Patent Publication Number: US-2022231345-A1

Title: Battery, and battery pack and vehicle including the same

Description:
RELATED APPLICATION DATA 
     This non-provisional application claims the benefit under 35 U.S.C. § 119(a) to Patent Application No. 10-2021-0007278, filed in the Republic of Korea on Jan. 19, 2021, Patent Application No. 10-2021-0022881, filed in the Republic of Korea on Feb. 19, 2021, Patent Application No. 10-2021-0022891, filed in the Republic of Korea on Feb. 19, 2021, Patent Application No. 10-2021-0022894, filed in the Republic of Korea on Feb. 19, 2021, Patent Application No. 10-2021-0022897, filed in the Republic of Korea on Feb. 19, 2021, Patent Application No. 10-2021-0024424, filed in the Republic of Korea on Feb. 23, 2021, Patent Application No. 10-2021-0030291, filed in the Republic of Korea on Mar. 8, 2021, Patent Application No. 10-2021-0030300, filed in the Republic of Korea on Mar. 8, 2021, Patent Application No. 10-2021-0046798, filed in the Republic of Korea on Apr. 9, 2021, Patent Application No. 10-2021-0058183, filed in the Republic of Korea on May 4, 2021, Patent Application No. 10-2021-0077046, filed in the Republic of Korea on Jun. 14, 2021, Patent Application No. 10-2021-0084326, filed in the Republic of Korea on Jun. 28, 2021, Patent Application No. 10-2021-0131205, filed in the Republic of Korea on Oct. 1, 2021, Patent Application No. 10-2021-0131207, filed in the Republic of Korea on Oct. 1, 2021, Patent Application No. 10-2021-0131208, filed in the Republic of Korea on Oct. 1, 2021, Patent Application No. 10-2021-0131215, filed in the Republic of Korea on Oct. 1, 2021, Patent Application No. 10-2021-0131225, filed in the Republic of Korea on Oct. 1, 2021, Patent Application No. 10-2021-0137001, filed in the Republic of Korea on Oct. 14, 2021, Patent Application No. 10-2021-0137856, filed in the Republic of Korea on Oct. 15, 2021, Patent Application No. 10-2021-0142196, filed in the Republic of Korea on Oct. 22, 2021, Patent Application No. 10-2021-0153472, filed in the Republic of Korea on Nov. 9, 2021, Patent Application No. 10-2021-0160823, filed in the Republic of Korea on Nov. 19, 2021, Patent Application No. 10-2021-0163809, filed in the Republic of Korea on Nov. 24, 2021, Patent Application No. 10-2021-0165866, filed in the Republic of Korea on Nov. 26, 2021, Patent Application No. 10-2021-0172446, filed in the Republic of Korea on Dec. 3, 2021, Patent Application No. 10-2021-0177091, filed in the Republic of Korea on Dec. 10, 2021, Patent Application No. 10-2021-0194572, filed in the Republic of Korea on Dec. 31, 2021, Patent Application No. 10-2021-0194593, filed in the Republic of Korea on Dec. 31, 2021, Patent Application No. 10-2021-0194610, filed in the Republic of Korea on Dec. 31, 2021, Patent Application No. 10-2021-0194611, filed in the Republic of Korea on Dec. 31, 2021, Patent Application No. 10-2021-0194612, filed in the Republic of Korea on Dec. 31, 2021, and Patent Application No. 10-2022-0001802, filed in the Republic of Korea on Jan. 5, 2022, all of which are hereby expressly incorporated by reference in their entireties into the present application. 
     TECHNICAL FIELD 
     The present disclosure relates to a battery, and a battery pack and a vehicle including the battery. More particularly, the present disclosure relates to a cylindrical battery in which both a positive electrode terminal and a negative electrode terminal are adjacently disposed at one side of the cylindrical battery, without greatly deforming the structure of a conventional cylindrical battery, and a battery pack and a vehicle including the cylindrical battery. 
     BACKGROUND ART 
     Secondary batteries that are easily applicable to various product groups and have electrical characteristics such as high energy density are universally applied not only to portable devices but also to electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by an electric drive source. 
     These secondary batteries are attracting attention as a new energy source to improve eco-friendliness and energy efficiency because they have the primary advantage that they can dramatically reduce the use of fossil fuels as well as the secondary advantage that no by-products are generated from the use of energy. 
     Secondary batteries currently widely used in the art include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and the like. A unit secondary battery has an operating voltage of about 2.5V to 4.5V. Therefore, when a higher output voltage is required, a battery pack is configured by connecting a plurality of batteries in series. In addition, a plurality of batteries may be connected in parallel to form a battery pack according to the charge/discharge capacity required for the battery pack. Accordingly, the number of batteries included in the battery pack and the form of electrical connection may be variously set according to the required output voltage and/or charge/discharge capacity. 
     Meanwhile, as a kind of secondary battery, there are known cylindrical, rectangular, and pouch-type batteries. In the case of a cylindrical battery, a separator serving as an insulator is interposed between a positive electrode and a negative electrode, and they are wound to form an electrode assembly in the form of a jelly roll, which is inserted into a battery can together with an electrolyte to configure a battery. In addition, a strip-shaped electrode tab may be connected to an uncoated region of each of the positive electrode and the negative electrode, and the electrode tab electrically connects the electrode assembly and an electrode terminal exposed to the outside. For reference, the positive electrode terminal is a cap of a sealing body that seals the opening of the battery can, and the negative electrode terminal is the battery can. 
     However, according to the conventional cylindrical battery having such a structure, since current is concentrated in the strip-shaped electrode tab coupled to the uncoated region of the positive electrode and/or the uncoated region of the negative electrode, the current collection efficiency is not good due to large resistance and large heat generation. 
     For small cylindrical batteries with a form factor of 18650 or 21700, resistance and heat are not a major issue. However, when the form factor is increased to apply the cylindrical battery to an electric vehicle, the cylindrical battery may ignite while a lot of heat is generated around the electrode tab during the rapid charging process. 
     In order to solve this problem, there is provided a cylindrical battery (so-called tab-less cylindrical battery) in which the uncoated region of the positive electrode and the uncoated region of the negative electrode are designed to be positioned at the top and bottom of the rolled electrode assembly, respectively, and the current collector is welded to the uncoated region to improve the current collecting efficiency. 
       FIGS. 1 to 3  are diagrams showing a process of manufacturing a tab-less cylindrical battery.  FIG. 1  shows the structure of an electrode,  FIG. 2  shows a process of winding the electrode, and  FIG. 3  shows a process of welding a current collector to a bent surface of an uncoated region.  FIG. 4  is a sectional view showing a tab-less cylindrical battery, taken along the longitudinal direction Z. 
     Referring to  FIGS. 1 to 4 , a positive electrode plate  210  and a negative electrode plate  211  have a structure in which a sheet-shaped current collector  220  is coated with an active material  221 , and include an uncoated region  222  at one long side along the winding direction X. 
     An electrode assembly A is manufactured by sequentially stacking the positive electrode  210  and the negative electrode  211  together with two sheets of separators  212  as shown in  FIG. 2  and then winding them in one direction X. At this time, the uncoated region of the positive electrode  210  and the uncoated region of the negative electrode  211  are arranged in opposite directions. 
     After the winding process, the uncoated region  210   a  of the positive electrode  210  and the uncoated region  211   a  of the negative electrode  211  are bent toward the core. After that, current collectors  230 ,  231  are welded and coupled to the uncoated regions  210   a ,  211   a , respectively. 
     An electrode tab is not separately coupled to the positive electrode uncoated region  210   a  and the negative electrode uncoated region  211   a , the current collectors  230 ,  231  are connected to external electrode terminals, and a current path is formed with a large cross-sectional area along the winding axis direction of electrode assembly A (see arrow), which has an advantage of lowering the resistance of the battery. This is because resistance is inversely proportional to the cross-sectional area of the path through which the current flows. 
     However, when the form factor of the cylindrical battery increases and the magnitude of the charging current during rapid charging increases, the heat problem occurs again in the tab-less cylindrical battery. 
     Specifically, the conventional tab-less cylindrical battery  240  includes a battery can  241  and a sealing body  242  as shown in  FIG. 4 . The sealing body  242  includes a cap  242   a  having a plate shape, a sealing gasket  242   b  and a connection plate  242   c . The sealing gasket  242   b  surrounds the edge of the cap  242   a  and is fixed by a crimping portion  243 . In addition, the electrode assembly A is fixed in the battery can  241  by a beading portion  244  to prevent vertical movement. 
     Typically, the positive electrode terminal is the cap  242   a  of the sealing body  242 , and the negative electrode terminal is the battery can  241 . Therefore, the current collector  230  coupled to the uncoated region  210   a  of the positive electrode  210  is electrically connected to the connection plate  242   c  attached to the cap  242   a  through lead  245  in a strip form. In addition, the current collector  231  coupled to the uncoated region  211   a  of the negative electrode  211  is electrically connected to the bottom of the battery can  241 . The insulator  246  covers the current collector  230  to prevent the battery can  241  and the uncoated region  210   a  of the positive electrode  210  having different polarities from contacting each other and causing a short circuit. 
     When the current collector  230  is connected to the connection plate  242   c , the lead  245  of a strip form is used. The lead  245  is separately attached to the current collector  230  or is manufactured integrally with the current collector  230 . However, since the lead  245  is in the form of a thin strip, its sectional area is small, and thus, when a rapid charging current flows, a lot of heat is generated. In addition, excessive heat generated from the lead  245  is transferred toward the electrode assembly A to shrink the separator  212 , which may cause an internal short circuit that is a main cause of thermal runaway. 
     The lead  245  also occupies a significant installation space inside the battery can  241 . Therefore, the cylindrical battery  240  including the lead  245  has low space efficiency, so there is a limit in increasing the energy density. 
     Moreover, in order to connect the conventional tab-less cylindrical batteries  240  in series and/or in parallel, it is necessary to connect a bus bar component to the cap  242   a  of the battery can  241  and the bottom surface of the sealing body  242 , so space efficiency is reduced. A battery pack mounted to an electric vehicle includes hundreds of cylindrical batteries  240 . Accordingly, the inefficiency of the electrical wiring causes considerable inconvenience in the electric vehicle assembling process and the maintenance of the battery pack. 
     Meanwhile, as the cylindrical battery is recently applied to an electric vehicle, the form factor of the cylindrical battery is increasing. That is, the diameter and height of the cylindrical battery are increasing compared to the conventional cylindrical batteries having a form factor of 18650, 21700, or the like. The increase in the form factor leads to an increased energy density, enhanced safety against thermal runaway, and improved cooling efficiency. 
     The energy density of the cylindrical battery may be further increased when the unnecessary space inside the battery can is minimized along with the increase of the form factor. Therefore, components used for electrical insulation between the electrode assembly and the battery can or components used for current collection from the positive electrode and the negative electrode need to be optimally designed to increase the capacity of the battery and lower the overall resistance of the battery. 
     DISCLOSURE 
     Technical Problem 
     The present disclosure is designed in consideration of the above problems, and therefore the present disclosure is directed to providing a cylindrical battery having a structure in which a positive electrode terminal and a negative electrode terminal are applied in the same direction. 
     The present disclosure is directed to securing a sufficient area for welding an electric connection component such as a bus bar with an electrode terminal of a cylindrical battery while manufacturing a battery pack by utilizing a wide area of a closed portion of a battery can as an electrode terminal, in a case where a plurality of cylindrical batteries are to be electrically connected in one direction. 
     In another aspect, the present disclosure is directed to optimally designing so that the area occupied by the upper surface of the terminal (first electrode terminal) and the area occupied by the outer surface (second electrode terminal) of the closed portion may be sufficient for coupling with a bus bar. 
     In still another aspect, the present disclosure is directed to minimizing the resistance of the cylindrical battery by enlarging a contact area of the electrode assembly and the current collector (first current collector) and/or a contact area of the terminal and the current collector (first current collector) through improvement of the structure of the uncoated region of the electrode assembly. 
     In still another aspect, the present disclosure is directed to improving the electrical connection structure between the current collector (second current collector) and the battery can to multiplex a current path and directed to maximizing the contact area to minimize the resistance of the cylindrical battery. 
     In still another aspect, the present disclosure is directed to reducing the current path by improving the electrical connection structure of the current collector (second current collector) and the battery can, thereby minimizing the resistance of the cylindrical battery. 
     In still another aspect, the present disclosure is directed to minimizing the dead space by improving the structure of the uncoated region of the electrode assembly and/or optimally designing the height of the terminal and/or optimally designing the thickness of the battery can, thereby maximizing the energy density. 
     However, the technical object to be solved by the present disclosure is not limited to the above, and other objects not mentioned herein will be clearly understood by those skilled in the art from the following disclosure. 
     Technical Solution 
     In one aspect of the present disclosure, there is provided a battery, comprising: a rolled electrode assembly having a first electrode and a second electrode and a separator interposed therebetween, each of the first electrode and the second electrode having a first uncoated region and a second uncoated region not coated with an active material and exposed out of the separator at long side ends thereof; a battery can accommodating the electrode assembly through an opening at a lower end thereof and electrically connected to the second uncoated region; a terminal electrically connected to the first uncoated region and exposed out of the battery can through a closed portion of the battery can located opposite to the opening; and a cap covering and sealing the opening of the battery can. 
     The cap may be configured to have no polarity. 
     The terminal may be configured to penetrate a center of the closed portion. 
     An insulating gasket interposed between the battery can and the terminal may be provided at the closed portion side of the battery can, and a sealing gasket interposed between the battery can and the cap such that the cap seals the opening may be provided at the opening side of the battery can. 
     A surface of the terminal exposed out of the battery can may serve as a first electrode terminal to which a first bus bar terminal is coupled, and a region of an outer surface of the closed portion of the battery can, which is occupied by an exposed surface parallel to an upper surface of the first electrode terminal, may serve as a second electrode terminal to which a second bus bar terminal is coupled. 
     The first bus bar terminal may overlap with the first electrode terminal on a plane to form a first overlapping region, and the second bus bar terminal may overlap with the second electrode terminal on a plane to form a second overlapping region. 
