Battery manufacturing method

Abstract

To reduce the time required for the liquid injection process. [Solution] In the electrolyte injection process S20, with the battery assembly placed with the injection port facing upwards, a first process S21 is performed to inject electrolyte into the case to a position higher than a reference height set to be higher than the upper end of the electrode body inside the case; a second process S22 is performed to depressurize the case by reducing the pressure inside the case, thereby maintaining the liquid level of the electrolyte injected in the first process S21 at a position higher than the reference height; and a third process S23 is performed to release the inside of the case after the pressure inside the case has been reduced to a predetermined pressure. These steps are repeated, and a predetermined amount of electrolyte is injected in multiple batches.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a battery.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2022-90917 discloses a method for manufacturing a battery, which includes a battery case having a liquid injection hole, an electrode body housed in the battery case, and an electrolytic solution housed in the battery case. The electrode body includes an electrode facing portion where the positive electrode active material layer of the positive electrode plate and the negative electrode active material layer of the negative electrode plate face each other. This method for manufacturing a battery includes a liquid injection step of injecting an electrolytic solution into the battery case through the liquid injection hole. The liquid injection step includes a first liquid injection step and a second liquid injection step. In the first liquid injection step, with the air pressure in the battery case set to a first air pressure P1 lower than the atmospheric pressure, an electrolytic solution with a first liquid injection volume V1 is injected. The first liquid injection volume V1 is an amount such that the liquid level height H of the injected electrolytic solution is within an intermediate liquid level range (Ha ≦ H < Hb), where Ha is the first reference height at which the entire electrode facing portion of the electrode body is immersed in the electrolytic solution and Hb is the second reference height at which the electrolytic solution adheres to the liquid injection hole. In the second liquid injection step, while increasing the air pressure in the battery case to a second air pressure P2 (P2 > P1) higher than the first air pressure P1, the remaining second liquid injection volume V2 (V2 = V - V1) of the electrolytic solution is injected while maintaining the liquid level height H of the electrolytic solution within the intermediate liquid level range.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the inventor of the present invention wants to shorten the time required for the liquid injection step.

Means for Solving the Problems

[0005] The battery manufacturing method disclosed herein includes the steps of preparing a battery assembly in which electrode bodies are housed in a rectangular case having a liquid injection port, and an electrolyte injection step in which electrolyte is injected into the case through the liquid injection port with the battery assembly placed with the liquid injection port facing upward. The electrolyte injection step includes a first process in which, with the battery assembly placed with the liquid injection port facing upward, electrolyte is injected into the case to a position higher than a reference height set to be above the upper end of the electrode bodies inside the case; a second process in which the case is indented by reducing the pressure inside the case to maintain the liquid level of the electrolyte injected in the first process at a position above the reference height; and a third process in which the inside of the case is released after the pressure inside the case has been reduced to a predetermined pressure. These steps are repeated, and a predetermined amount of electrolyte is injected in multiple batches. This manufacturing method makes it possible to shorten the time required for the electrolyte injection step. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a schematic perspective view of a battery. [Figure 2] Figure 2 is a cross-sectional view of AA in Figure 1. [Figure 3] Figure 3 is a schematic diagram of the electrode body. [Figure 4] Figure 4 is a flowchart showing an example of a battery manufacturing method. [Figure 5] Figure 5 is a schematic diagram showing an example of a liquid injection device. [Figure 6] Figure 6 is a graph showing the time-dependent changes in the internal pressure of the case and the electrolyte level during the liquid injection process. [Figure 7] Figure 7 is a side cross-sectional view of the case during the second process. [Figure 8] Figure 8 is a graph showing the time-dependent changes in the internal pressure and electrolyte level of the case during the liquid injection process for other configurations. [Figure 9] Figure 9 is a flowchart showing an example of a battery manufacturing method for another form. [Figure 10] Figure 10 is a flowchart showing an example of a battery manufacturing method for other forms. [Modes for carrying out the invention]

[0007] Hereinafter, an embodiment of the technology disclosed herein will be described with reference to the drawings. The embodiment described herein is, of course, not intended to particularly limit the present invention. Each drawing is schematic and does not necessarily reflect the actual object. Furthermore, components and parts that perform the same function are appropriately denoted by the same reference numeral, and redundant explanations are omitted where appropriate. In the drawings, the reference numerals X, Y, and Z represent the depth, width, and height directions, respectively. The Y direction is perpendicular to the X direction. The Z direction is perpendicular to both the X and Y directions. However, these are merely directions for the sake of explanation and do not in any way limit the installation configuration of the battery 10. The notation "A~B" indicating a numerical range means "A or greater and B or less" unless otherwise specified.

[0008] Figure 1 is a schematic perspective view of the battery 10. Figure 2 is a cross-sectional view of AA in Figure 1. In Figure 2, the electrode body 20 is shown in a partially broken section. In this specification, a lithium-ion secondary battery is described as the battery 10. However, the type of battery 10 is not limited to a lithium-ion secondary battery, and may be a sodium-ion secondary battery, a magnesium-ion secondary battery, a nickel-metal hydride secondary battery, etc. The battery 10 comprises a rectangular case 11, an electrode body 20, and an electrolyte 30.

