Patent ID: 12224445

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. The cylindrical battery of the present disclosure may be a primary battery, or may be a secondary battery. Additionally, the cylindrical battery may be a battery using an aqueous electrolyte, or may be a battery using a non-aqueous electrolyte. In the following, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte will be exemplified as a cylindrical battery10of the embodiment. However, the cylindrical battery of the present disclosure is not limited to this.

In a case where a plurality of embodiments and modifications and the like are included in the following, it is assumed from the beginning that a new embodiment is constructed by appropriately combining those feature portions. In the following embodiments, the same components are denoted by the same reference numerals in the drawings, and duplicate descriptions are omitted. Schematic diagrams are included in a plurality of the drawings, and the dimensional ratios such as lengths, widths and heights of each member between different drawings are not necessarily the same. In this specification, for convenience of explanation, the direction along the axial direction of a battery case15is defined as the height direction, the sealing assembly17side in the height direction is “up”, and the bottom side of an exterior can16in the height direction is defined as “bottom”. Of the components described below, components that are not described in the independent claim indicating the highest level concept are arbitrary components, and are not essential components.

FIG.1is an axial sectional view of the cylindrical battery10according to the embodiment of the present disclosure, andFIG.2is a perspective view of an electrode assembly14of the cylindrical battery10. As illustrated inFIG.1, the cylindrical battery10comprises the wound-type electrode assembly14, a non-aqueous electrolyte (not illustrated), and the battery case15that houses the electrode assembly14and the non-aqueous electrolyte. As illustrated inFIG.2, the electrode assembly14includes a positive electrode11, a negative electrode12, and a separator13interposed between the positive electrode11and the negative electrode12, and has a wound structure in which the positive electrode11and the negative electrode12are wound via the separator13. Referring toFIG.1again, the battery case15is composed of the bottomed cylindrical exterior can16and the sealing assembly17that blocks an opening of the exterior can16. The cylindrical battery10comprises a resin gasket28disposed between the exterior can16and the sealing assembly17.

The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For a non-aqueous solvent, for example, esters, ethers, nitriles, amides, and two or more groups of mixed solvents thereof, or the like may be used. The non-aqueous solvent may contain a halogen substitution compound obtained by substituting at least a part of hydrogen of these solvents with a halogen atom such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may be a solid electrolyte using gelatinous polymer, or the like. As the electrolyte salt, a lithium salt such as LiPF6is used.

As illustrated inFIG.2, the electrode assembly14has the long positive electrode11, the long negative electrode12, and the two long separators13. The electrode assembly14has a positive electrode lead20joined to the positive electrode11and a negative electrode lead21joined to the negative electrode12. The negative electrode12is formed to be one size larger than the positive electrode11in order to suppress precipitation of lithium, and is longer in the longitudinal direction and the width direction (short direction) than the positive electrode11. The two separators13are each formed to be at least one size larger than the positive electrode11, and are each disposed so as to interpose, for example, the positive electrode11therebetween.

The positive electrode11has a positive electrode current collector and a positive electrode mixture layer formed on both surfaces of the current collector. As the positive electrode current collector, it is possible to use foil of a metal stable in a potential range of the positive electrode11, such as aluminum and an aluminum alloy, a film including such a metal disposed on a surface layer thereof, or the like. The positive electrode mixture layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode11can be produced by, for example, applying a positive electrode mixture slurry including a positive electrode active material, a conductive agent, a binder, and the like on a positive electrode current collector, drying the applied film, and thereafter compressing and forming a positive electrode mixture layer 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 elements 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. An example of the lithium-containing metal composite oxide is preferably a composite oxide containing at least one of the group consisting of Ni, Co, Mn and Al.

Examples of conductive agents included in the positive electrode mixture layer include carbon powders such as carbon black, acetylene black, Ketjen black, and graphite. As the binder included in the positive electrode mixture layer, fluororesin such as polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVdF), and polyacrylonitrile (PAN), polyimide, acrylic resin, polyolefin, and the like can be exemplified. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or salts thereof, polyethylene oxide (PEO), or the like.

The negative electrode12has a negative electrode current collector, and a negative electrode mixture layer formed on both surfaces of the current collector. As the negative electrode current collector, it is possible to use foil of a metal stable in a potential range of the negative electrode12, such as copper and a copper alloy, a film including such a metal disposed on a surface layer thereof, or the like. The negative electrode mixture layer includes a negative electrode active material, and a binder. The negative electrode12can be produced by, for example, applying a negative electrode mixture slurry including a negative electrode active material, a binder, and the like on a negative electrode current collector, drying the applied film, and thereafter compressing and forming a negative electrode mixture layer on both surfaces of the current collector.

