JPWO2013151094A1 - Lithium ion battery - Google Patents

Abstract

Provided is a lithium ion battery having improved safety without deteriorating capacity characteristics and life characteristics. A positive electrode plate 1 containing a positive electrode active material and a negative electrode plate 3 containing a negative electrode active material constitute an electrode group 7 arranged via a separator 5. The electrode group 7 is housed in the battery can 11 in a state of being wound around the shaft core 9. A flame retardant is contained or applied to one or both of the shaft core 9 and the battery can 11.

Description

  The present invention relates to a lithium ion battery configured by winding an electrode group in which a positive electrode plate and a negative electrode plate are arranged via a separator.

  In the lithium ion battery, a flammable non-aqueous electrolyte is used to increase the energy density. Therefore, when a lithium ion battery is placed in a high temperature environment or abnormally generates heat due to thermal runaway, there is a problem that the battery ignites or smokes, or the battery expands or ruptures due to an increase in battery internal pressure. In response to these problems, the safety of batteries has conventionally been improved by making lithium ion batteries flame-retardant. For example, Japanese Patent Laying-Open No. 2006-286571 (Patent Document 1) discloses a technique for adding a flame retardant to a nonaqueous electrolytic solution. Japanese Patent Laid-Open No. 5-151971 (Patent Document 2) discloses a technique for forming a positive electrode plate of a lithium ion battery by adding a flame retardant to a positive electrode mixture. Japanese Patent Laid-Open No. 2000-173619 (Patent Document 3) discloses a technique for forming a separator of a lithium ion battery using a porous film containing a flame retardant.

JP 2006-286571 A JP-A-5-151971 JP 2000-173619 A

  However, in the technique of Patent Document 1, since a flame retardant is added to the nonaqueous electrolytic solution, a side reaction may be induced during the charge / discharge reaction, which may reduce the battery life. Further, in the techniques of Patent Documents 2 and 3, the flame retardant contained in the electrode plate or the separator may inhibit the ion permeability and the charge / discharge capacity of the battery may be reduced.

  An object of the present invention is to provide a lithium ion battery capable of ensuring safety without deteriorating capacity characteristics and life characteristics.

  The lithium ion battery to be improved by the present invention includes an electrode group, a shaft core, and a battery can. The electrode group is configured by arranging a positive electrode plate containing a positive electrode active material and a negative electrode plate containing a negative electrode active material via a separator. An electrode group is wound around the shaft core. The battery can accommodates an electrode group wound around the shaft core. In the lithium ion battery of the present invention, a flame retardant is contained or applied to one or both of the shaft core and the battery can. That is, the target containing or applying the flame retardant may be only the shaft core, only the battery can, or both the shaft core and the battery can. In the configuration in which the flame retardant is disposed on either the shaft core or the battery can, since the flame retardant is not added to the non-aqueous electrolyte, side reactions due to flame retardant can be prevented, and the battery life can be reduced. Decline can be prevented. In addition, the flame retardant placed in the shaft core and battery can is present in the battery in a state isolated from any of the positive electrode plate, the negative electrode plate, and the separator, and therefore impedes ion permeability during charging and discharging. Therefore, the charge / discharge characteristics can be prevented from deteriorating. Furthermore, if a flame retardant is placed on both the shaft core and the battery can, the amount of the flame retardant placed in the battery can be increased. Compared with the case where an agent is arranged, it is possible to reliably prevent the deterioration of the life characteristics and charge / discharge characteristics.

  In addition, in a lithium ion battery, since the axial center located in the center part of a battery becomes higher temperature than the battery can located in the outer edge part of a battery, it is preferable to arrange | position a flame retardant to an axial center. . In particular, if a flame retardant is contained in the material forming the shaft core, the flame retardant can be efficiently dissolved in the battery during abnormal heat generation to exhibit a flame retardant function.

