JP2018160345A - Alkali storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali storage battery which can suppress the gas retention between electrodes, and which can smoothly supply an electrolyte solution to a separator and the electrode.SOLUTION: An alkali storage battery 1 comprises an electrode assembly 11 in which a plurality of electrodes 2 are laminated through a separator 3. The plurality of electrodes 2 each have metal foil 24, and an active material layer 25 disposed on one or each face of the metal foil 24. The active material layer 25 has: a thin region 251 disposed in at least a part of a peripheral edge of the active material layer 25 in plane view when viewed from a lamination direction of the electrode assembly 11; and a thick region 252 which connects to the thin region 251, and has a fixed thickness larger than that of the thin region 251. The thin region 251 has such a form that at any position, a thickness of the thin region at that position is equal to or smaller than a thickness at a position closer to the thick region 252.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an alkaline storage battery.

  Alkaline storage batteries such as nickel-metal hydride storage batteries are used in batteries for vehicles such as forklifts, hybrid cars, and electric cars. This type of alkaline storage battery has an electrode assembly in which a plurality of electrodes are stacked via a separator. As the electrode, a foil electrode having a metal foil and an active material layer disposed on one or both surfaces of the metal foil may be used. Moreover, the nonwoven fabric is used as a separator and electrolyte solution is hold | maintained in the clearance gap between the fibers which comprise a nonwoven fabric. The electrode is disposed in close contact with the separator so that the supply of the electrolytic solution from the separator can be quickly received (for example, Patent Document 1).

JP 2013-191381 A

  In alkaline storage batteries, the positive electrode contracts and the negative electrode expands during charging. Since the contraction amount of the positive electrode at this time is not exactly the same as the expansion amount of the negative electrode, the distance between the electrodes in the stacking direction of the electrode assembly varies according to the charging rate. In addition, during discharging, the positive electrode expands and the negative electrode contracts, contrary to charging. Since the amount of expansion of the positive electrode at this time is not exactly the same as the amount of contraction of the negative electrode, the distance between the electrodes in the stacking direction of the electrode assembly varies according to the charging rate, as in charging.

  When the distance between the electrodes becomes narrow during charging / discharging, the separator disposed between the electrodes is compressed, and the electrolytic solution held in the separator is pushed out of the electrode assembly. On the other hand, when the distance between the electrodes is increased, the thickness of the separator is restored as the distance between the electrodes increases. Then, the electrolytic solution is absorbed into the separator as the thickness of the separator is restored.

  At this time, the electrolyte existing outside the separator is absorbed into the separator from the peripheral edge of the separator, and moves to the inside of the separator through a gap between fibers in the nonwoven fabric. For this reason, a portion having a relatively large distance from the peripheral edge in the separator requires a longer time for the electrolytic solution to reach than a portion having a relatively small distance.

  Further, during charging / discharging of the alkaline storage battery, gas may be generated from the electrode. If this gas stays between the electrodes, there is a possibility that a portion where the electrolyte does not exist locally is generated in the separator in some cases.

  When the above-described delay in the absorption of the electrolytic solution into the separator or the retention of gas occurs, the supply of the electrolytic solution to the electrode is hindered, causing problems such as an increase in the internal resistance of the alkaline storage battery and a shortened life. There is a fear.

  This invention is made | formed in view of this background, and it is going to provide the alkaline storage battery which can perform the supply of the electrolyte solution to an electrode or a separator while suppressing the stay of the gas between electrodes. Is.

One aspect of the present invention is an alkaline storage battery having an electrode assembly in which a plurality of electrodes are stacked via a separator,
The electrode is
Metal foil,
Having an active material layer disposed on one or both sides of the metal foil,
The active material layer is
A thin region disposed in at least part of the peripheral edge of the active material layer in a plan view as viewed from the stacking direction of the electrode assembly;
The thin region is connected to the thin region, the thickness is thicker than the thin region, and has a constant thickness.
The thin region is in an alkaline storage battery having a shape in which the thickness at the position is equal to or less than the thickness of the position closer to the thick region than the position at any position.

