Battery cell, manufacturing method therefor and battery assembly comprising same

Abstract

A battery cell manufacturing method of the present disclosure comprises: an insertion step of inserting a cap part into an opening; and a connection step of irradiating a laser at the cap part and a body part so as to connect the cap part to the body part, wherein, a welding bead for connecting the cap part to the body part is formed in the connection step, and the welding bead can satisfy formula 1. (Formula 1) T ≤ D (In formula 1, D is the thickness of a welding bead with respect to the cross-section of a battery cell in the thickness direction of a cap part, and T is the thickness of the cap part.)

Description

Battery cell, manufacturing method thereof, and battery assembly including same

[0001] The present disclosure relates to a battery cell, a method for manufacturing the same, and a battery assembly including the same. Specifically, the disclosure relates to a battery cell with improved stability and performance, a method for manufacturing the same, and a battery assembly including the same.

[0002] Secondary batteries convert electrical energy into chemical energy, allowing them to be stored and reused multiple times through charging and discharging. Due to their economical and environmentally friendly properties, secondary batteries are widely used across various industries. Lithium secondary batteries, in particular, are widely used in portable devices requiring high energy density, as well as in various industries.

[0003] Secondary batteries can be manufactured by welding to connect their components. The welding method can significantly affect the stability and performance of the finished secondary battery. Furthermore, when multiple secondary batteries are grouped together for use, the shape of the weld bead formed by welding must be considered during manufacturing to maximize space efficiency.

[0004] The problem to be solved by the present disclosure is to provide a battery cell with improved stability and performance, a method for manufacturing the same, and a battery assembly including the same.

[0005] In addition, the present disclosure provides a battery cell, a method for manufacturing the same, and a battery assembly including the same, in which post-processing of a welding bead is omitted to improve manufacturing efficiency.

[0006] In addition, the present disclosure can be widely applied in green technology fields such as electric vehicles, battery charging stations, and solar and wind power generation using batteries.

[0007] Additionally, the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, etc. to prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0008] The present disclosure relates to a method for manufacturing a battery cell, comprising: a body portion that accommodates a battery cell therein and includes an opening open to one side; and a cap portion that includes a bottom surface facing the battery cell and a ceiling surface facing the outside, the bottom surface covering the opening and including a recessed portion formed by recessing at least a portion of an edge of the ceiling surface.

[0009] It includes an insertion step of inserting the cap part into the opening and a connecting step of connecting the cap part and the body part by irradiating a laser on the cap part and the body part, and in the connecting step, a welding bead connecting the cap part and the body part is formed, and the welding bead satisfies the following equation 1.

[0010] (Formula 1)

[0011] T ≤ D

[0012] (In Equation 1, D is the thickness of the welding bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and T is the thickness of the cap portion.)

[0013] The above connecting step may be such that the welding bead is positioned inside the outer surface of the body portion and inside the ceiling surface.

[0014] The above connection step can satisfy the following equation 2.

[0015] (Formula 2)

[0016] B ≤ A ≤ 4B

[0017] (In Equation 2, A is the cross-sectional area of ​​the weld bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and B is the cross-sectional area of ​​the corner region formed by the outer surface of the body portion, the ceiling surface, and the weld bead.)

[0018] The above A may be 1.5B to 3.5B.

[0019] The above insertion step can satisfy the following equation 3.

[0020] (Formula 3)

[0021] F ≤ P / Q

[0022] (In Equation 3, F is the overlapping length of the recessed portion and the body portion overlapping along the thickness direction of the cap portion based on the battery cell cross-section in the thickness direction of the cap portion, P is the cross-sectional area of ​​the recessed portion, and Q is the thickness of the body portion.)

[0023] The above-mentioned recessed portion may have a structure in which a step is formed along the thickness direction of the cap portion.

[0024] The width of the above step may be 0.3 mm to 1 mm, and the height of the above step may be 0.2 mm or less.

[0025] The above-mentioned recessed portion may have a structure having a slope along the thickness direction of the cap portion.

[0026] The above body portion may include a stopper formed along the inner surface so as to be in contact with the bottom surface of the cap portion.

[0027] In addition, the battery cell of the present disclosure includes a body portion that accommodates a battery cell therein and includes an opening that is open on one side; a cap portion that is at least partially inserted into the opening and covers the opening; and the body portion and the cap portion are connected to each other by a welding bead, and the welding bead satisfies the following equation 1.

[0028] (Formula 1)

[0029] T ≤ D

[0030] (In Equation 1, D is the thickness of the welding bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and T is the thickness of the cap portion.)

[0031] The above welding bead may be located inside the outer surface of the body portion and inside the cap portion.

[0032] The above welding bead can satisfy the following equation 2.

