Storage battery employing separator having electrically conductive layer

Abstract

Provided is a storage battery including a positive electrode 1 having a positive electrode tab 2, a negative electrode 3 having a negative electrode tab 4, and a separator 5, characterized in that: the separator 5 is disposed between the positive electrode 1 and the negative electrode 3; the separator 5 has protruding portions that protrude from both electrodes, and includes a base material and an electrically conductive layer that covers a portion of the base material; the covered range reaches an end portion of the base material adjacent to the tab 2 or 4; and (I) the electrically conductive layer is in electrical contact with the positive electrode 1, and the shortest distance between the electrically conductive layer and the negative electrode tab 4 at the end portion of the base material adjacent to the negative electrode tab is at least 500 μm, and / or (II) the electrically conductive layer is in electrical contact with the negative electrode 3, and the shortest distance between the electrically conductive layer and the positive electrode tab 2 at the end portion of the base material adjacent to the positive electrode tab 2 is at least 500 μm.

Description

Storage battery using a separator with a conductive layer

[0001] The present disclosure relates to a storage battery using a separator having a conductive layer.

[0002] In recent years, techniques have been reported for improving battery performance by using a separator whose surface is made electrically conductive. For example, Patent Document 1 reports a technique for improving the charge acceptance and cycle life of a storage battery by using a separator coated with an electrically conductive carbon material.

[0003] International Publication No. 2015 / 171595

[0004] However, when a conductive material is added to a separator that is supposed to ensure insulation between electrodes, there is a concern that the insulation between electrodes, such as voltage resistance, may be reduced. Therefore, there is room for improvement in systematic battery design to increase voltage resistance.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a storage battery with high withstand voltage using a separator having a conductive layer on a substrate.

[0006] The above problems can be solved by the following technical means: Examples of embodiments of the present disclosure are listed below. (1) A storage battery including a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, the separator is made of at least a substrate and a conductive layer that covers a portion of the substrate, and the coverage area of ​​the conductive layer reaches at least the substrate end of the substrate adjacent to the positive electrode tab or the negative electrode tab, and (I) the conductive layer is in electrical contact with the positive electrode, and the shortest distance between the conductive layer at the substrate end adjacent to the negative electrode tab and the negative electrode tab is 500 μm or more; and / or (II) the conductive layer is in electrical contact with the negative electrode, and the shortest distance between the conductive layer at the substrate end adjacent to the positive electrode tab and the positive electrode tab is 500 μm or more. (2) A storage battery including a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, and the separator is made of at least a substrate and a conductive layer that covers a portion of the substrate, and wherein: (III) the conductive layer is in electrical contact with the positive electrode, and an end portion of the substrate adjacent to the negative electrode tab does not have the conductive layer; and / or (IV) the conductive layer is in electrical contact with the negative electrode, and an end portion of the substrate adjacent to the positive electrode tab does not have the conductive layer.(3) A storage battery including a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, the separator comprising at least a substrate and a conductive layer covering a portion of the substrate, and the covering area of ​​the conductive layer reaches at least an end portion of the substrate adjacent to the positive electrode tab or the negative electrode tab, and (V) the conductive layer is in electrical contact with the positive electrode, and the surface of the negative electrode tab is covered with an insulating material; and / or (VI) the conductive layer is in electrical contact with the negative electrode, and the surface of the positive electrode tab is covered with an insulating material. (4) The storage battery according to item 1, wherein the shortest distance is 1500 μm or less. (5) The storage battery according to item 1, wherein the shortest distance is 655 μm or more. (6) The storage battery according to item 1, wherein the shortest distance is 950 μm or more. (7) The storage battery according to any one of items 1 to 6, wherein the substrate is in the form of a rectangular sheet. (8) The storage battery according to any one of items 1 to 7, wherein the surface electrical resistance of the conductive layer is 5,000 Ω or less. (9) The storage battery according to any one of items 1 to 8, wherein the conductive layer contains a carbon material. (10) The storage battery according to any one of items 1 to 9, wherein the substrate contains polyolefin. (11) The storage battery according to any one of items 1 to 10, wherein the positive electrode tab and the negative electrode tab contain lead. (12) The storage battery according to any one of items 1 to 11, wherein the positive electrode tab contains aluminum and the negative electrode tab contains nickel. (13) The storage battery according to any one of items 1 to 12, wherein the storage battery is a lead-acid battery. (14) The storage battery according to any one of items 1 to 13, wherein the storage battery is a lithium-ion battery.

[0007] According to the present disclosure, a storage battery with high withstand voltage can be provided by using a separator having a conductive layer on a substrate.

[0008] 1A shows a case where a separator without a conductive layer is disposed between a positive electrode and a positive electrode tab, and a negative electrode and a negative electrode tab; FIG. 1B shows a schematic diagram of the laminate observed from the negative electrode side; and FIG. 1C shows a cross-sectional view taken along the dotted line a-b in the side view of FIG. 1B. 1A shows a case where a separator without a conductive layer is disposed between a positive electrode and a negative electrode with the conductive layer of the separator facing the positive electrode; FIG. 1B shows a schematic diagram of the laminate observed from the negative electrode side with the separator electrically in contact with the positive electrode; and FIG. 1C shows a cross-sectional view taken along the dotted line a-b in the side view of FIG. 1B. 1A shows a case where a separator without a conductive layer is disposed between a positive electrode and a negative electrode with the conductive layer of the separator facing the negative electrode; FIG. 1B shows a schematic diagram of the laminate observed from the negative electrode side with the separator electrically in contact with the negative electrode; and FIG. 1C shows a cross-sectional view taken along the dotted line a-b in the side view of FIG. 1B. 1A shows a case where a separator is disposed between positive and negative electrodes with a conductive layer coated on the entire surface of the separator substrate facing the positive electrode, (b) a schematic diagram illustrating the shortest distance between the conductive layer at the separator substrate end and the negative electrode tab, and (c) a cross-sectional view taken along dotted lines a-b according to an embodiment of the present invention. 1A shows a case where a separator is disposed between positive and negative electrodes with a conductive layer coated on a portion of the separator substrate surface facing the positive electrode, (b) a schematic diagram illustrating the shortest distance between the conductive layer at the separator substrate end and the negative electrode tab, and (c) a cross-sectional view taken along dotted lines a-b according to an embodiment of the present invention. 1A shows a case where a separator is disposed between positive and negative electrodes with a conductive layer coated on the entire surface of the separator substrate facing the negative electrode, (b) a schematic diagram illustrating the shortest distance between the conductive layer at the separator substrate end and the positive electrode tab, and (c) a cross-sectional view taken along dotted lines a-b according to another embodiment of the present invention. 1A shows a case where a separator is disposed between a positive and negative electrode such that a conductive layer coated on a portion of the separator substrate surface faces the negative electrode, (b) is a schematic diagram illustrating the shortest distance between the conductive layer at the separator substrate end and the positive electrode tab, and (c) is a cross-sectional view taken along the dotted line a-b. 1A shows a case where a separator is disposed between a positive and negative electrode in another embodiment of the present invention, in which a conductive layer is not provided at the separator end facing the negative electrode tab or the positive electrode tab, but has conductive layers on other surfaces, (b) is a schematic diagram illustrating a case where the separator is electrically connected to the positive or negative electrode but has no conductive layer at the a-b portion, and (c) is a cross-sectional view taken along the dotted line a-b.1A shows a case where a separator having a conductive layer is disposed between positive and negative electrodes by covering a positive electrode tab with an insulating material in yet another embodiment of the present invention, (a) a schematic view observed from the negative electrode side of the laminate, (b) a cross-sectional view (c) between dotted lines a-b. 1B shows a case where a separator having a conductive layer is disposed between positive and negative electrodes by covering a negative electrode tab with an insulating material in yet another embodiment of the present invention, (a) a schematic view observed from the negative electrode side of the laminate, (b) a cross-sectional view (c) between dotted lines a-b. 1C shows a case where a separator not having a conductive layer is disposed between positive and negative electrodes in a striped pattern on at least a portion of the substrate surface of a separator sample for voltage resistance measurement, (a) a schematic view observed from the negative electrode side of the laminate, and (b) a cross-sectional view (c) between dotted lines a-b. 9A is a layout diagram showing components and their dimensions for measuring the shortest distance between the conductive layer at the separator substrate end and the negative electrode tab or positive electrode tab; FIG. 9B is a schematic diagram of the measurement sample observed from the negative electrode side; and FIG. 9C is a cross-sectional view of the voltage resistance measurement sample taken in a direction perpendicular to the dotted line a-b in the same plane.

