JP2024044869A - Lead-acid battery - Google Patents

Abstract

[Problem] To provide a lead-acid battery that exhibits excellent life performance in a life test simulating how an auxiliary battery is used while a car is parked. [Solution] A lead-acid battery comprising a negative electrode 9 containing a negative electrode active material 13, a positive electrode 10 containing a positive electrode active material 15, a separator 11 disposed between the negative electrode 9 and the positive electrode 10, and a nonwoven fabric 20 disposed at least one of between the negative electrode 9 and the separator 11 and between the positive electrode 10 and the separator 11, wherein the ratio of the mass of the positive electrode active material 15 to the mass of the negative electrode active material 13 is 1.50 or more. [Selected Figure] Figure 2

Description

The present invention relates to lead-acid batteries.

Lead-acid batteries are used as batteries for starting automobile engines (internal combustion engines). Until now, various efforts have been made to improve the life performance of lead-acid batteries for engine starting. For example, Patent Document 1 discloses a technique for improving the life performance of a lead-acid battery for engine starting by incorporating Ketjenblack into the negative electrode material and setting the density of the negative electrode material to 3 g/cm ³ or more.

JP 2019-50229 A

In recent years, the amount of power supplied to devices while parked has increased due to the widespread use of hybrid cars, electric vehicles, and other electric vehicles (xEVs), and the increase in cars equipped with various functions, such as automatic door opening and closing and automatic start-up of car navigation systems. This has increased the importance of auxiliary batteries that provide this power.

Currently, lead-acid batteries for engine starting are being reused as batteries for auxiliary equipment, but lead-acid batteries for engine starting do not always show sufficient life performance in life tests that assume how the battery will be used while parked. do not have.

Therefore, one aspect of the present invention aims to provide a lead-acid battery that exhibits excellent life performance in a life test that simulates how an auxiliary battery is used while a vehicle is parked.

Some aspects of the present invention provide the following [1] to [4].

[1]
a negative electrode including a negative electrode active material;
a positive electrode including a positive electrode active material;
a separator disposed between the negative electrode and the positive electrode;
a nonwoven fabric disposed at least one between the negative electrode and the separator and between the positive electrode and the separator;
A lead-acid battery, wherein the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material is 1.50 or more.

[2]
The lead-acid battery according to [1], wherein the nonwoven fabric is disposed between the negative electrode and the separator.

[3]
The lead-acid battery according to [1] or [2], which is used to supply electricity required while parking a car without an internal combustion engine.

[4]
The lead-acid battery according to [1] or [2] is used as the lead-acid battery of an automobile equipped with an internal combustion engine, a storage battery that supplies power to start the internal combustion engine, and a lead-acid battery that supplies power required while the automobile is parked.

According to one aspect of the present invention, it is possible to provide a lead-acid battery that exhibits excellent life performance in a life test assuming how an auxiliary battery is used while a car is parked.

1 is a perspective view showing an overall configuration and an internal structure of a lead-acid battery according to one embodiment; FIG. 2 is a perspective view showing an electrode group of the lead-acid battery shown in FIG. 1. FIG. 3 is a schematic cross-sectional view showing a cross section taken along line III-III in FIG. 2.

In this specification, a numerical range indicated using "~" indicates a range that includes the numerical values before and after "~" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values before and after "~" are the same. In the numerical ranges described in stages in this specification, the upper or lower limit of a numerical range of a certain stage may be replaced with the upper or lower limit of a numerical range of another stage. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. Furthermore, the upper and lower limits described individually can be combined in any way.

<Lead-acid battery>
One embodiment of the present invention relates to a lead-acid battery comprising: a negative electrode including a negative electrode active material; a positive electrode including a positive electrode active material; a separator disposed between the negative electrode and the positive electrode; and a nonwoven fabric disposed at least one of between the negative electrode and the separator and between the positive electrode and the separator, wherein the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material is 1.50 or more.

The above-mentioned lead-acid battery exhibits better life performance than a lead-acid battery not having the above-mentioned configuration (e.g., a lead-acid battery for starting an engine) in a life test assuming the usage of an auxiliary battery while a car is parked (e.g., supplying power required to operate a function for automatically opening and closing a door, a function for automatically starting a car navigation system, etc.). Therefore, the above-mentioned lead-acid battery is preferably used to supply power required while a car is parked. Here, the life test assuming the usage of an auxiliary battery while a car is parked is a life test (hereinafter referred to as "life test A") in which the following (I) is repeatedly performed in a temperature environment of 25°C, and the life performance is relatively evaluated by the total discharge amount X until the terminal voltage during discharge reaches 7.2V.
(I): After discharging under the following condition (1), charging is performed under the following condition (2).
Condition (1): Discharge current = 25 A, discharge time = 240 seconds Condition (2): Charge voltage = 14.8 V, charge time = 600 seconds

