Electrode assembly

Abstract

An electrode assembly is provided. An electrode assembly, according to one aspect of the present specification, comprises: an electrode-separator assembly including two layers of separators, each having a rectangular shape, and a first electrode disposed between the two layers of separators in a rectangular shape extending in a direction corresponding to the two layers of separators; and a second electrode separated from the first electrode by means of the separators, wherein at least a portion of the edge region of the two layers of separators is thermally fused in a state in which the first electrode is disposed between the two layers of separators, the electrode-separator assembly in the thermally fused state is folded in a zigzag pattern along the longitudinal direction, and the second electrode is disposed between layers of the folded and stacked electrode-separator assembly.

Description

electrode assembly

[0001] The present invention relates to an electrode assembly. More specifically, it relates to an electrode assembly that can be manufactured efficiently while preventing battery fire and battery runaway.

[0002] Secondary batteries, unlike primary batteries, are rechargeable and have the potential for miniaturization and large capacity, leading to extensive research and development in recent years. With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing.

[0003] Secondary batteries can be classified into coin-shaped batteries, cylindrical batteries, square batteries, or pouch-shaped batteries, depending on the shape of the battery case. In secondary batteries, the electrode assembly mounted inside the battery case is a rechargeable power generation device composed of a laminated structure of electrodes and a separator.

[0004] Secondary batteries can be classified based on the structure of the electrode assembly, which consists of a cathode / separator / cathode structure. Representative examples of electrode assembly structures include the jelly-roll type (winding type), which consists of long sheet-shaped cathodes and anodes wound together with a separator, and the stack type (laminated type), which consists of a number of cathodes and anodes cut into units of a predetermined size and sequentially stacked with a separator between them.

[0005] However, the jelly-roll type electrode assembly is prone to deformation of the electrode assembly, which causes the gap between the electrodes to become uneven, resulting in a rapid deterioration in battery performance and a decrease in battery safety due to the occurrence of short circuits between the electrodes. In addition, since the long sheet-shaped positive and negative electrodes must be rolled, there was a limit to quickly rolling them while maintaining a constant gap between the positive and negative electrodes. In addition, the stack-type electrode assembly required a large number of positive and negative electrode units to be sequentially stacked, which required a lot of time and effort for the sequential stacking process, resulting in a decrease in productivity.

[0006] To address these issues, a stack-and-fold electrode assembly, a hybrid of jelly-roll and stack types, has been introduced. The stack-and-fold electrode assembly comprises a structure in which continuous separators are folded in a zigzag pattern, with a predetermined number of positive and negative electrodes interposed between the folded separators.

[0007] However, in the process of manufacturing a conventional stack-and-fold type electrode assembly, there was a problem in that the manufacturing process of the electrode assembly required a relatively large amount of time and effort, since the cathode and anode had to be individually inserted between zigzag folded separators.

[0008] In addition, in conventional stack-and-fold type electrode assemblies, the separator separating the negative and positive electrodes contracts when the temperature exceeds a certain level, causing the negative and positive electrodes to come into contact with each other, resulting in a short circuit. This short circuit can cause battery fire or battery overheating.

[0009] In addition, in the conventional stack-and-fold type electrode assembly, there was a problem that battery fire was promoted due to the inflow of air when the venting phenomenon of the battery cell occurred.

[0010] The problem to be solved by this specification is to provide an electrode assembly that can be manufactured simply and efficiently, and is intended to solve at least some of the problems of the prior art.

[0011] In addition, it provides an electrode assembly with improved stability by preventing short circuit between the cathode and anode due to shrinkage of the separator, thereby preventing battery fire or battery runaway.

[0012] In addition, when a venting phenomenon occurs in a battery cell, an electrode assembly is provided that can further suppress battery ignition by sealing the separator and blocking contact with external air.

[0013] According to one aspect of the present invention for achieving the above object, the electrode assembly comprises an electrode-separator assembly including two layers of separators, each layer being rectangular, and a first electrode disposed between the two layers of separators in a rectangular shape extending in a direction corresponding to the two layers of separators, and a second electrode separated from the first electrode by the separator, wherein at least a portion of an edge region of the two layers of separators is thermally fused while the first electrode is disposed between the two layers of separators, and the electrode-separator assembly in a thermally fused state is folded in a zigzag shape along the length direction, and the second electrode can be disposed between each layer of the folded and laminated electrode-separator assembly.

[0014] Through this, electrode assemblies can be manufactured simply and efficiently.

[0015] In addition, it is possible to prevent battery fire or battery runaway by preventing short circuit between the negative and positive electrodes due to shrinkage of the separator, thereby improving the stability of the electrode assembly.

[0016] In addition, when venting of the battery cell occurs, the battery fire can be further suppressed by sealing the separator to block contact with the outside air.

[0017] Additionally, it may include a tab protruding from the first electrode and partially exposed to the outside from the two-layer separator, and a sealing member provided between the two layers of separators at least at a position where the tab is positioned among the edge regions of the two layers of separators and a peripheral region of the position where the tab is positioned.

[0018] Additionally, the first electrode may include a plurality of first electrode plates that are folded together and separated as the electrode-separator assembly is folded in a zigzag manner, and a tab may be provided on each of the plurality of first electrode plates, and may be disposed adjacent to each of any two adjacent first electrode plates among the plurality of first electrode plates, and the sealing member may be provided to cover at least both of the adjacent tabs.

[0019] Additionally, the sealing member may be provided on one side and the other side of the tab.

