JP2008053092A - Non-aqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte battery provided with a non-aqueous electrolyte containing lithium salt, organic solvent, and ionic liquid and superior in high rate discharge characteristics. <P>SOLUTION: The non-aqueous electrolyte battery is constituted of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, and the non-aqueous electrolyte contains lithium salt, organic solvent, and ionic liquid, and the separator is arranged with fluorine-contained resin on a porous substrate. When the non-aqueous electrolyte contains both the organic solvent and ionic liquid, by arranging the fluorine-contained resin on the porous substrate, high-rate discharge characteristics can be improved more than anticipation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte battery, and more particularly to improvement of a separator used in a non-aqueous electrolyte battery using a non-aqueous electrolyte containing an ionic liquid.

  In recent years, non-aqueous electrolyte batteries typified by lithium-ion batteries have attracted attention as power supplies for electronic equipment, power storage power supplies, power supplies for electric vehicles, and the like that have been improved in performance and size.

  A general nonaqueous electrolyte battery includes a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator, and a microporous film made of polyethylene, polypropylene, or the like is generally used as the separator. As the non-aqueous electrolyte, generally, a non-aqueous electrolyte that is liquid at room temperature is used. The non-aqueous electrolyte is generally obtained by dissolving a lithium salt that is solid at room temperature in an organic solvent that is liquid at room temperature. Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl. Organic solvents such as carbonate, methyl ethyl carbonate, γ-butyrolactone, dimethoxyethane, diethoxyethane, methoxyethoxyethane and the like are used.

  On the other hand, it has been proposed to use an ionic liquid that is liquid at room temperature as a non-aqueous electrolyte. The ionic liquid itself is liquid at room temperature but is substantially non-volatile and has high flame retardancy. In particular, for relatively large applications such as power storage power sources and electric vehicle power sources, it is desired to use a non-aqueous electrolyte having characteristics such as no risk of ignition, and there is a technique for using the ionic liquid as an electrolyte. Proposed. (For example, see Patent Documents 1 to 3).

  However, since these ionic liquids have a higher melting point and higher viscosity than general non-aqueous electrolytes composed of an organic solvent and a lithium salt, the mobility of carrier ions such as lithium ions is sufficiently high. There was a problem that it was not possible. Therefore, a non-aqueous electrolyte battery using a non-aqueous electrolyte made of an ionic liquid has a problem that high-rate discharge characteristics are not sufficient as compared with a non-aqueous electrolyte battery using a general non-aqueous electrolyte. Furthermore, ionic liquids are liquid at room temperature, but non-aqueous electrolytes made of ionic liquids are more viscous than conventional non-aqueous electrolytes using organic solvents and have low wettability to separators and electrode materials. There is a problem that it is difficult to retain a sufficient amount of electrolyte.

  In contrast, by using a non-aqueous electrolyte containing an ionic liquid and an organic solvent at the same time, an attempt has been proposed to improve the high-rate discharge characteristics of a non-aqueous electrolyte battery while maintaining the flame retardancy of the non-aqueous electrolyte. (For example, refer to Patent Documents 4 to 6).

  However, the non-aqueous electrolytes shown in these patent documents also have a higher viscosity than conventional non-aqueous electrolytes using an organic solvent in an electrolyte composition that can maintain the flame retardancy of the non-aqueous electrolyte. The problem of low wettability with respect to separators and electrode materials has not been completely solved.

  On the other hand, a technique for improving the wettability of a non-aqueous electrolyte with respect to a separator has been proposed by using a porous film conventionally used as a separator as a base material and compositing an organic polymer layer thereon (for example, a patent) Reference 7-10). However, when the organic polymer layer is combined, the thickness increases, and the pore size and the open area ratio tend to decrease. Compared to the case where the original porous film not combined with the organic polymer layer is used as the separator. There was a problem that the high rate discharge characteristics were inferior.

