Secondary battery

Abstract

The present invention relates to a secondary battery in which weld strength during welding is improved due to surface-treating a welding area to be welded on a current collector plate by laser etching to remove oil from the surface such that the dyne pen level and surface tension of the welding area are higher than those of other areas. One embodiment of the present invention provides a secondary battery comprising: an electrode assembly having a first electrode plate, a separator, and a second electrode plate; a case accommodating the electrode assembly and having an open bottom; a terminal coupled to the case by penetrating the top surface; a first current collector plate interposed between the top surface of the electrode assembly and the case and electrically connecting the first electrode plate and the terminal; and a cap plate sealing the bottom of the case, wherein a welding area of the first current collector plate to be welded to the electrode assembly has greater surface tension than other areas.

Description

secondary battery

[0001] The present disclosure relates to a secondary battery.

[0002] Rechargeable batteries are power storage systems that provide excellent energy density by converting electrical energy into the form of chemical energy for storage. Unlike primary batteries, which are non-rechargeable, rechargeable batteries are widely used in IT devices such as smartphones, cellular phones, laptops, and tablet PCs. Recently, interest in electric vehicles has increased due to the need to prevent environmental pollution, leading to the adoption of high-capacity rechargeable batteries in these vehicles. These rechargeable batteries require characteristics such as high density, high output, and stability.

[0003] The information described above disclosed in the background technology of this invention is intended only to enhance understanding of the background of the present invention and may therefore include information that does not constitute prior art.

[0004] The present invention can improve welding strength during welding by surface treating the welding area requiring welding on a current collector plate by laser etching, thereby removing oil from the surface and making the Dynefen value and surface tension higher than other areas.

[0005] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems can be clearly understood by those skilled in the art from the description of the invention below.

[0006] A secondary battery according to an embodiment of the present invention for solving the above technical problem comprises an electrode assembly having a first electrode plate, a separator, and a second electrode plate; a case having an open bottom end that accommodates the electrode assembly; a terminal coupled by penetrating the top surface of the case; a first current collector plate interposed between the top surface of the electrode assembly and the case and electrically connecting the first electrode plate and the terminal; and a cap plate that seals the bottom end of the case, wherein the surface tension of the weld area of ​​the first current collector plate that is welded to the electrode assembly may be greater than that of other areas.

[0007] The first current collector plate may include a terminal connection portion that is in contact with and electrically connected to the lower surface of the terminal in the shape of a flat circular plate, and an electrode plate connection portion that is welded to the first electrode tab of the first electrode plate exposed to the upper surface of the electrode assembly and is located on the outer side of the terminal connection portion.

[0008] The first current collector plate has a welding area on the lower surface of the electrode plate connection part, and the welding area is surface-treated so that the value of the Dyne Pen may be larger than that of other areas.

[0009] The above welding area may have a Dynefen value greater than 36 and less than 40.

[0010] The upper surface of the terminal connection part above is surface-treated by laser etching, so that the numerical value of the dyne pen may be larger than that of the lower surface of the terminal connection part.

[0011] The above welded area can be surface treated by laser etching.

[0012] It may further include a fuse portion located between the terminal connection portion and the electrode plate connection portion.

[0013] The fuse portion may include a fuse hole formed along a part of the outer circumference of the terminal connection portion and a plate connection portion connecting the terminal connection portion and the plate connection portion.

[0014] It may further include a second current collector plate welded to the second electrode tab of the second electrode plate exposed to the lower surface of the electrode assembly, having a circular plate shape corresponding to the lower surface of the electrode assembly.

[0015] The second current collector plate may include a circular flat portion in contact with the lower surface of the electrode assembly and an extension portion extending downward from the edge of the flat portion.

[0016] The second current collector plate includes a welding area on the upper surface of the flat portion that is welded to the lower surface of the second electrode assembly, and the welding area is surface-treated by laser etching so that the value of the Dyne Pen may be larger than that of the lower surface of the flat portion.

[0017] The above case is

[0018] A beading portion recessed into the interior of the case on the upper part of the cap plate; and

[0019] The lower part of the cap plate may include a crimping portion that fixes the cap plate by bending the lower part of the case inward.

[0020] It further includes a cap gasket interposed between the cap plate and the beading portion and between the cap plate and the crimping portion, and the cap plate may be nonpolar.

