Unit Cell Preparation Apparatus and Method

An apparatus for preparing a unit cell is provided. The apparatus includes a center electrode reel from which a center electrode sheet is unwound, wherein the center electrode sheet is configured to form a plurality of center electrodes, separator reels from which separator sheets to be stacked with the center electrodes are unwound, a laminator configured to laminate a stack which is formed by stacking the plurality of center electrodes with the separator sheets while the plurality of center electrodes are spaced apart from each other and disposed in a row in a longitudinal direction of the separator sheets, a first nozzle configured to apply an adhesive to an upper surface of the separator sheet disposed on an uppermost layer of the laminated stack, and an upper electrode reel from which an upper electrode sheet is unwound.

TECHNICAL FIELD

The present invention relates to unit cell preparation apparatus and method, and more particularly, to unit cell preparation apparatus and method which may prevent a displacement in position of an upper electrode when the upper electrode is stacked on a stack that is formed by stacking a center electrode and a separator.

BACKGROUND ART

In general, types of secondary batteries include a nickel cadmium battery, a nickel hydride battery, a lithium ion battery, and a lithium ion polymer battery. These secondary batteries are not only applied and used in small products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and E-bikes, but are also applied and used in large products requiring high output, such as electric vehicles and hybrid vehicles, and a power storage device and a power storage device for backup which store surplus generated power or renewable energy.

In order to prepare such a secondary battery, first, a positive electrode collector and a negative electrode collector are respectively coated with electrode active material slurries to prepare a positive electrode and a negative electrode, and the positive electrode and the negative electrode are then stacked on both sides of a separator to form an electrode assembly having a predetermined shape. Then, after the electrode assembly is accommodated in a battery case and an electrolyte solution is injected, the battery case is sealed.

The electrode assembly is classified into various types. For example, there are a simple stack type in which a unit cell is not prepared and positive electrodes, separators, and negative electrodes are simply crossed and continuously stacked, a lamination & stack type (L&S) in which a unit cell is first prepared using a positive electrode, a separator, and a negative electrode and these unit cells are then stacked, a stack & folding type (S&F) in which a plurality of electrodes or unit cells are spaced apart and attached to one surface of a separator sheet having a greater length in one side and the separator sheet is repeatedly folded in the same direction from one end, and a Z-folding type that alternatingly repeats a process in which a plurality of electrodes or unit cells are alternatingly attached to one surface and the other surface of a separator sheet having a greater length in one side and the separator sheet is folded in a specific direction from one end and then folded in an opposite direction.

Among them, in order to prepare the lamination & stack type (L&S) electrode assembly, first, a unit cell must be prepared. In general, in order to prepare the unit cell, separators are respectively stacked on upper and lower surfaces of a center electrode while the center electrode is moved to one side by a conveyor belt or the like, and thereafter, an upper electrode is further stacked on an uppermost end. In addition, in some cases, a lower electrode may be further stacked on a lowermost end. Then, a laminating process is performed in which heat and pressure are applied to a stack in which the electrodes and the separators are stacked. Since the laminating process is performed, the electrodes and the separators may be bonded together to firmly form a unit cell.

However, typically, the laminating process was performed after the lower separator, the center electrode, the upper separator, and the upper electrode were all stacked. Accordingly, since an overall thickness was large, heat was not transferred to the inside of the stack, and thus, there was a problem in that adhesion was reduced. Particularly, the adhesion was reduced at an interface between the innermost center electrode and the upper separator, and, accordingly, since the electrode and the separator were not adhered to each other, there was a problem in that the electrode was out of position.

DISCLOSURE OF THE INVENTION

Technical Problem

An aspect of the present invention provides unit cell preparation apparatus and method which may prevent a displacement in position of an upper electrode when the upper electrode is stacked on a stack that is formed by stacking a center electrode and separator sheets.

The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below.

Technical Solution

According to an aspect of the present invention, there is provided an apparatus for preparing a unit cell which includes: a center electrode reel from which a center electrode sheet, which is to be a plurality of center electrodes, is unwound; separator reels from which separator sheets to be stacked with the center electrodes are unwound; a laminator for laminating a stack which is formed by stacking the plurality of center electrodes with the separator sheets while the plurality of center electrodes are spaced apart from each other and disposed in a row in a longitudinal direction of the separator sheets; a first nozzle for applying an adhesive to an upper surface of the separator sheet disposed on an uppermost layer of the stack; and an upper electrode reel from which an upper electrode sheet, which is to be a plurality of upper electrodes to be stacked on an upper surface of the stack to which the adhesive has been applied, is unwound.

Also, the apparatus for preparing a unit cell may further include a first vision sensor disposed above the center electrode to photograph the center electrode before the center electrodes are stacked with the separator sheets.

Furthermore, the apparatus for preparing a unit cell may further include a second vision sensor disposed above the upper electrode to photograph the upper electrode before the upper electrode is stacked with the stack.

