Lead-acid battery electrode and lead-acid battery using the same

Abstract

To provide an electrode for a lead-acid battery having a coating layer containing non-conductive inorganic particles on the electrode surface, thereby suppressing a decrease in the initial capacity of the battery and stratification.SOLUTION: There is provided a pair of positive and negative electrodes containing an active material for a lead-acid battery, and a coating layer containing non-conductive inorganic particles is formed on the surface of at least one of the positive and negative electrodes, the coating layer has a basis weight of 3 g / sqm or more and 100 g / sqm or less, and the mass proportion of the inorganic particles in the coating layer is 40 mass% or more and 99 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an electrode for a lead-acid battery and a storage battery using the same. [Background technology]

[0002] Lead-acid batteries are widely used worldwide in automotive applications such as passenger cars, buses, trucks, motorcycles, and golf carts, as well as industrial applications such as forklifts, farm machinery, railways, uninterruptible power supplies (UPS), and communication equipment. In particular, in recent automotive applications, lead-acid batteries are used in electric vehicles (EVs), hybrid electric vehicles (HEVs), and idling start-stop (ISS) vehicles.

[0003] When a lead-acid battery is charged, the lead sulfate in the positive and negative electrodes decomposes, releasing a high concentration of sulfate ions into the electrolyte, which can cause stratification (a phenomenon in which the sulfuric acid concentration is higher at the bottom of the battery container than at the top).Stratification is particularly likely to occur during charge-discharge cycles in a partially charged state, as the electrolyte is less likely to be stirred.Stratification accelerates the deterioration mode of lead-acid batteries, shortening their lifespan, so preventing stratification is an important issue.

[0004] Patent Document 1 proposes an electrode for a lead-acid battery that improves the cycle life, which is a technical problem for lead-acid batteries, by coating the surface of the electrode with carbon. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2014-505968 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the lead acid battery electrode described in Patent Document 1 improves the PSOC cycle life by adsorbing protons and cations using a carbon material having a capacitor function, and there is no description of improving the cycle life by suppressing stratification.

[0007] The invention of the present disclosure has been made in view of the above circumstances, and aims to provide an electrode for a lead-acid battery having a coating layer containing non-conductive inorganic particles on the electrode surface, thereby suppressing a decrease in the initial capacity of the battery and stratification. [Means for solving the problem]

[0008] The above problems are solved by the following technical means. (1) A pair of positive and negative electrodes containing an active material for a lead-acid battery, wherein a coating layer containing non-conductive inorganic particles is formed on the surface of at least one of the positive and negative electrodes, the coating layer has a basis weight of 3 g / sqm or more and 100 g / sqm or less, and the mass percentage of the inorganic particles in the coating layer is 40 mass% or more and 99 mass% or less. (2) The electrode according to item 1, wherein the non-conductive inorganic particles have a median diameter of 3 μm or more and 65 μm or less. (3) The electrode according to item 1 or 2, wherein the DOA absorption of the non-conductive inorganic particles is 110 (ml / 100 g) or more. (4) The electrode according to any one of items 1 to 3, wherein the non-conductive inorganic particles include at least one selected from the group consisting of silica, alumina, kaolin, titania, aluminum silicate, barium sulfate, and sodium aluminosilicate. (5) The electrode according to any one of items 1 to 4, wherein the non-conductive inorganic particles are silica. (6) The electrode according to any one of items 1 to 5, wherein the coating layer contains a resin binder, and the content of the resin binder in 100 parts by mass of the coating layer is 1 part by mass or more and 60 parts by mass or less. (7) A lead-acid battery including a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, wherein the lead-acid battery includes a pair of positive and negative electrodes according to any one of items 1 to 6. (8) A lead-acid battery comprising a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, wherein the electrode of the pair of positive and negative electrodes according to any one of items 1 to 6, on the surface of which is formed a coating layer containing the non-conductive inorganic particles, is disposed as the positive electrode or the negative electrode. [Effects of the Invention]

[0009] According to the present disclosure, in a lead-acid battery using an electrode having a coating layer containing non-conductive inorganic particles on the electrode surface, it is possible to provide an electrode that suppresses stratification without reducing the initial capacity of the battery. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present disclosure (hereinafter abbreviated as "the present embodiment") will be described in detail. Note that the present disclosure is not limited to the following embodiment, and can be implemented in various modifications within the scope of the gist thereof.