[0009] The case 11 comprises a case body 12 and a sealing plate 14. The case body 12 is formed in a substantially rectangular parallelepiped shape. The case body 12 has a bottom wall 12a, a pair of narrow walls 12b, and a pair of wide walls 12c. The bottom wall 12a extends in the X and Y directions. The pair of narrow walls 12b are opposite each other in the Y direction. The pair of narrow walls 12b extend upward from both ends of the bottom wall 12a in the Y direction. The pair of wide walls 12c are opposite each other in the X direction. The pair of wide walls 12c extend upward from both ends of the bottom wall 12a in the X direction. The pair of narrow walls 12b and the pair of wide walls 12c constitute the side walls of the case body 12. The top of the case body 12 is open. The case body 12 is made of, for example, aluminum or an aluminum alloy mainly composed of aluminum, from the viewpoint of reducing weight and ensuring the required rigidity.

[0010] The sealing plate 14 is fitted into the opening of the case body 12. The sealing plate 14 closes the opening of the case body 12. The sealing plate 14 is joined to the case body 12 by means of welding, for example. By joining the sealing plate 14 to the case body 12, the inside of the case 11 is sealed. The sealing plate 14 constitutes the top surface of the case 11. The sealing plate 14 may be made of the same material as the case body 12. The sealing plate 14 may be made of aluminum or an aluminum alloy mainly composed of aluminum, for example, from the viewpoint of weight reduction and ensuring the required rigidity. The sealing plate 14 is provided with a gas discharge valve 15, a positive electrode terminal 16, a negative electrode terminal 17, and a liquid injection port 18.

[0011] The gas discharge valve 15 is located in the center of the sealing plate 14 in the Y direction. The gas discharge valve 15 ruptures when the internal pressure of the case 11 rises above a predetermined value. As a result, when the internal pressure of the case 11 exceeds a predetermined value, the gas inside the case 11 is discharged to the outside of the case 11.

[0012] The positive terminal 16 and the negative terminal 17 are provided in pairs at both ends of the sealing plate 14 in the Y direction. The positive terminal 16 comprises an external terminal 16a and an internal terminal 16b. The external terminal 16a is attached to the upper side of the sealing plate 14 via a gasket 19a. The internal terminal 16b is attached to the lower side of the sealing plate 14 via an insulator 19b. The internal terminal 16b extends in the vertical direction. The internal terminal 16b is electrically connected to the electrode body 20 inside the case 11.

[0013] The negative terminal 17 comprises an external terminal 17a and an internal terminal 17b. The external terminal 17a is attached to the upper side of the sealing plate 14 via a gasket 19a. The internal terminal 17b is attached to the lower side of the sealing plate 14 via an insulator 19b. The internal terminal 17b extends in the vertical direction. The internal terminal 17b is electrically connected to the electrode body 20 inside the case 11.

[0014] The liquid injection port 18 is an opening for injecting the electrolyte 30 into the case 11 after the sealing plate 14 has been assembled to the case body 12. The liquid injection port 18 is formed as a through hole that penetrates the sealing plate 14 in the Z direction. The liquid injection port 18 is located between the gas discharge valve 15 and the positive electrode terminal 16 in the Y direction. Note that the arrangement of the liquid injection port 18 is not limited to the configuration shown in Figure 1. For example, the liquid injection port 18 may be located between the gas discharge valve 15 and the negative electrode terminal 17 in the Y direction.

[0015] FIG. 3 is a schematic view of the electrode body 20. The electrode body 20 of the present embodiment is a so-called wound electrode body. The electrode body 20 includes a positive electrode sheet 21, a negative electrode sheet 22, and sheet-like separators 24 and 25. The electrode body 20 is configured by being wound in the longitudinal direction around a winding axis WL in a flat shape with the positive electrode sheet 21, the separators 24 and 25, and the negative electrode sheet 22 being overlapped. As shown in FIG. 2, the electrode body 20 is housed inside the case 11. In the form shown in FIG. 2, the electrode body 20 is arranged inside the case 11 so that the winding axis WL is substantially parallel to the Y direction. Note that the electrode body 20 may be a so-called laminated electrode body in which a plurality of rectangular positive electrodes and a plurality of rectangular negative electrodes are stacked in an insulated state.

