Electrolyte solution, electrolyte composition, and electrochemical element

Abstract

Provided are an electrolyte solution, an electrolyte composition, and an electrochemical element with which it is possible to increase the transference number of ions contributing to energy conversion. The electrolyte contains a non-aqueous solvent, and b * > = 2 in color coordinates of a CIE 1976L * a * b * color space. It is preferable that the electrolyte solution 1 < = L * < = 3, and the chroma represented by c * = {(a *) 2 + (b *) 2} 1 / 2 is 2 < = c * < = 8. The electrolyte composition includes an electrolyte solution and particles of an oxide solid electrolyte. The electrochemical element is provided with an electrode containing an electrolyte solution.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrolyte solution containing a nonaqueous solvent, an electrolyte composition, and an electrochemical element. BACKGROUND

[0002] An electrochemical element such as a lithium ion secondary battery converts chemical energy into electrical energy. Patent Literature 1 discloses a prior art in which an electrolyte solution containing a nonaqueous solvent is contained in an electrochemical element. The electrolyte solution functions as a medium for moving ions.

[0003] PRIOR ART DOCUMENT

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2011-44252 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Since not only ions contributing to energy conversion but also ions not contributing to energy conversion move in the electrolyte solution, the prior art has a problem that the number of ions contributing to energy conversion migrating is low.

[0008] The present application has been achieved in order to solve the problem, and aims to provide an electrolyte solution, an electrolyte composition, and an electrochemical element capable of increasing the number of ions contributing to energy conversion migrating.

[0009] METHOD FOR SOLVING THE PROBLEM

[0010] A first mode for achieving the object is an electrolyte solution containing a nonaqueous solvent, wherein, in color coordinates of a CIE 1976 L * a * b * the b * ≥ 2.

[0011] A second mode is as follows: in the first mode, 1 ≤ L * ≤ 3.

[0012] A third mode is as follows: in the first mode or the second mode, the chroma represented by c * ={(a * ) 2 +(b * ) 2} 1 / 2 is 2 ≤ c * ≤ 8.

[0013] A fourth mode is as follows: in any one of the first mode to the third mode, a lithium salt is dissolved in the nonaqueous solvent.

[0014] The 5th aspect is as follows: in any one of the 1st to 4th aspects, the compound is other than an aromatic compound (non-aromatic compound), and a signal of the proton nuclear magnetic resonance spectrum exists in a range of 6 ppm to 8 ppm in chemical shift.

[0015] The 6th aspect is as follows: in the 5th aspect, an absorption spectrum based on Fourier transform infrared spectroscopy exists in a range of 1100 cm -1 to 1120 cm -1 .

[0016] The 7th aspect is an electrolyte composition including the electrolyte solution of any one of the 1st to 6th aspects and particles of an oxide solid electrolyte.

[0017] The 8th aspect is as follows: in the 7th aspect, the oxide solid electrolyte has a garnet-type crystal structure including Li, La, and Zr.

[0018] The 9th aspect is an electrochemical element, which is an electrochemical element including an electrode, wherein the electrode includes the electrolyte solution of any one of the 1st to 6th aspects.

[0019] The 10th aspect is as follows: in the 9th aspect, the electrode is a positive electrode.

[0020] Effects of Invention

[0021] With regard to the electrolyte solution, the electrolyte composition including the electrolyte solution, and the electrochemical element of the present application, the electrolyte solution has b * a * b * in the color coordinates of the CIE1976 L * a b ≥ 2, and thus the mobility of ions contributing to energy conversion increases, and the number of transits can be increased. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a cross-sectional view of an electrochemical element of a first embodiment.

[0023] Figure 2 is a diagram schematically showing a garnet-type crystal structure.

[0024] Figure 3 is a cross-sectional view of an electrochemical element of a second embodiment. DETAILED DESCRIPTION

[0025] Hereinafter, preferred embodiments of the present application will be described with reference to the accompanying drawings. Figure 1is a schematic cross-sectional view of an electrochemical element 10 of a first embodiment. The electrochemical element 10 is an element that directly converts chemical energy and electric energy. Ions (hereinafter referred to as "charge carriers") that contribute to energy conversion of the electrochemical element 10 can exemplify Li + , Na + , K + , Mg 2+ , Cu + , Ag + , and the like cations.

[0026] As an example of the electrochemical element 10, a power storage device is described. The power storage device can exemplify an ion battery such as a lithium ion battery, an electrochemical capacitor that utilizes an oxidation-reduction reaction of an electrode, an oxidation-reduction reaction of ions in an electrolyte, a double layer. The electrochemical element 10 includes, in order, a positive electrode 11, a separator 14, and a negative electrode 15.

[0027] The separator 14 is composed of a porous body that has durability against the active material 19, 20 contained in the positive electrode 11, the negative electrode 15, and an electrolyte, and through which the charge carriers pass but does not have electron conductivity. The separator 14 can exemplify a nonwoven fabric, a porous film composed of cellulose, polypropylene, polyethylene, polyimide, alumina, and the like.

[0028] The positive electrode 11 has a current collector 12 and an active material layer 13 superimposed therein. The current collector 12 is a member having conductivity. The material of the current collector 12 can exemplify a metal selected from Ni, Ti, Fe, and Al, an alloy containing two or more elements among them, stainless steel, a carbon material.

[0029] The active material layer 13 contains the active material 19. The active material 19 can be appropriately selected depending on the charge carriers and the kind of the power storage device. In the case where the power storage device is an electrochemical capacitor, the active material 19 adopts a material capable of reversibly loading anions, and can exemplify a carbon-based material such as porous carbon, natural graphite, artificial graphite, easily graphitizable carbon (hard carbon), hardly graphitizable carbon (soft carbon), carbon fiber.