[0011] ≪Electrode≫ The electrode according to this embodiment is for a lead-acid battery, and is characterized in that a coating layer containing non-conductive inorganic particles is formed on the surface of at least one of the positive and negative electrodes, the coating layer having a basis weight of 10 g / sqm to 100 g / sqm, and the proportion of inorganic particles being 40% to 99%. By satisfying the above relationship, the electrode for a lead-acid battery according to this embodiment can suppress stratification without reducing the initial capacity. This embodiment also provides a pair of positive and negative electrodes containing an active material for a lead-acid battery and satisfying the above relationship. In this specification, the abbreviation "sqm" means square meter.

[0012] <Inorganic particles in the coating layer> The coating layer of the lead-acid battery electrode according to the present embodiment preferably contains inorganic particles, more preferably non-conductive inorganic particles, from the viewpoint of forming pores in the coating layer and suppressing stratification. In this specification, a coating layer containing inorganic particles may be referred to as an inorganic material coating layer or an inorganic particle-containing coating layer.

[0013] Examples of inorganic particle materials used in the coating layer include silica (amorphous silica, precipitated silica, gelled silica, fumed silica, etc.), alumina, sulfates (e.g., barium sulfate, calcium sulfate), titania (rutile type, anatase type), gibbsite, bayerite, boehmite, zirconia, magnesia, ceria, yttria, oxide-based ceramics such as zinc oxide and iron oxide; nitride-based ceramics such as silicon nitride, titanium nitride and boron nitride; silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, magnesium hydroxide, potassium titanate, talc, synthetic kaolinite, kaolin clay, kaolin (kaolinite, dickite, narcite), calcined kaolin, flybonite, stevensite, dickite, nacrite, halloysite, pyrophyllite, audinite, montmorillonite, beidellite, nontronite, boronite, and the like. Conscoite, saponite, hectorite, fluorine hectorite, sauconite, swinholdite, vermiculite, fluorine vermiculite, berthelline, sericite, amesite, keryaite, fleiponite, prindriite, bentonite, zeolite, biotite, phlogopite, fluorine phlogopite, iron mica, eastonite, taeniolite, siderophyllite, tetraferriferric mica, lepidolite, fluorine tetrasilicic mica, polylithium Examples of inorganic particles include cionite, muscovite, celadonite, ferro-celadonite, ferro-aluminoceladonite, aluminoceladonite, tobe mica, sodalite, klinite, kinoshite, vite mica, anandite, nacre, clinochlore, chamosite, pennantite, nimite, bailichlore, donbassite, cookesite, sudoite, hydrotalcite, calcium silicate, magnesium silicate, aluminum silicate, diatomaceous earth, and silica sand. The inorganic particles according to the present embodiment can be used singly or in combination of two or more.

[0014] Among the above examples, the inorganic particle material is preferably at least one selected from the group consisting of silica, alumina, kaolin, titania, aluminum silicate, barium sulfate, and sodium aluminosilicate, which have excellent acid resistance and oxidation resistance and high hydrophilicity. For example, in lead-acid batteries, maintaining a spatially uniform sulfuric acid concentration in the electrolyte is necessary to prevent stratification. To achieve a uniform sulfuric acid concentration within the battery container, it is preferable to retain sulfate ions released from the positive and negative electrodes during the battery reaction within the pores of the coating layer and prevent sulfate ion precipitation. More specifically, the inorganic particles are preferably silica, since the surfaces of the inorganic particles exhibit a positive charge in acidic solutions, thereby preventing sulfate ion precipitation through electrostatic interaction with negatively charged sulfate ions. Precipitated silica, gelled silica, or fumed silica can be used as the silica, but precipitated silica is most preferred from the standpoints of cost and ease of handling, such as ease of measuring the powder.

