JP7524898B2 - Lead-acid battery - Google Patents

Description

The present invention relates to a lead-acid battery.

Lead-acid batteries are used in a variety of applications, including automotive and industrial use. Lead-acid batteries contain negative and positive plates, a separator (or mat), and an electrolyte. Additives are sometimes added to the components of lead-acid batteries to impart various functions.

Patent Document 1 proposes a lead acid battery characterized in that a copolymer of propylene oxide and ethylene oxide is added to the negative electrode plate active material in combination with lignin sulfonate.
Patent Document 2 proposes a lead-acid battery characterized in that an activator containing an organic polymer is enclosed in a small sealed container having a cleavage mechanism into the battery case, and the small sealed container is attached to the battery case or the lid.

Patent Document 3 proposes a fiber-attached mat that includes a plurality of fibers coated with a sizing composition, a binder composition, and one or more additives, the additives including one or more of rubber additives, rubber derivatives, aldehydes, metal salts, ethylene-propylene oxide block copolymers, sulfates, sulfonates, phosphates, polyacrylic acid, polyvinyl alcohol, lignin, phenol-formaldehyde resins, cellulose, and wood flour, and the like, and that can function to reduce water loss in lead-acid batteries.

Japanese Unexamined Patent Publication No. 182662/1983 JP 2000-149980 A Special table 2017-525092 publication

In a lead-acid battery, as the battery is discharged, the specific gravity of the electrolyte in the lower part of the container becomes higher than that in the upper part of the container. Furthermore, during charging, the difference in specific gravity of the electrolyte increases even further. This phenomenon in which a difference in specific gravity between the upper and lower electrolytes occurs is called stratification. It is believed that repeated charging and discharging in a stratified state shortens not only the charge and discharge characteristics but also the battery life. Electrolyte stratification can be eliminated by overcharging the lead-acid battery and agitating the electrolyte by generating gas on the electrode plates, but this gas generation causes a problem of reduction in electrolyte (reduction in electrolyte).

One aspect of the present invention relates to a negative electrode plate for a lead-acid battery comprising a negative electrode current collector and a negative electrode material, the negative electrode material including a polymer compound, the negative electrode plate being divided into 32 equal parts in a matrix of 8 rows and 4 columns, with the direction from the top end to the bottom end of the negative electrode plate being the X direction and the direction intersecting the X direction being the Y direction, the Y direction being the row direction and the X direction being the column direction, and the average content of the polymer compound in the negative electrode material in all 32 regions being C0, the number N(1-4) of 16 regions in the first to fourth rows from the top end side that have a content of the polymer compound less than C0, and the number N(5-8) of 16 regions in the fifth to eighth rows that have a content of the polymer compound less than C0 satisfy N(1-4) < N(5-8).

Another aspect of the present invention is a negative electrode plate for a lead-acid battery comprising a negative electrode current collector and a negative electrode material, the negative electrode material including a polymer compound, the direction from the upper end to the lower end of the negative electrode plate being the X direction, the direction intersecting the X direction being the Y direction, the negative electrode plate being divided into 32 equal parts in a matrix of 8 rows and 4 columns with the Y direction being the row direction and the X direction being the column direction, and the average content of the polymer compound in the negative electrode material in all 32 regions being C0, the first and second eight regions from the upper end side being the polymer compound, The number N(1-2) of regions in which the polymer compound content is smaller than C0 and the number N(3-4) of the regions in which the polymer compound content is smaller than C0 among the eight regions in the third and fourth rows satisfy N(1-2) < N(3-4), and the number N(5-6) of the regions in which the polymer compound content is smaller than C0 among the eight regions in the fifth and sixth rows and the number N(7-8) of the regions in which the polymer compound content is smaller than C0 among the eight regions in the seventh and eighth rows satisfy N(5-6) < N(7-8).

In lead-acid batteries, it suppresses both electrolyte stratification and loss of electrolyte.

1 is a partially cutaway exploded perspective view showing the external appearance and internal structure of a lead-acid battery according to the present invention. FIG. FIG. 2 is a schematic diagram showing a negative electrode plate divided into 32 regions in a matrix. FIG. 2 is a diagram showing the distribution of a polymer compound in a negative electrode plate according to the first aspect of the first embodiment. FIG. 11 is a diagram showing the distribution of a polymer compound in a negative electrode plate according to a second aspect of the first embodiment. FIG. 11 is a diagram showing the distribution of a polymer compound in a negative electrode plate according to a third aspect of the first embodiment. FIG. 11 is a diagram showing the distribution of a polymer compound in a negative electrode plate according to a fourth aspect of the first embodiment. FIG. 13 is a diagram showing the distribution of a polymer compound in a negative electrode plate according to the first aspect of the second embodiment. FIG. 13 is a diagram showing the distribution of a polymer compound in a negative electrode plate according to the second aspect of the second embodiment. FIG. 1 shows the distribution of polymer compounds in the negative electrode plates of batteries A1 to A4. FIG. 1 shows the distribution of polymer compounds in the negative electrode plates of batteries A5 to A8. FIG. 13 is a graph showing the distribution of polymer compounds in the negative electrode plates of batteries A9 to A12. FIG. 13 is a diagram showing the distribution of polymer compounds in the negative electrode plates of batteries B1 to B5. 1 is a bar graph showing the difference in specific gravity of the electrolyte between the batteries of the Example and the Comparative Example. 1 is a line graph showing the difference in specific gravity of the electrolyte between the batteries of the Example and the Comparative Example. 1 is a bar graph showing the overcharged electric charge of batteries of an example and a comparative example. 1 is a line graph showing the overcharged electric quantity of batteries of an example and a comparative example.

[Lead-acid battery]
A lead-acid battery according to an embodiment of the present invention includes a positive plate, a negative plate, and an electrolyte, the positive plate includes a positive electrode current collector and a positive electrode material, the negative plate includes a negative electrode current collector and a negative electrode material, and the negative electrode material includes a polymer compound that increases the overvoltage of the negative electrode material.

In the negative plate, in the portion where the negative electrode material contains the polymer compound, hydrogen is less likely to be generated during overcharging, and the higher the content of the polymer compound in the negative electrode material, the greater the tendency to suppress hydrogen generation. In this portion, the reduction in electrolyte is suppressed. In addition, the polymer compound has the effect of suppressing the amount of electricity in overcharging.
It is believed that the above-mentioned effect is obtained by covering the surface of the lead in the negative electrode material with the polymer compound. Generally, it is expected that polymer compounds (especially those that tend to have a linear structure) are unlikely to remain in the negative electrode material and are likely to diffuse into the electrolyte, but in fact, it has been found that even when a small amount of polymer compound is contained in the negative electrode material, a significant effect of increasing the hydrogen overvoltage is obtained.

On the other hand, hydrogen is relatively more likely to be generated in parts of the negative electrode material that do not contain polymer compounds or in parts of the negative electrode material that have a low content of polymer compounds. By providing a part where hydrogen is more likely to be generated on the lower end side of the electrode plate, the electrolyte is efficiently stirred by hydrogen generation. In other words, stratification of the electrolyte is less likely to progress.

In view of the above, in this embodiment, the direction from the upper end (the side having the ear portion (tab)) of the negative electrode plate toward the lower end is defined as the X direction, and the direction intersecting the X direction is defined as the Y direction. The negative electrode plate is divided into 32 equal parts in an 8 row by 4 column matrix with the Y direction as the row direction and the X direction as the column direction. When the average value of the polymer compound content in the negative electrode material in all 32 regions is C0, the number N(1-4) of the 16 regions in the 1st to 4th rows from the upper end side that have a polymer compound content less than C0, and the number N(5-8) of the 16 regions in the 5th to 8th rows that have a polymer compound content less than C0 satisfy N(1-4) < N(5-8).

Alternatively, the number N(1-2) of the eight regions in the first and second rows from the top that have a polymer compound content less than C0 and the number N(3-4) of the eight regions in the third and fourth rows that have a polymer compound content less than C0 satisfy N(1-2) < N(3-4), and the number N(5-6) of the eight regions in the fifth and sixth rows that have a polymer compound content less than C0 and the number N(7-8) of the eight regions in the seventh and eighth rows that have a polymer compound content less than C0 satisfy N(5-6) < N(7-8).

The X direction corresponds to the up-down direction, i.e. the vertical direction, of a lead-acid battery in normal use. The Y direction corresponds to the horizontal direction.

Below, each of the 32 regions in the matrix is represented as R(x, y), where x is an integer from 1 to 8 indicating the row position, and y is an integer from 1 to 4 indicating the column position. Figure 2 is a schematic diagram showing a negative electrode plate divided into 32 regions in a matrix.

The content of the polymer compound in the negative electrode material in R(x,y) is defined as C(x,y). That is, in the region R(x,y) where the content of the polymer compound is smaller than C0, C(x,y)<C0 is satisfied. In addition, taking into account the error due to the measurement method of C0 and C(x,y), if the ratio of the actual value of C0 to the actual value of C(x,y): C0/C(x,y) satisfies 0.95≦C0/C(x,y)≦1.05, C0=C(x,y) is considered. In other words, the region R(x,y) where C0/C(x,y) is greater than 1.05 is considered to be the region where C(x,y)<C0 is satisfied. The region where C(x,y)<C0 does not need to contain the polymer compound (C(x,y)=0 ppm may be used).

When measuring the content of the negative electrode material in each region, the target negative electrode plate can be divided into 32 in the above-mentioned 8-row, 4-column matrix to prepare a sample for each region. Multiple identical negative electrode plates can be prepared and similarly divided into 32, and the amount of sample can be adjusted by mixing samples from regions with the same (x, y) values.

The negative electrode plate may further satisfy at least one of the following conditions:
(1) In at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(5,y) through C(8,y).
(2) In at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(6,y) through C(8,y).
(3) In at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(7,y) through C(8,y).
(4) In at least one column, the average value of C(1,y) through C(4,y) is greater than C(8,y).
(5) In at least one column, any of C(5,y) through C(8,y) is smaller than any of the rest.
(6) In at least one column, C(8,y) is smaller than any of the rest.
(7) In at least one column, C(8,y) is smaller than any of C(5,y) through C(7,y).

The average value C0 of the polymer compound content may be, for example, 3 ppm or more and 400 ppm or less. In addition, the maximum value of the polymer compound content in the 16 regions in the first to fourth rows from the top end side may be, for example, 400 ppm or less.

A lead-acid battery can be obtained by a manufacturing method including a step of assembling a lead-acid battery by placing a positive electrode plate, a negative electrode plate, and an electrolyte in a battery case. In the step of assembling a lead-acid battery, a separator is usually disposed between the positive electrode plate and the negative electrode plate. The step of assembling a lead-acid battery may include a step of chemically forming the positive electrode plate and/or the negative electrode plate, as necessary, after the step of placing the positive electrode plate, the negative electrode plate, and the electrolyte in the battery case. The positive electrode plate, the negative electrode plate, the electrolyte, and the separator are each prepared before being placed in the battery case.

FIG. 1 shows an external appearance of an example of a lead-acid battery according to an embodiment of the present invention.
The lead-acid battery 1 includes a battery case 12 that contains a plate group 11 and an electrolyte (not shown). The battery case 12 is divided into a plurality of cell chambers 14 by partitions 13. Each cell chamber 14 contains one of the plate groups 11. The opening of the battery case 12 is closed by a lid 15 that includes a negative electrode terminal 16 and a positive electrode terminal 17. The lid 15 is provided with a vent plug 18 for each cell chamber. When rehydrating, the vent plug 18 is removed and rehydration liquid is replenished. The vent plug 18 may have a function of discharging gas generated in the cell chamber 14 to the outside of the battery.

