Method for manufacturing an electricity storage device

Abstract

To reduce an error in a height position of a sealing plate of a power storage device to prevent contact failure of a thermistor when a power storage pack is constructed.SOLUTION: A manufacturing method includes: a fitting step of fitting a sealing plate 12 to a case body 14; a fixing step of fixing the sealing plate 12 to the case body 14 by sandwiching the case body 14 between a pair of sidewall pressing tools J10; and a welding step of welding the sealing plate 12 and the case body 14. In the manufacturing method disclosed herein, a convex portion J14 that protrudes toward a first sidewall 14c in the vicinity of a thermistor mounting portion 50 is provided in part of a pressing surface J12 of the sidewall pressing tool J10, and the convex portion J14 is made of an elastic material. According to a manufacturing method of such a configuration, since the welding step can be carried out in a state where the sealing plate 12 is suitably fixed to the case body 14 in the entire width direction, loose connection of the thermistor caused by local warpage of the sealing plate 12 can be prevented.SELECTED DRAWING: Figure 10

Description

[Technical Field]

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

[0002] Electricity storage devices such as lithium-ion secondary batteries are used in a variety of fields. This type of electricity storage device is constructed by housing an electrode assembly in a case. The case of this electricity storage device includes a box-shaped case body with an opening at the top and a sealing plate with a pair of electrode terminals. In manufacturing an electricity storage device with such a configuration, first, the electrode assembly is attached to the electrode terminals of the sealing plate. Next, after housing the electrode assembly inside the case body, the sealing plate is fitted into the opening at the top of the case body. Then, the case body and the sealing plate are welded together using a laser or the like.

[0003] In the above-mentioned manufacturing process, if the sealing plate is not properly fitted to the case body, poor welding may occur. For this reason, techniques for properly fitting the sealing plate have been proposed (see Patent Documents 1 to 4). For example, the manufacturing method described in Patent Document 1 includes a step of fitting a sealing body (sealing plate) to the opening of an outer can (case body) to form a fitted body, a temporary welding step of welding a portion of the sealing body to the outer can while pressing the fitted body from the sealing body side, and a main welding step of welding the outer periphery of the sealing body to the outer can. This is said to suppress warping of the sealing body and prevent poor welding between the sealing body and the outer can. Furthermore, Patent Document 1 uses a manufacturing apparatus equipped with an upper mold that presses the fitted body from the sealing body side and a horizontal mold that presses both side surfaces of the outer can. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-277593 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-185099 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-185092 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-231908 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, an electricity storage device having the above configuration may be used in the form of an electricity storage pack in which a plurality of electricity storage devices are arranged. This electricity storage pack may include a temperature measurement member that measures the temperature of each of the plurality of electricity storage devices. This temperature measurement member includes a thermistor as a temperature measurement element and a bracket that fixes the plurality of thermistors. Each of the plurality of thermistors contacts the upper surface (thermistor installation portion) of the sealing plate of each of the plurality of electricity storage devices. The temperature measurement member having such a configuration can monitor temperature changes of the plurality of electricity storage devices.

[0006] However, in the electricity storage pack configured as described above, poor contact of the thermistor occurred in some electricity storage devices. After investigating the cause of this poor contact, the present inventor discovered that even in electricity storage devices in which the case body and the sealing plate were properly welded, there was a slight error (of about 0.1 to 0.2 mm) in the welding position of the sealing plate in the height direction. It was also found that if the height positions of the sealing plates differ among multiple electricity storage devices, the tip of the thermistor may not reach the thermistor installation portion of the sealing plate, resulting in poor contact in some electricity storage devices.

[0007] The technology disclosed herein has been made to solve such problems, and provides a technology that reduces errors in the height position of the sealing plate of an electricity storage device and prevents poor contact of the thermistor when assembling an electricity storage pack. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present inventors investigated the causes of minute errors in the height position of the sealing plate after welding and discovered the following. First, electrode terminals are attached to the sealing plate of an electricity storage device. In an electricity storage device with such a configuration, the crimping process used to attach the electrode terminals can cause slight expansion and deformation (approximately 0.05 to 0.1 mm) in the sealing plate near the electrode terminals. When a sealing plate with such expansion near the electrode terminals is fitted to a case body, a minute gap is formed between the sealing plate and the case body in an area away from the electrode terminals. Even in an assembly with such a gap, pressing the side wall of the case body with a pressing tool causes the case body to deform toward the sealing plate, making it appear as if the gap has been eliminated. However, the present inventors' investigations revealed that almost no frictional force is generated between the case body and the sealing plate in the area where this gap was present. This makes it impossible to restrict deformation of the sealing plate in the height direction, which can lead to the sealing plate warping due to the heat generated during welding. If this local warping of the sealing plate occurs in the area where the thermistor is installed, it can cause poor contact of the thermistor when the electricity storage pack is assembled.

