JP7060190B2 - Non-aqueous electrolyte for batteries and lithium secondary batteries - Google Patents

Description

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

In recent years, lithium secondary batteries have been widely used as power sources for electronic devices such as mobile phones and notebook computers, electric vehicles, and power storage. 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 installed in hybrid vehicles and electric vehicles.
Conventionally, various additives have been contained in the non-aqueous electrolytic solution of a battery such as the above-mentioned lithium secondary battery.
For example, attempts have been made to improve battery performance by incorporating various cyclic sulfate ester compounds into a non-aqueous electrolytic solution of a lithium secondary battery (see, for example, Patent Documents 1 to 7).

Japanese Unexamined Patent Publication No. 10-189042 Japanese Patent Application Laid-Open No. 2003-151623 Japanese Patent Application Laid-Open No. 2003-308875 Japanese Unexamined Patent Publication No. 2004-22523 Japanese Unexamined Patent Publication No. 2005-011762 International Publication No. 2012/053644 U.S. Patent Application Publication No. 2016/0359196

However, as an additive in the non-aqueous electrolytic solution for a battery, it may be required to reduce the battery resistance by using a cyclic sulfate ester compound having a structure different from that of the conventional cyclic sulfate ester compound.
For example, depending on the combination of the type of the cyclic sulfate ester compound and the type of the negative electrode active material, when the cyclic sulfate ester compound is added to the non-aqueous electrolytic solution, it is compared with the case where the cyclic sulfate ester compound is not added. On the contrary, the battery resistance may increase.
An object of the present disclosure is a non-aqueous electrolytic solution for a battery, which contains a cyclic sulfuric acid ester compound different from the conventional cyclic sulfuric acid ester compound as an additive in the non-aqueous electrolytic solution for a battery and can reduce the battery resistance. The present invention is to provide a lithium secondary battery using this non-aqueous electrolytic solution for a battery.

The means for solving the above problems include the following aspects.
<1> A non-aqueous electrolytic solution for a battery used for a battery including a negative electrode containing a negative electrode active material containing natural graphite, which contains a compound represented by the following formula (1).

In the formula (1), R ¹ and R ² independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or an alkyl halide group having 1 to 3 carbon atoms. ]

<2> The non-aqueous electrolytic solution for batteries according to <1>, wherein the content of the compound represented by the above formula (1) with respect to the total amount of the non-aqueous electrolytic solution for batteries is 0.001% by mass to 10% by mass. ..

<3> The non-aqueous electrolytic solution for a battery according to <1> or <2>, which further contains a boron compound (X) containing a structure in which three oxygen atoms are bonded to one boron atom.
<4> The non-aqueous electrolytic solution for a battery according to <3>, wherein the boron compound (X) has a molecular weight of 1000 or less.
<5> The battery according to <3> or <4>, wherein the boron compound (X) is at least one selected from the group consisting of compounds represented by the following formulas (X1) to (X3). For non-water electrolyte.

In the formula (X1), ^RX11 to ^RX13 each independently represent an unsubstituted aryl group or an aliphatic group having 1 to 12 carbon atoms.
In the formula (X2), n represents an integer of 1 to 5, and M ⁺ represents a Li ⁺ ion or an H ⁺ ion. When n is an integer of 2 to 5, the plurality of M ⁺ may be the same or different.
In the formula (X3), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by the formula (RX). In the formula (RX), ^RX31 to ^RX33 independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. , And * represents the bond position.

<6> In the formula (X1), ^RX11 to ^RX13 are independently methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, cyclohexyl group, respectively. Or represents a phenyl group
In equation (X2), M ⁺ represents Li ⁺ ion.
In the formula (X3), R is the non-aqueous electrolyte solution for a battery according to <5>, which represents a group represented by the formula (RX).

<7> Positive electrode and
Negative electrode containing natural graphite Negative electrode containing active material and negative electrode
The non-aqueous electrolyte solution for a battery according to any one of <1> to <6>,
Lithium secondary battery including.
<8> A lithium secondary battery obtained by charging / discharging the lithium secondary battery according to <7>.

According to the present disclosure, as an additive in the non-aqueous electrolytic solution for a battery, a non-aqueous electrolytic solution for a battery containing a cyclic sulfuric acid ester compound different from the conventional cyclic sulfuric acid ester compound and capable of reducing battery resistance, and a non-aqueous electrolytic solution for a battery, and , A lithium secondary battery using this non-aqueous electrolytic solution for a battery is provided.

It is a schematic perspective view which shows the example of the laminated type battery which is an example of the lithium secondary battery of this disclosure. FIG. 3 is a schematic cross-sectional view in the thickness direction of a laminated electrode body housed in the laminated battery shown in FIG. 1. It is the schematic which shows the example of the coin type battery which is another example of the lithium secondary battery of this disclosure.

In the present specification, the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
In the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means.

[Non-water electrolyte for batteries]
The non-aqueous electrolyte solution for batteries (hereinafter, also simply referred to as “non-aqueous electrolyte solution”) of the present disclosure is a non-aqueous electrolyte solution for batteries used in a battery including a negative electrode containing a negative electrode active material containing natural graphite. As an additive in the non-aqueous electrolytic solution for a battery, a compound represented by the following formula (1) is contained as a cyclic sulfuric acid ester compound different from the conventional cyclic sulfuric acid ester compound.
According to the non-aqueous electrolytic solution of the present disclosure, battery resistance can be reduced.
More specifically, the battery resistance is reduced by using the non-aqueous electrolytic solution containing the compound represented by the formula (1) as the non-aqueous electrolytic solution of the battery including the negative electrode containing the negative electrode active material containing natural graphite. Will be done.
Although the reason why such an effect is exhibited is not clear, it corresponds to natural graphite having a smaller crystallite size and higher amorphousness than artificial graphite, and also to a cyclic sulfate ester compound and a fused cyclic compound. It is considered that the combination with the compound represented by the formula (1) forms a low resistance film derived from the compound represented by the formula (1) on the negative electrode of the battery.
On the other hand, when the non-aqueous electrolytic solution containing the compound represented by the formula (1) is used as the non-aqueous electrolytic solution of the battery including the negative electrode containing the negative electrode active material containing artificial graphite, the battery resistance ( In particular, the battery resistance at a low temperature) may rather increase (see Comparative Examples 102 and 103 in Table 3 described later).

As shown in the structure below, the compound represented by the following formula (1) corresponds to a cyclic sulfate ester compound and also corresponds to a condensed cyclic compound.
The compound represented by the following formula (1) has a lower open voltage reduction rate as compared with conventional cyclic sulfate ester compounds (for example, comparative compounds (C1) and (C2) described later) which do not correspond to the condensed cyclic compound. It is excellent in the effect of improving (that is, reducing) and the effect of improving the battery capacity.

<Compound represented by the formula (1)>

In the formula (1), R ¹ and R ² independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or an alkyl halide group having 1 to 3 carbon atoms.