[0021] The extension of the second collector plate can be interposed between the cap gasket and the beading portion.

[0022] The extension of the second current collector plate can be surface-treated by laser etching.

[0023] The first electrode plate protrudes upward from the upper surface of the electrode assembly and further includes a plurality of first electrode tabs that are bent and compacted in the winding axis direction of the electrode assembly, and the second electrode plate protrudes upward from the lower surface of the electrode assembly and further includes a plurality of second electrode tabs that are bent and compacted in the winding axis direction of the electrode assembly, and the electrode assembly may have a plurality of first electrode tabs exposed on the upper surface and a plurality of second electrode tabs exposed on the lower surface.

[0024] According to the present invention, a secondary battery can be provided that can improve welding strength during welding by surface treating the welding area requiring welding in the current collector plate by laser etching to remove oil from the surface, thereby making the Dynefen value and surface tension higher than other areas.

[0025] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description of the invention below.

[0026] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0027] FIG. 1 is a perspective view illustrating a secondary battery according to the present invention.

[0028] Figure 2 is a cross-sectional view of the secondary battery shown in Figure 1.

[0029] Figure 3 is an exploded perspective view of the electrode assembly and current collector plate in the secondary battery of Figure 1.

[0030] Figure 4 is a cross-sectional view of Figure 3.

[0031] FIGS. 5A and 5B are a bottom view showing a surface-treated area on the lower surface of the first current collector plate in the secondary battery of FIG. 1, and a top view showing a surface-treated area on the tkd surface of the first current collector plate.

[0032] FIGS. 6a and FIGS. 6b are perspective views illustrating a battery pack including an exemplary secondary battery according to the present invention.

[0033] FIGS. 7a and FIGS. 7b are a perspective view and a side view illustrating an automobile including an exemplary battery pack according to the present invention.

[0034] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe their invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. It should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0035] Additionally, as used herein, “comprise, include” and / or “comprising, including” specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0036] Additionally, to aid in understanding the invention, the attached drawings are not drawn to actual scale, and the dimensions of some components may be exaggerated. Furthermore, the same reference numerals may be assigned to identical components in different embodiments.

[0037] The statement that two subjects of comparison are 'identical' means that they are 'substantially identical.' Therefore, substantial identity may include deviations considered low in the industry, for example, deviations within 5%. Additionally, the statement that a parameter is uniform in a given area may mean that it is uniform from an average perspective.

[0038] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0039] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0040] The fact that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0041] Furthermore, where it is stated that one component is "connected," "coupled," or "connected" to another component, it should be understood that while said components may be directly connected or connected to each other, another component may be "interposed" between each component, or that each component may be "connected," "coupled," or "connected" through another component. Additionally, when it is stated that a part is electrically coupled with another part, this includes not only cases where they are directly connected but also cases where they are connected with another component in between.

[0042] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise. That is, "and / or" includes any combination or any combination of the enumerated items. "C to D" means C or more and D or less, unless specifically stated otherwise.

[0043] The terms used in this specification are intended to describe embodiments of the present disclosure and are not intended to limit the present disclosure.

[0044] FIG. 1 is a perspective view illustrating a secondary battery according to the present invention, and FIG. 2 is a cross-sectional view of the secondary battery illustrated in FIG. 1.

[0045] As illustrated in FIGS. 1 and 2, a secondary battery (100) may include an electrode assembly (110), a case (120) that contains the electrode assembly (110) and an electrolyte inside, a terminal (150) coupled to a terminal hole (122a) provided at one end of the case (120), for example, an upper end, and a cap plate (160) that seals the other end of the case (110), for example, a lower end. In some examples, the secondary battery (100) may have a terminal hole provided on the cap plate (160) so that the terminal (150) can be coupled to the cap plate (160).

[0046] The secondary battery (100) may further include a first current collector plate (130) that electrically connects the first electrode (111) of the electrode assembly (110) and the terminal (150), and a second current collector plate (140) that electrically connects the second electrode (112) of the electrode assembly (110) and the case (120).

[0047] The electrode assembly (110) may include a separator (113), a first electrode plate (111) and a second electrode plate (112) positioned between the separator (113), and may be wound in the form of a jelly roll.

