JP2017142888A - Lead storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress both of the stratification of an electrolytic solution and the increase in internal resistance and to enhance the endurance of a hydrophilic coating.SOLUTION: A lead storage battery comprises: a positive electrode plate 7; a negative electrode plate 5; a separator 6 disposed between the positive electrode plate 7 and the negative electrode plate 5; an electrolytic solution; and a battery case 1 containing them. The negative electrode plate 5 has a film body 8 provided on a surface thereof. The film body 8 includes a base material 18, and a hydrophilic coating 9 covering the surface of the base material 18. The hydrophilic coating 9 includes a hydrophilic material 10, and a retainer material 11. The hydrophilic material 10 is alumina or silica. The retainer material 11 is acrylic amide, silica sol or a silane coupling agent. The base material 18 has a fiber diameter smaller than 10 μm. The base material 18 has a porosity smaller than 90%.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lead-acid battery.

  Lead-acid batteries are widely used for industrial purposes, and are used, for example, for automobile batteries, backup power supplies, and main power supplies for electric vehicles. In recent automobiles, an idling stop-and-start system (hereinafter referred to as “ISS”) that stops the engine during power generation control or waiting for a signal is adopted for the purpose of carbon dioxide emission regulation measures and fuel efficiency reduction. Became.

  Since power generation by the alternator is not performed during idling stop, all electric power to the electric equipment is supplied from the lead storage battery, and the lead storage battery is charged deeper than before. Moreover, since the power generation of the alternator is controlled even during traveling, the battery is in a state of insufficient charging.

  In Patent Document 1, a sheet-like member having holes that transmit ions contained in the electrolytic solution is provided between a positive electrode and a negative electrode of a lead-acid battery, and the sheet-like member is made of a hydrophobic resin as a base material, A technique is disclosed that comprises a porous hydrophilic coating layer provided on the surface of a hydrophobic resin. Patent Document 1 also describes that the hydrophilic coating layer desirably contains particles of silicon dioxide, aluminum oxide, zirconium dioxide, or titanium dioxide.

  Patent Document 2 discloses a technique for imparting hydrophilicity by supporting semiconductor particles such as titanium oxide on a nonwoven fabric made of polypropylene having a fiber diameter of about 3 μm and irradiating light with respect to a battery separator.

  When deep discharge and insufficient charging are repeated in a lead storage battery, stratification of the electrolyte occurs, which has become apparent as a cause of shortening the life of the lead storage battery. In the positive electrode, water generated at the time of discharge promotes the mixing of the electrolytic solution, so that the influence of stratification is small. On the other hand, since there is no such effect in the negative electrode, stratification is likely to occur. Here, stratification refers to a phenomenon in which a difference in the specific gravity of the electrolyte occurs between the top and bottom of the battery case due to repeated charge and discharge.

  In addition, in lead-acid batteries for ISS cars, in addition to extending the life by suppressing the stratification of electrolyte, technologies for improving battery performance such as high-rate discharge performance and charge acceptance, which are engine startability, and reducing internal resistance Development is also an issue. In order to improve the performance of lead-acid batteries for ISS vehicles used in harsh environments, it is indispensable to extend the life and improve battery performance. It is thought that these problems can be solved by improving the diffusion rate of sulfate ions while keeping the concentration of sulfate ions in the battery case uniform.

JP 2014-194911 A JP-A-9-289007

  In the sheet-like member described in Patent Document 1, from the viewpoint of suppressing the stratification of the electrolyte solution of the lead storage battery, oxide particles and the like constituting the hydrophilic coating layer have been studied. However, the fiber diameter of the sheet-like member is approximately 10 to 20 μm, and the porosity is 90 to 98%. Therefore, since the specific surface area of a sheet-like member is small and there is little space which can hold | maintain a sulfate ion, it is thought that the suppression effect of stratification is inadequate.

  The battery separator described in Patent Document 2 is obtained by chemically changing the functional group on the surface of the nonwoven fabric to a hydrophilic one, and the hydrophilicity on the surface of the nonwoven fabric is not maintained over a long period of time. In other words, there is a problem that durability is low.

  An object of the present invention is to achieve both suppression of stratification of an electrolytic solution and suppression of increase in internal resistance, and improve the durability of a hydrophilic film.

  A lead-acid battery according to the present invention includes a positive electrode plate, a negative electrode plate, a separator disposed between the positive electrode plate and the negative electrode plate, an electrolytic solution, and a battery case that accommodates them, on the surface of the negative electrode plate. Is provided with a film body, the film body includes a base material and a hydrophilic film covering the surface of the base material, the hydrophilic film includes a hydrophilic material and a support material, and the hydrophilic material is alumina. Alternatively, it is silica, and the support material is acrylamide, silica sol, or a silane coupling agent, the fiber diameter of the substrate is smaller than 10 μm, and the porosity of the substrate is smaller than 90%.

  ADVANTAGE OF THE INVENTION According to this invention, suppression of stratification of electrolyte solution and suppression of a raise of internal resistance are compatible, and durability of a hydrophilic film can be improved.

It is a schematic perspective view which shows the whole structure of the lead acid battery of this invention. It is a schematic cross section which shows a part of electrode group of the lead acid battery of embodiment. It is a schematic perspective view which shows the combination of a pair of positive electrode and negative electrode in the lead acid battery of embodiment. It is a figure which shows the structure of a part of electrode group of the lead acid battery by the Example of this invention, especially the structure around a negative electrode plate. It is a graph which shows the relationship between the porosity of a base material, and the internal resistance of a real battery. It is a measurement result of the specific surface area of a film body.

The lead acid battery according to the present invention has the following characteristics. A positive electrode plate containing lead dioxide, a negative electrode plate containing metallic lead, a separator disposed between the positive electrode plate and the negative electrode plate, and a dilute sulfuric acid electrode group consisting of the positive electrode plate, the negative electrode plate and the separator are immersed. And a battery case containing the electrode group and the electrolyte solution, and a porous film body such as an organic woven fabric and an organic nonwoven fabric disposed around the negative electrode plate. A hydrophilic film (hereinafter also referred to as “hydrophilic film”) is formed on the surface of the substrate. The hydrophilic film is a hydrophilic material made of SiO ₂ (silica) or Al ₂ O ₃ (alumina), or a hydrophilic material made of a mixture of Al ₂ O ₃ and SiO _2, and a carrier material made of an inorganic material or an organic polymer material. (Binder).