[0009] The manufacturing method for an electricity storage device disclosed herein (hereinafter also simply referred to as the "manufacturing method") was made based on the above-mentioned findings. Specifically, the manufacturing method disclosed herein includes a preparation step of preparing a sealing plate having electrode terminals and a thermistor installation portion and a box-shaped case body having a top opening, a fitting step of fitting the sealing plate into the top opening of the case body, a fixing step of clamping upper portions of both side walls of the case body with a pair of side wall pressers to fix the sealing plate to the case body, and a welding step of welding the sealing plate to the case body. In the manufacturing method disclosed herein, protrusions that protrude toward both side walls of the case body near the thermistor installation portion are provided on parts of the pressing surfaces of the pair of side wall pressers, and the protrusions are made of an elastic material.

[0010] In the fixing step of the manufacturing method configured as described above, a protrusion protruding from the pressing surface of the sidewall presser presses the case body near the thermistor mounting portion. This allows the sealing plate near the thermistor mounting portion to be fixed to the case body even when a gap occurs near the thermistor mounting portion due to the use of a sealing plate that has undergone expansion and deformation near the electrode terminals. Additionally, this protrusion is made of an elastic material. This allows the protrusion to elastically deform when the sidewall presser clamps the case body, thereby adequately fixing the sealing plate in an area away from the thermistor mounting portion. As described above, the manufacturing method disclosed herein allows welding to be performed with the sealing plate properly fixed to the case body near both the thermistor mounting portion and the electrode terminals (typically, across the entire width). This prevents poor thermistor contact due to local warping of the sealing plate.

[0011] In one aspect of the manufacturing method disclosed herein, the electrode terminals are provided at both widthwise ends of the sealing plate, and the thermistor installation portion is provided at the center in the widthwise direction relative to the electrode terminals. In an electricity storage device configured in this manner, gaps are likely to occur near the thermistor installation portion, and therefore the effects of the technology disclosed herein are particularly favorable.

[0012] In one embodiment of the manufacturing method disclosed herein, a load of 20 N or more is applied to both side walls of the case body near the thermistor installation portion during the fixing step, which generates a more appropriate frictional force between the case body and the sealing plate and effectively prevents warping of the sealing plate during welding.

[0013] In one aspect of the manufacturing method disclosed herein, the fixing step uses an upper surface pressing tool that presses the sealing plate downward, which prevents poor welding when a sealing plate that is significantly curved upward in the height direction is supplied.

[0014] In addition, in an embodiment in which an upper surface pressing tool is used, it is preferable that the upper surface pressing tool presses the thermistor mounting portion, thereby further reducing the error in the height position of the thermistor mounting portion.

[0015] In addition, in an embodiment in which an upper surface pressing tool is used, it is preferable to prepare a sealing plate that is convexly curved upward in the height direction in the preparation step, which can prevent poor contact of the thermistor due to the sealing plate curving downward in the height direction. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view schematically showing the appearance of a secondary battery. [Figure 2] FIG. 2 is a vertical cross-sectional view schematically showing the internal structure of the secondary battery shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing the structure in the vicinity of the electrode terminal of the secondary battery shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a plan view of an electricity storage pack constructed using the secondary battery shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a contact portion between a secondary battery and a thermistor. [Figure 7] FIG. 7 is a flowchart illustrating a manufacturing method according to one embodiment. [Figure 8] FIG. 8 is a plan view of the assembly constructed in the mating process. [Figure 9] FIG. 9 is a plan view showing the assembly and the jig before the fixing step is started. [Figure 10] FIG. 10 is a cross-sectional view taken along line XX in FIG. [Figure 11] FIG. 11 is a cross-sectional view showing the assembly and the jig after the fixing step has been performed. [Figure 12] FIG. 12 is a cross-sectional view showing the assembly and the jig in the welding process. [Figure 13] FIG. 13 is a cross-sectional view showing the assembly and the jig after the fixing step in another embodiment has been performed. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field.

[0018] In this specification, the term "electricity storage device" refers to a concept that encompasses devices in which charging and discharging occur by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. That is, the electricity storage device in the technology disclosed herein encompasses secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, as well as capacitors such as lithium-ion capacitors and electric double-layer capacitors.

[0019] 1. Structure of secondary batteries First, the structure of a secondary battery will be described as an example of a target (electricity storage device) for the manufacturing method according to this embodiment. FIG. 1 is a perspective view schematically showing the appearance of a secondary battery. FIG. 2 is a longitudinal sectional view schematically showing the internal structure of the secondary battery shown in FIG. 1. FIG. 3 is a sectional view showing the structure near the electrode terminals of the secondary battery shown in FIG. 1. FIG. 4 is a sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a plan view of an electricity storage pack constructed using the secondary battery shown in FIG. 1. FIG. 6 is a sectional view schematically showing a contact portion between the secondary battery and a thermistor. In the drawings, the symbol X indicates the width direction, the symbol Y indicates the depth direction, and the symbol Z indicates the height direction. Furthermore, the symbols L, R, F, Rr, U, and D indicate left, right, front, rear, up, and down, respectively. However, these directions are defined for convenience of explanation and are not intended to limit the installation mode of the secondary battery during use or manufacturing.