  The electrode assembly in the alkaline storage battery includes an electrode including a metal foil and an active material layer disposed on one or both surfaces of the metal foil. In addition, the active material layer has a thin region disposed at the peripheral portion thereof, and a thick region having a constant thickness that is connected to the thin region. By alternately laminating the electrodes and the separator, the porosity of the portion disposed on the thin region in the separator can be made higher than the porosity of the portion disposed on the thick region. Further, in some cases, it can be expected that the separator is disposed apart from the thin region and a gap is formed between the separator and the thin region.

  And the part with the high porosity of the separator mentioned above, and the clearance gap between a separator and a thin area | region are formed in the position which faces the peripheral part of a thin area | region, ie, an active material layer. Therefore, these portions serve as passages for the electrolytic solution and gas, and the electrolytic solution can be absorbed from the outside to the inside of the separator and the gas generated from the electrode can be discharged out of the separator smoothly and quickly.

  As a result, according to the alkaline storage battery, it is possible to suppress the stagnation of gas between the electrodes and to smoothly supply the electrolytic solution to the electrodes and the separator.

FIG. 3 is a cross-sectional view showing a main part of an alkaline storage battery in Example 1. FIG. 2 is an enlarged view of the vicinity of a thin region in FIG. 1. 1 is a plan view of a bipolar electrode viewed from a positive electrode active material layer side in Example 1. FIG. 3 is a plan view of a bipolar electrode as viewed from the negative electrode active material layer side in Example 1. FIG. In Example 2, it is a partial cross section figure which shows the principal part of the bipolar electrode with the constant thickness of a thin area | region. In Example 3, it is a partial cross section figure which shows the principal part of the bipolar electrode in which the thin area | region is exhibiting step shape.

  The electrode assembly in the alkaline storage battery employs any form of electrode as long as it has at least one single cell in which a positive electrode active material layer and a negative electrode active material layer as active material layers face each other with a separator interposed therebetween. May be. For example, the electrode may have a positive electrode in which a positive electrode active material layer is disposed on a metal foil and a negative electrode in which a negative electrode active material layer is disposed on a metal foil. In this case, the positive electrode active material layer and the negative electrode active material layer can be opposed to each other via the separator by arranging the positive electrode and the negative electrode alternately in the stacking direction.

  The electrode assembly includes, as electrodes, termination electrodes disposed at both ends in the stacking direction of the electrode assembly, and bipolar electrodes disposed between the termination electrodes. The bipolar electrode is an active material. As a layer, you may have the positive electrode active material layer arrange | positioned on the front side surface of metal foil, and the negative electrode active material layer arrange | positioned on the back side surface. In this case, the single cell in which the positive electrode active material layer and the negative electrode active material layer face each other via the separator can be connected in series with a simple configuration in which a plurality of bipolar electrodes are stacked via the separator. . As a result, the electromotive force of the alkaline storage battery can be further increased.

  In addition, when bipolar electrodes are used, the number of single cells can be increased with respect to the total number of electrodes, compared with the case where unipolar electrodes are used. Therefore, when the total number of electrodes is the same, the number of single cells can be increased as compared with the case where unipolar electrodes are used. In addition, when the number of single cells is the same, the total number of electrodes can be reduced and the size of the alkaline storage battery in the stacking direction can be reduced compared to the case where unipolar electrodes are used.

  As the metal foil of the electrode, for example, a metal foil known for alkaline storage batteries such as nickel foil can be employed. The thickness of metal foil can be suitably set, for example from the range of 5-100 micrometers.

  An active material layer is disposed on one or both sides of the metal foil. The active material layer includes, for example, an active material such as nickel hydroxide or a hydrogen storage alloy, and a binder that binds the active materials to each other. Moreover, the active material layer may contain additives, such as a conductive support agent, as needed.