[0030] In the case where the power storage device is an ion battery, the active material 19 can exemplify a metal oxide having a transition metal, a sulfur-based active material, an organic-based active material. In the case where the charge carriers are Li + , the metal oxide having a transition metal can exemplify a metal oxide containing one or more elements selected from Mn, Co, Ni, Fe, Cr, and V, and Li. The metal oxide having a transition metal can exemplify LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiMn2O4, LiNiVO4, LiNi 0.5 Mn 1.5 O2, LiNi1 / 3 Mn 1 / 3 Co 1 / 3 O2 and LiFePO4.

[0031] Examples of sulfur-based active substances include S, TiS2, NiS, FeS2, Li2S, MoS3, and sulfur-carbon composites. Examples of organic active substances include free radical compounds such as 2,2,6,6-tetramethylpiperidinoxy-4-yl methacrylate and polytetramethylpiperidinoxy vinyl ether, quinone compounds, axialene compounds, tetracyanobenzoquinone dimethane, and phenazine oxides.

[0032] To reduce the resistance of the active material layer 13, a conductive additive may be included in the active material layer 13. Examples of conductive additives include carbon black, acetylene black, Ketjen black, carbon fiber, Ni, Pt, and Ag.

[0033] In this embodiment, the active material layer 13 comprises an electrolyte composition. The electrolyte composition comprises oxide solid electrolyte particles 18 and an electrolyte solution. Particles 18 may be exemplified as oxides having a NASICON (sodium superionic conductor) type structure, oxides having a perovskite structure, or oxides having a garnet type structure. Oxides having a NASICON type structure may include oxides containing at least Li, M (M being one or more elements selected from Ti, Zr, and Ge), and P, such as Li(Al, Ti)₂(PO₄)₃ and Li(Al, Ge)₂(PO₄)₃. Oxides having a perovskite structure may include oxides containing at least Li, Ti, and La, such as La. 2 / 3-X Li 3X TiO3.

[0034] Particle 18 is preferably a composite oxide having a garnet-type crystal structure containing Li, La, and Zr. This is because it has a 10 -3 It exhibits ionic conductivity on the order of S / cm and is resistant to reduction by metallic lithium. The garnet-type crystal structure is based on the general formula C3A2B3O. 12 express.

[0035] Figure 2This diagram schematically illustrates a garnet-type crystal structure. In this structure, the C site Sc is dodecahedral coordinated with the oxygen atom Oa, the A site Sa is octahedral coordinated with Oa, and the B site Sb is tetrahedral coordinated with Oa. In a typical garnet-type crystal structure, oxide solid electrolytes can contain Li at sites octahedral coordinated with Oa, forming vacancies V. Vacancy V is, for example, a site sandwiched between B sites Sb1 and Sb2. The Li present in vacancy V is octahedral coordinated with the oxygen atom Oa forming the octahedron containing the tetrahedron face Fb1 forming B site Sb1 and the tetrahedron face Fb2 forming B site Sb2. For example, Li7La3Zr2O has a garnet-type crystal structure. 12 In this context, La can occupy site C (Sc), Zr can occupy site A (Sa), and Li can occupy site B (Sb) and the void (V).

[0036] Garnet-type crystal structures can be identified using X-ray diffraction. The garnet-type crystal structure corresponds to X-ray diffraction file No. 422259 (Li7La3Zr2O) in the CSD (Cambridge Structural Database). 12 Similar XRD patterns. Solid electrolytes sometimes differ from No. 422259 in the types of constituent elements, Li concentration, etc., thus resulting in different diffraction angles and intensity ratios. This representative crystal structure is cubic (space group Ia-3d (- indicates an overline signifying rotation-inversion operation), JCPDS: 84-1753).

[0037] Solid electrolytes with garnet-type crystal structures can typically be exemplified by Li7La3Zr2O. 12 In solid electrolytes, Li7La3Zr2O 12 A portion of the constituent elements may be replaced by other elements, or trace amounts of other elements may be added without replacing the constituent elements. Other elements may be exemplified by at least one element selected from the group consisting of Mg, Al, Si, Ca, Ti, V, Ga, Sr, Y, Nb, Sn, Sb, Ba, Hf, Ta, W, Bi, Rb and the lanthanides (excluding La).

[0038] Solid electrolytes, for example, include Li6La3Zr. 1.5 W 0.5 O 12 Li 6.15 La3Zr 1.75 Ta 0.25 Al 0.2 O 12 Li 6.15 La3Zr 1.75 Ta0.25 Ga 0.2 O 12 Li 6.25 La3Zr2Ga 0.25 O 12 Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li 6.5 La3Zr 1.75 Te 0.25 O 12 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 Li 6.9 La3Zr 1.675 Ta 0.289 Bi 0.036 O 12 Li 6.46 Ga 0.23 La3Zr 1.85 Y 0.15 O 12 Li 6.8 La 2.95 Ca 0.05 Zr 1.75 Nb 0.25 O 12 Li 7.05 La 3.00 Zr 1.95 Gd 0.05 O 12 Li 6.20 Ba 0.30 La 2.95 Rb 0.05 Zr2O 12 .

[0039] The solid electrolyte is particularly preferred to be a solid electrolyte containing at least one of Mg and element A (A being at least one element selected from the group consisting of Ca, Sr, and Ba) and the molar ratio of each element satisfies all of the following (1) to (3); or, a solid electrolyte containing both Mg and element A and the molar ratio of each element satisfies all of the following (4) to (6). To improve the ionic conductivity of the solid electrolyte, element A is preferably Sr.

