Sealed battery

Abstract

To provide a battery excellent in safety and reliability at high temperature.SOLUTION: A sealed battery comprises: a battery case which is in bottomed-cylindrical shape having an aperture, and in which a diametrically reduced portion is provided on the open side of a cylinder portion; an electrode body which is housed in the battery case; electrolyte; a sealing member which seals the open of the battery case; and a gasket which is arranged between the sealing member and an open end portion positioned more the open side than the diametrically reduced portion of the battery case, and comes in contact with an inner peripheral side surface of the open end portion and an outer peripheral side surface of the sealing member. The sealing member includes a heat sensitive resistance element (PTC), and is caulked by the open end portion via the gasket. A ring-like member having a heat resistance higher than that of the gasket is arranged between the sealing member and the diametrically reduced portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sealed battery including a battery case, an electrode body housed in the battery case, and a sealing member that closes an opening of the battery case.

Background Art

[0002] As a sealing method for sealed batteries, a method of crimping the open end of a bottomed cylindrical battery case to a sealing member via a gasket is generally used. This enables high sealing performance to be obtained by the repulsive force of the gasket while closing the opening of the battery case with the sealing member.

[0003] When a battery is used in a high-temperature environment or when abnormal heat generation occurs, the gasket may soften or melt due to high temperature. Softening or melting of the gasket not only reduces sealing performance, but also makes the battery case more likely to come into contact with the sealing member, which may cause a short circuit.

[0004] Patent Document 1 discloses that a polymer resin having a melting point of 200°C or higher, a hardness of 100D or less based on the Shore hardness standard, and containing a monomer unit represented by a specific chemical formula is used for a gasket. Accordingly, Patent Document 1 proposes that providing a gasket made of a high heat-resistant polymer resin in a cylindrical secondary battery prevents short-circuiting caused by thermal deformation even when the gasket is exposed to a high-temperature environment due to a rise in the internal temperature of the secondary battery.

[0005] Patent Document 2 proposes that a gasket is composed of at least two layers: a first insulating layer forming a surface layer on the battery case side, and a second insulating layer disposed closer to the sealing body than the first insulating layer, wherein the first material forming the first insulating layer has a higher melting point than the second material forming the second insulating layer, and the melting point is 230°C or higher.

Prior Art Literature

Patent Literature

[0006] [Patent Document 1] Patent No. 5767407 specification [Patent Document 2] Patent No. 6033876 specification [Overview of the project] [Problems that the invention aims to solve]

[0007] As described in Patent Document 1, when the gasket is made of a high-melting-point resin collectively known as engineering plastic, molding and processing are not easy, and cracks are likely to occur during the molding process when the gasket is molded into a gasket shape and crimped.

[0008] When the gasket has a two-layer structure as in Patent Document 2, it has the same problems as in Patent Document 1, as well as the complexity of the sealing structure, the number of parts increasing, and the volume of the sealing part increasing. In addition, if a gap occurs between the first and second layers of the gasket, that gap can become a leakage path, making it easier for liquid leakage to occur. [Means for solving the problem]

[0009] In view of the above, one aspect of the present invention relates to a sealed battery comprising: a bottomed cylindrical shape having an opening, with a reduced diameter portion provided on the opening side of the cylindrical portion; an electrode body housed in the battery case; an electrolyte; a sealing member that closes the opening of the battery case; and a gasket disposed between the opening end of the battery case on the opening side of the reduced diameter portion and the sealing member, and in contact with the inner circumferential surface of the opening end and the outer circumferential surface of the sealing member, wherein the sealing member includes a thermal resistance element (PTC), the sealing member is crimped by the opening end via the gasket, and a ring-shaped member having higher heat resistance than the gasket is disposed between the sealing member and the reduced diameter portion. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a battery with superior safety and reliability while suppressing valve operation caused by thermal deformation of the gasket even at high temperatures. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing an example of a sealed battery according to one embodiment of the present disclosure. [Figure 2] This is a schematic cross-sectional view showing another example of a sealed battery according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0012] The following describes an embodiment of the sealed battery relating to this disclosure with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either the given lower limit and either the given upper limit can be arbitrarily combined as long as the lower limit is not greater than or equal to the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0013] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0014] A sealed battery (hereinafter sometimes simply referred to as "battery") according to one embodiment of the present disclosure comprises a battery case having a bottomed cylindrical shape with an opening, a reduced diameter portion provided on the opening side of the cylindrical portion, an electrode body housed in the battery case, an electrolyte, a sealing member that closes the opening of the battery case, and a gasket. The gasket is positioned between the opening end of the battery case on the opening side of the reduced diameter portion and the sealing member, and is in contact with the inner circumferential surface of the opening end and the outer circumferential surface of the sealing member. The sealing member is crimped by the opening end via the gasket.

