JP5598850B2 - Electrolyte and lithium ion secondary battery - Google Patents

Description

  The present invention relates to an electrolytic solution and a lithium ion secondary battery.

Conventionally, low molecular weight or high molecular weight organic gelling agents have been used to solidify organic liquids in various industrial fields. As a low molecular weight gelling agent, for example, a low molecular weight compound group having a hydrogen bonding functional group such as an amino group, an amide group or a urea group in the molecule is known. Low molecular weight gelling agents are suitably used in fields such as cosmetics, cosmetics, and sludge treatment.
On the other hand, the polymer gelling agent is a group of polymer compounds having a three-dimensional network structure in the molecule. As polymer gelling agents, for example, polyether compounds are well known.
There are many examples of research on polymer gelling agents, which are being developed in various fields.

  Development of low molecular weight organic gelling agents is relatively slow compared to high molecular weight ones, and there are few known types of gelling agents. As low molecular weight organic gelling agents, for example, dialkyl urea derivatives (see, for example, Patent Document 1) and perfluoroalkyl derivatives (see, for example, Patent Document 2 and Non-Patent Document 1) are known.

JP-A-8-231942 International Publication No. 2007/083843

J. et al. Fluorine Chem. 110, p47-58 (2001)

At present, various electrochemical devices are used in accordance with recent development of electronic technology and increasing interest in environmental technology. In particular, there are many requests for energy saving, and expectations for what can contribute to it are increasing. For example, a solar cell is mentioned as a power generation device, and a secondary battery, a capacitor, a capacitor, etc. are mentioned as an electrical storage device. A lithium ion secondary battery, which is a typical example of an electricity storage device, has been mainly used as a charging place for portable devices, but in recent years, it is expected to be used as a battery for hybrid vehicles and electric vehicles.
Since these electrochemical devices are used over a long period of several years to several tens of years, long life (high durability) and high safety are required in addition to high efficiency and low cost. However, in electrochemical devices, there are still problems to achieve long life and high safety.

A typical lithium ion secondary battery as an electricity storage device generally has a configuration in which a positive electrode and a negative electrode mainly composed of an active material capable of inserting and extracting lithium are arranged via a separator. In a lithium ion secondary battery, the positive electrode is LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, etc. as a positive electrode active material, carbon book or graphite as a conductive agent, polyvinylidene fluoride, latex, rubber, etc. as a binder Is mixed with a positive electrode current collector made of aluminum or the like. The negative electrode is formed by coating a negative electrode mixture made of copper or the like with a negative electrode mixture in which coke or graphite as a negative electrode active material and polyvinylidene fluoride, latex, rubber, or the like as a binder are mixed. The The separator is made of porous polyolefin or the like, and its thickness is very thin, from several μm to several hundred μm. The positive electrode, the negative electrode, and the separator are impregnated with an electrolytic solution in the battery. Examples of the electrolytic solution include an electrolytic solution in which a lithium salt such as LiPF ₆ or LiBF ₄ is dissolved in an aprotic solvent such as propylene carbonate or ethylene carbonate or a polymer such as polyethylene oxide.

Currently, lithium ion secondary batteries are mainly used as rechargeable batteries for portable devices. However, an organic solvent-based electrolyte is used for the lithium ion secondary battery, and further improvement of its safety is a major issue. In order to improve safety, for example, an ionic liquid is used as an electrolytic solution, a polymer battery or a gel battery is used, an additive for improving safety is added to the electrolytic solution, or a fluoro solvent is used. Development of batteries and the like used as electrolytes is underway.
At present, however, safety and battery characteristics are in a trade-off relationship, and both safety and battery characteristics (charge / discharge characteristics, low temperature operability, high temperature durability, etc.) are compatible. It is difficult. For example, in addition to battery safety, polymer (gel) batteries are expected from the viewpoint of battery miniaturization and increased form flexibility, but existing dry polymer batteries have high battery characteristics (especially low-temperature operability). I can't say that. Further, the gel polymer battery has an effect of improving battery characteristics (particularly rate characteristics and low temperature operability) as compared with the dry polymer battery, but does not reach the liquid electrolyte battery.

On the other hand, there are currently few examples of research on batteries using low molecular weight organic gelling agents.
Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide an electrolytic solution and a lithium ion secondary battery that have high battery characteristics and at the same time realize high safety.

  In order to achieve the above object, the present inventors have examined the possibility of applying a low molecular weight organic gelling agent to an electrolytic solution and a lithium ion secondary battery. As a result, it has been found that by using an electrolytic solution containing a specific low molecular weight organic gelling agent, both high battery characteristics and high safety can be achieved, and the present invention has been completed.

That is, the present invention is as follows.
[1]
An electrolytic solution containing a nonaqueous solvent, an electrolyte, and a compound represented by the following general formula (1).
R—O—Ar—X—C (1)
In formula (1),
R represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms in the main chain;
Ar represents a substituted or unsubstituted divalent aromatic hydrocarbon group or alicyclic hydrocarbon group having 5 to 30 nuclear atoms,
X represents a divalent group of any one of the following formulas (1a) to (1g) or a divalent group in which any one of the following formulas (1a) to (1g) is bonded;
C represents a coumarin moiety represented by the following formula (1z). In the following formula (1z), R ¹ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom.
[2]
The electrolytic solution according to [1], wherein Ar is a group selected from the group consisting of a phenylene group, a biphenylene group, a naphthylene group, a terphenylene group, and an anthranylene group.
[3]
The electrolytic solution according to [1] or [2], wherein X is a divalent group selected from the group consisting of formula (1a), formula (1e), and formula (1g).
[4]
The electrolyte solution according to any one of [1] to [3], wherein the electrolyte is a lithium salt.
[5]
The electrolytic solution according to any one of [1] to [4], wherein the electrolytic solution is gelled.
[6]
A positive electrode containing at least one material selected from the group consisting of materials capable of inserting and extracting lithium ions as a positive electrode active material;
A negative electrode containing at least one material selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium;
A lithium ion secondary battery comprising the electrolyte solution according to any one of [1] to [5].
[7]
The lithium ion secondary battery according to [6], wherein the positive electrode includes a lithium-containing compound as the positive electrode active material.
[8]
The negative electrode contains, as the negative electrode active material, one or more materials selected from the group consisting of metallic lithium, a carbon material, a material containing an element capable of forming an alloy with lithium, and a lithium-containing compound. ] Or the lithium ion secondary battery as described in [7].

According to the present invention, high battery characteristics (e.g., charge-discharge characteristics, low temperature operability) simultaneously high safety as having (e.g., leakage-reducing, Dendorai preparative inhibitory) electrolyte and lithium ion secondary also realize A battery can be provided.

