KR20090008075A - Stack/folding-typed electrode assembly of noble structure and method for preparation of the same - Google Patents

Abstract

An electrode assembly is provided to show the performance and safety equal to a conventional stack / folding type electrode assembly and to ensure excellent operation performance and safety even in the long-term use. An electrode assembly is interposed with successive separation film sheets to a part where a plurality of electrochemical cells as a basic unit of an anode/separation film/cathode structure are overlapped. A unit electrode(200) surrounded with a separation film sheet is positioned at a central part which is a winding starting point(101) among the overlapped electrochemical cells. The full cells(201,202,203,204) positioned at the top and bottom of the unit electrode has an electrode direction of a symmetrical structure.

Description

Stack / folding-typed Electrode Assembly of Noble Structure and Method for Preparation of the Same}

The present invention relates to a novel stack / foldable electrode assembly and a method of manufacturing the same, and more particularly, to a plurality of electrochemical cells in which a full cell of an anode / separator / cathode structure is a basic unit. In the electrode assembly having a structure in which a continuous separator sheet is interposed in each overlapping portion, a unit electrode wrapped with a separator sheet is positioned at a central portion of the overlapping electrochemical cells, which is a winding start point. Each of the full cells located above and below relates to an electrode assembly having a structure in which the electrode directions thereof are symmetrical with each other.

As technology development and demand for mobile devices increase, the demand for batteries as energy sources is rapidly increasing, and accordingly, many studies on batteries that can meet various demands have been conducted.

Representatively, there is a high demand for rectangular secondary batteries and pouch secondary batteries, which can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and lithium ion batteries with high energy density, discharge voltage, and output stability in terms of materials. There is a high demand for lithium secondary batteries such as lithium ion polymer batteries.

In addition, secondary batteries are classified according to the structure of the electrode assembly having a cathode / separation membrane / cathode structure. Representatively, a jelly having a structure in which long sheet-shaped anodes and cathodes are wound with a separator interposed therebetween -Roll (electrode) electrode assembly, a plurality of positive and negative electrodes cut in a unit of a predetermined size is divided into a stacked (stacked) electrode assembly sequentially stacked with a separator.

However, these conventional electrode assemblies have some problems.

First, since the jelly-roll electrode assembly is wound around a long sheet-like anode and cathode in a dense state to form a cylindrical or oval structure in cross section, stress caused by expansion and contraction of the electrode during charge and discharge accumulates inside the electrode assembly. If the stress accumulation exceeds a certain limit, deformation of the electrode assembly occurs. Due to the deformation of the electrode assembly, the spacing between the electrodes is non-uniform, leading to a problem that the performance of the battery is sharply lowered and the safety of the battery is threatened due to internal short circuit. In addition, since the long sheet-type positive electrode and the negative electrode must be wound, it is difficult to quickly wind the coil while keeping the distance between the positive electrode and the negative electrode, which also has a problem in that the productivity is lowered.

Second, since the stack type electrode assembly has to stack a plurality of positive and negative electrode units in sequence, the electrode plate transfer process is required separately for manufacturing the unit, and the productivity is low because a lot of time and effort are required for the sequential lamination process. Has a problem.

In order to solve this problem, the electrode assembly of the advanced structure in the mixed form of the jelly-roll type and the stack type, the bi-cell (full cell) or the full cell in which the positive electrode and the negative electrode of a predetermined unit laminated with a separator; Stacked / foldable electrode assemblies have been developed in which full cells are wound using a continuous membrane sheet of long length, which is disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059 and 2001. -0082060 and the like.

1 and 2 schematically show an exemplary structure and manufacturing process of such a stack / foldable electrode assembly.

Referring to these drawings, as a unit cell, a plurality of full cells 10, 11, 12, 13, 14... Where the anode / separation membrane / cathode is sequentially arranged are superimposed, and each membrane overlaps the membrane sheet 20. Is interposed. Separator sheet 20 has a unit length to wrap the full cell, bend inward for each unit length, starting from the center full cell 10 to the outermost full cell 14 to surround each full cell in succession of the full cell Intervened in The end of the separator sheet 20 is finished by heat fusion or by attaching an adhesive tape 25 or the like.

The stack / foldable electrode assembly may, for example, arrange full cells 10, 11, 12, 13, 14... On a long separator sheet 20, and one end 21 of the separator sheet 20. It is prepared by winding up sequentially starting at.