  When charging with a large current as in an ISS application, a large amount of sulfate ions are released from the electrode plate. Therefore, it is preferable that the membrane body has a higher ability to retain sulfate ions. By making the fiber diameter of the base material smaller than 10 μm (preferably a fiber diameter of several μm) and making the porosity of the base material smaller than 90%, the specific surface area of the film body is increased and the space for holding sulfate ions Therefore, the sulfate ion retention ability of the film body can be improved. When the fiber diameter of the base material is smaller than 1 μm, the fiber is easily cut and the film body is easily broken, which causes a problem in durability. Therefore, the fiber diameter of the base material is desirably 1 μm or more. On the other hand, if the porosity of the substrate is smaller than 40%, the movement of the liquid in the film body is hindered, the diffusion of sulfate ions becomes insufficient, and the internal resistance increases. Therefore, the porosity of the substrate is desirably 40% or more.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(1) Electrolyte stratification Electrolyte stratification in lead-acid batteries, particularly liquid lead-acid batteries, causes the sulfate and hydrogen sulfate ions in the electrolyte to settle, resulting in a difference in the specific gravity of the electrolyte above and below the battery case. Is a phenomenon that occurs. Hereinafter, sulfate ions (SO ₄ ²⁻ ) and hydrogen sulfate ions (HSO ₄ ⁻ ) are collectively referred to as “sulfate ions”.
As will be described later, by providing a film body (organic woven fabric, organic nonwoven fabric or porous membrane as a base material) in close contact with the surface of the negative electrode plate, the accumulation of sulfate ions in the lower part of the battery case is suppressed. The stratification of the electrolytic solution can be suppressed. In other words, the concentration of sulfate ions inside the battery case can be kept uniform.

(2) Internal resistance The internal resistance of lead-acid batteries is greatly affected by the diffusion rate of sulfate ions. When there are many obstacles that inhibit the behavior of sulfate ions, the diffusion rate of sulfate ions decreases, so the internal resistance is considered to increase. Conversely, when the number of obstacles is small, the diffusion rate of sulfate ions is improved, so that the internal resistance is considered to be small. In order to improve the performance of lead-acid batteries, it is necessary to suppress an increase in internal resistance. For this reason, a battery configuration that does not inhibit the behavior of sulfate ions must be devised.

  Factors affecting the behavior of sulfate ions include a separator and a film attached to the surface of the negative electrode plate. Since the diffusion rate of sulfate ions is greatly influenced by the structural characteristics such as the pore diameter and basis weight (porosity, density) of the separator and the membrane body, it is necessary to optimize these structures. Here, the porosity means the percentage of the gap per unit volume of the film body expressed as a percentage.

(3) High-rate discharge performance The high-rate discharge performance was better when a hydrophilic film was provided on the substrate of the film body than when a hydrophilic film was not provided. This is presumably because a chemical interaction works between the sulfate ion and the hydrophilic film. _On the surface of SiO ₂ or Al ₂ O ₃ used for the hydrophilic film, —OH groups are generated. This —OH group exists in the form of —OH ₂ ⁺ as a result of protonation in an aqueous sulfuric acid solution that is an electrolytic solution. It is considered that sulfate ions (SO ₄ ²⁻ and HSO ₄ ⁻ ) are attracted to this —OH ₂ ⁺ to cause a chemical interaction.

  That is, it is considered that the hydrophilic film provided on the base material of the film body interacts with sulfate ions, adsorbs and collects sulfate ions, and supplies them to the electrodes. Therefore, it is considered that the supply efficiency of sulfate ions from the hydrophilic film to the electrode affects the high rate discharge performance.

  Therefore, in order to improve the supply efficiency of sulfate ions from the hydrophilic film to the electrode, the material of the hydrophilic film was examined based on the following points.

  When the amount of -OH groups and other hydrophilic functional groups present on the surface of the hydrophilic film is large, that is, when the hydrophilicity is high, the force with which the hydrophilic film interacts with sulfate ions works greatly, and the sulfuric acid in the battery case Since the concentration distribution is eliminated, it is considered that the supply rate of sulfate ions to the electrode is improved.

  In order to form such a hydrophilic film surface, it is necessary to control the orientation of functional groups on the surface of the hydrophilic film. If the orientation of the functional groups on the surface of the hydrophilic film is not controlled, the hydrophilic material surface may be coated with hydrophobic functional groups derived from the support material, which is not preferable.

In general, a contact angle is used as a hydrophilicity index. However, when the contact angle of water or sulfuric acid of the hydrophilic film is 10 ° or less, the hydrophilicity is particularly excellent and preferable. However, in the case of using a hydrophilic material having a high sulfate ion adsorbing power, such as Al ₂ O ₃ , if a certain level of hydrophilicity with a contact angle of about 30 ° is obtained, synergisticity with the adsorption of sulfate ions is obtained. In order to obtain an effect, it is not always necessary to select a material having a contact angle of 10 ° or less.

  In order to control the functional groups on the surface of the hydrophilic film, it is necessary to select the carrier material according to the functional group composition on the surface of the porous film body such as organic woven fabric and organic nonwoven fabric that is the base material of the hydrophilic film. It becomes.

  Hereinafter, the organic woven fabric, the organic nonwoven fabric, the hydrophilic material, and the holding material will be described in detail.

The hydrophilic film is composed of a hydrophilic material and a holding material. The hydrophilic film is formed by applying a hydrophilic paint obtained by diluting a mixed liquid composed of a hydrophilic material and a support material with a water-soluble solvent (for example, an alcohol solvent or water) to the surface of the substrate. . In consideration of the chemical interaction between sulfate ions and the hydrophilic film, the hydrophilic material includes SiO ₂ , Al ₂ O ₃ , a mixture of Al ₂ O ₃ and SiO ₂ , BaSO ₄ and TiO ₂ . It is preferable to use at least one.

