JP4880879B2 - Non-aqueous electrolyte secondary battery inspection method and non-aqueous electrolyte secondary battery manufacturing method - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery inspection method.

  In recent years, electronic devices such as mobile communication devices, notebook computers, palmtop computers, integrated video cameras, portable CD (MD) players, cordless telephones, etc. have been reduced in size and weight. As a power source, a battery having a small size and a large capacity is particularly demanded.

  Examples of batteries that are widely used as power sources for these electronic devices include primary batteries such as alkaline manganese batteries, and secondary batteries such as nickel cadmium batteries and lead storage batteries. Among them, non-aqueous electrolyte secondary batteries using a lithium composite oxide for the positive electrode and an active material such as a carbonaceous material capable of occluding and releasing lithium ions for the negative electrode are small and light, have a high single cell voltage, It is known that energy density can be obtained.

  In recent years, as an exterior member for housing an electrode group having a positive electrode and a negative electrode, a heat-fusible resin layer such as polyethylene and polyethylene terephthalate are formed on both surfaces of a metal layer made of aluminum or the like that exhibits a barrier action against water vapor and the like. A laminate film formed by laminating such a synthetic resin layer is molded into a bag shape or a cup shape, and this makes it possible to further reduce the weight and size of the nonaqueous electrolyte secondary battery.

  However, in the secondary battery having such a configuration, the negative electrode terminal connected to the negative electrode and the metal layer constituting the laminate film of the exterior member are in electrical contact, and the resin layer on the inner surface of the laminate film has a pinhole or the like. When present, a battery comprising an electrolyte in contact with the metal layer, the metal layer, and a negative electrode is formed. Here, since aluminum or aluminum alloy in the metal layer has a higher potential than the negative electrode, lithium ions in the electrolyte react with aluminum or aluminum alloy in the metal layer to generate a lithium-aluminum alloy. Since the lithium-aluminum alloy produced in the metal layer has a large volume expansion and high reactivity with moisture, there is a risk that the metal layer will collapse with time and the barrier property against moisture, which is its original purpose, may be reduced. is there. When the barrier property of the metal layer is lost, moisture enters the battery from the location, reacts with the electrolyte, and decomposed gas is generated. Generation of cracked gas leads to battery swelling and performance degradation.

  In order to solve such problems, it has been studied to electrically connect in advance a metal layer made of aluminum or an aluminum alloy of a laminate film of an exterior member and a positive electrode terminal. For example, Patent Document 1 describes a method of connecting a metal layer of a laminate film and a positive electrode terminal using a sealing mold having a convex portion when the positive electrode terminal is heat-sealed with a laminate film.

  However, in the invention of Patent Document 1, when the negative electrode terminal and the metal layer of the laminate film are in contact with each other during use, the positive electrode and the negative electrode through this metal layer are in an external short circuit state. For this reason, heat is generated from the battery, and in some cases, ignition may occur, which is very dangerous.

In addition, it has been studied to eliminate defective products by inspection during the manufacturing process. For example, Patent Document 2 describes performing an insulation test between a metal layer of a laminate film and a positive electrode terminal during the manufacturing process.
However, in the invention of Patent Document 2, since the inspection is performed in the middle of the manufacturing process, it cannot be detected when a defect occurs in the subsequent process. In addition, when there is a pinhole or the like in the synthetic resin layer on the inner surface of the laminate film, the insulation resistance is high immediately after manufacture, but the electrolyte penetrates into the resin layer with time and the insulation resistance decreases, and lithium-aluminum Since an alloy is produced, defective products cannot be accurately detected.
JP-A-2002-260603 JP2002-324572

  The present invention provides a highly reliable nonaqueous electrolyte in which an internal electrode group and a nonaqueous electrolyte by an exterior member are sufficiently protected and an external short circuit does not occur when a negative electrode terminal contacts a metal layer of the exterior member during use. Provided is a nonaqueous electrolyte secondary battery inspection method capable of appropriately discriminating a secondary battery.

  The present invention provides a method for manufacturing a non-aqueous electrolyte secondary battery that can select defective high-performance and high-reliability non-aqueous electrolyte secondary batteries by using the above inspection method.

