Manufacturing method of power storage device

Abstract

To provide a technology for efficiently injecting an electrolyte.SOLUTION: A manufacturing method disclosed herein includes a case expansion step S40 of placing an assembly in a first chamber of a liquid injection device, and connecting a first through hole of the assembly to a second chamber of the liquid injection device, and expanding the battery case by a pressure difference between the first chamber and the second chamber, and a liquid injection step S30 of injecting electrolyte into the battery case, and the battery case is expanded by the case expansion step S40 at least either before or after at least a portion of the electrolyte is injected into the battery case in the liquid injection step S30.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed herein relates to a method for manufacturing an electricity storage device. [Background technology]

[0002] An electricity storage device typically includes an electrode assembly, an electrolyte, and a battery case that contains the electrode assembly and the electrolyte. Patent Documents 1 to 3 are examples of prior art documents related to manufacturing methods for such electricity storage devices.

[0003] For example, Patent Document 1 discloses a manufacturing method including a first step of applying an external force to a vertical wall portion of a rectangular parallelepiped battery case to elastically deform the vertical wall portion in a direction away from the electrode body, and a second step of injecting an electrolyte into the elastically deformed battery case. Patent Document 1 describes that the above-mentioned configuration can increase the injection speed of the electrolyte and shorten the injection time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-251084 A [Patent Document 2] JP 2018-170210 A [Patent Document 3] JP 2008-091065 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, in the first step, a pair of narrow vertical walls of a battery case are pressed toward each other with a pressing tool, and the center of the wide vertical wall is pulled with a suction tool, so that the wide vertical wall is curved outward. According to the inventors' study, this method takes time to inflate the battery case. Therefore, the total time required for manufacturing the power storage device is long, and there is a risk of productivity decreasing.

[0006] The technology disclosed herein has been made in consideration of the above circumstances, and has an object to provide a manufacturing method that can efficiently inject an electrolyte and is less susceptible to a decrease in productivity. [Means for solving the problem]

[0007] The technology disclosed herein provides a method for manufacturing an electricity storage device including an electrode assembly including a positive electrode and a negative electrode, an electrolyte, and a battery case that houses the electrode assembly and the electrolyte. The manufacturing method includes an assembly construction step of housing an electrode body inside a battery case having a first through hole to construct an assembly; an apparatus preparation step of preparing a liquid injection device including a first chamber having a volume capable of housing the assembly, a second chamber, a switching member that switches between a connected state and a disconnected state between the first through hole of the assembly housed in the first chamber and the second chamber, and a pressure adjustment device that adjusts the pressure of at least one of the first chamber and the second chamber; a case expansion step of placing the assembly in the first chamber to bring the first through hole of the assembly into communication with the second chamber and expanding the battery case by the pressure difference between the first chamber and the second chamber; and a first liquid injection step of injecting electrolyte into the battery case, wherein the battery case is expanded by the case expansion step at least either before or after injecting at least a portion of the electrolyte into the battery case in the first liquid injection step.

[0008] With the above-described configuration, the battery case can be easily expanded, so that the electrolyte can be injected efficiently and a decrease in productivity can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view that illustrates a power storage device according to an embodiment. [Diagram 2] FIG. 2 is a vertical cross-sectional view that typically shows the internal structure of the electricity storage device shown in FIG. [Diagram 3]FIG. 3 is a flow chart illustrating a manufacturing method according to an embodiment. [Figure 4] FIG. 4 is a perspective view that shows a schematic view of an electrode body attached to a sealing plate. [Diagram 5] FIG. 5 is a schematic diagram showing the configuration of a liquid injection device according to one embodiment. [Figure 6] FIG. 6 is a graph showing the pressure change from the attachment process to the removal process. [Figure 7] 7(A) to (E) are schematic diagrams showing the procedures of the mounting step and the liquid injection step. [Figure 8] FIG. 8 is a schematic diagram showing the procedure of the case expansion step. [Figure 9] 9(A) and (B) are schematic diagrams showing the procedure of the removal step. [Figure 10] FIG. 10 is a view equivalent to FIG. 6 of the embodiment. [Figure 11] FIG. 11 is a diagram of a comparative example corresponding to FIG. [Figure 12] FIG. 12 is a graph showing the change in cell thickness in the examples. [Figure 13] FIG. 13 is a graph showing the change in cell thickness in the comparative example. [Figure 14] FIG. 14 is a bar graph showing the limit injection amount in the embodiment. [Figure 15] FIG. 15 is a bar graph showing the limit injection amount of the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, some embodiments of the technology disclosed herein will be described in detail with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of a power storage device that does not characterize the technology disclosed herein) can be understood as design matters of a person skilled in the art based on the conventional technology in the field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the field. In addition, in the following drawings, the same reference numerals are used to denote members and parts that perform the same function. In this specification, the expression "A to B" indicating a range includes the meaning of "greater than A" and "smaller than B" as well as the meaning of "greater than A" and "smaller than B".

[0011] In this specification, the term "electricity storage device" refers to a general electricity storage device that can repeatedly be charged and discharged by the movement of charge carriers between a positive electrode and a negative electrode via an electrolyte. The concept of "electricity storage device" includes secondary batteries such as lithium ion secondary devices, nickel hydrogen batteries, and nickel cadmium batteries, as well as capacitors such as lithium ion capacitors and electric double layer capacitors. In addition, in this specification, "pressure" refers to gauge pressure based on atmospheric pressure (0 kPa, normal pressure) (i.e., the difference obtained by subtracting atmospheric pressure from absolute pressure).

[0012] <1. Configuration of the power storage device> FIG. 1 is a perspective view showing a typical example of the energy storage device 100. FIG. 2 is a vertical cross-sectional view showing a typical internal structure of the energy storage device 100. In FIG. 1 and FIG. 2, the symbol X in the drawings indicates the width direction, the symbol Y indicates the depth direction, and the symbol Z indicates the height direction. Furthermore, the symbols L, R, F, Rr, U, and D indicate the left, right, front, rear, upper, and lower directions, respectively. However, these directions are determined for the convenience of explanation, and do not limit the installation mode of the energy storage device 100 in any way.

[0013] 2, the power storage device 100 includes a battery case 10, an electrode assembly 20, and an electrolyte 30. Here, the power storage device 100 is a lithium ion secondary battery. The power storage device 100 is preferably a secondary battery, and more preferably a lithium ion secondary battery.

