JP5182462B2 - Non-aqueous electrolyte and battery equipped with the same - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte containing a room temperature molten salt among non-aqueous electrolytes and a battery including the same.

  In recent years, non-aqueous electrolyte batteries typified by lithium ion secondary batteries are frequently used as power supplies for electronic devices whose performance and size are becoming smaller. The non-aqueous electrolyte used for this is obtained by dissolving a lithium salt in an organic solvent. Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, Organic solvents such as γ-butyrolactone, propiolactone, valerolactone, tetrahydrofuran, dimethoxyethane, diethoxyethane, and methoxyethoxyethane are used. Since these organic solvents are generally volatile and flammable, they are classified as flammable substances.

  Recently, studies are being made to expand nonaqueous electrolyte batteries to large-scale applications such as power storage power supplies and electric vehicle power supplies. In such applications, since it is required to provide a non-aqueous electrolyte having flame retardancy or self-extinguishing properties, a non-aqueous electrolyte flame-retardant technology has attracted attention.

  As a technique related to a non-aqueous electrolyte having flame retardancy or self-extinguishing properties, there is a method of adding a flame retardant to a non-aqueous electrolyte. For example, Patent Documents 1 to 4 disclose techniques for adding phosphate esters which are high flash point solvents known as flame retardants for resin materials. For example, Patent Documents 5 to 6 disclose techniques for adding a phosphazene compound.

  However, phosphate esters need to be added in large amounts (for example, 20 to 40% by volume according to Patent Document 4) in order for the nonaqueous electrolyte to exhibit sufficient flame retardancy. When used in a battery, there is a problem that the battery characteristics are not sufficient. Moreover, since the phosphazene compound is difficult to mix and dissolve with other organic solvents and lithium salts constituting the non-aqueous electrolyte, there is a problem that the addition amount is limited.

  On the other hand, it has been proposed to use a room temperature molten salt that is liquid at room temperature as a nonaqueous electrolyte. The room temperature molten salt itself is liquid at room temperature but has substantially no volatility and is nonflammable or highly flame retardant (see Patent Documents 7 to 11).

  However, since the room temperature molten salt has a higher melting point and higher viscosity than a general non-aqueous electrolyte, the mobility of carrier ions such as lithium ions cannot be sufficiently high. There was a point. Therefore, a battery using a non-aqueous electrolyte made of a room temperature molten salt has a problem that high rate charge / discharge characteristics and low-temperature characteristics are not sufficient as compared with a battery using a general non-aqueous electrolyte.

  As a method for reducing the viscosity of the electrolyte and sufficiently increasing the mobility of carrier ions, the organic solvent used in a general non-aqueous electrolyte is mixed with a room temperature molten salt. Although the technique used is also examined (see Patent Document 10), since such organic solvents are classified as flammable substances as described above, they are non-flammable or self-extinguishing in large battery applications. In order to satisfy the requirement for providing a water electrolyte, there is a problem that such an organic solvent cannot be substantially contained.

Patent Document 11 discloses non-aqueous solvents such as γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-octanolactone, β-butyrolactone, δ-valerolactone, and ε-caprolactone for the purpose of ensuring safety. Although a technique for containing cyclic phosphazene in the nonaqueous electrolytic solution to be contained is disclosed in the column of the background art, the volume ratio of the phosphazene derivative to the total solvent of the electrolytic solution was as high as about 40% by volume. Since the phosphazene derivative has a relatively high viscosity and a low dielectric constant, there is a concern that the battery performance may be deteriorated due to a decrease in electrical conductivity when the phosphazene derivative is contained in the electrolytic solution at such a high blending amount. " Thus, even if phosphazene is contained in an electrolyte solution generally used for lithium batteries, improvement in high-rate discharge characteristics cannot be expected or deteriorated on the contrary. It was known.
Japanese Patent Laid-Open No. 7-114940 JP-A-8-88023 Japanese Patent Laid-Open No. 11-40193 JP 2001-307768 A JP-A-6-13108 Japanese Patent Laid-Open No. 11-191431 JP-A-4-349365 Japanese Patent Laid-Open No. 10-92467 JP 11-86905 A JP 11-260400 A JP 2006-24380 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 non-aqueous electrolyte that can be made into a battery excellent in high-rate discharge characteristics in a non-aqueous electrolyte having flame retardancy or self-extinguishing properties. One purpose. Another object of the present invention is to provide a battery having a high rate discharge characteristic in a battery provided with a non-aqueous electrolyte having flame retardancy or self-extinguishing properties.

