Electrode tab for secondary battery, electrode assembly, secondary battery, battery pack, and vehicle

Abstract

The present invention relates to an electrode tab for a secondary battery, the electrode tab including a first member and a second member having different resistances, the second member being positioned in at least a portion of the electrode tab, having a resistance greater than that of the first member, and including a cutting portion that melts due to self-resistance heat when an overcurrent of 10 A or more flows, thereby cutting off the current.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0073927, filed with the Korean Intellectual Property Office on June 9, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrode tab for a secondary battery, an electrode assembly including the same, a secondary battery, a battery pack, and a vehicle. [Background technology]

[0003] Generally, a secondary battery is a battery that can be charged and discharged, unlike a primary battery that cannot be charged. Such secondary batteries are widely used in advanced electronic devices such as telephones, laptop computers, and camcorders.

[0004] Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal battery case, and pouch batteries, in which the electrode assembly is housed in a pouch-type battery case made of an aluminum laminate sheet.

[0005] Generally, materials used in secondary batteries (e.g., positive electrode active material, negative electrode active material, binder, electrolyte, current collector, etc.) are electrochemically stable at the battery's operating voltage (2.5V to 4.3V). However, when the battery's voltage exceeds this operating voltage, the constituent materials decompose, generating gas at their respective decomposition voltages. The generated gas increases the pressure inside the lithium secondary battery, causing the voltage to continuously rise. At this time, if there is a small short circuit or if lithium metal electrodeposited on the negative electrode penetrates the separator and meets the positive electrode, a large amount of current flows through this area, accelerating the generation of heat and gas. This heat and gas are released to the outside through vulnerable parts of the battery, ultimately causing the battery to ignite or explode.

[0006] In a cylindrical secondary battery, a notch is formed in the CID and safety vent included in the cap assembly, allowing heat and gas to burst the CID and safety vent and be released to the outside, thereby preventing the secondary battery from catching fire or exploding.

[0007] However, the rupture of the CID and safety vent occurs due to the progression of gas generation inside the secondary battery, and if the reaction progresses quickly, such as in thermal runaway, the secondary battery may catch fire or explode before the CID and safety vent rupture. Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-mentioned problems of the prior art, an object of the present invention is to provide an electrode tab for a secondary battery that prevents fire and explosion of the secondary battery by interrupting the current using heat generated by a large amount of current. [Means for solving the problem]

[0009] One embodiment of the present invention provides an electrode tab for a secondary battery, the electrode tab including a first member and a second member having different resistances, the second member being positioned in at least a portion of the electrode tab, having a resistance greater than that of the first member, and including a cutting portion that melts due to self-resistance heat when an overcurrent of 10 A or more flows, thereby cutting off the current.

[0010] One embodiment of the present invention provides an electrode assembly including the electrode tab.

[0011] One embodiment of the present invention provides a secondary battery including the electrode assembly.

[0012] One embodiment of the present invention provides a battery pack including the secondary battery.

[0013] One embodiment of the present invention provides a means of transportation including the battery pack. [Effects of the Invention]

[0014] The electrode tab for a secondary battery according to an embodiment of the present invention includes a material having a higher resistance than nickel, nickel alloy, or aluminum, which are generally used to form electrode tabs. When a large amount of current flows through the electrode tab, the electrode tab breaks due to the high resistance material, thereby cutting off the current, thereby improving the safety of the secondary battery. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a front view of an electrode tab according to the present invention; [Figure 2] 1A and 1B are front and side views of an electrode tab according to the present invention, in which (a) is an electrode tab according to one embodiment, (b) is an electrode tab according to another embodiment, (c) is an electrode tab according to yet another embodiment, and (d) is an electrode tab according to yet another embodiment. [Figure 3] 1 is a cross-sectional view of a secondary battery including an electrode tab according to an embodiment of the present invention. [Figure 4] 1 is a perspective view showing a battery pack including a secondary battery according to an embodiment of the present invention; [Figure 5] 1 is a perspective view showing a vehicle including a battery pack according to an embodiment of the present invention; [Explanation of symbols]