[0014] The battery case 10 is a housing that contains the electrode assembly 20 and the electrolyte 30. As shown in FIG. 1, the battery case 10 has a flat, bottomed rectangular parallelepiped (rectangular) outer shape. The battery case 10 is preferably rectangular. The material of the battery case 10 may be the same as that conventionally used, and is not particularly limited. The battery case 10 is preferably made of metal, and more preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0015] Although not particularly limited, the internal volume of the battery case 10 is 500 cm 3 More than 1000cm is preferable. 3 More preferably, the upper limit of the internal volume of the battery case 10 is 3000 cm 3 Less than 1500cm is also acceptable. 3 The technology disclosed herein also provides a method for manufacturing a vacuum pump having an internal volume of 300 cm 3 Less than (typically 150cm 3 This can also be applied to small batteries (see below).

[0016] 2, the battery case 10 here includes a case body 14 having an opening 14a, and a sealing plate (lid) 12 that closes the opening 14a. The battery case 10 preferably includes the case body 14 and the sealing plate 12. The battery case 10 is integrated by joining (for example, welding) the sealing plate 12 to the periphery of the opening 14a of the case body 14. The battery case 10 is hermetically sealed (sealed).

[0017] The case body 14 is a box-shaped body with an open top. As shown in FIG. 1, the case body 14 includes a substantially rectangular bottom wall 14b, a pair of first side walls 14c extending from the long sides of the bottom wall 14b and facing each other, a pair of second side walls 14d extending from the short sides of the bottom wall 14b and facing each other, and an opening 14a (see FIG. 2) surrounded by the upper ends of the first side wall 14c and the second side wall 14d. The area of ​​the first side wall 14c is larger than the area of ​​the second side wall 14d. In this specification, the term "substantially rectangular" includes not only a perfect rectangular shape (rectangular shape), but also a shape in which the corners connecting the long and short sides of the rectangle are rounded, a shape in which the corners have notches, and the like.

[0018] The dimensions of the case body 14 can be appropriately changed, for example, according to the size of the electrode body 20, as long as the effect of the technology disclosed herein is not significantly impaired. Therefore, although not particularly limited, for example, the width (length in the width direction X) of the first side wall 14c is preferably 20 cm or more, more preferably 25 cm or more. The height (length in the height direction Z) of the first side wall 14c is preferably 5 cm or more, more preferably 8 cm or more. In this way, by forming the first side wall 14c having a certain width and height (i.e., area) or more, the first side wall 14c becomes easier to deform in the manufacturing method described later.

[0019] The width of the first side wall 14c may be 35 cm or less, or may be 30 cm or less. The height of the first side wall 14c may be 12 cm or less, or may be 10 cm or less. The aspect ratio (ratio of height to width) of the first side wall 14c is preferably 2 or more, and more preferably 3 or more. This makes it easier to deform the first side wall 14c in the manufacturing method described below. The upper limit of the aspect ratio of the first side wall 14c may be, for example, 8 or less, or 5 or less.

[0020] Furthermore, the thickness (length in the depth direction Y) of the first side wall 14c is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less. This makes it easier to deform the first side wall 14c in the manufacturing method described below. On the other hand, from the viewpoint of ensuring the strength of the battery case 10, the thickness of the first side wall 14c is preferably 0.1 mm or more, more preferably 0.2 mm or more, and even more preferably 0.3 mm or more.

[0021] Moreover, the width (length in the depth direction Y) of the second side wall 14d is preferably 5 cm or less, and more preferably 4 cm or less. In this way, by narrowing the width of the second side wall 14d, deformation of the second side wall 14d can be suitably suppressed. The lower limit of the width of the second side wall 14d may be 1 cm or more, or may be 3 cm or more. The height (length in the height direction Z) of the second side wall 14d is set to the same height as the first side wall 14c. Moreover, the thickness (length in the width direction X) of the second side wall 14d is preferably 0.15 mm or more, and more preferably 0.2 mm or more. The thickness of the second side wall 14d is preferably the same as or thicker than the thickness of the first side wall 14c. This makes it possible to suppress deformation of the second side wall 14d. On the other hand, in consideration of the weight and material costs of the power storage device 100, the thickness of the second side wall 14d is preferably 3 mm or less, more preferably 2 mm or less, and further preferably 1.5 mm or less.

[0022] The thickness of the bottom wall 14b is preferably 0.5 mm or more, and more preferably 1 mm or more. The thickness of the bottom wall 14b is preferably the same as or thicker than the thickness of the first side wall 14c. This can suitably suppress deformation of the bottom wall 14b. On the other hand, in consideration of the weight and material cost of the power storage device 100, the thickness of the bottom wall 14b is preferably 4 mm or less, more preferably 3 mm or less, and even more preferably 2.5 mm or less.

[0023] The sealing plate 12 is a plate-like member that seals the opening 14a. As shown in FIG. 1, the sealing plate 12 has a substantially rectangular shape in a plan view. The sealing plate 12 faces the bottom wall 14b. The thickness of the sealing plate 12 is preferably 1 mm or more, and more preferably 1.5 mm or more. The sealing plate 12 is preferably thicker than the first side wall 14c. This makes it possible to suppress deformation of the sealing plate 12 in a manufacturing method described later. On the other hand, in consideration of the weight and material costs of the power storage device 100, the thickness of the sealing plate 12 is preferably 5 mm or less, and more preferably 4 mm or less.

[0024] 2, the sealing plate 12 in this embodiment is provided with an electrolyte injection hole 12a and a gas exhaust valve 12b. The electrolyte injection hole 12a is for injecting the electrolyte 30 into the battery case 10 after the sealing plate 12 is assembled to the case body 14. The electrolyte injection hole 12a is a through-hole that penetrates the sealing plate 12 in the thickness direction (height direction Z). The electrolyte injection hole 12a is an example of a "first through-hole."

[0025] The electrolyte injection hole 12a is preferably provided in the sealing plate 12. However, in other embodiments, the electrolyte injection hole 12a may be provided in the case body 14. The electrolyte injection hole 12a is sealed with a sealing member 16 after the electrolyte 30 is injected. As the sealing member 16, any conventionally known member can be used without any particular restrictions. One example of the sealing member 16 is a metal member such as a blind rivet.

