TWI830832B - Electrolytes and electrochemical devices - Google Patents

Abstract

In one aspect, the present invention provides an electrolyte solution which, as measured by ¹⁹ F-NMR, is at least 1 of -180 ppm or more and -150 ppm or less, and -150 ppm or less and -130 ppm or less. Displays peaks within chemical shift ranges.

Description

Electrolytes and electrochemical devices

The invention relates to an electrolyte solution and an electrochemical device.

In recent years, due to the popularization of portable electronic devices, electric vehicles, etc., high-performance electrochemical devices are considered necessary. These high-performance electrochemical devices are non-aqueous electrolyte diodes represented by lithium-ion secondary batteries. Secondary batteries, capacitors, etc. As a means of improving the performance of an electrochemical device, a method of adding a specific additive to an electrolyte solution has been studied, for example. Patent Document 1 discloses an electrolyte for non-aqueous electrolyte batteries containing a specific siloxane compound in order to improve cycle characteristics and internal resistance characteristics. [Prior technical literature] (patent document)

Patent Document 1: Japanese Patent Application Publication No. 2015-005329

[Problem to be solved by the invention] The object of the present invention is to provide an electrolyte solution that can improve the performance of electrochemical devices. [Technical means to solve problems]

As a first aspect, the present invention provides an electrolyte solution that is -180 ppm or more and -150 ppm or less, and exceeds -150 ppm and -130 ppm or less, as measured by 19 fluorine nuclear magnetic resonance ( ¹⁹ F-NMR). Display peaks within at least 1 chemical shift range.

According to this electrolyte, in one aspect, the performance as an electrochemical device can improve the cycle characteristics of the electrochemical device.

In the first aspect, the electrolyte solution may further exhibit a peak in a chemical shift range of more than -130 ppm and less than -110 ppm in measurement by ¹⁹ F-NMR.

As a second aspect, the present invention provides an electrochemical device including a positive electrode, a negative electrode, and the electrolyte solution described above.

In the second aspect, the negative electrode preferably contains a carbon material. The carbon material preferably contains graphite. The negative electrode preferably further contains a material containing at least one element selected from the group consisting of silicon and tin.

In the second aspect, the electrochemical device may be a non-aqueous electrolyte secondary battery or a capacitor. [Efficacy of the invention]

According to the present invention, an electrolyte solution can be provided that can improve the performance of an electrochemical device.

Hereinafter, embodiments of the present invention will be described with appropriate reference to the drawings. However, the present invention is not limited to the following embodiments.

Fig. 1 is a perspective view showing an electrochemical device according to an embodiment. In this embodiment, the electrochemical device is a non-aqueous electrolyte secondary battery. As shown in Figure 1, the non-aqueous electrolyte secondary battery 1 includes: an electrode group 2, which is composed of a positive electrode, a negative electrode, and a separator; and a bag-shaped battery outer case 3, which can accommodate the electrode group 2 . For the positive electrode and the negative electrode, a positive current collecting terminal 4 and a negative current collecting terminal 5 are respectively provided. The positive current collecting terminal 4 and the negative current collecting terminal 5 protrude from the inside of the battery outer case 3 to the outside so that the respective positive and negative electrodes can be electrically connected to the outside of the non-aqueous electrolyte secondary battery 1 . The battery outer casing 3 is filled with electrolyte (not shown). The non-aqueous electrolyte secondary battery 1 does not need to be in the above-mentioned form, that is, it may be a battery of other shapes (coin type, cylindrical type, laminated type, etc.) other than the "laminated type".

The battery outer case 3 may be, for example, a container formed of laminated films. The laminated film may be, for example, a laminated film in which a resin film, a metal foil, and a sealing layer are laminated in this order. The resin film is a polyethylene terephthalate (PET) film, and the metal foil is aluminum or copper. , stainless steel, etc. metal foil, the sealing layer is polypropylene, etc.

Fig. 2 is an exploded perspective view showing an embodiment of the electrode group 2 in the non-aqueous 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 their surfaces on the positive electrode 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 current collector 9 is provided with a positive current collecting terminal 4 .

The positive electrode current collector 9 is made of, for example, aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass, or the like. The positive electrode current collector 9 can be made by treating the surface of aluminum, copper, etc. with carbon, nickel, titanium, silver, etc. for the purpose of improving adhesion, conductivity, and oxidation resistance. From the viewpoint of electrode strength and energy density, the thickness of the positive electrode current collector 9 is, for example, 1 to 50 μm.

In one embodiment, the positive electrode mixture layer 10 contains a positive electrode active material, a conductive agent, and a binder. The thickness of the positive electrode mixture layer 10 is, for example, 20 to 200 μm.