[0033] (Formula 2)

[0034] B ≤ A ≤ 3.5B

[0035] (In Equation 2, A is the cross-sectional area of ​​the weld bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and B is the cross-sectional area of ​​the corner region formed by the outer surface of the body portion, the ceiling surface, and the weld bead.)

[0036] The above A may be 1.5B to 3B.

[0037] The cap portion may include a different material from the body portion.

[0038] The above body portion may include a stopper formed along the inner surface so as to be in contact with the bottom surface of the cap portion.

[0039] Additionally, the battery assembly of the present disclosure may include the battery cell.

[0040] According to one embodiment of the present disclosure, a battery cell and a method for manufacturing a battery cell with improved stability and improved performance can be provided.

[0041] In addition, the present disclosure can provide a battery cell and a battery cell manufacturing method in which post-processing of a welding bead is omitted, thereby improving manufacturing efficiency.

[0042] FIG. 1 is a flowchart illustrating a method for manufacturing a battery cell according to one embodiment of the present disclosure.

[0043] FIGS. 2 and 3 illustrate a battery cell according to one embodiment of the present disclosure.

[0044] Figures 4 and 5 illustrate other examples of battery cells of the present disclosure.

[0045] FIGS. 6A and 6B illustrate a body portion and a cap portion according to one embodiment of the present disclosure.

[0046] FIGS. 7A and 7B illustrate a body portion and a cap portion according to another embodiment of the present disclosure.

[0047] FIGS. 8 and 9 illustrate a welding bead according to one embodiment of the present disclosure.

[0048] FIGS. 10A to 10E illustrate various embodiments of the welding bead of the present disclosure.

[0049] FIG. 11 illustrates the area of ​​a weld bead and a corner region according to various embodiments of the present disclosure.

[0050] FIG. 12 and FIG. 13 illustrate various embodiments of the battery assembly of the present disclosure.

[0051] Hereinafter, the present disclosure will be described in detail with reference to the attached drawings. However, these are merely exemplary and the present disclosure is not limited to the specific embodiments described as examples.

[0052] Certain terms used in this specification are for convenience of explanation only and are not intended to limit the illustrated embodiments.

[0053] For example, expressions such as "same" and "same as" not only indicate a strictly identical state, but also indicate a state in which there is a difference in tolerance, or the degree to which the same function is obtained.

[0054] For example, expressions indicating relative or absolute arrangements such as “in which direction,” “along which direction,” “parallel,” “perpendicular,” “centered,” “concentric,” or “coaxial” not only strictly indicate such arrangements, but also indicate a state of relative displacement with an angle or distance that allows for tolerance, or the degree to which the same function is obtained.

[0055] In order to explain the present disclosure, the following description is based on a spatial orthogonal coordinate system with mutually orthogonal X-axis, Y-axis, and Z-axis. Each axis direction (X-axis direction, Y-axis direction, Z-axis direction) means both directions in which each axis extends.

[0056] The X-direction, Y-direction, and Z-direction mentioned below are for the purpose of explanation so that the present disclosure can be clearly understood, and it is of course possible to define each direction differently depending on where the standard is set.

[0057] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0058] FIG. 1 is a flowchart for explaining a method for manufacturing a battery cell according to one embodiment of the present disclosure, FIGS. 2 and 3 illustrate a battery cell (10) according to one embodiment of the present disclosure, and FIGS. 4 and 5 illustrate other examples of the battery cell (10) of the present disclosure.

[0059] Referring to FIG. 1, a method for manufacturing a battery cell according to an embodiment of the present disclosure includes an insertion step (S10) and a connection step (S30). Referring to FIG. 2, a battery cell (10) may include an outer material (11), and the outer material (11) may include a body portion (13) and a cap portion (12). The body portion (13) may include an opening portion (131) that is open to one side.

[0060] The battery cell manufacturing method of the present disclosure may include an insertion step (S10) of inserting a cap portion (12) into an opening. The insertion step (S10) will be described in detail with reference to FIGS. 2 to 5 below.

[0061] After the insertion step (S10), a connection step (S30) may be performed. The battery cell manufacturing method of the present disclosure may include a connection step (S30) of connecting the cap part (12) and the body part (13) by irradiating the cap part (12) and the body part (13) with a laser (L). The connection step (S30) may be performed by irradiating the laser (L) under the supply of the laser (L). The connection step (S30) will be described in detail with reference to FIGS. 6A to 9 below.

[0062] By irradiating the laser (L), a welding bead (20 in FIG. 8) connecting the cap portion (12) and the body portion (13) can be formed. The welding bead (20) may be formed by melting and then solidifying at least a portion of the cap portion (12) and the body portion (13). The welding bead (20) will be described in detail with reference to FIGS. 8 to 11 below.

[0063] The battery cell (10) described herein refers to a secondary battery that can be repeatedly used by charging and discharging electrical energy. For example, it may refer to a lithium secondary battery or a lithium ion battery, but is not limited thereto. As another example, it may refer to an all-solid-state battery.

