Electricity storage device

Abstract

A power storage device (10) is provided with: an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) interposed therebetween; a bottomed cylindrical outer case (15) that accommodates the electrode body (14) and has an opening; a sealing body (16) for sealing the opening; and a first insulating member (17) and a second insulating member (18), the first insulating member (17) being disposed between the electrode body (14) and the safety valve, the first insulating member (17) being disposed between the electrode body (14) and the safety valve, the second insulating member (18) being disposed between the first insulating member (17) and the safety valve, and the first insulating member (17) being disposed between the first insulating member (17) and the safety valve (17), the second insulating member (18) being disposed between the first insulating member (17) and the second insulating member (18). The second insulating member (18) is disposed at a position facing the first insulating member (17) across the electrode body (14), and the amount of gas generated from the second insulating member (18) at a predetermined temperature is greater than the amount of gas generated from the first insulating member (17) at the predetermined temperature.

Description

Technical Field

[0001] The present disclosure relates to a power storage device. Background Art

[0002] As one of the power storage devices, a cylindrical battery having a wound electrode body, a bottomed cylindrical outer case housing the electrode body, and a sealing body sealing an opening of the outer case is known. Cylindrical batteries are sometimes used as assembled batteries (battery packs) formed by connecting a plurality of cylindrical batteries.

[0003] Cylindrical batteries are generally provided with a safety valve that discharges the high-temperature gas inside the battery to the outside when the internal pressure inside the battery rises due to abnormal heat. In addition, cylindrical batteries are provided with insulating plates between the electrode body and the sealing body and between the electrode body and the bottom of the outer shell to prevent internal short circuits. Patent document 1 discloses a cylindrical battery having an insulating plate with a through hole of a predetermined area formed between the electrode body and the bottom of the outer shell.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2016 / 067510 Summary of the invention

[0007] The above cylindrical battery improves the reliability of the power storage device. However, it is important to further improve the safety of the power storage device.

[0008] An object of the present invention is to provide a power storage device having excellent safety.

[0009] In order to solve the above-mentioned problems, the storage device involved in the present disclosure comprises: an electrode body, which is formed by winding a positive electrode and a negative electrode with a separator between them; an outer shell with a bottom cylindrical shape, which accommodates the electrode body and has an opening; a sealing body, which seals the opening of the outer shell; and a first insulating member and a second insulating member, wherein a safety valve for releasing the internal pressure of the outer shell when the internal pressure of the outer shell rises to above a specified level is provided on either the bottom of the outer shell or the sealing body, the first insulating member is arranged between the electrode body and the safety valve, and the second insulating member is arranged at a position opposite to the first insulating member across the electrode body, and the amount of gas generated from the second insulating member at a specified temperature is greater than the amount of gas generated from the first insulating member at the specified temperature.

[0010] According to the power storage device according to the present disclosure, safety is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view showing a power storage device as an example of an embodiment.

[0012] Figure 2A It is a perspective view showing a second insulating plate as an example of an embodiment.

[0013] Figure 2B This is a cross-sectional view perpendicular to the radial direction of the second insulating plate as an example of the embodiment.

[0014] Figure 3A It is a perspective view showing a second insulating plate as another example of the embodiment.

[0015] Figure 3B This is a cross-sectional view perpendicular to the radial direction of a second insulating plate as another example of the embodiment.

[0016] Figure 4A It is a perspective view showing a second insulating plate as another example of the embodiment.

[0017] Figure 4B This is a cross-sectional view perpendicular to the radial direction of a second insulating plate as another example of the embodiment. DETAILED DESCRIPTION

[0018] Hereinafter, an example of an embodiment of a battery as an example of an electric storage device according to the present disclosure will be described in detail with reference to the drawings. In addition, a configuration in which a plurality of embodiments and modifications described below are selectively combined is included in the present disclosure.

