JP2019145330A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a non-aqueous electrolyte secondary battery that is excellent in safety even when subjected to external pressure.SOLUTION: A non-aqueous electrolyte secondary battery is a wound body in which an electrode body group including a positive electrode, a negative electrode, and a separator is wound such that the separator is positioned between the positive electrode and the negative electrode, and the electrode body group has a portion that does not have the positive electrode and the negative electrode in an outermost peripheral portion that forms an outermost periphery of the wound body, and the wound body has an outermost periphery area including a separator when seen from an axial direction.SELECTED DRAWING: Figure 3

Description

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

  Nonaqueous electrolyte secondary batteries are also widely used as power sources for mobile devices such as mobile phones and notebook computers, and hybrid cars. With the development of these fields, it is required to improve various performances of nonaqueous electrolyte secondary batteries.

  One of the performances is safety. A non-aqueous electrolyte secondary battery generates abnormal heat when an internal short circuit occurs. Abnormal heat generation of the non-aqueous electrolyte secondary battery can cause failure of other elements.

  Patent Document 1 describes that in a wound body constituting a power generation unit of a nonaqueous electrolyte secondary battery, a region where no active material is applied is provided on the outermost or innermost circumference at least once. . When the internal short circuit occurs, the metal foils are in direct contact with each other, so that the temperature of the nonaqueous electrolyte secondary battery is prevented from rising abnormally.

JP-A-8-153542

  However, with the recent increase in energy density of the positive electrode active material layer, abnormal heat generation may not be sufficiently suppressed in a state where the charging depth is high.

  The present invention has been made in view of the above problems, and an object thereof is to provide a nonaqueous electrolyte secondary battery that is excellent in safety even when subjected to external pressure.

If the outermost periphery of the wound body is an insulating separator, the surface of the nail is covered with the insulating separator even when a metal material such as a nail is stuck in the non-aqueous electrolyte secondary battery. It was found that abnormal heat generation due to a short circuit can be suppressed.
That is, in order to solve the above problems, the following means are provided.

(1) In the nonaqueous electrolyte secondary battery according to the first aspect, an electrode body group including a positive electrode, a negative electrode, and a separator is wound so that the separator is positioned between the positive electrode and the negative electrode. The wound body, wherein the electrode body group has a portion that does not include the positive electrode and the negative electrode at an outermost peripheral portion that forms an outermost periphery of the wound body, and the wound body is viewed from an axial direction. The outermost peripheral region made of a separator.

(2) In the non-aqueous electrolyte secondary battery according to the above aspect, the positive electrode includes a positive electrode current collector and a positive electrode active material layer applied to at least one surface of the positive electrode current collector, and the negative electrode includes: A negative electrode current collector and a negative electrode active material layer applied to at least one surface of the negative electrode current collector, and the electrode body group is arranged on an outer peripheral part on a winding center side from the outermost peripheral part of the wound body, The winding body has a portion not having the positive electrode active material layer and the negative electrode active material layer, and the winding body has a positive electrode current collector and a negative electrode current collector inside the outermost peripheral region when viewed from the axial direction. You may have the outer periphery area | region which consists of a body and a separator.

(3) The non-aqueous electrolyte secondary battery according to the above aspect further includes an exterior body that covers the wound body, and an adhesive portion that includes an adhesive substance between the wound body and the exterior body. May be provided.

(4) In the electrode body group of the nonaqueous electrolyte secondary battery according to the above aspect, the separator that forms the outermost periphery and the separator that forms another part may be separate members.

(5) In the non-aqueous electrolyte secondary battery according to the above aspect, the thickness of the separator that forms the outermost peripheral portion may be greater than the thickness of the separator that forms the other portion.

  The non-aqueous electrolyte secondary battery according to the above aspect is excellent in safety even when subjected to external pressure.

It is a schematic diagram of the non-aqueous electrolyte secondary battery according to the present embodiment. It is the figure which expand | deployed the winding body in the nonaqueous electrolyte secondary battery concerning this embodiment. It is a cross-sectional schematic diagram of the non-aqueous electrolyte secondary battery according to the present embodiment. It is a schematic diagram for demonstrating the nonaqueous electrolyte secondary battery in an Example and a comparative example.

