Positive electrode for lead-acid battery

Abstract

To provide a positive electrode for a lead-acid battery that can be fully discharged and recharged even after a long period of non-use without the positive electrode active material falling off.SOLUTION: A positive electrode for a lead-acid battery includes a positive electrode current collector and a positive electrode active material layer, the positive electrode current collector contains a substance that suppresses a local cell reaction on a surface thereof, and the positive electrode active material layer contains a positive electrode active material and a sugar.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a positive electrode for a lead storage battery and a lead storage battery using the same.

Background Art

[0002] Lead storage batteries have stable quality and economy, and are mainly used as automobile batteries, accounting for nearly 30% of the secondary battery production value in Japan. In particular, high-performance lead storage batteries are indispensable for hybrid cars and idling stop cars that are being put into practical use in recent years, and the demand for lead storage batteries is increasing rapidly. In addition, in recent years, research for power storage has been active. Lead storage batteries have a long history since their development to the present, but there are still unclear points regarding the reactions inside the battery.

[0003] If a lead storage battery is over-discharged, subsequent charging becomes difficult, so it is necessary to charge before completely discharging. Also, in lead storage batteries, the positive electrode active material easily falls off from the battery. For example, depending on the shape of the positive electrode current collector, it may fall off from the manufacturing stage, and also, the positive electrode active material is deformed and falls off by repeating charge and discharge, so charge and discharge cannot be continued. For this reason, at present, lead storage batteries can only be effectively used to about 10% or less of the theoretical capacity.

[0004] For the lead storage battery as described above, as the positive electrode, usually, a layer of lead oxide is formed as the positive electrode active material on lead as the positive electrode current collector, and the reaction formula during charge and discharge is as follows: Positive electrode: PbO2 + 4H + + SO4 2- + 2e - ⇔ PbSO4 + 2H2O Negative electrode: Pb + SO4 2- ⇔ PbSO4 + 2e - It is represented as follows.

[0005] PbO2, which is used as a positive electrode active material, exists in the form of α-PbO2 and β-PbO2. It is known that in a region with a low pH (acidic region), it exists as β-PbO2, and in a region with a high pH (alkaline region), it exists as α-PbO2. Since an aqueous sulfuric acid solution is usually used as the electrolyte of a lead-acid battery, charge and discharge are carried out in a state with a low pH, so it is expected that β-PbO2 exists. However, it is actually known that α-PbO2 and β-PbO2 coexist. However, the relationship between the coexistence of α-PbO2 and β-PbO2 and the inability to fully utilize the theoretical capacity remains unclear.

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described above, in a lead-acid battery, it is difficult to say that the theoretical capacity is fully utilized. Therefore, if the positive electrode active material does not fall off and can be charged and discharged even after sufficient discharge, it is expected to increase the capacity that can be effectively utilized. From such a perspective, an object of the present invention is to provide a positive electrode for a lead-acid battery that can be charged again even after sufficient discharge and long-term stop without the positive electrode active material falling off.

Means for Solving the Problems

[0007] As a result of intensive research, the inventors of the present invention have found that a local battery reaction occurs between PbO2 (especially β-type PbO2), which is a positive electrode active material, and lead, which is a positive electrode current collector, when the lead-acid battery is in an open circuit state (when not in use). Specifically, it has been found that β-type PbO2 serves as the positive electrode and lead serves as the negative electrode, and the battery reaction occurs to generate α-type PbO2, which has an adverse effect on the performance of the lead-acid battery. The inventors of the present invention use a positive electrode current collector having a substance for suppressing the local battery reaction on the surface, and also include not only the positive electrode active material but also saccharides in the positive electrode active material layer, so that the local battery reaction during the open circuit is suppressed, and thus it is possible to charge again even after sufficient discharge and long-term stop, and it has also been found that the positive electrode active material does not fall off even when charge and discharge are repeated. The inventors of the present invention have further conducted research and completed the present invention. That is, the present invention includes the following configurations.

[0008] Item 1. A positive electrode for a lead-acid battery, comprising a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode current collector contains a substance for suppressing a local battery reaction on the surface, and the positive electrode active material layer contains a positive electrode active material and saccharides. Positive electrode for a lead-acid battery.

[0009] Item 2. The positive electrode for a lead-acid battery according to Item 1, wherein the positive electrode active material layer contains 2.0 to 15.0% by mass of saccharides based on a total amount of 100% by mass.

[0010] Item 3. The positive electrode for a lead-acid battery according to Item 1 or 2, wherein the positive electrode active material layer contains 70.0 to 95.0% by mass of the positive electrode active material based on a total amount of 100% by mass.

[0011] Item 4. The positive electrode current collector is composed of a positive electrode current collector layer containing a substance for suppressing the local battery reaction, or coated with a coating layer containing a substance for suppressing the local battery reaction. The positive electrode for a lead-acid battery according to any one of Items 1 to 3.

[0012] Item 5. The positive electrode for a lead storage battery according to any one of Items 1 to 4, wherein the substance that suppresses the local battery reaction is a substance that suppresses the local battery reaction during open circuit. Item 6. The positive electrode for a lead storage battery according to any one of Items 1 to 5, wherein the substance that suppresses the local battery reaction is a substance having an electrode potential higher than -0.75 V compared to the positive electrode active material in the positive electrode active material layer.

[0013] Item 7. The positive electrode for a lead storage battery according to Item 6, wherein the substance that suppresses the local battery reaction is at least one selected from the group consisting of gold, platinum, palladium, and iridium.

[0014] Item 8. The positive electrode for a lead storage battery according to any one of Items 1 to 5, wherein the substance that suppresses the local battery reaction is a substance electrochemically inert to sulfuric acid.

[0015] Item 9. The positive electrode for a lead storage battery according to Item 8, wherein the substance that suppresses the local battery reaction is a carbon material and / or a polymer compound.

