JP4458841B2 - Nonaqueous electrolyte for battery and nonaqueous electrolyte battery provided with the same - Google Patents

Description

  The present invention relates to a battery non-aqueous electrolyte and a non-aqueous electrolyte battery including the same, and more particularly to a battery non-aqueous electrolyte in which the risk of ignition in an emergency is greatly reduced.

  In recent years, there has been a demand for a lightweight, long-life, high-energy-density battery as a main power source or auxiliary power source for electric vehicles and fuel cell vehicles, or as a power source for small electronic devices. In contrast, a non-aqueous electrolyte battery using lithium as a negative electrode active material is known as one of batteries having a high energy density because the electrode potential of lithium is the lowest among metals and the electric capacity per unit volume is large. Many types of batteries, whether primary batteries or secondary batteries, have been actively researched, and some have been put into practical use and supplied to the market. For example, non-aqueous electrolyte primary batteries are used as power sources for cameras, electronic watches, and various memory backups. In addition, non-aqueous electrolyte secondary batteries are used as drive power sources for notebook computers and mobile phones, and are also being considered for use as main power sources or auxiliary power sources for electric vehicles and fuel cell vehicles. .

  In these non-aqueous electrolyte batteries, lithium as the negative electrode active material reacts violently with compounds having active protons such as water and alcohol, so that the electrolyte used in the batteries is non-ester compounds and ether compounds. Limited to protic organic solvents.

  However, although the aprotic organic solvent has low reactivity with the lithium of the negative electrode active material, for example, when a battery is short-circuited, a large current flows suddenly, and when the battery abnormally generates heat, it is vaporized and decomposed. Therefore, there is a high risk of generating gas, causing the battery to rupture or ignite due to the generated gas and heat, and sparks generated during a short circuit.

  In contrast, a phosphazene compound is added to the battery non-aqueous electrolyte to impart non-flammability, flame retardancy or self-extinguishing properties to the non-aqueous electrolyte, and the battery ignites and ignites in the event of a short circuit or other emergency A non-aqueous electrolyte battery with a greatly reduced risk has been developed (see Patent Document 1).

JP-A-6-13108

  The battery non-aqueous electrolyte to which the phosphazene compound is added has greatly reduced the risk of ignition and ignition, but the phosphazene compound is aprotic when the temperature of the battery rises during an emergency such as a short circuit. When vaporized before the organic solvent, the remaining aprotic organic solvent was vaporized and decomposed alone to generate gas, and the generated gas and heat caused the battery to rupture and ignite, or occurred during a short circuit. The risk of sparks igniting aprotic organic solvents cannot be eliminated. Further, when the aprotic organic solvent is vaporized prior to the phosphazene compound, the vaporized aprotic organic solvent may leak out of the battery and ignite.

  Therefore, the object of the present invention is to ignite and ignite the aprotic organic solvent remaining in the battery and the aprotic organic solvent that evaporates and leaks outside the battery when the temperature of the battery rises abnormally. An object of the present invention is to provide a non-aqueous electrolyte for batteries with reduced risk. Another object of the present invention is to provide a non-aqueous electrolyte battery comprising such a non-aqueous electrolyte and having reduced risk of ignition and the like inside and outside the battery even if the temperature rises abnormally. There is.

  As a result of intensive studies to achieve the above object, the inventors of the present invention, in a battery non-aqueous electrolyte containing at least one aprotic organic solvent, further corresponding to each aprotic organic solvent, Risk of ignition or ignition of aprotic organic solvent remaining in the battery and aprotic organic solvent leaking out of the battery due to vaporization, etc. by adding phosphorus and / or nitrogen-containing compounds having close boiling points Has been found to be significantly reduced, and the present invention has been completed.

That is, the battery non-aqueous electrolyte of the present invention is a battery non-aqueous electrolyte containing at least one aprotic organic solvent and a supporting salt. Each containing a compound having a difference in boiling point with a protic organic solvent of 25 ° C. or less and having phosphorus and / or nitrogen in the molecule;
The compound having phosphorus and / or nitrogen in the molecule is a phosphazene compound, and the phosphazene compound is represented by the following formula (II):
(NPR ⁴ ₂ ) _n ... (II)
A cyclic phosphazene compound in which n is 3 and 3 out of 6 R ⁴ are methoxy groups and 3 are fluorine, represented by the above formula (II), and n in the formula Is a cyclic phosphazene compound in which one of six R ⁴ is an ethoxy group and five is fluorine, represented by the above formula (II), wherein n is 4, and eight R A cyclic phosphazene compound in which all ⁴ are fluorine, represented by the above formula (II), wherein n is 3, and all six R ⁴ are fluorine, A cyclic phosphazene compound represented by formula (II), wherein n is 3 and one of six R ⁴ is methoxy group and five is fluorine, a n in the 3, the cyclic phosphazene with one isopropoxy group of the six R ^4, is a five thereof are fluorine It is at least one selected from the group consisting of compounds,
The aprotic organic solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and methyl formate.

