Secondary battery and method for manufacturing a secondary battery

Abstract

The present invention relates to a secondary battery and a method for manufacturing a secondary battery, and moreover, to a secondary battery and a method for manufacturing a secondary battery that utilize a liquefied gas electrolyte obtained by liquefying a gas-phase electrolyte under high pressure, thereby improving impregnation with the active material compared to conventional electrolytes, making it possible to design and realize a high-power battery, and that low-temperature performance can be ensured more easily than with general electrolytes, and that this can be achieved more easily and efficiently than in conventional methods.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0118454 filed on September 6, 2023, and all contents disclosed in the document of the corresponding Korean patent application are incorporated as a part of the present specification.

[0002] The present invention relates to a secondary battery and a method for manufacturing a secondary battery. By using a liquefied gas electrolyte obtained by liquefying a gaseous electrolyte under high pressure, the present invention can design and implement a high-output battery by improving impregnation properties with active materials compared with conventional electrolytes, can more easily secure low-temperature performance compared with common electrolytes, and further relates to a secondary battery and a method for manufacturing a secondary battery that can be implemented more simply and efficiently than conventional techniques.

Background Art

[0003] Secondary batteries are classified into cylindrical batteries and prismatic batteries, in which an electrode assembly is contained in a cylindrical or prismatic metal can, and pouch-type batteries, in which an electrode assembly is contained in a pouch-type casing made of an aluminum laminate sheet, depending on the shape of the battery case.

[0004] In addition, the electrode assembly contained in the battery case is a chargeable and dischargeable power generating element having a stacked structure of positive electrode / separator / negative electrode, and is classified into: a jelly-roll type structure obtained by interposing a separator between a long sheet-shaped positive electrode coated with an active material and a long sheet-shaped negative electrode coated with an active material and then winding the same; a stack-type structure obtained by sequentially stacking a large number of positive electrodes and negative electrodes each having a predetermined size with separators interposed therebetween; and a stack / folding type electrode assembly having a structure obtained by winding bicells or full cells formed by stacking positive electrodes and negative electrodes in predetermined units with separators interposed therebetween.

[0005] Among these, the jelly roll type electrode assembly is widely manufactured due to its ease of production and high energy density per unit weight. The jelly roll type electrode assembly can be manufactured by assembling a laminate consisting of a long sheet-like positive electrode, a negative electrode, and a separator interposed between them, and then winding the sheet in the longitudinal direction with a winding core in contact with one end of the electrode laminate. Furthermore, such a jelly roll type electrode assembly can be inserted into a battery case made of a cylindrical metal can to form a cylindrical secondary battery.

[0006] These cylindrical rechargeable batteries are designed to have a high energy density, and this increased energy density necessitates a high level of stability in lithium rechargeable batteries, which in turn is leading to an increasing demand for cylindrical batteries.

[0007] Conventionally, in cylindrical secondary batteries, the liquid electrolyte was inserted into the battery case along with the electrode assembly. An electrolyte is a substance that chemically dissociates into cations and anions in water or a polar solvent, and whose solution exhibits conductivity. Such electrolytes were usually injected into the inside of the battery case in a liquid state. However, the impregnation of such liquid electrolytes into the electrodes has limitations, which has limited the realization of high-power batteries. Furthermore, secondary batteries generate heat internally during manufacturing and use, so low-temperature performance is necessary to cool these high temperatures. Conventional liquid electrolytes also had limitations in terms of low-temperature performance. Therefore, the use of liquefied gaseous electrolytes, which are in a state where the gaseous electrolyte is liquefied under high pressure, has become an issue. However, such liquefied gaseous electrolytes are not easy to handle or use under normal room temperature and pressure conditions, so research into easier and more efficient methods is needed. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention was derived to solve the above-mentioned problems, and the object of the present invention is to provide a secondary battery and a method for manufacturing a secondary battery that utilize a liquefied gas electrolyte obtained by liquefying a gas-phase electrolyte under high pressure, thereby improving impregnation with the active material compared to conventional electrolytes, enabling the design and realization of a high-power battery, making it easier to ensure low-temperature performance compared to general electrolytes, and enabling this to be achieved more easily and efficiently than in conventional methods. [Means for solving the problem]

[0009] The secondary battery according to the present invention includes an electrode assembly including a positive electrode, a separator, and a negative electrode; a case in which the electrode assembly is housed; and a liquefied gas electrolyte housed inside the case together with the electrode assembly. The case includes a side wall portion located on the side of the electrode assembly, and a locking portion extending inward from the upper end of the side wall portion at a predetermined angle to the side wall portion. The case includes a main body with an upper opening formed inside the locking portion and a lower opening formed below the side wall portion, a top cap unit coupled to the upper opening of the main body, and a bottom unit coupled to the lower opening of the main body. As the top cap unit is pressurized outward by the internal pressure of the case formed by the liquefied gas electrolyte, the top cap unit is locked to the locking portion and sealed to the upper opening.

