WO2006052082A1 - Method for manufacturing gelled polymer cell having cross-linked interface and lithium secondary cell obtained by using the method - Google Patents

Method for manufacturing gelled polymer cell having cross-linked interface and lithium secondary cell obtained by using the method Download PDF

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Publication number
WO2006052082A1
WO2006052082A1 PCT/KR2005/003787 KR2005003787W WO2006052082A1 WO 2006052082 A1 WO2006052082 A1 WO 2006052082A1 KR 2005003787 W KR2005003787 W KR 2005003787W WO 2006052082 A1 WO2006052082 A1 WO 2006052082A1
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Prior art keywords
polymer
cell
electrolytic solution
functional
separation film
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PCT/KR2005/003787
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French (fr)
Inventor
Hyeon Taik Hong
Seung Taek Myung
Myung Hun Cho
Tae Hyuk Kang
Chi Su Kim
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Vk Corporation
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Publication of WO2006052082A1 publication Critical patent/WO2006052082A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
    • H01M10/38—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0085—Immobilising or gelification of electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a method of producing a gelled polymer cell having a cross-linked interface and a lithium secondary cell using the same. More particularly, the present invention pertains to a method of producing a polymer cell which has a cross-linked interface and in which large current charge and discharge and cyclic lifespan characteristics are excellent due to desirable mterfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of the cell between the separation film and a polar plate, and a lithium secondary cell using the same.
  • mterfacial stability between an electrolyte and a coated separation film layer, and shape preservation of a cell between the separation film and a polar plate are important characteristics directly affecting stability of the cell.
  • a liquid electrolyte or a solid electrolyte is used as an electrolyte of a lithium secondary cell.
  • an electrolytic solution may be leaked from the lithium secondary cell while in use. Accordingly, use of the solid electrolyte, from which leakage ofanelectrolytic solution isnotan issue, is suggestedinstead of the liquid electrolyte.
  • the solid electrolyte from which the electrolytic solution cannot leak, is flexible, thus being advantageous in that it is easy to process it to form a desired shape.
  • the known polymer solid electrolyte may be classified into a complete solid-type electrolyte havingno organic electrolytic solution and a gel-type electrolyte having an organic electrolytic solution.
  • the gel-type polymer electrolyte may not be easily diffused into a cell due to an increase in viscosity of the electrolyte during dissolution of a polymer. If the electrolytic solution is not easily diffused, the electrolytic solution may be nonuniformly distributed in the cell. This is accompanied by local concentration of current, causing a fatal problem, such as reduction of performance, in the cell.
  • a shape preservation characteristic of a cell is poor as adhesive power is weak between a polar plate and a separation film during operation of the cell, internal resistance is increased, thus undesirably reducing cyclic lifespan and large current discharge characteristics.
  • Japanese Patent Laid-Open Publication No. Hei.10-177865 discloses a lithium secondary cell whichcomprises an anode, a cathode, a separation film having sides for holding an electrolytic solution, and a resin layer.
  • the resin layer includes a mixed phase of an electrolytic solution phase, a polymer gel phase having the electrolytic solution, and a polymer solid phase, and is positioned on the sides of the separation film to attach the anode to the cathode.
  • Japanese Patent Laid-Open Publication No. Hei.10-189054 discloses a method of producing a lithium secondarycell.
  • the lithium secondary cell disclosed in the above-mentioned patent is problematic in that wrinkles are formed during shape preservation of the cell, internal resistance is high, and the lifespan characteristic is poor.
  • U.S. Pat. Nos. 5,639,573, 5,716,421, 5,631,103, and 5, 849,433, andE.P. No.0933824A2 discloseamultilayeredpolymer electrolytewhichcomprisesafirstpolymerconstitutingaporous separation film, and a second polymer gelled by a liquid electrolyte.
  • ionic conductivity is reducedin comparisonwith use of only the liquid electrolyte, and the two layers are insufficiently attached to each other, thus, undesirably, swelling occurs due to impregnation of the liquid electrolyte or the structure is destroyed during operation of the cell for a long time.
  • U.S. Pat. No. 5,296,318 discloses a lithium polymer secondary cell produced using a process which comprises compressing electrodes and a polymer film at high temperatures so as to apply a polyvinylidene fluoride-based material having excellentprocessabilitytoapolymergel electrolyticmaterial, extracting an additive, and adding an electrolytic solution.
  • a process which comprises compressing electrodes and a polymer film at high temperatures so as to apply a polyvinylidene fluoride-based material having excellentprocessabilitytoapolymergel electrolyticmaterial, extracting an additive, and adding an electrolytic solution.
  • Korean Patent Laid-Open Publication No. 1999-0086381 discloses a method of producing a cell, which comprises coating a polymer electrolyte using a cosolvent.
  • a method of producing a cell which comprises coating a polymer electrolyte using a cosolvent.
  • moisture control must be conducted in a process, and that an anode and a cathode must be coated, thus the process is complicated.
  • Korean Patent Laid-Open Publication No. 2004-0006057 discloses an electrolytic composition which includes lithium salts and an organic solvent as main components, a nitrogen-contained compound, and biphenyl, and is used to produce a lithiumsecondary cell.
  • Ahalogen or epoxy-contained compound is addedas an additive to the electrolytic composition so as to convert the electrolytic composition into a gelled polymer electrolyte, thereby assuring overcharge stability.
  • Korean Patent Laid-Open Publication No. 2002-0064590 disclosesamulti-componentcomplexfilmwhichisusedtoproduce a polymer electrolyte and a cell, and comprises a support layer film and a gelled polymer layer fused on one side or both sides of the support layer film by heating.
  • the present inventors have conducted studies into avoidance of the above-mentioned problems, resulting in the finding that, when diffusion or distribution of an electrolytic solution into a coated separation film layer is made uniform to conduct cross-linking and gelation and to obtain desired adhesive power, lifespan and charge/discharge characteristics are excellent due to desirable interfacial stability between an electrolyte and the coated separation film layer and desirable shape preservation of a cell between the separation film and a polar plate, thereby accomplishing the present invention.
  • an object of the present invention is to provide a method of producing a gelled polymer cell which has a cross-linked interface and in which lifespan and charge/discharge characteristics are excellent due to desirable interfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of a cell between the separation film and a polar plate, and a lithium secondary cell using the same.
  • the present invention provides a method of producing a gelled polymer cell having a crosslinked interface.
  • the method comprises:
  • the adhesive first polymer of the step (1) is selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, polyvinyl chloride, polyvinylidene chloride, polychlorot ⁇ fluoroethylene, a polychlorotrifluoroethylene vinylidene fluoride copolymer, poly-1,2-difluoroethylene, polymethylmethacrylate, polyethylene oxide, polypropylene oxide, polysiloxane, and copolymers thereof.
  • the functional second polymer of the steps (1) and (3) is selected from the group consisting of amine, acid anhydride, and imidazole, polyethylimine, polyvinylpyndine, a copolymer containing polyvinylpyridme, a poly-N-vinylpyridine-styrene copolymer, poly-N-vinylpyridine butyl methacrylate, and poly-2-ethyl-2-oxazoline.
  • a content of the first polymer of the step (1) is a 0.1 - 40 ratio by weight based on 100 weight of the organic solvent
  • a content of the second polymer is a 0.1 - 100 ratio by weight based on 100 weight of the first polymer.
  • the heatpressing of the step (2) it is preferable to conduct the heatpressing of the step (2) at 70-100 0 C and apre-pressure of 10 - 80 kg, which is applied to left and right load cells of a roll laminator.
  • the organic solvent of the step (3) is a polar organic solvent having a carbonate group, which is amixed solvent of two ormore selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, vinylidene carbonate, and ⁇ -butyrolactone.
  • the lithiumsalt which is dissolved in the organic solvent in the step (3) , is one or more selected from the group consisting of LiPF 6 , LiAsF 6 ,
  • LiClO 4 LiN (CF 3 SO 2 ) 2 , LiBF 4 , LiCF 3 SO 3 , LlSbF 6 , LlB (C 2 O 4 ) 2 , LiN(SO 2 CF 2 CF 3 ) 3 / and LiPF 3 (CF 2 CF 3 ) J .
  • the crosslinkmg agent of the step (4) has a chain end containing an epoxy ring, which is any one or a combination of two or more selected from the groupconsistingofaprimaryfunctionalepoxygroup, asecondary functional epoxy group, a tertiary functional epoxy group, a quaternary functional epoxy group, halogen-contained epoxy, and isocyanate-contained epoxy.
  • contents of the functional second polymer and the crosslinkmg agent of the step (4) are controlled so that the content of the functional second polymer is a 0.1 - 10 ratio by weight based on 100 weight ofthe firstelectrolyticsolutionofthe step (3) andthe content of the crosslinkmg agent is a 0.1 - 100 ratio by weight based on 100 weight of the functional second polymer, or the content of only the crosslinkmg agent is controlled so as to be a 0.1 - 10 ratiobyweightbasedon 100 weight of the firstelectrolytic solution.
  • the aging of the steps (6) and (7) is conducted at 20 - ⁇ V for 1 - 5 days.
  • the crosslmkmg of the step (7) is conducted at 30 - 100 ° C for 1 - 48 hours.
  • the present invention provides a lithium secondary cell which is produced using the above-mentioned method of producing the gelled polymer cell and which comprises a coated separation film layer including an adhesive first polymer and a functional second polymer, and an electrolyte including the functional secondpolymer capable of being gelled and a crosslmkmg agent in an electrolytic solution.
  • the methodofproducing the gelledpolymer cell having the crosslinked interface according to the present invention, convenience of a process is assured during the production of a cell having a large area, and an amount of the electrolytic solutionandviscosityofagel formationpolymerarecontrolled, thus it is possible to obtain uniformity during diffusion of the electrolytic solution into the cell, thereby it is possible toprovide a unit forpreventing local concentration of current.
