Manufacturing method for energy storage devices

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 energy storage device. [Background technology]

[0002] A typical energy storage device comprises an electrode body, an electrolyte, and a battery case that houses the electrode body and the electrolyte. Prior art documents relating to a method for manufacturing such an energy storage device include Patent Documents 1 to 3.

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

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-251084 [Patent Document 2] Japanese Patent Publication No. 2018-170210 [Patent Document 3] Japanese Patent Publication No. 2008-091065 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In Patent Document 1, in the first step, a pair of narrow vertical walls of the battery case are pressed together with a pressing jig in a direction toward each other, or the center of the wide vertical wall is pulled with a suction cup jig to curve the wide vertical wall outwards. According to the inventors' research, this method takes time to inflate the battery case. As a result, the total time required to manufacture the energy storage device increases, and there is a risk of decreased productivity.

[0006] The technology disclosed herein has been developed in view of the above circumstances and aims to provide a manufacturing method that allows for efficient injection of electrolyte and is less likely to reduce productivity. [Means for solving the problem]

[0007] The technology disclosed herein provides a method for manufacturing an energy storage device comprising an electrode body including a positive electrode and a negative electrode, an electrolyte, and a battery case housing the electrode body and the electrolyte. The manufacturing method includes: an assembly construction step of constructing an assembly by housing an electrode body inside a battery case having a first through-hole; an apparatus preparation step of preparing an electrolyte injection apparatus comprising a first chamber and a second chamber having a volume capable of housing the assembly, a switching member that switches between a state in which the first through-hole of the assembly housed in the first chamber and the second chamber are in communication and a state in which they are not, and a pressure adjustment device that adjusts the pressure in at least one of the first chamber and the second chamber; a case expansion step of placing the assembly in the first chamber, connecting the first through-hole of the assembly and the second chamber, and expanding the battery case due to the pressure difference between the first chamber and the second chamber; and a first electrolyte injection step of injecting electrolyte into the battery case, wherein in the first electrolyte injection step, the battery case is expanded by the case expansion step at least one of the time before and after injecting at least a portion of the electrolyte into the battery case.

[0008] With the above configuration, the battery case can be easily expanded, allowing for efficient injection of electrolyte and suppressing a decrease in productivity. [Brief explanation of the drawing]

[0009] [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 showing the internal structure of the energy storage device shown in Figure 1. [Figure 3]FIG. 3 is a flowchart for explaining a manufacturing method according to an embodiment. [Figure 4] FIG. 4 is a perspective view schematically showing an electrode body attached to a sealing plate. [Figure 5] FIG. 5 is a schematic diagram showing the configuration of a liquid injection device according to an embodiment. [Figure 6] FIG. 6 is a graph showing the pressure change from the mounting step to the removal step. [Figure 7] FIGS. 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] FIGS. 9(A) and (B) are schematic diagrams showing the procedure of the removal step. [Figure 10] FIG. 10 is a diagram corresponding to FIG. 6 of the example. [Figure 11] FIG. 11 is a diagram corresponding to FIG. 6 of the comparative example. [Figure 12] FIG. 12 is a graph showing the change in the cell thickness of the example. [Figure 13] FIG. 13 is a graph showing the change in the cell thickness of the comparative example. [Figure 14] FIG. 14 is a bar graph showing the limit liquid injection amount of the example. [Figure 15] FIG. 15 is a bar graph showing the limit liquid injection amount of the comparative example.

DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, several embodiments of the technology disclosed herein will be described in detail with reference to the drawings. Matters other than those specifically mentioned herein but necessary for 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 technology disclosed herein can be carried out based on the content disclosed herein and common technical knowledge in the art. Furthermore, in the following drawings, the same reference numerals are used to denote components and parts that perform the same function. In this specification, the notation "A~B" indicating a range encompasses not only the meaning of "greater than A and less than or equal to B," but also "greater than A" and "less than B."

[0011] In this specification, "energy storage device" refers to all energy storage devices that can repeatedly charge and discharge by the movement of a charge carrier between a positive electrode and a negative electrode via an electrolyte. The concept of "energy storage device" includes secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, as well as capacitors such as lithium-ion capacitors and electric double-layer capacitors. Furthermore, in this specification, "pressure" refers to gauge pressure (i.e., the difference obtained by subtracting atmospheric pressure from absolute pressure) with respect to atmospheric pressure (0 kPa, normal pressure).

[0012] <1. Configuration of the energy storage device> Figure 1 is a schematic perspective view of the energy storage device 100. Figure 2 is a schematic longitudinal cross-sectional view of the internal structure of the energy storage device 100. In Figures 1 and 2, the symbol X 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, up, and down directions, respectively. However, these directions are defined for the convenience of explanation and do not in any way limit the installation configuration of the energy storage device 100.