[0010] The bottom unit can be attached to the lower opening of the main body by welding.

[0011] The top cap unit may include a protruding portion that is inserted into the upper opening of the main body, and an edge extension portion that extends from the periphery of the protruding portion toward the side wall and is locked into a locking portion.

[0012] The edge extension can extend from the lower peripheral edge of the protruding portion toward the side wall portion.

[0013] As the top cap unit is pressurized outward by the internal pressure of the case formed by the liquefied gas electrolyte, the edge extension can be brought into close contact with the locking portion.

[0014] The positive electrode tab connected to the positive electrode can be electrically connected to the top cap unit, and the negative electrode tab connected to the negative electrode can be electrically connected to the bottom unit.

[0015] The method for manufacturing a secondary battery according to the present invention relates to the method for manufacturing a secondary battery as described above, and includes: an electrode tab connecting step of electrically connecting a positive electrode tab connected to the positive electrode of an electrode assembly to a top cap unit, and a negative electrode tab connected to the negative electrode of an electrode assembly to a bottom unit; an electrode assembly housing step of housing the electrode assembly in the internal space of the main body by coupling the top cap unit to the upper opening of the main body; a bottom unit coupling step of coupling the bottom unit to the lower opening of the main body; an electrolyte injection step of injecting a liquefied gas electrolyte into the internal space of the main body; and a sealing coupling step of locking the top cap unit to the locking portion and sealing it to the upper opening as the top cap unit is pressurized outward by the internal pressure of the case formed by the liquefied gas electrolyte.

[0016] The top cap unit includes a protruding portion that is inserted into the upper opening of the main body, and an edge extension portion that extends from the periphery of the protruding portion toward the side wall and is locked into a locking portion. The electrolyte injection step allows the liquefied gaseous electrolyte to be injected into the internal space of the main body through the separation space G1 between the edge extension portion and the locking portion, with the edge extension portion and the locking portion separated.

[0017] The sealed coupling step allows the top cap unit to be sealed to the upper opening as the top cap unit is pressurized outward by the internal pressure of the case formed by the liquefied gas electrolyte, causing the edge extension to come into close contact with the locking portion.

[0018] Another form of the secondary battery according to the present invention may further include a venting unit coupled with the top cap unit that expels internal gases from the case to the outside of the case when the internal temperature of the case exceeds a critical temperature.

[0019] The venting unit may include a base portion positioned on the surface of the edge extension portion facing the locking portion, and a variable portion positioned on the base portion so as to face the locking portion, and whose shape changes above the critical temperature.

[0020] The variable portion may include a metal layer assembly formed by joining a first metal layer laminated on a base portion and a second metal layer laminated on the first metal layer so as to face the locking portion, and having a different coefficient of thermal expansion than the first metal layer.

[0021] In the metal layer joint, one side is fixed onto the base, and the other side changes shape above the critical temperature, pressurizing the locking portion. The force exerted by the other side of the metal layer joint on the locking portion above the critical temperature can be greater than the force F exerted outward on the top cap unit by the internal pressure of the case formed by the liquefied gas electrolyte.

[0022] When the other side of the metal layer joint pressurizes the locking portion, the edge extension separates from the locking portion, forming a separation space G2, through which the internal gas of the case can be discharged to the outside of the case.

[0023] The base is formed in the shape of a disc with a through hole formed inside, and the protruding part of the top cap unit can be inserted into the through hole.