When Al ₂ O ₃ is used, a hydrophilic alumina sol can be used as the hydrophilic material. When a mixture of Al ₂ O ₃ and SiO ₂ is used, a mixture of alumina sol and colloidal silica is used as the hydrophilic material. Can be used. As the support material, an inorganic material or an organic polymer material can be used. For example, silica sol, acrylamide, or alkoxysilane can be used.

  The thickness of the film body is preferably 0.03 mm to 0.1 mm in consideration of the ability to prevent the precipitation of sulfate ions, the influence on the battery reaction, the strength, and the like. When an organic woven fabric or organic nonwoven fabric is used as the substrate, the thickness can be determined according to the fiber of the organic woven fabric or organic nonwoven fabric. On the other hand, when a porous membrane is used as the substrate, the thickness can be determined according to the pore size and material of the porous membrane.

  Organic woven fabrics and organic nonwoven fabrics have the advantage that they are easier to manufacture than inorganic woven fabrics and inorganic nonwoven fabrics. For this reason, in the lead acid battery of this invention, it is desirable to use an organic woven fabric or an organic nonwoven fabric. The pore size of the film body is preferably 100 nm to 100 μm, more preferably 1 μm to 50 μm. The pore structure may be a regular structure generated between the fibers of the organic woven fabric or an irregular structure generated between the fibers of the organic nonwoven fabric.

  The hydrophilic film is preferably formed with a thickness of 10 nm to 1000 nm. By making the thickness of the hydrophilic film 10 nm or more, the effect of adsorbing and holding sulfate ions can be sufficiently exhibited. By setting the thickness of the hydrophilic film to 1000 nm or less, an increase in the internal resistance of the battery can be suppressed. The range of 10 nm to 500 nm is particularly preferable from the viewpoint of the internal resistance of the battery.

  In particular, in the lead-acid battery according to the present invention, when a film body having a hydrophilic film is provided around the negative electrode plate separately from the separator, the film body is arranged in close contact with the negative electrode plate, so that the effect of suppressing stratification on the separator is achieved. The effect of suppressing stratification is higher than in the case of providing Here, “around the negative electrode plate” means “the surface of the negative electrode plate” or “between the negative electrode plate and the separator”.

  Hereinafter, the configuration of the lead storage battery to which the present invention is applied will be described.

  FIG. 1A is a schematic perspective view showing the overall configuration of the lead storage battery of the present invention.

  In this figure, the lead storage battery 100 includes a battery case 1 and a terminal 2 as an exterior part. Inside the battery case 1, a pole 3 and an electrode group 4 are accommodated. The pole 3 is connected to the terminal 2 and the electrode group 4. The lead storage battery 100 normally has a terminal 2 on its upper surface.

  FIG. 1B is a schematic cross-sectional view showing a part of the electrode group of the lead storage battery of the present invention.

The electrode group 4 is disposed between a negative electrode plate 5 containing metal lead (Pb) as an active material, a positive electrode plate 7 containing lead dioxide (PbO ₂ ) as an active material, and the negative electrode plate 5 and the positive electrode plate 7. And a separator 6. The negative electrode plate 5 and the positive electrode plate 7 are plate-shaped. The negative electrode plate 5 and the positive electrode plate 7 are alternately stacked via the separator 6, and these constitute the electrode group 4. The electrode group 4 is immersed in an electrolytic solution made of dilute sulfuric acid and stored in the battery case 1 to constitute a lead storage battery. On the surface of the negative electrode plate 5, a film body 8 (organic woven fabric, organic nonwoven fabric or porous membrane as a base material) is provided in close contact.

  In addition, as shown to FIG. 1A and 1B, the negative electrode plate 5 and the positive electrode plate 7 are laminated | stacked in the horizontal direction. Therefore, the negative electrode plate 5 and the positive electrode plate 7 have a flat portion with a large area spreading in the vertical direction.

  FIG. 1C is a schematic perspective view showing a combination of a pair of a positive electrode plate and a negative electrode plate included in the electrode group of FIG. 1B.

  The separator 6 shown in this figure is bag-shaped, and the negative electrode plate 5 is accommodated therein. Therefore, both surfaces of the negative electrode plate 5 are covered with one separator 6. In this figure, a separator 6 covering one surface of the negative electrode plate 5 is sandwiched between the negative electrode plate 5 and the positive electrode plate 7.

  FIG. 2 is a perspective view schematically showing a combination of a pair of positive and negative electrodes in the lead storage battery of the present invention, and a schematic enlarged view showing fibers of the film body 8 covering the negative electrode plate.

  In this figure, a film body 8 (based on an organic woven fabric, organic nonwoven fabric or porous membrane) is provided on the surface of the negative electrode plate 5 in close contact. The separator 6 may be plate-shaped or bag-shaped, and is disposed between the film body 8 and the positive electrode plate 7 provided around the negative electrode plate 5. When the separator 6 has a bag shape, the negative electrode plate 5 and the film body 8 are accommodated inside the separator 6.

  The enlarged view of the film body 8 shows an organic nonwoven fabric having a configuration in which thread-like fibers are entangled irregularly.

  Furthermore, in the figure which expanded the fiber, the film | membrane body 8 is comprised with the base material 18 and the hydrophilic membrane | film 9 which covers the surface of the base material 18. FIG. The hydrophilic film 9 includes a hydrophilic material 10 and a holding material 11. The film body 8 is provided on at least the surface of the negative electrode plate 5 that faces the separator 6 and the surface of the negative electrode plate 5 that contacts the back side of this surface. Furthermore, the film body 8 may be provided on the side surface portion (peripheral edge portion having a small width) of the negative electrode plate 5 or may be provided on the bottom surface of the negative electrode plate 5.

  For example, the film body 8 may be provided on the entire surface of the negative electrode plate 5 by being wound around the negative electrode plate 5.

  The shape of the film body 8 may be a bag shape and the negative electrode plate 5 may be accommodated. The hydrophilic film 9 may be formed on the surface of the separator 6 in addition to the substrate 18. Alternatively, the hydrophilic film 9 may be formed on the surface of the separator 6 without providing the film body 8 around the negative electrode plate 5.

  FIG. 3 is a graph showing the relationship between the porosity of the film body and the internal resistance of the actual battery. The internal resistance when a film body such as an organic nonwoven fabric was not disposed around the negative electrode plate was set to 100 (reference value). The thickness of the film body was constant. This figure shows that the internal resistance increases as the porosity of the film body decreases.

