JP5223395B2 - Non-aqueous electrolyte solution for non-aqueous electrolyte battery and non-aqueous electrolyte battery - Google Patents

Abstract

Disclosed is a nonaqueous electrolyte solution which enables to obtain a battery with high capacity which generates only a small amount of gas, while being excellent in storage characteristics and cycle characteristics. This nonaqueous electrolyte solution contains an electrolyte and a nonaqueous solvent dissolving the electrolyte, and further contains a compound represented by the general formula (1) below in an amount of not less than 0.001% by volume but less than 1% by volume in the nonaqueous solvent. Alternatively, the nonaqueous electrolyte solution contains the compound represented by the general formula (1) below in an amount of not less than 0.001% by volume but less than 5% by volume in the nonaqueous solvent, and further contains at least one compound selected from the group consisting of cyclic carbonate compounds having a carbon-carbon unsaturated bond, cyclic carbonate compounds having a fluorine atom, monofluorophosphates and difluorophosphates. In the general formula (1), R<1>-R<3> independently represent an alkyl group having 1-12 carbon atoms which may be substituted by a halogen atom; and n represents an integer of 0-6.

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte battery using the same.

  Non-aqueous electrolyte batteries such as lithium secondary batteries are being put to practical use in a wide range of applications from so-called consumer power sources such as mobile phones and laptop computers to in-vehicle power sources for automobiles and the like. However, the demand for higher performance of non-aqueous electrolyte batteries in recent years is increasing, and there is a demand for improvement in battery characteristics.

  The electrolyte used for a non-aqueous electrolyte battery is usually composed mainly of an electrolyte and a non-aqueous solvent. The main components of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate and propylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone. It is used.

  In order to improve battery characteristics such as load characteristics, cycle characteristics, and storage characteristics of such non-aqueous electrolyte batteries, various studies have been made on non-aqueous solvents and electrolytes.

  For example, Patent Document 1 discloses a non-aqueous solvent composed of a phosphoric ester compound having a specific structure, which is non-flammable and safe, can generate a high voltage, and has excellent battery charge / discharge performance. Aqueous electrolytes have been proposed.

Further, in Patent Document 2, when a mixture of an asymmetric chain carbonate and a cyclic carbonate having a double bond is used as a non-aqueous solvent, the cyclic carbonate having a double bond reacts preferentially with the negative electrode, and the negative electrode surface. It has been proposed that a good-quality film is formed, which suppresses the formation of a non-conductive film on the negative electrode surface due to the asymmetric chain carbonate, thus improving storage characteristics and cycle characteristics.
Japanese Patent Laid-Open No. 10-189039 Japanese Patent Laid-Open No. 11-185806

  However, the demand for higher performance of batteries in recent years is increasing, and it is required to achieve high capacity, high temperature storage characteristics, and cycle characteristics at a high level.

  Conventionally, as a method for increasing the capacity of a battery, it has been studied to pack as many active materials as possible in a limited battery volume. Designs that minimize the volume occupied by materials other than active materials have become common. However, if the active material layer of the electrode is pressed to increase the density, or the amount of the electrolyte is reduced to reduce the volume occupied by the active material other than the active material inside the battery, the active material cannot be used uniformly and is not uniform. As a result of this reaction, the deterioration of the active material is promoted, and a problem that sufficient characteristics cannot be obtained easily occurs.

  Furthermore, the increase in the capacity reduces the voids inside the battery, and there arises a problem that the internal pressure of the battery significantly increases even if a small amount of gas is generated by the decomposition of the electrolyte. In particular, in non-aqueous electrolyte two batteries, in most cases used as a backup power source in the event of a power failure or as a power source for portable equipment, a weak current is always supplied to make up for the self-discharge of the battery, and the battery is continuously charged. In such a continuously charged state, the activity of the electrode active material is always high, and at the same time, due to the heat generated by the device, the capacity of the battery is reduced, or the electrolyte is decomposed and gas is easily generated. If a large amount of gas is generated, a safety valve may be activated in a battery that senses this when the internal pressure is abnormally increased due to an abnormality such as overcharge and activates the safety valve. Further, in a battery without a safety valve, the battery may expand due to the pressure of the generated gas, and the battery itself may become unusable.

  In the non-aqueous electrolyte secondary battery using the electrolyte described in Patent Documents 1 and 2, as described above, it has not yet been satisfactory in terms of suppression of gas generation and high-temperature storage characteristics.

  The present invention has been made in view of the above-described conventional situation, and includes a non-aqueous electrolyte that can realize a non-aqueous electrolyte battery that generates less gas, has a high capacity, and has excellent storage characteristics and cycle characteristics. An object is to provide a high-performance non-aqueous electrolyte battery that can be miniaturized using a non-aqueous electrolyte.

  As a result of various studies to achieve the above object, the present inventors have found that the above problems can be solved by including a compound having a specific structure in the electrolytic solution, thereby completing the present invention. It came to let you.

That is, the gist of the present invention is as follows.
In a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent that dissolves the electrolyte, the non-aqueous electrolyte solution contains 0.001% by volume or more and less than 1% by volume of the compound represented by the following general formula (1) in the non-aqueous solvent. A non-aqueous electrolyte solution for a non-aqueous electrolyte battery , comprising:
And a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent that dissolves the electrolyte, wherein the non-aqueous electrolyte solution contains 0.001% by volume or more and 5% by volume of the compound represented by the following general formula (1) in the non-aqueous solvent. A cyclic carbonate compound having a carbon-carbon unsaturated bond, a cyclic carbonate compound having a fluorine atom, at least one compound selected from the group consisting of monofluorophosphates and difluorophosphates. A nonaqueous electrolyte solution for a nonaqueous electrolyte battery ,
Exist.

（一般式（１）中、Ｒ^１〜Ｒ^３は、それぞれ独立して、ハロゲン原子で置換されていてもよい、炭素数１〜１２のアルキル基を示し、ｎは０〜６の整数を示す。）

(In General Formula (1), R ^{1 to} R ³ each independently represents an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and n represents an integer of 0 to 6). .)

Another gist of the present invention is a non-aqueous electrolyte battery including a negative electrode and a positive electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is the non-aqueous electrolyte battery described above. The present invention resides in a nonaqueous electrolyte battery characterized by being a nonaqueous electrolyte solution.

  According to the present invention, it is possible to provide a non-aqueous electrolyte battery that generates less gas, has a high capacity, and has excellent storage characteristics and cycle characteristics, and achieves downsizing and high performance of the non-aqueous electrolyte battery. be able to.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified by these contents.

[Non-aqueous electrolyte]
The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, as in the case of a conventional non-aqueous electrolyte solution.

<Electrolyte>
As the electrolyte, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples include the following.

For example, inorganic lithium salts such as LiPF ₆ and LiBF ₄ ; LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide , Lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ ( C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ ( _{CF 3 SO 2) 2, LiBF} 2 (C 2 F 5 SO 2) fluorine-containing organic lithium salt and lithium bis _2, etc. (oxalate) volley , And lithium difluoro (oxalato) borate and the like.