[0020] Additionally, some areas of the sealing member may overlap the first electrode.

[0021] Additionally, the sealing member may be made of polyimide material.

[0022] Additionally, the two-layer separator may be formed by folding a single sheet of separator in half, and the electrode-separator assembly may be formed by heat-welding the remaining edges of the two-layer separator other than the folded edges.

[0023] Additionally, the fold line formed by folding the membrane can be formed parallel to the length direction of the two layers of membrane.

[0024] Additionally, thermal bonding can be achieved in an area of ​​the two-layer separator that does not overlap with the first electrode.

[0025] Additionally, the second electrode may be a cathode composed of lithium metal, and the first electrode may be a cathode.

[0026] According to one aspect of the present invention for achieving the above object, a method for manufacturing an electrode assembly may include a step of supplying two layers of separators, each layer being rectangular, a step of arranging a first electrode having a rectangular shape extending in a direction corresponding to the two layers of separators between the two layers of separators, a step of thermally fusing at least a portion of an edge region of the two layers of separators to form an electrode-separator assembly composed of the two layers of separators and the first electrode, and a step of arranging a second electrode between each layer of the folded and laminated electrode-separator assembly while folding the electrode-separator assembly in a zigzag shape.

[0027] In addition, the step of supplying two layers of separators includes a step of folding one sheet of separator, and a fold line formed by folding one sheet of separator may be formed parallel to the length direction of the two layers of separators.

[0028] In addition, the electrode assembly includes a tab protruding from the first electrode and partially exposed to the outside from the two layers of separators, and a sealing member provided between the two layers of separators at least at a position where the tab is positioned and a peripheral area of ​​the position where the tab is positioned, and the method for manufacturing the electrode assembly may include a step of attaching the sealing member to at least one surface of the tab after the first electrode is positioned between the two layers of separators.

[0029] Additionally, the first electrode may include a plurality of first electrode plates that are folded together and separated as the electrode-separator assembly is folded in a zigzag manner, and the method for manufacturing the electrode assembly may include a step of forming tabs for each of the plurality of first electrode plates by notching one edge of the first electrode, which is provided in a rectangular shape, before placing the first electrode between the two layers of separators.

[0030] In addition, when supplying two layers of separators by folding one sheet of separator, the thermal bonding is performed by covering one outer surface of the two layers of separators with a release film and then pressing the top of the release film with a hot press, and at least a part of the edge area of ​​the two layers of separators may be the edges of the three sides other than the folded edge of the one sheet of separator.

[0031] By using the electrode assembly according to the present specification, the electrode assembly can be manufactured simply and efficiently.

[0032] In addition, it is possible to prevent battery fire or battery runaway by preventing short circuit between the negative and positive electrodes due to shrinkage of the separator, thereby improving the stability of the electrode assembly.

[0033] In addition, when venting of the battery cell occurs, the battery fire can be further suppressed by sealing the separator to block contact with the outside air.

[0034] Figures 1 to 4 illustrate a manufacturing process of an electrode assembly according to one embodiment of the present specification.

[0035] FIG. 5 is a cross-sectional view of an electrode assembly according to one embodiment of the present specification.

[0036] FIG. 6 is a graph comparing the short-circuit time and ignition time of a battery cell including an electrode assembly according to one embodiment of the present specification with the short-circuit time and ignition time of a battery cell including an electrode assembly according to a comparative example.

[0037] Before going into the detailed description of the present invention, it should be noted that the terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted with meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term in order to explain his own invention in the best way. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical idea of ​​the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of this application.

[0038] The same reference numbers or symbols used in each drawing attached to this specification represent parts or components that perform substantially the same functions. For convenience of explanation and understanding, the same reference numbers or symbols may be used in different embodiments. In other words, even if components with the same reference numbers are depicted in multiple drawings, they do not necessarily represent a single embodiment.

[0039] In the following description, singular expressions include plural expressions unless the context clearly indicates otherwise. Terms such as "comprises" or "comprises" should be understood to indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0040] In addition, in the description below, expressions such as top, upper, lower, lower, side, front, and rear are expressed based on the direction shown in the drawing, and it is noted in advance that they may be expressed differently if the direction of the object in question changes.

[0041] Additionally, terms including ordinal numbers, such as "first," "second," etc., may be used in this specification and claims to distinguish between components. These ordinal numbers are used to distinguish identical or similar components from each other, and the use of these ordinal numbers should not be interpreted in a limited manner. For example, components associated with these ordinals should not be interpreted in a restricted manner, such as in the order of use or arrangement, based on their numbers. If necessary, each ordinal number may be used interchangeably.

[0042] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. However, the spirit of the present invention is not limited to the presented embodiments. For example, those skilled in the art who understand the spirit of the present invention may propose other embodiments within the spirit of the present invention by adding, modifying, or deleting components, etc., but such embodiments will also be considered within the spirit of the present invention. The shapes and sizes of elements in the drawings may be exaggerated for clarity.

[0043] Figures 1 to 4 illustrate a manufacturing process of an electrode assembly according to one embodiment of the present specification. Figure 5 is a cross-sectional view of an electrode assembly according to one embodiment of the present specification.

[0044] An electrode assembly (100) according to one embodiment of the present specification may include a separator (111), a first electrode (112), and a second electrode (120), but some of these may be omitted and implemented, and additional configurations are not excluded.

