Patent Description:
A secondary battery is a power storage system that provides excellent energy density for converting electrical energy into chemical energy and storing same. Compared to primary batteries that are not rechargeable, secondary batteries are rechargeable and are widely used in IT devices such as smartphones, cellular phones, laptops, and tablet PCs. Recently, interest in electric vehicles has increased to prevent environmental pollution, and thus, high-capacity secondary batteries are being adopted for electric vehicles. Such secondary batteries are required to have characteristics such as high density, high output, and stability. <CIT> relates to a battery and manufacturing method thereof. Furthermore <CIT> discloses a cylindrical battery wherein the cap-up (<NUM>) "curls" around the safety plate (<NUM>).

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not constitute prior art.

Various embodiments of the present invention relates to a secondary battery, wherein an electrode tab of an electrode assembly and a pack tab for modularization are electrically connected by a cap-up without any other configuration, so as to reduce resistance and heat generation, which may occur on a current path.

Various embodiments of the present invention provide a secondary battery including a cylindrical can having an upper end opening, an electrode assembly received in the cylindrical can and having an electrode tab, and a cap assembly for sealing the upper end opening of the cylindrical can. The cap assembly includes: a circular-plate-shaped safety plate having a bent, and a cap-up disposed on the upper portion of the safety plate and surrounding the edge portion of the safety plate, and the electrode tab is in contact with and coupled to the cap-up. The cap-up includes a terminal portion in the shape of a flat circular plate, a connection portion that is bent downwardly from an edge of the terminal portion, a first extension portion that extends outwardly from a lower end of the connection portion in the horizontal direction, a bent portion that is bent downwardly from an edge of the first extension portion, and a second extension portion that extends inwardly from a lower end of the bent portion in the horizontal direction.

The edge portion of the safety plate may have an upper surface in contact with the first extension portion, a side surface in contact with the bent portion, and a lower surface in contact with the second extension portion.

The edge portion of the safety plate may be interposed between the first extension portion of the cap-up and the second extension portion parallel to the first extension portion.

The second extension portion may include a plurality of slits that are cut from the upper end to the lower end.

The safety plate may have a circular ring-shaped groove in which the vent is located under the terminal portion and is formed in a downward direction from the top surface.

The connection portion may have at least one opening.

The electrode tab may be welded to the second extension portion.

The safety plate may include a central portion that has a flat circular plate shape and includes the vent formed on the upper surface thereof, a stepped portion that is bent downwardly from the edge portion of the central portion; and an edge portion that extends outwardly from the lower end of the stepped portion.

The cap assembly may further include an insulating gasket interposed between the cap-up and the cylindrical can.

Various embodiments of the present invention provide a secondary battery, wherein an electrode tab of an electrode assembly and a pack tab for modularization are electrically connected by a cap-up without any other configuration, so as to reduce resistance and heat generation, which may occur on a current path.

Hereinafter, example embodiments of the present disclosure will be described in detail.

Embodiments of the present invention are provided to more completely explain the present invention to one skilled in the art, and the following example embodiments may be modified in various other forms and the present invention should not be construed as being limited to the embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete and will convey the aspects and features of the present disclosure to those skilled in the art.

In addition, in the accompanying drawings, sizes or thicknesses of various components are exaggerated for brevity and clarity. In addition, it will be understood that when an element A is referred to as being "connected to" an element B, the element A can be directly connected to the element B or an intervening element C may be present therebetween such that the element A and the element B are indirectly connected to each other.

As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It will be further understood that the terms that the terms "comprise or and/or "comprising" when used in this specification, specify the presence of stated features, numbers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms first, second, etc. may be used herein to describe various members, elements, regions, layers and/or sections, these members, elements, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one member, element, region, layer and/or section from another. Thus, for example, a first member, a first element, a first region, a first layer and/or a first section discussed below could be termed a second member, a second element, a second region, a second layer and/or a second section without departing from the teachings of the present disclosure.

Spatially relative terms, such as "beneath," "below," "lower," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. For example, if the element or feature in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "on" or "above" the other elements or features.