Of these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ or LiN (C ₂ F ₅ SO ₂ ) ₂ are preferable from the viewpoint of improving battery performance, and LiPF ₆ or LiBF ₄ is particularly preferable. preferable.

  These lithium salts may be used alone or in combination of two or more.

A preferable example in the case of using two or more lithium salts in combination is a combination of LiPF ₆ and LiBF ₄ , which has an effect of improving cycle characteristics. In this case, the proportion of LiBF _{4 in} the total of both is preferably 0.01% by weight or more, particularly preferably 0.1% by weight or more, preferably 20% by weight or less, particularly preferably 5% by weight or less. is there. If the ratio of LiBF ₄ is below this lower limit, the desired effect may be difficult to obtain, and if it exceeds the upper limit, battery characteristics after high-temperature storage may be reduced.

Another example is the combined use of an inorganic lithium salt and a fluorine-containing organic lithium salt. In this case, the proportion of the inorganic lithium salt in the total of both is 70% by weight or more and 99% by weight or less. It is desirable. Examples of the fluorine-containing organic lithium salt include LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane. It is preferably any of disulfonylimide. The combined use of both has the effect of suppressing deterioration due to high temperature storage.

Further, when the non-aqueous solvent is intended to include γ- butyrolactone 55 volume% or more, as the lithium salt, LiBF _4, or in combination with LiBF ₄ and other lithium salts are preferred. In this case, LiBF ₄ preferably accounts for 40 mol% or more of the total lithium salt. Particularly preferably, the proportion of LiBF _{4 in} the lithium salt is 40 mol% or more and 95 mol% or less, and the remainder is LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) is a combination of one or more selected from the group consisting of ₂ .

  The concentration of these electrolytes in the non-aqueous electrolytic solution is not particularly limited in order to exhibit the effects of the present invention, but is usually 0.5 mol / liter or more, preferably 0.6 mol / liter or more, more Preferably it is 0.7 mol / liter or more. The upper limit is usually 3 mol / liter or less, preferably 2 mol / liter or less, more preferably 1.8 mol / liter or less, and still more preferably 1.5 mol / liter or less. If the concentration of the electrolyte in the non-aqueous electrolyte is too low, the electrical conductivity of the electrolyte may be insufficient, whereas if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity. Battery performance may be reduced.

<Non-aqueous solvent>
The non-aqueous solvent can also be appropriately selected from conventionally known solvents for non-aqueous electrolyte solutions. Examples thereof include cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, cyclic carboxylic acid esters, chain carboxylic acid esters, sulfur-containing organic solvents, and phosphorus-containing organic solvents.

  Examples of the cyclic carbonates include alkylene carbonates having an alkylene group having 2 to 4 carbon atoms such as ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are used for improving battery characteristics. Particularly preferred is ethylene carbonate.

  As the chain carbonates, dialkyl carbonates are preferable, and the number of carbon atoms of the constituting alkyl group is preferably 1 to 5 and particularly preferably 1 to 4 for each of the two alkyl groups. Specifically, for example, symmetric chain alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; asymmetric chain alkyls such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate Examples thereof include dialkyl carbonates such as carbonates. Among these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable from the viewpoint of improving battery characteristics (particularly, high load discharge characteristics).

  Examples of cyclic ethers include tetrahydrofuran and 2-methyltetrahydrofuran.

  Examples of chain ethers include dimethoxyethane and dimethoxymethane.

  Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone.

  Examples of chain carboxylic acid esters include methyl acetate, methyl propionate, ethyl propionate, and methyl butyrate.

  Examples of the sulfur-containing organic solvent include sulfolane, 2-methylsulfolane, 3-methylsulfolane, and diethylsulfone.

  Examples of the phosphorus-containing organic solvent include trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, and the like.

  These non-aqueous solvents may be used alone or in combination of two or more, but it is preferable to use in combination of two or more compounds. For example, it is preferable to use a high dielectric constant solvent such as alkylene carbonates or cyclic carboxylic acid esters in combination with a low viscosity solvent such as dialkyl carbonates or chain carboxylic acid esters.

  One preferable combination of the non-aqueous solvents is a combination mainly composed of alkylene carbonates and dialkyl carbonates. Among them, the total of alkylene carbonates and dialkyl carbonates in the nonaqueous solvent is 70% by volume or more, preferably 80% by volume or more, more preferably 90% by volume or more, and the alkylene carbonates and dialkyl carbonates. The proportion of the alkylene carbonate with respect to the total of 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, usually 50% by volume or less, preferably 35% by volume or less, more preferably 30% by volume. Hereinafter, it is more preferably 25% by volume or less. Use of a combination of these non-aqueous solvents is preferable because the balance between cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent is improved.

  Specific examples of preferable combinations of alkylene carbonates and dialkyl carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate, Examples include ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

  A combination in which propylene carbonate is further added to a combination of these ethylene carbonate and dialkyl carbonates is also mentioned as a preferable combination.

  When ethylene carbonate and propylene carbonate are contained as alkylene carbonates, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50. Furthermore, the proportion of propylene carbonate in the whole non-aqueous solvent is 0.1% by volume or more, preferably 1% by volume or more, more preferably 2% by volume or more, and the upper limit is usually 20% by volume or less, preferably 8% by volume. % Or less, more preferably 5% by volume or less. It is preferable to contain propylene carbonate in this concentration range, since the low temperature characteristics are further excellent while maintaining the combination characteristics of ethylene carbonate and dialkyl carbonates.

  Among the combinations of ethylene carbonate and dialkyl carbonates, those containing asymmetrical chain alkyl carbonates as dialkyl carbonates are more preferred, especially ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl. Methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, which contain ethylene carbonate, symmetric chain alkyl carbonates, and asymmetric chain alkyl carbonates, have a good balance between cycle characteristics and large current discharge characteristics. preferable. Among them, the asymmetric chain alkyl carbonate is preferably ethyl methyl carbonate, and the alkyl group of the dialkyl carbonate preferably has 1 to 2 carbon atoms.

  When diethyl carbonate is contained in the non-aqueous solvent, the proportion of diethyl carbonate in the total non-aqueous solvent is 10% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, and still more preferably. Is 30% by volume or more, and the upper limit is usually 90% by volume or less, preferably 80% by volume or less, more preferably 75% by volume or less, and still more preferably 70% by volume or less. This is preferable because the swelling of the battery during high-temperature storage is suppressed.

  Further, when dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is 10% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, and further preferably. Is 30 volume% or more, and the upper limit is usually 90 volume% or less, preferably 80 volume% or less, more preferably 75 volume% or less, and still more preferably 70 volume% or less. The load characteristics are improved.

  In addition, in the combination mainly composed of the alkylene carbonates and dialkyl carbonates, other solvents may be mixed.

