TW202032848A - Electrolyte solution and electrochemical device - Google Patents

Abstract

The present invention provides an electrolyte solution which, according to one aspect, exhibits a peak within the range of a chemical shift from -180 ppm to -150 ppm and/or a chemical shift from over -150 ppm to -130 ppm or less, as determined by 19F-NMR measurement.

Description

Electrolyte and electrochemical device

The invention relates to an electrolyte and an electrochemical device.

In recent years, due to the popularization of portable electronic devices, electric vehicles, etc., high-performance electrochemical devices are deemed necessary. These high-performance electrochemical devices are non-aqueous electrolytes represented by lithium ion secondary batteries. Secondary batteries, capacitors, etc. As a means to improve the performance of an electrochemical device, for example, a method has been explored in which a specific additive is added to the electrolyte. In Patent Document 1, in order to improve cycle characteristics and internal resistance characteristics, an electrolyte solution for a non-aqueous electrolyte battery containing a specific silicone compound is disclosed. [Prior Technical Literature] (Patent Document)

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

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

As a first aspect, the present invention provides an electrolytic solution which, in a measurement performed by ¹⁹ F-NMR (fluorine 19 nuclear magnetic resonance), is above -180 ppm and below -150 ppm, and exceeds -150 ppm and below -130 ppm At least one of them shows a peak in the chemical shift range.

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

In the first aspect, the electrolyte solution can further show a peak in a chemical shift range exceeding -130 ppm and below -110 ppm in a measurement performed by ¹⁹ F-NMR.

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

In the second aspect, the negative electrode preferably contains a carbon material. The carbon material preferably contains graphite. The negative electrode preferably further contains the following material, which contains 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. [Effect of Invention]

According to the present invention, it is possible to provide an electrolyte that can improve the performance of an electrochemical device.

Hereinafter, embodiments of the present invention will be described while referring to the drawings as appropriate. 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 composed of a positive electrode, a negative electrode, and a separator; and a pouch-shaped battery case 3 that can house the electrode group 2 . For the positive electrode and the negative electrode, a positive electrode collector terminal 4 and a negative electrode collector terminal 5 are respectively provided. The positive electrode current collector terminal 4 and the negative electrode current collector terminal 5 protrude from the inside of the battery 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 case 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 in a shape other than the "stacked type" (coin type, cylindrical shape, stacked type, etc.).

The battery case 3 may be, for example, a container formed of a laminated film. The laminated film may be, for example, a laminated film formed by sequentially laminating a resin film, a metal foil, and a sealing layer. The resin film is a polyethylene terephthalate (PET) film, etc., and the metal foil is aluminum or copper. , Stainless steel and other metal foil, the sealing layer is polypropylene or the like.

Fig. 2 is an exploded perspective view showing one embodiment of the electrode group 2 in the non-aqueous electrolyte secondary battery 1 shown in Fig. 1. As shown in Figure 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 such that the 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 electrode current collector 9 is provided with a positive electrode current collector terminal 4.

The positive electrode current collector 9 is formed of, for example, aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass, or the like. The positive electrode current collector 9 aims at improving adhesion, conductivity, and oxidation resistance, and may be obtained by treating the surface of aluminum, copper, etc. with carbon, nickel, titanium, silver, or the like. 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 lithium oxide, for example. 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 , 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 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) (wherein M is an element different from the other elements in each formula). And meet 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 can 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: 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 can be Li _x Ni _1-(y3+y4) Co _y3 Al _y4 O _z (where x and z are the same as above, y3=0～0.9 , Y4=0 to 0.9 and y3+y4=0 to 0.9), for example, it may be LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

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

The conductive agent may be: carbon black such as acetylene black and Ketjen black; carbon material such as graphite, graphene, carbon nanotube, etc. The content of the conductive agent is based on the total amount of the positive electrode mixture layer. For example, it can be 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more, and can be 50% by mass or less, 30% by mass or less, or 15% by mass or less. .

Examples of the binder include resins such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber, etc.; styrene-butadiene -Styrenic block copolymer or its hydrogenated product, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer Thermoplastic elastomer such as segment copolymer or its hydrogenated product; soft resin such as syndiotactic-1,2-polybutadiene, polyethyl acetate, ethylene-vinyl 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 is based on the total amount of the positive electrode mixture layer. For example, it can be 0.1% by mass or more, 1% by mass or more, or 1.5% by mass or more, and can be 30% by mass or less, 20% by mass or less or 10% by mass or less. .

