Manufacturing method for energy storage devices

Abstract

The present invention provides a method for manufacturing an energy storage device that can suppress the occurrence of internal short circuits. [Solution] The manufacturing method disclosed herein includes a construction step (S1) of constructing a battery assembly by housing an electrode body having a positive electrode and a negative electrode and an electrolyte inside a case, and an ultrasonic application step (S4) of applying ultrasonic waves to the battery assembly. The negative electrode active material layer has a facing region that faces the positive electrode active material layer and a non-facing region that does not face the positive electrode active material layer. In the ultrasonic application step (S4), the ultrasonic waves are applied to the battery assembly while there is excess electrolyte between the case and the electrode body and a load is applied to at least a part of the facing region.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a power storage device.

Background Art

[0002] Patent Documents 1-3 disclose a power storage device including an electrode body having a positive electrode and a negative electrode, an electrolytic solution, and a case housing the electrode body and the electrolytic solution. The positive electrode typically has a positive electrode active material layer, and the negative electrode typically has a negative electrode active material layer. The negative electrode is produced, for example, by applying a negative electrode composite material containing a negative electrode active material onto a negative electrode current collector.

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] Among electrode bodies, there are those in which the negative electrode active material layer has an opposing region facing the positive electrode active material layer and a non-opposing region not facing the positive electrode active material layer. According to the study by the present inventor, in such an electrode body, for example, when the electrode body is impregnated with an electrolytic solution, the adhesiveness decreases, or when the negative electrode active material layer expands during charging, small pieces of the negative electrode composite material may peel off from the negative electrode active material layer (particularly the non-opposing region). Since the small pieces of the peeled-off negative electrode composite material are conductive, if the negative electrode side is bridged to the positive electrode side or the case by the negative electrode composite material, there is a risk of a minute short circuit (so-called internal short circuit) occurring inside the power storage device.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing an energy storage device that can suppress the occurrence of internal short circuits caused by negative electrode composite material peeling off from the negative electrode active material layer. [Means for solving the problem]

[0006] The present invention provides a method for manufacturing an energy storage device, comprising: a construction step of constructing a battery assembly by housing an electrode body having a positive electrode having a positive electrode active material layer on a positive electrode current collector and a negative electrode having a negative electrode active material layer on a negative electrode current collector, and an electrolyte inside a case; and an ultrasonic application step of applying ultrasonic waves to the battery assembly after the construction step. The negative electrode active material layer has a facing region facing the positive electrode active material layer and a non-facing region not facing the positive electrode active material layer, and the ultrasonic application step includes applying the ultrasonic waves to the battery assembly while excess electrolyte is present between the case and the electrode body and a load is applied to at least a part of the facing region.

[0007] In the manufacturing method disclosed herein, during the ultrasonic application process, small pieces of the negative electrode composite material that have peeled off from the negative electrode active material layer can be crushed by ultrasonic vibration. This suppresses the occurrence of internal short circuits caused by the peeled-off negative electrode composite material. Furthermore, by applying ultrasound while a load is applied to the opposing region, it is possible to suppress the peeling off of new small pieces of the negative electrode composite material from the opposing region. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic perspective view showing an energy storage device according to one embodiment. [Figure 2] Figure 2 is a schematic longitudinal cross-sectional view along the line II-II in Figure 1. [Figure 3] Figure 3 is a schematic diagram showing the structure of a wound electrode body. [Figure 4] Figure 4 is a flowchart of a manufacturing method according to one embodiment. [Figure 5] Figure 5 is a schematic diagram of the ultrasonic application process according to one embodiment. [Figure 6] Figure 6 is a schematic diagram of the ultrasonic application process according to a modified example. [Modes for carrying out the invention]

[0009] Hereinafter, several preferred embodiments of the technology disclosed herein will be described with reference to the drawings. Matters other than those specifically mentioned herein but necessary for carrying out the technology disclosed herein (for example, the general configuration and manufacturing process of energy storage devices that do not characterize the technology disclosed herein) can be understood as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the content disclosed herein and common technical knowledge in the art. In this specification, the notation "A to B" indicating a range encompasses not only the meaning of A or greater and B or less, but also the meanings of "greater than A" and "less than B".

[0010] In this specification, "energy storage device" refers to all energy storage devices that can be repeatedly charged and discharged by the movement of charge carriers between the positive and negative electrodes via an electrolyte. The concept of energy storage devices includes not only so-called secondary batteries such as lithium-ion secondary batteries and nickel-metal hydride secondary batteries, but also capacitors that utilize chemical reactions, such as lithium-ion capacitors and pseudocapacitance capacitors.

[0011] <Structure of an energy storage device> First, the energy storage device 100 manufactured by the manufacturing method disclosed herein will be described. Figure 1 is a perspective view of the energy storage device 100. Figure 2 is a schematic longitudinal cross-sectional view along line II-II in Figure 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, back, up, and down, respectively, and 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 height direction perpendicular to the short side direction and the long side direction of the energy storage device 100, respectively. The height direction Z here coincides with the vertical direction. However, these are merely directions for the convenience of explanation and do not limit the installation configuration of the energy storage device 100 in any way.

[0012] As shown in Figure 2, the energy storage device 100 comprises a case 10, an electrode body 20, and an electrolyte 80. The energy storage device 100 further comprises a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, and a negative electrode current collector 60. The energy storage device 100 is here a non-aqueous electrolyte secondary battery, more specifically a lithium-ion secondary battery. It is preferable that the energy storage device 100 is a lithium-ion secondary battery.

[0013] Case 10 is a housing that contains the electrode body 20 and the electrolyte 80. As shown in Figure 1, case 10 has a flattened, bottomed rectangular parallelepiped (square) shape. The material of case 10 can be the same as that conventionally used, and there are no particular restrictions. Case 10 is preferably made of metal, and more preferably of aluminum, aluminum alloy, iron, iron alloy (e.g., stainless steel). As shown in Figure 2, case 10 comprises a case body 12 and a sealing plate 14 (lid).

[0014] As shown in Figure 2, the case body 12 is a flat, bottomed rectangular container with an opening 12h on its top surface. As shown in Figure 1, the case body 12 comprises a substantially rectangular bottom wall 12a, a pair of long side walls 12b extending in the height direction Z from the long side of the bottom wall 12a and facing each other, and a pair of short side walls 12c extending in the height direction Z from the short side of the bottom wall 12a and facing each other. The bottom wall 12a faces the opening 12h. The area of ​​the long side walls 12b is larger than the area of ​​the short side walls 12c. In this specification, "substantially rectangular" is a term that includes not only a perfect rectangle (rectangular shape), but also shapes such as those in which the corners connecting the long and short sides of a rectangle are rounded, or shapes with notches in the corners.

