Patent Description:
The present invention relates to unit cell manufacturing apparatus and method, and more particularly, to unit cell manufacturing apparatus and method which may prevent the reduction in adhesion force of the side of a unit cell.

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.

A single electrode assembly is formed by assembling unit cells, each of which is formed by stacking a cathode, a separator, and an anode. Also, the electrode assembly is accommodated in a specific case, thereby manufacturing a lithium secondary battery.

These unit cells include full-cells and bi-cells. Each of the full-cells is a cell in which a cathode and an anode are disposed at both the outermost portions of the cell, respectively. As the most basic structure of the full-cell, there is a cathode/separator/anode structure, a cathode/separator/anode/separator/cathode/separator/anode structure, or the like.

Each of the bi-cells is a cell in which electrodes having the same polarity are disposed at both the outermost portions of the cell. As the most basic structure of the bi-cell, there is an A-type bi-cell having a cathode/separator/anode/separator/cathode structure, a C-type bi-cell having an anode/separator/cathode/separator/anode structure, or the like. That is, the cell in which cathodes are disposed at both the outermost portions thereof is referred to as an A-type bi-cell, and the cell in which anodes are disposed at both the outermost portions thereof is referred to as a C-type bi-cell.

In general, in order to prepare such a 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 and a lower electrode are further stacked. If the unit cell is a bi-cell, the center electrode may be provided in an odd number such as one, and if the unit cell is a full-cell, the center electrode may be provided in an even number such as two.

Meanwhile, it is very important to evaluate and secure the safety of the electrode assembly. First of all, it should be considered that errors in operation of the electrode assembly should not cause damage to users. For this purpose, the Safety Regulation strictly regulates ignition and explosion in the electrode assembly. In the safety characteristics of the electrode assembly, thermal runaway caused by overheating of the electrode assembly or puncture of a separator may increase the risk of explosion. In particular, a polyolefin-based porous substrate commonly used as a separator of an electrode assembly shows extreme thermal shrinking behavior at a temperature of <NUM> or higher due to the features of its material and its manufacturing process such as elongation, thereby resulting in an electric short circuit between a cathode and an anode.

In order to solve the above safety-related problems of the electrode assembly, there is suggested a separator having a porous organic-inorganic coating layer formed by coating at least one surface of a porous polymer substrate having a plurality of pores with a slurry containing a mixture of excess inorganic particles and a polymer binder. Since inorganic particles contained in the porous organic-inorganic coating layer have excellent heat resistance, even when the electrode assembly is overheated, an electric short circuit between a cathode and an anode is prevented.

However, when the porous coating layer is thinly coated, for example, to a thickness of less than <NUM> based on the cross-section of the porous substrate, the adhesion between the separator and the electrode is insufficient, resulting in a decrease in assembly properties. When the adhesion between the separator and the electrode is excellent, it is possible to prevent an increase in interfacial resistance caused by detachment of the separator and the electrode by gas generated as an electrolyte decomposition product during the cycle of the electrode assembly. In addition, it is possible to prevent an increase in the interfacial resistance between the separator and the electrode due to volume expansion of the electrode during cycling, and it is possible to improve the strength of the electrode assembly by suppressing the bending of the electrode assembly in the form of jelly-roll or stack & folding. In this regard, the adhesion between the separator and the electrode is a very important factor in the electrode assembly.

<FIG> is a schematic view illustrating a non-adhesive region <NUM> of a unit cell <NUM>.

In the related art, a separator <NUM> (shown in <FIG>) was prepared by applying a slurry to a polymer substrate <NUM> (shown in <FIG>) to form a porous coating layer <NUM> (shown in <FIG>). In addition, electrodes <NUM> (shown in <FIG>) are stacked on the separator <NUM> and heat and pressure are applied thereon to manufacture a unit cell <NUM> as shown in <FIG>.

However, because the porous coating layer <NUM> is formed by applying a liquid or gel slurry onto the polymer substrate <NUM> and then solidifying it, there is a certain height difference from the surface even if the slurry is applied evenly and uniformly. In particular, the slurries were more aggregated in the center <NUM> (shown in <FIG>) than in the side <NUM> (shown in <FIG>) of the separator <NUM>, and thus the height of the slurry was formed lower in the side <NUM> than in the center <NUM>. Therefore, in the side <NUM> and the center <NUM> of the separator <NUM>, there is a height difference even in the porous coating layer <NUM> obtained by solidifying the slurry, and thus even if the electrode <NUM> is stacked to manufacture the unit cell <NUM>, deviation occurred in the adhesion of the separator <NUM>. Therefore, as shown in <FIG>, there was a problem in that the electrode <NUM> and the separator <NUM> did not adhere to each other or poorly adhered to each other, forming the non-adhesive region <NUM> on a portion of the side <NUM> of the unit cell <NUM>.

As a prior art document, there is <CIT>. Further examples of background art can be found in <CIT> and <CIT>.

An object of the present invention is to prevent the reduction in adhesion force of the side of a unit cell.

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

According to an aspect of the present invention, there is provided a unit cell manufacturing apparatus including: an electrode reel from which an electrode sheet, which is to be a plurality of electrodes, is unwound; a separator reel from which a separator sheet to be stacked with the electrodes is unwound; and a sealer, in a stack which is formed by stacking the plurality of electrodes with the separator sheet while the plurality of electrodes are spaced apart from each other and disposed in a row in the longitudinal direction of the separator sheet, the sealer which is disposed between the plurality of electrodes and applies heat and pressure to at least one of corners of the electrodes or edges of the electrodes ; and a laminator which laminates the stack.