[0015] The inorganic particles according to this embodiment preferably have a large median diameter in order to prevent surface cracks due to aggregation of inorganic particles. Furthermore, the higher the DOA oil absorption of the inorganic particles, the more the structure of the secondary particles made up of the primary particles of the inorganic particles develops, and the more easily the resin binder is consumed inside the secondary particles. As a result, the resin binder is less likely to contribute to binding between the secondary particles, making it easier for surface cracks to occur due to aggregation of inorganic particles. Therefore, a lower DOA oil absorption is preferred.

[0016] The median diameter X (μm) of inorganic particles in this specification is determined by dispersing the inorganic particles in water and measuring them using a Microtrac-Bell MT3300EXII (optical bench) and SDC (sample circulator) under the following measurement and analysis conditions. MicrotracII measurement software is used. [Measurement conditions] SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 [Analysis conditions] Transparency: Drop Particle refractive index: 1.46 (example for silica particles) Shape: Non-spherical Solvent refractive index: 1.333 Distribution: Volume

[0017] In this specification, the DOA oil absorption (ml / 100 g) is a value measured in accordance with ISO 19246 using an absorptometer (automatic oil absorption measuring device) when inorganic particles are kneaded while being dropped with DOA (dioctyl adipate), and the amount of dropped DOA is measured when a predetermined torque value is reached.

[0018] If the median diameter of the inorganic particles is small, the coating layer becomes dense and the density increases, and the ionic resistance as a lead-acid battery electrode increases, resulting in a decrease in the initial capacity of the battery. Therefore, the median diameter is preferably 3 μm or more, more preferably 4 μm or more, even more preferably 5 μm or more, even more preferably 6 μm or more, even more preferably 7 μm or more, even more preferably 8 μm or more, even more preferably 9 μm or more, even more preferably 10 μm or more, even more preferably 11 μm or more, even more preferably 12 μm or more, even more preferably 13 μm or more, even more preferably 14 μm or more, even more preferably 15 μm or more, even more preferably 16 μm or more, even more preferably 17 μm or more, even more preferably 18 μm or more, even more preferably 19 μm or more, and still more preferably 20 μm or more.

[0019] Furthermore, if the median diameter of the inorganic particles is large, the inorganic particles are likely to fall off from the coating layer due to the expansion and contraction of the electrode during charge and discharge. Therefore, the median diameter of the inorganic particles is preferably less than 70 μm, more preferably 69 μm or less, even more preferably 68 μm or less, even more preferably 67 μm or less, even more preferably 66 μm or less, even more preferably 65 μm or less, even more preferably 66 μm or less, even more preferably 65 μm or less, even more preferably 64 μm or less, even more preferably 63 μm or less, even more preferably 62 μm or less, even more preferably 61 μm or less, even more preferably 60 μm or less, even more preferably 58 μm or less, even more preferably 56 μm or less, even more preferably 54 μm or less, or even more preferably 52 μm or less.

[0020] Furthermore, the higher the DOA oil absorption of the inorganic particles, the more developed the structure of the secondary particles made up of the primary particles of the inorganic particles becomes, and ions can more easily permeate and diffuse inside the secondary particles, thereby lowering the ionic resistance as an electrode for a lead-acid battery. Therefore, the DOA oil absorption is preferably more than 15 (ml / 100g), more preferably 30 (ml / 100g) or more, even more preferably 50 (ml / 100g) or more, even more preferably 70 (ml / 100g) or more, even more preferably 110 (ml / 100g) or more, even more preferably 130 (ml / 100g) or more, even more preferably 140 (ml / 100g) or more, even more preferably 150 (ml / 100g) or more, even more preferably 160 (ml / 100g) or more, even more preferably 170 (ml / 100g) or more, or even more preferably 180 (ml / 100g) or more.

[0021] Furthermore, the higher the DOA oil absorption of inorganic particles, the more the structure of the secondary particles made up of the primary particles of the inorganic particles develops, and the more easily the resin binder is consumed inside the secondary particles. As a result, the resin binder is less likely to contribute to binding between the secondary particles, and surface cracks are more likely to occur due to aggregation of the inorganic particles. Therefore, the DOA oil absorption is preferably 700 (ml / 100g) or less, more preferably 600 (ml / 100g) or less, even more preferably 500 (ml / 100g) or less, and even more preferably 400 (ml / 100g) or more.

