Secondary battery and manufacturing method thereof

Abstract

A secondary battery according to one aspect of the present invention comprises an electrode assembly, an electrode lead, and a fixing unit. The electrode assembly may have an electrode portion and a foil tab portion formed at one end of the electrode portion and bent in one direction. The electrode lead may have a connecting portion and an extension portion that is bent and extended relative to the connecting portion, and the connecting portion may be welded to the foil tab portion. A fixing unit may be disposed at one end of the electrode assembly. The fixing unit may have an upper bracket having a first pressure surface and a first contact surface, and a lower bracket having a second pressure surface and a second contact surface.

Description

Technology Field

[0001] The present invention relates to a secondary battery and a method for manufacturing the same. Background Technology

[0002] Recently, as the demand for portable electronic products such as laptops, video cameras, and mobile phones has increased rapidly, and the development of electric vehicles, energy storage batteries, robots, and satellites has accelerated, research on high-performance secondary batteries capable of repeated charging and discharging is actively underway.

[0003] Currently commercialized rechargeable batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium-ion batteries. Among these, lithium-ion batteries are gaining attention for their advantages, such as the ability to freely charge and discharge with almost no memory effect compared to nickel-based batteries, a very low self-discharge rate, and high energy density.

[0004] These lithium secondary batteries primarily use lithium-based oxides and carbon materials as the positive and negative active materials, respectively. Additionally, the lithium secondary battery comprises a positive plate and a negative plate coated with these positive and negative active materials, respectively; an electrode assembly in which the positive and negative plates are arranged with a separator in between; and an outer casing that seals and encloses the electrode assembly together with an electrolyte.

[0005] Meanwhile, lithium secondary batteries can be classified according to the shape of the battery case into can-type secondary batteries, in which the electrode assembly is embedded in a metal can, and pouch-type secondary batteries, in which the electrode assembly is embedded in a pouch of aluminum laminate sheets. Furthermore, can-type secondary batteries can be further classified into cylindrical batteries and prismatic batteries depending on the shape of the metal can.

[0006] In the case of pouch-type secondary batteries, multiple thin-film tabs connected to electrode plates are welded to electrode leads, and the electrode assembly is housed within the pouch. At this stage, space must be secured for the welding of the tabs and electrode leads, which presents a problem in that it is difficult to increase the energy density per unit volume of the battery. The problem to be solved

[0007] To solve the above problem, the objective of the present invention is to provide a secondary battery and a method for manufacturing the same that can increase energy density per unit volume by reducing the space occupied by thin film tabs, etc., inside the battery case.

[0008] To solve the above problem, the object of the present invention is to provide a secondary battery and a method for manufacturing the same that can easily weld a tab and an electrode lead. means of solving the problem

[0009] A secondary battery according to one embodiment of the present invention comprises an electrode assembly, an electrode lead, and a fixing unit. The electrode assembly may have an electrode portion and a foil tab portion formed at one end of the electrode portion and bent in one direction. The electrode lead may have a connecting portion and an extension portion that is bent and extended relative to the connecting portion, and the connecting portion may be welded to the foil tab portion. A fixing unit may be disposed at one end of the electrode assembly. The fixing unit may have an upper bracket having a first pressure surface and a first contact surface, and a lower bracket having a second pressure surface and a second contact surface.

[0010] A secondary battery according to one embodiment of the present invention may further include an insulating member surrounding a portion of the lead portion.

[0011] A secondary battery according to one embodiment of the present invention may further include a battery case having a first case and a second case. The first case may have a first electrode assembly receiving portion and a first bump region formed at least one end of the first electrode assembly receiving portion. The second case may have a second electrode assembly receiving portion and a second bump region formed at least one end of the second electrode assembly receiving portion. An electrode assembly may be received in the first electrode assembly receiving portion and the second electrode assembly receiving portion.

[0012] In a secondary battery according to one embodiment of the present invention, the lead portion may be extended outside the battery case.

[0013] In a secondary battery according to one embodiment of the present invention, the foil tab portion may be pre-welded.

[0014] In a secondary battery according to one embodiment of the present invention, an upper bracket and a lower bracket may be combined such that a first contact surface of the upper bracket contacts one surface of the lead portion and a second contact surface of the lower bracket contacts the other surface of the lead portion.

[0015] In a secondary battery according to one embodiment of the present invention, the first pressure surface of the upper bracket contacts the foil tab portion, and the second pressure surface of the lower bracket contacts the connection portion.

[0016] In a secondary battery according to one embodiment of the present invention, a pair of grooves are formed at both ends of an upper bracket, and a pair of locking parts that engage with the pair of grooves may be provided at both ends of a lower bracket.

[0017] In a secondary battery according to one embodiment of the present invention, the length (l) of the first contact surface may be the same as the width (Wc) of the lead portion.

[0018] In a secondary battery according to one embodiment of the present invention, the distance (d) between the first contact surface and the second contact surface may be equal to the thickness of the lead portion.

[0019] In a secondary battery according to one embodiment of the present invention, inclined surfaces may be formed at both ends of the upper bracket and the lower bracket.

[0020] In a secondary battery according to one embodiment of the present invention, the unit electrode plate of the electrode portion may comprise a positive plate and a negative plate. The electrode portion may be formed by alternately stacking such that a separator is positioned between the positive plate and the negative plate.

[0021] In a secondary battery according to one embodiment of the present invention, the width of the foil tab portion may be 40 to 70% of the width of the electrode assembly.

[0022] In a secondary battery according to one embodiment of the present invention, the lead portion may be perpendicular to one end surface of the electrode assembly.

[0023] In a secondary battery according to one embodiment of the present invention, the inner walls of the first bump region and the second bump region may be made of the same material as the battery case.

[0024] In a secondary battery according to one embodiment of the present invention, the inner walls of the first bump region and the second bump region may be made of a material different from that of the battery case.

[0025] In a secondary battery according to one embodiment of the present invention, the first bump region and the second bump region may be symmetrical with respect to the center of the thickness direction of the electrode assembly.

