JP2015210877A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of suppressing deformation of a lid even when an internal pressure of a case increases.SOLUTION: A lid 14 of a secondary battery 10 has a thick part 40 at a position including at least a central part in at least one direction of a longer-side direction and a shorter-side direction and at a site apart from junctions 14d between a case body 13 and the lid 14. In a region R2 between terminals, the thick part 40 has the thickest thickness, and the thickness gradually decreases toward each junction 14d from the thick part 40 by a tapered part T.

Description

  The present invention relates to a power storage device having a case body, a lid, a case, an electrode assembly, and an electrode terminal.

  Conventionally, lithium ion secondary batteries, nickel-hydrogen secondary batteries, and the like are well known as power storage devices mounted on vehicles such as EVs (Electric Vehicles) and PHVs (Plug-in Hybrid Vehicles). As a secondary battery, there is a battery configured by housing an electrode assembly in a case. The case includes a case main body and a lid joined to the opening edge of the case main body. In addition, the electrode assembly is electrically connected to the electrode assembly housed in the case, and the electrode terminal protrudes from the inside of the case body to the outside through the pole column portion of the electrode assembly. (For example, refer to Patent Document 1).

JP 2013-246878 A

  However, when the secondary battery is overcharged, the internal pressure of the case may increase. In this case, the pressure in the case acts on the lid of the case. The lid body is likely to be deformed as it is separated from the joint portion to the case main body along the surface thereof, and the lid body may be deformed by receiving pressure in the case.

  The present invention has been made paying attention to such problems existing in the prior art, and an object thereof is to provide a power storage device capable of suppressing deformation of the lid.

  A power storage device for solving the above problems includes a case main body having an opening, and a pair of insertion holes that are joined to an opening edge of the case main body to close the opening and through which electrode terminals are inserted. A lid, a case in which the case main body and the lid are integrated, and a pair of electrode terminals disposed in the case and projecting from the inside of the case through the insertion hole. In the power storage device, when the direction connecting the pair of insertion holes in the lid body is the first direction of the lid body, along the surface of the lid body, and the orthogonal direction of the first direction is the second direction, The lid body has a thick portion at a position including at least a central portion of at least one of the first direction and the second direction, and at a portion away from the joint portion to the case body, and the joint The part closer to the thick part than the part, Than the wall section and the spirit that is thinner thickness.

  According to this, when the internal pressure of the case rises and the internal pressure acts on the lid, the case is separated from the joint portion at a position including at least the central portion of at least one of the first direction and the second direction. The lid becomes easier to be deformed as the area is longer. At this time, the thickness is increased from the joint portion toward the thick portion along at least one of the first direction and the second direction. That is, the lid body is thickened at a portion that is easily deformed in the lid, and the lid body is not thickened at a portion that is close to the joint and hardly deforms. Therefore, it can suppress that a cover body deform | transforms under the pressure in a case.

In the power storage device, the thick portion has a flat outer surface and an inner surface and a constant thickness.
According to this, even if it is a cover body which is hard to deform | transform even if it receives the internal pressure of a case, the manufacture becomes easy.

In the power storage device, it is preferable that the lid body has a pressure release valve for releasing the pressure in the case to the outside of the case, and the pressure release valve is disposed in the thick portion.
According to this, by providing the pressure relief valve in the flat-walled thick part, it is possible to suppress the variation in the thickness of the pressure relief valve along the direction along the surface of the thick part. For this reason, in the pressure release valve that is cleaved by receiving the pressure in the case, it can be cleaved at the same operating pressure at any position along the surface of the thick portion.

  In the power storage device, the lid includes a liquid injection hole for injecting an electrolyte into the case and a sealing member for sealing the liquid injection hole, and the liquid injection hole is disposed in the thick portion. It is preferable.

