Patent Description:
The document <CIT> discloses a lithium secondary battery and the document <CIT> discloses a cylindrical alkaline storage battery. There has been conventionally known a cylindrical battery comprising a sealing assembly that seals an opening of an exterior housing can (for example, PATENT LITERATURE <NUM>). In the sealing assembly of the above-described cylindrical battery, a rupture disk and a metal plate are stacked with an insulating plate interposed therebetween, and the rupture disk and the metal plate are joined to each other by welding to thereby form a current pathway inside the sealing assembly. In the sealing assembly, if an internal pressure of the battery increases in an abnormal case, the rupture disk is deformed, and the metal plate breaks, resulting in cutting off of the current pathway, and if the internal pressure further increases, the rupture disk ruptures, resulting in formation of a gas venting port.

Incidentally, the above-described cylindrical battery is used as, for example, a power supply of an electronic apparatus such as a cellular phone, a digital camera, a video camera, and a notebook type personal computer. In the case where cylindrical batteries are incorporated into an electronic apparatus, a lead plate is joined to each of a positive electrode external terminal and a negative electrode external terminal to connect the cylindrical batteries to one another. In recent years, the joining is performed by various joining methods such as wire bonding, laser welding, and resistance welding.

PATENT LITERATURE <NUM>: International Publication No. <CIT>.

In the above-described cylindrical battery, the rupture disk serves as a positive electrode external terminal, and therefore, depending on the joining method, heat or shock may be applied to a joining part between the rupture disk and the metal plate. At this time, the metal plate is detached from the rupture disk due to heat or shock during welding, which may lead to functional loss of the sealing assembly. In the case where a conventional terminal cap is applied to the above-described cylindrical battery, gas venting ability may be inhibited.

It is an advantage of the present disclosure to provide a cylindrical battery that can avoid functional loss of a sealing assembly when a lead plate is welded to a positive electrode external terminal and has a good gas venting function.

The cylindrical battery of an aspect of the present disclosure is a cylindrical battery comprising: an electrode assembly in which a positive electrode plate and a negative electrode plate are wound with a separator interposed between the positive electrode plate and the negative electrode plate; an electrolyte; a bottomed cylindrical exterior housing can that houses the electrode assembly and the electrolyte; and a sealing assembly that seals an opening of the exterior housing can, wherein the sealing assembly includes a rupture disk that is fixed by crimping to the opening of the exterior housing can with a gasket interposed between the exterior housing can and the rupture disk, and an external terminal that is not fixed by crimping to the opening of the exterior housing can, the rupture disk has a vent part that ruptures when an internal pressure of the battery increases, and the external terminal is fixed to an upper face part of the vent part.

According to an aspect of the present disclosure, there can be provided a cylindrical battery that can avoid functional loss of a sealing assembly when a lead plate is welded to a positive electrode external terminal and has a good gas venting function.

The shapes, materials, and numbers described below are examples for explanation, and may be appropriately modified in accordance with specifications of cylindrical batteries. Hereinafter, explanation will be made with similar elements being represented by the same reference signs in all drawings.

A cylindrical battery <NUM> will be described with reference to <FIG> is a sectional view of the cylindrical battery <NUM>.

As illustrated in <FIG>, the cylindrical battery <NUM> of an example of an embodiment comprises an electrode assembly <NUM>, an electrolyte, an exterior housing can <NUM> that houses the electrode assembly <NUM> and the electrolyte, and a sealing assembly <NUM> that seals an opening of the exterior housing can <NUM>. The electrode assembly <NUM> includes a positive electrode plate <NUM>, a negative electrode plate <NUM>, and a separator <NUM>, and has a wound structure in which the positive electrode plate <NUM> and the negative electrode plate <NUM> are spirally wound with the separator <NUM> interposed therebetween. Hereinafter, for convenience of description, the sealing assembly <NUM> side (an opening side of the exterior housing can <NUM>) of the cylindrical battery <NUM> will be described as "the upper side", and a bottom face part 20A side of the exterior housing can <NUM> will be described as "the lower side.