[0026] In a secondary battery according to one embodiment of the present invention, the first bump region and the second bump region may be located at the center of the battery case along the width direction of the electrode assembly.

[0027] In a secondary battery according to one embodiment of the present invention, the shape of the inner wall surface of the first bump region and the second bump region can be matched with the outer surface of the upper bracket and the lower bracket, respectively.

[0028] In a secondary battery according to one embodiment of the present invention, the battery case may be a pouch.

[0029] A method for manufacturing a secondary battery according to one embodiment of the present invention comprises: a preparation step of preparing an electrode assembly having an electrode portion and a foil tab portion; a joining step of joining the connecting portion and the foil tab portion of an electrode lead having a connecting portion and a lead portion extending vertically from the connecting portion; a rotation step of rotating the electrode lead joined to the foil tab portion by 90°; and a fixing unit assembly step in which a fixing unit having an upper bracket and a lower bracket is assembled at one end of the electrode assembly, wherein the first contact surface of the upper bracket contacts one side of the lead portion of the electrode lead and the second contact surface of the lower bracket contacts the other side of the lead portion of the electrode lead.

[0030] A secondary battery manufacturing method according to one embodiment of the present invention may further include an insulating member placement step in which the insulating member is arranged to surround a portion of the lead portion.

[0031] A method for manufacturing a secondary battery according to one embodiment of the present invention may further include a packaging step of accommodating an electrode assembly within a battery case. Effects of the invention

[0032] As described above, according to one aspect of the present invention, the energy density per unit volume can be increased by reducing the space occupied by thin film tabs, etc., inside the battery case.

[0033] In addition, according to one aspect of the present invention, the tab and the electrode lead can be easily welded. Brief explanation of the drawing

[0034] FIG. 1 is a drawing showing a secondary battery in which foil tab portions are formed in both directions according to an embodiment of the present invention. FIG. 2 is a drawing showing an anode plate and a cathode plate according to one embodiment of the present invention. FIG. 3 is a drawing showing an electrode lead according to one embodiment of the present invention. FIG. 4 is a drawing showing the foil tab portion and electrode lead of a secondary battery joined together according to one embodiment of the present invention. FIG. 5 is a drawing showing a foil tab portion of a secondary battery according to one embodiment of the present invention that is bent after being joined with an electrode lead. FIG. 6 is a drawing showing a fixed unit of a secondary battery according to one embodiment of the present invention. FIG. 7 is a drawing showing the upper bracket and lower bracket of a fixed unit combined in a secondary battery according to one embodiment of the present invention. FIG. 8 is a side cross-sectional view of a secondary battery according to one embodiment of the present invention in which the foil tab portion and the electrode lead are fixed by a fixing unit. FIG. 9 is a drawing showing that the locking part of the lower bracket is coupled to the groove of the upper bracket of the fixed unit in a secondary battery according to one embodiment of the present invention. FIG. 10 is a cross-sectional view showing the state in which a lower bracket’s catch is coupled to a groove of an upper bracket of a fixed unit in a secondary battery according to one embodiment of the present invention. FIG. 11 is a drawing showing that the catch portion of the lower bracket is coupled to the groove of the upper bracket of the fixed unit in a secondary battery according to another embodiment of the present invention. FIG. 12 is a cross-sectional view showing the state in which the locking part of the lower bracket is coupled to the groove of the upper bracket of the fixed unit in a secondary battery according to one embodiment of the present invention. FIG. 13 is a drawing showing an electrode assembly in a secondary battery according to one embodiment of the present invention, which is cased by a battery case. FIG. 14 is a cross-sectional view of an electrode assembly in a secondary battery according to one embodiment of the present invention, in a state where the electrode assembly is cased by a battery case. FIG. 15 is a flowchart illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention. Specific details for implementing the invention

[0035] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0036] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this invention, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0037] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that in the accompanying drawings, identical components are indicated by the same reference numerals whenever possible. Furthermore, detailed descriptions of known functions and configurations that may obscure the essence of the present invention will be omitted. For the same reason, some components in the accompanying drawings may be exaggerated, omitted, or schematically depicted.

[0039] Hereinafter, a secondary battery according to one embodiment of the present invention will be described.

[0040] FIG. 1 is a drawing showing a secondary battery in which a foil tab portion is formed in both directions according to an embodiment of the present invention, FIG. 2 is a drawing showing a positive plate and a negative plate according to an embodiment of the present invention, FIG. 3 is a drawing showing an electrode lead according to an embodiment of the present invention, FIG. 4 is a drawing showing the foil tab portion and the electrode lead of a secondary battery according to an embodiment of the present invention being joined, and FIG. 5 is a drawing showing the foil tab portion of a secondary battery according to an embodiment of the present invention being bent after being joined with the electrode lead.

[0041] As illustrated in FIG. 1, a secondary battery (1000) according to an embodiment of the present invention includes an electrode assembly (1100), an electrode lead (1200), an insulating part (1300), a fixing part (1400), and a battery case (1500).

[0042] The electrode assembly (1100) comprises an electrode portion (1110) and a foil tab portion (1120). The electrode portion (1110) comprises a plurality of unit electrode plates (1111, 1112) and a separator (1113). An active material may be coated on the unit electrode plates (1111, 1112). The plurality of unit electrode plates (1111, 1112) may comprise an anode plate (1111) on which an active material, such as a transition metal oxide, is coated on a metal plate such as aluminum, and a cathode plate (1112) on which an active material, such as graphite or carbon, is coated on a metal plate such as copper or nickel. The separator (1113) is positioned between the plurality of unit electrode plates (1111, 1112) to prevent short circuits between the unit electrode plates (1111, 1112). The material of the separator (1113) may be polyethylene, polypropylene, or a composite thereof.

