Patent Application
20230098011
The present disclosure relates to a sealed battery.
There has hitherto been widely known a sealed battery comprising a bottomed cylindrical outer housing can and a sealing assembly that closes the opening of the outer housing can (e.g., see Patent Literature 1). As disclosed in Patent Literature 1, the sealing assembly has a structure in which, for example, an internal terminal plate, a lower vent member, an insulating member, an upper vent member, and a cap are laminated in this order. The lower vent member and the upper vent member are connected to each other at central portions thereof, and between respective peripheries thereof, the insulating member is interposed. In this case, when an abnormality occurs in the battery and internal pressure rises, the lower vent member is deformed so as to push the upper vent member toward the cap and is broken, whereby a current path between the lower vent member and the upper vent member is cut off. When the internal pressure further rises, the upper vent member is broken, and gas is discharged from the opening of the cap.
As described above, according to the conventional sealing assembly, when an abnormality occurs in the battery and the internal pressure rises, the current path of the battery is cut off, and a gas discharge path is formed, thus ensuring the safety of the battery at the time of occurrence of an abnormality. However, the conventional sealing assembly has problems such as a large thickness, a large number of parts, and complicated shapes of parts. Therefore, there is a need for a sealing assembly having a small thickness, a simple structure, and a small number of parts while ensuring a function as a safety valve.
A sealed battery according to one aspect of the present disclosure is a sealed battery comprising: an electrode assembly having an electrode tab; an outer housing can in a shape of a bottomed cylinder that accommodates the electrode assembly; and a sealing assembly that closes an opening of the outer housing can. The sealing assembly includes a first thin portion formed in an annular shape, a valve portion that is surrounded by the first thin portion, and deforms to protrude outward of the battery when internal pressure of the battery rises, and a second thin portion in a linear shape formed in the valve portion, and the electrode tab or a metal plate to which the electrode tab is connected is disposed to intersect the second thin portion and is joined to an inner surface of the valve portion to sandwich the second thin portion.
According to an aspect of the present disclosure, it is possible to provide a sealed battery comprising a sealing assembly having a small thickness, a simple structure, and a small number of parts while ensuring a function as a safety valve. According to the sealed battery of the present disclosure, for example, when the internal pressure rises due to an abnormality of the battery, the valve portion is deformed so as to protrude outward of the battery, the linear thin portion formed in the valve portion is broken to form an exhaust port, and the electrode tab is detached from the sealing assembly to rapidly cut off the current path of the battery.
An example of an embodiment of the present disclosure will be described below in detail. In the following description, as an example of an embodiment of the sealed battery according to the present disclosure, a cylindrical battery in which a bottomed cylindrical outer housing can 16 accommodates a wound type electrode assembly 14 is exemplified, but the battery may be a square battery comprising a rectangular outer housing can. The electrode assembly may be of a laminated type in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with separators interposed therebetween. In the present specification, for convenience of description, a sealing assembly 17 side is referred to as “upper,” and the bottom side of an outer housing can 16 is referred to as “lower.”
The electrolyte may be either an aqueous electrolyte or a non-aqueous electrolyte. An example of the suitable sealed battery 10 is a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte, such as a lithium-ion battery. The non-aqueous electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, esters, ethers, nitriles, amides, or a mixed solvent of two or more of them may be used. The non-aqueous solvent may contain a halogen substitution in which at least a part of hydrogen in the solvent is substituted with a halogen atom such as fluorine. Note that the non-aqueous electrolyte is not limited to a liquid electrolyte but may be a solid electrolyte. As the electrolyte salt, for example, a lithium salt such as LiPF6 is used.
The electrode assembly 14 includes the elongated positive electrode 11, the elongated negative electrode 12, two elongated separators 13, the positive electrode tab 20 joined to the positive electrode 11, and the negative electrode tab 21 joined to the negative electrode 12. The negative electrode 12 is formed to have a size larger than that of the positive electrode 11 in order to prevent the precipitation of lithium. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in the longitudinal direction and the shorter direction (vertical direction). The two separators 13 are formed to have at least one size larger than the positive electrode 11 and are disposed to sandwich the positive electrode 11, for example.
The positive electrode 11 has a positive electrode core and positive electrode mixture layers provided on both sides of the positive electrode core. As the positive electrode core, it is possible to use a foil of a metal stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, a film in which the metal is disposed on the surface layer, or the like. The positive electrode mixture layer includes a positive electrode active material, a conductive agent such as acetylene black, and a binder such as a polyvinylidene fluoride (PVdF). The positive electrode 11 can be produced by coating a positive electrode mixture slurry including a positive electrode active material, a conductive agent, a binder, and the like on the positive electrode core, drying the coating film, and then compressing the coating film to form positive electrode mixture layers on both sides of the positive electrode core.
