Electrochemical cell and method of manufacturing electrochemical cell

Abstract

To provide an electrochemical cell which has high sealing properties and is suitable for downsizing.SOLUTION: There is provided an electrochemical cell 1 including: an outer container 2 having a negative electrode can 10 and a positive electrode can 30 caulked and fixed to the negative electrode can through an insulating film gasket 20; and a power generation element 3. The negative electrode can is formed into a topped cylindrical shape having a top wall part 11 and an inner wall part 12. The positive electrode can is formed into a bottomed cylindrical shape having a bottom wall part 31 and an outer wall part 32 surrounding the inner wall part from the radial outside. The film gasket is welded, over the whole circumferences, with at least each of an inner peripheral surface of the outer wall part and an upper opening end 32a of the outer wall part, of the positive electrode can, and the film gasket is tightly pressed against an outer peripheral surface of the inner wall part when the positive electrode can is caulked and fixed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A known example of an electrochemical cell is a small coin-type (button-type) battery having a metal outer container with a positive electrode can and a negative electrode can. In this case, a gasket is placed between the positive electrode can and the negative electrode can, and the opening of the positive electrode can is pressed against the negative electrode can, thereby crimping the opening of the positive electrode can to the negative electrode can with the gasket sandwiched between them.

[0003] Among these types of coin-type batteries, there are known button batteries that use a thin-walled sealing gasket to ensure a large internal volume inside the outer container and, for example, increase the capacity (volumetric energy density) of the battery (for example, Patent Document 1). This button battery includes an outer container with a metal cup portion (positive electrode can) and a metal lid portion (negative electrode can) between which a sealing gasket is placed, and a power generating element housed inside the outer container. The cup portion and the lid portion are hermetically joined to each other by the gasket. The power generating element is a composite of strip-shaped positive and negative electrodes and a strip-shaped separator wound into a roll. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2012-517658 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional button battery described above, a gasket is attached to the side wall of the lid during assembly. The lid with the attached gasket is then inserted into the cup containing the power generating element and combined. The cup side wall is then crimped by applying radial inward pressure. This allows the side wall of the cup to be pressed against the side wall of the lid with the gasket sandwiched between them, sealing the inside of the outer container.

[0006] However, conventional assembly (manufacturing) methods require a sealing gasket to be attached to the topped cylindrical lid first, which poses a problem that assembly becomes more difficult as the battery (electrochemical cell) becomes smaller. In particular, since the lid portion, which functions as the negative electrode can, is smaller in size than the cup portion, which functions as the positive electrode can, it becomes even more difficult to accurately attach the gasket to the lid portion when attempting to further reduce the battery size. Moreover, considering that the gasket is a sealing type, it becomes extremely difficult to attach it to the lid portion.

[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 that has high sealing properties and is suitable for miniaturization. [Means for solving the problem]

[0008] (1) An electrochemical cell according to the present invention comprises an outer container having an anode can and a cathode can crimped to the anode can via an insulating film gasket, and a power generating element accommodated inside the outer container, wherein the anode can is formed into a topped cylindrical shape having a top wall and an inner wall formed along the outer peripheral edge of the top wall, and the cathode can is formed into a bottomed cylindrical shape having a bottom wall disposed opposite the top wall in a direction along the battery axis, and an outer wall formed along the outer peripheral edge of the bottom wall and surrounding the inner wall from the outside in the radial direction, and the film gasket is welded to at least the entire inner peripheral surface and the upper open end of the outer wall of the cathode can, and is pressed tightly against the outer peripheral surface of the inner wall as the cathode can is crimped.

[0009] In the electrochemical cell according to the present invention, a film gasket is welded to at least the inner circumferential surface of the outer wall of the positive electrode can and the upper open end of the positive electrode can, thereby integrating the positive electrode can and the film gasket. Furthermore, the film gasket is tightly pressed against the outer circumferential surface of the inner wall of the negative electrode can when the positive electrode can is crimped to the negative electrode can, thereby achieving a high level of sealing between the negative electrode can and the film gasket. This allows the interior of the outer container housing the power generating element to be properly sealed in a hermetic state. The film gasket not only covers the entire inner circumferential surface of the outer wall of the positive electrode can, but also continuously covers the entire upper open end of the outer wall, effectively preventing electrical conduction between the positive electrode can and the negative electrode can.

[0010] In particular, since the film gasket is welded to the positive electrode can, the film gasket can be attached to the positive electrode can before assembling the negative electrode can. Therefore, unlike conventional methods, the film gasket can be attached to the positive electrode can, which is larger than the negative electrode can, making assembly easier and improving manufacturing efficiency. In addition, this makes it easier to accommodate further reductions in battery size, resulting in an electrochemical cell that is suitable for miniaturization. Furthermore, because a thin film gasket is used, even if the external size is the same, the battery capacity (volumetric energy density) can be improved, thereby improving the battery performance.

[0011] (2) The film gasket may be further welded to the bottom surface of the outer periphery of the bottom wall portion, and may be disposed between the lower opening end of the inner wall portion of the negative electrode can and the bottom wall portion.

[0012] In this case, the film gasket not only covers the entire inner peripheral surface of the outer wall, but also continuously covers the bottom surface of the outer peripheral portion of the bottom wall, and is disposed between the lower opening edge of the inner wall of the negative electrode can and the bottom wall of the positive electrode can. Therefore, the film gasket can be used to prevent electrical conduction between the inner wall of the negative electrode can and the bottom wall of the positive electrode can, further improving product reliability. In addition, during assembly, the film gasket can be used to position the negative electrode can relative to the positive electrode can in the axial direction of the battery, making assembly even easier and improving manufacturing efficiency.

