Electrochemical cell and method for manufacturing electrochemical cell

Abstract

To provide an electrochemical cell having an excellent discharge characteristics.SOLUTION: The present invention provides an electrochemical cell 1 comprising: an exterior body 2 comprising a positive electrode exterior member 10 and a negative electrode exterior member 20 that forms a housing space 4 between the positive electrode exterior member and the negative electrode exterior member 20; and an electrode body 3 that includes a positive electrode 30 and a negative electrode 50 disposed in such a way as to face each other with an electrolyte 40 interposed therebetween and is housed in a housing space. The negative electrode includes: a sheet-like 51 including at least metallic lithium or a lithium alloy; and a negative electrode current collector 55 that is welded to the negative electrode exterior member and in close contact with a lithium portion. The negative electrode current collector includes a current collector body 56 disposed between the lithium portion and the positive electrode, and a SEI film 60 is formed on an entire surface of a facing surface 51b of the lithium portion facing the current collector body.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrochemical cell and a method for manufacturing an electrochemical cell. [Background technology]

[0002] Electrochemical cells such as lithium-ion secondary batteries and electrochemical capacitors have been widely used as power sources for small electronic devices and wearable devices, including wristwatches, smartwatches, smartphones, headsets, and hearing aids. In recent years, there has been an increasing demand for smaller, thinner electrochemical cells of this type. One reason for this is that, as the performance of ICs (integrated circuits) mounted on various electronic devices has improved due to their ultra-miniaturization and reduced power consumption, electronic devices equipped with unprecedented high-spec functions have begun to be proposed.

[0003] As an example of this type of electrochemical cell, Patent Document 1 discloses a thin battery including first and second exterior members made of stainless steel and a power generating element housed between the first and second exterior members. The power generating element is constructed by laminating a positive electrode made of a composite oxide of lithium and a transition metal, a solid electrolyte, and a negative electrode made of metallic lithium.

[0004] Furthermore, as an electrochemical cell using metallic lithium as the negative electrode, for example, Patent Document 2 below discloses a technique in which a thick metallic lithium material is crimped to a negative electrode can (exterior member) using a crimping punch or the like. In this case, the metallic lithium material can be rolled, and the metallic lithium film can be evenly adhered to the negative electrode can. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-15004 [Patent Document 2] Japanese Patent Application Publication No. 1-231266 Summary of the Invention [Problem to be solved by the invention]

[0006] Generally, metallic lithium has the property of easily oxidizing in air, and therefore an oxide film is easily formed on the surface of metallic lithium. As a result, for example, contact resistance due to the oxide film occurs between metallic lithium and the current collector, making it difficult to increase the discharge current. In particular, rolling metallic lithium has the advantage of improving adhesion to the current collector, but the area exposed to air increases, making it easier for an oxide film to form on the surface of the metallic lithium, which makes the above-mentioned problems more likely to occur. The same problems as described above also occur between metallic lithium and the solid electrolyte or separator, so there is room for improvement.

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an electrochemical cell having excellent discharge characteristics and a method for manufacturing the electrochemical cell. [Means for solving the problem]

[0008] (1) An electrochemical cell according to the present invention comprises: an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms a storage space between the positive electrode exterior member and the exterior body; and an electrode body having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween and accommodated in the storage space, wherein the negative electrode includes a sheet-like lithium part containing at least metallic lithium or a lithium alloy, and a negative electrode current collector welded to the negative electrode exterior member and in close contact with the lithium part, and the negative electrode current collector includes a current collector body that is arranged between the lithium part and the positive electrode, and an SEI film is formed over the entire surface of the lithium part that faces the current collector body.

[0009] In the electrochemical cell according to the present invention, the negative electrode current collector is welded to the negative electrode exterior member, allowing the two to be integrated while maintaining high electrical conductivity. Furthermore, the current collector body of the negative electrode current collector is in close contact with the surface facing the lithium portion. In particular, an SEI film (Solid Electrolyte Interphase film) is formed over the entire surface of the surface facing the lithium portion, preventing the formation of an oxide film. Therefore, since the lithium portion and the current collector body can be in close contact with each other via the SEI film, the contact resistance between the lithium portion and the current collector body can be reduced, and high electrical conductivity can be ensured, compared to when the lithium portion and the current collector body are in close contact with each other via an oxide film.

[0010] Therefore, the discharge current can be increased, resulting in an electrochemical cell with excellent discharge characteristics. Furthermore, since the sheet-shaped lithium portion is used, the negative electrode itself can be made thin, and since the negative electrode current collector is directly welded to the negative electrode exterior member, it can be easily constructed with a small number of parts. Therefore, an electrochemical cell with a thin overall shape can be obtained.

[0011] (2) The negative electrode current collector may include a first negative electrode current collector disposed between the lithium portion and the negative electrode exterior member, and a second negative electrode current collector formed integrally with the first negative electrode current collector, disposed between the lithium portion and the positive electrode, and functioning as the current collector main body, wherein the first negative electrode current collector is welded to the negative electrode exterior member, the lithium portion is positioned via a weld of the first negative electrode current collector and disposed in a state of being sandwiched between the first negative electrode current collector and the second negative electrode current collector, and the SEI film may be formed on a surface of the lithium portion facing the second negative electrode current collector.

[0012] In this case, the first negative electrode current collector disposed between the lithium part and the negative electrode exterior member is welded to the negative electrode exterior member. This allows the negative electrode current collector and the negative electrode exterior member to be more reliably joined together without being affected by the size of the lithium part, thereby maintaining high electrical conductivity. In particular, an anchor effect occurs around the welded portion of the first negative electrode current collector formed during welding due to surface activation of the negative electrode exterior member by heating. Therefore, the anchor effect can be utilized to position the lithium part and sandwich it between the first negative electrode current collector and the second negative electrode current collector. This allows the entire electrode assembly to be accommodated in a more stable position within the accommodation space, resulting in stable battery performance.

[0013] (3) The negative electrode may further include a negative electrode active material layer capable of absorbing lithium ions, the negative electrode active material layer being formed on the current collector body and in close contact with the lithium portion.

[0014] In this case, the electrochemical cell can be used as a lithium-ion secondary battery that appropriately charges and discharges using the redox reaction caused by the absorption and desorption of lithium ions. In particular, the SEI film can be used to ensure high conductivity between the lithium part and the negative electrode active material.

[0015] (4) A solid electrolyte that moves lithium ions during charging and discharging may be disposed between the positive electrode and the negative electrode as the electrolyte.

[0016] In this case, the electrochemical cell can be used as, for example, an all-solid-state battery using a solid electrolyte.

[0017] (5) A method for producing an electrochemical cell according to the present invention is a method for producing an electrochemical cell including an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms a storage space between the positive electrode exterior member and the exterior body, and an electrode body having a positive electrode and a negative electrode that are arranged to face each other via an electrolyte and that is housed in the storage space, the method comprising: placing a block-shaped lithium part containing at least metallic lithium or a lithium alloy on an inner surface of the negative electrode exterior member; and depositing an SEI film-forming agent on a surface of the lithium part that faces a surface that contacts the inner surface. a step of pressing the lithium part from the opposing surface side to roll the lithium part into a sheet shape and diffusing the SEI film-forming agent in a planar shape to form an SEI film over the entire surface of the opposing surface; a step of setting a negative electrode current collector so as to be located between the lithium part and the positive electrode and welding the negative electrode current collector to the negative electrode exterior member, wherein a current collector body of the negative electrode current collector that is located between the lithium part and the positive electrode is in close contact with the lithium part via the SEI film.

[0018] According to the method for producing an electrochemical cell of the present invention, a block-shaped lithium part placed on the inner surface of a negative electrode exterior member is pressed from the opposing surface side (e.g., by pressing), thereby rolling it into a sheet. This makes it possible to form a sheet-shaped lithium part at low cost. Specifically, unlike when a lithium part is formed by sputtering, vapor deposition, or the like, a sheet-shaped lithium part can be obtained by a simple method of simply pressing a block-shaped lithium part. Therefore, the entire electrochemical cell can be produced at low cost. Furthermore, since the SEI film forming agent can be spread on the surface at the same time as the block-shaped lithium part is pressed, the SEI film (Solid Electrolyte Interphase film) can be formed at the stage when the sheet-shaped lithium part is formed. Therefore, the SEI film can be properly formed before the oxide film forms on the lithium part.

