dimension S3 = 100.0 mm, and the dimension S4 = 45.0 mm, the thickness (cross-sectional area perpendicular to the longitudinal direction) of the backbone 112 is the entire They are the same and are 0.85 mm or more and 1.00 mm or less.
The positive electrode current collector 1 can be obtained by a conventional method such as a punching method, an expanding method, or a gravity casting method.

[Positive electrode current collector of second embodiment]
As shown in FIG. 3, the positive electrode current collector 1A of the second embodiment has a rectangular grid-like substrate 11A and ears 12 continuous to the grid-like substrate 11A, and the positive electrode mixture is held on the grid-like substrate 11A. has been done. The lattice-shaped substrate 11A includes an upper bone 111 along one side of the rectangle forming the lattice-shaped substrate 11A, and a plurality of middle bones connected to the upper bone 111 and existing below the upper bone 111. The thickness of the back bone changes at an intermediate position in the vertical direction, and the middle bone 112a above the middle position (on the upper bone 111 side) is thinner than the thickness of the middle bone 112b below the middle position.
The ear 12 protrudes upward from a position shifted to one side (to the right in FIG. 3) from the center of one side of the upper bone 111.

Among the divided bodies produced by cutting the positive electrode current collector 1A along the diagonal line T passing through the right (one side) corner of the rectangle forming the grid-like substrate 11A, the divided body in which the ears are present is shown in FIG. show. This divided body 2A is divided into a first portion 21A and a second portion 22A by a reference line K passing through a center point P on a boundary line L between the ear 12 and the upper bone 111 and perpendicular to the upper bone 111. The first portion 21A has a larger area than the second portion 22A.

The first portion 21A has a cut surface of 13 midribs. The cutting surfaces C1 to C5 are the cutting surfaces of the midrib 112a, and the cutting surfaces C6 to C13 are the cutting surfaces of the midrib 112b. On a coordinate plane where both the x-axis and y-axis are linear scales, each resistance value R1 to R13 between each of the 13 cutting planes C1 to C13 and the center point P is expressed as the y coordinate, and the center of each cutting plane C1 to C13. When each distance X1 to X13 between a point and the center point P is plotted as an x coordinate, all plots can be approximated to two straight lines with different slopes with x=H as the intersection. The ratio A/B of the average value A of each resistance value Rn at each distance Xn where x<H and the average value B of each resistance value Rn at each distance Xn where x≧H is 0.35. It is 0.55 or less.

For example, when the dimension S1=115.0 mm, the dimension S2=110.0 mm, the dimension S3=100.0 mm, and the dimension S4=45.0 mm, the thickness (cross-sectional area perpendicular to the longitudinal direction) of the backbone 112a is 0.0 mm. The thickness of the backbone 112b is 75 mm or more and 0.85 mm or less, and the thickness of the backbone 112b is 1.15 mm or more and 1.25 mm or less.
The positive electrode current collector 1A can be obtained by a conventional method such as a punching method, an expanding method, or a gravity casting method.

[action, effect]
The smaller the ratio A/B of the positive electrode current collector of a liquid lead-acid battery, the more easily the lower part of the positive electrode plate is polarized than the upper part during charging, which promotes gas generation from the lower part, resulting in a partially charged state. Even in this case, the stirring action of the electrolyte solution can be obtained. However, when the ratio A/B is less than 0.35, the resistance value of the path from the bottom of the positive electrode current collector to the ear is significantly higher than the resistance value of the path from the top to the ear, so that The charge/discharge reaction becomes difficult to proceed. Therefore, the amount of gas generated from the lower part is insufficient to obtain an electrolyte stirring action in a partially charged state.
In liquid lead-acid batteries where the ratio A/B of the positive electrode current collector is greater than 0.55, the charging/discharging reaction is difficult to proceed on the entire positive electrode plate, so the amount of gas generated is due to the electrolyte stirring action in the partially charged state. It will be insufficient to obtain.

