WO2023190273A1

WO2023190273A1 - Nonaqueous electrolytic solution and electrochemical device

Info

Publication number: WO2023190273A1
Application number: PCT/JP2023/012070
Authority: WO
Inventors: 裕之米丸
Original assignee: 日本ゼオン株式会社
Priority date: 2022-03-30
Filing date: 2023-03-27
Publication date: 2023-10-05

Abstract

Disclosed are: a nonaqueous electrolytic solution; and an electrochemical device. The nonaqueous electrolytic solution includes an ionic component and a non-ionic solvent component. The non-ionic solvent component contains a heteroelement-containing organic solvent substance (A) and a fluorine-containing organic solvent substance (B). The fluorine-containing organic solvent substance (B) includes, in the molecule, a ring structure using carbon atoms as constituents and/or a carbon-carbon unsaturated bond, and has a fluorination rate of 40% or more. The proportion of the fluorine-containing organic solvent substance (B) relative to 100 vol% of the non-ionic solvent component is 10 vol% or more. The molar amount of the heteroelement-containing organic solvent substance (A) is at most 5 times the cation amount of the ionic component.

Description

Non-aqueous electrolytes and electrochemical devices

The present invention relates to a nonaqueous electrolyte that can be used in nonaqueous electrochemical devices such as lithium ion primary batteries, lithium ion secondary batteries, and capacitors, and to electrochemical devices that include the nonaqueous electrolyte.

In general, electrochemical devices such as primary batteries, secondary batteries, and capacitors include an exterior body and contents sealed therein, such as electrolyte, electrodes, and separators, for realizing the functions of the device. Equipped with
Generally, an electrolytic solution includes an ionic component that functions as a so-called electrolyte and a nonionic solvent component that primarily functions as a solvent. As the electrolytic solution, a non-aqueous electrolytic solution containing a non-aqueous solvent as a solvent is often used.

It is known to use a so-called high-concentration electrolyte solution, which has an extremely high electrolyte concentration, as a non-aqueous electrolyte solution (for example, Patent Document 1).

Japanese Patent Application Publication No. 2014-241198

Highly concentrated electrolytes have high chemical stability, electrochemical stability, and low volatility, but they also have disadvantages such as easy salt precipitation, low ionic conductivity at low temperatures, and low capacity retention. It may be disadvantageous. Highly concentrated electrolytes may also have low impregnability into other components such as separators and electrodes due to physical properties such as high viscosity.

Therefore, it is an object of the present invention to provide a highly concentrated non-aqueous electrolyte that has high chemical and electrochemical stability and low volatility due to the high electrolyte concentration, while suppressing salt precipitation. The object of the present invention is to provide a non-aqueous electrolyte having high ionic conductivity at low temperatures, high capacity retention, and high impregnating property; and an electrochemical device that enjoys such advantages.

The present inventor conducted studies to solve the above problems. As a result, the inventors discovered that the above-mentioned problems could be solved by employing specific components constituting a high-concentration non-aqueous electrolyte and blending them in specific proportions, thereby completing the present invention.
That is, the present invention is as follows.