In Patent Document 10, the use of a separator having an organic polymer layer formed on a porous substrate can improve the wettability of a non-aqueous electrolyte separator containing a room temperature molten salt (ionic liquid) having an imidazolium cation. Are listed. Patent Document 9 describes a separator in which an organic polymer layer containing polyvinylidene fluoride or polyacrylonitrile as a raw material is formed on a porous substrate. However, in any of the above documents, there is a description that the high rate discharge characteristics of a battery using a nonaqueous electrolyte containing an ionic liquid can be improved by using a separator in which a fluorine-containing resin material is arranged on a porous substrate. Absent.
JP 2001-319688 A Japanese Patent No. 2981545 JP 2003-331918 A JP 11-260400 A JP 2004-303642 A JP 2002-373704 A JP 2002-56894 A JP 2002-298820 A JP 2003-59480 A JP 2002-324579 A Study Group of Molten Salt / Thermal Technology “Basics of Molten Salt / Thermal Technology”, Agne Technology Center, 1993, 313p (ISBN 4-900041-24-6)

  The present invention has been made in view of the above problems, and provides a nonaqueous electrolyte battery including a nonaqueous electrolyte containing a lithium salt, an organic solvent, and an ionic liquid, and having excellent high rate discharge characteristics. Objective.

  The configuration of the present invention for solving the above-described problems is as follows. However, the action mechanism includes estimation, and the success or failure of the action mechanism does not limit the present invention.

  The invention provides a nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, wherein the nonaqueous electrolyte includes a lithium salt, an organic solvent, and an ionic liquid. A nonaqueous electrolyte battery characterized in that a contained resin material is disposed.

  As described above, when a conventional nonaqueous electrolyte composed of an organic solvent and a lithium salt is used in combination with a separator in which a polymer layer is disposed on a porous substrate, the porous layer in which the polymer layer is not disposed is used. It has been known that the high-rate discharge characteristics are inferior to the case where a general separator made of a substrate is used. However, a porous substrate in which a polymer layer is not disposed by using a nonaqueous electrolyte containing a lithium salt, an organic solvent and an ionic liquid in combination with a separator in which a fluorine-containing resin material is disposed on a porous substrate. Compared to the case of using a general separator comprising the following, a surprisingly surprising phenomenon has been found in which the high-rate discharge characteristics are improved, leading to the present invention.

In addition, the ionic liquid as used in this application means the ionic compound which at least one part exhibits liquid state at normal temperature. The normal temperature is a temperature range in which an electrochemical device using the normal operation is assumed to normally operate. The upper limit is about 100 ° C., in some cases about 60 ° C., and the lower limit is about −50 ° C., in some cases −20 It is about ℃. On the other hand, the inorganic molten salt such as Li ₂ CO ₃ —Na ₂ CO ₃ —K ₂ CO ₃ used for various electrodepositions as described in Non-Patent Document 3 has a melting point of 300 ° C. or higher. However, it does not exhibit a liquid form within the temperature range in which the electrochemical device is normally assumed to operate, and is not included in the ionic liquid in the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte battery provided with the nonaqueous electrolyte containing lithium salt, an organic solvent, and an ionic liquid can be provided which was excellent in the high rate discharge characteristic.

  The porous substrate constituting the separator according to the present invention is not particularly limited, but is preferably a polyolefin porous membrane, and is generally made of polyethylene or polypropylene, which is generally used as a separator for nonaqueous electrolyte batteries. A single membrane or a composite membrane can be used.

  The resin material disposed on the porous substrate needs to be a fluorine-containing resin material. For example, PEO-based resins and PAN-based resins that do not contain fluorine may not achieve the effects of the present invention. As the fluorine-containing resin, a fluorine-containing resin material made of polyvinylidene fluoride or a polyvinylidene fluoride-hexafluoropropylene copolymer is preferable.