[0019] Figure 1 1 is a cross-sectional view of a battery 10 as an example of an embodiment of the present disclosure. Figure 1 As shown, the battery 10 includes an electrode body 14, an electrolyte, a bottomed cylindrical outer shell 15 that accommodates the electrode body 14 and the electrolyte, and a sealing body 16 that seals the opening of the outer shell 15. In the present embodiment, the sealing body 16 is provided with a safety valve that releases the internal pressure of the outer shell 15 when the internal pressure of the outer shell 15 rises to a predetermined level or more, and the details are described later. The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13 inserted between the positive electrode 11 and the negative electrode 12, and the electrode body 14 has a winding structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. In the following, the sealing body side 16 side of the outer shell 15 is sometimes set as "upper" and the bottom side of the outer shell 15 is set as "lower" for explanation.

[0020] The electrode body 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13. In addition, the electrode body 14 has a positive electrode lead 19 connected to the positive electrode 11 and a negative electrode lead 20 connected to the negative electrode 12 as electrode leads. The negative electrode 12 is formed to be one size larger than the positive electrode 11 to suppress the precipitation of lithium. The two separators 13 are formed to be at least one size larger than the positive electrode 11, and the two separators 13 are arranged, for example, in a manner of sandwiching the positive electrode 11.

[0021] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer arranged on both sides of the positive electrode core. The positive electrode core can use a foil of a metal such as aluminum or aluminum alloy that is stable within the potential range of the positive electrode 11, a thin film of the metal configured on the surface, etc. The positive electrode mixture layer contains a positive electrode active material, a conductive material such as acetylene black, and a binding material such as polyvinylidene fluoride (PVdF). The positive electrode 11 can be made by coating a positive electrode mixture slurry containing a positive electrode active material, a conductive material, and a binding material on the positive electrode core, and compressing the coating after drying to form a positive electrode mixture layer on both sides of the positive electrode core.

[0022] The positive electrode active material uses, for example, a lithium transition metal composite oxide. As metal elements contained in the lithium transition metal composite oxide, Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. can be cited. An example of a preferred lithium transition metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co, and Mn. As a specific example, a composite oxide containing Ni, Co, and Mn and a composite oxide containing Ni, Co, and Al can be cited.

[0023] The negative electrode 12 has a negative electrode core and negative electrode mixture layers arranged on both sides of the negative electrode core. The negative electrode core can use a foil of a metal such as copper or copper alloy that is stable within the potential range of the negative electrode, a thin film of the metal arranged on the surface, etc. The negative electrode mixture layer contains a negative electrode active material and a binding material such as styrene-butadiene rubber (SBR). The negative electrode 12 can be manufactured by coating a negative electrode mixture slurry containing a negative electrode active material and a binding material on the negative electrode core, and compressing the coating after drying to form the negative electrode mixture layers on both sides of the negative electrode core.

[0024] The negative electrode active material uses graphite, such as natural graphite such as flaky graphite, block graphite, and earthy graphite, block artificial graphite, and artificial graphite such as graphitized secondary carbon microbeads. The negative electrode active material can also use metals such as Si and Sn that are alloyed with lithium, alloys containing the metals, compounds containing the metals, etc., and they can also be used together with graphite. A preferred example of the active material is a silicate phase such as SiO2 phase or lithium silicate, or a Si-containing material in which Si particles are dispersed in an amorphous carbon phase.

[0025] The electrolyte is a non-aqueous electrolyte, comprising a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more thereof. The non-aqueous solvent may contain a halogen substituted product obtained by replacing at least a portion of the hydrogen in these solvents with a halogen atom such as fluorine. As an example of a non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and mixed solvents thereof may be cited. Examples of the electrolyte salt include lithium salts such as LiPF6.

[0026] The outer shell 15 is a metal container with a bottom and a cylindrical shape with an opening on the upper end. A gasket 25 is provided between the outer shell 15 and the sealing body 16 to ensure the airtightness of the interior of the battery 10 and the insulation between the outer shell 15 and the sealing body 16. The outer shell 15 is formed with a groove 21 that protrudes inwardly from a part of the inner surface of the side portion and supports the sealing body 16. Preferably, the groove 21 is formed in an annular shape along the circumference of the outer shell 15, and the sealing body 16 is supported by the upper surface of the groove 21. The sealing body 16 is fixed to the upper part of the outer shell 15 by the groove 21 and the open end of the outer shell 15 that is pressed against the sealing body 16.

