Secondary battery and manufacturing method thereof

Abstract

A secondary battery according to an 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 including a safety vent that is exposed to the outside at its upper end. The safety vent has a discharge hole formed therein, and the discharge hole is filled with a block.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0045794 dated April 8, 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, with the depletion of fossil fuels causing rising energy prices and increasing concerns about environmental pollution, the demand for environmentally friendly alternative energy sources has become an essential factor for future life. As a result, research into various power generation technologies, such as nuclear, solar, wind, and tidal power, is ongoing, and there is also great interest in power storage devices to more efficiently use the energy produced in this way.

[0004] In particular, the demand for batteries as an energy source is rapidly increasing due to technological developments and increasing demand for mobile devices, and accordingly, 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 stacked structure consisting of a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. Representative examples include a jelly-roll electrode assembly, in which long sheet-like positive and negative electrodes are wound with a separator interposed therebetween, and a stack electrode assembly, in which multiple positive and negative electrodes cut into predetermined sizes are stacked in order with a separator interposed therebetween. Recently, to solve the problems associated with the jelly-roll electrode assembly and stack electrode assembly, a stack / folded electrode assembly has been developed, which is a hybrid of the jelly-roll and stack types, in which unit cells, each consisting of a predetermined number of positive and negative electrodes stacked with a separator interposed therebetween, are positioned on a separator film and then wound in order.

[0007] Secondary batteries can also 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-shaped case made of an aluminum laminate sheet.

[0008] Meanwhile, for secondary batteries to be effectively utilized in the market, they must be safe while also meeting the performance requirements for their intended use. When designing a secondary battery, design factors are determined by considering both performance and safety. Once the design and manufacturing of a battery is complete, it can undergo performance evaluations such as lifespan, high-rate characteristics, and high / low temperature characteristics, as well as safety evaluations such as overcharge, over-discharge, impact, nail tests, and hot box tests.

[0009] Among various types of secondary batteries, cylindrical secondary batteries may include a current interrupt device (CID) that cuts off the current between the electrode terminal and the electrode tab to prevent further reactions when gas is rapidly generated inside the secondary battery due to an abnormal condition such as overcharging, causing the internal pressure to exceed 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 the open top of the cylindrical case 30, thereby fabricating 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 (43, Current Interrupt Device, CID). The upper cap 41 and the safety vent 42 may form a tightly fitted structure, and the safety vent 42 may be connected to the center of the current interrupt device 43. A first electrode tab 21t protruding from the first electrode 21 may be connected to the lower end of the current interrupt device 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 upper end 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] In addition, a gasket 70 for sealing between the cap assembly 40 and the cylindrical case 30 and a CID gasket 80 surrounding the edge of the current interrupting member 43 may be disposed.

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

[0017] 2, when cylindrical secondary battery 10 is exposed to high temperatures or placed in an abnormal operating state, and internal pressure increases, safety vent 42 reverses its shape, separating current interruption member 43 to interrupt current. Specifically, current interruption member 43 is divided into portion 43a connected to safety vent 42 and portion 43b connected to first electrode tab 21t, interrupting the flow of current between top cap 41, which functions as an electrode terminal, and first electrode tab 21t. Furthermore, when internal pressure increases significantly, the notch in safety vent 42 breaks, opening safety vent 42 and allowing internal gas to be released.

[0018] When a top cap 41 is provided as in the conventional cylindrical secondary battery 10, structural rigidity is excellent, but there is a drawback in that when the safety vent 42 is opened to release internal gas, the safety vent 42 does not open completely due to the reduced spatial area caused by the top cap 41, and gas release is restricted.

[0019] Lithium secondary batteries typically undergo a formation process, or activation process, during their manufacturing process. This activation process involves charging and discharging the battery after assembly to activate it. During charging, lithium ions released from the positive electrode migrate to and are inserted into the negative electrode, forming a solid electrolyte interface (SEI) on the negative electrode surface. This activation process is typically 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 water inside the cell. Since the amount of gas generated during the activation process is large and it reacts continuously with the electrode coating, a process to exhaust this gas is required. This is called the degassing process.