  The fluorine-containing resin is provided on at least a part of the surface of the base material composed of the front surface, the back surface, and the inner wall surface of the hole of the porous base material. Even if the amount of fluorine-containing resin disposed on the porous substrate is very small, the effect of the present invention can be achieved, but if it is too much, ion migration in the non-aqueous electrolyte contained in the separator is inhibited, It is not preferable also from the point that a rate discharge characteristic falls. That is, it is preferable that the fluorine-containing resin is arranged to such an extent that the pores of the porous substrate are not blocked, or the fluorine resin itself has very high air permeability. It is sufficient that the porous substrate on which the fluorine-containing resin is arranged has air permeability. About having air permeability, it can be determined by Japanese Industrial Standard (JIS P8117). Especially, in order to implement | achieve smooth ion movement in a separator, as for the separator which concerns on this invention, it is more preferable that air permeability is 500 second / 100 ml.

  The fluorine-containing resin disposed on the porous substrate is preferably porous from the viewpoint of liquid retention and ion conduction. As shown in the examples, the porous fluorine-containing resin is prepared by, for example, dissolving polyvinylidene fluoride in a soluble solvent and applying it to a porous substrate, and then immersing it in a non-solvent such as water. It can be obtained by the microphase separation action in the process of substitution.

The anion constituting the lithium salt and the ionic liquid in the present invention is not particularly limited, but ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CN ⁻ , COO ⁻ , SO ₂ CF ₂ −, N (CF ₃ SO ₂ ) ₂ ⁻ , N (C ₂ F ₅ SO ₂ ) ₂ ⁻ , N (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ ) ⁻ , N (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) ⁻ , C (CF ₃ SO ₂ ) ₃ ⁻ , C (C ₂ F ₅ SO ₂ ) ₃ ^{— and the} like, but are not limited thereto. These room temperature molten salts having a quaternary ammonium organic cation may be used alone or in admixture of two or more. Among them, at least one of them is PF ₆ ⁻ , and N (CF ₃ SO ₂ ) ₂ ⁻ , N (C ₂ F ₅ SO ₂ ) ₂ ⁻ , N (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) ⁻ , C (CF ₃ SO ₂ ) ₃ ⁻ , and C (C ₂ F ₅ SO ₂ ) ₃ ^— are preferably composed of a total of two or more compounds including at least one compound selected from C (C ₂ F ₅ SO ₂ ) ₃ ^— .

  In order to contain two or more kinds of anions, a room temperature molten salt of two or more kinds of anions may be mixed with a lithium salt composed of one kind of anion, and a lithium salt of two or more kinds of anions may be mixed with one kind of anion. A room temperature molten salt may be mixed, and further, a room temperature molten salt and a lithium salt having different anion species may be mixed.

  Examples of the cation constituting the ionic liquid in the present invention include a quaternary ammonium cation and a phosphonium cation. Examples of the quaternary ammonium cation include imidazolium cation, tetraalkylammonium cation, pyridinium cation, pyrrolium cation, pyrazolium cation, pyrrolium cation, pyrrolidinium cation, and piperidinium cation.

  Examples of the imidazolium cation include 1,3-dimethylimidazolium ion, 1-ethyl-3-methylimidazolium ion, 1,3-diethylimidazolium ion, 1-butyl-3-yl as dialkylimidazolium cation. Methyl imidazolium ion, etc., and trialkyl imidazolium cation, 1,2,3-trimethylimidazolium ion, 1,2-dimethyl-3-ethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion Ions, 1-butyl-2,3-dimethylimidazolium ions, and the like, but are not limited thereto.

  Examples of the tetraalkylammonium cation include, but are not limited to, trimethylethylammonium ion, trimethylpropylammonium ion, trimethylhexylammonium ion, and tetrapentylammonium ion.

  Examples of the pyridinium cation include N-methylpyridinium ion, N-ethylpyridinium ion, N-propylpyridinium ion, N-butylpyridinium ion 1-ethyl-2-methylpyridinium, 1-butyl-4-methylpyridinium, 1-butyl Examples include -2,4-dimethylpyridinium, but are not limited thereto.

