Manufacturing method of energy storage devices

Abstract

This disclosure provides a technique for suppressing residual air bubbles within the electrode body during charging. The manufacturing method disclosed herein is a method for manufacturing an energy storage device, which includes an electrode body, a non-aqueous electrolyte, and a housing containing the electrode body and the non-aqueous electrolyte. The manufacturing method includes: preparing an assembly containing the electrode body and the non-aqueous electrolyte within the housing; applying pressure (P1) to the assembly; after applying pressure (P1), applying a pressure (P2) less than the pressure (P1) to the assembly; and charging the assembly while applying pressure (P2).

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing energy storage devices. Background Technology

[0002] Japanese Patent Application Publication No. 2020-149802 discloses a method for manufacturing a non-aqueous electrolyte secondary battery, wherein the battery casing of the non-aqueous electrolyte secondary battery contains wound electrodes and a non-aqueous electrolyte. The manufacturing method includes an assembly construction step, a restraint step, an initial charging step, and an aging step. In the assembly construction step, a battery assembly is constructed, wherein the battery assembly contains wound electrodes and a non-aqueous electrolyte containing LiBOB within the battery casing, and residual electrolyte exists between the wound electrodes and the battery casing. In the restraint step, the battery assembly is restrained at a predetermined pressure. In the initial charging step, the battery assembly is initially charged. In the aging step, the initially charged battery assembly is held for a predetermined time. A key feature of this manufacturing method is that, after the initial charging step, a pumping step is performed to reapply restraint pressure after the restraint pressure on the battery assembly has been eased. The bulletin states that by implementing a pumping process, the residual electrolyte outside the wound electrode body can be mixed with the holding electrolyte inside the wound electrode body, and the LiBOB remaining in the residual electrolyte can be decomposed during the aging process. Therefore, the increase in battery resistance after the manufacturing process can be suppressed.

[0003] [Existing Technical Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-149802 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Furthermore, in the manufacturing process of energy storage devices, an assembly is sometimes prepared by housing an electrode body within a casing and subsequently injecting an electrolyte. During the electrolyte injection process in assembly preparation, air bubbles may sometimes be introduced into the electrode body. Subsequently, charging with air bubbles remaining in the electrode body can become a significant cause of uneven charging within the electrode body, and is therefore not preferred. Here, the inventors aim to suppress the presence of air bubbles remaining in the electrode body during charging.

[0008] means for solving problems

[0009] The manufacturing method disclosed herein is a method for manufacturing an energy storage device, which includes an electrode body, a non-aqueous electrolyte, and a housing containing the electrode body and the non-aqueous electrolyte. The manufacturing method includes: preparing an assembly in which the electrode body and the non-aqueous electrolyte are housed within the housing; applying a pressure P1 to the assembly; after applying pressure P1, applying a pressure P2 less than P1 to the assembly; and charging the assembly while applying pressure P2. This configuration helps to suppress residual air bubbles within the electrode body during charging. Attached Figure Description

[0010] Figure 1 This is a schematic perspective view of the energy storage device 1.

[0011] Figure 2 for Figure 1 Section II-II.

[0012] Figure 3 This is a schematic perspective view of the sealing plate 14 and the electrode body 20.

[0013] Figure 4 This is a schematic perspective view of the second current collector 52 and the electrode body 20.

[0014] Figure 5 This is a schematic diagram of electrode body 20.

[0015] Figure 6 This is a flowchart of the manufacturing process.

[0016] Figure 7 This is a schematic diagram illustrating the application of pressure to the housing 10.

[0017] Figure 8 This is a schematic diagram illustrating the application of pressure to the housing 10.

[0018] Figure 9 This is a graph showing the change in pressure applied to the test battery cell over time in the embodiment.

[0019] Figure 10 This is a graph showing the change in pressure applied to the test battery cell over time in the comparative example. Detailed Implementation

[0020] The following describes one embodiment of the energy storage device disclosed herein. The embodiment described herein does not specifically limit the technology disclosed herein. Unless otherwise stated, the technology disclosed herein is not limited to the embodiment described herein. The accompanying drawings are schematic and do not necessarily reflect the actual object. Components and parts that perform the same function are labeled with the same reference numerals as appropriate, and sometimes repeated descriptions are omitted. The expression "A~B" indicating a numerical range, unless otherwise stated, means "A or more and B or less," and also includes the meaning of "greater than A and less than B."

[0021] In this specification, "energy storage device" refers to a device that generates charge and discharge by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. Energy storage devices include secondary batteries such as lithium-ion secondary batteries, capacitors such as lithium-ion capacitors, and double-layer capacitors. The following describes an implementation where the energy storage device is a lithium-ion secondary battery.

[0022] Hereinafter, with reference to the accompanying drawings, the energy storage device that is the object of the manufacturing method of the energy storage device disclosed herein (hereinafter also referred to as the "manufacturing method") will be described. Figure 1 This is a schematic perspective view of the energy storage device 1. Figure 2 for Figure 1 Section II-II. (See diagram.) Figure 1 and Figure 2 As shown, the energy storage device 1 includes a housing 10, an electrode body 20, a positive terminal 30, a negative terminal 40, external conductive components 35 and 45, a positive current collector 50, a negative current collector 60, various insulating components, and a non-aqueous electrolyte (not shown).

[0023] The housing 10 is an outer packaging container for housing the electrode body 20 and the non-aqueous electrolyte. Here, the housing 10 is a flat, rectangular housing. There are no particular limitations on the material constituting the housing 10; for example, the material used to construct the housing of such an energy storage device can be suitably used.

[0024] like Figure 1 and Figure 2 As shown, the casing 10 includes an outer packaging body 12 and a sealing plate 14. The outer packaging body 12 has a bottom wall 12a, a pair of opposing first side walls 12b, and a pair of opposing second side walls 12c. The bottom wall 12a is rectangular. Figure 2 As shown, the opposite portion to the bottom wall 12a is an opening 12h. A pair of opposing first sidewalls 12b are rectangular, extending from a pair of opposing long sides of the bottom wall 12a. A pair of opposing second sidewalls 12c are rectangular, extending from a pair of opposing short sides of the bottom wall 12a. In this embodiment, the area of ​​the pair of opposing first sidewalls 12b is larger than the area of ​​the pair of opposing second sidewalls 12c.