At this time, the arrangement combination of the full cells as the unit cell, the first full cell 10 and the second full cell 11 is located at a distance separated by a width interval corresponding to at least one full cell, so that the first in the winding process After the outer surface of the full cell 10 is completely coated with the separator sheet 20, the bottom electrode of the first full cell 10 is in contact with the top electrode of the second full cell 11.

Since the coating lengths of the separator sheets 20 increase in the subsequent lamination process by winding the full cells 11, 12, 13, 14... After the second full cell, the interval between them increases sequentially in the winding direction. Is arranged.

In addition, when winding the full cells, the anode and the cathode should be configured to face each other at the stacked interface. The first full cell 10 and the second full cell 11 are full cells in which the upper electrode is the anode, and the third full cell 12 ) Is a full cell in which the top electrode is a cathode, the fourth full cell 13 is a full cell in which the top electrode is an anode, and the fifth full cell 14 is composed of a full cell in which the top electrode is a cathode. That is, except for the first full cell 10, the upper electrode has a sequential arrangement in which a full cell whose anode is an anode and a full cell whose cathode is an upper surface electrode are alternated. Although not shown, when the unit cell is a bicell, the bicells are mounted in an arrangement in which two cells are alternately arranged.

Therefore, the stack / foldable electrode assembly substantially compensates for the disadvantages of the jelly-roll and the stacked electrode assembly, but in order to be stacked so that the electrodes are opposite to each other at the contact interface between the unit cells, the unit cell bicell or Since the full cell must be mounted according to a predetermined rule by dividing the full cells, there is a problem that the manufacturing process becomes complicated and productivity is lowered. Moreover, it is very difficult to distinguish the unit cells by type, so that if one of the unit cells is missing or misplaced due to various reasons such as inadvertent operation or errors in the process of mounting on the separator sheet, the same polarity When the electrode having the contact with each other at the interface there is a fear that the performance of the battery.

To sum up the above, the stack / folding electrode assembly is preferable in terms of the operation performance and safety of the battery, but the above problems exist in terms of productivity. There is a growing need for an electrode assembly that can provide.

In particular, large battery modules used in medium and large devices such as electric vehicles and hybrid electric vehicles, which have recently attracted a lot of attention, require a large number of battery cells (unit cells) and their long life characteristics are required for their manufacture. There is an urgent need for an electrode assembly having a new structure that solves all of the above problems.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After various experiments and in-depth studies, the inventors of the present application use a full cell as a unit cell and have a separator sheet interposed at an overlapping portion of the unit cells. It has led to the development of a novel electrode assembly with this structure, which can be manufactured with high productivity while exhibiting the performance and safety of a battery comparable to that of a conventional stack / folding electrode assembly. Furthermore, the inventors have found that they can provide excellent operating performance and safety even in prolonged use, and have completed the present invention.

In the electrode assembly according to the present invention, a plurality of electrochemical cells in which a full cell of a cathode / membrane / cathode structure is a basic unit are overlapped, and each electrode overlaps with a continuous separator sheet. In the center portion of the overlapping electrochemical cells, the winding unit is located in the center portion of the unit electrode wrapped with a separator sheet, the full cells positioned respectively up and down around the unit electrode has a structure in which the electrode direction is symmetrical with each other It is.

In some cases, a bi-cell ('type A bi-cell') or ii) a cathode having an anode / separation membrane / cathode / separation membrane / anode structure is surrounded by a separator sheet at the center of the overlapping electrochemical cells. A bicell ('C-type bicell') having a / membrane / anode / separation membrane / cathode structure is located, and the full cells positioned above and below the bicell may be symmetrical with each other.

This novel structure of the electrode assembly is a stack / folding structure can effectively use the space, and in particular can maximize the content of the electrode active material can implement a battery of high density. Furthermore, the manufacturing process can be performed by arranging on the separator sheet so that all the unit cells have the same electrode alignment direction without winding the electrode alignment directions of the unit cells in a predetermined unit. Simplification can greatly improve production efficiency.

In one preferred embodiment, the separator sheet has a unit length to wrap the electrochemical cell, bent inward for each unit length to wrap in the separator sheet continuously starting from the central unit electrode or bicell to the outermost full cell Can be. Conventionally, if the interface contact between the electrode and the separator sheet is not maintained as the battery is repeatedly charged and discharged, the capacity and performance of the battery are drastically deteriorated. Thus, the pressure for stably compressing the interface to maintain contact continuously This is necessary. In this regard, the electrode assembly of the structure as described above, as the full cell is stacked, the separator sheet is interposed so that not only the electrode between the full cells can be used efficiently, but also the pressure generated when winding the separator sheet to form all the cells. Since the interface between the electrode and the separator sheet can be pressed, it is very excellent in terms of battery performance and capacity.

