Energy storage devices

Abstract

To reduce the stress generated in the case. [Solution] The energy storage device 1 disclosed herein comprises a case 100 and an electrode body housed in the case 100. The case 100 comprises a first wall 110 having an outer edge including a first side 111 and a second side 112 facing the first side 111, and a second wall facing the first wall 110. The electrode body has a laminated portion stacked along the opposing direction of the first wall 110 and the second wall, with the positive electrode and the negative electrode insulated from each other. The first wall 110 has a base portion 115 and a recessed portion 116 protruding from the base portion 115 toward the electrode body. The recessed portion 116 comprises an inclined portion 116a that slopes toward the electrode body from the base portion 115 and a bottom portion 116b that is closer to the electrode body than the base portion 115. The base portion 115 has a recess 115a between the recessed portion 116 and the first side 111, which is recessed toward the inside or outside of the case 100.

Description

Technical Field

[0001] This disclosure relates to a power storage device.

Background Art

[0002] JP-A-11-31523, JP-A-2000-67821, and JP-A-2024-116777 each disclose a case having a side surface recessed toward the electrode body side inside the case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the electrode body expands upon charging. As a result, a force is generated that pushes the wall portion constituting the case from the inside toward the outside. When the wall portion is pushed, stress concentrates at the end portion of the wall portion (for example, the corner portion of the case). When stress concentrates, it can cause damage to the case. Therefore, a technique for reducing the stress generated at the end portion of the wall portion is desired.

Means for Solving the Problems

[0005] One aspect of the technology disclosed herein is an energy storage device comprising a case and an electrode body housed in the case. The case comprises a first wall having an outer edge including a first side and a second side facing the first side, and a second wall facing the first wall. The electrode body has a laminated portion stacked along the opposing direction between the first wall and the second wall, with the positive electrode and the negative electrode insulated from each other. The first wall has a base portion and a recessed portion projecting from the base portion toward the electrode body. The recessed portion comprises an inclined portion sloping toward the electrode body from the base portion and a bottom portion closer to the electrode body than the base portion. The base portion has a recess between the recessed portion and the first side that is recessed toward the inside or outside of the case.

[0006] In the above energy storage device, the stress generated at the end of the first wall constituting the case is reduced. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic perspective view showing the configuration of the energy storage device 1. [Figure 2] Figure 2 is a schematic diagram showing the internal structure of the energy storage device 1. [Figure 3] Figure 3 is a schematic cross-sectional view along the line III-III in Figure 1. [Figure 4] Figure 4 is a schematic diagram of Case 100 in disassembled form. [Figure 5] Figure 5 is a schematic diagram of the electrode body 20 in an exploded state. [Figure 6] Figure 6 is a schematic perspective view showing the configuration of a modified energy storage device 1A. [Figure 7] Figure 7 is a schematic cross-sectional view along the line VII-VII in Figure 6. [Modes for carrying out the invention]

[0008] Hereinafter, several embodiments of the technology disclosed herein will be described in detail with reference to the drawings. Matters other than those specifically mentioned herein but necessary for implementation (e.g., general configuration and manufacturing processes of energy storage devices not characterizing this disclosure) can be understood as design matters for those skilled in the art based on the prior art. This disclosure can be implemented based on the content disclosed herein and common technical knowledge in the art.

[0009] In this specification, "energy storage device" is a concept that encompasses devices in which a charge-discharge reaction occurs through the movement of a charge carrier between a pair of electrodes (positive electrode and negative electrode). In other words, energy storage devices include batteries such as secondary batteries (e.g., lithium-ion secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries) and capacitors (physical batteries) such as lithium-ion capacitors and electric double-layer capacitors.

[0010] In this specification, "approximately rectangular" includes shapes other than a perfect rectangle. For example, it includes shapes where the corners connecting the long and short sides of a rectangle are rounded, shapes with notches, etc.

[0011] <Energy storage devices> The following describes an energy storage device 1 according to one embodiment. Figure 1 is a schematic perspective view showing the configuration of the energy storage device 1. Figure 2 is a schematic diagram showing the internal structure of the energy storage device 1. Figure 3 is a schematic cross-sectional view along line III-III in Figure 1. Figure 4 is a schematic diagram of the case 100 in an exploded view. The symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, back, top, and bottom. The symbols X, Y, and Z in the drawings represent the short side direction, the long side direction perpendicular to the short side direction, and the up and down direction of the energy storage device 1, respectively. However, these are merely directions for the convenience of explanation and do not limit the installation configuration of the energy storage device 1. Note that each drawing is schematic, and the dimensional relationships (length, width, thickness, etc.) do not necessarily reflect the actual dimensional relationships. In addition, in the drawings described below, the same symbols are used for members and parts that perform the same function, and redundant explanations may be omitted or simplified.