[0021] However, referring again to Figures 1 and 2, conventional cylindrical secondary batteries 10 must be kept sealed after the electrolyte is injected, making it difficult to vent gas generated during the activation process. If gas generated during the activation process cannot be vented, it can interfere with the battery reaction between the positive and negative electrodes, adversely affecting the battery's initial capacity, formation of a stable solid electrolyte interface (SEI), and life performance characteristics. Furthermore, if gas cannot be vented, it can affect the results of the safety evaluations described above.

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

[0023] SUMMARY OF THE INVENTION An object of the present invention is to provide a secondary battery capable of discharging gas after a pre-activation process or an activation process, 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 can 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 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 including a safety vent that is exposed to the outside at its upper end. The safety vent has a discharge hole formed therein, and the discharge hole is filled with a block.

[0026] The block may be joined to the discharge hole by ball welding.

[0027] An upper end of the battery case may be bent to surround the outer periphery of the safety vent to form a crimping portion.

[0028] The safety vent may include a curling portion bent at the outer periphery of the safety vent, and the crimping portion may surround the curling portion to form a crimped connection.

[0029] The cap assembly may include a current interrupting member positioned below the safety vent, and a central portion of the safety vent and the current interrupting member may be connected to each other. The exhaust hole may be positioned between the central portion and the outer periphery of the safety vent.

[0030] A method for manufacturing a secondary battery according to an embodiment of the present invention includes the steps of: placing an electrode assembly in a battery case having an open top; attaching a cap assembly having a vent hole formed in the open top of the battery case; discharging gas from inside the battery case to the outside through the vent hole; and sealing the vent hole by filling a block into the vent hole. The cap assembly includes a safety vent exposed to the outside at an upper end, and the vent hole is formed in the safety vent.

[0031] In the sealing step, the block may be joined to the discharge hole by ball welding.

[0032] The diameter of the block may be larger than the inner diameter of the discharge hole, and the block may be projected into the discharge hole and inserted into the discharge hole.

[0033] The step of joining the cap assembly may include bending an upper end of the battery case to form a crimped portion surrounding the safety vent.

[0034] The safety vent may include a curled portion curved around a periphery of the safety vent, and the crimped connection may be made such that the crimped portion surrounds the curled portion.

[0035] The method for manufacturing a secondary battery may further include a pre-activation step of activating the electrode assembly in advance, and the gas discharge step may discharge gas generated during the pre-activation step to the outside through the discharge hole.

[0036] The method for manufacturing a secondary battery may further include an activation step of activating the electrode assembly, which may be performed after the sealing step.

[0037] The method for manufacturing a secondary battery may further include a temporary sealing step of temporarily sealing the exhaust hole, an activation step of activating the electrode assembly, and a temporary unsealing step of unsealing the exhaust hole. In the gas exhausting step, gas generated in the activation step may be exhausted to the outside through the exhaust hole.

[0038] The gas venting step may be performed simultaneously with the temporary unsealing step or immediately after the temporary unsealing step.

[0039] The sealing step may be performed after the gas evacuation step. [Effects of the Invention]

[0040] According to an embodiment of the present invention, by removing the top cap and exposing the safety vent to the outside, and eliminating spatial constraints on the safety vent, the safety vent can be fully opened when the internal pressure increases, and can be effective in discharging gas.

[0041] In addition, since the safety vent is exposed to the outside, a separate exhaust hole can be formed in the safety vent to easily exhaust gas generated during the pre-activation process or activation process, thereby resolving problems such as expansion and deformation of the electrode assembly due to gas and problems such as lithium deposition due to residual gas bubbles.

[0042] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned above will be clearly understood by those skilled in the art from the claims. [Brief explanation of the drawings]

[0043] [Figure 1] FIG. 1 is a partial cross-sectional view showing a cross section of an upper portion of a conventional cylindrical secondary battery. [Figure 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. [Figure 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. FIG. [Figure 5] 1 is a cross-sectional view of an upper portion of a secondary battery according to an embodiment of the present invention; [Figure 6] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 7] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 8] 2A to 2C are cross-sectional views illustrating a method for manufacturing a secondary battery 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] 5A to 5C are cross-sectional views illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention. [Figure 11] 5A to 5C are cross-sectional views illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention. [Figure 12] 5A to 5C are cross-sectional views illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention. [Figure 13] 5A to 5C are cross-sectional views illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention may be embodied in various different forms and is not limited to the embodiments set forth herein.

