JP2016021340A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device in which a spacer is disposed in an adequate position with respect to an electrode assembly.SOLUTION: A secondary battery 10 as a power storage device comprises: an electrode assembly 12 composed of a layered structure including a positive electrode 14 and a negative electrode 15 which are insulated from each other; a sheet-like spacer 26 disposed on the electrode assembly on at least one side in a thickness direction thereof; and a case 11 in which the electrode assembly and the spacer are enclosed. The spacer 26 is shaped in a rectangular form, and has a protrusion 27 at each end of one side; the protrusions 27 protrude from a peripheral edge of the electrode assembly 12 in the state of being disposed on the one side of the electrode assembly 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device, and more specifically, an electrode assembly having a layered structure in which a positive electrode and a negative electrode are insulated is accommodated in a case with a sheet-like spacer disposed on at least one side surface in the thickness direction. It is related with the made electrical storage apparatus.

  Power storage devices such as secondary batteries and capacitors are widely used as power sources because they can be recharged and can be used repeatedly. For example, as a power storage device mounted on a vehicle such as an EV (Electric Vehicle) or a PHV (Plug-in Hybrid Vehicle), a lithium ion secondary battery, a nickel hydride secondary battery, or the like is well known. The power storage device has a sheet-like positive electrode and a sheet-like negative electrode each having an active material layer formed by coating a metal foil with a slurry-like active material mixture containing an active material, with a separator in between The electrode assembly is stacked or wound so as to form a layer in the state of being.

  By the way, an assembled battery mounted on a vehicle such as an automobile is assumed to be used in a state in which vibration is generated in addition to limiting the mounting space, and therefore a large number of single cells constituting the assembled battery are arranged. And the assembled battery of the state (namely, the state which fixed each cell) mutually is constructed | assembled. 2. Description of the Related Art Conventionally, a method has been proposed in which an assembled battery having an accurate shape and size can be manufactured by uniformizing the thickness in the arrangement direction of each cell constituting the assembled battery in a restrained state (see Patent Document 1).

  In this manufacturing method, as shown in FIG. 8, the gap between the inner surface of the unit cell container 40 and the wound electrode body (wound electrode assembly) 41 accommodated in the container 40 is a wound electrode body 41. The gaps are blocked by inserting an appropriate number of thin sheet-like insulating gap fillers (spacers) 42 in accordance with the size of the gaps. Further, the electrode body is not limited to the wound electrode body but may be a laminated electrode body.

  By the way, regardless of whether the electrode assembly is a laminated type or a wound type, a part of the positive electrode and the negative electrode protrude from the electrode assembly, specifically, a rectangular portion thereof. For example, in the case of a stacked-type lithium ion battery, the positive electrode includes a positive electrode main body in which a positive electrode active material layer is formed in a rectangular shape and a tab in which the positive electrode active material layer is not formed. The negative electrode is composed of a negative electrode main body in which a negative electrode active material layer is formed in a rectangular shape and a tab in which the negative electrode active material layer is not formed. In order to suppress lithium deposition, the size (area) of the positive electrode main body is set smaller than that of the negative electrode main body, but the position of the positive electrode can be detected by protruding the tab. Specifically, as shown in FIG. 9, in the manufacturing process, while the outer shape is detected by the detection device (camera) 45 disposed above, the positive electrode 46 and the negative electrode 47 are alternately interposed with the separator 48 interposed therebetween. Are stacked on the stacking table 49. Since the external shape of the positive electrode body is inside the negative electrode, it is difficult to recognize with high accuracy. However, the position of the positive electrode can be accurately grasped by detecting the external shape of the protruding positive electrode tab.

JP 2008-108457 A

  When the spacer is disposed on the side surface of the electrode assembly, the positional accuracy is important. In the power storage device, the electrode assembly is expanded by charging and discharging. If the spacer is displaced during expansion, the load applied to the electrode assembly varies, which adversely affects battery performance. Particularly in the case of a lithium ion battery, such a variation in load contributes to lithium deposition inside the electrode assembly. Therefore, it is necessary to detect the positional deviation of the spacer with high accuracy in the manufacturing process. However, the spacer does not have a part suitable for detection based on the outer shape, and the detection accuracy is poor. In particular, when the spacer is set smaller than the main body of the electrode assembly, it is difficult to detect misalignment.

