JP2017076476A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the creasing or Li precipitation on an electrode assembly and to elongate the life of a power storage device.SOLUTION: A power storage device (secondary battery 10) comprises: an electrode assembly 12 arranged by laminating a positive electrode 15 including a positive electrode active material layer 14 formed on a piece of metal foil 13, and a negative electrode 17 having a negative electrode active material layer 16 formed on a piece of metal foil 13 with a separator 18 interposed therebetween; an electrolytic solution L; a case 11 having a bottomed box-like case main body 11a and a lid 11b for covering an opening of the case main body 11a, in which the electrode assembly is encased together with the electrolytic solution; and an elastic body 30 which is provided between at least one side face 12a of the electrode assembly 12 and an inner face of the case 11 so as to abut against the side face (i.e. the one side face 12a) overall. The elastic body 30 is formed by a polymeric foam having a corrosion resistance against the electrolytic solution L.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device.

  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. In general, a power storage device with a large capacity includes a case for accommodating an electrode assembly, and the electrode assembly is accommodated in the case. And extraction of the electric power from an electrical storage apparatus is performed through the electrode terminal connected to the positive electrode and negative electrode of an electrode assembly.

  By the way, when the secondary battery is used in a state where vibration is generated, it is not preferable that the electrode assembly is housed in a state that can vibrate with respect to the case because the electrode assembly moves in the case due to vibration. .

  Patent Document 1 discloses a secondary battery having a configuration capable of easily discharging gas accumulated inside a stacked electrode group, and a storage battery system that exhibits stable charge / discharge capacity over a long period of time using the secondary battery. Has been proposed.

  As shown in FIG. 5, in Patent Document 1, a stacked electrode group 54 is housed in a battery can 53 that is hermetically sealed by an outer case 51 and a lid member 52 as a secondary battery 50, A secondary battery 50 provided with an electrode group pressing member 55 that exhibits a function of receiving a driving force to press the electrode group 54 to degas the inside of the electrode group 54 is disclosed. The electrode group pressing member 55 connects the electrode group 54 to the lid member 52 via an elastic member 56 such as a spring or a rubber body. The elastic members 56 are provided at a plurality of predetermined locations that press the secondary battery 50 uniformly.

  In the secondary battery 50, when the gas is accumulated in the electrode group 54, the electrode group pressing member 55 is driven in the direction of arrow D1 in FIG. As a driving force for driving the electrode group pressing member 55 in the direction of the arrow D1, for example, a vibration force and a centrifugal force are used. The vibration force can be added by repeatedly vibrating a predetermined frequency range with strength. In addition, centrifugal force is applied by installing a secondary battery 50 in a bottomed cylindrical centrifugal force application device and repeatedly rotating and driving within a predetermined frequency, thereby adding a centrifugal force as a predetermined driving force. Can do.

JP 2013-157167 A

  In a lithium ion secondary battery, in order to increase the charge / discharge cycle life, it is important to suppress generation of wrinkles in the electrode assembly and prevention of Li precipitation at the negative electrode. The inventor of the present application can suppress wrinkles and Li precipitation by adjusting the thickness and clearance of the electrode assembly, but in the life evaluation, the load applied to the electrode assembly during the use of the secondary battery affects the life. And found that the load tends to be worse when the load is large.

  In Patent Document 1, when the electrode group pressing member 55 receives a predetermined driving force such as centrifugal force or vibration force and presses the electrode group 54 (electrode assembly) in the stacking direction, the electrode group pressing member 55 It is described that the electrode group pressing member 55 is connected to the lid member 52 via the stretchable member 56 in order to face the upper surface (stacked surface) of the electrode group 54 and to be in proper contact with the upper surface (stacked surface) without being displaced. Has been. However, there is no description regarding the relationship between wrinkles or Li deposition during expansion of the electrode assembly during charging and the load applied to the electrode assembly.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a power storage device that can suppress wrinkles and Li deposition of an electrode assembly and extend the lifetime.