Each electrode plate group 11 is formed by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 via a separator 4. Here, a bag-shaped separator 4 that houses the negative electrode plates 2 is shown, but the shape of the separator is not particularly limited. In the cell chamber 14 located at one end of the battery case 12, the negative electrode shelf part 6 that connects the plurality of negative electrode plates 2 in parallel is connected to the through connector 8, and the positive electrode shelf part 5 that connects the plurality of positive electrode plates 3 in parallel is connected to the positive electrode column 7. The positive electrode column 7 is connected to a positive electrode terminal 17 outside the lid 15. In the cell chamber 14 located at the other end of the battery case 12, the negative electrode column 9 is connected to the negative electrode shelf part 6, and the through connector 8 is connected to the positive electrode shelf part 5. The negative electrode column 9 is connected to the negative electrode terminal 16 outside the lid 15. Each through connector 8 passes through a through hole provided in the partition wall 13 to connect the electrode plate groups 11 of the adjacent cell chambers 14 in series.

The positive electrode shelf 5 is formed by welding the ears provided on the upper part of each positive electrode plate 3 together using a cast-on-strap method or a burning method. The negative electrode shelf 6 is also formed by welding the ears provided on the upper part of each negative electrode plate 2 together in the same manner as the positive electrode shelf 5.

The lid 15 of the lead-acid battery has a single structure (single lid), but this is not limited to the illustrated example. The lid 15 may have a double structure, for example, with an inner lid and an outer lid (or top lid). A lid with a double structure may have a reflux structure between the inner lid and the outer lid for returning the electrolyte to the inside of the battery (inside the inner lid) from a reflux port provided in the inner lid.

First Embodiment
A further exemplary case where the negative electrode plates satisfy N(1-4)<N(5-8) will be described.
(First aspect)
3 is a diagram showing the distribution of the polymer compound in the negative electrode plate according to the first aspect of this embodiment. In the region where C(x, y)<C0 is satisfied, "C<C0" is displayed, and in other regions, "-" is displayed. The same applies to the following Figs. 4 to 12. N(1-4)=0, N(5-8)=4, and N(1-4)<N(5-8) is satisfied.

In the negative electrode plate of FIG. 3, only the negative electrode material in the eighth row region (R(8,y)) at the bottom end does not contain a polymer compound or has a low polymer compound content. In this case, hydrogen is more likely to be generated in the bottom end region of the negative electrode plate than in other regions, so the electrolyte can be stirred more efficiently.

The distribution is not limited to that shown in FIG. 3, and may satisfy C(8,y)<C0 in at least one column. In this case, in the negative electrode plate of this embodiment, the following is satisfied in at least one column.

(1) The average value of C(1,y) to C(4,y) is greater than the average value of C(5,y) to C(8,y).
(2) The average value of C(1,y) to C(4,y) is greater than the average value of C(6,y) to C(8,y).
(3) The average value of C(1,y) to C(4,y) is greater than the average value of C(7,y) to C(8,y).
(4) The average value of C(1,y) to C(4,y) is greater than C(8,y).
(5) Any of C(5,y) to C(8,y) is smaller than any of the rest.
(6) C(8,y) is smaller than any of the rest.
(7) C(8,y) is smaller than any of C(5,y) to C(7,y).

(Second Aspect)
4 is a diagram showing the distribution of the polymer compound in the negative electrode plate according to the second aspect of the present embodiment, where N(1-4)=0 and N(5-8)=4, and N(1-4)<N(5-8) is satisfied.

In the negative electrode plate of Figure 4, only the negative electrode material in the seventh row region (R(7,y)) does not contain a polymer compound or has a low polymer compound content. In this case, too, hydrogen is more likely to be generated in the region near the bottom end of the negative electrode plate than in other regions, so the electrolyte can be stirred more efficiently.

Note that the distribution is not limited to that shown in FIG. 4, and C(7,y)<C0 may be satisfied in at least one column. In this case, in the negative electrode plate of this embodiment, the following is satisfied in at least one column.

(1) The average value of C(1,y) to C(4,y) is greater than the average value of C(5,y) to C(8,y).
(2) The average value of C(1,y) to C(4,y) is greater than the average value of C(6,y) to C(8,y).
(3) An example in which the average value of C(1,y) to C(4,y) is greater than the average value of C(7,y) to C(8,y).
(5) Any of C(5,y) to C(8,y) is smaller than any of the rest.

(Third aspect)
5 is a diagram showing the distribution of the polymer compound in the negative electrode plate according to the third aspect of this embodiment. N(1-4)=0, N(5-8)=4, and N(1-4)<N(5-8) are satisfied.

In the negative electrode plate of Figure 5, only the negative electrode material in the fifth row region (R(5,y)) does not contain a polymer compound or has a low polymer compound content. In this case, too, hydrogen is more likely to be generated in the region near the bottom end of the negative electrode plate than in the region near the top end, so the electrolyte can be stirred relatively efficiently.

In addition, the distribution is not limited to that shown in Fig. 5, and C(5,y) < C0 may be satisfied in at least one column. In this case, in the negative electrode plate of this embodiment, the following is satisfied in at least one column.
(1) The average value of C(1,y) to C(4,y) is greater than the average value of C(5,y) to C(8,y).
(5) Any of C(5,y) to C(8,y) is smaller than any of the rest.

(Fourth aspect)
6 is a diagram showing the distribution of the polymer compound in the negative electrode plate according to the fourth aspect of the present embodiment. N(1-4)=4, N(5-8)=8, and N(1-4)<N(5-8) are satisfied.

In the negative electrode plate of FIG. 6, only the negative electrode material in the fourth row region (R(4,y)) and the seventh and eighth row regions (R(7,y), R(8,y)) does not contain a polymer compound or has a low polymer compound content. Even in this case, hydrogen is more likely to be generated in a wider region including the bottom end of the negative electrode plate than in other regions, so the electrolyte can be stirred relatively efficiently. In addition, since the negative electrode material in the fourth row region near the center does not contain a polymer compound or has a low polymer compound content, the electrolyte stirring efficiency can be further improved.

The distribution is not limited to that shown in FIG. 6, and may satisfy C(4,y)<C0, C(7,y)<C0, and C(8,y)<C0 in at least one column. In this case, in the negative electrode plate of this embodiment, the following is satisfied in at least one column.

(1) The average value of C(1,y) to C(4,y) is greater than the average value of C(5,y) to C(8,y).
(2) The average value of C(1,y) to C(4,y) is greater than the average value of C(6,y) to C(8,y).
(3) The average value of C(1,y) to C(4,y) is greater than the average value of C(7,y) to C(8,y).
(4) The average value of C(1,y) to C(4,y) is greater than C(8,y).

Second Embodiment
Next, a case where the negative electrode plates satisfy N(1-2)<N(3-4) and N(5-6)<N(7-8) will be further exemplarily described.
(First aspect)
7 is a diagram showing the distribution of the polymer compound in the negative electrode plate according to the first aspect of this embodiment. N(1-2)=0, N(3-4)=4, and N(1-2)<N(3-4). In addition, N(5-6)=0, N(7-8)=4, and N(5-6)<N(7-8).

In the negative electrode plate of FIG. 7, only the negative electrode material in the fourth row region (R(4,y)) and the eighth row region (R(8,y)) does not contain a polymer compound or has a low polymer compound content. In this case, hydrogen is more likely to be generated in the region at the bottom end of the negative electrode plate than in other regions, so the electrolyte can be stirred relatively efficiently. In addition, since the negative electrode material in the fourth row region near the center does not contain a polymer compound or has a low polymer compound content, the electrolyte stirring efficiency can be further improved.

Note that the distribution is not limited to that shown in Figure 7, and at least one column may satisfy C(4, y) < C0 and C(8, y) < C0.

(Second Aspect)
8 is a diagram showing the distribution of the polymer compound in the negative electrode plate according to the second aspect of this embodiment. N(1-2)=0, N(3-4)=8, and N(1-2)<N(3-4). In addition, N(5-6)=0, N(7-8)=4, and N(5-6)<N(7-8).

In the negative electrode plate of FIG. 8, only the negative electrode material in the third and fourth row regions (R(3,y), R(4,y)) and the eighth row region (R(8,y)) does not contain a polymer compound or has a low polymer compound content. In this case, hydrogen is more likely to be generated in the region at the bottom end of the negative electrode plate than in other regions, so the electrolyte can be stirred relatively efficiently. In addition, since the negative electrode material in the third and fourth row regions near the center does not contain a polymer compound or has a low polymer compound content, the electrolyte stirring efficiency can be further improved.

In addition, the distribution is not limited to that shown in Figure 8, and at least one column may satisfy C(3, y) < C0, C(4, y) < C0, and C(8, y) < C0.

The above first and second embodiments are merely examples, and any configuration in which more hydrogen gas is generated near the lower end may be used.

The polymer compound contained in the negative electrode material may have the effect of increasing the overvoltage of the negative electrode material. In addition, such a polymer compound may also have the effect of suppressing the amount of electricity in overcharging at the same time. A detailed description is given below of a preferred polymer compound, which is a polymer compound having a peak in the range of 3.2 ppm to 3.8 ppm in the chemical shift of the ¹ H-NMR spectrum, or a polymer compound containing a repeating structure of an oxy C _2-4 alkylene unit. The peak appearing in the range of 3.2 ppm to 3.8 ppm in the ¹ H-NMR spectrum is derived from the oxy C _2-4 alkylene unit. Here, ^{the 1} H-NMR spectrum is measured using deuterated chloroform as a solvent.

To obtain the effect of the polymer compound, it is necessary for the polymer compound to be present in the vicinity of lead or lead sulfate. Therefore, in the lead-acid battery according to the present invention, the negative electrode material contains the above-mentioned polymer compound. It is important that the negative electrode material contains a polymer compound, regardless of whether or not the components of the lead-acid battery other than the negative electrode material contain a polymer compound. By including a polymer compound in the negative electrode material at a desired location on the negative plate, the hydrogen overvoltage at that location can be increased.

In general, in a lead-acid battery, the reaction during overcharging is greatly influenced by the reduction reaction of hydrogen ions at the interface between lead and the electrolyte. Therefore, in the lead-acid battery according to the present invention, the surface of the lead, which is the negative electrode active material, is covered with a polymer compound, and it is considered that the hydrogen overvoltage increases and the side reaction in which hydrogen is generated from protons during overcharging is inhibited. Since the polymer compound has an oxy-C _2-4 alkylene unit and is likely to have a linear structure, it is expected that the polymer compound is unlikely to remain in the negative electrode material and is likely to diffuse into the electrolyte. However, the present inventors have found that, in reality, even if a very small amount of the polymer compound is contained in the negative electrode material, the effect of increasing the hydrogen overvoltage can be obtained. From this, it is considered that by including the polymer compound in the negative electrode material, it can be present in the vicinity of lead, and this causes the oxy-C _2-4 alkylene unit to exhibit a high adsorption effect on lead. In addition, even a very small amount of polymer compound can increase the hydrogen overvoltage, so the polymer compound spreads thinly over the lead surface, and it is considered that the reduction reaction of hydrogen ions is suppressed over a wide area of the lead surface. This is not inconsistent with the fact that polymer compounds tend to have a linear structure. In addition, suppressing hydrogen generation during overcharging reduces loss of electrolyte, which is advantageous for extending the life of lead-acid batteries.