Since the ratio A/B of the positive electrode current collector 1 of the first embodiment and the positive electrode current collector 1A of the second embodiment is in the range of 0.35 or more and 0.55 or less, the first embodiment and the second embodiment In liquid type lead-acid batteries, the charging and discharging reactions occur uniformly across the entire positive electrode plate, so the amount of gas generated from the bottom is sufficient to stir the electrolyte in the partially charged state. . Therefore, according to the liquid lead-acid batteries of the first embodiment and the second embodiment, when used in a partially charged state, stratification of the electrolytic solution is suppressed, and the life span can be extended.

Furthermore, in a liquid lead-acid battery using the positive electrode current collector 1 of the first embodiment and a liquid lead-acid battery using the positive electrode current collector 1A of the second embodiment, the base part of the separator was measured by the mercury intrusion method. When the porosity is 45 to 70%, the amount of diffusion of sulfate ions passing through the pores of the separator is improved, an increase in internal resistance is suppressed, and the gas generated from the bottom of the positive electrode plate is This prevents the electrolyte from being trapped in the pores, and the stirring action of the electrolyte in the partially charged state is more effective.

If the porosity of the base portion is less than 45%, the amount of diffusion of sulfate ions passing through the separator will not improve, and therefore the effect of suppressing an increase in internal resistance will not be obtained. If the porosity of the base portion is greater than 70%, gas generated from the lower part of the positive electrode plate is likely to be trapped in the pores of the separator, making it impossible to sufficiently stir the electrolyte. More preferably, the porosity of the base portion is 55 to 70%. Within this range, increase in internal resistance can be further suppressed.

[Aspects of the method]
A second aspect of the present invention includes a method for designing a positive electrode current collector that constitutes a positive electrode plate (after chemical formation) of a liquid lead-acid battery. This design method has the following configurations (a) to (c).
(a) The positive electrode current collector has a rectangular lattice-shaped substrate and ears continuous to the lattice-shaped substrate, a positive electrode mixture is held on the lattice-shaped substrate, and the lattice-shaped substrate has and a plurality of middle bones that are connected to the upper bone and exist below the upper bone, and the ears protrude upward from a position shifted to one side from the center of one side of the upper bone.
(b) Among the divided bodies created by cutting the positive electrode current collector along the diagonal line passing through one corner of the rectangle, the divided body where the ear exists is located at the center point P on the boundary line with the upper bone of the ear. It is divided into a first part and a second part by a reference line perpendicular to the upper bone.
(c) On a coordinate plane where both the x-axis and y-axis are linear scales, the distance between each cutting plane Cn of the plurality of midbones and the center point P in the first part having a larger area than the second part. All plots made with each resistance value Rn as the y coordinate and each distance Xn between the center point of each cut plane Cn and the center point P as the x coordinate are two straight lines with different slopes with x=H as the intersection point. The ratio A/B can be approximated by the average value A of each resistance value Rn at each distance Xn where x<H, and the average value B of each resistance value Rn at each distance Xn where x≧H, The value should be 0.35 or more and 0.55 or less.

[Preparation of test battery]
Lead-acid batteries of samples No. 1 to No. 7 were produced as lead-acid batteries having the same structure as the lead-acid battery of the embodiment.
The lead-acid batteries of samples No. 1 to No. 7 are D23 type liquid lead-acid batteries for idling stop, and have a different configuration of the grid-like substrate of the positive electrode current collector, but otherwise have the same configuration. has.

<Sample No.1>
The lead-acid battery of sample No. 1 has a positive electrode current collector 1 having the shape shown in FIG. The thickness of the backbone 112 (cross-sectional area perpendicular to the longitudinal direction) is 1.05 mm.
First, a step of punching out a strip-shaped lead alloy sheet (size corresponding to a plurality of positive electrode current collectors 1), a step of filling the grid-shaped substrate 11 with the positive electrode active material paste, a preheating drying step, an aging drying step, and By performing the cutting process, a positive electrode plate having the positive electrode current collector 1 shown in FIG. 1 before chemical formation was produced. Each step was carried out in the usual manner.