As the halogen atom represented by R ¹ or R ² , a fluorine atom, a chlorine atom, a bromine atom or an iodine atom is preferable, a fluorine atom, a chlorine atom or a bromine atom is more preferable, and a fluorine atom or a chlorine atom is further preferable. Fluorine atoms are particularly preferred.

As the alkyl group having 1 to 3 carbon atoms represented by R ¹ or R ² , a methyl group or an ethyl group is preferable, and a methyl group is particularly preferable.

The halogen atom in the halogenated alkyl group having 1 to 3 carbon atoms represented by R ¹ or R ² is preferably a fluorine atom, a chlorine atom, a bromine atom or an iodine atom, and a fluorine atom, a chlorine atom or a bromine atom is preferable. More preferably, a fluorine atom or a chlorine atom is further preferable, and a fluorine atom is particularly preferable.
Examples of the alkyl halide group having 1 to 3 carbon atoms represented by R ¹ or R ² include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, or perfluoroethyl. Groups are preferred, fluoromethyl groups, difluoromethyl groups, or trifluoromethyl groups are more preferred, and trifluoromethyl groups are particularly preferred.

R ¹ and R ² are independently hydrogen atom, fluorine atom, methyl group, ethyl group, luolomethyl group, difluoromethyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, or perfluoro. Ethyl groups are preferred, hydrogen atoms, fluorine atoms, methyl groups, or trifluoromethyl groups are more preferred, and hydrogen atoms are particularly preferred.

Specific examples of the compound represented by the formula (1) include the compounds represented by the following formulas (1-1) to the following formula (1-11) (hereinafter, each of the compounds (1-1) to the compound (1). -11)), but the compound represented by the formula (1) is not limited to these specific examples.

For the method for synthesizing the compound represented by the formula (1), for example, publicly known documents such as US Patent Application Publication No. 2016/0359196 can be appropriately referred to.

The non-aqueous electrolytic solution of the present disclosure may contain only one type of the compound represented by the formula (1), or may contain two or more types.
The content of the compound represented by the formula (1) with respect to the total amount of the non-aqueous electrolytic solution of the present disclosure is preferably 0.001% by mass to 10% by mass, more preferably 0.005% by mass to 5% by mass. 0.01% by mass to 2% by mass is more preferable, and 0.1% by mass to 1% by mass is particularly preferable.

The non-aqueous electrolytic solution of the present disclosure may contain other additives other than the compound represented by the formula (1).
When the non-aqueous electrolytic solution of the present disclosure contains other additives, the other additives contained may be only one kind or two or more kinds.

<Boron compound (X)>
The non-aqueous electrolytic solution of the present disclosure may contain a boron compound (X) containing a structure in which three oxygen atoms are bonded to one boron atom as other additives.
When the non-aqueous electrolytic solution of the present disclosure contains a boron compound (X), the non-aqueous electrolytic solution of the present disclosure does not contain a boron compound (X) and contains other boron compounds other than the boron compound (X). Compared with the case of containing, the battery resistance (particularly, the initial battery resistance before storing the battery) can be further reduced.
Although the reason for this is not clear, the boron compound (X) binds to B as compared with, for example, a boron compound containing a structure in which four oxygen atoms are bonded to one boron atom (for example, LiBOB described later). It is considered that since the number of O's formed is small, the reactivity on the edge surface of graphite is superior, and as a result, a more uniform film is formed on the negative electrode. More specifically, by using the compound represented by the formula (1) and the boron compound in combination as an additive for the non-aqueous electrolytic solution, the compound represented by the formula (1) and the boron compound are mixed. It is considered that a low resistance film is formed on the negative electrode. At this time, it is considered that by selecting the boron compound (X) as the boron compound, a more homogeneous low resistance film is formed on the negative electrode, and as a result, the battery resistance is reduced more effectively.

The boron compound (X) may contain only one structure in which three oxygen atoms are bonded to one boron atom (in other words, a boron atom to which three oxygen atoms are bonded), or 2 It may contain one or more.
Further, the boron compound (X) may contain a boron atom other than the boron atom to which the three oxygen atoms are bonded.

The boron compound (X) may be a low molecular weight compound or a high molecular weight compound, but is preferably a low molecular weight compound.
The molecular weight of the boron compound (X) is preferably 1000 or less, more preferably 500 or less, still more preferably 400 or less, still more preferably 300 or less.

When the non-aqueous electrolytic solution of the present disclosure contains a boron compound (X), the contained boron compound (X) may be only one kind or two or more kinds.
When the non-aqueous electrolytic solution of the present disclosure contains a boron compound (X), the content of the boron compound (X) with respect to the total amount of the non-aqueous electrolytic solution of the present disclosure is preferably 0.001% by mass to 10% by mass. , 0.005% by mass to 5% by mass, more preferably 0.01% by mass to 2% by mass, and particularly preferably 0.1% by mass to 1% by mass.

When the non-aqueous electrolytic solution of the present disclosure contains the boron compound (X), the preferable range of the content of the compound represented by the formula (1) is the above-mentioned formula with respect to the total amount of the non-aqueous electrolytic solution of the present disclosure. It is the same as the preferable range of the content of the compound represented by (1).

The boron compound (X) is preferably at least one selected from the group consisting of compounds represented by the following formulas (X1) to (X3).

In the formula (X1), ^RX11 to ^RX13 each independently represent an unsubstituted aryl group or an aliphatic group having 1 to 12 carbon atoms.
In the formula (X2), n represents an integer of 1 to 5, and M ⁺ represents a Li ⁺ ion or an H ⁺ ion. When n is an integer of 2 to 5, the plurality of M ⁺ may be the same or different.
In the formula (X3), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by the formula (RX). In the formula (RX), ^RX31 to ^RX33 independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. , And * represents the bond position.

In the formula (X1), examples of the unsubstituted aryl group represented by ^RX11 to ^RX13 are independently a phenyl group, a naphthyl group, an anthrasenyl group, a phenanthryl group and the like, but a phenyl group is preferable.

In the formula (X1), the aliphatic groups having 1 to 12 carbon atoms represented by ^RX11 to ^RX13 may be independently linear aliphatic groups or branched aliphatic groups. It may be an aliphatic group having a cyclic structure.
In the formula (X1), the aliphatic groups having 1 to 12 carbon atoms represented by ^RX11 to ^RX13 may be independently saturated aliphatic groups (that is, alkyl groups) or unsaturated fats. It may be a group group (that is, an alkenyl group or an alkynyl group).