[0043] The electrode portion (1110) of the electrode assembly (1100) can be formed by placing a separator (1113) between an anode plate (1111) and a cathode plate (1112) that are alternately arranged. That is, in one embodiment, the electrode portion (1110) is formed by alternately stacking an anode plate (1111), a separator (1113), a cathode plate (1112), and a separator (1113). Accordingly, the electrode assembly (1100) can have a rectangular shape with a height (H) and a width (W). In another embodiment, the electrode portion (1110) can be formed by arranging an anode plate (1111), a separator (1113), and a cathode plate (1112) in that order and then winding it up.

[0044] As illustrated in FIG. 2, a plurality of unit electrode plates (1111, 1112) have a non-active tab (1121, 1122) formed thereon without an active material applied. In this embodiment, the positive plate (1111) may have a non-active tab (1121) formed at one end, and the negative plate (1112) may have a non-active tab (1122) formed at the other end opposite to the one end, but is not limited thereto. In one embodiment, the unit electrode plates (1111, 1112) and the non-active tab (1121, 1122) may be formed integrally by cutting a predetermined portion of a single metal plate using a laser or the like to leave the unit electrode plates (1111, 1112) and the non-active tab (1121, 1122).

[0045] The non-blocking tabs (1121) of the positive plate (1111) overlap each other at a first position, and the non-blocking tabs (1122) of the negative plate (1112) overlap each other at a second position. In another embodiment, there may be two or more positions where the non-blocking tabs (1121, 1122) overlap on each of the positive plate (1111) and the negative plate (1112).

[0046] The foil tab portion (1120; 1121A, 1122A) can be formed by connecting multiple non-foil tabs (1121, 1122) that are overlapped at the same location to each other using ultrasonic welding, laser welding, etc. By forming the foil tab portion (1120; 1121A, 1122A), the movement of current generated in the electrode portion (1110) becomes easier.

[0047] The width of the foil tab portion (1120; 1121A, 1122A) may be 40 to 70% of the width of the electrode assembly (1100). The present invention can increase the bonding stability with the electrode lead (1200) by forming the width of the foil tab portion (1120) wide.

[0048] The foil tab portion (1121A) formed by connecting the non-foil tab (1121) of the positive plate (1111) becomes the positive tab, and the foil tab portion (1122A) formed by connecting the non-foil tab (1122) of the negative plate (1112) becomes the negative tab. In this embodiment, the positive tab is formed in a direction perpendicular to one surface of the electrode assembly (1100), and the negative tab is formed in a direction perpendicular to the other surface of the electrode assembly (1100). In this embodiment, the positive tab (1121A) and the negative tab (1122A) are described as protruding in different directions, but are not necessarily limited thereto, and the positive tab (1121A) and the negative tab (1122A) may protrude in the same direction.

[0049] An electrode lead (1200) that supplies electricity to the outside of the secondary battery (10) is connected to the foil tab portion (1120; 1121A, 1122A) of the electrode assembly (1100) by spot welding or the like. Specifically, the positive lead is connected to the positive tab (1121A) and extends outward, and the negative lead is connected to the negative tab (1122A) and extends outward.

[0050] The electrode lead (1200) is joined to the foil tab portion (1120). As illustrated in FIG. 3, the electrode lead (1200) has a connecting portion (1210) and an extraction portion (1220). The connecting portion (1210) is joined to the foil tab portion (1120), and the extraction portion (1220) extends outside the battery case (1500). The connecting portion (1210) and the extraction portion (1220) have the same width (Wc). Preferably, the length in the width (Wc) direction of the connecting portion (1210) and the length in the width (Wt) direction of the foil tab portion (1120) are also the same. The extraction portion (1220) is bent at a predetermined angle relative to the connecting portion (1210). In this embodiment, the angle at which the extraction portion (1220) is bent relative to the connecting portion (1210) is approximately 90°.

[0051] In this embodiment, the electrode lead (1200) may be an anode lead (1200a) and a cathode lead (1200b). The anode lead (1200a) and the cathode lead (1200b) may each extend in the same direction from one side of the electrode assembly, or they may each extend in different directions from one side and the other side of the electrode assembly.

[0052] The positive lead (1200a) and the negative lead (1200b) may be made of different materials. That is, the positive lead (1200a) may be made of the same aluminum material as the first electrode (1111), which is the positive electrode, and the negative lead (1200b) may be made of the same copper material as the second electrode (1112), which is the negative electrode, or nickel-coated copper material. Additionally, a portion of the electrode leads (1200; 1200a, 1200b) extending outside the battery case (1500) may be electrically connected to an external terminal.

[0053] As illustrated in FIG. 4, the electrode lead (1200) is joined to the foil tab portion (1120). More specifically, the connecting portion (1210) of the electrode lead (1200) and the foil tab portion (1120) can be joined by a method such as spot welding. In this embodiment, the electrode lead (1200) may be an anode lead joined to the anode foil tab portion (1121A) and a cathode lead joined to the cathode foil tab portion (1122A).

[0054] In this embodiment, the connecting portion (1210) of the electrode lead (1200) can be joined to the lower side of the foil tab portion (1120). When joining the connecting portion (1210) and the foil tab portion (1120), the connecting portion (1210) can be positioned in a direction perpendicular to one end surface of the electrode assembly (1100), and the leading portion (1220) can be positioned in a direction parallel to one end surface of the electrode assembly (1100). The connecting portion (1210) is positioned to the lower side of the foil tab portion (1120), and welding, etc., can be performed on the upper side of the foil tab portion (1120), i.e., on side A. Accordingly, the connecting portion (1210) and the foil tab portion (1120) can be joined.

[0055] After joining the connecting portion (1210) and the foil tab portion (1120), the electrode lead (1200) is rotated upward by 90° (Fig. 5). The electrode lead (1200) can be rotated so that the joined foil tab portion (1120) faces one side of the electrode assembly (1100). Due to the rotation of the electrode lead (1200), the foil tab portion (1120) is bent, and the lead portion (1220) becomes perpendicular to one side of the electrode assembly (1100). Due to the bending of the foil tab portion (1120), the space occupied by the foil tab portion (1120) within the battery case (1500) is reduced, and the energy density can be increased accordingly.

