JP2010050023A - Nonaqueous electrolyte for battery and nonaqueous electrolyte secondary battery having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte for a battery capable of giving high charge and discharge efficiency and high safety to the battery. <P>SOLUTION: The nonaqueous electrolyte for a battery includes a ring phosphazen compound expressed by formula (I) of (NPR<SP>1</SP><SB>2</SB>)<SB>n</SB>, a nonaqueous solvent, an aniline dielectric expressed by formula (II), and supporting salt. Here, R<SP>1</SP>each independently shows fluorine, alkoxy, or aryloxy; and n shows 3-4. R<SP>2</SP>in formula (II) is each independently hydrogen, methyl, or methoxy. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte for a battery and a non-aqueous electrolyte secondary battery including the same, and in particular, a non-aqueous electrolyte for a battery having nonflammability, and a non-aqueous electrolyte having high charge / discharge efficiency and high safety. The present invention relates to a water electrolyte secondary battery.

Non-aqueous electrolytes are used as electrolytes for lithium batteries, lithium-ion secondary batteries, electric double layer capacitors, etc., and these devices have high voltage and high energy density, so they drive personal computers and mobile phones. Widely used as a power source. As these nonaqueous electrolytic solutions, generally used are solutions in which a supporting salt such as LiPF ₆ is dissolved in an aprotic organic solvent such as an ester compound and an ether compound. However, since the aprotic organic solvent is flammable, it may ignite and burn when it leaks from the device, and has a safety problem.

  To solve this problem, methods for making non-aqueous electrolytes flame-retardant have been studied. For example, phosphoric acid esters such as trimethyl phosphate are used for non-aqueous electrolytes, or phosphoric acid is used for aprotic organic solvents. Methods for adding esters have been proposed (see Patent Documents 1 to 3). However, these phosphate esters have low reduction resistance and are reductively decomposed at the negative electrode, so that there is a problem that the irreversible capacity of the battery is increased and charge / discharge efficiency is remarkably deteriorated.

  Japanese Patent Application Laid-Open No. 6-13108 (Patent Document 4) discloses a method of adding a phosphazene compound to a nonaqueous electrolytic solution in order to impart flame retardancy to the nonaqueous electrolytic solution. Although the phosphazene compound exhibits high flame retardancy, the irreversible capacity of the battery increases and charge / discharge efficiency decreases depending on the type, structure, or battery electrode material type and other non-aqueous electrolyte component types used. Sometimes.

In recent years, battery devices have been required to have higher capacities, and irreversible capacities such as those described above are not involved in discharge, and are therefore preferably smaller from the viewpoint of higher capacities of batteries, and have higher charge / discharge efficiency. However, in this respect, it cannot be said that the prior art has reached a sufficiently satisfactory level.
JP-A-4-184870 JP-A-8-22839 JP 2000-182669 A JP-A-6-13108

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a non-flammable non-aqueous electrolyte for a battery and a non-aqueous electrolyte for the battery, which has high charge / discharge efficiency and high safety. The object is to provide a water electrolyte secondary battery.

  As a result of intensive studies to achieve the above object, the present inventor has a high electrolyte solution by configuring a non-aqueous electrolyte by combining a specific cyclic phosphazene compound and a non-aqueous solvent with a specific aniline derivative. It has been found that a non-aqueous electrolyte secondary battery using the electrolyte can impart flame retardancy and exhibits excellent charge / discharge efficiency with a small irreversible capacity, leading to the completion of the present invention. It was.

［式中、Ｒ²は、それぞれ独立して水素、メチル基又はメトキシ基である］で表されるアニリン誘導体と、
・支持塩と
を含むことを特徴とする。 That is, the non-aqueous electrolyte for a battery of the present invention is
-The following general formula (I):
(NPR ¹ ₂ ) _n ... (I)
[Wherein R ¹ independently represents a fluorine, an alkoxy group or an aryloxy group; n represents 3 to 4], and a cyclic phosphazene compound represented by:
A non-aqueous solvent,
-The following general formula (II):

Wherein R ² is independently hydrogen, methyl group or methoxy group; and
-It is characterized by including supporting salt.