[0016] Item 10. The positive electrode for a lead storage battery according to Item 9, wherein the carbon material contains graphite and / or carbon black.

[0017] Item 11. The positive electrode for a lead storage battery according to any one of Items 4 to 10, wherein the positive electrode current collector layer or the coating layer contains 30 to 70% by mass of a conductive carbon material based on a total amount of 100% by mass.

[0018] Item 12. The positive electrode for a lead storage battery according to any one of Items 4 to 12, wherein the positive electrode current collector layer or the coating layer contains 30 to 70% by mass of a polymer compound based on a total amount of 100% by mass.

[0019] Item 13. The positive electrode for a lead storage battery according to any one of Items 1 to 12, wherein the positive electrode active material contains lead oxide.

[0020] Item 14. A lead storage battery including the positive electrode for a lead storage battery according to any one of Items 1 to 13.

Advantages of the Invention

[0021] According to the present invention, by using a positive electrode current collector having a substance for suppressing local battery reaction on its surface and including not only a positive electrode active material but also a saccharide in the positive electrode active material layer, the local battery reaction during open circuit is suppressed, so that it can be fully discharged and recharged even after being stopped for a long time, and the positive electrode active material does not fall off even when charge and discharge are repeated.

Brief Description of Drawings

[0022]

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Modes for Carrying Out the Invention

[0023] In this specification, "contain" is a concept encompassing any of "comprise", "consist essentially of", and "consist of".

[0024] In this specification, when a numerical range is expressed as A to B, it indicates A or more and B or less.

[0025] 1. Positive electrode for lead-acid battery The positive electrode for a lead-acid battery of the present invention includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector contains a substance on its surface that suppresses the local battery reaction, and the positive electrode active material layer contains a positive electrode active material and a saccharide.

[0026] (1-1) Positive electrode current collector As described above, the positive electrode current collector contains a substance on its surface that suppresses the local battery reaction (particularly, the local battery reaction that occurs between the positive electrode current collector and the positive electrode active material). Specifically, it preferably consists of a positive electrode current collector layer containing a substance that suppresses the local battery reaction (particularly, the local battery reaction that occurs between the positive electrode current collector and the positive electrode active material), or is coated with a coating layer containing a substance that suppresses the local battery reaction (particularly, the local battery reaction that occurs between the positive electrode current collector and the positive electrode active material). In order to suppress this local battery reaction, it is preferable that the substance that suppresses the local battery reaction does not contain a substance having an electrode potential that is lower and more base than the electrode active material. Thus, by consisting of a positive electrode current collector layer containing a substance that suppresses the local battery reaction (particularly, the local battery reaction that occurs between the positive electrode current collector and the positive electrode active material), or being coated with a coating layer containing a substance that suppresses the local battery reaction (particularly, the local battery reaction that occurs between the positive electrode current collector and the positive electrode active material), during open circuit, for example, when the battery is not in use, the generation of a local battery with the positive electrode active material (particularly lead oxide) as the positive electrode and the electrode current collector (particularly lead, etc.) as the negative electrode can be controlled, and deterioration of the battery due to the local battery reaction can be suppressed.

[0027] As such a configuration of the positive electrode current collector, it preferably comprises a positive electrode current collector layer made of a substance having an electrode potential not lower than that of the electrode active material and / or a substance electrochemically inert to sulfuric acid, or is coated with a coating layer made of a substance having an electrode potential not lower than that of the electrode active material and / or a substance electrochemically inert to sulfuric acid. Further, when using a conductive assistant, an additive, etc., the conductive auxiliary material, the additive, etc. also preferably consist of a substance having an electrode potential not lower than that of the electrode active material and / or a substance electrochemically inert to sulfuric acid, or is coated with a coating layer made of a substance having an electrode potential not lower than that of the electrode active material and / or a substance electrochemically inert to sulfuric acid. By adopting such a configuration, more surely, during open circuit, the reaction of the local battery with the positive electrode active material (such as lead oxide) as the positive electrode and the positive electrode current collector (such as lead) as the negative electrode can be suppressed, and thus the deterioration of the electrode material due to the local battery reaction can be suppressed, and the durability and capacity can be improved.

[0028] In this specification, the "substance having an electrode potential not lower than that of the electrode active material" is not limited to only a substance having an electrode potential not significantly lower than that of the electrode active material, but also includes a "substance electrochemically inert to sulfuric acid".

[0029] Such substances are not particularly limited, but substances having an electrode potential higher than -0.75 V are preferred, substances having an electrode potential higher than -0.50 V are more preferred, and substances having an electrode potential higher than -0.25 V are even more preferred, compared with the electrode active material. Also, a "substance electrochemically inert to sulfuric acid" can be preferably used. Conversely, as a "substance having an electrode potential significantly lower than that of the electrode active material", it is preferably free of substances having an electrode potential equal to or lower than -0.75 V compared with the electrode active material. Specifically, compared with PbO2 (+1.69 V vs SHE), which is usually used as the positive electrode active material of a lead-acid battery, gold, platinum, palladium, iridium, etc. having an electrode potential higher than -0.75 V are preferred, gold, platinum, etc. having an electrode potential higher than -0.50 V are preferred, and gold having an electrode potential higher than -0.25 V is more preferred.

[0030] On the one hand, it is preferable that lithium, potassium, titanium, zinc, iron, nickel, copper, rhodium, silver, etc., whose potential is lower than -0.75V compared to PbO2 commonly used as the positive electrode active material of a lead-acid battery, are not present on the surface of the electrode current collector. Further, when using a conductive aid, an additive, etc., it is also preferable that these substances are not present on the surface of the conductive aid, the additive, etc.

