Patent Application
20240313305
The present disclosure relates to a cylindrical battery.
PATENT LITERATURE 1 discloses a conventional cylindrical battery. This cylindrical battery comprises a sealing assembly having a sealing plate, a metal plate as an internal terminal plate, and an insulating member interposed between the sealing plate and the metal plate. In this cylindrical battery, the inside is hermetically sealed by the sealing assembly being crimped and fixed to the opening of a bottomed cylindrical metal-made exterior can via a resin-made gasket. On the sealing plate of the cylindrical battery, there is provided an inclined portion that is displaced outward in the axial direction and the thickness of which is continuously decreasing as going from the inner periphery to the outer periphery in the radial direction. This cylindrical battery operates a safety mechanism when its internal pressure rises due to abnormal heat generation. In detail, when the internal pressure of the cylindrical battery rises due to abnormal heat generation thereof, the inclined portion of the sealing plate is inverted to disconnect the current path inside the battery. Moreover, when the internal pressure further rises, the inclined portion ruptures to allow gas inside the battery to be discharged to the outside. The sealing plate functions as a safety valve.
In a wound electrode assembly, gas generated on electrode plates flows out from both end faces of the electrode assembly in the axial direction. When the safety valve is provided in the sealing assembly sealing the opening of the exterior can, gas flowing out from the end face, of the electrode assembly, that is on the bottom side thereof diffuses to the hollow portion of the electrode assembly and the inner side of the lateral surface. Although the gas that has diffused to the hollow portion of the electrode assembly may reach the safety valve without damaging the exterior can, the gas that has diffused to the outer side of the electrode assembly may cause a concern that the lateral surface of the exterior can is damaged, for example, an open hole to be generated on the relevant lateral surface.
In such a background, when in the case where abnormal beat generation of the cylindrical battery occurs, high temperature gas blows out from the lateral surface of the exterior can other than the safety valve, there arises a case, for example, for a group battery comprising a plurality of cylindrical batteries, where the high temperature gas causes a cylindrical battery and/or a device therearound to be damaged.
It is therefore an advantage of the present disclosure to provide a cylindrical battery that, in the case of abnormal heat generation, scarcely causes the lateral surface to be damaged and readily allows high temperature gas to be smoothly discharged to the outside via the safety valve.
In order to solve the aforementioned problem, there is provided a cylindrical battery of the present disclosure, comprising: an electrode assembly having a positive electrode and a negative electrode wound via a separator; a bottomed tubular exterior can housing the electrode assembly; and a sealing assembly sealing an opening of the exterior can, wherein a bottom of the exterior can has an inversion portion that has a projecting shape protruding to the electrode assembly side in an axial direction and that is inverted when a battery internal pressure reaches a first pressure, and the sealing assembly has a safety valve that discharges gas inside the battery by rupturing when the battery internal pressure reaches a second pressure larger than the first pressure.
According to the cylindrical battery according to the present disclosure, in the case of abnormal heat generation, the lateral surface is scarcely caused to be damaged, and high temperature gas is readily allowed to be smoothly discharged to the outside via the safety valve.
Hereafter, embodiments of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. Notably, the cylindrical battery of the present disclosure may be a primary battery or may be a secondary battery. Otherwise, it may be a battery using an aqueous electrolyte or may be a battery using a non-aqueous electrolyte. While there is hereafter exemplarily illustrated, as a cylindrical battery 10 which is one of the embodiments, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte, the cylindrical battery of the present disclosure is not limited to this.
It is originally supposed from the first that, when a plurality of embodiments, modifications, and the like are included below, characteristic portions of these be properly combined to configure a new embodiment. For embodiments below, the same configurations are given the same signs in the drawings and their duplicate description is omitted. Moreover, the plurality of drawings include schematic diagrams, and dimension ratios between lengths, depths, heights, and the like of components do not necessarily coincide between different diagrams. The axial direction of the cylindrical battery 10 coinciding with the height direction of the cylindrical battery 10, for convenience of description, a sealing assembly 17 side in the axial direction is regarded as being on the “upside”, and a bottom side of an exterior can 16 in the axial direction is regarded as being on the “downside”. Out of the constituents described below, constituents that are not disclosed in the independent claim(s), showing the most generic concept, are optional constituents, not the essential constituents.
The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, there may be used, for example, esters, ethers, nitriles, amides, a mixed solvent of two or more of these, and the like. The non-aqueous solvent may contain a halogen-substituted substance having halogen atom(s) such as fluorine substituted for at least one or some of hydrogen atoms of these solvents. Notably, the non-aqueous electrolyte is not limited to a liquid electrolyte but may be a solid electrolyte using a gelatinous polymer or the like. For the electrolyte salt, a lithium salt such as LiPF6 is used.