Also, the laminator may include a heating roller for applying heat and pressure to the stack while rotating.

Furthermore, the laminator may further include a heater for applying heat and pressure to an entire surface of the stack.

Also, the separator reels may include an upper separator reel from which an upper separator sheet to be stacked on an upper surface of the center electrode is unwound; and a lower separator reel from which a lower separator sheet to be stacked on a lower surface of the center electrode is unwound.

Furthermore, the apparatus for preparing a unit cell may further include a lower electrode reel from which a lower electrode sheet, which is to be a plurality of lower electrodes to be stacked on a lower surface of the stack, is unwound.

Also, the apparatus for preparing a unit cell may further include a second nozzle for applying an adhesive to an upper surface of the lower electrode.

Furthermore, the apparatus for preparing a unit cell may further include a third vision sensor disposed above the lower electrode to photograph the lower electrode before the lower electrode is stacked with the stack.

Also, the apparatus for preparing a unit cell may further include nip rollers which apply pressure to the upper electrode and the stack while rotating when the upper electrode is stacked with the stack.

Furthermore, the first nozzle may be provided in plurality spaced apart from each other in a width direction of the separator sheets.

Also, at least one of spraying cycle, spraying area, and spraying amount of the adhesive may be different from each other with respect to the plurality of first nozzles.

Furthermore, the upper separator sheet may include a first base material layer; and a first coating layer coated on an upper surface of the first base material layer and bonded to the upper electrode while the adhesive is applied. The lower separator sheet may include a second base material layer; and a second coating layer coated on an upper surface of the second base material layer and bonded to the center electrode. A binder content of the first coating layer may be lower than a binder content of the second coating layer.

Also, the binder content of the first coating layer may be in a range of 2 wt % to 3 wt %.

Furthermore, the second coating layer may have the binder content of 10 wt % to 20 wt % and may be a safety reinforced separator (SRS) coating layer.

Also, the upper separator sheet may include a first base material layer bonded to the upper electrode while the adhesive is applied. The lower separator sheet may include a second base material layer; and a coating layer coated on an upper surface of the second base material layer and bonded to the center electrode.

According to another aspect of the present invention, there is provided a method of preparing a unit cell which includes: cutting a center electrode sheet unwound from a center electrode reel to form a plurality of center electrodes; forming a stack by stacking the plurality of center electrodes on separator sheets unwound from separator reels while the plurality of center electrodes are spaced apart from each other and disposed in a row in a longitudinal direction of the separator sheets; laminating the stack with a laminator; applying an adhesive by a first nozzle on an upper surface of the separator sheet disposed on an uppermost layer of the stack;

cutting an upper electrode sheet unwound from an upper electrode reel to form a plurality of upper electrodes; and stacking the plurality of upper electrodes on an upper surface of the stack to which the adhesive has been applied.

Also, the method may further include photographing the center electrode with a first vision sensor disposed above the center electrode, before the forming of the stack.

Furthermore, the method may further include photographing the upper electrode with a second vision sensor disposed above the upper electrode, before the stacking of the upper electrode.

Also, the stacking of the upper electrode may stack the plurality of upper electrodes on the upper surface of the stack while the plurality of upper electrodes are spaced apart from each other and disposed in a raw in a length direction of the separator sheet.

Furthermore, the laminating may include applying heat and pressure to the stack by a heating roller while the heating roller rotates.

Also, the laminating may further include applying heat and pressure to an entire surface of the stack by a heater, before the heating roller applies the heat and the pressure.

Furthermore, when the forming of the upper electrode is performed, forming a plurality of lower electrodes by cutting a lower electrode sheet unwound from a lower electrode reel may also be performed, and, when the stacking of the upper electrode is performed, stacking the plurality of lower electrodes on a lower surface of the stack may also be performed.

Also, when the applying of the adhesive on the upper surface of the stack is performed, applying an adhesive on an upper surface of the lower electrode by a second nozzle may also be performed.

Furthermore, in the applying of the adhesive on the upper surface of the stack, a region to which the adhesive is applied may correspond to at least a portion of an edge of the upper electrode.

Also, in the applying of the adhesive on the upper surface of the stack, a region to which the adhesive is applied may include regions corresponding to four vertices of the upper electrode.

Furthermore, in the applying of the adhesive on the upper surface of the stack, a region to which the adhesive is applied may form a plurality of rows parallel to a movement direction of the stack.

Also, a spacing between the regions to which the adhesive is applied in one row may be smaller than a spacing between the regions to which the adhesive is applied in another row.

Furthermore, a size of each region to which the adhesive is applied in one row may be smaller than a size of each region to which the adhesive is applied in another row.

Also, the one row may be located outer side than the another row with respect to a width direction of the stack.

Furthermore, the one row may correspond to an electrode tab of the upper electrode.

Other specific details of the present invention are included in the detailed description and drawings.

Advantageous Effects

According to the embodiments of the present invention, at least the following effects may be achieved.