[0045] In order to clearly explain the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0046] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown. In the drawings, thicknesses are exaggerated to clearly show multiple layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0047] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly above" that 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. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" or "above" the opposite direction of gravity.

[0048] Also, throughout the specification, when a part is said to "comprise" a certain element, this means that it may further include other elements, rather than excluding other elements, unless otherwise specified to the contrary.

[0049] Also, throughout the specification, "on a plane" means when the subject part is viewed from above, and "on a cross section" means when the subject part is cut vertically and viewed from the side.

[0050] 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 the upper part of a secondary battery according to an embodiment of the present invention. In particular, Fig. 5 is a cross-sectional view showing the upper part of a single surface cut along the xz plane after assembling the components of the secondary battery of Fig. 3.

[0051] 3 to 5, a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 200; a battery case 300 that houses the electrode assembly 200 and has an open top; and a cap assembly 400 that is coupled to the open top of the battery case 300.

[0052] First, the electrode assembly 200 according to this 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.

[0053] 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.

[0054] 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.

[0055] In this case, the first electrode 210 may be a positive electrode, and the second electrode 220 may be a negative electrode. Therefore, 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 the direction where the cap assembly 400 is located (z-axis direction), and the second electrode tab 223 may protrude in the direction where the bottom of the battery case 300 is located (-z-axis direction).

[0056] Meanwhile, the battery case 300 is a structure that houses the electrode assembly 200 impregnated with an electrolyte, and may be made of a metal material and may be a cylindrical case.

[0057] The cap assembly 400 according to this embodiment includes a safety vent (410) exposed to the outside at its upper end. A discharge hole 410H is formed in the safety vent 410, and a block 500 is filled in the discharge hole 410H. The discharge hole 410H and the block 500 will be described later. Meanwhile, the cap assembly 400 may include a current interrupt device (420, CID) located below the safety vent 410.

[0058] The cap assembly 400 according to this embodiment differs from the conventional cylindrical secondary battery (10, see FIG. 1) in that the top cap is removed, and the safety vent 410 can be exposed to the outside at the top.

[0059] The safety vent 410 may be positioned on the current interrupting member 420 and electrically connected to the current interrupting member 420. Specifically, a central portion of the safety vent 410 may be physically and electrically connected to a first portion 421 of the current interrupting member 420, which will be described later. A first electrode tab 213 protruding from the first electrode 210 may be connected to a lower end of the current interrupting member 420.

[0060] The safety vent 410 is a thin film structure that allows current to pass through, and may be a disc-shaped plate. The safety vent 410, the current interrupting member 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.

[0061] According to this embodiment, the current interrupting member 420 is a plate member through which current passes and may have through-holes 420H formed therein for gas discharge. The current interrupting member 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 in the center of the current interrupting member 420, and the second portion 422 may be located in the outer periphery of the current interrupting member 420.

[0062] When the internal pressure of the secondary battery 100 increases, the shape of the safety vent 410 may reverse. As the shape of the safety vent 410 reverses, the first portion 421 of the current interrupting member 420 may rise, causing the first portion 421 and the second portion 422 of the current interrupting member 420 to separate from each other. To induce such separation due to an increase in internal pressure, the gap between the first portion 421 and the second portion 422 may be designed to have a somewhat weak strength. The separation of the first portion 421 and the second portion 422 interrupts the current between the safety vent 410 and the first electrode tab 213.

[0063] Although not specifically shown, the safety vent 410 has a notch structure, such as a groove. When the internal pressure increases, this notch structure tears or tears, opening the safety vent 410 and allowing internal gas to escape. In the case of a conventional cylindrical secondary battery (10, see FIG. 1), the top cap 41 is positioned over the safety vent 42, resulting in a reduced spatial area and allowing the safety vent 42 to fully open. This prevents effective gas escape. Furthermore, the top cap 41 itself obstructs gas escape. In contrast, the secondary battery 100 according to this embodiment does not have a top cap, and the safety vent 410 is exposed to the outside at the top. This allows the safety vent 410 to freely invert or separate when the internal pressure increases. This provides a more effective gas escape than the conventional cylindrical secondary battery 10.

[0064] The structure of the discharge hole 410H and the block 500 according to this embodiment will be described in detail below.