<FIG> shows a perspective view illustrating a secondary battery <NUM> according to an embodiment of the present invention, and <FIG> shows a longitudinal cross-sectional view illustrating the secondary battery <NUM> shown in <FIG>. Here, the longitudinal cross-section is a cross-section of the secondary battery <NUM> cut in the longitudinal direction.

As illustrated in <FIG> and <FIG>, the secondary battery <NUM> according to the present invention includes a cylindrical can <NUM>, an electrode assembly <NUM> accommodated in the cylindrical can <NUM>, and a cap assembly <NUM> sealing the upper opening of the cylindrical can <NUM>. In addition, the present invention may further include a center pin <NUM> coupled to the electrode assembly <NUM>.

The cylindrical can <NUM> includes a circular bottom portion <NUM> and a side portion <NUM> extending a predetermined length upward from the bottom portion <NUM>. During the manufacturing process of the secondary battery, the upper part of the cylindrical can <NUM> is opened. Therefore, during the assembly process of the secondary battery, the electrode assembly <NUM> may be inserted into the cylindrical can <NUM> together with the electrolyte. The cylindrical can <NUM> may be formed of steel, a steel alloy, aluminum, an aluminum alloy, or an equivalent thereof, but the material thereof is not limited thereto. In addition, the cylindrical can <NUM> may have an inwardly recessed beading part <NUM> formed under the cap assembly <NUM> to prevent the cap assembly <NUM> from being separated to the outside, and an inwardly bent crimping part <NUM> formed on the cap assembly <NUM>.

The electrode assembly <NUM> is accommodated in the cylindrical can <NUM>. The electrode assembly <NUM> may include two electrode tabs <NUM> and <NUM> protruding in upper and lower directions, respectively. The electrode assembly <NUM> may include a negative electrode plate <NUM> coated with a negative active material (e.g., graphite, carbon, etc.), a positive electrode plate122 coated with a positive active material (e.g., transition metal oxide (LiCoO<NUM>, LiNiO<NUM>, LiMn<NUM>O<NUM>, etc.)), and a separator <NUM> positioned between the negative electrode plate <NUM> and the positive electrode plate <NUM> to prevent a short circuit and allow only movement of lithium ions. The negative electrode plate <NUM>, the positive electrode plate <NUM>, and the separator <NUM> are wound in a substantially cylindrical shape. Here, the negative electrode plate <NUM> may be a copper (Cu) or nickel (Ni) foil, the positive electrode plate <NUM> may be an aluminum (Al) foil, and the separator <NUM> may be made of polyethylene (PE) or polypropylene (PP), but the present invention is not limited thereto. In addition, a negative electrode tab <NUM> protruding downward by a predetermined length may be welded to the negative electrode plate <NUM>, and a positive electrode tab <NUM> protruding upward by a predetermined length may be welded to the positive electrode plate <NUM>, but vice versa. In addition, the negative electrode tab <NUM> may be made of copper or nickel, and the positive electrode tab <NUM> may be made of aluminum, but the present invention is not limited thereto.

Also, the negative electrode tab <NUM> of the electrode assembly <NUM> may be welded to the bottom portion <NUM> of the case <NUM>. Accordingly, the case <NUM> may operate as a negative electrode. Of course, on the contrary, the positive electrode tab <NUM> may be welded to the bottom portion <NUM> of the case <NUM>, and in such a case, the case <NUM> may operate as a positive electrode.

In addition, a first insulating plate <NUM> that is coupled to the cylindrical can <NUM> and has a first hole 126a in the center and a second hole 126b on the exterior side thereof may be disposed between the electrode assembly <NUM> and the bottom portion <NUM>. The first insulating plate <NUM> serves to prevent the electrode assembly <NUM> from electrically contacting the bottom portion <NUM> of the cylindrical can <NUM>. Specifically, the first insulating plate <NUM> serves to prevent the positive electrode plate <NUM> of the electrode assembly <NUM> from electrically contacting the bottom portion <NUM>. Here, when a large amount of gas is generated due to an abnormality in the secondary battery, the first hole 126a serves to allow the gas to quickly move upward through the center pin <NUM>, and the second hole 126b serves to allow the negative electrode tab <NUM> to penetrate therethrough to then be welded to the bottom portion <NUM>.

