Secondary Battery and Method of Manufacturing the Same

Abstract

The present invention provides a secondary battery and a method for manufacturing a secondary battery, wherein the alignment of the electrode plate inside the separator can be maintained by fusion and folding the edge of the separator containing the electrode plate in alignment with the end line of the electrode plate, and the heat-fused portion of the separator itself performs the function of a retainer, thereby maintaining a stable position of the electrode assembly inside the battery can without using a separate retainer. The secondary battery comprises: a battery can having a bottom portion and a side wall portion and open to the outside through an opening; an electrode assembly mounted inside the battery can having a stacked structure of a positive plate, a separator, and a negative plate; and a cap assembly fixed to the opening of the battery can and connected to the electrode assembly, and includes a bottom fusion folding portion formed by folding the edge of the separator after heat-fusion, which contacts the bottom portion of the battery can and supports the electrode assembly.

Description

Technology Field

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

[0002] Batteries include non-rechargeable primary batteries and rechargeable secondary batteries. High-capacity secondary batteries are widely used as power sources for motor drives and energy storage in hybrid and electric vehicles.

[0003] Such secondary batteries include an electrode assembly, an outer casing such as a battery can housing the assembly, and electrode terminals connected to the electrode assembly. The electrode assembly has a structure in which a positive plate and a negative plate are stacked and separated from each other by a separator. However, since the positive plate and the negative plate are not completely fixed to the separator in the electrode assembly, they may move slightly during handling. If the positive plate and the negative plate move, the alignment is disrupted, which can cause a degradation in the performance of the battery cell.

[0004] Meanwhile, in the case of top-terminal type secondary batteries, if the weight of the electrode assembly increases, the electrode assembly may shift to one side or sag within the battery can, causing electrical contact with the bottom of the battery can and resulting in a short circuit. To solve this problem, a separate component called a bottom retainer is applied between the bottom of the battery can and the electrode assembly.

[0005] 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. The problem to be solved

[0006] The present invention aims to provide a secondary battery and a method for manufacturing a secondary battery that can maintain the alignment of electrode plates within a separator and allow the separator itself to perform the function of a retainer, thereby maintaining a stable posture of the electrode assembly without using a separate retainer. means of solving the problem

[0007] A secondary battery according to one feature of the present invention for solving the above problem comprises: a battery can having a bottom portion and a side wall portion and open to the outside through an opening; an electrode assembly mounted inside the battery can having a stacked structure of a positive plate, a separator, and a negative plate; and a cap assembly fixed to the opening of the battery can and connected to the electrode assembly, wherein a bottom fusion folding portion is provided on the lower part of the electrode assembly, formed by folding the edge of the separator after heat fusion, and which contacts the bottom portion of the battery can and supports the electrode assembly.

[0008] In addition, a method for manufacturing a secondary battery according to another feature of the present invention for solving the above problem comprises: a stacking step of repeatedly stacking a positive plate, a separator, and a negative plate to form an electrode assembly; a heat fusion and folding step of heat-fusion and folding a separator at the lower edge of the electrode assembly to form a bottom fusion folding part; a cap assembly welding step of connecting a cap assembly to the electrode assembly after the heat fusion and folding step; an insert step of inserting the electrode assembly with the welded cap assembly into a battery can; and a can welding step of fixing the cap assembly to the battery can after the insert step is completed.

[0009] However, the technical problems and means for solving problems that the present invention aims to solve are not limited to the above-mentioned contents, and other unmentioned problems and means for solving problems can be clearly understood by those skilled in the art from the description of the invention below. Effects of the invention

[0010] The secondary battery manufacturing method of the present invention, as described above, can maintain the alignment of the electrode plates inside the separator by fusing the edges of the separator containing the electrode plates to the end lines of the electrode plates and then folding them.

[0011] In addition, since the heat-fused portion of the separator itself performs the function of a retainer, the electrode assembly can be maintained in a stable position within the battery can without using a separate retainer.