  Moreover, when arrange | positioning a flame retardant to a shaft core, you may apply | coat a flame retardant to the surface of a shaft core. Since the flame retardant applied on the surface of the shaft core is easily dissolved in the non-aqueous electrolyte during abnormal heat generation, it can impart high flame retardancy to the battery. In addition, since the flame retardant is simply applied to the surface of the shaft core, the work of making the flame retardant is easy.

  When arrange | positioning a flame retardant in a battery can, you may apply | coat a flame retardant to the inner surface of a battery can. By applying the flame retardant to the inner surface of the battery can, as with the case where the flame retardant is applied to the surface of the shaft core, high flame retardancy can be imparted to the battery, Work is easy.

  As the flame retardant, it is preferable to use a flame retardant that is solid at room temperature and has a melting point of 90 ° C. or higher. A flame retardant with such properties does not dissolve in the battery in the normal state, but starts to dissolve in the event of abnormal heat generation, thus preventing side reactions in the normal state and exhibiting a flame retardant function only during abnormal heat generation. Can do. As such a flame retardant, at least one selected from phosphazene compounds, phosphate ester compounds, and fluorinated alkyl compounds, or a mixture thereof can be used.

1 is an enlarged perspective view of an electrode group and an axial core constituting a lithium ion battery according to an embodiment of the present invention. It is sectional drawing of the principal part of the lithium ion battery which is embodiment of this invention.

  Hereinafter, embodiments of a lithium ion battery according to the present invention will be described in detail with reference to the drawings.

<Preparation of positive electrode plate>
Lithium manganese complex oxide as a positive electrode active material, scaly graphite as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed at a weight ratio of 85: 10: 5. A slurry kneaded with N-methylpyrrolidone (NMP) as a dispersion solvent was applied to both sides of an aluminum foil having a thickness of 20 μm. Then, the positive electrode plate 1 with a thickness of 170 μm was obtained by drying, pressing, and cutting. Note that one side in the longitudinal direction of the aluminum foil was cut out in a rectangular shape, and the remainder of the cutout was used as the positive electrode lead piece 2.

In the present embodiment, lithium manganese double oxide is exemplified as the positive electrode active material, but in addition, the composition formula LiαMn _x M1 _y M2 _z O ₂ (wherein M1 is at least selected from Co and Ni) One type, M2, is at least one type selected from Co, Ni, Al, B, Fe, Mg, Cr, and x + y + z = 1, 0 <α <1.2, 0.2 ≦ x ≦ 0.6, 0.2 ≦ y ≦ 0.4, 0.05 ≦ z ≦ 0.4) may be used. Among them, it is more preferable that M1 is Ni or Co and M2 is Co or Ni. LiMn _1/3 Ni _1/3 Co _1/3 O ₂ is more preferable. When Ni in the composition is increased, the capacity can be increased. Further, when Co is increased, the output at low temperature can be improved. Furthermore, material cost can be suppressed when Mn is increased. The element to be added is effective in stabilizing the cycle characteristics. In addition, the general formula LiM _x PO ₄ (M: Fe or Mn, 0.01 ≦ X ≦ 0.4) or LiMn _1-x M _x PO ₄ (M: a divalent cation other than Mn, 0.01 It is also possible to use an orthorhombic phosphoric acid compound having the symmetry of the space group Pmnb where ≦ X ≦ 0.4).

<Preparation of negative electrode plate>
10 parts by mass of PVDF as a binder was added to 90 parts by mass of amorphous carbon powder as the negative electrode active material. A slurry kneaded with NMP as a dispersion solvent was applied to both sides of an electrolytic copper foil having a thickness of 10 μm. Then, the negative electrode plate 3 with a thickness of 130 μm was obtained by performing dry pressing and cutting. Note that one side in the longitudinal direction of the electrolytic copper foil was cut out in a rectangular shape, and the remainder of the cutout was used as the negative electrode lead piece 4.