  Hereinafter, the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, there are cases where the characteristic parts are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. is there. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately modified and implemented without departing from the scope of the invention.

[Nonaqueous electrolyte secondary battery]
FIG. 1 is a schematic diagram of a non-aqueous electrolyte secondary battery according to this embodiment. A nonaqueous electrolyte secondary battery 100 shown in FIG. 1 includes a wound body 10 and an exterior body 20. The wound body 10 is accommodated in an accommodation space K provided in the exterior body 20. In FIG. 1, for easy understanding, a state immediately before the wound body 10 is accommodated in the exterior body 20 is illustrated.

(Turned body)
FIG. 2 is a developed view of the wound body 10 in the nonaqueous electrolyte secondary battery according to the present embodiment. FIG. 2 shows an enlarged end on the side that becomes the outer periphery when wound. The wound body 10 is produced by winding the electrode body group 5 shown in FIG. The electrode body group 5 has an outermost peripheral portion R1 that forms the last round after winding, an outer peripheral portion R2 that is inside thereof, and a central portion R3 that stores electricity. The center of the wound body 10 is approached in the order of the central portion R3, the outer peripheral portion R2, and the outermost peripheral portion R1.

  The electrode body group 5 includes a positive electrode 1, a negative electrode 2, and a separator 3. The separator 3 is located between the positive electrode 1 and the negative electrode 2 when the electrode body group 5 is wound. The positive electrode 1 has a plate-like (film-like) positive electrode current collector 1A and a positive electrode active material layer 1B. The positive electrode active material layer 1B is formed on at least one surface of the positive electrode current collector 1A. The negative electrode 2 has a plate-like (film-like) negative electrode current collector 2A and a negative electrode active material layer 2B. The negative electrode active material layer 2B is formed on at least one surface of the negative electrode current collector 2A.

  The electrode body group 5 is formed by laminating a positive electrode 1, a negative electrode 2 and a separator 3 extending in one direction. The positive electrode 1 and the negative electrode 2 do not extend to the outermost peripheral portion R1 of the electrode group 5. That is, the outermost peripheral portion R1 is made of the separator 3. Further, the positive electrode active material layer 1B and the negative electrode active material layer 2B are not formed on the outer peripheral portion R2 of the electrode body group 5. That is, the outer peripheral portion R2 is composed of the positive electrode current collector 1A, the negative electrode current collector 1B, and the separator 3. A central portion R3 of the electrode group 5 includes a positive electrode 1, a negative electrode 2, and a separator 3. The central portion R3 generates power.

  FIG. 3 is a schematic cross-sectional view of the nonaqueous electrolyte secondary battery according to this embodiment. As shown in FIG. 3, when the wound body 10 is viewed from the axial direction of the winding, the outermost peripheral area A <b> 1 is composed of the separator 3. The outermost peripheral region A1 corresponds to the outermost peripheral portion R1 in the electrode body group 5. The outermost peripheral region A1 is a portion that is located on the outer periphery of the wound body 10 and in which only the separator 3 is wound. The outermost peripheral area A1 is preferably an area of at least one round from the outer circumference of the wound body 10, and more preferably an area of at least two rounds from the outer circumference. On the other hand, from the viewpoint of heat dissipation, the outermost peripheral area A1 is preferably an area within 3 laps from at least the outer circumference of the wound body 10, and more preferably an area within 2 laps.

  When a metal body such as a nail is stuck in the wound body 10, first, it is stuck in the separator 3 in the outermost peripheral area A1. At that time, the separator 3 is attached to a metal body such as a nail. Since the separator 3 has an insulating property, even when a metal body such as a nail is stuck, an internal short circuit is suppressed.

  3 has an outer peripheral area A2 on the inner side of the outermost peripheral area A1 when viewed from the axial direction. The outer peripheral area A <b> 2 corresponds to the outer peripheral part R <b> 2 in the electrode body group 5. The outer peripheral region A2 is located on the outer periphery of the wound body 10 and is a portion where the positive electrode current collector 1A, the negative electrode current collector 2A, and the separator 3 are wound.