  Examples of the pyrrolium cation include 1,1-dimethylpyrrolium ion, 1-ethyl-1-methylpyrrolium ion, 1-methyl-1-propylpyrrolium ion, 1-butyl-1-methylpyrrolium ion, It is not limited to these.

  Examples of the pyrazolium cation include 1,2-dimethylpyrazolium ion, 1-ethyl-2-methylpyrazolium ion, 1-propyl-2-methylpyrazolium ion, 1-butyl-2-methylpyrazolium ion, and the like. However, it is not limited to these.

  Examples of the pyrrolium cation include 1,2-dimethylpyrrolium ion, 1-ethyl-2-methylpyrrolium ion, 1-propyl-2-methylpyrrolium ion, 1-butyl-2-methylpyrrolium ion, and the like. Although it is mentioned, it is not limited to these.

  Examples of the pyrrolidinium cation include 1,1-dimethylpyrrolidinium ion, 1-ethyl-1-methylpyrrolidinium ion, 1-methyl-1-propylpyrrolidinium ion, 1-butyl-1-methylpyrrolidinium ion, and the like. However, it is not limited to these.

  Examples of the piperidinium cation include 1,1-dimethylpiperidinium ion, 1-ethyl-1-methylpiperidinium ion, 1-methyl-1-propylpiperidinium ion, 1-butyl-1-methylpiperidinium ion, and the like. However, it is not limited to these.

  In addition, the ionic liquid which has these cations may be used independently, and may be used in mixture of 2 or more types.

  The nonaqueous electrolyte of the present invention preferably contains cyclic carbonates and chain carbonates as the organic solvent. Cyclic carbonates include ethylene carbonate, propylene carbonate, γ-butyrolactone, propiolactone, valerolactone, butylene carbonate, vinylene carbonate, catechol carbonate, 1-phenyl vinylene carbonate, 1,2-diphenyl vinylene carbonate, styrene carbonate, vinyl Examples thereof include, but are not limited to, ethylene carbonate and 4-methyl-4-vinyl-1,3-dioxan-2-one. The chain carbonates include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl propyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, dimethoxyethane, diethoxyethane, methoxy Although ethoxyethane etc. are mentioned, it is not limited to these.

  The cyclic carbonates, the chain carbonates, and the ionic liquid can be mixed at an arbitrary mixing ratio, but the non-aqueous electrolyte exhibits both flame retardancy and electrochemical characteristics, and the effects of the present invention. In order to obtain effectively, it is desirable that the content ratio of the chain carbonates and the cyclic carbonates is in the range of 40 volume percent: 60 volume percent to 70 volume percent: 30 volume percent, and the ionic liquid is used. It is desirable to contain 40 volume percent or more. When the content ratio of the chain carbonates and the cyclic carbonates is not less than the lower limit of the above range, it becomes easy to set the melting point and the viscosity of the nonaqueous electrolyte low, and it becomes easy to maintain high ionic conductivity. When the content ratio of the chain carbonates and the cyclic carbonates is not more than the upper limit of the above range, the degree of dissociation of the lithium salt can be made sufficient, and the maintenance of high ionic conductivity is facilitated. In addition, when the content of the ionic liquid is 40 volume percent or more, the proportion of the organic compound that is flammable by itself does not become too large. When the separator according to the present invention, which is the most important effect of the present invention, is used, it becomes easier to obtain the effect of improving the high rate discharge characteristics as compared with the case of using the conventional separator.

  Note that a phosphoric acid ester, which is a flame retardant solvent, may be added to the nonaqueous electrolyte. Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoroethyl) phosphate, and tri (pentafluoro) phosphate. Propyl), tri (heptafluorobutyl) phosphate, and the like, but are not limited thereto. These may be used alone or in combination of two or more.