[0012] 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. Brief explanation of the drawing

[0013] 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 the drawings. FIG. 1 is a perspective view illustrating the external appearance of a secondary battery according to one embodiment of the present invention. Figure 2 is a cross-sectional view of the secondary battery illustrated in Figure 1. FIG. 3 is a drawing separately illustrating an electrode assembly applied to a secondary battery according to one embodiment of the present invention. Figure 4 is an enlarged view of the fusion folding section of Figure 3. FIG. 5 is a flowchart for explaining a method for manufacturing a secondary battery according to one embodiment of the present invention. FIGS. 6 to 15 are drawings sequentially illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. FIG. 16 is a drawing illustrating a modified example of an electrode assembly applicable to a secondary battery according to one embodiment of the present invention. FIG. 17 is an enlarged view of the fusion folding section illustrated in FIG. 16. FIGS. 18 and FIGS. 19 are cross-sectional views illustrating other examples of the pressing plate shown in FIG. 17. FIG. 20 is a flowchart illustrating another example of a secondary battery manufacturing method according to one embodiment of the present invention. FIGS. 21 and 22 are drawings for explaining another embodiment of a method for manufacturing a secondary battery according to one embodiment of the present invention. FIG. 23 is a cross-sectional view illustrating another example of a secondary battery according to one embodiment of the present invention. FIG. 24 is a drawing for explaining the taping method for the bottom fusion folding section and the side fusion folding section illustrated in FIG. 23. FIG. 25 is a perspective view of a secondary battery pack having a secondary battery built in according to one embodiment of the present invention. FIG. 26 is a schematic diagram illustrating a vehicle equipped with the secondary battery pack of FIG. 25. Specific details for implementing the invention

[0014] 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, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, 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; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0015] 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 thereof.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0020] 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.

[0021] Furthermore, where one component is described as being "on," "connected to," or "coupled to" another component, it should be understood that while the components may be directly connected or coupled to each other, another component may be "interposed" between each component, or that each component may be "connected," "coupled," or "coupled" through another component.

[0022] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Additionally, the use of “may” when describing embodiments of the invention relates to “one or more embodiments of the invention.” Expressions such as “one or more” and “one or more” preceding a list of elements modify the entire list of elements and do not modify individual elements of the list.

[0023] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise, and "C to D" means C or more and D or less, unless specifically stated otherwise.

[0024] When syntax such as "at least one of A, B, and C", "at least one of A, B, or C", "at least one selected from the group of A, B, and C", or "at least one selected from A, B, and C" is used to specify a list of elements A, B, and C, the syntax can refer to any suitable combination.

[0025] The term "use" may be considered synonymous with the term "utilize." As used herein, terms such as "substantially," "about," and similar terms are used as terms of approximation rather than degree, and are intended to account for the inherent variation of a measured or calculated value that would be recognized by a person skilled in the art.

[0026] In this specification, terms such as first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or sections, but these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Accordingly, the first element, component, region, layer, or section discussed below may be named the second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0027] Spatial relative terms such as "beneath," "below," "lower," "above," and "upper" may be used in the specification for ease of description to explain the relationship between one element or feature and other element(s) or feature(s) as illustrated in the drawings. Spatially relative positions are to be understood as encompassing different orientations of the device in use or operation, in addition to the orientations depicted in the figures. For example, if the device in the drawing is inverted, the other element is understood as "below" or "below," and the described element is understood as "above" or "upper" of the other element. Thus, the term "below" may encompass both the up and down directions.

[0028] The terms used in this specification are for describing embodiments of the invention and are not intended to limit the invention.

[0029] FIG. 1 is a perspective view showing the external appearance of a secondary battery (10) according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view of the secondary battery shown in FIG. 1.

[0030] The battery can (11) forms the overall exterior of the secondary battery (10) and may be formed of a conductive metal such as aluminum, an aluminum alloy, or nickel-plated steel. Additionally, the battery can (11) may provide an internal space for accommodating an electrode assembly. The battery can (11) includes a bottom portion (11c) and a side wall portion (11a) and may be opened upward through an opening. The top opening of the battery can (11) may be welded to a cap assembly (13).

[0031] The cap assembly (13) may include a cap plate (13a) covering the opening of the battery can (11). In some embodiments, the battery can (11) and the cap plate (13a) may be made of a conductive material. Additionally, a first terminal (13e) and a second terminal (15f) are disposed on the cap plate (13a). The first terminal (13e) and the second terminal (13f) are electrically connected to the negative and positive tabs inside the battery can (11). The first and second terminals (13e, 13f) are exposed to the outside of the cap plate (13a). The cap assembly (13) is electrically connected to the electrode assembly (20) through a current collector plate (15) while welded to the opening of the battery can (11).