[0015] The sealing member includes a positive temperature coefficient (PTC). A positive temperature coefficient (PTC) is an element whose electrical resistance increases with increasing temperature. When an abnormal current flows through the battery, the temperature of the PTC rises due to heat generation, and consequently, the resistance of the PTC increases. This reduces the current flowing through the battery, suppressing abnormal heat generation before the explosion-proof valve activates.

[0016] An example of a sealing member including a thermal resistance element is a sealing member comprising a terminal plate and a bottom plate that electrically connects the terminal plate and one of the electrodes of the electrode body. The thermal resistance element is interposed between the terminal plate and the bottom plate. In this case, if an abnormal current flows through the battery, the resistance of the thermal resistance element increases, thereby reducing the current flowing from the bottom plate to the terminal plate to a small current that does not cause abnormalities.

[0017] On the other hand, as the battery temperature rises, the gasket is also exposed to high temperatures. If the gasket undergoes thermal deformation such as softening or melting due to the rising battery temperature, the terminal plate of the sealing member may come into contact with the crimped portion at the opening end, or the bottom plate of the sealing member may come into contact with the reduced diameter portion of the battery case, potentially causing a short circuit between the sealing member and the battery case. In this case, even if the terminal plate of the sealing member comes into contact with the crimped portion at the opening end, the current flowing through the terminal plate is reduced by the thermal resistance element, and the flow of a short-circuit current is suppressed. However, if the bottom plate of the sealing member comes into contact with the reduced diameter portion of the battery case, a short-circuit current path that does not go through the thermal resistance element is created, and an abnormal current continues to flow. As a result, the electrolyte decomposes due to the excessive temperature rise of the battery, generating gas. When the internal pressure exceeds the threshold due to the gas generation, the explosion-proof valve is activated.

[0018] However, according to the battery of this embodiment, a ring-shaped member having higher heat resistance than the gasket is placed between the sealing member and the reduced-diameter portion. The ring-shaped member restricts contact between the sealing member and the reduced-diameter portion of the battery case, even if the gasket softens or melts, thereby suppressing short circuits. As a result, a safe and reliable battery can be realized while minimizing the operation of the explosion-proof valve.

[0019] The ring-shaped member extends over the reduced diameter portion, along the outer or inner circumferential surface of the gasket. However, it does not extend further toward the opening end towards the crimped portion. In other words, the gasket is in contact with the inner circumferential surface of the opening end and the outer circumferential surface of the sealing member along its entire circumference, and the ring-shaped member does not protrude above the sealing member. In this case, the ring-shaped member is less likely to deform when the opening end of the battery case is crimped to the sealing member via the gasket, thus suppressing the occurrence of cracks. Furthermore, since the interface between the ring-shaped member and the gasket does not form a leakage path, the occurrence of liquid leakage is suppressed. Therefore, a highly reliable and safe battery can be realized.

[0020] The ring-shaped member may be disposed so as to be sandwiched between the reduced diameter portion and the gasket. That is, the ring-shaped member may be disposed between the reduced diameter portion and the outer peripheral side surface of the portion of the gasket extending along the reduced diameter portion (see FIG. 1). Alternatively, the ring-shaped member may be disposed so as to be sandwiched between the gasket and the sealing member. That is, the ring-shaped member may be disposed between the sealing member and the inner peripheral side surface of the portion of the gasket extending along the reduced diameter portion (see FIG. 2).