[0026] The gas release valve 12b is configured to break when the internal pressure of the battery case 10 reaches or exceeds a predetermined value, thereby releasing the gas inside the battery case 10 to the outside. Here, the gas release valve 12b is a thin-walled portion that is thinner than other portions of the sealing plate 12. The thickness of the gas release valve 12b is preferably 0.5 mm or less, and more preferably 0.3 mm or less. The lower limit of the thickness of the gas release valve 12b is preferably 0.05 mm or more, and more preferably 0.1 mm or more. This makes it possible to suppress malfunction of the gas release valve 12b in the manufacturing method described below.

[0027] As shown in FIG. 2, a pair of electrode terminals 40 are attached to both ends (left and right ends in FIG. 2) of the sealing plate 12 in the width direction X. Here, each electrode terminal 40 is a structure combining a plurality of conductive members, and extends along the height direction Z. A current collecting member 40a constituting the lower end of the electrode terminal 40 is connected to the electrode body 20 inside the battery case 10. In this embodiment, as shown in FIG. 4, a current collecting member 40a is attached to each electrode body 20, so that each of the pair of electrode terminals 40 has a plurality of current collecting members 40a (three in FIG. 4). On the other hand, an external terminal 40b constituting the upper end of the electrode terminal 40 is exposed to the outside of the battery case 10. The structure of the electrode terminal 40 may be similar to that of a general power storage device, and is not intended to limit the technology disclosed herein, so a detailed description thereof will be omitted.

[0028] As shown in Fig. 2, the electrode body 20 is housed inside the battery case 10. As shown in Fig. 4, in this embodiment, a plurality of electrode bodies 20 (three in Fig. 4) are housed inside the battery case 10. However, the number of electrode bodies 20 housed inside one battery case 10 is not particularly limited, and in other embodiments, there may be only one.

[0029] The electrode body 20 includes a positive electrode and a negative electrode. The electrode body 20 is a wound electrode body here. Specifically, the electrode body 20 is formed by winding a laminate formed by stacking a strip-shaped positive electrode and a strip-shaped negative electrode with a strip-shaped separator interposed therebetween in the longitudinal direction around a winding axis. However, in other embodiments, the electrode body 20 may be a laminated electrode body formed by stacking a rectangular positive electrode and a rectangular negative electrode in an insulated state.

[0030] The electrode body 20 has a flat outer shape here. The electrode body 20 is housed inside the battery case 10 with the winding axis oriented along the width direction X here. For this reason, in this embodiment, the flat surface of the electrode body 20 faces the first side wall 14c of the case body 14. However, the electrode body 20 may be housed inside the battery case 10 with the winding axis oriented along the height direction Z, for example. Note that each member (positive electrode, negative electrode, separator, etc.) constituting the electrode body 20 may be similar to that of a general electricity storage device, and detailed description thereof will be omitted since it does not limit the technology disclosed herein.

[0031] The electrolytic solution 30 is accommodated in the battery case 10 together with the electrode assembly 20. The electrolytic solution 30 permeates the inside of the electrode assembly 20 (for example, between the positive and negative electrodes). As shown in FIG. 2, a part of the electrolytic solution 30 may be present outside the electrode assembly 20 (between the battery case 10 and the electrode assembly 20) as excess electrolytic solution 32. The electrolytic solution is, for example, a nonaqueous liquid electrolyte (nonaqueous electrolyte) containing a nonaqueous solvent and a supporting salt. Note that the components of the electrolytic solution 30 may be the same as those of a general electricity storage device, and detailed description thereof will be omitted since it does not limit the technology disclosed herein.

[0032] 2. Method for manufacturing electricity storage device FIG. 3 is a flow chart for explaining a manufacturing method according to one embodiment. As shown in FIG. 3, the manufacturing method according to this embodiment includes the following steps: an assembly construction step (step S10a), a device preparation step (step S10b), an attachment step (step S20), a liquid injection step (step S30), a case expansion step (step S40), a degassing step (step S50), a removal step (step S60), and a sealing step (step S70). Here, the case expansion step (step S40) is included in the middle of the liquid injection step (step S30). Here, the degassing step (step S50) is also included in the middle of the liquid injection step (step 30). The liquid injection step (step S30) is an example of a "first liquid injection step".

[0033] However, the order of the assembly construction step (step S10a) and the device preparation step (step S10b) may be reversed. Also, as described in the modified example described later, in other embodiments, the case expansion step may be performed before the liquid injection step. Also, in other embodiments, the case expansion step (step S40) and / or the degassing step (step S50) may be performed after the liquid injection step (step S30). Also, the manufacturing method of this embodiment may further include other steps at any stage. For example, between the assembly construction step (step S10a) and the liquid injection step (step S30), a drying step for removing moisture from inside the battery case 10 (particularly inside the electrode body 20) may be further included.

[0034] The assembly construction step (step S10a) is a step of constructing an assembly 100a by accommodating an electrode body 20 in a battery case 10 having a first through hole (here, an electrolyte injection hole 12a). In this step, for example, first, as shown in FIG. 4, a current collecting member 40a of an electrode terminal 40 is connected to each of the plurality of electrode bodies 20. This produces an integrated body in which the sealing plate 12 and the plurality of electrode bodies 20 are integrated. Next, the sealing plate 12 is fitted into the opening 14a of the case body 14 to accommodate the plurality of electrode bodies 20 inside the case body 14. This causes the plurality of electrode bodies 20 to be accommodated inside the case body 14 with the winding axis oriented along the width direction X, as shown in FIG. 2. Next, with the electrode body 20 disposed inside the case body 14, the sealing plate 12 is joined (for example, welded) to the periphery of the opening 14a of the case body 14 to integrate the case body 14 and the sealing plate 12. Note that any conventionally known joining means can be used without any particular restrictions for joining the sealing plate 12 and the case body 14. A suitable example of such a joining means is laser welding. In this manner, the assembly 100a (battery case 10 housing the electrode body 20) can be constructed.

[0035] The device preparation step (step S10b) is a step of preparing a liquid injection device to be used in a liquid injection step, a case expansion step, and the like, which will be described later. Fig. 5 is a schematic diagram showing a configuration of a liquid injection device 200 according to one embodiment. As shown in Fig. 5, the liquid injection device 200 of this embodiment has a lower chamber 110, an upper chamber 120, a communication port 130, a needle valve 140, an electrolyte supply mechanism 150, and a control device (not shown).

