Lead-acid battery and its manufacturing method

Abstract

To provide a lead acid battery capable of suppressing seepage short circuit during chemical conversion treatment.SOLUTION: A lead acid battery 100 includes a positive electrode 20, a negative electrode 30, a separator 40, and a porous membrane 50, the separator 40 and the porous membrane 50 contain glass fibers and are arranged between the positive electrode 20 and the negative electrode 30, the porous membrane 50 is disposed at least between the positive electrode 20 and the separator 40 or between the negative electrode 30 and the separator 40, and the porosity obtained by X-ray CT measurement of the porous membrane 50 is 18.0% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a lead-acid battery, a method for manufacturing a lead-acid battery, and the like. [Background technology]

[0002] Lead-acid batteries are one type of secondary battery that has been used for a long time, and are widely used as secondary batteries for industrial or consumer purposes due to their reliability, low cost, etc. For example, lead-acid batteries can be used as lead-acid batteries for automobiles, lead-acid batteries for electric vehicles, lead-acid batteries for power supply devices, etc.

[0003] In some cases, higher output is required for lead-acid batteries, and studies have been conducted to increase the number of electrodes in a battery container by reducing the thickness of the separator placed between the positive and negative electrodes. However, if the separator is made thinner, lead sulfate is more likely to leach into the separator during chemical conversion treatment in the battery manufacturing process, which can cause permeation short circuits during charging and discharging. In response to this, techniques are known that solve permeation short circuits and the like by improving the separator (see, for example, Patent Documents 1 and 2 listed below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-260335 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-151033 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the wide variety of configurations that can be adopted in lead-acid batteries, new techniques are required to solve the problem of permeation short circuits.

[0006] An object of one aspect of the present disclosure is to provide a lead-acid battery capable of suppressing permeation short-circuiting during chemical conversion treatment.An object of another aspect of the present disclosure is to provide a method for manufacturing such a lead-acid battery. [Means for solving the problem]

[0007] The present inventors have conceived the idea of ​​using a porous membrane in addition to a separator as a member disposed between a positive electrode and a negative electrode, but have found that even when a porous membrane with a high porosity is used from the viewpoint of improving the diffusibility of the electrolyte and promoting the battery reaction well, permeation short-circuiting during chemical conversion treatment may not be suppressed. On the other hand, the present inventors have found that selecting a porous membrane based on the porosity obtained by X-ray CT measurement of the porous membrane is effective in suppressing permeation short-circuiting.

[0008] Some aspects of the present disclosure relate to the following [1] to [6], etc. [1] A lead-acid battery comprising a positive electrode, a negative electrode, a separator, and a porous membrane, wherein the separator and the porous membrane contain glass fibers and are disposed between the positive electrode and the negative electrode, and the porous membrane is disposed at least one between the positive electrode and the separator and between the negative electrode and the separator, and the porosity of the porous membrane obtained by X-ray CT measurement is 18.0% or more. [2] The lead-acid battery according to [1], wherein the porous membrane has a porous membrane disposed between the negative electrode and the separator. [3] The lead-acid battery according to [1] or [2], wherein the porous membrane is a nonwoven fabric. [4] The lead-acid battery according to any one of [1] to [3], wherein the thickness of the porous membrane is smaller than the thickness of the separator. [5] The lead-acid battery according to any one of [1] to [4], wherein the porous film has a thickness of 0.01 to 0.50 mm. [6] A method for producing a lead-acid battery according to any one of [1] to [5], wherein the porous membrane is disposed between the positive electrode and the negative electrode. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, it is possible to provide a lead-acid battery capable of suppressing permeation short-circuiting during chemical conversion treatment. According to another aspect of the present disclosure, it is possible to provide a method for manufacturing such a lead-acid battery. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an end view showing an example of a lead-acid battery. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described, but the present disclosure is not limited to these embodiments.

[0012] In this specification, numerical ranges indicated with "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of those multiple substances present in the composition, unless otherwise specified. The term "film" encompasses not only structures that are formed over the entire surface when observed in a plan view, but also structures that are formed only partially. The term "process" does not only refer to independent processes, but also includes processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved. Since the specific gravity varies depending on the temperature, in this specification it is defined as the specific gravity converted at 25° C. The term "(meth)acrylic" means at least one of acrylic and its corresponding methacrylic.

[0013] The lead-acid battery according to this embodiment includes a positive electrode, a negative electrode, a separator, and a porous membrane, and the separator and the porous membrane contain glass fibers and are disposed between the positive electrode and the negative electrode, and the porous membrane is disposed at least one of between the positive electrode and the separator (between the positive electrode and the separator) and between the negative electrode and the separator (between the negative electrode and the separator). In the lead-acid battery according to this embodiment, the porosity obtained by X-ray CT measurement of the porous membrane is 18.0% or more.

[0014] The lead-acid battery according to this embodiment can suppress permeation short-circuiting during chemical conversion treatment. The lead-acid battery according to this embodiment can prevent permeation short-circuiting while achieving high output by reducing the thickness of the separator.

[0015] In the lead-acid battery according to this embodiment, the porous membrane is disposed, thereby suppressing an excessive increase in the lead ion content in the separator. On the other hand, if the porosity of the porous membrane is low, the electrolyte is difficult to sufficiently diffuse, which may cause unevenness in the specific gravity of the electrolyte inside the separator. In this case, lead sulfate may precipitate due to differences in the solubility of lead sulfate, which may cause a permeation short circuit. On the other hand, in the lead-acid battery according to this embodiment, the porosity is within the above-mentioned range, which allows the electrolyte to easily diffuse sufficiently, thereby suppressing unevenness in the specific gravity of the electrolyte inside the separator and thereby suppressing a permeation short circuit. However, the factors that suppress a permeation short circuit are not limited to the above.