  The present invention has been made in view of the above problems, and an object thereof is to provide a power storage device in which a spacer is disposed at an appropriate position with respect to an electrode assembly.

  In a power storage device that solves the above problems, an electrode assembly having a layered structure in which a positive electrode and a negative electrode are insulated, and a sheet-like spacer disposed on at least one side surface in the thickness direction are accommodated in a case. Power storage device. The spacer is formed in a rectangular shape and has a protrusion on at least one side end portion of one side, and the protrusion protrudes from a peripheral edge of the electrode assembly in a state of being disposed on one side surface of the electrode assembly. . Here, the “rectangular shape” includes not only a rectangle in which two opposing sides are completely parallel to each other but also a square in which the two sides are slightly deviated from parallel.

  In the sheet-like spacer, a protrusion is formed on at least one end of one side, and the protrusion protrudes from the peripheral edge of the electrode assembly. Therefore, even when the electrode assembly is overlaid, it is easy to detect the position of the spacer, and thus it is possible to detect a positional deviation from the electrode assembly. By detecting the positional displacement of the spacer, it is possible to prevent an uneven load from being applied to the electrode assembly due to the positional displacement of the spacer. Further, it is possible to provide a power storage device in which spacers are arranged at appropriate positions with respect to the electrode assembly.

  The spacer is formed in a rectangular shape and has a protrusion on at least one end of one side, and a notch having the same shape as the protrusion is formed on a side opposite to the side on which the protrusion is formed. Yes. Therefore, when the spacer is cut out from the raw material sheet wound in a roll shape, the protrusion portion and the cutout portion having the same shape as the protrusion are simultaneously cut to form the spacer, so that the end material does not come out. Further, even when the electrode assembly and the spacer are accommodated in the case via the insulating film, the protruding portion is disposed at a position where it does not contact the insulating film, so that the insulating film is not damaged. Therefore, the power storage device of the present invention can prevent the end material from coming out during the manufacture of the spacer and prevent the corners of the spacer from damaging the insulating film.

  The electrode assembly is a stacked electrode assembly, and the spacer preferably has an area of a portion excluding the protrusion that is not less than the area of the positive electrode and less than the area of the negative electrode. When the electrode assembly is a laminated type, the area of the positive electrode is set smaller than the area of the negative electrode in a lithium ion battery or the like. By setting the spacer so as to cover the positive electrode and smaller than the negative electrode, it is possible to save a resin sheet as a material.

  The spacer preferably has the protrusions formed on both sides. When the protrusions are formed on both sides, the position of the spacer can be detected with higher accuracy than when the protrusions are formed only on one side.

  It is preferable that the protrusion is formed in a right triangle shape in which a right angle portion is located at an end portion of the side. Since the protrusion having this shape has a straight line on two sides, it is advantageous in the accuracy of detecting the position of the spacer.

  It is preferable that a plurality of the spacers are arranged. Since the size of the gap between the electrode assembly and the inner surface of the case is not constant, it is necessary to prepare a number of spacers having different thicknesses in order to fill the gap with a single spacer. However, when a plurality of spacers are used to fill the gap, it is possible to cope with gaps of different sizes by adjusting the number of spacers having the same thickness, and the number of types of spacers having different thicknesses may be small.

  ADVANTAGE OF THE INVENTION According to this invention, the electrical storage apparatus with which the spacer is arrange | positioned in the appropriate position with respect to an electrode assembly can be provided.

(A) is a disassembled perspective view which shows the structure of a secondary battery, (b) is a perspective view which shows a positive electrode, a separator, and a negative electrode typically. The schematic front view which shows the relationship of the positive electrode of the state which accumulated the spacer on the electrode assembly, the negative electrode, the separator, and the spacer. The schematic diagram which shows the cutting method of a spacer. The schematic diagram which shows the positioning method of a spacer. The schematic diagram explaining the effect | action with respect to the insulating film of a spacer. The front view of the spacer of another embodiment. The front view of the spacer of another embodiment. The schematic cross section which shows presence of the spacer in the restraint state of the cell in a prior art. The figure which shows a lamination apparatus typically.

Hereinafter, an embodiment in which the present invention is embodied in a secondary battery including a stacked electrode assembly will be described with reference to FIGS.
As shown in FIG. 1A, a secondary battery 10 as a power storage device is provided in a rectangular box-shaped case 11 constituted by a bottomed box-shaped case body 11a and a lid 11b covering the opening. The stacked electrode assembly 12 is accommodated. Both the case main body 11a and the lid body 11b are made of metal (for example, made of stainless steel or aluminum). Although not shown, the electrode assembly 12 has chamfered corners.

