JP2005190870A - Electrolyte for polymer battery, and the polymer battery equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for a polymer battery having a high flexibility of design, in addition to high safety, and to provide a polymer battery equipped with the electrolyte for polymer battery. <P>SOLUTION: This electrolyte for a polymer battery is prepared by heating an electrolyte composition comprising a phosphazene compound, tetralkylthiuram disulfides and a support electrolyte at 60°C or higher. This polymer battery is equipped with the electrolyte for a polymer battery, a positive electrode and a negative electrode. Since the phosphazene compound in the electrolyte composition is copolymerized by heating in the electrolyte for a polymer battery, electrolyte leakage will not occur. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrolyte for a polymer battery and a polymer battery including the same, and more particularly to an electrolyte for a polymer battery having high safety and high design freedom.

  Conventionally, nickel-cadmium batteries have been mainly used as memory backups for AV and information devices such as personal computers and VTRs, and as secondary batteries for their drive power. On the other hand, as an alternative to a NiCad battery, a non-aqueous electrolyte secondary battery having high voltage and high energy density and excellent self-discharge characteristics has been developed and commercialized. For example, more than half of notebook computers and mobile phones are driven by non-aqueous electrolyte secondary batteries. In the non-aqueous electrolyte secondary battery, a separator is used to prevent contact between the positive electrode and the negative electrode, and the separator is a porous thin film that does not hinder the movement of ions in the electrolyte. Etc. are used. However, since the thin layer film does not have the ability to retain the electrolyte, the battery using the thin layer film as a separator has a risk of liquid leakage.

  On the other hand, a polymer battery using a polymer as an electrolyte has been developed as a battery that does not cause a liquid leakage. In recent years, the polymer battery has been actively researched because it does not have to worry about liquid leakage, can be formed into a film, can be easily incorporated into an electronic device, and can effectively use a space. As an electrolyte used for the polymer battery, an intrinsic polymer electrolyte in which a lithium salt is held in a polymer and a gel electrolyte in which an organic solvent is swollen in the polymer are known (see Patent Document 1).

  Since the polymer battery electrolyte uses a material that easily burns, such as a polymer or an organic solvent, for example, when a polymer battery is short-circuited, a large current flows suddenly, and the battery is heated abnormally. Vaporizes and decomposes to generate gas, the generated gas and heat cause battery rupture / ignition, and sparks generated during short-circuiting ignite polymers and organic solvents. In contrast, adding phosphazene compounds to polymer battery electrolytes gives the electrolyte nonflammability, flame retardancy, or self-extinguishing properties, greatly increasing the risk of polymer batteries igniting and igniting in the event of a short circuit or other emergency. A polymer battery having a reduced thickness has been developed (see Patent Document 2).

JP-A-5-307975 WO03 / 005478 pamphlet

  However, in the conventional polymer battery, the electrolyte has to be formed into a predetermined shape before assembling the cell, and the degree of design freedom is low compared to the non-aqueous electrolyte secondary battery.

  Therefore, an object of the present invention is to provide an electrolyte for a polymer battery that has a high degree of freedom in design in addition to high safety. Another object of the present invention is to provide a polymer battery using the polymer battery electrolyte.

  As a result of intensive studies to achieve the above object, the inventors of the present invention filled a battery cell with a mixed solution of a phosphazene compound, a tetraalkylthiuram disulfide and a supporting salt, and then heated the phosphazene compound. The polymer solution was polymerized to become a polymer electrolyte, and it was found that a polymer battery without risk of liquid leakage was obtained, and the present invention was completed.

  That is, the polymer battery electrolyte of the present invention is characterized in that an electrolyte composition comprising a phosphazene compound, a tetraalkylthiuram disulfide and a supporting salt is heated at 60 ° C. or higher. Here, in the polymer battery electrolyte of the present invention, since the phosphazene compound in the electrolyte composition is polymerized by heating, there is no possibility of liquid leakage.