In this embodiment, amorphous carbon is exemplified as the negative electrode active material, but other than that, natural graphite, a film formed on natural graphite by a dry CVD (Chemical Vapor Deposition) method or a wet spray method is used. Composite carbonaceous material formed, carbonaceous material such as artificial graphite, amorphous carbon material, etc. produced by firing from resin raw materials such as epoxy and phenol, or pitch-based materials obtained from petroleum and coal, or lithium Lithium metal that can occlude and release lithium by forming a compound, an oxide or nitride of a group 14 element such as silicon, germanium, and tin that can form and compound lithium with lithium and occlude and release lithium by being inserted into the crystal gap Can be used. In particular, the carbonaceous material is a material having high conductivity, and excellent in terms of low temperature characteristics and cycle stability. Among the carbonaceous materials, a material having a wide carbon network surface layer (d ₀₀₂ ) is excellent in rapid charge / discharge and low temperature characteristics, and is suitable. However, since a material with a wide d ₀₀₂ may have a reduced capacity and low charge and discharge efficiency at the initial stage of charging, d ₀₀₂ is preferably 0.39 nm or less. May be called. Further, a carbonaceous material having high conductivity such as graphite, amorphous, activated carbon or the like may be mixed in order to constitute the electrode. Alternatively, a material having the characteristics shown in (1) to (3) below may be used as the graphite material.

(1) peak in the range of 1300～1400Cm ^-1 measured by Raman spectrum intensity (I _D) and the peak intensity in the range of 1580～1620Cm ^-1 as measured by Raman spectroscopy spectra (I _G) and the The R value (I _D / I _G ), which is an intensity ratio, is 0.2 or more and 0.4 or less.

(2) half-value width Δ value of the peak in the range of 1300～1400Cm ^-1 as measured by Raman spectroscopy spectra is 40 cm ^-1 or more 100 cm ^-1 or less.

(3) peak intensity of the X-ray diffraction (110) plane (I ₍₁₁₀₎₎ and (004) plane peak intensity (I ₍₀₀₄₎₎ the intensity ratio X value of (I ₍₁₁₀₎ / I ₍₀₀₄₎ ) Is 0.1 or more and 0.45 or less.

<Production of battery>
As shown in FIG. 1, the produced positive electrode plate 1 and negative electrode plate 3 are arranged with a microporous separator 5 made of polyethylene having a thickness of 40 μm sandwiched therebetween so that the both electrode plates do not directly contact each other. The electrode group 7 (see FIG. 2) was produced by winding. A hollow cylindrical shaft core 9 made of polypropylene was used at the center of winding. A solid flame retardant was applied to the surface of the shaft core 9 using a binder. In this embodiment, a phosphazene compound that is solid at room temperature and has a melting point of 90 ° C. or higher is used as the flame retardant. In addition, the application quantity of a flame retardant is shown in the below-mentioned Example. In this embodiment, the phosphazene compound is exemplified as the flame retardant, but a general solid flame retardant may be used, and the solid flame retardant used in the present invention is particularly Not limited. For example, a flame retardant such as a phosphate ester-based compound or a compound containing a fluorinated alkyl group, or a mixture of two or more of these may be used, and the mixing ratio is not limited. In this embodiment, PVDF is exemplified as the binder for the flame retardant, but polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide Polymers such as rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and mixtures thereof may be used.

  As shown in FIG. 2, the produced electrode group 7 was inserted into a nickel-plated steel cylindrical battery container (battery can 11). In the present embodiment, a cylindrical lithium ion battery is exemplified, but the present invention is not limited to a cylindrical shape, and may be applied to, for example, a square battery.