[0015] As shown in Fig. 2, the sealing plate 14 is a plate-like member that closes the opening 12h of the case body 12. As shown in Fig. 1, the sealing plate 14 is substantially rectangular in plan view. The sealing plate 14 faces the bottom wall 12a of the case body 12. The case 10 is integrated by joining (e.g., welding) the sealing plate 14 to the peripheral edge of the opening 12h of the case body 12. The case 10 is hermetically sealed.

[0016] As shown in Fig. 2, the sealing plate 14 is provided with a liquid injection hole 15, a gas discharge valve 17, and two terminal lead-out holes 18 and 19. The liquid injection hole 15 is a through hole for injecting the electrolytic solution 80 into the case 10 after assembling the sealing plate 14 to the case body 12. It is preferable that the sealing plate 14 is provided with the liquid injection hole 15. After injecting the electrolytic solution 80, the liquid injection hole 15 is sealed by a sealing member 16. The gas discharge valve 17 is configured to break (open) when the pressure in the case 10 reaches a predetermined value or more and discharge the gas in the case 10 to the outside. The terminal lead-out holes 18 and 19 are formed at both ends in the long side direction Y of the sealing plate 14 (the left end and the right end in Fig. 2), respectively. The terminal lead-out holes 18 and 19 penetrate the sealing plate 14 in the thickness direction (height direction Z). A positive electrode terminal 30 and a negative electrode terminal 40 are attached to the terminal lead-out holes 18 and 19, respectively.

[0017] The positive electrode terminal 30 is arranged on one side in the long side direction Y of the sealing plate 14 (the left end in Figs. 1 and 2). The negative electrode terminal 40 is arranged on the other side in the long side direction Y of the sealing plate 14 (the right end in Figs. 1 and 2). As shown in Fig. 2, the positive electrode terminal 30 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 18. The negative electrode terminal 40 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 19. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are caulked and fixed to the peripheral portion surrounding the terminal lead-out holes 18 and 19 of the sealing plate 14 by caulking. Caulking portions 30c and 40c are formed at the ends on the side of the case body 12 of the positive electrode terminal 30 and the negative electrode terminal 40 (the lower ends in Fig. 2).

[0018] As shown in Figure 2, the positive electrode terminal 30 is electrically connected to the positive electrode 22 of the electrode body 20 (see Figure 3, specifically the positive electrode tab group 23) via the positive electrode current collector 50 inside the case 10. The positive electrode terminal 30 is insulated from the sealing plate 14 by an insulating member 70 and a gasket 90. The positive electrode terminal 30 is preferably made of metal, and more preferably of aluminum or an aluminum alloy.

[0019] The negative electrode terminal 40 is electrically connected to the negative electrode 24 of the electrode body 20 (see Figure 3, specifically the negative electrode tab group 25) via the negative electrode current collector 60 inside the case 10. The negative electrode terminal 40 is insulated from the sealing plate 14 by an insulating member 70 and a gasket 90. The negative electrode terminal 40 is preferably made of metal, and more preferably of copper or a copper alloy. The negative electrode terminal 40 may be constructed by joining and integrating two conductive members. For example, the portion of the negative electrode terminal 40 connected to the negative electrode current collector 60 may be made of copper or a copper alloy, and the portion exposed on the outer surface of the sealing plate 14 may be made of aluminum or an aluminum alloy.

[0020] Plate-shaped positive electrode external conductive member 32 and negative electrode external conductive member 42 are attached to the outer surface (upper surface in Figures 1 and 2) of the sealing plate 14. The positive electrode external conductive member 32 and negative electrode external conductive member 42 are members to which busbars are attached when multiple energy storage devices 100 are electrically connected to each other. The positive electrode external conductive member 32 is electrically connected to the positive electrode terminal 30. The negative electrode external conductive member 42 is electrically connected to the negative electrode terminal 40. The positive electrode external conductive member 32 and negative electrode external conductive member 42 are insulated from the sealing plate 14 by an external insulating member 92. The positive electrode external conductive member 32 and negative electrode external conductive member 42 are preferably made of metal, and more preferably made of aluminum or an aluminum alloy, for example. However, the positive electrode external conductive member 32 and negative electrode external conductive member 42 are not essential and can be omitted in other embodiments.

[0021] The electrode body 20 is housed inside the case 10 (more specifically, inside the case body 12), as shown in Figure 2. The number of wound electrode bodies arranged inside one case 10 is not particularly limited; there may be one or two or more (multiple, for example, two or three). In some embodiments, it is preferable that multiple electrode bodies 20 are arranged side by side in the short-side direction X. One or more electrode bodies 20 may be placed inside the case 10 covered by an insulating electrode body holder. In other words, an electrode body holder may be interposed between the electrode body 20 and the case 10 (more specifically, the case body 12). The electrode body holder is preferably made of resin.

[0022] Figure 3 is a schematic diagram showing the configuration of the electrode body 20. As shown in Figure 3, the electrode body 20 has a positive electrode 22 having a positive electrode active material layer 22a on a positive electrode current collector 22c, and a negative electrode 24 having a negative electrode active material layer 24a on a negative electrode current collector 24c. The positive electrode 22 and the negative electrode 24 are insulated from each other by a separator 26. The electrode body 20 in this embodiment is a wound electrode body in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are stacked in an insulated state (here via a strip-shaped separator 26) and wound around a winding axis WL. However, in other embodiments, the electrode body 20 may be a laminated electrode body in which a plurality of rectangular positive electrodes and a plurality of rectangular negative electrodes are stacked in an insulated state.

[0023] In this embodiment, the electrode body 20 is positioned inside the case 10 with the winding axis WL oriented substantially parallel to the long side direction Y. The winding axis WL direction is the width direction of the electrode body 20, and in this embodiment, it coincides with the long side direction Y. The electrode body 20 is positioned inside the case 10 with the winding axis WL oriented along the bottom wall 12a and substantially perpendicular to the long side wall 12b and the short side wall 12c. However, in other embodiments, the electrode body 20 may be positioned inside the case 10 with the winding axis WL oriented substantially parallel to the height direction Z.

[0024] The electrode body 20 has a flattened outer shape. The electrode body 20 has a pair of flat portions 20f that extend along the long side direction Y (winding axis WL direction) and a pair of curved portions 20r (R portion) that connect the pair of flat portions 20f. When the outer shape of the electrode body 20 is flattened, for example, when forming the curved portion 20r, the negative electrode composite material may easily fall off from the negative electrode active material layer 24a. Therefore, it is preferable to apply the technology disclosed herein.

[0025] The flat portion 20f has a flat outer surface. The pair of flat portions 20f each face the pair of long side walls 12b of the case body 12. The pair of flat portions 20f each extend along the long side walls 12b. In this specification, "flat outer surface" is not limited to perfectly flat surfaces, but includes cases where there are slight steps, curves, recesses, protrusions, etc., when viewed microscopically.