  • the lithium secondary cell produced according to the present invention is flexible, and has excellent large current charge/discharge and cyclic lifespan characteristics due to desirable interfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of the cell between the separation film and a polar plate.
  • FIG. 1 illustrates a structure in which a blend of a first polymer and a second polymer is applied on both sides of a separation film according to the present invention
  • FIG. 2 illustrates a cell structure m which an anode/a separation film/a cathode/a separation film/an anode or a cathode/a separation film/an anode/a separation film/a cathode are sequentially layered according to the present invention
  • FIG.3 illustrates agelledsysteminwhichanelectrolyte is cross-linked with a coated separation film layer at an interface thereof according to the present invention
  • FIG. 4 is a graph showing a high rate discharge characteristic of a gelled polymer secondary cell produced according to the present invention.
  • FIG. 5 is a graph showing a lifespan characteristic of the gelled polymer secondary cell produced according to the present invention.
  • FIGS.6to 9 illustratearrangementofananode, acathode, and arrangement of polar plates, and a cell structure according to the present invention.
  • gel formation interface 40 gel formation functional second polymer and electrolytic solution containing crosslikmg agent
  • adescriptionwillbegivenofamethodofproducing a separation film which comprises uniformly applying apolymer blend layer on the separation film to form a coated layer, and drying the resulting film.
  • the separation film functions to intercept an internal short circuit between two electrodes and to hold an electrolytic solution.
  • An adhesive firstpolymeranda functional secondpolymer are blended with a solvent, which is capable of simultaneously dissolving the adhesive firstpolymer and the functional second polymer and is easily removed during drying, in the amount of a 0.1 - 40 ratio by weight based on 100 weight of the solvent and a 0.1 - 100 ratio by weight based on 100 weight of the first polymer, respectively, to prepare a coating solution.
  • first polymer content is less than a 0.1 ratio by weight, it is impossible to obtain desirable adhesive power. If the first polymer content is more than a 40 ratio by weight, flexibility is reduced due to high viscosity, thus coating ability and processability regarding control of a coating thickness are poor. Furthermore, if the second polymer content is less than a 0.1 ratio by weight, it is not easy to form a gel. If the content is more than a 100 ratiobyweight, since a gel structure is stiff, ionic conductivity is reduced and layer separation fromthe solvent occurs, thusperformance ofthe cell is reduced.
  • the solvent is any one or a mixed solvent of two or more selected from the group consisting of dimethyl sulfoxide, l-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, benzene, toluene, methanol, ethanol, methylene chloride, cyclohexane, dioxane, ethyl acetate, diethyl ether, acetone, tetrahydrofuran, and chloroform.
  • it is any one or a mixed solvent of two or more selected from the group consisting of acetone, tetrahydrofuran (THF) , and chloroform, which are capable of simultaneously dissolving the adhesive first polymer and the functional second polymer, are easily removed during drying, and have a boiling point of 100 ° C or less.
  • THF tetrahydrofuran
  • chloroform a mixed solvent of two or more selected from the group consisting of acetone, tetrahydrofuran (THF) , and chloroform
  • the reason why the solvents having a boiling point that is lower than the melting point (Tm) of the separation film are selected is as follows. Ifacontinuousprocess is conducted using a coating device, for example, a winder and an unwinder, underapredetermineddryingcondition, itispossibletoobserve deformation of a separation filmmatrix due to a winding tension applied to the matrix as temperature increases.
  • a coating device for example, a winder and an unwinder, underapredetermineddryingcondition
  • the separation film having a microporous structure is impregnated with the coating solution containing the adhesive first polymer and the functional second polymer to form coated layers, each having a thickness of 0.1 - 20 fm,on both sides ofthe separation film.
  • a thickness of the coated film which is a polymer blend layer
  • adhesion holding strength is poor and a desired function is not obtained.
  • the thickness of the coated film is more than 20 IM, undesirably, internal resistance depending on the thickness of the coated film is increasedandinterfacial adhesivepowerbetween the separation film and the coated layer is poor.
  • An application method that is used to form the coated layer maybe suitably selectedaccording to the use.
  • the method include a spray method, a dipping method, a doctor blade method, and a graveure method.
  • an additive which is used to improve performance of the cell is dissolved or dispersed in an electrolytic solution or m a polar plate.
  • it is a polymer type, has two polymers mixed with each other, andis appliedon aporous separation filmto realize functions thereof.
  • the second polymer which is of a functional group capable of opening an epoxy group during cross-linking of the interface, is applied on the coated separation film layer so as to easily control viscosity of the second functional polymer used as a gel formation supporter and an initiator during the production of a first electrolytic solution.
  • it is easy to produce an electrolytic composition uniformly dispersed in the cell.
  • the adhesive first polymer provides desirable contact and adhesion to the separation film
  • the functional second polymer can effectively remove an acid, such as HF or a Lewis acid (for example, PF 3 ) , causing deterioration in performance of the cell, and comprises apolymer, a copolymer, or an oligomer including a reactive group capable of conducting gelation, or a functional group containing a unit for improving performance of the cell as a main chain or a side chain.
  • theadhesive first polymer which has excellent contact and adhesion while it includes a nonaqueous electrolytic solution and which also has high lithium ionic conductivity, is used.
  • connection wxth this the selection of the adhesive first polymer is a critically important factor affecting application of the coated layer onto the separation film and mterfacial adhesion therebetween. This is theoretically 5 basedonasurfacetension.
  • ⁇ c (mN/m) critical surface tension
  • I 1 S polyethylene oxide, polypropylene oxide, polysiloxane, and copolymers thereof. It is more preferable to select polychlorotrifluoroethylene (PCTFE) or polyvmylidene fluoride (PVF) .
  • PCTFE polychlorotrifluoroethylene
  • PVF polyvmylidene fluoride
  • the functional second polymer can effectively remove an acid or a Lewis acid which is conventionally considered a cause of lifespan reduction of the cell and of deterioration in performance of the cell, and comprises a polymer, a copolymer, an oligomer including a reactive group capable of conducting gelation or a functional group containing a unit for improving performance of the cell.
  • the second polymer also comprises a polymer or a copolymer in which primary amine, secondary amine, tertiary amine, or a heterocyclic ring, containing one or more selected from the above amines, is positioned on a main chain or a side chain.
  • polyethylimine polyvmylpyridine
  • a copolymer containing polyvmylpyridine a poly-N-vmylpyridine-styrene copolymer
  • a poly-N-vinylpyridine-butyl methacrylate copolymer poly-2-ethyl-2-oxazoline
  • a polymer or a copolymer in which an epoxy group is positioned on a side chain thereof a polyethylene methacrylate glycidyl methacrylate copolymer, a polymeroracopolymercontaininganalcoholgroup, polyethylene monoalcohol, polyvinyl alcohol, a polyvinyl alcohol-contained copolymer, and a polymer or a copolymer containing a double bond or a double bond capable of realizing a resonant structure.
  • a viscous electrolytic solution may not be easily diffused into the cell.
  • a material such as the functional polymer capable of being gelled, is applied on the coatedseparation filmlayer, to easily control viscosity of the electrolytic solution; thereby it is possible to assure convenience of a process.
  • the functional polymer which is applied on a surface of the separation film to form the gel, and another functional polymer, which is added to the electrolytic solution in a small amount, are cross-linked and form the gel, thereby it is possible to obtain a uniform interface. Accordingly, in the production of the cell, performance of the cell is improved due to a uniform and stable interface, and it is possible to avoid fatal problems, such as gas generation and heat congestion, caused by local concentration of current.
  • a microporous polyolefm separation fxlm include polyethylene (PE) or polypropylene (PP) having excellent mechanical strength. More preferably, the polyethylene resin separation film, in which a resin is fused by heating to clog micropores so as to provide a so-called shutdown function to the cell, is used.
  • the polyethylene resin used in the present invention includes an ethylene homopolymer, and a copolymer of ethylene and ⁇ -olefins, for example, propylene, butene, or hexane.
  • the microporous polyethylene separation film may have a double-layered structure, such as PE/PP layers, orathree-layeredstructure, suchasPE/PP/PElayersorPP/PE/PP layers, in addition to a single-layered structure, such as a PE layer or a PP layer.
  • a polyvinylidene fluoride-based separation film as long as it is not dissolved in a solvent capable of dissolving the adhesive and functional polymers.
  • a thickness of the separation film as a matrix used to apply the polymer blend solution be 5 - 45 ⁇ m. If the thickness of the separation film is less than 5 ⁇ sa, tensile strength is reduced, thus an internal short circuit may occur in electrodes if it is used as a separation film for a cell. If the thickness is more than 45 ⁇ m, distance between electrodes is excessively long, thus, undesirably, internal resistance of the electrode is excessively high.
  • the drying be conducted at 25 - 10Ot,. If the drying temperature is low, drying time is long and any remaining solvent may cause a problem on an interface of the separation film and the coated layer. On the other hand, if the drying temperature is high, the separation film is shrunken and distorted, causing problems during the production of the cell.
  • a coating solution in which an adhesive first polymer (21) and a functional second polymer (22) are blended, is applied on both sides of a separation film (10) .
  • an anode active material 80 - 100 parts by weight of an anode active material, 2 - 20 parts by weight of a conductive agent, and 2 - 7 parts by weight of a binder are suspended in 30 - 100 parts byweight of a solvent (for example, N-methylpyrrolidone;
  • a solvent for example, N-methylpyrrolidone
  • NMP NMP
  • the anode active material may be exemplified by various oxides, for example, chalcogenides, such as manganese dioxide, lithium manganese complex oxides, nickel oxides containing lithium, cobalt oxides containing lithium, nickel cobaltoxides containing lithium, iron oxides containing lithium, vanadium oxides containing lithium, titanium disulfate, and molybdenumdisulfate.