As the negative electrode active material, a carbon material that reversibly occludes and releases lithium ions is generally used. A preferable carbon material is graphite such as natural graphite such as flaky graphite, lump graphite and earthy graphite, and artificial graphite such as lump artificial graphite and graphited mesophase carbon microbeads. The negative electrode mixture layer may include a Si-containing compound as the negative electrode active material. As the negative electrode active material, a metal alloyed with lithium other than Si, an alloy containing such a metal, a compound containing such a metal, and the like may be used.

As the binder included in the negative electrode mixture layer, fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like may be used like the case of the positive electrode11, and a styrene-butadiene rubber (SBR) or a modification thereof is preferably used. As the negative electrode mixture layer, for example, in addition to SBR and the like, CMC or the salts thereof, poly acrylic acid (PAA) or the salts thereof, polyvinyl alcohol, or the like may be included.

As each separator13, a porous sheet having ion permeability and insulation is used. Specific examples of the porous sheet include microporous thin films, woven fabric, and non-woven fabric. As a material for the separator13, olefin resins such as polyethylene and polypropylene, cellulose, or the like is preferable. The separator13may be either a single layer structure or a laminated structure. A heat-resistant layer or the like may be formed on a surface of the separator13. The negative electrode12may compose a winding start end of the electrode assembly14, but the separator13generally extends beyond a winding start side end of the negative electrode12, and a winding start side end of the separator13becomes a winding start end of the electrode assembly14.

In the example illustrated inFIG.1andFIG.2, the positive electrode lead20is electrically connected to an intermediate portion such as a central portion in the winding direction of a positive electrode current collector, and the negative electrode lead21is electrically connected to a winding finish end in the winding direction of a negative electrode current collector. However, the negative electrode lead may be electrically connected to a winding start end in the winding direction of the negative electrode current collector. Alternatively, the electrode assembly has two negative electrode leads, one of the negative electrode lead is electrically connected to the winding start end in the winding direction of the negative electrode current collector, and the other negative electrode lead may be electrically connected to a winding finish end in the winding direction of the negative electrode current collector. Alternatively, an end on the winding finish side in the winding direction of the negative electrode current collector is brought into contact with an inner surface of the exterior can, so that the negative electrode and the exterior can may be electrically connected.

As illustrated inFIG.1, the cylindrical battery10has an insulating plate18disposed on the upper side of the electrode assembly14, and an insulating plate19disposed on the lower side of the electrode assembly14. In the example illustrated inFIG.1, the positive electrode lead20attached to the positive electrode11extends toward the sealing assembly17through a through hole of the insulating plate18, and the negative electrode lead21attached to the negative electrode12passes through the outside of the insulating plate19to extend toward a bottom of the exterior can16. The positive electrode lead20is connected to a lower surface of the terminal plate23, which is a bottom plate of the sealing assembly17, by means of welding or the like, and the vent member27, which is a top plate of the sealing assembly17electrically connected to the terminal plate23, serves as the positive electrode terminal. The negative electrode lead21is connected to an inner surface of the bottom of the exterior can16by means of welding or the like, and the exterior can16serves as the negative electrode terminal.

The exterior can16is a metal container having a bottomed cylindrical portion. A portion between the exterior can16and the sealing assembly17is sealed by the annular gasket28, and an internal space of the battery case15is closed. The gasket28has a role of a seal material for maintaining the airtightness of the inside of the battery, and has a role of preventing leakage of an electrolytic solution. In addition, the gasket28has a role as an insulating material to prevent a short circuit between the exterior can16and the sealing assembly17. The exterior can16has, for example, a grooving portion22formed by spinning a side surface portion from the outside. The grooving portion22is preferably formed in an annular shape along the circumferential direction of the exterior can16, and the sealing assembly17is supported on an upper surface of the grooving portion22. The exterior can16has a bottomed cylindrical portion30that houses the electrode assembly14and the non-aqueous electrolyte, and an annular shoulder portion33, and the shoulder portion33is bent to the inward side in the radial direction from an end of the bottomed cylindrical portion30on the opening side to extend to the inward side. The shoulder portion33is formed when an upper end of the exterior can16is bent to the inside and caulked to a circumferential edge31of the sealing assembly17.