  As shown in FIG. 1B, the electrode assembly 12 includes a plurality of positive electrodes 14 having active material layers 14 a on both surfaces of a metal foil 13 as a current collector, and active material layers 15 a on both surfaces of the metal foil 13. A plurality of negative electrodes 15 are laminated with a separator 16 interposed therebetween. When the secondary battery 10 is a lithium ion secondary battery, the metal foil 13 for the positive electrode 14 is preferably an aluminum foil, and the metal foil 13 for the negative electrode 15 is preferably a copper foil.

  In the positive electrode 14 and the negative electrode 15, the portions where the active material layers 14 a and 15 a are formed are formed in a rectangular shape, and the active material non-applied portions 14 b and 15 b to which the active material is not applied are above the active material layers 14 a and 15 a. Is provided. A positive electrode tab 14c is formed protruding from the active material non-applied portion 14b, and a negative electrode tab 15c is formed protruding from the active material non-coated portion 15b. The positive electrode tab 14 c is formed on the upper right side of the positive electrode 14, and the negative electrode tab 15 c is formed on the upper left side of the negative electrode 15.

The separator 16 is made of a resin and formed in a bag shape, and the positive electrode 14 is accommodated in the separator 16 with the positive electrode tab 14c protruding from the top of the bag.
As shown in FIG. 2, the separator 16 has a rectangular shape larger than the rectangular portions of the positive electrode 14 and the negative electrode 15 excluding the positive electrode tab 14 c and the negative electrode tab 15 c in order to ensure electrical insulation between the positive electrode 14 and the negative electrode 15. It is formed into a shape. The positive electrode 14 is formed such that the portion excluding the positive electrode tab 14 c is smaller than the portion of the negative electrode 15 excluding the negative electrode tab 15 c. The negative electrode 15 has the same width as the separator 16 and is shorter than the separator 16 in the direction perpendicular to the width direction. In FIG. 2, the spacer 26 is disposed in front of the electrode assembly 12.

  As shown in FIG. 1A, the positive electrode terminal 21 is welded to the positive electrode tab 14c via a plate-like conductive member 21a, and the positive electrode tab 14c extends so that the tip end side extends along the upper end surface of the electrode assembly 12. It is welded to the conductive member 21a in a bent state. In this embodiment, the conductive member 21a is formed in a rectangular shape and is welded to the positive electrode tab 14c on one end side in a state extending in a direction orthogonal to the extending direction of the positive electrode tab 14c.

  Similarly, the negative electrode terminal 22 is welded to the negative electrode tab 15c via the plate-like conductive member 22a, and the negative electrode tab 15c is bent in such a manner that the tip end side extends along the upper end surface of the electrode assembly 12. It is welded to 22a.

  As shown in FIG. 1A, in the state where the electrode assembly 12 is housed in the case 11, a ring-shaped insulating member in which the positive terminal 21 and the negative terminal 22 are attached to the hole 11c formed in the lid 11b. 23 is formed so as to protrude from the lid 11b in a state of penetrating through the cover 23b.

  As shown in FIG. 1A, in the case 11, the electrode assembly 12 accommodated in the case body 11a is prevented from moving (shaking) in the case 11 in order to prevent the electrode assembly 12 from being moved. The spacer 26 for adjusting the thickness is accommodated in a state in which a gap between the surface of the electrode assembly 12 and the inner surface of the case main body 11a in the thickness direction (stacking direction of the positive electrode 14 and the negative electrode 15) is filled.

  The spacer 26 is made of resin (for example, made of polypropylene). The spacer 26 is formed in a rectangular shape, and has protrusions 27 at both end portions of one side. A cutout portion 28 having the same shape as the protrusion 27 is formed on a side 26 b opposite to the side 26 a on which the protrusion 27 is formed. Is formed. The “rectangular shape” includes not only a rectangle in which two opposing sides are completely parallel to each other but also a quadrangle in which the two sides are slightly deviated from parallel. The protrusion 27 is formed in a right triangle shape having a right angle portion located at an end portion of the side 26a. The required number of the spacers 26 varies depending on the size of the gap and the thickness of the spacers 26. For example, when the manufacturing error of the electrode assembly 12 is 1 mm, the maximum number of 5 to 10 is 1 mm. Is set.

