JP2017084487A - Lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead-acid battery capable of achieving both excellent cycle characteristics and low-temperature high-rate discharge characteristics.SOLUTION: A lead-acid battery includes a positive electrode and a negative electrode. The negative electrode includes a negative electrode collector and a negative electrode material held by the negative electrode collector. The density of the negative electrode material at the inside of the negative electrode is higher than the density of the negative electrode material at the surface of the negative electrode.SELECTED DRAWING: None

Description

  The present invention relates to a lead-acid battery.

  In recent years, various measures for improving fuel efficiency have been studied for automobiles in order to prevent air pollution or global warming. Examples of automobiles with measures to improve fuel efficiency include micro-hybrids such as idling stop system cars (hereinafter referred to as “ISS cars”) that reduce engine operating time and power generation control cars that reduce alternator power generation by engine power. Cars are being considered.

  In an ISS vehicle, the number of engine starts increases, so the number of repeated charge / discharge cycles of the lead storage battery increases. Therefore, the cycle life characteristics (hereinafter referred to as “cycle characteristics”) are regarded as important.

  It is known that the cycle characteristics of a lead-acid battery depend on the configuration and structure of the positive electrode plate and the negative electrode plate that are electrodes.

  For example, Patent Document 1 relates to a lead-acid battery that has excellent cycle characteristics by containing spongy lead that has a low utilization factor and only the surface portion is involved in the charge / discharge reaction and has small expansion and contraction. Technology is disclosed.

JP2011-187387A

  By the way, in the lead storage battery for ISS cars, since the engine starts many times, the large current discharge of the lead storage battery is repeated.

  In particular, high-rate discharge characteristics of lead-acid batteries are required under low-temperature conditions where it is difficult to start the engine.

  Therefore, in addition to excellent cycle characteristics, the lead-acid battery for ISS cars is required to have excellent low-temperature high-rate discharge characteristics. However, in the technique described in Patent Document 1, it is expected that the low-temperature high-rate discharge characteristics are not sufficient when applied to a lead storage battery for an ISS vehicle.

  This invention is made | formed in view of the said situation, and it aims at providing the lead storage battery which can make the outstanding cycling characteristics and low-temperature high-rate discharge characteristics compatible.

  The present inventors have found that the above problem can be solved by using a lead storage battery in which the negative electrode material density in the negative electrode is larger than the negative electrode material density in the surface portion of the negative electrode.

  That is, the lead storage battery according to the present invention includes a positive electrode and a negative electrode, and the negative electrode includes a negative electrode current collector and a negative electrode material held by the negative electrode current collector, and an internal negative electrode material in the negative electrode It is a lead acid battery whose density is larger than the negative electrode material density of the surface part in the said negative electrode.

  By making the inside of the negative electrode material have a higher density structure, it is considered that the shrinkage when the active materials aggregate inside the negative electrode material can be suppressed, and the cycle characteristics can be improved.

  On the other hand, by making the surface portion of the negative electrode material a structure having a lower density with respect to the inside of the negative electrode material, by increasing the specific surface area in the surface portion of the negative electrode material and increasing the utilization rate, It is considered that the low temperature high rate discharge characteristics can be improved.

  Therefore, according to the present invention, by using a lead storage battery in which the negative electrode material density in the negative electrode is larger than the negative electrode material density in the surface portion of the negative electrode, not only the cycle characteristics are improved, but also the low temperature high rate discharge characteristics. Can be improved at the same time.

In the lead storage battery according to the present invention, the density of the surface portion of the negative electrode material is preferably less than 4.0 g / cm ³ . Thereby, since the specific surface area in the surface part of the said negative electrode material can be enlarged and a utilization factor can be made high, the more excellent low temperature discharge characteristic can be obtained.

In the lead storage battery according to the present invention, the density inside the negative electrode material is preferably 4.0 g / cm ³ or more. Thereby, since shrinkage | contraction at the time of active material having aggregated inside a negative electrode material can be suppressed, the more excellent cycling characteristics can be acquired.

  According to the present invention, both excellent cycle characteristics and low temperature high rate discharge characteristics can be achieved. Such a lead storage battery is particularly excellent as an application for an ISS vehicle, a micro hybrid vehicle, or the like.

  According to the present invention, it is possible to achieve both excellent cycle characteristics and low temperature high rate discharge characteristics. The lead acid battery according to the present invention can be suitably used in an ISS vehicle, a micro hybrid vehicle, and the like that are required to have excellent low temperature and high rate discharge characteristics in addition to excellent cycle characteristics.

It is drawing which shows the separator which consists of a microporous sheet. It is sectional drawing of the separator which consists of a microporous sheet, and an electrode plate. It is a figure which shows the electrode accommodated in a bag separator and a bag separator. It is sectional drawing of an electrode group.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, since specific gravity changes with temperature, in this specification, it defines as specific gravity converted at 20 degreeC.

<Lead battery>
The lead storage battery according to the present embodiment includes, for example, an electrode (electrode plate or the like), an electrolytic solution (sulfuric acid or the like), and a separator. The electrode has a positive electrode (positive electrode plate or the like) and a negative electrode (negative electrode plate or the like). Examples of the lead storage battery according to this embodiment include a liquid lead storage battery, a control valve type lead storage battery, a sealed lead storage battery, and the like, and a liquid lead storage battery is preferable. The positive electrode has a current collector (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 conversion (for example, in a fully charged state). When the electrode material is unformed, the electrode material (unformed positive electrode material and unformed negative electrode material) contains a raw material of an electrode active material (positive electrode active material and negative electrode active material) and the like. The current collector constitutes a conductive path for current from the electrode material. A configuration similar to that of a conventional lead-acid battery can be used.

  In this embodiment, the negative electrode material contains a negative electrode active material, and may further contain an additive as necessary. The lead acid battery according to this embodiment is a lead acid battery in which at least the negative electrode material density inside the negative electrode is larger than the negative electrode material density of the surface portion of the negative electrode. The negative electrode material density is a negative electrode material density in the negative electrode plate after chemical conversion.