  Other examples of preferred non-aqueous solvents include one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, γ-butyrolactone and γ-valerolactone, or two or more organic solvents selected from the group The mixed solvent becomes 60% by volume or more of the whole. The non-aqueous electrolyte using this mixed solvent is less likely to evaporate or leak when used at high temperatures. Among these, the total of ethylene carbonate and γ-butyrolactone in the nonaqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate and γ-butyrolactone is 5:95 to 45%. : 55, or the total of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate to propylene carbonate is 30:70 to Use of 60:40 generally improves the balance between cycle characteristics and high temperature storage characteristics.

  In the present specification, the capacity of the non-aqueous solvent is a measured value at 25 ° C., but a measured value at the melting point is used for a solid at 25 ° C. such as ethylene carbonate.

<Compound represented by the general formula (1)>
The non-aqueous electrolyte solution according to the present invention contains the above-described electrolyte and a non-aqueous solvent, and the compound represented by the following general formula (1) (hereinafter sometimes referred to as “compound (1)” in the non-aqueous solvent. .)).

（一般式（１）中、Ｒ^１〜Ｒ^３は、それぞれ独立して、ハロゲン原子で置換されていてもよい、炭素数１〜１２のアルキル基を示し、ｎは０〜６の整数を示す。）

(In General Formula (1), R ^{1 to} R ³ each independently represents an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and n represents an integer of 0 to 6). .)

In said general formula (1), as a C1-C12 alkyl group, a methyl group, an ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl is mentioned, for example. And linear, branched or cyclic alkyl groups such as a group, tert-butyl group, pentyl group, cyclopentyl group and cyclohexyl group. The carbon number of R ^{1 to} R ³ is 1 or more, preferably 2 or more as the lower limit, and 12 or less, preferably 8 or less, more preferably 4 or less as the upper limit.

  Furthermore, the alkyl group may be substituted with a halogen atom such as a fluorine atom. Examples of the group substituted with a fluorine atom include the alkyl group such as a trifluoromethyl group, a trifluoroethyl group, and a pentafluoroethyl group. Examples include partially fluorinated alkyl groups and perfluoroalkyl groups.

  Specific examples of the compound (1) include the following.

<Compound with n = 0>
Trimethylphosphonoformate,
Methyl diethylphosphonoformate,
Methyldipropylphosphonoformate,
Methyldibutylphosphonoformate,
Triethylphosphonoformate,
Ethyldimethylphosphonoformate,
Ethyldipropylphosphonoformate,
Ethyldibutylphosphonoformate,
Tripropylphosphonoformate,
Propyldimethylphosphonoformate,
Propyl diethylphosphonoformate,
Propyldibutylphosphonoformate,
Tributylphosphonoformate,
Butyldimethylphosphonoformate,
Butyl diethylphosphonoformate,
Butyl dipropyl phosphonoformate,
Methylbis (2,2,2-trifluoroethyl) phosphonoformate,
Ethylbis (2,2,2-trifluoroethyl) phosphonoformate,
Propylbis (2,2,2-trifluoroethyl) phosphonoformate,
Butylbis (2,2,2-trifluoroethyl) phosphonoformate, etc.

<Compound with n = 1>
Trimethylphosphonoacetate,
Methyl diethylphosphonoacetate,
Methyldipropylphosphonoacetate,
Methyldibutylphosphonoacetate,
Triethylphosphonoacetate,
Ethyldimethylphosphonoacetate,
Ethyldipropylphosphonoacetate,
Ethyl dibutylphosphonoacetate,
Tripropylphosphonoacetate,
Propyldimethylphosphonoacetate,
Propyl diethylphosphonoacetate,
Propyl dibutyl phosphonoacetate,
Tributylphosphonoacetate,
Butyldimethylphosphonoacetate,
Butyl diethylphosphonoacetate,
Butyl dipropyl phosphonoacetate,
Methylbis (2,2,2-trifluoroethyl) phosphonoacetate,
Ethyl bis (2,2,2-trifluoroethyl) phosphonoacetate,
Propylbis (2,2,2-trifluoroethyl) phosphonoacetate,
Butyl bis (2,2,2-trifluoroethyl) phosphonoacetate, etc.

<Compound with n = 2>
Trimethyl-3-phosphonopropionate,
Methyldiethyl-3-phosphonopropionate,
Methyldipropyl-3-phosphonopropionate,
Methyldibutyl 3-phosphonopropionate,
Triethyl-3-phosphonopropionate,
Ethyldimethyl-3-phosphonopropionate,
Ethyldipropyl-3-phosphonopropionate,
Ethyldibutyl 3-phosphonopropionate,
Tripropyl-3-phosphonopropionate,
Propyldimethyl-3-phosphonopropionate,
Propyl diethyl-3-phosphonopropionate,
Propyl dibutyl 3-phosphonopropionate,
Tributyl-3-phosphonopropionate,
Butyldimethyl-3-phosphonopropionate,
Butyl diethyl-3-phosphonopropionate,
Butyldipropyl-3-phosphonopropionate,
Methylbis (2,2,2-trifluoroethyl) -3-phosphonopropionate,
Ethylbis (2,2,2-trifluoroethyl) -3-phosphonopropionate,
Propylbis (2,2,2-trifluoroethyl) -3-phosphonopropionate,
Butylbis (2,2,2-trifluoroethyl) -3-phosphonopropionate, etc.

<Compound with n = 3>
Trimethyl-4-phosphonobutyrate,
Methyldiethyl-4-phosphonobutyrate,
Methyldipropyl-4-phosphonobutyrate,
Methyldibutyl 4-phosphonobutyrate,
Triethyl-4-phosphonobutyrate,
Ethyldimethyl-4-phosphonobutyrate,
Ethyldipropyl-4-phosphonobutyrate,
Ethyl dibutyl 4-phosphonobutyrate,
Tripropyl-4-phosphonobutyrate,
Propyldimethyl-4-phosphonobutyrate,
Propyl diethyl-4-phosphonobutyrate,
Propyl dibutyl 4-phosphonobutyrate,
Tributyl-4-phosphonobutyrate,
Butyldimethyl-4-phosphonobutyrate,
Butyl diethyl-4-phosphonobutyrate,
Butyldipropyl-4-phosphonobutyrate etc.

  Among these, from the viewpoint of improving battery characteristics after high temperature storage, compounds with n = 0, 1, 2 are preferable, and compounds with n = 1, 2 are particularly preferable.

  Compound (1) may be used alone or in combination of two or more.

  The proportion of the compound (1) in the non-aqueous electrolyte is such that the non-aqueous electrolyte has a carbon-carbon unsaturated bond described later, a cyclic carbonate compound having a fluorine atom, a monofluorophosphate, and difluorophosphoric acid. When not containing at least one compound selected from the group consisting of salts, it is usually 0.001% by volume or more, preferably 0.05% by volume or more, more preferably 0.1% by volume or more, and particularly preferably 0.2% by volume. % Or more. If the concentration is lower than this, the effects of the present invention may not be easily exhibited. On the contrary, if the concentration of the compound (1) is too high, the storage characteristics of the battery may be deteriorated. Therefore, the upper limit is usually less than 1% by volume, preferably 0.8% by volume or less, more preferably 0.7%. The capacity is less than%.