[0013] (3) The film gasket may be further welded to the entire outer periphery of the outer wall portion.

[0014] In this case, the film gasket covers the entire outer peripheral surface of the outer wall, so the outer wall can be protected by using the film gasket. Therefore, for example, external impacts are less likely to be directly transmitted to the outer wall, and unintended scratches, deformations, and other problems on the cathode can can be prevented. This contributes to improving product quality. Furthermore, the outer wall of the cathode can can be easily insulated from external components without using a separate component such as a heat-shrinkable tube.

[0015] (4) The film gasket may be made of a thermoplastic resin.

[0016] In this case, the film gasket can be made of a thermoplastic resin such as PFA resin (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin), PEEK resin (polyether ether ketone resin), or PTFE resin (polytetrafluoroethylene resin). Therefore, the film gasket can have excellent heat resistance, cold resistance, water repellency, chemical resistance, and moisture permeation suppression. Therefore, the electrochemical cell can be used in a manner that allows for reflow soldering (reflow mounting), for example. Furthermore, when PFA resin is used, it has excellent properties for suppressing moisture permeation, so it is possible to use a film gasket to prevent moisture (water) from entering from the outside, etc. Therefore, it is possible to create an electrochemical cell in which the inside of the outer container is sealed with high airtightness.

[0017] (5) The inner wall portion comprises an inner inclined wall portion extending radially outward as it moves downward from the outer peripheral edge of the top wall portion, and an inner straight wall portion extending downward from the inner inclined wall portion along the battery axis, and the outer wall portion comprises an outer straight wall portion extending upward from the outer peripheral edge of the bottom wall portion along the battery axis, and an outer inclined wall portion extending radially inward as it moves upward from the outer straight wall portion, and the film gasket may be pressed tightly against the outer peripheral surfaces of the inner inclined wall portion and the inner straight wall portion as the positive electrode can is crimped.

[0018] In this case, by crimping the positive electrode can to the negative electrode can, the outer straight wall portion can be pressed radially inward, thereby crimping the film gasket against the inner straight wall portion. Furthermore, by pressing the outer inclined wall portion radially inward and downward, the film gasket can be crimped against the inner inclined wall portion. Therefore, the positive electrode can can be crimped in two directions, radially inward and downward, preventing the negative electrode can from slipping out upward and more firmly combining the positive electrode can and the negative electrode can. This allows the interior of the outer container to be sealed with even higher hermeticity.

[0019] (6) A method for manufacturing an electrochemical cell according to the present invention is a method for manufacturing an electrochemical cell including an outer container having a cylindrical anode can with a top wall and an inner wall, and a cathode can with a bottom wall and an outer wall, the cathode can being fixed to the anode can by crimping via an insulating film gasket, and a power generating element housed inside the outer container, the method comprising the steps of: welding the film gasket in advance to at least the inner peripheral surface of the outer wall and the entire opening edge of the outer wall of the cathode can; assembling the cathode can and the anode can while housing the power generating element between the anode can and the cathode can so that the bottom wall and the top wall face each other in a direction along the battery axis and the inner wall is located radially inside the outer wall; and crimping the outer wall of the cathode can toward the inner wall, thereby pressing the film gasket welded to the outer wall tightly against the outer peripheral surface of the inner wall of the anode can.

[0020] According to the method for manufacturing an electrochemical cell of the present invention, a film gasket can be pre-welded to the positive electrode can before assembling the negative electrode can to the positive electrode can. Therefore, unlike conventional methods, the film gasket can be assembled to the positive electrode can, which is larger than the negative electrode can, facilitating assembly and improving manufacturing efficiency. In addition, the method can easily accommodate further reductions in battery size, resulting in an electrochemical cell suitable for miniaturization. Furthermore, because a thin film gasket is used, the battery capacity (volumetric energy density) can be improved even with the same external size. Therefore, battery performance can be improved.

[0021] (7) The film gasket may be welded to the positive electrode can by any of heat welding, induction heating welding, ultrasonic welding, and laser welding.

[0022] In this case, the film gasket is welded to the positive electrode can by any of heat welding, induction heating welding (high frequency welding), ultrasonic welding, and laser welding, so that efficient welding can be performed depending on, for example, the material, thickness, and welding range of the film gasket. [Effects of the Invention]

[0023] According to the present invention, an electrochemical cell can be obtained which has high sealing properties, is suitable for miniaturization, and further allows for improved battery performance. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a longitudinal sectional view showing a first embodiment of a secondary battery (electrochemical cell) according to the present invention. [Figure 2] FIG. 2 is a vertical cross-sectional view showing an example of the power generating element shown in FIG. [Figure 3] FIG. 2 is a diagram showing one process for manufacturing the secondary battery shown in FIG. [Figure 4] FIG. 4 is a vertical cross-sectional view of a secondary battery showing a modified example of the first embodiment. [Figure 5]FIG. 4 is a vertical cross-sectional view of a secondary battery showing another modified example of the first embodiment. [Figure 6] FIG. 2 is a longitudinal sectional view showing a second embodiment of a secondary battery (electrochemical cell) according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] (First embodiment) A first embodiment of an electrochemical cell according to the present invention will now be described with reference to the drawings. In this embodiment, a non-aqueous electrolyte secondary battery will be described as an example of an electrochemical cell. In the following description, the non-aqueous electrolyte secondary battery will be simply referred to as a secondary battery.

[0026] 1, the secondary battery 1 of this embodiment is a so-called coin (button) type battery, and mainly comprises an outer case 2 and a power generating element 3 housed inside the outer case 2. The size of the secondary battery 1 is not particularly limited, but may be, for example, about 5 mm in outer diameter and about 2 mm in thickness.