[0056] In this embodiment, the connecting portion (1210) of the electrode lead (1200) is joined to the lower side of the foil tab portion (1120), but is not limited thereto and in other embodiments, the connecting portion (1210) may be joined to the upper side of the foil tab portion (1120). In this case as well, the electrode lead (1200) is rotated 90° so that the joined foil tab portion (1120) faces one side of the electrode assembly (1100). Due to the rotation of the electrode lead (1200), the lead portion (1220) of the electrode lead (1200) can be positioned at the center of the electrode assembly (1100) along the thickness direction of the electrode assembly (1100).

[0057] When joining the connecting part (1210) and the foil tab part (1120), it is preferable to align the end of the connecting part (1210) and the end of the foil tab part (1120). If the end of the connecting part (1210) and the end of the foil tab part (1120) do not align, a step difference occurs at the joint between the connecting part (1210) and the foil tab part (1120), and the battery case (1500) may be damaged due to this step difference.

[0058] The insulating portion (1300) is positioned on one side of the lead portion (1220) of the electrode lead (1200) and covers a portion of the electrode lead (1200). The lead portion (1220) is drawn out to the outside of the battery case (1500), and the insulating portion (1300) is positioned at a location where the battery case (1500) is heat-fused. By means of the insulating portion (1300), the electrode lead (1200) can be drawn out to the outside of the battery case (1500) without contacting the battery case (1500). Accordingly, the insulating portion (1300) prevents electricity generated from the electrode assembly (1100) from flowing to the battery case (1500) through the electrode lead (1200) and can maintain the sealing of the battery case (1500). The insulating part (1300) is easy to attach to the electrode lead (1200) and mainly uses insulating tape with a relatively thin thickness, but is not limited to this and can use various materials capable of insulating the electrode lead (1200).

[0059] The insulating portion (1300) has a length greater than the width of the electrode lead (1200) for the protection of the electrode lead (1200). Additionally, it is formed with a width greater than the width of the heat-sealed surface at the corner of the battery case (1500).

[0060] The fixing unit (1400) fixes the bent foil tab portion (1120) and the electrode lead (1200). Due to the properties of the metal, the bent foil tab portion (1120) tends to return to its original shape. If the foil tab portion (1120) is unfolded and restored, the space occupied by the foil tab portion (1120) within the battery case increases, and the battery case may be torn by the edges of the foil tab portion (1120). Additionally, there is a problem that the withdrawal direction of the electrode lead (1200) is not aligned in a certain direction, resulting in a higher defect rate of the manufactured secondary battery. The fixing unit (1400) of the present invention fixes the bent foil tab portion (1120) and the electrode lead (1200) to maintain the foil tab portion (1120) in a bent state.

[0061] Even if the width of the foil tab portion (1120) and the electrode lead (1200) is formed wide, the present invention can stably fix the foil tab portion (1120) and the electrode lead (1200) by the fixing unit (1400).

[0062] The battery case (1500) is a pouch manufactured by forming a pouch film having a flexible material that accommodates an electrode assembly (1100) inside. Hereinafter, the battery case (1500) is described as a pouch. When a flexible pouch film (P) is drawn using a punch and a die, a portion of it is stretched to form a pocket-shaped receiving space.

[0063] The battery case (1500) accommodates and seals the electrode assembly (1100) so that a portion of the electrode lead (1200) is exposed to the outside. The battery case (1500) includes a first case (1510) and a second case (1520). A first electrode assembly receiving portion (1511) is formed in the first case (1510). A second electrode assembly receiving portion (1521) is formed in the second case (1520). The electrode assembly is accommodated within the first and second electrode assembly receiving portions (1511, 1521). The electrode assembly (1100) can be cased by accommodating the electrode assembly (1100) in the first electrode assembly receiving portion (1511), covering the second case (1520) toward the first case (1510), and sealing the edges of the first and second cases (1510, 1520). The first case (1510) and the second case (1520) may be manufactured with one side connected to the other as shown in FIG. 1, but are not limited thereto and may be manufactured in various ways, such as being separated from each other and manufactured separately.

[0064] Bump regions (1512, 1522) may be formed at both ends of the electrode assembly receiving portions (1511, 1521). The bump regions (1512, 1522) are areas where the fixing unit (1400) and the lead are positioned when the electrode assembly (1100), in which the electrode lead (1200) is fixed by the fixing unit (1400), is received in the first electrode assembly receiving portion (1511) and the second electrode assembly receiving portion (1521). The bump regions (1512, 1522) are formed as concave surfaces so that the inner wall surface in contact with the fixing unit (1400) aligns with the outer surface of the fixing unit (14400). The bump regions (1512, 1522) casing the electrode assembly (1100) and serving to support the fixing unit (1400) so that it does not detach from one end of the electrode assembly (1100). In this embodiment, the thickness of the bump regions (1512, 1522) is formed to be the same as the thickness of the battery case (1500), but is not limited thereto, and the inner wall of the bump regions (1512, 1522) may be formed to be thicker than the thickness of the battery case (1500).

[0065] The bump area (1512, 1522) can be located in the center of the battery case along the width direction of the electrode assembly.

[0066] When forming electrode assembly receiving portions (1511, 1521) on a pouch film (P), only one electrode assembly receiving portion (1511, 1521) may be formed on a single pouch film, but is not limited thereto, and two electrode assembly receiving portions may be drawn and formed adjacent to each other on a single pouch film. The electrode assembly receiving portions (1511, 1521) formed on the first case (1510) and the second case (1520) may have the same depth, but are not limited thereto, and may have different depths.