[0016] As shown in FIG. 3, the positive electrode sheet 21 includes a foil-like positive electrode current collector 21a and positive electrode active material layers 21b formed along the longitudinal direction on both surfaces of the positive electrode current collector 21a. The positive electrode active material layer 21b contains various materials such as a positive electrode active material, a binder, and a conductive material. Regarding the materials included in the positive electrode current collector 21a and the positive electrode active material layer 21b that constitute the positive electrode sheet 21, those that can be used in conventional general lithium-ion secondary batteries can be used without particular limitation. Further, on one side edge portion of the electrode body 20 in the Y direction of the battery 10, an unformed portion 21a1 where the positive electrode active material layer 21b is not formed and the positive electrode current collector 21a is exposed is provided. A plurality of positive electrode tabs 21t are intermittently provided at predetermined positions along the longitudinal direction of the positive electrode sheet 21 in the unformed portion 21a1. The plurality of positive electrode tabs 21t each project toward the Y direction of the positive electrode sheet 21. In the form shown in FIG. 3, the plurality of positive electrode tabs 21t are arranged so that their positions align in the wound state. As shown in FIG. 2, the positive electrode tab 21t is electrically connected to the internal terminal 16b of the positive electrode terminal 16.

[0017] As shown in Figure 3, the negative electrode sheet 22 comprises a foil-shaped negative electrode current collector 22a and a negative electrode active material layer 22b formed along the longitudinal direction on one or both sides of the negative electrode current collector 22a. The negative electrode active material layer 22b contains various materials such as negative electrode active material and binder. The materials contained in the negative electrode current collector 22a and the negative electrode active material layer 22b that constitute the negative electrode sheet 22 can be those that can be used in conventional lithium-ion secondary batteries without any particular limitations. In addition, the other side edge of the electrode body 20 in the Y direction of the battery 10 is provided with an unformed portion 22a1 where the negative electrode active material layer 22b is not formed and the negative electrode current collector 22a is exposed. Multiple negative electrode tabs 22t are intermittently provided in the unformed portion 22a1 at predetermined positions along the longitudinal direction of the negative electrode sheet 22. Each of the multiple negative electrode tabs 22t protrudes toward the Y direction of the negative electrode sheet 22. In the configuration shown in Figure 3, multiple negative electrode tabs 22t are arranged so that their positions are aligned when the cable is wound. The negative electrode tabs 22t are electrically connected to the internal terminals 17b of the negative electrode terminal 17.

[0018] Separators 24 and 25 are interposed between the positive electrode sheet 21 and the negative electrode sheet 22 to prevent direct contact between them. Although not shown in the figures, separators 24 and 25 have multiple fine pores. These fine pores are configured to allow charge carriers to move between the positive electrode sheet 21 and the negative electrode sheet 22. Charge carriers are free particles that carry electric charge. In the case of lithium-ion secondary batteries, the charge carriers are lithium ions. Separators 24 and 25 are made of resin sheets or the like with the required heat resistance. As separators 24 and 25, any material that can be used in conventional lithium-ion secondary batteries can be used without any particular restrictions.

[0019] As shown in FIG. 2, the electrolytic solution 30 is housed in the case 11 together with the electrode body 20. The electrolytic solution 30 is a non-aqueous electrolytic solution containing a non-aqueous solvent and an electrolyte salt with a predetermined concentration. Various conventionally used substances can be used for the non-aqueous solvent and the electrolyte salt. For example, as the non-aqueous solvent, a mixed solvent obtained by mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) may be used. For example, as the electrolyte salt, lithium hexafluorophosphate (LiPF6) may be used. Further, an additive may be added to the electrolytic solution 30 as necessary.

[0020] FIG. 4 is a flowchart showing an example of a method for manufacturing the battery 10 according to an embodiment. The method for manufacturing the battery 10 includes a preparation step S10, a liquid injection step S20, and a sealing step S30.

[0021] In the preparation step S10, a battery assembly in which the electrode body 20 is housed in a rectangular case 11 having a liquid injection port 18 is prepared. In this specification, the "battery assembly" refers to a battery assembled up to the stage before the electrolytic solution 30 is injected into the case 11. In the preparation step S10, the battery assembly may be manufactured according to a conventionally known procedure, or a previously manufactured battery assembly may be prepared. The size of the electrode body 20 in the battery assembly prepared in the preparation step S10 is not particularly limited. For example, the width of the electrode body 20 may be 20 cm or more. By using such a relatively large electrode body 20, a high-capacity battery 10 can be obtained.

[0022] The liquid injection step S20 is a step of injecting the electrolytic solution 30 into the battery assembly prepared in the preparation step S10. In the liquid injection step S20, the electrolytic solution 30 is injected into the case 11 from the liquid injection port 18 with the battery assembly placed with the liquid injection port 18 facing upward. In the liquid injection step S20, the electrolytic solution 30 is injected into the case 11 using the liquid injection device 50. The liquid injection step S20 includes a first process S21, a second process S22, and a third process S23.

[0023] Figure 5 is a schematic diagram showing an example of a liquid injection device 50. The liquid injection device 50 includes a containment chamber 51, an electrolyte tank 54, an injection nozzle 55, a vacuum pump 56, a vacuum regulator 57, pressure sensors 58 and 59, a three-way valve 60, vacuum valves 61 and 62, open valves 63 and 64, and piping 70 to 77. The liquid injection device 50 may be operated manually or automatically. If the liquid injection device 50 is operated automatically, it may be equipped with a control device that controls the operation of the vacuum pump 56, vacuum regulator 57, three-way valve 60, vacuum valves 61 and 62, and open valves 63 and 64.