According to the present invention, a laminate film in which at least a heat-fusible resin layer, a metal layer made of aluminum or an aluminum alloy, and a synthetic resin layer are laminated in this order is formed into a bag shape, and the heat-fusible resin layers at the periphery of the opening are bonded together. An exterior member that is heat-sealed to form a heat-sealed portion, an electrode group having a positive electrode, a negative electrode, and a separator and a nonaqueous electrolyte that are housed in the exterior member, and are led out from the exterior member and connected to the positive electrode A positive electrode terminal and a negative electrode terminal connected to the negative electrode, wherein the positive electrode and the positive electrode terminal have a potential of 3.90 V to 4.05 V with respect to metallic lithium, and the voltage is 3.75 V to 3.90 V In inspecting non-aqueous electrolyte secondary batteries,
The voltage between the positive electrode terminal and the metal layer located at the heat seal portion of the exterior member is measured with a voltmeter having an input impedance of 1 G ohm or more , and the one in the voltage range of 0.2V to 3.1V is good. A method for inspecting a non-aqueous electrolyte secondary battery is provided.

Further, according to the present invention, a laminate film in which at least a heat-fusible resin layer, a metal layer made of aluminum or an aluminum alloy, and a synthetic resin layer are laminated in this order is formed into a bag shape, An exterior member in which a heat-sealed portion is formed by heat-sealing, an electrode group having a positive electrode, a negative electrode, and a separator and a non-aqueous electrolyte housed in the exterior member, and led out from the exterior member to the positive electrode A positive electrode terminal connected to the negative electrode terminal and a negative electrode terminal connected to the negative electrode, the positive electrode terminal and the positive electrode terminal have a potential of 3.90 V to 4.05 V with respect to metallic lithium, and a voltage of 3.75 V to 3.90 V In manufacturing non-aqueous electrolyte secondary batteries,
The voltage between the positive electrode terminal after assembly and the metal layer located at the heat seal portion of the exterior member is measured with a voltmeter having an input impedance of 1 G ohm or more, and the voltage is 0.2V to 3.1V A method for producing a non-aqueous electrolyte secondary battery is provided, wherein the non-aqueous electrolyte secondary battery is selected as a non-defective product.

According to the present invention, a highly reliable nonaqueous electrolyte secondary battery that has a high internal protection effect by the exterior member and does not cause an external short circuit when the negative electrode terminal contacts the metal layer of the exterior member during use is a non-defective product. Can be properly determined.
In addition, according to the present invention, it is possible to provide a method for producing a non-aqueous electrolyte secondary battery capable of accurately selecting a high-performance, high-reliability non-aqueous electrolyte secondary battery by using the inspection method.

  Hereinafter, the present invention will be described in detail.

  A non-aqueous electrolyte secondary battery to be inspected according to the present invention has a bag-like laminate film in which at least a heat-fusible resin layer, a metal layer made of aluminum or an aluminum alloy, and a synthetic resin layer are laminated in this order. An exterior member in which the heat-sealing resin layers on the periphery are heat-sealed to form a heat-sealed portion, an electrode group having a positive electrode, a negative electrode, and a separator and a non-aqueous electrolyte housed in the exterior member, and the exterior member And a negative electrode terminal connected to the negative electrode and having a voltage of 3.75V to 3.90V. The voltage between the positive electrode terminal of such a non-aqueous electrolyte secondary battery and the metal layer located at the heat seal portion of the exterior member is measured with a voltmeter having an input impedance of 1 G ohm or more, and 0.2V to 3.1V. The quality range is determined as a determination index, and the quality is determined and inspected.

The voltage measurement between the positive electrode terminal and the metal layer of the exterior member is performed by, for example, bringing one measurement terminal tip of the pair of measurement terminals into contact with the positive electrode terminal and the other measurement terminal tip being the exterior. It can be carried out by penetrating a synthetic resin layer located at the seal portion of the member and contacting the metal layer.
Before measuring the voltage between the positive electrode terminal and the metal layer of the exterior member with the pair of measurement terminals, the tip of the auxiliary measurement terminal penetrates the synthetic resin layer positioned at the seal portion of the exterior member It is preferable that the metal layer is pierced and the voltage between the other measurement terminal and the auxiliary measurement terminal is measured to confirm conduction between the other measurement terminal and the metal layer.
The other measurement terminal and the auxiliary measurement terminal are synthetic resin of the seal portion of the exterior member folded so as to be in contact with two side surfaces adjacent to the side surface from which the positive electrode terminal and the negative electrode terminal are derived. It is preferable to penetrate each of the metal layers through the layers.
If the input impedance of the voltmeter is less than 1 G ohm during the voltage measurement, accurate voltage measurement becomes difficult. A more preferable input impedance of the voltmeter is 1 to 10 Gohm.
The reason why the voltage range, which is a quality determination index of the secondary battery, is defined as 0.2 to 3.1 V will be described.