In addition, the sealer may include a first body and a second body vertically extending from the first body.

Furthermore, the sealer may further include: a first protrusion which protrudes downward from a lower surface of the first body and is elongated in a longitudinal direction of the first body; and a second protrusion which protrudes downward from a lower surface of the second body and is elongated in a longitudinal direction of the second body.

In addition, the laminator may include a heater which applies heat and pressure to the entire surface of the stack.

Also, the laminator may further include a heating roller which applies heat and pressure to the stack while rotating.

Furthermore, the electrode reel may include a center electrode reel from which a center electrode sheet, which is to be a plurality of center electrodes, is unwound, and the separator reel may include: an upper separator reel from which an upper separator sheet to be stacked on an upper surface of the center electrode, which is formed by cutting the center electrode sheet, 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.

In addition, the electrode reel may further include: an upper electrode reel from which an upper electrode sheet, which is to be upper electrodes to be stacked on the upper surface of the upper separator sheet, is unwound; and a lower electrode reel from which a lower electrode sheet, which is to be lower electrodes to be stacked on the lower surface of the lower separator sheet, is unwound.

According to an aspect of the present invention, there is provided a unit cell manufacturing method including: cutting an electrode sheet unwound from an electrode reel to form a plurality of electrodes; forming a stack by stacking the plurality of electrodes on separator sheet unwound from a separator reel while the plurality of electrodes are spaced apart from each other and disposed in a row in a longitudinal direction of the separator sheet; disposing a sealer between the plurality of electrodes in the stack; and applying, with the sealer, heat and pressure to at least one of corners of the electrode or edges of the electrode, and laminating the stack after the forming of the stack and before the disposing of the sealer.

Also, in the applying heat and pressure, the first body may apply heat and pressure to a first edge, which is directed toward the outside of the stack, among the edges of the electrode, and the second body may apply heat and pressure to a second edge, which faces another neighboring electrode and crosses with the first edge to form the corner, among the edges of the electrode.

Also, in the applying heat and pressure, the first protrusion may apply heat and pressure to a first region, which extends to the outside from the first edge of the electrode, of the separator sheet, and the second protrusion may apply heat and pressure to a second region, which is formed between the plurality of electrodes, of the separator sheet.

Also, the laminating may further include: applying heat and pressure to an entire surface of the stack by a heater; and applying heat and pressure to the stack by a heating roller while the heating roller rotates.

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

The embodiments of the present invention may have at least the following effects.

In a stack which is formed by stacking the plurality of electrodes on the separator sheet, a sealer applies heat and pressure to at least one of the corners of the electrode or the edges of the electrode, and thus it may prevent the formation of non-adhesive regions on the side of a unit cell, thereby preventing the reduction of the adhesion between the electrode and the separator.

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.

Advantages and features of the present invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Further, the present invention is only defined by scopes of claims.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be intended to have meanings commonly understood by those skilled in the art. Also, unless defined clearly and apparently in the description, the terms as defined in a commonly used dictionary are not ideally or excessively construed as having formal meaning.

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> is a schematic view of a separator <NUM> according to an embodiment of the present invention.

As shown in <FIG>, the separator <NUM> according to an embodiment of the present invention is prepared by coating a slurry containing a mixture of inorganic particles and a polymer binder on at least one surface of a porous polymer substrate <NUM> to form a porous coating layer <NUM>.

The porous polymer substrate <NUM> is not limited but includes a variety of substrates as long as it is a planar porous substrate commonly used in an electrode assembly, such as a porous polymer film substrate formed of various polymers or a porous polymer non-woven fabric substrate. For example, a polyolefin-based porous polymer film such as polyethylene or polypropylene, which is used as the separator <NUM> in an electrode assembly, particularly, a lithium secondary battery, or a non-woven fabric made of polyethylene terephthalate fiber may be used, and their material or form may be variously selected depending on a desired purpose. This polyolefin porous polymer film may be formed of a polyolefin-based polymer, for example, polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene and ultra-high molecular weight polyethylene, polypropylene, polybutylene, polypentene, either individually or as a mixture thereof. Also, the porous polymer film substrate may be prepared by using various polymers such as polyester in addition to polyolefin. In addition, the porous polymer substrate may be formed in a structure in which two or more film layers are stacked, and each film layer may be formed of polymer such as polyolefin and polyester as described above, either individually or as a mixture of two or more of these.

The porous polymer non-woven fabric substrate may be non-woven fabric formed of polymers including polyolefin-based polymers as described above, or other polymers with higher heat resistance, for example, polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetheramide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenyleneoxide, a cyclic olefin copolymer, polyphenylenesulfide, polyethylenenaphthalene, either individually or as a mixture thereof. In addition, the non-woven fabric may be a spun-bond or melt-blown fabric consisting of a long fiber in structure. However, the porous polymer material <NUM> is not limited thereto, and may be selected variously in material or form.

The thickness of the porous polymer substrate <NUM> is not particularly limited, but preferably <NUM>-<NUM>, and more preferably <NUM>-<NUM>. Also, a pore size and a porosity in the porous polymer substrate <NUM> are not particularly limited, but preferably <NUM>-<NUM>, and <NUM>-<NUM>%, respectively.