Since a laminating process is first performed on a stack, which is formed by stacking a center electrode and a separator, and an upper electrode is then stacked, heat is transferred to the inside of the stack during the laminating process, and thus, a problem of reducing adhesion between the electrode and the separator may be prevented.

Also, since the upper electrode is stacked after an adhesive is applied on an upper surface of the stack subjected to the laminating process, a displacement in position of the upper electrode may be prevented.

The effects according to the present invention are not limited to the contents as exemplified above, but more various effects are included in the specification.

DETAILED DESCRIPTION

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be intended to have meanings understood by those skilled in the art. In addition, terms defined in general dictionaries should not be interpreted abnormally or exaggeratedly, unless clearly specifically defined.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. In the specification, the terms of a singular form may include plural forms unless referred to the contrary. It will be further understood that the terms “comprises” and/or “comprising” when used in this specification, specify the presence of stated components, but do not preclude the presence or addition of one or more other components.

FIG.1is a flowchart of a method of preparing a unit cell according to an embodiment of the present invention.

According to an embodiment of the present invention, since a laminating process is first performed on a stack20, which is formed by stacking a center electrode1112and a separator12, and an upper electrode1122is then stacked, heat is transferred to the inside of the stack20during the laminating process, and thus, a problem of reducing adhesion between an electrode11and the separator12may be prevented. Also, since the upper electrode1122is stacked after an adhesive is applied on an upper surface of the stack20subjected to the laminating process, a displacement in position of the upper electrode1122may be prevented.

For this purpose, the method of preparing a unit cell according to the embodiment of the present invention includes the steps of: cutting a center electrode sheet1111unwound from a center electrode reel111to form a plurality of center electrodes1112(S101); forming a stack20by stacking the plurality of center electrodes1112on separator sheets1211and1221unwound from separator reels121and122while the plurality of center electrodes1112are spaced apart from each other and disposed in a row in a longitudinal direction of the separator sheets1211and1221(S102); laminating the stack20with a laminator (S103); applying an adhesive by a first nozzle14on an upper surface of the separator sheet1211and1221disposed on an uppermost layer of the stack20(S104); cutting an upper electrode sheet1121unwound from an upper electrode reel112to form a plurality of upper electrodes1122; and stacking the plurality of upper electrodes1122on an upper surface of the stack20to which the adhesive has been applied (S105).

Hereinafter, each step illustrated in the flowchart ofFIG.1will be described in detail with reference toFIGS.2and3.

FIG.2is a schematic view of an apparatus1for preparing a unit cell according to an embodiment of the present invention.

As illustrated inFIG.2, the apparatus1for preparing a unit cell according to the embodiment of the present invention may include a center electrode reel111from which a center electrode sheet1111, which is to be a plurality of center electrodes1112, is unwound; separator reels121and122from which separator sheets1211and1221to be stacked with the center electrode1112are unwound; a laminator for laminating a stack20which is formed by stacking the plurality of center electrodes1112with the separator sheets1211and1221while the plurality of center electrodes1112are spaced apart from each other and disposed in a row in a longitudinal direction of the separator sheets1211and1221; a first nozzle14for applying an adhesive to an upper surface of the separator sheet1211and1221disposed on an uppermost layer of the laminated stack20; and an upper electrode reel112from which an upper electrode sheet1121, which is to be a plurality of upper electrodes1122to be stacked on an upper surface of the stack20to which the adhesive has been applied, is unwound. In addition, the separator reels121and122may include an upper separator reel121from which an upper separator sheet1211to be stacked on an upper surface of the center electrode1112is unwound; and a lower separator reel122from which a lower separator sheet1221to be stacked on a lower surface of the center electrode1112is unwound.

The center electrode reel111is a reel on which the center electrode sheet1111is wound, and the center electrode sheet1111is unwound from the center electrode reel111. Then, the center electrode sheet1111is cut to form the center electrode1112. The electrode sheets1111and1121may be prepared by coating a slurry of an electrode active material, a conductive agent, and a binder on an electrode collector, drying, and then pressing the coated electrode collector.

The upper separator reel121and the lower separator reel122are reels on which the separator sheets1211and1221are wound. In addition, the upper separator sheet1211unwound from the upper separator reel121is stacked on the upper surface of the central electrode1112which is formed by cutting the center electrode sheet1111, and the lower separator sheet1221unwound from the lower separator reel122is stacked on the lower surface of the center electrode1112. As a result, the stack20is formed in which the lower separator sheet1221, the center electrode1112, and the upper separator sheet1211are sequentially stacked. The stack20is formed by stacking the plurality of center electrodes1112on the separator sheets1211and1221while the plurality of center electrodes1112are spaced apart from each other and disposed in a row in a longitudinal direction of the separator sheets1211and1221.

The laminator laminates an entire surface of the stack which is formed by stacking the center electrode1112and the separator12. The expression “laminating” refers to bonding the center electrode1112and the separator12by applying heat and pressure to the stack20. As illustrated inFIG.2, the laminator may include a heater15for applying heat and pressure to the entire surface of the stack20and a heating roller16for applying pressure to the stack20while rotating.