[0045] Hereinafter, the present specification will be described on the assumption that the electrode assembly (100) is used in a lithium metal battery. However, the present specification is not limited thereto, and the electrode assembly (100) according to one embodiment of the present specification may be used in a lithium ion battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0046] Referring to FIGS. 1 to 5, the electrode assembly (100) may include an electrode-separator assembly (110). The electrode-separator assembly (110) may be understood to have a structure in which a first electrode (112) is surrounded by a separator (111), and the first electrode (112) is blocked from external air by the separator (111).

[0047] The electrode-separator assembly (110) may include a separator (111). The separator (111) may be provided in two layers. Each layer of the two layers of separators (111) may be provided in a longitudinal direction. For example, referring to FIGS. 1 to 4, each layer of the two layers of separators (111) may have a horizontally long rectangular shape.

[0048] Referring to Fig. 1, the two-layer separator (111) can be formed by folding a single sheet of separator (111) in half. For example, a fold line (F) formed by folding a single sheet of separator (111) can be parallel to the longitudinal direction of the two-layer separator (111). That is, the fold line (F) can form one of the long sides of the four edges of the rectangular two-layer separator (111). Through this, since the part that is completely sealed by folding among the four edges of the two-layer separator (111) can become the long side, the first electrode (112) can be more effectively isolated from the outside. However, it is not limited thereto, and depending on the shape of the provided sheet of separator (111), the fold line (F) formed by folding the sheet of separator (111) may constitute one of the short sides of the four edges of the rectangular two-layer separator (111).

[0049] The separator (111) is a physical separator that has the function of physically separating the first electrode (112) and the second electrode (120). If it is used as a normal separator, it can be used without any special restrictions, and in particular, it is preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity.

[0050] The separator (111) separates or insulates the first electrode (112) and the second electrode (120) from each other and enables lithium ion transport between the positive and negative electrodes, and may be made of a porous non-conductive or insulating material.

[0051] Any porous substrate that forms the separator (111) can be used as long as it is a porous substrate typically used in a lithium metal battery, and a porous polymer film can be used alone or by laminating these. For example, the porous substrate may be a polyolefin such as polyethylene, polypropylene, etc., a polyester such as polyethyleneterephthalate, polybutyleneterephthalate, polyamide, polyacetal, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylchloride, polyacrylonitrile, cellulose, nylon, It may include at least one material selected from the group consisting of poly(p-phenylenebenzobisoxazole) and polyarylate.

[0052] The thickness of the porous substrate is not particularly limited, but may be 1 to 100 μm, preferably 5 to 50 μm. The thickness range of the porous substrate is not limited to the aforementioned range, but if the thickness is excessively thinner than the aforementioned lower limit, the mechanical properties may deteriorate, and the separator may be easily damaged during battery use. In addition, the average diameter and porosity of the pores present in the porous substrate are also not particularly limited, but may be 0.1 to 50 μm and 10 to 95%, respectively.

[0053] Referring to FIGS. 1 and 2, the electrode-separator assembly (110) may include a first electrode (112). The first electrode (112) may be provided in a rectangular shape extending in a direction corresponding to the two layers of separators (111). That is, with reference to FIG. 1, the first electrode (112) may have a rectangular shape extending horizontally. The first electrode (112) may be placed between the two layers of separators (111).

[0054] Referring to FIGS. 1 to 3, the first electrode (112) may be provided with a smaller size than the two-layer separator (111). Accordingly, when the first electrode (112) is placed between the two-layer separator (111), a margin area (M) that does not overlap with the first electrode (112) may be formed in the two-layer separator (111). The margin area (M) may be a portion where heat fusion occurs. The presence of the margin area (M) can prevent heat from being directly applied to the first electrode (112), and minimize the phenomenon of the first electrode (112) being deformed or damaged by heat.

[0055] Referring to FIG. 1, the first electrode (112) may include a plurality of first electrode plates (112a). The plurality of first electrode plates (112a) may be formed by folding the first electrodes (112) together and separating them as the electrode-separator assembly (110) is folded in a zigzag pattern. Referring to FIG. 1, each first electrode plate (112a) may be understood as a portion separated by a dotted line in the first electrode (112) extending horizontally. Each first electrode plate (112a) may correspond to a second electrode (120) of each side that is arranged with a separator (111) therebetween after the electrode-separator assembly (110) is folded in a zigzag pattern.

[0056] The first electrode (112) may preferably be an anode. Specifically, in the case of a lithium metal battery, the anode may be composed of lithium metal, but lithium metal is vulnerable to heat and can easily be deformed or damaged. Therefore, if a lithium metal anode, which is vulnerable to heat, is placed between two layers of separators (111) and then heat is applied to the separator (111), the lithium metal anode may be deformed or damaged. On the other hand, if the first electrode (112) placed between two layers of separators (111) is an anode, the above-mentioned problem can be minimized.

[0057] In contrast, in the case of a lithium metal battery, if the heat resistance of the lithium metal constituting the negative electrode is sufficient, or in the case of a lithium ion battery that does not use metal, the first electrode (112) placed between two layers of separators (111) may be the negative electrode.

[0058] The first electrode (112) may include a current collector and a positive electrode active material layer applied to at least one surface of the current collector.

[0059] The cathode current collector supports the cathode active material and is not particularly limited as long as it has high conductivity and does not induce chemical changes in the battery. Examples of materials that can be used include copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., and aluminum-cadmium alloys.