  According to this, by providing the liquid injection hole in the flat-walled thick wall portion, deformation of the thick wall portion is suppressed even when subjected to the pressure in the case, so that the hole diameter of the liquid injection hole may be displaced. It is suppressed. Therefore, the state in which the liquid injection hole is sealed by the sealing member can be maintained.

  In the power storage device, the lid body is rectangular in plan view, the longitudinal direction of the lid body is the first direction, and the short side direction of the lid body is the second direction, and the lid body Has the thick part in a part away from the joint part at both ends in the second direction.

According to this, a deformation | transformation of a cover body can be suppressed in a 2nd direction (short direction).
Moreover, about an electrical storage apparatus, the said thick part may be formed by bulging toward the outer side of the said case, and the inner surface of a cover body may be flat surface shape.

According to this, in the case, the lid body does not swell toward the case main body, and the volume in the case does not decrease for suppressing deformation of the lid body.
Moreover, about an electrical storage apparatus, the said cover body may have the taper part which spreads toward the said junction part from the said thick part in the cross-sectional shape along the thickness direction.

  According to this, the thickness of the lid can be gradually increased by the taper portion from the joint portion toward the thick portion. Therefore, for example, as compared with the case where the lid is formed in a stepped shape from the joint portion toward the thick portion to increase the thickness, it is easy to manufacture a lid that is not easily deformed even under the internal pressure of the case. Become.

  The power storage device is a secondary battery.

  According to the present invention, deformation of the lid can be suppressed.

The perspective view which shows the secondary battery of embodiment. Sectional drawing along the longitudinal direction which shows a cover body and a pressure release valve. Sectional drawing along the transversal direction which shows a cover body and a pressure release valve. Sectional drawing along the longitudinal direction which shows a cover body, a liquid injection hole, and a sealing member. Sectional drawing along the transversal direction which shows a cover body, a liquid injection hole, and a sealing member. Sectional drawing along the longitudinal direction which shows the cover body of another example. Sectional drawing along the transversal direction which shows the cover body of another example. Sectional drawing along the longitudinal direction which shows the cover body of another example. Sectional drawing along the longitudinal direction which shows the cover body of another example.

Hereinafter, an embodiment in which the power storage device is embodied as a secondary battery will be described with reference to FIGS.
As shown in FIG. 1, a secondary battery 10 as a power storage device has a case 11, and an electrode assembly 12 is accommodated in the case 11. The case 11 also contains an electrolyte solution together with the electrode assembly 12. The case 11 includes a bottomed cylindrical case main body 13 and a rectangular flat plate-like cover body 14 that closes an opening 13 a into which the electrode assembly 12 is inserted into the case main body 13. Both the case main body 13 and the lid body 14 are made of metal (for example, stainless steel or aluminum). In addition, the secondary battery 10 of this embodiment is a rectangular battery whose appearance is a rectangular shape because the case body 13 has a bottomed rectangular tube shape and the lid body 14 has a rectangular flat plate shape. Moreover, the secondary battery 10 of this embodiment is a lithium ion battery.

  The electrode assembly 12 has a structure in which a sheet-like positive electrode and a negative electrode are stacked with a separator interposed therebetween. The positive electrode and the negative electrode have active material layers on both sides of the metal foil. The metal foil of the positive electrode is, for example, an aluminum foil, and the positive electrode has a positive electrode active material layer on both sides of the aluminum foil. Moreover, the metal foil of a negative electrode is copper foil, for example, and a negative electrode has a negative electrode active material layer on both surfaces of copper foil. The positive electrode is electrically connected to the conductive member and is electrically connected to the positive electrode terminal 15 via the conductive member. The negative electrode is electrically connected to the conductive member and is electrically connected to the negative electrode terminal 16 via the conductive member.

  For example, as shown in FIG. 2, the positive electrode is electrically connected to the positive electrode terminal 15 via a conductive member 15a. Although not shown, the negative electrode is electrically connected to the negative electrode terminal 16 via a negative conductive member.