In general, storage batteries use an aqueous sulfuric acid solution as the electrolyte, so if an organic additive (such as oil, polymer, or organic shrinkage inhibitor) is included in the negative electrode material, it becomes difficult to balance dissolution into the electrolyte and adsorption to lead. For example, if an organic additive with low adsorption to lead is used, it will be more likely to dissolve into the electrolyte, making it difficult to increase hydrogen overvoltage. On the other hand, if an organic additive with high adsorption to lead is used, it will be difficult to adhere thinly to the lead surface, and the organic additive will tend to be unevenly distributed within the pores of the lead.

In addition, generally, when the surface of lead is covered with organic additives, the reduction reaction of hydrogen ions is less likely to occur, and the overcharge quantity of electricity tends to decrease. When the surface of lead is covered with organic additives, lead sulfate generated during discharge is less likely to dissolve during charging, and charge acceptance decreases. Therefore, there is a trade-off between suppressing the decrease in charge acceptance and reducing the overcharge quantity of electricity, and it has been difficult to achieve both in the past. Furthermore, when the organic additives are unevenly distributed within the pores of the lead, the content of the organic additives in the negative electrode material needs to be increased in order to ensure a sufficient effect of reducing the overcharge quantity of electricity. However, increasing the content of the organic additives significantly reduces charge acceptance.

When organic additives become unevenly distributed within the pores of the lead, the steric hindrance of the unevenly distributed organic additives inhibits the movement of ions (such as lead ions and sulfate ions). This also reduces low-temperature high-rate (HR) performance. If the content of organic additives is increased in order to ensure a sufficient reduction in the amount of overcharge electricity, the movement of ions within the pores will be further inhibited, and low-temperature HR discharge performance will also decrease.

In contrast, in the lead-acid battery according to the present invention, by incorporating a polymer compound having an oxy-C _2-4 alkylene unit in the negative electrode material, the lead surface is covered with the polymer compound in a thinly spread state as described above. Therefore, compared with the case of using other organic additives, even if the content in the negative electrode material is small, the effect of increasing hydrogen overvoltage and the effect of reducing the overcharge charge amount can be secured. In addition, since the polymer compound thinly covers the lead surface, the elution of lead sulfate generated during discharge during charging is less likely to be inhibited, and this can also suppress the decrease in charge acceptance. Therefore, it is possible to suppress the decrease in charge acceptance while increasing hydrogen overvoltage and reducing the overcharge charge amount. Since the uneven distribution of the polymer compound in the pores of the lead is suppressed, ions can easily move, and the decrease in low-temperature HR discharge performance can also be suppressed.

In the lead acid battery according to one aspect of the present invention, the polymer compound may contain an oxygen atom bonded to an end group, and a -CH ₂ - group and/or a -CH< group bonded to the oxygen atom. In the ¹ H-NMR spectrum, the ratio of the integral value of the peak at 3.2 ppm to 3.8 ppm to the total integral value of this peak, the integral value of the peak of the hydrogen atom of the -CH ₂ - group bonded to the oxygen atom, and the integral value of the peak of the hydrogen atom of the -CH< group bonded to the oxygen atom is preferably 85% or more. Such a polymer compound contains a large number of oxy C _2-4 alkylene units in the molecule. Therefore, it is considered that it is easily adsorbed to lead, and that it is easy to take a linear structure, so that it is easy to thinly cover the lead surface. Therefore, it is possible to more effectively increase the hydrogen overvoltage and reduce the overcharge electricity quantity. In addition, it is possible to further enhance the effect of suppressing the deterioration of the charge acceptance and/or the low-temperature HR discharge performance.

A polymer compound having a peak in the chemical shift range of 3.2 ppm to 3.8 ppm in a ¹ H-NMR spectrum preferably contains a repeating structure of an oxy C _2-4 alkylene unit. When a polymer compound containing a repeating structure of an oxy C _2-4 alkylene unit is used, it is considered that the polymer compound is more likely to be adsorbed to lead and is more likely to have a linear structure, which makes it easier to thinly cover the lead surface. Therefore, it is possible to more effectively increase the hydrogen overvoltage and reduce the overcharge electricity quantity.

In this specification, the polymer compound refers to one having a repeating unit of an oxyC _2-4 alkylene unit and/or a number average molecular weight (Mn) of 500 or more.

The oxy C _2-4 alkylene unit is a unit represented by —O—R ¹ — (R ¹ represents a C _2-4 alkylene group).

The polymer compound may contain at least one selected from the group consisting of an etherified product of a hydroxy compound having a repeating structure of an oxy C _2-4 alkylene unit and an esterified product of a hydroxy compound having a repeating structure of an oxy C _2-4 alkylene unit. Here, the hydroxy compound is at least one selected from the group consisting of polyC _2-4 alkylene glycol, a copolymer containing a repeating structure of an oxy C _2-4 alkylene, and a C _2-4 alkylene oxide adduct of a polyol. When such a polymer compound is used, the decrease in charge acceptance can be further suppressed. In addition, since the effect of increasing the hydrogen overvoltage and reducing the overcharge electricity amount is high, hydrogen gas generation can be more effectively suppressed and a high effect of suppressing the reduction in the liquid loss can be obtained.

The repeating structure of the oxy _C2-4 alkylene unit may contain at least a repeating structure of an oxypropylene unit (-O-CH( _-CH3 ) _-CH2- ). Such a polymer compound is considered to have an excellent balance between high adsorption to lead and ease of spreading thinly on the lead surface.

In this way, the polymer compound has high adsorption to lead, but can also thinly cover the lead surface, so that even if the content of the polymer compound in the negative electrode material is small (for example, less than 400 ppm), it can increase the hydrogen overvoltage and reduce the overcharge charge. In addition, even if the content is small, it is possible to ensure a sufficient effect of reducing the overcharge charge, so that it is also possible to suppress a decrease in charge acceptance. Since it is possible to reduce the steric hindrance of the polymer compound in the lead pores and to suppress the structural change of the negative electrode active material caused by the collision of hydrogen gas, it is also possible to suppress a decrease in low-temperature HR discharge performance even after a high-temperature light-load test. From the viewpoint of ensuring a higher effect, it is preferable that the content of the polymer compound in the negative electrode material is more than 8 ppm.

The polymer compound preferably contains a compound having an Mn of at least 1000. In this case, the polymer compound is more likely to remain in the negative electrode material and has higher adsorption to lead, thereby further enhancing the effect of increasing hydrogen overvoltage and the effect of reducing the overcharge electricity quantity.
In addition, the structure of the negative electrode active material can be prevented from being changed due to collision of hydrogen gas with the negative electrode material, and therefore, even after a high-temperature light-load test in which the structure of the negative electrode active material is likely to be changed, the effect of preventing the deterioration of low-temperature HR discharge performance can be improved.

Note that the origin of the polymer compound contained in the negative electrode material is not particularly limited as long as the polymer compound can be contained in a larger or smaller amount in the negative electrode material at a predetermined location of the negative plate. The polymer compound may be contained in any of the components of the lead-acid battery (e.g., the negative plate, the positive plate, the electrolyte, and/or the separator, etc.) when the lead-acid battery is produced. The polymer compound may be contained in one component, or in two or more components (e.g., the negative plate and the electrolyte, etc.).

The negative electrode material may further contain an organic shrinkage inhibitor (first organic shrinkage inhibitor) having a sulfur element content of 2000 μmol/g or more. By using such an organic shrinkage inhibitor in combination with a polymer compound, the decrease in charge acceptance can be further suppressed. The charge acceptance is governed by the dissolution rate of lead sulfate during charging in the negative electrode plate. When the first organic shrinkage inhibitor is used, the particle size of lead sulfate generated during discharge is smaller than that when an organic shrinkage inhibitor (second organic shrinkage inhibitor) having a small sulfur element content (e.g., less than 2000 μmol/g, preferably 1000 μmol/g or less) is used, and the specific surface area of lead sulfate is larger, when the first organic shrinkage inhibitor is used, compared to when the second organic shrinkage inhibitor is used. Therefore, when the first organic shrinkage inhibitor is used, the proportion of the surface of lead sulfate covered by the polymer compound is smaller than that when the second organic shrinkage inhibitor is used. Therefore, it is considered that the dissolution of lead sulfate is less likely to be inhibited, and the decrease in charge acceptance is suppressed.

The negative electrode material may contain a second organic shrinkage inhibitor. By using the second organic shrinkage inhibitor in combination with a polymer compound, the colloid particle size can be reduced, thereby further enhancing the effect of suppressing the deterioration of low-temperature HR discharge performance.

The negative electrode material may contain a second organic shrinkage inhibitor in addition to the first organic shrinkage inhibitor. By using the first organic shrinkage inhibitor and the second organic shrinkage inhibitor in combination with a polymer compound, the effect of suppressing the decrease in charge acceptance can be synergistically enhanced.

The first organic shrinkage inhibitor includes a condensate containing a unit of an aromatic compound having a sulfur-containing group, and the condensate may include at least one selected from the group consisting of a unit of a bisarene compound and a unit of a monocyclic aromatic compound as the unit of the aromatic compound. The condensate may also include a unit of a bisarene compound and a unit of a monocyclic aromatic compound. The unit of the monocyclic aromatic compound may include a unit of a hydroxyarene compound. Such a condensate is more advantageous in suppressing the deterioration of the low-temperature HR discharge performance after a high-temperature light-load test because the low-temperature HR discharge performance is not impaired even when the condensate experiences an environment higher than room temperature.

The sulfur element content in an organic shrinkage inhibitor is X μmol/g, which means that the sulfur element content per 1 g of the organic shrinkage inhibitor is X μmol.

The content of the polymer compound in the negative electrode material and the concentration of the polymer compound in the electrolyte shall be determined for a lead-acid battery in a fully charged state.

The lead-acid battery may be either a valve-regulated (sealed) lead-acid battery or a flooded (vented) lead-acid battery.

In this specification, the fully charged state of a liquid-type lead-acid battery is defined by the definition of JIS D 5301:2006. More specifically, the fully charged state is a state in which a lead-acid battery is charged at a current (A) 0.2 times the value listed as the rated capacity (Ah) until the terminal voltage during charging or the electrolyte density converted to a temperature of 20°C, measured every 15 minutes, shows a constant value with three significant digits three times in a row. In addition, the fully charged state of a valve-regulated lead-acid battery is a state in which constant current and constant voltage charging of 2.23 V/cell is performed in an air tank at 25°C ± 2°C at a current (A) 0.2 times the value listed as the rated capacity (Ah), and charging is terminated when the charging current during constant voltage charging becomes 0.005 times the value listed as the rated capacity (Ah). The value listed as the rated capacity is in Ah units. The unit of current set based on the value listed as the rated capacity is A.

A fully charged lead-acid battery is a lead-acid battery that has already been chemically prepared and has been fully charged. A lead-acid battery can be fully charged immediately after chemical preparation, or after some time has passed since chemical preparation (for example, a lead-acid battery that has been in use (preferably in the early stages of use) after chemical preparation can be fully charged). An early stage battery is one that has not been in use for very long and has hardly deteriorated at all.

In this specification, the number average molecular weight Mn is determined by gel permeation chromatography (GPC). The standard substance used to determine Mn is polyethylene glycol.