  As described above, the lithium-aluminum alloy is produced when the negative electrode terminal connected to the negative electrode and the metal layer constituting the laminate film of the exterior member are in electrical contact with each other and an electrolyte is interposed therebetween. The formation of this lithium-aluminum alloy occurs in the vicinity of 0.8 V with respect to the potential of the lithium metal because the negative electrode terminal and the metal layer of the laminate film constituting the exterior member are in electrical contact. For this reason, in order to prevent the formation of a lithium-aluminum alloy, the potential of the aluminum layer of the laminate film constituting the exterior member or the metal layer of the aluminum alloy needs to be 0.8 V or more with respect to the metal lithium. When the voltage of the nonaqueous electrolyte secondary battery of the present invention is specified to be 3.75 V to 3.90 V, the positive electrode and the positive electrode terminal have a potential of 3.90 V to 4.05 V with respect to metallic lithium. In order to prevent the formation of a lithium-aluminum alloy, the voltage between the positive electrode terminal and the metal layer should be 3.1 V or less in order to make the potential of the metal layer 0.8 V or more with respect to the potential of the lithium metal. It is necessary. Such a non-aqueous electrolyte secondary battery does not produce the above-described lithium-aluminum alloy, and the internal electrode group and the non-aqueous electrolyte by the exterior member are sufficiently protected and has high reliability. On the other hand, when the voltage between the positive electrode terminal and the aluminum layer of the laminate film constituting the exterior member is less than 0.2 V, the positive electrode terminal and the metal layer may be in electrical contact. If the negative electrode terminal comes into contact with the metal layer of the exterior member during use, an external short circuit may occur, which may cause heat generation or ignition. The voltage range which is a more preferable quality determination index is 0.5V to 2.8V.

  The positive electrode, the negative electrode, the separator, the non-aqueous electrolyte, and the laminate film used for the exterior member constituting the non-aqueous electrolyte secondary battery will be described.

1) Positive electrode The positive electrode includes a current collector and a positive electrode layer supported on one or both surfaces of the current collector.

  The positive electrode layer includes a positive electrode active material, a binder, and a conductive agent.

Examples of the positive electrode active material include various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt oxide, lithium-containing nickel cobalt oxide, lithium-containing iron oxide, and lithium. Examples thereof include vanadium oxide and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Among them, lithium-containing cobalt oxide (for example, LiCoO ₂ ), lithium-containing nickel cobalt oxide (for example, LiNi _0.8 Co _0.2 O ₂ ), and lithium manganese composite oxide (for example, LiMn ₂ O ₄ , LiMnO ₂ ) It is preferable because a secondary battery is obtained. As the positive electrode active material, one kind of oxide may be used alone, or two or more kinds of oxides may be mixed and used.

  Examples of the conductive agent include acetylene black, carbon black, and graphite.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyether sulfone, ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR). Can be used.

  The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates are made of, for example, aluminum or stainless steel.

  The positive electrode is produced, for example, by suspending a conductive agent and a binder in a positive electrode active material in a suitable solvent, and applying the suspension to a current collector and drying to form a positive electrode layer.

2) Negative electrode The negative electrode includes a current collector and a negative electrode layer carried on one or both sides of the current collector.

  The negative electrode layer includes an active material that absorbs and releases lithium ions and a binder.