  The non-aqueous electrolyte for a battery of the present invention preferably further contains vinylene carbonate. Here, the content of the vinylene carbonate is preferably in the range of 0.5 to 1.0% by mass of the whole battery non-aqueous electrolyte. In addition, the non-aqueous electrolyte for a battery consisting only of the cyclic phosphazene compound represented by the formula (I), the non-aqueous solvent, the aniline derivative represented by the formula (II), vinylene carbonate and the supporting salt is used for the battery of the present invention. This is a preferred embodiment of the non-aqueous electrolyte.

In the non-aqueous electrolyte for a battery of the present invention, the cyclic phosphazene compound is preferably a compound in which at least four of R ¹ in the general formula (I) are fluorine.

  In a preferred example of the battery non-aqueous electrolyte of the present invention, the content of the cyclic phosphazene compound represented by the general formula (I) is 10 to 60% by volume of the whole battery non-aqueous electrolyte.

  In another preferred embodiment of the battery non-aqueous electrolyte of the present invention, the content of the aniline derivative represented by the general formula (II) is 0.01 to 0.05% by mass of the whole battery non-aqueous electrolyte.

  In another preferred embodiment of the non-aqueous electrolyte for a battery of the present invention, the non-aqueous solvent is an aprotic organic solvent, and the aprotic organic solvent includes ethylene carbonate (EC), ethyl methyl carbonate (EMC). And at least one selected from the group consisting of methyl propionate.

  Moreover, the non-aqueous electrolyte secondary battery of the present invention comprises the above-described non-aqueous electrolyte for a battery, a positive electrode, and a negative electrode.

  According to the present invention, a specific cyclic phosphazene compound is added to a non-aqueous solvent, and preferably has a high flame retardancy by adding 10% by volume or more, and further by using a specific aniline derivative in combination, When used in a liquid secondary battery, it is possible to provide a nonaqueous electrolytic solution that has a small irreversible capacity and exhibits high charge / discharge efficiency. Moreover, the nonaqueous electrolyte secondary battery provided with this nonaqueous electrolyte and having high safety and excellent battery characteristics can be provided.

  In the non-aqueous electrolyte for batteries of the present invention, it is considered that a highly incombustible gas component produced by reaction and thermal decomposition of a cyclic phosphazene compound exhibits high flame retardancy. Although the reason is not necessarily clear, the synergistic effect of the two compounds, the cyclic phosphazene compound and the aniline derivative, quickly produces a thin and highly efficient film on the electrode surface, which suppresses excessive decomposition of the electrolyte. Therefore, it is considered that the irreversible capacity can be reduced.

<Non-aqueous electrolyte for batteries>
Below, the non-aqueous electrolyte for batteries of the present invention will be described in detail. A nonaqueous electrolytic solution for a battery according to the present invention includes a cyclic phosphazene compound represented by the general formula (I), a nonaqueous solvent, and an aniline derivative represented by the general formula (II). Furthermore, it is preferable to contain vinylene carbonate, and it is preferable to contain an aprotic organic solvent as the non-aqueous solvent.

The cyclic phosphazene compound contained in the nonaqueous electrolytic solution for batteries of the present invention is represented by the above general formula (I). R ¹ in formula (I) each independently represent fluorine, an alkoxy group or an aryloxy radical, n represents 3-4.

Examples of the alkoxy group in R ¹ of the formula (I) include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, an allyloxy group containing a double bond, or an alkoxy-substituted alkoxy such as a methoxyethoxy group and a methoxyethoxyethoxy group. Groups and the like. Furthermore, examples of the aryloxy group in R ¹ include a phenoxy group, a methylphenoxy group, a xylenoxy group (that is, a xylyloxy group), a methoxyphenoxy group, and the like. The hydrogen element in the alkoxy group and aryloxy group may be substituted with a halogen element, and is preferably substituted with fluorine. R ¹ in formula (I) may be linked to other R ^1, and in this case, two R ¹ are bonded to each other to form an alkylenedioxy group, an aryleneoxy group or an oxyalkylene arylene. Examples of the divalent group that forms an oxy group include an ethylenedioxy group, a propylenedioxy group, and a phenylenedioxy group.

R ¹ in the general formula (I) may be the same or different. Further, R ¹ in the formula (I) is preferably 4 or more of R ¹ in terms of both nonflammability and low viscosity.