[0019] Furthermore, since the negative electrode current collector is welded to the negative electrode exterior member, the two can be integrated while maintaining high electrical conductivity. Furthermore, since the lithium part and the current collector body can be closely attached via the SEI film, the contact resistance between the lithium part and the current collector body can be reduced compared to when the lithium part and the current collector body are closely attached via an oxide film, and high electrical conductivity can be ensured. Therefore, the discharge current can be increased, resulting in an electrochemical cell with excellent discharge characteristics. Furthermore, since the sheet-shaped lithium portion is used, the negative electrode itself can be made thin, and since the negative electrode current collector is directly welded to the negative electrode exterior member, it can be easily constructed with a small number of parts. Therefore, an electrochemical cell with a thin overall shape can be obtained.

[0020] (6) A method for producing an electrochemical cell according to the present invention is a method for producing an electrochemical cell including an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member forming an accommodation space between the positive electrode exterior member and the exterior body, and an electrode body having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween and accommodated in the accommodation space, the method including the steps of: setting a negative electrode current collector having a first negative electrode current collector and a second negative electrode current collector integrally formed with each other such that the first negative electrode current collector is placed on the inner surface of the negative electrode exterior member; and welding the inner surface and the first negative electrode current collector together; and positioning a block-shaped lithium part containing at least metallic lithium or a lithium alloy on the welded first negative electrode current collector via the welded part of the first negative electrode current collector. the second anode current collector is placed in a welded state and an SEI film-forming agent is allowed to remain on the surface of the lithium part that faces the contact surface with the first anode current collector; the lithium part is pressed from the side of the facing surface to roll the lithium part into a sheet shape and the SEI film-forming agent is spread in a planar shape to form an SEI film over the entire facing surface; and the second anode current collector is set so as to be located between the lithium part and the positive electrode, wherein the lithium part is positioned via the weld and disposed in a sandwiched state between the first anode current collector and the second anode current collector, and the second anode current collector is in close contact with the lithium part via the SEI film.

[0021] According to the method for manufacturing an electrochemical cell of the present invention, the first negative electrode current collector is welded to the negative electrode exterior member, so the negative electrode current collector and the negative electrode exterior member can be more reliably joined together without being affected by the size of the lithium part, and high conductivity can be maintained. In particular, an anchor effect occurs in the welded portion of the first negative electrode current collector due to surface activation of the negative electrode exterior member by heating. Therefore, when a block-shaped lithium part is placed, the anchor effect can be utilized to position the lithium part. This leads to a more stable positioning of the entire electrode assembly within the storage space, resulting in stable battery performance.

[0022] Furthermore, since a sheet-shaped lithium part can be obtained by the simple method of simply pressing a block-shaped lithium part, the entire electrode chemical cell can be manufactured inexpensively. Furthermore, since the SEI film-forming agent can be diffused into a planar shape simultaneously with pressing the block-shaped lithium part, an SEI film (Solid Electrolyte Interphase film) can be formed at the stage of forming the sheet-shaped lithium part. Therefore, the SEI film can be properly formed before an oxide film forms on the lithium part. Furthermore, since the lithium part and the second negative electrode current collector can be closely attached via the SEI film, high conductivity can be ensured. Therefore, the discharge current can be increased, resulting in an electrochemical cell with excellent discharge characteristics. Furthermore, since the sheet-shaped lithium portion is used, the negative electrode itself can be made thin, and since the negative electrode current collector is directly welded to the negative electrode exterior member, it can be simply constructed with a small number of parts. Therefore, an electrochemical cell with an overall thin design can be obtained. [Effects of the Invention]

[0023] According to the present invention, an electrochemical cell can be obtained that is excellent in discharge characteristics and is thin. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view showing a first embodiment of a secondary battery (electrochemical cell) according to the present invention. [Figure 2] 2 is a longitudinal cross-sectional view of the secondary battery taken along line AA shown in FIG. [Figure 3] 3 is a vertical cross-sectional view of the positive electrode exterior member and the first sealing material shown in FIG. 2. FIG. [Figure 4] FIG. 4 is an enlarged longitudinal cross-sectional view of the periphery of the heating region shown in FIG. 3. [Figure 5] 3 is a vertical cross-sectional view of the negative electrode exterior member and the second sealing material shown in FIG. 2. FIG. [Figure 6] FIG. 3 is a plan view of the negative electrode shown in FIG. [Figure 7]FIG. 3 is a perspective view of the positive electrode shown in FIG. 2. [Figure 8] FIG. 3 is a diagram showing one step in the production of the secondary battery shown in FIG. 2, and is a vertical cross-sectional view showing a state in which a block-shaped lithium part is placed on the bottom wall part of the negative electrode exterior member and an SEI film-forming agent is placed on the opposing surface. [Figure 9] FIG. 9 is a vertical cross-sectional view showing a state in which the block-shaped lithium part shown in FIG. 8 is pressed to form a sheet-shaped lithium part, and an SEI film is formed on the opposing surface. [Figure 10] 10 is a vertical cross-sectional view showing a state in which a negative electrode current collector is set on the sheet-like lithium part shown in FIG. 9 and the negative electrode current collector and a negative electrode exterior member are welded together. FIG. [Figure 11] 11 is a vertical cross-sectional view showing a state in which a solid electrolyte is set on the negative electrode current collector shown in FIG. 10 and a positive electrode is set on the solid electrolyte. FIG. [Figure 12] FIG. 4 is a vertical cross-sectional view showing a state in which a positive electrode exterior member is superimposed on a negative electrode exterior member from above. [Figure 13] FIG. 2 is a longitudinal sectional view showing a second embodiment of a secondary battery (electrochemical cell) according to the present invention. [Figure 14] FIG. 14 is a diagram showing one step in the production of the secondary battery shown in FIG. 13, and is a vertical cross-sectional view showing a state in which a first negative electrode current collector is placed on the bottom wall portion of the negative electrode exterior member and the first negative electrode current collector and the negative electrode exterior member are welded together. [Figure 15] 15 is a vertical cross-sectional view showing a state in which a block-shaped lithium portion is placed on the first negative electrode current collector shown in FIG. 14 and an SEI film-forming agent is placed on the opposing surface. FIG. [Figure 16] FIG. 16 is a vertical cross-sectional view showing a state in which the block-shaped lithium part shown in FIG. 15 is pressed to form a sheet-shaped lithium part, and an SEI film is formed on the opposing surface. [Figure 17] 17 is a vertical cross-sectional view showing a state in which a second negative electrode current collector is set on the sheet-like lithium part shown in FIG. 16. FIG. [Figure 18] FIG. 2 is a perspective view of a secondary battery showing a modified example of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] (First embodiment) Hereinafter, an embodiment of an electrochemical cell according to the present invention will be described with reference to the drawings. In this embodiment, a lithium ion secondary battery (hereinafter simply referred to as a secondary battery), which is a type of non-aqueous electrolyte secondary battery, will be described as an example of the electrochemical cell.

[0026] 1 and 2, the secondary battery 1 of this embodiment is a small and ultra-thin battery (a so-called paper battery) and includes a metal exterior body 2 and an electrode body (power generating element) 3 housed inside the exterior body 2. In the illustrated example, the secondary battery 1 has an external shape that is square in plan view. However, this is not limited to this case, and the external shape of the secondary battery 1 may be changed as appropriate. For example, the shape may be circular, elliptical, polygonal, L-shaped, or the like in plan view, depending on the installation space and application of various electronic devices in which the secondary battery 1 is mounted.

[0027] The exterior body 2 includes a metallic positive electrode exterior member 10 and a metallic negative electrode exterior member 20 that is sealed to the positive electrode exterior member 10 and forms an accommodation space 4 between itself and the positive electrode exterior member 10. The electrode body 3 has a positive electrode 30 and a negative electrode 50 arranged to face each other with a solid electrolyte 40 interposed therebetween, and is housed in a housing space 4 formed inside the exterior body 2.

[0028] In this embodiment, the axis that passes through the center of the exterior body 2 and extends in the vertical direction is referred to as the battery axis O. In addition, in a plan view seen from the direction of the battery axis O, the direction that intersects with the battery axis O is referred to as the radial direction, and the direction that goes around the battery axis O is referred to as the circumferential direction. Furthermore, in Fig. 2, the direction from the negative electrode exterior member 20 toward the positive electrode exterior member 10 along the battery axis O is referred to as the upward direction, and the opposite direction is referred to as the downward direction. Note that Fig. 1 and Fig. 2 illustrate the secondary battery 1 in a state in which it is turned upside down. That is, Fig. 1 illustrates the secondary battery 1 in a state in which it is turned upside down so that the negative electrode exterior member 20 shown in Fig. 2 faces upward.

