Method for manufacturing an electricity storage device, and electricity storage device

Abstract

To provide technology that suppresses the residue of gases in an electrode body.SOLUTION: A manufacturing method for a power storage device comprises an electrode body 20, a case 10, and an electrolytic solution. The electrode body 20 is a wound electrode body having a pair of wide faces 20a facing each other. The case 10 is of a rectangular parallelepiped shape, and has an outer package 12 having a wide rectangular first wall 12a and an opening 12h facing the first wall 12a, and a sealing plate 14 for sealing the opening 12h. The manufacturing method includes an accommodation step, a liquid injection step, an initial charging step, and a sealing step. In the accommodation step, the electrode body 20 is accommodated in the outer package 12 so that the wide face 20a and the first wall 12a face each other. In the liquid injection step, an electrolytic solution is injected into the outer package 12 after the accommodation step. In the initial charging step, the electrode body 20 is initially charged after the liquid injection step. In the sealing step, the opening 12h of the outer package 12 is sealed with the sealing plate 14 after the initial charging step.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electricity storage device, and to an electricity storage device. [Background technology]

[0002] Patent Document 1 discloses a method for producing a lithium-ion secondary battery in which lithium bis(oxalato)borate is added to the electrolyte at a concentration in the range of 0.8 to 1.2 wt%. This production method is characterized by the following steps: after initial charging, the battery container is sealed and aging is performed by maintaining a temperature in the range of 70 to 80°C; after aging, gas is released to release the sealed state of the battery container; and after gas release, the battery container is sealed again to perform final sealing. This document also states that with this production method, even if the electrolyte contains lithium bis(oxalato)borate, the problem of increased internal pressure in the battery does not occur during use.

[0003] The nonaqueous electrolyte secondary battery disclosed in Patent Document 2 includes an electrode stack and a case that houses the electrode stack, and a pressure member is attached to apply pressure to the electrode stack in the electrode stacking direction. This nonaqueous electrolyte secondary battery uses a thin flat spring processed into a shape that generates elasticity in a direction perpendicular to the plate surface as the pressure member. The thin flat spring is disposed in the gap between the inner surface of the case and the electrode stack. This document describes how the electrode stack can be compressed by a simple configuration in which a thin flat spring is processed into a predetermined shape and disposed in the gap between the inner surface of the case and the electrode stack. It also describes how this configuration can extend the charge / discharge cycle life of the nonaqueous electrolyte secondary battery.

[0004] In the flat prismatic battery disclosed in Patent Document 3, the main case is formed as a half-shell made of a processed metal plate with a flange around the opening of the recess. A plate assembly is housed in the recess. A metal cover plate is disposed with its peripheral portion overlapping the flange and welded to the flange. Furthermore, in this battery, a recess is formed in the main case and / or cover plate in a direction that reduces the thickness of the battery. This publication states that when the plate assembly housed in the case expands or internal pressure increases, causing a force in the bulging direction to act on the case, the recess in the cover plate, which has lower deformation strength than the main case, bulges outward. This does not affect the overall thickness of the case, and the bulging does not affect the device in which the flat prismatic battery is installed. Therefore, it is stated that this configuration can contribute to achieving thinner devices. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-107020 [Patent Document 2] Japanese Patent Application Publication No. 10-334879 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-103368 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the present inventors wish to suppress residual gas in the electrode assembly in the manufacture of an electricity storage device including a so-called wound electrode assembly. [Means for solving the problem]

[0007] The technology disclosed herein discloses a method for manufacturing an electricity storage device including an electrode assembly having a long sheet-like positive electrode and a long sheet-like negative electrode wound in the sheet longitudinal direction with a separator interposed therebetween, the electrode assembly having a pair of opposing wide surfaces; a rectangular case that houses the electrode assembly, the case having a wide rectangular first wall and an opening facing the first wall, and a wide rectangular sealing plate facing the first wall and sealing the opening; and an electrolyte. This manufacturing method includes a housing step of housing the electrode assembly in the housing so that the wide surface faces the first wall; a liquid injection step of injecting the electrolyte into the housing after the housing step; an initial charging step of initially charging the electrode assembly after the liquid injection step; and a sealing step of sealing the opening of the housing after the initial charging step with a sealing plate. This manufacturing method can reduce residual gas in the electrode assembly.

[0008] In a preferred embodiment of the manufacturing method disclosed herein, the initial charging step is carried out under a negative pressure state, which can improve the effect of suppressing gas remaining in the electrode assembly.

[0009] In another preferred embodiment, the manufacturing method disclosed herein includes a pressing step of applying a pressing force to the wide surface of the electrode assembly after the initial charging step and before the sealing step. This configuration can improve the efficiency of gas removal from the electrode assembly.

[0010] In another preferred embodiment of the manufacturing method disclosed herein, in the pressing step, a greater pressing force is applied to a central region of the wide surface, the central region being the intersection of a first center line passing through the midpoints of a pair of opposing long sides of the wide surface and a second center line passing through the midpoints of a pair of opposing short sides of the wide surface, than to edge regions excluding the central region. This manufacturing method can suppress residual gas in the electrode body.