In the present invention, a unit electrode or a bicell is positioned at the central portion of the winding start point, and the remaining basic units except for this are full cells.

The unit electrode means an electrode of one object having a positive electrode or a negative electrode structure. The bicell refers to a cell in which the same electrode is positioned on both sides of the cell, such as a unit structure of an anode / separator / cathode / separator / anode and a unit structure of a cathode / separator / anode / separator / cathode. As a representative example thereof is disclosed in FIG. 3, in the present specification, a cell having an anode / separation membrane / cathode / separation membrane / anode structure, that is, a cell in which anodes are positioned at both sides is referred to as a “type A bicell” and a cathode / separation membrane. The cell of the anode / separation membrane / cathode structure, that is, the cell in which the cathodes are located at both sides is called a 'C-type bicell'. Such bicells are not particularly limited in number if the electrodes on both sides of the cell have the same structure.

The full cell, which is a basic unit, is not particularly limited as long as the top electrode and the bottom electrode of the cell are opposite electrodes, for example, i) an anode / separator / cathode, or ii) an anode / separator / cathode / separator / Laminated structure of an anode / a separator / an anode, etc. are mentioned. The number of full cells wound up on the separator sheet may be determined by various factors such as the structure of each full cell and a desired capacity of the final manufactured battery, and may be preferably 6 to 30.

On the other hand, when a plurality of full cells are stacked in a cathode / cathode facing structure, the negative electrode occupies as much area as possible, for example, when used in a lithium secondary battery, lithium metal or the like grows dendritic on the negative electrode during charge and discharge. The phenomenon of (dendrite) can be suppressed as much as possible.

Therefore, in one preferred example for this, when the unit electrode is located in the central portion that is the winding start point is preferably a negative electrode, when the bi-cell is located the C-type bi-cell is preferred.

In another preferred example, the cathode may be configured in the uppermost layer and the lowermost layer respectively forming the outer surface of the electrode assembly. For example, when the anode or the A-type bi-cell is located in the central portion which is the starting point of the winding, it is preferable that the C-type bi-cell is laminated on the uppermost layer and the lowermost layer, respectively, which form the outer surface of the electrode assembly.

The full cells are placed on the separator sheet having a long length and then wound in a structure in which the separator sheet is interposed therebetween. Each full cell should be laminated so that the anode and the cathode face each other while the separator film is interposed therebetween.

The separator sheet may have an extended length surrounding the electrode assembly once after winding up, and the outermost end of the separator sheet may be fixed by heat fusion or tape. For example, a thermal welder or a hot plate is brought into contact with the finished separator sheet so that the separator sheet itself is melted by heat and adhesively fixed. This enables stable interfacial contact between the electrode and the separator sheet, allowing the pressure to be maintained continuously.

If the separator interposed between the anode and the cathode of the separator sheet or cell is an insulating structure and a porous structure capable of moving ions, the material thereof is not particularly limited, and the separator and the separator sheet may or may not be the same material. It may be.

As the separator or the separator sheet, for example, an insulating thin film having high ion permeability and mechanical strength may be used, and the pore diameter of the separator or the separator sheet is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. As such a separator or a separator sheet, For example, Olefin-type polymers, such as chemical-resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator. Preferably, the multilayer film or polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or poly film produced by polyethylene film, polypropylene film, or a combination of these films It may be a polymer film for polymer electrolyte or gel polymer electrolyte, such as a vinylidene fluoride hexafluoropropylene (polyvinylidene fluoride hexafluoropropylene) copolymer.

It is preferable that the separator has an adhesive function by thermal fusion to form a full cell or a bicell, and the separator sheet does not necessarily have such a function, but an adhesive function is used to easily perform a winding process. It is desirable to. In one preferred embodiment, the separator and / or the separator sheet is a microporous first polymer layer and polyvinylidene fluorine described in Korean Patent Application No. 1999-57312, which is a prior application of the inventors having an adhesive function by thermal fusion. A polymer film for polymer electrolyte comprising a gelling second polymer layer of a lide-chlorotrifluoroethylene copolymer can be used. The contents of this application are incorporated into the contents of the present invention by reference.

The unit electrode is divided into an anode or a cathode, and the full cell and the bicell are manufactured by mutually bonding the anode and the cathode with a separator interposed therebetween. The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder onto a positive electrode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture.