The negative electrode plate has a negative electrode current collector having the same shape as the positive electrode current collector 1 shown in FIG. 0 mm, dimension S4=45.0 mm, and the thickness (cross-sectional area perpendicular to the longitudinal direction) of the backbone 112 is 0.75 mm. The negative electrode plate before chemical formation was also produced by performing the same steps as those for the positive electrode plate in a normal manner.
Next, seven of the obtained unformed negative electrode plates placed in a polyethylene bag-like separator and six obtained unformed positive electrode plates were alternately laminated to obtain a laminate. Next, using a COS (cast-on-strap) type casting device, a strap, an intermediate pole, and a terminal pole were formed on the positive and negative plates of each laminate to obtain a plate group.

The bag-shaped separator has a film-shaped base portion with a thickness of 0.3 mm, and a plurality of ribs that protrude from the surface of the base portion and have a protruding height of 0.5 mm. The bag-shaped separator is formed into a bag by folding a film-like material with a width of 110 mm and a length of 230 mm so that the surface on which the ribs are formed faces outward, and gear-sealing both side edges. This is what I did. As a result of measurement by mercury porosimetry, the porosity of the base portion of the separator was 60%.

Prepare six of these electrode plate groups, put them into each cell chamber of the battery case, resistance weld the intermediate pole between adjacent cell chambers, heat weld the battery case and the lid, and insert them into each cell chamber from the injection hole. A D23 type liquid lead-acid battery for idling stop was assembled by performing normal steps such as injecting an electrolyte and closing the injection hole. Thereafter, the specific gravity after the container formation was made to be 1.285 (20° C. equivalent value) by performing the container formation in a usual manner. In this way, the No. 1 lead-acid battery was obtained.

<Sample No.2>
The lead-acid battery of sample No. 2 has a positive electrode current collector 1 having the shape shown in FIG. is the same as sample No.1. After assembling a D23 type idling stop liquid lead-acid battery using the same method as sample No. 1 except that the positive electrode current collector 1 of sample No. I got a storage battery.

<Sample No.3>
The lead-acid battery of sample No. 3 has a positive electrode current collector 1 having the shape shown in FIG. is the same as sample No.1. A D23 type idling stop liquid lead-acid battery was assembled using the same method as sample No. 1, except that the positive electrode current collector 1 of sample No. 3 was used, and then battery cell formation was performed and the lead I got a storage battery.

<Sample No.4>
The lead-acid battery of sample No. 4 has a positive electrode current collector 1 having the shape shown in FIG. is the same as sample No.1. A D23 type idling stop liquid lead-acid battery was assembled using the same method as sample No. 1, except that the positive electrode current collector 1 of sample No. 4 was used, and then battery cell formation was performed to form the lead-acid battery of No. 4. I got a storage battery.

<Sample No.5>
The lead-acid battery of sample No. 5 has a positive electrode current collector 1 having the shape shown in FIG. is the same as sample No.1. A D23 type idling stop liquid lead-acid battery was assembled using the same method as sample No. 1 except that the positive electrode current collector 1 of sample No. I got a storage battery.

<Sample No.6>
The lead-acid battery of sample No. 6 has a positive electrode current collector 1 having the shape shown in FIG. is the same as sample No.1. A D23 type idling stop liquid lead-acid battery was assembled using the same method as sample No. 1 except that the positive electrode current collector 1 of sample No. 6 was used, and then a battery cell formation was performed and the lead-acid battery of No. 6 was used. I got a storage battery.

<Sample No.7>
The lead acid battery of sample No. 7 has a positive electrode current collector 1A having the shape shown in FIG. 3, and has dimensions S1 = 115.0 mm, dimensions S2 = 110.0 mm, dimensions S3 = 100.0 mm, and dimensions S4 = 45. The thickness of the backbone 112a (cross-sectional area perpendicular to the longitudinal direction) is 0.80mm, and the thickness of the backbone 112b is 1.20mm. A D23 type idling stop liquid lead-acid battery was assembled using the same method as sample No. 1 except that the positive electrode current collector 1A of sample No. 7 was used. I got a storage battery.

