Secondary battery

Abstract

The present invention relates to a secondary battery. The secondary battery according to the present invention includes an electrode assembly in which electrodes and separators are alternately stacked and wound, a cylindrical can having an opening at the top and a receiving portion for receiving the electrode assembly, and a cap assembly for covering the opening of the can. The cap assembly includes a safety vent having a notch formed therein that ruptures when internal pressure of the battery increases, the notch having a circular shape in a plan view. The electrode assembly includes electrode tabs connected to the electrodes. The safety vent is connected to the electrode tabs and external terminals, and the electrode tabs and the external terminals are connected to different sides of the safety vent, either inside or outside, of the notch in a plan view.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0098168 filed on August 5, 2020 and Korean Patent Application No. 10-2021-0102809 filed on August 4, 2021, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a secondary battery. [Background technology]

[0003] Unlike primary batteries, secondary batteries are rechargeable and have the potential to be small and have large capacity, and thus have been much researched and developed in recent years. As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is rapidly increasing.

[0004] Secondary batteries are classified into coin type batteries, cylindrical batteries, square batteries, and pouch type batteries according to the shape of the battery case. In secondary batteries, the electrode assembly installed inside the battery case is a power generating element capable of charging and discharging, which is made of a laminated structure of electrodes and separators.

[0005] Electrode assemblies can be roughly classified into a jelly-roll type in which a separator is interposed between a sheet-like positive electrode and a negative electrode coated with an active material and the electrode is wound up; a stack type in which a number of positive electrodes and negative electrodes are sequentially stacked with a separator interposed therebetween; and a stack / folded type in which a stack type unit cell is wound up as a long separating film.

[0006] Among these, the jelly-roll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per weight, and is therefore widely used.

[0007] In a conventional cylindrical secondary battery including a jelly-roll type electrode assembly, a notch is provided at the bottom of the top cap assembly to facilitate venting of gas inside the battery when an event occurs that increases the internal pressure.

[0008] In the case of a cylindrical secondary battery without a top cap or a separate CID (current interrupt device), the positive electrode tab of the battery is welded to the lower part inside the cutout, and the terminal of the pack or application is welded to the upper part to allow current to flow.

[0009] This current path configuration has a problem in that even if an event occurs inside the battery and venting occurs, current continues to be applied, which can lead to an explosion.

[0010] Meanwhile, in the case of a cylindrical secondary battery with a conventional top cap and a separate CID (current interrupt device), the CID (current interrupt device), safety vent, and top cap are sequentially arranged from the bottom to the top of the cylindrical top cap assembly, and the center of the safety vent is bent downward and connected to the top of the CID. When gas is generated inside the battery, the center of the safety vent is inverted upward due to an increase in pressure, and the connection between the CID and the safety vent is released, causing a short circuit; the pressure required for such a short circuit is called the CID short circuit pressure.

[0011] If gas continues to be generated after the CID is short-circuited, the safety vent breaks and releases the internal gas. The pressure at this time is called the venting pressure. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Korean Patent Publication No. 10-2016-0010121 Summary of the Invention [Problem to be solved by the invention]

[0013] One aspect of the present invention is to provide a secondary battery in which current can be cut off when venting occurs due to an internal factor of the battery. [Means for solving the problem]

[0014] A secondary battery according to an embodiment of the present invention includes an electrode assembly in which electrodes and separators are alternately stacked and wound, a cylindrical can having an opening at an upper portion and a receiving portion for receiving the electrode assembly, and a cap assembly for covering the opening of the can, the cap assembly including a safety vent having a notch formed therein that ruptures when an internal pressure of the battery increases, the notch being formed in a circular shape in a plan view, the electrode assembly including an electrode tab connected to the electrode, the safety vent being connected to the electrode tab and an external terminal, and the electrode tab and the external terminal being connected to different sides of the safety vent, either an inner side or an outer side, based on the notch in a plan view.

