Secondary battery manufacturing method

Abstract

Provided is a method for manufacturing a secondary battery, comprising: a precharging step for precharging at least one electrode body that includes a positive electrode material, a negative electrode material, and an electrolyte; one or more pressurization steps for putting the electrode body in a pressurized state by mechanical pressure in the period of the precharging step and in the following period; and one or more depressurization steps for putting the atmosphere of the electrode body in a depressurized state in the period of the precharging step and in the following period.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a secondary battery. [Background technology]

[0002] Patent Document 1 discloses an example of a method for manufacturing a lithium-ion secondary battery. The manufacturing method includes the following steps: a liquid injection step, a first pressing step, a pre-charging step, a second pressing step, and a main charging step. The liquid injection step is a step of injecting an electrolyte into an unfilled lithium-ion secondary battery. The first pressing step is a step of pressing the electrode assembly with a first pressure in the stacking direction of the positive electrode plate, separator, and negative electrode plate after the liquid injection step. The pre-charging step is a step of pre-charging the lithium secondary battery to a first battery voltage while the electrode assembly is pressed with the first pressure. The second pressing step is a step of pressing the electrode assembly with a second pressure higher than the first pressure in the stacking direction after the pre-charging step, while heating the lithium-ion battery to reduce the viscosity of the electrolyte. The main charging step is a step of conditioning charging the lithium secondary battery to a second battery voltage higher than the first battery voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-21510 Summary of the Invention [Means for solving the problem]

[0004] A method for manufacturing a secondary battery according to one embodiment of the present disclosure includes a pre-charging step of pre-charging at least one electrode assembly including a positive electrode material, a negative electrode material, and an electrolyte, one or more pressurizing steps of pressurizing the electrode assembly by mechanical pressure during the pre-charging step and a period thereafter, and one or more depressurizing steps of depressurizing the atmosphere of the electrode assembly during the pre-charging step and a period thereafter. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is a perspective view showing the appearance of a secondary battery according to the present disclosure. [Figure 2] FIG. 1 is a perspective view showing the appearance of a unit cell according to the present disclosure. [Figure 3] FIG. 2 is an exploded model diagram showing a cross section taken along line III-III in FIG. [Figure 4] FIG. 4 is an exploded model diagram showing a cross section taken along line IV-IV in FIG. [Figure 5] FIG. 2 is a model diagram showing a specific structure of an electrode body. [Figure 6] 1 is a flowchart illustrating an example of a method for manufacturing a secondary battery according to the present disclosure. [Figure 7] 1 is a schematic diagram illustrating an example of a schematic configuration of a pre-charging device according to the present disclosure. [Figure 8] FIG. 10 is an exploded model diagram showing a state in which a spacer is arranged between two trays adjacent in the vertical direction. [Figure 9] 10 is a flowchart illustrating an example of a process performed by a pre-charging device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] In this embodiment, a specific process for pre-charging a secondary battery during manufacture will be mainly described. The pre-charging may be the first charging of the secondary battery during manufacture. In this embodiment, prior to describing the specific process, a configuration of the secondary battery and an example of a manufacturing process for the secondary battery will be described.

[0007] [Configuration of secondary battery] FIG. 1 is a perspective view showing the appearance of a secondary battery 1. The secondary battery 1 is a battery that can be charged or discharged by being electrically connected to an external terminal. For example, at least one secondary battery 1 may be mounted in an electricity storage device for use in a home, a base station, an automobile, a robot such as a drone, or a medical device. The secondary battery 1 may include a unit cell 10, connection terminals 21 and 22, and a second housing 50. The configuration of the unit cell 10 will be described later.

[0008] The second housing 50 may house the unit cells 10. The second housing 50 may be formed of, for example, an aluminum pouch film or a laminate film having a metal foil layer such as stainless steel or nickel. The aluminum pouch film may be a film on which aluminum is vapor-deposited, or a film laminated with aluminum foil. The film material may be, for example, polypropylene, polyethylene, nylon, or polyethylene terephthalate. The thickness of the second housing 50 may be 50 μm or more and 300 μm or less, for example, 200 μm.

[0009] When the second housing 50 is an aluminum pouch film, the second housing 50 may have a configuration in which two aluminum pouch films are located on both sides in the stacking direction (Z-axis direction) of the unit cell 10. Furthermore, when the second housing 50 is an aluminum pouch film, the second housing 50 may have a configuration in which one aluminum pouch film is folded in half and the unit cell 10 is located inside it.

[0010] The connection terminals 21 and 22 may be terminals that are connected to external terminals in order to extract power from or supply power to the secondary battery 1. The connection terminals 21 and 22 may protrude from the inside to the outside of the second housing 50. The connection terminals 21 and 22 may be made of, for example, copper, aluminum, or nickel. The connection terminals 21 and 22 may have a thickness of 50 μm or more and 500 μm or less, for example, 200 μm. The connection terminals 21 and 22 may also be subjected to a surface treatment to improve adhesion to an adhesive member (not shown). The adhesive member bonds the connection terminals 21 and 22 to the second housing 50 located above and below the connection terminals 21 and 22 to determine the positions of the connection terminals 21 and 22 relative to the second housing 50.

[0011] 2 is a perspective view showing the appearance of the unit cell 10. As shown in FIG. 2, the unit cell 10 may include an electrode assembly 14 and a first housing 15. The electrode assembly 14 may have a sheet-like shape. The sheet-like electrode assembly 14 may include a positive electrode 11 and a negative electrode 12.

[0012] The first housing 15 may house the electrode assembly 14. When a plurality of first housings 15 housing the electrode assembly 14 are stacked, the plurality of first housings 15 may be adhered to each other by an adhesive layer (not shown). The material of the first housing 15 may be, for example, a film-like PET (polyethylene terephthalate) or nylon. More specifically, for example, two first housings 15 may be configured to be located on both sides in the stacking direction (Z-axis direction) of the unit cells 10. The thickness of the base material of the first housing 15 may be, for example, 10 μm or more and 40 μm or less, for example, 25 μm. The material of the adhesive layer may be, for example, polypropylene or polyethylene.

[0013] The first housing 15 may be transparent, for example. Figure 2 is a diagram showing how the electrode assembly 14 can be seen through the first housing 15 by using a transparent first housing 15 for the unit cell 10.

[0014] The first housing 15 may have a cutout 16. For example, the cutout 16 may be provided in both the first housing 15 on the positive electrode 11 side and the first housing 15 on the negative electrode 12 side. By providing the cutout 16 as an unsealed portion in a portion of the unit cell 10, gas generated by a decomposition reaction of the electrolyte or a trace amount of water inside the unit cell 10 can be released to the outside of the unit cell 10. Furthermore, by providing the cutout 16, a configuration may be adopted in which a portion on the positive electrode 11 side and a portion on the negative electrode 12 side are exposed from the first housing 15. Alternatively, a configuration may be adopted in which a portion on the positive electrode 11 side and a portion on the negative electrode 12 side are not exposed from the first housing 15. In the latter case, the internal space on the positive electrode 11 side of the unit cell 10 may be connected to the external space of the unit cell 10, and the internal space on the negative electrode 12 side of the unit cell 10 may be connected to the external space of the unit cell 10. Furthermore, the first housing 15 on the negative electrode 12 side may be exposed at the position of the cutout 16 on the positive electrode 11 side, and the first housing 15 on the positive electrode 11 side may be exposed at the position of the cutout 16 on the negative electrode 12 side.