The heater15is composed of an upper heater151and a lower heater152, wherein the upper heater151and the lower heater152each may apply heat and pressure to the entire surface of upper and lower surfaces of the stack20. In the heater15, surfaces in contact with the stack20, that is, a lower surface of the upper heater151and an upper surface of the lower heater152may be formed substantially flat. Thus, heat and pressure may be uniformly applied to the entire surface of the stack20.

After the heater15applies heat and pressure to the stack20, the heating roller16may apply heat and pressure to the stack20while rotating. In general, the heating roller16, which applies pressure while rotating, applies a higher pressure than the heater15that simply applies pressure with a flat surface. Thus, after the heater15applies heat and pressure to the stack20, the heating roller16applies heat and pressure greater than those of the heater15to the stack so that the heat and pressure applied to the stack (20) may be increased step by step. That is, the stack20may be laminated more strongly while preventing the inside of the stack20from being damaged due to rapid changes in temperature and pressure.

The nozzle14applies an adhesive to the upper surface of the laminated stack20. In this case, since the upper separator sheet1211is stacked on the uppermost layer of the stack20, the adhesive is applied to an upper surface of the upper separator sheet1211.

The nozzles14may be provided in plurality spaced apart from each other along a width direction of the separator sheets1211and1221. Accordingly, the adhesive may be simultaneously applied to different regions of the upper surface of the upper separator sheet1211. Thus, an adhesive application operation by the nozzle14may be quickly performed.

For example, some of the plurality of nozzles14may apply the adhesive near both edges in a width direction of the upper separator sheet1211, and the others thereof may apply the adhesive near a center of the upper separator sheet1211.

A spraying speed, spraying amount, or spraying area of the adhesive sprayed from the plurality of nozzles14may be individually adjusted. With respect to the plurality of first nozzles14, at least one of spraying cycle, spraying area, and spraying amount of the adhesive may be adjusted to be different from each another.

It is desirable that the adhesive is uniformly applied to the upper surface of the stack20. However, if the adhesive is applied to an entire surface of the upper surface of the stack20, an amount of the adhesive applied may be excessively large. Accordingly, the adhesive may flow to the outside of the stack20to contaminate other parts, and a function of generating power may not be smooth when a secondary battery is prepared. Thus, the adhesive may be applied to the upper surface of the stack20by a spot application method of applying the adhesive in the form of a dot or a line application method of applying the adhesive in the form of a line.

In contrast, if the amount of the adhesive applied is excessively small, the upper electrode1122is still not fixed to the stack20while the stack20is moved, and the upper electrode1122may be out of position. Thus, it is desirable that a spacing between regions to which the adhesive is applied is not excessively large.

The adhesive must maintain adhesiveness even if the separator12is impregnated with an electrolyte solution. Thus, it is desirable that the adhesive has a property of corrosion resistance that is not modified by chemical causes. Such an adhesive is a hot melt adhesive, wherein the adhesive may include a modified olefin-based thermoplastic resin.

The upper electrode reel112is a reel on which the upper electrode sheet1121is wound, and the upper electrode sheet1121is unwound from the upper electrode reel112. The upper electrode sheet1121is cut to form a plurality of upper electrodes1122, and the plurality of upper electrodes1122are stacked on the upper surface of the stack20to which the adhesive is applied. In this case, the plurality of upper electrodes1122may be stacked on the upper surface of the stack20while being spaced apart from each other and disposed in a row in the longitudinal direction of the separator sheets1211and1221. Since the upper electrode1122and the center electrode1112have different sizes, spaced-apart spacings may be different. However, it is desirable that both the upper electrode1122and the center electrode1112are aligned and disposed so that their centers coincide.

The method of preparing a unit cell according to the embodiment of the present invention may be performed as follows, using the apparatus1for preparing a unit cell as described above.

As illustrated inFIG.2, when the center electrode sheet1111is first unwound from the center electrode reel111, a first cutter131cuts the center electrode sheet1111(S101). Then, the plurality of center electrodes1112are formed. The upper separator sheet1211is unwound from the upper separator reel121and stacked on the upper surface of the center electrode1112, and the lower separator sheet1221is unwound from the lower separator reel122and stacked on the lower surface of the center electrode1112to form the stack20(S102). In this case, in order for the lower separator sheet1221, the center electrode1112, and the upper separator sheet1211to be easily and strongly adhered to one another, first nip rolls181may be disposed on both sides of the stack20, respectively, and may apply pressure to the stack20while rotating.

After forming the stack20, the laminator laminates the stack20(S103). As described above, the laminator includes the heater15and the heating roller16, and, when laminating, after the heater15applies heat and pressure to the entire surface of the stack20, the heating roller16may apply heat and pressure to the stack20while rotating.