In addition, a second insulating plate <NUM> that is coupled to the cylindrical can <NUM> and has a first hole 127a in the center and a second hole 127b on the exterior side thereof may be disposed between the electrode assembly <NUM> and the cap assembly <NUM>. The second insulating plate <NUM> serves to prevent the electrode assembly <NUM> from electrically contacting the cap assembly <NUM>. Specifically, the second insulating plate <NUM> serves to prevent the negative electrode plate <NUM> of the electrode assembly <NUM> from electrically contacting the cap assembly <NUM>. Here, when a large amount of gas is generated due to an abnormality in the secondary battery, the first hole 127a serves to allow the gas to quickly move toward the cap assembly <NUM>, and the second hole 127b serves to allow the positive electrode tab <NUM> to penetrate therethrough to then be welded to the cap-up <NUM>. In addition, the remaining second holes 127b serve to allow the electrolyte to quickly flow into the electrode assembly <NUM> in an electrolyte injection process.

In addition, the diameters of the first holes 126a and 127a of the first and second insulating plates <NUM> and <NUM> are smaller than the diameter of the center pin <NUM>, and thus prevents the center pin <NUM> from electrically contacting the bottom portion <NUM> of the cylindrical can <NUM> or the cap assembly <NUM> due to an external impact.

The center pin <NUM> has a hollow circular pipe shape, and may be coupled to the approximately center of the electrode assembly <NUM>. The center pin <NUM> may be formed of steel, a steel alloy, aluminum, an aluminum alloy, or polybutylene terephthalate, but the material thereof is not limited thereto. The center pin <NUM> serves to suppress deformation of the electrode assembly <NUM> during charging and discharging of the battery, and serves as a passage for gas generated inside the secondary battery. In some cases, the center pin <NUM> may be omitted.

The cap assembly <NUM> includes a cap-up <NUM> having a plurality of through-holes <NUM> formed therein, a safety plate <NUM> installed under the cap-up <NUM>, and an insulating gasket <NUM> for insulating the cap-up <NUM> from the side portion <NUM> of the cylindrical can <NUM>. The cap-up <NUM> surrounds the edge portion of the safety plate <NUM>. In addition, the cap-up <NUM> may have a lower surface thereof contacting the positive electrode tab <NUM> to then be welded thereto. The configuration and coupling relationship of the cap-up <NUM> and the safety plate <NUM> will be described in detail below.

Here, the insulating gasket <NUM> is substantially formed along the beading part <NUM> and the crimping part <NUM> formed on the side portion <NUM> of the cylindrical can <NUM>, and thus is compressed between the cap-up <NUM> and the insulating gasket <NUM>. That is, the insulating gasket <NUM> may be interposed between the cap-up <NUM> and the beading part <NUM> and between the cap-up <NUM> and the crimping part <NUM> in a compressed state. In addition, through-holes <NUM> formed in the cap-up <NUM> serve to discharge the internal gas to the outside when an abnormal internal pressure is generated inside the cylindrical can <NUM>. Of course, the vent 142a of the safety plate <NUM> is first ruptured and torn by the internal pressure, and the gas inside is released to the outside.

The cap assembly <NUM> may be formed of any one selected from general aluminum, aluminum alloy, steel, steel alloy, nickel, nickel alloy, and equivalents thereof, and the material thereof is not limited in the present invention.

In addition, an electrolyte (not shown) is injected into the cylindrical can <NUM>, and this allows for movement of lithium ions generated by electrochemical reactions in the negative electrode plate <NUM> and the positive electrode plate <NUM> inside the battery during charging and discharging. The electrolyte may be a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent. In addition, the electrolyte may be a polymer using a polymer electrolyte or a solid electrolyte, and the type of the electrolyte is not limited thereto.