FIG. 1 is an infrared absorption (IR) spectrum of the compound (3) obtained in Production Example 1. FIG. 2 is a nuclear magnetic resonance ( ¹ H-NMR) spectrum of the compound (3) obtained in Production Example 1. FIG. 3 is an infrared absorption (IR) spectrum of the compound (3) ′ obtained in Production Example 2. FIG. 4 is a nuclear magnetic resonance ( ¹ H-NMR) spectrum of the compound (3) ′ obtained in Production Example 2.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The electrolytic solution of the present embodiment contains a nonaqueous solvent, an electrolyte, and a compound having a coumarin moiety represented by the following general formula (1) (hereinafter also referred to as “compound (1)”). It is. The electrolyte solution of this embodiment is preferably gelled.
R—O—Ar—X—C (1)
(In the formula (1), R represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms in the main chain, and Ar is a divalent group having 5 to 30 substituted or unsubstituted nuclear atoms. An aromatic hydrocarbon group or an alicyclic hydrocarbon group, wherein X is any one of the following divalent groups of the following formulas (1a) to (1g) or the following formulas (1a) to (1g): A divalent group in which a plurality of groups are bonded, C represents a coumarin moiety represented by the following formula (1z), and R ¹ in the following formula (1z) independently represents a hydrogen atom or an alkyl group. Represents an alkoxy group or a halogen atom.
In addition, the lithium ion secondary battery of the present embodiment includes a positive electrode containing the above electrolyte and at least one material selected from the group consisting of materials capable of inserting and extracting lithium ions as a positive electrode active material. And a negative electrode containing at least one material selected from the group consisting of a material capable of occluding and releasing lithium ions as a negative electrode active material and metallic lithium.

<Electrolyte>
The electrolytic solution according to this embodiment contains (i) a nonaqueous solvent, (ii) an electrolyte, and (iii) a compound (1) as a gelling agent.
<(I) Nonaqueous solvent>
(I) Various solvents can be used as the nonaqueous solvent. For example, alcohols, ethers, esters, carbonates, lactones, carboxylic acid esters, phosphate triesters, heterocyclic compounds , Nitriles, ketones, amides and the like. When the electrolytic solution according to the present embodiment is used as an electrolytic solution for a lithium ion secondary battery and a lithium ion capacitor, (i) the nonaqueous solvent is preferably an aprotic solvent, and more preferably an aprotic polar solvent. . Specific examples thereof include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, and trans-2,3. -Cyclic carbonates typified by pentylene carbonate, cis-2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate and 4,5-difluoroethylene carbonate; typified by γ-butyrolactone and γ-valerolactone Lactone; cyclic sulfone represented by sulfolane; cyclic ether represented by tetrahydrofuran and dioxane; methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate Bonates, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate and chain carbonate represented by methyl trifluoroethyl carbonate; nitrile represented by acetonitrile; chain ether represented by dimethyl ether; Examples thereof include a chain carboxylic acid ester represented by methyl propionate; a chain ether carbonate compound represented by dimethoxyethane. These are used singly or in combination of two or more.

  In particular, when the electrolytic solution according to the present embodiment is used for a lithium ion secondary battery and a lithium ion capacitor, (ii) in order to increase the ionization degree of an electrolyte (for example, lithium salt) that contributes to charge / discharge, ( i) The non-aqueous solvent preferably contains one or more cyclic aprotic polar solvents. From the same viewpoint, (i) the nonaqueous solvent more preferably contains one or more cyclic carbonates typified by ethylene carbonate and propylene carbonate. The cyclic compound has a high dielectric constant, and (ii) assists the ionization of the electrolyte (for example, lithium salt) and increases the gelation ability.

(I) An ionic liquid can also be used as the non-aqueous solvent. An ionic liquid is a liquid composed of ions obtained by combining an organic cation and an anion.
Examples of the organic cation include imidazolium ions such as a dialkylimidazolium cation and a trialkylimidazolium cation, a tetraalkylammonium ion, an alkylpyridinium ion, a dialkylpyrrolidinium ion, and a dialkylpiperidinium ion.

Examples of the anion serving as a counter for these organic cations include PF ₆ anion, PF ₃ (C ₂ F ₅ ) ₃ anion, PF ₃ (CF ₃ ) ₃ anion, BF ₄ anion, and BF ₂ (CF ₃ ) ₂ anion. BF ₃ (CF ₃ ) anion, bisoxalatoborate anion, Tf (trifluoromethanesulfonyl) anion, Nf (nonafluorobutanesulfonyl) anion, bis (fluorosulfonyl) imide anion, bis (trifluoromethanesulfonyl) imide anion, bis (Pentafluoroethanesulfonyl) imide anion and dicyanoamine anion can be used.

<(Ii) Electrolyte>
In the electrolytic solution according to the present embodiment, (ii) the electrolyte is not particularly limited as long as it is used as a normal nonaqueous electrolyte, and any electrolyte may be used. When the electrolytic solution according to the present embodiment is used in a lithium ion secondary battery and a lithium ion capacitor, it is preferable that (ii) a lithium salt is used as the electrolyte. Specific examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _{2k + 1} [k is an integer of 1 to 8], LiN (SO ₂ C _k F _{2k + 1} ) ₂ [k is an integer of 1 to 8], LiPF _n (C _k F _{2k + 1} ) _6-n [n is an integer of 1 to 5, k is an integer of 1 to 8], LiBF _n (( C _k F _{2k + 1} ) _4-n [n is an integer of 1 to 3, k is an integer of 1 to 8], lithium bisoxalyl borate represented by LiB (C ₂ O ₂ ) ₂ , LiBF ₂ (C ₂ lithium difluoro oxalyl borate represented by O _2), include lithium trifluoromethane oxalyl phosphate represented by _{LiPF 3 (C 2 O 2)} .

Moreover, the lithium salt represented by the following general formula (3a), (3b) or (3c) can also be used as (ii) electrolyte.
LiC (SO ₂ R ¹¹ ) (SO ₂ R ¹² ) (SO ₂ R ¹³ ) (3a)
LiN (SO ₂ OR ¹⁴ ) (SO ₂ OR ¹⁵ ) (3b)
LiN (SO ₂ R ¹⁶ ) (SO ₂ OR ¹⁷ ) (3c)
Here, in the formula, R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ may be the same or different from each other, and are a C 1-8 perfluoroalkyl group. Indicates.

These electrolytes are used singly or in combination of two or more. In the applications of lithium ion secondary batteries and lithium ion capacitors, among these electrolytes, LiPF ₆ , LiBF ₄ and LiN (SO ₂ C _k F _{2k + 1} ) ₂ [k is an integer of 1 to 8] is preferable.

  (Ii) The concentration of the electrolyte is arbitrary and not particularly limited, but is preferably 0.1 to 3 mol / liter, more preferably 0.5 to 2 mol / liter in the electrolytic solution.

<(Iii) Gelling agent>
In the electrolytic solution according to the present embodiment, (iii) a compound represented by the following general formula (1) is used as the gelling agent.
R—O—Ar—X—C (1)
(In the formula (1), R represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms in the main chain, and Ar is a divalent group having 5 to 30 substituted or unsubstituted nuclear atoms. An aromatic hydrocarbon group or an alicyclic hydrocarbon group, wherein X is any one of the following divalent groups of the following formulas (1a) to (1g) or the following formulas (1a) to (1g): A divalent group in which a plurality of groups are bonded, C represents a coumarin moiety represented by the following formula (1z), and R ¹ in the following formula (1z) independently represents a hydrogen atom or an alkyl group. Represents an alkoxy group or a halogen atom.