When the laminating process is completed, a second cutter132cuts the stack20at a predetermined interval, and the nozzle14applies an adhesive to the upper surface of the cut stack20(S104). When the upper electrode sheet1121is unwound from the upper electrode reel112, a third cutter133cuts the upper electrode sheet1121to form the upper electrode1122. In addition, the upper electrode1122is stacked on the upper surface of the stack20to which the adhesive has been applied (S105). As a result, a unit cell2is prepared in which the lower separator sheet1221, the center electrode1112, the upper separator sheet1211, and the upper electrode1122are sequentially stacked. In this case, in order for the upper electrode1122and the stack20to be easily and strongly adhered to each other, second nip rolls182may be disposed on both sides of the upper electrode1122and the stack20, respectively, and may apply pressure to the upper electrode1122and the stack20while rotating.

FIG.3is a schematic side view illustrating in detail the apparatus1for preparing a unit cell according to the embodiment of the present invention.

As illustrated inFIG.3, the apparatus1for preparing a unit cell according to the embodiment of the present invention may further include a first vision sensor171disposed above the center electrode1112to photograph the center electrode1112before the center electrode1112is stacked with the separator sheets1211and1221; and a second vision sensor172disposed above the upper electrode1122to photograph the upper electrode1122before the upper electrode1122is stacked with the stack20.

The first and second vision sensors171and172acquire an image by photographing a specific region and receiving an image signal for the specific region. For this purpose, a vision sensor generally includes an imaging device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). Particularly, the first and second vision sensors171and172according to an embodiment of the present invention may acquire images by photographing the center electrode1112and the upper electrode1122, respectively.

Although not shown in the drawings, the apparatus1for preparing a unit cell may further include a controller (not shown) which may determine whether the center electrode1112and the upper electrode1122are defective or not through the images of the center electrode1112and the upper electrode1122. The controller may determine whether sizes and shapes of the center electrode1112and the upper electrode1122are defective or damaged or not by comparing the obtained images with previously stored images of the center electrode1112and the upper electrode1122of a good product.

When these first and second vision sensors171and172are used, the first vision sensor171disposed above the center electrode1112may photograph the center electrode1112before the center electrode1112and the separator sheets1211and1221are stacked to form the stack20, and the second vision sensor172disposed above the upper electrode1122may photograph the upper electrode1122before stacking the upper electrode1122on the stack20. That is, before the electrode11is stacked with the separator12, whether only the electrode11is defective or not may be confirmed in advance.

FIG.4is a cross-sectional view of an upper separator sheet according to an embodiment of the present invention, and

FIG.5is a cross-sectional view of a lower separator sheet according to an embodiment of the present invention.

The separator sheets1211and1221may include base material layers1211aand1221aand coating layers1211band1221b,respectively.

The base material layers1211aand1221aare porous base materials, wherein the base material layers1211aand1221amay include a polyethylene or polypropylene resin.

The coating layers1211band1221bmay be formed by respectively coating the base material layers1211aand1221awith a ceramic slurry including a filler and a binder. The coating layers1211band1221bmay be ceramic coating layers. For example, the filler may include alumina (aluminum oxide), and the binder may include polyvinylidene fluoride (PVDF).

Specifically, the upper separator sheet1211may include the first base material layer1211aand the first coating layer1211bcoated on an upper surface of the first base material layer1211a,and the lower separator sheet1221may include the second base material layer1221aand the second coating layer1221bcoated on an upper surface of the second base material layer1221a.

Thus, the center electrode1112may be bonded to an upper surface of the second coating layer1221bby the laminating process described above. The second coating layer1221bmay be a safety reinforced separator (SRS) coating layer.

For example, an amount of the binder in the second coating layer1221bmay be in a range of 10 wt % to 20 wt %.

Also, the nozzle14may apply an adhesive to an upper surface of the first coating layer1211b,and the upper electrode1122may be bonded to the upper surface of the first coating layer1211bby the adhesive. Thus, an amount of the binder in the first coating layer1211bmay be lower than the amount of the binder in the second coating layer1221b.Specifically, the amount of the binder in the first coating layer1211bmay be less than half of the amount of the binder in the second coating layer1221b.As a result, a thickness t1of the first coating layer1211bmay be smaller than a thickness t2of the second coating layer1221b.

That is, since the amount of the binder in the first coating layer1211bis decreased, a thickness of the upper separator sheet1211may be reduced and energy density of the unit cell2may be improved.

Specifically, the amount of the binder in the first coating layer1211bmay be in a range of 2 wt % to 3 wt %. Accordingly, bonding between the first coating layer1211band the first base material layer1211amay be maintained while maintaining the thickness of the first coating layer1211bas thin as possible. If the amount of the binder in the first coating layer1211bis less than 2 wt %, there is a problem that the bonding between the first coating layer1211band the first base material layer1211ais not maintained. Also, if the amount of the binder in the first coating layer1211bis greater than 3 wt %, the thickness of the first coating layer1211bmay be increased.