  The positive electrode current collector 1A and the negative electrode current collector 2A are metal foils and are excellent in heat dissipation. Therefore, heat generation of the wound body 10 can be suppressed by providing the outer peripheral region A2. Moreover, even when a metal body such as a nail is stuck in the outer peripheral region A2 and short-circuited, the abnormal heat generation of the wound body 10 can be suppressed by short-circuiting the low-resistance metal foils. The outer peripheral area A1 is preferably an area of one or more rounds from the outermost peripheral area R1 of the wound body 10. On the other hand, in order to prevent the winding body 10 from increasing in size, the outer peripheral area A1 is preferably an area within three laps from the outermost peripheral area R1, and more preferably an area within two laps.

  Further, the wound body 10 shown in FIG. 3 has a center region A3 at the center when viewed from the axial direction. The center region A3 corresponds to the center portion R3 in the electrode body group 5. The center region A3 is a region in which the positive electrode active material layer 1A and the negative electrode active material layer 2A are disposed to face each other with the separator 3 interposed therebetween. As ions are conducted between the positive electrode active material layer 1A and the negative electrode active material layer 2A, electricity is stored in the central region A3.

  The positive electrode current collector 1A may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used. Further, it is preferable to form an insulating coating film such as aluminum oxide on the surface of the positive electrode current collector 1A. The thickness of the coating film is preferably 50 μm or less. When the coating film is formed, the internal short circuit can be further suppressed. In addition, although a coating film reduces the electroconductivity of 1 A of positive electrode collectors a little, it does not affect the whole.

  The positive electrode active material used for the positive electrode active material layer 1B can reversibly advance ion storage and release, ion desorption and insertion (intercalation), or ion and counteranion doping and dedoping. Any electrode active material can be used. As the ions, for example, lithium ions, sodium ions, magnesium ions and the like can be used, and it is particularly preferable to use lithium ions.

For example, in the case of a lithium ion secondary battery, lithium cobalt oxide (LiCoO _2), lithium nickelate (LiNiO _2), lithium manganate (LiMnO _2), lithium manganese spinel (LiMn ₂ O _4), and the general formula: LiNi _x Co _y Mn _z M _a O ₂ (x + y + z + a = 1, 0 ≦ x <1, 0 ≦ y <1, 0 ≦ z <1, 0 ≦ a <1, M is Al, Mg, Nb, Ti, Cu, Zn , One or more elements selected from Cr), lithium vanadium compound (LiV ₂ O ₅ ), olivine-type LiMPO ₄ (where M is Co, Ni, Mn, Fe, Mg, One or more elements selected from Nb, Ti, Al, and Zr, or VO), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), LiNi _x Co _y Al _z A composite metal oxide such as O ₂ (0.9 <x + y + z <1.1), polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene, or the like can be used as the positive electrode active material.

  The positive electrode active material layer 1B may have a conductive material. Examples of the conductive material include carbon powder such as carbon black, carbon nanotube, carbon material, fine metal powder such as copper, nickel, stainless steel and iron, a mixture of carbon material and fine metal powder, and conductive oxide such as ITO. It is done. In the case where sufficient conductivity can be ensured with only the positive electrode active material, the positive electrode active material layer 1B may not include a conductive material.

  The positive electrode active material layer 1B contains a binder. A well-known thing can be used for a binder. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoro Fluorine resins such as ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and polyvinyl fluoride (PVF).

  In addition to the above, as the binder, for example, vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based) Fluororubber), vinylidene fluoride-pentafluoropropylene-based fluororubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride Ride-perfluoromethyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF-CTFE-based fluorine rubber) may be used vinylidene fluoride-based fluorine rubbers such.

The negative electrode active material used for the negative electrode active material layer 2B may be a compound that can occlude / release ions, and a negative electrode active material used for a known nonaqueous electrolyte secondary battery can be used. Examples of the negative electrode active material include alkali or alkaline earth metals such as lithium metal, graphite capable of occluding and releasing ions (natural graphite, artificial graphite), carbon nanotube, non-graphitizable carbon, graphitizable carbon, low temperature Carbon materials such as calcined carbon, metals that can be combined with metals such as lithium such as aluminum, silicon, and tin, amorphous materials mainly composed of oxides such as SiO _x (0 <x <2) and tin dioxide Examples thereof include particles containing a compound, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), and the like.