[0064] The battery cell (10) may be classified into a pouch-type secondary battery, a prismatic secondary battery, or a cylindrical secondary battery depending on its shape. In this specification, a prismatic secondary battery is illustrated as an example for convenience of explanation, but the present invention is not limited thereto.

[0065] The battery cell (10) includes an electrode assembly. The electrode assembly may include a positive electrode, a negative electrode, and a separator. The electrode assembly may be classified into a stacking type, a winding type, a stack-folding type, and a Z-stacking type depending on the method by which the positive electrode, negative electrode, and separator are stacked. The battery cell (10) of the present disclosure is not limited to any one stacking method and may include an electrode assembly stacked in various ways.

[0066] The positive electrode and the negative electrode may include a current collector. The positive electrode may include a positive current collector, and the negative electrode may include a negative current collector. The current collector may include a known conductive material that does not cause a chemical reaction within a lithium secondary battery. For example, the current collector may include any one of stainless steel, nickel (Ni), aluminum (Al), titanium (Ti), copper (Cu), and alloys thereof, and may be provided in various forms such as a film, a sheet, or a foil.

[0067] The positive electrode and the negative electrode may include active materials. The positive electrode may include a positive electrode active material, and the negative electrode may include a negative electrode active material. The positive electrode active material may be a material into which lithium ions can be inserted and deintercalated, and the negative electrode active material may be a material into which lithium ions can be inserted and deintercalated. For example, the positive electrode active material may be a lithium metal oxide, and the negative electrode active material may be a carbonaceous material such as crystalline carbon, amorphous carbon, a carbon composite, or carbon fiber, a lithium alloy, silicon (Si), or tin (Sn).

[0068] Additionally, the positive and negative electrodes may further include a binder and a conductive material, respectively, to improve mechanical stability and electrical conductivity.

[0069] The separator can be configured to prevent electrical short-circuiting between the anode and cathode and to allow ion flow. The type of separator is not particularly limited, but may include a porous polymer film. For example, the separator may include a porous polymer film or a porous nonwoven fabric.

[0070] The electrolyte may include an electrolyte. The electrolyte may be a non-aqueous electrolyte. The electrolyte may include a lithium salt and an organic solvent. The electrolyte may further include an additive. The additive may form a film on the positive or negative electrode through a chemical reaction within the battery. For example, an anode interface film may be formed on the positive electrode, and an anode interface film may be formed on the negative electrode.

[0071] The battery cell (10) may further include an outer case (11) that accommodates the electrode assembly therein. The electrode assembly and an electrolyte may be accommodated within the outer case (11). The outer case (11) may include an outer insulating layer made of a polymer material, an inner adhesive layer, and a metal layer interposed between the outer insulating layer and the inner adhesive layer. The outer case (11) may include a material having high mechanical strength to protect the battery cell (10) from external impact. For example, the case may include an aluminum layer.

[0072] The battery cell (10) may further include an electrode tab (14) protruding outward from the outer casing (11) for electrical connection to the outside. The electrode tab (14) may be connected to the positive and negative electrodes of the battery cell (10), respectively. The electrode tab (14) may include a positive electrode tab (14a) connected to the positive electrode and a negative electrode tab (14b) connected to the negative electrode.

[0073] Referring to FIGS. 2 and 3, the outer material (11) may include a body portion (13) and a cap portion (12). The body portion (13) may accommodate a battery cell (10) therein. The battery cell (10) may be inserted into the body portion (13). To this end, the body portion (13) may include an opening (131) that is open on one side. The body portion (13) may include an opening (131) that is open on at least one side.

[0074] Referring to FIGS. 2 and 3, in the case of a unidirectional battery cell (10) in which the positive and negative tabs protrude in the same direction, one side of the body portion (13) facing the Z direction can be opened to form an opening (131).

[0075] Referring to FIGS. 4 and 5, in the case of a bidirectional battery cell (10_1) in which the positive and negative tabs protrude in opposite directions, both sides of the body portion (13_1) facing the Z direction may be opened to form an opening (131_1). In other words, the electrode tabs (14_1) may protrude in opposite directions.

[0076] The cap portion (12) can cover the opening portion (131). For this purpose, the cap portion (12) can be provided with a shape corresponding to the opening portion (131). The outer surface of the cap portion (12) can contact the inner surface of the body portion (13). The cap portion (12) and the body portion (13) can be combined to protect the components inside the body portion (13). The cap portion (12) can include a different material from the body portion (13).

[0077] Referring again to FIG. 3, the cap portion (12) may include a bottom surface (122) facing the battery cell (10) and a ceiling surface (121) facing the outside. When the cap portion (12) and the body portion (13) are connected, the bottom surface (122) may face the inside of the body portion (13), and the ceiling surface (121) may be provided on the opposite side of the bottom surface (122).