  The lithium cation content in the non-aqueous electrolyte is preferably in the range of 0.5 to 3 mol / l. When the content of the lithium salt is 0.5 mol / l or more, the electrolyte resistance can be kept low, and the possibility that the charge / discharge efficiency of the battery is lowered can be reduced. When the content of the lithium salt is 3 mol / l or less, it is possible to reduce the possibility that the melting point of the nonaqueous electrolyte will rise and it will be difficult to maintain a liquid state at room temperature. In view of the above, the content of the lithium salt in the nonaqueous electrolyte is preferably in the range of 0.5 to 3 mol / l, more specifically in the range of 0.5 to 2 mol / l.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these descriptions.

(Comparative electrolyte 1)
1 mol of LiPF ₆ is mixed with 1 liter of a mixed solvent (hereinafter referred to as mixed solvent A) in which propylene carbonate (PC), DMC, and EMC, which are EC and cyclic carbonates, are mixed at a volume ratio of 30: 10: 30: 30. As a result, a non-aqueous electrolyte was obtained. The content ratio of the chain carbonates and the cyclic carbonates in the mixed solvent A is 40 volume percent: 60 volume percent.

(Comparative electrolyte 2)
By mixing 1 mol of LiN (CF ₃ SO ₂ ) ₂ (LiTFSI) with 1 liter of 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMI-TFSI), a non-aqueous electrolyte is obtained. It was.

(Comparative electrolyte 3)
A mixed solvent in which ethylene carbonate (EC), which is a cyclic carbonate, dimethyl carbonate (DMC), which is a chain carbonate, and methyl ethyl carbonate (EMC), which is a chain carbonate, are mixed at a volume ratio of 30:35:35 (hereinafter referred to as a mixed solvent). A nonaqueous electrolyte was obtained by mixing 1 mol of LiPF ₆ in 1 liter of mixed solvent B). The content ratio of the chain carbonates and the cyclic carbonates in the mixed solvent B is 30 volume percent: 70 volume percent.

(Comparative electrolyte 4)
1 mol of LiPF ₆ is mixed with 1 liter of a mixed solvent (hereinafter referred to as mixed solvent C) in which EC, cyclic carbonates such as propylene carbonate (PC), DMC, and EMC are mixed at a volume ratio of 30: 30: 20: 20. As a result, a non-aqueous electrolyte was obtained. The content ratio of the chain carbonates and the cyclic carbonates in the mixed solvent C is 60 volume percent: 40 volume percent.

(Comparative electrolyte 5)
By mixing 1 mol of LiPF ₆ with 1 liter of a mixed solvent (hereinafter referred to as mixed solvent D) in which EC, PC, DMC and EMC are mixed at a volume ratio of 30: 40: 15: 15, a non-aqueous electrolyte is obtained. It was. The content ratio of the chain carbonates and the cyclic carbonates in the mixed solvent D is 70 volume percent: 30 volume percent.

(Comparative electrolyte 6)
By mixing 1 mol of LiPF ₆ with 1 liter of a mixed solvent (hereinafter referred to as mixed solvent E) in which EC, PC and chain carbonates diethyl carbonate (DEC) are mixed at a volume ratio of 50:40:10. A non-aqueous electrolyte was obtained. The content ratio of the chain carbonates and the cyclic carbonates in the mixed solvent E is 90 volume percent: 10 volume percent.