[0033] In each example and comparative example, a schematic cross-sectional view for schematically illustrating a cross section corresponding to the dotted line a-b in FIG. 9A is a schematic perspective view showing an application example for using a circular substrate in an embodiment of the present invention.

[0034] In one embodiment of the present invention, a schematic perspective view showing an application example of double-sided coating of a conductive layer on a substrate, showing a case where a tab contacts a conductive layer that contacts the substrate end (a) and a case where a tab contacts a conductive layer that does not contact the substrate end (b).

[0009] 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 various modifications can be made within the scope of the gist thereof.

[0010] <Storage Battery> A storage battery according to the present embodiment is a storage battery including a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, the separator includes at least a substrate, at least a portion of the substrate is coated with a conductive layer, and the coverage of the conductive layer reaches at least an end of the substrate adjacent to the tab, and is characterized in that: (I) the conductive layer is in electrical contact with the positive electrode, and the shortest distance between the conductive layer at the end of the substrate adjacent to the negative electrode tab and the negative electrode tab is 500 μm or more; and / or (II) the conductive layer is in electrical contact with the negative electrode, and the shortest distance between the conductive layer at the end of the substrate adjacent to the positive electrode tab and the positive electrode tab is 500 μm or more.

[0011] In this specification, the shortest distance is the shortest distance between the conductive layer and the electrode tab whose surface is not insulated. In one embodiment, by satisfying the above (I) and / or (II), a storage battery with high withstand voltage can be provided.

[0012] The substrate in this specification refers to an insulating film having micropores, and is preferably an insulating film containing polyolefin and / or inorganic particles. The insulating film substrate may be a single layer or a multilayer, and an example is a substrate in which an inorganic layer composed of inorganic particles and a resin binder is provided on one or both sides of a microporous film containing polyolefin.

[0013] In the present embodiment, even if the separator has a layer structure of three or more layers, such as substrate / conductive layer / substrate, a high withstand voltage can be obtained if the above (I) and / or (II) is satisfied. Therefore, the separator according to the present embodiment may have not only a two-layer structure of a substrate and a conductive layer, but also a multilayer structure, such as substrate / conductive layer / substrate or conductive layer / substrate / conductive layer, as long as the above (I) and / or (II) is satisfied.

[0014] From the viewpoint of increasing the withstand voltage at the electrode ends, the separator is preferably larger than the positive electrode and negative electrode and has protruding portions, more preferably 0.5 mm or more larger than the positive electrode and negative electrode ends, even more preferably 1.0 mm or more larger, still more preferably 2.0 mm or more larger, and particularly preferably 3.0 mm or more larger.

[0015] Furthermore, the storage battery preferably contains an electrolytic solution or an electrolyte (in the case of an all-solid-state battery). As illustrated in FIG. 1, when a separator (5) without a conductive layer is disposed between a positive electrode (1) and a positive electrode tab (2) and a negative electrode (3) and a negative electrode tab (4), a high withstand voltage is exhibited. On the other hand, when the separator (5) has a conductive layer (7) on its surface and the conductive layer (7) is electrically connected to the positive electrode (1), the conductive layer (7) can be regarded as part of the positive electrode (1). Therefore, as shown in FIG. 2, the shortest distance between the conductive layer (7) and the negative electrode tab (4) is shortened (FIG. 2(c)), thereby reducing the withstand voltage. Therefore, the withstand voltage can be increased by designing the storage battery so that the shortest distance between the conductive layer at the end of the substrate and the negative electrode tab is at least a certain value apart, as described above in (I). Similarly, when the separator (5) has a conductive layer (7) and the conductive layer (7) is in electrical contact with the negative electrode (3), the conductive layer (7) can be considered part of the negative electrode (3). Therefore, as shown in FIG. 3 , the shortest distance between the conductive layer (7) and the positive electrode tab (2) is shortened ( FIG. 3(c) ), resulting in a decrease in withstand voltage. Therefore, by designing a storage battery so that the shortest distance between the conductive layer at the end of the substrate and the positive electrode tab is at least a certain distance, as described in (II) above, the withstand voltage can be increased. As described above, the unique issue that arises when a separator having a conductive layer is used in a storage battery, i.e., a decrease in withstand voltage, can be addressed by controlling the distance between the electrode tab and the conductive layer. Therefore, the effect of the present invention is not limited to a specific battery, but can be achieved in any storage battery using a separator having a conductive layer. Specifically, examples of the storage battery according to this embodiment include lead-acid batteries, lithium-ion batteries, and redox flow batteries.

[0016] In the storage battery according to this embodiment, when the conductive layer is in electrical contact with the positive electrode, the shortest distance between the conductive layer at the substrate end and the negative electrode tab is preferably 500 μm or more, more preferably 600 μm or more, from the viewpoint of increasing the withstand voltage to 0.50 kV or more. From the viewpoint of increasing the withstand voltage to 1.00 kV or more, the shortest distance between the conductive layer at the substrate end and the negative electrode tab is preferably 655 μm or more, more preferably 700 μm or more, even more preferably 800 μm or more, still more preferably 850 μm or more, and particularly preferably 900 μm or more. Furthermore, from the viewpoint of increasing the withstand voltage to 1.50 kV or more, the shortest distance between the conductive layer at the substrate end and the negative electrode tab is preferably 950 μm or more, most preferably 1000 μm or more. The shortest distance between the conductive layer at the end of the substrate and the negative electrode tab in this embodiment is the shortest distance (d １ As shown in FIG. 4A(b) or FIG. 4B(b), by increasing the thickness of the substrate (6) or using a substrate (6) having a convex structure such as a conductive layer (7) on its surface, the shortest distance (d １ 4A(c) and 4B(c), the location where the conductive layer (7) is provided is adjusted based on the end of the substrate adjacent to the negative electrode tab (4), and the shortest distance (d １ By adjusting the thickness to 500 μm or more, the withstand voltage is improved.

[0017] Furthermore, from the viewpoint of reducing the inter-electrode ionic resistance in the storage battery by shortening the shortest distance between the conductive layer at the end of the substrate and the negative electrode tab, the shortest distance between the conductive layer at the end of the substrate and the negative electrode tab is preferably 5000 μm or less, more preferably 4000 μm or less, even more preferably 3000 μm or less, still more preferably 2000 μm or less, and particularly preferably 1500 μm or less.

[0018] In the storage battery according to this embodiment, when the conductive layer is in electrical contact with the negative electrode, the shortest distance between the conductive layer at the end of the substrate and the positive electrode tab is preferably 500 μm or more, more preferably 600 μm or more, from the viewpoint of increasing the withstand voltage to 0.50 kV or more. From the viewpoint of increasing the withstand voltage to 1.00 kV or more, the shortest distance between the conductive layer at the end of the substrate and the positive electrode tab is preferably 655 μm or more, more preferably 700 μm or more, even more preferably 800 μm or more, still more preferably 850 μm or more, and particularly preferably 900 μm or more. Furthermore, from the viewpoint of increasing the withstand voltage to 1.50 kV or more, the shortest distance between the conductive layer at the end of the substrate and the positive electrode tab is preferably 950 μm or more, most preferably 1000 μm or more. The shortest distance between the conductive layer at the end of the substrate and the positive electrode tab according to the embodiment of the present invention is the shortest distance (d ２ As shown in FIG. 5A(b) or FIG. 5B(b), by increasing the thickness of the substrate (6) or using a substrate (6) having a convex structure such as a conductive layer (7) on its surface, the shortest distance (d ２ 5A(c) and 5B(c), the location where the conductive layer (7) is provided is adjusted based on the end of the substrate adjacent to the positive electrode tab (2), and the shortest distance (d ２ By adjusting the thickness to 500 μm or more, the withstand voltage is improved.