The positive electrode active material may be, for example, lithium oxide. Examples of lithium oxides 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 , and 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 (in each formula, M represents a member selected from Na (sodium), Mg (magnesium), Sc (scandium), Y ( Yttrium), Mn (manganese), Fe (iron), Co (cobalt), Cu (copper), Zn (zinc), Al (aluminum), Cr (chromium), Pb (lead), Sb (antimony), V ( At least one element in the group consisting of vanadium) and B (boron) (where M is an element different from other elements in each formula). And satisfy the following conditions: x=0~1.2; y=0 ~0.9; z=2.0~2.3.). The lithium oxide represented by Li _x Ni _1-y M _y O _z may be Li _x Ni _1-(y1+y2) Co _y1 Mn _y2 O _z (where x and z are the same as above, y1=0~0.9 , y2=0~0.9 and y1+y2=0~0.9), for example, it can be: 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 . The lithium oxide represented by Li _x Ni _1-y M _y O _z may be Li _x Ni _1-(y3+y4) Co _y3 Al _y4 O _z (where x and z are the same as above, y3 = 0 to 0.9 , y4=0~0.9 and y3+y4=0~0.9), for example, it can be LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

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

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

The conductive agent may be: carbon black such as acetylene black and Ketjen black; carbon materials such as graphite, graphene, and carbon nanotubes. The content of the conductive agent, based on the total amount of the positive electrode mixture layer, may be, for example, 0.01 mass% or more, 0.1 mass% or more, or 1 mass% or more, and may be 50 mass% or less, 30 mass% or less, or 15 mass% or less. .

Binders include, for example, resins such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; Rubber such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; styrene-butadiene -Styrene block copolymer or its hydrogenated product, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer Thermoplastic elastomers such as segmented copolymers or their hydrogenated products; soft resins such as syndiotactic-1,2-polybutadiene, polyethyl acetate, ethylene-vinylidene acetate copolymer, propylene-α-olefin copolymer, etc. ; Fluorine-containing resins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene-ethylene copolymer, polytetrafluoroethylene-polyvinylidene fluoride copolymer, etc.; Resins having nitrile group-containing monomers as monomer units; polymer compositions having ion conductivity of alkali metal ions (such as lithium ions), etc.

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

The separator 7 is not particularly limited as long as it can electronically insulate the positive electrode 6 and the negative electrode 8 and allow ions to pass therethrough, and has oxidation resistance on the positive electrode 6 side and reduction resistance on the negative electrode 8 side. Examples of the material (material) of such spacer 7 include resin, inorganic substances, and the like.

Examples of the resin include olefin polymers, fluorine polymers, cellulose polymers, polyimide, nylon, and the like. From the viewpoint of being stable to the electrolyte solution and having excellent liquid retention properties, the separator 7 is preferably a porous sheet or nonwoven fabric made of polyolefin such as polyethylene or polypropylene.

Examples of inorganic substances include oxides such as aluminum oxide and silicon dioxide; nitrides such as aluminum nitride and silicon nitride; and sulfates such as barium sulfate and calcium sulfate. The spacer 7 may be, for example, a spacer in which a fibrous or particulate inorganic substance is adhered to a film-like base material such as nonwoven fabric, woven fabric, or 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 terminal 5 .

The negative electrode current collector 11 is made of copper, stainless steel, nickel, aluminum, titanium, carbon electrode, conductive polymer, conductive glass, aluminum-cadmium alloy, etc. The negative electrode current collector 11 can be made by treating the surface of copper, aluminum, etc. with carbon, nickel, titanium, silver, etc. for the purpose of improving adhesion, conductivity, and reduction resistance. From the viewpoint of electrode strength and energy density, the thickness of the negative electrode current collector 11 is, for example, 1 to 50 μm.

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 can insert and detach lithium ions. Examples of the negative electrode active material include: carbon materials; metal composite oxides; oxides or nitrides of Group IV elements such as tin, germanium, silicon, etc.; elemental elements of lithium; lithium alloys such as lithium aluminum alloys; lithium alloys that can be combined with lithium Metals such as tin and silicon that form alloys. 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 a single type of these, or a mixture of two or more types. The negative electrode active material may be in the form of particles, for example.

Examples of the carbon material include: amorphous carbon materials, natural graphite, composite carbon materials in which a film of an amorphous carbon material is formed on natural graphite, and artificial graphite (resin raw materials such as epoxy resin and phenol resin) Or those obtained by burning asphalt-based raw materials obtained from petroleum, coal, etc.), etc. From the viewpoint of high current density charge and discharge characteristics, the metal composite oxide preferably contains one or both of titanium and lithium, and more preferably contains lithium.