  A power storage device that solves the above problems includes an electrode assembly in which a positive electrode and a negative electrode each having an active material layer formed on a metal foil are stacked with a separator in between, and a bottomed box-shaped case body. A power storage device housed together with an electrolyte in a case having a lid that covers the opening of the case body. An elastic body is provided between at least one side surface of the electrode assembly and the inner surface of the case so as to contact 50% or more of the side surface, and the elastic body is in contact with the electrolytic solution. It is formed of a polymer foam having corrosion resistance. Here, the “side surface” means an end surface in the stacking direction of the positive electrode, the negative electrode, and the separator in the electrode assembly. However, in the case of a wound-type electrode assembly, the pair of flat portions are side surfaces on the assumption that the electrode assembly is flat.

  In this configuration, for example, when the power storage device is mounted on a vehicle and used, an elastic body exists between the side surface of the electrode assembly and the inner surface of the case, so that vibration of the electrode assembly with respect to the case is suppressed. Is done. In addition, since the electrode assembly expands in the stacking direction of the electrode and the separator when the power storage device is charged, a reaction force of the force that the electrode assembly presses the inner surface of the case due to the expansion of the electrode assembly is applied to the electrode assembly as a load. .

  In a state in which the electrode assembly is in direct contact with the inner surface of the case or in a state in which a spacer (thickness adjusting film) is provided between the inner surface of the case, the reaction force directly acts on the electrode assembly. Therefore, the load applied to the electrode assembly is increased. However, when an elastic body exists between the side surface of the electrode assembly and the inner surface of the case, the elastic body contracts to reduce the load applied to the electrode assembly and extend the life of the power storage device. Therefore, by using an electrode assembly formed in a state in which wrinkles and Li precipitation are suppressed, wrinkles and Li precipitation of the electrode assembly can be suppressed and the life can be extended.

  The elastic body is preferably formed so as to be able to contact the entire surface of the side surface of the electrode assembly. If the elastic body is provided in contact with 50% or more of the side surface of the electrode assembly, the load applied to the electrode assembly due to the reaction force from the inner surface of the case accompanying the expansion of the electrode assembly during charging of the power storage device Is negatively affected by the value of the power storage device. However, it is preferable that the elastic body is in contact with the entire side surface of the electrode assembly because the pressing force that the inner surface of the case presses the electrode assembly is applied in a state of being uniformly dispersed in the electrode assembly.

  The polymer foam is preferably foamed EPDM or foamed polyolefin. The material of the polymer foam is not particularly limited as long as it has corrosion resistance to the electrolytic solution, but foamed EPDM (ethylene propylene diene rubber) and foamed polyolefin are easily available.

The case is preferably provided with an outer elastic body on the outer surface of the side wall facing at least one of the side surfaces of the electrode assembly.
The power storage device is generally used in a state of being restrained on the outer surface of the side wall of the case. For example, in the case of being mounted on a vehicle and used as a power source for a traveling motor or a power source for other electrical equipment, the battery pack is used in a state where a plurality of power storage devices are electrically connected. Since the assembled battery is assumed to be used in a state where vibration is generated in addition to the limited mounting space, a large number of unit cells constituting the assembled battery are arranged and restrained (that is, each An assembled battery in a state where the cells are fixed to each other is constructed. In that case, if the outer elastic body is provided on the outer surface of the side wall of the case, the power storage device is restrained via the outer elastic body, so that the load applied to the power storage device is relieved by the outer elastic body.

  ADVANTAGE OF THE INVENTION According to this invention, while suppressing the wrinkle and Li precipitation of an electrode assembly, the lifetime of an electrical storage apparatus can be extended.

(A) is a partial fracture | rupture schematic perspective view of the secondary battery in 1st Embodiment, (b) is a schematic cross section which cut | disconnected the secondary battery in the thickness direction of the electrode assembly. (A) is a schematic diagram which shows the effect | action at the time of charge, (b) is a schematic diagram which shows the effect | action at the time of discharge. The schematic cross section which cut | disconnected the secondary battery in 2nd Embodiment in the thickness direction of the electrode assembly. The graph which shows the relationship between the load added to an elastic body, and the amount of compression. The schematic sectional drawing of the secondary battery of a prior art.

(First embodiment)
A first embodiment embodying the present invention will be described below with reference to FIGS.
As shown in FIGS. 1 (a) and 1 (b), a secondary battery 10 as a power storage device includes a stacked electrode assembly 12 and an electrolyte L (see FIG. 1 (b)) in a rectangular box-like case 11. (Shown) is housed. The case 11 includes a case main body 11a and a lid 11b that covers the opening, and the case main body 11a and the lid 11b are joined by welding. The secondary battery 10 is embodied as a lithium ion secondary battery.

