Patent ID: 12244040

DETAILED DESCRIPTION

Herein, some embodiments of the present invention will be described in further detail with reference to the accompanying drawings.

The present disclosure is provided to more fully describe embodiments of the present invention to those skilled in the art. The following embodiments may be modified in many different forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the present invention to those skilled in the art.

Also, in the drawings, the thickness and size of each layer may be exaggerated for convenience and clarity of illustration, and like reference numerals refer to like elements throughout. As used in this specification, the term “and/or” may include any and all combinations of one or more of the associated listed items. Also, in this specification, it is to be understood that when a member A is referred to as being “connected to” a member B, the member A may be directly connected to the member B, or one or more members C may be interposed between the members A and B such that the member A is indirectly connected to the member B.

The terms used herein are for the purpose of describing various embodiments and are not intended to limit the present invention. As used in this specification, a singular form may, unless definitely indicating a particular case in terms of the context, include a plural form. Also, it is to 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, members, elements, and/or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, members, elements, and/or groups thereof.

In the specification, although the terms “first,” “second,” etc. may be used to describe various members, components, regions, layers, and/or portions, these members, components, regions, layers, and/or portions are not to be limited by these terms. These terms are used to distinguish one member, component, region, layer, or portion from another member, component, region, layer, or portion. Thus, a first member, component, region, layer, or portion, described below may also refer to a second member, component, region, layer, or portion, without departing from the teachings of the present invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” may be used herein for easy understanding of one element or feature and another element(s) or feature(s) as illustrated in the drawings. These spatially relative terms are intended for ease of comprehension of the present invention according to various process states or usage states of the present invention, and, thus, the present invention is not limited thereto. For example, when an element or feature in the drawings is turned over, the element or feature described as “beneath” or “below” may be changed into “above” or “upper.” Thus, the term “below” may encompass the term “above” or “below.”

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the inventive concept pertains. It is also to be understood that terms defined in commonly used dictionaries should be interpreted as having meanings consistent with the meanings in the context of the related art, and are expressly defined herein unless they are interpreted in an ideal or overly formal sense.

FIGS.1A and1Bare a perspective view and a cross-sectional view, respectively, illustrating a secondary battery100according to an embodiment of the present disclosure.

As illustrated inFIGS.1A and1B, the secondary battery100according to an embodiment of the present disclosure may include: a cylindrical can, or case,110; a cylindrical electrode assembly120; and a current interrupt device130. In one or more embodiments, the current interrupt device130may include a cap assembly, or may be referred to as a cap assembly.

In an embodiment, the cylindrical can110may include a bottom portion111having an approximately circular shape and a side wall112extending upward by a certain length from the bottom portion111. During a manufacturing process of the secondary battery, an upper portion of the cylindrical can110is open. Thus, during the manufacturing process of the secondary battery, the electrode assembly120may be integrated in the form of a single structure and may be inserted into the cylindrical can110. In an embodiment, subsequently, an electrolyte may optionally be additionally injected into the cylindrical can110.

The cylindrical can110may be made of steel, a steel alloy, nickel-plated steel, a nickel-plated steel alloy, aluminum, an aluminum alloy, or an equivalent thereof, but the material thereof is not limited thereto. Further, to prevent or substantially prevent the current interrupt device130from being separated to the outside, the cylindrical can110may include: a beading part113recessed inward below the current interrupt device130; and a crimping part114bent inward above the current interrupt device130.

The electrode assembly120may be accommodated in the cylindrical can110. The electrode assembly120may include: a negative electrode plate121coated with a negative electrode active material (e.g., graphite, carbon, etc.); a positive electrode plate122coated with a positive electrode active material (e.g., a transition metal oxide, such as LiCoO2, LiNiO2, LiMn2O4, etc.); and a separator123which is positioned between the negative electrode plate121and the positive electrode plate122, and prevents or substantially prevents a short circuit and, in an embodiment, allows only lithium ions to move. The negative electrode plate121, the positive electrode plate122, and the separator123may be wound in an approximately cylindrical shape. In an embodiment, the negative electrode plate121may be copper (Cu) foil, the positive electrode plate122may be aluminum (Al) foil, and the separator123may be polyethylene (PE) or polypropylene (PP), but the materials are not limited thereto according to the present invention. In an embodiment, a negative electrode tab124protruding and extending a certain length downward may be welded to the negative electrode plate121, and a positive electrode tab125protruding and extending a certain length upward may be welded to the positive electrode plate122, or vice versa. In an embodiment, the negative electrode tab124may be copper (Cu) or nickel (Ni), and the positive electrode tab125may be aluminum (Al), but the materials are not limited thereto according to the present invention.