[0065] As described above, the safety vent 410 has a through-hole-shaped discharge hole 410H, which is filled with a block 500. As an example, the discharge hole 410H may be a circular through-hole, and the block 500 may be ball-shaped. The ball-shaped block 500 may be joined to the discharge hole 410H by ball welding. Here, ball welding refers to a joining method in which a ball-shaped element is thrust into a hole with a smaller diameter than the ball to block the hole. That is, as will be described later, the diameter of the ball-shaped block 500 before being filled into the discharge hole 410H may be larger than the inner diameter of the discharge hole 410H. The discharge hole 410H can be blocked by thrusting the block 500 forcefully into the discharge hole 410H.

[0066] As mentioned above, lithium secondary batteries undergo a formation process, or activation process, during their manufacturing process. This activation process is generally performed by repeatedly charging and discharging at a constant current or voltage within a certain range. During this activation process, a large amount of gas is generated due to the formation of an electrode coating and the decomposition of water inside the cell. Since the gas generated during the activation process is large in quantity and continues to react with the electrode coating, a process to release it is required. This is called the degassing or degassing process.

[0067] The secondary battery 100 according to this embodiment can discharge gas generated during a pre-activation process or an activation process (described later) to the outside through the discharge hole 410H formed in the safety vent 410. Specifically, the pre-activation process or the activation process is performed on the secondary battery 100, which is formed by combining the battery case 300 and the cap assembly 400, and gas generated during the process is discharged to the outside through the discharge hole 410H. Once the gas discharge is complete, the discharge hole 410H can be filled with a block 500 using the ball welding method described above to seal the secondary battery 100. The secondary battery 100 according to this embodiment can easily discharge gas from inside the battery case 300, thereby preventing an increase in internal pressure and performance degradation. In other words, problems such as expansion and deformation of the electrode assembly due to gas and problems of lithium deposition due to residual gas bubbles can be solved.

[0068] In particular, the safety vent 410 according to this embodiment is exposed to the outside by removing the top cap, making it easy to form a vent hole 410H for gas release. In the case of a conventional cylindrical secondary battery (10, see FIG. 1), the presence of the top cap 41 makes it structurally very difficult to re-close the vent hole provided for gas release after gas release. To release gas, vent 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 complex and difficult to close the vent hole formed in the safety vent 42. In contrast, the cap assembly 400 according to this embodiment has a structure in which the safety vent 410 is exposed at the top, making it easy to seal the vent hole 410H after gas release. Ball welding, a mechanical joining method described above, can also be used without limitation.

[0069] Meanwhile, the number of the exhaust holes 410H is not particularly limited, and may be one or more depending on the degree of gas exhaust.

[0070] 5, the battery case 300 according to this 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.

[0071] The crimping portion 300C is located on the beading portion 300B and refers to a portion that surrounds 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.

[0072] The sealing gasket 700 is attached to the inner surfaces 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. That is, 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 and crimped to form the crimping portion 300C. That is, the cap assembly 400 is attached and the secondary battery 100 is sealed by the crimping. The gasket 700 may be positioned between the crimping portion 300C and the safety vent 410.

[0073] Meanwhile, the safety vent 410 according to this embodiment may have a bent portion 410B. Specifically, as shown in FIGS. 4 and 5, a portion of the safety vent 410 may be bent upward to form the bent portion 410B. The formation of this bent portion 410B reduces deformation transmitted to the safety vent 410 during crimping. As described above, in an abnormal operating state, the shape of the safety vent 410 reverses, causing the first portion 421 of the current interrupting member 420 to rise and the first portion 421 and second portion 422 of the current interrupting member 420 to separate from each other. Therefore, while the flow of current is interrupted, it is preferable to form a certain amount of space between the safety vent 410 and the current interrupting member 420 for effective current interruption. Therefore, the height of the cap assembly 400 itself may be minimized, and the bent portion 410B bent upward may be formed to increase the space between the safety vent 410 and the current interrupting member 420.

[0074] Meanwhile, in the case of the above-described crimping connection, a strong physical pressure may be applied to the cap assembly 400, which may result in damage to 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 damage to the safety vent 410. However, if the thickness of the safety vent 410 is made thicker than before to supplement the rigidity of the safety vent 410, there is a high possibility that the safety vent 410 will not properly reverse its shape or separate when the internal pressure increases.

