JP2019179613A - Electrolyte solution for batteries and lithium secondary battery - Google Patents

Abstract

To provide an electrolyte solution for batteries, which is superior in capacity-keeping rate during a charge/discharge cycle.SOLUTION: An electrolyte solution for batteries comprises: an electrolyte; a nonaqueous solvent; additive agent A which is a compound represented by the formula (A); and an additive agent B which is a compound represented by the formula (B); and an additive agent C which is a compound represented by the formula (C), wherein Rrepresents a fluoridated hydrocarbon group with C1-6, Rrepresents a hydrocarbon group with C1-6, a fluoridated hydrocarbon group with C1-6, Ris a F atom, or a fluoridated hydrocarbon group with C1-6, Rto Rrepresent an H atom, an F atom, a hydrocarbon group with C1-6, or a fluoridated hydrocarbon group with C1-6, and Rto Rrepresent an H atom, an F atom, a hydrocarbon group with C1-3, or a fluoridated hydrocarbon group with C1-3.SELECTED DRAWING: None

Description

  The present disclosure relates to a non-aqueous electrolyte for a battery and a lithium secondary battery.

  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, Patent Document 1 includes [A] a fluorinated carbonate, a cyclic carbonate, and a chain carbonate as a non-aqueous electrolyte having excellent safety, high conductivity, and low viscosity, and (i) The cyclic carbonate content is 2 to 63 mol%, (ii) the chain carbonate content is 2 to 63 mol%, and (iii) the fluorinated carbonate content is 60 to 96 mol% (however ( i) to (iii) do not exceed 100 mol%), and the fluorinated carbonate is a compound having a specific chemical structure, and [B] an electrolyte. Non-aqueous electrolytes are disclosed.

  Patent Document 2 discloses a charge / discharge cycle at a high temperature in an electrochemical element (particularly a high-voltage lithium secondary battery) in which a positive electrode potential in a fully charged state is 4.35 V or more with respect to a metal lithium potential. As a non-aqueous electrolyte with little battery capacity reduction and low gas generation during high-temperature storage, a non-aqueous solvent containing a cyclic carbonate and a chain carbonate as main components and an electrolyte solute, 60 wt. % Or more is 4-fluoroethylene carbonate, and 25% by weight or more of the chain carbonate is methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate and di-2, At least one fluorinated chain carbonate selected from the group consisting of 2,2-trifluoroethyl carbonate Non-aqueous electrolysis for electrochemical devices in which the positive electrode potential in a fully charged state in which the weight ratio of cyclic carbonate to chain carbonate is 3:97 to 35:65 is 4.35 V or more based on the potential of metallic lithium A liquid is disclosed.

  Patent Document 3 discloses a non-aqueous solution in which the decomposition reaction of the solvent on the negative electrode is suppressed, and the battery capacity reduction, gas generation, and battery load characteristic deterioration are suppressed even when stored at high temperatures. A non-aqueous electrolyte containing a specific unsaturated sultone, a non-aqueous solvent and an electrolyte as the electrolytic solution, and the amount of the specific unsaturated sultone added is 0.001 to 10 mass with respect to the whole non-aqueous electrolyte. % Non-aqueous electrolyte is disclosed.

Japanese Patent No. 4392726 Japanese Patent No. 4976715 Japanese Patent No. 4190162

However, there are cases where it is required to further improve the capacity retention rate during the charge / discharge cycle compared to conventional non-aqueous electrolytes for batteries and batteries.
Therefore, the subject of this indication is providing the non-aqueous electrolyte for batteries which is excellent in the capacity maintenance rate at the time of a charge / discharge cycle, and the lithium secondary battery using this non-aqueous electrolyte for batteries.

Means for solving the above problems include the following aspects.
<1> electrolyte,
A non-aqueous solvent;
Additive A which is a compound represented by the following formula (A);
Additive B which is a compound represented by the following formula (B);
A non-aqueous electrolyte for batteries containing

In formula (A), R ^a1 represents a fluorinated hydrocarbon group having 1 to 6 carbon atoms, and R ^a2 represents a hydrocarbon group having 1 to 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. To express.