[0022] From the viewpoint of forming voids capable of retaining sulfate ions in the coating layer by the inorganic particles to suppress stratification, or from the viewpoint of reducing the ionic resistance of the lead-acid battery, the content of the inorganic particles is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 55 parts by mass or more, even more preferably 60 parts by mass or more, even more preferably 61 parts by mass or more, even more preferably 62 parts by mass or more, even more preferably 65 parts by mass or more, even more preferably 70 parts by mass or more, even more preferably 71 parts by mass or more, even more preferably 72 parts by mass or more, even more preferably 73 parts by mass or more, even more preferably 74 parts by mass or more, even more preferably 75 parts by mass or more, even more preferably 76 parts by mass or more, even more preferably 77 parts by mass or more, even more preferably 78 parts by mass or more, even more preferably 79 parts by mass or more, or even more preferably 80 parts by mass or more.

[0023] Furthermore, from the viewpoint of increasing the binding strength of the inorganic particles in the coating layer by the resin binder or binding the coating layer to the electrode, the content of the inorganic particles is preferably 99 parts by mass or less, more preferably 98 parts by mass or less, even more preferably 97 parts by mass or less, even more preferably 96 parts by mass or less, even more preferably 95 parts by mass or less, even more preferably 94 parts by mass or less, even more preferably 93 parts by mass or less, even more preferably 92 parts by mass or less, even more preferably 91 parts by mass or less, or even more preferably 90 parts by mass or less, relative to 100 parts by mass of the coating layer.

[0024] <Resin binder for coating layer> The coating layer according to the present embodiment preferably contains a resin binder from the viewpoint of increasing the binding property of the inorganic particles in the coating layer or binding the coating layer to the electrode. Examples of resin binder materials include acrylic resins, styrene resins, acrylic-urethane resins, acrylic-styrene resins, vinyl acetate-acrylic resins, styrene-butadiene resins, acrylonitrile-butadiene resins, natural rubber resins, polybutadiene resins (BR resins), methyl methacrylate-butadiene resins, 2-vinylpyridine-styrene-butadiene resins (VP ​​resins), chloroprene resins, polyolefin resins such as polyethylene, polypropylene, polybutene, or copolymers of these monomers, modified polyolefin resins obtained by chlorinating or acid-modifying such polyolefin resins, fluorine-containing resins such as polyvinylidene fluoride or polytetrafluoroethylene, fluorine-containing rubbers such as vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers or ethylene-tetrafluoroethylene copolymers, (meth)acrylic acid-styrene-butadiene copolymer resins and hydrogenated products thereof, polyvinyl alcohol resins, and polyvinyl alcohol-polyacetate copolymer resins.

[0025] Among the above resins, acrylic resins and / or styrene resins are preferred from the viewpoint of improving acid resistance, adhesion to inorganic particles and electrodes, and heat resistance, and among these, acrylic resins are most preferred. In this specification, "acrylic resin" includes acrylic copolymer resins, such as acrylic-urethane resins, acrylic-styrene resins, acrylic-styrene-butadiene resins, and vinyl acetate-acrylic resins, as well as polymers such as acrylic resins. In this specification, "styrene resin" includes styrene copolymer resins, such as acrylic-styrene resins, styrene-butadiene resins, acrylic-styrene-butadiene resins, and 2-vinylpyridine-styrene-butadiene resins, as well as polymers such as styrene resins.

[0026] From the viewpoint of acid resistance, the acrylic resin preferably contains at least one selected from the group consisting of styrene, α-methylstyrene, and methyl methacrylate, or preferably contains a structural unit derived from at least one selected from the group consisting of styrene, α-methylstyrene, and methyl methacrylate. Furthermore, in order to alleviate shrinkage stress during drying, the acrylic resin more preferably contains butadiene or a structural unit derived therefrom.

[0027] From the viewpoint of increasing the binding strength of the inorganic particles in the coating layer or binding the coating layer to the electrode, the resin binder is preferably contained in an amount of 1 part by mass or more per 100 parts by mass of the coating layer, and the content of the resin binder is more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, even more preferably 4 parts by mass or more, or even more preferably 5 parts by mass or more.