[0029] (exterior body) The exterior body 2 will now be described in detail. 1 and 2, the positive electrode exterior member 10 is formed in the shape of a thin sheet and is formed in a square shape in a plan view. The positive electrode exterior member 10 is disposed above the negative electrode exterior member 20 and the electrode body 3. The thickness of the positive electrode exterior member 10 is, for example, about 0.01 mm to 0.30 mm. However, in each drawing, the thickness of the positive electrode exterior member 10 is exaggerated to make it easier to see the positive electrode exterior member 10. The positive electrode exterior member 10 functions as an external connection terminal for the positive electrode that is electrically connected to the electrode body 3.

[0030] Stainless steel, for example, is preferably used as a specific metal material for the positive electrode exterior member 10. However, the material for the positive electrode exterior member 10 is not limited to stainless steel, and other metal materials, clad materials, etc. may also be used.

[0031] Examples of stainless steel include ferritic stainless steels such as SUS430 and SUS444, austenitic-ferritic duplex stainless steels such as SUS329J4L, and various austenitic stainless steels such as SUS201, SUS202, SUS303, SUS304, SUS305, SUS316, SUS317, SUS321, and SUS347.

[0032] In particular, when the secondary battery 1 of this embodiment is used in applications such as a watch with a built-in magnetic sensor, an electronic compass using a magnetic sensor, or a biosensor that detects the internal magnetic fields of otoliths and the organs containing them, it is preferable that the metallic material for the positive electrode exterior member 10 be highly corrosion-resistant and nonmagnetic. In this case, it is preferable to use austenitic stainless steel, which contains more Cr and Ni as its main components than other components, as the positive electrode exterior member 10. In this case, for example, so-called highly corrosion-resistant super stainless steels such as UNS S32053 and UNS N08354, which are based on the UNS standard (Unified Numbering System), may also be used.

[0033] 1 and 2, the negative electrode exterior member 20 is formed in a square shape in plan view and in a cylindrical shape with a bottom that opens upward, and is disposed below the positive electrode exterior member 10 with the electrode body 3 sandwiched therebetween. The thickness of the negative electrode exterior member 20 is uniform throughout and is approximately the same as that of the positive electrode exterior member 10. Note that in each drawing, the thickness of the negative electrode exterior member 20 is also illustrated exaggerated.

[0034] Specifically, the negative electrode exterior member 20 is formed in a bottomed cylindrical shape having a bottom wall portion 21, a peripheral wall portion 22 extending upward from the peripheral edge of the bottom wall portion 21, and a flange portion 23 extending radially outward from the upper end of the peripheral wall portion 22. The negative electrode exterior member 20 functions as an external connection terminal for the negative electrode that is electrically connected to the electrode body 3. The specific metal material of the negative electrode exterior member 20 may be the same as or a different type of metal material from that of the positive electrode exterior member 10. However, it is preferable to use stainless steel, particularly austenitic stainless steel, as the negative electrode exterior member 20.

[0035] As shown in FIGS. 2 and 3, a ring-shaped first sealing material 5 extending continuously in the circumferential direction is fixed to the lower surface of the outer peripheral edge portion of the positive electrode exterior member 10 configured as described above, over the entire circumference of the positive electrode exterior member 10. The first sealing material 5 is not limited to a particular material, but is, for example, a thermoplastic resin. In particular, it is preferable to use PFA resin, which has excellent moisture permeation suppression properties, as the first sealing material 5. PFA resin (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) is classified as a thermoplastic resin and is included in the so-called fluororesin. In addition to being excellent at suppressing moisture permeation, it also has excellent properties such as heat resistance, cold resistance, water repellency, and chemical resistance.

[0036] The first sealing material 5 is formed in a ring shape having an outer shape that is square in plan view so as to fit along the outer peripheral edge of the positive electrode exterior member 10. The first sealing material 5 is fixed to the lower surface of the positive electrode exterior member 10 by laser welding. Specifically, a laser beam is irradiated from above the positive electrode exterior member 10 to heat the interface between the lower surface of the positive electrode exterior member 10 and the upper surface of the first sealing material 5. This laser heating bonds the positive electrode exterior member 10 and the first sealing material 5 together by laser welding. In particular, by irradiating the positive electrode exterior member 10 and the first sealing member 5 with a laser beam over the entire periphery, the positive electrode exterior member 10 and the first sealing member 5 are fixed together over the entire periphery by laser welding. In each drawing including FIG. 2, the heated region M heated by irradiation with the laser beam is schematically shown by a thick line.

[0037] During laser welding, the so-called workpiece movement method may be used, in which the laser welding is performed while moving the positive electrode outer casing member 10, which is the workpiece to be welded, with a laser irradiator (not shown) fixed, or the so-called head movement method may be used, in which the positive electrode outer casing member 10, which is the workpiece to be welded, is fixed and the laser irradiator is moved while laser welding is performed. As the laser irradiator, for example, a laser irradiator such as a fiber laser or a YAG laser, or a galvano scanning type laser irradiator or the like may be used.

[0038] In particular, in this embodiment, the laser beam is irradiated from above the positive electrode exterior member 10, and therefore, as shown in Figures 1 and 4, laser marks 6 are formed on the upper surface of the positive electrode exterior member 10. The laser marks 6 are formed continuously around the entire circumference of the positive electrode exterior member 10. Note that the laser marks 6 are exaggerated in Figure 4.

[0039] The laser mark 6 includes a heat-affected zone (HAZ) formed around the heated region M heated by irradiation with a laser beam. The heat-affected zone is a part (region) that has a structure (composition) different from the original structure due to the influence of heating or alteration caused by oxidation, etc. 4, in the heated region M heated by the irradiation of the laser beam, an anchor effect is generated due to surface activation of the underside of the positive electrode exterior member 10. This makes it possible to bond the positive electrode exterior member 10 and the first sealing member 5 with high welding strength.

[0040] Similar to the positive electrode exterior member 10, a ring-shaped second sealing material 7 extending continuously in the circumferential direction is fixed to the upper surface of the flange portion 23 of the negative electrode exterior member 20 around the entire circumference of the flange portion 23, as shown in FIGS. 2 and 5 . The second sealing material 7 is made of the same material as the first sealing material 5, and is formed in a ring shape having a square outer shape in plan view so as to fit along the flange portion 23 of the negative electrode exterior member 20. The second sealing material 7 is fixed to the upper surface of the flange portion 23 by laser welding. Specifically, a laser beam is irradiated from below the flange portion 23, thereby laser heating the interface between the upper surface of the flange portion 23 and the lower surface of the second sealing material 7. As a result, the flange portion 23 and the second sealing material 7 are fixed to each other over the entire periphery by laser welding.

[0041] Therefore, in the heated region heated by the irradiation of the laser beam, an anchor effect occurs due to surface activation of the upper surface of the flange portion 23. As a result, it is possible to bond the flange portion 23 and the second sealing material 7 with high welding strength. The laser welding method is the same as that for the positive electrode exterior member 10. Furthermore, laser marks (not shown) are formed on the lower surface of the flange portion 23.

[0042] 1 and 2, the positive electrode exterior member 10 and the flange portion 23 of the negative electrode exterior member 20 are welded and sealed to each other via thermal welding of the first sealing material 5 and the second sealing material 7. The first sealing material 5 fixed to the positive electrode exterior member 10 and the second sealing material 7 fixed to the flange portion 23 of the negative electrode exterior member 20 are made of the same material, and therefore the interface between them is melted by thermal welding, resulting in strong adhesion. As a result, the positive electrode exterior member 10 and the flange portion 23 of the negative electrode exterior member 20 are integrated while being melted to each other over the entire periphery. 2, for ease of viewing, the first sealing material 5 and the second sealing material 7 are shown separately. In reality, the first sealing material 5 and the second sealing material 7 are melted together and exist as a single, unified resin.

