JP4645559B2 - Nonaqueous electrolyte secondary battery and manufacturing method thereof - Google Patents

Description

    The present invention relates to an electrode having a lead protected with a tape, and more particularly to an electrode for preventing an internal short circuit of a battery.

In a battery using a spirally wound electrode group, a positive electrode and a negative electrode are opposed to each other with a separator having a thickness of about 30 μm, and therefore an internal short circuit is likely to be caused at the uneven portion of the electrode. For this reason, sticking a protective tape to the joint part of the electrode lead used as a convex part has been implemented from before. Japanese Utility Model Publication Nos. Sho 61-204340 and Hei 2-14665 describe that a protective tape is applied to both the front and back surfaces of an electrode. In particular, in JP-A-2-14665, the protective tape is applied not only to the electrode but also to the lead portion protruding from the electrode, and the lead electrode is connected to the opposite electrode of which polarity is opposite. A short circuit can be prevented even when the electrode protrudes beyond the other electrode.
However, when the lead portion protected by the tape comes into contact with the electrolytic solution, there is a problem that the tape is peeled off due to deterioration of the adhesive of the tape. In addition, since there is a distance between the electrode and the battery terminal portion, there is a problem in that a lead that electrically connects the electrode and the battery terminal portion contacts a battery can or an electrode having a different polarity.

  The subject of this invention is providing the electrode which can reduce the internal short circuit of a battery, Furthermore, it is providing the high performance secondary battery using the same.

According to one aspect of the present invention, a method for producing a nonaqueous electrolyte secondary battery includes: (a) a step of accommodating an electrode group formed by winding a positive electrode, a negative electrode, and a separator in a battery can; and (b) the step ( a step of forming a beading portion in the battery can after (a), (c) a step of welding the sealing body and the positive electrode lead after the step (b), and (d) the step. After (c), the positive lead is bent using a leading end guide and the sealing body is caulked so that the radius of curvature of the bent portion of the positive lead is 0.15 to 0.5 mm. Process.

  According to the present invention, by providing the insulating tape so as to be sandwiched between the current collector and the lead, an internal short circuit of the battery can be prevented.

  (1) A sheet-like electrode formed by applying an electrode mixture on a sheet-like metal foil current collector, a lead bonded to the exposed portion of the current collector, and sandwiched between the current collector and the lead An electrode for a battery comprising an insulating tape positioned so as to be positioned.

  (2) Item (1) is characterized in that the lead is covered with an insulating tape except for a junction with a current collector and a junction with a metal part for connection to a battery terminal. Battery electrode.

  (3) The battery electrode according to Item 1 or 2, wherein the insulating tape is covered so as to wind a lead, and the overlapping portion is heat-sealed and closed.

  (4) The battery electrode according to any one of Items 1 to 3, wherein the insulating tape has an adhesive.

  (5) The battery electrode according to any one of Items 1 to 4, wherein the insulating tape is hot-pressed on the lead.

  (6) The insulating tape has a base material and an adhesive, the base material includes any one of polypropylene, polyphenylene sulfide, kapton, and polyethylene, and the adhesive is an acrylic adhesive. Item 6. The battery electrode according to any one of Items 1 to 5.

  (7) An electrode group formed by winding a positive electrode, a negative electrode, and a separator; a battery can having a beading portion for accommodating the electrode group; a sealing body for sealing the battery can; the positive electrode; A non-aqueous electrolyte secondary battery having a positive electrode lead connected to a sealing body, wherein the positive electrode lead portion facing the beading portion of the battery can has a radius of curvature of 0.15 to 0.5 mm. Non-aqueous electrolyte secondary battery characterized.

  (8) The nonaqueous electrolyte secondary battery according to item 7, wherein the positive electrode and the positive electrode lead are battery electrodes according to any one of items 1 to 6.

  (9) A method for producing an electrode for a battery, comprising: a step of covering an electrode lead with an insulating tape; and a step of subsequently connecting the electrode lead to the electrode.

  The form of the Example of this invention is explained in full detail below.