[0032] An electrolyte injection port (13h) and a gas vent (13k) may be formed in the cap plate (15c). The electrolyte injection port (13h) provides a passage for injecting the electrolyte. Additionally, the gas vent (13k) is opened by gas generated inside the battery can (11) to perform a degassing function.

[0033] An electrode assembly (20) is installed inside the secondary battery (10). The electrode assembly (20) is a laminate composed of a positive plate (23), a separator (21), and a negative plate (24). A positive active material is coated on the positive plate (23), and a negative active material is coated on the negative plate (24). The electrode assembly (20) may be a Z-stacking structure as shown in FIG. 6, or may have a structure in which a plurality of separators are stacked sequentially together with the positive and negative plates as shown in FIG. 21.

[0034] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0035] 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.

[0036] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mnb X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0037] 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; L 1 is Mn, Al, or a combination thereof.

[0038] A positive electrode for a secondary battery may include a current collector 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.

[0039] 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.

[0040] Al may be used for the above-mentioned current collector, but is not limited thereto.

[0041] 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.

[0042] 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.

[0043] 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 is silicon, a silicon-carbon composite, or SiO₂. x (0 <x≤2), Si계 합금, 또는 이들의 조합일 수 있다.

[0044] 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.

[0045] 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.

[0046] A negative electrode for a lithium secondary battery comprises a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer comprises a negative electrode active material and may further comprise a binder and / or a conductive material.

[0047] 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.

[0048] 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.

[0049] As the above-mentioned cathode current collector, 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.

[0050] The electrolyte for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0051] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0052] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof, and may be used alone or in a mixture of two or more types.

[0053] In addition, when using carbonate-based solvents, cyclic carbonates and chain carbonates can be mixed and used.

[0054] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used.

[0055] 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.

[0056] The above organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0057] 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.

[0058] 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.

[0059] As described above, the electrode assembly (20) includes a positive plate (23), a separator (21), and a negative plate (24), and in particular, has a bottom fusion folding portion (21a) in the lower part. The bottom fusion folding portion (21a) is a portion formed by folding the lower edge of the separator (21) after heat fusion. The bottom fusion folding portion (21a) can act as a bottom retainer, for example, by contacting the bottom part (11c) of the battery can (11) and supporting the electrode assembly.

[0060] The bottom fusion folding part (21a) is a part of the electrode assembly (20) and can provide support while in close contact with the bottom part (11c) of the battery can (11). That is, it supports the electrode assembly (20) to prevent the electrode assembly (20) from sagging downwards or tilting to one side due to its own weight, or coming into contact with the bottom part (11c). If the electrode assembly (20) comes into contact with the bottom part (11c), the positive plate or negative plate may cause an electrical short circuit with the bottom part (11c). In this way, the bottom fusion folding part (21a) stably supports the electrode assembly and also serves an electrical insulation function.

[0061] The bottom fusion folding section (21a) is a part formed by fusing the separator on the lower side of the electrode assembly (20) and folding it to one side. Since the separator (21) itself is fused and folded in this way, the positive plate or negative plate between the separators (21) cannot escape to the bottom of the separator. In other words, it has a 'closed structure' in which the positive plate or negative plate cannot escape to the outside of the separator.

[0062] Ultimately, the secondary battery according to the present embodiment has a structure in which the edge portion of the separator (21) is fused and then folded to stably fix the positions of the positive plate and the negative plate between the separators. The folded separator maintains a stable alignment state by physically restricting the movement of the electrode plates (positive plate, negative plate), thereby improving the stability and reliability of the secondary battery (10). In particular, even without applying a bottom retainer as a separate component, the electrode assembly (20) can be stably supported and electrical short circuits can be prevented.

[0063] As shown in FIG. 2, a plurality of folding retaining tapes (26) are attached to the lower part of the electrode assembly (20). The folding retaining tapes (26) can prevent the bottom fusion folding part (21a) from unfolding again. Additionally, adhesive tapes (25) can be attached to the upper part and both sides of the electrode assembly (20). The adhesive tapes (25) can maintain the adhesive state of the electrode assembly (20).