The compound represented by the general formula (1) (hereinafter also referred to as “compound (1)”) is an aromatic compound having a coumarin moiety.
In the general formula (1), Ar represents a substituted or unsubstituted divalent aromatic hydrocarbon group or alicyclic hydrocarbon group having 5 to 30 nucleus atoms. The divalent aromatic hydrocarbon group is a cyclic divalent group exhibiting so-called “aromaticity”. This divalent aromatic hydrocarbon group may be a carbocyclic group or a heterocyclic group. These divalent aromatic hydrocarbon groups may be substituted with a substituent or may be an unsubstituted one that is not substituted. A substituent of the divalent aromatic hydrocarbon group can be selected from the viewpoint of synthesis or availability of raw materials. Alternatively, the substituent of the divalent aromatic hydrocarbon group can be selected from the viewpoint of the melting temperature and gelling ability of the gelling agent.

The carbocyclic group has 6 to 30 nuclear atoms, may be substituted with a substituent, or may be unsubstituted or unsubstituted. Specific examples thereof include divalent groups having a nucleus represented by a phenylene group, a biphenylene group, a terphenylene group, a naphthylene group, an anthranylene group, a phenanthrylene group, a pyrenylene group, a chrysenylene group, and a fluoranthenylene group. It is done.
The heterocyclic group has 5 to 30 nuclear atoms, and includes, for example, a nucleus represented by a pyrrolene group, a furylene group, a thiophenylene group, a triazolen group, an oxadiazolene group, a pyridylene group, and a pyrimidylene group. And a divalent group.
Ar is preferably a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 20 nuclear atoms, from the viewpoints of availability of raw materials and ease of synthesis, and gelation ability in an electrolyte solution. A group selected from the group consisting of a group, a biphenylene group, a naphthylene group, a terphenylene group, and an anthranylene group is more preferable. More preferred are a phenylene group, a biphenylene group, a naphthylene group, and a terphenylene group.
Moreover, as said substituent, the alkyl group represented by the methyl group and the ethyl group, and a halogen atom are mentioned.

  The alicyclic hydrocarbon group has 5 to 30 nuclear atoms, and examples thereof include a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group.

  An aromatic hydrocarbon group or an alicyclic hydrocarbon group has a combination of a plurality of groups as long as the number of nuclear atoms is within the above range, or has both a carbocyclic ring and a heterocyclic ring. It can also have both an alicyclic group.

R represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms in the main chain, and may be saturated or unsaturated. R may be an aliphatic hydrocarbon group and may further have an aromatic hydrocarbon group. Part or all of the hydrocarbon group may be substituted with a halogen atom. When this hydrocarbon group is a monovalent aliphatic hydrocarbon group, it may be branched or unbranched, and a part or all of the branched chain may be substituted with a halogen atom. One or more oxygen and / or sulfur atoms may be contained in the main chain.
Furthermore, when the monovalent hydrocarbon group has an aromatic hydrocarbon group, the aromatic hydrocarbon group may or may not further have a substituent. However, the monovalent hydrocarbon group includes an arylalkyl group typified by a benzyl group in order for the compound (1) to be dissolved in a non-aqueous solvent and to gel an electrolyte solution containing the non-aqueous solvent. It must be a hydrocarbon group that makes the compound (1) soluble in a non-aqueous solvent. When the monovalent hydrocarbon group has 21 or more carbon atoms, it becomes difficult to obtain the raw material. The monovalent hydrocarbon group represented by R is preferably an alkyl group having 4 to 18 carbon atoms, more preferably an alkyl group having 4 to 14 carbon atoms, from the viewpoint of more effectively and reliably achieving the above-described effects in the present embodiment. More preferably. R is preferably a linear alkyl group from the viewpoints of gelling ability and handling properties.

X represents a divalent group of any one of the above formulas (1a) to (1g) or a divalent group in which any one of the above formulas (1a) to (1g) is bonded. From the viewpoint of the balance between gelling ability and battery characteristics, X is preferably a divalent group selected from the group consisting of the above formula (1a), the above formula (1e) and the above formula (1g).
X needs to be selected from the point that it is stable for a long time and the gelling ability when the compound (1) is used in an electrochemical device. When X is a divalent group represented by the above formula (1a), a very stable gel tends to be formed. Further, when X is a divalent group represented by the above formula (1e), the gel-sol transition can be induced not only by temperature but also by light irradiation, leading to expansion of applications.
C represents a coumarin moiety represented by the above formula (1z). In the following formula (1z), R ¹ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom.

Examples of the compound (1) include the compounds described in the liquid crystal discussion conference proceedings collection p44 (2007), and the compound is a known compound. Moreover, the compound (1) which has an azo group is compoundable by the following reaction pathways, for example.
Examples of the compound (1) having an azo group synthesized as described above include a compound represented by the following formula (I) (hereinafter also referred to as “compound (I)”) and a compound represented by the following formula (II). (Hereinafter also referred to as “compound (II)”).
Hereafter, the synthesis method of compound (I) and (II) is demonstrated in detail.
[Synthesis Method of Compound (I)]
Step 1: Synthesis of compound (a)
Add a mixed solution of concentrated nitric acid and concentrated sulfuric acid to the eggplant flask. While cooling the eggplant flask in an ice bath, coumarin is gradually added so that the temperature of the mixed solution does not exceed 20 ° C. When all the coumarin has been added, remove the ice bath and stir at room temperature for 1 hour to react. The reaction solution is poured into water, and the precipitated solid is collected by filtration. The solid collected by filtration is recrystallized from toluene to obtain a light yellow solid compound (a).
Step 2: Synthesis of compound (b)
In an eggplant flask, the compound (a) is dissolved in a mixed solution of ethanol and toluene, and a hydrogenation reaction is performed in the presence of Pd / C. After the hydrogenation reaction, Pd / C is collected by filtration, and the filtrate is concentrated by an evaporator. The precipitated solid is recrystallized from toluene to obtain a yellow solid compound (b).
Step 3: Synthesis of compound (c)
In an eggplant flask, an aqueous solution of 12N hydrochloric acid and water is prepared under ice-cooling at 5 ° C. Compound (b) and sodium nitrite (NaNO ₂ ) are added to the aqueous solution and stirred for 20 minutes. Further, a mixed solution of phenol, sodium hydroxide and water is added and stirred. The precipitated solid is recrystallized from toluene to obtain compound (c).
Step 4: Synthesis of Compound (I)
In an eggplant flask, compound (c) is dissolved in 3-pentanone. 1-Bromooctane and potassium carbonate are added to the obtained solution and refluxed for 15 hours. The obtained solid is recrystallized from toluene and purified by column chromatography to obtain compound (I). In the column chromatography, silica gel is used as a filler and chloroform is used as a developing solvent.
[Synthesis Method of Compound (II)]
In an eggplant flask, compound (c) is dissolved in 3-pentanone. 1-Bromohexane and potassium carbonate are added to the obtained solution and refluxed for 15 hours. The obtained solid is recrystallized from toluene and purified by column chromatography to obtain compound (II). In the column chromatography, silica gel is used as a filler and chloroform is used as a developing solvent.

  However, the manufacturing method of compound (1) is not limited to the said method.