[0048] The first electrode plate (111) includes a first substrate and a first active material layer located on the first substrate. A first electrode tab (111b) may be extended outwardly from a first electrode non-part (111a) in the first substrate where the first active material layer is not located, and the first electrode tab (111b) may be electrically connected to a terminal (150) through a first current collector plate (130).

[0049] The second electrode plate (112) includes a second substrate and a second active material layer located on the second substrate. A second electrode tab (112b) may be extended outwardly from a second electrode non-part (112a) in the second substrate where the second active material layer is not located, and the second electrode tab (112b) may be electrically connected to a case (120) through a second current collector plate (140).

[0050] The first electrode tab (111b) and the second electrode tab (112b) may be located in opposite directions in the electrode assembly (110). The first electrode plate (111) may function as an anode. In this case, the first substrate may be composed of, for example, aluminum foil, and the first active material layer may include, for example, a transition metal oxide. The second electrode plate (112) may function as a cathode. In this case, the second substrate may be composed of, for example, copper foil or nickel foil, and the second active material layer may include, for example, graphite.

[0051] The separator (113) functions to prevent a short circuit between the first electrode (111) and the second electrode (112) while allowing the movement of lithium ions. The separator (113) may be composed of, for example, a polyethylene film, a polypropylene film, a polyethylene-polypropylene film, etc.

[0052] In some examples, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used as the positive electrode active material. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0053] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0054] As an example, compounds represented by any one of the following chemical formulas may be used. LiaA1-bXbO2-cDc(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiaMn2-bXbO4-cDc(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiaNi1-b-cCobXcO2-αDα(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); LiaNi1-b-cMnbXcO2-αDα(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); LiaNibCocL1dGeO2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); LiaNiGbO2(0.90≤a≤1.8, 0.001≤b≤0.1); LiaCoGbO2(0.90≤a≤1.8, 0.001≤b≤0.1); LiaMn1-bGbO2 (0.90≤a≤1.8, 0.001≤b≤0.1); LiaMn2GbO4 (0.90≤a≤1.8, 0.001≤b≤0.1); LiaMn1-gGgPO4(0.90≤a≤1.8, 0≤g≤0.5); Li(3-f)Fe2(PO4)3(0≤f≤2); LiaFePO4(0.90≤a≤1.8).

[0055] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L1 is Mn, Al, or a combination thereof.

[0056] A positive electrode for a lithium secondary battery may include a current collector (e.g., a first substrate) and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may include a positive electrode active material and may further include a binder and / or a conductive material.

[0057] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer, and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer.

[0058] Aluminum may be used as the current collector mentioned above, but is not limited thereto.

[0059] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0060] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite, such as natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0061] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The above Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-based alloy, or a combination thereof.

[0062] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles.

[0063] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0064] A negative electrode for a lithium secondary battery may include a current collector (e.g., a second substrate) and a negative electrode active material layer formed on the current collector. The negative electrode active material layer may include a negative electrode active material and may further include a binder and / or a conductive material.

[0065] For example, the negative electrode active material layer may comprise 90% to 99% by weight of negative electrode active material, 0.5% to 5% by weight of binder, and 0% to 5% by weight of conductive material.

[0066] As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used. When an aqueous binder is used as the cathode binder, a cellulose-based compound capable of imparting viscosity may be further included.

[0067] As the current collector mentioned above, a material selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof may be used.

[0068] The electrolyte for a lithium secondary battery may include a non-aqueous organic solvent and a lithium salt.

[0069] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0070] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, a non-protic solvent, or a combination thereof, and may be used alone or in a mixture of two or more types.

[0071] In addition, when using carbonate-based solvents, cyclic carbonates and chain carbonates can be mixed and used.

[0072] As described above, a separator may be present between the positive and negative electrodes of a lithium secondary battery. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used.

[0073] The above separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0074] The above organic material may include a polyvinylidene fluoride-based antibody or a (meth)acrylic-based polymer.

[0075] The above inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but is not limited thereto.

[0076] The above organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0077] The case (120) accommodates the electrode assembly (110) and the electrolyte, and together with the terminal (150) and the cap plate (160), forms the outer shape of the secondary battery (100). The case (120) may include a roughly cylindrical body portion (121) and an upper portion (122) connected to one side of the body portion (121). A beading portion (123) deformed toward the inside may be located on the body portion (121), and a crimping portion (124) bent toward the inside may be located at the opening end of the body portion (121). A terminal hole (122a) penetrating the center may be provided on the upper portion (122). The upper portion (122) may be coupled by inserting a terminal (150) into the terminal hole (122a). A terminal gasket (125) for sealing and electrical insulation may be further interposed between the terminal hole (122a) and the terminal (150).