(1) A non-aqueous electrolyte containing an ionic component and a non-ionic solvent component,
The nonionic solvent component is
a hetero element-containing organic solvent substance (A) which is an organic compound with a fluorination rate of less than 40%;
and a fluorine-containing organic solvent substance (B), which is an organic compound with a fluorination rate of 40% or more,
The fluorine-containing organic solvent substance (B) contains a fluorine-containing organic solvent substance (Bx) which is a compound containing a ring structure composed of carbon atoms, a carbon-carbon unsaturated bond, or both of these in the molecule. including,
The proportion of the fluorine-containing organic solvent substance (Bx) in 100 volume% of the non-aqueous electrolyte is 10 volume% or more,
The molar amount of the hetero element-containing organic solvent substance (A) is within 5 times the cation amount of the ionic component,
Non-aqueous electrolyte.
(2) The nonionic solvent component contains the hetero element-containing organic solvent substance (A), the fluorine-containing organic solvent substance (B), or an additive (P) as another nonionic solvent component. including,
The non-aqueous electrolyte according to (1), wherein the additive (P) is one or more selected from the group consisting of a cyclic sulfate compound, a vinyl ethylene carbonate compound, and a cyclic fluorine compound having an unsaturated bond.
(3) the ionic component contains a fluorine-containing sulfonylimide anion,
The non-aqueous electrolyte according to (1) or (2), wherein the proportion of the imide anion to the anions constituting the ionic component is 50 mol% or more.
(4) The non-aqueous electrolyte according to (3), wherein the fluorine-containing sulfonylimide anion is a bisfluorosulfonylimide anion.
(5) the ionic component contains a boron anion,
The non-aqueous electrolyte according to (1) or (2), wherein the proportion of the boron anion to the anions constituting the ionic component is 50 mol% or more.
(6) The non-aqueous electrolyte according to any one of (1) to (5), wherein the ionic component includes an ionic liquid.
(7) The nonaqueous electrolyte according to any one of (1) to (6), wherein the nonionic solvent component contains acetonitrile as the hetero element-containing organic solvent substance (A).
(8) The nonionic solvent component contains one or more types selected from the group consisting of ethylene carbonate, fluorinated ethylene carbonate, propylene carbonate, γ-butyrolactone, and sulfolane as the hetero element-containing organic solvent substance (A). The non-aqueous electrolyte according to any one of (1) to (7).
(9) The nonaqueous electrolyte according to any one of (1) to (8), wherein the nonionic solvent component contains two or more types of compounds as the hetero element-containing organic solvent substance (A). .
(10) the nonionic solvent component contains a flame retardant solvent substance (AR) as the hetero element-containing organic solvent substance (A),
The flame retardant solvent substance (AR) is a compound (R1) which is a phosphoric acid ester or a phosphite ester and has 1 to 6 carbon atoms per molecule, and the hydrogen of the compound (R1) is partially removed. The non-aqueous electrolyte according to any one of (1) to (9), which is one or more selected from the group consisting of a fluorinated compound (R2) and a compound having a phosphazene ring (R3).
(11) The nonionic solvent according to any one of (1) to (10), wherein the nonionic solvent component contains a substance having a carbon-carbon unsaturated bond as the fluorine-containing organic solvent substance (Bx). Water electrolyte.
(12) The nonaqueous electrolyte according to any one of (1) to (11), wherein the nonionic solvent component contains a substance having an ether bond as the fluorine-containing organic solvent substance (Bx).
(13) The nonionic solvent component contains a fluorine-containing organic solvent substance (C) other than the fluorine-containing organic solvent substance (Bx) as the fluorine-containing organic solvent substance (B), (1) to (12) ) The non-aqueous electrolyte according to any one of the above.
(14) The non-aqueous electrolyte according to any one of (1) to (13), which does not have a flash point.
(15) An electrochemical device comprising the non-aqueous electrolyte according to any one of (1) to (14).
(16) having a structure in which the non-aqueous electrolyte is sealed in a sealed space inside the exterior, and having a mechanism in which the space is opened when the pressure in the space becomes equal to or higher than a threshold; The electrochemical device according to (15), wherein the threshold value is 2 atm to 10 atm.

According to the present invention, a highly concentrated non-aqueous electrolyte has high chemical stability, electrochemical stability and low volatility due to the high electrolyte concentration, while salt precipitation is suppressed and low temperature is achieved. Provided are nonaqueous electrolytes that have high ionic conductivity, high capacity retention, and high impregnating properties; and electrochemical devices that enjoy such advantages.

FIG. 1 is a graph showing the results of Example 3. FIG. 2 is a graph showing the results of Example 4.

Hereinafter, the present invention will be described in detail by showing embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and may be implemented with arbitrary changes within the scope of the claims of the present invention and equivalents thereof.

In the present application, the "anion amount" of an anion is the molar equivalent of the ion, for example, the anion amount for 1 mole of monovalent anions is 1 mole, and the anion amount for 1 mole of divalent anions is also 1 mole. "Amount of cation" is also a molar equivalent.

In the present application, the volume of a substance for determining the volume ratio and specific gravity is the volume at the temperature and pressure during the preparation and use of the non-aqueous electrolyte, specifically, the volume ratio at 25° C. and 1 atmosphere. Moreover, the boiling point is the temperature at 1 atmosphere.

In the following description, the term "solvent" is interpreted in a broad sense and includes the meaning of dispersion medium. In other words, "solvent" refers to not only a medium in a solution (i.e., a mixture of a liquid medium substance and a solute substance dissolved therein) but also a dispersion liquid (i.e., a liquid medium substance and a solute substance dissolved therein). (a mixture of a substance in a medium and a substance that is a dispersion present dispersed therein as solid particles or emulsion particles) and a medium in a mixture containing both a solute and a dispersion. Also includes.