On at least one surface of the porous polymer substrate <NUM>, a slurry containing containing a mixture of inorganic particles and a polymer binder is coated to form the porous coating layer <NUM>. The coating method of the slurry is not limited, and a variety of methods may be used, but a dip coating method is preferably used. Dip coating is a method for coating a substrate by immersing the substrate in a tank containing a coating solution, and the thickness of the porous coating layer <NUM> can be adjusted according to the concentration of the coating solution and the speed at which the substrate is taken out of the coating solution tank. Thereafter, the substrate is dried in an oven to form the porous coating layer <NUM> on at least one surface of the porous polymer substrate <NUM>.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that may be used in the present invention are not particularly limited as long as an oxidation and/or a reduction reaction are/is not generated within an operating voltage range (for example, <NUM>-<NUM> V with respect to Li/Li+) of the applied electrode assembly. Particularly, when inorganic particles having high permittivity are used as inorganic particles, it may contribute to an increase in a dissociation rate of an electrolyte salt such as a lithium salt in a liquid electrolyte, thereby enhancing the ionic conductivity of the electrolyte solution.

For these reasons, the inorganic particles preferably include high-permittivity inorganic particles having a dielectric constant of <NUM> or more, preferably, <NUM> or more. Non-limiting examples of the inorganic particles having a dielectric constant of <NUM> or more may include, for example, BaTiO<NUM>, Pb(Zr,Ti)O<NUM> (PZT), Pb<NUM>-xLaxZr<NUM>-yTiyO<NUM> (PLZT, <NUM><x<<NUM>, <NUM><y<<NUM>), Pb(Mg<NUM>/<NUM>Nb<NUM>/<NUM>)O<NUM>-PbTiO<NUM> (PMN-PT), hafnia (HfO<NUM>) , SrTiO<NUM>, SnO<NUM>, CeO<NUM>, MgO, NiO, CaO, ZnO, ZrO<NUM>, Y<NUM>O<NUM>, Al<NUM>O<NUM>, boehmite (γ-Al(OH)), TiO<NUM>, SiC or a mixture thereof.

In particular, the inorganic particles such as of BaTiO<NUM>, Pb(Zr,Ti)O<NUM> (PZT), Pb<NUM>-xLaxZr<NUM>-yTiyO<NUM> (PLZT), Pb(Mg<NUM>/<NUM>Nb<NUM>/<NUM>)O<NUM>-PbTiO<NUM> (PMN-PT) and hafnia (HfO<NUM>) show a high permittivity characteristic, which is a dielectric constant of <NUM> or more, and also have piezoelectricity since charges are generated to make a potential difference between both surfaces when a certain pressure is applied thereto to extend or shrink them, so that the above inorganic particles may prevent generation of an internal short circuit of both electrodes <NUM> caused by an external impact and thus improve the safety of the electrochemical device. In addition, when the aforementioned high-permittivity inorganic particles and inorganic particles having lithium ion transfer capability are used in combination, the synergetic effect thereof may double.

The inorganic particles having lithium ion transferring capability, that is, inorganic particles, which contain lithium elements but have a function of moving lithium ions without storing the lithium, may be used. Because the inorganic particles having lithium ion transferring capability may transfer and move lithium ions due to a kind of defect existing in the particle structure, the lithium ion conductivity in the battery may be improved, thereby improving the performance of the battery. In addition, non-limiting examples of inorganic particles having lithium ion transfer capability may include lithium phosphate (Li<NUM>PO<NUM>), lithium titanium phosphate (LixTiy(PO<NUM>)<NUM>, <NUM> < x < <NUM>, <NUM> < y < <NUM>), lithium aluminum titanium phosphate (LixAlyTiz(PO<NUM>)<NUM>, <NUM> < x < <NUM>, <NUM> < y < <NUM>, <NUM> < z < <NUM>), (LiAlTiP)xOy-based glass (<NUM> < x < <NUM>, <NUM> < y < <NUM>) such as 14Li<NUM>O-9Al<NUM>O<NUM>-38TiO<NUM>-39P<NUM>O<NUM>, lithium lanthanum titanate (LixLayTiO<NUM>, <NUM> < x < <NUM>, <NUM> < y < <NUM>), lithium germanium thiophosphate (LixGeyPzSw, <NUM> < x < <NUM>, <NUM> < y < <NUM>, <NUM> < z < <NUM>, <NUM> < w < <NUM>) such as Li<NUM>Ge<NUM>P<NUM>S<NUM>, lithium nitride (LixNy, <NUM> < x < <NUM>, <NUM> < y < <NUM>) such as Li<NUM>N, SiS<NUM>-based glass (LixSiySz, < x < <NUM>, <NUM> < y < <NUM>, <NUM> < z < <NUM>) such as Li<NUM>PO<NUM>-Li<NUM>S-SiS<NUM>, P<NUM>S<NUM>-based glass (LixPySz, <NUM> < x < <NUM>, <NUM> < y < <NUM>, <NUM> < z < <NUM>), such as LiI-Li<NUM>S-P<NUM>S<NUM>, or a mixture thereof.