（式中、Ｒ¹、Ｒ²及びＲ³は、それぞれ独立して一価の置換基又はハロゲン元素を表し；Ｘは、炭素、ケイ素、ゲルマニウム、スズ、窒素、リン、ヒ素、アンチモン、ビスマス、酸素、硫黄、セレン、テルル及びポロニウムからなる群から選ばれる元素の少なくとも１種を含む置換基を表し；Ｙ¹、Ｙ²及びＹ³は、それぞれ独立して２価の連結基、２価の元素又は単結合を表す）又は下記式(II)：

(ＮＰＲ⁴ ₂)_n ・・・ (II)
（式中、Ｒ⁴はそれぞれ独立して一価の置換基又はハロゲン元素を表し；ｎは３〜１５を表す）で表される。また、前記電解質組成物におけるホスファゼン化合物の含有量は、3〜20質量％の範囲が好ましい。 In a preferred example of the polymer battery electrolyte of the present invention, the phosphazene compound is represented by the following formula (I):

(Wherein R ¹ , R ² and R ³ each independently represents a monovalent substituent or a halogen element; X represents carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic, antimony, bismuth, Represents a substituent containing at least one element selected from the group consisting of oxygen, sulfur, selenium, tellurium and polonium; Y ¹ , Y ² and Y ³ are each independently a divalent linking group, divalent Represents an element or a single bond) or the following formula (II):

(NPR ⁴ ₂ ) _n ... (II)
(Wherein R ⁴ independently represents a monovalent substituent or a halogen element; n represents 3 to 15). The content of the phosphazene compound in the electrolyte composition is preferably in the range of 3 to 20% by mass.

（式中、Ｒ⁵、Ｒ⁶、Ｒ⁷及びＲ⁸は、それぞれ独立して炭素数１〜４のアルキル基を示す）で表される。また、前記電解質組成物におけるテトラアルキルチウラムジスルフィド類の含有量は、1〜3質量％の範囲が好ましい。 In another preferred embodiment of the polymer battery electrolyte of the present invention, the tetraalkylthiuram disulfides are represented by the following formula (III):

(Wherein R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group having 1 to 4 carbon atoms). Moreover, the content of tetraalkylthiuram disulfides in the electrolyte composition is preferably in the range of 1 to 3% by mass.

  Moreover, the polymer battery of this invention is equipped with the said electrolyte for polymer batteries, a positive electrode, and a negative electrode, It is characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, the electrolyte for polymer batteries with a high safety | security and a high design freedom which heats the mixed solution of a phosphazene compound, tetraalkyl thiuram disulfides, and support salt can be provided. Further, a polymer battery having the polymer battery electrolyte and having high safety and high design freedom can be provided.

<Electrolyte for polymer battery>
Hereinafter, the polymer battery electrolyte of the present invention will be described in detail. The polymer battery electrolyte of the present invention is obtained by heating an electrolyte composition containing a phosphazene compound, a tetraalkylthiuram disulfide, and a supporting salt at 60 ° C. or higher. In the present invention, the phosphazene compound in the electrolyte composition is polymerized by heating to form an electrolyte for a polymer battery. However, in the present invention, it is not necessary to polymerize all of the phosphazene compounds, and the phosphazene compounds may be polymerized to such an extent that there is no risk of liquid leakage. The polymer battery electrolyte of the present invention does not need to be molded into a predetermined shape in advance in the production of a polymer battery. For example, the electrolyte composition is filled in a battery case in which a positive electrode and a negative electrode are incorporated, and then heated. Can be formed. Therefore, the polymer battery design flexibility is increased by using the polymer battery electrolyte of the present invention.

  Further, in the polymer battery electrolyte of the present invention, the risk of the electrolyte burning is reduced by the action of nitrogen gas derived from the phosphazene compound and its polymer. In addition, the phosphorus constituting the phosphazene compound and the polymer thereof has a function of generating a phosphate ester and the like to suppress chain decomposition of the polymer material constituting the battery, and therefore, risk of ignition and ignition of the battery. Can be effectively reduced. Furthermore, when the phosphazene compound contains a halogen, the halogen functions as an active radical scavenger in the unlikely event of combustion, reducing the risk of electrolyte combustion.

  In the polymer battery electrolyte of the present invention, it is necessary to heat the electrolyte composition at 60 ° C. or higher, and heating in the range of 60 to 80 ° C. is preferable in terms of preventing deterioration of battery characteristics. Moreover, the heating time of the said electrolyte composition is suitably selected according to heating temperature, for example, when heating at 60 degreeC, it is preferable to heat for 10 to 20 minutes.