[0025] like Figure 1 and Figure 2 As shown, the sealing plate 14 is a rectangular flat plate with a shape corresponding to the opening 12h. Here, the sealing plate 14 has an injection hole 15, a safety valve 17, and terminal mounting holes 18 and 19. The injection hole 15 is the portion for injecting a non-aqueous electrolyte into the housing 10. Figure 1 and Figure 2 As shown, the injection port 15 is sealed by the sealing member 16. The safety valve 17, for example, is a thin-walled portion, configured to release internal pressure if the internal pressure of the housing 10 rises above a specified level. The terminal mounting holes 18 and 19 are through holes for mounting the positive terminal 30 or the negative terminal 40. The sealing plate 14 seals the opening 12h and is welded (e.g., laser welded) to the outer packaging body 12.

[0026] Figure 3 This is a schematic perspective view of the sealing plate 14 and the electrode body 20. Figure 3 The electrode body 20, which is equipped with a sealing plate 14, is schematically shown in the figure. Figure 4 This is a schematic perspective view of the second current collector 52 and the electrode body 20. Figure 4 The image schematically shows the electrode body 20 on which the second current collector 52 is mounted. For example... Figure 3 As shown, the energy storage device 1 has three electrode bodies 20. Figure 3 and Figure 4 As shown, in the electrode body 20, the second current collector 52 of the positive current collector 50 is installed on one side in the long side direction Y. Figure 3 and Figure 4 (On the left side), the second current collector 62 of the negative current collector 60 is installed on the other side in the long side direction Y. Figure 3 and Figure 4 (The right side). For example, Figure 2 As shown, the electrode body 20 is disposed inside the outer packaging body 12 while being covered by an electrode body retainer 29 made of a resin sheet such as polypropylene (PP). Furthermore, the number of electrode bodies 20 in the energy storage device 1 is not particularly limited; for example, it can have one, two, or four or more.

[0027] Figure 5 This is a schematic diagram of electrode body 20. (See diagram below.) Figure 5 As shown, the electrode body 20 includes a positive electrode 22, a negative electrode 24, and a separator 26. The electrode body 20 is a flat, wound electrode body, with a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 sandwiching a strip-shaped separator 26, and stacked together, wound along the length of the strip. Figures 2-4 As shown, the electrode body 20 includes a main body 20a, a positive electrode tab group 23, and a negative electrode tab group 25. The main body 20a is a portion in which the positive electrode 22, the negative electrode 24, and the diaphragm 26 are stacked, for example, in a flat shape.

[0028] There is no particular limitation on the width of the main body portion 20a; it can be 10 cm or more, 20 cm or more, or 30 cm or more. The width of the main body portion 20a can be 50 cm or less, or 40 cm or less. In this specification, "width of the main body portion 20a" refers to the length of the main body portion 20a of the electrode body 20 in the direction along the winding axis WL.

[0029] like Figure 1 , Figure 2 and Figure 5 As shown, the electrode body 20 is disposed inside the outer packaging body 12 with its winding axis WL parallel to the width direction Y. In this embodiment, the electrode body 20 is disposed inside the outer packaging body 12 with its winding axis WL parallel to the bottom wall 12a and orthogonal to the second side wall 12c. Furthermore, the two end faces of the electrode body 20 along the direction of the winding axis WL are opposite to the second side wall 12c of the outer packaging body 12. In this embodiment, the two end faces of the electrode body 20 along the direction of the winding axis WL are open faces that open to the outside of the electrode body 20. For ease of explanation, in this embodiment, the side closest to the positive current collector 50 ( Figure 2 and Figure 4 The end face of the electrode body 20 (main body 20a) opposite the second sidewall 12c (on the left side of the width direction Y) is called the "first open surface 20a1". The side closest to the negative electrode current collector 60 ( Figure 2 and Figure 4 The end face of the electrode body 20 (main body 20a) opposite the second sidewall 12c (to the right of the width direction Y) is called the "second open face 20a2".

[0030] like Figure 3 and Figure 4 As shown, the electrode body 20 has a rectangular surface 20a3. The rectangular surface 20a3 is the end face of the positive electrode 22 and the negative electrode 24 in the stacking direction (see reference). Figure 4 and Figure 5 In this embodiment, the rectangular surface 20a3 is opposite to the first sidewall 12b of the housing 10 (see reference). Figure 1 ).

[0031] The positive electrode 22 has a strip-shaped positive electrode current collector foil 22c (e.g., aluminum foil) and a positive electrode active material layer 22a fixed to at least one surface of the positive electrode current collector foil 22c. While not particularly limited, a protective layer 22p may be provided as needed on one side edge of the positive electrode 22 in the width direction Y. Furthermore, the materials constituting the positive electrode active material layer 22a and the protective layer 22p can be any materials used in such energy storage devices without particular limitation.

[0032] At one end of the positive electrode current collector foil 22c in the width direction Y ( Figure 5 At the left end), multiple positive electrode tabs 22t are provided. The multiple positive electrode tabs 22t are respectively positioned on one side of the width direction Y ( Figure 5 The positive electrode tabs 22t protrude from the left side. Multiple positive electrode tabs 22t are spaced apart (intermittently) along the length direction of the positive electrode 22. The positive electrode tabs 22t are part of the positive electrode current collector foil 22c, and are the exposed portions of the current collector foil 22c where the positive electrode active material layer 22a and protective layer 22p are not formed. In this embodiment, the multiple positive electrode tabs 22t protrude from the separator 26 in the width direction Y. The multiple positive electrode tabs 22t protrude from one end in the width direction Y (… Figure 5 The left end) is stacked to form the positive electrode tab group 23 (refer to Figures 2-4 ).

[0033] The negative electrode 24 has a strip-shaped negative electrode current collector foil 24c (e.g., copper foil) and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector foil 24c. In addition, the material constituting the negative electrode active material layer 24a may be any material used in this type of energy storage device without particular limitation.