The positive electrode current collector is generally made to a thickness of 3 to 500 ㎛. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

When the positive electrode active material is a lithium secondary battery, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

The conductive material is typically added in an amount of 1 to 50% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding the active material and the conductive material to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials, such as glass fiber and carbon fiber, are used.

On the other hand, the negative electrode is prepared by coating, drying and pressing the negative electrode active material on the negative electrode current collector, and optionally, the conductive material, binder, filler, etc. may be further included as necessary.

The negative electrode current collector is generally made of a thickness of 3 ~ 500 ㎛. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like, aluminum-cadmium alloy, and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode active material may be, for example, carbon such as hardly graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ _x ≦ 1), Li _x WO ₂ (0 ≦ _x ≦ 1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The electrode assembly according to the present invention can be applied to an electrochemical cell that produces electricity by the electrochemical reaction of the positive electrode and the negative electrode, a representative example of the electrochemical cell, a super capacitor (super capacitor), ultra capacitor (ultra capacitor) ), Secondary batteries, fuel cells, various sensors, electrolysis devices, electrochemical reactors, and the like, and secondary batteries are particularly preferred.

The secondary battery has a structure in which the electrode assembly capable of charging and discharging is embedded in a battery case in a state impregnated with an ion-containing electrolyte solution. In one preferred embodiment, the secondary battery may be a lithium secondary battery.

Recently, a lithium secondary battery has attracted much attention as a power source for a large mobile device as well as a small mobile device, and it is desirable to have a small weight when applied to such a field. As one way to reduce the weight of the secondary battery, a structure in which the electrode assembly is incorporated in a pouch type case of an aluminum laminate sheet may be preferable. Since such a lithium secondary battery is known in the art, the description thereof will be omitted.

In addition, as described above, when used as a power source for a medium-to-large device, a secondary battery having a structure capable of minimizing the deterioration of operation performance even during long-term use, having excellent life characteristics, and capable of mass production at low cost is preferable. In this regard, the secondary battery including the electrode assembly of the present invention may be preferably used in a medium-large battery module having the unit cell.

The medium-large battery module is configured to provide a high output capacity by connecting a plurality of unit cells in series or in series / parallel manner, which is well known in the art, and thus, description thereof is omitted herein.

The present invention also provides a method of manufacturing an electrode assembly having a structure in which a plurality of electrochemical cells in which a full cell of an anode / separation membrane / cathode structure is a basic unit are overlapped, and a separator sheet is interposed in each overlapping portion.

1) stacking a long length of the positive electrode sheet and the negative electrode sheet with the separator interposed, and cut to a predetermined size to produce a plurality of full cells;

2) placing the unit electrodes of the positive electrode or the negative electrode at the first end of the long-length separator sheet, and the full cells (first full cell, second full cell, third) prepared in step 1) at predetermined intervals from the second end Positioning the full cell…) in the same electrode orientation manner; And

3) winding the unit electrode once with a separator sheet, and folding the separator sheets from the first full cell to the outside where the adjacent full cell is located, and folding each of the full cells overlapping each other;

It provides a method for producing an electrode assembly comprising a.

In some cases, the A-type bi-cell or the C-type bi-cell may be placed in the first stage of the separator sheet,

1) stacking a long length of the positive electrode sheet and the negative electrode sheet with the separator interposed, and cut to a predetermined size to produce a plurality of full cells;

2) full cell (first full cell), which is a unit cell manufactured in step 1) by placing an A-type bicell or a C-type bicell on the first end of the membrane sheet having a long length, and at a predetermined interval from the second end; Positioning the second full cell, the third full cell…) in the same electrode orientation manner; And

3) winding the bicell once with a separator sheet, and then folding the separator sheets from the first full cell to the outside where the adjacent full cells are located, and then folding and folding each full cell;

It may be prepared by a process comprising a.

As described above, in manufacturing a conventional stack / foldable battery, it is necessary to distinguish the type of the unit cell and to arrange the electrode alignment directions of the unit cells in an alternating alignment manner at predetermined intervals. If any one of the unit cells is missing or misplaced due to an unexpected mistake, there is a concern that the performance of the battery may be deteriorated by the contact of electrodes having the same polarity at the interface.

