JP6062297B2 - Non-aqueous electrochemical device electrolyte and lithium ion secondary battery - Google Patents

Description

  The present invention relates to an electrolyte for a non-aqueous electrochemical device and a lithium ion secondary battery.

  With the recent development of electronic technology and increasing interest in environmental technology, various electrochemical devices have been developed. In particular, there is a strong demand for the development of electrochemical devices for the purpose of energy saving, and expectations for electrochemical devices that can contribute to energy saving are increasing. Examples of such electrochemical devices include solar cells as power generation devices, and secondary batteries, capacitors, capacitors, and the like as power storage devices. Lithium ion secondary batteries, which are representative examples of power storage devices, have been conventionally used mainly as rechargeable batteries for portable devices, but in recent years, they are also expected to be used as batteries for hybrid vehicles and electric vehicles.

A lithium ion secondary battery generally has a configuration in which a positive electrode and a negative electrode mainly composed of an active material capable of inserting and extracting lithium are arranged via a separator. The positive electrode of the lithium ion secondary battery includes LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ as a positive electrode active material, carbon black or graphite as a conductive agent, and polyvinylidene fluoride, latex or rubber as a binder. Is formed by covering a positive electrode current collector made of aluminum or the like. The negative electrode is formed by coating a negative electrode mixture made of copper or the like with a negative electrode mixture obtained by mixing coke or graphite as a negative electrode active material and polyvinylidene fluoride, latex, rubber, or the like as a binder. It is formed. Further, the separator is made of porous polyolefin or the like, and its thickness is very thin, from several μm to several hundred μm. The positive electrode, the negative electrode, and the separator are immersed in the electrolytic solution in the battery. Examples of the electrolytic solution include an electrolytic solution in which a lithium salt such as LiPF ₆ or LiBF ₄ is dissolved in an aprotic solvent such as propylene carbonate or ethylene carbonate, or a polymer such as polyethylene oxide.

  Currently, lithium ion secondary batteries are mainly used as batteries for portable devices and the like. In recent years, it has also begun to be used as a battery for automobiles such as hybrid cars and electric cars, and the use and market of lithium ion secondary batteries tend to expand further.

  As a component of such a non-aqueous electrolyte for a lithium ion secondary battery, a fluorinated carbonate compound typified by 4-fluoro-1,3-dioxolan-2-one is widely used. These fluorine-containing carbonate compounds are very useful as materials that contribute to the interface control of the electrode and can contribute to the improvement of the oxidation resistance of the electrolytic solution.

  The electrode interface control capability (hereinafter also referred to as “SEI molding capability”) is a performance required for all lithium ion batteries. In general, a decomposition product of a non-aqueous electrolyte called Solid Electrolyte Interface (SEI) plays a role as a protective film on the negative electrode surface of a battery, and fluorine-containing carbonate compounds are widely used as excellent SEI forming agents. When good SEI is formed, reductive decomposition of the nonaqueous electrolytic solution can be suppressed, and charging / discharging of the battery can be performed stably. It has been reported that non-aqueous electrolytes using 4-fluoro-1,3-dioxolan-2-one can form such SEI (see, for example, Patent Document 1 and Patent Document 2). Recently, the concept of SEI has been extended to the surface of the positive electrode, and non-aqueous electrolyte using 4-fluoro-1,3-dioxolan-2-one can reduce deterioration of the non-aqueous electrolyte derived from the positive electrode. Has been reported (see, for example, Patent Document 3 and Patent Document 4).

  The improvement in oxidation resistance of the non-aqueous electrolyte is a performance particularly required for a battery driven at a high voltage using a positive electrode having a high potential. In order to enable long-time use of a smart phone and long-distance driving of an electric vehicle, a battery having a high energy density is required. For this purpose, a battery driven at a high voltage is indispensable. However, when a conventional non-aqueous electrolyte is used under a high voltage, the non-aqueous electrolyte is oxidized and decomposed, resulting in significant battery deterioration. Here, it is known that when a fluorine-containing carbonate compound is used as a constituent component of a non-aqueous electrolyte, oxidation resistance is improved by the effect of fluorine, and it can be used stably even under high voltage conditions ( For example, see Patent Literature 5 and Patent Literature 6).

JP 2008-140760 A JP 2006-196250 A JP 2008-97954 A JP 2008-34334 A JP 2008-108689 A International Publication 2012/133902

  As described above, a fluorine-containing carbonate compound represented by a fluorine-containing cyclic carbonate compound exhibits good performance, but has a problem of high reactivity and instability. Therefore, in order to express the above-mentioned good performance, it is necessary to control the reactivity by aging or conditioning immediately after the production of the battery, which is one reason why it is difficult to use the fluorine-containing cyclic carbonate compound. Yes.

  The present invention has been made in view of the above problems, and provides an electrolyte solution for a non-aqueous electrochemical device that realizes a non-aqueous secondary battery having both high-temperature durability and oxidation resistance (high voltage) performance, and the non-aqueous electrolyte device. It aims at providing the lithium ion secondary battery containing the electrolyte solution for water electrochemical devices.

  As a result of intensive studies to solve the above-mentioned problems, the inventors have added a predetermined amount of a compound having two or more carbonate groups in the molecule to the electrolyte solution, so that in various battery use conditions, A good and stable SEI was formed, and it was found that the above problems could be solved, and the present invention was completed. That is, the present invention is as follows.

[1]
A carbonate compound having a fluorine atom;
0.0001 parts by mass or more and 10 parts by mass or less of a compound having 2 or more carbonate groups with respect to 100 parts by mass of the carbonate compound having fluorine atoms,
Lithium salt,
An electrolyte for non-aqueous electrochemical devices.
[2]
The electrolyte solution for nonaqueous electrochemical devices according to [1] above, wherein the carbonate compound having a fluorine atom contains a cyclic carbonate compound having a fluorine atom.
[3]
The electrolyte solution for nonaqueous electrochemical devices according to [1] or [2] above, wherein the compound having two or more carbonate groups has a cyclic carbonate group.
[4]
The electrolyte solution for a nonaqueous electrochemical device according to any one of [1] to [3], further including an aprotic solvent having a viscosity of 2 cP or less.
[5]
The electrolyte solution for a non-aqueous electrochemical device according to any one of [1] to [4], wherein the aprotic solvent includes a solvent having a fluorine atom.
[6]
An electrolyte solution for a lithium ion secondary battery, comprising the electrolyte solution for a nonaqueous electrochemical device according to any one of [1] to [5] above.
[7]
The electrolyte for a nonaqueous electrochemical device according to any one of the preceding items [1] to [5] or the electrolyte for a lithium ion secondary battery according to [6], a positive electrode, and a negative electrode,
The positive electrode contains one or more positive electrode active materials that are materials capable of inserting and extracting lithium ions,
The negative electrode contains one or more negative electrode active materials selected from the group consisting of a material capable of inserting and extracting lithium ions and metallic lithium.
Lithium ion secondary battery.
[8]
The lithium ion secondary battery according to [7], wherein the positive electrode active material includes a lithium-containing compound.
[9]
[7] or [8] above, wherein the negative electrode active material includes one or more materials selected from the group consisting of metallic lithium, carbon materials, silicon materials, and materials containing elements capable of forming an alloy with lithium. The lithium ion secondary battery described in 1.