[0020] 1 to 4 includes a case 10, an electrode assembly 20, and an electrolyte solution 30. Each of these components will be described below.

[0021] (1) Case The case 10 is a flat, box-shaped container having an internal space 10a. The internal space 10a of the case 10 contains an electrode assembly 20 and an electrolyte solution 30. The case 10 is preferably made of a metal member having a certain level of strength or more. Examples of materials for the case 10 include aluminum and aluminum alloys. The case 10 includes a case main body 14 and a sealing plate 12. Each of these components will be described below.

[0022] (a) Case body The case body 14 is a box-shaped container having an upper opening 14a. Specifically, the case body 14 includes a bottom 14b that is a long rectangular plate-like member, a pair of first side walls 14c that extend upward D from long sides (sides along the width direction X) of the bottom 14b, and a pair of second side walls 14d that extend upward D from short sides (sides along the depth direction Y) of the bottom 14b. In other words, the first side walls 14c are side walls with a relatively large area. On the other hand, the second side walls 14d are side walls with a relatively small area.

[0023] The specific dimensions of the case body 14 can be changed as appropriate as long as the effects of the technology disclosed herein are not significantly impaired. For example, the width (dimension in the width direction X) of the case body 14 can be set to 75 mm to 175 mm (preferably 100 mm to 150 mm). The depth (dimension in the depth direction Y) of the case body 14 can be set to 7.5 mm to 17.5 mm (preferably 10 mm to 15 mm). The height (dimension in the height direction Z) of the case body 14 can be set to 25 mm to 100 mm (preferably 50 mm to 75 mm). Furthermore, the thickness of each member constituting the case body 14 (the bottom portion 14b, the first side wall 14c, and the second side wall 14d) can be set to 1 mm to 2 mm (preferably about 1.5 mm).

[0024] (b) Sealing plate The sealing plate 12 is a plate-like member that seals the top opening 14a of the case body 14. Specifically, as shown in FIG. 4, the sealing plate 12 is fitted into the top opening 14a of the case body 14. After manufacture, the case 10 has a weld 60 formed across the sealing plate 12 and the case body 14. This weld 60 is formed by irradiating the boundary between the sealing plate 12 and the case body 14 with a laser. This weld 60 is formed around the entire outer periphery of the sealing plate 12 (see FIG. 1).

[0025] The specific dimensions of sealing plate 12 can also be changed as appropriate, provided that the effects of the technology disclosed herein are not significantly impaired. For example, the width of sealing plate 12 can be set to 75 mm to 175 mm (preferably 100 mm to 150 mm). The depth of sealing plate 12 can be set to 7.5 mm to 17.5 mm (preferably 10 mm to 15 mm). The thickness of sealing plate 12 can be set to 1 mm to 2 mm (preferably about 1.5 mm). Such thin and wide sealing plates 12 are prone to warping due to the heat generated during laser welding, and are therefore particularly suitable for application of the technology disclosed herein.

[0026] The sealing plate 12 also has an electrode terminal 40 and a thermistor installation portion 50. Each component will be described below.

[0027] (b-1) Electrode terminal The electrode terminals 40 are conductive members electrically connected to the electrode assembly 20 inside the case 10. In the secondary battery 1 shown in FIG. 1, an electrode terminal 40 is provided at each end of the sealing plate 12 in the width direction X. Of the pair of electrode terminals 40, one electrode terminal 40 (on the left side L in FIG. 1) serves as a positive electrode terminal 42 connected to the positive electrode of the electrode assembly 20. The other electrode terminal 40 (on the right side R in FIG. 1) serves as a negative electrode terminal 44 connected to the negative electrode of the electrode assembly 20. As shown in FIGS. 2 and 3, each electrode terminal 40 is a structure combining multiple conductive members and extends along the height direction Z. Specifically, as shown in FIG. 2, a current collecting member 40a constituting the lower end of the electrode terminal 40 is connected to the electrode assembly 20 inside the case 10. Meanwhile, an external terminal 40b constituting the upper end of the electrode terminal 40 is exposed to the outside of the case 10. 3, the current collecting member 40a and the external terminal 40b are electrically connected via the shaft 40s that penetrates the sealing plate 12. An insulating member 40c made up of a combination of multiple gaskets is disposed between the electrode terminal 40 and the sealing plate 12. This prevents electrical conduction between the electrode terminal 40 and the sealing plate 12. When attaching the electrode terminal 40 to the sealing plate 12, a conductive member (such as the external terminal 40b and the shaft 40s) and the insulating member 40c are assembled into the terminal insertion hole 12c of the sealing plate 12, and a crimping process is performed to deform these members under pressure.

