KR20210096213A - Electrolytes and Electrochemical Devices - Google Patents

Abstract

식 (1) 중, R¹~R³은, 각각 독립적으로, 알킬기 또는 불소 원자를 나타내고, R⁴는 알킬렌기를 나타내며, R⁵는, 황 원자를 포함하는 유기기를 나타낸다.One aspect of the present invention is an electrolyte solution containing a compound represented by the following formula (1) and a cyclic compound having a ring containing a sulfur atom without having a silicon atom.
[Formula 1]

In formula (1), R ¹ to R ³ each independently represent an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom.

Description

Electrolytes and Electrochemical Devices

The present invention relates to an electrolytic solution and an electrochemical device.

In recent years, with the spread of portable electronic devices and electric vehicles, high-performance electrochemical devices such as non-aqueous electrolyte secondary batteries and capacitors typified by lithium ion secondary batteries are required. As a means of improving the performance of an electrochemical device, the method of adding a predetermined|prescribed additive to electrolyte solution is examined, for example. Patent Document 1 discloses an electrolyte solution for a nonaqueous electrolyte battery containing a specific siloxane compound in order to improve cycle characteristics and internal resistance characteristics.

Patent Document 1: Japanese Patent Application Laid-Open No. 2015-005329

An object of the present invention is to provide an electrolytic solution capable of improving the performance of an electrochemical device.

One aspect of the present invention is an electrolyte solution containing a compound represented by the following formula (1) and a cyclic compound having a ring containing a sulfur atom without having a silicon atom.

[Formula 1]

In formula (1), R ¹ to R ³ each independently represent an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom.

According to this electrolytic solution, in one aspect, as the performance of the electrochemical device, it is possible to suppress an increase in volume after the electrochemical device is stored at a high temperature. Moreover, according to this electrolyte solution, in another aspect, improvement of the cycle characteristics of an electrochemical device (in particular, improvement of the capacity retention rate after a cycle test, and suppression of a raise of discharge DCR after a cycle test) is achieved. Moreover, according to this electrolyte solution, another one side WHEREIN: The discharge DCR after storing an electrochemical device under high temperature can be reduced.

At least one of R ¹ to R ³ may be a fluorine atom. The number of silicon atoms in 1 molecule of the compound represented by Formula (1) may be one.

R ⁵ may also be a contribution represented by any of the following formulas (3), (4), or (5).

[Formula 2]

In Formula (3), R<^8> represents an alkyl group, and * represents a bond.

[Formula 3]

In formula (4), R ⁹ represents an alkyl group, and * represents a bond.

[Formula 4]

In formula (5), R ¹⁰ represents an alkyl group, and * represents a bond.

The cyclic compound may also contain a cyclic sulfonic acid ester compound. The cyclic sulfonic acid ester compound may also contain the compound represented by following formula (X).

[Formula 5]

In formula (X), A ¹ represents a group containing an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and the hydrogen atom in the alkylene group and the alkenylene group is an alkyl group, a cycloalkyl group, It may be substituted with an aryl group or a fluoro group.

The compound represented by Formula (X) may also contain at least 1 sort(s) chosen from the group which consists of 1, 3- propane sultone and 1-propene-1, 3- sultone.

A cyclic compound may also contain at least 1 sort(s) chosen from the group which consists of the compound represented by Formula (Y), and the compound represented by Formula (Z).

[Formula 6]

In the formula (Y), A ² represents an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and a hydrogen atom in the alkylene group and the alkenylene group is substituted with an alkyl group, a cycloalkyl group or an aryl group it may be

[Formula 7]

In the formula (Z), A ³ represents an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and a hydrogen atom in the alkylene group and the alkenylene group is substituted with an alkyl group, a cycloalkyl group or an aryl group it may be

10 mass % or less may be sufficient as the sum total of content of the compound represented by Formula (1), and content of a cyclic sulfonic acid ester compound on the basis of electrolyte solution whole quantity.

Another aspect of the present invention is an electrochemical device including a positive electrode, a negative electrode, and the electrolyte solution.

The negative electrode may contain a carbon material. The carbon material may contain graphite. The negative electrode may further contain a material containing at least one element selected from the group consisting of silicon and tin.

The electrochemical device may be a non-aqueous electrolyte secondary battery or a capacitor.

ADVANTAGE OF THE INVENTION According to this invention, the electrolyte solution which can improve the performance of an electrochemical device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows the nonaqueous electrolyte solution secondary battery as an electrochemical device which concerns on one Embodiment.
FIG. 2 is an exploded perspective view illustrating an electrode group of the secondary battery shown in FIG. 1 .

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings suitably. However, this invention is not limited to the following embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows the electrochemical device which concerns on one Embodiment. In the present embodiment, the electrochemical device is a non-aqueous electrolyte secondary battery. As shown in FIG. 1 , the non-aqueous electrolyte secondary battery 1 includes an electrode group 2 composed of a positive electrode, a negative electrode, and a separator, and a bag-shaped battery exterior body 3 accommodating the electrode group 2 . are doing The positive electrode and the negative electrode are provided with a positive electrode current collecting tab 4 and a negative electrode current collecting tab 5 , respectively. The positive electrode current collecting tab 4 and the negative electrode current collecting tab 5 protrude from the inside of the battery exterior body 3 to the outside so that the positive electrode and the negative electrode can be electrically connected to the outside of the nonaqueous electrolyte secondary battery 1, respectively. . The battery exterior body 3 is filled with an electrolyte solution (not shown). The nonaqueous electrolyte secondary battery 1 may be a battery (coin type, cylindrical shape, stacked type, etc.) having a shape other than the so-called "laminate type" as described above.