[0013] As shown in Figure 2, the energy storage device 100 comprises a battery case 10, an electrode body 20, and an electrolyte 30. In this case, the energy storage device 100 is a lithium-ion secondary battery. The energy 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 body 20 and the electrolyte 30. As shown in Figure 1, the battery case 10 has a flattened, bottomed rectangular parallelepiped (square) shape. The battery case 10 is preferably square. The material of the battery case 10 can be the same as that used conventionally, and there are no particular restrictions. The battery case 10 is preferably made of metal, and more preferably of aluminum, aluminum alloy, iron, iron alloy, etc.

[0015] While not particularly limited, the internal volume of the battery case 10 is 500 cm³. 3 The above is preferable, 1000cm 3 The above is more preferable. The upper limit of the internal volume of the battery case 10 is 3000 cm³. 3 The following is also acceptable: 1500cm 3 The following is also acceptable. Furthermore, the technology disclosed herein has an internal volume of 300 cm³. 3 Below (typically 150cm) 3 It can also be applied to the following small batteries.

[0016] As shown in Figure 2, the battery case 10 comprises a case body 14 having an opening 14a and a sealing plate (lid) 12 that closes the opening 14a. Preferably, the battery case 10 comprises a case body 14 and a sealing plate 12. The battery case 10 is integrated by joining (e.g., welding) the sealing plate 12 to the periphery of the opening 14a of the case body 14. The battery case 10 is airtightly sealed.

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

[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 it does not significantly impede the effects of the technology disclosed herein. For this reason, 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, and 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, and more preferably 8 cm or more. By forming the first side wall 14c having a certain width and height (i.e., area) or more in this way, it becomes easier to deform the first side wall 14c in the manufacturing method described later.

[0019] The width of the first side wall 14c may be 35 cm or less, or 30 cm or less. The height of the first side wall 14c may be 12 cm or less, or 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 further deform the first side wall 14c in the manufacturing method described later. 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 of the first side wall 14c (length in the depth direction Y) 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 later. 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] Furthermore, 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. By narrowing the width of the second side wall 14d in this way, deformation of the second side wall 14d can be effectively suppressed. The lower limit of the width of the second side wall 14d may be 1 cm or more, or 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. Furthermore, 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 the thickness of the first side wall 14c, or thicker than the first side wall 14c. This suppresses deformation of the second side wall 14d. On the other hand, considering the weight and material cost of the energy storage device 100, the thickness of the second side wall 14d is preferably 3 mm or less, more preferably 2 mm or less, and even more 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 effectively suppresses deformation of the bottom wall 14b. On the other hand, considering the weight and material cost of the energy 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-shaped member that seals the opening 14a. As shown in Figure 1, the sealing plate 12 is substantially rectangular in 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. It is preferable that the sealing plate 12 is thicker than the first side wall 14c. This suppresses deformation of the sealing plate 12 in the manufacturing method described later. On the other hand, considering the weight and material cost of the energy storage device 100, the thickness of the sealing plate 12 is preferably 5 mm or less, and more preferably 4 mm or less.

[0024] As shown in Figure 2, the sealing plate 12 in this embodiment is provided with an electrolyte injection hole 12a and a gas discharge valve 12b. The electrolyte injection hole 12a is for injecting the electrolyte 30 into the inside of the battery case 10 after the sealing plate 12 has been 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 has been injected. Conventionally known members can be used as the sealing member 16 without any particular limitations. An example of the sealing member 16 is a metal member such as a blind rivet.

[0026] The gas discharge valve 12b is configured to rupture when the internal pressure of the battery case 10 exceeds a predetermined value, thereby discharging gas from the battery case 10 to the outside. The gas discharge valve 12b is a thin-walled portion that is thinner than the other parts of the sealing plate 12. The thickness of the gas discharge 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 discharge valve 12b is preferably 0.05 mm or more, and more preferably 0.1 mm or more. This helps to suppress malfunction of the gas discharge valve 12b in the manufacturing method described later.

[0027] As shown in Figure 2, a pair of electrode terminals 40 are attached to both ends of the sealing plate 12 in the width direction X (the left and right ends in Figure 2). Each electrode terminal 40 is a structure made up of multiple conductive members and extends along the height direction Z. The current collector member 40a that constitutes 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 Figure 4, a current collector member 40a is attached to each electrode body 20, so each of the pair of electrode terminals 40 has multiple (three in Figure 4) current collector members 40a. On the other hand, the external terminal 40b that constitutes 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 the same as that of a general energy storage device and does not limit the technology disclosed herein, so a detailed explanation is omitted.

[0028] As shown in Figure 2, the electrode body 20 is housed inside the battery case 10. As shown in Figure 4, in this embodiment, multiple (three in Figure 4) electrode bodies 20 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. In this case, the electrode body 20 is a wound electrode body. Specifically, the electrode body 20 is formed by winding a laminate, which is made by stacking a strip-shaped positive electrode and a strip-shaped negative electrode with a strip-shaped separator in between, in the longitudinal direction around a winding axis. However, in other embodiments, the electrode body 20 may be a laminate electrode body in which a rectangular positive electrode and a rectangular negative electrode are stacked in an insulated state.