  The active material layer has a thin area having a relatively small thickness and a thick area having a thickness larger than that of the thin area. The thin region may be disposed at a part of the peripheral edge of the active material layer in a plan view as viewed from the stacking direction of the electrode assembly, or may be disposed over the entire periphery of the peripheral edge. If the thin region is disposed at least at a part of the peripheral portion of the active material layer, the porosity of the separator disposed on the thin region can be increased. As a result, the electrolyte can be absorbed and the gas can be discharged smoothly and quickly. From the viewpoint of more effectively obtaining these functions and effects, the thin-walled region is preferably disposed over the entire periphery of the peripheral portion of the active material layer in a plan view viewed from the stacking direction.

  For example, the following method can be employed to form the thin region. That is, after applying a slurry containing an active material and a binder onto a metal foil, the slurry is dried to form an active material layer. A thin region and a thick region can be formed by cutting the peripheral portion of the active material layer to make the peripheral portion thinner than the central portion.

  In addition, when the slurry is applied onto the metal foil, the coating thickness and the coating speed of the slurry are changed to make the coating thickness of the peripheral edge of the slurry thinner than the central portion. Then, a thin area | region and a thick area | region can be formed by drying a slurry.

  The thin region has a shape in which the thickness at the position is equal to or less than the thickness of the position closer to the thick region than the position at any position. For example, the thin region may have a certain thickness. Such a thin-walled region can be formed by, for example, a method in which an active material layer having a certain thickness is disposed on a metal foil, and then the peripheral portion of the active material layer is scraped to reduce the thickness.

  Moreover, the thin area | region may exhibit the taper shape which thickness becomes thin, so that it leaves | separates from a thick area | region. Such a thin region can be formed by, for example, disposing an active material layer on a metal foil while changing the thickness. Therefore, in this case, the thin region can be formed by a simple process as compared with the case where the thin region having a constant thickness is formed.

  Moreover, the thin area | region may exhibit the step shape provided with the several flat part from which thickness differs mutually, and the step part which connects flat parts. In the thin-walled region having such a shape, the active material layer having a certain thickness is disposed on the metal foil, and then the peripheral portion of the active material layer is scraped to reduce the thickness in a stepped manner, as in the case where the thickness is constant. Or the like.

  When the total width of the active material layer in the plan view is 100%, the width of the thin region, that is, the distance from the edge of the active material layer to the boundary between the thin region and the thick region is the total width of the active material layer. Of 2.5 to 5%. Here, the total width of the active material layer refers to the distance from the edge of the active material layer having a thin region to be measured to the edge opposite to the edge. For example, when the active material layer has a rectangular shape in plan view and a thin region is provided along the short side, the length of the long side of the active material layer is the total width of the active material layer. Become.

  By setting the width of the thin area to 2.5% or more of the total width of the active material layer, the width of the gap between the separator and the thin area formed on the thin area is increased. Can be wide enough. Thereby, absorption of the electrolyte solution mentioned above and discharge of gas can be performed more smoothly and rapidly.

  Further, by setting the width of the thin region to 5% or less of the total width of the active material layer, it is possible to avoid the width of the thin region being excessively widened and the proportion of the thick region being relatively small. Therefore, in this case, it is possible to avoid a decrease in battery capacity due to a reduction in the thick region while ensuring the above-described effect of smoothly and quickly absorbing the electrolyte and discharging the gas.

  The thick region is continuous with the thin region and has a certain thickness. Here, the state where the thickness of the thick region is constant means a state where there are no protrusions or the like protruding from the surroundings in the thick region, and a slight thickness generated due to manufacturing variations or the like. Variations are acceptable. The thickness of the thick region can be appropriately set from a range of 30 to 150 μm, for example. Further, the variation in the thickness of the thick region due to manufacturing variations or the like may be in the range of 95 to 105% when the average thickness is 100%.

  When the thickness of the thick region exceeds the specific range or falls below the specific range, the variation in the interelectrode distance increases, and the electrode reaction may be uneven. As a result, the battery capacity of the alkaline storage battery may be reduced.