[0021] When the ring-shaped member is disposed between the reduced diameter portion and the outer peripheral side surface of the gasket, the ring-shaped member only needs to cover the outer peripheral side surface of the gasket on the electrode body side relative to the boundary between the reduced diameter portion and the opening end. It is preferable that the ring-shaped member does not cover the outer peripheral side surface of the gasket along the opening end, and the entire inner peripheral side wall of the opening end is in direct contact with the gasket.

[0022] When the ring-shaped member is disposed between the sealing member and the inner peripheral side surface of the gasket, the ring-shaped member only needs to cover the inner peripheral side surface of the gasket at least in the portion of the gasket bent along the reduced diameter portion. The ring-shaped member may further cover the inner peripheral side surface of the gasket below (on the electrode body side from) the position where the thermosensitive resistance element is provided. The ring-shaped member does not need to cover the inner peripheral side surface of the gasket above (on the side opposite to the electrode body from) the position where the thermosensitive resistance element is provided. The thermosensitive resistance element and a part of the sealing member (for example, a terminal plate) provided above the thermosensitive resistance element (on the side opposite to the electrode body) may be in direct contact with the gasket.

[0023] The ring-shaped member has higher heat resistance than the gasket. The heat resistance can be evaluated, for example, based on the melting point (or softening point) of the resins used for the gasket and the ring-shaped member. The melting point of the ring-shaped member is, for example, 180°C or higher, and may be 200°C or higher or 230°C or higher. Further, even if the melting points (or softening points) of the resins used for the gasket and the ring-shaped member are approximately the same, the heat resistance of the ring-shaped member can be made higher than that of the gasket by including a heat-resistant filler in the resin used for the ring-shaped member.

[0024] Examples of high-melting-point resins that can be used for ring-shaped members include polyphenylene sulfide (PPS) resin, polyimide (PI) resin, polyamide-imide (PAI) resin, polyarylate (PAR) resin, fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) resin and polytetrafluoroethylene (PTFE) resin, polyetheretherketone (PEEK) resin, polyethersulfone (PES) resin, and polybutylene terephthalate (PBT) resin. Among these, at least one selected from the group consisting of polyphenylene sulfide (PPS) resin and polyimide (PI) resin is preferred.

[0025] On the other hand, polypropylene (PP), polyethylene (PE), copolymers of propylene and ethylene, or polyamide resins (nylon) are commonly used as resin materials for gaskets because they are easy to mold. These resin materials may also be used for ring-shaped members. In that case, heat resistance can be imparted to the ring-shaped member by incorporating inorganic fillers into the resin material.

[0026] Inorganic fillers enhance the heat resistance of ring-shaped components by maintaining their shape even in high-temperature environments where resins soften. Examples of inorganic fillers include ceramic particles such as silica, alumina, and titania. These ceramic particles possess excellent thermal conductivity in addition to mechanical strength, improving heat dissipation during abnormal heat generation in batteries and further enhancing heat resistance. Other inorganic fillers that can be used include potassium titanate, calcium silicate (zonotlite, tobermorite), mica, and talc.

[0027] The inorganic filler may include fibers. For example, the inorganic filler may include at least one selected from the group consisting of glass fibers, carbon fibers, and aramid fibers. Among these, it is preferable that the inorganic filler includes glass fibers. For example, the ring-shaped member may be made of glass fiber reinforced polymer (GFRP). The inorganic filler may be included in an amount ranging from 10% to 60% by mass relative to the entire ring-shaped member.

[0028] The gasket preferably does not contain inorganic fillers, but it may contain them. In that case, the mass-based proportion of inorganic fillers in the gasket is smaller than the mass-based proportion of inorganic fillers in the ring-shaped member.