[0043] (electrode body) 2, the electrode body 3 is housed in a sealed state in a housing space 4 formed inside the exterior housing 2. Specifically, the electrode body 3 is housed in a state where it is sandwiched between the bottom wall portion 21 of the negative electrode exterior member 20 and the positive electrode exterior member 10 in the direction of the battery axis O. The electrode assembly 3 includes a positive electrode 30, a negative electrode 50, and a solid electrolyte (electrolyte according to the present invention) 40 disposed between the positive electrode 30 and the negative electrode 50, and is stacked in the direction of the battery axis O. Therefore, the positive electrode 30 and the negative electrode 50 are disposed so as to face each other in the direction of the battery axis O with the solid electrolyte 40 sandwiched between them.

[0044] (negative electrode) First, the negative electrode 50 will be described. As shown in FIG. 2, the negative electrode 50 includes a sheet-like lithium part 51 and a negative electrode current collector 55 joined to the negative electrode exterior member 20 by welding. The lithium portion 51 is formed in a thin sheet shape, and is formed, for example, in a square shape in plan view, corresponding to the shape of the secondary battery 1. The sheet-like lithium portion 51 is made of metallic lithium or a lithium alloy. Examples of the lithium alloy that can be used include a lithium-aluminum (Li-Al) alloy and a lithium-silicon (Li-Si) alloy. The thickness of the sheet-like lithium portion 51 is, for example, 1 to 100 μm, and preferably about 5 to 20 μm. In addition, in each of the drawings including FIG. 2, the thickness of the sheet-like lithium portion 51 is exaggerated.

[0045] The sheet-like lithium portion 51 is placed on the inner surface of the bottom wall portion 21 of the negative electrode exterior member 20. At this time, the entire placing surface (lower surface) 51a of the sheet-like lithium portion 51 is in close contact with the inner surface of the bottom wall portion 21. In particular, sheet-like lithium portion 51 is formed into a sheet by rolling block-like lithium portion 51 by applying pressure by press working or the like. Therefore, mounting surface 51a of sheet-like lithium portion 51 is in close contact with the inner surface of bottom wall portion 21.

[0046] The upper surface of the sheet-like lithium portion 51 is an opposing surface 51b that faces the current collector body 56 of the negative electrode current collector 55 in the direction of the battery axis O. An SEI film (Solid Electrolyte Interphase film) 60 is formed over the entire surface of this opposing surface 51b. The SEI film 60 is formed by an SEI film forming agent 70, which will be described later, and functions as a protective film containing, for example, an inorganic lithium compound or an organic compound.

[0047] As shown in FIGS. 2 and 6, the negative electrode current collector 55 is formed to a size that covers the entire sheet-like lithium portion 51 from above, and is formed, for example, in a rectangular shape in plan view. The portion of the negative electrode current collector 55 that covers the sheet-like lithium portion 51 from above and is disposed between the sheet-like lithium portion 51 and the positive electrode 30 functions as a current collector main body 56 .

[0048] A remaining portion 57 of the negative electrode current collector 55 other than the current collector body 56 is welded to the inner surface of the bottom wall portion 21 of the negative electrode exterior member 20 via a weld 61 in contact with the inner surface from above. The method for welding the negative electrode current collector 55 to the bottom wall portion 21 is not particularly limited, and examples of methods that can be used include laser welding, ultrasonic welding, and seam welding. As a result, the negative electrode current collector 55 and the negative electrode exterior member 20 are integrated together while maintaining high electrical conductivity between them, and therefore the negative electrode exterior member 20 can function as an external connection terminal for the negative electrode.

[0049] The negative electrode current collector 55 is formed in the form of a thin sheet (metal foil) using various metal materials. Examples of metal materials suitable for the negative electrode current collector 55 include copper, copper alloy, nickel, and stainless steel. The thickness of the negative electrode current collector 55 is, for example, about 4 μm to 20 μm. In addition, in each drawing including FIG. 2, the thickness of the negative electrode current collector 55 is exaggerated.

[0050] For the negative electrode current collector 55, it is preferable to use a smooth metal foil generally called a plain foil, or a foil with a rough surface having irregularities generated during production by electrolytic deposition, a foil whose surface has been roughened by etching, or a foil whose surface has been roughened by embossing with an irregular roll. Furthermore, the negative electrode current collector 55 may be modified, including surface roughening, by a vertically driven punch other than a roll.

[0051] 6, a plurality of through holes 62 penetrating the negative electrode current collector 55 in the thickness direction are formed over the entire surface of the negative electrode current collector 55. In the example shown in the figure, the through holes 62 formed in a slit shape are arranged in a so-called staggered pattern over the entire surface of the negative electrode current collector 55. However, the shape and arrangement of the through holes 62 are not limited to these cases.

[0052] Furthermore, a negative electrode active material layer 63 capable of absorbing lithium ions is coated on the main surface of the negative electrode current collector 55. The negative electrode active material layer 63 is coated on one surface of the negative electrode current collector 55 facing the solid electrolyte 40. Note that the negative electrode active material layer 63 is not shown in FIG. The negative electrode active material layer 63 is applied to, for example, a portion of the negative electrode current collector 55 that functions as the current collector body 56, and the remaining portion 57 that is welded to the bottom wall portion 21 is left uncoated.

[0053] The negative electrode active material layer 63 is formed, for example, by applying a coating liquid (slurry) containing constituent materials for forming the negative electrode active material layer 63 to the negative electrode current collector 55, and then drying the coating liquid at a predetermined temperature for a predetermined time. As a material for forming the negative electrode active material layer 63, a negative electrode slurry (coating liquid) can be prepared by mixing the negative electrode active material with a conductive additive (e.g., carbon black, graphite, etc.), a binder (e.g., a dispersion of styrene-butadiene rubber (SBR)), a thickener (e.g., cellulose nanofiber (CNF), carboxymethyl cellulose (CMC), etc.), and a solvent (e.g., any solvent such as pure water). The negative electrode active material layer 63 can be formed by applying the negative electrode slurry to the negative electrode current collector 55 and drying it. Examples of the negative electrode active material include silicon, silicon oxide, graphite (including needle coke and MCMB), hard carbon, lithium titanate (LTO), LiAl, and the like, either singly or in mixture.

[0054] 2 , in the negative electrode 50 configured as described above, the current collector body 56 of the negative electrode current collector 55 is in close contact with the lithium part 51 via the SEI film 60. In this embodiment, an electrode layer 65 is formed between the lithium part 51 and the current collector body 56. The electrode layer 65 is formed, for example, on the surface of the negative electrode current collector 55 opposite to the surface on which the negative electrode active material layer 63 is formed. As a result, the current collector body 56 of the negative electrode current collector 55 is in close contact with the lithium part 51 via the electrode layer 65. 2 and other drawings, the thickness of the electrode layer 65 is exaggerated. Furthermore, the electrode layer 65 is not essential and may not be provided.

[0055] (positive electrode) 2 and 7, the positive electrode 30 is disposed in a state where it is sandwiched between the solid electrolyte 40 and the positive electrode exterior member 10 in the direction of the battery axis O. The positive electrode 30 includes a positive electrode current collector 31 and a positive electrode active material layer 32 coated on one surface of the positive electrode current collector 31 facing the solid electrolyte 40. In FIG. 2, the positive electrode active material layer 32 is omitted.

[0056] The positive electrode current collector 31 is formed in the form of a thin sheet (metal foil) made of various metal materials and is formed in a square shape in a plan view. Metal materials suitable for the positive electrode current collector 31 include, for example, aluminum, aluminum alloy, and stainless steel. The thickness of the positive electrode current collector 31 is, for example, about 4 μm to 20 μm. In addition, in each drawing including FIG. 2, the thickness of the positive electrode current collector 31 is exaggerated.

[0057] As with the negative electrode current collector 55, the positive electrode current collector 31 may preferably be a smooth metal foil generally called a plain foil, or may be a foil with a rough surface having irregularities generated during production by electrolytic deposition, a foil whose surface has been roughened by etching, or a foil whose surface has been roughened by embossing with an irregular roll. Furthermore, the positive electrode current collector 31 may be modified, including surface roughening, by a vertically driven punch other than a roll. The positive electrode current collector 31 does not necessarily need to have the through-holes 62 formed therein.

[0058] As a material for forming the positive electrode active material layer 32, a positive electrode slurry (coating liquid) can be prepared by mixing a conductive additive (e.g., carbon black, graphite, etc.), a binder (e.g., polyvinylidene fluoride, etc.), and a solvent (e.g., any solvent such as N-methylpyrrolidone) in addition to the positive electrode active material. The positive electrode active material layer 32 can be formed by applying the positive electrode slurry to the positive electrode current collector 31 and drying it. Examples of the positive electrode active material include composite oxides containing lithium and transition metals, such as nickel-manganese-cobalt lithium oxide (NMC), nickel-cobalt lithium aluminum oxide (NCA), lithium titanate (LTO), and lithium manganese oxide (LMO).