Referring to <FIG>, an exploded perspective view illustrating an enlarged view of a cap assembly of the secondary battery <NUM> shown in <FIG> and <FIG> before a cap-up <NUM> and a safety plate <NUM> are coupled is illustrated. Referring to <FIG>, a cross-sectional view in which the safety plate <NUM> is inserted into the cap-up <NUM> shown in <FIG> is illustrated, and referring to <FIG>, a cross-sectional view in which the cap-up <NUM> and the safety plate <NUM> are coupled is illustrated. In addition, referring to <FIG>, a bottom view in which the cap-up <NUM> shown in <FIG> and the safety plate <NUM> are coupled is illustrated.

Hereinafter, the configuration and coupling relationship of the cap-up <NUM> and the safety plate <NUM> will be described with reference to <FIG>, <FIG>, <FIG> and <FIG>.

The cap-up <NUM> includes a terminal portion 141a, a connection portion 141b, an extension portion 141c, a bent portion 141d, and a second extension portion 141e sequentially positioned in an outward direction from the center.

The terminal portion 141a may be approximately flat and may be located approximately at the center of the cap-up <NUM>. In addition, when a plurality of secondary batteries <NUM> are connected in series or in parallel to then be modularized, a pack tab (PT) for connecting between the plurality of secondary batteries <NUM> is welded to the upper surface of the terminal portion 141a.

The connection portion 141b is formed by bending downwardly from an edge portion of the terminal portion 141a, and includes at least one opening <NUM>. The opening <NUM> releases the gas inside the cylindrical can <NUM> to the outside when the vent 142a of the safety plate <NUM> is ruptured.

In addition, the first extension portion 141c extends outwardly from the lower end of the connection portion 141b in the horizontal direction. The first extension portion 141c may have a horizontal size larger than that of the safety plate <NUM>. The first extension portion 141c may have a lower surface 141ca in contact with the upper surface 142ba of the edge portion 142b of the safety plate <NUM>.

In addition, the bent portion 141d may be bent substantially vertically downward from the edge portion of the first extension portion 141c. The inner surface 141da of the bent portion 141d may be in contact with the side surface 142c of the safety plate <NUM>.

Also, the second extension portion 141e extends from the lower end of the bent portion 141d in the inward horizontal direction. The second extension portion 141e may maintain a state in which it extends downward from the lower end of the bent portion 141d as shown in <FIG> and <FIG> before being coupled to the safety plate <NUM>. In addition, the second extension portion 141e may be bent toward the lower surface 142bb of the safety plate <NUM> in a state in which the safety plate <NUM> is in contact with the lower surface 141ca of the first extension portion 141c and the inner surface 141da of the bent portion 141d. Here, the upper surface 141ea of the second extension portion 141e may be in contact with the lower surface 142bb of the safety plate <NUM>. In addition, the edge portion 142b of the safety plate <NUM> may be interposed between the first extension portion 141c and the second extension portion 141e. The second extension portion 141e may be parallel to the first extension portion 141c.

The second extension portion 141e may include a plurality of slits 141f. The plurality of slits 141f may be cut from the upper portion to the lower end of the second extension portion 141e. In addition, the plurality of slits 141f may be more spaced apart from each other in the lower part than in the upper part. The plurality of slits 141f may be provided to prevent the second extension portion 141e from overlapping or wrinkling when the second extension portion 141e is bent toward the lower surface of the safety plate <NUM>. After the cap-up <NUM> and the safety plate <NUM> are coupled to each other, as shown in <FIG> and <FIG>, the second extension portion 141e can be brought into close contact with the edge portion 142b of the safety plate <NUM> by the plurality of slits 141f to then be kept flat. Although six of the plurality of slits 141f are shown in <FIG> and <FIG>, the number of the plurality of slits 141f may be any one of four or more, and the present invention does not limit the number of the plurality of slits 141f. However, for the convenience of the bending process of the second extension portion 141e, four or six slits are preferably formed.

In addition, the second extension portion 141e may have the positive electrode tab <NUM> of the electrode assembly <NUM> welded to the lower surface 141eb. That is, the positive electrode tab <NUM> and the pack tab PT may be electrically connected only with the cap-up <NUM> without any other configuration.