As a specific example of the aliphatic group having 1 to 12 carbon atoms represented by ^RX11 to ^RX13 ,
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 , N-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert -Linear or branched saturated aliphatic groups such as heptyl group, n-octyl group, isooctyl group, sec-octyl group, tert-octyl group, nonyl group, decyl group, undecyl group, dodecyl group. Alkyl group);
Vinyl group, 1-propenyl group, allyl group (2-propenyl group), isopropenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, pentenyl group, hexenyl group, 2-methyl-2-propenyl group , 1-Methyl-2-propenyl group, 2-methyl-1-propenyl group, hexenyl group, ethynyl group, 1-propynyl group, 2-propynyl group (synonymous with propargyl group), 1-butynyl group, 2-butynyl group , 3-Butynyl group, 1-Pentynyl group, 2-Pentynyl group, 3-Pentynyl group, 4-Pentynyl group, 5-Hexinyl group, 1-Methyl-2-propynyl group, 2-Methyl-3-butynyl group, 2 -Methyl-3-pentynyl group, 1-methyl-2-butynyl group, 1,1-dimethyl-2-propynyl, 1,1-dimethyl-2-butynyl group, 1-hexynyl group, etc., linear or branched Unsaturated aliphatic group (ie, alkenyl group or alkynyl group);
An aliphatic group having a cyclic structure such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a 1-cyclopentenyl group, a 1-cyclohexenyl group;
And so on.

The aliphatic groups having 1 to 12 carbon atoms represented by ^RX11 to ^RX13 are independently methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and t-butyl. A group or a cyclohexyl group is preferable, a methyl group, an ethyl group, or an isopropyl group is more preferable, and a methyl group is further preferable.

In formula (X1), ^RX11 to ^RX13 independently have a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a cyclohexyl group, or a phenyl group. It is preferably a methyl group, an ethyl group, an isopropyl group, or a phenyl group, more preferably a methyl group or a phenyl group, and particularly preferably a methyl group.

In the formula (X2), n represents an integer of 1 to 5, and M ⁺ represents a Li ⁺ ion or an H ⁺ ion. When n is an integer of 2 to 5, the plurality of M ⁺ may be the same or different.

In the formula (X2), n is preferably an integer of 1 to 3, and 2 is particularly preferable.
In the formula (X2), Li ⁺ ion is particularly preferable as M ⁺ .

In the formula (X3), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by the formula (RX). In the formula (RX), ^RX31 to ^RX33 independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. , And * represents the bond position.

In the formula (X3), as the alkyl group having 1 to 12 carbon atoms represented by R, an alkyl group having 1 to 10 carbon atoms is more preferable, an alkyl group having 1 to 8 carbon atoms is further preferable, and an alkyl group having 1 to 8 carbon atoms is more preferable. The alkyl group of 6 is more preferable, and the alkyl group having 1 to 4 carbon atoms is further preferable.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group and a neopentyl group. , Trt-pentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, Examples thereof include a sec-octyl group and a tert-octyl group.
The alkyl group having 1 to 12 carbon atoms represented by R may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

In the formula (X3), as the alkenyl group having 2 to 12 carbon atoms represented by R, an alkenyl group having 2 to 10 carbon atoms is more preferable, an alkenyl group having 2 to 8 carbon atoms is further preferable, and an alkenyl group having 2 to 8 carbon atoms is more preferable. The alkenyl group of 6 is more preferable, and the alkenyl group having 2 to 4 carbon atoms is further preferable.
Examples of the alkenyl group include an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group and the like.
The alkenyl group having 2 to 12 carbon atoms represented by R may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

In the formula (X3), as R, a group represented by the formula (RX) is preferable.
In the formula (RX), ^RX31 to ^RX33 independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Represents.

Examples of the halogen atom represented by ^RX31 to ^RX33 include a fluorine atom, a chlorine atom and a bromine atom, and a fluorine atom is preferable.

As the alkyl group having 1 to 12 carbon atoms represented by ^RX31 to ^RX33 , an alkyl group having 1 to 10 carbon atoms is more preferable, an alkyl group having 1 to 8 carbon atoms is further preferable, and an alkyl group having 1 to 6 carbon atoms is more preferable. Alkyl groups are more preferable, alkyl groups having 1 to 4 carbon atoms are further preferable, and alkyl groups having 1 to 3 carbon atoms are further preferable.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group and a neopentyl group. , Trt-pentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, Examples thereof include a sec-octyl group and a tert-octyl group.
The alkyl group having 1 to 12 carbon atoms represented by ^RX31 to ^RX33 may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

As the alkenyl group having 2 to 12 carbon atoms represented by ^RX31 to ^RX33 , an alkenyl group having 2 to 10 carbon atoms is more preferable, an alkenyl group having 2 to 8 carbon atoms is further preferable, and an alkenyl group having 2 to 6 carbon atoms is more preferable. An alkenyl group is more preferable, and an alkenyl group having 2 to 4 carbon atoms is further preferable.
Examples of the alkenyl group include an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group and the like.
The alkenyl group having 2 to 12 carbon atoms represented by ^RX31 to ^RX33 may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

As the aryl group having 6 to 12 carbon atoms represented by ^RX31 to ^RX33 , an aryl group having 6 to 10 carbon atoms is more preferable.
Examples of the aryl group include a phenyl group, a group in which one hydrogen atom is removed from alkylbenzene (for example, a benzyl group, a tolyl group, a xylyl group, a mesityl group, etc.), a naphthyl group, and a hydrogen atom from an alkyl group substituent of naphthalene. Examples include a group in which one is removed.
The aryl group having 6 to 12 carbon atoms represented by ^RX31 to ^RX33 may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

In the formula (X3), at least one of ^RX31 to ^RX33 is preferably an alkyl group, an alkenyl group, or an aryl group, and at least two of ^RX31 to ^RX33 are an alkyl group, an alkenyl group, or an aryl group. It is more preferably an aryl group. In this case, the preferred embodiments of the alkyl group, the alkenyl group, and the aryl group are as described above, and the alkyl group is preferable among the alkyl group, the alkenyl group, and the aryl group.

The boron compound represented by the formula (X3) can be synthesized, for example, by the method described in Chemische Berichte, Volume 68, Issue 6, Pages 1949-55, 1965.

Particularly preferred embodiments of the formulas (X1) to (X3) are
In formula (X1), ^RX11 to ^RX13 independently have a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a cyclohexyl group, or a phenyl group. Represents
In equation (X2), M ⁺ represents Li ⁺ ion.
In the formula (X3), R is an embodiment representing a group represented by the formula (RX).

Hereinafter, specific examples of the compound represented by the formula (X1) will be shown, but the compound represented by the formula (X1) is not limited to the following specific examples.

Hereinafter, specific examples of the compound represented by the formula (X2) will be shown, but the compound represented by the formula (X2) is not limited to the following specific examples.
Specific examples of the compound represented by the formula (X2) include
Lithium triborate (a compound in which n is 1 and M ⁺ is Li ⁺ ion),
Lithium borate (a compound in which n is 2 and two M ⁺ are Li ⁺ ions; a compound described later (X2-1)),
Lithium borate (a compound in which n is 3 and 3 M ⁺ are Li ⁺ ions),
Lithium borate (a compound in which n is 4 and 4 M ⁺ are Li ⁺ ions),
Lithium borate (a compound in which n is 5 and 5 M ⁺ are Li ⁺ ions),
And so on.