Now, the sealing assembly17will be described.FIG.3is an enlarged sectional view of a part located on one side of a central axis in a sealing assembly peripheral portion of the cylindrical battery10. As illustrated inFIG.3, the sealing assembly17has a structure in which the terminal plate23, an annular insulating plate25, and the vent member27are laminated in this order from the electrode assembly14side. The vent member27has a circular shape in plan view. The vent member27can be produced by, for example, pressing a plate material of aluminum or an aluminum alloy. The aluminum and the aluminum alloy are excellent in flexibility, and therefore are preferably as a material of the vent member27.

The vent member27has a circular shape in plan view, and a thin wall portion27cis formed in an intermediate portion connecting a central portion27aand an outer circumferential portion27b. When battery internal pressure rises, the thin wall portion27creverses and breaks, so that the vent member27functions as an explosion-proof valve. The central portion27ais formed so as to project toward the terminal plate23, so that connection between the vent member27and the terminal plate23is facilitated.

The insulating plate25is formed in an annular shape in plan view, and has a through hole25ain the center. The insulating plate25is fitted and fixed to a projection27dformed so as to project downward in the outer circumferential portion27bof the vent member27. The insulating plate25is provided so as to ensure an insulation property, and is preferably composed of a material that does not affect a battery characteristic. As the material of the insulating plate25, polymer resin is included, and polypropylene (PP) resin and polybutylene terephthalate (PBT) resin can be exemplified. The insulating plate25has a vent hole25bpenetrating the insulating plate in the height direction on the outer circumferential side. The insulating plate25has an annular skirt portion25cextending downward on an outer circumferential edge.

The terminal plate23has a circular outer shape with a diameter smaller than that of the insulating plate25in plan view, and a central portion23ais a thin portion. The terminal plate23is disposes so as to face the vent member27with the insulating plate25interposed between the terminal plate23and the vent member27. The terminal plate23is attached to the insulating plate25by fitting an outer circumferential surface of the terminal plate23into an inner circumferential surface of the skirt portion25cof the insulating plate25and fixing the terminal plate23. The center of the vent member27and the center of the terminal plate23are connected to each other through the through hole25aof the insulating plate25.

The terminal plate23is preferably formed from aluminum or an aluminum alloy like the vent member27, so that the connection between the central portion of the vent member27and the central portion of the terminal plate23can be easily performed. As the connecting method, metallurgical joint is preferably used, and laser welding is exemplified as the metallurgical joint. A vent hole23bthat penetrates the terminal plate23in the height direction is formed on the outer circumferential side of the terminal plate23. The vent hole23bcommunicates with the vent hole25bof the insulating plate25. As illustrated inFIG.3, the inner circumferential surface of the skirt portion25cmay have a conical trapezoidal shape having an inner diameter that decreases toward the lower side. Alternatively, the outer circumferential surface of the terminal plate23may have a conical trapezoidal shape corresponding to the inner circumferential surface thereof. In such a case, the terminal plate23is press-fitted and fixed to the skirt portion25c, so that it is possible to reliably prevent positional shift of the terminal plate23to the vent member27.

Now, the structure (shape) of the gasket28, and the positional relationship of the gasket28with respect to the shoulder portion33of the exterior can16and the sealing assembly17will be described. As illustrated inFIG.3, the gasket28has the annular extending portion29extending from between an inward tip33aof the shoulder portion33of the exterior can16, and the sealing assembly17. An upper surface41of the sealing assembly17includes an annular first inclined surface portion41athat goes upward (side opposite to the electrode assembly14in the height direction) while extending radially inward at an inward portion40located on the radially inward side with respect to the shoulder portion33. The extending portion29has a covering portion39that covers the first inclined surface portion41a. The covering portion39extends along the first inclined surface portion41a, and the extending portion29is bent upward by vertical force from the first inclined surface portion41a.

The upper surface41of the sealing assembly17further includes a second inclined surface portion41b. The second inclined surface portion41bis connected to an inward end of the first inclined surface portion41a, and inclines so as to go downward toward the radially inside. An upper surface47of the shoulder portion33(outer surface of the shoulder portion33on a side opposite to the electrode assembly14in the height direction) is located on the upper side with respect to the sealing assembly17. The upper surface47of the shoulder portion33includes a third inclined surface portion47a, and the third inclined surface portion47ainclines so as to go downward toward the radially inside. In the embodiment, in the sectional view illustrated inFIG.3, the second inclined surface portion41band the third inclined surface portion47aare located on substantially the same straight line.