     A diameter of the first electrode terminal and a width of the second electrode terminal may satisfy the following formulas: 
         W   1   ≤E   1   ≤D− 2 R   d −2 G− 2 W   2  
 
         E   2 =0.5*( D− 2 R   d −2 G−E   1 )
 
     (E 1 : diameter of the terminal exposed out of the battery can (diameter of the first electrode terminal), E 2 : width of the exposed surface of the outer surface of the closed portion of the battery can parallel to the upper surface of the terminal (width of the second electrode terminal), D: outer diameter of the battery can, R d : width of a round region at an edge of the battery can measured on a plane, G: exposure width of an insulating gasket exposed out of an edge of the first electrode terminal on a plane, W 1 : maximum value among distances between arbitrarily selected two points at an edge of the first overlapping region; W 2 : maximum value among distances between two points at which a plurality of straight lines passing through a center of the first electrode terminal meet an edge of the second overlapping region). 
     An area occupied by the first electrode terminal may be 2% to 30% compared to an area occupied by the second electrode terminal. 
     A form factor ratio obtained by dividing a diameter of the battery by a height thereof may be greater than 0.4. 
     At least a part of the first uncoated region may include a plurality of segments divided along a winding direction of the electrode assembly, and the plurality of segments may be bent along a radial direction of the electrode assembly. 
     The plurality of bent segments may be overlapped in multiple layers along the radial direction. 
     The electrode assembly may include a welding target region in which the number of overlapping layers of the segments of the first uncoated region is kept constant along the radial direction of the electrode assembly. 
     At least a part of the second uncoated region may include a plurality of segments divided along a winding direction of the electrode assembly, and the plurality of segments may be bent along a radial direction of the electrode assembly. 
     The plurality of bent segments may be overlapped in multiple layers along the radial direction. 
     The electrode assembly may include a welding target region in which the number of overlapping layers of the segments of the second uncoated region is kept constant along the radial direction of the electrode assembly. 
     The battery can may be made of steel, stainless steel, or nickel-plated steel. 
     The battery can may be configured to have different thicknesses depending on locations. 
     The battery can may be configured such that a thickness of a sidewall thereof is smaller than a thickness of the closed portion. 
     The closed portion may have a thickness of 0.4 mm to 1.2 mm. 
     A sidewall of the battery can may have a thickness of 0.3 mm to 0.8 mm. 
     The battery can may have a nickel-plated layer formed on a surface thereof. 
     The nickel-plated layer may have a thickness of 1.5 μm to 6.0 μm. 
     The battery can may include a round region for connecting a sidewall thereof and the closed portion. 
     The battery can may include a beading portion formed by press-fitting a periphery of an outer circumferential surface of the battery can at the opening side. 
     The beading portion may include an upper beading portion and a lower beading portion located above and below based on an innermost portion located at an innermost side along the pressing-fitting direction. 
     The upper beading portion and the lower beading portion may have asymmetric shapes. 
     The lower beading portion may include a flat portion parallel to the closed portion. 
     The upper beading portion may be at least partially inclined upward toward the innermost portion. 
     The upper beading portion may be configured to press and fix a lower portion of the electrode assembly. 
     The battery can may include a crimping portion formed below the beading portion and having a shape extending and bent from the beading portion to surround an outer circumferential surface of the cap and a part of a lower surface of the cap. 
     The battery may include a sealing gasket interposed between the battery can and the cap at the crimping portion. 
     The cap may include a venting portion configured to be ruptured when an internal pressure of the battery can increases over a predetermined level to discharge gas generated inside the battery can. 
     The venting portion may be a region of the cap having a smaller thickness than surrounding regions. 
     The venting portion may be formed to partially reduce a thickness of the battery can by forming a notch at one surface or both surfaces of the cap. 
     The venting portion may be formed along a periphery of an edge portion of a central region protruding downward, among the entire region of the cap. 
     The venting portion may be formed continuously or discontinuously. 
     The venting portion may be formed in a central region protruding downward, among the entire region of the cap, and the central region protruding downward may be located higher than a lower end of the battery can. 
     The terminal may include a terminal exposing portion exposed out of the battery can; and a terminal insert portion provided through the closed portion of the battery can and located inside the battery can. 
     The terminal insert portion may include an electric connection portion electrically connected to the first uncoated region; and a flange portion formed at a periphery of the electric connection portion and having a shape bent toward an inner surface of the closed portion of the battery can so as to be riveted on the inner surface. 
     The terminal may be made of aluminum. 
     A step may be formed between an upper surface of the terminal exposing portion and an upper surface of the battery can. 
     The terminal exposing portion may protrude out of the battery can through the upper surface of the battery can. 
     The height of the step may be 0.8 mm or more. 
     An insulating gasket may be interposed between the terminal and the battery can, and the insulating gasket may include a gasket exposing portion interposed between the terminal exposing portion and the battery can; and a gasket insert portion interposed between the terminal insert portion and the battery can. 
     The gasket exposing portion may have a thickness of 0.3 mm to 1 mm. 
     The gasket exposing portion may extend longer than the terminal exposing portion to be exposed out of the terminal exposing portion. 
     The gasket insert portion may be deformed together when the flange portion of the terminal insert portion is riveted, so as be in close contact with the inner surface of the closed portion of the battery can. 
     A region of the gasket insert portion exposed out of the terminal exposing portion may have a width in the range of 0.1 mm to 3.0 mm. 
     The battery may include a first current collector coupled to an upper portion of the electrode assembly and coupled to the terminal to electrically connect the first uncoated region of the electrode assembly and the terminal. 
     A flat portion parallel to an inner surface of the closed portion of the battery can may be formed in at least a part of a bottom surface of the terminal, and the first current collector may be coupled to the flat portion of the terminal. 
     The first current collector may be coupled onto a coupling surface formed by bending an end of the first uncoated region. 
     The battery may include a first current collector coupled to an upper portion of the electrode assembly and coupled to the terminal to electrically connect the first uncoated region of the electrode assembly and the terminal, and the first current collector may be coupled to the first uncoated region inside the welding target region. 
     The first current collector may include an edge portion disposed on the electrode assembly; a first uncoated region coupling portion configured to extend inward from the edge portion and coupled to the first uncoated region; and a terminal coupling portion configured to extend inward from the edge portion and coupled to the terminal. 
     The first uncoated region coupling portion and the terminal coupling portion may be not directly connected but indirectly connected by the edge portion. 
     The terminal coupling portion may be provided at a location corresponding to a hole formed at a winding center of the electrode assembly. 
     The terminal coupling portion may be configured to cover the hole formed at the winding center so that the hole formed at the winding center of the electrode assembly is not exposed out of the terminal coupling portion. 
     The terminal coupling portion may have a diameter substantially equal to or greater than a diameter of a flat portion formed at a bottom surface of the terminal. 
     The first current collector may further include a bridge portion configured to extend inward from the edge portion and connected to the terminal coupling portion. 
     The bridge portion may include a notching portion formed to partially reduce a sectional area of the bridge portion. 
     At least a part of the first uncoated region may include a plurality of segments divided along a winding direction of the electrode assembly, and the plurality of segments may be bent along a radial direction of the electrode assembly to be overlapped in multiple layers, and the notching portion may be provided in a region corresponding to a welding target region in which the number of overlapping layers of the segments of the first uncoated region is kept constant along the radial direction of the electrode assembly. 
     The notching portion may be provided at a location corresponding to a center in the radial direction of the electrode assembly. 
     A welding pattern drawn by welding beads formed on one surface of the terminal coupling portion of the first current collector may be drawn to surround a center of a bottom surface of the terminal. 
     The welding pattern may be formed continuously or discontinuously. 
     A welding portion formed between the terminal coupling portion of the first current collector and a bottom surface of the terminal may have a tensile force of 2 kgf or more. 
     A welding pattern drawn by welding beads formed on one surface of the terminal coupling portion of the first current collector may have a converted diameter of 2 mm or more. 
     A flat portion formed at the bottom surface of the terminal may have a diameter of 3 mm to 14 mm. 
     A ratio of an area of a welding pattern drawn by welding beads formed on one surface of the terminal coupling portion of the first current collector to an area of a flat portion formed at the bottom surface of the terminal may be 2.04% to 44.4%. 
     The battery may include a second current collector coupled to a lower portion of the electrode assembly and coupled to the battery can to electrically connect the second uncoated region of the electrode assembly and the battery can. 
     The second current collector may be coupled onto a coupling surface formed by bending an end of the first uncoated region. 
     The battery may include a second current collector coupled to a lower portion of the electrode assembly and coupled to the battery can to electrically connect the second uncoated region of the electrode assembly and the battery can, and the second current collector may be coupled to the second uncoated region inside the welding target region. 
     The second current collector may include a support portion disposed below the electrode assembly; a second uncoated region coupling portion configured to extend from the support portion and coupled to the second uncoated region; and a can coupling portion configured to extend from the support portion and coupled to the battery can. 
     The second uncoated region coupling portion and the can coupling portion may be indirectly connected through the support portion. 
     The second current collector may include a second uncoated region coupling portion coupled to the second uncoated region; and a can coupling portion coupled to the battery can. 
     The can coupling portion may be provided in plural, and the plurality of can coupling portions may be configured to radially extend toward a sidewall of the battery can. 
     The second current collector and the battery can may be electrically connected at a plurality of points. 
     The battery can may include a beading portion formed by press-fitting a periphery of an outer circumferential surface of the battery can at the opening side, and the can coupling portion may be electrically coupled to a lower surface of the beading portion. 
     The battery can may include a crimping portion formed below the beading portion and having a shape extending and bent from the beading portion to surround an outer circumferential surface of the cap and a part of a lower surface of the cap, the battery may include a sealing gasket interposed between the battery can and the cap at the crimping portion, and the can coupling portion may be interposed between the sealing gasket and the lower surface of the beading portion. 
     A flat portion parallel to the closed portion may be formed on the lower surface of the beading portion, and the can coupling portion may be electrically coupled onto the flat portion. 
     The can coupling portion may include a contact portion coupled onto an inner surface of the battery can; and a connection portion configured to connect a center of the second current collector and the contact portion to each other. 
     The battery can may include a beading portion formed by press-fitting a periphery of an outer circumferential surface of the battery can at the opening side, and the contact portion may have a shape extending by a predetermined length along a circumferential direction of the battery can on the beading portion. 
     The second current collector may have a current collector hole formed at a location corresponding to a hole formed at a winding center of the electrode assembly. 
     The current collector hole may have a diameter substantially equal to or greater than the hole formed at the winding center of the electrode assembly. 
     The battery can may include a beading portion formed by press-fitting a periphery of an outer circumferential surface of the battery can at the opening side, and a maximum distance from a center of the second current collector to an end of the second uncoated region coupling portion along the radial direction of the electrode assembly may be substantially equal to or smaller than an inner diameter of the battery can in a region where the beading portion is formed. 
     An insulator may be interposed between the first current collector and an inner surface of the closed portion of the battery can. 
     The insulator may have a thickness corresponding to the distance between the inner surface of the closed portion of the battery can and the first current collector. 
     The terminal may be coupled to the first current collector through a hole formed in the insulator. 
     The insulator may have a thickness substantially equal to or greater than the distance between the inner surface of the closed portion of the battery can and a bottom surface of the terminal. 
     The insulator may be interposed between the first uncoated region and a sidewall of the battery can. 
     An upper surface of the insulator may be in contact with the inner surface of the closed portion of the battery can, and a lower surface of the insulator may be in contact with an upper surface of the first current collector. 
     Resistance measured between a positive electrode and a negative electrode of the battery may be 4 mohm or below. 
     In another aspect of the present disclosure, there is also provided a battery pack, comprising a plurality of batteries according to the present disclosure. 
     In the battery pack of the present disclosure, the plurality of batteries may be arranged in a predetermined number of columns, and the terminal of each cylindrical battery and an outer surface of the closed portion of the battery can may be disposed to face upward. 
     The battery pack may comprise a plurality of bus bars configured to connect the plurality of batteries in series and in parallel, the plurality of bus bars may be disposed on top of the plurality of batteries, and each of the bus bars may include a body portion configured to extend between terminals of neighboring batteries; a plurality of first bus bar terminals configured to extend in one side direction of the body portion and electrically coupled to a terminal of a battery located in the one side direction; and a plurality of second bus bar terminals configured to extend in the other side direction of the body portion and electrically coupled to an outer surface of the closed portion of the battery can of a battery located in the other side direction. 
     In another aspect of the present disclosure, there is also provided a vehicle, comprising at least one battery pack according to the present disclosure. 
     Advantageous Effects 
     According to one aspect of the present disclosure, by improving the electrode terminal structure of the cylindrical battery to increase the space efficiency in the battery can, it is possible to lower the internal resistance of the cylindrical battery and increase the energy density. 
     According to another aspect of the present disclosure, by improving the structure of the electrode terminal of the cylindrical battery to enlarge the sectional area of the current path, it is possible to improve the problem of internal heat generated during rapid charging. 
     According to still another aspect of the present disclosure, an electrical wiring operation for serial and/or parallel connection of the batteries may be performed at one side of the batteries. 
     According to still another aspect of the present disclosure, in the case of electrically connecting a plurality of batteries in one direction, it is possible to utilize the wide surface of the closed portion of the battery can as an electrode terminal, thereby securing a sufficient area for welding electrical connection components such as bus bars for manufacturing a battery pack to electrode terminals of the batteries. 
     According to still another aspect of the present disclosure, it is possible to optimally design such that the area occupied by the upper surface of the terminal (first electrode terminal) and the area occupied by the outer surface (second electrode terminal) of the closed portion are sufficient for coupling with the bus bar. 
     According to still another aspect of the present disclosure, through improvement of the structure of the uncoated region of the electrode assembly, the contact area of the electrode assembly and the current collector (first current collector) and/or the contact area of the terminal and the current collector (first current collector) may be enlarged, thereby minimizing the resistance of the cylindrical battery. 
     According to still another aspect of the present disclosure, the current path may be multiplexed through improvement of the electrical connection structure of the current collector (second current collector) and the battery can, and the contact area between these parts may be maximized to minimize the resistance of the cylindrical battery. 
