WO 2023/146069
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`PCT/KR2022/01 7044
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`SECONDARY BATTERY
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`TECHNICAL FIELD
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`[o001] An embodiment of the present inverition relates fo a secondary battery.
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`BACKGROUND ART
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`
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`{[G003] A secondary battery may be constructed by incorporating a stacked or wound
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`electrode assembly and an electrolyte in a case with a separator interposed between
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`@ positive electrode plate and a negative electrode plate, and installing @ cap piate in
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`the case. In the electrode assembly, an uncoated portion tab may protrude in a lateral
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`or upward direction, and a current collecting structure may be connected to the
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`uncoated portion tab. Some sections of a welded portion of the current collecting
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`structure are sections where heat is generated, and, in order to solve this, the material
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`of the corresponding portion is designed to be thick. This leads to a decrease in the
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`capacity of the electrode assembly, and itis necessary to develop a structure to secure
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`cell competitiveness.
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`PCT/KR20 22/03 7044
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`foco4] The above information disclosed in this Background section is only for
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`enhancement of understanding of the background of the invention and therefore it may
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`contain information that does not constitute prior art.
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`DESCRIPTION OF EMBODIMENTS
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`TECHNICAL PROBLEM
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`jo005] An embodiment of the present invention provides a secondary battery that can
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`reduce heal generated by a current collector.
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`SOLUTION TO PROBLEM
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`jo006] A secondary battery according to an embodiment of the present invention may
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`include: a case that has one side open to form an opening; an electrode assembly that
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`includes a first electrode plate accommodated in the case and having a first electrode
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`substrate tab disposed on one side of the case in the longitudinal direction, a second
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`electrode plate having a secand electrode substrate tab disposed on the other side in
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`ine longitudinal direction of the case, and a separator interposed between the first
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`electrode plate and the second electrode plate, and is wound or stacked: and @ cap
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`assembly including a cap plate coupled to the opening of the case, a first current
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`collecting part arid a second current collecting part respectively including a first current
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`collector and a second current collecior disposed in paraile!l with the upper end of the
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`lengthwise cirection of the electrode assembly and respectively electrically connected
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`to the first electrode substrate tab and the second electrode substrate tab, a first
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`terminal part and a second terminal part respectively electrically connected to the first
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`current collecting part anc the second current collecting part, and a plurality of
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`insulation members coupied to at least one of the cap plate, the first current collector
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`and the second current collector, and the first terminal part and the second termina!
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`part, wherein the first current collecting part further comprises a sub-plate that
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`electrically connects the first current collector and the first substrate tab, the second
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`current collecting part further comprises a sub-plate that electrically connects the
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`second current collector and the second substrate tab, and at isast one of the sub-
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`plates of the first current collecting part and the second current collecting part is
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`partially or wholly made of a material having lower resisiarice than the first current
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`collector or the second current collector.
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`{O007] The first current collecting part may further
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`include a connection plate
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`electrically connected to the first current collector and having one end bent in a
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`direction of the first substrate tab, and the sub-plate may be electrically connected to
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`the connection plaie and the first substrate tab, and ine second current collecting part
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`may further include a connection plate electrically connected to the second current
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`collector and having one end bent in a direction of the second substrate tab, and the
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`sub-piate may be electrically cannected to the cornection plate and the second
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`subsirate tab.
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`{o008] The sub-plate of the first current collecting part may include a first connection
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`part electrically cornmected to the connection plate and a second connection part
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`electrically connected to the first substrate tab, anc the sub-plate of ihe second current
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`collecting part may include a first corinection part elecirically cormnected to the
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`connection plate and a second connection part electrically connected to the second
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`substrate tab.
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`[e009] One end of the connection plate and the first connection part of the sub-plate
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`may be welded to each other, the second connection part and the first substrate tab
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`of the first current collecting part may be weided to eacn other, and the second
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`connection part and the second substrate tab of ine second current collecting part may
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`be weided to each other.
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`([o010] A heat generation preventing part may be provided between a welding spot of
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`the first connection part and a first welding spat of the second connection part adjacent
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`to the first connection part.