[0036] The lower chamber 110 is a container having an internal volume capable of accommodating the assembly 100a. The lower chamber 110 is a vacuum chamber here. The lower chamber 110 is an example of a "first chamber." The lower chamber 110 has a lift table 111 on which the assembly 100a is placed and which can be moved up and down by a lift mechanism (not shown), a pump 112 which pressurizes and depressurizes the lower chamber 110, and a release valve 113 which releases (pressurizes) the lower chamber 110. The lower chamber 110 may further be provided with a gauge for measuring the internal pressure. The lift mechanism of the lift table 111, the pump 112, and the release valve 113 are electrically connected to a control device. The lift mechanism is, for example, a ball screw mechanism. The lift table 111 is configured to be movable upward and downward by the control device. The pump 112 is configured to be switched between driving and stopping by the control device. The release valve 113 is configured to be switchable between an open state and a closed state by a control device. The pump 112 and the release valve 113 are an example of a “pressure adjusting device” that adjusts the pressure in the lower chamber 110.

[0037] The upper chamber 120 is disposed above (directly above) the lower chamber 110 in this embodiment. The upper chamber 120 is disposed at a position overlapping the lower chamber 110 in a plan view. The upper chamber 120 is a vacuum chamber in this embodiment. The upper chamber 120 is an example of a "second chamber." The upper chamber 120 has a storage tank 121 for storing an electrolytic solution, a pump 122 for pressurizing and depressurizing the upper chamber 120, and a release valve 123 for depressurizing (pressurizing) the upper chamber 120. A gauge for measuring the internal pressure may be further attached to the upper chamber 120. The electrolytic solution is supplied to the storage tank 121 by an electrolytic solution supply mechanism 150 described later. The lower wall of the storage tank 121 is formed in a tapered shape toward the communication port 130. The pump 122 and the release valve 123 are electrically connected to a control device. The pump 122 is configured to be switchable between driving and stopping by the control device. The release valve 123 is configured to be switchable between an open state and a closed state by a control device. The pump 122 and the release valve 123 are an example of a “pressure regulator” that regulates the pressure in the upper chamber 120.

[0038] In this embodiment, an open valve 113 is provided in the lower chamber 110 and an open valve 123 is provided in the upper chamber 120, but in other embodiments, instead of the open valves 113, 123, for example, a pressure pump, a compressor, a gas cylinder, etc. may be provided.

[0039] The communication port 130 penetrates the partition wall between the lower chamber 110 and the upper chamber 120 in the vertical direction. Here, the communication port 130 communicates between the lower chamber 110 and the storage tank 121. The communication port 130 is provided so as to enable communication between the electrolyte injection hole 12a of the assembly 100a accommodated in the lower chamber 110 and the upper chamber 120 (more specifically, the storage tank 121).

[0040] The needle valve 140 is configured to be able to communicate the electrolyte injection hole 12a of the assembly 100a housed in the lower chamber 110 with the upper chamber 120 (more specifically, the storage tank 121) by switching the communication port 130 between an open state and a closed state. Here, the needle valve 140 is disposed inside the storage tank 121. The needle valve 140 is housed in an outer (not shown) and is configured to be able to move up and down inside the outer. The needle valve 140 is biased downward (in the valve closing direction) by a spring (not shown). This causes the communication port 130 to be closed. The needle valve 140 moves upward against the biasing force of the spring by an actuator (not shown). The actuator is electrically connected to a control device. When the needle valve 140 moves upward by the control device, the communication port 130 is opened. The needle valve 140 is an example of a "switching member" that switches between a communicated state and a non-communicated state between the electrolyte injection hole 12a and the upper chamber 120. However, in other embodiments, the switching member may be an on-off valve, a solenoid valve, or the like.

[0041] The electrolyte supply mechanism 150 is configured to supply the electrolyte to the storage tank 121 of the upper chamber 120. The electrolyte supply mechanism 150 has a main tank 151 for the electrolyte and a supply flow path 152 whose upstream end is connected to the main tank 151. The electrolyte is supplied to the storage tank 121 through the supply flow path 152. A liquid delivery pump 153 and a supply nozzle 154 are provided in the middle of the supply flow path 152 from the upstream side. A valve body may be further provided in the middle of the supply flow path 152. The liquid delivery pump 153 is configured to supply a predetermined amount of the electrolyte 30 in the main tank 151 to the storage tank 121. At least a lower end of the supply nozzle 154 is disposed in the upper chamber 120. The supply nozzle 154 is configured to be movable up and down by an actuator (not shown). The liquid delivery pump 153 and the actuator of the supply nozzle 154 are electrically connected to a control device. The liquid delivery pump 153 is configured so that it can be switched between being driven and stopped by a control device.

[0042] The control device is electrically connected to the lifting mechanism of the lifting table 111, the pump 112, the release valve 113, the pump 122, the release valve 123, the actuator of the needle valve 140, and the actuators of the liquid feed pump 153 and the supply nozzle 154, and is configured to be able to control these. The hardware configuration of the control device is not particularly limited. The control device includes, for example, an interface (I / F), a central processing unit (CPU: Central Processing Unit) that executes instructions of a control program, a ROM (Read Only Memory) that stores the program executed by the CPU, a RAM (Random Access Memory) used as a working area for expanding the program, and a storage device such as a memory that stores the above program and various data.

[0043] The attachment step (step S20) is a step of attaching the assembly 100a to the liquid injection device 200. FIG. 6 is a graph showing the pressure change inside the liquid injection device 200 (more specifically, the lower chamber 110 and the upper chamber 120) from this step to the removal step (step S60). In FIG. 6, the pressure inside the battery case 10 is shown by a dashed line. Also, FIGS. 7(A) to (E) are schematic diagrams showing the procedure of this step and the liquid injection step (step S30). Note that in the subsequent drawings, only the essential parts of the liquid injection device 200 are shown, and some components may not be shown.

[0044] In this step, for example, first, the door of the lower chamber 110 (not shown) is opened, and the assembly 100a is placed on the lift table 111 of the lower chamber 110 as shown in FIG. 7(A). At this time, the outer surface of the battery case 10 of the assembly 100a is exposed in the lower chamber 110. In addition, the electrolyte injection hole 12a (not shown in FIG. 7(A)) of the assembly 100a is in an open state. The assembly 100a placed on the lift table 111 is not in contact with the upper wall of the lower chamber 110. The assembly 100a is not in contact with the needle valve 140. The lower chamber 110 and the upper chamber 120 are not in communication with each other. In this state, the door of the lower chamber 110 is closed, and the lower chamber 110 is sealed. In this step, both the lower chamber 110 and the upper chamber 120 are at atmospheric pressure (see FIG. 6(0)).