[0016] The lead-acid battery according to this embodiment can be used as a valve-regulated lead-acid battery. The lead-acid battery according to this embodiment can be used in automobiles, power supply devices, etc. Examples of power supply devices include UPS (Uninterruptible Power Supply), power supplies for disaster prevention (emergency) radios, and power supplies for telephones. The automobile, electric vehicle, or power supply device according to this embodiment is equipped with the lead-acid battery according to this embodiment.

[0017] The lead-acid battery according to this embodiment includes an electrode group according to this embodiment and a battery case that houses the electrode group. The electrode group according to this embodiment is an electrode group for a lead-acid battery, and includes the above-described positive electrode, negative electrode, separator, and porous membrane. A lead-acid battery and electrode group before chemical formation can be used as the lead-acid battery and electrode group according to this embodiment. The battery case is hollow and has an internal space that houses the electrode group. The lead-acid battery according to this embodiment may include a lid that seals the battery case. The lid may be provided with a control valve that controls the pressure inside the battery case, a positive electrode terminal that connects the positive electrode to the outside, and a negative electrode terminal that connects the negative electrode to the outside.

[0018] The lead-acid battery and electrode group may have at least one positive electrode, or may have multiple positive electrodes. The lead-acid battery and electrode group may have at least one negative electrode, or may have multiple negative electrodes. The lead-acid battery and electrode group may have the same number of positive electrodes and negative electrodes, or may not have the same number. If the number of positive electrodes and negative electrodes is not the same, the number of negative electrodes may be more than the positive electrodes. The number of positive electrodes or negative electrodes may be 3 or more, or 4 or more. The number of positive electrodes or negative electrodes may be 10 or less, 8 or less, 6 or less, 5 or less, 4 or less, or 3 or less. From these perspectives, the number of positive electrodes or negative electrodes may be 3 to 10, 3 to 8, or 3 to 5. At least one (one or both) of the outermost electrodes in the electrode group may be a negative electrode.

[0019] The positive electrode has a positive electrode current collector and a positive electrode active material supported on the positive electrode current collector. The negative electrode has a negative electrode current collector and a negative electrode active material supported on the negative electrode current collector. The positive electrodes and negative electrodes may be arranged alternately with a separator and a porous membrane interposed between them. The positive electrode excluding the positive electrode current collector is referred to as the "positive electrode active material," and the negative electrode excluding the negative electrode current collector is referred to as the "negative electrode active material."

[0020] The positive electrode current collector serves as a conductive path for current from the positive electrode active material and holds the positive electrode active material. The negative electrode current collector serves as a conductive path for current from the negative electrode active material and holds the negative electrode active material. The negative electrode current collector may be the same as or different from the positive electrode current collector. Examples of materials constituting the current collector include lead alloys such as lead-calcium-tin alloys and lead-antimony-arsenic alloys. Depending on the application, selenium, silver, bismuth, etc. may be added to the current collector. The current collector has, for example, a lattice shape and may be a cast lattice, an expanded lattice, etc. The current collector can be obtained by forming a lead alloy into a lattice shape using a gravity casting method, an expanding method, a punching method, etc.

[0021] The plurality of positive electrodes may be electrically connected to one another by connecting the lugs provided on the positive electrode current collectors via straps. The positive electrode straps may be provided with positive electrode poles for connecting the positive electrodes to positive electrode terminals. The plurality of negative electrodes may be electrically connected to one another by connecting the lugs provided on the negative electrode current collectors via straps. The negative electrode straps may be provided with negative electrode poles for connecting the negative electrodes to negative electrode terminals.

[0022] The positive electrode active material may contain β-PbO2 as a Pb component. The positive electrode active material may contain α-PbO2 or may not contain α-PbO2. The positive electrode active material may contain Pb components other than PbO2 (e.g., PbSO4), additives, etc., as necessary.

[0023] Additives that can be contained in the positive electrode active material include carbon materials (excluding carbon fiber), short reinforcing fibers, etc. Examples of carbon materials include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black, and ketjen black. Examples of short reinforcing fibers include acrylic fiber, polyethylene fiber, polypropylene fiber, polyethylene terephthalate fiber, and carbon fiber.

[0024] The negative electrode active material may contain Pb as a Pb component. The negative electrode active material may contain porous spongy lead. The negative electrode active material may contain Pb components other than Pb (e.g., PbSO4), additives, etc., as necessary.

[0025] Additives that can be included in the negative electrode active material include resins having sulfo groups and / or sulfonate groups, barium sulfate, carbon materials (excluding carbon fiber), and short reinforcing fibers. Examples of resins having sulfo groups and / or sulfonate groups include lignin sulfonic acid, lignin sulfonate salts (e.g., sodium lignin sulfonate), and condensates of phenols, aminoarylsulfonic acid, and formaldehyde (e.g., condensates of bisphenol, aminobenzenesulfonic acid, and formaldehyde). The negative electrode active material may contain at least one selected from the group consisting of lignin sulfonic acid, lignin sulfonate salts, and bisphenol-based resins, which facilitates excellent charge acceptance. In particular, the negative electrode active material may contain a bisphenol-based resin, which facilitates excellent charge acceptance. Examples of carbon materials include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black, and ketjen black. Examples of reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and carbon fibers.

