Patent Description:
In general, a cylindrical secondary battery is configured such that electrode tabs are welded to its opposite sides (top and bottom portions) to draw positive and negative electrodes to the outside, respectively. In this case, however, since the electrode tabs are drawn out from the opposite sides, there is spatial limitation. Accordingly, in order to maximize design and space utilization efficiency, in recent years, there has been increasing demand for methods for drawing positive and negative electrodes to the outside by welding both of the positive and negative electrode tabs to one side (e.g., top end) of the cylindrical secondary battery. That is to say, the positive electrode tab is welded to a cap-up, and the negative electrode tab is welded to a top end of a case, thereby drawing both of the positive and negative electrode tabs from the top end of the secondary battery. However, a round beading part for fixing the electrode assembly with a gasket is formed at the top end of the case in the course of forming the case. Accordingly, it is difficult to weld the electrode tab to the round beading part. The documents <CIT>, <CIT>, <CIT>, <CIT> and <CIT> are relevant prior art disclosures.

The present invention provides a secondary battery, which can facilitate welding of an electrode tab and can maximize space utilization by forming a conductive cover electrically connected to a case and having a flat part at an upper part of the case.

The broadest scope of protection of the current invention is defined in claim <NUM>. Claims <NUM> to <NUM> define preferred embodiments.

In accordance with an aspect of the present invention, the above and other objects can be accomplished by providing a secondary battery including: an electrode assembly; a case for accommodating the electrode assembly; a cap assembly which is coupled to an upper part of the case so as to seal the case, and has a terminal part; and a conductive cover which is coupled to an upper part of the case and fixed to a lateral plate of the case.

The conductive cover may include: a flat part covering the upper part of the case and flatly formed; an extending part downwardly extending from the flat part; and a coupling part inwardly protruding from the extending part and contacting the lateral plate of the case.

A hole exposing the terminal part to the outside may be formed in the flat part.

The hole may have a larger diameter than the terminal part.

The coupling part may include a first region contacting the lateral plate of the case, and a second region positioned at opposite side of the first region and connecting the first region to the extending part.

The conductive cover may further include an electrode tab formed by cutting a portion of the flat part and bending the cut portion.

The conductive cover may further include an electrode tab formed by cutting a portion of the extending part and bending the cut portion.

The electrode assembly may include a first electrode, a second electrode and a separator interposed between the first electrode and the second electrode, wherein the terminal part is electrically connected to the first electrode, and the conductive cover is electrically connected to the second electrode.

The secondary battery may further include an insulation member positioned between the case and the flat part and having a hole exposing the terminal part.

The insulation member may include an insulating adhesive tape.

As described above, in the secondary battery according to an embodiment of the present invention, a conductive cover electrically connected to a case and having a flat part is formed at a top end of the case, thereby facilitating welding an electrode tab to the flat part. According to the present invention, since electrode tabs electrically connected to a first electrode and a second electrode in a cylindrical secondary battery, respectively, are both drawn out to one side, space utilization can be maximized.

Hereinafter, a preferred embodiment of the present invention will be described in detail.

Various embodiments of the present invention may be embodied in many different forms and should not be construed as being limited to the example embodiments set forth herein. Rather, these example embodiments of the disclosure are provided so that this disclosure will be thorough and complete and will convey inventive concepts of the disclosure to those skilled in the art.

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 and 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 "comprise or include" and/or "comprising or including," 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.

<FIG> is a perspective view of a secondary battery according to an embodiment of the present invention. <FIG> is an exploded perspective view of the secondary battery according to an embodiment of the present invention. <FIG> is a cross-sectional view of the secondary battery according to an embodiment of the present invention. <FIG> is a perspective view of a conductive cover shown in <FIG>. <FIG> and <FIG> are perspective views of a variety of electrode tabs positioned on the conductive cover according to an embodiment of the present invention.