[0040] (1) 1.33≤Li / (La+A)≤3

[0041] (2) 0 ≤ Mg / (La+A) ≤ 0.5

[0042] (3) 0 ≤ A / (La+A) ≤ 0.67

[0043] (4) 2.0 ≤ Li / (La+A) ≤ 2.5

[0044] (5) 0.01 ≤ Mg / (La+A) ≤ 0.14

[0045] (6) 0.04 ≤ A / (La+A) ≤ 0.17

[0046] The electrolyte contained in the active material layer 13 is a medium for charge carrier movement and is a solution in which the supporting electrolyte is dissolved in a non-aqueous solvent. Non-aqueous solvents are broadly classified into molecular solvents, which are mostly composed of molecules, and ionic liquids, which are composed of cations and anions. One reason for using a non-aqueous solvent in the electrolyte is that it widens the potential window compared to electrolytes using water as a solvent. Ionic liquids are preferred because they can widen the potential window compared to electrolytes using water as a solvent.

[0047] When using molecular solvents as non-aqueous solvents, aprotic solvents are preferred to broaden the potential window of the electrolyte. Examples of aprotic solvents include cyclic esters, chain esters, aliphatic carboxylic acid esters, phosphate esters, nitriles, amides, sulfur compounds, ketones, ethers, nitro compounds, and fluorinated solvents. Mixtures of these may also be used.

[0048] Examples of cyclic esters include propylene carbonate, ethylene carbonate, butyl carbonate, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, and other cyclic carbonates; β-propiolactone, γ-butyrolactone, δ-valerolactone, α-pyranone, coumarin, and other lactones. Examples of chain esters include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and other chain carbonates. Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, and ethyl propionate. Examples of phosphate esters include trimethyl phosphate. Examples of nitriles include acetonitrile, propionitrile, butyronitrile, and benzonitrile.

[0049] Amides can be exemplified as formamide, N-methylformamide, dimethylformamide, N-methylacetamide, dimethylacetamide, N-methylpropionamide, hexamethylphosphoramide, and N-methylpyrrolidone. Sulfur compounds can be exemplified as dimethyl sulfoxide, sulfolane, dimethylthioformamide, and N-methylthiopyrrolidone. Ketones can be exemplified as acetone, 4-methyl-2-pentanone, and acetylacetone. Ethers can be exemplified as tetrahydrofuran and ethylene glycol dimethyl ether. Nitro compounds can be exemplified as nitromethane and nitrobenzene. Fluorinated solvents are compounds and their derivatives in which hydrogen atoms of hydrocarbons are replaced with fluorine atoms.

[0050] The higher the relative permittivity of the solvent and the easier it is for ions to solvate, the easier it is for the reaction that supports the dissolution of the electrolyte into free ions in the molecular solvent to proceed. Therefore, solvents with a relatively high permittivity εr (εr > 20) are preferred. Examples of molecular solvents with a relative permittivity greater than 20 include cyclic esters, nitriles, amides, sulfur compounds, acetone, acetylacetone, and nitro compounds. It is also possible to mix solvents with a relative permittivity greater than 20 with solvents with a relative permittivity less than 20 to adjust the viscosity, etc.

[0051] Ionic liquids are compounds composed of cations and anions, and are liquids at room temperature and pressure. Using an ionic liquid as the solvent in an electrolyte can improve its flame retardancy. Preferred ionic liquids are those made from ammonium or imidazole. pyrrolidine and piperidine One or more species in the group are classified as cationic species.

[0052] There are no particular limitations on the anionic composition of ionic liquids. An example of anionic composition is BF4. - N(SO2F)2 - Inorganic anions, B(C6H5)4 - CH3SO3 - CF3SO3 - N(SO2CF3)2 - N(SO2C4F9)2 - Organic anions, etc.

[0053] Ionic liquids can also be solvated ionic liquids. Examples of solvated ionic liquids include substances formed by dissolving a supporting electrolyte in sulfone solvents such as sulfolane or sulfolane derivatives, or in ethylene glycol dimethyl ether solvents such as tetraethylene glycol dimethyl ether.

[0054] With Li as the charge carrier + In this case, the supporting electrolyte is a lithium salt. An example of a supporting electrolyte anion is OH-. - , halide ions (I - Cl - ,Br - etc.), SCN - BF4 - BF3 (CF3) - BF3 (C2F5) - PF6 - ClO4 - SbF6 - N(SO2F)2 - N(SO2CF3)2 - N(SO2C2F5)2- B(C6H5)4 - B(O2C2H4)2 - C(SO2F)3 - C(SO2CF3)3 - CF3COO - CF3SO2O - C6F5SO2O - B(O2C2O2)2 - RCOO - (R is an alkyl, phenyl, or naphthyl group with 1-4 carbon atoms, etc.) The supporting electrolyte can also be a mixture of them.

[0055] The supporting electrolyte concentration of the electrolyte solution is 0.2 mol / dm³. 3 The above is preferably 0.5 mol / dm 3 The above, more preferably 1.0 mol / dm 3 The above describes the process. As the concentration of the supporting electrolyte increases, the number of solvent molecules coordinated to the charge carrier increases, resulting in less uncoordinated solvent and dominance of coordination based on counter anions (so-called ion association). Consequently, reductive decomposition of the electrolyte is suppressed, while the oxidation potential increases and the potential window widens. The preferred concentration of the supporting electrolyte is 4.0 mol / dm³. 3 The following is more preferably 2.0 mol / dm 3 The following is true. This is because the concentration of the supporting electrolyte exceeds 4.0 mol / dm³. 3 At that time, the ionic conductivity tends to decrease significantly due to the increase in electrolyte viscosity.

