JP2009266438A - Non-aqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte battery in which a non-aqueous electrolyte and a separator have fire retardancy and these are compatible with high-rate discharge characteristics excellently. <P>SOLUTION: The non-aqueous electrolyte battery uses a separator made of polyimide and uses a non-aqueous electrolyte containing fluorinated aliphatic carbonate. When polyimide separator is used, by using the non-aqueous electrolyte containing fluorinated aliphatic carbonate, the rate of improvement of the high-rate discharge characteristics becomes about 30%. This is a remarkable difference compared with the case in which the rate of improvement stays at about 3% when a polyethylene separator is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte battery, and more particularly to improvement of a separator and a non-aqueous electrolyte of a non-aqueous electrolyte battery.

Currently, nonaqueous electrolyte batteries represented by lithium ion secondary batteries are widely used as power sources for portable devices such as mobile phones, PHS (simple mobile phones), and small computers. LiCoO ₂ is mainly used as a positive electrode active material constituting such a lithium ion secondary battery, graphite is mainly used as a negative electrode active material, and an electrolyte such as LiPF ₆ is mainly used as a nonaqueous electrolyte such as ethylene carbonate. Those dissolved in a non-aqueous solvent as a main constituent are used.

Lithium ion secondary batteries using a positive electrode containing LiCoO ₂ may cause thermal runaway when the temperature reaches approximately 150 ° C. Therefore, in such a case, avoid the battery from falling into a dangerous state. For this reason, the separator is required to have a so-called shutdown function that closes the hole in the event of an abnormality to cut off the current and prevent the battery from being heated and ignited. That is, it is easy to shrink at high temperature, and when the battery becomes hot, the current interruption effect is surely expressed, and from the viewpoint of improving the safety of the battery, polyolefins are adopted as the material of the separator, In order to exhibit a shutdown function at an appropriate temperature, a polyethylene-based material is used.

  In Patent Documents 1 to 4, a phosphate compound that is a high flash point solvent known as a flame retardant for resin materials is added in order to realize a non-aqueous electrolyte having flame retardancy or self-extinguishing properties. Technology has been proposed. Further, a technique for adding a carbonate compound containing a halogen such as a fluorinated alkyl group has been studied and proposed. For example, Patent Document 5 discloses a technique using a halogenated chain carbonate, particularly a fluorinated chain carbonate, and Patent Document 6 discloses a technique using a halogenated cyclic carbonate, particularly a fluorinated cyclic carbonate. ing. Among these compounds, fluorine-containing compounds are said to have excellent electrochemical stability and high flash point properties.

  However, in order for these already proposed nonaqueous electrolytes to exhibit sufficient flame retardancy, it is necessary to add such a compound in a large amount (for example, 20 to 40 vol% according to Patent Document 4). Therefore, there is a problem that sufficient battery characteristics such as high rate discharge characteristics cannot be obtained. Also, depending on the type of compound, the solubility of the lithium salt constituting the non-aqueous electrolyte or the compatibility with other organic solvents is low, and a large amount cannot be added, so that the non-aqueous electrolyte cannot exhibit sufficient flame retardancy. There was a problem. Furthermore, these compounds have a problem that they are very expensive compared to organic solvents constituting general non-aqueous electrolytes, and it is not practical to use them in large quantities as a main solvent. .

  Patent Document 7 proposes a polyimide porous membrane as a separator that can be used in a nonaqueous electrolyte battery. However, since the polyimide porous membrane cannot be expected to have the shutdown effect, a general-purpose lithium ion secondary battery is proposed. Has not been adopted.

On the other hand, in recent years, studies have been actively conducted to apply nonaqueous electrolyte batteries as relatively large industrial batteries such as power storage power supplies and electric vehicle power supplies. For such batteries, not only high energy density characteristics but also safety is important, and it is required to be a “non-burning battery”. Therefore, phosphoric acid with extremely high thermal stability as a positive electrode active material. A polyanion-type positive electrode material typified by iron lithium is adopted, and a non-aqueous electrolyte material or a separator material is required to use a material having flame retardancy or self-extinguishing properties.
Japanese Patent Laid-Open No. 7-114940 JP-A-8-88023 Japanese Patent Laid-Open No. 11-40193 JP 2001-307768 A Japanese Patent Laid-Open No. 7-6786 Japanese Patent Laid-Open No. 10-247519 JP 2003-138057 A

  An object of the present invention is to provide a non-aqueous electrolyte battery in which the non-aqueous electrolyte and the separator have flame retardancy and have good high rate discharge characteristics.