[0064] FIG. 3 is a drawing showing an electrode assembly (20) applied to a secondary battery (10) according to one embodiment of the present invention, and FIG. 4 is a drawing showing an enlarged view of the fusion folding part of FIG. 3.

[0065] As described above, a positive tab (23a) and a negative tab (24a) are arranged on both upper sides of the electrode assembly (20). The positive tab (23a) is a portion extending from the positive plate (23), and the negative tab (24a) is a portion extending from the negative plate (24). The positive tab (23a) and the negative tab (24a) can be electrically connected to the cap assembly (13) through the current collector plate (15).

[0066] Adhesive tapes (25) may be attached to both sides and the top of the electrode assembly (20). The adhesive tape (25) is attached to the electrode assembly (20) and is a stacking maintenance part that maintains the stacked state of the electrode assembly (20). The adhesive tape (25) as a stacking maintenance part can maintain the alignment state of the electrode assembly while attached to the electrode assembly. Through the adhesive tape (25) and the folding maintenance tape (26), the electrode assembly (20) can be stably maintained without coming loose.

[0067] In addition, the lower part of the separator (21) that accommodates the positive plate (23) and the negative plate (24) can be folded in a fused state and then maintained in a folded state through a plurality of folding retaining tapes (26). The reason the separator (21) can be fused and folded is that, as shown in FIG. 8, the area of ​​the separator (21) is relatively larger than that of the positive plate and the negative plate.

[0068] The bottom fusion folding section (21a) is the part that is folded after the fusion target section (21c) of FIG. 8 is compressed and heated. By fusing and folding the fusion target section (21c), there is no risk of the internal positive plate or negative plate escaping to the bottom of the separator. In other words, the vertical alignment state of the positive plate and the negative plate is maintained.

[0069] The fold line of the above-mentioned bottom fusion folding part (21a) may be parallel to the end line of the positive plate or negative plate. That is, it is parallel to the bottom edge line of the square-shaped positive plate or negative plate.

[0070] Furthermore, the above folding maintenance tape (26) can serve as a folding maintenance part that maintains the folded state of the bottom fusion folding part (21a). The folding maintenance tape (26) as a folding maintenance part can be adhesively fixed to the electrode assembly while covering the bottom fusion folding part (21a). The bottom fusion folding part (21a) can maintain the folded state by the folding maintenance tape (26). The folding maintenance tape (26) can also serve as a stacking maintenance part that maintains the stacked state of the electrode assembly (20).

[0071] The separator (21) may have a Z-folding structure that is repeatedly folded in a Z shape as shown in FIG. 6. Alternatively, as shown in FIG. 21, it may take the form of a single sheet in a rectangular state. The single sheets of separator (21) are stacked on top of each other.

[0072] FIG. 5 is a flowchart for explaining a method for manufacturing a secondary battery according to an embodiment of the present invention, and FIGS. 6 to 15 are drawings sequentially showing a method for manufacturing a secondary battery according to an embodiment of the present invention.

[0073] As described above, a secondary battery manufacturing method according to one embodiment of the present invention may include a stacking step (101), a heat fusion and folding step (103), a taping step (107), a current collector welding step (109), a cap assembly welding step (111), an insert step (113), and a can welding step (115).

[0074] The stacking step (101) is a process of forming an electrode assembly by repeatedly stacking a positive plate (23), a separator (21), and a negative plate (24). For example, as shown in FIG. 6, the positive plate (23) and the negative plate (24) are alternately stacked between the folds of the repeatedly folded separator (21). As mentioned, the separator (21) may be a separated square flat plate separator in addition to the Z-folding type separator of FIG. 6.

[0075] FIG. 7 is a plan view of a laminate after the stacking step (101) is completed, and FIG. 8 is a side view of the laminate. As shown, it can be seen that the area of ​​the separator (21) is larger than the area of ​​the cathode plate (24). Accordingly, a remaining area (hereinafter referred to as 'separator margin') may be created between the end line of the separator (21) and the end line of the cathode plate (24). In particular, the separator margin on the lower side of the laminate can be fused by a fusion head (80) as a fusion target part (21c) as shown in FIG. 9.

[0076] The heat fusion and folding step (103) is a process of forming a bottom fusion folding part (21a) by heating and fusing and folding the lower edge of the electrode assembly, i.e., the fusion target part (21c).