  By adding a small amount of a compound (1) of about 5% or less to an electrolytic solution containing various nonaqueous solvents, the electrolytic solution can be gelled. The compound (1) is added to an electrolyte solution containing a non-aqueous solvent, dissolved by heating, and the resulting solution is gelled by returning it to room temperature. An electrolyte containing a high dielectric constant solvent suitable for the electrolyte, such as a cyclic carbonate represented by propylene carbonate and butylene carbonate; a lactone represented by γ-butyrolactone and γ-valerolactone; a nitrile represented by acetonitrile, etc. For example, by adding a small amount of the compound (1) of about 0.3 to 5% by mass, preferably about 0.5 to 3% by mass, the electrolytic solution can be gelled. By gelling the electrolyte, safety can be improved in terms of leakage reduction and combustion delay.

When the electrolytic solution containing the compound (1) is used in the lithium ion secondary battery of this embodiment described later, the electrolytic solution includes LiClO ₄ , LiPF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ An electrolyte solution in which a lithium salt such as F ₅ SO ₂ ) ₂ , LiBF ₄ , or LiOSO ₂ CF ₃ is dissolved in a non-aqueous solvent and then compounded with the compound (1) is preferred.

  The gelling agent mentioned above is used individually by 1 type or in combination of 2 or more types.

  The mixing ratio of the gelling agent and the non-aqueous solvent is arbitrary, but the gelling agent: non-aqueous solvent is 0.1: 99.9 on a mass basis from the viewpoint of improving the gelling ability and handling properties. -20: 80, preferably 0.3: 99.7 to 10:90, and more preferably 0.3: 99.7 to 5:95. The more the gelling agent, the stronger the phase transition point and the stronger the gel. The less the gelling agent, the lower the viscosity and the easier to handle the gel.

The mixing ratio of the nonaqueous solvent, the electrolyte (for example, lithium salt), and the gelling agent can be selected according to the purpose. The gelling agent is preferably used on a mass basis with respect to a mixed solution in which an electrolyte (for example, a lithium salt) is mixed in a non-aqueous solvent preferably in an amount of 0.1 to 3 mol / liter, more preferably 0.5 to 2 mol / liter. Gelling agent: non-aqueous solvent, preferably 0.1: 99.9 to 20:80, more preferably 0.3: 99.7 to 10:90, still more preferably 0.3: 99.7 to 5 : It is preferable to add 95. By preparing the electrolytic solution with such a composition, all of the battery characteristics, handleability and safety can be further improved.
<Lithium ion secondary battery>
The lithium ion secondary battery of the present embodiment includes a positive electrode containing one or more materials selected from the group consisting of materials capable of inserting and extracting lithium ions as a positive electrode active material, and lithium ions as a negative electrode active material. A negative electrode containing at least one material selected from the group consisting of a material capable of occluding and releasing lithium and metallic lithium, and the above-described electrolytic solution.

<Positive electrode>
In the lithium ion secondary battery of this embodiment, the positive electrode is not particularly limited as long as it functions as the positive electrode of the lithium ion secondary battery, and may be a known one. In the lithium ion secondary battery of this embodiment, the positive electrode contains one or more materials selected from the group consisting of materials capable of inserting and extracting lithium ions as the positive electrode active material. Examples of such materials include composite oxides represented by the following general formulas (6a) and (6b), metal chalcogenides and metal oxides having a tunnel structure and a layered structure.
Li _x MO ₂ (6a)
Li _y M ₂ O ₄ (6b)
Here, in the formula, M represents one or more metals selected from transition metals, x represents a number from 0 to 1, and y represents a number from 0 to 2.

More specifically, for example, lithium cobalt oxide typified by LiCoO ₂ ; lithium manganese oxide typified by LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ ; lithium nickel typified by LiNiO ₂ Oxide; represented by Li _z MO ₂ (M represents two or more elements selected from the group consisting of Ni, Mn, Co, Al, and Mg, and z represents a number greater than 0.9 and less than 1.2). And lithium-containing composite metal oxide; and iron phosphate olivine represented by LiFePO ₄ . Further, as the positive electrode active material, for example, a metal other than lithium represented by S, MnO ₂ , FeO ₂ , FeS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS ₂ , MoS ₂ and NbSe ₂ is used. Oxides are also exemplified. Furthermore, conductive polymers represented by polyaniline, polythiophene, polyacetylene, and polypyrrole are also exemplified as the positive electrode active material.

In the lithium ion secondary battery of this embodiment, the positive electrode preferably includes a lithium-containing compound as a positive electrode active material.
In the lithium ion secondary battery of the present embodiment, it is preferable that the positive electrode contains a lithium-containing compound as a positive electrode active material because high voltage and high energy density tend to be obtained. As such a lithium-containing compound, any compound containing lithium may be used. For example, a composite oxide containing lithium and a transition metal element, a phosphate compound containing lithium and a transition metal element, and lithium and a transition metal element (For example, Li _{t Mu} SiO ₄ , where M is as defined in the above formula (6a), t is a number from 0 to 1, and u is a number from 0 to 2). . From the viewpoint of obtaining a higher voltage, lithium, cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), vanadium ( V) and composite oxides containing at least one transition metal element selected from the group consisting of titanium (Ti) and phosphate compounds are preferred.

More specifically, the lithium-containing compound is preferably a metal oxide having lithium, a metal chalcogenide having lithium, and a metal phosphate compound having lithium. For example, the lithium-containing compounds are represented by the following general formulas (7a) and (7b), respectively. The compound which is made is mentioned.
^{_{Li v M I O 2 (7a}} )
Li _w M ^II PO ₄ (7b)
Here, in the formula, M ^I and M ^II each represent one or more transition metal elements, and the values of v and w vary depending on the charge / discharge state of the battery, but usually v is 0.05 to 1.10, w Indicates a number from 0.05 to 1.10.

  The compound represented by the general formula (7a) generally has a layered structure, and the compound represented by the general formula (7b) generally has an olivine structure. In these compounds, for the purpose of stabilizing the structure, a part of the transition metal element is substituted with Al, Mg, other transition metal elements or included in the crystal grain boundary, a part of the oxygen atom And those substituted with a fluorine atom or the like. Furthermore, what coat | covered the other positive electrode active material to at least one part of the positive electrode active material surface is mentioned.

  The positive electrode active material mentioned above is used individually by 1 type or in combination of 2 or more types. When using in combination of 2 or more types, it may be a mixture or a solid solution.

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

The positive electrode is obtained, for example, as follows. That is, first, a positive electrode mixture-containing paste is prepared by dispersing, in a solvent, a positive electrode mixture obtained by adding a conductive additive, a binder, or the like to the positive electrode active material as necessary. Next, this positive electrode mixture-containing paste is applied to a positive electrode current collector and dried to form a positive electrode mixture layer, which is pressurized as necessary to adjust the thickness, thereby producing a positive electrode.
Here, the solid content concentration in the positive electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass.
The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil or a stainless steel foil.

<Negative electrode>
In the lithium ion secondary battery of this embodiment, the negative electrode is not particularly limited as long as it functions as the negative electrode of the lithium ion secondary battery, and may be a known one. In the lithium ion secondary battery of the present embodiment, the negative electrode contains at least one material selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium.
In the lithium ion secondary battery of the present embodiment, the negative electrode is selected from the group consisting of metallic lithium, a carbon material, a material containing an element capable of forming an alloy with lithium, and a lithium-containing compound as the negative electrode active material. It is preferable to contain one or more materials.
As a material constituting the negative electrode active material, in addition to lithium metal, for example, amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, a fired body of an organic polymer compound, Examples include carbon materials represented by mesocarbon microbeads, carbon fibers, activated carbon, graphite, carbon colloid, and carbon black. Among these, examples of the coke include pitch coke, needle coke, and petroleum coke. Further, the fired body of the organic polymer compound is obtained by firing and polymerizing a polymer material such as a phenol resin or a furan resin at an appropriate temperature. In the present embodiment, a battery employing metallic lithium as the negative electrode active material is also included in the lithium ion secondary battery.

