Solid-state battery and method for manufacturing solid-state battery

Abstract

To provide a new laminated solid battery.SOLUTION: A solid battery has a first current collector layer 11, a first active substance layer 21, a solid electrolyte layer 30, a second active substance layer 22, and a second current collector layer 12 in this order, wherein the first current collector layer 11 and the second current collector layer 12 have extension parts 11a and 12a, the first current collector layer and the second current collector layer are joined to each other through a thermoplastic resin layer between the extension parts, and (i) an extension part 30a of the solid electrolyte layer and the second current collector layer 12 are joined to each other through the thermoplastic resin layer, or (ii) an extension part 21a of the first active substance layer and the second current collector layer 12 are joined to each other through the thermoplastic resin layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to solid-state batteries and methods for manufacturing solid-state batteries. [Background technology]

[0002] In recent years, various structures for stacked batteries, particularly thin stacked batteries, and manufacturing methods thereof have been proposed (Patent Documents 1 to 3).

[0003] For example, Patent Document 2 discloses a method for manufacturing an all-solid-state battery, which includes a first step of stacking a plurality of current collector layers, positive electrode mixture layers, solid electrolyte layers, and negative electrode mixture layers to obtain a stacked battery having both end faces in the stacking direction and side surfaces; a second step of supplying a liquid resin only to the side surfaces of the stacked battery; and a third step of hardening the liquid resin, in which in the first step, at least one layer of the current collector layers, positive electrode mixture layers, solid electrolyte layers, and negative electrode mixture layers is made to extend beyond the other layers to form an extension layer, and a plurality of extension layers are formed on the side surfaces of the stacked battery, and in the second step, the liquid resin is supplied only to the side surfaces of the stacked battery, thereby allowing the liquid resin to fill gaps between one extension layer and the other extension layers. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-278141 [Patent Document 2] Japanese Patent Application Publication No. 2017-220447 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-129913 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, various structures and manufacturing methods for stacked batteries, particularly thin stacked batteries, have been proposed, but newer stacked batteries are still required depending on the application.

[0006] In response to this, the present disclosure provides a novel stacked solid-state battery, particularly a thin solid-state battery, and a method for manufacturing the same. [Means for solving the problem]

[0007] The present inventors have conducted extensive research and found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows:

[0008] <Aspect 1> a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer in this order; the first current collector layer and the second current collector layer have extending portions that extend outwardly beyond the first active material layer, the solid electrolyte layer, and the second active material layer over the entire periphery of the first active material layer, the solid electrolyte layer, and the second active material layer, the first current collector layer and the second current collector layer are bonded to each other via a thermoplastic resin layer between their extensions; and (i) the first active material layer and the solid electrolyte layer have an extending portion extending outward from the second active material layer around the entire periphery of the second active material layer, and the extending portion of the solid electrolyte layer and the second current collector layer are bonded to each other via the thermoplastic resin layer, or (ii) the first active material layer has an extending portion extending outward from the second active material layer and the solid electrolyte layer around the entire periphery of the second active material layer and the solid electrolyte layer, and the extending portion of the first active material layer and the second current collector layer are bonded to each other via the thermoplastic resin layer. solid state battery. <Aspect 2> 2. The solid-state battery of aspect 1, wherein a thickness in a stacking direction from an outer surface of the first current collector layer to an outer surface of the second current collector layer is 0.05 mm or more and 2.0 mm or less. <Aspect 3> the first current collector layer, the first active material layer, the solid electrolyte layer, the second active material layer, and the second current collector layer are sealed by a first insulating film laminated on the outer surface of the first current collector layer and a second insulating film laminated on the outer surface of the second current collector layer, the thermoplastic resin layer has an extension portion that extends outward beyond the first current collector layer and the second current collector layer over the entire periphery of the first current collector layer and the second current collector layer, a first current collecting tab laminated on the outer surface of the first current collecting layer or a protruding portion of the first current collecting layer protrudes from the first and second insulating films beyond the extending portion of the thermoplastic resin layer, a second current collecting tab laminated on the outer surface of the second current collecting layer or a protruding portion of the second current collecting layer protrudes from the first and second insulating films beyond the extending portion of the thermoplastic resin layer, the first current collecting tab or the protruding portion of the first current collecting layer and the second current collecting tab or the protruding portion of the second current collecting layer are insulated from each other by being offset from each other in a plane direction of the solid-state battery; 3. The solid-state battery according to claim 1 or 2. <Aspect 4> A method for producing the solid-state battery of any one of aspects 1 to 3, comprising: forming an unsealed solid-state battery by stacking the first current collector layer, the first active material layer, the solid electrolyte layer, the second active material layer, and the second current collector layer in this order while disposing a thermoplastic resin annular sealing member between the extended portion of the first current collector layer and the extended portion of the second current collector layer over the entire circumference thereof; and The unsealed solid-state battery is hot-pressed in a state in which the air pressure in the inner space of the thermoplastic resin annular sealing member is lower than the air pressure in the outer space of the thermoplastic resin annular sealing member, causing the thermoplastic resin annular sealing member to flow into at least the inner space, thereby forming the thermoplastic resin layer. <Aspect 5> The method according to aspect 4, wherein the unsealed solid state battery is hot-pressed in a state in which the air pressure in the inner space of the thermoplastic resin annular sealing member is equal to or lower than atmospheric pressure, causing the thermoplastic resin annular sealing member to flow at least toward the inner side, thereby forming the thermoplastic resin layer. [Effects of the Invention]