In formula (B), R ^b1 represents a fluorine atom or a fluorinated hydrocarbon group having 1 to 6 carbon atoms, and R ^{b2 to} R ^b4 each independently represent a hydrogen atom, a fluorine atom, or a carbon number of 1 to Represents a hydrocarbon group having 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In formula (C), R ^{c1 to} R ^c4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms.

<2> The content of the additive A is 0.001% by mass to 10% by mass with respect to the total amount of the non-aqueous electrolyte for a battery,
The content of the additive B is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte. The content of the additive C is based on the total amount of the battery non-aqueous electrolyte. The nonaqueous electrolytic solution for batteries according to <1>, which is 0.001% by mass to 10% by mass.
<3> The nonaqueous electrolytic solution for batteries according to <1> or <2>, wherein the nonaqueous solvent includes a cyclic carbonate compound and a chain carbonate compound other than the compound represented by the formula (A). .
<4> The total proportion of the cyclic carbonate compound and the chain carbonate compound other than the compound represented by the formula (A) in the non-aqueous solvent is 80% by mass or more. Non-aqueous electrolyte for batteries.
<5> The nonaqueous electrolytic solution for a battery according to any one of <1> to <4>, wherein a ratio of the nonaqueous solvent in the nonaqueous electrolytic solution for a battery is 80% by mass or more.

<6> a positive electrode;
Lithium metal, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped / undoped with lithium ions, transition metal nitrides that can be doped / undoped with lithium ions, and lithium A negative electrode containing, as a negative electrode active material, at least one selected from the group consisting of carbon materials capable of ion doping and dedoping;
<1>-<5> any one of the battery non-aqueous electrolyte solutions,
Including lithium secondary battery.
<7> A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to <6>.

  According to the present disclosure, there are provided a nonaqueous electrolytic solution for a battery excellent in capacity retention rate during a charge / discharge cycle, and a lithium secondary battery using the nonaqueous electrolytic solution for a battery.

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

In this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In this specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. Means.

[Non-aqueous electrolyte for batteries]
The non-aqueous electrolyte for a battery of the present disclosure (hereinafter also simply referred to as “non-aqueous electrolyte”) includes an additive A that is a compound represented by the following formula (A) and a compound represented by the formula (B) And additive B,
Containing.

In formula (A), R ^a1 represents a fluorinated hydrocarbon group having 1 to 6 carbon atoms, and R ^a2 represents a hydrocarbon group having 1 to 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. To express.

Wherein ^{(B), R b1} is a fluorine atom, or represents a fluorinated hydrocarbon group having 1 to 6 carbon ^atoms, R b2 ^{to R b4} are each independently a hydrogen atom, a fluorine atom, 1 to carbon atoms Represents a hydrocarbon group having 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In formula (C), R ^{c1 to} R ^c4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms.

According to the nonaqueous electrolytic solution of the present disclosure, it is possible to improve the capacity retention rate during the charge / discharge cycle.
The reason for this effect is not clear, but a film is formed on the electrode by a combination of additive A, additive B, and additive C before storage of the battery, and the battery is charged and discharged during the charge / discharge cycle. This is probably because the coating film is less deteriorated.

  Hereinafter, each component of the nonaqueous electrolytic solution of the present disclosure will be described.

<Additive A>
Additive A is a compound represented by the following formula (A).
The additive A may be only one kind of compound corresponding to the compound represented by the following formula (A), or two or more kinds of compounds corresponding to the compound represented by the following formula (A). May be.

In formula (A), R ^a1 represents a fluorinated hydrocarbon group having 1 to 6 carbon atoms, and R ^a2 represents a hydrocarbon group having 1 to 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. To express.

  In the formula (A), the fluorinated hydrocarbon group having 1 to 6 carbon atoms means a hydrocarbon group having 1 to 6 carbon atoms substituted by at least one fluorine atom. The fluorinated hydrocarbon group having 1 to 6 carbon atoms is not limited to a perfluorohydrocarbon group.