The effect of improving the life performance by making the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material 1.50 or more was not confirmed in a life test assuming the use of an engine start battery, and this was a surprising result for the inventors. The reason why the above effect is obtained is not clear, but is presumed as follows. That is, while a lead-acid battery for starting an engine is used in an engine room where the temperature is relatively high, a lead-acid battery used to supply power to an auxiliary device while the vehicle is parked is used indoors at a relatively low temperature, and since no load is applied for starting the engine, it is presumed that the stratification of the electrolyte caused by gassing (a phenomenon in which gas is generated from the electrolyte due to a charging reaction) is less likely to occur when the auxiliary device battery is used while the vehicle is parked, compared to when the lead-acid battery is used for starting the engine. Therefore, it is presumed that the stratification suppression effect expected from the use of the nonwoven fabric is not sufficiently obtained when the auxiliary device battery is used while the vehicle is parked, and the reaction proceeds locally at the top of the positive electrode, making the positive electrode active material more likely to become muddy and fall off. In contrast, the lead-acid battery has a ratio of the mass of the positive electrode active material to the mass of the negative electrode active material of 1.50 or more, which makes it relatively difficult for local reactions to occur at the top of the positive electrode, and prevents the positive electrode active material from becoming muddy and falling off, which is thought to be why the life-prolonging effect is achieved.

Vehicles that use the above-mentioned lead-acid batteries include vehicles without an internal combustion engine, storage batteries that supply electricity to start the internal combustion engine, and lead-acid batteries that supply the electricity required while the engine is parked. Examples include automobiles equipped with the following. Examples of such vehicles include electric vehicles such as hybrid vehicles and electric vehicles. That is, the lead-acid battery is suitably used as an auxiliary battery for electric vehicles (particularly hybrid vehicles and electric vehicles).

In recent years, the number of automobiles equipped with a function of automatically updating the software of the in-vehicle OS (operating system) by a technology of transmitting and receiving data by wireless communication called OTA (Over The Air) is increasing. Although such a function is also one of the functions that operate while the vehicle is parked, when transmitting and receiving data by wireless communication, a large amount of power is temporarily consumed compared to when other functions are operated. Therefore, when power is supplied to an in-vehicle device that transmits and receives data by wireless communication (for example, power supply during wireless communication by OTA technology), the lead-acid battery may reach an early end of life. On the other hand, the above-mentioned lead-acid battery tends to show a better life performance than a lead-acid battery not having the above-mentioned configuration (for example, a lead-acid battery for starting an engine) even in a life test assuming power supply to an in-vehicle device that transmits and receives data by wireless communication. Therefore, the above-mentioned lead-acid battery is suitably used for supplying power to an in-vehicle device that transmits and receives data by wireless communication. Here, the life test assuming power supply to an in-vehicle device that transmits and receives data via wireless communication is a life test (hereinafter referred to as "life test B") in which the following (II) is repeatedly performed in a temperature environment of 25°C, and the life performance is relatively evaluated based on the total discharge amount Y until the terminal voltage during discharge under the following condition (3) reaches 7.2 V.
(II): Discharging under the above condition (1) and charging under the above condition (2) are repeated three times in this order, and then discharging under the following condition (3) and charging under the following condition (4) are performed in this order.
Condition (3): Discharge current = 25 A, discharge time = 600 seconds Condition (4): Charge voltage = 14.8 V, charge time = 1500 seconds

Hereinafter, a lead-acid battery according to one embodiment will be described in detail with reference to the drawings as appropriate.

Figure 1 is a perspective view showing the overall configuration and internal structure of a lead-acid battery according to one embodiment. The lead-acid battery 1 shown in Figure 1 is a flooded lead-acid battery. As shown in Figure 1, the lead-acid battery 1 includes a battery case 2 with an open top and a lid 3 that closes the opening of the battery case 2. The battery case 2 and the lid 3 are made of, for example, polypropylene. The lid 3 is provided with a negative terminal 4, a positive terminal 5, and a liquid inlet plug 6 that closes a liquid inlet provided in the lid 3.