[0027] The sealing body 16 is a disc-shaped member equipped with a safety valve. The sealing body has a structure in which an internal terminal plate 22, an insulating plate 24, and a burst plate 23 are stacked in order from the electrode body 14 side. The internal terminal plate 22 is a metal plate including a thick peripheral portion 22A connected to the positive lead 19 and a thin central portion 22B separated from the annular portion 22A when the internal pressure of the battery exceeds a predetermined threshold. A plurality of vent holes 22C are formed in the peripheral portion 22A.

[0028] The bursting plate 23 is arranged to face the internal terminal plate 22 with the insulating plate 24 sandwiched therebetween. An opening 24A is formed in the radial center of the insulating plate 24, and a vent 24B is formed in the portion of the insulating plate 24 that overlaps with the vent 22C of the internal terminal plate 22. The bursting plate 23 has a valve portion 23A that ruptures when the internal pressure of the battery 10 exceeds a predetermined threshold value, and the valve portion 23A passes into the opening 24A of the insulating plate 24 and is connected to the central portion 22B of the internal terminal plate 22 by welding or the like. The insulating plate 24 insulates the outer peripheral portion 22A from the portion of the valve portion other than the portion connected to the central portion 22B. In addition, the outer peripheral portion of the bursting plate 23 surrounding the valve portion 23A is held between the rivet portion and the groove portion 21 by means of a gasket 25, and the rivet portion is formed by bending the opening of the outer shell can 15 inward.

[0029] The valve portion 23A includes: a joint portion, which is provided in the radial center and protrudes toward the inner side of the battery; and a thin-walled portion, which is formed around the joint portion, and the valve portion 23A is formed in the radial center of the burst plate 23. The joint portion of the valve portion 23A passes into the opening portion 24A and is joined to the central portion 22B. In the battery 10, the internal terminal plate 22 connected to the positive lead 19 is electrically connected to the burst plate 23, thereby forming a current path from the electrode body 14 to the burst plate 23. When the battery 10 is abnormal and the internal pressure rises, the burst plate 23 is pushed upward by the gas, the internal terminal plate 22 is broken, the central portion 22B is separated from the outer peripheral portion 22A, and the valve portion 23A is deformed in a manner protruding toward the outside of the battery. As a result, the current path in the sealing body 16 is cut off. Moreover, after the current path is cut off, when the internal pressure of the battery 10 further rises, the thin-walled portion of the valve portion 23A is broken to form a gas discharge port in the burst plate 23.

[0030] In addition, the structure of the sealing body 16 is not limited to Figure 1 The sealing body 16 may have a laminated structure including two valve bodies, or may have a convex sealing body cover covering the valve body. In addition, the safety valve may be provided at the bottom of the outer shell 15 instead of the sealing body 16. For example, the safety valve may be provided by forming a thin-walled portion at the bottom of the outer shell 15 that ruptures when the internal pressure of the battery 10 rises.

[0031] The battery 10 also includes a first insulating plate 17 as a first insulating member of the present disclosure and a second insulating plate 18 as a second insulating member of the present disclosure. The first insulating plate 17 is arranged between the electrode body 14 and the sealing body 16 to prevent conduction between the negative electrode 12 and the sealing body 16. The second insulating plate 18 is arranged at a position facing the first insulating plate 17 across the electrode body 14. In other words, the second insulating plate 18 is arranged between the electrode body 14 and the bottom of the outer shell 15. The second insulating plate 18 prevents conduction between the positive electrode 11 and the outer shell 15. In the present embodiment, the outer shell 15 is a bottomed cylindrical shape, so the first insulating plate 17 and the second insulating plate 18 have a disc shape. In addition, the first insulating member and the second insulating member may not be plate-shaped like the first insulating plate 17 and the second insulating plate 18. The first insulating member and the second insulating member may also be block-shaped.

