JP2020057622A - Lead acid battery - Google Patents

Abstract

To provide a lead acid battery capable of obtaining excellent charge acceptance and cycle characteristics.SOLUTION: The lead acid battery includes a positive electrode, a negative electrode, and an electrolytic solution. The electrolytic solution contains aluminum ions and potassium ions. The specific gravity of the electrolytic solution after formation is 1.28 to 1.32.SELECTED DRAWING: None

Description

  The present invention relates to a lead storage battery.

  2. Description of the Related Art In recent years, various measures for improving fuel efficiency of automobiles have been studied to prevent air pollution or global warming. Examples of vehicles that have taken measures to improve fuel efficiency include an idling stop vehicle (hereinafter referred to as an “ISS vehicle”) that reduces the operation time of an engine, and a micro hybrid vehicle (power generation control) that uses the rotation of the engine for power without waste. Cars) are being considered.

  In an ISS vehicle, since the number of engine starts is increased, the large current discharge of the lead storage battery is repeated. In addition, in an ISS vehicle and a micro hybrid vehicle (power generation control vehicle or the like), the amount of power generated by the alternator decreases, and the charging of the lead storage battery is performed intermittently, resulting in insufficient charging.

  The lead storage battery used as described above is used in a partially charged state called a PSOC (Partial State Of Charge). A lead storage battery has a shorter life when used under PSOC than when used in a fully charged state.

  In recent years, in Europe, the chargeability of a lead storage battery during a charge / discharge cycle in accordance with control of a micro-hybrid vehicle has been regarded as important, and DCA (Dynamic Charge Acceptance) evaluation of such a form is being standardized. is there. That is, the use of the lead storage battery as described above has been regarded as important.

  In contrast, Patent Literature 1 below discloses a technique using an electrolytic solution containing a specific concentration of aluminum ions or the like in order to improve the charging efficiency and life characteristics of a battery when used under PSOC. I have.

International Publication No. 2007/036979

  By the way, when a lead-acid battery is used in a state where the battery is not fully charged and the battery is insufficiently charged, the difference in the concentration of dilute sulfuric acid as an electrolyte between the upper and lower electrodes (electrode plates, etc.) in the battery. Stratification occurs. In this case, the concentration of dilute sulfuric acid at the lower part of the electrode increases, and sulfation occurs. Therefore, the reactivity of the lower part of the electrode is reduced, and only the upper part of the electrode reacts intensively. As a result, deterioration such as weakening of the connection between the active materials progresses, and the active material peels off from the grid at the upper part of the electrode, leading to a decrease in battery performance and an early life.

  For this reason, in recent automotive lead-acid batteries, it is extremely important to improve the charge acceptability and cycle characteristics (life characteristics) of batteries when used under PSOC. However, with the technology described in Patent Document 1, it was difficult to obtain sufficient charge acceptability and cycle characteristics.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lead storage battery capable of obtaining excellent charge acceptability and cycle characteristics.

  Means for Solving the Problems As a result of intensive studies, the present inventors have found that in a lead-acid battery, the above-described problem can be solved by the electrolyte containing aluminum ions and potassium ions.

  That is, the present invention provides a lead storage battery including a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte contains aluminum ions and potassium ions.

  The lead storage battery according to the present invention can obtain excellent charge acceptability and cycle characteristics. In particular, the lead storage battery according to the present invention can achieve excellent charge acceptability and cycle characteristics even when used under PSOC.

  The details of the cause of the decrease in charge acceptability (charging performance) of the lead-acid battery when used under the PSOC and the reason why such a decrease in the charging performance can be suppressed in the present invention are not clear. They speculate as follows. That is, when used under the PSOC, the rate of generation of lead sulfate, which is a discharge product, is low, and as a result, lead sulfate particles are aggregated and coarsened, and charging performance is reduced. On the other hand, in the lead storage battery according to the present invention, specific ions (potassium ions and aluminum ions) contained in the electrolytic solution suppress aggregation and coarsening of the lead sulfate particles. The formation of sulfate ions is promoted. Thus, the lead storage battery according to the present invention has excellent charge acceptability and cycle characteristics even when used under the PSOC.

  In the lead storage battery of the present invention, the concentration of the aluminum ion in the electrolytic solution is preferably 0.01 to 0.2 mol / L, and the concentration of the potassium ion is 0.001 to 0.03 mol / L. preferable. In this case, the charge acceptability and cycle characteristics of the lead storage battery can be further improved.

  In the lead storage battery of the present invention, the mass ratio of the cathode material after formation in the positive electrode to the anode material after formation in the negative electrode (mass of the cathode material / mass of the anode material) is 0.9 to 1.4. Is preferred. In this case, the charge acceptability and cycle characteristics of the lead storage battery can be further improved.

  In the lead storage battery of the present invention, the specific gravity of the electrolytic solution after the formation is preferably from 1.26 to 1.32. In this case, the charge acceptability and cycle characteristics of the lead storage battery can be further improved.

  ADVANTAGE OF THE INVENTION According to this invention, the lead storage battery which can obtain the outstanding charge acceptance and cycle characteristics can be provided. In particular, according to the present invention, it is possible to provide a lead-acid battery capable of obtaining excellent charge acceptability and cycle characteristics even when used under PSOC.

  Further, according to the present invention, it is possible to provide an application of a lead storage battery to an automobile in which charging by an alternator is performed in a partial state of charge (PSOC) after charging is performed intermittently. According to the present invention, an application of a lead storage battery to a micro hybrid vehicle can be provided. According to the present invention, it is possible to provide an application of a lead storage battery to an ISS vehicle.

  Hereinafter, embodiments of the present invention will be described in detail. Since the specific gravity changes depending on the temperature, it is defined in this specification as the specific gravity converted at 20 ° C.

<Lead storage battery>
The lead storage battery according to the present embodiment includes, for example, a battery case, an electrode (such as an electrode plate), an electrolytic solution (such as sulfuric acid), and a separator. The electrode and the electrolyte are housed in a battery case. The electrode has a positive electrode (a positive electrode plate or the like) and a negative electrode (a negative electrode plate or the like) facing each other with a separator interposed therebetween. Examples of the lead storage battery according to the present embodiment include a liquid lead storage battery, a control valve lead storage battery, and the like, and a liquid lead storage battery is preferable.