[0012] As shown in Figures 1 to 3, the energy storage device 1 comprises a case 100 and an electrode body 20. The electrode body 20 is housed in the case 100. The energy storage device 1 further comprises a positive electrode terminal 30 and a negative electrode terminal 40. The energy storage device 1 is a lithium-ion secondary battery. The energy storage device 1 is a so-called sealed battery. In this embodiment, the energy storage device 1 further comprises a non-aqueous electrolyte (not shown).

[0013] (1) Case 100 As shown in Figures 1-4, the case 100 has a roughly rectangular prism shape. The case 100 comprises a first wall 110, a second wall 120, a first side wall 130, a second side wall 140, a third side wall 150, and a fourth side wall 160.

[0014] The first wall 110 and the second wall 120 form a pair of wide surfaces of the case 100. The first wall 110 and the second wall 120 have outer surfaces with a larger area than the other surfaces of the case 100. The first wall 110 and the second wall 120 face each other in the short-side direction Y. The first wall 110 is plate-shaped in this case. When viewed from side F to side Rr in the short-side direction Y in the figure, the first wall 110 has a substantially rectangular outer edge. The first wall 110 has an outer edge that includes a first side 111 and a second side 112 that faces the first side 111. The outer edge of the first wall 110 includes a pair of long sides and a pair of short sides. In this embodiment, the first wall 110 has a pair of long sides, which are the first side 111 and the second side 112, and a pair of short sides, which are the third side 113 and the fourth side 114.

[0015] The second wall 120 faces the first wall 110. The second wall 120 is plate-shaped in this respect. When viewed from the Rr side toward the F side in the short-side direction Y in the figure, the second wall 120 has a substantially rectangular outer edge. The outer edge of the second wall 120 includes a pair of long sides and a pair of short sides.

[0016] The first side wall 130 and the second side wall 140 face each other and form a pair of side walls. Here, the first side wall 130 and the second side wall 140 are plate-shaped. When viewed from the vertical direction Z in the figure, the first side wall 130 and the second side wall 140 have a substantially rectangular outer edge. The first side wall 130 extends from the first side 111, which is the long side of the first wall 110, to the long side of the second wall 120. The second side wall 140 extends from the second side 112, which is the long side of the first wall 110, to the long side of the second wall 120.

[0017] The third side wall 150 and the fourth side wall 160 face each other and form a pair of side walls. Here, the third side wall 150 and the fourth side wall 160 are plate-shaped. When viewed from the long side direction X in the figure, the third side wall 150 and the fourth side wall 160 have a substantially rectangular outer edge. The third side wall 150 extends from the third side 113, which is the short side of the first wall 110, to the short side of the second wall 120. The fourth side wall 160 extends from the fourth side 114, which is the short side of the first wall 110, to the short side of the second wall 120.

[0018] As shown in FIG. 4, in the present embodiment, the case 100 includes a case body 170 having an opening 170h and a sealing body 180 attached to the opening 170h. In the case 100, the case body 170 has the second wall 120, the first side wall 130, the second side wall 140, the third side wall 150, and the fourth side wall 160. The sealing body 180 is the main member constituting the first wall 110. In the present embodiment, the case body 170 and the sealing body 180 are each formed of aluminum or an aluminum alloy mainly containing aluminum.

[0019] The case body 170 has a substantially rectangular parallelepiped angular shape with an opening 170h on one side surface. The case body 170 has a second wall 120 as a bottom wall. From a pair of long sides of the second wall 120, a first side wall 130 and a second side wall 140 respectively rise up. From a pair of long sides of the second wall 120, a third side wall 150 and a fourth side wall 160 respectively rise up. The opening 170h is formed surrounded by the first side wall 130, the second side wall 140, the third side wall 150, and the fourth side wall 160. In the present embodiment, as shown in FIG. 4, a step 170s recessed along the inner edge is provided in the opening 170h.

