KR101710060B1 - Stack and folding-type electrode assembly and method for fabricating the same - Google Patents

Abstract

A stack-folding type electrode assembly capable of reducing the number of times of folding and having high cell manufacturing efficiency and a method of manufacturing the same are provided. The stack-folding type electrode assembly according to the present invention has quad cells of anode / separator / cathode / separator / anode / separator / cathode structures superimposed on each other, Wherein a C type bi-cell having a negative electrode / separator / anode / separator / cathode structure is disposed at the center of the winding start point, and the folding separator sheet is an asymmetric separator having different properties on both surfaces.

Description

[0001] Stack-folding electrode assembly and method of fabricating the same [0002]

The present invention relates to a stack-folding type electrode assembly and a manufacturing method thereof, and more particularly, to a stack-folding type electrode assembly capable of reducing the number of times of folding and a method of manufacturing the same.

Due to the development of technology and demand for mobile devices, the demand for secondary batteries is also rapidly increasing. Among them, lithium secondary batteries, which have high energy density, high operating voltage and excellent storage and life characteristics, It is widely used as an energy source.

The secondary battery is roughly classified into a cylindrical battery, a prismatic battery and a pouch-shaped battery according to the structural characteristics of the outside and the inside. Among them, the secondary battery can be stacked with a high degree of integration, and prismatic batteries and pouch- .

The electrode assembly of the anode / separator / cathode structure constituting the secondary battery is largely classified into a jelly-roll type (winding type) and a stack type (laminate type) depending on its structure. In the jelly-roll type electrode assembly, an electrode active material or the like is coated on a metal foil used as a current collector, dried and pressed, cut into a band shape having a desired width and length, and a cathode and an anode are diaphragm- . The jelly-roll type electrode assembly is suitable for a cylindrical battery. However, when applied to a square or pouch type battery, it has disadvantages such as peeling of an electrode active material and low space utilization. On the other hand, the stacked electrode assembly has a structure in which a plurality of positive electrode and negative electrode unit cells are sequentially stacked and has a merit that it is easy to obtain a rectangular shape. However, when the manufacturing process is troublesome and impact is applied, .

In order to solve such a problem, the jelly-roll type and stack type mixed type electrode assemblies have been proposed in which a full cell or a positive electrode (cathode) / separator / cathode (anode) / separator A stack-folding type electrode assembly having a structure in which a bicell having an anode / cathode structure is folded by using a continuous long folding separator sheet has been developed.

Figs. 1 and 2 schematically show an exemplary structure and a manufacturing process of such a stack-folding type electrode assembly.

Referring to these drawings, C type bi-cells 10, 13, and 14 having a structure of a cathode / separator / anode / separator / cathode are sequentially formed as a unit cell and an A type bi- 11 and 12 are alternately stacked, and a folding separator sheet 20 is interposed in each of the overlapping portions. The folding separator sheet 20 has a unit length that can wrap around the bicells and is folded inward for each unit length to start from the center bicycle 10 and continue to the outermost bicycle 14, And is interposed in the overlapped portion of the bi-cell. The distal end of the folding sheet 20 is thermally fused or bonded with an adhesive tape 25 or the like.

This stack-folding type electrode assembly can be formed by, for example, arranging bicells 10, 11, 12, 13, and 14 on a long-length folding separator sheet 20, (21) and sequentially winding them.

The first bi-cell 10 and the second bi-cell 11 have a width corresponding to at least one bi-cell, and the first bi-cell 10 and the second bi- The outer surface of the first bi-cell 10 is completely coated with the folding separator sheet 20 and then the lower surface electrode (negative electrode) of the first bi-cell 10 is exposed. (Positive electrode, +) of the second bi-cell 11. Since the coating length of the folding separator sheet 20 is increased in the sequential lamination process by winding the bi-cells 12, 13, and 14 after the second bi-cell 11, And are disposed so as to sequentially extend. The bi-cells 10, 11, 12, 13, and 14 should be configured such that the positive electrode and the negative electrode face each other at the interface between the first and second bi- Cell and the second bi-cell 11 and the third bi-cell 12 are bi-cells having an upper surface electrode as an anode, and the fourth bi-cell 13 and the fifth bi- In-cell. That is, the bi-cells are mounted in an alternating arrangement of two units.