(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 chemical conversion after obtaining an unformed active material by aging and drying a positive electrode material paste containing a raw material of the positive electrode active material. The positive electrode active material after chemical conversion preferably contains β-lead dioxide (β-PbO ₂ ), and may further contain α-lead dioxide (α-PbO ₂ ). There is no restriction | limiting in particular as a raw material of a positive electrode active material, For example, lead powder is mentioned. As the lead powder, for example, lead powder manufactured by a ball mill type lead powder manufacturing machine or a barton pot type lead powder manufacturing machine (in the ball mill type lead powder manufacturing machine, a mixture of powder of main component PbO and scale-like metal lead) ). Red lead (Pb ₃ O ₄ ) may be used as a raw material for the positive electrode active material. The unformed positive electrode material preferably contains an unformed positive electrode active material containing tribasic lead sulfate as a main component.

  The average particle diameter 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 acceptance 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 even more preferably 1.5 μm or less from the viewpoint of further improving the cycle characteristics. The average particle diameter of the positive electrode active material is an average particle diameter of the positive electrode active material in the positive electrode material after chemical conversion. The average particle diameter of the positive electrode active material is, for example, the long side of all active material particles in the image of a scanning electron micrograph (1000 times) in the range of 10 μm in length × 10 μm in the positive electrode material at the center of the positive electrode after chemical conversion It can be obtained as a numerical value obtained by arithmetically averaging the length (maximum particle size) 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 excellent battery characteristics (capacity, low-temperature high-rate discharge performance, charge acceptance, cycle characteristics, etc.), 97 The mass% or more is more preferable, and 99 mass% or more is still more preferable.

[Positive electrode additive]
The positive electrode material may further contain an additive. Examples of the additive include carbon materials (carbonaceous conductive materials), reinforcing short fibers, and the like. Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black (Ketjen black, etc.), channel black, acetylene black, thermal black, and the like. 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 lower limit of the specific surface area of the positive electrode material is preferably 3 m ² / g or more, more preferably 4 m ² / g or more, and still more preferably 5 m ² / g or more, from the viewpoint of further excellent charge acceptance performance. The upper limit of the specific surface area of the cathode material is not particularly limited, from the viewpoint of excellent practical point of view and utilization, preferably 15 m ² / g or less, 12m ² / g and more preferably less, 7m ² / g or less Further preferred. The specific surface area of the positive electrode material is the specific surface area of the positive electrode material after chemical conversion. 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 the positive electrode material paste, a method of refining the active material at the stage of the unformed active material, a method of changing the conversion conditions, etc. Can be adjusted.

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

  The porosity of the positive electrode material is preferably 40% or more, more preferably 45% or more, from the viewpoint that the area where sulfuric acid enters the pores in the positive electrode material increases and the capacity tends to increase. Although there is no restriction | limiting in particular in the upper limit of the porosity of a positive electrode material, 70% or less is preferable from a viewpoint that the amount of sulfuric acid impregnation to the void | hole part in a positive electrode material is moderate, and can maintain the bonding force of active materials favorably. The upper limit of the porosity is more preferably 60% or less from a practical viewpoint. The porosity of the positive electrode material is the porosity of the positive electrode material after chemical conversion. The porosity of the positive electrode material is, for example, a value (ratio based on volume) obtained from mercury porosimeter measurement. The porosity of the positive electrode material can be adjusted, for example, by preparing an unmodified positive electrode plate by appropriately changing the amount of dilute sulfuric acid added when preparing the positive electrode material paste.

(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 chemical conversion after obtaining an unformed active material by aging and drying a negative electrode material paste containing a raw material of the negative electrode active material. Examples of the negative electrode active material after chemical conversion include spongy lead. The spongy lead tends to react with sulfuric acid in the electrolyte and gradually change to lead sulfate (PbSO ₄ ). Examples of the raw material for the negative electrode active material include lead powder. As the lead powder, for example, lead powder manufactured by a ball mill type lead powder manufacturing machine or a Burton pot type lead powder manufacturing machine (in the ball mill type lead powder manufacturing machine, a mixture of powder of the main component PbO and scale-like metal lead) Is mentioned. The unformed negative electrode material is composed of, for example, basic lead sulfate, metallic lead, and a lower oxide.

  The average particle diameter 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 charge acceptance performance and 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 even more preferably 1.5 μm or less from the viewpoint of further improving cycle characteristics. The average particle diameter of the negative electrode active material is an average particle diameter of the negative electrode active material in the negative electrode material after chemical conversion. The average particle diameter of the negative electrode active material is, for example, the long side length of all particles in an image of a scanning electron micrograph (1000 times) in the range of 10 μm in length × 10 μm in the center of the negative electrode material after chemical conversion ( The value of (maximum particle size) can be obtained as a numerical value obtained by arithmetic averaging.

  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 excellent battery characteristics (capacity, low-temperature high-rate discharge performance, charge acceptance, cycle characteristics, etc.), 95 More preferably, it is more preferably 98% by mass or more.

[Negative electrode additive]
The negative electrode material may further contain an additive. As the negative electrode additive, a resin having at least one selected from the group consisting of a sulfone group (sulfonic acid group, sulfo group) and a sulfonic acid group (a group in which hydrogen of the sulfone group is substituted with an alkali metal) (sulfone group and And / or a resin having a sulfonate group), barium sulfate, a carbon material (carbonaceous conductive material), a reinforcing short fiber, and the like. From the viewpoint of further improving the charge / discharge performance, the negative electrode material preferably contains a resin having at least one selected from the group consisting of a sulfone group and a sulfonate group.

[Resin having sulfone group and / or sulfonate group]
Examples of the resin having a sulfone group and / or a sulfonate group include bisphenol resins, lignin sulfonic acid, and lignin sulfonate. Among these, from the viewpoint of further improving the charge acceptability, bisphenol-based resins are preferable. From the group consisting of bisphenol-based compounds and aminoalkyl sulfonic acids, aminoalkyl sulfonic acid derivatives, aminoaryl sulfonic acids and aminoaryl sulfonic acid derivatives. A bisphenol-based resin that is a condensate of at least one selected with at least one selected from the group consisting of formaldehyde and a formaldehyde derivative is more preferable.