As shown in
The positive electrode 11 has a positive electrode current collector and positive electrode mixture layers formed on both surfaces of the current collector. For the positive electrode current collector, there can be used foil of a metal, such as aluminum or aluminum alloy, that is stable in the potential range of the positive electrode 11, a film having the metal disposed on its surface layers, and the like. The positive electrode mixture layers include a positive electrode active material, a conductive agent, and a binder agent. The positive electrode 11 can be produced, for example, by applying, on the positive electrode current collector, positive electrode mixture slurry including the positive electrode active material, the conductive agent, the binder agent, and the like, drying and afterward compressing the coating film to form the positive electrode mixture layers on both surfaces of the current collector.
The positive electrode active material is composed of a lithium-containing metal composite oxide as a main component. Examples of metal element(s) contained in the lithium-containing metal composite 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. A preferable example of the lithium-containing metal composite oxide is a composite oxide containing at least one of the group consisting of Ni, Co, Mn, and Al.
Examples of the conductive agent included in the positive electrode mixture layers can include carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. Examples of the binder agent included in the positive electrode mixture layers can include fluorine resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like. There may be used, together with these resins, a cellulose derivative such as carboxymethylcellulose (CMC) or its salt, polyethylene oxide (PEO), or the like.
The negative electrode 12 has a negative electrode current collector and negative electrode mixture layers formed on both surfaces of the current collector. For the negative electrode current collector, there can be used foil of a metal, such as copper or copper alloy, that is stable in the potential range of the negative electrode 12, a film having the metal disposed on its surface layers, and the like. The negative electrode mixture layers include a negative electrode active material and a binder agent. The negative electrode 12 can be produced, for example, by applying, on the negative electrode current collector, negative electrode mixture slurry including the negative electrode active material, the binder agent, and the like, drying and afterward compressing the coating film to form the negative electrode mixture layers on both surfaces of the current collector.
For the negative electrode active material, there is generally used a carbon material that reversibly stores and releases lithium ions. Preferably examples of the carbon material include graphite such as natural graphite such as flaky graphite, massive graphite, and earthy graphite and artificial graphite such as massive artificial graphite and graphitized mesophase carbon microbeads. In the negative electrode mixture layers, there may be included, as the negative electrode active material, a Si material containing silicon (Si). Moreover, for the negative electrode active material, there may be used a metal, other than Si, that is alloyed with lithium, an alloy containing the metal, a compound containing the metal, and the like.
While for the binder agent included in the negative electrode mixture layers, there may be used fluorine resins, PAN, polyimide resins, acrylic resins, polyolefin resins, and the like as in the case of the positive electrode 11, there is preferably used styrene-butadiene rubber (SBR) or its modified substance. In the negative electrode mixture layers, for example, in addition to SBR or the like, there may be included CMC or its salt, polyacrylic acid (PAA) or its salt, polyvinyl alcohol, and/or the like.
For the separators 13, there are used porous sheets having ion permeability and insulation ability. Specific examples of the porous sheet include a microporous thin film, woven fabric, nonwoven fabric, and the like. Preferable materials for the separators 13 are polyolefin resins such as polyethylene and polypropylene, cellulose, and the like. Each separator 13 may have any of a single layer structure and a laminate structure. A heat resistant layer and/or the like may be formed on a surface of the separator 13. Notably, while the negative electrode 12 may form the winding starting end of the electrode assembly 14, the separators 13 generally extend beyond the end of the negative electrode 12 on the winding starting side, the ends of the separators 13 on the winding starting side forming the winding starting end of the electrode assembly 14.
In the example shown in
As shown in
The exterior can 16 is a metal-made container having a bottomed tubular portion. By hermetical sealing between the exterior can 16 and the sealing assembly 17 with the annular gasket 28, the inner space of the battery case 15 is hermetically sealed. Moreover, the gasket 28 includes a pinched portion 32 pinched and held by the exterior can 16 and the sealing assembly 17 and insulates the sealing assembly 17 from the exterior can 16. In other words, the gasket 28 has a role as a sealing material for holding gastightness inside the battery and a role as an insulating material which prevents short circuit between the exterior can 16 and the sealing assembly 17.