  • chalcogenides such as manganese dioxide, lithium manganese complex oxides, nickel oxides containing lithium, cobalt oxides containing lithium, nickel cobaltoxides containing lithium, iron oxides containing lithium, vanadium oxides containing lithium, titanium disulfate, and molybdenumdisulfate.
  • cobalt oxides containing lithium e.g. LiCoO 2
  • nickel cobalt oxides containing lithium e.g. LiNio ⁇ COO 2O2
  • lithium manganese complexoxides e.g. LiMn 2 Ci, Li
  • the conductive agent may be exemplified by acetylene black, carbon black, and graphite.
  • the binder functions to hold the active materials in the collector and to connect the active materials to each other.
  • Thebinder maybe exemplifiedbypolytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) , an ethylene-propylene-diene copolymer (EPDM) , and a styrene-butadiene rubber (SBR) .
  • PTFE polytetrafluoroethylene
  • PVDF polyvinylidene fluoride
  • EPDM ethylene-propylene-diene copolymer
  • SBR styrene-butadiene rubber
  • the activematerial, the conductive agent, and the binder be combined in a ratio of 80 - 100 parts by weight, 2 - 20 parts by weight, and 2 - 7 parts by weight, respectively.
  • NMP N-methylpyrrolidone
  • the cathode includes a carbon active material which adsorbs and desorbs lithium ions, the conductive agent, and the binder.
  • the cathode active material may be exemplified by a graphite material ora carbonmaterial, such as graphite, cokes, carbon fibers, and globular carbon, and a graphite material or a carbon material, which is obtained by heat treating thermosetting resin, isotropic pitches, mesophase pitches, mesophase pitch-based carbon fibers, and mesophase micro-spherule at 500 - 3000 ° C.
  • a secondary cell that is provided with the cathode including the above-mentioned graphite material as the cathode active material can significantly improve cell capacity and a large current discharge characteristic.
  • the conductive agent may be exemplified by acetylene black, carbon black, and graphite.
  • the binder functions may be exemplified by polytetrafluoroethylene (PTFE) , polyvinylidene fluoride
  • PVDF polyvinyl-propylene-diene copolymer
  • EPDM ethyl-propylene-diene copolymer
  • SBR styrene-butadiene rubber
  • the separation film, the anode plate, and the cathode plate which are produced through the above-mentioned procedure, are processed to have a predetermined size, arrangedto forma laminate structure shown in FIG. 2, and heat pressed to produce a laminate type cell.
  • the laminate type cell may have a structure in which a coated separation film is interposed between a cathode and an anode, a structure which comprises a cathode, separation films attachedto both sides of the cathode, andanodes attached to external sides of the separation films, or a structure which comprises an anode, separation films attached to both sides of the anode, and cathodes attached to external sides of the separation films.
  • the laminate structure provides a high energy/voltage battery, and the layers constituting the structure are brought into tight contact with each other using an adhesive polymer to optimize ion mobility and to improve performance of the cell.
  • polar plates of a cell having a large area is conducted using various methods, such as a stack method, a bag-like method, a winding method, a polymer glue method, and a heat pressing method.
  • the arrangement methods other than the heat pressing method are problematic in that, since size of the separation film increases as size of the polar plate increases, the separation film is wrinkled during vacuum packaging, thus there are many difficulties in the cell arrangement. Accordingly, in the present invention, a cell having an excellent shape preservation characteristic is produced using the heat pressing method.
  • a bi-cell structure In the formation of a bi-cell structure according to the present invention, it is preferable to conduct the heat pressing at 70 - 100 ° C and a pre-pressure of 10 - 80 kg which is applied to left and right load cells of a roll laminator. More particularly, the pre-pressure is maintained at 20 - 60 kg and the temperature is 85 - 95 ° C . Subsequently, a group of electrodes having the bi-cell structure is injected into an aluminum packaging material, and a first electrolytic solution including lithium salts and an organic solvent is produced.
  • an organic solvent is preferably a polar organic solvent having a carbonate group, which is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, vinylidene carbonate, and ⁇ -butyrolactone.
  • the lithium salt is one or more selected from the group consisting of LiPF 6 , LiAsF 6 , LiClO 4 , LiN(CF 3 SO 2 ) 2 , LiBF 4 , LiCF 3 SO 3 , LiSbF 6 , LiB(C 2 O 4 J 2 , LiN(SO 2 CF 2 CF 3 J 3 , andLiPF 3 (CF 2 CF 3 ) 3 .
  • the lithium salt is dissolved in the organic solvent to produce a first electrolytic solution.
  • the first electrolytic solution is produced so that a content of the functional second polymer is a 0.1 - 10 ratio by weight basedon 100 weight of the first electrolytic solution and a content of a crosslinking agent is a 0.1 - 100 ratio by weight based on 100 weight of the functional second polymer, or that a content of only the crosslinking agent is a 0.1 - 10 ratio by weight based on 100 weight of the first electrolytic solution.
  • the first electrolytic solution is injected into a packaging material (for example, an aluminum packaging material) containing a group of electrodes having the laminate type cell structure, and packaging is conducted to produce the lithium secondary cell.
  • the polymer added to the electrolytic solution may or may not be the same as the functional second polymer.
  • Any crosslinking agent may be added to the electrolytic solution as long as it has a chain end including an epoxy ring which is exemplified by primary functional epoxy, secondary functional epoxy, tertiary functional epoxy, and quaternary functional epoxy. Furthermore, epoxy substitutedwithbromine, or halogen-contained epoxy may be used. Particularly, it is preferable to add a fire-retardant material to the chain so as to increase stability, anditmay include isocyanates capable of conducting an ion bond or a covalent bond.
  • the packaged cell is aged at 20 - 60°C for 1 - 5 days.
  • the functional second polymer for example, PCTFE solef 32008
  • An early agingprocess aims to improve adhesion power ofthecell
  • afinalagingprocess aimstouseagelelectrolyte as a supporter through a crosslinkmg process.
  • a final gelation process must not be conducted if the electrolytic solution is not uniformly diffused into the cell. The reason is that if the gelation is conducted in the early aging process, performance of the cell is reduced due to nonuniformity. Accordingly, it is necessary to carefully set an earlyagingtemperature, andtodesign openingefficiency of the functional polymer to conduct opening of epoxy.
  • the coated separation film layer is aged in an atmospheric pressure at 30 - 100 ° C for 1 - 48 hours to be crosslinked so as to form a gel, thereby producing a gelled polymer cell according to the present invention.
  • the gel electrolyte can act as the supporter by the crosslinkmg process.
  • a coated layer (20) in which an adhesive first polymer (21) and a functional second polymer (22) are blended on both sides of a separation film (10) , is aged so that the functional second polymer capable of being gelled is crosslinked with an electrolyte (40) including a crosslinking agent (41) , thereby creating a gelation system which has a crosslinked interface and in which a gel (30) is formed at an interface of the coated separation film layer and the electrolyte.
  • a functional second polymer additive layer including pyridines may be used as an acid scanvenger due to a function of pyridine. Furthermore, it may react with an epoxy group to form an ion type gel. This is additionally conducted in view of stability.
  • LiMn ? ⁇ 4 is usedas ananode activematerial, itacts as anadditive capable of preventing dissolution of manganese due to HF.
  • an overcharge additive such as BP
  • oxidationpolymerization occurs inearlystagesdue tocatalysis of HF or a Lewis acid, thus it is possible to avoid a cause of rapidly increasing the self-discharge speed of a cell.
  • an adhesive first polymer is used as a support layer and heat pressed so that adhesive power to an active material and conductivity are increased, interfacial adhesion between the separation film and the polar plate is achieved during the cell arrangement to avoid the wrinkle problem, and a shape of the cell is nicely preserved in handling to assure convenience of a process during the production of a cell having a large area.
  • the functional second polymer including a unit capable of effectively removing the above-mentioned acid, is used to be blended with the adhesive first polymer, thereby improving performance and the lifespan characteristic of the cell.
  • the functional polymer for initiating the cross-linking agent acting as a gel formation supporter and improving performance of the cell, is mixedwith the adhesive firstpolymer andapplied on the coated separation film layer so as to control viscosity of a gel formation electrolyte injected into the cell, thereby the electrolytic solution is easily diffused into the cell.
  • this process is advantageous in that interfacial stability between the coated separation film layer, including the gel formation polymer and the electrolyte, is excellent; thus stability of the cell is improved.
  • the lithium secondary cell of the present invention produced according to the above-mentioned procedure is advantageous in that convenience and flexibility of a process are fair during the production of the cell having a large area, andinterfacial stabilitybetweentheelectrolyte andthecoated separation filmlayer andshapepreservation of the cellbetween the separation film and the polar plate are improved, and large current charge/discharge and cyclic lifespan characteristics are excellent.
  • the first polymer was selected from materials having a surface tension that was less than or was the same as that of an olefin-based separation film.
  • An active material (L1C0O2) , a conductive agent, and a binder were dispersed in NMP in a weight ratio of 95 : 2 :3 to produce a slurry.
  • the slurry was applied on an aluminum foil, dried at 120°C, and pressed to produce an anode having a thickness of 107 ⁇ m.
  • the anode is shown in FIG. 6.
  • a cathode active material (graphite) , a conductive agent, and a binder were dispersed in NMP in a weight ratio of 90 : 7 : 3 to produce a slurry.
  • the slurry was applied on a cathode copper foil, dried at 120°C, and pressed to produce a cathode having a thickness of 130 ⁇ m-
  • the cathode is shown in FIG. 7.
