Electrode assembly and manufacturing method thereof

Abstract

The present invention relates to an electrode assembly capable of preventing damage to the separator that occurs when the electrode is wound into a jelly roll shape, and a method for manufacturing the same. An electrode assembly according to an embodiment of the present invention is a jelly-roll type electrode assembly wound with a separator interposed between an anode and a cathode. The anode includes a free edge formed at the same position as the end of the anode composite layer and the anode current collector. The anode composite layer includes a sliding portion formed to reduce friction with the separator.

Description

Technology Field

[0001] The present invention relates to an electrode assembly capable of preventing damage to the separator that occurs when the electrode is wound into a jelly roll shape, and a method for manufacturing the same. Background Technology

[0003] Recently, with the increasing technological development and demand for mobile devices, the demand for rechargeable secondary batteries as an energy source has been rapidly rising, and consequently, extensive research is being conducted on secondary batteries capable of meeting various requirements. Furthermore, secondary batteries are also attracting attention as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (Plug-in HEVs), which are being proposed as solutions to address air pollution caused by conventional gasoline and diesel vehicles that use fossil fuels.

[0004] Accordingly, electric vehicles (EVs) that can be operated solely on secondary batteries and hybrid electric vehicles (HEVs) that use secondary batteries in combination with conventional engines have been developed, and some have been commercialized. While nickel-metal hydride (Ni-MH) secondary batteries are mainly used as power sources for EVs and HEVs, research on the use of lithium secondary batteries, which have high energy density, high discharge voltage, and output stability, is currently being actively conducted and some have been commercialized.

[0005] These lithium secondary batteries are classified according to the shape of the battery case into cylindrical and prismatic batteries, in which the electrode assembly is embedded in a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is embedded in a pouch-type case made of an aluminum laminate sheet.

[0006] In addition, the electrode assembly embedded in the battery case is a power generation element capable of charging and discharging, having a structure comprising a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. It is classified into a jelly-roll type, which is wound by interposing a separator between a long sheet-type positive electrode and a negative electrode coated with an active material; a stack type, which is sequentially stacked with a plurality of positive and negative electrodes of a predetermined size interposed in a separator; and a stack-folding type, which is wound by placing unit cells, such as a full cell (e.g., positive-separator-negative electrode) or a bicell (e.g., positive-separator-negative electrode) composed of electrodes with opposite polarities on both sides, on a long sheet-type separator.

[0007] Among them, jelly-roll type electrode assemblies are easy to manufacture and possess high energy-to-weight ratios. Cylindrical or prismatic batteries containing these assemblies offer high safety and exhibit no volume change; consequently, demand for prismatic or cylindrical secondary batteries is surging alongside the expansion of the market for EVs and HEVs that utilize them as power sources.

[0009] Referring to FIG. 1, an example of an electrode assembly used in a conventional secondary battery is described. FIG. 1 is a cross-sectional view illustrating an example of an electrode assembly used in a conventional secondary battery, schematically illustrating an example in which an electrode having an active material-free portion formed thereon is laminated on a separator.

[0010] Referring to FIG. 1, the electrode (1) has electrode composite layers (2, 2') applied to both sides of an electrode current collector (3) in the form of a long sheet, and the electrode composite layers (2, 2') are applied so that an active material blank portion (a) is formed at the end of the electrode current collector (3) where the electrode composite layers (2, 2') are not applied.

[0011] When an electrode is laminated onto a separator to form an electrode assembly and then wound into a jelly roll shape, the electrode end, more precisely the end of the electrode winding where the electrode winding ends, may press against the separator. However, due to the active material-free portion (a), the phenomenon of the electrode winding where the end of the electrode winding ends pressing against the separator is mitigated or reduced, thereby reducing the stress on the separator and preventing the phenomenon of the separator breaking.

[0012] However, when using an electrode (1) in which an active material-free portion (a) is formed, when coating the electrode active material, particularly the positive active material, the active material slurry is scattered in the active material-free portion of the electrode current collector, forming an active material island. This island causes an internal short circuit in the battery when the electrode current collector sheet is stretched due to repeated shrinkage and expansion of the jelly roll during high-capacity model life tests, etc.