[0059] 2, the positive electrode 30 configured as described above is electrically connected to the positive electrode exterior member 10. Examples of the electrical connection include contact via a carbon-based material, welding of metals to each other, or contact of metals to each other. In the illustrated example, a conductive paste 33 is formed by coating or the like on the inner surface of the positive electrode exterior member 10. The positive electrode 30 is in contact with the conductive paste 33 over the entire surface, and is therefore electrically connected to the positive electrode exterior member 10 via the conductive paste 33. This allows the positive electrode exterior member 10 to function as an external connection terminal for the positive electrode. In addition, in each drawing including FIG. 2, the thickness of the conductive paste 33 is exaggerated.

[0060] However, when the positive electrode 30 is electrically connected to the positive electrode exterior member 10, for example, a positive electrode terminal tab may be formed on a part of the positive electrode current collector 31, and this positive electrode terminal tab may be electrically connected directly or indirectly to the positive electrode exterior member 10.

[0061] (solid electrolyte) As shown in FIG. 2, a solid electrolyte 40 that allows lithium ions to move during charging and discharging is disposed between the negative electrode 50 and the positive electrode 30. The solid electrolyte 40 is formed in a sheet shape and may be, for example, an oxide-based solid electrolyte or a sulfide-based solid electrolyte. The composition of the solid electrolyte 40 may be any known composition and is not limited to a specific composition. In each of the drawings including FIG. 2, the thickness of the solid electrolyte 40 is exaggerated.

[0062] (Action of secondary batteries) 1 and 2, the secondary battery 1 configured as described above can be electrically connected to the outside through the positive electrode exterior member 10 and the negative electrode exterior member 20, which function as external connection terminals for the positive electrode and the negative electrode. This allows the secondary battery 1 to be used.

[0063] In particular, since the positive electrode exterior member 10 and the negative electrode exterior member 20 are welded and sealed to each other via the first sealing material 5 and the second sealing material 7, the storage space 4 in which the electrode body 3 is housed can be properly sealed. Moreover, because the first sealing material 5 is laser welded to the outer peripheral edge of the positive electrode exterior member 10, the metal positive electrode exterior member 10 and the resin first sealing material 5 can be bonded together with high welding strength due to local melting and deformation of the positive electrode exterior member 10 during laser welding or an anchor effect (see FIG. 4) caused by surface activation of the positive electrode exterior member 10. Similarly, the metal negative electrode exterior member 20 and the resin second sealing material 7 can also be bonded together with high welding strength.

[0064] Furthermore, because the first sealing material 5 and the second sealing material 7, which are made of the same material, are heat-welded to each other, the positive electrode exterior member 10 and the negative electrode exterior member 20 can be welded and sealed while maintaining high sealing performance. Furthermore, when a moisture permeation suppressing resin such as PFA is used as the first sealing material 5 and the second sealing material 7, it is possible to prevent the intrusion of moisture (water) from the outside, and the inside of the accommodation space 4 can be sealed while maintaining even higher airtightness. This allows the accommodation space 4 to be reliably sealed, resulting in a high-quality secondary battery 1 with high operational reliability.

[0065] Therefore, the secondary battery 1 of this embodiment can provide reliable sealing. Furthermore, since there is no need to use multiple resins of different materials for sealing, it is possible to reduce the usage rate of resin in the secondary battery 1. Therefore, even in a high-temperature environment of, for example, 150°C or higher, deterioration of sealing due to deformation of the resin or the like can be suppressed, making it easier to maintain operational reliability.

[0066] If the positive electrode exterior member 10 and the negative electrode exterior member 20 are made of austenitic stainless steel, the exterior body 2 can be highly corrosion-resistant and non-magnetic. Therefore, the secondary battery 1 can be used in applications that require high reliability and non-magnetic properties, and can be suitably used as a power source for, for example, a watch with a built-in magnetic sensor, an electronic compass using a magnetic sensor, or a biosensor that detects the internal magnetism of otoliths and the organs containing them.

[0067] Furthermore, it can be easily recognized that the first sealing material 5 and the second sealing material 7 are fixed to the positive electrode exterior member 10 and the negative electrode exterior member 20 by the laser marks 6 formed on the outer peripheral edge portion of the positive electrode exterior member 10 and the flange portion 23 of the negative electrode exterior member 20. Therefore, it can be easily distinguished that the inside of the housing space 4 is reliably sealed and that the secondary battery 1 is of high quality with high operational reliability.

[0068] In particular, according to the secondary battery 1 of this embodiment, the negative electrode current collector 55 is welded to the negative electrode exterior member 20, so that the two can be integrated while maintaining high conductivity. Furthermore, the current collector body 56 of the negative electrode current collector 55 is in close contact with the opposing surface 51b of the lithium part 51 via the electrode layer 65. The SEI film 60 is formed over the entire opposing surface 51b of the lithium part 51, which prevents the formation of an oxide film. Therefore, the lithium part 51 and the current collector body 56 can be brought into close contact with each other via the electrode layer 65 and the SEI film 60, and therefore the contact resistance between the lithium part 51 and the current collector body 56 can be reduced compared to when the lithium part 51 and the current collector body 56 are brought into close contact with each other via, for example, an oxide film. Therefore, high conductivity can also be ensured between the lithium part 51 and the negative electrode current collector 55.

[0069] Therefore, the discharge current can be increased, and the secondary battery 1 can have excellent discharge characteristics. Furthermore, since the sheet-like lithium part 51 is used, the negative electrode 50 itself can be configured to be thin, and since the negative electrode current collector 55 is directly welded to the negative electrode exterior member 20, the battery can be simply configured with a small number of parts. Therefore, the secondary battery 1 can be configured to be thin overall.

[0070] As described above, the secondary battery 1 of this embodiment has excellent discharge characteristics and can be a thin battery (lithium ion secondary battery). In addition, the inside of the housing space 4 is securely sealed, resulting in a high-quality secondary battery 1 with high operational reliability. Furthermore, since the solid electrolyte 40 is used, the secondary battery 1 can be, for example, an all-solid-state battery.

[0071] (Secondary battery manufacturing method) Next, an example of a method for manufacturing the secondary battery 1 will be briefly described below. As shown in FIG. 8, after placing a block-shaped lithium part 51 on the inner surface of the bottom wall part 21 of the negative electrode exterior member 20, a step is performed in which an SEI film-forming agent 70 is allowed to remain on the opposing surface 51b of the lithium part 51 that faces the mounting surface 51a.

[0072] Specifically, after cutting out and processing block-shaped lithium portion 51 from the material of lithium portion 51, concave recessed portion 71 is formed on opposing surface (upper surface) 51b of block-shaped lithium portion 51. Recessed portion 71 is formed, for example, in the central portion of opposing surface 51b of lithium portion 51 so as to be recessed downward. However, the shape, formation position, number, etc. of the recessed portion 71 may be changed as appropriate. For example, the recessed portion 71 may be formed so as to be recessed downward in a hemispherical shape, or multiple recessed portions 71 may be formed evenly over the entire surface of the opposing surface 51b. At this stage, the thickness of the block-shaped lithium portion 51 is, for example, about 2 to 9 times the thickness of the sheet-shaped lithium portion 51 described above (for example, 1 to 100 μm, preferably about 5 to 20 μm).

[0073] Then, the block-shaped lithium part 51 with the recessed part 71 formed therein is placed in the center of the inner surface of the bottom wall part 21, and then the SEI film-forming agent 70 is accommodated in the recessed part 71 by, for example, pouring or dropping. This makes it possible to keep the SEI film-forming agent 70 on the opposing surface 51b of the block-shaped lithium part 51. It should be noted that, for example, an ionic liquid, lithium bis(fluorosulfonyl)imide (LiFSI), or the like can be used as the SEI film-forming agent 70. Furthermore, simultaneously with, or before or after, the above-described process, a process of previously fixing the second sealing material 7 to the flange portion 23 of the negative electrode exterior member 20 around the entire periphery by laser welding is performed.