  Further, examples of the material capable of inserting and extracting lithium ions include a material containing an element capable of forming an alloy with lithium. This material may be a single metal or semi-metal, an alloy or a compound, and may have at least a part of one or more of these phases. .

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

  Examples of such metal elements and metalloid elements include titanium (Ti), tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), and antimony (Sb). Bismuth (Bi), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium (Zr) and yttrium (Y).

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

  As an alloy of tin, for example, as a second constituent element other than tin, silicon, magnesium (Mg), nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium (Ti), germanium, bismuth, Examples thereof include those having one or more elements selected from the group consisting of antimony and chromium (Cr).

  Examples of the silicon alloy include, as the second constituent element other than silicon, tin, magnesium, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. Those having one or more elements selected from the above are listed.

  Examples of the titanium compound, the tin compound, and the silicon compound include those having oxygen (O) or carbon (C), and in addition to titanium, tin, or silicon, the second constituent element described above is included. It may be.

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

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

A negative electrode is obtained as follows, for example. That is, first, a negative electrode mixture-containing paste is prepared by dispersing, in a solvent, a negative electrode mixture prepared by adding a conductive additive or a binder to the negative electrode active material, if necessary. Next, the negative electrode mixture-containing paste is applied to a negative electrode current collector and dried to form a negative electrode mixture layer, which is pressurized as necessary to adjust the thickness, thereby producing a negative electrode.
Here, the solid content concentration in the negative electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass.
The negative electrode current collector is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  Examples of the conductive aid used as necessary in the production of the positive electrode and the negative electrode include graphite, carbon black typified by acetylene black and ketjen black, and carbon fiber. The number average particle size (primary particle size) of the conductive assistant is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm, and is measured in the same manner as the number average particle size of the positive electrode active material. Examples of the binder include polyvinylidene fluoride (PVDF), a copolymer containing polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber.

<Separator>
The lithium ion secondary battery of the present embodiment preferably includes a separator between the positive electrode and the negative electrode from the viewpoint of providing safety such as prevention of short circuit between the positive and negative electrodes and shutdown. The separator may be the same as that provided for a known lithium ion secondary battery, and is preferably an insulating thin film having high ion permeability and excellent mechanical strength. Examples of the separator include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable. As the synthetic resin microporous membrane, for example, a microporous membrane containing polyethylene or polypropylene as a main component or a polyolefin microporous membrane such as a microporous membrane containing both of these polyolefins is preferably used. As the nonwoven fabric, a porous film made of a heat-resistant resin such as ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, or aramid is used.
The separator may be a single microporous membrane or a laminate of a plurality of microporous membranes, or may be a laminate of two or more microporous membranes.

<Method for manufacturing lithium ion secondary battery>
The lithium ion secondary battery of this embodiment is produced by a known method using the above-described electrolytic solution, positive electrode, negative electrode, and, if necessary, a separator. For example, a plurality of positive electrodes in which a positive electrode and a negative electrode are wound in a laminated state with a separator interposed therebetween to be formed into a laminate having a wound structure, or they are alternately laminated by bending or laminating a plurality of layers. Or a laminate in which a separator is interposed between the electrode and the negative electrode. Next, the laminated body is accommodated in a battery case (exterior), the electrolytic solution according to the present embodiment is injected into the case, and the laminated body is immersed in the electrolytic solution and sealed. The lithium ion secondary battery can be manufactured. Alternatively, an electrolyte membrane containing a gelled electrolyte solution is prepared in advance, and a positive electrode, a negative electrode, an electrolyte membrane, and a separator as necessary are formed by bending or stacking as described above, and then a battery case A lithium ion secondary battery can also be produced by being housed inside. The shape of the lithium ion secondary battery of the present embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, and a laminated shape are suitably employed.

  Since the electrolytic solution of the present embodiment can achieve high conductivity (diffusion of lithium ions and transport number of lithium ions) and high safety (for example, liquid retention), the lithium of the present embodiment provided with the electrolytic solution. The ion secondary battery has high battery characteristics (for example, charge / discharge characteristics, low temperature operability, etc.) and at the same time realizes high safety (suppression of lithium dendrite). Specifically, since the electrolytic solution of the present embodiment contains a gelling agent that has little influence on its properties, the lithium ion secondary battery of the present embodiment including the electrolytic solution is particularly suitable for conventional polymer batteries. It is possible to suppress a significant decrease in the conductivity at low temperatures and battery characteristics. In addition, since the electrolytic solution contains the gelling agent, it is possible to prevent leakage of the electrolytic solution to the outside of the battery, and the lithium ion secondary battery of the present embodiment has a risk of lithium dendrite and combustion. This risk can be further reduced.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the said embodiment. The present invention can be variously modified without departing from the gist thereof.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. Various characteristics and safety of the electrolytic solution and the lithium ion secondary battery were measured and evaluated as follows.

(I) Evaluation of gelling ability of electrolyte solution After preparing an electrolyte solution in a glass sample bottle and leaving it to stand at 25 ° C for 2 hours, the sample bottle is turned upside down to check the fluidity at that time. Noh was evaluated. Those that do not flow are evaluated as “gels”, the mixing ratio of the non-aqueous solvent and the gelling agent is changed, and the minimum concentration of gelling agent required to gel the electrolyte (based on the total amount of electrolyte) The concentration of the gelling agent) was determined as the gelation concentration.

(Ii) Liquid retention test of electrolytic solution After sufficiently impregnating a 5 cm ² × 0.012 cm polypropylene nonwoven fabric (porosity 73%) with an electrolytic solution component, the nonwoven fabric is sandwiched between two glass plates. Samples were prepared. The sample was placed on a table, the sample was pressurized from one side (upper surface) with a hydraulic press, and the pressure at the start of liquid leakage was measured. Moreover, the sample which impregnated the electrolyte solution to the said nonwoven fabric was pressurized to 4 kgf / cm < ² > (about 0.39 MPa), and the liquid retention amount was calculated | required by measuring a sample weight. Furthermore, since the theoretical amount of impregnation of the pressurized nonwoven fabric is 0.0214 g, the liquid retention rate was determined by the following formula.
Retention rate (%) = retention amount (g) /0.0214×100

(Iii) Measurement of discharge capacity of lithium ion secondary battery The discharge capacity of a lithium ion secondary battery was evaluated by measuring the discharge capacity at a specific discharge current. As a lithium ion secondary battery for measurement, a small battery with 1C = 6 mA was prepared and used. The measurement was performed using a charge / discharge device ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-63S (trade name) manufactured by Futaba Kagaku Co., Ltd. After charging at a constant current of 6 mA and reaching 4.2 V, charging was performed at a constant voltage of 4.2 V for a total of 3 hours. Then, the discharge capacity when discharging to 3.0 V with a constant current was measured. The discharge capacity was measured by setting the discharge current to 6 mA and 18 mA. The battery ambient temperature at this time was set to 25 ° C.