[0031] Note that the standard electrode potential of each substance is, respectively, lithium (Li + +e - →Li; -3.04V vs SHE), potassium (K + +e - →K; -2.925V vs SHE), titanium (Ti 2+ +2e - →Ti; -1.63V vs SHE), zinc (Zn 2+ +2e - →Zn; -0.763V vs SHE), iron (Fe 2+ +2e - →Fe; -0.440V vs SHE), nickel (Ni 2+ +2e - →Ni; -0.257V vs SHE), copper (Cu 2+ +e - →Cu + ; +0.337V vs SHE), rhodium (Rh 3+ +3e - →Rh; +0.758V vs SHE), silver (Ag + +e - →Ag; +0.799V vs SHE), palladium (Pd 2+ +2e - →Pd; +0.987V vs SHE), iridium (Ir 3+ +3e - →Ir; +1.156V vs SHE), platinum (Pt 2+ +2e - →Pt; +1.188V vs SHE), gold (Au + +e - →Au; +1.83V vs SHE).

[0032] In addition, as the "substance electrochemically inert to sulfuric acid," carbon materials, polymer compounds, etc. can preferably be used.

[0033] The carbon material is not particularly limited, and carbon blacks such as channel black, furnace black, ketjen black, acetylene black, and lamp black; graphite (expanded graphite sheets, isotropic graphite, etc.) such as natural graphite, artificial graphite, and expanded graphite; activated carbon; amorphous carbon, etc. can preferably be adopted.

[0034] The polymer compound is not particularly limited, but it is preferable to use a polymer compound that is inert to lead oxide which is the positive electrode active material and sulfuric acid which is the electrolyte. The polymer compound originally functions as a binder and is included for the purpose of improving the adhesiveness between the positive electrode current collector and the positive electrode active material layer. By using a polymer compound that is inert to lead oxide which is the positive electrode active material and sulfuric acid which is the electrolyte, it is possible to impart sulfuric acid non-wettability and further suppress the deterioration of the lead storage battery. Examples of such polymer compounds include phenolic resins, rubber-based resins, polyolefin resins, polyethylene terephthalate resins (PET resins), acrylonitrile-butadiene-styrene resins (ABS resins), polyvinylidene fluoride resins (PVDF resins), polytetrafluoroethylene resins (PTFE resins), polyethersulfone resins (PES resins), conductive polymers (especially conductive organic polymers), etc. The phenolic resin is not particularly limited, and examples include novolac-type phenolic resins, resol-type phenolic resins, xylene resin-modified resol-type resins, rosin-modified phenolic resins, etc. Examples of the rubber-based resin include styrene-butadiene resins which are diene-based rubbers and ethylene-propylene-diene resins which are non-diene-based rubbers. Examples of the polyolefin resin include polyethylene resins, polypropylene resins, etc. The conductive polymer is not particularly limited, and polythiophene, polyacetylene, polyaniline, polypyrrole, polythiazyl, etc. can preferably be adopted.

[0035] These substances can be used alone or in combination of two or more.

[0036] In the case of employing a positive electrode current collector coated with a coating layer containing a substance having an electrode potential not lower than that of the positive electrode active material and / or a substance electrochemically inert to sulfuric acid, the central portion other than the surface may be a substance having an electrode potential not lower than that of the positive electrode active material, or may be a substance having an electrode potential lower than that of the positive electrode active material, or may also be a substance electrochemically inert to sulfuric acid. That is, even if it is a substance having an electrode potential lower than that of the positive electrode active material, if a layer composed of a substance having an electrode potential not lower than that of the positive electrode active material and / or a substance electrochemically inert to sulfuric acid is formed on its surface, it can be used as a positive electrode current collector. At this time, "forming a layer composed of a substance having an electrode potential not lower than that of the positive electrode active material and / or a substance electrochemically inert to sulfuric acid on the surface" means that the surface may be completely coated with a coating layer containing the above specific substance, or it is not necessary to be completely coated with a coating layer, and the case where the above specific substance is scattered on the surface is also included. Therefore, by using an inexpensive material as the central portion of the positive electrode current collector and forming a coating layer containing a substance having an electrode potential not lower than that of the positive electrode active material and / or a substance electrochemically inert to sulfuric acid on its surface, the positive electrode for a lead-acid battery of the present invention can be manufactured at a lower cost. However, also in this case, considering the corrosion resistance to sulfuric acid, it is preferable to use lead, gold, palladium, platinum, etc. for the central portion other than the surface. Also, considering the corrosion resistance to sulfuric acid, an alloy of lead and at least one of tin, silver, etc. can also be employed. Also, it is possible to use a carbon sheet.

[0037] When such a coating layer contains a substance (such as the above-mentioned metal species) having an electrode potential not much lower than that of the electrode active material, it can also be composed only of a substance (such as the above-mentioned metal species) having an electrode potential not much lower than that of the electrode active material. In this case, a metal sheet, metal plating, metal vapor deposition film, etc. can also be adopted. Further, when the coating layer contains a substance (carbon material, polymer compound, etc., particularly a polymer compound) electrochemically inert to sulfuric acid, it can further contain an amount of conductive carbon agent.

[0038] The conductive carbon material used at this time is a substance inert to sulfuric acid as the electrolyte, and no local battery reaction occurs between the central part of the above-mentioned positive electrode current collector and lead oxide which is the positive electrode active material to be described later. Therefore, by including a conductive carbon material in the coating layer, it is easy to suppress the local battery reaction during open circuit, and it is easy to recharge again even after sufficient discharge and long-term stop. There is no particular limitation on such a conductive carbon material, and carbon blacks such as channel black, furnace black, ketjen black, acetylene black, and lamp black; graphite (expanded graphite sheet, isotropic graphite, etc.) such as natural graphite, artificial graphite, and expanded graphite; activated carbon; amorphous carbon, etc. can be preferably adopted. These conductive carbon materials can be used alone or in combination of two or more.