Although the stack-folding type electrode assembly compensates for the disadvantages of the jelly-roll and stacked electrode assembly, increasing the number of bi-cell stacks for high energy density increases the number of folding times, There arises a problem of an increase in the process time. As shown in FIG. 2, since the types of electrodes placed on the folding separator sheet periodically change, a time loss occurs due to replacement of the cell type (A-type bi-cell or C-type bi-cell)

Therefore, there is a demand for a stack-folding type electrode assembly capable of reducing the number of times of folding and having high cell manufacturing efficiency and a method for manufacturing the same.

A problem to be solved by the present invention is to provide a stack-folding type electrode assembly capable of reducing the number of times of folding and having high cell manufacturing efficiency and a method of manufacturing the same.

According to an aspect of the present invention, there is provided a stack-folding type electrode assembly in which quad cells of an anode / separator / cathode / separator / anode / separator / cathode structure are superimposed, A folding separator sheet having a structure in which a C type bi-cell having a negative electrode / separator / positive electrode / separator / negative electrode structure is located at the center of the winding start point and the folding separator sheet is an asymmetric separator having different properties on both surfaces .

The cathode may be located at the outermost edge of the electrode assembly. The folding separator sheet may have a unit length that can wrap the quad cells, and may be formed by bending inwardly for each unit length, starting from the center C type bi-cell, and continuously wrapping up to the outermost quad cell. The quad cells located on the upper and lower sides of the central C type bi-cell may have their electrode directions symmetrical to each other.

In a preferred embodiment, the folding separator sheet comprises a separator fabric; A coating layer including an inorganic material for a negative electrode and a binder formed on one surface of the separator; And a coating layer comprising a negative electrode active material and a binder formed on the other surface of the separation membrane, wherein the negative electrode of the C type bi-cell and the quad cells is placed in the coating layer including the negative electrode material and the binder, The positive electrode of the C type bi-cell and the quad cells is placed in a coating layer containing an inorganic material and a binder.

In another preferred embodiment, the folding separator sheet is a laminated structure of a first separator and a second separator, and the negative electrode of the C type bi-cell and the quad cells is placed in one of the first separator and the second separator, And the anode of the C-type bi-cell and quad-cell is placed in the other of the first separator and the second separator.

The present invention also provides a secondary battery including the stack-folding type electrode assembly.

The present invention also provides a method of manufacturing such a stack-folding electrode assembly. The method comprises the steps of positioning a central C type bicycle at a first end of a folding separator sheet and successively positioning quad cells at predetermined intervals, and winding the central C type bicycle through the folding separator sheet once Folding the folding separator sheet to the outside where adjacent quad cells are located, and folding and folding each quad cell.

When manufacturing the stack-folding type electrode assembly, the negative electrode of the C type bi-cell and the quad cells may be positioned and wound on a specific surface of the folding separator sheet.

According to the present invention, since the quad cell having more electrodes than the bicycle is used, the number of folds can be reduced because the unit assembly can be reduced at the same number of electrodes compared to the conventional one. Accordingly, the folding dimensional tolerance and the defective ratio can be reduced, and the lamination and folding process time can be reduced.

Compared with the conventional manufacturing method in which the two types of A-type bi-cells and C-type bi-cells are manufactured and then the respective bi-cells are wound alternately, The time loss can be reduced, thereby maximizing the battery manufacturing efficiency. Since the electrodes of all the unit cells can be arranged on the folding separator sheet and wound up without needing to arrange the electrode alignment directions of the unit cells by the alternate orientation method, .

In particular, the battery performance can be improved by selectively contacting the specific surface of the asymmetric separation membrane with the positive and negative electrodes of the unit cells.