In an embodiment, the negative electrode tab124of the electrode assembly120may be welded to the bottom portion111of the cylindrical can110. Thus, the cylindrical can110may operate as a negative electrode. However, in an embodiment, the positive electrode tab125may be welded to the bottom portion111of the cylindrical can110, and, in this case, the cylindrical can110may operate as a positive electrode.

Further, a first insulating plate126, which is coupled to the cylindrical can110and has a first hole126aformed at a center thereof and a second hole126bformed outside of the center, may be interposed between the electrode assembly120and the bottom portion111. The first insulating plate126prevents or substantially prevents the electrode assembly120from coming into electrical contact with the bottom portion111of the cylindrical can110. In particular, the first insulating plate126prevents or substantially prevents the positive electrode plate122of the electrode assembly120from coming into electrical contact with the bottom portion111. Here, when a large amount of gas is produced due to abnormalities of the secondary battery100, the first hole126aallows the gas to rapidly move upward through a center pin140. Also, the second hole126bserves to allow the negative electrode tab124to pass therethrough and be welded to the bottom portion111.

In an embodiment, a second insulating plate127, which is coupled to the cylindrical can110and has a first hole127aformed at a center thereof and a plurality of second holes127bformed outside of the center, may be interposed between the electrode assembly120and the current interrupt device130. The second insulating plate127prevents or substantially prevents the electrode assembly120from coming into electrical contact with the current interrupt device130. In particular, the second insulating plate127prevents or substantially prevents the negative electrode plate121of the electrode assembly120from coming into electrical contact with the current interrupt device130. In some examples, when a large amount of gas is produced due to abnormalities of the secondary battery100, the first hole127aallows the gas to rapidly move to the current interrupt device130. Also, a second hole127ballows the positive electrode tab125to pass therethrough and be welded to the current interrupt device130, and the other second holes127ballow an electrolyte to rapidly flow into the electrode assembly120during an electrolyte injection process.

In an embodiment, the first holes126aand127aof the respective first and second insulating plates126and127are formed to have diameters smaller than that of the center pin140, and, thus, the center pin140is prevented or substantially prevented from coming into electrical contact with the bottom portion111of the cylindrical can110or the current interrupt device130due to external impact.

In an embodiment, the center pin140, which may be optionally provided, has a hollow circular pipe shape and may be coupled to an approximately central region of the electrode assembly120. In an embodiment, the center pin140may be made of steel, stainless steel, aluminum, an aluminum alloy, or polybutylene terephthalate, but a material thereof is not limited thereto. The center pin140may suppress deformation of the electrode assembly120during charging and discharging of a battery and also serves as a movement path for the gas generated inside the secondary battery100.

In an embodiment, the current interrupt device130seals an opening of the can110to protect the electrode assembly120from an external environment, and interrupts the flow of current when a charging and discharging current is higher than a reference value. In some examples, the current interrupt device130may serve as a positive electrode terminal.

In an embodiment, the current interrupt device130may include a cap-down131, a safety vent132, and an insulating gasket133.

The cap-down131may be electrically connected to the electrode assembly120via the positive electrode tab125. In one or more embodiments, the cap-down131may include: an approximately flat first flat portion1311; a second flat portion1312which extends from the first flat portion1311and has a thickness greater than that of the first flat portion1311; and a third flat portion1313which is bent upward from the second flat portion1312and then extends. In one or more embodiments, the first flat portion1311may include a vent groove13111which is formed on a lower surface of the first flat portion1311to a certain depth. In one or more embodiments, an upper surface of the first flat portion1311may be ultrasonic and/or laser welded to the safety vent132. In one or more embodiments, a lower surface of the second flat portion1312may be ultrasonic and/or laser welded to the positive electrode tab125. In one or more embodiments, the second flat portion1312may include a plurality of through-holes13121. The through-holes13121allow internal pressure or internal gas to be rapidly delivered to the safety vent132when the internal pressure of the secondary battery100rises. In an embodiment, the cap-down131may be made of aluminum or an aluminum alloy.

The safety vent132may be positioned above the cap-down131. In one or more embodiments, the safety vent132may include: an approximately flat first flat portion1321; an approximately flat second flat portion1322which is bent upward from the first flat portion1321and then extends; an approximately flat third flat portion1323which is bent upward from the second flat portion1322and then extends; and a fourth flat portion1324which is bent approximately 180 degrees from the third flat portion1323and extends. In one or more embodiments, the thickness of the first flat portion1321may be greater than the thicknesses of the second, third, and fourth flat portions1322,1323, and1324, and a lower surface of the first flat portion1321may be ultrasonic and/or laser welded to the cap-down131. In one or more embodiments, the second flat portion1322may further include a vent groove13221which is formed on an upper surface of the second flat portion1322to a certain depth.