[0015] Meanwhile, a battery pack according to an embodiment of the present invention may include the secondary battery according to the embodiment of the present invention. Effect of the Invention

[0016] According to the present invention, the electrode tab and the external terminal are connected to different sides, either the inside or the outside, of the notch in a plan view of the safety vent, so that as the internal pressure of the battery increases, the notch bursts, thereby cutting off the current during venting. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing a secondary battery according to one embodiment of the present invention. [Diagram 2] 4 is a cross-sectional view showing a state in which a notch of a safety vent has burst in a secondary battery according to an embodiment of the present invention; FIG. [Diagram 3] 1 is a cross-sectional view showing a cap assembly of a secondary battery according to an embodiment of the present invention. [Figure 4] FIG. 2 is a bottom view showing a safety vent in the secondary battery according to one embodiment of the present invention. [Diagram 5] FIG. 4 is a cross-sectional view showing a secondary battery according to another embodiment of the present invention. [Figure 6] FIG. 11 is a cross-sectional view showing a state in which a notch of a safety vent is ruptured in a secondary battery according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The object, particular advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings. In this specification, when reference numbers are used to designate components in each drawing, it should be noted that the same numbers are used as much as possible for the same components even if they are displayed in different drawings. In addition, the present invention can be realized in various different forms and is not limited to the embodiments described herein. In addition, in describing the present invention, detailed descriptions of related publicly known technologies that may unnecessarily obscure the gist of the present invention will be omitted.

[0019] Secondary battery according to an embodiment FIG. 1 is a cross-sectional view showing a secondary battery according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a state in which a notched portion of a safety vent in the secondary battery according to one embodiment of the present invention has been broken.

[0020] 1 and 2, a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 110 in which electrodes 113 and separators 114 are alternately stacked and wound, an open can 120 in which the electrode assembly 110 is housed, and a cap assembly 130 that covers the opening of the can 120. In addition, the cap assembly 130 includes a safety vent 131 having a notch 131a formed therein that ruptures when the internal pressure of the battery increases.

[0021] The secondary battery 100 according to one embodiment of the present invention will be described in more detail below.

[0022] 1 and 2, the electrode assembly 110 is a power generating element capable of charging and discharging, and has a structure in which electrodes 113 and separators 114 are assembled and stacked alternately. Here, the electrode assembly 110 may be formed in a form in which the electrodes 113 and the separators 114 are assembled alternately and wound up. In this case, the electrode assembly 110 may be wound into a cylindrical shape wound around a central axis.

[0023] The electrodes 113 may include a positive electrode 112 and a negative electrode 111. The separator 114 separates the positive electrode 112 and the negative electrode 111 to electrically insulate them from each other.

[0024] The positive electrode 112 may include a positive electrode current collector and a positive electrode active material provided on one surface of the positive electrode current collector. In this case, the positive electrode 112 may include a positive electrode uncoated portion, which is a region where the positive electrode active material is not laminated.

[0025] The positive electrode current collector may be made of, for example, an aluminum foil.

[0026] The positive electrode active material may be lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or a compound or mixture containing at least one of these.

[0027] The negative electrode 111 may include a negative electrode current collector and a negative electrode active material provided on one surface of the negative electrode current collector. In this case, the negative electrode 111 may include a negative electrode uncoated portion which is a region where the negative electrode active material is not laminated.

[0028] The negative electrode current collector may be, for example, a copper foil made of copper (Cu).

[0029] The negative electrode active material may be, for example, artificial graphite, lithium metal, lithium alloy, carbon, petroleum coke, activated carbon, graphite, silicon compound, tin compound, titanium compound, or an alloy thereof. In this case, the negative electrode active material may further include, for example, non-graphite-based SiO (silica) or SiC (silicon carbide).

[0030] The separator 114 is made of an insulating material and can provide insulation between the positive electrode 112 and the negative electrode 111 .

[0031] The separator 114 may also be, for example, a multilayer film made of microporous polyethylene, polypropylene, or a combination thereof, or a polymer film for a solid polymer electrolyte or a gel-type polymer electrolyte, such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride-hexafluoropropylene copolymer.

[0032] In the secondary battery 100 according to the present invention, the electrode assembly 110 may include an electrode tab 140 connected to an electrode.