[0039] The content of the conductive carbon material is not particularly limited. From the viewpoint of more easily suppressing the local battery reaction during open circuit and more easily improving the conductivity, when the total amount of the coating layer is 100% by mass, the content of the conductive carbon material is preferably 30 to 70% by mass, and more preferably 40 to 60% by mass. When a plurality of conductive carbon materials are contained, it is preferable to adjust the total amount so as to be within the above range. When carbon black is contained as the conductive carbon material, from the viewpoint of more easily suppressing the local battery reaction during open circuit and more easily improving the conductivity, its content is preferably 5 to 20% by mass, and more preferably 7 to 15% by mass when the total amount of the coating layer is 100% by mass. When graphite is contained as the conductive carbon material, from the viewpoint of more easily suppressing the local battery reaction during open circuit and more easily improving the conductivity, its content is preferably 10 to 65% by mass, and more preferably 25 to 55% by mass when the total amount of the coating layer is 100% by mass.

[0040] Also, the content of the polymer compound is not particularly limited. From the viewpoint of more easily suppressing the local battery reaction during open circuit and more easily improving the conductivity, when the total amount of the coating layer is 100% by mass, the content of the polymer compound is preferably 30 to 70% by mass, and more preferably 40 to 60% by mass. When a plurality of polymer compounds are contained, it is preferable to adjust the total amount so as to be within the above range.

[0041] The thickness of the layer composed of a substance having an electrode potential not greater and not lower than that of the positive electrode active material and / or a substance electrochemically inert to sulfuric acid is not particularly limited, but from the viewpoint of more easily suppressing the deterioration of the electrode material due to the local battery reaction and more easily improving the capacity, durability, etc., it is preferably 5 nm to 10 mm, and more preferably 10 nm to 1 mm.

[0042] The shape of such a positive electrode current collector is not particularly limited, and any of a lattice shape, a thin plate shape, a cylindrical shape (circular column shape), etc. can be adopted. Among them, the lattice shape is preferable from the viewpoint of being easy to hold and easy to secure a conductive path.

[0043] The thickness of such a positive electrode current collector can be appropriately adjusted from the viewpoint of functioning as a support for the positive electrode active material layer described later.

[0044] The method for forming a layer composed of a substance having an electrode potential not lower and not nobler than that of the positive electrode active material and / or a substance electrochemically inert to sulfuric acid on the surface of the positive electrode current collector is not particularly limited. For example, a coating method, a plating method, a vapor deposition method, etc. can be adopted. When adopting the coating method, for example, roller coating such as an applicator roll; screen coating; doctor blade method; spin coating; means such as a bar coater can be used for coating. For example, a paint containing a conductive carbon material, a polymer compound, and an organic solvent can be obtained by coating it on a metal material or the like, for example, at the center of the positive electrode current collector, and drying it by a conventional method. The organic solvent that can be used at this time is not particularly limited, and a wide range of general organic solvents can be used. When using a phenol resin as the polymer compound, ether solvents such as butyl carbitol, diisopropyl ether, butyl cellosolve, tetrahydrofuran, dioxane, etc. are preferable. When using a rubber-based resin as the polymer compound, xylene, toluene, etc. are preferable from the viewpoint of solubility, and xylene is more preferable. When adopting the plating method, either electrolytic plating or electroless plating may be used.

[0045] Note that the paint containing a conductive carbon material, a polymer compound, and an organic solvent can be manufactured by mixing each component, but it is also possible to use a commercially available paint containing a conductive carbon material, a polymer compound, and an organic solvent. Specific examples of such commercially available products include, when using a phenol resin as the polymer compound, Ebrium T-30PLB-UL(BC) manufactured by Nippon Carbon Co., Ltd., Ebrium T-30PLB-U manufactured by Nippon Carbon Co., Ltd., and the like.

[0046] In the present invention, the positive electrode current collector can be manufactured as a new product, or it is also possible to take out the positive electrode current collector from a commercially available lead storage battery which is a ready-made product and form a coating layer thereon as described above.

[0047] The above-described positive current collector can be used as it is, or can be laminated on another base material. In particular, even when the thickness of the positive current collector is thinner than the above-described range, it is also possible to use it by laminating it on another base material. For example, when the thickness of the positive current collector is thin (about 1 μm to 0.1 mm) and it is difficult to stand alone as a support for the positive electrode active material layer described later, it is preferable to laminate it on another base material. Examples of such other base materials include ceramics such as alumina; polymers such as polyethersulfone resin. The thickness of such other base materials is preferably about 0.1 mm to 10 mm.

[0048] (1-2) Positive electrode active material layer The positive electrode for a lead storage battery of the present invention has a positive electrode active material layer containing lead oxide and a saccharide formed on the above-described positive current collector (when the positive current collector is coated with a coating layer, on the coating layer). As described above, the substance that suppresses the local battery reaction contained in the positive current collector can suppress the local battery reaction (especially the local battery reaction during open circuit) between the positive current collector and the positive electrode active material layer. Therefore, it is possible to suppress the generation of α-type PbO2 due to the local battery reaction during open circuit, and it is possible to charge and discharge again even after sufficient discharge and long-term stop (open circuit). Further, when a polymer compound is contained in the coating layer, the adhesion between the positive current collector and the positive electrode active material layer can be improved by its action.

[0049] In the lead storage battery of the present invention, it is preferable to employ lead oxide (lead monoxide (PbO), lead dioxide (PbO2), etc.) that has been conventionally used as the positive electrode active material contained in the positive electrode active material layer. The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but it is easy to suppress the deterioration of the electrode material due to the local battery reaction, and it is easy to improve the capacity, durability, etc. From the viewpoint that the positive electrode active material layer is not easily detached from the positive current collector, when the total amount of the positive electrode active material layer is 100% by mass, 70 to 95% by mass is preferable, and 85 to 95% by mass is more preferable.