[0060] The positive electrode current collector can form fine irregularities on its surface to strengthen the bonding strength with the positive electrode active material, and can be used in various forms such as a film, sheet, foil, mesh, net, porous body, foam, and non-woven fabric.

[0061] The positive electrode active material layer includes a positive electrode active material and may further include a conductive material, a binder, and additives.

[0062] The cathode active material can be a lithium-containing transition metal oxide, for example, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(Ni a Co b Mn c )O2(0 <a<1,0<b<1,0<c<1,a+b+c=1),LiNi1- y Co y O2,LiCo1- y Mn y O2,LiNi1- y Mn y O2(O<1),Li(Ni a Co b Mn c )O4(0 <a<2,0<b<2,0<c<2,a+b+c=2),LiMn2- z Ni z O4,LiMn2- z Co zO4(0 <z<2),LiCoPO4및 LiFePO4로 이루어진 군에서 선택되는 어느 하나 또는 이들 중 2종 이상의 혼합물을 사용할 수 있다. 또한, 이러한 산화물(oxide) 외에 황화물(sulfide), 셀렌화물(selenide) 및 할로겐화물(halide) 등도 사용될 수 있다.

[0063] The cathode active material contains a sulfur compound, and the sulfur compound is elemental sulfur (S8), an organic sulfur compound Li2S. n (n≥1) and carbon-sulfur polymer (C2S x ) n :x=2.5~50,n≥1) may be at least one selected from the group consisting of. Preferably, inorganic sulfur (S8) can be used.

[0064] Since the positive electrode active material includes a sulfur compound, an electrochemical device including an electrode assembly (100) according to one embodiment of the present specification may be a lithium-sulfur battery.

[0065] Since sulfur contained in the positive electrode active material does not exhibit electrical conductivity on its own, it can be used in combination with a conductive material, such as carbon. Accordingly, sulfur is included in the form of a sulfur-carbon complex, and preferably, the positive electrode active material may be a sulfur-carbon complex.

[0066] A conductive material is a material that electrically connects the electrolyte and the positive electrode active material and acts as a path for electrons to move from the current collector to the positive electrode active material. Any conductive material can be used without restriction.

[0067] For example, conductive materials may be used alone or in combination with graphite such as natural graphite or artificial graphite; carbon black such as Super-P, Denka Black, acetylene black, Ketjen Black, channel black, furnace black, lamp black, or summer black; carbon derivatives such as carbon nanotubes or fullerene; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; or conductive polymers such as polyaniline, polythiophene, polyacetylene, or polypyrrole.

[0068] The binder maintains the positive electrode active material on the positive electrode current collector and organically connects the positive electrode active materials to increase the bonding strength between them. Any binder known in the industry can be used.

[0069] For example, the binder may be a fluororesin binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); a rubber binder including styrenebutadiene rubber (SBR), acrylonitrile-butidiene rubber, and styrene-isoprene rubber; a cellulose binder including carboxyl methyl cellulose (CMC), starch, hydroxy propyl cellulose, and regenerated cellulose; a polyalcohol binder; a polyolefin binder including polyethylene and polypropylene; a polyimide binder; a polyester binder; and a silane binder. One, two or more mixtures or copolymers selected from the group consisting of may be used.

[0070] Referring to FIG. 3, at least a portion of the edge region of the two-layer separator (111) can be thermally bonded while the first electrode (112) is positioned between the two-layer separator (111). The thermal bonding can be performed in the region of the two-layer separator (111) that does not overlap with the first electrode (112), i.e., the margin region (M).

[0071] The electrode-separator assembly (110) can be formed by thermally fusing the remaining edges of the two-layer separator (111) other than the folded edges. For example, referring to FIG. 4, a fold line (F) formed by folding a single sheet of separator (111) constitutes one long side of the two-layer separator (111), and thermal fusing can be performed on the remaining three edges of the two-layer separator (111).

[0072] In contrast, if the fold line (F) is formed on one short side of the two-layer separator (111), thermal bonding can be performed on the remaining short sides and two long sides of the two-layer separator (111). For example, referring to FIG. 3, if the fold line (F) formed by folding one sheet of separator (111) constitutes the left edge of the two-layer separator (111), thermal bonding can be performed on the remaining three edges.

[0073] In addition, unlike the above, when the two-layer separator (111) is formed by overlapping two separate separators (111) rather than by folding one sheet of separator (111), heat bonding can be performed on all four edge areas of the two-layer separator (111).

[0074] In this way, since the edges of the two layers of separators (111) can be sealed by the folding line (F) and / or thermal fusion, battery ignition or battery runaway can be suppressed, thereby improving battery stability. Specifically, even if the temperature of the electrode assembly (100) rises and shrinkage of the separator (111) occurs, the first electrode (112) may not be exposed to the outside due to the sealing of the two layers of separators (111), and thus, short circuiting between the first electrode (112) and the second electrode (120) is prevented, thereby suppressing battery ignition or battery runaway. In addition, since the sealing of the two layers of separators (111) can minimize the contact of the first electrode (112) with the outside air, it is possible to prevent battery ignition from being promoted due to contact with air.

[0075] Referring to FIGS. 1 to 3, the electrode assembly (100) may include a tab (113). The tab (113) may protrude from the first electrode (112). The tab (113) may be exposed to the outside from the two-layer separator (111).