A configuration, in which the upper separator sheet1211does not include the first coating layer1211b,is also possible. In this case, the nozzle14may apply an adhesive to the upper surface of the first base material layer1211a,and a lower surface of the upper electrode1122may be bonded to the upper surface of the first base material layer1211aby the adhesive.

Thus, there is an advantage that the thickness of the upper separator sheet1211becomes thinner. However, application of the configuration, in which the upper separator sheet1211does not include the first coating layer1211b,when the upper electrode1122is a positive electrode is desirable in terms of stability.

FIG.6is a view illustrating a nozzle according to an embodiment of the present invention.

The nozzle14according to the present embodiment may spray an adhesive S in the form of a mist by spraying adhesive particles and compressed air together. Specifically, the nozzle14may include a housing141having an inner space, a tube142for supplying the adhesive S to the inside of the housing141, and a line143for supplying the compressed air to the inside of the housing141.

Also, a spraying portion141afor spraying the adhesive S and the compressed air together toward the upper separator sheet1211of the stack20may be formed at a lower end of the housing141.

That is, when the adhesive S supplied to the housing141through the tube142is discharged to the spraying portion141a,the compressed air is injected into the housing141from the line143so that the adhesive S may be discharged through the spraying portion141atogether with the compressed air.

In a process of being discharged with the compressed air, the adhesive S becomes a mist while the adhesive particles are split by the compressed air, and, in that state, the adhesive S may be applied to the upper surface of the upper separator sheet1211, more particularly, the first coating layer1211b.

Since the adhesive S applied by such a spraying method may be applied in the form of small particles by a predetermined amount at a predetermined position, the adhesive S may be uniformly applied to the upper surface of the first coating layer1211bof the upper separator sheet1211and may penetrates evenly throughout a region where the adhesive has been applied, and thus, optimum adhesion may be provided without wasting the adhesive S.

However, a configuration of the nozzle14is not limited thereto, and it is, of course, possible to adopt an inkjet spraying method (seeFIG.10) to be described later.

FIG.7is views illustrating adhesive regions between the upper separator sheet and the upper electrode ofFIG.3by the adhesive.

The upper electrode1122may have a rectangular shape having a relatively short pair of short sides and a relatively long pair of long sides. The upper electrode1122may be stacked on the upper separator sheet1211so that the long side is parallel to the width direction of the upper separator sheet1211.

An adhesive region A1bonded to each other by the adhesive may be positioned between the upper electrode1122and the upper separator sheet1211. That is, the adhesive region A1may mean a region in which the nozzle14applies the adhesive on the upper surface of the upper separator sheet1211.

As a first example, as illustrated in (a) ofFIG.7, the adhesive region A1may extend along a circumference of the upper electrode1122. In this case, the adhesive region A may have a rectangular ring shape, and may surround a non-adhesive region A2.

Thus, an edge portion of the lower surface of the upper electrode1122may be adhered to the upper separator sheet1211. Also, the adhesive region A may protrude to correspond to an electrode tab protruding from the upper electrode1122.

As a second example, as illustrated in (b) ofFIG.7, the adhesive region A1may extend along both short sides of the upper electrode1122. Thus, portions of the lower surface of the upper electrode1122adjacent to the both short sides may be adhered to the upper separator sheet1211. In this case, the non-adhesive region A2may include regions adjacent to both long sides of the lower surface of the upper electrode1122. Also, the adhesive region A may protrude to correspond to an electrode tab protruding from the upper electrode1122.

As a third example, as illustrated in (c) ofFIG.7, the adhesive region A1may extend along both long sides of the upper electrode1122. Thus, portions of the lower surface of the upper electrode1122adjacent to the both long sides may be adhered to the upper separator sheet1211. In this case, the non-adhesive region A2may include regions adjacent to both short sides of the lower surface of the upper electrode1122.

As in the first to third examples, in the step of applying the adhesive to the upper surface of the stack20, a region to which the adhesive is applied may correspond to at least a portion of the edge of the upper electrode1122.

As a fourth example, as illustrated in (d) ofFIG.7, the adhesive region A1may be located in regions corresponding to four vertices of the upper electrode1122. Thus, portions adjacent to the four vertices of the lower surface of the upper electrode1122may be adhered to the upper separator sheet1211. In this case, the non-adhesive region A2may include a portion of regions adjacent to both long sides of the lower surface of the upper electrode1122and a portion of regions adjacent to both short sides thereof.

With respect to the first to fourth examples, the adhesive region A may additionally include a region (not shown) corresponding to a center of the upper electrode1122. As a fifth example, as illustrated in (e) ofFIG.7, the adhesive region A1may include a first region extending along the circumference of the upper electrode1122and a second region extending parallel to the short side or the long side of the upper electrode1122and passing through the center of the upper electrode1122in addition to the first region. Thus, more robust adhesion than that of the first example is possible.