[0033] The electrode tab 140 is attached to the electrode 113 and is electrically connected to the electrode 113 .

[0034] The electrode tabs 140 may include a positive electrode tab 141 connected to the positive electrode 112 and a negative electrode tab connected to the negative electrode 111 .

[0035] The positive electrode tab 141 may be formed in the direction in which the cap assembly 130 is positioned, which is the upper direction when referring to FIG.

[0036] The can 120 may be formed in a tubular shape with an opening at the top and a receiving portion 121 for receiving the electrode assembly 110. In this case, the can 120 may be formed in a cylindrical shape, for example.

[0037] The can 120 may be curved on the inside 131b so that the cap assembly 130 can be attached, and may have a beading portion 122 that forms a recess on the outside 131c. In this case, the cap assembly 130 can be seated on the beading portion 122 to cover the opening of the can 120.

[0038] The can 120 may include a crimping portion formed at the top to surround an end of the cap assembly 130. Here, the crimping portion 123 may include an outer periphery formed in the length direction of the can 120 and an upper end portion perpendicular to the length direction of the can 120.

[0039] FIG. 3 is a cross-sectional view showing a cap assembly of a secondary battery according to an embodiment of the present invention, and FIG. 4 is a bottom view showing a safety vent in the secondary battery according to an embodiment of the present invention.

[0040] 1 to 4, a cap assembly 130 may be attached to the top of the can 120 to cover the opening of the can 120.

[0041] The cap assembly 130 may include a safety vent 131 having a notch formed therein that ruptures when the internal pressure of the battery increases, and a gasket 132 that provides sealing and insulation between the safety vent 131 and the can 120.

[0042] The safety vent 131 may be coupled to the electrode tab 140 and the external terminal 150 .

[0043] The cutout portion 131a may be formed in a circular shape in a plan view and in the center of the safety vent 131. That is, the cutout portion 131a may be formed in a circular shape in the center on the bottom view shown in FIG.

[0044] The cutout portion 131a may be formed in the lower surface of the safety vent 131. In this case, the cutout portion 131a may be formed as, for example, a groove having a triangular cross section.

[0045] The distance from the central axis of the safety vent 131 to the notch 131 a may be equal to or less than half the radius of the safety vent 131 .

[0046] The safety vent 131 has a rupture portion R formed along the cutout 131a at the center, and when the internal pressure of the battery is equal to or greater than the venting pressure, the cutout 131a ruptures and the rupture portion R can separate from the safety vent 131. Here, the venting pressure refers to the pressure at which the safety vent 131 ruptures and releases the internal gas as the internal pressure increases due to gas generation inside the battery. Ultimately, when the internal pressure of the battery due to gas generation inside the battery reaches or exceeds the venting pressure, the cutout 131a ruptures and the rupture portion R separates from the safety vent 131, thereby cutting off the current.

[0047] The gasket 132 may be provided along the outer circumferential surface of the safety vent 131 and may surround the edge of the safety vent 131. In this case, the crimping portion 123 of the can 120 may be formed to surround the outer side 131c of the gasket 132 and may provide a seal between the can 120 and the cap assembly 130.

[0048] Meanwhile, the cap assembly 130 of the secondary battery according to an embodiment of the present invention may be composed of the safety vent 131 and the gasket 132 without a CID (Current Interrupt Device) filter and a CID gasket. This allows for simplified components and reduced material costs. As a result, the simplified components have the effect of reducing battery resistance and improving performance.

[0049] On the other hand, the electrode tab 140 and the external terminal 150 may be connected to different sides, that is, the inner side 131b and the outer side 131c, of the cutout portion 131a in a plan view, in the safety vent 131. Here, the electrode tab 140 may be connected to the outer side 131c of the cutout portion 131a in a plan view, in the safety vent 131, and the external terminal 150 may be connected to the inner side 131b of the cutout portion 131a in a plan view, in the safety vent 131.

[0050] In the electrode tab 140 , the positive electrode tab 141 may be provided on the upper side of the electrode assembly 110 and connected to the lower end of the safety vent 131 , and the external terminal 150 may be connected to the upper end of the safety vent 131 .