     According to still another aspect of the present disclosure, it is possible to reduce the current path through the improvement of the electrical connection structure of the current collector (second current collector) and the battery can, thereby minimizing the resistance of the cylindrical battery. 
     According to still another aspect of the present disclosure, it is possible to minimize the dead space by improving the structure of the uncoated region of the electrode assembly and/or optimally designing the height of the terminal and/or optimally designing the thickness of the battery can, thereby maximizing the energy density. 
     According to still another aspect of the present disclosure, it is possible to provide a battery pack manufactured using the cylindrical battery having an improved structure and a vehicle including the same. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The accompanying drawings illustrate an example embodiment of the present disclosure and together with the foregoing disclosure, serve to provide further understanding of the technical features of the present disclosure, and thus, the present disclosure is not construed as being limited to the drawing. 
         FIG. 1  is a plan view showing a structure of an electrode used for a conventional tab-less cylindrical battery. 
         FIG. 2  is a diagram showing a process of winding an electrode assembly included in the conventional tab-less cylindrical battery. 
         FIG. 3  is a diagram showing a process of welding a current collector to a bent surface of an uncoated region in the electrode assembly of  FIG. 2 . 
         FIG. 4  is a sectional view showing a conventional tab-less cylindrical battery, taken along a longitudinal direction Z. 
         FIG. 5  is a diagram showing an appearance of a cylindrical battery according to an embodiment of the present disclosure. 
         FIG. 6  is a diagram showing an internal structure of the cylindrical battery according to an embodiment of the present disclosure. 
         FIGS. 7 and 8  are partially sectioned views showing an upper structure of the cylindrical battery according to an embodiment of the present disclosure. 
         FIGS. 9 and 10  are plan views showing a coupling portion of a first current collector and a terminal, viewed along arrow directions of  FIGS. 7 and 8 . 
         FIGS. 11 and 12  are diagrams showing the first current collector and an example form of the first current collector applied in the present disclosure. 
         FIG. 13  is a partially sectioned view showing a lower structure of the cylindrical battery according to an embodiment of the present disclosure. 
         FIG. 14  is a diagram showing a lower surface of the cylindrical battery according to an embodiment of the present disclosure. 
         FIG. 15  is a diagram showing an example form of a second current collector applied in the present disclosure. 
         FIG. 16  is a plan view exemplarily showing an electrode structure according to an example embodiment of the present disclosure. 
         FIG. 17  is a sectional view showing an electrode assembly in which an uncoated region segmentation structure of a first electrode according to an embodiment of the present disclosure is also applied to a second electrode, taken along the longitudinal direction Z. 
         FIG. 18  is a sectional view showing an electrode assembly in which the uncoated region is bent according to an embodiment of the present disclosure, taken along the longitudinal direction Z. 
         FIG. 19  is a perspective view showing an electrode assembly in which the uncoated region is bent according to an embodiment of the present disclosure. 
         FIG. 20  is a top plan view showing that a plurality of cylindrical batteries according to the present disclosure are connected in series and in parallel using a bus bar. 
         FIG. 21  is a partially enlarged view of  FIG. 20 . 
         FIGS. 22 and 23  are diagrams exemplarily showing parameters used to define a diameter of the electrode terminal and an exposure width of an outer surface of a bottom of the battery can according to an embodiment of the present disclosure. 
         FIG. 24  is a diagram showing a schematic configuration of a battery pack including the cylindrical batteries according to an embodiment of the present disclosure. 
         FIG. 25  is a diagram showing a schematic configuration of a vehicle including the battery pack according to an embodiment of the present disclosure. 
     
    
    
     BEST MODE 
     Hereinafter, example embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications could be made thereto without departing from the scope of the disclosure. 
     In addition, in order to help the understanding of the present disclosure, the accompanying drawings are not drawn to scale, but dimensions of some components may be exaggerated. Also, the same reference signs may be assigned to the same components in different embodiments. 
     When it is explained that two objects are identical, this means that these objects are ‘substantially identical’. Accordingly, the substantially identical objects may include deviations considered low in the art, for example, deviations within 5%. Also, when it is explained that certain parameters are uniform in a predetermined region, this may mean that the parameters are uniform in terms of an average. 
     Referring to  FIGS. 5 to 7 , a cylindrical battery  1  according to an embodiment of the present disclosure includes an electrode assembly  10 , a battery can  20 , a cap  30 , and a penetrating terminal  40 . In addition to the above components, the cylindrical battery  1  may further include an insulation gasket  50  and/or a first current collector  60  and/or an insulator  70  and/or a second current collector  80  and/or a sealing gasket  90 . In various embodiments, the cylindrical battery  1  may have at least one gasket at opposite ends of the battery can  20 . For example, a closed end may have one gasket (e.g., the insulation gasket  50 ) and an open end may have one gasket (e.g., the sealing gasket  90 ), but such is not required, and additional gaskets can be used. Meanwhile, the battery can  20  may be referred to as a battery housing. 
     The electrode assembly  10  includes a first electrode having a first polarity, a second electrode having a second polarity, and a separator interposed between the first electrode and the second electrode. The first electrode is a positive electrode or a negative electrode, and the second electrode corresponds to an electrode having a polarity opposite to that of the first electrode. 
     The electrode assembly  10  may have, for example, a jelly-roll structure. That is, the electrode assembly  10  may be manufactured by preparing a stack that is formed by stacking a first electrode and a second electrode having a sheet shape at least once with a separator interposed therebetween, and winding the stack based on a winding center C. In this case, an additional separator may be provided on an outer circumferential surface of the electrode assembly  10  for insulation from the battery can  20 . The jelly-roll structure known in the art can be applied to the present disclosure without limitations. 
     The first electrode includes a first electrode current collector and a first electrode active material coated on one surface or both surfaces of the first electrode current collector. At one end of the first electrode current collector in a width direction (parallel to the Z-axis), there is an uncoated region that is not coated with the first electrode active material. Hereinafter, the uncoated region functioning as a first electrode tab  11  will be called the first uncoated region  11 . The first uncoated region  11  is provided at an upper portion of the electrode assembly  10  accommodated in the battery can  20  in a height direction (parallel to the Z-axis). That is, the first electrode current collector includes a first uncoated region  11  that is not coated with an active material layer at a long side end thereof and is exposed out of the separator, and a part of the first uncoated region  11  is used as an electrode tab by itself. The first uncoated region  11  may be, for example, a positive electrode tab. 
     Meanwhile, at least a part of the first uncoated region  11  may include a plurality of segments divided along a winding direction of the electrode assembly  10 . In this case, the plurality of segments may be bent along a radial direction of the electrode assembly  10 . The plurality of bent segments may be overlapped in multiple layers. In this case, a first uncoated region coupling portion  62  of the first current collector  60 , explained later, may be coupled to a region in which the plurality of segments are overlapped in multiple layers. Meanwhile, the electrode assembly  10  may include a welding target region that is a region in which the number of overlapping layers of the segments of the first uncoated region  11  is kept constant along the radial direction of the electrode assembly  10 . In this region, since the number of overlapping layers is kept to the maximum, it may be advantageous that the first current collector  60 , explained later, and the first uncoated region  11  are welded in this region. This is, for example, in the case of applying laser welding, to prevent the laser beam from passing through the first uncoated region  11  and damaging the electrode assembly  10  when the output of the laser is increased, in order to improve welding quality. In addition, this is to effectively prevent foreign substances such as welding spatters from flowing into the electrode assembly  10 . 
     The second electrode includes a second electrode current collector and a second electrode active material coated on one surface or both surfaces of the second electrode current collector. At the other end of the second electrode current collector in the width direction (parallel to the Z-axis), there is an uncoated region that is not coated with the second electrode active material. Hereinafter, the uncoated region functioning as a second electrode tab  12  will be called the second uncoated region  12 . The second uncoated region  12  is provided at a lower portion of the electrode assembly  10  accommodated in the battery can  20  in the height direction (parallel to the Z-axis). That is, the second electrode current collector includes a second uncoated region  12  that is not coated with an active material layer at a long side end thereof and is exposed out of the separator, and at least a part of the second uncoated region  12  is used as an electrode tab by itself. The second uncoated region  12  may be, for example, a negative electrode tab. Meanwhile, at least a part of the second uncoated region  12  may include a plurality of segments divided along the winding direction of the electrode assembly  10 . In this case, the plurality of segments may be bent along the radial direction of the electrode assembly  10 . The plurality of bent segments may be overlapped in multiple layers. In this case, a second uncoated region coupling portion  82  of the second current collector  80 , explained later, may be coupled to a region in which the plurality of segments are overlapped in multiple layers. Meanwhile, the electrode assembly  10  may include a welding target region that is a region in which the number of overlapping layers of the segments of the second uncoated region  12  is kept constant along the radial direction of the electrode assembly  10 . In this region, since the number of overlapping layers is kept to the maximum, it may be advantageous that the second current collector  80 , explained later, and the second uncoated region  12  are welded within this region. This is, for example, in the case of applying laser welding, to prevent the laser beam from passing through the second uncoated region  12  and damaging the electrode assembly  10  when the output of the laser is increased, in order to improve welding quality. In addition, this is to effectively prevent foreign substances such as welding spatters from flowing into the electrode assembly  10 . 
     The first uncoated region  11  and the second uncoated region  12  extend in opposite directions along the height direction (parallel to the Z-axis) of the cylindrical battery  1 . The first uncoated region  11  extends toward a closed portion located opposite to an opening formed at the lower end of the battery can  20 , and the second uncoated region  12  extends toward the opening of the battery can  20 . 
     In the present disclosure, a positive electrode active material coated on the positive electrode plate and a negative electrode active material coated on the negative electrode plate may employ any active material known in the art without limitation. 
     In one example, the positive electrode active material may include an alkali metal compound expressed by a general formula A[A x M y ]O 2+z  (A includes at least one element among Li, Na and K; M includes at least one element selected from is Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Al, Mo, Sc, Zr, Ru, and Cr; x≥0, 1≤x+y≤2, −0.1≤z≤2; and the stoichiometric coefficients x, y and z are selected so that the compound maintains electrical neutrality). 
     In another example, the positive electrode active material may be an alkali metal compound xLiM 1 O 2 -(1-x)Li 2 M 2 O 3  disclosed in U.S. Pat. Nos. 6,677,082, 6,680,143, et al., wherein M 1  includes at least one element having an average oxidation state 3; M 2  includes at least one element having an average oxidation state 4; and 0≤x≤1). 
     In still another example, the positive electrode active material may be lithium metal phosphate expressed by a general formula Li a M 1   x Fe 1-x M 2   y P 1-y M 3   z O 4-z  (M 1  includes at least one element selected from the Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg and Al; M 2  includes at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, Al, As, Sb, Si, Ge, V and S; M 3  includes a halogen element optionally including F; 0&lt;a≤2, 0≤x≤1, 0≤y&lt;1, 0≤z&lt;1; the stoichiometric coefficients a, x, y and z are selected so that the compound maintains electrical neutrality), or Li 3 M 2 (PO 4 ) 3  (M includes at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al, Mg and Al). 
     Preferably, the positive electrode active material may include primary particles and/or secondary particles in which the primary particles are aggregated. 
     In one example, the negative electrode active material may employ carbon material, lithium metal or lithium metal compound, silicon or silicon compound, tin or tin compound, or the like. Metal oxides such as TiO 2  and SnO 2  with a potential of less than 2V may also be used as the negative electrode active material. As the carbon material, a low-crystalline carbon and/or a high-crystalline carbon may be used. 
     The separator may employ a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, ethylene/methacrylate copolymer, or the like, or laminates thereof. As another example, the separator may employ a common porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like. 
     A coating layer of inorganic particles may be included in at least one surface of the separator. It is also possible that the separator itself is made of a coating layer of inorganic particles. Particles in the coating layer may be coupled with a binder so that an interstitial volume exists between adjacent particles. 
     The inorganic particles may be made of an inorganic material having a dielectric constant of 5 or more. As a non-limiting example, the inorganic particles may include at least one material selected from the group consisting of Pb(Zr,Ti)O 3  (PZT), Pb 1-x La x Zr 1-y Ti y O 3  (PLZT), PB(Mg 3 Nb 2/3 )O 3 —PbTiO 3  (PMN-PT), BaTiO 3 , hafnia (HfO 2 ), SrTiO 3 , TiO 2 , Al 2 O 3 , ZrO 2 , SnO 2 , CeO 2 , MgO, CaO, ZnO and Y 2 O 3 . 
     The electrolyte may be a salt having a structure like A + B − . Here, A +  includes an alkali metal cation such as Li + , Na + , or K + , or a combination thereof and B −  includes at least one anion selected from the group consisting of F − , Cl − , Br − , I − , NO 3   − , N(CN) 2   − , BF 4   − , ClO 4   − , AlO 4   − , AlCl 4   − , PF 6   − , SbF 6   − , AsF 6   − , BF 2 C 2 O 4   − , BC 4 O 8 , (CF 3 ) 2 PF 4   − , (CF 3 ) 3 PF 3   − , (CF 3 ) 4 PF 2   − , (CF 3 ) 5 PF − , (CF 3 ) 6 P − , CF 3 SO 3   − , C 4 F 9 SO 3   − , CF 3 CF 2 SO 3   − , (CF 3 SO 2 ) 2 N − , (FSO 2 ) 2 N − , CF 3 CF 2  (CF 3 ) 2 CO − , (CF 3 SO 2 ) 2 CH − , (SF 5 ) 3 C − , (CF 3 SO 2 ) 3 C − , CF 3  (CF 2 ) 7 SO 3   − , CF 3 CO 2   − , CH 3 CO 2   − , SCN −  and (CF 3 CF 2 SO 2 ) 2 N − . 
     The electrolyte may also be dissolved in an organic solvent. The organic solvent may employ propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or a mixture thereof. 