[0024] Piping 70 connects the electrolyte tank 54 to the three-way valve 60. Piping 71 connects the three-way valve 60 to the injection nozzle 55. Piping 71 is provided to pass through the containment chamber 51. Piping 72 is connected to the three-way valve 60. Piping 72 is provided to pass through the containment chamber 51. Piping 73 is connected to the containment chamber 51. Piping 73 is provided to pass through the containment chamber 51. Piping 74 connects the electrolyte tank 54 to the vacuum regulator 57. Piping 75 is provided to branch off from piping 74. Piping 76 connects the vacuum pump 56 to the vacuum regulator 57. Furthermore, piping 76 is connected to piping 73. Piping 77 is connected to the containment chamber 51. Piping 77 is provided to pass through the containment chamber 51.

[0025] The storage chamber 51 is configured to accommodate a battery assembly. The storage chamber 51 comprises a chamber body 52 and a lid 53. The chamber body 52 is formed in a rectangular parallelepiped shape with an open top. The lid 53 is configured to open and close the opening of the chamber body 52. ​​When the chamber body 52 is closed by the lid 53, the inside of the storage chamber 51 is sealed.

[0026] The electrolyte tank 54 stores electrolyte 30. The electrolyte tank 54 is connected to the injection nozzle 55 via pipes 70 and 71. The injection nozzle 55 is configured to be inserted through the injection port 18 of the battery 10. The shape of the injection nozzle 55 is not particularly limited. With the injection nozzle 55 inserted through the injection port 18, the electrolyte 30 flows from the electrolyte tank 54 through pipes 70 and 71 to the injection nozzle 55, thereby injecting the electrolyte 30 into the inside of the case 11.

[0027] The vacuum pump 56 is connected to the inside of the containment chamber 51 via pipes 73 and 76. By operating the vacuum pump 56, air inside the containment chamber 51 is drawn into the vacuum pump 56 through pipes 73 and 76. This reduces the pressure inside the containment chamber 51. The vacuum pump 56 is also connected to the inside of the electrolyte tank 54 via pipes 74 and 76. By operating the vacuum pump 56, air inside the electrolyte tank 54 is drawn into the vacuum pump 56 through pipes 74 and 76. This reduces the pressure inside the electrolyte tank 54.

[0028] The vacuum regulator 57 is located between the electrolyte tank 54 and the vacuum pump 56. The vacuum regulator 57 is a device that adjusts the amount of air drawn into the vacuum pump 56 when the vacuum pump 56 is operated, thereby adjusting the pressure inside the electrolyte tank 54.

[0029] Pressure sensor 58 is attached to the containment chamber 51. Pressure sensor 58 is a sensor that measures the pressure inside the containment chamber 51. Pressure sensor 59 is attached to the piping 74. Pressure sensor 59 is a sensor that measures the pressure inside the electrolyte tank 54.

[0030] The three-way valve 60 is connected to the piping 70-72. When the three-way valve 60 is operated, the path of the fluid flowing through the piping 70-72 is changed. The three-way valve 60 can change the fluid flow path between a path through piping 70 and 71 and a path through piping 71 and 72. If the path through piping 70 and 71 is selected, the electrolyte 30 can be injected from the electrolyte tank 54 into the case 11. If the path through piping 71 and 72 is selected, air can be flowed between the case 11 and the containment chamber 51.

[0031] Vacuum valve 61 is located in piping 73. Vacuum valve 61 is located between the containment chamber 51 and the vacuum pump 56. Vacuum valve 62 is located in piping 74. Vacuum valve 62 is located between the electrolyte tank 54 and the vacuum pump 56.

[0032] The release valve 63 is located in the piping 77. When the release valve 63 is opened, the inside of the containment chamber 51 is opened to the atmosphere. The release valve 64 is located in the piping 75. When the release valve 64 is opened while the vacuum valve 62 is closed, the inside of the electrolyte tank 54 is opened to the atmosphere.

[0033] Figure 6 is a graph showing the time change in the internal pressure of case 11 and the liquid level of the electrolyte 30 during the liquid injection process S20. In the graph of Figure 6, the solid line represents the time change in the internal pressure of case 11. In the graph of Figure 6, the dashed line represents the time change in the liquid level of the electrolyte 30 inside case 11. In the graph of Figure 6, the symbol P0 represents atmospheric pressure. The symbol P1 represents reference pressure. Reference pressure P1 is a predetermined pressure and is lower than atmospheric pressure P0. The symbol Hb represents reference height. Reference height Hb is a predetermined height and is set to a height above the upper end of the electrode body 20. In this embodiment, the reference height Hb is set to a height equal to the upper end of the electrode body 20. In the graph of Figure 6, the elapsed time is the elapsed time from the start of the liquid injection process S20. Note that the graph in Figure 6 shows the internal pressure and electrolyte level of Case 11 from the start of the liquid injection process S20 to the second first treatment S21. In the graph in Figure 6, the internal pressure and electrolyte level of Case 11 from the second second treatment S22 onwards are not shown.