  For example, the bisphenol-based resin preferably has at least one of a structural unit represented by the following general formula (II) and a structural unit represented by the following general formula (III).

［式（ＩＩ）中、Ｘ²は、２価の基を示し、Ａ²は、炭素数１〜４のアルキレン基、又は、アリーレン基を示し、Ｒ²¹、Ｒ²³及びＲ²⁴は、それぞれ独立にアルカリ金属又は水素原子を示し、Ｒ²²は、メチロール基（−ＣＨ₂ＯＨ）を示し、ｎ２１は、１〜１５
０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。また、ベンゼン環を構成する炭素原子に直接結合している水素原子は、炭素数１〜５のアルキル基で置換されていてもよい。］

[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, and R ²¹ , R ²³ and R ²⁴ are each independently selected. Represents an alkali metal or a hydrogen atom, R ²² represents a methylol group (—CH ₂ OH), and n21 represents 1 to 15
An integer of 0 is shown, n22 is an integer of 1 to 3, and n23 is 0 or 1. Moreover, the hydrogen atom directly bonded to the carbon atom constituting the benzene ring may be substituted with an alkyl group having 1 to 5 carbon atoms. ]

［式（ＩＩＩ）中、Ｘ³は、２価の基を示し、Ａ³は、炭素数１〜４のアルキレン基、又は、アリーレン基を示し、Ｒ³¹、Ｒ³³及びＲ³⁴は、それぞれ独立にアルカリ金属又は水素原子を示し、Ｒ³²は、メチロール基（−ＣＨ₂ＯＨ）を示し、ｎ３１は、１〜１
５０の整数を示し、ｎ３２は、１〜３の整数を示し、ｎ３３は、０又は１を示す。また、ベンゼン環を構成する炭素原子に直接結合している水素原子は、炭素数１〜５のアルキル基で置換されていてもよい。］

[In Formula (III), X ³ represents a divalent group, A ³ represents an alkylene group having 1 to 4 carbon atoms, or an arylene group, and R ³¹ , R ^33, and R ³⁴ are each independently selected. Represents an alkali metal or a hydrogen atom, R ³² represents a methylol group (—CH ₂ OH), and n31 represents 1-1.
50 represents an integer, n32 represents an integer of 1 to 3, and n33 represents 0 or 1. Moreover, the hydrogen atom directly bonded to the carbon atom constituting the benzene ring may be substituted with an alkyl group having 1 to 5 carbon atoms. ]

  The ratio of the structural unit represented by the formula (II) and the structural unit represented by the formula (III) 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 (II) and the structural unit represented by the formula (III) may be used.

Examples of X ² and X ³ include alkylidene groups (methylidene group, ethylidene group, isopropylidene group, sec-butylidene group, etc.), cycloalkylidene groups (cyclohexylidene group, etc.), phenylalkylidene groups (diphenylmethylidene group). , A sulfonyl group, and the isopropylidene group (—C (CH ₃ ) ₂ —) group is preferable from the viewpoint of further excellent charge acceptance, and from the viewpoint of further excellent discharge characteristics. Is preferably a sulfonyl group (—SO ₂ —). X ² and X ³ may be substituted with a halogen atom such as a fluorine atom. When X ² and X ³ are cycloalkylidene groups, the hydrocarbon ring may be substituted with an alkyl group or the like.

Examples of A ² and A ³ include alkylene groups having 1 to 4 carbon atoms such as a methylene group, an ethylene group, a propylene group, and a butylene group; and divalent arylene groups 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 for R ²¹ , R ²³ , R ²⁴ , R ³¹ , R ³³ and R ³⁴ include sodium and potassium. n21 and n31 are preferably 1 to 150, and more preferably 10 to 150, from the viewpoint of further excellent cycle characteristics and solubility in a solvent. n22 and n32 are preferably 1 or 2, and more preferably 1, from the viewpoint that the cycle characteristics, the discharge characteristics, and the charge acceptability are easily improved in a balanced manner. Although n23 and n33 change with manufacturing conditions, 0 is preferable from a viewpoint which is further excellent in cycling characteristics and the storage stability of bisphenol-type resin.

  The weight average molecular weight of a resin having a sulfonic group and / or a sulfonic acid group (such as a bisphenol-based resin) suppresses the elution of a resin having a sulfonic group and / or a sulfonic acid group from an electrode to an electrolytic solution in a lead storage battery. Is preferably 3000 or more, more preferably 10,000 or more, still more preferably 20000 or more, and particularly preferably 30000 or more. The weight average molecular weight of the resin having a sulfone group and / or a sulfonate group is 200000 or less from the viewpoint that the cycle characteristics are easily improved by suppressing the adsorptivity to the electrode active material and the dispersibility. Is preferable, 150,000 or less is more preferable, and 100,000 or less is still more preferable.

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 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 mmol / L) and triethylamine (200 mmol / L) 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: 1.06 × 10 ² ; manufactured by Kishida Chemical Co., Ltd.), dibutylhydroxytoluene (molecular weight: 2.20 × 10 ² ; manufactured by Kishida Chemical Co., Ltd.)

  Lead-acid batteries mounted on ISS cars, micro hybrid cars, etc. are used in a partially charged state called PSOC. In a lead-acid battery used under such circumstances, a phenomenon called sulfation, in which lead sulfate, which is an insulator generated in the negative electrode active material during discharge, becomes coarse with repeated charging and discharging, is an early phenomenon. To occur. When sulfation occurs, the charge acceptability and discharge performance of the negative electrode active material are significantly reduced. By adding a carbonaceous conductive material to the negative electrode active material, it suppresses the coarsening of lead sulfate, maintains the lead sulfate in a fine state, and suppresses the decrease in the concentration of lead ions that dissolve from the lead sulfate. The effect of maintaining a state with high charge acceptance performance is obtained.