Hereinafter, specific examples of the compound represented by the formula (X3) will be shown, but the compound represented by the formula (X3) is not limited to the following specific examples.

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

(Non-aqueous solvent)
The non-aqueous electrolyte solution generally contains a non-aqueous solvent.
As the non-aqueous solvent, various known ones can be appropriately selected, but it is preferable to use at least one selected from a cyclic aprotic solvent and a chain aprotic solvent.

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

(Cyclic aprotic solvent)
As the cyclic aprotic solvent, a cyclic carbonate, a cyclic carboxylic acid ester, a cyclic sulfone, and a 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 such a ratio, the conductivity of the electrolytic solution related 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, and 2,3-pentylene carbonate. 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 alkyl substituents such as γ-butyrolactone, δ-valerolactone, methyl γ-butyrolactone, ethyl γ-butyrolactone, and ethyl δ-valerolactone.
The cyclic carboxylic acid ester has a low vapor pressure, a low viscosity, and a high dielectric constant, and can reduce the viscosity of the electrolytic solution without lowering the flash point of the electrolytic solution and the degree of dissociation of the electrolyte. Therefore, it has a 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. It is preferable to use a cyclic carboxylic acid ester as the cyclic aprotic solvent. γ-Butyrolactone is most preferred.

Further, 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.

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 methylethyl carbonate, γ-butyrolactone and propylene carbonate and diethyl carbonate, γ-Butyrolactone, ethylene carbonate and propylene carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate and dimethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate and methylethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate and diethyl carbonate, γ-Buchirolactone, ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate and dimethyl carbonate. And methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate and dimethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate. And methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and sulfolane, γ-butyrolactone and ethylene carbonate and sulforane, γ-butyrolactone and propylene carbonate. Sulfolane, γ-butyrolactone, ethylene carbonate, propylene carbonate, sulfolane, γ-bu Examples thereof include tyrolactone, sulfolane and dimethyl carbonate.

Examples of the cyclic sulfone include sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, dipropylsulfone, methylethylsulfone, methylpropylsulfone and the like.
Dioxolane can be mentioned as an example of the cyclic ether.

(Chain aprotic solvent)
As the chain aprotic solvent, a chain carbonate, a chain carboxylic acid ester, a chain ether, a chain phosphate ester and 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.

Specifically, as the chain carbonate, 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 thereof include ethylpentyl carbonate, dipentyl carbonate, methylheptyl carbonate, ethylheptyl carbonate, diheptyl carbonate, methylhexyl carbonate, ethylhexyl carbonate, dihexyl carbonate, methyloctyl carbonate, ethyloctyl carbonate, dioctyl carbonate, methyltrifluoroethyl carbonate and the like. Two or more kinds of these chain carbonates may be mixed and used.

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

(Combination of solvents)
The non-aqueous solvent contained in the non-aqueous electrolytic solution of the present disclosure may be only one kind or two or more kinds.
Further, even if only one or more kinds of cyclic aprotic solvents are used, one or more kinds of chain aprotic solvents are used, or cyclic aprotic solvents and chain-like protonic properties are used. Solvents may be mixed and used. When it is particularly intended to improve the load characteristics and low temperature characteristics of the battery, it is preferable to use a combination of a cyclic aprotic solvent and a chain aprotic solvent as the non-aqueous solvent.

Further, from the viewpoint 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 also be enhanced by the combination of the cyclic carboxylic acid ester and the cyclic carbonate and / or the chain carbonate.

Specific combinations of cyclic carbonate and 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. Ethylene 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, methyl ethyl carbonate and diethyl. Examples thereof include 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. It is ~ 55: 45. By setting such a ratio, it is possible to suppress an increase in the viscosity of the electrolytic solution and increase the degree of dissociation of the electrolyte, so that the conductivity of the electrolytic solution 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 the electrolytic solution having excellent electrical conductivity at normal temperature or low temperature can be obtained, the load characteristics of the battery at normal temperature to low temperature can be improved.

(Other solvents)
Examples of the non-aqueous solvent include other solvents other than the above.
Specific examples of the other solvent include amides such as dimethylformamide, chain carbamates such as methyl-N and N-dimethylcarbamate, cyclic amides such as N-methylpyrrolidone, and N, N-dimethylimidazolidinone. Examples thereof include boron compounds such as cyclic urea, trimethyl borate, triethyl borate, tributyl borate, trioctyl borate, and trimethylsilyl borate, and polyethylene glycol derivatives represented by the following general formulas.
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, and 5 ≦ g + h ≦ 250, 5 ≦ i + j ≦ 250.

(Electrolytes)
As the non-aqueous electrolyte solution of the present disclosure, various known electrolytes can be used, and any one that is usually used as an electrolyte for a non-aqueous electrolyte solution can be used.

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 _{(2 k + 1)} (integer of k = 1 to 8), (C ₂ H ₅ ) ₄ NPF _n [C _k F _{(2 k + 1)} ] _(6-n) Tetraalkylammonium salts such as (n = 1-5, k = 1-8 integers), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F. Lithium salts such as _{(2k + 1)} (integer of k = 1 to 8), LiPF _n [ _Ck F _{(2k + 1)} ] _(6-n) (n = 1 to 5, integer of k = 1 to 8) can be mentioned. .. Further, a 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 ) (here R ⁷ to R ¹³ may be the same or different from each other, and are a fluorine atom or a perfluoroalkyl group having 1 to 8 carbon atoms). 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 Ck F (2 _{k + 1)} (integer of k = 1 to 8), LiClO ₄ , LiAsF ₆ , LiNSO ₂ [C _k F _{( 2k + 1)} ] ₂ (integer of k = 1 to 8), LiPF _n [ _Ck F _{(2k + 1)} ] _(6-n) (n = 1 to 5, integer of k = 1 to 8) are preferable.

The electrolyte is usually preferably contained in a non-aqueous 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 non-aqueous electrolytic solution of the present disclosure, when a cyclic carboxylic acid ester such as γ-butyrolactone is used in combination as the non-aqueous solvent, it is particularly desirable to contain LiPF ₆ . Since LiPF ₆ has a high degree of dissociation, it can increase the conductivity of the electrolytic solution and further has an effect of suppressing the reduction decomposition reaction of the electrolytic solution on the negative electrode. LiPF ₆ may be used alone, or LiPF ₆ and other electrolytes may be used. As the other electrolyte, any one that is usually used as an electrolyte for a non-aqueous electrolyte solution can be used, but among the specific examples of the above-mentioned lithium salts, lithium salts other than LiPF ₆ are preferable. ..
Specific examples include LiPF ₆ and LiBF ₄ , LiPF ₆ and LiN [SO ₂ C _k F _{(2 k + 1)} ] ₂ (integer of k = 1 to 8), LiPF ₆ and LiBF ₄ and LiN [SO ₂ C _k F ₍ SO 2 C k F). _{2k + 1)} ] (k = an integer of 1 to 8) and the like are exemplified.