FIG. 4 shows the measurement results of the specific surface area of the film body. Specific surface area when a SiO ₂ film or an Al ₂ O ₃ film is formed on a base material A having a hydrophilic functional group composition on the base material surface and a base material B having a lipophilic functional group composition on the substrate surface Show. The specific surface area is a value measured by the BET method using nitrogen adsorption.

  It can be seen that the specific surface area is increased as compared with that before the surface treatment. That is, by using such a film body, the point of interaction with sulfate ions is increased, and the ability to retain sulfate ions is further improved by adjusting the fiber diameter, pore diameter, and porosity of the substrate 18. It is possible.

  The desirable configuration in the above embodiment is summarized as follows.

  The functional group on the surface of the substrate is substantially composed of a hydrophobic functional group, and the holding material is a silane coupling agent having a vinyl group, a methacryl group, an acrylic group or a styryl group. Here, “consisting essentially of a hydrophobic functional group” means a state in which the surface of the substrate exhibits hydrophobicity.

  The functional group on the surface of the substrate is substantially composed of a hydrophilic functional group, and the support material is a silane coupling agent having an epoxy group. Here, “consisting essentially of a hydrophilic functional group” means a state in which the surface of the substrate exhibits hydrophilicity.

  As will be described later, it is desirable that the mass ratio of the solid component of the hydrophilic material and the support material is 90:10 to 70:30. The hydrophilic film preferably has a thickness of 10 nm to 1000 nm.

  The film body has a thickness of 0.03 mm to 0.1 mm.

  A hydrophilic film is formed on the surface of the substrate.

  The substrate is an organic woven fabric, an organic nonwoven fabric or a porous membrane. In the examples described later, an organic nonwoven fabric is used. However, an organic woven fabric or a porous membrane may be used as a base material as long as the electrolyte solution can permeate.

  The film body is in close contact with the surface of the negative electrode plate. Here, “adhesion” refers to a state in which the apparent outer surface of the film body is in contact with the surface of the negative electrode plate without any gap. In this case, it is desirable that the film body is fixed to the surface of the negative electrode plate.

  Hereinafter, the lead acid battery according to the present embodiment will be described.

[1] Separator Examples of the material of the separator include polyethylene (PE) and polypropylene (PP). Fabric formed of these materials, nonwoven, may be used in which the film body such as a porous membrane by adhering inorganic particles such as SiO ₂ or Al ₂ O _3. The thickness of the separator is preferably in the range of 0.1 mm to 0.5 mm, and more preferably in the range of 0.2 mm to 0.3 mm. If it is thinner than 0.1 mm, the strength of the separator is inferior, and if it is thicker than 0.5 mm, the internal resistance of the battery increases, which is not preferable. Further, the pore diameter range of the separator is preferably 10 nm to 500 nm, and the average pore diameter is particularly preferably 30 nm to 200 nm. If the pore size is smaller than 10 nm, it is difficult to pass sulfate ions, and the diffusion rate of sulfate ions is greatly reduced. If the pore size is larger than 500 nm, lead dendrites may grow and cause a short circuit. In this invention, it examined using the separator whose thickness is 0.2 mm and whose hole diameter range is 30 nm-200 nm.

[2] Film body The film body is produced by forming a hydrophilic film on the surface of an organic woven fabric, organic nonwoven fabric or porous film as a base material. Examples of the material used for the organic woven fabric, organic nonwoven fabric or porous membrane include polypropylene, cellulose, polyethylene, nylon, aramid, polyester and the like. A hydrophilic coating can be formed on the surface of an organic woven fabric, an organic nonwoven fabric or a porous membrane by applying the hydrophilic coating described below to the substrate and heating and curing it. The base material may be untreated or hydrophilized.

  The hydrophilization treatment may be either application of a surfactant such as polyglycerin or silicone or a dry surface treatment such as plasma treatment. However, the holder material contained in the hydrophilic paint is selected according to the type of functional group present on the surface of the substrate, and will be described in detail in [3] (b) Holder material described later.

  In addition, the mass of the hydrophilic film formed on the surface of the film body can be adjusted by adjusting the concentration of the paint or changing the pressure when removing the extra paint.

[3] Hydrophilic paint The hydrophilic paint for forming the hydrophilic film comprises (a) a hydrophilic material, (b) a support material, and (c) a solvent. In both the hydrophilic material and the support material, solid components are present in the dispersion medium at a constant concentration. The mass ratio of the solid component of the hydrophilic material to the support material is preferably 90:10 to 70:30. When the mass ratio of the solid components is within this range, it is suitable for preparing a hydrophilic paint by mixing the hydrophilic material and the support material. After the dispersion containing the hydrophilic material and the dispersion containing the holding material are mixed, the total concentration of the solid components of the hydrophilic material and the holding material is mixed into the dispersion (mixed dispersion) obtained by mixing. On the other hand, this mixed dispersion is diluted with a solvent so as to be 0.5 to 5% by mass. When the concentration of the solid component is less than 0.5% by mass, the thickness of the hydrophilic film becomes nonuniform, and when it is more than 5% by mass, it is difficult to form the hydrophilic film, which is not preferable.

(A) Hydrophilic material An inorganic material that does not dissolve even when immersed in an acidic aqueous solution is preferable as a hydrophilic material because it can maintain hydrophilicity for a long period of time. Examples of such inorganic materials include hydrophilic silica particles and hydrophilic alumina sol. Specific examples include colloidal silica IPA-ST-UP, IPA-ST, ST-OXS, ST-K2 and LSS-35 manufactured by Nissan Chemical Industries, Ltd., and alumina sol AS-200 manufactured by Nissan Chemical Industries, Ltd. It is done. Since colloidal silica uses alcohol as a dispersion medium and alumina sol uses water as a dispersion medium, they can be easily mixed together.

Colloidal silica has a specific surface area preferably used particles is 130m ² / g~1000m ² / g approximately. Assuming that the colloidal silica has a spherical shape, the particle diameter is 2 nm to 20 nm. Alumina sol, preferably the specific surface area of the contained alumina particles to use those which are 200m ² / g~400m ² / g approximately. Assuming that the shape of the alumina particles is plate-like, for example, an alumina sol containing alumina particles having dimensions (length, width, and height) of 10 nm × 10 nm × 100 nm can be used.