The average particle diameter of the inorganic particles is not particularly limited, but is preferably in a range of <NUM>-<NUM> in order to form the porous coating layer <NUM> having a uniform thickness and ensure suitable porosity. If the average particle diameter is less than <NUM>, a dispersing property of inorganic particles may be deteriorated. If the average particle diameter is greater than <NUM>, the thickness of the porous coating layer <NUM> to be formed is increased, which may deteriorate mechanical properties. Also, an excessively large pore size may increase the probability of internal short circuit while a battery is charged or discharged.

A polymer having a glass transition temperature (Tg) ranging from -<NUM> to <NUM> is preferably used as the polymer binder, since this polymer may improve mechanical properties such as flexibility and elasticity of the finally formed porous coating layer <NUM>.

In addition, the ion transferring capability is not essential to the polymer binder, but using the polymer having ion transferring capability may further improve the performance of an electrode assembly. Therefore, the polymer binder preferably has a dielectric constant as high as possible. In fact, because a dissociation degree of salts in an electrolyte solution depends on a dielectric constant of an electrolyte solvent, as a dielectric constant of the polymer binder is higher, the dissociation degree of salts in the electrolyte solution may increase. The polymer binder may have a dielectric constant of <NUM> to <NUM> (measuring frequency = <NUM>), preferably <NUM> or higher.

In addition to the aforementioned functions, the polymer binder may be gelatinized when impregnated with a liquid electrolyte solution to thus exhibit a high degree of swelling in an electrolyte solution. Accordingly, a polymer having a solubility parameter ranging from <NUM> Mpa<NUM>/<NUM> to <NUM> Mpa<NUM>/<NUM> is preferably used, and the solubility parameter more preferably ranges from <NUM> Mpa<NUM>/<NUM> to <NUM> Mpa<NUM>/<NUM> and <NUM> Mpa<NUM>/<NUM> to <NUM> Mpa<NUM>/<NUM>. Thus, hydrophilic polymers having many polar groups are preferably used rather than hydrophobic polymers such as polyolefin. When the solubility parameter of the polymer is less than <NUM> MPa<NUM>/<NUM> or higher than <NUM> MPa<NUM>/<NUM>, the polymer is difficult to be swelled by a typical liquid electrolyte solution for a battery.

Non-limiting examples of the polymer binder may include, for example, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxyl methyl cellulose.

Furthermore, the polymer binder may also include PVDF-HFP. The term "PVDF-HFP polymer binder" refers to a vinylidene fluoride copolymer including a constituent unit of vinylidene fluoride (VDF) and a constituent unit of hexafluoropropylene (HFP). However, the polymer binder is not limited thereto, and may include a variety of materials.

The weight ratio of the inorganic particles and the polymer binder may be preferably, for example, in the range of <NUM>:<NUM> to <NUM>:<NUM>, and more preferably, <NUM>:<NUM> to <NUM>:<NUM>. If the content ratio of the organic particles to the polymer binder is less than <NUM>:<NUM>, the content of polymer is so great that the pore size and porosity of the formed coating layer <NUM> may be reduced. If the content of the organic particles is greater than <NUM> parts by weight, the content of polymer is so small that the peeling resistance of the formed coating layer <NUM> may be weakened.

A solvent for the polymer binder preferably has a solubility parameter similar to that of the polymer binder to be used and a low boiling point. This is intended to facilitate uniform mixture and removal of the solvent afterward. Non-limiting examples of a usable solvent may include, for example, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-<NUM>-pyrrolidone (NMP), cyclohexane, water, or a mixture thereof.

A slurry in which inorganic particles are dispersed and a polymer binder is dissolved in a solvent may be prepared by dissolving the polymer binder in the solvent and then adding the inorganic particles thereto and dispersing the same. The inorganic particles may be pulverized in a suitable size and then added, but it is preferred that after the inorganic particles are added to the solution of the polymer binder, the inorganic particles are dispersed while being pulverized using a ball mill, etc..

As described above, because the porous coating layer <NUM> is formed by applying a liquid or gel slurry onto the polymer substrate <NUM> and then solidifying it, there is a certain height difference d from the surface even if the slurry is applied evenly and uniformly. In particular, since the attraction between the materials constituting the slurry acts on the side <NUM> more than the center <NUM>, the height of the slurry in the side <NUM> is formed lower than that in the center <NUM>. Therefore, as illustrated in <FIG>, in the side <NUM> and the center <NUM> of the separator <NUM>, there is a height difference d even in the porous coating layer <NUM> obtained by solidifying the slurry, and thus even if the electrode <NUM> is stacked to manufacture the unit cell <NUM>, deviation occurred in the adhesion of the separator <NUM>. Therefore, there was a problem in that the electrode <NUM> and the separator <NUM> did not adhere to each other or poorly adhered to each other, forming the non-adhesive region <NUM> on a portion of the side <NUM> of the unit cell <NUM>.

<FIG> is a flowchart of a unit cell manufacturing method according to an embodiment of the present invention.

According to an embodiment of the present invention, in a stack <NUM> in which the electrode <NUM> is tacked on separator sheets <NUM> and <NUM>, a sealer <NUM> applies heat and pressure to at least one of the corners of the electrode <NUM> or the edges of the electrode, and thus it may prevent the formation of non-adhesive regions <NUM> on the side <NUM> of the unit cell <NUM>, thereby preventing the reduction of the adhesion between the electrode <NUM> and the separator <NUM>.