The battery exterior body 3 may be, for example, a container formed of a laminate film. The laminate film may be, for example, a laminate film in which a resin film such as a polyethylene terephthalate (PET) film, a metal foil such as aluminum, copper, or stainless steel, and a sealant layer such as polypropylene are laminated in this order.

FIG. 2 is an exploded perspective view showing an embodiment of the electrode group 2 in the nonaqueous electrolyte secondary battery 1 shown in FIG. 1 . As shown in FIG. 2 , the electrode group 2 includes a positive electrode 6 , a separator 7 , and a negative electrode 8 in this order. The positive electrode 6 and the negative electrode 8 are arranged so that the surfaces of the positive mixture layer 10 side and the negative electrode mixture layer 12 side face the separator 7 , respectively.

The positive electrode 6 includes a positive electrode current collector 9 and a positive electrode mixture layer 10 provided on the positive electrode current collector 9 . The positive electrode current collector 9 is provided with a positive electrode current collector tab 4 .

The positive electrode current collector 9 is made of, for example, aluminum, titanium, stainless steel, nickel, fired carbon, a conductive polymer, or conductive glass. The positive electrode current collector 9 may be one in which the surface of aluminum or copper is treated with carbon, nickel, titanium, silver, or the like for the purpose of improving adhesion, conductivity, and oxidation resistance. The thickness of the positive electrode current collector 9 is, for example, 1 to 50 µm in terms of electrode strength and energy density.

The positive mix layer 10 contains a positive electrode active material, a electrically conductive agent, and a binder in one Embodiment. The thickness of the positive mix layer 10 is 20-200 micrometers, for example.

The positive electrode active material may be, for example, lithium oxide. Examples of the lithium oxide include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , Li _x Co _y M _1-y O _z , Li _x Ni _{1- y} M _y O _z , Li _x Mn ₂ O ₄ and Li _x Mn _2-y M _y O ₄ (wherein M is, Na, Mg, Sc, Y, Mn, Fe, Co, Cu, Zn, Al , Cr, Pb, Sb, V and at least one element selected from the group consisting of B (however, M is an element different from other elements in each formula) x = 0 to 1.2, y = 0 to 0.9, z = 2.0 to 2.3). Lithium oxide represented by Li _x Ni _1-y M _y O _{z is Li x} Ni _1-(y1+y2) Co _y1 Mn _y2 O _z (where x and z are the same as described above, and y1=0 to 0.9) , y2=0 to 0.9, and y1+y2=0 to 0.9) may be used, for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ may be sufficient. Lithium oxide represented by Li _x Ni _1-y M _y O _{z is Li x} Ni _1-(y3+y4) Co _y3 Al _y4 O _z (provided that x and z are the same as described above, and y3=0-0.9 , y4=0 to 0.9, and y3+y4=0 to 0.9) may be sufficient, for example, LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

The positive electrode active material may be, for example, a phosphate of lithium. Examples of lithium phosphate salts include lithium manganese phosphate (LiMnPO ₄ ), lithium iron phosphate (LiFePO ₄ ), tritium cobalt phosphate (LiCoPO ₄ ), and lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ). can

The content of the positive electrode active material may be 80% by mass or more, or 85% by mass or more, or 99% by mass or less, based on the total amount of the positive electrode material layer.

The conductive agent may be a carbon material such as carbon black such as acetylene black or Ketjen black, graphite, graphene, or carbon nanotube. The content of the conductive agent may be, for example, 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more, 50% by mass or less, 30% by mass or less, or 15% by mass based on the total amount of the positive electrode mixture layer. The mass % or less may be sufficient.

Examples of the binder include resins such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubbers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; Styrene butadiene styrene block copolymer or its hydrogenated substance, EPDM (ethylene propylene diene terpolymer), styrene ethylene butadiene ethylene copolymer, styrene isoprene styrene Thermoplastic elastomers, such as a ren block copolymer or its hydrogenated substance; soft resins such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate copolymer, and propylene/α-olefin copolymer; fluorine-containing resins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyvinylidene fluoride, polytetrafluoroethylene/ethylene copolymer, and polytetrafluoroethylene/vinylidene fluoride copolymer; resin having a nitrile group-containing monomer as a monomer unit; and polymer compositions having ion conductivity of alkali metal ions (eg lithium ions).

The content of the binder may be, for example, 0.1 mass% or more, 1 mass% or more, or 1.5 mass% or more, based on the total amount of the positive mix layer, 30 mass% or less, 20 mass% or less, or 10 The mass % or less may be sufficient.

The separator 7 electronically insulates between the positive electrode 6 and the negative electrode 8 and transmits ions, and has oxidative properties on the positive electrode 6 side and reducing properties on the negative electrode 8 side. It will not restrict|limit especially as long as it has tolerance with respect to it. As a material (material) of such a separator 7, resin, an inorganic substance, etc. are mentioned.

Examples of the resin include an olefin-based polymer, a fluorine-based polymer, a cellulosic polymer, a polyimide, and nylon. The separator 7 is preferably a porous sheet or nonwoven fabric formed of polyolefin such as polyethylene or polypropylene from the viewpoint of being stable to the electrolyte and excellent in liquid retention.