  As shown in FIG. 1, the lid body 14 has a rectangular shape in plan view. The lid body 14 has four outer edge portions joined to the opening edge 13b of the case main body 13, and the lid body 14 has a joint portion 14d to the opening edge 13b of the case main body 13 at the outer edge portion along the four sides.

  As shown in FIG. 2, the lid body 14 has insertion holes 14c on both sides in the longitudinal direction. In the present embodiment, the direction connecting the pair of insertion holes 14c, that is, the longitudinal direction is the first direction of the lid body 14, the short side direction of the lid body 14 is along the surface of the lid body 14 and the first direction. The second direction, which is the orthogonal direction of In the lid body 14, when the direction connecting the outer surface 14 a and the inner surface 14 b with the shortest distance is the thickness direction of the lid body 14, the insertion hole 14 c penetrates the lid body 14 in the thickness direction. The lid body 14 has both sides in the longitudinal direction and has a terminal attachment region R1 at a site surrounding each insertion hole 14c. The terminal attachment region R1 is a region having a rectangular shape in plan view, and is a portion having a constant thickness along the longitudinal direction and the short direction of the lid body 14.

Next, the structure of the positive electrode terminal 15 will be described. The structure of the negative electrode terminal 16 is the same as that of the positive electrode terminal 15.
The electrode terminal 15 includes a square plate-shaped base portion 19 and a cylindrical pole column portion 20 erected from the base portion 19. The pole column portion 20 has a screw portion 21 at a part of the outer periphery. In the electrode terminal 15, the base portion 19 is joined to the conductive member 15 a, and the screw portion 21 of the pole column portion 20 is exposed to the outside of the case 11 through the insertion hole 14 c of the lid body 14. The cross-sectional area of the base 19 along the direction orthogonal to the axial direction of the electrode terminal 15 is larger than the opening area of the insertion hole 14c. As a result, the base 19 located inside the case 11 cannot be pulled out of the case 11 through the insertion hole 14 c of the lid 14.

  A resin insulating member 25 is interposed between the inner periphery of the insertion hole 14 c and the outer periphery of the pole column portion 20. The insulating member 25 includes an annular cylindrical portion 26 and a flange portion 27 that extends radially outward from one axial end of the cylindrical portion 26. The cylindrical portion 26 is interposed between the inner periphery of the insertion hole 14 c and the outer periphery of the polar column portion 20. The flange portion 27 is locked around the insertion hole 14 c on the outer surface 14 a of the lid body 14. The insulating member 25 insulates the inner periphery of the insertion hole 14 c from the outer periphery of the pole column portion 20. In addition, an annular seal member 28 that surrounds the pole column 20 is provided on the surface of the base 19 that faces the inner surface 14 b of the lid 14. The seal member 28 is located between the inner surface 14 b of the lid body 14 and the surface of the base portion 19 inside the case 11. The seal member 28 is, for example, an O-ring.

  A nut 29 is screwed into the threaded portion 21 of the polar column portion 20. A flange portion 27 of the insulating member 25 is sandwiched between the outer surface 14 a of the lid body 14 and the nut 29, and the lid body 14 and the nut 29 are insulated by the flange portion 27. When the nut 29 is screwed into the pole portion 20, the flange portion 27, the lid body 14, and the seal member 28 are sandwiched between the nut 29 and the base portion 19, and the electrode terminal 15 is secured to the lid body 14 ( Fastened to case 11). In this fastened state, the seal member 28 is in close contact with the inner surface 14b and the base 19 of the lid body 14 in a compressed state, and seals the periphery of the insertion hole 14c.

  As shown in FIG. 1, the lid body 14 has an inter-terminal region R2 in a region sandwiched between two insertion holes 14c (electrode terminals 15 and 16) along the longitudinal direction. This inter-terminal region R2 is also a region sandwiched between two terminal attachment regions R1 in the longitudinal direction of the lid body 14.