[Carbon material (carbonaceous conductive material)]
Examples of the carbonaceous conductive material include graphite, carbon black, activated carbon, carbon fiber, and carbon nanotube. The addition amount of the carbonaceous conductive material is preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the fully charged negative electrode active material (spongy metal lead). From the viewpoint of improving charge acceptability, graphite is preferable, and from the viewpoint of improving charge acceptability, scaly graphite is more preferable. The average primary particle diameter of the flaky graphite is preferably 100 μm to 500 μm, more preferably 100 μm to 350 μm, and still more preferably 100 μm to 220 μm from the viewpoint of improving charge acceptance.

  The scaly graphite here refers to that described in JIS M 8601 (2005). The electrical resistivity of the scaly graphite is 0.02 Ω · cm or less, which is an order of magnitude less than about 0.1 Ω · cm of carbon blacks such as acetylene black. Therefore, by using scaly graphite instead of carbon blacks used in conventional lead-acid batteries, the electrical resistance of the negative electrode active material can be lowered and the charge acceptance performance can be improved.

  Here, the average primary particle diameter of scaly graphite is determined in accordance with the laser diffraction / scattering method described in JISM8511 (2005). Using a laser diffraction / scattering type particle size distribution measuring device (Nikkiso Co., Ltd .: Microtrac 9220FRA), a commercially available surfactant polyoxyethylene octylphenyl ether (for example, Roche Diagnostics Co., Ltd .: Triton) as a dispersant. An appropriate amount of a scaly graphite sample is put into an aqueous solution containing 0.5 vol% of X-100), 40 W ultrasonic waves are irradiated for 180 seconds while stirring, and then measurement is performed. The obtained average particle diameter (median diameter: D50) is defined as the average primary particle diameter.

[Reinforcing short fibers]
Examples of the reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and carbon fibers.

[Negative electrode density]
According to the present invention, it is possible to achieve both excellent cycle characteristics and low-temperature high-rate discharge characteristics by making the internal negative electrode material density in the negative electrode larger than the negative electrode material density in the surface portion of the negative electrode. The possible reasons for this are described below. It is thought that it is a part of the negative electrode surface layer that affects the low-temperature high-rate discharge characteristics. Therefore, when the negative electrode surface portion has a lower density than the inside, it is presumed that the negative electrode surface is likely to react, and an effect is likely to appear in improving the low-temperature high-rate discharge characteristics. In addition, it is considered that by increasing the density of the negative electrode, aggregation of the negative electrode active material associated with the charge / discharge reaction is easily suppressed, and the cycle performance is excellent. Therefore, if the negative electrode material density inside the negative electrode is larger than the negative electrode material density of the surface part of the negative electrode, the surface part contributes to the improvement of low-temperature high-rate discharge characteristics, and the inside contributes to the improvement of cycle characteristics. It is presumed that both cycle characteristics and low-temperature high-rate discharge characteristics can be achieved.

The density range of the negative electrode material will be described. From the viewpoint of excellent low-temperature high-rate discharge characteristics, the negative electrode material density on the negative electrode surface portion is preferably less than 4.0 g / cm ³ . Further, from the viewpoint of filling property of the negative electrode material paste into the current collector, the negative electrode material density of the negative electrode surface portion is preferably 2.0 g / cm ³ or more, more preferably 2.5 g / cm ³ or more, and 3.0 g. / Cm ³ or more is more preferable.

Further, from the viewpoint of excellent cycle characteristics, the negative electrode material density inside the negative electrode is preferably 4.0 g / cm ³ or more. Furthermore, from the viewpoint of filling of the negative electrode material paste into the current collector, the negative electrode material density inside the negative electrode is preferably 5.0 g / cm ³ or less, more preferably 4.8 g / cm ³ or less, and 4.6 g / cm 2. More preferred is cm ³ or less.

  The density of the negative electrode material is determined by, for example, a method of adjusting the amount 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 conversion conditions, etc. Can be adjusted. Among these methods, from the viewpoint of production and quality, it is preferable to adjust the density by a method of adjusting the addition amount of sulfuric acid and water at the stage of paste preparation.

[Measurement of density of anode material]
The density of the negative electrode material can be measured as follows. The formed negative electrode plate is washed with water for about 1 hour and then dried at 60 ° C. for 20 hours in a nitrogen atmosphere. Next, negative electrode materials are respectively collected from the surface portion and the inside of the dried negative electrode plate. Using a porosimeter (Autopore IV9500) manufactured by Shimadzu Corporation as an analysis device, the density of the negative electrode material is measured from the relationship between the pore volume at a measurement pressure of 2.00 psi and the dry mass by a mercury intrusion method. Details of the measurement conditions are as follows.

{Measurement conditions of density (apparent density) of negative electrode material}
Analyzer: Autopore IV9500 (manufactured by Shimadzu Corporation)
Mercury pressure: 0 to 354 kPa (low pressure), atmospheric pressure to 414 MPa (high pressure)
Pressure holding time at each measurement pressure: 900 s (low pressure), 1200 s (high pressure)
Contact angle between sample and mercury: 130 ° C
Mercury surface tension: 480-490 mN / m
Mercury density: 13.5335 g / mL

[Range of surface portion of negative electrode material]
The range of the surface portion of the negative electrode material will be described. The negative electrode material is disposed in the order of the surface portion, the inside, and the surface portion with respect to the thickness direction of the negative electrode plate. From the viewpoint of cycle characteristics, the range of the surface portion of the negative electrode material is preferably up to 25% from the surface of the negative electrode plate to the thickness direction of the negative electrode plate. Further, from the viewpoint that both low-temperature high-rate discharge characteristics and cycle characteristics can be easily achieved, the above range is more preferably up to 20%, still more preferably up to 15%, particularly preferably up to 12%, and particularly preferably up to 10%. From the viewpoint of production, the above range is preferably larger than 5%.

(Current collector)
Examples of the current collector include a current collector grid such as a cast grid and an expanded grid. Examples of the material of the current collector include a lead-calcium-tin alloy, a lead-calcium alloy, and a lead-antimony alloy. A small amount of selenium, silver, bismuth or the like can be added to these. For example, the current collector can be obtained by forming these materials in a lattice shape by a gravity casting method, an expanding method, a punching method, or the like. The current collectors of the positive electrode and the negative electrode may be the same as each other or different from each other.