[0015] The positive electrode 11 may have an exposed portion 11e exposed from the first housing 15. The negative electrode 12 may have an exposed portion 12e exposed from the first housing 15. The connection terminals 21 and 22 may be electrically connected to the exposed portions 11e and 12e, respectively, by, for example, ultrasonic welding, laser welding, or resistance welding. The positive electrode 11 and the negative electrode 12 will be described in detail later.

[0016] The secondary battery 1 may have a configuration in which a unit cell 10, in which the positive electrode 11 and the negative electrode 12 are housed in a first housing 15, is further housed in a second housing 50. With this configuration, the electrode assembly 14 is housed doubly, thereby improving the safety of the secondary battery 1. The second housing 50 may also be housed in an additional housing. However, the secondary battery 1 only needs to include the positive electrode 11 and the negative electrode 12, and only needs to be housed in at least one housing.

[0017] In the first embodiment, the secondary battery 1 has a configuration in which a plurality of unit cells 10 are stacked, for example, ten layers of unit cells 10 are stacked. However, the secondary battery 1 according to the present disclosure may have a plurality of layers of unit cells 10 other than ten, or may have only one layer. When the secondary battery 1 has a plurality of layers of unit cells 10, the unit cells 10 may be stacked. When the secondary battery 1 shown in FIG. 1 is viewed from above, the portion excluding the connection terminals 21 and 22 may be substantially rectangular or may have a different shape. When the unit cell 10 shown in FIG. 2 is viewed from above, the portion excluding the exposed portions 11e and 12e may be substantially rectangular or may have a different shape.

[0018] Fig. 3 is a model diagram showing an exploded cross section taken along line III-III in Fig. 1. Fig. 4 is a model diagram showing an exploded cross section taken along line IV-IV in Fig. 1. For simplicity, the second container 50 is omitted from Figs. 3 and 4. Figs. 3 and 4 mainly show the positional relationship of each component. Therefore, the thickness relationships of each component are not necessarily as shown in Figs. 3 and 4.

[0019] As shown in FIGS. 3 and 4, the secondary battery 1 may further include a first protective member 30. The first protective member 30 may protect a first connection portion electrically connecting the exposed portions 11e exposed from the first housing 15 of each unit cell 10 to each other, and a second connection portion electrically connecting the exposed portions 12e exposed from the first housing 15 of each unit cell 10 to each other. The exposed portions 11e and the exposed portions 12e may be connected to each other by, for example, ultrasonic welding, laser welding, or resistance welding. Although the exposed portions 11e of the positive electrode 11 and the exposed portions 12e of the negative electrode 12 are not connected to each other in FIGS. 3 and 4 , they are actually connected as described above.

[0020] The material of the first protective member 30 may be, for example, a film-like polyolefin or polyimide. The first protective member 30 may be adhered to the exposed portions 11e and 12e by an adhesive layer (not shown). The material of the adhesive layer of the first protective member 30 may be any material that is not easily dissolved in the electrolytic solution (electrolyte). The material of the adhesive layer may be, for example, an acrylic adhesive.

[0021] In this embodiment, the first protective member 30 may cover the first and second connecting portions and a portion of the first housing 15. This makes it difficult for stress concentration to occur when stress occurs in the exposed portion 11e or 12e, thereby reducing the possibility of the exposed portion 11e or 12e being damaged or broken near the first and second connecting portions. However, it is sufficient for the first protective member 30 to protect at least the first and second connecting portions, and it is not necessary for the first protective member 30 to cover the first and second connecting portions and a portion of the first housing 15.

[0022] 3 and 4, the positive electrode 11 may have an electrode conductor 11a and a positive electrode active material layer 11b, and the negative electrode 12 may have an electrode conductor 12a and a negative electrode active material layer 12b.

[0023] The electrode conductor 11a may be, for example, an aluminum foil. The thickness of the electrode conductor 11a may be 5 μm or more and 25 μm or less, for example, 10 μm. The electrode conductor 12a may be, for example, a copper foil. The thickness of the electrode conductor 12a may be 5 μm or more and 25 μm or less, for example, 10 μm.

[0024] FIG. 5 is a cross-sectional view showing a specific structure of the electrode body 14. As shown in FIG. 5, the positive electrode active material layer 11b may be a layer of a positive electrode material that is a mixture of a positive electrode active material 11c and a conductive additive 11d. The negative electrode active material layer 12b may be a layer of a negative electrode material that is a mixture of a negative electrode active material 12c and a conductive additive 12d. The positive electrode active material 11c may be, for example, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or lithium manganese oxide. The negative electrode active material 12c may be, for example, graphite or lithium titanate. The conductive additives 11d and 12d may be, for example, carbon black or acetylene black. However, the positive electrode active material 11c, the negative electrode active material 12c, and the conductive additives 11d and 12d are not limited to these.

[0025] The positive electrode material may have a clay-like property, obtained by mixing an electrolyte into a mixture of a positive electrode active material 11c and a conductive additive 11d. The negative electrode material may have a clay-like property, obtained by mixing an electrolyte into a mixture of a negative electrode active material 12c and a conductive additive 12d. The positive electrode 11 may be an electrode in which the positive electrode material is coated on an electrode conductor 11a. The negative electrode 12 may be an electrode in which the negative electrode material is coated on an electrode conductor 12a.

[0026] The electrolytic solution is a solution in which a lithium salt, which is an electrolyte, is dissolved in a non-aqueous solvent. The non-aqueous solvent may be a carbonate-based solvent. The carbonate-based solvent may be γ-butyrolactone, ethylene carbonate, or both γ-butyrolactone and ethylene carbonate. Furthermore, as long as the carbonate-based solvent contains at least one of γ-butyrolactone and ethylene carbonate, it may also contain other solvents. Examples of other solvents include propylene carbonate, dimethyl carbonate, dimethoxyethane, diethyl carbonate, tetrahydrofuran, and triethylene glycol dimethyl ether. The electrolyte may be lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide (LiFSI).

[0027] The electrode assembly 14 may further include a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 may be positioned such that the positive electrode active material layer 11b and the negative electrode active material layer 12b are in contact with the separator 13. That is, the unit cell 10 may have a structure in which the positive electrode 11 and the negative electrode 12 are stacked with the separator 13 interposed therebetween. The separator 13 may function as an insulating member that insulates the positive electrode 11 and the negative electrode 12. The separator 13 may be, for example, a sheet-like nonwoven fabric or a porous material.

[0028] When a porous material is used as separator 13, specifically, a porous film made of a thermoplastic resin having a melting point of about 80° C. to 140° C. may be used. As the thermoplastic resin, for example, a polyolefin polymer such as polypropylene or polyethylene, or polyethylene terephthalate may be used.