[0078] The cap portion (12) may include a recessed portion (120) formed by recessing at least a portion of the edge. In an embodiment, the recessed portion (120) may be formed on the ceiling surface (121). The recessed portion (120) may be formed along an edge of the ceiling surface (121). In other words, the recessed portion (120) may be formed in an edge area of ​​the ceiling surface (121).

[0079] This is to form the shape of the welding bead (20) according to the preset conditions during welding. The recessed portion (120) will be described in detail with reference to FIGS. 6a to 9.

[0080] Meanwhile, the opening (131) provided in the body portion (13) may be covered by the cap portion (12). At least a portion of the cap portion (12) may be inserted into the body portion (13). To this end, the size of the cap portion (12) may be formed to be smaller than the size of the opening portion (131). For example, referring to FIG. 3, the length of the cap portion (12) along the X direction and the length along the Y direction may be provided to be less than the length of the opening portion (131) in each direction.

[0081] When a plurality of openings (131) are provided, a plurality of cap parts (12) may be provided to correspond to each of the openings (131). For example, referring to FIG. 5, the body part (13_1) may include an opening (131_1) that is open on both sides along the Y direction. The cap parts (12_1) may be provided in two pieces to cover the two openings (131_1).

[0082] FIGS. 6a and 6b illustrate a body part (13) and a cap part (12) according to one embodiment of the present disclosure, and FIGS. 7a and 7b illustrate a body part (13) and a cap part (12_2) according to another embodiment of the present disclosure.

[0083] The cap part (12, 12_2 of FIG. 7a) and the body part (13) can be connected by irradiating the laser (L) onto them. The laser (L) can be supplied by a welding system (150). In an embodiment, the laser (L) can be irradiated in a direction parallel to the contact surface of the cap part (12) and the body part (13). In another example, the laser (L) can be irradiated in a direction inclined to the contact surface of the cap part (12) and the body part (13). As long as the body part (13) and the cap part (12) can be connected, the irradiation direction of the laser (L) is not particularly limited.

[0084] Specifically, FIGS. 6A and 6B illustrate cross-sections of the body portion (13) and the cap portion (12). Here, FIGS. 6A and 6B may illustrate cross-sections of the battery cell (10) cut along the thickness direction of the cap portion (12). Specifically, the cross-section of the battery cell (10) cut along the thickness direction of the cap portion (12) may mean a cross-section cut by an imaginary first plane parallel to the thickness direction of the cap portion (12). In addition, the cross-section of the battery cell (10) may mean a weld cross-section cut so that the area of ​​the weld bead (20) is minimized.

[0085] As a practical example, as shown in FIG. 3, the virtual first surface may mean a virtual first surface that is parallel to the thickness direction (k1) of the cap portion (12) and parallel to the thickness direction (k2) of the body portion (13), and the cross-section of the battery cell (10) may mean a cross-section cut by the above-described virtual first surface.

[0086] Referring to FIGS. 6A and 6B, the recessed portion (120) may have a structure in which a step is formed along the thickness direction of the cap portion (12). The recessed portion (120) may form a step along the edge. In other words, the thickness of the center of the cap portion (12) may be formed smaller than the thickness of the edge due to the recessed portion (120). This is to prevent a part of the body portion (13) from melting and moving to the cap portion (12) during welding, thereby preventing the welding bead (20) from protruding to the upper portion of the cap portion (12).

[0087] In the embodiment, the cap portion (12) and the body portion (13) may be melted by irradiating the laser (L). The heat capacity value of the cap portion (12) may be formed to be higher than the heat capacity value of the body portion (13). As a result, the body portion (13) may be melted first, so that a part of the body portion (13) may move to the cap portion (12), and the welding bead (20) may be raised to the upper part of the cap portion (12).

[0088] When the welding bead (20) is raised, assembly errors, stacking errors, etc. may occur during the process of manufacturing a bundle of battery cells (10) (battery module, battery pack) in which multiple battery cells (10) are grouped. As a result, the energy density of the bundle of grouped battery cells (10) (battery module, battery pack) will decrease, and the high output and high capacity conditions will not be satisfied.

[0089] In addition, when the body portion (13) and the cap portion (12) are covered simultaneously with an insulating material or an insulating material, an unattached space may be created due to the protrusion of the welding bead (20). The unattached space may reduce the adhesive strength and the assembly of the battery cell (10).

[0090] The battery cell manufacturing method of the present disclosure can provide a battery cell (10) with improved stability and improved performance by preventing the welding bead (20) from rising by considering the shape of the body portion (13), the shape of the cap portion (12), and the insertion length of the cap portion (12).