[0028] Furthermore, from the viewpoint of forming voids consisting of inorganic particles within the coating layer and forming spaces in which sulfate ions are retained, the content of the resin binder is preferably 60 parts by mass or less per 100 parts by mass of the coating layer, more preferably 55 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, even more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, or even more preferably 20 parts by mass or less.

[0029] Furthermore, from the viewpoint of forming voids consisting of inorganic particles within the coating layer and reducing the ionic resistance of the electrode, the content of the resin binder is preferably 40 parts by mass or less, more preferably 39 parts by mass or less, even more preferably 38 parts by mass or less, even more preferably 36 parts by mass or less, even more preferably 34 parts by mass or less, even more preferably 32 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 28 parts by mass or less, even more preferably 26 parts by mass or less, even more preferably 24 parts by mass or less, even more preferably 22 parts by mass or less, or even more preferably 20 parts by mass or less, relative to 100 parts by mass of the coating layer.

[0030] These resins may contain one or more other components in addition to the above-mentioned composition. The resin is not limited to one type, and multiple types can be used in combination. For example, a combination of an acrylic resin and a styrene resin can be exemplified.

[0031] <Thickener for coating layer> The coating layer according to the present embodiment may contain a thickener to prevent peeling of the coating layer from the electrode or to prevent the inorganic particles from falling off the coating layer. The thickener is preferably a polysaccharide from the viewpoint of the binding ability between the electrode and the inorganic particles.

[0032] ≪Polysaccharides≫ Examples of polysaccharides include cellulose derivatives such as carboxymethyl cellulose (CMC), carbomethoxy cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; natural polysaccharides such as xanthan gum, diutan gum, welan gum, gellan gum, guar gum, carrageenan gum, and pectin; and starches such as dextrin and pregelatinized starch. The coating layer according to this embodiment preferably contains carboxymethyl cellulose (CMC) from the viewpoint of binding strength between the electrode and the inorganic particles. Carboxymethyl cellulose (CMC) is more preferred when the inorganic particles are made of a non-conductive material, and is particularly preferred when the inorganic particles are made of a non-conductive material with a DOA oil absorption of 15 ml / 100 g to 700 ml / 100 g. Polysaccharides can be used singly or in combination of two or more.

[0033] From the viewpoint of suppressing peeling of the coating layer from the electrode or suppressing falling off of inorganic particles from the coating layer, it is preferable that the coating layer contains 0.1 parts by mass or more of a thickener such as a polysaccharide per 100 parts by mass of the coating layer, and the content of the thickener is more preferably 0.2 parts by mass or more, even more preferably 0.3 parts by mass or more, even more preferably 0.4 parts by mass or more, and even more preferably 0.5 parts by mass or more.

[0034] Furthermore, from the viewpoint of suppressing aggregation of inorganic particles within the coating layer, the content of the thickener such as a polysaccharide is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, even more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, or even more preferably 1 part by mass or less, per 100 parts by mass of the coating layer.

[0035] <Coating layer density> The density of the coating layer is set to 1 g / cm in order to form voids in the coating layer and reduce the ionic resistance as an electrode for a lead-acid battery. 3 It is preferable that the concentration is 0.9 g / cm or less, and more preferably 0.9 g / cm 3 More preferably, it is 0.8 g / cm or less. 3 More preferably, it is 0.7 g / cm or less. 3More preferably, it is 0.6 g / cm or less. 3 More preferably, it is 0.5 g / cm or less. 3 or less, or more preferably 0.4 g / cm 3 The following is the result.