（但し、Ｒ１、Ｒ３は、炭素数１〜６のアルキル基、Ｒ２、Ｒ４、Ｒ５は、水素原子又は炭素数１〜６のアルキル基のいずれかである）
（３）前記ホスファゼン化合物は、次の（化学式２）で示される環状型ホスファゼン化合物を含む上記（１）項又は（２）項に記載の非水電解液。

（但し、Ｒ１〜Ｒ６は一価の置換基又はハロゲン元素である）
（４）上記（１）項〜（３）項のいずれかに記載の非水電解液を備えた電池。
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.
(1) and 20 vol% to 80 vol% of the phosphazene compound, an organic material the balance being essentially of a room temperature molten salt containing a quaternary ammonium organic cation, ing contains a lithium salt, a non-aqueous electrolyte liquid.
(2) the quaternary ammonium organic cation is a non-aqueous electrolyte according to the above item (1) comprising imidazolium cation having a skeleton represented by the following (Formula 1).

(However, R1 and R3 are alkyl groups having 1 to 6 carbon atoms, and R2, R4, and R5 are either hydrogen atoms or alkyl groups having 1 to 6 carbon atoms.)
( 3 ) The non-aqueous electrolyte according to (1) or ( 2 ), wherein the phosphazene compound includes a cyclic phosphazene compound represented by the following (Chemical Formula 2).

(However, R1 to R6 are monovalent substituents or halogen elements)
( 4 ) A battery comprising the nonaqueous electrolytic solution according to any one of (1) to ( 3 ).

The normal temperature molten salt referred to in the present specification means a salt that is at least partially liquid 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, an 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 1 has a melting point of 300 ° C. or higher. However, it does not exhibit a liquid form within a temperature range in which an electrochemical device is normally assumed to operate, and is not included in the room temperature molten salt in the present invention. Further, a room temperature molten salt containing an aluminum halide ion (for example, AlCl ₄ ⁻ ) as an anion as described in Patent Document 7 is also known. However, aluminum halide is generally corrosive or highly reactive. Therefore, those containing aluminum halide ions are also excluded from the room temperature molten salt in the present invention, and an anion consisting only of a nonmetallic element is used in the room temperature molten salt in the present invention.

  According to the configuration of the present invention, it is characterized by room temperature molten salt having high incombustibility because it is liquid at room temperature but has substantially no volatility, and forms a flame retardant atmosphere by volatilization and decomposition by heat. Since both of the characteristics of the phosphazene compound having a high flame retarding effect can be utilized, a non-aqueous electrolyte solution that exhibits high flame retardancy over a wide temperature range can be obtained. In particular, in the present invention, by containing a phosphazene compound, even if it contains a large amount of a high-viscosity and high-melting-point room temperature molten salt, the characteristics of the low-viscosity phosphazene compound can be utilized. A non-aqueous electrolyte having low viscosity and high ionic conductivity can be provided. It should also be noted that phosphazene compounds are difficult to mix and dissolve with common organic solvents and lithium salts currently used in electrolytes for lithium batteries, so the solubility of lithium salts is poor and the amount of addition is low. Although limited, mixing with a lithium salt becomes relatively easy by mixing with a room temperature molten salt. As a result, the battery provided with the non-aqueous electrolyte of the present invention is a non-aqueous electrolyte battery that ensures high safety, has a high energy density, and is excellent in high rate charge / discharge characteristics and low temperature characteristics. can do.