The battery case 2 contains an electrode group (electrode plate group) 7 and an electrolyte such as dilute sulfuric acid. Although not shown, the battery case 2 has multiple cell chambers for housing the electrode groups 7, and each cell chamber houses one electrode group 7. Of the multiple electrode groups 7, the electrode group 7 housed in the cell chamber closest to the negative terminal 4 is connected to the negative terminal 4 via a negative pole 8. Also, although not shown, of the multiple electrode groups 7, the electrode group 7 housed in the cell chamber closest to the positive terminal 5 is connected to the positive terminal 5 via a positive pole. In addition to sulfuric acid, the electrolyte may contain ions (e.g., sodium ions) at about 0.01 to 0.1 mol/L.

FIG. 2 is a perspective view showing the electrode group 7, and FIG. 3 is a schematic cross-sectional view taken along the line III--III in FIG. As shown in FIGS. 2 and 3, the electrode group 7 includes a plate-shaped negative electrode (negative electrode plate) 9, a plate-shaped positive electrode (positive electrode plate) 10, and a separator disposed between the negative electrode 9 and the positive electrode 10. 11, and a nonwoven fabric 20 disposed between the negative electrode 9 and the separator 11. The nonwoven fabric 20 may be arranged between the positive electrode 10 and the separator 11 instead of between the negative electrode 9 and the separator 11, or in addition to the space between the negative electrode 9 and the separator 11. When disposed between the negative electrode 9 and the separator 11, the effect of improving life performance tends to be enhanced by setting the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material to be 1.50 or more. The electrode group 7 has more negative electrodes 9 than the positive electrodes 10, and the number of negative electrodes 9 in the electrode group 7 is eight, and the number of positive electrodes 10 is seven. The negative electrode 9 includes a negative electrode current collector (negative electrode grid) 12 and a negative electrode active material 13 held by the negative electrode current collector 12, and the positive electrode 10 includes a positive electrode current collector (positive electrode grid) 14, A positive electrode active material 15 held by a positive electrode current collector 14 is included.

The electrode group 7 has a structure in which a plurality of negative electrodes 9 and a plurality of positive electrodes 10 are alternately stacked in a direction approximately parallel to the opening surface of the battery case 2, with separators 11 and nonwoven fabrics 20 interposed between them. In other words, the negative electrodes 9 and positive electrodes 10 are arranged so that their main surfaces extend in a direction perpendicular to the opening surface of the battery case 2.

In the electrode group 7 , the negative electrode ears 12 a of the negative electrode current collectors 12 in the plurality of negative electrodes 9 are collectively welded together by a negative electrode strap 16 . Similarly, the positive electrode ears 10a of each positive electrode current collector 14 in the plurality of positive electrodes 10 are collectively welded together using a positive electrode strap 17. Although not shown, the plurality of electrode groups 7 are connected by a negative electrode strap 16 or a positive electrode strap 17. Further, the negative electrode strap 16 of the electrode group 7 housed in the cell chamber closest to the negative electrode terminal 4 is connected to the negative electrode column 8, and the positive electrode strap 17 of the electrode group 7 housed in the cell chamber closest to the positive electrode terminal 5 is connected to the positive electrode column 8. connected to the pillar.

For example, the electrode group 7 is in a sufficiently compressed state within the cell chamber, the negative electrode 9 and the nonwoven fabric 20 are in contact with each other, the positive electrode 10 and the separator 11 are in contact with each other, and the separator 11 and the nonwoven fabric 20 are in contact with each other. It's okay to do so.

The separator 11 is formed in a bag shape and contains the negative electrode 9. The separator 11 is formed of, for example, polyethylene (PE), polypropylene (PP), or the like. The separator 11 may be a woven fabric or a porous film formed of these materials, and may be one to which inorganic particles such as SiO ₂ and Al ₂ O ₃ are attached. Conventionally, nonwoven fabrics have been used as separators for lead-acid batteries, but in this specification, the nonwoven fabric used as a separator corresponds to the nonwoven fabric 20 described below, and does not correspond to a separator. The thickness of the separator 11 (thickness measured when unfolded into a sheet) is, for example, 0.1 to 1.5 mm. The separator 11 may be in a shape other than a bag shape (for example, a sheet shape).

The nonwoven fabric 20 is in the form of a sheet, and is provided in close contact with the negative electrode 9 so as to cover the surface of the negative electrode 9. The sheet-like nonwoven fabric 20 may be wrapped around the negative electrode 9 to cover the surface of the negative electrode 9. The nonwoven fabric 20 may have a shape other than a sheet shape (for example, a bag shape). When the nonwoven fabric 20 is bag-shaped, the negative electrode 9 may be housed within the bag-shaped nonwoven fabric 20. When the nonwoven fabric 20 is arranged between the positive electrode 10 and the separator 11, the "negative electrode 9" in these embodiments may be read as the "positive electrode 10."