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`[0041] The heat generation preventing part may be plated with a material having lower
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`resistance than the first current collector or ihe second current collector or may be a
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`clad metal.
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`{6012] A weiced portion of the connection plate and the sub-plate may be cisposed
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`closer to the bottom surface of the case than to the top of the electrode assambly.
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`[O0F3] in the sub-plate, the second connection part may be bent toward the electrode
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`assembly from the first coninection part, and the bent partion may be disposed closer
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`to the bottom surface of the case than the upper end of the electrode assembly.
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`(6074) In the second connection part, a plate surface facing the electrode assembly
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`may be disposed on the sare plane as a plate surface of the connection plate facing
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`ine electrode assembly.
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`{O075] In the second connection part, a plate surface facing the electrode assembly
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`may be disposed closer to the electrode assembly than a plate surface of the
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`connection plate facing the electrode assembly.
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`[6018] The second connection part may have a weiding groove concavely formed on
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`the plate surface facing the case.
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`[0047] A thickness of the first current collector or the second current collector may be
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`greater than that of the connection plate and the sub-plate.
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`fo048] The thickness of ithe first current collector or the second current collector may
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`be 4 to 5 times the thickness of the connection plate and the sub-plate.
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`{O079] In addition, in an embodiment of the present invention is provided a secondary
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`batiery comprising: an electrode assembly; a case accommodating the electrode
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`assembly, and a cap assembly coupled to the case and including a first current
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`collector anc’ a second current collector electrically connected to the electrode
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`assembly and disposed parallel to the upper end of the electrode assembly, wherein
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`the cap assembly further comprises @ pair of sub-plates electrically connecting the first
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`current collector and the second current collector to the electrode assembly,
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`respectively, and at leasi one of the sub-plates is made of a material having lower
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`resistance than the first current collector or the second current collector.
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`foG20] The cap assembly may include: a cap plate coupled to the case) a first current
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`collecting part having the sub-plate electrically connected to 4 first substrate tab
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`provided on the first electrode plate of the electrode assembiy, and a connection plate
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`electrically connected to the first current collector and the sub-plate: a second currant
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`collecting part having the sub-plate electrically connected fo a second substrate tab
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`provided on the second electrode plate of the electrode assermbiy, and a connection
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`plate electrically connected io the second current collector and the sub-plate; a first
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`terminal part having a first terminal pin coupled to and electrically connected to the
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`first current collector and a2 first terminal plate coupled to and electrically connected to
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`ine first terminal pin, a second terminal part having @ second terminal pin coupled to
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`anc electrically commected to the second current collector, a second terminal plate
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`coupled fo and electrically comnected to the second terminal pin, and a conductive
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`plate: and an insulation member mace of an insulating material provided between the
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`cap plate and the first current collector, between the frst current collector and the
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`electrode assembly, between the second current collector and the electrode assembly,
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`between the first terminal pin and the second terminal pin and the cap plate.
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`fog21] The connection plate may have one end disposed paraliel to the first current
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`collector or the second current collector and the other end bent toward the electrode
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`assembly, and the sub-piate may be weided to the bent end.
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`[6022] The sub-plate may include a first connection part welded to the connection plate,
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`and a second connection part bent toward the electrode assembly from the first
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`connection part and electrically connected to the electrode assembly.
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`fo023] A heat generation preventing part may be provided between a welding spot of
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`the first connection pari and a first welding spot of the second connection pari adjacent
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`to the first connection part.
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`fo024] The heat generation preventing part may be plated with a material having lower
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`resistance than the first curreni collector or the second current collector or may be a
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`clad metal.
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`ADVANTAGEOUS EFFECTS OF INVENTION
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`[0028] According to an embodiment of ihe present invention,
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`&@ material having iow
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`resistance is added fo the current coliection area where heat aeaneration is the greatest
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`to flower ihe resistance, thereby allowing generation of heat fo ba reduced.
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`BRIEF DESCRIPTION OF DRAWINGS
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`[0026] FIG.