(Invention electrolyte 1)
A nonaqueous electrolyte was obtained by mixing 300 ml of EMI-TFSI and 700 ml of mixed solvent A, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Invention electrolyte 2)
A nonaqueous electrolyte was obtained by mixing 400 ml of EMI-TFSI and 600 ml of mixed solvent A, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Invention electrolyte 3)
A nonaqueous electrolyte was obtained by mixing 500 ml of EMI-TFSI and 500 ml of mixed solvent A, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Invention electrolyte 4)
A nonaqueous electrolyte was obtained by mixing 700 ml of EMI-TFSI and 300 ml of mixed solvent A, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Invention electrolyte 5)
A nonaqueous electrolyte was obtained by mixing 500 ml of EMI-TFSI and 500 ml of mixed solvent B, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Invention electrolyte 6)
A nonaqueous electrolyte was obtained by mixing 500 ml of EMI-TFSI and 500 ml of mixed solvent C, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Invention electrolyte 7)
A nonaqueous electrolyte was obtained by mixing 500 ml of EMI-TFSI and 500 ml of mixed solvent D, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Invention electrolyte 8)
A nonaqueous electrolyte was obtained by mixing 500 ml of EMI-TFSI and 500 ml of mixed solvent E, and further mixing LiPF ₆ so as to be 1 mol / liter.

(Electrolyte flammability test)
An electrolyte flammability test was performed on the above-described electrolytes 1 to 8 and comparative electrolytes 2 to 6. A glass filter was impregnated with each electrolyte, and the presence of ignition / combustion was confirmed by bringing the fire of an alcohol lamp closer to 10 seconds.

(Preparation of battery separator of the present invention)
12 weight percent of polyvinylidene fluoride powder and N-methyl-2-pyrrolidone on the surface of a polyethylene microporous membrane (average pore size 0.1 μm, porosity 50%, thickness 23 μm, air permeability 89 seconds / 100 ml): A mixed and completely dissolved solution was applied to 88 weight percent and immersed in water. In this process, N-methyl-2-pyrrolidone is replaced with water to form a porous layer made of polyvinylidene fluoride. Next, the moisture was dried to obtain a separator a for a battery of the present invention having a thickness of 26 μm and an air permeability of 158 seconds / 100 ml.

  The polyethylene microporous membrane used above (with no porous layer formed, average pore size 0.1 μm, open area ratio 50%, thickness 23 μm, air permeability 89 seconds / 100 ml) was used as a separator for comparative batteries b It was.

(Preparation of non-aqueous electrolyte battery)
A cross-sectional view of the nonaqueous electrolyte battery according to the example is shown in FIG. The non-aqueous electrolyte battery according to the example is composed of a pole group 4 including a positive electrode 1, a negative electrode 2, and a separator 3, a non-aqueous electrolyte, and a metal resin composite film 5 as an exterior material. The positive electrode 1 is formed by applying a positive electrode mixture 11 on a positive electrode current collector 12. The negative electrode 2 is formed by applying a negative electrode mixture 21 on a negative electrode current collector 22. The nonaqueous electrolyte is impregnated in the pole group 4. The metal resin composite film 5 covers the pole group 4 and is sealed on all four sides by heat welding.

Next, a method for manufacturing the nonaqueous electrolyte battery having the above configuration will be described. The positive electrode 1 was obtained as follows. First, LiCoO ₂ and acetylene black, which is a conductive agent, are mixed, and further, a N-methyl-2-pyrrolidone solution of polyvinylidene fluoride is mixed as a binder, and this mixture is used as a positive electrode current collector 12 made of an aluminum foil. After coating on one side, it was dried and pressed so that the positive electrode mixture 11 had a predetermined thickness. The positive electrode 1 was obtained by the above process. The negative electrode 2 was obtained as follows. First, the non-graphitizable carbon (the (002) plane spacing 0.345 nm by X-ray wide angle diffraction method) as the negative electrode active material and the N-methyl-2-pyrrolidone solution of polyvinylidene fluoride as the binder are mixed. The mixture was applied to one side of the negative electrode current collector 22 made of copper foil, dried, and pressed so that the thickness of the negative electrode mixture 21 was a predetermined thickness. The negative electrode 2 was obtained by the above process. The pole group 4 was configured by facing the positive electrode mixture 11 and the negative electrode mixture 21, placing the separator 3 therebetween, and laminating the positive electrode 1, the separator 3, and the negative electrode 2 in this order. Next, the electrode group 4 was impregnated with the non-aqueous electrolyte by immersing the electrode group 4 in the non-aqueous electrolyte. Furthermore, the pole group 4 was covered with the metal resin composite film 5, and the four sides were sealed by heat welding.

