JP2017045722A - Nonaqueous electrolyte for battery and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte for a battery, capable of reducing battery resistance while containing at least one of lithium monofluorophosphate and lithium difluorophosphate.SOLUTION: A nonaqueous electrolyte for a battery contains at least one of lithium monofluorophosphate and lithium difluorophosphate, the content of a copper element relative to the total amount of the nonaqueous electrolyte for a battery being 0.001 mass ppm or more and less than 5 mass ppm.SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous electrolyte for a battery, and a chargeable / dischargeable lithium secondary battery used for a power source of a portable electronic device, a vehicle-mounted device, and power storage.

2. Description of the Related Art In recent years, lithium secondary batteries have been widely used as electronic devices such as mobile phones and laptop computers, electric vehicles, and power storage sources. In particular, recently, there has been a rapid increase in demand for batteries with high capacity, high output, and high energy density that can be mounted on hybrid vehicles and electric vehicles.
The lithium secondary battery includes, for example, a positive electrode and a negative electrode containing a material capable of occluding and releasing lithium, and a non-aqueous electrolyte for a battery containing a lithium salt and a non-aqueous solvent.
As the positive electrode active material used for the positive electrode, for example, lithium metal oxides such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , and LiFePO ₄ are used.
Moreover, as a non-aqueous electrolyte for batteries, a mixed solvent (non-aqueous solvent) of carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) _2. A solution in which a Li electrolyte such as LiN (SO ₂ CF ₂ CF ₃ ) ₂ is mixed is used.
On the other hand, negative electrode active materials used for negative electrodes include metal lithium, metal compounds capable of occluding and releasing lithium (metal simple substance, oxide, alloy with lithium, etc.) and carbon materials, particularly lithium. Lithium secondary batteries using coke, artificial graphite, and natural graphite that can be occluded and released have been put into practical use.

In order to improve the performance of a battery (for example, a lithium secondary battery) containing a battery non-aqueous electrolyte, various additives are added to the battery non-aqueous electrolyte.
For example, as a battery non-aqueous electrolyte that can improve battery storage characteristics, a battery non-aqueous electrolyte containing at least one of lithium monofluorophosphate and lithium difluorophosphate as an additive is known (for example, Patent Document 1).
Moreover, as a non-aqueous electrolyte secondary battery capable of suppressing the generation of dendrites and suppressing the occurrence of internal short circuits by capturing metal impurities, a compound having a β-diketone partial structure, and iron, nickel of β-diketone, A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte solution containing at least one metal complex selected from copper, cobalt and zinc is known (for example, see Patent Document 2).

Japanese Patent No. 3439085 JP 2006-172726 A

However, as a result of studies by the present inventors, it has been found that the battery resistance may increase in a battery including a nonaqueous electrolyte for a battery containing at least one of lithium monofluorophosphate and lithium difluorophosphate.
Accordingly, an object of the present invention is to provide a battery non-aqueous electrolyte solution that can reduce battery resistance while including a battery non-aqueous electrolyte solution containing at least one of lithium monofluorophosphate and lithium difluorophosphate, and the battery. The present invention provides a lithium secondary battery including a non-aqueous electrolyte for use.

As a result of intensive studies, the present inventors have found that battery resistance may increase in a battery including a nonaqueous electrolyte for a battery containing at least one of lithium monofluorophosphate and lithium difluorophosphate, and the battery The present inventors have found that the battery resistance can be reduced by limiting the content of the copper element in the non-aqueous electrolyte for battery in the above to 0.001 mass ppm or more and less than 5 mass ppm, and completed the present invention.
That is, the means for solving the above problems are as follows.

<1> Nonaqueous battery for battery which contains at least one of lithium monofluorophosphate and lithium difluorophosphate, and the content of copper element with respect to the total amount of nonaqueous electrolyte for battery is 0.001 mass ppm or more and less than 5 mass ppm. Electrolytic solution.
<2> The nonaqueous electrolytic solution for batteries according to <1>, which contains lithium difluorophosphate.
<3> The total content of lithium monofluorophosphate and lithium difluorophosphate is 0.001% by mass to 5% by mass with respect to the total amount of the nonaqueous electrolytic solution for battery, according to <1> or <2>. Non-aqueous electrolyte for batteries.
<4> The nonaqueous electrolytic solution for a battery according to any one of <1> to <3>, further comprising a cyclic sulfate ester compound represented by the general formula (I).

[In General Formula (I), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a group represented by General Formula (II), or Formula (III). or a group represented by or, R ¹ and R ² together, with the carbon atom to the carbon atom and R ² wherein R ¹ is bonded are bonded, represents a group forming a benzene ring or a cyclohexyl ring.
In general formula (II), R ³ is a halogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a formula (IV). Represents a group. The wavy line in general formula (II), formula (III), and formula (IV) represents a bonding position.
When the cyclic sulfate ester compound represented by the general formula (I) includes two groups represented by the general formula (II), the two groups represented by the general formula (II) are the same. Or they may be different from each other. ]

<5> Positive electrode, negative electrode current collector containing copper element, and metal negative electrode, lithium-containing alloy, metal or alloy capable of alloying with lithium, and doping / de-doping of lithium ions as negative electrode active material A negative electrode comprising at least one substance selected from the group consisting of oxides capable of being doped, transition metal nitrides capable of doping and undoping lithium ions, and carbon materials capable of doping and undoping lithium ions; A non-aqueous electrolyte for a battery according to any one of <1> to <4>, and a lithium secondary battery.
<6> A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to <5>.

  According to the present invention, a battery non-aqueous electrolyte containing at least one of lithium monofluorophosphate and lithium difluorophosphate, which can reduce battery resistance, and a battery non-aqueous electrolyte A lithium secondary battery containing a water electrolyte is provided.

It is a schematic perspective view which shows an example of the laminate type battery which is an example of the lithium secondary battery of this invention. It is a schematic sectional drawing of the thickness direction of the laminated electrode body accommodated in the laminate type battery shown in FIG.

  Hereinafter, the non-aqueous electrolyte for batteries and the lithium secondary battery of the present invention will be described in detail.

[Non-aqueous electrolyte for batteries]
The battery non-aqueous electrolyte of the present invention (hereinafter also simply referred to as “non-aqueous electrolyte”) is at least one of lithium monofluorophosphate and lithium difluorophosphate (hereinafter also referred to as “lithium fluorophosphate”). The content of copper element (hereinafter also referred to as “Cu element”) with respect to the total amount of the non-aqueous electrolyte for a battery is 0.001 mass ppm or more and less than 5 mass ppm.

As described above, as a conventional battery non-aqueous electrolyte (non-aqueous electrolyte), a non-aqueous electrolyte containing lithium fluorophosphate (see, for example, Patent Document 1), a compound having a β-diketone partial structure, A non-aqueous electrolyte solution containing at least one metal complex selected from iron, nickel, copper, cobalt and zinc of β-diketone (for example, see Patent Document 2) is known.
In particular, paragraph 0048 (Table 2) of Patent Document 2 discloses “battery 15 of example” and “battery 19 of example” as examples using a copper complex of acetylacetone as a β-diketone. Yes. In these batteries, a solution obtained by adding lithium hexafluorophosphate to a solvent in which 3 parts by volume of ethyl methyl carbonate is mixed with 1 part by volume of ethylene carbonate so as to have a concentration of 1.25 mol / dm ³ (basic electrolyte solution). ; See paragraph 0044 of the same document), a nonaqueous electrolyte solution in which acetylacetone and a copper complex of acetylacetone are added to a concentration of 0.01 mol / dm ³ is used. Here, the specific gravity of ethylene carbonate is 1.32, the specific gravity of ethyl methyl carbonate is 1.01, the atomic weight of copper element is 63.5, the molecular weight of acetylacetone is 100, and the molecular weight of lithium hexafluorophosphate is When calculated as 152, the non-aqueous electrolytes of the “battery 15 of the example” and “battery 19 of the example” both contain about 500 mass ppm of Cu element.