     Referring to  FIGS. 5 to 8 , the battery can  20  is a substantially cylindrical container having an opening at a lower side, and is made of, for example, a material having conductivity such as metal. As a material of the battery can  20 , for example, steel, stainless steel or nickel-plated steel may be applied. The bottom of the battery can  20  having the opening will be referred to as an opened end. The upper surface located opposite to the opening (or, the opened end) will be referred to as a closed portion or a closed end. A side surface (outer circumferential surface) and an upper surface of the battery can  20  may be integrally formed. Alternatively, the sidewall and the closed portion of the battery can  20  may be provided separately from each other and be coupled to each other by welding or the like. The upper surface of the battery can  20  (a surface parallel to the X-Y plane), namely an outer surface  20   a  of the closed portion, has an approximately flat shape. The battery can  20  accommodates the electrode assembly  10  through the opening formed at the bottom, and also accommodates an electrolyte together. 
     The battery can  20  is electrically connected to the electrode assembly  10 . The battery can  20  is electrically connected to, for example, the second uncoated region  12  of the electrode assembly  10 . In this case, the battery can  20  has the same polarity as the second uncoated region  12 . 
     Referring to  FIGS. 6 and 13 , the battery can  20  may include a beading portion  21  and a crimping portion  22  formed at a lower end thereof. The beading portion  21  is located below the electrode assembly  10 . The beading portion  21  is formed by press-fitting a periphery of the outer circumferential surface of the battery can  20 . The upper beading portion  21   a  and the lower beading portion  21   b  respectively located above and below based on an innermost portion  21   c  of the beading portion  21  located at an innermost side along the pressing-fitting direction may have an asymmetric shape. This asymmetric shape may be formed in the process of compressing the battery can  20  along the height direction (parallel to the Z-axis) through a sizing process. The sizing process is a process of matching the height of the cylindrical battery  1  to a design form factor by pressing the battery can  20  along the winding axis direction of the electrode assembly  10 . 
     The lower beading portion  21   b  may include a flat portion substantially parallel to the closed portion of the battery can  20 . Meanwhile, due to the asymmetrical formation, the upper beading portion  21   a  may have a shape inclined upward at least partially along a direction toward the innermost portion  21   c . Accordingly, the upper beading portion  21   a  may compress and fix the lower portion of the electrode assembly  10 . The beading portion  21  prevents the electrode assembly  10  having a size approximately corresponding to the inner diameter of the battery can  20  from coming out through the opening formed at the lower end of the battery can  20 , and may function as a support portion on which the cap  30  is placed. The lower beading portion  21   b  may function as a support portion for fixing the contact portion  83   a  of the second current collector  80 , the sealing gasket  90 , and the like as well as the cap  30 , explained later. 
     The crimping portion  22  is formed below the beading portion  21 . The crimping portion  22  extends from the lower beading portion  21 . The crimping portion  22  has a shape extending and bent to surround the outer circumferential surface of the cap  30  disposed below the beading portion  21  and a part of the lower surface of the cap  30 . The crimping portion  22  may fix the sealing gasket  90  in addition to the cap  30 . 
     However, the present disclosure does not exclude the case where the battery can  20  does not include the beading portion  21  and/or the crimping portion  22 . In the present disclosure, if the battery can  20  does not include the beading portion  21  and/or the crimping portion  22 , it is possible to fix the electrode assembly  10  and/or fix the cap  30  and/or seal the battery can  20  by, for example, additionally applying a component that can function as a stopper for the electrode assembly  10  and/or additionally applying a structure on which the cap  30  can be placed and/or welding the battery can  20  and the cap  30  to each other. 
     Meanwhile, the battery can  20  may be configured to have different thicknesses depending on locations. In the battery can  20 , the thickness of the sidewall may be formed smaller than the thickness of the closed portion. In this case, since the electrode assembly  10  may be formed to have a greater diameter, it may be advantageous in terms of energy density. 
     The closed portion of the battery can  20 , namely a region forming the upper surface, may have a thickness in the range of, for example, about 0.4 mm to 1.2 mm, more preferably in the range of about 0.6 mm to 1.0 mm. If the thickness of the closed portion of the battery can  20  is too great, the risk of deformation of the battery can  20  may increase when the internal pressure rises or welding is performed. Conversely, if the thickness of the closed portion of the battery can  20  is too small, it may be disadvantageous in terms of processing the battery can  20 , and loss in terms of energy density may increase. Therefore, it is necessary to manage the thickness of the closed portion of the battery can  20  at an appropriate level. 
     Meanwhile, in the battery can  20 , the sidewall constituting the outer circumferential surface may have, for example, a thickness in the range of about 0.3 mm to 0.8 mm, more preferably in the range of about 0.4 mm to 0.6 mm. If the thickness of the sidewall of the battery can  20  is too small, the possibility of fire spreading to neighboring cylindrical batteries  1  increase when fire and explosion occurs at the cylindrical battery  1 . For example, in a battery pack including a plurality of cylindrical batteries  1 , in the case where an abnormality occurs in some cylindrical batteries  1  to cause fire and explosion, if the thickness of the sidewall of the battery can  20  is too small, a pin hole may be generated, thereby increasing the risk of a chain ignition and explosion. Meanwhile, if the thickness of the sidewall of the battery can  20  is too small, it may be disadvantageous in terms of processing the battery can  20  and loss in terms of energy density may increase. Therefore, it is necessary to manage the thickness of the sidewall of the battery can  20  at an appropriate level. Meanwhile, a plating layer may be formed on the battery can  20 . In this case, the plating layer may include, for example, nickel (Ni). The thickness of the plating layer may be in the range of approximately 1.5 μm to 6.0 μm. 
     Referring to  FIGS. 6 and 13 , the cap  30  may be made of, for example, a metal material to ensure rigidity. The cap  30  seals the opening (or, the opened end) formed at a bottom end of the battery can  20 . That is, the cap  30  functions as the lower surface of the cylindrical battery  1 . In the cylindrical battery  1  of the present disclosure, the cap  30  may not have a polarity even if it is made of a conductive metal material. The cap  30  having no polarity may mean that the cap  30  is not electrically connected to the electrode assembly  10 . If the cap  30  is not electrically connected to the electrode assembly  10  as above, the cap  30  does not function as a positive electrode terminal or a negative electrode terminal. That is, in the present disclosure, the cap  30  does not need to be electrically connected to the electrode assembly  10  and the battery can  20 , and its material does not necessarily have to be a conductive metal. 
     If the battery can  20  of the present disclosure includes the beading portion  21 , the cap  30  may be supported by the lower surface of the beading portion  21  formed on the battery can  20 . In addition, if the battery can  20  of the present disclosure includes the crimping portion  22 , the cap  30  is fixed by the crimping portion  22 . That is, the upper surface of the cap  30  may be supported by the beading portion  21 , and the outer circumferential surface and the lower surface of the cap  30  may be supported by the beading portion  21 . The sealing gasket  90  may be interposed between the cap  30  and the crimping portion  22  of the battery can  20  to secure the airtightness of the battery can  20 . Meanwhile, as described above, the battery can  20  of the present disclosure may not include the beading portion  21  and/or the crimping portion  22 , and in this case, the sealing gasket  90  may be interposed between a fixing structure provided at a side of the battery can  20  having the opening and the cap  30  in order to secure the airtightness of the battery can  20 . 
     Referring to  FIGS. 13 and 14 , the cap  30  may further include a venting portion  31  formed to prevent an inner pressure from increasing over a preset value due to a gas generated inside the battery can  20 . The preset inner pressure value may be about 15 kgf/cm 2  to 35 kgf/cm 2 . The venting portion  31  corresponds to a region having a smaller thickness compared to the peripheral region of the cap  30 . The venting portion  31  is structurally weak compared to the peripheral region. Accordingly, if an abnormal situation occurs in the cylindrical battery  1  so that the inner pressure of the battery can  20  increases over a certain level, the venting portion  31  is ruptured so that the gas generated inside the battery can  20  is discharged. The venting portion  31  may be formed by reducing the thickness of the battery can  20  partially, for example by notching any one surface or both surfaces of the cap  30 . 
     The cylindrical battery  1  according to an embodiment of the present disclosure has a structure in which both a positive electrode terminal and a negative electrode terminal are provided at an upper portion thereof as will be described later, and thus the upper structure is more complicated than the lower structure. Accordingly, the venting portion  31  may be formed at the cap  30  that functions as a lower surface of the cylindrical battery  1  in order to smoothly discharge the gas generated inside the battery can  20 . As shown in  FIG. 7 , the lower end of the cap  30  is preferably located higher than the lower end of the battery can  20 . In this case, even if the lower end of the battery can  20  touches the ground or the bottom surface of the housing for a module or pack configuration, the cap  30  does not touch the ground or the bottom surface of the housing for the module or pack configuration. Accordingly, it is possible to prevent the pressure required to rupture the venting portion  31  from being different from a design value due to the weight of the cylindrical battery  1 , thereby securing smooth rupture of the venting portion  31 . 
     Meanwhile, the venting portion  31  may have a shape extending continuously or discontinuously to surround the central region of the cap  30  as shown in  FIGS. 13 and 14 . In this case, a greater distance is advantageous from the center of the cap  30  to the venting portion  31  in terms of ease of rupture of the venting portion  31  due to the increase of internal pressure. This is because, when the same internal pressure is applied, as the distance from the center point of the cap  30  to the venting portion  31  is greater, the force acting on the venting portion  31  increases further to secure easy rupture. In addition, a greater distance is also advantageous from the center point of the cap  30  to the venting portion  31  in terms of the smooth discharge of the venting gas since the area opened by venting is increased. From this point of view, the venting portion  31  may be advantageously formed along an edge circumference of the central region having an approximately flat shape and protruding downward (in a lower direction based on  FIG. 13 ), in the entire region of the cap  30 . 
       FIGS. 13 and 14  depict a case in which the venting portion  31  is continuously formed in an approximately circular shape on the cap  30 , but the present disclosure is not limited thereto. The venting portion  31  may have an approximately elliptical shape or other geometric shape that is formed to include the center point of the cap  30  therein. In addition, the venting portion  31  may be formed discontinuously instead of continuously. 
     Referring to  FIGS. 5 to 7 , the terminal  40  is made of a metal material with conductivity. The material of the terminal  40  may be aluminum (Al). If the material of the terminal  40  is aluminum, the riveting process, explained later, may be performed easily, and aluminum of 10 series having a relatively low electrical resistance may be applied. The terminal  40  penetrates an upper surface of the battery can  20 , namely a surface (parallel to the XY plane) located at a side of the battery can  20  opposite to the opening. The terminal  40  is electrically connected to the first uncoated region  11  of the electrode assembly  10 , for example. In this case, the terminal  40  has a first polarity. Accordingly, the terminal  40  may function as a first electrode terminal in the cylindrical battery  1  of the present disclosure. If the terminal  40  has the first polarity like this, the terminal  40  is electrically insulated from the battery can  20  with the second polarity. The electrical insulation between the terminal  40  and the battery can  20  may be realized in various ways. For example, the insulation may be realized by interposing an insulation gasket  50 , explained later, between the terminal  40  and the battery can  20 . Alternatively, the insulation may be realized by forming an insulating coating layer on a portion of the terminal  40 . Alternatively, any method of structurally fixing the terminal  40  securely such that the terminal  40  and the battery can  20  cannot contact each other may be applied. Alternatively, some of the above methods may be applied together. 
     The terminal  40  includes a terminal exposing portion  41  and a terminal insert portion  42 . The terminal insert portion  42  may include an electric connection portion  42   a  and a flange portion  42   b . The terminal exposing portion  41  is exposed out of the battery can  20 . The terminal exposing portion  41  may be located approximately at the center of the closed portion of the battery can  20 . The maximum width of the terminal exposing portion  41  may be formed larger than the maximum width of the hole formed in the battery can  20  for the insertion of the terminal  40 . The terminal insert portion  42  may pass through approximately the center of the closed portion of the battery can  20 , and the electric connection portion  42   a  of the terminal insert portion  42  may be electrically connected to the first uncoated region  11 . The flange portion  42   b  of the terminal insert portion  42  is formed at the periphery of the electric connection portion  42   a , and may be riveted on the inner surface of the closed portion of the battery can  20 . That is, the flange portion  42   b  of the terminal insert portion  42  may have a shape curved toward the inner surface of the closed portion of the battery can  20 . Therefore, the maximum width of the terminal insert portion  42  after the riveting process for fixing the terminal  40  is performed may be formed larger than the maximum width of the hole formed in the battery can  20  so that the terminal insert portion  42  passes therethrough. 
     Meanwhile, when the cylindrical battery  1  of the present disclosure includes the first current collector  60 , the electric connection portion  42   a  of the terminal insert portion  42  may be coupled to the first current collector  60 . The electric connection portion  42   a  of the terminal insert portion  42  may have, for example, a substantially cylindrical shape. Of course, the shape of the electric connection portion  42   a  of the terminal insert portion  42  is not limited thereto. The electric connection portion  42   a  of the terminal insert portion  42  may have various shapes, such as, for example, a cylindrical shape having an elliptical cross-section, a square pillar shape, a hexagonal pillar shape, an octagonal pillar shape, or the like. The bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  may be formed to be substantially flat at least partially. 
     Referring to  FIGS. 9 and 10  along with  FIGS. 7 and 8 , the bottom surface of the central region of the terminal insert portion  42  and the first current collector  60  may be coupled by, for example, laser welding, spot welding or ultrasonic welding. 
     The welding may be performed by irradiating a laser through a hole formed at the winding center C of electrode assembly  10  or inserting a tool for ultrasonic welding or spot welding to form a welding bead W on one surface of the first current collector  60  (a surface facing the hole formed at the winding center C of the electrode assembly  10 ). A guide pipe (not shown) for welding may be inserted into the hole formed at the winding center C. When welding is carried out in a state where the guide pipe is inserted, the risk of damage to the separator forming the inner wall of the hole formed at the winding center C may be reduced. 
     The welding pattern drawn by the welding bead W formed on one surface of the terminal coupling portion  63  of the first current collector  60  may be drawn to surround the center P of the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42 . The welding pattern may be, for example, approximately circular, and alternatively, the welding pattern may have an approximately elliptical shape, or a polygonal shape such as approximately square, hexagonal and octagonal shapes. The welding pattern formed by the welding bead W may be formed continuously (see  FIG. 9 ) or discontinuously (see  FIG. 10 ). The circular, elliptical and polygonal shapes, which are examples of the shape of the welding pattern formed by the welding bead W, do not mean geometrically perfect circles, ovals and polygons. 