[0032] Here, the amount of gas generated from the second insulating plate 18 at a predetermined temperature is greater than the amount of gas generated from the first insulating plate 17 at the predetermined temperature. For example, when the second insulating plate 18 is heated to 500°C, the amount of gas generated from the second insulating plate 18 is greater than the amount of gas generated from the first insulating plate 17 when the first insulating plate 17 is heated to 500°C. As a method for increasing the amount of gas generated from the second insulating plate 18, for example, as described later, it is possible to cite increasing the thickness of the second insulating plate 18, increasing the volume of the second insulating plate 18, or using a material that generates a large amount of gas when burned to make the second insulating plate 18. In addition, a gas generating layer that generates a large amount of gas at a high temperature may be provided on the surface of the second insulating plate 18. In addition, in the battery 10, the first insulating plate 17 may not generate gas at the above-mentioned predetermined temperature.

[0033] The amount of gas generated from the second insulating plate 18 at a predetermined temperature is preferably 110% or more, more preferably 150% or more, and even more preferably 200% or more of the amount of gas generated from the first insulating plate 17 at the same temperature.

[0034] The amount of gas generated from the first insulating plate 17 and the second insulating plate 18 can be measured, for example, using a gas chromatography-mass spectrometry technique (GC-MS method). Specifically, the first insulating plate 17 and the second insulating plate 18 to be measured are respectively placed in a temperature-raising heating device, and after the inside of the device is replaced with an inert gas (He gas), the temperature is raised from 25°C to 500°C at a heating rate of 20°C / min. The amount of gas generated from the sample during this period can be measured by a gas chromatography-mass spectrometry device.

[0035] Figure 2A 2 is a perspective view showing the second insulating plate 18 of this embodiment. Figure 2B is a cross-sectional view perpendicular to the radial direction of the second insulating plate 18. Figure 2A and Figure 2B As shown, the second insulating plate 18 has a stacked structure in which insulating plates 18A, 18B, and 18C are stacked in order from the lower layer side. The thicknesses of the insulating plates 18A, 18B, and 18C are equal. By making the second insulating plate 18 a stacked structure, the thickness and volume of the second insulating plate 18 can be increased.

[0036] The second insulating plate 18 may be composed of a plurality of insulating plates as in the present embodiment, or may be composed of a single insulating plate. When the second insulating plate 18 is composed of a plurality of insulating plates, it is preferred that the second insulating plate 18 is composed of ten or less insulating plates from the viewpoint of productivity. In addition, when the second insulating plate 18 is composed of a plurality of insulating plates, the thickness of each insulating plate may be equal or different. For example, the thickness of the insulating plate on the upper layer side may be greater than the thickness of the insulating plate on the lower layer side.

[0037] The insulating plates 18A, 18B, and 18C are provided with a through hole at the center. The through hole penetrates each insulating plate in the stacking direction of the insulating plates 18A, 18B, and 18C (the direction in which the winding axis of the electrode body 14 extends). Figure 2B As shown, in this embodiment, the apertures of the through holes of the insulating plates 18A, 18B, and 18C are all the same. In addition, the inner diameter of the through hole refers to the average value of the aperture in the up and down direction of the battery 10. The through hole provided in the insulating plate may be one or more. In addition, there is no particular limitation on the shape of the first insulating plate 17, and one through hole may be provided in the center, or multiple through holes may be provided. In addition, the outer diameter of a part of the insulating plate may be smaller than the outer diameter of other insulating plates to facilitate gas movement in the battery 10.

[0038] From the viewpoint of controlling the flow of the generated gas, the opening ratio of the through holes of the insulating plates 18A, 18B, and 18C is preferably 5% or more. In addition, the opening ratio refers to the ratio of the area of ​​the through holes to the total area of ​​the insulating plate (including the area of ​​the portion where the through holes are formed). In addition, from the viewpoint of increasing the volume of the second insulating plate 18, the opening ratio of the through holes of the insulating plates 18A, 18B, and 18C is preferably 50% or less. Therefore, an example of the range of the preferred opening ratio of the second insulating plate 18 is 2% or more and 50% or less.

[0039] It is preferable that the maximum thickness of the second insulating plate 18 is greater than the maximum thickness of the first insulating plate 17. Thus, the amount of gas generated from the second insulating plate 18 can be easily increased compared to the amount of gas generated from the first insulating plate 17. In addition, the maximum thickness of the second insulating plate 18 represents the total of the maximum thicknesses of the laminated insulating plates 18A, 18B, and 18C. In addition, the maximum thickness represents the thickness of the portion where the thickness of the battery 10 in the vertical direction becomes the largest within the surface of the insulating plate.