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`1
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`is a perspective view illustrating a secondary battery according to an
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`embodiment of the present invention.
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`[0027] FIG. 2 is an exploded perspective view illustrating @ cap assembly of the
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`secondary battery according to FIG. 4.
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`{0028] FIG. 3 is a cross-sectional view of the secondary battery according to FIG. 1.
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`[0028] FIG. 4 is an enlarged cross-sectional view Hlustrating major parts of FIG. 3.
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`BEST MODE
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`[0030] Examples of ihe present invention are provided to more completely explain the
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`present invention to those skilled in the ari, and the faliowing examples may be
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`modiied in various other forms. The present invention, however, may be embodied in
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`many different forms and should not be construed as being limited to the example (or
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`exemplary) embodiments set forth herein. Rather, these example embodiments are
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`provided so that this invention will be thorough and complete and will convey the
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`aspects and features of the present invention to those skilled in the ari.
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`fOG31] In addition,
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`in the accompanying drawings, sizes or thicknesses of various
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`components are exaggerated for brevity and clarity, and like numbers refer to like
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`elements throughout As used herein,
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`the term “and/or” includes any and all
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`combinations of one or more of the associated listed items.
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`In addition, # will be
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`understood that when an element A is referred to as being "connected to" an element
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`B, the element A can be directly connecied to the element B or an intervening clement
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`C may be present therebetween such that the element A and the element B are
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`indirectly connected to each other.
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`f0032] The terminology used herein is for the purpose of describing particular
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`embodiments only and is not intended to be limiting of the invention. As used herein,
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`the singular forms are intended to include the plural forms as well, unless the context
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`clearly indicates otherwise.
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`it will be further understood that the terms that the terms
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`“comprise or inciude’ and/or “comprising or including,” when used in this specification,
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`specify the presence of stated features, numbers, steps, operations, elements, and/or
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`components, but do not preclude the presence or addition of one or more other
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`features, numbers, steps, operations, elernents, cormponents, and/or groups thereof.
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`[6033] it will be understood that, although the terms first, second, etc. may be used
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`herein to describe various members, clernents, regions, layers and/or sections, these
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`members, slerenis, regions, layers and/or sections should not be limited by these
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`terms. These terms are only used to distinguish one member, slement, region, layer
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`and/or section from another. Thus, for example, a first member, a first element, a first
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`region, a first layer and/or a first section discussed below could be termed a second
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`member, a second element, a second region, a second layer and/or a second section
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`without departing fram the teachings of the present invention.
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`[6034] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,”
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`and the like, may be used herein for ease of description toa describe one element or
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`feature's relationship to another element(s) or feature(s) as llustrated in the figures. it
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`wil be understood that the spatially relative terms are intended to encompass different
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`orientations of the device in use or operation in addition to the oriertation depicted in
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`the figures. For exampie,
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`if the element or feature in the figures is turned over,
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`elements described as “below” or “beneath” other slements or features would then be
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`oriented “on” or “above” the other elements or features. Thus, the exernplary term
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`“below” can encompass both an orientation of above and below.
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`[00345] Hereinafter, a secondary battery according to an embodiment of the present
`
`invention will be described in detail with reference to the accompanying drawings (for
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`convenience, on the basis of FIGS.
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`1 and 3, the following description will be given by
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`defining the upper part as ihe upper direction and the lower part as the lower direction).
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`([0036] FIG.
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`1
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`is @ perspective viewillustrating a secondary battery according to an
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`embodiment of the present
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`invention. FIG. 2 is an exploded perspective view
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`ilustrating a cap assembly of the secondary battery according to FIG. 1. FIG. 2is a
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`cross-sectional view of ihe secondary battery accarding to FG. 1. FIG. 4 is an
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`eriarged cross-sectional view illustrating maior parts of FIG. 3.
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`{[0037] As shown in FIGS.
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`1 and 2,
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`the secondary battery 10 according to an
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`embodiment of the present invention may include an electrode assembly 100, a case
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`2060 accommodating the electrode assembly 100, arid a cap assembly 300 coupled to
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`the case 200.