[0019] Furthermore, from the viewpoint of reducing the inter-electrode ionic resistance in the storage battery by shortening the shortest distance between the conductive layer at the end of the substrate and the positive electrode tab, the shortest distance between the conductive layer at the end of the substrate and the positive electrode tab is preferably 5000 μm or less, more preferably 4000 μm or less, even more preferably 3000 μm or less, still more preferably 2000 μm or less, and particularly preferably 1500 μm or less.

[0020] Another embodiment of the present invention provides a storage battery comprising: a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes; the separator includes at least a substrate, and at least a portion of the substrate is coated with a conductive layer; and wherein: (III) the conductive layer is in electrical contact with the positive electrode, and an end of the substrate adjacent to the negative electrode tab does not have the conductive layer; and / or (IV) the conductive layer is in electrical contact with the negative electrode, and an end of the substrate adjacent to the positive electrode tab does not have the conductive layer;

[0021] In another embodiment, even when the separator has a layer structure of three or more layers, such as substrate / conductive layer / substrate, a high withstand voltage can be obtained if the above (III) and / or (IV) is satisfied. Therefore, the separator according to another embodiment may have not only a two-layer structure of a substrate and a conductive layer, but also a multilayer structure, such as substrate / conductive layer / substrate or conductive layer / substrate / conductive layer, as long as the above (III) and / or (IV) is satisfied.

[0022] From the viewpoint of increasing the withstand voltage at the electrode ends, the separator is preferably larger than the positive electrode and negative electrode and has protruding portions, more preferably 0.5 mm or more larger than the positive electrode and negative electrode ends, even more preferably 1.0 mm or more larger, still more preferably 2.0 mm or more larger, and particularly preferably 3.0 mm or more larger.

[0023] In another embodiment, the storage battery preferably contains an electrolytic solution or electrolyte (in the case of an all-solid-state battery). As illustrated in Figure 6, by designing the separator end facing the negative electrode tab (4) or the positive electrode tab (2) without a conductive layer (7), the above (III) and / or (IV) can be satisfied, thereby increasing the withstand voltage between the conductive layer (not shown) electrically contacting the positive electrode and the negative electrode tab, or between the conductive layer (Figure 6(b)) electrically contacting the negative electrode and the positive electrode tab. In Figure 6, the separator end facing the negative electrode tab (4) or the positive electrode tab (2) is referred to as the a-b portion. From the viewpoint of increasing the withstand voltage, the conductive layer is preferably not provided for a distance of 500 μm or more, more preferably 600 μm or more, even more preferably 700 μm or more, still more preferably 800 μm or more, and particularly preferably 900 μm or more, and from the viewpoint of increasing the withstand voltage to 1.50 kV or more, the conductive layer is most preferably not provided for a distance of 1.00 mm or more, from the separator end facing the negative electrode tab or the positive electrode tab, toward the inward side of the plane. As described above, in order to address a specific issue that arises when a separator having a conductive layer is used in a storage battery, i.e., a decrease in withstand voltage, by not providing a conductive layer at the separator end adjacent to the electrode tab, an effect of increasing withstand voltage can be obtained. Therefore, in principle, the effect of the present invention is not obtained only in a specific battery, but can be achieved in any storage battery as long as it uses a separator having a conductive layer. Specifically, examples of the storage battery according to another embodiment include a lead storage battery, a lithium ion battery, and a redox flow battery.

[0024] Furthermore, a storage battery according to yet another embodiment of the present invention is a storage battery including a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, the separator includes at least a substrate, at least a portion of the substrate is coated with a conductive layer, and the coverage of the conductive layer reaches at least an end of the substrate adjacent to the tab, and (V) the conductive layer is in electrical contact with the positive electrode, and the surface of the negative electrode tab is coated with an insulating material; and / or (VI) the conductive layer is in electrical contact with the negative electrode, and the surface of the positive electrode tab is coated with an insulating material.

[0025] In yet another embodiment, even when the separator has a layer structure of three or more layers, such as substrate / conductive layer / substrate, a high withstand voltage can be obtained when the above (V) and / or (VI) is satisfied. Therefore, the separator according to yet another embodiment may have not only a two-layer structure of a substrate and a conductive layer, but also a multilayer structure, such as substrate / conductive layer / substrate or conductive layer / substrate / conductive layer, as long as the above (V) and / or (VI) is satisfied.

[0026] From the viewpoint of increasing the withstand voltage at the electrode ends, the separator is preferably larger than the positive electrode and negative electrode and has protruding portions, more preferably 0.5 mm or more larger than the positive electrode and negative electrode ends, even more preferably 1.0 mm or more larger, still more preferably 2.0 mm or more larger, and particularly preferably 3.0 mm or more larger.

[0027] In yet another embodiment, the storage battery preferably contains an electrolytic solution or electrolyte (in the case of an all-solid-state battery). As illustrated in Figures 7A and 7B, by covering the negative electrode tab (4) or the positive electrode tab (2) with an insulating material (8) (Figures 7A(a)-(c) or 7B(a)-(c)), short-circuiting between the conductive layer (7) of the separator (5) and the positive electrode tab (2) or between the conductive layer (7) of the separator (5) and the negative electrode tab (4) can be suppressed. By covering the entire surface of the negative electrode tab or the positive electrode tab with an insulating material, the withstand voltage can be improved.

[0028] Furthermore, when a portion of the negative electrode tab is covered with an insulating material, the shortest distance between the conductive layer at the separator end and the negative electrode tab that is not partially covered with the insulating material is preferably 500 μm or more, more preferably 600 μm or more, even more preferably 655 μm or more, still more preferably 700 μm or more, still more preferably 800 μm or more, still more preferably 850 μm or more, particularly preferably 900 μm or more, and most preferably 1000 μm or more.

[0029] Furthermore, when a portion of the positive electrode tab is covered with an insulating material, the shortest distance between the conductive layer at the separator end and the positive electrode tab that is not partially covered with the insulating material is preferably 500 μm or more, more preferably 600 μm or more, even more preferably 655 μm or more, still more preferably 700 μm or more, still more preferably 800 μm or more, still more preferably 850 μm or more, particularly preferably 900 μm or more, and most preferably 1000 μm or more.

[0030] The insulating material covering the electrode tab is not particularly limited as long as it can ensure insulation, but specific examples include epoxy resin, silicone resin, fluorine-based polymer, polyolefin (e.g., polyethylene, polypropylene, etc.), polyamide, acrylic resin, polyimide, polyvinyl chloride, etc. Coating methods include applying a liquid resin to the electrode tab and curing it (which can be further dried as necessary), or covering the electrode tab with insulating tape. From the viewpoint of increasing the withstand voltage, the thickness of the insulating material covering the electrode tab is preferably 1.0 μm or more, more preferably 10 μm or more, even more preferably 100 μm or more, even more preferably 300 μm or more, particularly preferably 500 μm or more, and most preferably 1000 μm or more.

[0031] As described above, the use of a separator having a conductive layer in a storage battery addresses a particular issue of reduced withstand voltage, and the effect of increasing withstand voltage can be achieved by covering the electrode tabs with an insulating material. Therefore, the effect of the present invention is not limited to a specific battery in principle, but can be achieved in any battery that uses a separator having a conductive layer. Specifically, examples of storage batteries according to further embodiments include lead-acid batteries, lithium-ion batteries, and redox flow batteries.

[0032] The storage battery according to the present embodiment can arbitrarily combine the above battery design or features (I) to (VI), and a storage battery that satisfies at least one of the above (I) to (VI) is also an aspect of the present invention. Common or preferred configurations for storage batteries that satisfy at least one of the above (I) to (VI) and their manufacturing methods are described below.

[0033] <<Substrate>> The substrate according to the present embodiment is preferably an insulating film having micropores, more preferably an insulating film containing polyolefin and / or inorganic particles, in order to allow ions to pass therethrough and prevent electrical short circuits. The insulating film substrate may be a single layer or a multilayer, and an example is a substrate in which an inorganic layer composed of inorganic particles and a resin binder is provided on one or both sides of a microporous film containing polyolefin.

[0034] Furthermore, regarding the shape of the substrate, a rectangular sheet is described as being preferred in this embodiment, but a circular sheet may also be used as long as the effects of the present invention are achieved. An application example using a circular substrate is shown in Figure 11. When a circular substrate (6) is used, the shortest distance according to the present invention, as shown in Figure 11, refers to the shortest distance (d) between the conductive layer (7) and the tab (T) at the end of the substrate, and does not refer to the distance or path (not shown) along the periphery of the circular substrate.