[0076] The tabs (113) may be provided on each of the plurality of first electrode plates (112a). The tabs (113) connected to each of the plurality of first electrode plates (112a) may be positioned so as to overlap each other in the vertical direction when the electrode-separator assembly (110) is folded in a zigzag shape, as illustrated in FIG. 5. For example, referring to FIG. 1, it may be understood that the tabs (113) provided on one first electrode plate (112a) and the tabs (113) provided on a first electrode plate (112a) adjacent to one of the first electrode plates (112a) are positioned at positions that are symmetrical with respect to a line (dotted line) along which the two first electrode plates (112a) are folded. Through this, the tab (113) can be aligned in the vertical direction while the electrode-separator assembly (110) is folded in a zigzag pattern, so that the structure for connecting the lead to the tab (113) can be simplified.

[0077] The tab (113) can be formed by notching the first battery (112). For example, in a rectangular first electrode (112) having a size of about 6 cm * 24.5 cm, a tab (113) can be formed on each of a plurality of first electrode plates (112a) separated by a size of about 3.5 cm, by notching and removing a portion of one edge of the first battery (112) except for the portion where the tab (113) is to be formed, a tab (113) protruding from the first battery (112) can be formed.

[0078] Referring to FIG. 1, a structure can be created in which tabs (113) are arranged adjacent to each other on each of two adjacent first electrode plates among a plurality of first electrode plates (112a).

[0079] Referring to FIGS. 1 and 2, the electrode assembly (100) may include a sealing member (130). The sealing member (130) may be placed in a portion of the edge area of ​​the two-layer separator (111) where heat sealing is not properly performed due to the tab (113), thereby serving to reinforce the sealing of the two-layer separator (111).

[0080] Specifically, the sealing member (130) may be provided between the two layers of separators (111) at least at a position where the tabs (113) are arranged among the edge regions of the two layers of separators (111) and a peripheral region of the position where the tabs (113) are arranged. Specifically, the sealing member (130) may be provided so as to cover at least two tabs (113) arranged adjacent to each other on each of any two adjacent first electrode plates (112a) among the plurality of first electrode plates (112a). In a portion where the two tabs (113) are arranged adjacent to each other, there is a high possibility that the two layers of separators (111) do not properly contact each other and thus the sealing of the separators (111) by thermal fusion may not be properly performed. Therefore, it may be preferable that the sealing member (130) be provided so as to cover at least both adjacent tabs (113).

[0081] In FIGS. 1 and 2, a sealing member (130) is shown as being provided for each of two adjacent tabs (113), but this is not limited thereto, and the sealing member (130) may be provided along the entire length of the electrode-separator assembly (110) along the edge of the two-layer separator (111) where the tab (113) is located (the upper edge based on FIGS. 1 to 3).

[0082] The sealing member (130) may be provided on one side and the other side of the tab (113). The sealing member (130) may be attached to one side and the other side of the tab (113) before the thermal fusion step of the two layers of separators (111), or may be attached to opposite sides of the two layers of separators (111). In addition, a part of the sealing member (130) may overlap the first electrode (112). That is, with reference to FIG. 3, the sealing member (130) may be provided so that the lower part partially overlaps the first electrode (112). Through this structure, the sealing of the separator (111) in the area around the tab (113) can be more reliably reinforced.

[0083] The sealing member (130) may be a material having mechanical strength, chemical resistance, heat resistance, excellent insulating properties, and electrical properties with low dielectric constant. For example, the sealing member (130) may be a polyimide material. When the sealing member (130) is arranged in the peripheral area of ​​the tab (113) and heat fusion is performed on the edge of the two-layer separator (111), the sealing member (130) fills the portion where the two-layer separator (111) is not in complete contact with each other due to the tab (113), thereby reinforcing the sealing of the separator (111) in the peripheral area of ​​the tab (113).

[0084] Referring to Fig. 5, the electrode-separator assembly (110) in a thermally fused state can be folded in a zigzag shape along the longitudinal direction. In this process, it can be understood that the separator (111) and the first electrode (112) constituting the electrode-separator assembly (110) are folded together in a zigzag shape. When the electrode-separator assembly (110) is folded in a zigzag shape, the sealing state of the separator (111) by thermal fusion can be maintained.

[0085] As described above, by wrapping the first electrode (112) with two layers of separators (111) and then sealing the edges of the separators (111) to form an electrode-separator assembly (110), the position of the first electrode (112) with respect to the separator (111) can be relatively fixed, and accordingly, zigzag folding of the electrode-separator assembly (110) can be easily performed, and further, the electrode assembly (100) can be manufactured simply and efficiently.

[0086] The electrode assembly (100) may include a second electrode (120). Unlike the first electrode (112), the second electrode (120) may be provided in a plurality of pieces. The second electrode (120) may be provided corresponding to a plurality of first electrode plates (112a). The second electrode (120) may be arranged between each layer of the folded and laminated electrode-separator assembly (110). At this time, the second electrode (120) may be separated from the first electrode (112) by a separator (111).

[0087] The second electrode (120) may be a cathode. When the electrode assembly (100) according to one embodiment of the present specification is used in a lithium metal battery, the second electrode (120) may be composed of lithium metal.

[0088] When the second electrode (120) is an anode for a lithium metal battery, the second electrode (120) may include a porous substrate. The porous substrate may be a porous polymer substrate that does not undergo lithiation. Since the tensile strength and elongation of the anode are significantly reduced when the porous substrate, which acts as a support for lithium, undergoes lithiation, it may be preferable to use a substrate that does not undergo lithiation as the porous substrate.