[0024] The variable portion is formed in a shape corresponding to the base portion, and four metal layer assemblies can be arranged on the base portion at 90-degree intervals. [Effects of the Invention]

[0025] The present invention relates to a secondary battery and a method for manufacturing a secondary battery. By utilizing a liquefied gas electrolyte obtained by liquefying a gaseous electrolyte under high pressure, it is possible to design and realize a high-power battery by improving the impregnation with the active material compared to conventional electrolytes. Furthermore, low-temperature performance can be ensured more easily than with general electrolytes, and this can be achieved more easily and efficiently than in conventional methods. [Brief explanation of the drawing]

[0026] [Figure 1] It is a cross-sectional view illustrating the secondary battery according to Embodiment 1 of the present invention. [Figure 2] It is an exploded view illustrating the secondary battery of FIG. 1 in an exploded state. [Figure 3] It is a diagram illustrating a method for manufacturing a secondary battery according to Embodiment 2 of the present invention. [Figure 4] It is a cross-sectional view showing an electrode tab connecting step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. [Figure 5] It is a cross-sectional view showing an electrode assembly housing step and a bottom unit coupling step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. [Figure 6] It is a cross-sectional view showing an electrolyte injecting step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. [Figure 7] It is a cross-sectional view showing a hermetic sealing coupling step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. [Figure 8] It is a cross-sectional view illustrating the secondary battery according to Embodiment 3 of the present invention. [Figure 9] It is a view illustrating a venting unit in the secondary battery according to Embodiment 3 of the present invention, showing a state where the form of the venting unit has not changed. [Figure 10] It is a view illustrating a state where the venting unit illustrated in FIG. 9 has changed its form at a temperature equal to or higher than a critical temperature. [Figure 11] It is a view illustrating the secondary battery according to Embodiment 3 of the present invention, and is a cross-sectional view illustrating a state where internal gas of the secondary battery is discharged to the outside of a case at a temperature equal to or higher than the critical temperature. Mode for Carrying Out the Invention

[0027] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in a variety of different forms and is not limited or restricted by the embodiments described below.

[0028] For the purpose of clearly describing the present invention, detailed descriptions of relevant prior art that are irrelevant to the description or that could obscure the gist of the invention have been omitted. In this specification, when assigning reference numerals to components in the drawings, the same or similar reference numerals are used throughout the specification for components that are the same or similar.

[0029] Furthermore, the terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0030] Embodiment 1 Figure 1 is a cross-sectional view illustrating a secondary battery according to Embodiment 1 of the present invention. Figure 2 is an exploded view showing the secondary battery of Figure 1 disassembled.

[0031] In the following, a secondary battery 100 according to Embodiment 1 of the present invention will be described with reference to Figures 1 and 2.

[0032] The secondary battery 100 according to Embodiment 1 of the present invention includes an electrode assembly 110, a case 120, and a liquefied gas electrolyte 130.

[0033] The electrode assembly 110 can be formed by arranging positive electrodes, separators, and negative electrodes alternately. The electrode assembly 110 can be a jelly roll type electrode assembly 110 having a form in which electrodes and separators are arranged alternately and wound together. Such an electrode assembly 110 can be an electrode winding body in which one or more positive electrodes, one or more negative electrodes, and one or more separators are wound together.

[0034] The case 120 can be configured to house the electrode assembly 110. The case 120 has an internal space into which the electrode assembly 110 can be inserted vertically. Inserting vertically may mean that the electrode assembly 110 is inserted such that its winding shaft is perpendicular to the bottom surface of the case 120.

[0035] The electrolyte can be housed in the case 120 together with the electrode assembly 110. In this invention, a liquefied gas electrolyte 130, which is different from a normal liquid electrolyte, can be used as the electrolyte. The liquefied gas electrolyte 130 may mean an electrolyte in which the gas phase electrolyte has been liquefied under high pressure.

[0036] Referring to Figure 2, the case 120 may include a main body 121, a top cap unit 122, and a bottom unit 123.

[0037] First, the main body 121 may include a side wall portion 121-1 and a locking portion 121-2. The side wall portion 121-1 may be located on the side of the electrode assembly 110. The locking portion 121-2 may extend inward from the upper end of the side wall portion 121-1 at a predetermined angle to the side wall portion 121-1. Figure 1 illustrates that the side wall portion 121-1 and the locking portion 121-2 are at a 90-degree angle. The locking portion 121-2 may be bent or folded from the side wall portion 121-1. This can be manufactured by various methods such as pressing, casting, forging, rolling, and injection molding. The case 120 may be made of can material.