  According to the knowledge of the present inventors, when a polyimide separator is used for a non-aqueous electrolyte battery, the separator film thickness, porosity, and air permeability are lower than when a polyolefin separator is used. In spite of the same characteristics, there is a problem that the high rate discharge characteristics tend to be low.

  In order to solve the above-mentioned problems, the present inventors have surprisingly made use of a separator containing polyimide and a non-aqueous electrolyte containing a fluorinated carbonate compound as a result of intensive studies. The present inventors have found that a nonaqueous electrolyte battery having not only flame retardancy but also good high rate discharge characteristics can be obtained. That is, the technical configuration and operational effects of the present invention are as follows. However, the action mechanism includes estimation, and the correctness does not limit the present invention.

  The present invention is a non-aqueous electrolyte battery comprising a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte, wherein the separator contains a polyimide, and the non-aqueous electrolyte contains a fluorinated carbonate compound. It is a nonaqueous electrolyte battery.

  According to such a configuration, by containing the above-mentioned fluorinated carbonate compound in the non-aqueous electrolyte, the flash point of the non-aqueous electrolyte rises or disappears, and the non-aqueous electrolyte has flame retardancy or self-extinguishing properties. As shown. Furthermore, by using a separator containing polyimide, not only thermal decomposition is suppressed by its high thermal stability, but also pyrolysis gas exhibits flame retardancy even when pyrolysis is performed at a higher temperature. Therefore, since it is a combination of an electrolyte exhibiting self-extinguishing properties or flame retardancy and a separator, a nonaqueous electrolyte battery having excellent flame retardancy in a wide temperature range and excellent in safety can be obtained. Furthermore, it should be noted that the combination of the non-aqueous electrolyte and the separator described above also includes a relatively large amount of the chain carbonate compound so that the non-aqueous electrolyte exhibits sufficient flame retardancy. Thus, a nonaqueous electrolyte battery having good high rate discharge characteristics can be constructed. Therefore, it is possible to provide a non-aqueous electrolyte battery that can achieve both flame retardancy and good high-rate discharge characteristics.

  The nonaqueous electrolyte battery of the present invention is characterized in that the content of the fluorinated carbonate compound is 5% by weight or more based on the total weight of the nonaqueous electrolyte.

  According to such a configuration, the content of the chain carbonate compound is 5% by weight or more with respect to the total weight of the nonaqueous electrolyte, so that the nonaqueous electrolyte battery has flame retardancy and a good high rate. It is possible to reliably achieve both discharge characteristics.

  The nonaqueous electrolyte battery of the present invention is characterized by containing a lithium-containing polyanion metal composite compound.

  According to such a configuration, since the lithium-containing polyanion metal composite compound has excellent thermal stability and does not decompose and release oxygen even at high temperatures, it can be used as a positive electrode active material for a nonaqueous electrolyte battery. In addition, the safety of the nonaqueous electrolyte battery that has both non-flammable electrolyte and separator and flame retardancy and good high-rate discharge characteristics can be dramatically improved.

  According to the present invention, it is possible to provide a non-aqueous electrolyte battery in which the non-aqueous electrolyte and the separator are flame retardant and have both good high rate discharge characteristics.

  Embodiments of the present invention are illustrated below, but the present invention is not limited to these descriptions.

  A nonaqueous electrolyte battery according to the present invention includes a positive electrode having a positive electrode active material as a main constituent, a negative electrode having a negative electrode active material as a main constituent, and a separator containing polyimide provided between the positive electrode and the negative electrode. And a non-aqueous electrolyte containing at least a lithium salt and a fluorinated carbonate compound.