[0034] At one end of the negative electrode current collector foil 24c in the width direction Y ( Figure 5 At the right end), multiple negative electrode tabs 24t are provided. The multiple negative electrode tabs 24t are positioned towards one side in the width direction Y ( Figure 5 The right side of the negative electrode 24 protrudes. Multiple negative electrode tabs 24t are spaced apart (intermittently) along the length of the negative electrode 24. Here, the negative electrode tabs 24t are part of the negative electrode current collector foil 24c, and are the exposed portions of the current collector foil 24c where the negative electrode active material layer 24a is not formed. In this embodiment, the negative electrode tabs 24t protrude more than the separator 26 in the width direction Y. The multiple negative electrode tabs 24t protrude at one end in the width direction Y (… Figure 5 The right end of the electrode is stacked to form the negative electrode tab group 25 (refer to the right end of the electrode). Figures 2-4 ).

[0035] The separator 26 insulates the positive electrode active material layer 22a of the positive electrode 22 from the negative electrode active material layer 24a of the negative electrode 24. The separator 26 forms the outer surface of the electrode body 20. For example, a porous sheet made of resin composed of polyolefin resins such as polyethylene (PE) and polypropylene (PP) is used as the separator 26.

[0036] like Figures 1-3 As shown, the positive terminal 30 and the negative terminal 40 are mounted on the sealing plate 14. In this embodiment, the positive terminal 30 is disposed at one end of the sealing plate 14 in the long side direction Y. Figures 1-3 (The left end). In this embodiment, the negative end 40 is disposed at the other end of the sealing plate 14 in the long side direction Y ( Figures 1-3 (the right end).

[0037] like Figure 2 As shown, the positive terminal 30 is located inside the outer packaging 12 via the positive current collector 50 and the positive terminal 22 of the electrode body 20 (see reference). Figure 5 Electrical connection. Inside the outer casing 12, a portion of the positive terminal 30 is engaged with the positive current collector 50. A portion of the positive terminal 30 is inserted into the through-hole 51h of the first current collector member 51 of the positive current collector 50 and is riveted to the edge of the through-hole 51h. The positive terminal 30 passes through the insertion terminal mounting hole 18 and extends outward from the inside of the sealing plate 14. The positive terminal 30 is insulated from the sealing plate 14 by means of a first insulating member 71 and a second insulating member 72. The positive terminal 30 is preferably made of aluminum or aluminum alloy, for example. An external conductive member 35 is fixed to the positive terminal 30. The positive terminal 30 is engaged with the external conductive member 35 (made of aluminum or aluminum alloy).

[0038] like Figure 2 As shown, the negative terminal 40 is located inside the outer packaging 12 via the negative current collector 60 and the negative terminal 24 of the electrode body 20 (see reference). Figure 5 Electrical connection. Inside the outer casing 12, a portion of the negative terminal 40 is engaged with the negative current collector 60. A portion of the negative terminal 40 is inserted into the through-hole 61h of the first current collector member 61 of the negative current collector 60 and is riveted to the edge of the through-hole 61h. The negative terminal 40 passes through the insertion terminal mounting hole 19 and extends outward from the inside of the sealing plate 14. The negative terminal 40 is insulated from the sealing plate 14 by means of a first insulating member 71 and a second insulating member 72. The negative terminal 40 is preferably made of copper or a copper alloy, for example. An external conductive member 45 (made of copper or a copper alloy) is fixed to the negative terminal 40. The negative terminal 40 is engaged with the external conductive member 45.

[0039] like Figure 2 As shown, the positive current collector 50 electrically connects the positive electrode 22 of the electrode body 20 to the positive terminal 30 inside the outer packaging 12 (see reference). Figure 5 In this embodiment, a portion of the positive current collector 50 is connected to the positive terminal 30. The remaining portion of the positive current collector 50 is connected to the positive electrode tab assembly 23 of the electrode body 20. The positive current collector 50 is preferably made of aluminum or an aluminum alloy, for example.

[0040] like Figure 2 As shown, the positive current collector 50 has a first current collector 51 and a second current collector 52. In this embodiment, the first current collector 51 has an L-shaped cross-section and has a first plate portion 511 and a second plate portion 512. Here, the first plate portion 511 is plate-shaped and extends from the second plate portion 512 towards the bottom wall 12a of the outer packaging body 12. The second current collector 52 is connected to the first plate portion 511. Here, the second plate portion 512 is plate-shaped. Figure 2 As shown, the second plate portion 512 is disposed along the inner surface of the sealing plate 14. In the second plate portion 512, on the second sidewall 12c (refer to...) Figure 1 The first plate portion 511 is connected to the end of the side.

[0041] like Figures 2-4 As shown, the second current collector 52 extends toward the bottom wall 12a of the outer packaging body 12. The second current collector 52 has a first connecting portion 52a and a second connecting portion 52b. The first connecting portion 52a is electrically connected to the first current collector 51. In this embodiment, the first connecting portion 52a is connected to the first current collector 51 via a connecting portion 521. The first connecting portion 52a extends in the vertical direction Z. In this embodiment, the first connecting portion 52a is arranged substantially perpendicular to the winding axis WL of each electrode body 20.

[0042] like Figure 3 and Figure 4 As shown, a fuse 52f is formed in the first connection portion 52a. The first connection portion 52a is configured such that when a current of 1000A or more (e.g., a short-circuit current) flows through the energy storage device 1, the fuse 52f melts. The cross-sectional area of ​​the fuse 52f is smaller than the other parts of the first connection portion 52a except for the fuse 52f and the connection portion 521. The fuse 52f is, for example, an opening or a thin-walled portion. The first connection portion 52a is configured such that, due to the formation of the fuse 52f, it will melt when such a current flows through.

[0043] The second connecting portion 52b engages with the positive electrode tab assembly 23. In this embodiment, the second connecting portion 52b extends along the vertical direction Z. The second connecting portion 52b is arranged substantially perpendicular to the winding axis WL of each electrode body 20. The surface of the second connecting portion 52b that connects with the plurality of positive electrode tabs 22t is arranged substantially parallel to the second sidewall 12c of the outer packaging body 12.