[0026] The curved portion 20r has a curved outer surface. The pair of curved portions 20r face the bottom wall 12a and the sealing plate 14 of the case body 12, respectively. In this embodiment, it is preferable that the electrode body 20 is arranged inside the case 10 such that the stacking direction of the positive electrode 22 and the negative electrode 24 in the flat portion 20f (the thickness direction of the electrode body 20) coincides with the short side direction X (the direction perpendicular to the long side wall 12b).

[0027] The positive electrode 22 can be the same as in the conventional design and is not particularly limited. As shown in Figure 3, the positive electrode 22 of this embodiment has a positive electrode current collector 22c and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed to at least one surface of the positive electrode current collector 22c. Any conventionally known material that can be used in general energy storage devices (e.g., lithium-ion secondary batteries) can be used for each component constituting the positive electrode 22 without particular limitation. The positive electrode current collector 22c is in the shape of a strip here. The positive electrode current collector 22c is made of a conductive metal such as aluminum, aluminum alloy, nickel, or stainless steel. The positive electrode current collector 22c is a metal foil, specifically aluminum foil, here.

[0028] Multiple positive electrode tabs 22t are provided at one end (the left end in Figure 3) of the positive electrode current collector 22c in the long side direction Y (width direction, winding axis WL direction). The positive electrode tabs 22t are part of the positive electrode current collector 22c and are made of metal foil (aluminum foil). The multiple positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the positive electrode 22. Each of the multiple positive electrode tabs 22t is convex and protrudes toward one side in the long side direction Y (the left side in Figure 3). The multiple positive electrode tabs 22t extend beyond the separator 26 in the long side direction Y. The multiple positive electrode tabs 22t are stacked at one end (the left end) in the long side direction Y to form a positive electrode tab group 23. As shown in Figure 2, the positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collector 50.

[0029] As shown in Figure 3, 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 a positive electrode active material (for example, a lithium transition metal composite oxide such as a lithium nickel cobalt manganese-containing 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 positive electrode active material, such as conductive materials, binders, and various additives. As a conductive material, for example, a carbon material such as acetylene black (AB) can be used. As a binder, for example, polyvinylidene fluoride (PVdF) can be used.

[0030] Although not particularly limited, in high-capacity energy storage devices 100 used for automotive applications, etc., as shown in Figure 3, the length Lc (average value, excluding the portion formed on the positive electrode tab 22t) of the positive electrode active material layer 22a in the long side direction Y (width direction, winding axis WL direction) is preferably 150 mm or more, more preferably 200 mm or more, and even more preferably 250 mm or more. The length Lc is shorter than the length La in the long side direction Y of the negative electrode active material layer 24a, which will be described later, and may be approximately 400 mm or less, for example, 350 mm or less.

[0031] The positive electrode protective layer 22p is a layer configured to have lower electrical conductivity than the positive electrode active material layer 22a. As shown in Figure 3, the positive electrode protective layer 22p is provided between the positive electrode current collector 22c and the positive electrode active material layer 22a in the long side direction Y. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p preferably contains an inorganic filler (for example, ceramic particles such as alumina). The positive electrode protective layer 22p may also contain optional components other than the inorganic filler, such as conductive materials, binders, and various additives. The conductive materials and binders may be the same as those exemplified as those that can be included in the positive electrode active material layer 22a. However, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments.

[0032] As shown in Figure 3, the negative electrode 24 includes a negative electrode current collector 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector 24c. The components constituting the negative electrode 24 can be made of conventionally known materials that can be used in general energy storage devices (e.g., lithium-ion secondary batteries) without particular limitation. The negative electrode current collector 24c is in the form of a strip. The negative electrode current collector 24c is made of a conductive metal such as copper, copper alloy, nickel, or stainless steel. Preferably, the negative electrode current collector 24c contains copper or a copper alloy. In this case, the negative electrode current collector 24c is a metal foil, specifically a copper foil.

[0033] Multiple negative electrode tabs 24t are provided at the other end (right end in Figure 3) of the negative electrode current collector 24c in the long side direction Y (width direction, winding axis WL direction). The negative electrode tabs 24t are here part of the negative electrode current collector 24c and are made of metal foil (copper foil). The multiple negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the negative electrode 24. Each of the multiple negative electrode tabs 24t is convex and protrudes toward the other side (right side in Figure 3) in the long side direction Y. The multiple negative electrode tabs 24t extend beyond the separator 26 in the long side direction Y. The multiple negative electrode tabs 24t are stacked at the other end (right end) in the long side direction Y to form a negative electrode tab group 25. As shown in Figure 2, the negative electrode tab group 25 is here electrically connected to the negative electrode terminal 40 via the negative electrode current collector 60.

[0034] As shown in Figure 3, 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 a negative electrode active material (for example, a carbon material such as graphite or a silicon-containing material) that can reversibly absorb and release charge carriers. The negative electrode active material layer 24a may also contain optional components other than the negative electrode active material, such as binders, thickeners, and various additives. When the total solid content of the negative electrode active material layer 24a is taken as 100% by mass, the negative electrode active material may account for approximately 80% by mass or more, typically 90% by mass or more, for example, 95% by mass or more.

[0035] As a binder, for example, rubbers such as styrene-butadiene rubber (SBR) and its modified forms, or acrylic resins such as polyacrylic acid (PAA) can be used. As a thickener, for example, celluloses such as carboxymethylcellulose (CMC) and methylcellulose (MC) can be used. The negative electrode active material layer 24a preferably contains the negative electrode active material and the binder. When a binder is used, the proportion of the binder in the negative electrode active material layer 24a is preferably 0.1 to 10% by mass, and more preferably 0.2 to 5% by mass. When a thickener is used, the proportion of the thickener in the negative electrode active material layer 24a is preferably 0.1 to 10% by mass, and more preferably 0.2 to 5% by mass.

[0036] As shown in Figure 3, in this embodiment, the length La (average value, excluding the portion formed on the negative electrode tab 24t) of the negative electrode active material layer 24a in the long side direction Y (width direction, winding axis WL direction) is longer than the length Lc of the positive electrode active material layer 22a in the long side direction Y. Although not particularly limited, the length La of the negative electrode active material layer 24a is preferably 200 mm or more, and more preferably 250 mm or more, from the viewpoint of increasing capacity. The length La may be, for example, 1000 mm or less, or 500 mm or less.

[0037] The negative electrode active material layer 24a of this embodiment has a facing region A1 that faces the positive electrode active material layer 22a and a non-facing region A2 that does not face the positive electrode active material layer 22a. The facing region A1 and the non-facing region A2 are each provided in a strip shape along the longitudinal direction of the strip-shaped negative electrode current collector 24c. In the long side direction Y (width direction, winding axis WL direction), the facing region A1 is provided in the center. The non-facing region A2 is provided at both ends of the facing region A1 in this embodiment. However, in other embodiments, the non-facing region A2 may be provided only on one side in the long side direction Y.