[0027] The outer container 2 includes a negative electrode can 10 and a positive electrode can 30 that is crimped to the negative electrode can 10 via an insulating film gasket 20. The negative electrode can 10 and the positive electrode can 30 are assembled by crimping so that a top wall 11 (described later) of the negative electrode can 10 faces a bottom wall 31 (described later) of the positive electrode can 30. In this embodiment, the axis that passes through the centers of the top wall 11 and the bottom wall 31 and extends along the direction in which the top wall 11 and the bottom wall 31 face each other is referred to as the battery axis O, and 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, the direction from the bottom wall 31 toward the top wall 11 along the battery axis O is referred to as the upward direction, and the opposite direction is referred to as the downward direction.

[0028] 1 and 2, the power generating element 3 includes an electrode assembly 40 having a positive electrode 41, a negative electrode 42, and a separator 43, and an electrolytic solution (electrolyte) (not shown), and is housed in a sealed state inside an outer container 2. Note that in the drawings other than FIG. 2, the power generating element 3 is illustrated simply. The positive electrode 41 is disposed on the positive electrode can 30 side, and the negative electrode 42 is disposed on the negative electrode can 10 side. The separator 43 is disposed between the positive electrode 41 and the negative electrode 42. The positive electrode 41, the negative electrode 42, and the separator 43 are housed inside the outer container 2 in an integrated combined state by being stacked in the direction of the battery axis O.

[0029] (Outer container) The outer container 2 will now be described in detail. As shown in FIG. 1, the outer container 2 includes a negative electrode can 10 made of metal and formed into a cylindrical shape with a top, and a positive electrode can 30 made of metal and formed into a cylindrical shape with a bottom.

[0030] (negative electrode can) The negative electrode can 10 is formed in the shape of a cylinder with a top, and includes a top wall portion 11 formed in a circular shape in a plan view, and an annular inner wall portion 12 formed around the outer peripheral edge of the top wall portion 11 in the circumferential direction of the top wall portion 11 and extending straight downward. The negative electrode can 10 is assembled to the positive electrode can 30 from above so that the inner wall 12 fits inside the outer wall 32 of the positive electrode can 30, which will be described later. In this embodiment, the negative electrode can 10 is assembled to the positive electrode can 30 so that the lower open end 12a of the inner wall 12 is positioned above and spaced from the bottom wall 31 of the positive electrode can 30, which will be described later.

[0031] The material of the anode can 10 is not limited to a specific material, but may be, for example, SUS316L, SUS329J4L, or the like. It is also possible to use SUS304-BA or other conventionally known stainless steel. Furthermore, metal materials other than stainless steel may be used for the anode can 10. For example, a clad material obtained by crimping copper, nickel, or the like onto stainless steel may be used for the anode can 10.

[0032] (Positive electrode can) The positive electrode can 30 is formed in a cylindrical shape with a bottom, and includes a bottom wall portion 31 formed in a circular shape in a plan view, and an annular outer wall portion 32 formed around the outer peripheral edge of the bottom wall portion 31 in the circumferential direction of the bottom wall portion 31 and extending straight upward. The bottom wall 31 is disposed to face the top wall 11 of the negative electrode can 10 in the direction of the battery axis O, and is formed to have an outer diameter larger than that of the top wall 11. The outer wall 32 surrounds the entire inner wall 12 of the negative electrode can 10 from the outside in the radial direction. The outer wall 32 is pressed radially inward and crimped to the inner wall 12 of the negative electrode can 10 with the film gasket 20 sandwiched therebetween.

[0033] The material of the positive electrode can 30 is not limited to a specific material, but examples thereof include SUS316L, SUS329J4L, etc., similar to the negative electrode can 10. Conventionally known stainless steels may also be used. Furthermore, metal materials other than stainless steel may also be used for the positive electrode can 30.

[0034] (Film gasket) The film gasket 20 is formed in the form of, for example, an extremely thin film that is thinner than the thickness of the positive electrode can 30 and the negative electrode can 10. However, the thickness of the film gasket 20 is exaggerated in the drawings. The film gasket 20 is disposed between the positive electrode can 30 and the negative electrode can 10, and provides a seal between them. Specifically, the film gasket 20 includes an annular gasket body 21 disposed between the outer wall 32 of the positive electrode can 30 and the inner wall 12 of the negative electrode can 10, and an annular flange 22 extending radially outward from the upper end of the gasket body 21 and disposed on the upper open end 32a of the outer wall 32 of the positive electrode can 30 from above.

[0035] The film gasket 20 is welded to the inner circumferential surface and the upper opening end 32a of the outer wall portion 32 of the positive electrode can 30 via welded portions 50 along the entire periphery. Therefore, the welded portions 50 are formed at the interface between the film gasket 20 and the inner circumferential surface of the outer wall portion 32, and at the interface between the film gasket 20 and the upper opening end 32a of the outer wall portion 32. In each drawing, the welded portions 50 are shown by thick solid lines.

[0036] The welding method is not particularly limited, but may be, for example, heat welding, laser welding using a laser beam, induction heating welding (high frequency welding) using electromagnetic waves for induction heating, or ultrasonic welding using ultrasonic waves for frictional heat.

[0037] In the case of thermal welding, for example, the film gasket 20 can be welded to the inner circumferential surface and upper opening end 32a of the outer wall portion 32 by heating the film gasket 20 with a heater or the like and applying pressure with a roller or the like. In contrast, methods using laser welding, induction heating welding, and ultrasonic welding can perform heating locally and selectively in a shorter time than thermal welding, making it possible to perform welding efficiently.