[0089] For example, the porous substrate may be a polyolefin such as polyethylene, polypropylene, etc., a polyester such as polyethyleneterephthalate, polybutyleneterephthalate, polyamide, polyacetal, polycarbonate, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalate, polytetrafluoroethylene, polyvinylidenefluoride, polyvinylchloride, polyacrylonitrile, cellulose, nylon, It may include a polymer selected from the group consisting of poly(pphenylenebenzobisoxazole), polyarylate, and combinations thereof, preferably polyethylene terephthalate, but is not particularly limited thereto. However, polyimide, which is a polymer capable of causing lithiation, may not be preferable for use as the porous substrate.

[0090] The second electrode (120), which is a negative electrode for a lithium metal battery, includes a carbon coating layer formed on the surface of a porous substrate, and the carbon coating layer may include carbon particles having a plate-like structure.

[0091] The carbon coating layer formed on the surface of the porous substrate may include conductive carbon particles. Due to the conductive carbon particles included in the carbon coating layer, the affinity between the porous substrate, which serves as a support for the negative electrode, and lithium metal is enhanced, thereby enabling the formation of a stable structure during lithium plating, thereby improving lithium efficiency and enhancing the manufacturing processability of the lithium negative electrode.

[0092] The carbon coating layer may include carbon particles having a plate-like structure, and for example, the carbon coating layer may include graphene or a graphene derivative having a plate-like structure. The carbon coating layer may preferably include a material selected from the group consisting of graphene, reduced graphene oxide (RGO), graphene oxide (GO), and combinations thereof, and more preferably may be graphene. When the carbon particles having a plate-like structure are included in the carbon coating layer, the pores on the surface of the porous substrate may be reduced, and the effect of controlling the plating of lithium without being affected by the relative distance from the positive electrode may be achieved.

[0093] The second electrode (120), which is a negative electrode for a lithium metal battery, includes a lithium metal layer. The lithium metal layer refers to a metal layer containing a lithium metal element. The material of the lithium metal layer may be a lithium alloy, lithium metal, an oxide of a lithium alloy, or lithium oxide. As a non-limiting example, the negative electrode may be a thin film of lithium metal, or an alloy of lithium and one or more metals selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, and Sn. At this time, the lithium metal layer may have a surface oxide film or a portion thereof that is altered by oxygen or moisture or may contain impurities.

[0094] A lithium metal layer can be laminated on a carbon coating layer formed on a porous substrate and then subjected to a rolling process to become in close contact with the porous substrate and the carbon coating layer structure. Due to the rolling, some or all of the lithium can penetrate into the porous substrate and be located within the pores of the porous substrate. In addition, a release film that does not have adhesion properties with lithium can be used on the surface where the lithium directly touches the roll during the rolling process. Additionally, in order to stabilize the interface between the porous substrate, which is a support, and the lithium metal layer, an aging process can be performed in which oxygen and moisture are blocked and the lithium metal layer is sealed in a pouch and stored for several hours to several days.

[0095] The second electrode (120), which is a negative electrode for a lithium metal battery, can be manufactured by preparing the porous substrate, coating a dispersion containing plate-shaped carbon particles on the surface of the porous substrate, vacuum drying to form a carbon coating layer, and then laminating a lithium metal foil thereon and then rolling. The coating method may preferably be a dip coating method, but is not particularly limited thereto. In addition, the rolling method is not particularly limited, and a method commonly used in the art may be used.

[0096] The second electrode (120), which is a negative electrode for a lithium metal battery, may have a structure in which a carbon coating layer is formed on one side of a porous substrate and a lithium metal layer is laminated on one side of the carbon coating layer facing in the opposite direction from the porous substrate. In the case of a negative electrode having a structure in which a lithium metal layer is laminated on one side of the carbon coating layer, it can preferably be utilized in a monocell or coin cell.

[0097] The second electrode (120), which is an anode for a lithium metal battery, may have a multilayer structure in which a porous substrate is positioned in the center, carbon coating layers are formed on both sides of the porous substrate, and lithium metal layers are laminated on each side of the carbon coating layers facing in the opposite direction to the porous substrate. In the case of a multilayer structured anode, it can be utilized in various types of cells that form a stacking structure.

[0098] Hereinafter, a method for manufacturing an electrode assembly according to one embodiment of the present specification will be described.

[0099] Referring to FIG. 1, a method for manufacturing an electrode assembly may include a step of supplying two layers of separators (111), each layer having a rectangular shape.

[0100] The step of supplying two layers of separators (111) may include a step of folding a single layer of separators (111). At this time, the folding line (F) formed by folding the single layer of separators (111) may be parallel to the longitudinal direction of the two layers of separators (111). That is, referring to FIG. 1, the folding line (F) of the separator (111) may constitute one of the long sides of the rectangular two layers of separators (111).

[0101] However, the present invention is not limited thereto, and a fold line (F) formed by folding a single sheet of separator (111) may constitute one of the short sides of a rectangular double-layer separator (111). In this case, the single sheet of separator (111) may be provided with a length corresponding to approximately twice the length of the electrode-separator assembly (110).

[0102] Referring to FIG. 2, a method for manufacturing an electrode assembly may include a step of placing a first rectangular electrode (112) extending in a direction corresponding to the two layers of separators (111) between two layers of separators (111). At this time, the first electrode (112) may be inserted between the two layers of separators (111) after folding a single sheet of separator (111) in advance, or the first electrode (112) may be placed on a single sheet of separator (111) before folding the single sheet of separator (111), and then the single sheet of separator (111) may be folded so that the first electrode (112) is placed between the two layers of separators (111).