(Non-aqueous electrolyte)
The nonaqueous electrolyte of the present invention includes an ionic component and a nonionic solvent component.

(ionic component)
The ionic component is a component that functions as an electrolyte in the electrolytic solution. The ionic component is composed of one or more types of ionic substances. Ionic substances are commonly represented as anionic and cationic salts. Examples of anions and cations include various types known as constituents of electrolytes.

Specific examples of anions include F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , BF ₄ ⁻ , B(C ₂ O ₄ )F ₂ ⁻ , B(C ₂ O ₄ ) ₂ ^- , SbF ₆ ^- , AlCl ₄ ^- , ClO ₄ ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ COO ^- , (CF ₃ CO) ₂ N ^- , (CF ₃ SO ₂ ) ₃ C ^- , (FSO ₂ ) ₂ N ^- (FSI, bisfluorosulfonylimide), (CF ₃ SO ₂ ) ₂ N ^- (TFSI, bistrifluoromethanesulfonylimide), and (C ₂ F ₅ SO ₂ ) N ^- are mentioned. It will be done. As the anion, imide anions and boron-containing anions are particularly preferred from the viewpoint of obtaining a non-aqueous electrolyte having both heat resistance and oxidation resistance. Further, as the imide anion, fluorine-containing sulfonylimide anions such as bisfluorosulfonylimide anion and bistrifluoromethanesulfonylimide anion are preferred from the viewpoint of ionic conductivity, and bisfluorosulfonylimide anion is particularly preferred. From the viewpoint of expressing the preferable properties, when the ionic component contains multiple types of anions, the proportion of imide anions, especially fluorine-containing sulfonylimide anions, to the anions constituting the ionic component is 50 mol% or more. It is preferable that the proportion of boron anions to the anions constituting the ionic component is 50 mol % or more.

Specific examples of cations include Li ⁺ , Na ⁺ , Mg ²⁺ , TEA (triethylammonium cation), TBA (tributylammonium cation), and EMI (ethylmethylimidazolium cation).

The ionic component may include an ionic liquid as an ionic substance that constitutes the ionic component. Here, the ionic liquid is a salt composed of cations and anions, and is liquid at 25° C. and 1 atm, for example. An example of an ionic liquid is EMI-TFSI.

The proportion of the ionic component and the solvent substance (A) in the non-aqueous electrolyte of the present invention is not particularly limited, but it should be a high proportion from the perspective of enjoying the advantages of a so-called high-concentration non-aqueous electrolyte. is preferred. Specifically, the proportion of the ionic component and the solvent substance (A) in the entire non-aqueous electrolyte is preferably 30% by volume or more, more preferably 40% by volume or more.

(Nonionic solvent component)
The nonionic solvent component is a component that functions as a solvent to maintain an appropriate concentration of ionic components in the electrolytic solution. In the nonaqueous electrolyte of the present invention, the nonionic solvent component includes one or more types of hetero element-containing organic solvent substances (A) and one or more types of fluorine-containing organic solvent substances (B). Below, these may be simply referred to as "solvent substance (A)" and "solvent substance (B)."

(Solvent substance (A))
The solvent substance (A) is a substance containing a hetero element, and its fluorination rate is less than 40%. The solvent substance (A) is a substance that is liquid and can function as a solvent in the environment in which the non-aqueous electrolyte is used. Examples of heteroelements that the solvent substance (A) may contain include O, S, N, P and B. Preferably, the solvent substance (A) may contain O, N, or both as heteroelements. One molecule of the solvent substance (A) may contain one or more hetero elements, and when it contains two or more hetero elements, they may be the same or different.

As the solvent substance (A), among known substances used as solvents for electrolyte solutions, those applicable to substances other than the solvent substance (B) can be appropriately selected and used. The nonionic solvent component may contain only one type of compound as the solvent substance (A), or may contain two or more types of compounds. When the nonionic solvent component contains two or more types of compounds as the solvent substance (A), desired physical properties of the nonaqueous electrolyte can be easily obtained by adjusting their types and proportions.

The solvent substance (A) may be a substance that has a cyclic molecular structure, or may be a substance that does not include a cyclic molecular structure and only has a chain-like molecular structure. The solvent substance (A) may be a substance having a carbon-carbon unsaturated bond, or the solvent substance (A) may be a substance having no carbon-carbon unsaturated bond. However, the solvent substance (A) is a substance whose fluorination rate is less than 40%.