In the formula (A), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^a1 may be a linear fluorinated hydrocarbon group or a branched fluorinated hydrocarbon group. It may be a hydrogen group.

In the formula (A), examples of the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^a1 include:
Fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, perfluoroethyl group, 2,2,3,3- Fluoroalkyl groups such as tetrafluoropropyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, perfluoroisopropyl group, perfluoroisobutyl group;
2-fluoroethenyl group, 2,2-difluoroethenyl group, 2-fluoro-2-propenyl group, 3,3-difluoro-2-propenyl group, 2,3-difluoro-2-propenyl group, 3,3 -Fluoroalkenyl groups such as difluoro-2-methyl-2-propenyl group, 3-fluoro-2-butenyl group, perfluorovinyl group, perfluoropropenyl group, perfluorobutenyl group;
Etc.
The fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^a1 is preferably a fluoroalkyl group having 1 to 6 carbon atoms, more preferably a fluoroalkyl group having 1 to 3 carbon atoms, and a fluoromethyl group or difluoro group. Methyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, perfluoroethyl group, 2,2,3,3-tetrafluoropropyl group, Alternatively, a perfluoropropyl group is more preferable, and a 2,2,2-trifluoroethyl group is particularly preferable.

In the formula (A), specific examples and preferred embodiments of the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^a2 are specific examples of the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^a1. Examples and preferred embodiments are

In the formula (A), examples of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^a2 include:
Methyl group, ethyl group, n-propyl group, isopropyl group, 1-ethylpropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 2-methylbutyl group, 3,3-dimethylbutyl group Alkyl groups such as n-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group;
Vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, pentenyl group, hexenyl group, isopropenyl group, 2-methyl-2-propenyl group, 1-methyl-2 An alkenyl group such as a propenyl group or a 2-methyl-1-propenyl group;
Etc.
As a C1-C6 hydrocarbon group represented by R ^<a2> , a C1-C6 alkyl group is preferable, a C1-C3 alkyl group is more preferable, a methyl group or an ethyl group is still more preferable, A methyl group is particularly preferred.

In formula (A), R ^a2 is preferably a hydrocarbon group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, a methyl group or ethyl A group is further preferred, and a methyl group is particularly preferred.

As the compound represented by the formula (F2),
2,2,2-trifluoroethyl methyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, perfluoroethyl methyl carbonate, or bis (perfluoroethyl) carbonate is preferred,
2,2,2-trifluoroethyl methyl carbonate (hereinafter sometimes referred to as “MFEC”) is particularly preferred.

  The content of additive A (the total content when additive A is two or more compounds) is preferably 0.001% by mass to 30% by mass with respect to the total amount of the non-aqueous electrolyte. 0.001% by mass to 20% by mass is more preferable, and 0.01% by mass to 10% by mass is even more preferable.

<Additive B>
Additive B is a compound represented by the following formula (B).
The additive B may be only one kind of compound corresponding to the compound represented by the following formula (B), or two or more kinds of compounds corresponding to the compound represented by the following formula (B). May be.

In formula (B), R ^b1 represents a fluorine atom or a fluorinated hydrocarbon group having 1 to 6 carbon atoms, and R ^{b2 to} R ^b4 each independently represent a hydrogen atom, a fluorine atom, or a carbon number of 1 to Represents a hydrocarbon group having 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In formula (B), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^b1 has the same meaning as the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^a1 in formula (A). The preferred embodiments are also the same.
Wherein ^(B), a hydrocarbon group having 1 to 6 carbon atoms represented by R b2 ^{to R b4} are each a hydrocarbon group having 1 to 6 carbon atoms represented by ^{R a2} in formula (A) It is synonymous and a preferable aspect is also the same.
In formula (B), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ^{b2 to} R ^b4 is a fluorinated group having 1 to 6 carbon atoms represented by R ^a1 in formula (A). It is synonymous with a hydrocarbon group, and its preferable aspect is also the same.

In formula (B), R ^b1 is preferably a fluorine atom.
In formula (B), R ^{b2 to} R ^b4 are each independently preferably a hydrogen atom, a fluorine atom, or a methyl group, more preferably a hydrogen atom or a fluorine atom, and particularly preferably a hydrogen atom.