[0026] The positive electrode active material and the negative electrode active material can be obtained by aging and drying an active material paste containing raw materials for the active materials to obtain an unformed active material, and then chemically converting the unformed active material. The positive electrode and the negative electrode can be obtained by aging and drying an active material paste supported on a current collector to obtain an unformed active material, and then chemically converting the unformed active material. The active material paste may contain a solvent and / or sulfuric acid. Examples of the solvent include water (e.g., ion-exchanged water) and organic solvents. The unformed positive electrode active material may contain tribasic lead sulfate as a main component. Examples of raw materials for the positive electrode active material include lead powder and red lead (Pb3O4). The unformed negative electrode active material may contain tribasic lead sulfate as a main component. Examples of raw materials for the negative electrode active material include lead powder.

[0027] The lead-acid battery according to this embodiment includes a separator disposed between the positive electrode and the negative electrode. The separator disposed between the positive electrode and the negative electrode may be at least a portion of the separator disposed between the positive electrode and the negative electrode.

[0028] The separator may be in contact with the positive electrode, or may not be in contact with the positive electrode. The separator may cover at least a portion of the active material region of the positive electrode (the region where the positive electrode active material is arranged), or may cover the entire active material region of the positive electrode. The separator may be in contact with the negative electrode, or may not be in contact with the negative electrode. The separator may cover at least a portion of the active material region of the negative electrode (the region where the negative electrode active material is arranged), or may cover the entire active material region of the negative electrode. The porosity of the separator obtained by X-ray CT measurement may be less than 18.0%. The lead-acid battery and the electrode group may have at least one separator, or may have multiple separators. The separator may be bag-shaped or may be sheet-shaped (it does not have to be bag-shaped). The separator may be folded to wrap around the positive electrode or negative electrode, and the folded portion may be located vertically downward in the lead-acid battery.

[0029] The separator may have a rib on at least one main surface selected from the group consisting of the one surface and the other surface, or may not have a rib on at least one main surface selected from the group consisting of the one surface and the other surface. The separator can have at least one rib, and may have multiple ribs.

[0030] The separator contains glass fibers. The separator may contain an organic material (e.g., an organic binder) or may not contain an organic material. The weight loss rate (thermal weight loss rate) of the separator when heated at 800°C for 15 minutes, which corresponds to the weight loss rate A described below, may be 5% or less, less than 5%, or 1% or less, based on the weight of the separator before heating at 800°C.

[0031] The thickness of the separator before or after being housed in a lead-acid battery may be within the following ranges. From the viewpoint of easily achieving high output, the thickness of the separator may be 0.1 mm or more, 0.15 mm or more, 0.2 mm or more, more than 0.2 mm, 0.25 mm or more, 0.3 mm or more, more than 0.3 mm, 0.35 mm or more, or 0.4 mm or more. From the viewpoint of easily suppressing permeation short circuits, the thickness of the separator may be 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, 1 mm or less, less than 1 mm, 0.9 mm or less, 0.8 mm or less, 0.7 mm or less, 0.65 mm or less, 0.6 mm or less, 0.55 mm or less, 0.5 mm or less, 0.45 mm or less, or 0.4 mm or less. From these viewpoints, the thickness of the separator may be 0.1 to 5 mm, 0.2 to 5 mm, more than 0.2 mm but not more than 5 mm, 0.3 to 5 mm, more than 0.3 mm but not more than 5 mm, 0.4 to 5 mm, 0.1 to 1 mm, 0.2 to 1 mm, more than 0.2 mm but not more than 1 mm, 0.3 to 1 mm, more than 0.3 mm but not more than 1 mm, or 0.4 to 1 mm. The thickness of the separator may be the average value (average thickness) of measurements taken at a total of nine points (for example, one point in the center and eight equally spaced points around it).

[0032] The lead-acid battery according to this embodiment includes a porous membrane (porous membrane for lead-acid battery) disposed between the positive electrode and the negative electrode. As the porous membrane disposed between the positive electrode and the negative electrode, at least a part of the porous membrane may be disposed between the positive electrode and the negative electrode. In addition, the porous membrane is disposed at least one of between the positive electrode and the separator and between the negative electrode and the separator. As the porous membrane disposed between the positive electrode and the separator, at least a part of the porous membrane may be disposed between the positive electrode and the separator. As the porous membrane disposed between the negative electrode and the separator, at least a part of the porous membrane may be disposed between the negative electrode and the separator.

[0033] The porous membrane may be in contact with the positive electrode, or may not be in contact with the positive electrode. The porous membrane may cover at least a portion of the active material region of the positive electrode, or may cover the entire active material region of the positive electrode. The porous membrane may be in contact with the negative electrode, or may not be in contact with the negative electrode. The porous membrane may cover at least a portion of the active material region of the negative electrode, or may cover the entire active material region of the negative electrode. From the viewpoint of easily suppressing permeation short-circuiting, the porous membrane of the lead-acid battery according to this embodiment may have a porous membrane disposed between the negative electrode and the separator, or may not have a porous membrane disposed between the positive electrode and the separator. The lead-acid battery and the electrode group may have at least one porous membrane, or may have a plurality of porous membranes. The porous membrane may be bag-shaped or may be a sheet (not necessarily bag-shaped). The porous membrane may be folded so as to wrap around the positive electrode or the negative electrode, and the folded portion may be located vertically downward in the lead-acid battery.

[0034] The porous membrane contains glass fibers and may contain an organic material. Examples of the organic material include resin materials such as (meth)acrylic resins (e.g., (meth)acrylic binders), olefin resins, urethane resins, and styrene resins. Examples of the olefin resin include polyethylene and polypropylene. When a porous membrane containing a (meth)acrylic resin is used, the porous membrane adsorbs lead ions, suppressing an excessive increase in the lead ion content inside the separator and making it easier to suppress permeation short circuits. The porous membrane may be a nonwoven fabric, which makes it easier to suppress permeation short circuits.

