JP2011150819A - Lithium secondary battery and method for manufacturing electrode thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable lithium secondary battery in which electrode reaction is performed with high density and high efficiency by covering current collecting leads of positive and negative electrode plates with an insulating layer having dissolution resistance to an organic electrolyte in a battery with a higher regard for input and output performance, and to solve a problem that a burr, a chip or the like in electrode processing (cutting) is one of causes of the internal short circuit of the battery, and the short circuit is further liable to be generated by a volume change of the electrode by charge and discharge, remarkably impairing the reliability of the battery. <P>SOLUTION: The current collecting leads of the strip-like positive and negative electrode plates are covered with a synthetic resin selected from at least one of thermoplastic resin having dissolution resistance to an organic electrolyte and curing resin cross-linked by heating, ultraviolet irradiation or electron beam irradiation, or a mixture of the synthetic resin with an insulating filler as an insulating layer having a thickness of the thickness of a mixture layer or smaller. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrode used for a lithium secondary battery and a method for producing the same.

  Lithium secondary batteries represented by organic electrolyte secondary batteries are mainly used in portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. Particularly in recent years, so-called lithium secondary batteries using a material capable of occluding and releasing lithium such as a carbon material for the negative electrode have become widespread.

  On the other hand, in the automobile industry, in order to cope with environmental problems, electric vehicles without exhaust gas with a power source made entirely of batteries, and hybrid (electric) vehicles with both internal combustion engine engines and batteries as power sources are used. Development has been accelerated and some have already been put into practical use. Such a battery serving as a power source for electric vehicles is required to have not only high energy density but also high output and high capacity performance. Lithium ion secondary batteries are attracting attention as batteries that meet these requirements. Some have been put to practical use. In addition, a battery for an electric vehicle is required to have a long-life performance so as to correspond to a long use period of the electric vehicle. In general, not only for electric vehicles, but for cars, the time for parking (battery storage) is overwhelmingly longer than when riding (using batteries). Improving) has great significance for maintaining the performance of the automobile over a long period of time.

  The internal structure of this battery is usually wound as described below. That is, the active material is applied to the metal foil for both the positive electrode and the negative electrode. And it rolls so that a positive electrode and a negative electrode may not contact directly on both sides of a separator, and it is sealed in the cap after accommodating in the cylindrical can used as a container, electrolyte solution injection.

When the battery is assembled, the carbon material used as the negative electrode active material is in a state where lithium is completely released, that is, in a discharged state. Accordingly, an active material in a discharged state is usually used for the positive electrode, for example, LiCoO ₂ (lithium cobaltate) or LiNiO ₂ (lithium nickelate). And it can be made to function as a battery by carrying out initial charge. In this way, the lithium secondary battery can be charged and discharged as required.

  In general, a lithium secondary battery is a material in which a substance involved in an electrode reaction is a chemically active material, and a volume change of a mixture layer occurs due to charge / discharge, and an organic electrolyte whose performance deteriorates due to moisture mixing For example, the battery exterior and the battery internal components are completely isolated from each other. If a short circuit occurs inside or outside the battery for some reason, it will generate heat, sometimes causing thermal runaway, and the battery may burst, damaging peripheral devices.

  In order to improve the input / output characteristics of lithium secondary batteries, the current density per unit area is reduced by increasing the thickness of the positive and negative electrodes and separator, and the electrode reaction is made uniform and the amount of active material in a certain volume is increased. To increase the capacity.

  In particular, a lithium secondary battery for a hybrid electric vehicle has a very large charge / discharge current, so that the electrode thickness is thin and the electrode area is also very large.

  As described above, since the lithium secondary battery is dangerously broken such as rupture and explosion due to misuse, misoperation, and malfunction, ensuring the safety of the battery is a most important issue. Furthermore, in order to ensure the safety of the battery, it is necessary to ensure the safety even if troubles occur in addition to the above-mentioned structure and attention to the usage environment. For this reason, it is necessary to take measures to prevent defects in the wound group inside the battery and also in the electrodes.

  The problem to be solved by the present invention is to cover one of the causes of internal short circuits such as burrs and chips during electrode processing (cutting) with an insulating layer and to insulate current collecting leads that are likely to be short-circuited due to volume changes due to charge and discharge Thus, a highly reliable lithium secondary battery is provided.

