Secondary battery and manufacturing method thereof

Abstract

A secondary battery according to one embodiment of the present invention includes an electrode assembly; a battery case that houses the electrode assembly and has an open top; and a cap assembly that is coupled to the open top of the battery case. The cap assembly also includes a safety vent and a CID filter positioned below the safety vent. The safety vent is exposed to the outside at its top, and a vent hole is formed in the safety vent, penetrating vertically. The CID filter has a CID hole that penetrates vertically and connects to the vent hole. A first electrode tab extending from the electrode assembly is attached to the CID filter, and the CID hole is closed or opened by the first electrode tab.

Description

[Technical field]

[0001] Cross-reference to related application(s) This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0072370 filed on June 3, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a secondary battery and a manufacturing method thereof, and more particularly to a secondary battery capable of discharging gas generated during an activation process and a manufacturing method thereof. [Background technology]

[0003] Recently, as the price of energy sources rises due to the depletion of fossil fuels and concerns about environmental pollution grow, the demand for environmentally friendly alternative energy sources is becoming an essential factor for future life. Therefore, research into various power generation technologies such as atomic, solar, wind, and tidal power is ongoing, and there has been a great interest in power storage devices to use the energy produced in this way more efficiently.

[0004] In particular, with technological development and increasing demand for mobile devices, the demand for batteries as an energy source is rapidly increasing, and as a result, much research is being conducted into batteries that can meet various demands.

[0005] 2. Description of the Related Art There is a high demand for lithium secondary batteries, such as lithium ion batteries and lithium ion polymer batteries, which have advantages such as high energy density, discharge voltage, and output stability.

[0006] Secondary batteries are also classified according to the structure of the electrode assembly, which is a stack of positive electrodes, negative electrodes, and a separator interposed between the positive and negative electrodes. Representative examples include a jelly-roll type electrode assembly in which a long sheet-shaped positive electrode and negative electrode are wound with a separator interposed therebetween, and a stack type electrode assembly in which a number of positive electrodes and negative electrodes cut into units of a predetermined size are stacked in sequence with a separator interposed therebetween. Recently, in order to solve the problems of the jelly-roll type electrode assembly and the stack type electrode assembly, a stack / folding type electrode assembly has been developed as a hybrid of the jelly-roll type and the stack type, in which unit cells, in which a predetermined unit of positive electrodes and negative electrodes are stacked with a separator interposed therebetween, are positioned on a separator film and then wound in sequence.

[0007] In addition, secondary batteries can be classified according to the shape of the case into cylindrical batteries in which the electrode assembly is housed in a cylindrical case, prismatic batteries in which the electrode assembly is housed in a prismatic case, and pouch batteries in which the electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet.

[0008] Meanwhile, secondary batteries can only be used appropriately in the market if they meet the performance required for their intended use and are also safe. When designing secondary batteries, design factors are determined by considering both performance and safety at the same time. Once the design and manufacture is complete, batteries are evaluated for performance such as lifespan, high rate characteristics, high / low temperature characteristics, etc., as well as safety such as overcharging, over-discharging, impact, nail tests, and hot boxes.

[0009] Among the various types of secondary batteries, cylindrical secondary batteries can include a Current Interrupt Device (CID) filter that cuts off the current between the electrode terminals and electrode tabs to prevent additional reactions from occurring when gas is suddenly generated inside the secondary battery in an abnormal state such as overcharging and the internal pressure exceeds a certain level.

[0010] FIG. 1 is a partial cross-sectional view showing a cross section of the upper part of a conventional cylindrical secondary battery.

[0011] Referring to FIG. 1, an electrode assembly 20 is housed in a cylindrical case 30, and a cap assembly 40 is attached to an open top of the cylindrical case 30, thereby manufacturing a cylindrical secondary battery 10.

[0012] The electrode assembly 20 may be a jelly-roll type electrode assembly in which the first electrode 21, the second electrode 22, and the separator 23 are wound up.

[0013] The cap assembly 40 may include an upper cap 41, an internal pressure drop safety vent 42, and a current interrupt device (CID) 43. The upper cap 41 and the safety vent 42 may form a structure in close contact with each other, and the safety vent 42 may be connected to a center of the current interrupt device 43. A first electrode tab 21t protruding from the first electrode 21 may be connected to a lower end of the CID filter 43. Here, the first electrode 21 may be a positive electrode, and the first electrode tab 21t may be a positive electrode tab.

[0014] As described above, the top cap 41 can be directly or indirectly connected to the safety vent 42, the current interrupting member 43 and the first electrode tab 21t to be electrically connected to the electrode assembly 20 and function as an electrode terminal.

[0015] Meanwhile, a gasket 70 for sealing between the cap assembly 40 and the cylindrical case 30 and a CID gasket 80 surrounding the periphery of the current interrupting member 43 may be disposed.

[0016] FIG. 2 is a partial cross-sectional view showing a state when the internal pressure of the cylindrical secondary battery of FIG. 1 increases.

[0017] 2, when the cylindrical secondary battery 10 is exposed to high temperatures or is in an abnormal operating state and the internal pressure rises, the shape of the safety vent 42 is reversed and the CID filter 43 is separated to block the current. Specifically, the CID filter 43 is divided into a portion 43a connected to the safety vent 42 and a portion 43b connected to the first electrode tab 21t, thereby blocking the flow of current between the top cap 41, which functions as an electrode terminal, and the first electrode tab 21t. In addition, when the internal pressure rises significantly, the notch portion of the safety vent 42 is cut, opening the safety vent 42 and discharging the internal gas.