[0016] 1...Secondary battery 2-pack housing 3 Battery pack 100...electrode assembly 10 Electrode tab 11...Cut section 11a...1st cutting section 11b...Second cutting section 12...Uncut part 200 Battery Case 210 Beading section 220 Crimping section 300 Cap Assembly 310 Top Cap 320 Safety Vent 330 Current interruption element 340 Sealing gasket 350 CID gasket V...Transportation means C Core DETAILED DESCRIPTION OF THE INVENTION

[0017] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. Throughout the specification, when a part is described as "comprising" a certain element or as "featuring" a certain structure and shape, this does not mean that other elements, structures, and shapes are excluded, but that other elements, structures, and shapes may be included, unless otherwise specified to the contrary.

[0018] The present invention can be modified in various ways and can have various embodiments, and specific examples will be presented and described in detail in the detailed description. However, this is not intended to limit the content of the present invention to the embodiments, and should be understood to include all modifications, equivalents, or alternatives that fall within the spirit and technical scope of the present invention.

[0019] The present invention will be described in detail below with reference to the drawings. However, the drawings are for illustrative purposes only and the scope of the present invention is not limited by the drawings.

[0020] Fig. 1 is a front view of an electrode tab according to the present invention, and Fig. 2 is a front view and a side view of an electrode tab according to the present invention. In Fig. 2, (a) is an electrode tab according to one embodiment, (b) is an electrode tab according to another embodiment, (c) is an electrode tab according to yet another embodiment, and (d) is an electrode tab according to yet another embodiment.

[0021] The electrode tab 10 according to the present invention includes a first member and a second member. The first member has a lower resistance than the second member. In other words, the second member has a higher resistance than the first member. Therefore, if a local short circuit occurs in the positive or negative electrode of an electrode assembly including the electrode tab 10 according to the present invention, causing the positive and negative electrodes to come into contact with each other and a large amount of current to flow through that portion, the large amount of current will cause the first or second member to break.

[0022] The second member may comprise a metal or non-conductor having a higher resistance than the first member. For example, the first member may comprise nickel, a nickel alloy, or aluminum, preferably nickel or a nickel-copper alloy, and more preferably nickel.

[0023] The second member may be a metal having a higher resistance than the first member, that is, a high-resistance element may include any one of lead, tin, zinc, copper, and iron, and the non-conductor may include plastic or rubber.

[0024] In one embodiment, when the second member is a high-resistance material, when an overcurrent flows, the electrode tab 10 according to the present invention increases in temperature due to the self-resistance heat of the second member, and the temperature rises faster than the internal temperature of the battery, reaching the melting point. As a result, the internal temperature of the battery rises, and the electrode tab 10 can melt before the battery explodes or catches fire.

[0025] In other words, in the electrode tab 10 according to the present invention, when the second member is melted, the cross-sectional area of the electrode tab 10 through which current flows is reduced from the first member and the second member to the first member, and as a result, the resistance of the first member increases and the first member is melted by its own resistance heat and the resistance heat of the second member, thereby cutting the electrode tab 10 and interrupting the current in the electrode tab 10.

[0026] In another embodiment, when the second member is a non-conductor, the electrode tab 10 of the present invention allows current to flow only through the first member, and when an overcurrent flows through the electrode tab 10, the resistance and resistive heat of the first member increase, causing the first member to melt and cut off the current in the electrode tab 10.

[0027] Therefore, the electrode tab 10 according to the present invention is cut off to cut off the current flow before the internal pressure of the secondary battery due to heat and gas causes physical deformation of the CID or safety vent, thereby improving the safety of the secondary battery.

[0028] 2(a), (c), and (d), the second member is located inside a portion of the electrode tab 10. In other words, the electrode tab 10 may be mostly made of the first member, with the second member located in a portion thereof. Therefore, the second member can be surrounded by the first member, and the second member is not exposed to the outside.

[0029] The electrode tab 10 may include a cut portion 11 that melts due to self-resistance heat when an overcurrent of 10 A or more flows, thereby cutting off the current. The electrode tab 10 may also include a non-cut portion 12 that is a portion other than the cut portion 11.