(Electrolyte)
The electrolytic solution preferably contains aluminum ions from the viewpoint of suppressing a short circuit during overdischarge. When the electrolytic solution contains aluminum ions, aluminum hydroxide is precipitated in the separator, in particular, in the surface layer portion, so that it is presumed that a short circuit can be suppressed because precipitation of lead is suppressed.

<Method for producing lead-acid battery>
The method for manufacturing a lead storage battery according to the present embodiment includes, for example, an electrode manufacturing process for obtaining electrodes (positive electrode and negative electrode) and an assembly process for obtaining a lead storage battery by assembling constituent members including the electrodes.

  In the electrode manufacturing process, for example, an electrode material paste (a positive electrode material paste and a negative electrode material paste) is filled in a current collector (for example, a current collector grid such as a cast grid or an expanded grid), and then ripened and dried. Thus, an unformed electrode is obtained. 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 for 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. Further, other additives may be further contained.

The positive electrode material paste can be obtained, for example, by the following method. First, an additive (such as reinforcing short fibers) and water are added to the raw material of the positive electrode active material. Next, after adding dilute sulfuric acid, the mixture is kneaded to obtain a positive electrode material paste. In producing the positive electrode material paste, lead (Pb ₃ O ₄ ) may be used as a raw material for the positive electrode active material from the viewpoint of shortening the chemical formation time. A non-chemically formed positive electrode can be obtained by aging and drying after filling the positive electrode material paste into the current collector.

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

  As aging conditions for obtaining an unchemically formed positive electrode, 15 to 60 hours are preferable in an atmosphere of a temperature of 35 to 85 ° C. and a humidity of 50 to 98 RH%. The drying conditions are preferably 45 to 80 ° C. and 15 to 30 hours.

  The negative electrode material paste can be obtained, for example, by the following method. First, an additive (a resin having a sulfone group and / or a sulfonate group, a reinforcing short fiber, barium sulfate, etc.) is added to the raw material of the negative electrode active material and dry mixed to obtain a mixture. And a negative electrode material paste is obtained by adding and knead | mixing a sulfuric acid (diluted sulfuric acid etc.) and a solvent (water, such as ion-exchange water, an organic solvent) to this mixture. Two negative electrode material pastes having different densities are produced by the above method. First, of the two negative electrode material pastes, a negative electrode material paste having a higher density is filled into a current collector (for example, a current collector lattice such as a cast lattice body or an expanded lattice body). Subsequently, of the two negative electrode material pastes, a negative electrode material paste having a lower density is filled into the current collector. Later, aging and drying can be performed to obtain an unformed negative electrode.

  In the negative electrode material paste, when 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, the amount of each component is preferably in the following range. The blending amount of the resin having a sulfonic group and / or a sulfonic acid group is preferably 0.01 to 2.0% by mass in terms of resin solid content, based on the total mass of the negative electrode active material (lead powder, etc.). 0.05-1.0 mass% is more preferable, 0.1-0.5 mass% is still more preferable, 0.1-0.3 mass% is especially preferable. The blending 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 blending amount of the reinforcing short fibers is preferably 0.05 to 0.15% by mass based on the total mass of the negative electrode active material (lead powder or the like). The blending amount of barium sulfate is preferably 0.01 to 2.0 mass%, more preferably 0.01 to 1.0 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, 15 to 30 hours are preferable in an atmosphere of a temperature of 45 to 65 ° C. and a humidity of 70 to 98 RH%. The drying conditions are preferably 45 to 60 ° C. and 15 to 30 hours.

  In the assembling process, for example, the unformed negative electrode and the unformed positive electrode produced as described above are alternately stacked via separators, and the current collectors of the same polarity electrodes are connected (welded, etc.) with a strap. An electrode group is obtained. This electrode group is arranged in a battery case to produce an unformed battery. Next, after injecting an electrolytic solution into the non-chemical cell, a direct current is applied to form a battery case. The lead acid battery can be obtained by adjusting the specific gravity of the electrolyte after the formation to an appropriate specific gravity.

  The electrolytic solution contains, for example, sulfuric acid and aluminum ions, and can be obtained by mixing sulfuric acid and aluminum sulfate powder. Aluminum sulfate to be dissolved in the electrolytic solution can be added as an anhydride or a hydrate.

  The specific gravity after the formation of the electrolytic solution (in the case of containing aluminum ions, the electrolytic solution containing aluminum ions) is preferably in the following range. The specific gravity of the electrolytic solution is preferably 1.25 or more, more preferably 1.28 or more, further preferably 1.285 or more, and 1.29 or more from the viewpoint of suppressing osmotic short-circuiting or freezing and further improving discharge characteristics. Particularly preferred. The specific gravity of the electrolytic solution is preferably 1.33 or less, more preferably 1.32 or less, still more preferably 1.315 or less, and particularly preferably 1.31 or less, from the viewpoint of further improving charge acceptance performance and cycle characteristics. The value of the specific gravity of the electrolytic solution can be measured by, for example, a floating hydrometer or a digital hydrometer manufactured by Kyoto Electronics Industry Co., Ltd.

  The aluminum ion concentration of the electrolytic solution is preferably 0.001 mol / L or more, more preferably 0.004 mol / L or more, based on the total amount of the electrolytic solution, from the viewpoint of further improving the charge acceptance performance and cycle characteristics. The aluminum ion concentration of the electrolytic solution is preferably 0.2 mol / L or less based on the total amount of the electrolytic solution from the viewpoint of further improving the charge acceptance performance and cycle characteristics. The aluminum ion concentration of the electrolytic solution can be measured by, for example, ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy).

  Although the details of the mechanism for improving the charge acceptance performance when the aluminum ion concentration of the electrolytic solution is within the predetermined range are not clear, it is presumed as follows. That is, when the aluminum ion concentration is within the predetermined range, the solubility of the crystalline lead sulfate, which is a discharge product, in the electrolytic solution increases under any low SOC, or due to the high ion conductivity of aluminum ions. This is presumably because the diffusibility of the electrolytic solution into the electrode active material is improved.