  FIG. 2 is a cross-sectional view of a cylinder type battery. The battery shape can be applied to both cylinders and corners. A cylindrical battery can be manufactured by making the winding core into a cylinder shape, and a rectangular battery can be manufactured by making the winding core into a square shape. In the battery, the positive electrode sheet 3 and the negative electrode sheet 2 wound together with the separator 4 are inserted into the battery can 1, the battery can 1 and the negative electrode sheet 2 are electrically connected through the negative electrode lead 19, and an electrolyte is injected and sealed. To form. The terminal cap 13 also serves as a positive electrode terminal and is fitted into the upper opening of the battery can 1 via the gasket 7. The positive electrode sheet 3 is electrically connected to a terminal cap 13 via a positive electrode lead 8, an explosion-proof valve body 9, a current cutoff switch 10, and a positive temperature coefficient resistor (hereinafter referred to as PTC) ring 11.

  In the sealing body, the terminal cap 13, the PTC ring 11, the current cutoff switch 10, and the explosion-proof valve body 9 are stacked in order from the top, and are fitted and supported by the gasket 7. The terminal cap 13 is a surface exposed portion of the battery, and the explosion-proof valve body 9 is inside the battery. The current cutoff switch 10 includes a first conductive body 10a, a second conductive body 10b, and an insulating ring 10c.

  The electrode group 18 is obtained by winding the positive electrode sheet 3 and the negative electrode sheet 2 with the separator 4 interposed therebetween. The upper insulating plate 6 is disposed between the electrode group 18 and the explosion-proof valve body 9. The upper insulating plate 6 insulates the electrode group 18 from the sealing body and insulates the electrode group 18 from the battery can 1. The lower insulating plate 5 is disposed between the electrode group 18 and the battery can 1 to insulate the electrode group 18 and the battery can 1 and insulate the electrode group 18 and the negative electrode lead 19 from each other.

  The battery can 1 has a beading portion 17 for sealing the sealing body. The beading portion 17 is constricted to support the lower portion of the gasket 7. Since the beading portion 17 is constricted inside the battery, it is necessary to prevent contact between the beading portion 17 and the positive electrode lead 8. Specifically, it is necessary to prevent the bent portion 8 c of the positive electrode lead 8 from contacting the beading portion 17 by sewing between the gasket 7 and the upper insulating plate 6. Since the beading part 17 is connected to the negative electrode sheet 2 via the negative electrode lead 19, when the beading part 17 and the positive electrode lead come into contact with each other, an internal short circuit accident occurs. In order to prevent such an accident, the bent portion 8c of the positive electrode lead 8 is covered with an insulating tape.

  FIG. 1 is a cross-sectional view of the battery showing the positive electrode lead 8 and its periphery. The positive electrode lead 8 is covered with an insulating tape 21. FIG. 3 is a cross-sectional view taken along the line AA in FIG. The positive electrode lead 8 is wound with an insulating tape 21, and the surface of the positive electrode lead 8 is covered with the insulating tape. The insulating tape 21 and the positive electrode lead 8 are bonded by hot pressing. Furthermore, the insulating tape 21 wound around the positive electrode lead 8 has its both end portions 21a overlapped and bonded by a heat sink. The insulating tape 21 is preferably made of a base material and an adhesive.

  In FIG. 1, a part of the battery manufacturing process will be described. First, the central portion of the positive electrode lead 8 is covered with the insulating tape 21. Thereafter, the exposed lower end 8 a of the positive electrode lead 8 is welded to the positive electrode sheet 3. Thereafter, the exposed upper end portion 8 b of the positive electrode lead 8 is welded to the explosion-proof valve body 9. Thereafter, the bent portion 8 c of the positive electrode lead 8 is bent, and the sealing body is sealed in the battery can 1. The insulating tape 21 is covered on the central portion excluding the lower end portion 8 a and the upper end portion 8 b of the positive electrode lead 8. That is, the positive electrode lead 8 covers the portion excluding the bonding portion 8 a with the positive electrode sheet 3 and the bonding portion 8 b with the explosion-proof valve body 9 with the insulating tape 21. The insulating tape 21 has a portion positioned so as to be sandwiched between the positive electrode sheet 3 and the positive electrode lead 8.