[0038] An upper opening 121-3 can be formed inside the locking portion 121-2. This upper opening 121-3 can be processed with a punch; that is, it can be a hole punched out by a punch. In addition, a lower opening 121-4 can be formed below the side wall portion 121-1. The electrode assembly 110 can be inserted into this lower opening 121-4, as will be explained below.

[0039] Referring to Figures 1 and 2, the top cap unit 122 can be configured to connect to the upper opening 121-3 of the main body 121. The top cap unit 122 may include a projection 122a and an edge extension 122b. The projection 122a may be the portion inserted into the upper opening 121-3 of the main body 121. The edge extension 122b may be the portion extending from the periphery of the projection 122a toward the side wall 121-1 and being locked by the locking portion 121-2. The edge extension 122b may be configured to extend from the lower periphery of the projection 122a toward the side wall 121-1. In this configuration, the edge extension 122b can be effectively locked to the locking portion 121-2 of the main body 121 and can also be supported by the locking portion 121-2. This prevents the top cap unit 122 from detaching from the main body 121.

[0040] The bottom unit 123 can be configured to connect to the lower opening 121-4 of the main body 121. The bottom unit 123 can be welded to the lower opening 121-4 of the main body 121. By welding in this way, the bottom unit 123 can seal the lower part of the main body 121. This prevents electrolyte and internal gases from leaking out from the lower side of the main body 121.

[0041] Referring to Figure 1, in the secondary battery 100 according to Embodiment 1 of the present invention, the top cap unit 122 can be pressurized outward by the internal pressure of the case 120 formed by the liquefied gas electrolyte 130 (see arrow F in Figure 1). When the top cap unit 122 is pressurized outward in this way by the internal pressure of the case 120 formed by the liquefied gas electrolyte 130, the edge extension portion 122b can be tightly attached to the locking portion 121-2. In this manner, the top cap unit 122 can be locked to the locking portion 121-2 and sealed to the upper opening 121-3. Furthermore, this makes it possible to achieve battery sealing.

[0042] The secondary battery 100 according to Embodiment 1 of the present invention, manufactured in this manner, utilizes a liquefied gas electrolyte 130 obtained by liquefying a gas-phase electrolyte under high pressure. Compared to conventional electrolytes, it improves impregnation with the active material, enabling the design and realization of a high-power secondary battery. Furthermore, because the liquefied gas electrolyte 130 is used, low-temperature performance can be more easily ensured compared to general electrolytes.

[0043] In the secondary battery 100 according to Embodiment 1 of the present invention described above, when the top cap unit 122 moves further down from the state shown in Figure 1, and consequently the locking portion 121-2 of the main body 121 and the edge extension portion 122b of the top cap unit 122 move apart from each other, a separation space (see G1 in Figure 6) can be formed between the locking portion 121-2 of the main body 121 and the edge extension portion 122b of the top cap unit 122. Furthermore, internal gas and electrolyte can be discharged through this separation space. That is, internal gas and vaporized electrolyte can pass through the separation space between the locking portion 121-2 of the main body 121 and the edge extension portion 122b of the top cap unit 122 and be discharged outside the case 120 through the upper opening 121-3 of the main body 121.

[0044] However, because the internal pressure of the case 120 formed by the liquefied gas electrolyte 130 strongly pressurizes the top cap unit 122 upwards F, the edge extension portion 122b adheres tightly to the locking portion 121-2, and therefore no separation space is formed between the edge extension portion 122b and the locking portion 121-2. As a result, secondary batteries using the liquefied gas electrolyte 130 can be realized more easily and efficiently than conventional batteries.

[0045] In the secondary battery 100 according to Embodiment 1 of the present invention, the positive electrode tab 140 connected to the positive electrode of the electrode assembly 110 can be electrically connected to the top cap unit 122. Furthermore, the negative electrode tab 150 connected to the negative electrode of the electrode assembly 110 can be electrically connected to the bottom unit 123. As a result, the upper end of the protrusion 122a of the upper top cap unit 122 can function as a positive electrode terminal, and the lower surface of the bottom unit 123 can function as a negative electrode terminal.

[0046] Embodiment 2 Figure 3 is a diagram illustrating the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. Figure 4 is a cross-sectional view showing the electrode tab connection step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. Figure 5 is a cross-sectional view showing the electrode assembly housing step and the bottom unit coupling step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. Figure 6 is a cross-sectional view showing the electrolyte injection step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention. Figure 7 is a cross-sectional view showing the sealed coupling step in the method for manufacturing a secondary battery according to Embodiment 2 of the present invention.