Example 1
Examples of the alkaline storage battery will be described with reference to the drawings. As shown in FIG. 1, the alkaline storage battery 1 has an electrode assembly 11 in which a plurality of electrodes 2 (21, 22, 23) are stacked via a separator 3. The electrode 2 includes a metal foil 24 and an active material layer 25 (25p, 25n) disposed on one or both surfaces of the metal foil 24. The active material layer 25 is connected to the thin region 251 (251p, 251n) disposed in at least a part of the peripheral portion of the active material layer 25 in a plan view as viewed from the stacking direction of the electrode assembly 11, and the thin region 251. And a thick region 252 (252p, 252n) having a certain thickness and a thickness greater than that of the thin region 251. Further, the thin region 251 has a shape in which the thickness at the position is equal to or less than the thickness of the position closer to the thick region 252 than the position.

  The electrode assembly 11 of this example includes, as the electrode 2, termination electrodes 21 and 23 disposed at both ends in the stacking direction, and a plurality of bipolar electrodes 22 disposed between the termination electrode 21 and the termination electrode 23. doing. The bipolar electrode 22 includes a metal foil 24 as a current collector, a positive electrode active material layer 25p as an active material layer 25, and a negative electrode active material layer 25n. The positive electrode active material layer 25 p is disposed on the front side surface of the metal foil 24, and the negative electrode active material layer 25 n is disposed on the back side surface of the metal foil 24.

  As shown in FIG. 3, the metal foil 24 of the bipolar electrode 22 has a rectangular shape in plan view as viewed from the stacking direction of the electrode assembly 11. The positive electrode active material layer 25p is disposed inside the peripheral edge 241 of the metal foil 24, and has a rectangular shape in the plan view. The positive electrode active material layer 25p of this example has a rectangular shape with a long side of 150 mm and a short side of 100 mm.

  As shown in FIGS. 1 to 3, the positive electrode active material layer 25 p includes a thin region 251 p and a thick region 252 p that is thicker than the thin region 251 p. The thin region 251p is disposed over the entire periphery of the peripheral edge portion of the positive electrode active material layer 25p in a plan view as viewed from the stacking direction of the electrode assembly 11. Further, the thick region 252p is disposed inside the thin region 251p in the plan view.

  The thickness of the thick region 252p in this example is 90 μm. As shown in FIGS. 1 and 2, the thin region 251p of this example has a tapered shape with a thickness that decreases as the distance from the thick region 252p increases.

The width w _ps (see FIG. 3) of the thin region 251p arranged along the short side 253p of the positive electrode active material layer 25p in the above-described plan view is 2.5 of the length of the long side 254p of the positive electrode active material layer 25p. It can set suitably from the range of -5%. The width w _pl of the thin region 251p arranged along the long side 254p of the positive electrode active material layer 25p in the plan view is 2.5 to 5% of the length of the short side 253p of the positive electrode active material layer 25p. It can set suitably from the range.

  As shown in FIG. 4, the negative electrode active material layer 25 n is disposed on the inner side of the peripheral edge 241 of the metal foil 24 in the plan view. Further, as shown in FIGS. 3 and 4, the negative electrode active material layer 25 n has a rectangular shape larger than the positive electrode active material layer 25 p in the plan view. Specifically, the negative electrode active material layer 25n of this example has a rectangular shape having a long side of 152 mm and a short side of 102 mm.

  As shown in FIGS. 1, 2, and 4, the negative electrode active material layer 25n includes a thin region 251n and a thick region 252n that is thicker than the thin region 251n. The thin region 251n is disposed over the entire periphery of the peripheral edge portion of the negative electrode active material layer 25n in a plan view as viewed from the stacking direction of the electrode assembly 11. Further, the thick region 252n is arranged inside the thin region 251n in the plan view.

  The thickness of the thick region 252n in this example is 80 μm. Further, as shown in FIGS. 1 and 2, the thickness of the thin region 251n decreases as the distance from the thick region 252n increases.