[0034] In the first process S21, the battery assembly is placed inside the housing chamber 51 with the liquid injection port 18 facing upwards. Next, the three-way valve 60 is operated so that the fluid can flow through the pipes 70 and 71. As a result, with the battery assembly placed with the liquid injection port 18 facing upwards, the electrolyte 30 is injected into the case 11 from the liquid injection port 18. In the first process S21, the electrolyte 30 is injected so that the liquid level of the electrolyte 30 inside the case 11 is higher than a predetermined reference height Hb.

[0035] When the electrolyte 30 is poured into the case 11, the electrolyte 30 impregnates the electrode body 20. As the electrolyte 30 impregnates the electrode body 20, the liquid level of the electrolyte 30 in the case 11 decreases. In the configuration shown in Figure 6, when the electrolyte 30 has impregnated the electrode body 20 and the liquid level of the electrolyte 30 reaches the reference height Hb, the second process S22 is performed. The liquid level of the electrolyte 30 may be measured using a liquid level sensor. The liquid level sensor may, for example, measure the liquid level by irradiating the case 11 with X-rays. Alternatively, the liquid level of the electrolyte 30 may be measured based on the time elapsed since the electrolyte 30 was poured into the case 11. When the liquid level is measured based on the time elapsed since the electrolyte 30 was poured into the case 11, it is preferable to know in advance, through experiments or other means, the relationship between the time elapsed since the electrolyte 30 was poured into the case 11 and the liquid level.

[0036] Figure 7 is a schematic side cross-sectional view of case 11 during the second process S22. In the second process S22, with vacuum valve 61 closed, vacuum valve 62 is opened to operate the vacuum pump 56 and reduce the pressure in the electrolyte tank 54. Furthermore, in the second process S22, the three-way valve 60 is operated to allow fluid to flow through pipes 70 and 71. As a result, air flows from inside case 11 to the electrolyte tank 54 via pipes 70 and 71, thereby reducing the pressure inside case 11 simultaneously with the electrolyte tank 54. When the pressure inside case 11 is reduced, a pressure difference is created between the internal pressure of case 11 and the external pressure of case 11. Due to this pressure difference, case 11 dents, as shown in Figure 7. When case 11 dents, the liquid level of the electrolyte 30 injected inside case 11 rises.

[0037] Meanwhile, the electrolyte 30 poured into the case 11 impregnates the electrode body 20. As the electrolyte 30 impregnates the electrode body 20, the liquid level of the electrolyte 30 decreases. In the second process S22, the inside of the case 11 is depressurized in accordance with the decrease in the liquid level of the electrolyte 30 due to impregnation of the electrode body 20, thereby raising the liquid level of the electrolyte 30 and maintaining the liquid level of the electrolyte 30 at or above the reference height Hb. In other words, in the second process S22, the inside of the case 11 is depressurized to create a depression in the case 11, and the liquid level of the electrolyte 30 poured in in the first process S21 is maintained at or above the reference height Hb.

[0038] In the configuration shown in Figure 6, the pressure inside case 11 is intermittently reduced to maintain the electrolyte level 30 at or above the reference height Hb. In the second process S22, the internal pressure of case 11 is reduced to prevent the electrolyte 30 from overflowing. In the configuration shown in Figure 6, the internal pressure of case 11 is reduced in four stages. In the configuration shown in Figure 6, the pressure reduction is performed when the electrolyte level 30 reaches the reference height Hb. However, the internal pressure of case 11 may be reduced in two or three stages, or in five or more stages. The number of stages in which the pressure reduction is performed can be appropriately changed depending on the dimensions of case 11 and the amount of pressure reduction in each stage. Also, the amount of pressure reduction in each stage may be equal or different from each other.

[0039] The second process S22 is performed until the internal pressure of case 11 falls below a predetermined reference pressure P1. When the internal pressure of case 11 falls below the reference pressure P1 and the liquid level of the electrolyte 30 falls below a reference height Hb, the third process S23 is performed. While the second process S22 is being performed, the internal pressure of the electrolyte tank 54 and case 11 is measured by the pressure sensor 59. Therefore, in this embodiment, the decision to proceed to the third process S23 is made based on whether the measurement result of the pressure sensor 59 is below the reference pressure P1. In this embodiment, the predetermined reference pressure P1 is approximately -0.09 MPa to -0.05 MPa in gauge pressure. However, the predetermined reference pressure P1 is not limited to this and may be approximately -0.05 MPa to -0.02 MPa in gauge pressure.