On the other hand, as a result of studies by the present inventors, it has been found that battery resistance may increase in a battery containing a nonaqueous electrolyte for a battery containing lithium fluorophosphate.
The reason for this increase in battery resistance is not clear, but is presumed as follows.
In a battery including a non-aqueous electrolyte containing lithium fluorophosphate, Cu element contained in the negative electrode current collector elutes into the non-aqueous electrolyte due to interaction with lithium fluorophosphate in the non-aqueous electrolyte. Conceivable. That is, it is considered that the elution of this Cu element causes a change in the surface of the negative electrode current collector, and the decomposition reaction of the nonaqueous solvent in the nonaqueous electrolytic solution easily occurs on this surface. As a result, it is considered that the decomposition product of the nonaqueous solvent is deposited on the surface of the negative electrode current collector, and the battery resistance is increased.

As a result of further studies, the present inventors have determined that the content of Cu element in the non-aqueous electrolyte in the battery including the non-aqueous electrolyte containing lithium fluorophosphate is the total amount of the non-aqueous electrolyte. The inventors have found that the resistance of the battery can be reduced by limiting the range to 0.001 mass ppm or more and less than 5 mass ppm, thereby completing the present invention.
That is, the nonaqueous electrolytic solution of the present invention is a nonaqueous electrolytic solution that can suppress an increase in battery resistance while being a nonaqueous electrolytic solution containing lithium fluorophosphate.
Therefore, the nonaqueous electrolytic solution of the present invention is expected to have an effect of extending the life of the battery.

In the non-aqueous electrolyte of the present invention, “content of Cu element” means the content of Cu element with respect to the total amount of the electrolyte in the battery when the non-aqueous electrolyte of the present invention is used as the battery electrolyte. Means quantity.
That is, the non-aqueous electrolyte of the present invention is, in other words, a non-aqueous electrolyte containing lithium fluorophosphate, and a battery (preferably a positive electrode and a negative electrode including a negative electrode current collector containing Cu element) When used as an electrolyte solution of a lithium secondary battery of the present invention, which will be described later, the Cu element content is 0.001 with respect to the total amount of the electrolyte solution in the battery. It is a nonaqueous electrolytic solution having a mass ppm or more and less than 5 mass ppm.
For example, a Cu element is added to a non-aqueous electrolyte used for manufacturing a battery (that is, a non-aqueous electrolyte before being incorporated into a battery; hereinafter, also referred to as “raw material non-aqueous electrolyte”), and this non-aqueous electrolyte When a part of the Cu element of the negative electrode current collector is eluted in the non-aqueous electrolyte in the battery incorporating the electrolyte, the above “content of Cu element” is added to the raw non-aqueous electrolyte. This is the total amount of the amount of Cu element that has been removed and the amount of Cu element that has eluted from the negative electrode current collector into the non-aqueous electrolyte.

As described above, in the present specification, the content of the Cu element means the content of the Cu element in the nonaqueous electrolytic solution in the battery unless otherwise specified.
On the other hand, in the present specification, the content of each component other than the Cu element in the nonaqueous electrolytic solution means the content of each component in the raw material nonaqueous electrolytic solution unless otherwise specified.

<Lithium fluorophosphate>
The nonaqueous electrolytic solution of the present invention contains lithium fluorophosphate (at least one of lithium monofluorophosphate (LiPO ₃ F) and lithium difluorophosphate (LiPO ₂ F ₂ )). This improves the storage characteristics of the battery.
From the viewpoint of more effectively achieving the effects of the present invention, the nonaqueous electrolytic solution of the present invention preferably contains lithium difluorophosphate.

  Although there is no restriction | limiting in particular in content (it is total content in the case of 2 types) of lithium fluorophosphate in a non-aqueous electrolyte, From a viewpoint by which the effect of this invention is show | played more effectively, 0. The content is preferably 001% by mass to 5% by mass, and more preferably 0.05% by mass to 5% by mass.

In addition, when the lithium fluorophosphate is actually used for producing a secondary battery as a non-aqueous electrolyte, even if the battery is disassembled and the non-aqueous electrolyte is taken out again, the content thereof changes. There is a case. Therefore, in the case of a battery in which the lithium fluorophosphate is contained in a non-aqueous electrolyte in a predetermined amount, when at least the lithium fluorophosphate of the present invention can be detected from the non-aqueous electrolyte extracted from the battery. Can be considered that the non-aqueous electrolyte contains the lithium fluorophosphate of the present invention. The same applies to other additives described later.
In this specification, the terms “content of additive” and “addition amount of additive” both mean the content of the additive with respect to the total amount of the non-aqueous electrolyte.

<Cu element>
When the nonaqueous electrolytic solution of the present invention is used as an electrolytic solution for a battery, the content of Cu element with respect to the entire electrolytic solution in the battery is 0.001 mass ppm or more and less than 5 mass ppm.
In this case, the “content of Cu element with respect to the total amount of the electrolytic solution” means the amount of Cu element dissolved in the nonaqueous electrolytic solution.
In the present invention, elution of Cu element from the negative electrode current collector of the battery is suppressed, and as a result, the content of Cu element in the non-aqueous electrolyte in the battery is limited to less than 5 ppm by mass. Thereby, battery resistance is reduced. Further, when the content of the Cu element is less than 5 ppm by mass, an effect of suppressing the formation of dendrite is expected.
The lower limit (0.001 mass ppm) of the content of Cu element is a lower limit from the viewpoint of productivity (manufacturability) of the non-aqueous electrolyte or battery.

The content of the Cu element with respect to the entire electrolyte solution in the battery is preferably 4 mass ppm or less, more preferably 3 mass ppm or less from the viewpoint of reducing battery resistance, and 2 mass ppm or less. More preferably.
The content of the Cu element with respect to the entire electrolytic solution in the battery is preferably 0.01 mass ppm or more from the viewpoint of productivity (manufacturability) of the nonaqueous electrolytic solution or the battery, and is 0.1 mass ppm. More preferably, it is more preferably 0.5 mass ppm or more.

  In the present specification, the content of Cu element in the non-aqueous electrolyte means a value measured by inductively coupled plasma mass spectrometry.

  In the present invention, as a result, the Cu element content in the non-aqueous electrolyte in the battery may be limited to a range of 0.001 mass ppm or more and less than 5 mass ppm, and the Cu element content is within the above range. There are no particular restrictions on the specific means for limiting. In short, as a result, the elution of Cu element from the negative electrode current collector is suppressed, and the content of Cu element in the non-aqueous electrolyte in the battery is limited to a range of 0.001 mass ppm to less than 5 mass ppm. That's fine.

In an embodiment in which a trace amount of Cu element is contained in the raw material non-aqueous electrolyte in advance, the elution of Cu element from the negative electrode current collector is suppressed, and the content of Cu element in the electrolyte is 0.001 mass ppm or more. It is preferable at the point which can maintain in the range of less than 5 mass ppm. In this case, the content of the Cu element with respect to the total amount of the raw material nonaqueous electrolytic solution is preferably 0.001 mass ppm or more and less than 5 mass ppm.
The content of Cu element in the raw material non-aqueous electrolyte is more preferably 4 mass ppm or less, further preferably 3 mass ppm or less, further preferably 2 mass ppm or less, and 1 mass ppm. More preferably, it is as follows.
The content of Cu element in the raw material non-aqueous electrolyte is preferably 0.01 mass ppm or more, more preferably 0.1 mass ppm or more, based on the total amount of the raw material non-aqueous electrolyte. More preferably, it is 2 ppm by mass or more.
As a mode in which a trace amount of Cu element is contained in the raw material non-aqueous electrolyte in advance, a copper compound (hereinafter also referred to as “Cu compound”) described later is contained in the raw material non-aqueous electrolyte in advance. Embodiments are preferred.