[0038] In the flat portion 20f of the electrode body 20, the length of the opposing region A1 in the long side direction Y is the same as the length Lc of the positive electrode active material layer 22a in the long side direction Y. Within the flat portion 20f, the opposing region A1 is a region with length Lc × height Hf. Although not particularly limited, the height Hf is preferably 110 mm or less, more preferably 50 to 110 mm, and even more preferably 70 to 100 mm.

[0039] As shown in Figure 3, the separator 26 is a component that insulates the positive electrode active material layer 22a of the positive electrode 22 and the negative electrode active material layer 24a of the negative electrode 24. The length Ls of the separator 26 in the long side direction Y (width direction, winding axis WL direction) is typically the same as or longer than the length La of the negative electrode active material layer 24a in the long side direction Y. As the separator 26, a porous sheet made of resin, such as polyethylene (PE) or polypropylene (PP), is preferred. The separator 26 may have functional layers such as an adhesive layer or a heat resistance layer (HRL) on the surface of the base material portion made of a porous sheet made of resin. The adhesive layer is a layer containing a binder. The heat resistance layer is a layer containing, for example, an inorganic filler such as alumina, silica, boehmite, magnesia, or titania, and a binder such as PVdF. The heat resistance layer can also serve as the adhesive layer. The composition of the heat-resistant layer and adhesive layer may be the same as in the conventional method.

[0040] The electrolyte 80 may be the same as in the conventional method and is not particularly limited. Typically, the electrolyte 80 is a non-aqueous electrolyte containing a non-aqueous solvent (organic solvent) and a supporting salt (electrolyte salt). It is preferable that the electrolyte 80 is a non-aqueous electrolyte. Examples of non-aqueous solvents include carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorine-containing lithium salts such as LiPF6 and LiBF4, and fluorine-containing sodium salts such as NaPF6. The electrolyte 80 may contain additives as needed. The viscosity of the electrolyte 80 is generally preferably 1 to 10 mPa·s, and more preferably 2 to 5 mPa·s. In this specification, "viscosity" refers to the shear rate of 10 to 600 s measured at a temperature of 25°C using a commercially available rheometer. -1 This refers to viscosity (mPa·s) measured using a thermometer.

[0041] As shown in Figure 2, in this embodiment, there is excess electrolyte 80 (hereinafter also referred to as "excess electrolyte") that is not impregnated into the electrode body 20 between the case 10 and the electrode body 20. The liquid level H of the excess electrolyte 80 is located above the center of the height Z of the side walls (long side wall 12b and short side wall 12c) of the case 10. For example, when the state of charge (SOC) is less than 10%, it is preferable that the liquid level H of the excess electrolyte 80 is located vertically above the lower end of the negative electrode tab group 25 (multiple negative electrode tabs 24t). That is, it is preferable that at least a portion of the negative electrode tab group 25 (multiple negative electrode tabs 24t) is immersed in the excess electrolyte 80.

[0042] <Manufacturing method for energy storage devices> The energy storage device 100 described above can be manufactured by a manufacturing method that includes the following steps: a construction step of constructing a battery assembly, and an ultrasonic application step of applying ultrasonic waves to the battery assembly after the construction step. Other manufacturing processes may be the same as conventional methods. As will be described in detail later, in the manufacturing method disclosed herein, small pieces of negative electrode composite material that have peeled off from the negative electrode active material layer 24a can be crushed (pulverized) in the ultrasonic application step after the construction step. As a result, the energy storage device 100 can suppress the occurrence of internal short circuits caused by peeled-off negative electrode composite material.

[0043] Figure 4 is a flowchart of a manufacturing method according to one embodiment. The manufacturing method in Figure 4 includes, in this order, a construction step (step S1), an impregnation step (step S2), a pre-charging step (step S3), an ultrasonic application step (step S4), an activation step (step S5), and an injection hole sealing step (step S6). However, steps other than the construction step (step S1) and the ultrasonic application step (step S4) are optional, and some or all of them may be omitted in other embodiments. For example, the impregnation step (step S2) and / or the pre-charging step (step S3) may be omitted. Furthermore, the manufacturing method disclosed herein may include other steps at any stage. For example, a wound electrode fabrication step may be included before the construction step (step S1). Alternatively, an aging step may be included after the injection hole sealing step (step S6). Each step will be described in detail below.

[0044] In the construction step (step S1), the electrode body 20 and the electrolyte 80 are housed inside the case 10 to construct the battery assembly. This step can be carried out in the same manner as in the conventional method. In a preferred embodiment, this step typically includes a placement step (step S1-1), a welding and joining step (step S1-2), and a liquid injection step (step S1-3) in this order. In addition, other steps may be included at any stage. In this specification, "battery assembly" refers to an intermediate product comprising the case 10, the electrode body 20, and the electrolyte 80 in the manufacturing process of the energy storage device 100.

[0045] In the arrangement step (step S1-1), the electrode body 20 is placed inside the case body 12. In this embodiment, for example, first, an electrode body 20 is prepared, which has a positive electrode 22 having a positive electrode active material layer 22a on a positive electrode current collector 22c, and a negative electrode 24 having a negative electrode active material layer 24a on a negative electrode current collector 24c. In this embodiment, the negative electrode active material layer 24a is wider than the positive electrode active material layer 22a and has a facing region A1 that faces the positive electrode active material layer 22a and a non-facing region A2 that does not face the positive electrode active material layer 22a. Next, the electrode body 20 is integrated with the sealing plate 14 to create a combined product. Next, the sealing plate 14 is fitted into the opening 12h of the case body 12. As a result, the electrode body 20 is housed inside the case body 12 with the winding axis WL oriented along the bottom wall 12a. Next, in the welding process (process S1-2), the sealing plate 14 is welded to the periphery of the opening 12h of the case body 12, thereby integrating the case body 12 and the sealing plate 14.

[0046] Next, in the liquid injection step (step S1-3), a predetermined amount of electrolyte 80 is injected into the case 10 through the injection hole 15 of the sealing plate 14. The injection may be carried out under atmospheric pressure, or it may be carried out under reduced pressure below atmospheric pressure inside the case 10, for example, to improve the impregnation of the electrolyte 80 into the electrode body 20. The predetermined amount of electrolyte 80 may be injected all at once, or it may be injected in multiple stages in N steps (where N is an integer of 2 or more).

[0047] In this embodiment, the amount of electrolyte 80 injected is adjusted so that excess electrolyte 80 (electrolyte not impregnated into the electrode body 20) is secured between the case 10 and the electrode body 20 during the ultrasonic application process (step S4) described later. In other words, the amount of electrolyte 80 injected is adjusted so that the liquid level H (see Figure 2) of the excess electrolyte 80 is at a desired position during the ultrasonic application process (step S4). In a preferred example, considering the amount of electrolyte 80 impregnated into the electrode body 20 during the impregnation process (step S2) described later, it is advisable to inject a larger amount of electrolyte 80 so that the liquid level is higher than the desired liquid level H during the ultrasonic application process (step S4).