As a compound represented by the formula (B),
4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, or 4-trifluoromethylethylene carbonate is preferred,
4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, or 4,5-difluoroethylene carbonate is more preferable,
4-fluoroethylene carbonate (hereinafter sometimes referred to as “FEC”) is particularly preferred.

  The content of additive B (the total content when additive B is two or more compounds; the same applies hereinafter) is 0.001% by mass to 10% by mass with respect to the total amount of the non-aqueous electrolyte. It is preferably 0.001% by mass to 5% by mass, more preferably 0.001% by mass to 3% by mass, and still more preferably 0.01% by mass to 3% by mass. The content is more preferably 0.1 to 3% by mass, and still more preferably 0.1 to 2% by mass.

  In the non-aqueous electrolyte, the content ratio of the additive B to the additive A (hereinafter referred to as content mass ratio [additive B / additive A]) is more effective than the above-described effect of the non-aqueous electrolyte of the present disclosure. In view of the above, it is preferably 0.05 or more and 2.0 or less, more preferably 0.05 or more and less than 1.0, still more preferably 0.1 or more and 0.9 or less, and still more preferably Is 0.1 or more and 0.5 or less.

<Additive C>
Additive C is a compound represented by the following formula (C).
The additive C may be only one kind of compound corresponding to the compound represented by the following formula (C), or may be two or more kinds of compounds corresponding to the compound represented by the following formula (C). May be.

In formula (C), R ^{c1 to} R ^c4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms.

In the formula (C), the hydrocarbon group having 1 to 3 carbon atoms represented by R ^{c1 to} R ^c4 is preferably an alkyl group, an alkenyl group, or an alkynyl group, more preferably an alkyl group or an alkenyl group, and an alkyl group. Is particularly preferred.
In the formula (C), the number of carbon atoms of the hydrocarbon group having 1 to 3 carbon atoms represented by R ^{c1 to} R ^c4 is preferably 1 or 2, and particularly preferably 1.

Wherein (C), as the fluorinated hydrocarbon group having 1 to 3 carbon atoms represented by R ^c1 to R ^c4, fluorinated alkyl groups, fluorinated alkenyl group, or a fluorinated alkynyl group preferably fluorinated alkyl Group or an alkenyl fluoride group is more preferable, and a fluorinated alkyl group is particularly preferable.
In the formula (C), the carbon number of the fluorinated hydrocarbon group having 1 to 3 carbon atoms represented by R ^{c1 to} R ^c4 is preferably 1 or 2, and particularly preferably 1.

In formula (C), R ^{c1 to} R ^c4 are each independently preferably a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a trifluoromethyl group, or a pentafluoroethyl group, more preferably a hydrogen atom or a methyl group. Preferably, a hydrogen atom is particularly preferable.

Specific examples of the compound represented by the formula (C) include compounds represented by the following formula (C-1) to the following formula (C-21) (hereinafter, compound (C-1) to compound (C, respectively). -21)), but the compound represented by the formula (B) is not limited to these specific examples.
Among these, the compound (C-1) (that is, 1,3-propene sultone; hereinafter, also referred to as “PRS”) is particularly preferable.

  The content of the additive C (the total content when the additive C is two or more compounds; the same applies hereinafter) is 0.001% by mass to 10% by mass with respect to the total amount of the nonaqueous electrolytic solution. It is preferably 0.001% by mass to 5% by mass, more preferably 0.001% by mass to 3% by mass, and still more preferably 0.01% by mass to 3% by mass. The content is more preferably 0.1 to 3% by mass, further preferably 0.1 to 2% by mass, and further preferably 0.1 to 1% by mass.

  In the non-aqueous electrolyte, the content ratio of the additive C to the additive A (hereinafter referred to as content mass ratio [additive C / additive A]) is more effective than the above-described effect of the non-aqueous electrolyte of the present disclosure. In view of the above, it is preferably 0.01 or more and 2.0 or less, more preferably 0.01 or more and less than 1.0, still more preferably 0.01 or more and 0.5 or less, and still more preferably Is 0.01 or more and 0.2 or less.