However, according to the method of manufacturing an electrode assembly of the present invention, as described below, the full cells in which the electrodes are located after the second end are opposite to the unit electrode or the bottom electrode of the bicell located in the first end of the separator sheet. By arrange | positioning in the same electrode orientation system so that the electrode used may become an upper surface, it is not necessary to change the electrode orientation direction of the full cell which is a unit cell. That is, since the full cells may be manufactured by winding the full cells on the separator sheet in the same electrode alignment method, the production process may be simplified to greatly improve the production efficiency, and as described above, may occur due to mistakes during work. It is possible to solve the problem of deterioration of battery performance.

In one preferred example, the method may further include attaching the unit electrode or bicell and the full cells positioned in the step 2) on the separator sheet before winding to facilitate the winding of the cells on the separator sheet. Can be. Such attachment may preferably be achieved by thermal fusion. For example, lamination is easy due to low TG (glass temperature), so that polymers such as PVDF, HFD, PMMA, PEO, and PMMA, which are electrochemically stable in the 0 to 5 V potential range, are dissolved in a predetermined solvent. It can be achieved by preparing a binder-coated separator sheet by applying the solution to the separator and then drying, mounting a unit electrode or cells on the separator sheet, and then applying a predetermined pressure and heat. The binder-coated separator sheet may be used as a separator material of the cell itself, and the binder-coated separator serves to help the full cells maintain the stacked structure in the manufacturing process of the electrode assembly by the bonding force with the electrode. can do.

In the step 2), since the full cells are placed on the separator sheet having a long length, the overlap part is wound in a structure in which the separator sheet is interposed therebetween, so that the electrodes having opposite polarities face each other at the interface of the full cells. Each of the full cells is arranged in the same electrode alignment manner so that such a structure can be formed. Specifically, the full cells are formed of the first electrode of the separator sheet or the lower electrode of the bi-cell and the opposite electrode of the full cell. Position it so that it is In this winding method, the bottom electrode of the first full cell and the top electrode of the third full cell have opposite electrode relationships, and the electrode relationship of which the bottom electrode of the second full cell and the top electrode of the fourth full cell are opposite to each other The winding of the lower surface of the third full cell and the electrode of the upper surface of the fifth full cell has an electrode relationship opposite to each other.

In one preferred embodiment, at least the width of the unit electrode is between the end of the separator sheet where the winding is started in step 2) and the unit electrode or bicell, or between the unit electrode or bicell and the first full cell. And the thicknesses may be spaced apart by the sum of the distances, and the full cells of the second full cell or more may be spaced apart by the sum of the thicknesses of the thicknesses of the full cell and the thickness of the increasing film.

Accordingly, the unit electrode or bicell is overlapped with the first full cell in a state in which the unit electrode or bicell is wound and wrapped with a separator sheet once, and is disposed on an upper surface of the first full cell and an electrode disposed on the upper surface of the unit electrode or bicell. The separator sheet is interposed therebetween.

In order to suppress dendritic growth as described above, the bottom electrode of the n-th cell and the bottom electrode of the n-th cell, which form the outer surface of the electrode assembly, that is, the upper surface and the lower surface, respectively, are composed of a cathode. It is desirable to.

In one preferred example, the bottom electrode of the unit cell (n-th cell) positioned at the last end of the separator sheet and the bottom electrode of the n-1 cell adjacent to the n-th cell are respectively configured to be cathodes. Can be. In a specific example, when the anode or the A-type bi-cell is located at the first end on the separator sheet, the n-th cell and the n-th cell may be a C-type bicell.

Hereinafter, the content of the present invention will be described with reference to the drawings according to some embodiments of the present invention, but the scope of the present invention is not limited thereto.

4 and 5 are schematic views of the electrode assembly structure according to the embodiments of the present invention.

Referring to these drawings, unit electrodes 200 and 300 or bi-cells (not shown) wrapped with a separator sheet may be positioned at a central portion of the overlapping full cells, which are winding start points 101, based on this. As a result, full cells, which are unit cells located in the upper and lower parts, have a symmetrical structure. The distal end of the separator sheet 100 may be finished by, for example, heat fusion bonding or an adhesive tape 105. First, FIG. 4 illustrates a structure of an electrode assembly in which a cathode 200 is positioned at a central portion of a winding start point 101 according to a first embodiment of the present invention, and includes full cells positioned on an upper portion of the cathode 200. The 202 and 204 and the full cells 201 and 203 positioned at the lower portion have a symmetrical structure.