Examples of the inorganic substance include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate. The separator 7 may be, for example, a separator in which a fibrous or particulate inorganic substance is adhered to a thin film substrate such as a nonwoven fabric, a woven fabric, or a microporous film.

The negative electrode 8 includes a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on the negative electrode current collector 11 . The negative electrode current collector 11 is provided with a negative electrode current collector tab 5 .

The negative electrode current collector 11 is made of copper, stainless steel, nickel, aluminum, titanium, fired carbon, a conductive polymer, conductive glass, an aluminum-cadmium alloy, or the like. The negative electrode current collector 11 may be one in which the surface of copper or aluminum is treated with carbon, nickel, titanium, silver, or the like for the purpose of improving adhesion, conductivity, and reduction resistance. The thickness of the negative electrode current collector 11 is, for example, 1 to 50 µm in terms of electrode strength and energy density.

The negative electrode mixture layer 12 contains, for example, a negative electrode active material and a binder.

The negative electrode active material is not particularly limited as long as it is a material capable of occluding and releasing lithium ions. Examples of the negative electrode active material include a carbon material, a metal composite oxide, an oxide or nitride of a Group 4 element such as tin, germanium, and silicon, a single element of lithium, a lithium alloy such as a lithium aluminum alloy, Sn, and metals capable of forming an alloy with lithium such as Si. From the viewpoint of safety, the negative electrode active material is preferably at least one selected from the group consisting of carbon materials and metal composite oxides. The negative electrode active material may be used alone or as a mixture of two or more thereof. The shape of the negative electrode active material may be, for example, particulate.

As the carbon material, an amorphous carbon material, natural graphite, a composite carbon material in which a film of an amorphous carbon material is formed on natural graphite, artificial graphite (a resin raw material such as an epoxy resin or a phenol resin, or a pitch-based raw material obtained from petroleum, coal, etc.) obtained by calcining) and the like. From the viewpoint of high current density charge/discharge characteristics, the metal composite oxide preferably contains either or both of titanium and lithium, and more preferably contains lithium.

Among the negative electrode active materials, the carbon material has high conductivity and is particularly excellent in low-temperature characteristics and cycle stability. Among carbon materials, graphite is preferable from the viewpoint of increasing the capacity. In graphite, Preferably, the carbon reticulum interlayer (d002) in X-ray wide-angle diffraction method is less than 0.34 nm, More preferably, they are 0.3354 nm or more and 0.337 nm or less. The carbon material which satisfies such a condition may be called pseudo-anisotropic carbon.

The negative electrode active material may further contain a material containing at least one element selected from the group consisting of silicon and tin. The material containing at least one element selected from the group consisting of silicon and tin may be a compound containing at least one element selected from the group consisting of silicon or tin, and silicon and tin. The compound may be an alloy containing at least one element selected from the group consisting of silicon and tin, for example, nickel, copper, iron, cobalt, manganese, zinc, indium, silver in addition to silicon and tin. , titanium, germanium, bismuth, antimony, and an alloy containing at least one selected from the group consisting of chromium. The compound containing at least one element selected from the group consisting of silicon and tin may be an oxide, nitride, or carbide, specifically, for example, silicon oxide such as _{SiO, SiO 2 , LiSiO, Si 3} N _4, or may be such as tin oxide, such as silicon carbide, SnO, SnO _2, LiSnO of silicon nitride, SiC, etc., such as Si ₂ N ₂ O.

From the viewpoint of further improving the performance of the electrochemical device such as low-temperature input characteristics, the negative electrode 8, as a negative electrode active material, preferably contains a carbon material, more preferably contains graphite, more preferably, A mixture of a carbon material and a material containing at least one element selected from the group consisting of silicon and tin is included, and particularly preferably, a mixture of graphite and silicon oxide is included. The content of the carbon material (graphite) with respect to the material (silicon oxide) containing at least one element selected from the group consisting of silicon and tin in the mixture is 1% by mass based on the total amount of the mixture. or more, or 3 mass % or more may be sufficient, and 30 mass % or less may be sufficient.

The content of the negative electrode active material may be 80% by mass or more, 85% by mass or more, or 99% by mass or less based on the total amount of the negative electrode mixture layer.

A binder and its content may be the same as the binder and its content in the positive mix layer mentioned above.

The negative mix layer 12 may contain a thickener in order to adjust a viscosity. Although the thickener in particular is not restrict|limited, Carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, these salts, etc. may be sufficient. These thickeners may be used individually by 1 type or a mixture of 2 or more types may be sufficient as them.

When the negative mix layer 12 contains a thickener, the content in particular is not restrict|limited. The content of the thickener may be 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.5% by mass or more, based on the total amount of the negative electrode mixture layer, from the viewpoint of applicability of the negative electrode mixture layer. The content of the thickener may be 5% by mass or less, preferably 3% by mass or less, based on the total amount of the negative electrode mixture layer, from the viewpoint of suppressing a decrease in battery capacity or an increase in resistance between negative electrode active materials, more preferably Preferably, it is 2 mass % or less.

In one embodiment, the electrolytic solution includes a compound represented by the following formula (1), a cyclic compound having a ring containing a sulfur atom without a silicon atom (hereinafter, simply referred to as a “cyclic compound”), and an electrolyte salt and a non-aqueous solvent.

[Formula 8]

In formula (1), R ¹ to R ³ each independently represent an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom.