<Additive D>
The nonaqueous electrolytic solution of the present disclosure may further contain an additive D that is a compound represented by the following formula (D).

In formula (D), R ^d1 and R ^d2 each independently represent a hydrogen atom, a methyl group, an ethyl group, or a propyl group.

Examples of the compound represented by the formula (D) include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, propyl vinylene carbonate, dimethyl vinylene carbonate, diethyl vinylene carbonate, and dipropyl vinylene carbonate.
Among these, vinylene carbonate (a compound in which R ^d1 and R ^d2 are both hydrogen atoms in the formula (D)) is particularly preferable.

  When the nonaqueous electrolytic solution of the present disclosure contains the additive D, the content of the additive D is preferably 0.001% by mass to 10% by mass, and 0.001% by mass with respect to the total amount of the nonaqueous electrolytic solution. -5% by mass is more preferable, 0.001% by mass to 3% by mass is further preferable, 0.01% by mass to 3% by mass is further preferable, and 0.1 to 3% by mass is preferable. Is more preferable, 0.1 to 2% by mass is further preferable, and 0.1 to 1% by mass is particularly preferable.

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

<Nonaqueous solvent>
The nonaqueous electrolytic solution contains a nonaqueous solvent.
The nonaqueous solvent contained in the nonaqueous electrolytic solution may be only one type or two or more types.
Various known solvents can be appropriately selected as the non-aqueous solvent.
As the non-aqueous solvent, for example, the non-aqueous solvent described in paragraphs 0069 to 0087 of JP-A-2017-45723 can be used.

The non-aqueous solvent preferably contains a cyclic carbonate compound and a chain carbonate compound other than the compound represented by the formula (A) (hereinafter also referred to as “specific chain carbonate compound”).
In this case, each of the cyclic carbonate compound and the specific chain carbonate compound contained in the non-aqueous solvent may be only one kind or two or more kinds.

Examples of the cyclic carbonate compound 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 preferable. In the case of a battery using a negative electrode active material containing graphite, the non-aqueous solvent more preferably contains ethylene carbonate.

  Specific chain carbonate compounds 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, ethyl Examples include 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, and dioctyl carbonate.

  Specific combinations of cyclic carbonate and specific chain carbonate include 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, and 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 And 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 Examples include ethyl carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate.

  The mixing ratio of the cyclic carbonate compound and the specific chain carbonate compound is expressed by mass ratio, and the cyclic carbonate compound: specific chain carbonate compound is, for example, 5:95 to 80:20, preferably 10:90 to 70:30, More preferably, it is 15: 85-55: 45. By setting such a ratio, the increase in the viscosity of the non-aqueous electrolyte can be suppressed and the degree of dissociation of the electrolyte can be increased, so the conductivity of the non-aqueous electrolyte related to the charge / discharge characteristics of the battery can be increased. . In addition, the solubility of the electrolyte can be further increased. Therefore, since it can be set as the non-aqueous electrolyte 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.

The non-aqueous solvent may contain other compounds other than the cyclic carbonate compound and the specific chain carbonate compound.
In this case, only 1 type may be sufficient as the other compound contained in a nonaqueous solvent, and 2 or more types may be sufficient as it.
Other compounds include cyclic carboxylic acid ester compounds (eg, γ-butyrolactone), cyclic sulfone compounds, cyclic ether compounds, chain carboxylic acid ester compounds, chain ether compounds, chain phosphate ester compounds, amide compounds, and chain carbamates. Compounds, cyclic amide compounds, cyclic urea compounds, boron compounds, polyethylene glycol derivatives, and the like.
Regarding these compounds, the description in paragraphs 0069 to 0087 of JP-A-2017-45723 can be appropriately referred to.

The ratio of the cyclic carbonate compound and the specific chain carbonate compound in the non-aqueous solvent is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more.
The proportion of the cyclic carbonate compound and the specific chain carbonate compound in the non-aqueous solvent may be 100% by mass.