[0028] (b-2) Thermistor installation area The thermistor installation portion 50 is provided on a portion of the upper surface of the sealing plate 12. This thermistor installation portion 50 is a portion that comes into contact with the thermistor of the temperature measurement member when the electricity storage pack is assembled. For example, an electricity storage pack (battery assembly) 100 shown in FIG. 5 is constructed by arranging multiple secondary batteries 1 along a predetermined arrangement direction (depth direction Y in FIG. 5). In this electricity storage pack 100, the electrode terminals 40 of each secondary battery 1 are electrically connected via bus bars 110. The electricity storage pack 100 also includes a temperature measurement member 120 that measures the temperature of the secondary batteries 1. This temperature measurement member 120 includes a thermistor 124 that is a temperature measurement element and a bracket 122 that secures the multiple thermistors 124. As shown in FIG. 6, each thermistor 124 protrudes downward from the bracket 122. A tip 124a of each thermistor 124 comes into contact with the thermistor installation portion 50 of each of the multiple secondary batteries 1. This allows the temperature measuring member 120 to monitor the temperature change of the secondary battery 1.

[0029] 1 and 2, the thermistor installation portion 50 is provided at a more central portion in the width direction X than the pair of electrode terminals 40. As will be described in detail later, when a sealing plate 12 having such a configuration is used, a gap S between the sealing plate 12 and the case body 14 tends to occur near the thermistor installation portion 50 during the fixing process. However, according to the technology disclosed herein, even if such a gap S occurs, welding can be performed while the sealing plate 12 is sufficiently fixed to the case body 14. Therefore, the sealing plate 12 having the above configuration can particularly effectively exhibit the effects of the technology disclosed herein. Note that in the secondary battery 1 shown in FIGS. 1 and 2, a pair of thermistor installation portions 50 are provided to sandwich the gas release valve 12b in the width direction X.

[0030] (c) Other components The sealing plate 12 shown in FIG. 1 also has a liquid inlet 12a and a gas release valve 12b in addition to the electrode terminal 40 and the thermistor installation portion. The liquid inlet 12a is an opening for injecting the electrolyte 30 into the inside of the case 10. In the secondary battery 1 after manufacture, the liquid inlet 12a is sealed with a sealing member 16. Meanwhile, the gas release valve 12b is a thin-walled portion formed to be thinner than other portions of the sealing plate 12. This gas release valve 12b ruptures when the internal pressure of the case 10 suddenly increases due to the generation of decomposition gas or the like. This prevents excessive deformation of the secondary battery 1 during charging and discharging.

[0031] (2) Electrode body As shown in FIG. 2, the electrode assembly 20 is housed inside the case 10. In this embodiment, one electrode assembly 20 is housed inside the case 10. The number of electrode assemblies 20 is not particularly limited and may be plural. For example, the electrode assembly 20 is formed by laminating a positive electrode and a negative electrode with a separator interposed therebetween. The positive electrode includes a positive electrode core (e.g., aluminum foil) and a positive electrode active material layer applied to the surface of the positive electrode core. On the other hand, the negative electrode includes a negative electrode core (e.g., copper foil) and a negative electrode active material layer applied to the surface of the negative electrode core. The materials of the components (positive electrode, negative electrode, separator, etc.) that make up the electrode assembly 20 can be materials that can be used in general secondary batteries without any particular restrictions, and detailed description thereof will be omitted as they do not limit the technology disclosed herein.

[0032] A positive electrode connection portion 20A is provided on one side edge of the electrode body 20 in the width direction X. A negative electrode connection portion 20B is provided on the other side edge of the electrode body 20. The positive electrode connection portion 20A is formed by bundling positive electrode cores that are not coated with a positive electrode active material layer. On the other hand, the negative electrode connection portion 20B is formed by bundling negative electrode cores that are not coated with a negative electrode active material layer. The positive electrode terminal 42 is connected to the positive electrode of the electrode body 20 via the positive electrode connection portion 20A. The negative electrode terminal 44 is connected to the negative electrode of the electrode body 20 via the negative electrode connection portion 20B. An insulating sheet (not shown) is disposed between the electrode body 20 and the case body 14. This prevents electrical conduction between the electrode body 20 and the case 10.