(B) Holder material An organic polymer material or an inorganic material can be used for the holder material. Examples of the organic polymer material used for the holding material include a polymer obtained by heating polyethylene glycol, polyvinyl alcohol, or the like. Examples of the inorganic material used for the holder material include materials that become the holder when heated, such as silica sol and silane coupling agents. Specific examples of the silica sol include Colcoat PX manufactured by Colcoat Co., Ltd.

  As the silane coupling agent, a silane coupling agent commercially available from Shin-Etsu Chemical Co., Ltd. may be used. In addition, although many silane coupling agents are actually classified into organic materials, in this specification, they are described as inorganic materials because they are used to impart hydrophilic functional groups to a substrate. . Among them, acrylamide, silica sol and silane coupling agent are excellent in long-term stability in an acidic aqueous solution. In particular, a silane coupling agent is preferable because the orientation of the support material can be controlled as follows depending on the type of functional group constituting the silane coupling agent.

  The holding material is selected as follows according to the type of functional group on the surface of the substrate.

  When the substrate is not treated, it is considered that the surface has a large amount of hydrophobic functional groups. Examples of the hydrophobic functional group include a methyl group and a methylene group. In that case, when a silane coupling agent having a functional group such as vinyl group, methacryl group, acrylic group or styryl group is selected as the support material, vinyl group, methacryl group, acrylic group, styryl group, etc. It is considered that the silanol groups that are oriented on the surface side and produced by the hydrolysis reaction are oriented on the opposite side.

  On the other hand, when the base material is hydrophilized, it is considered that the surface has many hydrophilic functional groups. Examples of the hydrophilic functional group include a hydroxyl group (—OH group), a carboxyl group, and an amino group. In that case, if a silane coupling agent having an amino group or an epoxy group is selected as the support material, the amino group or epoxy group reacts with a functional group on the surface of the substrate, so that the silanol group generated by hydrolysis is reversed. It is considered to be oriented to the side. In particular, an amino group is particularly preferable because it easily forms a hydrogen bond with a hydroxyl group, so that the silanol group is easily oriented on the outermost surface side of the hydrophilic film.

  Thus, by selecting the support material according to the type of functional group on the surface of the base material, the orientation of the functional group can be controlled, and a silanol group, that is, —OH, is provided on the outer surface (surface in contact with the electrolyte) of the hydrophilic film. Groups can be formed.

  In particular, selecting a silane coupling agent having a non-treated base material and a functional group such as a vinyl group, a methacryl group, an acrylic group, or a styryl group as a support material does not require a hydrophilic treatment of the base material. Therefore, it is particularly preferable because the process can be shortened.

(C) Solvent The solvent used for diluting the mixed dispersion of the hydrophilic material and the support material has good dispersibility and compatibility with the hydrophilic material and the support material, and is likely to volatilize during thermosetting. desirable. As a solvent satisfying these conditions, an alcohol solvent or water is preferable. Furthermore, considering the heat resistance of the substrate, the boiling point is more preferably 100 ° C. or lower. Specific examples of the solvent include water, methanol, ethanol and isopropyl alcohol.

  Table 1 shows the configuration of the lead storage battery of the example, the effect of suppressing the stratification of the electrolyte, and the evaluation of the internal resistance. In this table, as a configuration of the lead storage battery, the porosity and fiber diameter of the film body covering the negative electrode, the composition of the hydrophilic film formed on the surface of the film body, and the specific surface area of the film body are described. Further, this table also describes a lead storage battery manufactured as a comparative example.

In the following Examples and Comparative Examples 2 to 4, the film body 8 was provided around the negative electrode plate 5. In Examples 1 to 9 and Comparative Examples 2 to 4, the thickness of the base material 18 before forming the hydrophilic film 9 is 0.1 mm, and the material is unified to polypropylene (surface functional groups: —CH ₂ groups, —CH ₃ groups). did.

  About the fiber diameter (diameter of the fiber which forms a nonwoven fabric) of a base material, the fiber diameter was measured using the SEM image (200-times multiplication factor), and the average value of five places was defined as the representative value. In this specification, this average value is called the fiber diameter of the substrate. The fiber diameter of the substrate does not change even after the hydrophilic film is formed.

  The porosity of the base material 18 was calculated from the actual volume and the apparent volume according to the following formula by cutting the base material 18 into an appropriate size.

Porosity (%) = {1− (actual volume / apparent volume)} × 100 (Formula 1)
Actual volume (cm ³ ) = actual value of weight (g) / density (g / cm ³ ) (Formula 2)
In addition, the apparent volume when the base material 18 is cut into a 5 cm square can be calculated by the following Equation 3.

Apparent volume (cm ³ ) = 5 (cm) × 5 (cm) × measured value of thickness (cm) (Formula 3)
The film thickness of the hydrophilic film 9 was unified to 100 nm. It was confirmed by SEM observation of the base material on which the hydrophilic film was formed that the film thickness of the hydrophilic film produced under the conditions of the example was about 100 nm. Moreover, the specific surface area of the film body 8 was calculated by the gas adsorption BET multipoint method using nitrogen and the BET theory.

  In Examples 1 to 5, the range of the porosity and fiber diameter of the substrate 18 and the material composition of the hydrophilic film 9 formed on the surface of the substrate 18 were changed.

  Table 1 is a table showing the configuration of the lead storage battery according to the embodiment of the present invention, the evaluation of the effect of suppressing the stratification of the electrolytic solution, and the evaluation of the internal resistance. As the configuration of the lead storage battery, the porosity of the base material 18 disposed around the upper part / lower part of the negative electrode plate, the type and film thickness of the hydrophilic film 9 formed on the base material 18 are described.

Table 1 also shows a lead storage battery manufactured as a comparative example. In the following Examples and Comparative Example 2, a film body 8 was provided around the negative electrode plate 5. In Examples 1 to 5 and Comparative Example 2, the thickness of the substrate 18 is 0.1 mm, the material of the substrate 18 before forming the hydrophilic film is polypropylene, and PP (surface functional group: —CH ₂ group, —CH ₃ units).