[0009] According to the present disclosure, a novel stacked solid state battery, particularly a thin stacked solid state battery, and a method for manufacturing the same are provided. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are cross-sectional schematic diagrams showing two embodiments of a solid-state battery according to the present disclosure. [Figure 2] 2(a) is a cross-sectional schematic diagram showing one embodiment of a solid-state battery of the present disclosure, and FIGS. 2(b) and 2(c) are top schematic diagrams showing two embodiments of a solid-state battery of the present disclosure. [Figure 3] 1(a) is a cross-sectional schematic view showing a method for manufacturing the solid state battery of the present disclosure. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the embodiments shown in the drawings are merely examples of the present disclosure and are not intended to limit the present disclosure.

[0012] 《Solid-state battery》 The solid-state battery of the present disclosure comprises a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer, in this order; the first current collector layer and the second current collector layer have extending portions that extend outward beyond the first active material layer, the solid electrolyte layer, and the second active material layer around the entire periphery of the first active material layer, the solid electrolyte layer, and the second active material layer; and the first current collector layer and the second current collector layer are joined to each other via a thermoplastic resin layer between their extending portions. Furthermore, in the solid-state battery of the present disclosure, (i) the first active material layer and the solid electrolyte layer have an extension portion that extends outward more than the second active material layer around the entire periphery of the second active material layer, and the extension portion of the solid electrolyte layer and the second current collector layer are joined to each other via a thermoplastic resin layer, or (ii) the first active material layer has an extension portion that extends outward more than the second active material layer and the solid electrolyte layer around the entire periphery of the second active material layer and the solid electrolyte layer, and the extension portion of the first active material layer and the second current collector layer are joined to each other via a thermoplastic resin layer.

[0013] In such a solid-state battery according to the present disclosure, the extension of the solid electrolyte layer and the second current collector layer are bonded to each other via a thermoplastic resin layer (the above (i)), or the extension of the first active material layer and the second current collector layer are bonded to each other via a thermoplastic resin layer (the above (ii)), thereby providing high structural stability for the solid electrolyte layer and the active material layer. Furthermore, in such a solid-state battery according to the present disclosure, the peripheral space required for sealing can be reduced, thereby increasing the energy density. Furthermore, in such a solid-state battery according to the present disclosure, the layers are bonded and sealed using a thermoplastic resin layer, which facilitates manufacturing and allows for a high degree of freedom in material selection.

[0014] Such a solid-state battery according to the present disclosure can have a relatively small thickness; for example, the thickness in the stacking direction from the outer surface of the first current collector layer to the outer surface of the second current collector layer may be 0.01 mm or more, 0.05 mm or more, 0.10 mm or more, 0.50 mm or more, or 1.00 mm or more, and may be 5.00 mm or less, 4.00 mm or less, 3.00 mm or less, 2.00 mm or less, 1.50 mm or less, or 1.00 mm or less.