1 is a schematic diagram of an exemplary structure of a conventional stack-folding type electrode assembly.
FIG. 2 is a schematic diagram illustrating an exemplary arrangement of unit cells in a manufacturing process of the stack-folding type electrode assembly of FIG. 1;
FIG. 3 illustrates a C-type bi-cell and a quad cell which constitute a unit cell of the stack-folding type electrode assembly according to the present invention.
4 is a schematic view of a stack-folding type electrode assembly structure according to an embodiment of the present invention.
5 is a schematic diagram showing an arrangement combination of unit cells in the manufacturing process of the stack-folding type electrode assembly of FIG.
6 shows another example of a C-type bi-cell and a quad cell constituting a unit cell of the stack-folding type electrode assembly according to the present invention.
7 is a schematic view of a stack-folding type electrode assembly structure according to another embodiment of the present invention.
8 is a schematic diagram showing an arrangement combination of unit cells in the manufacturing process of the stack-folding type electrode assembly of FIG.
Fig. 9 shows possible examples in the case where the number of stacks is three or more in the electrode assembly according to the present invention, wherein (a) to (d) schematically show the cell internal lamination structure, It is.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is provided to let you know.

In addition, the battery or the electrode assembly included in the present invention is not particularly limited in its shape and may include various shapes. For example, the stacked unit cells may be stacked on a stack of folded separator sheets A folding type electrode assembly, a Z stack electrode assembly for folding in the zigzag direction when the stacked unit cells are wound with a folding separator sheet, and the like.

FIG. 3 illustrates a C-type bi-cell and a quad cell which constitute a unit cell of the stack-folding type electrode assembly according to the present invention.

The C type bi-cell has a cathode / separator / anode / separator / cathode structure, and the quad cell has a cathode / separator / cathode / separator / anode / separator / cathode structure. The unit cell anode is prepared, for example, by coating a mixture of a cathode active material, a conductive material and a binder on both surfaces of a cathode current collector, followed by drying and pressing, and if necessary, a filler may be further added to the mixture. The unit cell negative electrode is prepared by applying, drying and pressing an anode active material on a negative electrode current collector, and may optionally further include a conductive material, a binder, a filler, and the like as described above. As described above, the positive electrode and the negative electrode may be coated with a positive electrode active material or a negative electrode active material on both sides of each current collector (electrode sheet), but they are not shown for convenience.

4 is a schematic view of a stack-folding type electrode assembly structure according to an embodiment of the present invention.

Referring to FIG. 4, a plurality of unit cells 110, 111, and 112 are stacked in a stack-folding type electrode assembly, and a folding separator sheet 120 is interposed in each of the stacking units. The folding separator sheet 120 has a unit length capable of wrapping the unit cells 110, 111 and 112 and is folded inward for each unit length to start from the center unit cell 110 to the outermost unit cell 112 111, and 112 in a structure in which the unit cells 110, 111, and 112 are continuously surrounded by the unit cells 110, 111, and 112, respectively. In addition, the distal end of the folding sheet 120 is thermally fused or bonded with an adhesive tape 125 or the like.

The C type bi-cell 110 is located at the center of winding of the unit cells, and the other unit cells are the quad cells 111 and 112. The quad cells 111 and 112 located on the upper and lower sides of the center C type bi-cell 110 have symmetrical structures with respect to each other. The cathode is located at the outermost edge of the electrode assembly.

When a plurality of unit cells are stacked in a positive electrode / negative electrode facing structure, if possible, the negative electrode occupies a large area. For example, when the unit cells are used in a lithium secondary battery, lithium metal, dendrite) can be suppressed as much as possible. Accordingly, the cathode may be formed to have a wider area than the anode, and / or the outermost electrode assembly may be constituted of the cathode.

In particular, in the electrode assembly shown in Fig. 4, the folding separator sheet 120 is an asymmetric separator having different properties on both surfaces. Concretely, the first separator 122 and the second separator 123 have a laminated structure. The cathodes of the C-type bi-cell 110 and the quad cells 111 and 112 are disposed in the first separator 122, And the cathodes of the C type bi-cell 110 and the quad cells 111 and 112 are placed in the second separation film 123. [ For example, the first and second separation membranes 122 and 123 may have different design structures such as pore size, distribution, and thickness. This design can be modified to optimize for both positive and negative characteristics. Therefore, according to the present invention, battery performance can be improved by selectively contacting the specific surface of the asymmetric separation membrane with the positive and negative electrodes of the unit cells.