[0047] Embodiment 2 of the present invention differs from Embodiment 1 in that it relates to a manufacturing method for producing a secondary battery according to Embodiment 1 of the present invention.

[0048] We will omit as much as possible the content that is common to Embodiment 1 and describe Embodiment 2. In other words, it is obvious that any content not described in Embodiment 2 that is necessary can be considered as content of Embodiment 1.

[0049] Referring to Figure 3, the method for manufacturing a secondary battery according to Embodiment 2 of the present invention may include an electrode tab linking step (S1), an electrode assembly housing step (S2), a bottom unit coupling step (S3), an electrolyte injection step (S4), and a sealing coupling step (S5).

[0050] First, referring to Figure 4, the electrode tab connecting step (S1) can be the step of connecting the positive electrode tab 140 and the negative electrode tab 150 to the electrode assembly 110, which is formed by winding the positive electrode, separator, and negative electrode. Specifically, the positive electrode tab 140 connected to the positive electrode of the electrode assembly 110 can be electrically connected to the lower surface of the top cap unit 122. This connection can be made by welding (see W1). Also, the negative electrode tab 150 connected to the negative electrode of the electrode assembly 110 can be electrically connected to the upper surface of the bottom unit 123. This connection can also be made by welding (see W2). With such connections, in the completed secondary battery, the upper part of the protrusion 122a of the top cap unit 122 can become the positive electrode terminal, and the lower part of the bottom unit 123 can become the negative electrode terminal.

[0051] Referring to Figure 5, the electrode assembly housing step (S2) can be the step of housing the combined electrode assembly 110, top cap unit 122, and bottom unit 123 manufactured by the electrode tab connecting step (S1) into the main body 121 of the secondary battery case 120. That is, the combined electrode assembly 110, top cap unit 122, and bottom unit 123, which is positioned below the main body 121, can be moved upward and inserted into the main body 121 through the lower opening 121-4. Here, the top cap unit 122 can be connected to the upper opening 121-3 of the main body 121, and the electrode assembly 110 can be housed in the internal space of the main body 121. In other words, the protruding portion 122a of the top cap unit 122 can be inserted into the upper opening 121-3 of the main body 121, and the combined body of the electrode assembly 110, the top cap unit 122, and the bottom unit 123 can be housed inside the main body 121.

[0052] The bottom unit coupling step (S3) can be the step of coupling the bottom unit 123 to the lower opening 121-4 of the main body 121 after the combined electrode assembly 110, top cap unit 122, and bottom unit 123 has been inserted into and housed within the main body 121. The method of coupling the bottom unit 123 to the lower opening 121-4 of the main body 121 can be welding (W3). When coupled by welding in this manner, the bottom unit 123 can seal the lower part of the main body 121. This prevents the electrolyte and internal gases from escaping to the lower side of the main body 121.

[0053] Referring to Figure 6, the electrolyte injection step (S4) can be the step of injecting the liquefied gaseous electrolyte 130 into the internal space of the main body 121. The liquefied gaseous electrolyte 130 can be an electrolyte obtained by liquefying a gaseous electrolyte under high pressure.

[0054] As described above, the top cap unit 122 includes a protruding portion 122a and an edge extension portion 122b. In the electrolyte injection step (S4), the liquefied gas electrolyte 130 can be injected into the internal space of the main body 121 through the separation space G1 between the edge extension portion 122b and the locking portion 121-2, while the edge extension portion 122b and the locking portion 121-2 are separated. That is, as shown in Figure 6, by pressing the top cap unit 122 slightly downward, a separation space G1 can be formed between the edge extension portion 122b and the locking portion 121-2. In this state, the liquefied gas electrolyte 130 can pass through the space between the protruding portion 122a and the upper opening 121-3 of the main body 121, and be injected into the interior of the main body 121 of the case 120 through the separation space G1 between the locking portion 121-2 and the edge extension portion 122b (see Q in Figure 6). When the liquefied gaseous electrolyte 130 is injected into the main body 121, it is injected in a liquid state, but once inside the main body 121, a portion of it can be rapidly vaporized due to the pressure difference, and this action can increase the internal pressure of the main body 121.