[0030] The cutting portion 11 of the electrode tab 10 may have a structure in which the second member is located inside the electrode tab 10, and the cutting portion 11 includes a first member and a second member, with the first member being located on both sides of the second member.

[0031] The cutting portion 11 may include one or more second members, and may be provided in the width direction of the electrode tab 10. In this case, the width direction of the electrode tab 10 refers to the length between the opposing ends in a direction parallel to the diameter of the electrode assembly.

[0032] When the cutting portion 11 includes one second member, for example, the second member may be included in a rectangular shape that is long in the width direction of the electrode tab 10. The width of the second member may be narrower than the width of the electrode tab 10, and therefore the cutting portion 11 may include a portion that does not include the second member and is provided with only the first member.

[0033] When a large amount of current flows through the electrode assembly, the portion having only the first member can be cut by heat transferred from the portion having the second member or can be easily cut by pressure generated by gas generated inside the secondary battery. Therefore, safety can be ensured before pressure sufficient to cause physical deformation of the secondary battery case, CID, and safety vent is reached.

[0034] When two or more second members are included in the cutting portion 11, the second members may be spaced apart. For example, the cutting portion 11 may include a plurality of first cutting portions 11a formed of the second members and second cutting portions 11b formed of only the first members between the first cutting portions 11a, and the lengths of the first cutting portions 11a and the second cutting portions 11b may be the same, and the width ratio may be 1:2 to 1:4.

[0035] 2(b) and 2(c), the electrode tab 10 may have different thicknesses between the cut portion 11 and the non-cut portion 12. For example, the cut portion 11 may have a thickness that is 10% to 90% of the thickness of the non-cut portion 12. Preferably, the cut portion 11 may have a thickness that is 20% to 90% of the thickness of the non-cut portion 12, and more preferably, 30% to 80%.

[0036] In (c) of Figure 2, the thickness of the first member of the cut portion 11 is thinner, and the overall thickness of the cut portion 11 is thinner than the non-cut portion 12, but in the electrode tab 10 according to the present invention, the thickness of the second member of the cut portion 11 is thinner, and the overall thickness of the cut portion 11 can be reduced.

[0037] Furthermore, since the thickness of the cut portion 11 is thinner than the thickness of the non-cut portion 12, the resistance of the cut portion 11 increases, and when an overcurrent flows through the electrode tab 10, the cut portion 11 becomes easier to melt and cut, making it easier to interrupt the current in the electrode tab 10.

[0038] The electrode tab 10 may include a first cut portion 11 a, a second cut portion 11 b, and an uncut portion 12.

[0039] For example, if the second cutting portion 11b includes a second member of high resistance, the second cutting portion 11b is melted and cut by resistance heat, and after the second cutting portion 11b is cut, the first cutting portion 11a is melted by its own resistance heat and the resistance heat of the second cutting portion 11b, thereby cutting the electrode tab 10.

[0040] Alternatively, if the second cutting portion 11b includes a non-conductive second member, the first cutting portion 11a may be melted and cut by resistance heat, thereby cutting off the current in the electrode tab 10.

[0041] The first cutting portion 11a may include only the second member, or may include the first member and the second member.

[0042] 2(b), when the first cut portion 11a is formed of only the second member, the thickness of the second member may be 10% to 90% of the thickness of the non-cut portion 12. In this case, in the electrode tab 10 for a secondary battery according to the present invention, the second member may be exposed at the first cut portion 11a.

[0043] 2(c), when the first cut portion 11a is formed of a first member and a second member, the first member may be positioned on both sides of the second member. The combined thickness of the second member and the first members positioned on both sides of the second member may be 10% to 100% of the thickness of the non-cut portion 12. Preferably, the combined thickness of the second member and the first members positioned on both sides of the second member may be 10% to 90% of the thickness of the non-cut portion 12.

[0044] In this case, the first member may be thinner than the second member, and the second member is not exposed to the outside. For example, if the thickness of the non-cut portion 12 is 50 μm to 300 μm, the thickness of the second member may be 40 μm to 250 μm, and the thickness of the first member located on one side of the second member may be 10 μm to 50 μm.