  The bent portion 8 c of the positive electrode lead 8 faces the beading portion 17 (FIG. 2) of the battery can 1. The curvature radius of the bent portion 8c is preferably 0.15 to 0.5 mm, particularly preferably 0.2 to 0.4 mm.

  FIG. 4 is a diagram showing the connection between the positive electrode sheet 3 and the positive electrode lead 8. The positive electrode sheet 3 is manufactured by applying a positive electrode mixture to a part of a metal foil current collector and drying it. The positive electrode sheet 3 includes a current collector exposed portion 3a and a positive electrode mixture application portion 3b. The current collector exposed portion 3 a is located at the end of the positive electrode sheet 3 on the center side of the electrode group 18 (FIG. 2). The current collector exposed portion 3a has a length (longitudinal dimension of the positive electrode sheet 3) of L1 (for example, 30 mm) and a width in a direction orthogonal to the length of L2 (for example, 56.0 mm).

  The positive electrode lead 8 has a length (a dimension in the longitudinal direction of the positive electrode lead 8 and the width direction of the positive electrode sheet 3) of L3 (for example, 71.4 mm), and has a welded portion 8a and a welded portion 8b. The welded portion 8a is a portion where the positive electrode lead 8 is welded to the current collector exposed portion 3a, and the size thereof is, for example, 2 mm × 30 mm. The welded portion 8b is a portion where the positive electrode lead 8 is welded to the explosion-proof valve body (FIG. 1).

  The positive electrode lead 8 is bonded in the width direction of the positive electrode sheet 3. The lower end of the positive electrode lead 8 is provided above the lower end of the positive electrode sheet 3 at a position having a length L5 (for example, 1.5 mm). The right end of the positive electrode lead 8 is provided at a position of a length L6 (for example, 5 mm) to the left of the right end of the positive electrode sheet 3 (end on the center side of the electrode group 18).

  The insulating tape 21 is wound between the welded part 8 a and the welded part 8 b in the positive electrode lead 8. The lower end of the insulating tape 21 is provided at a position having a length L4 (for example, 5 mm) below the upper end of the positive electrode sheet 3. The upper end of the insulating tape 21 is provided at a position below the lower end of the welded portion 8b. The insulating tape 21 is positioned so as to be sandwiched between the current collector exposed portion 3 a and the positive electrode lead 8.

  The positive electrode sheet 3 can make a collector come out in the collector exposed part 3a by apply | coating a positive electrode mixture only to the positive electrode mixture application part 3b. Alternatively, the positive electrode sheet 3 may be formed by applying the positive electrode mixture to the entire surface of the current collector and then peeling off the electrode mixture in the current collector exposed portion 3a.

  Although a specific configuration example has been described, the shape of the positive electrode lead 8 varies depending on the shape of the battery and the like. In a cylindrical or rectangular battery used by winding a sheet-like electrode, the thickness is 0.03 to 1 mm, more preferably 0.05 to 0.3 mm, and the width is 1.5 to 10 mm, more preferably 2 to 2. A metal piece of 5 mm is used.

  The material of the positive electrode lead 8 depends on the type of the electrode current collector to be joined. When the current collector is a metal foil such as stainless steel, nickel, aluminum, titanium, or copper, it is necessary to select a material that can be welded thereto.

  When the positive electrode current collector is an aluminum foil, the positive electrode lead 8 is preferably aluminum or an aluminum alloy. The aluminum content in the aluminum or aluminum alloy is preferably 99.3% or more and 99.99% or less. Examples of contained elements other than aluminum include silicon, iron, copper, manganese, magnesium, and zinc. When the negative electrode current collector is a copper foil, the negative electrode lead 19 is preferably nickel, nickel-plated steel, copper, or nickel-plated copper.

  As the material of the insulating tape 21, the base material is aramid fiber, polyamide such as nylon or kapton, polyolefin such as polyimide, polypropylene, polyethylene, ultrahigh molecular weight polyethylene, teflon, polyphenylene sulfide, polyethylene terephthalate (PET), polybutylene terephthalate ( Polyester such as PBT), hard vinyl chloride, vinyl, polyurethane, acrylic foam, urethane foam, elastomer foam, crepe paper, thin paper, paper such as flat paper, and cloth such as nonwoven fabric, glass cloth, and alumina cloth are preferable. In particular, polypropylene, polyphenylene sulfide, kapton, and polyethylene are preferable.