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`[6038] As shown in FIG. 2, the electrode assembly 100 may be provided by winding a
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`unit stack composed of a first electrode plate 110 and a second electrode plate 120 in
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`the form of @ thin plate or film, ancl a separator 130 infersosed therebetween, or
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`stacking @ plurality of stack units. Vvhen the electrode assembly 100 is forrned by
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`winding, the winding shafi may be disposed in a horizontal direction substantially
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`parallel to the longitudinal direction of the cap assembly 300 or in a vertical direction
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`substantially perpendicular to the longitudinal direction of the cap assembly S00. Wher
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`ine electrode assembly 100 is formed by stacking, the long sides of the plurality of unit
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`stacks may be disposed adiacent to each other.
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`foc3s] As an example, the first electrode plate 110 may serve as a negative electrode,
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`and the second electrode plaie may serve as a positive electrode, or vice versa.
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`[6040] VWWhen the first electrode plate 110 is a negative electrode plate,
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`the first
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`electrode plate 110 may be formed by applying a first electrode active material, such
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`as graphite ar carbon, to a first electrode current collector provided with a metal foil,
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`such as copper, a copper alloy, nickel, or a nickel alloy. A first substrate tab (or a first
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`uncoated portion), which is an area to which the first electrode active material is not
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`applied, may be formed on the first electrode plate 110. After a plurality of first
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`substrate tabs 112 are gathered and tack-welded, the tack-weided first substrate tabs
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`112 and the cap assembly 200 may be electrically connected. That
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`is,
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`the first
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`substrate tab 112 may serve as a passage for current flow between the first electrode
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`plate 110 and the first terminal part 350 of the cap assembly 300.
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`[0047] VW/hen the second electrode plate 120 is a positive electrode plate, the second
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`electrode plate 120 may be formed by applying a second electrode active material,
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`such as a transition metal oxide, to a second electrode current collector provided with
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`a metal foil, such as aluminum or an aluminum alloy. A second substrate tab (or a
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`second uncoated portion), which is an area to which the second electrode active
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`material is not aoplied, may be formed on the second electrode plate 120. After a
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`plurality of second substrate tabs 122 are gathered and tack-welded, the tack-welded
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`second substrate taos 122 and the cap assembly 300 may be slectricaily connected.
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`That is, the second substrate tab 122 may be a passage for current flaw between the
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`second electrode plate 120 and the second terminal part 360 of the cap assembly 300.
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`[6042] in some examples, the first substrate tab 112 and the second substrate tab 122
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`may be formed by cutting one side of each of the first electrode plaie 110 and the
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`second electrode plate 120, respectively, when manufacturing the first electrode
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`plate 110 and ihe second electrode plate 120. That is, the first substrate tab 112 may
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`be integrally formed with the first electrode plate 110, and the second substrate tab
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`122 may be integrally formed with the second electrode plate 120. The first substrate
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`tab 112 may be disposed in one cirection of the electrade assembly 100, and the
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`second substrate tab 122 may be disposed in the other direction of the electrode
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`assembly 100. For example, as shown in FG. 2, the first substrate tab 112 may be
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`disposed toward the left short side of the case 200, and the second substrate tab 122
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`may be disposed toward the right short side of the case 200.
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`fo043] The separator 130 is disposed between the first electrode plate 110 and the
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`second electrode plate 120 to prevent a short circuit and enable the movement of
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`ithium)
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`ions. As an example,
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`the separator 130 may include polyethylene,
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`polypropylene, or a composite film of polyethylene and polypropylene.
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`in some
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`examples, the separator 130 may be replaced with an inorganic solid electrolyte such
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`as @ sulfide, oxide, or phosphate compound that does not require a liquid or ge!
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`electrolyte.
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`fo044] The electrode assembly 100 may be accommodated in the case 200 together
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`with an electrolyte.