Examples of the active material include graphite materials, carbonaceous materials such as graphite, coke, carbon fiber, spherical carbon, pyrolytic vapor phase carbonaceous material, and resin fired body; thermosetting resin, isotropic pitch, mesophase pitch system Graphite material or carbon obtained by heat-treating carbon, mesophase pitch-based carbon fiber, mesophase microsphere, etc. (especially mesophase pitch-based carbon fiber is preferable because of its high capacity and charge / discharge cycle characteristics) at 500 to 3000 ° C. Materials such as: chalcogen compounds such as titanium disulfide, molybdenum disulfide and niobium selenide; light metals such as aluminum, aluminum alloy, magnesium alloy, lithium and lithium alloy; Among them, it is desirable to use a graphite material having a graphite crystal having a (002) plane spacing _d002 of 0.34 nm or less, more preferably 0.337 nm or less. A nonaqueous electrolyte secondary battery including a negative electrode containing such a graphite material as an active material can greatly improve battery capacity and large current discharge characteristics.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like. Can be used.

  The mixing ratio of the active material and the binder is preferably in the range of 90 to 98% by weight of the active material and 2 to 20% by weight of the binder.

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates are made of, for example, copper, stainless steel, or nickel.

  The negative electrode is prepared by, for example, kneading an active material and a binder in the presence of a solvent, applying the obtained suspension to a current collector, drying, and then pressing once at a desired pressure or 2 to 5 It is produced by pressing multiple times.

3) Separator As this separator, a microporous film, a woven fabric, a non-woven fabric, a laminate of the same material or different materials among these can be used. In particular, the microporous membrane causes a so-called shutdown phenomenon in which the resin constituting the separator plastically deforms and closes the fine pores when the temperature of the electrode group rises abnormally due to heat generated by overcharging, etc., and the flow of lithium ions Is prevented, and further overheating is prevented, and the overcharge state can be safely terminated, which is preferable. Examples of the material for forming the separator include polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer. As a material for forming the separator, one type or two or more types selected from the types described above can be used.

  A flat electrode group is formed by combining the positive electrode, the negative electrode, and the separator. For example, (i) the positive electrode and the negative electrode are wound in a flat shape with a separator interposed therebetween, or (ii) the positive electrode and the negative electrode are wound in a spiral shape with a separator interposed therebetween. Either compressing in the radial direction, (iii) bending the positive electrode and the negative electrode one or more times with a separator interposed therebetween, or (iv) laminating the positive electrode and the negative electrode with a separator interposed therebetween, It is produced by the method.

  The electrode group need not be pressed, but is preferably pressed to increase the integration and adhesion strength of the positive electrode, the negative electrode and the separator. It is also possible to heat at the time of pressing.

  The electrode group can contain an adhesive polymer in order to increase the adhesion strength of the positive electrode, the negative electrode, and the separator. It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Specific examples include polyacrylonitrile (PAN), polyacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), and polyethylene oxide (PEO).

4) Nonaqueous electrolyte The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte (for example, a lithium salt) dissolved in the nonaqueous solvent. The form of the non-aqueous electrolyte can be liquid (non-aqueous electrolyte) or gel.

  Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ- BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. The non-aqueous solvent may be used alone or in combination of two or more.

Examples of the non-aqueous electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), and trifluoromethanesulfone. Examples thereof include lithium salts such as lithium acid lithium (LiCF ₃ SO ₃ ). The electrolytes may be used alone or in combination of two or more. The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.2 mol / l to 2 mol / l.

  The non-aqueous solvent is allowed to contain at least one kind of halogenated toluene selected from the group consisting of toluene chloride (CT) and orthofluorinated toluene (o-FT). Halogenated toluene is added in order to more reliably proceed with the shutdown of the separator.

  The non-aqueous solvent may contain a surfactant such as trioctyl phosphate (TOP) in order to improve the wettability with the separator. The addition amount of the surfactant is preferably 3% or less, and more preferably in the range of 0.1 to 1%.

  In the non-aqueous solvent, the following solvents can be contained as subcomponents.

  As an auxiliary component, for example, vinylene carbonate, vinyl ethylene carbonate, phenyl ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, γ-valerolactone, methyl propionate, ethyl propionate, 2-methylfuran, furan, thiophene, Examples thereof include catechol carbonate, ethylene sulfite, 12-crown-4, and tetraethylene glycol dimethyl ether.

  The amount of the non-aqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh of battery unit capacity. A more preferable range of the amount of the nonaqueous electrolytic solution is 0.25 to 0.55 g / 100 mAh.

5) Laminate film This laminate film has a heat-fusible resin layer such as polyethylene or polypropylene on the side in contact with the electrode group, and a metal layer (metal foil) made of aluminum or an alloy thereof, polyethylene, polyester, A film in which synthetic resin layers such as terephthalate are sequentially laminated can be used.