  Moreover, n of Formula (I) is 3-4, The said cyclic phosphazene compound may be used individually by 1 type, and may mix and use 2 or more types.

  In the battery non-aqueous electrolyte of the present invention, the content of the cyclic phosphazene compound is preferably 5 to 70% by volume of the whole battery non-aqueous electrolyte, from the viewpoint of the balance between safety and battery characteristics, A range of 10 to 60% by volume is more preferable. When the content of the cyclic phosphazene compound exceeds 70% by volume, the battery capacity and load characteristics are deteriorated, which is not preferable. In addition, incombustibility may not be exhibited.

The non-aqueous electrolyte for a battery according to the present invention further includes an aniline derivative represented by the above general formula (II). In the formula (II), R ² is hydrogen, methyl group or methoxy group, and each R ² may be the same or different.

  Specific examples of aniline derivatives of formula (II) include N, N-dimethylaniline, 2-methyl-N, N-dimethylaniline, 3-methyl-N, N-dimethylaniline, 4-methyl-N, N- Dimethylaniline, 2-methoxy-N, N-dimethylaniline, 3-methoxy-N, N-dimethylaniline, 4-methoxy-N, N-dimethylaniline, N, N, 3,5-tetramethylaniline, 3, 5-Dimethoxy-N, N-dimethylaniline, 2,4-dimethoxy-N, N-dimethylaniline and the like. Among these, 3-methyl-N, N-dimethylaniline, N, N, 3,5-tetramethylaniline, and 3-methoxy-N, N-dimethylaniline are preferable. These aniline derivatives may be used alone or in combination of two or more.

  The content of the aniline derivative is preferably in the range of 0.01 to 0.1% by mass of the whole non-aqueous electrolyte for batteries, more preferably in the range of 0.01 to 0.05% by mass from the viewpoint of balance of battery performance, and 0.02 to 0.05% by mass. The range of is more preferable.

  Moreover, it is preferable that the non-aqueous electrolyte for batteries of the present invention further contains vinylene carbonate in that the battery capacity can be improved. The content of the vinylene carbonate is preferably in the range of 0.2 to 2.0% by mass of the whole battery non-aqueous electrolyte, and more preferably in the range of 0.5 to 1.0% by mass from the viewpoint of the synergistic effect with the aniline derivative.

  In the non-aqueous electrolyte for batteries of the present invention, various non-protonic organic solvents conventionally used in non-aqueous electrolytes for secondary batteries are used as the non-aqueous solvent as long as the object of the present invention is not impaired. can do. The content of the non-aqueous solvent is preferably 30 to 95% by volume of the entire non-aqueous electrolyte for batteries, and more preferably in the range of 40 to 90% by volume from the viewpoint of the balance between safety and battery characteristics. .

  Specific examples of the aprotic organic solvent include saturated carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), diphenyl carbonate, ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC). Carboxylic acid esters such as methyl acetate, methyl propionate and methyl butyrate, ethers such as 1,2-dimethoxyethane (DME), tetrahydrofuran (THF) and diethyl ether (DEE), γ-butyrolactone (GBL), γ -Lactones such as valerolactone, nitriles such as acetonitrile, amides such as dimethylformamide, sulfones such as dimethyl sulfoxide, sulfides such as ethylene sulfide, and the like. Among these, it is preferable to use carbonic acid esters and carboxylic acid esters from the viewpoint of compatibility with the cyclic phosphazene compound and battery performance. Among them, ethylene carbonate (EC), ethyl methyl carbonate (EMC), propion are preferable. More preferably, methyl acid is used. These aprotic organic solvents may be used individually by 1 type, and 2 or more types may be mixed and used for them.

As the supporting salt used in the non-aqueous electrolyte for a battery of the present invention, a supporting salt serving as a lithium ion source is preferable. The supporting salt is not particularly limited. For example, LiClO ₄ , LiBF ₄ , LiBC ₄ O ₈ , LiPF ₆ , LiCF ₃ SO ₃ , LiAsF ₆ , LiC ₄ F ₉ SO ₃ , Li (FSO ₂ ) ₂ N Suitable examples include lithium salts such as Li (CF ₃ SO ₂ ) ₂ N and Li (C ₂ F ₅ SO ₂ ) ₂ N. Among these, LiPF ₆ , Li (FSO ₂ ) ₂ N, Li (CF ₃ SO ₂ ) ₂ N, and Li (C ₂ F ₅ SO ₂ ) ₂ N are more preferable in terms of excellent nonflammability and battery performance. These supporting salts may be used alone or in combination of two or more.