(Iv) Capacity maintenance rate measurement of lithium ion secondary battery (cycle test)
The capacity retention rate was measured using a charge / discharge device ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-63S (trade name) manufactured by Futaba Kagaku Co., Ltd. As the lithium ion secondary battery for measurement, a battery produced in the same manner as “(iii) Measurement of discharge capacity of lithium ion secondary battery” was used. In the charge / discharge cycle test, first, the battery was charged at a constant current of 6 mA, reached 4.2 V, and then charged at a constant voltage of 4.2 V for a total of 3 hours. Thereafter, the battery was discharged at a constant current of 6 mA, and when it reached 3.0 V, charging was repeated again. Charging and discharging were performed once each as one cycle, and 100 cycles of charging and discharging were performed. The discharge capacity at the 100th cycle when the discharge capacity at the second cycle was taken as 100% was taken as the capacity retention rate. The ambient temperature of the battery was set to 25 ° C.

(V) Measurement of discharge capacity of lithium ion secondary battery at low temperature The battery ambient temperature was set to −20 ° C., −10 ° C., and 0 ° C. respectively, and “(iii) Measurement of discharge capacity of lithium ion secondary battery” Similarly, the discharge capacity was measured. The discharge capacity was measured with a discharge current of 3 mA.

(Vi) Lithium Deposition Test for Lithium Ion Secondary Battery As a lithium ion secondary battery for the lithium deposition test, a single layer laminate type battery with 1C = 45.0 mA was prepared and used. The battery charged to 4.2 V at a constant current of 9.0 mA was discharged to 3.0 V at 9.0 mA, and further charged for 1.5 hours at a constant current of 45 mA. The rechargeable battery was disassembled in an atmosphere having a dew point of -60 ° C. or lower and a water concentration of 10 ppm or lower. The negative electrode surface of the disassembled battery was observed with an optical microscope having a magnification of 2000 times, and the lithium deposition behavior was evaluated according to the following criteria.
A: No precipitation of lithium is observed.
B: Precipitation of lithium is observed, but the surface of the precipitate is smooth.
C: Precipitation of lithium is observed, and sharp dendrites are observed on the surface of the precipitate.
In addition, precipitation of dendrite causes a short circuit of the battery, and causes a decrease in battery safety.
(Production Example 1)
[Method for Synthesizing Compound (3)]
Step 1: Synthesis of compound (a)
A mixed solution of 34.5 ml of concentrated nitric acid and 34.5 ml of concentrated sulfuric acid was added to a 300 ml eggplant flask. While cooling the eggplant flask in an ice bath, 15.0 g of coumarin was gradually added so that the temperature of the mixed solution did not exceed 20 ° C. When all the coumarin was added, the ice bath was removed and the reaction was allowed to stir at room temperature for 1 hour. The reaction solution was poured into 200 ml of water, and the precipitated solid was collected by filtration. The solid collected by filtration was recrystallized from toluene to obtain 13.1 g of light yellow solid compound (a) (yield: 66%). The melting point of the compound (a) was 188 to 189 ° C. IR data and ¹ H-NMR data of the compound (a) are shown below.
・ IR (KBr)
^{ν N-O; 1350cm -1,} 1530cm -1
ν C = O; 1700 cm ^-1
・¹ H-NMR (DMSO-d6)
δ = 6.69 (1H, d, J = 8.9 Hz), 7.62 (1H, d, J = 8.9 Hz), 8.23 (1H, d, J = 9.9 Hz), 8.41 (1H, dd, J = 9.9, 2.6 Hz), 8.73 (1H, d, J = 2.6 Hz) ppm
Step 2: Synthesis of compound (b)
In a 300 ml eggplant flask, 5.02 g of compound (a) was dissolved in a mixed solution of 100 ml of ethanol and 100 ml of toluene, and a hydrogenation reaction was performed in the presence of Pd / C. After the hydrogenation reaction, Pd / C was collected by filtration, and the filtrate was concentrated with an evaporator. The precipitated solid was recrystallized from toluene to obtain 1.97 g of a yellow solid compound (b) (yield: 78%). The melting point of the compound (b) was 160 to 162 ° C. IR data and ¹ H-NMR data of the compound (b) are shown below.
・ IR (KBr)
ν C = O; 1700 cm ^-1
ν N—H; 3360 cm ⁻¹ , 3470 cm ⁻¹
・¹ H-NMR (DMSO)
δ = 5.24 (2H, s), 6.33 (1H, d, J = 9.6 Hz), 6.72 (1H, d, J = 2.6 Hz), 6.83 (1H, dd, J = 8.6, 2.6 Hz), 7.09 (1H, d, J = 8.6 Hz), 7.87 (1H, d, J = 9.6 Hz) ppm
Step 3: Synthesis of compound (c)
In a 300 ml eggplant flask, an aqueous solution of 12.7 ml of 12N hydrochloric acid and 14.4 ml of water was prepared under ice cooling at 5 ° C. To the aqueous solution, 1.97 g of the compound (b) and 1.13 g of sodium nitrite (NaNO ₂ ) were added and stirred for 20 minutes. Furthermore, a mixed solution of 1.93 g of phenol, 0.96 g of sodium hydroxide and 14.7 ml of water was added and stirred. The precipitated solid was recrystallized from toluene to obtain 2.69 g of compound (c) (yield: 84%). The melting point of the compound (c) was 250 ° C. or higher. IR data and ¹ H-NMR data of the compound (c) are shown below.
・ IR (KBr)
ν C = O; 1700 cm ^-1
ν O—H; 3200 cm ⁻¹
・¹ H-NMR (DMSO)
δ = 4.24 (1H, s), 6.55 (1H, d, J = 9.6 Hz), 6.77 (2H, d, J = 8.9 Hz), 7.51 (1H, d, J = 8.9 Hz), 7.73 (2H, d, J = 8.9 Hz), 8.02 (1H, dd, J = 8.9, 2.3 Hz), 8.15 (1H, d, J = 2.3 Hz), 8.20 (1H, d, J = 9.6 Hz) ppm
Step 4: Synthesis of compound (3)
In a 300 ml eggplant flask, 2.03 g of compound (c) was dissolved in 150 ml of 3-pentanone. To the resulting solution, 1.66 g of 1-bromooctane and 1.07 g of potassium carbonate were added and refluxed for 15 hours. The obtained solid was recrystallized from toluene and purified by column chromatography to obtain 1.40 g of compound (3) (yield: 44%). In the column chromatography, silica gel was used as a filler and chloroform was used as a developing solvent.
The melting point of the compound (3) was 136 to 138 ° C. IR data and ¹ H-NMR data of the compound (3) are shown below. The IR spectrum and ¹ H-NMR spectrum of the compound (3) are shown in FIGS.
・ IR (KBr)
ν C = O; 1700 cm ^-1
ν C—H; 3070 cm ⁻¹
・¹ H-NMR (CDCl ₃ )
δ = 0.89 (3H, t, J = 6.6 Hz), 1.27-1.58 (10H, m), 1.83 (2H, q, J = 6.6 Hz), 4.05 (2H) Q, J = 6.6 Hz), 6.49 (1H, d, J = 9.6 Hz), 7.01 (2H, d, J = 8.9 Hz), 7.43 (1H, d, J = 8.6 Hz), 7.81 (1H, d, J = 9.6 Hz), 7.91 (2H, d, J = 8.9 Hz), 8.00 (1H, d, J = 2.3 Hz), 8.10 (1H, dd, J = 8.9, 2.3 Hz) ppm
(Production Example 2)
[Method for Synthesizing Compound (3) ′]
In a 300 ml eggplant flask, 3.00 g of compound (c) was dissolved in 150 ml of 3-pentanone. To the obtained solution, 1.99 g of 1-bromohexane and 1.57 g of potassium carbonate were added and refluxed for 15 hours. The obtained solid was recrystallized from toluene and purified by column chromatography to obtain 1.00 g of compound (3) (yield: 43%). In the column chromatography, silica gel was used as a filler and chloroform was used as a developing solvent.
The melting point of the compound (3) ′ was 140 to 143 ° C. IR data and ¹ H-NMR data of the compound (3) ′ are shown below. Further, the IR spectrum and ¹ H-NMR spectrum of the compound (3) ′ are shown in FIGS.
・ IR (KBr)
ν C═O; 1730 cm ⁻¹
ν C—H; 2940 cm ⁻¹
・¹ H-NMR (CDCl ₃ )
δ = 0.92 (3H, t, J = 6.9 Hz), 1.33-1.57 (6H, m), 1.83 (2H, quin., J = 6.6 Hz), 4.03 ( 2H, q, J = 6.6 Hz), 6.52 (1H, d, J = 9.5 Hz), 7.02 (2H, d, J = 8.9 Hz), 7.46 (1H, d, J = 8.6 Hz), 7.80 (1H, d, J = 9.5 Hz), 7.92 (2H, d, J = 8.9 Hz), 8.00 (1H, d, J = 2.3 Hz) , 8.09 (1H, dd, J = 8.6, 2.3 Hz) ppm