The non-aqueous electrolyte for batteries of the present invention is particularly suitable as an electrolyte for non-aqueous electrolyte secondary batteries.

Moreover, the non-aqueous electrolyte 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, the battery-containing non-aqueous electrolyte containing at least one aprotic organic solvent is further provided with phosphorus and / or nitrogen-containing compounds having close boiling points corresponding to the respective aprotic organic solvents, respectively. By adding, it is possible to provide a non-aqueous electrolyte for a battery that greatly reduces the risk of ignition and ignition of an aprotic organic solvent remaining in the battery or leaking out of the battery. In addition, it is possible to provide a non-aqueous electrolyte battery that includes such a non-aqueous electrolyte and that greatly reduces the risk of ignition and the like inside and outside the battery even if the temperature rises abnormally.

<Non-aqueous electrolyte for batteries>
Below, the non-aqueous electrolyte for batteries of the present invention will be described in detail. The non-aqueous electrolyte for a battery of the present invention contains at least one aprotic organic solvent and a supporting salt, and further has a difference in boiling point between each of the aprotic organic solvents of 25 ° C. or less and phosphorus in the molecule. Each containing a compound having nitrogen and / or a compound having phosphorus and / or nitrogen in the molecule is a phosphazene compound, the phosphazene compound is represented by the above formula (II), and n in the formula is A cyclic phosphazene compound in which three of the six R ⁴ groups are methoxy groups and three are fluorine groups, represented by the above formula (II), wherein n is 3, and six R ⁴ groups A cyclic phosphazene compound in which one is an ethoxy group and five are fluorines, and is a cyclic phosphazene represented by the above formula (II), wherein n is 4, and all eight R ⁴ are fluorine A compound represented by the above formula (II), wherein n A 3, cyclic phosphazene compounds all six R ⁴ is fluorine, represented by the above-mentioned formula (II), an n in formula is 3, six one of a methoxy group of R ⁴ A cyclic phosphazene compound in which five are fluorine, and the above formula (II), wherein n is 3, one of six R ⁴ is an isopropoxy group and five is fluorine Is at least one selected from the group consisting of cyclic phosphazene compounds , and the aprotic organic solvent is at least selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and methyl formate. It is a type.

  In the nonaqueous electrolyte for battery of the present invention, the compound having phosphorus and / or nitrogen in the molecule generates nitrogen gas and / or phosphate ester, etc., and the nonaqueous electrolyte is made nonflammable, flame retardant or self Fire extinguishing has the effect of reducing the risk of battery ignition and the like. However, when the non-aqueous electrolyte containing the aprotic organic solvent does not contain phosphorus and / or nitrogen-containing compounds having a boiling point close to that of the aprotic organic solvent, the aprotic organic solvent is in either the gas phase or the liquid phase. Because of the wide temperature range where phosphorus and / or nitrogen-containing compounds do not coexist, when the battery temperature rises abnormally, ignition of the aprotic organic solvent vaporized or the aprotic organic solvent remaining in the battery The risk of ignition cannot be reduced. In contrast, the battery non-aqueous electrolyte of the present invention contains an aprotic organic solvent and a phosphorus and / or nitrogen-containing compound having a boiling point close to that of the aprotic organic solvent, and the battery temperature rises abnormally. In addition, since the aprotic organic solvent and the phosphorus and / or nitrogen-containing compound are vaporized at a temperature close to the aprotic organic solvent, the aprotic organic solvent is present in both a liquid state and a gas state. And phosphorus and / or nitrogen-containing compounds coexist, and as a result, the risk of non-aqueous electrolyte ignition and ignition is greatly reduced.