The safety plate <NUM> may have a substantially flat circular plate shape. The safety plate <NUM> may include a vent 142a, which is a groove formed in the downward direction from an upper surface. The vent 142a may be formed in a circular ring on the approximately central portion of the safety plate <NUM>. The vent 142a may be located under the terminal portion 141a of the cap-up <NUM>. The region where the vent 142a is formed may have a smaller thickness than other portions of the safety plate <NUM>. When the pressure inside the cylindrical can <NUM> increases due to an internal short circuit or overcharge/discharge, the vent 142a may be ruptured by the pressure. The safety plate <NUM> may release the internal gas through the opening <NUM> of the cap-up <NUM> to the outside while the vent 142a is torn by the internal pressure of the cylindrical can <NUM>.

In addition, the safety plate <NUM> may have an edge portion 142b interposed between the first extension portion 141c and the second extension portion 141e. Also, the edge portion 142b may have an upper surface, a side surface, and a lower surface surrounded by the first extension portion 141c, the bent portion 141d, and the second extension portion 141e.

Since the secondary battery <NUM> of the present invention is electrically connected between the positive electrode tab <NUM> of the electrode assembly <NUM> and the pack tab PT for modularization by the cap-up <NUM> without any other configuration, heat generation due to increased resistance, which may occur on a current path, can be reduced.

For example, a cap assembly <NUM> of Comparative Example, as shown in <FIG>, may include a cap-up <NUM> having a plurality of through-holes 11a formed therein, a safety plate <NUM> installed under the cap-up <NUM>, a connecting ring <NUM> installed under the safety plate <NUM>, a cap-down <NUM> coupled to the connecting ring <NUM> and having a through-hole 14a formed therein, and a sub-plate <NUM> fixed to the lower portion of the through-hole 14a of the cap-down <NUM>. In the cap assembly <NUM> , a pack tab PT may be welded to a substantially central upper surface of the cap-up <NUM>, and a positive electrode tab ET of the electrode assembly may be welded to the lower surface of the cap down <NUM>.

In the cap assembly <NUM>, the current path may be connected to the cap-down <NUM>, the sub plate <NUM>, the safety plate <NUM> and the cap up <NUM> through the pack tab (PT) in the positive tab (ET). That is, since the positive electrode tab ET and the pack tab PT are electrically connected through four components (the cap-down <NUM>, the sub plate <NUM>, the safety plate <NUM>, and the cap-up <NUM>), the current path becomes longer, and thus the resistance of the current path may increase, resulting in increased heat generation. <FIG> is a graph illustrating the result of measuring the heating state of the cap assembly of Comparative Example and a temperature change according to current. As shown in <FIG>, it can be seen that when the current is 30C, the heating temperature of the cap assembly <NUM> of Comparative Example is measured up to <NUM> degrees. In addition, when the current is 40C, the heating temperature of the cap assembly <NUM> of Comparative Example was extremely high, and thus the progress of temperature measurement was unfeasible.

In addition, <FIG> is a graph illustrating the result of measuring the heating state of the secondary battery <NUM> shown in <FIG> by using a thermal imaging camera and a temperature change according to current. As shown in <FIG> , it can be seen that when the current is 40C, the heating temperature of the cap-up of the secondary battery of the present invention is measured up to <NUM> degrees.

That is, in the secondary battery <NUM> of the present invention, the positive electrode tab <NUM> and the pack tab PT are connected by the cap-up <NUM> without any other configuration, and thus heat generation due to the resistance of the current path is reduced compared to Comparative Example.

Referring to <FIG>, a cross-sectional view illustrating a secondary battery <NUM> according to another embodiment of the present invention is illustrated.

As shown in <FIG>, the secondary battery <NUM> according to the present invention includes a cylindrical can <NUM>, an electrode assembly <NUM> accommodated in the cylindrical can <NUM>, and a cap assembly <NUM> that seals an upper opening of the cylindrical can <NUM>. In addition, the present invention may further include a center pin <NUM> coupled to the electrode assembly <NUM>.