  The electrolyte composition used for the polymer battery electrolyte of the present invention contains a phosphazene compound. Specific examples of the phosphazene compound include a chain phosphazene compound represented by the above formula (I) and a cyclic phosphazene compound represented by the above formula (II). Of the phosphazene compounds represented by formula (I) or formula (II), those which are liquid at 25 ° C. (room temperature) are preferred. The viscosity at 25 ° C. of the liquid phosphazene compound is preferably 300 mPa · s (300 cP) or less, more preferably 20 mPa · s (20 cP) or less, and particularly preferably 5 mPa · s (5 cP) or less. In the present invention, the viscosity is measured at 1 rpm, 2 rpm, 3 rpm, 5 rpm, 7 rpm, 10 rpm, 20 rpm and 50 rpm using a viscometer [R-type viscometer Model RE500-SL, manufactured by Toki Sangyo Co., Ltd.] The measurement was performed at a speed of 120 seconds, and the rotation speed when the indicated value reached 50 to 60% was set as an analysis condition, and the viscosity was measured at that time. If the viscosity of the phosphazene compound at 25 ° C exceeds 300 mPa · s (300 cP), the supporting salt will be difficult to dissolve, and the ionic conductivity of the electrolyte will be significantly reduced, especially when used under low temperature conditions such as below the freezing point. It becomes.

In the formula (I), R ¹ , R ² and R ³ are not particularly limited as long as they are monovalent substituents or halogen elements. Examples of the monovalent substituent include an alkoxy group, an alkyl group, a carboxyl group, an acyl group, and an aryl group. Among these, an alkoxy group is preferable in that the phosphazene compound has low viscosity. On the other hand, preferred examples of the halogen element include fluorine, chlorine, bromine and the like. R ^{1 to} R ³ may all be the same type of substituent, and some of them may be different types of substituents. Here, examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and an alkoxy-substituted alkoxy group such as a methoxyethoxy group and a methoxyethoxyethoxy group. Among these, a methoxy group, An ethoxy group, a methoxyethoxy group, and a methoxyethoxyethoxy group are preferable, and a methoxy group or an ethoxy group is particularly preferable from the viewpoint of low viscosity and high dielectric constant. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group. Examples of the acyl group include a formyl group, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, and a valeryl group. Examples of the aryl group include a phenyl group, a tolyl group, and a naphthyl group. The hydrogen element in these monovalent substituents is preferably substituted with a halogen element. As the halogen element, fluorine, chlorine and bromine are preferred, fluorine is most preferred, and chlorine is then preferred. When the hydrogen element in the monovalent substituent is substituted with fluorine, the effect of improving the cycle characteristics of the polymer battery tends to be greater than when the hydrogen element is substituted with chlorine.

In the formula (I), examples of the divalent linking group represented by Y ¹ , Y ² and Y ³ include CH ₂ group, oxygen, sulfur, selenium, nitrogen, boron, aluminum, scandium, gallium, Yttrium, indium, lanthanum, thallium, carbon, silicon, titanium, tin, germanium, zirconium, lead, phosphorus, vanadium, arsenic, niobium, antimony, tantalum, bismuth, chromium, molybdenum, tellurium, polonium, tungsten, iron, cobalt, And divalent linking groups containing at least one element selected from the group consisting of nickel. Among these, at least one element selected from the group consisting of CH ₂ groups and oxygen, sulfur, selenium, and nitrogen is included. A divalent linking group containing a seed is preferred, and a divalent linking group containing a sulfur and / or selenium element is particularly preferred. Y ¹ , Y ² and Y ³ may be a divalent element such as oxygen, sulfur or selenium, or a single bond. Y ^{1 to} Y ³ may all be the same type, or some of them may be different types.

［式(IV)、式(V)及び式(VI)において、Ｒ⁹〜Ｒ¹³は、それぞれ独立に一価の置換基又はハロゲン元素を表し；Ｙ⁹〜Ｙ¹³は、それぞれ独立に２価の連結基、２価の元素又は単結合を表し；Ｚは２価の基又は２価の元素を表す。］ In the formula (I), X is preferably a substituent containing at least one element selected from the group consisting of carbon, silicon, nitrogen, phosphorus, oxygen and sulfur from the viewpoints of toxicity, environment and the like. . Of these substituents, substituents having a structure represented by the following formula (IV), formula (V) or formula (VI) are more preferred.

[In Formula (IV), Formula (V) and Formula (VI), R ^{9 to} R ¹³ each independently represents a monovalent substituent or a halogen element; Y ^{9 to} Y ¹³ each independently represent a divalent group. A linking group, a divalent element or a single bond; Z represents a divalent group or a divalent element. ]

In formula (IV), formula (V) and formula (VI), R ^{9 to} R ¹³ are the same monovalent substituents or halogen elements as those described for R ^{1 to} R ³ in formula (I). Any of these is preferably mentioned. In addition, these may be the same type within the same substituent, or some of them may be different from each other. R ⁹ and R ^{10 in} formula (IV) and R ¹² and R ^{13 in} formula (VI) may be bonded to each other to form a ring.