  The total concentration of the supporting salt in the non-aqueous electrolyte is preferably 0.3 to 2.5 mol / L (M), more preferably 0.8 to 2.0 mol / L (M). If the total concentration of the supporting salt is less than 0.3 mol / L, the conductivity of the electrolyte cannot be sufficiently secured, which may hinder battery discharge characteristics and charge characteristics. As the viscosity of the electrolyte increases and the mobility of lithium ions cannot be sufficiently secured, the conductivity of the electrolyte cannot be sufficiently secured in the same manner as described above, which may hinder battery discharge characteristics and charge characteristics. is there.

  Further, when forming a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte for a battery of the present invention can be used as it is. For example, an appropriate polymer, a porous support, or a gel material is impregnated. It can also be used by a method of holding it.

<Nonaqueous electrolyte secondary battery>
Next, the nonaqueous electrolyte secondary battery of the present invention will be described in detail. The non-aqueous electrolyte secondary battery of the present invention includes the above-described non-aqueous electrolyte for a battery, a positive electrode, and a negative electrode, and is usually used in the technical field of a non-aqueous electrolyte secondary battery such as a separator as necessary. It includes other members that are used. In addition to the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery of the present invention includes a polarizable carbon electrode in the positive electrode and lithium ions in the negative electrode in advance and reversibly occludes lithium ions. An electric double layer capacitor (lithium ion capacitor or hybrid capacitor) using a nonpolarizable carbon electrode that can be detached is also included.

As the positive electrode active material of the non-aqueous electrolyte secondary battery of the present invention, metal oxides such as V ₂ O ₅ , V ₆ O ₁₃ , MnO ₂ , MnO ₃ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFeO Preferred examples include lithium-containing composite oxides such as ₂ and LiFePO ₄ , metal sulfides such as TiS ₂ and MoS ₂ , conductive polymers such as polyaniline, and carbon materials such as activated carbon. 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, Al, and Ni. In this case, the composite oxide LiMn _x Co _y Ni _(1-xy) O ₂ [where 0 ≦ x <1, 0 ≦ y <1, 0 <x + y ≦ 1], LiMn _x Ni _(1-x) O ₂ [wherein , 0 ≦ x <1], LiMn _x Co _(1-x) O ₂ [where 0 ≦ x <1], LiCo _x Ni _(1-x) O ₂ [where 0 ≦ x <1], LiCo _x Ni _y Al [wherein, 0 ≦ x <1,0 ≦ y <1,0 <x + y ≦ 1] (1-xy) O 2, LiFe x Co y Ni (1-xy) O 2 [ wherein , 0 ≦ x <1, 0 ≦ y <1, 0 <x + y ≦ 1], or LiMn _x Fe _y O _{2 -xy} . These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together. In the present invention, the effect is particularly high for a positive electrode active material containing Mn.

As the negative electrode active material of the non-aqueous electrolyte secondary battery of the present invention, lithium metal itself, an alloy of lithium and Al, In, Sn, Si, Pb, Zn or the like, metal oxide such as TiO ₂ doped with lithium ions And metal oxide composite materials such as TiO ₂ —P ₂ O ₄ , carbon materials such as graphite, and the like. 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 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.

  Other members that can be used in the non-aqueous electrolyte secondary battery of the present invention include a separator interposed in the non-aqueous electrolyte secondary battery between positive and negative electrodes to prevent current short-circuit due to contact between both electrodes. It is done. As the material of the separator, it is possible to reliably prevent contact between the two electrodes and to allow the electrolyte to pass through or to contain, for example, synthesis of polytetrafluoroethylene, polypropylene, polyethylene, cellulose, polybutylene terephthalate, polyethylene terephthalate, etc. Preferred examples include resin non-woven fabrics and thin layer films. These may be a single substance, a mixture or a copolymer. 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 separators described above, known members that are normally used in secondary batteries can be suitably used.