Below, the lead-acid battery according to an embodiment of the present invention will be described in terms of its main components, but the present invention is not limited to the following embodiment.

[Lead-acid battery]
(Negative plate)
A negative electrode plate usually includes a negative electrode current collector in addition to a negative electrode material. The negative electrode material is the negative electrode plate excluding the negative electrode current collector. Note that a member such as a mat or pasting paper may be attached to the negative electrode plate. Such members (attaching members) are used integrally with the negative electrode plate, and are therefore included in the negative electrode plate. In addition, when the negative electrode plate includes such members, the negative electrode material is the negative electrode material excluding the negative electrode current collector and the attaching member. However, when an attaching member such as a mat is attached to the separator, the thickness of the attaching member is included in the thickness of the separator.

The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead sheet or a lead alloy sheet. Examples of processing methods include expanding and punching. It is preferable to use a negative electrode grid as the negative electrode current collector because it is easy to support the negative electrode material.

The lead alloy used in the negative electrode current collector may be any of Pb-Sb alloy, Pb-Ca alloy, and Pb-Ca-Sn alloy. These lead or lead alloys may further contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element. The negative electrode current collector may have a surface layer. The surface layer and the inner layer of the negative electrode current collector may have different compositions. The surface layer may be formed on the ear of the negative electrode current collector. The surface layer of the ear may contain Sn or an Sn alloy.

In at least a portion of the negative plate, the negative electrode material contains the above polymer compound. The negative electrode material further contains a negative electrode active material (lead or lead sulfate) that develops capacity through an oxidation-reduction reaction. The negative electrode material may contain a shrinkage inhibitor, a carbonaceous material, and/or other additives. Examples of additives include, but are not limited to, barium sulfate and fibers (such as resin fibers). Note that the negative electrode active material in a charged state is sponge-like lead, but unformed negative plates are usually made using lead powder.

(Polymer Compound)
The polymer compound has a peak in the range of 3.2 ppm or more and 3.8 ppm or less in the chemical shift of the ¹ H-NMR spectrum. Such a polymer compound has an oxy C _2-4 alkylene unit. Examples of the oxy C _2-4 alkylene unit include an oxyethylene unit, an oxypropylene unit, an oxytrimethylene unit, an oxy 2-methyl-1,3-propylene unit, an oxy 1,4-butylene unit, and an oxy 1,3-butylene unit. The polymer compound may have one type of such oxy C _2-4 alkylene unit, or may have two or more types.

The polymer compound preferably contains a repeating structure of an oxy _C2-4 alkylene unit. The repeating structure may contain one type of oxy _C2-4 alkylene unit, or may contain two or more types of oxy _C2-4 alkylene units. The polymer compound may contain one type of the repeating structure, or may contain two or more types of repeating structures.

Examples of the polymer compound include hydroxy compounds having a repeating structure of oxy _C2-4 alkylene units (poly _C2-4 alkylene glycol, copolymers containing a repeating structure of oxy _C2-4 alkylene, _C2-4 alkylene oxide adducts of polyols, etc.), and ethers or esters of these hydroxy compounds.

The copolymers include copolymers containing different oxy C _2-4 alkylene units, poly C _2-4 alkylene glycol alkyl ethers, poly C _2-4 alkylene glycol esters of carboxylic acids, etc. The copolymers may be block copolymers.

The polyol may be any of aliphatic polyols, alicyclic polyols, aromatic polyols, and heterocyclic polyols. From the viewpoint of facilitating thin spreading of the polymer compound on the lead surface, aliphatic polyols and alicyclic polyols (e.g., polyhydroxycyclohexane, polyhydroxynorbornane, etc.) are preferred, and among them, aliphatic polyols are preferred. Examples of aliphatic polyols include aliphatic diols and polyols having a triol or more (e.g., glycerin, trimethylolpropane, pentaerythritol, sugar alcohols, etc.). Examples of aliphatic diols include alkylene glycols having 5 or more carbon atoms. The alkylene glycol may be, for example, C _5-14 alkylene glycol or C _5-10 alkylene glycol. Examples of sugar alcohols include erythritol, xylitol, mannitol, sorbitol, etc. In the alkylene oxide adduct of polyol, the alkylene oxide corresponds to the oxy _C2-4 alkylene unit of the polymer compound and contains at least _C2-4 alkylene oxide. From the viewpoint that the polymer compound is likely to have a linear structure, the polyol is preferably a diol.

The etherified product has an -OR2 group (wherein _R2 is an organic group) in which at least some of the terminal -OH groups (composed of a hydrogen atom of the terminal group and an oxygen atom bonded to this hydrogen atom) of the hydroxy compound having the above repeating structure of oxy ^C2-4 alkylene units have been etherified. Of the terminals of the polymer compound, some or all of the terminals may be etherified. For example, one terminal of ^the main chain of a linear polymer compound may be an -OH group and the other terminal may be an ^-OR2 group.

The esterified product has an -O-C(=O ₎ -R3 group in which at least some of the terminal -OH groups (-OH groups consisting of a hydrogen atom of the terminal group and an oxygen atom bonded to this hydrogen atom) of the ^hydroxy compound having a repeating structure of the above oxy C2-4 alkylene unit are esterified (wherein ^R3 is an organic group). Of the terminals of the polymer compound, some or all of the terminals may be esterified. For example, one terminal of the main chain of a linear polymer compound may be an -OH group and the other terminal may be an -O-C(=O) ^-R3 group.

Each of the organic groups ^R2 and ^R3 includes a hydrocarbon group. The hydrocarbon group may have a substituent (e.g., a hydroxy group, an alkoxy group, and/or a carboxy group). The hydrocarbon group may be any of aliphatic, alicyclic, and aromatic. The aromatic hydrocarbon group and the alicyclic hydrocarbon group may have an aliphatic hydrocarbon group (e.g., an alkyl group, an alkenyl group, an alkynyl group, etc.) as a substituent. The number of carbon atoms of the aliphatic hydrocarbon group as a substituent may be, for example, 1 to 20, 1 to 10, 1 to 6, or 1 to 4.

Examples of aromatic hydrocarbon groups include aromatic hydrocarbon groups having 24 or less carbon atoms (e.g., 6 to 24). The number of carbon atoms in the aromatic hydrocarbon group may be 20 or less (e.g., 6 to 20), 14 or less (e.g., 6 to 14), or 12 or less (e.g., 6 to 12). Examples of aromatic hydrocarbon groups include aryl groups and bisaryl groups. Examples of aryl groups include phenyl groups and naphthyl groups. Examples of bisaryl groups include monovalent groups corresponding to bisarenes. Examples of bisarenes include biphenyl and bisarylalkanes (e.g., bisC _6-10 aryl C _1-4 alkanes (2,2-bisphenylpropane, etc.)).

Examples of alicyclic hydrocarbon groups include alicyclic hydrocarbon groups having 16 or less carbon atoms. The alicyclic hydrocarbon group may be a cross-linked cyclic hydrocarbon group. The number of carbon atoms in the alicyclic hydrocarbon group may be 10 or less or 8 or less. The number of carbon atoms in the alicyclic hydrocarbon group may be, for example, 5 or more, or 6 or more.

The number of carbon atoms in the alicyclic hydrocarbon group may be 5 (or 6) or more and 16 (or less), 5 (or 6) or more and 10 (or less), or 5 (or 6) or more and 8 (or less).

Examples of alicyclic hydrocarbon groups include cycloalkyl groups (cyclopentyl, cyclohexyl, cyclooctyl, etc.), cycloalkenyl groups (cyclohexenyl, cyclooctenyl, etc.), etc. Alicyclic hydrocarbon groups also include hydrogenated products of the above aromatic hydrocarbon groups.

From the viewpoint of facilitating a thin adhesion of the polymer compound to the lead surface, among the hydrocarbon groups, an aliphatic hydrocarbon group is preferred. Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and a dienyl group. The aliphatic hydrocarbon group may be either a straight chain or a branched chain.

The number of carbon atoms in the aliphatic hydrocarbon group is, for example, 30 or less, and may be 26 or less or 22 or less, 20 or less or 16 or less, 14 or less or 10 or less, or 8 or less or 6 or less. The lower limit of the number of carbon atoms depends on the type of aliphatic hydrocarbon group; for alkyl groups, it is 1 or more, for alkenyl groups and alkynyl groups, it is 2 or more, and for dienyl groups, it is 3 or more. Among these, alkyl and alkenyl groups are preferred from the viewpoint of facilitating thin adhesion of the polymer compound to the lead surface.

Specific examples of alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, neopentyl, i-pentyl, s-pentyl, 3-pentyl, t-pentyl, n-hexyl, 2-ethylhexyl, n-octyl, n-decyl, i-decyl, lauryl, myristyl, cetyl, stearyl, and behenyl.

Specific examples of alkenyl groups include vinyl, 1-propenyl, allyl, palmitoleyl, oleyl, etc. The alkenyl group may be, for example, a C _2-30 alkenyl group or a C _2-26 alkenyl group, a C _2-22 alkenyl group or a C _2-20 alkenyl group, or a C _10-20 alkenyl group.

Among the polymer compounds, it is preferable to use an etherified product of a hydroxy compound having a repeating structure of an oxy _C2-4 alkylene unit and/or an esterified product of a hydroxy compound having a repeating structure of an oxy _C2-4 alkylene unit, since this can further enhance the effect of suppressing the decrease in charge acceptance. Furthermore, even when these polymer compounds are used, a high effect of suppressing the decrease in the electrolyte can be ensured.

The negative electrode material may contain one type of polymer compound or two or more types.

From the viewpoint of further enhancing the effect of increasing hydrogen overvoltage and the effect of reducing the overcharged quantity of electricity, and also enhancing the effect of suppressing the deterioration of charge acceptance and/or low-temperature HR discharge performance, it is preferable that the repeating structure of oxyC _2-4 alkylene contains at least a repeating structure of an oxypropylene unit. A polymer compound containing an oxypropylene unit has peaks derived from -CH< and -CH ₂ - of the oxypropylene unit in the chemical shift of a ¹ H-NMR spectrum in the range of 3.2 ppm to 3.8 ppm. Since the electron density around the atomic nucleus of the hydrogen atom in these groups is different, the peak is in a split state. Such a polymer compound has peaks in the chemical shift of a ¹ H-NMR spectrum, for example, in the range of 3.2 ppm to 3.42 ppm and in the range of more than 3.42 ppm to 3.8 ppm. The peaks in the range of 3.2 ppm to 3.42 ppm are derived from -CH ₂ -, and the peaks in the range of more than 3.42 ppm to 3.8 ppm are derived from -CH< and -CH ₂ -.

Examples of such polymer compounds include polypropylene glycol, copolymers containing a repeating structure of oxypropylene, propylene oxide adducts of the above polyols, or etherified or esterified products thereof. Examples of copolymers include oxypropylene-oxyalkylene copolymers (wherein oxyalkylene is a _C2-4 alkylene other than oxypropylene), polypropylene glycol alkyl ethers, polypropylene glycol esters of carboxylic acids, etc. Examples of oxypropylene-oxyalkylene copolymers include oxypropylene-oxyethylene copolymers and oxypropylene-oxytrimethylene copolymers. The oxypropylene-oxyalkylene copolymer may be a block copolymer.

In a polymer compound containing a repeating oxypropylene structure, the proportion of oxypropylene units is, for example, 5 mol% or more, and may be 10 mol% or more or 20 mol% or more.