[0011] In another preferred embodiment of the manufacturing method disclosed herein, the pressing step includes a pumping process in which a pressing force is applied to the wide surface, the pressing force is released, and then the pressing force is applied again to the wide surface. This manufacturing method can suppress gas from remaining in the electrode body.

[0012] In another preferred embodiment of the manufacturing method disclosed herein, a sealing plate having a protrusion is used. Furthermore, in the pressing step, the protrusion of the sealing plate is brought into contact with the wide surface, thereby applying a pressing force to the wide surface. In addition to the above-described advantages, this manufacturing method can also omit the need for a separate pressing member.

[0013] In another preferred aspect of the manufacturing method disclosed herein, the opening of the exterior body is sealed while pressing the wide surface of the electrode body with the sealing plate. With this configuration, it is possible to improve the effect of suppressing gas from remaining in the electrode body.

[0014] The technology disclosed herein also provides an electricity storage device comprising: an electrode assembly in which a long, sheet-like positive electrode and a long, sheet-like negative electrode are wound in the sheet longitudinal direction with a separator interposed therebetween, the electrode assembly having a pair of opposing wide surfaces; a rectangular case housing the electrode assembly, the case having a wide, rectangular first wall and an opening facing the first wall; and a wide, rectangular sealing plate facing the first wall and sealing the opening; and an electrolyte. In this electricity storage device, at least one of the sealing plate and the first wall of the exterior case is provided with a pressing portion that applies a relatively greater pressing force to a central region of the wide surface of the electrode assembly, the central region being centered at the intersection of a first center line passing through the midpoints of a pair of opposing long sides of the wide surface and a second center line passing through the midpoints of a pair of opposing short sides of the wide surface, than to edge regions excluding the central region. This configuration can suppress residual gas in the electrode assembly.

[0015] In a preferred aspect of the electricity storage device disclosed herein, the pressing portion is a convex portion that curves in a dome shape from a base end of the pressing portion toward a central region. With this configuration, it is possible to improve the effect of suppressing gas remaining in the electrode assembly.

[0016] In another preferred aspect of the electricity storage device disclosed herein, the pressing portion is a convex portion having a first region that protrudes toward the central region and a second region that is provided around the first region and whose protruding height from the base end of the pressing portion gradually increases from the base end toward the first region. This configuration can improve the effect of suppressing gas residue in the electrode body. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of an electricity storage device 1. FIG. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is an exploded perspective view of the case 10. As shown in FIG. [Figure 5] FIG. 5 is a schematic diagram of the electrode body 20. As shown in FIG. [Figure 6] FIG. 6 is a plan view of the sealing plate 214. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the technology disclosed herein will be described below. The embodiment described herein is not intended to limit the technology disclosed herein. The technology disclosed herein is not limited to the embodiment described herein unless otherwise specified. The drawings are schematic and do not necessarily reflect the actual product. Furthermore, members and parts that perform the same function are appropriately designated by the same reference numerals, and redundant explanations will be omitted. Furthermore, the notation "A to B" indicating a numerical range means "greater than or equal to A and less than or equal to B" unless otherwise specified, and also encompasses the meaning of "greater than A and less than B."

[0019] In this specification, the term "electricity storage device" refers to a device in which charging and discharging occur by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. Such electricity storage devices include secondary batteries such as lithium ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries; and capacitors such as lithium ion capacitors and electric double layer capacitors. In the following, an embodiment will be described in which a lithium ion secondary battery is used as an example of the above-mentioned electricity storage device.

[0020] When the electrode body is initially charged, gas may be generated inside the electrode body due to, for example, a reaction between components constituting the electrode body and components constituting the electrolyte. If gas remains in the electrode body, uneven battery reactions may occur within the electrode body when an electricity storage device having such an electrode body is charged and discharged. The present inventors wanted to suppress the gas remaining in the electrode body, and studied the structure of the electricity storage device and the manufacturing process for the electricity storage device.

[0021] FIG. 1 is a perspective view of the electricity storage device 1. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 2 shows a cross-sectional view taken along the first wall 12a of the case 10. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 3 shows a cross-sectional view taken along the second walls 12b and 12c of the case 10. FIG. 4 is an exploded perspective view of the case 10. FIG. 4 shows the exterior body 12 and the sealing plate 14 removed from the opening 12h of the exterior body 12.

[0022] <Electricity storage device 1> The technology disclosed herein provides an electricity storage device 1. As shown in Figures 1 and 2, the electricity storage device 1 includes a case 10, an electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, a negative electrode current collector 60, an electrolyte (not shown), and various insulating members.

[0023] -Case 10- The case 10 is, for example, a rectangular parallelepiped (hexahedral) member that houses the electrode assembly 20. As shown in FIGS. 1 to 4, the case 10 includes an exterior body 12 and a sealing plate 14. The exterior body 12 is, for example, the main body of the case 10 that houses the electrode assembly 20 therein. As shown in FIGS. 1 to 4, the exterior body 12 has an opening 12h, a first wall 12a, a pair of opposing second walls 12b and 12c, and a pair of opposing third walls 12d and 12e. In this embodiment, the first wall 12a has a wide rectangular shape and faces the opening 12h. The pair of second walls 12b and 12c extend from a pair of opposing long sides of the first wall 12a. As shown in FIGS. 1 to 3, the lower second wall 12c forms the bottom surface of the electricity storage device 1. The upper second wall 12b is the top surface facing the bottom surface and serves as an attachment surface for electrode terminals. The pair of third walls 12d, 12e extend from a pair of opposing short sides of the first wall 12a. In this specification, the term "rectangular" includes shapes in which linear long and short sides are joined to each other via curves, and shapes in which at least one of the long and short sides is not linear but is curved, uneven, or bent and composed of multiple straight or curved lines.