The positive electrode plate <NUM> has a positive electrode core, and a positive electrode mixture layer formed on at least one face of the core. For the positive electrode core, there can be used a foil of a metal such as aluminum or an aluminum alloy, which is stable in a potential range of the positive electrode plate <NUM>, a film in which such a metal is provided on a surface layer thereof, and the like. The positive electrode mixture layer contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride, and is preferably formed on each side of the positive electrode core. For the positive electrode active material, there is used, for example, a lithium-transition metal composite oxide. The positive electrode plate <NUM> can be manufactured by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and the like on the positive electrode core, drying the resulting coating film, and then compressing it to form a positive electrode mixture layer on each side of the core.

The negative electrode plate <NUM> has a negative electrode core, and a negative electrode mixture layer formed on at least one face of the core. For the negative electrode core, there can be used a foil of a metal such as copper or a copper alloy, which is stable in a potential range of the negative electrode plate <NUM>, a film in which such a metal is provided on a surface layer thereof, and the like. The negative electrode mixture layer contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is preferably formed on each side of the negative electrode core. For the negative electrode active material, there is used, for example, graphite, or a silicon-containing compound. The negative electrode plate <NUM> can be manufactured by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, and the like on the negative electrode core, drying the resulting coating film, and then rolling it to form a negative electrode mixture layer on each side of the core.

For the electrolyte, a non-aqueous electrolyte is used, for example. The non-aqueous electrolyte contains a non-aqueous solvent, and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, there can be used esters, ethers, nitriles, amides, a mixed solvent containing at least two of those mentioned above, and the like. The non-aqueous solvent may also contain a halogen substitute in which at least a part of hydrogen of these solvents 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. For the electrolyte salt, there is used, for example, a lithium salt such as LiPF<NUM>. The kind of the electrolyte is not limited to a particular kind of electrolyte, but may also be an aqueous electrolyte.

The cylindrical battery <NUM> has insulating plates <NUM> and <NUM> arranged on the upper and lower sides of the electrode assembly <NUM>, respectively. In the example illustrated in <FIG>, a positive electrode lead <NUM> connected to the positive electrode plate <NUM> extends to the sealing assembly <NUM> side through a through hole of the insulating plate <NUM>, and a negative electrode lead <NUM> connected to the negative electrode plate <NUM> extends to the bottom face part 20A side of the exterior housing can <NUM> along the outside of the insulating plate <NUM>. The positive electrode lead <NUM> is connected to a lower face of a metal plate <NUM>, which is a bottom plate of the sealing assembly <NUM>, by welding or the like, and a rupture disk <NUM> of the sealing assembly <NUM> electrically connected to the metal plate <NUM> serves as a positive electrode external terminal. The negative electrode lead <NUM> is connected, by welding or the like, to an inner face of the bottom face part 20A of the exterior housing can <NUM>, and the exterior housing can <NUM> serves as a negative electrode external terminal.

As described above, the cylindrical battery <NUM> has the exterior housing can <NUM>, and the sealing assembly <NUM> that seals the opening of the exterior housing can <NUM>. The exterior housing can <NUM> is a bottomed cylindrical metallic container including the bottom face part 20A and a lateral face part 20B. The bottom face part 20A has a disk shape, and the lateral face part 20B is formed into a cylindrical shape along an outer peripheral edge of the bottom face part 20A. The sealing assembly <NUM> has the rupture disk <NUM> fixed by crimping to the opening of the exterior housing can <NUM> with the gasket <NUM> interposed between the exterior housing can <NUM> and the rupture disk <NUM>.