The gasket28intersects with all arbitrary straight lines connecting the upper surface47of the shoulder portion33and the upper surface41of the sealing assembly17. For example, the arbitrary straight lines include a straight line L1connecting a shoulder portion upper end60on the uppermost side of the upper surface47of the shoulder portion33, and a sealing assembly upper end (not illustrated) farthest from the shoulder portion upper end60in a portion located on the uppermost side of the upper surface41of the sealing assembly17, in the cross section illustrated inFIG.3. Herein, the sealing assembly upper end is a point line-symmetrical to an intersection61of the first inclined surface portion41aand the second inclined surface portion41bwith respect to the central axis P in the cross section illustrated inFIG.3. The upper surface47of the shoulder portion33composes a first surface, and the upper surface41of the sealing assembly17composes a second surface.

For example, the above arbitrary straight lines also include a straight line L2including the second inclined surface portion41band the third inclined surface portion47a, in the cross section illustrated inFIG.3. InFIG.3, a straight line L3is a straight line that is orthogonal to the height direction and passes through the shoulder portion upper end (point located on the uppermost side of the exterior can16)60. As illustrated in a partial enlarged view illustrated by a circle of a dashed line inFIG.3, an extending portion upper end (upper end of the gasket28)65located on the uppermost side of the extending portion29is located on the lower side in the height direction (electrode assembly14side in the height direction) with respect to the straight line L3, and the extending portion upper end65is located on the lower side with respect to the shoulder portion upper end60. The extending portion upper end65composes a first place, and the shoulder portion upper end60composes a second place.

As described above, according to the cylindrical battery10of the present disclosure, the gasket28includes the extending portion29extending from between the inward tip33aof the shoulder portion33and the sealing assembly17, and the upper surface47of the shoulder portion33, and the gasket28intersects with the all arbitrary straight lines connecting the upper surface47of the shoulder portion33and the upper surface of the inward portion. Therefore, a flat plate-like conductive plate cannot be located across the upper surface47of the shoulder portion33and the upper surface41of the sealing assembly17. Accordingly, it is possible to significantly suppress the short circuit between the shoulder portion33and the sealing assembly17caused by the flat plate-like conductive plate.

Specifically, as illustrated inFIG.4, that is, an enlarged sectional view corresponding toFIG.3, of a cylindrical battery310of a reference example, in a case where an arbitrary straight line connecting an upper surface341of an inward portion340located on the radially inward side with respect to a shoulder portion333in a sealing assembly317, and an upper surface347of the shoulder portion333includes a straight line L11that does not intersects with an extending portion329of a gasket328, a conductive plate (metal plate)385having a lower surface380including the straight line L11can be located across the upper surface347of the shoulder portion333and the upper surface341of the sealing assembly317, and a short circuit between the shoulder portion347and the sealing assembly317easily occurs through the conductive plate (metal plate)385. On the other hand, like the cylindrical battery10of the present disclosure illustrated inFIG.3, in a case where the gasket28intersects with all arbitrary straight lines connecting the upper surface41of the sealing assembly17and the upper surface47of the shoulder portion33, the location of the conductive plate as illustrated inFIG.4is impossible by the extending portion329. Accordingly, it is possible to significantly suppress the short circuit between the exterior can16and the sealing assembly17due to the conductive member that exists outside the battery.

The first inclined surface portion41athat goes in a direction opposite to the electrode assembly14in the height direction (axial direction) as the upper surface41of the inward portion40goes toward the radially inner side may be included, and the gasket28may have the covering portion39that is in contact with at least a part of the first inclined surface portion41aand covers at least the part of the first inclined surface portion41a.

According to the aforementioned configuration, the extending portion29of the gasket28can be deformed diagonally upward by force from the first inclined surface portion41a, and can extend diagonally upward along the first inclined surface portion41a. Therefore, the length in the height direction of the extending portion29can be easily increased, and the position of the extending portion29can be precisely positioned. Accordingly, it is possible to easily realize a configuration in which the extending portion29intersects with the aforementioned all arbitrary straight lines.

The sealing assembly17may be located closer to the electrode assembly14in the axial direction than the upper surface47of the shoulder portion33. The upper surface41of the inward portion40may include the annular second inclined surface portion41bthat goes toward the electrode assembly14in the height direction toward the radially inner side, on the radially inward side with respect to the first inclined surface portion41a.