Accordingly, when an internal pressure of the secondary battery100becomes greater than a reference pressure, the vent groove13111of the cap-down131and the vent groove13221of the safety vent132are ruptured, and the internal pressure or internal gas can be discharged to the outside. Thus, safety of the secondary battery100can be ensured or improved.

In one or more embodiments, a lower surface of the fourth flat portion1324may be in close contact with an upper surface of the third flat portion1323. In an embodiment, the safety vent132may be made of aluminum or an aluminum alloy. In one or more embodiments, the second and third flat portions1322and1323of the safety vent132may be spaced apart from the second and third flat portions1312and1313of the cap-down131.

The insulating gasket133is interposed between the cap-down131and the safety vent132and may cover outer circumferences of the cap-down131and the safety vent132. In one or more embodiments, the insulating gasket133may include an interposer, or interposing portion,1331, an upward extension portion1332, an upper horizontal portion1333, and a downward extension portion1334.

The interposer1331may be interposed between an upper surface of the cap-down131and a lower surface of the safety vent132. In one or more embodiments, the interposer1331may be interposed between the third flat portion1313of the cap-down131and the third flat portion1323of the safety vent132.

The upward extension portion1332may extend from the interposer1331and cover the outer circumference of the safety vent132. In one or more embodiments, the upward extension portion1332may cover outer circumferences of the third flat portion1323and the fourth flat portion1324of the safety vent132.

The upper horizontal portion1333may extend from the upward extension portion1332and cover an upper surface of the safety vent132. In one or more embodiments, the upper horizontal portion1333may cover the fourth flat portion1324of the safety vent132. In one or more embodiments, the upward extension portion1332and the upper horizontal portion1333may be in close contact with the crimping part114of the can110and supported thereby.

The lower extension portion1334may extend from the interposer1331and cover an outer circumference of the cap-down131. In one or more embodiments, the width of the downward extension portion1334may be equal or similar to a thickness of the interposer1331. In one or more embodiments, the downward extension portion1334may be in close contact with the beading part113of the can110and supported thereby.

In an embodiment, the interposer1331, the upward extension portion1332, the upper horizontal portion1333, and the downward extension portion1334, all of which constitute the insulating gasket133, may be provided by injection molding polymer resin. In an embodiment, the interposer1331, the upward extension portion1332, the upper horizontal portion1333, and the downward extension portion1334may be integrated into a single body.

In one or more embodiments, the insulating gasket133may include polyethylene which is injection-molded and then naturally cross-linked at a room temperature (about 1° C. to about 35° C.). In one or more embodiments, the thickness of the insulating gasket133may not be changed before/after the crosslinking, and a heat deflection temperature or heat distortion temperature (HDT) may be about 400° C. to about 600° C. Substantially, the insulating gasket133according to one or more embodiments of the present disclosure is not thermally deformed within a temperature range from about 400° C. to about 600° C.

In an example, when a polyethylene insulating gasket sheet is injection-molded and then naturally cross-linked at a room temperature, a change in thickness (unit: mm) before/after the crosslinking is examined as in Table 1 below. Here, each of 1 to 10 in the vertical axis represents a sample number, and each of 1 to 4 in the horizontal axis represents a number of test.

TABLE 11234After 10After 10After 10After 10BeforedaysBeforedaysBeforedaysBeforedays10.4390.4350.4390.4330.4400.4330.4360.43420.4370.4340.4400.4350.4400.4350.4380.43530.4360.4350.4410.4340.4360.4330.4360.43440.4360.4340.4390.4320.4360.4340.4380.43250.4360.4350.4390.4350.4370.4320.4370.43460.4370.4360.4390.4330.4370.4340.4370.43570.4410.4360.4400.4340.4390.4320.4380.43480.4360.4370.4390.4330.4390.4330.4360.43590.4370.4380.4400.4320.4390.4350.4390.434100.4360.4360.4420.4330.4390.4340.4370.436AVG0.4370.4360.4400.4330.4380.4340.4370.434MIN0.4360.4340.4390.4320.4360.4320.4360.432MAX0.4410.4380.4420.4350.4400.4350.4390.436STDEV0.0020.0010.0010.0010.0020.0010.0010.001Difference0.0010.0060.0050.003between beforeand after

As shown in Table 1, a change in thickness of a polyethylene insulating gasket sheet before/after (10 days) crosslinking is about 0.001 mm to 0.006 mm, and thus it can be seen that there is almost no change in thickness. Also, when a polyethylene insulating gasket is cut from an injection-molded sheet (a slitting process), there is almost no change in shape due to the slitting.