Referring to <FIG>, the secondary battery <NUM> according to an embodiment of the present invention includes an electrode assembly <NUM>, a case <NUM> accommodating the electrode assembly <NUM>, a cap assembly <NUM> coupled to a top opening of the case <NUM>, a gasket <NUM> allowing the case <NUM> and the cap assembly <NUM> to be tightly contacted with each other, a conductive cover <NUM> coupled to an upper part of the case <NUM> and the cap assembly <NUM>, and an insulation member <NUM> positioned between the upper part of the case <NUM> and the conductive cover <NUM>.

The electrode assembly <NUM> includes a first electrode <NUM>, a second electrode <NUM>, and a separator <NUM> interposed between the first electrode <NUM> and the second electrode <NUM>. The electrode assembly <NUM> may be formed by winding a stacked structure of the first electrode <NUM>, the separator <NUM> and the second electrode <NUM> in a jelly-roll configuration. Here, the first electrode <NUM> may function as a positive electrode, and the second electrode <NUM> may function as a negative electrode. A first electrode tab <NUM> is connected to the cap assembly <NUM> at an upper part of the electrode assembly <NUM>, and a second electrode tab <NUM> is connected to a bottom plate <NUM> of the case <NUM> at a lower part of the electrode assembly <NUM>.

The first electrode <NUM> is formed by coating a first electrode active material, such as a transition metal oxide, on a first electrode current collector formed of a metal foil made of, for example, aluminum. A first electrode non-coating portion that is not coated with the first electrode active material is formed on the first electrode <NUM>, and the first electrode tab <NUM> is attached to the first electrode non-coating portion. One end of the first electrode tab <NUM> is electrically connected to the first electrode <NUM>, and the other end of the first electrode tab <NUM> protrudes upwardly from the electrode assembly <NUM> to then be electrically connected to the cap assembly <NUM>.

The second electrode <NUM> is formed by coating a second electrode active material, such as graphite or carbon, on a second electrode current collector formed of a metal foil made of, e.g., copper or nickel. A second electrode non-coating portion that is not coated with the second electrode active material is formed on the second electrode <NUM>, and the second electrode tab <NUM> is attached to the second electrode non-coating portion. One end of the second electrode tab <NUM> is electrically connected to the second electrode <NUM>, and the other end of the second electrode tab <NUM> protrudes downwardly from the electrode assembly <NUM> to then be electrically connected to the bottom plate <NUM> of the case <NUM>.

The separator <NUM> is positioned between the first electrode <NUM> and the second electrode <NUM> to prevent an electrical short while allowing lithium ions to move. The separator <NUM> may include polyethylene (PE), polypropylene (PP), or a composite film of PE and PP.

The case <NUM> includes a lateral plate <NUM> shaped of a cylinder having a predetermined diameter to produce a space in which the electrode assembly <NUM> is accommodated, and the bottom plate <NUM> sealing a bottom portion of the lateral plate <NUM>. The top opening of the case <NUM> is opened to seal the case <NUM> after the electrode assembly <NUM> is inserted into the case <NUM>. In addition, a beading part <NUM> for preventing movement of the electrode assembly <NUM> is formed at the upper part of the case <NUM>. In addition, a crimping part <NUM> for fixing the cap assembly <NUM> and the gasket <NUM> is formed at the topmost end of the case <NUM>. The crimping part <NUM> is formed to have a substantially round shape in the course of a forming process for fixing the cap assembly <NUM> with the gasket <NUM>, and protrudes outwardly more than the lateral plate <NUM> of the case <NUM>.

The cap assembly <NUM> includes a cap-up <NUM>, a safety vent <NUM> installed at a lower part of the cap-up <NUM>, a cap-down <NUM> installed at a lower part of the safety vent <NUM>, an insulator <NUM> interposed between the safety vent <NUM> and the cap-down <NUM>, and a sub-plate <NUM> fixed to a bottom surface of the cap-down <NUM> to then be electrically connected to the first electrode tab <NUM>.