  Although the details of the mechanism for improving the charge acceptance performance when the aluminum ion concentration of the electrolytic solution is within the predetermined range are not clear, it is presumed as follows. That is, when the aluminum ion concentration is within the predetermined range, the solubility of the crystalline lead sulfate, which is a discharge product, in the electrolytic solution increases under any low SOC, or due to the high ion conductivity of aluminum ions. This is presumably because the diffusibility of the electrolytic solution into the electrode active material is improved.

  The battery case can accommodate an electrode (electrode plate or the like) inside. The battery case preferably has a box body whose upper surface is opened and a lid body that covers the upper surface of the box body from the viewpoint of easily accommodating the electrode. Note that an adhesive, heat welding, laser welding, ultrasonic welding, or the like can be appropriately used for bonding the box and the lid. The shape of the battery case is not particularly limited, but a rectangular shape is preferable so that an ineffective space is reduced when an electrode (a plate plate or the like) is accommodated.

  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 battery case material 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 cost.

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

  Examples of the separator include a separator made of at least one selected from glass, pulp, and synthetic resin. In the present invention, it is preferable to use the separator described below.

  In the present invention, it is preferable to use the separator described in FIG. FIG. 1A is a front view showing a polyolefin separator (hereinafter simply referred to as a separator) made of a microporous sheet, and FIG. 1B is a cross-sectional view of the separator. FIG. 2 is a cross-sectional view of the separator and the electrode. As shown in FIG. 1, the separator 10 includes a flat base portion 11, a plurality of convex (for example, linear) ribs 12, and mini-ribs 13. The base portion 11 supports the rib 12 and the mini rib 13. The ribs 12 are arranged substantially parallel to each other on the one surface 10 a of the separator 10. The interval between the ribs 12 is, for example, 3 to 15 mm. One end in the height direction of the rib 12 is integrally connected to the base portion 11, and the other end in the height direction of the rib 12 is in contact with one electrode 14a of the positive electrode and the negative electrode (see FIG. 2). ). The base portion 11 faces the electrode 14 a in the height direction of the rib 12. Ribs are not disposed on the other surface 10b of the separator 10, and the other surface 10b of the separator 10 faces or is in contact with the other electrode 14b (see FIG. 2) of the positive electrode and the negative electrode.

  A large number of the mini-ribs 13 are formed on both sides of the separator 10 in the width direction so as to extend in the longitudinal direction of the separator 10. The mini-rib 13 has a function of improving the separator strength in order to prevent the corners of the electrodes from breaking through the separator when the lead storage battery vibrates in the lateral direction. Note that the height, width, and interval of the mini-ribs 13 are preferably smaller than the ribs 12. Further, the cross-sectional shape of the mini-rib 13 may be the same as or different from that of the rib 12. The cross-sectional shape of the mini-rib 13 is preferably a semicircular shape. Moreover, the minirib 13 does not need to be formed.

  FIG. 3 is a diagram showing a state in which the bag separator 20 and the electrode (for example, the negative electrode) 14 accommodated in the bag separator 20 are inserted. As shown to Fig.1 (a), the separator 10 used for preparation of the bag separator 20 is formed in the elongate sheet form, for example. The bag separator 20 is obtained by cutting the separator 10 into an appropriate length, folding it in the longitudinal direction of the separator 10 and arranging the electrodes 14 on the inside thereof, and then mechanically sealing, crimping, or heat-welding both sides ( For example, reference numeral 22 in FIG. 3 is a mechanical seal portion). Thereby, the bag separator 20 shown in FIG. 3 is obtained.

  The upper limit of the thickness T of the base part 11 is 0.25 mm or less from the viewpoint of obtaining excellent charge acceptability and discharge characteristics. When thickness T exceeds 0.25 mm, there exists a tendency for charge acceptance and a discharge characteristic to fall. The upper limit of the thickness T of the base portion 11 is preferably 0.2 mm or less, and more preferably 0.15 mm or less, from the viewpoint of obtaining further excellent charge acceptance and discharge characteristics. The lower limit of the thickness T of the base portion 11 is not particularly limited, but is preferably 0.05 mm or more and more preferably 0.1 mm or more from the viewpoint of easily suppressing a short circuit.

  The upper limit of the height of the rib 12 (the height in the facing direction of the base portion 11 and the electrode 14) H is preferably 1.25 mm or less, more preferably 1.0 mm or less, from the viewpoint of obtaining further excellent charge acceptance. More preferably, it is 0.75 mm or less. The lower limit of the height H of the rib 12 is preferably 0.3 mm or more, more preferably 0.4 mm or more, and still more preferably 0.5 mm or more, from the viewpoint of suppressing oxidative deterioration at the positive electrode.

  The lower limit of the ratio H / T of the height H of the rib 12 to the thickness T of the base part 11 is 2 or more from the viewpoint of excellent oxidation resistance of the separator. When the ratio H / T is 2 or more, a portion that does not contact the electrode (for example, the positive electrode) can be sufficiently secured, so that it is estimated that the oxidation resistance of the separator is improved.

  The lower limit of the ratio H / T is preferably 2.4 or more, and more preferably 3 or more, from the viewpoint of further improving the oxidation resistance and productivity of the separator. The upper limit of the ratio H / T is 6 or less from the viewpoint of excellent rib shape retention and the suppression of short circuits. If the ratio H / T is 6 or less, the distance between the positive and negative electrodes is sufficient, and it is estimated that short-circuiting is suppressed. Further, when the ratio H / T is 6 or less, it is presumed that the battery characteristics such as charge acceptability are favorably maintained without damaging the ribs when the lead storage battery is assembled. The upper limit of the ratio H / T is preferably 5 or less, more preferably 4.5 or less, and still more preferably 4 or less, from the viewpoint of easily suppressing a short circuit and the viewpoint of further excellent rib shape retention.