[0035] Before being housed in a lead-acid battery or after being housed in a lead-acid battery, the thickness of the porous membrane may be in the following ranges. The thickness of the porous membrane may be 0.01 mm or more, 0.03 mm or more, 0.05 mm or more, 0.08 mm or more, 0.10 mm or more, 0.12 mm or more, 0.15 mm or more, 0.18 mm or more, 0.20 mm or more, 0.22 mm or more, 0.25 mm or more, 0.28 mm or more, or 0.30 mm or more, from the viewpoint of easily achieving high output. The thickness of the porous membrane may be 0.50 mm or less, 0.45 mm or less, 0.40 mm or less, less than 0.40 mm, 0.35 mm or less, 0.30 mm or less, less than 0.30 mm, 0.28 mm or less, 0.25 mm or less, 0.22 mm or less, 0.20 mm or less, less than 0.20 mm, 0.18 mm or less, 0.15 mm or less, 0.12 mm or less, or 0.1 mm or less, from the viewpoint of easily suppressing permeation short-circuiting. From these viewpoints, the thickness of the porous membrane may be 0.01 to 0.50 mm, 0.01 to 0.40 mm, 0.01 mm or more and less than 0.40 mm, 0.01 to 0.30 mm, 0.01 mm or more and less than 0.30 mm, 0.01 to 0.20 mm, 0.01 mm or more and less than 0.20 mm, 0.01 to 0.10 mm, 0.10 to 0.50 mm, 0.10 to 0.40 mm, 0.10 to 0.30 mm, 0.10 mm or more and less than 0.30 mm, 0.10 to 0.20 mm, 0.10 mm or more and less than 0.20 mm, 0.20 to 0.50 mm, 0.20 to 0.40 mm, 0.20 mm or more and less than 0.40 mm, or 0.20 to 0.30 mm. The thickness of the porous membrane may be the average value (average thickness) of measurements taken at a total of nine points (for example, one point at the center and eight equally spaced points around the center). The thickness of the porous membrane may be smaller than the thickness of the separator, from the viewpoint of easily suppressing permeation short-circuiting.

[0036] Before being housed in a lead-acid battery or after being housed in a lead-acid battery, the ratio of the thickness of the porous membrane to the thickness of the separator (thickness of the porous membrane / thickness of the separator) may be in the following ranges. From the viewpoint of easily suppressing permeation short circuit, the thickness ratio may be 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.35 or more, 0.4 or more, 0.45 or more, 0.5 or more, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, or 0.75 or more. From the viewpoint of easily suppressing permeation short circuits, the thickness ratio may be 1 or less, less than 1, 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, 0.75 or less, 0.7 or less, 0.65 or less, 0.6 or less, 0.55 or less, 0.5 or less, 0.45 or less, 0.4 or less, 0.35 or less, 0.3 or less, or 0.25 or less. From these viewpoints, the thickness ratio may be 0.1 to 1, 0.1 or more and less than 1, 0.1 to 0.8, 0.1 to 0.75, 0.1 to 0.5, 0.1 to 0.3, 0.1 to 0.25, 0.2 to 1, 0.2 or more and less than 1, 0.2 to 0.8, 0.2 to 0.75, 0.2 to 0.5, 0.2 to 0.3, 0.2 to 0.25, 0.25 to 1, 0.25 or more and less than 1, 0.25 to 0.8, 0.25 to 0.75, 0.25 to 0.5, or 0.25 to 0.3.

[0037] The porosity of the porous membrane obtained by X-ray CT measurement (3D CT measurement) is 18.0% or more from the viewpoint of suppressing permeation short-circuiting. That is, the porous membrane may include at least a part of a region having such a porosity, and the entire porous membrane may have such a porosity.

[0038] From the viewpoint of easily suppressing permeation short-circuiting, the porosity may be 19.0% or more, 20.0% or more, 21.0% or more, 22.0% or more, 23.0% or more, 24.0% or more, 25.0% or more, or 26.0% or more. From the viewpoint of easily suppressing permeation short-circuiting, the porosity may be 50.0% or less, 45.0% or less, 40.0% or less, 35.0% or less, 30.0% or less, 29.0% or less, 28.0% or less, 27.0% or less, or 26.0% or less. From these viewpoints, the porosity may be 18.0 to 50.0%, 20.0 to 50.0%, 23.0 to 50.0%, 25.0 to 50.0%, 18.0 to 30.0%, 20.0 to 30.0%, 23.0 to 30.0%, or 25.0 to 30.0%. The porosity of the porous membrane can be adjusted by the method for producing the porous membrane (wet method, dry method, spunbonding method, meltblowing method, thermal bonding method, chemical bonding method, needle punching method, hydroentanglement method, etc.), the fiber diameter of the glass fiber used when producing the porous membrane, etc.

[0039] The porosity of the porous membrane can be obtained by X-ray CT measurement (tube voltage: 55 kV, X-ray source: tungsten filament) of a measurement area adjusted to a cylindrical shape with a diameter of 10.178 mm and a height of 8.588 mm, and more specifically, it can be measured by the following procedure. (1) The porous film is irradiated with X-rays (X-ray source: tungsten filament, aluminum window) under the conditions of a tube voltage of 55 kV and a brightness of 100 (max). (2) Set the settings to "SID (Source Image Distance): 210 mm, SOD (Source Object Distance): 35 mm, detector inch size: 4 inches," and perform X-ray CT measurement of the measurement area adjusted to a cylindrical shape with a diameter of 10.178 mm and a height of 8.588 mm under the conditions of "measurement mode: full scan, number of views: 1200, number of accumulations: 6 times x 2 rotations, scaling coefficient: 100, image size: 512 x 512 pixels." (3) A 3D image is obtained by performing 3D reconstruction of the measurement results of the X-ray CT measurement. (4) The 3D image is rotated so that the main surface of the 3D image faces forward, and the 3D image is converted into image data. (5) After extracting only the areas corresponding to the porous membrane (areas that constitute the porous membrane) from the image data, binarization is performed (the areas corresponding to the porous membrane and areas that do not correspond to the porous membrane (void areas) are binarized). (6) The area ratio of the black areas (areas not corresponding to the porous membrane) after binarization is obtained as the porosity.