5 is a schematic diagram showing an arrangement combination of unit cells in the manufacturing process of the stack-folding type electrode assembly of FIG.

A method of manufacturing the stack-folding type electrode assembly is as follows. First, an anode and a cathode are laminated with a separator interposed therebetween, and a plurality of quad cells and a bi- ). After the folding separator sheet 120 is cut and prepared, the unit cells 110, 111, and 112 are arranged as shown in FIG. The folding separator sheet 120 has a width slightly larger than the unit cells 110, 111 and 112 while exposing electrode tabs (not shown) of the unit cells 110, 111 and 112, And the outermost end of the folding sheet 120 may be thermally fused or may be affixed with a tape. For example, the folding separator sheet 120 itself can be melted and adhered and fixed by contact with a folding separator sheet 120 to be finished, such as a heat welder or a hot plate, have.

This stack-folding type electrode assembly is configured to arrange the unit cells 110, 111, and 112 on the long folding separator sheet 120 and sequentially start from one end 121 of the folding separator sheet 120 . At this time, after the central unit cell 110 is once wound around the folding separator sheet 120, the folding separator sheet 120 is folded outward where the adjacent unit cells 111 and 112 are located, 111, and 112 are folded and folded.

The C type bi-cell as the central unit cell 110 is positioned at the first end of the folding separator sheet 120 and the unit cells 111, 112 are successively positioned. The first unit cell, i.e., the central unit cell 110 and the second unit cell 111 are located at a distance spaced by a width corresponding to at least one unit cell, The lower surface electrode (cathode) of the central unit cell 110 is brought into contact with the upper surface electrode (anode) of the second unit cell 111 after the outer surface is completely coated with the folding separator sheet 120.

The number of unit cells wound on the folding separator sheet 120 may be determined by various factors such as the structure of each unit cell such as each quad cell, the bi-cell, and the desired capacity of the final cell. 3, the number of unit cells included in the stack-folding type electrode assembly may be less than or greater than the number of unit cells included in the stack-folding type electrode assembly.

The folding separator sheet 120 is an asymmetric separator having a laminated structure of the first separator 122 and the second separator 123 and having different properties on both surfaces. In this embodiment, the cathodes of the C type bi-cell 110 and the quad cells 111 and 112 are positioned and laminated on the first separator 122, and then the laminate is wound around the conventional A type bi-cell and C type bi- The time loss due to the exchange of the cell type (A-type bi-cell, C-type bi-cell) can be reduced as compared with the manufacturing method in which each bi-cell is wound alternately after manufacturing the type, can do. Since the electrodes of all the unit cells can be arranged on the folding separator sheet and wound up without needing to arrange the electrode alignment directions of the unit cells by the alternate orientation method, .

The folding separator sheet 120 may be the same material as the separator constituting the unit cell. In this case, the C-type bi-cell and the quad-cell, which are unit cells, can have a structure as shown in FIG.

The folding separator sheet or separator may be a polyethylene film containing micropores, a polypropylene film, or a multilayer film produced by a combination of these films, and a layered film made of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene Fluorinated hexafluoropropylene copolymer, and polymer film for polymer electrolyte of fluorinated hexafluoropropylene copolymer, and may be a folding separator sheet or separator composed of a multilayer or more of a double layer or more manufactured by using the material have.

The subsequent battery manufacturing process is as follows. The positive electrode and the negative electrode lead are welded to the electrode tab portion of the stack-folding type electrode assembly manufactured. At this time, it is effective to use aluminum as the positive electrode and copper as the negative electrode. After the packing of the welded cells into an aluminum pouch, an electrolyte is injected.

The electrolytic solution used in the art is not particularly limited. Specific examples of the solvent include dimethyl carbonate (DMC), ethylene carbonate (EC), ethyl methyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (EC), ethylene carbonate (EC), dimethyl carbonate (DMA) At least one selected from the group consisting of N, N-dimethylformamide (DMF), N-methyl-2-pyrrolidinone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), propylene carbonate use.

According to the present invention, since the quad cell having more electrodes than the bicycle is used, the number of folds can be reduced because the unit assembly can be reduced at the same number of electrodes compared to the conventional one. Accordingly, the folding dimensional tolerance and the defective ratio can be reduced, and the lamination and folding process time can be reduced.