[0029] The configuration of the sealed battery according to this embodiment will be described below with reference to the drawings. However, this embodiment is not limited thereto. In the following illustrated examples, components having the same function are denoted by the same reference numerals.

[0030] Figure 1 is a schematic longitudinal cross-sectional view of an example of a sealed battery. The battery 100 comprises a bottomed cylindrical battery case (battery can) 9, a cylindrical electrode body 10 housed in the battery case 9 together with an electrolyte (not shown), a sealing member 20, and a ring-shaped member 28, with the opening of the battery case 9 being closed by the sealing member. The sealing member 20 includes a PTC element 25 and a gasket 26. In the example of Figure 1, in addition to the PTC element 25 and gasket 26, the sealing member 20 further comprises a terminal plate 21, a bottom plate 22, a valve body 23, and a spacer (valve body support plate) 24.

[0031] The battery case 9 has a reduced diameter portion 9X on its opening side. At the opening end 9Y on the opening side of the reduced diameter portion 9X, the sealing member 20 is inserted into the opening end 9Y, and the opening end 9Y is crimped to the sealing member 20 via a gasket 26, thereby sealing the opening of the battery case with the sealing member.

[0032] The electrode body 10 may be constructed by winding a positive electrode 1 and a negative electrode 2 via a separator 3. The positive electrode lead 4 connected to the current collector 1a of the positive electrode 1 is connected to the bottom plate 22. The negative electrode lead 5 connected to the negative electrode 2 is connected to the case 9. In addition, an upper insulating plate 6 and a lower insulating plate 7 are placed at the top and bottom of the electrode body 10, respectively, to prevent internal short circuits.

[0033] The base plate 22 is, for example, a ring-shaped member having an opening in the center, and its outer edge is bent and folded in the circumferential direction. The bent and extended folded portion sandwiches the valve body 23 and spacer 24 between the base plate 22, fixing the valve body 23 and spacer 24 to the base plate 22. In other words, the valve body 23 is crimped to the base plate 22 via the spacer 24 and fixed to the base plate 22. The base plate 22 is electrically connected to one electrode (positive electrode 1) of the electrode body via the positive electrode lead 4, and is also electrically connected to the terminal plate 21 via the folded portion and the PTC element 25.

[0034] The valve body 23 is provided between the connection portion of the bottom plate 22 to the positive lead 4 and the terminal plate 21. A PTC element 25 is interposed between the terminal plate 21 and the bottom plate 22.

[0035] The valve body 23 is, for example, a disc-shaped plate material without an opening. When the internal pressure of the battery 100 rises, pressure is applied to the portion of the valve body 23 not covered by the spacer 24 in an outward-bulging direction. When the internal pressure exceeds the desired valve operating pressure, at least a portion of the valve body 23 ruptures due to tensile stress. The gas inside the battery 100 is discharged to the outside through the rupture in the valve body 23 and the hole 21a in the terminal plate. This activates the explosion-proof function and releases the internal pressure.

[0036] The valve body 23 may be, for example, a metal plate (e.g., aluminum foil), and both sides of its surface may be coated with a resin material. This suppresses corrosion of the valve body even if electrolyte comes into contact with its surface.

[0037] The spacer (valve support plate) 24 interposed between the valve body 23 and the folded portion of the bottom plate 22 is a ring-shaped member. When the valve body 23 expands due to an increase in internal pressure, the spacer 24 restricts the area in which the valve body 23 expands to the central region of the ring where it is not interposed. By adjusting the width of the ring, the valve operating pressure can be controlled to a desired value.

[0038] The PTC (Positive Temperature Coefficient) element 25 is a ring-shaped component containing a material whose electrical resistance increases with temperature. When an abnormally large current flows through the battery 100, the temperature inside the PTC element 25 rises due to heat generation. As a result, the electrical resistance of the PTC element 25 increases, reducing the current flowing through the battery 100.

[0039] The terminal board 21, the PTC element 25, and the bottom plate 22 to which the valve body 23 and spacer 24 are fixed are stacked and crimped to the battery case 9 via a gasket 26, thereby sealing the opening of the battery case 9.