[0018] The conventional cylindrical secondary battery 10 having the top cap 41 has excellent structural rigidity, but has the disadvantage that when the safety vent 42 is opened to release internal gas, the safety vent 42 does not open completely and gas release is restricted due to the inferior spatial portion of the top cap 41. Also, there may be cases where the CID filter 43 is not completely separated, which may cause a problem that current continues to flow even in an abnormal operating state.

[0019] Meanwhile, lithium secondary batteries generally undergo a formation process, or activation process, during the manufacturing process. The activation process is a process in which the battery is activated by charging and discharging after assembly. During charging, lithium ions released from the positive electrode move to and are inserted into the negative electrode, forming a solid electrolyte interface (SEI) film on the surface of the negative electrode. This activation process is generally performed by repeatedly charging and discharging at a constant current or voltage within a certain range.

[0020] During this activation process, a large amount of gas is generated due to the formation of the electrode coating and the decomposition of moisture inside the cell, and since the amount of gas generated during the activation process is large and it reacts continuously with the electrode coating, a process to exhaust the gas is required. This is called the degassing process.

[0021] However, referring again to Figures 1 and 2, the conventional cylindrical secondary battery 10 must be kept sealed after the electrolyte is injected, making it difficult to exhaust the gas generated during the activation process. If the gas generated during the activation process is not exhausted, it may interfere with the battery reaction between the positive and negative electrodes, adversely affecting the initial capacity of the battery, stable solid electrolyte interface (SEI) formation, and life performance characteristics. In addition, if the gas is not exhausted, it may affect the results of the safety evaluation described above.

[0022] Therefore, there is a need to develop a cylindrical secondary battery capable of discharging gas generated during the activation process. Summary of the Invention [Problem to be solved by the invention]

[0023] An object of the present invention is to provide a secondary battery capable of discharging gas after an activation step, and a method for manufacturing the same.

[0024] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems, and may be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0025] A secondary battery according to an embodiment of the present invention includes an electrode assembly; a battery case in which the electrode assembly is housed and whose top is open; and a cap assembly coupled to the open top of the battery case. The cap assembly includes a safety vent and a CID filter located below the safety vent. The safety vent is exposed to the outside at an upper end, a vent hole penetrating vertically is formed in the safety vent, and a CID hole penetrating vertically and connected to the vent hole is formed in the CID filter. A first electrode tab extending from the electrode assembly is joined to the CID filter, and the CID hole is closed or opened by the first electrode tab.

[0026] The vent hole and the CID hole may be positioned on the same vertical line, and the first electrode tab closing the CID hole may be visible from the outside through the vent hole and the CID hole.

[0027] The vent hole may have a larger diameter than the CID hole.

[0028] The first electrode tab may include an upper tab portion and a lower tab portion, the lower tab portion may be connected to the electrode assembly, and one end of the upper tab portion connected to the lower tab portion may be bonded to the CID filter.

[0029] The other end of the upper tab portion may be in close contact with or spaced from the lower surface of the CID filter to close or open the CID hole.

[0030] The first electrode tab may include a material having an elastic restoring force, and the other end of the upper tab portion may be elastically attached to a lower surface of the CID filter.

[0031] A lower end of an inner periphery of the CID hole and the upper tab portion may be welded to each other.

[0032] The first electrode tab may include a protrusion that is inserted into the CID hole.

[0033] The secondary battery may further include a sealing ball inserted into the CID hole.

[0034] An upper end of the battery case may be bent to surround an outer periphery of the safety vent to form a crimping portion.

[0035] According to an embodiment of the present invention, a method for manufacturing a secondary battery includes the steps of: housing an electrode assembly in a battery case having an open top; coupling a cap assembly including a safety vent and a CID filter to the open top of the battery case; activating the electrode assembly; and discharging a gas generated during the activation step to the outside through a vent hole formed in the safety vent and a CID hole formed in the CID filter. The safety vent is exposed to the outside at an upper end, and a first electrode tab extended from the electrode assembly is joined to the CID filter with the CID hole closed. In the gas discharging step, the first electrode tab is pushed downward through the vent hole and the CID hole to open the CID hole, and the gas can be discharged to the outside through the CID hole and the vent hole.

[0036] In the gas discharging step, a rod member or an inhalation device may be inserted through the vent hole and the CID hole to push the first electrode tab downward.

[0037] After the gas discharge step, the force pressing the first electrode tab may be removed to return the first electrode tab to its original position, thereby closing the CID hole again.

[0038] The method of manufacturing a secondary battery may further include, after the gas exhausting step, welding a lower end of an inner periphery of the CID hole to the first electrode tab.

[0039] The method of manufacturing a secondary battery may further include inserting a sealing ball into the CID hole through the vent hole.

[0040] The method of manufacturing a secondary battery may further include melting the sealing ball inserted into the CID hole. Effect of the Invention

[0041] According to an embodiment of the present invention, by removing the top cap and exposing the safety vent to the outside, eliminating spatial constraints on the safety vent, the safety vent can be fully opened when internal pressure increases and can be effective for gas release.

[0042] In addition, since the safety vent is exposed to the outside, a separate vent hole can be formed in the safety vent to easily exhaust gas generated during the activation process, thereby resolving problems such as expansion and deformation of the electrode assembly due to gas and problems such as lithium precipitation due to residual gas bubbles.