[0078] The beading portion (123) can prevent the electrode assembly (110) from moving inside the case (120) and facilitate the seating of the cap gasket (127) and the cap plate (160). The crimping portion (124) can firmly secure the cap plate (160) by pressing the edge of the cap plate (160) through the cap gasket (127). The case (123) may be made of, for example, nickel-plated iron.

[0079] One side of the first current collector plate (130) may be in contact with and coupled to the first electrode tab (111b) of the electrode assembly (110), and the other side may be in contact with and coupled to the terminal (150). The first current collector plate (130) may be welded to the first electrode tab (111b) of the electrode assembly (110) to be electrically connected. The first current collector plate (130) may be welded and electrically connected while the other side is in contact with the terminal (150).

[0080] The second current collector plate (140) may have its center (141) in contact with and coupled to the second electrode tab (112b) of the electrode assembly (110), and its edge portion (142) may be in contact with and coupled to the body portion (121) of the case (120). The second current collector plate (140) may be electrically connected by welding its center (141) to the second electrode tab (112b) of the electrode assembly (110). The second current collector plate (140) may be electrically connected by welding its edge portion (142) in contact with the beading portion (123) of the case (120).

[0081] The terminal (150) may include a head (151) located on the outside of the case (120) and a fastening portion (152) extending from the center of the head (151) toward the inside of the case (120). The terminal (150) may be secured and sealed by the fastening portion (152) being coupled to the terminal hole (122a) together with the terminal gasket (125), thereby pressing the upper part (122) of the case (120) from the inside through the terminal gasket (125). The terminal (150) may further be provided with a terminal groove (153) extending from the center of the head (151) toward the fastening portion (152). The terminal (150) may be welded externally to the first current collector plate (130) through the terminal groove (153). The terminal (150) can be electrically connected to the first electrode (111) of the electrode assembly (110) through the first collector plate (130). The terminal (150) and the case (120) may have different polarities.

[0082] The cap plate (160) can be fixed to the inside of the crimping portion (124) through the cap gasket (127) to seal the case (120). The cap plate (160) may include a safety vent (165) that is thinner than other areas by means of a notch. In the event that gas is generated due to overcharging or abnormal operation of the secondary battery (100), the safety vent (165) provided in the cap plate (160) may be cut along the notch. The cut safety vent (165) can release the gas to the outside to prevent the explosion of the secondary battery (100).

[0083] FIG. 3 is an exploded perspective view of the electrode assembly (110), the first current collector plate (130), and the second current collector plate (140) in the secondary battery of FIG. 1, and FIG. 4 is a cross-sectional view of FIG. 3. Hereinafter, with reference to FIG. 3 and FIG. 4, the structure and relationship of the electrode assembly (110), the first current collector plate (130), and the second current collector plate (140) will be explained.

[0084] The first electrode plate (111) may be provided with a first electrode blank portion (111a) on its upper end, which is not coated with a first electrode active material. Such a first electrode blank portion (111a) may protrude in the upward direction of the electrode assembly (110). Additionally, the first electrode blank portion (111a) may include a plurality of first electrode tabs (111b). The plurality of first electrode tabs (111b) may be located on the upper end of the first electrode blank portion (111a) and may be arranged to be spaced apart from each other in one direction prior to winding. Such a plurality of first electrode tabs (111b) may not be provided at the winding front end and / or winding end. Such a plurality of first electrode tabs (111b) may be formed on the first electrode blank portion (111a) by laser notching, ultrasonic cutting, punching, etc. The first electrode tab (111b) may protrude further in an upward direction compared to the second electrode plate (112) and separator (113) in the electrode assembly (110).