A solid flame retardant was also applied to the surface of the battery can 11 (contact surface with the electrode group) using a binder. In addition, the application quantity of a flame retardant is shown in the below-mentioned Example. Thereafter, the positive electrode lead piece 2 and the negative electrode lead piece 4 were ultrasonically welded and connected to the pole column 13. Further, the positive electrode lead piece 2 was folded and covered with the battery lid 15, and the battery lid 15 was caulked and fixed to the battery can 11 via the EPDM resin gasket and the current cutoff valve 17. Thereafter, a predetermined amount of a non-aqueous electrolyte solution that can infiltrate the entire electrode group 7 is injected into the battery can 11 from the electrolyte solution injection port 19, and the electrolyte solution injection port 19 is sealed. An ion battery (cylindrical lithium ion secondary battery) was completed. The nonaqueous electrolyte includes lithium hexafluorophosphate in a mixed solution in which ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1: 1: 1. A solution in which (LiPF ₆ ) was dissolved at 1 mol / liter and vinylene carbonate (VC) was mixed as an additive was used.

In the present embodiment, a nonaqueous electrolytic solution in which LiPF ₆ is dissolved as a lithium salt in a mixed solution of EC, DEC, and DMC containing VC as an additive is illustrated, but a general lithium salt is used as an electrolyte. A nonaqueous electrolytic solution in which this is dissolved in an organic solvent may be used. The present invention is not particularly limited to the organic solvent, lithium salt and additive used. For example, as an organic solvent, ethylene carbonate (EC), trifluoropropylene carbonate (TFPC), chloroethylene carbonate (ClEC), trifluoroethylene carbonate (TFEC), difluoroethylene carbonate (DFEC), vinylethylene carbonate (VEC) Etc. can be used. In particular, it is preferable to use EC from the viewpoint of film formation on the negative electrode. In addition, addition of a small amount (2 vol% or less) of ClEC, TFEC, or VEC also contributes to the formation of the electrode film and provides good cycle characteristics. Furthermore, TFPC and DFEC may be used by adding a small amount (2 vol% or less) from the viewpoint of film formation on the positive electrode plate. Furthermore, as a solvent, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), trifluoromethyl ethyl carbonate (TFMEC), 1,1 1, 1-trifluoroethyl methyl carbonate (TFEMC) or the like can be used. These two or more kinds of mixed solvents may be used, and the mixing ratio is not limited. DMC is a highly compatible solvent and is suitable for use in a mixture with EC or the like. DEC has a lower melting point than DMC and is suitable for low temperature (−30 ° C.) characteristics. EMC is suitable for low temperature characteristics because of its asymmetric molecular structure and low melting point. Since EPC and TFMEC have propylene side chains and an asymmetric molecular structure, they are suitable as adjusting solvents for low temperature characteristics. TFEMC fluorinates part of the molecule and has a large dipole moment, which is suitable for maintaining the dissociation property of the lithium salt at a low temperature, and is suitable for low temperature characteristics. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiI, LiCl, LiBr and the like for inorganic lithium salts, and LiB [OCOCF ₃ ] ₄ and LiB [OCOCF ₂ CF ₃ ] for organic lithium salts. ₄ , LiPF ₄ (CF ₃ ) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ or the like can be used. Two or more kinds of mixed lithium salts may be used, and the mixing ratio is not limited. LiPF ₆ frequently used in consumer batteries is a suitable material because of its quality stability. LiB [OCOCF ₃ ] ₄ is an effective material because it has good dissociation and solubility and exhibits high conductivity at a low concentration. As the additive, vinylene carbonate (VC), methyl vinylene carbonate (MVC), dimethyl vinylene carbonate (DMVC), ethyl vinylene carbonate (EVC), diethyl vinylene carbonate (DEVC), dimethallyl carbonate (DMAC), or the like is used. be able to. These two or more kinds of mixed additives may be used, and the mixing ratio is not limited. VC has a low molecular weight and is considered to form a dense electrode film. MVC, DMVC, EVC, DEVC, and the like in which an alkyl group is substituted for VC are considered to form an electrode film having a low density in accordance with the size of the alkyl chain, and are considered to act effectively to improve low-temperature characteristics.