  As described later, the nonaqueous electrolytic solution of the present invention includes, in addition to the compound (1), a cyclic carbonate compound having a carbon-carbon unsaturated bond, a cyclic carbonate compound having a fluorine atom, a monofluorophosphate, and difluorophosphorus. It may contain at least one compound selected from the group consisting of acid salts. In this case, the ratio of the compound (1) in the nonaqueous solvent is usually 0.001% by volume or more, preferably 0.05% by volume or more, more preferably 0.1% by volume or more, and particularly preferably 0.2% by volume. % Or more. If the concentration is lower than this, the effects of the present invention may not be easily exhibited. On the contrary, if the concentration of the compound (1) is too high, the storage characteristics of the battery may be deteriorated. Therefore, the upper limit is usually less than 5% by volume, preferably 3% by volume or less, more preferably 2% by volume or less, More preferably, it is 1 volume% or less, Most preferably, it is 0.8 volume% or less.

  When the non-aqueous electrolyte solution according to the present invention is used, the reason why the gas generation of the non-aqueous electrolyte secondary battery is small and the storage characteristics are excellent is not clear, and the present invention is limited to the following principle of operation. However, compound (1) partially reacts on the positive electrode in the charged state to form a film, and this film suppresses side reactions between other electrolyte components and the electrode active material even in a high temperature atmosphere. As a result, it is considered that side reactions occurring inside the battery during high-temperature storage can be suppressed, gas generation can be suppressed, and storage characteristics can be improved.

  However, compound (1) tends to be reductively decomposed on the negative electrode side, and when the addition amount increases, side reactions on the negative electrode side increase, and battery characteristics may be deteriorated. When compound (1) is used in combination with at least one compound selected from the group consisting of a cyclic carbonate compound having a carbon-carbon unsaturated bond, a cyclic carbonate compound having a fluorine atom, a monofluorophosphate and a difluorophosphate Is a negative electrode film derived from at least one compound selected from the group consisting of a cyclic carbonate compound having a carbon-carbon unsaturated bond, a cyclic carbonate compound having a fluorine atom, a monofluorophosphate and a difluorophosphate. It is considered that the excessive reaction on the negative electrode side of 1) can be suppressed.

<Cyclic carbonate compound having a carbon-carbon unsaturated bond>
Since the cyclic carbonate compound having a carbon-carbon unsaturated bond forms a stable protective film on the surface of the negative electrode, the cycle characteristics of the battery can be improved.

  Examples of the cyclic carbonate compound having a carbon-carbon unsaturated bond include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, fluoro vinylene carbonate, trifluoromethyl. Vinylene carbonate compounds such as vinylene carbonate; vinyl ethylene carbonate, 4-methyl-4-vinylethylene carbonate, 4-ethyl-4-vinylethylene carbonate, 4-n-propyl-4-vinylethylene carbonate, 5-methyl-4 -Vinylethylene carbonate compounds such as vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-divinylethylene carbonate; 4,4-dimethyl- - methylene ethylene carbonate, methylene ethylene carbonate compounds such as 4,4-diethyl-5-methylene ethylene carbonate. Among these, vinylene carbonate, vinyl ethylene carbonate, 4-methyl-4-vinyl ethylene carbonate or 4,5-divinyl ethylene carbonate is preferable from the viewpoint of improving cycle characteristics, and among them, vinylene carbonate or vinyl ethylene carbonate is more preferable. Vinylene carbonate is preferred.

  These cyclic carbonate compounds having a carbon-carbon unsaturated bond may be used alone or in combination of two or more. When two or more kinds of cyclic carbonate compounds having a carbon-carbon unsaturated bond are used in combination, it is preferable to use vinylene carbonate and vinyl ethylene carbonate in combination.

  When the non-aqueous electrolyte contains a cyclic carbonate having a carbon-carbon unsaturated bond, the proportion in the non-aqueous electrolyte is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably. It is 0.3% by weight or more, most preferably 0.5% by weight or more. If there are too few cyclic carbonates having a carbon-carbon unsaturated bond, the effect of improving the cycle characteristics of the battery may not be sufficiently exhibited. In addition, the cyclic carbonate having a carbon-carbon unsaturated bond easily reacts with the positive electrode material in a charged state, and if the electrolyte contains a cyclic carbonate having a carbon-carbon unsaturated bond, the amount of gas generated increases during high-temperature storage. In some cases, battery characteristics may not be obtained sufficiently, but when used in combination with compound (1), side reactions with the positive electrode material can be suppressed, and both cycle characteristics can be improved and gas generation can be suppressed. . However, if the content of the cyclic carbonate having a carbon-carbon unsaturated bond is too large, the amount of gas generated may increase during storage at high temperatures or the discharge characteristics at low temperatures may deteriorate. % By weight or less, preferably 4% by weight or less, particularly preferably 3% by weight or less.

<Cyclic carbonate compound having a fluorine atom>
Since the cyclic carbonate compound having a fluorine atom also forms a stable protective film on the surface of the negative electrode, the cycle characteristics of the battery can be improved.

  Examples of the cyclic carbonate compound having a fluorine atom include fluoroethylene carbonate (4-fluoro-1,3-dioxolan-2-one), 4,5-difluoro-1,3-dioxolan-2-one, 4,4. -Difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5,5-tetrafluoro-1,3-dioxolane-2 -One, 4-fluoro-5-methyl-1,3-dioxolan-2-one, 4-fluoro-4-methyl-1,3-dioxolan-2-one, 4,5-difluoro-4-methyl-1 , 3-dioxolan-2-one, 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one, trifluoromethyl-1,3-dioxolan-2-one and the like It is below. Of these, fluoroethylene carbonate, 4,5-difluoro-1,3-dioxolan-2-one, and 4-fluoro-5-methyl-1,3-dioxolan-2-one are preferred from the viewpoint of improving cycle characteristics.

  These cyclic carbonate compounds having a fluorine atom may be used alone or in combination of two or more.

  When the non-aqueous electrolyte contains a cyclic carbonate compound having a fluorine atom, the proportion in the non-aqueous electrolyte is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably 0.3%. % By weight or more, most preferably 0.5% by weight or more. If there are too few cyclic carbonates having fluorine atoms, the effect of improving the cycle characteristics of the battery may not be sufficiently exhibited. In addition, when the electrolytic solution contains a cyclic carbonate having a fluorine atom, the amount of gas generated during high-temperature storage may be increased, or battery characteristics may not be sufficiently obtained. This is particularly preferable since both improvement of gas and suppression of gas generation can be achieved. However, if the content of the cyclic carbonate having fluorine atoms is too large, the amount of gas generated during high-temperature storage may increase or the discharge characteristics at low temperatures may decrease, so the upper limit is usually 20% by weight or less, Preferably it is 10 weight% or less, More preferably, it is 5 weight% or less, Most preferably, it is 3 weight% or less.