The separator 7 is not particularly limited as long as it can electrically insulate the positive electrode 6 and the negative electrode 8 and allow ions to pass through, and has oxidation resistance on the positive electrode 6 side and reduction resistance on the negative electrode 8 side. As a material (material) of such a spacer 7, resin, an inorganic substance, etc. are mentioned.

Examples of resins include olefin-based polymers, fluorine-based polymers, cellulose-based polymers, polyimide, nylon, and the like. From the viewpoint of stability to electrolyte and excellent liquid retention, the spacer 7 is preferably a porous sheet or non-woven fabric formed of polyolefin such as polyethylene and polypropylene.

Examples of inorganic substances 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 spacer 7 may be, for example, a spacer formed by attaching a fibrous or particulate inorganic substance to a film-like substrate such as a non-woven 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 terminal 5.

The negative electrode current collector 11 is formed of copper, stainless steel, nickel, aluminum, titanium, carbon electrode, conductive polymer, conductive glass, aluminum-cadmium alloy, and the like. The negative electrode current collector 11 aims to improve adhesion, conductivity, and reduction resistance, and may be obtained by treating the surface of copper, aluminum, etc., with carbon, nickel, titanium, silver, or the like. 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, and silicon; simple substances of lithium; lithium alloys such as lithium aluminum alloys; 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 one of these alone or a mixture of two or more. The shape of the negative electrode active material may be, for example, particulate.

Examples of carbon materials include amorphous carbon materials, natural graphite, composite carbon materials formed by forming a film of amorphous carbon material on natural graphite, and artificial graphite (resin raw materials such as epoxy resins and phenol resins). Or those obtained by firing 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 either 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, and 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 following alloy. In addition to silicon and tin, the alloy also includes nickel, copper, iron, At least one of the group consisting of cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium. A compound containing at least one element selected from the group consisting of silicon and tin, which may be oxide, nitride, or carbide, specifically, for example, silicon oxide such as SiO, SiO ₂ , and LiSiO ; Si ₃ N ₄ , Si ₂ N ₂ O and other silicon nitrides; SiC and other silicon carbides; SnO, SnO ₂ , LiSnO and other tin oxides.

The negative electrode mixture layer 12, from the viewpoint of further improving the performance of the electrochemical device, as the negative electrode active material, preferably contains a carbon material, more preferably contains graphite, and still more preferably contains the following mixture, which has a carbon material , And a material containing at least one element selected from the group consisting of silicon and tin, particularly preferably a mixture of 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, based on the total amount of the mixture, may be 1% by mass or more or 3% by mass Above, and may be 30% by mass or less.

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

The binder and its content may be the same as the aforementioned binder and its content in the positive electrode mixture layer.

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

When the negative electrode mixture layer 12 contains a thickener, its content is not particularly limited. From the viewpoint of the coatability 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% by mass or more, preferably 0.2% by mass or more, more preferably 0.5% by mass the above. From the viewpoint of suppressing the decrease in battery capacity or the increase in the resistance between the 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 is preferably 3%. % By mass or less, more preferably 2% by mass or less.

In order to improve the performance of the electrochemical device, the electrolyte shall have at least one chemical shift among -180ppm or more and -150ppm or more than -150ppm and -130ppm in ¹⁹ F-NMR (fluorine 19 nuclear magnetic resonance) measurement Peaks are displayed within the range.

The electrolyte can show peaks in any chemical shift range from -180ppm to -150ppm, and from -150ppm to -130ppm. The electrolyte solution may show peaks in two ranges of chemical shift ranges of -180 ppm or more and -150 ppm or less, and more than -150 ppm and -130 ppm or less.

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

In one embodiment, the electrolyte solution shows a peak (peak A) in a chemical shift range of -180 ppm or more and -150 ppm or less. The chemical shift range of peak A can be -175ppm or more and -155ppm or less, -170ppm or more and -158ppm or less, -168ppm or more and -160ppm or less, -165ppm or more and -160ppm or less, or -163ppm or more and -161ppm or less . The peak A may be a peak group consisting 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 shows a peak (peak B) in a chemical shift range exceeding -150 ppm and -130 ppm. The chemical shift range of peak B can be -145ppm or more and -130ppm or less, -143ppm or more and -133ppm or less, -140ppm or more and -130ppm or less, -140ppm or more and -133ppm or less, -140ppm or more and -135ppm or less, Or -138ppm or more and -133ppm or less. The peak B may be a peak group consisting of a plurality of peaks existing in a chemical shift range exceeding -150 ppm and -130 ppm.