[0040] In the third process S23, the inside of case 11 is released. In this embodiment, the inside of case 11 is released to the atmosphere by closing the vacuum valve 62 and opening the release valve 64. As a result, the internal pressure of case 11 becomes equal to the atmospheric pressure P0, and the indentation in case 11 is eliminated. As the indentation in case 11 is eliminated, the liquid level of the electrolyte 30 decreases.

[0041] The processes from the first process S21 to the third process S23 are repeated until a predetermined amount of electrolyte 30 has been injected. If the total amount of electrolyte 30 injected into case 11 is less than the predetermined amount (S26: No), the processes from the first process S21 to the third process S23 are repeated after the completion of the third process S23. If the total amount of electrolyte 30 injected into case 11 is equal to or greater than the predetermined amount (S26: Yes), the injection process S20 is completed when the third process S23 is finished. Therefore, in the injection process S20, the processes from the first process S21 to the third process S23 are repeated, and a predetermined amount of electrolyte 30 is injected in multiple installments.

[0042] Once the liquid injection process S20 is completed, the sealing process S30 is performed. In the sealing process S30, the liquid injection port 18 is sealed. The method for sealing the liquid injection port 18 is not particularly limited, and various conventionally known methods can be used. For example, the liquid injection port 18 may be sealed by attaching a metal stopper to the liquid injection port 18 and performing laser welding or the like.

[0043] As shown in Figure 4, the manufacturing method of the battery 10 includes a preparation step S10 and an electrolyte injection step S20. The electrolyte injection step S20 includes a first process S21, a second process S22, and a third process S23. In the first process S21, with the battery assembly placed with the injection port 18 facing upwards, electrolyte 30 is injected into the case 11 to a position higher than a reference height Hb set to be above the upper end of the electrode body 20. In the second process S22, the liquid level of the electrolyte 30 injected in the first process S21 is maintained at a position above the reference height Hb while the case 11 is indented by reducing the internal pressure of the case 11. After the internal pressure of the case 11 has been reduced to a predetermined reference pressure P1, the third process S23 is performed. In the third process S23, the inside of the case 11 is released. According to this manufacturing method, the air inside the electrode body 20 is discharged by reducing the pressure inside the case 11 and indenting the case 11. Therefore, the electrolyte 30 easily impregnates the electrode body 20. This reduces the time required for the electrolyte injection process S20.

[0044] In this embodiment, as shown in Figure 6, in the second process S22, the internal pressure of the case 11 is intermittently reduced to maintain the liquid level of the electrolyte 30 at or above the reference height Hb. This allows the liquid level of the electrolyte 30 to be maintained at or above the reference height Hb using a relatively simple method.

[0045] According to this embodiment, the second process S22 is performed when the electrolyte 30 has impregnated the electrode body 20 and the liquid level of the electrolyte 30 reaches the reference height Hb. As a result, the entire electrode body 20 is immersed in the electrolyte 30 from the end of the first process S21 until the end of the second process S22. Therefore, the time required for the electrolyte injection process S20 can be further reduced.

[0046] According to this embodiment, in the third process S23, the inside of the case 11 is released to the atmosphere. In the third process S23, there is no need to perform precise pressure control.

[0047] Incidentally, if the internal pressure of case 11 is significantly reduced, there is a risk that case 11 may undergo plastic deformation or the electrolyte 30 may volatilize. However, according to this embodiment, the predetermined pressure is -0.09 MPa to -0.05 MPa in gauge pressure. This prevents case 11 from undergoing plastic deformation and the electrolyte 30 from volatilizing.

[0048] Furthermore, with relatively large electrode bodies 20 having a width of 20 cm or more, it takes time for the electrolyte 30 to completely impregnate the electrode body 20. However, by using the manufacturing method of this embodiment, the time required for the electrolyte injection process S20 can be shortened. Therefore, the manufacturing method of this embodiment can be used particularly effectively when manufacturing a relatively large battery 10 having a relatively large electrode body 20 having a width of 20 cm or more.

[0049] The above describes one embodiment of the proposed technology. However, the above-described embodiment is merely an example, and the technology can be implemented in other ways.

[0050] Figure 8 is a graph showing the time change of the internal pressure of case 11 and the liquid level of the electrolyte 30 during the liquid injection process S20 in another configuration. As shown in Figure 8, in the second process S22, the liquid level of the electrolyte 30 may be maintained at a position above the reference height Hb by continuously reducing the pressure inside case 11. By performing the second process S22 in this way, the liquid level of the electrolyte 30 can be precisely controlled.