  The form of the non-aqueous electrolyte secondary battery of the present invention described above is not particularly limited, and various known forms such as a coin type, a button type, a paper type, a square type or a spiral type cylindrical battery are available. Preferably mentioned. In the case of the button type, a non-aqueous electrolyte secondary battery can be manufactured by preparing a sheet-like positive electrode and negative electrode and sandwiching a separator between the positive electrode and the negative electrode. In the case of a spiral structure, for example, a non-aqueous electrolyte secondary battery is manufactured by, for example, preparing a sheet-like positive electrode, sandwiching a current collector, and superimposing and winding up the sheet-like negative electrode on the current collector. Can do.

  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
In the above general formula (I), n is 3 and ^one of all R ¹ is a trifluoroethoxy group and 5 is fluorine. 10% by volume of cyclic phosphazene compound, 13% by volume of ethylene carbonate, 37% of diethyl carbonate LiBETTI [Li (C ₂ F ₅ SO ₂ ) ₂ N] was dissolved at 1.0 mol / L in a mixed solvent consisting of volume% and methyl propionate 40 volume%, and 3-methyl- A non-aqueous electrolyte was prepared by adding 0.01% by mass of N, N-dimethylaniline. Next, the flame retardancy of the obtained non-aqueous electrolyte was evaluated by the following method, and the results shown in Table 1 were obtained.

(1) Flame Retardancy Evaluation The combustion length and combustion time of a flame ignited in an atmospheric environment were measured and evaluated by a method in which the UL94HB method of UL (Underwriting Laboratory) standard was arranged. Specifically, based on the UL test standard, a 127 mm × 12.7 mm SiO ₂ sheet was impregnated with 1.0 mL of the electrolytic solution, and a test piece was prepared and evaluated. The evaluation criteria for nonflammability, flame retardancy, self-extinguishing properties, and flammability are shown below.
<Evaluation of nonflammability> When the test flame was ignited, it was not ignited at all (burning length: 0 mm).
<Evaluation of Flame Retardancy> The case where the ignited flame did not reach the 25 mm line of the apparatus and the fallen object from the net was not ignited was evaluated as flame retardant.
<Evaluation of self-extinguishing property> When the ignited flame was extinguished on the 25 to 100 mm line and no ignition was observed on the falling object from the net, it was evaluated as having self-extinguishing property.
<Evaluation of flammability> The case where the ignited flame exceeded the 100 mm line was evaluated as flammability.

(2) Production of Battery Using LiMn _0.9 Co _0.1 O ₂ as a positive electrode active material, the oxide, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder are in a mass ratio of 94: 3: 3 The slurry was dispersed in N-methylpyrrolidone and applied to an aluminum foil as a positive electrode current collector, followed by drying and pressing to obtain a positive electrode sheet having a thickness of 70 μm. . This was cut into a rectangle (4 cm × 50 cm), and an aluminum foil current collecting tab was welded to produce a positive electrode. Further, artificial graphite is used as the negative electrode active material, and the artificial graphite and polyvinylidene fluoride as a binder are mixed at a mass ratio of 90:10, and this is mixed with an organic solvent (50/50 mass of ethyl acetate and ethanol). % Mixed solvent) was applied to a copper foil as a negative electrode current collector, followed by drying and pressing to obtain a negative electrode sheet having a thickness of 50 μm. This was cut into a rectangle (4 cm × 50 cm), and a nickel foil current collecting tab was welded to produce a negative electrode. Next, the separator (microporous film: made of polyethylene) is cut into a rectangle (4 cm x 50 cm), sandwiched between the positive electrode and the negative electrode, and flattened using a 4 cm x 3 cm spacer as a base Inserted into a heat-sealed aluminum laminate film (polyethylene terephthalate / aluminum / polypropylene) exterior material, injected the electrolyte, vacuumed and quickly heat-sealed to obtain a flat laminate battery (non-aqueous electrolyte 2 Secondary battery).