[0050] The saccharides are not particularly limited, and monosaccharides, disaccharides, oligosaccharides, polysaccharides, sugar alcohols, etc. can be used without limitation. Specifically, glucose, fructose, sucrose, lactose, maltose, trehalose, isomaltooligosaccharide, galactooligosaccharide, fructooligosaccharide, palatinose, lactosucrose, glycosylsucrose, nigerooligosaccharide, cyclodextrin, gentiooligosaccharide, xylooligosaccharide, lactulose, raffinol, sorbitol, erythritol, xylitol, maltitol, mannitol, lactitol, reduced palatinose, etc. can be used. These saccharides can be used alone or in combination of two or more.

[0051] From the viewpoint of easily improving the capacity, durability, etc. and making the positive electrode active material layer less likely to peel off from the positive electrode current collector, the content of the saccharide in the positive electrode active material layer is preferably 2.0 to 15.0% by mass, more preferably 3.0 to 10.0% by mass, with the total amount of the positive electrode active material layer being 100% by mass.

[0052] In the present invention, a conductive assistant can also be included in the positive electrode active material layer. As the conductive assistant, an electron conductive material and a material in which a local battery reaction hardly occurs (a substance electrochemically inert to lead oxide and sulfuric acid) are preferably employed. Specifically, graphite such as natural graphite and artificial graphite (isotropic graphite, etc.); carbon black; acetylene black; ketjen black; carbon whiskers; carbon fibers; conductive materials such as vapor-grown carbon can be included as one kind or a mixture thereof. The content of the conductive assistant in the positive electrode active material layer is not particularly limited, and from the viewpoint of easily suppressing the deterioration of the electrode material due to the local battery reaction, easily improving the capacity, durability, etc., and making the positive electrode active material layer less likely to peel off from the positive electrode current collector, the content is preferably 1.0 to 35.0% by mass, more preferably 2.0 to 20.0% by mass, with the total amount of the positive electrode active material layer being 100% by mass.

[0053] In addition, the positive electrode active material layer can also contain a binder, a thickener, etc. in addition to the above components. In the present invention, since the saccharide also functions as a binder, it is not necessary to separately use a binder.

[0054] As the binder, usually, thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene, and polypropylene; polymers having rubber elasticity such as ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber can be used as one or a mixture of two or more.

[0055] As the thickener, usually, polysaccharides such as carboxymethyl cellulose and methyl cellulose can be used as one or a mixture of two or more.

[0056] When using a binder and / or a thickener, the content of the binder and the thickener in the positive electrode active material layer is not particularly limited. From the viewpoint of easily suppressing the deterioration of the electrode material due to the local battery reaction, easily improving the capacity, durability, etc., and the positive electrode active material layer being difficult to peel off from the positive electrode current collector, taking the total amount of the positive electrode active material layer as 100% by mass, the total amount of the binder and the thickener is preferably 0.1 to 15% by mass, and more preferably 0.5 to 10% by mass.

[0057] The mixing method of these components is physical mixing, and uniform mixing is preferred. Therefore, it is possible to use powder mixers such as V-type mixers, S-type mixers, kneaders, ball mills, planetary ball mills, etc. in a dry or wet manner.

[0058] In the present invention, the method for forming the positive electrode active material layer is not particularly limited. For example, various components such as the positive electrode active material are mixed with water to prepare a paste composition for forming the positive electrode active material layer, and then the paste composition is impregnated or coated on the carbon-containing layer and dried.

[0059] Regarding the coating method, for example, roller coating such as an applicator roll; screen coating; doctor blade method; spin coating; bar coater; dip coating and other means can be used for coating. Also, the drying conditions are not particularly limited and can be employed within the range usually adopted in lead-acid batteries.

[0060] In the present invention, the positive electrode active material layer can be manufactured as a new product, or it is also possible to take out the positive electrode active material layer from a commercially available lead-acid battery which is a ready-made product.

[0061] 2. Lead-acid battery The lead-acid battery of the present invention includes the positive electrode for a lead-acid battery of the present invention.

[0062] Examples of members other than the positive electrode include a negative electrode for a lead-acid battery, an electrolyte for a lead-acid battery, a separator for a lead-acid battery, etc. These may be appropriately manufactured ones, or commercially available products, and members and materials in known lead-acid batteries can be adopted.

[0063] In the present invention, members other than the positive electrode can be manufactured as new products, or it is also possible to take them out from a commercially available lead-acid battery which is a ready-made product.

Examples

[0064] Hereinafter, the present invention will be described in more detail by giving examples and comparative examples. Note that the present invention is not limited to the following examples.

[0065] Example 1: Positive electrode for lead-acid battery with nominal voltage of 2V The lead grid (made in China) which is a positive electrode current collector was prepared in a lattice shape with the thickness of the lattice frame being 1.2 mm ± 0.1 mm and the thickness being 2.5 mm.

[0066] As a raw material for forming the carbon-containing layer, conductive paint EBLIOHM T-30PLB-UL(BC) (total of 50% by mass of flaky graphite and acetylene black, 50% by mass of phenolic resin, 300% by mass of butyl carbitol; viscosity 109.5 mPa·s; electrical resistance value 40.8 Ω / sq) manufactured by Nippon Carbon Co., Ltd. was used. The above lead grid was immersed in this conductive paint for several seconds, and butyl carbitol was evaporated and dried at 150 °C for 30 minutes, and then dip-coated on the lead serving as the positive electrode current collector so that the thickness of the coating layer after drying was 0.1 to 0.2 mm.