[0014] Accordingly, as shown in FIG. 2, an electrode (1) having a free edge is proposed by applying electrode composite layers (2, 2') to both sides of an electrode current collector (3) and cutting so that no part of the active material exists. Here, the term "free edge" means that, as shown in FIG. 2, both the electrode composite layer and the electrode current collector form ends at the same location.

[0015] The free edge can be formed by vertically cutting the active material retaining portion (2a) of the electrode composite layer (2, 2') applied using a shim for a die coater as shown in FIG. 3, together with the electrode current collector (3) as shown in FIG. 4.

[0016] Although the electrode with the free edge of Fig. 2 prevents the formation of islands due to scattering of the active material, the electrode composite layer and the electrode current collector form ends at the same location, and when rolled up due to the volume expansion of the electrode during charging and discharging, the free edge portion of the anode located at the center of the roll slides, and as a result, the frictional force between the anode and the separator increases, causing deformation in the cathode as well, which damages the separator and causes a short circuit. Prior art literature

[0018] Korean Registered Patent No. 10-1696964 The problem to be solved

[0019] The present invention aims to provide an electrode assembly capable of preventing damage to the separator that occurs when the electrode is wound into a jelly roll shape, and a method for manufacturing the same. means of solving the problem

[0021] An electrode assembly according to an embodiment of the present invention is a jelly-roll type electrode assembly wound with a separator interposed between an anode and a cathode. The anode includes a free edge formed at the same position as the end of the anode composite layer and the anode current collector. The anode composite layer includes a sliding portion formed to reduce friction with the separator.

[0022] In an electrode assembly according to an embodiment of the present invention, the sliding portion may be a space formed in the separator side portion of the end of the anode composite layer.

[0023] In an electrode assembly according to an embodiment of the present invention, the sliding portion may be a space formed at the core portion side end of the anode composite layer.

[0024] In an electrode assembly according to an embodiment of the present invention, the sliding portion may be a space formed on one side of the core portion end of the anode composite layer.

[0025] In an electrode assembly according to an embodiment of the present invention, the positive electrode composite layer includes a retaining portion coated with a positive electrode active material and a non-retaining portion not coated with a positive electrode active material, and the sliding portion may be formed in a retaining portion region disposed at the core portion side end of the positive electrode composite layer.

[0027] A method for manufacturing an electrode assembly according to an embodiment of the present invention is,

[0028] The method includes: a step of forming an anode and a cathode; a step of forming a unit cell by stacking the cathode and the anode together with a separator as a boundary; and a winding step of winding the unit cell. Herein, the anode forming step includes a process of forming a free edge by arranging the ends of the anode composite layer and the anode current collector at the same position, and forming a sliding portion in the anode composite layer to reduce friction with the separator.

[0029] In a method for manufacturing an electrode assembly according to an embodiment of the present invention, the sliding portion may be a space formed in the separator side portion of the core portion side end of the anode composite layer.

[0030] In a method for manufacturing an electrode assembly according to an embodiment of the present invention, a positive active material can be coated on at least one surface of the positive current collector using a die coater in a concavely recessed pattern, and the sliding portion can be formed by cutting the recessed pattern using a cutter.

[0031] In a method for manufacturing an electrode assembly according to an embodiment of the present invention, the die coater may include a plurality of guides arranged in parallel having a predetermined width, a base extending laterally from the ends of the plurality of guides, and a sub-guide located between the plurality of guides to divert a discharged slurry.

[0032] In a method for manufacturing an electrode assembly according to an embodiment of the present invention, when the height of each of the plurality of guides is 100, the height of the sub-guide may be formed to a size of 60 to 80.

[0033] In a method for manufacturing an electrode assembly according to an embodiment of the present invention, the width of the sub-guide may be 1 to 5 cm.