  In Examples 1 to 5 to be described next, the porosity and the fiber diameter range of the base material 18 and the material composition of the hydrophilic film 9 formed on the base material 18 were changed.

In the lead-acid battery according to Example 1, a PP film body 8 having a hydrophilic film 9 formed thereon is disposed around the negative electrode plate 5 as shown in FIG. The porosity of the substrate 18 was 70%, and the fiber diameter forming the substrate 18 was 5 μm. The specific surface area of the film body 8 was 20 m ² / g.

As the base material 18, untreated polypropylene (PP) was used. Only colloidal silica (SiO ₂ ) was used as the hydrophilic material, and silica sol was used as the holding material. That is, the hydrophilic material contains 100% by mass of colloidal silica (SiO ₂ ). Specifically, colloidal silica IPA-ST-UP manufactured by Nissan Chemical Industries, Ltd. was used as colloidal silica, and Colcoat PX manufactured by Colcoat was used as the support material.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 80:20. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  After the base material 18 was immersed in this hydrophilic paint, the base material 18 was pulled up at a speed of 156 mm / min. Rolling the roller while pressing about 5 kg from above with the film body 8 coated with a hydrophilic paint on Kim Towel (registered trademark) to remove the excess hydrophilic paint adhering to the film body 8, the film body 8 is kept at 60 ° C. The solvent was removed by placing in a constant temperature bath heated to 1 hour.

  In this way, the film 8 was produced by forming the hydrophilic film 9 on the substrate 18. The film body 8 on which the hydrophilic film 9 was formed was disposed around the negative electrode plate 5, and a dilute sulfuric acid was used as the electrolytic solution to produce a lead storage battery as shown in FIG. 1A. Here, the lead storage battery is a 2V single cell, and the battery size is M42 (B size).

  First, this lead storage battery was evaluated for the effect of suppressing stratification of the electrolyte.

  In the cycle test, the battery was discharged at a 5 hour rate current (6A) for 30 minutes, the SOC (State Of Charge) was adjusted to 90%, paused for 6 hours, and 2.33 V (upper limit of 100 A). ) For 10 minutes was defined as one cycle. The charge / discharge cycle was repeated so that the SOC fluctuated between 90% and 100%. The difference in specific gravity of the electrolyte solution between the upper part and the lower part in the battery case in the initial cycle (50th) in which the stratification of the electrolysis solution appears remarkably was used as the stratification index. That is, in the 50th cycle, the specific gravity of the electrolyte solution in the lower part of the battery case and the specific gravity of the electrolyte solution in the upper part are measured, and these specific gravities are obtained. evaluated.

  The upper part in the battery case is a position 1 cm above the upper end of the electrode group 4, and the lower part in the battery case is a position 1 cm below the lower end of the electrode group 4. The height of the electrode group 4 indicates a length of 116 mm from the lower part of the electrode group 4 to the upper end of the separator 6. Specific evaluation criteria are “A” when the specific gravity difference is 0.02 or less, “B” when 0.02 or more and 0.04 or less, and “B” or more than 0.04 and 0.07 or less. The case where “C” was greater than 0.07 was designated “D”. In this evaluation standard, stratification is suppressed in the order of A, B, C, and D.

  The lead battery according to this example has a small specific gravity difference of 0.03, which is evaluated as B, indicating that stratification is suppressed.

  Next, the internal resistance of the lead storage battery was evaluated. The internal resistance was evaluated with a 1 kHz AC mΩ meter. A specific evaluation criterion is “A” when the rate of increase of the internal resistance is less than 5% when the case where there is no film body 8 is 100, and the rate of increase of 5% or more and less than 10%. The case was “B”, the case of an increase rate of 10% or more and less than 20% was “C”, and the case of an increase rate of 20% or more was “D”. In this evaluation standard, an increase in internal resistance is suppressed in the order of A, B, C, and D.

  The lead storage battery according to this example was evaluated as A when the rate of increase in internal resistance was 104. That is, it was found that the lead storage battery according to this example can achieve both suppression of increase in internal resistance and suppression of stratification.

  The lead acid battery according to Example 2 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below.

In the lead storage battery according to this example, a film body 8 having a porosity of 60% and a fiber diameter of 5 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 22 m ² / g. Only colloidal silica (SiO ₂ ) was used as the hydrophilic material, and silica sol was used as the holding material. That is, the hydrophilic material contains 100% by mass of colloidal silica (SiO ₂ ). Specifically, colloidal silica IPA-ST-UP manufactured by Nissan Chemical Industries, Ltd. was used as colloidal silica, and Colcoat PX manufactured by Colcoat was used as the support material.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 80:20. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this example had a small specific gravity difference of 0.02 as the electrolyte, and was evaluated as A, indicating that stratification was suppressed. In addition, the lead storage battery according to this example has an internal resistance of 103, which is evaluated as A, and it has been found that the suppression of the increase in internal resistance and the suppression of stratification can be achieved at the same time.

  The lead acid battery according to Example 3 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below.

In the lead storage battery according to this example, a film body 8 having a porosity of 70% and a fiber diameter of 5 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 18 m ² / g. Only alumina sol (Al ₂ O ₃ ) was used as the hydrophilic material, and silica sol was used as the holding material. That is, the hydrophilic material contains 100% by mass of alumina sol (Al ₂ O ₃ ). Specifically, alumina sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the support material.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this example had a small specific gravity difference of 0.03 as the electrolyte, and was evaluated as B, indicating that stratification was suppressed. In addition, the lead storage battery according to this example had an internal resistance of 102, which was evaluated as A, and it was found that an increase in the internal resistance could be suppressed.

  The lead acid battery according to Example 4 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below.

In the lead storage battery according to this example, a film body 8 having a porosity of 70% and a fiber diameter of 5 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 15 m ² / g.

Colloidal silica (SiO ₂ ) and alumina sol (Al ₂ O ₃ ) were used as the hydrophilic material, and silica sol was used as the holding material. In the hydrophilic material, the mass ratio of alumina sol to colloidal silica was 80:20. That is, the hydrophilic material contains 80% by mass of alumina sol (Al ₂ O ₃ ). Specifically, IPA-ST-UP was used as colloidal silica, Alumina Sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the silica sol.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 80:20.