式(1)中，R¹ ～R³ 各自獨立地表示烷基或氟原子，R⁴ 表示伸烷基，R⁵ 表示包含硫原子或氮原子之有機基團，R¹ ～R³ 中的至少1個是氟原子。In one embodiment, each of the above-mentioned peaks (peaks A and B) are derived from the compound represented by the following formula (1) contained in the electrolytic solution. That is, in one embodiment, the electrolytic solution contains a compound represented by the following 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, R ⁵ represents an organic group containing a sulfur atom or a nitrogen atom, and at least one of R ¹ to R ³ One is a fluorine atom.

When R ¹ to R ³ are an alkyl group, the carbon number of the alkyl group may be 1 or more, and may be 3 or less. R ¹ to R ³ may be methyl, ethyl, or propyl, and may be linear or branched.

式(2)中，R² 和R³ 各自獨立地表示烷基，R⁴ 表示伸烷基，R⁵ 表示包含硫原子或氮原子之有機基團。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 electrolytic solution contains a compound represented by the following formula (2), the electrolytic solution shows the aforementioned peak A in the ¹⁹ F-NMR measurement.

In 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.

式(3)中， R³ 表示烷基，R⁴ 表示伸烷基，R⁵ 表示包含硫原子或氮原子之有機基團。

式(4)中， R⁴ 表示伸烷基，R⁵ 表示包含硫原子或氮原子之有機基團。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 contains a compound represented by the following formula (3) or (4), The electrolytic solution showed the aforementioned 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 the 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 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.

式(5)中，R⁶ 表示烷基。烷基，可與上述的由R¹ ～R³ 表示的烷基相同。*表示鍵結鍵(以下相同)。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 the 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 a bonding key (the same below).

式(6)中，R⁷ 表示烷基。烷基，可與上述的由R¹ ～R³ 表示的烷基相同。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 the 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.

式(7)中，R⁸ 表示烷基。烷基，可與上述的由R¹ ～R³ 表示的烷基相同。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 the 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.

式(8)中，R⁹ 和R¹⁰ 各自獨立地表示氫原子或烷基。烷基，可與上述的由R¹ ～R³ 表示的烷基相同。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 a silicon atom.

From the viewpoint of further improving the performance of the electrochemical device, the content of the compound represented by formula (1), based on the total amount of electrolyte, is preferably 0.001% by mass or more, 0.005% by mass or more, or 0.01% by mass or more , 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% by mass or less or 1% by mass or less.

In the electrolytic solution measured by ¹⁹ F-NMR, in addition to the above-mentioned peak A and peak B, a peak (peak C) can be further shown in a chemical shift range exceeding -130 ppm and -110 ppm.

The chemical shift range of peak C 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. The peak C may be a group of peaks composed of a plurality of peaks existing in a chemical shift range exceeding -130 ppm and below -110 ppm.

In one embodiment, the peak C is derived from the fluorine-containing cyclic carbonate that may be contained in the electrolyte. That is, in one embodiment, the electrolyte 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 is a cyclic carbonate containing a fluorine group. For example, it may be: 4-fluoro-1,3-dioxolane-2-one (fluorocarbon Ethyl ester, FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-carbonate Tetrafluoroethylene and so on. From the viewpoint of suppressing side reactions on the negative electrode, the fluorine-containing cyclic carbonate is preferably 4-fluoro-1,3-dioxolane-2-one (fluoroethylene carbonate, FEC).

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

When the electrolytic solution contains both the compound represented by the formula (1) and the fluorine-containing cyclic carbonate, from the viewpoint of further improving the performance of the electrochemical device, the compound represented by the formula (1) and the fluorine-containing cyclic ester The total amount of carbonate content, based on the total amount of electrolyte, is preferably 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.1% by mass or more, or 0.5% by mass or more, and more 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 electrolytic solution may further contain an electrolyte salt, a non-aqueous solvent, and additives.

The electrolyte salt may be a lithium salt, for example. The lithium salt may be selected from 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(fluorosulfonyl)imide), LiN(SO ₂ CF ₃ ) ₂ (Li[TFSI], lithium bis(trifluoromethanesulfonyl)imide), and LiN(SO ₂ CF ₂ CF ₃ ) At least one of the group consisting of ₂ . From the viewpoints of further excellent solubility in the following non-aqueous solvents, performance of electrochemical devices, etc., the lithium salt preferably contains LiPF ₆ .