[0056] The electrical conduction of an electrolyte is primarily ionic conduction. The ionic conductivity of an electrolyte is proportional to the product of the concentration and mobility of charge carriers within the electrolyte. It is believed that the mobility of charge carriers in the electrolyte is related to the solvation of solvent molecules by ions that support the dissociation of the electrolyte, and the interactions between the ions that constitute the electrolyte. CIE 1976L includes quantities related to the lightness, chroma, and hue of the electrolyte. * a * b * Color coordinates in a color space are one of the indicators of solvation.

[0057] CIE 1976L * a * b * A color space is a system recommended by the CIE (International Commission on Illumination) in 1976, defined by plotting L on orthogonal coordinates. * a * b *The resulting three-dimensional color space is roughly equal. (CIE 1976L) * a * b * The color space is defined by JIS Z8781-4:2013. In CIE 1976L... * a * b * In the color space, use L * To indicate brightness, the chroma (showing hue and saturation) is represented by a. * b * It means. a * b * Indicates the direction of color, a * Indicates the red direction, -a * Indicates the green direction, b * Indicates the yellow direction, -b * Indicates the blue direction. The larger the value, the more vibrant the color; the closer to the origin, the duller the color. Chroma (c) * Use {(a * ) 2 +(b * ) 2} 1 / 2 (a * and b * The sum of squares and the square root of the sum of squares are represented by L. * a * b * The measurements can be performed using a spectrophotometer CM-5 (Konica Minolta Co., Ltd.).

[0058] L * a * b * The values ​​of these properties are not independent and completely controllable, and there are many unclear aspects. However, it is believed that if the color of the electrolyte b... * If the number is ≥2, the mobility of anions decreases, while the mobility of cations (charge carriers) increases. This can increase the transport number of charge carriers that facilitate energy conversion.

[0059] The mobility of charge carriers contained in the electrolyte is related to b * The reason for the relationship is unclear, but it is presumed that the decrease in solvent molecules coordinating with the cations supporting the electrolyte's dissolution in the solvent, and the increase in solvent molecules coordinating with the anions, leads to the color change of the electrolyte. * It gets bigger.

[0060] To distinguish this from discoloration caused by impurities such as water, alcohols, epoxides, alkyl lithium carbonates, and their further reaction products with the electrolyte, the discoloration caused by these impurities is... * The increase of b *The maximum value is preferably 30. The impurities contained in the electrolyte are preferably 200 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less. This is to reduce the degradation of the electrolyte over time caused by the presence of impurities.

[0061] The brightness (L) of the electrolyte * Preferably 1≤L * ≤3, chroma c of the electrolyte * Preferably, 2≤c * ≤8. This is all to further increase the transference number of charge carriers.

[0062] L of electrolyte * a * b * c * An example of this adjustment is modifying the surface of particle 18 to allow it to contact the electrolyte. This, in turn, affects the electrolyte's... * c * The surface of particle 18 can be modified by chemical treatment. Chemical treatment can make the surface of particle 18 acidic or alkaline. Examples of chemical treatment include methods of adsorbing a modifier onto the surface of particle 18 in a liquid phase such as a non-aqueous solvent, and methods of reacting the modifier with particle 18 in a gas phase. As a pretreatment for surface modification, it is preferable to apply compressive or shear forces to particle 18 by using a rotating container or rotating blades alone or in combination, or to disperse particle 18 in a high-speed gas flow to apply an impact force, thereby increasing the surface activity of particle 18.

[0063] When the composite oxide with a garnet-type crystal structure containing Li, La, and Zr is particle 18, lithium hydroxide and lithium carbonate are generated on the surface of particle 18 through a gas-phase reaction between carbon dioxide, water, and particle 18, thus modifying the surface of particle 18 to be alkaline. Since the surface modification of particle 18 is simple, an electrolyte can be easily prepared by contacting particle 18.

[0064] The particles 18 can be placed together with the electrolyte in the active material layer 13 after contacting the particles 18, or the particles 18 can be separated from the electrolyte after contacting the particles 18, and only the electrolyte can be supplied to the active material layer 13. Examples of methods for separating the particles 18 from the electrolyte include filtration, sedimentation, and centrifugation. The electrolyte can be prepared in the active material layer 13 by injecting the electrolyte into the active material layer 13 containing the particles 18, thereby bringing the particles 18 into contact with the electrolyte.

[0065] Preferably, the electrolyte is composed of compounds other than aromatic compounds (non-aromatic compounds) (including mixtures of non-aromatic compounds), and proton nuclear magnetic resonance spectroscopy using a combination of pulse method and Fourier transform method is employed.1 H-NMR determination of electrolyte 1 H-NMR spectroscopy 1 The H-NMR spectrum signal exists in the range of 6 ppm to 8 ppm chemical shift. The chemical shift is obtained by setting the resonance frequency of the methyl group in tetramethylsilane to 0 and dividing the difference between this resonance frequency and the measured frequency by the resonance frequency.

[0066] The electrolyte was further optimized using Fourier transform infrared spectroscopy (FT-IR) to obtain absorption spectra at wavenumber 1100 cm⁻¹. -1 ~1120cm -1 The range. For the determination of absorption spectra using FT-IR, the attenuated total reflection (ATR) method is preferred.

[0067] An adhesive for binding the active material 19 may also be included in the active material layer 13. There are no particular limitations on the adhesive as long as it binds the active material 19. Examples of adhesives include fluorinated resins, polyolefins, polyimides, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, styrene-butadiene rubber, and other rubber-like polymers. Examples of fluorinated resins include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.

[0068] The volume ratio (volume %) of the electrolyte relative to the total volume of the electrolyte and active material 19 contained in the active material layer 13 is preferably 10% or more and 20% or less. This is to reduce the interfacial resistance of the active material 19, which serves as the reaction field for the charge and discharge reaction, while ensuring the equilibrium potential of the positive electrode 11.