[0040] A ring-shaped member 28 is provided between the sealing member 20 and the reduced-diameter portion 9X. In the example shown in Figure 1, the ring-shaped member 28 is interposed between the outer peripheral surface of the gasket 26 and the reduced-diameter portion 9X, along the inner peripheral side wall of the reduced-diameter portion 9X. The ring-shaped member 28 has higher heat resistance than the gasket 26.

[0041] When the battery 100 is exposed to a high-temperature environment, or when a large current flows through the battery 100 due to abnormal discharge, the resistance of the PTC element 25 increases with the rise in temperature, and the current flowing from the bottom plate 22 to the terminal plate 21 decreases. This suppresses the flow of a large current through the battery 100.

[0042] However, as the temperature of the battery 100 rises, the gasket 26 becomes more susceptible to softening or melting due to the high temperature, and is more prone to thermal deformation. If the ring-shaped member 28 is not provided, thermal deformation of the gasket 26 may cause the terminal plate 21 to come into contact with the crimped portion of the open end 9Y, resulting in a short circuit, or the bottom plate 22 to come into contact with the reduced diameter portion 9X, resulting in a short circuit.

[0043] In the case where the terminal plate 21 is in contact with the open end 9Y, the current flowing from the bottom plate 22 to the terminal plate 21 is reduced by passing through the PTC element 25, thus suppressing the flow of a large current due to a short circuit. However, when the bottom plate 22 is in contact with the reduced diameter portion 9X, a current path is formed that does not pass through the PTC element 25, so a large current continues to flow between the bottom plate 22 and the reduced diameter portion 9X. As a result, excessive temperature rise in the battery can lead to the decomposition of the electrolyte and the generation of gas, and the internal pressure of the battery may exceed a threshold, causing the explosion-proof function to activate and the valve body 23 to rupture.

[0044] The ring-shaped member 28 maintains its shape even at high temperatures where the gasket 26 is susceptible to thermal deformation, and insulates the bottom plate 22 from the reduced-diameter portion 9X. The ring-shaped member 28 restricts contact between the bottom plate 22 and the reduced-diameter portion 9X even in high-temperature environments, thereby suppressing short circuits between the bottom plate 22 and the reduced-diameter portion 9X. In other words, it is possible to suppress the flow of abnormal current to the battery 100 without activating the explosion-proof function.

[0045] The ring-shaped member 28 only needs to serve to insulate the sealing member 20 (especially the bottom plate 22) from the battery case (especially the reduced diameter portion 9X). Therefore, it is not limited to being provided between the outer peripheral surface of the gasket 26 and the reduced diameter portion 9X as shown in Figure 1, but may also be provided between the inner peripheral surface of the gasket 26 and the sealing member. Figure 2 shows an example of a battery 101 in which the ring-shaped member 28 is interposed between the inner peripheral surface of the gasket 26 and the bottom plate 22 so as to be along the side and bottom surfaces of the bottom plate 22 of the sealing member.

[0046] The thickness of the ring-shaped member 28 may be, for example, 5 μm or more, or 500 μm or less, in order to ensure insulation between the sealing member and the battery case. The ring-shaped member 28 may be a ring-shaped film or plate. If the ring-shaped member is a film or plate, molding is not required in its manufacture, and therefore a resin with higher heat resistance than that of a gasket but with low moldability can be used for the ring-shaped member.

[0047] The material of the battery case 9 is not particularly limited, and examples include iron and / or iron alloys (including stainless steel), aluminum, aluminum alloys (such as alloys containing trace amounts of other metals such as manganese and copper).

[0048] Next, using a lithium primary battery as an example, other configurations of battery 100 will be explained illustratively.

[0049] (positive electrode) The positive electrode contains a positive electrode active material, and manganese dioxide can be used as the positive electrode active material. The positive electrode comprises, for example, a positive electrode current collector and a positive electrode mixture layer attached to the positive electrode current collector. In addition to the positive electrode active material, the positive electrode mixture layer may contain a resin material such as fluororesin as a binder. The positive electrode mixture layer may also contain a conductive material such as carbon material as a conductive agent. The positive electrode current collector is, for example, expanded metal, net, or perforated metal made of stainless steel.