[0077] In order to perform the heat fusion and folding step (103), first, as shown in FIG. 9, the fusion target part (21c) is heat-compressed using a fusion head (80). A heating element (not shown) is built inside the fusion head (80). When the fusion target part (21c) is compressed using the fusion head (80), the fusion target part (21c) melts and fuses. FIG. 10 shows the fusion target part (21c) of the separator fused.

[0078] Once the above fusion process is completed, the fused portion is folded down in the direction of arrow a in Fig. 10 so that the fused portion covers the lower thickness surface of the laminate. By folding the fused portion in the direction of arrow a, a bottom fused folding portion (21a) can be formed. However, the bottom fused folding portion (21a) may not maintain the folded state but may have a springback tendency to unfold again.

[0079] The subsequent taping step (107) is a process of preventing the bottom fusion folding part (21a) from unfolding again. The taping step (107) is a process of maintaining the folded state of the bottom fusion folding part (21a) using a folding maintenance tape (26) after the completion of the heat fusion and folding step (103).

[0080] FIGS. 11 and 12 show the bottom fusion folding portion (21a) being wrapped and fixed using a folding retaining tape (26). The folding retaining tape (26) itself may be an adhesive tape, such as a sealing tape (25). The folding retaining tape (26) covers the bottom fusion folding portion (21a), and both ends are attached and fixed to both sides of the electrode assembly (20). FIG. 12 shows the bottom fusion folding portion (21a) supported by the folding retaining tape (26).

[0081] The current collector plate welding step (109) is a process of welding the current collector plate (15) after it is in close contact with the positive tab (23a) and the negative tab (24a), as shown in FIG. 13. The welding of the current collector plate may be laser welding.

[0082] The cap assembly welding step (111) is a process of welding a cap assembly (13) to an electrode assembly (20) on which a current collector plate (15) is welded. One side of the current collector plate (15) is welded to the first terminal (13e), and the other side of the current collector plate (15) is welded to the second terminal (13f).

[0083] After the above cap assembly welding step (111) is completed, an insert step (113) may be performed. The insert step (113) is a process of inserting the electrode assembly (20), in which the cap assembly (13) is welded, into the battery can (11) as shown in FIG. 14. When the insert step (113) is completed, the folding retaining tape (26) and the bottom fusion folding part (21a) come into contact with the bottom part (11c) of the battery can. In addition, the cap plate (13a) of the cap assembly comes into contact with the top opening of the battery can (11).

[0084] The can welding step (115) is a process of fixing the cap assembly to the battery can after the insert step (113) is completed. That is, the cap plate (13a) is welded to the upper part of the battery can (11).

[0085] FIG. 16 is a drawing illustrating a modified example of an electrode assembly (20) applicable to a secondary battery according to one embodiment of the present invention, and FIG. 17 is an enlarged drawing of the bottom fusion folding part (21a) shown in FIG. 16.

[0086] As described above, a pressing plate (28) may be further applied between the floor fusion folding section (21a) and the folding retaining tape (26). The pressing plate (28) may have the shape of a rectangular plate and may possess physical properties that prevent deformation by external force. Additionally, the pressing plate (28) may be made of synthetic resin. The pressing plate (28) is supported in the direction of arrow c by the folding retaining tape (26) and can press and support the floor fusion folding section (21a). By applying the pressing plate (28), the portion of the floor fusion folding section (21a) that is not supported by the folding retaining tape (26) can also be pressed and supported with uniform pressure.

[0087] FIGS. 18 and FIGS. 19 are cross-sectional views illustrating other examples of the pressing plate (28) shown in FIG. 17.

[0088] As illustrated in FIG. 18, a sealed space (28a) may be formed inside the pressing plate (28). By applying the sealed space (28a), the weight of the pressing plate (28) can be reduced, and the heat flow area transferred from the electrode assembly (20) to the bottom part (11c) of the battery can (11) can also be reduced.

[0089] Additionally, as shown in FIG. 19, an uneven portion (28c) may be formed on the pressing plate (28). The uneven portion (28c) can prevent the pressing plate (28) from sliding against the bottom fusion folding portion (21a). That is, it prevents the pressing plate (28) from moving slightly back and forth and side to side.

[0090] FIG. 20 is a flowchart illustrating another example of a method for manufacturing a secondary battery according to one embodiment of the present invention. Drawing symbols identical to those shown in FIG. 5 indicate the same manufacturing process, and a repeated description thereof is omitted.