The number of carbon atoms of the alkyl group represented by R ¹ ~ R ³ is may be either greater than or equal to 1, 3 or less is even. R ¹ to R ³ may be a methyl group, an ethyl group, or a propyl group, and may be linear or branched. At least one of R ¹ to R ³ is preferably a fluorine atom. R ¹ ~ R any one of the ^three and even a fluorine atom, R ¹ ~ R which two are fluorine atoms, and even ^triple, both R ¹ ~ R ³ is or may be a fluorine atom.

1 or more or 2 or more may be sufficient as carbon number of the alkylene group represented by R<^{4>, and 5 or less or 4 or less may be sufficient as it.} The ^{alkylene group represented by R 4 may} be a methylene group, an ethylene group, a propylene group, a butylene group, or a pentylene group, and may be linear or branched.

In one embodiment, the number of silicon atoms in one molecule of the compound represented by Formula (1) is one. That is, in one embodiment ^{, the organic group represented by R 5} does not contain a silicon atom.

From the viewpoint of further improving the performance of the electrochemical device, R ⁵ may preferably be a contribution represented by any one of the following formulas (3), (4) or (5).

[Formula 9]

In Formula (3), R<^8> represents an alkyl group. The alkyl group may be the same as the alkyl group represented ^{by R 1} to R ^{3 described above.} * indicates a bond.

[Formula 10]

In formula (4), R ⁹ represents an alkyl group. The alkyl group may be the same as the alkyl group represented ^{by R 1} to R ^{3 described above.} * indicates a bond.

[Formula 11]

In formula (5), R ¹⁰ represents an alkyl group. The alkyl group may be the same as the alkyl group represented ^{by R 1} to R ^{3 described above.} * indicates a bond.

Content of the compound represented by Formula (1) is preferably 0.001 mass % or more, 0.005 mass % or more, 0.01 mass % on the basis of electrolyte solution whole quantity from a viewpoint which can further improve the performance of an electrochemical device. or more, 0.05 mass % or more, or 0.1 mass % or more, and is 8 mass % or less, 5 mass % or less, 3 mass % or less, 2 mass % or less, or 1 mass % or less.

A cyclic compound is a compound which has a ring (heterocyclic) containing a sulfur atom. In addition, a cyclic compound is a compound other than the compound represented by the said Formula (1). In other words, a cyclic compound is a compound which does not have a silicon atom.

The cyclic compound may contain at least 1 type of a cyclic sulfonic acid ester compound (it is also called a sultone compound), for example. Cyclic sulfonic acid ester compounds, -OSO ₂ - is a compound having a ring containing groups. The cyclic sulfonic acid ester compound has a ring containing one or two _{-OSO 2 - groups.}

-OSO ₂ - cyclic sulfonic acid ester compounds having a ring containing one group, for may be a compound represented by the following formula (X), for example.

[Formula 12]

In the formula (X), A ¹ represents an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and the hydrogen atom in the alkylene group and the alkenylene group is an alkyl group, a cycloalkyl group, an aryl group, Alternatively, it may be substituted with a fluoro group.

1-12 may be sufficient as carbon number of the said alkyl group, for example. The carbon number of the said cycloalkyl group may be 3-6, for example. 6-12 may be sufficient as carbon number of the said aryl group, for example.

A ¹ is preferably an alkylene group having 3 carbon atoms or an alkenylene group having 3 carbon atoms. That is, the cyclic sulfonic acid ester compound is preferably a compound represented by the following formula (X-1) or (X-2).

[Formula 13]

In the formula, R ¹¹ to R ²⁰ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a fluoro group. The number of carbon atoms of the alkyl group, the cycloalkyl group and the aryl group represented by R ¹¹ to R ²⁰ is the same as the number of carbon atoms of the alkyl group, the cycloalkyl group and the aryl group described for the formula (X), respectively. R ¹¹ to R ²⁰ are preferably a hydrogen atom.

Examples of the cyclic sulfonic acid ester compound represented by the formula (X) include 1,3-propanesultone, 1,4-butanesultone, 2,4-butanesultone, 1,3-propensultone, 1 ,4-butenesultone, 1-methyl-1,3-propanesultone, 3-methyl-1,3-propanesultone, 1-fluoro-1,3-propanesultone, 3-fluoro-1, Monosulfonic acid esters, such as 3-propane sultone, etc. are mentioned. Among these, from the viewpoint of further improving the performance of the electrochemical device, 1,3-propanesultone (a ^{compound in which R 11} to R ¹⁶ are all hydrogen atoms in the formula (X-1)) or 1-propane Phen-1,3-sultone (a ^{compound in which R 17} to R ²⁰ are all hydrogen atoms in the formula (X-2)) is preferred.

-OSO ₂ - group may be a cyclic sulfonic acid ester compounds are, for compounds represented by the following formula (X-3) having such a ring containing two or more.

[Formula 14]

In the formula, B ¹ and B ² each independently represent an alkylene group having 1 to 5 carbon atoms or an alkenylene group having 1 to 5 carbon atoms, and the hydrogen atom in the alkylene group and the alkenylene group is an alkyl group or a cycloalkyl group , an aryl group, or a fluoro group may be substituted.

B ¹ and B ² are preferably an unsubstituted alkylene group having 1 or 2 carbon atoms. The cyclic sulfonic acid ester compound may be a disulfonic acid ester such as methylenemethanedisulfonic acid ester or ethylenemethanedisulfonic acid ester.

The cyclic compound may contain at least 1 sort(s) chosen from the group which consists of a compound represented by Formula (Y), and a compound represented by Formula (Z), for example.