  The positive electrode and the negative electrode constitute an electrode group (electrode plate group or the like) by being laminated via a separator, for example. The positive electrode has a current collector (a positive electrode current collector) and a positive electrode material held by the current collector. The negative electrode has a current collector (negative electrode current collector) and a negative electrode material held by the current collector. In the present embodiment, the positive electrode material and the negative electrode material are, for example, electrode materials after chemical formation (for example, in a fully charged state). When the electrode material is not formed, the electrode material (unformed positive electrode material and unformed negative electrode material) contains the raw material and the like. The current collector forms a conductive path for the current from the electrode material. In the present embodiment, the electrolytic solution contains aluminum ions and potassium ions. As a basic configuration of a lead storage battery, a configuration similar to a conventional lead storage battery can be used.

  The lead storage battery according to the embodiment is useful as a lead storage battery in which charging by an alternator is performed in a partially charged state (PSOC) after charging is performed intermittently. The lead storage battery according to the present embodiment is suitably used in an automobile (ISS vehicle, micro hybrid vehicle, or the like) including the lead storage battery.

(Positive electrode material)
[Positive electrode active material]
The positive electrode material contains a positive electrode active material. The positive electrode active material can be obtained by aging and drying a positive electrode material paste containing a raw material of the positive electrode active material to obtain an unformed active material, followed by chemical formation. The positive electrode active material after the formation preferably contains β-lead dioxide (β-PbO ₂ ), and may further contain α-lead dioxide (α-PbO ₂ ). The raw material of the positive electrode active material is not particularly limited, and examples thereof include lead powder. As the lead powder, for example, lead powder produced by a ball mill type lead powder production machine or a barton pot type lead powder production machine (in a ball mill type lead powder production machine, a mixture of a main component PbO powder and flaky metal lead) ). Lead red (Pb ₃ O ₄ ) may be used as a raw material of the positive electrode active material. It is preferable that the unformed positive electrode material contains, as a main component, an unformed positive electrode active material containing tribasic lead sulfate.

  The average particle size of the positive electrode active material is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more, from the viewpoint of further improving charge acceptability and cycle characteristics. The average particle diameter of the positive electrode active material is preferably 2.5 μm or less, more preferably 2 μm or less, and still more preferably 1.5 μm or less, from the viewpoint of further improving the cycle characteristics. The average particle size of the positive electrode active material is the average particle size of the positive electrode active material in the positive electrode material after chemical formation. The average particle size of the positive electrode active material is, for example, the length of all the positive electrode active material particles in an image of a scanning electron micrograph (× 1000) in a range of 10 μm × 10 μm in the center of the positive electrode material after chemical formation. The value of the side length (maximum particle size) can be obtained as an arithmetically averaged numerical value.

  The content of the positive electrode active material is preferably 95% by mass or more based on the total mass of the positive electrode material, from the viewpoint of further improving the battery characteristics (capacity, low-temperature high-rate discharge performance, charge acceptability, cycle characteristics, and the like). % By mass or more, more preferably 99% by mass or more.

[Positive electrode additive]
The positive electrode material may further contain an additive. Examples of the additive include a carbon material (carbonaceous conductive material), a reinforcing short fiber, and the like. Examples of the carbon material include carbon black and graphite. Examples of the carbon black include furnace black (such as Ketjen black), channel black, acetylene black, and thermal black. Examples of the reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and carbon fibers.

[Physical properties of positive electrode material]
The specific surface area of the cathode material, from the viewpoint of enhancing the reactivity with a liquid electrolyte and the positive electrode active material, preferably at least ^2m 2 / g, more preferably at least ^3m 2 / g, more ^4m 2 / g is more preferable. The specific surface area of the cathode material, from the viewpoint of excellent utilization, is preferably from ^12m 2 / g, more preferably not more than ^{11m 2 / g, 10m 2 /} g or less is more preferable. The specific surface area of the positive electrode material is the specific surface area of the positive electrode material after chemical formation. The specific surface area of the positive electrode material is, for example, a method of adjusting the amount of sulfuric acid and water added when preparing a positive electrode material paste, a method of refining the active material at the stage of an unformed active material, a method of changing the formation conditions, and the like. Can be adjusted.

  The specific surface area of the positive electrode material can be measured, for example, by the BET method. The BET method is a method in which an inert gas (for example, nitrogen gas) having a known size of one molecule is adsorbed on the surface of a measurement sample, and the surface area is obtained from the adsorbed amount and the occupied area of the inert gas. This is a general method for measuring surface area.

(Negative electrode material)
[Negative electrode active material]
The negative electrode material contains a negative electrode active material. The negative electrode active material can be obtained by aging and drying a negative electrode material paste containing a raw material of the negative electrode active material to obtain an unformed active material and then forming the same. Examples of the negative electrode active material after chemical formation include spongy lead. The spongy lead tends to react with sulfuric acid in the electrolytic solution and gradually change to lead sulfate (PbSO ₄ ). Examples of the raw material of the negative electrode active material include lead powder and the like. As the lead powder, for example, lead powder produced by a ball mill type lead powder production machine or a barton pot type lead powder production machine (in a ball mill type lead powder production machine, a mixture of a main component PbO powder and flaky metal lead) ). The unformed negative electrode active material is composed of, for example, basic lead sulfate and metallic lead, and a lower oxide.

  The average particle size of the negative electrode active material is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more, from the viewpoint of further improving the cycle characteristics. The average particle diameter of the negative electrode active material is preferably 2.5 μm or less, more preferably 2 μm or less, and still more preferably 1.5 μm or less, from the viewpoint of further improving the cycle characteristics. The average particle size of the negative electrode active material is the average particle size of the negative electrode active material in the negative electrode material after chemical formation. The average particle diameter of the negative electrode active material is, for example, the length of all negative electrode active material particles in an image of a scanning electron micrograph (× 1000) in a range of 10 μm × 10 μm in the negative electrode material at the center of the negative electrode after formation. The value of the side length (maximum particle size) can be obtained as an arithmetically averaged numerical value.

  The content of the negative electrode active material is preferably 93% by mass or more based on the total mass of the negative electrode material, from the viewpoint of further improving the battery characteristics (capacity, low-temperature high-rate discharge performance, charge acceptability, cycle characteristics, and the like). It is more preferably at least 98% by mass, even more preferably at least 98% by mass.