  When manufacturing the spacer 26, as shown in FIG. 3, the resin film 31 is intermittently paid out from a reel (not shown) in which a belt-shaped resin film 31 as a raw material sheet is wound in a coil shape. In the stopped state of 31, the resin film 31 is cut by the cutting means. For example, the cutting means moves the cutting blade along the line L to be cut and cuts the cutting blade or moves the cutting blade having the shape of the line L to be cut perpendicularly to the resin film 31 for cutting. Things are used. When the spacer 26 is cut out from the raw material sheet wound in a roll shape, the portion of the protrusion 27 and the cutout portion 28 having the same shape as the protrusion 27 are simultaneously cut to form the spacer 26. Absent.

  Next, the lamination process in the manufacturing process of the secondary battery 10 will be described. In the laminating step, the rectangular sheet-like positive electrode 14 and the rectangular sheet-like negative electrode 15 are laminated with the separator 16 therebetween, and are fixed with a tape (not shown) to form the laminated electrode assembly 12. Further, spacers are arranged on one side of the electrode assembly and fixed to each other. More specifically, as shown in FIG. 1A, after arranging a plurality of sheet-like thickness adjusting spacers 26 on one side in the thickness direction of the electrode assembly 12, a tape (not shown) Then, the spacer 26 is fixed to the electrode assembly 12.

  The spacer 26 and the electrode assembly 12 described above are wrapped in an insulating film (not shown) in a later process, and the electrode assembly 12 and the spacer 26 are inserted into the case body 11a in this state. The Thereafter, after the opening of the case body 11a is closed by the lid body 11b, the lid body 11b is fixed to the case body 11a by welding, for example.

  When the spacers 26 are fixed to the electrode assembly 12 in a state where a plurality of layers are stacked, it is necessary to use the plurality of spacers 26 in an aligned state. As a method for aligning the spacers 26, a plurality of spacers 26 are aligned together, fixed with a tape or the like, and then fixed to the electrode assembly 12, or the spacers 26 are aligned one by one. There is a method to put on.

  In the method of aligning a plurality of spacers 26 together, for example, as shown in FIG. 4, a positioning device 33 arranged at a position facing the side 26 a where the protrusion 27 of the spacer 26 is formed, and a notch This is performed by using a positioning device 34 disposed at a position facing the side 26b on which 28 is formed. The positioning device 33 includes a pair of engaging portions 33a and 33b that can come into contact with the slope of the protrusion 27 and a part of the side 26a. Both engaging portions 33a and 33b are configured to be capable of reciprocating simultaneously in a direction orthogonal to the side 26a. The positioning device 34 includes a pair of engaging portions 34a and 34b that can come into contact with the slope of the notch 28 and a part of the side 26b. Both the engaging portions 34a and 34b are configured to be capable of reciprocating simultaneously in a direction orthogonal to the side 26b. In this method, alignment can be performed regardless of the size of the spacer 26. Further, when the spacer 26 is rectangular, an engaging portion that moves in a direction orthogonal to the sides 26a and 26b of the spacer 26 and an engaging portion that moves in a direction parallel to the sides 26a and 26b are required. The space for positioning the positioning device is widened, but when the spacer 26 has the protrusion 27 and the notch 28, the space for positioning the positioning device can be narrowed.

  Even when a plurality of spacers 26 are aligned together, when the spacers 26 are placed on the electrode assemblies 12 one by one, when the spacers 26 are rectangular, when the spacers 26 are smaller than the electrode assemblies 12, It is difficult to detect and hold (hold) the position during alignment.

  However, since the spacer 26 only needs to be large enough to cover the positive electrode 14, if the spacer 26 can be aligned, forming the spacer 26 smaller than the electrode assembly 12 contributes to weight reduction and cost reduction. When the spacer 26 has the protrusion 27, the size of a part of the protrusion 27 protruding outside the electrode assembly 12 even if the size of the portion excluding the protrusion 27 of the spacer 26 is smaller than the size of the electrode assembly 12. The spacer 26 can be aligned.