[0044] Negative current collector 60, such as Figure 2 As shown, inside the outer packaging 12, the negative electrode 24 of the electrode body 20 is electrically connected to the negative terminal 40 (see reference). Figure 5 In this embodiment, a portion of the negative current collector 60 is connected to the negative terminal 40. The remaining portion of the negative current collector 60 is connected to the negative electrode tab assembly 25 of the electrode body 20. The negative current collector 60 is preferably made of copper or a copper alloy, for example. The structure of the negative current collector 60, its connection to the negative electrode tab assembly 25, etc., can be the same as the structure of the positive current collector 50 and the connection between the positive current collector 50 and the positive electrode tab assembly 23 described above. Therefore, further explanation is omitted here. Additionally, in Figure 4In the figure, reference numeral "621" indicates the connection part, reference numeral "62a" indicates the first connection part, reference numeral "62b" indicates the second connection part, and reference numeral "62f" indicates the fuse.

[0045] Various insulating components include, for example, the electrode holder 29, the first insulating component 71, the second insulating component 72, and the third insulating component 73 (see reference). Figure 2 ).like Figure 2 As shown, the first insulating member 71 is disposed between the positive current collector 50 and the sealing plate 14, and between the negative current collector 60 and the sealing plate 14. The first insulating member 71 may, for example, have a portion that insulates the electrode body 20 from the sealing plate 14 (see reference). Figure 2 The second insulating member 72 is disposed between the positive terminal 30 and the sealing plate 14, and between the negative terminal 40 and the sealing plate 14. The third insulating member 73 is disposed between the external conductive member 35 and the sealing plate 14, and between the external conductive member 45 and the sealing plate 14. The materials used to construct the first insulating member 71, the second insulating member 72, and the third insulating member 73 may, for example, be the same as the materials used to construct insulating members for the same purpose in such energy storage devices.

[0046] As a non-aqueous electrolyte, the non-aqueous electrolyte used as the electrolyte for this type of energy storage device can be used without particular restrictions.

[0047] The energy storage device 1 can be used for various purposes, such as preferably as a power source (drive power supply) for an electric motor in vehicles such as cars and trucks. There is no particular limitation on the type of vehicle; examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). The energy storage device 1 can, for example, be used as a single battery included in an energy storage module.

[0048] Figure 6 This is a flowchart of the manufacturing process. For example... Figure 6 As shown, the manufacturing method includes a preparation step S1, a first pressurization step S2, a second pressurization step S3, an initial charging step S4, a first aging step S5, a second aging step S6, a resistance detection step S7, a third pressurization step S8, a fourth pressurization step S9, a charge-discharge step S10, a third aging step S11, a fourth aging step S12, and a self-discharge detection step S13. The manufacturing method will be described below with reference to the accompanying drawings as appropriate.

[0049] In preparation step S1, an assembly containing electrode bodies 20 and a non-aqueous electrolyte within the housing 10 is prepared. In this embodiment, a first structure is first prepared in preparation step S1. The first structure includes, for example, a sealing plate 14, a positive terminal 30, a negative terminal 40, external conductive members 35 and 45, a positive current collector 50, a negative current collector 60, a first insulating member 71, a second insulating member 72, and a third insulating member 73. The steps for preparing the first structure are not particularly limited and can be the same as in the prior art.

[0050] Next, a second structure is prepared. The second structure includes, for example, the first structure and the electrode body 20. In preparing the second structure, for example, the positive electrode tab group 23 and the negative electrode tab group 25 of the electrode body 20, prepared by conventionally known methods, are joined with a current collector of the same polarity. Furthermore, as a joining method in the preparation process, for example, laser welding, ultrasonic welding, resistance welding, etc., can be used.

[0051] Next, a third structure is prepared. This third structure includes, for example, the second structure, an electrode holder 29, and an outer packaging 12. In preparing the third structure, the electrode 20 from the second structure is housed within the electrode holder 29. Then, with the electrode 20 housed within the electrode holder 29, it is housed within the outer packaging 12. The sealing plate 14 is then overlapped and joined to the opening 12h of the outer packaging 12. While not particularly limited, the third structure may be dried as needed. The drying conditions are not particularly limited and can be appropriately set according to the moisture content of the third structure and the type of resin material contained in the third structure.

[0052] Subsequently, a non-aqueous electrolyte is injected into the third structure. Here, the non-aqueous electrolyte is injected into the housing 10 through the injection hole 15 provided in the sealing plate 14. The injection is preferably carried out under atmospheric pressure or a reduced pressure atmosphere. Although not particularly limited, after the non-aqueous electrolyte is injected, the pressure inside the housing 10 can be reduced or increased as needed. Then, the injection hole 15 is sealed.

[0053] Figure 7 and Figure 8 This is a schematic diagram illustrating the application of pressure to the housing 10. Figure 7 The image shows a schematic side view of the shell 10 under pressure, viewed from the second side wall 12c. Figure 8 The image shows a schematic side view of the housing 10 under pressure, viewed from the first sidewall 12b side. In the first pressurization step S2, pressure P1 is applied to the assembly. In this embodiment, pressure P1 is applied to the first sidewall 12b of the housing 10. Figure 7In the illustrated configuration, a pair of first sidewalls 12b of the housing 10 are clamped by a pair of restraint fixtures 92, and pressure P1 is applied. The pair of restraint fixtures 92 can be, for example, a pair of restraint plates. In this case, pressure P1 can be applied to the housing 10 by bridging the pair of restraint plates using a bridging member.

[0054] like Figure 8 As shown, in the first pressurization step S2, the restraint fixture 92 preferably overlaps the central region 12r1 of the first sidewall 12b. Here, the central region 12r1 is the region that includes the center C of the first sidewall 12b. The center C is the intersection of the center line CL1 of the long side 12b1 of the first sidewall 12b and the center line CL2 of the short side 12b2 of the first sidewall 12b. If the area of ​​the first sidewall 12b is 100%, then the area of ​​the central region 12r1 is, for example, 40% or more, preferably 50% or more, more preferably 60% or more, approximately 90% or less, and possibly 80% or less. In addition, the restraint fixture 92 may not be provided in the end region 12r2 of the first sidewall 12b located at the periphery of the central region 12r1.