[0050] (Negative electrode) The negative electrode contains a negative electrode active material, and metallic lithium or a lithium alloy can be used as the negative electrode active material. The metallic lithium or lithium alloy is extruded, for example, into a long sheet and used as the negative electrode. As lithium alloys, alloys such as Li-Al, Li-Sn, Li-Ni-Si, and Li-Pb can be used, but Li-Al alloy is preferred. The content of metallic elements other than lithium in the lithium alloy is preferably 0.1% by mass or more and 5% by mass or less from the viewpoint of ensuring discharge capacity and stabilizing internal resistance.

[0051] (Separator) As separators, microporous membranes or nonwoven fabrics made of resin are preferably used. As separator materials (resins), polyolefins, polyamides, and polyamide-imides are preferred.

[0052] (electrolyte) A non-aqueous solvent containing a dissolved lithium salt can be used as the electrolyte. The non-aqueous solvent is not particularly limited, but propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, γ-butyrolactone, etc., can be used. As for the lithium salt, lithium borofluoride, lithium hexafluoride phosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, etc., can be used.

[0053] [Examples] The present disclosure will be described in detail below based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0054] Example 1 (1) Preparation of the positive electrode A wet positive electrode mixture was prepared by mixing 100 parts by mass of electrolytic manganese dioxide with 5 parts by mass of Ketjenblack, a conductive agent, and then adding 5 parts by mass of polytetrafluoroethylene, a binder, and an appropriate amount of pure water, and kneading the mixture.

[0055] A positive electrode was obtained by pressing a positive electrode mixture onto an expanded metal (positive electrode current collector) made of stainless steel using a roll, and then drying it. The thickness of the positive electrode after rolling was 520 μm, and the weight of the positive electrode mixture per unit area was 0.134 g / cm². 2 That's what I decided.

[0056] Next, the positive electrode was cut into a strip 38 mm wide and 192 mm long. Subsequently, a portion of the filled positive electrode mixture was peeled off, and a stainless steel tab lead was resistance-welded to the exposed portion of the positive electrode current collector.

[0057] (2) Fabrication of the negative electrode A sheet of Li-Al alloy (Al content: 0.3 mass%) with a thickness of 200 μm was cut to a predetermined size to obtain a strip-shaped negative electrode. Nickel tab leads were connected to predetermined locations on the negative electrode by pressure welding.

[0058] (3) Fabrication of electrodes An electrode body was fabricated by stacking the positive and negative electrodes with a separator in between and winding them in a spiral pattern along a 3.5 mm diameter core. A 25 μm thick microporous polyethylene membrane was used as the separator.

[0059] (4) Preparation of the electrolyte An electrolyte was prepared by dissolving lithium trifluoromethanesulfonate at a concentration of 0.7 mol / L in a non-aqueous solvent prepared by mixing propylene carbonate (PC) and 1,2-dimethoxyethane (DME) in a volume ratio of 4:6. The viscosity of the electrolyte was 0.0014 Pa·s at 20°C.

[0060] (5) Assembly of cylindrical battery A ring-shaped base plate (made of stainless steel, 0.3 mm thick) with an inner diameter of 4.0 mm was prepared. The valve body and a spacer (made of stainless steel, 0.3 mm thick) were placed on the base plate, and the valve body was crimped via the spacer by bending the outer edge of the base plate inwards, thereby creating a lower sealing member including the base plate and valve body. The valve body was made of 25 μm thick aluminum foil, with both sides coated with a 50 μm thick polyethylene (PE) film.

[0061] A bottomed cylindrical battery case made of nickel-plated steel sheet of a specified size was prepared. The electrode body was inserted into the battery case with a ring-shaped lower insulating plate placed at its bottom. Then, the tab lead of the negative electrode was connected to the inner bottom surface of the battery case.