[0015] Furthermore, such a solid state battery according to the present disclosure can have any shape in the planar direction of the solid state battery, such as a circular shape or a polygonal shape (triangular, rectangular, hexagonal).

[0016] In one embodiment, the solid-state battery of the present disclosure may have a structure shown in FIG. 1(a), for example. Specifically, as shown in FIG. 1(a), the solid-state battery 100 of the present disclosure includes a first current collector layer 11, a first active material layer 21, a solid electrolyte layer 30, a second active material layer 22, and a second current collector layer 12, in this order. The first current collector layer 11 and the second current collector layer 12 have extension portions 11a, 12a that extend outward from the first active material layer 21, the solid electrolyte layer 30, and the second active material layer 22 around the entire periphery of the first active material layer 21, the solid electrolyte layer 30, and the second active material layer 22. The first current collector layer 11 and the second current collector layer 12 are bonded to each other via a thermoplastic resin layer 40 between the extension portions 11a, 12a. Furthermore, in the solid-state battery of the present disclosure, (i) the first active material layer 21 and the solid electrolyte layer 30 have an extension portion 30a that extends outward from the second active material layer 22 around the entire periphery of the second active material layer 22, and the extension portion 30a of the solid electrolyte layer and the second current collector layer 12 are joined to each other via a thermoplastic resin layer 40.

[0017] In another embodiment, the solid-state battery of the present disclosure may have a structure shown in FIG. 1(b), for example. Specifically, as shown in FIG. 1(b), the solid-state battery 200 of the present disclosure includes a first current collector layer 11, a first active material layer 21, a solid electrolyte layer 30, a second active material layer 22, and a second current collector layer 12, in this order. The first current collector layer 11 and the second current collector layer 12 have extensions 11a, 12a extending outward from the first active material layer 21, the solid electrolyte layer 30, and the second active material layer 22 around the entire periphery 22 of the first active material layer 21, the solid electrolyte layer 30, and the second active material layer. The first current collector layer 11 and the second current collector layer 12 are bonded to each other via a thermoplastic resin layer 40 between the extensions 11a, 12a. Furthermore, in the solid-state battery of the present disclosure, (ii) the first active material layer 21 has an extending portion 21a that extends outward from the second active material layer 22 and the solid electrolyte layer 30 around the entire periphery of the second active material layer 22 and the solid electrolyte layer 30, and the extending portion 21a of the first active material layer 21 and the second current collector layer 12 are joined to each other via a thermoplastic resin layer 40.

[0018] 2(a) and 2(b), the first current collector layer 11, the first active material layer 21, the solid electrolyte layer 30, the second active material layer 22, and the second current collector layer 12 may be sealed by a first insulating film 91 laminated on the outer surface of the first current collector layer 11 and a second insulating film 92 laminated on the outer surface of the second current collector layer 12. Here, in the solid battery 500 of the present disclosure, the thermoplastic resin layer 40 has an extending portion 40a extending outward beyond the first current collector layer 11 and the second current collector layer 12 around the entire periphery of the first current collector layer 11 and the second current collector layer 12. A first current collecting tab 51 is laminated on the outer surface of the first current collecting layer 11, and this first current collecting tab 51 protrudes from the first and second insulating films 91, 92 beyond the extending portion 40a of the thermoplastic resin layer 40. A second current collecting tab 52 is laminated on the outer surface of the second current collecting layer 12, and this second current collecting tab 52 protrudes from the first and second insulating films 91, 92 beyond the extending portion 40a of the thermoplastic resin layer 40. In addition, the first current collecting tab 51 and the second current collecting tab 52 are insulated from each other by being offset (misaligned) from each other in the surface direction of the solid state battery 500.

[0019] 2(a) and 2(b), the first current collecting tab 51 and the second current collecting tab 52 protrude in opposite directions from the first and second insulating films 91, 92 beyond the extending portion 40a of the thermoplastic resin layer 40. However, the first current collecting tab 51 and the second current collecting tab 52 may also protrude in the same direction from the first and second insulating films 91, 92 beyond the extending portion 40a of the thermoplastic resin layer 40 so as to be offset from each other in the plane direction of the solid state battery 500, as shown in FIG.