The width w _ns (see FIG. 4) of the thin region 251n arranged along the short side 253n of the negative electrode active material layer 25n in the above-described plan view is 2.5 of the length of the long side 254n of the negative electrode active material layer 25n. It can set suitably from the range of -5%. Further, the width w _nl of the thin region 251n disposed along the long side 254n of the negative electrode active material layer 25n in the plan view is 2.5 to 5% of the length of the short side 253n of the negative electrode active material layer 25n. It can set suitably from the range.

  Although not shown in the drawing, one of the two termination electrodes 21 and 23 has the same configuration as the bipolar electrode 22 except that it does not have the negative electrode active material layer 25n. The other terminal electrode 23 has the same configuration as the bipolar electrode 22 except that it does not have the positive electrode active material layer 25p.

  As shown in FIG. 1, the termination electrodes 21 and 23 and the bipolar electrode 22 are arranged such that the positive electrode active material layers 25p and the negative electrode active material layers 25n are alternately arranged in the stacking direction. Further, the thick region 252p of the positive electrode active material layer 25p faces the thick region 252n of the negative electrode active material layer 25n via the separator 3. Thus, the electrode assembly 11 of the present example has a single cell composed of the separator 3 and the positive electrode active material layer 25p and the negative electrode active material layer 25n facing the separator 3 between the adjacent metal foils 24. doing. The single cells are electrically connected in series via a metal foil 24 as a current collector.

  The separator 3 of this example is a nonwoven fabric made of polyolefin resin fibers. The separator 3 has a larger rectangular shape than the negative electrode active material layer 25n, and as shown in FIGS. 1 and 2, the thick region 252p of the positive electrode active material layer 25p and the thick region 252n of the negative electrode active material layer 25n. Is sandwiched between. As shown in FIG. 2, the portion 31 arranged on the thin region 251 of each active material layer 25 in the separator 3 has a higher porosity than the portion 32 sandwiched between the thick regions 252. ing. In this example, the portion 31 of the separator 3 disposed on the thin region 251 is separated from the thin region 251, and a gap is formed between the separator 3 and the thin region 251.

  As shown in FIG. 1, the side peripheral surface of the electrode assembly 11 is covered with a seal portion 12. In addition, the peripheral portion 241 of the metal foil 24 in the bipolar electrode 22 and the peripheral portion 241 of the metal foil 24 in the termination electrode 21 are held by the seal portion 12.

  Metal restraining members 13 are disposed at both ends of the electrode assembly 11 in the stacking direction. The restraining member 13 is held by a holding plate (not shown) in contact with the metal foil 24 of the termination electrodes 21 and 23. In the alkaline storage battery 1 of this example, the electrode assembly 11 and an external circuit can be electrically connected via the restraining member 13.

  The effect of the alkaline storage battery 1 of this example is demonstrated. As shown in FIG. 1, the electrode assembly 11 in the alkaline storage battery 1 includes an electrode 2 including a metal foil 24 and an active material layer 25 disposed on one or both surfaces of the metal foil 24. The active material layer 25 includes a thin region 251 disposed at the peripheral edge thereof, and a thick region 252 that is continuous with the thin region 251 and has a certain thickness. Therefore, by alternately laminating the electrode 2 and the separator 3, the porosity of the portion 31 disposed on the thin region 251 in the separator 3 is disposed on the thick region 252 as shown in FIG. 2. The porosity of the portion 32 can be made higher. Further, as in the present example, the separator 3 can be arranged apart from the thin region 251, and a gap can be formed between the separator 3 and the thin region 251.

  The portion 31 having a high porosity of the separator 3 and the gap between the separator 3 and the thin region 251 are formed on the thin region 251, that is, at a position facing the peripheral portion of the active material layer 25. Therefore, these portions serve as passages for the electrolyte and gas, so that the electrolyte is absorbed from the outside to the inside of the separator 3 and the gas generated from the electrode 2 is discharged out of the separator 3 smoothly and quickly. Can do.

  As a result, according to the alkaline storage battery 1, it is possible to suppress the stagnation of gas between the electrodes 2 and to smoothly supply the electrolytic solution to the electrodes 2 and the separator 3.