<Cu compound>
The nonaqueous electrolytic solution of the present invention contains a Cu compound as a compound containing a Cu element (that is, the Cu compound is contained and the content of the Cu element is 0.001 mass relative to the total amount of the nonaqueous electrolytic solution). It is preferably not less than ppm and less than 5 mass ppm.
As the Cu compound, an ionic compound in which the oxidation number of the Cu element is +1 or +2 is preferable.

Cu compounds include copper phosphate (II), copper sulfate (II), copper nitrate (II), copper acetate (I), copper acetate (II), copper carbonate (II), copper cyanide (I), Shu Copper (II) citrate, Copper (II) citrate, Copper (II) gluconate, Copper (II) perchlorate, Copper fluoride (II), Copper chloride (I), Copper chloride (II), Copper hydroxide (II), tetrakis (acetonitrile) copper (I) hexafluorophosphate, copper (II) hexafluorophosphate, tetrakis (acetonitrile) copper (I) tetrafluoroborate, copper (II) tetrafluoroborate, trifluoromethane Copper (I) sulfonate, copper (II) trifluoromethanesulfonate, copper (II) difluorophosphate, copper (II) monofluorophosphate, copper (II) bis (ethoxide), copper (I) acetylacetonate, Bis (acetylacetonate) copper (II) and the like can be mentioned.
Among these, from the viewpoint of easy availability and handling, tetrakis (acetonitrile) copper (I) hexafluorophosphate, tetrakis (acetonitrile) copper (I) tetrafluoroborate, copper (II) trifluoromethanesulfonate, or Bis (acetylacetonate) copper (II) is preferred.

When the nonaqueous electrolytic solution of the present invention contains a Cu compound, the contained Cu compound may be only one kind or two or more kinds.
When the non-aqueous electrolytic solution of the present invention contains a Cu compound, the content of the Cu compound (the total content in the case of two types; the same shall apply hereinafter) is not particularly limited. From the viewpoint of more effectively achieving the effects of the present invention, the content of the Cu compound is preferably 0.001 ppm by mass to 15 ppm by mass with respect to the total amount of the non-aqueous electrolyte, and is 0.05 mass. More preferably, it is ppm to 15 mass ppm.
As for content of the said Cu compound, it is more preferable that it is 10 mass ppm or less, and it is still more preferable that it is 5.0 mass ppm or less.
The content of the Cu compound is more preferably 0.01 mass ppm or more, still more preferably 0.1 mass ppm or more, and particularly preferably 0.5 mass ppm or more.

<Other additives>
Moreover, the nonaqueous electrolytic solution of the present invention may contain other additives other than those described above.
Other additives include carbonate compounds having a carbon-carbon unsaturated bond; carbonate compounds substituted with fluorine atoms; fluorophosphate compounds other than lithium monofluorophosphate and lithium difluorophosphate; oxalate compounds; sultone compounds; Cyclic sulfate compounds; and the like.
When the nonaqueous electrolytic solution of the present invention contains other additives, the other additives contained may be only one type or two or more types.
As other additives, cyclic sulfate compounds are preferable, and cyclic sulfate compounds represented by the general formula (I) described later (hereinafter also referred to as “compounds represented by the general formula (I)”) are particularly preferable. .

(Carbonate compound having a carbon-carbon unsaturated bond)
Examples of the carbonate compound having a carbon-carbon unsaturated bond include methyl vinyl carbonate, ethyl vinyl carbonate, divinyl carbonate, methyl propynyl carbonate, ethyl propynyl carbonate, dipropynyl carbonate, methyl phenyl carbonate, ethyl phenyl carbonate, diphenyl carbonate, and the like. Carbonates; vinylene carbonate, methyl vinylene carbonate, 4,4-dimethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, ethynyl ethylene carbonate, 4,4-diethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, propylene Le ethylene carbonate, 4,4-propynyl carbonate, cyclic carbonates such as 4,5-di-propynyl carbonate; and the like. Among these, preferably, methyl phenyl carbonate, ethyl phenyl carbonate, diphenyl carbonate, vinylene carbonate, vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, more preferably vinylene carbonate, Vinyl ethylene carbonate.

(Carbonate compound having fluorine atom)
Examples of the carbonate compound having a fluorine atom include methyl trifluoromethyl carbonate, ethyl trifluoromethyl carbonate, bis (trifluoromethyl) carbonate, methyl (2,2,2-trifluoroethyl) carbonate, ethyl (2,2,2). -Chain carbonates such as trifluoroethyl) carbonate and bis (2,2,2-trifluoroethyl) carbonate; 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4 -Cyclic carbonates such as trifluoromethylethylene carbonate; Of these, 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate are preferable.

(Fluorophosphate compound)
Examples of fluorophosphoric acid compounds other than lithium monofluorophosphate and lithium difluorophosphate include difluorophosphoric acid, monofluorophosphoric acid, methyl difluorophosphate, ethyl difluorophosphate, dimethyl fluorophosphate, and diethyl fluorophosphate. It is done. Moreover, difluorophosphates other than the above-mentioned lithium difluorophosphate, monofluorophosphates other than the above-mentioned lithium monofluorophosphate, and fluorosulfonates are also included.

(Oxalato compound)
Examples of the oxalato compound include lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, tris (oxalato) lithium phosphate, lithium difluoro (oxalato) borate, and lithium bis (oxalato) borate. . Of these, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, and lithium bis (oxalato) borate are preferable.

(Sultone compound)
Examples of sultone compounds include 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1-methyl-1,3-propene sultone, 2-methyl-1,3-propene sultone, and 3-methyl. Examples include sultone such as -1,3-propene sultone (excluding cyclic sulfate compounds). Of these, 1,3-propane sultone and 1,3-propene sultone are preferable.

(Cyclic sulfate compound)
As the cyclic sulfate compound, a sulfate compound represented by the following general formula (I) (hereinafter also referred to as “compound represented by the general formula (I)”) is preferable.

In general formula (I), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a group represented by general formula (II), or a group represented by formula (III). R ¹ and R ² together represent a group that forms a benzene ring or a cyclohexyl ring together with the carbon atom to which R ¹ is bonded and the carbon atom to which R ² is bonded.
In general formula (II), R ³ is a halogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a formula (IV). Represents a group. The wavy line in general formula (II), formula (III), and formula (IV) represents the bonding position.
When the cyclic sulfate ester compound represented by the general formula (I) includes two groups represented by the general formula (II), the two groups represented by the general formula (II) are the same. Or they may be different from each other.

Specific examples of the “halogen atom” in the general formula (II) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
As the halogen atom, a fluorine atom is preferable.

In the general formulas (I) and (II), the “alkyl group having 1 to 6 carbon atoms” is a linear or branched alkyl group having 1 to 6 carbon atoms, methyl group, ethyl group Propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, 2-methylbutyl group, 1-methylpentyl group, neopentyl group, 1-ethylpropyl group, hexyl group, 3 Specific examples include a 1,3-dimethylbutyl group and the like.
As a C1-C6 alkyl group, a C1-C3 alkyl group is more preferable.