[0055] Here, pressure P1 is sufficient to expel air bubbles and non-aqueous electrolyte present in the electrode body 20 and crush the space between the positive and negative electrodes. Pressure P1 can be appropriately set, for example, to achieve the technical effects disclosed herein, at 25 kN or more, preferably 30 kN or more, more preferably 35 kN or more, and even more preferably 40 kN or more. From the viewpoint of not damaging the casing 10 and maintaining a suitable level of non-aqueous electrolyte within the electrode body 20 for charging, pressure P1 is, for example, 100 kN or less, preferably 90 kN or less, more preferably 80 kN or less, and even more preferably 70 kN or less.

[0056] There is no particular limitation on the duration of applying pressure P1; however, from the viewpoint of achieving the technical effects disclosed herein, it is preferably 1 second or more, more preferably 2 seconds or more, more preferably 3 seconds or more, and even more preferably 5 seconds or more. From the viewpoint of improving the production efficiency of the energy storage device 1, the duration of applying pressure P1 is, for example, 60 seconds or less, preferably 50 seconds or less, more preferably 40 seconds or less, and even more preferably 30 seconds or less.

[0057] In the second pressurization step S3, pressure P2 is applied to the assembly. In this embodiment, pressure P2 is applied to the first sidewall 12b of the housing 10. In the second pressurization step S3, similar to the first pressurization step S2, it is preferable to utilize... Figure 7The restraint fixture 92 shown applies pressure P2 to the central region 12r1 of the first sidewall 12b. In this embodiment, the first pressurization step S2 and the second pressurization step S3 are consecutive. Therefore, the restraint fixture 92 can be maintained in the housing 10 from the first pressurization step S2.

[0058] Pressure P2 is less than pressure P1. Here, pressure P2 is the pressure that forms a space between the positive and negative electrodes and allows non-aqueous electrolyte to immerse into the electrode body 20. The magnitude of pressure P2 is not particularly limited as long as the technical effects disclosed herein are achieved. From the viewpoint of achieving a suitable inter-electrode distance when charging or discharging the assembly, pressure P2 is preferably 1 / 10 or more of pressure P1, more preferably 1 / 8 or more. From the same viewpoint, pressure P2 is preferably 1 / 2 or less of pressure P1. Pressure P2 is preferably 3 kN or more and less than 25 kN, more preferably 5 kN to 23 kN.

[0059] Here, during the initial charging step S4, the first aging step S5, and the second aging step S6 described later, pressure P2 is maintained on the assembly. Therefore, there is no particular limitation on the duration of applying pressure P2.

[0060] In the initial charging step S4, the assembly is initially charged. In this embodiment, the initial charging is the first charging performed on the assembly after it has been prepared. By implementing the initial charging step S4, for example, a coating (SEI film) can be formed on the surface of the negative electrode active material layer 24a. Here, such a coating may contain decomposition products such as non-aqueous electrolytes and additives that decompose upon contact with the negative electrode active material (e.g., carbon materials such as graphite, silicon (Si)) in the negative electrode active material layer 24a.

[0061] In the initial charging process S4, for example, a constant current is used for charging at a predetermined current value until the depth of charge (SOC) of the assembly reaches the desired value. The SOC of the assembly after the initial charging is, for example, 5% to 50%, preferably 10% to 40%, more preferably 20% to 30%. The current value during the initial charging is, for example, 0.05C to 5C, preferably 0.1C to 3C. The temperature conditions for the initial charging in the initial charging process S4 are, for example, 10°C to 40°C, preferably 20°C to 30°C.

[0062] In the first aging process S5, the assembly after the initial charging process S4 is maintained within a predetermined temperature range. In this embodiment, the temperature range for maintaining the assembly in the first aging process S5 is, for example, 40°C to 80°C, preferably 50°C to 70°C, and more preferably 55°C to 65°C. The maintenance time of the assembly is, for example, 6 hours to 72 hours, preferably 12 hours to 48 hours, and more preferably 18 hours to 24 hours.

[0063] In the second aging process S6, for example, the assembly after the first aging process S5 is maintained in a temperature region lower than the temperature region of the first aging process S5. In this embodiment, in the second aging process S6, the temperature region in which the assembly is maintained is, for example, 10°C or higher and lower than 40°C, preferably 15°C to 35°C, more preferably 20°C to 30°C. The holding time of the assembly is, for example, 6 hours to 72 hours, preferably 12 hours to 48 hours, more preferably 18 hours to 24 hours.

[0064] In the resistance detection step S7, the internal resistance of the assembly after the second aging step S6 is calculated. In this embodiment, it is preferable to perform the resistance detection step S7 in the temperature range of the second aging step S6. In the calculation of the internal resistance of the assembly in the resistance detection step S7, the assembly is discharged for 10 seconds with a discharge current of 100A (0.5C), and the voltages before and after the discharge are V1 and V2, respectively, and the discharge current is A, using the following formula (1):

[0065] Internal resistance = (V1 - V2) / A (1)

[0066] While there are no specific limitations in the resistance testing step S7, a charge / discharge device such as a lithium-ion battery charge / discharge cycle test system manufactured by IEM Co., Ltd. can be used. Furthermore, the timing of performing the resistance testing step S7 does not necessarily have to be... Figure 6 The situation shown can be set appropriately.

[0067] In the third pressurization step S8, pressure P3 is applied to the assembly. In this embodiment, pressure P3 is applied to the assembly after the resistance detection step S7. Here, pressure P3 is applied to the first sidewall 12b of the housing 10. In the third pressurization step S8, similar to the first pressurization step S2 and the second pressurization step S3, pressure P3 can be used... Figure 7 The restraint fixture 92 shown applies pressure P3 to the central region 12r1 of the first sidewall 12b.

[0068] The pressure P3 can be appropriately set, for example, to achieve the technical effects disclosed herein, at 25 kN or more, preferably 30 kN or more, more preferably 35 kN or more, and even more preferably 40 kN or more. From the viewpoint of not damaging the housing 10 and maintaining a suitable level of non-aqueous electrolyte within the electrode body 20 for charging, the pressure P3 is, for example, 100 kN or less, preferably 90 kN or less, more preferably 80 kN or less, and even more preferably 70 kN or less. The magnitude of pressure P3 can be the same as or different from the magnitude of pressure P1. Therefore, pressure P1 can also be applied to the assembly in the third pressurization step S8.