  Further, for example, when the non-aqueous electrolyte for a battery of the present invention contains a low-boiling aprotic organic solvent and a high-boiling aprotic organic solvent, the temperature at which the low-boiling aprotic organic solvent vaporizes is reduced. Since the corresponding phosphorus and / or nitrogen-containing compound is vaporized in the vicinity, the risk of ignition and ignition of the vaporized aprotic organic solvent can be reduced. In addition, after the low boiling point aprotic organic solvent and the phosphorus and / or nitrogen-containing compound having a boiling point close to that of the low boiling point aprotic organic solvent are vaporized, together with the high boiling point aprotic organic solvent, the high boiling point Since phosphorus and / or nitrogen-containing compounds having a boiling point close to that of the aprotic organic solvent are present in the electrolytic solution, the risk of ignition and ignition of the remaining nonaqueous electrolytic solution can also be reduced.

The battery non-aqueous electrolyte of the present invention contains at least one aprotic organic solvent. The aprotic organic solvent can keep the viscosity of the non-aqueous electrolyte low without reacting with the negative electrode. Aprotic organic solvents are dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), esters selected from methyl formate (MF) It is . Among these, propylene carbonate is preferred as the aprotic organic solvent for the non-aqueous electrolyte of the primary battery, while ethylene carbonate, as the aprotic organic solvent for the non-aqueous electrolyte of the secondary battery, Propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and methyl formate are preferred. Incidentally, cyclic esters, are preferred in view of excellent solubility of the higher support salt dielectric constant, whereas, chain esters are the low viscosity, in terms of low viscosity of the electrolyte solution Is preferred. These aprotic organic solvents may be used alone or in combination of two or more.

The battery non-aqueous 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.

  The concentration of the supporting salt in the battery non-aqueous electrolyte of the present invention is preferably 0.2 to 1.5 mol / L (M), more preferably 0.5 to 1 mol / L (M). When the concentration of the supporting salt is less than 0.2 mol / L (M), the conductivity of the electrolytic solution cannot be sufficiently ensured, and the discharge characteristics and charging characteristics of the battery may be hindered, and 1.5 mol / L ( (M) exceeds the viscosity of the electrolyte and the mobility of lithium ions cannot be sufficiently secured, so that the conductivity of the electrolyte cannot be sufficiently secured as described above. May cause trouble.

  The nonaqueous electrolytic solution for a battery of the present invention contains a compound having a boiling point difference of 25 ° C. or less and phosphorus and / or nitrogen in the molecule, with an aprotic organic solvent contained in the electrolytic solution. When the difference in boiling point between the aprotic organic solvent and the phosphorus and / or nitrogen-containing compound contained in the non-aqueous electrolyte exceeds 25 ° C, the aprotic organic solvent is vaporized first, and the gaseous aprotic organic solvent Is ignited, and phosphorus and / or nitrogen-containing compounds are vaporized first, and the remaining liquid aprotic organic solvent is ignited. Here, from the viewpoint of further reducing the risk of ignition of the aprotic organic solvent, the difference in boiling point between the aprotic organic solvent and the compound having phosphorus and / or nitrogen in the molecule is 20 ° C. or less. preferable. The non-aqueous electrolyte for a battery of the present invention may contain at least a phosphorus and / or nitrogen-containing compound having a boiling point of 25 ° C. or less from each of the aprotic organic solvents, and the difference in boiling point is 25. Phosphorus and / or nitrogen-containing compounds that exceed ° C. may further be included.

Compound with phosphorus and / or nitrogen in the molecule is a phosphazene compound, a compound having a phosphorus and nitrogen in the molecule. The phosphorus and / or nitrogen-containing compound is appropriately selected according to the aprotic organic solvent used in the electrolytic solution.

Compounds containing phosphorus and / or nitrogen in the molecule, from the viewpoint of cycle characteristics of the secondary battery, a phosphazene compound, also from the viewpoint of improvement of improved and high-temperature storage characteristics of the thermal stability of the battery, the phosphazene it is a compound.

As the phosphazene compound, specifically, by the following formula (II):
(NPR ⁴ ₂ ) _n ... (II)
A cyclic phosphazene compound in which n is 3 and 3 out of 6 R ⁴ are methoxy groups and 3 are fluorine, represented by the above formula (II), and n in the formula Is a cyclic phosphazene compound in which one of six R ⁴ is an ethoxy group and five is fluorine, represented by the above formula (II), wherein n is 4, and eight R A cyclic phosphazene compound in which all ⁴ are fluorine, represented by the above formula (II), wherein n is 3, and all six R ⁴ are fluorine, A cyclic phosphazene compound represented by formula (II), wherein n is 3 and one of six R ⁴ is methoxy group and five is fluorine, a n in the 3, the cyclic phosphazene with one isopropoxy group of the six R ^4, is a five thereof are fluorine Use at least one selected from the group consisting of compounds.