[0033] (3) Electrolyte The electrolyte solution 30 is accommodated inside the case 10 together with the electrode assembly 20. Specifically, the electrolyte solution 30 permeates the inside of the electrode assembly 20 (between the positive and negative electrodes). A portion of the electrolyte solution 30 may be present outside the electrode assembly 20 (between the electrode assembly 20 and the case 10) as excess electrolyte solution 32. This allows the excess electrolyte solution 32 to be supplied to the inside of the electrode assembly 20 when the electrolyte solution 30 is decomposed inside the electrode assembly 20. Note that the components of the electrolyte solution 30 can be any components that can be used in general secondary batteries without any particular restrictions, and detailed description thereof will be omitted as they do not limit the technology disclosed herein.

[0034] 2. Manufacturing method A method for manufacturing the secondary battery 1 having the above configuration will be described below as one embodiment of a method for manufacturing an electricity storage device disclosed herein. FIG. 7 is a flowchart illustrating the manufacturing method according to this embodiment. FIG. 8 is a plan view of the assembly constructed in the fitting step. FIG. 9 is a plan view showing the assembly and the jig before the fixing step is started. FIG. 10 is a cross-sectional view taken along line XX in FIG. 9. FIG. 11 is a cross-sectional view showing the assembly and the jig after the fixing step has been performed. FIG. 12 is a cross-sectional view showing the assembly and the jig in the welding step.

[0035] 7, the manufacturing method according to this embodiment includes a preparation step S10, a fitting step S20, a fixing step S30, and a welding step S40. Each step will be described below.

[0036] (1) Preparation process S10 In the preparation step S10, a sealing plate 12 having an electrode terminal 40 and a thermistor installation portion 50, and a box-shaped case body 14 having a top opening 14a are prepared. The structures of the sealing plate 12 and the case body 14 have already been explained, so redundant explanations will be omitted. Note that in this step, the current collecting member 40a of the electrode terminal 40 and the current collecting tab 20T of the electrode body 20 may be joined. This integrates the sealing plate 12 and the electrode body 20 via the electrode terminal 40.

[0037] (2) Fitting process S20 In the fitting step S20, the sealing plate 12 is fitted into the top opening 14a of the case body 14. Specifically, first, the electrode body 20 is inserted into the top opening 14a of the case body 14. Then, the electrode body 20 and the sealing plate 12 are further lowered. This causes the sealing plate 12 to fit into the top opening 14a of the case body 14. In the following description, the structure in which the sealing plate 12 is fitted into the case body 14 will be referred to as "assembly A."

[0038] As shown in FIG. 8 , in this assembly A, a minute gap S may occur between the sealing plate 12 and the case body 14 in a plan view. Specifically, when the electrode terminal 40 is attached to the sealing plate 12, a crimping process is performed to deform the electrode terminal 40 under pressure. The pressure applied at this time may cause the sealing plate 12 to expand and deform radially outward from the electrode terminal 40 (e.g., the shaft portion 40s) (see arrow E in FIG. 8 ). When the sealing plate 12 with such expansion and deformation near the electrode terminal 40 is fitted into the case body 14, the sealing plate 12 is positioned with no gap between it and the inner wall of the case body 14 near the electrode terminal 40. On the other hand, in a region away from the electrode terminal 40 (the center in the width direction X in FIG. 8 ), the dimension in the depth direction Y is shorter than the region near the expanded and deformed electrode terminal 40, resulting in a minute gap S between the sealing plate 12 and the case body 14. When the first side wall 14c of this assembly A is pressed with a side wall pressing tool with a flat pressing surface, the case body 14 deforms toward the sealing plate 12, making it appear as if the gap S has been eliminated. However, the inventors' investigations revealed that the case body 14 and the sealing plate 12 are only in contact with each other in the area where the gap S existed, and almost no friction is generated. In this state, deformation of the sealing plate in the height direction cannot be restricted. Therefore, when the sealing plate 12 and the case body 14 are welded, slight thermal deformation (warping) (approximately 0.05 to 0.1 mm) may occur near the location where the gap S existed. If this local warping of the sealing plate 12 occurs in the thermistor installation portion 50, when the electricity storage pack 100 shown in FIG. 5 is constructed, a secondary battery 1 may be produced in which the tip 124a of the thermistor 124 (see FIG. 6) does not reach the thermistor installation portion 50. In the manufacturing method according to this embodiment, in order to prevent such local warping of the sealing plate 12 from occurring in the thermistor installation portion 50, the next step, a fixing step S30, is carried out.

[0039] (3) Fixed process S30 In the fixing step S30, the upper portions of both side walls (first side walls 14c) of the case body 14 are clamped by a pair of side wall pressers J10, and the closure plate 12 is fixed to the case body 14. Specifically, as shown in FIG. 9, in the fixing step S30 of this embodiment, a fixing jig J1 equipped with a pair of side wall pressers J10 is used. The side wall pressers J10 are a pair of plate-like members extending along the first side wall 14c of the case body 14 (i.e., the width direction X). As shown in FIG. 10, the height dimension of the side wall pressers J10 is set so as to press only the upper portion of the first side wall 14c. In the fixing step S30, with the assembly A disposed between the pair of side wall pressers J10, the pair of side wall pressers J10 are moved inward in the depth direction Y. As a result, the assembly A is clamped between the pair of side wall pressers J10, and the closure plate 12 is fixed to the case body 14.