<Monofluorophosphate and difluorophosphate>
Since monofluorophosphate and difluorophosphate also form a stable protective film on the surface of the negative electrode, the cycle characteristics of the battery can be improved.

  The counter cation of monofluorophosphate and difluorophosphate is not particularly limited, and examples thereof include lithium, sodium, potassium, magnesium, calcium, etc. Among these, lithium is preferable.

Specific examples of monofluorophosphate and difluorophosphate include lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, and potassium difluorophosphate. And lithium monofluorophosphate and lithium difluorophosphate are preferable, and lithium difluorophosphate is more preferable.
These may be used alone or in combination of two or more.

  In addition, monofluorophosphate and / or difluorophosphate may be used in combination with a cyclic carbonate compound having a carbon-carbon unsaturated bond or a cyclic carbonate compound having a fluorine atom, from the viewpoint of improving cycle characteristics. Is preferably used in combination with vinylene carbonate, vinyl ethylene carbonate, or fluoroethylene carbonate.

  When the non-aqueous electrolyte contains a monofluorophosphate and / or difluorophosphate, the proportion in the non-aqueous electrolyte is usually 0.001% by weight or more, preferably 0.01% by weight or more, particularly Preferably it is 0.1 weight% or more, Most preferably, it is 0.2 weight% or more. If the content of monofluorophosphate and / or difluorophosphate is too small, the effect of improving the cycle characteristics of the battery may not be sufficiently exhibited. The upper limit is usually 5% by weight or less, preferably 3% by weight or less, particularly preferably 2% by weight or less.

  In addition, when a non-aqueous electrolyte contains both the cyclic carbonate compound which has a carbon-carbon unsaturated bond, and the cyclic carbonate compound which has a fluorine atom, the content is the upper limit and the minimum of content of each compound, and For the same reason, the total amount is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably 0.3% by weight or more, most preferably 0.5% by weight or more, usually 20% by weight. Hereinafter, it is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 3% by weight or less.

  Further, when the nonaqueous electrolytic solution contains a cyclic carbonate compound having a carbon-carbon unsaturated bond and / or a cyclic carbonate compound having a fluorine atom, and a monofluorophosphate and / or a difluorophosphate, The content is generally 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably 0.3% by weight or more, most in total for the same reason as the upper and lower limits of the content of each compound. It is preferably 0.5% by weight or more, usually 20% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 3% by weight or less.

<Other compounds>
The non-aqueous electrolyte solution according to the present invention may contain various other compounds such as a conventionally known overcharge inhibitor as an auxiliary agent as long as the effects of the present invention are not impaired.
Conventionally known overcharge inhibitors include alkylbiphenyls such as biphenyl and 2-methylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclopentylbenzene, cyclohexylbenzene, cis-1-propyl-4-phenylcyclohexane, trans Aromatic compounds such as -1-propyl-4-phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran Partial hydrocarbons of the aromatic compounds such as 2-fluorobiphenyl, 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4′-difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; Fluoride-containing anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like.

  Among these, biphenyl, alkylbiphenyl such as 2-methylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclopentylbenzene, cyclohexylbenzene, cis-1-propyl-4-phenylcyclohexane, trans-1-propyl-4 -Aromatic compounds such as phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the aromatic compounds such as 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4′-difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene are preferred. Partially hydrogenated terphenyl, cyclopentylbenzene, cyclohexylbenzene, cis-1-propyl-4-phenylcyclohexane, trans-1-propyl-4-phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1 -Butyl-4-phenylcyclohexane, t-butylbenzene, t-amylbenzene, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene are more preferable, and a partially hydrogenated terphenyl and cyclohexylbenzene are particularly preferable.

  These overcharge inhibitors may be used alone or in combination of two or more.

  When two or more overcharge inhibitors are used in combination, in particular, a partially hydrogenated terphenyl, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, Those selected from oxygen-free aromatic compounds such as partially hydrogenated phenyl, cyclohexylbenzene, t-butylbenzene, and t-amylbenzene; and those selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran. Use in combination is preferable in terms of the balance between overcharge prevention characteristics and high-temperature storage characteristics.

  The proportion of these overcharge inhibitors in the non-aqueous electrolyte is usually 0.1% by weight or more, preferably 0.2% by weight or more, particularly preferably 0.3% by weight or more, most preferably 0.5% by weight. The upper limit is usually 5% by weight or less, preferably 3% by weight or less, particularly preferably 2% by weight or less. If the concentration is lower than this lower limit, the desired effect of the overcharge inhibitor may hardly be exhibited. Conversely, when the concentration of the overcharge inhibitor is too high, battery characteristics such as high-temperature storage characteristics tend to deteriorate.

  Other auxiliaries include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, itaconic anhydride, citraconic anhydride, Carboxylic anhydrides such as glutaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; dimethyl succinate, diethyl succinate, diallyl succinate, maleic acid Dimethyl, diethyl maleate, diallyl maleate, dipropyl maleate, dibutyl maleate, bis (trifluoromethyl) maleate, bis (pentafluoroethyl) maleate, bis (2,2,2-trifluoroethyl maleate) etc Dicarboxylic acid diester compounds; spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane Ethylene sulfite, propylene sulfite, 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1,4-butene sultone, methyl methane sulfonate, ethyl methane sulfonate, methyl-methoxy methane sulfonate, methyl 2-methoxyethanesulfonate, busulfan, diethylene glycol dimethanesulfonate, 1,2-ethanediol bis (2,2,2-trifluoroethanesulfonate), 1,4-butanediol bis (2,2,2-trifluoro) Ethanesulfonate), sulfo , Sulfolene, dimethylsulfone, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide and other sulfur-containing compounds; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3 -Nitrogen-containing compounds such as methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; heptane, octane, nonane, decane, cycloheptane, methylcyclohexane, ethylcyclohexane, propylcyclohexane , N-butylcyclohexane, t-butylcyclohexane, dicyclohexyl and other hydrocarbon compounds; fluorobenzene, difluorobenzene, hexafluorobenzene and other fluorinated benzenes; acetonitrile, propionitrile, butyronitrile, malono Examples thereof include nitrile compounds such as nitrile, succinonitrile, glutaronitrile, adiponitrile and the like. Two or more of these may be used in combination.

  The ratio of these auxiliaries in the non-aqueous electrolyte solution is not particularly limited in order to exhibit the effects of the present invention, but is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably. Is 0.2% by weight or more, and the upper limit is usually 10% by weight or less, preferably 5% by weight or less, more preferably 3% by weight or less, and particularly preferably 1% by weight or less. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high-temperature storage can be improved, but if the concentration is lower than this lower limit, the effect of the auxiliaries may be hardly expressed. On the other hand, if the concentration is too high, battery characteristics such as high load discharge characteristics may deteriorate.