Examples of the fluorinated carbonate compound include fluorinated cyclic carbonate compounds and fluorinated chain carbonate compounds. Here, a fluorinated cyclic carbonate compound may be used. However, if a fluorinated chain carbonate compound is selected, the influence of a drop in boiling point on a carbonate ester having the same structure that is not fluorinated can be reduced. From the viewpoint of Examples of the fluorinated chain carbonate include those represented by Chemical Formula 1.
(W and z are each an integer of 1 to 3, x and y are each an integer of 0 to 2, and n and m are integers of 0 to 7, respectively.)

  Here, although a fluorine atom may be bonded to the carbon atom adjacent to the ester structure portion, it cannot be said that the synthesis is easy. Further, either one of w and z may be 0, but such a thing cannot be said to be easy to synthesize. Therefore, the fluorinated chain carbonate compound having the structure exemplified in Chemical Formula 1 is preferable.

  Examples of the fluorinated chain carbonate compound represented by Chemical Formula 1 include di (1,1,1-trifluoroethyl) carbonate, (1,1,1-trifluoroethyl) methyl carbonate, and di (1,1 -Difluoroethyl) carbonate, di (1,1,2,2-tetrafluoropropyl) carbonate, di (1,1,2,2,3,3, -hexafluorobutyl) carbonate, di (1H, 1H, 5H -Octafluoropentyl) carbonate, di (1H, 1H, 7H-dodecafluoroheptyl) carbonate, di (1H, 1H, 3H, 7H-perfluoroheptyl) carbonate, di (1H, 1H, 9H-hexadecafluoro Nonyl) carbonate and the like alone or a mixture of two or more thereof may be mentioned, but are not limited thereto. . Among them, in the present invention, di (1,1,1-trifluoroethyl) carbonate, (1,1,1-trifluoroethyl) methyl carbonate, di (1,1-difluoroethyl) carbonate, di (1, Particularly preferred is at least one selected from 1,2,2-tetrafluoropropyl) carbonate.

  In addition, the content of the fluorinated carbonate compound in the present invention is preferably 5% by weight or more based on the total weight of the nonaqueous electrolyte, and can particularly achieve both excellent flame retardancy and high rate discharge characteristics. In order to obtain a water electrolyte, it is more preferably 10 wt% or more and 50 wt% or less.

  As the organic solvent constituting the nonaqueous electrolyte, in addition to the fluorinated carbonate compound, an organic solvent generally used for a nonaqueous electrolyte for a nonaqueous electrolyte battery can be used. For example, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate; cyclic esters such as γ-butyrolactone, γ-valerolactone, propiolactone; dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, diphenyl carbonate, etc. Chain carbonates; chain esters such as methyl acetate and methyl butyrate; ethers such as tetrahydrofuran or derivatives thereof, 1,3-dioxane, dimethoxyethane, diethoxyethane, methoxyethoxyethane, methyldiglyme; acetonitrile, benzonitrile, etc. Nitriles of dioxalane or derivatives thereof alone or a mixture of two or more thereof, but not limited thereto.

  In addition, in this invention, since the effect of this invention can fully be exhibited by containing the cyclic carbonate which has a carbon-carbon double bond in a nonaqueous electrolyte, Especially, vinylene carbonate, styrene carbonate, catechol carbonate It is preferable to contain at least one selected from vinylethylene carbonate, 1-phenyl vinylene carbonate, and 1,2-diphenyl vinylene carbonate. These may be used singly or in combination of two or more, but it is particularly preferable to contain at least vinylene carbonate.

  The content of the cyclic carbonate having a carbon-carbon double bond is preferably 0.01% by weight to 10% by weight, more preferably 0.10% by weight to 5% by weight with respect to the total weight of the nonaqueous electrolyte. %, More preferably 0.10 wt% to 2 wt%. When the content of the cyclic carbonate having a carbon-carbon double bond is 0.01% by weight or more based on the total weight of the nonaqueous electrolyte, other organic solvents constituting the nonaqueous electrolyte at the time of initial charge Disassembly can be suppressed almost completely, and charging can be performed more reliably. Further, when the content is 10% by weight or less, deterioration of battery performance due to decomposition of the cyclic carbonate having a carbon-carbon double bond on the positive electrode hardly occurs, and sufficient battery performance can be exhibited.