In formula (IV), formula (V) and formula (VI), the group represented by Y ^{9 to} Y ¹³ is a divalent linkage similar to that described for Y ^{1 to} Y ³ in formula (I). In the same manner, a group containing a sulfur and / or selenium element is particularly preferable because the risk of ignition and ignition of the electrolyte is reduced. These may be the same type within the same substituent, or some of them may be different from each other.

In the formula (IV), as Z, for example, CH ₂ group, CHR (R represents an alkyl group, an alkoxyl group, a phenyl group, etc .; the same shall apply hereinafter) group, NR group, oxygen, sulfur, selenium, Boron, aluminum, scandium, gallium, yttrium, indium, lanthanum, thallium, carbon, silicon, titanium, tin, germanium, zirconium, lead, phosphorus, vanadium, arsenic, niobium, antimony, tantalum, bismuth, chromium, molybdenum, tellurium, Examples include divalent groups containing at least one element selected from the group consisting of polonium, tungsten, iron, cobalt and nickel. Among these, in addition to CH ₂ groups, CHR groups, NR groups, oxygen, sulfur A divalent group containing at least one element selected from the group consisting of selenium is preferred. In particular, a divalent group containing an element of sulfur and / or selenium is preferable because the risk of ignition and ignition of the electrolyte is reduced. Z may be a divalent element such as oxygen, sulfur, or selenium.

  As these substituents, a substituent containing phosphorus as represented by the formula (IV) is particularly preferable in that the risk of ignition / flammability can be particularly effectively reduced. In addition, when the substituent is a substituent containing sulfur as represented by the formula (V), it is particularly preferable from the viewpoint of reducing the interface resistance of the electrolyte.

In the formula (II), R ⁴ is not particularly limited as long as it is a monovalent substituent or a halogen element. Examples of the monovalent substituent include an alkoxy group, an alkyl group, a carboxyl group, an acyl group, and an aryl group. Among these, an alkoxy group is preferable in that the phosphazene compound has low viscosity. On the other hand, preferred examples of the halogen element include fluorine, chlorine, bromine and the like. Here, examples of the alkoxy group include a methoxy group, an ethoxy group, a methoxyethoxy group, a propoxy group, and a phenoxy group, and among these, a methoxy group, an ethoxy group, a methoxyethoxy group, and a phenoxy group are particularly preferable. The hydrogen element in these monovalent substituents is preferably substituted with a halogen element. Preferred examples of the halogen element include fluorine, chlorine, bromine and the like. Examples of the substituent substituted with a fluorine atom include Examples thereof include a trifluoroethoxy group.

By appropriately selecting R ^{1 to} R ⁴ , R ^{9 to} R ¹³ , Y ^{1 to} Y ³ , Y ^{9 to} Y ¹³ , and Z in formulas (I), (II), and (IV) to (VI), A phosphazene compound having suitable viscosity, solubility suitable for addition and mixing, and the like can be obtained. These phosphazene compounds may be used alone or in combination of two or more.

Among the phosphazene compounds of the above formula (II), a phosphazene compound represented by the following formula (VII) is preferable from the viewpoint of improving the deterioration resistance and safety of the electrolyte.

(NPF ₂ ) _n ... (VII)
(In the formula, n represents 3 to 13.)

  In the formula (VII), n is preferably 3 to 5, more preferably 3 to 4, and particularly preferably 3. When the value of n is small, the boiling point is low, and the unpolymerized phosphazene compound improves the ignition prevention property at the time of flame contact. On the other hand, since the boiling point increases as the value of n increases, it can be used stably even at high temperatures. A plurality of phosphazenes can be selected and used in a timely manner in order to obtain the desired performance using the above properties.

  By appropriately selecting the n value in formula (VII), a phosphazene compound having a more suitable viscosity, solubility suitable for mixing, and the like can be obtained. These phosphazene compounds may be used alone or in combination of two or more.

  The viscosity of the phosphazene compound represented by the formula (VII) is not particularly limited as long as it is 20 mPa · s or less, but is preferably 10 mPa · s or less, and more preferably 5 mPa · s or less.

Among the phosphazene compounds of the above formula (II), phosphazene compounds represented by the following formula (VIII) are also preferable from the viewpoint of improving the deterioration resistance and safety of the electrolyte.