  The inter-terminal region R2 is a rectangular region in plan view. The inter-terminal region R <b> 2 has a thick portion 40, and the thick portion 40 is formed by the lid body 14 bulging toward the outside of the case 11. The thick wall portion 40 is located at a position equidistant from the joint portions 14d located at both ends of the lid body 14 in the longitudinal direction and at a position away from the joint portions 14d located at both ends of the lid body 14 in the short direction. The thick portion 40 is provided at a position including the central portion of the longitudinal direction (first direction) and the short direction (second direction) of the lid body 14.

  As shown in FIGS. 2 and 3, the thick portion 40 has a constant thickness along the longitudinal direction and the short direction of the lid body 14, and the outer surface 14 a and the inner surface of the lid body 14 in the thick portion 40. 14b is a flat surface shape. And the thick part 40 is a thickest part in the cover body 14, and is a thick part from the terminal attachment area | region R1 and the junction part 14d.

  The inter-terminal region R <b> 2 has a square annular taper portion T that surrounds the thick portion 40. The taper portion T spreads and inclines from the thick portion 40 toward the joint portions 14d located at both ends in the longitudinal direction, and spreads and slopes from the thick portion 40 toward the joint portions 14d located at both ends in the short direction. . The inclined surface at the taper portion T located on the outer surface 14 a of the lid body 14 is linear in cross section along the longitudinal direction and the lateral direction of the lid body 14. In the inter-terminal region R2, the thick portion 40 is the thickest, and the thickness is reduced by the tapered portion T from the thick portion 40 toward each joint portion 14d.

  Therefore, in the lid body 14, the thickness is gradually increased by the taper portion T as it goes from the terminal attachment region R <b> 1 to the thick portion 40 along the longitudinal direction thereof, and is thickest at the central portion in the longitudinal direction. Further, in the lid body 14, the thickness is gradually increased by the taper portion T toward the thick portion 40 from each joint portion 14 d along the short direction, and the thickness is greatest at the center portion in the short direction. . Accordingly, in the inter-terminal region R2, the thickness increases as the distance from the joint portion 14d increases in either the longitudinal direction or the lateral direction.

  The lid 14 has a pressure release valve 30, and the pressure release valve 30 is disposed in the thick portion 40. The pressure release valve 30 is opened when the pressure in the case 11 reaches an open pressure that is a predetermined pressure so that the pressure in the case 11 does not increase excessively, and the inside and outside of the case 11 are communicated. The pressure release valve 30 is disposed in the thick portion 40 so as to be located in the center portion in the longitudinal direction and the short direction of the lid body 14. The pressure release valve 30 has a thin plate-like valve body 30 a that is thinner than the thickness of the thick portion 40. The valve body 30 a is located at the bottom of the recess 32 provided in the outer surface 14 a and the inner surface 14 b of the thick portion 40, and is formed integrally with the thick portion 40. Further, the valve body 30a is formed by pressing the thick portion 40.

  As shown in FIGS. 4 and 5, the lid body 14 has a liquid injection hole 18 for injecting an electrolytic solution into the case 11 (case body 13), and the liquid injection hole 18 is disposed in the thick portion 40. Has been. The liquid injection hole 18 is disposed closer to one joint portion 14d in the longitudinal direction than the central portion in the longitudinal direction of the lid body 14. In addition, the liquid injection hole 18 is disposed closer to one joint portion 14d in the short direction than the central portion in the short direction of the lid body 14. The liquid injection hole 18 penetrates the thick part 40 in the thickness direction. The liquid injection hole 18 is sealed with a sealing member 31. The sealing member 31 includes a shaft portion 31a that is press-fitted into the liquid injection hole 18, and a head portion 31b that is provided at one end of the shaft portion 31a in the axial direction and has a larger diameter than the shaft portion 31a. The sealing member 31 is fixed in a state where the shaft portion 31 a is press-fitted into the liquid injection hole 18 and the head portion 31 b is in close contact with the outer surface 14 a of the thick portion 40.