[Formula 15]

[Formula 16]

In formulas (Y) and (Z), A ² and A ³ each independently represent an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and hydrogen in the alkylene group and the alkenylene group The atom may be substituted with an alkyl group, a cycloalkyl group, or an aryl group.

The number of carbon atoms of the alkyl group, the cycloalkyl group, and the aryl group in A ² and A ³ is the same as the number of carbon atoms of the alkyl group, the cycloalkyl group, and the aryl group described for the formula (X), respectively.

As a compound represented by Formula (Y), for example, sulfolane, 2-methylsulfolane, 3-methylsulfolane, 2-ethylsulfolane, 3-ethylsulfolane, 2,4-di Methylsulfolane, 2-phenylsulfolane, 3-phenylsulfolane, sulfolene, 3-methylsulfolene, etc. are mentioned. The compound represented by Formula (Y) is a viewpoint which can further improve the performance of an electrochemical device, Preferably it is sulfolane.

As a compound represented by Formula (Z), ethylene sulfite, propylene sulfite, butylene sulfite, vinylene sulfite, phenylethylene sulfite, etc. are mentioned, for example. The compound represented by Formula (Z) is from a viewpoint which can further improve the performance of an electrochemical device, Preferably it is ethylene sulfite.

A cyclic compound may contain at least 1 sort(s) chosen from the group which consists of a cyclic sulfonic acid ester compound, the compound represented by Formula (Y), and the compound represented by Formula (Z), The compound represented by Formula (X), Formula (Y ) may contain at least one selected from the group consisting of the compound represented by the compound and the formula (Z), and at least one selected from the group consisting of the compound represented by the formula (X) and the compound represented by the formula (Z). may include

The content of the cyclic compound is preferably 0.001 mass % or more, 0.005 mass % or more, 0.01 mass % or more, 0.05 mass % based on the total amount of the electrolyte from the viewpoint of further improving the performance of the electrochemical device. or more, or 0.1 mass % or more, 5 mass % or less, 3 mass % or less, 2 mass % or less, or 1 mass % or less.

From the viewpoint of further improving the performance of the electrochemical device, the total of the content of the compound represented by the formula (1) and the content of the cyclic compound is preferably 0.001% by mass or more, 0.005 based on the total amount of the electrolytic solution. It is mass % or more, 0.01 mass % or more, 0.1 mass % or more, or 0.5 mass % or more, Preferably, it is 10 mass % or less, 7 mass % or less, 5 mass % or less, 3 mass % or less, or 2 mass % or less. am.

The mass ratio of the content of the compound represented by Formula (1) to the content of the cyclic compound (content of the compound represented by Formula (1)/content of the cyclic compound) is preferable from the viewpoint of further improving the performance of the electrochemical device. Preferably, they are 0.01 or more, 0.05 or more, 0.1 or more, 0.2 or more, or 0.25 or more, and preferably, 500 or less, 100 or less, 50 or less, 20 or less, 10 or less, 5 or less, or 4 or less.

The electrolyte salt may be, for example, a lithium salt. Lithium salts are, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiB(C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , CF ₃ SO ₂ OLi, LiN(SO ₂ F) ₂ (Li[FSI], lithiumbisfluorosulfonylimide), LiN(SO ₂ CF ₃ ) ₂ (Li[TFSI], lithium bistrifluoromethanesulfonylimide), and LiN(SO ₂ CF ₂ CF ₃ ) ₂ At least 1 type selected from may be sufficient. _{The lithium salt preferably contains LiPF 6} from the viewpoint of more excellent solubility in a solvent, charge/discharge characteristics of a secondary battery, output characteristics, cycle characteristics, and the like.

The concentration of the electrolyte salt is preferably 0.5 mol/L or more, more preferably 0.7 mol/L or more, still more preferably 0.8 mol/L or more, based on the total amount of the non-aqueous solvent from the viewpoint of excellent charge and discharge characteristics. and, preferably 1.5 mol/L or less, more preferably 1.3 mol/L or less, and still more preferably 1.2 mol/L or less.

The non-aqueous solvent is, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, acetonitrile, 1,2-dimethoxyethane, dimethoxymethane , tetrahydrofuran, dioxolane, methylene chloride, methyl acetate, or the like may be used. The non-aqueous solvent may be used alone or as a mixture of two or more thereof, and is preferably a mixture of two or more thereof.

The electrolyte solution may further contain other materials other than the compound represented by Formula (1), a cyclic compound, an electrolyte salt, and a non-aqueous solvent. Other materials include, for example, cyclic carbonates such as fluorine-containing cyclic carbonates and cyclic carbonates having a carbon-carbon double bond, compounds having nitrogen atoms, compounds represented by formula (1) and sulfur atoms other than cyclic compounds. A compound, a cyclic carboxylic acid ester, etc. may be sufficient.

The fluorine-containing cyclic carbonate is, for example, 4-fluoro-1,3-dioxolan-2-one (fluoroethylene carbonate; FEC), 1,2-difluoroethylene carbonate, 1,1-difluoro Roethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, etc. may be used, Preferably 4-fluoro-1,3-dioxolane-2 -one (fluoroethylene carbonate; FEC). The cyclic carbonate having a carbon-carbon double bond may be, for example, vinylene carbonate. Nitrile compounds, such as succinonitrile, may be sufficient as the compound containing a nitrogen atom, for example.