[0085] The second electrode plate (112) may be provided with a second electrode blank portion (112a) at its lower end, which is not coated with the second electrode active material. Additionally, the second electrode blank portion (112a) may include a plurality of second electrode tabs (112b). The plurality of second electrode tabs (112b) may be located at the lower end of the second electrode blank portion (112a) and may be arranged to be spaced apart from each other in one direction prior to winding. The plurality of second electrode tabs (112b) may not be provided at the winding front end and / or winding end. The plurality of second electrode tabs (112b) may be formed on the second electrode blank portion (112a) by laser notching, ultrasonic cutting, punching, etc. A plurality of such second electrode tabs (112b) may protrude further downward from the first electrode plate (111) and separator (113) in the electrode assembly (110).

[0086] In the electrode assembly (110), the first electrode tab (111b) may protrude upward, and the second electrode tab (112b) may protrude downward. The first electrode tab (111b) and the second electrode tab (112b) may be bent toward the winding core. That is, a plurality of first electrode tabs (111b) and a plurality of second electrode tabs (112b) may be bent and compacted from the winding leading edge region toward the winding core. At this time, the first electrode tab (111b) and the second electrode tab (112b) may not be provided in a part of the winding leading edge region so that they do not cover the winding core hole of the electrode assembly (110).

[0087] The electrode assembly (110) may have a first electrode tab (111b) located on the upper surface (110a) and a second electrode tab (112b) located on the lower surface (110b).

[0088] The first current collector plate (130) may be a circular metal plate having a shape corresponding to the upper surface (110a) of the electrode assembly (110). The planar size of the first current collector plate (130) may be equal to or smaller than the size of the upper surface (110a) of the electrode assembly (110). The first current collector plate (130) may be fixed and electrically connected to the first electrode tab (111b) of the electrode assembly (110) by welding while the lower surface (130b) of the first current collector plate (130) is in contact with the upper surface (110a) of the electrode assembly (110). The first current collector plate (130) may be fixed and electrically connected to the terminal (150) by welding while the upper surface (130a) of the first current collector plate (130) is in contact with the lower surface of the terminal (150). The first current collector plate (130) serves as a passage for current flow between the first electrode plate (111) of the electrode assembly (110) and the terminal (150). The first current collector plate (130) can be welded to the electrode assembly (110), housed in the case (120), and then welded to the terminal (150).

[0089] The first current collector plate (130) may include a terminal connection part (131), a electrode plate connection part (132), and a fuse part (135). The terminal connection part (131) is located at the center of the first current collector plate (130) and may be formed in a roughly circular shape. The lower surface of the fastening part (152) of the terminal (150) may be welded to the upper surface of the terminal connection part (131). The electrode plate connection part (132) may be located on the outside of the terminal connection part (131).

[0090] The electrode plate connection portion (132) can be electrically connected to the first electrode tab (111b) of the electrode assembly (110) on its lower surface. For example, the electrode plate connection portion (132) can be welded to the first electrode tab (111b) on which the lower surface is exposed to the upper surface (110a) of the electrode assembly (110).

[0091] The electrode plate connection portion (132) has a lower surface that is welded to the electrode assembly (110) that is laser-etched to remove surface oil. Referring to FIG. 5a, a bottom view of the first current collector plate (130) is shown, and referring to FIG. 5b, a top view of the first current collector plate (130) is shown.

[0092] Here, the welding area (132a) of the electrode plate connection portion (132), which is welded to the electrode assembly (110) on the lower surface, can be surface-treated to remove oil. Here, the welding area (132a) can be surface-treated by laser etching to remove any oil remaining on the surface. The welding area (132a) can be provided symmetrically with respect to the terminal connection portion (131). Although four welding areas (132a) are shown in FIG. 5, they can be provided in various shapes with two or more, symmetrically with respect to the terminal connection portion (131). Additionally, although the welding area (132a) is shown as being provided in a roughly rectangular shape, it may have a circular or bar shape, but the shape is not limited.

[0093] The electrode plate connection part (132) can be surface treated by laser etching only at the welding area (132a) on the lower surface. Generally available oil removal treatment methods include plasma treatment, corona treatment, or chemical treatment, but masking treatment is required to treat only a part rather than the entire area of ​​the current collector plate; however, laser etching can etch only a part without a separate mask, thereby simplifying the process. Of course, the entire lower surface of the electrode plate connection part (132) can be surface treated by laser etching, but this may only result in an increase in process time.

[0094] The weld area (132a) can be surface-treated by laser etching to increase the tensile strength by welding. The weld area (132a) can have a higher Dynefen value and surface tension compared to other areas of the electrode plate connection part (132). Additionally, the weld area (132a) can have a higher surface tension and Dynefen value compared to other areas of the first current collector plate (130).