Next, the operation of the secondary battery 10 will be described.
In the secondary battery 10, when the pressure in the case 11 increases due to overcharging of the electrode assembly 12, the internal pressure acts on the inner surface 14 b of the lid body 14. At this time, the lid body 14 is more easily deformed as it is separated from the joint portion 14d along the longitudinal direction and the short direction, but the taper portion T and the thickness are increased as the distance from the joint portion 14d is separated along the longitudinal direction and the transverse direction. Since the thickness is increased by the meat portion 40, the deformation of the lid body 14 is suppressed.

According to the above embodiment, the following effects can be obtained.
(1) The lid body 14 has an inter-terminal region R2 inside the joint portion 14d. The inter-terminal region R2 is joined along the longitudinal direction and the short direction by the taper portion T and the thick portion 40. The further away from 14d, the thicker the thickness. For this reason, even if the pressure in the raised case 11 acts on the cover body 14, it can suppress that the cover body 14 deform | transforms in any of a longitudinal direction and a transversal direction.

  (2) The lid body 14 has an inter-terminal region R2 at a portion sandwiched between the terminal attachment regions R1 in the longitudinal direction, and has a thick portion 40 in the inter-terminal region R2. Since the terminal attachment region R1 is a region that is close to the joint portion 14d in the longitudinal direction of the lid body 14 and is not easily deformed, the terminal attachment region R1 has a flat surface. Therefore, in order to attach the electrode terminals 15 and 16 to the terminal attachment region R1, the insulating member 25 and the nut 29 are attached, and the seal member 28 is provided to seal the insertion hole 14c. However, the flange portion 27 of the insulating member 25 is covered. The insertion hole 14c can be sealed by bringing the sealing member 28 into close contact with the inner surface 14b of the lid body 14 in close contact with the outer surface 14a of the body 14. Moreover, the material cost of the cover body 14 can be suppressed by making the thickness of the terminal attachment region R1 constant without increasing it.

  (3) Although the lid body 14 is easily deformed at the central portion in the longitudinal direction and the short side direction, the thickest thick portion 40 is located at the central portion in the longitudinal direction and the lateral direction of the lid body 14. The deformation of the lid body 14 can be suitably suppressed.

  (4) The thick portion 40 is a flat surface having a certain thickness, and the pressure release valve 30 is disposed in the thick portion 40. For this reason, the thickness of the valve body 30a of the pressure release valve 30 can be made constant. Therefore, the valve body 30a can be cleaved at the same operating pressure at any position of the valve body 30a.

  (5) The thick portion 40 is a flat surface having a certain thickness, and the liquid injection hole 18 is disposed in the thick portion 40. And even if it receives the pressure in case 11, since a deformation | transformation of the thick part 40 is suppressed, it is suppressed that the hole diameter of the injection hole 18 displaces. Therefore, the state where the sealing member 31 is press-fitted into the liquid injection hole 18 can be maintained, and the state where the liquid injection hole 18 is sealed with the sealing member 31 can be maintained.

  Further, in the head portion 31b of the sealing member 31, the surface facing the lid body 14 is in close contact with the flat outer surface 14a. For this reason, the liquid injection hole 18 can be sealed from the periphery by the head portion 31 b of the sealing member 31.

  (6) For example, in the lid body 14 in which the taper portion T and the thick portion 40 are not formed, when the lid body 14 is deformed in the short direction, the lid body 14 is disposed closer to the one joint portion 14d in the short direction. In the liquid injection hole 18, the hole diameter is more likely to be displaced toward the center portion in the short direction, and the sealing performance of the liquid injection hole 18 is likely to be deteriorated. However, in the present embodiment, the lid body 14 increases in thickness from each joint portion 14d toward the thick portion 40 along the short side direction, and deformation of the lid body 14 along the short side direction is suppressed. Therefore, even if the liquid injection hole 18 is disposed near the one joint portion 14d in the short direction, the displacement of the hole diameter of the liquid injection hole 18 is suppressed. As a result, the state where the inner peripheral surface of the liquid injection hole 18 and the outer peripheral surface of the shaft portion 31a of the sealing member 31 are kept in close contact with each other, and the state where the liquid injection hole 18 is sealed with the sealing member 31 is maintained. be able to.