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`in sore examples, the electrolyte may include a lithium salt such
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`as LIPFG or LIBF4 in an organic solvent such as ethylene carbonate (EC), propylene
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`carbonate (PC), diethyl carbonate (DEC), ethyimethyl carbonate (EMC), or dimethy!
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`carbonate (DMC). In addition, the sleciroiyte may be in a4 liquid or gel state. In some
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`examples, when an inerganic-based solid electrolyte is used, the electrolyte may be
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`omitted.
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`foo45] As shown in FIGS. 7 and 3, the case 200 may have a substantially rectangular
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`parallelepiped box shape, anc may nave an open upper portion in @ longitudinal
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`direction and an accommodation space formed therein. The electrode assembly 100
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`and the electrolyte may be accommodated in the case 200 through the open upper
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`portion. Sorne components of the cap assembly 300 may be exposed to the outside
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`of the case 200, and some components may be accommodated inside the case 200.
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`The case 200 may have a rectangular bottom surface 210 and four side surfaces
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`connected to the bottom surface 210. Among the side surfaces, sides having a
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`relatively large area are defined as long side portions 220, and sides having a relatively
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`small area are defineci as short side portions 230. As an example,
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`the electrode
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`assembly 100 may be disposed so that a plate surface faces the long side portions
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`220. in a state in which the electrode assembly 100 is accommodated in the case 200,
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`the cap assembly 300 is coupled to the case 200 and electrically comnected to the
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`electrode assermbly 100.
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`In this case, an insulating film 240 for insulation framthe
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`current collector may be coupled or attached to the short side portions 230 of the case
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`200.
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`[0046] As shown in FIGS.
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`1 to 4, the cap assembly 300 may include a cap plate 310
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`coupied to the case 200, a plurality of insulation members, 4 first current collecting
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`part 330 and a second current collecting part 340, and a first terminal part 350 and a
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`second terminal part 360.
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`[0047] As shown in FIG. 2, the cap plate 310 has a substantially rectangular plate
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`shape. The cap plate S10 may be formed of ine same material as the case 200. As an
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`example, ihe cap plaie 310 may have @ size corresponding to an inner size of the
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`opening of the case 200. in addition, as an example, the cap plate 310 may be coupied
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`to the case 200 by laser welding, etc. In the cap plate 310, terminal holes 312 for being
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`coupled with the first ferrninal part S50 and the second terminal part 360, grooves,
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`injection holes, a vent hole 3714 for being coupied with a vent 316, etc. may be formed.
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`VVinen the internal pressure of the secondary battery 10 rises, the vent 316 is broken
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`to function fo discharge gas, and a general vent structure can be applied thereto.
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`[9048] The insulation members include an insulation plate 322, a pair of
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`lower
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`insulation paris 324, a pair of pin insulation paris 326, and an upper insulation part
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`328. The insulation members are all made of an insulating material and can be
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`manufactured by, for example, an injection method.
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`[6049] The insulation plate 322 has a substantially rectangular plate shape. The
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`insulation plate S22 is in close contact with the lower surface of the cap plate 310 to
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`insulate the cap plate 310 and the electrode assembly 100 from each other. in addition,
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`the insulation plate 222 serves to insulate a current collecting structure to be described
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`later and the cap plate 310 from each other. Therefore, the insulation plate 322 may
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`have @ side surface extending downward along an edge. The side surface may be
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`shaped to connect the entire edge of the insulation plate 322 or may be formed only
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`in part. The shape of the plate surface or side surface of the insulation plate S22 may
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`vary according to the shape of a component requiring insulation. Through-holes 322a
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`located to correspond to ihe terminal holes 312 and the vent holes 314 of the cap plate
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`310 may be formed in the insulation plate 322 . A part of the current caliector and the
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`lower insulation parts S24 may be disposed under the insulation plate S22.
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`fogS0] The lower insulation parts 324 are provided for insulating some componenis of
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`the current collector and have a@ substantially rectangular plate shape. The lower
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`insulation paris 324 may be provided as 4 pair and disposed on the first terminal part
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`350 and the second terminal part 360, respectively.