[0068] FIG. 6 is a drawing showing a fixing unit of a secondary battery according to one embodiment of the present invention, FIG. 7 is a drawing showing an upper bracket and a lower bracket of a fixing unit combined in a secondary battery according to one embodiment of the present invention, FIG. 8 is a side cross-sectional view showing a state in which a foil tab portion and an electrode lead of a secondary battery according to one embodiment of the present invention are fixed by a fixing unit, FIG. 9 is a drawing showing a locking portion of a lower bracket coupled to a groove of an upper bracket of a fixing unit in a secondary battery according to one embodiment of the present invention, FIG. 10 is a cross-sectional view showing a state in which a locking portion of a lower bracket coupled to a groove of an upper bracket of a fixing unit in a secondary battery according to one embodiment of the present invention, FIG. 11 is a drawing showing a locking portion of a lower bracket coupled to a groove of an upper bracket of a fixing unit in a secondary battery according to another embodiment of the present invention, FIG. 12 is a cross-sectional view showing a state in which a locking portion of a lower bracket coupled to a groove of an upper bracket of a fixing unit in a secondary battery according to one embodiment of the present invention.

[0069] For convenience of explanation, the explanation is based on the case where the bending direction of the foil tab portion (1120) of the electrode assembly (1100) faces downward.

[0070] As illustrated in FIG. 6, the fixing unit (1400) is provided with an upper bracket (1410) and a lower bracket (1420). The upper bracket (1410) and the lower bracket (1420) are positioned at one end of the electrode assembly (1100) and are joined vertically with the electrode lead (1200) in between. Accordingly, the fixing unit (1400) is joined to the electrode lead (1200) to fix the bent foil tab portion (1120) and the electrode lead (1200). The material of the fixing unit (1400) may be an insulating material such as plastic.

[0071] The upper bracket (1410) is provided with a first pressure surface (1411), a first contact surface (1412), a support portion (1415), and a groove (1417). The first pressure surface (1411) is a surface that contacts the bent foil tab portion (1120) during assembly of the fixing unit (1400). A concave surface may be formed on the first pressure surface (1411) to correspond to the curved foil tab portion (1120). The first pressure surface (1411) supports the foil tab portion (1120) to maintain its bent shape. An adhesive material may be applied to the first pressure surface (1411) so that it can be fixed to the foil tab portion (1120).

[0072] The first contact surface (1412) is the lower surface of the upper bracket (1410) and is a surface that contacts one side of the lead portion (1200) of the electrode lead (1200) when assembled with the electrode assembly (1100). The length of the first contact surface (1412) may be equal to or greater than the width (Wc) of the lead portion. By the first contact surface (1412) contacting the lead portion (1220) of the electrode lead (1200), the electrode lead (1200) can be firmly supported without detaching from the electrode assembly (1100).

[0073] A support member (1415) is formed at a predetermined height at the lower ends of both ends of the upper bracket (1410). When the upper bracket (1410) and the lower bracket (1420) are joined, the support member (1415) comes into contact with the upper surface of the lower bracket (1420). As shown in FIG. 7, a spaced portion is formed between the upper bracket (1410) and the lower bracket (1420) by the support member (1415). The distance (d) between the upper bracket (1410) and the lower bracket (1420) may be equal to the thickness of the lead portion (1220) of the electrode lead (1200).

[0074] The lead portion (1220) of the electrode lead (1200) is drawn out through the slit formed by the support portion (1415), that is, the spaced-apart space between the upper bracket (1410) and the lower bracket (1420).

[0075] The groove (1417) is a space formed from the lower surface of the upper bracket (1410) to the inside of the upper bracket (1410). The groove (1417) is L-shaped, extends vertically into the inside of the upper bracket (1410), and extends horizontally at the end. The catch portion (1423) of the lower bracket (1420) is coupled to the horizontally extended space of the groove (1417).

[0076] The lower bracket (1420) is provided with a second pressure surface (1421), a second contact surface (1422), and a locking portion (1423). The second pressure surface (1421) is a surface that contacts the connection portion (1210) of the electrode lead (1200) when the fixed unit (1400) is assembled. The second pressure surface (1421) presses the other side of the connection portion (1210), on which the foil tab portion (1120) is attached to one side, thereby preventing the foil tab portion (1120) from unfolding due to the restoring force. The second pressure surface (1421) may have a flat surface like the connection portion (1210). The bent shape of the foil tab portion (1120) is maintained by the first pressure surface (1411) and the second pressure surface (1421), and the electrode lead (1200) can maintain a constant shape without tilting or shaking due to external force. An adhesive material may be applied to the second pressure surface (1421) so that it can be fixed to the connecting part (1210).

[0077] The second contact surface (1422) is the upper surface of the lower bracket (1420) and is a surface that contacts the other side of the lead portion (1220) of the electrode lead (1200) when the electrode assembly (1100) and the fixing unit (1400) are assembled. The length of the second contact surface (1422) may be equal to or greater than the width (Wc) of the lead portion. By the second contact surface (1422) contacting the lead portion (1220) of the electrode lead (1200), the electrode lead (1200) can be firmly supported without detaching from the electrode assembly (1100).

[0078] The first contact surface (1412) and the second contact surface (1422) are spaced apart by a predetermined distance (d) when the upper bracket (1410) and the lower bracket (1420) are combined. The distance (d) between the first contact surface (1412) and the second contact surface (1422) may be equal to the thickness of the lead portion (1220). The lead portion (1220) of the electrode lead (1200) is drawn out through the spaced gap, and by supporting contact between the lead portion (1220) and the first contact surface (1412) and the second contact surface (1422), the electrode lead (1200) is integrated with the fixed unit (1400) (Fig. 8).

[0079] The catch portion (1423) is formed to protrude from the upper surface of the lower bracket (1420). A hook-shaped projection is provided at the end of the catch portion (1423). The catch portion (1423) is inserted into the groove (1417) of the upper bracket (1410), and the upper bracket (1410) and the lower bracket (1420) are joined together by the hook-shaped projection being fitted into the horizontal extension space of the groove (1417).

[0080] After the upper bracket (1410) and the lower bracket (1420) are assembled, the gap between the upper and lower brackets (1410, 1420) may be equal to the thickness of the electrode lead (1200). The gap between the upper bracket (1410) and the lower bracket (1420) may be secured by the support portion (1415) of the upper bracket (1410).