The cap-up <NUM> includes a terminal part 131a having an upwardly convex portion positioned at its center, and the terminal part 131a is electrically connected to an external circuit. The terminal part 131a is electrically connected to the first electrode tab <NUM> and may function as a positive electrode, for example. The cap-up <NUM> has gas exhaustion holes 131b formed to provide paths for exhausting internal gases generated in the case <NUM> to the outside. The cap-up <NUM> is electrically connected to the electrode assembly <NUM> and transfers electric current generated in the electrode assembly <NUM> to the external circuit.

The safety vent <NUM> is shaped of a circular plate corresponding to the cap-up <NUM>. A downwardly protruding protrusion part 132a is formed at the center of the safety vent <NUM>. The safety vent <NUM> is electrically connected to the sub-plate <NUM> fixed to the bottom surface of the cap-down <NUM> using the protrusion part 132a passing through a throughhole 134a of the cap-down <NUM>. Here, the protrusion part 132a of the safety vent <NUM> and the sub-plate <NUM> may be welded to each other by laser welding, ultrasonic welding, resistance welding or equivalents thereof. In addition, a notch 132b that guides rupture of the safety vent <NUM> is formed at an outer periphery of the protrusion part 132a.

The outer periphery of the safety vent <NUM> is installed to be tightly adhered to portions of the cap-up <NUM>, except for the terminal part 131a. That is to say, the outer periphery of the safety vent <NUM> and the outer periphery of the cap-up <NUM> may come into contact with each other. When an abnormal internal pressure is generated in the case <NUM>, the safety vent <NUM> may release internal gases while cutting off the current. If the internal pressure of the case <NUM> exceeds an operating pressure of the safety vent <NUM>, the protrusion part 132a of the safety vent <NUM> rises upwardly by the gases released through a gas exhaustion hole 134b of the cap-down <NUM> to then be electrically disconnected from the sub-plate <NUM>. Here, the sub-plate <NUM> is electrically disconnected from the safety vent <NUM> as a welded portion of the protrusion part 132a is ripped apart. Then, if the internal pressure of the case <NUM> exceeds a rupture pressure higher than the operating pressure of the safety vent <NUM>, the notch 132b may be ruptured, thereby allowing the safety vent <NUM> to prevent the secondary battery <NUM> from exploding.

The insulator <NUM> is interposed between the safety vent <NUM> and the cap-down <NUM> to insulate the safety vent <NUM> and the cap-down <NUM> from each other. In detail, the insulator <NUM> is interposed between the outer periphery of the safety vent <NUM> and the outer periphery of the cap-down <NUM>. The insulator <NUM> may be formed of a resin material, such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET).

The cap-down <NUM> is shaped of a circular plate. The throughhole 134a is formed at the center of the cap-down <NUM>, and the protrusion part 132a of the safety vent <NUM> passes through the throughhole 134a. In addition, the gas exhaustion hole 134b is formed at one side of the cap-down <NUM>. When an excessive internal pressure is generated in the case <NUM>, the gas exhaustion hole 134b may function to release internal gases to the outside. Here, the protrusion part 132a of the safety vent <NUM> rises due to the gases released through the gas exhaustion hole 134b, so that the protrusion part 132a is separated from the sub-plate <NUM>.

The sub-plate <NUM> is positioned under the cap-down <NUM>. The sub-plate <NUM> is welded to a region between the protrusion part 132a of the safety vent <NUM> passing through the throughhole 134a of the cap-down <NUM> and the first electrode tab <NUM>. Accordingly, the sub-plate <NUM> electrically connects the first electrode tab <NUM> and the safety vent <NUM> to each other.

The gasket <NUM> is installed at the top opening of the case <NUM>. That is to say, the gasket <NUM> is brought into close contact with regions between the outer peripheries of the cap-up <NUM> and the safety vent <NUM> and the top opening of the case <NUM>. The gasket <NUM> may prevent the cap assembly <NUM> from being separated from the case <NUM>.