[0029] When using positive and negative electrode materials with clay-like properties, a binder is not required between the positive and negative electrodes and the separator. Furthermore, an electrolyte is mixed into the positive and negative electrode materials before forming the positive and negative electrodes. This improves the performance of the positive and negative electrodes. By mixing the electrolyte into the positive and negative electrode materials, the number of steps required for forming the positive and negative electrodes can be reduced compared to when using positive and negative electrode materials that do not contain an electrolyte. Furthermore, the step of injecting the electrolyte can be eliminated from the secondary battery manufacturing process. Furthermore, compared to when using positive and negative electrode materials that do not contain an electrolyte, the positive and negative electrode materials can be applied thicker to the electrode conductors. Therefore, when realizing a secondary battery with a predetermined storage capacity, fewer electrode conductors and separators can be used than when using positive and negative electrode materials that do not contain clay-like properties. This reduces component costs and increases energy density.

[0030] The positive electrode material and the negative electrode material do not need to have clay-like properties. In this case, the positive electrode active material 11c and the negative electrode active material 12c do not need to contain an electrolyte solution. For example, the positive electrode material may be a positive electrode slurry composed of a mixture of the positive electrode active material 11c and the conductive additive 11d, a binder, and a solvent. The positive electrode slurry may be applied to the electrode conductor 11a and dried to form the positive electrode active material layer 11b. Alternatively, the negative electrode material may be a negative electrode slurry composed of a mixture of the negative electrode active material 12c and the conductive additive 12d, a binder, and a solvent. The negative electrode slurry may be applied to the electrode conductor 12a and dried to form the negative electrode active material layer 12b. The binder may be polyvinylidene fluoride (PVdF), polyethylene oxide (PEO), or the like. The solvent may be an organic solvent such as N-methyl-2-pyrrolidone (NMP). In this case, the unit cell 10 is filled with an electrolyte, and the separator 13 may be impregnated with the electrolyte and hold the electrolyte.

[0031] The secondary battery according to the present disclosure may include an electrode assembly containing at least a positive electrode material, a negative electrode material, and an electrolyte solution. The secondary battery according to the present disclosure may be any secondary battery that is precharged during manufacturing and generates gas from the electrode assembly of the secondary battery.

[0032] [Secondary Battery Manufacturing Process] 6 is a flowchart showing an example of a manufacturing process (manufacturing method) for the secondary battery 1. The second housing body 50 is made up of two aluminum pouch films.

[0033] In the manufacturing process of the secondary battery 1, a manufacturing device (not shown) for manufacturing the secondary battery 1 first manufactures the positive electrode 11 and the negative electrode 12 (S1 and S2).

[0034] The positive electrode 11 is manufactured, for example, as follows. A manufacturing apparatus pulverizes the raw materials, the positive electrode active material 11c and the conductive additive 11d, and then mixes the positive electrode active material 11c and the conductive additive 11d. The manufacturing apparatus kneads the mixture of the positive electrode active material 11c and the conductive additive 11d while introducing an electrolyte solution, thereby manufacturing a clay-like positive electrode material (forming a slurry). The manufacturing apparatus then applies the clay-like positive electrode material to an electrode conductor 11a formed by, for example, punching a metal foil (e.g., aluminum foil). That is, the electrode conductor 11a and the positive electrode active material layer 11b are stacked to manufacture an integrated positive electrode 11. Alternatively, a first housing 15 may be laminated on one surface of the electrode conductor 11a in advance, and then the positive electrode material may be applied to the other surface. That is, a positive electrode 11 laminated with the first housing 15 may be manufactured.

[0035] The negative electrode 12 is manufactured, for example, as follows. A manufacturing apparatus pulverizes the raw materials, negative electrode active material 12c and conductive additive 12d, and then mixes the negative electrode active material 12c and conductive additive 12d. The manufacturing apparatus kneads the mixture of the negative electrode active material 12c and conductive additive 12d while introducing an electrolyte solution, thereby manufacturing a clay-like negative electrode material (forming a slurry). The manufacturing apparatus then applies the clay-like negative electrode material to an electrode conductor 12a formed by, for example, punching a metal foil (e.g., copper foil). That is, the electrode conductor 12a and the negative electrode active material layer 12b are stacked to manufacture an integrated negative electrode 12. Alternatively, a first housing 15 may be laminated on one surface of the electrode conductor 12a in advance, and then the negative electrode material may be applied to the other surface. That is, a negative electrode 12 laminated with the first housing 15 may be manufactured.

[0036] Next, the manufacturing equipment forms an electrode assembly 14 by bonding the positive electrode 11 and the negative electrode 12 together with the separator 13 sandwiched between them. Then, first housings 15 are placed on the positive electrode 11 side and the negative electrode 12 side of the electrode assembly 14, respectively, and the first housings 15 are bonded together at portions of the first housings 15 that are outside the outer periphery of the electrode assembly 14, thereby sealing the electrode assembly 14 between the first housings 15. The first housings 15 are not bonded together at the portions of the cutouts 16 of the first housings 15, resulting in a configuration in which the internal space of the unit cell 10 communicates with the external space of the unit cell 10. In other words, the electrode assembly 14 is sealed at the outer periphery except for a portion of the outer periphery of the first housing 15 on the positive electrode 11 side and the first housing 15 on the negative electrode 12 side. The unsealed portion becomes the cutout 16. In this manner, the unit cell 10 is manufactured (S3).

[0037] A plurality of unit cells 10 are manufactured through steps S1 to S3. The manufacturing equipment stacks the manufactured plurality of unit cells 10 (S4). Next, the manufacturing equipment welds connection terminals 21 and 22 to the electrode conductors 11a and 12a of the stacked unit cells 10 (S5). Specifically, the manufacturing equipment welds the exposed portions 11e of the plurality of electrode conductors 11a together, and welds the connection terminal 21 to the outermost exposed portion 11ea. The manufacturing equipment also welds the exposed portions 12e of the plurality of electrode conductors 12a together, and welds the connection terminal 22 to the outermost exposed portion 12ea.

[0038] Furthermore, the manufacturing equipment welds the unit cells 10 together at their outer peripheries excluding the cutouts 16 (S6). The unit cells 10 may be welded together at their outer peripheries by, for example, ultrasonic welding, heat welding, or adhesive tape.

[0039] Next, the manufacturing equipment temporarily heat-welds an aluminum pouch film, which is the material of the second housing body 50, to the outermost surfaces of one unit cell 10 and the other unit cell 10, which are located on the outermost sides of the plurality of unit cells 10 whose peripheries have been welded (S7). The temporary heat welding is for determining the position of the aluminum pouch film relative to the unit cells 10. The temporary heat welding may be low-strength welding that allows the aluminum pouch film to be peeled off from the unit cells 10 as needed. After determining the position of the aluminum pouch film, the manufacturing equipment bonds the aluminum pouch films together at locations outside the peripheries of the unit cells 10, and welds three of the four sides of the approximately rectangular aluminum pouch film (S8). In a configuration in which a single aluminum pouch film is folded in half and the unit cells 10 are located inside it, it is sufficient to weld two of the remaining three sides. Next, the manufacturing equipment cuts the aluminum pouch film into a desired shape with the three sides of the aluminum pouch film still welded (S9). The aluminum pouch film may be cut into a desired shape before the preliminary heat welding in S7, for example.