[0081] Meanwhile, as illustrated in FIG. 10, in this embodiment, the groove (1417) has an internal space that extends vertically, whereas in other embodiments, the groove (1417) may be formed in a shape that is inclined toward the outside of the upper bracket (1410). When the extension direction of the groove (1417) is inclined, the catch portion (1423) is inserted into the groove (1417) and is bent outward toward the upper bracket (1410) along the inner wall of the groove (1417), reaching a horizontal space where the protrusion is fitted into the horizontal space. At this time, the catch portion (1423) can be strongly fastened by the elastic force acting toward the inside of the lower bracket (1420). The inclination angle of the groove (1417) may be 5 to 10°. If the inclination angle exceeds 10°, there is a risk that the catch portion (1423) will be excessively deformed and will not be restored.

[0082] In this embodiment, the locking part (1423) has a single body and a projection, but is not limited thereto, and the locking part (1423) may have various shapes. As shown in FIG. 11, the locking part (1423) may have a pair of bodies and projections. To accommodate a pair of bodies and projections, the groove (1417) of the upper bracket (1410) may form a T-shaped space. The pair of bodies and projections of the locking part (1423) move through the vertical space of the groove (1417) and are fixed by fitting the projections outward in the horizontal space.

[0083] A pair of bodies and protrusions of the catch portion (1423) can be arranged in a V-shape. That is, one end of the pair of bodies can be adjacent to each other and extended apart at a predetermined angle. When the catch portion (1423) is inserted into the groove (1417), the protrusions come into contact with the inner wall of the groove (1417), so the pair of bodies move closer to each other as they move through the vertical space of the groove (1417). When the pair of protrusions reach the horizontal space and are each fitted to the outside of the horizontal space of the groove (1417), the distance between the pair of bodies widens again, and the upper bracket (1410) and the lower bracket (1420) are fixed (Fig. 12).

[0084] Meanwhile, inclined surfaces may be formed at both ends of the upper bracket (1410) and the lower bracket (1420) so as not to impact the battery case (1500). Additionally, the corners of the upper bracket (1410) and the lower bracket (1420) may be formed as smooth curved surfaces. Due to the inclined surfaces and the curved corners of the upper bracket (1410) and the lower bracket (1420), the battery case (1500) is not torn or damaged even by the protrusion of the fixing unit (1400).

[0086] FIG. 13 is a drawing showing an electrode assembly in a secondary battery according to one embodiment of the present invention being cased by a battery case, and FIG. 14 is a cross-sectional view of an electrode assembly in a secondary battery according to one embodiment of the present invention being cased by a battery case.

[0087] As illustrated in FIG. 13, after the electrode assembly (1100) is received in the electrode assembly receiving portion (1511) formed in the first case (1510), the second case (1520) can be folded so that the two electrode assembly receiving portions (1511, 1521) face each other. By doing so, the electrode assembly (1100) is received within the two electrode assembly receiving portions (1511, 1521). Since the first and second electrode assembly receiving portions (1511, 1521) facing each other receive a single electrode assembly (1100), a thicker electrode assembly can be received than when there is only one electrode assembly receiving portion. Additionally, when the first case (1510) and the second case (1520) are integrally connected to each other, the number of sides to be sealed can be reduced when performing a sealing process later. Therefore, the process speed can be improved, and the number of sealing processes can be reduced.

[0088] Bump regions (1512, 1513) are formed at both ends of the electrode assembly receiving portion (1511). The bump regions (1512, 1513) are areas where the fixed unit (1400) and the electrode lead (1200) being drawn out are placed when the electrode assembly (1100), with the electrode lead (1200) fixed thereto, is received in the first electrode assembly receiving portion (1511). The assembly of the fixed unit (1400) combined with the foil tab portion (1120) and the electrode lead (1200) protrudes beyond the cross-section of the electrode assembly (1100). In the case of a rectangular pouch, due to the protruding part of the electrode assembly structure, a portion is created that cannot be cased in close contact with the electrode assembly (1100). The bump area (1512, 1513) is formed along the shape of the fixed unit (1400) of the electrode assembly (1100) so that the electrode assembly (1100) can be received and sealed in close contact with the pouch (1500).

[0089] As illustrated in FIG. 14, a bump region (1512) is formed at one end of the first electrode assembly receiving portion (1511). The bump region (1512) has an inner surface shape that matches the outer surface of the upper bracket (1410) of the fixing unit (1400).

[0090] Likewise, bump regions (1522) are formed at both ends of the second electrode assembly receiving portion (1521). The bump regions (1522) have an inner surface shape that matches the outer surface of the lower bracket (1420) of the fixed unit (1400). The first bump region (1512) of the first electrode assembly receiving portion (1511) and the second bump region (1522) of the second electrode assembly receiving portion (1521) may have a symmetrical shape with respect to the slit from which the electrode lead (1200) is drawn, that is, with respect to the center of the thickness direction of the electrode assembly (1100).

[0091] In another embodiment, the inner wall forming the bump region (1512, 1522) may be formed to be thicker than the thickness of other regions of the battery case (1500). For example, the thickness of the inner wall of the bump region (1512, 1522) may be 2 to 3 times the thickness of other regions of the battery case (1500) (Fig. 14(b)). By forming the inner wall of the bump region (1512, 1522) thickly, the fixing unit (1400) and the electrode lead (1200) can be supported more stably. The inner wall of the bump region (1512, 1522) may be formed of the same material as the battery case (1500), but is not limited thereto and may be formed of a different material from the battery case (1500). For example, the inner wall of the bump region (1512, 1522) may be formed of an insulating material with a predetermined thickness. A pad made of insulating material may be attached to the inner wall of the bump area (1512, 1522). The pad attached to the inner wall of the bump area (1512, 1522) may be a heat dissipation material.