  According to the present invention, an electrolyte for a nonaqueous electrochemical device that realizes a nonaqueous secondary battery having both high temperature durability and oxidation resistance (high voltage) performance, and lithium ion containing the electrolyte for the nonaqueous electrochemical device A secondary battery can be provided.

  Hereinafter, a mode for carrying out the present invention (hereinafter, also simply referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. Can be modified.

[Electrolyte for non-aqueous electrochemical devices]
The electrolyte solution for non-aqueous electrochemical devices according to the present embodiment (hereinafter also referred to as “non-aqueous electrolyte solution”) is
A carbonate compound having a fluorine atom;
0.0001 parts by mass or more and 10 parts by mass or less of a compound having 2 or more carbonate groups with respect to 100 parts by mass of the carbonate compound having fluorine atoms,
Lithium salt.

[Carbonate compound having fluorine atom]
The nonaqueous electrolytic solution according to this embodiment includes a carbonate compound having a fluorine atom. The carbonate compound having a fluorine atom has the functions of electrode electrolyte interface control (Solid Electrolyte Interface (SEI) formation) and improvement of the oxidation resistance (high voltage characteristics) of the electrolyte in the non-aqueous electrolyte according to the present embodiment. Fulfill. Here, the “carbonate compound having a fluorine atom” refers to a compound having a carbonate group (—O— (C═O) —O—) and one or more fluorine atoms. Although it does not specifically limit as such a carbonate compound which has a fluorine atom, For example, the compound represented by following formula (1) or (2) is mentioned. Among these, the cyclic carbonate compound which has a fluorine atom like the compound represented by Formula (1) is preferable. By including the cyclic carbonate compound, the function of the carbonate compound having a fluorine atom tends to be more excellent. The carbonate compound having a fluorine atom is preferably a compound having one carbonate group.
(In Formula (1), R1 to R4 each independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 3 carbon atoms or a fluorine-containing alkyl group, and any one or more of R1 to R4 are fluorine atoms. Including one or more.)

(In Formula (2), Ra and Rb each independently represent an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group, and at least one of Ra and Rb contains one or more fluorine atoms. )

  In formula (1), R1 to R4 each independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 3 carbon atoms or a fluorine-containing alkyl group, and any one or more of R1 to R4 represent a fluorine atom. Contains one or more. At least one of R1 to R4 preferably represents a fluorine atom, a fluoromethyl group, a difluoromethyl group, or a trifluoromethyl group. By using a carbonate compound having such a group, various battery characteristics tend to be improved, including high-temperature durability and oxidation resistance (high voltage) performance. The compound represented by the formula (1) is not particularly limited, and examples thereof include 4-fluoro-1,3-dioxolan-2-one and 4,4-difluoro-1,3-dioxolane-2- ON, cis-4,5-difluoro-1,3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, 4,4-difluoro-5-methyl-1, 3-dioxolan-2-one, 4-fluoromethyl-1,3-dioxolan-2-one, 4,4-difluoromethyl-1,3-dioxolan-2-one, 4,4,4-trifluoromethyl 1,3-dioxolan-2-one is preferred. Among these, 4-fluoro-1,3-dioxolane-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro-1,3-dioxolane-2- ON, trans-4,5-difluoro-1,3-dioxolan-2-one is more preferred.

  In formula (2), Ra and Rb each independently represent an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group, and at least one of Ra and Rb contains one or more fluorine atoms. Such Ra and Rb are not particularly limited, and examples thereof include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl attachment, a 1-fluoroethyl group, a 1,1-difluoroethyl group, and a 1,1,1-trimethyl group. Fluoroethyl group, 2-fluoroethyl group, 2,2-difluoroethyl group, 1,2-difluoroethyl group, 1,1,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 1, It is preferably any of 1,1,2-tetrafluoroethyl group, 1,1,2,2, -tetrafluoroethyl group, and 1,1,1,2,2, -pentafluoroethyl group. Among these, fluoromethyl group, difluoromethyl group, trifluoromethyl attachment, 1-fluoroethyl group, 1,1-difluoroethyl group, 1,1,1-trifluoroethyl group, 2-fluoroethyl group, 2, 2-difluoroethyl group and 1,2-difluoroethyl group are more preferable. By using a carbonate compound having such a group, various battery characteristics tend to be improved, including high-temperature durability and withstand voltage performance.

  These carbonate compounds having a fluorine atom can be used alone or in combination of two or more. When two or more compounds are used in combination, the mixing ratio of the two can be arbitrarily selected.

  The carbonate compound having a fluorine atom is preferably contained in an amount of 0.1 to 50% by mass, more preferably 0.2 to 20% by mass with respect to 100% by mass of the total amount of the non-aqueous electrolyte. More preferably, it is contained in an amount of 1 to 15% by mass. When the content is in the above range, the function of the carbonate compound having a fluorine atom is more excellent, and ion conduction tends to be excellent.

[Compound having two or more carbonate groups]
The nonaqueous electrolytic solution according to this embodiment includes a compound having two or more carbonate groups. The compound having two or more carbonate groups preferably has a cyclic carbonate group. By having a cyclic carbonate group, the electrode electrolyte solution interface control ability is improved, and long-term battery characteristics (cycle characteristics) tend to be more excellent. In addition, the compound having two or more carbonate groups may contain other functional groups. By using such a compound containing two or more carbonate groups, when SEI derived from a carbonate compound having a fluorine atom is generated by charge / discharge, a substance derived from a compound containing two or more carbonate groups in SEI is used. Can be included. A compound having two or more carbonate groups has excellent affinity and reactivity with a carbonate compound having a fluorine atom, and therefore can form a stable and good SEI with few defects and unevenness, high temperature durability, withstand voltage performance The battery characteristics such as are improved. In addition, the compound which has 2 or more carbonate groups remove | excludes the thing applicable to the carbonate compound which has the said fluorine atom.