[0062] A fixed amount of electrolyte was injected into the battery case, impregnating the electrode body with the electrolyte. The upper insulating plate was placed on top of the electrode group. A ring-shaped member made of PPS was placed on the reduced diameter section of the battery case. Then, with the tab lead of the positive electrode connected to the inner surface of the bottom plate, the lower sealing member, PTC element (thickness 0.3 mm, inner diameter 5.0 mm), and terminal plate (made of SUS, thickness 0.3 mm) were stacked on top of each other, and these components were sealed by crimping them into the battery case via a gasket made of a block copolymer of polypropylene (PP) and polyethylene (PE), completing a test lithium primary battery (diameter 17 mm, height 45.5 mm).

[0063] In this way, 30 sealed cylindrical lithium primary batteries A1 having the structure shown in Figure 1 were fabricated.

[0064] Example 2 In Example 1, a cylindrical battery was assembled using a ring-shaped member made of PI instead of a ring-shaped member made of PPS. Thirty sealed cylindrical lithium primary batteries A2 having the structure shown in Figure 1 were manufactured in the same manner as in Example 1.

[0065] Example 3 In Example 1, a gasket made of polypropylene (PP) was used. Thirty sealed cylindrical lithium primary batteries A3 having the structure shown in Figure 1 were fabricated in the same manner as in Example 1.

[0066] Example 4 In Example 1, a ring-shaped member was made of glass fiber reinforced polymer (GFRP) composed of polypropylene (PP) and containing glass fibers as an inorganic filler. The proportion of glass fibers in the total reinforcing resin was 20% by mass. Aside from the above, 30 sealed cylindrical lithium primary batteries A4 having the structure shown in Figure 1 were manufactured in the same manner as in Example 1.

[0067] Comparative Example 1 In Example 1, a cylindrical battery was assembled without using a ring-shaped member. Thirty sealed cylindrical lithium primary batteries B1 having the structure shown in Figure 1 were manufactured in the same manner as in Example 1.

[0068] Comparative Example 2 In Example 1, a gasket made of tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) was used. Thirty sealed cylindrical lithium primary batteries B2 having the structure shown in Figure 1 were fabricated in the same manner as in Example 1.

[0069] Comparative Example 3 In Example 1, the gasket had a two-layer structure consisting of a first gasket made of PPS on the outer circumference and a second gasket made of PP on the inner circumference. Thirty sealed cylindrical lithium primary batteries B3 having the structure shown in Figure 1 were manufactured in the same manner as in Example 1.

[0070] [evaluation] Thirty lithium primary batteries were divided into three groups of 10. One group of 10 lithium primary batteries was placed in a test chamber immediately after fabrication, and the chamber temperature was increased from room temperature to 125°C at a rate of 5°C / minute. The batteries were then kept at 125°C for 10 minutes.

[0071] After being held at 125°C, the batteries were removed from the test chamber and cooled to room temperature. Valve operation and leakage were then visually inspected. The number of batteries showing valve operation or leakage was defined as n1, and the ratio of batteries showing valve operation to the total number of batteries (=n1 / 10) was evaluated.

[0072] For the other set of 10 lithium primary batteries, the battery holding temperature was changed from 125°C to 160°C. After holding at 160°C, the batteries were visually inspected for valve activation and leakage in the same manner. The number of batteries in which valve activation or leakage was confirmed was defined as n2, and the ratio of batteries in which valve activation was confirmed to the total number of batteries (=n2 / 10) was evaluated.

[0073] For the remaining set of 10 lithium primary batteries, the battery holding temperature was changed from 125°C to 170°C. After holding at 170°C, the batteries were visually inspected for valve activation and leakage in the same manner. The number of batteries in which valve activation or leakage was confirmed was defined as n3, and the ratio of batteries in which valve activation was confirmed to the total number of batteries (=n3 / 10) was evaluated.