[0035] The mean flow pore diameter of the microporous substrate is preferably 500 nm or less, more preferably 400 nm or less, even more preferably 300 nm or less, still more preferably 200 nm or less, still more preferably 175 nm or less, even more preferably 150 nm or less, significantly more preferably 125 nm or less, particularly preferably 100 nm or less, and most preferably 80 nm or less. On the other hand, from the viewpoint of preventing the micropores of the substrate from becoming blocked by by-products accompanying the charge / discharge reactions of the storage battery, the mean flow pore diameter is preferably 1 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, and still more preferably 20 nm or more.

[0036] Furthermore, from the viewpoint of suppressing electrical short circuits, the maximum pore size of the substrate is preferably 2000 nm or less, more preferably 1000 nm or less, even more preferably 800 nm or less, even more preferably 500 nm or less, even more preferably 400 nm or less, even more preferably 300 nm or less, even more preferably 200 nm or less, even more preferably 175 nm or less, even more preferably 150 nm or less, even more preferably 125 nm or less, or even more preferably 100 nm or less. Furthermore, from the viewpoint of suppressing the micropores of the substrate from being blocked by by-products accompanying the charge / discharge reactions of the storage battery, the maximum pore size of the substrate is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 20 nm or more, and particularly preferably 30 nm or more.

[0037] The maximum pore size and mean flow pore size of a substrate can be determined as follows.

[0038] <Maximum pore size> A PMI Perm Porometer (model: CFP-1500AL) is used as the measuring device, and a substrate is used as the sample to be measured. Compressed air is passed through the substrate while all pores are filled with a test liquid having a known surface tension, and the pore size of the substrate is measured. As the test liquid, Galwick liquid manufactured by PMI is used for samples to be measured with a maximum pore size of less than 100 μm, and pure water is used for samples to be measured with a maximum pore size of 100 μm or more. First, a substrate cut to 25 mm diameter is immersed in the test liquid, and after removing excess test liquid, measurement is performed. The pore size of the pore can be calculated from the pressure when air passes through the pores filled with the test liquid and the surface tension of the test liquid, and the following formula is used for the calculation. d ｐｏｒｅ = C γ / P {where d ｐｏｒｅis the pore size of the substrate, γ is the surface tension of the test liquid, P is the minimum air pressure at which air passes through the pore size, and C is a constant. First, the air flow rate (wet flow rate) is measured when the pressure P applied to the substrate immersed in the test liquid is continuously increased. At the beginning of the measurement, all pores of the sample to be measured, such as a nonwoven fabric, are filled with the test liquid, so the air flow rate is 0. However, as the pressure increases, air eventually begins to pass through the pore with the largest pore size, and a positive air flow rate is first observed (this point is called the bubble point). The maximum pore size d ｍａｘ means the pore size of the substrate derived at the bubble point.

[0039] <Mean Flow Pore Diameter> In the above <Maximum Pore Diameter> measurement, after the bubble point, as the pressure is further increased, the air flow rate increases and approaches the air flow rate when the substrate is dry (dry flow rate). The air flow rate after the smallest pore opens completely matches the dry flow rate. In this measurement method, the cumulative filter flow rate (unit: %) is defined as the wet flow rate at a certain air pressure divided by the dry flow rate at the same pressure. In this specification, the pore size that opens at an air pressure where the cumulative filter flow rate is 50% is defined as the mean flow pore size.

[0040] The substrate is not particularly limited as long as it has micropores that allow ions to pass through. Preferred examples include porous membranes made from natural or synthetic materials, such as thermoplastic polymers such as polyvinyl and polyolefins (polypropylene, polyethylene), thermosetting polymers such as phenolic resins, rubber materials such as natural or synthetic rubber and latex, fibrous materials such as synthetic wood pulp (SWP), glass fiber, synthetic fiber, and cellulose fiber, and combinations thereof. Among these, when the substrate is used in a lead-acid battery, it preferably contains polyethylene. From the viewpoint of improving membrane strength or durability within the battery, the polyethylene is preferably a high-molecular-weight polyethylene with a weight-average molecular weight of 600,000 or more. The polyethylene is more preferably ultra-high molecular weight polyethylene (UHMWPE), i.e., polyethylene with a weight-average molecular weight of 1,000,000 or more, particularly preferably a weight-average molecular weight of 4,000,000 or more, and most preferably a weight-average molecular weight of 5,000,000 to 8,000,000. In this specification, ultra-high molecular weight polyethylene means polyethylene having a weight average molecular weight of 1,000,000 or more.

[0041] When the substrate according to this embodiment is used in a lead-acid battery, it preferably contains 10 to 40 parts by mass of polyethylene per 100 parts by mass of the substrate. From the viewpoint of enhancing the mechanical film strength and oxidation resistance of the substrate by polyethylene, the polyethylene content is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more per 100 parts by mass of the substrate. Furthermore, from the viewpoint of reducing the blending ratio of hydrophobic polyethylene in the substrate and reducing the electrical resistance of the substrate inside the lead-acid battery, the substrate preferably contains hydrophilic inorganic particles. In this case, the polyethylene content is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less per 100 parts by mass of the substrate. When the substrate is used in a storage battery other than a lead-acid battery, the lower limit of the polyethylene content per 100 parts by mass of the substrate is not particularly limited, but may be, for example, more than 0 parts by mass or 1 part by mass or more.

[0042] When the substrate according to this embodiment is used in a lead-acid battery, the inorganic particles are preferably contained in an amount of 40 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the substrate. From the viewpoint of enhancing the hydrophilicity of the substrate, the inorganic particles are preferably contained in an amount of 40 parts by mass or more, more preferably 45 parts by mass or more, and even more preferably 50 parts by mass or more per 100 parts by mass of the substrate. Furthermore, since a large mass ratio of inorganic particles in the substrate relatively reduces the mass ratio of polyethylene and weakens the binding strength between the inorganic particles and polyethylene, the inorganic particles are preferably contained in an amount of 70 parts by mass or less, more preferably 69 parts by mass or less, even more preferably 68 parts by mass or less, even more preferably 67 parts by mass or less, even more preferably 66 parts by mass or less, even more preferably 65 parts by mass or less, even more preferably 64 parts by mass or less, even more preferably 63 parts by mass or less, even more preferably 62 parts by mass or less, or even more preferably 61 parts by mass or less per 100 parts by mass of the substrate.

[0043] Examples of inorganic particulate materials contained in the substrate 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 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, volkonsco Icite, 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, polylithiolite Examples of suitable mineral species include muscovite, celadonite, ferro-celadonite, ferro-aluminoceladonite, aluminoceladonite, tobe mica, sodalite, klinite, kinoshite, vite mica, anandite, nacre, clinochlore, chamosite, pennantite, nimite, bailichlore, dombassite, cookesite, sudoite, hydrotalcite, calcium silicate, magnesium silicate, aluminum silicate, diatomaceous earth, and silica sand.

[0044] Among the above examples, the inorganic particles used in the substrate are preferably particles of silica, alumina, kaolin, titania, aluminum silicate, or barium sulfate, which have excellent acid resistance and oxidation resistance and are highly hydrophilic, more preferably silica particles, and even more preferably amorphous silica particles produced by a precipitation method.

[0045] The inorganic particles according to the present embodiment may be used alone or in combination of two or more kinds.

[0046] When the substrate according to the present embodiment is used in a lead-acid battery, it is preferable that the substrate contains 0.1 to 35 parts by mass of a plasticizer relative to 100 parts by mass of the substrate in order to improve the oxidation resistance of the substrate. The plasticizer is preferably oil, and may be petroleum, paraffin-based mineral oil, mineral oil, or any combination thereof.

[0047] The thickness of the substrate according to the present embodiment is not particularly limited, but from the viewpoint of reducing the ionic resistance in the battery, it is preferably 5.0 mm or less, more preferably 3.0 mm or less, even more preferably 2.0 mm or less, and still more preferably 1.5 mm or less. Furthermore, from the viewpoint of increasing the withstand voltage by lengthening the shortest distance between the conductive layer and the electrode tab, the thickness of the substrate is preferably 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, even more preferably 15 μm or more, even more preferably 50 μm or more, even more preferably 100 μm or more, even more preferably 200 μm or more, even more preferably 300 μm or more, even more preferably 400 μm or more, even more preferably 500 μm or more, even more preferably 600 μm or more, even more preferably 670 μm or more, even more preferably 700 μm or more, even more preferably 800 μm or more, even more preferably 900 μm or more, even more preferably 950 μm or more, or even more preferably 1000 μm or more.