[Negative electrode additive]
The negative electrode material may further contain an additive. Examples of the additives include barium sulfate; carbon materials (carbonaceous conductive materials); reinforcing short fibers; sulfone groups (sulfonic acid groups and sulfo groups) and sulfonate groups (groups in which the hydrogen of the sulfone group has been replaced by an alkali metal). A) a resin having at least one selected from the group consisting of (a resin having a sulfone group and / or a sulfonate group). When the negative electrode material contains a resin having at least one selected from the group consisting of a sulfone group and a sulfonate group, the low-temperature high-rate discharge performance can be further improved.

  Examples of the carbon material include carbon black and graphite. As the carbon material, carbon black is preferable from the viewpoint of further improving charge acceptability and cycle characteristics. Examples of the carbon black include furnace black (such as Ketjen black), channel black, acetylene black, and thermal black. Among the carbon blacks, furnace black produced by the furnace method is preferred. Examples of the reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and carbon fibers.

  When carbon black is used as the additive, the average particle size of the carbon black is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 25 nm or more from the viewpoint of excellent handleability. The average particle size of the carbon black is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less, from the viewpoint of further improving charge acceptability and cycle characteristics. From these viewpoints, the average particle size of the carbon black is preferably from 10 to 100 nm, more preferably from 20 to 50 nm, still more preferably from 25 to 40 nm. When the average particle size of the carbon black is 100 nm or less, the specific surface area of the carbon black as a whole is large, so that the conductivity between the active materials is improved. Therefore, it is estimated that the charge acceptability and the cycle characteristics are further improved. The average particle size of carbon black is, for example, the length of all particles in an image of a scanning electron micrograph in the range of 100 μm × 100 μm in the center of the substrate after the carbon black particles are deposited on the substrate. The value of the side length (maximum particle size) can be obtained as an arithmetically averaged numerical value. When the average particle size is small (when the average particle size can be expected to be 0.1 μm or less), the long side length of all the particles in the image of the scanning electron microscope photograph in the range of 1 μm × 1 μm is measured. The value can be obtained as an arithmetically averaged numerical value. In addition, as a method for automatically obtaining the average particle diameter, image analysis software for two-dimensional images (manufactured by Sumitomo Metal Technology, particle analysis Ver3.5) can be used.

  When graphite is used as an additive, the average particle size of the graphite is preferably as small as possible. The average particle size of graphite is preferably 1 μm or more from a practical viewpoint. The average particle size of the graphite is preferably 500 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less, from the viewpoint of further improving charge acceptability and cycle characteristics. From these viewpoints, the average particle size of graphite is preferably 1 to 500 μm, more preferably 1 to 100 μm, and still more preferably 1 to 50 μm. The average particle size of graphite can be measured by the same method as the average particle size of carbon black.

  The content of the carbon material is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on the total mass of the raw material of the negative electrode active material, from the viewpoint of further improving charge acceptability and cycle characteristics. , 0.15% by mass or more is more preferable. The content of the carbon material is preferably 0.5% by mass or less, more preferably 0.4% by mass or less, based on the total mass of the raw material of the negative electrode active material, from the viewpoint of further improving charge acceptability and cycle characteristics. , 0.3 mass% or less.

  Examples of the resin having a sulfone group and / or a sulfonate group include bisphenol resins, ligninsulfonic acid, and ligninsulfonic acid salts. Lignin sulfonic acid is a compound in which a part of a decomposition product of lignin is sulfonated. Examples of the lignin sulfonate include potassium lignin sulfonate and sodium lignin sulfonate. Among these, a bisphenol-based resin is preferable from the viewpoint of further improving charge acceptability.

  The bisphenol-based resin is selected from the group consisting of a bisphenol-based compound, an aminoalkylsulfonic acid, an aminoalkylsulfonic acid derivative, an aminoarylsulfonic acid and an aminoarylsulfonic acid derivative, and at least one selected from the group consisting of formaldehyde and a formaldehyde derivative. It is preferable to use a resin obtained by reacting at least one of the resins.

  Bisphenol compounds are compounds having two hydroxyphenyl groups. Examples of bisphenol compounds include 2,2-bis (4-hydroxyphenyl) propane (hereinafter, referred to as “bisphenol A”), bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) butane, bis (4-hydroxy Phenyl) diphenylmethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, bis (4-hydroxyphenyl) sulfone (hereinafter referred to as “ Bisphenol S ").

Examples of the aminoalkylsulfonic acid include aminomethanesulfonic acid, 2-aminoethanesulfonic acid, 3-aminopropanesulfonic acid, and 2-methylaminoethanesulfonic acid. Examples of the aminoalkylsulfonic acid derivative include a compound in which a hydrogen atom of aminoalkylsulfonic acid is substituted with an alkyl group (for example, an alkyl group having 1 to 5 carbon atoms) or the like, and a sulfone group (—SO ₃ H) of aminoalkylsulfonic acid. Examples thereof include an alkali metal salt in which a hydrogen atom is substituted with an alkali metal (for example, sodium or potassium). Examples of the aminoarylsulfonic acid include aminobenzenesulfonic acid (such as 4-aminobenzenesulfonic acid) and aminonaphthalenesulfonic acid. Examples of the aminoarylsulfonic acid derivative include a compound in which a hydrogen atom of aminoarylsulfonic acid is substituted with an alkyl group (for example, an alkyl group having 1 to 5 carbon atoms) or the like, and a sulfonate group of aminoarylsulfonic acid (—SO ₃ H). Examples thereof include an alkali metal salt in which a hydrogen atom is substituted with an alkali metal (for example, sodium or potassium).

  Examples of the formaldehyde derivative include paraformaldehyde, hexamethylenetetramine, trioxane and the like.

  The bisphenol-based resin preferably has at least one selected from the group consisting of a structural unit represented by the following formula (I) and a structural unit represented by the following formula (II).