[0069] There is no particular limitation on the duration of applying pressure P3, but from the viewpoint of achieving the technical effects disclosed herein, it is preferably 0.5 seconds or more, more preferably 1 second or more, more preferably 2 seconds or more, even more preferably 3 seconds or more, and particularly preferably 5 seconds or more. From the viewpoint of improving the production efficiency of the energy storage device 1, the duration of applying pressure P3 is, for example, 60 seconds or less, preferably 50 seconds or less, more preferably 40 seconds or less, and even more preferably 30 seconds or less.

[0070] In the fourth pressurization step S9, pressure P4 is applied to the assembly following the third pressurization step S8. In this embodiment, pressure P4 is applied to the first sidewall 12b of the housing 10. In the fourth pressurization step S9, similar to the first pressurization steps S2, second pressurization steps S3, and third pressurization steps S8, pressure P4 can be applied to the first sidewall 12b of the housing 10. Figure 7 The restraint fixture 92 shown applies pressure P4 to the central region 12r1 of the first sidewall 12b. In this embodiment, the third pressurization step S8 and the fourth pressurization step S9 are consecutive. Therefore, the restraint fixture 92 can be maintained in the housing 10 from the third pressurization step S8.

[0071] Pressure P4 is less than pressure P3. The magnitude of pressure P4 is not particularly limited as long as the technical effect disclosed herein can be achieved. From the viewpoint of achieving a suitable inter-electrode distance when charging or discharging the assembly, pressure P4 is preferably 1 / 10 or more of pressure P3, more preferably 1 / 8 or more. From the same viewpoint, pressure P4 is preferably 1 / 2 or less of pressure P3. Pressure P4 is preferably 3 kN or more and less than 25 kN, more preferably 5 kN to 23 kN. The magnitude of pressure P4 can be the same as or different from the magnitude of pressure P2. Therefore, pressure P2 can also be applied to the assembly in the fourth pressurization step S9.

[0072] Here, during the implementation of the charging / discharging process S10, the third aging process S11, and the fourth aging process S12 described later, pressure P4 is maintained on the assembly. Therefore, there is no particular limitation on the duration of applying pressure P4.

[0073] In the charge-discharge process S10, charging and discharging of the assembly are performed. In the charge-discharge process S10, for example, first the assembly is charged until the SOC reaches 100%. After the SOC of the assembly reaches 100%, the assembly is discharged until the SOC reaches 25%. The temperature conditions in the charge-discharge process S10 can be the same as those in the initial charging process S4. There is no particular limitation on the current value during charging and discharging in the charge-discharge process S10, and it can be set appropriately.

[0074] In the third aging process S11, the assembly after the charge-discharge process S10 is maintained in a prescribed temperature range. For each condition such as the temperature condition and time condition in the third aging process S11, they can be set appropriately by referring to the conditions described in the first aging process S5.

[0075] In the fourth aging process S12, the assembly after the third aging process S11 is maintained in a temperature range lower than that in the third aging process S11. For each condition such as the temperature condition and time condition in the fourth aging process S12, they can be set appropriately by referring to the conditions described in the second aging process S6.

[0076] In the self-discharge detection process S13, the assembly after the fourth aging process S12 is placed at a predetermined detection temperature for a predetermined detection period to allow self-discharge, and the degree of self-discharge is detected. Judgment is made based on the value obtained by dividing the difference between the voltage detection V3 after 50 hours or more from the completion of the third aging process S11 and the voltage detection V4 after 108 hours or more from the measurement time of V3 by the elapsed time between V3 and V4. For example, an assembly with self-discharge of the assembly obtained by detection within a predetermined range can be regarded as a qualified product (good product), and an assembly not within this range can be regarded as a non-qualified product (bad product). For the detection temperature, for example, it is set appropriately within the range of 20°C to 30°C.

[0077] In the present embodiment, by implementing the above processes, the electrical storage device 1 can be manufactured. The above manufacturing process is only an example, and some processes can be appropriately omitted, or processes included in the manufacturing of such electrical storage devices can be appropriately added.

[0078] The above manufacturing method is a manufacturing method of the electrical storage device 1, and the electrical storage device 1 includes an electrode body 20, a non-aqueous electrolyte, and a housing 10 that houses the electrode body 20 and the non-aqueous electrolyte. This manufacturing method includes: preparing an assembly in which the electrode body 20 and the non-aqueous electrolyte are housed in the housing 10 (preparation process S1); applying a pressure P1 to the assembly (first pressurization process S2); after applying the pressure P1, applying a pressure P2 smaller than the pressure P1 to the assembly (second pressurization process S3); and charging the assembly while applying the pressure P2 to the assembly (initial charging process S4).

[0079] In other words, in the manufacturing method, before charging while confining the assembly with pressure P2, a pressure P1 greater than pressure P2 is applied to the assembly. By applying pressure P1 to the assembly, the gaps within the electrode body 20 can be crushed. This allows air bubbles remaining within the electrode body 20 to be expelled. Therefore, the retention of air bubbles within the electrode body 20 during charging can be suppressed, thereby suppressing the generation of uneven charging within the electrode body 20. Furthermore, since air bubbles are sufficiently expelled from the electrode body 20 during the application of pressure P1, air bubbles become easier to expel from the electrode body 20 during the application of pressure P2. Thus, a suitable confinement state of the electrode body 20 can be maintained during the application of pressure P2.

[0080] Applying pressure P1 and applying pressure P2 to the assembly can be performed continuously. This avoids a situation where no pressure is applied to the assembly between the application of pressure P1 and pressure P2. Therefore, the amount of non-aqueous electrolyte immersed in the electrode body 20 can be limited between the application of pressure P1 and pressure P2. Thus, during the application of pressure P2 to the assembly, the pressure applied to the electrode body 20 is better suppressed from being squeezed out of the electrode body 20, thereby maintaining a suitable restraint state on the electrode body 20. Furthermore, the backflow of gas discharged from the electrode body 20 between the application of pressure P1 and pressure P2 can be suppressed. Therefore, the technical effects disclosed herein can be better achieved.

[0081] The aforementioned charging can also be an initial charge. If initial charging is performed while air bubbles remain in the electrode body 20, uneven initial charging will occur in the electrode body 20, potentially leading to a significant reduction in the battery performance of the energy storage device 1. Therefore, applying pressure P1 to the assembly and then applying pressure P2 while performing initial charging can better achieve the technical effects disclosed herein and improve the battery performance of the energy storage device 1.