[0051] In addition, the positive electrode tab 141 may be welded to the lower end of the safety vent 131 , and the external terminal 150 may be welded to the upper end of the safety vent 131 .

[0052] The external terminal 150 may be a connecting conductor for an external pack or application.

[0053] Referring to FIG. 1, the secondary battery 100 according to one embodiment of the present invention configured as described above is configured such that, in a plan view, the safety vent 131 has an external terminal 150 connected to the inner side 131b of the cutout portion 131a and an electrode tab 140 connected to the outer side 131c.

[0054] 2, as the internal pressure increases due to an increase in the internal gas, the notch 131a bursts and vents, thereby cutting off the current. That is, when the notch 131a, which forms a circular notch line in a plan view, bursts, the burst portion R is separated from the safety vent 131, and the electrical connection between the external terminal 150 fixed to the burst portion R, which is the inside 131b of the safety vent 131, and the electrode tab 140 fixed to the outside 131c of the safety vent 131 is released.

[0055] As a result, due to an increase in the internal pressure of the battery, the inner side 131b of the notch 131a connected to the external terminal 150 in the safety vent 131 ruptures during venting, and becomes separated from the outer side 131c of the notch 131a connected to the electrode tab 140, completely cutting off the current, thereby preventing an explosion due to the continuous application of current.

[0056] Secondary battery according to another embodiment Secondary batteries according to other embodiments will now be described.

[0057] FIG. 5 is a cross-sectional view showing a secondary battery according to another embodiment of the present invention, and FIG. 6 is a cross-sectional view showing a state in which a notch of a safety vent in a secondary battery according to another embodiment of the present invention has burst.

[0058] 5 and 6, a secondary battery 200 according to another embodiment of the present invention includes an electrode assembly 110 in which electrodes 113 and separators 114 are alternately stacked and wound, an open can 120 in which the electrode assembly 110 is housed, and a cap assembly 130 that covers the opening of the can 120. In addition, the cap assembly 130 includes a safety vent 131 having a notch 131a formed therein that ruptures when the internal pressure of the battery increases.

[0059] The secondary battery 200 according to the second embodiment of the present invention is different from the secondary battery according to the above-described embodiment in the connection positions of the electrode tabs 240 and the external terminals with the safety vent 131. Therefore, in this embodiment, the contents overlapping with the first embodiment will be omitted or briefly described, and the description will focus on the differences.

[0060] More specifically, the electrode assembly 110 is a power generating element capable of charging and discharging, and has a structure in which electrodes 113 and separators 114 are assembled and stacked alternately. Here, the electrode assembly 110 may be formed in a form in which the electrodes 113 and the separators 114 are assembled and wound alternately. In this case, the electrode assembly 110 may be wound into a cylindrical shape wound around a central axis.

[0061] The electrodes 113 may include a positive electrode 112 and a negative electrode 111. The separator 114 separates the positive electrode 112 and the negative electrode 111 to electrically insulate them from each other.

[0062] In the secondary battery 200 according to the present invention, the electrode assembly 110 may include an electrode tab 240 connected to the electrode 113 .

[0063] The electrode tab 240 is attached to the electrode 113 and is electrically connected to the electrode 113 .

[0064] The electrode tabs 240 may include a positive electrode tab 241 connected to the positive electrode 112 and a negative electrode tab connected to the negative electrode 111 .

[0065] The positive electrode tab 241 may be formed in the direction toward the top, where the cap assembly 130 is positioned.

[0066] The can 120 may be formed in a tubular shape with an opening at the top and a receiving portion 121 for receiving the electrode assembly 110. In this case, the can 120 may be formed in a cylindrical shape, for example.

[0067] The can 120 may be curved on the inside 131b so that the cap assembly 130 can be attached, and may have a beading portion 122 that forms a recess on the outside 131c. In this case, the cap assembly 130 can be seated on the beading portion 122 to cover the opening of the can 120.