(3) Charging / discharging efficiency evaluation Using the laminated battery prepared as described above, a charging / discharging cycle was performed at an upper limit voltage of 4.2 V, a lower limit voltage of 3.0 V, and a current density of 0.25 mA / cm ² in an environment of 20 ° C. The initial charge capacity (mAh / g) and the initial discharge capacity (mAh / g) are determined by dividing the initial charge capacity and initial discharge capacity from the known positive electrode weight, respectively.
Initial discharge efficiency = initial discharge capacity / initial charge capacity x 100 (%)
The initial discharge efficiency was calculated according to the above and used as an index of charge / discharge efficiency. The results are shown in Table 1.

(4) Overcharge safety test The same laminated battery as the above was produced, and the battery safety test by overcharge conditions was conducted. In the overcharge test method, a charge / discharge cycle with a current density of 0.25 mA / cm ² was repeated twice in a voltage range of 4.2 to 3.0 V in an environment of 20 ° C., and further charged to 4.2 V. Place the cell on temperature control with battery holders (stainless steel), 20 by the current density of the battery temperature 5.0 mA / cm ² of ℃ was charged to 12.0 V, yet 0.25 mA / cm ² at the same voltage Charging was continued until the current density reached, and the presence or absence of rupture or ignition was examined. The results are shown in Table 1.

(Example 2)
In the above general formula (I), n is 3, and 5% by volume of the cyclic phosphazene compound in which one of all R ¹ is an allyloxy group and 5 is fluorine, and in the above general formula (I), n is 3. Then, LiPF ₆ is added to a mixed solvent composed of 25% by volume of a cyclic phosphazene compound in which two of the total R ¹ are methoxy groups and four are fluorines, 14% by volume of ethylene carbonate, and 56% by volume of ethyl methyl carbonate. Dissolve it to mol / L, add 0.05% by mass of N, N, 3,5-tetramethylaniline to this to prepare a non-aqueous electrolyte, and flame retardant of the resulting non-aqueous electrolyte Was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Example 3)
In the above general formula (I), n is 3, cyclic phosphazene compound 40% by volume of ethylene, 10% by volume of ethylene carbonate, 50% by volume of ethyl methyl carbonate, ^one of which is butoxy group and 5 is fluorine. LiPF ₆ is dissolved in a mixed solvent consisting of 0.1% by weight to 1.0 mol / L, and 0.02% by mass of N, N, 3,5-tetramethylaniline and 0.5% by mass of vinylene carbonate are added thereto to add non- A water electrolyte was prepared, and the flame retardancy of the obtained nonaqueous electrolyte was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