  In addition, the electrode assembly 11 of the present example includes, as the electrode 2, the termination electrodes 21 and 23 disposed at both ends in the stacking direction of the electrode assembly 11, and the bipolar disposed between the termination electrode 21 and the termination electrode 23. The bipolar electrode 22 has a positive electrode active material layer 25p disposed on the front side surface of the metal foil 24 and a negative electrode active material layer 25n disposed on the back side surface. . Therefore, a single cell in which the positive electrode active material layer 25p and the negative electrode active material layer 25n face each other via the separator 3 is connected in series by a simple configuration in which a plurality of bipolar electrodes 22 are stacked via the separator 3. Can do. As a result, the electromotive force of the alkaline storage battery 1 can be further increased.

  Further, by using the bipolar electrode 22, the number of single cells can be increased with respect to the total number of electrodes as compared with the case of using a unipolar electrode. Therefore, when the total number of electrodes is the same, the number of single cells can be increased as compared with the case where unipolar electrodes are used. Moreover, when the number of single cells is the same, the total number of electrodes can be reduced compared with the case of using unipolar electrodes, and the size of the alkaline storage battery 1 in the stacking direction can be further reduced.

  Further, the width of the thin region 251 arranged along the short side 253 (253p, 253n) in each active material layer 25 is the entire width of the active material layer 25 in a plan view, that is, the long side 254 (254p) of the active material layer 25. 254n) is 2.5 to 5%. Similarly, the width of the thin region 251 disposed along the long side 254 in each active material layer 25 is 2.5 to 5% of the short side 253 of the active material layer 25. Therefore, it is possible to avoid a decrease in battery capacity due to a decrease in the thick region 252 while ensuring the effect of smoothly and quickly absorbing the electrolyte and discharging the gas.

  In addition, the thickness of the thin region 251 in this example becomes thinner as the distance from the thick region 252 increases. Therefore, the thin region 251 can be formed by a simple process as compared with the case where the thin region 251 having a constant thickness is formed.

(Example 2)
This example is an example of the electrode 2 including the thin region 255 having a constant thickness. Of the reference numerals used in and after the present embodiment, the same reference numerals as those used in the above-described embodiments indicate the same constituent elements as those in the above-described embodiments unless otherwise specified.

  The electrode 2 of this example includes a metal foil 24, a positive electrode active material layer 25 p disposed on the front side surface of the metal foil 24, and a negative electrode active material layer 25 n disposed on the back side surface of the metal foil 24. The bipolar electrode 26 is configured. The positive electrode active material layer 25p includes a thin region 255p provided over the entire circumference in a plan view as viewed from the stacking direction of the electrode assembly 11, and a thick region 252p disposed inside the thin region 255p. ing. Similarly to the positive electrode active material layer 25p, the negative electrode active material layer 25n also has a thin region 255n provided over the entire circumference in the plan view and a thick region 252n disposed inside the thin region 255n. ing.

  As shown in FIG. 5, the thin region 255 (255p, 255n) of this example is thinner than the thick region 252 and has a constant thickness. Others are the same as in the first embodiment.

(Example 3)
This example is an example of the electrode 2 including the thin region 256 whose thickness is reduced stepwise.

  The electrode 2 of this example includes a metal foil 24, a positive electrode active material layer 25 p disposed on the front side surface of the metal foil 24, and a negative electrode active material layer 25 n disposed on the back side surface of the metal foil 24. The bipolar electrode 27 is configured. The positive electrode active material layer 25p has a thin region 256p provided over the entire circumference in a plan view viewed from the stacking direction of the electrode assembly 11, and a thick region 252p disposed inside the thin region 256p. ing. Similarly to the positive electrode active material layer 25p, the negative electrode active material layer 25n also includes a thin region 256n provided over the entire circumference in the plan view and a thick region 252n disposed inside the thin region 256n. ing.