  • the prepared anode was cut to a size of 85 X 150 cm, except for a tap portion, and the cathode was cut to a size of 87 X 152 cm, except for a tap portion, as in the case of the anode.
  • a coated separation film which had a size that was larger than the size of the cut cathode by 1.5 mm lengthwise and crosswise, was prepared, and polar plates were arranged (FIG.8) toproduce abi-cell structure (FIG. 9) .
  • Apre-pressure was maintained at 40 kg which was applied to left and right load cells of a roll laminator, and heat pressing was conducted at 90°C to produce a bi-cell.
  • Epoxy substituted with bromine (Kukdo Chemical, Inc.) was added in the amount of a 0.3 ratio by weight as a crosslinkmg agent based on the weight of the second polymer, agitated so as to be sufficiently dissolved in the first electrolytic solution, and stored to create a second electrolytic solution.
  • a lifespan characteristic of the lithium secondary cell thatwasproducedaccordingto example 1 ofthepresent invention was tested.
  • charge and discharge were repeated 120 times using a current of l.OC at normal temperature to evaluate the characteristic. The results are shown in FIG. 5.
  • a capacity preservation ratio is 95 % or more when the lithium secondary cell according to the present invention reaches the 120th cycle, thus the lifespancharacteristicisexcellent.
  • the capacity preservation ratio at the 120th cycle denotes a dischargecapacityatthe 120thcycleassumingthatthedischarge capacity at the 1st cycle is 100 %.
  • a method of producing a gelledpolymer cell according to the present invention convenience of a process is assured during the production of a cell having a large area, and the amount and composition of a gel electrolytic solution are controlled to provide a unit forpreventing local concentration of current.
  • Agelled lithiumsecondary cellproducedaccording to the present invention has excellent large current charge/discharge and cyclic lifespan characteristics due to desirable interfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of the cell between the separation film and a polar plate.

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Abstract

Disclosed is a method of manufacturing a gelled polymer cell and a lithium secondary cell using the method. The method comprises (1) applying a polymer blend layer, in which an adhesive first polymer and a functional second polymer are dissolved in an organic solvent, on a separation film, and drying the resulting layer, (2) interposing the separation filmbetween an anode and a cathode to form layered electrodes, and heat pressing the electrodes, (3) producing a first electrolytic solution, (4) addingthe secondpolymer anda crosslinkmg agent, or only the crosslinkmg agent, to the first electrolytic solution to produce a second electrolytic solution, (5) inserting the electrodes into a packaging material, injecting the second electrolytic solution, and sealing the resulting structure to produce the cell, (6) aging the cell to swell the coated separation film, and (7) crosslinkmg the resulting film and the electrolytic solution to form a gel.

Description

[DESCRIPTION]
[invention Title]
METHOD OF MANUFACTURING GELLED POLYMER CELL HAVING CROSS-LINKED INTERFACE AND LITHIUM SECONDARY CELL OBTAINED BY USING THE METHOD
[Technical Field]
The present invention relates to a method of producing a gelled polymer cell having a cross-linked interface and a lithium secondary cell using the same. More particularly, the present invention pertains to a method of producing a polymer cell which has a cross-linked interface and in which large current charge and discharge and cyclic lifespan characteristics are excellent due to desirable mterfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of the cell between the separation film and a polar plate, and a lithium secondary cell using the same.
[Background Art]
Generally, in a secondary cell, particularly in a gelled polymer electrolyte for a lithium ion secondary cell, mterfacial stability between an electrolyte and a coated separation film layer, and shape preservation of a cell between the separation film and a polar plate are important characteristics directly affecting stability of the cell.
Typically, a liquid electrolyte or a solid electrolyte is used as an electrolyte of a lithium secondary cell. However, in the case of the liquid electrolyte, an electrolytic solution may be leaked from the lithium secondary cell while in use. Accordingly, use of the solid electrolyte, from which leakage ofanelectrolytic solution isnotan issue, is suggestedinstead of the liquid electrolyte.
The solid electrolyte, from which the electrolytic solution cannot leak, is flexible, thus being advantageous in that it is easy to process it to form a desired shape. Hence, many studies regarding this havebeenmade. Particularly, many studies have been conducted of a polymer solid electrolyte. The known polymer solid electrolyte may be classified into a complete solid-type electrolyte havingno organic electrolytic solution and a gel-type electrolyte having an organic electrolytic solution.
The gel-type polymer electrolyte may not be easily diffused into a cell due to an increase in viscosity of the electrolyte during dissolution of a polymer. If the electrolytic solution is not easily diffused, the electrolytic solution may be nonuniformly distributed in the cell. This is accompanied by local concentration of current, causing a fatal problem, such as reduction of performance, in the cell.
Furthermore, if a shape preservation characteristic of a cell is poor as adhesive power is weak between a polar plate and a separation film during operation of the cell, internal resistance is increased, thus undesirably reducing cyclic lifespan and large current discharge characteristics.
To avoid the above-mentioned problems, Japanese Patent Laid-Open Publication No. Hei.10-177865 discloses a lithium secondary cell whichcomprises an anode, a cathode, a separation film having sides for holding an electrolytic solution, and a resin layer. The resin layer includes a mixed phase of an electrolytic solution phase, a polymer gel phase having the electrolytic solution, and a polymer solid phase, and is positioned on the sides of the separation film to attach the anode to the cathode.
Furthermore, Japanese Patent Laid-Open Publication No. Hei.10-189054 discloses a method of producing a lithium secondarycell. Themethodcomprises formingelectrodes onanode and cathode collectors, drying the electrodes while they are in contact with a separation film to vaporize a solvent so as to form a cell laminate, and impregnating the cell laminate with an electrolytic solution.
However, the lithium secondary cell disclosed in the above-mentioned patent is problematic in that wrinkles are formed during shape preservation of the cell, internal resistance is high, and the lifespan characteristic is poor.
U.S. Pat. Nos. 5,639,573, 5,716,421, 5,631,103, and 5, 849,433, andE.P. No.0933824A2discloseamultilayeredpolymer electrolytewhichcomprisesafirstpolymerconstitutingaporous separation film, and a second polymer gelled by a liquid electrolyte. However, it is problematic in that ionic conductivity is reducedin comparisonwith use of only the liquid electrolyte, and the two layers are insufficiently attached to each other, thus, undesirably, swelling occurs due to impregnation of the liquid electrolyte or the structure is destroyed during operation of the cell for a long time.
U.S. Pat. No. 5,296,318 discloses a lithium polymer secondary cell produced using a process which comprises compressing electrodes and a polymer film at high temperatures so as to apply a polyvinylidene fluoride-based material having excellentprocessabilitytoapolymergel electrolyticmaterial, extracting an additive, and adding an electrolytic solution. However, it is problematic in that the cell is undesirably adhered to the electrodes, thus the shape preservation characteristic of the cell is poor.
Additionally, Korean Patent Laid-Open Publication No. 1999-0086381 discloses a method of producing a cell, which comprises coating a polymer electrolyte using a cosolvent. However, it is problematic in that moisture control must be conducted in a process, and that an anode and a cathode must be coated, thus the process is complicated.
Korean Patent Laid-Open Publication No. 2004-0006057 discloses an electrolytic composition which includes lithium salts and an organic solvent as main components, a nitrogen-contained compound, and biphenyl, and is used to produce a lithiumsecondary cell. Ahalogen or epoxy-contained compound is addedas an additive to the electrolytic composition so as to convert the electrolytic composition into a gelled polymer electrolyte, thereby assuring overcharge stability.
Korean Patent Laid-Open Publication No. 2002-0064590 disclosesamulti-componentcomplexfilmwhichisusedtoproduce a polymer electrolyte and a cell, and comprises a support layer film and a gelled polymer layer fused on one side or both sides of the support layer film by heating.
Based on the above description, the present inventors have conducted studies into avoidance of the above-mentioned problems, resulting in the finding that, when diffusion or distribution of an electrolytic solution into a coated separation film layer is made uniform to conduct cross-linking and gelation and to obtain desired adhesive power, lifespan and charge/discharge characteristics are excellent due to desirable interfacial stability between an electrolyte and the coated separation film layer and desirable shape preservation of a cell between the separation film and a polar plate, thereby accomplishing the present invention.
[Disclosure]
[Technical Problem]
Accordingly, thepresent inventionhasbeenmade keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method of producing a gelled polymer cell which has a cross-linked interface and in which lifespan and charge/discharge characteristics are excellent due to desirable interfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of a cell between the separation film and a polar plate, and a lithium secondary cell using the same.
[Technical Solution]
In order to accomplish the above object, the present invention provides a method of producing a gelled polymer cell having a crosslinked interface. The method comprises:
(1) applying a polymer blend layer, in which an adhesive first polymer and a functional second polymer capable of being gelled are dissolved in an organic solvent, on a separation film, and drying the resulting polymer blend layer to produce a coated separation film;
(2) interposing the separation film produced in the step (1) between an anode and a cathode to form a group of layered electrodes, and heat pressing the electrodes;
(3) producing a first electrolytic solution including a lithium salt and the organic solvent;
(4) adding the functional second polymer and a crosslinkmg agent mixed with each other in a predetermined mixing ratio, or only the crosslmking agent, to the first electrolytic solution of the step (3) to produce a second electrolytic solution;
(5) inserting the group of electrodes of the step (2) into a packaging material, injecting the second electrolytic solution of the step (4) thereinto, and sealing a resulting structure to produce the cell;
(6) aging the cell produced in the step (5) to swell the coated separation film layer; and
(7) crosslinkmg the coated separation film layer and the electrolytic solution to form a gel.