As the lithium salt constituting the non-aqueous electrolyte, a lithium salt that is stable in a wide potential region generally used for a non-aqueous electrolyte battery can be used. For example, LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) _{3 and the} like, but are not limited thereto. These may be used alone or in combination of two or more.

  The concentration of the electrolyte salt in the non-aqueous electrolyte is preferably 0.1 mol / l to 5 mol / l, more preferably 1 mol / l to obtain a non-aqueous electrolyte battery having excellent high rate discharge characteristics. 2.5 mol / l.

  As a separator containing a polyimide used for the battery of the present invention, a separator containing another polymer component together with a polyimide component can be used, but a higher ratio of the polyimide component is preferable from the viewpoint of the effect of the present invention. Specifically, the ratio of the polyimide component is preferably 60% or more, more preferably 75% or more, still more preferably 90% or more, and most preferably 100%. For example, a microporous film made of polyimide resin is preferable. As a form of the separator, a woven fabric or a non-woven fabric may be used in addition to the microporous membrane. Moreover, the separator which bonded together the microporous film made from a polyimide, and the microporous film made from polyolefin which has polyethylene as a main component may be used, and such a thing can be used for the battery use as which a shutdown function is calculated | required. However, in battery applications that do not require a shutdown function, such as when using a positive electrode that contains a lithium-containing polyanion metal composite compound, the ratio of the polyimide component is reduced. In view of the effects of the present invention, it is preferable not to use a separator to which a microporous film is bonded. A microporous film made of a polymer alloy containing a polyimide component, a woven fabric, or a non-woven fabric may be used. However, since a polyimide resin has a high softening point, blending with other polymer components is not always easy. The polyimide in the present invention is preferably an aromatic polyimide.

  The porosity of the non-aqueous electrolyte battery separator is preferably 98% by volume or less from the viewpoint of strength. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge / discharge characteristics.

  The average pore diameter of the separator is 0.01 μm to 5 μm because it is preferably small enough to prevent short-circuiting between the electrodes and large so that the electrical resistance between the positive electrode and the negative electrode does not become too high. It is preferable. When the average pore diameter exceeds 5 μm, micro short-circuiting is likely to occur due to contact between the positive electrode active material fine particles and the negative electrode active material fine particles. Tends to decrease. Thus, in order to avoid a minute short circuit, the average pore diameter of the separator is preferably 0.01 μm to 5 μm, more preferably 0.01 μm to 1 μm, and still more preferably 0.05 μm to 0.1 μm. .

  As the separator, a sheet-like porous substrate having a thickness of 30 μm or less can be suitably used, and the air permeability from the front surface to the back surface of the sheet-like porous substrate is preferably 20 seconds / 100 ml to 500 seconds / 100 ml, It is preferably 40 seconds / 100 ml to 200 seconds / 100 ml, more preferably 50 seconds / 100 ml to 150 seconds / 100 ml. When the air permeability is less than 20 seconds / 100 ml, a micro short-circuit is likely to occur due to contact between the positive electrode active material fine particles and the negative electrode active material fine particles. As a result, battery characteristics tend to deteriorate.

  As the shape of the separator for a nonaqueous electrolyte battery in the present invention, it is preferable to use a microporous membrane, a nonwoven fabric, a woven fabric or the like alone or in combination.