Japanese Patent No. 3010781 Japanese Patent No. 3303319

  In the present invention, for the battery with an emphasis on input / output performance, the current collector leads of the positive and negative electrode plates are coated with an insulating layer that does not dissolve in the organic electrolyte solution, so that the electrode reaction is performed with high density and high efficiency. An object is to provide a lithium secondary battery having high performance.

  The present invention includes an electrode group in which strip-like positive and negative electrode plates are wound, and plate-like current collecting members respectively disposed on both sides in the axial direction of the electrode group, and each is derived from the positive and negative electrode plates. In the organic electrolyte secondary battery in which the tip portion of the current collecting lead is joined to the current collecting member, the current collecting lead of the strip-like positive and negative electrode plates is a thermoplastic resin having resistance to the organic electrolyte or heating. A synthetic resin selected from at least one of curable resins that are crosslinked by ultraviolet irradiation and electron beam irradiation, or a mixture of the insulating filler and the synthetic resin is coated with an insulating layer having a thickness equal to or less than the thickness of the mixture layer. It is characterized by being.

  An electrode group in which a belt-like positive and negative electrode plate is wound, and a disk-shaped current collecting member disposed on each side of the electrode group, and a tip portion of a current collecting lead led out from the positive and negative electrode plate, In the organic electrolyte secondary battery bonded to the current collecting member, the current collecting lead of the strip-like positive and negative electrode plates is a thermoplastic resin that does not dissolve in the organic electrolyte solution or is cured by crosslinking by heating, ultraviolet irradiation, or electron beam irradiation. By covering the synthetic resin selected from at least one of the functional resins or a mixture of the insulating filler and the synthetic resin with an insulating layer having a thickness equal to or less than the thickness of the mixture layer, the battery with an emphasis on input / output performance By coating the current collecting leads of the positive and negative electrode plates with an insulating layer that does not dissolve in the organic electrolyte, the electrode reaction can be performed with high density and high efficiency, and a highly reliable lithium secondary battery can be provided. so That.

This figure is a schematic diagram showing one form of a wound group cross section of the lithium secondary battery of the present invention.

  The lithium secondary battery electrode of the present invention and the method for producing the lithium secondary battery will be described in the following order.

(Production of electrodes)
The negative electrode plate constituting the electrode plate group has a rolled copper foil having a thickness of 10 μm as a negative electrode current collector. On both surfaces of the rolled copper foil, a negative electrode mixture containing graphite powder capable of occluding and releasing lithium ions as a negative electrode active material is uniformly and uniformly applied. For example, 8 parts by mass of a binder (binder) polyvinylidene fluoride (hereinafter abbreviated as PVDF) is blended with 92 parts by mass of graphite powder in the negative electrode mixture. When applying the negative electrode mixture to the rolled copper foil, a dispersion solvent N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) is used. The amount of the graphite powder applied is set so that the amount of lithium ions released from the positive electrode plate and the amount of lithium ions occluded in the negative electrode plate at the time of initial charge after battery preparation is 1: 1 or more. An uncoated portion of a negative electrode mixture having a width of 30 mm is formed on the side edge on one side in the longitudinal direction of the rolled copper foil. The uncoated part is notched in a comb shape, and a negative electrode lead piece is formed in the notch remaining part. The interval between the adjacent negative electrode lead pieces is set to 50 mm, and the width of the negative electrode lead piece is set to 5 mm.

  After drying, the negative electrode plate is pressed with a heatable roll press so that the porosity of the negative electrode mixture layer is about 35% by volume, and then applied to the negative electrode lead piece that is an uncoated portion of the negative electrode mixture. After applying a solution in which a mixture of bisphenol A type epoxy resin and acrylic acid copolymer is dissolved in N-methyl-2-pyrrolidone to a thickness of 5 μm on one side with a die coater, drying with hot air and crosslinking It is naturally cooled to room temperature and cut to a width of 86 mm.