  In this embodiment, both the shaft core 9 and the battery can 11 are provided with a solid flame retardant, but only the shaft core or only the battery can can be provided with a flame retardant. Of course. Furthermore, in the present embodiment, a flame retardant is applied to the surface of the shaft core and / or the inner surface of the battery can, but the flame retardant is not contained in the non-aqueous electrolyte, and the positive electrode plate, As long as both the negative electrode plate and the separator are isolated, the added flame retardant may be contained in the material forming the shaft core.

<Battery evaluation>
(Life evaluation)
About the lithium ion battery shown in the below-mentioned Example and comparative example, the capacity | capacitance maintenance factor was measured. In the capacity maintenance rate measurement, each lithium ion battery is charged at a constant current and a constant voltage up to 4.2 V to be in a fully charged state, and discharged to measure the initial discharge capacity. And after making it a full charge state on the same conditions again, it is left to stand in a 40 degreeC environment. Under this condition, the discharge capacity is measured every month, and the ratio to the initial discharge capacity is calculated as the capacity maintenance rate.

(Safety evaluation)
The overcharge test was done about the lithium ion battery shown in the below-mentioned Example and comparative example. In the overcharge test, the presence or absence of ignition was observed as the behavior of the battery when it was continuously charged at a current value of 1C.

<Battery behavior and flame retardant mechanism in abnormal conditions>
Here, the behavior (operation) when the lithium ion battery of the present embodiment falls into a battery abnormal state and the flame-retardant mechanism will be briefly described. When the lithium ion battery falls into an abnormal battery state such as overcharging, the nonaqueous electrolyte solution decomposes with heat generation, and gas is generated in the battery at an accelerated rate. Although the internal pressure of the battery rises due to this gas, the current cutoff valve 17 maintains continuity up to a predetermined pressure (shutoff pressure, for example, 0.5 to 2.5 MPa) determined by the shape, dimensions, material, etc. of the current cutoff valve 17. . When the battery internal pressure exceeds the cutoff pressure, the current cutoff valve 17 instantaneously cuts off the current.

  Further, when the battery becomes high temperature, the solid flame retardant held in the shaft core 9 and the battery can 11 elutes into the non-aqueous electrolyte, and the non-aqueous electrolyte becomes flame-retardant and explosive due to an internal short circuit. Combustion can be suppressed. When the battery internal pressure further rises, the gas in the battery container is released to the outside, but since the released gas is flame-retardant, it does not cause combustion due to an external fire point or the like. Therefore, according to the lithium ion battery of the present embodiment, the battery can be safely and reliably guided to an unusable state when the battery is abnormal.

  Examples of the lithium ion battery produced as described above will be described. In addition, it describes together about the battery of the comparative example produced for the comparison. Table 1 shows configurations and evaluation results of Examples and Comparative Examples.

<Example 1>
Using lithium manganate as the positive electrode active material, using amorphous carbon as the negative electrode active material, adding 1% by weight of vinylene carbonate (VC), and using a phosphazene compound as a solid flame retardant, flame retardant A battery using PVDF as a binder was prepared. The amount of the flame retardant applied to the surface of the shaft core was 2 g, and the amount of the flame retardant applied to the inner surface of the battery can was 1 g.

<Example 2>
The battery is the same as in Example 1 except that the amount of the flame retardant applied to the surface of the shaft core is 1.5 g and the amount of the flame retardant applied to the inner surface of the battery can is 1.5 g. Was made.

<Example 3>
A battery was fabricated in the same manner as in Example 1 except that the amount of the flame retardant applied to the surface of the shaft core was 1 g and the amount of the flame retardant applied to the inner surface of the battery can was 2 g.

<Example 4>
Using nickel, cobalt, and lithium manganate as the positive electrode active material, using amorphous carbon as the negative electrode active material, adding 1% by weight of vinylene carbonate (VC), and using a phosphazene compound as a solid flame retardant, A battery using PVDF as a binder for the flame retardant was prepared. The amount of the flame retardant applied to the surface of the shaft core was 2 g, and the amount of the flame retardant applied to the inner surface of the battery can was 1 g.