The positive electrode active material that can be used for the positive electrode included in the nonaqueous electrolyte battery according to the present invention is not limited, but can significantly improve the safety of the battery. The compound is preferably a main constituent component, for example, LiFePO ₄ , LiCoPO ₄ , LiVOPO ₄ , LiVPO ₄ F, LiMnPO ₄ , LiMn _x Fe _1-x PO ₄ , LiNiVO ₄ , LiCoVO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , LiFeP ₂ O ₇ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Li ₂ CoSiO ₄ , Li ₂ MnSiO ₄ , Li ₂ FeSiO ₄ , LiTePO _4, etc.). These may be used alone or in combination of two or more. Various oxides and sulfides can be used for these lithium-containing polyanion metal composite compounds. For example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (eg, Li _x NiO ₂ ) , Lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel cobalt composite oxide (for example, LiNi _1-y Co _y O ₂ ), lithium nickel cobalt manganese composite oxide (LiNi _x Co _y Mn _1-yz O) _2), spinel type lithium-manganese-nickel composite oxide _{(Li x Mn 2-y Ni} y O 4), iron sulfate _{(Fe 2 (SO 4),} and the like 3), vanadium oxide (e.g. _V 2 _{O 5)} . Further, conductive polymer materials such as polyaniline and polypyrrole, disulfide-based polymer materials, organic materials such as sulfur (S) and carbon fluoride, and inorganic materials are also included. These may be used alone or in combination of two or more.

  Hereinafter, although the further detail of this invention is demonstrated by an Example, this invention is not limited to these description.

(Invention battery)
A cross-sectional view of a nonaqueous electrolyte battery in the battery of the present invention is shown in FIG.

  The lithium battery in the present invention includes a pole group 4 including a positive electrode 1, a negative electrode 2, and a separator 3, a nonaqueous electrolyte, and a metal resin composite film 5. 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 battery having the above configuration will be described.

The positive electrode 1 was obtained as follows. A positive electrode current collector made of an aluminum foil made of a paste containing LiFePO _{4 as a} positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder, and using N-methyl-2-pyrrolidone as a solvent. After apply | coating to the single side | surface of the body 12, it dried and pressed so that the thickness of the positive mix 11 might be set to 0.1 mm. The positive electrode 1 was obtained by the above process.

  Moreover, the negative electrode 2 was obtained as follows. After applying a paste containing negative electrode active material graphite and polyvinylidene fluoride as binder and using N-methyl-2-pyrrolidone as a solvent to one side of negative electrode current collector 22 made of copper foil, It dried and pressed so that the negative mix 21 thickness might be set to 0.1 mm. The negative electrode 2 was obtained by the above process.

  As the separator 3, a polyimide microporous film (thickness: 25 μm, porosity: 50%) 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.

The non-aqueous electrolyte was mixed with 1 liter of a mixed solvent (specific gravity 1.258) in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1, and di (1,2) as a fluorinated carbonate compound with respect to the mixed solvent. It was obtained by mixing 3% by weight of 1,1-trifluoroethyl) carbonate and 2% by weight of vinylene carbonate and further dissolving 1 mol of LiPF ₆ . This is designated as electrolyte a1.

  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.

  The nonaqueous electrolyte battery obtained by the above production method is referred to as the present invention battery A1. The design capacity of the battery A1 of the present invention is 10 mAh.

As a non-aqueous electrolyte, 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1, and di (1,1,1-trifluoro) as a fluorinated carbonate compound with respect to the mixed solvent. Except for using 5% by weight of ethyl) carbonate and 2% by weight of vinylene carbonate and further dissolving 1 mol of LiPF ₆ (electrolyte a2), the same raw materials and production method as in the present invention battery A1, A non-aqueous electrolyte battery having a capacity of 10 mAh was produced and designated as a battery A2 of the present invention.

As a non-aqueous electrolyte, 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1, and di (1,1,1-trifluoro) as a fluorinated carbonate compound with respect to the mixed solvent. Ethyl) 20% by weight of carbonate, 2% by weight of vinylene carbonate, and 1 mol of LiPF ₆ dissolved (electrolyte a3) were used, except for using the same raw materials and production method as in the present invention battery A1, A non-aqueous electrolyte battery having a capacity of 10 mAh was produced and designated as a battery A3 of the present invention.

As a non-aqueous electrolyte, 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1, and di (1,1,1-trifluoro) as a fluorinated carbonate compound with respect to the mixed solvent. Except for using 50% by weight of ethyl) carbonate and 2% by weight of vinylene carbonate and further dissolving 1 mol of LiPF ₆ (electrolyte a4), the same raw materials and production method as in the present invention battery A1, A non-aqueous electrolyte battery having a design capacity of 10 mAh was produced and designated as the present invention battery A4.