[0020] The case 100 has a safety valve 132. Here, the safety valve 132 is provided on the first side wall 130. The safety valve 132 is configured to break when the pressure inside the case 100 reaches a predetermined value or more and discharge the gas inside the case 100 to the outside. Here, the safety valve 132 is formed to be the thinnest among the first side walls 130. Note that the safety valve 132 may be provided on a wall other than the first side wall 130 of the case 100.

[0021] The case 100 has a first through hole 152 and a second through hole 162 that communicate the inside and the outside of the case 100. The first through hole 152 is provided on the third side wall 150. A positive electrode terminal 30 is attached to the first through hole 152. The second through hole 162 is provided on the fourth side wall 160. A negative electrode terminal 40 is attached to the second through hole 162. Note that the positions of the first through hole 152 and the second through hole 162 are not particularly limited. For example, the first through hole 152 and the second through hole 162 may be provided on the same wall.

[0022] The sealing body 180 seals the opening 170h of the case body 170. The sealing body 180 is fitted into the step 170s of the case body 170. The boundary between the outer edge of the sealing body 180 and the inner surface of the case body 170 is laser welded. In this embodiment, the first wall 110 is composed of the outer surface of the sealing body 180 and the end faces of each side wall of the case body 170 that are in contact with the outer edge of the sealing body 180. In this embodiment, the first side 111 of the first wall 110 is the long side of the first side wall 130 on the opening 170h side. The second side 112 of the first wall 110 is the long side of the second side wall 140 on the opening 170h side. The third side 113 of the first wall 110 is the long side of the third side wall 150 on the opening 170h side. The first side 111 of the first wall 110 is the longer side of the first side wall 130 on the opening 170h side.

[0023] The first wall 110 (here referred to as the sealing body 180) has a base portion 115 and a recessed portion 116. The base portion 115 has a recess 115a.

[0024] As shown in Figure 1, the base portion 115 is the part between the outer edge of the first wall 110 and the recessed portion 116. The base portion 115 is, for example, plate-shaped. There is a space between the base portion 115 and the electrode body 20, and the inner surface of the base portion 115 is configured not to come into contact with the electrode body 20.

[0025] The recessed portion 116 is a part that protrudes from the base portion 115 toward the inside of the case 100. That is, the recessed portion 116 is a part that protrudes from the base portion 115 toward the electrode body 20. The recessed portion 116 has an inclined portion 116a and a bottom portion 116b. The bottom portion 116b is closer to the electrode body 20 than the base portion 115.

[0026] The bottom 116b of the recessed portion 116 is the portion that is pressed against by the electrode body 20 when the electrode body 20 expands. The bottom 116b faces the electrode body 20. More specifically, the bottom 116b faces the stacked portion 28 of the electrode body 20, which will be described later. Here, the bottom 116b is in direct contact with the electrode body 20. The bottom 116b is formed in a continuous manner with the inclined portion 116a. The bottom 116b is surrounded by the inclined portion 116a. When viewed from the F side towards the Rr side in the short side direction Y in Figure 1, the bottom 116b is approximately rectangular in shape with R-shaped (curved) corners 116c. Here, the bottom 116b has a pair of long sides parallel to the first side 111 and the second side 112 of the first wall 110, and a pair of short sides parallel to the third side 113 and the fourth side 114. The rounded shape of corner 116c reduces the stress on corner 116c, thus preventing damage.

[0027] The bottom 116b of the recess 116 is spaced apart from the outer edge of the first wall 110. In this embodiment, the pair of long sides (first side 111 and second side 112) of the first wall 110 are closer to the bottom 116b than the pair of short sides (third side 113 and fourth side 114). As shown in Figure 3, when the length from the first side 111 to the second side 112 of the first wall 110 is L, it is preferable that the bottom 116b is at least 1 / 5L away from the first side 111 and the second side 112, and more preferably at least 1 / 4L away. When the bottom 116b is pressed by the electrode body 20, the portion of the outer edge of the first wall 110 closer to the bottom 116b tends to experience stronger stress. Therefore, the greater the distance between the first side 111 and the second side 112 and the bottom 116b, the greater the stress generated on the first side 111 and the second side 112.