  On the other hand, the positive electrode plate has an aluminum foil having a thickness of 20 μm as a positive electrode current collector. On both sides of the aluminum foil, for example, 8 parts by mass of graphite powder as a main conductive material, subordinate conductivity with respect to 85 parts by mass of the positive electrode in which the lithium transition metal double oxide prepared by the above-described method and an inorganic substance are combined. 2 parts by mass of acetylene black as a material and 5 parts by mass of PVDF as a binder are blended. When applying the positive electrode mixture to the aluminum foil, a dispersion solvent NMP is used. On the side edge on one side in the longitudinal direction of the aluminum foil, a non-coated portion of a positive electrode mixture having a width of 30 mm is formed as in the negative electrode plate, and a positive electrode lead piece is formed. The interval between the adjacent positive electrode lead pieces is set to 50 mm, and the width of the positive electrode lead piece 2 is set to 5 mm. After drying, the positive electrode plate is pressed in the same manner as the negative electrode plate so that the porosity of the positive electrode mixture layer is 30% by volume, and then the same insulating resin is formed and cut into a width of 82 mm. .

(Cell production)
As shown in FIG. 1, the cylindrical lithium ion secondary battery of the present embodiment is a nickel-plated steel bottomed cylindrical battery container and a polypropylene hollow cylindrical shaft core with a strip-shaped positive battery. The negative electrode plate has a group of electrode plates wound in a spiral shape through a separator.

  On the upper side of the electrode plate group, an aluminum positive electrode current collecting ring for collecting the electric potential from the positive electrode plate is disposed substantially on the extension line of the shaft core. The positive electrode current collecting ring is fixed to the upper end portion of the shaft core. The edge part of the positive electrode lead piece led out from the positive electrode plate is ultrasonically welded to the peripheral edge of the flange portion integrally protruding from the periphery of the positive electrode current collecting ring. A disc-shaped battery lid serving as a positive external terminal is disposed above the positive current collecting ring. The battery lid is composed of a lid case, a lid cap, a valve retainer that keeps airtightness, and a cleavage valve that cleaves when the internal pressure rises, and these are stacked and assembled by crimping the periphery of the lid case Yes. One end of two positive electrode lead plates formed by stacking a plurality of aluminum ribbons is fixed to the upper part of the positive electrode current collecting ring, and the other end of the other one is fixed to the lower surface of the lid case. Are welded. The other ends of the two positive electrode lead plates are connected by welding.

  On the other hand, a negative electrode current collector ring made of copper for collecting electric potential from the negative electrode plate is disposed below the electrode plate group. The outer peripheral surface of the lower end portion of the shaft core is fixed to the inner peripheral surface of the negative electrode current collecting ring. The end of the negative electrode lead piece led out from the negative electrode plate is welded to the outer peripheral edge of the negative electrode current collecting ring. A copper negative electrode lead plate for electrical conduction is welded to the lower part of the negative electrode current collecting ring, and the negative electrode lead plate is welded to the inner bottom of the battery container. In this example, the battery container has an outer diameter of 40 mm and an inner diameter of 39 mm.

The battery lid is fixed by caulking to the upper part of the battery container via an insulating and heat resistant EPDM resin gasket. For this reason, the inside of the lithium ion secondary battery is sealed. Further, a non-aqueous electrolyte (not shown) is injected into the battery container. As the non-aqueous electrolyte, a solution obtained by dissolving 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) as a lithium salt in a mixed solvent of a carbonate ester ethylene carbonate and dimethyl carbonate in a volume ratio of 2: 3 is used. It has been. The lithium ion secondary battery is electrically operated in response to an increase in battery temperature, for example, a PTC (Positive Temperature Coefficient) element or a positive or negative electrical lead is disconnected in response to an increase in battery internal pressure. The current interruption mechanism to be performed is not arranged.

  In the electrode plate group, the positive electrode plate and the negative electrode plate are wound around the shaft core through a separator made of porous polyethylene having a width of 90 mm and a thickness of 40 μm so that the two electrode plates do not directly contact each other. The positive electrode lead piece and the negative electrode lead piece are respectively disposed on opposite end surfaces of the electrode plate group. Insulation coating is applied to the entire circumference of the collar surface of the electrode plate group and the positive electrode current collector ring. For the insulation coating, an adhesive tape in which a hexamethacrylate adhesive is applied to one side of a polyimide base material is used. The pressure-sensitive adhesive tape is wound one or more times from the collar peripheral surface to the electrode plate outer peripheral surface. By adjusting the lengths of the positive electrode plate, the negative electrode plate, and the separator, the diameter of the electrode plate group is set to 38 ± 0.1 mm.