  Further, the upper base width B (see FIG. 1B) of the rib 12 is preferably 0.1 to 2 mm, more preferably 0.2 to 1 mm, from the viewpoint of excellent rib shape retention and oxidation resistance. 0.2-0.8 mm is still more preferable. The lower bottom width A of the rib is preferably 0.2 to 4 mm, more preferably 0.3 to 2 mm, and still more preferably 0.4 to 1 mm, from the viewpoint of excellent shape retention of the rib. The ratio of the upper base width B to the lower base width A (B / A) is preferably 0.1 to 1, more preferably 0.2 to 0.8, from the viewpoint of excellent rib shape retention. -0.6 is still more preferable.

  The separator is preferably in the form of a bag that encloses at least one of a positive electrode and a negative electrode. For example, a mode in which one of the positive electrode and the negative electrode is accommodated in a bag-shaped separator and is alternately laminated with the other of the positive electrode and the negative electrode is preferable. For example, when a bag-shaped separator is applied to the positive electrode, it is preferable that the negative electrode is accommodated in the bag-shaped separator because there is a possibility of passing through the separator due to the elongation of the positive electrode current collector.

  The chemical conversion conditions and the specific gravity of sulfuric acid can be adjusted according to the properties of the electrode active material. 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 conversion).

  The mass ratio of the positive electrode material to the negative electrode material (positive electrode material / negative electrode material) is preferably 0.9 or more, more preferably 1 or more, from the viewpoint that sufficient battery capacity is easily obtained and high charge acceptability is easily obtained. 1.05 or more is still more preferable. The mass ratio of the positive electrode material to the negative electrode material is preferably 1.3 or less, more preferably 1.2 or less, and even more preferably 1.15 or less, from the viewpoint that a sufficient battery capacity can be easily obtained. The mass ratio of the positive electrode material to the negative electrode material is preferably 0.9 to 1.3, more preferably 1 to 1.2, from the viewpoint that sufficient battery capacity is easily obtained and high charge acceptability is easily obtained. 0.05 to 1.15 is more preferable. The said mass ratio of the positive electrode material with respect to a negative electrode material is a mass ratio of the negative electrode material and positive electrode material after chemical conversion.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to the following examples.

(Example 1)
[Production of positive electrode plate]
As a raw material of the positive electrode active material, lead powder having an oxidation degree of 70% and lead powder (Pb ₃ O ₄ ) having an oxidation degree of 90% were used (lead powder: red lead = 85: 15 (mass ratio)). The raw material for the positive electrode active material, 0.2% by mass of reinforcing short fibers (acrylic fibers) based on the total mass of the positive electrode active material, and water were mixed and kneaded. Subsequently, dilute sulfuric acid (specific gravity 1.280, equivalent to 20 ° C. or lower) was kneaded while being added little by little to prepare a positive electrode material paste. This positive electrode material paste was filled into an expandable current collector produced by subjecting a rolled sheet made of a lead alloy to an expanding process. Next, the current collector filled with the positive electrode material paste was aged in an atmosphere of a temperature of 50 ° C. and a humidity of 98% for 24 hours. Then, it dried and produced the unchemically formed positive electrode plate.

[Production of negative electrode plate]
Lead powder having an oxidation degree of 70% was used as a raw material for the negative electrode active material. 0.2% by mass of bisphenol-based resin (converted to solid content, manufactured by Nippon Paper Industries Co., Ltd., trade name: Vispaz P215), 0.1% by mass of reinforcing short fibers (acrylic fibers), and 1.0% by mass of barium sulfate %, A carbon material (flaky graphite (particle size: 180 μm)) containing 1.5 mass% was added to the lead powder and then dry-mixed (the blending amount is based on the total mass of the negative electrode active material) The blended amount). The weight average molecular weight of the bisphenol-based resin was 53900 as measured by GPC under the conditions described above. The particle size of the flake graphite was obtained as an arithmetically averaged numerical value by the method described above. Then, by adding water and dilute sulfuric acid to the mixture, paste density after conversion becomes 3.8g / cm ³ (A) and the density after the conversion is 4.2 g / cm ³ paste (B) Each was produced. In the above (A) and (B), the density was adjusted by a method of adjusting the amount of water added. Then, the above-mentioned (B) was filled in an expanded current collector produced by subjecting a rolled sheet made of a lead alloy to an expanding process. Subsequently, the above (A) was filled from above so that (A) was 10% from the surface to the thickness direction of the negative electrode plate. Next, the current collector filled with the negative electrode material paste was aged in an atmosphere of a temperature of 50 ° C. and a humidity of 98% for 24 hours. Then, it dried and produced the unchemically formed negative electrode plate.

[Battery assembly]
A cross-sectional view of an electrode plate group in which positive and negative electrode plates and separators are laminated is shown in FIG. First, a polyethylene separator made of a microporous sheet having a predetermined length (with a base portion thickness of 0.2 mm and a rib height of 0.6 mm) is creased in the width direction at the center in the length direction. Then, it is bent into a U shape, and an unformed negative electrode plate is disposed inside the U shape. And the both sides of the length direction of the polyethylene separator which consists of a microporous sheet | seat bent in the U-shape were sealed. Eight unformed negative electrode plates and seven unformed positive electrode plates contained in a bag-like double separator were alternately laminated. Subsequently, the ears of the same polarity electrode plates were welded together by a cast on strap (COS) method to produce an electrode plate group. The electrode plate group was inserted into the battery case to assemble a 2V single cell battery (corresponding to a D23 size single cell defined in JIS D 5301). Dilute sulfuric acid (specific gravity 1.280) in which aluminum sulfate anhydride was dissolved so that the aluminum ion concentration was 0.04 mol / L was injected into this battery. Then, in a 40 degreeC water tank, it formed in 20-hour conditions with the energizing current 20A, and obtained the lead acid battery. Moreover, the mass ratio (positive electrode material / negative electrode material) of the positive electrode material to the negative electrode material after chemical conversion was set to 1.2.