[0040] Next, the manufacturing equipment pre-charges the electrode assembly 14 of the secondary battery with three sides of the aluminum pouch film welded (S10). Pre-charging may be performed by a pre-charging device 4 included in the manufacturing equipment. The configuration and processing of the pre-charging device 4 will be described in detail later. Pre-charging is performed to form a high-quality SEI (Solid Electrolyte Interphase) on the surface of the negative electrode 12. Furthermore, particularly during pre-charging, gas is generated from the electrode assembly 14. This gas is, for example, a by-product generated during SEI formation due to a reaction between the electrolyte and the negative electrode material. Furthermore, this gas is generated, for example, by electrolysis of a small amount of water contained in the electrolyte. This gas can be discharged from the cutout 16 and the unwelded portion of the aluminum pouch film.

[0041] Furthermore, three sides of the aluminum pouch film containing the multiple unit cells 10 are closed and one side is open. That is, the aluminum pouch film only has an opening large enough to allow gas to escape. Therefore, even if electrolyte leaks from the unit cells 10 during pre-charging, the electrolyte can be contained within the aluminum pouch film. This reduces the possibility of production problems.

[0042] Next, the manufacturing equipment removes the air from inside the second housing 50 and welds one side of the aluminum pouch film that was not welded until the pre-charging step of S10, thereby manufacturing the secondary battery 1. In other words, the interior of the aluminum pouch film is vacuum-sealed (S11). In the vacuum sealing, the last side of the aluminum pouch film is welded, thereby forming the second housing 50 and manufacturing the secondary battery 1.

[0043] The above-described steps may be interchanged as necessary. For example, the manufacture of the positive electrode 11 and the manufacture of the negative electrode 12 may be performed in parallel, or the manufacture of the negative electrode 12 may be performed after the manufacture of the positive electrode 11, or the manufacture of the positive electrode 11 may be performed after the manufacture of the negative electrode 12. Furthermore, for example, the step S5 may be performed before the step S4, and the steps S10 and S11 may be performed before the step S9.

[0044] [Pre-charging details] The following describes in detail the preliminary charging in S10 of Fig. 6. As described above, the preliminary charging is performed by the preliminary charging device 4. Below, an example of the configuration of the preliminary charging device 4 will be described, and then an example of the processing performed by the preliminary charging device 4 will be described.

[0045] <Configuration of backup charging device> The pre-charging device 4 may be a device that performs pre-charging on a secondary battery under manufacture. The secondary battery under manufacture that is the target of pre-charging may have a structure that allows the electrode body 14 to be charged by the pre-charging device 4 and that allows gas generated inside the electrode body 14 to be discharged to the outside of the electrode body 14. In this embodiment, the secondary battery under manufacture that is the target of pre-charging is a secondary battery that is closed by welding three sides of an aluminum pouch film, for example, and has one side that is not welded. In the following description, the secondary battery under manufacture will be referred to as secondary battery 1a.

[0046] Fig. 7 is a schematic diagram showing an example of the general configuration of the pre-charging device 4. Fig. 7 is a schematic diagram of the pre-charging device 4 as seen from the side (front side) where an operator places the secondary battery 1a. Fig. 8 is an exploded model diagram showing a state in which a spacer 5 is placed between two vertically adjacent trays 44. Fig. 8 shows the state before the secondary battery 1a is placed in the tray 44.

[0047] As shown in FIG. 7, the pre-charging device 4 may include a pressurizing section 41 and a receiving section .

[0048] The pressurizing unit 41 may be a mechanism that applies mechanical pressure to the electrode body 14 of the secondary battery 1a. For example, an air cylinder or a hydraulic cylinder may be used as the pressurizing unit 41. The accommodation unit 42 may be a housing that accommodates the secondary battery 1a that is pressurized by the pressurizing unit 41.

[0049] The "pressurized state" refers to the state after the application of mechanical pressure to the electrode assembly 14 has begun. In other words, the "pressurized state" refers to the state from when mechanical pressure is applied to the electrode assembly 14 until it reaches a predetermined specified value, and also refers to the state in which mechanical pressure of the specified value is being applied to the electrode assembly 14. The specified value may be set, for example, in consideration of efficient gas release from the electrode assembly 14. Furthermore, the pressure direction may be along the normal direction of the two main surfaces (the surfaces with the widest areas) that form the front and back of the secondary battery 1a.

[0050] The storage section 42 may include a base 43, a tray 44, and a clamp 45. Area A1 of Figure 7 shows a state in which the tray 44 has been removed from the base 43.

[0051] A tray 44 may be placed on the pedestal 43. The pedestal 43 may be provided in the storage section 42 so as to be movable in the vertical direction (z-axis direction). The tray 44 may store at least two of the multiple secondary batteries 1a (electrode assemblies 14) stored in the storage section 42. The tray 44 may have, for example, a shallow, generally box-like shape with one side open, and may be capable of storing multiple secondary batteries 1a stacked together. In other words, the tray 44 may be capable of storing multiple sheet-like electrode assemblies 14 constituting the secondary batteries 1a, stacked in the stacking direction of the positive electrodes 11 and negative electrodes 12 constituting the electrode assembly 14. In the example of FIG. 7, the storage section 42 is provided with two rows of four pedestals 43 arranged vertically. The arrangement and number of pedestals 43 are not limited to this. The base 43 may have a plurality of trays 44 stacked along the pressure direction of the pressure unit 41 so that the pressure unit 41 can apply mechanical pressure to the secondary batteries 1a housed in the trays 44. In other words, the plurality of trays 44 may be arranged so as to overlap in the pressure direction, with each tray housing a plurality of secondary batteries 1a. The mechanical pressure applied by the pressure unit 41 to the secondary batteries 1a in the upper tray 44 is then applied to the secondary batteries 1a housed in the lower tray 44 via the upper tray 44. The pressure direction may be along the normal direction to the main surfaces of the secondary batteries 1a (electrode body 14).

[0052] In this embodiment, the pressurizing unit 41 may apply mechanical pressure from above (the ceiling 42a side) of the stacked trays 44 by descending from the ceiling 42a to the bottom 42b of the storage unit 42. Specifically, the pressurizing unit 41 presses the topmost tray 44 downward as it descends. As a result of this pressing, the topmost pedestal 43 descends. As the pressurizing unit 41 further descends, the topmost pedestal 43 presses the pedestal 43 below it downward. In other words, as the pressurizing unit 41 descends, the upper pedestal 43 pushes the lower pedestal 43, thereby applying mechanical pressure to the multiple secondary batteries 1a arranged between the topmost pedestal 43 and the bottommost pedestal 43. In this way, the pressurizing unit 41 may press each of the multiple secondary batteries 1a accommodated in the tray 44 in a pressurized state.