  As the pressure-sensitive adhesive, silicone, acrylic, epoxy, and rubber are preferable, and acrylic is particularly preferable.

  Among these, the base material is preferably polypropylene, polyphenylene sulfide, kapton, polyethylene, and the adhesive is an acrylic tape.

  As shown in FIG. 2, the non-aqueous electrolyte secondary battery includes an electrode group 18 in which a positive electrode 3, a negative electrode 2, and a separator 4 are stacked and wound, inserted into the battery can 1, and a negative electrode lead 19 at the bottom of the battery can 1. It is made by welding and sealing after injecting electrolyte. The sealing body is obtained by fitting a cap 13 serving also as a positive electrode terminal, a PTC element 11, a current cutoff switch 10, a metallic explosion-proof valve body 9, and the like to the gasket 7. In the battery can 1 that also serves as the negative electrode terminal, after the winding electrode group 18 is inserted, the concave portion 17 is formed by beading to fix the sealing portion. The positive electrode lead 8 having one end welded to the positive electrode 3 is welded to the sealing body electrically connected to the positive electrode terminal 13 at the other end. The sealing body joined to the positive electrode lead 8 is inserted into the upper part of the battery can 1 and crimped. At this time, the beading portion 17 and the positive electrode lead 8 of the battery can 1 having different polarities should not be in contact with each other and should have a proper distance. Even if the beading portion 17 and the positive electrode lead 8 come into contact with each other, the positive electrode lead 8 is covered with the insulating tape 21, and therefore an internal short circuit can be prevented.

  The battery can 1 is made of nickel-plated steel plate, stainless steel plate (SUS304, SUS304L, SUS304N, SUS316, SUS316L, SUS430, SUS444, etc.), nickel-plated stainless steel plate (same as above), aluminum or an alloy thereof. Nickel, titanium, and copper, and the shapes are a perfect circular cylinder, an elliptical cylinder, a square cylinder, and a rectangular cylinder. In particular, when the battery can 1 also serves as a negative electrode terminal, a stainless steel plate and a nickel-plated steel plate are preferable, and when the battery can 1 also serves as a positive electrode terminal, a stainless steel plate, aluminum, or an alloy thereof is preferable.

  The gasket 7 is made of an olefin polymer, a fluorine polymer, a cellulose polymer, polyimide, or polyamide as a material, and is preferably an olefin polymer, particularly a propylene-based polymer, from the viewpoint of organic solvent resistance and low moisture permeability. Furthermore, a block copolymer of propylene and ethylene is preferable.

  As an example, a cylindrical non-aqueous secondary battery using lithium as an active material will be described in detail below. The positive and negative electrodes used in the non-aqueous secondary battery can be prepared by coating and molding a positive electrode mixture or a negative electrode mixture on a current collector. In addition to the positive electrode active material or the negative electrode material, the positive electrode or the negative electrode mixture can contain a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and various additives, respectively.

  The active material in the positive electrode may be any material that can insert and release light metals, but is preferably a lithium-containing transition metal oxide, more preferably Lix CoO2, Lix NiO2, Lix Coa Ni1-a O2, Lix Cob V1-. b Oz, Lix Cob Fe1-b Oz, Lix Mn2 O4, Lix MnO2, Lix Mn2 O3, Lix Mnb Co2-b Oz, Lix Mnb Ni2-b Oz, Lix Mnb V2-bOz, Lix Mnb Fe1-b Oz (where x = 0.05 to 1.2, a = 0.1 to 0.9, b = 0.8 to 0.98, z = 1.5 to 5).

  Hereinafter, the light metal referred to in the present specification is an element belonging to Group 1A (excluding hydrogen) and Group 2A of the periodic table, preferably lithium, sodium, or potassium, and particularly preferably lithium.

  The negative electrode material may be any material that can insert and release light metals, but preferably graphite (natural graphite, artificial graphite, vapor-grown graphite), coke (coal or petroleum), organic polymer fired product (polyacrylonitrile resin or Fiber, furan resin, cresol resin, phenol resin), calcined mesophase pitch, metal oxide, metal chalcogenide, lithium-containing transition metal oxide and chalcogenide.