[0055] Referring to Figure 7, the sealing step (S5) can be a step in which, after the electrolyte injection step (S4), the top cap unit 122 is pressurized outward by the internal pressure of the case 120 formed by the liquefied gas electrolyte 130 (see arrow F in Figure 7), causing the top cap unit 122 to lock into the locking portion 121-2 and sealing to the upper opening 121-3.

[0056] Specifically, in the sealed coupling step (S5), as the top cap unit 122 is pressurized outward F by the internal pressure of the case 120 formed by the liquefied gas electrolyte 130, the edge extension 122b can tightly adhere to the locking portion 121-2. When it is tightly adhered in this way, the internal electrolyte and other internal gases cannot be discharged to the outside of the case 120, and as a result, the top cap unit 122 can be tightly coupled to the upper opening 121-3 of the main body 121.

[0057] The secondary battery 100 according to Embodiment 1 described above can be manufactured by the secondary battery manufacturing method according to Embodiment 2 of the present invention described above. Therefore, the secondary battery manufacturing method according to Embodiment 2 of the present invention utilizes a liquefied gas electrolyte obtained by liquefying a gas-phase electrolyte under high pressure, making it possible to design and realize a high-output battery with improved impregnation with the active material compared to conventional electrolytes.

[0058] Furthermore, the secondary battery 100 realized by the secondary battery manufacturing method according to Embodiment 2 of the present invention makes it easier to ensure low-temperature performance compared to general electrolytes. In addition, the secondary battery manufacturing method according to Embodiment 2 of the present invention makes it possible to realize such an advanced secondary battery more easily and efficiently than conventional methods.

[0059] Embodiment 3 Figure 8 is a cross-sectional view illustrating a secondary battery according to Embodiment 3 of the present invention. Figure 9 is a diagram illustrating the venting unit 260 in the secondary battery according to Embodiment 3 of the present invention, showing the state in which the shape has not changed. Figure 10 is a diagram illustrating the state in which the venting unit 260 shown in Figure 9 has changed shape when it is above the critical temperature. Figure 11 is a diagram illustrating the secondary battery according to Embodiment 3 of the present invention, showing a cross-sectional view illustrating the state in which the internal gas of the secondary battery is discharged to the outside of the case when it is above the critical temperature.

[0060] Embodiment 3 of the present invention differs from Embodiments 1 and 2 of the present invention in that it further includes a venting unit 260, compared to the secondary battery and method for manufacturing the secondary battery according to Embodiments 1 and 2 of the present invention.

[0061] We will omit as much as possible the content common to Embodiments 1 and 2, and describe Embodiment 3. In other words, it is self-evident that any content not described in Embodiment 3 that is necessary can be considered as content of Embodiments 1 and 2.

[0062] Referring to Figure 8, the secondary battery 200 according to Embodiment 3 of the present invention may further include a venting unit 260 that discharges internal gas in the form of the secondary battery according to Embodiment 1. The venting unit 260 is coupled to the top cap unit 122 and can be configured to discharge the internal gas of the case 120 to the outside of the case 120 when the internal temperature of the case 120 exceeds the critical temperature.

[0063] Referring to Figures 8 to 10, the venting unit 260 may include a base portion 261 and a variable portion 262. The base portion 261 may be the portion of the surface of the edge extension portion 122b that faces the locking portion 121-2. The variable portion 262 may be installed on the base portion 261 so as to face the locking portion 121-2. The venting unit 260 may have a shape similar to a washer before the shape of the variable portion 262 changes.

[0064] The variable part 262 can be a part whose shape changes when the temperature exceeds a critical temperature. When the variable part 262 changes shape when the temperature exceeds a critical temperature, the tight seal between the edge extension 122b of the top cap unit 122 and the locking part 121-2 of the main body 121 can be released. This allows the internal gas generated inside the main body 121 to be discharged to the outside of the battery case 120. This prevents the secondary battery from igniting or exploding due to the internal gas pressure generated at high temperatures.

[0065] The base portion 261 can be formed in the shape of a disc with a through hole 261-1 formed inside. The base portion 261 may have a form corresponding to the edge extension portion 122b in the top cap unit 122. Alternatively, the base portion 261 can be arranged overlapping with the edge extension portion 122b. For this reason, the protrusion 122a of the top cap unit 122 can be configured to be inserted into the through hole 261-1 of the base portion 261.