More specifically, the rupture disk <NUM> is supported by a grooved part 20C of the exterior housing can <NUM>, and is fixed by crimping by a shoulder part 20D of the exterior housing can <NUM>. The grooved part 20C is formed into an annular shape along the circumferential direction of the exterior housing can <NUM> to have a part of its lateral face part 20B configured to project to the inside in the vicinity of the opening of the exterior housing can <NUM>. The shoulder part 20D is formed into an annular shape along the circumferential direction of the exterior housing can <NUM> at the opening end.

The sealing assembly <NUM> will be described in detail with reference to <FIG> and <FIG> is an enlarged view of the sealing assembly <NUM> and its vicinity.

The sealing assembly <NUM> is a disk-shaped member that seals the opening of the exterior housing can <NUM> as described above, and functions as a current interrupt device and a safety valve. The sealing assembly <NUM> has a stacked structure of the metal plate <NUM>, an insulating plate <NUM>, the rupture disk <NUM>, and the external terminal <NUM> in this order from the electrode assembly <NUM> side. In the rupture disk <NUM>, there is formed a vent part 33B that ruptures when an internal pressure of the battery increases.

The metal plate <NUM> is a metal plate including an annular part 31A to which the positive electrode lead <NUM> is connected, and a thin central part 31B that is disconnected from the annular part 31A when an internal pressure of the battery exceeds a predetermined threshold. The insulating plate <NUM> is a plate for insulating a part other than a connecting part between the central part 31B of the metal plate <NUM> and the vent part 33B. In the insulating plate <NUM>, an opening 32A is formed at a central part in the radial direction.

The rupture disk <NUM> is disposed to face the metal plate <NUM> with the insulating plate <NUM> interposed between the rupture disk <NUM> and the metal plate <NUM>. The rupture disk <NUM> is formed into a circular shape in plan view, and is produced by pressing a plate material made of, for example, aluminum or an aluminum alloy. The rupture disk <NUM> has an outer peripheral part 33A that is supported by the grooved part 20C of the exterior housing can <NUM>, and is fixed by crimping by the shoulder part 20D of the exterior housing can <NUM>. A step part <NUM> is formed on the upper face part of the outer peripheral part 33A, and the vent part 33B is formed inside of the outer peripheral part 33A.

The vent part 33B functions as the safety valve that ruptures when the internal pressure of the battery increases and vents gas inside the battery. When viewed in a cross section in the radial direction, the vent part 33B includes a inclined part 33C that is inclined downward from the outside to the inside, and a central part 33D that has a projection projecting toward the inside of the battery. The inclined part 33C is interposed between the outer peripheral part 33A and the central part 33D, and a thickness of the inclined part 33C is smaller than each thickness of the outer peripheral part 33A and the central part 33D. The thickness of the inclined part 33C continuously decreases from the central part 33D side toward the outer peripheral part 33A side. Forming the inclined part 33C makes it easy to invert and rupture the vent part 33B when the internal pressure of the battery increases. The projection of the central part 33D is connected, by welding or the like, to the central part 31B of the metal plate <NUM> through the opening 32A of the insulating plate <NUM>.

In the cylindrical battery <NUM>, the metal plate <NUM> to which the positive electrode lead <NUM> is connected is electrically connected to the rupture disk <NUM>, whereby there is formed a current pathway connecting from the electrode assembly <NUM> to the rupture disk <NUM>. The cylindrical battery <NUM> activates the current interrupt device and the safety valve to secure the safety, in the case where the gas inside the battery rises as described above.

If the internal pressure of the cylindrical battery <NUM> increases, the metal plate <NUM> breaks, and the central part 31B is disconnected from the annular part 31A, whereby the vent part 33B is deformed to be inverted. Thus, the current pathway is cut off. If the internal pressure of the battery further increases, the vent part 33B ruptures as described above, resulting in formation of a gas venting port.