［式（Ｉ）中、Ｘ^１は、２価の基を示し、Ａ^１は、炭素数１〜４のアルキレン基、又は、アリーレン基を示し、Ｒ^１１は、アルカリ金属又は水素原子を示し、Ｒ^１２は、メチロール基（−ＣＨ_２ＯＨ）を示し、Ｒ^１３及びＲ^１４は、それぞれ独立にアルカリ金属又は水素原子を示し、ｎ１１は、１〜６００の整数を示し、ｎ１２は、１〜３の整数を示し、ｎ１３は、０又は１を示す。］

[In the formula (I), X ¹ represents a divalent group, A ¹ represents an alkylene group having 1 to 4 carbon atoms or an arylene group, R ¹¹ represents an alkali metal or a hydrogen atom, R ¹² represents a methylol group (—CH ₂ OH), R ¹³ and R ¹⁴ each independently represent an alkali metal or a hydrogen atom, n11 represents an integer of 1 to 600, and n12 represents 1 to 3 And n13 represents 0 or 1. ]

［式（ＩＩ）中、Ｘ^２は、２価の基を示し、Ａ^２は、炭素数１〜４のアルキレン基、又は、アリーレン基を示し、Ｒ^２１は、アルカリ金属又は水素原子を示し、Ｒ^２２は、メチロール基（−ＣＨ_２ＯＨ）を示し、Ｒ^２３及びＲ^２４は、それぞれ独立にアルカリ金属又は水素原子を示し、ｎ２１は、１〜６００の整数を示し、ｎ２２は、１〜３の整数を示し、ｎ２３は、０又は１を示す。］

[In formula (II), X ² represents a divalent group, A ² represents an alkylene group having 1 to 4 carbon atoms or an arylene group, R ²¹ represents an alkali metal or a hydrogen atom, R ²² represents a methylol group _(-CH 2 ^{OH), R 23} and ^{R 24} each independently represents an alkali metal or a hydrogen atom, n21 is an integer of 1 to 600, n22 is 1-3 And n23 represents 0 or 1. ]

  The ratio of the structural unit represented by the formula (I) and the structural unit represented by the formula (II) is not particularly limited, and may vary depending on synthesis conditions and the like. As the bisphenol-based resin, a resin having only one of the structural unit represented by the formula (I) and the structural unit represented by the formula (II) may be used.

As X ¹ and X ² , for example, an alkylidene group (methylidene group, ethylidene group, isopropylidene group, sec-butylidene group, etc.), a cycloalkylidene group (cyclohexylidene group, etc.), a phenylalkylidene group (diphenylmethylidene group, An organic group such as a phenylethylidene group); a sulfonyl group; an isopropylidene group (—C (CH ₃ ) ₂ —) group is preferred from the viewpoint of more excellent charging performance, and a sulfonyl group is preferred from the viewpoint of more excellent discharge characteristics. group (-SO ₂ -) preferably. X ¹ and X ² may be substituted by a halogen atom such as a fluorine atom. When X ¹ and X ² are cycloalkylidene groups, the hydrocarbon ring may be substituted by an alkyl group or the like.

Examples of A ¹ and A ² include a C 1-4 alkylene group such as a methylene group, an ethylene group, a propylene group, and a butylene group; and a divalent arylene group such as a phenylene group and a naphthylene group. The arylene group may be substituted with an alkyl group or the like.

Examples of the alkali metal of R ¹¹ , R ¹³ , R ¹⁴ , R ²¹ , R ²³ and R ²⁴ include sodium and potassium. n11 and n21 are preferably from 5 to 300 from the viewpoint of further improving the cycle characteristics and the solubility of the bisphenol resin in the solvent. n12 and n22 are preferably 1 or 2, and more preferably 1, from the viewpoint of improving the charge performance, discharge characteristics and cycle characteristics in a well-balanced manner. n13 and n23 vary depending on the production conditions, but are preferably 0 from the viewpoint of further improving the cycle characteristics and the storage stability of the bisphenol-based resin.

  The weight average molecular weight of a resin having a sulfone group and / or a sulfonate group (such as a bisphenol-based resin) is to prevent the resin having a sulfone group and / or a sulfonate group from being eluted from an electrode to an electrolytic solution in a lead-acid battery. From the viewpoint that the cycle characteristics are more easily improved, 3000 or more is preferable, 10,000 or more is more preferable, 20,000 or more is more preferable, and 30,000 or more is particularly preferable. The weight average molecular weight of the resin having a sulfone group and / or a sulfonate group is 200,000 or less, from the viewpoint that the cycle characteristics are easily improved by suppressing the decrease in the adsorptivity to the electrode active material and the decrease in the dispersibility. , Preferably 150,000 or less, more preferably 100,000 or less.

The weight average molecular weight of the resin having a sulfone group and / or a sulfonate group can be measured, for example, by gel permeation chromatography (hereinafter, referred to as “GPC”) under the following conditions.
(GPC conditions)
Apparatus: High-performance liquid chromatograph LC-2200 Plus (manufactured by JASCO Corporation)
Pump: PU-2080
Differential refractometer: RI-2031
Detector: UV-visible absorption spectrophotometer UV-2075 (λ: 254 nm)
Column oven: CO-2065
Column: TSKgel SuperAW (4000), TSKgel SuperAW (3000), TSKgel SuperAW (2500) (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Eluent: methanol solution containing LiBr (10 mM) and triethylamine (200 mM) Flow rate: 0.6 mL / min Molecular weight standard sample: polyethylene glycol (molecular weight: 1.10 × 10 ⁶ , 5.80 × 10 ⁵ , 2.55 × 10 ⁵ , 1.46 × 10 ⁵ , 1.01 × 10 ⁵ , 4.49 × 10 ⁴ , 2.70 × 10 ⁴ , 2.10 × 10 ⁴ ; manufactured by Tosoh Corporation; diethylene glycol (molecular weight: 1) 0.06 × 10 ² ; manufactured by Kishida Chemical Co., Ltd.), dibutylhydroxytoluene (molecular weight: 2.20 × 10 ² ; manufactured by Kishida Chemical Co., Ltd.)

  When a resin having a sulfone group and / or a sulfonate group is used, the content of the resin having a sulfone group and / or a sulfonate group is determined based on the total mass of the negative electrode material from the viewpoint of more excellent discharge characteristics. It is preferably at least 0.01% by mass, more preferably at least 0.05% by mass, even more preferably at least 0.1% by mass in terms of minutes. The content of the resin having a sulfone group and / or a sulfonate group is preferably 2% by mass or less, and more preferably 1% by mass or less in terms of resin solid content, based on the total mass of the negative electrode material, from the viewpoint of more excellent charge acceptability. Is more preferable, and 0.5 mass% or less is further preferable.