[0036] In order to prevent the inorganic particles in the coating layer from falling off, the density of the coating layer is set to 0.01 g / cm 3 It is preferable that the concentration is equal to or higher than 0.02 g / cm. 3 More preferably, it is 0.03 g / cm 3 More preferably, it is 0.04 g / cm 3 More preferably, it is 0.05 g / cm 3 More preferably, it is 0.06 g / cm 3 More preferably, it is 0.07 g / cm 3 More preferably, it is 0.08 g / cm 3 More preferably, it is 0.09 g / cm 3 More preferably, it is 0.1 g / cm 3 More preferably, it is 0.11 g / cm or more. 3 More preferably, it is 0.12 g / cm 3 More preferably, it is 0.13 g / cm 3 More preferably, it is 0.14 g / cm or more. 3 More preferably, it is 0.15 g / cm 3 More preferably, it is 0.16 g / cm 3 More preferably, it is 0.17 g / cm 3 More preferably, it is 0.18 g / cm 3 More preferably, it is 0.19 g / cm 3 or more, or more preferably 0.2 g / cm 3 That's all.

[0037] <Weight of coating layer> From the viewpoint of reducing the ionic resistance as a lead-acid battery electrode and suppressing a decrease in the initial capacity of the battery, the coating layer according to this embodiment has a basis weight of preferably 100 g / sqm or less, more preferably 90 g / sqm or less, more preferably 80 g / sqm or less, more preferably 70 g / sqm or less, more preferably 65 g / sqm or less, more preferably 60 g / sqm or less, more preferably 55 g / sqm or less, more preferably 50 g / sqm or less, more preferably 45 g / sqm or less, more preferably 40 g / sqm or less, more preferably 35 g / sqm or less, or even more preferably 30 g / sqm or less.

[0038] Furthermore, from the viewpoint of retaining sulfate ions released from the positive and negative electrodes of the lead-acid battery into the electrolyte during charging within the coating layer and suppressing stratification, the coating layer preferably has a basis weight of 3 g / sqm or more, more preferably 4 g / sqm or more, more preferably 5 g / sqm or more, more preferably 6 g / sqm or more, more preferably 7 g / sqm or more, more preferably 8 g / sqm or more, more preferably 9 g / sqm or more, more preferably 10 g / sqm or more, more preferably 11 g / sqm or more, more preferably 12 g / sqm or more, more preferably 13 g / sqm or more, more preferably 14 g / sqm or more, or even more preferably 15 g / sqm or more.

[0039] ≪Lead-acid battery≫ The shape of the lead-acid battery electrode can be determined so as to be compatible with each component of the lead-acid battery. One embodiment of the lead-acid battery according to the present invention is a lead-acid battery including a battery case, a separator, and dilute sulfuric acid as an electrolyte, and having the lead-acid battery electrode according to the present invention disposed therein.

[0040] The positive electrode grid constituting the positive electrode may be lead or a lead alloy, and the positive electrode active material may be lead oxide, such as lead dioxide. The negative electrode grid constituting the negative electrode may be lead or a lead alloy, and the negative electrode active material may be lead, and the lead negative electrode itself may be, for example, in a spongy form. Furthermore, the active materials of these positive and negative electrodes may contain 50% by mass or less of other metal elements. Furthermore, the dilute sulfuric acid is sulfuric acid with a specific gravity of 1.1 to 1.4, and may further contain additives such as aluminum ions or lithium ions.

[0041] In the lead-acid battery electrode of this embodiment, from the viewpoint of retaining within the coating layer sulfate ions released from the positive electrode or negative electrode of the lead-acid battery into the electrolyte during charging, the coating layer of the lead-acid battery electrode of the present invention preferably has a coating layer on at least one surface of the electrode. From the viewpoint of further suppressing stratification, it is preferable that a coating layer be provided on the surface of the positive electrode facing the negative electrode, more preferably that a coating layer be provided on both surfaces of all positive electrodes, and even more preferably that a coating layer be provided on both surfaces of all electrodes.

[0042] The lead-acid battery electrode according to the present embodiment can suppress stratification without reducing the initial capacity, and therefore can be used in both open-type lead-acid batteries and valve-regulated lead-acid batteries in which stratification is suppressed.