[0038] In the case of laser welding using laser beam irradiation, a laser irradiator such as a fiber laser or 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 to the region (interface) where the film gasket 20 and the inner circumferential surface and upper opening end 32a of the outer wall portion 32 of the positive electrode can 30 overlap, the film gasket 20 and the outer wall portion 32 of the positive electrode can 30 can be appropriately welded together.

[0039] When induction heating welding is performed using induction heating, electromagnetic waves are applied from above, which allows localized melting and welding of only the interface where the film gasket 20 and the outer wall portion 32 of the positive electrode can 30 come into contact, similar to laser beam irradiation. For induction heating, electromagnetic waves in the frequency band from very low frequency (VLF) to centimeter frequency (SHF) can be used. Specifically, so-called microwaves in the frequency band from 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.

[0040] Furthermore, by previously performing a surface treatment on the contact surface of the outer wall portion 32 of the positive electrode can 30 with which the film gasket 20 comes into contact, it is possible to improve the adhesion between the film gasket 20 and the outer wall portion 32. Specifically, for example, the surface of the outer wall portion 32 can be made clean by removing an oxide film on the metal surface using electron beam irradiation or the like. Furthermore, the surface of the film gasket 20 can be modified and its properties adjusted using techniques such as electron beam irradiation or ozone oxidation.

[0041] When ultrasonic welding is performed using ultrasound, ultrasonic vibrations within a predetermined frequency range are transmitted from a resonator such as a horn, which generates frictional heat at the interface where the film gasket 20 and the outer wall portion 32 of the positive electrode can 30 come into contact, thereby causing local melting and welding.

[0042] As described above, the gasket body 21 of the film gasket 20 welded to the inner peripheral surface of the outer wall 32 of the positive electrode can 30 is pressed tightly against the outer peripheral surface of the inner wall 12 of the negative electrode can 10 as the outer wall 32 of the positive electrode can 30 is crimped and fixed. This allows the film gasket 20 to provide a high level of sealing between the negative electrode can 10 and the film gasket 20.

[0043] The above-described film gasket 20 is formed, for example, from a thermoplastic resin. In particular, the film gasket 20 is preferably formed from a thermoplastic resin with a heat distortion temperature of 230°C or higher. If the resin material used for the film gasket 20 has a heat distortion temperature of 230°C or higher, it is possible to prevent problems such as significant deformation of the film gasket 20 due to reflow soldering or heating during use of the secondary battery 1, which can lead to leakage of the electrolyte.

[0044] Examples of materials for this type of film gasket 20 include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), polyether ether ketone resin (PEEK), and polytetrafluoroethylene resin (PTFE resin). However, the material of the foam gasket is not limited to these cases, and other materials such as polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyamide, liquid crystal polymer (LCP), polyether nitrile resin (PEN), polyether ketone resin (PEK), polyarylate resin, polybutylene terephthalate resin (PBT), polycyclohexane dimethylene terephthalate resin, polyether sulfone resin (PES), polyamino bismaleimide resin, polyetherimide resin, and fluororesin may also be used.

[0045] Therefore, it is possible to provide a film gasket 20 that is excellent in heat resistance, cold resistance, water repellency, chemical resistance, and moisture permeation inhibition, for example. In particular, PFA resin has excellent properties for inhibiting moisture permeation, so when the film gasket 20 is formed from PFA resin, it becomes possible to prevent moisture (water) from entering from the outside, and the inside of the outer container 2 can be sealed with high airtightness. Furthermore, when PPS resin or PEEK resin is used, it is possible to prevent the film gasket 20 from being significantly deformed during use or storage in a high-temperature environment, for example, and therefore the sealing performance of the secondary battery 1 can be further improved.

[0046] Note that the above-mentioned resin to which, for example, glass fiber, mica whisker, ceramic fine powder, or the like has been added in an amount of 30 mass % or less may be suitably used for the film gasket 20. In this case, it is possible to prevent the film gasket 20 from being significantly deformed by heating during reflow.

[0047] (power generation element) The power generating element 3 will now be described. 1 and 2, the power generating element 3 includes a positive electrode 41, a negative electrode 42, and a separator 43, and is housed inside an outer container 2 together with an electrolyte (not shown). In this case, the positive electrode 41, the negative electrode 42, and the separator 43 are impregnated with the electrolyte filled in the outer container 2.

[0048] The positive electrode 41 is electrically connected to the upper surface of the bottom wall 31 of the positive electrode can 30 via, for example, a positive electrode current collector. The negative electrode 42 is electrically connected to the lower surface of the top wall 11 of the negative electrode can 10 via, for example, a negative electrode current collector. However, this is not limited to this case, and for example, the positive electrode current collector and the negative electrode current collector may be omitted, and the positive electrode active material layer may be directly connected to the positive electrode can 30, allowing the positive electrode can 30 to function as a current collector, or the negative electrode active material layer may be directly connected to the negative electrode can 10, allowing the negative electrode can 10 to function as a current collector.

[0049] (positive electrode) The positive electrode 41 is formed in the form of a single sheet including a positive electrode current collector (positive electrode current collector foil) formed in the form of a thin sheet from a metal material such as aluminum or stainless steel, and a positive electrode active material layer formed by coating or the like on one or both sides of the positive electrode current collector. The positive electrode active material layer contains, for example, a conductive additive, a binder, etc. in addition to the positive electrode active material. Specifically, a positive electrode slurry (coating liquid) can be prepared by mixing the positive electrode active material with a conductive additive (e.g., carbon black, graphite, etc.), a binder (e.g., polyvinylidene fluoride, etc.), a solvent (e.g., any solvent such as N-methylpyrrolidone, etc.). Then, the positive electrode slurry can be applied to a positive electrode current collector and dried to form a positive electrode active material layer.