In the method of producing the gelled polymer cell according to the present invention, preferably, the adhesive first polymer of the step (1) is selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, polyvinyl chloride, polyvinylidene chloride, polychlorotπfluoroethylene, a polychlorotrifluoroethylene vinylidene fluoride copolymer, poly-1,2-difluoroethylene, polymethylmethacrylate, polyethylene oxide, polypropylene oxide, polysiloxane, and copolymers thereof.
In the method of producing the gelled polymer cell according to the present invention, preferably the functional second polymer of the steps (1) and (3) is selected from the group consisting of amine, acid anhydride, and imidazole, polyethylimine, polyvinylpyndine, a copolymer containing polyvinylpyridme, a poly-N-vinylpyridine-styrene copolymer, poly-N-vinylpyridine butyl methacrylate, and poly-2-ethyl-2-oxazoline.
In the method of producing the gelled polymer cell according to the present invention, preferably a content of the first polymer of the step (1) is a 0.1 - 40 ratio by weight based on 100 weight of the organic solvent, and a content of the second polymer is a 0.1 - 100 ratio by weight based on 100 weight of the first polymer.
In the method of producing the gelled polymer cell according to the present invention, it is preferable to conduct the heatpressing of the step (2) at 70-1000C and apre-pressure of 10 - 80 kg, which is applied to left and right load cells of a roll laminator.
In the method of producing the gelled polymer cell according to the present invention, preferably the organic solvent of the step (3) is a polar organic solvent having a carbonate group, which is amixed solvent of two ormore selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, vinylidene carbonate, and γ-butyrolactone.
In the method of producing the gelled polymer cell accordingtothepresentinvention, preferablythe lithiumsalt, which is dissolved in the organic solvent in the step (3) , is one or more selected from the group consisting of LiPF6, LiAsF6,
LiClO4, LiN (CF3SO2)2, LiBF4, LiCF3SO3, LlSbF6, LlB (C2O4)2, LiN(SO2CF2CF3)3/ and LiPF3(CF2CF3)J.
In the method of producing the gelled polymer cell according to the present invention, the crosslinkmg agent of the step (4) has a chain end containing an epoxy ring, which is any one or a combination of two or more selected from the groupconsistingofaprimaryfunctionalepoxygroup, asecondary functional epoxy group, a tertiary functional epoxy group, a quaternary functional epoxy group, halogen-contained epoxy, and isocyanate-contained epoxy.
In the method of producing the gelled polymer cell according to the present invention, preferably contents of the functional second polymer and the crosslinkmg agent of the step (4) are controlled so that the content of the functional second polymer is a 0.1 - 10 ratio by weight based on 100 weight ofthe firstelectrolyticsolutionofthe step (3) andthe content of the crosslinkmg agent is a 0.1 - 100 ratio by weight based on 100 weight of the functional second polymer, or the content of only the crosslinkmg agent is controlled so as to be a 0.1 - 10 ratiobyweightbasedon 100 weight of the firstelectrolytic solution.
In the method of producing the gelled polymer cell according to the present xnvention, preferably the aging of the steps (6) and (7) is conducted at 20 - ζθV for 1 - 5 days.
In the method of producing the gelled polymer cell accordingtothepresent invention, preferablythe crosslmkmg of the step (7) is conducted at 30 - 100°C for 1 - 48 hours.
Furthermore, m order to accomplish the above object, the present invention provides a lithium secondary cell which is produced using the above-mentioned method of producing the gelled polymer cell and which comprises a coated separation film layer including an adhesive first polymer and a functional second polymer, and an electrolyte including the functional secondpolymer capable of being gelled and a crosslmkmg agent in an electrolytic solution.
In the methodofproducing the gelledpolymer cell having the crosslinked interface according to the present invention, convenience of a process is assured during the production of a cell having a large area, and an amount of the electrolytic solutionandviscosityofagel formationpolymerarecontrolled, thus it is possible to obtain uniformity during diffusion of the electrolytic solution into the cell, thereby it is possible toprovide a unit forpreventing local concentration of current. The lithium secondary cell produced according to the present invention is flexible, and has excellent large current charge/discharge and cyclic lifespan characteristics due to desirable interfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of the cell between the separation film and a polar plate.
[Description of Drawings]
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a structure in which a blend of a first polymer and a second polymer is applied on both sides of a separation film according to the present invention;
FIG. 2 illustrates a cell structure m which an anode/a separation film/a cathode/a separation film/an anode or a cathode/a separation film/an anode/a separation film/a cathode are sequentially layered according to the present invention; FIG.3 illustrates agelledsysteminwhichanelectrolyte is cross-linked with a coated separation film layer at an interface thereof according to the present invention;
FIG. 4 is a graph showing a high rate discharge characteristic of a gelled polymer secondary cell produced according to the present invention;
FIG. 5 is a graph showing a lifespan characteristic of the gelled polymer secondary cell produced according to the present invention; and FIGS.6to 9 illustratearrangementofananode, acathode, and arrangement of polar plates, and a cell structure according to the present invention.
<Descπption of codes in drawings> 10: separation film
20: polymer bleding coated layer
21: adhesive first polymer
22: functional second polymer
30: gel formation interface 40: gel formation functional second polymer and electrolytic solution containing crosslikmg agent
41: crosslikmg agent
[Best Mode] Hereinafter, a detailed description will be given of the present invention.
First, adescriptionwillbegivenofamethodofproducing a separation film, which comprises uniformly applying apolymer blend layer on the separation film to form a coated layer, and drying the resulting film. The separation film functions to intercept an internal short circuit between two electrodes and to hold an electrolytic solution. An adhesive firstpolymeranda functional secondpolymer are blended with a solvent, which is capable of simultaneously dissolving the adhesive firstpolymer and the functional second polymer and is easily removed during drying, in the amount of a 0.1 - 40 ratio by weight based on 100 weight of the solvent and a 0.1 - 100 ratio by weight based on 100 weight of the first polymer, respectively, to prepare a coating solution. If the first polymer content is less than a 0.1 ratio by weight, it is impossible to obtain desirable adhesive power. If the first polymer content is more than a 40 ratio by weight, flexibility is reduced due to high viscosity, thus coating ability and processability regarding control of a coating thickness are poor. Furthermore, if the second polymer content is less than a 0.1 ratio by weight, it is not easy to form a gel. If the content is more than a 100 ratiobyweight, since a gel structure is stiff, ionic conductivity is reduced and layer separation fromthe solvent occurs, thusperformance ofthe cell is reduced.
In connection with this, preferably, the solvent is any one or a mixed solvent of two or more selected from the group consisting of dimethyl sulfoxide, l-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, benzene, toluene, methanol, ethanol, methylene chloride, cyclohexane, dioxane, ethyl acetate, diethyl ether, acetone, tetrahydrofuran, and chloroform. More preferably, it is any one or a mixed solvent of two or more selected from the group consisting of acetone, tetrahydrofuran (THF) , and chloroform, which are capable of simultaneously dissolving the adhesive first polymer and the functional second polymer, are easily removed during drying, and have a boiling point of 100°C or less. The selection of a solvent suitable to simultaneously dissolve the first and second polymers is best, but, if the polymers have different solubilities, it is possible to select a combination of solvents having a boiling point that is lower than a melting point of the separation film.
The reason why the solvents having a boiling point that is lower than the melting point (Tm) of the separation film are selectedis as follows. Ifacontinuousprocess is conducted using a coating device, for example, a winder and an unwinder, underapredetermineddryingcondition, itispossibletoobserve deformation of a separation filmmatrix due to a winding tension applied to the matrix as temperature increases.
The separation film having a microporous structure is impregnated with the coating solution containing the adhesive first polymer and the functional second polymer to form coated layers, each having a thickness of 0.1 - 20 fm,on both sides ofthe separation film. In connectionwiththis, ifa thickness of the coated film, which is a polymer blend layer, is less than 0.1 μm, undesirably, adhesion holding strength is poor and a desired function is not obtained. If the thickness of the coated film is more than 20 IM, undesirably, internal resistance depending on the thickness of the coated film is increasedandinterfacial adhesivepowerbetween the separation film and the coated layer is poor.
An application method that is used to form the coated layermaybe suitably selectedaccording to the use. In detail, illustrative, but non-limiting examples of the method include a spray method, a dipping method, a doctor blade method, and a graveure method.
Generally, an additive which is used to improve performance of the cell is dissolved or dispersed in an electrolytic solution or m a polar plate. In the present invention, it is a polymer type, has two polymers mixed with each other, andis appliedon aporous separation filmto realize functions thereof. Furthermore, the second polymer, which is of a functional group capable of opening an epoxy group during cross-linking of the interface, is applied on the coated separation film layer so as to easily control viscosity of the second functional polymer used as a gel formation supporter and an initiator during the production of a first electrolytic solution. Thus, it is easy to produce an electrolytic composition uniformly dispersed in the cell.
The adhesive first polymer provides desirable contact and adhesion to the separation film, and the functional second polymer can effectively remove an acid, such as HF or a Lewis acid (for example, PF3) , causing deterioration in performance of the cell, and comprises apolymer, a copolymer, or an oligomer including a reactive group capable of conducting gelation, or a functional group containing a unit for improving performance of the cell as a main chain or a side chain.
In the production of the separation film including the adhesive polymer according to the present invention, with respect to a conventional problem in which wrinkles are formed ona separation filmduringvacuumpackageofacell, theadhesive first polymer, which has excellent contact and adhesion while it includes a nonaqueous electrolytic solution and which also has high lithium ionic conductivity, is used. In connection wxth this, the selection of the adhesive first polymer is a critically important factor affecting application of the coated layer onto the separation film and mterfacial adhesion therebetween. This is theoretically 5 basedonasurfacetension. Itispreferabletoselectamateπal having a critical surface tension (γc (mN/m) ) that is less than or is the same as that of the separation film acting as a matrix coated with a polymer blend solution used in the present invention. For example, preferably, it is selected from the
10 group consisting of polyvinyl fluoride, polyvmylidene fluoride, polyhexafluoropropylene, polyvinyl chloride, polyvmylidene chloride, polychlorotrifluoroethylene, a polychlorotrifluoroethylene vinylidene fluoride copolymer, poly-1, 2-difluoroethylene, polymethylmethacrylate,
I1S polyethylene oxide, polypropylene oxide, polysiloxane, and copolymers thereof. It is more preferable to select polychlorotrifluoroethylene (PCTFE) or polyvmylidene fluoride (PVF) .