[0091] Meanwhile, the recessed portion (120) may have a preset width and a preset height. The width of the recessed portion (120) refers to the length of the recessed portion (120) measured along the direction from the outside to the inside of the cap portion (12). In addition, the height of the recessed portion (120) refers to the length of the recessed portion (120) measured along the thickness direction of the cap portion (12). For example, referring to FIGS. 6A and 6B, the width (W) of the recessed portion (120) may be measured along the X direction, and the height (H) of the recessed portion (120) may be measured along the Z direction.

[0092] Advantageously, the width of the step may be 0.3 mm to 1 mm. The height of the step may be 0.2 mm or less. This allows the welding bead (20) to be formed according to the set specifications.

[0093] The cross-sectional area of ​​the recessed portion (120) can be measured through the width and height of the recessed portion (120). The insertion depth of the cap portion (12) can be determined by comparing the measured cross-sectional area of ​​the recessed portion (120) with the area provided in one area of ​​the body. In another example, the area of ​​the recessed portion (120) can be measured using a known method.

[0094] In the embodiment, the insertion step (S10) of the present disclosure can satisfy the following equation 3. In other words, the body part (13) and the cap part (12) of the present disclosure can satisfy the following equation 3.

[0095] In the embodiment, when the body part (13) and the cap part (12) satisfy the following equation 3, the welding bead (20) can satisfy equations 1 and 2 described below. However, this is not necessarily the case.

[0096] <Formula 3>

[0097] F ≤ P / Q

[0098] In Equation 3, F is the overlapping length of the recessed portion (120) and the body portion (13) along the thickness direction of the cap portion (12) based on the cross-section of the battery cell (10) in the thickness direction of the cap portion (12), P is the cross-sectional area of ​​the recessed portion (120), and Q is the thickness of the body portion (13).

[0099] Here, the unit of F is mm and the unit of P is mm 2 , and the unit of Q can be mm.

[0100] Specifically, referring to FIGS. 6A and 6B, at least a portion of the cap portion (12) may be inserted into the body portion (13). The depth at which the cap portion (12) is inserted into the body portion (13) may be less than or equal to a preset depth. The depth at which the cap portion (12) is inserted into the body portion (13) may be correlated with the overlapping length of the recessed portion (120) and the body portion (13). Specifically, as the depth at which the cap portion (12) is inserted into the body portion (13) increases, the overlapping length (F) at which the recessed portion (120) and the body portion (13) overlap may increase.

[0101] The depth at which the cap portion (12) is inserted into the body portion (13) can be derived based on the cross-sectional area (P) of the recessed portion (120) and the protruding area (S) of the body portion (13). Here, the protruding area (S) of the body portion (13) can mean the area where the recessed portion (120) and the body portion (13) overlap along the thickness direction of the body portion (13). In other words, it can mean the area of ​​the body portion (13) that protrudes along the thickness direction of the body portion (13) based on an area where the recessed portion (120) comes into contact with the body portion (13).

[0102] The protruding area (S) of the body part (13) may vary depending on the depth to which the cap part (12) is inserted. Based on this, the protruding area (S) of the body part (13) can be calculated. As the cap part (12) is inserted deeper into the body part (13), the area where the recessed part (120) and the body part (13) overlap increases, and the protruding area (S) of the body part (13) may increase.

[0103] Referring to Fig. 6b, the cross-sectional area (P) of the recessed portion (120) is determined according to the shape of the cap portion (12), and the protruding area (S) of the body portion (13) may vary depending on the insertion depth of the cap portion (12). The cap portion (12) may be inserted until the protruding area (S) of the body portion (13) becomes equal to the cross-sectional area (P) of the recessed portion (120).

[0104] In one embodiment, the body portion (13) may have a preset thickness. The thickness of the body portion (13) may be the length of the body portion (13) along the direction from the inside to the outside of the cap portion (12). For example, referring to FIGS. 6a and 6b, the thickness (Q) of the body portion (13) may be the length of the body portion (13) along the X direction.

[0105] As illustrated in Fig. 6a, when the body portion (13) does not protrude, the protruding area of ​​the body portion (13) may be 0. As illustrated in Fig. 6b, when the body portion (13) protrudes, the overlapping length of the recessed portion (120) and the body portion (13) may be measured from an area in contact with the recessed portion (120). In a specific embodiment, the length of the body portion (13) protruding along the thickness direction of the cap portion (12) from an area in which the recessed portion (120) contacts the body portion (13) may be defined as the overlapping length of the recessed portion (120) and the body portion (13).

[0106] Based on the overlapping length of the recessed portion (120) and the body portion (13) measured through the above method and the thickness of the body portion (13), the protruding area of ​​the body portion (13) can be measured. Without being limited thereto, the protruding area of ​​the body portion (13) can be measured through a known method.

[0107] The range of the protrusion length of the body part (13) can be set. Ultimately, the overlapping length of the recessed part (120) and the body part (13) should be less than or equal to the value obtained by dividing the unit area of ​​the recessed part (120) by the thickness (Q) of the body part (13).