The conductive cover <NUM> is coupled to the upper part of the case <NUM> coupled to the cap assembly <NUM>. The conductive cover <NUM> includes a flat part <NUM> shaped of a substantially planar circle, an extending part <NUM> downwardly extending from the flat part <NUM> and covering the upper part of the case <NUM>, and a coupling part <NUM> inwardly protruding to the extending part <NUM> to be coupled to the lateral plate <NUM> of the case <NUM>. The conductive cover <NUM> is made of a metal and is electrically connected to the case <NUM>. Therefore, the conductive cover <NUM> may function as an electrode having the same polarity with the case <NUM> (e.g., a negative electrode). In addition, the conductive cover <NUM> covers the crimping part <NUM> positioned at the topmost part of the case <NUM>, thereby facilitating welding of an electrode tab at an edge part of the secondary battery <NUM>.

The crimping part <NUM> is generally formed to have a roughly round shape during the forming process of the case <NUM>. Therefore, since the round crimping part <NUM> has a narrow space for welding and bubbles may be generated during welding, welding failures may be undesirably generated. Hence, according to the present invention, the conductive cover <NUM> covering the crimping part <NUM> and having a flat upper part is coupled to the upper part of the case <NUM>, welding of the electrode tab can be facilitated.

The flat part <NUM> is substantially planar and is shaped of a circular plate. The flat part <NUM> is mounted on the upper part of the case <NUM> and covers the upper part of the case <NUM>. In addition, a central hole 151a is formed at the center of the flat part <NUM>, and the central hole 151a exposes the terminal part 131a of the cap-up <NUM>. The central hole 151a has a larger diameter than the terminal part 131a. Therefore, the flat part <NUM> is electrically insulated from the cap-up <NUM>. Consequently, the flat part <NUM> is positioned to correspond to the outer periphery of the cap-up <NUM> to cover the crimping part <NUM>. In such a manner, since the flat part <NUM> is flatly formed while covering the crimping part <NUM>, and is electrically connected to the case <NUM>, the electrode tab can be easily welded to the flat part <NUM>.

The extending part <NUM> downwardly extends a predetermined length from the flat part <NUM> and covers the lateral plate <NUM> of the case <NUM>. Therefore, the extending part <NUM> is shaped of a cylinder having a predetermined diameter to correspond to the lateral plate <NUM> of the case <NUM>. Here, since the extending part <NUM> is coupled to an exterior portion of the lateral plate <NUM>, the diameter of the extending part <NUM> is larger than that of the lateral plate <NUM>. In addition, the extending part <NUM> covers the beading part <NUM> of the case <NUM>. The coupling part <NUM> is formed to protrude inwardly to the extending part <NUM>, that is, toward the lateral plate <NUM> of the case <NUM>.

The coupling part <NUM> includes a plurality of coupling parts formed to be spaced a predetermined distance apart from the extending part <NUM>. The coupling part <NUM> is a portion inwardly protruding from the extending part <NUM> and substantially contacts the lateral plate <NUM> of the case <NUM>. In addition, the coupling part <NUM> is coupled to the case <NUM> in an interferential fit manner to prevent the conductive cover <NUM> from being separated from the case <NUM>. That is to say, the coupling part <NUM> may fix the conductive cover <NUM> to the case <NUM>. In addition, the coupling part <NUM> is positioned under the beading part <NUM>. Therefore, since the coupling part <NUM> inwardly protruding to the extending part <NUM> is hung on the crimping part <NUM> positioned at an upper part of the beading part <NUM> even if the conductive cover <NUM> is pulled, the conductive cover <NUM> is not separated from the case <NUM>.

The coupling part <NUM> includes a first region 153a inwardly protruding from the extending part <NUM> and contacting the lateral plate <NUM> of the case <NUM>, and a second region 153b positioned at opposite sides of the first region 153a and connecting the first region 153a and the extending part <NUM>. The first region 153a is substantially flatly formed. The second region 153b is slantingly formed to connect the first region 153a inwardly protruding from the extending part <NUM> to the extending part <NUM>.