  In particular, an oxide or chalcogenide made of Ge, Sn, Pb, Bi, Al, Ga, Si, or Sb alone or a combination thereof is preferable. Further, those made amorphous by adding SiO2, B2 O3, P2 O5, Al2 O3, V2 O5, etc., which are known as network formers, to these are particularly preferred. These may be of stoichiometric composition or non-stoichiometric compounds.

  Although the following can be mentioned as a preferable example of these compounds, It is not limited to these.

  GeO, GeO2, SnO, SnO2, SnSiO3, PbO, SiO, Sb2O5, Bi2O3, Li2SiO3, Li4Si2O7, Li2GeO3, SnAl0.4 B0.5 P0.5 K0.1 O3.65, SnAl0.4B0.5 P0.5 Cs0.1 O3.65, SnAl0.4 B0.5 P0.5 K0.1 Ge0.05 O3.85, SnAl0.4 B0.5 P0.5 K0.1 Mg0.1 Ge0.02 O3.83, SnAl0. 4 B0.4 P0.4 Ba0.08O3.28, SnAl0.5 B0.4 P0.5 Mg0.1 F0.2 O3.65, SnAl0.4B0.5 P0.5 Cs0.1 Mg0.1 F0.2 O3 .65, SnB0.5 P0.5 Cs0.05 Mg0.05F0.1 O3.03, Sn1.1 Al0.4B0.4 P0.4 Ba0.08 O3.34, Sn1.2 Al0.5 B0.3 P0.4 Cs0 .2 O3.5, SnSi0.5 Al0.2 B0.1 P0.1 Mg0.1 O2.8, SnSi0.5 Al0.3 B0.4 P0.5 O4.30, SnSi0.6 Al0.1 B0.1 P0 .1 Ba0.2 O2.95, SnSi0.6Al0.4 B0.2 Mg0.1 O3.2, Sn0.9 Mn0.3 B0.4 0.4 Ca0.1 Rb0.1 O2.95, Sn0.9 Fe0.3 B0.4 P0.4 Ca0.1 Rb0.1 O2.95, Sn0.3 Ge0.7 Ba0.1 P0.9 O3.35, Sn0. 9 Mn0.1 Mg0.1 P0.9 O3.35, Sn0.2Mn0.8 Mg0.1 P0.9 O3.35 Further, the negative electrode material can be used by inserting a light metal, particularly lithium. The lithium insertion method is preferably an electrochemical, chemical or thermal method.

  The amount of lithium inserted into the negative electrode material may be close to the lithium deposition potential, but is preferably 50 to 700 mol% per the above preferred negative electrode material. 100 to 600 mol% is particularly preferable.

  The conductive agent in the positive electrode and the negative electrode is graphite, acetylene black, carbon black, ketjen black, carbon fiber or metal powder, metal fiber or polyphenylene derivative, and graphite and acetylene black are particularly preferable.

  The binder in the positive electrode and the negative electrode is polyacrylic acid, carboxymethylcellulose, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, starch, regenerated cellulose, diacetylcellulose, hydroxypropylcellulose, polyvinylchloride, polyvinylpyrrolidone, polyethylene, polypropylene SBR (styrene-butadiene-rubber), ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, fluororubber, polybutadiene, polyethylene oxide, especially polyacrylic acid, Carboxymethyl cellulose, polytetrafluoroethylene, and polyvinylidene fluoride are preferred. . These are more preferably used as an aqueous dispersion latex having a particle size of 1 micron or less.

  The positive electrode and negative electrode support, that is, the current collector is made of aluminum, stainless steel, nickel, titanium, or an alloy thereof for the positive electrode, and copper, stainless steel, nickel, titanium, or an alloy thereof for the negative electrode. As the form, foil, expanded metal, punching metal, and wire mesh are used. In particular, an aluminum foil is preferable for the positive electrode and a copper foil is preferable for the negative electrode.