[0051] Figure 9 is a flowchart illustrating a method for manufacturing the battery 10 according to another embodiment. As shown in Figure 9, the liquid injection step S20 may include an initial depressurization process S24. The initial depressurization process S24 may be performed before the first process S21. In the initial depressurization process S24, the inside of the containment chamber 51, the inside of the case 11, and the inside of the electrolyte tank 54 may be depressurized. In the initial depressurization process S24, the three-way valve 60 may be operated to allow fluid to flow through the pipes 71 and 72, and the vacuum valve 61 may be opened to operate the vacuum pump 56. As a result, air inside the case 11 flows through the pipes 71 and 72 to the containment chamber 51, and air inside the containment chamber 51 is sucked into the vacuum pump 56. Therefore, the inside of the case 11 and the inside of the containment chamber 51 can be depressurized simultaneously. Alternatively, in the initial depressurization process S24, the vacuum pump 56 may be operated with the vacuum valve 62 open. As a result, the air inside the electrolyte tank 54 is drawn through the pipes 74 and 76 to the vacuum pump 56. Consequently, the pressure inside the electrolyte tank 54 is reduced. Performing the initial pressure reduction treatment S24 further promotes the removal of air from inside the electrode body 20, thereby further shortening the time required for the electrolyte injection process S20.

[0052] Figure 10 is a flowchart showing a method for manufacturing a battery 10 in another embodiment. As shown in Figure 10, the method for manufacturing a battery 10 may include an initial depressurization process S24 and an opening process S25. The initial depressurization process S24 in the embodiment shown in Figure 10 may be performed in the same manner as in the embodiment shown in Figure 9. In the opening process S25, the inside of the containment chamber 51, the inside of the case 11, and the inside of the electrolyte tank 54 may be opened to the atmosphere. In the opening process S25, the three-way valve 60 may be operated to allow fluid to flow through the pipes 71 and 72, and with the vacuum valve 61 closed, the opening valve 63 may be opened. This allows air to flow from the outside to the inside of the containment chamber 51, opening the inside of the containment chamber 51 to the atmosphere. Furthermore, the air inside the containment chamber 51 flows through the pipes 71 and 72 to the inside of the case 11, opening the inside of the case 11 to the atmosphere. In addition, in the opening process S25, the opening valve 64 may be opened with the vacuum valve 62 closed. As a result, air from outside the electrolyte tank 54 flows through pipes 74 and 75 into the electrolyte tank 54, and the inside of the electrolyte tank 54 is opened to the atmosphere.

[0053] In the opening process S25, the liquid surface of the electrolyte 30 is pushed from above by the air flowing from the containment chamber 51 into the inside of the case 11, which can promote the impregnation of the electrolyte 30 into the electrode body 20. Also, if the second process S22 is performed after the initial depressurization process S24 without performing the opening process S25, the second process S22 starts with the pressure inside the containment chamber 51 reduced from atmospheric pressure. Therefore, in the second process S22, when the case 11 is indented, it is necessary to reduce the absolute pressure inside the case 11 by a relatively large amount. However, in the configuration shown in Figure 10, the second process S22 can be started with the pressure inside the case 11 at atmospheric pressure. This eliminates the need to significantly reduce the absolute pressure inside the case 11 and prevents the electrolyte 30 from volatilizing.

[0054] The following describes test examples of the manufacturing method disclosed herein. However, the present invention is not intended to be limited to the following test examples.

[0055] In the test example, a battery assembly was prepared in which the electrode body was housed in a rectangular aluminum case. The dimensions of the case were 103 mm in height, 40 mm in depth, and 308 mm in width, with a bottom and side wall thickness of 0.8 mm. A wound electrode body with a height of 90 mm was prepared as the electrode body.

[0056] In the test example, the following electrolyte was prepared. The solvent of the electrolyte was a mixed solvent of EC, DMC, and EMC. The volume ratio of EC, DMC, and EMC was EC:DMC:EMC = 3:3:4. Lithium hexafluorophosphate was used as the electrolyte salt of the electrolyte. The concentration of lithium hexafluorophosphate was 1.15 mol / L.

[0057] In the test example, as the first treatment, electrolyte was poured into the case under atmospheric pressure so that the liquid level reached 100 mm. Then, the electrolyte was allowed to impregnate the electrode body until the liquid level reached 90 mm. Next, as the second treatment, the internal pressure of the case was reduced to maintain a liquid level of 90 mm or more, causing the case to dent. In the test example, the internal pressure of the case was reduced in 18 steps. In the test example, the amount of reduction per step was 0.005 MPa. That is, in the test example, the second treatment was performed until the internal pressure of the case reached a gauge pressure of -0.09 MPa. When the internal pressure of the case reached a gauge pressure of -0.09 MPa, the third treatment was performed. In the test example, as the third treatment, the inside of the case was opened to the atmosphere. In the test example, the above treatments from the first to the third were repeated four times so that the total amount of electrolyte poured was a predetermined amount. In the fourth first treatment, the electrolyte was injected until the liquid level reached approximately 96 mm, ensuring that the total amount of electrolyte injected was a predetermined amount.

[0058] In the comparative example, the same battery assembly as in the test example was prepared. In the comparative example, the same electrolyte as in the test example was prepared. In the comparative example, first, the electrolyte was poured into the case so that the liquid level reached 100 mm. Then, without reducing the pressure inside the case, the electrolyte was allowed to impregnate the electrodes until the liquid level reached 0 mm. When the liquid level reached 0 mm, the electrolyte was poured again. In the second pour, the total amount of electrolyte poured was predetermined.