In addition, battery performance can be improved by using an asymmetric separator. For example, in this embodiment, the first separation membrane 122 may be formed of a composition and / or thickness for selectively modifying the contact surface between the cathode and the separation membrane, and the second separation membrane 123 may be formed by selectively modifying the contact surface between the anode and the separation membrane. It is possible to improve the performance of the battery by selectively contacting the positive and negative electrodes on the asymmetric separation membrane surface.

In the conventional case described with reference to FIGS. 1 and 2, since the polarity of the electrode placed on the folding separator sheet alternates, the asymmetric separator structure can not be applied.

 FIG. 7 is a schematic view of a stack-folding type electrode assembly structure according to another embodiment of the present invention, and FIG. 8 is a schematic diagram illustrating an arrangement combination of unit cells in the manufacturing process of the stack-folding type electrode assembly of FIG.

The example shown in FIGS. 7 and 8 is a modification of the folding sheet 120 'in comparison with the example shown in FIGS.

As shown in the figure, the folding separator sheet 120 'includes a separating membrane fabric 127, a coating layer 126 including a negative electrode inorganic material and a binder formed on one surface of the separating membrane fabric 127, And a coating layer 128 including a positive electrode active material and a binder. At this time, a coating layer 128 including a negative electrode for a positive electrode and a binder and a negative electrode for a C type bi-cell 110 and quad cells 111 and 112 is disposed in a coating layer 126 including an inorganic material for a negative electrode and a binder. The anode of the C type bi-cell 110 and the quad cells 111 and 112 are placed.

The separator fabric 127 may be formed of fibers, preferably polyamides, polyacrylonitriles, polyesters such as polyethylene terephthalate (PET) and / or polyolefins such as polyethylene (PE) or polypropylene (PP) Fibers selected from glass fibers or ceramic fibers. Preferably, the polymer may include polymer fibers having a melting point exceeding 100 캜 and a melting point exceeding 110 캜. In addition, the separator fabric 127 and / or coating layers 126 and 128 may preferably comprise Li ₂ CO ₃ , Li ₃ N or LiAlO ₃ . The ion conductivity through the folding separator sheet 120 'can be thereby preferably increased. Inorganic material to form the coating layer 126, 128 may include _{SiO 2, Al 2 O 3,} ZrO 2 or SiC.

According to the present invention, as shown in FIG. 8, the electrode alignment direction of the unit cells is not required to be arranged by the alternate orientation method, The negative electrode of all the unit cells may be arranged so as to be placed on the coating layer 126 including the inorganic material for the negative electrode of the folding separator sheet 120 'and the binder, and then rolled, thereby simplifying the manufacturing process, .

The folding separator sheet 120 'is a separation membrane coated with a binder and an inorganic material to improve the performance of the secondary battery cell. The negative electrode of the unit cells is always placed in the coating layer 126 including the inorganic material for the negative electrode and the binder, And the anode of the unit cells are always placed in the coating layer 128 including the binder, the asymmetric separator effect can be maximized.

As described above, the stack-folding electrode assembly according to the present invention includes at least two quad cells having an anode / separator / cathode / separator / anode / separator / cathode structure as a unit cell, / Separator / anode / separator / cathode structure. As the total number of unit assemblies decreases at the same number of electrodes, the number of times of lamination can be reduced, and the number of folding decreases and design freedom increases due to the decrease in unit assembly.

Hereinafter, the degree of freedom of design increase and the cell designing step of the present invention will be described in more detail.

Fig. 9 illustrates possible examples when the number of stacks is three or more in an electrode assembly according to the present invention. (a) to (d), the number of quad cells increases by two. This is based on the result of a cell design in which the number of electrodes is increased by eight while adding two quad cells based on an electrode assembly including two quad cells and one C type bi-cell as shown in (a). Table 1 shows the number of stacks and the number of electrodes in the electrode assembly according to the present invention.