  Next, elements other than the electrodes in the battery shown in FIG. 2 will be described. The separator 4 has only high ion permeability, has a predetermined mechanical strength, and may be an insulating thin film. The material is olefin polymer, fluorine polymer, cellulose polymer, polyimide, nylon, glass fiber, alumina. Fibers are used, and the form is a non-woven fabric, a woven fabric, or a microporous film. In particular, the material is preferably polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polypropylene and Teflon, or a mixture of polyethylene and Teflon, and the form is preferably a microporous film. In particular, a microporous film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferable.

  The electrolyte is an organic solvent such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, dioxolane, 1,3. -Dioxolane, formamide, dimethylformamide, nitromethane, acetonitrile, methyl formate, methyl acetate, methyl propionate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydro derivatives, A mixture of at least one of diethyl ether and 1,3-propane sultone, and as an electrolyte, LiClO4, Li What dissolved one or more salts of F4, LiPF6, LiCF3 SO3, LiCF3 CO2, LiAsF6, LiSbF6, LiB10Cl10, lower aliphatic lithium lithium, LiAlCl4, LiCl, LiBr, LiI, lithium chloroborane, and lithium tetraphenylborate preferable. In particular, a solution in which LiCF3SO3, LiClO4, LiBF4, and / or LiPF6 is dissolved in a mixed solvent of propylene carbonate or ethylene carbonate and 1,2-dimethoxyethane and / or diethyl carbonate is preferable, and at least ethylene carbonate and LiPF6 are included. Is preferred.

  The battery is covered with an exterior material as necessary. Examples of the exterior material include a heat-shrinkable tube, an adhesive tape, a metal film, paper, cloth, paint, and a plastic case. Further, at least a part of the exterior may be provided with a portion that changes color by heat so that the heat history during use can be known.

  A plurality of batteries are assembled in series and / or in parallel as required, and stored in a battery pack. In addition to safety elements such as positive temperature coefficient resistors, temperature fuses, fuses and / or current interrupting elements, the battery pack also requires safety circuits (monitoring the voltage, temperature, current, etc. of each battery and / or the entire battery pack) In this case, a circuit having a function of interrupting current may be provided. In addition to the positive and negative terminals of the entire assembled battery, the battery pack should be provided with the positive and negative terminals of each battery, the entire assembled battery, the temperature detection terminal of each battery, the current detection terminal of the entire assembled battery, etc. as external terminals. You can also. The battery pack may incorporate a voltage conversion circuit (such as a DC-DC converter). The connection of each battery may be fixed by welding a lead plate, or may be fixed so that it can be easily attached and detached with a socket or the like. Further, the battery pack may be provided with display functions such as the remaining battery capacity, the presence / absence of charging, and the number of uses.

  Batteries are used in various devices. In particular, video movie, portable video deck with built-in monitor, movie camera with built-in monitor, compact camera, single-lens reflex camera, disposable camera, film with lens, notebook computer, notebook type word processor, electronic notebook, mobile phone, cordless phone, beard, It is preferably used for electric tools, electric mixers, automobiles and the like.

Hereinafter, the present invention will be described in more detail with specific examples. However, the present invention is not limited to the examples unless it exceeds the gist of the invention.

  (Preparation of positive electrode sheet) As a positive electrode material, 92.71% by weight of LiCoO2, 3.26% by weight of acetylene black, 0.93% by weight of sodium hydrogen carbonate, and 1% by weight of polyvinylidene fluoride as a binder Then, 1.66% by weight of a copolymer of ethylhexyl acrylate mainly composed of ethylhexyl acrylate and acrylic acid and 0.44% by weight of carboxymethylcellulose were added and kneaded using water as a medium to obtain a slurry. The obtained slurry was applied to both sides of an aluminum foil (current collector) having a thickness of 20 μm and dried to prepare a positive electrode sheet having a thickness of 270 μm excluding the current collector. At this time, intermittent application was performed such that the length of the portion where the slurry was applied was 403 mm, and the length of the current collector exposed portion was 33 mm. The positive electrode sheet was compressed to a thickness of 190 μm after being dried with a roll press and slit to a width of 56 mm to produce a long roll positive electrode sheet.