[0024] Opening 12h is, for example, a portion where sealing plate 14 is attached. Here, opening 12h is formed by being surrounded by the upper edges of the pair of second walls 12b and 12c and the upper edges of the pair of third walls 12d and 12e, and has a wide rectangular shape. As shown in FIGS. 3 and 4, opening 12h has a recessed step 121 along its inner edge. Here, sealing plate 14 is fitted into step 121. Furthermore, by joining (e.g., welding) sealing plate 14 to step 121, exterior body 12 and sealing plate 14 are integrated, and case 10 is airtightly sealed.

[0025] As shown in FIGS. 1 to 4, the second wall 12b is provided with a discharge valve 123, a first terminal mounting portion 124, and a second terminal mounting portion 125. The discharge valve 123 is, for example, a thin-walled portion. Here, the discharge valve 123 is configured to break when the pressure inside the case 10 reaches a predetermined value or higher, thereby discharging gas inside the case 10 to the outside. The first terminal mounting portion 124 is, for example, a portion to which the positive electrode terminal 30 is attached. In the embodiment shown in FIGS. 2 and 4, the first terminal mounting portion 124 is a step recessed from the second wall 12b. A through-hole 18 through which the positive electrode terminal 30 is inserted is provided at the bottom of the first terminal mounting portion 124. The second terminal mounting portion 125 is, for example, a portion to which the negative electrode terminal 40 is attached. In the embodiment shown in FIG. 4, the second terminal mounting portion 125 is a step recessed from the second wall 12b. The second terminal attachment portion 125 has a bottom provided with a through-hole 19 through which the negative electrode terminal 40 is inserted.

[0026] The sealing plate 14 is, for example, a flat plate-like member that seals the opening 12h. Therefore, the shape of the sealing plate 14 may correspond to the shape of the opening 12h. In this embodiment, the sealing plate 14 is a wide rectangle. Here, when the sealing plate 14 is attached to the opening 12h, the sealing plate 14 faces the first wall 12a. As shown in FIG. 4, the sealing plate 14 has a pair of opposing long sides 14a, 14b and a pair of opposing short sides 14c, 14d. Here, the long side 14a rests on the bottom of the step 121 in the second wall 12b. The long side 14b rests on the bottom of the step 121 in the second wall 12c. The short side 14c rests on the bottom of the step 121 in the third wall 12d. The short side portion 14d rests on the bottom of the step 121 in the third wall 12e.

[0027] As shown in FIGS. 1, 3, and 4, the sealing plate 14 has a flat portion 141 and a pressing portion 142. The flat portion 141 is, for example, a flat region without irregularities, through-holes, or the like. Here, the flat portion 141 is the region excluding the pressing portion 142. The pressing portion 142 is, for example, a region that applies a relatively greater pressing force to the central region 20CR of the wide surface 20a of the electrode body 20 than to the end region 20PR (see FIG. 2). Here, the central region 20CR is a region whose center point is the intersection CP of a first center line CL1 passing through a midpoint A of a pair of opposing long sides of the wide surface 20a and a second center line CL2 passing through a midpoint B of a pair of opposing short sides of the wide surface 20a. The length of the central region 20CR in the long side direction of the wide surface 20a may be, for example, 20% to 90% of the long side of the wide surface 20a. The length of the central region 20CR in the short-side direction of the wide surface 20a may be, for example, 20% to 90% of the short side of the wide surface 20a. Here, the edge region 20PR is the region of the wide surface 20a excluding the central region 20CR. In the embodiment shown in FIG. 2, the central region 20CR is the region of the wide surface 20a surrounded by a dotted line. The edge region 20PR is the region of the wide surface 20a outside the dotted line. In this embodiment, the pressing force applied to the central region 20CR is greater than the pressing force applied to the edge region 20PR.

[0028] 3 and 4, the pressing portion 142 is a convex portion that curves in a dome shape from the base end 142B of the pressing portion 142 toward the central region 20CR (toward the inside of the case 10). Here, the base end 142B is the boundary between the flat portion 141 and the pressing portion 142. Because the pressing portion 142 is a convex portion that curves in a dome shape, the pressing force against the wide surface 20a can be gradually increased toward the contact point with the curved apex in the central region 20CR. This can better suppress residual gas within the electrode body 20.

[0029] In this embodiment, the case 10 is not provided with a liquid injection hole for injecting the electrolyte into the case 10. As will be described later in the description of the manufacturing method, the electrolyte is injected into the case 10 through the opening 12h. By not providing a liquid injection hole in the case 10, it is possible to omit providing such a liquid injection hole. This allows for improved productivity of the electricity storage device 1. However, a liquid injection hole may be provided in the case 10 as needed.