In the general formula (II), the “halogenated alkyl group having 1 to 6 carbon atoms” is a linear or branched halogenated alkyl group having 1 to 6 carbon atoms, such as a fluoromethyl group and a difluoromethyl group. Group, trifluoromethyl group, 2,2,2-trifluoroethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, perfluoroisopropyl group, perfluoro Specific examples include isobutyl, chloromethyl, chloroethyl, chloropropyl, bromomethyl, bromoethyl, bromopropyl, methyl iodide, ethyl iodide, propyl iodide and the like.
As the halogenated alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms is more preferable.

In the general formula (II), the “C1-C6 alkoxy group” is a linear or branched alkoxy group having 1 to 6 carbon atoms, and includes a methoxy group, an ethoxy group, a propoxy group, Isopropoxy group, butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, 2-methylbutoxy group, 1-methylpentyloxy group, neopentyloxy group, 1-ethylpropoxy group, hexyloxy Specific examples include a group and a 3,3-dimethylbutoxy group.
As a C1-C6 alkoxy group, a C1-C3 alkoxy group is more preferable.

In a preferred embodiment of the general formula (I), R ¹ is a group represented by the general formula (II) (in the general formula (II), R ³ is a fluorine atom, an alkyl group having 1 to 3 carbon atoms, carbon A halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by formula (IV).) Or a group represented by formula (III), and , R ² is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a group represented by the general formula (II), or a group represented by the formula (III), or R ¹ and R ² are It is an embodiment that is a group that forms a benzene ring or a cyclohexyl ring together with the carbon atom to which R ¹ is bonded and the carbon atom to which R ² is bonded.

R ² in the general formula (I) is more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a group represented by the general formula (II) (in the general formula (II), R ³ is And a fluorine atom, an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by the formula (IV). Or a group represented by the formula (III), more preferably a hydrogen atom or a methyl group.

When R ¹ in the general formula (I) is a group represented by the general formula (II), R ³ in the general formula (II) is a halogen atom, having 1 to 6 carbon atoms as described above. An alkyl group, a halogenated alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a group represented by the formula (IV), R ³ is more preferably a fluorine atom or a carbon number of 1 Or an alkyl group having 1 to 3, a halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by the formula (IV), and more preferably a fluorine atom, a methyl group, An ethyl group, a trifluoromethyl group, a methoxy group, an ethoxy group, or a group represented by the formula (IV).
When R ² in the general formula (I) is a group represented by the general formula (II), a preferable range of R ^{3 in} the general formula (II) is as follows. ^This is the same as the preferred range of R ³ when ¹ is a group represented by the general formula (II).

As a preferable combination of R ¹ and R ² in the general formula (I), R ¹ is a group represented by the general formula (II) (in the general formula (II), R ³ is a fluorine atom, a carbon number An alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by the formula (IV)), or the formula (III R ² is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a group represented by the general formula (II) (in the general formula (II), R ³ is a fluorine atom) Or an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by the formula (IV)). A combination which is a group represented by the formula (III).
As a more preferable combination of R ¹ and R ² in the general formula (I), R ¹ is a group represented by the general formula (II) (in the general formula (II), R ³ is a fluorine atom, a methyl group) , An ethyl group, a trifluoromethyl group, a methoxy group, an ethoxy group, or a group represented by the formula (IV)) or a group represented by the formula (III), and R ² is hydrogen. A combination that is an atom or a methyl group.

Examples of the cyclic sulfate compound represented by the general formula (I) include catechol sulfate, 1,2-cyclohexyl sulfate, and compounds represented by the following exemplified compounds 1 to 30. However, the cyclic sulfate compound represented by the general formula (I) is not limited thereto.
In the structures of the following exemplary compounds, “Me” represents a methyl group, “Et” represents an ethyl group, “Pr” represents a propyl group, “iPr” represents an isopropyl group, “Bu” represents a butyl group, and “tBu” Is a tertiary butyl group, “Pent” is a pentyl group, “Hex” is a hexyl group, “OMe” is a methoxy group, “OEt” is an ethoxy group, “OPr” is a propoxy group, “OBu” Represents a butoxy group, “OPent” represents a pentyloxy group, and “OHex” represents a hexyloxy group. Further, the “wavy line” in R ^{1 to} R ³ represents a coupling position.
In some cases, stereoisomers derived from the substituents at the 4-position and 5-position of the 2,2-dioxo-1,3,2-dioxathiolane ring may be formed, and both are compounds included in the present invention.
Further, among the sulfate ester compounds represented by the general formula (I), when two or more asymmetric carbons are present in the molecule, stereoisomers (diastereomers) exist, but are not particularly described. To the extent it is a mixture of the corresponding diastereomers.

  Among the cyclic sulfate compounds represented by the general formula (I), when two or more asymmetric carbons exist in the molecule, stereoisomers (diastereomers) exist, respectively, unless otherwise specified. , A mixture of the corresponding diastereomers.

  Although there is no restriction | limiting in particular in the method to synthesize | combine the cyclic sulfate ester compound represented by general formula (I), For example, it can synthesize | combine by the synthesis method of Paragraphs 0062-0068 of international publication 2012/053644. .

  Other additives include vinylene carbonate, vinyl ethylene carbonate, 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, lithium monofluorophosphate, lithium difluorophosphate, difluorobis (Oxalato) lithium phosphate, tetrafluoro (oxalato) lithium phosphate, tris (oxalato) lithium phosphate, difluoro (oxalato) lithium borate, bisbisoxalatoborate, 1,3-propane sultone, 1,3-propene Particularly preferred is at least one selected from the group consisting of sultone and a cyclic sulfate compound (particularly preferably, a cyclic sulfate compound represented by formula (I)).

When the nonaqueous electrolytic solution of the present invention contains the other additive, the other additive contained may be only one kind or two or more kinds.
When the non-aqueous electrolyte of the present invention contains the above-mentioned other additives, the content (the total content in the case of two or more) is not particularly limited, but the effects of the present invention described above are more effective. From the viewpoint of being effectively exhibited, the content is preferably 0.001% by mass to 10% by mass and more preferably 0.05% by mass to 5% by mass with respect to the total amount of the nonaqueous electrolytic solution. More preferably, it is in the range of 0.1% by mass to 4% by mass, more preferably in the range of 0.1% by mass to 2% by mass, and in the range of 0.1% by mass to 1% by mass. It is particularly preferred.

Next, other components of the nonaqueous electrolytic solution will be described.
The nonaqueous electrolytic solution generally contains an electrolyte and a nonaqueous solvent.

<Non-aqueous solvent>
Various known solvents can be appropriately selected as the non-aqueous solvent, but at least one selected from a cyclic aprotic solvent and a chain aprotic solvent is preferably used.

  In order to improve the safety of the battery, when aiming to improve the flash point of the solvent, it is preferable to use a cyclic aprotic solvent as the non-aqueous solvent.

(Cyclic aprotic solvent)
As the cyclic aprotic solvent, cyclic carbonate, cyclic carboxylic acid ester, cyclic sulfone, and cyclic ether can be used.

The cyclic aprotic solvent may be used alone or in combination of two or more.
The mixing ratio of the cyclic aprotic solvent in the non-aqueous solvent is 10% by mass to 100% by mass, more preferably 20% by mass to 90% by mass, and particularly preferably 30% by mass to 80% by mass. By setting it as such a ratio, the electroconductivity of the electrolyte solution relating to the charge / discharge characteristics of the battery can be increased.

  Specific examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and the like. Of these, ethylene carbonate and propylene carbonate having a high dielectric constant are preferably used. In the case of a battery using graphite as the negative electrode active material, ethylene carbonate is more preferable. Moreover, you may use these cyclic carbonates in mixture of 2 or more types.

  Specific examples of the cyclic carboxylic acid ester include γ-butyrolactone, δ-valerolactone, alkyl substitution products such as methyl γ-butyrolactone, ethyl γ-butyrolactone, and ethyl δ-valerolactone.