The phosphazene compound is a liquid at 25 ° C. (room temperature), the viscosity at 25 ° C. or less 5mPa · s (5cP). 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. When the viscosity of the phosphazene compound at 25 ° C exceeds 300 mPa · s (300 cP), the supporting salt becomes difficult to dissolve, the wettability to the positive electrode material, negative electrode material, separator, etc. decreases, and the viscosity resistance of the electrolyte increases. The ionic conductivity is remarkably lowered, and the performance becomes insufficient particularly when used under low temperature conditions such as below the freezing point. Further, since these phosphazene compounds are in a liquid state, they have the same conductivity as that of a normal liquid electrolyte, and exhibit excellent cycle characteristics when used in an electrolyte solution for a secondary battery.

In the formula (II), R ⁴ is a methoxy group, an ethoxy group, an isopropoxy group or fluorine. In that the electrolytic solution may lower the viscosity, a methoxy group, an ethoxy group, an isopropoxy group rather preferred, a methoxy group, an ethoxy group are particularly preferred.

The said phosphazene compound may be used individually by 1 type, and may use 2 or more types together.

Among the phosphazene compound, the electrolytic solution was lower viscosity to improve the low-temperature characteristics of the battery, from the viewpoint of further improving the degradation resistance and safety of the electrolyte, represented by above-mentioned formula (II), wherein a n of 4, the cyclic phosphazene compound all eight R ⁴ is fluorine, and, represented by above-mentioned formula (II), a wherein n is 3, six R ⁴ Cyclic phosphazene compounds , all of which are fluorine, are preferred .

A cyclic phosphazene compound represented by the above formula (II), wherein n is 4 and all 8 R ⁴ are fluorine, and the above formula (II), The cyclic phosphazene compound in which n is 3 and all six R ⁴ are fluorine is a low-viscosity liquid at room temperature (25 ° C.) and has a freezing point depressing action. Therefore, by adding the phosphazene compound to the electrolyte, it is possible to impart excellent low-temperature characteristics to the electrolyte, also, the low viscosity of the electrolyte solution is achieved, the low internal resistance and high conductivity It becomes possible to provide the nonaqueous electrolyte battery which has. For this reason, it is possible to provide a nonaqueous electrolyte battery that exhibits excellent discharge characteristics over a long period of time even when used under low temperature conditions, particularly in regions and times when the temperature is low.

The electrolyte solution can be provided with excellent low-temperature characteristics and can be reduced in viscosity, and is represented by the above formula (II). In the formula, n is 3, and the total of six R ^{4 s} . Particularly preferred are cyclic phosphazene compounds which are all fluorine . When the value of n is small, the boiling point is low, and the ignition prevention property at the time of flame contact can be improved. 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 the formula (VI), it is possible to prepare an electrolytic solution having a more suitable viscosity, solubility suitable for mixing, low temperature characteristics, and the like. These phosphazene compounds may be used alone or in combination of two or more.

Among the phosphazene compound, from the viewpoint of improving the degradation resistance and safety of the electrolyte, represented by above-mentioned formula (II), a wherein n is 3, three of the six R ⁴ A cyclic phosphazene compound having three methoxy groups, fluorine represented by the above formula (II), wherein n is 3, one of six R ⁴ is an ethoxy group and five are fluorine A cyclic phosphazene compound represented by the above formula (II), wherein n is 3, one of six R ⁴ groups is a methoxy group, and five are fluorines, and the above formula ( Preferred is a cyclic phosphazene compound represented by II), wherein n is 3, 1 of 6 R ⁴ is an isopropoxy group and 5 is fluorine .

If the phosphazene compound is contained, the electrolyte solution can be provided with excellent self-extinguishing properties or flame retardancy to improve the safety of the electrolyte solution, but represented by the above formula (II), n in the formula Is a cyclic phosphazene compound in which three of the six R ⁴ groups are methoxy groups and three are fluorine, represented by the above formula (II), wherein n is 3, ^A cyclic phosphazene compound in which one of four is an ethoxy group and five is fluorine, represented by the above formula (II), wherein n is 3, and one of six R ⁴ is a methoxy group, A cyclic phosphazene compound wherein 5 is fluorine, and a cyclic phosphazene compound represented by the above formula (II), wherein n is 3, 1 of 6 R ⁴ is an isopropoxy group and 5 is fluorine if at least one selected from the group consisting of phosphazene compound, the electrolyte It is possible to impart more excellent safety. That is, compared with the phosphazene compound containing no fluorine, the phosphazene compound has an effect of hardly burn more electrolyte solution, it is possible to impart more excellent safety to the electrolyte solution.