[0040] In the manufacturing method according to this embodiment, a protrusion J14 is provided on a portion of the pressing surface J12 of the pair of sidewall pressing tools J10, protruding toward both sidewalls (first sidewalls 14c on both sides) of the case main body 14 near the thermistor installation portion 50. This protrusion J14 contacts the first sidewall 14c near the thermistor installation portion 50 and presses that area before the other pressing surfaces J12 of the sidewall pressing tool J10 do. This allows a strong frictional force to be generated between the sealing plate 12 and the case main body 14 near the gap S, even if a gap S is generated near the thermistor installation portion 50. In addition, this protrusion J14 is made of an elastic material. As a result, when the sidewall pressing tool J10 clamps the case body 14, the protrusion J14 elastically deforms, and a strong frictional force can be generated between the sealing plate 12 and the case body 14, even in areas away from the thermistor installation area 50 (for example, both ends of the assembly A in the width direction X in FIG. 9). As described above, according to the manufacturing method disclosed herein, the welding step S40, which will be described later, can be performed with the sealing plate 12 properly fixed to the case body 14 over the entire area in the width direction X, thereby preventing poor contact of the thermistor 124 (see FIG. 6) due to local warping of the sealing plate 12.

[0041] The elastic material constituting the protrusion J14 may be any material that elastically deforms under the restraining load of the sidewall presser J10. Examples of such elastic materials include synthetic rubber and natural rubber. The protrusion J14 may also be a mechanically elastic material that uses a spring. For example, the protrusion J14 may be composed of a contact plate that contacts the first sidewall 14c of the case body 14 and a spring body disposed between the sidewall presser J10 and the contact plate. In a protrusion J14 configured in this manner, the elastic force of the spring body can be adjusted to appropriately secure the sealing plate 12 to the case body 14 throughout the width direction X. On the other hand, the sidewall presser J10 is preferably composed of a material that is harder than the case 10 and the protrusion J14. This allows the case 10 to be pressed stably. Examples of materials for the sidewall presser J10 include metal materials such as copper, copper alloy, molybdenum, and stainless steel.

[0042] The conditions for the fixing step S30 (e.g., the restraining load and the dimensions of the protrusion J14) are preferably set appropriately taking into consideration the structure of the object to be pressed (assembly A) so that a predetermined load is locally applied to the first side wall 14c near the thermistor installation portion 50. For example, according to experiments conducted by the inventors, the load applied to the first side wall 14c near the thermistor installation portion 50 is preferably 20 N or more, more preferably 30 N or more, even more preferably 40 N or more, and particularly preferably 50 N or more. This generates an appropriate frictional force between the sealing plate 12 and the case body 14 near the thermistor installation portion 50, thereby more preferably preventing warping of the thermistor installation portion 50. The upper limit of the load applied near the thermistor installation portion 50 is not particularly limited and may be 100 N or less, 90 N or less, 80 N or less, or 70 N or less.

[0043] An example of a condition for applying the above-described localized load to the first side wall 14c near the thermistor mounting portion 50 will be described below. Note that the conditions described below are merely an example of a condition for applying an appropriate restraining load near the thermistor mounting portion 50 and are not intended to limit the manufacturing method disclosed herein. Specifically, as described above, the load applied near the thermistor mounting portion 50 is affected by the structure of the object to be pressed (assembly A), the restraining load, the structure of the protrusion J14, the size of the gap S generated in the fitting process, and other factors. For this reason, when performing the manufacturing method according to this embodiment, it is preferable to conduct a preliminary test on multiple (approximately three) assemblies A to measure the depth dimension s1 of the gap S generated in the fitting process S20 and the load applied near the thermistor mounting portion 50 in the fixing process S30, and then appropriately set the dimensions of the protrusion J14, the restraining load, and other factors based on the results of the preliminary test.