  As shown in FIG. 1B, the electrode assembly 12 includes a plurality of positive electrodes 15 having a positive electrode active material layer 14 on both surfaces of a metal foil 13 and a plurality of negative electrode active material layers 16 on both surfaces of the metal foil 13. A negative electrode 17 is laminated with a separator 18 between them. Each of the positive electrode 15 and the negative electrode 17 has a rectangular shape in which the positive electrode active material layer 14 or the negative electrode active material layer 16 is formed. The positive electrode 15 has a positive electrode tab 15 a formed by protruding a metal foil 13 from one edge of the positive electrode active material layer 14, and the negative electrode 17 has a metal foil 13 formed from one edge of the negative electrode active material layer 16. The negative electrode tab 17a is formed to protrude.

  As shown in FIG. 1A, a positive electrode terminal 20 as an electrode terminal is electrically connected to a positive electrode tab 15a through a plate-like conductive member 20a, and the positive electrode tab 15a has a distal end side above the electrode assembly 12. It is welded to the conductive member 20a while being bent so as to extend along the end face.

  As shown in FIGS. 1A and 1B, a negative electrode terminal 22 as an electrode terminal is electrically connected to a negative electrode tab 17a through a plate-like conductive member 22a. The conductive member 22a is welded in a state of being bent so as to extend along the upper end surface of the solid body 12. The negative electrode terminal 22 is fixed to the lid body 11b so as to pass through the insulating ring 23 that fits into the hole 11c formed in the lid body 11b. Similarly, the positive electrode terminal 20 is also fixed to the lid body 11b in a state of penetrating an insulating ring 23 fitted in a hole 11c formed in the lid body 11b.

  As shown in FIGS. 1A and 1B, the secondary battery 10 is provided between one side surface 12a of the electrode assembly 12 and the inner surface of the case 11 (in this embodiment, the inner surface of the case body 11a). The elastic body 30 is provided. The elastic body 30 is formed so as to be able to contact the entire surface of the one side surface 12a of the electrode assembly 12. In this embodiment, the elastic body 30 is formed such that the area of the surface facing the one side surface 12a of the electrode assembly 12 is larger than the area of the one side surface 12a. The elastic body 30 is composed of a polymer foam having corrosion resistance to the electrolytic solution L. In this embodiment, a foamed polyolefin such as foamed polyethylene is used as the polymer foam.

  There are a closed cell body and an open cell body in a foam, However, A closed foam is preferable. Moreover, even if it is a closed-cell body, a wrinkle may generate | occur | produce in the electrode assembly 12 by the relationship between the applied load and a compressibility. When the thickness of the elastic body 30 is about 2 mm, the load is preferably 10 to 20 kN and the compression rate is preferably 30% or less.

  As shown in FIG. 1B, the secondary battery 10 is provided with a thickness adjusting film (spacer) 32 between the other side surface 12b of the electrode assembly 12 and the inner surface of the case. When the length of the electrode assembly 12 in the stacking direction is shorter than a preset value, that is, when a gap is generated between the electrode assembly 12 and the inner surface of the case 11, the thickness adjusting film 32 is 12 and the inner surface of the case 11 to fill the gap. As the thickness adjusting film 32, a film having corrosion resistance with respect to the electrolytic solution L, for example, a film made of polyethylene having a thickness of about 150 μm is used, and the number of sheets used is changed depending on the size of the gap.

Next, the operation of the secondary battery 10 configured as described above will be described.
The electrode assembly 12 is accommodated in the case body 11a in a state where the elastic body 30 is disposed on one side surface 12a and the thickness adjusting film 32 is disposed on the other side surface 12b. The thickness of the elastic body 30 is such that even when the electrode assembly 12 is most contracted by electric discharge, the elastic body 30 is between the inner surface of the case body 11a and the elastic body 30, between the elastic body 30 and the electrode assembly 12, And the thickness adjusting film 32 and between the thickness adjusting film 32 and the inner surface of the case main body 11a are set so as not to exist.

  The secondary battery 10 is used in a state in which the case 11 is restrained in a state where movement in the direction orthogonal to the one side surface 12a of the electrode assembly 12 is suppressed. For example, when used as an assembled battery mounted on a vehicle such as an automobile, the assembled battery is configured with a large number of secondary batteries 10 constituting the assembled battery fixed to each other.