To this end, a unit cell manufacturing method according to an embodiment of the present invention includes: cutting electrode sheets <NUM>, <NUM>, and <NUM> unwound from electrode reels <NUM>, <NUM>, and <NUM> to form a plurality of electrodes <NUM>; forming a stack <NUM> by stacking the plurality of electrodes <NUM> on separator sheets <NUM> and <NUM> unwound from separator reels <NUM> and <NUM> while the plurality of electrodes <NUM> are spaced apart from each other and disposed in a row in the longitudinal direction of the separator sheets <NUM> and <NUM>; disposing a sealer <NUM> between the plurality of electrodes <NUM> in the stack <NUM>; and applying, with the sealer <NUM>, heat and pressure to at least one of the corners of the electrode <NUM> or the edges of the electrode <NUM>.

Hereinafter, each step illustrated in the flowchart of <FIG> will be described in detail with reference to <FIG> and <FIG>.

<FIG> is a schematic view of a unit cell manufacturing apparatus <NUM> according to an embodiment of the present invention.

As illustrated in <FIG>, the unit cell manufacturing apparatus <NUM> according to an embodiment of the present invention includes: electrode reels <NUM>, <NUM>, and <NUM> from which electrode sheets <NUM>, <NUM>, and <NUM>, which is to be a plurality of electrodes <NUM>, are unwound; separator reels <NUM> and <NUM> from which separator sheets <NUM> and <NUM> to be stacked with the electrodes <NUM> are unwound; and in a stack which is formed by stacking the plurality of electrodes with the separator sheets while the plurality of electrodes <NUM> are spaced apart from each other and disposed in a row in the longitudinal direction of the separator sheets <NUM> and <NUM>, sealers <NUM> which are disposed between the plurality of electrodes <NUM> and applies heat and pressure to at least one of the corners of the electrodes <NUM> or the edges of the electrodes <NUM>. In addition, the electrode reel may include a center electrode reel <NUM> from which a center electrode sheet <NUM>, which is to be a plurality of center electrodes <NUM>, is unwound, and the separator reels <NUM> and <NUM> may include an upper separator reel <NUM> from which an upper separator sheet <NUM> to be stacked on an upper surface of the center electrode <NUM>, which is formed by cutting the center electrode sheet <NUM>, is unwound; and a lower separator reel <NUM> from which a lower separator sheet <NUM> to be stacked on a lower surface of the center electrode <NUM> is unwound.

As described above, unit cells <NUM> include full-cells and bi-cells. As described above, if the unit cell <NUM> is a bi-cell, the center electrode <NUM> may be provided in an odd number such as one, and if the unit cell <NUM> is a full-cell, the center electrode <NUM> may not be provided or may be provided in an even number such as two. Hereinafter, the unit cell <NUM> will be described as a bi-cell that has three electrodes <NUM> and two separators <NUM>. However, this is just for convenience of description, and is not to limit the scope of the present invention.

The center electrode reel <NUM> is a reel on which the center electrode sheet <NUM> is wound, and the center electrode sheet <NUM> is unwound from the center electrode reel <NUM>. If the unit cell <NUM> is an A-type bi-cell, the center electrode sheet <NUM> is an anode sheet, and if the unit cell <NUM> is a C-type bi-cell, the center electrode sheet <NUM> is a cathode sheet. These electrode sheets <NUM>, <NUM> and <NUM> may be prepared by coating a slurry of an electrode active material, a conductive agent, and a binder on an electrode collector, and then drying and pressing the coated electrode collector.

An upper separator reel <NUM> and a lower separator reel <NUM> are reels on which the separator sheets <NUM> and <NUM> are wound. In addition, the upper separator sheet <NUM> unwound from the upper separator reel <NUM> is stacked on the upper surface of the central electrode <NUM> which is formed by cutting the center electrode sheet <NUM>, and the lower separator sheet <NUM> unwound from the lower separator reel <NUM> is stacked on the lower surface of the center electrode <NUM>.

The electrode reel may further include: an upper electrode reel <NUM> from which an upper electrode sheet <NUM>, which is to be upper electrodes <NUM> to be stacked on the upper surface of the upper separator sheet <NUM>, is unwound; and a lower electrode reel <NUM> from which a lower electrode sheet <NUM>, which is to be lower electrodes <NUM> to be stacked on the lower surface of the lower separator sheet <NUM>, is unwound.

The upper electrode reel <NUM> is a reel on which the upper electrode sheet <NUM> is wound, and the upper electrode sheet <NUM> is unwound from the upper electrode reel <NUM>. In addition, the lower electrode reel <NUM> is a reel on which the lower electrode sheet <NUM> is wound, and the lower electrode sheet <NUM> is unwound from the lower electrode reel <NUM>. If the unit cell <NUM> is a full-cell, the upper electrode <NUM> and the lower electrode <NUM> have a different polarity. In addition, if the unit cell <NUM> is a bi-cell, the upper electrode <NUM> and the lower electrode <NUM> have the same polarity, and have a different polarity from the center electrode <NUM>. If the unit cell <NUM> is an A-type bi-cell, the center electrode sheet <NUM> is an anode sheet, but the upper electrode sheet <NUM> and the lower electrode sheet <NUM> are cathode sheets, and if the unit cell <NUM> is a C-type bi-cell, the center electrode sheet <NUM> is a cathode sheet, but the upper electrode sheet <NUM> and the lower electrode sheet <NUM> are anode sheets.