MEANS TO SOLVE THE PROBLEM The present inventors discovered that the performance of an electrochemical device could be improved by applying the compound and cyclic compound represented by Formula (1) mentioned above to electrolyte solution, as a result of examining the compound which has various structures and a functional group. MEANS TO SOLVE THE PROBLEM The present inventors estimate the effect by using the compound and cyclic compound represented by Formula (1) for electrolyte solution as follows. That is, the compound and the cyclic compound represented by the formula (1) each act on the site where the effect is most likely to be expressed in the lithium ion secondary battery, and for example, it contributes to the stable film formation of the positive electrode or the negative electrode, or the stabilization of the electrolyte solution. I think to do it. As a result, the performance of the electrochemical device such as the nonaqueous electrolyte secondary battery 1 is improved.

Specifically, according to the electrolyte solution of one embodiment, the volume increase after storing the electrochemical device under high temperature can be suppressed as performance of an electrochemical device. Moreover, according to the electrolyte solution of one Embodiment, the improvement of the cycle characteristic of an electrochemical device (in particular, the improvement of the capacity retention rate after a cycle test, and suppression of the raise of the discharge DCR after a cycle test) is achieved. Moreover, according to the electrolyte solution of one Embodiment, the discharge DCR after storing an electrochemical device under high temperature can be reduced.

Next, the manufacturing method of the nonaqueous electrolyte secondary battery 1 is demonstrated. The manufacturing method of the nonaqueous electrolyte secondary battery 1 includes a first step of obtaining a positive electrode 6 , a second step of obtaining a negative electrode 8 , and a first step of accommodating the electrode group 2 in the battery exterior body 3 . The 3rd process and the 4th process of pouring electrolyte solution into the battery exterior body 3 are provided.

In the first step, the material used for the positive electrode mixture layer 10 is dispersed in a dispersion medium using a kneader, a disperser, or the like to obtain a slurry-like positive mixture, and then this positive mixture is subjected to a doctor blade method, a dipping method, a spray method, etc. The positive electrode 6 is obtained by coating on the positive electrode current collector 9 and then volatilizing the dispersion medium. After volatilizing the dispersion medium, if necessary, a compression molding process by roll pressing may be provided. The positive mixture layer 10 may be formed as a positive mixture layer having a multilayer structure by performing the steps from application of the above-described positive mixture to volatilization of the dispersion medium a plurality of times. The dispersion medium may be water, 1-methyl-2-pyrrolidone (hereinafter also referred to as NMP.) or the like.

The second step may be the same as the first step described above, and the method of forming the negative electrode mixture layer 12 on the negative electrode current collector 11 may be the same as that of the first step described above.

In the third step, the separator 7 is sandwiched between the produced positive electrode 6 and negative electrode 8 to form the electrode group 2 . Next, this electrode group 2 is accommodated in the battery exterior body 3 .

In the fourth step, the electrolytic solution is injected into the battery exterior body 3 . The electrolyte solution can be prepared, for example, by first dissolving an electrolyte salt in a solvent and then dissolving other materials.

As another embodiment, the electrochemical device may be a capacitor. The capacitor may include, similarly to the nonaqueous electrolyte secondary battery 1 described above, an electrode group composed of a positive electrode, a negative electrode, and a separator, and a bag-shaped battery outer body for accommodating the electrode group. The details of each component in the capacitor may be the same as those of the nonaqueous electrolyte secondary battery 1 .

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

(Example 1)

[Production of positive electrode]

Acetylene black (AB) (4 mass %) as a conductive agent and a binder (4 mass %) were sequentially added to lithium nickel cobalt manganese oxide (92 mass %) as a positive electrode active material, and they were mixed. To the obtained mixture, NMP as a dispersion medium was added and kneaded to prepare a slurry-like positive electrode mixture. A predetermined amount of the positive electrode mixture was uniformly and homogeneously applied to an aluminum foil having a thickness of 20 μm as a positive electrode current collector. Then, after volatilizing a dispersion medium, ^{it compacted to density 2.8 g/cm<3>} by pressing, and obtained the positive electrode.

[Production of negative electrode]

A binder and carboxymethylcellulose as a thickener were added to the negative electrode active material containing graphite and silicon oxide. About these mass ratios, graphite: silicon oxide: binder: thickener = 92:5:1.5:1.5. To the obtained mixture, water as a dispersion medium was added and kneaded to prepare a slurry-like negative electrode mixture. A predetermined amount of this negative electrode mixture was uniformly and homogeneously applied to a 10 µm-thick rolled copper foil as a negative electrode current collector. Then, after volatilizing a dispersion medium, ^{it compacted to a density of 1.6 g/cm<3>} by pressing, and the negative electrode was obtained.

[Production of lithium ion secondary battery]

13.5cm a positive electrode cut in the ^second of the rectangle, the separator polyethylene porous sheet: cutting a rectangle of 14.3cm ² further sandwiched between (trade name: Hi-Pore (R), manufactured by Asahi Kasei Co., Ltd., thickness 30μm), An electrode group was prepared by overlapping one negative electrode. This electrode group was accommodated in a container (battery exterior body) formed of a laminated film made of aluminum (trade name: aluminum laminated film, manufactured by Dai-Nippon Insatsu Co., Ltd.). Next, 1 mL of electrolyte solution was added in the container, the container was heat-sealed, and the lithium ion secondary battery for evaluation was produced. As the electrolyte solution, in a mixed solution of ethylene carbonate, dimethyl carbonate, and ethylmethyl carbonate containing 1 mol/L LiPF ₆ , 1% by mass of vinylene carbonate (VC), 4-fluoro-1 based on the total amount of the mixed solution 0.5 mass % of 3-dioxolan-2-one (fluoroethylene carbonate; FEC), 0.5 mass % of compound A represented by following formula (6), and 0.5 mass % of 1,3-propane sultone (based on the total amount of electrolyte solution) ) was added.