The nonwoven fabric 20 may be made of organic fibers or inorganic fibers. As a constituent material of the nonwoven fabric, mixed fibers containing inorganic fibers and pulp may be used, or mixed organic-inorganic fibers containing organic fibers and inorganic fibers may be used. Examples of organic fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyethylene terephthalate fibers, and the like. Examples of inorganic fibers include glass fibers (chopped strands, milled fibers, etc.). The nonwoven fabric preferably includes glass fibers. Examples of nonwoven fabrics containing glass fibers include glass mats formed by processing glass fibers into a felt shape. The glass mat may be made of only glass fibers, or may contain other materials other than glass fibers (for example, the above-mentioned organic fibers, etc.). The content of glass fibers in the nonwoven fabric may be, for example, 90% by mass or more.

The thickness of the nonwoven fabric 20 may be 0.1 mm or more, 0.3 mm or more, or 0.4 mm or more from the viewpoint of obtaining better life performance in the above-mentioned life tests A and B, and may be 1.0 mm or less, 0.7 mm or less, or 0.5 mm or less from the viewpoint of suppressing an increase in internal resistance and obtaining higher performance. From these viewpoints, the thickness of the nonwoven fabric 20 may be, for example, 0.1 to 1.0 mm, 0.3 to 0.5 mm, or 0.4 to 0.7 mm.

The total thickness of the nonwoven fabric 20 and the thickness of the separator 11 is 0.5 mm or more, 0.8 mm or more, or 1.2 mm or more, from the viewpoint that better life performance is likely to be obtained in the above life tests A and B. From the viewpoint of suppressing the increase in internal resistance and easily obtaining higher performance, the thickness may be 2.0 mm or less, 1.7 mm or less, or 1.4 mm or less. From these viewpoints, the total thickness of the nonwoven fabric 20 and the thickness of the separator 11 may be, for example, 0.5 to 2.0 mm, 0.8 to 1.7 mm, or 1.2 to 1.4 mm. Note that the sum of the thickness of the nonwoven fabric and the thickness of the separator may be equal to the distance between the electrodes (the distance between the negative electrode and the positive electrode).

The negative electrode current collector 12 and the positive electrode current collector 14 are each made of a lead alloy. The lead alloy may be an alloy containing tin, calcium, antimony, selenium, silver, bismuth, etc. in addition to lead, and specifically, for example, an alloy containing lead, tin, and calcium (Pb-Sn -Ca-based alloy).

The negative electrode active material 13 contains at least Pb as a Pb component, and further contains a Pb component other than Pb (for example, PbSO ₄ ) and an additive as necessary. The negative electrode active material 13 preferably contains porous spongy lead.

The content of the Pb component in the negative electrode active material 13 may be 90% by mass or more or 95% by mass or more, and 99% by mass or less or 98% by mass or less, based on the total mass of the negative electrode active material 13. The total mass of the negative electrode active material 13 can be calculated, for example, by removing the negative electrode 9 (negative electrode current collector 12 and negative electrode active material 13) from the lead-acid battery 1, washing it with water, and thoroughly drying the negative electrode 9, and then calculating the difference between the mass of the negative electrode 9 and the mass of the negative electrode current collector 12. Drying is performed, for example, at 50°C for 24 hours.

Examples of additives include resins having sulfo groups and/or sulfonic acid groups, barium sulfate, carbon materials (excluding carbon fibers), and fibers (acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, carbon fibers, etc.) can be mentioned. Resins having sulfo groups and/or sulfonic acid groups include lignin sulfonic acid, lignin sulfonate salts, and condensates of phenols, aminoarylsulfonic acids, and formaldehyde (for example, condensates of bisphenol, aminobenzenesulfonic acid, and formaldehyde). It may be at least one selected from the group consisting of condensates). Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black, and Ketjen black.

The positive electrode active material 15 contains PbO ₂ as a Pb component, and preferably contains β-PbO _2. The positive electrode active material 15 may further contain α-PbO ₂ as a Pb component. That is, in one embodiment, the positive electrode active material 15 may contain only β-PbO ₂ as a Pb component, and in another embodiment, the positive electrode active material 15 may contain α-PbO ₂ and β-PbO ₂ as Pb components. The positive electrode active material 15 may further contain a Pb component other than PbO ₂ (e.g., PbSO ₄ ) and an additive, as necessary.