  The room temperature molten salt in the present invention has a quaternary ammonium organic cation. Examples of the quaternary ammonium organic cation include imidazolium cation, tetraalkylammonium cation, pyridinium cation, pyrrolium cation, pyrazolium cation, pyrrolinium cation, pyrrolidinium cation, and piperidinium cation. Among these, an imidazolium cation having a skeleton represented by (Chemical Formula 1) is particularly preferable in that it easily forms a low-temperature room temperature molten salt.

  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 normal temperature molten salt which has these quaternary ammonium organic substance cations may be used independently, and may be used in mixture of 2 or more types.

  By using a room temperature molten salt having an imidazolium cation having a skeleton represented by (Chemical Formula 1) as the quaternary ammonium organic cation, a room temperature molten salt having a low melting point can be easily formed. It is preferable because sufficient mobility of carrier ions can be obtained.

  The nonaqueous electrolytic solution of the present invention contains a phosphazene compound as an organic compound. Examples of the phosphazene compound include, but are not limited to, a chain-type phosphazene compound having a skeleton represented by (Chemical Formula 3) and a cyclic phosphazene compound represented by (Chemical Formula 4). These may be used alone or in combination of two or more.

（但し、ｎ＝２〜１５である）

(However, n = 2 to 15)

（但し、ｎ＝２〜１５である）

(However, n = 2 to 15)

  R in the phosphazene derivative represented by (Chemical Formula 2) or (Chemical Formula 3) is not particularly limited as long as it is a monovalent substituent. Examples of the monovalent substituent include a hydrogen atom, a fluorine atom, a chlorine atom, and bromine. Halogen elements such as atoms, alkoxy groups such as methoxy groups, ethoxy groups, propoxy groups, butoxy groups, methoxyethoxy groups, methoxyethoxyethoxy groups, alkoxy groups having substituents, phenoxy groups, phenoxy groups having substituents, methyl groups Alkyl group such as ethyl group, propyl group, butyl group, pentyl group, carboxyl group, formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group and other acyl groups, phenyl group, tolyl group, naphthyl group And functional groups containing sulfur, phosphorus, nitrogen and the like. R may be all the same type of substituents, and some of them may be different types of substituents.

  The monovalent substituent further preferably contains a halogen element. As the number of substituents containing a halogen element in the molecular structure of the phosphazene derivative increases, a higher flame retarding effect can be obtained.

  In particular, by using a cyclic phosphazene compound having a skeleton represented by (Chemical Formula 2), the phosphazene compound itself has a low-viscosity and high flame-retarding effect, so that the above action can be effectively obtained. Therefore, it is preferable.

The anion contained in the room temperature molten salt electrolyte of the present invention is not particularly limited, but is 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, among which PF ₆ ⁻ , BF ₄ ⁻ , 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} ^- 1 kind selected from the group consisting of or to two or more Even when lithium salt, which is solid at room temperature, coexists with the room temperature molten salt, there is no risk of solidification of the non-aqueous electrolyte containing both, and the properties of room temperature molten salt that is liquid at room temperature are reliably retained. Therefore, the room temperature molten salt electrolyte containing the room temperature molten salt is preferable because it can maintain a liquid state satisfactorily. Especially, an organic electrolytic solution of the present ^{_{invention, N (CF 3 SO 2)}} 2 -, N (C 2 F 5 SO 2) 2 - or _{N (CF 3 SO 2) (} C 4 F 9 SO 2) - anion The inclusion as an essential component is particularly preferable because the degree of dissociation of the lithium salt is increased.