Details of Examples 2 to 7 are described below.
(Example 2)
Obtained by filling the paste in the same manner as in Example 1 so that the negative electrode material density inside the negative electrode plate after the formation was 4.2 g / cm ³ and the negative electrode material density on the surface portion was 3.6 g / cm ³ . A lead-acid battery manufactured using a negative electrode plate.
Example 3
It was obtained by filling the paste in the same manner as in Example 1 so that the negative electrode material density inside the negative electrode plate after conversion was 4.2 g / cm ³ and the negative electrode material density on the surface was 3.4 g / cm ³ . A lead-acid battery manufactured using a negative electrode plate.
Example 4
Negative electrode material density inside the negative electrode plate after the chemical conversion is 4.4 g / cm ^3, as negative electrode material density of the surface portion is 3.8 g / cm ^3, obtained by filling a paste in Example 1 a similar manner A lead-acid battery manufactured using a negative electrode plate.
(Example 5)
Negative electrode material density inside the negative electrode plate after the chemical conversion is 4.6 g / cm ^3, as negative electrode material density of the surface portion is 3.8 g / cm ^3, obtained by filling a paste in Example 1 a similar manner A lead-acid battery manufactured using a negative electrode plate.
Example 6
Obtained by filling the paste in the same manner as in Example 1 so that the negative electrode material density inside the negative electrode plate after the formation was 4.4 g / cm ³ and the negative electrode material density on the surface portion was 3.6 g / cm ³ . A lead-acid battery manufactured using a negative electrode plate.
(Example 7)
Obtained by filling the paste in the same manner as in Example 1 so that the negative electrode material density inside the negative electrode plate after the formation was 4.6 g / cm ³ and the negative electrode material density on the surface portion was 3.4 g / cm ³ . A lead-acid battery manufactured using a negative electrode plate.

Details of Comparative Examples 1 to 6 will be described below.
(Comparative Example 1)
Prepared in the same manner as in Example 1 except that the paste was filled so that the density of the negative electrode material after formation was 4.0 g / cm ^{3 on} the surface and inside of the negative electrode plate, and the obtained negative electrode plate was used. Lead-acid battery.
(Comparative Example 2)
Fabricated in the same manner as in Example 1, except that the paste was filled so that the density of the negative electrode material after formation was 4.6 g / cm ³ both on the surface and inside of the negative electrode plate, and the obtained negative electrode plate was used. Lead-acid battery.
(Comparative Example 3)
Prepared in the same manner as in Example 1 except that the paste was filled so that the density of the negative electrode material after the chemical conversion was 4.4 g / cm ³ both on the surface and inside of the negative electrode plate, and the obtained negative electrode plate was used. Lead-acid battery.
(Comparative Example 4)
Prepared in the same manner as in Example 1, except that the paste was filled so that the density of the negative electrode material after formation was 3.4 g / cm ^{3 on} both the surface and the inside of the negative electrode plate, and the obtained negative electrode plate was used. Lead-acid battery.
(Comparative Example 5)
Negative electrode material density inside the negative electrode plate after the chemical conversion is 4.2 g / cm ^3, as negative electrode material density of the surface portion is 3.8 g / cm ^3, obtained by filling a paste in Example 1 a similar manner A lead-acid battery manufactured using a negative electrode plate.
(Comparative Example 6)
Obtained by filling the paste in the same manner as in Example 1 so that the density of the negative electrode material inside the formed negative electrode plate was 3.4 g / cm ³ and the density of the negative electrode material on the surface was 4.6 g / cm ³ . A lead-acid battery manufactured using a negative electrode plate.

(Measurement of low temperature high rate discharge duration)
Each lead-acid battery was allowed to stand for 16 hours under an atmosphere of −15 ° C., then discharged at a current value of 300 A to a final voltage of 1.0 V, and the duration was measured. Table 1 shows the low-temperature high-rate discharge duration of each lead-acid battery with respect to Comparative Example 1, where Comparative Example 1 is 100.

(Evaluation of cycle characteristics)
The lead storage battery for which the measurement of the low temperature high rate discharge duration was completed was discharged at a constant current of 25 A for 4 minutes in an environment of 40 ° C., and subsequently charged for 10 minutes at a constant voltage of 2.47 V and 25 A. This discharging and charging cycle was performed once, and discharging was performed at a constant current of 582 A for 30 seconds every 480 cycles, and the terminal voltage at 30 seconds was measured. The point of time when it was confirmed that the terminal voltage dropped to 1.2 V or less and did not rise again was defined as the life cycle number. The greater the number of life cycles, the better the cycle characteristics. Table 1 shows the cycle characteristics of each lead-acid battery with respect to Comparative Example 1, with the cycle characteristic of Comparative Example 1 being 100.

  About these lead acid batteries, the measurement result of low temperature high rate discharge duration and cycling characteristics is shown in Table 1. The example using the present invention was excellent in both the duration of low-temperature high-rate discharge and the cycle characteristics. The following reasons can be considered as these reasons. It is considered that the low temperature high rate discharge characteristics are affected by a part of the surface layer of the negative electrode, and the reason why the low temperature high rate discharge characteristics are excellent is that a paste having a small specific surface area and a large density is arranged on the surface of the negative electrode. It is guessed. Further, it is presumed that the reason why the cycle characteristics are good is that aggregation of the active material is suppressed as a result of disposing a paste having a high density inside the negative electrode.

DESCRIPTION OF SYMBOLS 10 ... Separator, 10a ... One side, 10b ... Other side, 11 ... Base part, 12 ... Rib,
13 ... Mini rib, 14, 14a, 14b ... Electrode, 20 ... Bag separator, 22 ... Mechanical seal part, A ... Rib bottom width, B ... Rib top width, H ... Rib height, T ... Base part Thickness 1: negative electrode plate, 2: separator made of microporous sheet, 3: positive electrode plate

Claims (2)

  A negative electrode current collector, and a negative electrode material held by the negative electrode current collector, wherein the negative electrode material density inside the negative electrode is a negative electrode in a surface portion of the negative electrode Lead-acid battery larger than material density. 2. The lead acid battery according to claim 1, wherein a negative electrode material density in a surface portion of the negative electrode is less than 4.0 g / cm ³ , and an internal negative electrode material density in the negative electrode is 4.0 g / cm ³ or more.

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