  Next, examples of lithium ion batteries manufactured according to this embodiment will be described.

(Example)
Lithium nickel manganese cobalt complex oxide (LiMn _0.3 Co _0.3 Ni _0.4 O ₂ ) having an average particle diameter of 6 μm was synthesized as a positive electrode active material. The obtained lithium nickel manganese cobalt composite oxide, scaly graphite as a conductive material, and polyvinylidene fluoride (hereinafter referred to as PVDF) as a binder were mixed at a weight ratio of 85: 10: 5, and this mixture A slurry in which N-methylpyrrolidone (hereinafter referred to as NMP) as a dispersion solvent was added and kneaded was applied to both sides of an aluminum foil having a thickness of 20 μm. At this time, an uncoated part with a width of 30 mm was left on one side edge in the positive electrode longitudinal direction. Then, after drying and pressing, a notch is left in the uncoated part left on the side edge, and the remaining part of the notch is used as a positive electrode lead piece, and this positive electrode lead piece is used as a bisphenol A type epoxy resin and an acrylic acid copolymer. A solution prepared by dissolving the mixture in N-methyl-2-pyrrolidone was coated with an insulating resin with a thickness of 5 μm on one side using a die coater, dried with hot air and cross-linked, allowed to cool naturally to room temperature, and cut to a width of 82 mm Thus, a positive electrode plate was obtained.

  On the other hand, 92 parts by mass of graphite powder as a negative electrode active material was mixed with 8 parts by mass of polyvinylidene fluoride, and NMP as a dispersion solvent was added to this mixture, and the kneaded slurry was applied to both sides of a rolled copper foil having a thickness of 10 μm. Applied. An uncoated portion of the negative electrode mixture having a width of 30 mm was left on the side edge on one side in the longitudinal direction of the rolled copper foil. Then, after drying and pressing, a notch is made in the uncoated part left on the side edge, and after the remaining part of the notch is used as a negative electrode lead piece, an insulating resin is applied in the same manner as the positive electrode lead piece, After crosslinking, it was naturally cooled to room temperature and cut to a width of 86 mm to obtain a negative electrode plate. The interval between the adjacent negative electrode lead pieces is set to 50 mm, and the width of the negative electrode lead piece is set to 5 mm.

(Comparative example)
A positive and negative electrode plate was produced in the same manner as described above without providing an insulating layer on the lead piece.

(Output measurement of the fabricated cylindrical cell)
About each battery of an Example and a comparative example, after measuring battery weight, battery capacity and battery resistance were measured. In the measurement of battery capacity, the battery was subjected to constant current and constant voltage charge (upper limit voltage 4.1 V) for 3 hours in an atmosphere of 25 ± 2 ° C. at a rate of 1 hour (1 C), and then a constant current of 1 hour rate (1 C). The discharge capacity when discharged to 2.7 V was measured. In the measurement of battery resistance, the battery was charged at a constant voltage of 4.1 V at an hour rate of 25 ± 2 ° C. for 3 hours and then fully charged for 11 seconds at current values of 1A, 3A, and 6A, respectively. The battery voltage was discharged and the battery voltage at 5 seconds was measured. When the voltage value was plotted against each current value, the absolute value of the slope of the straight line was taken as the battery resistance.

(Crush test of the produced cylindrical cell)
About each battery of an Example and a comparative example, after fully charging, it put between two flat plates, and was crushed with the force of 13 kN with the hydraulic ram. After the maximum pressure was obtained, the external pressure of the battery was released and the appearance of the battery after occurrence of phenomena such as voltage drop, cleavage of the cleavage valve and ejection of internal gas was visually observed.

  As shown in Table 1, the lithium secondary battery of the present embodiment is excellent in safety while having high capacity and high output.

  Although there is no difference in battery performance, the cutting process during electrode fabrication is likely to cause burrs, burr, and other defects due to wear of the blade, and the degree of the cutting increases. When charging / discharging is repeated, pressure is applied to a part of the current collecting lead piece due to expansion / contraction of the positive / negative electrode mixture layer, and the above-described defects strongly press the separator and cause an internal short circuit. In this invention, since the part which causes this internal short circuit is coat | covered with the insulating layer, even if it is a case where a cut surface deteriorates, a reliable battery can be obtained.