[0053] By stacking and accommodating multiple secondary batteries 1a across multiple trays 44, the posture of the secondary batteries 1a can be more stable when pressure is applied than when all of the secondary batteries 1a are stacked together. Also, by stacking multiple trays 44 and applying mechanical pressure from above the stacked multiple trays 44, all of the secondary batteries 1a can be pressurized together with a single pressure unit 41.

[0054] In the present embodiment, the pressure applying unit 41 is provided on the ceiling 42a side and applies mechanical pressure to the electrode assembly 14 of the secondary battery 1a by moving from the ceiling 42a to the bottom 42b, but this is not limiting. For example, the pressure applying unit 41 may be provided on the bottom 42b side and apply mechanical pressure to the electrode assembly 14 of the secondary battery 1a by moving from the bottom 42b to the ceiling 42a. Alternatively, pressure applying units 41 may be provided on both the ceiling 42a and the bottom 42b. That is, it is sufficient that mechanical pressure is applied to the electrode assembly 14 of the secondary battery 1a housed in a plurality of stacked trays 44 from at least one of above and below the plurality of trays 44.

[0055] As described above, the pre-charging device 4 shown in FIG. 7 has a structure in which mechanical pressure is applied from above the pre-charging device 4 when the secondary battery 1a is placed in the housing 42 so that the main surface of the secondary battery 1a is approximately parallel to the horizontal plane. However, the pre-charging device 4 may also apply mechanical pressure from the side of the pre-charging device 4 when the secondary battery 1a is placed in the housing 42 so that the main surface of the secondary battery 1a is approximately perpendicular to the horizontal plane. In this case, the multiple trays 44 may be arranged so that one open surface faces the side of the pre-charging device 4. In other words, it is sufficient that the multiple trays 44 are arranged along the pressure direction.

[0056] In other words, the multiple secondary batteries 1a (electrode bodies 14) may be arranged side by side in the housing section 42 so that at least one of the two main surfaces of a secondary battery 1a faces a main surface of another secondary battery 1a. In this state, the pre-charging device 4 may apply mechanical pressure from at least one side of the two outermost electrode bodies. In this case, the pre-charging device 4 can pressurize the multiple secondary batteries 1a collectively.

[0057] The clamps 45 may be connection parts through which the pre-charging device 4 supplies (passes) current to the electrode assembly 14 of the secondary batteries 1a. As shown in FIG. 7 , the clamps 45 are provided on the rear side of the pre-charging device 4. The clamps 45 are provided facing the trays 44 arranged on each pedestal 43. The clamps 45 clamp the connection terminals 21 and 22 of the multiple secondary batteries 1a stacked and housed in each tray 44, thereby electrically connecting the pre-charging device 4 to the connection terminals 21 and 22. However, the mechanism for supplying current to the connection terminals 21 and 22 is not limited to a mechanism that clamps the connection terminals 21 and 22, as with the clamps 45, as long as it is capable of electrically connecting the pre-charging device 4 to the connection terminals 21 and 22. The pre-charging device 4 pre-charges the electrode assembly 14 by supplying current to the electrode assembly 14 when, for example, approximately 2 to 10 secondary batteries 1a housed in one tray 44 are electrically connected. The pre-charging device 4 may supply a current of, for example, 5 A or more and 80 A or less to the connection terminals 21 and 22. The magnitude of the current may be adjusted as appropriate so that a predetermined current flows through one electrode body 14.

[0058] As described above, the plurality of unit cells 10 are connected to the connection terminals 21 and 22, respectively. Therefore, the electrode assemblies 14 of the plurality of unit cells 10 can be charged simultaneously simply by electrically connecting the connection terminals 21 and 22 to the pre-charging device 4. This improves the manufacturing efficiency of the secondary battery 1, and therefore the productivity of the secondary battery 1.

[0059] 8, four secondary batteries 1a are stacked and housed in the tray 44, but the number is not limited to four and multiple secondary batteries 1a may be stacked and housed. The number of secondary batteries 1a housed in the tray 44 may be predetermined, and for example, 2 to 10 secondary batteries 1a may be stacked and housed.

[0060] 8, a spacer 5 may be disposed between two adjacent trays 44. With the spacer 5 disposed, the pressurizing unit 41 may pressurize each of the multiple secondary batteries 1a. The upper surface 5a and the lower surface 5b of the spacer 5 may be large enough to accommodate the batteries in the trays 44. The height (thickness) HS of the spacer 5 may be large enough to prevent two adjacent trays 44 from coming into contact with each other when the pressurizing unit 41 presses the trays 44 with a specified number of secondary batteries 1a accommodated therein. By disposing such a spacer 5, it is possible to reduce the possibility of the trays 44 coming into contact with each other when the pressurizing unit 41 applies pressure, thereby preventing the electrode assembly 14 from being properly pressed.

[0061] The mechanical pressure applied by the pressurizing unit 41 to the secondary battery 1a may be the same as the mechanical pressure applied to the secondary batteries 1 in an electricity storage device (not shown) modularized by stacking a plurality of secondary batteries 1. In other words, the mechanical pressure applied to the electrode body 14 during pre-charging may be the same as the mechanical pressure applied to the electrode body 14 in the electricity storage device as a completed product. In the electricity storage device, elastic members may be provided on both sides of the housing constituting the electricity storage device, so that mechanical pressure can be applied to the stacked secondary batteries 1 from both sides of the plurality of secondary batteries 1. The mechanical pressure may be, for example, 0.1 kgf / cm 2 Over 1.4kgf / cm 2 below It may be.

[0062] In this embodiment, a plurality of trays 44 are provided in the storage section 42, but it is sufficient to provide at least one tray 44. In this embodiment, a plurality of secondary batteries 1a are stored in one tray 44, but it is sufficient to store at least one secondary battery 1a. In other words, it is sufficient for the pre-charging device 4 to be able to apply mechanical pressure to at least one electrode body 14.

[0063] The tray 44 and the spacer 5 may be made of an insulating material, such as a plastic, such as polyethylene or polyvinyl chloride. The tray 44 and the spacer 5 may be made of the same material or different materials. The shape of the tray 44 is not limited to a shallow box-like shape, as long as the tray 44 can accommodate the secondary battery 1a. The tray 44 may be shaped like a tray, such as a flat plate, or a tray-shaped plate with guide pins for positioning the area where the secondary battery 1a will be placed.

[0064] In this specification, accommodating a secondary battery 1a (electrode body 14) in a tray 44 refers to placing at least one secondary battery 1a (electrode body 14) in a predetermined position on the tray 44. Furthermore, although the above description has been given using an example in which a secondary battery 1a is accommodated in the tray 44, a unit cell 10 may be accommodated in the tray 44, and the pre-charging device 4 may apply mechanical pressure to the unit cell 10.

[0065] <Handling of standby charging device> Next, a specific process performed by the pre-charging device 4 when pre-charging the electrode assembly 14 will be described with reference to the flowchart of Fig. 9. Fig. 9 is a flowchart showing an example of the process performed by the pre-charging device 4.