[0050] 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).

[0051] (negative electrode) The negative electrode 42 is formed in the form of a single sheet including a negative electrode current collector (negative electrode current collector foil) formed in the form of a thin sheet from a metal material such as copper, nickel, aluminum, or stainless steel, and a negative electrode active material layer formed by coating or the like on one or both sides of the negative electrode current collector. The negative electrode active material layer contains, for example, a conductive additive, a binder, a thickener, etc. in addition to the negative electrode active material. Specifically, the negative electrode active material is mixed with a conductive additive (e.g., carbon black or graphite), a binder (e.g., a dispersion of styrene-butadiene rubber (SBR)), a thickener (e.g., cellulose nanofiber (CNF) or carboxymethyl cellulose (CMC)), a solvent (e.g., any solvent such as pure water), etc. to prepare a negative electrode slurry (coating liquid). This negative electrode slurry is then applied to a negative electrode current collector and dried to form the negative electrode active material layer.

[0052] 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.

[0053] (separator) The separator 43 is formed of, for example, a microporous film made of a resin such as polyolefin, a nonwoven fabric made of glass or resin, a laminate of fibers such as cellulose fibers, or the like, and is capable of passing lithium ions through ion permeable pores (not shown). Further, the separator 43 may be, for example, a porous body capable of retaining an electrolyte solution in the pores, or a resin layer having lithium ion conductivity.

[0054] Furthermore, as described above, the separator 43 can be a microporous film made of a material such as polyolefin, but it is preferable to use a nonwoven fabric other than microporous or a heat-resistant material. For example, the separator 43 can be made of polyamide, cellulose, glass fiber, etc.

[0055] 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 41 or the negative electrode 42 to form a coating film, which can be used as the separator 43. In addition, by using the fine particles in combination with the separator 43 made of the above-mentioned microporous film or the like, the separator 43 can be reinforced.

[0056] (electrolyte) The electrolyte may be, for example, a liquid in which a supporting salt is dissolved in an aprotic, non-aqueous solvent. The supporting salt may be, for example, lithium fluorophosphate (LiPF6). The solvent may be, for example, ethylene carbonate (EC) and a low-boiling-point solvent.

[0057] (Secondary battery manufacturing method) Next, an example of a method for manufacturing the secondary battery 1 configured as described above will be briefly described below. As shown in Fig. 3, before combining the negative electrode can 10 with the positive electrode can 30, a process of assembling by welding the film gasket 20 to the positive electrode can 30 is performed. Specifically, the film gasket 20 is inserted so as to cover the outer wall portion 32 of the positive electrode can 30 from above, and the gasket body 21 is placed inside the outer wall portion 32, and the flange portion 22 is placed on the upper opening end 32a of the outer wall portion 32. At this time, because the flange portion 22 can be brought into contact with the upper opening end 32a of the outer wall portion 32 from above, the film gasket 20 can be combined with the positive electrode can 30 in an appropriately positioned state.

[0058] Next, the interface between the inner peripheral surface of the outer wall portion 32 and the gasket body 21, and the interface between the upper opening end 32a of the outer wall portion 32 and the flange portion 22 are welded via the welding portion 50. This allows the film gasket 20 to be welded in advance to the inner peripheral surface of the outer wall portion 32 and the upper opening end 32a of the outer wall portion 32 over the entire circumference. As mentioned above, the welding method can be any of heat welding, laser welding, induction heating welding, and ultrasonic welding. Therefore, the film gasket 20 can be efficiently welded depending on the material, thickness, welding area, etc. of the film gasket 20.

[0059] Next, while the power generating element 3 is housed between the positive electrode can 30 to which the film gasket 20 has been previously welded and the negative electrode can 10, a step is performed in which the negative electrode can 10 is assembled to the positive electrode can 30 from above, as indicated by arrow F1 in FIG. 3 , so that the bottom wall portion 31 and the top wall portion 11 face each other vertically and the inner wall portion 12 is positioned radially inside the outer wall portion 32. When the power generating element 3 is housed, the electrode body 40 is set appropriately and the electrolyte is poured appropriately.

[0060] Next, a step is performed in which the outer wall 32 of the positive electrode can 30 combined with the negative electrode can 10 is pressed radially inward (toward the inner wall 12) as indicated by arrow F2 in Fig. 3. This allows the outer wall 32 of the positive electrode can 30 to be crimped and fixed to the inner wall 12 of the negative electrode can 10 with the film gasket 20 sandwiched therebetween. Furthermore, the gasket body 21 of the film gasket 20 welded to the outer wall 32 of the positive electrode can 30 can be pressed tightly against the outer peripheral surface of the inner wall 12 of the negative electrode can 10. In this way, the secondary battery 1 shown in FIG. 1 can be obtained.

[0061] (Action of secondary batteries) In the secondary battery 1 of this embodiment, the film gasket 20 is welded to the entire inner circumferential surface and the upper open end 32a of the outer wall 32 of the positive electrode can 30, so that the positive electrode can 30 and the film gasket 20 can be integrated. Furthermore, the film gasket 20 is pressed tightly against the outer circumferential surface of the inner wall 12 of the negative electrode can 10 when the positive electrode can 30 is crimped to the negative electrode can 10, so that the gap between the negative electrode can 10 and the film gasket 20 can be sealed with high sealing properties. Therefore, the interior of the outer container 2 in which the power generating element 3 is housed can be appropriately sealed in a hermetic state.