[0030] -Electrode body 20- The electrode assembly 20 is a power generating element of the electricity storage device 1, having, for example, a positive electrode and a negative electrode. FIG. 5 is a schematic diagram of the electrode assembly 20. As shown in FIG. 5, the electrode assembly 20 is a wound electrode assembly in which a long sheet-like positive electrode 22 and a long sheet-like negative electrode 24 are wound in the sheet longitudinal direction LD with a separator 23 interposed therebetween. The electrode assembly 20 can be produced, for example, by winding the positive electrode 22, the negative electrode 24, and the separator 23 into a cylindrical body and press-molding the cylindrical body. Therefore, the electrode assembly 20 has a flat shape and has a pair of wide surfaces 20a (see FIGS. 2 and 3).

[0031] As shown in FIGS. 2 and 5, the electrode assembly 20 is housed in the exterior housing 12 so that the winding axis direction WD is approximately parallel to the up-down direction of the electricity storage device 1. In this embodiment, the winding axis WL of the electrode assembly 20 is approximately parallel to the first wall 12a, the third walls 12d and 12e, and the sealing plate 14, and is approximately perpendicular to the second walls 12b and 12c. The wide surface 20a of the electrode assembly 20 faces the first wall 12a and the sealing plate 14. One end face of the electrode assembly 20 faces the second wall 12b, and the other end face faces the second wall 12c. Here, the end faces of the electrode assembly 20 are the stacking surfaces of the positive electrode 22, the negative electrode 24, and the separator 23, and are open surfaces.

[0032] 5, the positive electrode 22 has a long, strip-shaped positive electrode current collector foil 22c (e.g., aluminum foil) and a positive electrode active material layer 22a fixed to at least one surface of the positive electrode current collector foil 22c. Although not particularly limited, a protective layer 22p may be provided on one side edge portion in the winding axis direction WD of the positive electrode 22, as necessary. Note that, as the constituent materials of the positive electrode active material layer 22a and the protective layer 22p, materials used in this type of electricity storage device (in this embodiment, a lithium ion secondary battery) may be used without particular limitation.

[0033] A plurality of positive electrode tabs 22t are provided at one end of the positive electrode current collector foil 22c in the winding axis direction WD (the upper end in FIG. 5). The plurality of positive electrode tabs 22t protrude toward one end of the winding axis direction WD (the upper end in FIG. 5). The plurality of positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction LD of the positive electrode 22. The positive electrode tabs 22t are part of the positive electrode current collector foil 22c, and are portions of the positive electrode current collector foil 22c where the positive electrode active material layer 22a is not formed (active material layer unformed portions). In the embodiment shown in FIG. 5, a protective layer 22p is provided on the base end side of the positive electrode tab 22t. In this embodiment, the plurality of positive electrode tabs 22t protrude further in the winding axis direction WD than the separator 23. The plurality of positive electrode tabs 22t are stacked at one end of the winding axis direction WD (the upper end in FIG. 5) to form a positive electrode tab group. Therefore, the height (length in the winding axis direction WD) of each positive electrode tab 22t and the width (length in the longitudinal direction LD) of each positive electrode tab 22t do not need to be the same. As shown in Fig. 2, a positive electrode current collector 50 is joined to the stacked positive electrode tabs 22t (positive electrode tab group).

[0034] 5, the negative electrode 24 has a long, strip-shaped negative electrode current collector foil 24c (e.g., copper foil) and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector foil 24c. Note that, as a constituent material of the negative electrode active material layer 24a, any material used in this type of electricity storage device (in this embodiment, a lithium ion secondary battery) may be used without any particular limitation.

[0035] A plurality of negative electrode tabs 24t are provided at one end of the negative electrode current collector foil 24c in the winding axis direction WD (the upper end in FIG. 5). The plurality of negative electrode tabs 24t protrude toward one end of the winding axis direction WD (the upper end in FIG. 5). The plurality of negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction LD of the negative electrode 24. The negative electrode tabs 24t are part of the negative electrode current collector foil 24c, and are portions of the negative electrode current collector foil 24c where the negative electrode active material layer 24a is not formed (active material layer unformed portions). In this embodiment, the plurality of negative electrode tabs 24t protrude further in the winding axis direction WD than the separator 23. For example, the plurality of negative electrode tabs 24t are stacked at one end of the winding axis direction WD (the upper end in FIG. 5) to form a negative electrode tab group. Therefore, the height (length in the winding axis direction WD) of each negative electrode tab 24t and the width (length in the longitudinal direction LD) of each negative electrode tab 24t do not need to be the same. As shown in Fig. 2, a negative electrode current collector 60 is joined to the stacked negative electrode tabs 24t (negative electrode tab group).

[0036] The separator 23 is a member that insulates the positive electrode active material layer 22a of the positive electrode 22 from the negative electrode active material layer 24a of the negative electrode 24. In this embodiment, the separator 23 forms the outer surface of the electrode body 20. The separator 23 is, for example, a porous sheet made of a resin such as a polyolefin resin, such as polyethylene (PE) or polypropylene (PP).