  As shown in FIG. 4, an aluminum positive electrode lead 8 having a thickness of 100 μm, a width of 4 mm, and a length of 71.4 mm was ultrasonically welded to the current collector exposed portion 3 a of the positive electrode sheet 3 at 40 kHz. The positive electrode lead 8 was previously coated with an insulating tape 21 except for a welded portion 8a (49.5 mm) with the positive electrode sheet 3 and a welded portion 8b (6.9 mm) with the sealing body. The insulating tape 21 has a base material of polyethylene, an adhesive is acrylic, and has a width of 9 mm. The insulating tape 21 is wound around the positive electrode lead 8, and the overlapping portion 0.5 mm of the end 21 a (FIG. 3) is heated at about 200 ° C. Sealed. The coated surface of the lead was pressed with a heat roller of about 100 ° C.

  The welding of the positive electrode lead 8 to the positive electrode sheet 3 is performed by installing the positive electrode lead 8 at a position of L5 = 1.5 mm from the end of the long positive electrode sheet 3 in the width direction of the slurry application end, Welding was performed using a horn having a width of 2 mm and a length of 30 mm. After welding, it was cut from the slurry application end of the long positive electrode sheet 3 at a position of L1 = 30 mm to prepare a positive electrode sheet (C-1) having a length of 436 mm.

  (Preparation of negative electrode sheet) 77.5% by weight of SnB0.5 P0.5 O3 as a negative electrode material, 17.01% by weight of scaly graphite, 0.94% by weight of lithium acetate, and polyvinylidene fluoride as a binder 3.78% by weight and 0.77% by weight of carboxymethylcellulose were added and kneaded using water as a medium to prepare a negative electrode slurry. The slurry was applied to both sides of a 18 μm thick copper foil (current collector) by an extrusion method and dried. The coating width of the obtained negative electrode was 500 mm, and the thickness of the negative electrode after drying was 90 μm excluding the current collector. Thereafter, the thickness of the negative electrode excluding the current collector was compression molded to 78 μm with a roll press. The negative electrode was made by applying intermittently so that the total length was 461 mm, the width was 57.5 mm, and the front end 3 mm and the rear end 15 mm when winding were the current collector exposed part. The negative electrode lead 19 made of nickel was ultrasonically welded to the current collector exposed portion at the rear end.

  As the separator 4, a sheet was prepared by cutting a polyethylene microporous film into a width of 60.5 mm and a length of 520 mm.

  (Assembly of Cylinder Battery) The negative electrode sheet 2 and the positive electrode sheet 3 were dehydrated and dried at 230 ° C. for 30 minutes in dry air having a dew point of −40 ° C. or lower. Furthermore, the positive electrode sheet 3 after dehydration and drying, the microporous polyethylene film separator, the negative electrode sheet 2 after dehydration and drying, and the separator 4 were laminated in this order, and this was wound in a spiral shape with a wrapping machine. The wound body 18 was housed in an iron-bottomed cylinder-type battery can 1 made of nickel and also serving as a negative electrode terminal. After the upper insulating plate 6 was inserted into the battery can 1, the battery can 1 was beaded to form a groove 17. Thereafter, an electrolyte composed of a mixed solution containing 0.9 and 0.1 mol of LiPF6 and LiBF4 per liter and having a volume ratio of ethylene carbonate, butylene carbonate and dimethyl carbonate of 2: 2: 6 as a battery can 1 Injected into.

  Next, a plate-shaped explosion-proof valve body 9 with a welding plate welded to its lower surface, a polypropylene-made gasket 7 coated with a sealant on the outside, an insulation cover for the explosion-proof valve body 9, a current cutoff switch 10, a PTC ring 11, a positive electrode A sealing body fitted in the order of the terminal cap 13 was assembled. Then, the welding plate of this sealing body and the positive electrode lead 8 were welded. The positive electrode lead 8 was bent using a bending tip guide with a tip radius of curvature of 0.25 mm, and the lead 8 after being crimped had a radius of curvature of 0.3 mm. The sealing body was inserted into the opening of the battery can 1 and caulked to produce a cylindrical battery (D-1).