[Formula 17]

(Example 2)

In Example 1, except having changed the addition amount of the compound A to 2.0 mass %, it carried out similarly to Example 1, and produced the lithium ion secondary battery.

(Example 3)

In Example 1, it replaced with the compound A, and except having added 0.3 mass % of the compound B represented by following formula (7), it carried out similarly to Example 1, and produced the lithium ion secondary battery.

[Formula 18]

(Example 4)

In Example 1, it replaced with the compound A, and except having added 0.1 mass % of the compound C represented by following formula (8), it carried out similarly to Example 1, and produced the lithium ion secondary battery.

[Formula 19]

(Example 5)

In Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that 1,3-propenesultone was used instead of 1,3-propenesultone.

(Example 6)

In Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that methylenemethanedisulfonic acid ester (MMDS) was used instead of 1,3-propanesultone.

(Example 7)

In Example 1, except having used ethylene sulfite instead of 1, 3- propane sultone, it carried out similarly to Example 1, and produced the lithium ion secondary battery.

(Comparative Example 1)

In Example 1, except not using the compound A and 1, 3- propane sultone, it carried out similarly to Example 1, and produced the lithium ion secondary battery.

(Comparative Example 2)

In Example 1, except not using the compound A, it carried out similarly to Example 1, and produced the lithium ion secondary battery.

[Evaluation of high temperature storage characteristics]

Each produced secondary battery was subjected to constant current charging at a voltage of 0.1 C in an environment of 25°C to an upper limit voltage of 4.2 V, followed by constant voltage charging at 4.2 V. The charging termination condition was set to a total grinding value of 0.01C. Then, these secondary batteries were stored in a 60 degreeC thermostat for 2 weeks.

The volume (V1) of each secondary battery before the storage, and the volume (V2) of each secondary battery left still for 30 minutes in an environment of 25° C. after the storage, were measured using a hydrometer (electron hydrometer MDS-300, alpha) based on the Archimedes method. It was measured by Mira Injection). Using the measured V1 and V2, the volume change rate (%) = V2/V1 x 100 was computed. A result is shown in Table 1.

[Evaluation of cycle characteristics]

(Initial charge/discharge)

About each produced secondary battery, initial charging/discharging was implemented by the method shown below. First, in the environment of 25 degreeC, constant current charging was performed to the upper limit voltage 4.2V with the electric voltage of 0.1C, and then, constant voltage charging was performed at 4.2V. The charge termination conditions were set to a total grinding value of 0.01C. Thereafter, constant current discharge with a final voltage of 2.7 V was performed at a total voltage of 0.1 C. This charge/discharge cycle was repeated 3 times. In addition, "C" used as a unit of the total value means "the total value (A)/battery capacity (Ah)" (the same hereinafter).

(Measurement of discharge DCR)

For each secondary battery after the initial charge and discharge, the DC resistance (discharge DCR) at the time of discharge was measured as follows.

First, constant current charging at 0.2 C was performed to the upper limit voltage of 4.2 V, and then constant voltage charging was performed at 4.2 V. The charge termination conditions were set to a total grinding value of 0.02C. Thereafter, constant current discharge with a final voltage of 2.7V was performed at a voltage of 0.2C, and the voltage at this time was set to I _0.2C and the voltage change 10 seconds after the start of the discharge was set _{to ΔV 0.2C.} Next, constant current charging of 0.2C is performed to the upper limit voltage of 4.2V, and after constant voltage charging is continuously performed at 4.2V (charging termination condition was set to a total voltage of 0.02C), a final voltage of 2.7 at a total voltage of 0.5C A constant current discharge of V was performed, the _{voltage change at this time was set to I 0.5C} , and the voltage change 10 second after the start of discharge was made _{into ΔV 0.5C.} From the same charge/discharge, I _{1C and voltage change ΔV 1C} 10 seconds after the start of discharging were evaluated for the voltage at 1C. Using the least squares method, draw a linear approximate straight line on the three-point plots (I _0.2C , ΔV _0.2C ), (I _0.5C , ΔV _0.5C ), and (I _1C , ΔV _{1C ) of the voltage change.} , the slope was taken as the value R1 of the discharge DCR.

(cycle test)

Each secondary battery after the initial charge and discharge was subjected to a cycle test in which the following charge and discharge were repeated. As a charging pattern, the secondary battery was subjected to constant current charging up to an upper limit voltage of 4.2V at a voltage of 0.5C in an environment of 45°C, followed by constant voltage charging at 4.2V. The charging termination conditions were set to a total grinding value of 0.05C. About the discharge, constant current discharge was performed to 2.7V at 1C, and the discharge capacity was calculated|required. This series of charging and discharging was repeated 630 cycles. Discharge capacity retention rate (%) = Q1/Q2 x 100 was calculated|required using the discharge capacity Q1 after charging/discharging at the 1st cycle, and the discharge capacity Q2 after charging/discharging at the 630th cycle. A result is shown in Table 1.