From the viewpoint of increasing the adsorption to lead and facilitating the formation of a linear structure, it is preferable that the polymer compound contains a large number of oxy C _2-4 alkylene units. Such a polymer compound contains, for example, an oxygen atom bonded to an end group, and a -CH ₂ - group and/or a -CH< group bonded to the oxygen atom. In the ¹ H-NMR spectrum of the polymer compound, the ratio of the integral value of the peak at 3.2 ppm to 3.8 ppm to the total integral value of this peak, the integral value of the peak of the hydrogen atom of the -CH ₂ - group, and the integral value of the peak of the hydrogen atom of the -CH< group becomes large. This ratio is, for example, 50% or more, and may be 80% or more. From the viewpoint of further increasing the effect of reducing the overcharge quantity of electricity and further increasing the effect of suppressing the deterioration of the charge acceptance and/or the low-temperature HR discharge performance, the above ratio is preferably 85% or more, and more preferably 90% or more. For example, when a polymer compound has an -OH group at its terminal and a -CH ₂ - group or a -CH< group bonded to the oxygen atom of the -OH group, the peak of the hydrogen atom of the -CH ₂ - group or the -CH< group has a chemical shift in the range of more than 3.8 ppm to 4.0 ppm in the ¹ H-NMR spectrum.

The polymer compound may include a compound having an Mn of 500 or more, may include a compound having an Mn of 600 or more, or may include a compound having an Mn of 1000 or more. The Mn of such a compound is, for example, 20,000 or less, and may be 15,000 or less, or 10,000 or less. From the viewpoint of making it easier to retain the compound in the negative electrode material and to spread it more thinly on the lead surface, the Mn of the above compound is preferably 5,000 or less, and may be 4,000 or less, or 3,000 or less.

The Mn of the above compounds may be 500 or more (or 600 or more) and 20,000 or less, 500 or more (or 600 or more) and 15,000 or less, 500 or more (or 600 or more) and 10,000 or less, 500 or more (or 600 or more) and 5,000 or less, 500 or more (or 600 or more) and 4,000 or less, 500 or more (or 600 or more) and 3,000 or less, 1,000 or more and 20,000 or less (or 15,000 or less), 1,000 or more and 10,000 or less (or 5,000 or less), or 1,000 or more and 4,000 or less (or 3,000 or less).

It is preferable that the polymer compound contains at least a compound having an Mn of 1000 or more. The Mn of such a compound may be 1000 or more and 20000 or less, 1000 or more and 15000 or less, or 1000 or more and 10000 or less. From the viewpoint of making it easier to retain the compound in the negative electrode material and to spread it more thinly on the lead surface, the Mn of the above compound is preferably 1000 or more and 5000 or less, may be 1000 or more and 4000 or less, or may be 1000 or more and 3000 or less. When a compound having such Mn is used, it is easier to increase the hydrogen overvoltage and reduce the overcharged electric quantity. In addition, it is possible to suppress the structural change of the negative electrode active material caused by the collision of hydrogen gas with the negative electrode active material. Therefore, it is also possible to enhance the effect of suppressing the deterioration of the low-temperature HR discharge performance after the high-temperature light load test. As the polymer compound, two or more compounds having different Mn may be used. In other words, the polymer compound may have multiple Mn peaks in the molecular weight distribution.

As described above, when the negative plate is divided into 32 equal parts and the average value of the content of the polymer compound in the negative electrode material in all 32 regions is C0, the average value C0 of the content of the polymer compound is, for example, more than 8 ppm, preferably 13 ppm or more, more preferably 15 ppm or more or 16 ppm or more, by mass. When the average value C0 is in such a range, it is easier to increase the hydrogen generation voltage and the effect of reducing the overcharged amount of electricity can be further improved. From the viewpoint of easily ensuring higher low-temperature HR discharge performance, the average value C0 may be 50 ppm or more or 80 ppm or more. The average value C0 is, for example, 400 ppm or less, preferably 360 ppm or less, and more preferably 350 ppm or less. When the average value C0 is 400 ppm or less, the surface of the lead is prevented from being excessively covered with the polymer compound, so that the deterioration of the low-temperature HR discharge performance can be effectively suppressed. From the viewpoint of easily ensuring higher low-temperature HR discharge performance, the average value C0 is preferably 240 ppm or less, more preferably 200 ppm or less, and may be 165 ppm or less or 164 ppm or less. These lower and upper limits can be combined in any manner.

In addition, the maximum content of the polymer compound in the 16 regions in the first to fourth rows from the upper end side of the negative electrode plate may be, for example, 400 ppm or less, preferably 190 ppm or less, and more preferably 180 ppm or less, from the viewpoint of preventing the lead surface from being excessively covered with the polymer compound.

The average value C0 is 3 ppm or more (or 13 ppm or more) 400 ppm or less, 3 ppm or more (or 13 ppm or more) 360 ppm or less, 3 ppm or more (or 13 ppm or more) 350 ppm or less, 3 ppm or more (or 13 ppm or more) 240 ppm or less, 3 ppm or more (or 13 ppm or more) 200 ppm or less, 3 ppm or more (or 13 ppm or more) 165 ppm or less, 3 ppm or more (or 13 ppm or more) 164 ppm or less, 15 ppm or more (or 16 ppm or more) 400 ppm or less, 15 ppm or more (or 16 ppm or more) 360 ppm or less, 15 ppm or more (or 16 ppm or more) 350 ppm or less, 15 ppm or more (or 16 ppm or more) It may be 240 ppm or less, 15 ppm or more (or 16 ppm or more) and 200 ppm or less, 15 ppm or more (or 16 ppm or more) and 165 ppm or less, 15 ppm or more (or 16 ppm or more) and 164 ppm or less, 50 ppm or more (or 80 ppm or more) and 400 ppm or less, 50 ppm or more (or 80 ppm or more) and 360 ppm or less, 50 ppm or more (or 80 ppm or more) and 350 ppm or less, 50 ppm or more (or 80 ppm or more) and 240 ppm or less, 50 ppm or more (or 80 ppm or more) and 200 ppm or less, 50 ppm or more (or 80 ppm or more) and 165 ppm or less, or 50 ppm or more (or 80 ppm or more) and 164 ppm or less.

(Shrinkage inhibitor)
The negative electrode material may contain a shrinkage inhibitor. As the shrinkage inhibitor, an organic shrinkage inhibitor is preferable. As the organic shrinkage inhibitor, lignins and/or synthetic organic shrinkage inhibitors may be used. Examples of lignins include lignin and lignin derivatives. Examples of lignin derivatives include lignin sulfonic acid or its salts (alkali metal salts (sodium salts, etc.)). Organic shrinkage inhibitors are generally broadly classified into lignins and synthetic organic shrinkage inhibitors. It can also be said that synthetic organic shrinkage inhibitors are organic shrinkage inhibitors other than lignins. Synthetic organic shrinkage inhibitors are organic polymers containing sulfur elements, and generally contain multiple aromatic rings in the molecule and sulfur elements as sulfur-containing groups. Among the sulfur-containing groups, sulfonic acid groups or sulfonyl groups, which are stable forms, are preferable. The sulfonic acid groups may exist in an acid form or in a salt form such as a Na salt. The negative electrode material may contain one type of shrinkage inhibitor, or may contain two or more types of shrinkage inhibitors.

As the organic shrink-proofing agent, it is preferable to use a condensation product containing at least an aromatic compound unit. Examples of such condensation products include condensation products of aromatic compounds with aldehyde compounds (aldehydes (e.g., formaldehyde) and/or condensates thereof, etc.). The organic shrink-proofing agent may contain one type of aromatic compound unit, or may contain two or more types of aromatic compound units.
The aromatic compound unit refers to a unit derived from an aromatic compound incorporated in the condensation product.

The organic shrinkage inhibitor may be synthesized by a known method or may be a commercially available product. A condensation product containing an aromatic compound unit can be obtained, for example, by reacting an aromatic compound with an aldehyde compound. For example, this reaction can be performed in the presence of a sulfite salt or by using an aromatic compound containing a sulfur element (such as bisphenol S), to obtain an organic shrinkage inhibitor containing a sulfur element. For example, the sulfur element content in the organic shrinkage inhibitor can be adjusted by adjusting the amount of sulfite salt and/or the amount of an aromatic compound containing a sulfur element. When using other raw materials, the organic shrinkage inhibitor can also be obtained in a similar manner.

Examples of aromatic rings that aromatic compounds have include benzene rings and naphthalene rings. When an aromatic compound has multiple aromatic rings, the multiple aromatic rings may be linked by direct bonds or linking groups (e.g., alkylene groups (including alkylidene groups), sulfone groups, etc.). Examples of such structures include bisarene structures (biphenyl, bisphenylalkane, bisphenylsulfone, etc.). Examples of aromatic compounds include compounds having the above aromatic rings and hydroxyl groups and/or amino groups. The hydroxyl groups and amino groups may be directly bonded to the aromatic rings, or may be bonded as alkyl chains having hydroxyl groups and amino groups. The hydroxyl groups include salts of hydroxyl groups (-OMe). The amino groups include salts of amino groups (salts with anions). Examples of Me include alkali metals (Li, K, Na, etc.) and metals of Group 2 of the periodic table (Ca, Mg, etc.).

Preferred aromatic compounds include bisarene compounds (bisphenol compounds, hydroxybiphenyl compounds, bisarene compounds having an amino group (bisarylalkane compounds having an amino group, bisarylsulfone compounds having an amino group, biphenyl compounds having an amino group, etc.), hydroxyarene compounds (hydroxynaphthalene compounds, phenol compounds, etc.), aminoarene compounds (aminonaphthalene compounds, aniline compounds (aminobenzenesulfonic acid, alkylaminobenzenesulfonic acid, etc.)), etc. The aromatic compounds may further have a substituent. The organic shrinkage inhibitor may contain one or more of the residues of these compounds. Preferred bisphenol compounds include bisphenol A, bisphenol S, bisphenol F, etc.

It is preferable that the condensate contains at least a unit of an aromatic compound having a sulfur-containing group. In particular, the use of a condensate containing at least a unit of a bisphenol compound having a sulfur-containing group can enhance the effect of suppressing the deterioration of low-temperature HR discharge performance after a high-temperature light-load test. From the viewpoint of enhancing the effect of suppressing the loss of liquid, it is preferable to use a condensate of an aldehyde compound of a naphthalene compound having a sulfur-containing group and a hydroxyl group and/or an amino group.

The sulfur-containing group may be directly bonded to an aromatic ring contained in the compound, or may be bonded to the aromatic ring as an alkyl chain having a sulfur-containing group. Examples of the sulfur-containing group include, but are not limited to, a sulfonyl group, a sulfonic acid group, or a salt thereof.

As the organic shrinkage inhibitor, for example, at least one condensate containing at least one selected from the group consisting of the above-mentioned bisarene compound units and monocyclic aromatic compound units (hydroxyarene compounds and/or aminoarene compounds, etc.) may be used. The organic shrinkage inhibitor may contain at least a condensate containing a bisarene compound unit and a monocyclic aromatic compound (especially a hydroxyarene compound). Such a condensate may be a condensate of a bisarene compound and a monocyclic aromatic compound with an aldehyde compound. As the hydroxyarene compound, a phenolsulfonic acid compound (such as phenolsulfonic acid or a substituted product thereof) is preferable. As the aminoarene compound, aminobenzenesulfonic acid, alkylaminobenzenesulfonic acid, etc. are preferable. As the monocyclic aromatic compound, a hydroxyarene compound is preferable. Such a condensate does not impair low-temperature HR discharge performance even when it experiences an environment higher than room temperature, so it is more advantageous in suppressing the deterioration of low-temperature HR discharge performance after a high-temperature light-load test.