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

Non-aqueous solvents, such as ethylene 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 one of these alone, or a mixture of two or more, and preferably a mixture of two or more of these.

The additives are compounds other than the compound represented by the 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, and the like. The content of the additive is based on the total amount of the electrolyte, and may be, for example, 0.001% by mass or more and 5% by mass or less.

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

Nitrile compound is a compound having at least one cyano group (nitrile group). The nitrile compound may have, for example, 1, 2, or 3 cyano groups. The nitrile compound having one cyano group may be, for example, butyronitrile, valeronitrile, n-heptanonitrile, and the like. The nitrile compound having two cyano groups may be, for example, succinonitrile, glutaronitrile, adiponitrile, pimelic nitrile, suberonitrile, and the like. The nitrile compound having 3 cyano groups may be, for example, 1,2,3-propanetricarbonitrile, 1,3,5-pentatricarbonitrile and the like. From the standpoint of forming a stable coating on the positive electrode or negative electrode and being able to suppress battery swelling caused by the decomposition of the electrolyte, the nitrile compound preferably has two or more cyano groups except for the carbon atoms of the cyano group A compound 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 atoms of the cyano group. The nitrile compound is more preferably succinonitrile, glutaronitrile, adiponitrile, pimelic nitrile, suberonitrile, 1,2,3-propanetricarbonitrile or 1,3,5-glutaronitrile, which can be further From the viewpoint of improving the performance of the electrochemical device, succinonitrile is particularly preferred.

The cyclic sulfonate compound is a compound having a ring containing one or two -OSO ₂ -groups. The cyclic sulfonate compound, for example, may be: 1,3-propane sultone, 1-propene-1,3-sultone, 1,3-propane sultone, 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 ,3-propane sultone, 1-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone and other monosulfonates; methylene disulfonate, methane Disulfonates such as ethylene sulfonate, etc.; from the viewpoint of further improving the chemical properties of the shop, 1,3-propane sultone or 1-propene-1,3-sultone is preferred.

Next, the manufacturing method of the non-aqueous electrolyte secondary battery 1 is demonstrated. The method of manufacturing the non-aqueous electrolyte secondary battery 1 includes: a first step, which can obtain a positive electrode 6; a second step, which can obtain a negative electrode 8; and a third step, which accommodates the electrode group 2 in the battery case 3 And, the fourth step, which injects 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 material used for the positive electrode mixture layer 10 is dispersed in a dispersion medium using a kneader, disperser, etc. to obtain a slurry positive electrode mixture, and then a doctor blade method or a dipping method is used. , Spray 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 can also be provided as needed. The positive electrode mixture layer 10 can be formed into a multi-layered positive electrode mixture layer by performing the steps from applying the positive electrode mixture to volatilizing the dispersion medium multiple 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 method as the first step described above.

In the third step, the spacer 7 is sandwiched between the manufactured positive electrode 6 and the negative electrode 8 to form the electrode group 2. Then, the electrode group 2 is housed in the battery case 3.

In the fourth step, the electrolyte is injected into the battery case 3. The electrolyte can be prepared by 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 non-aqueous electrolyte secondary battery 1 described above, the capacitor may include: an electrode group consisting of a positive electrode, a negative electrode, and a separator; and a pouch-shaped battery case capable of accommodating the electrode group. The details of each component in the capacitor may be the same as the non-aqueous electrolyte secondary battery 1. [Example]

Hereinafter, the present invention will be specifically explained through examples, but the present invention is not limited to these examples.