Example 1
Preparation of electrolyte solution Ethylene carbonate and methyl ethyl carbonate are mixed at a mass ratio of 1: 2, and LiPF ₆ is added to the mixture solution to a concentration of 1 mol / L, and electrolysis is not gelled. A liquid (A) was prepared (hereinafter, the electrolytic solution before addition of the gelling agent is referred to as “mother electrolytic solution”). To the mother electrolyte (A), a compound represented by the following formula (2) is added as a gelling agent, heated to 70 ° C. and uniformly mixed, then cooled to 25 ° C., and the electrolyte ( a) was obtained. In addition, when the gelling agent was gradually added to the mother electrolyte from a small amount, when the addition amount reached 2.0% by mass with respect to the total amount of the electrolyte, The addition of gelling agent was stopped. That is, the content of the gelling agent with respect to the total amount of the electrolytic solution (a) was 2.0% by mass.
In addition, compound (2) is Mol. Cryst. Liq. Cryst. Vol. 439, p209-220.

(Example 2)
Instead of the mother electrolyte (A), ethylene carbonate, propylene carbonate, and γ-butyrolactone were mixed at a mass ratio of 1: 1: 2, and LiBF ₄ was added to the mixture at 1.5 mol / L. An electrolytic solution (b) was obtained in the same manner as in Example 1 except that the mother electrolytic solution (B) prepared by adding the same was used. The content of the gelling agent with respect to the total amount of the electrolytic solution (b) was 2.0% by mass.

(Example 3)
As a gelling agent, an electrolytic solution (c) was obtained in the same manner as in Example 1 except that a compound represented by the following formula (3) was used instead of the compound represented by the above formula (2). . The content of the gelling agent with respect to the total amount of the electrolytic solution (c) was 1.0% by mass.

Example 4
An electrolytic solution (d) was obtained in the same manner as in Example 2, except that the compound represented by the above formula (2) was used as the gelling agent instead of the compound represented by the above formula (2). . The content of the gelling agent with respect to the total amount of the electrolytic solution (d) was 1.0% by mass.

  About the electrolyte solution obtained in Examples 1-4, evaluation as described in the said "(i) Evaluation of the gelatinization ability of electrolyte solution" was performed. The results are shown in Table 1.

(Example 5)
The electrolytic solution (a) was subjected to the test described in the above “(ii) Electrolytic solution retention test”. The results are shown in Table 2.
(Example 6)
The electrolyte solution (c) was subjected to the test described in the above “(ii) Electrolyte solution retention test”. The results are shown in Table 2.
(Comparative Example 1)
The mother electrolyte (A) was subjected to the test described in “(ii) Liquid retention test of electrolyte”. The results are shown in Table 2.

(Example 7)
<Preparation of positive electrode>
Lithium nickel, manganese and cobalt mixed oxide having a number average particle diameter of 11 μm as a positive electrode active material, graphite carbon powder having a number average particle diameter of 6.5 μm and acetylene black powder having a number average particle diameter of 48 nm as a conductive auxiliary agent, and a binder Polyvinylidene fluoride (PVDF) as a mixed oxide: graphite carbon powder: acetylene black powder: PVDF = 100: 4.2: 1.8: 4.6. N-methyl-2-pyrrolidone was added to the obtained mixture so as to have a solid content of 68% by mass and further mixed to prepare a slurry solution. This slurry-like solution was applied to one side of an aluminum foil having a thickness of 20 μm, and the solvent was dried and removed, followed by rolling with a roll press. The rolled product was punched into a disk shape having a diameter of 16 mm to obtain a positive electrode (α).

<Production of negative electrode>
Graphite carbon powder I having a number average particle diameter of 12.7 μm and graphite carbon powder II having a number average particle diameter of 6.5 μm as a negative electrode active material, a carboxymethylcellulose solution (solid content concentration 1.83% by mass) as a binder, and a diene system Rubber (glass transition temperature: −5 ° C., number average particle size upon drying: 120 nm, dispersion medium: water, solid content concentration 40% by mass), graphite carbon powder I: graphite carbon powder II: carboxymethyl cellulose solution: diene A rubber-like rubber was mixed at a solid content mass ratio of 90: 10: 1.44: 1.76 so that the total solid content concentration was 45% by mass to prepare a slurry solution. The slurry solution was applied to one side of a 10 μm thick copper foil, and the solvent was removed by drying, followed by rolling with a roll press. The rolled product was punched into a disk shape with a diameter of 16 mm to obtain a negative electrode (β).

<Battery assembly>
A laminate in which the positive electrode (α) and the negative electrode (β) produced as described above are superimposed on both sides of a polyethylene separator (film thickness: 25 μm, porosity: 50%, pore diameter: 0.1 μm to 1 μm) It was inserted into a SUS disk type battery case. Next, 0.5 mL of the electrolyte solution (a) heated to 70 ° C. was injected into the battery case, and the laminate was immersed in the electrolyte solution (a). Then, the battery case was sealed and a lithium ion secondary battery (small size) Battery). This lithium ion secondary battery was held at 70 ° C. for 1 hour, and then cooled to 25 ° C. to obtain a battery (a).

(Example 8)
A battery (c) was obtained in the same manner as in Example 7 except that the electrolytic solution (c) was used instead of the electrolytic solution (a).
(Comparative Example 2)
A battery (A) was obtained in the same manner as in Example 7 except that the mother electrolyte (A) was used instead of the electrolyte (a).