If further speaking, the organic anion having a perfluoroalkyl group, PF ₆ having no perfluoroalkyl groups ^- in the case of containing both anions is to realize both high flame retardancy expressing low melting point and low viscosity Can do. This is because two or more kinds of anions coexist, and therefore the arrangement of ions constituting the room temperature molten salt tends to be highly amorphous, so that the molecular level crystallization of the nonaqueous electrolyte is suppressed, and the carrier It is presumed that ion mobility can be kept high. It should be noted that an organic anion having a perfluoroalkyl group generally has a relatively base potential (for example, N (CF ₃ SO ₂ ) ₂ ⁻ is 3.8 V (vs. Li / Li) in the presence of an organic solvent. ⁺ )), A phenomenon that corrodes aluminum used in a positive electrode current collector of a nonaqueous electrolyte battery is known. However, an organic anion having a perfluoroalkyl group and PF ₆ having no perfluoroalkyl group are known. ^- by containing anions together is that such a phenomenon does not occur. As a result, it becomes easy to set the melting point and viscosity of the nonaqueous electrolyte lower, so that the electrochemical characteristics of the nonaqueous electrolyte can be made excellent, and the nonaqueous electrolyte battery according to the present invention has high safety. It is possible to obtain a non-aqueous electrolyte battery that secures high performance, has high energy density, and is excellent in high rate charge / discharge characteristics and low temperature characteristics.

  When two or more kinds of anions are contained, a room temperature molten salt having two or more different anions and a lithium salt composed of one kind of anions may be mixed, and two or more different lithium salts and one anion may be mixed. A room temperature molten salt composed of the following may be mixed, and further, a room temperature molten salt having a different anion species and a lithium salt may be mixed.

  The “organic material containing a phosphazene compound and a room temperature molten salt containing a quaternary ammonium organic cation” constituting the non-aqueous electrolyte of the present invention is an ethylene used in a general lithium ion secondary battery. Those containing a large amount of flammable organic solvents such as carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, propiolactone, valerolactone, dimethoxyethane, diethoxyethane, methoxyethoxyethane, etc. It is preferable from the viewpoint that the non-aqueous electrolyte is flame retardant or self-extinguishing, but the non-aqueous electrolyte is flame retardant. Inflammable organic solvents as long as they are self-extinguishing or self-extinguishing It may contain.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous electrolyte which can be set as the battery excellent in the high rate discharge characteristic can be provided. Moreover, the battery excellent in the high rate discharge characteristic can be provided.

  The method for producing the nonaqueous electrolytic solution of the present invention is not limited in any way. For example, it can be obtained by mixing a phosphazene compound, a room temperature molten salt containing a quaternary ammonium organic cation, and a lithium salt. Can do.

  The non-aqueous electrolyte of the present invention preferably contains lithium cations at a concentration of 0.5 mol / l or more, and by containing lithium cations at a concentration of 0.5 mol / l or more, Since two or more types of quaternary ammonium cations having greatly different ion sizes coexist, the arrangement of ions constituting the room temperature molten salt tends to be highly amorphous. It is estimated that crystallization can be suppressed and the mobility of carrier ions in the nonaqueous electrolytic solution can be kept high.

  The mixing ratio of the room temperature molten salt and the phosphazene compound is not limited, but in view of the electrochemical characteristics of the nonaqueous electrolyte, in particular, in order to contain lithium cations at a concentration of 0.5 mol / l or more, It is desirable to contain the room temperature molten salt in the range of 20 volume percent to 80 volume percent.

  In addition, from the viewpoint of providing a non-aqueous electrolyte capable of reliably improving high rate discharge characteristics, a phosphazene compound and a phosphazene compound constituting an organic material containing a quaternary ammonium organic cation and a normal temperature melting The mixing ratio with the salt is preferably 20 volume percent or more and 80 volume percent or less, and more preferably 25 volume percent or more and 80 volume percent or less, with respect to the volume of the phosphazene compound and the room temperature molten salt. Furthermore, 50 volume% or more and 80 volume percent or less are especially preferable.