  The cyclic carboxylic acid ester has a low vapor pressure, a low viscosity, a high dielectric constant, and can lower the viscosity of the electrolytic solution without lowering the degree of dissociation between the flash point of the electrolytic solution and the electrolyte. For this reason, since it has the feature that the conductivity of the electrolytic solution, which is an index related to the discharge characteristics of the battery, can be increased without increasing the flammability of the electrolytic solution, when aiming to improve the flash point of the solvent, It is preferable to use a cyclic carboxylic acid ester as the cyclic aprotic solvent. Of the cyclic carboxylic acid esters, γ-butyrolactone is most preferred.

  The cyclic carboxylic acid ester is preferably used by mixing with another cyclic aprotic solvent. For example, a mixture of a cyclic carboxylic acid ester and a cyclic carbonate and / or a chain carbonate can be mentioned.

Examples of the cyclic sulfone include sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, dipropyl sulfone, methylethyl sulfone, methylpropyl sulfone and the like.
An example of a cyclic ether is dioxolane.

(Chain aprotic solvent)
As the chain aprotic solvent, a chain carbonate, a chain carboxylic acid ester, a chain ether, a chain phosphate, or the like can be used.

  The mixing ratio of the chain aprotic solvent in the non-aqueous solvent is 10% by mass to 100% by mass, more preferably 20% by mass to 90% by mass, and particularly preferably 30% by mass to 80% by mass.

  Specific examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, dipropyl carbonate, methyl butyl carbonate, ethyl butyl carbonate, dibutyl carbonate, methyl pentyl carbonate, Examples include ethyl pentyl carbonate, dipentyl carbonate, methyl heptyl carbonate, ethyl heptyl carbonate, diheptyl carbonate, methyl hexyl carbonate, ethyl hexyl carbonate, dihexyl carbonate, methyl octyl carbonate, ethyl octyl carbonate, dioctyl carbonate, and methyltrifluoroethyl carbonate. These chain carbonates may be used as a mixture of two or more.

Specific examples of the chain carboxylic acid ester include methyl pivalate.
Specific examples of the chain ether include dimethoxyethane.
Specific examples of the chain phosphate ester include trimethyl phosphate.

(Solvent combination)
The nonaqueous solvent used in the nonaqueous electrolytic solution of the present invention may be used alone or in combination. Further, only one or more types of cyclic aprotic solvents may be used, or only one or more types of chain aprotic solvents may be used, or cyclic aprotic solvents and chain proticity may be used. You may mix and use a solvent. When the load characteristics and low temperature characteristics of the battery are particularly intended to be improved, it is preferable to use a combination of a cyclic aprotic solvent and a chain aprotic solvent as the nonaqueous solvent.

  Furthermore, in view of the electrochemical stability of the electrolytic solution, it is most preferable to apply a cyclic carbonate to the cyclic aprotic solvent and a chain carbonate to the chain aprotic solvent. Further, the conductivity of the electrolytic solution related to the charge / discharge characteristics of the battery can be increased by a combination of the cyclic carboxylic acid ester and the cyclic carbonate and / or the chain carbonate.

  As a combination of cyclic carbonate and chain carbonate, specifically, ethylene carbonate and dimethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, propylene carbonate and methyl ethyl carbonate, propylene carbonate and Diethyl carbonate, ethylene carbonate and propylene carbonate and methyl ethyl carbonate, ethylene carbonate and propylene carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and methyl ethyl carbonate Diethyl carbonate, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate and methyl ethyl carbonate And diethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate.

  The mixing ratio of the cyclic carbonate and the chain carbonate is expressed by mass ratio, and the cyclic carbonate: chain carbonate is 5:95 to 80:20, more preferably 10:90 to 70:30, and particularly preferably 15:85. ~ 55: 45. By setting it as such a ratio, since the raise of the viscosity of electrolyte solution can be suppressed and the dissociation degree of electrolyte can be raised, the conductivity of the electrolyte solution in connection with the charge / discharge characteristic of a battery can be raised. In addition, the solubility of the electrolyte can be further increased. Therefore, since it can be set as the electrolyte solution excellent in the electrical conductivity in normal temperature or low temperature, the load characteristic of the battery from normal temperature to low temperature can be improved.

  Specific examples of combinations of cyclic carboxylic acid esters and cyclic carbonates and / or chain carbonates include γ-butyrolactone and ethylene carbonate, γ-butyrolactone and ethylene carbonate and dimethyl carbonate, and γ-butyrolactone and ethylene carbonate and methylethyl. Carbonate, γ-butyrolactone and ethylene carbonate and diethyl carbonate, γ-butyrolactone and propylene carbonate, γ-butyrolactone and propylene carbonate and dimethyl carbonate, γ-butyrolactone and propylene carbonate and methyl ethyl carbonate, γ-butyrolactone and propylene carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, γ-butyrolactone, Tylene carbonate and propylene carbonate and dimethyl carbonate, γ-butyrolactone and ethylene carbonate, propylene carbonate and methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate And professional Ren carbonate, dimethyl carbonate and methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate Propylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and sulfolane, γ-butyrolactone and ethylene carbonate and sulfolane, γ-butyrolactone and propylene carbonate and sulfolane, γ-butyrolactone, ethylene carbonate, propylene carbonate and sulfolane, γ -Butyrolactone and sul Such as orchids and dimethyl carbonate.

(Other solvents)
Examples of the non-aqueous solvent include other solvents other than those described above.
Specific examples of other solvents include amides such as dimethylformamide, chain carbamates such as methyl-N, N-dimethylcarbamate, cyclic amides such as N-methylpyrrolidone, N, N-dimethylimidazolidinone, and the like. Examples thereof include boron compounds such as cyclic urea, trimethyl borate, triethyl borate, tributyl borate, trioctyl borate, trimethylsilyl borate, and polyethylene glycol derivatives represented by the following general formula.
HO (CH ₂ CH ₂ O) _a H
HO [CH ₂ CH (CH ₃ ) O] _b H
CH ₃ O (CH ₂ CH ₂ O) _c H
CH ₃ O [CH ₂ CH (CH ₃ ) O] _d H
CH ₃ O (CH ₂ CH ₂ O) _e CH ₃
CH ₃ O [CH ₂ CH (CH ₃ ) O] _f CH _{3
C 9 H 19 PhO (CH 2} CH 2 O) g [CH (CH 3) O] h CH 3
(Ph is a phenyl group)
CH ₃ O [CH ₂ CH (CH ₃ ) O] _i CO [OCH (CH ₃ ) CH ₂ ] _j OCH ₃
In the above formula, a to f are integers of 5 to 250, g to j are integers of 2 to 249, 5 ≦ g + h ≦ 250, and 5 ≦ i + j ≦ 250.

<Electrolyte>
The nonaqueous electrolytic solution of the present invention can contain various known electrolytes. Any electrolyte can be used as long as it is normally used as an electrolyte for a non-aqueous electrolyte.

Specific examples of the electrolyte include alkali metal salts excluding the above-mentioned lithium fluorophosphate. Furthermore, specific examples of the electrolyte include (C ₂ H ₅ ) ₄ NPF ₆ , (C ₂ H ₅ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NAsF ₆ , ( C ₂ H ₅ ) ₄ N ₂ SiF ₆ , (C ₂ H ₅ ) ₄ NOSO ₂ C _k F _{(2k + 1)} (k = 1 to 8), (C ₂ H ₅ ) ₄ NPF _n [C _k F _{( 2k + 1)} ] _(6-n) (integers of n = 1-5, k = 1-8), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C Lithium salts such as _k F _{(2k + 1)} (k = 1 to 8), LiPF _n [C _k F _{(2k + 1)} ] _(6-n) (n = 1 to 5, k = 1 to 8) Can be mentioned. Moreover, the lithium salt represented by the following general formula can also be used.