  2A and 2B are schematic views showing the relationship among the case 11, the elastic body 30, and the electrode assembly 12 when the secondary battery 10 is in use. The secondary battery 10 is arranged in a state where the outer surface of the case 11 corresponding to the side surface of the electrode assembly 12 is restrained by the restraining plate 34. In addition, illustration of electrolyte solution L, the cover body 11b, and the thickness adjustment film 32 is abbreviate | omitted.

  As shown in FIG. 2A, at the time of charging, the electrode assembly 12 expands in the stacking direction of the electrodes and the separator, that is, the left-right direction in FIG. Due to the expansion of the electrode assembly 12, the electrode assembly 12 generates an expansion force in the direction of arrow A, and one side surface 12a of the electrode assembly 12 presses the elastic body 30 against the inner surface of the case body 11a. The side wall 11 d presses the restraint plate 34. The restraint plate 34 does not move even when pressed, and a reaction force in the direction of arrow B acts from the restraint plate 34 on the side wall 11d of the case body 11a. The elastic body 30 transmits the reaction force from the restraint plate 34 to the electrode assembly 12 in a state where the elastic body 30 is contracted and deformed by absorbing the expansion amount of the electrode assembly 12. As a result, a smaller load is applied to the electrode assembly 12 in the direction of arrow B than when the elastic body 30 does not exist between the electrode assembly 12 and the side wall 11d.

If the elastic body 30 is too hard or too thin, the load cannot be reduced, and an excessive load is applied to the electrode assembly 12 during charging.
As shown in FIG. 2B, at the time of discharge, the electrode assembly 12 contracted in the electrode and separator stacking direction, that is, in the direction of arrow C in FIG. 2B, and contracted and deformed when the electrode assembly 12 expanded. The elastic body 30 is free from contraction deformation. With the electrode assembly 12 contracted, between the inner surface of the case body 11a and the elastic body 30, between the elastic body 30 and the electrode assembly 12, between the electrode assembly 12 and the thickness adjusting film 32, and thickness adjustment. If a gap is generated between the film 32 and the inner surface of the case body 11a, the electrode assembly 12 can move with respect to the case 11, which is not preferable.

  If the elastic body 30 is too thick and soft, the elastic body 30 compressed as the electrode assembly 12 expands during charging cannot return to its original state even when the pressing force from the electrode assembly 12 is released during discharging. A gap is formed between the electrode assembly 12 and the case body 11a.

  An experiment was conducted to examine the presence or absence of wrinkles by using foamed polyethylene having a different foamed state as the elastic body 30 and changing the load. The results are shown in Table 1.

From Table 1, the compression ratio of the foam affects whether or not wrinkles are generated in the electrode assembly 12. When the load is 15 to 20 kN and the compression ratio is 30% or less, wrinkles are unlikely to occur. Seem. It can also be seen that when the compression ratio is 50% or more, wrinkles are likely to occur even when the load is as small as 10 kN. Further, when the foam was an open cell body, wrinkles were generated even when the compressibility was as small as 10% and the load was as small as 5 kN. Therefore, the polymer foam used as the elastic body 30 is preferably a closed cell body than an open cell body.

According to this embodiment, the following effects can be obtained.
(1) In the secondary battery 10, the positive electrode 15 in which the positive electrode active material layer 14 is formed on the metal foil 13 and the negative electrode 17 in which the negative electrode active material layer 16 is formed are in a state where the separator 18 exists between them. The stacked electrode assembly 12 is a power storage device housed together with the electrolyte L in a case 11 having a bottomed box-like case main body 11a and a lid 11b covering an opening of the case main body 11a. An elastic body 30 is provided between at least one side surface 12a of the electrode assembly 12 and the inner surface of the case 11 so as to be in contact with the entire side surface (one side surface 12a). It is formed of a polymer foam having corrosion resistance to the liquid L.