[0108] In order to prevent excessive insertion of the cap portion (12), the body portion (13) may include a stopper (132). In other words, the stopper (132) may protrude from a preset area of ​​the body portion (13) in accordance with the overlapping length of the recessed portion (120) and the body portion (13) to prevent insertion of the cap portion (12). The stopper (132) may be formed along the inner surface of the body portion (13) so as to be in contact with the bottom surface (122) of the cap portion (12).

[0109] For example, referring to FIG. 3 and FIG. 6a, the cap portion (12) can be inserted into the opening (131) along the Z direction. At this time, in order to prevent the cap portion (12) from being inserted below a preset depth along the Z direction, a stopper (132) can be formed to protrude along the inner surface of the body portion (13).

[0110] The bottom surface (122, 122_2 in FIG. 7a) of the cap portion (12) may come into contact with the stopper (132) to restrict the insertion of the cap portion (12). This may protect the electrode assembly provided inside the body portion (13). In addition, the positions of the body portion (13) and the cap portion (12) may be easily adjusted.

[0111] In another embodiment, referring to FIGS. 7A and 7B, the recessed portion (120) may have an inclined surface. Specifically, the recessed portion (120) may have a structure having an inclined surface along the thickness direction of the cap portion (12_2). The edge of the recessed portion (120) may form an inclined surface so that the contacting surface of the body portion (13) and the inclined surface of the recessed portion (120) may form an acute angle.

[0112] Even when the recessed portion (120) includes a slope, the insertion depth of the cap portion (12_2) can be determined by considering the area (P_1) of the recessed portion (120) and the protruding area (S_1) of the body portion (13) as described above. Based on this, the range of the overlapping length in which the recessed portion and the body portion overlap can be calculated.

[0113] FIG. 8 and FIG. 9 illustrate a welding bead (20) according to one embodiment of the present disclosure.

[0114] After the body part (13) and the cap part (12) are positioned at preset positions, the body part (13) and the cap part (12) can be connected by irradiating the laser (L). By irradiating the laser (L), a welding bead (20) connecting the body part (13) and the cap part (12) can be formed.

[0115] Referring to Fig. 8, a welding bead (20) can be formed between the cap portion (12) and the body portion (13). In an embodiment, the welding bead (20) can satisfy the following equation 1.

[0116] <Formula 1>

[0117] T ≤ D

[0118] (In Equation 1, D is the thickness of the welding bead (20) based on the cross-section of the welding bead (20) in the thickness direction of the cap portion (12), and T is the thickness of the cap portion (12).)

[0119] Here, the units of D and T can be mm.

[0120] The above-described equation 1 may be particularly important when the body portion (13) and the cap portion (12) are made of different materials. That is, when T is greater than D in welding dissimilar materials, the stability of the weld bead (20) may be reduced.

[0121] The thickness of the welding bead (20) can be formed to be greater than the thickness of the cap portion (12) based on the thickness direction of the cap portion (12). The thickness of the welding bead (20) refers to the length from the intersection point (CR) where the body portion (13), the cap portion (12) and the welding bead (20) meet to the outer surface (L3) of the welding bead.

[0122] The farther the intersection is from the outer surface of the body portion (13), the thicker the welding bead (20) may be. In addition, the farther the intersection is from the outer surface of the cap portion (12), the thicker the welding bead (20) may be.

[0123] The thickness of the weld bead (20) may not be uniform. For example, referring to FIG. 8, the thickness of the weld bead (20) may mean the distance from the intersection to the first reference point provided on the outer surface (L3) of the weld bead (20) or the distance from the intersection to the second reference point provided on the outer surface (L3) of the weld bead (20). In other words, the smallest value among the thicknesses of the weld bead (20) should be formed to be greater than the thickness of the cap portion (12).

[0124] If the thickness of the welding bead (20) is formed to be smaller than the thickness of the cap portion (12), the bonding strength of the welding bead (20) may be low. In other words, the durability of the welding bead (20) is reduced, so that the body portion (13) and the cap portion (12) cannot be stably connected and may be easily damaged by external impact.

[0125] In the embodiment, the welding bead (20) may be located inside the outer surface of the body portion (13) and inside the ceiling surface (121). Specifically, the welding bead (20) may be located inside a virtual surface including the outer surface of the body portion (13).

[0126] The welding bead (20) may be positioned inside the outer surface of the body portion (13). Specifically, the welding bead (20) may be positioned inside an imaginary line extending from the outer edge of the body portion (13) based on the cross-section of the battery cell (10) in the thickness direction of the cap portion (12). In other words, the welding bead (20) may not protrude outside the body portion (13). For example, referring to FIG. 8, the welding bead (20) may be positioned closer to the inside of the body portion (13) than an imaginary line (L2) extending along the Z direction from the outer edge of the body portion (13).