_{^{LiC (SO 2 R 27) (}} SO 2 R 28) (SO 2 R 29), LiN (SO 2 OR 30) (SO 2 OR 31), LiN (SO 2 R 32) (SO 2 R 33) ( where R ^{27 to} R ³³ may be the same as or different from each other, and are a C 1-8 perfluoroalkyl group). These electrolytes may be used alone or in combination of two or more.

Of these, lithium salts are particularly desirable, and LiPF ₆ , LiBF ₄ , LiOSO ₂ C _k F _{(2k + 1)} (k = 1 to 8), LiClO ₄ , LiAsF ₆ , LiNSO ₂ [C _k F _{( 2k + 1)] 2 (k} = 1~8 _{integer), LiPF n [C k F} (2k + 1)] (6-n) (n = 1~5, k = 1~8 integer) are preferred.

  The electrolyte is usually preferably contained in the nonaqueous electrolytic solution at a concentration of 0.1 mol / L to 3 mol / L, preferably 0.5 mol / L to 2 mol / L.

In the nonaqueous electrolytic solution, when a cyclic carboxylic acid ester such as γ-butyrolactone is used in combination as the nonaqueous solvent, it is particularly desirable to contain LiPF ₆ . Since LiPF ₆ has a high degree of dissociation, the conductivity of the electrolytic solution can be increased, and the reductive decomposition reaction of the electrolytic solution on the negative electrode can be suppressed. LiPF ₆ may be used alone, or LiPF ₆ and other electrolytes may be used. Any other electrolyte can be used as long as it is normally used as an electrolyte for a non-aqueous electrolyte, but lithium salts other than LiPF ₆ are preferred among the specific examples of the lithium salts described above. (Excluding the above-mentioned lithium fluorophosphate).

Specific examples include LiPF ₆ and LiBF ₄ , LiPF ₆ and LiN [SO ₂ C _k F _{(2k + 1)} ] ₂ (k = 1 to 8), LiPF ₆ , LiBF ₄ and LiN [SO ₂ C _k F _{( 2k + 1)} ] (k = 1 to 8).

The ratio of LiPF _{6 in} the lithium salt is 1% by mass to 100% by mass, preferably 10% by mass to 100% by mass, and more preferably 50% by mass to 100% by mass. Such an electrolyte is preferably contained in the nonaqueous electrolytic solution at a concentration of 0.1 mol / L to 3 mol / L, preferably 0.5 mol / L to 2 mol / L.

Moreover, the non-aqueous electrolyte of the present invention can also contain an overcharge inhibitor.
As the overcharge preventing agent, biphenyl, alkylbiphenyl, terphenyl (o-, m-, p-isomer), partially hydrogenated terphenyl (o-, m-, p-isomer) (for example, 1, 2) -Dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), cyclohexylbenzene, t-butylbenzene, 1,3-di-t-butylbenzene, t-amylbenzene, diphenylether, dibenzofuran Aromatic compounds such as fluorotoluene (o-, m-, p-isomer), difluorotoluene, trifluorotoluene, tetrafluorotoluene, pentafluorotoluene, fluorobenzene, difluorobenzene (o-, m-, p-isomer) ), 1-fluoro-4-t-butylbenzene, 2-fluoro Partially fluorinated products of aromatic compounds such as phenyl and fluorocyclohexylbenzene (for example, 1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene); 2,4-difluoro Examples thereof include fluorine-containing anisole compounds such as anisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole.
Among these, the aromatic compounds exemplified above are preferable.
Moreover, an overcharge inhibitor may be used individually by 1 type, or may use 2 or more types together.
When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge prevention property and a high temperature storage property. From the standpoint of balance.

When the non-aqueous electrolyte of the present invention contains an overcharge inhibitor, the content of the overcharge inhibitor is not particularly limited, but for example 0.1% by mass or more, preferably 0.2% by mass or more, and Preferably it is 0.3 mass% or more, Most preferably, it is 0.5 mass% or more.
Moreover, content of the said overcharge inhibitor is 10 mass% or less, for example, Preferably it is 5 mass% or less, More preferably, it is 3 mass% or less, More preferably, it is 2 mass% or less.

The nonaqueous electrolytic solution of the present invention may contain at least one compound other than the above-mentioned compounds as an additive as long as the object of the present invention is not hindered.
Specific examples of other compounds include sulfate esters such as dimethyl sulfate, diethyl sulfate, ethylene sulfate, propylene sulfate, butene sulfate, pentene sulfate and vinylene sulfate; and sulfur compounds such as sulfolane, 3-sulfolene and divinyl sulfone, Can be mentioned.
These compounds may be used alone or in combination of two or more.
Of these, ethylene sulfate, propylene sulfate, butene sulfate, and pentene sulfate are preferred.

  The non-aqueous electrolyte of the present invention is not only suitable as a non-aqueous electrolyte for a lithium secondary battery, but also a non-aqueous electrolyte for a primary battery, a non-aqueous electrolyte for an electrochemical capacitor, and an electric double layer capacitor. It can also be used as an electrolytic solution for aluminum electrolytic capacitors.

[Lithium secondary battery]
The lithium secondary battery of the present invention includes a positive electrode, a negative electrode including a negative electrode current collector containing Cu element, and the above-described nonaqueous electrolytic solution of the present invention.
In other words, the lithium secondary battery of the present invention includes a positive electrode, a negative electrode including a negative electrode current collector containing Cu element, and a non-aqueous electrolyte, and the non-aqueous electrolyte is lithium monofluorophosphate. And a lithium secondary battery containing at least one of lithium difluorophosphate and a Cu element having a content of 0.001 mass ppm to less than 5 mass ppm with respect to the total amount of the non-aqueous electrolyte. The non-aqueous electrolyte in the lithium secondary battery of the present invention is the above-described non-aqueous electrolyte of the present invention. The preferred embodiment of the non-aqueous electrolyte in the lithium secondary battery of the present invention is the same as the preferred embodiment of the non-aqueous electrolyte of the present invention described above.

(Negative electrode)
The negative electrode in the present invention contains a negative electrode active material.
Negative electrode active materials include metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped / undoped with lithium ions, and transition metals that can be doped / undoped with lithium ions At least one selected from the group consisting of nitrides and carbon materials capable of doping and undoping lithium ions (may be used alone or a mixture containing two or more of these may be used) Is used.
Examples of metals or alloys that can be alloyed with lithium (or lithium ions) include silicon, silicon alloys, tin, and tin alloys. Further, lithium titanate may be used.
Among these, carbon materials that can be doped / undoped with lithium ions are preferable. Examples of such carbon materials include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), amorphous carbon materials, and the like. The form of the carbon material may be any of a fibrous form, a spherical form, a potato form, and a flake form.

Specific examples of the amorphous carbon material include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500 ° C. or less, and mesophase pitch carbon fiber (MCF).
Examples of the graphite material include natural graphite and artificial graphite. As artificial graphite, graphitized MCMB, graphitized MCF, and the like are used. Further, as the graphite material, a material containing boron can be used. As the graphite material, those coated with a metal such as gold, platinum, silver, copper and tin, those coated with amorphous carbon, and those obtained by mixing amorphous carbon and graphite can be used.

These carbon materials may be used alone or in combination of two or more.
As the carbon material, a carbon material having a (002) plane distance d (002) of 0.340 nm or less as measured by X-ray analysis is particularly preferable. Further, as the carbon material, graphite having a true density of 1.70 g / cm ³ or more or a highly crystalline carbon material having properties close thereto is also preferable. When the carbon material as described above is used, the energy density of the battery can be further increased.