[0028] The area of ​​the bottom 116b of the recess 116 is preferably, for example, 20% to 60% of the area of ​​the first wall 110. If the area of ​​the bottom 116b is too small, the contact area between the electrode body 20 and the bottom 116b will be small, which may cause damage to the electrode body 20. Therefore, the area ratio of the bottom 116b to the area of ​​the first wall 110 is preferably, for example, 30% or more. Also, if the area of ​​the bottom 116b is too large, the distance between the bottom 116b and the outer edge of the first wall 110 will be small, which may increase the stress on the outer edge of the first wall 110. Therefore, the area ratio of the bottom 116b to the area of ​​the first wall 110 may be, for example, 50% or less, or 40% or less. Note that the area of ​​the first wall 110 and the area of ​​the bottom 116b of the recess 116 refer to the area in the field of view from the opposing direction of the first wall 110 and the second wall 120 (the field of view from the F side to the Rr side in the short side direction Y of Figure 1).

[0029] The inclined portion 116a is positioned between the bottom portion 116b and the base portion 115. The inclined portion 116a slopes from the base portion 115 toward the bottom portion 116b. In other words, the inclined portion 116a slopes from the base portion 115 toward the electrode body 20. Here, the inclined portion 116a slopes linearly from the base portion 115 toward the bottom portion 116b. In some embodiments, the inclined portion 116a may be curved toward the inside or outside of the case 100.

[0030] The angle θ of the inclined portion 116a with respect to the base portion 115 is not particularly limited, but is preferably less than 30°, and more preferably 20° or less. If the angle θ is too large, the boundary between the inclined portion 116a and the base portion 115 becomes prone to damage. The lower limit of the angle θ is not particularly limited, but may be, for example, 5° or more, 10° or more, or 15° or more. If the angle θ is too small, the depth of the recessed portion 116 may not be sufficient, and the electrode body 20 and the base portion 115 may come into contact more easily.

[0031] The recessed portion 116 can be formed, for example, by press working. The thickness of the inclined portion 116a and the bottom portion 116b of the recessed portion 116 may be approximately the same as that of the base portion 115 (for example, within a range of ±10% of the thickness of the base portion 115).

[0032] The recess 115a is provided at least between the first side 111 of the first wall 110 and the recessed portion 116. Here, the recess 115a surrounds the recessed portion 116. That is, the recess 115a is provided in an annular shape between the outer edge of the first wall 110 and the recessed portion 116. Here, the recess 115a is provided continuously (groove-shaped). In some embodiments, the recess 115a may be provided intermittently.

[0033] The recess 115a is recessed inward or outward from the case 100. The recess 115a may be a bent portion formed by bending a part of the first wall 110. The bottom of the recess 115a protrudes from the inner surface of the case 100 toward the electrode body 20, or protrudes from the outer surface of the case 100 toward the outside of the case 100. Preferably, the recess 115a is a curved portion that curves inward or outward from the case 100. Here, the recess 115a is curved inward from the case 100. Because the recess 115a is recessed inward (curved in this case) from the case 100, no protrusion is formed on the outside of the first wall 110 of the case 100. This makes it possible to reduce variations in restraint pressure when restraint pressure is applied from the outside of the case 100 in the opposing direction between the first wall 110 and the second wall 120.

[0034] The thickness of the recess 115a (i.e., the thickness of the material constituting the recess 115a) may be approximately the same as that of the base portion 115 (for example, within a range of ±10% of the thickness of the base portion 115). The recess 115a can be formed, for example, by pressing or bending.

[0035] There is a space between the recess 115a and the electrode body 20, and the inner surface of the base portion 115 and the electrode body 20 are configured not to come into contact. In this embodiment, since the recess 115a is recessed toward the inside of the case 100, the depth of the recess 115a is smaller than the depth of the recess 116.

[0036] Through the inventors' studies, it was found that stress is reduced by increasing the length of the member constituting the first wall 110 between the bottom 116b of the recess 116 of the first wall 110 that contacts the electrode body 20 and the outer edge of the first wall 110. Although details are omitted, computer simulations confirmed that the first wall 110 in this embodiment reduces the maximum stress by approximately 60% compared to the case where a flat plate (i.e., a plate without the recess 116 and recess 115a) is used instead of the first wall 110. The mechanism by which stress is reduced can be explained based on so-called beam theory, although it is not particularly limited. In short, the presence of the recess 115a increases the length of the member constituting the first wall 110 from the bottom 116b of the recess 116 to the outer edge of the first wall 110 (the length of the member before deformation processing to create the recess 115a). The longer this length becomes, the more stress can be relieved. In particular, because the recess 115a is curved, stress concentration in the recess 115a is suppressed, thus a stress relaxation effect can be favorably obtained.