[0069] When the active material layer 13 includes particles 18, the volume ratio (volume %) of particles 18 to the total volume of particles 18 and active material 19 is preferably 15% or more and 20% or less. This is to ensure the equilibrium potential of the positive electrode 11 and to ensure the contact interface between particles 18 and active material 19.

[0070] The contents (volume %) of particles 18, active material 19, and electrolyte can be determined by analysis using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS), with a randomly selected 5000x field of view from the cross-section of the active material layer 13 as the object. In the analysis, the area of ​​particles 18, the area of ​​active material 19, and the area of ​​electrolyte are determined by determining the elemental distribution or by image analysis of the contrast of the reflected electron image. The content (volume %) of particles 18 is obtained by considering the proportion of the area of ​​particles 18 to the total area of ​​active material 19 as the volume proportion. Similarly, the content (volume %) of electrolyte is obtained by considering the proportion of the area of ​​electrolyte to the total area of ​​active material 19 to the total volume proportion.

[0071] The cross-section of the active material layer 13 used in the analysis is a polished surface, a surface obtained by irradiation with a focused ion beam (FIB), or a surface obtained by ion milling. The polished surface is, for example, a surface obtained by freezing the active material layer 13, or by embedding the active material layer 13 in a tetrafunctional epoxy resin and then polishing it.

[0072] The negative electrode 15 has a current collector 16 and an active material layer 17 superimposed on it. The current collector 16 is a conductive component. Examples of materials for the current collector 16 include metals selected from Ni, Ti, Fe, Cu and Si, alloys containing two or more of these elements, stainless steel, and carbon materials.

[0073] The active material layer 17 contains active material 20. To reduce the resistance of the active material layer 17, a conductive additive may be included in the active material layer 17. Examples of conductive additives include carbon black, acetylene black, Ketjen black, carbon fiber, Ni, Pt, and Ag. In this embodiment, particles 18 are included in the active material layer 17.

[0074] The active material 20 only needs to be capable of adsorption / release of charge carriers; there are no restrictions on the material. The active material 20 can be appropriately selected according to the type of charge carrier. Examples of active materials 20 include porous carbon, natural graphite, artificial graphite, easily graphitized carbon, difficult-to-graphitize carbon, carbon fibers, and other carbon-based materials, as well as Li4Ti5O. 12 Lithium oxides, Si, Si-Li alloys, compounds whose constituent elements include Si and O (hereinafter referred to as "SiOx", where 0.5 ≤ X ≤ 1.5), metallic lithium, Li-Al alloys, Li-Sn alloys, Li-Si alloys, Li-Mg alloys, Li-Si alloys and other lithium alloys, In-Sb alloys, and Si-Li alloys. SiOx can refer to oxides of Si and substances having a structure in which microcrystalline or amorphous Si is dispersed in an amorphous SiO2 matrix.

[0075] Electrochemical element 10 is manufactured, for example, as follows: A slurry is prepared by mixing particles 18, active material 19, and conductive additive, and further mixing the resulting solution obtained by dissolving a binder in a solvent. After coating the slurry onto current collector 12, it is dried to obtain a positive electrode.

[0076] Particles 18, active material 20, and conductive additives are mixed, and the resulting solution, obtained by dissolving the binder in a solvent, is further mixed to prepare a slurry. After coating the slurry onto the current collector 16, it is dried to obtain the negative electrode sheet.

[0077] A cylindrical or square battery is manufactured by winding the separator 14 (which separates the positive and negative electrodes) and the positive and negative electrodes simultaneously using a winding machine. Terminals (not shown) are connected to the current collectors 12 and 16, and color b is filled into a container (not shown) housing the battery. * After adding ≥2% electrolyte, the container is sealed to obtain an electrochemical element 10 containing a positive electrode 11, a diaphragm 14, and a negative electrode 15.

[0078] According to the electrochemical element 10, the active material layer 13 of the positive electrode 11 is filled with a colorimetric b with high charge carrier mobility. * With an electrolyte thickness of ≥2, even if the thickness of the active material layer 13 is increased, thus lengthening the movement distance of the charge carriers during charging and discharging within the active material layer 13, the moving resistance of the charge carriers can remain unchanged. Because the thickness of the active material layer 13 can be increased, an electrochemical element 10 with large capacity and high-speed charging capability can be obtained.

[0079] Color b * Electrolytes with a concentration of ≥2 can increase the transference number of charge carriers compared to conventional electrolytes, thus reducing concentration polarization that is prone to occur during high-speed charging and discharging. Since the operating voltage (terminal voltage) of the electrochemical element 10 can be maintained for a short period of time, this contributes to the longevity of the electrochemical element 10.

[0080] Because the active material layer 13 of the positive electrode 11 is filled with an electrolyte with high charge carrier mobility, the mobility of charge carriers in the active material layer 13 at locations in contact with the particles 18 is ensured, as well as the mobility of charge carriers at locations away from the particles 18. The migration speed (diffusion speed) of the charge carriers is highly temperature-dependent and decreases at lower temperatures; however, because the mobility of the charge carriers is ensured, the operation of the electrochemical element 10 is guaranteed even at low temperatures around it.

[0081] Reference Figure 3The second embodiment will be described. In the first embodiment, the separator 14 separating the positive electrode 11 and the negative electrode 15 was described as a nonwoven fabric or porous membrane made of cellulose, polypropylene, or the like. In contrast, in the second embodiment, the separator 22 separating the positive electrode 11 and the negative electrode 15 includes an electrochemical element 21 containing an electrolyte 23. In the second embodiment, the same reference numerals are used for parts that are the same as in the first embodiment, and the following description is omitted.