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 simple substance of silicon or tin, or a compound containing at least one element selected from the group consisting of silicon and tin. The compound may also be an alloy containing at least one element selected from the group consisting of silicon and tin. For example, the compound may be an alloy containing, in addition to silicon and tin, an alloy selected from the group consisting of nickel, copper, iron, At least one member from the group consisting of cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium. The compound containing at least one element selected from the group consisting of silicon and tin may be an oxide, a nitride or a carbide. Specifically, it may be a silicon oxide such as SiO, SiO ₂ , LiSiO, etc. ; Silicon nitrides such as Si ₃ N ₄ and Si ₂ N ₂ O; silicon carbides such as SiC; tin oxides such as SnO, SnO ₂ and LiSnO, etc.

From the viewpoint of further improving the performance of the electrochemical device, the negative electrode mixture layer 12 preferably contains a carbon material as the negative electrode active material, more preferably graphite, and still more preferably contains a mixture having a carbon material , and a material containing at least one element selected from the group consisting of silicon and tin, particularly preferably a mixture containing graphite and silicon oxide. The content of the material (silicon oxide) containing at least one element selected from the group consisting of silicon and tin in the mixture may be 1 mass % or more or 3 mass % based on the total amount of the mixture. or above, and may be 30 mass% or less.

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

The binder and its content can be the same as the binder and its content in the above-mentioned positive electrode mixture layer.

In order to adjust the viscosity, the negative electrode mixture layer 12 may further contain a tackifier. The tackifier is not particularly limited and can be: carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and the like. Salts etc. The thickening agent may be one type alone or a mixture of two or more types among these.

When the negative electrode mixture layer 12 contains a thickening agent, its content is not particularly limited. From the viewpoint of the coating properties of the negative electrode mixture layer, the content of the thickening agent, based on the total amount of the negative electrode mixture layer, may be 0.1 mass% or more, preferably 0.2 mass% or more, and more preferably 0.5 mass%. above. From the viewpoint of suppressing a decrease in battery capacity or an increase in resistance between negative electrode active materials, the content of the thickener may be 5% by mass or less based on the total amount of the negative electrode mixture layer, and preferably 3% by mass. mass% or less, more preferably 2 mass% or less.

In order to improve the performance of the electrochemical device, the electrolyte must have at least one chemical shift between -180 ppm and -150 ppm, and between -150 ppm and -130 ppm in ¹⁹ F-NMR (Fluorine 19 Nuclear Magnetic Resonance) measurement. Peaks are displayed within the range.

The electrolyte solution can display a peak in any chemical shift range between -180 ppm and -150 ppm, and between -150 ppm and -130 ppm. The electrolyte solution may display peaks in two chemical shift ranges, namely -180 ppm and above and -150 ppm and below, and chemical shift ranges between -150 ppm and -130 ppm.

In this specification, ¹⁹ F-NMR measurement of an electrolyte solution is performed based on the following conditions. Measuring device: Avance neo manufactured by Bruker Japan Measuring method: Single pulse wave method Nuclear species observed: ¹⁹ F Spectral width: 90kHz Pulse width: 15μs (90° pulse) Pulse repetition time: 1s Reference material: C ₆ H ₅ CF ₃ (External reference: -63.9ppm) Temperature: 23℃ Sample rotation number: 20Hz

In one embodiment, the electrolyte solution exhibits a peak (Peak A) within a chemical shift range of -180 ppm or more and -150 ppm or less. The chemical shift range of peak A can be -175ppm and -155ppm, -170ppm and -158ppm, -168ppm and -160ppm, -165ppm and -160ppm, or -163ppm and -161ppm. . Peak A may be a peak group composed of a plurality of peaks existing in the chemical shift range of -180 ppm or more and -150 ppm or less.

In another embodiment, the electrolyte solution exhibits a peak (Peak B) in a chemical shift range exceeding -150 ppm and -130 ppm or less. The chemical shift range in which peak B exists can be -145ppm and below -130ppm, -143ppm and below -133ppm, -140ppm and below -130ppm, -140ppm and -133ppm, -140ppm and -135ppm, Or -138ppm or more and -133ppm or less. Peak B may be a peak group composed of a plurality of peaks existing in a chemical shift range of more than -150 ppm and less than -130 ppm.

In one embodiment, each of the above peaks (peaks A and B) originates from a compound represented by the following formula (1) contained in the electrolyte solution. That is, in one embodiment, the electrolyte solution contains a compound represented by the following formula (1). In formula (1), R ¹ to R ³ each independently represents an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, R ⁵ represents an organic group containing a sulfur atom or a nitrogen atom, and at least one of R ¹ to R ³ 1 is a fluorine atom.

When R ¹ to R ³ are alkyl groups, the number of carbon atoms in the alkyl group may be 1 or more and may be 3 or less. 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 a fluorine atom. When any one of R ¹ to R ³ is a fluorine atom, that is, when the electrolyte solution contains a compound represented by the following formula (2), the electrolyte solution shows the above-mentioned peak A in ¹⁹ F-NMR measurement. In the formula (2), R ² and R ³ each independently represent an alkyl group, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom or a nitrogen atom.