[0037] (2) Electrode body 20 The electrode body 20 is a power generation element in the energy storage device 1. Figure 5 is a schematic diagram of the electrode body 20 in an exploded view. As shown in Figure 5, the electrode body 20 comprises a positive electrode 22 and a negative electrode 24. The electrode body 20 has a laminated portion 28 in which the positive electrode 22 and the negative electrode 24 are stacked in an insulated state (see Figure 3). Here, the positive electrode 22 and the negative electrode 24 are insulated by a separator 26. The electrode body 20 is a flat-shaped wound electrode body in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are stacked via a strip-shaped separator 26 and wound around a winding axis WL. The electrode body 20 is housed inside the case 100 such that the winding axis WL is approximately parallel to the long side direction X. Furthermore, the electrode body 20 is arranged so that the laminated portion 28 is aligned with the opposing direction (short side direction Y) between the first wall 110 and the second wall 120 of the case 100. The laminated portion 28 faces the bottom 116b of the recess 116 provided in the first wall 110 of the case 100. Although not shown in the figures, an insulating material (for example, an insulating film made of resin) is placed between the electrode body 20 and the case 100 to prevent electrical conductivity.

[0038] As shown in Figure 3, the electrode body 20 has a pair of curved portions 20r. Each of the pair of curved portions 20r faces the first side wall 130 and the second side wall 140 of the case 100. The laminated portion 28 is formed between the pair of curved portions 20r. The laminated portion 28 is the flat portion of the electrode body 20. The laminated portion 28 tends to undergo a larger volume change during charging compared to the curved portions 20r.

[0039] The positive electrode 22 comprises a positive electrode current collector 22c, which is a conductive metal foil; a positive electrode active material layer 22a disposed on the surface of the positive electrode current collector 22c; and a positive electrode protective layer 22p. The positive electrode current collector 22c is in the form of a strip. The positive electrode current collector 22c is made of a conductive metal such as aluminum, aluminum alloy, nickel, or stainless steel. In this case, the positive electrode current collector 22c is a metal foil, specifically an aluminum foil.

[0040] The positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the strip-shaped positive electrode current collector 22c. The positive electrode active material layer 22a contains an active material (for example, a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide) that can reversibly intercept and release charge carriers. The positive electrode active material layer 22a may also contain optional components other than the active material, such as conductive materials, binders, and various additives. As a conductive material, for example, a carbon material such as acetylene black (AB) may be used. As a binder, for example, polyvinylidene fluoride (PVdF) may be used.

[0041] The positive electrode protective layer 22p is provided adjacent to the positive electrode tab 22t side of the positive electrode active material layer 22a in the width direction (long side direction X) of the positive electrode 22. The material of the positive electrode protective layer 22p may be the same as in the conventional method. The positive electrode protective layer 22p may include, for example, an inorganic filler (e.g., alumina), a binder (e.g., PVDF), a conductive material (e.g., acetylene black), etc.

[0042] The positive electrode 22 is provided with a positive electrode tab 22t. The positive electrode tab 22t is, in this case, part of the positive electrode current collector 22c. The positive electrode tab 22t protrudes from the edge of the positive electrode current collector 22c in the width direction (long side direction X) of the positive electrode 22. Here, the positive electrode tab 22t protrudes toward the third side wall 150 of the case 100 (see Figure 2). At least a portion of the positive electrode tab 22t has a region where the positive electrode current collector 22c is exposed. Here, the positive electrode tab 22t is electrically connected to the positive electrode terminal 30 via the positive electrode current collector 32. Note that the positive electrode tab 22t may be a separate component from the positive electrode current collector 22c.

[0043] The negative electrode 24 comprises a negative electrode current collector 24c, which is a conductive metal foil, and a negative electrode active material layer 24a disposed on the surface of the negative electrode current collector 24c. The negative electrode current collector 24c is in the shape of a strip. The negative electrode current collector 24c is made of a conductive metal such as copper, copper alloy, nickel, or stainless steel. In this case, the negative electrode current collector 24c is a metal foil, specifically a copper foil.