  As shown in FIG. 6, the thin region 256 (256p, 256n) of this example includes a plurality of flat portions 257 (257a, 257b) having different thicknesses and a step portion 258 that connects the flat portions 257 to each other. It has a staircase shape. More specifically, the thin region of the present example includes a first flat portion 257a disposed on the peripheral portion of the active material layer 25, a first flat portion 257a, and a thick region 252 (252p, 252n). It has two flat portions 257 with a second flat portion 257b disposed between them.

  The thickness of the first flat portion 257a is thinner than the thickness of the second flat portion 257b closer to the thick region 252 than the flat portion 257a. Further, a step portion 258 is disposed between the first flat portion 257a and the second flat portion 257b, and the flat portions 257 are connected to each other via the step portion 258. Others are the same as in the first embodiment.

  As shown in Examples 1 to 3, the shape of the thin region can take various forms. For example, it may be tapered like the thin region 251 (see FIG. 2) of the first embodiment, or may be constant like the thin region 255 (see FIG. 5) of the second embodiment. Good. Moreover, you may exhibit step shape like the thin area | region 256 (refer FIG. 6) of this example. These thin regions 251, 255, 256 have a shape in which the thickness at the position is equal to or less than the thickness of the position closer to the thick region than the position. The porosity of the separator 3 can be increased, and the electrolyte can be absorbed and the gas can be discharged smoothly and quickly.

  The specific aspect of the alkaline storage battery 1 according to the present invention is not limited to the aspect shown in the above-described embodiments, and can be appropriately changed within a range not impairing the gist thereof. For example, in Example 1, although the example of the alkaline storage battery 1 provided with the termination electrode 21 and the bipolar electrode 22 was shown, it can replace with the bipolar electrode 22 and the unipolar electrode 2 can also be used. In this case, for example, if the positive electrode provided with the positive electrode active material layer 25p on both surfaces of the metal foil 24 and the negative electrode provided with the negative electrode active material layer 25n on both surfaces of the metal foil 24 are alternately stacked via the separator 3 Good.

  Moreover, although Example 1-3 showed the example which formed the thin region 251, 255, 256 over the perimeter of the peripheral part of the active material layer 25, the thin region 251, 255, 256 is active material What is necessary is just to be formed in at least one part of the peripheral part of the layer 25. FIG. For example, in the case of the active material layer 25 having a rectangular shape, the thin region 251, 255, 256 may be formed along any one side, or the thin region 251 along two or three sides. 255, 256 may be formed.

DESCRIPTION OF SYMBOLS 1 Alkaline storage battery 11 Electrode assembly 2, 21, 22, 23, 26, 27 Electrode 24 Metal foil 25 Active material layer 251, 255, 256 Thin area 252 Thick area 3 Separator

Claims (6)

An alkaline storage battery having an electrode assembly in which a plurality of electrodes are stacked via a separator,
The electrode is
Metal foil,
Having an active material layer disposed on one or both sides of the metal foil,
The active material layer is
A thin region disposed in at least part of the peripheral edge of the active material layer in a plan view as viewed from the stacking direction of the electrode assembly;
The thin region is connected to the thin region, the thickness is thicker than the thin region, and has a constant thickness.
The thin region has a shape in which the thickness at the position is equal to or less than the thickness of the position closer to the thick region than the position at any position.
Alkaline storage battery.   The alkaline storage battery according to claim 1, wherein the thin region is disposed over the entire periphery of the peripheral portion of the active material layer in a plan view as viewed from the stacking direction.   The alkaline storage battery according to claim 1, wherein the thin region has a constant thickness.   3. The alkaline storage battery according to claim 1, wherein the thin region has a tapered shape with a thickness that decreases with distance from the thick region. 4.   The alkaline storage battery according to claim 1, wherein the thin region has a stepped shape including a plurality of flat portions having different thicknesses and a step portion connecting the flat portions.   The electrode assembly includes, as the electrodes, termination electrodes disposed at both ends in the stacking direction of the electrode assembly, and bipolar electrodes disposed between the termination electrodes. The active material layer has a positive electrode active material layer disposed on the front side surface of the metal foil and a negative electrode active material layer disposed on the back side surface. The alkaline storage battery according to item 1.

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