Although it does not specifically limit as a compound which has 2 or more carbonate groups, For example, the compound shown to following formula (3) is mention | raise | lifted.
XZY (3)
(X and Y are each independently groups represented by the following formula (4) or formula (5), Z is O, S, SO ₂ , a divalent hydrocarbon group having 1 to 4 carbon atoms, or And a divalent group having an ester group, a carbonate group, an ether group, a thioether group, or a sulfonyl group.)

(In Formula (4), Ri, Rii, and Riii each independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 3 carbon atoms, or a fluorine-containing alkyl group. Riv represents a single bond or 1 to 1 carbon atoms. 3 represents an alkylene group or a fluorine-containing alkylene group.)

(In formula (5), RA represents an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group, and RB represents an alkylene group having 1 to 5 carbon atoms or a fluorine-containing alkylene group.)

In the formula (3), Z is O (ether group), S (thioether group), SO ₂ (sulfonyl group), a divalent hydrocarbon group having 1 to 4 carbon atoms, or an ester group, a carbonate group, A divalent group having an ether group, a thioether group, or a sulfonyl group. Of these, O (ether group), methylene group, ethylene group, or a divalent group having an ether group, a carbonate group, or an ester group is preferable. O (ether group), an ether having 1 or 2 carbon atoms A divalent group having a structural group, a carbonate group, or an ester group is more preferable.

  In the above formula (4), Ri, Rii, and Riii each independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 3 carbon atoms, or a fluorine-containing alkyl group, and include a hydrogen atom, a fluorine atom, a methyl group, or a fluorine-containing group. A fluorine alkyl group is preferable, and a hydrogen atom or a methyl group is more preferable.

  In the above formula (4), Riv represents a single bond, an alkylene group having 1 to 3 carbon atoms or a fluorine-containing alkylene group, preferably a single bond, a methyl group or a fluorine-containing alkylene group, and is a single bond or a methylene group. Is more preferable.

  In the above formula (5), RA represents an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group, and is preferably a methyl group, an ethyl group, or a fluorine-containing alkyl group, and is a methyl group or an ethyl group. It is more preferable.

  In the above formula (5), RB represents an alkylene group having 1 to 5 carbon atoms or a fluorine-containing alkylene group, preferably a methylene group, an ethylene group or a fluorine-containing alkylene group, and preferably a methylene group or an ethylene group. Is more preferable.

  These compounds having two or more carbonate groups can be synthesized by a conventional method and added to the electrolytic solution, or can be synthesized in-situ in the electrolytic solution.

  The compound having two or more carbonate groups is contained in an amount of 0.0001 to 10 parts by mass with respect to 100 parts by mass of the carbonate compound having a fluorine atom. The amount is preferably 0.0001 part by mass or more and 1 part by mass or less, more preferably 0.0001 part by mass or more and 0.1 part by mass or less. When the addition amount is within the above range, a carbonate compound having a fluorine atom and a compound having two or more carbonate groups have a good affinity, a stable SEI is formed, and battery characteristics such as high temperature durability and withstand voltage performance Becomes more stable.

[Lithium salt]
The nonaqueous electrolyte according to this embodiment includes a lithium salt. Although it does not specifically limit as lithium salt, For example, the inorganic lithium salt which does not contain a carbon atom in an anion, and the organic lithium salt which contains a carbon atom in an anion are mentioned. In addition, as lithium salt, inorganic lithium salt or organic lithium salt may be used individually by 1 type, or these may be used together.

The said inorganic lithium salt is not specifically limited, What is used as a normal nonaqueous electrolyte can be used. Such an inorganic lithium salt is not particularly limited. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , Li ₂ B ₁₂ F _b H _{12 -B} (b is an integer of 0 to 3), lithium salt bonded to a polyvalent anion, and the like. These inorganic lithium salts may be used alone or in combination of two or more. Among these, an inorganic lithium salt having a fluorine atom is preferable. By using such an inorganic lithium salt, a passive film is formed on the surface of the positive electrode current collector foil, which is preferable from the viewpoint of suppressing an increase in internal resistance. Also preferably also inorganic lithium salt having a phosphorus atom or a boron atom, LiPF _6, and one or more inorganic lithium salt is more preferably selected from the group consisting of LiBF _4, LiPF ₆ is more preferable. By using such an inorganic lithium salt, free fluorine atoms tend to be easily released.

The organic lithium salt is not particularly limited, and those used as a normal nonaqueous electrolyte can be used. Such an organic lithium salt is not particularly limited. For example, LiN (SO ₂ C _m F _{2m + 1} ) ₂ (m is LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) _2, etc. organic lithium salt represented by an integer of 1 to _{8); LiPF 5 (CF 3)} LiPF such _{n (C p F 2p + 1} ) 6-n (n is an integer of from 1 to 5, p is an integer of 1 to 8) An organic lithium salt represented by LiBF _q (C _s F _{2s + 1} ) _4-q (where q is an integer of 1 to 3, s is an integer of 1 to 8) such as LiBF ₃ (CF ₃ ) salt; _{LiB (C 2} O ₄₎ lithium bis represented by ₂ (oxalato) borate (LiBOB); halogenated _LiBOB; LiBF ₂ lithium oxa Lato difluoro borate represented by _{(C 2 O 4) (LiODFB} ); _{iB (C 3 O 4 H 2} ) lithium bis represented by ₂ (malonate) borate _{(LiBMB); LiPF 4 (C} 2 O 2) lithium tetrafluoro-oxa Lato phosphate represented by; formula (5a), The organic lithium salt represented by (5b) and (5c) is mentioned.
^{_{LiC (SO 2 R 3) (}} SO 2 R 4) (SO 2 R 5) (5a)
LiN (SO ₂ OR ⁶ ) (SO ₂ OR ⁷ ) (5b)
LiN (SO ₂ R ⁸ ) (SO ₂ OR ⁹ ) (5c)
(In formula, R < ³ >, R < ⁴ >, R < ⁵ >, R < ⁶ >, R <^7> , R < ⁸ > and R < ⁹ > may be the same or different from each other, and represent a C1-C8 perfluoroalkyl group. .)

  Among these, an organic lithium salt having a boron atom is preferable. The lithium salt is structurally stable and tends to further suppress dimerization of the carbonate compound having a fluorine atom.

  In addition, it is preferable to use an organic lithium salt having an organic ligand. Specifically, LiBOB, halogenated LiBOB, LiODFB, and LiBMB are more preferably used, and LiBOB is more preferably used. By using such an organic lithium salt, an organic ligand participates in an electrochemical reaction and SEI is formed on the electrode surface, so that an increase in internal resistance including the positive electrode tends to be further suppressed. The said organic lithium salt may be used individually by 1 type, or may use 2 or more types together.