[0066] First, an operator prepares at least one tray 44 and places multiple secondary batteries 1a in the tray 44 (S21). The operator then places the tray 44 in the storage section 42 of the pre-charging device 4. At this time, the operator may stack multiple trays 44, or may place a spacer 5 between two adjacent trays 44. Next, upon receiving an input operation from the operator to start pre-charging, the pre-charging device 4 clamps the connection terminals 21 and 22 with the clamp 45, thereby electrically connecting the clamp 45 to the connection terminals 21 and 22 (S22). In the state of S22, the pre-charging device 4 is not supplying current to the connection terminals 21 and 22. In this state, the pre-charging device 4 controls the pressurizing unit 41 to start pressurizing the secondary battery 1a (S23). That is, in S23, the pre-charging device 4 starts applying mechanical pressure to the electrode assembly 14 of the secondary battery 1a. The process of S23 may be executed before the process of S22, or the processes of S22 and S23 may be executed in parallel.

[0067] Next, the pre-charging device 4 may reduce the pressure of the atmosphere surrounding the electrode assembly 14 of the secondary battery 1a (first pressure reduction step: S24). This reduction in pressure makes it possible to remove gas from the secondary battery 1a before pre-charging the electrode assembly 14, even if gas has been generated in the electrode assembly 14. Furthermore, the first pressure reduction step makes it possible to remove gas from the electrode assembly 14, thereby improving the adhesion between the components of the secondary battery 1a.

[0068] The above-mentioned "atmosphere surrounding the electrode body 14 (atmosphere of the electrode body 14)" refers to the gas filling the environment in which the secondary battery 1a is placed, and may be air, for example. However, the area around the secondary battery 1a may be filled with a gas other than air (for example, nitrogen). In this embodiment, the atmosphere of the electrode body 14 refers to the air filling the housing portion 42.

[0069] Furthermore, the "reduced pressure state" refers to a state in which the pressure around the electrode assembly 14 (in this embodiment, the atmospheric pressure inside the housing 42) is lower than the pressure immediately before the change. In other words, the "reduced pressure state" includes a state in which the pressure around the electrode assembly 14 is between the pressure immediately before the change and a predetermined first specified value, and a state in which the pressure is maintained at the first specified value. The first specified value may be set, for example, in consideration of efficient pre-charging of the electrode assembly 14 and efficient degassing of the secondary battery 1a.

[0070] After reducing the pressure in the atmosphere around the electrode assembly 14, the pre-charging device 4 may start pre-charging the electrode assembly 14 (S25). That is, in S25, the pre-charging device 4 starts supplying current to the electrode assembly 14 via the clamp 45.

[0071] Next, the pre-charging device 4 may place the atmosphere around the electrode assembly 14 in a pressurized state (pressurization step: S26). The "pressurized state" refers to a state in which the pressure around the electrode assembly 14 is higher than the pressure immediately before the change. In other words, the "pressurized state" includes a state in which the pressure around the electrode assembly 14 is between the pressure immediately before the change and a predetermined second specified value, and a state in which the pressure is maintained at the second specified value. The second specified value may also be set, for example, in consideration of efficient pre-charging of the electrode assembly 14 and efficient degassing from the secondary battery 1a.

[0072] For example, in the first pressure reduction step of S24, the pre-charging device 4 may change the atmosphere of the electrode assembly 14 from atmospheric pressure to a vacuum state. Also, in the pressure increase step of S26, the pre-charging device 4 may change the atmosphere of the electrode assembly 14 from a vacuum state to atmospheric pressure. In this case, the first specified value is about 10 -1 ~10 -3 The second predetermined pressure may be about 1 atmosphere.

[0073] For example, a first valve may be provided in a connecting pipe (not shown) connecting the storage unit 42 and a vacuum pump (not shown). A second valve may be provided in a connecting pipe (not shown) connecting the inside and outside of the storage unit 42 or in a connecting pipe (not shown) connecting the storage unit 42 and a gas supply unit (not shown) such as nitrogen. In this case, the pre-charging device 4 may open the first valve and close the second valve to reduce the pressure inside the storage unit 42 (i.e., the atmosphere around the electrode body 14). The pre-charging device 4 may open the second valve and close the first valve to increase the pressure inside the storage unit 42.

[0074] The pre-charging device 4 starts the voltage step-up step in S26 after starting pre-charging of the electrode assembly 14 in S25, but this is not limited to this. The pre-charging device 4 may start pre-charging of the electrode assembly 14 in S25 after starting the voltage step-up step in S26, or the start of pre-charging of the electrode assembly 14 in S25 and the start of the voltage step-up step in S26 may be executed simultaneously. The voltage step-up step in S26 may be executed after the first pressure reduction step in S24.

[0075] Specifically, the pre-charging device 4 may start pre-charging the electrode assembly 14 before opening the second valve and closing the first valve. In this case, pre-charging will be started during the first pressure reduction step. Alternatively, the pre-charging device 4 may start pre-charging the electrode assembly 14 at the same time as opening the second valve and closing the first valve. Alternatively, the pre-charging device 4 may start pre-charging the electrode assembly 14 after opening the second valve and closing the first valve, but before the pressure around the electrode assembly 14 reaches the second specified value. Alternatively, the pre-charging device 4 may start pre-charging after opening the second valve and closing the first valve, but after the pressure around the electrode assembly 14 reaches the second specified value.

[0076] Next, the pre-charging device 4 may reduce the pressure of the atmosphere around the electrode assembly 14 (second pressure reduction step: S27). For example, in the second pressure reduction step, the pre-charging device 4 may also reduce the pressure of the atmosphere around the electrode assembly 14 from atmospheric pressure to a vacuum state. Next, the pre-charging device 4 determines whether the pressure increase step of S26 and the second pressure reduction step of S27 have been performed a first specified number of times (S28). In this embodiment, the first specified number of times may be set to a plurality of times. For example, the first specified number of times may be set so that the pressure increase step and the second pressure reduction step are each performed 2 to 10 times. If the pre-charging device 4 determines that the pressure increase step of S26 and the second pressure reduction step of S27 have been performed a first specified number of times (YES in S28), the pre-charging device 4 ends the pre-charging of the electrode assembly 14. On the other hand, when the pre-charging device 4 determines that the voltage increase step in S26 and the second pressure decrease step in S27 have not been executed the first specified number of times (NO in S28), the pre-charging device 4 executes the process of S26 again.

[0077] As described above, the pre-charging device 4 starts pre-charging the electrode assembly 14 in S25 and ends pre-charging the electrode assembly 14 in S29. That is, in this embodiment, the pre-charging device 4 may execute a pre-charging step of pre-charging the electrode assembly 14 during the first pressure reduction step in S24 or in S25 to S29 after the first pressure reduction step. Furthermore, the pre-charging device 4 may execute a pressure increase step in S26 after the first pressure reduction step in S24, and execute a second pressure reduction step in S27 after the pressure increase step. The pressure increase step and second pressure reduction step enable the entire electrode assembly 14 to be charged approximately uniformly (without unevenness) in the pressure-increased state, and enable a greater amount of gas to escape from the electrode assembly 14 per unit time in the pressure-reduced state than in the pressure-increased state. Therefore, the electrode assembly 14 can be efficiently charged while efficiently removing gas from the electrode assembly 14.