[0045] The liquid injection step (step S30) is a step of injecting the electrolyte 30 into the assembly 100a through the electrolyte injection hole 12a. In this embodiment, it is a step of injecting the electrolyte 30 into the assembly 100a using the liquid injection device 200. Specifically, first, the pump 112 of the lower chamber 110 is driven to reduce the pressure inside the lower chamber 110 to a predetermined first pressure (see (1) in FIG. 6). The first pressure is not particularly limited, but is preferably -10 to -200 kPa, more preferably -50 to -120 kPa, and is -90 kPa in FIG. 6, for example. As a result, the lower chamber 110 and the inside of the assembly 100a become negative pressure (reduced pressure state) while the upper chamber 120 remains at atmospheric pressure.

[0046] After the pressure inside the lower chamber 110 is reduced to the first pressure, the assembly 100a is moved upward by the lifting mechanism of the lifting table 111, as shown in FIG. 7(B). As a result, the surface of the assembly 100a on the sealing plate 12 side is pressed against the upper wall of the lower chamber 110, and the electrolyte injection hole 12a is brought into close contact with the communication hole 130. A packing is provided on the periphery of the communication hole 130. The packing is crushed by the sealing plate 12, thereby sealing the electrolyte injection hole 12a and closing the assembly 100a. At this time, as shown in FIG. 6, the upper chamber 120 is at atmospheric pressure. The lower chamber 110 is maintained in the reduced pressure state. In addition, the needle valve 140 closes the communication hole 130. The inside of the assembly 100a is not communicated with the upper chamber 120. The air flow between the upper chamber 120 and the assembly 100a is blocked.

[0047] Next, the electrolyte supply mechanism 150 stores a first amount A1 of the electrolyte 30 in the storage tank 121 of the upper chamber 120. Specifically, as shown in FIG. 7(C), the actuator of the supply nozzle 154 is first driven to move the supply nozzle 154 downward. As a result, the lower end of the supply nozzle 154 is disposed in the storage tank 121. Next, the liquid delivery pump 153 (not shown in FIG. 7(C)) is driven to store the first amount A1 of the electrolyte 30 in the storage tank 121 from the main tank 151 through the supply flow path 152 and the supply nozzle 154. The first amount A1 is not particularly limited, but is, for example, 340±30 g. At this time, as shown in FIG. 6, the upper chamber 120 is at atmospheric pressure. The lower chamber 110 is maintained in the above-mentioned reduced pressure state. In addition, the needle valve 140 closes the communication port 130. The interior of the assembly 100 a is not in communication with the upper chamber 120 .

[0048] When the first amount A1 of the electrolyte 30 is stored in the storage tank 121, the actuator of the supply nozzle 154 is driven to move the supply nozzle 154 upward. Next, as shown in FIG. 7(D), in a state in which the upper chamber 120 is sealed, the pump 122 (not shown in FIG. 7(D)) is driven to reduce the pressure in the upper chamber 120 to a predetermined second pressure (see FIG. 6(2)). The second pressure is not particularly limited, but is typically lower in pressure reduction (closer to atmospheric pressure) than the first pressure in the lower chamber 110, for example, −70 kPa in FIG. 6. At this time, as shown in FIG. 6, the lower chamber 110 is maintained in the above-mentioned reduced pressure state. In addition, the needle valve 140 closes the communication port 130. The inside of the assembly 100a is not communicated with the upper chamber 120.

[0049] After the pressure inside the upper chamber 120 is reduced to the second pressure, the actuator of the needle valve 140 is driven to move the needle valve 140 upward, as shown in FIG. 7(E). This opens the communication port 130, and the assembly 100a communicates with the storage tank 121 of the upper chamber 120. As a result, as shown in FIG. 6(3), the pressure inside the battery case 10 becomes equal to the pressure in the upper chamber 120, and the electrolyte 30 in the storage tank 121 is supplied to the inside of the assembly 100a, more specifically, to the inside of the battery case 10. The amount of electrolyte 30 supplied to the battery case 10 at this time is typically less than the first amount A1.

[0050] In this embodiment, since the assembly 100a is located directly below the communication port 130, the electrolyte 30 is easily supplied to the assembly 100a by gravity. Furthermore, since the degree of reduced pressure in the assembly 100a is higher than that in the upper chamber 120 when the communication port 130 is opened, the electrolyte 30 is easily supplied to the assembly 100a due to the difference in reduced pressure. This allows the electrolyte 30 to efficiently spread throughout the inside of the electrode body 20, and the time required for the electrolyte 30 to permeate can be shortened. Preferably, the amount of electrolyte that can be injected can be further increased.

[0051] In the case expansion step (step S40), the battery case 10 is expanded by generating a pressure difference between the lower chamber 110 and the upper chamber 120 using the liquid injection device 200. This step is preferably a step of expanding the battery case 10 by reducing the pressure in the lower chamber 110. FIG. 8 is a schematic diagram showing the procedure of this step. As shown in FIG. 8, after the electrolyte 30 in the storage tank 121 is supplied to the assembly 100a, the release valve 123 (not shown in FIG. 8) is opened to return the upper chamber 120 to atmospheric pressure (depressurize, see also (4) in FIG. 6). As a result, as shown in FIG. 6, the inside of the assembly 100a is communicated with the upper chamber 120 and returns to atmospheric pressure. Meanwhile, the lower chamber 110 is maintained in the reduced pressure state. Therefore, a pressure difference occurs between the lower chamber 110 and the inside of the assembly 100a, and the battery case 10 expands due to the pressure difference. As a result, impregnation of the electrolyte 30 into the electrode body 20 is promoted. Furthermore, since the needle valve 140 is in an open state in this step, if electrolyte 30 remains in the storage tank 121, the internal volume of the battery case 10 increases, so that the electrolyte 30 remaining in the storage tank 121 is additionally injected.