  A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass. A film body 8 having a porosity of 70% and a fiber diameter of 5 μm was disposed on the negative electrode plate 5.

  The lead acid battery according to this example had a small specific gravity difference of 0.03 as the electrolyte, and was evaluated as B, indicating that stratification was suppressed. In addition, the lead storage battery according to this example had an internal resistance of 102, which was evaluated as A, and it was found that an increase in the internal resistance could be suppressed.

The lead acid battery according to Example 5 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below. In the lead storage battery according to this example, a film body 8 having a porosity of 70% and a fiber diameter of 2 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 18 m ² / g.

Only alumina sol (Al ₂ O ₃ ) was used as the hydrophilic material, and silica sol was used as the holding material. That is, the hydrophilic material contains 100% by mass of alumina sol (Al ₂ O ₃ ). Specifically, alumina sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the support material.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this example had a small specific gravity difference of 0.02 as the electrolyte, and was evaluated as A, indicating that stratification was suppressed. In addition, the lead storage battery according to this example had an internal resistance of 102, which was evaluated as A, and it was found that an increase in the internal resistance could be suppressed.

The lead acid battery according to Example 6 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below. In the lead storage battery according to this example, a film body 8 having a porosity of 85% and a fiber diameter of 8 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 14 m ² / g.

Colloidal silica (SiO ₂ ) and alumina sol (Al ₂ O ₃ ) were used as the hydrophilic material, and silica sol was used as the holding material. In the hydrophilic material, the mass ratio of alumina sol to colloidal silica was 90:10. That is, the hydrophilic material contains 80% by mass of alumina sol (Al ₂ O ₃ ). Specifically, IPA-ST-UP was used as colloidal silica, Alumina Sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the silica sol.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this example had a small specific gravity difference of 0.02 as the electrolyte, and was evaluated as A, indicating that stratification was suppressed. In addition, the lead storage battery according to this example had an internal resistance of 103, which was evaluated as A, and it was found that an increase in the internal resistance could be suppressed.

The lead acid battery according to Example 7 has the same configuration as the lead acid battery according to Example 1, except for the following points. Only the differences will be described below. In the lead storage battery according to this example, a film body 8 having a porosity of 85% and a fiber diameter of 2 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 17 m ² / g.

Colloidal silica (SiO ₂ ) and alumina sol (Al ₂ O ₃ ) were used as the hydrophilic material, and silica sol was used as the holding material. In the hydrophilic material, the mass ratio of alumina sol to colloidal silica was 90:10. That is, the hydrophilic material contains 80% by mass of alumina sol (Al ₂ O ₃ ). Specifically, IPA-ST-UP was used as colloidal silica, Alumina Sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the silica sol.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this example had a small specific gravity difference of 0.02 as the electrolyte, and was evaluated as A, indicating that stratification was suppressed. In addition, the lead storage battery according to this example had an internal resistance of 102, which was evaluated as A, and it was found that the increase in internal resistance could be suppressed.

The lead-acid battery according to Example 8 has the same configuration as the lead-acid battery according to Example 1, except for the following points. Only the differences will be described below. In the lead storage battery according to this example, a film body 8 having a porosity of 50% and a fiber diameter of 8 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 16 m ² / g.

Colloidal silica (SiO ₂ ) and alumina sol (Al ₂ O ₃ ) were used as the hydrophilic material, and silica sol was used as the holding material. In the hydrophilic material, the mass ratio of alumina sol to colloidal silica was 90:10. That is, the hydrophilic material contains 80% by mass of alumina sol (Al ₂ O ₃ ). Specifically, IPA-ST-UP was used as colloidal silica, Alumina Sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the silica sol.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this example had a small specific gravity difference of 0.03 as the electrolyte, and was evaluated as B, indicating that stratification was suppressed. In addition, the lead storage battery according to this example had an internal resistance of 104, which was evaluated as A, and it was found that an increase in the internal resistance could be suppressed.

The lead acid battery according to Example 9 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below. In the lead storage battery according to this example, a film body 8 having a porosity of 50% and a fiber diameter of 2 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 18 m ² / g.

Colloidal silica (SiO ₂ ) and alumina sol (Al ₂ O ₃ ) were used as the hydrophilic material, and silica sol was used as the holding material. In the hydrophilic material, the mass ratio of alumina sol to colloidal silica was 90:10. That is, the hydrophilic material contains 80% by mass of alumina sol (Al ₂ O ₃ ). Specifically, IPA-ST-UP was used as colloidal silica, Alumina Sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the silica sol.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this example had a small specific gravity difference of 0.03 as the electrolyte, and was evaluated as B, indicating that stratification was suppressed. In addition, the lead storage battery according to this example had an internal resistance of 103, which was evaluated as A, and it was found that an increase in the internal resistance could be suppressed.

(Comparative Example 1)
The lead acid battery according to Comparative Example 1 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below.

  In the lead storage battery according to this comparative example, the film body 8 was not provided around the negative electrode plate 5. The lead acid battery according to this comparative example has an extremely large specific gravity difference of 0.08, which is evaluated as D, and it has been found that stratification cannot be suppressed. Moreover, since the lead acid battery according to this comparative example does not have the porous film 8 around the negative electrode plate 5, the internal resistance is 100, which is an evaluation standard.

  From this comparative example and Examples 1 to 5, it was confirmed that by providing the film body 8 around the negative electrode plate 5, the specific gravity difference of the electrolytic solution can be reduced and the stratification of the electrolytic solution can be suppressed.

(Comparative Example 2)
The lead acid battery according to Comparative Example 2 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below.

In the lead storage battery according to this example, a film body 8 having a porosity of 95% and a fiber diameter of 20 μm was arranged with respect to the negative electrode plate 5. Only colloidal silica (SiO ₂ ) was used as the hydrophilic material, and silica sol was used as the holding material. That is, the hydrophilic material contains 100% by mass of colloidal silica (SiO ₂ ). Specifically, colloidal silica IPA-ST-UP manufactured by Nissan Chemical Industries, Ltd. was used as colloidal silica, and Colcoat PX manufactured by Colcoat was used as the support material.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid component of the hydrophilic material 10 (X) and the support material 11 (Y) was 80:20. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this comparative example was evaluated C when the specific gravity difference of the electrolyte was 0.05, and the internal resistance was evaluated B at 105. In this comparative example, it was suggested that the electrolyte solution was slightly inferior in terms of suppression of stratification.