When two of R ¹ to R ³ are fluorine atoms, or when all of R ¹ to R ³ are fluorine atoms, that is, when the electrolyte solution contains a compound represented by the following formula (3) or (4), The electrolyte solution shows the above-mentioned peak B in ¹⁹ F-NMR measurement. In the formula (3), R ³ represents an alkyl group, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom or a nitrogen atom. In formula (4), R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom or a nitrogen atom.

The carbon number of the alkylene group represented by R ⁴ in the above formulas (1) to (4) may be 1 or more or 2 or more, and may be 5 or less or 4 or less. The alkylene group represented by R ⁴ may be methylene, ethylene, propylene, butylene or pentylene, and may be linear or branched.

In one embodiment, R ⁵ in the above formulas (1) to (4) may be an organic group containing a sulfur atom.

When R ⁵ is an organic group containing a sulfur atom, in one embodiment, R ⁵ may be a group represented by the following formula (5). In formula (5), R ⁶ 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 bonding key (the same below).

When R ⁵ is an organic group containing a sulfur atom, in another embodiment, R ⁵ may be a group represented by the following formula (6). In formula (6), R ⁷ represents an alkyl group. The alkyl group may be the same as the alkyl group represented by R ¹ to R ³ described above.

When R ⁵ is an organic group containing a sulfur atom, in another embodiment, R ⁵ may be a group represented by the following formula (7). In formula (7), 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.

In another embodiment, R ⁵ may be an organic group containing a nitrogen atom.

When R ⁵ is an organic group containing a nitrogen atom, in one embodiment, R ⁵ may be a group represented by the following formula (8). In formula (8), R ⁹ and R ¹⁰ each independently represent a hydrogen atom or an alkyl group. The alkyl group may be the same as the alkyl group represented by R ¹ to R ³ described above.

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 silicon atoms.

From the viewpoint of further improving the performance of the electrochemical device, the content of the compound represented by formula (1) is preferably 0.001 mass % or more, 0.005 mass % or more, or 0.01 mass % or more based on the total amount of the electrolyte solution. , 0.05 mass% or more, 0.1 mass% or more, 0.3 mass% or more or 0.5 mass% or more, and preferably 10 mass% or less, 7 mass% or less, 5 mass% or less, 3 mass% or less, 2 mass% or less , 1.5 mass% or less or 1 mass% or less.

In addition to the above-mentioned peak A and peak B, the electrolyte solution may further exhibit a peak (peak C) in a chemical shift range exceeding -130 ppm and -110 ppm or less in measurement by ¹⁹ F-NMR.

The chemical shift range in which peak C exists may be -128 ppm or more and -115 ppm or less, -126 ppm or more and -120 ppm or less, -125 ppm or more and -122 ppm or less, or -123 ppm or more and -120 ppm or less. Peak C may be a peak group composed of a plurality of peaks existing in the chemical shift range of more than -130 ppm and less than -110 ppm.

In one embodiment, peak C originates from fluorine-containing cyclic carbonate that may be contained in the electrolyte. That is, in one embodiment, the electrolyte solution may contain a fluorine-containing cyclic carbonate.

Fluorine-containing cyclic carbonate is a cyclic carbonate that contains fluorine atoms in the molecule. In one embodiment, the fluorine-containing cyclic carbonate is a cyclic carbonate containing a fluorine group. The fluorine-containing cyclic carbonate is not particularly limited as long as it contains a fluorine group. For example, it may be: 4-fluoro-1,3-dioxolane-2-one (fluorine carbonate). Ethyl ester, FEC), 1,2-difluoroethylidene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-carbonate Ethyl tetrafluoride, etc. From the viewpoint of suppressing side reactions at the negative electrode, the fluorine-containing cyclic carbonate is preferably 4-fluoro-1,3-dioxolan-2-one (fluoroethyl carbonate, FEC).

From the viewpoint of further improving the performance of the electrochemical device, the content of the fluorine-containing cyclic carbonate is preferably 0.001 mass % or more, 0.005 mass % or more, 0.01 mass % or more, 0.05 mass % or more based on the total amount of the electrolyte solution. Mass% or more or 0.1 mass% or more, and 5 mass% or less, 3 mass% or less, 2 mass% or less, or 1 mass% or less.

When the electrolyte solution contains both the compound represented by formula (1) and the fluorine-containing cyclic carbonate, from the viewpoint of further improving the performance of the electrochemical device, the compound represented by formula (1) and the fluorine-containing cyclic carbonate The total amount of carbonate content is preferably 0.001 mass% or more, 0.005 mass% or more, 0.01 mass% or more, 0.1 mass% or more, or 0.5 mass% or more, based on the total amount of the electrolyte solution, and preferably 10 mass% or less, 7 mass% or less, 5 mass% or less, 3 mass% or less, 2 mass% or less, 1.5 mass% or less, or 1 mass% or less.