In the laminated film, it is allowed to further provide an adhesive layer or a gas barrier layer between the layers.
An example of the non-aqueous electrolyte secondary battery (thin lithium ion secondary battery) will be specifically described with reference to FIGS. FIG. 1 is a perspective view showing the thin lithium ion secondary battery, and FIG. 2 is a sectional view taken along line II-II in FIG.

  As shown in FIGS. 1 and 2, the electrode group 1 has a flat, rectangular shape in which the positive electrode 2, the separator 3, the negative electrode 4, and the separator 3 are wound in a spiral shape, and are further shaped. The positive electrode 2 has a structure in which, for example, a positive electrode active material layer containing an active material and a binder is supported on both sides of a current collector. The negative electrode 4 has a structure in which, for example, a negative electrode active material layer containing a carbonaceous material that occludes / releases lithium ions and a binder is supported on both sides of the current collector. Positive and negative terminals 5 and 6 connected to the positive and negative electrodes 2 and 4 are extended from the same side surface of the electrode group 1 to the outside.

As shown in FIG. 1, the electrode group 1 is housed and wrapped in a cup 8 of, for example, a folded cup-type exterior film 7. As shown in FIG. 2, the exterior film 7 has a laminate structure in which a heat-sealing resin film 9 located on the inner surface side, an aluminum or aluminum alloy metal layer 10 and a synthetic resin film 11 are laminated in this order. Three side portions of the exterior film 7 excluding the bent portion are formed with seal portions 12a, 12b, 12c in which the heat-sealing resin films 9 are heat-sealed, and the seal portions 12a, 12b, 12c The electrode group 1 is sealed. Positive and negative terminals 5 and 6 connected to the positive and negative electrodes 2 and 4 of the electrode group 1 are extended to the outside through a seal portion 12b on the opposite side to the bent portion. A non-aqueous electrolyte is impregnated and contained in the electrode group 1 and the exterior film 11 sealed by the seal portions 12a, 12b, and 12c. The two seal portions 12 a and 12 c adjacent to the seal portion 12 b from which the external terminals 5 and 6 are extended are bent so as to contact the side surface of the cup 8.
According to the inspection method according to the present invention described above, when the voltage between the positive electrode terminal and the metal layer located on the heat seal portion of the exterior member is measured with a voltmeter having an input impedance of 1 G ohm or more, the above-described reason The voltage range of 0.2V to 3.1V can be determined as a determination index, and those within this range can be appropriately determined as good products and those outside the range as defective products. The non-aqueous electrolyte secondary battery determined as a non-defective product has no lithium-aluminum alloy formed on the metal layer made of aluminum or aluminum alloy of the laminate film constituting the exterior member, and the internal electrode group and the non-aqueous electrolyte are formed by the exterior member. Is sufficiently protected, and has high reliability that does not cause an external short circuit when the negative electrode terminal contacts the metal layer of the exterior member during use.
Further, when the measuring terminal is brought into contact with the metal layer made of aluminum or aluminum alloy of the laminate film constituting the exterior member, by passing through the synthetic resin layer where the seal portion of the exterior member is located and contacting the metal layer The sealing performance of the non-aqueous electrolyte secondary battery after inspection is not impaired, and high reliability can be maintained.
Furthermore, before measuring the voltage between the positive electrode terminal and the metal layer of the exterior member with the pair of measurement terminals, the synthetic resin layer in which the tip of the auxiliary measurement terminal is positioned at the seal portion of the exterior member The other measurement terminal and the auxiliary measurement terminal are measured to measure the resistance between the other measurement terminal and the metal layer, thereby confirming the continuity between the other measurement terminal and the auxiliary measurement terminal. It can be confirmed that the service terminal is in reliable contact with the metal layer of the exterior member, and the reliability of the inspection can be improved.
Further, the sealing part of the exterior member is folded so that the other measurement terminal and the auxiliary measurement terminal are brought into contact with two side surfaces adjacent to the side surface from which the positive electrode terminal and the negative electrode terminal are led out. When the seal part through which the positive electrode terminal and the negative electrode terminal extend is narrow by penetrating the metal layer through the resin layer, the seal part having a larger area than the seal part can be used. Inspection can be performed without impairing the sealing performance.