[0103] Referring to FIGS. 1 and 2, the method for manufacturing an electrode assembly may include a step of attaching a sealing member (130) to at least one surface of a tab (113) before or after placing a first electrode (112) between two layers of separators (111). Preferably, the step of placing the first electrode (112) may include a step of attaching the sealing member (130) to one surface and the other surface of the tab (113).

[0104] The step of attaching the sealing member (130) to at least one surface of the tab (113) may be performed before arranging the first electrode (112) between the two layers of separators (111), as illustrated in FIGS. 1 and 3. However, alternatively, the step of attaching the sealing member (130) to at least one surface of the tab (113) may be performed after arranging the first electrode (112) between the two layers of separators (111).

[0105] Meanwhile, unlike as illustrated in FIGS. 1 and 2, the sealing member (130) may be disposed on at least one of the facing inner surfaces of the two layers of separators (111). Preferably, the sealing member (130) may be disposed on each of the facing inner surfaces of the two layers of separators (111). In this case, the sealing member (130) may be disposed in an area corresponding to a position overlapping the tab (113) on the inner surface of the two layers of separators (111) and a surrounding area thereof. The step of attaching the sealing member (130) to the inner surface of the two layers of separators (111) may be performed at any time before or after the first electrode (112) is disposed between the two layers of separators (111).

[0106] Referring to FIG. 3, the method for manufacturing an electrode assembly may include a step of forming an electrode-separator assembly (110) composed of two layers of separators (111) and a first electrode (112) by thermally fusing at least a portion of an edge region of two layers of separators (111).

[0107] Thermal bonding can be performed by pressing the edge portion of the two-layer separator (111) with a hot press (not shown). At this time, a release film (not shown) can be placed between the two-layer separator (111) and the hot press. That is, thermal bonding can be performed by covering one outer surface of the two-layer separator (111) with a release film and then pressing the top of the release film with a hot press. The release film may have poor adhesion properties with the separator (111). By using a release film during thermal bonding, the edge of the separator (111) can be fused in a flat state without being pushed in any one direction.

[0108] Referring to FIG. 4, the method for manufacturing an electrode assembly may include a step of folding an electrode-separator assembly (110) in a zigzag shape and placing a second electrode (120) between each layer of the folded and laminated electrode-separator assembly (110). It may be understood that the electrode-separator assembly (110) is folded in a zigzag shape along the dotted lines illustrated in FIGS. 1 to 3. The second electrodes (120) may be placed one by one during the folding process of the electrode-separator assembly (110), or may be placed in each layer of the folded and laminated electrode-separator assembly (110) after the electrode-separator assembly (110) is completely folded in advance.

[0109] FIG. 6 is a graph comparing the short-circuit time and ignition time of a battery cell including an electrode assembly according to one embodiment of the present specification with the short-circuit time and ignition time of a battery cell including an electrode assembly according to a comparative example.

[0110] An embodiment is an electrode assembly having a structure in which a first electrode is wrapped with two layers of separators, edges of the two layers of separators are thermally fused to form an electrode-separator assembly, and the electrode-separator assembly is folded in a zigzag pattern while a second electrode is alternately placed between the zigzag-folded electrode-separator assembly, as in an electrode assembly according to one embodiment of the present specification.

[0111] A comparative example is an electrode assembly having a structure in which a positive electrode, a negative electrode, and a separator are each provided in multiples, the positive electrode, the negative electrode, and the separator are simply stacked, and the positive electrode and the negative electrode are simply separated by a single sheet of separator.

[0112] Figure 6 shows the point in time at which battery ignition occurs in the examples and comparative examples during the process of raising the ambient temperature of the electrode assembly to 130°C at a rate of 5°C / min through a hot-box evaluation, maintaining it at 130°C for 30 minutes, and then raising it again to 250°C at a rate of 5°C / min.

[0113] In Fig. 6, the thick solid line represents the temperature of the electrode assembly according to the embodiment, the thin solid line represents the open circuit voltage (OCV) of the electrode assembly according to the embodiment, the thick dotted line represents the temperature of the electrode assembly according to the comparative example, and the thin dotted line represents the open circuit voltage of the electrode assembly according to the comparative example.

[0114] Referring to Fig. 6, comparing the open circuit voltages of the embodiment and the comparative example, it can be seen that in the comparative example, a short circuit occurs when the temperature of the electrode assembly reaches 130°C, causing a sharp drop in the open circuit voltage. On the other hand, in the embodiment, a short circuit does not occur when the temperature of the electrode assembly is 130°C, and it can be seen that a short circuit occurs when the temperature of the electrode assembly reaches approximately 150°C while increasing the temperature of the hot-box.

[0115] In addition, when comparing the ignition timing of the embodiment and the comparative example with reference to Fig. 6, it can be seen that in the comparative example, the battery ignition occurs with a rapid temperature rise immediately after the temperature of the electrode assembly reaches 130°C. On the other hand, in the case of the embodiment, the battery ignition does not occur when the temperature of the electrode assembly is 130°C, and when the temperature of the hot-box is raised thereafter and the temperature of the electrode assembly reaches about 180°C, the battery ignition occurs.

[0116] Depending on the overall structure and environment of the electrode assembly, there may be a difference between the time of short circuit and the time of ignition of the electrode assembly.