[0040] The maximum thickness of the second insulating plate 18 is preferably 110% or more, more preferably 150% or more, and further preferably 200% or more of the maximum thickness of the first insulating plate 17. For example, the maximum thickness of the second insulating plate 18 is 0.6 mm, and the maximum thickness of the first insulating plate 17 is 0.3 mm.

[0041] The greater the maximum thickness of the second insulating plate 18 relative to the maximum thickness of the first insulating plate 17, the greater the amount of gas generated from the second insulating plate 18 can be than the amount of gas generated from the first insulating plate 17. However, when the maximum thickness of the second insulating plate 18 is too large, the volume occupied by the electrode body 14 in the battery 10 is reduced when the volume in the battery 10 is fixed, resulting in a decrease in battery capacity. Therefore, the maximum thickness of the second insulating plate 18 is preferably less than 1000% of the maximum thickness of the first insulating plate 17, more preferably less than 900%, and further preferably less than 800%. Therefore, an example of a preferred range of the maximum thickness of the second insulating plate 18 is greater than 110% and less than 1000% of the maximum thickness of the first insulating plate 17. As long as the maximum thickness of the second insulating plate 18 is within this range, it is easy to achieve both suppression of the ejection of high-temperature gas from the side of the outer shell and good battery characteristics.

[0042] The maximum thickness of the second insulating plate 18 is preferably 0.01 mm or more, more preferably 0.2 mm or more, and further preferably 0.4 mm or more. The upper limit of the maximum thickness of the second insulating plate 18 is, for example, 1.5 mm.

[0043] Preferably, the volume of the second insulating plate 18 is larger than the volume of the first insulating plate 17. Thus, the amount of gas generated from the second insulating plate 18 can be greater than the amount of gas generated from the first insulating plate 17. In addition, the volume of the second insulating plate 18 represents the total volume of the stacked insulating plates 18A, 18B, and 18C. In addition, the volume of the insulating plate represents the volume of a portion where no voids such as through holes are formed.

[0044] The volume of the second insulating plate 18 is preferably 110% or more of the volume of the first insulating plate 17, more preferably 150% or more, and further preferably 200% or more. In addition, from the viewpoint of suppressing the decrease in battery capacity, the volume of the second insulating plate 18 is preferably 1000% or less of the volume of the first insulating plate 17, more preferably 900% or less, and further preferably 800% or less. Therefore, an example of a preferred range of the volume of the second insulating plate 18 is 110% or more and 1000% or less of the volume of the first insulating plate 17. As long as the volume of the second insulating plate 18 is within this range, it is easy to achieve both suppression of the ejection of high-temperature gas from the side of the outer shell and good battery characteristics.

[0045] There is no particular limitation on the material of the first insulating plate 17 and the second insulating plate 18, but resins such as polypropylene (PP), polyethylene (PE), and nylon (PA) are preferred. The first insulating plate 17 and the second insulating plate 18 may be made of the same material or different materials. By using a material that generates a large amount of gas when the temperature rises to make the second insulating plate 18, it is easy to make the amount of gas generated from the second insulating plate 18 greater than the amount of gas generated from the first insulating plate 17. As a combination of materials, for example, the first insulating plate 17 may be made of polypropylene (PP) and the second insulating plate 18 may be made of nylon (PA). In addition, in the case where the second insulating plate has a stacked structure in which a plurality of insulating plates are stacked as in the present embodiment, each insulating plate may be made of the same material or different materials. For example, the insulating plate on the upper side of the stacked structure may be made of a material that generates a large amount of gas, and the insulating plate on the lower side of the stacked structure may be made of a material that generates a small amount of gas.