[0068] The can 120 may include a crimping portion formed at the top to surround an end of the cap assembly 130. Here, the crimping portion 123 may include an outer periphery formed in the length direction of the can 120 and an upper end portion perpendicular to the length direction of the can 120.

[0069] The cap assembly 130 may be attached to the top of the can 120 to cover the opening of the can 120 .

[0070] The cap assembly 130 may include a safety vent 131 having a notch 131 a formed therein that ruptures when the internal pressure of the battery increases, and a gasket 132 that provides sealing and insulation between the safety vent 131 and the can 120 .

[0071] The safety vent 131 may be coupled to the electrode tab 240 and the external terminal 250 .

[0072] The cutout portion 131a may be formed in the center of the safety vent 131 in plan view.

[0073] The distance between the central axis of the safety vent 131 and the notch 131 a may be equal to or less than half the radius of the safety vent 131 .

[0074] The safety vent 131 has a rupture portion R formed along the cutout portion 131a at the center, and when the internal pressure of the battery is equal to or greater than the venting pressure, the cutout portion 131a ruptures and the rupture portion R can detach from the safety vent 131.

[0075] Meanwhile, the electrode tab 240 and the external terminal 250 may be connected to different sides, that is, the inner side 131b and the outer side 131c, of the cutout portion 131a in a plan view, in the safety vent 131. Here, the electrode tab 240 may be connected to the inner side 131b of the cutout portion 131a in a plan view, in the safety vent 131, and the external terminal 250 may be connected to the outer side 131c of the cutout portion 131a in a plan view, in the safety vent 131.

[0076] Meanwhile, the positive electrode tab 241 may be provided on the upper side of the electrode assembly 110 and connected to a lower end of the safety vent 131 , and the external terminal 250 may be connected to an upper end of the safety vent 131 .

[0077] The positive electrode tab 241 may be welded to the lower end of the safety vent 131 , and the external terminal 250 may be welded to the upper end of the safety vent 131 .

[0078] The external terminal 250 may be a connecting conductor for an external pack or application.

[0079] Referring to FIG. 5, the secondary battery 200 according to another embodiment of the present invention configured as described above is configured to connect an external terminal 250 to the outer side 131c of the safety vent 131 based on the cutout portion 131a in a plan view, and to connect an electrode tab 240 to the inner side 131b.

[0080] 6, when the internal pressure increases due to an increase in the internal gas, the notch 131a bursts and vents, thereby cutting off the current. That is, when the notch 131a, which forms a circular notch line in a plan view, bursts, the burst part R is separated from the safety vent 131, and the electrical connection between the electrode tab 240 fixed to the burst part R, which is the inner side 131b of the notch 131a in the safety vent 131, and the external terminal 250 connected to the outer side 131c of the notch 131a is released.

[0081] Ultimately, when venting occurs due to an increase in the internal pressure of the battery, the inner side 131b of the notch 131a connected to the positive electrode tab 241 from the electrode tab 240 in the safety vent 131 ruptures and separates from the outer side 131c of the notch 131a connected to the external terminal 250, completely cutting off the current, thereby preventing an explosion due to the continuous application of current.

[0082] At this time, an insulating film is coated on the outer surface of the positive electrode tab 241, so that when the rupture portion R separates from the safety vent 131 and the positive electrode tab 241 fixed to the rupture portion R moves, the positive electrode tab 241 comes into contact with the outer side 131c of the cutout portion 131a to which the external terminal 250 is fixed in the safety vent 131, completely blocking electrical reconnection.

[0083] Meanwhile, a battery pack may be configured including a plurality of the secondary batteries configured as described above. The battery pack may be configured in a form in which a plurality of secondary batteries are electrically connected and housed in a battery pack case. Here, the plurality of secondary batteries may be connected by a connecting conductor. In this case, the connecting conductor may be an external terminal and may be connected to an upper end of a safety vent in the secondary battery.

[0084] Although the present invention has been described in detail above through specific examples, these are merely for the purpose of specifically explaining the present invention, and the present invention is not limited thereto. It can be said that various implementations are possible by those having ordinary skill in the art within the scope of the technical concept of the present invention.