  (7) In the lid 14, the tapered portion T and the thick portion 40 are formed so as to bulge outward from the case 11, and the inner surface 14 b of the lid 14 is flat. For this reason, even if the thickness of the lid 14 is increased, the volume in the case 11 is not reduced, and the electrode assembly 12 that can be accommodated in the case 11 is not reduced. Therefore, even if it has the structure which suppresses a deformation | transformation of the cover body 14, the energy density of the secondary battery 10 does not become small.

  (8) The inter-terminal region R <b> 2 has a tapered portion T that surrounds the thick portion 40. Therefore, for example, in the inter-terminal region R2, the inter-terminal region R2 is simplified compared to the case where the portion surrounding the thick portion 40 is stepped from the joint portion 14d toward the thick portion 40 to increase the thickness. Can be formed.

  (9) The inter-terminal region R2 has a tapered portion T surrounding the thick portion 40. For this reason, for example, in the inter-terminal region R2, the portion surrounding the thick portion 40 is stepped from the joining portion 14d toward the thick portion 40 to increase the thickness. There are no corners where stress is concentrated. Therefore, deformation of the lid 14 around the thick portion 40 can be suppressed.

  (10) The inter-terminal region R <b> 2 is thick along the longitudinal direction and the short direction of the lid body 14. For this reason, when the pressure in the raised case 11 acts on the cover body 14, the deformation | transformation in both the longitudinal direction and the transversal direction of the cover body 14 can be suppressed.

In addition, you may change the said embodiment as follows.
As shown in FIG. 6, in the longitudinal direction of the lid body 14, the inner surface 14 b of the lid body 14 swells toward the inside of the case 11 to form a thick portion 40, and as shown in FIG. The thick portion 40 may be formed in a state where the inner surface 14b of the lid 14 swells toward the inside of the case 11 in the short direction of the lid 14. If comprised in this way, the outer surface 14a of the cover body 14 will become flat surface shape. In the inter-terminal region R2, the portion surrounding the thick portion 40 may be the tapered portion T, or may be other than that.

  As shown in FIG. 8, the lid body 14 may gradually increase in thickness from the joint portion 14d to the center in the longitudinal direction and the lateral direction, including the terminal attachment region R1. In this case, for the purpose of clamping the flange portion 27 and the lid body 14 by the nut 29 and the base portion 19 around the insertion hole 14c, the portion corresponding to the flange portion 27 is preferably a flat surface.

As shown in FIG. 9, the lid body 14 may be thickened stepwise from the terminal attachment region R1 toward the thick portion 40 in the longitudinal direction and the short direction.
In the lid body 14, the joint portion 14d may be thicker than the terminal attachment region R1. In this case, the thickness is increased by the taper portion T from the terminal attachment region R1, which is a portion separated from the joint portion 14d along at least one of the longitudinal direction and the short-side direction, toward the thick portion 40. Increase the thickness to the maximum.

  In the embodiment, the liquid injection hole 18 is disposed near the one joint portion 14d in the short direction of the lid body 14, but the position of the liquid injection hole 18 is not limited to this, and may be a central part in the short direction. The position of the liquid injection hole 18 may be changed as appropriate.

  The electrode terminals 15 and 16 are not limited to the structure fastened to the lid body 14 by the nut 29. For example, the electrode terminals 15 and 16 may be fixed to the lid body 14 by caulking or the like.