[0030] The electrode body 20 in this embodiment has a flattened outer shape. The electrode body 20 is housed inside the battery case 10 with its winding axis oriented along the width direction X. Therefore, in this embodiment, the flattened surface of the electrode body 20 faces the first side wall 14c of the case body 14. However, the electrode body 20 may also be housed inside the battery case 10 with, for example, its winding axis oriented along the height direction Z. Note that the components constituting the electrode body 20 (positive electrode, negative electrode, separator, etc.) may be the same as those in a general energy storage device and do not limit the technology disclosed herein, so a detailed explanation is omitted.

[0031] The electrolyte 30 is housed inside the battery case 10 together with the electrode body 20. The electrolyte 30 permeates into the inside of the electrode body 20 (for example, between the positive and negative electrodes). As shown in Figure 2, a portion of the electrolyte 30 may exist outside the electrode body 20 as excess electrolyte 32 (between the battery case 10 and the electrode body 20). The electrolyte is, for example, a non-aqueous liquid electrolyte (non-aqueous electrolyte) containing a non-aqueous solvent and a supporting salt. The components of the electrolyte 30 may be the same as those of a general energy storage device and do not limit the technology disclosed herein, so a detailed explanation is omitted.

[0032] <2. Manufacturing method of energy storage device> Figure 3 is a flowchart illustrating a manufacturing method according to one embodiment. As shown in Figure 3, the manufacturing method of this embodiment includes the following steps: assembly construction step (step S10a), apparatus preparation step (step S10b), mounting step (step S20), liquid injection step (step S30), case expansion step (step S40), degassing step (step S50), removal step (step S60), and sealing step (step S70). The case expansion step (step S40) is included in the middle of the liquid injection step (step S30). Similarly, the degassing step (step S50) is also included in the middle of the liquid injection step (step S30). 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 apparatus preparation step (step S10b) may be reversed. Also, as described in the modified examples below, 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). Furthermore, the manufacturing method of this embodiment may 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 to remove moisture from inside the battery case 10 (particularly inside the electrode body 20) may be included.

[0034] The assembly construction process (step S10a) is a process of constructing an assembly 100a by housing the electrode bodies 20 in a battery case 10 having a first through hole (in this case, an electrolyte injection hole 12a). In this process, for example, first, as shown in Figure 4, the current collector members 40a of the electrode terminals 40 are connected to each of the multiple electrode bodies 20. This creates a combined object in which the sealing plate 12 and the multiple electrode bodies 20 are integrated. Next, the sealing plate 12 is fitted into the opening 14a of the case body 14, housing the multiple electrode bodies 20 inside the case body 14. As a result, as shown in Figure 2, the multiple electrode bodies 20 are housed inside the case body 14 with their winding axes oriented along the width direction X. Next, with the electrode bodies 20 positioned inside the case body 14, the sealing plate 12 is joined (for example, by welding) to the periphery of the opening 14a of the case body 14, integrating the case body 14 and the sealing plate 12. In addition, conventionally known joining methods can be used without any particular limitations for joining the sealing plate 12 and the case body 14. Preferred examples of such joining methods include laser welding. In this way, the assembly 100a (battery case 10 housing the electrode body 20) can be constructed.

[0035] The apparatus preparation step (step S10b) is the process of preparing the liquid injection apparatus to be used in the liquid injection process, case expansion process, etc., which will be described later. Figure 5 is a schematic diagram showing the configuration of the liquid injection apparatus 200 according to one embodiment. As shown in Figure 5, the liquid injection apparatus 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. In this case, the lower chamber 110 is a vacuum chamber. The lower chamber 110 is an example of the "first chamber". The lower chamber 110 has a lifting table 111 on which the assembly 100a is placed and which can move up and down by a lifting mechanism (not shown), a pump 112 for pressurizing the inside of the lower chamber 110, and a release valve 113 for depressurizing (pressurizing) the inside of the lower chamber 110. The lower chamber 110 may also be fitted with a gauge for measuring the internal pressure. The lifting mechanism of the lifting table 111, the pump 112, and the release valve 113 are electrically connected to the control device. The lifting mechanism is, for example, a ball screw mechanism. The lifting table 111 is configured to be movable upward and downward by the control device. The pump 112 is configured to be switchable between being driven and stopped by the control device. The release valve 113 is configured to be switchable between an open state and a closed state by the control device. The pump 112 and the release valve 113 are an example of a "pressure regulating device" that adjusts the pressure in the lower chamber 110.