<Preparation of non-aqueous electrolyte solution>
The nonaqueous electrolytic solution of the present invention can be prepared by dissolving the electrolyte, the compound (1), and other compounds and auxiliaries blended as necessary in a nonaqueous solvent. In preparing the non-aqueous electrolyte solution of the present invention, each raw material is preferably dehydrated in advance in order to reduce the water content when the electrolyte solution is used, and the water content is usually 50 ppm or less, preferably 30 ppm or less, particularly It is preferable to use after dehydrating to 10 ppm or less. Moreover, you may implement dehydration, a deoxidation process, etc. after electrolyte solution preparation.

  The non-aqueous electrolyte of the present invention is suitable for use as a secondary battery among non-aqueous electrolyte batteries, that is, as an electrolyte for a non-aqueous electrolyte secondary battery, for example, a lithium secondary battery.

  Hereinafter, a non-aqueous electrolyte secondary battery using the electrolyte of the present invention will be described.

[Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte battery including a negative electrode and a positive electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte solution, and the non-aqueous electrolyte solution of the present invention described above. It is a non-aqueous electrolyte solution.

<Battery configuration>
A non-aqueous electrolyte secondary battery according to the present invention is similar to a conventionally known non-aqueous electrolyte secondary battery except that it is prepared using the above-described electrolyte of the present invention. A non-aqueous electrolyte battery including a positive electrode and a non-aqueous electrolyte solution, usually obtained by housing the positive electrode and the negative electrode in a case through a porous membrane impregnated with the non-aqueous electrolyte solution according to the present invention. . The shape of the secondary battery according to the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

<Electrode>
(Negative electrode active material)
As the negative electrode active material, a carbonaceous material or a metal compound capable of inserting and extracting lithium, lithium metal, a lithium alloy, and the like can be used. These negative electrode active materials may be used alone or in combination of two or more. Among these, a carbonaceous material and a metal compound capable of occluding and releasing lithium are preferable.

  Among the carbonaceous materials, graphite and graphite whose surface is coated with amorphous carbon as compared with graphite are particularly preferable.

  Graphite preferably has a lattice plane (002 plane) d value (interlayer distance) of 0.335 to 0.338 nm, particularly 0.335 to 0.337 nm, as determined by X-ray diffraction using the Gakushin method. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, particularly preferably 100 nm or more. The ash content is usually 1 part by weight or less, preferably 0.5 part by weight or less, particularly preferably 0.1 part by weight or less.

  The graphite surface coated with amorphous carbon is preferably graphite having a d-value of 0.335 to 0.338 nm on the lattice plane (002 plane) in X-ray diffraction as a core material. A carbonaceous material having a larger d-value on the lattice plane (002 plane) in X-ray diffraction than the core material is attached, and the d-value on the lattice plane (002 plane) in X-ray diffraction is greater than that of the core material and the core material. The ratio with respect to the carbonaceous material having a large is 99/1 to 80/20 by weight. When this is used, a negative electrode having a high capacity and hardly reacting with the electrolytic solution can be produced.

  The particle size of the carbonaceous material is a median diameter measured by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, most preferably 7 μm or more, and usually 100 μm or less, preferably 50 μm or less. More preferably, it is 40 micrometers or less, Most preferably, it is 30 micrometers or less.

The specific surface area of the carbonaceous material by the BET method is usually 0.3 m ² / g or more, preferably 0.5 m ² / g or more, more preferably 0.7 m ² / g or more, and most preferably 0.8 m ² / g. or more, usually 25.0 m ² / g or less, preferably 20.0 m ² / g, more preferably 15.0 m ² / g or less, and most preferably 10.0 m ² / g or less.

Further, the carbonaceous material is analyzed by Raman spectrum using argon ion laser light, the peak is the peak intensity of the peak _{P A} in the range of 1570~1620cm ^-1 _I A, in the range of 1300~1400cm ^-1 P If the peak intensity of the _B was _{I B,} R value represented by the ratio of _{I B} and _{I a (= I B / I} a) is what is preferably in the range of 0.01 to 0.7. Further, the half width of the peak in the range of 1570～1620Cm ^-1 is, 26cm ^-1 or less, are preferred in particular 25 cm ^-1 or less.

  Examples of metal compounds capable of inserting and extracting lithium include compounds containing metals such as Ag, Zn, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi, Cu, Ni, Sr, and Ba. These metals are used as simple substances, oxides, alloys with lithium, and the like. In the present invention, those containing an element selected from Si, Sn, Ge and Al are preferred, and oxides or lithium alloys of metals selected from Si, Sn and Al are more preferred. These may be in the form of powder or thin film, and may be crystalline or amorphous.

  Lithium is a metal compound that can occlude and release lithium, or its oxides and alloys with lithium generally have higher capacity per unit weight than carbonaceous materials typified by graphite. It is suitable for a secondary battery.

  The average particle diameter of the metal compound capable of occluding and releasing lithium or the oxide or an alloy thereof with lithium is not particularly limited in order to exhibit the effects of the present invention, but is usually 50 μm or less, preferably 20 μm or less. Particularly preferably, it is 10 μm or less, usually 0.1 μm or more, preferably 1 μm or more, particularly preferably 2 μm or more. When this upper limit is exceeded, the expansion of the electrode increases, and the cycle characteristics may deteriorate. Moreover, when less than this minimum, it becomes difficult to collect current and there is a possibility that the capacity is not sufficiently developed.

(Positive electrode active material)
The positive electrode active material is not particularly limited as long as it can occlude / release lithium ions. However, a material containing lithium and at least one transition metal is preferable, for example, lithium transition metal composite oxide, lithium containing Examples include transition metal phosphate compounds.

V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable as the transition metal of the lithium transition metal composite oxide. Specific examples include lithium-cobalt composite oxides such as LiCoO ₂ and LiNiO ₂ . Lithium / nickel composite oxide, lithium / manganese composite oxide such as LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _3, etc., and some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and those substituted with other metals such as Si. As specific examples of the substituted ones, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4 and the} like.

As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

  These positive electrode active materials may be used alone or in combination.

  In addition, a material in which a substance having a composition different from that of the substance constituting the main cathode active material is attached to the surface of the cathode active material can be used. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

  The amount of the surface-adhering substance is not particularly limited in order to exhibit the effects of the present invention, but is preferably 0.1 ppm or more, more preferably 1 ppm or more as a lower limit by mass with respect to the positive electrode active material. The upper limit is preferably 10 ppm or more, preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. If the amount is too large, the resistance may increase in order to inhibit the entry and exit of lithium ions.

(Binders, thickeners, etc.)
As the binder for binding the active material, any material can be used as long as it is a material that is stable with respect to the solvent and the electrolyte used in manufacturing the electrode. For example, fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene, polyolefins such as polyethylene and polypropylene, polymers having unsaturated bonds such as styrene / butadiene rubber, isoprene rubber and butadiene rubber, and copolymers thereof, ethylene-acrylic Examples thereof include acrylic acid polymers such as acid copolymers and ethylene-methacrylic acid copolymers, and copolymers thereof. These may be used alone or in combination.