  In the positive electrode lead 8, the coated end portion 21a of the insulating tape 21 was not heat-sealed, and other than that, the positive electrode sheet C-2 was made in the same manner as the positive electrode sheet C-1. A positive electrode sheet C-3 was produced in the same manner as C-1, except that the length of the insulating tape 21 was 6 mm (overlapping portion with the positive electrode) was L4 = 5 mm, and the portion not overlapping with the positive electrode was 1 mm. Further, the positive electrode lead 8 was sharply bent at C-1 and C3 so that the radius of curvature of the positive electrode lead 8 was 0.1 mm, thereby producing positive electrode sheets C-4 and C5, respectively. Using these positive electrode sheets C-2 to C-5, batteries D-2 to D-5 were made in the same manner as the battery D-1.

  5000 pieces of each of these batteries were produced and stored at 105 ° C. for 2 days, and then the number of short-circuited batteries and the number of pieces of the insulating tape 21 peeled off after being disassembled were examined. The number of decomposition was 100, and the results shown in the following table [Table 1] were obtained.

  From the results of [Table 1], in the batteries D-1, D-3, D-4, and D-5, the insulating tape 21 of the positive electrode lead 8 did not peel off. Since the battery D-2 did not heat seal the coated end portion 21a of the insulating tape 21, the insulating tape 21 was peeled off in ten batteries. It is preferable to heat-seal the covering end portion 21a of the insulating tape 21 because the insulating tape 21 is unlikely to peel off as in the batteries D-1, D-3 to D-5.

  In batteries D-3 and D-5, the length of the insulating tape 21 was as short as 6 mm. If the part (15 mm) excluding the welded portion 8a and the welded portion 8b of the insulating tape 21 is covered with the long insulating tape 21 as in the batteries D-1, D-2, and D-4, an internal short circuit can be prevented. Therefore, it is preferable.

  In the batteries D-4 and D-5, the positive electrode lead 8 had a radius of curvature that was too small at 0.1 mm, and therefore, an internal short circuit occurred. If the radius of curvature is small, the lead 8 may be sandwiched between the protruding portion of the upper insulating plate 6 and the lower portion of the gasket 7, and the sealing body may be caulked to the battery can 1. In this case, the lead 8 is broken. The broken lead 8 comes into contact with the beading portion 17 of the battery can 1 due to its size, and an internal short circuit is likely to occur. Since the curvature radius of the positive electrode lead 8 was as large as 0.3 mm, the batteries D-1 and D-3 had fewer internal short circuits than the batteries D-4 and D-5, respectively. The radius of curvature of the positive electrode lead 8 is preferably 0.15 to 0.5 mm.

It is a figure which shows the positive electrode lead which connects a positive electrode sheet and an explosion-proof valve body. It is sectional drawing of a cylinder type battery. It is sectional drawing of the positive electrode lead coat | covered with the insulating tape. It is a figure which shows the positive electrode lead welded to the positive electrode sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery can 2 Negative electrode 3 Positive electrode 4 Separator 5 Lower insulating plate 6 Upper insulating plate 7 Gasket 8 Positive electrode lead 9 Explosion-proof valve body 10 Current interruption switch 10a First conducting body 10b Second conducting body 10c Insulating ring 11 PTC ring 13 Terminal cap 17 Beading section 18 Electrode group 19 Negative electrode lead 21 Insulating tape

Claims (2)

(A) The process of accommodating the electrode group formed by winding a positive electrode, a negative electrode, and a separator in a battery can;
(B) a step of forming a beading portion in the battery can, which is performed after the step (a) ;
(C) a step that is performed after the step (b) and welds the sealing body and the positive electrode lead;
(D) After the step (c), the positive lead is bent using a leading end guide, and the sealing body is caulked, so that the radius of curvature of the bent portion of the positive lead is 0.15 to 0.5 mm. A process for producing a nonaqueous electrolyte secondary battery. Furthermore, (a1) is performed before the step (a), and a step of covering the positive electrode lead with the insulating tape by winding an insulating tape so as to surround a central portion excluding both ends of the positive electrode lead;
(A2) is performed after said step (a1), according to claim 1, further comprising a step of a portion of the insulating tape is connected to the electrode of the positive electrode lead so as to be interposed between the positive electrode current collector lead Of manufacturing a non-aqueous electrolyte secondary battery.

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