As a non-aqueous electrolyte, 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was further mixed with (1,1,1-trifluoroethyl) as a fluorinated carbonate compound with respect to the mixed solvent. ) Except for using 20 wt% methyl carbonate, 2 wt% vinylene carbonate, and further dissolving 1 mol of LiPF ₆ (electrolyte b), the same raw materials and production method as in the present invention battery A1, A non-aqueous electrolyte battery having a design capacity of 10 mAh was produced and designated as a battery B of the present invention.

As a non-aqueous electrolyte, 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1, and di (1,1-difluoroethyl) carbonate as a fluorinated carbonate compound with respect to the mixed solvent. 20% by weight, vinylene carbonate 2% by weight, and 1 mol of LiPF ₆ dissolved (electrolyte c) was used. A non-aqueous electrolyte battery was produced and designated as the battery C of the present invention.

As a nonaqueous electrolyte, 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was further mixed with di (1,1,2,2-) as a fluorinated carbonate compound with respect to the mixed solvent. Tetrafluoropropyl) carbonate 20 wt%, vinylene carbonate 2 wt% mixed, and 1 mol of LiPF ₆ dissolved (electrolyte d) was used, except for using the same raw material and manufacturing method as the present invention battery A1 Thus, a non-aqueous electrolyte battery having a design capacity of 10 mAh was produced, and this battery D was obtained.

(Comparison battery)
As a non-aqueous electrolyte containing no fluorinated carbonate compound, 2% by weight of vinylene carbonate was mixed with 1 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 was} further mixed. A non-aqueous electrolyte battery having a design capacity of 10 mAh was produced as a comparative battery E using the same raw materials and production method as in the battery A1 of the present invention, except that a solution in which the electrolyte was dissolved (electrolyte e) was used.

  A non-aqueous electrolyte battery with a design capacity of 10 mAh was produced by the same raw material and production method as the battery A3 of the present invention, except that a polyethylene microporous membrane (thickness 25 μm, porosity 50%) was used as a separator. A comparative battery F was obtained.

  A non-aqueous electrolyte battery having a design capacity of 10 mAh was produced as a comparative battery G using the same raw materials and manufacturing method as those of the comparative battery F except that the electrolyte e was used as the non-aqueous electrolyte.

(Electrolytic salt flammability test)
First, an electrolyte flammability test was performed on the nonaqueous electrolytes (electrolytes a1 to a4 and be). 5 ml of each electrolyte was taken on a watch glass, and the presence of ignition / combustion was confirmed by bringing the fire of an alcohol lamp closer to 10 seconds. The results are shown in Table 1. As shown in Table 1, the electrolyte e used for the comparative batteries E and G had combustibility. In contrast, the electrolytes a to d used in the batteries A1 to B, B, C, and D of the present invention and the comparative battery F exhibited self-extinguishing properties or flame retardancy, and were confirmed to have high safety.

  In this specification, flame retardancy refers to the property of not burning even when exposed to flame. Self-extinguishing refers to the property of burning while exposed to a flame but extinguishing within at least a few seconds when the flame is released.

(Separator flammability test)
Next, separator combustibility of the microporous membrane made of polyimide used for the separators of the inventive batteries A1 to A4, B, C, D and the comparative battery E and the microporous membrane made of polyethylene used for the separators of the comparative batteries F and G A test was conducted. 1 g of each separator was taken on a wire mesh with a glass filter and heated with a cassette stove to check for ignition and combustion. As a result, when the polyethylene microporous film used for the comparative batteries F and G was held over the flame of the cassette stove, combustion was observed after melting, whereas the present batteries A1 to B, B, C, D, and Combustion was not observed when the polyimide microporous film used for Comparative Battery E was held over the flame of a cassette stove. Moreover, by putting both separator pieces into the bottom of a test tube equipped with a rubber stopper with a glass tube, heating the bottom of the test tube with a gas burner, and bringing the flame of another gas burner close to the outlet of the glass tube When the pyrolysis gas was tested for flammability, the polyethylene microporous membrane ignited the pyrolysis gas and continued combustion, whereas the polyimide microporous membrane The pyrolysis gas seemed to ignite for a moment, but immediately extinguished. From this, it was confirmed that the polyimide microporous film exhibits flame retardancy and has high safety.