[0044] For example, the restraining load applied by the side wall pressing tool J10 to the entire first side wall 14c can be set in the range of 150N to 300N (preferably 200N to 300N). The protrusion amount t of the protrusion J14 can be set to be at least twice (more preferably at least three times, even more preferably at least four times, and particularly preferably at least five times) the average depth dimension s1 of the gap S. The specific protrusion amount t of the protrusion J14 is preferably at least 0.01mm, more preferably at least 0.05mm, and particularly preferably at least 0.1mm. This can suitably prevent local warping of the thermistor mounting portion 50. From the viewpoint of preventing local warping of the thermistor mounting portion 50, the upper limit of the protrusion amount t of the protrusion J14 is not particularly limited and may be 5mm or less, 4mm or less, 3mm or less, or 2mm or less. In consideration of the cooling performance in the welding step S40 described later, the upper limit of the protrusion amount t of the protrusion J14 before pressing (see FIG. 10) is preferably 1.5 mm or less, more preferably 1 mm or less, and particularly preferably 0.5 mm or less. As a result, as shown in FIG. 11, when the protrusion J14 elastically deforms, the metal side wall pressing tool J10 comes into contact with the case body 14, thereby achieving favorable cooling performance.

[0045] Furthermore, the height z2 of the protrusion J14 only needs to be greater than the thickness of the sealing plate 12. For example, if the thickness of the sealing plate 12 is approximately 1.5 mm, the height z2 of the protrusion J14 is preferably 2 mm or greater, and more preferably 2.5 mm or greater. This allows the sealing plate 12 to be properly fixed to the case body 14. On the other hand, the upper limit of the height z2 of the protrusion J14 is not particularly limited, and may be 10 mm or less, 7.5 mm or less, or 5 mm or less.

[0046] In consideration of the cooling performance in the welding step S40, it is preferable to set the ratio (z2 / z1) of the height z2 of the protrusion J14 to the height z1 of the side wall pressing tool J10 to a certain value or less. This allows the metallic sidewall pressing tool J10 to be in sufficient contact with the case body 14, thereby achieving favorable cooling performance. Specifically, the ratio (z2 / z1) is preferably 85% or less, more preferably 80% or less, even more preferably 75% or less, and particularly preferably 70% or less. On the other hand, the lower limit of the ratio (z2 / z1) is not particularly limited from the viewpoint of cooling performance, and may be 20% or more, 30% or more, or 40% or more.

[0047] 9, the fixing jig J1 in this embodiment includes, in addition to the sidewall presser J10, a pair of holding members J20 that hold the shape of the assembly A. Each of the holding members J20 has a holding protrusion J22 that protrudes inward in the width direction X. The holding protrusion J22 is inserted between the sidewall presser J10 that hold the assembly A. This restricts the movement of the sidewall presser J10 inward in the depth direction Y, thereby preventing the assembly A from being deformed more than necessary by the pressure from the sidewall presser J10.

[0048] (4) Welding process S40 In the welding step S40, the sealing plate 12 and the case body 14 are welded together. Specifically, as shown in FIG. 12 , in this step, a laser beam L is irradiated onto the boundary between the sealing plate 12 and the case body 14 while the sealing plate 12 is fixed to the case body 14 by the sidewall pressing tool J10. This forms a weld 60 (see FIG. 4 ) that straddles the sealing plate 12 and the case body 14. In this embodiment, the first sidewall 14c near the thermistor installation portion 50 is pressed by the protrusion J14, generating sufficient friction between the sealing plate 12 and the case body 14 near the thermistor installation portion 50. This prevents the thermistor installation portion 50 from warping due to heat during welding, thereby suppressing variations in the height position of the thermistor installation portion 50 in the manufactured secondary battery 1. Therefore, according to the manufacturing method of this embodiment, when the electricity storage pack 100 as shown in FIG. 5 is constructed, it is possible to prevent contact failure from occurring in some of the thermistors 124.

[0049] 3. Other Embodiments One embodiment of the technology disclosed herein has been described above. Note that the technology disclosed herein is not limited to the above embodiment, and includes other embodiments with various configuration changes. Other examples of the embodiment of the technology disclosed herein will be described below.

[0050] FIG. 13 is a cross-sectional view showing the fixing step in another embodiment. As shown in FIG. 13 , the fixing step may use an upper pressing tool J30 that presses the sealing plate 12 from the upper U toward the lower D. Specifically, if the sealing plate 12 is significantly curved upward toward the upper U in the height direction Z due to manufacturing tolerances or the like, a portion of the sealing plate 12 may be positioned above the top surface of the case body 14. If laser welding is performed in this state, a defective weld will occur, in which the weld 60 spanning the sealing plate 12 and the case body 14 is not formed. In contrast, as shown in FIG. 13 , pressing the sealing plate 12 downward toward the lower D with the upper pressing tool J30 can correct the sealing plate 12 that is significantly curved upward toward the upper U, thereby preventing the occurrence of a defective weld. Note that the upper pressing tool J30 preferably presses the thermistor mounting portion 50. This further reduces the error in the height position of the thermistor mounting portion 50, thereby more effectively preventing poor contact of the thermistor when the electricity storage pack is assembled.