The adhesive region A1may surround the non-adhesive region A2. A plurality of non-adhesive regions A2, which are partitioned from each other by the second region of the adhesive region A1, may be formed. Also, the adhesive region A1may protrude to correspond to an electrode tab protruding from the upper electrode1122.

With respect to the first to fifth examples, an area of the adhesive region A1may be smaller than an area of the non-adhesive region A2. As a sixth example, as illustrated in (f) ofFIG.7, the adhesive region A1may have a shape corresponding to the upper electrode1122. Thus, the entire lower surface of the upper electrode1122may be adhered to the upper separator sheet1211. In this case, the non-adhesive region A2does not exist.

As in the first to sixth examples, in the step of applying the adhesive to the upper surface of the stack20, the region to which the adhesive is applied may include regions corresponding to the four vertices of the upper electrode1122.

FIG.8is a schematic view of an apparatus la for preparing a unit cell according to another embodiment of the present invention, andFIG.9is a schematic side view illustrating in detail the apparatus la for preparing a unit cell according to the another embodiment of the present invention.

According to embodiments of the present invention, a laminating process is first performed on the stack20, which is formed by stacking the center electrode1112and the separator12, and the upper electrode1122is then stacked. As a result, since heat is transferred to the inside of the stack20in the laminating process, a problem of reducing the adhesion between the electrode11and the separator12may be prevented. Thus, there is no need to apply excessive heat and pressure to the stack20in the laminating process.

Therefore, in the apparatus la for preparing a unit cell according to the another embodiment of the present invention, as illustrated inFIGS.8and9, the heater15is removed from the laminator, and only the heating roller16laminates the stack20. In general, since the heating roller16may apply a higher pressure to the stack20than the heater15, the heating roller16alone may sufficiently laminate the stack20.

As described above, since the heater15is removed from the laminator, complication of the apparatus la for preparing a unit cell may be prevented, an overall volume may be reduced, and costs may be reduced. However, in order to prevent the inside of the stack20from being damaged due to rapid changes in temperature and pressure, the heating roller16must be adjusted so that the heat and pressure applied to the stack20are not excessively large.

FIG.10is a view illustrating a nozzle according to another embodiment of the present invention.

The nozzle14′ according to the present embodiment may inkjet spray an adhesive S in the form of fine droplets by a pressure change in a pressure chamber141a′. Specifically, the nozzle14′ may include a housing141′ having the pressure chamber141a′, a wall142′ which is provided on one side of the housing141′ and moves to cause a change in volume of the pressure chamber141a,and a tube143′ for supplying the adhesive S to the pressure chamber141a′.

Also, a discharge port141bthrough which the adhesive S is discharged toward the upper separator sheet1211of the stack20may be formed at a lower end of the housing141′.

The adhesive S, in a state in which it is filled in the pressure chamber141a′, is not discharged through the discharge port141bdue to viscosity of the adhesive S. In this state, if the wall142′ moves in a direction of reducing the volume of the pressure chamber141a′, an internal pressure of the pressure chamber141a′ increases, and the adhesive S is discharged to the outside through the discharge port141bto be applied to the upper surface of the upper separator sheet1211. In addition, when the wall142′ is restored to its original state, the discharge of the adhesive S is stopped.

Since the adhesive S applied by such an inkjet spraying method may be applied in the form of small particles by a predetermined amount at a predetermined position, the adhesive S may be uniformly applied to the upper surface of the first coating layer1211bof the upper separator sheet1211and may penetrates evenly throughout a region where the adhesive has been applied, and thus, optimum adhesion may be provided without wasting the adhesive S.

However, a configuration of the nozzle14′ is not limited thereto, and it is, of course, possible to adopt the previously described spraying method (seeFIG.6).

FIG.11is a view illustrating adhesive regions between the upper electrode and the upper separator sheet ofFIG.9by the adhesive.

Adhesive regions A3, A4, and A5, which are adhered to each other by the adhesive, may be located between the upper electrode1122and the upper separator sheet1211. With respect to the present embodiment, the adhesive regions A3, A4, and A5may be disposed along a plurality of rows parallel to a movement direction of the upper separator sheet1211. Each of the adhesive regions A3, A4, and A5may be formed by spot application of the adhesive. Thus, the plurality of adhesive regions A3, A4, and A5located in the same row may be spaced apart from each other with respect to the movement direction of the upper separator sheet1211.

That is, in the step of applying the adhesive to the upper surface of the stack20, the region to which the adhesive is applied may form a plurality of rows parallel to a movement direction of the stack20.

Specifically, the adhesive regions A3, A4, and A5may include a plurality of first adhesive regions A3forming a row adjacent to the short side of the upper electrode1122, a plurality of second adhesive regions A4forming a row corresponding to the electrode tab of the upper electrode1122, and a plurality of third adhesive regions A5forming a row located inside the first adhesive regions A3and the second adhesive regions A4.

In addition, a spacing between the adhesive-applied regions in a specific row may be different from a spacing between the adhesive-applied regions in another row by controlling spraying cycles of the plurality of nozzles14′ differently.