[0045] 2(d), the electrode tab 10 may further have a second member laminated at a position corresponding to the second member. That is, the electrode tab 10 may have one or more second members laminated or coated on one or both sides. The positions of the laminated or coated second members may be the same as the positions of the second members located inside the electrode tab 10.

[0046] In other words, the electrode tab 10 may include a cut portion 11 that melts due to self-resistance heat when an overcurrent of 10 A or more flows, thereby cutting off the current. The electrode tab 10 may include the cut portion 11 and a non-cut portion 12. That is, the electrode tab 10 may include a first cut portion 11a, a second cut portion 11b, and the non-cut portion 12. The first cut portion 11a may be formed of a first member and a second member, and a side end of the first cut portion 11a may be provided in a structure in which the first member is positioned between the second member.

[0047] The first cut portion 11a of the electrode tab 10 includes an internal second member located inside the electrode tab 10, a first member surrounding the internal second member, and an external second member located on one surface of the first member corresponding to the internal second member. Therefore, the first cut portion 11a can be formed thicker than the non-cut portion 12 or the second cut portion 11b.

[0048] By positioning the second member inside and outside the first cutting portion 11a, when an overcurrent flows through the secondary battery, the first member can easily reach its melting point due to the self-resistance heat of the second member positioned on both sides of the first member, heating the first member from both sides and raising the internal temperature of the battery, making it easy to cut off the current before the battery explodes or catches fire.

[0049] 3 is a cross-sectional view of a secondary battery including an electrode tab according to an embodiment of the present invention. The secondary battery 1 includes an electrode assembly 100, a battery case 200, and a cap assembly 300.

[0050] The electrode assembly 100 is a power generating element that includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, and is capable of charging and discharging.

[0051] The electrode assembly 100 may include a jelly roll structure in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound.

[0052] The positive electrode may include a positive electrode current collector, a positive electrode active material portion, and a positive electrode uncoated portion. The positive electrode current collector may be a thin metal plate having excellent conductivity, such as aluminum (Al) foil.

[0053] The positive electrode is formed by coating a positive electrode active material on at least one of both surfaces of a positive electrode current collector. The area coated with the positive electrode active material is the positive electrode active material portion, and the area not coated with the positive electrode active material is the positive electrode uncoated portion. The positive electrode uncoated portion does not have a positive electrode active material layer applied thereto, and can be joined to a first electrode tab.

[0054] The positive electrode active material may include lithium cobalt oxide, which has a high working voltage and excellent capacity characteristics; lithium nickel oxide, which has a high reversible capacity and is easy to realize a large-capacity battery; lithium nickel cobalt oxide, in which nickel is partially substituted with cobalt; lithium nickel cobalt metal oxide, in which nickel is partially substituted with manganese, cobalt, or aluminum; lithium manganese-based oxide, which is excellent in thermal stability and inexpensive; and lithium iron phosphate, which is excellent in stability.

[0055] The negative electrode may include a negative electrode current collector, a negative electrode active material portion, and a negative electrode uncoated portion. The negative electrode current collector may include a highly conductive thin metal plate, such as a copper (Cu) or nickel (Ni) foil.

[0056] The negative electrode is formed by coating one or both sides of a negative electrode current collector with a negative electrode active material, and the negative electrode active material portion is formed by coating or spreading the negative electrode active material, while the negative electrode uncoated portion is a region of the negative electrode current collector that is not coated or spread with the negative electrode active material and where a second electrode tab can be bonded.

[0057] The negative electrode active material may be, for example, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, or carbon fiber, or lithium metal or a lithium alloy. In this case, the negative electrode active material may further include, for example, non-graphite-based silica (SiO2) or silicon carbide (SiC) for a high capacity design.

[0058] The first and second electrode tabs transmit electrons collected in the current collector to an external circuit and may protrude in opposite directions from the electrode assembly of the jelly roll structure. The electrode tab according to the present invention includes at least one of the first and second electrode tabs. That is, the first and second electrode tabs may include a first member and a second member having different resistances, and the second member may be located inside a portion of the electrode tab.

[0059] The separator prevents an internal short circuit that may occur when the positive electrode and the negative electrode come into contact with each other, and may include a porous material to facilitate the movement of ions between the electrodes.