R ⁴ in formula (II), from the viewpoint of excellent improvement of safety of the electrolytic solution, a methoxy group, an ethoxy group are particularly preferred. Moreover, a methoxy group is preferable in terms of reducing the viscosity of the electrolytic solution.

It said phosphazene compound comprises a fluorine, those containing fluorine tends effect of improving the cycle characteristics of the secondary battery as compared with those containing chlorine is large.

  In the nonaqueous electrolytic solution for a battery of the present invention, the content of the compound containing phosphorus and / or nitrogen in the molecule is preferably 3% by volume or more, and 5% by volume or more from the viewpoint of improving the safety of the electrolytic solution. Is more preferable.

<Nonaqueous electrolyte battery>
Next, the nonaqueous electrolyte battery of the present invention will be described in detail. The non-aqueous electrolyte 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 non-aqueous electrolyte batteries such as a separator as necessary. Other members are provided.

The positive electrode active material of the non-aqueous electrolyte battery of the present invention is partially different between the primary battery and the secondary battery. For example, as the positive electrode active material of the non-aqueous electrolyte primary battery, fluorinated graphite [(CF _x ) _n ], MnO ₂ (which may be electrochemical synthesis or chemical synthesis), V ₂ O ₅ , MoO ₃ , Ag ₂ CrO ₄ , CuO, CuS, FeS ₂ , SO ₂ , SOCl ₂ , TiS _2, etc. Among these, MnO ₂ and fluorinated graphite are preferable from the viewpoints of high capacity and high safety, and high discharge potential and excellent wettability of the electrolytic solution. These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together.

On the other hand, as the positive electrode active material of the non-aqueous electrolyte secondary battery, 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 _{2 are used.} Preferable examples include lithium-containing composite oxides such as LiFePO ₄ , 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 in terms of high capacity, high safety, and excellent electrolyte wettability. These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together.

  The negative electrode active material of the nonaqueous electrolyte battery of the present invention is partially different between the primary battery and the secondary battery. For example, as the negative electrode active material of the nonaqueous electrolyte primary battery, lithium metal itself, lithium alloy, etc. Is mentioned. Examples of the metal that forms an alloy with lithium include Sn, Pb, Al, Au, Pt, In, Zn, Cd, Ag, and Mg. Among these, Al, Zn, and Mg are preferable from the viewpoints of rich reserves and toxicity. These negative electrode active materials may be used individually by 1 type, and may use 2 or more types together.

  On the other hand, preferred examples of the negative electrode active material of the non-aqueous electrolyte secondary battery include lithium metal itself, an alloy of lithium and Al, In, Pb or Zn, a carbon material such as graphite doped with lithium, and the like. Among these, a carbon material such as graphite is preferable, and graphite is particularly preferable in view of higher safety and excellent wettability of the electrolytic solution. 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 in the same mixing ratio as in the past. Specifically, in the case of a positive electrode of a primary battery, the mass ratio of positive electrode active material: binder: conductive agent is 8: 1: 0.2. ~ 8: 1: 1 is preferable, and in the case of a positive electrode and a negative electrode of a secondary battery, the mass ratio of active material: binder: conductive agent is preferably 94: 3: 3.

  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 cylindrical shape, a plate shape, a spiral shape, and the like can be given.

  As another member used in the nonaqueous electrolyte battery of the present invention, a separator interposed in the nonaqueous electrolyte battery between the positive and negative electrodes to prevent a short circuit of current due to contact of both electrodes can be mentioned. 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. 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 batteries can be suitably used.

  The form of the non-aqueous electrolyte battery of the present invention described above is not particularly limited, and various known forms such as a coin-type, button-type, paper-type, square-type or spiral-type cylindrical battery are suitable. Can be mentioned. In the case of the button type, a non-aqueous electrolyte battery can be produced 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 battery can be manufactured by preparing a sheet-like positive electrode, sandwiching a current collector, and stacking and winding a sheet-like negative electrode on the current collector. it can.