<Example 5>
The battery is the same as in Example 4 except that the amount of the flame retardant applied to the surface of the shaft core is 1.5 g and the amount of the flame retardant applied to the inner surface of the battery can is 1.5 g. Was made.

<Example 6>
A battery was fabricated in the same manner as in Example 4 except that the amount of the flame retardant applied to the surface of the shaft core was 1 g and the amount of the flame retardant applied to the inner surface of the battery can was 2 g.

<Example 7>
Using a mixture of equal amounts of lithium manganate and nickel / cobalt / lithium manganate as the positive electrode active material, using amorphous carbon as the negative electrode active material, and adding 1 wt% of vinylene carbonate (VC) A battery using a phosphazene compound as a flame retardant and PVDF as a binder for the flame retardant was prepared. The amount of the flame retardant applied to the surface of the shaft core was 2 g, and the amount of the flame retardant applied to the inner surface of the battery can was 1 g.

<Example 8>
The battery is the same as in Example 7, except that the amount of the flame retardant applied to the surface of the shaft core is 1.5 g and the amount of the flame retardant applied to the inner surface of the battery can is 1.5 g. Was made.

<Example 9>
A battery was fabricated in the same manner as in Example 7, except that the amount of the flame retardant applied to the surface of the shaft core was 1 g and the amount of the flame retardant applied to the inner surface of the battery can was 2 g.

<Example 10>
A solid flame retardant using a mixture of equal amounts of lithium manganate and nickel / cobalt / lithium manganate as the positive electrode active material, graphite as the negative electrode active material, and 1 wt% of vinylene carbonate (VC). A battery using a phosphazene compound as a binder and PVDF as a binder for a flame retardant was prepared. The amount of the flame retardant applied to the surface of the shaft core was 2 g, and the amount of the flame retardant applied to the inner surface of the battery can was 1 g.

<Example 11>
The battery was the same as in Example 10, except that the amount of the flame retardant applied to the surface of the shaft core was 1.5 g and the amount of the flame retardant applied to the inner surface of the battery can was 1.5 g. Was made.

<Example 12>
A battery was fabricated in the same manner as in Example 10, except that the amount of the flame retardant applied to the surface of the shaft core was 1 g and the amount of the flame retardant applied to the inner surface of the battery can was 2 g.

<Example 13>
A battery was fabricated in the same manner as in Example 10 except that the addition amount of VC was 2 wt%.

<Example 14>
A battery was fabricated in the same manner as in Example 11 except that the addition amount of VC was 2 wt%.

<Example 15>
A battery was fabricated in the same manner as in Example 12 except that the addition amount of VC was 2 wt%.

<Comparative Example 1>
A conventional lithium ion battery was prepared in which a flame retardant was added to the non-aqueous electrolyte. As the non-aqueous electrolyte, a mixed solution in which ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1: 1 was used. In this mixed solution, 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) and 1 wt% of vinylene carbonate (VC) are dissolved, and 3 g of a phosphazene compound as a flame retardant is contained in the battery can. It adjusted so that it might contain. Further, lithium manganate was used as the positive electrode active material, and amorphous carbon was used as the negative electrode active material.

<Comparative Example 2>
A lithium ion battery was produced in the same manner as in Comparative Example 1 except that nickel, cobalt, and lithium manganate were used as the positive electrode active material.

<Comparative Example 3>
A lithium ion battery was produced in the same manner as in Comparative Example 1 except that an equivalent mixture of lithium manganate and nickel / cobalt / lithium manganate was used as the positive electrode active material.

<Comparative Example 4>
A lithium ion battery was produced in the same manner as in Comparative Example 3 except that graphite was used as the negative electrode active material.

<Comparative Example 5>
A lithium ion battery was produced in the same manner as in Comparative Example 4 except that the concentration of vinylene carbonate (VC) was 2 wt%.