[0046] As described above, the battery 10 of the present embodiment includes: the electrode body 14, which is formed by winding the positive electrode 11 and the negative electrode 12 with the separator 13 interposed therebetween; the outer case 15 having a bottomed cylindrical shape, which accommodates the electrode body 14 and has an opening; the sealing body 16, which blocks the opening; and the first insulating plate 17 and the second insulating plate 18. In addition, the sealing body 16 is provided with a safety valve for releasing the internal pressure of the outer case 15 when the internal pressure rises to a predetermined level or more, the first insulating plate 17 is arranged between the electrode body 14 and the sealing body 16 having the safety valve, and the second insulating plate 18 is arranged at a position facing the first insulating plate 17 across the electrode body 14. That is, the second insulating plate 18 is arranged between the electrode body 14 and the bottom of the outer case 15. In addition, when the safety valve is formed at the bottom of the outer case 15, the first insulating plate 17 is arranged between the electrode body 14 and the bottom of the outer case 15 having the safety valve, and the second insulating plate 18 is arranged between the electrode body 14 and the sealing body 16.

[0047] Here, the amount of gas generated from the second insulating plate 18 at a predetermined temperature is greater than the amount of gas generated from the first insulating plate 17 at the predetermined temperature. Thus, even when the electrode body inside the battery is abnormally heated, it is possible to suppress the high-temperature gas from being ejected from the side of the outer shell. As a mechanism for the above effect, it is speculated as follows. First, when the electrode body 14 inside the battery is abnormally heated, the first insulating plate 17 and the second insulating plate 18 are heated, and gases such as carbon dioxide are generated from the second insulating plate 18. Moreover, when the amount of gas generated from the second insulating plate 18 is greater than the amount of gas generated from the first insulating plate 17, the internal pressure near the second insulating plate 18 increases, generating a force that pushes the electrode body 14 to the upper side, that is, the side where the safety valve is provided. As a result, the abnormally heated electrode body 14 is easily discharged from the safety valve to the outside of the battery before the high-temperature gas is ejected from the side of the outer shell 15. In addition, when the electrode body 14 is discharged to the outside of the battery through the safety valve, it is believed that even if there is an area with an inner diameter smaller than the outer diameter of the electrode body 14 in the outer shell 15, the sealing plate 16, etc., the electrode body 14 can pass through the area. Although the reasons cannot be clearly determined, it is believed that: the electrode body 14 is deformed and passes through the above-mentioned area, or the material constituting the electrode body 14 is gradually discharged to the outside of the battery 10 together with the exhaust gas, thereby reducing the density of the electrode body 14, or the material in the electrode body 14 is decomposed at high temperature, thereby miniaturizing the electrode body 14, etc.

[0048] Next, another example of the embodiment of the battery 10 according to the present disclosure will be described with reference to FIG. 3 and FIG. 4 .

[0049] Figure 3A 1 is a perspective view showing a second insulating plate 18 of another embodiment. Figure 3B is a cross-sectional view perpendicular to the radial direction of the second insulating plate 18. Figure 3A and Figure 3B As shown, the second insulating sheet 18 has a stacked structure in which insulating sheets 18A, 18B, and 18C are stacked in order from the bottom. The thicknesses of the insulating sheets 18A, 18B, and 18C are uniform, for example, 0.2 mm.

[0050] A through hole is provided at the center of the insulating plates 18A, 18B, and 18C. Figure 3B As shown in FIG. 1 , the inner diameter of the through hole provided in each insulating plate is smaller as the insulating plate is provided at the upper layer side of the stacked structure. In other words, the inner diameter of the insulating plate 18A at the bottom layer is the largest, and the inner diameter of the insulating plate 18C at the top layer is the smallest. As a result, the gas generated from the second insulating plate 18 is easily discharged to the upper part of the battery through the through hole provided in the insulating plate.

[0051] Figure 4A 1 is a perspective view showing a second insulating plate 18 of another embodiment. Figure 4B is a cross-sectional view perpendicular to the radial direction of the second insulating plate 18. Figure 4A and Figure 4B As shown, the second insulating plate 18 has a stacked structure in which insulating plates 18A, 18B, and 18C are stacked in order from the bottom layer side, and the thickness of each insulating plate is uniform. A through hole is provided in the center of each insulating plate 18A, 18B, and 18C. Figure 4B As shown in FIG. 1 , the inner diameter of the through hole provided in each insulating plate is larger as the insulating plate provided at the upper layer of the stacked structure is located. In other words, the hole diameter of the bottom insulating plate 18A is the smallest, and the inner diameter of the top insulating plate 18C is the largest. In this way, the volume of the second insulating plate 18 can be ensured, and a vent can be formed to discharge the generated gas to the upper part of the battery.