[0043] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a partial cross-sectional view showing a cross section of an upper portion of a conventional cylindrical secondary battery. [Diagram 2] 2 is a partial cross-sectional view showing a state when the internal pressure of the cylindrical secondary battery of FIG. 1 increases. FIG. [Diagram 3] 1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention; [Figure 4] 4 is a cross-sectional perspective view of a safety vent included in the secondary battery of FIG. 3. [Diagram 5] 2 is a cross-sectional view of an upper portion of a secondary battery according to an embodiment of the present invention; [Figure 6] 6 is an enlarged partial view of part "A" in FIG. 5. [Figure 7] 11 is a partial view showing a first electrode tab having a protrusion formed thereon according to a modified embodiment of the present invention. [Figure 8] 1 is a partial view showing a sealing ball inserted into a CID hole according to an embodiment of the present invention. [Figure 9] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 10]2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 11] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 12] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 13] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 14] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 15] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may, however, be embodied in various different forms and should not be construed as being limited to the embodiments set forth herein.

[0046] In order to clearly describe the present invention, parts unnecessary for the description are omitted, and the same reference numerals are used throughout the specification to refer to the same or similar components.

[0047] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and the present invention is not necessarily limited to those shown in the drawings. In the drawings, thicknesses are enlarged to clearly show multiple layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0048] In addition, when a part such as a layer, film, region, or plate is said to be "above" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. In addition, being "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" in the opposite direction to gravity.

[0049] Furthermore, throughout the specification, when a part is said to "comprise" a certain element, this does not mean that it excludes other elements and may further include other elements, unless specifically stated to the contrary.

[0050] Also, throughout the specification, a reference to "in a plane" means when the subject part is viewed from above, and a reference to "in cross section" means when the subject part is cut vertically and viewed from the side.

[0051] Fig. 3 is an exploded perspective view of a secondary battery according to an embodiment of the present invention. Fig. 4 is a cross-sectional perspective view of a safety vent included in the secondary battery of Fig. 3. Fig. 5 is a cross-sectional view of an upper part of a secondary battery according to an embodiment of the present invention. In particular, Fig. 5 is a cross-sectional view showing an upper part of a cross section cut along an xz plane after assembling each part of the secondary battery of Fig. 3.

[0052] 3 to 5, a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 200; a battery case 300 in which the electrode assembly 200 is housed and which has an open top; and a cap assembly 400 which is coupled to the open top of the battery case 300.

[0053] First, the electrode assembly 200 according to the present embodiment may include a first electrode 210, a second electrode 220, and a separator 230. The first electrode 210, the second electrode 220, and the separator 230 may be wound together to form a jelly roll type electrode assembly 200. The separator 230 may be interposed between the first electrode 210 and the second electrode 220.

[0054] Although not specifically shown, the first electrode 210 may be formed by coating an electrode active material on a first electrode collector, and a first electrode tab 213 may be attached by welding or the like to a portion of the first electrode collector where the electrode active material is not coated and the first electrode collector is exposed.

[0055] The second electrode 220 may be formed by coating an electrode active material on a second electrode collector, and a second electrode tab 223 may be attached by welding or the like to a portion of the second electrode collector where the electrode active material is not coated and the second electrode collector is exposed.

[0056] In this case, the first electrode 210 may be a positive electrode, and the second electrode 220 may be a negative electrode. To this end, the first electrode tab 213 may be a positive electrode tab, and the second electrode tab 223 may be a negative electrode tab. Meanwhile, the first electrode tab 213 and the second electrode tab 223 may protrude in opposite directions with respect to the wound electrode assembly 200. As shown in FIG. 3, the first electrode tab 213 may protrude in a direction in which the cap assembly 400 is located (z-axis direction), and the second electrode tab 223 may protrude in a direction in which the bottom of the battery case 300 is located (-z-axis direction). The first electrode tab 213 may be connected to the cap assembly 400, and the second electrode tab 223 may be connected to the bottom of the battery case 300. That is, the cap assembly 400 and the battery case 300 may each function as an electrode terminal of the secondary battery 100.

[0057] Meanwhile, the battery case 300 is a structure for housing the electrode assembly 200 impregnated with an electrolyte, and may be made of a metal material and may be a cylindrical case.

[0058] The cap assembly 400 according to this embodiment includes a safety vent 410 and a CID (Current Interrupt Device) filter 420 located below the safety vent 410. The safety vent 410 is exposed to the outside at an upper end. A vent hole 410H penetrating vertically is formed in the safety vent 410, and a CID hole 420H penetrating vertically and connected to the vent hole 410H is formed in the CID filter 420. Here, the fact that the vent hole 410H and the CID hole 420H are connected means that the spaces inside the holes formed by each are connected to each other.

[0059] The cap assembly 400 according to the present embodiment is different from the conventional cylindrical secondary battery 10 (see FIG. 1) in that the upper end cap is removed and a safety vent 410 is exposed to the outside at the upper end.

[0060] The safety vent 410 may be located on the CID filter 420 and electrically connected to the CID filter 420. Specifically, a central portion of the safety vent 410 excluding the vent hole 410H may be physically and electrically connected to a first portion 421 of the CID filter 420 (described below) excluding the CID hole 420H. A first electrode tab 213 extending from the electrode assembly 200 may be joined to the CID filter 420. Specifically, the first electrode tab 213 protruding from the first electrode 210 may be joined to a lower end of the CID filter 420.

[0061] The safety vent 410 is a thin film structure that conducts current and may be a disk-shaped plate. The safety vent 410, the CID filter 420, and the first electrode tab 213 are sequentially connected, and the safety vent 410 may function as an electrode terminal that guides the electrical connection of the electrode assembly 200.

[0062] The CID filter 420 according to this embodiment is a plate member through which current flows, and may have an exhaust port 422H for discharging gas. The CID filter 420 may include a first portion 421 connected to the safety vent 410 and a second portion 422 connected to the first electrode tab 213. The first portion 421 may be located at a central portion of the CID filter 420, and the second portion 422 may be located at an outer periphery of the CID filter 420.