     Meanwhile, the diameter of the flat portion formed on the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  may be determined in consideration of welding strength with the first current collector  60 . The tensile force of the welding portion between the flat portion and the first current collector  60  may be at least about 2 kgf or more, 3 kgf or more, 4 kgf or more, 5 kgf or more, 6 kgf or more, 7 kgf or more, 8 kgf or more, 9 kgf or more, or 10 kgf or more. It is preferable to increase the tensile force of the welding portion as much as possible within an allowable range by optimally selecting a welding method. 
     The diameter (or, the maximum width) of the welding pattern formed on the flat portion to satisfy the tensile force condition of the welding portion may be at least about 2 mm. The diameter of the welding pattern may be defined as a converted diameter (2*(S/π) 0.5 ) of a circle when the area (S) of the welding bead W displayed on the surface of the welding portion is converted to an area (πr 2 ) of the corresponding circle. 
     The flat portion formed on the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  corresponds to a weldable region. The diameter of the weldable region may be approximately 3 mm to 14 mm. If the diameter of the weldable region is less than about 3 mm, it is difficult to secure a welding pattern with a diameter (converted diameter) of 2 mm or more. In particular, in the case of forming a welding pattern using laser welding, it is difficult to secure a welding pattern having a diameter of 2 mm or more due to laser beam interference. If the diameter of the weldable region exceeds approximately 14 mm, the diameter of the terminal exposing portion  41  of the terminal  40  is inevitably increased beyond that, and thus it is difficult to sufficiently secure the area of the outer surface  20   a  of the battery can  20  to be used as an electrode terminal having an opposite polarity to the terminal  40 . 
     Considering the diameter condition of the welding pattern and the diameter condition of the weldable region, the ratio of the area of the welding pattern to the area of the weldable region required to secure a welding portion tensile force of at least about 5 kgf or more is preferably approximately 2.04% (π1 2 /π7 2 ) to 44.4% (π1 2 /π1.5 2 ). 
     In one example, when the flat portion formed on the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  and the first current collector  60  are welded by a laser while the welding bead W is drawing a continuous or discontinuous line in the form of an approximately arc pattern, the diameter of the arc welding pattern is about 2 mm or more, preferably about 4 mm or more. When the diameter of the arc welding pattern satisfies the corresponding condition, it is possible to secure sufficient welding strength by increasing the welding portion tensile force to about 5 kgf or more. 
     In another example, when the flat portion formed on the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  and the first current collector  60  are welded by ultrasonic waves in a circular pattern, the diameter of the circular welding pattern is preferably about 2 mm or more. When the diameter of the circular welding pattern satisfies the corresponding condition, it is possible to secure sufficient welding strength by increasing the welding portion tensile force to about 5 kgf or more. 
     The diameter of the flat portion formed on the bottom surface of the terminal  40  corresponding to the weldable region may be adjusted in the range of approximately 3 mm to 14 mm. If the radius of the flat portion is less than about 3 mm, it is difficult to form a welding pattern having a diameter of about 2 mm or more by using a laser welding tool, an ultrasonic welding tool, or the like. 
     In another aspect, the distance from the center of the upper surface of the terminal  40  to the outermost side, namely the radius R 1  of the terminal exposing portion  41 , may be approximately 10% to 70% of the radius (R 2 , ½ of the outer diameter of the battery can) of the upper surface of the battery can  20 . If R 1  decreases, the welding space becomes insufficient when welding components (bus bars) used for the electrical connection of the terminal  40 . In addition, when R 1  increases, the welding space decreases when welding components (bus bars) used for electrical connection in a remaining area except for the terminal  40  on the upper surface of the battery can  20 . 
     If the ratio R 1 /R 2  is adjusted between approximately 10% and 70%, the welding space for the terminal  40  and the welding space for the outer surface  20   a  of the closed portion of the battery can  20  may be properly secured. 
     In addition, the radius R 3  of the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  may be approximately 4% to 30% compared to the R 2 . 
     If the R 3  decreases, the welding space becomes insufficient when welding the first current collector  60  to the flat portion formed on the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42 , and the contact resistance may increase since the welding area of the terminal  40  decreases. In addition, R 3  should be smaller than R 1 , and if R 3  increases, the thickness of the flange portion  42   b  of the terminal insert portion  42  inevitably decreases, which weakens the force of the flange portion  42   b  to compress the insulating gasket  50 , thereby deteriorating the sealing ability of the insulating gasket  50 . 
     If R 3 /R 2  is adjusted between approximately 4% and 30%, the welding process may be easily performed by sufficiently securing the welding area between the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  and the first current collector  60 , and also it is possible to reduce the contact resistance of the welding area and to prevent the sealing ability of the insulating gasket  50  from deteriorating. 
     Meanwhile, the cylindrical battery  1  according to an embodiment of the present disclosure has a structure in which the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42  is welded onto the first current collector  60  as described above, thereby maximizing the binding area between the first current collector  60  and the terminal  40 . That is, at least a part of the bottom surface of the electric connection portion  42   a  is formed to be flat, and thus the coupling area between the terminal  40  and the first current collector  60  may be maximized. Therefore, the cylindrical battery  1  according to an embodiment of the present disclosure may secure a smooth current flow at the coupling portion of the first current collector  60  and the terminal  40  in the case where a large amount of current flows due to rapid charging, thereby giving the effects of shortening the charging time and reducing the amount of heat generated. 
     In the present disclosure, the upper surface of the battery can  20 , namely the outer surface  20   a  of the closed portion of the battery can  20 , and the upper surface of the terminal exposing portion  41  of the terminal  40  exposed out of the battery can  20  have opposite polarities and face in the same direction. In addition, a step may be formed between the upper surface of the terminal exposing portion  41  and the upper surface of the battery can  20 . That is, as shown in  FIGS. 7 and 8 , the terminal exposing portion  41  may protrude to the outside of the battery can  20  by a predetermined height through the upper surface of the battery can  20 . In this case, the height of the step may be in the range of approximately 0.08 mm to 4 mm. If the height of the step is formed too low beyond this range, the possibility that the bus bar coupled to the upper surface of the terminal exposing portion  41  comes into contact with the upper surface of the battery can  20  having a polarity opposite to the terminal exposing portion  41  and/or the possibility that the terminal exposing portion  41  is deformed when the terminal  40  is riveted may increase. The thickness of the gasket exposing portion  51 , explained later, may be formed in the range of about 0.3 mm to 1 mm in consideration of insulation and sealing properties. Considering the thickness of the gasket exposing portion  51 , if the height of the terminal exposing portion  41  protruding to the upper surface  20   a  of the battery can  20  is less than approximately 0.08 mm, it becomes difficult to secure the mechanical rigidity of the terminal exposing portion  41 . In particular, this is more serious when the terminal  40  is made of aluminum. Meanwhile, when the height of the step is formed to be too high beyond the above range, the size of the cylindrical battery  1  increases in the height direction, which may increase the loss in terms of energy density. 
     Meanwhile, in the drawings of the present disclosure, only the case where the terminal  40  protrudes higher than the upper surface of the battery can  20  functioning as the electrode terminal  20   a  having an opposite polarity to the terminal  40  is shown, but the present disclosure is not necessarily limited thereto. 
     For example, if the upper surface of the battery can  20  has a shape concavely indented from the center downward, namely toward the electrode assembly  10 , the upper surface of the battery can  20  may be located higher than the terminal exposing portion  41  of the electrode terminal  40 . 
     Meanwhile, in the case where the upper surface of the battery can  20  has a shape concavely indented from the center downward, namely toward the electrode assembly  10 , the upper surface of the battery can  20  and the upper surface of the terminal exposing portion  41  may form the same plane according to the indented depth and the thickness of the terminal exposing portion  41  of the electrode terminal  40 . In this case, a step may not be formed between the upper surface of the battery can  20  and the upper surface of the terminal exposing portion  41 . 
     The insulation gasket  50  is interposed between the battery can  20  and the terminal  40  to prevent the battery can  20  and the terminal  40  having opposite polarities from contacting each other. Accordingly, the upper surface of the battery can  20  having an approximately flat shape may function as a second electrode terminal of the cylindrical battery  1 . 
     The insulation gasket  50  includes a gasket exposing portion  51  and a gasket insert portion  52 . The gasket exposing portion  51  is interposed between the terminal exposing portion  41  of the terminal  40  and the battery can  20 . The gasket exposing portion  51  may extend longer than the terminal exposing portion  41 , and thus may be exposed out of the terminal exposing portion  41  when the cylindrical battery  51  is viewed from the above. The gasket insert portion  52  is interposed between the terminal insert portion  42  of the terminal  40  and the battery can  20 . When the flange portion  42   b  of the terminal insert portion  42  is riveted, the gasket insert portion  52  may be deformed together to come into close contact with the inner surface of the closed portion of the battery can  20 . The insulation gasket  50  may be made of, for example, a resin material having insulation and elasticity. 
     Referring to  FIG. 8 , the gasket exposing portion  51  of the insulation gasket  50  may have an extended shape to cover the outer circumferential surface of the terminal exposing portion  41  of the terminal  40 . If the insulation gasket  50  covers the outer circumferential surface of the terminal  40  in this way, it is possible to prevent a short circuit from occurring in the process of coupling an electric connection component such as a bus bar to the upper surface of the battery can  20  and/or the terminal  40 . Although not shown in the drawings, the gasket exposing portion  51  of the insulation gasket  50  may also have an extended shape to cover not only the outer circumferential surface of the terminal exposing portion  41  but also a portion of the upper surface thereof. 
     In the case where the insulation gasket  50  is made of a resin material, the insulation gasket  50  may be coupled to the battery can  20  and the terminal  40  by thermal fusion. In this case, the airtightness at the coupling interface between the insulation gasket  50  and the terminal  40  and at the coupling interface between the insulation gasket  50  and the battery can  20  may be strengthened. Meanwhile, in the case where the gasket exposing portion  51  of the insulation gasket  50  extends to the upper surface of the terminal exposing portion  41 , the terminal  40  may be coupled to the insulation gasket  50  by insert injection molding. 
     Meanwhile, referring to  FIGS. 7 and 8 , preferably, the height H 3  of the flange portion  42   a  of the terminal insert portion  42  protruding to the inside of the battery can  20  may be approximately 0.5 mm to 3.0 mm. If the protrusion height H 3  of the terminal insert portion  42  is less than about 0.5 mm, it is difficult to ensure sufficient sealing properties. In addition, if the protrusion height H 3  of the terminal insert portion  42  exceeds 3 mm, the internal space of the battery can  20  that can be occupied by the electrode assembly  10  is reduced. 
     Preferably, the total height of the terminal  40  may be approximately 1.5 mm to 7 mm. The total height of the terminal  40  means the distance from the upper surface of the terminal exposing portion  41  to the bottom surface of the terminal insert portion  42 . If the total height of the terminal  40  is less than about 1.5 mm, it is difficult to increase the thickness of the gasket insert portion  52  enough to secure sealing properties due to the thickness of the closed portion of the battery can  20 . For reference, the thickness of the closed portion of the battery can  20  may be formed in the range of about 0.4 mm to 1.2 mm. In addition, if the total height of the terminal  40  exceeds approximately 7 mm, the inner space of the battery can  20  that can be occupied by the electrode assembly  10  is excessively reduced and the total height of the cylindrical battery  1  is increased, so that the energy density per unit area is lowered as much. 
     Meanwhile, the terminal  40  may have a riveted structure such that the terminal insert portion  42  is substantially parallel to the inner surface of the closed portion of the battery can  20 . Accordingly, the angle formed by and the inner surface of the closed portion and the surface of the terminal insert portion  42  opposite to the inner surface of the closed portion of the battery can  20  may be formed substantially close to zero. In addition, the height H 3  of the flange portion  42   b  of the terminal insert portion  42  protruding toward the inside of the battery can  20  with respect to the inner surface of the closed portion of the battery can  20  may be formed equal to or greater than the height H 2  of the gasket insert portion  52  protruding toward the inside of the battery can  20 . In addition, the height H 1  of the electric connection portion  42   a  protruding toward the inside of the battery can  20  with respect to the inner surface of the closed portion of the battery can  20  may be equal to or greater than the protrusion height H 3  of the flange portion  42   b . In addition, the inner edge portion of the hole of the battery can  20  for the passage of the terminal  40  and the insulating gasket  50  has an arc shape with a predetermined curvature. In addition, the electric connection portion  42   a  of the terminal insert portion  42  of the terminal  40  may have a shape gradually narrowing toward its bottom surface. 
     Preferably, the thickness of the insulating gasket  50  may gradually decrease downward from an intermediate region where the gasket exposing portion  51  and the gasket insert portion  52  are connected, and then slightly increase at the distal end of the gasket insert portion  52 . The compression structure of the insulating gasket  50  may further improve the sealing properties for the space between the terminal  40  and the battery can  20 . 
     Preferably, the riveting structure of the terminal  40  according to an embodiment of the present disclosure as described above may be applied to a cylindrical battery having a form factor greater than 21700. 
     Recently, as the cylindrical battery is applied to an electric vehicle, the form factor of the cylindrical battery is increasing compared to the conventional  18650 ,  21700 , and the like. An increase in the form factor leads to increased energy density, increased safety against thermal runaway, and improved cooling efficiency. 
     Also, as will be explained later, the cylindrical battery  1  to which the riveting structure of the terminal  40  is applied may perform all electrical wiring for the positive electrode/negative electrode in one direction. In addition, the terminal  40  having the riveting structure as described above has a large sectional area and low electric resistance, which is very advantageous for rapid charging. 
     According to an embodiment of the present disclosure, the insulation gasket  50 , the insulator  70 , and the sealing gasket  90  may be made of the same material. However, this is not essential. The insulation gasket  50  and the insulator  70  may have substantially the same thickness. However, this is not essential. If they have different thicknesses, the insulator  70  may be thinner than the insulation gasket  50 , and vice versa. 
     In the entire area of the upper surface of the battery can  20 , viewed from a location above the cylindrical battery  1 , the entire area except for the area occupied by the terminal  40  and the insulation gasket  50  corresponds to the second electrode terminal having the opposite polarity to the terminal  40 . 