[Measurement of each resistance value of the cut surface of the divided body]
First, the lead-acid batteries of samples No. 1 to No. 7 obtained were disassembled, the positive electrode plate was taken out, and the positive electrode active material was removed from the positive electrode plate and washed. A positive electrode current collector 1.1A was obtained. Next, by cutting the positive electrode current collectors 1 and 1A with scissors along the diagonal line T shown in FIGS. 1 and 3, respectively, the divided bodies 2 and 2A with ears shown in FIGS. 2 and 4 are obtained. Obtained. In the divided body 2 where the ears are present, the first portion 21 divided by the reference line K has 13 cut surfaces of the midrib 112. In the divided body 2A where the ears are present, the first portion 21A divided by the reference line K has a total of 13 cut surfaces of the midribs 112a and 112b.

Next, each resistance value Rn (R1 to R13) between the center point P of the ear 12 and the cut surfaces C1 to C13 of each backbone was measured three times using a resistance meter (3554 BATTERY HiTESTER manufactured by HIOKI). were measured and the average value was calculated. Further, each distance Xn (X1 to X13) between the center point P and the center point of each of the cut surfaces C1 to C13 was measured with a ruler. The results of these measurements (each resistance value Rn is the average value of three measurements) are shown in Tables 1 to 7.

Next, for each sample, the measurement results were plotted on a coordinate plane in which both the x-axis and the y-axis were linear scales, with the resistance value Rn (average value of three measurements) as the y-coordinate and the distance Xn as the x-coordinate. As a result, graphs shown in FIGS. 5 to 11 were obtained. Figure 5 shows the results of No. 1, Figure 6 shows the results of No. 2, Figure 7 shows the results of No. 3, Figure 8 shows the results of No. 4, Figure 9 shows the results of No. 5, FIG. 10 shows the results of No. 6, and FIG. 11 shows the results of No. 7.

As shown in FIG. 5, in sample No. 1, all plots could be approximated to two straight lines T1 and T2 having different slopes with x=H (value between X8 and X9) as the intersection point. Next, each resistance value (average value of three measurements) at each distance X1 to X8 where x<H, the average value A of R1 to R8, and each resistance value at each distance X9 to X13 where x≧H (Average value of three measurements) The average value B of Rn was calculated, and the ratio A/B was calculated from these calculated values. The results are shown in Table 8.

As shown in Table 8, the ratio A/B of sample No. 1 was 0.31.
In addition, as shown in Figures 6 to 10, in samples No. 2 to No. 6, all plots have two lines with different slopes with x = H (value between X9 and X10) as the intersection point. It was possible to approximate straight lines T1 and T2. Next, each resistance value (average value of three measurements) at each distance X1 to X9 where x<H, the average value A of R1 to R9, and each resistance value at each distance X10 to X13 where x≧H (Average value of three measurements) The average value B of Rn was calculated, and the ratio A/B was calculated from these calculated values. The results are shown in Tables 9 to 13.

As shown in Tables 9 to 13, the ratio A/B of sample No. 2 is 0.35, the ratio A/B of sample No. 3 is 0.45, and the ratio A/B of sample No. 4 is 0.35. 50, the ratio A/B of sample No. 5 was 0.55, and the ratio A/B of sample No. 6 was 0.65.
Further, as shown in FIG. 11, in sample No. 7, all plots could be approximated to two straight lines T1 and T2 having different slopes with x=H (value of X10) as the intersection point. Next, each resistance value (average value of three measurements) at each distance X1 to X9 where x<H, the average value A of R1 to R9, and each resistance value at each distance X10 to X13 where x≧H (Average value of three measurements) The average value B of Rn was calculated, and the ratio A/B was calculated from these calculated values. The results are shown in Table 14.

As shown in Table 14, the ratio A/B of sample No. 7 was 0.55.