[0052] The pressure difference (differential pressure) between the lower chamber 110 and the upper chamber 120 is preferably adjusted so that the battery case 10 expands to a certain level or more. By setting the pressure difference to a predetermined value or more, the battery case 10 can be expanded significantly, and the amount of electrolyte that can be injected can be suitably increased. The pressure difference is not particularly limited, but is preferably 10 to 200 kPa, more preferably 50 to 120 kPa, and is, for example, about 100 kPa in FIG. 6.

[0053] As described above, when a flat battery case 10 is used, the first side walls 14c having a relatively large area expand preferentially, making it easier to control the amount of deformation. Therefore, in some embodiments, it is preferable that in this step, the battery case 10 is expanded so that the thickness of the central portion of the pair of first side walls 14c is displaced (expanded) by, for example, about 2.5 to 4.0 mm.

[0054] In some embodiments, the space volume V1 in the battery case 10 before this step (before expansion) is 150 to 200 cm 3 For example, 180 cm 3 In addition, the space volume V2 in the battery case 10 after this step (after expansion) is 220 to 300 cm 3 For example, 270 cm 3 In this specification, the term "space volume" refers to the volume of the portion of the battery case 10 where gas exists (in other words, the volume of the space in the battery case 10 where the electrode body 20, the current collecting member 40a, etc. do not exist), and can be obtained by subtracting the volume occupied by the electrode body 20, the current collecting member 40a, etc. from the internal volume of the battery case 10. Alternatively, as described in the test example below, it can be obtained by the amount of electrolyte injected when the electrolyte is injected until it overflows from the electrolyte injection hole (limit injection amount).

[0055] Although not particularly limited, the ratio of the spatial volumes before and after this step (V2 / V1) is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 1.8 or more. This can promote the impregnation of the electrolyte 30 into the electrode body 20. Also, preferably, the amount of electrolyte that can be injected can be suitably increased. Therefore, the effects of the technology disclosed herein can be exerted at a high level.

[0056] In some embodiments, the increase V3 (=V2-V1) in the internal volume of the battery case 10 after the step (after the expansion) is set to 10 cm or less from the viewpoint of achieving a high level of the effects of the technology disclosed herein. 3 More than 20cm is preferable. 3 More than 50cm is preferable. 3 The increase in the internal volume V3 is preferably 150 cm from the viewpoint of preventing damage to the battery case 10 (for example, the portion where the gas release valve 12b is provided, the joint between the sealing plate 12 and the case body 14, etc.). 3 Less than 120cm is preferable 3 Less than 100cm is preferable. 3 The following is even more preferred:

[0057] The degassing step (step S50) is a step of degassing gas remaining in the assembly 100a (particularly, in the electrode body 20) by changing the pressure in the assembly 100a at least once after the liquid injection step (step S30). In this embodiment, the pump 122 is driven to reduce the pressure again at least once until the pressure in the upper chamber 120 reaches a predetermined third pressure (see (5) in FIG. 6). The third pressure is not particularly limited, but is typically a higher degree of reduction than the second pressure in the liquid injection step (step S30), for example, −75 kPa in FIG. 6. It is preferable that the third pressure is a lower degree of reduction than the first pressure (closer to atmospheric pressure).

[0058] At this time, as shown in FIG. 6, the lower chamber 110 is maintained in the above-mentioned reduced pressure state. In addition, since the inside of the assembly 100a is connected to the upper chamber 120, the pressure is the same as that in the upper chamber 120. By maintaining such a pressure state, bubbles (gas) remaining or generated in the assembly 100a during injection of the electrolyte 30 can be suitably moved to the upper chamber 120 side, and the assembly 100a can be degassed. As a result, the impregnation of the electrolyte 30 into the electrode body 20 can be promoted. Furthermore, since the needle valve 140 is in an open state in this process, if the electrolyte 30 remains in the storage tank 121 and there is a gap in the battery case 10, the electrolyte 30 remaining in the storage tank 121 can be additionally injected by pressurizing and depressurizing the battery case 10.

[0059] In this step, as shown in Fig. 6, it is preferable to maintain the reduced pressure for a predetermined time after the pressure of the assembly 100a reaches the third pressure. The reduced pressure maintenance time is preferably 1 second or more, more preferably 4 seconds or more, and more preferably 5 seconds or more. After the reduced pressure maintenance time has elapsed, the release valve 123 is opened to return the upper chamber 120 to atmospheric pressure (to release the pressure, see also (6) of Fig. 6).

[0060] The assembly 100a may be depressurized once, but in some embodiments, the pressure in the assembly 100a may be changed multiple times, for example, by repeatedly depressurizing and depressurizing (or pressurizing) the upper chamber 120. For example, while maintaining the reduced pressure state of the lower chamber 110, the following operations may be repeated multiple times (e.g., 2 to 5 times): (S1) drive the pump 122 to reduce the pressure in the upper chamber 120 to a predetermined pressure, and preferably maintain the reduced pressure state of the upper chamber 120 for a predetermined time; and (S2) open the release valve 123 to return the upper chamber 120 to atmospheric pressure (depressurize), and preferably maintain the atmospheric pressure state of the upper chamber 120 for a predetermined time. This allows gas to be degassed in more detail in the assembly 100a, and further promotes impregnation of the electrolyte 30 into the electrode body 20.

[0061] The removal step (step S60) is a step of removing the assembly 100a from the liquid injection device 200. In this step, first, the release valve 113 is opened to return the lower chamber 110 to atmospheric pressure (to depressurize, see also (7) in FIG. 6). Note that, from the viewpoint of preventing an overshoot that temporarily makes the pressure unstable, for example, the pump 112 may be further driven to pressurize the lower chamber 110, or the pump 122 may be driven to pressurize the upper chamber 120. Then, the pressure is held for a predetermined time to stabilize. FIG. 9 is a schematic diagram showing the procedure of this step. Next, as shown in FIG. 9(A), the actuator of the needle valve 140 is driven to move the needle valve 140 downward. This closes the communication port 130, and the assembly 100a is blocked from communicating with the upper chamber 120. Next, as shown in FIG. 9(B), the assembly 100a is moved downward by the lifting mechanism of the lifting table 111. Then, the assembly 100a is taken out of the injection device 200, and the electrolyte injection hole 12a is temporarily sealed with a rubber-like material or the like.