  The method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention is to inspect a non-aqueous electrolyte secondary battery having a voltage after assembly of 3.75V to 3.90V by the above-described method, that is, the positive electrode terminal and the exterior member. Measure the voltage between the metal layer located in the heat seal part with a voltmeter with an input impedance of 1G ohm or more, and the measured value is within the voltage range of 0.2V to 3.1V or out of the voltage range And inspecting those items that are within that voltage range.

  According to such a method, a high-performance, high-reliability non-aqueous electrolyte secondary battery can be selected accurately and reproducibly, and as described in the inspection method, High reliability can be maintained without impairing the sealing performance.

[Example]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1
<Preparation of positive electrode>
First, 90% by weight of lithium cobalt oxide (Li _x CoO ₂ ; X is 0 <X ≦ 1) powder, 5% by weight of acetylene black, and 5% by weight of polyvinylidene fluoride (PVdF) dimethylformamide (DMF) solution was added and mixed to prepare a slurry. The slurry was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm, then dried and pressed to produce a positive electrode having a structure in which the positive electrode layer was supported on both sides of the current collector. The thickness of the positive electrode layer was 60 μm per side.

<Production of negative electrode>
As a carbonaceous material, 95% by weight of powder of mesophase pitch-based carbon fiber (having a (002) plane interval (d ₀₀₂ ) of 0.336 nm determined by powder X-ray diffraction) heat-treated at 3000 ° C. and polyvinylidene fluoride ( (PVdF) 5% by weight dimethylformamide (DMF) solution was mixed to prepare a slurry. The slurry was applied to both surfaces of a current collector made of a copper foil having a thickness of 12 μm, dried, and pressed to prepare a negative electrode having a structure in which the negative electrode layer was supported on the current collector. The thickness of the negative electrode layer was 55 μm per side.

The surface spacing d ₀₀₂ of (002) plane of the carbonaceous material were respectively determined by the powder X-ray diffraction spectrum half width midpoint method. At this time, scattering correction such as Lorentz scattering was not performed.

<Separator>
A separator made of a microporous polyethylene film having a thickness of 25 μm and a porosity of 45% was prepared.

<Production of electrode group>
After the positive electrode terminal made of a strip-shaped aluminum foil (thickness: 100 μm) is ultrasonically welded to the positive electrode current collector, and the negative electrode terminal made of a band-shaped nickel foil (thickness: 100 μm) is ultrasonically welded to the negative electrode current collector The positive electrode and the negative electrode were spirally wound through the separator between them to prepare an electrode group. The electrode group was formed into a flat shape by applying pressure with a press while heating.

<Preparation of non-aqueous electrolyte>
A nonaqueous solvent was prepared by mixing ethylene carbonate (EC), γ-butyrolactone (GBL), and orthochlorotoluene so that the weight ratio (EC: GBL: o-CT) was 35: 60: 5. Lithium tetrafluoroborate (LiBF ₄ ) was dissolved in the obtained non-aqueous solvent so that its concentration was 1.5 mol / L to prepare a non-aqueous electrolyte.

<Battery assembly>
A rectangular cup was formed with a press on a 100 μm thick laminate film in which polyethylene films were laminated on both sides of an aluminum foil, and the flat film portion was bent 90 ° at the short side of the cup to obtain an exterior film material. . After storing the flat electrode group in the cup of the exterior film material so that the positive and negative terminals protrude from the end opposite to the bent portion to the outside, the flat film portion is a film portion having a cup. And an outer film containing the electrode group was obtained by heat-sealing the three perimeters except for the bent portion. At this time, a part of the heat seal was left unsealed for degassing and electrolyte injection. Subsequently, the exterior film was vacuum-dried at 80 ° C. for 12 hours in a glove box to remove moisture contained in the electrode group and the laminate film. Thereafter, the non-aqueous electrolyte is injected into the electrode group in the exterior film so that the amount per battery capacity 1Ah is 4.8 g, and the unsealed portion is heat-sealed and sealed, as described above. A non-aqueous electrolyte secondary battery having the structure shown in FIG. 2, having a thickness of 3.6 mm, a width of 35 mm, a height of 62 mm, and a nominal capacity of 0.65 Ah was assembled.