[0037] The upper chamber 120 is located above (more specifically, directly above) the lower chamber 110. In a plan view, the upper chamber 120 is positioned to overlap with the lower chamber 110. The upper chamber 120 is a vacuum chamber in this case. The upper chamber 120 is an example of a "second chamber". The upper chamber 120 has a storage tank 121 for storing electrolyte, a pump 122 for pressurizing the inside of the upper chamber 120, and a release valve 123 for depressurizing (pressurizing) the inside of the upper chamber 120. The upper chamber 120 may also be fitted with a gauge for measuring the internal pressure. Electrolyte is supplied to the storage tank 121 by an electrolyte supply mechanism 150, which will be described later. The lower wall of the storage tank 121 is tapered toward the communication port 130. The pump 122 and the release valve 123 are electrically connected to the control device. The pump 122 is configured to be switchable between being driven and stopped by the control device. The release valve 123 is configured to be switchable between an open state and a closed state by the control device. The pump 122 and the release valve 123 are an example of a "pressure regulating device" that adjusts the pressure in the upper chamber 120.

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

[0039] The communication port 130 penetrates vertically through the partition wall between the lower chamber 110 and the upper chamber 120. In this case, the communication port 130 connects the lower chamber 110 and the storage tank 121. The communication port 130 is provided to allow communication between the electrolyte injection hole 12a of the assembly 100a housed in the lower chamber 110 and the upper chamber 120 (specifically the storage tank 121).

[0040] The needle valve 140 is configured to communicate between the electrolyte injection hole 12a of the assembly 100a housed in the lower chamber 110 and the upper chamber 120 (specifically the storage tank 121) by switching between an open state and a closed state of the communication port 130. In this case, the needle valve 140 is located inside the storage tank 121. The needle valve 140 is housed in an outer casing (not shown) and is configured to move vertically within the outer casing. The needle valve 140 is biased downward (in the closing direction) by a spring (not shown). This closes the communication port 130. 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 control device moves the needle valve 140 upward, the communication port 130 is opened. The needle valve 140 is an example of a "switching member" that switches between a state in which the electrolyte injection hole 12a and the upper chamber 120 are in communication and a state in which they are not. 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 electrolyte to the storage tank 121 in the upper chamber 120. The electrolyte supply mechanism 150 has an electrolyte main tank 151 and a supply channel 152 whose upstream end is connected to the main tank 151. The electrolyte is supplied to the storage tank 121 through the supply channel 152. A liquid transfer pump 153 and a supply nozzle 154 are provided in the middle of the supply channel 152, from the upstream side. A valve body may also be provided in the middle of the supply channel 152. The liquid transfer pump 153 is configured to supply a predetermined amount of electrolyte 30 from the main tank 151 to the storage tank 121. At least the lower end of the supply nozzle 154 is located inside the upper chamber 120. The supply nozzle 154 is configured to be movable up and down by an actuator (not shown). The actuators of the liquid transfer pump 153 and the supply nozzle 154 are electrically connected to a control device. The liquid transfer pump 153 is configured to be switchable between being driven and stopped by the 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 actuators of the pump 122, the release valve 123, the needle valve 140, and the actuators of the liquid transfer pump 153 and the supply nozzle 154, and is configured to control them. The hardware configuration of the control device is not particularly limited. For example, the control device includes an interface (I / F), a central processing unit (CPU) that executes instructions for the 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 memory that stores the program and various data.

[0043] The installation process (step S20) is the process of attaching the assembly 100a to the liquid injection device 200. Figure 6 is a graph showing the pressure changes inside the liquid injection device 200 (specifically the lower chamber 110 and upper chamber 120) from this process to the removal process (step S60). In Figure 6, the pressure inside the battery case 10 is shown by a dashed line. Figures 7(A) to 7(E) are schematic diagrams showing the procedures for this process and the liquid injection process (step S30). In subsequent drawings, only the essential parts of the liquid injection device 200 are shown, and the illustration of some components may be omitted.

[0044] In this process, for example, first, the door of the lower chamber 110 (not shown) is opened, and the assembly 100a is placed on the lifting table 111 of the lower chamber 110, as shown in Figure 7(A). At this time, the battery case 10 of the assembly 100a has its outer surface exposed inside the lower chamber 110. Also, the electrolyte injection hole 12a of the assembly 100a (not shown in Figure 7(A)) is open. The assembly 100a placed on the lifting 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. In this state, the door of the lower chamber 110 is closed to seal the lower chamber 110. Note that in this process, both the lower chamber 110 and the upper chamber 120 are under atmospheric pressure (see Figure 6(0)).

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

[0046] Once the pressure inside the lower chamber 110 has been reduced to the first pressure, the assembly 100a is then moved upward by the lifting mechanism of the lifting table 111, as shown in Figure 7(B). This presses the side of the assembly 100a facing the sealing plate 12 against the upper wall of the lower chamber 110, causing the electrolyte injection hole 12a to be in close contact with the communication port 130. A packing is provided around the periphery of the communication port 130. The packing is compressed by the sealing plate 12, sealing the electrolyte injection hole 12a and closing the assembly 100a. At this time, as shown in Figure 6, the upper chamber 120 is at atmospheric pressure. The lower chamber 110 maintains the reduced pressure state described above. The needle valve 140 also closes the communication port 130. The inside of the assembly 100a is not in communication with the upper chamber 120. Airflow between the upper chamber 120 and the assembly 100a is blocked.