[0048] The substrate in this specification may be in a state where multiple insulating layers are laminated, for example, a nonwoven fabric (cellulose, polyethylene terephthalate, etc.) may be laminated on the surface of a polyethylene microporous film, and the thickness mentioned above means the total thickness in a state where the insulating layers are laminated.

[0049] In addition, when the substrate of the lead-acid battery separator of this embodiment is produced by, for example, extrusion molding, ribs (convex shapes) can be imparted to the separator surface in any shape using a mechanical press, a calendar stack, a calendar roll, or a pattern roll after the separator is extruded. In some embodiments, the separator can have ribs on at least the surface of the separator. For example, when a conductive layer is provided on the surface of a substrate having a smooth surface and a rib on the back surface, and the conductive layer is in electrical contact with the positive electrode, the presence of the rib on the back surface can increase the distance between the conductive layer at the separator end and the negative electrode tab. While increasing the overall thickness of the substrate can also increase the distance between the conductive layer at the separator end and the negative electrode tab, increasing the overall thickness of the separator reduces ionic conductivity, so it is preferable to have ribs on the surface of the substrate opposite the surface having the conductive layer.

[0050] <<Conductive Layer of Separator>> Examples of conductive materials for forming the conductive layer according to this embodiment include conductors such as carbon materials, metals, and metal oxides, conductive polymers, semiconductors, and inorganic or organic compounds that have been made conductive by doping or the like. The method for forming the conductive layer is not particularly limited, and an example includes a method in which a coating liquid containing the conductive material is applied to a substrate and dried. Examples of application methods include die coating, gravure coating, spray coating, roller coating, screen printing, and inkjet printing. Another example of a method for forming the conductive layer is a method in which the conductive material (e.g., a metal or a metal oxide) is vapor-deposited (sputtering, vacuum deposition, etc.) on a substrate.

[0051] Examples of carbon materials include carbon clusters such as graphite, soft carbon, hard carbon, activated carbon, carbon black, graphene, carbon nanotubes, and fullerenes, monolithic carbon materials, and mixtures thereof. Among the above carbon materials, from the viewpoint of reducing surface electrical resistance, it is preferable to select one or more from the group consisting of furnace black, acetylene black, ketjen black, graphite, and carbon nanotubes. When carbon nanotubes are used, it is more preferable that they are single-walled carbon nanotubes from the viewpoint of uniform dispersion.

[0052] The metal is not particularly limited, but examples thereof include iron, aluminum, copper, zinc, nickel, chromium, titanium, silver, gold, platinum, palladium, tungsten, lithium, cobalt, manganese, sodium, and alloys containing these metals. Examples of metal oxides include conductive materials such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO).

[0053] The conductive layer can be disposed on one or both sides of the substrate. Examples of single-sided coating of the conductive layer on the substrate are shown in, but not limited to, Figures 2 to 8. On the other hand, Figure 12 is a schematic perspective view showing an application example of double-sided coating of the conductive layer on the substrate in one embodiment of the present invention.

[0054] As shown in FIG. 12( a), with the substrate (6) of the separator (5) as the reference, one conductive layer (7) is located between the substrate end of the substrate (5) and the electrode active material layer E Ａ When the conductive layer (7) contacts the electrode tab (T) attached to the other conductive layer (7), the shortest distance according to the present invention is measured by regarding the conductive layer (7) as part of the electrode tab (T), and means the shortest distance d between the other conductive layer (7) and the electrode tab (T).

[0055] As shown in FIG. 12(b), with the substrate (6) of the separator (5) as a reference, one conductive layer (7) is located at the electrode active material layer E ＡIn the case where one conductive layer (7) contacts the electrode tab (T) attached to the other conductive layer (7) but does not contact the substrate end of the substrate (5), the shortest distance according to the present invention is measured by regarding one conductive layer (7) as part of the electrode tab (T), and means the shortest distance d between the other conductive layer (7) and the electrode tab (T).

[0056] When forming the conductive layer on a portion of the substrate surface, a portion of the substrate is first coated with a masking material, and a conductive material is applied to the exposed surface of the substrate (e.g., by vapor deposition or coating), followed by removing the mask material. The conductive layer can be applied to the desired position on the substrate by, for example, screen printing the desired pattern using a screen mask, pattern printing using die coating or gravure coating, or pattern coating using inkjet printing. For example, FIG. 8 shows an example of forming a striped pattern on at least a portion of the substrate surface of a separator. In FIG. 8(a), there is a substrate (6) as a portion without a conductive layer, and a separator (5) on which a conductive layer (7) is arranged so that a portion of the substrate does not have the conductive layer (7) in a striped pattern is placed between the positive and negative electrodes so that the conductive layer (7) and the negative electrode (3) face each other to form a laminate. FIG. 8(b) is a schematic diagram (b) of the laminate observed from the negative electrode side, and FIG. 8(c) is a cross-sectional view (c) of the laminate taken along dotted line a-b.

[0057] When a conductive layer with a low surface electrical resistance value is in electrical contact with the positive electrode or negative electrode of a storage battery, the conductive layer acts as a grid or current collector of the electrode and promotes the transfer of electrons to and from the active material. Therefore, the surface electrical resistance value of the conductive layer is preferably 10,000 Ω or less, more preferably 5,000 Ω or less, even more preferably 800 Ω or less, and still more preferably 600 Ω or less.

[0058] The thickness of the conductive layer according to the present embodiment is not particularly limited, but from the viewpoint of reducing the surface electrical resistivity by increasing the thickness of the conductive layer, the thickness of the conductive layer is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 20 nm or more, even more preferably 30 nm or more, even more preferably 40 nm or more, even more preferably 50 nm or more, even more preferably 60 nm or more, even more preferably 100 nm or more, even more preferably 200 nm or more, even more preferably 400 nm or more, even more preferably 600 nm or more, even more preferably 800 nm or more, or even more preferably 1000 nm or more. Furthermore, since the ionic resistance in the storage battery increases as the conductive layer becomes thicker, the thickness of the conductive layer is preferably 5 mm or less, more preferably 0.1 mm or less, even more preferably 0.01 mm or less, even more preferably 0.005 mm or less, or even more preferably 0.003 mm or less.

[0059] From the viewpoint of reducing the ionic resistance in the battery, the thickness of the conductive layer is preferably 5.0 mm or less, more preferably 3.0 mm or less, even more preferably 2.0 mm or less, and still more preferably 1.5 mm or less. The thickness of the conductive layer is determined by observing a cross section with a scanning electron microscope (SEM), measuring the thickness in five different regions of the observed portion, and then calculating the arithmetic mean value of the thicknesses in the five regions.

[0060] <Positive Electrode, Positive Electrode Tab, Negative Electrode, Negative Electrode Tab, Electrolyte or Electrolyte> When the storage battery of the present invention is a lead-acid battery, one embodiment of the lead-acid battery includes a battery case, a positive electrode made of a grid made of lead or a lead alloy and a lead dioxide positive electrode active material, a positive electrode tab made of lead or a lead alloy, a negative electrode made of a grid made of lead or a lead alloy and a lead or lead alloy active material, a negative electrode tab made of lead or a lead alloy, and dilute sulfuric acid can be used as the electrolyte.

[0061] Furthermore, when the storage battery of the present invention is a lithium ion battery, examples of one embodiment of the lithium ion battery include a positive electrode in which a positive electrode active material is applied onto an aluminum foil positive electrode current collector, an aluminum positive electrode tab electrically connected to the positive electrode current collector, a negative electrode in which a negative electrode active material is applied onto a copper foil negative electrode current collector, a nickel negative electrode tab electrically connected to the negative electrode current collector, and a carbonate-based organic solvent in which a lithium salt such as lithium hexafluorophosphate (LiPF) or lithium borofluoride (LiBF) is dissolved.