[0117] Through these experimental results, it can be confirmed that in the case of the embodiment, even if the ambient temperature of the electrode assembly rises and shrinkage of the separator occurs, the first electrode can be isolated from the second electrode by the sealing of the separator, so that a short circuit between the negative electrode and the positive electrode can be prevented, and the first electrode can also be prevented from coming into contact with the outside air by the sealing of the separator, so that battery ignition is suppressed.

[0118] Any or all of the embodiments of this specification described above are not mutually exclusive or distinct. Any or all of the embodiments of this specification described above may have their respective components or functions combined or used together.

[0119] For example, it means that a configuration A described in a particular embodiment and / or drawing can be combined with a configuration B described in another embodiment and / or drawing. That is, even if a combination between configurations is not directly described, it means that a combination is possible, except in cases where a combination is described as impossible.

[0120] The above detailed description should not be construed as limiting in any respect and should be considered illustrative only. The scope of this specification should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of this specification are intended to be embraced therein.

[0121] [Explanation of symbols]

[0122] 100: Electrode assembly

[0123] 110: Electrode-separator assembly

[0124] 111: Membrane

[0125] 112: First electrode

[0126] 112a: First electrode plate

[0127] 113: Tap

[0128] 120: Second electrode

[0129] 130: Sealing member

[0130] M: Margin area

[0131] F: Fold line

Claims

1. An electrode-separator assembly comprising two layers of separators, each layer being rectangular, and a first electrode disposed between the two layers of separators in a rectangular shape extending in a direction corresponding to the two layers of separators; and A second electrode is included, which is separated from the first electrode by the separator, At least a portion of the edge area of ​​the two layers of separators is heat-welded while the first electrode is positioned between the two layers of separators, The above electrode-separator assembly in a heat-fused state is folded in a zigzag shape along the length direction, The above second electrode is an electrode assembly disposed between each layer of the folded and laminated electrode-separator assembly.

2. In paragraph 1, An electrode assembly comprising a tab protruding from the first electrode and partially exposed to the outside from the two layers of separators, and a sealing member provided between the two layers of separators at least at a position where the tab is positioned and a peripheral area of ​​the position where the tab is positioned.

3. In paragraph 2, The above first electrode comprises a plurality of first electrode plates which are folded together and separated as the electrode-separator assembly is folded in a zigzag manner, The above tab is provided on each of the plurality of first electrode plates, and is arranged adjacent to each of two adjacent first electrode plates among the plurality of first electrode plates, An electrode assembly wherein the sealing member is provided to cover at least two adjacent tabs.

4. In paragraph 2, The above sealing member is an electrode assembly provided on one side and the other side of the tab.

5. In paragraph 2, An electrode assembly wherein a portion of the sealing member overlaps the first electrode.

6. In paragraph 2, The above sealing member is an electrode assembly made of polyimide material.

7. In paragraph 1, The above two-layer separator is formed by folding one sheet of separator in half. The above electrode-separator assembly is an electrode assembly formed by heat-fusing the remaining edges of the two-layer separator except for the folded edges.

8. In paragraph 7, An electrode assembly in which a folding line formed by folding the above-mentioned single sheet of separator is formed parallel to the longitudinal direction of the above-mentioned two layers of separators.

9. In paragraph 1, An electrode assembly in which thermal fusion is performed in an area of ​​the two-layer separator that does not overlap with the first electrode.

10. In paragraph 1, The above second electrode is a cathode composed of lithium metal, An electrode assembly wherein the first electrode is an anode.

11. A step of supplying two layers of membranes, each layer being rectangular; A step of arranging a first rectangular electrode extending in a direction corresponding to the two layers of separators between the two layers of separators; A step of forming an electrode-separator assembly comprising the two layers of separators and the first electrode by thermally fusing at least a portion of the edge area of ​​the two layers of separators; and A method for manufacturing an electrode assembly, comprising the step of folding the electrode-separator assembly in a zigzag shape and placing a second electrode between each layer of the folded and laminated electrode-separator assembly.

12. In paragraph 11, The step of supplying the above two layers of membranes is: Comprising the step of folding a single sheet of membrane, A method for manufacturing an electrode assembly, wherein a folding line formed by folding the above-mentioned single sheet of separator is formed parallel to the longitudinal direction of the above-mentioned two layers of separators.

13. In paragraph 11, The electrode assembly includes a tab protruding from the first electrode and partially exposed to the outside from the two layers of separators, and a sealing member provided between the two layers of separators at least at a position where the tab is positioned and a peripheral area of ​​the position where the tab is positioned. A method for manufacturing an electrode assembly, comprising the step of placing the first electrode between the two layers of separators, and then attaching the sealing member to at least one surface of the tab.

14. In paragraph 11, The above first electrode comprises a plurality of first electrode plates which are folded together and separated as the electrode-separator assembly is folded in a zigzag manner, A method for manufacturing an electrode assembly, comprising the step of forming a tab for each of the plurality of first electrode plates by notching one edge of the first electrode, which is provided in a rectangular shape, before arranging the first electrode between the two layers of separators.

15. In paragraph 11, The step of supplying the above two layers of membranes is: Comprising the step of folding a single sheet of membrane, A method for manufacturing an electrode assembly, wherein the above-described heat bonding is performed by covering one outer surface of the two-layer separator with a release film and then pressing the top of the release film with a hot press, and at least a portion of the edge area of ​​the two-layer separator is the edge of the three sides other than the folded edge of the one sheet of separator.

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