[0078] It has been empirically determined that when the pressure is reduced, a phenomenon occurs in which charging cannot be performed uniformly across the entire electrode body 14. This phenomenon is believed to occur because when the pressure is reduced, gas that remains in the electrode body 14 without escaping expands, increasing the resistance of the electrode body 14. Therefore, in the pre-charging step, the pre-charging device 4 not only efficiently removes gas from the electrode body 14 by performing a second depressurization step, but also increases the charging efficiency of the electrode body 14 by performing a pressure increase step.

[0079] Furthermore, the pre-charging device 4 may improve the adhesion of the components of the secondary battery 1a in the first pressure reduction step in S24, and then start the voltage increase steps in S25 and S26 at approximately the same time as the start of pre-charging, thereby enabling the pre-charging device 4 to charge the entire electrode assembly 14 more uniformly.

[0080] Furthermore, it has been empirically determined that the amount of gas released per unit time from the electrode body 14 is greater when the pressure of the atmosphere around the electrode body 14 is intermittently reduced rather than continuously reduced. According to this empirical rule, by performing the second pressure reduction step and the pressure increase step as described above, gas can be efficiently released from the electrode body 14 during pre-charging. In other words, the electrode body 14 can be efficiently charged while gas is efficiently released from the electrode body 14.

[0081] Furthermore, during the period during which the electrode body 14 is pre-charged in the pre-charging step, the period of the increased pressure state due to the pressure increase step in S26 may be longer than the period of the reduced pressure state due to the second pressure decrease step in S27. By making the period of the increased pressure state longer than the period of the reduced pressure state, it becomes possible to charge the entire electrode body 14 more uniformly.

[0082] The duration of the pressure increase state in S26 may be set to, for example, 5 minutes or more and 20 minutes or less. The duration of the pressure reduction state in S27 may be set to, for example, 1 minute or more and 10 minutes or less. The durations of the pressure increase state and pressure reduction state may be set taking into consideration the amount of current, the duration of the pre-charging step, the number of times the pressure increase step in S26 and the second pressure reduction step in S27 are performed, etc., so as to enable efficient pre-charging and degassing.

[0083] Furthermore, in this embodiment, as described above, the first specified number of times is set to a plurality of times. That is, the pre-charging device 4 may alternately perform the pressure increase step S26 and the second pressure decrease step S27 a plurality of times during the pre-charging step. This allows the second pressure decrease step, whose main purpose is to remove gas from the electrode assembly 14, to be performed intermittently, thereby enabling uniform removal of gas from the electrode assembly 14. However, the first specified number of times may be set to a single time instead of a plurality of times. The first specified number of times may be set taking into consideration the amount of current, the first and second specified values, the value of mechanical pressure, the duration of the pressure increase step and the second pressure decrease step, and the like, so as to enable efficient pre-charging and degassing.

[0084] Furthermore, the pre-charging device 4 may terminate the pre-charging of the electrode body 14 during the second depressurization step in S27. Pre-charging of the electrode body 14 is likely to cause gas to be generated from the electrode body 14. Therefore, by terminating the pre-charging during the second depressurization step, the pre-charging device 4 can efficiently remove gas from the electrode body 14. However, the pre-charging device 4 may also terminate the pre-charging of the electrode body 14 simultaneously with the end of the second depressurization step. Furthermore, the pre-charging device 4 may terminate the pre-charging of the electrode body 14 during or simultaneously with the end of the pressure increase step in S30, which is performed after the pressure increase step and the second depressurization step have been performed a first specified number of times.

[0085] The duration of the preliminary charging step may be, for example, 50 minutes or more and 150 minutes or less. The charge rate may be, for example, 0.05 C or more and 0.3 C or less. The charge rate (C rate) is an index representing the magnitude of the current when charging or discharging a secondary battery. 1 C is defined as the current value when a fully charged state changes to a discharged state in 1 hour, or when a discharged state changes to a fully charged state. For example, 2 C means the current value when a fully charged state changes to a discharged state in 1 / 2 hour, or when a discharged state changes to a fully charged state. It is sufficient to charge the electrode body 14 with an amount of electricity equal to or greater than the irreversible capacity, and the charge rate at the end of charging may be, for example, 10% or more and 30% or less.

[0086] In this embodiment, after completing the preliminary charging of the electrode assembly 14 in S29, the preliminary charging device 4 may increase the pressure of the atmosphere around the electrode assembly 14 (pressure increase step: S30). Next, the preliminary charging device 4 may reduce the pressure of the atmosphere around the electrode assembly 14 (second pressure decrease step: S31). In this way, the preliminary charging device 4 may execute the pressure increase step and the second pressure decrease step after completing the preliminary charging. The pressure increase step and the second pressure decrease step allow gas to be released from the electrode assembly 14 even after the preliminary charging is completed. Furthermore, according to the above-mentioned rule of thumb, executing the pressure increase step together with the second pressure decrease step allows gas to be efficiently released from the electrode assembly 14 during the period after the preliminary charging is completed. Even if the preliminary charging of the electrode assembly 14 is completed during or simultaneously with the pressure increase step in S30, the preliminary charging device 4 may execute the pressure increase step in S30 and the second pressure decrease step in S31 after the preliminary charging is completed.

[0087] Furthermore, after the completion of preliminary charging, the period of the depressurized state due to the second depressurization step of S31 may be longer than the period of the increased pressure state due to the increased pressure step of S30. During preliminary charging, emphasis is placed on charging the electrode body 14, while after the completion of preliminary charging, emphasis is placed on removing from the electrode body 14 any gas generated in the electrode body 14 during charging to the electrode body 14. Therefore, by making the period of the second depressurized state longer than the period of the increased pressure state, gas can be efficiently removed from the electrode body 14 in the period after the completion of preliminary charging.

[0088] The duration of the pressurized state in S30 may be, for example, 1 minute or more and 10 minutes or less. The duration of the depressurized state in S31 may be, for example, 5 minutes or more and 20 minutes or less. The lengths of the periods of the pressurized state and the depressurized state may be set in consideration of the number of times the pressurization step in S30 and the second depressurization step in S31 are performed, so as to enable efficient degassing.

[0089] In this embodiment, as described above, the pre-charging device 4 performs the voltage increase step and the second pressure reduction step at least once each during the pre-charging step (S25 to S29) and during the post-pre-charging step (S30 to S34). If one cycle is defined as a cycle consisting of one voltage increase step and one second pressure reduction step, the time required for one cycle may be longer during the post-pre-charging step (S30 and S31) than during the pre-charging step (S26 and S27). The primary objectives of performing the voltage increase step and the second pressure reduction step during the pre-charging step are to efficiently charge the electrode assembly 14 uniformly and to efficiently vent gas from the electrode assembly 14. On the other hand, the primary objectives of performing the voltage increase step and the second pressure reduction step during the post-pre-charging step are to efficiently vent gas from the electrode assembly 14. Setting the time required for one cycle as described above facilitates achieving the primary objective.