  The lithium salt is preferably contained in the non-aqueous electrolyte according to the present embodiment at a concentration of 0.1 to 5 mol / L, more preferably 0.5 to 3 mol / L. More preferably, it is contained at a concentration of 0.8 to 2 mol / L. When the concentration of the lithium salt is within the above range, the conductivity of the non-aqueous electrolyte is kept high, and the charge / discharge efficiency of the non-aqueous secondary battery using the non-aqueous electrolyte is also kept high.

〔solvent〕
The nonaqueous electrolytic solution according to this embodiment may further use another nonaqueous solvent in combination. By using other non-aqueous solvents, the solubility, conductivity and ionization degree of the lithium salt tend to be further improved. Such other non-aqueous solvent is not particularly limited, but for example, alcohols other than the monoalcohol and polyhydric alcohol such as methanol, ethanol, isopropanol, butanol and octanol; methyl acetate, ethyl acetate, acetic acid Acid esters such as propyl, butyl acetate, methyl propionate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone; ketones such as dimethyl ketone, diethyl ketone, methyl ethyl ketone, 3-pentanone, and acetone; Hydrocarbons such as pentane, hexane, octane, cyclohexane, benzene, toluene, xylene, fluorobenzene and hexafluorobenzene; dimethyl ether, diethyl ether, 1,2-dimethoxyethane, 1,4-dioxane, Ethers such as launethers, glymes, tetrahydrofuran and fluorine-containing ethers; amides such as N, N-dimethylacetamide and N, N-dimethylformamide; amines such as ethylenediamine and pyridine; propylene carbonate, ethylene carbonate and vinylene Carbonate, fluoroethylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, trans-2,3-pentylene carbonate, cis -2,3-pentylene carbonate, vinyl ethylene carbonate, trifluoromethyl ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propylene Carbonates such as carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate and methyl trifluoroethyl carbonate; acetonitrile, propionitrile, adiponitrile, succinonitrile, malononitrile, methoxyacetonitrile, etc. Nitriles; Lactams such as N-methylpyrrolidone (NMP); Sulfones such as sulfolane and 3-methylsulfolane, dimethylsulfone and ethylmethylsulfone; Sulfonic esters such as propane sultone and butane sultone; Sulfoxides such as dimethyl sulfoxide Industrial oils such as silicon oil and petroleum; and edible oils.

  Moreover, an ionic liquid can also be used as a non-aqueous solvent. An ionic liquid is a liquid composed of ions obtained by combining an organic cation and an anion.

  The organic cation is not particularly limited, and examples thereof include imidazolium ions such as dialkylimidazolium cation and trialkylimidazolium cation; tetraalkylammonium ion; alkylpyridinium ion; dialkylpyrrolidinium ion; and dialkylpiperidinium ion. .

The anion serving as a counter for these organic cations is not particularly limited. For example, PF ₆ anion, PF ₃ (C ₂ F ₅ ) ₃ anion, PF ₃ (CF ₃ ) ₃ anion, BF ₄ anion, BF ₂ ( CF ₃ ) ₂ anion, BF ₃ (CF ₃ ) anion, bisoxalatoborate anion, Tf (trifluoromethanesulfonyl) anion, Nf (nonafluorobutanesulfonyl) anion, bis (fluorosulfonyl) imide anion, bis (trifluoromethanesulfonyl) ) Anion anion, bis (pentafluoroethanesulfonyl) imide anion, dicyanoamine anion, halide anion.

  The said non-aqueous solvent may be used individually by 1 type, or may use 2 or more types together.

(Aprotic solvent with lower viscosity than 4-fluoro-1,3-dioxolan-2-one)
The non-aqueous solvent preferably further includes an aprotic solvent having a viscosity lower than that of 4-fluoro-1,3-dioxolan-2-one (hereinafter also referred to as “FEC”). Specifically, it is preferable to further include an aprotic solvent having a viscosity of 2 cP or less. By using such an aprotic solvent, the mobility of lithium ions that contribute to charge / discharge of the non-aqueous secondary battery tends to be further increased. Such an aprotic solvent is not particularly limited, and examples thereof include an aprotic solvent having a fluorine atom, a chain carbonate compound, or a chain ether compound.

  The aprotic solvent having a fluorine atom is not particularly limited. For example, a chain carbonate compound or a chain ether compound in which at least one hydrogen atom is substituted with a fluorine atom can also be used.

  The chain carbonate compound is not particularly limited. For example, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, methyl fluoro Examples include methyl carbonate, difluoromethyl carbonate, and methyl trifluoroethyl carbonate.

  The chain ether compound is not particularly limited, and examples thereof include dimethyl ether, diethyl ether, 1,2-dimethoxyethane, 1,4-dioxane, crown ethers, glymes, tetrahydrofuran, and fluorine-containing ether.

  The viscosity can be measured with a viscometer.

(Hydrofluoric acid)
In addition, the nonaqueous electrolytic solution according to the present embodiment preferably contains 0.5 to 50 ppm of hydrofluoric acid, more preferably 1 to 30 ppm, and more preferably 2 to 20 ppm. Further preferred. When the content of hydrofluoric acid is in the above range, the continuous repair and formation of the SEI film tend to be easier.

(water)
The nonaqueous electrolytic solution according to the present embodiment preferably does not contain moisture, but may contain a very small amount of moisture as long as the solution of the problem of the present embodiment is not hindered. The content of such moisture is preferably 0 to 100 ppm, more preferably 1 to 50 ppm, and further preferably 1 to 30 ppm with respect to the total amount of the nonaqueous electrolytic solution.

(Additive)
The non-aqueous electrolyte according to the present embodiment may further contain an additive as necessary. Although it does not specifically limit as an additive used by this embodiment, For example, the substance which plays the role as a solvent which melt | dissolves lithium salt is mentioned. Such materials may substantially overlap with the non-aqueous solvent described above. Further, the additive is preferably a substance that contributes to improving the performance of the non-aqueous electrolyte and the non-aqueous secondary battery according to this embodiment, and a substance that does not directly participate in the electrochemical reaction can also be used. . In addition, an additive may be used individually by 1 type, or may use 2 or more types together.