[0062] Furthermore, the film gasket 20 not only covers the entire inner circumferential surface of the outer wall portion 32 of the positive electrode can 30, but also continuously covers the entire upper open end 32a of the outer wall portion 32. Therefore, the film gasket 20 can effectively prevent electrical conduction between the positive electrode can 30 and the negative electrode can 10.

[0063] In particular, during assembly, the film gasket 20 can be pre-welded to the positive electrode can 30 before combining the negative electrode can 10 with the positive electrode can 30. Therefore, unlike conventional methods, the film gasket 20 can be assembled to the positive electrode can 30, which is larger in size than the negative electrode can 10, making assembly easier and improving manufacturing efficiency. In addition, the secondary battery 1 can be easily adapted to further miniaturization of the battery size and is suitable for miniaturization. Furthermore, since a thin film gasket 20 is used, the battery capacity (volumetric energy density) can be improved even with the same external size, for example. Therefore, the battery performance can be improved.

[0064] As described above, the secondary battery 1 of this embodiment can be a battery that has high sealing properties, is suitable for miniaturization, and can further improve battery performance. Furthermore, because the film gasket 20 is made of a thermoplastic resin, it can have excellent heat resistance, cold resistance, water repellency, chemical resistance, and moisture permeation suppression, for example. Therefore, it is possible to obtain a secondary battery 1 that can be subjected to, for example, reflow soldering (reflow mounting), and it is also possible to seal the inside of the outer container 2 in a highly airtight state and to make the film gasket 20 less likely to deform due to reflow soldering or heating during use of the secondary battery 1.

[0065] (Modification of the first embodiment) In the first embodiment, an example was described in which the film gasket 20 was welded in advance to the inner circumferential surface and upper opening end 32a of the outer wall portion 32 of the positive electrode can 30, but the present invention is not limited to this case. 4, for example, the film gasket 20 may be further welded to the entire outer periphery of the outer wall portion 32 of the positive electrode can 30. In this case, the film gasket 20 extends downward from the outer periphery of the flange portion 22 and includes an annular outer gasket portion 23 that covers the outer periphery of the outer wall portion 32 of the positive electrode can 30 from the outside in the radial direction. The outer gasket portion 23 is welded to the outer periphery of the outer wall portion 32 via a weld portion 50.

[0066] In the case of the secondary battery 60 configured in this manner, in addition to being able to achieve the same effects as those of the first embodiment, the film gasket 20 covers the entire outer peripheral surface of the outer wall portion 32, so that the film gasket 20 can be used to protect the outer wall portion 32. Therefore, it is possible to prevent the occurrence of inconveniences such as unintended scratches and deformations in the positive electrode can 30 due to, for example, external stress, etc., which can contribute to improving product quality.

[0067] Furthermore, depending on the usage environment or application of the secondary battery 60, the outer wall 32 of the positive electrode can 30 may be insulated to prevent an external short circuit between the positive electrode can 30 and the negative electrode can 10. In this case, it has been known to take an insulating measure by covering the outer wall 32 from the outside in the radial direction using a separate member such as a heat shrink tube. In this regard, according to the secondary battery 60 of this embodiment, insulation between the outer wall portion 32 of the positive electrode can 30 and an external member can be achieved by utilizing the outer gasket portion 23 of the film gasket 20, without using a separate member such as a heat-shrinkable tube. Therefore, insulation measures for the outer wall portion 32 from the external member can be achieved with a small number of parts, resulting in a secondary battery 60 that is easy to use and has excellent convenience.

[0068] (Another modification of the first embodiment) In the secondary battery 60 shown in FIG. 4, an example has been described in which a film gasket 20 is further welded to the entire outer periphery of the outer wall portion 32 of the positive electrode can 30, but the present invention is not limited to this case. 5, the film gasket 20 may be further welded to the bottom surface of the outer periphery of the bottom wall 31 of the positive electrode can 30. In this case, the film gasket 20 includes an annular inner gasket portion 24 that protrudes radially inward from the lower end of the gasket body 21. The inner gasket portion 24 is welded to the bottom surface of the bottom wall 31 via a weld portion 50.

[0069] The inner gasket portion 24 is formed so as to protrude radially inward beyond the inner wall portion 12 of the negative electrode can 10. As a result, the inner gasket portion 24 is disposed between the lower opening end 12a of the inner wall portion 12 of the negative electrode can 10 and the bottom wall portion 31.

[0070] In the case of secondary battery 70 configured in this manner, film gasket 20 not only covers the entire inner peripheral surface of outer wall 32, but also continuously covers the bottom surface of the outer peripheral portion of bottom wall 31, and is disposed between lower opening end 12a of inner wall 12 of negative electrode can 10 and bottom wall 31 of positive electrode can 30. Therefore, film gasket 20 can be used to prevent electrical conduction between inner wall 12 of negative electrode can 10 and bottom wall 31 of positive electrode can 30, further improving product reliability.

[0071] In addition, during assembly, the film gasket 20 can be used to position the negative electrode can 10 relative to the positive electrode can 30 in the direction of the battery axis O. This makes assembly even easier and improves manufacturing efficiency.

[0072] 5, for example, the outer gasket portion 23 is not essential and may not be provided. However, it is preferable to use a film gasket 20 that includes both the inner gasket portion 24 and the outer gasket portion 23.