[0082] Figure 3 This is a cross-sectional view of the electrochemical element 21 according to the second embodiment. The electrochemical element 21 (energy storage device) sequentially includes a positive electrode 11, a separator 22, and a negative electrode 15. The separator 22 includes an electrolyte 23. The electrolyte 23 may be a solid or gel-like electrolyte with ion conductivity. Alternatively, a mixture of the electrolyte 23 and an electrolyte solution may be disposed in the separator 22.

[0083] Electrolyte 23 comprises one or more selected from sulfide, oxide, hydride, halide, and organic systems. Examples of sulfide-based electrolytes include crystalline Thio-LISICON (thio-lithium superionic conductor) type, Li... 10 GeP2S 12 Type, sulfide-germanium ore type, Li7P3S 11 Electrolytes of the oxide type, represented by Li₂S-P₂S₅, are glass and glass-ceramic systems. Examples of oxide-based electrolytes include oxides with NASICON-type structures, oxides with perovskite structures, and oxides with garnet-type structures.

[0084] Examples of hydride-based electrolytes include solid solutions of LiBH4 with lithium halides (LiI, LiBr, LiCl) and lithium amides (LiNH2). Examples of halide-based solid electrolytes include Li3YCl6. Examples of organic-based solid electrolytes include polyethylene oxide, polypropylene oxide, and polyacrylonitrile.

[0085] Electrochemical element 21 is manufactured, for example, as follows: Active material 19 is mixed with a mixture of a non-aqueous solvent containing dissolved lithium salt and particles 18, and a solvent containing dissolved binder is further mixed to prepare a slurry. After coating the slurry onto the current collector 12, it is dried to obtain an active material layer 13.

[0086] A slurry for preparing a separator is prepared by mixing a non-aqueous solvent containing dissolved lithium salt with a solvent containing dissolved binder in a mixture of particles 18. After coating the separator slurry onto the active material layer 13, the mixture is dried to obtain a positive electrode sheet.

[0087] Active material 20 is mixed into a mixture of a non-aqueous solvent containing dissolved lithium salt and particles 18, and a solvent containing dissolved binder is further mixed in to prepare a slurry. After coating the slurry onto the current collector 16, it is dried to obtain an active material layer 17. After coating the active material layer 17 with a separator slurry, it is dried to obtain a negative electrode sheet.

[0088] After cutting the positive and negative electrode sheets into specified shapes, they are overlapped and pressed together to form a separator 22 between the positive electrode 11 and the negative electrode 15 to fabricate a battery. Terminals (not shown) are connected to the current collectors 12 and 16 respectively, and the battery is sealed in a container (not shown) to obtain an electrochemical element 21 containing the positive electrode 11, the separator 22, and the negative electrode 15.

[0089] Since the electrochemical element 21 in the second embodiment contains an electrolyte in the positive electrode 11, the negative electrode 15, and the separator 22, it is similar to the electrochemical element 10 in the first embodiment in terms of large capacity and high-speed charging.

[0090] Example

[0091] The invention will be described in more detail through embodiments, but the invention is not limited to these embodiments.

[0092] (Example 1)

[0093] To become Li 6.95 Mg 0.15 La 2.75 Sr 0.25 Zr 2.0 O 12 The following method was used: Li₂CO₃, MgO, La(OH)₃, SrCO₃, and ZrO₂ were weighed. Considering the volatilization of Li during calcination, Li₂CO₃ was added in excess by approximately 15 mol%. The weighed raw materials and ethanol were added together with zirconium oxide pellets into a nylon can and pulverized and mixed using a ball mill for 15 hours. The slurry removed from the can was dried and calcined at 1100°C on an MgO plate for 15 hours. The calcined powder was pulverized and placed in an MgO crucible for further calcination at 1100°C for 4 hours. The calcined powder was then pulverized in an argon-atmospheric glove box to obtain the oxide solid electrolyte (hereinafter referred to as "LLZ").

[0094] The crystal structure of LLZ was confirmed to be garnet-type by powder X-ray diffraction. The median diameter (D50) of the LLZ particle size distribution, determined by laser diffraction / scattering, was 74 μm.

[0095] The LLZ was pulverized using a dry jet mill (Aishin Nano Technologies, Inc., Nano Jetmizer (registered trademark) NJ-50 model) with an initial nozzle pressure of 2.0 MPa, passing through the mill three times under a nitrogen atmosphere at a throughput of 480 g / Hr. The pulverized LLZ was then stored for 24 hours under an argon atmosphere with a dew point of -70°C to obtain the particles of Example 1.

[0096] (Example 2)

[0097] The LLZ particles were pulverized twice in a jet mill, otherwise the process was the same as in Example 1, to obtain the particles of Example 2.

[0098] (Example 3)

[0099] The LLZ particles were pulverized in a jet mill once by setting the processing rate to 960 g / Hr, and otherwise operated in the same manner as in Example 1 to obtain the particles of Example 3.

[0100] (Example 4)

[0101] The LLZ was pulverized by passing it through a jet mill 10 times, otherwise the operation was the same as in Example 1, to obtain the particles of Example 4.

[0102] (Determination of particle size distribution and specific surface area)

[0103] The median diameter (D50) of the particle size distribution of the particles in Examples 1-4 was determined by laser diffraction / scattering. Additionally, the specific surface area of ​​the particles in Examples 1-4 was determined according to JIS R1626:1996.

[0104] (Preparation of electrolyte and determination of color)

[0105] In a non-aqueous solvent prepared by mixing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a 1:1:1 (volume ratio), the supporting electrolyte LiPF6 is mixed to achieve a concentration of 1 mol / dm³. 3 Further mixing with 1% by weight of vinylene carbonate to prepare the electrolyte. The particles from Examples 1-4 and the electrolyte were added to test tubes at a ratio of 16.5:83.5 (mass ratio) and mixed for 30 minutes. Then, the test tubes were capped and allowed to stand for 24 hours to allow the particles to settle and separate. The supernatant was collected to obtain the electrolytes from Examples 1-4. The electrolyte before mixing with the particles was used as the electrolyte for Comparative Example 1.