[0051] Furthermore, when using the above-described upper surface pressing tool J30, it is preferable to prepare a sealing plate 12 that is pre-curved in a convex shape toward the upward U in the height direction Z in the preparation step. Specifically, due to manufacturing tolerances and the like, a sealing plate 12 that is curvature toward the downward D in the height direction Z may be supplied in the preparation step. This sealing plate 12 that is curvature toward the downward D does not cause poor fixing or welding, but it may cause an error in the height position of the thermistor installation portion 50. In contrast, if a sealing plate 12 that is pre-curved (bent) toward the upward U is prepared and then the curvature toward the upward U is corrected using the upper surface pressing tool J30 in the fixing step, the error in the height position of the thermistor installation portion 50 in both the upward U and downward D directions can be further reduced.

[0052] When the sealing plate 12 is bent upward in the U direction in advance, it is preferable to bend the sealing plate 12 so that the center (thermistor installation portion 50) is positioned 0.1 mm or more above the U with respect to both end portions in the width direction X (near the electrode terminals 40). This makes it possible to suitably prevent the thermistor installation portion 50 from shifting downward in the height direction Z. On the other hand, in consideration of ease of correction in the fixing process, it is preferable to bend the sealing plate 12 upward in the U direction so that the height position of the center is 0.3 mm or less with respect to both end portions in the width direction X.

[0053] The technology disclosed herein has been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. In other words, the technology disclosed herein encompasses the aspects described in items 1 to 6 below.

[0054] <Item 1> a preparation step of preparing a sealing plate having an electrode terminal and a thermistor installation portion and a box-shaped case body having an upper opening; a fitting step of fitting the sealing plate into the top opening of the case body; a fixing step of clamping upper portions of both side walls of the case body with a pair of side wall pressing tools to fix the sealing plate to the case body; a welding step of welding the sealing plate and the case body; It is equipped with a pair of side wall pressing tools each having a pressing surface provided with a protrusion protruding toward each side wall of the case body near the thermistor installation portion; The method for manufacturing an electricity storage device, wherein the protrusion is made of an elastic material.

[0055] <Item 2> 2. The manufacturing method according to item 1, wherein the electrode terminals are provided at both widthwise ends of the sealing plate, and the thermistor installation portion is provided at a center portion in the widthwise direction relative to the electrode terminals.

[0056] <Item 3> 3. The manufacturing method according to item 1 or 2, wherein the protrusion from the pressing surface is 0.1 mm to 1 mm.

[0057] <Item 4> 4. The manufacturing method according to any one of items 1 to 3, wherein in the fixing step, an upper surface pressing tool is used to press the sealing plate downward from above.

[0058] <Item 5> The manufacturing method according to claim 4 , wherein the upper surface pressing tool presses the thermistor mounting portion.

[0059] <Item 6> Item 6. The manufacturing method according to item 4 or 5, wherein in the preparing step, a sealing plate that is curved convexly upward in the height direction is prepared. [Explanation of symbols]

[0060] 1 Secondary battery 10 cases 10a Internal space 12c Terminal insertion hole 14 Case body 14b bottom 14c 1st side wall 14d 2nd side wall 20 Electrode body 20T current collecting tab 30 Electrolyte 32 Excess electrolyte 40 electrode terminal 40a Current collecting member 40b External terminal 40c Insulating member 40s shaft 42 Positive terminal 44 Negative terminal 50 Thermistor installation section 60 Welded Section 100 battery packs (batteries) 110 Busbar 120 Temperature measuring element 122 Bracket 124 Thermistor A assembly J1 Fixture J10 Side wall presser J12 pressing surface J14 convex part J20 retaining member J22 Retaining protrusion J30 Upper pressing tool S Gap

Claims

1. a preparation step of preparing a sealing plate having an electrode terminal and a thermistor installation portion and a box-shaped case body having an upper opening; a fitting step of fitting the sealing plate into the top opening of the case body; a fixing step of clamping upper portions of both side walls of the case body with a pair of side wall pressing tools to fix the sealing plate to the case body; a welding step of welding the sealing plate and the case body; It is equipped with a pair of side wall pressing tools each having a pressing surface provided with a protrusion protruding toward each side wall of the case body near the thermistor installation portion; The protrusion is made of an elastic material, The electrode terminals are provided at both widthwise ends of the sealing plate, and the thermistor installation portion is provided at a central portion in the widthwise direction relative to the electrode terminals.

2. The manufacturing method according to claim 1 , wherein in the fixing step, a load of 20 N or more is applied to both side walls of the case body in the vicinity of the thermistor installation portion.

3. The manufacturing method according to claim 1 or 2, wherein the fixing step uses an upper surface pressing tool that presses the sealing plate downward from above.

4. The manufacturing method according to claim 3 , wherein the upper surface pressing tool presses the thermistor mounting portion.

5. The manufacturing method according to claim 3 , wherein the preparing step includes preparing a sealing plate that is curved upward in a convex shape in the height direction.

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