[0082] Pressure P2 can be 1 / 10 to 1 / 2 of pressure P1. In other words, pressure P1 can be 2 to 10 times pressure P2. By setting the ratio of pressure P1 to pressure P2 within such a range, the technical effects disclosed herein can be well achieved.

[0083] The time for applying pressure P1 can also be from 1 second to 60 seconds. This allows for the effective implementation of the disclosed technical properties and prevents the manufacturing time of the energy storage device 1 from becoming excessively long.

[0084] The electrode body 20 can be a flat, wound electrode body, formed by stacking a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 with a separator 26 sandwiched between them and winding them along the length of the sheet. In the wound electrode body 20, the outlets for air bubbles present inside are limited to two open surfaces (a first open surface 20a1 and a second open surface 20a2). Therefore, air bubbles are easily retained inside the electrode body 20. Thus, the technical effects disclosed herein can be better achieved with the wound electrode body 20.

[0085] In recent years, due to increasing demands for higher capacity, it is anticipated that the width of the main body 20a of the electrode body 20 in the energy storage device 1 will increase. Therefore, the width of the main body 20a of the electrode body 20 can be appropriately set within the aforementioned range. This allows for higher capacity in the energy storage device 1 and better realization of the technical effects disclosed herein, achieving higher battery performance. Furthermore, the greater the width of the main body 20a of the electrode body 20, the easier it is for gas to remain within the electrode body 20. Therefore, the greater the width of the main body 20a of the electrode body 20, the better the technical effects disclosed herein can be achieved.

[0086] The housing 10 may also have a rectangular bottom wall 12a and a pair of opposing first sidewalls 12b extending from a pair of opposing long sides of the bottom wall 12a. The electrode body 20 may also have rectangular surfaces 20a3 at both ends in the stacking direction of the positive electrode 22 and the negative electrode 24. The rectangular surfaces 20a3 may also be opposite to the first sidewalls 12b. Pressures P1 and P2 may also be applied to the first sidewalls 12b. By applying pressures P1 and P2 to the first sidewalls 12b, these pressures can be applied to the rectangular surfaces 20a3 of the electrode body 20. This allows for more efficient removal of air bubbles from the electrode body 20.

[0087] The manufacturing method may further include: applying pressure P3 to the charged assembly (third pressurization step S8); applying a pressure P4 less than P3 to the assembly after applying pressure P3 (fourth pressurization step S9); and charging while applying pressure P4 (charge-discharge step S10). This allows for the efficient removal of air bubbles generated within the electrode body 20 due to other processes performed on the charged assembly (e.g., first aging step S5, second aging step S6, etc.) to the outside of the electrode body 20.

[0088] The embodiments of the technology disclosed herein have been described above, but these embodiments are merely examples and do not limit the scope of protection of the claims. The technology described in the claims includes various modifications and alterations to the above exemplary embodiments.

[0089] For example, in the above embodiments, the manufacturing method includes both a combination of the first pressurizing step S2 and the second pressurizing step S3, and a combination of the third pressurizing step S8 and the fourth pressurizing step S9. However, the technology disclosed herein is not limited to this. The manufacturing method may include at least one of the combinations of the first pressurizing step S2 and the second pressurizing step S3, and the combinations of the third pressurizing step S8 and the fourth pressurizing step S9. The manufacturing method may also include only the combination of the first pressurizing step S2 and the second pressurizing step S3, without including the combination of the third pressurizing step S8 and the fourth pressurizing step S9. Alternatively, the manufacturing method may include only the combination of the third pressurizing step S8 and the fourth pressurizing step S9, without including the combination of the first pressurizing step S2 and the second pressurizing step S3.

[0090] The following describes test examples related to the technology disclosed herein, but it is not intended to limit the technology disclosed herein to the test examples described below. Furthermore, for the reference numerals used in the description of the test examples, please refer to the reference numerals shown in the accompanying drawings as appropriate.

[0091] A test battery cell was prepared as the subject of this test. This test battery cell has three such... Figure 4 and Figure 5 The electrode body 20 shown is a wound electrode body, a non-aqueous electrolyte, and a square housing 10 that houses the three electrode bodies 20 and the non-aqueous electrolyte (see reference). Figure 3 Regarding the dimensions of each electrode body 20: The width of the main body 20a (the length of the long side of the rectangular surface 20a3) is 292 mm. The height of the main body 20a (the length of the short side of the rectangular surface 20a3) is 95 mm. The thickness of the main body 20a (the distance between the rectangular surfaces 20a3) is 12 mm. Regarding the dimensional relationships of the housing 10: The length of the long side 12b1 of the first sidewall 12b is 308 mm, the length of the short side 12b2 of the first sidewall 12b is 103 mm, and the thickness of the housing 10 (the distance between the first sidewalls 12b) is 40 mm.

[0092] - Example -

[0093] The test battery cell was held between a pair of SUS plates, and a load was applied to the thickness of the test battery cell using a universal testing machine. In this example, the load was applied to a central region 12r1 of 290mm × 77mm in the first sidewall 12b. First, a load of 49kN was applied to the test battery cell for 8 seconds. Then, part of the load was removed, and a load of 6.0kN was applied to the test battery cell for 2 seconds. Next, a load of 8.2kN was applied to the test battery cell for 300 seconds. During the application of the load, the thickness of the test battery cell was measured using a laser displacement gauge. Based on the change in thickness of the test battery cell during this period, the pressure applied to the test battery cell during the application of the 8.2kN load was calculated. Based on this pressure, the degree of load release during this period was calculated. The results are as follows... Figure 9 As shown. Figure 9 This is a graph illustrating the pressure applied to the test battery cell over time in the embodiment. Figure 9 In the diagram, the X-axis represents the load application time (s). Figure 10 Similarly). The Y-axis represents the pressure (kN) applied to the test battery cell. Figure 10 Similarly). Furthermore, the universal testing machine used in the test examples was a precision universal testing machine (Universal Testing Machine AGX-V) manufactured by Shimadzu Corporation. The laser displacement gauge used in the test examples was an LK-G157 manufactured by Keyence Corporation.