[0037] 5, in the electrode assembly 20, the lower end P3 of the separator 23 is the lowest, followed by the lower end P2 of the negative electrode 24, and the lower end P1 of the positive electrode 22 is the highest. The widths of the sheets (in FIG. 5, the length in the winding direction WD, excluding the positive electrode tab 22t and the negative electrode tab 24t) are largest in the order of the separator 23, the negative electrode 24, and the positive electrode 22.

[0038] -Positive terminal 30- The positive electrode terminal 30 is, for example, a member electrically connected to the positive electrode 22 of the electrode assembly 20. As shown in FIG. 2, the positive electrode terminal 30 is inserted through the through-hole 18 and exposed to the outside of the exterior body 12. Here, the positive electrode terminal 30 has a first conductive member 31 and a second conductive member 32. In this embodiment, the first conductive member 31 has a shaft portion 31a and a base portion 31b. The shaft portion 31a is, for example, cylindrical and is a portion inserted into the through-hole 18 and the through-hole of the second conductive member 32. The base portion 31b is, for example, flat and is a portion disposed along the outer surface of the exterior body 12 (here, the second wall 12b). The second conductive member 32 is, for example, flat and is a portion connected to a bus bar when constructing a battery pack. In this embodiment, the second conductive member 32 is rectangular. The first conductive member 31 and the second conductive member 32 are connected to each other outside the case 10. The first conductive member 31 is made of, for example, aluminum or an aluminum alloy. The second conductive member 32 is made of, for example, aluminum, an aluminum alloy, copper, a copper alloy, or the like.

[0039] -Negative terminal 40- The negative electrode terminal 40 is, for example, a member electrically connected to the negative electrode 24 of the electrode body 20. As shown in FIG. 2, the negative electrode terminal 40 is inserted into the through-hole 19 and exposed to the outside of the exterior body 12. Here, the negative electrode terminal 40 has a first conductive member 41 and a second conductive member 42. The first conductive member 41 is made of, for example, copper or a copper alloy. The negative electrode terminal 40 may have a configuration similar to that of the positive electrode terminal 30, for example. Therefore, a description of the configuration of the negative electrode terminal 40 will be omitted here.

[0040] -Positive current collector 50- The positive electrode current collector 50 is, for example, a member that electrically connects the positive electrode tab 22t and the positive electrode terminal 30. The positive electrode current collector 50 is, for example, a plate-shaped conductive member. As shown in FIG. 2, the positive electrode current collector 50 extends along the inner surface of the exterior body 12 (here, the inside of the second wall 12b) in the direction of the longer side of the second wall 12b. The positive electrode tab 22t (here, a group of positive electrode tabs) is connected to one end (the right end in FIG. 2) of the positive electrode current collector 50. Furthermore, the lower end of the shaft portion 31a of the positive electrode terminal 30 is inserted into a through-hole 50h at the other end (the left end in FIG. 2) of the positive electrode current collector 50 and crimped. The positive electrode current collector 50 is made of, for example, aluminum or an aluminum alloy.

[0041] -Negative electrode current collector 60- The negative electrode current collector 60 is, for example, a member that electrically connects the negative electrode tab 24t and the negative electrode terminal 40. The negative electrode current collector 60 is, for example, a plate-shaped conductive member. As shown in FIG. 2, the negative electrode current collector 60 extends along the inner surface of the exterior body 12 (here, the inside of the second wall 12b) in the direction of the longer side of the second wall 12b. The negative electrode tab 24t (here, a group of negative electrode tabs) is connected to one end (the left end in FIG. 2) of the negative electrode current collector 60. Furthermore, the lower end of the negative electrode terminal 40 is inserted into a through-hole 60h at the other end (the right end in FIG. 2) of the negative electrode current collector 60 and crimped. The negative electrode current collector 60 is made of, for example, copper or a copper alloy.

[0042] -Electrolyte- The electrolyte solution contains, for example, an electrolyte salt and a non-aqueous solvent. Examples of the electrolyte salt include LiPF6. The concentration of the electrolyte salt in the electrolyte solution is, for example, 0.7 mol / L to 1.3 mol / L. The non-aqueous solvent may be, for example, a carbonate. Examples of carbonates include ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyl difluoromethyl carbonate (F-DMC), trifluorodimethyl carbonate (TFDMC), etc. These may be used alone or in combination of two or more.

[0043] -Insulating materials- Various insulating members are used in the electricity storage device 1. For example, as shown in FIG. 2 , an external insulating member 91 is disposed on the outside of the case 10 between the second conductive member 32 of the positive electrode terminal 30 and the second wall 12b, and between the second conductive member 42 of the negative electrode terminal 40 and the second wall 12b. Also, on the outside of the case 10, a gasket 92 is disposed between the first conductive member 31 and the second wall 12b, and between the first conductive member 41 and the second wall 12b. The gasket 92 has a cylindrical portion 921 disposed on the inner periphery of the through hole 18 and the inner periphery of the through hole 19. Also, an internal insulating member 93 is disposed on the inside of the case 10 between the positive electrode current collector 50 and the second wall 12b, and between the negative electrode current collector 60 and the second wall 12b.