[0074] Next, as indicated by arrow F1 in FIG. 8, the block-shaped lithium part 51 is pressed from above (the opposing surface 51b side) to roll the lithium part 51 into a sheet as shown in FIG. 9, and the SEI film-forming agent 70 is diffused in a planar manner to form an SEI film 60 over the entire surface of the opposing surface 51b. By pressing, the block-shaped lithium part 51 is rolled to about 1 / 2 to 1 / 9 of its original thickness, thereby forming the sheet-shaped lithium part 51. As a method of pressing, for example, it is possible to support the negative electrode exterior member 20 with a pressing jig (not shown), and then press the lithium part 51 using a pressing jig (not shown). However, the pressing method is not limited to this case.

[0075] Next, as shown in FIG. 10, a step is performed in which a negative electrode current collector 55 is set so as to be positioned between the lithium part 51 and the positive electrode 30 (see FIG. 1), and the negative electrode current collector 55 is welded to the negative electrode exterior member 20. Specifically, the negative electrode current collector 55 is placed so as to overlap the sheet-like lithium part 51 from above, and a remaining part 57 of the negative electrode current collector 55 other than the current collector main body 56 is brought into contact with the inner surface of the bottom wall part 21 of the negative electrode exterior member 20. Then, in this state, the remaining part 57 of the negative electrode current collector 55 that is in contact with the inner surface of the bottom wall part 21 is welded to the bottom wall part 21. This allows the negative electrode current collector 55 and the negative electrode exterior member 20 to be integrated together via the weld part 61. Moreover, the current collector body 56 of the negative electrode current collector 55 is in close contact with the sheet-like lithium portion 51 via the electrode layer 65 and the SEI film 60 .

[0076] Next, as shown in FIG. 11, the solid electrolyte 40 is placed on top of the negative electrode current collector 55, and the positive electrode 30 is placed on top of the solid electrolyte 40. 12, the positive electrode exterior member 10, in which the first sealing material 5 is fixed to the entire outer peripheral edge portion of the positive electrode exterior member 10 and the conductive paste 33 is formed, is overlapped from above on the negative electrode exterior member 20. Next, the first sealing material 5 and the second sealing material 7 are thermally welded together, thereby welding and sealing the positive electrode exterior member 10 and the negative electrode exterior member 20 while maintaining high sealing properties.

[0077] The method for thermally welding the first sealing material 5 and the second sealing material 7 is not particularly limited. For example, in addition to heating with a heater, methods such as heating by irradiation with a laser beam and induction heating using high frequency may be employed. By using these methods, heating can be performed locally and selectively in a shorter time than when heating is performed with a heater, and thermal welding can be performed efficiently.

[0078] In the case of laser beam irradiation, a laser irradiator such as a fiber laser or a YAG laser can be used. The laser beam irradiation diameter is about several tens of micrometers, and the laser beam can be irradiated linearly either continuously or as pulses. Therefore, by irradiating the laser beam in the region where the first sealing material 5 and the second sealing material 7 overlap, the first sealing material 5 and the second sealing material 7 can be thermally welded together in a ring shape.

[0079] When induction heating is performed, electromagnetic waves are irradiated from above, and similarly to laser beam irradiation, only the interface portion where the first sealing material 5 and the second sealing material 7 come into contact is locally melted and adhered. For induction heating, electromagnetic waves in the frequency bands of, for example, very low frequency (VLF) to centimeter frequency (SHF) can be used. Specifically, so-called microwaves in the frequency band of, for example, 300 MHz to 30 GHz can be used. In particular, by using an oscillator with a magnetron in the 2.45 GHz frequency band, the irradiation device can be constructed inexpensively. Furthermore, it is also suitable to use a coil-type device to irradiate electromagnetic waves in the frequency band of 10 to 500 kHz, particularly in the frequency band of 20 to 100 kHz used in electromagnetic induction heating cookers.

[0080] Furthermore, by previously performing a surface treatment on the contact surfaces of the first sealing material 5 and the second sealing material 7, respectively, it is possible to improve the adhesion between the first sealing material 5 and the second sealing material 7. Specifically, for example, an oxide film on the metal surface can be removed using electron beam irradiation or the like to make the surface clean. Furthermore, the resin surface can be modified and its properties adjusted using techniques such as electron beam irradiation or ozone oxidation.

[0081] As described above, by thermally welding the first sealing material 5 and the second sealing material 7 together, the positive electrode exterior member 10 and the negative electrode exterior member 20 can be welded and sealed while maintaining high sealing properties. As a result, the housing space 4 in which the electrode body 3 is housed can be appropriately sealed, and the secondary battery 1 shown in FIGS. 1 and 2 can be obtained.

[0082] In particular, since the block-shaped lithium part 51 placed on the inner surface of the negative electrode exterior member 20 is pressed and rolled into a sheet, the sheet-shaped lithium part 51 can be formed at low cost. Specifically, unlike when the lithium part 51 is formed by sputtering, vapor deposition, or the like, the sheet-shaped lithium part 51 can be obtained by a simple method of simply pressing a mass of the block-shaped lithium part 51. Therefore, a single secondary battery can be manufactured at low cost. Furthermore, since the SEI film-forming agent 70 can be spread in a planar manner at the same time as the block-shaped lithium portion 51 is pressed, the SEI film 60 can be formed at the stage of forming the sheet-shaped lithium portion 51. Therefore, the SEI film 60 can be properly formed before an oxide film is formed on the lithium portion 51.

[0083] (Second embodiment) Next, a second embodiment of the electrochemical cell according to the present invention will be described with reference to the drawings. In this second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

[0084] As shown in FIG. 13, a secondary battery (electrochemical cell according to the present invention) 80 of this embodiment differs from that of the first embodiment in the configuration of the negative electrode 50. The negative electrode current collector 55 constituting the negative electrode 50 of this embodiment includes a first negative electrode current collector 81 arranged between the sheet-like lithium portion 51 and the bottom wall portion 21 of the negative electrode exterior member 20, and a second negative electrode current collector (current collector main body according to the present invention) 82 formed integrally with the first negative electrode current collector 81 and arranged between the sheet-like lithium portion 51 and the positive electrode 30.

[0085] The negative electrode current collector 55 of this embodiment is formed in a strip-like, rectangular shape in plan view when unfolded, and is accommodated in the accommodation space 4 of the exterior body 2 in a state where it is folded back 180 degrees. Therefore, the first negative electrode current collector 81 and the second negative electrode current collector 82 are integrally formed with the folded portion 83 interposed therebetween.

[0086] The first negative electrode current collector 81 is welded to the bottom wall portion 21 in a state where it overlaps the inner surface of the bottom wall portion 21 of the negative electrode exterior member 20. As a result, the first negative electrode current collector 81 is integrated with the bottom wall portion 21 via the welded portion 61. In the illustrated example, the first negative electrode current collector 81 is welded to the bottom wall portion 21 at two welded portions 61. However, the number of welded portions is not limited to two.

[0087] The second negative electrode current collector 82 is disposed so as to overlap the sheet-like lithium portion 51 from above, and sandwiches the lithium portion 51 between itself and the first negative electrode current collector 81 in the direction of the battery axis O. The second negative electrode current collector 82 is in close contact with the sheet-like lithium portion 51 via the electrode layer 65 and the SEI film 60.

[0088] The sheet-like lithium part 51 is sandwiched between the first negative electrode current collector 81 and the second negative electrode current collector 82 in a state where it is positioned via the welded part 61 of the first negative electrode current collector 81 . In particular, around the welded portion 61 of the first negative electrode current collector 81 formed during welding, an anchor effect similar to that described above is generated due to surface activation of the inner surface of the bottom wall portion 21 by heating (see FIG. 4). Therefore, due to this anchor effect, the sheet-like lithium portion 51 is sandwiched between the first negative electrode current collector 81 and the second negative electrode current collector 82 in a positioned state.

[0089] (Action of secondary batteries) The secondary battery 80 of this embodiment configured as described above can also achieve the same effects as those of the first embodiment. In particular, because the first negative electrode current collector 81 is welded to the bottom wall portion 21 of the negative electrode exterior member 20, the negative electrode current collector 55 and the negative electrode exterior member 20 can be more reliably joined together without being affected by the size of the lithium part 51, and high conductivity can be maintained. Moreover, by utilizing the anchor effect, the lithium part 51 can be positioned and disposed so as to be sandwiched between the first negative electrode current collector 81 and the second negative electrode current collector 82. Therefore, the entire electrode body 3 can be accommodated in the accommodation space 4 in a more stable orientation, allowing stable battery performance to be achieved.