[0091] As illustrated in FIG. 20, a pressing plate installation step (106) may be performed between the heat fusion and folding step (103) and the taping step (107). The pressing plate installation step (106) is a process of mounting a pressing plate (28) on the bottom fusion folding part (21a). When the folding retaining tape (26) is taped while the pressing plate (28) is positioned on the bottom fusion folding part (21a), the bottom fusion folding part (21a) can be pressed with an even pressure over the entire area by the pressing plate (28).

[0092] FIGS. 21 and 22 are drawings for explaining another embodiment of a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0093] As illustrated in FIG. 21, the separator (21) constituting the electrode assembly (20) can be applied as a single sheet. That is, an anode plate (23) and a cathode plate (24) are alternately inserted between the sheets of the separator (21). The width of the separator (21) is wider than that of the anode plate (23) and the cathode plate (24), similar to the Z-stack type electrode assembly. FIG. 22 is a plan view of an electrode assembly (20) composed of a plurality of separators (21), anode plates (23), and cathode plates (24) stacked together. As illustrated, a separator margin is provided on the outside of the cathode plate (24).

[0094] FIG. 23 is a cross-sectional view illustrating another example of a secondary battery (10) according to one embodiment of the present invention, and FIG. 24 is a drawing for explaining the taping method for the bottom fusion folding part (21a) and the side fusion folding part (21b) illustrated in FIG. 23.

[0095] As illustrated in FIG. 23, side fusion folding portions (21b) may be formed on both sides of the electrode assembly (20). The side fusion folding portions (21b) are formed by heating, fusing, and folding the separator margins located on both sides of the electrode assembly (20). The method of forming the side fusion folding portions (21b) is the same as the method of forming the bottom fusion folding portions (21a). By applying the side fusion folding portions (21b) in this way, the positive plate (23) and the negative plate (24) sandwiched between the separators (21) cannot move laterally.

[0096] The side fusion folding portion (21b) is formed by folding the two sides of the separator after heat fusion, and can come into contact with the side wall portion (11a) of the battery can (11). That is, it can be supported by the side wall portion (11a). In addition, the side fusion folding portion (21b) can maintain its folded state by a folding retaining tape (26), which is a folding retaining portion.

[0097] The folding maintenance portion may include a folding maintenance tape (26) to maintain the folded state of the bottom fusion folding portion (21a) and the side fusion folding portion (21b). The folding maintenance tape (26) is attached to the electrode assembly while covering the bottom fusion folding portion and the side fusion folding portion. Additionally, the folding maintenance tape (26) attached to the lower left and right corner portions of the electrode assembly (20) can simultaneously fix the bottom fusion folding portion (21a) and the side fusion folding portion (21b). Furthermore, a pressing plate (28) may also be applied to the side fusion folding portion (21b).

[0098] FIG. 25 is a perspective view of a secondary battery pack (40) having a secondary battery built in according to one embodiment of the present invention.

[0099] The secondary battery pack (40) can be manufactured by embedding a plurality of secondary battery modules in a pack housing designed to be mounted on an actual product. The pack housing may include a fastening part and an electrical outlet part necessary for mounting on the product. In FIG. 25, for convenience of illustration, the illustration of related elements such as a busbar for electrical connection of the secondary batteries, a cooling unit, and external terminals has been omitted. The secondary battery pack can be mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle includes a four-wheel drive or two-wheel drive vehicle.

[0100] FIG. 26 is a schematic diagram illustrating a vehicle equipped with the secondary battery pack of FIG. 25.

[0101] FIG. 26 illustrates a secondary battery pack (40) according to one embodiment of the present invention mounted on the lower body of a vehicle. The vehicle operates by receiving power from the secondary battery pack (40) according to one embodiment of the present invention.