The upper electrode <NUM> formed by cutting the upper electrode sheet <NUM> is stacked on the upper surface of the upper separator sheet <NUM>, and the lower electrode <NUM> formed by cutting the lower electrode sheet <NUM> is stacked on the lower surface of the lower separator sheet <NUM>. As a result, a stack <NUM> is prepared in which the lower electrode <NUM>, the lower separator sheet <NUM>, the center electrode <NUM>, the upper separator sheet <NUM>, and the upper electrode <NUM> are sequentially stacked.

The stack <NUM> is formed by stacking the plurality of electrodes <NUM> on the separator sheets <NUM> and <NUM> while the plurality of center electrodes <NUM> are spaced apart from each other and disposed in a row in the longitudinal direction of the separator sheets <NUM> and <NUM>. In this case, the upper electrode <NUM>, the center electrode <NUM>, and the lower electrode <NUM> may have different spacings apart from each other, but, because the electrodes <NUM> with the same polarity have the same size, it is preferable that the spacing is always constant. In addition, it is desirable that the upper electrode <NUM>, the center electrode <NUM>, and the lower electrode <NUM> are all aligned and disposed so that centers thereof coincide.

The sealers <NUM> are disposed between the plurality of electrodes <NUM> in the stack <NUM> and apply heat and pressure to at least one of the corners of the electrodes <NUM> or the edges of the electrodes <NUM>. Therefore, the formation of the non-adhesive regions <NUM> on the side <NUM> of the unit cell <NUM> including the corner of the electrode <NUM> may be prevented, and the reduction of the adhesion between the electrode <NUM> and the separator <NUM> may be prevented. The sealers <NUM> will be described later in detail.

The laminator laminates an entire surface of the stack <NUM> which is formed by stacking the electrode <NUM> and the separator <NUM>. The term "laminating" refers to bonding the electrode <NUM> and the separator <NUM> by applying heat and pressure to the stack <NUM>. As illustrated in <FIG>, the laminator may include a heater <NUM> which applies heat and pressure to the entire surface of the stack <NUM> and may further include a heating roller <NUM> which applies pressure to the stack <NUM> while rotating.

The heater <NUM> is composed of an upper heater <NUM> and a lower heater <NUM>, which may apply heat and pressure to the entire surface of upper and lower surfaces of the stack <NUM>, respectively. In the heater <NUM>, surfaces in contact with the stack <NUM>, that is, the lower surface of the upper heater <NUM> and the upper surface of the lower heater <NUM> may be formed substantially flat. Thus, heat and pressure may be uniformly applied to the entire surface of the stack <NUM>.

When the heater <NUM> applies heat and pressure to the stack <NUM>, the heating roller <NUM> may apply heat and pressure to the stack <NUM> while rotating. In general, the heating roller <NUM>, which applies pressure while rotating, applies a higher pressure than the heater <NUM> that simply applies pressure with a flat surface. Thus, after the heater <NUM> applies heat and pressure to the stack <NUM>, the heating roller <NUM> applies heat and pressure greater than those of the heater <NUM> to the stack <NUM> so that the heat and pressure applied to the stack (<NUM>) may be increased step by step. That is, this may prevent the inside of the stack <NUM> from being damaged due to rapid changes in temperature and pressure.

When the center electrode sheet <NUM> is first unwound from the center electrode reel <NUM>, a first cutter <NUM> cuts the center electrode sheet <NUM> (S301). Then, the plurality of center electrodes <NUM> are formed. In addition, the upper separator sheet <NUM> is unwound from the upper separator reel <NUM> and stacked on the upper surface of the center electrode <NUM>, and the lower separator sheet <NUM> is unwound from the lower separator reel <NUM> and stacked on the lower surface of the center electrode <NUM>.

Meanwhile, when the upper electrode sheet <NUM> is unwound from the upper electrode reel <NUM>, a second cutter <NUM> cuts the upper electrode sheet <NUM> to form the upper electrode <NUM>, and when the lower electrode sheet <NUM> is unwound from the lower electrode reel <NUM>, a third cutter <NUM> cuts the lower electrode sheet <NUM> to form the lower electrode <NUM>. The upper electrode <NUM> is stacked on the upper surface of the upper separator sheet <NUM>, and the lower electrode <NUM> is stacked on the lower surface of the lower separator sheet <NUM>. As a result, the stack <NUM> is prepared in which the lower electrode <NUM>, the lower separator sheet <NUM>, the center electrode <NUM>, the upper separator sheet <NUM>, and the upper electrode <NUM> are sequentially stacked (S302).

In the stack <NUM>, at least one of the upper electrode <NUM> or the lower electrode <NUM> may be omitted, and furthermore, at least one of the upper separator sheet <NUM> or the lower separator sheet <NUM> may be omitted. Hereinafter, it will be described that in the stack <NUM>, these electrodes <NUM> and separators <NUM> are not omitted. However, this is just for convenience of description, and is not to limit the scope of the present invention.

After the formation of the stack <NUM>, the laminator laminates the stack <NUM>. As described above, the laminator includes the heater <NUM> and the heating roller <NUM>, and, when laminating, after the heater <NUM> applies heat and pressure to the entire surface of the stack <NUM>, the heating roller <NUM> may apply heat and pressure to the stack <NUM> while rotating.

<FIG> is a perspective view of a sealer <NUM> according to an embodiment of the present invention.