(NPR ¹⁴ ₂ ) _n ... (VIII)
(Wherein R ¹⁴ independently represents a monovalent substituent or fluorine, and at least one of all R ¹⁴ is a monovalent substituent or fluorine containing fluorine, and n represents 3 to 8) (However, not all R ¹⁴ are fluorine.)

If the phosphazene compound of the above formula (II) is contained, the electrolyte can be provided with excellent self-extinguishing properties or flame retardancy, and the safety of the electrolyte can be improved. ^If at least one of ¹⁴ contains a phosphazene compound which is a monovalent substituent containing fluorine, it is possible to impart superior safety to the electrolyte. Furthermore, if a phosphazene compound represented by the formula (VIII) and at least one of all R ¹⁴ is fluorine is contained, further excellent safety can be imparted. That is, as compared with a phosphazene compound not containing fluorine, a phosphazene compound represented by the formula (VIII) in which at least one of all R ¹⁴ is a monovalent substituent containing fluorine or fluorine is effective in making the electrolyte more difficult to burn. And can provide further excellent safety to the electrolyte.

  Examples of the monovalent substituent in the formula (VIII) include an alkoxy group, an alkyl group, an acyl group, an aryl group, and a carboxyl group, and an alkoxy group is preferable because it is particularly excellent in improving the safety of the electrolyte. . Here, examples of the alkoxy group include methoxy group, ethoxy group, n-propoxy group, i-propoxy group, butoxy group and the like, alkoxy group-substituted alkoxy groups such as methoxyethoxy group, and the like. A methoxy group, an ethoxy group, and an n-propoxy group are particularly preferable in terms of excellent improvement.

  In the formula (VIII), n is preferably 3 to 5 and more preferably 3 to 4 because it can provide excellent safety to the electrolyte.

The monovalent substituent is preferably substituted with fluorine. When R ^{14 in} formula (VIII) is not fluorine, at least one monovalent substituent contains fluorine.

  The fluorine content in the phosphazene compound of the formula (VIII) is preferably 3 to 70% by mass, more preferably 7 to 45% by mass. When the fluorine content is 3 to 70% by mass, “excellent safety” can be particularly suitably imparted to the electrolyte.

  The phosphazene compound of the formula (VIII) may contain a halogen element such as chlorine and bromine in addition to the above-mentioned fluorine. However, fluorine is most preferred, followed by chlorine. Those containing fluorine tend to have a greater effect of improving the cycle characteristics of the polymer battery than those containing chlorine.

By appropriately selecting R ¹⁴ and n value in the formula (VIII), a phosphazene compound having more suitable safety, viscosity, solubility suitable for mixing, and the like can be obtained. These phosphazene compounds may be used alone or in combination of two or more.

  The viscosity of the phosphazene compound of the formula (VIII) is not particularly limited as long as it is 20 mPa · s or less, but is preferably 10 mPa · s or less, and more preferably 5 mPa · s or less.

  In the electrolyte composition used for the polymer battery electrolyte of the present invention, the content of the phosphazene compound is preferably 3 to 20% by mass, more preferably 8 to 20% by mass, from the viewpoint of improving the safety of the electrolyte. Moreover, in the polymer battery electrolyte of the present invention, it is preferable that a phosphazene compound in an amount corresponding to 8 to 15% by mass of the electrolyte composition is polymerized from the viewpoint of preventing electrolyte leakage.

The electrolyte composition used for the polymer battery electrolyte of the present invention contains tetraalkylthiuram disulfides. As the tetraalkylthiuram disulfides, specifically, a compound represented by the above formula (III) is preferable. Here, as the alkyl group having 1 to 4 carbon atoms in R ⁵ , R ⁶ , R ⁷ and R ⁸ in the formula (III), a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group , Sec-butyl group, isobutyl group, t-butyl group and the like. Among these alkyl groups, a methyl group and an ethyl group are preferable from the viewpoint of promoting the polymerization reaction. The said tetraalkyl thiuram disulfides may be used individually by 1 type, and may use 2 or more types together.

  In the electrolyte composition used in the polymer battery electrolyte of the present invention, the content of the tetraalkylthiuram disulfides is preferably 1 to 3% by mass, and 1 to 1.5% by mass from the viewpoint of preventing adverse effects on battery characteristics. Further preferred.

In the electrolyte composition, the tetraalkylthiuram disulfides function as radical polymerization initiators, generate radicals in the phosphazene compound, and initiate radical polymerization of the phosphazene compound. For example, taking a cyclic phosphazene compound of the formula (II) and a tetraalkylthiuram disulfide of the formula (III) as examples, radical polymerization of the phosphazene compound proceeds as follows.