[0044] The negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the strip-shaped negative electrode current collector 24c. The negative electrode active material layer 24a contains an active material (for example, a carbon material such as graphite, or a silicon-containing material such as silicon oxide or silicon-containing graphite) that can reversibly absorb and release charge carriers. The negative electrode active material layer 24a may also contain optional components other than the active material, such as binders, dispersants, and other additive components. For example, styrene-butadiene rubber (SBR) can be used as a binder. For example, celluloses such as carboxymethylcellulose (CMC) can be used as a dispersant.

[0045] The negative electrode 24 is provided with a negative electrode tab 24t. The negative electrode tab 24t is, in this case, part of the negative electrode current collector 24c. The negative electrode tab 24t protrudes from the edge of the negative electrode current collector 24c in the width direction (long side direction X) of the negative electrode 24. Here, the negative electrode tab 24t protrudes toward the fourth side wall 160 of the case 100 (see Figure 2). At least a portion of the negative electrode tab 24t has a region where the negative electrode current collector 24c is exposed. Here, the negative electrode tab 24t is electrically connected to the negative electrode terminal 40 via the negative electrode current collection section 42. Note that the negative electrode tab 24t may be a separate component from the negative electrode current collector 24c.

[0046] As shown in Figure 5, the separator 26 is a component that insulates the positive electrode 22 and the negative electrode 24. For the separator 26, a porous sheet made of polyolefin resin such as polyethylene (PE) or polypropylene (PP) is preferred. The separator 26 may have a base material made of a porous sheet made of resin, and a heat-resistant layer (HRL) containing an inorganic filler, provided on at least one surface of the base material. Examples of inorganic fillers include alumina, boehmite, aluminum hydroxide, and titania.

[0047] The positive terminal 30 and the negative terminal 40 are fixed to opposing surfaces of the case 100, respectively. The positive terminal 30 is attached to the third side wall 150 (the left side in the long side direction X in Figure 2). The positive terminal 30 is inserted through the first through hole 152 such that a portion of it is exposed to the outside of the case 100 and the other portion is located inside the case 100. The positive terminal 30 is preferably made of metal, and more preferably of aluminum or an aluminum alloy. As shown in Figure 2, the positive terminal 30 is electrically connected to the positive tab 22t inside the case 100 via the positive current collector 32. In other embodiments, the positive current collector 32 may be omitted.

[0048] The negative electrode terminal 40 is mounted on the fourth side wall 160 (to the right in the long side direction X in Figure 2). The negative electrode terminal 40 is inserted through the second through hole 162 such that a portion of it is exposed to the outside of the case 100 and a portion of it is located inside the case 100. The negative electrode terminal 40 is preferably made of metal, and more preferably of copper or a copper alloy. As shown in Figure 2, the negative electrode terminal 40 is electrically connected to the negative electrode tab 24t inside the case 100 via the negative electrode current collector 42. In other embodiments, the negative electrode current collector 42 may be omitted. Also, in some embodiments, the positive electrode terminal 30 and the negative electrode terminal 40 may be provided on the same wall.

[0049] Insulating members 50 are placed between the positive terminal 30 and the case 100, and between the negative terminal 40 and the case 100, so that the positive terminal 30 and the negative terminal 40 do not conduct electricity with the case 100. The insulating members 50 can be made of, for example, a fluororesin such as perfluoroalkoxyalkane (PFA) or polytetrafluoroethylene (PTFE), or a synthetic resin material such as polyphenylene sulfide (PPS).

[0050] The non-aqueous electrolyte is housed inside case 100. The non-aqueous electrolyte may be the same as conventional ones and is not particularly limited. The non-aqueous electrolyte is a non-aqueous liquid electrolyte containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent includes, for example, carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). The supporting salt (electrolyte salt) includes, for example, a fluorine-containing lithium salt such as LiPF6. In some embodiments, the non-aqueous electrolyte may be in gel form, or it may be in solid form (solid electrolyte) and integrated with the electrode body.

[0051] As described above, the energy storage device 1 comprises a case 100 having a first wall 110. The first wall 110 has a base portion 115 and a recessed portion 116 protruding from the base portion 115 toward the electrode body 20. The recessed portion 116 comprises an inclined portion 116a that slopes toward the electrode body 20 from the base portion 115 and a bottom portion 116b that is closer to the electrode body 20 than the base portion 115. The base portion 115 has a recess 115a between the recessed portion 116 and the first side 111 that is recessed toward the inside or outside of the case 100.