20 Next, adescriptionwillbegivenofthe functional second polymer.
In the forming of the coated separation film layer of the present invention, the functional second polymer can effectively remove an acid or a Lewis acid which is conventionally considered a cause of lifespan reduction of the cell and of deterioration in performance of the cell, and comprises a polymer, a copolymer, an oligomer including a reactive group capable of conducting gelation or a functional group containing a unit for improving performance of the cell. The second polymer also comprises a polymer or a copolymer in which primary amine, secondary amine, tertiary amine, or a heterocyclic ring, containing one or more selected from the above amines, is positioned on a main chain or a side chain. For example, it ispreferably selected fromthe group consisting of polyethylimine, polyvmylpyridine, a copolymer containing polyvmylpyridine, a poly-N-vmylpyridine-styrene copolymer, a poly-N-vinylpyridine-butyl methacrylate copolymer, poly-2-ethyl-2-oxazoline, a polymer or a copolymer in which an epoxy group is positioned on a side chain thereof, a polyethylene methacrylate glycidyl methacrylate copolymer, a polymeroracopolymercontaininganalcoholgroup, polyethylene monoalcohol, polyvinyl alcohol, a polyvinyl alcohol-contained copolymer, and a polymer or a copolymer containing a double bond or a double bond capable of realizing a resonant structure.
Furthermore, it is possible to remove the acid using a added reactant in which the above-mentioned polymer is added to an electrolyte. Additionally, a polymer or a copolymer, which simultaneously includes an acid scanvenger functional group and a halogen-based material for a fxre-retardant mechanism, or is substituted therewith, may be used.
One of important performances capable of being obtained from use of the gel is stability of the cell. Generally, a viscous electrolytic solution may not be easily diffused into the cell. However, in the present invention, a material, such as the functional polymer capable of being gelled, is applied on the coatedseparation filmlayer, to easily control viscosity of the electrolytic solution; thereby it is possible to assure convenience of a process. As described above, the functional polymer, which is applied on a surface of the separation film to form the gel, and another functional polymer, which is added to the electrolytic solution in a small amount, are cross-linked and form the gel, thereby it is possible to obtain a uniform interface. Accordingly, in the production of the cell, performance of the cell is improved due to a uniform and stable interface, and it is possible to avoid fatal problems, such as gas generation and heat congestion, caused by local concentration of current.
In the present invention, among separation films that prevent a short circuit between an anode and a cathode and act as an important supporter for forming the cell, it is preferable that a microporous polyolefm separation fxlm include polyethylene (PE) or polypropylene (PP) having excellent mechanical strength. More preferably, the polyethylene resin separation film, in which a resin is fused by heating to clog micropores so as to provide a so-called shutdown function to the cell, is used. The polyethylene resin used in the present invention includes an ethylene homopolymer, and a copolymer of ethylene and α-olefins, for example, propylene, butene, or hexane. Additionally, the microporous polyethylene separation filmmay have a double-layered structure, such as PE/PP layers, orathree-layeredstructure, suchasPE/PP/PElayersorPP/PE/PP layers, in addition to a single-layered structure, such as a PE layer or a PP layer. Furthermore, it is preferable to use a polyvinylidene fluoride-based separation film as long as it is not dissolved in a solvent capable of dissolving the adhesive and functional polymers.
In the production of the separation film of the present invention, it is preferable that a thickness of the separation film as a matrix used to apply the polymer blend solution be 5 - 45 μm. If the thickness of the separation film is less than 5 μsa, tensile strength is reduced, thus an internal short circuit may occur in electrodes if it is used as a separation film for a cell. If the thickness is more than 45 μm, distance between electrodes is excessively long, thus, undesirably, internal resistance of the electrode is excessively high.
In the production of the separation film including the functional polymer according to the present invention, it is preferable that the drying be conducted at 25 - 10Ot,. If the drying temperature is low, drying time is long and any remaining solvent may cause a problem on an interface of the separation film and the coated layer. On the other hand, if the drying temperature is high, the separation film is shrunken and distorted, causing problems during the production of the cell.
Referring to FIG. 1, in the separation film including the functional polymer according to the present invention, a coating solution, in which an adhesive first polymer (21) and a functional second polymer (22) are blended, is applied on both sides of a separation film (10) .
Subsequently, 80 - 100 parts by weight of an anode active material, 2 - 20 parts by weight of a conductive agent, and 2 - 7 parts by weight of a binder are suspended in 30 - 100 parts byweight of a solvent (for example, N-methylpyrrolidone;
NMP) to produce a slurry. The slurry is applied on an anode collector made of an anode aluminum foil, sufficiently dried at 120 - 130°C, and pressed to produce an anode.
The anode active material may be exemplified by various oxides, for example, chalcogenides, such as manganese dioxide, lithium manganese complex oxides, nickel oxides containing lithium, cobalt oxides containing lithium, nickel cobaltoxides containing lithium, iron oxides containing lithium, vanadium oxides containing lithium, titanium disulfate, and molybdenumdisulfate. Of these, it is preferable that cobalt oxides containing lithium (e.g. LiCoO2), nickel cobalt oxides containing lithium (e.g. LiNio ΘCOO 2O2) , and lithium manganese complexoxides (e.g. LiMn2Ci, LiMnO2) beusedbecausehighvoltage is obtained when they are used.
The conductive agent may be exemplified by acetylene black, carbon black, and graphite.
The binder functions to hold the active materials in the collector and to connect the active materials to each other. Thebindermaybe exemplifiedbypolytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) , an ethylene-propylene-diene copolymer (EPDM) , and a styrene-butadiene rubber (SBR) .
It ispreferable that the activematerial, the conductive agent, and the binder be combined in a ratio of 80 - 100 parts by weight, 2 - 20 parts by weight, and 2 - 7 parts by weight, respectively.
Subsequently, 80 - 95 parts by weight of the cathode active material, 2 -20 parts by weight of the conductive agent, and 2 - 7 parts by weight of the binder are suspended in 30
100 parts by weight of a solvent (for example,
N-methylpyrrolidone; NMP) to produce a slurry. The slurry is applied on a cathode collector made of a cathode copper foil, and dried to produce a cathode.
The cathode includes a carbon active material which adsorbs and desorbs lithium ions, the conductive agent, and the binder.
The cathode active material may be exemplified by a graphite material ora carbonmaterial, such as graphite, cokes, carbon fibers, and globular carbon, and a graphite material or a carbon material, which is obtained by heat treating thermosetting resin, isotropic pitches, mesophase pitches, mesophase pitch-based carbon fibers, and mesophase micro-spherule at 500 - 3000°C. Of them, it is preferable to usethegraphitematerialthatisproducedthroughheattreatment at 2000°C or higher and includes graphite crystals having a surface interval of 0.34 nm or less. A secondary cell that is provided with the cathode including the above-mentioned graphite material as the cathode active material can significantly improve cell capacity and a large current discharge characteristic.
The conductive agent may be exemplified by acetylene black, carbon black, and graphite.
The binder functions may be exemplified by polytetrafluoroethylene (PTFE) , polyvinylidene fluoride
(PVDF) , an ethyl-propylene-diene copolymer (EPDM) , a styrene-butadiene rubber (SBR) , and carboxymethylcellulose
(CMC) .
Subsequently, the separation film, the anode plate, and the cathode plate, which are produced through the above-mentioned procedure, are processed to have a predetermined size, arrangedto forma laminate structure shown in FIG. 2, and heat pressed to produce a laminate type cell.
The laminate type cell may have a structure in which a coated separation film is interposed between a cathode and an anode, a structure which comprises a cathode, separation films attachedto both sides of the cathode, andanodes attached to external sides of the separation films, or a structure which comprises an anode, separation films attached to both sides of the anode, and cathodes attached to external sides of the separation films. The laminate structure provides a high energy/voltage battery, and the layers constituting the structure are brought into tight contact with each other using an adhesive polymer to optimize ion mobility and to improve performance of the cell.
Currently, arrangement of polar plates of a cell having a large area is conducted using various methods, such as a stack method, a bag-like method, a winding method, a polymer glue method, and a heat pressing method. However, the arrangement methods other than the heat pressing method are problematic in that, since size of the separation film increases as size of the polar plate increases, the separation film is wrinkled during vacuum packaging, thus there are many difficulties in the cell arrangement. Accordingly, in the present invention, a cell having an excellent shape preservation characteristic is produced using the heat pressing method.
In the formation of a bi-cell structure according to the present invention, it is preferable to conduct the heat pressing at 70 - 100°C and a pre-pressure of 10 - 80 kg which is applied to left and right load cells of a roll laminator. More particularly, the pre-pressure is maintained at 20 - 60 kg and the temperature is 85 - 95°C . Subsequently, a group of electrodes having the bi-cell structure is injected into an aluminum packaging material, and a first electrolytic solution including lithium salts and an organic solvent is produced. In detail, an organic solvent is preferably a polar organic solvent having a carbonate group, which is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, vinylidene carbonate, and γ-butyrolactone. Furthermore, the lithium salt is one or more selected from the group consisting of LiPF6, LiAsF6, LiClO4, LiN(CF3SO2) 2, LiBF4, LiCF3SO3, LiSbF6, LiB(C2O4J2, LiN(SO2CF2CF3J3, andLiPF3(CF2CF3) 3. The lithium salt is dissolved in the organic solvent to produce a first electrolytic solution.