[0034] Specific details of embodiments according to various aspects of the present invention are included in the following detailed description. Effects of the invention

[0036] According to an embodiment of the present invention, by providing a space in which the free edge portion of the core anode located at the center of the roll can slide due to the volume expansion of the electrode during charging and discharging of a jelly-roll type secondary battery, the frictional force between the anode and the separator can be reduced. Accordingly, deformation of the negative electrode and damage to the separator can be prevented. Brief explanation of the drawing

[0038] FIG. 1 is a cross-sectional view showing an example of an electrode assembly used in a conventional secondary battery. FIG. 2 is a cross-sectional view schematically illustrating an example in which a free edge electrode is laminated on a separator. Figures 3 and 4 are drawings for explaining the process of forming a free edge. FIG. 5 is a cross-sectional view showing the pre-winding state of a jelly-roll type electrode assembly according to one embodiment of the present invention. Figure 6 is an enlarged cross-sectional view of part A of Figure 5. FIG. 7 is a cross-sectional view showing the pre-winding state of a jelly-roll type electrode assembly according to another embodiment of the present invention. FIG. 8 is a flowchart illustrating a method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention. Figure 9 is a drawing showing a die coater shim used to form a sliding portion on an anode current collector. FIG. 10 is a side view of an anode current collector coated with an anode active material using the die coater core of FIG. 9. Specific details for implementing the invention

[0039] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0040] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Hereinafter, an electrode assembly and a method for manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings.

[0042] FIG. 5 is a cross-sectional view showing the pre-winding state of a jelly-roll type electrode assembly according to one embodiment of the present invention.

[0043] Referring to FIG. 5, the jelly-roll type electrode assembly (100) according to the present invention has a structure in which a separator (130) is interposed between an anode (110) and a cathode (120) and is wound in the direction of the arrow.

[0044] The anode (110) includes a core portion and an outer portion, and overall, has a structure in which an anode composite layer (112) is formed on an anode current collector (111). The core portion and the outer portion are distinguished based on the length (l) from the winding start point to the winding end point of the electrode assembly, and the core portion can be formed within 50% of the total length (l) from the winding start point.

[0045] The positive current collector (111) and the positive composite layer (112) have their ends formed at the same location to form a free edge. Additionally, a sliding portion (113) is formed at the end of the positive composite layer (112).

[0046] In one specific example, the sliding portion (113) may be a space formed on one side of the core portion end of the anode composite layer.

[0047] The sliding portion (113) is an empty space formed in the separator (130) side portion of the end of the anode composite layer (112). Preferably, the sliding portion (113) is formed in the core side portion of the anode composite layer (112).

[0048] The sliding portion (113) can reduce the frictional force between the anode (110) and the separator (130) by providing a space in which the free edge portion of the core portion anode (110) located at the center of the roll can slide due to the volume expansion of the electrode during charging and discharging of the jelly-roll type secondary battery. Accordingly, deformation of the negative electrode and damage to the separator can be prevented.

[0049] The size of the sliding part (113) is explained with reference to FIG. 6. FIG. 6 is a cross-sectional view showing an enlarged view of part A of FIG. 5.

[0050] Referring to FIG. 6, the width (w) of the sliding part (113) is 0.1 cm to 2 cm, and preferably 0.2 cm to 1.5 cm.

[0051] Meanwhile, the cathode (120) has a structure in which a cathode composite layer (122) is formed on a cathode current collector (121).

[0052] Next, a jelly-roll type electrode assembly according to another embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is a cross-sectional view showing the state of a jelly-roll type electrode assembly before winding according to another embodiment of the present invention.

[0053] A jelly-roll type electrode assembly according to another embodiment of the present invention differs from the aforementioned embodiment only in that it includes a plurality of retaining portions (112a) and unretaining portions (112b) alternately formed on an anode composite layer (112), but otherwise has substantially the same configuration.

[0054] The retaining portion (112a) is an area coated with positive active material, and the uncoated portion (112b) is an area not coated with positive active material. The sliding portion (113) is formed in the retaining portion (112a) area located at the core portion side end of the positive composite layer (112).