     The cylindrical sidewall of the battery can  20  may be formed in one piece with the second electrode terminal so that there is no discontinuous portion therebetween. The connection portion from the sidewall of the battery can  20  to the second electrode terminal may have a smooth curve. That is, a round region may be provided at the edge circumference of the upper surface  20   a  of the battery can  20 . However, the present disclosure is not limited thereto, and the connecting portion may include at least one corner having a predetermined angle. When the round region is formed at the edge of the upper surface  20   a  of the battery can  20 , among the entire area of the upper surface of the battery can  20  viewed from a position above the cylindrical battery  1 , a region occupied by the terminal  40  and the insulating gasket  50  and the entire region except for the round region may function as a second electrode terminal having a polarity opposite to the terminal  40 . 
     Referring to  FIGS. 7 and 8 , the first current collector  60  is coupled to an upper portion of the electrode assembly  10 . In addition, the first current collector  60  is coupled to the terminal  40 . That is, the first current collector  60  electrically connects the first uncoated region  11  of the electrode assembly  10  and the terminal  40 . The first current collector  60  is made of a metal material with conductivity and is connected to the first uncoated region  11 . Although not shown in the drawings, the first current collector  60  may include a plurality of unevenness radially formed on a lower surface thereof. If the unevenness is formed, the unevenness may be pressed into the first uncoated region  11  by pressing the first current collector  60 . 
     A flat portion approximately parallel to the inner surface of the closed portion of the battery can  20  may be formed in at least part of the bottom surface of the terminal  40 , namely the bottom surface of the electric connection portion  42   a  of the terminal insert portion  42 , and the first current collector  60  is coupled to the flat portion. 
     The first current collector  60  is coupled to an end of the first uncoated region  11 . The coupling between the first uncoated region  11  and the first current collector  60  may be performed, for example, by laser welding. The laser welding may be performed by partially melting a base material of the first current collector  60 , or may be performed in a state where a solder for welding is interposed between the first current collector  60  and the first uncoated region  11 . In this case, the solder preferably has a lower melting point than the first current collector  60  and the first uncoated region  11 . 
     The first current collector  60  may be coupled to a coupling surface of the first uncoated region  11 , which is formed by bending an end of the first uncoated region  11  in a direction parallel to the first current collector  60 . The bending direction of the first uncoated region  11  may be, for example, a direction toward the winding center C, namely core, of the electrode assembly  10 . If the first uncoated region  11  has a bent shape as above, the space occupied by the first uncoated region  11  may be reduced, thereby improving energy density. In addition, as the coupling area between the first uncoated region  11  and the first current collector  60  increases, the coupling force may be improved and the resistance may be reduced. 
     An example form of the first current collector  60  of the present disclosure will be described with reference to  FIG. 11  along with  FIGS. 7 and 8 . Referring to  FIG. 11  along with  FIGS. 7 and 8 , the first current collector  60  applied to the present disclosure may include an edge portion  61 , a first uncoated region coupling portion  62 , and a terminal coupling portion  63 . The edge portion  61  is disposed on the electrode assembly  10 . The edge portion  61  may have a substantially rim shape having an empty space S formed therein. In the drawings of the present disclosure, only a case in which the edge portion  61  has a substantially circular rim shape is illustrated, but the present disclosure is not limited thereto. The edge portion  61  may have a substantially rectangular rim shape, a hexagonal rim shape, an octagonal rim shape, or other rim shapes, unlike the illustrated one. 
     The terminal coupling portion  63  may have a diameter substantially equal to or greater than the diameter of the flat portion formed on the bottom surface of the terminal  40  in order to secure a welding area for coupling with the flat portion formed on the bottom surface of the terminal  40 . 
     The first uncoated region coupling portion  62  extends inward from the edge portion  61  and is coupled to the first uncoated region  11 . The terminal coupling portion  63  is spaced apart from the first uncoated region coupling portion  62  and is located inside the edge portion  61 . The terminal coupling portion  63  may be coupled to the terminal  40  by welding. The terminal coupling portion  63  may be located approximately at the center of the inner space, for example, surrounded by the edge portion  61 . The terminal coupling portion  63  may be provided at a location corresponding to the hole formed at the winding center C of the electrode assembly  10 . The terminal coupling portion  63  may be configured to cover the hole formed at the winding center C of the electrode assembly  10  so that the hole formed at the winding center C of the electrode assembly  10  is not exposed out of the terminal coupling portion  63 . If the hole formed at the winding center C of the electrode assembly  10  is covered as above, it is possible to prevent that the separator positioned inside the hole is damaged due to the flow rate of the electrolyte passing through the hole and thus the electrode is leaked. To this end, the terminal coupling portion  63  may have a larger diameter or width than the hole formed at the winding center C of the electrode assembly  10 . 
     The first uncoated region coupling portion  62  and the terminal coupling portion  63  may not be directly connected, but may be disposed to be spaced apart from each other and indirectly connected by the edge portion  61 . Since the first current collector  60  has a structure in which the first uncoated region coupling portion  62  and the terminal coupling portion  63  are not directly connected to each other but are connected through the edge portion  61  as above, when shock and/or vibration occurs at the cylindrical battery  1 , it is possible to disperse the shock applied to the coupling portion between the first uncoated region coupling portion  62  and the first uncoated region  11  and the coupling portion between the terminal coupling portion  63  and the terminal  40 . In the drawings of the present disclosure, only a case in which four first uncoated region coupling portions  62  are provided is illustrated, but the present disclosure is not limited thereto. The number of the first uncoated region coupling portions  62  may be variously determined in consideration of manufacturing difficulty according to the complexity of the shape, electric resistance, the space inside the edge portion  61  considering electrolyte impregnation, and the like. 
     The first current collector  60  may further include a bridge portion  64  extending inward from the edge portion  61  and connected to the terminal coupling portion  63 . At least a part of the bridge portion  64  may have a smaller sectional area compared to the first uncoated region coupling portion  62  and the edge portion  61 . For example, at least a part of the bridge portion  64  may be formed to have a smaller width and/or thickness compared to the first uncoated region coupling portion  62 . In this case, the electric resistance increases in the bridge portion  64 , and thus when a current flows through the bridge portion  64 , the relatively large resistance causes a part of the bridge portion  64  to be melted due to overcurrent heating, which irreversibly blocks the overcurrent. The sectional area of the bridge portion  64  may be adjusted to an appropriate level in consideration of the overcurrent blocking function. 
     The bridge portion  64  may include a taper portion  64   a  whose width is gradually decreased from the inner surface of the edge portion  61  toward the terminal coupling portion  63 . When the taper portion  64   a  is provided, the rigidity of the component may be improved at the connection portion between the bridge portion  64  and the edge portion  61 . When the taper portion  64   a  is provided, in the process of manufacturing the cylindrical battery  1 , for example, a transfer device and/or a worker may easily and safely transport the first current collector  60  and/or a coupled body of the first current collector  60  and the electrode assembly  10  by gripping the taper portion  64   a . That is, when the taper portion  64   a  is provided, it is possible to prevent product defects that may occur by gripping a portion where welding is performed with other components such as the first uncoated region coupling portion  62  and the terminal coupling portion  63 . 
     The first uncoated region coupling portion  62  may be provided in plural. The plurality of first uncoated region coupling portions  62  may be disposed substantially at regular intervals from each other in the extending direction of the edge portion  61 . An extension length of each of the plurality of first uncoated region coupling portions  62  may be substantially equal to each other. The first uncoated region coupling portion  62  may be coupled to the first uncoated region  11  by welding. 
     The terminal coupling portion  63  may be disposed to be surrounded by the plurality of first uncoated region coupling portions  62 . The terminal coupling portion  63  may be coupled to the terminal  40  by welding. The bridge portion  64  may be positioned between a pair of first uncoated region coupling portions  62  adjacent to each other. In this case, the distance from the bridge portion  64  to any one of the pair of first uncoated region coupling portions  62  along the extending direction of the edge portion  61  may be substantially equal to the distance from the bridge portion  64  to the other one of the pair of first uncoated region coupling portions  62  along the extending direction of the edge portion  61 . The plurality of first uncoated region coupling portions  62  may be formed to have substantially the same sectional area. The plurality of first uncoated region coupling portions  62  may be formed to have substantially the same width and thickness. 
     Although not shown in the drawings, the bridge portion  64  may be provided in plural. Each of the plurality of bridge portions  64  may be disposed between a pair of first uncoated region coupling portions  62  adjacent to each other. The plurality of bridge portions  64  may be disposed substantially at regular intervals to each other in the extending direction of the edge portion  61 . A distance from each of the plurality of bridge portions  64  to one of the pair of first uncoated region coupling portions  62  adjacent to each other along the extending direction of the edge portion  61  may be substantially equal to a distance from each of the plurality of the bridge portion  64  to the other first uncoated region coupling portion  62 . 
     In the case where the first uncoated region coupling portion  62  and/or the bridge portion  64  is provided in plural as described above, if the distance between the first uncoated region coupling portions  62  and/or the distance between the bridge portions  64  and/or the distance between the first uncoated region coupling portion  62  and the bridge portion  64  is uniformly formed, a current flowing from the first uncoated region coupling portion  62  toward the bridge portion  64  or a current flowing from the bridge portion  64  toward the first uncoated region coupling portion  62  may be smoothly formed. 
     Meanwhile, the first current collector  60  and the first uncoated region  11  may be coupled by welding. In this case, for example, laser welding, ultrasonic welding, spot welding, or the like may be applied. Another example form of the first current collector  60  of the present disclosure will be described with reference to  FIG. 12  along with  FIGS. 7 and 8 . Referring to  FIG. 12  along with  FIGS. 7 and 8 , the bridge portion  64  may include a notching portion N formed to partially reduce a sectional area of the bridge portion  64 . The sectional area of the notching portion N may be adjusted, for example, by partially reducing the width and/or thickness of the bridge portion  64 . When the notching portion N is provided, electric resistance is increased in the region where the notching portion N is formed, thereby enabling rapid current interruption when overcurrent occurs. 
     In the case where the bridge portion  64  includes the taper portion  64   a , the notching portion N may be located closer to the taper portion  64   a  than the terminal coupling portion  63 . Heat is generated relatively more in the narrowest part of the taper portion  64   a , and thus the notching portion N adjacent to the taper portion  64   a  may quickly cut off the overcurrent. 
     Meanwhile, the notching portion N is preferably provided in a region corresponding to the welding target region of the electrode assembly  10  described above in order to prevent foreign substances such as welding spatters generated during rupturing from flowing into the electrode assembly  10 . This is because, in this region, the first uncoated region  11  maintains the maximum number of overlapping layers of segments and thus the overlapped segments may function as a mask. For example, the notching portion N may be provided at approximately the center in the radial direction of the electrode assembly  10 . 
     Referring to  FIGS. 6 to 8 , the insulator  70  is provided between a top end of the electrode assembly  10  and the inner surface of the battery can  20  or between the first current collector  60  coupled to the upper portion of the electrode assembly  10  and the inner surface of the closed portion of the battery can  20 . The insulator  70  prevents contact between the first uncoated region  11  and the battery can  20  and/or contact between the first current collector  60  and the battery can  20 . The insulator  70  may also be interposed between a top end of the outer circumferential surface of the electrode assembly  10  and the sidewall of the battery can  20 . That is, the insulator  70  may also be interposed between the uncoated region  11  and the sidewall of the battery can  20 . The first current collector  60  may be a plate extending completely across the top of the outer circumferential surface of the electrode assembly  10 . However, the present disclosure is not limited thereto, and the first current collector  60  may be formed to extend across the top of the outer circumferential surface of the electrode assembly  10  only partially. 
     If the cylindrical battery  1  according to an embodiment of the present disclosure includes the insulator  70 , the terminal insert portion  42  of the terminal  40  is coupled to the first current collector  60  or the first uncoated region  11  through the insulator  70 . The hole formed in the insulator  70  may be formed at a location corresponding to the hole formed at the winding center C of the electrode assembly  10 . In addition, the hole formed in the insulator  70  may be formed at a location corresponding to the terminal coupling portion  63  of the first current collector  60 . 
     Meanwhile, if the welding portion between the terminal  40  and the terminal coupling portion  63  of the first current collector  60  is located inside the hole formed at the winding center C of the electrode assembly  10 , the electrode assembly  10  may be damaged. In order to prevent this, the flat portion formed at the lower end of the terminal  40  coupled to the terminal coupling portion  43  may be located substantially at the same height as the lower surface of the insulator  70  or located higher. In this case, the welding portion between the terminal  40  and the first current collector  60  is located outside the hole formed at the winding center C of the electrode assembly  10 . 
     In consideration of this, the thickness of the insulator  70  may have a thickness substantially equal to or greater than the distance from the inner surface of the closed portion of the battery can  20  to the flat portion provided at the lower end of the terminal  40 . Meanwhile, the insulator  70  may have a thickness corresponding to the distance between the inner surface of the closed portion of the battery can  20  and the first current collector  60  by filling the space between the inner surface of the closed portion of the battery can  20  and the first current collector  60  along the height direction so that a space where the electrode assembly  10  can move is not generated. 
     In another aspect, the upper surface of the insulator  70  may be in contact with the inner surface of the closed portion of the battery can  20 , and the lower surface of the insulator  70  may be in contact with the upper surface of the first current collector  60 . 
     Referring to  FIG. 13 , the second current collector  80  is disposed below the electrode assembly  10 . In addition, the second current collector  80  may be configured to electrically connect the second uncoated region  12  of the electrode assembly  10  and the battery can  20 . The second current collector  80  is made of a metal material with conductivity and is connected to the second uncoated region  12 . In addition, the second current collector  80  is electrically connected to the battery can  20 . The second current collector  80  may be interposed and fixed between the inner surface of the battery can  20  and the sealing gasket  90 . More specifically, the second current collector  80  may be interposed between the lower surface of the beading portion  21  of the battery can  20  and the sealing gasket  90 . However, the present disclosure is not limited thereto. Alternatively, the second current collector  80  may be welded to the inner wall surface of the battery can  20  in a region where the beading portion  21  is not formed. 