[0075] In the cap assembly according to this embodiment, rather than simply increasing the thickness of the safety vent 410, a curling portion (410C) may be provided in a portion of the safety vent 410 corresponding to the crimping portion 300C. Specifically, the safety vent 410 may include a curling portion 410C that is bent at the outer periphery of the safety vent 410. For convenience of explanation, FIGS. 3 and 4 show the flange portion (410F) before the curling portion 410C is formed, and FIG. 5 shows the flange portion 410F bent inward to form the curling portion 410C.

[0076] The crimping portion 300C of the battery case 300 may surround the safety vent 410 with the gasket 700 interposed therebetween, and crimping may be performed around the curling portion 410C of the safety vent 410. Therefore, the central portion of the safety vent 410 is single-layered, while the outer periphery of the safety vent 410 surrounded by the crimping portion 300C is double-layered. In other words, the curling portion 410C prevents damage to the safety vent 410 that may occur during crimping and also prevents the safety vent 410 from being reversed or separated when the internal pressure increases.

[0077] Meanwhile, the location of the exhaust hole 410H is not particularly limited, but it is preferable that the location is one that does not restrict gas exhaust. As an example, the exhaust hole 410H according to this embodiment may be located between the central portion and the outer periphery of the safety vent 410. Here, the central portion of the safety vent 410 refers to the portion connected to the first portion 421 of the current interrupting member 420, and the outer periphery of the safety vent 410 refers to the portion where the curled portion 410C is formed.

[0078] 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. 6 to Fig. 9. However, parts that overlap with the contents previously described will be omitted to avoid repetition.

[0079] 6 to 9 are cross-sectional views illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention, showing a cross section of an upper portion of the secondary battery.

[0080] 3 and 6, 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 an open-top battery case 300 and attaching a cap assembly 400 having a discharge hole 410H formed therein to the open top of the battery case 300. As described above, the electrode assembly 200 may be in a jelly-roll form with the first electrode 210, the second electrode 220, and the separator 230 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 attaching the cap assembly 400.

[0081] The cap assembly 400 includes a safety vent 410 exposed to the outside at its upper end, and a discharge hole 410H is formed in the safety vent 410. The specific structures of the safety vent 410 and the discharge hole 410H have been previously described and will not be described further.

[0082] 6 and 7, 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.

[0083] In this case, the safety vent 410 may include a curled portion 410C bent at the outer periphery of the safety vent 410, and the crimping portion 300C may be crimped to surround the curled portion 410C. The curled portion 410C may be formed by bending an upward flange portion (410F, see FIG. 4) inward.

[0084] Next, referring to FIG. 7, the method for manufacturing a secondary battery according to this embodiment includes a gas exhausting step of exhausting gas inside the battery case 300 to the outside through the exhaust hole 410H.

[0085] More specifically, the method for manufacturing a secondary battery according to this embodiment may further include a pre-activation step of activating the electrode assembly 200 housed in the battery case 300. Here, the pre-activation step is a step performed to pre-evacuate gas before the activation step. That is, the pre-activation step is a step performed before the activation step for the purpose of gas generation. For example, in the pre-activation step, only charging at a low SOC (state of charge) may be performed. However, the specific content of the pre-activation step may vary depending on the model, and in another embodiment, it may be a form in which charging and discharging are repeated at a constant current or voltage within a certain range.

[0086] During the pre-activation step, charging can be performed or charging and discharging can be repeated through the safety vent 410, which functions as an electrode terminal, and the battery case 300. The pre-activation step can be performed after the cap assembly 400 is coupled to the open top of the battery case 300 by crimping. During the gas exhaust step, gas generated during the pre-activation step can be exhausted from the inside of the secondary battery 100 to the outside through the exhaust hole 410H. That is, the pre-activation step is performed with the exhaust hole 410H open, and gas generated during the pre-activation step can be exhausted to the outside through the exhaust hole 410H.

[0087] 8, the method for manufacturing a secondary battery according to this embodiment includes a sealing step of filling the discharge hole 410H with a block 500. During the sealing step, the block 500 may be joined to the discharge hole 410H by ball welding. The discharge hole 410H may be a circular through-hole, and the block 500 may be ball-shaped. The ball-shaped block 500 may be joined to the discharge hole 410H by ball welding.