[0063] When the internal pressure of the secondary battery 100 increases, the shape of the safety vent 410 may be reversed. Due to the shape reversal of the safety vent 410, the first portion 421 of the CID filter 420 may rise together, and the first portion 421 and the second portion 422 of the CID filter 420 may be separated from each other. In order to induce such separation due to the increase in internal pressure, the first portion 421 and the second portion 422 may be designed to have a somewhat weak strength between them. Due to the separation of the first portion 421 and the second portion 422, the current between the safety vent 410 and the first electrode tab 213 is interrupted.

[0064] Also, as shown in FIG. 5, the safety vent 410 may be provided with a notch structure such as a kind of groove. When the internal pressure increases, the notch structure is cut or torn, and the safety vent 410 opens, and the internal gas is discharged. In the case of the conventional cylindrical secondary battery 10 (see FIG. 1), since the upper end cap 41 is located on the safety vent 42, the space is inferior and the safety vent 42 does not open completely. Therefore, the gas is not effectively discharged. In addition, the upper end cap 41 itself may be an obstacle to gas discharge. In contrast, in the secondary battery 100 according to the present embodiment, since the safety vent 410 is exposed to the outside at the upper end without an upper end cap, the safety vent 410 may freely reverse its shape or separate when the internal pressure increases. Therefore, compared to the conventional cylindrical secondary battery 10, gas discharge is more effective, and current interruption due to separation of the first part 421 and the second part 422 in an abnormal operating state may be more reliably performed.

[0065] Hereinafter, the structures of the vent hole 410H, the CID hole 420H, and the first electrode tab 213 according to this embodiment will be described in detail.

[0066] FIG. 6 is an enlarged partial view of part "A" in FIG.

[0067] 5 and 6, as described above, the first electrode tab 213 extending from the electrode assembly 200 is bonded to the CID filter 420. The CID hole 420H is closed or opened by the first electrode tab 213.

[0068] In addition, the vent hole 410H and the CID hole 420H are connected to each other. In particular, the safety vent 410 and the CID filter 420 are combined, and the vent hole 410H and the CID hole 420H may be connected to each other at a portion where the safety vent 410 and the CID filter 420 are combined. More specifically, the CID hole 420H may be formed in a first portion 421 of the CID filter 420 that is connected to the safety vent 410.

[0069] Specifically, when the first electrode tab 213 is in close contact with the CID filter 420, the CID hole 420H is closed, and when the first electrode tab 213 is separated from the CID filter 420, the CID hole 420H is opened.

[0070] As described below, a long rod is inserted through the vent hole 410H of the safety vent 410 and the CID hole 420H of the CID filter 420, and then the first electrode tab 213 closing the CID hole 420H can be pushed downward. As a result, the CID hole 420H is opened, and gas generated during an activation process, which will be described later, can be discharged to the outside through the CID hole 420H and the vent hole 410H. This solves problems such as expansion and deformation of the electrode assembly due to residual gas and problems of lithium deposition due to residual gas bubbles.

[0071] In addition, since the secondary battery 100 according to this embodiment has a structure in which the upper end cap is removed, it is easy to pass a long rod through the vent hole 410H and the CID hole 420H. In other words, the rod can be inserted to push the first electrode tab 213 without damaging the vent hole 410H and the CID hole 420H.

[0072] The secondary battery 100 according to this embodiment can stably charge and discharge during the activation process because the CID hole 420H is closed by the first electrode tab 213. After the activation process, the first electrode tab 213 is pressed downward to allow the internal gas to be discharged to the outside through the opened CID hole 420H. Once the gas discharge is complete, the first electrode tab 213 and the CID hole 420H are welded to be sealed to prevent electrolyte leakage. This series of manufacturing processes will be described in detail again with reference to Figures 9 to 15.

[0073] Meanwhile, vent hole 410H and CID hole 420H may have a minimum diameter into which a rod can be inserted. For example, vent hole 410H and CID hole 420H may have a diameter of 1 to 3 mm, thereby allowing gas inside battery case 300 to be discharged to the outside while preventing foreign matter from entering through vent hole 410H and CID hole 420H.

[0074] Meanwhile, the vent hole 410H and the CID hole 420H may be located on the same vertical line. The vent hole 410H and the CID hole 420H may be arranged in the up-down direction and located on the same vertical line. Therefore, the first electrode tab 213 closing the CID hole 420H can be seen from the outside through the vent hole 410H and the CID hole 420H. As a result, it is possible to easily check whether the CID hole 420H is closed from the outside of the secondary battery 100. Furthermore, since the secondary battery 100 according to the present embodiment has a shape in which the upper end cap is removed, it is possible to more easily check whether the CID hole 420H is closed.

[0075] In addition, since the vent hole 410H and the CID hole 420H are aligned in a straight line, the CID hole 420H can be opened by more effectively pressing the first electrode tab 213. Here, the vent hole 410H is formed at the center of the safety vent 410, and the CID hole 420H is formed at the center of the CID filter 420, thereby minimizing weakening of the strength.

[0076] Meanwhile, in another embodiment of the present invention, the vent hole 410H and the CID hole 420H may be partially located on the same vertical line. For example, the vent hole 410H and the CID hole 420H may be partially located on the same vertical line, and the remaining half may be located on different vertical lines. This can prevent unwanted objects or foreign matter from entering the vent hole 410H and the CID hole 420H, and can also prevent the first electrode tab 213 from being pressed by unwanted objects.