5 is a schematic diagram of an electrode assembly structure according to a second embodiment of the present invention. As a structure in which the anode 300 is positioned at the center of the winding start point 101, as shown in FIG. 4, the full cells 302 and 304 positioned above the anode 300 and the full cells positioned below the cathode 300 are positioned. 301 and 303 have a symmetrical structure with each other. The cells 303 and 304 located at the top and bottom layers respectively forming the outer surface of the electrode assembly may be full cells of a symmetrical structure (not shown), but the dendrite is grown at the cathode by configuring the cathode to occupy a large area. It can also be configured as a type A bicell in order to suppress the phenomenon.

6 to 8 are schematic views showing the manufacturing process of the electrode assembly using the unit electrode and the full cell according to an embodiment of the present invention.

Referring to these drawings, the separator sheet 100 is a long sheet-like film and has a porous structure, such as a separator of a full cell, and may have an extended length wrapping the electrode assembly once after winding. A unit electrode or a bicell is positioned at the first end in the longitudinal direction of the separator sheet 100, and each full cell is arranged at the second end.

First, a process of manufacturing the electrode assembly of FIG. 4 is schematically illustrated in FIG. 6. Looking at the arrangement of the unit electrode 200 and the full cells 201, 202, 203, 204..., The unit electrodes 200 are arranged at one end 101 of the separator sheet 100 where the folding starts. Then, the first full cell 201 is arranged at a position spaced apart by the length L corresponding to the sum of the width and the thickness of the unit electrode. In the separation process L between the unit electrode 200 and the first full cell 201, the first surface of the unit electrode 200 is completely coated with the separator sheet 100 during the first winding. The lower surface of the unit electrode 200 is wound on the top of the first full cell 201 in a state where the separator sheet 100 is interposed by the winding. The upper surface of the electrode 200 is in contact with the upper surface electrode (anode) of the second full cell 202 in a state where the separator sheet is interposed.

Referring to FIG. 7 as another example of manufacturing the electrode assembly of FIG. 4, the length corresponding to the sum of the width and thickness of the unit electrode 210 at one end 101 of the separator sheet 100 at which folding starts is performed. The unit electrodes 210 are arranged at positions spaced by the length L '. The separation portion L 'between the one end 101 of the separator sheet 100 and the unit electrode 210 is completely coated with the separator sheet 100 when the outer surface of the unit electrode 210 is wound once. When wound in this state, it is a portion that faces the top electrode of the first full cell 211. That is, the separation portions L and L ′ for maintaining the electrical separation between the unit electrodes 200 and 210 and the full cell may be positioned before or after the unit electrodes 200 and 210.

Referring back to FIG. 6, the full cells 201, 202, 203, 204..., Of the first full cell or more are positioned to sequentially increase spaced apart by the sum of the thickness of the full cell and the thickness of the film that increases while winding. That is, since the coating length of the separator sheet 100 is increased in the sequential lamination process by winding, the full cells 201, 202, 203, 204 ... are arranged so that the interval therebetween is sequentially increased in the winding direction. have.

At the time of winding, each full cell is configured such that the positive electrode and the negative electrode face each other at the stacked interface. The lower electrode of the first full cell 201 (cathode) and the upper electrode of the third full cell 203 are in contact with each other. The process of contacting the bottom surface (cathode) of the second full cell 202 and the top surface electrode (anode) of the fourth full cell 204 is repeated. Therefore, when the unit electrode 200 is a cathode, each of the full cells 201, 202, 203, 204... Are arranged such that the cathode is positioned at the bottom surface.

When the unit electrode 200 and the full cells 201, 202, 203, 204... Are positioned on the separator sheet, the unit electrodes 200 and the full cells 201, 202, 203, 204. Such attachment may preferably be achieved by thermal fusion.

Meanwhile, referring to FIG. 8, the unit electrode 300 is an anode, and each of the full cells 301, 302... Is arranged such that the anode is located on the bottom surface. At this time, the bottom electrode of the cell 300n in the final position and the bottom electrode of the cell 300n-1 adjacent to each other form an outer surface in the electrode assembly, and instead of the full cell in the final position and the adjacent position so as to be the cathode The A-type bicell may be arranged to be positioned.

9 and 10 are schematic views showing a process of manufacturing an electrode assembly using bi-cells and full cells according to the third and fourth embodiments of the present invention.