  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
Ethylene carbonate (EC, boiling point 238 ° C.) 50% by volume, diethyl carbonate (DEC, boiling point 127 ° C.) 40% by volume, additive A [in formula (II), n is 3 and 3 of 6 R ⁴ A cyclic phosphazene compound having one methoxy group (CH ₃ O—) and three fluorines, viscosity at 25 ° C .: 3.9 mPa · s, boiling point 230 ° C., 5% by volume and additive B [in the formula (II), n is 3 A cyclic phosphazene compound in which one of the six R ⁴ groups is an ethoxy group (CH ₃ CH ₂ O—) and five are fluorine, viscosity at 25 ° C .: 1.2 mPa · s, boiling point 125 ° C.] from 5% by volume A non-aqueous electrolyte was prepared by dissolving LiPF ₆ (supporting salt) at a concentration of 1 mol / L (M) in the mixed solution. Moreover, the safety | security of the obtained non-aqueous electrolyte was evaluated by the following method. The results are shown in Table 1.

(1) Safety of electrolyte solution The safety of the non-aqueous electrolyte solution was evaluated from the combustion behavior of flames ignited in an atmospheric environment by the method of arranging the 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 standard, a non-combustible quartz fiber was impregnated with 1.0 mL of the electrolytic solution, and a test piece of 127 mm × 12.7 mm was produced. Here, when the test flame does not ignite the test piece (combustion length: 0 mm), it is “non-flammable”. 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, 3 parts by mass of acetylene black (conductive agent) and 3 parts by mass of polyvinylidene fluoride (binder) are added to 94 parts by mass of LiMn ₂ O ₄ (positive electrode active material), and an organic solvent (acetic acid (50/50 mass% mixed solvent of ethyl and ethanol), kneaded product was coated on aluminum foil (current collector) with a thickness of 25μm with a doctor blade, and dried with hot air (100 ~ 120 ℃) Thus, a positive electrode sheet having a thickness of 80 μm was produced.

  A 150 μm-thick lithium metal foil was overlapped and wound on the positive electrode sheet via a 25 μm-thick separator (microporous film: made of polypropylene) to produce a cylindrical electrode. The positive electrode length of the cylindrical electrode was about 260 mm. The electrolyte was poured into the cylindrical electrode and sealed to prepare an AA lithium battery (non-aqueous electrolyte secondary battery). The obtained battery was subjected to a nail penetration test and an overcharge test by the following methods. The results are shown in Table 1.

(2) Nail penetration test After fully charging the test battery, a nail with a diameter of 5 mm penetrates in the middle of the battery in the direction perpendicular to the electrode surface and is allowed to stand for 24 hours. Observed whether or not.

(3) Overcharge test
The test battery was overcharged to 250% of the rated capacity with a current value of 1C (current value that reached full charge in 1 hour), and whether or not the battery ignited was observed. However, a safety circuit is not included with the test battery.

(Examples 2-9 and Comparative Examples 1-6)
A mixed solution having the composition shown in Table 1 or 2 was prepared, and LiPF ₆ (supporting salt) was dissolved in the mixed solution at a concentration of 1 mol / L (M) to prepare a non-aqueous electrolyte. The safety of the obtained nonaqueous electrolytic solution was evaluated in the same manner as in Example 1. Further, a non-aqueous electrolyte secondary battery was produced using the non-aqueous electrolyte in the same manner as in Example 1, and a nail penetration test and an overcharge test were performed on the battery. The results are shown in Tables 1 and 2.

  In Tables 1 and 2, PC is propylene carbonate (boiling point 242 ° C.), DMC is dimethyl carbonate (boiling point 90 ° C.), EMC is ethyl methyl carbonate (boiling point 108 ° C.), and MF is methyl formate (boiling point). 32 ° C).

Additive C is a cyclic phosphazene compound (viscosity at 25 ° C .: 0.8 mPa · s, boiling point 86 ° C.) in which n is 4 and all 8 R ⁴ are fluorine in formula (II). Yes; additive D is a cyclic phosphazene compound (viscosity at 25 ° C .: 0.8 mPa · s, boiling point 51 ° C.) in which n is 3 and all six R ⁴ are fluorine in formula (II) Yes; Additive E is a cyclic phosphazene compound (viscosity at 25 ° C.) in which n is 3 and one of six R ⁴ is methoxy group (CH ₃ O—) and five are fluorine in formula (II) The additive F is represented by formula (II) in which n is 3, and three of the six R ⁴ groups are ethoxy groups (CH ₃ CH ₂ O—), Three are cyclic phosphazene compounds (viscosity at 25 ° C .: 4.0 mPa · s, boiling point> 300 ° C.); additive G is represented by formula (II) Te, n is a 3, one isopropoxy group of the six _{^{R 4 [(CH 3) 2}} CHO -], 5 one the viscosity of the cyclic phosphazene compound (25 ° C. is fluorine: 1.1 mPa · s, a boiling point 137 ° C).