[0092] The bump area (1512, 1522) may be formed as a concave surface so that the surface in contact with the fixed unit (1400) aligns with the outer surface of the fixed unit (1400). The bump area (1512, 1522) casing the electrode assembly (1100) and serving to support the fixed unit (1400) so that it does not detach from one end of the electrode assembly (1100).

[0093] Meanwhile, the battery case (1500) may include a degassing section (not shown) formed on the side of the electrode assembly receiving section (1511, 1521) that accommodates the electrode assembly (1100) and discharges gas generated inside the electrode assembly receiving section (1511, 1521) through a degassing hole (not shown). After housing the electrode assembly (1100) in the electrode assembly receiving section (1511, 1521) of the battery case (1500) and injecting an electrolyte, an activation process is performed, and gas is generated inside the battery case (1500), and a degassing process is performed to discharge this gas to the outside through the degassing section.

[0094] When the degassing process is completed, the degassing portion protruding to the side is removed, and the remaining side is folded at least once and fixed to the side of the battery case (1500) with tape.

[0096] FIG. 15 is a flowchart illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0097] As illustrated in FIG. 15, to manufacture a secondary battery according to an embodiment of the present invention, an electrode assembly is prepared (S3100). The electrode assembly (1100) comprises an electrode portion (1110) and a foil tab portion (1120). The electrode portion (1110) comprises a plurality of unit electrode plates (1111, 1112) and a separator (1113). The electrode portion (1110) of the electrode assembly (1100) can be formed by positioning a separator (1113) between an anode plate (1111) and a cathode plate (1112) that are alternately arranged. In one embodiment, the electrode portion (1110) is formed by alternately stacking the anode plate (1111), separator (1113), cathode plate (1112), and separator (1113). Accordingly, the electrode assembly (1100) may have a rectangular shape with height (H) and width (W). In another embodiment, the electrode portion (1110) may be formed by arranging the positive electrode plate (1111), the separator (1113), and the negative electrode plate (1112) in that order and then winding them up.

[0098] A plurality of unit electrode plates (1111, 1112) have a non-active tab (1121, 1122) formed thereon without an active material coating. In this embodiment, a non-active tab (1121) may be formed at one end of the positive electrode plate (1111), and a non-active tab (1122) may be formed at the other end of the negative electrode plate (1112) opposite to the one end, but is not limited thereto. The unit electrode plates (1111, 1112) and the non-active tab (1121, 1122) may be formed integrally.

[0099] The non-removable tabs (1121) of the positive plate (1111) overlap each other at a first position, and the non-removable tabs (1122) of the negative plate (1112) overlap each other at a second position. Multiple non-removable tabs (1121, 1122) overlapped at the same position can be connected to each other by ultrasonic welding, laser welding, etc., to facilitate the movement of current, thereby forming foil tabs (1120; 1121A, 1122A).

[0100] Next, the connection portion and the foil tab portion of the electrode lead are joined (S3200). The electrode lead (1200) is joined to the foil tab portion (1120). The electrode lead (1200) is provided with a connection portion (1210) and an extraction portion (1220). The connection portion (1210) and the foil tab portion (1120) of the electrode lead (1200) can be joined by a method such as spot welding.

[0101] The connecting portion (1210) of the electrode lead (1200) can be joined to the lower side of the foil tab portion (1120). When joining the connecting portion (1210) and the foil tab portion (1120), the connecting portion (1210) can be positioned in a direction perpendicular to one end surface of the electrode assembly (1100), and the leading portion (1220) can be positioned in a direction parallel to one end surface of the electrode assembly (1100). The connecting portion (1210) and the foil tab portion (1120) can be joined by performing welding or the like on the upper surface of the foil tab portion (1120).

[0102] The electrode lead joined to the foil tab portion is rotated 90° (S3300). The electrode lead (1200) can be rotated so that the joined foil tab portion (1120) faces one side of the electrode assembly (1100). By rotating the electrode lead (1200), the foil tab portion (1120) is bent, and the lead portion (1220) becomes perpendicular to one side of the electrode assembly (1100). Due to the bending of the foil tab portion (1120), the space occupied by the foil tab portion (1120) within the battery case (1500) is reduced, and thus the energy density can be increased.

[0103] An insulating member is positioned to surround a portion of the lead portion (S3400). The insulating portion (1300) surrounds a portion of the electrode lead (1200). The insulating portion (1300) is positioned on one side of the lead portion (1220) of the electrode lead (1200).

[0104] The extraction portion (1220) is drawn out to the outside of the battery case (1500), and the insulating portion (1300) is positioned at a location where the battery case (1500) is heat-fused. By means of the insulating portion (1300), the electrode lead (1200) can be drawn out to the outside of the battery case (1500) without contacting the battery case (1500). Accordingly, the insulating portion (1300) prevents electricity generated from the electrode assembly (1100) from flowing to the battery case (1500) through the electrode lead (1200) and can maintain the sealing of the battery case (1500). The insulating portion (1300) mainly uses insulating tape that is easy to attach to the electrode lead (1200) and has a relatively thin thickness, but is not limited thereto and various materials capable of insulating the electrode lead (1200) can be used.

[0105] The insulating portion (1300) has a length greater than the width of the electrode lead (1200) for the protection of the electrode lead (1200). Additionally, it is formed with a width greater than the width of the heat-sealed surface at the corner of the battery case (1500).

[0106] A fixing unit is assembled at one end of the electrode assembly (S3500). The fixing unit (1400) fixes the bent foil tab portion (1120) and the electrode lead (1200).

[0107] The fixing unit (1400) is equipped with an upper bracket (1410) and a lower bracket (1420). The upper bracket (1410) and the lower bracket (1420) are positioned at one end of the electrode assembly (1100) and are joined vertically with the electrode lead (1200) in between to fix the bent foil tab portion (1120) and the electrode lead (1200).

[0108] The first contact surface of the upper bracket contacts one side of the lead portion of the electrode lead, and the second contact surface of the lower bracket contacts the other side of the lead portion of the electrode lead.

[0109] An electrode assembly is housed within a battery case (S3600). The battery case (1500) houses and seals the electrode assembly (1100) such that a portion of the electrode lead (1200) is exposed to the outside.