The ratio of LiPF ₆ to the lithium salt is preferably 1% by mass to 100% by mass, more preferably 10% by mass to 100% by mass, and further preferably 50% by mass to 100% by mass. Such an electrolyte is preferably contained in the non-aqueous electrolyte 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 electrolytic solution of the present disclosure is not only suitable as a non-aqueous electrolytic solution for a lithium secondary battery, but also a non-aqueous electrolytic solution for a primary battery, a non-aqueous electrolytic solution for an electrochemical capacitor, and an electric double layer capacitor. , 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 containing a negative electrode active material containing natural graphite, and a non-aqueous electrolytic solution of the present disclosure.

<Negative electrode>
The negative electrode contains a negative electrode active material containing natural graphite.
The negative electrode active material may be in any of fibrous, spherical, potato-like, and flake-like forms.

As described above, natural graphite has a smaller crystallite size and higher amorphousness than artificial graphite. The effect of reducing the battery resistance by the non-aqueous electrolytic solution of the present disclosure is achieved by a combination of natural graphite having such properties and the compound represented by the above formula (1).

Here, the amorphous property can be evaluated by the R value [I (1350) / I (1850)] of the Raman spectrum (hereinafter, also simply referred to as “R value [I (1350) / I (1850)]”). ..
The R value [I (1350) / I (1850)] is the ratio of the intensity at Raman shift 1350 cm ^-1 (I (1350)) to the intensity at Raman shift 1850 cm ^-1 (I (1850)).
I (1850) is the intensity of the G peak reflecting the graphite structure.
I (1350) is the intensity of the D peak reflecting the irregularity.
The higher the R value [I (1350) / I (1850)], the higher the amorphousness.

The R value [I (1350) / I (1850)] of natural graphite is preferably 0.090 or more, more preferably 0.100 or more, still more preferably 0.110 or more, still more preferably 0.110 or more. It is 0.120 or more.
The upper limit of the R value [I (1350) / I (1850)] of natural graphite is not particularly limited. The upper limit is, for example, 0.300, preferably 0.200, and more preferably 0.150.

The crystallite size of natural graphite can be measured by X-ray analysis.
The crystallite size of natural graphite is preferably 120 Å or less, more preferably 100 Å or less, and further preferably 80 Å or less.
The lower limit of the crystallite size of natural graphite is, for example, 30 Å, preferably 40 Å.

The interplanar spacing d (002) of the (002) plane of natural graphite is preferably 0.340 nm or less.
The lower limit of the interplanar spacing d (002) of the (002) plane of natural graphite is, for example, 0.334 nm.
The interplanar spacing d (002) of the (002) plane of natural graphite can be measured by X-ray analysis.

The ratio of natural graphite to the negative electrode active material is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 80% by mass or more.

The negative electrode active material may contain a component other than natural graphite.
Examples of components other than natural graphite include carbon materials such as carbon black, activated carbon, artificial graphite, and amorphous carbon materials; metals or alloys such as silicon, silicon alloys, tin, and tin alloys; lithium titanate; and the like.
Examples of the amorphous carbon material include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500 ° C. or lower, mesophase pitch carbon fiber (MCF), and the like.
Further, as the negative electrode active material, natural graphite coated with an amorphous carbon material; natural graphite coated with a metal such as gold, platinum, silver, copper or tin; or the like may be used.

The negative electrode may include a negative electrode current collector.
The material of the negative electrode current collector in the negative electrode is not particularly limited, and any known material can be used.
Specific examples of the negative electrode current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of 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.
Examples of the positive electrode active material in the positive electrode include transition metal oxides or transition metal sulfides such as MoS ₂ , TiS ₂ , MnO ₂ , and V2 O ₅ , LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , _{LiNiO 2 ,} and LiNi _X Co. _(1-X) O ₂ [0 <X <1], Li _{1 + α} Me _1-α O ₂ having an α-NaFeO type ₂ crystal structure (Me is a transition metal element containing Mn, Ni and Co, 1.0. ≦ (1 + α) / (1-α) ≦ 1.6), LiNi _x Coy 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 composite oxides consisting of lithium and transition metals, Examples thereof include conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiazol, and polyaniline complex. Among these, a composite oxide composed of lithium and a transition metal is particularly preferable. When the negative electrode is a lithium metal or a lithium alloy, a carbon material can also be used as the positive electrode. Further, as the positive electrode, a mixture of a composite oxide of lithium and a transition metal and a carbon material can also be used.
The positive electrode active material may be used alone or in combination of two or more. If the positive electrode active material has insufficient conductivity, it can be used together with a conductive auxiliary agent to form a positive electrode. Examples of the conductive auxiliary agent include carbon materials such as carbon black, amorphous whiskers, and graphite.

The material of the positive electrode current collector in the positive electrode is not particularly limited, and any known material can be used.
Specific examples of the positive electrode current collector include metal materials such as aluminum, aluminum alloys, stainless steel, nickel, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper; and the like.

<Separator>
The lithium secondary battery of the present disclosure preferably contains a separator between the negative electrode and the positive electrode.
The separator is a membrane that electrically insulates the positive electrode and the negative electrode and allows lithium ions to pass through, and examples thereof include a porous membrane and a polyelectrolyte.
As the porous film, a microporous polymer film is preferably used, and examples thereof include polyolefin, polyimide, polyvinylidene fluoride, polyester and the like.
In particular, porous polyolefin is preferable, and 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. The porous polyolefin film may be coated with another resin having excellent thermal stability.
Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer inflated with an electrolytic solution, and the like.
The non-aqueous electrolyte solution of the present disclosure may be used for the purpose of swelling a polymer to obtain a polymer electrolyte.

<Battery configuration>
The lithium secondary battery of the present disclosure can take various known shapes, and can be formed into a cylindrical type, a coin type, a square type, a laminated type, a film type, 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.