[0043] <Method for forming coating layer> The following is an example of a method for forming a coating layer on the surface of an electrode, but the method is not limited thereto. An example of a method for forming a coating layer on the surface of an electrode is as follows: mixing a material for forming a coating layer with a dispersion medium to prepare a slurry; applying the slurry to the electrode surface; a step of drying the coated area to remove the dispersion medium; The material for forming the coating layer may be the coating layer constituent material described above for the coating layer according to this embodiment, and is preferably homogenized in a dispersion medium to form a mixture. The dispersion medium may be water or an organic solvent. The coating method may include applying the slurry in a wet state to the surface of the electrode using, for example, a die coating method, a gravure coating method, or a spray method. [Example]

[0044] Examples of the present disclosure will be described in detail below, but these are described for the purpose of explanation, and the scope of the present disclosure is not limited to the following examples. Various evaluation results of the electrodes and lead-acid batteries obtained in the examples and comparative examples are shown in Table 1. Evaluation methods for various physical properties are described below.

[0045] <Median diameter> The inorganic particles were dispersed in water and measured using a Microtrac-Bell MT3300EXII (optical bench) and SDC (sample circulator) under the following measurement and analysis conditions. The measurement software used was MicrotracII, and the measurement results are shown in Table 1. [Measurement conditions] SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 [Analysis conditions] Transparency: Drop Particle refractive index: 1.46 (example for silica particles) Shape: Non-spherical Solvent refractive index: 1.333 Distribution: Volume

[0046] ≪DOA oil absorption≫ The DOA oil absorption (ml / 100g) was measured in accordance with ISO19246 using an absorptometer (automatic oil absorption measuring device) by adding dioctyl adipate (DOA) dropwise to inorganic particles while kneading them, and the amount of DOA added when a predetermined torque value was reached was measured. The value is shown in Table 1.

[0047] <Weight of coating layer> The weights of the electrode before and after providing the coating layer were designated A and B, respectively, and the value obtained by dividing this by the area C of the coated part of the electrode was taken as the basis weight of the coating layer, expressed in g / sqm.

[0048] ≪Initial capacity≫ A ribbed PE separator was cut into a rectangle, folded in half along its long edge so that the rib was on the inside, and both ends of the separator were closed perpendicular to the folded edge to produce a pouch-shaped separator with one side open. A lead-acid battery (2V single cell) was fabricated using a polycarbonate battery case, two of the pouch-shaped separators (each of which had a lead oxide positive electrode inserted according to each embodiment), and one lead negative electrode. Dilute sulfuric acid with a specific gravity of 1.28 was poured into the battery as an electrolyte. A charge-discharge cycle test was conducted using this lead-acid battery to evaluate the 20-hour rate initial capacity (initial capacity). The specific conditions for the charge-discharge cycle test were as follows: 25°C, initial charging and resting as shown in (1) and (2) below, followed by five cycles consisting of (3) to (6). The fifth discharge capacity was defined as the initial capacity. Table 1 shows the ratio (%) of the initial capacity in each embodiment to the initial capacity when an electrode without a coating layer was used. (1) Initial charging: Current 0.2A (0.1C), voltage 2.67V, 24 hours of constant current-constant voltage charging (2) Suspension: 24 hours (3) Discharge: Constant current discharge with a current value of 0.1A (0.05C) and a voltage value of 1.75V. (4) Break: 1 hour (5) Charging: Current 0.2A (0.1C), voltage 2.47V, 24-hour constant current-constant voltage charging (6) Break: 1 hour

[0049] Stratification A charge-discharge cycle test was conducted in a PSOC using the lead-acid battery that had undergone the 20-hour rate initial capacity evaluation. The test was conducted using an ACD-01 G-Version charge-discharge tester manufactured by Asuka Electronics Co., Ltd. The specific conditions for the charge-discharge cycle test were as follows: At 25°C, a fully charged lead-acid battery was subjected to the initial discharge shown in (1) below, followed by (2) and (3) as one cycle. Immediately after completing the 200th cycle, the battery was charged at a current rate of 0.35C (7 x I20) for 10 minutes, and the specific gravity of the electrolyte in the upper and lower parts of the battery case was immediately measured. (1) Initial discharge: Current rate 0.2C (4 x I20), constant current discharge for 150 minutes (2) Charging: Current rate 0.35C (7 x I20), voltage value 2.4V, constant current-constant voltage charging for 40 minutes (3) Discharge: Current rate 0.35C (7 x I20), voltage value 1.75V, constant current-constant voltage discharge for 30 minutes The difference between the measured specific gravity values ​​was taken as the difference between the specific gravity of the electrolyte in the lower part of the battery case and the specific gravity of the electrolyte in the upper part of the battery case. The ratio of the specific gravity difference between the upper and lower parts of the cell in each embodiment to the specific gravity difference when an electrode without a coating layer is used is shown in Table 1. The smaller the specific gravity difference between the upper and lower parts of the cell, the more effectively stratification is suppressed.