[0090] Furthermore, compared to the first embodiment, the size of the sheet-like lithium portion 51 can be increased, and the space within the accommodation space 4 can be used effectively, making it easy to increase the size of the entire electrode body 3.

[0091] (Secondary battery manufacturing method) Next, an example of a method for manufacturing the secondary battery 80 of this embodiment will be briefly described below. 14 , after the negative electrode current collector 55 is set so that the first negative electrode current collector 81 is placed on the inner surface of the bottom wall portion 21 of the negative electrode exterior member 20, a step is performed in which the inner surface of the bottom wall portion 21 and the first negative electrode current collector 81 are welded together. As a result, the first negative electrode current collector 81 is integrated with the bottom wall portion 21 via the welded portion 61. The method for welding the first negative electrode current collector 81 and the bottom wall portion 21 is not particularly limited, but may be, for example, laser welding, ultrasonic welding, seam welding, or the like. Simultaneously with, or before or after, the above-described process, a process of previously fixing the second sealing material 7 to the flange portion 23 of the negative electrode exterior member 20 over the entire periphery by laser welding is carried out.

[0092] Next, as shown in FIG. 15 , a step is performed in which the block-shaped lithium part 51 is placed on the welded first negative electrode current collector 81 in a state where it is positioned via the weld part 61, and the SEI film-forming agent 70 is allowed to remain on the opposing surface 51b of the lithium part 51 that faces the mounting surface 51a facing the first negative electrode current collector 81.

[0093] Specifically, similarly to the manufacturing method of the first embodiment, after cutting out the block-shaped lithium portion 51, a concave recess 71 is formed on the facing surface (upper surface) 51a of the block-shaped lithium portion 51. Then, the block-shaped lithium portion 51 with the recess 71 formed therein is placed on the first negative electrode current collector 81 by utilizing the anchor effect generated around the welded portion 61. Then, by accommodating the SEI film-forming agent 70 in the recess 71 by, for example, pouring or dripping, it becomes possible to keep the SEI film-forming agent 70 on the facing surface 51b of the block-shaped lithium portion 51.

[0094] Next, as indicated by arrow F1 in FIG. 15, the block-shaped lithium part 51 is pressed from above (the opposing surface 51b side) to roll the lithium part 51 into a sheet as shown in FIG. 16, and the SEI film forming agent 70 is diffused in a planar manner to form an SEI film 60 over the entire surface of the opposing surface 51b.

[0095] Next, as shown in Fig. 17, a step of setting the second negative electrode current collector 82 is performed so as to be positioned between the lithium part 51 and the positive electrode 30 (see Fig. 13). Specifically, as shown by arrow F2 in Fig. 16, the second negative electrode current collector 82 is folded using the folded part 83 as a base point, so that the second negative electrode current collector 82 is disposed so as to overlap the sheet-like lithium part 51 from above, as shown in Fig. 17. This brings the second negative electrode current collector 82 into close contact with the sheet-like lithium part 51 via the electrode layer 65 and the SEI film 60.

[0096] Next, similar to the manufacturing method of the first embodiment, the solid electrolyte 40 is placed on top of the negative electrode current collector 55, and the positive electrode 30 is placed on top of the solid electrolyte 40. Next, the positive electrode exterior member 10, in which the first sealing material 5 is fixed to the entire outer peripheral edge portion of the positive electrode exterior member 10 and a conductive paste is formed, is placed on the negative electrode exterior member 20 from above. Next, the first sealing material 5 and the second sealing material 7 are thermally welded together, thereby welding and sealing the positive electrode exterior member 10 and the negative electrode exterior member 20 while maintaining high sealing properties.

[0097] This allows the positive electrode exterior member 10 and the negative electrode exterior member 20 to be welded and sealed while maintaining high sealing properties. As a result, the housing space 4 in which the electrode body 3 is housed can be properly sealed, and the secondary battery 80 shown in FIG. 13 can be obtained.

[0098] In particular, because the first negative electrode current collector 81 is welded to the negative electrode exterior member 20, the negative electrode current collector 55 and the negative electrode exterior member 20 can be more reliably joined together and high conductivity can be maintained without being affected by the size of the lithium part 51, etc. Furthermore, because the lithium part 51 can be positioned by utilizing the anchor effect, the entire electrode body 3 can be accommodated in the accommodation space 4 in a more stable posture, allowing stable battery performance to be achieved.

[0099] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments and their modifications include, for example, those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are equivalent.

[0100] For example, in each of the above embodiments, the shapes of the positive electrode exterior member 10 and the negative electrode exterior member 20 may be changed as appropriate. For example, in each of the above embodiments, the positive electrode exterior member 10 is formed in a sheet shape, and the negative electrode exterior member 20 is formed in a bottomed cylindrical shape, but the positive electrode exterior member 10 may be formed in a topped cylindrical shape, and the negative electrode exterior member 20 may be formed in a sheet shape. Furthermore, the positive electrode exterior member 10 may be formed in a topped cylindrical shape, and the negative electrode exterior member 20 may be formed in a bottomed cylindrical shape. Furthermore, in order to achieve even thinner dimensions, both the positive electrode exterior member 10 and the negative electrode exterior member 20 may be formed into a sheet shape.

[0101] Furthermore, in each of the above embodiments, the positive electrode exterior member 10 also functions as an external connection terminal for the positive electrode that is electrically connected to the electrode body 3, similar to the negative electrode exterior member 20, but this is not limited to this. For example, as shown in FIG. 18 , a part of the positive electrode current collector 31 may be used as a positive electrode terminal tab, and this positive electrode terminal tab may be pulled out and exposed to the outside from the first sealing material 5 and the second sealing material 7 to which the positive electrode current collector 31 is thermally welded. In this case, since the positive electrode terminal tab can be used as an external connection terminal for the positive electrode, there is no need to electrically connect the positive electrode exterior member 10 to the positive electrode 30.

[0102] Furthermore, in the above first embodiment, the case where the negative electrode current collector 55 is welded to the bottom wall portion 21 of the negative electrode exterior member 20 has been described as an example, but the present invention is not limited to this case. For example, the negative electrode current collector 55 may be welded to the peripheral wall portion 22 of the negative electrode exterior member 20.

[0103] Furthermore, in each of the above embodiments, the solid electrolyte 40 is used as the electrolyte, but this is not limited to this. For example, a separator may be used instead of the solid electrolyte 40, and an electrolytic solution may be injected into the housing space 4. In this case, the electrolyte may be, for example, a liquid in which a supporting salt is dissolved in an aprotic, non-aqueous solvent. For example, lithium fluorophosphate (LiPF6) or the like may be used as the supporting salt. For example, a low-boiling-point solvent may be used together with ethylene carbonate (EC).

[0104] The separator may be formed of, for example, a microporous film made of a resin such as polyolefin, a nonwoven fabric made of glass or resin, or a laminate of fibers such as cellulose fibers, and is capable of passing lithium ions through ion permeable pores (not shown).Furthermore, the separator may be, for example, a porous body capable of retaining an electrolyte solution in the pores, or a resin layer having lithium ion conductivity. Furthermore, as described above, a microporous film made of a material such as polyolefin can be used as the separator, but it is preferable to use a nonwoven fabric other than the microporous material or a heat-resistant material to avoid the influence of heat transfer from lasers, etc. For example, polyamide, cellulose, glass fiber, etc. can be used as the separator.

[0105] Furthermore, for the purpose of retaining the electrolyte, inorganic material particles can be added and used in a mixed state with the electrolyte. Examples of liquid-retaining particles that can be used include aluminum oxide, alumina hydroxide (boehmite, etc.), titanium oxide (rutile, anatase, brookite), silicon dioxide, zinc oxide, magnesium oxide, zirconium dioxide, and niobium pentoxide, either singly or as a mixture. The average particle size (D50) of these liquid-retaining particles is preferably 100 μm or less, and more preferably 5 nm or more and 1 μm or less. The fine particles mixed with the electrolyte solution can be applied as paint to the positive electrode 30 or the negative electrode 50 to form a coating film, which can be used as a separator. In addition, by using the fine particles in combination with a separator made of the above-mentioned microporous film or the like, the separator can be reinforced.