The lid 14 may be thick only in the longitudinal direction and may be constant in the short direction.
The lid 14 may be thick only in the short direction and may be constant in the long direction.

  The cross-section in the thickness direction along the longitudinal direction of the lid body 14 is triangular, and the thick portion 40 may be a portion that becomes the apex of the triangle, and the thick portion 40 may not be flat. . In addition, the lid body 14 has a triangular cross section in the thickness direction along the short direction, and the thick portion 40 may be a vertex of the triangle, and the thick portion 40 is not flat. Also good.

  In the embodiment, the lid body 14 has a rectangular shape in plan view, but the lid body 14 may have a square shape in plan view. In this case, in the lid body 14, the length along the first direction is the same as the length along the second direction.

Alternatively, the lid body 14 may have a polygonal shape in plan view. In this case, the first direction and the second direction are appropriately set.
○ At least one of the liquid injection hole 18 and the pressure release valve 30 may be disposed not in the thick portion 40 but in the tapered portion T or the terminal mounting region R1.

The positive electrode and the negative electrode may have a structure having an active material layer on one side of a metal foil.
The secondary battery 10 may be a lithium ion secondary battery or another secondary battery. In short, any ion may be used as long as ions move between the active material for the positive electrode and the active material for the negative electrode and charge is transferred. Further, a capacitor may be used as the power storage device.

The electrode assembly 12 is not limited to the laminated type, and may be a wound type in which a belt-like positive electrode and a belt-like negative electrode are wound and laminated in layers.
Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.

  (A) The liquid injection hole is a power storage device that is disposed closer to one joint than the center in the short direction.

  T ... taper portion, 10 ... secondary battery as power storage device, 11 ... case, 13 ... case main body, 13a ... opening, 13b ... opening edge, 14 ... lid, 14a ... outer surface, 14b ... inner surface, 14c ... insertion Holes, 14d: joints, 15, 16 ... electrode terminals, 18 ... liquid injection holes, 20 ... polar column parts, 30 ... pressure release valve, 31 ... sealing member, 40 ... thick part.

Claims (8)

A case body having an opening;
A lid having a pair of insertion holes that are joined to the opening edge of the case body to close the opening and through which the electrode terminals are inserted;
A case in which the case body and the lid are integrated;
In the power storage device having a pair of electrode terminals disposed in the case and projecting from the inside of the case through the insertion hole,
When the direction connecting the pair of insertion holes in the lid is the first direction of the lid, along the surface of the lid, and the orthogonal direction of the first direction is the second direction,
The lid body has a thick portion at a position including at least a central portion of at least one of the first direction and the second direction, and at a portion away from the joint portion to the case body, and the joint A power storage device in which the portion closer to the thicker portion than the thicker portion is thinner than the thicker portion.   The power storage device according to claim 1, wherein the thick portion has a flat outer surface and an inner surface and a constant thickness.   The power storage device according to claim 2, wherein the lid includes a pressure release valve that releases the pressure in the case to the outside of the case, and the pressure release valve is disposed in the thick portion.   The said cover body has the injection member which inject | pours electrolyte solution in the said case, and the sealing member which seals this injection hole, The said injection hole is arrange | positioned at the said thick part. Alternatively, the power storage device according to claim 3.   The lid body has a rectangular shape in plan view, the longitudinal direction of the lid body is the first direction, the short side direction of the lid body is the second direction, and the lid body has the second direction. The electrical storage apparatus as described in any one of Claims 2-4 which has the said thick part in the site | part away from the junction part of the both ends in a direction.   The power storage device according to any one of claims 1 to 5, wherein the thick portion is formed by bulging outward from the case, and an inner surface of the lid is flat.   The power storage device according to any one of claims 1 to 6, wherein the lid has a tapered portion that extends in a cross-sectional shape along a thickness direction from the thick portion toward the joint portion.   The power storage device according to any one of claims 1 to 7, wherein the power storage device is a secondary battery.