[0062] The sealing step (step S70) is a step of sealing the electrolyte injection hole 12a of the battery case 10. In this step, first, preferably, the assembly 100a removed from the injection device 200 is moved to a charging facility, the temporary seal is released (with the electrolyte injection hole 12a open), and the assembly 100a is initially charged at least once. During the initial charge, gas may be generated due to decomposition of the electrolyte 30, but by initially charging the assembly 100a with the electrolyte injection hole 12a open, the generated gas can be discharged from the electrolyte injection hole 12a.

[0063] Then, the electrolyte injection hole 12a is sealed with a sealing member 16. The sealing member 16 is, for example, a metal member, and may be attached to the sealing plate 12 by welding so as to seal the electrolyte injection hole 12a. The sealing member 16 is, for example, a blind rivet, and may be attached to the sealing plate 12 by crimping so as to seal the electrolyte injection hole 12a. Furthermore, after sealing the electrolyte injection hole 12a with a blind rivet, the blind rivet may be further welded to the sealing plate 12. In this manner, an electricity storage device 100 (see FIG. 1 ) is constructed in which the electrode body 20 and the electrolyte 30 are accommodated in the sealed battery case 10.

[0064] As described above, the manufacturing method disclosed herein can easily expand the battery case 10 by performing the case expansion step (step S40) using the liquid injection device 200. Also, preferably, the internal volume of the battery case 10 can be increased, and the amount of electrolyte solution that can be supplied in one injection can be increased. Therefore, the electrolyte solution 30 can be injected efficiently, and a decrease in productivity can be suppressed.

[0065] <3. Other embodiments> In the embodiment of FIG. 3 described above, the liquid injection step is performed only once. In some embodiments, however, it is preferable to perform a second liquid injection step (second liquid injection step) after, for example, the case expansion step (step S40) or the degassing step (step S50). According to the knowledge of the present inventors, the electrolyte 30 is filled between the battery case 10 and the electrode body 20 by the first liquid injection step (first liquid injection step), but in order to impregnate the electrolyte 30 into the electrode body 20, impregnation by capillary action is necessary. Therefore, it takes a certain amount of time to impregnate the electrolyte 30 into the electrode body 20. By performing the second liquid injection step, the electrolyte 30 used by capillary action can be suitably replenished.

[0066] In the second liquid injection step, for example, first, a second amount A2 of the electrolyte 30 is stored in the storage tank 121 in the same manner as when the first amount A1 of the electrolyte 30 is stored in the storage tank 121 in FIG. 7(C) described above. The second amount A2 is preferably smaller than the amount of electrolyte injected in the first liquid injection step (first amount A1). The second amount A2 is not particularly limited, but is, for example, 195±20 g. The ratio (V2 / V1) of the second amount A2 to the first amount A1 is, for example, preferably 0.47 to 0.68, more preferably 0.53 to 0.59, and is, for example, 0.57.

[0067] When the second amount A2 of the electrolyte solution 30 is stored in the storage tank 121, for example, the upper chamber 120 is depressurized to a state (close to atmospheric pressure, for example, the above-mentioned second pressure) that is lower than the first pressure of the lower chamber 110, according to Fig. 7(D) described above. Then, in a state in which the upper chamber 120 has a lower degree of depressurization than the lower chamber 110, the electrolyte solution 30 is supplied into the battery case 10 according to Fig. 7(E). At this time, the amount of the electrolyte solution 30 supplied into the battery case 10 is typically less than the second amount A2.

[0068] Next, for example, the case expansion step (FIG. 8) is not performed, and the release valve 113 is immediately opened to return the lower chamber 110 to atmospheric pressure (depressurize). As a result, the upper chamber 120 is in a state of a higher degree of decompression than the lower chamber 110. Therefore, the remaining electrolyte 30 can be additionally injected in a state in which the expansion of the battery case 10 is smaller than that in the previous case expansion step (step S40). The pressure difference between the lower chamber 110 and the upper chamber 120 is, for example, preferably 10 to 200 kPa, and more preferably 50 to 120 kPa. In one example, it is more preferable that the lower chamber 110 is at normal pressure (absolute pressure value: small) and the upper chamber 120 is at negative pressure (absolute pressure value: large). In this way, the remaining electrolyte 30 is additionally injected while the thickness of the battery case 10 is returned to approximately the original state, thereby improving productivity.

[0069] After the second liquid injection step, a second degassing step may be performed in which the pressure inside the upper chamber 120 is reduced again at least once, similar to the degassing step described above, while the lower chamber 110 is at atmospheric pressure. After the second liquid injection step or the second degassing step, the removal step (step S60) of the above embodiment may be performed.

[0070] <4. Uses of electricity storage devices> The power storage device 100 can be used for various purposes, but can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, a truck, etc. The type of vehicle is not particularly limited, but examples thereof include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), a battery electric vehicle (BEV), etc.

[0071] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to these examples.

[0072] When injecting the electrolyte, the change in cell thickness and the limit injection amount were compared between the case expansion step as shown in FIG. 8 (Example, N=2) and the case expansion step not performed (Comparative Example, N=2). The cell thickness was obtained by measuring the thickness of the center (the center in the width direction X and the center in the height direction Z) of the side surface (first side wall 14c in FIG. 1) with a large area of ​​the battery case using a laser displacement meter. The limit injection amount is the spatial volume obtained by subtracting the volume of the electrode body and the like from the internal volume of the battery case, and the injection amount when the electrolyte was injected until the electrolyte overflowed from the electrolyte injection hole was obtained using a weight sensor. In order to measure the limit injection amount, the storage tank 121 of the electrolyte injection device 200 was filled with electrolyte more than the first amount A1.

[0073] FIG. 10 is a graph showing the pressure change in the liquid injection device 200 (more specifically, the lower chamber 110 and the upper chamber 120) from the attachment step to the removal step, which corresponds to FIG. 6 of the embodiment. In the embodiment, similar to the embodiment of FIG. 3 described above, the liquid injection step (step S30), the case expansion step (step S40), and the degassing step (step S50) were performed, followed by the second liquid injection step and the second degassing step, and then the removal step (step S60). In the degassing step (step S50), the pressure in the assembly 100a was changed three times by repeatedly depressurizing and releasing the pressure in the upper chamber 120. In FIG. 10, the measurement points after the first liquid injection step are indicated as "after 1 injection" and after the second liquid injection step are indicated as "after 2 injection".