  The non-aqueous electrolyte solution of the example in which the phosphazene compound having a near boiling point is added to each of the aprotic organic solvents is highly safe, and the non-aqueous electrolyte solution 2 of the example using the non-aqueous electrolyte solution 2 The secondary battery did not ignite in both the nail penetration test and the overcharge test, and it was confirmed that the safety was high even in an emergency.

  On the other hand, the batteries of Comparative Examples 1 and 2 using the non-aqueous electrolyte containing no phosphorus and / or nitrogen-containing compound ignited in the nail penetration test and the overcharge test. In addition, the battery of Comparative Example 3 using a nonaqueous electrolytic solution containing a phosphazene compound having a boiling point close to that of DEC but not including phosphorus and / or a nitrogen-containing compound having a boiling point close to EC, phosphorus having a boiling point close to EC and / or The battery of Comparative Example 4 using a non-aqueous electrolyte containing no nitrogen-containing compound, phosphorus having a boiling point close to that of DEC, and / or a phosphazene compound not containing a nitrogen-containing compound and having a boiling point not close to either EC or DEC, Comparison using a non-aqueous electrolyte containing a phosphazene compound having a boiling point close to that of EC and not containing a phosphorus and / or nitrogen-containing compound having a boiling point close to that of MF, and further containing a phosphazene compound having a boiling point close to that of EC and MF The battery of Example 6 ignited in the nail penetration test and the overcharge test. Furthermore, the battery of Comparative Example 5 using a non-aqueous electrolyte containing a phosphazene compound having a boiling point close to that of DEC but not containing a phosphorus and / or nitrogen-containing compound having a boiling point close to that of EC did not ignite in the nail penetration test. However, it ignited in the overcharge test.

  From the above results, by adding a compound having a close boiling point and having phosphorus and / or nitrogen in the molecule to each of the aprotic organic solvents constituting the non-aqueous electrolyte, It can be seen that safety can be improved, and that the safety of the nonaqueous electrolyte secondary battery in an emergency can be remarkably improved by using the nonaqueous electrolyte in a nonaqueous electrolyte secondary battery.

(Example 10)
Propylene carbonate (PC, boiling point 242 ° C.) 60% by volume, 1,2-dimethoxyethane (DME, boiling point 84 ° C.) 30% by volume, additive A [in the formula (II), n is 3 and 6 R Cyclic phosphazene compound in which 3 out of ⁴ are methoxy groups (CH ₃ O—) and 3 are fluorine, viscosity at 25 ° C .: 3.9 mPa · s, boiling point 230 ° C. 5% by volume and additive C [in the formula (II) , N is 4 and cyclic phosphazene compound in which all 8 R ⁴ are fluorine, viscosity at 25 ° C .: 0.8 mPa · s, boiling point 86 ° C.] 5% by volume is prepared and mixed. LiBF ₄ (supporting salt) was dissolved in the solution at a concentration of 0.75 mol / L (M) to prepare a non-aqueous electrolyte. The safety of the obtained nonaqueous electrolytic solution was evaluated in the same manner as in Example 1. The results are shown in Table 3.

Next, after mixing and kneading MnO ₂ (positive electrode active material), acetylene black (conductive agent), and polyvinylidene fluoride (binder) in a ratio (mass ratio) of 8: 1: 1, The kneaded product was pressure-bonded and pelletized on a nickel foil (current collector) having a thickness of 25 μm, and further heated and dried (100 to 120 ° C.) to produce a positive electrode pellet having a thickness of 500 μm.

  The positive electrode pellet punched to φ16 mm is used as the positive electrode, the lithium foil (thickness 0.5 mm) punched out to φ16 mm is used as the negative electrode, and the positive and negative electrodes are opposed to each other through a cellulose separator [TF4030 manufactured by Nippon Kogyo Paper Industries Co., Ltd.]. The electrolyte solution was injected and sealed to produce a CR2016 type non-aqueous electrolyte primary battery (lithium primary battery). A heating test was performed on the obtained battery by the following method. The results are shown in Table 3.