Number of stacks (Examples) 3 5 7 9
Electrode number (example) 11 19 27 35
Stack count converted to conventional electrode assembly 3.67 (*) 6.33 (*) 9.00 11.67 (*)

In the present invention, (a) to (d) are converted into the stack number of the conventional stack-folding electrode assembly, as shown in Table 2, 3.67, 6.33, 9.00, and 11.67. As indicated by an asterisk (*), 3.67, 6.33, and 11.67 are the number of stacks that can not be implemented in a conventional stack-folding electrode assembly (Figs. 1 and 2) As described above, according to the present invention, the degree of freedom of cell design is increased.

As described above, according to the present invention, since the number of stacks that can not be realized by the conventional method is realized, not only the degree of freedom in design is high, but also the number of stacks is reduced even when the number of electrodes is the same, thereby reducing the number of times of lamination and folding In Table 1, the actual number of stacks is 7, and the number of stacks converted into the existing structure is larger than 9). Accordingly, the folding dimensional tolerance and the defective ratio can be reduced, and the lamination and folding process time can be reduced. In addition, since the unit cells constituting the electrode assembly are one C-type bi-cell and the remainder are quad-cells, the cell manufacturing efficiency is higher than that of the conventional manufacturing method considering cell type change. The asymmetric separator is applied to further improve the battery characteristics.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the appended claims.

110 ... C type bi-cell 111, 112 ... quad cell
120, 120 '... folding separator sheet 125 ... tape

Claims (11)

The present invention relates to an electrode assembly having a structure in which quad cells of an anode / separator / cathode / separator / anode / separator / cathode structure are superimposed and continuous folding separator sheets are interposed therebetween, Wherein the C-type bi-cell of the cathode / separator / anode / separator / cathode structure is located, and the folding separator sheet is an asymmetric separator having different properties on both surfaces. The stack-folding electrode assembly of claim 1, wherein the cathode is located at an outermost periphery of the electrode assembly. The folding separator sheet according to claim 1, wherein the folding separator sheet has a unit length capable of wrapping the quad cells, and is folded inward for each unit length and starts from the center C type bi-cell and continuously surrounds the quad cell at the outermost periphery Wherein the stacked electrode assembly is a stacked electrode assembly. The method according to claim 1,
Wherein the quad cells located above and below the central C type bi-cell are symmetrical with respect to their electrode directions. The foldable sheet according to claim 1,
Membrane fabric;
A coating layer including an inorganic material for a negative electrode and a binder formed on one surface of the separator; And
And a coating layer comprising an inorganic material for a positive electrode and a binder formed on the other surface of the separation membrane raw material,
The cathode of the C type bi-cell and the quad cells is placed in the coating layer including the inorganic material for the anode and the binder, and the anode of the C type bi-cell and the quad cells is placed in the coating layer including the inorganic material for the anode and the binder Wherein the stacked electrode assembly is a stacked-type electrode assembly. The foldable sheet according to claim 1,
A first separation membrane and a second separation membrane,
The cathode of the C type bi-cell and the quad cells is placed in one of the first separator and the second separator, and the anode of the C type bi-cell and the quad cells is placed in the other of the first separator and the second separator. Wherein the stacked-folded electrode assembly comprises: A secondary battery comprising a stack-folding type electrode assembly according to claim 1. A method of manufacturing a stack-folding type electrode assembly according to claim 1,
Placing the central C type bi-cell at the first end of the folding separator sheet and continuously positioning the quad cells at predetermined intervals; And
Folding the central C type bi-cell into the folding separator sheet once, folding the folding separator sheet to the outside where adjacent quad cells are located, and folding each quad cell, Type electrode assembly. 9. The method of claim 8, wherein a cathode is positioned at an outermost periphery of the electrode assembly. The foldable sheet as claimed in claim 8,
Membrane fabric;
A coating layer including an inorganic material for a negative electrode and a binder formed on one surface of the separator; And
And a coating layer comprising an inorganic material for a positive electrode and a binder formed on the other surface of the separation membrane raw material,
Wherein the negative electrode of the C type bi-cell and the quad cell is positioned and wound on the coating layer including the negative electrode inorganic material and the binder. The foldable sheet as claimed in claim 8,
A first separation membrane and a second separation membrane,
Wherein the cathodes of the C-type bi-cell and the quad cells are positioned and wound on any one of the first separator and the second separator.

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