[0095] Here, the Dyne pen is used to measure the surface tension (spreadability) of a solid surface, and the adhesive strength of the surface is determined by the wetting pattern. When a line of 2 to 4 cm is drawn on the surface to be measured using the Dyne pen, if the line of the pen shrinks, it means that the surface tension of the surface is lower than the value of the Dyne pen, and if there is no change in the line, it means that the surface tension is equal to or higher than the numerical value of the Dyne pen.

[0096] The weld area (132a) may have a surface tension of 36 mN / m or more according to the Dyne Pen standard. The surface tension of the weld area (132a) can be measured using a Dyne Pen according to the methods of ISO 8296 and ASTM D2578-84. That is, when a line is drawn on the surface of the laser-etched weld area (132a) with a 36 Dyne Pen, the oil on the surface is removed so that the line can be marked without change. More preferably, the weld area (132a) may have a Dyne Pen value greater than 36 and less than 40. Table 1 shows the weld strength measurements according to the Dyne Pen values.

[0097] Dyne Pen (mN / m) Welding Strength (kgf) 32 or less 6.5 32~34 9.1 36~38 12.5 38~40 14.5

[0098] Through Table 1, it can be seen that as the Dynefen value (surface tension) increases due to laser etching, the welding strength also increases. That is, it can be seen that as the Dynefen value (surface tension) of the welding area (132a) of the first current collector plate (130) increases, the weldability with the first electrode tab (111b) increases. In other words, if the welding area (132a) of the first current collector plate (130) is surface-treated by laser etching and the Dynefen value becomes 36 or higher, the welding strength between the first electrode tab (111b) of the electrode assembly (110) can be secured and improved by 10 kgf or more. Generally, since the Dynefen value of a metal surface is in the range of 25 to 30, increasing the Dynefen value of the welding area (132a) by laser etching can improve the welding strength with the electrode assembly (110). Similarly, the upper surface of the terminal connection part (131) is also surface-treated by laser etching so that the Dyne Pen value may be larger than that of the lower surface. That is, the upper surface of the terminal connection part (131) is surface-treated by laser etching so that any oil remaining on the surface can be removed. The terminal connection part (131) can improve the welding strength with the terminal (150) by surface treatment.

[0099] A fuse section (135) may be formed between a terminal connection section (131) and a electrode plate connection section (132). The fuse section (135) may include a fuse hole (136) and an electrode plate connection section (137). When a short circuit or overcurrent occurs in the secondary battery (100), the fuse section (135) can cut off the current flowing to the secondary battery (100) by melting and cutting the electrode plate connection section (137) by the heat generated.

[0100] The fuse hole (136) is formed in a roughly 'C' shape along a part of the outer periphery of the terminal connection part (131), so that the two ends of the fuse hole (136) can face each other. The fuse hole (136) can separate the terminal connection part (131) and the electrode plate connection part (132). That is, the terminal connection part (131) and the electrode plate connection part (132) can be separated from each other by the fuse hole (136).

[0101] The electrode plate connecting portion (137) can connect the terminal connecting portion (131) and the electrode plate connecting portion (132). The electrode plate connecting portion (137) can improve safety by melting and cutting due to the heat generated when a short circuit or overcurrent occurs in the secondary battery (100), thereby cutting off the current.

[0102] The shape of the first current collector plate (130) can be changed to various forms, for example, having a terminal connection part (131), a electrode plate connection part (132), and a fuse part (135).

[0103] The second current collector plate (140) may include a circular flat portion (141) corresponding to the lower surface (110b) of the electrode assembly (110), and an extension portion (142) extending downward from the edge of the flat portion (141).

[0104] The surface roughness of the upper surface (140a) of the second current collector plate (140) may be greater than the surface roughness of the lower surface (130b) of the first current collector plate (130). Since the surface roughness of the lower surface (110b) of the electrode assembly (110) is greater than the surface roughness of the upper surface (110a), it is preferable that the surface roughness of the upper surface (110a) of the second current collector plate (140) be greater than the surface roughness of the lower surface (110b) of the first current collector plate (130) in order to increase the contact area with the lower surface (110b) which has a greater surface roughness.