[0055] The uncoated portion (112b) is composed of an empty space where the positive active material is not coated, thereby providing a space for storing the electrolyte inside the electrode assembly. The uncoated portion (112b) prevents the electrolyte inside the electrode assembly from accumulating outside the electrode assembly as it is compressed during battery charging and discharging, and enables the electrolyte to be impregnated more effectively.

[0056] The width of the uncoated portion (112b) may be 0.1 mm to 10 mm, and more specifically, 0.5 mm to 5 mm. The width refers to the length in the winding direction, and in the case where the retaining portion (112a) and the uncoated portion (112b) are coated in an alternating arrangement, it refers to the length in the alternating arrangement direction.

[0057] The spacing of each non-retaining portion (112b), that is, the width of the retaining portion (112a), can be 1 mm to 200 mm.

[0058] If the width of the uncoated portion (112b) is too large or the spacing is too small, the area occupied by the uncoated portion (112b) is too large, and consequently, the portion occupied by the active material layer is reduced, which is undesirable in terms of energy density. If the width of the uncoated portion (112b) is too small or the spacing is too wide, the uncoated area is formed too small, and thus the substantial effect according to the present invention cannot be obtained, which is undesirable.

[0059] Accordingly, it is preferable that the unoccupied portion (112b) has an area greater than a certain portion of the area where the entire anode composite layer (112) is formed. Specifically, the cross-sectional area of ​​the unoccupied portion (112b) may be 1% to 20% based on the total area of ​​the retaining portion (112a) and the unoccupied portion (112b), and more specifically, 5% to 15%.

[0060] The coating form of the anode composite layer (112) is not limited, and the uncoated portion (112b) can be formed in various shapes, for example, linear (striped), circular, or polygonal shapes, as long as it includes an uncoated portion (112b) and a retaining portion (112a).

[0061] However, considering the ease of the process, the retaining portion (112a) and the unretained portion (112b) may be arranged alternately in a linear form, and the spacing may be constant or not constant.

[0063] Next, a method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention will be described with reference to FIGS. 8 to 10. FIG. 8 is a flowchart illustrating a method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention, FIG. 9 is a drawing illustrating a die coater shim used to form a sliding portion on an anode current collector, and FIG. 10 is a side view of an anode current collector coated with an anode active material using the die coater shim of FIG. 9.

[0064] Referring to FIG. 8, a method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention includes an electrode forming step (S110), a stacking step (S120), and a winding step (130).

[0065] First, an electrode active material is coated on at least one surface of an electrode current collector (111, 121) using a die coater to form an electrode composite layer (112, 122), thereby forming an anode (110) and a cathode (120). (S110)

[0066] At this time, a sliding portion (113) is formed on the separator (130) side portion of the end of the anode composite layer (112). Preferably, a sliding portion (113) is formed on the core side end of the anode composite layer (112). This will be explained with reference to FIGS. 9 and FIGS. 10.

[0067] As shown in FIG. 9, a positive active material is coated on at least one surface of a positive current collector (111) using a die coater shim (10). The die coater shim (10) is applied to a die coater that applies a slurry (positive active material, negative active material, etc.) onto electrode current collectors (111, 121).

[0068] Specifically, the die coater shim (10) includes a base (11) and a plurality of guides (12) and sub-guides (13).

[0069] The base (11) is formed to extend laterally from the ends of the plurality of guides (12). The base (11) supports the plurality of guides (12) by connecting the ends of the plurality of guides (12). The base (11) may be formed in a simple straight shape, but is not limited thereto.

[0070] A plurality of guides (12) have a predetermined width and are formed parallel to each other. The ends (12a) of the plurality of guides (12) protrude a predetermined length in opposite directions, and the space between the ends (12a) of the guides (12) forms a space for discharging slurry.

[0071] The sub-guide (13) is positioned between the multiple guides (12) to divert the discharged slurry. The space between the guide (12) ends (12a) can be divided into two slots (S1, S2) by the sub-guide (13).