[0060] In one embodiment, the separator may include a substrate layer made of a porous material, such as polyethylene (PE), polystyrene (PS), polypropylene (PP), or a copolymer of polyethylene (PE) and polypropylene (PP).

[0061] In another embodiment, the separation membrane may include a safety-reinforced separator (SRS) membrane. That is, the separation membrane may include a substrate layer made of a porous material and a coating layer formed by coating the substrate layer with a mixed slurry of inorganic particles and a binder polymer. Preferably, the coating layer includes ceramic particles and has a uniform pore structure formed by the interstitial volume between the ceramic particles, which are the active layer components, along with the pore structure contained in the separation membrane substrate itself.

[0062] The coating layer may include ceramic particles including at least one selected from the group consisting of alumina, silica, TiO2, SiC, and MgAl2O4. The inclusion of such a coating layer can enhance the safety of the electrode assembly. The coating layer may further include a lithium salt.

[0063] The battery case 200 may have a columnar structure with a space formed therein. The battery case 200 may accommodate an electrode assembly 100 including electrodes and a separator, and an electrolyte (not shown) in the space. The battery case 200 may have a structure in which one side is open (hereinafter referred to as an opening) and the other side is sealed. Here, the terms "one side" and "other side" refer to the ends located at the top and bottom along the direction of gravity or the central axis of the battery case 200.

[0064] The upper side of the opened battery case 200 may be provided with a beading portion 210 folded toward the center of the secondary battery 1. The battery case 200 may be provided with a crimping portion 220 above the beading portion 210. That is, the crimping portion 220 may be located at the top of the battery case 200. Here, the upper portion refers to the area from the center of the battery case 200 toward the opening.

[0065] The battery case 200 may be made of a lightweight conductive metal material such as aluminum or an aluminum alloy.

[0066] The cap assembly 300 can be coupled to the open side of the battery case 200 and may include a top cap 310 , a safety vent 320 , and a current interrupt device 330 .

[0067] The top cap 310 may be located at the top of the cap assembly 300 and may protrude in a direction opposite to the center of the battery case 200. The top cap 310 may serve as an electrode terminal such that the protruding portion is electrically connected to the outside, for example, the top cap 310 may serve as a positive electrode terminal.

[0068] The top cap 310 may have a sealing gasket 340 coupled to its edge. The sealing gasket 340 may be positioned inside the crimped portion 220 of the battery case 200. The sealing gasket 340 may increase the sealing force between the top cap 310 and the battery case 200.

[0069] The top cap 310 may include a protrusion protruding from an upper portion, a frame portion that contacts and is coupled to the sealing gasket 340, and a first connecting portion that connects the protrusion and the frame portion.

[0070] The safety vent 320 may be positioned below the top cap 310 and electrically connected to the top cap 310. At least a portion of the surface of the safety vent 320 facing the top cap 310 may be in contact with the top cap 310. A predetermined length from an end of the safety vent 320 may be in contact with the top cap 310, and the remaining portion of the safety vent 320 may be spaced a predetermined distance from the top cap 310. The portion of the safety vent 320 in contact with the top cap 310 may be coupled to a sealing gasket 340.

[0071] The safety vent 320 may have a distance from the top cap 310 that increases toward the center of the safety vent 320 in a region that comes into contact with the top cap 310 .

[0072] The safety vent 320 may include a contact portion that contacts the top cap 310, a central portion that is located at the center of the safety vent 320 and that contacts the current interrupting device, and a second connecting portion that connects the contact portion and the central portion. The safety vent 320 may also include bent portions (or notches) at the portions where the contact portion and the second connecting portion and the second connecting portion and the central portion contact each other.

[0073] In one embodiment, the safety vent 320 may be provided with an end portion perpendicular to the axial direction of the battery case 200. In this case, the top cap 310 may be provided so that it is perpendicular to the axial direction of the battery case 200, just like the safety vent 320. In other words, the safety vent 320 and the top cap 310 may be positioned horizontally.

[0074] In another embodiment, the safety vent 320 may be provided in a form in which the end portion is bent and surrounds the outer periphery of the top cap 310 .