[0066] Figure 9(a) is a plan view of the venting unit 260, and Figure 9(b) is a front view of the venting unit 260 shown in Figure 9(a). Both Figure 9(a) and Figure 9(b) show the venting unit 260 in a state where the shape of the variable part 262 has not changed.

[0067] Figure 10(a) is a plan view of the venting unit 260, and Figure 10(b) is a front view of the venting unit 260 shown in Figure 10(a). Figure 10 illustrates the state in which the shape of the variable part 262 has changed.

[0068] Referring to Figures 9 and 10, the variable portion 262 can be configured to change shape as the temperature rises, based on the principle of a bimetal, which is formed by joining two metals with different coefficients of thermal expansion. Specifically, the variable portion 262 may include a metal layer joint 263 formed by joining a first metal layer 263-1 laminated on the base portion 261 and a second metal layer 263-2 laminated on the first metal layer 263-1 so as to face the locking portion 121-2.

[0069] Here, the second metal layer 263-2 can be formed of a metal having a different coefficient of thermal expansion than the first metal layer 263-1. For example, the coefficient of thermal expansion of the second metal layer 263-2 can be greater than that of the first metal layer 263-1. This allows the metal layer assembly 263 to bend in the direction of the first metal layer 263-1.

[0070] The variable portion 262 can be formed in a shape corresponding to the base portion 261. The metal layer assembly 263 of the variable portion 262 can be considered a type of bimetal placed on the base portion 261. Four metal layer assembly 263s can be arranged on the base portion 261 at 90-degree intervals. One side portion 263a of the metal layer assembly 263 is fixed on the base portion 261, and the other side portion 263b changes shape above a critical temperature, allowing it to pressurize the locking portion 121-2. The one side portion 263a of the metal layer assembly 263 fixed on the base portion 261 can be fixed on the base portion 261 by a fixing member 264. Such a fixing member 264 may be a bolt or a rivet.

[0071] Figure 11 illustrates the state in which the venting unit 260 is mounted on a secondary battery 200 according to Embodiment 3 of the present invention, and the shape of the variable part changes, allowing for venting of the internal gas. Referring to Figures 10 and 11, the force exerted by the other side portion 263b of the metal layer assembly 263 on the locking portion 121-2 at temperatures above the critical temperature can be greater than the force F exerted by the internal pressure of the case 120 formed by the liquefied gas electrolyte 130, which pressurizes the top cap unit 122 outward. As a result, when the other side portion 263b of the metal layer assembly 263 pressurizes the locking portion 121-2, the edge extension portion 122b separates downward from the locking portion 121-2, forming a separation space G2. Furthermore, the internal gas of the case 120 can be discharged to the outside of the case 120 through this formed separation space.

[0072] This makes it easier and more efficient to realize high-power secondary batteries with high impregnation properties with the active material, as well as secondary batteries that can more easily ensure low-temperature performance, thereby enabling safe use.

[0073] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible by persons with ordinary skill in the art to which the present invention pertains, within the equivalent scope of the technical concept of the present invention and the claims described below. [Explanation of Symbols]

[0074] 100, 200 secondary battery 110 Electrode assembly 120 cases 121 Main Unit 121-1 Side wall section 121-2 Locking part 121-3 Upper opening 121-4 Lower opening 122 Top Cap Unit 122a Protrusion 122b Edge extension 123 Bottom Unit 130 Liquefied Gas Electrolytes 140 Positive Tab 150 Negative Electrode Tabs 260 Venting Units 261 Base section 261-1 Through hole 262 Variable part 263 Metal layer assembly 263-1 1st metal layer 263-2 2nd metal layer 263a One side part 263b Other side part 264 Fixing member S1 Electrode tab linking step S2 Electrode assembly 110 housing step S3 Bottom unit joining step S4 Electrolyte Infusion Step S5 Sealed coupling step

Claims

1. An electrode assembly including a positive electrode, a separator, and a negative electrode, A case in which the aforementioned electrode assembly is housed, The case contains a liquefied gas electrolyte housed together with the electrode assembly, The aforementioned case is, The electrode assembly includes a side wall portion located on the side, and a locking portion extending inward from the upper end of the side wall portion at a predetermined angle to the side wall portion, with an upper opening formed on the inside of the locking portion and a lower opening formed on the lower side of the side wall portion. A top cap unit that connects to the upper opening of the main body, It includes a bottom unit that connects to the lower opening of the main body, A secondary battery in which, as the top cap unit is pressurized outward by the internal pressure of the case formed by the liquefied gas electrolyte, the top cap unit is locked to the locking portion and sealed to the upper opening.