The content of the Pb component in the positive electrode active material 15 may be 90% by mass or more or 95% by mass or more, and 99.9% by mass or less or 98% by mass or less, based on the total mass of the positive electrode active material 15. It's okay. The total mass of the positive electrode active material 15 is, for example, the positive electrode 10 measured after taking out the positive electrode 10 (positive electrode current collector 14 and positive electrode active material 15) from the lead-acid battery 1, washing it with water, and thoroughly drying the positive electrode 10. and the mass of the positive electrode current collector 14. Drying is performed, for example, at 50° C. for 24 hours.

Examples of the additive include carbon materials (excluding carbon fibers) and fibers (acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, carbon fibers, etc.). Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black, and Ketjen black.

The ratio (hereinafter, (referred to as "p/n ratio") is 1.50 or more, and from the viewpoint of easily obtaining better life performance in the above life tests A and B, 1.55 or more, 1.60 or more, or 1.65 or more. It may be. The p/n ratio may be 1.85 or less, 1.80 or less, 1.75 or less, or 1.70 or less, from the viewpoint of easily obtaining better life performance in the above life tests A and B. It's okay. From these points of view, the p/n ratio may be, for example, 1.50-1.80, 1.55-1.80, 1.60-1.75 or 1.65-1.70. The p/n ratio is the ratio of the mass of the positive electrode active material after chemical formation to the mass of the negative electrode active material after chemical formation. The p/n ratio can be adjusted by the number of electrode plates used and the amount of active material filled in the current collector (for example, the thickness of the electrode plate).

The total discharge amount (total discharge amount X and Y) in the above-mentioned life tests A and B of the lead acid battery 1 is a life test (hereinafter referred to as "life test C") for evaluating the life performance of a lead acid battery for engine starting. ) tends to be higher than the total discharge amount Z. For example, the ratio (X/Z ) can be 1.3 or more (eg, 1.3 to 4.1). For example, for the total discharge amount Z until reaching the end of life in life test C, the total discharge until reaching end of life in life test B (until the final voltage at the time of discharge under condition (3) becomes 7.2 V) The ratio of the quantity Y (Y/Z) can be 1.2 or more (eg, 1.2 to 3.7). In the embodiment described above, X/Z and Y/Z can also be set to larger values (for example, 2.0 or more or 3.0 or more) by adjusting the p/n ratio. Here, the life test C is a life test based on JIS D 5301:2019 10.5, in which the following (III) is repeated in a temperature environment of 40°C, and during continuous discharge at the rated cold cranking current. This is a life test in which the life performance is relatively evaluated based on the total discharge amount Z until the terminal voltage of the battery reaches 7.2V.
(III): After repeating discharging under the above condition (1) and charging under the above condition (2) in this order 480 times, and leaving it for 56 hours, Perform continuous discharge for seconds.

The lead-acid battery 1 is manufactured by a manufacturing method that includes, for example, an electrode manufacturing process for obtaining electrodes (a negative electrode and a positive electrode), and an assembly process for assembling constituent members including the electrodes to obtain the lead-acid battery 1. The method for manufacturing the lead-acid battery 1 includes a step of chemically forming an unformed negative electrode and a positive electrode (chemical formation step). The chemical conversion step may be carried out in the electrode manufacturing process, or may be carried out in the assembly process. The electrode manufacturing process and assembly process will be explained below.

The electrode manufacturing process includes a negative electrode manufacturing process and a positive electrode manufacturing process.

In the negative electrode manufacturing process, for example, a paste-like negative electrode active material (negative electrode active material paste) is held in the negative electrode current collector 12 and then aged and dried to obtain an unformed negative electrode. The negative electrode active material paste contains, for example, lead powder, additives, and sulfuric acid (for example, dilute sulfuric acid). The negative electrode active material paste is obtained, for example, by mixing lead powder and additives to obtain a mixture, and then adding a solvent and sulfuric acid to this mixture and kneading the mixture. The water content in the negative electrode active material paste is, for example, 5% by mass or more, 10% by mass or more, or 15% by mass or more, and 30% by mass or less, 25% by mass or less, or 20% by mass or less.

In the positive electrode manufacturing process, for example, after holding a paste-like positive electrode active material (positive electrode active material paste) in the positive electrode current collector 14, an unformed positive electrode is obtained by aging and drying. The positive electrode active material paste contains, for example, lead powder, additives, and sulfuric acid (for example, dilute sulfuric acid). The positive electrode active material paste can be obtained, for example, by mixing lead powder and additives to obtain a mixture, and then adding a solvent and sulfuric acid to this mixture and kneading the mixture. The water content in the positive electrode active material paste is, for example, 5% by mass or more, 10% by mass or more, or 15% by mass or more, and 30% by mass or less, 25% by mass or less, or 20% by mass or less.