[0073] (Second embodiment) Next, a second embodiment of the electrochemical cell according to the present invention will be described with reference to the drawings. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0074] As shown in FIG. 6, a secondary battery (electrochemical cell according to the present invention) 80 of this embodiment includes an outer container 2 having an anode can 10 and a cathode can 30. The inner wall portion 12 of the negative electrode can 10 has an inner inclined wall portion 81 that extends radially outward as it moves downward from the outer peripheral edge portion of the top wall portion 11, and an inner straight wall portion 82 that extends straight downward from the lower end portion of the inner inclined wall portion 81. In the illustrated example, the inner inclined wall portion 81 is inclined with respect to the battery axis O, but this is not limited to this case, and for example, it may be curved with a constant radius of curvature so as to be convex outward, and extend radially outward as it moves downward from the outer peripheral edge of the top wall portion 11.

[0075] The outer wall portion 32 of the positive electrode can 30 includes an outer straight wall portion 85 that extends straight upward from the outer peripheral edge portion of the bottom wall portion 31, and an outer inclined wall portion 86 that extends radially inward as it extends upward from the upper end portion of the outer straight wall portion 85. In the illustrated example, the outer inclined wall portion 86 is inclined with respect to the battery axis O, but this is not limited to this. For example, if the inner inclined wall portion 81 is formed to be curved as described above, the outer inclined wall portion 86 may extend radially inward from the upper end of the outer straight wall portion 85 upward while correspondingly curving with a constant radius of curvature so as to be convex outward.

[0076] The film gasket 20 of this embodiment has an inner gasket portion 24, similar to the embodiment shown in Fig. 5, in addition to a gasket body 21 and a flange portion 22. The gasket body 21 is welded to the inner peripheral surface of the outer straight wall portion 85 and the inner peripheral surface of the outer inclined wall portion 86 over the entire circumference. Furthermore, as the positive electrode can 30 is crimped and fixed, the gasket body 21 of the film gasket 20 is pressed tightly against the outer peripheral surfaces of the inner inclined wall portion 81 and the inner straight wall portion 82 of the negative electrode can 10 .

[0077] The secondary battery 80 of this embodiment configured as described above can achieve the same effects as those of the first embodiment. In addition, during assembly, by crimping the positive electrode can 30 to the negative electrode can 10, the outer straight wall portion 85 can be pressed radially inward as indicated by arrow F3 in Fig. 6, thereby crimping the film gasket 20 against the inner straight wall portion 82 with the film gasket 20 sandwiched therebetween. Furthermore, by pressing the outer inclined wall portion 86 radially inward and downward as indicated by arrow F4 in Fig. 6, the film gasket 20 can be crimped against the inner inclined wall portion 81 with the film gasket 20 sandwiched therebetween.

[0078] Therefore, the positive electrode can 30 can be crimped in two directions, radially inward and downward, and the positive electrode can 30 and the negative electrode can 10 can be more firmly combined. As a result, the negative electrode can 10 can be prevented from coming out upward, and the inside of the outer container 2 can be sealed with even higher airtightness.

[0079] In the second embodiment, the inner gasket portion 24 is not essential and may not be provided. Furthermore, the film gasket 20 may further include the outer gasket portion 23 shown in Fig. 4 in addition to the inner gasket portion 24, or may be configured to include only the outer gasket portion 23 without including the inner gasket portion 24.

[0080] 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.

[0081] For example, in each of the above embodiments, the configuration of the power generating element 3 is merely an example and is not limited to a specific form. For example, the positive electrode 41 and the negative electrode 42 may be alternately stacked by being wound with the separator 43 sandwiched therebetween, or the positive electrode 41 and the negative electrode 42 may be alternately stacked by being folded in a zigzag shape from directions in which the positive electrode 41 and the negative electrode 42 intersect with each other. Furthermore, a so-called pellet-type electrode body may be used, in which the positive electrode 41 and the negative electrode 42 are provided on both sides of the separator 43. Furthermore, the negative electrode 42 may be made of metallic lithium or a lithium alloy.

[0082] Furthermore, in each of the above embodiments, an electrolytic solution is used as the electrolyte. However, instead of the electrolytic solution, an electrolyte such as a solid electrolyte or a polymer electrolyte may be used. When a solid electrolyte is used, the solid electrolyte may be disposed between the negative electrode 42 and the positive electrode 41 instead of the separator 43. Examples of the polymer electrolyte include polyethylene oxide (PEO), polypropylene oxide (PPO), blend polymers containing these, polyacrylic acid ester, polymethacrylic acid ester, polysiloxane, and polyphosphazene. Furthermore, a gel electrolyte containing poly(vinylidene fluoride-co-hexafluoropropylene, PVdF-HFP) may be used as the electrolyte solution.