[0067] The active material was lead dioxide, and lead dioxide, sugar, and carbon black were used. Specifically, first, 40.91 g of β-type PbO2 (lead dioxide manufactured by Johnson Matthey), 2.04 g of commercially available sugar (granulated sugar), and 2.03 g of acetylene black were added and preliminarily mixed, and then dispersed in 7.01 g of water to form a paste, and stirred and mixed for 5 minutes with a self-revolving and revolving stirring device (Mazelsstar KK-250S manufactured by Kurashiki Boseki Co., Ltd.) to prepare a paste for forming the positive electrode active material layer. This paste was filled into the grid with a spatula on the lead grid having the above coating layer, and naturally dried, and the positive electrode active material layer was adjusted so that the thickness after drying was 1 to 3 mm on the coating layer. In this way, the positive electrode for a lead storage battery of Example 1 was obtained.

[0068] For the positive electrode for a lead storage battery thus obtained, even when strongly shaken, the formed positive electrode active material layer did not fall off at all, and it was found that the positive electrode active material layer was difficult to fall off.

[0069] Example 2: Positive electrode for lead-acid battery with nominal voltage of 2V The lead grid (made in China) serving as the positive electrode current collector was prepared in a lattice shape with the thickness of the lattice ribs being 1.2 mm ± 0.1 mm and the thickness being 2.5 mm.

[0070] A gold coating layer was formed on the lead grid by conventional gold plating.

[0071] The active material was lead dioxide, and lead dioxide, sugar, and carbon black were used. Specifically, first, 40.91 g of β-type PbO2 (lead dioxide manufactured by Johnson Matthey), 2.04 g of commercially available sugar (granulated sugar), and 2.03 g of acetylene black were added and preliminarily mixed. Then, they were dispersed in 7.01 g of water to form a paste, and stirred and mixed for 5 minutes using a planetary stirrer (Mazelsstar KK-250S manufactured by Kurashiki Boseki Co., Ltd.) to prepare a paste for forming a positive electrode active material layer. This paste was filled into the grid of the above-mentioned lead grid having the gold coating layer with a spatula, dried at 100 °C for 1 hour, and the positive electrode active material layer was adjusted to have a dried thickness of 1 to 3 mm on the coating layer. In this way, the positive electrode for a lead storage battery of Example 2 was obtained.

[0072] In the positive electrode for a lead storage battery thus obtained, even when strongly shaken, the formed positive electrode active material layer did not fall off at all, and it was found that the positive electrode active material layer was difficult to fall off.

[0073] Example 3: Positive electrode for lead-acid battery with nominal voltage of 12V The lead grid (made in China), which is a positive electrode current collector, was prepared in a grid shape with a grid bar thickness of 1.2 mm ± 0.1 mm and a thickness of 2.5 mm.

[0074] A gold coating layer was formed on the lead grid by conventional gold plating.

[0075] The active material was lead dioxide. The positive electrode active material layer was taken out from a commercially available lead storage battery (YB2.5L manufactured by GS Yuasa Corporation), which is a ready-made product. Then, 15 parts by mass of a 50% by mass aqueous sugar solution (the sugar is commercially available granulated sugar) was added to 100 parts by mass of the total amount of the taken-out positive electrode active material layer, and kneaded by hand until uniform to prepare a paste for forming a positive electrode active material layer. This paste was filled into the grid of the above-mentioned lead grid having the gold coating layer with a spatula, dried at 100 °C for 1 hour, and the positive electrode active material layer was adjusted to have a dried thickness of 1 to 3 mm on the coating layer. In this way, the positive electrode for a lead storage battery of Example 3 was obtained. In the positive electrode active material layer of the obtained positive electrode for a lead storage battery of Example 3, sugar was contained in an amount of 7.5% by mass based on the total amount of 100% by mass.

[0076] The positive electrode for a lead storage battery thus obtained was found to be such that the formed positive electrode active material layer did not fall off at all even when strongly shaken, indicating that the positive electrode active material layer is difficult to fall off.

[0077] Example 4: Positive electrode for lead-acid battery with nominal voltage of 12V The lead grid (made in China), which is the positive electrode current collector, was prepared in a lattice shape with the thickness of the lattice ribs being 1.2 mm ± 0.1 mm and the thickness being 2.5 mm.

[0078] As a raw material for forming the carbon-containing layer, conductive paint Ebrium T-30PLB-UL(BC) (total of 50% by mass of flaky graphite and acetylene black, 50% by mass of phenolic resin, 300% by mass of butyl carbitol; viscosity 109.5 mPa·s; electrical resistance value 40.8 Ω / sq) manufactured by Nippon Graphite Industry Co., Ltd. was used. The above lead grid was immersed in this conductive paint for several seconds, and butyl carbitol was evaporated and dried at 150 °C for 30 minutes, and a coating layer was dip-coated on the lead that is the positive electrode current collector so that the thickness after drying is 0.1 to 0.2 mm.

[0079] The active material was lead dioxide. The positive electrode active material layer was taken out from a commercially available lead storage battery (YB2.5L manufactured by GS Yuasa Corporation), and then, 15 parts by mass of a 50% by mass aqueous sugar solution (the sugar is commercially available granulated sugar) was added to 100 parts by mass of the total amount of the taken-out positive electrode active material layer, and it was kneaded by hand until it became uniform to prepare a paste for forming the positive electrode active material layer. This paste was filled into the lattice with a spatula on the lead grid having the above coating layer, and naturally dried, and the positive electrode active material layer was adjusted so that the thickness after drying is 1 to 3 mm on the coating layer. Thus, the positive electrode for a lead storage battery of Example 4 was obtained. In addition, in the positive electrode active material layer of the obtained positive electrode for a lead storage battery of Example 4, sugar was contained at 7.5% by mass with the total amount being 100% by mass.

[0080] The positive electrode for a lead storage battery thus obtained was found to be such that the formed positive electrode active material layer did not fall off at all even when strongly shaken, indicating that the positive electrode active material layer is difficult to fall off.