The content of the organic shrinkage inhibitor contained in the negative electrode material is, for example, 0.01% by mass or more, and may be 0.05% by mass or more. The content of the organic shrinkage inhibitor is, for example, 1.0% by mass or less, and may be 0.5% by mass or less. These lower and upper limits can be combined in any combination.

The content of the organic shrinkage inhibitor contained in the negative electrode material may be 0.01 to 1.0 mass%, 0.05 to 1.0 mass%, 0.01 to 0.5 mass%, or 0.05 to 0.5 mass%.

(Carbonaceous materials)
Carbonaceous materials contained in the negative electrode material can be carbon black, graphite, hard carbon, soft carbon, etc. Examples of carbon black include acetylene black, ketjen black, furnace black, and lamp black. Graphite may be any carbonaceous material containing a graphite-type crystal structure, and may be either artificial graphite or natural graphite. The carbonaceous material may be used alone or in combination of two or more.

The content of the carbonaceous material in the negative electrode material is, for example, 0.05% by mass or more, and may be 0.10% by mass or more. The content of the carbonaceous material is, for example, 5% by mass or less, and may be 3% by mass or less. These lower and upper limits can be combined in any combination.

The content of the carbonaceous material in the negative electrode material may be 0.05 to 5 mass%, 0.05 to 3 mass%, 0.10 to 5 mass%, or 0.10 to 3 mass%.

(Barium Sulfate)
The content of barium sulfate in the negative electrode material is, for example, 0.05% by mass or more, and may be 0.10% by mass or more. The content of barium sulfate in the negative electrode material is 3% by mass or less, and may be 2% by mass or less. These lower and upper limits can be combined in any manner.

The barium sulfate content in the negative electrode material may be 0.05 to 3 mass%, 0.05 to 2 mass%, 0.10 to 3 mass%, or 0.10 to 2 mass%.

(1) Analysis of polymer compounds Prior to analysis, the lead-acid battery after chemical conversion is fully charged and then disassembled to obtain the negative plate to be analyzed. The obtained negative plate is washed with water to remove sulfuric acid from the negative plate. The washing is continued until a pH test paper is pressed against the washed surface of the negative plate and no change in color of the test paper is confirmed. However, the washing time should be within 2 hours. The washed negative plate is dried in a reduced pressure environment at 60±5°C for about 6 hours. If an attached material is present after drying, the attached material is removed from the negative plate by peeling.
Next, the direction from the top end to the bottom end of the negative electrode plate is defined as the X direction, and the direction intersecting the X direction is defined as the Y direction, and the negative electrode plate is divided into 32 equal parts in a matrix of 8 rows and 4 columns, with the Y direction being the row direction and the X direction being the column direction, and negative electrode material is collected from all 32 regions to obtain samples of 32 regions (hereinafter also referred to as sample A). Sample A is crushed as necessary and subjected to analysis.
(1-1) Qualitative Analysis of Polymer Compounds 150.0±0.1 mL of chloroform is added to 100.0±0.1 g of crushed sample A, and the mixture is stirred at 20±5° C. for 16 hours to extract the polymer compound. Thereafter, the solid content is removed by filtration. The polymer compound is identified by obtaining information from infrared spectroscopy, ultraviolet-visible absorption spectroscopy, NMR spectroscopy, LC-MS and/or pyrolysis GC-MS, etc., for the chloroform solution in which the polymer compound obtained by extraction is dissolved, or the polymer compound obtained by drying the chloroform solution.

From the chloroform solution in which the polymer compound obtained by extraction is dissolved, chloroform is distilled off under reduced pressure to recover a chloroform-soluble fraction. The chloroform-soluble fraction is dissolved in deuterated chloroform, and ^{a 1} H-NMR spectrum is measured under the following conditions. From this ¹ H-NMR spectrum, a peak in the chemical shift range of 3.2 ppm to 3.8 ppm is confirmed. Furthermore, from the peak in this range, the type of oxy C _2-4 alkylene unit is identified.

Apparatus: AL400 type nuclear magnetic resonance apparatus manufactured by JEOL Ltd. Observation frequency: 395.88 MHz
Pulse width: 6.30 μs
Pulse repetition time: 74.1411 seconds Number of integrations: 32
Measurement temperature: room temperature (20-35℃)
Standard: 7.24 ppm
Sample tube diameter: 5 mm

From the ¹ H-NMR spectrum, the integral value (V ₁ ) of the peaks present in the chemical shift range of 3.2 ppm or more and 3.8 ppm or less is obtained. In addition, the sum (V 2 ) of the integral values of the peaks in the ¹ H-NMR spectrum is obtained for each of the hydrogen _atoms of the -CH ₂ - groups and -CH< groups bonded to the oxygen atoms bonded to the end groups of the polymer compound. Then, from V ₁ and V ₂ , the proportion of V ₁ to the sum of V ₁ and V ₂ (= V ₁ / (V ₁ + V ₂ ) × 100 (%)) is obtained.

In addition, when determining the integral value of a peak in a ¹ H-NMR spectrum in a qualitative analysis, two points on the ¹ H-NMR spectrum that have no significant signals are determined so as to sandwich the relevant peak, and each integral value is calculated using a straight line connecting these two points as a baseline. For example, for a peak that exists in a chemical shift range of 3.2 ppm to 3.8 ppm, a straight line connecting two points on the spectrum, 3.2 ppm and 3.8 ppm, is used as the baseline. For example, for a peak that exists in a chemical shift range of more than 3.8 ppm to 4.0 ppm, a straight line connecting two points on the spectrum, 3.8 ppm and 4.0 ppm, is used as the baseline.

(1-2) Quantitative Analysis of Polymer Compounds An appropriate amount of the chloroform-soluble matter is dissolved in deuterated chloroform together with tetrachloroethane (TCE) having m _r (g) measured to an accuracy of ±0.0001 g, and a ¹ H-NMR spectrum is measured. The integral value (S _a ) of the peak present in the chemical shift range of 3.2 to 3.8 ppm and the integral value (S _r ) of the peak derived from TCE are obtained, and the content C _n (ppm) of the polymer compound in the negative electrode material is calculated from the following formula. Here, the mass-based content of the polymer compound in the negative electrode material in all 32 regions and its average value C0 are calculated.

C _n =S _a /S _r ×N _r /N _a ×M _a /M _r ×m _r /m × 1000000
(In the formula, M _a is the molecular weight of a structure that exhibits a peak in the chemical shift range of 3.2 to 3.8 ppm (more specifically, the molecular weight of a repeating structure of an oxyC _2-4 alkylene unit), and N _a is the number of hydrogen atoms bonded to the carbon atoms of the main chain of the repeating structure. _{Nr and Mr} are the number of hydrogen atoms contained in the molecule of the reference substance and the molecular weight of the reference substance, respectively, and m (g) is the extraction is the mass of the negative electrode material used.)
In addition, since the reference substance in this analysis is TCE, N _r =2 and M _r =168. Also, m=100.

For example, when the polymer compound is polypropylene glycol, M _a is 58 and N _a is 3. When the polymer compound is polyethylene glycol, M _a is 44 and N _a is 4. In the case of a copolymer, N _a is a value obtained by averaging the N _a value of each monomer unit using the molar ratio (mol %) of each monomer unit contained in the repeating structure, and M _a is determined according to the type of each monomer unit.

In the quantitative analysis, the integral value of the peak in the ¹ H-NMR spectrum is determined using data processing software "ALICE" manufactured by JEOL Ltd.

(1-3) Mn Measurement of Polymer Compound GPC measurement of polymer compounds is performed using the following apparatus under the following conditions. A calibration curve (calibration curve) is separately created from a plot of Mn of a standard substance versus elution time. The Mn of the polymer compound is calculated based on this calibration curve and the GPC measurement results of the polymer compound.

Analysis system: 20A system (manufactured by Shimadzu Corporation)
Column: GPC KF-805L (Shodex), two columns connected in series Column temperature: 30°C
Mobile phase: tetrahydrofuran Flow rate: 1 mL/min.
Concentration: 0.20% by mass
Injection volume: 10 μL
Standard substance: polyethylene glycol (Mn = 2,000,000, 200,000, 20,000, 2,000, 200)
Detector: Differential refractive index detector (Shodex RI-201H)

(others)
The negative electrode plate can be formed by applying or filling a negative electrode paste onto a negative electrode current collector, aging and drying to prepare an unformed negative electrode plate, and then chemically forming the unformed negative electrode plate. The negative electrode paste is prepared by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as necessary, and kneading them. When aging, it is preferable to age the unformed negative electrode plate at a temperature higher than room temperature and at a high humidity.

Formation can be carried out by immersing a plate group including unformed negative plates in an electrolyte containing sulfuric acid in a lead-acid battery container and then charging the plate group. However, formation may also be carried out before assembling the lead-acid battery or the plate group. Formation produces spongy lead.

(Positive electrode plate)
The positive electrode plate of a lead-acid battery can be classified into a paste type, a clad type, and the like. The paste type positive electrode plate includes a positive electrode collector and a positive electrode material. The positive electrode material is held by the positive electrode collector. In the paste type positive electrode plate, the positive electrode material is the positive electrode plate excluding the positive electrode collector. The positive electrode collector may be formed by casting lead (Pb) or a lead alloy, or may be formed by processing a lead sheet or a lead alloy sheet. Examples of the processing method include an expanding process and a punching process. It is preferable to use a lattice-shaped collector as the positive electrode collector because it is easy to support the positive electrode material. The clad type positive electrode plate includes a plurality of porous tubes, a core inserted into each tube, a current collecting portion connecting the plurality of cores, a positive electrode material filled in the tube into which the core is inserted, and a link connecting the plurality of tubes. In the clad type positive plate, the positive electrode material does not include the tube, the core metal, the current collector, and the connecting seat. In the clad type positive plate, the core metal and the current collector are collectively referred to as the positive electrode current collector.

A positive electrode plate may have materials such as a mat or pasting paper affixed to it. Such materials (affixing materials) are used integrally with the positive electrode plate and are therefore considered to be included in the positive electrode plate. Furthermore, when the positive electrode plate includes such materials, the positive electrode material, in the case of a pasted positive electrode plate, is the positive electrode plate excluding the positive electrode collector and the affixing materials.

As the lead alloy used for the positive electrode collector, in terms of corrosion resistance and mechanical strength, a Pb-Sb alloy, a Pb-Ca alloy, or a Pb-Ca-Sn alloy is preferred. The positive electrode collector may have a surface layer. The surface layer and the inner layer of the positive electrode collector may have different compositions. The surface layer may be formed on a part of the positive electrode collector. The surface layer may be formed only on the lattice portion, the lug portion, or the frame portion of the positive electrode collector.

The positive electrode material contained in the positive plate contains a positive electrode active material (lead dioxide or lead sulfate) that develops capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives as necessary.

An unformed paste-type positive plate is obtained by filling a positive current collector with a positive electrode paste, aging it, and drying it. The positive electrode paste is prepared by kneading lead powder, additives, water, and sulfuric acid. An unformed clad-type positive plate is formed by filling a porous tube into which a core metal connected by a current collector is inserted with lead powder or lead powder in a slurry form, and connecting multiple tubes with a linking member. The unformed positive plates are then formed to obtain a positive plate. Formation can be performed by charging the plate group, with the plate group including the unformed positive plate immersed in an electrolyte containing sulfuric acid in a lead-acid battery container. However, formation may be performed before assembling the lead-acid battery or the plate group.