[0040] The porosity of the porous membrane may be 50% by volume or more, 55% by volume or more, 60% by volume or more, 65% by volume or more, 70% by volume or more, 75% by volume or more, or 80% by volume or more, from the viewpoint of easily suppressing permeation short-circuiting. The porosity of the porous membrane may be 95% by volume or less, 90% by volume or less, 85% by volume or less, or 80% by volume or less, from the viewpoint of easily suppressing permeation short-circuiting. From these viewpoints, the porosity of the porous membrane may be 50 to 95% by volume, 70 to 90% by volume, 70 to 80% by volume, or 80 to 90% by volume. The porosity of the porous membrane can be measured by mercury intrusion porosimetry. The porosity of the porous membrane can be adjusted by the method for producing the porous membrane (wet method, dry method, spunbonding method, melt-blowing method, thermal bonding method, chemical bonding method, needle punching method, hydroentanglement method, etc.), the fiber diameter of the glass fiber used in producing the porous membrane, etc. As the porosity of the porous membrane after contact with an electrolytic solution (sulfuric acid, etc.), a porosity equivalent to the porosity of the porous membrane before contact with the electrolytic solution can be used.

[0041] The weight loss rate A (thermal weight loss rate) of the porous membrane when heated at 800°C for 15 minutes may be in the following ranges based on the porous membrane before heating at 800°C. From the viewpoint of easily suppressing permeation short-circuiting, the weight loss rate A may be 1% or more, more than 1%, 3% or more, 5% or more, more than 5%, 8% or more, 10% or more, 12% or more, 14% or more, 15% or more, 15.5% or more, or 15.8% or more. From the viewpoint of easily suppressing permeation short-circuiting, the weight loss rate A may be 30% or less, 25% or less, 20% or less, 18% or less, 17% or less, 16% or less, or 15.8% or less. From these viewpoints, the weight loss rate A may be 1 to 30%, more than 1% and 30% or less, 5 to 25%, more than 5% and 25% or less, or 10 to 20%. The weight loss rate A indicates the content of organic material removed when the porous membrane is heated at 800°C for 15 minutes. From the viewpoint of removing moisture, the porous membrane may be heated at 100°C for 60 minutes before being heated at 800°C for 15 minutes.

[0042] The basis weight of the porous membrane may be in the following range before being housed in the lead-acid battery or after being housed in the lead-acid battery. 2 More than 15g / m 2 More than 20g / m 2 More than 25g / m 2 or more than 30g / m 2 The basis weight of the porous membrane may be 50 g / m or more. 2 Below 45g / m 2 Below 40g / m 2 Below 35g / m 2 Below 30g / m 2 or less than 25g / m 2 From these viewpoints, the basis weight of the porous membrane is 10 to 50 g / m 2 , 20~40g / m 2 , 25~50g / m 2 , or 10 to 30 g / m 2 It may be.

[0043] The lead-acid battery according to this embodiment may include an electrolyte. The electrolyte may be accommodated in a battery case. The electrolyte may contain sulfuric acid and may contain sulfate ions. The electrolyte may contain metal ions such as aluminum ions.

[0044] The specific gravity of the electrolyte (before chemical conversion) may be within the following ranges. From the viewpoint of easily suppressing permeation short circuits, the specific gravity of the electrolyte may be 1.30 or less, 1.25 or less, 1.24 or less, 1.23 or less, 1.22 or less, 1.21 or less, 1.20 or less, or 1.19 or less. From the viewpoint of easily suppressing permeation short circuits, the specific gravity of the electrolyte may be 1.10 or more, 1.12 or more, 1.14 or more, 1.15 or more, 1.16 or more, 1.18 or more, or 1.19 or more. From these viewpoints, the specific gravity of the electrolyte may be 1.10 to 1.30, 1.12 to 1.25, or 1.15 to 1.20.

[0045] An example of a lead-acid battery is shown in Figure 1. Figure 1 is an end view of a lead-acid battery as viewed vertically.

[0046] The lead-acid battery 100 shown in Fig. 1 includes an electrode group 10, an electrolyte (not shown), and a battery case (not shown) that accommodates the electrode group 10 and the electrolyte. The electrode group 10 includes a plurality of positive electrodes 20, a plurality of negative electrodes 30, a plurality of separators 40 disposed between the positive electrodes 20 and the negative electrodes 30, and a plurality of porous membranes 50 disposed between the negative electrodes 30 and the separators 40. The positive electrodes 20 and the negative electrodes 30 are alternately arranged with the separators 40 and the porous membranes 50 interposed therebetween, and the separators 40 and the porous membranes 50 are disposed between the positive electrodes 20 and the negative electrodes 30.

[0047] The separator 40 is formed by folding a sheet of separator so as to wrap the positive electrode 20. One surface of the separator 40 (the inner surface when the separator 40 is folded) abuts against the positive electrode 20, and the other surface of the separator 40 (the outer surface when the separator 40 is folded) abuts against the porous membrane 50. The separator 40 covers the entire active material region of the positive electrode 20.