The ratio of the non-aqueous solvent in the non-aqueous electrolyte is preferably 60% by mass or more, more preferably 70% by mass or more.
The upper limit of the ratio of the nonaqueous solvent in the nonaqueous electrolytic solution depends on the content of other components (additive A, additive B, electrolyte, etc.), but the upper limit is, for example, 99% by mass, Preferably it is 97 mass%, More preferably, it is 90 mass%.

<Electrolyte>
The nonaqueous electrolytic solution of the present disclosure contains an electrolyte.
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 (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) Tetraalkylammonium salts such as (n = 1 to 5, k = 1 to 8), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F Lithium salts such as _{(2k + 1)} (k = 1 to 8), LiPF _n [C _k F _{(2k + 1)} ] _(6-n) (n = 1 to 5, k = 1 to 8) are included. . Moreover, the lithium salt represented by the following general formula can also be used.

LiC (SO ₂ R ⁷ ) (SO ₂ R ⁸ ) (SO ₂ R ⁹ ), LiN (SO ₂ OR ¹⁰ ) (SO ₂ OR ¹¹ ), LiN (SO ₂ R ¹² ) (SO ₂ R ¹³ ) (where R ^{7 to} R ¹³ may be the same as or different from each other, and are a fluorine atom or 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 of the present disclosure, 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. .
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 the LiPF ₆ occupying the lithium salt is preferably 1 mass% to 100 mass%, more preferably 10 to 100 mass%, more preferably 50 wt% to 100 wt%. 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.

  The non-aqueous electrolyte of the present disclosure 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 disclosure includes a positive electrode, a negative electrode, and the nonaqueous electrolytic solution of the present disclosure.

(Negative electrode)
The negative electrode may include a negative electrode active material and a negative electrode current collector.
The negative electrode active material in the negative electrode is metal lithium, lithium-containing alloy, metal or alloy that can be alloyed with lithium, oxide that can be doped / undoped with lithium ions, and lithium ion doped / undoped At least one selected from the group consisting of transition metal 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) Good) can be 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.

There is no restriction | limiting in particular in the material of the negative electrode electrical power collector in a negative electrode, A well-known thing can be used arbitrarily.
Specific examples of the negative electrode current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Among these, copper is particularly preferable from the viewpoint of ease of processing.

(Positive electrode)
The positive electrode may include a positive electrode active material and a positive electrode current collector.
The positive electrode active material in the positive _{electrode, MoS 2, TiS 2, MnO} 2, transition metal oxides such as V 2 _{O 5} or a transition metal _{sulfide, 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 of the positive electrode current collector include metal materials such as aluminum, aluminum alloy, stainless steel, nickel, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper;

(Separator)
The lithium secondary battery of the present disclosure 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 disclosure may be used for the purpose of obtaining a polymer electrolyte by swelling a polymer.

(Battery configuration)
The lithium secondary battery of the present disclosure 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 (nonaqueous electrolyte secondary battery) of the present disclosure, a laminate type battery can be given.
FIG. 1 is a schematic perspective view showing an example of a laminated battery that is an example of the lithium secondary battery of the present disclosure, 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 nonaqueous electrolytic solution of the present disclosure.
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.

As another example of the lithium secondary battery of the present disclosure, a coin-type battery is also included.
FIG. 3 is a schematic perspective view illustrating an example of a coin-type battery that is another example of the lithium secondary battery of the present disclosure.
In the coin-type battery shown in FIG. 3, a disc-shaped negative electrode 12, a separator 15 into which a non-aqueous electrolyte is injected, a disc-shaped positive electrode 11, and spacer plates 17 and 18 such as stainless steel or aluminum as necessary are arranged in this order. In a laminated state, the positive electrode can 13 (hereinafter also referred to as “battery can”) and a sealing plate 14 (hereinafter also referred to as “battery can lid”) are accommodated. The positive electrode can 13 and the sealing plate 14 are caulked and sealed via a gasket 16.
In this example, the nonaqueous electrolytic solution of the present disclosure is used as the nonaqueous electrolytic solution injected into the separator 15.