  In this configuration, when the secondary battery 10 is used mounted on a vehicle, for example, the elastic body 30 exists between the side surface 12a of the electrode assembly 12 and the inner surface of the case 11, so that the electrode assembly The vibration with respect to 12 cases 11 is suppressed. Further, since the electrode assembly 12 expands in the stacking direction of the positive electrode 15, the negative electrode 17, and the separator 18 during charging, the reaction force of the force that the electrode assembly 12 presses the inner surface of the case 11 due to the expansion of the electrode assembly 12 is Applied to the assembly 12 as a load. When the elastic body 30 exists between the side surface 12 a of the electrode assembly 12 and the inner surface of the case 11, the load applied to the electrode assembly 12 is reduced by the elastic body 30 contracting, and the secondary battery 10. The lifespan of is extended. Therefore, by using the electrode assembly 12 formed in a state in which wrinkles and Li precipitation are suppressed, wrinkles and Li precipitation of the electrode assembly 12 can be suppressed and the life can be extended.

(2) The polymer foam is a foamed polyolefin. The material of the polymer foam is not particularly limited as long as it has corrosion resistance to the electrolytic solution L, but the foamed polyolefin is easily available.
(3) In the secondary battery 10, a thickness adjusting film (spacer) 32 is provided between the other side surface 12 b of the electrode assembly 12 and the inner surface of the case 11. Since the electrode assembly 12 includes a large number of positive electrodes 15, negative electrodes 17, and separators 18 stacked, the length of the electrodes and separators in the stacking direction of the electrode assembly 12 varies with respect to a preset value. Therefore, the electrode assembly 12 is configured such that a gap is generated between the length in the stacking direction of the electrode assembly 12 and the inner surface of the case 11, and an appropriate number of thickness adjusting films 32 are filled in the gap. Then, it is housed in the case 11 together with the elastic body 30. In this case, in the discharged state of the secondary battery 10, even if the electrode assembly 12 contracts, a gap is formed between the inner surface of the case 11 and the electrode assembly 12 is prevented from vibrating with respect to the case 11. Is done.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. Note that this embodiment is different from the first embodiment in that an elastic body is also provided on the outside of the case 11, and the other configurations are the same. Detailed description is omitted.

  As shown in FIG. 3, the case 11 is provided with an outer elastic body 36 on the outer surface of the side wall 11 d facing the side surfaces 12 a and 12 b of the electrode assembly 12. The outer elastic body 36 is formed in a size that covers the entire surface of each side wall 11d. The material of the outer elastic body 36 does not need to have corrosion resistance to the electrolytic solution L, unlike the elastic body 30 that is used in contact with the electrolytic solution L.

  The secondary battery 10 is used in a state of being restrained on the outer surface of the side wall 11 d of the case 11. In that case, if the outer elastic body 36 is provided on the outer surface of the side wall 11 d of the case 11, the secondary battery 10 is restrained via the outer elastic body 36, so that the load applied to the secondary battery 10 is the outer elastic force. Relieved by body 36.

  Regarding the secondary battery 10 using the outer elastic body 36 made of polyurethane and EPDM (ethylene propylene diene rubber), the maximum load and the increase rate of resistance (internal resistance) when charging and discharging are repeated 100 times are investigated. It was. The results are shown in Table 2. FIG. 4 shows the relationship between the load of each material amount and the compression amount. In addition, the material A of Table 2 is BF-500 of the urethane vibration-proof material made from Inoac Corporation, and the material B is also BF-300. The material C is EPDM.

FIG. 4 shows that the load of material C increases greatly in proportion to the amount of compression from the beginning of compression. On the other hand, the material A and the material B have a small increase amount of the load accompanying the compression amount when the compression amount is small, and the rate of increase of the load suddenly increases after being compressed to some extent. When the elastic body 30 having a thickness of 3 mm is used, the load when the compression amount is 0.5 mm is 3.94 kN or more and 10 kN or less, and the load when the compression amount is 1.0 mm is 7.4 kN or more and 60 kN. The following is preferred. Therefore, it can be seen from FIG. 4 that the material C is not suitable as a material for the outer elastic body 36 in terms of the rate of increase in load during compression. On the other hand, the material A and the material B are suitable as materials for the outer elastic body 36 in terms of the rate of increase in load during compression.

  The rate of increase in resistance of the secondary battery 10 is as large as 119.8% for material A and 109.5% for material A and 109.3% for material B. From the point of view, it was found that the material is suitable as a material for the outer elastic body 36.

The embodiment is not limited to the above, and may be embodied as follows, for example.
The position of the thickness adjusting film 32 is not limited to the side opposite to the side where the elastic body 30 is provided across the electrode assembly 12, and may be provided between the electrode assembly 12 and the elastic body 30.