In addition to the compound represented by formula (1) and the fluorine-containing cyclic carbonate, the electrolyte solution may further contain an electrolyte salt, a non-aqueous solvent, and additives.

The electrolyte salt may be, for example, a lithium salt. The lithium salt may be selected from the group consisting of 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], Lithium bis(fluoromethanesulfonyl)imide), LiN(SO ₂ CF ₃ ) ₂ (Li[TFSI], lithium bis(trifluoromethanesulfonyl)imide), and LiN(SO ₂ CF ₂ CF ₃ ) At least 1 of the groups consisting of ₂ . The lithium salt preferably contains LiPF ₆ from the viewpoint of further excellent solubility in the non-aqueous solvent described below and performance of the electrochemical device.

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

Non-aqueous solvents, for example, can be: ethyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, acetonitrile, 1,2-dimethoxy Ethane, dimethoxymethane, tetrahydrofuran, dioxolane, methylene chloride, methyl acetate, etc. The non-aqueous solvent may be a single type of these solvents or a mixture of two or more types thereof, preferably a mixture of two or more types of these solvents.

The additive is a compound other than the compound represented by formula (1) and the fluorine-containing cyclic carbonate, and may be, for example, a cyclic carbonate having a carbon-carbon double bond, a nitrile compound, a cyclic sulfonate compound, or the like. The content of the additive may be, for example, 0.001 mass % or more and 5 mass % or less based on the total amount of the electrolyte solution.

Cyclic carbonate having carbon-carbon double bonds is a cyclic carbonate having carbon-carbon double bonds. In one embodiment, the two carbon atoms constituting the ring in the cyclic carbonate may form a double bond. Cyclic carbonates can be: vinyl carbonate, vinyl carbonate, methyl vinyl carbonate, dimethyl vinyl carbonate (4,5-dimethyl vinyl carbonate), ethyl vinyl carbonate ester, diethyl vinyl carbonate (4,5-diethyl vinyl carbonate), etc.; from the viewpoint of further improving the performance of the electrochemical device, vinyl carbonate is preferred.

A nitrile compound is a compound having at least one cyano group (nitrile group). Nitrile compounds may have, for example, 1, 2 or 3 cyano groups. Examples of the nitrile compound having one cyano group include butyronitrile, valeronitrile, n-heptyl nitrile, and the like. Examples of the nitrile compound having two cyano groups include succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and the like. Examples of the nitrile compound having three cyano groups include 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, and the like. From the viewpoint of forming a stable coating on the positive electrode or the negative electrode and being able to suppress battery expansion due to decomposition of the electrolyte, the nitrile compound is preferably a nitrile compound having two or more cyano groups and excluding carbon atoms of the cyano group. Compounds with 2 or more carbon atoms. The nitrile compound is more preferably a compound having 2 or 3 cyano groups and having 2 or more carbon atoms other than the carbon atom of the cyano group. The nitrile compound is more preferably succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, 1,2,3-propanetricarbonitrile or 1,3,5-pentanetricarbonitrile, from which it is possible to further From the viewpoint of improving the performance of electrochemical devices, succinonitrile is particularly preferred.

The cyclic sulfonate compound is a compound having a ring containing 1 or 2 -OSO ₂ - groups. Cyclic sulfonate compounds include, for example: 1,3-propane sultone, 1-propene-1,3-sultone, 1,3-propane sultone, and 1,4-butane sultone. , 2,4-butane sultone, 1,3-propene sultone, 1,4-butene sultone, 1-methyl-1,3-propane sultone, 3-methyl-1 , monosulfonate esters of 3-propane sultone, 1-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, etc.; methylene methane disulfonate, methane di Disulfonate esters such as ethylidene sulfonate, etc.; from the viewpoint of further improving chemical properties, 1,3-propane sultone or 1-propene-1,3-sultone is preferred.

Next, a method of manufacturing the non-aqueous electrolyte secondary battery 1 will be described. The manufacturing method of non-aqueous electrolyte secondary battery 1 includes: a first step to obtain a positive electrode 6; a second step to obtain a negative electrode 8; and a third step to accommodate the electrode group 2 in the battery outer casing 3 ; and, the fourth step is to inject the electrolyte into the battery outer casing 3. The order of the first step to the fourth step is arbitrary.

In the first step, the materials used for the positive electrode mixture layer 10 are dispersed in the dispersion medium using a kneader, a disperser, etc. to obtain a slurry positive electrode mixture. , spraying method, etc., apply the positive electrode mixture on the positive electrode current collector 9, and then volatilize the dispersion medium to obtain the positive electrode 6. After volatilizing the dispersion medium, a compression molding step using a roller press may be provided as needed. The positive electrode mixture layer 10 can be formed into a multi-layered positive electrode mixture layer by performing a plurality of the above steps from applying the positive electrode mixture to volatilizing the dispersion medium. 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 method as 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 . Then, the electrode group 2 is accommodated in the battery outer case 3 .