As shown in the above reaction scheme, first, tetraalkylthiuram disulfides of formula (III) are cleaved to generate a plurality of types of radicals. Next, the generated radical draws R ⁴ · from the phosphazene compound of formula (II), and a radical is generated in the phosphazene compound of formula (II). Next, the phosphazene compound of the formula (II) having a radical and another phosphazene compound are polymerized, and then polymerization proceeds until the radical is quenched to produce polyphosphazene. Although the reaction scheme is not shown, for the chain phosphazene compound of the formula (I), the radicals generated from the tetraalkylthiuram disulfides extract R ¹ Y ¹ , R ² Y ² , and R ² Y ^2. As a result, polymerization of the phosphazene compound is started, and polyphosphazene is produced.

The electrolyte composition used for the polymer battery electrolyte of the present invention contains a supporting salt. The supporting salt is preferably a supporting salt that serves as an ion source for lithium ions. The supporting salt is not particularly limited, and for example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiAsF ₆ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N and Li ( Preferable examples include lithium salts such as C ₂ F ₅ SO ₂ ) ₂ N. These supporting salts may be used alone or in combination of two or more. Here, the content of the supporting salt is preferably blended so that the electric conductivity of the electrolyte is 5 mS / cm or more.

  The electrolyte composition related to the polymer battery electrolyte of the present invention contains an aprotic organic solvent in addition to the phosphazene compound, tetraalkylthiuram disulfides and supporting salt. Examples of the aprotic organic solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), diphenyl carbonate, ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), γ Preferred examples include esters such as valerolactone and methyl formate (MF), and ethers such as 1,2-dimethoxyethane (DME) and tetrahydrofuran (THF). Among these, ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and methyl formate are preferable. Cyclic esters are preferred in that they have a high relative dielectric constant and excellent solubility of the supporting salt, while chain esters and chain ethers have low viscosity and are therefore suitable for batteries. It is preferable in terms of easy filling. The aprotic organic solvent can further easily improve the ionic conductivity of the electrolyte without reacting with the negative electrode. The aprotic organic solvent preferably has a viscosity at 25 ° C. of 10 mPa · s (10 cP) or less, and more preferably 5 mPa · s (5 cP) or less. These aprotic organic solvents may be used alone or in combination of two or more. Here, when the aprotic organic solvent is contained in the electrolyte composition, the composition of the aprotic organic solvent is preferably blended so that the electric conductivity of the electrolyte is 5 mS / cm or more.

<Polymer battery>
Next, the polymer battery of the present invention will be described in detail. The polymer battery of the present invention includes the above-described polymer battery electrolyte, a positive electrode, and a negative electrode, and includes other members that are usually used in the technical field of polymer batteries as necessary. The polymer battery of the present invention has no risk of liquid leakage, has a low risk of ignition and ignition, and has a high degree of design freedom.

There is no restriction | limiting in particular as a positive electrode active material of the polymer battery of this invention, It can select from a well-known positive electrode active material suitably, and can use it. Specific examples of the positive electrode active material include metal oxides such as V ₂ O ₅ , V ₆ O ₁₃ , MnO ₂ and MnO ₃ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFeO ₂ and LiFePO ₄ . Preferable examples include lithium-containing composite oxides, metal sulfides such as TiS ₂ and MoS ₂ , and conductive polymers such as polyaniline. The lithium-containing composite oxide may be a composite oxide containing two or three transition metals selected from the group consisting of Fe, Mn, Co, and Ni. In this case, the composite oxide includes: LiFe _x Co _y Ni (wherein, 0 ≦ x <1,0 ≦ y <1,0 <x + y ≦ 1) (1-xy) O 2, or represented by LiMn _x Fe _y O _2-xy like. Among these, LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ are particularly preferable because they have a high capacity and high safety, and are excellent in wettability of the electrolyte composition. These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together.

  Preferred examples of the negative electrode active material of the polymer battery of the present invention include lithium metal itself, an alloy of lithium and Al, In, Pb, Zn, or the like, a carbon material such as graphite doped with lithium, and among these, From the viewpoint of higher properties, a carbon material such as graphite is preferable, and graphite is particularly preferable. Here, examples of graphite include natural graphite, artificial graphite, mesophase carbon microbeads (MCMB), and the like, and widely include graphitizable carbon and non-graphitizable carbon. These negative electrode active materials may be used individually by 1 type, and may use 2 or more types together.