[0127] The welding bead (20) may be positioned inside the ceiling surface (121). Specifically, the welding bead (20) may be positioned inside an imaginary line (L1) extending from the ceiling surface (121) based on the cross-section of the battery cell (10) in the thickness direction of the cap portion (12). In other words, the welding bead (20) may not protrude outside the cap portion (12). For example, referring to FIG. 8, the welding bead (20) may be positioned closer to the inside of the body portion (13) than an imaginary line (L1) extending from the ceiling surface (121) in the X direction.

[0128] Finally, referring to FIG. 8, the welding bead (20) may be located inside the outer surface of the body portion (13) and inside the ceiling surface (121).

[0129] The thickness of the above-described welding bead (20) may affect the cross-sectional area of ​​the welding bead (20). Accordingly, in another embodiment, the welding bead (20) may satisfy the following equation 2.

[0130] <Formula 2>

[0131] B ≤ A ≤ 4B

[0132] In Equation 2, A is the cross-sectional area of ​​the welding bead (20) based on the cross-section of the welding bead in the thickness direction of the cap portion (12), and B is the cross-sectional area of ​​the corner region formed by the outer surface of the body portion (13), the outer surface of the cap portion (12), and the welding bead (20).

[0133] Here, the units of A and B can be mm2.

[0134] The cross-sectional area of ​​the corner region may mean the cross-sectional area of ​​the region formed by the imaginary line extending from the outer edge of the body part (13), the imaginary line extending from the ceiling surface (121), and the welding bead (20).

[0135] For example, referring to FIG. 9, the edge region may mean an area surrounded by a virtual line (L1) extending along the Z direction from the outer edge of the body portion (13), a virtual line (L2) extending along the X direction from the outer edge of the ceiling surface (121), and an outer surface (L3) of the welding bead (20).

[0136] When the cross-sectional area of ​​the welding bead (20) is smaller than the cross-sectional area of ​​the edge region, the performance of the welding bead (20) may not be guaranteed. In addition, when the cross-sectional area of ​​the welding bead (20) exceeds 4B, various problems such as reduced welding strength, occurrence of cracks in the weld, and protrusion of the welding bead (20) may occur. More preferably, A can satisfy 1.5B to 3.5B.

[0137] Ultimately, when the cross-sectional area of ​​the welding bead (20) is satisfied, it can exhibit excellent welding characteristics with improved tensile strength and low contact resistance, and can exhibit constant welding characteristics without being substantially affected by specific welding conditions.

[0138] The welding bead (20) can simultaneously satisfy the above-described equations 1 and 2. Whether equations 1 and 2 are satisfied depending on the shape of the welding bead (20) is described in detail with reference to FIGS. 10a, 10b, and 11.

[0139] FIGS. 10A to 10E illustrate various embodiments of a welding bead (20) of the present disclosure, and FIG. 11 illustrates the area of ​​a welding bead (20) and a corner region according to various embodiments of the present disclosure.

[0140] Example 1 of FIG. 11 is illustrated in FIG. 10a, Example 2 is illustrated in FIG. 10b, Example 3 is illustrated in FIG. 10d, Example 4 is illustrated in FIG. 10d, and Example 5 is illustrated in FIG. 10e.

[0141] Example 1 shows a welding bead (20) in which the thickness of the welding bead (20a) is greater than the thickness of the cap portion (12). In this case, the area of ​​area A is 0.39, area B is 0.56, and A / B is measured as 0.70. Therefore, the welding bead (20a) of Example 1 does not satisfy Equation 1, and also does not satisfy Equation 2. In other words, the welding bead (20a) of Example 1 falls short of the set standard and a welding bead (20) of inferior quality will be formed.

[0142] The welding beads (20b, 20c, 20d) of FIGS. 10b to 10d satisfy Equation 1. As a result, the ratios of A / B are 1.56, 3.1, and 3.36, respectively, and Equation 2 can be satisfied. Since Equations 1 and 2 are satisfied, a welding bead (20) with improved stability can be formed.

[0143] The weld bead (20e) of Fig. 10e satisfies Equation 1. However, the weld bead (20e) may be raised and protrude outward from the ceiling surface (121) of the cap portion (12). The value of A / B is 4.39, which does not satisfy Equation 2. In other words, if there is a rise in the weld bead (20), Equation 2 may not be satisfied.

[0144] FIG. 12 and FIG. 13 illustrate various embodiments of the battery assembly of the present disclosure.

[0145] According to another embodiment of the present disclosure, a battery assembly including the aforementioned battery cell may be provided. The battery assembly may include a battery cell and a housing (210, 310) that accommodates the battery cell therein.

[0146] A battery assembly may refer to a battery module that is grouped in groups of one or more and placed in a case to protect battery cells from external shock, heat, vibration, etc. and to have high output and high capacity characteristics.

[0147] In another embodiment, the battery assembly (100) may mean a battery pack that groups one or more battery cells or battery modules.