[0020] In addition, in the embodiment shown in FIG. 2, the first and second current collecting tabs laminated on the outer surfaces of the first and second current collecting layers, respectively, protrude from the first and second insulating films. However, instead of using such current collecting tabs, protruding portions of the first and second current collecting layers may protrude from the first and second insulating films.

[0021] The solid-state battery of the present disclosure may be a battery that uses any ion as a charge carrier, such as a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, or a calcium-ion battery. Of these, the solid-state battery of the present disclosure is preferably a lithium-ion battery or a sodium-ion battery, and more preferably a lithium-ion battery.

[0022] The solid-state battery of the present disclosure is preferably a sulfide solid-state battery, i.e., a solid-state battery in which at least one of the cathode layer, solid electrolyte layer, and anode layer constituting the battery contains a sulfide solid electrolyte. The solid-state battery of the present disclosure may be a lithium-ion sulfide solid-state battery, a sodium-ion sulfide solid-state battery, a magnesium-ion sulfide solid-state battery, or a calcium-ion sulfide solid-state battery. Of these, the solid-state battery of the present disclosure is preferably a lithium-ion sulfide solid-state battery or a sodium-ion sulfide solid-state battery, and more preferably a lithium-ion sulfide solid-state battery.

[0023] The sulfide solid laminate battery of the present disclosure may be either a primary battery or a secondary battery, but is preferably a secondary battery. Therefore, the sulfide solid laminate battery of the present disclosure is preferably a lithium-ion sulfide solid secondary battery.

[0024] In one embodiment of the solid-state battery of the present disclosure, the first current collector layer can be a negative electrode current collector layer, the first active material layer can be a negative electrode active material layer, the second active material layer can be a positive electrode active material layer, and the second current collector layer can be a positive electrode current collector layer. In another embodiment of the solid-state battery of the present disclosure, the first current collector layer can be a positive electrode current collector layer, the first active material layer can be a positive electrode active material layer, the second active material layer can be a negative electrode active material layer, and the second current collector layer can be a negative electrode current collector layer.

[0025] In the solid-state battery according to the present disclosure, layers of any material, particularly layers of any known material, can be used as the negative electrode current collector layer, the negative electrode active material layer, the solid electrolyte layer, the positive electrode active material layer, the positive electrode current collector layer, and the thermoplastic resin layer.

[0026] Therefore, for example, the thermoplastic resin layer can be a layer of polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, polyamide, polycarbonate, etc. In particular, the thermoplastic resin layer can be a layer of an olefin polymer, such as polyethylene or polypropylene.

[0027] Furthermore, at least one of the negative electrode active material layer, the solid electrolyte layer, and the positive electrode active material layer may have a solid electrolyte, particularly a sulfide-based solid electrolyte and / or an oxide-based solid electrolyte, more particularly a sulfide-based solid electrolyte. Solid electrolytes generally have relatively high heat resistance and can therefore withstand the heat pressing that occurs when the solid-state battery of the present disclosure is produced by the method of the present disclosure.

[0028] The solid electrolyte layer used in the solid state battery of the present disclosure may contain a liquid electrolyte in addition to the solid electrolyte.

[0029] <<Solid-state battery manufacturing method>> The solid-state battery of the present disclosure can be manufactured by any manufacturing method, for example, the method of the present disclosure.

[0030] The disclosed manufacturing method for producing a solid state battery of the present disclosure includes: forming an unsealed solid-state battery by stacking the first current collector layer, the first active material layer, the solid electrolyte layer, the second active material layer, and the second current collector layer in this order while disposing a thermoplastic resin annular sealing member between the extended portion of the first current collector layer and the extended portion of the second current collector layer over the entire periphery thereof; and In a state where the air pressure in the inner space of the thermoplastic resin annular sealing member is lower than the air pressure in the outer space of the thermoplastic resin annular sealing member, the unsealed solid state battery is hot-pressed to cause the thermoplastic resin annular sealing member to flow at least toward the inner side, thereby forming a thermoplastic resin layer.