[0081] Comparative Example 1: Positive electrode for lead-acid battery with nominal voltage of 12V The positive electrode was taken out from a commercially available lead storage battery (YB2.5L manufactured by GS Yuasa Corporation) which is an off-the-shelf product, and used as it is as the positive electrode for the lead storage battery of Comparative Example 1 (the positive electrode current collector is uncoated lead, and the positive electrode active material is PbO2).

[0082] However, it was found that the positive electrode for this lead storage battery was liable to have the formed positive electrode active material layer peeled off because the formed positive electrode active material layer peeled off by strong shaking.

[0083] Comparative Example 2: Positive electrode for lead-acid battery with nominal voltage of 2V The lead grid (made in China) which is the positive electrode current collector was made into a lattice shape and finished to have a grid bar thickness of 1.2 mm ± 0.1 mm and a thickness of 2.5 mm for preparation.

[0084] The active material was lead dioxide, and lead dioxide, sugar and carbon black were used. Specifically, first, 40.91 g of β-type PbO2 (lead dioxide manufactured by Johnson Matthey), 2.04 g of commercially available sugar (granulated sugar), and 2.03 g of acetylene black were added respectively and preliminarily mixed, and then dispersed in 7.01 g of water to form a slurry, and stirred and mixed for 5 minutes with a self-revolving and revolving type stirring device (Mazelsstar KK-250S manufactured by Kurashiki Boseki Co., Ltd.) to prepare a paste for forming a positive electrode active material layer. This paste was filled into the grids of the above lead grid with a spatula and naturally dried, and the thickness of the positive electrode active material layer on the lead grid was adjusted to be 1 to 3 mm after drying. In this way, the positive electrode for the lead storage battery of Comparative Example 2 was obtained.

[0085] It was found that the positive electrode for the lead storage battery thus obtained was not liable to have the formed positive electrode active material layer peeled off because the formed positive electrode active material layer did not peel off at all even by strong shaking.

[0086] Comparative Example 3: Positive electrode for lead-acid battery with nominal voltage of 12V The lead grid (made in China) which is the positive electrode current collector was made into a lattice shape and finished to have a grid bar thickness of 1.2 mm ± 0.1 mm and a thickness of 2.5 mm for preparation.

[0087] The active material was lead dioxide. The positive electrode active material layer was taken out from a commercially available lead storage battery (YB2.5L manufactured by GS Yuasa Corporation) which is an off-the-shelf product. Then, 15 parts by mass of a 50% by mass aqueous sugar solution (the sugar was commercially available granulated sugar) was added to 100 parts by mass of the total amount of the taken-out positive electrode active material layer, and it was kneaded by hand until it became uniform, to prepare a paste for forming a positive electrode active material layer. This paste was filled into the above-mentioned lead grid with a spatula to fill the grid, and naturally dried, and the thickness of the positive electrode active material layer on the lead grid was adjusted to be 1 to 3 mm after drying. In this way, a positive electrode for a lead storage battery of Comparative Example 3 was obtained. In the positive electrode active material layer of the obtained positive electrode for a lead storage battery of Comparative Example 3, sugar was contained in an amount of 7.5% by mass with the total amount being 100% by mass.

[0088] In the positive electrode for a lead storage battery thus obtained, even when strongly shaken, the formed positive electrode active material layer did not fall off at all, so it was found that the positive electrode active material layer was difficult to fall off.

[0089] Comparative Example 4: Positive electrode for lead-acid battery with nominal voltage of 2V The lead grid (made in China) which is a positive electrode current collector was prepared in a lattice shape with the thickness of the lattice frame being 1.2 mm ± 0.1 mm and the thickness being 2.5 mm.

[0090] The active material was lead dioxide, and lead dioxide and carbon black were used. Specifically, first, 40.91 g of β-type PbO2 (lead dioxide manufactured by Johnson Matthey) and 2.03 g of acetylene black were respectively added and preliminarily mixed, then dispersed in 7.01 g of water to form a slurry, and stirred and mixed for 5 minutes with a self-revolving and revolving stirring device (Mazelsstar KK-250S manufactured by Kurashiki Boseki Co., Ltd.) to prepare a paste for forming a positive electrode active material layer. This paste was filled into the above-mentioned lead grid with a spatula to fill the grid, and naturally dried, and the thickness of the positive electrode active material layer on the lead grid was adjusted to be 1 to 3 mm after drying. In this way, a positive electrode for a lead storage battery of Comparative Example 4 was obtained.

[0091] However, it was found that the positive electrode for the lead storage battery obtained in this manner was liable to have the formed positive electrode active material layer peeled off because the positive electrode active material layer peeled off.

[0092] Comparative Example 5: Positive electrode for lead-acid battery with nominal voltage of 2V The lead grid (made in China) as the positive current collector was made lattice-shaped and finished to have a grid bar thickness of 1.2 mm ± 0.1 mm and a thickness of 2.5 mm.

[0093] A gold coating layer was formed on the lead grid by conventional gold plating.

[0094] The active material was lead dioxide, and lead dioxide and carbon black were used. Specifically, first, 40.91 g of β-type PbO2 (lead dioxide manufactured by Johnson Matthey) and 2.03 g of acetylene black were added and premixed respectively, and then dispersed in 7.01 g of water to form a paste, which was stirred and mixed for 5 minutes with a self-revolving and revolving stirring device (Mazelsstar KK-250S manufactured by Kurashiki Boseki Co., Ltd.) to prepare a paste for forming a positive electrode active material layer. This paste was filled into the grids of the lead grid having the above-mentioned gold coating layer with a spatula, dried at 100 °C for 1 hour, and the thickness of the positive electrode active material layer after drying was adjusted to be 1 to 3 mm on the coating layer. Thus, a positive electrode for a lead storage battery of Comparative Example 5 was obtained.