     Although not shown in the drawings, the second current collector  80  may include a plurality of unevenness radially formed on one surface thereof. If the unevenness is formed, the unevenness may be pressed into the second uncoated region  12  by pressing the second current collector  80 . 
     The second current collector  80  is coupled to an end of the second uncoated region  12 . The coupling between the second uncoated region  12  and the second current collector  80  may be performed, for example, by laser welding. The laser welding may be performed by partially melting a base material of the second current collector  80 , or may be performed in a state where a solder for welding is interposed between the second current collector  80  and the second uncoated region  12 . In this case, the solder preferably has a lower melting point than the second current collector  80  and the second uncoated region  12 . 
     The second current collector  80  may be coupled to a coupling surface of the second uncoated region  12 , which is formed by bending an end of the second uncoated region  12  in a direction parallel to the second current collector  80 . The bending direction of the second uncoated region  12  may be, for example, a direction toward the winding center C, namely the core, of the electrode assembly  10 . If the second uncoated region  12  has a bent shape as above, the space occupied by the second uncoated region  12  may be reduced, thereby improving energy density. In addition, as the coupling area between the second uncoated region  12  and the second current collector  80  increases, the coupling force may be improved and the resistance may be reduced. 
     Referring to  FIG. 15 , an example form of the second current collector  80  of the present disclosure is shown. Referring to  FIG. 15  along with  FIG. 13 , the second current collector  80  electrically connects the electrode assembly  10  and the battery can  20 . 
     The second current collector  80  may include a support portion  81  disposed below the electrode assembly  10 , a second uncoated region coupling portion  82  extending from the support portion  81  approximately along the radial direction of the electrode assembly  10  and coupled to the second uncoated region  12 , and a can coupling portion  83  extending from the support portion  81  approximately along the radial direction of the electrode assembly  10  and coupled to the inner surface of the battery can  20 . The second uncoated region coupling portion  82  and the can coupling portion  83  are indirectly connected through the support portion  81 , and are not directly connected to each other. Therefore, when an external shock is applied to the cylindrical battery  1  of the present disclosure, it is possible to minimize the possibility of damage to the coupling portion of the second current collector  80  and the electrode assembly  10  and the coupling portion of the second current collector  80  and the battery can  20 . However, the second current collector  80  of the present disclosure is not limited to the structure where the second uncoated region coupling portion  82  and the can coupling portion  83  are only indirectly connected. For example, the second current collector  80  may have a structure that does not include the support portion  81  for indirectly connecting the second uncoated region coupling portion  82  and the can coupling portion  83  and/or a structure in which the second uncoated region  12  and the can coupling portion  83  are directly connected to each other. 
     The support portion  81  and the second uncoated region coupling portion  82  are disposed below the electrode assembly  10 . The second uncoated region coupling portion  82  is coupled to the second uncoated region  12  of the electrode assembly  10 . In addition to the second uncoated region coupling portion  82 , the support portion  81  may also be coupled to the second uncoated region  12 . The second uncoated region coupling portion  82  and the second uncoated region  12  may be coupled by welding. The support portion  81  and the second uncoated region coupling portion  82  are located higher than the beading portion  21  when the beading portion  21  is formed on the battery can  20 . 
     The support portion  81  has a current collector hole  80   a  formed at a location corresponding to the hole formed at the winding center C of the electrode assembly  10 . The hole of the electrode assembly  10  and the current collector hole  80   a  communicating with each other may function as a passage for inserting a welding rod for welding between the terminal  40  and the terminal coupling portion  63  of the first current collector  60  or for irradiating a laser beam. The current collector hole  80   a  may have a diameter substantially equal to or greater than the hole formed at the winding center C of the electrode assembly  10 . When the second uncoated region coupling portion  82  is provided in plural, the plurality of second uncoated region coupling portions  82  may have a shape extending approximately radially from the support portion  81  of the second current collector  80  toward the sidewall of the battery can  20 . Each of the plurality of second uncoated region coupling portions  82  may be positioned to be spaced apart from each other along the periphery of the support portion  81 . Meanwhile, in order to secure coupling force and reduce electrical resistance by increasing the coupling area between the second current collector  80  and the electrode assembly  10 , not only the second uncoated region coupling portion  82  but also the support portion  81  may be coupled to the second uncoated region  12 . At least a part of the second uncoated region  12  may be formed in a bent shape such that an end thereof is substantially parallel to the second uncoated region coupling portion  82 . In this case, the second uncoated region  12  may be bent toward the winding center C of the electrode assembly  10 , for example. If the end of the second uncoated region  12  is formed as above and coupled to the second uncoated region coupling portion  82  in a state of being parallel to the second uncoated region coupling portion  82 , the coupling area is increased, thereby improving coupling force and reducing electric resistance. In addition, by minimizing the total height of the electrode assembly  10 , the energy density may be improved. Meanwhile, the bent end of the second uncoated region  12  may be overlapped in multiple layers. If the second uncoated region  12  may be overlapped in multiple layers, the second uncoated region coupling portion  82  of the second current collector  80  may be coupled to a region where the second uncoated region  12  is bent and overlapped in multiple layers. 
     The can coupling portion  83  may be provided in plural. In this case, the plurality of can coupling portions  83  may have a shape extending approximately radially from the center of the second current collector  80  toward the sidewall of the battery can  20 . Accordingly, the electrical connection between the second current collector  80  and the battery can  20  may be made at a plurality of points. Since the coupling for electrical connection is made at a plurality of points, the coupling area may be maximized, thereby minimizing electric resistance. The plurality of can coupling portions  83  may be positioned to be spaced apart from each other along the periphery of the support portion  81 . At least one can coupling portion  83  may be positioned between the second uncoated region coupling portions  82  adjacent to each other. The plurality of can coupling portions  83  may be coupled to, for example, the beading portion  21  in the inner surface of the battery can  20 . The can coupling portions  83  may be coupled, particularly, to the lower surface of the beading portion  21 . If this structure is applied to the cylindrical battery  1  of the present disclosure, the can coupling portion  83  may be naturally placed on the lower surface of the beading portion  21  through the process of accommodating the electrode assembly  10  coupled with the second current collector  80  into the battery can  20 . Therefore, the battery can  20  and the second current collector  80  may be welded easily. The welding for bonding the battery can  20  and the current collector  80  may use, for example, laser welding, ultrasonic welding, or spot welding. By coupling the can coupling portion  83  on the beading portion  21  by welding in this way, the resistance level may be limited to about 4 milliohms or less, and above about 0.5 milliohms. In addition, as the lower surface of the beading portion  21  has a shape extending in a direction approximately parallel to the upper surface of the battery can  20 , namely in a direction approximately perpendicular to the sidewall of the battery can  20 , and the can coupling portion  83  also has a shape extending in the same direction, namely in the radial direction and the circumferential direction, the can coupling portion  83  may be stably in contact with the beading portion  21 . In addition, as the can coupling portion  83  is stably in contact with the flat portion of the beading portion  21 , the two components may be welded smoothly, thereby improving the coupling force between the two components and minimizing the increase in resistance at the coupling portion. 
     The can coupling portion  83  may include a contact portion  83   a  coupled onto the inner surface of the battery can  20  and a connection portion  83   b  for connecting the support portion  81  and the contact portion  83   a.    
     The contact portion  83   a  is coupled onto the inner surface of the battery can  20 . In the case where the beading portion  21  is formed on the battery can  20 , the contact portion  83   a  may be coupled onto the beading portion  21  as described above. More specifically, the contact portion  83   a  may be electrically coupled to the flat portion formed at the lower surface of the beading portion  21  formed on the battery can  20 , and may be interposed between the lower surface of the beading portion  21  and the sealing gasket  90 . In this case, for stable contact and coupling, the contact portion  83   a  may have a shape extending from the beading portion  21  by a predetermined length along the circumferential direction of the battery can  20 . 
     Meanwhile, the maximum distance from the center of the second current collector  80  to the end of the second uncoated region coupling portion  82  along the radial direction of the electrode assembly  10  is preferably substantially equal to or smaller than the inner diameter of the battery can  20  in a region where the beading portion  21  is formed, namely the minimum inner diameter of the battery can  20 . This is to prevent interference from occurring between the second current collectors  80  by the beading portion  21  during the sizing process for compressing the battery can  20  along the height direction, and thus to prevent the electrode assembly  10  from being pressed by the second current collector. 
     Referring to  FIGS. 16 to 19 , the structure of the electrode assembly  10  will be described in more detail. In the following description, the first electrode will be described as an example among the first and second electrodes described above, but the structure of the first electrode may be equally applied to the second electrode. 
     Referring to  FIGS. 16 and 17 , the first electrode  110  includes a first electrode current collector  111  having a sheet shape made of a conductive foil, a first active material layer  112  formed on at least one surface of the first electrode current collector  111 , and a first uncoated region  11  formed by not coating an active material at a long side end of the first electrode current collector  111 . 
     Preferably, the first uncoated region  11  may include a plurality of notched segments  11   a . The plurality of segments  11   a  constitutes a plurality of groups, and the segments  11   a  included in each group may be identical in terms of the height (length in the Y-axis direction) and/or the width (length in the X-axis direction) and/or the separation pitch. The number of segments  11   a  belonging to each group may be increased or decreased than shown in the drawings. The segment  11   a  has a geometric shape in which at least one straight line and/or at least one curve are combined. Preferably, the segment  11   a  may have a trapezoidal shape, and may be deformed into a rectangular, parallelogram, semicircular or a semi-elliptical shape. 
     Preferably, the height of the segment  11   a  may be increased stepwise along one direction parallel to the winding direction of the electrode assembly  10 , for example, from the core toward the outer circumference. Also, a core-side uncoated region  11 - 1  adjacent to the core of the electrode assembly  10  may not include the segment  11   a , and the core-side uncoated region  11 - 1  may have a lower height than the uncoated region of other regions. In addition, an outer circumferential uncoated region  11 - 2  adjacent to the outer circumference of the electrode assembly  10  may not include the segment  11   a , and the outer circumferential uncoated region  11 - 2  may have a lower height than other uncoated regions. 
     Optionally, the first electrode  110  may include an insulation coating layer E that covers a boundary between the active material layer  112  and the first uncoated region  11 . The insulation coating layer E includes a polymer resin having an insulation property, and may optionally further include an inorganic filler. The insulation coating layer E may function to prevent the end of the active material layer  112  from contacting an active material layer having an opposite polarity facing through the separator, and to structurally support the bending of the segment  11   a . To this end, when the first electrode  110  is wound to form the electrode assembly  10 , at least a part of the insulation coating layer E is preferably exposed from the separator to the outside. 
     Referring to  FIGS. 16 and 17 , the electrode assembly  10  may be manufactured by the winding method described above with reference to  FIG. 2 . For convenience of explanation, the protruding structures of the uncoated regions  11 ,  12  extending out of the separator are illustrated in detail, and the winding structures of the first electrode, the second electrode and the separator are not illustrated. The first uncoated region  11  protruding upward extends from the first electrode, and the second uncoated region  12  protruding downward extends from the second electrode. 
     The pattern in which the heights of the uncoated regions  11 ,  12  change are schematically shown. That is, the heights of the uncoated regions  11 ,  12  may vary irregularly depending on the location where the cross section is cut. For example, if a side portion of the trapezoidal segment  11   a  is cut, the height of the uncoated region in the cross section is lower than the height of the segment  11   a . Therefore, it should be understood that the heights of the uncoated regions  11 ,  12  shown in the drawings showing the cross section of the electrode assembly  10  correspond to the average of the heights of the uncoated regions included in each winding turn. 
     Referring to  FIGS. 16 to 19 , the uncoated regions  11 ,  12  may be bent along the radial direction of the electrode assembly  10 , for example from the outer circumference toward the core. In the uncoated regions  11 ,  12 , the region where the bending occurs is indicated by a dotted line box in  FIG. 17 . When the uncoated regions  11 ,  12  are bent, bent surfaces  102  are formed on the upper and lower portions of the electrode assembly  10  as segments adjacent in the radial direction are overlapped in multiple layers. At this time, the core-side uncoated region  11 - 1  ( FIG. 16 ) is not bent due to its low height, and the height h of the segment  11   a , which is bent at the innermost side, is equal to or smaller than the radial length R of the winding area formed by the core-side uncoated region  11 - 1  without a segment structure. Therefore, the hole formed at the core C of the electrode assembly  10  is not closed. The hole is not closed, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency may be improved. In addition, by inserting a welding tool through the hole, it is possible to easily weld the terminal  40  and the first current collector  60  (see  FIG. 7 ). 
     Meanwhile, the cylindrical battery  1  according to an embodiment of the present disclosure has a structure in which the cap  30  does not necessarily have polarity, as described above. When the cap  30  has no polarity, the second current collector  80  is connected to the sidewall of the battery can  20 , and thus the outer surface  20   a  of the closed portion of the battery can  20  has a polarity opposite to the terminal  40 . Therefore, when a plurality of cylindrical batteries  1  are to be connected in series and/or in parallel, the wiring work such as connecting a bus bar may be formed at the upper portion of the cylindrical battery  1  using the terminal  40  and the outer surface  20   a  of the closed portion of the battery can  20 . Through this, energy density may be improved by increasing the number of cylindrical batteries  1  that can be mounted in the same space, and electrical wiring may be easily performed. That is, in the cylindrical battery  1  according to the present disclosure, the terminal  40  exposed out of the battery can  20  may function as a first electrode terminal, and the region of the outer surface  20   a  of the closed portion of the battery can  20  occupied by the exposed surface approximately parallel to the upper surface of the first electrode terminal may function as a second electrode terminal. Accordingly, when the plurality of cylindrical batteries  1  are to be electrically connected, a first bus bar may be coupled to the upper surface of the terminal  40  exposed out of the battery can  20 , and a second bus bar may be coupled to the region of the outer surface  20   a  of the closed portion of the battery can  20  occupied by the exposed surface approximately parallel to the upper surface of the first electrode terminal. 
     Referring to  FIG. 20 , a plurality of cylindrical batteries  1  may be connected in series and in parallel on top of the cylindrical batteries  1  using a bus bar  150 . The number of cylindrical batteries  1  may be increased or decreased in consideration of the capacity of the battery pack. 