[Physical properties of negative electrode material]
The specific surface area of the negative electrode material is preferably 0.5 m ² / g or more, more preferably 0.55 m ² / g or more, and 0.6 m ² / g or more from the viewpoint of increasing the reactivity between the electrolytic solution and the negative electrode active material. Is more preferred. The specific surface area of the negative electrode material, from the viewpoint of suppressing the shrinkage of the negative electrode is preferably ^2m 2 / g or less, more preferably ^{1.2m 2 / g, 0.8m 2 /} g or less is more preferable. The specific surface area of the negative electrode material is the specific surface area of the negative electrode material after chemical conversion. The specific surface area of the negative electrode material is, for example, a method of adjusting the amounts of sulfuric acid and water added when preparing the negative electrode material paste, a method of refining the active material at the stage of the unformed active material, a method of changing the formation conditions, and the like. Can be adjusted. The specific surface area of the negative electrode material can be measured by, for example, the BET method.

[Mass ratio of positive electrode material after chemical formation to negative electrode material after chemical formation]
The mass ratio of the positive electrode material after formation in the positive electrode to the negative electrode material after formation in the negative electrode (mass of the positive electrode material / mass of the negative electrode material) is preferably 0.9 to 1.4, and is 1.0 to 1.4. -1.3, more preferably 1.05-1.2. By setting the mass ratio between the positive electrode material and the negative electrode material within the above range, the charge acceptability and cycle characteristics of the lead storage battery can be further improved.

(Current collector)
Examples of the method for manufacturing the current collector include a casting method, an expanding method, and a punching method. Examples of the current collector material include a lead-calcium-tin alloy and a lead-antimony alloy. A small amount of selenium, silver, bismuth, or the like can be added to these. For example, a current collector can be obtained by forming these materials into a lattice or a mesh by the above-described manufacturing method. The manufacturing methods and materials of the current collectors of the positive electrode and the negative electrode may be the same or different from each other.

(Electrolyte)
The electrolyte of the lead storage battery according to the present embodiment contains aluminum ions and potassium ions. The concentration of potassium ions in the electrolyte is preferably 0.001 mol / L or more, more preferably 0.003 mol / L or more, based on the total amount of the electrolyte, from the viewpoint of further improving charge acceptability and cycle characteristics. 0.005 mol / L or more is more preferable, and 0.008 mol / L or more is particularly preferable. The concentration of potassium ions in the electrolyte is preferably 0.03 mol / L or less, more preferably 0.02 mol / L or less, based on the total amount of the electrolyte, from the viewpoint of further improving charge acceptability and cycle characteristics. 0.015 mol / L or less is more preferable. The concentration of potassium ions in the electrolytic solution is preferably from 0.001 to 0.03 mol / L, more preferably from 0.003 to 0.03 mol / L, from the viewpoint of further improving charge acceptability and cycle characteristics. -0.02 mol / L is more preferable, and 0.008-0.015 mol / L is particularly preferable.

  The concentration of aluminum ions in the electrolyte is preferably 0.01 mol / L or more, more preferably 0.03 mol / L or more, based on the total amount of the electrolyte, from the viewpoint of further improving charge acceptability and cycle characteristics. 0.05 mol / L or more is more preferable. The concentration of aluminum ions in the electrolyte is preferably 0.2 mol / L or less, more preferably 0.1 mol / L or less, based on the total amount of the electrolyte, from the viewpoint of further improving charge acceptability and cycle characteristics. 0.08 mol / L or less is more preferable. The concentration of aluminum ions in the electrolyte is preferably 0.01 to 0.2 mol / L, more preferably 0.03 to 0.1 mol / L, and more preferably 0.05 to 0.1 mol / L, from the viewpoint of further improving charge acceptability and cycle characteristics. -0.08 mol / L is more preferable.

  The concentrations of aluminum ions and potassium ions can be measured, for example, by ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy).

<Production method of lead storage battery>
The method for manufacturing a lead storage battery according to the present embodiment includes, for example, an electrode manufacturing process for obtaining electrodes (a positive electrode and a negative electrode), and an assembly process for assembling components including the electrodes to obtain a lead storage battery.

  In the electrode manufacturing process, for example, after filling an electrode material paste (a positive electrode material paste and a negative electrode material paste) into a current collector (for example, a cast lattice obtained by a casting method, an expanded lattice obtained by an expanding method, etc.), An unformed electrode is obtained by aging and drying. The positive electrode material paste contains, for example, a raw material (lead powder or the like) of the positive electrode active material, and may further contain other additives. The negative electrode material paste preferably contains a raw material of the negative electrode active material (such as lead powder) and preferably contains a resin having a sulfone group and / or a sulfonate group (such as a bisphenol-based resin) as a dispersant. , And may further contain other additives.

The positive electrode material paste can be obtained, for example, by the following method. First, an additive (a short fiber for reinforcement, etc.) and water are added to the raw material of the positive electrode active material. Next, after adding diluted sulfuric acid, the mixture is kneaded to obtain a positive electrode material paste. When producing the positive electrode material paste, lead tin (Pb ₃ O ₄ ) may be used as a raw material of the positive electrode active material from the viewpoint of shortening the formation time. An unformed positive electrode can be obtained by filling the current collector with this positive electrode material paste and then performing aging and drying.

  When the reinforcing short fibers are used in the positive electrode material paste, the compounding amount of the reinforcing short fibers is preferably 0.005 to 0.3% by mass, based on the total mass of the raw material (lead powder or the like) of the positive electrode active material, 0.05-0.3 mass% is more preferable.

  The aging conditions for obtaining an unformed positive electrode are preferably 15 to 60 hours in an atmosphere at a temperature of 35 to 85 ° C. and a relative humidity of 50 to 98% RH. Drying conditions are preferably at a temperature of 45 to 80 ° C. for 15 to 30 hours.

  The negative electrode material paste can be obtained, for example, by the following method. First, a mixture is obtained by adding an additive (a resin having a sulfone group and / or a sulfonate group, a reinforcing short fiber, barium sulfate, or the like) to the raw material of the negative electrode active material and dry-mixing. Then, sulfuric acid (dilute sulfuric acid or the like) and a solvent (water such as ion-exchanged water, an organic solvent, or the like) are added to the mixture and kneaded to obtain a negative electrode material paste. An unformed negative electrode can be obtained by filling the current collector with the negative electrode material paste and then performing aging and drying.