Example 4
In the above general formula (I), n is 4, cyclic phosphazene compound in which one of R ¹ is ethoxy group and seven is fluorine, 60% by volume, ethylene carbonate 5% by volume, methyl propionate 35% by volume % Of LiPF ₆ is dissolved in 1.0 mol / L and LiTFSI [Li (CF ₃ SO ₂ ) ₂ N] is dissolved in 1.0 mol / L, and 3-methoxy-N, N is dissolved therein. -Dimethylaniline 0.02 mass% and vinylene carbonate 1 mass% were added, the non-aqueous electrolyte solution was prepared, and the flame retardance of the obtained non-aqueous electrolyte solution was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Comparative Example 1)
LiBETTI [Li (C ₂ F ₅ SO ₂ ) ₂ N] is adjusted to 1.0 mol / L in a mixed solvent composed of 20% by volume of ethylene carbonate, 40% by volume of diethyl carbonate and 40% by volume of methyl propionate. After dissolving, 0.01% by mass of 3-methyl-N, N-dimethylaniline was added thereto to prepare a nonaqueous electrolytic solution, and the flame retardancy of the obtained nonaqueous electrolytic solution was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Comparative Example 2)
In the above general formula (I), n is 4, cyclic phosphazene compound in which one of R ¹ is ethoxy group and seven is fluorine, 60% by volume, ethylene carbonate 5% by volume, methyl propionate 35% by volume % Of LiPF ₆ and 1.0% of LiTFSI [Li (CF ₃ SO ₂ ) ₂ N] are dissolved in a mixed solvent of 1.0% by weight to obtain a non-aqueous electrolyte. The non-aqueous electrolyte was evaluated for flame retardancy. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Example 5)
In the above general formula (I), n is 3 and ^one of all R ¹ is trifluoroethoxy group and 5 is fluorine. 4% by volume of cyclic phosphazene compound, 14% by volume of ethylene carbonate, 42% of diethyl carbonate LiBETTI [Li (C ₂ F ₅ SO ₂ ) ₂ N] was dissolved at 1.0 mol / L in a mixed solvent consisting of volume% and methyl propionate 40 volume%, and 3-methyl- A non-aqueous electrolyte was prepared by adding 0.01% by mass of N, N-dimethylaniline, and the flame retardancy of the obtained non-aqueous electrolyte was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Example 6)
In the above general formula (I), a mixed solvent consisting of 75% by volume of a cyclic phosphazene compound in which n is 3 and ^one of all R ¹ is a butoxy group and 5 is fluorine, and 25% by volume of ethyl methyl carbonate. , LiPF ₆ was dissolved to 0.8 mol / L, and 0.02% by mass of N, N, 3,5-tetramethylaniline and 0.5% by mass of vinylene carbonate were added thereto to prepare a non-aqueous electrolyte. The flame retardancy of the obtained non-aqueous electrolyte was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Example 7)
In the above general formula (I), n is 4, cyclic phosphazene compound in which one of R ¹ is ethoxy group and seven is fluorine, 60% by volume, ethylene carbonate 5% by volume, methyl propionate 35% by volume % Of LiPF ₆ is dissolved in 1.0 mol / L and LiTFSI [Li (CF ₃ SO ₂ ) ₂ N] is dissolved in 1.0 mol / L, and 3-methoxy-N, N is dissolved therein. -Dimethylaniline 0.005 mass% was added, the nonaqueous electrolyte solution was prepared, and the flame retardance of the obtained nonaqueous electrolyte solution was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Example 8)
In the above general formula (I), n is 4, cyclic phosphazene compound in which one of R ¹ is ethoxy group and seven is fluorine, 60% by volume, ethylene carbonate 5% by volume, methyl propionate 35% by volume % Of LiPF ₆ is dissolved in 1.0 mol / L and LiTFSI [Li (CF ₃ SO ₂ ) ₂ N] is dissolved in 1.0 mol / L, and 3-methoxy-N, N is dissolved therein. -Dimethylaniline 0.2 mass% was added, the nonaqueous electrolyte solution was prepared, and the flame retardance of the obtained nonaqueous electrolyte solution was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

Example 9
In the above general formula (I), n is 4, cyclic phosphazene compound in which one of R ¹ is ethoxy group and seven is fluorine, 60% by volume, ethylene carbonate 5% by volume, methyl propionate 35% by volume % Of LiPF ₆ is dissolved in 1.0 mol / L and LiTFSI [Li (CF ₃ SO ₂ ) ₂ N] is dissolved in 1.0 mol / L, and 3-methoxy-N, N is dissolved therein. -Dimethylaniline 0.02 mass% and vinylene carbonate 0.1 mass% were added, the non-aqueous electrolyte was prepared, and the flame retardance of the obtained non-aqueous electrolyte was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

(Example 10)
In the above general formula (I), n is 4, cyclic phosphazene compound in which one of R ¹ is ethoxy group and seven is fluorine, 60% by volume, ethylene carbonate 5% by volume, methyl propionate 35% by volume % Of LiPF ₆ is dissolved in 1.0 mol / L and LiTFSI [Li (CF ₃ SO ₂ ) ₂ N] is dissolved in 1.0 mol / L, and 3-methoxy-N, N is dissolved therein. -Dimethylaniline 0.02 mass% and vinylene carbonate 3 mass% were added, the nonaqueous electrolyte solution was prepared, and the flame retardance of the obtained nonaqueous electrolyte solution was evaluated. Moreover, the nonaqueous electrolyte secondary battery was produced like Example 1, and charge / discharge efficiency evaluation and the overcharge safety test were each implemented. The results are shown in Table 1.