  The positive electrode and the negative electrode can be mixed with a conductive agent and a binder as necessary. Examples of the conductive agent include acetylene black, and the binder includes polyvinylidene fluoride (PVDF) and polytetrafluoro. Examples thereof include ethylene (PTFE), styrene / butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like. These additives can be used at a blending ratio similar to the conventional one.

  Moreover, there is no restriction | limiting in particular as a shape of the said positive electrode and a negative electrode, It can select suitably from well-known shapes as an electrode. For example, a sheet shape, a columnar shape, a plate shape, a spiral shape, and the like can be given.

  Another member used in the polymer battery of the present invention includes a separator interposed between positive and negative electrodes in a role of preventing current short-circuit due to contact between both electrodes. As the material of the separator, a material that can reliably prevent contact between both electrodes and can pass through or contain the electrolyte composition, such as polytetrafluoroethylene, polypropylene, polyethylene, cellulose, polybutylene terephthalate, polyethylene terephthalate, etc. A non-woven fabric made of a synthetic resin, a thin layer film, and the like are preferable. Of these, polypropylene or polyethylene microporous films having a thickness of about 20 to 50 μm, cellulose-based films, polybutylene terephthalate, polyethylene terephthalate, and the like are particularly suitable. In the present invention, in addition to the separator described above, known members that are usually used in polymer batteries can be suitably used.

  There is no restriction | limiting in particular as a form of the polymer battery of this invention demonstrated above, Various well-known forms, such as a coin type, a button type, a paper type, a square type or a cylindrical battery of a spiral structure, are mentioned suitably. In the case of the button type, a sheet-like positive electrode and negative electrode are prepared, the positive and negative electrodes are opposed to each other through a separator, the electrolyte composition is injected, sealed, and heated to produce a polymer battery. In the case of a spiral structure, for example, a sheet-like positive electrode is produced and a current collector is sandwiched between them, and a sheet-like negative electrode is stacked and rolled up, and the electrolyte composition is injected, sealed, and heated. Thus, a polymer battery can be manufactured.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Example 1)
With respect to 86 parts by mass of a mixed solution (volume ratio = 1/2) of ethylene carbonate (EC) / dimethyl carbonate (DMC) containing 1 M (mol / L) LiPF ₆ , phosphazene compound A [in formula (II), n Is a cyclic phosphazene compound in which two of the six R ⁴ groups are ethoxy groups (CH ₃ CH ₂ O—) and four are fluorine atoms, viscosity at 25 ° C .: 1.2 mPa · s] 12 parts by mass, An alkyl thiuram disulfide Z [a compound in which R ^{5 to} R ⁹ are methyl groups in the formula (III)] is added to prepare an electrolyte composition, and the electrolyte composition is heated for a polymer battery. The safety of the electrolyte was evaluated by the following method.

(1) Electrolyte Safety The safety of the polymer battery electrolyte was evaluated from the combustion behavior of flames ignited in an atmospheric environment by the method of arranging UL94HB method of UL (Underwriting Laboratory) standard. At that time, ignitability, combustibility, formation of carbides, and secondary ignition phenomena were also observed. Specifically, based on the UL test standards, impregnated 1.0 mL of the above electrolyte composition into non-combustible quartz fiber and heated at 60 ° C. for 20 minutes to form an electrolyte for a polymer battery, producing a 127 mm × 12.7 mm test piece I went there. Here, when the test flame does not ignite the test piece (combustion length: 0 mm), it is “non-flammable”, and when the ignited flame does not reach the 25 mm line and the fallen object is not ignited, “flame retardant” The case where the ignited flame was extinguished on the 25 to 100 mm line and the fallen object was not ignited was evaluated as “self-extinguishing”, and the case where the ignited flame exceeded the 100 mm line was evaluated as “combustible”.

Next, 10 parts by mass of acetylene black (conductive agent) and 10 parts by mass of polytetrafluoroethylene (binder) are added to 100 parts by mass of LiCoO ₂ (positive electrode active material), and an organic solvent (ethyl acetate) is added. And 50/50% by volume mixed solvent of ethanol), and a positive electrode sheet having a thickness of 100 μm and a width of 40 mm was produced by roll rolling. A graphite sheet having a thickness of 150 μm was used for the negative electrode. The graphite sheet was superposed on the positive electrode sheet via a separator having a thickness of 25 μm (microporous film: made of polypropylene) and wound up to produce a cylindrical electrode (positive electrode length: about 260 mm). The electrolyte composition was injected into the cylindrical electrode and sealed to produce a lithium ion battery, and the battery was heated at 60 ° C. for 20 minutes to produce an AA polymer battery (polymer gel battery). With respect to the obtained polymer battery, the battery capacity was measured by the following method, and a liquid leakage test was further conducted. The results are shown in Table 1.