  In the case where a resin having a sulfone group and / or a sulfonate group (such as a bisphenol-based resin), a carbon material, a reinforcing short fiber or barium sulfate is used in the negative electrode material paste, the compounding amounts of the respective components are preferably in the following ranges. The compounding amount of the resin having a sulfone group and / or a sulfonate group is preferably 0.01 to 2.0% by mass in terms of resin solid content, based on the total mass of the raw materials (lead powder and the like) of the negative electrode active material. , 0.05 to 1.0% by mass, more preferably 0.1 to 0.5% by mass, and particularly preferably 0.1 to 0.3% by mass. The compounding amount of the carbon material is preferably 0.1 to 3% by mass, more preferably 0.2 to 1.4% by mass, based on the total mass of the raw material (lead powder or the like) of the negative electrode active material. The compounding amount of the reinforcing short fibers is preferably 0.05 to 0.3% by mass based on the total mass of the raw material (lead powder or the like) of the negative electrode active material. The compounding amount of barium sulfate is preferably from 0.01 to 2.0% by mass, more preferably from 0.3 to 2.0% by mass, based on the total mass of the raw material (lead powder or the like) of the negative electrode active material.

  As aging conditions for obtaining an unformed negative electrode, it is preferable that the temperature is 45 to 65 ° C. and the relative humidity is 70 to 98% RH for 15 to 30 hours. Drying conditions are preferably at a temperature of 45 to 60 ° C. for 15 to 30 hours.

  In the assembling step, for example, the unformed negative electrode and the unformed positive electrode produced as described above are alternately stacked via a separator, and the current collectors of the electrodes of the same polarity are connected (eg, welded) by a strap. An electrode group is obtained. This electrode group is arranged in a battery case to produce an unformed battery. Next, after injecting the electrolytic solution into the unformed battery, a direct current is applied to form a battery case. By adjusting the specific gravity of the electrolytic solution after formation to an appropriate specific gravity, a lead storage battery can be obtained.

  The electrolytic solution contains, for example, sulfuric acid, potassium ions, and aluminum ions. The electrolytic solution may further contain ions (such as sodium ions, lithium ions, and titanium ions) other than potassium ions and aluminum ions.

  The electrolyte solution according to the present embodiment can be prepared, for example, by dissolving an ion source containing potassium ions and aluminum ions in sulfuric acid so as to have a predetermined ion concentration. The ion source is not particularly limited as long as it is a compound soluble in sulfuric acid, for example. Examples of the ion sources of potassium ions and aluminum ions include salts (eg, crystal salts), hydroxides, oxides, and metals. Examples of the salt include a sulfate, a sulfite, a carbonate, a bicarbonate, a borate, and a metal salt. The ion source may be an anhydride or a hydrate.

  The electrolyte to be injected into the battery case may be an electrolyte containing potassium ions and aluminum ions, or may be an electrolyte containing no potassium ions and aluminum ions. When the electrolytic solution to be injected does not contain potassium ions and aluminum ions, as a method for containing these ions in the electrolytic solution, a method in which the above-described ion source is added to the electrode material to elute the ions into the electrolytic solution, A method of disposing ions in the electrolytic solution by installing the above-mentioned ion source at a place in contact with the electrolytic solution in the battery case, and the like can be mentioned.

  The specific gravity of the electrolytic solution after the formation is preferably in the following range. The specific gravity of the electrolytic solution after chemical formation is preferably 1.26 or more, more preferably 1.27 or more, and even more preferably 1.275 or more, from the viewpoint of more excellent discharge characteristics and liquid reduction characteristics. The specific gravity of the electrolytic solution after chemical formation is preferably 1.32 or less, more preferably 1.31 or less, and still more preferably 1.30 or less, from the viewpoint of further improving charge acceptability and cycle characteristics. The specific gravity value of the electrolytic solution after formation can be measured by, for example, a floating hydrometer or a digital hydrometer manufactured by Kyoto Electronics Industry Co., Ltd. The specific gravity of the electrolytic solution after chemical formation should be adjusted to a desired range by adjusting the composition of the positive electrode material paste and the negative electrode material paste to be used, and adjusting the specific gravity of the electrolytic solution to be injected (the electrolytic solution before chemical formation). Can be.

  The battery case is capable of storing an electrode (electrode plate or the like) therein. From the viewpoint of easy storage of the electrodes, the battery case preferably has a box body having an open top surface and a lid body covering the top surface of the box body. Note that an adhesive, heat welding, laser welding, ultrasonic welding, or the like can be appropriately used for bonding the box body and the lid body. The shape of the battery case is not particularly limited, but a rectangular shape is preferable so that an ineffective space is reduced when the electrode (a plate-like electrode plate or the like) is stored.

  The material of the battery case is not particularly limited, but needs to be resistant to an electrolytic solution (such as dilute sulfuric acid). Specific examples of the material of the battery case include PP (polypropylene), PE (polyethylene), and ABS resin. When the material is PP, it is advantageous in terms of acid resistance, workability (difficult to heat weld the battery case and the lid with ABS resin), and economic efficiency.

  When the battery case is composed of a box and a lid, the material of the box and the lid may be the same material or different materials from each other. Therefore, materials having the same thermal expansion coefficient are preferable.

  Examples of the separator include a microporous polyethylene sheet and a nonwoven fabric made of glass fiber and a synthetic resin.

  The formation conditions and the specific gravity of sulfuric acid can be adjusted according to the properties of the electrode active material. Further, the chemical conversion treatment is not limited to being performed after the assembly process, and may be performed after aging and drying in the electrode manufacturing process (tank chemical formation).

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

<Preparation of bisphenol resin>
After adding 42 parts by mass (1.05 mol) of sodium hydroxide and 792.6 parts by mass (44 mol) of ion-exchanged water to a separable flask equipped with a Dimroth, a mechanical stirrer, and a thermometer, 150 rpm (= min ^-1 ) For 5 minutes to prepare an aqueous sodium hydroxide solution. After 173.2 parts by mass (1.0 mol) of 4-aminobenzenesulfonic acid was added to the aqueous sodium hydroxide solution, the mixture was stirred at 25 ° C. for 30 minutes to obtain a uniform solution A. 90.1 parts by mass of paraformaldehyde (3.0 mol in terms of formaldehyde, manufactured by Mitsui Chemicals, Inc.) was added to solution A, and the mixture was stirred for 5 minutes to dissolve paraformaldehyde to obtain uniform solution B. Next, after adding 219.2 parts by mass (0.96 mol) of bisphenol A and 10.4 parts by mass (0.04 mol) of bisphenol S to solution B, the mixture was stirred for 10 hours while heating using an oil bath set at 90 ° C. Thus, a solution C was obtained.