(Comparative Example 3)
The lead acid battery according to Comparative Example 3 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below. In the lead storage battery according to this example, a film body 8 having a porosity of 90% and a fiber diameter of 8 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 14 m ² / g.

Colloidal silica (SiO ₂ ) and alumina sol (Al ₂ O ₃ ) were used as the hydrophilic material, and silica sol was used as the holding material. In the hydrophilic material, the mass ratio of alumina sol to colloidal silica was 80:20. That is, the hydrophilic material contains 80% by mass of alumina sol (Al ₂ O ₃ ). Specifically, IPA-ST-UP was used as colloidal silica, Alumina Sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the silica sol.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this comparative example had a large specific gravity difference of 0.05, which was evaluated as C, and the internal resistance was evaluated as 104, which was evaluated as A. In this comparative example, it was suggested that the electrolyte solution was slightly inferior in terms of suppression of stratification.

(Comparative Example 4)
The lead acid battery according to Comparative Example 4 has the same configuration as that of the lead acid battery according to Example 1, except for the following points. Only the differences will be described below. In the lead storage battery according to this example, a film body 8 having a porosity of 80% and a fiber diameter of 20 μm was arranged with respect to the negative electrode plate 5. The specific surface area of the film body 8 was 9 m ² / g.

Colloidal silica (SiO ₂ ) and alumina sol (Al ₂ O ₃ ) were used as the hydrophilic material, and silica sol was used as the holding material. In the hydrophilic material, the mass ratio of alumina sol to colloidal silica was 80:20. That is, the hydrophilic material contains 80% by mass of alumina sol (Al ₂ O ₃ ). Specifically, IPA-ST-UP was used as colloidal silica, Alumina Sol AS-200 manufactured by Nissan Chemical Industries, Ltd. was used as the alumina sol, and Colcoat PX manufactured by Colcoat was used as the silica sol.

  The hydrophilic material 10 and the support material 11 were mixed so that the mass ratio (X: Y) of the solid components of the hydrophilic material 10 (X) and the support material 11 (Y) was 90:10. A hydrophilic paint was prepared by diluting this mixed solution with ethanol so that the concentration of the solid component was 5% by mass.

  The lead acid battery according to this comparative example had a large specific gravity difference of 0.05, which was evaluated as C, and its internal resistance was evaluated as 105. In this comparative example, it was suggested that the degree of stratification inhibition is slightly inferior.

  From the above results, it was found that the lead-acid battery according to this comparative example cannot achieve both suppression of stratification and suppression of increase in internal resistance. Further, according to this comparative example and Examples 1 to 4, by arranging the film body 8 having the hydrophilic film 9 formed on the base material 18 in the vicinity of the negative electrode, it is possible to achieve both suppression of stratification and suppression of increase in internal resistance. It was confirmed.

  About the above-mentioned Example, durability of the hydrophilic film was confirmed with the following method.

  After forming the hydrophilic film, it was immersed in an aqueous sulfuric acid solution having the same concentration as the electrolytic solution for 24 hours. Then, it washed with water and measured the contact angle.

  Here, the contact angle was measured by a general droplet method. The solvent used was 33% by mass sulfuric acid aqueous solution (electrolyte concentration), and the dropping amount was 1.0 microliter. The surface of the same sample was measured five times, and an average value of N = 3 excluding the minimum value and the maximum value was calculated.

  Then, when hydrophilicity equal to or higher than that before dipping in sulfuric acid was obtained, that is, after dipping in sulfuric acid, when the contact angle was less than that before dipping in sulfuric acid, it was judged to be durable.

  In the case of the above Examples, it was confirmed that there was no change in hydrophilicity and there was durability.

  On the other hand, when it was larger than the contact angle before being immersed in sulfuric acid, it was judged that durability was low.

  On the other hand, when dry-type surface treatment was applied to the nonwoven fabric as in the past, it was confirmed that the hydrophilicity of the surface after sulfuric acid immersion was lowered, that is, the durability was low because the surface was easily changed.

  In addition, this invention is not limited to said Example, Various modifications are included. For example, the above-described embodiments are described in detail for easy understanding of the present invention, and the present invention is not necessarily limited to an aspect including all the configurations described.

  1: battery case, 2: terminal, 3: pole column, 4: electrode group, 5: negative electrode plate, 6: separator, 7: positive electrode plate, 8: film body, 9: hydrophilic film, 10: hydrophilic material, 11: Retainer material, 18: base material, 100: lead acid battery.

Claims (8)

A positive electrode plate;
A negative electrode plate;
A separator disposed between the positive electrode plate and the negative electrode plate;
An electrolyte,
A battery case for housing these,
A film body is attached to the surface of the negative electrode plate,
The film body includes a base material, and a hydrophilic film covering the surface of the base material,
The hydrophilic film includes a hydrophilic material and a holding material,
The hydrophilic material is alumina or silica,
The holding material is acrylamide, silica sol or silane coupling agent,
The fiber diameter of the substrate is smaller than 10 μm,
The lead acid battery in which the porosity of the base material is smaller than 90%. The surface of the substrate has a hydrophobic functional group,
The lead-acid battery according to claim 1, wherein the holding material is a silane coupling agent having a vinyl group, a methacryl group, an acrylic group, or a styryl group. The surface of the substrate has a hydrophilic functional group,
The lead-acid battery according to claim 1, wherein the holding material is a silane coupling agent having an amino group or an epoxy group.   The lead acid battery according to any one of claims 1 to 3, wherein the hydrophilic material is made of alumina or silica alone or a mixture of alumina and silica.   The lead acid battery according to any one of claims 1 to 4, wherein the hydrophilic film has a mass ratio of a solid component between the hydrophilic material and the support material of 90:10 to 70:30.   The lead acid battery according to any one of claims 1 to 5, wherein the hydrophilic film has a thickness of 10 nm to 1000 nm.   The lead acid battery according to any one of claims 1 to 6, wherein the film body has a thickness of 0.03 mm to 0.1 mm.   The lead acid battery according to any one of claims 1 to 7, wherein the hydrophilic film is formed on a surface of the separator.

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