(Invention battery, comparative battery)
Using the separator a for a battery of the present invention or the separator b for a comparative battery as the separator 3, the present invention batteries and comparative batteries were prepared by combining the present electrolytes 1 to 8 and the comparative electrolytes 2 to 6, respectively, as nonaqueous electrolytes.

(Initial discharge capacity test)
An initial discharge capacity test was performed on the battery of the present invention and the comparative battery. The test temperature was 20 ° C. Charging was performed at a constant current and a constant voltage with a current of 2 mA and a final voltage of 4.2 V. The discharge was a constant current discharge with a current of 2 mA and a final voltage of 2.7 V. The obtained discharge capacity was defined as the initial discharge capacity. The design capacities of the battery of the present invention and the comparative battery are all 10 mAh.

(High rate discharge test)
A high rate discharge test was performed on the battery of the present invention and the comparative battery. The test temperature was 20 ° C. A battery whose initial capacity was confirmed under the same conditions as in the initial discharge capacity test was charged under the same conditions, and then a constant current discharge with a current of 10 mA and a final voltage of 2.7 V was performed. The obtained discharge capacity was defined as a high rate discharge capacity.

  The above results are summarized in Table 1.

  As is clear from Table 1, as for a battery using a comparative electrolyte that does not contain either an organic solvent or an ionic liquid as a non-aqueous electrolyte, the separator is for a comparative battery consisting only of a porous substrate. Compared with the case where a separator is used, when the separator for a battery of the present invention in which a fluorine-containing resin is arranged on a porous substrate is used, the high rate discharge characteristics are equivalent or reduced. On the other hand, if the battery using the electrolyte of the present invention containing both the organic solvent and the ionic liquid is used, the separator is more porous than the case where the separator for a comparative battery made only of a porous substrate is used. It can be seen that when the separator for a battery of the present invention in which a fluorine-containing resin is arranged on the substrate is used, the high rate discharge characteristics are improved. It can be seen that the effect of the present invention that can provide a battery with excellent high-rate discharge characteristics is reliably achieved at least in the range in which the nonaqueous electrolyte contains 30 to 70 volume percent of the ionic liquid.

  In addition, regarding the flame retardant test results of the nonaqueous electrolyte, the comparative electrolytes 3 to 6 have flammability, whereas the present electrolytes 1 to 8 and the comparative electrolyte 2 may have flame retardancy or self-extinguishing properties. I understand. Especially, a non-aqueous electrolyte can ensure a flame retardance by containing 40 volume% or more of ionic liquids.

  In addition, the organic solvent constituting the non-aqueous electrolyte has a high ratio because the content ratio of the chain carbonates and the cyclic carbonates is in the range of 40 volume percent: 60 volume percent to 70 volume percent: 30 volume percent. It can be seen that this is preferable in terms of discharge characteristics.

  In the present embodiment, the description has been made by taking polyvinylidene fluoride as an example as the fluorine-containing resin material of the porous layer composited on the separator surface, but a polyvinylidene fluoride-hexafluoropropylene copolymer is used. However, the same effect can be obtained.

  In the present embodiment, EMI-TFSI has been described as an example of the ionic liquid, but the same effect can be obtained by using other ionic liquids.

It is sectional drawing of the nonaqueous electrolyte battery which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 11 Positive electrode mixture 12 Positive electrode collector 2 Negative electrode 21 Negative electrode mixture 22 Negative electrode collector 3 Separator 4 Electrode group 5 Metal resin composite film

Claims (1)

In a non-aqueous electrolyte battery including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, the non-aqueous electrolyte includes a lithium salt, an organic solvent, and an ionic liquid, and the separator includes a porous substrate and a fluorine-containing resin. A non-aqueous electrolyte battery characterized by being arranged.