The negative electrode in the present invention includes a negative electrode current collector containing a Cu element.
The negative electrode current collector may contain an element other than the Cu element.
The negative electrode current collector may contain, for example, a metal material such as nickel, stainless steel, or nickel-plated steel.

(Positive electrode)
As the positive electrode active material in the positive electrode, transition metal oxides or transition metal sulfides such as MoS ₂ , TiS ₂ , MnO ₂ , V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _X Co _(1-X) O ₂ [0 <X <1], Li _{1 + α} Me _1-α O ₂ having an α-NaFeO ₂ type crystal structure (Me is a transition metal element containing Mn, Ni and Co, 1.0 ≦ (1 + α) / (1−α) ≦ 1.6), LiNi _x Co _y Mn _z O ₂ [x + y + z = 1, 0 <x <1, 0 <y <1, 0 <z <1] (for example, LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O _2, etc.), LiFePO ₄ , LiMnPO ₄ and other complex oxides composed of lithium and transition metals, Polyaniline, Li thiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazoles, conductive polymer materials such as polyaniline complex thereof. Among these, a composite oxide composed of lithium and a transition metal is particularly preferable. When the negative electrode is lithium metal or a lithium alloy, a carbon material can be used as the positive electrode. In addition, a mixture of a composite oxide of lithium and a transition metal and a carbon material can be used as the positive electrode.
A positive electrode active material may be used by 1 type, and may mix and use 2 or more types. When the positive electrode active material has insufficient conductivity, it can be used together with a conductive auxiliary agent to constitute a positive electrode. Examples of the conductive assistant include carbon materials such as carbon black, amorphous whiskers, and graphite.

There is no restriction | limiting in particular in the material of the positive electrode electrical power collector in a positive electrode, A well-known thing can be used arbitrarily.
Specific examples include metal materials such as aluminum, stainless steel, nickel, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper;

(Separator)
The lithium secondary battery of the present invention preferably includes a separator between the negative electrode and the positive electrode.
The separator is a film that electrically insulates the positive electrode and the negative electrode and transmits lithium ions, and examples thereof include a porous film and a polymer electrolyte.
A microporous polymer film is preferably used as the porous film, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, and polyester.
In particular, porous polyolefin is preferable. Specifically, a porous polyethylene film, a porous polypropylene film, or a multilayer film of a porous polyethylene film and a polypropylene film can be exemplified. On the porous polyolefin film, other resin excellent in thermal stability may be coated.
Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer swollen with an electrolytic solution, and the like.
The nonaqueous electrolytic solution of the present invention may be used for the purpose of obtaining a polymer electrolyte by swelling a polymer.

(Battery configuration)
The lithium secondary battery of the present invention can take various known shapes, and can be formed into a cylindrical shape, a coin shape, a square shape, a laminate shape, a film shape, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be changed according to the purpose.

As an example of the lithium secondary battery (non-aqueous electrolyte secondary battery) of the present invention, a laminate type battery can be mentioned.
FIG. 1 is a schematic perspective view showing an example of a laminated battery as an example of the lithium secondary battery of the present invention, and FIG. 2 shows the thickness of the laminated electrode body accommodated in the laminated battery shown in FIG. It is a schematic sectional drawing of a direction.
The laminate type battery shown in FIG. 1 contains a non-aqueous electrolyte (not shown in FIG. 1) and a laminated electrode body (not shown in FIG. 1) inside, and the periphery is sealed. The laminate outer package 1 is sealed inside. As the laminate exterior body 1, for example, an aluminum laminate exterior body is used.
As shown in FIG. 2, the laminated electrode body accommodated in the laminate outer package 1 includes a laminated body in which positive plates 5 and negative plates 6 are alternately laminated with separators 7 interposed therebetween. And a separator 8 surrounding the periphery. The positive electrode plate 5, the negative electrode plate 6, the separator 7, and the separator 8 are impregnated with the non-aqueous electrolyte of the present invention.
The plurality of positive electrode plates 5 in the laminated electrode body are all electrically connected to the positive electrode terminal 2 via a positive electrode tab (not shown), and a part of the positive electrode terminal 2 is part of the laminate outer package 1. It protrudes outward from the peripheral end (FIG. 1). The portion where the positive electrode terminal 2 protrudes at the peripheral end of the laminate outer package 1 is sealed with an insulating seal 4.
Similarly, each of the plurality of negative electrode plates 6 in the laminated electrode body is electrically connected to the negative electrode terminal 3 through a negative electrode tab (not shown), and a part of the negative electrode terminal 3 is part of the laminate exterior. It protrudes outward from the peripheral edge of the body 1 (FIG. 1). The portion where the negative electrode terminal 3 protrudes at the peripheral end of the laminate outer package 1 is sealed with an insulating seal 4.
In the laminate type battery according to the above example, the number of the positive plates 5 is 5 and the number of the negative plates 6 is 6, and the positive plates 5 and the negative plates 6 are separated from each other through the separators 7. All the outer layers are laminated in an arrangement to be the negative electrode plate 6. However, it is needless to say that the number of positive plates, the number of negative plates, and the arrangement in the laminated battery are not limited to this example, and various changes may be made.

The lithium secondary battery of the present invention is obtained by charging / discharging a lithium secondary battery (lithium secondary battery before charge / discharge) including a negative electrode, a positive electrode, and the non-aqueous electrolyte of the present invention. Lithium secondary batteries may be used.
That is, the lithium secondary battery of the present invention is prepared by first preparing a lithium secondary battery before charging / discharging including the negative electrode, the positive electrode, and the non-aqueous electrolyte of the present invention, and then before charging / discharging. It may be a lithium secondary battery (charged / discharged lithium secondary battery) produced by charging / discharging the lithium secondary battery one or more times.

  The use of the lithium secondary battery of the present invention is not particularly limited, and can be used for various known uses. For example, notebook computers, mobile computers, mobile phones, headphone stereos, video movies, LCD TVs, handy cleaners, electronic notebooks, calculators, radios, backup power applications, motors, automobiles, electric cars, motorcycles, electric bikes, bicycles, electric motors Bicycles, lighting fixtures, game machines, watches, electric tools, cameras, etc. can be widely used regardless of small portable devices or large devices.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.
In the following examples, “addition amount” represents the content in the finally obtained non-aqueous electrolyte (that is, the amount relative to the total amount of the finally obtained non-aqueous electrolyte).

[Example 1]
In the following procedure, a laminate type battery having the same configuration as the laminate type battery shown in FIG. 1 was produced as a lithium secondary battery (hereinafter also simply referred to as “battery”).

<Production of negative electrode>
98 parts by mass of artificial graphite, 1 part by mass of carboxymethylcellulose and 1 part by mass of SBR latex were kneaded with an aqueous solvent to prepare a paste-like negative electrode mixture slurry.
Next, the negative electrode mixture slurry is applied to both sides of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 12 μm, dried, and then compressed by a roll press to form a sheet formed of a negative electrode current collector and a negative electrode active material layer. Negative electrode (negative electrode plate) was obtained. The coating density of the negative electrode active material layer at this time was 12 mg / cm ² , and the packing density was 1.45 g / ml.
Six negative electrode plates as described above were produced, and a negative electrode tab was attached to each of the obtained six negative electrode plates.