  In addition, the non-aqueous electrolyte of the present invention may be used by solidifying it into a gel by combining a polymer in addition to the organic material and the lithium salt. Here, examples of the polymer include, for example, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, various acrylic monomers, methacrylic monomers, acrylamide monomers, allyl monomers, and styrene monomers. Examples include, but are not limited to, polymers. These may be used alone or in combination of two or more.

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

(Invention electrolyte 1)
0.2 liter of 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (BMITSI) and 0.8 liter of a phosphazene compound (hereinafter referred to as phosphazene (I)) represented by (Chemical Formula 5) are mixed. Furthermore, 1 mol of LiN (CF ₃ SO ₂ ) ₂ (LiTFSI) was mixed to obtain a non-aqueous electrolyte.

(Invention electrolyte 2)
A nonaqueous electrolytic solution was obtained by mixing 0.25 liter of BMITFSI and 0.75 liter of phosphazene (I), and further mixing 1 mol of LiTFSI.

(Invention electrolyte 3)
A nonaqueous electrolytic solution was obtained by mixing 0.5 liters of BMITFSI and 0.5 liters of phosphazene (I), and further mixing 1 mol of LiTFSI.

(Invention Electrolyte 4)
A non-aqueous electrolyte was obtained by mixing 0.75 liter of BMITFSI and 0.25 liter of phosphazene (I), and further mixing 1 mol of LiTFSI.

(Invention electrolyte 5)
BMITFSI 0.8 liter and phosphazene (I) 0.2 liter were mixed, and 1 mol of LiTFSI was further mixed to obtain a nonaqueous electrolytic solution.

(Invention electrolyte 6)
By mixing 0.5 liter of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF ₄ ) and 0.5 liter of phosphazene (I), and further mixing 1 mol of LiTFSI, a non-aqueous electrolyte is obtained. It was.

(Invention electrolyte 7)
By mixing 0.5 liter of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF ₆ ) and 0.5 liter of phosphazene (I), and further mixing 1 mol of LiTFSI, a non-aqueous electrolyte is obtained. It was.

(Invention Electrolyte 8)
A nonaqueous electrolytic solution was obtained by mixing 0.5 liters of BMITFSI and 0.5 liters of phosphazene (I), and further mixing 1 mol of LiN (C ₂ F ₅ SO ₂ ) ₂ (LiBETI).

(Invention Electrolyte 9)
A nonaqueous electrolytic solution was obtained by mixing 0.5 liters of BMITFSI and 0.5 liters of a phosphazene compound represented by (Chemical Formula 6) (hereinafter referred to as phosphazene (II)) and further mixing 1 mol of LiTFSI. .

(Comparative electrolyte 1)
By mixing 1 mol of LiTFSI with 1 liter of BMITFSI, a non-aqueous electrolyte was obtained.

(Comparative electrolyte 2)
A nonaqueous electrolytic solution was obtained by mixing 1 mol of LiPF ₆ with 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1.

(Reference Example 1)
Although 1 mol of LiTFSI was added to 1 liter of phosphazene (I) and mixed, a part of LiTFSI was not dissolved but was visually observed as a solid.

(Reference Example 2)
0.5 liter of phosphazene (I) was mixed with 0.5 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 and 1 mol of LiPF ₆ and mixed. It was not compatible.

(Reference Example 3)
1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF ₆ ) 0.5 liter and phosphazene (I) 0.5 liter were mixed, and 1 mol of LiPF ₆ was added and mixed. ₆ was observed as a solid without dissolving.

(Reference Example 4)
When 1 mol of LiPF ₆ was added to and mixed with 1.0 liter of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF ₆ ), LiPF ₆ was apparently completely dissolved.

(Electrolyte flammability test)
A flammability test was performed for each of the above-described electrolytic solutions 1 to 9 and comparative electrolytic solutions 1 and 2 described above. A glass filter (GB-100R manufactured by Toyo Roshi Kaisha, Ltd.) cut to a width of 20 mm and a length of 65 mm is impregnated with about 2 ml of each electrolyte, and installed so that the distance from the upper end of the alcohol lamp core to the lower end of the glass filter is 10 cm. Then, the presence of ignition / combustion was confirmed by bringing the fire of the alcohol lamp closer to 10 seconds.