The configurations of the cylindrical can <NUM>, the electrode assembly <NUM>, and the center pin <NUM> of the secondary battery <NUM> are the same as those of the secondary battery <NUM> illustrated in <FIG> and <FIG>, and in the configuration of the cap assembly <NUM>, the configurations of the cap-up <NUM> and the insulating gasket <NUM> are the same as those of secondary battery <NUM> illustrated in <FIG> and <FIG>.

Accordingly, the following description will focus on the safety plate <NUM> of the secondary battery <NUM>, which is different from the corresponding element of the secondary battery <NUM>.

In addition, referring to <FIG>, an exploded perspective view illustrating an enlarged view of a cap assembly <NUM> of the secondary battery <NUM> shown in <FIG> before a cap-up <NUM> and a safety plate <NUM> are coupled is illustrated. Referring to <FIG>, a cross-sectional view in which the safety plate <NUM> is inserted into the cap-up <NUM> shown in <FIG> is illustrated, and referring to <FIG>, a cross-sectional view in which the cap-up <NUM> and the safety plate <NUM> are coupled is illustrated.

Hereinafter, the configuration and coupling relationship of the cap-up <NUM> and the safety plate <NUM> will be described with reference to <FIG>, <FIG>.

The safety plate <NUM> may include a central portion 242d, a step portion 242e, and an edge portion 242b sequentially positioned in an outward direction from the center.

The central portion 242d is approximately flat and may be located approximately at the center of the safety plate <NUM>. Also, the central portion 242d may be located under the terminal portion 141a of the cap-up <NUM>.

In addition, the central portion 242d may include a vent 242a, which is a groove formed in the downward direction from an upper surface. The region where the vent 242a is formed may have a smaller thickness than other portions of the safety plate <NUM>. The vent 242a may be formed in a circular ring on the approximately central portion of the safety plate <NUM>. The vent 242a may be located under the cap-up <NUM>. When the pressure inside the cylindrical can <NUM> increases due to an internal short circuit or overcharge/discharge, the vent 242a may be ruptured by the pressure. The safety plate <NUM> may release the internal gas through the opening <NUM> of the cap-up <NUM> to the outside while the vent 242a is torn by the internal pressure of the cylindrical can <NUM>.

The stepped portion 242e may be bent downwardly from an edge portion of the central portion 242d. In addition, the stepped portion 242e may connect the central portion 242d and the edge portion 242b. Due to the stepped portion 242e, stress against the rupture of the vent 242a may be reduced.

The edge portion 242b may extend outwardly from the lower end of the step portion 242e. The edge portion 242b may be interposed between the first extension portion 141c and the second extension portion 141e. In addition, the edge portion 242b may have an upper surface, a side surface, and a lower surface surrounded by the first extension portion 141c, the bent portion 141d, and the second extension portion 141e.

While the foregoing embodiment has been described to practice the secondary battery of the present invention, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present disclosure as defined by the following claims.

Claim 1:
A secondary battery (<NUM>) comprising:
a cylindrical can (<NUM>) having an upper end opening;
an electrode assembly (<NUM>) received in the cylindrical can (<NUM>) and having an electrode tab (<NUM>, <NUM>); and
a cap assembly (<NUM>) for sealing the upper end opening of the cylindrical can (<NUM>),
wherein the cap assembly (<NUM>) includes:
a circular-plate-shaped safety plate (<NUM>); and
a cap-up (<NUM>) disposed on the upper portion of the safety plate (<NUM>) and surrounding the edge portion (142b) of the safety plate (<NUM>), and the electrode tab (<NUM>, <NUM>) is in contact with and coupled to the cap-up (<NUM>),
characterised in that the cap-up (<NUM>) comprises:
a terminal portion (141a) in the shape of a flat circular plate;
a connection portion (141b) that is bent downwardly from an edge of the terminal portion (141a);
a first extension portion (141c) that extends outwardly from a lower end of the connection portion (141b) in the horizontal direction;
a bent portion (141d) that is bent downwardly from an edge of the first extension portion (141c); and
a second extension portion (141e) that extends inwardly from a lower end of the bent portion (141d) in the horizontal direction.