  The following treatment was applied to the obtained non-aqueous electrolyte secondary battery as an initial charge / discharge step. First, constant current / constant voltage charging was performed for 12 hours at room temperature to 4.2 V at 0.2C. Thereafter, after aging at room temperature for 7 days, the battery was discharged at 1.0 C to 3.0 V, charged at 1.0 C for 30 minutes, and the non-aqueous electrolyte secondary battery having a battery voltage of 3.75 V to 3.90 V 1000 pieces were manufactured. Here, 1C is a current value necessary for discharging the nominal capacity (Ah) in one hour. Therefore, 0.2 C is a current value necessary for discharging the nominal capacity (Ah) in 5 hours.

  Subsequently, the voltage between the positive electrode terminal and the aluminum foil of the laminate film constituting the exterior film of the nonaqueous electrolyte secondary battery was measured by the method shown in FIGS.

  First, one measurement terminal 21 having a lower end with a flange on the heat seal portion 12b on the same surface as the surface of the exterior film 7 from which the positive and negative terminals 5 and 6 of the nonaqueous electrolyte secondary battery are led out and auxiliary measurement As shown in FIGS. 3 and 4, the terminals 22 penetrated through the polyethylene film 11 of the laminate film constituting the exterior film 7 and were brought into contact with the metal layer 10 made of aluminum. The resistance between the measurement terminals 21 and 22 is measured with an ohmmeter, and the measurement terminal 21 is electrically connected to the auxiliary measurement terminal 22 through the metal layer 10 made of aluminum of the laminate film, that is, the measurement terminal 21. Was in contact with the metal layer 10. Next, as shown in FIG. 3, the other measurement terminal 23 having a disk portion at the lower end that forms a pair with the measurement terminal 21 is brought into contact with the positive electrode terminal 5, and the other measurement terminal 23 and one measurement terminal 21 are brought into contact with each other. Was measured with a voltmeter having an internal impedance of 1 G ohm.

  When the inspection method was performed on 1000 secondary batteries manufactured, 990 out of 1000 secondary batteries were in a voltage range of 0.2 V to 3.1 V, and were selected as non-defective products. Ten batteries out of the voltage range were excluded as defective products.

  After 990 secondary batteries determined as non-defective products were stored at room temperature for 3 months, voltage, internal impedance, and appearance were examined, but no abnormality was found.

(Example 2)
About 1000 non-aqueous electrolyte secondary batteries manufactured by the same method as in Example 1, as shown in FIG. 5, one measurement terminal 21 and auxiliary measurement terminal 22 were raised vertically to the outer film 7. The polyethylene film 11 of the two heat seal parts 12a and 12c was penetrated and contacted with the metal layer 10 made of aluminum. The resistance between the measurement terminals 21 and 22 is measured with an ohmmeter, and the measurement terminal 21 is electrically connected to the auxiliary measurement terminal 22 through the metal layer 10 made of aluminum, that is, the measurement terminal 21 is the metal. The contact with the layer 10 was confirmed. Subsequently, the other measurement terminal 23 having a disk portion at the lower end which is paired with the measurement terminal 21 is brought into contact with the positive electrode terminal 5, and the voltage between the other measurement terminal 23 and one measurement terminal 21 is internally changed. Measured with a voltmeter having an impedance of 1 Gohm. According to this measurement, 989 out of 1000 secondary batteries were within the voltage range of 0.2V to 3.1V, and were selected as non-defective products, and 11 batteries out of the voltage range were excluded as defective products.

  989 secondary batteries judged as good were stored at room temperature for 3 months, and then the voltage, internal impedance, and appearance were examined.

(Comparative Example 1)
For 1000 non-aqueous electrolyte secondary batteries manufactured by the same method as in Example 1, the voltage test between the positive electrode terminal and the metal layer made of aluminum of the laminate film constituting the exterior film was not performed at room temperature. After storage for 3 months, voltage, internal impedance, and appearance inspection were performed. As a result, voltage drop, internal impedance increase, and swelling were observed in 9 out of 1000 batteries.

As is clear from the results of Examples 1 and 2 and Comparative Example 1 above, the non-aqueous electrolyte secondary having high reliability over a long period of time that does not cause problems such as swelling during use by using the inspection method of the present invention. Batteries can be appropriately selected as non-defective products.
In addition, this invention is not limited to the Example mentioned above, It can apply similarly in the combination of another kind of positive electrode, negative electrode, separator, and electrolyte.