In the assembly process, for example, the obtained unformed positive and negative electrodes are stacked with the separator 11 in between, and the current collecting parts of the electrodes of the same polarity are welded with a strap to obtain an unformed electrode group. After accommodating this electrode group in each cell in the battery case and connecting the negative electrode strap and positive electrode strap of the electrode group in adjacent cell chambers by the intercell connection part that penetrates the partition wall separating the cell chambers, A crude lead-acid battery is created by attaching a lid to the top of the battery case. Next, dilute sulfuric acid is poured into an unformed lead-acid battery and DC current is applied to form the battery. Subsequently, the lead acid battery 1 is obtained by adjusting the specific gravity (20° C.) of the sulfuric acid after chemical formation to an appropriate specific gravity of the electrolytic solution.

The specific gravity (20° C.) of sulfuric acid used for chemical formation may be 1.15 to 1.25. The specific gravity (20° C.) of sulfuric acid after chemical conversion is preferably 1.25 to 1.33, more preferably 1.26 to 1.30. The chemical formation conditions and the specific gravity of sulfuric acid can be adjusted depending on the size of the electrode. The chemical conversion treatment may be performed in the assembly process or in the electrode manufacturing process (tank chemical conversion).

Although one embodiment of a lead-acid battery and a method for manufacturing the same have been described above, the present invention is not limited to the above embodiment.

For example, the number of negative electrodes and positive electrodes constituting one electrode group is not particularly limited, and may be six negative electrodes and five positive electrodes, or seven negative electrodes and six positive electrodes. The number of positive electrodes may be the same as the number of negative electrodes, or the number of positive electrodes may be greater than the number of negative electrodes. For example, there may be five negative electrodes and five positive electrodes, six negative electrodes and six positive electrodes, seven negative electrodes and seven positive electrodes, or eight negative electrodes and eight positive electrodes.

Hereinafter, the present invention will be specifically explained with reference to Examples. However, the present invention is not limited to the following examples.

<Experiment example 1>
A lead-acid battery for evaluation of Experimental Example 1 was produced according to the following procedure. The number of negative electrode plates and positive electrode plates is 9 and 8, respectively, and the amount of negative electrode active material paste filling into the negative electrode current collector and the filling amount of positive electrode active material paste into the positive electrode current collector are based on the lead for evaluation. The ratio of the mass of the positive electrode active material to the mass of the negative electrode active material in the storage battery (p/n ratio) was adjusted to be 1.47.

(Preparation of unformed negative electrode plate)
Lead powder was prepared as the Pb component. A mixture of 0.2 parts by mass (resin solids) of Bispers P215 (a condensate of bisphenol, aminobenzenesulfonic acid, and formaldehyde, trade name, manufactured by Nippon Paper Industries Co., Ltd.), 0.1 parts by mass of acrylic fiber, 1.0 parts by mass of barium sulfate, and 0.2 parts by mass of furnace black was added to 100 parts by mass of the Pb component (lead powder), and dry-mixed. Next, water was added to this mixture and kneaded, and then dilute sulfuric acid having a specific gravity of 1.280 was added little by little and further kneaded to prepare a negative electrode active material paste. The negative electrode active material paste was filled into an expandable negative electrode current collector prepared by subjecting a rolled sheet made of a lead alloy to an expand processing. Next, the negative electrode active material paste was aged for 24 hours in an atmosphere at a temperature of 50 ° C. and a humidity of 98%, and then dried at a temperature of 50 ° C. for 16 hours to obtain an unformed negative electrode plate.

(Preparation of unformed positive electrode plate)
As the Pb component, lead powder and red lead (Pb ₃ O ₄ ) were prepared (lead powder: red lead = 96:4 (mass ratio)). The Pb component, 0.07% by mass of reinforcing short fibers (acrylic fiber) based on the total mass of the Pb component, and water were mixed and kneaded. Subsequently, dilute sulfuric acid (specific gravity: 1.280) was added little by little and kneaded to prepare a positive electrode active material paste. This positive electrode active material paste was filled into an expanded positive electrode current collector produced by expanding a rolled sheet made of a lead alloy. Next, the positive electrode active material paste was aged for 24 hours in an atmosphere with a temperature of 50° C. and a humidity of 98%, and then dried at a temperature of 60° C. for 24 hours or more to obtain an unformed positive electrode plate.