The solvent substance (A) preferably has an oxidation-resistant polar group in its molecular structure. Examples of oxidation-resistant polar groups include -F and other halogen atoms, -CN, -CH=N-, -SO ₄ -, -SO ₃ -, -SO ₂ -, -SO-, -C( =O)-, -C(=O)-O-, -O-C(=O)-O-, -P(=O)-, -P(-O-) ₂ -, -P(-O -) ₃ , -P(=O)(-O-) ₃ , -B=O, B(-O-) ₃ , -C(=O)NR ¹ -, -NR ¹ -C(=O)NR ^2- , -NO, and _-NO2 . Here, R ¹ and R ² are independently a hydrogen atom or an organic substituent. The organic substituent preferably has a bond extending from its carbon atom to the N atom. Specific examples of R ¹ and R ² include a methyl group, an ethyl group, and a propyl group.

Specific examples of the solvent substance (A) include esters; acid anhydrides such as succinic anhydride, glutaric anhydride, itaconic anhydride, maleic anhydride, and diglycolic anhydride; acetone, ethyl Ketones such as methyl ketone, cyclopentanone, and cyclohexanone; Nitriles such as acetonitrile, propionitrile, valeronitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, and various trinitrile compounds; Sulfoxides such as dimethyl sulfoxide Sulfones such as dimethylsulfone, ethylmethylsulfone, and diethylsulfone; Sultones such as propane sultone and butane sultone; Oxazoles such as oxazole; Isoxazoles such as isoxazole; Oxazolines such as methyloxazoline; Furazane such as furazane dioxolanes such as 1,2-dioxolane; dioxanes such as 1,3-dioxane and 1,4-dioxane; trioxanes such as trioxane; oxazolidones such as N-methyloxazolidone; and N,N-dimethylimidazo Examples include imidazolidinones such as lysinone.

Examples of esters include organic acid esters such as formate, acetate, propionate, γ-butyrolactone, valerolactone, glycolide, lactide, dimethyl oxalate, diethyl oxalate, and dimethyl succinate; dimethyl carbonate, carbonic acid Carbonic esters such as diethyl, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and fluorinated ethylene carbonate; Sulfuric esters such as dimethyl sulfate; Phosphite esters such as trimethyl phosphite and triethyl phosphite; Trimethyl phosphate, phosphorus Examples include phosphoric acid esters such as triethyl acid and tributyl phosphate; and boric acid esters such as trimethyl borate and triethyl borate.

In addition, a compound having two or more of the above characteristics can also be used as the solvent substance (A). Examples of such compounds include methyl cyanoacetate, ethyl cyanoacetate, methyl methanesulfonylacetate, methylsulfonylacetonitrile, methoxypropionitrile, and 3,3'-oxydipropionitrile.

In one embodiment, the nonionic solvent component preferably contains acetonitrile as the solvent substance (A). By using acetonitrile, the effect of excellent ionic conductivity at low temperatures can be obtained. In addition, when using the nonaqueous electrolyte of the present invention in an electrochemical device containing a carbonaceous material as a negative electrode active material, by using acetonitrile and an acid anhydride together, the current when using a carbonaceous material for the electrode can be increased. The effect of superior efficiency can be obtained.

In another embodiment, the nonionic solvent component may contain, as the solvent substance (A), one or more selected from the group consisting of ethylene carbonate, fluorinated ethylene carbonate, propylene carbonate, γ-butyrolactone, and sulfolane. preferable. By using these solvent substances (A), the boiling point of the obtained non-aqueous electrolyte becomes a high boiling point exceeding 200°C. Therefore, in the event of some kind of abnormal heating, the internal pressure created by the solvent substance (B) will cause the electrochemical device to fail. Even when cleaved, the effect of making it difficult for the flammable solvent to diffuse into the surrounding area can be obtained.

In addition, it is preferable that the nonionic solvent component includes a flame retardant solvent substance (AR) as the solvent substance (A). The flame-retardant solvent substance (AR) is a compound (R1) that is a phosphoric acid ester or a phosphite ester and has 1 to 6 carbon atoms per molecule, and the hydrogen of the compound (R1) is partially fluorinated. The compound is one or more selected from the group consisting of a compound (R2) having a phosphazene ring, and a compound (R3) having a phosphazene ring.