  In the said embodiment, although the example using lithium nickel manganese cobalt complex oxide was shown, this invention is not limited to this. The lithium-containing metal oxide may be lithium cobalt composite oxide, lithium nickel composite oxide, lithium nickel manganese cobalt composite oxide, spinel type lithium manganate, lithium iron composite oxide, or the like. Moreover, it is not restrict | limited also about Li / Mn ratio, It can be set as desired Li / Mn ratio with the preparation ratio of manganese oxide and lithium salt. Furthermore, by adding and mixing transition metal oxides such as Fe, Co, Ni, Cr, Al, and Mg as raw materials, some of the transition metal elements such as lithium and manganese in the crystals are transitioned. A lithium-containing metal oxide substituted or doped with a metal element may be used, or a material in which oxygen in a crystal is substituted or doped with S, P, or the like, or a material having a layered rock salt structure.

  Furthermore, in the above-described embodiment, the cylindrical battery is exemplified, but the present invention is not limited to the shape of the battery, and can be applied to a rectangular battery or other polygonal batteries. In addition, the structure to which the present invention can be applied may be other than a battery having a structure in which a battery lid is sealed by caulking on the battery container described above. As an example of such a structure, a battery in which positive and negative external terminals penetrate the battery lid and the positive and negative external terminals are pressed against each other via an axis in the battery container can be cited. Further, the present invention can be applied to a lithium secondary battery in which the positive electrode and the negative electrode have a stacked structure instead of a wound structure.

  Furthermore, in the above embodiment, an example in which amorphous carbon having excellent adhesion to the negative electrode current collector as compared with a case where a crystalline carbon material is used is used as the negative electrode active material. Various artificial graphite materials, carbon materials such as coke, etc. may be used, and the particle shape is not particularly limited, such as scaly, spherical, fibrous or massive. When such a carbon material is used for the negative electrode active material, it is excellent in flexibility when it is wound in a cross-sectional spiral shape to form an electrode group, and separation and separation of the negative electrode active material layer from the negative electrode can be prevented.

  Further, the present invention is not limited to the conductive material and binder (binder) exemplified in the above embodiment, and any commonly used material can be used. Examples of electrode plate active material binders for lithium secondary batteries that can be used in other embodiments include polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, and polysulfide. Examples thereof include polymers such as rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and mixtures thereof.

Furthermore, in the present embodiment, a non-aqueous electrolyte solution in which LiPF ₆ is dissolved in a mixed solvent in which EC, DMC, and DEC are mixed at a volume ratio of 1: 1: 1 is illustrated, but a general lithium salt is used as an electrolyte. A nonaqueous electrolytic solution in which is dissolved in an organic solvent may be used, and the present invention is not particularly limited to the lithium salt or organic solvent used. For example, as the electrolyte, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, or a mixture thereof can be used. Examples of the organic solvent include propylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, Sulfolane, methyl sulfolane, acetonitrile, propionitrile, etc., or a mixed solvent in which two or more of these are mixed can be used, and the mixing ratio is not limited. By using such a non-aqueous electrolyte, it is possible to improve battery capacity and adapt to use in cold regions.