The formation can be carried out by immersing the plate group including the unformed positive plate in an electrolyte containing sulfuric acid in a lead-acid battery container and charging the plate group. However, the formation can also be carried out before assembling the lead-acid battery or the plate group.

(Separator)
The separator may be in a sheet shape or may be formed in a bag shape. A sheet-shaped separator may be sandwiched between the positive electrode plate and the negative electrode plate. Also, the electrode plate may be sandwiched between a folded sheet-shaped separator. In this case, the positive electrode plate sandwiched between the folded sheet-shaped separator and the negative electrode plate sandwiched between the folded sheet-shaped separator may be stacked, or one of the positive electrode plate and the negative electrode plate may be sandwiched between the folded sheet-shaped separator and stacked with the other electrode plate. Also, the sheet-shaped separator may be folded into a bellows shape, and the positive electrode plate and the negative electrode plate may be sandwiched between the bellows-shaped separator so that the separator is interposed between them. When a separator folded like an accordion is used, the separator may be arranged so that the folded portion is along the horizontal direction of the lead-acid battery (e.g., so that the folded portion is parallel to the horizontal direction) or along the vertical direction (e.g., so that the folded portion is parallel to the vertical direction). In a separator folded like an accordion, recesses are formed alternately on both main surfaces of the separator. Since the upper part of the positive and negative plates usually has a lug, when the separator is arranged so that the folded portion is along the horizontal direction of the lead-acid battery, the positive and negative plates are arranged only in the recesses on one main surface side of the separator (i.e., a double separator is interposed between the adjacent positive and negative plates). When the separator is arranged so that the folded portion is aligned with the vertical direction of the lead-acid battery, the positive electrode plate can be accommodated in the recess on one main surface side, and the negative electrode plate can be accommodated in the recess on the other main surface side (that is, a single layer of separator can be interposed between adjacent positive and negative electrode plates.) When a pouch-shaped separator is used, the pouch-shaped separator may accommodate either the positive or negative electrode plate.
In this specification, the up-down direction of the electrode plate means the up-down direction in the vertical direction of the lead-acid battery.

(Electrolyte)
The electrolyte is an aqueous solution containing sulfuric acid, which may be gelled as necessary.
The electrolyte may contain the above-mentioned polymer compound.

The concentration of the polymer compound in the electrolyte may be, by mass, from 1 ppm to 500 ppm, from 1 ppm to 300 ppm, from 1 ppm to 200 ppm, from 5 ppm to 500 ppm, from 5 ppm to 300 ppm, or from 5 ppm to 200 ppm.

The concentration of the polymer compound in the electrolyte is determined by adding chloroform to a predetermined amount (m ₁ (g)) of electrolyte taken out of a fully charged lead-acid battery, mixing the mixture, leaving it to stand and separating it into two layers, and then taking out only the chloroform layer. After repeating this process several times, the chloroform is distilled off under reduced pressure to obtain a chloroform-soluble fraction. An appropriate amount of the chloroform-soluble fraction is dissolved in deuterated chloroform together with 0.0212±0.0001 g of TCE, and ^{the 1} H-NMR spectrum is measured. The integral value (S _a ) of the peak present in the chemical shift range of 3.2 to 3.8 ppm and the integral value (S _r ) of the peak derived from TCE are calculated, and the content of the polymer compound in the electrolyte, C _{e ,} is calculated from the following formula.
C _e = S _a / S _r × N _r / N _a × M _a / M _r × m _r / m ₁ × 1000000 (wherein M _a and N _a are the same as above.)

The electrolyte may optionally contain cations (e.g., metal cations such as sodium ions, lithium ions, magnesium ions, and/or aluminum ions) and/or anions (e.g., anions other than sulfate anions, such as phosphate ions).

The specific gravity of the electrolyte in a fully charged lead-acid battery at 20°C may be, for example, 1.20 or more, and may be 1.25 or more. The specific gravity of the electrolyte at 20°C is 1.35 or less, and preferably 1.32 or less. These lower and upper limits can be combined arbitrarily. The specific gravity of the electrolyte at 20°C may be 1.20 or more and 1.35 or less, 1.20 or more and 1.32 or less, 1.25 or more and 1.35 or less, or 1.25 or more and 1.32 or less.
(2) Evaluation A test battery of a single-plate cell with a rated capacity of 6.2 Ah was constructed using one negative electrode plate and two positive electrode plates, and various performance characteristics were evaluated.
(a) Specific Gravity Difference of Electrolyte In a water tank at 25 ° C., a fully charged test battery is discharged for 1 hour at a current (A) 0.2 times the value listed as the rated capacity (Ah), then charged at a constant current (A) 1.0 times the value listed as the rated capacity (Ah), and when the voltage reaches 2.5 V / cell, charging is performed at a constant voltage for 2 hours. The upper limit current during charging is a current value (A) 1.0 times the value listed as the rated capacity (Ah). The value listed as the rated capacity is a value in Ah. The unit of current set based on the value listed as the rated capacity is A. Then, electrolyte is collected from the upper part (within a range of 10 mm below the liquid level) and the lower part (within a range of 10 mm above the lower end of each plate) of the battery container, the specific gravity is measured, and the specific gravity difference is calculated.

(b) Overcharge quantity of electricity In order to make the overcharge conditions higher than the normal 4-10 minute test specified in JIS D5301, a test of 1 minute of discharge and 10 minutes of charge (1-10 minute test) is carried out in a water tank at 60°C ± 2°C (high temperature light load test). In the high temperature light load test, charge and discharge are repeated 450 cycles. The overcharge quantity of electricity (charge quantity of electricity - discharge quantity of electricity) in each cycle up to the 450th cycle is totaled and averaged to determine the overcharge quantity of electricity (Ah) per cycle.
Discharge: constant current 3.57A, 1 minute
Charging: constant voltage 2.47V/cell, upper limit current 1x the rated capacity (Ah), 10 minutes

(c) Low-temperature HR discharge performance The test battery after the high-temperature light-load test in (b) above is discharged at a constant current of 25 A at -15°C±1°C until the terminal voltage reaches 1.0 V/cell, and the discharge time (low-temperature HR discharge duration after light-load test) (s) is determined. The longer the discharge duration, the better the low-temperature HR discharge performance.

A lead-acid battery according to one aspect of the present invention will be described below.
(1) A negative electrode plate for a lead-acid battery comprising a negative electrode current collector and a negative electrode material,
the negative electrode material comprises a polymer compound;
The direction from the upper end to the lower end of the negative electrode plate is defined as the X direction, and the direction intersecting the X direction is defined as the Y direction. The negative electrode plate is divided into 32 equal parts in a matrix of 8 rows and 4 columns, with the Y direction being the row direction and the X direction being the column direction. When the average content of the polymer compound in the negative electrode material in all 32 regions is defined as C0,
A negative electrode plate in which the number N(1-4) of 16 regions in the first to fourth rows from the top end side, in which the content of the polymer compound is smaller than C0, and the number N(5-8) of 16 regions in the fifth to eighth rows, in which the content of the polymer compound is smaller than C0, satisfy N(1-4) < N(5-8).

(2) In the above (1), the polymer compound may have a peak in the range of 3.2 ppm to 3.8 ppm in terms of chemical shift in ¹ H-NMR spectrum.

(3) In the above (1), the polymer compound may contain a repeating structure of an oxy-C _2-4 alkylene unit.

(4) In the above (1) or (2), when the 32 matrix-like regions are represented by R(x, y) (where x is an integer of 1 to 8 indicating a row position, and y is an integer of 1 to 4 indicating a column position), and the content of the polymer compound in the negative electrode material in R(x, y) is defined as C(x, y), the following is true:
(a) in at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(5,y) through C(8,y);
(b) in at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(6,y) through C(8,y);
(c) in at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(7,y) through C(8,y);
(d) in at least one column, the average value of C(1,y) through C(4,y) is greater than C(8,y);
(e) in at least one column, any of C(5,y) through C(8,y) is smaller than any of the rest;
(f) in at least one column, C(8,y) is smaller than any of the rest;
(g) in at least one column, C(8,y) is smaller than any of C(7,y) through C(5,y);
At least one of the above conditions may be satisfied.

(5) A negative electrode plate for a lead-acid battery comprising a negative electrode current collector and a negative electrode material,
the negative electrode material comprises a polymer compound;
The direction from the upper end to the lower end of the negative electrode plate is defined as the X direction, and the direction intersecting the X direction is defined as the Y direction. The negative electrode plate is divided into 32 equal parts in a matrix of 8 rows and 4 columns, with the Y direction being the row direction and the X direction being the column direction. When the average content of the polymer compound in the negative electrode material in all 32 regions is defined as C0,
The number N(1-2) of the eight regions in the first and second rows from the top end side, in which the content of the polymer compound is smaller than C0, and the number N(3-4) of the eight regions in the third and fourth rows, in which the content of the polymer compound is smaller than C0, satisfy N(1-2)<N(3-4), and
A negative electrode plate in which the number N(5-6) of the eight regions in the 5th to 6th rows in which the content of the polymer compound is smaller than C0 and the number N(7-8) of the eight regions in the 7th to 8th rows in which the content of the polymer compound is smaller than C0 satisfy N(5-6) < N(7-8).

(6) A battery comprising a plurality of positive electrode plates, a plurality of negative electrode plates, and an electrolyte;
At least one of the plurality of negative electrode plates is any one of the negative electrode plates described above in (1) to (5).

The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1 to 4
(a) Preparation of negative electrode plate Raw material lead powder, barium sulfate, carbon black, polymer compound (polypropylene glycol (PPG), Mw = 2000), and organic shrinkage inhibitor (formaldehyde condensate of bisphenol compound with sulfonic acid group) are mixed with an appropriate amount of sulfuric acid aqueous solution to obtain a negative electrode paste. At this time, the content of the polymer compound in the negative electrode material is 0 ppm, 15 ppm, 66 ppm, 200 ppm or 370 ppm by mass, and the content of barium sulfate is 0.6 mass%, the content of carbon black is 0.3 mass%, and the content of the organic shrinkage inhibitor is 0.1 mass%, all of which are obtained by the above-mentioned procedure. Each component is mixed to obtain five types of negative electrode paste.

In the case of battery A1 of Example 1, a negative electrode paste is prepared so as to contain 15 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the area of rows 1 to 2 of the negative electrode plate.

In the case of battery A2 of Example 2, a negative electrode paste is prepared so as to contain 66 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the area of rows 1 to 2 of the negative electrode plate.

In the case of battery A3 of Example 3, a negative electrode paste is prepared so as to contain 200 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the area of rows 1 to 2 of the negative electrode plate.

In the case of battery A4 of Example 4, a negative electrode paste is prepared so as to contain 370 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the area of rows 1 to 2 of the negative electrode plate.

Next, a negative electrode paste containing 0 ppm polymer and no polymer compounds is filled into the remaining mesh portions of each expanded grid, and then the entire negative electrode material is aged and dried to obtain an unformed negative electrode plate.

(b) Preparation of Positive Plate The raw lead powder is mixed with an appropriate amount of sulfuric acid aqueous solution to obtain a positive paste. The positive paste is filled into the mesh of an expanded lattice made of a Pb-Ca-Sn alloy, and aged and dried to obtain an unformed positive plate.