[0062] Examples of the positive electrode active material include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate oxide (LiFePO4), nickel cobalt aluminum oxide (NCA), nickel manganese cobalt oxide (NMC), and lithium nickel oxide (LiNiO2). Examples of the negative electrode active material include graphite, silicon, and lithium titanium oxide (Li4Ti5O 12 ), lithium iron phosphate (LiFePO4), lithium metal, or a lithium alloy.

[0063] <Method for manufacturing substrate> Hereinafter, a method for manufacturing a substrate for a lead-acid battery separator will be described using an example of a substrate made of polyolefin, for example, ultra-high molecular weight polyethylene. However, the substrate is not limited to substrates obtained by the manufacturing method described below, as long as a layer according to the present disclosure can be formed thereon.

[0064] A method for producing a substrate includes the following steps: providing a thermoplastic polymer, such as ultra-high molecular weight polyethylene (hereinafter referred to as "UHMWPE"); providing a particulate filler such as particles; providing a processing plasticizer that is liquid at room temperature (25°C); mixing the UHMWPE, the particulate filler, and the processing plasticizer to form a mixture; extruding the mixture through a die, such as a slot die or an inflation die, to form a sheet; and an extraction step to partially or completely remove the plasticizer from the sheet, thereby forming a microporous membrane. After the sheet-forming step and before the extraction step, the sheet may be further processed by casting onto a chilled roller, calendering, or inflation. The cast, calendered, or other processed sheet can then be subjected to the extraction step to partially or completely remove the plasticizer, thereby forming micropores in the substrate.

[0065] The substrate obtained by the above method contains UHMWPE, a plasticizer (if partially extracted), and a particulate filler. The particulate filler is preferably inorganic particles from the viewpoint of acid resistance and heat resistance. The pores preferably occupy 25 to 90 percent of the total volume of the substrate, more preferably 30 to 80 percent, and even more preferably 40 to 70 percent.

[0066] In the method for producing the substrate, before or after the extraction step, a stretching step and / or an embossing roll or a calender roll may be used to impart any desired structure to the surface of the substrate.

[0067] Examples of the present disclosure will be described in detail below, but these are described for illustrative purposes only and the scope of the present disclosure is not limited to the following examples. Various evaluation results of the separators and storage batteries obtained in the examples and comparative examples are shown in Table 1. The evaluation methods for various layer properties are described below.

[0068] <<Preparation of Substrate>> The substrates used in Examples 1, 2, 7, and 14 and Comparative Example 4 were prepared as follows. Ultra-high molecular weight polyethylene resin powder, surfactant, mineral oil, and precipitated amorphous silica with a median diameter of 31 μm and a DOA oil absorption of 283 ml / 100 g were heated, melted, and mixed in a mixer to obtain a raw material composition. This raw material composition was extruded at a temperature above the melting point of the polyethylene using an extruder equipped with a T-die at the tip, and then passed through calendar rolls to obtain a film-like material. Next, the film-like material was immersed in a solvent to extract and remove a portion of the mineral oil, followed by drying and cooling to obtain a long separator (substrate) for evaluation having a composition of 22 parts by mass of polyethylene resin, 56 parts by mass of silica, 2 parts by mass of surfactant, and 20 parts by mass of mineral oil. Both sides of the substrate were flat, and the substrate thickness was 500 μm, the mean flow pore size was 30 nm, and the maximum pore size was 83 nm.

[0069] The substrates used in Examples 9, 10, 11, and 15 and Comparative Example 1 were prepared as follows. Ultra-high molecular weight polyethylene resin powder, surfactant, mineral oil, and precipitated amorphous silica with a median diameter of 31 μm and a DOA oil absorption of 283 ml / 100 g were heated, melted, and mixed in a mixer to obtain a raw material composition. This raw material composition was extruded at a temperature above the melting point of the polyethylene using an extruder equipped with a T-die at the tip, and then passed through calendar rolls to obtain a film-like material. Next, the film-like material was immersed in a solvent to extract and remove a portion of the mineral oil, followed by drying and cooling to obtain a long separator (substrate) for evaluation having a composition of 22 parts by mass of polyethylene resin, 56 parts by mass of silica, 2 parts by mass of surfactant, and 20 parts by mass of mineral oil. Both sides of the substrate were flat, and the substrate thickness was 250 μm, the mean flow pore size was 40 μm, and the maximum pore size was 82 nm.

[0070] The substrates used in Examples 12, 13, and 16 were prepared as follows. Ultra-high molecular weight polyethylene resin powder, surfactant, mineral oil, and precipitated amorphous silica with a median diameter of 31 μm and a DOA oil absorption of 283 ml / 100 g were heated, melted, and mixed in a mixer to obtain a raw material composition. This raw material composition was extruded using an extruder equipped with a T-die at a temperature above the melting point of the polyethylene, and then passed through calendar rolls to obtain a film-like material. The film-like material was then immersed in a solvent to extract and remove a portion of the mineral oil, followed by drying and cooling to obtain a long separator (substrate) for evaluation having a composition of 22 parts by weight of polyethylene resin, 56 parts by weight of silica, 2 parts by weight of surfactant, and 20 parts by weight of mineral oil. Both sides of the substrate were flat, and the thickness was 160 μm, the mean flow pore size was 32 nm, and the maximum pore size was 88 nm.

[0071] The substrate used in Comparative Example 2 was prepared as follows. Ultra-high molecular weight polyethylene resin powder, surfactant, mineral oil, and precipitated amorphous silica with a median diameter of 31 μm and a DOA oil absorption of 283 ml / 100 g were heated, melted, and mixed in a mixer to obtain a raw material composition. This raw material composition was extruded at a temperature above the melting point of the polyethylene using an extruder equipped with a T-die at the tip, and then passed through calendar rolls to obtain a film-like material. Next, the film-like material was immersed in a solvent to extract and remove a portion of the mineral oil, followed by drying and cooling to obtain a long separator (substrate) for evaluation having a composition of 22 parts by mass of polyethylene resin, 56 parts by mass of silica, 2 parts by mass of surfactant, and 20 parts by mass of mineral oil. Both sides of the substrate were flat, and the thickness was 400 μm, the mean flow pore size was 42 nm, and the maximum pore size was 78 nm.

[0072] The substrates used in Examples 3 and 8 and Comparative Example 3 were prepared as follows. Ultra-high molecular weight polyethylene resin powder, surfactant, mineral oil, and precipitated amorphous silica with a median diameter of 31 μm and a DOA oil absorption of 283 ml / 100 g were heated, melted, and mixed in a mixer to obtain a raw material composition. This raw material composition was extruded at a temperature above the melting point of the polyethylene using an extruder equipped with a T-die at the tip, and then passed through calendar rolls to obtain a film-like material. The film-like material was then immersed in a solvent to extract and remove a portion of the mineral oil, followed by drying and cooling to obtain a long separator (substrate) for evaluation having a composition of 22 parts by mass of polyethylene resin, 56 parts by mass of silica, 2 parts by mass of surfactant, and 20 parts by mass of mineral oil. One side of the substrate was flat, and the other side was formed with dot-like convex shapes. The thickness of the flat portion was 250 μm, the substrate thickness including the convex portions was 655 μm, the mean flow pore diameter was 40 nm, and the maximum pore diameter was 80 nm. In Examples 4, 5, and 6, nonwoven fabrics made of cellulose fibers of different thicknesses were laminated on the surface of the side having the convex portions of the substrate used in Example 3, and the substrate thickness in Example 4 was 754 μm, the substrate thickness in Example 5 was 893 μm, and the substrate thickness in Example 6 was 950 μm.

[0073] <<Preparation of Separators for Voltage Withstand Measurement>> To form the conductive layers of Examples 1, 2, and 14, a slurry was first prepared. Carbon black, an acrylic resin, an ionic surfactant, a thickener, and carbon nanotubes were dispersed and mixed in water to prepare a slurry with a solids concentration of 1% by mass. The slurry was formulated so that, based on 100 parts by mass of the total solids in the slurry (corresponding to the total mass of the resulting layer), it contained 65.5 parts by mass of carbon black (furnace black) with a median particle size (d50) of 0.8 μm, 19.7 parts by mass of an ionic surfactant, 13.0 parts by mass (solids equivalent) of an acrylic resin (aqueous latex), 1.3 parts by mass of a thickener, and 0.5 parts by mass of single-walled carbon nanotubes. Using an applicator, the slurry was manually applied (hand coated) to the entire surface of one side (flat side) of a 20 cm x 20 cm substrate prepared for Examples 1, 2, and 14, and dried in an oven at 80°C for 5 minutes. The applicator gap (clearance formed between the separator and the applicator) was 45 μm, and the layer obtained after drying was 5 μm. A central portion of the obtained sample was cut out to 7 cm x 7 cm, and a separator having a conductive layer covering the entire surface of one side of the substrate was obtained.