[0048] The porous membrane 50 is formed by folding a sheet of porous membrane so as to wrap the positive electrode 20 and the separator 40. One surface of the porous membrane 50 (the inner surface when the porous membrane 50 is folded) is in contact with the separator 40, and the other surface of the porous membrane 50 (the outer surface when the porous membrane 50 is folded) is in contact with the negative electrode 30. The porous membrane 50 covers the entire active material region of the negative electrode 30. The porous membrane 50 is disposed between the negative electrode 30 and the separator 40.

[0049] The manufacturing method of the lead-acid battery according to this embodiment is a manufacturing method of a lead-acid battery comprising a positive electrode, a negative electrode, a separator, and a porous membrane (a manufacturing method for obtaining the lead-acid battery according to this embodiment), and includes a porous membrane arranging step of arranging a porous membrane having a porosity of 18.0% or more obtained by X-ray CT measurement of the porous membrane between the positive electrode and the negative electrode, and in the lead-acid battery, the separator and the porous membrane contain glass fibers and are arranged between the positive electrode and the negative electrode, and the porous membrane is arranged at least one between the positive electrode and the separator and between the negative electrode and the separator. The respective configurations of the positive electrode, the negative electrode, the separator, and the porous membrane can be adopted, as described above for the lead-acid battery (for example, the thickness of the separator and the porous membrane).

[0050] The weight loss rate B of the porous membrane when the porous membrane placed in the porous membrane disposing step is immersed in sulfuric acid for 24 hours may be in the following ranges based on the porous membrane before immersion in sulfuric acid. From the viewpoint of easily suppressing permeation short-circuiting, the weight loss rate B may be 1% or more, more than 1%, 2% or more, 3% or more, 5% or more, more than 5%, 6% or more, 7% or more, or 7.5% or more. From the viewpoint of easily suppressing permeation short-circuiting, the weight loss rate B may be 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7.5% or less, 7% or less, 6% or less, 5% or less, less than 5%, 3% or less, or 2% or less. From these viewpoints, the weight loss rate B may be 1 to 15%, more than 1% and 15% or less, 1 to 10%, 1 to 5%, or 5 to 10%. The weight loss rate B indicates the content of organic material eluted when the porous membrane is immersed in sulfuric acid. In measuring the weight loss rate B, the porous membrane may be immersed in sulfuric acid (25°C) with a specific gravity of 1.28 for 24 hours.

[0051] In the porous membrane arranging step, the porous membrane may be arranged in a state where the separator is arranged between the positive electrode and the negative electrode, the porous membrane may be arranged between the positive electrode and the negative electrode in a state where the separator is not arranged between the positive electrode and the negative electrode, or the separator and the porous membrane may be arranged collectively between the positive electrode and the negative electrode.

[0052] In the porous membrane arranging step, when the porous membrane is arranged in a state where the separator is arranged between the positive electrode and the negative electrode, the manufacturing method of the lead-acid battery according to the present embodiment may include a separator arranging step of arranging the separator between the positive electrode and the negative electrode before the porous membrane arranging step. In the porous membrane arranging step, when the porous membrane is arranged between the positive electrode and the negative electrode in a state where the separator is not arranged between the positive electrode and the negative electrode, the manufacturing method of the lead-acid battery according to the present embodiment may include a separator arranging step of arranging the separator between the positive electrode and the negative electrode after the porous membrane arranging step. As a weight loss rate corresponding to the above-mentioned weight loss rate B, the weight loss rate of the separator when the separator arranged in the separator arranging step is immersed in sulfuric acid for 24 hours may be 5% or less, less than 5%, or 1% or less, based on the separator before immersion in sulfuric acid.

[0053] The method for manufacturing a lead-acid battery according to this embodiment may include an electrode group accommodating step of accommodating the electrode group obtained by the method for manufacturing an electrode group according to this embodiment in a battery case. The method for manufacturing a lead-acid battery according to this embodiment may include an electrolyte solution supplying step of supplying an electrolyte solution to the battery case before or after the electrode group accommodating step.

[0054] In the method for manufacturing a lead-acid battery and a method for manufacturing an electrode group according to this embodiment, general steps for obtaining a lead-acid battery and an electrode group can be adopted as steps other than the steps described above. [Example]

[0055] Hereinafter, the present disclosure will be described more specifically with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0056] <Preparation of electrodes> Lead powder and red lead (Pb3O4) were used as raw materials for the positive electrode active material (lead powder:red lead = 96:4 (mass ratio)). The raw materials for the positive electrode active material, 0.07 mass% of reinforcing short fibers (acrylic fibers) based on the total mass of the raw materials for the positive electrode active material, and water were mixed and kneaded. Subsequently, dilute sulfuric acid (specific gravity 1.280) was added little by little while kneading to prepare a paste-like positive electrode active material.

[0057] Lead powder was used as the raw material for the negative electrode active material. A mixture containing 0.2 mass% (solid content equivalent) of lignin-based resin (lignin sulfonate), 0.1 mass% of short reinforcing fiber (acrylic fiber), 1.0 mass% of barium sulfate, and 0.2 mass% of carbon material (furnace black) was added to the lead powder and then dry-mixed (the amounts are based on the total mass of the raw materials for the negative electrode active material). Next, water was added and the mixture was kneaded. Subsequently, dilute sulfuric acid (specific gravity 1.280) was added little by little and kneaded to prepare a paste-like negative electrode active material.

[0058] In a fully charged valve-regulated lead-acid battery, the ratio (N / P) of the total mass of the negative active material (N) to the total mass of the positive active material (P) was 0.7. The electrode plate (positive electrode current collector) was filled with a paste-like positive active material, and the electrode plate (negative electrode current collector) was filled with a paste-like negative active material. A cast grid made of a lead alloy was used as the electrode plate.