[0077] Meanwhile, the diameter d1 of the vent hole 410H may be larger than the diameter d2 of the CID hole 420H. When a long rod for pushing the first electrode tab 213 is inserted into the vent hole 410H, it may be difficult to insert the rod due to the looseness of the rod. For this reason, the vent hole 410H has a larger diameter than the CID hole 420H, so that the rod can be easily inserted. In particular, the vent hole 410H can be prevented from being damaged by the rod pushing the first electrode tab 213. As described above, the safety vent 410 must be inverted or separated to prevent the secondary battery 100 from exploding, but damage to the vent hole 410H and its surroundings may cause defects. To prevent this, the vent hole 410H may be larger than the diameter of the CID hole 420H. As an example, the diameter of the vent hole 410H may be 3 mm, and the diameter of the CID hole 420H may be 2 mm.

[0078] As described above, the safety vent 410 and the CID filter 420 may be coupled together, and the vent hole 410H and the CID hole 420H may be connected to each other at the portion where the safety vent 410 and the CID filter 420 are coupled together. In particular, the outer circumferential surface of the vent hole 410H and the outer circumferential surface of the CID hole 420H may be joined together. Specifically, the lower outer circumferential surface of the vent hole 410H and the upper outer circumferential surface of the CID hole 420H may be welded together to form a joint portion W. That is, the safety vent 410 and the CID filter 420 are joined to be hermetically sealed, thereby preventing foreign matter from entering the vent hole 410H and the CID hole 420H or electrolyte from leaking out through the gap between the safety vent 410 and the CID filter 420.

[0079] According to the present embodiment, the first electrode tab 213 may include an upper tab portion 213a and a lower tab portion 213b. The lower tab portion 213b may be connected to the electrode assembly 200. That is, the lower tab portion 213b may be an extended portion from the electrode assembly 200.

[0080] One end of the upper tab portion 213a connected to the lower tab portion 213b may be joined to the CID filter 420. In particular, the one end of the upper tab portion 213a may be welded to a lower surface of the CID filter 420 to form a joint portion W.

[0081] In addition, the other end of upper tab portion 213a can close or open CID hole 420H while being in close contact with or separated from the underside of CID filter 420. Specifically, when upper tab portion 213a, which closes CID hole 420H, is pressed with a rod, which will be described later, the other end of upper tab portion 213a moves away from CID filter 420 to open CID hole 420H. When the force pressing the other end of upper tab portion 213a is removed, the other end of upper tab portion 213a again comes into close contact with CID filter 420 due to the elastic restoring force of upper tab portion 213a, thereby closing CID hole 420H.

[0082] To this end, the first electrode tab 213 can stably seal the CID hole 420H during the activation process of the secondary battery 100, and after the activation process, the first electrode tab 213 can be separated from the CID filter 420 to open the CID hole 420H and discharge gas.

[0083] The first electrode tab 213 may include a material having an elastic restoring force, so that the other end of the upper tab portion 213a may elastically adhere to the lower surface of the CID filter 420. When the external force pressing the other end of the upper tab portion 213a is removed, the other end of the upper tab portion 213a quickly returns to its original position due to the elastic restoring force, so that the CID hole 420H can be quickly and stably closed. Here, the first electrode tab 213 may be an alloy steel containing a material having an elastic restoring force.

[0084] Meanwhile, after gas is discharged, a lower end of an inner circumferential surface of the CID hole 420H and the upper tab portion 213a of the first electrode tab 213 may be welded together. That is, the other end of the upper tab portion 213a, which is in close contact with the lower surface of the CID filter 420, is joined to the CID filter 420 after gas is discharged, thereby completely sealing the CID hole 420H. As a result, it is possible to prevent foreign matter from entering or electrolyte from leaking out after gas is discharged.

[0085] FIG. 7 is a partial view showing a first electrode tab having a protrusion according to a modified embodiment of the present invention.

[0086] 7, the first electrode tab 213 according to the modified embodiment of the present invention may include a protrusion 213a-1 to be inserted into a CID hole 420H. Specifically, as described above, the first electrode tab 213 may include an upper tab portion 213a and a lower tab portion 213b, and the protrusion 213a-1 may be formed in a protruding form on the upper tab portion 213a.

[0087] The protrusion 213a-1 is for increasing the sealing force between the first electrode tab 213 and the CID hole 420H, and may have the same diameter as the diameter of the CID hole 420H. The protrusion 213a-1 increases the sealing force between the first electrode tab 213 and the CID hole 420H when inserted into the CID hole 420H. In particular, the protrusion 213a-1 is formed in a hemispherical protuberance structure, so that the protrusion 213a-1 can be easily attached to and detached from the CID hole 420H.

[0088] FIG. 8 is a partial view showing a sealing ball inserted into a CID hole according to an embodiment of the present invention.

[0089] 5, 6 and 8, the secondary battery 100 according to this embodiment may further include a sealing ball 500 inserted into the CID hole 420H. After the gas generated after the activation process is completely discharged, the sealing ball 500 may be inserted into the CID hole 420H. The sealing ball 500 is for sealing the CID hole 420H and has a cylindrical or spherical shape and is inserted into the CID hole 420H through the vent hole 410H to seal the CID hole 420H.

[0090] At this time, the cylindrical or spherical sealed ball 500 may be joined to the CID hole 420H by ball welding. Here, ball welding refers to a joining method in which a ball-shaped component is fired into a hole having a smaller diameter than the ball to fill the hole. That is, the diameter of the sealed ball 500 before filling the CID hole 420H may be larger than the inner diameter of the CID hole 420H. The sealed ball 500 may be fired strongly to be forcibly inserted into the CID hole 420H, thereby blocking the CID hole 420H. FIG. 8 is a view showing a state in which the sealed ball 500 is inserted and joined to the CID hole 420H by ball welding.

[0091] In addition, the sealing ball 500 may be fused by a heat fusion device (not shown) after being inserted into the CID hole 420H. As a result, the sealing ball 500 is bonded to the inner circumferential surface of the CID hole 420H, thereby increasing the sealing force between the CID hole 420H and the sealing ball 500.