  The same thing as the positive electrode 1 can be used for 2 A of negative electrode collectors, a electrically conductive material, and a binder. The binder used for the negative electrode may be, for example, cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, acrylic resin, etc. in addition to those listed for the positive electrode.

  Each of the positive electrode 1 and the negative electrode 2 is provided with a positive electrode terminal 12 and a negative electrode terminal 14 for electrical connection with the outside (see FIG. 1). The positive electrode terminal 12 and the negative electrode terminal 14 are made of a conductive material such as aluminum, nickel, or copper. The positive terminal 12 is connected to the positive electrode 1, and the negative terminal 14 is connected to the negative electrode 2. The connection method may be welding or screwing. The positive terminal 12 and the negative terminal 14 are preferably protected with an insulating tape in order to prevent a short circuit.

  The separator 3 only needs to be formed of an electrically insulating porous structure. For example, a single layer of a film made of polyolefin such as polyethylene or polypropylene, a stretched film of a laminate or a mixture of the above resins, or cellulose or polyester , A fiber nonwoven fabric made of at least one constituent material selected from the group consisting of polyacrylonitrile, polyamide, polyethylene and polypropylene.

  The separator 3 does not need to be the same member from the winding center to the outer periphery. For example, the separator that forms the outermost peripheral portion R1 and the separator that forms other portions may be separate members. The outermost peripheral portion R1 forms the outermost peripheral region A1 of the wound body 10, and the separator 3 in this portion is intended to prevent a short circuit. On the other hand, the separator 3 forming another part (for example, the central region A3) is intended to electrically separate the positive electrode 1 and the negative electrode 2. By making the separator that forms the outermost peripheral portion R1 and the separator that forms the other portion as separate members, a material suitable for the purpose can be selected.

  The thickness of the separator that forms the outermost periphery is preferably thicker than the thickness of the separator that forms the other part. The thickness of the separator 3 in the central region A3 responsible for power generation is preferably 5 μm or more and 40 μm or less, more preferably 10 μm or more and 25 μm or less, and even more preferably 10 μm. On the other hand, the thickness of the separator 3 in the outermost peripheral region A1 for preventing a short circuit is preferably 5 μm or more and 40 μm or less, and more preferably 15 μm or more and 25 μm or less.

(Nonaqueous electrolyte)
As the non-aqueous electrolyte, an electrolyte solution (an electrolyte aqueous solution or an electrolyte solution using an organic solvent) containing a lithium salt or the like can be used. However, since the electrolytic aqueous solution has a low decomposition voltage electrochemically, the withstand voltage during charging is limited to be low. Therefore, an electrolyte solution (nonaqueous electrolyte solution) using an organic solvent is preferable.

  The nonaqueous electrolytic solution has an electrolyte dissolved in a nonaqueous solvent, and may contain a cyclic carbonate and a chain carbonate as a nonaqueous solvent.

  As cyclic carbonate, what can solvate electrolyte can be used. For example, ethylene carbonate, propylene carbonate, butylene carbonate, and the like can be used. The cyclic carbonate preferably contains at least propylene carbonate.

  The chain carbonate can reduce the viscosity of the cyclic carbonate. Examples thereof include diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. In addition, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane and the like may be used in combination.

  The ratio of the cyclic carbonate and the chain carbonate in the non-aqueous solvent is preferably 1: 9 to 1: 1 by volume.

As the electrolyte, a metal salt can be used. For example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (CF ₃ CF ₂ CO) ₂ , lithium salts such as LiBOB can be used. In addition, these lithium salts may be used individually by 1 type, and may use 2 or more types together. In particular, from the viewpoint of the degree of ionization, it is preferable to include LiPF ₆ as the electrolyte.

When LiPF ₆ is dissolved in a non-aqueous solvent, the concentration of the electrolyte in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L. When the concentration of the electrolyte is 0.5 mol / L or more, the lithium ion concentration of the nonaqueous electrolytic solution can be sufficiently secured, and a sufficient capacity can be easily obtained during charging and discharging. Moreover, by suppressing the electrolyte concentration to within 2.0 mol / L, it is possible to suppress an increase in the viscosity of the non-aqueous electrolyte, to sufficiently secure the mobility of lithium ions, and to obtain a sufficient capacity during charging and discharging. It becomes easy.