[0052] In addition, a gap for gas to pass through may be formed between a pair of insulating plates adjacent to each other among the insulating plates 18A, 18B, and 18C. According to this structure, the gas can be easily moved in the second insulating plate 18. As a method of forming the above-mentioned gap, the pair of insulating plates may be not bonded but only abutted against each other. In addition, a groove may be formed on the surface of at least one of the insulating plates of the pair of insulating plates facing the other insulating plate. Through this structure, a gap surrounded by the groove and the other insulating plate is formed. In addition, in the case where the insulating plate is formed with a through hole, one end of the groove may be connected to the through hole, and the other end of the groove may extend to the outer periphery of one insulating plate. Through this structure, the gas passing through the through hole can be more easily moved in the second insulating plate. When a plurality of through holes are formed in one insulating plate, the groove may be connected to adjacent through holes among the plurality of through holes through the two ends of the groove. In addition, a cutout may be formed on the outer periphery of one insulating plate.

[0053] Example

[0054] Hereinafter, the present disclosure will be described in further detail by way of examples, but the present disclosure is not limited to these examples.

[0055] <Example>

[0056] After the electrode body formed by winding the positive electrode and the negative electrode with a separator is housed in an outer shell with a bottom cylindrical shape made of low-carbon steel and injected with a non-aqueous electrolyte, the outer shell is spun to form a groove. An internal terminal plate is arranged on the groove with a gasket in between, and the positive electrode lead is welded to the upper surface of the internal terminal plate by ultrasonic welding. After that, a bursting plate is arranged on the internal terminal plate after decompression and degassing, and the bursting plate is welded to the internal terminal plate. Finally, the battery is obtained by pressing the upper end of the outer shell. In addition, the internal terminal plate, the bursting plate and the gasket constitute Figure 1 The sealing body shown includes a safety valve.

[0057] A second insulating plate is disposed between the bottom of the outer shell and the electrode body. The second insulating plate has a stacked structure in which three insulating plates A1 are stacked. Details of the insulating plate A1 are as follows.

[0058] Diameter: 19mm, thickness: 0.2mm, volume: 56mm 3

[0059] Material: Polypropylene (PP)

[0060] Through hole shape: A through hole with a diameter of 6 mm is formed in the center of the insulating plate A1.

[0061] A first insulating plate (thickness: 0.3 mm, volume: 81 mm) made of polypropylene (PP) was placed between the sealing body and the electrode body. 3 ).

[0062] <Comparative Example>

[0063] A cylindrical battery was produced in the same manner as in the example except that the number of the insulating plates A1 constituting the second insulating plate was changed from three to one.

[0064] [Evaluation of gas generation amount]

[0065] The amount of gas generated from the first insulating plate and the second insulating plate of the embodiment and the comparative example was measured using gas chromatography-mass spectrometry (GC-MS method). The first insulating plate 17 and the second insulating plate 18 of the embodiment and the comparative example were respectively placed in a temperature-raising heating device, and after the inside of the device was replaced with an inert gas (He gas), the temperature was raised from 25°C to 500°C at a heating rate of 20°C / min, and the amount of gas generated was measured. As a result, in the embodiment, the amount of gas generated from the second insulating plate was greater than the amount of gas generated from the first insulating plate, and in the comparative example, the amount of gas generated from the second insulating plate was less than the amount of gas generated from the first insulating plate.

[0066] [Evaluation of battery heating test]

[0067] Eight batteries of each of the embodiment and comparative example were made, and they were placed in an oven at 500°C and heated for 10 minutes before stopping. In addition, the presence or absence of openings on the side (whether there is gas injection from the side) was evaluated by observing the appearance of the side of the outer shell. As a result, no openings were confirmed for the eight batteries in the battery of the embodiment. On the other hand, openings were confirmed for six batteries in the battery of the comparative example. In addition, in this heating test, the safety valves of the batteries of the embodiment and the safety valves of the batteries of the comparative example both worked. However, compared with the batteries of the comparative example, the weight of the battery of the embodiment decreased faster after the safety valve worked, so it is believed that the discharge of the electrode body of the battery of the embodiment is smoother than that of the battery of the comparative example.