[0092] At this time, since the safety vent 410 according to the present embodiment is structured to be exposed to the outside by removing the top cap, it is easy to seal the CID hole 420H. In the case of the conventional cylindrical secondary battery 10 (see FIG. 1), even if a CID hole is formed, it is structurally very difficult to close the CID hole again after gas is discharged because of the presence of the top cap 41. In order to discharge gas, holes must be formed in both the top cap 41 and the safety vent 42, but the presence of the top cap 41 makes it structurally complicated and difficult to close the holes formed in the safety vent 42 and the CID filter 43. In contrast, since the cap assembly 400 according to the present embodiment is structured such that the safety vent 410 is exposed at the top end, it is easy to seal the CID hole 420H after gas is discharged by welding the lower end of the inner circumferential surface of the CID hole 420H to the upper tab portion 213a or by inserting a sealing ball 500, as described above.

[0093] 3 to 5, the battery case 300 according to the present embodiment may include a crimping portion 300C and a beading portion 300B. The beading portion 300B refers to a portion of the cylindrical battery case 300 that is recessed toward the center of the electrode assembly 200, and serves to prevent the electrode assembly 200 from moving freely.

[0094] The crimping portion 300C is located on the upper portion of the beading portion 300B and refers to a portion surrounding the cap assembly 400, for stable coupling of the cap assembly 400. One upper end of the battery case 300 may be bent to surround the cap assembly 400, thereby forming the crimping portion 300C. More specifically, one upper end of the battery case 300 may be bent to surround the outer periphery of the safety vent 410, thereby forming the crimping portion 300C.

[0095] The sealing gasket 700 is attached to the inner surface of the crimping portion 300C and the beading portion 300B to increase the sealing force between the cap assembly 400 and the battery case 300. In addition, the gasket 700 can block the electrical connection between the cap assembly 400 and the battery case 300. The gasket 700 is positioned between the battery case 300 and the cap assembly 400, and the upper end of the battery case 300 is bent to perform crimping coupling to form the crimping portion 300C. That is, the cap assembly 400 can be attached, the secondary battery 100 can be sealed, and the battery case 300 and the cap assembly 400 can be insulated by the crimping coupling. The gasket 700 can be positioned between the crimping portion 300C and the safety vent 410.

[0096] Meanwhile, the safety vent 410 according to the present embodiment may have a bent portion 410B. Specifically, as shown in FIG. 4 and FIG. 5, a portion of the safety vent 410 may be bent upward to form the bent portion 410B. The bent portion 410B may be formed to reduce deformation transferred to the safety vent 410 during crimping. In addition, as described above, the shape of the safety vent 410 may be inverted in an abnormal operating state, causing the first portion 421 of the CID filter 420 to rise together, and the first portion 421 and the second portion 422 of the CID filter 420 to be separated from each other. This blocks the flow of current, and it is preferable that a certain amount of space is formed between the safety vent 410 and the CID filter 420 for effective current blocking. Therefore, the height of the cap assembly 400 itself may be minimized, and the bent portion 410B may be formed bent upward to increase the space between the safety vent 410 and the CID filter 420.

[0097] Meanwhile, in the case of the above-mentioned crimping connection, a strong physical pressure may be applied to the cap assembly 400, which may cause a problem of damaging the cap assembly 400. In particular, in a structure in which the safety vent 410 is exposed without an upper end cap, as in the present embodiment, there is a risk of the safety vent 410 being damaged. Nevertheless, if the safety vent 410 is made thicker than before in order to supplement the rigidity of the safety vent 410, there is a high possibility that the safety vent 410 will not reverse its shape or separate properly when the internal pressure increases.

[0098] In the cap assembly according to the present embodiment, instead of simply increasing the thickness of the safety vent 410, a curling part 410C may be provided at a portion of the safety vent 410 corresponding to the crimping part 300C. Specifically, the safety vent 410 may include a curling part 410C curved at the outer periphery of the safety vent 410. For convenience of explanation, Figs. 3 and 4 show the flange part 410F before the curling part 410C is formed, and Fig. 5 shows the flange part 410F curved inward to form the curling part 410C.

[0099] The crimping portion 300C of the battery case 300 may surround the safety vent 410 with the gasket 700 therebetween, and in particular, the crimping coupling may be performed while surrounding the curling portion 410C of the safety vent 410. Thus, the central portion of the safety vent 410 may be formed as a single layer, but the outer peripheral portion of the safety vent 410 surrounded by the crimping portion 300C may be formed as a double layer. In other words, the provision of the curling portion 410C prevents damage to the safety vent 410 that may occur during the crimping coupling, and at the same time, does not interfere with the reversal of shape or separation of the safety vent 410 when the internal pressure increases.

[0100] Hereinafter, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described in detail with reference to Fig. 9 to Fig. 15. However, parts that have been previously described will be omitted to avoid repetition.

[0101] 9 to 15 are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention, each of which shows a cross section of an upper portion of a secondary battery.

[0102] 3, 4 and 9, a method for manufacturing a secondary battery according to an embodiment of the present invention includes the steps of placing an electrode assembly 200 in a battery case 300 with an open top, and coupling a cap assembly 400 including a safety vent 410 and a CID filter 420 to the open top of the battery case 300. As described above, the electrode assembly 200 is in a jelly roll form in which the first electrode 210, the second electrode 220 and the separator 230 are wound together, and the battery case 300 may be a cylindrical case. In addition, an electrolyte may be injected into the battery case 300 together with the electrode assembly 200 before coupling the cap assembly 400.