[0047] Next, the electrolyte supply mechanism 150 stores a predetermined first quantity A1 of electrolyte 30 in the storage tank 121 of the upper chamber 120. Specifically, as shown in Figure 7(C), first, the actuator of the supply nozzle 154 is driven to move the supply nozzle 154 downward. This positions the lower end of the supply nozzle 154 inside the storage tank 121. Next, by driving the liquid transfer pump 153 (not shown in Figure 7(C)), the first quantity A1 of electrolyte 30 is stored in the storage tank 121 from the main tank 151 via the supply channel 152 and the supply nozzle 154. The first quantity A1 is not particularly limited, but for example, it is 340 ± 30 g. At this time, as shown in Figure 6, the upper chamber 120 is at atmospheric pressure. The lower chamber 110 maintains the reduced pressure state described above. Also, the needle valve 140 closes the communication port 130. The interior of assembly 100a is not connected to the upper chamber 120.

[0048] When the first amount A1 of electrolyte 30 has accumulated 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 Figure 7(D), with the upper chamber 120 sealed, the pump 122 (not shown in Figure 7(D)) is driven to reduce the pressure inside the upper chamber 120 until a predetermined second pressure is reached (see Figure 6(2)). The second pressure is not particularly limited, but is typically less reduced than the first pressure in the lower chamber 110 (closer to atmospheric pressure), for example, -70kPa in Figure 6. At this time, as shown in Figure 6, the lower chamber 110 maintains the reduced pressure state. Also, the needle valve 140 closes the communication port 130. The inside of the assembly 100a is not in communication with the upper chamber 120.

[0049] Once the pressure inside the upper chamber 120 is reduced to the second pressure, the actuator of the needle valve 140 is then driven, as shown in Figure 7(E), to move the needle valve 140 upward. This opens the communication port 130, and the assembly 100a is connected to the storage tank 121 in the upper chamber 120. As a result, as shown in Figure 6(3), the pressure inside the battery case 10 becomes equal to the pressure in the upper chamber 120, and the electrolyte 30 from the storage tank 121 is supplied to the inside of the assembly 100a, more specifically, to the inside of the battery case 10. At this time, the amount of electrolyte 30 supplied to the battery case 10 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. Also, when the communication port 130 is opened, the degree of reduced pressure in the assembly 100a is higher than the degree of reduced pressure in the upper chamber 120, so the electrolyte 30 is easily supplied to the assembly 100a due to the difference in reduced pressure. As a result, the electrolyte 30 is efficiently distributed throughout the inside of the electrode body 20, and the time required for the electrolyte 30 to penetrate can be shortened. Preferably, the amount of electrolyte that can be injected can be further increased.

[0051] In the case expansion process (step S40), the battery case 10 is expanded by creating a pressure difference between the lower chamber 110 and the upper chamber 120 using the electrolyte injection device 200. Preferably, this process expands the battery case 10 by reducing the pressure in the lower chamber 110. Figure 8 is a schematic diagram showing the procedure of this process. As shown in Figure 8, after the electrolyte 30 from the storage tank 121 is supplied to the assembly 100a, the release valve 123 (not shown in Figure 8) is opened to return the upper chamber 120 to atmospheric pressure (pressure release, see also (4) in Figure 6). As a result, as shown in Figure 6, the inside of the assembly 100a is connected to the upper chamber 120 and returns to atmospheric pressure. On the other hand, the lower chamber 110 remains in the reduced pressure state. Therefore, a pressure difference is created between the lower chamber 110 and the inside of the assembly 100a, and the battery case 10 expands due to this pressure difference. As a result, the incorporation of the electrolyte 30 into the electrode body 20 is promoted. Furthermore, since the needle valve 140 is open during this process, if there is electrolyte 30 remaining in the storage tank 121, the internal volume of the battery case 10 increases, causing additional electrolyte 30 remaining in the storage tank 121 to be 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 higher, the battery case 10 can be greatly expanded, and the amount of electrolyte that can be injected can be suitably increased. The above pressure difference is not particularly limited, but it is preferably 10 to 200 kPa, more preferably 50 to 120 kPa, and for example, in Figure 6 it is about 100 kPa.

[0053] As mentioned above, when a flat battery case 10 is used, the first sidewall 14c, which has a relatively large surface area, expands preferentially, making it easier to control the amount of deformation. Therefore, in some embodiments, it is preferable in this step to expand the battery case 10 so that the thickness of the center of the pair of first sidewalls 14c is displaced (expands) by, for example, 2.5 to 4.0 mm.