Even when LiPF ₆ is mixed with another electrolyte, the lithium ion concentration in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L, and the lithium ion concentration from LiPF ₆ is 50 mol%. More preferably, it is contained.

(Exterior body)
The exterior body 20 seals the wound body 10 and the electrolytic solution therein. The exterior body 20 is not particularly limited as long as it can prevent leakage of the electrolytic solution to the outside and entry of moisture and the like into the nonaqueous electrolyte secondary battery 100 from the outside.

  For example, a metal laminate film in which a metal foil is coated with a polymer film from both sides can be used as the exterior body 20. For example, an aluminum foil can be used as the metal foil, and a film such as polypropylene can be used as the polymer film. For example, the material of the outer polymer film is preferably a polymer having a high melting point, such as polyethylene terephthalate (PET) or polyamide, and the material of the inner polymer film is polyethylene (PE) or polypropylene (PP). preferable.

  It is preferable to provide the adhesive part 30 containing an adhesive substance between the exterior body 20 and the wound body 10. The adhesive part 30 can be a double-sided tape with electrolyte resistance. For example, a material in which a polyisobutylene rubber adhesive layer is formed on a polypropylene substrate, rubber such as butyl rubber, saturated hydrocarbon resin, or the like can be used. Even when a metal body such as a nail is stabbed, the adhesive substance is attached to the metal body such as a nail and suppresses a short circuit.

[Method for producing non-aqueous electrolyte secondary battery]
First, the positive electrode 1 and the negative electrode 2 are produced. The positive electrode 1 and the negative electrode 2 are different from each other only in a substance that becomes an active material, and can be manufactured by the same manufacturing method.

  A positive electrode active material, a binder, and a solvent are mixed to prepare a paint. A conductive material may be further added as necessary. As the solvent, for example, water, N-methyl-2-pyrrolidone, N, N-dimethylformamide or the like can be used. The constituent ratio of the positive electrode active material, the conductive material, and the binder is preferably 80 wt% to 90 wt%: 0.1 wt% to 10 wt%: 0.1 wt% to 10 wt% in mass ratio. These mass ratios are adjusted so as to be 100 wt% as a whole.

  The mixing method of these components constituting the paint is not particularly limited, and the mixing order is not particularly limited. The paint is applied to the positive electrode current collector 1A. There is no restriction | limiting in particular as an application | coating method, The method employ | adopted when producing an electrode normally can be used. Examples thereof include a slit die coating method and a doctor blade method. Similarly, for the negative electrode, a paint is applied on the negative electrode current collector 2A.

  Subsequently, the solvent in the paint applied on the positive electrode current collector 1A and the negative electrode current collector 2A is removed. The removal method is not particularly limited. For example, the positive electrode current collector 1A and the negative electrode current collector 2A to which the paint is applied may be dried in an atmosphere of 80 ° C. to 150 ° C. Then, the positive electrode 1 and the negative electrode 2 are completed.

  Next, the separator 3 is disposed between the produced positive electrode 1 and the negative electrode 2 and in a portion that becomes the outside when it is rolled. Then, the positive electrode 1, the negative electrode 2, and the separator 3 are wound around one end side as an axis.

  Finally, the wound body 10 is enclosed in the exterior body 20. The nonaqueous electrolytic solution is injected into the outer package 20. The wound body 10 is impregnated with the nonaqueous electrolytic solution by performing decompression, heating, or the like after the nonaqueous electrolytic solution is injected. The exterior body 20 is sealed by applying heat or the like.

  As described above, in the non-aqueous electrolyte secondary battery 100 according to the present embodiment, the outermost peripheral area A1 of the wound body 10 is composed only of the separator 3. For this reason, even when a metal body such as a nail is inserted, the short circuit of the nonaqueous electrolyte secondary battery 100 can be suppressed by the insulating separator 3 being attached to the surface of the metal body.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the configurations and combinations of the embodiments in the embodiments are examples, and the addition and omission of configurations are within the scope not departing from the gist of the present invention. , Substitutions, and other changes are possible.

  For example, the nonaqueous electrolyte secondary battery 100 may not have the outer peripheral region A2. Even in the outermost peripheral area A1 alone, the effect of suppressing the short circuit is exhibited.