[0044] The electricity storage device 1 can be used for a variety of purposes, and is particularly preferably used as a power source (driving power source) for motors mounted on vehicles such as passenger cars, trucks, etc. The type of vehicle is not particularly limited, but suitable examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0045] As described above, the electricity storage device 1 includes an electrode assembly 20, a case 10, and an electrolyte. The electrode assembly 20 is an electrode assembly in which a long, sheet-like positive electrode 22 and a long, sheet-like negative electrode 24 are wound in the sheet longitudinal direction with a separator 23 interposed therebetween, and has a pair of opposing wide surfaces 20a. The case 10 is a rectangular (hexahedral) case that houses the electrode assembly 20, and has an exterior body 12 that has a wide, rectangular first wall 12a and an opening 12h facing the first wall 12a, and a wide, rectangular sealing plate 14 that faces the first wall 12a and seals the opening 12h. In this embodiment, the sealing plate 14 is provided with a pressing portion 142 that applies a relatively greater pressing force to a central region 20CR on the wide surface 20a of the electrode body 20, the central region 20CR having a center point at the intersection CP between the center line CL1 of the long side of the wide surface 20a and the center line CL2 of the short side of the wide surface 20a, than to the end region 20PR excluding the central region 20CR.

[0046] In the electricity storage device 1 having such a configuration, the sealing plate 14 has a pressing portion 142 that presses the central region 20CR of the wide surface 20a of the electrode body 20 more strongly than the end regions 20PR. This makes it possible to prevent gas generated during, for example, initial charging from remaining inside the electrode body 20.

[0047] In the above description, pressing portion 142 is provided on sealing plate 14, but this is not limiting. Pressing portion 142 may be provided on first wall 12a of exterior body 12 instead of sealing plate 14, or together with sealing plate 14.

[0048] <Method of Manufacturing Electricity Storage Device 1> The technology disclosed herein provides a method for manufacturing the electricity storage device 1. This manufacturing method includes, for example, a housing step, a bonding step, a liquid injection step, an initial charging step, a pressing step, and a sealing step.

[0049] -Containment process- The accommodation step is, for example, a step of accommodating the electrode assembly 20 in the exterior body 12. Here, the electrode assembly 20 is accommodated in the exterior body 12 so that the wide surface 20a faces the first wall 12a (see FIG. 2). Prior to the accommodation step, it is preferable to attach the positive electrode terminal 30, the negative electrode terminal 40, the positive electrode current collector 50, the negative electrode current collector 60, and various insulating members to the second wall 12b of the exterior body 12.

[0050] -Joining process- The joining step is, for example, a step of joining an electrode tab and an electrode current collector. In this embodiment, after the electrode body 20 is housed in the exterior body 12 (after the housing step), the positive electrode tab 22t is joined to the positive electrode current collector 50, and the negative electrode tab 24t is joined to the negative electrode current collector 60. The means for joining the electrode tabs and the electrode current collectors is, for example, laser welding. The joining step provides a first combined body in which the electrode body 20 and the exterior body 12 are integrated.

[0051] -Liquid injection process- The liquid injection step is, for example, a step of injecting an electrolyte into the exterior body 12 after the accommodation step (here, after the bonding step that follows the accommodation step). In this embodiment, the electrolyte is poured into the exterior body 12 through the opening 12h. From the viewpoint of increasing the efficiency of impregnation of the electrode body 20 with the electrolyte, it is preferable to carry out the liquid injection step under a negative pressure state. For example, it is preferable to place the first combined body obtained in the bonding step in a negative pressure environment (such as in a negative pressure chamber), and then carry out the liquid injection step.

[0052] -Initial charging process- The initial charging step is, for example, a step of initially charging the electrode body. In this embodiment, this step is performed after the liquid injection step and before the opening 12h is sealed with the sealing plate 14. Although not particularly limited, it is preferable to perform the initial charging step under a negative pressure state. This makes it easier for gas generated during the initial charging of the electrode body 20 to escape from the inside of the electrode body 20. This improves the effect of suppressing gas from remaining in the electrode body 20.

[0053] -Pressing process- The pressing step is, for example, a step of applying a pressing force to the wide surface 20a of the electrode body 20. In this embodiment, the pressing step is performed after the initial charging step and before the sealing step. This allows gas to be removed from the inside of the electrode body more efficiently. Note that the pressing step is not an essential step and can be omitted in other embodiments.

[0054] In the pressing step, for example, a greater pressing force may be applied to the central region 20CR of the wide surface 20a than to the end regions 20PR. Gas generated during initial charging is likely to remain in, for example, the central region 20CR of the wide surface 20a of the electrode body 20. Therefore, by applying a relatively greater pressing force to the central region 20CR in the pressing step, gas can be more efficiently removed from that region, thereby improving the effect of suppressing gas from remaining in the electrode body 20. The application of a relatively greater pressing force to the central region 20CR can be achieved, for example, by attaching the sealing plate 14 to the opening 12h. A relatively greater pressing force is applied to the central region 20CR by the pressing portion 142 shown in FIGS. 1 and 4.

[0055] Although not particularly limited, in the pressing step, a pumping process is preferably performed on the wide surface 20a of the electrode assembly 20. Here, the pumping process is a process in which a pressing force is applied to the wide surface 20a, the pressing force is released, and then the pressing force is applied to the wide surface 20a again. By performing the pumping process, gas can be more efficiently removed from the inside of the electrode assembly 20. For example, it is possible to attach the sealing plate 14 to the opening 12h, apply a pressing force to the sealing plate 14, release the pressing force, and then apply the pressing force again. Because the sealing plate 14 is provided with a pressing portion 142, the pumping process can be efficiently performed on the central region 20CR of the wide surface 20a of the electrode assembly 20.