In addition, the lithium secondary battery of this indication is obtained by charging / discharging a lithium secondary battery (lithium secondary battery before charging / discharging) containing a negative electrode, a positive electrode, and the non-aqueous electrolyte of the said indication. Lithium secondary batteries may be used.
That is, a lithium secondary battery according to the present disclosure is prepared by first preparing a lithium secondary battery before charge / discharge including a negative electrode, a positive electrode, and the non-aqueous electrolyte according to the present disclosure, and then, before the charge / discharge. 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 disclosure 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 supply 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.

Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples.
In the following examples, “addition amount” means 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).
“Wt%” means mass%.

[Example 1]
A coin-type battery (test battery), which is a lithium secondary battery, was produced by the following procedure.
<Production of negative electrode>
Amorphous coated natural graphite (97 parts by mass), carboxymethylcellulose (1 part by mass) and SBR latex (2 parts by mass) were kneaded with an aqueous solvent to prepare a paste-like negative electrode mixture slurry.
Next, this negative electrode mixture slurry was applied to a negative electrode current collector made of a strip-shaped copper foil having a thickness of 10 μm, dried, and then compressed by a roll press to form a sheet-shaped negative electrode comprising a negative electrode current collector and a negative electrode active material layer Got. The coating density of the negative electrode active material layer at this time was 10 mg / cm ² , and the packing density was 1.5 g / ml.

<Preparation of positive electrode>
LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (90 parts by mass), acetylene black (5 parts by mass) and polyvinylidene fluoride (5 parts by mass) are kneaded using N-methylpyrrolidinone as a solvent to form a paste A positive electrode mixture slurry was prepared.
Next, this positive electrode mixture slurry is applied to a positive electrode current collector made 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 positive electrode comprising a positive electrode current collector and a positive electrode active material layer Got. The coating density of the positive electrode active material layer at this time was 30 mg / cm ² , and the packing density was 2.5 g / ml.

<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 30:30:40 (mass ratio), respectively, to obtain a mixed solvent.
In a mixed solvent obtained, a LiPF ₆ as an electrolyte, the concentration of LiPF ₆ in the final non-aqueous electrolyte solution obtained was dissolved at a 1.0 mol / L.
For the solution obtained above,
2,2,2-trifluoroethyl methyl carbonate (MFEC) as additive A (addition amount 10% by mass),
Additive B 4-fluoroethylene carbonate (FEC) (addition amount 2 mass%) and Additive C 1,3-propene sultone (PRS) (addition amount 0.5 mass%)
Was added to obtain a non-aqueous electrolyte.
The ratio of the nonaqueous solvent (that is, the above-mentioned mixed solvent of EC, DMC and EMC) in the obtained nonaqueous electrolytic solution is 77.5% by mass.

<Production of coin-type battery>
The negative electrode was 14 mm in diameter and the positive electrode was 13 mm in diameter, and each was punched into a disk shape to obtain a coin-shaped negative electrode and a coin-shaped positive electrode. Further, a microporous polyethylene film having a thickness of 20 μm was punched into a disk shape having a diameter of 17 mm to obtain a separator.
The obtained coin-shaped negative electrode, separator, and coin-shaped positive electrode were laminated in this order in a stainless steel battery can (2032 size), and then the above-mentioned non-aqueous electrolyte 20 μL was placed in the battery can. This was injected and impregnated in the separator, the positive electrode, and the negative electrode.
Next, an aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring were placed on the positive electrode, and the battery was sealed by caulking the battery can lid through a polypropylene gasket.
As a result, a coin-type battery (that is, a coin-type lithium secondary battery) having a configuration shown in FIG. 3 having a diameter of 20 mm and a height of 3.2 mm was obtained.

<Battery evaluation>
Conditioning was performed on the obtained coin-type battery, and the following evaluation was performed on the coin-type battery after conditioning.
Here, “conditioning” means that the coin-type battery is repeatedly charged and discharged three times between 2.75 V and 4.2 V at 25 ° C. in a thermostatic chamber.

-Initial discharge capacity (0.2C)-
The coin-type battery after conditioning was charged to SOC 100% at a charge rate of 0.2 C, and then the initial discharge capacity (0.2 C) was measured at 25 ° C. and a discharge rate of 0.2 C.