(Battery performance test)
Furthermore, the initial discharge capacity and the high-rate discharge capacity were measured for the inventive batteries A1 to A4, B, C, D and the comparative batteries E, F, G. The initial discharge capacity is a constant current constant voltage charge at 20 ° C. with a current of 10 mA and a final voltage of 3.7 V, and then at 20 ° C., a constant current discharge with a current of 2 mA and a final voltage of 2.0 V is performed. Was defined as “initial discharge capacity (mAh)”. Next, after charging at a constant current and a constant voltage with a current of 10 mA and a final voltage of 3.7 V at 20 ° C., a constant current discharge with a current of 30 mA and a final voltage of 2.0 V was performed at 20 ° C., and the discharge capacity at this time was expressed as “ High rate discharge capacity (mAh) ". In addition, the improvement rate of the high rate discharge capacity of the nonaqueous electrolyte battery mixed with the fluorinated carbonate compound to the high rate discharge capacity of the nonaqueous electrolyte battery not mixed with the fluorinated carbonate compound using the same separator. “High rate discharge capacity improvement rate (%)”. The above results are summarized in Table 2.

  From the results of the electrolyte salt flammability test and the separator flammability test, the present invention batteries A1 to B, B, C, and D, which are combinations of the self-extinguishing or flame retardant electrolyte and the separator, are in a wide temperature range. A “non-burning battery” having excellent flame retardancy can be obtained.

  In addition, as shown in Table 2, the batteries A1 to 4, B, C, and D of the present invention have not only the same initial discharge capacity as the comparison battery E, but also excellent high-rate discharge capacity. It was confirmed that Here, it should be noted that when the battery A3 of the present invention is compared with the comparative battery E and between the comparative batteries F and G, the high rate discharge capacity of the comparative battery F with respect to the comparative battery G using the polyethylene microporous membrane as a separator is improved It was confirmed that the high rate discharge capacity improvement rate of the battery A3 of the present invention relative to the comparative battery E using the polyimide microporous membrane as a separator was better than the rate. Therefore, the present invention batteries A1 to A4, B, C, and D, which are a combination of a separator made of a microporous membrane made of polyimide and an electrolyte containing a fluorinated carbonate compound, have particularly good high rate discharge characteristics. It was confirmed to have.

  Therefore, the present invention batteries A1 to A4, B, C, and D are non-aqueous electrolyte batteries that have both flame retardancy and good high rate discharge characteristics as compared with comparative batteries E, F, G, and H. Was confirmed.

  In addition, in order to obtain a non-aqueous electrolyte battery having particularly excellent flame retardancy and high rate discharge characteristics, the content of the fluorinated carbonate compound is 5% by weight or more by comparison between the batteries A1 to A4 of the present invention. Was confirmed to be preferable.

In order to obtain a non-aqueous electrolyte battery having further excellent flame retardancy, a lithium-containing polyanion metal composite compound that is excellent in thermal stability and does not decompose and release oxygen even at high temperatures is used as a positive electrode active material. It is particularly preferred. In this example, LiFePO ₄ was used as the positive electrode active material, but the same effect can be obtained with other lithium-containing polyanion metal composite compounds such as LiMnPO ₄ .

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

Explanation of symbols

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

Claims (3)

A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the separator contains a polyimide, and the non-aqueous electrolyte contains a fluorinated carbonate compound. battery. The nonaqueous electrolyte battery according to claim 1, wherein the content of the fluorinated carbonate compound is 5% by weight or more based on the total weight of the nonaqueous electrolyte. The non-aqueous electrolyte battery according to claim 1, wherein the positive electrode contains a lithium-containing polyanion metal composite compound.