[0088] Specifically, the diameter d2 of the ball-shaped block 500 may be larger than the inner diameter d1 of the discharge hole 410H, and the block 500 may be inserted into the discharge hole 410H by being thrust strongly into the discharge hole 410H. The discharge hole 410H may be sealed using ball welding in this manner.

[0089] As described above, the secondary battery 100 according to this embodiment has a structure in which the upper end cap is removed and the safety vent 410 is exposed at the top end, so that it is easy to seal the exhaust hole 410H using the ball welding method after exhausting the gas.

[0090] Referring to FIG. 9, the method for manufacturing a secondary battery according to this embodiment may further include an activation step of activating the electrode assembly 200. The activation step may be performed after the sealing step. That is, after gas generated in the pre-activation step is discharged, the exhaust hole 410H is sealed in the sealing step. In this manner, the activation step may be performed by repeatedly charging and discharging the secondary battery 100 at a constant current or constant voltage within a certain range while the secondary battery 100 is completely sealed. The activation step is a process in which charging and discharging are repeated to form a solid electrolyte interface (SEI) film on the negative electrode surface and for low-voltage screening. Charge and discharge may be repeated by applying a constant current or constant voltage to the safety vent 410, which functions as an electrode terminal, and the battery case 300.

[0091] As described above, the secondary battery 100 manufactured according to an embodiment of the present invention can solve problems such as expansion and deformation of the electrode assembly due to residual gas and problems of lithium deposition due to residual gas bubbles by performing the pre-activation step and discharging gas generated during the pre-activation step.

[0092] Hereinafter, a method for manufacturing a secondary battery according to another embodiment of the present invention will be described in detail with reference to Figs. 10 to 13. However, parts that overlap with the contents previously described will be omitted to avoid repetition.

[0093] 10 to 13 are cross-sectional views illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention, showing a cross section of an upper portion of the secondary battery.

[0094] 3 and 6, a method for manufacturing a secondary battery according to another embodiment of the present invention includes the steps of placing an electrode assembly 200 in a battery case 300 having an open top and attaching a cap assembly 400 having a discharge hole 410H formed therein to the open top of the battery case 300. These steps are the same as those previously described, and therefore further description will be omitted.

[0095] 10 and 11, the method for manufacturing a secondary battery according to this embodiment may include a temporary sealing step of temporarily sealing the discharge hole 410H. Specifically, to temporarily close the discharge hole 410H, the discharge hole 410H may be covered with a cover member 600. For example, the cover member 600 may have a portion corresponding to the diameter of the discharge hole 410H and may be inserted into the discharge hole 410H.

[0096] 11, the method for manufacturing a secondary battery according to this embodiment may include an activation step of activating the electrode assembly 200. The activation step may be performed after the temporary sealing step. The activation step may be performed by repeatedly charging and discharging at a constant current or voltage within a certain range while the discharge hole 410H is temporarily sealed by the cover member 600. The activation step is a process in which charging and discharging are repeated for the purposes of forming a solid electrolyte interface (SEI) film on the surface of the negative electrode and for low-voltage selection.

[0097] 12, the method for manufacturing a secondary battery according to this embodiment may include a temporary unsealing step of unsealing the discharge hole 410H. Specifically, the cover member 600 may be removed from the discharge hole 410H to reopen the discharge hole 410H. The temporary unsealing step may be performed after the activation step.

[0098] In the gas exhausting step, gas generated in the activation step may be exhausted to the outside through the exhaust hole 410H. The gas exhausting step may be performed simultaneously with or immediately after the temporary unsealing step. In other words, the temporary unsealing step reopens the exhaust hole 410H, allowing gas generated inside the secondary battery 100 during the activation step to be exhausted to the outside through the exhaust hole 410H.

[0099] 13, this is followed by a sealing step in which the exhaust hole 410H is filled with a block 500. The sealing step may be performed after the gas exhaust step.

[0100] In the sealing step, the block 500 may be joined to the discharge hole 410H by ball welding. The discharge hole 410H may be a circular through-hole, and the block 500 may be ball-shaped. The block 500 may be thrust hard into the discharge hole 410H, and then the block 500 may be inserted into the discharge hole 410H. That is, ball welding may be performed. This sealing step may be the same as or similar to the content previously described with reference to FIG. 8. To avoid repetition, detailed description of the sealing step will be omitted.