[0074] The above evaluations were performed for each of the lithium primary batteries A1-A4 and B1-B3. The evaluation results for lithium batteries A1-A4 and B1-B3 are shown in Table 1. Table 1 also shows the configuration of the gaskets and ring-shaped members used in each battery.

[0075] [Table 1]

[0076] As shown in Table 1, in battery B1, which does not have a ring-shaped member, no valve activation or leakage occurred in any of the batteries when held at 125°C, but valve activation was observed in some batteries when held at 160°C or higher. In contrast, in batteries A1 to A4, which have a heat-resistant ring-shaped member, no valve activation or leakage occurred in any of the batteries, even when held at 170°C or higher.

[0077] In battery B2, which lacked a ring-shaped component and whose entire gasket was constructed from a heat-resistant resin material (PFA), a significant number of batteries exhibited valve activation even when held at 125°C. This is likely because, in battery B2, PFA, which has poor moldability and processability, was used for the gasket, making it prone to cracking during gasket molding and crimping. Under high temperatures, moisture and other substances entered the battery through these cracks, increasing gas generation and causing the valve to activate prematurely.

[0078] In battery B3, which had a two-layer structure consisting of a first gasket containing high heat-resistant resin (PPS) and a second gasket, no valve activation or leakage occurred in any of the batteries when held at 125°C. However, leakage was observed in some batteries when held at 160°C or higher. This is thought to be because a gap formed between the first and second gaskets, and at high temperatures, the gap widened, forming a leakage path. [Industrial applicability]

[0079] The sealed battery according to the present invention is suitable for powering various electronic devices because it offers excellent safety and reliability at high temperatures. [Explanation of Symbols]

[0080] 1 positive electrode 1a Positive electrode current collector 2 negative electrode 3 Separators 4 Positive lead 5. Negative lead 6. Upper insulating plate 7. Lower insulating plate 9 Battery case 9X reduced diameter section 9Y open end 10 Electrode body 20 Sealing material 21 Terminal board 21a hole 22 Bottom plate 23 Valve body 24 Spacers 25 PTC elements 26 Gasket 28 Ring-shaped member 100, 101 battery

Claims

1. A battery case having a bottomed cylindrical shape with an opening, and a reduced diameter portion provided on the opening side of the cylindrical part, The electrode body housed in the aforementioned battery case, Electrolyte and A sealing member that closes the opening of the battery case, The battery case comprises a gasket positioned between the opening end on the opening side of the reduced diameter portion of the battery case and the sealing member, and in contact with the inner circumferential surface of the opening end and the outer circumferential surface of the sealing member, The sealing member includes a thermal resistance element (PTC), The sealing member is crimped by the open end via the gasket, A ring-shaped resin member having higher heat resistance than the gasket is disposed between the sealing member and the reduced diameter portion. The aforementioned sealing member is Terminal board and The terminal plate and the electrode of one polarity of the electrode body are electrically connected by a bottom plate, A sealed battery in which the thermal resistance element is interposed between the lower surface of the terminal plate and the bottom plate.

2. The sealed battery according to claim 1, wherein the ring-shaped member is disposed between the reduced diameter portion and the outer peripheral surface of the portion of the gasket that extends along the reduced diameter portion.

3. The sealed battery according to claim 1, wherein the ring-shaped member is disposed between the sealing member and the inner circumferential surface of the portion of the gasket that extends along the reduced diameter portion.

4. The sealed battery according to any one of claims 1 to 3, wherein the ring-shaped member comprises at least one selected from the group consisting of polyphenylene sulfide (PPS) resin, polyimide (PI) resin, polyamide-imide (PAI) resin, polyarylate (PAR) resin, tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) resin, polytetrafluoroethylene (PTFE) resin, polyetheretherketone (PEEK) resin, polyethersulfone (PES) resin, and polybutylene terephthalate (PBT) resin.

5. The ring-shaped member comprises an inorganic filler, as described in any one of claims 1 to 3, for a sealed battery.

6. The sealed battery according to claim 5, wherein the inorganic filler comprises at least one selected from the group consisting of glass fibers, carbon fibers, and aramid fibers.

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