For example, the adhesive may be sprayed more densely to regions corresponding to the electrode tab of the upper electrode1122and the edge of the upper electrode1122which require great adhesion. Specifically, a spacing between the plurality of first adhesive regions A3may be greater than a spacing between the plurality of second adhesive regions A4and may be smaller than a spacing between the plurality of third adhesive regions A5.

Also, areas of the regions to which the adhesive is applied in a specific row may be formed to be greater than areas of the regions to which the adhesive is applied in another row by controlling spraying amounts or spraying areas of the plurality of nozzles14′ differently.

For example, the adhesive may be sprayed more widely in a region corresponding to the center of the upper electrode1122where there is no risk of leakage of the adhesive. Specifically, a size of each first adhesive region A3may be greater than a size of each second adhesive region A4and may be smaller than a size of each third adhesive region A5.

FIG.12is a schematic view of an apparatus1bfor preparing a unit cell according to another embodiment of the present invention.

As described above, an electrode assembly is classified into various types. For example, there are a simple stack type, a lamination & stack type (L&S), a stack & folding type (S&F), and a Z-folding type.

According to an embodiment and another embodiment of the present invention, the unit cell2is prepared in which the separator12, the electrode11, the separator12, and the electrode11are sequentially stacked. Thus, the electrode11is formed on one surface of the unit cell2and the separator12is formed on the other surface thereof. These unit cells2are mainly used when a lamination & stack type electrode assembly is prepared. However, when a stack & folding type or Z-folding type electrode assembly is prepared, a unit cell2ahaving the electrodes11formed on both surfaces thereof is mainly used.

The apparatus1bfor preparing a unit cell according to the another embodiment of the present invention, as illustrated inFIG.12, further includes a lower electrode reel113from which a lower electrode sheet1131, which is to be a plurality of lower electrodes1132to be stacked on a lower surface of the stack20, is unwound.

The lower electrode reel113is a reel on which the lower electrode sheet1131is wound, and the lower electrode sheet1131is unwound from the lower electrode reel113and the lower electrode sheet1131is cut to form the plurality of lower electrodes1132. In addition, when a first nozzle14aapplies an adhesive to the upper surface of the cut stack20, a second nozzle14bmay also apply an adhesive to an upper surface of the lower electrode1132. The lower electrode1132to which the adhesive is applied is stacked on the lower surface of the stack20. In this case, the plurality of lower electrodes1132may be stacked on the lower surface of the stack20while being spaced apart from each other and disposed in a row in a length direction of the separator sheets1211and1221. The upper electrode1122, the center electrode1112, and the lower electrode1132may have different spacings apart from each other, but, since the electrodes11with the same polarity have the same size, it is desirable that the spacings are always constant. Thus, if the upper electrode1122and the lower electrode1132are the electrodes11with the same polarity, spacings apart from the separator sheets1211and1221may be constant. In addition, it is desirable that the upper electrode1122, the center electrode1112, and the lower electrode1132are all aligned and disposed so that centers thereof coincide.

When a laminating process of the stack20is completed, the second cutter132cuts the stack20at a predetermined interval, and the first nozzle14aapplies the adhesive to the upper surface of the cut stack20(S104). When the upper electrode sheet1121is unwound from the upper electrode reel112, the third cutter133cuts the upper electrode sheet1121to form the upper electrode1122. In addition, when the lower electrode sheet1131is unwound from the lower electrode reel113, a fourth cutter134cuts the lower electrode sheet1131to form the lower electrode1132. Then, the second nozzle14bapplies the adhesive to the upper surface of the lower electrode1132.

The upper electrode1122is stacked on the upper surface of the stack20to which the adhesive has been applied, and the lower electrode1132to which the adhesive has been applied is stacked on the lower surface of the stack20. As a result, the unit cell2bis prepared in which the lower electrode1132, the lower separator sheet1221, the center electrode1112, the upper separator sheet1211, and the upper electrode1122are sequentially stacked.

FIG.13is a schematic side view illustrating in detail the apparatus1bfor preparing a unit cell according to the another embodiment of the present invention.

The apparatus1bfor preparing a unit cell according to the another embodiment of the present invention may further include a third vision sensor173disposed above the lower electrode1132to photograph the lower electrode1132before the lower electrode1132is stacked with the stack20, particularly, before the second nozzle14bapplies the adhesive on the upper surface of the lower electrode1132. That is, the third vision sensor173may acquire an image by photographing the lower electrode1132. As a result, the third vision sensor173may determine whether size and shape of the lower electrode1132are defective or damaged or not, before the lower electrode1132is stacked with the stack20.

It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims. Accordingly, it is to be understood that the invention has been described by way of illustration and not limitation. Thus, the scope of the invention is defined by the following claims rather than the foregoing detailed description, and it is to be interpreted that all changes or modifications derived from the meaning, scope and equivalent concept of the appended claims are within the scope of the present invention.

DESCRIPTION OF THE SYMBOLS