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`In addition, the lower insulation
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`parts 324 are disposed under the current collectors 332 and 342 to be described later,
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`and may be sized to cover the current collectors 332 and 342. The lower insulation
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`parts 324 may be combined with the insulation piate 222 in a state in which the current
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`collectors 332 and 342 are assembled.
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`fo0S1] The pin insulation parts 326 are provided for insulating the terminal pins 352
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`and 362 of the first terminal part 350 and the second terminal part 360 from ithe cap
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`plate 310, which will be described later, arid have a substantially cylindrical shape.
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`The upper insulation part 3238 includes a flange 326a extending outward fram an upper
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`end of the outer circumferential surface. The flange 226a is in cortact with a lower
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`portion of one side of each of the terminal pins 352 and 362, and the lower end of the
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`upper insulation part 328 is inserted into the through hole 322a of the insulation plate
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`322.
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`fogs2] The upper insulation part 32d is a component applied only to the first terminal
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`part 350 and is disposed between the first terminal plate 354 and the cap plate 310,
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`which will be described later. The upper insulation part 328 may have a rectangular
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`plate shape substantially corresponding to the shape of the first terminal plate 354.
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`The upper insulation part 328 is formed to be larger than the Tirst terminal plate 354
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`and has a groove in which the first terminal plate 354 is seated. On the upper insulation
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`part 328, a nole is formed through at a pasition corresponding to the terminal hale 3712
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`of ihe cap plate 310. The flange 352a of the first terminal pin 352 is disposed in the
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`formed-through hole.
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`[0053] As shown in FIGS. 2 to 4,
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`the first current collecting part 330 serves to
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`electrically connect the first electrode plate 110, which is a negalive electrode plate,
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`and the first terminal part 350. The first current collecting part 330 may include a first
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`current collector 332 electrically connected to the first terminal part 350, a connection
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`plate 334 electrically connected to the first current collector 332, and a sub-piate 336
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`electrically connected to the connection plate S34 and the first substrate tab 172.
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`[0054] The first current collector 332 may be mace of a conductive material having a
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`preset thickness and may have a substantially plate shape. in addition, the first current
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`collector 332 has a plate shape without a bent or bent portion. On the first current
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`collector 332, through-holes 322a are formed through al positions corresponding to
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`the terminal hole 312 of the cap plate 310 and the through-noie 322a of the insulation
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`plate 322. First terminal pins 352 to be described later are inserted into the through-
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`holes 322a. A portion of the upper surface ofthe first current collector 332 ts in contact
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`with the lower surface of the insulation plate 322, and the lower surface is insulated
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`from the electrode assernbiy 100 by the lower insulation parts S24. The connection
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`plate 334 is in contact with one side of the upper surface of the first current collector
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`332. Ta this end, a seating groove 332b may be concavely farmed on ane side of the
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`upper surface of the first current collector 332. Since the seating groove 332b is formed
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`to a depth corresponding to the thickness of the connection plate 334, the upper
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`surface of the connection plate 334 and the upper surface of the first current collector
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`332 may be disposed on the same plane. As an example, the vertical thickness of the
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`first current collector 332 may be 4-5 times the thickness of the connection plate 334
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`and the sub-plate 336.
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`fooss] The connection plate 334 is made of a conductive material having a relatively
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`smaller thickness than the first current collector 332, ancl may have a shape obtained
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`by bending a plate shape substantially in a vertical direction. On the basis of the bent
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`portion of the connection plate 334, the upper sicie is defined as an upper portion, and
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`the downwardly extending portion is defined as a lower partion. The iower surface of
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`the upper portion of the connection plate 334is seated in the seating groove 332b
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`formed on the upper surface of the first current collector $32, and the upper surface of
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`the upper partion is in close contact with the lower surface of the insulation plate 322.
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`The outer surface of tne lower portion of the cannection plate 334 is in contact with
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`one side of the sub-plate 336. When the first current collector 332 is fixed in a state in
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`which the connection plate 334 is seated on the first current collector 332,
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`the
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`connection plate 334 may also be fixed between the insulation plate 322 and the first
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`current collector 332. Accordingly, ihe connection plate 334 may be physically and
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`electrically conmected to the first current collector 332 without separate welding.