According to the aforementioned configuration, the upper surface41of the inward portion40of the sealing assembly17is easily disposed on the side of the electrode assembly14in the height direction. Therefore, even when the extending portion29is not much projected in the height direction, the configuration in which the gasket28intersects with the all arbitrary straight lines is easily realized. Accordingly, the cylindrical battery10is easily configured to be compact.

The extending portion upper end65of the gasket28located farthest from the electrode assembly14in the height direction is preferably located closer to the electrode assembly14in the height direction than the shoulder portion upper end60of the shoulder portion33located farthest from the electrode assembly14in the height direction.

According to the aforementioned configuration, the shoulder portion upper end60located on the uppermost side of the shoulder portion33is located on the upper side with respect to the extending portion upper end65located on the uppermost side of the gasket28. Consequently, the volume of the electrode assembly14to be housed in the cylindrical battery10is increased, and therefore the cylindrical battery10having high volume energy density is easily realized.

The present disclosure is not limited to the aforementioned embodiment and the modification thereof, and various improvements and changes can be made within the scope of the claims of the present application and the equivalent scope thereof.

For example, in the above embodiment, as illustrated inFIG.3, the upper surface of the extending portion29of the gasket28goes upward in the height direction toward the radially inner side. However, as illustrated inFIG.5, that is, the enlarged sectional view corresponding toFIG.3, of a cylindrical battery110of a modification, the shape of a gasket128before battery built-in is devised, so that a tip side188of an extending portion129of the gasket128may be projected radially outward toward the upper side in the height direction. According to this modification, the volume of the gasket128is easily reduced, and a material cost of the gasket128is easily reduced. The definition of a straight line L1and a straight line L3illustrated inFIG.5is the same as the definition of the straight line L1and the straight line L3illustrated inFIG.3.

In the above embodiment, a case where the upper surface41of the inward portion40includes the annular first inclined surface portion41athat goes downward in the height direction toward the radially inner side is described. However, the upper surface of the inward portion may include a non-annular first inclined surface portion that goes downward toward the radially inner side. Furthermore, the upper surface of the inward portion of the sealing assembly may not have an inclined surface.

Specifically, as illustrated inFIG.6, that is, the enlarged sectional view corresponding toFIG.3, of a cylindrical battery210of another modification, a sealing assembly217may comprise a cap221disposed on a vent member222, and the cap221may have a bulge230that bulges in the height direction at a radially central portion. More specifically, the cap221may have an annular portion250, a cylindrical portion251and a disk portion252. Each of the annular portion250and the disk portion252is substantially located on a plane orthogonal to the height direction, and the cylindrical portion251may extend in the height direction. The cylindrical portion251may connect a radially inward edge of the annular portion250and an outer circumferential edge of the disk portion252.

The cylindrical battery210may include an annular gasket228between an exterior can216and the sealing assembly217, and the gasket228may include an extending portion229extending from between a radially inward tip233ain a shoulder portion233and the sealing assembly217. The extending portion229extends upward in the height direction, so that the extending portion229may intersect with all arbitrary straight lines connecting an upper surface247of the shoulder portion233, and an upper surface241of the sealing assembly217. The bulge230of the cap221may be located on the upper side with respect to the upper surface247of the shoulder portion233. A straight line L4illustrated inFIG.6is a straight line tangent to both the upper surface247of the shoulder portion233and the upper surface241of the cap221, and is a straight line included in the above arbitrary straight lines.

The case where the extending portion upper end65of the gasket28located farthest from the electrode assembly14in the height direction is located closer to the electrode assembly14in the height direction than the shoulder portion upper end60of the shoulder portion33located farthest from the electrode assembly14in the height direction is described. However, the first place of the gasket located farthest from the electrode assembly in the height direction (axial direction) may be located on the upper side in the height direction with respect to the second place of the shoulder portion located farthest from the electrode assembly in the height direction.

REFERENCE SIGNS LIST

10,110,210cylindrical battery,11positive electrode,12negative electrode,13separator,14electrode assembly,16,216exterior can,17,217sealing assembly,28,128,228gasket,29,129,229extending portion,30bottomed cylindrical portion,33,233shoulder portion,33a,233aradially inward tip of shoulder portion,39covering portion,41,241upper surface of inward portion (second surface),41afirst inclined surface portion,41bsecond inclined surface portion,47,247upper surface of shoulder portion (first surface),60shoulder portion upper end (second place),65extending portion upper end (first place)