[0048] In some embodiments, it is preferable to pour the electrolyte 80 such that the liquid level H of the excess electrolyte 80 is approximately 1 cm or more, for example 3 cm or more, from the bottom wall 12a of the case 10 during the ultrasonic application process (process S4). In particular, it is preferable to pour the electrolyte 80 such that the liquid level H of the excess electrolyte 80 is vertically above the lower end of the negative electrode tab group 25 (multiple negative electrode tabs 24t) during the ultrasonic application process. By setting the amount of excess electrolyte 80 in the ultrasonic application process to a predetermined amount or more, small pieces of negative electrode composite material that peel off from the negative electrode active material layer 24a during the ultrasonic application process are more easily broken down.

[0049] In some embodiments, the ratio of the volume Vl of the electrolyte 80 injected to the internal volume Va of case 10 (Vl / Va) is preferably about 0.2 to 0.4, and more preferably about 0.25 to 0.3. For example, when the length La of the long side Y of the negative electrode active material layer 24a is 200 mm or more (preferably 250 mm or more), the amount of electrolyte 80 injected can be about 200 to 600 g, for example, 300 to 500 g or 400 to 450 g.

[0050] In the impregnation process (process S2), after the construction process (specifically the electrolyte injection process), the impregnation of the electrolyte 80 into the interior of the electrode body 20, particularly the central part in the long side direction Y, is enhanced. This process can be carried out in the same manner as in the conventional process. In some embodiments, it is preferable to leave (hold) the battery assembly at atmospheric pressure for a predetermined time. In some embodiments, the battery assembly may be housed in a pressure-adjustable chamber, and the chamber may be pressurized and / or depressurized with the electrolyte injection hole 15 open (in other words, with no pressure difference between the inside and outside of the case 10). This promotes the impregnation of the electrolyte 80, making it easier to impregnate the interior of the electrode body 20 with the electrolyte 80 in a short time. This process may be carried out in a room temperature environment (approximately 25°C ± 10°C). The required time for this process is generally 1 to 200 hours, preferably 2 to 100 hours.

[0051] In the pre-charging step (step S3), after the construction step (in this case, after the impregnation step) and before the ultrasonic application step, the battery assembly is charged to a state of charge (SOC) of 10% or less. This step is typically the first charge of the battery assembly. By charging the battery assembly, small pieces of negative electrode composite material that have peeled off from the negative electrode active material layer 24a in the ultrasonic application step (step S4) described later are more easily broken down. Therefore, the effects of the technology disclosed herein are more easily realized at a high level. Charging can be carried out in the same manner as conventional methods, except that the SOC is within the above range. In some embodiments, an external power supply is connected between the positive electrode terminal 30 and the negative electrode terminal 40 of the battery assembly, and charging is performed until a predetermined target voltage is reached between the terminals. Preferably, the battery assembly is charged to a state of charge (SOC) of 1% or more, more preferably to 2% or more, and even more preferably to 5% or more. The charging rate can be, for example, about 0.01 to 1C. Charging can be done once, or it can be repeated two or more times, for example, with a discharge in between. This process can also be carried out in a normal temperature environment (approximately 25°C ± 10°C).

[0052] In some embodiments, it is preferable to charge the battery assembly with a load applied to at least a portion of the opposing region A1 of the electrode body 20 during this process. For example, if the electrode body 20 is a flat-shaped wound electrode body as in this embodiment, it is preferable to charge the battery assembly with a load applied to at least a portion (preferably 50% or more, more preferably 80% or more, for example, the entire opposing region A1 located on the flat portion 20f) of the opposing region A1 located on the flat portion 20f. As another example, if the electrode body 20 is a laminated electrode body, it is preferable to charge the battery assembly with a load applied to substantially the entire opposing region A1. By charging the battery assembly with a load applied to at least a portion of the opposing region A1, even if the electrode body 20 (particularly the negative electrode active material layer 24a) expands during charging, the negative electrode active material layer 24a is less likely to peel off from the negative electrode current collector 24c in the opposing region A1.

[0053] Furthermore, in light of the above objective (suppression of peeling of the negative electrode active material layer 24a in the opposing region A1 during charging), the non-opposing region A2 may or may not be under load. Also, the curved portion 20r (opposing region A1 located in the curved portion 20r) is subjected to a force similar to that of the flat portion 20f (opposing region A1 located in the flat portion 20f) due to the tension applied during winding and the restraint of the flat portion 20f, so peeling of the negative electrode active material layer 24a is unlikely to occur. Therefore, it is not necessary to apply a load in this process.

[0054] The load on the opposing region A1 is preferably applied from the stacking direction of the positive electrode 22 and the negative electrode 24 (the thickness direction of the electrode body 20). In one preferred embodiment, the case 10 of the battery assembly is restrained from the thickness direction of the electrode body 20 (here, the short side direction X), and a specified load (restraining pressure) is applied to the flat portion 20f. Specifically, first, a cell press machine equipped with a pair of restraining plates is prepared. Also, a pair of pressing members for pressing the opposing region A1 is prepared. Typically, the pressing members preferably have a surface area that is the same as or smaller than the long side wall 12b of the case 10. The pressing members preferably have a surface area that is the same as or larger than the area of ​​the opposing region A1 located on the flat portion 20f.

[0055] The length of the pressing member in the long side direction Y is preferably the same as or longer than the length of the opposing region A1 (length Lc of the positive electrode active material layer 22a). The length of the pressing member in the long side direction Y may also be the same as or longer than the length La of the negative electrode active material layer 24a. Furthermore, the length (height) of the pressing member in the height direction Z is preferably the same as or longer than the height Hf of the opposing region A1.

[0056] Next, the pair of pressing members prepared are positioned opposite the pair of long side walls 12b of the battery assembly, and the electrode body 20 inside the case 10 is sandwiched between the pair of pressing members from both sides in the short-side direction X. At this time, by aligning the centers of the pressing members with the centers of the long side walls 12b, a balanced load can be applied to the long side walls 12b. In this state, the battery assembly and the pair of pressing members are placed between the pair of restraining plates of the press machine, and a predetermined pressing force (load) is applied to the battery assembly. From the viewpoint of stably exhibiting the above effect (suppression of peeling of the negative electrode active material layer 24a during charging) at a high level, the load is preferably about 1kN or more, and more preferably 5kN or more. There is no particular upper limit to the load, but for example, 50kN or less is preferred, 20kN or less is more preferred, and 10kN or less is even more preferred.

[0057] In the ultrasonic application step (step S4), ultrasonic waves are applied to the battery assembly after the construction step (in this case, after the pre-charging step). Specifically, ultrasonic waves are applied to the battery assembly when there is excess electrolyte 80 between the case 10 and the electrode body 20, and a load is applied to at least a part of the opposing region A1. The ultrasonic waves may be applied once, or two or more times with a pause in between. This step may be carried out in a room temperature environment (approximately 25°C ± 10°C).