The exterior can 16 has an annular grooved portion 35 on a part of its cylindrical outer peripheral surface in the axial direction. The grooved portion 35 can be formed, for example, by performing spinning processing inward in the radial direction on a part of the cylindrical outer peripheral surface to recess it inward in the radial direction. The exterior can 16 has a bottomed tubular portion 30 including the grooved portion 35 and an annular shoulder portion 33. The bottomed tubular portion 30 houses the electrode assembly 14 and the non-aqueous electrolyte, and the shoulder portion 33 is folded inward in the radial direction from the end on the opening side of the bottomed tubular portion 30 to extend inward. The shoulder portion 33 is formed when an upper end of the exterior can 16 is folded inward and crimped onto a peripheral edge 31 of the sealing assembly 17. The sealing assembly 17 is pinched and held by the shoulder portion 33 and the grooved portion 35 via the gasket 28 through this crimping and is fixed to the exterior can 16.
Next, a structure of the bottom 40 of the exterior can 16 is described in detail. As shown in
Next, a structure of the sealing assembly 17 is described in detail.
The sealing plate 27 is circular in plan view. The sealing plate 27 can be produced, for example, by pressing a plate material of aluminum or aluminum alloy. Since aluminum and aluminum alloy have excellent flexibility, they are preferably materials for the sealing plate 27 which functions as a safety valve (explosion proof valve). The sealing plate 27 is circular in plan view. The sealing plate 27 has a center portion 27a, an outer peripheral portion 27b, and an inclined portion 270 connecting the center portion 27a and the outer peripheral portion 276. An upper surface of the thin portion 23c of the terminal plate 23 and a lower surface of the center portion 27a of the sealing plate 27 are joined by metallurgical joining such, for example, as laser welding. When the terminal plate 23 is formed of aluminum or aluminum alloy as with the sealing plate 27, the sealing plate 27 and the terminal plate 23 can be readily joined.
A thickness of the inclined portion 27c is smaller than that of the center portion 27a. A lower surface of the inclined portion 27e is positioned more on the upper side than the lower surface of the center portion 27a, and connects to the lower surface of the center portion 27a via an annular step portion 29. An annular upper surface 26a of the inclined portion 27c is an inclined surface that is positioned more on the upper side as going outward in the radial direction, and an annular lower surface 26b of the inclined portion 27c is also an inclined surface that is positioned more on the upper side as going outward in the radial direction. The thickness of the inclined portion 27e becomes smaller as going outward in the radial direction.
The insulating plate 25 is press fitted and fixed, for example, onto an outer peripheral surface of the annular step portion 29. The insulating plate 25 has, on the outer periphery side in the radial direction, an annular protruding portion 25a bent downward in the axial direction, and the thick portion 23b of the terminal plate 23 is press fitted and fixed, for example, onto an inner peripheral surface of the annular protruding portion 25a. The insulating plate 25 is provided for securing insulation ability to prevent the thick portion 23b of the terminal plate 23 from being electrically connected to the sealing plate 27.
The insulating plate 25 is preferably composed of a material that does not affect battery characteristics. Examples of the material of the insulating plate 25 include polymer resins and, for example, can include a polypropylene (PP) resin and a polybutylene terephthalate (PBT) resin. The insulating plate 25 has one or more vent holes 25b that penetrate in the axial direction, at places overlapping with the inclined portion 27c of the sealing plate 27 in the axial direction, and the terminal plate 23 has one or more vent holes 23d that penetrate in the axial direction, at places overlapping with the insulating plate 25 in the axial direction. With this configuration, gas generated in the electrode assembly 14 can pass through the vent hole(s) 23d, between the insulating plate 25 and the insulating plate 25, and through the vent hole(s) 25b to flow into a space 36 provided between the inclined portion 27e and the insulating plate 25 with respect to the axial direction.
With the configuration above, when abnormal beat generation of the cylindrical battery 10 occurs and an internal pressure of the cylindrical battery 10 reaches a predetermined value, the sealing assembly 17 performs the current interruption operation and the gas discharging operation as follows. In detail, when abnormal beat generation of the cylindrical battery 10 occurs and the internal pressure of the cylindrical battery 10 reaches the predetermined value, as shown in
When the internal pressure further rises, as shown in
A first pressure at which the sealing plate 27 as the safety valve ruptures can be adjusted, for example, with a thickness of the annular end 39 of the inclined portion 27c on the outer side in the radial direction. A second pressure at which the inversion portion 43 is inverted can be adjusted, for example, with a thickness, of the tapered portion 43a of the bottom 40, at the annular end 48 on the outer side in the radial direction. The second pressure is adjusted so as to be smaller than the first pressure, being preferably adjusted so as to be smaller than a pressure at which the sealing assembly 17 performs current interruption.
The inventors confirmed that when a cylindrical battery of the following example was produced, its inversion portion was able to be inverted to the opposite side to the electrode assembly side in the axial direction before the sealing plate (safety valve) ruptured.