[0106] Furthermore, as the electrolyte, for example, a polymer electrolyte, a gel electrolyte, or the like may be used. Examples of polymer electrolytes include polyethylene oxide (PEO), polypropylene oxide (PPO), blend polymers containing these, polyacrylic acid esters, polymethacrylic acid esters, polysiloxanes, polyphosphazenes, etc. Also, a gel electrolyte containing poly(vinylidene fluoride-co-hexafluoropropylene, PVdF-HFP) in the electrolyte solution may be used.

[0107] The present invention further includes the following aspects. <1> an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms an accommodation space between the metallic negative electrode exterior member and the positive electrode exterior member; an electrode assembly having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween, the electrode assembly being accommodated in the accommodation space; The negative electrode is a sheet-like lithium portion containing at least metallic lithium or a lithium alloy; a negative electrode current collector welded to the negative electrode exterior member and in close contact with the lithium portion, the negative electrode current collector includes a current collector body disposed between the lithium portion and the positive electrode, An electrochemical cell, characterized in that an SEI film is formed over the entire surface of the lithium portion facing the current collector body. <2> <1> In the electrochemical cell according to The negative electrode current collector is a first negative electrode current collector disposed between the lithium portion and the negative electrode exterior member; a second negative electrode current collector that is integrally formed with the first negative electrode current collector, that is disposed between the lithium portion and the positive electrode, and that functions as the current collector main body; the first negative electrode current collector is welded to the negative electrode exterior member, the lithium part is positioned via a welded part of the first negative electrode current collector and is disposed in a state of being sandwiched between the first negative electrode current collector and the second negative electrode current collector, an SEI film formed on a surface of the lithium portion facing the second negative electrode current collector; <3> <1> or <2> In the electrochemical cell according to The negative electrode further includes a negative electrode active material layer capable of absorbing lithium ions, The negative electrode active material layer is formed on the current collector body and in intimate contact with the lithium portion. <4> <1> from <3> In the electrochemical cell according to any one of the above items, An electrochemical cell, wherein a solid electrolyte that moves lithium ions during charging and discharging is disposed between the positive electrode and the negative electrode as the electrolyte. <5> an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms an accommodation space between the metallic negative electrode exterior member and the positive electrode exterior member; an electrode assembly having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween, the electrode assembly being accommodated in the accommodation space, a step of placing a block-shaped lithium part containing at least metallic lithium or a lithium alloy on an inner surface of the negative electrode exterior member, and then leaving an SEI film-forming agent on a surface of the lithium part that faces a contact surface with the inner surface; a step of pressing the lithium part from the opposing surface side to roll the lithium part into a sheet shape and diffusing the SEI film-forming agent in a planar manner to form an SEI film over the entire surface of the opposing surface; a step of setting a negative electrode current collector so as to be positioned between the lithium part and the positive electrode, and joining the negative electrode current collector to the negative electrode exterior member by welding, a current collector body of the negative electrode current collector disposed between the lithium portion and the positive electrode, the current collector body being in close contact with the lithium portion via the SEI film. <6> an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms an accommodation space between the metallic negative electrode exterior member and the positive electrode exterior member; an electrode assembly having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween, the electrode assembly being accommodated in the accommodation space, a step of setting a negative electrode current collector having a first negative electrode current collector and a second negative electrode current collector formed integrally with each other so that the first negative electrode current collector is placed on an inner surface of the negative electrode exterior member, and then welding and joining the inner surface and the first negative electrode current collector; a step of placing a block-shaped lithium part containing at least metallic lithium or a lithium alloy on the welded first negative electrode current collector in a state where the block-shaped lithium part is positioned via the welded part of the first negative electrode current collector, and leaving an SEI film-forming agent on a surface of the lithium part facing a contact surface with the first negative electrode current collector; a step of pressing the lithium part from the opposing surface side to roll the lithium part into a sheet shape and diffusing the SEI film-forming agent in a planar manner to form an SEI film over the entire surface of the opposing surface; and setting the second negative electrode current collector so as to be located between the lithium part and the positive electrode, the lithium part is positioned via the welded part and is disposed in a state of being sandwiched between the first negative electrode current collector and the second negative electrode current collector, a second negative electrode current collector in intimate contact with the lithium portion via the SEI film; [Explanation of symbols]

[0108] 1, 80...Secondary battery (electrochemical cell) 2...Exterior body 3...Electrode body 4. Containment space 10...Positive electrode exterior member 20...Negative electrode exterior member 30...Positive electrode 40...Solid electrolyte (electrolyte) 50...Negative electrode 51...Lithium section 51b...Facing surface of lithium part 55...Negative electrode current collector 56...Collector body 60...SEI membrane 61...Welded section 63...Negative electrode active material layer 70...SEI film forming agent 81...First negative electrode current collector 82...Second negative electrode current collector (current collector body)

Claims

1. an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms an accommodation space between the metallic negative electrode exterior member and the positive electrode exterior member; an electrode assembly having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween, the electrode assembly being accommodated in the accommodation space; The negative electrode is a sheet-like lithium portion containing at least metallic lithium or a lithium alloy; a negative electrode current collector welded to the negative electrode exterior member and in close contact with the lithium portion, the negative electrode current collector includes a current collector body disposed between the lithium portion and the positive electrode, An electrochemical cell, characterized in that an SEI film is formed over the entire surface of the lithium portion facing the current collector body.

2. 10. The electrochemical cell of claim 1, The negative electrode current collector is a first negative electrode current collector disposed between the lithium portion and the negative electrode exterior member; a second negative electrode current collector that is integrally formed with the first negative electrode current collector, that is disposed between the lithium portion and the positive electrode, and that functions as the current collector main body; the first negative electrode current collector is welded to the negative electrode exterior member, the lithium portion is positioned via a welded portion of the first negative electrode current collector and is disposed in a state of being sandwiched between the first negative electrode current collector and the second negative electrode current collector, an SEI film formed on a surface of the lithium portion facing the second negative electrode current collector;

3. 10. The electrochemical cell of claim 1, The negative electrode further includes a negative electrode active material layer capable of absorbing lithium ions, The negative electrode active material layer is formed on the current collector body and in intimate contact with the lithium portion.

4. 4. The electrochemical cell according to claim 1, An electrochemical cell, wherein a solid electrolyte that moves lithium ions during charging and discharging is disposed between the positive electrode and the negative electrode as the electrolyte.

5. an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms an accommodation space between the metallic negative electrode exterior member and the positive electrode exterior member; an electrode assembly having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween, the electrode assembly being accommodated in the accommodation space, a step of placing a block-shaped lithium part containing at least metallic lithium or a lithium alloy on the inner surface of the negative electrode exterior member, and then leaving an SEI film-forming agent on a surface of the lithium part facing a contact surface with the inner surface; a step of pressing the lithium part from the opposing surface side to roll the lithium part into a sheet shape and diffusing the SEI film-forming agent in a planar manner to form an SEI film over the entire surface of the opposing surface; a step of setting a negative electrode current collector so as to be positioned between the lithium part and the positive electrode, and joining the negative electrode current collector to the negative electrode exterior member by welding, a current collector body of the negative electrode current collector disposed between the lithium portion and the positive electrode, the current collector body being in close contact with the lithium portion via the SEI film.

6. an exterior body including a metallic positive electrode exterior member and a metallic negative electrode exterior member that forms an accommodation space between the metallic negative electrode exterior member and the positive electrode exterior member; an electrode assembly having a positive electrode and a negative electrode arranged to face each other with an electrolyte interposed therebetween, the electrode assembly being accommodated in the accommodation space, a step of setting a negative electrode current collector having a first negative electrode current collector and a second negative electrode current collector formed integrally with each other such that the first negative electrode current collector is placed on an inner surface of the negative electrode exterior member, and then welding the inner surface and the first negative electrode current collector together; a step of placing a block-shaped lithium part containing at least metallic lithium or a lithium alloy on the welded first negative electrode current collector in a state where the block-shaped lithium part is positioned via the welded part of the first negative electrode current collector, and leaving an SEI film-forming agent on a surface of the lithium part facing a contact surface with the first negative electrode current collector; a step of pressing the lithium part from the opposing surface side to roll the lithium part into a sheet shape and diffusing the SEI film-forming agent in a planar manner to form an SEI film over the entire surface of the opposing surface; and setting the second negative electrode current collector so as to be located between the lithium part and the positive electrode, the lithium portion is positioned via the welded portion and is disposed in a state of being sandwiched between the first negative electrode current collector and the second negative electrode current collector, the second negative electrode current collector is in intimate contact with the lithium portion via the SEI film.

Images