  Although it does not specifically limit as an additive, For example, unsaturated bond containing cyclic carbonate represented by vinylene carbonate and vinyl ethylene carbonate; (gamma) -butyrolactone, (gamma) -valerolactone, (gamma) -caprolactone, (delta) -valerolactone, (delta) -caprolactone Lactone represented by ε-caprolactone; cyclic ether represented by 1,2-dioxane; methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl formate, ethyl acetate, ethyl propionate, Ethyl butyrate, n-propyl formate, n-propyl acetate, n-propyl propionate, n-propyl butyrate, isopropyl formate, isopropyl acetate, isopropyl propionate, isopropyl butyrate n-butyl formate, n-butyl acetate, n-butyl propionate, n-butyl butyrate, isobutyl formate, isobutyl acetate, isobutyl propionate, isobutyl butyrate, sec-butyl formate, sec-butyl acetate , Sec-butyl propionate, sec-butyl butyrate, tert-butyl formate, tert-butyl acetate, tert-butyl propionate, tert-butyl butyrate, methyl pivalate, n-butyl pivalate, n-hexylpi Carboxyl represented by barate, n-octyl pivalate, dimethyl oxalate, ethyl methyl oxalate, diethyl oxalate, diphenyl oxalate, malonic acid ester, fumaric acid ester, maleic acid ester Esters; amides represented by N-methylformamide, N, N-dimethylformamide, N, N-dimethylacetamide; ethylene sulfite, propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3-methylsulfolane, 3 -Cyclic sulfur compounds represented by sulfolene, 1,3-propane sultone, 1,4-butane sultone, 1,3-propanediol sulfate, tetramethylene sulfoxide, thiophene 1-oxide; monofluorobenzene, biphenyl, fluorinated biphenyl A nitro compound represented by nitromethane; a Schiff base; a Schiff base complex; an oxalate complex, an aromatic compound represented by substituted or unsubstituted benzene, biphenyl, naphthalene, and terphenyl; Trimethyl phosphate, triethyl phosphate, trimethyl phosphite, triethyl phosphite, phosphoric acid represented by fluorine-substituted phosphoric acid or phosphite; phosphite, difluorophosphate, monofluorophosphate And those having a salt structure typified by nitrate and carbonate; and alcohols such as methanol, ethanol, ethylene glycol, propylene glycol and fluoroethanol. These may be used alone or in combination of two or more.

  The electrolyte solution for non-aqueous electrochemical devices according to the present embodiment is not particularly limited. For example, for an electrochemical device such as an electrolyte solution for a lithium ion secondary battery, an electrolyte solution for a lithium ion capacitor, or an electrolyte solution for a lithium air battery. Can be used. In particular, by using it as an electrolyte for a lithium ion secondary battery, it is possible to realize a non-aqueous secondary battery having both high-temperature durability and withstand voltage performance.

[Lithium ion secondary battery]
The lithium ion secondary battery according to the present embodiment includes the non-aqueous electrolyte or the electrolyte for a lithium ion secondary battery and one or more materials capable of inserting and extracting lithium ions as a positive electrode active material. And a negative electrode containing at least one material selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium. A positive electrode, a negative electrode, and a separator are demonstrated below, for example.

[Positive electrode]
A positive electrode will not be specifically limited if it acts as a positive electrode of a lithium ion secondary battery, A well-known thing may be used. A positive electrode contains 1 or more types of materials which can occlude and discharge | release lithium ion as a positive electrode active material. Such a positive electrode active material is not particularly limited. For example, lithium-containing compounds; metal chalcogenides and metal oxides having tunnel structures and layer structures; olivine-type phosphate compounds; oxides of metals other than lithium; Examples include polymers. By using a lithium-containing compound as the positive electrode active material, a lithium ion secondary battery having a higher voltage and higher energy density tends to be obtained.

  Although it does not specifically limit as said lithium containing compound, For example, the composite oxide containing lithium and a transition metal element, the phosphoric acid compound containing lithium and a transition metal element, and the metal silicate compound containing lithium and a transition metal element Etc.

The composite oxide containing lithium and a transition metal element is not particularly limited, and examples thereof include compounds represented by the following formulas (6a) and (6b). More specifically, lithium cobalt oxide typified by LiCoO ₂ ; lithium manganese oxide typified by LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ ; lithium nickel oxide typified by LiNiO ₂ Li _z MO ₂ (M represents two or more elements selected from the group consisting of Ni, Mn, Co, Al, and Mg, and z represents a number of more than 0.9 and less than 1.2) Examples thereof include lithium-containing composite metal oxides. Among these, lithium, cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), vanadium (V) and titanium (Ti A composite oxide and a phosphate compound containing one or more transition metal elements selected from the group consisting of: By using such a lithium-containing compound, a higher voltage tends to be obtained. The compound represented by the following formula (6a) generally has a layered structure. As the compound, for the purpose of stabilizing the structure, a part of the transition metal element is substituted with Al, Mg, other transition metal elements or included in the crystal grain boundary, a part of the oxygen atom And those substituted with a fluorine atom or the like. Furthermore, what coat | covered the other positive electrode active material to at least one part of the positive electrode active material surface is mentioned.
Li _x MO ₂ (6a)
Li _y M ₂ O ₄ (6b)
(In the formula, M represents one or more metals selected from transition metals, x represents the number of 0 to 1, and y represents the number of 0 to 2.)

Examples of the phosphoric acid compound containing lithium and a transition metal element is not particularly limited, for example, iron phosphate olivine represented by LiFePO _4; include compounds represented by the formula (7b). The compound represented by the following formula (7b) generally has an olivine structure. In the compound, for the purpose of stabilizing the structure, a part of the transition metal element is substituted with Al, Mg, Co, Ti or other transition metal elements or included in the crystal grain boundary, The thing which partially substituted with the fluorine atom etc. is also mentioned. Furthermore, what coat | covered the other positive electrode active material to at least one part of the positive electrode active material surface is mentioned.
Li _w M ^II PO ₄ (7b)
(In the formula, M ^II represents one or more transition metal elements, and the value of w varies depending on the charge / discharge state of the battery, but usually w represents a number of 0.05 to 1.10.)

The silicic acid metal compound containing the lithium and a transition metal element is not particularly limited, for example, a compound represented by Li _t M _u SiO ₄ and the like. Here, M is synonymous with said Formula (6a), t shows the number of 0-1 and u shows the number of 0-2.

  The olivine-type phosphate compound is not particularly limited, and examples thereof include manganese olivine phosphate and cobalt olivine phosphate.

The oxide of a metal other than the lithium, but are not limited to, for _{example, S, MnO 2, FeO 2} , FeS 2, V 2 O 5, V 6 O 13, TiO 2, TiS 2, MoS 2 and NbSe ₂ Is mentioned.

  The conductive polymer is not particularly limited, and examples thereof include polyaniline, polythiophene, polyacetylene, and polypyrrole.

  A positive electrode active material is used individually by 1 type or in combination of 2 or more types.