[0101] As described above, the secondary battery 100 manufactured according to another embodiment of the present invention is finally sealed after discharging gas generated during the activation step, thereby solving problems such as expansion and deformation of the electrode assembly due to residual gas and problems of lithium deposition due to residual gas bubbles.

[0102] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are used for convenience of explanation and may change depending on the position of the object of interest, the position of the observer, etc.

[0103] A plurality of secondary batteries according to the present embodiment may be assembled to form a battery module, and the battery module may be attached to various control and protection systems, such as a battery management system (BMS) and a cooling system, to form a battery pack.

[0104] The secondary battery, the battery module, or the battery pack may be applied to various devices, specifically, but not limited to, transportation means such as electric bicycles, electric cars, and hybrid vehicles, and may be applied to various devices that can use secondary batteries.

[0105] 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 following claims also fall within the scope of the present invention. [Explanation of symbols]

[0106] 100 Secondary battery 400 Cap Assembly 410 Safety Vent 410H Discharge hole 500 blocks

Claims

1. electrode assembly; a battery case containing the electrode assembly and having an open top; and a cap assembly coupled to the open top of the battery case; the cap assembly includes a safety vent exposed to the outside at an upper end; The safety vent is formed with a discharge hole; The drain hole is filled with a block, The block is joined to the discharge hole by ball welding. Secondary battery.

2. electrode assembly; a battery case containing the electrode assembly and having an open top; and a cap assembly coupled to the open top of the battery case; the cap assembly includes a safety vent exposed to the outside at an upper end; The safety vent is formed with a discharge hole; The drain hole is filled with a block, an upper end of the battery case is bent to surround an outer periphery of the safety vent and form a crimping portion; The block is joined to the discharge hole by ball welding. Secondary battery.

3. the safety vent includes a curved curling portion at the periphery of the safety vent; The secondary battery according to claim 2 , wherein the crimping portion surrounds the curling portion to form a crimped connection.

4. the cap assembly includes a current interrupting member located below the safety vent; the central portion of the safety vent and the current interrupting member are connected to each other; The secondary battery of claim 3 , wherein the exhaust hole is located between the central portion and the outer periphery portion of the safety vent.

5. placing the electrode assembly in a battery case with an open top; attaching a cap assembly having a drain hole to the open top of the battery case; a gas exhaust step of exhausting gas from the inside of the battery case to the outside through the exhaust hole; and a sealing step of filling the discharge hole with a block; the cap assembly includes a safety vent exposed to the outside at an upper end; The method for manufacturing a secondary battery, wherein the discharge hole is formed in the safety vent.

6. The method of manufacturing a secondary battery according to claim 5 , wherein the sealing step is performed by joining the block to the discharge hole by ball welding.

7. The diameter of the block is larger than the inner diameter of the discharge hole, The method for manufacturing a secondary battery according to claim 6 , wherein the block is ejected into the discharge hole, and the block is inserted into the discharge hole.

8. The method of claim 5 , wherein the joining of the cap assembly includes bending an upper end of the battery case to form a crimped portion surrounding the safety vent.

9. the safety vent includes a curled portion curved at a periphery of the safety vent; The method of manufacturing a secondary battery according to claim 8 , wherein the crimping is performed so that the crimping portion surrounds the curling portion.

10. The method further includes a pre-activation step of activating the electrode assembly in advance, The method of claim 5 , wherein in the gas exhausting step, gas generated in the pre-activation step is exhausted to the outside through the exhaust hole.

11. The method further includes activating the electrode assembly, The method of claim 10 , wherein the activation step is performed after the sealing step.

12. a temporary sealing step of temporarily sealing the discharge hole; activating the electrode assembly; and The method further includes a step of releasing a temporary sealing state of the discharge hole, The method of claim 5 , wherein in the gas exhausting step, gas generated in the activation step is exhausted to the outside through the exhaust hole.

13. The method of manufacturing a secondary battery according to claim 12 , wherein the gas discharge step is performed simultaneously with or immediately after the temporary unsealing step.

14. The method of claim 12 , wherein the sealing step is performed after the gas exhausting step.

Images