(Production of battery)
Batteries were produced using the above-described electrolytic solutions 1 to 9 and comparative electrolytic solutions 1 and 2, respectively, to make the inventive batteries 1 to 9 and comparative batteries 1 and 2. A cross-sectional view of the produced battery is shown in FIG. The produced battery is composed of a pole group 4 composed of 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 non-aqueous electrolyte is impregnated in the electrode 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 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 an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride is further 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, Li ₄ Ti ₅ O ₁₂ that is a negative electrode active material and acetylene black that is a conductive agent are mixed, and an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride is further mixed as a binder. After apply | coating to the single side | surface of the negative electrode collector 22 which consists of foil, it dried and pressed so that the negative mix 21 thickness might become predetermined thickness. The negative electrode 2 was obtained by the above process. As the separator 3, a cellulose separator was used. 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 nonaqueous electrolyte solution by immersing the electrode group 4 in the nonaqueous electrolyte solution. Furthermore, the pole group 4 was covered with the metal resin composite film 5, and the four sides were sealed by heat welding.

  Next, it used for the initial stage charge / discharge process. That is, at a temperature of 20 ° C., a constant current charge with a current of 1 mA and a final voltage of 4.2 V and a constant current discharge with a current of 1 mA and a final voltage of 3.0 V were performed. The discharge capacity at this time was defined as the initial discharge capacity. Thus, Invention batteries 1 to 9 and comparative batteries 1 and 2 having a design capacity of 10 mAh were produced.

(High rate discharge test)
The inventive batteries 1 to 9 and comparative batteries 1 and 2 produced as described above were subjected to a high rate discharge test. After charging under the same conditions as in the initial charge / discharge step at 20 ° C., constant current discharge with a current of 5 mA and a final voltage of 3.0 V was performed. The obtained discharge capacity was defined as a high rate discharge capacity.

  The above results are summarized in Table 1. Here, as for the combustion test results, those where combustion was not recognized 10 seconds after the fire of the alcohol lamp was approached were indicated by ◎, and those where combustion was recognized were indicated by ×.

  As is clear from Table 1, the comparative battery 2 provided with the comparative electrolyte 2 which is a general non-aqueous electrolyte has good initial discharge capacity and high rate discharge capacity, but the electrolyte has combustibility. Therefore, it is impossible to satisfy the precondition that the battery includes a non-aqueous electrolyte having flame retardancy or self-extinguishing properties. On the other hand, the comparative electrolytic solution 1 which is a conventional room temperature molten salt electrolyte exhibits flame retardancy, but the comparative battery 1 having the comparative electrolytic solution 1 is greatly inferior in initial discharge capacity and high rate discharge capacity.

  On the other hand, the present invention batteries 1 to 9 equipped with the non-aqueous electrolyte of the present invention have not only the electrolyte exhibiting flame retardancy but also the comparative electrolyte 1 which is a conventional room temperature molten salt electrolyte. Compared with the comparative battery 1 provided, both the initial discharge capacity and the high rate discharge capacity are excellent. From this, it can be seen that by using the non-aqueous electrolyte of the present invention, a battery having excellent high rate discharge characteristics can be provided.

  Especially, since the high rate discharge characteristic of the battery 3 of the present invention is remarkably superior to the high rate discharge characteristic of the battery 9 of the present invention, the non-aqueous electrolyte of the present invention is represented by (Chemical Formula 2) as a phosphazene compound. It turns out that the high-rate discharge characteristic of the battery provided with this can be made more excellent by containing a cyclic type phosphazene compound.