An example of the lithium secondary battery of the present disclosure is a laminated battery.
FIG. 1 is a schematic perspective view showing an example of a laminated battery which is an example of the lithium secondary battery of the present disclosure, and FIG. 2 is a thickness of a laminated electrode body housed in the laminated battery shown in FIG. It is a schematic sectional view of a direction.
The laminated battery shown in FIG. 1 contains a non-aqueous electrolytic solution (not shown in FIG. 1) and a laminated electrode body (not shown in FIG. 1), and the peripheral edge thereof is sealed. A laminated exterior body 1 whose inside is hermetically sealed is provided. As the laminated exterior body 1, for example, a laminated exterior body made of aluminum is used.
As shown in FIG. 2, the laminated electrode body housed in the laminated exterior body 1 is a laminated body in which a positive electrode plate 5 and a negative electrode plate 6 are alternately laminated via a separator 7, and a laminated body of the laminated body. A separator 8 that surrounds the periphery is provided. The positive electrode plate 5, the negative electrode plate 6, the separator 7, and the separator 8 are impregnated with the non-aqueous 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 the positive electrode tab (not shown), and a part of the positive electrode terminal 2 is the laminated exterior body 1. It protrudes outward from the peripheral end (Fig. 1). A portion of the peripheral end of the laminated exterior body 1 on which the positive electrode terminal 2 protrudes is sealed by an insulating seal 4.
Similarly, the plurality of negative electrode plates 6 in the laminated electrode body are all electrically connected to the negative electrode terminal 3 via the negative electrode tab (not shown), and a part of the negative electrode terminal 3 is the laminated exterior. It protrudes outward from the peripheral end of the body 1 (FIG. 1). A portion of the peripheral end of the laminated exterior body 1 on which the negative electrode terminal 3 protrudes is sealed by an insulating seal 4.
In the laminated battery according to the above example, the number of positive electrode plates 5 is 5 and the number of negative electrode plates 6 is 6, and the positive electrode plate 5 and the negative electrode plate 6 are located on both sides of the separator 7 via the separator 7. The outer layers are all laminated so as to be the negative electrode plate 6. However, it goes without saying that the number of positive electrode plates, the number of negative electrode plates, and the arrangement of the laminated battery are not limited to this example, and various changes may be made.

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

The lithium secondary battery of the present disclosure 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 electrolytic solution of the present disclosure. It may be a lithium secondary battery.
That is, in the lithium secondary battery of the present disclosure, first, a lithium secondary battery before charging / discharging including a negative electrode, a positive electrode, and the non-aqueous electrolytic solution of the present disclosure is prepared, and then the lithium secondary battery before charging / discharging is manufactured. It may be a lithium secondary battery (charged / discharged lithium secondary battery) manufactured 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 it can be used for various known uses. For example, notebook computer, mobile computer, mobile phone, headphone stereo, video movie, LCD TV, handy cleaner, electronic notebook, calculator, radio, backup power supply application, motor, car, electric car, bike, electric bike, bicycle, electric It can be widely used regardless of whether it is a small portable device or a large device such as a bicycle, a lighting device, a game machine, a clock, an electric tool, a camera, etc.

Hereinafter, examples of the present disclosure will be shown, but the present disclosure is not limited to the following examples.
In the following, "addition amount" means the content with respect to the total amount of the finally obtained non-aqueous electrolytic solution, and "wt%" means mass%.

[Example 1]
A coin-type lithium secondary battery (hereinafter, also referred to as “coin-type battery”) having the configuration shown in FIG. 3 was produced by the following procedure.

<Manufacturing of negative electrode>
Amorphous coated natural graphite (97 parts by mass), carboxymethyl cellulose (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 is 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 composed of a negative electrode current collector and a negative electrode active material layer. Got At this time, the coating density of the negative electrode active material layer was 10 mg / cm ² , and the packing density was 1.5 g / ml.
Here, the amorphous coated natural graphite is an example of a negative electrode active material containing natural graphite, and is a natural graphite coated with amorphous carbon.
The ratio of natural graphite to the amorphous coated natural graphite is 99% by mass.
Hereinafter, the above-mentioned amorphous coated natural graphite may be referred to as "natural graphite 1".

The R value, interplanar spacing d (002), and crystallite size of natural graphite 1 (amorphous coated natural graphite) were as follows. Since the ratio of natural graphite to natural graphite 1 (amorphous coated natural graphite) is 99% by mass, these values are substantially the values of natural graphite in natural graphite 1 (amorphous coated natural graphite). be.
R-value of Raman spectrum [I (1350) / I (1850)] = 0.123
The surface spacing d (002) of the (002) surface measured by X-ray analysis = 0.33601 nm.
・ Crystallite size measured by X-ray analysis = 61.61 Å

<Manufacturing of positive electrode>
LiCoO ₂ (90 parts by mass), acetylene black (5 parts by mass) and polyvinylidene fluoride (5 parts by mass) were kneaded with N-methylpyrrolidinone as a solvent to prepare a paste-like positive electrode mixture slurry.
Next, this positive electrode mixture slurry is applied to 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-shaped positive electrode composed of a positive electrode current collector and a positive electrode active material layer. Got At this time, the coating density of the positive electrode active material layer was 30 mg / cm ² , and the packing density was 2.5 g / ml.

<Preparation of non-aqueous electrolyte solution>
As a non-aqueous solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) were mixed at a ratio of 34:33:33 (mass ratio), respectively, and the electrolyte LiPF ₆ was finally added. It was dissolved so that the electrolyte concentration in the obtained non-aqueous electrolyte solution was 1 mol / liter.
With respect to the obtained solution, the following compound (1-1), which is a specific example of the compound represented by the formula (1), is contained as an additive in an amount of 0.5% by mass based on the total amount of the non-aqueous electrolytic solution. A non-aqueous electrolytic solution was obtained.

<Making coin-type batteries>
The above-mentioned negative electrode was punched in a disk shape with a diameter of 14 mm and the above-mentioned positive electrode was punched in a disk shape, respectively, to obtain a coin-shaped negative electrode and a coin-shaped positive electrode, respectively. 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 20 μl of a non-aqueous electrolytic solution was injected into the battery can. It was 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 crimping the battery can lid via a polypropylene gasket.
As a result, a coin-type battery having a diameter of 20 mm and a height of 3.2 mm and having the configuration shown in FIG. 3 (that is, a coin-type lithium secondary battery) was obtained.

<Evaluation>
The following evaluations were carried out on the obtained coin-type batteries.
Hereinafter, "conditioning" refers to repeating charging and discharging of a coin-type battery between 2.75V and 4.2V three times at 25 ° C. in a constant temperature bath.
Hereinafter, "high temperature storage" means an operation of storing a coin-type battery at 60 ° C. for 120 hours in a constant temperature bath.

(Battery resistance; impedance before high temperature storage (25 ° C, -10 ° C))
The coin-type battery obtained above was conditioned.
The SOC (abbreviation of State of Charge) of the coin-type battery after conditioning was adjusted to 80%, and then the impedance of the coin-type battery was measured, and the obtained result was taken as the impedance before high temperature storage. Impedance was measured under two temperature conditions of 25 ° C and −10 ° C.
Similarly, the impedance of the coin-type battery of Comparative Example 1 described later was measured before storage at high temperature.
The impedance (relative value) before high temperature storage in Example 1 was obtained as a relative value when the impedance before high temperature storage in Comparative Example 1 was set to 100.
The results are shown in Table 1.

(Battery resistance; impedance after high temperature storage (25 ° C, -10 ° C))
An operation of CC-CV charging a coin-type battery after conditioning but before adjusting the SOC to 80% at a constant temperature bath at 25 ° C. at a charging rate of 0.2 C to 4.25 V, and then performing high-temperature storage. The impedance after high temperature storage was measured in the same manner as the above-mentioned measurement of impedance before high temperature storage except that.
Similarly, the impedance of the coin-type battery of Comparative Example 1 described later was measured after high-temperature storage.
The impedance (relative value) after high temperature storage in Example 1 was obtained as a relative value when the impedance after high temperature storage in Comparative Example 1 was set to 100.
The results are shown in Table 1.