The first electrolytic solution is produced so that a content of the functional second polymer is a 0.1 - 10 ratio by weight basedon 100 weight of the first electrolytic solution and a content of a crosslinking agent is a 0.1 - 100 ratio by weight based on 100 weight of the functional second polymer, or that a content of only the crosslinking agent is a 0.1 - 10 ratio by weight based on 100 weight of the first electrolytic solution. The first electrolytic solution is injected into a packaging material (for example, an aluminum packaging material) containing a group of electrodes having the laminate type cell structure, and packaging is conducted to produce the lithium secondary cell.
In connection with this, if the contents are within the above-mentioned ranges, a gel is not formed. If the contents deviate from the above-mentioned ranges, since viscosity of the electrolyte is increased due to dissolution of the polymer, diffusion into the cell is not easily conducted, thus fatal problems, such as nonuniform performance and local concentration of current, occurs in the cell.
The polymer added to the electrolytic solution may or may not be the same as the functional second polymer.
Any crosslinking agent may be added to the electrolytic solution as long as it has a chain end including an epoxy ring which is exemplified by primary functional epoxy, secondary functional epoxy, tertiary functional epoxy, and quaternary functional epoxy. Furthermore, epoxy substitutedwithbromine, or halogen-contained epoxy may be used. Particularly, it is preferable to add a fire-retardant material to the chain so as to increase stability, anditmay include isocyanates capable of conducting an ion bond or a covalent bond.
Next, the packaged cell is aged at 20 - 60°C for 1 - 5 days. In connection with this, the functional second polymer (for example, PCTFE solef 32008) is swollen by a typical electrolytic solution. Thus, when an aging process is completed after the injection of the electrolytic solution, theelectrolyticsolutionisdiffusedintothe functionalsecond polymer applied on the separation film like in a typical gel process. An early agingprocess aims to improve adhesion power ofthecell, andafinalagingprocessaimstouseagelelectrolyte as a supporter through a crosslinkmg process. In connection with this, a final gelation process must not be conducted if the electrolytic solution is not uniformly diffused into the cell. The reason is that if the gelation is conducted in the early aging process, performance of the cell is reduced due to nonuniformity. Accordingly, it is necessary to carefully set an earlyagingtemperature, andtodesign openingefficiency of the functional polymer to conduct opening of epoxy.
Subsequently, the coated separation film layer is aged in an atmospheric pressure at 30 - 100°C for 1 - 48 hours to be crosslinked so as to form a gel, thereby producing a gelled polymer cell according to the present invention.
As described above, the gel electrolyte can act as the supporter by the crosslinkmg process. With reference to FIG. 3, a coated layer (20) , in which an adhesive first polymer (21) and a functional second polymer (22) are blended on both sides of a separation film (10) , is aged so that the functional second polymer capable of being gelled is crosslinked with an electrolyte (40) including a crosslinking agent (41) , thereby creating a gelation system which has a crosslinked interface and in which a gel (30) is formed at an interface of the coated separation film layer and the electrolyte.
In connection with this, a functional second polymer additive layer including pyridines may be used as an acid scanvenger due to a function of pyridine. Furthermore, it may react with an epoxy group to form an ion type gel. This is additionally conducted in view of stability. Excitingly, when LiMn?θ4 is usedas ananode activematerial, itacts as anadditive capable of preventing dissolution of manganese due to HF. Additionally, when an overcharge additive, such as BP, is used, oxidationpolymerizationoccurs inearlystagesdue tocatalysis of HF or a Lewis acid, thus it is possible to avoid a cause of rapidly increasing the self-discharge speed of a cell.
In a method of producing of a gelled polymer cell having a crosslinked interface according to the present invention, in order to avoid wrinkling of the separation film, which is considered a conventional problem occurring during cell arrangement, an adhesive first polymer is used as a support layer and heat pressed so that adhesive power to an active material and conductivity are increased, interfacial adhesion between the separation film and the polar plate is achieved during the cell arrangement to avoid the wrinkle problem, and a shape of the cell is nicely preserved in handling to assure convenience of a process during the production of a cell having a large area.
As well, in order to avoid deterioration in performance of the cell and a short lifespan thereof due to HF or a Lewis acid, the functional second polymer, including a unit capable of effectively removing the above-mentioned acid, is used to be blended with the adhesive first polymer, thereby improving performance and the lifespan characteristic of the cell.
Moreover, in order to avoid heat congestion due to local concentration of current caused by undesirable diffusion into the cell when an electrolytic solution, in which a polymer is dissolved and which has high viscosity, is added to form a gel, the functional polymer for initiating the cross-linking agent, acting as a gel formation supporter and improving performance of the cell, is mixedwith the adhesive firstpolymer andapplied on the coated separation film layer so as to control viscosity of a gel formation electrolyte injected into the cell, thereby the electrolytic solution is easily diffused into the cell. Furthermore, this process is advantageous in that interfacial stability between the coated separation film layer, including the gel formation polymer and the electrolyte, is excellent; thus stability of the cell is improved.
The lithium secondary cell of the present invention produced according to the above-mentioned procedure is advantageous in that convenience and flexibility of a process are fair during the production of the cell having a large area, andinterfacial stabilitybetweentheelectrolyte andthecoated separation filmlayer andshapepreservation of the cellbetween the separation film and the polar plate are improved, and large current charge/discharge and cyclic lifespan characteristics are excellent.
[Mode for Invention] A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but arenot tobe construedas the limit of thepresent invention.
<EXAMPLE 1>
(1) Production of separation film
2 ratio by weight of polyvmylidene fluoride-chlorotπfluoroethylene copolymer 32008 (Solvey,
Inc.), which was a first polymer, and 20 ratio by weight of poly-4-vmylpyridine-styrene (Aldπch, Inc.), which was a second polymer, based on the wexght of the first polymer, were dissolved m a solvent of acetone (245 g) and tetrahydrofuran (THF, 245g) , mixedwitheachothertoproduceacoatingsolution. A polyethylene film of 20 μm, having a microporous structure, was impregnated with the coating solution so that both sides thereof were coated in a thickness of 1 ~ 2 μm. Subsequently, the coated separation film was dried in an oven at 60°C for 24 hours.
Particularly, as described in the following Table 1, the first polymer was selected from materials having a surface tension that was less than or was the same as that of an olefin-based separation film.
[Table l]
Figure imgf000035_0001
Figure imgf000036_0001
(2) Production of anode film
An active material (L1C0O2) , a conductive agent, and a binder were dispersed in NMP in a weight ratio of 95 : 2 :3 to produce a slurry. The slurry was applied on an aluminum foil, dried at 120°C, and pressed to produce an anode having a thickness of 107 μm. The anode is shown in FIG. 6.
(3) Production of cathode film
A cathode active material (graphite) , a conductive agent, and a binder were dispersed in NMP in a weight ratio of 90 : 7 : 3 to produce a slurry. The slurry was applied on a cathode copper foil, dried at 120°C, and pressed to produce a cathode having a thickness of 130 μm- The cathode is shown in FIG. 7.
(4) Production of bi-cell
The prepared anode was cut to a size of 85 X 150 cm, except for a tap portion, and the cathode was cut to a size of 87 X 152 cm, except for a tap portion, as in the case of the anode. Subsequently, a coated separation film, which had a size that was larger than the size of the cut cathode by 1.5 mm lengthwise and crosswise, was prepared, and polar plates were arranged (FIG.8) toproduce abi-cell structure (FIG. 9) . Apre-pressure was maintained at 40 kg which was applied to left and right load cells of a roll laminator, and heat pressing was conducted at 90°C to produce a bi-cell.
(5) Production of electrolytic solution
0.5 ratio by weight of poly-4-vmylpyridme-styrene (Aldrich, Inc.), which was a functional second polymer, was dissolved in a first electrolytic solution which included 1.15
M LiPF6 and EC/DMC/EMC in a weight composition ratio of 1:1:1.
Epoxy substituted with bromine (Kukdo Chemical, Inc.) was added in the amount of a 0.3 ratio by weight as a crosslinkmg agent based on the weight of the second polymer, agitated so as to be sufficiently dissolved in the first electrolytic solution, and stored to create a second electrolytic solution.
(6) Production of secondary cell The prepared bi-cell that was produced through the above-mentioned procedure was inserted into an aluminum packaging material, the second electrolytic solution produced instep (5) was injected thereinto, andpackagingwas conducted. (7) Aging was conducted at normal temperature for 2 days afterthepackaging, andstorageandcrosslinkingwereconducted in an oven at 60°C for 2 days.
COMPARATIVE EXAMPLE 1>
The procedure of the example 1 was repeated to produce a lithiumsecondarycell exceptthataconventionalelectrolytic solution composition (EC/DMC/EMC = 1: 1: 1 (weight ratio) , LiPF6
1.15M) was used instead of an electrolytic solution produced according to the present invention.
EXPERIMENTAL EXAMPLE 1>
Ingelledpolymer cellsproducedaccordingto the example 1 and the comparative example 1, interfacial stability was evaluated between a gelled polymer electrolyte and an olefin separation filmpolymerblendingcoatedlayerduringovercharge. The results are described in the following Table 2.
[Table 2]
Figure imgf000038_0001
EXPERIMENTAL EXAMPLE 2> 0.2C, 0.5C, l.OC, and 2.0C hxgh rate discharge characteristics of the cells that were produced according to the above examples were evaluated using a charge and discharge cycler at normal temperature. The results are shown in FIG. 4.