(Assembly of lead-acid battery for evaluation)
An unformed negative electrode plate was inserted into a polyethylene separator (thickness: 0.75 mm) processed into a bag shape. Next, eight unformed positive electrode plates and nine unformed negative electrode plates inserted into the bag-shaped separator were alternately stacked. Next, the ears of the electrode plates of the same polarity were welded together using the cast-on-strap (COS) method to prepare an electrode group. Six of these electrode groups were prepared and inserted into a battery case having six cell chambers. Next, the negative electrode strap and the positive electrode strap of the electrode group were connected between the cells, and then the lid was heat-welded to the top of the battery case to assemble a 12V battery (corresponding to the B24 size specified in JIS D 5301). Then, an electrolyte (sodium ion concentration: 0.05 mol/L) prepared by adding an aqueous sodium sulfate solution to dilute sulfuric acid was injected into each cell of the battery, and the battery was placed in a water tank at 40 ° C. and left to stand for 1 hour. Then, formation was performed at a constant current of 17 A for 18 hours to obtain a lead-acid battery for evaluation. The specific gravity of the electrolytic solution (sulfuric acid solution) after the formation was adjusted to 1.28 (20° C.).

(Measurement of p/n ratio)
First, the lead-acid battery for evaluation was disassembled, the negative electrode plate and the positive electrode plate were taken out, washed with water, and then dried at 50° C. for 24 hours. Next, the negative electrode active material and the positive electrode active material were removed from the dried negative electrode plate and the dried positive electrode plate to obtain a negative electrode current collector and a positive electrode current collector. The mass of the negative electrode active material and the mass of the positive electrode active material are determined from the mass difference between the negative electrode plate and the negative electrode current collector after drying, and the mass difference between the positive electrode plate and the positive electrode current collector after drying, and the mass of the negative electrode active material is determined. The ratio of the mass of the positive electrode active material to the mass of the positive electrode active material (p/n ratio) was calculated. Note that the p/n ratio is the ratio of the total mass of all the positive electrode active materials included in the electrode group to the total mass of all the negative electrode active materials included in the electrode group. ) was taken as the average value of the p/n ratios obtained for each.

<Experimental Example 2>
The number of negative plates (and bag-shaped separators), the amount of negative active material paste filled in the negative current collector, and the amount of positive active material paste filled in the positive current collector were changed so that the ratio (p/n ratio) of the mass of the negative active material to the mass of the positive active material in the lead-acid battery for evaluation was the value shown in Table 1, and a nonwoven fabric (manufactured by Nippon Sheet Glass Co., Ltd., product name: FM111, thickness: 0.3 mm, fiber type: glass fiber) was inserted between the negative plate and the bag-shaped separator. The lead-acid battery for evaluation was assembled in the same manner as in Experimental Example 1. Next, the p/n ratio was measured in the same manner as in Experimental Example 1. The results are shown in Table 1. The number of negative and positive plates in Table 1 is the number per electrode group (the same applies below).

<Experimental Example 3>
The number of negative plates (and bag-shaped separators), the amount of negative active material paste filled into the negative current collector, and the amount of positive active material paste filled into the positive current collector were changed so that the ratio of the mass of the positive active material to the mass of the negative active material in the lead-acid battery for evaluation (p/n ratio) was the value shown in Table 1, and a nonwoven fabric (manufactured by Nippon Sheet Glass Co., Ltd., product name: SSG-MSL, thickness: 0.4 mm, fiber type: glass fiber) was inserted between the positive plate and the bag-shaped separator. The lead-acid battery for evaluation was assembled in the same manner as in Experimental Example 1. Next, the p/n ratio was measured in the same manner as in Experimental Example 1. The results are shown in Table 1.

<Experimental Example 4>
A lead-acid battery for evaluation was assembled in the same manner as in Experimental Example 3, except that the amount of the negative electrode active material paste filled in the negative electrode current collector and the amount of the positive electrode active material paste filled in the positive electrode current collector were changed so that the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material (p/n ratio) in the lead-acid battery for evaluation had the value shown in Table 1. Next, the p/n ratio was measured in the same manner as in Experimental Example 1. The results are shown in Table 1.

<Experiment example 5>
The size of the positive electrode plate and negative electrode plate was changed to assemble a 12V battery corresponding to the LN1 size of the EN standard, and the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material in the lead-acid battery for evaluation (p/n The number of negative electrode plates (and bag-shaped separators), the number of positive electrode plates, the amount of negative electrode active material paste filled into the negative electrode current collector, and the amount of positive electrode active material paste were adjusted so that the ratio) was the value shown in Table 1. A lead-acid battery for evaluation was assembled in the same manner as in Experimental Example 3, except that the filling amount to the positive electrode current collector was changed. Then, in the same manner as in Experimental Example 1, the p/n ratio was measured. The results are shown in Table 1.