(Example 1) [Preparation of electrolytic solution] In a mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate containing 1 mol/L of LiPF6, 1% by mass relative to the total amount of the mixed solution was added Vinylene carbonate (VC) and 1% by mass of the compound A represented by the following formula (9) (based on the total amount of the electrolyte) were used to prepare an electrolyte.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement in accordance with the above measurement conditions. As a result, the following spectrum is obtained: the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -100 ppm or more and -70 ppm or less, and the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -180 ppm or more and -150 ppm or less Peak derived from compound A. The spectrum showing the peak derived from compound A is 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] For Example 1, except for adding 1% by mass (based on the total amount of electrolyte solution) of compound B represented by the following formula (10) instead of compound A, Example 1 was carried out in the same manner to prepare an electrolytic solution.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum is obtained: the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -100 ppm or more and -70 ppm or less, and the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -180 ppm or more and -150 ppm or less Peak derived from compound B. The spectrum showing the peak derived from compound B is 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] About 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 was subjected to ¹⁹ F-NMR measurement. As a result, a spectrum was obtained in which a peak derived from PF ₆ ^- and its reactants was shown in a 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] For Example 1, except that Compound A was not used and 1% by mass (based on the total amount of electrolyte as the basis) of 4-fluoro-1,3-dioxolane-2-one (fluoroethylene carbonate) was added. Except for FEC), the same procedure as in Example 1 was carried out to prepare an electrolyte.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum is obtained: the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -100 ppm or more and -70 ppm or less, and it is in the chemical shift range of more than -130 ppm and -110 ppm or less The peak derived from FEC is shown. The spectrum of the peak derived from FEC is 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] For Example 1, except for adding 1% by mass (based on the total amount of electrolyte solution) of compound C represented by the following formula (11) instead of compound A, Example 1 was carried out in the same manner to prepare an electrolytic solution.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum is obtained: the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -100 ppm or more and -70 ppm or less, and the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of more than -150 ppm and -110 ppm or less Peak derived from compound C. The spectrum showing the peak derived from compound C is 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] For Example 1, except for adding 1% by mass (based on the total amount of electrolyte solution) of compound D represented by the following formula (12) instead of compound A, Example 1 was carried out in the same manner to prepare an electrolytic solution.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum is obtained: the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -100 ppm or more and -70 ppm or less, and the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of more than -150 ppm and -110 ppm or less Peak derived from compound D. The spectrum showing the peak derived 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 same procedure as in Example 1 was performed except that the content of the compound A was changed to 0.5% by mass and 0.5% by mass (all based on the total amount of the electrolyte solution) FEC was added to prepare an electrolyte solution.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum was obtained: peaks derived from PF ₆ ^- and its reactants were shown in the chemical shift range of -100 ppm or more and -70 ppm, and the source was shown in the chemical shift range of -180 ppm or more and -150 ppm. It is derived from the peak of compound A, and shows a peak derived from FEC in a chemical shift range exceeding -130 ppm or more and -110 ppm or less. The spectrum showing the peak derived from compound A and the peak 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 same procedure as in Example 3 was performed except that the content of the compound C was changed to 0.5% by mass and 0.5% by mass (all based on the total amount of the electrolyte solution) FEC was added to prepare an electrolyte solution.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum is obtained: the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -100 ppm or more and -70 ppm or less, and the source is shown in the chemical shift range of more than -150 ppm and -130 ppm or less. It is derived from the peak of compound C, and shows a peak derived from FEC in a chemical shift range exceeding -130 ppm or more and -110 ppm or less. The spectrum showing the peak derived from compound C and the peak 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, except that the content of the compound D was changed to 0.5% by mass and 0.5% by mass (all based on the total amount of the electrolyte solution) FEC was added, the same procedure was performed as in Example 4 to prepare an electrolyte solution.

[ ¹⁹ F-NMR Measurement] The prepared electrolyte was subjected to ¹⁹ F-NMR measurement. As a result, the following spectrum is obtained: the peak derived from PF ₆ ^- and its reactants is shown in the chemical shift range of -100 ppm or more and -70 ppm, and the source is shown in the chemical shift range of more than -150 ppm and -130 ppm It is derived from the peak of compound D, and shows a peak derived from FEC in a chemical shift range exceeding -130 ppm or more and -110 ppm or less. The spectrum showing the peak derived from compound D and the peak 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

[Production of positive electrode] In lithium cobalt oxide (95% by mass) as the active material of the positive electrode, fibrous graphite (1% by mass) and acetylene black (AB, 1% by mass) as conductive agents are sequentially added and mixed, And adhesive (3% by mass). To the obtained mixture, NMP as a dispersion medium was added and kneaded to prepare a slurry-like positive electrode mixture. This positive electrode mixture was uniformly and homogeneously coated on an aluminum foil having a thickness of 20 μm as a positive electrode current collector. After that, the dispersion medium was volatilized, and the density was densified to 3.6 g/cm ³ by pressing to obtain a positive electrode.