  Immediately after the addition of bisphenol A and bisphenol S (at the start of the reaction), the pH of the solution was measured under the following measurement conditions. pH was 8.6.

｛PH measurement conditions｝
Testing machine: Twin pH (manufactured by As One Corporation)
Calibration solution: pH 6.86 (25 ° C), pH 4.01 (25 ° C)
Measurement temperature: 25 ° C
Measurement procedure: Two-point calibration was performed using a calibration solution. After cleaning the sensor unit of the test machine, the measurement solution was sucked with a dropper, and 0.1 to 0.3 mL was dropped on the sensor unit. The pH at the time when the display indicating the end of the measurement appeared on the screen was taken as the measured value.

  The solution C prepared above was transferred to a heat-resistant container. The heat-resistant container containing the solution C is put into a vacuum drier set at 60 ° C., and then dried under reduced pressure of 1 kPa or less for 10 hours to obtain a bisphenol-based resin powder (bisphenol / aminobenzenesulfonic acid / formaldehyde condensate). I got As a result of measuring the weight average molecular weight of the obtained bisphenol-based resin powder by GPC under the following conditions, the weight average molecular weight was 53900.

<< GPC measurement conditions >>
Apparatus: High-performance liquid chromatograph LC-2200 Plus (manufactured by JASCO Corporation)
Pump: PU-2080
Differential refractometer: RI-2031
Detector: UV-visible absorption spectrophotometer UV-2075 (λ: 254 nm)
Column oven: CO-2065
Column: TSKgel SuperAW (4000), TSKgel SuperAW (3000), TSKgel SuperAW (2500) (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Eluent: methanol solution containing LiBr (10 mM) and triethylamine (200 mM) Flow rate: 0.6 mL / min Molecular weight standard sample: polyethylene glycol (molecular weight: 1.10 × 10 ⁶ , 5.80 × 10 ⁵ , 2.55 × 10 ⁵ , 1.46 × 10 ⁵ , 1.01 × 10 ⁵ , 4.49 × 10 ⁴ , 2.70 × 10 ⁴ , 2.10 × 10 ⁴ ; manufactured by Tosoh Corporation; diethylene glycol (molecular weight: 1) 0.06 × 10 ² ; manufactured by Kishida Chemical Co., Ltd.), dibutylhydroxytoluene (molecular weight: 2.20 × 10 ² ; manufactured by Kishida Chemical Co., Ltd.)

<Production of lead storage battery>
(Example 1)
[Preparation of positive electrode plate]
Lead powder and lead red (Pb ₃ O ₄ ) were used as raw materials of the positive electrode active material (lead powder: lead red = 96: 4 (mass ratio)). A raw material for the positive electrode active material, 0.07 parts by mass of reinforcing short fibers (acrylic fiber) based on 100 parts by mass of the total mass of the raw material for the positive electrode active material, and water were mixed and kneaded. Subsequently, the mixture was kneaded while adding dilute sulfuric acid (specific gravity 1.280) little by little to prepare a positive electrode material paste. The positive electrode material paste was filled in an expanded lattice body (positive electrode current collector) produced by subjecting a rolled sheet made of a lead alloy to an expanding process. Next, the positive electrode material paste was aged for 24 hours in an atmosphere at a temperature of 50 ° C. and a humidity of 98%. Thereafter, it was dried to produce an unformed positive electrode plate.

[Preparation of negative electrode plate]
Lead powder was used as a raw material of the negative electrode active material. With respect to 100 parts by mass of lead powder, 0.2 parts by mass of the bisphenol-based resin obtained above (in terms of solid content), 0.1 part by mass of short fibers for reinforcement (acrylic fiber), 1.0 part by mass of barium sulfate, Then, a mixture consisting of 0.2 parts by mass of furnace black was added and dry-mixed. Next, water was added and kneaded. Subsequently, the mixture was kneaded while adding dilute sulfuric acid (specific gravity 1.260) little by little to prepare a negative electrode material paste. The negative electrode material paste was filled in an expanded grid (negative electrode current collector) produced by subjecting a rolled sheet made of a lead alloy to an expanding process. Next, the negative electrode material paste was aged for 24 hours in an atmosphere at a temperature of 50 ° C. and a humidity of 98%. After that, it was dried to produce an unformed negative electrode plate.

[Preparation of electrolyte solution]
An aqueous solution of aluminum sulfate and an aqueous solution of potassium sulfate were added to dilute sulfuric acid to prepare an electrolytic solution such that the aluminum ion concentration and the potassium ion concentration in the electrolytic solution were as shown in Table 1.

[Assembly of battery]
First, an unformed negative electrode plate was accommodated in a polyethylene-made separator processed into a bag shape (bag-shaped separator). Subsequently, after alternately laminating six non-chemically formed positive electrode plates and seven non-chemically formed negative electrode plates accommodated in the bag-shaped separator, the lugs of the same polarity electrode plates are cast-on-strap (COS). ) Welded by the method to produce an electrode plate group. The above electrode group was inserted into a battery case to assemble a 2 V single cell battery (corresponding to a B19 size single cell specified in JIS 50301). After injecting the electrolyte solution prepared above (adjusted so that the specific gravity after formation becomes 1.28) into this battery, it was formed in a 40 ° C. water tank at a current of 17.5 A for 16 hours to obtain a lead storage battery. Was. The specific gravity of the electrolytic solution after the formation was adjusted to 1.28.

[Measurement of specific surface area]
The measurement sample of the specific surface area was prepared by the following procedure. First, the formed battery was disassembled, the electrode plates (the positive electrode plate and the negative electrode plate) were taken out, washed with water, and dried at 50 ° C. for 24 hours. Next, 2 g of an electrode material (a positive electrode material and a negative electrode material) was sampled from the center of the electrode plate and dried at 130 ° C. for 30 minutes to prepare a measurement sample.