<Experimental Examples 6 to 7>
A lead-acid battery for evaluation was assembled in the same manner as in Experimental Example 2, except that the amount of the negative electrode active material paste filled in the negative electrode current collector and the amount of the positive electrode active material paste filled in the positive electrode current collector were changed so that the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material (p/n ratio) in the lead-acid battery for evaluation had the value shown in Table 1. Next, the p/n ratio was measured in the same manner as in Experimental Example 1. The results are shown in Table 1.

<Experimental Example 8>
The size of the positive and negative plates was changed to assemble a 12V battery equivalent to the LN1 size of the EN standard, and the number of negative plates (and bag-shaped separators), the number of positive plates, the amount of negative active material paste filled into the negative current collector, and the amount of positive active material paste filled into the positive current collector were changed so that the ratio of the mass of the positive active material to the mass of the negative active material in the lead-acid battery for evaluation (p/n ratio) was the value shown in Table 1. The lead-acid battery for evaluation was assembled in the same manner as in Experimental Example 2. Next, the p/n ratio was measured in the same manner as in Experimental Example 1. The results are shown in Table 1.

<Evaluation>
(Life Test A)
The evaluation lead-acid battery of each experimental example was repeatedly subjected to the following (I) in a temperature environment of 25° C., and the life performance was evaluated by comparing the total discharge amount X until the terminal voltage during discharge reached 7.2 V. The evaluation was a relative evaluation with the total discharge amount X of the evaluation lead-acid battery of Experimental Example 2 taken as 100. The results are shown in Table 2.
(I): After discharging under the following condition (1), charging is performed under the following condition (2).
Condition (1): Discharge current = 25 A, discharge time = 240 seconds Condition (2): Charge voltage = 14.8 V, charge time = 600 seconds

(Life Test B)
For the evaluation lead-acid batteries of each experimental example, the following (II) was repeatedly performed in a temperature environment of 25° C., and the life performance was evaluated by comparing the total discharge amount Y until the terminal voltage during discharge under the following condition (3) reached 7.2 V. The evaluation was a relative evaluation with the total discharge amount Y of the evaluation lead-acid battery of Experimental Example 2 taken as 100. The results are shown in Table 2.
(II): Discharging under the above condition (1) and charging under the above condition (2) are repeated three times in this order, and then discharging under the following condition (3) and charging under the following condition (4) are performed in this order.
Condition (3): Discharge current = 25 A, discharge time = 600 seconds Condition (4): Charge voltage = 14.8 V, charge time = 1500 seconds

(Life test C)
For the evaluation lead-acid batteries of each experimental example (excluding Experimental Examples 14 and 15), the following (III) was repeatedly performed in a temperature environment of 40°C, and the final voltage during continuous discharge at the rated cold cranking current was determined. Life performance was evaluated by comparing the total discharge amount Z until it reached 7.2V. The evaluation was a relative evaluation in which the total discharge amount Z of the evaluation lead acid battery of Experimental Example 2 was set to 100. The results are shown in Table 2.
(III): After repeating discharging under the above condition (1) and charging under the above condition (2) in this order 480 times, and leaving it for 56 hours, Perform continuous discharge for seconds.

(Comparison of total discharge amount)
The ratio (X/Z) of the total discharge amount and the ratio (Y/Z) of the total discharge amount were calculated from the total discharge amount X until the end of the life in the above-mentioned life test A, the total discharge amount Y until the end of the life in the above-mentioned life test B, and the total discharge amount Z until the end of the life in the above-mentioned life test C. The results are shown in Table 2.

DESCRIPTION OF SYMBOLS 1... Lead acid battery, 9... Negative electrode, 10... Positive electrode, 11... Separator, 12... Negative electrode current collector, 13... Negative electrode active material, 14... Positive electrode current collector, 15... Positive electrode active material, 20... Nonwoven fabric.

Claims (4)

a negative electrode including a negative electrode active material;
a positive electrode including a positive electrode active material;
a separator disposed between the negative electrode and the positive electrode;
a nonwoven fabric disposed at least one between the negative electrode and the separator and between the positive electrode and the separator;
A lead-acid battery, wherein the ratio of the mass of the positive electrode active material to the mass of the negative electrode active material is 1.50 or more. The lead acid battery according to claim 1, wherein the nonwoven fabric is disposed between the negative electrode and the separator. The lead-acid battery according to claim 1 or 2, which is used for supplying electric power required during parking of a motor vehicle not equipped with an internal combustion engine. The lead-acid battery according to claim 1 or 2, which is used as the lead-acid battery of an automobile equipped with an internal combustion engine, a storage battery that supplies power to start the internal combustion engine, and a lead-acid battery that supplies power required while the automobile is parked.

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