[0090] Next, the pre-charging device 4 determines whether the voltage increase step of S30 and the second pressure reduction step of S31 have been performed a second specified number of times (S32). In this embodiment, the second specified number of times may be set to a plurality of times. For example, the second specified number of times may be set so that the voltage increase step and the second pressure reduction step are each performed 2 to 10 times. That is, the pre-charging device 4 may perform the voltage increase step of S30 and the second pressure reduction step of S31 alternately and multiple times even after the end of pre-charging. However, the second specified number of times may be set to one time instead of multiple times. The second specified number of times may also be set taking into consideration the amount of current, the first and second specified values, the value of mechanical pressure, the duration of the voltage increase step and the second pressure reduction step, and the like, so as to enable efficient pre-charging and degassing.

[0091] If the pre-charging device 4 determines that the pressure increase step of S30 and the second pressure reduction step of S31 have been performed a second specified number of times (YES in S32), it may place the atmosphere around the electrode assembly 14 in a pressure increase state (S33). Next, the pre-charging device 4 stops pressurizing the secondary battery 1a (S34). The process of S34 may be performed prior to the process of S33, or the processes of S33 and S34 may be performed in parallel. On the other hand, if the pre-charging device 4 determines that the pressure increase step of S30 and the second pressure reduction step of S31 have not been performed the second specified number of times (NO in S32), it performs the process of S30 again.

[0092] As described above, the pre-charging device 4 starts applying mechanical pressure to the electrode body 14 in S23 and ends applying mechanical pressure to the electrode body 14 in S34. That is, in this embodiment, the pre-charging device 4 may continuously perform the pressurizing step of applying mechanical pressure to the electrode body 14 once during at least the pre-charging step and the period after the pre-charging step. charging During the process, the second depressurization process (depressurization process) of S27 is carried out at least once, and the backup charging In the period after the step, the second depressurization step (depressurization step) of S31 may be carried out at least once.

[0093] By performing the pressurizing step and the second depressurizing step during preliminary charging, gas generated during preliminary charging can be released from the electrode body 14. Furthermore, by performing the pressurizing step and the second depressurizing step in the period after preliminary charging is completed, gas remaining in or generated in the electrode body 14 can be released from the electrode body 14 in the period after preliminary charging is completed. Therefore, more gas generated from the electrode body 14 can be released from the electrode body 14.

[0094] Furthermore, if the pre-charging device 4 continuously performs the pressurization step once, the electrode assembly 14 will be continuously pressurized by mechanical pressure from the time of pre-charging through the time after pre-charging ends. This allows gas to be efficiently removed from the electrode assembly 14. Furthermore, if the pre-charging device 4 performs the second depressurization step at least once each during pre-charging and after pre-charging ends, the second depressurization step will be performed intermittently. According to the above-mentioned rule of thumb, performing the second depressurization step intermittently allows gas to be efficiently removed from the electrode assembly 14.

[0095] However, the backup charging device 4 is charging The pressurizing step may be performed multiple times during the pre-charging step and during the period after the pre-charging step. For example, the pre-charging device 4 may temporarily stop applying mechanical pressure to the electrode assembly 14 when pre-charging ends in S29. Thereafter, the pre-charging device 4 may again apply mechanical pressure to the electrode assembly 14 when performing the pressure increasing step in S30.

[0096] The backup charging device 4 is also charging The second pressure reduction step may be continuously performed once during the pre-charging step and the period after the pre-charging step. For example, the pre-charging device 4 may continuously perform the second pressure reduction step of S27 until the pressure increase step of S33 is performed. In this case, the pre-charging device 4 does not need to perform S28 and S30 to S32.

[0097] Furthermore, the pre-charging device 4 may continue to execute the first pressure reduction step (pressure reduction step) of S24 until the pressure increase step of S33 is executed. In this case, the pre-charging device 4 does not need to execute S26 to S28 and S30 to S32. Furthermore, the pre-charging device 4 may execute the first pressure reduction step of S24 at the start of pre-charging of S25 or after the start of pre-charging.

[0098] As described above, the method for manufacturing a secondary battery 1 according to the present disclosure allows for efficient pre-charging and efficient degassing of the electrode assembly 14. This reduces the possibility of producing defective secondary batteries 1. This saves energy and resources that would otherwise be consumed in manufacturing defective secondary batteries 1, thereby contributing to the achievement of the Sustainable Development Goals (SDGs).

[0099] [Additional Notes] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0100] For example, the pre-charging device 4 may start pre-charging the electrode body 14 before (e.g., immediately before) the start of the first pressure reduction step or simultaneously with the first pressure reduction step. However, as described above, by performing pre-charging of the electrode body 14 during or after the first pressure reduction step, gas can be removed from the electrode body 14 and pre-charging of the electrode body 14 can be performed in a state in which the adhesion between the components of the secondary battery 1a is improved. [Explanation of symbols]

[0101] 1 Secondary battery 4. Backup charging device 5 spacers 10 unit cells 11 Positive electrode 12 Negative electrode 13 Separator 14 Electrode body 21, 22 Connection terminals 41 Pressure section 42 Storage section 43 Pedestal 44 trays

Claims

1. a pre-charging step of pre-charging at least one electrode assembly including a positive electrode material, a negative electrode material, and an electrolyte; one or more pressurizing steps in which the electrode assembly is pressurized by mechanical pressure during the pre-charging step and a subsequent step; one or more decompression steps in which the atmosphere of the electrode body is decompressed during the pre-charging step and a subsequent step; Including, The pressure reducing step is performed at least once during each of the period of the preliminary charging step and the period thereafter. A method for manufacturing a secondary battery.

2. the pressurizing step is continuously performed once during the preliminary charging step and the subsequent period; The method for manufacturing the secondary battery according to claim 1 .

3. During the pre-charging step, one or more pressure increasing steps are included in which the atmosphere of the electrode body is increased in pressure. The method for manufacturing the secondary battery according to claim 1 or 2.

4. In a period after the preliminary charging step, one or more pressure increasing steps are included in which the atmosphere of the electrode body is increased in pressure. A method for manufacturing the secondary battery according to claim 1 .

5. A pre-charging step of pre-charging at least one electrode body including a positive electrode material, a negative electrode material, and an electrolyte; one or more pressurizing steps in which the electrode assembly is pressurized by mechanical pressure during the pre-charging step and a subsequent step; one or more decompression steps in which the atmosphere of the electrode body is decompressed during the pre-charging step and a subsequent step; Including, In each of the above steps, a plurality of electrode bodies each having two main surfaces, i.e., a front surface and a rear surface, are used as the electrode body, In the pressurizing step, the plurality of electrode bodies are arranged side by side such that at least one of the two main surfaces faces a main surface of another electrode body, and mechanical pressure is applied from at least one side of the two outermost electrode bodies to place each of the plurality of electrode bodies in a pressurized state; In the pressurizing step, a plurality of trays each accommodating at least two of the plurality of electrode assemblies are arranged along a pressurizing direction, and each of the plurality of electrode assemblies is placed in a pressurized state with a spacer disposed between two adjacent trays. A method for manufacturing a secondary battery.

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