  The number average particle diameter (primary particle diameter) of the positive electrode active material is preferably 0.05 μm to 100 μm, more preferably 1 μm to 10 μm. 100 particles observed with a transmission electron microscope are randomly extracted and analyzed with image analysis software (for example, image analysis software manufactured by Asahi Kasei Engineering Co., Ltd., trade name “A Image-kun”). It can also be obtained by calculation. In this case, when the number average particle diameter differs between measurement methods for the same sample, a calibration curve created for the standard sample may be used.

(Production method of positive electrode)
The positive electrode is obtained, for example, as follows. That is, first, a positive electrode mixture-containing paste is prepared by dispersing, in a solvent, a positive electrode mixture obtained by adding a conductive additive, a binder, or the like to the positive electrode active material as necessary. Next, this positive electrode mixture-containing paste is applied to a positive electrode current collector and dried to form a positive electrode mixture layer, which is pressurized as necessary to adjust the thickness, thereby producing a positive electrode.

  Here, the solid content concentration in the positive electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass.

  Although a positive electrode collector is not specifically limited, For example, metal foil, such as aluminum foil or stainless steel foil, is mentioned.

[Negative electrode]
A negative electrode will not be specifically limited if it acts as a negative electrode of a lithium ion secondary battery, A well-known thing may be used. The negative electrode contains at least one material selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium. Such a negative electrode preferably contains, as a negative electrode active material, at least one selected from the group consisting of metallic lithium, a carbon material, a silicon material, a material containing an element capable of forming an alloy with lithium, and a lithium-containing compound. . Among these, it is more preferable to contain one or more materials selected from the group consisting of metallic lithium, carbon materials, silicon materials, and materials containing elements capable of forming an alloy with lithium. By using such a negative electrode active material, the battery capacity tends to be superior.

  The carbon material is not particularly limited, for example, hard carbon, soft carbon, artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbeads, Examples thereof include carbon fiber, activated carbon, graphite, carbon colloid, and carbon black. Among these, the coke is not particularly limited, and examples thereof include pitch coke, needle coke, and petroleum coke. Further, the fired body of the organic polymer compound is not particularly limited. For example, a polymer material such as a phenol resin or a furan resin is fired at a suitable temperature and carbonized. In the present embodiment, a battery employing metallic lithium as the negative electrode active material is also included in the lithium ion secondary battery.

  The silicon material is not particularly limited, and examples thereof include crystalline silicon compounds, amorphous silicon compounds, organic silicon compounds, alloys and alloys of silicon and metal, and the like. In addition, various forms of silicon materials such as nano silicon materials and fibrous silicon materials can be used.

  Further, a material containing an element capable of forming an alloy with lithium is not particularly limited. For example, the material may be a metal or a semimetal alone, an alloy, or a compound. It may have a seed or two or more phases at least partially.

  In the present specification, “alloy” includes, in addition to an alloy composed of two or more metal elements, an alloy having one or more metal elements and one or more metalloid elements. In addition, the alloy may have a nonmetallic element as long as the alloy has metallic properties as a whole. In the alloy structure, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of these coexist.

  Such metal elements and metalloid elements are not particularly limited. For example, titanium (Ti), tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn) , Antimony (Sb), bismuth (Bi), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium (Zr) and yttrium (Y).

  Among these, metal elements and metalloid elements of Group 4 or 14 in the long-period periodic table are preferable, and titanium, silicon, and tin are particularly preferable.

  Although it does not specifically limit as an alloy of tin, For example, as a 2nd element other than tin, silicon, magnesium (Mg), nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium (Ti) , One having at least one element selected from the group consisting of germanium, bismuth, antimony and chromium (Cr).

  The silicon alloy is not particularly limited. For example, as the second constituent element other than silicon, tin, magnesium, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony And one having at least one element selected from the group consisting of chromium.

  The titanium compound, the tin compound, and the silicon compound are not particularly limited, and examples thereof include those having oxygen (O) or carbon (C). In addition to titanium, tin, or silicon, the second compound described above is used. It may have a constituent element.

  Also included are lithium-containing compounds. As the lithium-containing compound, the same compounds as those exemplified as the positive electrode material can be used.

  A negative electrode active material is used individually by 1 type or in combination of 2 or more types.

  The number average particle diameter (primary particle diameter) of the negative electrode active material is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm. The number average particle size of the negative electrode active material is measured in the same manner as the number average particle size of the positive electrode active material.

(Method for producing negative electrode)
A negative electrode is obtained as follows, for example. That is, first, a negative electrode mixture-containing paste is prepared by dispersing, in a solvent, a negative electrode mixture prepared by adding a conductive additive or a binder to the negative electrode active material, if necessary. Next, the negative electrode mixture-containing paste is applied to a negative electrode current collector and dried to form a negative electrode mixture layer, which is pressurized as necessary to adjust the thickness, whereby a negative electrode can be produced. .

  Here, the solid content concentration in the negative electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass.

  Although a negative electrode collector is not specifically limited, For example, metal foil, such as copper foil, nickel foil, or stainless steel foil, is mentioned.

  In the production of the positive electrode and the negative electrode, the conductive aid used as necessary is not particularly limited, and examples thereof include carbon black typified by graphite, acetylene black and ketjen black, and carbon fibers. The number average particle size (primary particle size) of the conductive assistant is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm, and is measured in the same manner as the number average particle size of the positive electrode active material. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber.

[Separator]
The lithium ion battery of this embodiment includes a separator between the positive electrode and the negative electrode in order to provide safety such as prevention of short circuit between the positive and negative electrodes. As the separator, an insulating thin film having high ion permeability and excellent mechanical strength is preferable.

  Although the material of the separator in this embodiment is not specifically limited, For example, a ceramic, glass, resin, and a cellulose are mentioned. The resin may be a synthetic resin or a natural resin (natural polymer), and may be an organic resin or an inorganic resin. From the viewpoint of excellent performance as a separator, An organic resin is preferred.

  Although it does not specifically limit as organic resin, For example, heat resistant resins, such as polyolefin, polyester, polyamide, liquid crystal polyester, and aramid, are mentioned.

  Moreover, it does not specifically limit as inorganic resin, For example, a silicone resin etc. are mentioned.

  The material of the separator is preferably ceramic and glass from the viewpoint of heat resistance, and polyester, polyamide, liquid crystal polyester, aramid, and cellulose are preferable from the viewpoint of handling properties and heat resistance. Further, from the viewpoint of cost and processability, polyolefin is preferable. Among these materials, when a resin is employed, it may be a homopolymer or a copolymer, and a mixture of a plurality of types of resins and an alloy may be used.