[0085] Moreover, the specific scope of protection of the present invention will be made clear by the appended claims. [Explanation of symbols]

[0086] 100, 200: Secondary battery 110: Electrode assembly 111: Negative electrode 112: Positive electrode 113: Electrode 114: Separator 120: Can 121: Storage unit 122: Beading section 123: Crimping section 130: Cap assembly 131: Safety vent 131a: Notch 131b: Inside 131c: Outside 132: Gasket 140, 240: Electrode tab 141, 241: Positive electrode tab 150, 250: External terminal R:Rupture area

Claims

1. an electrode assembly in which electrodes and separators are alternately stacked and wound; a cylindrical can having an opening at its top and a receiving portion for receiving the electrode assembly; a cap assembly for covering an opening of the can, the cap assembly includes a safety vent (excluding a vent having a convex shape on the inside of the can and inverted to become convex on the outside of the can when the internal pressure of the can reaches a predetermined pressure) having a notch formed therein that ruptures when the internal pressure of the battery increases; The cutout portion is formed in a circular shape in a plan view, The electrode assembly includes an electrode tab connected to the electrode, the safety vent is connected to the electrode tab and the external terminal; and the electrode tab and the external terminal are connected to different sides of the inside and the outside of the safety vent with respect to the notch in a plan view, the electrode tab is coupled to an inner side of the cutout portion in a plan view at the safety vent; The external terminal is connected to an outer side of the notch portion in a plan view in the safety vent; The safety vent has a rupture portion formed along the cutout portion on the central side, When the internal pressure of the battery is equal to or greater than a venting pressure, the notch ruptures and the rupture portion separates from the safety vent; The electrodes include a positive electrode and a negative electrode, the electrode tab includes a positive electrode tab connected to the positive electrode, the positive electrode tab is provided on an upper side of the electrode assembly and is connected to a lower end of the safety vent; The external terminal is connected to an upper end of the safety vent, The positive electrode tab is welded to a lower end of the safety vent, and the external terminal is welded to an upper end of the safety vent.

2. An electrode assembly in which electrodes and separators are alternately stacked and wound up; a cylindrical can having an opening at its top and a receiving portion for receiving the electrode assembly; a cap assembly for covering an opening of the can, the cap assembly includes a safety vent (excluding a vent having a convex shape on the inside of the can and inverted to become convex on the outside of the can when the internal pressure of the can reaches a predetermined pressure) having a notch formed therein that ruptures when the internal pressure of the battery increases; The cutout portion is formed in a circular shape in a plan view, The electrode assembly includes an electrode tab connected to the electrode, the safety vent is connected to the electrode tab and the external terminal; and the electrode tab and the external terminal are connected to different sides of the inside and the outside of the safety vent with respect to the notch in a plan view, the electrode tab is coupled to an inner side of the cutout portion in a plan view at the safety vent; The external terminal is connected to an outer side of the notch portion in a plan view in the safety vent; The safety vent has a rupture portion formed along the cutout portion on the central side, When the internal pressure of the battery is equal to or greater than a venting pressure, the notch ruptures and the rupture portion separates from the safety vent; The electrodes include a positive electrode and a negative electrode, the electrode tab includes a positive electrode tab connected to the positive electrode, the positive electrode tab is provided on an upper side of the electrode assembly and is connected to a lower end of the safety vent; The outer surface of the positive electrode tab is coated with an insulating film.

3. The secondary battery according to claim 1 or 2, wherein the external terminal comprises a connecting conductor of an external pack or application.

4. The secondary battery according to claim 1 , wherein the cutout portion is formed in a central portion of the safety vent in a plan view.

5. the cap assembly further includes a gasket that provides sealing and insulation between the safety vent and the canister; The secondary battery according to claim 1 , wherein the can includes a crimping portion formed at an upper portion thereof to surround the gasket and fix the cap assembly.

6. The secondary battery according to claim 1 , wherein a distance from a central axis of the safety vent to the notch is equal to or less than half a radius of the safety vent.

7. A battery pack comprising the secondary battery according to claim 1 .

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