[0102] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Explanation of the symbols

[0103] 10: Secondary battery 11: Battery can 11a: Side wall 11c: Bottom 13: Cap assembly 13a: Cap plate 13e: First terminal 13f: Second terminal 13h: Electrolyte inlet 13k: Gas vent 15: Current collector plate 20: Electrode assembly 21: Separator 21a: Bottom fusion folding part 21b: Side fusion folding part 21c: Fusion target part 23: Positive plate 23a: Positive tab 24: Negative plate 24a: Negative tab 25: Adhesive tape 26: Folding retention tape 28: Pressing plate 28a: Sealed space part 28c: Irregular / protruding part 40: Secondary battery pack 80: Fusion head

Claims

Claim 1 A secondary battery comprising: a battery can having a bottom portion and a side wall portion and open to the outside through an opening; an electrode assembly mounted inside the battery can having a laminated structure of a positive plate, a separator, and a negative plate; a cap assembly fixed to the opening of the battery can and connected to the electrode assembly, wherein a bottom fusion folding portion is provided on the lower side of the electrode assembly, formed by folding the edge of the separator after heat fusion, and which contacts the bottom portion of the battery can and supports the electrode assembly. Claim 2 In claim 1, the folding line of the bottom fusion folding part is parallel to the end line of the positive plate or negative plate, a secondary battery. Claim 3 A secondary battery according to claim 1, wherein the electrode assembly further comprises a fold-maintaining part that maintains the folded state of the bottom-fusion folding part. Claim 4 In paragraph 3, the folding retaining portion comprises a folding retaining tape that is adhered to an electrode assembly while covering a bottom fusion folding portion, in a secondary battery. Claim 5 In paragraph 3, the separator is a secondary battery having a Z-folding structure that is repeatedly folded into a Z shape. Claim 6 A secondary battery according to claim 5, wherein a stacking maintaining member for maintaining the alignment state of the electrode assembly is further provided on both sides of the electrode assembly. Claim 7 In claim 6, the above-mentioned stacking retainer is a secondary battery having an adhesive tape that is adhered to both sides of an electrode assembly. Claim 8 A secondary battery according to claim 4, wherein a pressing plate for pressing and supporting the bottom fusion folding part is further provided between the bottom fusion folding part and the folding maintenance tape. Claim 9 In paragraph 8, the above-mentioned pressing plate takes the form of a rectangular plate, a secondary battery. Claim 10 A secondary battery according to claim 9, wherein a sealed space is formed inside the above-mentioned pressing plate. Claim 11 In claim 9, the secondary battery, wherein the pressing plate has an uneven surface formed thereon to suppress slippage of the pressing plate relative to the bottom fusion folding part. Claim 12 A secondary battery according to claim 1, wherein on both sides of the electrode assembly, a side fusion folding portion is further formed to contact the side wall of a battery can, formed by folding the two sides of a separator after heat fusion. Claim 13 In claim 12, the electrode assembly further comprises a folding maintaining part that maintains the folded state of the bottom fusion folding part and the side fusion folding part, a secondary battery. Claim 14 In claim 13, the above-mentioned folding retaining portion comprises a folding retaining tape that is adhered to an electrode assembly while covering a bottom fusion folding portion and a side fusion folding portion, in a secondary battery. Claim 15 A method for manufacturing a secondary battery, comprising: a stacking step of repeatedly stacking a positive plate, a separator, and a negative plate to form an electrode assembly; a heat fusion and folding step of heat-fusion and folding a separator at the lower edge of the electrode assembly to form a bottom fusion folding portion; a cap assembly welding step of connecting a cap assembly to the electrode assembly after the heat fusion and folding step; an insert step of inserting the electrode assembly with the welded cap assembly into a battery can; and a can welding step of fixing the cap assembly to the battery can after the insert step is completed. Claim 16 A method for manufacturing a secondary battery according to claim 15, further comprising a taping step of maintaining the folded state of the bottom fusion folding part using tape after the completion of the heat fusion and folding step. Claim 17 A method for manufacturing a secondary battery according to claim 16, wherein, as a process performed between the heat fusion and folding step and the taping step, a pressing plate installation step is further included in which a pressing plate that presses the bottom fusion folding part is installed on the bottom fusion folding part. Claim 18 A method for manufacturing a secondary battery according to claim 17, wherein the above-mentioned pressing plate takes the form of a rectangular plate. Claim 19 A method for manufacturing a secondary battery according to claim 18, wherein a sealed space is formed inside the above-mentioned pressing plate. Claim 20 A method for manufacturing a secondary battery according to claim 18, wherein the pressing plate has an uneven surface formed thereon to suppress slippage of the pressing plate relative to the bottom fusion holding portion.

Images