The external terminal <NUM> is a positive electrode external terminal for connecting cylindrical batteries <NUM> in series or parallel when the cylindrical batteries <NUM> are incorporated into an electronic apparatus, for example. The external terminal <NUM> is provided on the upper face part of the rupture disk <NUM> on the inside of the opening end (a portion corresponding to an inner peripheral end of the shoulder part 20D) of the exterior housing can <NUM>. The external terminal <NUM> is fixed to the upper face part of the vent part 33B formed in the rupture disk <NUM>. The external terminal <NUM> is not fixed by crimping to the opening of the exterior housing can <NUM>. This can prevent the gas venting port formed in the vent part 33B from being sealed by the external terminal <NUM> and can secure a good gas venting function of the cylindrical battery <NUM>.

The external terminal <NUM> is made of metal, and is formed by metal principally containing aluminum or iron, for example. The external terminal <NUM> of the present embodiment is produced by pressing a metal plate and is formed into a substantial disk shape. The external terminal <NUM> includes a disk-shaped main body 35A, a recess 35B formed at a substantially central part of the main body 35A, and a leg part 35C formed in the outer peripheral edge of the main body 35A.

The main body 35A is a part in which the above-described lead plate is welded. The main body 35A is formed into a flat circular-plate shape. Forming the main body 35A to be flat makes it possible to have as large a welding area as possible and can facilitate a welding operation when the lead plate is welded to the external terminal <NUM>.

A position in an up-down direction of the main body 35A can be changed by changing a height of the recess 35B and a height of the leg part 35C. This can change the height of the main body 35A according to a space for incorporating the cylindrical batteries <NUM> into the electronic apparatus or a position of a lead plate for joining the cylindrical batteries <NUM> in the electronic apparatus, for example. An upper end position of the main body 35A of the present embodiment is preferably a position above an upper end position of the shoulder part 20D of the exterior housing can <NUM>. Note that in the case where the lead plate is welded to the upper end position of the shoulder part 20D, the upper end position of the main body 35A may be disposed on the same plane as the upper end position of the shoulder part 20D.

The main body 35A is disposed with a gap provided between the main body 35A and the rupture disk <NUM>. This makes the joining part between the rupture disk <NUM> and the metal plate <NUM> less likely to be affected by vibration or heat when the above-described lead plate is joined to the external terminal <NUM>. For example, even in the case where the joining is performed by wire bonding or laser welding accompanied by high-frequency vibrations, there can be avoided functional loss of the sealing assembly <NUM> such that the metal plate <NUM> is detached from the vent part 33B.

The recess 35B is formed at the substantially central part of the main body 35A. In the external terminal <NUM> of the present embodiment, the bottom face part of the recess 35B is joined to the vent part 33B by laser welding. The load of the laser can be optimized by adjusting the thickness of the bottom face part of the recess 35B.

The leg part 35C is formed by bending downward an outer peripheral edge or a part of the outer peripheral edge of the external terminal <NUM>. In the present embodiment, the leg part 35C is formed by being bent in an obliquely downward direction, but may be formed by being bent in a vertically downward direction. The leg part 35C of the present embodiment is formed into a projection shape at an arbitrary position in the outer peripheral edge of the main body 35A in plan view, but may be formed in a half-circumference or full circumference of the main body 35A in plan view.

The leg part 35C can support the main body 35A with respect to the rupture disk <NUM> by engaging with the step part <NUM> formed in an outer peripheral part 33A of the rupture disk <NUM>. This enables the external terminal <NUM> to be easily positioned when the external terminal <NUM> is welded to the rupture disk <NUM>.

As described above, the cylindrical battery <NUM> can avoid functional loss of the sealing assembly <NUM> when the lead plate is welded to the positive electrode side and can secure a good gas venting function.

An external terminal <NUM> of another example of an embodiment will be described in detail with reference to <FIG> is an enlarged view of a sealing assembly <NUM> and its vicinity.