  As an insulating synthetic resin, a mixture of a bisphenol A type epoxy resin and an acrylic acid copolymer was thermally cured to form an insulating layer, but the epoxy resin is not particularly limited. For example, a bisphenol A type epoxy Resin, tetrabromobisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, tetramethylbiphenyl type epoxy resin, etc. bifunctional aromatic glycidyl ether, phenol novolac type Polyfunctional aromatic glycidyl ether such as epoxy resin, cresol novolac type epoxy resin, dicyclopentadiene-phenol type epoxy resin, tetraphenylolethane type epoxy resin, polyethylene glycol type epoxy resin, Bifunctional alicyclics such as bifunctional aliphatic glycidyl ethers such as propylene glycol type epoxy resin, neopentyl glycol type epoxy resin, dibromoneopentyl glycol type epoxy resin, hexanediol type epoxy resin, and hydrogenated bisphenol A type epoxy resin Polyfunctional aliphatic glycidyl ethers such as glycidyl ether, trimethylolpropane type epoxy resin, sorbitol type epoxy resin, glycerin type epoxy resin, bifunctional aromatic glycidyl ester such as diglycidyl phthalate, tetrahydrophthalic acid diglycidyl ester, hexa Bifunctional alicyclic glycidyl ester such as hydrophthalic acid diglycidyl ester, dimer acid diglycidyl ester, hydrogenated dimer acid diglycidyl ester, N, N-diglycidyl aniline, , N-diglycidyltrifluoromethylaniline, etc., bifunctional aromatic glycidylamine, N, N, N ′, N′-tetraglycidyl-4,4-diaminodiphenylmethane, 1,3-bis (N, N-glycidylamino) Methyl) cyclohexane, polyfunctional aromatic glycidylamines such as N, N, O-triglycidyl-p-aminophenol, alicyclic diepoxy acetals, alicyclic diepoxy adipates, alicyclic diepoxycarboxylates, vinylcyclohexene Bifunctional alicyclic epoxy resins such as dioxide, bifunctional heterocyclic epoxy resins such as diglycidylhydantoin, polyfunctional heterocyclic epoxy resins such as triglycidyl isocyanurate, organopolysiloxane type epoxy resins, etc. Polyfunctional silicon-containing epoxy Resin, bifunctional epoxy resin and aliphatic dicarboxylic acid (succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosane diacid, alkylene ether bond-containing dicarboxylic acid, alkylene Carbonate-bonded dicarboxylic acid, butadiene-bonded dicarboxylic acid, hydrogenated butadiene-bonded dicarboxylic acid, dimethylsiloxane-bonded dicarboxylic acid, etc.) and / or alicyclic dicarboxylic acids (1,4-cyclohexanedicarboxylic acid, dimer acid, hydrogenated) And epoxy resins obtained by chain extension reaction with dimer acid and the like. These epoxy resins are used alone or in combination of two or more. A method in which lauryl acrylate / acrylic acid copolymer and polyoxazoline, polyisocyanate, melamine resin, polycarbodiimide, polyol, polyamine and other acrylic polyfunctional monomers are mixed and acrylic crosslinked by heating, ultraviolet irradiation, electron beam irradiation, and triazine Examples of the crosslinking method include a crosslinking agent using a silicone crosslinking agent, a silicone crosslinking agent, a vinylsilane crosslinking agent, and the like. These resins are treated with organic solvents, for example, amides such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, N, N-dimethylethyleneurea, N, N-dimethylpropyleneurea. , Ureas such as tetramethylurea, lactones such as γ-butyrolactone and γ-caprolactone, carbonates such as propylene carbonate, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, n-butyl acetate, butyl cellosolve acetate , Esters such as butyl carbitol acetate, ethyl cellosolve acetate and ethyl carbitol acetate, glymes such as diglyme, triglyme and tetraglyme, hydrocarbons such as toluene, xylene and cyclohexane, sulfur Sulfones such as holan can be used alone or in combination of two or more in a solvent.

  Examples of the insulating filler include zirconia powder, magnesium oxide, silicon nitride, and titanium oxide in addition to alumina powder. These may be used alone or in combination of two or more.

1 Positive mix layer 2 Positive current collector (aluminum foil)
3 Negative electrode mixture layer 4 Negative electrode current collector (copper foil)
5 Separator 6 Insulating layer

Claims (5)

An electrode group in which a belt-like positive and negative electrode plate is wound, and plate-like current collecting members respectively disposed on both sides in the axial direction of the electrode group, and current collecting leads respectively led out from the positive and negative electrode plates In the organic electrolyte secondary battery whose tip is joined to the current collecting member,
The lithium secondary battery, wherein the current collecting lead of the strip-like positive and negative electrode plates is covered with an insulating layer having resistance to organic electrolyte.   The lithium secondary battery according to claim 1, wherein the insulating layer is a synthetic resin selected from a thermoplastic resin and a curable resin that is crosslinked by heating, ultraviolet irradiation, or electron beam irradiation.   The lithium secondary battery according to claim 1, wherein the insulating layer is a mixture of an insulating filler and a synthetic resin.   The lithium secondary battery according to claim 1, wherein a thickness of the insulating layer is equal to or less than a thickness of the mixture layer.   After the electrode mixture is rolled, the insulating layer is applied to the current collecting lead portion of the positive and negative electrode plates only by roll coater method, gravure printing, offset printing, letterpress printing, or ink jet method, and cured. The method for producing an electrode for a lithium secondary battery according to any one of claims 1 to 4, wherein the method is produced.

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