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

As another embodiment, the electrochemical device may be a capacitor. Like the nonaqueous electrolyte secondary battery 1 described above, the capacitor may include an electrode group composed of a positive electrode, a negative electrode, and a separator, and a bag-shaped battery outer casing that can accommodate the electrode group. Details of each component in the capacitor may be the same as those in the non-aqueous electrolyte secondary battery 1 . [Example]

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

(Example 1) [Preparation of electrolyte solution] To a mixed solution of ethyl carbonate, dimethyl carbonate, and diethyl carbonate containing 1 mol/L LiPF6, 1 mass % of ethyl carbonate was added based on the total amount of the mixed solution. An electrolyte solution was prepared using vinyl carbonate (VC) and 1 mass % of compound A represented by the following formula (9) (based on the total amount of the electrolyte solution).

[ ¹⁹ F-NMR measurement] For the prepared electrolyte solution, ¹⁹ F-NMR measurement was performed according to the above-mentioned measurement conditions. As a result, the following spectrum was obtained: a peak derived from PF ₆ ^- and its reactants is displayed in the chemical shift range of -100 ppm or more and -70 ppm or less, and is displayed in the chemical shift range of -180 ppm or more and -150 ppm or less. Peak originating from compound A. A spectrum showing peaks derived from compound A, as shown in Figure 3(a). ¹⁹ F-NMR: -73.68ppm, -75.56ppm, -82.74ppm, -85.34ppm, -86.80ppm, -89.65ppm, -162.07ppm

(Example 2) [Preparation of Electrolyte Solution] In Example 1, except that 1 mass % (based on the total amount of the electrolyte solution) of compound B represented by the following formula (10) was added instead of compound A, The electrolyte solution was prepared in the same manner as in Example 1.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: a peak derived from PF ₆ ^- and its reactants is displayed in the chemical shift range of -100 ppm or more and -70 ppm or less, and is displayed in the chemical shift range of -180 ppm or more and -150 ppm or less. Peak originating from compound B. A spectrum showing peaks derived from compound B, as shown in Figure 3(b). ¹⁹ F-NMR: -73.26ppm, -75.14ppm, -82.65ppm, -85.26ppm, -86.79ppm, -89.64ppm, -162.02ppm

(Comparative example 1) [Preparation of electrolyte] Regarding Example 1, except not using compound A, it carried out similarly to Example 1, and prepared the electrolyte solution.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, a spectrum was obtained showing peaks derived from PF ₆ ⁻ and its reactants in the chemical shift range of -100 ppm or more and -70 ppm or less. ¹⁹ F-NMR: -75.03ppm, -75.28ppm, -76.91ppm, -77.16ppm, -88.07ppm, -90.92ppm

(Comparative example 2) [Preparation of electrolyte] Regarding Example 1, except that Compound A was not used and 1 mass % (based on the total amount of electrolyte solution) of 4-fluoro-1,3-dioxolane-2-one (ethyl fluoride carbonate) was added , FEC), the electrolyte solution was prepared in the same manner as in Example 1.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: a peak originating from PF ₆ ^- and its reactants was displayed in the chemical shift range of -100 ppm or more and -70 ppm or less, and it was in the chemical shift range of -130 ppm or more and -110 ppm or less. Peaks originating from FEC are shown. A spectrum showing peaks originating from FEC, as shown in Figure 4. ¹⁹ F-NMR: -73.69ppm, -75.57ppm, -82.62ppm, -85.22ppm, -86.82ppm, -89.67ppm, -121.30ppm

(Example 3) [Preparation of electrolyte solution] In Example 1, except that 1 mass % (based on the total amount of the electrolyte solution) of compound C represented by the following formula (11) was added in place of compound A, The electrolyte solution was prepared in the same manner as in Example 1.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: peaks originating from PF ₆ ^- and its reactants are displayed in the chemical shift range of -100 ppm or more and -70 ppm or less, and peaks originating from PF 6 - and its reactants are displayed in the chemical shift range of -150 ppm or more and -110 ppm or less. Peak originating from compound C. A spectrum showing peaks derived from compound C, as shown in Figure 5(a). ¹⁹ F-NMR: -73.66ppm, -75.54ppm, -82.65ppm, -85.25ppm, -86.81ppm, -89.66ppm, -135.13ppm