[0056] As described above, it is preferable to perform the pressing step using sealing plate 14 that is provided with a protrusion (here, pressing portion 142). For example, in the pressing step, pressing force can be applied to wide surface 20a by bringing pressing portion 142 of sealing plate 14 into contact with wide surface 20a. By using sealing plate 14 in the pressing step, it is possible to omit the need to separately prepare another member to press wide surface 20a.

[0057] -Sealing process- The sealing step is, for example, a step of sealing the opening 12h of the exterior body 12 with the sealing plate 14. Here, the sealing step is performed after the initial charging step. In the sealing step, for example, it is preferable to seal the opening 12h of the exterior body 12 while pressing the wide surface 20a of the electrode body 20 with the sealing plate 14. This allows gas to be removed from the inside of the electrode body 20 more efficiently. Furthermore, because the sealing plate 14 is provided with a pressing portion 142, when pressing the wide surface 20a in the sealing step, the pressing portion 142 can apply a stronger pressing force to the central region 20CR of the wide surface 20a. This can further enhance the effect of suppressing gas remaining in the electrode body 20.

[0058] Then, the exterior body 12 and the sealing plate 14 are welded (for example, by laser welding) to integrate them and seal the case 10, thereby obtaining a second combined body. Thereafter, the second combined body is subjected to an aging treatment under predetermined conditions, thereby obtaining the electricity storage device 1 in a usable state.

[0059] As described above, the manufacturing method of the electricity storage device 1 includes a housing step, a liquid pouring step, an initial charging step, and a sealing step. In the housing step, the electrode body 20 is housed in the exterior body 12 so that the wide surface 20a faces the first wall 12a. In the liquid pouring step, an electrolyte is poured into the exterior body 12 after the housing step. In the initial charging step, the electrode body 20 is initially charged after the liquid pouring step. In the sealing step, after the initial charging step, the opening 12h of the exterior body 12 is sealed with a sealing plate 14.

[0060] In this manufacturing method, the initial charging step is performed before the opening 12h is sealed with the sealing plate 14. In other words, the initial charging step is performed before the exterior body 12 is sealed with the sealing plate 14. Therefore, the electrode body 20 is initially charged in a state open to the outside. This makes it easier for gas generated within the electrode body 20 by initial charging, for example, to be released to the outside of the electrode body 20. Therefore, this manufacturing method can prevent gas from remaining in the electrode body 20 (wound electrode body).

[0061] In the above embodiment, the pressing portion 142 provided on the sealing plate 14 was a dome-shaped protrusion. However, this is not limited thereto. FIG. 6 is a plan view of the sealing plate 214. FIG. 6 shows the configuration of the outer surface of the sealing plate 214. As shown in FIG. 6, the sealing plate 214 has a flat portion 2141 and a pressing portion 2142. In the embodiment shown in FIG. 6, the pressing portion 2142 is a protrusion having a first region R1 and a second region R2. The first region R1 is, for example, a region that protrudes toward the central region 20CR (see FIG. 2) of the electrode body 20. Here, the first region R1 is a rectangular region. From the viewpoint of better suppressing gas remaining in the electrode body 20, it is preferable that the first region R1 abuts against the central region 20CR when the sealing plate 214 is attached to the exterior body 12. The second region R2 is, for example, a region provided around the first region R1. In this embodiment, in the second region R2, the protruding height of the pressing portion 2142 from the base end 214B gradually increases from the base end 214B toward the first region R1.

[0062] When the sealing plate 214 is used, the first region R1 of the pressing portion 2142 can apply a stronger pressing force to the central region 20CR of the wide surface 20a. This can better suppress residual gas in the electrode body 20. Note that in FIG. 6, the shape of the first region R1 is rectangular. However, this is not limited to this. The shape of the first region R1 may be, for example, a circle (a perfect circle, an ellipse, etc.), a triangle, or a polygon with five or more sides.