(c) Preparation of test battery The test battery has a rated voltage of 2V/cell and a rated 5-hour capacity of 32Ah. The plate assembly of the test battery is composed of one negative electrode sandwiched between two positive electrodes. The negative electrode plate is housed in a pouch-shaped separator and stacked with the positive electrode plate to form a plate assembly. The plate assembly is housed in a polypropylene battery case together with an electrolyte (aqueous sulfuric acid solution), and chemical formation is performed in the battery case to prepare a liquid-type lead-acid battery. The specific gravity of the electrolyte after chemical formation is 1.28 (calculated at 20°C).

In the ¹ H-NMR spectrum of the polymer compound measured by the above-mentioned procedure, a peak derived from -CH< of the oxypropylene unit is observed in the chemical shift range of 3.2 ppm to 3.42 ppm, and a peak derived from -CH ₂ - of the oxypropylene unit is observed in the chemical shift range of more than 3.42 ppm to 3.8 ppm. In the ¹ H-NMR spectrum, the integral of the peak from 3.2 ppm to 3.8 ppm accounts for 98.1% of the total integral of this peak, the integral of the peak of the hydrogen atom of the -CH ₂ - group bonded to the oxygen atom, and the integral of the peak of the hydrogen atom of the -CH< group bonded to the oxygen atom.

Figure 9 shows the distribution of polymer compounds in batteries A1 to A4. Areas where C(x, y) < C0 (i.e. areas that do not contain polymer compounds) are marked with "C < C0", and other areas (i.e. areas that contain polymer compounds) are marked with "-". N(1-4) = 8, N(5-8) = 16, and N(1-4) < N(5-8) is satisfied.

Examples 5 to 8
A lead acid battery was produced in the same manner as in Examples 1 to 4, except that the following points were changed in the method of producing the negative electrode plate.

In the case of battery A5 of Example 5, a negative electrode paste is prepared so as to contain 15 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 4 of the negative electrode plate.

In the case of battery A6 of Example 6, a negative electrode paste is prepared so as to contain 66 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 4 of the negative electrode plate.

In the case of battery A7 of Example 7, a negative electrode paste is prepared so as to contain 200 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 4 of the negative electrode plate.

In the case of battery A8 of Example 8, a negative electrode paste is prepared so as to contain 370 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 4 of the negative electrode plate.

Figure 10 shows the distribution of polymer compounds in batteries A5 to A8. Areas where C(x, y) < C0 (i.e. areas that do not contain polymer compounds) are marked with "C < C0", and other areas (i.e. areas that contain polymer compounds) are marked with "-". N(1-4) = 0, N(5-8) = 16, and N(1-4) < N(5-8) is satisfied.

Examples 9 to 12
A lead-acid battery is prepared in the same manner as in Examples 1 to 4, except that the method for preparing the negative electrode plate was changed as follows.

In the case of battery A9 of Example 9, a negative electrode paste is prepared so as to contain 15 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 6 of the negative electrode plate.

In the case of battery A10 of Example 10, a negative electrode paste is prepared so as to contain 66 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 6 of the negative electrode plate.

In the case of battery A11 of Example 11, a negative electrode paste is prepared so as to contain 200 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 6 of the negative electrode plate.

In the case of battery A12 of Example 12, a negative electrode paste is prepared so as to contain 370 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and is filled into the mesh portion of an expanded lattice made of a Pb-Ca-Sn alloy, which corresponds to the areas of rows 1 to 6 of the negative electrode plate.

Figure 11 shows the distribution of polymer compounds in batteries A9 to A12. Areas where C(x, y) < C0 (i.e. areas that do not contain polymer compounds) are marked with "C < C0", and other areas (i.e. areas that contain polymer compounds) are marked with "-". N(1-4) = 0, N(5-8) = 8, and N(1-4) < N(5-8) is satisfied.

Comparative Examples 1 to 5
A lead-acid battery is prepared in the same manner as in Examples 1 to 4, except that the method for preparing the negative electrode plate was changed as follows.

In the case of battery B1 of Comparative Example 1, a negative electrode paste was prepared so as to contain 15 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and was filled into the entire mesh portion of the expanded lattice made of a Pb-Ca-Sn alloy.

In the case of battery B2 of Comparative Example 2, a negative electrode paste was prepared so as to contain 66 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and was filled into the entire mesh portion of the expanded lattice made of a Pb-Ca-Sn alloy.

In the case of battery B3 of Comparative Example 3, a negative electrode paste was prepared so as to contain 200 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and was filled into the entire mesh portion of the expanded lattice made of a Pb-Ca-Sn alloy.

In the case of battery B4 of Comparative Example 4, a negative electrode paste was prepared so as to contain 370 ppm of the polymer compound in the negative electrode material, as determined by the procedure described above, and was filled into the entire mesh portion of the expanded lattice made of a Pb-Ca-Sn alloy.

In the case of battery B5 of Comparative Example 5, a negative electrode paste containing 0 ppm polymer and no polymer compound is filled into the entire mesh portion of the expanded lattice.

Figure 12 shows the distribution of polymer compounds in batteries B1 to B5. A "-" is displayed in the area where C(x, y) < C0 is not satisfied. N(1-4) = 0, N(5-8) = 0, and N(1-4) < N(5-8) is not satisfied.

[evaluation]
The (a) specific gravity difference of the electrolyte, (b) the amount of overcharge electricity, and (c) the low-temperature HR discharge performance were evaluated by the methods described above. The results are shown in Table 1.

Figure 13 shows the specific gravity difference of the electrolyte in a bar graph, and Figure 14 shows the specific gravity difference of the electrolyte in a line graph when the horizontal line is the PPG filling ratio. Here, the PPG filling ratio is 25% when the polymer compound is contained in the 1st to 2nd row region of the negative plate, 50% when it is contained in the 1st to 4th row region, 75% when it is contained in the 1st to 6th row region, 100% when it is contained in the 1st to 8th row region, and 0% in Comparative Example 5. It can be seen that the specific gravity difference of the electrolyte is smaller in the batteries A1 to A12 than in the batteries B1 to B4, and stratification is less likely to progress. In addition, in the battery B5, since there is a considerable amount of hydrogen generation in the entire region of the negative plate, the specific gravity difference is small as in the examples. However, the overcharged electric quantity of the battery B5 is significantly larger.

Figure 15 shows the overcharge quantity of electricity of the electrolyte in a bar graph, and Figure 16 shows the overcharge quantity of electricity in a line graph when the horizontal line represents the PPG filling ratio. The overcharge quantity of electricity is reduced in batteries A1 to 12 compared to battery B5. Also, the overcharge quantity of electricity tends to be reduced as the average polymer compound concentration C0 is higher overall and the number of regions in the examples where C<C0 is fewer. However, the overcharge quantity of electricity in batteries A4 to A12, where the number of regions where C<C0 is 50% or less, is at the same level as batteries B1 to B4.

The lead-acid battery according to the present invention can be suitably used, for example, as a power source for starting vehicles (cars, motorcycles, etc.) and industrial power storage devices such as electric vehicles (forklifts, etc.). Note that these uses are merely examples and are not intended to be limiting.

Reference Signs List 1: Lead-acid battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 5: Positive electrode shelf 6: Negative electrode shelf 7: Positive electrode column 8: Through connector 9: Negative electrode column 11: Plate group 12: Battery case 13: Partition wall 14: Cell chamber 15: Lid 16: Negative electrode terminal 17: Positive electrode terminal 18: Vent plug

Claims (6)

A negative electrode plate for a lead-acid battery comprising a negative electrode current collector and a negative electrode material,
The negative electrode material is
The negative electrode material has an effect of increasing the overvoltage (Condition A);
In the chemical shift of the ¹ H-NMR spectrum, a peak is present in the range of 3.2 ppm to 3.8 ppm (condition B); and
Contains a repeating structure of oxyC2-4 alkylene units (condition _C )
The polymer compound satisfies at least one of the following conditions :
The direction from the upper end to the lower end of the negative electrode plate is defined as the X direction, and the direction intersecting the X direction is defined as the Y direction. The negative electrode plate is divided into 32 equal parts in a matrix of 8 rows and 4 columns, with the Y direction being the row direction and the X direction being the column direction. When the average content of the polymer compound in the negative electrode material in all 32 regions is defined as C0,
A negative electrode plate in which the number N(1-4) of 16 regions in the first to fourth rows from the top end side, in which the content of the polymer compound is smaller than C0, and the number N(5-8) of 16 regions in the fifth to eighth rows, in which the content of the polymer compound is smaller than C0, satisfy N(1-4) < N(5-8). When the 32 matrix-like regions are represented by R(x, y) (where x is an integer of 1 to 8 indicating a row position, and y is an integer of 1 to 4 indicating a column position), and the content of the polymer compound in the negative electrode material in R(x, y) is defined as C(x, y), the following is true:
(1) In at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(5,y) through C(8,y);
(2) in at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(6,y) through C(8,y);
(3) in at least one column, the average value of C(1,y) through C(4,y) is greater than the average value of C(7,y) through C(8,y);
(4) In at least one column, the average value of C(1,y) through C(4,y) is greater than C(8,y);
(5) In at least one column, any of C(5,y) through C(8,y) is smaller than any of the rest;
(6) in at least one column, C(8,y) is smaller than any of the rest;
(7) In at least one column, C(8,y) is smaller than any of C(7,y) through C(5,y);
The negative electrode plate according to claim 1 , which satisfies at least one of the following conditions. A negative electrode plate for a lead-acid battery comprising a negative electrode current collector and a negative electrode material,
The negative electrode material is
The negative electrode material has an effect of increasing the overvoltage (Condition A);
In the chemical shift of the ¹ H-NMR spectrum, a peak is present in the range of 3.2 ppm to 3.8 ppm (condition B); and
Contains a repeating structure of oxyC2-4 alkylene units (condition _C )
The polymer compound satisfies at least one of the following conditions :
The direction from the upper end to the lower end of the negative electrode plate is defined as the X direction, and the direction intersecting the X direction is defined as the Y direction. The negative electrode plate is divided into 32 equal parts in a matrix of 8 rows and 4 columns, with the Y direction being the row direction and the X direction being the column direction. When the average content of the polymer compound in the negative electrode material in all 32 regions is defined as C0,
The number N(1-2) of the eight regions in the first and second rows from the top end side, in which the content of the polymer compound is smaller than C0, and the number N(3-4) of the eight regions in the third and fourth rows, in which the content of the polymer compound is smaller than C0, satisfy N(1-2)<N(3-4), and
A negative electrode plate in which the number N(5-6) of the eight regions in the 5th to 6th rows in which the content of the polymer compound is smaller than C0 and the number N(7-8) of the eight regions in the 7th to 8th rows in which the content of the polymer compound is smaller than C0 satisfy N(5-6) < N(7-8). The negative electrode plate according to any one of claims 1 to 3 , wherein an average value C0 of the content of the polymer compound is 3 ppm or more and 400 ppm or less. The negative electrode plate according to any one of claims 1 to 4 , wherein the maximum content of the polymer compound in the 16 regions in the first to fourth rows from the upper end side is 400 ppm or less. A battery comprising a plurality of positive electrode plates, a plurality of negative electrode plates, and an electrolyte;
A lead-acid battery, wherein at least one of the plurality of negative plates is the negative plate according to any one of claims 1 to 5 .

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