[0074] To form the conductive layers of Examples 3, 4, 5, 6, 12, 13, and 16 and Comparative Examples 1 and 2, a slurry was first prepared. Carbon black, an acrylic resin, an ionic surfactant, a thickener, and carbon nanotubes were dispersed and mixed in water to prepare a slurry with a solids concentration of 1% by mass. The slurry was formulated so that, based on 100 parts by mass of the total solids in the slurry (corresponding to the total mass of the resulting layer), it contained 65.6 parts by mass of carbon black (furnace black) with a median particle size (d50) of 0.8 μm, 19.7 parts by mass of an ionic surfactant, 13.1 parts by mass (solids equivalent) of an acrylic resin (aqueous latex), 1.3 parts by mass of a thickener, and 0.3 parts by mass of single-walled carbon nanotubes. Using an applicator, the slurry was manually applied (hand coated) to the entire surface of one side (flat side) of the substrate prepared for Examples 3, 4, 5, 6, 12, 13, and 16 and Comparative Examples 1 and 2, each measuring 20 cm x 20 cm, and then dried in an oven at 80°C for 5 minutes. The applicator gap (clearance formed between the separator and the applicator) was 45 μm, and the layer obtained after drying was 5 μm. A central portion of the obtained sample was cut out to a size of 7 cm x 7 cm, to obtain a separator having a conductive layer covering the entire surface of one side of the substrate.

[0075] To form the conductive layer of Example 7, a slurry was first prepared. Carbon black, an acrylic resin, an ionic surfactant, and a thickener were dispersed and mixed in water to prepare a slurry with a solids concentration of 1% by mass. The total mass of the solids in the slurry (corresponding to the total mass of the resulting layer) was 100 parts by mass, and the slurry was formulated to contain 65.8 parts by mass of carbon black (furnace black) with a median particle size (d50) of 1.0 μm, 19.7 parts by mass of an ionic surfactant, 13.2 parts by mass (solids equivalent) of an acrylic resin (water-based latex), and 1.3 parts by mass of a thickener. Using an applicator, the slurry was manually applied (hand coated) to one side (flat side) of the 20 cm x 20 cm substrate prepared for Example 7, and then dried in an oven at 80 ° C. for 5 minutes. At this time, the applicator gap (clearance formed between the separator and the applicator) was 45 μm, and the layer obtained after drying was 5 μm. The central portion of the obtained sample was cut into a piece of 7 cm × 7 cm to obtain a separator having a conductive layer on the entire surface of one side of the substrate.

[0076] To form the conductive layers of Examples 8 and 9, a slurry was first prepared. Carbon black, an acrylic resin, an ionic surfactant, a thickener, and carbon nanotubes were dispersed and mixed in water to prepare a slurry with a solids concentration of 1% by mass. The slurry was formulated so that, based on 100 parts by mass of the total solids in the slurry (corresponding to the total mass of the resulting layer), it contained 65.6 parts by mass of carbon black (furnace black) with a median particle size (d50) of 0.8 μm, 19.7 parts by mass of an ionic surfactant, 13.1 parts by mass (solids equivalent) of an acrylic resin (water-based latex), 1.3 parts by mass of a thickener, and 0.3 parts by mass of single-walled carbon nanotubes. A portion of one side (flat surface) of the 20 cm x 20 cm substrate prepared for Examples 8 and 9 was attached with 20 μm thick resin tape, and the slurry was manually applied (hand coated) to the entire surface of the substrate using an applicator, followed by drying in an oven at 80°C for 5 minutes. At this time, the applicator gap (clearance formed between the separator and the applicator) was 45 μm, and the layer obtained after drying was 5 μm. The resin tape was then peeled off, and the resulting sample was cut into a 7 cm x 7 cm piece. As shown in Figure 8, a sample was prepared in which a striped conductive layer (7) was not present on a portion of the surface of the substrate (6) of the separator (5) for voltage resistance measurement.

[0077] To form the conductive layers of Examples 10, 11, and 15, a slurry was first prepared. Carbon black, an acrylic resin, an ionic surfactant, a thickener, and carbon nanotubes were dispersed and mixed in water to prepare a slurry with a solids concentration of 1% by mass. The slurry was formulated so that, based on 100 parts by mass of the total solids in the slurry (corresponding to the total mass of the resulting layer), it contained 65.6 parts by mass of carbon black (furnace black) with a median particle size (d50) of 0.8 μm, 19.7 parts by mass of an ionic surfactant, 13.1 parts by mass (solids equivalent) of an acrylic resin (water-based latex), 1.3 parts by mass of a thickener, and 0.3 parts by mass of single-walled carbon nanotubes. A 20 μm thick resin tape was attached to a portion of one side (flat surface) of the 20 cm x 20 cm sized substrate prepared for Examples 10, 11, and 15. Using the tape as a mask, the slurry was manually applied (hand coated) to the entire surface of the substrate using an applicator, and the substrate was dried in an oven at 80°C for 5 minutes. The applicator gap (clearance formed between the separator and the applicator) was 45 μm, and the layer obtained after drying was 5 μm. The resin tape was then peeled off to obtain a 7 cm x 7 cm sized separator with no conductive layer within a 1 mm width of the outer periphery (no conductive layer at the substrate edge).

[0078] The separators for measuring the withstand voltage in Comparative Examples 3 and 4 did not have a conductive layer on the substrate surface, and were cut to a size of 7 cm × 7 cm for use in measuring the withstand voltage. The sample of Comparative Example 3 was used in measuring the withstand voltage with the convex portion on the substrate surface facing the positive electrode.

[0079] <Surface Electrical Resistance of Conductive Layer> The surface electrical resistance was measured using a resistance meter RM3545 Resistance Meter manufactured by Hioki E.E. Corporation, with a four-point probe (5.0 mm pitch) as the probe of the resistance meter. The four-point probe was pressed against the conductive layer of the separator, and the resistance of the conductive layer was measured at six points under the measurement conditions below. The average value of these measurements was calculated and is shown in Table 1 as the surface electrical resistance. The unit is Ω. A four-probe resistivity meter PC application was used as the measurement software for the resistance meter. The measurement mode was set to "normal measurement" and the measurement unit was set to "resistance [Ω]". The measurement conditions were as follows. The surface electrical resistance values ​​of the evaluated separators are shown in Table 1. [Measurement conditions] Long side of sample: 100 mm Short side of sample: 100 mm Thickness of sample: 10 μm X coordinate: 50 mm Y coordinate: 50 mm Probe used: 5.0 mm

[0080] <<Substrate Thickness>> The sample for measuring the withstand voltage was re-prepared and embedded in epoxy resin, and then the cross-section of the substrate was observed with a scanning electron microscope (SEM). The thickness of five different regions in the observed area was measured, and the substrate thickness was calculated as the arithmetic mean value of the thicknesses of the five regions. When the substrate surface had convex portions, the substrate thickness was calculated by cross-sectional SEM observation as the arithmetic mean value of the thickness including the convex portions. In addition, the substrate may be in a state where multiple insulating layers are laminated. When a nonwoven fabric is laminated on the surface of a polyethylene microporous film, the thickness was calculated as the total thickness when the insulating layers are laminated. The measured thicknesses are shown in Table 1.