As the positive electrode active material, for example, a lithium transition metal complex oxide is used. Examples of the metal element contained in the lithium transition metal complex oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, and the like. An example of a suitable lithium transition metal complex oxide is a lithium metal complex oxide containing at least one of Ni, Co, and Mn. Specific examples include composite oxides containing Ni, Co, and Mn and composite oxides containing Ni, Co, and Al.
The negative electrode 12 has a negative electrode core and negative electrode mixture layers provided on both surfaces of the negative electrode core. As the negative electrode core, it is possible to use a foil of a metal stable in the potential range of the negative electrode 12, such as copper or copper alloy, a film in which the metal is disposed on the surface layer, or the like. The negative electrode mixture layer includes a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). The negative electrode 12 can be produced by applying a negative electrode mixture slurry including a negative electrode active material, a binder, and the like on the negative electrode core, drying the coating film, and then compressing the coating film to form negative electrode mixture layers on both sides of the negative electrode core.
As the negative electrode active material, for example, a carbon-based active material is used, which is natural graphite such as scaly graphite, massive graphite, or earthy graphite, artificial graphite such as massive artificial graphite or graphitized mesophase carbon microbeads, or the like. As the negative electrode active material, an element which is alloyed with lithium, such as Si and Sn, an alloy containing the element, a compound containing the element, or the like may be used, and these may be used in combination with the carbon-based active material.
Insulating plates 18, 19 are disposed above and below the electrode assembly 14, respectively. In the example illustrated in
The outer housing can 16 is, for example, a metal container having a bottomed cylindrical shape. A resin gasket 23 is provided between the outer housing can 16 and the sealing assembly 17. A gap between the outer housing can 16 and the sealing assembly 17 is closed by a gasket 23, and the inside of the battery is sealed hermetically. The outer housing can 16 has a grooved portion 22 formed on a side surface portion by spinning from the outside of the side surface portion, for example, and supports the sealing assembly 17. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer housing can 16 and supports the sealing assembly 17 on the upper surface of the outer housing can 16. The upper end of the outer housing can 16 is bent inward of the can and caulked to the periphery of the sealing assembly 17.
Hereinafter, the sealing assembly 17 will be described in detail with further reference to
As illustrated in
The sealing assembly 17 is fixed to the outer housing can 16 by the annular portion 31 being held between the upper end of the outer housing can 16 and the grooved portion 22 via the gasket 23. On the other hand, the valve portion 30 is not held between the upper end of the outer housing can 16 and the grooved portion 22 and is deformable when the internal pressure rises. The sealing assembly 17 is formed of a single metal plate including the valve portion 30 and the annular portion 31 divided by the first thin portion 34. Therefore, the sealing assembly 17 has advantages such as a small thickness, a simple structure, and a small number of parts.
In the sealed battery 10, the positive electrode tab 20 is joined to the inner surface of the valve portion 30 by welding or the like. External wiring connected to an electric product (not illustrated), another sealed battery 10, or the like is connected to the outer surface of the sealing assembly 17 by welding or the like. Note that the external wiring may be connected to either the valve portion 30 or the annular portion 31 as long as being located so as not to prevent the inversion or breakage of the valve portion 30.
The valve portion 30 has a downward convex shape protruding inward of the battery and is configured to protrude outward of the battery when the internal pressure rises. As will be described in detail later, when the internal pressure reaches a predetermined pressure, the valve portion 30 is inverted so as to have an upward convex shape protruding outward of the battery. Then, the second thin portion 36 is broken to form an exhaust port, and the positive electrode tab 20 is detached from the valve portion 30 to cut off the current path of the battery. After the inversion of the valve portion 30 and before the breakage of the second thin portion 36, the positive electrode tab 20 may be detached from the valve portion 30 to cut off the current path.
The metal plate constituting the sealing assembly 17 is, for example, an aluminum alloy plate containing aluminum as a main component. The thickness of the metal plate is not particularly limited, but as an example, the thickness is 0.3 mm to 2 mm in a portion except for the first thin portion 34 and the second thin portion 36. The thicknesses of the valve portion 30 and the annular portion 31 may be the same or different. The sealing assembly 17 is manufactured, for example, by forming the annular first thin portion 34 and the linear second thin portion 36 on the single metal plate and pressing the valve portion 30 surrounded by the first thin portion 34 into a downward convex shape.