  The electrode may contain a thickener, a conductive material, a filler and the like in order to increase mechanical strength and electrical conductivity.

  Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used alone or in combination.

  Examples of the conductive material include metal materials such as copper and nickel, and carbon materials such as graphite and carbon black. These may be used alone or in combination.

(Manufacture of electrodes)
The electrode may be manufactured by a conventional method. For example, it can be formed by adding a binder, a thickener, a conductive material, a solvent or the like to a negative electrode or a positive electrode active material to form a slurry, applying the slurry to a current collector, drying it, and then pressing it.

  In addition, a material obtained by adding a binder or a conductive material to an active material is roll-formed as it is to form a sheet electrode, a pellet electrode is formed by compression molding, and an electrode is formed on the current collector by a technique such as vapor deposition, sputtering, or plating. A thin film of material can also be formed.

When graphite is used as the negative electrode active material, the density of the negative electrode active material layer after drying and pressing is usually 1.45 g / cm ³ or more, preferably 1.55 g / cm ³ or more, more preferably 1.60 g. / Cm ³ or more, particularly preferably 1.65 g / cm ³ or more.

The density of the positive electrode active material layer after drying and pressing is usually 2.0 g / cm ³ or more, preferably 2.5 g / cm ³ or more, more preferably 3.0 g / cm ³ or more.

(Current collector)
Various types of current collectors can be used, but metals and alloys are usually used. Examples of the current collector for the negative electrode include copper, nickel, and stainless steel, and copper is preferred. Examples of the current collector for the positive electrode include metals such as aluminum, titanium, and tantalum, and alloys thereof, and aluminum or an alloy thereof is preferable.

<Separator, exterior body>
A porous film (separator) is interposed between the positive electrode and the negative electrode to prevent a short circuit. In this case, the electrolytic solution is used by impregnating the porous membrane. The material and shape of the porous film are not particularly limited as long as it is stable to the electrolytic solution and excellent in liquid retention, and a porous sheet or nonwoven fabric made of a polyolefin such as polyethylene or polypropylene is preferable.

  The material of the battery case used in the battery according to the present invention is also arbitrary, and nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, a laminate film, or the like is used.

  The operating voltage of the non-aqueous electrolyte secondary battery of the present invention described above is usually in the range of 2V to 6V.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples unless it exceeds the gist.

  In addition, each evaluation method of the battery obtained by the following Example and the comparative example is shown below.

[Capacity evaluation]
The non-aqueous electrolyte secondary battery is charged to 4.2 V at a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to improve the adhesion between the electrodes, and then 0.2 C The battery was discharged to 3 V at a constant current of. This is done for 3 cycles to stabilize the battery. In the 4th cycle, after charging to 4.2V with a constant current of 0.5C, charging is performed until the current value reaches 0.05C with a constant voltage of 4.2V. The initial discharge capacity was determined by discharging to 3 V at a constant current of 0.2C.

  Here, 1C represents a current value for discharging the reference capacity of the battery in one hour, and 0.2C represents a current value of 1/5 thereof.

[Evaluation of continuous charge characteristics]
After the capacity evaluation test was completed, the volume was measured by immersing the battery in an ethanol bath. Then, constant current charging was performed at a constant current of 0.5 C at 60 ° C., and after reaching 4.25 V, constant voltage charging was performed. Switching was performed continuously for one week.

  After the battery was cooled, it was immersed in an ethanol bath to measure the volume, and the amount of gas generated from the volume change before and after continuous charging was determined.

  After measuring the amount of gas generated, discharge to 3 V at a constant current of 0.2 C at 25 ° C., measure the remaining capacity after the continuous charge test, and determine the ratio of the discharge capacity after the continuous charge test to the initial discharge capacity. Was the remaining capacity (%) after continuous charging.

[Evaluation of high-temperature storage characteristics]
The battery for which the capacity evaluation test has been completed is charged to 4.2 V at a constant current of 0.5 C at 25 ° C., and then charged to a current value of 0.05 C at a constant voltage of 4.2 V, and then at 85 ° C. Stored for 1 day. Next, it was discharged to 3 V at a constant current of 0.2 C at 25 ° C., the remaining capacity after the high-temperature storage test was measured, and the ratio of the discharge capacity after the storage test to the initial discharge capacity was obtained. The remaining capacity (%) was used.

[Example 1]
<Manufacture of negative electrode>
The d-value of the lattice plane (002 plane) in X-ray diffraction is 0.336 nm, the crystallite size (Lc) is 652 nm, the ash content is 0.07 wt%, the median diameter by laser diffraction / scattering method is 12 μm, and the ratio by BET method The half-value width of a peak whose surface area is 7.5 m ² / g and the R value (= I _B / I _A ) determined from Raman spectrum analysis using an argon ion laser beam is in the range of 0.12, 1570 to 1620 cm ^−1. Was mixed with 94 parts by weight of natural graphite powder having a weight of 19.9 cm ⁻¹ and 6 parts by weight of polyvinylidene fluoride, and N-methyl-2-pyrrolidone was added to form a slurry. This slurry was uniformly applied to one side of a 12 μm thick copper foil and dried, and then pressed to obtain a negative electrode active material layer having a density of 1.67 g / cm ³ to form a negative electrode.

<Production of positive electrode>
90 parts by weight of LiCoO ₂ , 4 parts by weight of carbon black and 6 parts by weight of polyvinylidene fluoride (manufactured by Kureha Chemical Co., Ltd., trade name “KF-1000”) are mixed, and N-methyl-2-pyrrolidone is added to form a slurry. After uniformly applying and drying on both surfaces of an aluminum foil having a thickness of 15 μm, the positive electrode active material layer was pressed to a density of 3.2 g / cm ³ to obtain a positive electrode.

<Preparation of electrolyte>
Under a dry argon atmosphere, a mixture of ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) so that the content of triethylphosphonoformate in the non-aqueous solvent is 0.5% by volume. Next, LiPF ₆ that was mixed and sufficiently dried was dissolved at a rate of 1.0 mol / liter to obtain an electrolytic solution.