(Example 4) [Preparation of Electrolyte Solution] In Example 1, except that 1 mass % (based on the total amount of the electrolyte solution) of compound D represented by the following formula (12) was added in place of compound A, The electrolyte solution was prepared in the same manner as in Example 1.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: peaks originating from PF ₆ ^- and its reactants are displayed in the chemical shift range of -100 ppm or more and -70 ppm or less, and peaks originating from PF 6 - and its reactants are displayed in the chemical shift range of -150 ppm or more and -110 ppm or less. Peak derived from compound D. A spectrum showing the peak originating from compound D is shown in Figure 5(b). ¹⁹ F-NMR: -73.62ppm, -75.49ppm, -82.76ppm, -85.37ppm, -86.78ppm, -89.63ppm, -136.60ppm

(Example 5) [Preparation of electrolyte] Regarding Example 1, the electrolyte solution was prepared in the same manner as in Example 1, except that the content of compound A was changed to 0.5 mass % and 0.5 mass % (both based on the total amount of the electrolyte solution) FEC was added.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: peaks originating from PF ₆ ^- and its reactants were shown in the chemical shift range of -100 ppm or more and -70 ppm or less, and peaks derived from the chemical shift range of -180 ppm or more and -150 ppm or less were obtained. A peak derived from compound A, and a peak derived from FEC is displayed in a chemical shift range exceeding -130 ppm or more and -110 ppm or less. A spectrum showing peaks derived from Compound A and peaks derived from FEC is shown in Figure 6(a). ¹⁹ F-NMR: -73.69ppm, -75.58ppm, -82.73ppm, -85.25ppm, -86.85ppm, -89.70ppm, -121.45ppm, -162.10ppm

(Example 6) [Preparation of electrolyte] Regarding Example 3, the electrolyte solution was prepared in the same manner as in Example 3, except that the content of compound C was changed to 0.5 mass % and 0.5 mass % (both based on the total amount of the electrolyte solution) FEC was added.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: peaks originating from PF ₆ ^- and its reactants were displayed in the chemical shift range of -100 ppm or more and -70 ppm or less, and peaks derived from the chemical shift range of -150 ppm to -130 ppm were obtained. A peak derived from compound C, and a peak derived from FEC is displayed in a chemical shift range exceeding -130 ppm or more and -110 ppm or less. A spectrum showing peaks derived from compound C and peaks derived from FEC is shown in Figure 6(b). ¹⁹ F-NMR: -73.67ppm, -75.55ppm, -82.68ppm, -85.25ppm, -86.80ppm, -89.65ppm, -121.23ppm, -135.14ppm

(Example 7) [Preparation of electrolyte] Regarding Example 4, the electrolyte solution was prepared in the same manner as in Example 4, except that the content of compound D was changed to 0.5 mass % and 0.5 mass % (both based on the total amount of the electrolyte solution) FEC was added.

[ ¹⁹ F-NMR measurement] The prepared electrolyte solution was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: peaks originating from PF ₆ ^- and its reactants were displayed in the chemical shift range of -100 ppm or more and -70 ppm or less, and peaks derived from the chemical shift range of -150 ppm to -130 ppm were obtained. A peak derived from compound D, and a peak derived from FEC is displayed in a chemical shift range exceeding -130 ppm or more and -110 ppm or less. A spectrum showing peaks derived from compound D and peaks derived from FEC is shown in Figure 6(c). ¹⁹ F-NMR: -73.68ppm, -75.57ppm, -82.57ppm, -85.17ppm, -86.83ppm, -89.68ppm, -121.35ppm, -136.69ppm

[Preparation of positive electrode] To lithium cobalt oxide (95 mass %) as the positive electrode active material, fibrous graphite (1 mass %) as a conductive agent and acetylene black (AB, 1 mass %) were sequentially added and mixed. and adhesive (3% by mass). NMP as a dispersion medium was added to the obtained mixture, and kneaded to prepare a slurry positive electrode mixture. This positive electrode mixture was uniformly and homogeneously applied on an aluminum foil having a thickness of 20 μm as a positive electrode current collector. Thereafter, the dispersion medium was volatilized, and the density was densified to 3.6 g/cm ³ by applying pressure to obtain a positive electrode.

[Preparation of Negative Electrode] To graphite and silicon oxide as negative electrode active materials, a binder and carboxymethyl cellulose as a thickener are added. The mass ratio of these is graphite:silicon oxide:binder:tackifier=92:5:1.5:1.5. To the obtained mixture, water as a dispersion medium was added and kneaded to prepare a slurry negative electrode mixture. This negative electrode mixture was uniformly and homogeneously applied on a rolled copper foil having a thickness of 10 μm as a negative electrode current collector. Thereafter, the dispersion medium was volatilized, and the density was densified to 1.6 g/cm ³ by applying pressure to obtain a negative electrode.