EXPERIMENTAL EXAMPLE 3>
A lifespan characteristic of the lithium secondary cell thatwasproducedaccordingto example 1 ofthepresent invention was tested. In detail, charge and discharge were repeated 120 times using a current of l.OC at normal temperature to evaluate the characteristic. The results are shown in FIG. 5.
From FIG. 5, it can be seen that a capacity preservation ratio is 95 % or more when the lithium secondary cell according to the present invention reaches the 120th cycle, thus the lifespancharacteristicisexcellent. Inconnectionwiththis, the capacity preservation ratio at the 120th cycle denotes a dischargecapacityatthe 120thcycleassumingthatthedischarge capacity at the 1st cycle is 100 %.
[industrial Applicability]
In a method of producing a gelledpolymer cell according to the present invention, convenience of a process is assured during the production of a cell having a large area, and the amount and composition of a gel electrolytic solution are controlled to provide a unit forpreventing local concentration of current. Agelled lithiumsecondary cellproducedaccording to the present invention has excellent large current charge/discharge and cyclic lifespan characteristics due to desirable interfacial stability between an electrolyte and a coated separation film layer and desirable shape preservation of the cell between the separation film and a polar plate.

Claims

[CLAIMS] [Claim l]
A method of producing a gelled polymer cell having a crosslinked interface, comprising: (1) applying a polymer blend layer, in which an adhesive first polymer and a functional second polymer capable of being gelled are dissolved in an organic solvent, on a separation film, and drying the resulting polymer blend layer to produce a coated separation film; (2) interposing the separation film produced in the step (1) between an anode and a cathode to form a group of layered electrodes, and heat pressing the electrodes;
(3) producing a first electrolytic solution including a lithium salt and the organic solvent; (4) adding the functional second polymer and a crosslmking agent mixed with each other, or only the crosslmking agent, to the first electrolytic solution of the step (3) to produce a second electrolytic solution;
(5) inserting the group of electrodes of the step (2) into a packaging material, injecting the second electrolytic solution of the step (4) thereinto, and sealing a resulting structure to produce the cell;
(6) aging the cell produced in the step (5) to swell the coated separation film layer; and (7) crosslinking the coated separation film layer and the electrolytxc solution to form a gel.
[Claim 2] The method as set forth in claim 1, wherein the adhesive firstpolymer of the step (1) is selected from a group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, polyvinyl chloride, polyvinylidene chloride, polychlorotrifluoroethylene, a polychlorotrifluoroethylene vinylidene fluoride copolymer, poly-1, 2-difluoroethylene, polymethylmethacrylate, polyethylene oxide, polypropylene oxide, polysiloxane, and copolymers thereof.
[Claim 3]
Themethodas set forth in claim1, wherein the functional second polymer of the steps (1) and (4) is selected from a group consisting of amine, acid anhydride, imidazole, polyethylimmes, polyvmylpyridme, a copolymer containing polyvinylpyπdine, a poly-N-vinylpyridme-styrene copolymer, poly-N-vinylpyridine butyl methacrylate, and poly-2-ethyl-2-oxazoline.
[Claim 4] The method as set forth in claim 1, wherein a content of the first polymer of the step (1) is a 0.1 - 40 ratio by weight based on 100 weight of the organic solvent, and a content of the second polymer is a 0.1 - 100 ratio by weight based on 100 weight of the first polymer.
[Claim 5]
The method as set forth m claim 1, wherein the organic solvent of the step (3) is a polar organic solvent having a carbonate group, which is amixedsolvent of two ormore selected from a group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, vmylidene carbonate, and γ-butyrolactone.
[Claim 6]
The method as set forth in claim 1, wherein the lithium salt of the step (3) is one ormore selected fromagroup consisting Of LiPF6, LiAsF6, LiClO4, LiN(CF3SO2J2, LiBF4, LiCF3SO3, LiSbF6, LiB(C2O4)Z, LiN(SO2CF2CF3)S, and LiPF3(CF2CF3J3.
[Claim 7]
The method as set forth in claim 1, wherein the crosslinking agent of the step (4) has a chain end containing an epoxy ring, which is any one or a combination of two or more selected from a group consisting of a primary functional epoxy group, a secondary functionalepoxygroup, atertiaryfunctional epoxy group, a quaternary functional epoxy group, halogen-contained epoxy, and lsocyanate-contamed epoxy.
[Claim 8]
The method as set forth in claim 1, wherein contents of the functional second polymer and the crosslmking agent of the step (4) are controlled so that the content of the functional second polymer is a 0.1 - 10 ratio by weight based on 100 weight of the first electrolytic solution of step (3) and the content of the crosslmking agent is a 0.1 - 100 ratio by weight based on 100 weight of the functional second polymer, or the content of only the crosslmking agent is controlled so as to be a 0.1 - 10 ratio by weight based on 100 weight of the first electrolytic solution.
[Claim 9]
Alithiumsecondarycellproducedaccording to themethod of claim 1.
PCT/KR2005/003787 2004-11-09 2005-11-09 Method for manufacturing gelled polymer cell having cross-linked interface and lithium secondary cell obtained by using the method WO2006052082A1 (en)

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Publication number Priority date Publication date Assignee Title
US7875204B2 (en) * 2006-12-25 2011-01-25 Industrial Technology Research Institute Flame retarding polymer electrolyte composition containing maleimides
US20140004406A1 (en) * 2011-03-03 2014-01-02 Lg Chem, Ltd. Unification-typed electrode assembly and secondary battery using the same
CN111542962A (en) * 2018-04-27 2020-08-14 株式会社Lg化学 Lithium secondary battery and method for manufacturing same
WO2021021597A1 (en) * 2019-07-29 2021-02-04 TeraWatt Technology Inc. Phase-change electrolyte separator for a solid-state battery
US20210175584A1 (en) * 2018-01-18 2021-06-10 Lg Chem, Ltd. Separator for secondary battery and lithium secondary battery including same
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US11271253B2 (en) 2019-07-29 2022-03-08 TeraWatt Technology Inc. Cylindrical anode-free solid state battery having a pseudo-solid lithium gel layer
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US11476458B2 (en) 2017-11-16 2022-10-18 Lg Energy Solution, Ltd. Cathode for lithium secondary batteries and method of manufacturing the same
US11721810B2 (en) 2018-04-04 2023-08-08 Lg Energy Solution, Ltd. Electrode for lithium secondary battery and lithium secondary battery including the same

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KR101868210B1 (en) * 2014-10-31 2018-06-15 주식회사 엘지화학 Lithium secondary battery and method for manufacturing the same
KR102013914B1 (en) 2015-11-12 2019-08-23 주식회사 엘지화학 Curing Die for Preparation of Gel Polymer Electrolyte and Method of Preparing Gel Polymer Battery Cell Using the Same
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KR102338540B1 (en) * 2018-04-10 2021-12-14 주식회사 엘지에너지솔루션 Lithium secondary battery and preperation method thereof
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4830938A (en) * 1985-06-04 1989-05-16 The Dow Chemical Company Secondary battery
JP2572897B2 (en) * 1990-04-06 1997-01-16 ウルトラセル，インコーポレイティド Method for producing radiation-cured solid electrolyte and electrochemical device using the same
KR20020068416A (en) * 2001-02-21 2002-08-27 삼성에스디아이 주식회사 Compositions for manufacturing sticky polymer electrolytes
KR20030005256A (en) * 2002-09-30 2003-01-17 한국과학기술연구원 A uv-cured multi-component polymer blend electrolyte, lithium secondary battery and their fabrication method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4830938A (en) * 1985-06-04 1989-05-16 The Dow Chemical Company Secondary battery
JP2572897B2 (en) * 1990-04-06 1997-01-16 ウルトラセル，インコーポレイティド Method for producing radiation-cured solid electrolyte and electrochemical device using the same
KR20020068416A (en) * 2001-02-21 2002-08-27 삼성에스디아이 주식회사 Compositions for manufacturing sticky polymer electrolytes
KR20030005256A (en) * 2002-09-30 2003-01-17 한국과학기술연구원 A uv-cured multi-component polymer blend electrolyte, lithium secondary battery and their fabrication method

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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US20140004406A1 (en) * 2011-03-03 2014-01-02 Lg Chem, Ltd. Unification-typed electrode assembly and secondary battery using the same
US9653718B2 (en) 2011-03-03 2017-05-16 Lg Chem, Ltd. Unification-typed electrode assembly and secondary battery using the same
US11476458B2 (en) 2017-11-16 2022-10-18 Lg Energy Solution, Ltd. Cathode for lithium secondary batteries and method of manufacturing the same
US11929519B2 (en) * 2018-01-18 2024-03-12 Lg Energy Solution, Ltd. Separator including coating layer with ethylenically unsaturated binder, and secondary battery including polymer network formed by gel polymer electrolyte and ethylenically unsaturated binder in coating layer of separator
US20210175584A1 (en) * 2018-01-18 2021-06-10 Lg Chem, Ltd. Separator for secondary battery and lithium secondary battery including same
US11721810B2 (en) 2018-04-04 2023-08-08 Lg Energy Solution, Ltd. Electrode for lithium secondary battery and lithium secondary battery including the same
CN111542962A (en) * 2018-04-27 2020-08-14 株式会社Lg化学 Lithium secondary battery and method for manufacturing same
CN111542962B (en) * 2018-04-27 2023-10-24 株式会社Lg新能源 Lithium secondary battery and method for manufacturing same
CN114207904A (en) * 2019-07-29 2022-03-18 太瓦技术公司 Anode-less solid-state battery with quasi-solid-state lithium gel layer
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US11271253B2 (en) 2019-07-29 2022-03-08 TeraWatt Technology Inc. Cylindrical anode-free solid state battery having a pseudo-solid lithium gel layer
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