     In each cylindrical battery  1 , the terminal  40  may have a positive polarity and the outer surface  20   a  of the closed portion of the battery can  20  may have a negative polarity, or vice versa. 
     Preferably, the plurality of cylindrical batteries  1  may be arranged in a plurality of columns and rows. Columns are provided in a vertical direction with respect to the ground, and rows are provided in a left and right direction with respect to the ground. In addition, in order to maximize space efficiency, the cylindrical batteries  1  may be arranged in a closest packing structure. The closest packing structure is formed when an equilateral triangle is formed by connecting the centers of the terminal exposing portions  41  of the terminal  40  exposed out of the battery can  20  to each other. Preferably, the bus bar  150  may be disposed on the plurality of cylindrical batteries  1 , more preferably between neighboring rows. Alternatively, the bus bar  150  may be disposed between neighboring rows. 
     Preferably, the bus bar  150  connects the cylindrical batteries  1  arranged in the same column in parallel to each other, and connects the cylindrical batteries  1  arranged in two neighboring columns in series with each other. 
     Preferably, the bus bar  150  may include a body portion  151 , a plurality of first bus bar terminals  152  and a plurality of second bus bar terminals  153  for serial and parallel connection. 
     The body portion  151  may extend between terminals  40  of neighboring cylindrical batteries  70 , preferably between rows of the cylindrical batteries  1 . Alternatively, the body portion  151  may extend along the row of the cylindrical batteries  1  and may be regularly bent like a zigzag shape. 
     The plurality of first bus bar terminals  152  may protrusively extend from one side of the body portion  151  toward the terminal  40  of each cylindrical battery  1  and may be electrically coupled to the terminal  40 . The electrical connection between the first bus bar terminal  152  and the terminal  40  may be accomplished by laser welding, ultrasonic welding, or the like. Also, the plurality of second bus bar terminals  153  may be electrically coupled to the outer surface  20   a  of each cylindrical battery  1  from the other side of the body portion  151 . The electrical connection between the second bus bar terminal  153  and the outer surface  20   a  may be achieved by laser welding, ultrasonic welding, or the like. 
     Preferably, the body portion  151 , the plurality of first bus bar terminals  152  and the plurality of second bus bar terminals  153  may be made of one conductive metal plate. The metal plate may be, for example, an aluminum plate or a copper plate, but the present disclosure is not limited thereto. In a modified example, the body portion  151 , the plurality of first bus bar terminals  152  and the second bus bar terminals  153  may be manufactured as separate pieces and then coupled to each other by welding or the like. 
     In the cylindrical battery  1  according to the present disclosure, since the terminal  40  having a positive polarity and the outer surface  20   a  of the closed portion of the battery can  20  having a negative polarity are located in the same direction, the cylindrical batteries  1  may be electrically connected easily using the bus bar  150 . 
     In addition, since the terminal  40  of the cylindrical battery  1  and the outer surface  20   a  of the closed portion of the battery can  20  have large areas, the coupling area of the bus bar  150  may be sufficiently secured to sufficiently lower the resistance of the battery pack including the cylindrical battery  1 . 
     Referring to  FIGS. 21 to 23 , in the cylindrical battery  1 , the diameter (E 1 ) of the electrode terminal  40  and the width (E 2 ) of the outer surface  20   a  having a ring shape may be adaptively adjusted in consideration of the dimensions of the contact areas of the bus bar terminals  152 ,  153 . 
     Here, the width (E 2 ) of the outer surface  20   a  of the closed portion of the battery can  20  is the width of the exposed surface parallel to the surface of the electrode terminal  40 . Specifically, the width (E 2 ) of the outer surface  20   a  is defined as the width of a line segment connecting two points where the straight line (Li) drawn in the radial direction from the center C of the electrode terminal  40  intersects inner and outer boundaries of the outer surface  20 . The width (E 2 ) of the outer surface  20   a  is the width of the flat exposed surface in the entire upper surface of the battery can  20 , excluding the round region R existing at the edge of the closed portion of the battery can  20  and the gasket exposing portion  51  of the insulating gasket  50 . 
     The closed portion of the battery can  20  may be divided into the terminal  40 , the gasket exposing portion  51  of the insulating gasket  50 , and the round region R formed at the edge of the outer surface  20   a  of the closed portion, when viewed from above. The round region R is a processing region (see  FIGS. 7 and 8 ) for smoothly connecting the closed portion of the battery can  20  and the sidewall of the battery can  20 , and has a predetermined width (R d ) on a plane. 
     The first bus bar terminal  152  of the bus bar  150  is branched to one side different from the traveling direction of the body portion  151  and is electrically coupled to the terminal exposing portion  41  of the terminal  40 . At this time, the electrode terminal  40  and the first bus bar terminal  152  form a first overlapping region (marked by hatching) on a plane, and the first overlapping region has a first width (W 1 ). Here, the first overlapping region is a region where the electrode terminal  40  and the first bus bar terminal  152  overlap on a plane. 
     The first width (W 1 ) is defined as a maximum value among distances between any two points selected at the edge of the first overlapping region. The definition of the first width (W 1 ) is applied equally to the case where the first overlapping region includes the center of the terminal  40  ( FIG. 22 ) and the case where the first overlapping region does not include the center of the terminal  40  ( FIG. 23 ). Referring to  FIGS. 22 and 23 , the distance indicated by W 1  corresponds to a maximum value among distances between any two points selected at the edge of the first overlapping region. 
     The second bus bar terminal  153  of the bus bar  150  extends in a direction opposite to the first bus bar terminal  152  based on the traveling direction of the body portion  151  and is electrically coupled to the outer surface  20   a  of the closed portion of the battery can  20 . At this time, the second bus bar terminal  153  and the outer surface  20   a  form a second overlapping region (marked by hatching) on a plane, and the second overlapping region has a second width (W 2 ). Here, the second overlapping region is a region where the outer surface  20   a  and the second bus bar terminal  153  overlap on a plane. 
     The second width (W 2 ) is defined as a maximum value among distances between two points where each straight line meets an edge of the second overlapping region, when a plurality of straight lines (L 2 ) are drawn from the center C of the terminal exposing portion  41  of the terminal  40  to pass through the second overlapping region. 
     Preferably, the diameter (E 1 ) of the terminal exposing portion  41  of the terminal  40  must be at least equal to or greater than the first width (W 1 ) of the first bus bar terminal  152 . This is because the first overlapping region of the first bus bar terminal  152  and the terminal exposing portion  41  must not deviate to the outside of the terminal exposing portion  41  on a plane. In addition, the diameter (E 1 ) of the terminal  40  may be increased to the maximum until the distance between the boundary of the electrode terminal  40  and the second bus bar terminal  153  corresponds to the width (G) of the gasket exposing portion  51  of the insulating gasket  50 . Therefore, the maximum value of the diameter (E 1 ) of the terminal exposing portion  41  of the terminal  40  is ‘D−2*R d −2*G−2*W 2 ’. 
     Preferably, the width (E 2 ) of the outer surface  20   a  is a factor dependent on the diameter (E 1 ) of the terminal exposing portion  41 , and must be at least equal to or greater than the second width (W 2 ) of the second bus bar terminal  153 . Only in this case, an overlapping region of the second bus bar terminal  153  and the outer surface  20   a  may be formed. In addition, the width (E 2 ) of the outer surface  20   a  may be increased up to 50% of ‘D−2*R d −2*G−E 1 ’, which is a value obtained by subtracting the diameter (E 1 ) of the terminal exposing portion  41 , the width ( 2 *G) occupied by the gasket exposing portion  51  and the width of the round region ( 2 *Ra) from the outer diameter (D) of the battery can  20 . 
     In conclusion, in the cylindrical battery  1  according to the present disclosure, the diameter (E 1 ) of the terminal exposing portion  41  of the terminal  40  and the width (E 2 ) of the outer surface  20   a  are preferably designed to satisfy the following formulas. 
         W   1   ≤E   1   ≤D− 2 R   d −2 G− 2 W   2  
 
         E   2 =0.5*( D− 2 R   d −2 G−E   1 )
 
     (E 1 : diameter of the terminal  40  exposed out of the battery can  20 , E 2 : width of the exposed surface of the outer surface  20   a  of the closed portion of the battery can  20  approximately parallel to the upper surface of the terminal  40 , D: outer diameter of the battery can  20 , R d : width of the round region R measured on a plane, G: exposure width of the insulating gasket  50  exposed out of the terminal  40  located outside the battery can  20 , W 1 : width of the first bus bar terminal  152 , W 2 : width of the second bus bar terminal  153 ) 
     In a specific example, when D is 46 mm, W 1  and W 2  are 6 mm, G is 0.5 mm and R d  is 1 mm, the diameter (E 1 ) of the terminal exposing portion  41  is 6 mm to 31 mm and the width (E 2 ) of the outer surface  20   a  is 6 mm and 18.5 mm. 
     As another example, when D is 46 mm, W 1  and W 2  are 6 mm, G is 0.5 mm and R d  is 1.5 mm, the diameter (E 1 ) of the terminal exposing portion  41  is 6 mm to 30 mm and the width (E 2 ) of the outer surface  20   a  is 6 mm and 18 mm. 
     Meanwhile, the area occupied by the terminal exposing portion  41  (the area occupied by the first electrode terminal) is preferably about 2% to 30% of the area of the exposed surface of the outer surface  20   a  of the closed portion of the battery can  20  approximately parallel to the upper surface of the terminal  40  (the area occupied by the second electrode terminal). This is due to the width of the bus bar applied considering that a current in the level of about 300 A flows. If the ratio of the area occupied by the terminal exposing portion  41  to the area occupied by the outer surface  20   a  exceeds the upper limit of the above range, the area may not be sufficient to connect the second bus bar terminal  153  to the outer surface  20   a . Conversely, if the ratio of the area occupied by the terminal exposing portion  41  to the area occupied by the outer surface  20   a  does not reach the lower limit of the above range, the area may not be sufficient in connecting the first bus bar terminal  153  to the terminal exposing portion  41 . 
     Meanwhile, the width (R d ) occupied by the gasket exposing portion  51  may be in the range of about 0.1 mm to 3.0 mm, preferably about 0.1 mm to 1.0 mm. If the width (R d ) occupied by the gasket exposing portion  51  is too large, the connection area of the bus bar terminals  152 ,  153  may not be sufficiently secured. Conversely, if the width (R d ) occupied by the gasket exposing portion  51  is too small, for example if charging and discharging is performed at a high C-rate of 300 A or more, the electrical insulation between the terminal  40  and the outer surface  20   a  of the battery can  20  may be broken on a plane. 
     Preferably, the cylindrical battery may be, for example, a cylindrical battery whose form factor ratio (defined as a value obtained by dividing the diameter of the cylindrical battery by height, namely a ratio of height (H) to diameter (Φ) is greater than about 0.4. 
     Here, the form factor means a value indicating the diameter and height of a cylindrical battery. The cylindrical battery according to an embodiment of the present disclosure may be, for example, a 46110 cell, a 48750 cell, a 48110 cell, a 48800 cell, or a 46800 cell. In the numerical value representing the form factor, first two numbers indicate the diameter of the cell, next two numbers indicate the height of the cell, and the last number “0” indicates that the cross-section of the cell is circular. 
     A battery according to an embodiment of the present disclosure may be a cylindrical battery having an approximately cylindrical shape, whose diameter is approximately 46 mm, height is approximately 110 mm, and form factor ratio is 0.418. 
     A battery according to another embodiment may be a cylindrical battery having a substantially cylindrical shape, whose diameter is about 48 mm, height is about 75 mm, and form factor ratio is 0.640. 
     A battery according to still another embodiment may be a cylindrical battery having an approximately cylindrical shape, whose diameter is approximately 48 mm, height is approximately 110 mm, and form factor ratio is 0.418. 
     A battery according to still another embodiment may be a cylindrical battery having an approximately cylindrical shape, whose diameter is approximately 48 mm, height is approximately 80 mm, and form factor ratio is 0.600. 
     A battery according to still another embodiment may be a cylindrical battery having an approximately cylindrical shape, whose diameter is approximately 46 mm, height is approximately 80 mm, and form factor ratio is 0.575. 
     Conventionally, batteries having a form factor ratio of about 0.4 or less have been used. That is, conventionally, for example, 18650 cell, 21700 cell, etc. were used. The 18650 cell has a diameter of approximately 18 mm, height of approximately 65 mm, and a form factor ratio of 0.277. The 21700 cell has a diameter of approximately 21 mm, a height of approximately 70 mm, and a form factor ratio of 0.300. 
     As described above, the cylindrical battery  1  of the present disclosure has a structure in which resistance is minimized by expanding a contact area between components, multiplexing current path, minimizing a current path length, and the like. After the product is finally manufactured, the AC resistance of the cylindrical battery  1  measured using a resistance measuring instrument between the positive electrode and the negative electrode, namely between the upper surface of the terminal  40  and the outer surface  20   a  of the closed portion of the battery can  20 , may be about 4 milliohms (mohm) or less, but greater than 0.5 milliohms (mohm). 
     Referring to  FIG. 24 , a battery pack  3  according to an embodiment of the present disclosure includes a secondary battery assembly in which a plurality of cylindrical batteries  1  according to an embodiment of the present disclosure as described above are electrically connected, and a pack housing  2  for accommodating the secondary battery assembly. In  FIG. 24  of the present disclosure, components for electrical connection such as a bus bar, a cooling unit and a power terminal are not depicted for convenience of illustration. The electrical connection structure of the plurality of batteries  1  for manufacturing the battery pack  3  has been exemplarily described above with reference to  FIGS. 20 and 21 . 
     Referring to  FIG. 25 , a vehicle  5  according to an embodiment of the present disclosure may be, for example, an electric vehicle, a hybrid electric vehicle or a plug-in vehicle, and includes the battery pack  3  according to an embodiment of the present disclosure. The vehicle  5  includes a four-wheeled vehicle and a two-wheeled vehicle. The vehicle  5  operates by receiving a power from the battery pack  3  according to an embodiment of the present disclosure. 
     The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating example embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description.