[Preparation of negative electrode] In graphite and silicon oxide as the negative electrode active material, a binder and carboxymethyl cellulose as a thickener are added. Regarding these mass ratios, it is assumed that graphite: silicon oxide: binder: tackifier = 92:5:1.5:1.5. To the obtained mixture, water as a dispersion medium is added and kneaded to prepare a slurry-like negative electrode mixture. This negative electrode mixture was uniformly and homogeneously coated on a rolled copper foil having a thickness of 10 μm as a negative electrode current collector. After that, the dispersion medium is volatilized, and then the density is densified to 1.6 g/cm ³ by pressing to obtain a negative electrode.

[Production of Lithium Ion Secondary Battery] A porous sheet made of polyethylene (trade name Hipore (registered trademark), manufactured by Asahi Kasei Co., Ltd., thickness 30μm) is clamped and cut into 13.5cm ² The rectangular positive electrode is further overlapped with the rectangular negative electrode cut into 14.3 cm ² to form an electrode group. The electrode group was housed in a container (battery case) formed of a laminated film made of aluminum (trade name: aluminum laminated film, manufactured by Dainippon Printing Co., Ltd.). Then, 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. .

[First charge and discharge] The produced lithium ion battery was charged and discharged for the first time by 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 a final voltage of 2.5V was performed at a current value of 0.1C. Repeat this charge and discharge cycle 3 times ("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 by using the electrolyte solutions of Examples 1 to 2 and Comparative Examples 1 to 2 were evaluated by repeated charge and discharge cycle tests. As the charging mode, in an environment of 45°C, 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 the discharge, a constant current discharge was performed at 1C to 2.5V, and the discharge capacity was obtained. This series of charging and discharging was repeated 200 cycles, and the discharge capacity was measured for each charge and discharge. The discharge capacity after charging and discharging in the first cycle of Comparative Example 1 was set to 1, and the relative value (discharge capacity ratio) of the discharge capacity in each cycle was obtained. The relationship between the number of cycles and the relative value of the discharge capacity is shown in Figure 7.

As shown in Figure 7, the lithium ion secondary batteries of Examples 1 and 2 use electrolytes that exhibit peaks in the chemical shift range of -180 ppm or more and -150 ppm in the measurement performed by ¹⁹ F-NMR. , The lithium ion secondary batteries of Comparative Examples 1 and 2 use electrolytes that do not show peaks in this range. Compared with the lithium ion secondary batteries of Comparative Examples 1 and 2, the lithium ion secondary batteries of Examples 1 and 2 The discharge capacity ratio at the 200th cycle is larger. Therefore, the lithium ion secondary batteries of Examples 1 to 2 exhibit excellent performance (cycle characteristics).

1: Non-aqueous electrolyte secondary battery (electrochemical device) 2: Electrode group 3: Battery case 4: Positive collector terminal 5: Negative collector terminal 6: positive 7: Spacer 8: negative electrode 9: Positive current 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 of the electrolytic solution of Example 1, (b) is a spectrum of the electrolytic solution of Example 2. Figure 4 is a spectrum of the electrolytic solution of Comparative Example 2 obtained by ¹⁹ F-NMR measurement. Fig. 5 is a spectrum obtained by ¹⁹ F-NMR measurement, (a) is a spectrum of the electrolytic solution of Example 3, and (b) is a spectrum of the electrolytic solution of Example 4. Figure 6 is the spectrum obtained by ¹⁹ F-NMR measurement, (a) is the spectrum of the electrolyte of Example 5, (b) is the spectrum of the electrolyte of Example 6, (c) It is a spectrum of the electrolyte of Example 7. Figure 7 is a graph showing the evaluation results of the cycle characteristics.

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Claims (7)

An electrolyte solution which shows a peak in at least one chemical shift range among -180 ppm or more and -150 ppm or less, and more than -150 ppm and -130 ppm or less in a measurement performed by fluorine 19 nuclear magnetic resonance. The electrolytic solution according to claim 1, which further shows a peak in a chemical shift range of more than -130 ppm and -110 ppm in a measurement performed by fluorine 19 nuclear magnetic resonance. An electrochemical device comprising: a positive electrode, a negative electrode, and the electrolyte according to claim 1 or 2. The electrochemical device according to claim 3, wherein the negative electrode contains a carbon material. The electrochemical device according to claim 4, wherein the carbon material contains graphite. The electrochemical device according to claim 4 or 5, wherein the negative electrode further contains the following material containing at least one element selected from the group consisting of silicon and tin. The electrochemical device according to any one of claims 4 to 6, wherein the electrochemical device is a non-aqueous electrolyte secondary battery or a capacitor.

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