[0072] The height of the sub-guide (13) is formed to be smaller than the height of the guide (12). For example, when the height (H1) of the guide (12) is 100, the height (H2) of the sub-guide (13) can be formed to be 60 to 80.

[0073] The slurry discharged through the two slots (S1, S2) partitioned by the sub-guide (13) is frictionally applied to the surfaces of the guide (12) and the sub-guide (13), and as shown in FIG. 10, is formed in an overall hemispherical shape, but the position corresponding to the position of the sub-guide (13) (P, for example, the center of the hemispherical shape) can be formed in a concavely sunken pattern. Then, the concavely sunken portion is cut using a cutter. The cross-sectional shape of the anode composite layer resulting from the cutting has a curve (C1, C2) formed on at least one side. The portion having the curve (C1, C2) in this way is placed at the core-side end of the anode composite layer (112) to form a sliding portion (113).

[0074] Next, a cathode and an anode are stacked together (S120) with a separator as the boundary to form a unit cell, and the unit cell is wound (S130) to manufacture an electrode assembly.

[0075] In the electrode assembly manufactured in this manner, the sliding portion (113) provides a space in which the free edge portion of the core portion positive electrode (110) located at the center of the roll can slide due to the volume expansion of the electrode during charging and discharging of the jelly-roll type secondary battery, thereby reducing the frictional force between the positive electrode (110) and the separator (130). Accordingly, deformation of the negative electrode and damage to the separator can be prevented.

[0077] Although an embodiment of the present invention has been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention. Explanation of the symbols

[0079] 100 : Electrode assembly 110 : Anode 111: Anode current collector 112: Anode composite layer 112a: Retaining part 112b: Non-retaining part 113 : Sliding part 120: Cathode 121: Cathode current collector 122: Cathode composite layer 130 : Separator

Claims

Claim 1 A jelly-roll type electrode assembly wound with a separator interposed between an anode and a cathode, wherein the anode includes a free edge formed at the same position as the end of the anode composite layer and the anode current collector, the anode composite layer includes a sliding portion formed to reduce friction with the separator, and the sliding portion is a space formed in the separator side portion of the core-side end of the anode composite layer. Claim 2 delete Claim 3 delete Claim 4 An electrode assembly according to claim 1, wherein the sliding portion is a space formed on one side of the core portion end of the anode composite layer. Claim 5 An electrode assembly according to claim 1, wherein the positive electrode composite layer comprises a retaining portion coated with a positive electrode active material and a non-retaining portion not coated with a positive electrode active material, and the sliding portion is formed in a retaining portion region disposed at the core portion side end of the positive electrode composite layer. Claim 6 A method for manufacturing an electrode assembly comprising: a step of forming an anode and a cathode; a step of forming a unit cell by stacking the cathode and the anode together with a separator as a boundary; and a winding step of winding the unit cell; wherein the anode forming step includes forming a free edge by arranging the ends of the anode composite layer and the anode current collector at the same position, and forming a sliding portion in the anode composite layer to reduce friction with the separator, wherein the sliding portion is a space formed in the separator side portion of the core portion side end of the anode composite layer. Claim 7 delete Claim 8 A method for manufacturing an electrode assembly according to claim 6, wherein a positive active material is coated on at least one surface of the positive current collector in a concavely recessed pattern using a die coater, and the recessed pattern is cut using a cutter to form the sliding portion. Claim 9 A method for manufacturing an electrode assembly according to claim 8, wherein the die coater comprises a plurality of guides arranged in parallel having a predetermined width, a base formed extending laterally from the ends of the plurality of guides, and a sub-guide positioned between the plurality of guides to branch out a discharged slurry. Claim 10 A method for manufacturing an electrode assembly according to claim 9, wherein when the height of each of the plurality of guides is 100, the height of the sub-guide is formed to a size of 60 to 80. Claim 11 A method for manufacturing an electrode assembly according to claim 9, wherein the width of the sub-guide is 1 to 5 cm.

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