[0075] In the secondary battery 1 according to the present invention, the electrode assembly 100 housed inside the battery case 200 reacts with the electrolyte, generating gas and heat, and causing an increase in internal pressure.

[0076] When the internal pressure of the secondary battery 1 increases, the safety vent 320 receives a force in the direction of the top cap 310, causing the bent portion to burst, thereby discharging the internal gas of the secondary battery 1.

[0077] A current interruptive device (CID) 330 may be located below the safety vent 320 and at least a portion thereof may be connected to the safety vent 320 .

[0078] When the safety vent 320 bursts due to an increase in the internal pressure of the secondary battery 1, the current interrupting device 330 separates from the safety vent 320 to interrupt the current.

[0079] More specifically, the current interruption device 330 may include a central portion connected to the safety vent 320, a connecting portion protruding in the direction of the safety vent 320, a peripheral portion excluding the connecting portion, and a joining portion connecting the connecting portion to the peripheral portion. A plurality of joining portions may be provided, and the plurality of joining portions may be spaced apart from one another.

[0080] When the safety vent 320 is deformed in the direction of the top cap 310, the joint breaks and the connecting portion can be separated from the edge portion. That is, the connecting portion can be separated in the direction of the top cap 310 while remaining connected to the safety vent 320.

[0081] The CID gasket 350 surrounds the edge of the current interrupting element 330 and can electrically isolate the edge and joint parts other than the connection parts of the current interrupting element 330 from the safety vent 320 .

[0082] According to an embodiment of the present invention, there is provided a battery pack including any one of the above-described secondary batteries.

[0083] In relation to this embodiment, referring to FIG. 4, a battery pack 3 including a secondary battery 1 in a pack housing 2 is shown.

[0084] The battery pack according to this embodiment has high output and high capacity. According to an embodiment of the present invention, there is provided a vehicle including the battery pack described above.

[0085] In relation to this embodiment, referring to FIG. 5, a vehicle V including a battery pack 3 is shown.

[0086] The vehicle according to the embodiment uses a battery pack with high output / high capacity, and is therefore excellent in terms of stability and safety.

[0087] Although the present invention has been described above with reference to preferred embodiments, it should be understood that those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the claims.

Claims

1. An electrode tab for a secondary battery, the electrode tab includes a first member and a second member having different resistances; the second member is positioned on at least a portion of the electrode tab and has a resistance greater than that of the first member; An electrode tab for a secondary battery, comprising a cutting portion that is melted by self-resistance heat when an overcurrent of 10 A or more flows, thereby cutting off the current.

2. The electrode tab for a secondary battery according to claim 1 , wherein the cutting portion is formed by the first member, and the second member is positioned inside the first member.

3. the cutting portion includes a first cutting portion that is a region where the second member is located, and a second cutting portion that is a region that includes only the first member, The electrode tab for a secondary battery according to claim 2 , wherein the cutting portion includes one or more first cutting portions.

4. The electrode tab for a secondary battery according to claim 3 , wherein two or more of the first cut portions are spaced apart from each other.

5. The electrode tab for a secondary battery according to claim 3 , wherein the first cut portion is provided in a width direction of the electrode tab.

6. The electrode tab includes a non-cutting portion that will not be cut even when an overcurrent of 10 A or more flows therethrough, 2. The electrode tab for a secondary battery according to claim 1, wherein the cut portion has a thickness that is 10% to 90% of the thickness of the non-cut portion.

7. The electrode tab for a secondary battery according to claim 6 , wherein the cutting portion is formed by the first member, and the second member is positioned inside the first member.

8. The electrode tab for a secondary battery according to claim 6 , wherein the cut portion includes only the second member, and the non-cut portion includes only the first member.

9. The electrode tab for a secondary battery according to claim 2 , wherein the cutting portion is formed by stacking the second member on one surface of the first member.

10. An electrode assembly comprising the electrode tab for a secondary battery according to any one of claims 1 to 9.

11. A secondary battery comprising the electrode assembly according to claim 10.

12. A battery pack comprising the secondary battery according to claim 11.

13. A means of transportation comprising the battery pack of claim 12.

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