LiNi0.8Co0.15Al0.05O2 was used as the positive electrode active material. One hundred pts. mass of the positive electrode active material. 1.7 pts. mass of polyvinylidene fluoride as the binder agent, and 2.5 pts. mass of acetylene black as the conductive agent were mixed in a dispersion medium to prepare the positive electrode mixture slurry. The positive electrode mixture slurry was applied and dried on both sides of the positive electrode current collector composed of aluminum foil except on the connection portion of the positive electrode lead, and was afterward rolled to a predetermined thickness thereby to obtain a positive electrode plate. The positive electrode plate was cut to have a predetermined size, and the positive electrode lead made of Al was connected to the exposed portion of the current collector by ultrasonic welding to produce the positive electrode.
Readily graphitizable carbon was used as the negative electrode active material. One hundred pts. mass of the negative electrode active material, 0.6 pts. mass of polyvinylidene fluoride as the binder agent, 1 pt. mass of carboxymethylcellulose as the thickener agent, and an appropriate amount of water were stirred by a double-arm kneader to obtain the negative electrode mixture slurry. The negative electrode mixture slurry was applied and dried on both sides of the negative electrode current collector composed of copper foil except on the connection portion of the negative electrode lead, and was afterward rolled to a predetermined thickness thereby to obtain a negative electrode plate. The negative electrode plate was cut to have a predetermined size, and the negative electrode lead composed of a Ni—Cu—Ni cladding material was connected to the exposed portion of the current collector by ultrasonic welding to produce the negative electrode.
In a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), lithium hexafluorophosphate (LiPF6) as the electrolyte was dissolved in 1.0 mol/L to prepare a non-aqueous electrolyte solution.
A sealing assembly having the structure shown in
An exterior can having the structure shown in
The aforementioned positive electrode and electrode plates were wound into a spiral shape via the polyolefin-based resin-made separators to produce the electrode assembly. The electrode assembly was inserted into the exterior can via a disc-shaped can bottom insulating plate, and the negative electrode lead connected to the negative electrode and the battery can bottom surface were electrically connected by welding. The electrode assembly was inserted into the exterior can via the disc-shaped can bottom insulating plate, and the negative electrode lead electrically connected to the negative electrode and the can bottom surface were electrically connected. After welding the positive electrode lead to the sealing assembly, a predetermined amount of the non-aqueous electrolyte solution was injected into the exterior can. Then, the sealing assembly was arranged on the grooved portion of the exterior can via the gasket. After that, the inside of the battery was hermetically sealed by crimping the sealing assembly onto the opening of the exterior to produce the cylindrical battery.
According to the present disclosure, before the sealing plate 27 functioning as the safety valve ruptures, there is inverted the inversion portion 43 which is provided in the bottom 40 of the cylindrical battery 10 and has the projecting shape protruding to the electrode assembly 14 side in the axial direction. Accordingly, before the sealing plate 27 discharges high temperature gas, a space 60 (refer to
The inversion portion 43 may include: the tapered portion 43a an inner diameter of which is decreasing as going to the electrode assembly 14 side in the axial direction; and the flat portion 43b connecting to an inner circumferential end of the tapered portion 43a and spreading substantially parallel to a plane substantially perpendicular to the axial direction. Moreover, the inversion portion 43 is preferably provided at a center of the bottom 40, and a planar shape of the inversion portion 43 is still preferably circular.
According to the aforementioned configurations, the inversion portion 43 is readily, smoothly inverted with the annular end 48 of the tapered portion 43a on the outer side in the radial direction being as a fulcrum. Moreover, since after the inversion, a distance between a lower surface of the hollow portion 57 of the electrode assembly 14 and the bottom 40 of the exterior can 16 increases, high temperature gas can be efficiently guided to the sealing assembly 17 side.
Notably, the present disclosure is not limited to the aforementioned embodiment and its modifications but various improvements and alterations thereof may occur without departing from the matters disclosed in the claims of the present application or their equivalents.
For example, for the aforementioned embodiment, there has been described a case where the inversion portion 43 has the tapered portion 43a and the flat portion 43b. Nevertheless, the inversion portion may have any projecting shape protruding to the electrode assembly side in the axial direction and, for example, the inversion portion may have a dome shape formed by horizontally rotating an arch around its top.
Moreover, while there has been described a case where the inversion portion 43 is provided at the center of the bottom 40, the inversion portion may include a portion, of the bottom, that is positioned on the outer side in the radial direction. Moreover, while there has been described a case where the planar shape of the inversion portion 43 is circular, the planar shape of the inversion portion may be any shape other than the circle shape and, for example, the planar shape of the inversion portion may be a square shape, a rectangle shape, or an ellipse shape.
Moreover, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-029949 | Feb 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/005107 | 2/9/2022 | WO |