[Test and evaluation]
The obtained lead-acid batteries No. 1 to No. 7 were subjected to a life test using the EUCAR power assist profile. FIG. 12 shows a charging/discharging pattern for one cycle of this test. C ₂ is the 2 hour rate capacity. In this charge/discharge pattern, there is a deep discharge in a partially charged state.
After 100 cycles of this life test, the specific gravity of the electrolytic solution was measured at the upper and lower parts of the container using an optical hydrometer, and the difference in specific gravity between the upper and lower parts was calculated from these measured values.
These results are shown in Table 15 together with the structure of the grid-like substrate of each sample.

As can be seen from Table 15, lead-acid batteries No. 1 and No. 6 that did not satisfy 0.35≦A/B≦0.55 had a difference in upper and lower specific gravity of the electrolyte of 0.070 and 0.040. On the other hand, lead-acid batteries No. 2 to No. 5 and No. 7, which satisfy 0.35≦A/B≦0.55, had a small difference in the upper and lower specific gravity of the electrolyte at 0.005 to 0.015. . In addition, the lifespan of No. 1 and No. 6 lead-acid batteries that do not satisfy 0.35≦A/B≦0.55 was 8000 to 8500 cycles, whereas 0.35≦A/B≦0 The lifespan of No. 2 to No. 5 and No. 7 lead-acid batteries satisfying .55 was long at 17,000 to 22,000 cycles.

From the above results, a liquid lead-acid battery equipped with a positive electrode current collector that satisfies 0.35≦A/B≦0.55 and has a porosity of 60% as measured by the mercury intrusion method at the base of the separator is It was confirmed that when used in a partially charged state, stratification of the electrolyte was suppressed and the lifespan could be extended. Note that when the porosity of the base portion of the separator is 45 to 70% as measured by mercury porosimetry, the amount of diffusion of sulfate ions passing through the pores of the separator is improved, and an increase in internal resistance is suppressed. At the same time, the gas generated from the lower part of the positive electrode plate is prevented from being trapped in the pores of the separator, and the stirring action of the electrolyte in a partially charged state is more preferably effective.

1 Positive electrode current collector 1A Positive electrode current collector 11 Grid-like substrate 11A Grid-like substrate 12 Ear 111 Upper bone 112 Middle bone 112a Middle bone 112b Middle bone 2 Divided body where ears are present 2A Divided body where ears are present 21 First Part 21A First part 22 Second part 22A Second part

Claims (2)

A liquid lead-acid battery comprising an electrode plate group in which a positive electrode plate having a positive electrode current collector and a positive electrode mixture, and a negative electrode plate having a negative electrode current collector and a negative electrode mixture are alternately stacked with a separator interposed therebetween. And,
The positive electrode current collector has a rectangular grid-like substrate and ears continuous with the grid-like substrate,
The positive electrode mixture is held on the grid-like substrate,
The lattice-shaped substrate has an upper bone along one side of the rectangle, and a plurality of middle bones connected to the upper bone and existing below the upper bone,
The ear protrudes upward from a position shifted to one side from the center of the one side of the upper bone,
Among the divided bodies produced by cutting the positive electrode current collector along a diagonal line passing through the corner of one side of the rectangle, the divided body where the ear exists is located at the center on the boundary line between the ear and the upper bone. It is divided into a first part and a second part by a reference line passing through point P and perpendicular to the upper bone, the first part having a larger area than the second part,
On a coordinate plane where both the x-axis and the y-axis are linear scales, each resistance value Rn between each cutting surface Cn of the plurality of backbones in the first part and the center point P is expressed as a y-coordinate, All the plots made with each distance Xn between the center point of each cut plane Cn and the center point P as the x coordinate can be approximated to two straight lines with different slopes with x = H as the intersection,
The ratio A/B of the average value A of each resistance value Rn at each distance Xn where x<H and the average value B of each resistance value Rn at each distance Xn where x≧H is 0.35. or more and 0.55 or less,
The separator has a film-like base portion, and the base portion has a porosity of 45 to 70% as measured by mercury porosimetry. The liquid lead-acid battery according to claim 1, wherein the separator has a film-like base portion, and the base portion has a porosity of 55 to 70% as measured by mercury porosimetry.

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