(Battery resistance; DCIR before high temperature storage (25 ° C, -20 ° C))
The coin-type battery obtained above was conditioned.
The SOC (State of Charge) of the coin-type battery after conditioning was adjusted to 80%, and then the DCIR (Direct current internal resistance) of the coin-type battery before high-temperature storage was measured by the following method. The DCIR measurement was performed under two temperature conditions of 25 ° C and −20 ° C.
Using the above-mentioned coin-type battery adjusted to SOC 80%, CC10s discharge at a discharge rate of 0.2C, pause for 300 seconds, CC10s discharge at a discharge rate of 1C, pause for 300 seconds, CC10s discharge at a discharge rate of 2C, Pause for 300 seconds and CC10s discharge at a discharge rate of 5C were performed in this order.
The CC10s discharge means to discharge at a constant current for 10 seconds.
The DC resistance was obtained based on the relationship between each discharge rate and the voltage 10 seconds after the start of discharge at each discharge rate, and the obtained DC resistance (Ω) was used as the battery resistance (Ω) before high-temperature storage of the coin-type battery. Ω).
The results are shown in Table 1.
Similarly, the DCIR before high temperature storage was measured for the coin-type battery of Comparative Example 1 described later.
The DCIR (relative value) before high temperature storage in Example 1 was obtained as a relative value when the DCIR before high temperature storage in Comparative Example 1 was set to 100.
The results are shown in Table 1.

(Battery resistance; DCIR after high temperature storage (25 ° C, -20 ° C))
An operation in which a coin-type battery after conditioning and before adjusting the SOC to 80% is charged with CC-CV to 4.25 V at a charging rate of 0.2 C at 25 ° C in a constant temperature bath, and then stored at a high temperature. The DCIR after the high temperature storage was measured in the same manner as the above-mentioned measurement of the DCIR before the high temperature storage except that the above-mentioned DCIR was measured.
Similarly, the DCIR of the coin cell battery of Comparative Example 1 described later was measured after high temperature storage.
The DCIR (relative value) after high temperature storage in Example 1 was obtained as a relative value when the DCIR after high temperature storage in Comparative Example 1 was set to 100.
The results are shown in Table 1.

(Discharge capacity after high temperature storage (residual capacity; 0.2C))
The coin-type battery obtained above was conditioned.
The conditioned coin-type battery was CC-CV charged to 4.25 V at a charging rate of 0.2 C at 25 ° C. in a constant temperature bath, and then stored at a high temperature.
The coin-type battery after high-temperature storage was CC-discharged at 25 ° C. at a discharge rate of 0.2C, and the discharge capacity (residual capacity; 0.2C) after high-temperature storage was measured.
Similarly, the discharge capacity (0.2C) of the coin-type battery of Comparative Example 1 described later was measured after high-temperature storage.
As a relative value when the discharge capacity (residual capacity; 0.2C) after high temperature storage in Comparative Example 1 is 100, the discharge capacity (residual capacity; 0.2C) (relative value) after high temperature storage in Example 1 is used. Asked.
The results are shown in Table 2.

(Discharge capacity after high temperature storage (recovery capacity; 0.2C))
The above-mentioned conditioning was applied to the coin-type battery obtained above.
The conditioned coin-type battery was CC-CV charged to 4.25 V at a charging rate of 0.2 C at 25 ° C. in a constant temperature bath, and then the coin-type battery was stored at a high temperature.
The coin-type battery after high-temperature storage is CC-discharged at 25 ° C. in a constant temperature bath at a discharge rate of 0.2 C until the SOC reaches 0%, and then CC-CV is charged to 4.2 V at a charge rate of 0.2 C. Then, CC discharge was performed at a discharge rate of 0.2 C, and the discharge capacity (recovery capacity; 0.2 C) after high temperature storage was measured.
Similarly for Comparative Example 1 described later, the discharge capacity (recovery capacity; 0.2C) of the coin-type battery after high-temperature storage was measured.
As a relative value when the discharge capacity (recovery capacity; 0.2C) after high temperature storage in Comparative Example 1 is 100, the discharge capacity (recovery capacity; 0.2C) (relative value) after high temperature storage in Example 1 is used. Asked.
The results are shown in Table 2.

(Rate of decrease in open circuit voltage after high temperature storage)
The above-mentioned conditioning was applied to the coin-type battery obtained above.
The conditioned coin-type battery was CC-CV charged to 4.25 V at a charging rate of 0.2 C at 25 ° C. in a constant temperature bath, and then the coin-type battery was stored at a high temperature.
The open circuit voltage (OCV) [V] was measured at 25 ° C. for the coin-type battery after high temperature storage, and the obtained value was taken as the open circuit voltage [V] after high temperature storage. Based on the obtained open circuit voltage [V] after high temperature storage, the open circuit voltage decrease rate was calculated by the following formula.
Open circuit voltage drop rate [%]
= ((4.25-Opening voltage after high temperature storage [V]) /4.25) × 100 [%]

Similarly for Comparative Example 1 described later, the open circuit voltage decrease rate after high temperature storage was measured.
The open-circuit voltage drop rate (relative value) after high-temperature storage in Example 1 was obtained as a relative value when the open-circuit voltage drop rate after high-temperature storage in Comparative Example 1 was 100.
The results are shown in Table 2.
The lower the open circuit voltage reduction rate of the battery, the more preferable.

[Comparative Example 1]
The same operation as in Example 1 was carried out except that the non-aqueous electrolytic solution did not contain the compound represented by the formula (1).
The results are shown in Tables 1 and 2.

[Comparative Examples 2 and 3]
The same operation as in Example 1 was carried out except that the compound (1-1) was changed to the following comparative compound (C1) or the following comparative compound (C2) having the same mass.
The results are shown in Tables 1 and 2.

In Tables 1 and 2, natural graphite 1 means the above-mentioned amorphous coated natural graphite.

As shown in Table 1, in Example 1 in which the non-aqueous electrolytic solution contained the compound represented by the formula (1), the non-aqueous electrolytic solution did not contain the compound represented by the formula (1). Compared with Example 1, the battery resistance (specifically, impedance and DCIR) was reduced.
As shown in Table 2, in Example 1 in which the non-aqueous electrolytic solution contained the compound represented by the formula (1), the non-aqueous electrolytic solution did not contain the compound represented by the formula (1). Compared with Example 1, the open circuit voltage reduction rate was improved (that is, reduced), and the battery capacity (discharge capacity) was also improved.

Further, by comparison between Example 1 and Comparative Examples 2 and 3 in Table 2, the compound represented by the formula (1) corresponding to the fused cyclic compound is a conventional cyclic sulfate ester not corresponding to the fused ring compound. It was confirmed that the compound (that is, the comparative compounds (C1) and (C2)) is superior in the effect of improving (that is, reducing) the open circuit voltage reduction rate and the effect of improving the battery capacity (discharge capacity). Was done.