Referring to these drawings, bicells 400 and 500 are arranged at one end 101 of the separator sheet 100 at which folding starts. Then, the first full cell 401 is arranged at a position spaced apart by a length corresponding to the combined length and width of the bicells 400 and 500. The spaced portion between the bicells 400 and 500 and the first full cell 401 may be formed in a winding process, in which the outer surface of the bicells 400 and 500 is completely coated with the separator sheet 100 during one winding. 1 This is a portion that faces the top electrodes of the full cells 401 and 501. Full cells below the first full cell are sequentially stacked without having a width gap between the full cells, and each full cell 401, 402, 403 when the A-type bicell 400 is positioned at the first end of the separator sheet 100. , 404... Are arranged such that the cathode is located on the bottom surface. On the other hand, when the C-shaped bi-cell 500 is located at the first end of the separator sheet 100, each of the full cells (501, 502 ...) is arranged so that the anode is located on the bottom surface, in this case the separator sheet The A-type bicells 500n and 500n−1 may be arranged at the final position of the 100 and adjacent positions thereof instead of the full cell.

6 to 9, according to the present invention, since the full cells as the basic unit are wound in a state where the electrodes thereof are placed in the separator sheet so that the electrodes face the same direction, the work process is simple and the productivity of the battery is increased. Can be.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the electrode assembly according to the present invention can be produced with high productivity while exhibiting the performance and safety of a battery comparable to that of a conventional stack / folding electrode assembly, and furthermore, excellent operating performance and safety even in long-term use. Can be provided.

1 is a schematic diagram of an exemplary structure of a conventional stack / foldable electrode assembly;

FIG. 2 is a schematic diagram illustrating an arrangement combination of unit cells in a manufacturing process of the stack / foldable electrode assembly of FIG. 1; FIG.

3 is a schematic diagram of one exemplary C-type and A-type bicell that can be used as a bicell in an electrode assembly according to the present invention;

4 is a schematic diagram of a structure of an electrode assembly according to a first embodiment of the present invention;

5 is a schematic diagram of a structure of an electrode assembly according to a second embodiment of the present invention;

6 is a schematic diagram of a process of manufacturing the electrode assembly of FIG. 4 according to one embodiment of the present invention;

7 is a schematic diagram of a process of manufacturing the electrode assembly of FIG. 4 according to another embodiment of the present invention;

8 is a schematic diagram of a process of manufacturing the electrode assembly of FIG. 5 in accordance with one embodiment of the present invention;

9 is a schematic diagram of a process of manufacturing an electrode assembly according to a third embodiment of the present invention;

10 is a schematic diagram of a process of manufacturing an electrode assembly according to a fourth embodiment of the present invention.

Claims (22)