[0148] Referring to FIG. 12, a battery module (200) may include a battery cell (10) and a module housing (210). The module housing (210) may accommodate a battery cell (10) within it. This allows the battery cell (10) to be safely protected from external impact.

[0149] Referring to FIG. 13, a battery pack (300) may include a battery cell (10) and a pack housing (310). The battery cell (10) may be positioned on the upper portion of the pack housing (310), and the battery cells (10) may be grouped in multiples to have high capacity and high output characteristics.

[0150] The battery pack (300) may be formed in a cell-to-pack structure. The cell-to-pack structure allows the battery cells (10) to be directly accommodated in the pack housing (310). This allows the battery pack to be lighter and its energy density to be improved.

[0151] In another embodiment, the battery cells (10) may be grouped to form a battery module, and the battery module may be positioned on the upper portion of the pack housing. As long as the battery cells are grouped in multiple units and can be electrically connected to the outside, the shape of the pack housing is not particularly limited.

[0152] The present disclosure may be implemented in various forms and modifications, and the scope of the present disclosure is not limited to the embodiments described above. Therefore, if a modified embodiment includes elements of the claims of the present disclosure, it should be considered to fall within the scope of the present disclosure.

Claims

1. A method for manufacturing a battery cell, comprising: a body portion that accommodates a battery cell therein and includes an opening open to one side; and a cap portion that covers the opening and includes a bottom surface facing the battery cell and a ceiling surface facing the outside, and includes a recessed portion formed by recessing at least a portion of an edge of the ceiling surface; an insertion step of inserting the cap part into the opening; and A connecting step for connecting the cap and the body by irradiating a laser on the cap and the body; The above connection step is, A welding bead connecting the cap portion and the body portion is formed, The above welding bead is a battery cell manufacturing method that satisfies the following equation 1. (Formula 1) T ≤ D (In Equation 1, D is the thickness of the welding bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and T is the thickness of the cap portion.) 2. In paragraph 1, The above connection step is A method for manufacturing a battery cell, wherein the welding bead is located inside the outer surface of the body and inside the ceiling surface.

3. In paragraph 1, The above connection step is a method for manufacturing a battery cell that satisfies the following equation 2. (Formula 2) B ≤ A ≤ 4B (In Equation 2, A is the cross-sectional area of ​​the weld bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and B is the cross-sectional area of ​​the corner region formed by the outer surface of the body portion, the ceiling surface, and the weld bead.) 4. In paragraph 3, The above A is a method for manufacturing a battery module of 1.5B to 3.5B.

5. In paragraph 1, The above insertion step is a method for manufacturing a battery cell that satisfies the following equation 3. (Formula 3) F ≤ P / Q (In Equation 3, F is the overlapping length of the recessed portion and the body portion overlapping along the thickness direction of the cap portion based on the battery cell cross-section in the thickness direction of the cap portion, P is the cross-sectional area of ​​the recessed portion, and Q is the thickness of the body portion.) 6. In paragraph 1, The above-mentioned depression A method for manufacturing a battery cell having a structure in which a step is formed along the thickness direction of the cap portion.

7. In paragraph 6, A method for manufacturing a battery cell, wherein the width of the step is 0.3 mm to 1 mm and the height of the step is 0.2 mm or less.

8. In paragraph 1, The above-mentioned depression A method for manufacturing a battery cell having a structure having an inclined surface along the thickness direction of the cap portion.

9. In paragraph 1, A battery cell manufacturing method wherein the body portion includes a stopper formed along the inner surface so as to be in contact with the bottom surface of the cap portion.

10. A body portion that houses a battery cell inside and includes an opening open on one side; and A cap portion having at least a portion inserted into the opening and covering the opening; The above body portion and the above cap portion are connected to each other by a welding bead, The above welding bead is a battery cell that satisfies the following equation 1. (Formula 1) T ≤ D (In Equation 1, D is the thickness of the welding bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and T is the thickness of the cap portion.) 11. In paragraph 10, The above welding bead A battery cell located inside the outer surface of the body portion and inside the cap portion.

12. In paragraph 11, The above welding bead is a battery cell that satisfies the following equation 2. (Formula 2) B ≤ A ≤ 3.5B (In Equation 2, A is the cross-sectional area of ​​the weld bead based on the cross-section of the battery cell in the thickness direction of the cap portion, and B is the cross-sectional area of ​​the corner region formed by the outer surface of the body portion, the ceiling surface, and the weld bead.) 13. In paragraph 12, The above A is a battery cell of 1.5B to 3B.

14. In paragraph 10, A battery cell in which the cap portion comprises a different material from the body portion.

15. In paragraph 10, A battery cell including a stopper formed along the inner surface of the body portion so as to be in contact with the bottom surface of the cap portion.

16. Battery cell of Article 10; and A battery assembly including a housing that houses the battery cell therein.

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