The external terminal <NUM> of another example of an embodiment includes a disk-shaped main body 35A, an annular recess 35B formed at a substantially central part of the main body 35A, and a leg part 35C supporting the main body 35A with respect to a rupture disk <NUM>. In the external terminal <NUM> of the present embodiment, the above-described lead plate is welded to the main body 35A surrounded by the annular recess 35B. The external terminal <NUM> has the same configuration as that of the external terminal <NUM> illustrated in <FIG> except for the above-described configuration.

According to the external terminal <NUM> of the present embodiment, an area of the bottom face part of the recess 35B can be increased by forming the recess 35B into an annular shape. This makes it possible to have a plurality of weld portions in the case where the bottom face part of the recess 35B and the vent part 33B are welded by spot welding, for example.

The external terminal <NUM> of another example of an embodiment includes a disk-shaped main body 35A having a predetermined thickness, and a recess 35B formed at a substantially central part of the main body 35A. The main body 35A has a predetermined thickness. A bottom face part of the main body 35A is formed along an upper face part of a rupture disk <NUM>. An upper face part of the main body 35A is formed to be flat.

According to the external terminal <NUM> of the present embodiment, the main body 35A has the predetermined thickness, which makes it possible to withstand a welding load even when it is necessary to increase the welding load such as an output from a laser, for example, when the lead plate is welded to the external terminal <NUM>. In the joint between the external terminal <NUM> and the vent part 33B, the recess 35B formed to be thinner than the thickness of the main body 35A is joined to the vent part 33B by laser welding, which makes it possible to reduce the laser welding load.

The external terminal <NUM> of another example of an embodiment includes a disk-shaped main body 35A, and an annular recess 35B formed at a substantially central part of the main body 35A. In the external terminal <NUM>, the above-described lead plate is welded to the main body 35A surrounded by the annular recess 35B. The external terminal <NUM> has the same configuration as that of the external terminal <NUM> illustrated in <FIG> except for the above-described configuration, and achieves the same effect as the external terminal <NUM> illustrated in <FIG>. Similar to the external terminal <NUM> illustrated in <FIG>, an area of the bottom face part of the recess 35B used for welding to the vent part 33B can be increased by forming the recess 35B into an annular shape.

The external terminal <NUM> of another example of an embodiment is formed into only a disk shape having a predetermined thickness. The external terminal <NUM> is joined to an upper face of a central part 33D of a vent part 33B. A radial size of the external terminal <NUM> is smaller than that of the central part 33D of the vent part 33B. According to the external terminal <NUM> of the present embodiment, the external terminal <NUM> is formed into only a disk shape having the predetermined thickness, which makes it possible to reduce the processing cost.

Note that the present invention is not limited to the above embodiment and modified example, and various changes and improvements are possible within the matters described in the claims of the present application.

Claim 1:
A cylindrical battery (<NUM>), comprising:
an electrode assembly (<NUM>) in which a positive electrode plate (<NUM>) and a negative electrode plate (<NUM>) are wound with a separator (<NUM>) interposed between the positive electrode plate (<NUM>) and the negative electrode plate (<NUM>);
an electrolyte;
a bottomed cylindrical exterior housing can (<NUM>) that houses the electrode assembly (<NUM>) and the electrolyte; and
a sealing assembly (<NUM>) adapted to seal an opening of the exterior housing can (<NUM>),
wherein the sealing assembly (<NUM>) includes a rupture disk (<NUM>) that is fixed by crimping to the opening of the exterior housing can (<NUM>) with a gasket (<NUM>) interposed between the exterior housing can (<NUM>) and the rupture disk (<NUM>), and an external terminal (<NUM>) that is not fixed by crimping to the opening of the exterior housing can (<NUM>),
the rupture disk (<NUM>) has a vent part (33B) adapted to rupture when an internal pressure of the battery increases, and
the external terminal (<NUM>) is fixed to an upper face part of the vent part (33B), characterized in that the external terminal (<NUM>) has a recess (35B) which is a recessed upper face part at a substantially central part, and in the recess (35B), the external terminal (<NUM>) and the vent part (33B) are welded to each other.