The specific surface areas of the positive electrode material and the negative electrode material after chemical formation were calculated according to the BET method by measuring the nitrogen gas adsorption amount at the liquid nitrogen temperature by a multipoint method while cooling the measurement sample prepared above with liquid nitrogen. The measurement conditions were as follows. As a result of the measurement, the specific surface area of the positive electrode material was 6 m ² / g, and the specific surface area of the negative electrode material was 0.7 m ² / g. The specific surface areas were the same in Examples 2 to 5 and Comparative Examples 1 to 4 below.
測定 Measurement conditions of specific surface area｝
Apparatus: Macsorb1201 (Mountech)
Deaeration time: 10 minutes at 130 ° C Cooling: 5 minutes with liquid nitrogen Adsorption gas flow rate: 25 mL / min

[Mass ratio of positive electrode material to negative electrode material]
The lead storage battery after the formation was disassembled, the positive electrode plate, the negative electrode plate accommodated in the separator were taken out of the battery, and the negative electrode plate was taken out of the separator. After the positive electrode plate and the negative electrode plate were washed with water for 1 hour, they were left to dry at 50 ° C. for about 1 day. Thereafter, the positive electrode material (positive conversion active material) and the negative electrode material (positive conversion active material) after formation of the dried positive electrode plate and negative electrode plate were removed from the positive electrode current collector and the negative electrode current collector, respectively. . The amount of change in the mass of the positive electrode plate and the mass of the negative electrode plate before and after the removal of the chemically activated material was determined as the mass of the chemically converted active material of the positive electrode and the mass of the chemically converted active material of the negative electrode, respectively. From the results, the mass ratio of the positive electrode active material to the negative electrode active material (positive electrode material / negative electrode material) was calculated.

(Example 2)
A lead-acid battery was produced in the same manner as in Example 1 except that the aluminum ion concentration and the potassium ion concentration in the electrolytic solution were adjusted to the concentrations shown in Table 1.

(Examples 3 to 5)
A lead-acid battery was produced in the same manner as in Example 1 except that the specific gravity of the injected electrolyte was adjusted so that the specific gravity of the electrolytic solution after the formation became the numerical value shown in Table 1.

(Comparative Example 1)
A lead-acid battery was produced in the same manner as in Example 1, except that dilute sulfuric acid was used as an electrolyte as it was (an aqueous solution of aluminum sulfate and an aqueous solution of potassium sulfate were not added).

(Comparative Example 2)
A lead-acid battery was produced in the same manner as in Example 1, except that an aqueous solution of aluminum sulfate was added to dilute sulfuric acid so that the aluminum ion concentration in the electrolytic solution became the concentration shown in Table 1.

(Comparative Example 3)
A lead-acid battery was produced in the same manner as in Example 1, except that an aqueous solution of potassium sulfate was added to dilute sulfuric acid so that the potassium ion concentration in the electrolytic solution became the concentration shown in Table 1.

(Comparative Example 4)
A lead was prepared in the same manner as in Example 1, except that an aqueous solution of aluminum sulfate and an aqueous solution of sodium sulfate were added to dilute sulfuric acid so that the aluminum ion concentration and the sodium ion concentration in the electrolytic solution became the concentrations shown in Table 1. A storage battery was manufactured.

<Evaluation of battery characteristics>
(Charge acceptance)
The formed lead-acid battery was allowed to stand for about 12 hours after formation, was subjected to a constant current discharge at 25 ° C. at a current value of 5.6 A for 30 minutes, and was further allowed to stand for 6 hours, followed by a current limit of 2.33 V and 100 A. , A constant voltage charge was performed for 60 seconds, and a current value was measured from the start of the charge to the fifth second. The relative ratio was evaluated using the measurement result of Comparative Example 1 as 100 as a reference. Table 1 shows the results.

(Low temperature high rate discharge performance)
The battery temperature of the prepared lead storage battery was adjusted to −15 ° C., the battery was discharged at a constant current of 150 A, and the discharge duration until the cell voltage became lower than 1.0 V was measured. The relative ratio was evaluated using the measurement result of Comparative Example 1 as 100 as a reference. Table 1 shows the results.

(Cycle characteristics)
The cycle characteristics (ISS life characteristics) were measured as follows. With respect to the prepared lead storage battery, the ambient temperature was adjusted so that the battery temperature became 25 ° C., a constant current discharge of 300 A for 1 second was performed for 45 A for 59 seconds, and then a limit current of 100 A for 2.3 A for 60 seconds was obtained. A test was performed in which the cycle of performing the constant current / constant voltage charging was one cycle. This test is a cycle test that simulates how lead storage batteries are used in ISS vehicles. In this cycle test, since the charge amount is small with respect to the discharge amount, if the charge is not completely performed, the charge gradually becomes insufficient. As a result, the first-second voltage when the discharge current is 300 A and the discharge is performed for 1 second is Decreases gradually. That is, when the negative electrode is polarized at the time of constant current / constant voltage charging and switched to constant voltage charging early, the charging current is attenuated, resulting in insufficient charging. In this cycle test, the total number of cycles when the first-second voltage at a discharge of 300 A was lower than 1.2 V was evaluated as the ISS life. The relative ratio was evaluated using the measurement result of Comparative Example 1 as 100 as a reference. Table 1 shows the results.

(Liquid reduction characteristics)
After leaving the produced lead storage battery in a water bath at 40 ° C. for 12 hours, it was subjected to constant voltage charging at 2.4 V for 672 hours, and the amount of liquid reduction was measured from the difference in mass before and after charging. It is preferable that the amount of liquid reduction is small, and the numerical value when the relative ratio is evaluated with the measurement result of Comparative Example 1 as 100 as a reference is "A" when less than 100, "B" when 100 or more and less than 105, The case of 105 or more and less than 110 was evaluated as "C", and the case of 110 or more was evaluated as "D". Table 1 shows the results.

Claims (3)

Comprising a positive electrode, a negative electrode and an electrolytic solution,
The electrolyte contains aluminum ions and potassium ions,
A lead-acid battery, wherein the specific gravity of the electrolytic solution after formation is 1.28 to 1.32.   The lead-acid battery according to claim 1, wherein the concentration of the aluminum ions in the electrolyte is 0.01 to 0.2 mol / L. 3. The lead-acid battery according to claim 1, wherein the concentration of the potassium ion in the electrolyte is 0.001 to 0.03 mol / L. 4.