  As shown in Examples 1 to 4 in Table 1, a non-aqueous electrolyte containing a compound of formula (I) and an aniline derivative of formula (II) is non-flammable, and a battery using the non-aqueous electrolyte is It can be seen that the irreversible capacity is small and the charge / discharge efficiency is high. Moreover, it turns out that the battery using this non-aqueous electrolyte shows high safety | security in an overcharge safety test. Thus, it was confirmed that the nonaqueous electrolyte solution of the present invention can provide a nonaqueous electrolyte secondary battery that exhibits high non-flammability and is excellent in high charge / discharge efficiency and safety.

  Further, as shown in Examples 3 and 4, it can be seen that a battery having a higher capacity can be obtained by further using vinylene carbonate in combination with the compound of formula (I) and the aniline derivative of formula (II).

  As shown in Comparative Example 2, it can be seen that when the aniline derivative of the formula (II) is not added, the irreversible capacity is large and the charge / discharge efficiency is low as compared with Example 4.

  Furthermore, as shown in Example 5, when the content of the compound represented by the formula (I) was less than 5% by volume, nonflammability was not exhibited, and rupture could not be suppressed even in the overcharge safety test.

  On the other hand, as shown in Example 6, when the content of the compound represented by formula (I) exceeds 70% by volume, although there is no problem in nonflammability and battery safety, vinylene carbonate is used in combination. Also, a tendency for the battery capacity to decrease was observed. Therefore, it can be seen that the content of the cyclic phosphazene compound of the formula (I) is preferably 10 to 60% by volume.

  Further, as shown in Example 7, when the amount of the aniline compound represented by the formula (II) is less than 0.01% by mass, the effect of improving the charge / discharge efficiency is small, and as shown in Example 8, When it exceeded 0.1% by mass, the initial capacity and charge / discharge efficiency tended to decrease significantly. Therefore, it can be seen that the amount of the aniline compound represented by the formula (II) is preferably about 0.01 to 0.05% by mass, more preferably about 0.02 to 0.05% by mass.

  Further, as shown in Example 9, when the amount of vinylene carbonate used in combination with the aniline compound is less than 0.2% by mass, the effect of improving the battery capacity is hardly recognized as compared with Example 4, and Example As shown in FIG. 10, in the case of exceeding 2% by mass, the effect of improving the charge / discharge efficiency was observed to be slow compared with Example 4. Therefore, it is understood that the amount of vinylene carbonate used in combination with the aniline compound is preferably about 0.5 to 1% by mass.

  From the above results, by using a non-aqueous electrolyte characterized by containing a cyclic phosphazene compound represented by formula (I) and an aniline derivative represented by formula (II), high charge and discharge efficiency and high It can be seen that a non-aqueous electrolyte secondary battery having both safety performance can be provided.

Claims (9)

The following general formula (I):
(NPR ¹ ₂ ) _n ... (I)
[Wherein R ¹ independently represents fluorine, an alkoxy group or an aryloxy group; n represents 3 to 4], a non-aqueous solvent, the following general formula (II ):

A non-aqueous electrolyte for a battery comprising an aniline derivative represented by the formula: wherein R ² is independently hydrogen, a methyl group or a methoxy group, and a supporting salt.   Furthermore, vinylene carbonate is included, The non-aqueous electrolyte for batteries of Claim 1 characterized by the above-mentioned. 2. The battery non-aqueous electrolyte according to claim 1, wherein in the general formula (I), at least four of R ¹ are fluorine.   2. The nonaqueous electrolytic solution for a battery according to claim 1, wherein the content of the cyclic phosphazene compound represented by the general formula (I) is 10 to 60% by volume of the entire nonaqueous electrolytic solution for the battery. .   2. The battery non-aqueous electrolyte according to claim 1, wherein the content of the aniline derivative represented by the general formula (II) is 0.01 to 0.05 mass% of the whole battery non-aqueous electrolyte.   The battery non-aqueous electrolyte according to claim 2, wherein the content of the vinylene carbonate is 0.5 to 1% by mass of the whole battery non-aqueous electrolyte.   The battery nonaqueous electrolyte solution according to claim 1, wherein the nonaqueous solvent is an aprotic organic solvent.   8. The non-battery for a battery according to claim 7, wherein the aprotic organic solvent includes at least one selected from the group consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and methyl propionate. Water electrolyte.   A nonaqueous electrolyte secondary battery comprising the battery nonaqueous electrolyte solution according to claim 1, a positive electrode, and a negative electrode.