As illustrated in <FIG>, and in accordance with the independent claims <NUM> and <NUM>, the sealer <NUM> includes: a first body <NUM>; and a second body <NUM> vertically extending from the first body <NUM>. Here, the second body <NUM> may extend from one end of the first body <NUM>, but preferably extends from the center of the first body <NUM>. That is, the sealer <NUM> may have a T-shape as a whole. Thus, with respect to the second body <NUM> of the sealer <NUM>, one electrode <NUM> is disposed on one side and another electrode <NUM> is disposed on the other side, and thus heat and pressure can be applied to both electrodes <NUM> simultaneously.

A heating coil (not shown) is included inside the sealer <NUM>. Therefore, when the sealer <NUM> is in contact with the stack <NUM> and applies pressure to the stack <NUM>, heat generated from the heating coil may also be applied to the stack <NUM>.

<FIG> is a plan view illustrating a state in which the sealers <NUM> according to an embodiment of the present invention applies heat and pressure to the stack <NUM>, and <FIG> is a side view illustrating a state in which the sealer <NUM> according to an embodiment of the present invention applies heat and pressure to the stack <NUM>.

As described above, there may be a height difference of the porous coating layer <NUM> in the side <NUM> and the center <NUM> of the separator <NUM>. Thus, deviation in the adhesion of the separator <NUM> occurs, and thus the non-adhesive region <NUM>, to which the electrode <NUM> does not adhere or poorly adheres, may be formed on the side <NUM> of the separator <NUM>.

Therefore, according to an embodiment of the present invention, when the stack <NUM> is formed, the laminator applies heat and pressure to the stack <NUM>, and then, as illustrated in <FIG>, the sealers <NUM> are disposed between the plurality of electrodes <NUM> in the stack <NUM> (S303). In addition, the sealers <NUM> apply heat and pressure to the side <NUM> of the stack <NUM>, that is, to at least one of the corners of electrodes <NUM> or the edges of the electrodes <NUM>. In this case, the sealers <NUM> are formed in plurality, and are disposed on both sides of the stack <NUM>, and thus may apply heat and pressure to each of both the sides <NUM> of the stack <NUM>. The sides <NUM> are preferably regions in which each length from both ends of the stack <NUM> is <NUM>% to <NUM>% with respect to the total length, more preferably, <NUM>% to <NUM>%.

If the sealers <NUM> are not used and heat and pressure being applied to the entire surface of the stack <NUM> by the laminator are merely increased, the center of the stack <NUM> excessively receives pressure compared to the side <NUM>. Then, pores of the porous coating layer <NUM> of the separator <NUM> are destroyed to reduce the air permeability, and thereby the electrode <NUM> and the separator <NUM> may not be fully impregnated in the electrolyte solution later.

The sealer <NUM> includes a first body <NUM> and a second body <NUM>. The first body <NUM> of the sealer <NUM> may apply heat and pressure to a first edge <NUM> toward the outside of the stack <NUM> in the electrode <NUM>, and the second body <NUM> may apply heat and pressure to a second edge <NUM>, which faces another neighboring electrode <NUM> and crosses with the first edge <NUM> to form the corner, in the electrode <NUM>.

The first edge <NUM> is the edge toward the outside of the stack <NUM> among several edges of the electrode <NUM>. In addition, the first body <NUM> of the sealer <NUM> is formed in a direction parallel to the first edge <NUM>. Thus, when the first body <NUM> is brought into contact with the stack <NUM>, the first body <NUM> can be brought into contact with the first edge <NUM> of the electrode <NUM>, thereby applying heat and pressure to the first edge <NUM>.

The second edge <NUM> is the edge, which forms the corner of the electrode <NUM> together with the first edge <NUM>, among several edges of the electrode <NUM>. As described above, on the stack <NUM>, the electrodes <NUM> are spaced apart from each other and disposed in a row in the longitudinal direction of the separator sheet. Therefore, the electrodes <NUM> are disposed adjacent to each other, and the second edge <NUM> faces another neighboring electrode <NUM>. In addition, the second body <NUM> of the sealer <NUM> is formed in a direction parallel to the second edge <NUM>. Thus, when the second body <NUM> is brought into contact with the stack <NUM>, the second body <NUM> can be brought into contact with the second edge <NUM> of the electrode <NUM>, thereby applying heat and pressure to the second edge <NUM>.

The sealers <NUM> are formed in plurality, and may be disposed at both the sides of the stack <NUM>. Moreover, the sealers <NUM> may each be disposed between electrodes <NUM> which are arranged in a row in the stack <NUM>. Therefore, as illustrated in <FIG>, heat and pressure are simultaneously applied to the plurality of electrodes <NUM> in the stack <NUM>, thereby increasing production efficiency of the unit cell <NUM>.

As described above, according to an embodiment of the present invention, the plurality of sealers <NUM> may apply heat and pressure to the corners of the electrodes <NUM>. Therefore, the formation of the non-adhesive regions <NUM> on the side <NUM> of the unit cell <NUM> may be prevented, and the reduction of the adhesion between the electrode <NUM> and the separator <NUM> may be prevented.