[Example 101]
A coin-type battery was produced in the same manner as in Example 1.
For the produced coin-type battery, DCIR (-20 ° C.) before high-temperature storage and DCIR (-20 ° C.) after high-temperature storage were measured in the same manner as in Example 1.
The results are shown in Table 3.
In Table 3 and Table 4 described later, the measurement results of DCIR are represented by absolute values (Ω).

[Comparative Example 101]
The same operation as in Example 101 was performed except that the non-aqueous electrolytic solution did not contain the compound represented by the formula (1).
The results are shown in Table 3.

[Comparative Example 102]
The same operation as in Example 101 was performed except that the natural graphite 1 was changed to the artificial graphite 1 having the same mass and having the following properties.
The results are shown in Table 3.

The R value, interplanar spacing d (002), and crystallite size of artificial graphite 1 were as follows.
R-value of Raman spectrum [I (1350) / I (1850)] = 0.076
The surface spacing d (002) of the (002) surface measured by X-ray analysis = 0.33534 nm
・ Crystallite size measured by X-ray analysis = 131.17 Å

[Comparative Example 103]
The same operation as in Comparative Example 102 was performed except that the non-aqueous electrolytic solution did not contain the compound represented by the formula (1).
The results are shown in Table 3.

In Table 3, in comparison with Example 101 and Comparative Example 101, under the condition that the negative electrode active material is natural graphite 1, the non-aqueous electrolytic solution contains the compound represented by the formula (1) (implementation). In Example 101), it can be seen that the DCIR is reduced as compared with the case where the non-aqueous electrolytic solution does not contain the compound represented by the formula (1) (Comparative Example 101).
On the other hand, in Table 3, the non-aqueous electrolytic solution contains the compound represented by the formula (1) under the condition that the negative electrode active material is artificial graphite 1 from the comparison between Comparative Example 102 and Comparative Example 103. In the case of (Comparative Example 102), it can be seen that the DCIR is rather increased as compared with the case where the non-aqueous electrolytic solution does not contain the compound represented by the formula (1) (Comparative Example 103).

[Examples 201 to 204]
A coin-type battery was produced in the same manner as in Example 1 except that the non-aqueous electrolytic solution further contained other additives. The amount of the other additives added was 0.5% by mass.
For the produced coin-type battery, the DCIR before high-temperature storage was measured in the same manner as the measurement of DCIR before high-temperature storage in Example 101.
The results are shown in Table 4.

Other additives used in Examples 201-204 are LiBOB, compound (X1-1), compound (X2-1), and compound (X3-25), as shown below.
All of these compounds are boron compounds, and among these, the compound (X1-1), the compound (X2-1), and the compound (X3-25) are the above-mentioned boron compound (X) (that is, 1). It is a specific example of a boron compound (X) containing a structure in which three O (oxygen atoms) are bonded to one B (boron atom).
LiBOB is a boron compound other than the boron compound (X), and does not contain a structure in which three O's are bonded to one B, but instead has a structure in which four O's are bonded to one B. Includes.

As shown in Table 4, as an additive for the non-aqueous electrolytic solution, a compound represented by the formula (1) and a boron compound (X) containing a structure in which three O's are bonded to one B are used in combination. In the case of (Examples 202 to 204), as an additive for the non-aqueous electrolytic solution, a compound represented by the formula (1) and a LiBOB containing a structure in which four O's are bonded to one B are used. Compared with the case of combined use (Example 201), the battery resistance before high temperature storage (that is, the initial battery resistance) was further reduced.
The reason for this is not clear, but since the boron compound (X) has a smaller number of O bonds to B than LiBOB, it is more reactive on the edge surface of graphite, resulting in more on the negative electrode. This is thought to be due to the formation of a homogeneous film. More specifically, by using the compound represented by the formula (1) and the boron compound in combination as an additive for the non-aqueous electrolytic solution, the compound represented by the formula (1) and the boron compound are mixed. It is considered that a low resistance film is formed on the negative electrode. At this time, by selecting the boron compound (X) as the boron compound, a more homogeneous low resistance film is formed on the negative electrode, and as a result, the battery resistance before high temperature storage (that is, the initial battery resistance) is increased. It is thought that it will be reduced more effectively.

1 Laminated exterior body 2 Positive electrode terminal 3 Negative electrode terminal 4 Insulation seal 5 Positive electrode plate 6 Negative electrode plate 7, 8 Separator 11 Positive electrode 12 Negative electrode 13 Positive electrode can 14 Seal plate 15 Separator 16 Gasket 17, 18 Spacer plate

Claims (8)

A non-aqueous electrolytic solution for a battery used for a battery including a negative electrode containing a negative electrode active material containing natural graphite and having a negative electrode in which the ratio of the natural graphite to the negative electrode active material is 80% by mass or more .
A non-aqueous electrolytic solution for a battery containing a compound represented by the following formula (1).

[In the formula (1), R ¹ and R ² independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or an alkyl halide group having 1 to 3 carbon atoms. ] The non-aqueous electrolytic solution for a battery according to claim 1, wherein the content of the compound represented by the above formula (1) with respect to the total amount of the non-aqueous electrolytic solution for a battery is 0.001% by mass to 10% by mass. The non-aqueous electrolytic solution for a battery according to claim 1 or 2, further comprising a boron compound (X) containing a structure in which three oxygen atoms are bonded to one boron atom. The non-aqueous electrolytic solution for a battery according to claim 3, wherein the boron compound (X) has a molecular weight of 1000 or less. The non-water for battery according to claim 3 or 4, wherein the boron compound (X) is at least one selected from the group consisting of compounds represented by the following formulas (X1) to (X3). Electrolyte.

[In the formula (X1), ^RX11 to ^RX13 each independently represent an unsubstituted aryl group or an aliphatic group having 1 to 12 carbon atoms.
In the formula (X2), n represents an integer of 1 to 5, and M ⁺ represents a Li ⁺ ion or an H ⁺ ion. When n is an integer of 2 to 5, the plurality of M ⁺ may be the same or different.
In the formula (X3), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by the formula (RX). In the formula (RX), ^RX31 to ^RX33 independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. , And * represents the bond position. ] In formula (X1), ^RX11 to ^RX13 independently have a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a cyclohexyl group, or a phenyl group. Represents
In equation (X2), M ⁺ represents Li ⁺ ion.
The non-aqueous electrolytic solution for a battery according to claim 5, wherein R in the formula (X3) represents a group represented by the formula (RX). With the positive electrode
A negative electrode containing a negative electrode active material containing natural graphite, wherein the ratio of the natural graphite to the negative electrode active material is 80% by mass or more .
The non-aqueous electrolyte solution for a battery according to any one of claims 1 to 6.
Lithium secondary battery including. A lithium secondary battery obtained by charging / discharging the lithium secondary battery according to claim 7.

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