  As shown in Table 1, when Comparative Example 1 and Example 1 in which the positive electrode active material and the negative electrode active material are the same and the amount of VC added is the same, no ignition of the battery can be confirmed, and safety evaluation There was no difference. However, the solid flame retardant is disposed on the surface of the shaft core 9 and the inner surface of the battery can 11 rather than the lithium ion battery (Comparative Example 1) containing the solid flame retardant in the non-aqueous electrolyte. It was found that the capacity retention rate of the lithium ion battery (Example 1) was higher. This tendency was observed even when other positive electrode active materials and negative electrode active materials were used. That is, when the comparative example 2 and the example 4, the comparative example 3 and the example 7, the comparative example 4 and the example 10, and the comparative example 5 and the example 13 are respectively compared, the shaft core 9 and the battery can 11 are difficult. When the flame retardant was arranged, the capacity retention rate was higher than when the flame retardant was added to the non-aqueous electrolyte. From these results, it was found that when a solid flame retardant is disposed on both the shaft core 9 and the battery can 11 as in the present embodiment, the battery can be made flame retardant while suppressing a decrease in battery life. . In this way, the decrease in battery life could be prevented because the non-aqueous electrolyte contained no flame retardant in this embodiment, and an environment in which side reactions were unlikely to occur in the battery was obtained. This is thought to be caused by this.

  Further, as in this example, the flame retardant disposed in the shaft core or the battery can can be present in the battery in a state of being isolated from any of the positive electrode plate 1, the negative electrode plate 3, and the separator 5. As a result, since it becomes difficult to inhibit the ion permeability at the time of charging / discharging, it is thought that the deterioration of charging / discharging characteristics could be prevented as shown in Table 1.

  Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to these embodiments and examples, and modifications based on the technical idea of the present invention are possible. Of course there is.

  According to the present invention, since the flame retardant is contained or applied to one or both of the shaft core and the battery can, it is not necessary to add the flame retardant to the non-aqueous electrolyte. Side reactions due to combustion can be prevented. In addition, the flame retardant placed in the shaft core and battery can is present in the battery in a state isolated from any of the positive electrode plate, the negative electrode plate, and the separator, and therefore impedes ion permeability during charging and discharging. There is no. Therefore, the safety of the lithium ion battery can be improved without deteriorating capacity characteristics and life characteristics.

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Positive electrode lead piece 3 Negative electrode plate 4 Negative electrode lead piece 5 Separator 7 Electrode group 9 Shaft core 11 Battery can 13 Electrode column 15 Battery cover 17 Current cutoff valve 19 Electrolyte injection port

Claims (7)

An electrode group configured by arranging a positive electrode plate containing a positive electrode active material and a negative electrode plate containing a negative electrode active material via a separator;
An axis for winding the electrode group;
In a lithium ion battery comprising a battery can that houses the electrode group wound around the shaft core,
A flame retardant is applied to the surface of the shaft core,
A lithium ion battery, wherein a flame retardant is applied to an inner surface of the battery can. An electrode group configured by arranging a positive electrode plate containing a positive electrode active material and a negative electrode plate containing a negative electrode active material via a separator;
An axis for winding the electrode group;
In a lithium ion battery comprising a battery can that houses the electrode group wound around the shaft core,
A flame retardant is contained in or applied to one or both of the shaft core and the battery can.   The lithium ion battery according to claim 2, wherein the flame retardant is contained in a material forming the shaft core.   The lithium ion battery according to claim 2, wherein the flame retardant is applied to a surface of the shaft core.   The lithium ion battery according to claim 2, wherein the flame retardant is applied to an inner surface of the battery can.   The lithium ion battery according to any one of claims 1 to 5, wherein the flame retardant is solid at normal temperature and has a melting point of 90 ° C or higher. The flame retardant is solid at normal temperature and has a melting point of 90 ° C. or higher,
The lithium ion battery according to any one of claims 1 to 5, wherein the flame retardant is at least one selected from a phosphazene compound, a phosphate ester compound, and an alkyl fluoride compound, or a mixture thereof.

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