[Preparation of lithium ion secondary battery] A porous sheet (trade name: Hipore (registered trademark), manufactured by Asahi Kasei Co., Ltd., thickness 30 μm) made of polyethylene was sandwiched and cut to 13.5 cm ² The square positive electrode was further overlapped with the square negative electrode cut into 14.3 cm ² to form an electrode group. This electrode group was housed in a container (battery outer case) made of an aluminum laminated film (trade name: aluminum laminated film, manufactured by Dainippon Printing Co., Ltd.). Next, 1 mL of the prepared electrolyte solution of Example 1, Example 2, Comparative Example 1 or Comparative Example 2 was added to the container, and the container was thermally welded to prepare a lithium ion secondary battery for evaluation. .

[Initial charge and discharge] The produced lithium-ion battery was first charged and discharged using the method shown below. First, in an environment of 25°C, constant current charging is performed at a current value of 0.1C until the upper limit voltage is 4.2V, and then constant voltage charging is performed at 4.2V. The charging end condition is set to a current value of 0.01C. After that, a constant current discharge with an end voltage of 2.5V is performed at a current value of 0.1C. Repeat this charge and discharge cycle three times (the "C" used as the unit of current value means "current value (A)/battery capacity (Ah)").

[Evaluation of cycle characteristics] After the initial charge and discharge, the cycle characteristics of each secondary battery obtained using the electrolyte solutions of Examples 1 to 2 and Comparative Examples 1 to 2 were evaluated through a cycle test of repeated charge and discharge. As the charging mode, in a 45°C environment, constant current charging is performed at a current value of 0.5C until the upper limit voltage is 4.2V, and then constant voltage charging is performed at 4.2V. The charging end condition is set to a current value of 0.05C. Regarding discharge, a constant current discharge is carried out at 1C until it reaches 2.5V, and the discharge capacity is obtained. This series of charge and discharge was repeated for 200 cycles, and the discharge capacity was measured for each charge and discharge. The discharge capacity after charge and discharge in the first cycle of Comparative Example 1 was set to 1, and the relative value of the discharge capacity in each cycle (discharge capacity ratio) was obtained. The relationship between the relative values of cycle number and discharge capacity is shown in Figure 7.

As shown in Figure 7, the lithium ion secondary batteries of Examples 1 and 2 used an electrolyte solution that showed a peak in the chemical shift range of -180 ppm or more and -150 ppm or less when measured by ¹⁹ F-NMR. , the lithium ion secondary batteries of Comparative Examples 1 to 2 use an electrolyte solution that does not show a peak in this range. Compared with the lithium ion secondary batteries of Comparative Examples 1 to 2, the lithium ion secondary batteries of Examples 1 to 2 The discharge capacity ratio at the 200th cycle is larger. Therefore, the lithium ion secondary batteries of Examples 1 and 2 show excellent performance (cycle characteristics).

1: Non-aqueous electrolyte secondary battery (electrochemical device) 2:Electrode group 3:Battery housing 4: Positive collector terminal 5: Negative collector terminal 6: Positive pole 7: Spacer 8: Negative pole 9: Positive collector 10: Positive electrode mixture layer 11: Negative current collector 12: Negative electrode mixture layer

FIG. 1 is a perspective view showing a non-aqueous electrolyte secondary battery as an electrochemical device according to an embodiment. Fig. 2 is an exploded perspective view showing the electrode group of the secondary battery shown in Fig. 1 . Figure 3 is a spectrum obtained by ¹⁹ F-NMR measurement, (a) is a spectrum for the electrolyte solution of Example 1, and (b) is a spectrum for the electrolyte solution of Example 2. Figure 4 is a spectrum of the electrolyte solution of Comparative Example 2 obtained by ¹⁹ F-NMR measurement. Figure 5 is a spectrum obtained by ¹⁹ F-NMR measurement, (a) is a spectrum for the electrolyte solution of Example 3, and (b) is a spectrum for the electrolyte solution of Example 4. Figure 6 is a spectrum obtained by ¹⁹ F-NMR measurement, (a) is a spectrum for the electrolyte solution of Example 5, (b) is a spectrum for the electrolyte solution of Example 6, (c) This is a spectrum for the electrolyte solution of Example 7. Fig. 7 is a graph showing evaluation results of cycle characteristics.

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Claims (6)

An electrolyte solution that exhibits a peak within at least one chemical shift range of -180 ppm or more and -150 ppm or less, and -150 ppm or less and -130 ppm or less, as measured by fluorine-19 nuclear magnetic resonance, and further In the measurement by fluorine-19 nuclear magnetic resonance, a peak was shown in the chemical shift range of more than -130 ppm and -110 ppm or less. An electrochemical device provided with: a positive electrode, a negative electrode, and the electrolyte solution described in claim 1. The electrochemical device according to claim 2, wherein the negative electrode contains carbon material. The electrochemical device according to claim 3, wherein the carbon material contains graphite. The electrochemical device according to claim 3 or 4, wherein the negative electrode further contains a material containing at least one element selected from the group consisting of silicon and tin. The electrochemical device according to claim 3, wherein the electrochemical device is a non-aqueous electrolyte secondary battery or a capacitor.

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