  Further, the separator may be a laminated body in which films made of a plurality of materials are laminated. When the separator is a laminate, the material of each layer may be the same or different.

(Manufacturing method of separator)
In the case of manufacturing a separator of a laminated body, it may be manufactured by sequentially stacking a certain layer on another layer, that is, by sequentially multilayering, and a plurality of separate films may be bonded together. Thus, a laminate may be produced.

  As the form of the separator in the present embodiment, for example, a synthetic resin microporous film produced by forming a synthetic resin film, a fiber spun from a synthetic resin or a natural polymer, a woven fabric processed from glass fiber or ceramic fiber, Nonwoven fabrics, knitted fabrics, papermaking, and films prepared by arranging synthetic resin, ceramic particles, and glass fine particles are listed.

  The separator in the present embodiment is a component other than the above, for example, an organic filler, an inorganic filler, an organic particle, and an inorganic particle on the surface and / or inside of the separator from the viewpoints of membrane reinforcement, charge / discharge assist, heat resistance improvement, and the like. May be included.

[Production method of lithium ion secondary battery]
A general method may be used as a method for manufacturing the lithium ion secondary battery in the present embodiment, and is not particularly limited. For example, the following method can be selected.

  First, a battery structure is produced by housing a laminate produced using a positive electrode, a negative electrode, and a separator in a battery case (exterior). And a battery can be produced by injecting the electrolytic solution of the present embodiment into it.

  For example, the laminated body is formed by first winding a positive electrode and a negative electrode in a laminated state with a separator interposed therebetween to form a laminated body having a wound structure, or by alternately bending or laminating them. It can produce by shape | molding into the laminated body in which a separator interposes between the some positive electrode and negative electrode which were laminated | stacked.

  The battery manufacturing method according to the present embodiment may include a step of pressurizing or depressurizing the inside of the battery. The method of pressurization or decompression is not particularly limited, and the heating and the decompression or pressurization may be performed simultaneously or separately. By passing through these steps, the impregnation property of the electrolyte into the electrode and separator of the battery structure may be improved.

  After passing through the above steps, if necessary, the remaining members are incorporated into the battery structure, and if the battery case (exterior) is not completely sealed (sealed), the battery is sealed. Can be obtained. In addition, after passing through each process mentioned above as needed, you may prepare shapes, such as removing the excess part of a battery, or may retighten or reseal a battery.

  The shape of the battery in the present embodiment is not particularly limited, and for example, a cylindrical shape, an oval shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, and a laminate shape are preferable. Among these, a coin type, a cylindrical type, a rectangular tube type, a flat type and a laminate type are more preferable, and a coin type and a laminate type are more preferable. The battery having such a shape can further enhance the affinity between the electrolytic solution and the battery structure, expresses various performances of the electrolytic solution in the present embodiment to a higher level, and is relatively easy to manufacture the battery. Easy. Also, the size of the battery is not particularly limited, and a structure in which a plurality of batteries are stacked or arranged can be used in combination with many kinds of batteries. Also, among laminated batteries, the battery case (exterior) is constructed by laminating an aluminum film and a resin like an aluminum laminate material from the viewpoint of lightness, durability, handleability, cost, etc. More preferably.

Although the lithium ion secondary battery of this embodiment can function as a battery by the first charge, it is stabilized when a part of the electrolytic solution containing the fluorinated carbonate is decomposed during the first charge. Although there is no restriction | limiting in particular about the method of the initial charge in this embodiment, It is preferable that initial charge is performed at 0.001-0.3C, It is more preferable to be performed at 0.002-0.25C, 0.003 More preferably, it is carried out at ~ 0.2C. In addition, it is also preferable that the initial charging is performed via the constant voltage charging in the middle. In addition, the constant current which discharges rated capacity in 1 hour is 1C. By setting the voltage range in which the lithium salt is involved in the electrochemical reaction to be long, SEI is formed on the electrode surface, which has an effect of suppressing an increase in internal resistance including the positive electrode. In addition, since the reaction product is not firmly fixed only on the negative electrode, and in some form it has a good effect on other members such as the positive electrode and the separator, the electrochemical property of the lithium salt dissolved in the electrolyte It is very effective to perform the first charge in consideration of the reaction.
The non-aqueous secondary battery of this embodiment can also be used in series or in parallel. In addition, from the viewpoint of managing the charge / discharge state of the battery pack, the operating voltage range is preferably 2 to 5 V, and more preferably 2.5 to 4.9 V.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further in detail, this invention is not limited to these Examples. Various characteristics of the nonaqueous secondary battery were measured and evaluated as follows.

(1) Preparation of non-aqueous electrolyte A predetermined amount of components constituting the non-aqueous electrolyte was prepared and stirred in an argon atmosphere to obtain an electrolyte. The composition is shown in Table 1.

(2) Preparation of lithium ion secondary battery

(Preparation of positive electrode)
The following positive electrode active material, the following conductive additive, and PVdF were mixed at a mass ratio of mixed oxide: graphite carbon powder: acetylene black powder: PVdF = 100: 4.2: 1.8: 4.6. To the obtained mixture, N-methyl-2-pyrrolidone was added so as to have a solid content of 68% by mass and further mixed to prepare a slurry-like solution. This slurry-like solution was applied to one side of an aluminum foil having a thickness of 20 μm, and the solvent was dried and removed, followed by rolling with a roll press. The rolled product was punched into a disk shape having a diameter of 16 mm to obtain a positive electrode.
(Positive electrode material)
Positive electrode active material:
Lithium, nickel, manganese and cobalt mixed oxide conductive assistant with a number average particle diameter of 11 μm:
Graphite carbon powder with a number average particle size of 6.5 μm Acetylene black powder PVdF with a number average particle size of 48 nm

(Preparation of negative electrode)
The following negative electrode active material and the following binder are mixed at a solid mass ratio of graphite carbon powder (I): graphite carbon powder (II): carboxymethyl cellulose solution: diene rubber = 90: 10: 1.44: 1.76. A slurry-like solution was prepared by mixing so that the total solid concentration was 45% by mass. The slurry solution was applied to one side of a 10 μm thick copper foil, and the solvent was removed by drying, followed by rolling with a roll press. The negative electrode was obtained by punching into a disk shape having a diameter of 16 mm after rolling.
(Anode raw material)
Negative electrode active material:
Graphite carbon powder (I) having a number average particle diameter of 12.7 μm
Graphite carbon powder (II) having a number average particle diameter of 6.5 μm
binder:
Carboxymethylcellulose solution (solids concentration 1.83% by mass)
Diene rubber (glass transition temperature: −5 ° C., number average particle size upon drying: 120 nm, dispersion medium: water, solid content concentration 40% by mass)

(Manufacture of lithium ion secondary batteries)
A laminate made by stacking a positive electrode and a negative electrode produced as described above on both sides of a separator made of polyethylene (film thickness: 25 μm, porosity: 50%, pore diameter: 0.1 μm to 1 μm) is a SUS disk type battery. Inserted into the case. Next, 0.4 mL of the electrolytic solution was injected into the battery case, and the laminate was immersed in the electrolytic solution. Then, the battery case was sealed to produce a lithium ion secondary battery (small battery). A lithium ion secondary battery for measurement was prepared so that 1C = 6.0 mA. The fabricated battery was completed by performing initial conditioning by charging at 0.2C and discharging at 0.3C.