"Example 1"
(Preparation of positive electrode)
Lithium cobaltate (LiCoO ₂ ) was used as the positive electrode active material. 1.90 parts by mass of this positive electrode active material, 5 parts by mass of acetylene black, and 5 parts by mass of polyvinylidene fluoride (PVDF) were dispersed in N-methyl-2-pyrrolidone (NMP), and the slurry was dispersed. Prepared. The obtained slurry was applied on both sides of an aluminum foil having a thickness of 20 μm. The coating amount is 0.325 g / 1540.25 mm ² . Then, it dried for 30 minutes at the temperature of 140 degreeC.

  Next, a roll of a positive electrode was obtained by a press treatment using a roll press apparatus at a linear pressure of 1000 kgf / cm. And the positive electrode 1 which has a 10 mm square tab welding location on one end side from the roll of the positive electrode was cut out. The positive electrode 1 had a length of 802 mm and a width of 77 mm (FIG. 4A). And the positive electrode active material (coating film) was scraped off from the tab welding location of the positive electrode with a cotton swab soaked with methyl ethyl ketone (MEK).

(Preparation of negative electrode)
A slurry was prepared by dispersing 90 parts by mass of natural graphite powder (negative electrode active material) and 10 parts by mass of PVDF in NMP. The obtained slurry was applied onto a copper foil having a thickness of 15 μm, and one surface of the copper foil was applied at an application amount of 0.162 g / 1540.25 mm ² . Thereafter, it was dried under reduced pressure at a temperature of 140 ° C. for 30 minutes.

  Subsequently, the negative electrode roll was obtained by pressing using a roll press apparatus. A negative electrode 2 having a 10 mm square tab weld on one end side was cut out from the negative electrode roll. The negative electrode 2 had a length of 954 mm and a width of 79 mm (FIG. 4B). And the negative electrode active material (coating film) was scraped off with the cotton swab impregnated with MEK from the tab welding location of the negative electrode, and the negative electrode was obtained.

(Preparation of separator)
A polyethylene microporous membrane having a thickness of 20 μm (porosity: 40%, shutdown temperature: 134 ° C.) was prepared. This separator was cut into a length of 1100 mm and a width of 80 mm.

(Preparation of wound body)
Two separators 3 were prepared and aligned. And between these, the negative electrode 2 was piled up so that the end of the negative electrode 2 might come 5 mm from the front-end | tip of the separator 3. FIG. Further, the positive electrode 1 was overlapped so that one end of the positive electrode 1 was 5 mm from one end of the negative electrode 2 (FIG. 4C). That is, the outermost peripheral part which consists of only the separator 3 with a width of 141 mm was formed at one end on the outermost side of the wound body.

  These were wound around a SUS plate 4 having a width of 67 mm and a thickness of 2 mm to obtain a wound body. The outermost peripheral edge of the separator was fixed with tape. The separator 3 is further wound around the end of the negative electrode 2 by one turn. Finally, a lead was attached to the tab portion by ultrasonic welding to produce a wound body. The lead used Al for the positive electrode and Ni for the negative electrode.

(Nonaqueous electrolyte)
A non-aqueous electrolyte solution in which LiPF ₆ was dissolved at 1.0 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was prepared as an electrolyte. The volume ratio of EC to DEC in the mixed solvent was EC: DEC = 30: 70.

(Production of battery)
The wound body was encapsulated in an aluminum laminate together with a non-aqueous electrolyte to produce a battery cell of Example 1.

(Measurement of battery surface temperature)
The produced battery cell of Example 1 was charged to a charge end voltage of 4.3 V (vs. Li ^/ Li ⁺ ) at a constant current density of 0.1 C. Further, a constant voltage of 4.3 V (vs. Li ^/ Li ⁺ ) was maintained, and constant voltage charging was performed until the current value decreased to a current density of 0.05C. The current density was measured with 1C as 158 mA / g. And the reached temperature of the surface of a battery was measured.

(Nail penetration test)
A nail with a diameter of 2.5 mm was inserted into the charged battery at a speed of 150 mm / s, and a nail penetration test was performed. The test was performed on 5 cells and visually evaluated.