[0063] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Section 1: an electrode body in which a long sheet-like positive electrode and a long sheet-like negative electrode are wound in the sheet longitudinal direction with a separator interposed therebetween, the electrode body having a pair of opposing wide surfaces; a rectangular parallelepiped case that houses the electrode assembly, the case having an exterior body that has a wide rectangular first wall and an opening facing the first wall, and a wide rectangular sealing plate that faces the first wall and seals the opening; An electrolyte; A method for manufacturing an electricity storage device comprising: an accommodating step of accommodating the electrode body in the exterior body so that the wide surface and the first wall face each other; a liquid injection step of injecting the electrolyte into the exterior body after the accommodation step; an initial charging step of initially charging the electrode body after the liquid injection step; a sealing step of sealing the opening of the exterior body with the sealing plate after the initial charging step; The manufacturing method includes the steps of: Section 2: Item 1. The manufacturing method according to item 1, wherein the initial charging step is carried out under negative pressure. Section 3: Item 3. The manufacturing method according to item 1 or 2, further comprising a pressing step of applying a pressing force to the wide surface of the electrode body after the initial charging step and before the sealing step. Section 4: Item 4. The manufacturing method according to Item 3, wherein in the pressing step, a greater pressing force is applied to a central region of the wide surface, the central region being the intersection of a first center line passing through the midpoints of a pair of opposing long sides of the wide surface and a second center line passing through the midpoints of a pair of opposing short sides of the wide surface, than to end regions excluding the central region. Section 5: Item 5. The manufacturing method according to item 3 or 4, wherein in the pressing step, a pumping process is carried out in which a pressing force is applied to the wide surface, the pressing force is released, and then the pressing force is applied to the wide surface again. Item 6: As the sealing plate, a sealing plate provided with a convex portion is used, 6. The manufacturing method according to any one of items 3 to 5, wherein in the pressing step, the protrusion of the sealing plate is brought into contact with the wide surface to apply a pressing force to the wide surface. Section 7: 7. The manufacturing method according to any one of items 1 to 6, wherein in the sealing step, the opening of the exterior body is sealed while pressing the wide surface of the electrode body with the sealing plate. Section 8: an electrode body in which a long sheet-like positive electrode and a long sheet-like negative electrode are wound in the sheet longitudinal direction with a separator interposed therebetween, the electrode body having a pair of opposing wide surfaces; a rectangular parallelepiped case that houses the electrode assembly, the case having an exterior body that has a wide rectangular first wall and an opening facing the first wall, and a wide rectangular sealing plate that faces the first wall and seals the opening; An electrolyte; An electricity storage device comprising: an electric storage device, wherein at least one of the sealing plate and the first wall of the outer casing is provided with a pressing portion that applies a relatively greater pressing force to a central region of the wide surface of the electrode body, the central region being the intersection of a first center line passing through the midpoints of a pair of opposing long sides of the wide surface and a second center line passing through the midpoints of a pair of opposing short sides of the wide surface, than to an end region excluding the central region. Section 9: Item 9. The electricity storage device according to item 8, wherein the pressing portion is a convex portion curved in a dome shape from a base end of the pressing portion toward the central region. Section 10: The pressing portion is a first region extending toward the central region; a second region provided around the first region, the protruding height of the pressing portion from the base end gradually increasing from the base end toward the first region; Item 9. The electricity storage device according to item 8, wherein the protrusions have the following structure.

[0064] Although the embodiments of the technology disclosed herein have been described above, it is not intended that the technology disclosed herein be limited to the above-described embodiments. The technology disclosed herein may also be implemented in other embodiments. The technology described in the claims includes various modifications and alterations of the above-described exemplary embodiments. For example, it is possible to replace part of the above-described embodiments with other modified embodiments, and it is also possible to add other modified embodiments to the above-described embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate. [Explanation of symbols]

[0065] 1. Energy storage devices 10 cases 12 Exterior body 12a 1st wall 12h opening 14 Sealing plate 20 Electrode body 22 Positive electrode 23 Separator 24 Negative electrode 30 Positive terminal 40 Negative terminal 50 Positive electrode current collector 60 Negative electrode current collector 91 External insulating member 92 Gasket 93 Internal insulating material 214 Sealing plate

Claims

1. an electrode body in which a long sheet-like positive electrode and a long sheet-like negative electrode are wound in the sheet longitudinal direction with a separator interposed therebetween, the electrode body having a pair of opposing wide surfaces; a rectangular parallelepiped case that houses the electrode assembly, the case having an exterior body that has a wide rectangular first wall and an opening facing the first wall, and a wide rectangular sealing plate that faces the first wall and seals the opening; An electrolyte; A method for manufacturing an electricity storage device comprising: an accommodating step of accommodating the electrode body in the exterior body so that the wide surface and the first wall face each other; a liquid injection step of injecting the electrolyte into the exterior body after the accommodation step; an initial charging step of initially charging the electrode body after the liquid injection step; a sealing step of sealing the opening of the exterior body with the sealing plate after the initial charging step; The manufacturing method includes the steps of:

2. The method according to claim 1 , wherein the initial charging step is carried out under a negative pressure.

3. The manufacturing method according to claim 1 , further comprising a pressing step of applying a pressing force to the wide surface of the electrode body after the initial charging step and before the sealing step.

4. 4. The manufacturing method according to claim 3, wherein in the pressing step, a greater pressing force is applied to a central region of the wide surface, the central region being the intersection of a first center line passing through the midpoints of a pair of opposing long sides of the wide surface and a second center line passing through the midpoints of a pair of opposing short sides of the wide surface, than to end regions excluding the central region.

5. The manufacturing method according to claim 3 , wherein the pressing step includes a pumping process in which, after applying a pressing force to the wide surface, the pressing force is released and then applied to the wide surface again.

6. As the sealing plate, a sealing plate provided with a convex portion is used, The manufacturing method according to claim 3 , wherein in the pressing step, the pressing force is applied to the wide surface by bringing the protrusion of the sealing plate into contact with the wide surface.

7. The manufacturing method according to claim 1 , wherein in the sealing step, the opening of the exterior body is sealed while pressing the wide surface of the electrode body with the sealing plate.

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