(3) Evaluation The following battery evaluation was performed using the electrolytic solution obtained as described above. These evaluations were performed using a charge / discharge device ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-63S (trade name) manufactured by Futaba Kagaku Co., Ltd.

(3) -1 Discharge capacity measurement The battery was charged with a constant current of 6.0 mA, reached 4.2 V, charged with a constant voltage of 4.2 V, and charged for a total of 8 hours. Then, the discharge capacity when discharging to 3.0 V with a constant current was determined. The discharge current was 6 mA. This measurement was performed in an environment of 25 ° C.

(3) -2 High-temperature cycle test After charging at a constant current of 6.0 mA and reaching 4.2 V, the battery was charged at a constant voltage of 4.2 V and charged for a total of 8 hours. Then, it discharged to 3.0V with the constant current of 6.0mA, and let it be 1 cycle charging / discharging cycle. This charge / discharge cycle was carried out at 50 ° C. for 100 cycles, and the value of the discharge capacity at the 100th cycle relative to the second cycle was calculated as the discharge capacity retention rate (A).

(3) -3 High-voltage cycle test After charging with a constant current of 6.0 mA and reaching 4.5 V, the battery was charged with a constant voltage of 4.5 V and charged for a total of 8 hours. Then, it discharged to 3.0V with the constant current of 6.0mA, and let it be 1 cycle charging / discharging cycle. This charge / discharge cycle was carried out at 50 ° C. for 50 cycles, and the value of the discharge capacity at the 100th cycle relative to the second cycle was calculated as the discharge capacity retention rate (B).

(3) -4 High-temperature storage test After charging at a constant current of 2.0 mA and reaching 4.2 V, the battery was charged at a constant voltage of 4.2 V and charged for a total of 8 hours. Thereafter, discharging was performed up to 3.0 V with a constant current of 3.0 mA. Subsequently, the battery is charged at a constant current of 6.0 mA, reaches a constant voltage of 4.2 V, is charged at a constant voltage of 4.2 V for a total of 8 hours, and after charging is completed, the charged battery is charged at 50 ° C. Stored for 20 days. The lithium ion secondary battery after storage was discharged to 3.0 V at a constant current of 6.0 mA at 25 ° C. The discharge capacity at this time was determined as the remaining capacity. After that, the battery is charged again to 4.2 V with a constant current of 6.0 mA, and after reaching 4.2 V, it is charged with a constant voltage of 4.2 V for a total of 8 hours, and is charged to 3.0 V with a constant current of 6.0 mA. Discharge was performed. The discharge capacity at this time was determined as the recovery capacity.

  Table 1 shows the results of battery evaluation. As shown in Examples 1 to 9, good battery characteristics were observed in any composition of the battery using the electrolytic solution of the present invention. On the other hand, in the comparative example, when the fluorine does not have an atom, the performance is low in the high temperature cycle test, and when the compound having two or more carbonate groups is not included, the performance is low in the high temperature cycle test and the high temperature storage test. . Moreover, when there were many compounds which have 2 or more carbonate groups, it became low performance in all, and it was shown that the introduction amount of the compound which has 2 carbonate groups needs to be appropriate.

FEC: 4-fluoro-1,3-dioxolane-2-one t-DFEC: 4,5-difluoro-1,3-dioxolane-2-one (trans form)
c-DFEC: 4,5-difluoro-1,3-dioxolan-2-one (cis isomer)
FDMC, DFDMC (1) to (2), TFDMC:
Fluorine-containing ether: Product name T-1216, manufactured by Daikin Industries
Carbonates (a) to (c):

  As described above, it is shown that the nonaqueous electrolyte of the present invention can realize a nonaqueous secondary battery having both high temperature durability and withstand voltage performance by forming better and stable SEI. It was.

  The nonaqueous electrolytic solution of the present invention has industrial applicability as an electrolytic solution for electrochemical devices, particularly as an electrolytic solution for lithium ion secondary batteries.

Claims (9)

A carbonate compound having a fluorine atom;
0.0001 parts by mass or more and 10 parts by mass or less of a compound having 2 or more carbonate groups with respect to 100 parts by mass of the carbonate compound having fluorine atoms,
Lithium salt,
An electrolyte for non-aqueous electrochemical devices.   The electrolyte solution for nonaqueous electrochemical devices according to claim 1, wherein the carbonate compound having a fluorine atom includes a cyclic carbonate compound having a fluorine atom.   The electrolyte solution for nonaqueous electrochemical devices according to claim 1 or 2, wherein the compound having two or more carbonate groups has a cyclic carbonate group.   The electrolyte solution for nonaqueous electrochemical devices according to any one of claims 1 to 3, further comprising an aprotic solvent having a viscosity of 2 cP or less.   The electrolyte solution for nonaqueous electrochemical devices according to claim 1, wherein the aprotic solvent contains a solvent having a fluorine atom.   The electrolyte solution for lithium ion secondary batteries containing the electrolyte solution for nonaqueous electrochemical devices of any one of Claims 1-5. An electrolyte solution for a non-aqueous electrochemical device according to any one of claims 1 to 5 or an electrolyte solution for a lithium ion secondary battery according to claim 6, a positive electrode, and a negative electrode.
The positive electrode contains one or more positive electrode active materials that are materials capable of inserting and extracting lithium ions,
The negative electrode contains one or more negative electrode active materials selected from the group consisting of a material capable of inserting and extracting lithium ions and metallic lithium.
Lithium ion secondary battery.   The lithium ion secondary battery according to claim 7, wherein the positive electrode active material includes a lithium-containing compound.   The negative electrode active material according to claim 7 or 8, comprising at least one material selected from the group consisting of metallic lithium, a carbon material, a silicon material, and a material containing an element capable of forming an alloy with lithium. Lithium ion secondary battery.