[0050] Example 1 To form a coating layer on the electrode surface, a slurry was prepared by adding 80 parts by mass of precipitated silica (amorphous) with a DOA oil absorption of 240 ml / 100 g, 19 parts by mass (solids content equivalent) of acrylic resin (water-based latex) as a resin binder, and 1 part by mass of carboxymethyl cellulose as a polysaccharide thickener to water to prepare an aqueous slurry with a solids content of 7.0% by mass.

[0051] The slurry was manually applied to both sides of the positive electrode using a spray nozzle and dried in an oven at 110°C for 15 minutes. A positive electrode having the coating layer on both sides was obtained. The spray time was adjusted to obtain the layer thickness shown in Table 1. The layer properties of the obtained positive electrode are shown in Table 1.

[0052] Examples 2 to 17 and Comparative Examples 1 to 5 This was the same as Example 1, except that the median diameter, DOA oil absorption, layer composition, and electrode provided with the coating layer of the precipitated amorphous silica in Example 1 were changed to the conditions shown in Table 1.

[0053] Example 18 This example is the same as Example 1, except that the precipitated amorphous silica in Example 1 was changed to sodium aluminosilicate, and the median diameter, DOA oil absorption, and layer composition were changed to the conditions shown in Table 1.

[0054] Example 19 This example is the same as Example 1, except that the precipitated amorphous silica of Example 1 was changed to aluminum silicate, and the median diameter, DOA oil absorption, and layer composition were changed to the conditions shown in Table 1.

[0055] <Results of Examples and Comparative Examples> The results of the Examples and Comparative Examples are shown in Table 1 below.

[0056] [Table 1]

[0057] The results of the examples and comparative examples show that stratification can be suppressed without a decrease in initial capacity by using an electrode in which a coating layer containing non-conductive inorganic particles is formed on the surface of at least one of the positive and negative electrodes, the coating layer has a basis weight of 10 g / sqm or more and 100 g / sqm or less, and the proportion of inorganic particles is 40% or more and 99% or less. [Industrial Applicability]

[0058] The lead-acid battery separator of the present disclosure is useful for lead-acid batteries, such as flooded batteries (FBs). Furthermore, the lead-acid battery electrode according to the present invention can contribute to suppressing stratification, and can therefore also be used as an electrode for valve-regulated lead-acid batteries (VRLAs).

Claims

1. A pair of positive and negative electrodes containing an active material for a lead-acid battery, wherein a coating layer containing non-conductive inorganic particles is formed on a surface of at least one of the positive and negative electrodes, the coating layer has a basis weight of 3 g / sqm or more and 100 g / sqm or less, and the mass proportion of the inorganic particles in the coating layer is 40 mass% or more and 99 mass% or less.

2. 2. The electrode according to claim 1, wherein the non-conductive inorganic particles have a median diameter of 3 μm or more and 65 μm or less.

3. 3. The electrode according to claim 1, wherein the non-conductive inorganic particles have a DOA absorption of 110 (ml / 100 g) or more.

4. 3. The electrode of claim 1, wherein the non-conductive inorganic particles comprise at least one selected from the group consisting of silica, alumina, kaolin, titania, aluminum silicate, barium sulfate, and sodium aluminosilicate.

5. 3. The electrode of claim 1, wherein the non-conductive inorganic particles are silica.

6. 3. The electrode according to claim 1, wherein the coating layer contains a resin binder, and the content of the resin binder per 100 parts by mass of the coating layer is 1 part by mass or more and 60 parts by mass or less.

7. A lead-acid battery comprising a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, the lead-acid battery comprising the pair of positive and negative electrodes according to claim 1 or 2 disposed therein.

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