-Discharge capacity after 100 cycles (0.2C)-
A high-temperature cycle test was performed on the coin-type battery whose initial discharge capacity (0.2 C) was measured.
Here, the high-temperature cycle test was an operation in which a cycle in which a coin-type battery was charged at a charge rate of 1 C and discharged at a discharge rate of 1 C at 55 ° C. was performed 100 cycles.
After charging the coin-type battery after the high-temperature cycle test (that is, after 100 cycles) to SOC 100% at a charge rate of 0.2 C, the discharge capacity after 100 cycles at 25 ° C. and a discharge rate of 0.2 C (0.2C) was measured.

Based on the initial discharge capacity (0.2 C) and the discharge capacity after 100 cycles (0.2 C), the 100-cycle discharge capacity retention rate (%) was determined by the following formula.
The results are shown in Table 1.

100 cycle discharge capacity maintenance rate (%)
= [Discharge capacity after 100 cycles (0.2 C) / initial discharge capacity (0.2 C)] × 100

[Comparative Example 1]
In the preparation of the non-aqueous electrolyte solution, the additive A was not used, and the additive B was added in an amount of 2% by mass and the additive C was added in an amount of 0.5% by mass. The same operation as in Example 1 was performed except that the amount and the amount of additive C were adjusted.
The results are shown in Table 1.

  As shown in Table 1, in Example 1 in which the non-aqueous electrolyte contains additive A, additive B, and additive C, 100 cycle discharge capacity retention rate (that is, capacity retention rate during charge / discharge cycle) ) Was excellent.

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 plates 7 and 8 Separator 11 Positive electrode 12 Negative electrode 13 Positive electrode can 14 Sealing plate 15 Separator 16 Gaskets 17 and 18 Spacer plate

Claims (7)

Electrolyte,
A non-aqueous solvent;
Additive A which is a compound represented by the following formula (A);
Additive B which is a compound represented by the following formula (B);
An additive C which is a compound represented by the following formula (C);
A non-aqueous electrolyte for batteries containing

[In the formula (A), R ^a1 represents a fluorinated hydrocarbon group having 1 to 6 carbon atoms, and R ^a2 represents a hydrocarbon group having 1 to 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. Represents. ]

[In Formula (B), R ^b1 represents a fluorine atom or a fluorinated hydrocarbon group having 1 to 6 carbon atoms, and R ^{b2 to} R ^b4 each independently represent a hydrogen atom, a fluorine atom, or a carbon number of 1 Represents a -6 hydrocarbon group or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. ]

[In Formula (C), R ^{c1 to} R ^c4 each independently represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms. ] The content of the additive A is 0.001% by mass to 30% by mass with respect to the total amount of the battery non-aqueous electrolyte,
The content of the additive B is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte. The content of the additive C is based on the total amount of the battery non-aqueous electrolyte. The nonaqueous electrolytic solution for battery according to claim 1, which is 0.001 mass% to 10 mass%.   The nonaqueous electrolytic solution for a battery according to claim 1 or 2, wherein the nonaqueous solvent includes a cyclic carbonate compound and a chain carbonate compound other than the compound represented by the formula (A).   4. The battery according to claim 3, wherein a total ratio of the cyclic carbonate compound and a chain carbonate compound other than the compound represented by the formula (A) in the non-aqueous solvent is 80% by mass or more. Non-aqueous electrolyte.   The nonaqueous electrolytic solution for a battery according to any one of claims 1 to 4, wherein a ratio of the nonaqueous solvent in the nonaqueous electrolytic solution for a battery is 60% by mass or more. A positive electrode;
Lithium metal, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped / undoped with lithium ions, transition metal nitrides that can be doped / undoped with lithium ions, and lithium A negative electrode containing, as a negative electrode active material, at least one selected from the group consisting of carbon materials capable of ion doping and dedoping;
The non-aqueous electrolyte for a battery according to any one of claims 1 to 5,
Including lithium secondary battery.   A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to claim 6.