[0081] <<Voltage Breakdown Measurement>> The voltage breakdown measurements for the Examples and Comparative Examples were performed using the following procedure. A KIKUSUI TOS5200 device was used for the evaluation. Various separators were cut into 7 cm square pieces. Following the procedure shown in FIG. 9 , the separator (5) was sandwiched between two 5 cm square electrodes with electrode tabs (the 5 cm square electrodes were positioned in the center of the 7 cm square cut separator (5)). The laminate was then sandwiched between 11 cm x 11 cm polycarbonate plates (9, 9). The four corners of the polycarbonate substrates (9, 9) were fixed with screws to create a voltage breakdown measurement sample. The electrode tabs were then clamped with clips, and the voltage breakdown measurement was performed. The electrode surfaces in contact with the separator's conductive layer are listed in Table 1. Table 1 also lists the presence or absence of a conductive layer at the substrate edge and the shortest distance between the conductive layer at the substrate edge and the electrode tab. Regarding the shortest distance between the conductive layer at the substrate edge and the negative or positive electrode tab, the above-mentioned sample for measuring voltage resistance was recreated using a separator having a conductive layer and embedded in epoxy resin. After that, a cross-section of the electrode tab portion was extracted using a cross-section grinder at the substrate edge position corresponding to the dotted line ab in Figure 9 . The shortest distance between the conductive layer at the substrate edge and the electrode tab was measured using a cross-section SEM, and the value was listed in Table 1. The unit is μm. When the conductive layer was in contact with the negative electrode, the shortest distance between the conductive layer at the substrate edge and the positive electrode tab was reported. When the conductive layer was in contact with the positive electrode, the shortest distance between the conductive layer at the substrate edge and the negative electrode tab was reported. Figure 10 shows a schematic cross-sectional view of the portion ab in Figure 9 for the examples and comparative examples.

[0082] In addition, for Examples 12 and 16, the entire surface of the positive electrode tab (a 2 cm wide x 1 cm high section at the very tip of the tab was left uncoated to ensure electrical continuity) was covered with 100 μm thick resin insulating tape, and for Example 13, the entire surface of the negative electrode tab (a 2 cm wide x 1 cm high section at the very tip of the tab was left uncoated to ensure electrical continuity) was covered with insulating tape. In the other Examples and Comparative Examples, the electrode tabs were not insulated. For Examples 12, 13, and 16, the shortest distance between the conductive layer at the end of the substrate and the substrate tab was 260 μm. However, because the electrode tab was covered with 100 μm thick insulating tape, the shortest distance between the conductive layer at the end of the substrate and the electrode tab is shown in parentheses as a reference value. In Examples 14 to 16, the positive electrode and positive electrode tab were made of aluminum, and the negative electrode and negative electrode tab were made of nickel. These positive electrode and negative electrode tab materials are materials commonly used in lithium-ion batteries. In Examples and Comparative Examples other than Examples 14 to 16, the positive electrode and the positive electrode tab were made of pure lead, and the negative electrode and the negative electrode tab were also made of pure lead. The lead in these positive electrode tabs and negative electrode tabs is a material used in lead-acid batteries.

[0083] The withstand voltage was measured by increasing the voltage between the electrodes from 0.0 kV to 1.5 kV over 2 seconds, and the voltage at which a current of 0.3 mA or more was detected was taken as the withstand voltage. If a current of 0.3 mA or more was not detected even after the voltage increased to 1.5 kV, the withstand voltage was taken as 1.50 kV. The withstand voltage measurement was performed at a temperature of 25°C, and the evaluation sample was left at a relative humidity of 50% RH for 30 minutes before the withstand voltage measurement. The measurement results of the withstand voltage are shown in Table 1.

[0084]

[0085]

[0086] <<Results of Examples and Comparative Examples>> Comparative Examples 3 and 4, which do not have a conductive layer on the separator surface, achieved a high withstand voltage of 1.5 kV or more, while Examples 1 to 9 and 14 and Comparative Examples 1 and 2, which used separators with a conductive layer on the substrate edge, showed that the withstand voltage was increased by increasing the shortest distance between the conductive layer on the substrate edge and the electrode tab. From the viewpoint of achieving a withstand voltage of 0.50 kV or more, the shortest distance is preferably 500 μm or more. From the viewpoint of achieving a withstand voltage of 1.00 kV or more, the shortest distance is preferably 655 μm or more. From the viewpoint of achieving a withstand voltage of 1.50 kV or more, the shortest distance is preferably 950 μm or more.

[0087] Examples 10, 11, and 15 show that a high withstand voltage is exhibited even when the conductive layer is in electrical contact with the positive electrode and the separator end facing the negative electrode tab does not have the conductive layer, or when the conductive layer is in electrical contact with the negative electrode and the separator end facing the positive electrode tab does not have the conductive layer. From the viewpoint of increasing the withstand voltage, it is preferable to provide a portion without a conductive layer extending 1 mm or more inward from the end of the substrate.

[0088] Examples 12, 13, and 16 show that even when the shortest distance between the conductive layer at the end of the substrate and the electrode tab is short, the withstand voltage can be increased by insulating the electrode tab.

[0089] The present invention can be used as a storage battery, particularly as a liquid secondary battery or a solid secondary battery, more specifically as a lead acid battery, a lithium ion battery, a redox flow battery, or the like.

[0090] 1 Positive electrode 2 Positive electrode tab 3 Negative electrode 4 Negative electrode tab 5 Separator 6 Substrate 6 Ｅ Base material end 7 Conductive layer 8 Insulating material 9 Polycarbonate plate 10 Positive electrode clip 11 Negative electrode clip T Electrode tab E Ａ Electrode active material layer d Shortest distance between conductive layer and electrode tab d １ Shortest distance between the conductive layer and the negative electrode tab: d ２ Shortest distance between the conductive layer and the positive electrode tab

Claims

1. A storage battery comprising a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, wherein the separator is made of at least a substrate and a conductive layer covering a portion of the substrate, and the covering area of ​​the conductive layer reaches at least the substrate end portion of the substrate adjacent to the positive electrode tab or the negative electrode tab, and wherein: (I) the conductive layer is in electrical contact with the positive electrode, and the shortest distance between the conductive layer at the substrate end portion adjacent to the negative electrode tab and the negative electrode tab is 500 μm or more; and / or (II) the conductive layer is in electrical contact with the negative electrode, and the shortest distance between the conductive layer at the substrate end portion adjacent to the positive electrode tab and the positive electrode tab is 500 μm or more.

2. A storage battery comprising a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, the separator comprises at least a substrate and a conductive layer that covers a portion of the substrate, and wherein: (III) the conductive layer is in electrical contact with the positive electrode, and an end portion of the substrate of the substrate adjacent to the negative electrode tab does not have the conductive layer; and / or (IV) the conductive layer is in electrical contact with the negative electrode, and an end portion of the substrate of the substrate adjacent to the positive electrode tab does not have the conductive layer.

3. A storage battery comprising a positive electrode having a positive electrode tab, a negative electrode having a negative electrode tab, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator has a protruding portion that protrudes from both electrodes, the separator is made of at least a substrate and a conductive layer covering a portion of the substrate, and the coverage area of ​​the conductive layer reaches at least the substrate end portion of the substrate adjacent to the positive electrode tab or the negative electrode tab, and (V) the conductive layer is in electrical contact with the positive electrode, and the surface of the negative electrode tab is covered with an insulating material; and / or (VI) the conductive layer is in electrical contact with the negative electrode, and the surface of the positive electrode tab is covered with an insulating material.

4. The storage battery according to claim 1, wherein the shortest distance is 1500 μm or less.

5. The storage battery according to claim 1, wherein the shortest distance is 655 μm or more.

6. The storage battery according to claim 1, wherein the shortest distance is 950 μm or more.

7. The storage battery according to any one of claims 1 to 6, wherein the substrate is in the form of a rectangular sheet.

8. The storage battery according to any one of claims 1 to 6, wherein the surface electrical resistance of the conductive layer is 5,000 Ω or less.

9. The storage battery according to any one of claims 1 to 6, wherein the conductive layer comprises a carbon material.

10. The storage battery according to any one of claims 1 to 6, wherein the substrate comprises a polyolefin.

11. The battery of any one of claims 1 to 6, wherein the positive and negative electrode tabs comprise lead.

12. The battery of any one of claims 1 to 6, wherein the positive electrode tab comprises aluminum and the negative electrode tab comprises nickel.

13. The storage battery according to any one of claims 1 to 6, wherein the storage battery is a lead-acid battery.

14. The storage battery according to any one of claims 1 to 6, wherein the storage battery is a lithium ion battery.

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