<Preparation of positive electrode>
A paste-like positive electrode mixture slurry was prepared by kneading 98 parts by mass of LiCoO ₂ , 1 part by mass of acetylene black and 1 part by mass of polyvinylidene fluoride using N-methylpyrrolidinone as a solvent.
Next, this positive electrode mixture slurry was applied to both sides of a positive electrode current collector of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and then compressed by a roll press to form a sheet-like material comprising a positive electrode current collector and a positive electrode active material. A positive electrode (positive electrode plate) was obtained. The coating density of the positive electrode active material layer at this time was 25 mg / cm ² , and the packing density was 3.6 g / ml.
Five positive electrode plates as described above were produced, and a positive electrode tab was attached to each of the obtained five positive electrode plates.

<Preparation of non-aqueous electrolyte>
As a non-aqueous solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) were mixed at a ratio of 30:35:35 (mass ratio), respectively, to obtain a mixed solvent.
In the obtained mixed solvent, LiPF ₆ as an electrolyte was dissolved so that the electrolyte concentration in the finally obtained nonaqueous electrolytic solution was 1 mol / liter.
To the solution obtained above, lithium difluorophosphate (addition amount 0.5 mass%) is added as lithium fluorophosphate, and bis (acetylacetonato) copper (II) (addition amount) as a Cu compound. 3.0 mass ppm (equivalent to 0.7 mass ppm as the amount of Cu element added) was added to obtain a non-aqueous electrolyte.

<Production of laminated electrode body>
The positive electrode tab and the negative electrode tab on the same side of the six negative electrode plates attached with the negative electrode tab and the five positive electrode plates attached with the positive electrode tab through a microporous polyethylene film (thickness 20 μm; separator). It was laminated in the direction in which it is arranged. At this time, the positive electrode plate and the negative electrode plate were alternately laminated so that the outermost layers on both sides were both negative electrode plates. An insulating tape (separator) was wound around the obtained laminated body to maintain the shape, thereby obtaining a laminated electrode body.

<Attachment of positive terminal and negative terminal>
Six negative electrode tabs extending from each of the six negative electrode plates were attached to one negative electrode terminal made of copper foil by ultrasonic welding.
Five positive electrode tabs extending from each of the five positive electrode plates were attached to one positive electrode terminal made of aluminum foil by ultrasonic welding.

<Production of laminated laminated battery>
The laminated electrode body to which the positive electrode terminal and the negative electrode terminal were attached was accommodated in an aluminum laminate outer body, and one side of the laminate outer body to which the positive electrode terminal and the negative electrode terminal were attached was heat-sealed. At this time, a part of the positive electrode terminal and a part of the negative electrode terminal protruded from the peripheral end of the laminate outer package. The portions where the positive electrode terminal and the negative electrode terminal protrude were each sealed with an insulating seal.
Next, two of the remaining three sides of the laminate outer package were heat-sealed.
Next, the nonaqueous electrolyte solution is injected into the laminate exterior body from one side of the laminate exterior body that is not thermally fused, and the positive electrode plate, each negative electrode plate, and each separator are impregnated with the nonaqueous electrolyte solution. I let you. Next, the laminate outer package was sealed by heat-sealing one side that was not heat-sealed. Thus, a laminate type battery was obtained.
Each measurement was implemented about the obtained lamination type battery (battery for a test).

[Evaluation method]
<Measurement of Cu element content in non-aqueous electrolyte in battery>
The laminated battery was charged at a constant voltage of 4.2 V, and then the laminated battery after charging was cooled to −20 ° C. in a constant temperature bath and discharged at −20 ° C. with a constant current of 50 mA.
Sampling the non-aqueous electrolyte in the laminated battery after discharge, wetting it with concentrated nitric acid in a PTFE container, measuring the volume, and measuring the Cu element content by inductively coupled plasma mass spectrometry did. Based on the measurement results, the content of Cu element in the non-aqueous electrolyte in the laminated battery after discharge was determined.
The obtained results are shown in Table 1.

<Battery resistance>
The battery resistance (initial battery resistance) of the laminate type battery was evaluated. Details are shown below.
The laminate type battery was charged at a constant voltage of 4.2 V, then the charged laminate type battery was cooled to −20 ° C. in a constant temperature bath, and discharged at −20 ° C. with a 50 mA constant current. The direct current resistance [Ω] (−20 ° C.) of the laminate type battery was measured by measuring the potential drop for 10 seconds, and the obtained value was defined as the resistance value [Ω] (−20 ° C.).
The resistance value [Ω] (−20 ° C.) was measured in the same manner for a laminate type battery of Comparative Example 1 described later.
From these results, according to the following formula, the resistance value (relative value;%) in Example 1 when the resistance value [Ω] (−20 ° C.) in Comparative Example 1 is set to 100% is expressed as “battery resistance [ %] ”.
The obtained results are shown in Table 1.

Battery resistance (relative value;%)
= (Resistance value in Example 1 [Ω] (−20 ° C.) / Resistance value in Comparative Example 1 [Ω] (−20 ° C.)) × 100

[Example 2]
During the preparation of the non-aqueous electrolyte, the same operation as in Example 1 was performed except that the exemplified compound 22 (addition amount 0.5% by mass) was further added as another additive.
Here, the exemplified compound 22 is a specific example of the cyclic sulfate compound represented by the general formula (I).
The results are shown in Table 1.

[Comparative Example 1]
The same operation as in Example 1 was performed except that lithium difluorophosphate and bis (acetylacetonato) copper (II) were not added during the preparation of the nonaqueous electrolytic solution.
The results are shown in Table 1.

  As shown in Table 1, a nonaqueous electrolyte containing lithium fluorophosphate was used, and the content of Cu element in the nonaqueous electrolyte in the battery was 0.001 mass ppm or more and less than 5 mass ppm. In Examples 2 and 2, the battery resistance was reduced in spite of the example using the non-aqueous electrolyte containing lithium fluorophosphate.

DESCRIPTION OF SYMBOLS 1 Laminate exterior body 2 Positive electrode terminal 3 Negative electrode terminal 4 Insulation seal 5 Positive electrode plate 6 Negative electrode plate 7, 8 Separator

Claims (6)

  A battery non-aqueous electrolyte containing at least one of lithium monofluorophosphate and lithium difluorophosphate and having a copper element content of 0.001 mass ppm or more and less than 5 mass ppm relative to the total amount of the battery non-aqueous electrolyte.   The nonaqueous electrolytic solution for a battery according to claim 1, comprising lithium difluorophosphate.   The total content of lithium monofluorophosphate and lithium difluorophosphate is 0.001% by mass to 5% by mass with respect to the total amount of the nonaqueous electrolyte solution for the battery. Water electrolyte. Furthermore, the non-aqueous electrolyte for batteries of any one of Claims 1-3 containing the cyclic sulfate ester compound represented by general formula (I).

[In General Formula (I), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a group represented by General Formula (II), or Formula (III). or a group represented by or, R ¹ and R ² together, with the carbon atom to the carbon atom and R ² wherein R ¹ is bonded are bonded, represents a group forming a benzene ring or a cyclohexyl ring.
In general formula (II), R ³ is a halogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a formula (IV). Represents a group. The wavy line in general formula (II), formula (III), and formula (IV) represents a bonding position.
When the cyclic sulfate ester compound represented by the general formula (I) includes two groups represented by the general formula (II), the two groups represented by the general formula (II) are the same. Or they may be different from each other. ] A positive electrode;
Negative electrode current collector containing copper element, and as a negative electrode active material, metal lithium, lithium-containing alloy, metal or alloy capable of alloying with lithium, oxide capable of doping and dedoping of lithium ions, A negative electrode comprising at least one substance selected from the group consisting of transition metal nitrides capable of doping and dedoping lithium ions, and carbon materials capable of doping and undoping lithium ions;
The nonaqueous electrolytic solution for a battery according to any one of claims 1 to 4,
Including lithium secondary battery.   A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to claim 5.