[0058] According to the inventors' findings, in a process prior to this step, small pieces of the negative electrode composite material may peel off from the negative electrode active material layer 24a (particularly the non-opposing region A2). According to the inventors' findings, the size of these small pieces is typically 5 mm. 2 (for example, 1-4mm) 2 (Approximately), but some are several hundred mm in size. 2 (For example, 100-200mm) 2 This can be the case to a certain extent. These small pieces of negative electrode composite material are typically detached from the negative electrode 24 and are either immersed in or floating in the excess electrolyte 80. In this process, the small pieces of negative electrode composite material that have peeled off from the negative electrode active material layer 24a can be broken down by ultrasonic vibration. Furthermore, by applying ultrasonic waves while a load is applied to the opposing region A1, it is possible to suppress the peeling off of new negative electrode composite material from the opposing region A1 that contributes to charging and discharging when ultrasonic waves are applied.

[0059] Although not intended to be interpreted in a particularly restrictive way, the mechanism by which ultrasonic waves can break down small pieces of negative electrode composite material is thought to be as follows: By applying ultrasonic waves to the battery assembly, tiny bubbles are generated in the electrolyte 80 (especially the excess electrolyte 80) inside the battery assembly. It is thought that the bursting of these bubbles can break down the small pieces of negative electrode composite material. In fact, as described in the test examples below, the larger the amount of excess electrolyte 80 (the area where bubbles are generated), the easier it is for the small pieces of negative electrode composite material to be broken down. In some embodiments, it is preferable that the liquid level H of the excess electrolyte 80 in this process is approximately 1 cm or more, for example 3 cm or more, from the bottom wall 12a of the case 10. In some other embodiments, it is preferable that the liquid level H of the excess electrolyte 80 is located above the center of the height Z of the side walls (long side wall 12b and short side wall 12c) of the case 10.

[0060] In some other embodiments, it is preferable that the liquid level H of the excess electrolyte 80 is located vertically above the lower end of the negative electrode tab group 25 (multiple negative electrode tabs 24t) in this process. In other words, it is preferable that at least a portion of the negative electrode tab group 25 (multiple negative electrode tabs 24t) is immersed in the excess electrolyte 80. According to the inventors' research, near the negative electrode tab group 25, detached negative electrode material is arranged to span across the positive electrode 22, making it easy for minute short circuits to occur. By immersing at least a portion of the negative electrode tab group 25 (multiple negative electrode tabs 24t) in the excess electrolyte 80, the negative electrode material adhering to the negative electrode tab group 25 and the negative electrode current collector 60 is more easily broken down. Therefore, the effects of the technology disclosed herein are exhibited at a high level. It is more preferable that the liquid level H of the excess electrolyte 80 is located at the same level as or above the upper end of the negative electrode tab group 25 (multiple negative electrode tabs 24t). In other words, it is more preferable that the entire negative electrode tab group 25 (multiple negative electrode tabs 24t) is immersed in the excess electrolyte 80.

[0061] In this embodiment, the positive electrode tab group 23 (multiple positive electrode tabs 22t) is positioned symmetrically to the negative electrode tab group 25 (multiple negative electrode tabs 24t) in the long side direction Y. In other words, the positive electrode tab group 23 and the negative electrode tab group 25 are at the same height from the bottom wall 12a. Therefore, if the liquid level H of the excess electrolyte 80 is above the lower end of the negative electrode tab group 25, the positive electrode tab group 23 is also immersed in the excess electrolyte 80. This allows for the effective dissolution of negative electrode material adhering to the positive electrode tab group 23 and the positive electrode current collector 50, and the effects of the technology disclosed herein are demonstrated at a high level.

[0062] In some embodiments, it is preferable to perform this process while maintaining the state of the battery assembly at the completion of the preceding pre-charging process (process S3). That is, it is preferable to perform this process with the state of charge (SOC) adjusted in the preceding pre-charging process (a state in which the SOC is charged to a range of 10% or less). Furthermore, if the battery assembly was restrained in the preceding pre-charging process (process S3), it is preferable to perform this process while maintaining the restrained state (restraining pressure). This improves workability and productivity. The load applied to the opposing region A1 in this process may be the same as that in the preceding pre-charging process, or it may be different. From the viewpoint of stably exhibiting the above effect (suppression of peeling of the opposing region A1) at a high level, the load is generally preferably 1kN or more, and more preferably 5kN or more. There is no particular upper limit to the load, but for example, it is preferably 50kN or less, more preferably 20kN or less, and even more preferably 10kN or less.

[0063] Regarding the non-opposing region A2, it may be under load or unloaded conditions, similar to the preliminary charging process (process S3). Furthermore, the curved portion 20r (opposing region A1 located at the curved portion 20r) is subjected to a force similar to that of the flat portion 20f (opposing region A1 located at the flat portion 20f) due to the tension applied during winding and the restraint of the flat portion 20f, making delamination of the negative electrode active material layer 24a unlikely. Therefore, it is not necessary to apply a load in this process.

[0064] The ultrasonic application conditions to the battery assembly (e.g., ultrasonic frequency and application time) are preferably adjusted as appropriate so that the small pieces of the negative electrode composite material are properly crushed. More specifically, the ultrasonic application conditions are preferably set so that the major axis of the small pieces of the negative electrode composite material is shorter than the phase difference between the negative electrode 24 near the positive electrode tab 22t and / or the phase difference between the positive electrode 22 near the negative electrode tab 24t. It is even more preferable to set the ultrasonic application conditions so that the major axis of the small pieces of the negative electrode composite material is shorter than the shortest distance between the negative electrode current collector 60 and the case 10 (specifically, the long side wall 12b and the sealing plate 14). In some embodiments, it is even more preferable to set the ultrasonic application conditions so that the major axis of the small pieces of the negative electrode composite material is approximately 1.5 mm or less, preferably 1.0 mm or less, and more preferably 0.5 mm or less.

[0065] According to the inventors' research, the optimal ultrasonic application conditions may vary depending on, for example, the size of the small pieces of the negative electrode material to be crushed and the amount of excess electrolyte 80. Table 1 below shows the sizes of the small pieces of the negative electrode material to be crushed, ranging from 1 to 4 mm. 2 The results of the preliminary experiment were obtained when the liquid level H of the excess electrolyte 80 was 1 cm from the bottom wall 12a. Table 2 below shows the results for when the size of the small pieces of the target negative electrode composite material is 100 to 200 mm. 2 The results of the preliminary experiment were obtained when the liquid level H of the excess electrolyte 80 was 1 cm from the bottom wall 12a. Table 3 below shows the results for small pieces of negative electrode material in question, with sizes ranging from 100 to 200 mm. 2 This is the result of a preliminary experiment where the liquid level H of the excess electrolyte 80 is 3 cm from the bottom wall 12a.