[0110] The battery case (1500) includes a first case (1510) and a second case (1520). A first electrode assembly receiving portion (1511) is formed in the first case (1510). A second electrode assembly receiving portion (1521) is formed in the second case (1520). An electrode assembly is received within the first and second electrode assembly receiving portions (1511, 1521). An electrode assembly (1100) can be cased by receiving the electrode assembly (1100) in the first electrode assembly receiving portion (1511), covering the second case (1520) toward the first case (1510), and sealing the edges of the first and second cases (1510, 1520).

[0112] Although an embodiment of the present invention has been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention. Explanation of the symbols

[0113] 1000 : Secondary battery 1100 : Electrode assembly 1110 : Electrode part 1120 : Foil tab section 1200 : Electrode lead 1210 : Connection part 1220 : Withdrawal section 1300 : Insulation part 1400 : Fixed unit 1410 : Upper bracket 1411: First compression surface 1412: First contact surface 1415 : Support 1417 : Home 1420 : Lower bracket 1421 : Second compression surface 1422 : Second contact surface 1423 : Hook 1500 : Battery case 1510: First case 1511: First electrode assembly receiving portion 1512 : Bump area 1520 : 2nd case 1521 : Second electrode assembly receiving portion 1522 : Bump area

Claims

Claim 1 A secondary battery characterized by comprising: an electrode assembly having an electrode portion and a foil tab portion formed at one end of the electrode portion and bent in one direction; an electrode lead having a connecting portion and a pull-out portion extended by being bent relative to the connecting portion, wherein the connecting portion is welded to the foil tab portion; and a fixing unit disposed at one end of the electrode assembly and having an upper bracket having a first pressure surface and a first contact surface and a lower bracket having a second pressure surface and a second contact surface. Claim 2 A secondary battery characterized by further including an insulating portion surrounding a part of the lead portion in claim 1. Claim 3 A secondary battery according to claim 1 or 2, further comprising a battery case having a first electrode assembly receiving portion, a first case having a first bump region formed at least one end of the first electrode assembly receiving portion, and a second case having a second electrode assembly receiving portion and a second bump region formed at least one end of the second electrode assembly receiving portion, wherein the electrode assembly is received in the first electrode assembly receiving portion and the second electrode assembly receiving portion. Claim 4 A secondary battery according to claim 3, characterized in that the withdrawal portion extends outside the battery case. Claim 5 A secondary battery according to claim 1 or 2, wherein the foil tab portion is pre-welded. Claim 6 A secondary battery according to claim 1 or 2, wherein the upper bracket and the lower bracket are joined such that the first contact surface of the upper bracket contacts one surface of the lead portion and the second contact surface of the lower bracket contacts the other surface of the lead portion. Claim 7 A secondary battery according to claim 1 or 2, characterized in that the first pressure surface of the upper bracket contacts the foil tab portion, and the second pressure surface of the lower bracket contacts the connection portion. Claim 8 A secondary battery according to claim 1 or 2, characterized in that a pair of grooves are formed at both ends of the upper bracket, and a pair of locking parts that engage with the pair of grooves are provided at both ends of the lower bracket. Claim 9 A secondary battery according to claim 1 or 2, characterized in that the length (l) of the first contact surface is the same as the width (Wc) of the lead portion. Claim 10 A secondary battery characterized in that, in claim 1 or 2, the distance (d) between the first contact surface and the second contact surface is the same as the thickness of the lead portion. Claim 11 A secondary battery according to claim 1 or 2, characterized in that inclined surfaces are formed at both ends of the upper bracket and the lower bracket. Claim 12 A secondary battery according to claim 1 or 2, wherein the unit electrode plate of the electrode portion comprises a positive plate and a negative plate, and the electrode portion is formed by alternately stacking such that a separator is positioned between the positive plate and the negative plate. Claim 13 A secondary battery according to claim 1 or 2, characterized in that the width of the foil tab portion is 40 to 70% of the width of the electrode assembly. Claim 14 A secondary battery according to claim 1 or 2, characterized in that the lead portion is perpendicular to one end surface of the electrode assembly. Claim 15 A secondary battery characterized in that, in paragraph 3, the inner walls of the first bump region and the second bump region are made of the same material as the battery case. Claim 16 A secondary battery characterized in that, in paragraph 3, the inner walls of the first bump region and the second bump region are made of a material different from the battery case. Claim 17 A secondary battery according to claim 3, wherein the first bump region and the second bump region are symmetrical with respect to the center of the thickness direction of the electrode assembly. Claim 18 A secondary battery according to claim 3, wherein the first bump region and the second bump region are located at the center of the battery case along the width direction of the electrode assembly. Claim 19 A secondary battery according to claim 3, characterized in that the shape of the inner wall surface of the first bump region and the second bump region matches the outer surface of the upper bracket and the lower bracket, respectively. Claim 20 A secondary battery characterized in that, in claim 3, the battery case is a pouch. Claim 21 A method for manufacturing a secondary battery, characterized by comprising: a preparation step of preparing an electrode assembly having an electrode portion and a foil tab portion; a joining step of joining the connecting portion and the foil tab portion of an electrode lead having a connecting portion and a lead portion extending vertically from the connecting portion; a rotation step of rotating the electrode lead joined to the foil tab portion by 90°; and a fixing unit assembly step in which a fixing unit having an upper bracket and a lower bracket is assembled at one end of the electrode assembly, wherein the first contact surface of the upper bracket contacts one surface of the lead portion of the electrode lead and the second contact surface of the lower bracket contacts the other surface of the lead portion of the electrode lead. Claim 22 A method for manufacturing a secondary battery, characterized by further including, in claim 21, an insulating member placement step in which the insulating member is arranged to surround a portion of the lead portion. Claim 23 A method for manufacturing a secondary battery, characterized by further including a packaging step of accommodating the electrode assembly within a battery case in accordance with claim 21 or 22.

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