When the sealers <NUM> apply heat and pressure to the corners of the electrodes <NUM>, the first body <NUM> and the second body <NUM> each may have a simple rectangular shape. However, the sealers <NUM> may not apply heat and pressure to the corners of the electrodes <NUM>, but to the edges of the electrodes, in particular, only to the edges of the electrodes included in both the sides <NUM> of the stack <NUM>. In this case, the parts of the sealers <NUM> corresponding to the corners of the electrodes <NUM> may be recessed. Even in this case, heat and pressure may also be applied to both the sides <NUM> of the stack <NUM>, and thus the formation of the non-adhesive regions <NUM> may be prevented.

After the sealers <NUM> apply heat and pressure to the sides <NUM> of the stack <NUM>, a fourth cutter <NUM> cuts the stack <NUM>, and thus the unit cell <NUM> may be prepared.

<FIG> is a schematic view of a unit cell manufacturing apparatus 1a according to another embodiment of the present invention.

According to another embodiment of the present invention, as illustrated in <FIG>, a laminator is not included. That is, neither a heater <NUM> nor a heating roller <NUM> are included.

If the sealers <NUM> are used, heat and pressure may be applied to both the sides <NUM> of the stack <NUM>, and thus the formation of the non-adhesive regions <NUM> in the sides <NUM> of the unit cell <NUM> may be prevented. Therefore, according to another embodiment of the present invention, even though the laminator does not laminate the entire surface of the stack <NUM>, the electrodes <NUM> and the separators <NUM> may be generally uniformly bonded. Moreover, the laminator is not included, and thus the overall process speed may increase, thereby increasing the production efficiency of the unit cells <NUM>.

<FIG> is a perspective view of a sealer 14a according to still another embodiment of the present invention.

According to still another embodiment of the present invention, as illustrated in <FIG>, the sealer 14a may further include: a first protrusion <NUM> which protrudes downward from the lower surface of the first body <NUM> and is elongated in the longitudinal direction of the first body <NUM>; and a second protrusion <NUM> which protrudes downward from the lower surface of the second body <NUM> and is elongated in the longitudinal direction of the second body <NUM>.

<FIG> is a side view illustrating a state in which a sealer 14a according to still yet another embodiment of the present invention applies heat and pressure to a stack 20a.

When the sealer 14a applies heat and pressure to the stack 20a, the first protrusion <NUM> may apply heat and pressure to a first region <NUM>, which extends to the outside from the first edge <NUM> of the electrode <NUM>, of the separator sheets <NUM> and <NUM>, and the second protrusion <NUM> may apply heat and pressure to a second region <NUM>, which is formed between the plurality of electrodes <NUM>, of the separator sheets <NUM> and <NUM>.

The first region <NUM> is a portion of the separator sheets <NUM> and <NUM>, which extends to the outside from the first edge <NUM> of the electrode <NUM>. Because the first edge <NUM> of the electrode <NUM> is toward the outside, the first region <NUM> is also toward the outside of the stack 20a. In addition, the first protrusion <NUM> of the sealer 14a pressurizes the first region <NUM> of the separator sheets <NUM> and <NUM>, thereby bonding the upper separator sheet <NUM> and the lower separator sheet <NUM> as illustrated in <FIG>.

The second region <NUM> is a portion of the separator sheets <NUM> and <NUM>, which is formed between the plurality of the electrodes <NUM>. That is, the region is extended from the second edge <NUM> of the electrode <NUM>. In addition, the second protrusion <NUM> of the sealer 14a pressurizes the second region <NUM> of the separator sheets <NUM> and <NUM>, thereby bonding the upper separator sheet <NUM> and the lower separator sheet <NUM>.

In order for the first protrusion <NUM> and the second protrusion <NUM> to pressurize the separator sheet <NUM> to be easily bonded to the lower separator sheet <NUM>, it is preferable that the first protrusion <NUM> and the second protrusion <NUM> are formed thicker than the total thickness of the center electrode <NUM> and the upper electrode <NUM>.

As described above, according to still another embodiment of the present invention, the adhesion between the separator <NUM> and the electrode <NUM> may be improved, as well as the upper separator sheet <NUM> and the lower separator sheet <NUM> may adhere to each other, thereby forming the unit cell <NUM> more firmly.

Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be carried out in other specific forms without changing the technical idea or essential features. Therefore, the above-described embodiments are to be understood in all aspects as illustrative and not restrictive. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein. Various modifications made within the meaning of an equivalent of the claims of the invention and within the claims are to be regarded to be in the scope of the present invention.

Claim 1:
A unit cell manufacturing apparatus (<NUM>) comprising:
an electrode reel (<NUM>, <NUM>, <NUM>) from which an electrode sheet (<NUM>, <NUM>, <NUM>), which is to be a plurality of electrodes (<NUM>), is unwound;
a separator reel (<NUM>, <NUM>) from which a separator sheet (<NUM>, <NUM>) to be stacked with the electrodes (<NUM>) is unwound;
a sealer (<NUM>), in a stack (<NUM>) which is formed by stacking the plurality of electrodes (<NUM>) with the separator sheet (<NUM>, <NUM>) while the plurality of electrodes (<NUM>) are spaced apart from each other and disposed in a row in the longitudinal direction of the separator sheet (<NUM>, <NUM>), the sealer (<NUM>) which is disposed between a pair of neighoring electrodes (<NUM>) of the plurality of electrodes (<NUM>) and applies heat and pressure to at least one of corners of the electrodes (<NUM>) or edges of the electrodes (<NUM>), and
a laminator which laminates the stack (<NUM>).