[0066] The negative electrode composite material used contained graphite (C) as the negative electrode active material, SBR as a binder, and CMC as a thickener in a mass ratio of C:SBR:CMC = 98.5:1:0.5. The electrolyte used was a mixed solvent containing EC, EMC, and DMC in a volume ratio of 3:3:4, with LiPF6 as a supporting salt at a concentration of 1.1 mol / L. In the judgment column of Tables 1 to 3, "×" indicates that the small pieces of the negative electrode composite material retain their shape without being crushed, "〇" indicates that the small pieces of the negative electrode composite material are partially crushed and have a major diameter of 0.5 mm or less, and "◎" indicates that the small pieces of the negative electrode composite material are completely crushed and have a major diameter of 0.5 mm or less.

[0067] [Table 1]

[0068] [Table 2]

[0069] [Table 3]

[0070] As shown in Tables 1 and 2, the above results show that the lower the ultrasonic frequency, the more effectively the small pieces of the negative electrode composite can be broken down. Therefore, in some embodiments, it is preferable to set the ultrasonic frequency to approximately 150 kHz or less, more preferably to 100 kHz or less, and even more preferably to 50 kHz or less when dealing with relatively large pieces of negative electrode composite, for example, 44 kHz or less, or 40 kHz or less. This shortens the time required for this process and improves productivity. On the other hand, since a low ultrasonic frequency may affect the electrode body 20, in some embodiments, it is more preferable to set the ultrasonic frequency to 20 kHz or higher, and even more preferably to 30 kHz or higher, for example, 38 kHz or higher.

[0071] Furthermore, as described above, the application time of ultrasound may vary depending on the amount of excess electrolyte 80 and the set frequency. The application time of ultrasound is not particularly limited as long as the small pieces of the negative electrode composite material are sufficiently broken down, but is generally preferred to be within 300 seconds (5 minutes), more preferably within 180 seconds (3 minutes), even more preferably within 120 seconds (2 minutes), and particularly preferably within 60 seconds (1 minute). This shortens the time required for this process and improves productivity. In addition, according to the inventors' research, heat is generated when ultrasound is applied, so if this process is prolonged, the electrolyte 80 may be heated. By shortening the application time of ultrasound, it is possible to suppress the heating and vaporization of the electrolyte 80.

[0072] Furthermore, as shown in Tables 2 and 3, increasing the volume of excess electrolyte 80 when applying ultrasound makes it easier to break down small pieces of the negative electrode composite, allowing the effects of the disclosed technology to be exhibited more stably and at a higher level. In addition, the time required for this process can be shortened.

[0073] In some embodiments, it is preferable to apply ultrasound with the case 10 open (without sealing the case 10). Here, it is preferable to apply ultrasound with the liquid injection hole 15 of the sealing plate 14 open. This allows the generated gas to be exhausted to the outside of the case 10 even if the electrolyte 80 decomposes and gas is generated due to the application of ultrasound. As a result, gas is less likely to remain inside the electrode body 20, and the occurrence of so-called gas jamming can be suppressed. Consequently, stable charge and discharge performance can be achieved.

[0074] The application of ultrasound to the battery assembly can be carried out in the same manner as in the conventional method. For example, this can be done using an ultrasonic device 200 as shown in Figure 5. The ultrasonic device 200 in Figure 5 comprises a bathtub 210 filled with liquid and an ultrasonic generating unit 220 that applies ultrasound to the bathtub 210. The bathtub 210 has a space capable of accommodating a battery assembly 100A with a load applied to it. The bottom surface of the bathtub 210 is larger than the bottom wall 12a of the battery assembly 100A. In this case, the bathtub 210 is configured to accommodate multiple battery assemblies 100A simultaneously. Specifically, it is configured to accommodate multiple battery assemblies 100A, with a pair of long side walls 12b sandwiched between pressing members PM, together with a press machine 110. The liquid in the bathtub 210 preferably has a viscosity equivalent to that of the electrolyte 80 (typically a non-aqueous electrolyte) used in the battery assembly 100A, and more preferably contains the same solvent (typically a non-aqueous solvent) as the electrolyte 80 used in the battery assembly 100A. The liquid level H1 in the bathtub 210 is preferably the same as or higher than the liquid level H of the electrolyte 80 in the battery assembly 100A. The ultrasonic generating unit 220 is configured to allow setting of the ultrasonic application conditions. In the ultrasonic device 200 of Figure 5, ultrasonic waves can be applied (in this case, irradiated) from the ultrasonic generating unit 220 with the battery assembly 100A housed in the bathtub 210.

[0075] In some embodiments, it is preferable to measure the battery characteristics of the battery assembly before and after applying ultrasound in this process. This allows for confirmation of the effect of applying ultrasound. Examples of battery characteristics to confirm the effect include, for example, the voltage between the positive terminal 30 and the negative terminal 40, the voltage between the case 10 and the negative terminal 40, and the self-discharge amount of the battery assembly. If no effect (improvement) can be confirmed by measuring such battery characteristics, the application conditions of the ultrasound (frequency, etc.) may be changed, and ultrasound may be applied to the battery assembly again.

[0076] In the activation step (step S5), after the ultrasonic application step, the battery assembly is charged until its state of charge (SOC) reaches 10% or more. This step can be carried out in the same manner as the conventional or earlier pre-charging step (step S3), except that the SOC is within the above range. The battery assembly is preferably charged until its state of charge (SOC) reaches 20% or more, more preferably until it reaches 50% or more, and may be charged to, for example, 20-90% or more. The charging rate can be, for example, around 0.1-2C. The charging rate may be higher than that of the earlier pre-charging step (step S3). Charging may be performed only once, or it may be repeated two or more times, for example, with a discharge in between. This step may be carried out in a room temperature environment (around 25°C ± 10°C).

[0077] In some embodiments, it is preferable to charge the battery assembly in this step with a load applied to at least a portion of the opposing region A1 of the electrode body 20. The region on the electrode body 20 to which the load is applied, the method of applying the load, the size of the pressing member PM, etc., may be the same as in the preceding pre-charging step (step S3). The load applied to the opposing region A1 may be the same as or different from that in the preceding pre-charging step (step S3) and / or ultrasonic application step (step S4). In some embodiments, it is preferable that the load is higher than that in the preceding pre-charging step (step S3) and / or ultrasonic application step (step S4). The load is generally preferably 1 kN or more, and more preferably 5 kN or more. There is no particular upper limit to the load, but for example, it is preferably 50 kN or less, and more preferably 20 kN or less.

[0078] In the liquid injection hole sealing step (step S6), the liquid injection hole 15 is sealed with a sealing member 16 while the inside of the case 10 is at atmospheric pressure or under reduced pressure. The sealing member 16 is, for example, a rivet. The sealing of the liquid injection hole 15 can be done in the same way as in the conventional method. This seals the case 10 airtight. In this way, the energy storage device 100 can be manufactured to suitability.