[0059] An unformed positive electrode (length 115 mm, width 58 mm, thickness 4.1 mm (dimensions of the active material region: length 115 mm, width 58 mm)) was produced by using a plate filled with a paste-like positive electrode active material and undergoing the aging process under the following aging conditions 1 to 3 and the drying process under the following drying conditions. Aging condition 1: Temperature: 80°C, Humidity: 98%, Time: 10 hours Aging condition 2: Temperature: 65°C, Humidity: 75%, Time: 13 hours Aging condition 3: Temperature: 40°C, humidity: 65%, time: 40 hours Drying conditions: Temperature: 60°C, Time: 24 hours

[0060] Using a plate filled with the paste-like negative electrode active material, an aging process was carried out under aging conditions of "temperature: 40°C, humidity: 98%, time: 40 hours" and a drying process under drying conditions of "temperature: 60°C, time: 24 hours" to produce an unformed negative electrode (length 116 mm, width 58 mm, thickness 2.5 mm (dimensions of the active material region: length 116 mm, width 58 mm)).

[0061] <Preparation of porous membrane> The following nonwoven fabric (length 250 mm, width 65 mm) was prepared as a porous membrane (porous membrane before being housed in a lead-acid battery). Porous membrane A: Basis weight 21g / m 2 , thickness 0.10 mm, porosity 80.5 vol%, porous membrane containing glass fiber and (meth)acrylic binder Porous membrane B: Basis weight 33.5g / m 2 , 0.30 mm thick, 79.6% porosity by volume, porous membrane containing glass fiber and (meth)acrylic binder Porous membrane C: basis weight 20g / m 2 , 0.07 mm thick, 71.2% porosity by volume, porous membrane containing polypropylene and pulp Porous membrane D: basis weight 28g / m 2 , 0.11 mm thick, 80.4% porosity by volume, porous membrane containing polyacrylonitrile and cellulose Porous membrane E: basis weight 21g / m 2 0.15mm thick, 95.1% porosity by volume, porous membrane containing glass fiber and binder

[0062] <Evaluation of porous membrane> (porosity) The porosity (as viewed from a direction perpendicular to the main surface) of the porous membranes A to E described above was measured using an X-ray CT device (Shimadzu Corporation, product name: SMX-160CTS) according to the following procedure. First, a 25mm x 15mm test piece was cut out from near the center of the porous membrane, and then this test piece was attached to the side of the tip of a sample holder (an acrylic resin rod with a diameter of about 5mm) with double-sided tape. At this time, the sample holder was attached to the center of the main surface of the test piece, and the test piece was placed so that a 15mm x 15mm area of ​​the test piece protruded above the tip of the sample holder. The specimen mounted on the sample stage was placed inside the X-ray CT scanner and irradiated with X-rays (X-ray source: tungsten filament, aluminum window) at an X-ray tube voltage of 55 kV and a maximum brightness of 100. The SID (Source Image Distance): 210 mm, SOD (Source Object Distance): 35 mm, and detector size: 4 inches were set, and the observation area was adjusted so that the 15 mm x 15 mm area was the target, with the sample stage excluded. Various instrument calibrations (horizontal, vertical, air, offset, mesh, etc.) were performed according to the X-ray CT scanner manual. Detailed central axis calibration was also performed using a reference sample. Measurement was initiated under the following conditions: measurement mode: full scan, view count: 1200, integration count: 6 times x 2 rotations, scaling factor: 100, image size: 512 x 512 pixels. A cylindrical measurement area with a diameter of 10.178 mm and a height of 8.588 mm was obtained. The measurement results were 3D constructed using 3D construction software (VOLUME GRAPHICS, product name: VG Studio MAX). The 3D image was rotated so that the main surface of the 3D image faced forward, and the 3D image was converted into image data. Using calculation software (MEDIA CYBERNETICS, product name: ImagePro), only the corresponding areas of the test piece in the image data (areas that make up the porous membrane) were extracted, and then the corresponding areas of the porous membrane and areas that did not correspond to the porous membrane (void areas) were binarized. Using this calculation software, the area ratio of the black areas (areas that did not correspond to the porous membrane) after binarization was obtained as the porosity. The results are shown in Table 1.

[0063] (Thermogravimetric reduction rate) The thermal weight loss rates of the porous membranes A, B, and E were measured by the following procedure. First, a test piece of about 10 mg was cut from the center of the porous membrane, and then the test piece was placed in a container (aluminum pan). The container containing the test piece was placed in a thermogravimetric and differential thermal analyzer (manufactured by Hitachi High-Tech Science Corporation, product name: STA7200). The test piece was heated under the following conditions: "Measurement atmosphere: air, flow rate: 100 mL / min, heating conditions: heating from 25 ° C (room temperature) to 100 ° C at 10 ° C / min → heating at 100 ° C for 60 minutes (removal of moisture) → heating from 100 ° C to 800 ° C at 5 ° C / min → heating at 800 ° C for 15 minutes." The difference between the weight W11 at the end of 60 minutes of heating at 100 ° C and the weight W12 at the end of 15 minutes of heating at 800 ° C was calculated as the weight loss (W11 - W12). The ratio of the weight loss (W11-W12) to the weight W11 ([(W11-W12) / W11] x 100) was calculated as the thermal weight loss rate (unit: %). The results are shown in Table 1.