Moreover, the value R2 of discharge DCR was calculated|required similarly to the above about the secondary battery after 500 cycles. Using the value R1 of the discharge DCR after the initial charge and discharge and the value R2 of the discharge DCR after the charge and discharge of the 630th cycle, the rate of increase (%) of the discharge DCR = R2/R1×100 was calculated. A result is shown in Table 1.

[Table 1]

As Table 1 shows, the lithium ion secondary battery to which the electrolyte solution of Examples 1-7 containing the compound and cyclic compound represented by Formula (1) is applied is one of the compound represented by Formula (1) and a cyclic compound, or Compared with the lithium ion secondary batteries of Comparative Examples 1 and 2 to which an electrolyte solution containing neither side is applied, high temperature storage characteristics are excellent (volume change rate after high temperature storage is small), and cycle characteristics are also excellent (capacity retention rate after cycle test is high, it is possible to suppress the rise of the discharge DCR). It is thought that this is because the compound represented by Formula (1) contributed to stabilization of electrolyte solution in addition to the cyclic compound forming the stable film by a positive electrode or a negative electrode.

Moreover, about the secondary battery of Example 1 and Comparative Examples 1 and 2, the discharge DCR after performing the said high temperature storage was also measured. As a result, the discharge DCR of Example 1 was 1.70 Ω, the discharge DCR of Comparative Example 1 was 1.98 Ω, and the discharge DCR of Comparative Example 2 was 1.79 Ω. The lithium ion secondary battery of Comparative Example 2 to which an electrolyte solution containing 1,3-propanesultone and not containing Compound A was applied, Comparative Example to which an electrolyte solution containing neither Compound A nor 1,3-propanesultone was applied Compared with the lithium ion secondary battery of No. 1, the discharge DCR after high temperature storage fell. This is considered to be because 1,3-propanesultone formed a stable film at the positive electrode or the negative electrode. In addition, the lithium ion secondary battery of Example 1 to which the electrolyte solution containing both Compound A and 1,3-propanesultone was applied, compared with the lithium ion secondary batteries of Comparative Examples 1 and 2, discharge DCR after high temperature storage These were about 15% and about 5% good, respectively. This is considered to be because 1,3-propanesultone formed a stable film at the positive electrode or the negative electrode, and the compound A contributed to the stabilization of the electrolyte solution.

One… Non-aqueous electrolyte secondary battery (electrochemical device)
6… positive pole
7… separator
8… negative electrode

Claims (14)

A compound represented by the following formula (1);
An electrolytic solution containing a cyclic compound having no silicon atom and a ring containing a sulfur atom.
[Formula 1]

[In formula (1), R ¹ to R ³ each independently represent an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom.] The method according to claim 1,
At least one of R ¹ to R ³ is a fluorine atom. The method according to claim 1 or 2,
The electrolyte solution whose number of silicon atoms in 1 molecule of the compound represented by said Formula (1) is one. 4. The method according to any one of claims 1 to 3,
Said R<^5> is group represented by any one of following formula (3), Formula (4), or Formula (5), Electrolytic solution.
[Formula 2]

[In formula (3), R ⁸ represents an alkyl group, and * represents a bond.]
[Formula 3]

[In formula (4), R ⁹ represents an alkyl group, and * represents a bond.]
[Formula 4]

[In formula (5), R ¹⁰ represents an alkyl group, and * represents a bond.] 5. The method according to any one of claims 1 to 4,
The electrolytic solution wherein the cyclic compound contains a cyclic sulfonic acid ester compound. 6. The method of claim 5,
The electrolyte solution in which the said cyclic sulfonic acid ester compound contains the compound represented by following formula (X).
[Formula 5]

[In formula (X), A ¹ represents a group containing an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and the hydrogen atom in the alkylene group and the alkenylene group is an alkyl group or a cycloalkyl group , an aryl group, or a fluoro group may be substituted.] 7. The method of claim 6,
The electrolyte solution in which the compound represented by the said Formula (X) contains at least 1 sort(s) chosen from the group which consists of 1, 3- propane sultone and 1-propene-1, 3- sultone. 8. The method according to any one of claims 1 to 7,
The electrolyte solution in which the said cyclic compound contains at least 1 sort(s) chosen from the group which consists of the compound represented by Formula (Y), and the compound represented by Formula (Z).
[Formula 6]

[In formula (Y), A ² represents an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and the hydrogen atom in the alkylene group and the alkenylene group is an alkyl group, a cycloalkyl group or an aryl group It may be substituted.]
[Formula 7]

[In formula (Z), A ³ represents an alkylene group having 3 to 5 carbon atoms or an alkenylene group having 3 to 5 carbon atoms, and the hydrogen atom in the alkylene group and the alkenylene group is an alkyl group, a cycloalkyl group or an aryl group It may be substituted.] 9. The method according to any one of claims 1 to 8,
The electrolyte solution whose sum total of content of the compound represented by said Formula (1), and content of the said cyclic compound is 10 mass % or less on the basis of the said electrolyte solution whole quantity. An electrochemical device provided with a positive electrode, a negative electrode, and the electrolyte solution in any one of Claims 1-9. 11. The method of claim 10,
The negative electrode contains a carbon material. 12. The method of claim 11,
wherein the carbon material contains graphite. 13. The method according to claim 11 or 12,
The said negative electrode further contains the material containing at least 1 sort(s) of element selected from the group which consists of silicon and tin. 14. The method according to any one of claims 10 to 13,
The electrochemical device is a non-aqueous electrolyte secondary battery or a capacitor.

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