  For example, as shown in FIG. 2, the spacer 26 is formed so that the length in the width direction is longer than the length in the width direction of the positive electrode 14 and shorter than the length in the width direction of the negative electrode 15, and the length in the direction orthogonal to the width direction. Is formed to have the same length as that in the direction orthogonal to the width direction of the negative electrode 15. In other words, the area of the spacer 26 excluding the protrusion 27 is set to be equal to or larger than the area of the positive electrode 14 and smaller than the area of the negative electrode 15. In this case, the reference position of the alignment of the spacer 26 with respect to the electrode assembly 12 is set to the surface opposite to the tab projecting surface 12a of the electrode assembly 12, and the electrode assembly 12 is aligned with the side 26b of the spacer 26 at the reference position. Using the two protrusions 27 protruding from the tab protruding surface 12a of the three-dimensional body 12, the width direction and the inclination are aligned.

  The secondary battery 10 configured as described above has a case 11 in which the spacer 26 is fixed to the electrode assembly 12 at the time of manufacture, and the electrode assembly 12 and the spacer 26 are wrapped in an insulating film (not shown). It is inserted into the main body 11a. As shown in FIG. 5, the insertion is performed until the surface of the electrode assembly 12 opposite to the tab protruding surface 12a reaches near the bottom of the case body 11a. Therefore, when the spacer 26 has a rectangular shape without chamfering, the corner of the spacer 26 may hit the inner surface of the case body 11a through the insulating film, and the insulating film may be destroyed. However, in this embodiment, since the spacer 26 is formed with the notches 28 at both ends of the side 26b on the side facing the inner surface of the case body 11a, the insulating film is prevented from being broken.

According to this embodiment, the following effects can be obtained.
(1) The spacer 26 is formed in a rectangular shape and has protrusions 27 at both ends of one side, and the protrusion 27 protrudes from the peripheral edge of the electrode assembly 12 in a state where the spacer 26 is disposed on one side surface of the electrode assembly 12. It is arranged in the state. By forming the protrusion 27 protruding from the periphery of the electrode assembly 12, it is possible to accurately detect the positional deviation of the spacer 26 with respect to the electrode assembly 12 in the manufacturing process, and to provide a secondary battery without the positional deviation of the spacer. Can do.

  (2) In the secondary battery 10 as the power storage device, the electrode assembly 12 having a layered structure in which the positive electrode 14 and the negative electrode 15 are insulated has a sheet-like thickness adjusting spacer on at least one side surface in the thickness direction. 26 is accommodated in the case 11 in a state where it is arranged. The spacer 26 is formed in a rectangular shape and has protrusions 27 at both ends of one side, and a notch 28 having the same shape as the protrusion 27 is formed on a side 26b opposite to the side 26a on which the protrusion 27 is formed. Has been. Therefore, even if the spacers 26 are accommodated in the case 11 in the state where the spacers 26 are wrapped in the insulating film together with the electrode assembly 12 without producing the end material at the time of manufacturing the spacer 26 for adjusting the thickness, the corners of the spacers 26 are formed in the insulating film. Can be prevented from being damaged.

  (3) The electrode assembly 12 is a stacked electrode assembly, and the area of the spacer 26 excluding the protrusions 27 is not less than the area of the positive electrode 14 and less than the area of the negative electrode 15. When the electrode assembly 12 is a laminated type, the area of the positive electrode 14 is set smaller than the area of the negative electrode 15 in a lithium ion battery or the like. By setting the spacer 26 to a size that can cover the positive electrode 14 and smaller than the negative electrode 15, a resin sheet as a material can be saved.

  (4) The spacer 26 has protrusions 27 formed on both sides. When the protrusions 27 are formed on both sides, the position and inclination of the spacer 26 can be detected with high accuracy, and the positional deviation of the spacer 26 with respect to the electrode assembly 12 can be detected with high accuracy.

  (5) The protrusion 27 is formed in a right triangle shape in which the right angle portion is located at the end of the side 26a. Since the protrusion 27 having this shape has two sides of a straight line portion, the detection accuracy is good, and is particularly advantageous when there is only one protrusion.

  (6) A plurality of spacers 26 are arranged. Since the size of the gap between the electrode assembly 12 and the inner surface of the case 11 is not constant, in order to fill the gap with one spacer 26, it is necessary to prepare a large number of spacers 26 having different thicknesses. Become. However, when a plurality of spacers 26 fill the gap, it is possible to cope with gaps of different sizes by adjusting the number of spacers 26 having the same thickness, and there are few types of spacers 26 having different thicknesses. Good.