[0064] (Weight loss rate when immersed in sulfuric acid) The weight loss rate when the above-mentioned porous membranes A, B, D, and E were immersed in sulfuric acid was measured by the following procedure. First, a test piece of approximately 0.5 g was cut from near the center of the above-mentioned porous membrane, and the weight W21 of the test piece was measured. The test piece was dried at 50 ° C for 1 hour while evacuating in a vacuum dryer. The test piece was immersed in sulfuric acid (25 ° C) with a specific gravity of 1.28 for 24 hours, and then removed from the sulfuric acid. The test piece was rinsed twice in ultrapure water and then immersed in a large amount of ultrapure water for 1 hour. After removing the test piece from the ultrapure water, the test piece was dried at 50 ° C. After visually confirming that the test piece was dry, it was further dried for 1 hour while evacuating. The weight W22 of the test piece was measured, and the difference between weight W21 and weight W22 was calculated as the weight loss (W21 - W22). The ratio of the weight loss (W21-W22) to the weight W21 ([(W21-W22) / W21] x 100) was obtained as the weight loss rate (unit: %) upon immersion in sulfuric acid. The results are shown in Table 1.

[0065] <Separator production> Separator A (thickness: 0.40 mm) and separator B (thickness: 0.60 mm) were prepared as separators (trade name: BMS-5, manufactured by Nippon Sheet Glass Co., Ltd.) measuring 250 mm in length and 65 mm in width. When the porosity of the separators was measured using the same procedure as for the porous membrane described above, the porosity of separator A and separator B was 1% or less. When the rate of weight loss due to heat was measured using the same procedure as for the porous membrane described above, the rate of weight loss due to heat of separator A and separator B was 1% or less. When the rate of weight loss due to weight loss of the separators when immersed in sulfuric acid was measured using the same procedure as for the porous membrane described above, the rate of weight loss of separator A and separator B was 1% or less. When the rate of weight loss due to ...

[0066] <Making a lead-acid battery> (Examples 1 to 2 and Comparative Examples 1 to 3) The separator A (thickness: 0.4 mm) was folded longitudinally, and both main surfaces of the unformed positive electrode (active material region of the positive electrode) were coated with the separator A to obtain a positive electrode member A. The porous membrane was also folded longitudinally, and both main surfaces of the positive electrode member A were coated with the porous membrane to obtain a positive electrode member B. The longitudinal directions of the positive electrode, separator A, and porous membrane were the same, and the folded portions of the separator A and porous membrane were positioned at one end side of the longitudinal direction of the positive electrode (the lower end side of the positive electrode in the vertical direction when the positive electrode is housed in a lead-acid battery). The separator A and porous membrane were then arranged. Subsequently, three positive electrode members B and four unformed negative electrodes were alternately stacked to produce an electrode group. After inserting the electrode group and spacers into a battery case, the positive electrode terminal and negative electrode terminal were welded to the electrode group, and the battery case was then sealed. At this time, the distance between the positive and negative electrodes was adjusted to 0.41 mm by adjusting the thickness of the spacer. Next, an electrolyte solution mainly composed of dilute sulfuric acid with a specific gravity of 1.19 was poured into the battery case through the exhaust plug, and then a battery case chemical formation cap was attached, thereby producing a total of two lead-acid batteries (battery capacity: 15 Ah) in each example and comparative example.

[0067] Comparative Example 4 A total of two lead-acid batteries (battery capacity: 15 Ah) were produced by performing the same operation as above, except that separator B (thickness: 0.6 mm) was used instead of separator A, and that an electrode group was produced by alternately stacking three positive electrode members A and four unformed negative electrodes without using a porous membrane.

[0068] <Permeation short circuit evaluation> To evaluate permeation short circuits, two of the above-mentioned lead-acid batteries were left in a water tank at 40°C for three hours, and then charged and discharged (battery tank formation) using the following procedure. Cases in which none of the two lead-acid batteries underwent permeation short circuits were evaluated as "A," and cases in which one or two lead-acid batteries underwent permeation short circuits were evaluated as "B." A drop in inter-terminal voltage to 1.0 V was determined to be a permeation short circuit. The results are shown in Table 1. {Charge / discharge conditions} First charge: Current 3.0A, 15.0 hours First discharge: Current 3.0A, 1.5 hours Second charge: Current 3.0A, 19.0 hours Second discharge: Current 3.0A, 3.0 hours Third charge: Current 3.0A, 16.0 hours Third discharge: 3.0A, 3.5 hours 4th charging: current 1.5A, 9.0 hours

[0069] [Table 1] [Explanation of symbols]

[0070] 10...electrode group, 20...positive electrode, 30...negative electrode, 40...separator, 50...porous membrane, 100...lead-acid battery.

Claims

1. A battery comprising a positive electrode, a negative electrode, a separator, and a porous membrane, the separator and the porous membrane contain glass fibers and are disposed between the positive electrode and the negative electrode, the porous membrane is disposed at least one between the positive electrode and the separator and between the negative electrode and the separator, A lead-acid battery, wherein the porosity obtained by X-ray CT measurement of the porous membrane is 18.0% or more.

2. A lead-acid battery as described in claim 1, wherein the porosity is 18.0 to 50.0%.

3. 2. The lead-acid battery of claim 1, wherein the porous membrane comprises a porous membrane disposed between the negative electrode and the separator.

4. The lead-acid battery according to claim 1 , wherein the porous membrane is a nonwoven fabric.

5. A lead-acid battery as described in claim 4, wherein the thickness of the porous membrane is 0.22 mm or more.

6. The lead-acid battery according to claim 1, wherein the thickness of the porous film is smaller than the thickness of the separator.

7. The lead acid battery according to claim 1, wherein the porous film has a thickness of 0.01 to 0.50 mm.

8. A method for producing a lead acid battery according to any one of claims 1 to 7, The method for manufacturing a lead-acid battery, wherein the porous membrane is disposed between the positive electrode and the negative electrode.

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