In the present embodiment, the annular first thin portion 34 is formed by the annular first groove 35. The first groove 35 is formed on the inner surface of the sealing assembly 17 but can be formed on the outer surface of the sealing assembly 17. The thickness of the first thin portion 34 is, for example, 10% to 50% of the maximum thickness of the valve portion 30 and can be adjusted by changing the depth of the first groove 35. The first thin portion 34 is preferably formed thicker than the second thin portion 36.
The first thin portion 34 (first groove 35) is preferably formed in a circular shape without corners in bottom view, and particularly preferably formed in a substantially perfect circular shape as illustrated in
Note that the first thin portion 34 is not limited to the linear thin portion formed by the first groove 35 but may be, for example, a wide thin portion in which the thickness of the metal plate continuously decreases from the inner side to the outer side of the sealing assembly 17 in the radial direction.
The valve portion 30 preferably has a substantially perfect circular shape in bottom view. In this case, the valve portion 30 is smoothly inverted when the internal pressure rises. As described above, the valve portion 30 and the annular portion 31 are separated by the first thin portion 34 (first groove 35), so that the shapes of the valve portion 30 and the annular portion 31 in bottom view are determined by the shape of the first thin portion 34 in bottom view. When the valve portion 30 has a perfect circular shape in bottom view, the annular portion 31 is formed in an annular shape in bottom view.
A diameter d of the valve portion 30 is, for example, 50% to 90%, preferably 55% to 85%, of a diameter D of the sealing assembly 17. When “diameter d/diameter D” is within this range, the sealing assembly 17 can be stably fixed to the outer housing can 16, and at the time of occurrence of an abnormality, a large exhaust port can be formed, and gas can be discharged smoothly.
The valve portion 30 has a downward convex shape protruding inward in a normal use state in which the internal pressure of the battery is low. That is, the valve portion 30 is recessed inward as viewed from the outside of the battery. The valve portion 30 bulges toward the electrode assembly 14 in a range where the valve portion 30 is not in contact with the electrode assembly 14. The shape of the valve portion 30 is not particularly limited as long as being deformable into an upward convex shape by internal pressure. However, the shape of the valve portion 30 is preferably a shape that can be inverted from a downward convex shape to an upward convex shape, and may be, for example, a shape formed by the whole valve portion 30 being curved in a dome shape.
In the present embodiment, the valve portion 30 has a flat bottom 32 that bulges most toward the electrode assembly 14, and an annular inclined portion 33 formed around the bottom 32. In the example illustrated in
As described above, the linear second thin portion 36 is formed in the valve portion 30. The second thin portion 36 is thinner than the first thin portion 34 and breaks preferentially over the first thin portion 34 when the internal pressure rises due to, for example, an abnormality of the battery. The second thin portion 36 is formed only on the valve portion 30. The sealing assembly 17 is configured such that an exhaust port is formed by the breakage of the second thin portion 36.
The second thin portion 36 is formed by a linear second groove 37. The second groove 37 preferably has the shape of a straight line but may be slightly bent as long as having the shape of a line. The second groove 37 is formed on the inner surface of the valve portion 30 but can be formed on the outer surface. The thickness of the second thin portion 36 is, for example, 30% to 90%, preferably 50% to 80%, of the maximum thickness of the valve portion 30 and can be adjusted by changing the depth of the second groove 37.
In the present embodiment, one second thin portion 36 is formed along the radial direction of the first thin portion 34 passing through a center a of the first thin portion 34 formed in the annular shape, that is, a center a of the valve portion 30. Stress is concentrated in the central portion of the valve portion 30 at the time of deformation of the valve portion 30, so that when the second thin portion 36 is formed to pass through the center a, the second thin portion 36 is easily broken with the deformation of the valve portion 30. The second thin portion 36 is formed over the entire radial length of the valve portion 30 and is connected to the first thin portion 34. The second groove 37 illustrated in
In order to break the second thin portion 36 (second groove 37) preferentially over the first thin portion 34 (first groove 35), the shapes of the grooves forming the respective thin portions may be made different from each other. For example, the first groove 35 may have a semicircular shape in cross section, and the second groove 37 may have a triangular shape in cross section. Alternatively, each of the grooves may have a triangular shape in cross section, and an angle θ of the triangle at the depth of the groove may be made different. For example, two or more second thin portions 36 may be formed in a range where the joining of the positive electrode tab 20 is not hindered, or may be formed in a cross shape so as to intersect at the center a of the valve portion 30.