In addition, results of the heat resistance test for the polyethylene insulating gasket sheet are shown in Table 2 below. Here, #1 (Sep. 18, 2020) and #2 (Sep. 21, 2020) represent test start dates, and 1 to 10 represent sample numbers. Also, the polyethylene insulating gasket sheet had been placed on a hot plate of 470° C. under a test condition such as for 90 seconds. Subsequently, the gasket sheet was brought out from the hot plate, and a change in thickness (unit: mm) was measured.

TABLE 2#1#2Product numberBeforeAfterBeforeAfter13.483.383.473.3823.463.363.483.3933.473.373.463.3643.463.353.473.3853.463.343.473.3963.473.383.473.3673.483.373.483.3583.483.373.463.3893.473.373.483.39103.473.363.473.38AVG3.473.373.473.38MIN3.463.343.463.35MAX3.483.383.483.39STDEV0.010.010.010.01Difference in AVGs−0.11−0.10of thicknessesbetween before andafter

As shown in Table 2, regarding the polyethylene insulating gasket sheet manufactured through the natural crosslinking process according to the present disclosure, it can be seen that the thickness thereof is reduced in an amount of about 0.1 mm to about 0.11 mm at about 470° C. That is, it can be seen that the naturally cross-linked polyethylene insulating gasket according to the present disclosure has a very small thermal strain rate at high temperature. Thus, when the naturally cross-linked polyethylene insulating gasket is used as a component of the current interrupt device in the secondary battery, it is possible to prevent or substantially prevent a direct short circuit between the can and the safety vent because the component is not melted at high temperature. Also, the naturally cross-linked polyethylene insulating gasket is not contracted in the inward direction and/or in the outward direction, and, thus, sealing strength of the secondary battery is not deteriorated. For reference, according to the related art, polyethylene is thermally deformed at about 200° C., and, thus, a can was directly electrically short-circuited with a safety vent. Also, a gasket was contracted over time, and, thus, sealing strength of a secondary battery was deteriorated.

Also, an electron beam crosslinking process may also be utilized in addition to the natural crosslinking process. In some examples, only the electron-beam crosslinking process may be utilized instead of the natural crosslinking process.

FIG.2is an enlarged cross-sectional view illustrating a current interrupt device130A of a secondary battery according to an embodiment of the present disclosure. In an example illustrated inFIG.2, the current interrupt device130A according to an embodiment of the present disclosure may further include: an upper tar-coated layer134interposed between an upper surface of an interposer1331and a lower surface of a safety vent132; and a lower tar-coated layer135interposed between a lower surface of the interposer1331and an upper surface of a cap-down131.

In one or more embodiments, the upper tar-coated layer134may be interposed between the upper surface of the interposer1331and a third flat portion1323of the safety vent132. In one or more embodiments, the lower tar-coated layer135may be interposed between the lower surface of the interposer1331and a third flat portion1313of the cap-down131.

In one or more embodiments, the upper tar-coated layer134and/or the lower tar-coated layer135can prevent or substantially prevent not only contraction of an insulating gasket133but corrosion of the safety vent132and/or the cap-down131. Thus, a sealing strength of the secondary battery may be further enhanced by the upper tar-coated layer134and/or the lower tar-coated layer135. In one or more embodiments, an acryl-based adhesive and/or a rubber-based adhesive may be further provided on the surfaces of the tar-coated layers134and135, and, thus, the sealing strength of the secondary battery may be even further enhanced.

FIG.3is an enlarged cross-sectional view illustrating a current interrupt device1306of a secondary battery according to an embodiment of the present disclosure. As illustrated inFIG.3, in the current interrupt device130B according to an embodiment of the present disclosure, an interposer1331may be in close contact with an entire lower surface of a third flat portion1323of a safety vent132and may be in close contact with an entire upper surface of a third flat portion1313of a cap-down131. In one or more embodiments, a width of a downward extension portion1334of an insulating gasket133may be greater than a thickness of the interposer1331.

Accordingly, in the current interrupt device130B according to an embodiment of the present disclosure, an insulating function between the cap-down131and the safety vent132and an insulating function between a can110and the cap-down131may be enhanced due to the relatively wider interposer1331and downward extension portion1334, and component deformation rates may also be lowered.

Embodiments of the present disclosure may provide a secondary battery capable of: preventing or substantially preventing leakage of an electrolyte while simplifying the structure of the current interrupt device; preventing or substantially preventing deformation of the current interrupt device; and preventing or substantially preventing a short circuit between the can and the current interrupt device due to a high heat deflection temperature.

While one or more embodiments have described herein for achieving a secondary battery according to the present invention, the present invention is not limited thereto, and the technical scope and spirit of the present invention include all ranges of technologies that may be variously modified by those of ordinary skill in the art, to which the present invention pertains, without departing from the subject matter of the present invention as set forth in the following claims.