[0094] - Comparative Example -

[0095] In this example, instead of applying a 49kN load and a 6.0kN load as in the previous embodiment, a 6.0kN load is applied for 7 seconds. Then, a 6.0kN load is applied to the test battery cell for 300 seconds. Otherwise, using the same apparatus and procedures as in the previous embodiment, the pressure applied to the test battery cell during the 300-second application of the 6.0kN load is calculated, and the degree of load release during that period is calculated. The results are as follows... Figure 10 As shown. Figure 10 This is a graph showing the change in pressure applied to the test battery cells in the comparative example over time.

[0096] -result-

[0097] In the embodiment, during the period when a load of 8.2 kN was applied for 300 seconds, the pressure applied to the test battery cell decreased from 8.2 kN to 8.0 kN. That is, the load release degree in the embodiment was 2%. Therefore, in the embodiment, the retention of air bubbles within the electrode body 20 was suppressed during the period when a load of 8.2 kN was applied for 300 seconds. On the other hand, in the comparative example, during the period when a load of 6.0 kN was applied for 300 seconds, the pressure applied to the test battery cell decreased from 6.0 kN to 3.1 kN. That is, the load release degree in the comparative example was 48%. Therefore, in the comparative example, during the period when a load of 6.0 kN was applied for 300 seconds, air bubbles remained within the electrode body 20, and these bubbles gradually dissipated outside the electrode body 20, thus it is considered that load release occurred for the test battery cell.

[0098] The technology disclosed herein may include the methods described in the following items.

[0099] Item 1:

[0100] A method for manufacturing an energy storage device, the energy storage device comprising an electrode body, a non-aqueous electrolyte, and a housing containing the electrode body and the non-aqueous electrolyte, the manufacturing method comprising:

[0101] An assembly is prepared to house the electrode body and the non-aqueous electrolyte within the housing.

[0102] Pressure P1 is applied to the assembly;

[0103] After applying pressure P1, a pressure P2 less than pressure P1 is applied to the assembly; and

[0104] While applying the pressure P2 to the assembly, the assembly is charged.

[0105] Item 2:

[0106] The manufacturing method as described in item 1, wherein applying pressure P1 to the assembly and applying pressure P2 to the assembly are performed continuously.

[0107] Item 3:

[0108] The manufacturing method as described in item 1 or 2, wherein the charging is an initial charging.

[0109] Item 4:

[0110] The manufacturing method according to any one of items 1 to 3, wherein the pressure P2 is 1 / 10 to 1 / 2 of the pressure P1.

[0111] Item 5:

[0112] The manufacturing method as described in any one of items 1 to 4, wherein the pressure P1 is applied for a period of 1 second to 60 seconds.

[0113] Item 6:

[0114] The manufacturing method according to any one of claims 1 to 5, wherein the electrode body is a flat wound electrode body, which is formed by stacking a strip-shaped positive electrode and a strip-shaped negative electrode with a separator sandwiched between them and winding them along the length of the sheet.

[0115] Item 7:

[0116] The manufacturing method as described in any one of items 1 to 6, wherein,

[0117] The housing has a rectangular bottom wall and a pair of opposing first side walls extending from a pair of opposing long sides of the bottom wall.

[0118] The electrode body has rectangular surfaces at both ends of the stacking direction of the positive electrode and the negative electrode, respectively.

[0119] The rectangular surface is opposite to the first sidewall.

[0120] The pressures P1 and P2 are applied to the first sidewall.

[0121] Item 8:

[0122] The manufacturing method as described in any one of items 1 to 7, further comprising:

[0123] Pressure P3 is applied to the charged assembly;

[0124] After applying pressure P3, a pressure P4 less than P3 is applied to the assembly; and

[0125] Charging is performed while the pressure P4 is applied.

[0126] Explanation of reference numerals in the attached figures

[0127] 1. Energy storage devices

[0128] 10. Shell

[0129] 12a Bottom wall

[0130] 12b First sidewall

[0131] 12c Second sidewall

[0132] 20 Electrode Body

[0133] 20a3 Rectangular surface

[0134] 22 Positive electrode

[0135] 24 Negative electrode

[0136] 26. Diaphragm

[0137] 30 Positive extremes

[0138] 40 Negative extremes

[0139] 50 Positive current collector

[0140] 60 Negative current collector

Claims

1. A method for manufacturing an energy storage device, the energy storage device comprising an electrode body, a non-aqueous electrolyte, and a housing containing the electrode body and the non-aqueous electrolyte, wherein, include: An assembly is prepared to house the electrode body and the non-aqueous electrolyte within the housing. Pressure P1 is applied to the assembly; After applying pressure P1, a pressure P2 less than pressure P1 is applied to the assembly; and While applying the pressure P2 to the assembly, the assembly is charged.

2. The method for manufacturing the energy storage device as described in claim 1, wherein, The pressure P1 applied to the assembly and the pressure P2 applied to the assembly are performed continuously.

3. The method for manufacturing the energy storage device as described in claim 1 or 2, wherein, The charging mentioned is the initial charging.

4. The method for manufacturing the energy storage device as described in claim 1 or 2, wherein, The pressure P2 is 1 / 10 to 1 / 2 of the pressure P1.

5. The method for manufacturing the energy storage device as described in claim 1 or 2, wherein, The pressure P1 is applied for a period of 1 to 60 seconds.

6. The method for manufacturing the energy storage device as described in claim 1 or 2, wherein, The electrode body is a flat, wound electrode body, which is formed by stacking a strip-shaped positive electrode and a strip-shaped negative electrode with a separator between them and winding them along the length of the sheet.

7. The method for manufacturing the energy storage device as described in claim 6, wherein, The housing has a rectangular bottom wall and a pair of opposing first side walls extending from a pair of opposing long sides of the bottom wall. The electrode body has rectangular surfaces at both ends of the stacking direction of the positive electrode and the negative electrode, respectively. The rectangular surface is opposite to the first sidewall. The pressures P1 and P2 are applied to the first sidewall.

8. The method for manufacturing the energy storage device as described in claim 1 or 2, wherein, Also includes: Pressure P3 is applied to the charged assembly; After applying pressure P3, a pressure P4 less than P3 is applied to the assembly; as well as Charging is performed while the pressure P4 is applied.

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