  The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Example 2"
Example 2 was the same as Example 1 except that the positive electrode active material was LiNi _0.83 Co _0.12 Al _0.05 O ₂ . The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Example 3"
Example 3 was the same as Example 1 except that the positive electrode active material was LiNi _0.6 Co _0.2 Al _0.2 O ₂ . The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

Example 4
An uncoated portion of the positive electrode active material is provided at a length of 280 mm from the terminal portion when the positive electrode is wound, and an uncoated portion of the negative electrode active material is formed at a length of 140 mm from the terminal portion when the negative electrode is wound. Example 1 was performed except that the length of the separator was 1240 mm. When the length of the electrode was uneven, it was cut and adjusted. The wound body has a region where the positive electrode to which the active material is not applied is wound twice as an outer peripheral region and a region where the negative electrode is wound once, and a region where the separator is wound once as an outermost peripheral region. The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Example 5"
Example 2 was the same as Example 1 except that an adhesive layer was provided between the wound body and the exterior body. The adhesive layer was larger than the area of the electricity storage element. An acrylic resin was used for the adhesive layer. The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Example 6"
Example 6 was the same as Example 5, except that the positive electrode active material was LiNi _0.83 Co _0.12 Al _0.05 O ₂ . The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Example 7"
Example 7 was the same as Example 5 except that the positive electrode active material was changed to LiNi _0.6 Co _0.2 Al _0.2 O ₂ . The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Example 8"
Example 8 was the same as Example 4 except that an adhesive layer was provided between the wound body and the exterior body. The adhesive layer was larger than the area of the electricity storage element. An acrylic resin was used for the adhesive layer. The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Comparative Example 1"
Example 1 was repeated except that the length of the separator was 810 mm. The outermost periphery of the wound body of Comparative Example 1 was a negative electrode. The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

"Comparative Example 2"
Comparative Example 2 was the same as Comparative Example 1 except that the positive electrode active material was LiNi _0.83 Co _0.12 Al _0.05 O ₂ . The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

“Comparative Example 3”
Comparative Example 3 was the same as Comparative Example 1 except that the positive electrode active material was LiNi _0.6 Co _0.2 Al _0.2 O ₂ . The essential points of the specific configuration of the wound body are summarized in Table 1, and the surface temperature of the battery and the results of the nail pointing test are summarized in Table 2.

DESCRIPTION OF SYMBOLS 1 Positive electrode 1A Positive electrode collector 1B Positive electrode active material layer 2 Negative electrode 2A Negative electrode collector 2B Negative electrode active material layer 3 Separator 5 Electrode body group 10 Winding body 12 Positive electrode terminal 14 Negative electrode terminal 20 Exterior body 30 Adhesive part 100 Nonaqueous electrolysis Liquid secondary battery K accommodation space R1 outermost peripheral part R2 outer peripheral part R3 central part A1 outermost peripheral area A2 outer peripheral area A3 central area

Claims (5)

A wound body in which an electrode body group including a positive electrode, a negative electrode, and a separator is wound so that a separator is positioned between the positive electrode and the negative electrode,
The electrode body group has a portion that does not have the positive electrode and the negative electrode in the outermost peripheral portion forming the outermost periphery of the wound body,
The winding body is a non-aqueous electrolyte secondary battery having an outermost peripheral region made of a separator when viewed from the axial direction. The positive electrode has a positive electrode current collector and a positive electrode active material layer applied to at least one surface of the positive electrode current collector,
The negative electrode has a negative electrode current collector and a negative electrode active material layer applied to at least one surface of the negative electrode current collector,
The electrode body group has a portion that does not have the positive electrode active material layer and the negative electrode active material layer in the outer peripheral portion on the winding center side from the outermost peripheral portion of the wound body,
The non-aqueous electrolysis according to claim 1, wherein the wound body has an outer peripheral region including a positive electrode current collector, a negative electrode current collector, and a separator inside the outermost peripheral region when viewed from the axial direction. Liquid secondary battery. An exterior body that covers the wound body;
The nonaqueous electrolyte secondary battery according to claim 1, further comprising an adhesive portion including an adhesive substance between the wound body and the exterior body.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein in the electrode body group, the separator that forms the outermost peripheral portion and the separator that forms another portion are separate members.   The nonaqueous electrolyte secondary battery according to claim 4, wherein a thickness of the separator that forms the outermost peripheral portion is greater than a thickness of the separator that forms the other portion.

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