(2) Battery capacity (2-1) Evaluation of charge / discharge cycle performance
Under an atmosphere of 25 ° C, charge / discharge is repeated up to 50 cycles under conditions of an upper limit voltage of 4.3V, a lower limit voltage of 3.0V, a discharge current of 100mA, and a charge current of 50mA, and the initial charge / discharge capacity and the charge / discharge capacity after 50 cycles are measured. did. A total of three batteries were measured and averaged.

(2-2) Measurement of low-temperature discharge capacity The obtained battery was charged at room temperature (25 ° C), then discharged at low temperature (-20 ° C), and the discharge capacity at low temperature was measured. A total of three batteries were measured and averaged.

(2-3) Evaluation of high-temperature storage characteristics The obtained battery was stored at 80 ° C for 10 days, and then the discharge capacity was measured at room temperature (25 ° C). A total of three batteries were measured and averaged.

(3) Liquid leak test A pinhole was opened in the completed battery, and it was determined whether or not liquid leaked from the pinhole.

(Comparative Example 1)
An electrolyte composition was prepared by adding 12 parts by mass of phosphazene compound A to 88 parts by mass of EC / DMC mixed solution (volume ratio = 1/2) containing 1M LiPF _6, and safety of the electrolyte composition Were evaluated in the same manner as in Example 1. However, the test piece used in the safety evaluation was prepared by impregnating the non-combustible quartz fiber of 127 mm × 12.7 mm with 1.0 mL of the electrolyte composition.

  In addition, a cylindrical electrode was produced in the same manner as in Example 1, and the electrolyte composition was injected into the cylindrical electrode and sealed to produce an AA lithium ion battery. For the obtained battery, the battery capacity was measured in the same manner as in Example 1, and a liquid leakage test was further conducted. The results are shown in Table 1.

(Example 2)
Example 1 except that 1.0 mL of the same electrolyte composition as in Example 1 was soaked in nonflammable quartz fiber and heated at 90 ° C. for 10 minutes to form an electrolyte for a polymer battery, and a test piece of 127 mm × 12.7 mm was produced. In the same manner, the safety of the polymer battery electrolyte was evaluated.

  Further, in the same manner as in Example 1, the electrolyte composition was injected into the cylindrical electrode and sealed, and then heated at 90 ° C. for 10 minutes to produce an AA polymer battery. For the obtained battery, the battery capacity was measured in the same manner as in Example 1, and a liquid leakage test was further conducted. The results are shown in Table 1.

  From the results in Table 1, it can be seen that the polymer battery of the example has no leakage and high safety. It can also be seen that the phosphazene compound in the electrolyte composition is sufficiently polymerized by heating at a relatively low temperature of about 60 ° C. to form an electrolyte for a polymer battery free from liquid leakage.

Claims (7)

  A polymer battery electrolyte obtained by heating an electrolyte composition comprising a phosphazene compound, a tetraalkylthiuram disulfide, and a supporting salt at 60 ° C. or higher.   The polymer battery electrolyte according to claim 1, wherein the phosphazene compound is polymerized by heating. The phosphazene compound has the following formula (I):

(Wherein R ¹ , R ² and R ³ each independently represents a monovalent substituent or a halogen element; X represents carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic, antimony, bismuth, Represents a substituent containing at least one element selected from the group consisting of oxygen, sulfur, selenium, tellurium and polonium; Y ¹ , Y ² and Y ³ are each independently a divalent linking group, divalent Represents an element or a single bond) or the following formula (II):

(NPR ⁴ ₂ ) _n ... (II)
2. The polymer battery electrolyte according to claim 1, wherein each R ⁴ independently represents a monovalent substituent or a halogen element; n represents 3 to 15. 3.   2. The polymer battery electrolyte according to claim 1, wherein the content of the phosphazene compound in the electrolyte composition is 3 to 20 mass%. The tetraalkyl thiuram disulfides are represented by the following formula (III):

(Wherein R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group having 1 to 4 carbon atoms), for a polymer battery according to claim 1, Electrolytes.   2. The polymer battery electrolyte according to claim 1, wherein the content of the tetraalkylthiuram disulfides in the electrolyte composition is 1 to 3 mass%.   A polymer battery comprising the electrolyte according to claim 1, a positive electrode, and a negative electrode.