[0106] In a non-aqueous solvent prepared by mixing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a 1:1:1 (volume ratio), the supporting electrolyte LiPF6 is mixed to achieve a concentration of 1 mol / dm³.3 The substance obtained therefrom was used as the electrolyte for Comparative Example 2. The electrolyte for Comparative Example 1 contained vinylene carbonate, but the electrolyte for Comparative Example 2 did not contain vinylene carbonate, which is a difference.

[0107] The particles from Example 1 and the electrolyte from Comparative Example 2 were placed in a test tube at a ratio of 16.5:83.5 (mass ratio) and mixed for 30 minutes. Then, the test tube was capped and allowed to stand for 24 hours to allow the particles to settle and separate. The supernatant was collected to obtain the electrolyte of Comparative Example 3. The electrolytes of Examples 1-4 and Comparative Examples 1-3 were formed from non-aromatic compounds.

[0108] Using a spectrophotometer CM-5 (Konica Minolta, Inc.), the colors of the electrolytes in Examples 1-4 and Comparative Examples 1-3 were measured at 25°C, and the CIE 1976L values ​​were determined. * a * b * L in color space * a * b * Further, a * b * Substitute chroma c * ={(a * ) 2 +(b * ) 2} 1 / 2 In the formula, the chroma c of the electrolytes of Examples 1-4 and Comparative Examples 1-3 is obtained. * .

[0109] ( 1 (Measurement of H-NMR spectrum)

[0110] The electrolytes from Examples 1-4 and Comparative Examples 1-3 were placed in solution sample tubes with an outer diameter of 5 mm under an argon atmosphere. The NMR spectra of proton nuclei were measured using a nuclear magnetic resonance (NMR) apparatus (JEOL ECZ700R) via pulsed Fourier transform. The observation frequency was 700 MHz, the magnetic field strength was 16.45 T, and the measurement temperature was 25 °C. The chemical shifts (ppm) of signals with chemical shifts in the range of 6 ppm to 8 ppm were measured, using the resonance position of tetramethylsilane as a reference.

[0111] (Determination of infrared absorption spectra based on FT-IR)

[0112] The electrolytes of Examples 1-4 and Comparative Examples 1-3 were brought into contact with crystals under an argon atmosphere. Infrared light was irradiated onto the electrolytes from the back of the crystals, and the infrared absorption spectra were measured by ATR method. A total of 32 measurements were performed, with a resolution of 4 cm⁻¹. -1The pore size is 80 μm, and the measurement temperature is 25 °C. The measured wavenumber is at 1100 cm⁻¹. -1 ~1120cm -1 wavenumber (cm) of infrared absorption spectrum within the range -1 ).

[0113] (Determination of migration numbers)

[0114] Lithium foil was adhered to two stainless steel plates with a diameter of 20 mm. Thirty-eight polypropylene separators, each 15 μm thick, were overlapped and clamped between the lithium foils. Electrolytes from Examples 1-4 and Comparative Examples 1-3 were injected into the separators and then fixed with polyimide adhesive tape to obtain symmetrical cells for Examples 1-4 and Comparative Examples 1-3. The fabrication of the symmetrical cells and the following measurements were performed in a glove box filled with argon gas at a dew point of -60°C.

[0115] The lithium-ion transport number is determined by combining AC impedance measurement and chronoamperometry. Specifically, after performing AC impedance measurement on a symmetrical battery, a DC polarization voltage ΔV is applied to the battery, and the change in current flowing through the battery over time is measured. After reaching steady state, AC impedance measurement is performed again. The lithium-ion transport number t is calculated using the following formula.

[0116] t={I S (ΔV-I0R0)} / {I0(ΔV-I S R S )}

[0117] Among them, I S I0 is the steady-state current value, I0 is the current value at the initial stage of voltage application, and R0 ... are the current values. S These are the interface resistances of the diaphragm and electrode before and after measurement using the chronoamperometry method. The applied voltage ΔV measured by the chronoamperometry method is 3mV.

[0118] The median diameter D50 and specific surface area of ​​the particles from Examples 1-4 and Comparative Example 3, and the L of the electrolytes from Examples 1-4 and Comparative Examples 1-3 were compared. * a * b * c * Chemical shift (ppm), wavenumber (cm) -1 The change rates (%) of lithium ion transport number and interfacial resistance R0 are recorded in Table 1. The change rates of R0 in Examples 1-4 are recorded as the change rates of R0 relative to the electrolyte of Comparative Example 1, and the change rates of R0 in Comparative Example 3 are recorded as the change rates of R0 relative to the electrolyte of Comparative Example 2.

[0119]

[0120] As shown in Table 1, the electrolytes of Examples 1-4 and Comparative Example 1 containing vinylene carbonate had a chemical shift in the range of 6 ppm to 8 ppm. 1 The H-NMR spectrum signal (7.15 ppm) was absent in the electrolytes of Comparative Examples 2 and 3 within the chemical shift range of 6 ppm to 8 ppm. 1 The signal from the H-NMR spectrum of the electrolytes in Examples 1-4 at a wavenumber of 1100 cm⁻¹. -1 ~1120cm -1 Infrared absorption spectra exist in the range of 1105-1118 cm⁻¹ -1 However, the electrolytes of Comparative Examples 1-3 at a wavenumber of 1100 cm⁻¹... -1 ~1120cm -1 There is no infrared absorption spectrum within the range.