[0083] The present invention further includes the following aspects. <1> an outer container having a negative electrode can and a positive electrode can fixed to the negative electrode can by crimping via an insulating film gasket; a power generating element housed inside the outer container, The negative electrode can is formed in a cylindrical shape with a top having a top wall portion and an inner wall portion formed along an outer peripheral edge portion of the top wall portion, the positive electrode can is formed in a bottomed cylindrical shape having a bottom wall portion disposed to face the top wall portion in a direction along the battery axis, and an outer wall portion formed along an outer peripheral edge portion of the bottom wall portion and surrounding the inner wall portion from the outside in the radial direction, an electrochemical cell, wherein the film gasket is welded to at least the entire inner circumferential surface of the outer wall portion and the entire upper opening end of the outer wall portion of the positive electrode can, and is pressed tightly against the outer circumferential surface of the inner wall portion as the positive electrode can is crimped and fixed. <2> <1> In the electrochemical cell according to an electrochemical cell, wherein the film gasket is further welded over the bottom surface of the outer periphery of the bottom wall portion and is disposed between the lower open end of the inner wall portion of the negative electrode can and the bottom wall portion. <3> <1> or <2> In the electrochemical cell according to The electrochemical cell, wherein the film gasket is further welded to the entire outer periphery of the outer wall portion. <4> <1> from <3> In the electrochemical cell according to any one of the above items, The electrochemical cell, wherein the film gasket is formed of a thermoplastic resin. <5> <1> from <4> In the electrochemical cell according to any one of the above items, the inner wall portion includes an inner inclined wall portion extending radially outward as it extends downward from the outer peripheral edge portion of the top wall portion, and an inner straight wall portion extending downward from the inner inclined wall portion along the battery axis, the outer wall portion includes an outer straight wall portion extending upward from an outer peripheral edge portion of the bottom wall portion along the battery axis, and an outer inclined wall portion extending radially inward as it extends upward from the outer straight wall portion, the film gasket is tightly pressed against the outer peripheral surfaces of the inner inclined wall portion and the inner straight wall portion as the positive electrode can is crimped. <6> an outer container including a cylindrical negative electrode can having a top wall and an inner wall, and a positive electrode can having a bottom wall and an outer wall and fixed to the negative electrode can by crimping via an insulating film gasket; a power-generating element housed inside the outer container, a step of previously welding the film gasket to at least the inner circumferential surface of the outer wall portion and the upper opening end of the outer wall portion of the positive electrode can along the entire periphery; a step of combining the positive electrode can and the negative electrode can while accommodating the power generating element between the negative electrode can and the positive electrode can, so that the bottom wall portion and the top wall portion face each other in a direction along the battery axis and the inner wall portion is located radially inside the outer wall portion; and crimping the outer wall portion of the positive electrode can toward the inner wall portion, thereby tightly pressing the film gasket welded to the outer wall portion against the outer peripheral surface of the inner wall portion of the negative electrode can. <7> <6> In the method for producing an electrochemical cell according to the present invention, The method for manufacturing an electrochemical cell includes welding the film gasket to the positive electrode can by any one of heat welding, induction heating welding, ultrasonic welding, and laser welding. [Explanation of symbols]

[0084] O…Battery axis 1, 60, 70, 80...Secondary battery (electrochemical cell) 2...Outer container 3...Power generation element 10...Anode can 11...Top wall part 12...Inner wall 12a...Lower opening end of inner wall 20...Film gasket 30...Positive electrode can 31...Bottom wall 32…Outer wall part 32a...upper opening end of outer wall 81...Inner inclined wall part 82…Inner straight wall part 85…Outer straight wall 86…Outer inclined wall

Claims

1. an outer container having a negative electrode can and a positive electrode can fixed to the negative electrode can by crimping via an insulating film gasket; a power generating element housed inside the outer container, The negative electrode can is formed in a cylindrical shape with a top having a top wall portion and an inner wall portion formed along an outer peripheral edge portion of the top wall portion, the positive electrode can is formed in a bottomed cylindrical shape having a bottom wall portion disposed to face the top wall portion in a direction along the battery axis, and an outer wall portion formed along an outer peripheral edge portion of the bottom wall portion and surrounding the inner wall portion from the outside in the radial direction, an electrochemical cell, wherein the film gasket is welded to at least the entire inner circumferential surface of the outer wall portion and the entire upper opening end of the outer wall portion of the positive electrode can, and is pressed tightly against the outer circumferential surface of the inner wall portion as the positive electrode can is crimped and fixed.

2. 10. The electrochemical cell of claim 1, an electrochemical cell, wherein the film gasket is further welded over the bottom surface of the outer periphery of the bottom wall portion and is disposed between the lower open end of the inner wall portion of the negative electrode can and the bottom wall portion.

3. 3. The electrochemical cell according to claim 1 or 2, The electrochemical cell, wherein the film gasket is further welded to the entire outer periphery of the outer wall portion.

4. 10. The electrochemical cell of claim 1, The electrochemical cell, wherein the film gasket is formed of a thermoplastic resin.

5. 10. The electrochemical cell of claim 1, the inner wall portion includes an inner inclined wall portion extending radially outward as it extends downward from the outer peripheral edge portion of the top wall portion, and an inner straight wall portion extending downward from the inner inclined wall portion along the battery axis, the outer wall portion includes an outer straight wall portion extending upward from an outer peripheral edge portion of the bottom wall portion along the battery axis, and an outer inclined wall portion extending radially inward as it extends upward from the outer straight wall portion, the film gasket is tightly pressed against the outer peripheral surfaces of the inner inclined wall portion and the inner straight wall portion as the positive electrode can is crimped.

6. an outer container including a cylindrical negative electrode can having a top wall and an inner wall, and a positive electrode can having a bottom wall and an outer wall and fixed to the negative electrode can by crimping via an insulating film gasket; a power-generating element housed inside the outer container, a step of previously welding the film gasket to at least the inner circumferential surface of the outer wall portion and the upper opening end of the outer wall portion of the positive electrode can along the entire periphery; a step of combining the positive electrode can and the negative electrode can while accommodating the power generating element between the negative electrode can and the positive electrode can, so that the bottom wall portion and the top wall portion face each other in a direction along the battery axis and the inner wall portion is located radially inside the outer wall portion; and crimping the outer wall portion of the positive electrode can toward the inner wall portion, thereby tightly pressing the film gasket welded to the outer wall portion against the outer peripheral surface of the inner wall portion of the negative electrode can.

7. 7. The method for manufacturing an electrochemical cell according to claim 6, The method for manufacturing an electrochemical cell includes welding the film gasket to the positive electrode can by any one of heat welding, induction heating welding, ultrasonic welding, and laser welding.

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