[0031] For example, the solid-state battery of the present disclosure shown in FIG. 1(a) can be manufactured by the method shown in FIG.

[0032] 3(a), first, a first current collector layer 11 and a first active material layer 21 on the first current collector layer 11 are provided, and a second current collector layer 12 and a second active material layer 21 on the second current collector layer 12 are provided. Here, the first current collector layer 11 and the second current collector layer 12 have extensions 11a and 12a, respectively.

[0033] Next, as shown in FIG. 3( b ), the top surface and, optionally, the side surfaces of the first active material layer 21 are covered with a solid electrolyte layer 30 .

[0034] 3(c), a thermoplastic resin annular sealing member 45 is placed on the first current collector layer 11 so as to surround the first active material layer 21 and the solid electrolyte layer 30. Here, the thermoplastic resin annular sealing member 45 may be a self-supporting film-like member or a coated film formed by applying a resin solution onto the first current collector layer 11.

[0035] Next, as shown in FIG. 3(d), the first current collector layer 11, the first active material layer 21, the solid electrolyte layer 30, the second active material layer 22, and the second current collector layer 12 are laminated in this order while a thermoplastic resin annular sealing member 45 is disposed between the extended portion 11a of the first current collector layer 11 and the extended portion 12a of the second current collector layer 12 over the entire periphery thereof, to form an unsealed solid state battery.

[0036] 3(d) and 3(e), the unsealed solid-state battery is heat-pressed (arrow) in a state where the air pressure in the inner peripheral space 45x of the thermoplastic resin annular sealing member 45 is lower than the air pressure in the outer peripheral space 45y of the thermoplastic resin sealing member 45, causing the thermoplastic resin annular sealing member 45 to flow into at least the inner peripheral space 45x, thereby forming the thermoplastic resin layer 40. Here, particularly, the unsealed solid-state battery is heat-pressed in a state where the air pressure in the inner peripheral space 45x of the thermoplastic resin annular sealing member 45 is equal to or lower than atmospheric pressure, causing the thermoplastic resin annular sealing member 45 to flow into at least the inner peripheral space 45x, thereby forming the thermoplastic resin layer 40. This heat-pressing can be performed at any temperature and pressure that allows the formation of a thermoplastic resin layer, for example, at a temperature in the range of 100°C to 200°C and a pressure of 0.1 MPa to 500 MPa, for example, 0.1 MPa to 100 MPa, 0.1 MPa to 10 MPa, or 0.1 MPa to 5 MPa. [Example]

[0037] In the embodiment shown in FIG. 3, the solid state battery of the example was fabricated using the first current collector layer 11 as the negative electrode current collector layer, the first active material layer 21 as the negative electrode active material layer, the second active material layer 22 as the positive electrode active material layer, and the second current collector layer 12 as the positive electrode current collector layer.

[0038] Specifically, the components of each active material layer, solid electrolyte layer, and current collector layer were as follows: Positive electrode active material layer: A mixture of positive electrode active material (lithium nickel manganese cobalt oxide), solid electrolyte (LiI-LiBr-Li2S-P2S5), conductive additive (vapor grown carbon fiber), and binder (styrene butylene rubber) Negative electrode active material layer: A mixture of negative electrode active material (graphite), solid electrolyte (LiI-LiBr-Li2S-P2S5), and binder (styrene-butylene rubber) Solid electrolyte layer: A mixture of solid electrolyte (LiI-LiBr-Li2S-P2S5) and binder (styrene-butylene rubber) Positive electrode current collector layer: Aluminum foil Negative electrode current collector layer: Nickel foil Thermoplastic resin annular seal: Polypropylene film

[0039] In the production of the positive electrode active material layer and the negative electrode active material layer, the above components dispersed in a solvent (butyl butyrate) were pattern-coated on the positive electrode current collector layer and the negative electrode current collector layer, and in the production of the solid electrolyte layer, the above components dispersed in a solvent (butyl butyrate) were pattern-coated so as to cover the negative electrode active material layer.

[0040] In addition, the unsealed solid-state battery obtained as shown in FIG. 3 was heated at 160° C. for 2 minutes in a reduced pressure atmosphere (1.4 kPa) and then hot-pressed (0.5 MPa) for 1 minute.