[0079] As described above, in the manufacturing method disclosed herein, in the ultrasonic application step (step S4), it is possible to suppress the peeling off of small pieces of negative electrode material from the opposing region A1 while crushing the peeled-off pieces of negative electrode material. Preferably, the pieces of negative electrode material can be crushed to a size that does not pose a risk of short circuits. This suppresses the occurrence of internal short circuits caused by peeled-off negative electrode material. Consequently, it is possible to suppress the deterioration of battery performance (e.g., voltage drop) and reduce the deterioration of the yield rate. Therefore, the productivity of the energy storage device 100 can be improved.

[0080] <Applications of energy storage devices> The energy storage device 100 can be used for various purposes, but it is particularly suitable as a power source (driving power supply) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0081] Although several embodiments of the present invention have been described above, these embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed herein and common technical knowledge in the art. 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, if a technical feature is not described as essential, it may be deleted as appropriate.

[0082] <Variation> For example, in the embodiment described above, the ultrasonic application process was performed using an ultrasonic device 200 as shown in Figure 5, but it is not limited to this. In the ultrasonic application process, an ultrasonic generator 300 as shown in Figure 6 can also be used. The ultrasonic generator 300 is, for example, a homogenizer or an ultrasonic horn. In Figure 6, a pair of long side walls of the battery assembly 100B are sandwiched between pressing members PM. In this state, the ultrasonic generator 300 is in contact with the negative electrode external conductive member 42 attached to the sealing plate 14. The ultrasonic generator 300 is connected to the negative electrode terminal 40 via the negative electrode external conductive member 42, and ultrasonic waves are applied. This allows for efficient disintegration of small pieces of negative electrode composite material adhering to the conductive path on the negative electrode side, for example, a group of negative electrode tabs 25 (a group of negative electrode tabs 24t), and / or the negative electrode current collector 60, using ultrasonic waves.

[0083] In this modified version, the ultrasonic generator 300 is also in contact with the positive electrode external conductive member 32. The ultrasonic generator 300 is connected to the positive electrode terminal 30 via the positive electrode external conductive member 32. This allows for efficient disintegration of the conductive path on the positive electrode side, for example, the multiple positive electrode tab groups 23 (multiple positive electrode tabs 22t), and / or small pieces of negative electrode composite material adhering to the positive electrode current collector 50, using ultrasound. In other modified versions, the ultrasonic generator 300 may be connected to the case 10 (for example, the side wall of the case body 12) and ultrasound may be applied.

[0084] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Item 1: A method for manufacturing an energy storage device, comprising: a construction step of constructing a battery assembly by housing an electrode body having a positive electrode having a positive electrode active material layer on a positive electrode current collector and a negative electrode having a negative electrode active material layer on a negative electrode current collector, and an electrolyte inside a case; and an ultrasonic application step of applying ultrasonic waves to the battery assembly after the construction step, wherein the negative electrode active material layer has a facing region facing the positive electrode active material layer and a non-facing region not facing the positive electrode active material layer, and in the ultrasonic application step, an excess electrolyte is present between the case and the electrode body, and a load is applied to at least a part of the facing region, while the ultrasonic waves are applied to the battery assembly. Item 2: The manufacturing method according to Item 1, further comprising a pre-charging step of charging the battery assembly to a depth of charge (SOC: state of charge) of 10% or less, after the construction step and before the ultrasonic application step. Item 3: The manufacturing method according to Item 2, wherein in the pre-charging step, the battery assembly is charged while a load is applied to at least a portion of the opposing region. Item 4: The manufacturing method according to item 2 or 3, further comprising an activation step of charging the battery assembly after the ultrasonic application step until the charge depth reaches 10% or more. Item 5: The manufacturing method according to any one of items 1 to 4, wherein the frequency of the ultrasound in the ultrasonic application step is 20 kHz or more and 50 kHz or less. Item 6: The manufacturing method according to any one of items 1 to 5, wherein the ultrasonic application step is performed with the case open. Item 7: The manufacturing method according to any one of items 1 to 6, wherein the negative electrode has a negative electrode tab, and in the ultrasonic application step, the liquid level of the excess electrolyte is located vertically above the lower end of the negative electrode tab. Item 8: The manufacturing method according to any one of Items 1 to 7, wherein in the ultrasonic application step, an ultrasonic device is prepared comprising a bathtub filled with liquid and an ultrasonic generating unit for applying the ultrasonic waves into the bathtub, the battery assembly is placed in the bathtub, and the ultrasonic waves are applied from the ultrasonic generating unit. [Explanation of Symbols]

[0085] 10 cases 20 Electrode body 22 Positive electrode 22a Cathode active material layer 24 Negative electrode 24a Negative active material layer A1 Opposing area A2 Non-opposed area 80 Electrolyte (Excess Electrolyte) H liquid level 100 Energy storage devices 200 Ultrasonic device

Claims

1. A construction step involves constructing a battery assembly by housing an electrode body having a positive electrode with a positive electrode active material layer on a positive electrode current collector, a negative electrode with a negative electrode active material layer on a negative electrode current collector, and an electrolyte inside a case. After the construction step, an ultrasonic application step is performed in which ultrasonic waves are applied to the battery assembly, Includes, The negative electrode active material layer has a facing region that faces the positive electrode active material layer and a non-facing region that does not face the positive electrode active material layer. In the ultrasonic application step, the ultrasonic waves are applied to the battery assembly while excess electrolyte is present between the case and the electrode body and a load is applied to at least a portion of the opposing region. A method for manufacturing an energy storage device.

2. The process further includes a pre-charging step, which is performed after the construction step and before the ultrasonic application step, in which the battery assembly is charged to a depth of charge (SOC) of 10% or less. The manufacturing method according to claim 1.

3. In the pre-charging step, the battery assembly is charged while a load is applied to at least a portion of the opposing region. The manufacturing method according to claim 2.

4. The process further includes, after the ultrasonic application step, an activation step in which the battery assembly is charged until the charge depth reaches 10% or more. The manufacturing method according to claim 2.

5. The frequency of the ultrasound in the ultrasonic application step is set to be between 20 kHz and 50 kHz. The manufacturing method according to any one of claims 1 to 4.

6. The ultrasonic application step is performed with the case open. The manufacturing method according to any one of claims 1 to 4.

7. The negative electrode has a negative electrode tab, In the ultrasonic application step, the liquid level of the excess electrolyte is located vertically above the lower end of the negative electrode tab. The manufacturing method according to any one of claims 1 to 4.

8. In the ultrasonic application step, an ultrasonic device is prepared, comprising a bathtub filled with liquid and an ultrasonic generating unit that applies the ultrasonic waves into the bathtub. The battery assembly is housed in the bathtub, and the ultrasonic waves are applied from the ultrasonic generating unit. The manufacturing method according to any one of claims 1 to 4.

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