[0121] The migration number of the electrolytes in Examples 1-4 was 0.125 greater than that of Comparative Example 1. Regarding the color b of the electrolyte... * Examples 1-4 showed a color value of 2.00 or higher, while Comparative Example 1 showed -0.95. This indicates that the color value b of the electrolyte after contact with particles that have undergone the prescribed treatment... * The color of the electrolyte increases. As can be seen from Examples 1-4 and Comparative Example 1, if the color b of the electrolyte... * If the value is 2.00 or higher, the transference number of lithium ions can be increased compared to the electrolyte before contact with the particles (Comparative Example 1).

[0122] Regarding the chroma c of the electrolyte * Examples 1-4 have a chroma c of 2.00 or higher and 8.00 or lower, while Comparative Example 1 has a chroma c of 1.01. It can be seen that the chroma c of the electrolyte after contact with particles that have undergone the prescribed treatment... * It increases. Therefore, if the chroma c of the electrolyte increases... * A value between 2.00 and 8.00 can increase the transference number of lithium ions.

[0123] Regarding the brightness (L) of the electrolyte * Examples 1-3 have a brightness value of 1.00 or higher and 3.00 or lower, while Comparative Example 1 has a brightness value of 3.76. It can be seen that if the brightness value L of the electrolyte... * A value between 1.00 and 3.00 can increase the transference number of lithium ions.

[0124] It was used in the range of 6 ppm to 8 ppm chemical shift. 1The rate of change of the interfacial resistance R0 of the symmetrical cells in Examples 1-4 of the H-NMR spectrum of the electrolyte was 70-88% of that in Comparative Example 1, where the signal was present in the chemical shift range of 6 ppm to 8 ppm. On the other hand, an electrolyte in the chemical shift range of 6 ppm to 8 ppm was used... 1 The rate of change of the interfacial resistance R0 of the symmetrical cell in Comparative Example 3, which exhibits no signal relative to the chemical shift range of 6 ppm to 8 ppm, is only 54% of that in Comparative Example 2. This indicates that by using electrolytes with a chemical shift range of 6 ppm to 8 ppm, the signal in the electrolyte is significantly different. 1 The electrolyte that produces the H-NMR spectrum signal is not compatible with the electrolyte used in the chemical shift range of 6 ppm to 8 ppm. 1 Compared to the electrolyte case, the H-NMR spectrum signal can reduce the interfacial resistance of the electrode.

[0125] The present invention has been described above based on the embodiments, but the present invention is not limited to any of the above embodiments, and it is easy to deduce that various modifications and variations can be made without departing from the spirit of the present invention.

[0126] In this embodiment, the electrochemical element 10 is described as an electrochemical element having a positive electrode 11 with an active material layer 13 disposed on one side of the current collector 12 and a negative electrode 15 with an active material layer 17 disposed on one side of the current collector 16, but it is not necessarily limited to this. For example, it is certainly possible to apply the elements in this embodiment to an electrochemical element having an electrode layer (so-called bipolar electrode) with an active material layer 13 and an active material layer 17 disposed on both sides of the current collector 12, respectively. If the bipolar electrode and the separator 14 are alternately stacked and housed in a housing (not shown), a so-called bipolar structure electrochemical element can be obtained.

[0127] In this embodiment, the active material layers 13 and 17 are described as containing particles 18, but this is not a limitation. It is also possible to omit particles 18 from at least one of the active material layers 13 and 17.

[0128] Although the description is omitted in the embodiments, it is of course possible to provide a protective layer between the active material layer 17 and the separators 14, 22, or between the current collector 16 and the active material layer 17. The protective layer comprises a composite oxide having a garnet-type crystal structure containing Li, La, and Zr. When a protective layer is provided between the active material layer 17 and the separators 14, 22, short circuits caused by dendrites can be reduced. When a protective layer is provided between the current collector 16 and the active material layer 17, the deterioration of the current collector 16 can be reduced.

[0129] In this embodiment, lithium-ion batteries, plasma batteries, and electrochemical capacitors are used as examples to describe electrochemical elements 10 and 21, but this is not a limitation. Other electrochemical elements include metal-air batteries and electrolytic capacitors that use oxygen from the air as the positive electrode active material and metals such as Li, Zn, Al, Mg, and Fe as the negative electrode active material.

[0130] Symbol Explanation

[0131] 10, 21 Electrochemical Components

[0132] 11 Positive electrode

[0133] 15. Negative electrode (electrode)

[0134] 18 particles

Claims

1. An electrolyte comprising a non-aqueous solvent, wherein, In CIE 1976L * a * b * In the color coordinates of the color space, b * ≥2.

2. The electrolyte according to claim 1, wherein, In the color coordinates, 1≤L * ≤3.

3. The electrolyte according to claim 1 or 2, wherein, In the color coordinates, c * ={(a * ) 2 +(b * ) 2 } 1 / 2 The chroma is represented as 2≤c * ≤8.

4. The electrolyte according to claim 1 or 2, wherein, Lithium salt is dissolved in the non-aqueous solvent.

5. The electrolyte according to claim 1 or 2, which is composed of non-aromatic compounds and has a proton nuclear magnetic resonance spectrum signal in the range of 6 ppm to 8 ppm chemical shift.

6. The electrolyte according to claim 5, wherein, Absorption spectra based on Fourier transform infrared spectroscopy exist at wavenumber 1100 cm⁻¹. -1 ~1120cm -1 Within the range.

7. An electrolyte composition comprising particles of the electrolyte and oxide solid electrolyte as described in claim 1 or 2.

8. The electrolyte composition according to claim 7, wherein, The oxide solid electrolyte has a garnet-type crystal structure containing Li, La, and Zr.

9. An electrochemical element comprising electrodes, wherein, The electrode comprises the electrolyte as described in claim 1 or 2.

10. The electrochemical element according to claim 9, wherein, The electrode is a positive electrode.

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