  The elastic body 30 is provided not only between at least one side surface 12 a of the electrode assembly 12 and the inner surface of the case 11 but also between the inner surface of the case 11 and both side surfaces 12 a and 12 b of the electrode assembly 12. May be.

  ○ If the elastic body 30 is provided in contact with 50% or more of the side surface of the electrode assembly 12, due to the reaction force from the inner surface of the case 11 accompanying the expansion of the electrode assembly 12 during charging of the power storage device, It is suppressed that the value of the load applied to the electrode assembly 12 adversely affects the life of the secondary battery 10. For this reason, the elastic body 30 is not limited to a state in which it is in contact with the entire side surfaces 12a, 12b of the electrode assembly 12, but is provided in a state in which it is in contact with at least 50% or more, preferably 80% or more, more preferably 90% or more. May be. However, if the elastic body 30 is in contact with the entire side surface 12 a of the electrode assembly 12, the pressing force with which the inner surface of the case 11 presses the electrode assembly 12 is uniformly dispersed in the electrode assembly 12. It is preferable because it adds.

  The elastic body 30 may be a polyolefin other than polyethylene, for example, a foam of polypropylene. Further, an EPDM foam may be used for the elastic body 30. However, the expansion ratio of the foam needs to be larger than that of polyethylene.

A plurality of elastic bodies 30 may be provided on the same side of the electrode assembly 12.
The present invention is not limited to the stacked electrode assembly 12 and may be applied to the secondary battery 10 having a wound electrode assembly.

  ○ A wound-type electrode assembly is generally provided so that the active material non-applied part of the strip-shaped positive electrode and the active material non-applied part of the strip-shaped negative electrode are located on opposite sides in the winding axis direction of the electrode assembly. It is done. However, as a wound-type electrode assembly, the positive electrode active material non-applied portion and the negative electrode active material non-applied portion are formed on the same side in the winding axis direction of the electrode assembly and formed as a tab. It may be a configured.

  In the stacked electrode assembly 12, the positive electrode tab 15 a and the negative electrode tab 17 a are not limited to a configuration that protrudes from the end surface on the same side of the electrode assembly 12, and may protrude from an end surface on a different side.

  The outer elastic body 36 provided on the outer surface of the side wall 11d of the case 11 does not necessarily need to be provided on both of the two opposing side walls 11d, and may be provided only on the outer side of one of the side walls 11d.

O The elastic body 30 may not be provided in the case 11 as the secondary battery 10, and the outer elastic body 36 may be provided on the outer surface of the side wall 11 d of the case 11 orthogonal to the stacking direction of the electrode assembly 12.
The case 11 that houses the electrode assembly 12 is provided at a position where the opening of the case body corresponds to the thickness direction of the electrode assembly 12 (stacking direction of the positive electrode, the separator, and the negative electrode). The wall from which the terminal 20 and the negative electrode terminal 22) protrude may be a wall other than the lid that covers the opening of the case body 11a.

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.

  L ... Electrolyte, 11 ... Case, 11a ... Case body, 11b ... Cover body, 11d ... Side wall, 12 ... Electrode assembly, 12a, 12b ... Side, 13 ... Metal foil, 15 ... Positive electrode, 17 ... Negative electrode, 18 ... Separator, 30 ... elastic body, 36 ... outer elastic body.

Claims (4)

An electrode assembly in which a positive electrode and a negative electrode each having an active material layer formed on a metal foil are stacked with a separator interposed therebetween covers a bottomed box-shaped case body and an opening of the case body A power storage device housed together with an electrolyte in a case having a lid,
An elastic body is provided between at least one side surface of the electrode assembly and the inner surface of the case so as to be in contact with 50% or more of the side surface, and the elastic body is corrosion resistant to the electrolytic solution. It is formed with the polymer foam which has this.   The power storage device according to claim 1, wherein the elastic body is formed so as to be able to contact the entire surface of the side surface of the electrode assembly.   The power storage device according to claim 1, wherein the polymer foam is foamed EPDM or foamed polyolefin.   The power storage device according to any one of claims 1 to 3, wherein the case is provided with an outer elastic body on an outer surface of a side wall facing at least one of the side surfaces of the electrode assembly.