(4) Heat test The battery was placed in an oven, heated to 160 ° C. at a rate of 5 ± 2 ° C./min, held at 160 ° C. for 60 minutes, and observed whether the battery ignited.

( Example 13 and Comparative Examples 7-12)
A mixed solution having the composition shown in Table 3 was prepared, and LiBF ₄ (supporting salt) was dissolved in the mixed solution at a concentration of 0.75 mol / L (M) to prepare a nonaqueous electrolytic solution. The safety of the obtained nonaqueous electrolytic solution was evaluated in the same manner as in Example 1. Moreover, the nonaqueous electrolyte primary battery was produced using this nonaqueous electrolyte like Example 10, and the heating test was implemented with respect to this battery. The results are shown in Table 3.

In Table 3, GBL represents γ-butyrolactone (boiling point 204 ° C.). The additive B is a cyclic phosphazene compound (25 ° C.) in which n is 3 and one of the six R ⁴ groups is an ethoxy group (CH ₃ CH ₂ O—) and five are fluorine atoms in the formula (II). In the formula (II), n is 3 and 3 out of 6 R ⁴ are ethoxy groups (CH ₃ CH ₂ O—). ), three of the cyclic phosphazene compound is a fluorine (viscosity at 25 ℃: 4.0 mPa · s, a boiling point of 300 ° C. greater).

  The nonaqueous electrolytic solution of the example in which the phosphazene compound having a near boiling point is added to each of the aprotic organic solvents has high safety, and the nonaqueous electrolytic solution 1 of the example using the nonaqueous electrolytic solution 1 The secondary battery did not ignite in the heating test and was confirmed to be highly safe even in an emergency.

  On the other hand, the batteries of Comparative Examples 7 and 8 using the non-aqueous electrolyte containing no phosphorus and / or nitrogen-containing compound ignited in the heating test. Further, the battery of Comparative Example 9 using a non-aqueous electrolyte containing a phosphazene compound having a boiling point close to PC but not containing phosphorus and / or a nitrogen-containing compound having a boiling point close to DME, phosphorus having a boiling point close to PC and / or The battery of Comparative Example 10 using a non-aqueous electrolyte containing no nitrogen-containing compound, phosphorus having a boiling point close to that of DME, and / or a phosphazene compound not containing a nitrogen-containing compound and having a boiling point not close to either PC or DME, In addition, the batteries of Comparative Examples 11 and 12 using a non-aqueous electrolyte containing a phosphazene compound not containing phosphorus and / or nitrogen having a boiling point close to that of GBL and not having a boiling point close to GBL ignited in the heating test.

  From the above results, by adding a compound having a close boiling point and having phosphorus and / or nitrogen in the molecule to each of the aprotic organic solvents constituting the non-aqueous electrolyte, It can be seen that safety can be improved, and that the safety of the non-aqueous electrolyte primary battery in an emergency can be remarkably improved by using the non-aqueous electrolyte in a non-aqueous electrolyte primary battery.

Claims (2)

In a non-aqueous electrolyte for a battery comprising at least one aprotic organic solvent and a supporting salt,
Furthermore, each of the aprotic organic solvents contains a compound having a difference in boiling point from the aprotic organic solvent of 25 ° C. or less and having phosphorus and / or nitrogen in the molecule,
The compound having phosphorus and / or nitrogen in the molecule is a phosphazene compound, and the phosphazene compound is represented by the following formula (II):
(NPR ⁴ ₂ ) _n ... (II)
A cyclic phosphazene compound in which n is 3 and 3 out of 6 R ⁴ are methoxy groups and 3 are fluorine, represented by the above formula (II), and n in the formula Is a cyclic phosphazene compound in which one of six R ⁴ is an ethoxy group and five is fluorine, represented by the above formula (II), wherein n is 4, and eight R A cyclic phosphazene compound in which all ⁴ are fluorine, represented by the above formula (II), wherein n is 3, and all six R ⁴ are fluorine, A cyclic phosphazene compound represented by formula (II), wherein n is 3 and one of six R ⁴ is methoxy group and five is fluorine, a n in the 3, the cyclic phosphazene with one isopropoxy group of the six R ^4, is a five thereof are fluorine It is at least one selected from the group consisting of compounds,
The non-aqueous electrolyte for a battery, wherein the aprotic organic solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and methyl formate.   A nonaqueous electrolyte battery comprising the battery nonaqueous electrolyte solution according to claim 1, a positive electrode, and a negative electrode.