[0052] In the energy storage device 1, when the electrode body 20 expands due to charging or other reasons, a force is generated in which the electrode body 20 pushes the bottom 116b of the recess 116 of the first wall 110 toward the outside of the case 100. This generates stress near the first side 111 of the first wall 110. The energy storage device 1 has a recess 115a between the bottom 116b and the first side 111. This reduces the stress near the first side 111 (near the corner of the case 100) compared to the case where the space between the bottom 116b and the first side 111 is flat (where the recess 115a is not provided).

[0053] The energy storage device 1 can be used for various applications. Suitable applications include automotive applications, specifically as a power source for vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The energy storage device 1 can also be used as a battery for small-scale power storage devices. The energy storage device 1 can typically be used in the form of a battery module, which consists of multiple devices connected in series and / or parallel.

[0054] Although embodiments disclosed herein have been described above, these embodiments are merely examples. This technology can be implemented in various other forms. The technologies described in the claims include various modifications and changes to the embodiments illustrated above. For example, it is possible to replace parts of the above embodiments with other variations, and it is also possible to add other variations to the above embodiments. Furthermore, technical features that are not described as essential may be deleted as appropriate.

[0055] In the above-described embodiment, the sealing body 180 is fitted into the step 170s of the opening 170h of the case body 170, and the first wall 110 is composed of the sealing body 180 and the end face of the side wall of the case body 170, but is not limited to this. Figure 6 is a schematic perspective view showing the configuration of a modified energy storage device 1A. Figure 7 is a schematic cross-sectional view along the line VII-VII in Figure 6. As shown in Figures 6 and 7, in the energy storage device 1A, the case 100A comprises the case body 170 and the sealing body 180A. The first wall 110A is composed of the sealing body 180A. The sealing body 180A has a bent portion 182A that is bent at the outer edge of the first wall 110A (specifically the first side 111A, the second side 112A, the third side 113A, and the fourth side 114A). The bent portion 182A extends along the outer surface of the side wall of the case body 170. In the energy storage device 1A, the bent portion 182A constitutes at least a part of the first side wall 130, the second side wall 140, the third side wall 150, and the fourth side wall 160. The sealing body 180A has a surface area (first wall 110A) that is larger than the opening 170h of the case body 170, and closes the opening 170h of the case body 170. The sealing body 180A and the case body 170 are joined, for example, by laser welding the bent portion 182A and the side wall of the case body 170. In the energy storage device 1A, there is no weld on the outer edge of the first wall 110A. Therefore, it is possible to prevent stress from concentrating at the weld.

[0056] Furthermore, in the embodiment described above, only one recess 115a was provided between the outer edge of the first wall 110 and the recessed portion 116, but this is not limited to this. Two or more recesses may be provided between the outer edge of the first wall 110 and the recessed portion 116. When two or more recesses 115a are provided, both recesses protruding inward from the case 100 and recesses protruding outward from the case 100 may be formed. For example, two or more recesses can be provided in a continuous manner by bending the first wall 110 into a corrugated shape so that it has irregularities in the direction from the recessed portion 116 toward the outer edge of the first wall 110. By providing two or more recesses (including a corrugated shape), the length of the members constituting the first wall 110 from the position where the electrode body 20 pushes the first wall 110 outward (bottom portion 116b) to the outer edge of the first wall 110 is extended, so that the stress generated at the outer edge of the first wall 110 can be further relieved.

[0057] Furthermore, although the electrode body 20 was a wound electrode body in the above-described embodiment, it is not limited to this. For example, the electrode body may be a laminated electrode body in which multiple rectangular (typically rectangular) sheet-like positive electrodes and multiple rectangular (typically rectangular) sheet-like negative electrodes are stacked in an insulated state.

[0058] Furthermore, although in the above-described embodiment one electrode body 20 was housed in the case 10, the case is not limited to this. In some embodiments, the number of electrode bodies housed in the case may be multiple.

[0059] Furthermore, in the above-described embodiment, the positive electrode tab 22t and the negative electrode tab 24t protruded from different end faces of the electrode body 20, but this is not limited to this. In some embodiments, the positive electrode tab and the negative electrode tab may protrude from the same end face of the electrode body.