[0041] The obtained battery of Example was capable of charging and discharging. Furthermore, when a cross section of the obtained battery of Example was observed, it was found that the first current collector layer and the second current collector layer were bonded to each other via a thermoplastic resin layer between their extended portions, and that the extended portion of the solid electrolyte layer and the second current collector layer were bonded to each other via a thermoplastic resin layer. [Explanation of symbols]

[0042] 11 First current collector layer 11a: Extension of first current collector layer 12 Second current collector layer 12a Extension of second current collector layer 21 First active material layer 21a: Extension of the first active material layer 22 Second active material layer 30 Solid electrolyte layer 30a: Extension of solid electrolyte layer 40 Thermoplastic resin layer 40a: Extension of thermoplastic resin layer 51 First current collecting tab 52 Second current collecting tab 91 First insulating film 92 Second insulating film 100, 200, 500, 550 Solid-state battery of the present disclosure

Claims

1. A solid-state battery having, in this order, a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer, the first current collector layer and the second current collector layer have extending portions extending outwardly beyond the first active material layer, the solid electrolyte layer, and the second active material layer over the entire periphery of the first active material layer, the solid electrolyte layer, and the second active material layer, the first current collector layer and the second current collector layer are bonded to each other via a thermoplastic resin layer between their extended portions, (i) the first active material layer and the solid electrolyte layer have an extending portion that extends outwardly beyond the second active material layer around the entire periphery of the second active material layer, and the extending portion of the solid electrolyte layer and the second current collector layer are bonded to each other via the thermoplastic resin layer, or (ii) the first active material layer has an extending portion that extends outwardly beyond the second active material layer and the solid electrolyte layer around the entire periphery of the second active material layer and the solid electrolyte layer, and the extending portion of the first active material layer and the second current collector layer are bonded to each other via the thermoplastic resin layer, the first current collector layer, the first active material layer, the solid electrolyte layer, the second active material layer, and the second current collector layer are sealed by a first insulating film laminated on an outer surface of the first current collector layer and a second insulating film laminated on an outer surface of the second current collector layer, the thermoplastic resin layer has an extension portion extending outward beyond the first current collector layer and the second current collector layer over the entire periphery of the first current collector layer and the second current collector layer, a first current collecting tab laminated on the outer surface of the first current collecting layer or a protruding portion of the first current collecting layer protrudes from the first and second insulating films beyond the extending portion of the thermoplastic resin layer, a second current collecting tab laminated on the outer surface of the second current collecting layer or a protruding portion of the second current collecting layer protrudes from the first and second insulating films beyond the extending portion of the thermoplastic resin layer; and the first current collecting tab or the protruding portion of the first current collecting layer and the second current collecting tab or the protruding portion of the second current collecting layer are offset from each other in a plane direction of the solid-state battery, thereby being insulated from each other; solid state battery.

2. 2. The solid state battery according to claim 1, wherein a thickness in a stacking direction from an outer surface of the first current collector layer to an outer surface of the second current collector layer is 0.05 mm or more and 2.0 mm or less.

3. A method for producing the solid state battery of claim 1 or 2, comprising: forming an unsealed solid-state battery by stacking the first current collector layer, the first active material layer, the solid electrolyte layer, the second active material layer, and the second current collector layer in this order while disposing a thermoplastic resin annular sealing member between the extended portion of the first current collector layer and the extended portion of the second current collector layer over the entire periphery thereof; and The unsealed solid-state battery is hot-pressed in a state in which the air pressure in the inner space of the thermoplastic resin annular sealing member is lower than the air pressure in the outer space of the thermoplastic resin annular sealing member, causing the thermoplastic resin annular sealing member to flow into at least the inner space, thereby forming the thermoplastic resin layer.

4. 4. The method according to claim 3, wherein the unsealed solid-state battery is hot-pressed in a state in which the air pressure in the inner space of the thermoplastic resin annular sealing member is equal to or lower than atmospheric pressure, causing the thermoplastic resin annular sealing member to flow at least toward the inner periphery, thereby forming the thermoplastic resin layer.

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