[0068] In addition, the present invention is not limited to the above-described embodiment and its modified examples, and various changes and improvements can be made within the scope of the matters described in the claims of the present application.

[0069] Description of Reference Numerals

[0070] 10: Battery (electricity storage device); 11: Positive electrode; 12: Negative electrode; 13: Diaphragm; 14: Electrode body; 15: Outer shell; 16: Sealing body; 17: First insulating plate (first insulating member); 18: Second insulating plate (second insulating member); 18A, 18B, 18C: Insulating plate; 19: Positive electrode lead; 20: Negative electrode lead; 21: Groove; 22: Internal terminal plate; 22A: Peripheral portion; 22B: Central portion; 22C: Vent; 23: Burst plate; 23A: Valve portion; 24: Insulating plate; 24A: Opening; 24B: Vent; 25: Gasket.

Claims

1. A power storage device comprising: The electrode body is formed by winding the positive electrode and the negative electrode with the separator between them; An outer shell having a bottomed cylindrical shape, which accommodates the electrode body and has an opening; a sealing body that seals the opening; and a first insulating member and a second insulating member, in, A safety valve is provided at one of the bottom of the outer shell and the sealing body to release the internal pressure when the internal pressure of the outer shell rises to a predetermined level or more. The first insulating member is disposed between the electrode body and the safety valve. The second insulating member is arranged at a position facing the first insulating member across the electrode body. The amount of gas generated from the second insulating member at a predetermined temperature is greater than the amount of gas generated from the first insulating member at the predetermined temperature.

2. The power storage device according to claim 1, wherein The first insulating member and the second insulating member are respectively in the form of plates, The maximum thickness of the second insulating member is greater than the maximum thickness of the first insulating member.

3. The power storage device according to claim 2, wherein: The maximum thickness of the second insulating member is greater than or equal to 110% and less than or equal to 1000% of the maximum thickness of the first insulating member.

4. The power storage device according to any one of claims 1 to 3, wherein: The maximum thickness of the second insulating member is greater than or equal to 0.01 mm.

5. The power storage device according to claim 1, wherein The volume of the second insulating member is larger than the volume of the first insulating member.

6. The power storage device according to claim 5, wherein: The volume of the second insulating member is greater than or equal to 110% and less than or equal to 1000% of the volume of the first insulating member.

7. The power storage device according to any one of claims 1 to 6, wherein: A material constituting the first insulating member is different from a material constituting the second insulating member.

8. The power storage device according to any one of claims 1 to 7, wherein: The second insulating member has a plurality of laminated insulating plates.

9. The power storage device according to claim 8, wherein: Through holes are formed in each of the plurality of insulating plates, The through holes overlap each other respectively, The inner diameters of the through holes are all the same.

10. The power storage device according to claim 8, wherein Through holes are formed in each of the plurality of insulating plates, The through holes overlap each other respectively, The inner diameter of the through hole of the insulating plate provided closer to the electrode body is smaller.

11. The power storage device according to claim 8, wherein Through holes are formed in each of the plurality of insulating plates, The through holes overlap each other respectively, The inner diameter of the through hole of the insulating plate provided closer to the electrode body is larger.

12. The power storage device according to any one of claims 8 to 11, wherein: The plurality of insulating plates include a pair of insulating plates adjacent to each other, A gap through which gas generated from the second insulating member passes is formed between the pair of insulating plates.

13. The power storage device according to claim 12, wherein: The pair of insulating plates each have a through hole, The through holes overlap each other, A groove is formed on a surface of at least one of the pair of insulating plates that faces the other insulating plate. One end of the groove is connected to the through hole of the one insulating plate.

14. The power storage device according to claim 12, wherein A notch is formed on an outer peripheral edge of at least one of the pair of insulating plates.

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