[0103] The safety vent 410 of the cap assembly 400 is exposed to the outside at the upper end, and a vent hole 410H is formed in the safety vent 410, and a CID hole 420H is formed in the CID filter 420. The specific structures of the safety vent 410 and the CID filter 420 have been described above and will not be described again.

[0104] 5 and 6, when the cap assembly 400 is disposed, the first electrode tab 213 extended from the electrode assembly 200 is bonded to the lower surface of the CID filter 420 while closing the CID hole 420H. As described above, the first electrode tab 213 may include an upper tab portion 213a and a lower tab portion 213b.

[0105] In the step of assembling the cap assembly 400, the upper tab portion 213a is brought into close contact with the lower surface of the CID filter 420, and then the other end of the upper tab portion 213a is moved to close the CID hole 420H. Then, one end of the upper tab portion 213a is welded to the lower surface of the CID filter 420. In other words, the other end of the upper tab portion 213a is brought into close contact with the lower surface of the CID filter 420 including the CID hole 420H to close the CID hole 420H, and one end of the upper tab portion 213a is welded to the CID filter 420. In this manner, the CID filter 420 and the first electrode tab 213 are connected. In particular, the first electrode tab 213 has an elastic force in the direction of the CID hole 420H, so that the CID hole 420H can be maintained in a closed state.

[0106] Meanwhile, as shown in FIG. 7, when a protrusion 213a-1 is formed on the upper tab portion 213a of the first electrode tab 213, the protrusion 213a-1 can be inserted into the CID hole 420H during the process of connecting the CID filter 420 and the first electrode tab 213.

[0107] 9 and 10, the step of coupling the cap assembly 400 may include a step of bending an upper end 300U of the battery case 300 to form a crimping portion 300C surrounding the safety vent 410. More specifically, the gasket 700 may be positioned between the safety vent 410 of the cap assembly 400 and the battery case 300, and the upper end 300U of the battery case 300 may be bent to perform the crimping coupling.

[0108] At this time, the safety vent 410 may include a curling portion 410C that is bent at the outer periphery of the safety vent 410, and the crimping portion 300C may be crimped to surround the curling portion 410C. Such curling portion 410C may be formed by bending the upward flange portion 410F (see FIG. 4) inward.

[0109] Referring to FIG. 10, the method of manufacturing a secondary battery according to the present embodiment includes an activation step of activating the electrode assembly 200. The activation step may be performed by repeatedly charging and discharging at a constant current or voltage within a certain range while the first electrode tab 213 closes the CID hole 420H. The activation step is a process of repeatedly charging and discharging for the purpose of forming a solid electrolyte interface (SEI) film on the negative electrode surface and low voltage screening. Charging and discharging may be repeated by applying a constant current or voltage to the safety vent 410, which functions as an electrode terminal, and the battery case 300. During the activation step, gas is generated inside the battery case 300 due to the interaction between the electrode assembly and the electrolyte, and the gas accumulates inside the battery case 300, increasing the pressure.

[0110] 11, the method of manufacturing a secondary battery according to this embodiment includes a gas exhausting step of exhausting gas generated in the activation step to the outside through vent hole 410H formed in safety vent 410 and CID hole 420H formed in CID filter 420. Specifically, in the gas exhausting step, first electrode tab 213 is pressed downward through vent hole 410H and CID hole 420H to open CID hole 420H, and the gas is exhausted to the outside through CID hole 420H and vent hole 410H. An upper tab portion 213a of first electrode tab 213 is pressed.

[0111] According to the present embodiment, in the gas discharging step, the rod member 1000 may be inserted through the vent hole 410H and the CID hole 420H to push the first electrode tab 213 downward. Similarly, the rod member 1000 may push the upper tab portion 213a of the first electrode tab 213 downward. Then, the CID hole 420H is opened, and gas generated inside the battery case 300 is discharged to the outside through the CID hole 420H and the vent hole 410H.

[0112] In particular, since the secondary battery 100 according to this embodiment has a structure in which the upper end cap is removed, the rod member 1000 can be easily passed through the vent hole 410H and the CID hole 420H. In other words, the rod can be inserted without damaging the vent hole 410H and the CID hole 420H to push the first electrode tab 213. In addition, since the upper end cap is removed, gas can be more smoothly discharged.

[0113] Meanwhile, referring to Fig. 12, the method of manufacturing a secondary battery according to a modified embodiment of the present invention may include a gas exhausting step using an aspirator 1100. Specifically, instead of the rod member 1000 in Fig. 11, a separate aspirator 1100 may be inserted through the vent hole 410H and the CID hole 420H to push the upper tab portion 213a of the first electrode tab 213 downward. With the CID hole 420H open, the aspirator 1100 may aspirate gas inside the battery case 300. Compared to the case of simply inserting the rod member 1000, the gas inside the battery case 300 may be more effectively removed.

[0114] 13, after the gas discharge step, the force pressing the first electrode tab 213 is removed, and the first electrode tab 213 is returned to its original position, so that the CID hole 420H can be closed again. Removing the force pressing the first electrode tab 213 means removing the rod member 1000 or the inhalation device 1100. When the CID hole 420H is closed, gas discharge is completed.

[0115] The method for manufacturing a secondary battery according to the present embodiment may further include a welding step of welding a lower end of an inner circumferential surface of the CID hole 420H to the first electrode tab 213 after the gas discharge step. Specifically, a separate welding device (not shown) is inserted through the vent hole 410H and the CID hole 420H to weld a lower end of an inner circumferential surface of the CID hole 420H to the first electrode tab 213. FIG. 13 shows that a joint portion W is formed at this portion by welding. In particular, the upper tab portion 213a is welded to the inner circumferential surface of the CID hole 420H while the upper tab portion 213a is in close contact with the CID hole 420H to seal the gap between the CID filter 420 and the first electrode tab 213. As a result, the CID hole 420H may be primarily sealed after the gas discharge step.