(Comparative Example 3)
An electrolytic solution (e) was obtained in the same manner as in Example 1 except that the compound represented by the following formula (4) was used as the gelling agent instead of the compound represented by the above formula (2). A battery (e) was obtained in the same manner as in Example 7 except that the electrolytic solution (e) was used instead of the electrolytic solution (a).
Compound (4) was synthesized according to the synthesis method described in JP2007-191626A.

Example 9
A laminated body in which the above positive electrode (α) and negative electrode (β) are superposed on both sides of a separator made of polyethylene (film thickness: 25 μm, porosity: 50%, pore diameter: 0.1 μm to 1 μm) is made of SUS. Inserted into the battery case. Next, 0.5 mL of electrolyte solution (b) solated by irradiation with ultraviolet light of 1 mW / cm ² was injected into the battery case, and the laminate was immersed in the electrolyte solution (b). A lithium ion secondary battery (small battery) was produced by sealing. This lithium ion secondary battery was held at 70 ° C. for 1 hour, and then cooled to 25 ° C. to obtain a battery (c2).

  For the batteries (a), (c), (c2), (A) and (e) of Examples 7-9 and Comparative Examples 2-3, the above “(iii) Measurement of discharge capacity of lithium ion secondary battery” and The measurement described in “(iv) Capacity maintenance rate measurement of lithium ion secondary battery (cycle test)” was performed. The results are shown in Table 3.

  For the batteries (a), (c) and (A) of Examples 7 to 8 and Comparative Example 2, the measurement described in the above “(v) Measurement of discharge capacity of lithium ion secondary battery at low temperature” was performed. It was. The results are shown in Table 4. All batteries were capable of low-temperature discharge, and no deterioration in low-temperature characteristics due to the gelling agent was observed.

(Example 10)
<Preparation of positive electrode>
Lithium cobalt acid (LiCoO ₂ ) as a positive electrode active material, acetylene black as a conductive additive, and polyvinylidene fluoride (PVdF) as a binder were mixed at a mass ratio of 89.5: 4.5: 6.0. N-methyl-2-pyrrolidone was further mixed with the obtained mixture to prepare a slurry solution. This slurry solution was applied to an aluminum foil having a thickness of 20 μm and a width of 200 nm, and the solvent was removed by drying, followed by rolling with a roll press and further vacuum drying at 150 ° C. for 10 hours to form a rectangular shape of 50 mm × 30 mm. A positive electrode (ε) was obtained by punching. In addition, about the compound material after the vacuum drying in the obtained electrode, the basis weight per one side is 24.8 g / cm ² ± 3%, the thickness on one side is 82.6 μm ± 3%, and the density is 3.0 g · The slurry-like solution was prepared while adjusting the amount of the solvent so that the coating width was 150 nm with respect to the width of 200 mm of the aluminum foil and cm ³ ± 3%.

<Production of negative electrode>
Graphite carbon powder (trade name “MCMB25-28”, manufactured by Osaka Gas Chemical Co., Ltd.) as the negative electrode active material, acetylene black as the conductive additive, and polyvinylidene fluoride (PVdF) as the binder in this order 93.0: Mixing was performed at a mass ratio of 2.0: 5.0. N-methyl-2-pyrrolidone was further mixed with the obtained mixture to prepare a slurry solution. This slurry solution was applied to a copper foil having a thickness of 14 μm and a width of 200 nm, and after removing the solvent by drying, it was rolled with a roll press, further vacuum dried at 150 ° C. for 10 hours, and punched to 52 mm × 32 mm. (Ζ) was obtained. In addition, about the composite material after the vacuum drying in the obtained electrode, the amount per unit area is 11.8 g / cm ² ± 3%, the thickness on one side is 84.6 μm ± 3%, and the density is 1.4 g · The slurry-like solution was prepared while adjusting the amount of solvent so that cm ³ ± 3% and the coating width was 150 nm with respect to the width of the copper foil of 200 nm.

<Battery assembly>
Two laminated films (no drawing, thickness 120 μm, 68 mm × 48 mm) laminated with an aluminum layer and a resin layer were stacked with the aluminum layer side facing out, and three sides were sealed to produce a laminate cell exterior. . Subsequently, a polyethylene microporous membrane (film thickness 20 μm, 53 mm × 33 mm) is prepared as a separator, and a plurality of positive electrodes (ε) and negative electrodes (ζ) produced as described above are alternately stacked via separators. The laminated body was placed in the laminate cell exterior. In accordance with the description of <Preparation of Positive Electrode> and <Preparation of Negative Electrode>, an electrolytic solution (a) heated to 75 ° C. was then injected into the cell exterior, and the laminate was immersed in the electrolytic solution. In addition, injection | pouring of electrolyte solution (a) was performed repeating the atmospheric pressure and pressure reduction of 100 mmHg until there was no bubble generation. The remaining side of the laminate cell exterior was sealed in an environment reduced to 100 mmHg to obtain a lithium ion secondary battery. The obtained battery was held at 75 ° C. for 2.5 hours, and then cooled to 25 ° C. to obtain a battery (a2).

(Comparative Example 4)
A battery (A2; single-layer laminated battery) was obtained in the same manner as in Example 10 except that the mother electrolyte (A) was used instead of the electrolyte (a).

The batteries described in Example 10 and Comparative Example 4 (a2) and (A2) were subjected to the test described in the above “(vi) Lithium deposition test of lithium ion secondary battery”. The results are shown in Table 5. In the battery (a2), precipitation was suppressed and a battery with improved safety was obtained.

  The lithium ion secondary battery of the present invention is expected to be used as a rechargeable battery for automobiles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, in addition to portable devices such as mobile phones, portable audio devices, and personal computers.

Claims (5)

A non-aqueous solvent, an electrolyte, and a compound represented by the following general formula (1),
An electrolyte for a lithium ion secondary battery or a lithium ion capacitor, wherein the electrolyte is LiPF ₆ and / or LiBF ₄ .
R—O—Ar—X—C (1)
(In the formula (1),
R represents a linear alkyl group having 4 to 18 carbon atoms in the main chain;
Ar is a group selected from the group consisting of a phenylene group, a biphenylene group, a naphthylene group, a terphenylene group and an anthranylene group ,
X represents a divalent group of the following formula (1a) or (1e), or a divalent group to which the following formulas (1a) and (1e) are bonded,
C represents a coumarin moiety represented by the following formula (1z), and R ¹ represents a hydrogen atom in the following formula (1z).
The lithium ion secondary battery or lithium ion capacitor electrolyte solution according to claim 1, wherein the electrolyte solution is gelled. A positive electrode containing at least one material selected from the group consisting of materials capable of inserting and extracting lithium ions as a positive electrode active material;
A negative electrode containing at least one material selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium;
Lithium ion secondary batteries comprising an electrolyte solution according to claim 1 or 2. The lithium ion secondary battery according to claim 3 , wherein the positive electrode includes a lithium-containing compound as the positive electrode active material. The negative electrode contains, as the negative electrode active material, at least one material selected from the group consisting of metallic lithium, a carbon material, a material containing an element capable of forming an alloy with lithium, and a lithium-containing compound. The lithium ion secondary battery according to 3 or 4 .