The perspective view which shows the thin lithium ion secondary battery which is an example of the nonaqueous electrolyte secondary battery concerning this invention. Sectional drawing which follows the II-II line | wire of the thin lithium ion secondary battery of FIG. FIG. 3 is a perspective view showing an inspection method for the thin lithium ion secondary battery of FIG. Sectional drawing which shows the contact state of the measurement terminal and the aluminum of a laminate film at the time of the test | inspection of FIG. FIG. 6 is a perspective view showing an inspection method of the thin lithium ion secondary battery of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrode group, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 5 ... Positive electrode terminal, 6 ... Negative electrode terminal, 7 ... Exterior film, 9 ... Heat-fusion resin film, 10 ... Metal layer, 11 ... Synthetic resin film , 12a, 12b, 12c ... heat seal portions, 21, 23 ... measuring terminals, 22 ... auxiliary measuring terminals.

Claims (5)

At least heat-sealable resin layer, metal layer made of aluminum or aluminum alloy, and synthetic resin layer are laminated in this order to form a bag, heat-sealing the heat-sealable resin layers at the periphery of the opening An exterior member in which a seal portion is formed; a positive electrode housed in the exterior member; an electrode group having a negative electrode and a separator; and a nonaqueous electrolyte; a positive electrode terminal that is led out from the exterior member and connected to the positive electrode; A negative terminal connected to the negative electrode,
The positive electrode and the positive electrode terminal have a potential of 3.90 V to 4.05 V with respect to metallic lithium,
And Upon the voltage to inspect the non-aqueous electrolyte secondary battery of 3.75V～3.90V,
Measuring the voltage between the positive electrode terminal and the metal layer located at the heat seal portion of the exterior member with respect to the assembled non-aqueous electrolyte secondary battery with a voltmeter having an input impedance of 1 G ohm or more; A method for inspecting a non-aqueous electrolyte secondary battery, wherein a battery in a voltage range of 2 V to 3.1 V is determined as a non- defective product . When measuring the voltage between the positive electrode terminal and the metal layer of the exterior member, one measurement terminal tip of the pair of measurement terminals is brought into contact with the positive electrode terminal, and the other measurement terminal tip is connected to the positive electrode terminal. The method for inspecting a non-aqueous electrolyte secondary battery according to claim 1, wherein the synthetic resin layer positioned at the seal portion of the exterior member is penetrated and brought into contact with the metal layer. Before measuring the voltage between the positive electrode terminal and the metal layer of the exterior member with the pair of measurement terminals, the tip of the auxiliary measurement terminal penetrates the synthetic resin layer positioned at the seal portion of the exterior member The metal layer is pierced, and the resistance between the other measurement terminal and the auxiliary measurement terminal is measured to confirm conduction between the other measurement terminal and the metal layer. The inspection method of the nonaqueous electrolyte secondary battery as described. The seal portion of the exterior member is folded so as to be in contact with two side surfaces adjacent to the side surface from which the positive electrode terminal and the negative electrode terminal are led out, and the other measurement terminal and the auxiliary measurement terminal are sealed. 4. The method for inspecting a non-aqueous electrolyte secondary battery according to claim 3, wherein the metal resin layer is pierced through each of the synthetic resin layers. At least heat-sealable resin layer, metal layer made of aluminum or aluminum alloy, and synthetic resin layer are laminated in this order to form a bag, heat-sealing the heat-sealable resin layers at the periphery of the opening An exterior member in which a seal portion is formed; a positive electrode housed in the exterior member; an electrode group having a negative electrode and a separator; and a non-aqueous electrolyte; a positive electrode terminal led out from the exterior member and connected to the positive electrode; A negative terminal connected to the negative electrode,
The positive electrode and the positive electrode terminal have a potential of 3.90 V to 4.05 V with respect to metallic lithium,
In manufacturing a nonaqueous electrolyte secondary battery having a voltage of 3.75V to 3.90V,
After assembly, the voltage between the positive electrode terminal and the metal layer located at the heat seal portion of the exterior member is measured with a voltmeter having an input impedance of 1 G ohm or more, and the voltage is 0.2V to 3.1.
A method for producing a non-aqueous electrolyte secondary battery, wherein V is selected as a non-defective product.

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