A separate electrode tab may be directly welded to the conductive cover <NUM>. Alternatively, as shown in <FIG>, a portion of the conductive cover <NUM> may be cut to be used as an electrode tab. That is to say, the conductive cover <NUM> may further include an electrode tab <NUM> positioned in the flat part <NUM>. The electrode tab <NUM> may be formed to upwardly protrude from the conductive cover <NUM> by cutting a portion of the flat part <NUM> and bending the cut portion <NUM> degrees. That is to say, the electrode tab <NUM> is formed to be perpendicular to the flat part <NUM>. Therefore, a bus bar or an external terminal may be electrically connected to the electrode tab <NUM>.

In addition, as shown in <FIG>, an electrode tab <NUM> may be formed by cutting a portion of the extending part <NUM> of the conductive cover <NUM>. The electrode tab <NUM> may be formed to upwardly protrude from the conductive cover <NUM> by cutting a portion of the extending part <NUM> and bending the cut portion <NUM> degrees. Therefore, the electrode tab <NUM> is formed to be perpendicular to the flat part <NUM>.

The insulation member <NUM> is positioned between the upper part of the case <NUM> and the conductive cover <NUM>. In detail, the insulation member <NUM>, which is positioned between the crimping part <NUM> and the flat part <NUM>, prevents the flat part <NUM> from being shorted to the cap-up <NUM>. That is to say, the insulation member <NUM> may be positioned on a bottom surface of the flat part <NUM>. In addition, the insulation member <NUM> is shaped of a ring and has a wider area than the flat part <NUM>. That is to say, the insulation member <NUM> has a hole <NUM> positioned at its center to expose the terminal part 131a of the cap-up <NUM> to the outside, and the hole <NUM> is smaller than the central hole 151a of the flat part <NUM>. In addition, the insulation member <NUM> is formed of, for example, an insulating adhesive tape, which is made of polypropylene (PP), polyimide (PI) or equivalents thereof. Therefore, the insulation member <NUM> may prevent an electrical short from occurring between the conductive cover <NUM> and the cap-up <NUM> while fixing the conductive cover <NUM> to the case <NUM>.

As described above, in the secondary battery according to an embodiment of the present invention, a conductive cover electrically connected to a case and having a flat part is formed at an upper part of the case, thereby easily welding an electrode tab to the flat part. According to the present invention, since electrode tabs electrically connected to a first electrode and a second electrode in a cylindrical secondary battery, respectively, are both drawn out to one side, space utilization can be maximized.

In addition, in the secondary battery according to an the present invention, an insulation member is formed between the case and the conductive cover, thereby preventing an electrical short from occurring between the conductive cover and a cap-up while fixing the conductive cover to the case.

In addition, in the secondary battery according to an embodiment of the present invention, a conductive cover is provided, the conductive cover including a flat part, an extending part downwardly extending from the flat part, and a coupling part inwardly protruding to the extending part, thereby preventing the conductive cover from being separated from the case.

Claim 1:
A cylindrical secondary battery comprising:
an electrode assembly;
a case for accommodating the electrode assembly;
a cap assembly which is coupled to an upper part of the case so as to seal the case, and has a terminal part;
a conductive cover which is coupled to an upper part of the case and fixed to a lateral plate of the case; and
an insulation member which is positioned between the upper part of the case and the conductive cover, wherein the conductive cover comprises:
a flat part covering the upper part of the case and flatly formed;
an extending part downwardly extending from the flat part; and
a coupling part inwardly protruding from the extending part and contacting the lateral plate of the case, wherein a hole exposing the terminal part to the outside is formed in the flat part, and, wherein the hole has a larger diameter than the terminal part,
wherein the electrode assembly includes a first electrode, a second electrode and a separator interposed between the first electrode and the second electrode, wherein the terminal part is electrically connected to the first electrode, and the conductive cover is electrically connected to the second electrode.