The embodiment is not limited to the above, and may be embodied as follows, for example.
As shown in FIG. 6, the shape of the protrusion 27 formed on the spacer 26 may be formed such that the shape of the cutout portion 28 is an arc shape (R surface).

  The shape of the protrusion 27 is not limited to a shape in which the shape of the notch 28 is a C surface or an R surface. For example, the protrusion 27 may have a rectangular shape and the cutout portion 28 may have a rectangular shape.

  In the secondary battery 10, the protrusion 27 may be bent in the thickness direction of the electrode assembly. The protrusion 27 only needs to be able to detect the position of the spacer 26 in the stacking process, and can be bent, for example, after being fixed to the electrode assembly with tape.

  The spacer 26 is formed in a rectangular shape and has a protrusion 27 on at least one side end portion of one side. A cutout portion having the same shape as the protrusion 27 is formed on the side 26b opposite to the side 26a on which the protrusion 27 is formed. As shown in FIG. 7, the protrusion 27 and the notch 28 may be formed on one side of both sides 26a and 26b. However, when the projection 27 and the notch 28 are formed on one side, the size of the spacer 26 is limited, and the corner of the spacer 26 where the notch 28 is not formed is located inside the electrode assembly 12. It is necessary that the notch portion 28 does not hit the positive electrode 14 in a state where the notch portion 28 is located. Therefore, the ratio of the size of the positive electrode 14 and the negative electrode 15 is larger in proportion of the negative electrode 15 than in the case of FIG.

The spacers 26 may be disposed on both sides of the electrode assembly 12 in the thickness direction.
The spacer 26 arrange | positioned between the electrode assembly 12 and the case 11 inner surface may be one sheet.

The separator 16 is not limited to a bag shape, and a sheet-like separator 16 may be used.
The positive electrode 14 and the negative electrode 15 are not limited to the configuration in which the active material layers 14 a and 15 a are formed on both surfaces of the metal foil (current collector) 13, and may be configured on one surface.

  The positive electrode tab 14c and the negative electrode tab 15c are not limited to a structure in which the positive electrode 14 or the negative electrode 15 protrudes from the active material non-applied portions 14b and 15b and is integrally formed. For example, it may be formed by welding a metal foil tab formed separately to the active material non-applied portions 14b and 15b.

  (Circle) the formation method of the active material layer of the positive electrode 14 and the negative electrode 15 is not limited to application | coating. For example, it is formed by other manufacturing methods, such as laminating a mixed powder of active material, binder, conductive additive, etc. on the positive electrode body (rectangular part) and forming an active material layer by pressing and heating. Also good.

The electrode assembly 12 is not limited to the laminated type, and may be a wound type electrode assembly 12.
The secondary battery 10 is not limited to a lithium ion secondary battery, and may be another secondary battery such as a nickel hydrogen secondary battery or a nickel cadmium secondary battery.

  The power storage device is not limited to the secondary battery 10 and may be a capacitor such as an electric double layer capacitor or a lithium ion capacitor.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery as a power storage device, 11 ... Case, 12 ... Electrode assembly, 14 ... Positive electrode, 15 ... Negative electrode, 16 ... Separator, 26 ... Spacer, 26a, 26b ... Side, 27 ... Projection, 28 ... Notch Department.

Claims (6)

An electrode assembly having a layered structure in which a positive electrode and a negative electrode are insulated, and a sheet-like spacer disposed on at least one side surface in the thickness direction are housed in a case,
The spacer is formed in a rectangular shape and has a protrusion on at least one side end portion of one side, and the protrusion protrudes from a peripheral edge of the electrode assembly in a state of being disposed on one side surface of the electrode assembly. A power storage device.   The power storage device according to claim 1, wherein a cutout portion having the same shape as the protrusion is formed on a side of the spacer facing the side on which the protrusion is formed.   3. The power storage device according to claim 1, wherein the electrode assembly is of a stacked type, and the area of the spacer excluding the protrusions is equal to or greater than the area of the positive electrode and less than the area of the negative electrode.   The power storage device according to any one of claims 1 to 3, wherein the spacer has the protrusions formed on both sides.   The power storage device according to any one of claims 1 to 4, wherein the protrusion is formed in a right triangle shape in which a right angle portion is located at an end of the side.   The power storage device according to any one of claims 1 to 5, wherein a plurality of the spacers are arranged.