2. The secondary battery according to claim 1, wherein the bottom unit is joined to the lower opening of the main body by welding.

3. The aforementioned top cap unit is A protruding portion inserted into the upper opening of the main body, The secondary battery according to claim 1, further comprising an edge extension portion which extends from the periphery of the protruding portion toward the side wall portion and is engaged with the locking portion.

4. The secondary battery according to claim 3, wherein the edge extension extends from the lower peripheral edge of the protruding portion toward the side wall portion.

5. As the top cap unit is pressurized outward by the internal pressure of the case formed by the liquefied gas electrolyte, The secondary battery according to claim 3, wherein the edge extension portion is in close contact with the locking portion.

6. The positive electrode tab connected to the positive electrode is electrically connected to the top cap unit. The secondary battery according to claim 1, wherein the negative electrode tab connected to the negative electrode is electrically connected to the bottom unit.

7. A method for manufacturing a secondary battery as described in claim 1, An electrode tab connecting step, in which the positive electrode tab connected to the positive electrode of the electrode assembly is electrically connected to the top cap unit, and the negative electrode tab connected to the negative electrode of the electrode assembly is electrically connected to the bottom unit, The electrode assembly housing step involves connecting the top cap unit to the upper opening of the main body and housing the electrode assembly in the internal space of the main body, A bottom unit coupling step involves coupling the bottom unit to the lower opening of the main body, An electrolyte injection step of injecting a liquefied gaseous electrolyte into the internal space of the main body, A method for manufacturing a secondary battery, comprising: a sealing coupling step in which the top cap unit is pressed outward by the internal pressure of the case formed by the liquefied gas electrolyte, thereby locking the top cap unit to the locking portion and sealing it to the upper opening.

8. The aforementioned top cap unit is The main body includes a protruding portion inserted into the upper opening, and an edge extension portion that extends from the periphery of the protruding portion toward the side wall and is locked into the locking portion, The electrolyte injection step is, A method for manufacturing a secondary battery according to claim 7, wherein the edge extension portion and the locking portion are separated, and the liquefied gas electrolyte is injected into the internal space of the main body through the separation space (G1) between the edge extension portion and the locking portion.

9. The aforementioned closed coupling step is, The method for manufacturing a secondary battery according to claim 8, wherein as the top cap unit is pressurized outward by the internal pressure of the case formed by the liquefied gas electrolyte, the edge extension portion comes into close contact with the locking portion, and the top cap unit is sealed and coupled to the upper opening.

10. The secondary battery according to claim 3, further comprising a venting unit coupled to the top cap unit, which discharges the internal gas of the case to the outside of the case when the internal temperature of the case exceeds a critical temperature.

11. The aforementioned venting unit is A base portion is disposed on the surface of the edge extension portion that faces the locking portion, The secondary battery according to claim 10, comprising a variable part which is installed on the base part so as to face the locking part and whose shape changes when the temperature exceeds the critical temperature.

12. The aforementioned variable part is The secondary battery according to claim 11, comprising a metal layer assembly formed by joining a first metal layer laminated on the base portion and a second metal layer laminated on the first metal layer so as to face the locking portion and having a different coefficient of thermal expansion than the first metal layer.

13. The aforementioned metal layer assembly is One side portion is fixed onto the base portion, The other side changes shape when it reaches a temperature above the critical temperature, pressurizing the locking portion. The secondary battery according to claim 12, wherein the force exerted by the other side of the metal layer assembly on the locking portion at a temperature above the critical temperature is greater than the force F exerted by the internal pressure of the case formed by the liquefied gas electrolyte on the top cap unit to the outside.

14. The secondary battery according to claim 13, wherein when the other side portion of the metal layer assembly pressurizes the locking portion, the edge extension portion separates from the locking portion to form a separation space (G2), and the internal gas of the case is discharged to the outside of the case through the separation space.

15. The base portion is formed in the shape of a disc with a through hole formed inside, The secondary battery according to claim 12, wherein the protruding portion of the top cap unit is inserted into the through hole.

16. The variable portion is formed in a shape corresponding to the base portion, The secondary battery according to claim 15, wherein four of the metal layer assemblies are arranged on the base portion at 90-degree intervals.

Images