[0105] The flat portion (141) of the second current collector plate (140) can be electrically connected to the lower portion (110b) of the electrode assembly (110) at its upper surface. The upper surface of the flat portion (141) can be fixed and electrically connected to the second electrode tab (112b) exposed to the lower portion of the electrode assembly (110) by welding while in contact with the lower portion (110b) of the electrode assembly (110).

[0106] The extension portion (142) may extend downward from the edge of the flat portion (141). For example, multiple extension portions (142) may be provided spaced apart from each other along the edge of the flat portion (141). Additionally, the extension portion (142) may come into contact with the inner surface of the beading portion (123). That is, the extension portion (142) may be rounded or bent along the beading portion (123). Here, the inner surface may be the inner surface of the case (120). The end portion of the extension portion (142) may be positioned between the beading portion (123) and the cap gasket (127). Such an extension portion (142) may come into contact with and be joined to the beading portion (123) of the case (120). For example, the extension portion (142) may be joined by welding while in contact with the inner surface of the beading portion (123) of the case (120). The second current collector plate (140) serves as a current flow path between the second electrode plate (112) of the electrode assembly (110) and the case (120). That is, the case (120) may be a negative terminal.

[0107] Additionally, the second current collector plate (140) may have a welded area in the region where the flat portion (141) is located on the upper surface (140a). Here, the welded area of ​​the second current collector plate (140) is surface-treated by laser etching, similar to the welded area of ​​the first current collector plate, so that the value of the Dyne Pen may be larger than that of other areas. That is, the welded area of ​​the second current collector plate (140) is surface-treated by laser etching so that oil remaining on the surface can be removed.

[0108] Additionally, the surface of the extension part (142) of the second current collector plate (140) can also be surface-treated by laser etching to improve contact and welding strength with the case (120).

[0109] In such a secondary battery (100), the welding area where the electrode assembly (110) is welded at the first current collector plate (130) and the second current collector plate (140) is surface-treated by laser etching to remove oil from the surface, thereby increasing the dyne pen value higher than in other areas and improving the welding strength with the electrode assembly (110). Additionally, the secondary battery (100) can also surface-treat the area where welding is required with the terminal (150) or case (120) at the first current collector plate (130) and the second current collector plate (140) by laser etching to remove oil from the surface, thereby increasing the dyne pen value higher than in other areas and improving the welding strength with the terminal (150) and case (120).

[0110] The secondary battery according to the above-described embodiment can be used to manufacture a battery pack.

[0111] FIGS. 6a and 6b are perspective views illustrating a battery pack including an exemplary secondary battery (100) according to the present invention. Referring to FIGS. 6a and 6b, the battery pack (300) may include a plurality of battery modules (200) and a housing (310) for accommodating the plurality of battery modules (200). For example, the housing (310) may include first and second housings (311, 312) that are coupled in a direction facing each other with the plurality of battery modules (200) interposed therebetween. The plurality of battery modules (200) may be electrically connected to each other using a bus bar (251), and the plurality of battery modules (200) may be electrically connected to each other in a series / parallel or mixed series / parallel manner to obtain the required electrical output. In the drawings, for convenience of illustration, components such as a bus bar for electrical connection of battery cells, a cooling unit, and external terminals are omitted. In some examples, the battery pack (300) may be mounted in a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may include a four-wheeled vehicle or a two-wheeled vehicle.

[0112] FIGS. 7a and 7b are a perspective view and a side view illustrating an automobile (400, 500) including an exemplary battery pack (300) according to the present invention. In FIG. 7a, the battery pack (300) may include a battery pack cover (311) (which may correspond to the first housing) which is part of the vehicle under body (410) and a pack frame (312) (which may correspond to the second housing) disposed at the bottom of the vehicle under body (410). The battery pack cover (311) and the pack frame (312) may be structures formed integrally with the vehicle floor portion (420). The vehicle under body (410) separates the interior and exterior of the vehicle, and the pack frame (312) may be disposed on the exterior of the vehicle.

[0113] As illustrated in FIG. 7b, the vehicle (500) may be formed by combining additional parts, such as a hood (510) at the front of the vehicle and fenders (520) located at the front and rear of the vehicle, respectively, with the vehicle body (400). The vehicle (500) includes a battery pack (300) comprising a battery pack cover (311) and a pack frame (312), and the battery pack (300) may be combined with the vehicle body part (400).