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

[0055] Although not particularly limited, the ratio of the space volume 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. Thereby, the impregnation of the electrolyte 30 into the electrode body 20 can be promoted. Also, preferably, the amount of electrolyte that can be injected can be suitably increased. Therefore, the effects of the technology disclosed herein can be exhibited at a high level.

[0056] In some embodiments, from the viewpoint of exhibiting the effects of the technology disclosed herein at a high level, the increase amount V3 (=V2 - V1) of the internal volume of the battery case 10 after performing this step (after inflation) is 10 cm 3 or more, preferably, more preferably 20 cm 3 or more, and even more preferably 50 cm 3 or more. From the viewpoint of suppressing damage to the battery case 10 (for example, the portion where the gas discharge valve 12b is provided, the joint portion between the sealing plate 12 and the case body 14, etc.), the increase amount V3 of the internal volume is preferably 150 cm 3 or less, more preferably 120 cm 3 or less, and even more preferably 100 cm 3 or less.

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

[0058] At this time, as shown in Figure 6, the lower chamber 110 maintains the reduced pressure state described above. Also, since the inside of the assembly 100a is in communication with the upper chamber 120, it is at the same pressure as inside the upper chamber 120. By maintaining this pressure state, any bubbles (gas) remaining or generated inside the assembly 100a during the injection of the electrolyte 30 can be moved to the upper chamber 120 side, allowing the inside of the assembly 100a to be degassed. As a result, the impregnation of the electrode body 20 with the electrolyte 30 can be promoted. Furthermore, since the needle valve 140 is open in this process, if there is electrolyte 30 remaining in the storage tank 121 and there is a gap inside the battery case 10, the battery case 10 can be depressurized, allowing additional electrolyte 30 remaining in the storage tank 121 to be injected.

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

[0060] While the depressurization of the assembly 100a may be performed only once, in some embodiments, the pressure inside the assembly 100a may be changed multiple times by repeatedly depressurizing and depressurizing (or pressurizing) the upper chamber 120, for example. For example, while maintaining the depressurized state of the lower chamber 110, the following operations may be repeated multiple times (for example, 2 to 5 times): (S1) driving the pump 122 to depressurize the upper chamber 120 to a predetermined pressure, preferably maintaining the depressurized state of the upper chamber 120 for a predetermined time, and (S2) opening the release valve 123 to return the upper chamber 120 to atmospheric pressure (depressurize), preferably maintaining the atmospheric pressure state of the upper chamber 120 for a predetermined time. This allows for degassing of even the finer details of the assembly 100a and further promotes the impregnation of the electrode body 20 with the electrolyte 30.

[0061] The removal process (step S60) is the process of removing the assembly 100a from the liquid injection device 200. In this process, first, the release valve 113 is opened to return the lower chamber 110 to atmospheric pressure (pressure relief; see also (7) in Figure 6). For example, to prevent overshoot, which is a temporary instability in pressure, the pump 112 may be driven to pressurize the lower chamber 110, or the pump 122 may be driven to pressurize the upper chamber 120. The pressure is then held for a predetermined time to stabilize. Figure 9 is a schematic diagram showing the procedure of this process. Next, as shown in Figure 9(A), the actuator of the needle valve 140 is driven to move the needle valve 140 downward. This closes the communication port 130, blocking the space between the assembly 100a and the upper chamber 120. Next, as shown in Figure 9(B), the assembly 100a is moved downward by the lifting mechanism of the lifting table 111. Then, the assembly 100a is removed from the liquid 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 in which the electrolyte injection hole 12a of the battery case 10 is sealed. In this step, preferably, first the assembly 100a removed from the electrolyte injection device 200 is moved to the charging equipment, the temporary seal is released (with the electrolyte injection hole 12a open), and the assembly 100a is charged at least once for the first time. During the first charge, gas may be generated due to the decomposition of the electrolyte 30, but by charging the assembly 100a for the first time 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 may be, for example, a metal member and may be attached to the sealing plate 12 by welding to seal the electrolyte injection hole 12a. The sealing member 16 may be, for example, a blind rivet and may be attached to the sealing plate 12 by crimping to seal the electrolyte injection hole 12a. Alternatively, after sealing the electrolyte injection hole 12a with a blind rivet, a blind rivet may be further welded to the sealing plate 12. In this way, an energy storage device 100 (see Figure 1) is constructed in which the electrode body 20 and electrolyte 30 are housed in a sealed battery case 10.

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

[0065] <3. Other Embodiments> In the embodiment shown in Figure 3 above, the electrolyte injection process was performed only once. However, in some embodiments, it is preferable to perform a second electrolyte injection process (second electrolyte injection process), for example, after the case expansion process (step S40) or after the degassing process (step S50). According to the inventors' findings, the first electrolyte injection process (first electrolyte injection process) fills the space between the battery case 10 and the electrode body 20 with electrolyte 30. However, impregnation by capillary action is necessary to allow the electrolyte 30 to penetrate into the inside of the electrode body 20. Therefore, it takes a certain amount of time for the electrolyte 30 to penetrate into the inside of the electrode body 20. By performing a second electrolyte injection process, the electrolyte 30 used by capillary action can be suitably replenished.