[0074] Fig. 11 is a diagram equivalent to Fig. 6 for a comparative example, that is, a graph showing the pressure change inside the liquid injection device 200 (more specifically, the lower chamber 110 and the upper chamber 120) from the attachment step to the removal step. In the comparative example, after the liquid injection step (step S30), the case expansion step was not performed, but the lower chamber 110 was returned to atmospheric pressure, and a degassing step was performed with the lower chamber 110 at atmospheric pressure, followed by an additional second liquid injection step and second degassing step, and then the removal step (step S60). The measurement points are indicated in Fig. 11 as "after 1 injection" and "after 2 injection".

[0075] FIG. 12 shows the change in cell thickness in the embodiment (N=2), and FIG. 13 shows the change in cell thickness in the comparative example (N=2). FIG. 14 shows the limit injection amount in the embodiment (N=2), and FIG. 15 shows the limit injection amount in the comparative example (N=2). As shown in FIG. 13, in the comparative example in which the lower chamber 110 was immediately returned to the atmospheric pressure state without performing the case expansion process, the cell thickness after one injection was smaller than that before injection, and the electrolyte once accommodated in the battery case was seen to flow back from the battery case to the storage tank 121. From a comparison of FIG. 12 and FIG. 13, in the embodiment, the case expansion process was performed, and the thickness of the battery case could be increased significantly compared to the comparative example. As a result, as shown in FIG. 14 and FIG. 15, the limit injection amount could be increased in the embodiment compared to the comparative example.

[0076] The embodiments of the technology disclosed herein have been described above. However, the above description is merely an example and does not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified in the above description.

[0077] The electrolyte injection hole 12a is an example of the "first through hole". However, in other embodiments, a first through hole may be provided in addition to the electrolyte injection hole 12a. The first through hole may be, for example, a through hole for adjusting the pressure inside the battery case 10. In such a case, for example, the case expansion step may be performed before the electrolyte injection step. Specifically, for example, the battery case 10 may be expanded first through the first through hole according to FIG. 8, and then the electrolyte 30 may be injected into the battery case 10 through the electrolyte injection hole 12a as shown in FIGS. 7(B) to (E).

[0078] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A manufacturing method for an electricity storage device including an electrode assembly including a positive electrode and a negative electrode, an electrolyte, and a battery case that accommodates the electrode assembly and the electrolyte, the manufacturing method including an assembly construction step of accommodating the electrode assembly inside a battery case having a first through hole to construct an assembly, a first chamber having a volume capable of accommodating the assembly, a second chamber, a switching member that switches between a communicated state and a non-communicated state between the first through hole of the assembly accommodated in the first chamber and the second chamber, and a pressure adjustment device that adjusts the pressure of at least one of the first chamber and the second chamber. a case expansion step of disposing the assembly in the first chamber, bringing the first through-hole of the assembly into communication with the second chamber, and expanding the battery case by a pressure difference between the first chamber and the second chamber; and a first liquid injection step of injecting electrolyte into the battery case, wherein the battery case is brought into an expanded state by the case expansion step at least either before or after injecting at least a portion of the electrolyte into the battery case in the first liquid injection step. Item 2: The manufacturing method according to item 1, wherein the first through hole is an electrolyte injection hole, and in the first injection step, the electrolyte is injected through the electrolyte injection hole. Item 3: The manufacturing method according to item 1 or 2, wherein in the case expansion step, the battery case is expanded such that, when a spatial volume inside the battery case before the case expansion step is taken as a reference, the spatial volume after the case expansion step is 1.1 times or more the reference. Item 4: The manufacturing method according to any one of Items 1 to 3, further comprising a second liquid injection step of injecting at least a portion of the electrolyte into the battery case after the first liquid injection step, in a state in which the bulge of the battery case is reduced compared to when the battery case is expanded by the case expansion step. Item 5: The manufacturing method according to item 4, wherein an amount of the electrolyte injected in the second electrolyte injection step is smaller than an amount of the electrolyte injected in the first electrolyte injection step. Item 6: A manufacturing method according to any one of items 1 to 3, wherein after the first liquid injection step, the pressure within the assembly is changed multiple times. [Explanation of symbols]

[0079] 10 Battery case 12a Electrolyte injection hole (1st through hole) 20 Electrode body 30 Electrolyte 100 Electricity storage device 100a Assembly 110 Lower room (1st room) 112 Pump (pressure regulator) 113 Release valve (pressure regulator) 120 Upper chamber (2nd chamber) 122 Pump (pressure regulator) 123 Release valve (pressure regulator) 140 Needle valve (switching member) 200 Liquid Injection Device

Claims

1. A method for manufacturing an electricity storage device including an electrode assembly including a positive electrode and a negative electrode, an electrolyte, and a battery case that accommodates the electrode assembly and the electrolyte, comprising: an assembly construction step of housing an electrode assembly inside a battery case having a first through hole to construct an assembly; an apparatus preparation step of preparing a liquid injection apparatus including a first chamber having a volume capable of accommodating the assembly, a second chamber, a switching member that switches between a communicated state and a non-communicated state between the first through-hole of the assembly accommodated in the first chamber and the second chamber, and a pressure adjustment device that adjusts a pressure of at least one of the first chamber and the second chamber; a case expansion step of placing the assembly in the first chamber, causing the first through-hole of the assembly to communicate with the second chamber, and expanding the battery case by a pressure difference between the first chamber and the second chamber; a first liquid injection step of injecting an electrolyte into the battery case; Including, the battery case is expanded in the case expansion step at least either before or after injecting at least a portion of the electrolyte into the battery case in the first liquid injection step.

2. The first through hole is an electrolyte injection hole, In the first injection step, the electrolyte is injected through the electrolyte injection hole. The method of claim 1 .

3. In the case expanding step, when a spatial volume inside the battery case before the case expanding step is taken as a reference, the battery case is expanded such that the spatial volume after the case expanding step is 1.1 times or more the reference. The method according to claim 1 or 2.

4. After the first liquid injection step, The method further includes a second liquid injection step of injecting at least a part of the electrolyte into the battery case in a state in which the bulge of the battery case is smaller than that in the case inflated by the case expansion step. The method according to claim 1 or 2.

5. The amount of the electrolyte injected in the second injection step is smaller than the amount of the electrolyte injected in the first injection step. The method according to claim 4.

6. After the first liquid injection step, the pressure in the assembly is changed multiple times. The method according to claim 1 or 2.

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