[0095] However, it was found that the positive electrode for the lead storage battery obtained in this manner was liable to have the formed positive electrode active material layer peeled off because the positive electrode active material layer peeled off.

[0096] Production Example 1: Cell for evaluation test As the following evaluation test cells, the positive electrodes of Examples 1 to 4 and Comparative Examples 1 to 3 described above were used as the positive electrodes respectively, a lead alloy grid filled with lead powder taken out from a commercially available lead storage battery was used as the negative electrode, a 35 mass% sulfuric acid aqueous solution was used as the electrolytic solution, and the cells shown in Fig. 1 (nominal voltages of 2 V and 12 V) were fabricated. In Comparative Examples 4 to 5, since the formed positive electrode active material layer peeled off, evaluation test cells could not be fabricated.

[0097] Test Example 1: Charge and discharge test (deep discharge test) For the evaluation test cells using the positive electrodes of Examples 1 to 4 and Comparative Examples 1 to 3, charge and discharge were performed under the following conditions. For the charge and discharge test, a charge and discharge device (HJ1001SD8) manufactured by Hokuto Denko Corporation was used.

[0098] First, to stabilize the battery reaction, discharging from 0.1C to 1.8V and charging from 0.5C to 2.3V were repeated 20 cycles, and then deep discharging was performed at 0.1C until it reached 0V. After that, it was left standing for 48 hours in an open-circuit state, and then shallow (2.3V to 1.8V) charge and discharge at 0.5C were repeated 20 cycles, and then deep discharging was performed at 0.5C until it reached 0V. Furthermore, after leaving it standing for 48 hours in an open-circuit state, deep (2.3V to 0V) charge and discharge at 0.5C were repeated.

[0099] The results are shown in Figures 2 to 8. Figure 2 Example 1 (lead grid coated with phenolic resin, with sugar) Nominal voltage 2V. Figure 3 Example 2 (lead grid coated with gold, with sugar) Nominal voltage 2V. Figure 4 Comparative Example 2 (lead grid, with sugar) Nominal voltage 2V. Figure 5 Comparative Example 1 (lead, without sugar) Nominal voltage 12V. Figure 6 Example 4 (lead grid coated with phenolic resin, with sugar) Nominal voltage 12V. Figure 7 Example 3 (lead grid coated with gold, with sugar) Nominal voltage 12V. Figure 8 Comparative Example 3 (lead grid, with sugar) Nominal voltage 12V.

[0100] As a result, in Comparative Example 1, since charge and discharge were not restarted after deep discharging, it is shown that in a commercial lead-acid battery, charge and discharge cannot be performed again after sufficient discharging.

[0101] Also, as in Comparative Examples 2 to 3, when the lead current collector is used as it is, even if sugar is contained in the positive electrode active material layer, whether the nominal voltage is 2V or 12V, when deep discharge is performed and then the battery is left idle for a long time, it can be understood that sufficient charge and discharge cannot be repeated even if an attempt is made to resume charge and discharge again.

[0102] On the other hand, as in Examples 1 to 4, when the lead current collector is coated with a phenolic resin or gold so that the lead and the positive electrode active material do not come into direct contact, and sugar is contained in the positive electrode active material layer, whether the nominal voltage is 2V or 12V, when deep discharge is performed and then the battery is left idle for a long time, it is possible to resume charge and discharge again. Further, as described above, since the positive electrode active material is less likely to fall off, the durability is also excellent.

Claims

1. A positive electrode for a lead storage battery, comprising a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode current collector contains a substance for suppressing a local battery reaction on its surface, and the positive electrode active material layer contains a positive electrode active material and a saccharide. A positive electrode for a lead storage battery.

2. The positive electrode for a lead storage battery according to claim 1, wherein the positive electrode active material layer contains 2.0 to 15.0% by mass of a saccharide based on 100% by mass in total.

3. The positive electrode for a lead storage battery according to claim 1, wherein the positive electrode active material layer contains 70.0 to 95.0% by mass of a positive electrode active material based on 100% by mass in total.

4. The positive electrode current collector consists of a positive electrode current collector layer containing a substance for suppressing the local battery reaction, or is coated with a coating layer containing a substance for suppressing the local battery reaction. The positive electrode for a lead storage battery according to claim 1.

5. The positive electrode for a lead storage battery according to claim 1, wherein the substance for suppressing the local battery reaction is a substance for suppressing the local battery reaction during open circuit.

6. The positive electrode for a lead storage battery according to claim 1, wherein the substance for suppressing the local battery reaction has an electrode potential higher than -0.75 V compared to the positive electrode active material in the positive electrode active material layer.

7. The positive electrode for a lead storage battery according to claim 6, wherein the substance for suppressing the local battery reaction is at least one selected from the group consisting of gold, platinum, palladium, and iridium.

8. The positive electrode for a lead storage battery according to claim 1, wherein the substance for suppressing the local battery reaction is electrochemically inert to sulfuric acid.

9. The positive electrode for a lead storage battery according to claim 8, wherein the substance for suppressing the local battery reaction is a carbon material and / or a polymer compound.

10. The positive electrode for a lead storage battery according to claim 9, wherein the carbon material contains graphite and carbon black.

11. The positive electrode for a lead storage battery according to claim 4, wherein the positive electrode current collector layer or the coating layer contains 30 to 70% by mass of a conductive carbon material based on 100% by mass in total.

12. The positive electrode for a lead storage battery according to claim 4, wherein the positive electrode current collector layer or the coating layer contains 30 to 70% by mass of a polymer compound based on 100% by mass in total.

13. The positive electrode for a lead storage battery according to claim 1, wherein the positive electrode active material contains lead oxide.

14. A lead storage battery comprising the positive electrode for a lead storage battery according to any one of claims 1 to 13.

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