In an electrode assembly having a structure in which a full cell of a cathode / membrane / cathode structure is a basic unit and a plurality of electrochemical cells overlap each other, and a continuous separator sheet is interposed in each overlapping portion, the overlapped electrochemical cells A unit electrode wrapped in a separator sheet is positioned at the center of the winding start point, and the full cells positioned above and below the unit electrode are symmetrical with respect to their electrode directions. In an electrode assembly having a structure in which a full cell of a cathode / membrane / cathode structure is a basic unit and a plurality of electrochemical cells overlap each other, and a continuous separator sheet is interposed in each overlapping portion, the overlapped electrochemical cells In the middle of the winding start point, the cell is surrounded by a membrane sheet; i) bipolar / membrane / cathode / membrane / bipolar bicell ('type A bicell') or ii) An electrode assembly having a structure in which a cell ('C-type bicell') is located, and full cells positioned up and down about the bicell have their electrode directions symmetric to each other. 3. The separator according to claim 1 or 2, wherein the separator sheet has a unit length for wrapping an electrochemical cell, and the membrane sheet is folded inward for every unit length and starts continuously from the central unit electrode or bicell to the outermost full cell. Electrode assembly with a structure wrapped in a sheet. The electrode assembly according to claim 1 or 2, wherein the full cell has i) an anode / separator / cathode structure, or ii) an anode / separator / cathode / separator / anode / separator / cathode structure. The electrode assembly according to claim 1 or 2, wherein the unit electrode or bicell located at the central portion of the winding start point is a cathode or a C-type bicell. The electrode assembly according to claim 1 or 2, wherein a cathode is positioned at an uppermost layer and a lowermost layer, each of which forms an outer surface of the electrode assembly. 7. The electrode assembly according to claim 6, wherein in the case where the anode or the A-type bicell is located at the center of the winding start point, the C-type bicell is stacked on the uppermost layer and the lowermost layer, respectively. The electrode assembly according to claim 1 or 2, wherein the outermost end of the separator sheet is fixed by heat fusion or tape. The method according to claim 1 or 2, wherein the separator or separator sheet is a multilayer film made by a polyethylene film, a polypropylene film, or a combination of these films including fine pores, and polyvinylidene fluoride, polyethylene oxide, An electrode assembly selected from the group consisting of a polymer film for polymer electrolyte of polyacrylonitrile or polyvinylidene fluoride hexafluoropropylene copolymer. The electrode assembly of claim 1 or 2, wherein the positive electrode is an electrode coated with a positive electrode material on both sides of the positive electrode current collector, and the negative electrode is an electrode coated with a negative electrode material on both sides of the negative electrode current collector. A secondary battery comprising the electrode assembly according to claim 1 or 2. The secondary battery of claim 11, wherein the battery is a lithium secondary battery. Medium and large battery module comprising a secondary battery according to claim 12 as a unit cell. A method of manufacturing an electrode assembly having a structure in which a plurality of electrochemical cells in which a full cell of a cathode / membrane / cathode structure is a basic unit is superimposed and a separator sheet is interposed therebetween, 1) stacking a long length of the positive electrode sheet and the negative electrode sheet with the separator interposed, and cut to a predetermined size to produce a plurality of full cells; 2) placing the unit electrodes of the positive electrode or the negative electrode at the first end of the long-length separator sheet, and the full cells (first full cell, second full cell, third) prepared in step 1) at predetermined intervals from the second end Positioning the full cell…) in the same electrode orientation manner; And 3) winding the unit electrode once with a separator sheet, and folding the separator sheets from the first full cell to the outside where the adjacent full cell is located, and folding each of the full cells overlapping each other; Method of manufacturing an electrode assembly comprising a. A method of manufacturing an electrode assembly having a structure in which a plurality of electrochemical cells in which a full cell of a cathode / membrane / cathode structure is a basic unit is superimposed and a separator sheet is interposed therebetween, 1) stacking a long length of the positive electrode sheet and the negative electrode sheet with the separator interposed, and cut to a predetermined size to produce a plurality of full cells; 2) Full cell (first full cell, second full cell) prepared in step 1) by placing A-type bicell or C-type bicell at the first end of the long-length separator sheet and at a predetermined interval from the second end Positioning the third full cell…) in the same electrode orientation manner; And 3) winding the bicell once with a separator sheet, and then folding the separator sheets from the first full cell to the outside where the adjacent full cells are located, and then folding and folding each full cell; Method of manufacturing an electrode assembly comprising a. 16. The method of claim 14 or 15, further comprising attaching the unit electrode or bicell and the full cells positioned in the step 2) onto a separator sheet before winding up. The method of claim 14 or 15, wherein in the step 2) the full cells are positioned so that the electrode opposite to the bottom electrode and the bottom electrode of the unit electrode or bicell located at the first end of the separator sheet is characterized in that the top electrode Method for producing an electrode assembly. The lower electrode of the first full cell and the upper electrode of the third full cell have opposite electrode relationships, and the lower electrode of the second full cell and the upper electrode of the fourth full cell are formed. The electrode assembly manufacturing method, characterized in that the pull cells are wound in a structure having an electrode relationship opposite to each other, the bottom surface of the third full cell and the top electrode of the fifth full cell have an opposite electrode relationship. The width and thickness of the unit electrode according to claim 14 or 15, wherein the end of the separator sheet in which the winding is started in step 2) and the unit electrode or the bicell positioned at the first end of the separator sheet are at least. Wherein the spaced apart by the sum of the distance, the full cell of the second full cell or more electrode assembly manufacturing method, characterized in that spaced apart by the distance of the sum of the thickness and the thickness of the film increasing while winding up. The method according to claim 14 or 15, wherein the unit electrode or bicell positioned at the first end of the separator sheet in step 2) and the first full cell ('first full cell') are at least the unit electrode or bi Wherein the width of the cell, and the thickness of the cell spaced apart by the distance, the full cell of the second full cell or more is a manufacturing method of the electrode assembly, characterized in that spaced apart by the distance of the sum of the thickness of the film and the increasing film thickness while winding up. The method of claim 14 or 15, wherein the bottom electrode of the unit cell (n-th cell) positioned at the last stage on the separator sheet in the step 2) and the bottom electrode of the n-1 cell adjacent to the n-th cell is Method for producing an electrode assembly, characterized in that configured to be each cathode. 22. The method of claim 21, wherein when the anode or the A-type bicell is positioned at the first end of the separator sheet, the n-th cell and the n-th cell are C-type bicells. .

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