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

[0067] Once the second amount A2 of electrolyte 30 has accumulated in the storage tank 121, the pressure inside the upper chamber 120 is reduced to a level lower than the first pressure in the lower chamber 110 (near atmospheric pressure, for example, the second pressure), as shown in Figure 7(D) above. Then, with the upper chamber 120 having a lower pressure than the lower chamber 110, the electrolyte 30 is supplied into the battery case 10 as shown in Figure 7(E). At this time, the amount of electrolyte 30 supplied into the battery case 10 is typically less than the second amount A2.

[0068] Next, without performing the case expansion process (Figure 8), for example, the release valve 113 is immediately opened to return the lower chamber 110 to atmospheric pressure (pressure release). As a result, the upper chamber 120 becomes less depressurized than the lower chamber 110. Therefore, compared to the previous case expansion process (step S40), the remaining electrolyte 30 can be added with less swelling of the battery case 10. The pressure difference between the lower chamber 110 and the upper chamber 120 is 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 (low absolute pressure) and the upper chamber 120 is at negative pressure (high absolute pressure). By adding the remaining electrolyte 30 while returning the thickness of the battery case 10 to approximately its original state in this way, productivity can be improved.

[0069] After the second liquid injection step, a second degassing step may be performed in which the upper chamber 120 is depressurized at least once, in accordance with the degassing step described above, while the lower chamber 110 is at atmospheric pressure. Alternatively, 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. 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).

[0071] The following describes some embodiments of the present invention, but it is not intended to limit the present invention to these embodiments.

[0072] The cell thickness change and limiting electrolyte injection volume were compared between two cases: one in which a case expansion process as shown in Figure 8 was performed during electrolyte injection (Example, N=2), and another in which the case expansion process was not performed (Comparative Example, N=2). The cell thickness was determined by measuring the thickness of the center of the largest side surface of the battery case (the first side wall 14c in Figure 1) (the center in the width direction X and the center in the height direction Z) using a laser displacement meter. The limiting electrolyte injection volume was the internal volume of the battery case minus the volume of the electrodes, etc., and the amount of electrolyte injected when it was injected until just before it overflowed from the electrolyte injection hole was determined using a weight sensor. In addition, to measure the limiting electrolyte injection volume, a larger amount of electrolyte than the first amount A1 was placed in the storage tank 121 of the electrolyte injection device 200.

[0073] Figure 10 is a graph showing the pressure changes inside the liquid injection device 200 (specifically the lower chamber 110 and upper chamber 120) from the installation process to the removal process, which corresponds to Figure 6 of the embodiment. In this embodiment, similar to the embodiment in Figure 3 described above, after performing the liquid injection process (step S30), case expansion process (step S40), and degassing process (step S50), a second liquid injection process and a second degassing process were added, followed by the removal process (step S60). In the degassing process (step S50), the pressure inside the assembly 100a was changed three times by repeatedly depressurizing and releasing the pressure in the upper chamber 120. In Figure 10, the measurement points are indicated as "After 1st Injection" after the first liquid injection process and "After 2nd Injection" after the second liquid injection process.

[0074] Figure 11 is a graph showing the pressure change inside the liquid injection device 200 (specifically the lower chamber 110 and upper chamber 120) from the installation process to the extraction process, which is equivalent to Figure 6 of the comparative example. In the comparative example, after the liquid injection process (step S30), the case expansion process was not performed, the lower chamber 110 was returned to atmospheric pressure, the degassing process was performed with the lower chamber 110 at atmospheric pressure, and then the second liquid injection process and second degassing process were added before the extraction process (step S60) was performed. The measurement points are indicated in Figure 11 as "After 1 injection" and "After 2 injections".

[0075] Figure 12 shows the change in cell thickness in Example (N=2), and Figure 13 shows the change in cell thickness in Comparative Example (N=2). Figure 14 shows the limit injection volume in Example (N=2), and Figure 15 shows the limit injection volume in Comparative Example (N=2). As shown in Figure 13, in the Comparative Example, where the case expansion process was not performed and the lower chamber 110 was immediately returned to atmospheric pressure, the cell thickness after one injection became smaller than before injection, and consequently, it was observed that the electrolyte, once contained in the battery case, flowed back from the battery case to the storage tank 121. Comparing Figures 12 and 13, it can be seen that in Example, the case expansion process significantly increased the thickness of the battery case compared to the Comparative Example. As a result, as shown in Figures 14 and 15, the limit injection volume could be increased in Example compared to the Comparative Example.

[0076] The embodiments of the technology disclosed herein have been described above. However, the above description is illustrative and does not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated in the above description.