[0060] Furthermore, in the embodiments described above, the bottom 116b of the recess 116 of the first wall 110 and the electrode body 20 were in direct contact, but the invention is not limited to this. In some embodiments, the bottom 116b of the recess 116 of the first wall 110 and the electrode body 20 may be indirectly in contact via other members. For example, an insulating member may be placed between the bottom 116b and the electrode body 20. Also, the bottom 116b of the recess 116 and the electrode body 20 do not always have to be in direct or indirect contact. For example, the electrode body 20 may be configured to first come into contact with the bottom 116b of the recess 116 within the first wall 110 when it expands (e.g., during charging).

[0061] As described above, specific embodiments of the technology disclosed herein include those described in the following sections.

[0062] Section 1: The case and, The electrode body housed in the above case and Equipped with, The above case is, A first wall having an outer edge including a first side and a second side opposite to the first side, The second wall opposite the first wall mentioned above and Equipped with, The electrode body has a laminated portion formed by stacking the first wall and the second wall in the opposing direction, with the positive electrode and the negative electrode insulated from each other. The first wall mentioned above is, The base part, A recessed portion protruding from the base portion toward the electrode body, It has, The above-mentioned recessed area is, A sloping portion that slopes from the base portion toward the electrode body, The bottom portion is closer to the electrode body than the base portion mentioned above. Equipped with, The base portion has a recess between the recessed portion and the first side that is recessed toward the inside or outside of the case. Energy storage device. Section 2: The energy storage device according to item 1, wherein, when the length from the first side to the second side of the first wall is L, the bottom of the recess is at least 1 / 5L away from the first side and the second side. Section 3: The energy storage device according to item 1 or 2, wherein the recess is provided surrounding the recessed portion. Section 4: An energy storage device according to any one of items 1 to 3, wherein the area of ​​the bottom of the recess is 20% or more and 60% or less when the area of ​​the first wall is taken as 100%. Section 5: The energy storage device according to any one of items 1 to 4, wherein the angle of the inclined portion of the recessed portion with respect to the base portion is less than 30°. Item 6: The energy storage device according to any one of items 1 to 5, wherein the above-mentioned recess is a curved portion. Section 7: The energy storage device according to any one of claims 1 to 6, wherein the first wall is substantially rectangular in shape, and the first side and the second side constitute a pair of long sides of the first wall. [Explanation of Symbols]

[0063] 1. Energy storage device 20 Electrode body 22 Positive electrode 24 Negative electrode 26 Separators 30 Positive terminal 40 Negative terminal 50 Insulating material 100 cases 110 1st wall 111 First side 112 Second side 113 Third side 114 Fourth side 115 Base section 115a recess 116 Recessed area 116a Slope 116b bottom 120 2nd wall 130 First side wall 140 Second side wall 150 Third side wall 160 Fourth side wall 170 Case Body 180 Sealing body

Claims

1. The case and The electrode body housed in the aforementioned case and Equipped with, The aforementioned case is, A first wall having an outer edge including a first side and a second side opposite to the first side, A second wall opposite the first wall and Equipped with, The electrode body has a laminated portion that is stacked along the opposing direction between the first wall and the second wall in a state in which the positive electrode and the negative electrode are insulated, The first wall is, The base part, A recessed portion protruding from the base portion toward the electrode body It has, The aforementioned recessed portion is, A sloping portion that slopes from the base portion toward the electrode body, The bottom portion is closer to the electrode body than the base portion. Equipped with, The base portion has a recess between the recessed portion and the first side that is recessed toward the inside or outside of the case. Energy storage device.

2. The energy storage device according to claim 1, wherein, when the length from the first side to the second side of the first wall is L, the bottom of the recess is at least 1 / 5L away from the first and second sides.

3. The energy storage device according to claim 1, wherein the recess is provided surrounding the recessed portion.

4. The energy storage device according to claim 1, wherein the area of ​​the bottom of the recess is 20% or more and 60% or less when the area of ​​the first wall is taken as 100%.

5. The energy storage device according to claim 1, wherein the angle of the inclined portion of the recess with respect to the base portion is less than 30°.

6. The energy storage device according to claim 1, wherein the recess is a curved portion.

7. The energy storage device according to any one of claims 1 to 6, wherein the first wall is substantially rectangular in shape, and the first side and the second side constitute a pair of long sides of the first wall.

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