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`Alternatively, the connection plate 334 may be connected to the first current collector
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`is
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`WO 2023/146069
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`PCT/KR20 22/03 7044
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`332 by laser welding. Connection between the connection plate 334 and the sub-plate
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`336 may be performed by laser welding, etc. To prevent damage to the insulation plate
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`322 during weiding, the lower end of the connection plate 334 is disposed at a lower
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`position than the upper end of the electrode assembly 100, and the welding portion
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`may also be formed adjacent to the lower end of the connection plate 334 (disposed
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`closer to the bottom surface of the case),
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`[6056] The sub-plate S36 may be made of a conductive material having a
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`predetermined width and length and may have a substantially plate shape. One end
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`(upper end) of the sub-plate 336 may be welded in contact with the lower portion of
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`the connection plate 334. When, of the plate surfaces of the sub-plate 336, the one
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`surface facing the electrode assembly 100 is defined as the inner side, and ithe other
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`surface facing the short side portions 230 of the case 200 is defined as the outer side,
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`the first substrate tab 172 may be connected to the inner side. A portion where the
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`sub-piate 336 is connected to the connection plate 334 may be defined as a4 first
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`connection part $364, and a portion comnected to the first suostraie tab 112 may be
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`defined as a second connection part 33Gb.
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`In the sub-plate 336, the first connection
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`part 336a and the second connection part 336Gb may be bent at a predetermined angle.
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`As an example, an inner side of the second connection part 356b may be bent toward
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`ine electrode assembly 100 fram the first connection part OSGa and positioned on the
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`same plane as the inner side of the connection plate 334. Ahernatively, the inner side
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`of the second connection part 336b may be disposed to be more inward in the
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`electrode assembly 10 than the inner side of the connection plate 334. The inner side
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`of the second connection part 336b may be connected to the first substrate tab 112
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`by welding. Accordingly, the vertical length of the second connection part 323Gb may
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`correspond to or be slightly larger than the vertical length of the first substrate tab 112.
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`WO 2023/146069
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`PCT/KR20 22/03 7044
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`The width of the second connection part 33Gb mayaiso correspond to or slightly larger
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`than the widths of the first substrate tabs 112 welded allogether. in addition, a plurality
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`of concave welding grooves 336c may be formed on the outer surface of the second
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`connection part 336b. On the basis of FIG. 2, a plurality of welding grooves 336c may
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`be formed along the width direction of the second connection part 3365. A welding
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`portion between ihe second connection part 336b and the first substrate tab 112 may
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`be formed on the weiding groove 336c. As an example, when the first current collector
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`332 has a thickness of 3.5 mm, the connection plate 334 and the sub-plate 336 may
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`be formed to have a thickness of 0.8 mm.
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`fo0S87] As described above, the relatively thick first current collector 332 is formed in a
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`straight line, and the thicknesses of the connection plate 334 and the sub-plate 336
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`are reduced, a space for increasing the size of the electrode assembly 100 can be
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`secured.
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`[6058] Meanwhile, as shown in FIGS. 2 to 4, heat generation occurs between a welding
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`spat where the connection plate 334 and ithe sub-plate 336 are welded arid a first
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`welding spot where the sub-plate 356 and the first substrate tab i112 (or second
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`substrate tab) are welded. The corresponding portion is an area where resistance is
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`increased due to welding and shape features (bending), and thus is an area where
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`heat generation inevitably occurs generating heat.
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`[0059] In order to prevent damage due to heat generation, a low-resistance material
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`may be plated on the connection plate 334 and the sub-plate 336. Alternatively, the
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`low-resisiance material may be plated only on the sub-clate 336. in this embodiment,
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`the term “low-resistanice material’ means a material having relatively low resistance
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`compared to the material of the first current collector 332 or the second current
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`collector 342 . Therefore,
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`in this embodiment, all materials having lower resistance
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`17
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