[0077] The electrolyte injection hole 12a is an example of a "first through-hole". However, in other embodiments, a first through-hole may be provided separately from the electrolyte injection hole 12a. The first through-hole may be, for example, a through-hole for pressure adjustment within the battery case 10. In such a case, for example, the case expansion process may be performed before the electrolyte injection process. Specifically, for example, first the battery case 10 may be expanded through the first through-hole according to Figure 8, and then the electrolyte 30 may be injected into the battery case 10 through the electrolyte injection hole 12a as shown in Figures 7(B) to (E).

[0078] 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 an electrode body including a positive electrode and a negative electrode, an electrolyte, and a battery case for housing the electrode body and the electrolyte, comprising: an assembly construction step of housing the electrode body inside a battery case having a first through hole to construct an assembly; a first chamber having a volume capable of housing the assembly; a second chamber; a switching member for switching between a state in which the first through hole of the assembly housed in the first chamber and the second chamber are in communication and a state in which they are not; and a pressure regulating device for adjusting the pressure in at least one of the first chamber and the second chamber. A method for manufacturing an energy storage device, comprising: a device preparation step of preparing a liquid injection device; a case expansion step of placing the assembly in the first chamber, connecting the first through-hole of the assembly 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 one of the following times: before and 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 the volume of space inside the battery case after the case expansion step is 1.1 times or more the volume of space inside the battery case after the case expansion step, with the volume of space inside the battery case before the case expansion step as the reference. Item 4: The manufacturing method according to any one of items 1 to 3, further comprising a second liquid injection step, after the first liquid injection step, injecting at least a portion of the electrolyte into the battery case while the battery case is less swollen than when the battery case is swollen by the case expansion step. Item 5: The manufacturing method according to Item 4, wherein the amount of electrolyte injected in the second injection step is less than the amount of electrolyte injected in the first injection step. Item 6: The manufacturing method according to any one of items 1 to 3, wherein the pressure inside the assembly is changed multiple times after the first liquid injection step described above. [Explanation of symbols]

[0079] 10 Battery Case 12a Electrolyte injection hole (1st through hole) 20 Electrode body 30 Electrolyte 100 Energy storage devices 100a Assembly 110 Lower room (1st room) 112 Pump (pressure regulator) 113. Opening valve (pressure regulating device) 120 Upper chamber (2nd chamber) 122 Pump (Pressure Regulator) 123. Opening valve (pressure regulating device) 140 Needle valve (switching component) 200 Injection device

Claims

1. A method for manufacturing an energy storage device comprising an electrode body including a positive electrode and a negative electrode, an electrolyte, and a battery case for housing the electrode body and the electrolyte, The assembly construction process involves constructing an assembly by housing an electrode body inside a battery case having a first through-hole, A liquid injection device is prepared, comprising: a first chamber having a volume capable of accommodating the assembly; a second chamber having a storage tank for storing electrolyte; a switching member that switches between a state in which the first through-hole of the assembly housed in the first chamber and the second chamber are in communication and a state in which they are not; and a pressure adjustment device for adjusting the pressure in the first chamber and the second chamber, respectively. A first injection step involves injecting a first amount of the electrolyte into the battery case of the assembly using the aforementioned liquid injection device, Includes, The first injection step is, The process involves placing the assembly in the first chamber with the first through-hole open, using the pressure adjustment device to reduce the pressure in the first chamber and the battery case to a first pressure, and reducing the pressure in the second chamber to a second pressure which is lower than the first pressure, then using the switching member to connect the first through-hole and the second chamber of the assembly, and injecting the electrolyte into the battery case from the first through-hole based on the difference in the degree of pressure reduction between the first chamber and the second chamber, After injecting the electrolyte, the process involves maintaining a reduced pressure in the first chamber while using the pressure adjustment device to return the second chamber and the battery case to atmospheric pressure, thereby creating a higher degree of reduced pressure in the first chamber than in the battery case, causing the battery case to expand due to the pressure difference, and injecting the remaining electrolyte; A method for manufacturing an energy storage device, including the method described above.

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 manufacturing method according to claim 1.

3. When inflating the battery case in the first liquid injection step, the battery case is inflated such that the volume of space inside the battery case before inflation is 1.1 times or more of the volume of space after inflation, based on the volume of space inside the battery case before inflation. The manufacturing method according to claim 1 or 2.

4. The process further includes a second liquid injection step, in which, after the first liquid injection step, a second amount of the electrolyte is injected into the battery case of the assembly using the liquid injection device. In the second injection step, After injecting the electrolyte due to the difference in pressure while the pressure in the second chamber is lower than that in the first chamber, the first chamber is returned to atmospheric pressure, and the second chamber is made to have a higher pressure than the first chamber, thereby reducing the swelling of the battery case compared to the process of expanding the battery case and injecting additional electrolyte, and the remaining electrolyte is then injected into the battery case. The manufacturing method according to claim 1 or 2.

5. The second amount in the second injection step is less than the first amount in the first injection step. The manufacturing method according to claim 4.

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

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