In the sealed battery 10, the positive electrode tab 20 is disposed to intersect the second thin portion 36 and is joined to the inner surface of the valve portion 30 by welding or the like so as to sandwich the second thin portion 36. The positive electrode tab 20 overlaps the second thin portion 36 in the vertical direction and intersects the second thin portion 36 as viewed from the bottom of the sealing assembly 17. Note that the leading end of the positive electrode tab 20 is bent along the bottom 32 of the valve portion 30 and is in contact with the inner surface of the bottom 32. In order not to inhibit the deformation of the valve portion 30, it is preferable that the leading end of the positive electrode tab 20 be disposed not to project from the bottom 32, and the bent portion of the positive electrode tab 20 be formed in a range overlapping the bottom 32.
In the example illustrated in
On the inner surface of the valve portion 30, the welding portions 25 are formed at least two locations on both sides in the width direction of the second groove 37. For example, the length from the second groove 37 to each welding portion 25 is substantially the same, and each welding portion 25 is formed to have substantially the same size. In this case, when the second thin portion 36 is broken, the two welding portions 25 are likely to be broken simultaneously. The length from the second groove 37 to the welding portion 25 is, for example, 50% or less, preferably 30% or less, and more preferably 20% or less, of the radius of the valve portion 30. The welding portion 25 is preferably formed in the vicinity of the second groove 37 in a range not overlapping the second groove 37.
The positive electrode tab 20 is preferably disposed at the center a of the valve portion 30 as described above. The two welding portions 25 formed on both sides in the width direction of the second groove 37 are preferably aligned in the radial direction of the valve portion 30. In this case, when the valve portion 30 is inverted and the second thin portion 36 is broken, the two welding portions 25 are likely to be broken simultaneously. When the positive electrode tab 20 is directly welded to the inner surface of the valve portion 30, it is preferable that the positive electrode tab 20 and the second groove 37 be substantially orthogonal to each other as viewed from the bottom of the sealing assembly 17.
When the internal pressure of the battery further rises, as illustrated in
In the example illustrated in
With reference to
As illustrated in
When the positive electrode tab 20 is directly welded to the inner surface of the valve portion 30, by welding the positive electrode tab 20 so as to be orthogonal to the second thin portion 36, the second thin portion 36 is easily broken when the internal pressure rises, and the current path is easily cut off. For this reason, the positive electrode tab 20 is preferably aligned so as to be orthogonal to the second thin portion 36, but the use of the tab welding plate 26 eliminates the need for such alignment. That is, when the tab welding plate 26 is welded in advance so as to sandwich the second thin portion 36, the positive electrode tab 20 may be welded to the tab welding plate 26 without concern for the direction of the positive electrode tab 20 with respect to the second thin portion 36.
The tab welding plate 26 may be a metal plate having a size capable of being disposed across the second thin portion 36 (second groove 37) and capable of welding the positive electrode tab 20, and the shape of the tab welding plate 26 is not particularly limited. However, the tab welding plate 26 is preferably smaller than the bottom 32 of the valve portion 30 so as not to inhibit the deformation of the valve portion 30. Further, the tab welding plate 26 is preferably broken together with the second thin portion 36, and for example, the tab welding plate 26 has a thickness similar to that of the second thin portion 36.
In the example illustrated in
Two notches 27 are formed in the tab welding plate 26 at positions overlapping the second groove 37. The two notches 27 are formed on two sides of the quadrangle opposite to each other while being aligned in a direction in which the second thin portion 36 extends, and the two notches 27 serve as starting points when the tab welding plate 26 is broken. In the example illustrated in
In the example illustrated in
As described above, the sealing assemblies 17, 17x each have excellent performance as a safety valve and have advantages such as a small thickness, a simple structure, and a small number of parts. Therefore, by using the sealing assemblies 17, 17x, for example, the manufacturing cost of the sealed battery 10 can be reduced, and the energy density can be improved.
Note that the design of the embodiment described above can be appropriately modified to the extent that the object of the present disclosure is not impaired. For example, in the embodiment described above, the sealing assemblies 17, 17x each including the downward-convex valve portion 30 have been exemplified, but the valve member may not have a downward convex shape, and the sealing assembly may have a flat disk shape. The tab welding plate 26 having two notches 27 has been exemplified, but the number of notches 27 may be one. Alternatively, instead of the tab welding plate 26, a metal plate without the notch 27 may be used.
10 sealed battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode assembly, 16 outer housing can, 17, 17x sealing assembly, 18, 19 insulating plate, 20 positive electrode tab, 21 negative electrode tab, 22 grooved portion, 23 gasket, 25, 28, 29 welding portion, 26 tab welding plate, 27 notch, 30 valve portion, 31 annular portion, 32 bottom, 33 inclined portion, 34 first thin portion, 35 first groove, 36 second thin portion, 37 second groove
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-039764 | Mar 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/006491 | 2/19/2021 | WO |