[0114] The above description is merely one embodiment for implementing a secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment. The technical spirit of the present invention extends to the scope in which various modifications can be made by anyone with ordinary knowledge in the field to which the invention belongs, without departing from the gist of the invention as claimed in the following patent claims.

[0115] The above description is merely one embodiment for implementing a secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment. The technical spirit of the present invention extends to the scope in which various modifications can be made by anyone with ordinary knowledge in the field to which the invention belongs, without departing from the gist of the invention as claimed in the following patent claims.

Claims

1. An electrode assembly having a first electrode plate, a separator, and a second electrode plate; A case in which the above electrode assembly is accommodated and the lower end is open; A terminal coupled by penetrating the upper surface of the above case; A first current collector plate interposed between the upper surface of the electrode assembly and the case, and electrically connecting the first electrode plate and the terminal; and It includes a cap plate that seals the lower part of the above case, and The above first current collector plate is a secondary battery in which the surface tension of the weld area welded to the electrode assembly is greater than that of other areas.

2. In Paragraph 1, The above-mentioned first collector plate is in the shape of a flat circular plate. A terminal connection part in contact with and electrically connected to the lower surface of the above terminal; and A secondary battery comprising a electrode plate connection portion that is welded to the first electrode tab of the first electrode plate exposed to the upper surface of the electrode assembly and is located on the outer side of the terminal connection portion.

3. In Paragraph 2, The above first collector plate is The welding area is provided on the lower surface of the above electrode plate connection part, The above welded area is surface-treated, resulting in a secondary battery with a larger Dynefen value compared to other areas.

4. In Paragraph 3, The above welding area is a secondary battery with a Dynefen value greater than 36 and less than 40.

5. In Paragraph 2, The upper surface of the terminal connection part is surface-treated by laser etching, and the dyne pen value is larger than that of the lower surface of the terminal connection part, in a secondary battery.

6. In Paragraph 3, The above welded area is a secondary battery surface-treated by laser etching.

7. In Paragraph 2, A secondary battery further comprising a fuse portion located between the terminal connection portion and the electrode plate connection portion.

8. In Paragraph 5, The above fuse part A fuse hole formed along a portion of the outer periphery of the terminal connection portion; and A secondary battery comprising a electrode connecting portion connecting the terminal connecting portion and the electrode connecting portion.

9. In Paragraph 1, A secondary battery further comprising a second current collector plate welded to a second electrode tab of the second electrode plate exposed to the lower surface of the electrode assembly, having a circular plate shape corresponding to the lower surface of the electrode assembly.

10. In Paragraph 9, The second current collector plate above has a circular flat portion in contact with the lower surface of the electrode assembly; and A secondary battery including an extension extending downward from the edge of the above-mentioned planar portion.

11. In Paragraph 10, The above second collector plate is The upper surface of the above-mentioned planar portion includes a welding area that is welded to the lower surface of the second electrode assembly, and The above welding area is surface-treated by laser etching, so that the value of the Dyne Pen is larger than that of the lower surface of the above flat part, in a secondary battery.

12. In Paragraph 10, The above case is A beading portion recessed into the interior of the case on the upper part of the cap plate; and A secondary battery comprising a crimping portion that fixes the cap plate by bending the lower part of the case inwardly at the lower part of the cap plate.

13. In Paragraph 12, It further includes a cap gasket interposed between the cap plate and the beading portion, and between the cap plate and the crimping portion, and The above cap plate is a nonpolar secondary battery.

14. In Paragraph 13, The extension of the second current collector plate is a secondary battery interposed between the cap gasket and the beading portion.

15. In Paragraph 13, The extension of the above-mentioned second current collector plate is a secondary battery surface-treated by laser etching 16. In Paragraph 1, The first electrode plate further includes a plurality of first electrode tabs that protrude upward from the upper surface of the electrode assembly and are bent and compacted in the winding axis direction of the electrode assembly. The second electrode plate protrudes downward and upward from the lower surface of the electrode assembly and further includes a plurality of second electrode tabs that are bent and compacted in the winding axis direction of the electrode assembly. The above electrode assembly is a secondary battery having a plurality of first electrode tabs exposed on the upper surface and a plurality of second electrode tabs exposed on the lower surface.

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