<Manufacture of lithium secondary batteries>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode to produce a battery element. The battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were coated with a resin layer while projecting positive and negative terminals, and then the electrolyte was poured into the bag and vacuum sealed. Then, a sheet-like lithium secondary battery was prepared, and the continuous charge characteristics and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 2]
In the preparation of the electrolytic solution of Example 1, a sheet-like lithium secondary battery was produced in the same manner as in Example 1 except that triethylphosphonoacetate was used instead of triethylphosphonoformate. Storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 3]
In the preparation of the electrolytic solution of Example 1, a sheet-like lithium secondary battery was produced in the same manner as in Example 1 except that triethyl-3-phosphonopropionate was used instead of triethylphosphonoformate. The continuous charge characteristics and high temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 4]
Mix with a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) so that the content of triethylphosphonoacetate in the non-aqueous solvent is 0.8% by volume. A sheet-like lithium secondary battery was prepared in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving dried LiPF ₆ to a ratio of 1.0 mol / liter was used. The high temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 5]
A mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) is mixed so that the content of triethylphosphonoformate in the non-aqueous solvent is 0.5% by volume. Use an electrolyte prepared by mixing the vinylene carbonate in the aqueous electrolyte so that the content is 2% by weight, and then dissolving LiPF ₆ sufficiently dried to a ratio of 1.0 mol / liter. Except that, a sheet-like lithium secondary battery was produced in the same manner as in Example 1, and the continuous charge characteristics and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 6]
A sheet-like lithium secondary battery was produced in the same manner as in Example 5 except that triethylphosphonoacetate was used instead of triethylphosphonoformate in the preparation of the electrolytic solution of Example 5, and the continuous charge characteristics and high temperature were high. Storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 7]
In the preparation of the electrolyte solution of Example 5, a sheet-like lithium secondary battery was produced in the same manner as in Example 5 except that triethyl-3-phosphonopropionate was used instead of triethylphosphonoformate. The continuous charge characteristics and high temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 8]
A mixture of ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) is mixed so that the content of triethylphosphonoacetate in the nonaqueous solvent is 0.5% by volume, and further nonaqueous system These were mixed so that the content of vinylene carbonate in the electrolytic solution was 1% by weight and the content of fluoroethylene carbonate was 1% by weight, and then sufficiently dried LiPF ₆ was added at a ratio of 1.0 mol / liter. A sheet-like lithium secondary battery was produced in the same manner as in Example 1 except that an electrolytic solution prepared by dissolution was used, and continuous charge characteristics and high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 9]
A mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) was mixed so that the content of triethylphosphonoacetate in the non-aqueous solvent was 1% by volume, and further in the non-aqueous solvent. This was conducted except that an electrolyte prepared by dissolving LiPF ₆ in a proportion of 1.0 mol / liter was mixed so that the content of vinylene carbonate was 2% by weight and then sufficiently dried. A sheet-like lithium secondary battery was produced in the same manner as in Example 1, and the continuous charge characteristics and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 10]
A mixture of ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) is mixed so that the content of triethylphosphonoacetate in the nonaqueous solvent is 2% by volume, and further, a nonaqueous electrolyte solution Except that an electrolyte prepared by dissolving LiPF ₆ in a proportion of 1.0 mol / liter was mixed so that the content of vinylene carbonate in the mixture was 2% by weight and then sufficiently dried. A sheet-like lithium secondary battery was produced in the same manner as in Example 1, and the continuous charge characteristics and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Example 11]
A mixture of ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) is mixed so that the content of triethylphosphonoacetate in the nonaqueous solvent is 2% by volume, and further, a nonaqueous electrolyte solution An electrolytic solution prepared by mixing the lithium difluorophosphate content in the mixture so as to be 0.5% by weight and then dissolving sufficiently dried LiPF ₆ at a ratio of 1.0 mol / liter. A sheet-like lithium secondary battery was produced in the same manner as in Example 1 except that it was used, and the continuous charge characteristics and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Comparative Example 1]
Use an electrolyte prepared by dissolving LiPF ₆ in a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) to a ratio of 1.0 mol / liter. Except that, a sheet-like lithium secondary battery was produced in the same manner as in Example 1, and the continuous charge characteristics and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

[Comparative Example 2]
A mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) was mixed so that the content of triethylphosphonoacetate in the non-aqueous solvent was 2% by volume, and then sufficiently dried. A sheet-like lithium secondary battery was produced in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving LiPF ₆ at a ratio of 1.0 mol / liter was used. The characteristics were evaluated. The evaluation results are shown in Table 1.

[Comparative Example 3]
A mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) was mixed so that the content of vinylene carbonate in the non-aqueous electrolyte solution was 2% by weight, and then sufficiently dried LiPF _A sheet-like lithium secondary battery was produced in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving ₆ to a ratio of 1.0 mol / liter was used. Continuous charging characteristics and high-temperature storage characteristics Was evaluated. The evaluation results are shown in Table 1.

[Comparative Example 4]
In a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3), the content of vinylene carbonate in the non-aqueous electrolyte is 1% by weight and the content of fluoroethylene carbonate is 1% by weight. In the same manner as in Example 1, except that an electrolytic solution prepared by mixing LiPF ₆ and then dissolving sufficiently dried LiPF ₆ at a ratio of 1.0 mol / liter was used. Secondary batteries were fabricated and evaluated for continuous charge characteristics and high temperature storage characteristics. The evaluation results are shown in Table 1.

[Comparative Example 5]
A mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 3: 3) is mixed so that the content of triethylphosphonoacetate in the non-aqueous solvent is 5% by volume, and further a non-aqueous electrolyte solution Except that an electrolyte prepared by dissolving LiPF ₆ in a proportion of 1.0 mol / liter was mixed so that the content of vinylene carbonate in the mixture was 2% by weight and then sufficiently dried. A sheet-like lithium secondary battery was produced in the same manner as in Example 1, and the continuous charge characteristics and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 1.

  As apparent from Table 1, from compound (1), or compound (1) and a cyclic carbonate compound having a carbon-carbon unsaturated bond, a cyclic carbonate compound having a fluorine atom, a monofluorophosphate and a difluorophosphate A battery according to the present invention using a non-aqueous electrolyte containing at least one compound selected from the group is excellent in continuous charge characteristics and high-temperature storage characteristics.

Claims (4)

In a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent that dissolves the electrolyte, the non-aqueous electrolyte solution contains 0.001% by volume or more and less than 1% by volume of the compound represented by the following general formula (1) in the non-aqueous solvent. A non-aqueous electrolyte solution for a non-aqueous electrolyte battery, comprising:

(In General Formula (1), R ^{1 to} R ³ each independently represents an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and n represents an integer of 0 to 6). .) In a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent that dissolves the electrolyte, the non-aqueous electrolyte solution contains 0.001% by volume or more and less than 5% by volume of the compound represented by the following general formula (1) in the non-aqueous solvent. And at least one compound selected from the group consisting of a cyclic carbonate compound having a carbon-carbon unsaturated bond, a cyclic carbonate compound having a fluorine atom, a monofluorophosphate, and a difluorophosphate. A non-aqueous electrolyte for a non-aqueous electrolyte battery .

(In General Formula (1), R ^{1 to} R ³ each independently represents an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and n represents an integer of 0 to 6). .) Negative and positive electrodes of lithium ion capable of occluding and releasing, and a nonaqueous electrolyte battery comprising a nonaqueous electrolyte solution, nonaqueous electrolyte solution in a non-aqueous electrolyte nonaqueous electrolyte battery according to claim 1 A non-aqueous electrolyte battery characterized by that. A non-aqueous electrolyte battery comprising a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is a non-aqueous electrolyte solution for a non-aqueous electrolyte battery according to claim 2. A non-aqueous electrolyte battery characterized by that.