  Moreover, since the high rate discharge characteristics of the batteries 1 to 4 of the present invention are remarkably superior to the high rate discharge characteristics of the battery 5 of the present invention, the nonaqueous electrolytic solution of the present invention includes a room temperature molten salt and a phosphazene compound. It can be seen that when the organic material contains 25% by volume or more and 80% by volume or less of the phosphazene compound, the high rate discharge characteristics of the battery including the compound can be further improved.

  In addition, since the high rate discharge characteristics of the batteries 1 to 3 of the present invention are further superior to the high rate discharge characteristics of the battery 4 of the present invention, the non-aqueous electrolyte of the present invention is an organic containing a room temperature molten salt and a phosphazene compound. It can be seen that when the material contains 50% by volume or more and 80% by volume or less of the phosphazene compound, the high rate discharge characteristics of a battery including the compound can be further improved.

As it can be seen from the findings of Reference Example 3, a non-aqueous electrolyte solution of the present invention to the organic material component comprising an ambient temperature molten salt and a phosphazene _{compound, N (CF 3 SO 2)} 2 -, N (C 2 F ₅ SO _{2) 2} ^- or _{N (CF 3 SO 2) (} C 4 F 9 SO 2) - by as including anion, it is understood that it is possible to present more lithium cations. Therefore, it goes without saying that the performance of a battery equipped with this is excellent. Furthermore, as is apparent Looking combined knowledge of Reference Example 4, in the present ^{_{invention, N (CF 3 SO 2)}} 2 -, N (C 2 F 5 SO 2) 2 - or _N (CF 3 _SO 2) _{(C 4 F 9 SO 2)} - effect of be those containing anions constituting the nonaqueous electrolytic solution of the present invention is characterized in that the organic material consisting including ambient temperature molten salt and a phosphazene compound as component It can be seen that it is not recognized in the structure of an electrolyte composed of a room temperature molten salt containing no phosphazene compound. In addition, the non-aqueous electrolyte of Reference Example 3 is according to the present invention.

In this example, PF ₆ ⁻ , BF ₄ ⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , and N (C ₂ F ₅ SO ₂ ) ₂ ⁻ are used as anions constituting the lithium salt and the room temperature molten salt. has been described as an _{example, N (CF 3 SO 2)} (C 4 F 9 SO 2) - the same effect can be obtained by using.

  In this example, an imidazolium cation was used as an example of the quaternary ammonium organic cation. However, other quaternary ammonium organic cations (tetraalkyl ammonium cation, pyridinium cation, pyrrolium cation, pyrazolium cation) , Pyrrolinium cation, pyrrolidinium cation, piperidinium cation, etc.) can be used to obtain the same effect.

  According to the present invention, a non-aqueous solution that ensures high safety obtained by using a room temperature molten salt for a non-aqueous electrolyte, has a high energy density, and is excellent in high rate charge / discharge characteristics and low temperature characteristics. Since an electrolyte battery can be provided, the applicability to a non-aqueous electrolyte battery used for relatively large applications such as a power storage power source and an electric vehicle power source is great.

It is sectional drawing of the nonaqueous electrolyte battery which concerns on an Example.

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 (4)

And 20 vol% to 80 vol% of the phosphazene compound, an organic material the balance being essentially of a room temperature molten salt containing a quaternary ammonium organic cation, ing contains a lithium salt, a non-aqueous electrolyte solution. The quaternary ammonium organic cation is a non-aqueous electrolyte according to claim 1 comprising an imidazolium cation having a skeleton represented by the following (Formula 1).

(However, R1 and R3 are alkyl groups having 1 to 6 carbon atoms, and R2, R4, and R5 are either hydrogen atoms or alkyl groups having 1 to 6 carbon atoms.) The phosphazene compound, a non-aqueous electrolyte according to claim 1 or 2, wherein a cyclic type phosphazene compound represented by the following (Formula 2).

(However, R1 to R6 are monovalent substituents or halogen elements) Battery comprising the nonaqueous electrolytic solution according to any one of claims 1-3.

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