[0059] As described above, the test example and comparative example were carried out, and the elapsed time from the start of the first treatment to the completion of impregnation was measured. In the test example and comparative example, impregnation was determined to be complete when the liquid level reached 0 mm after all of the predetermined amount of electrolyte had been poured into the case. The elapsed time to completion of impregnation in the test example was 18.5 hours. The elapsed time to completion of impregnation in the comparative example was 43 hours. From these results, it was found that the impregnation time could be shortened by using the method of the test example compared to the comparative example.

[0060] The technologies disclosed herein have been described in detail above. Unless otherwise specified, the embodiments and other details mentioned herein do not limit the present invention. Furthermore, the technologies disclosed herein can be modified in various ways, and each component and each process mentioned herein may be omitted or combined as appropriate, unless no particular problems arise. This specification also includes the disclosures described in the following sections.

[0061] Section 1: A step of preparing a battery assembly in which an electrode body is housed in a rectangular case having a liquid injection port, With the battery assembly placed with the liquid injection port facing upwards, the liquid injection step involves injecting the electrolyte into the case through the liquid injection port, Includes, In the aforementioned liquid injection step, With the battery assembly placed with the liquid injection port facing upwards, the first process involves pouring the electrolyte into the case to a position higher than a reference height set to be higher than the upper end of the electrode body, A second process in which the case is dented by reducing the pressure inside the case, thereby maintaining the liquid level of the electrolyte injected in the first process at a position above the reference height, A third process is performed to release the inside of the case after the pressure inside the case has been reduced to a predetermined pressure, A method for manufacturing a battery, wherein the process is repeated, and a predetermined amount of the electrolyte is injected in multiple portions.

[0062] Section 2: In the second process described above, The method for manufacturing a battery according to item 1, wherein the inside of the case is intermittently depressurized to maintain the liquid level of the electrolyte at a position equal to or greater than the reference height.

[0063] Section 3: In the second process described above, The method for manufacturing a battery according to item 1, wherein the inside of the case is continuously depressurized to maintain the liquid level of the electrolyte at a position equal to or greater than the reference height.

[0064] Section 4: A method for manufacturing a battery according to any one of items 1 to 3, wherein, after the first treatment, when the electrolyte has permeated the electrode body and the liquid level of the electrolyte has reached the reference height, the second treatment is performed.

[0065] Section 5: A method for manufacturing a battery according to any one of items 1 to 4, wherein in the third process, the inside of the case is opened to the atmosphere.

[0066] Item 6: A method for manufacturing a battery according to any one of items 1 to 5, wherein the predetermined pressure is -0.09 MPa to -0.05 MPa in gauge pressure.

[0067] Section 7: A method for manufacturing a battery according to any one of claims 1 to 6, wherein the width of the electrode body is 20 cm or more. [Explanation of symbols]

[0068] 10 batteries 11 cases 18 Inlet 20 Electrode body 30 Electrolyte S10 Preparation Process S20 Liquid injection process S21 First Processing S22 Second Processing S23 Third Processing

Claims

1. A step of preparing a battery assembly in which an electrode body is housed in a rectangular case having a liquid injection port, With the battery assembly placed with the liquid injection port facing upwards, the liquid injection step involves injecting the electrolyte into the case through the liquid injection port, Includes, In the aforementioned liquid injection step, With the battery assembly placed with the liquid injection port facing upwards, the first process involves pouring the electrolyte into the case to a position higher than a reference height set to be higher than the upper end of the electrode body, A second process in which the case is dented by reducing the pressure inside the case, thereby maintaining the liquid level of the electrolyte injected in the first process at a position above the reference height, A third process is performed to release the inside of the case after the pressure inside the case has been reduced to a predetermined pressure, A method for manufacturing a battery, wherein the process is repeated, and a predetermined amount of the electrolyte is injected in multiple portions.

2. In the second process described above, A method for manufacturing a battery according to claim 1, wherein the inside of the case is intermittently depressurized to maintain the liquid level of the electrolyte at a position equal to or greater than the reference height.

3. In the second process described above, A method for manufacturing a battery according to claim 1, wherein the inside of the case is continuously depressurized to maintain the liquid level of the electrolyte at a position equal to or greater than the reference height.

4. A method for manufacturing a battery according to claim 1, wherein, after the first treatment, when the electrolyte has permeated the electrode body and the liquid level of the electrolyte has reached the reference height, the second treatment is performed.

5. The method for manufacturing a battery according to claim 1, wherein in the third process, the inside of the case is opened to the atmosphere.

6. The method for manufacturing a battery according to claim 1, wherein the predetermined pressure is -0.09 MPa to -0.05 MPa in gauge pressure.

7. The method for manufacturing a battery according to claim 1, wherein the width of the electrode body is 20 cm or more.

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