[0116] 14, the method of manufacturing a secondary battery according to the present embodiment may further include a sealing ball inserting step of inserting a sealing ball 500 into the CID hole 420H through the vent hole 410H. In the sealing ball inserting step, the sealing ball 500 may be inserted into the CID hole 420H in an interference fit manner. Therefore, the CID hole 420H may be effectively sealed. Specifically, the sealing ball 500 may be joined to the CID hole 420H by ball welding. The CID hole 420H is a circular through hole, and the sealing ball 500 may be cylindrical or spherical. The sealing ball 500 may be strongly projected into the CID hole 420H, and the sealing ball 500 may be inserted into the CID hole 420H.

[0117] 15, the method of manufacturing a secondary battery according to this embodiment may further include the step of melting the sealing ball 500 inserted into the CID hole 420H. Specifically, a melting device 1200 may be inserted through the vent hole 410H, and heat may be applied to the sealing ball 500. As a result, the partially melted sealing ball 500 is bonded to the inner circumferential surface of the CID hole 420H. Then, the CID hole 420H may be completely sealed.

[0118] During the activation step, a large amount of gas is generated due to the formation of the electrode coating and the decomposition of water inside the cell, and since the amount of gas generated during the activation step is large and it continuously reacts with the electrode coating, a process for discharging the gas is required. As described above, the secondary battery 100 manufactured according to an embodiment of the present invention is finally sealed after discharging the gas generated during the activation step, thereby solving problems such as expansion and deformation of the electrode assembly due to the remaining gas and problems of lithium precipitation due to bubbles of the remaining gas.

[0119] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are merely for convenience of explanation and may change depending on the position of the target object, the position of the observer, etc.

[0120] A plurality of secondary batteries according to the present embodiment may be assembled to form a battery module, and the battery module may be mounted with various control and protection systems, such as a Battery Management System (BMS) and a cooling system, to form a battery pack.

[0121] The secondary battery, the battery module, and the battery pack may be applied to various devices, specifically, but not limited to, transportation means such as electric bicycles, electric cars, and hybrids, and ESS (Energy Storage Systems).

[0122] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims also fall within the scope of the present invention. [Explanation of symbols]

[0123] 100: Secondary battery 200: Electrode assembly 300: Battery case 400: Cap assembly 410: Safety vent 410H: Vent hole 420: CID filter 420H: CID Hall

Claims

1. electrode assembly; a battery case in which the electrode assembly is housed and which has an open top; and a cap assembly coupled to the open top of the battery case; the cap assembly includes a safety vent; and a CID filter located below the safety vent; The safety vent is exposed to the outside at an upper end, The safety vent has a vent hole penetrating vertically, The CID filter has a CID hole penetrating vertically and connected to the vent hole, a first electrode tab extending from the electrode assembly is joined to the CID filter; The vent hole and the CID hole can be in a closed or open state by the first electrode tab, and the secondary battery is capable of discharging gas generated during an activation process.

2. the vent hole and the CID hole are located on the same vertical line; The secondary battery of claim 1 , wherein the first electrode tab closing the CID hole is visible from the outside through the vent hole and the CID hole.

3. The secondary battery of claim 1 , wherein the vent hole has a larger diameter than the CID hole.

4. the first electrode tab includes an upper tab portion and a lower tab portion; the lower tab portion is connected to the electrode assembly, The secondary battery of claim 1 , wherein one end of the upper tab portion connected to the lower tab portion is joined to the CID filter.

5. The secondary battery of claim 4 , wherein the other end of the upper tab portion is in close contact with or spaced from the lower surface of the CID filter to close or open the CID hole.

6. the first electrode tab includes a material having an elastic restoring force; The secondary battery of claim 5 , wherein the other end of the upper tab portion is elastically in close contact with a lower surface of the CID filter.

7. The secondary battery according to claim 4 , wherein a lower end of an inner circumferential surface of the CID hole and the upper tab portion are welded to each other.

8. The secondary battery of claim 1 , wherein the first electrode tab includes a protrusion that is inserted into the CID hole.

9. The secondary battery of claim 1 , further comprising a sealing ball inserted into the CID hole.

10. The secondary battery according to claim 1 , wherein an upper end of the battery case is bent to form a crimped portion while surrounding an outer periphery of the safety vent.

11. placing the electrode assembly in a battery case having an open top; coupling a cap assembly including a safety vent and a CID filter to the open top of the battery case; activating the electrode assembly; and a gas exhaust step of exhausting the gas generated in the activation step to the outside through a vent hole formed in the safety vent and a CID hole formed in the CID filter; The safety vent is exposed to the outside at an upper end, a first electrode tab extending from the electrode assembly is attached to the CID filter while closing the CID hole; In the gas discharging step, the first electrode tab is pressed downward through the vent hole and the CID hole to open the CID hole, and the gas is discharged to the outside through the CID hole and the vent hole.

12. In the gas exhaust step, The method of claim 11, further comprising inserting a rod member or an inhalation device through the vent hole and the CID hole to push the first electrode tab downward.

13. 12. The method of claim 11, further comprising removing the force pressing the first electrode tab after the gas discharge step, and returning the first electrode tab to its original position to close the CID hole again.

14. The method of claim 11, further comprising the step of welding a lower end of an inner periphery of the CID hole to the first electrode tab after the gas exhausting step.

15. The method of claim 11 , further comprising inserting a sealing ball into the CID hole through the vent hole.

16. The method of claim 15, further comprising melting the sealing ball inserted into the CID hole.

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