Specific examples of the compound (R1) include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trisbutoxyethyl phosphate, and phosphorous esters corresponding to these. Examples of the compound (R3) include Nippon Kagaku Kogyo Co., Ltd., trade names "Hishicolin-E", "Hishicolin-O", and "Hishicolin-D". The proportion of the flame retardant solvent substance (AR) in 100% by volume of the nonionic solvent component is preferably 5% by volume or more, more preferably 10% by volume or more, while preferably 25% by volume or less, more Preferably it is 20% by volume or less. By setting the proportion of the flame-retardant solvent substance (AR) to the above-mentioned lower limit or more, the flame retardancy of the non-aqueous electrolyte can be improved, and the safety of the electrochemical device can be improved. On the other hand, by setting the proportion of the flame-retardant solvent substance (AR) below the above-mentioned upper limit, an increase in the resistance of the device can be avoided.

In the nonaqueous electrolyte of the present invention, the upper limit of the molar amount of the solvent substance (A) relative to the cation amount of the ionic component is within 5 times, preferably within 4 times, and more preferably within 3 times. When the molar amount of the solvent substance (A) is below this upper limit, the effect of the solvent substance (B) can be favorably obtained. Furthermore, the flammability of the non-aqueous electrolyte can be effectively reduced.

On the other hand, the lower limit of the molar amount of the solvent substance (A) relative to the cation amount of the ionic component can be 0.75 times or more, preferably 1.5 times or more, and more preferably 2.2 times or more. When the molar amount of the solvent substance (A) is at least this lower limit, the desired effect as an electrolytic solution can be satisfactorily expressed.

(Solvent substance (B))
The solvent substance (B), like the solvent substance (A), can be a substance that is liquid and functions as a solvent in the environment in which the non-aqueous electrolyte is used. The nonionic solvent component may contain only one type of substance or two or more types of substances as the solvent substance (B).

The solvent substance (B) has a fluorination rate of 40% or more. In this application, the fluorination rate of molecules of substances such as solvent substances (A) and (B) is determined by the number n of hydrogen atoms bonded to carbon in the molecule, n _H , and the number n of fluorine atoms bonded to carbon in the molecule. From _F , it is determined from the formula: fluorination rate (%)=(n _F /(n _F +n _H ))×100. When the fluorination rate is 40% or more, the oxidation stability of the nonaqueous electrolyte increases and the flammability decreases. However, it is preferable that the fluorination rate of the solvent substance is less than 100% (that is, it has one or more hydrogen atoms in the molecule). By having one or more hydrogen atoms in the molecule, the charge within the molecule becomes non-homogeneous, and the polarity becomes high, making it easier to create a highly concentrated electrolyte and a uniform solution.

The non-aqueous electrolyte of the present invention contains a solvent substance (Bx) as part or all of the solvent substance (B). The solvent substance (Bx) contains a ring structure composed of carbon atoms, a carbon-carbon unsaturated bond, or both of these in its molecule. By having a ring structure, it is possible to obtain a higher boiling point than chain molecules with similar molecular size and atomic composition, and the molecule can have fewer hydrogen substitution sites, making it easy to achieve a high fluorination rate. Obtainable. When the solvent substance (Bx) has a carbon-carbon unsaturated bond, it can also be a molecule with fewer hydrogen substitution sites, making it easy to obtain a high fluorination rate. In addition, when the solvent substance (Bx) has a carbon-carbon unsaturated bond, especially when the solvent substance (Bx) has a ring structure consisting of carbon atoms and contains a carbon-carbon unsaturated bond in the ring. When it has, the ability of the non-aqueous electrolyte to protect the negative electrode can be enhanced, and as a result, for example, the effect of increasing the capacity retention rate of an electrochemical device containing the non-aqueous electrolyte can be obtained.

When the solvent substance (Bx) contains a ring structure composed of carbon atoms, a carbon-carbon unsaturated bond, or both of these, and has a fluorination rate of 40% or more, ions are generated in the non-aqueous electrolyte. Precipitation of salts of chemical components can be suppressed. The reason for this is unknown, but one possible reason is that the solvent substance (Bx) is interposed between the anion and cation that constitute the salt and suppresses aggregation.

The solvent substance (Bx) has one or more structures selected from the group consisting of -CFH-, -CF ₂ H, -CH ₂ -CF ₂ -, -CH ₂ CF ₃ and -O-, It is preferable that the molecule contains one or more, and more preferably two or more. By having these structures, the polarity of the solvent substance (B) molecules becomes high, and as a result, the above-mentioned effects can be better obtained.

The molecules of the solvent substance (Bx) may be molecules consisting only of carbon atoms, hydrogen atoms, oxygen atoms, and fluorine atoms, or may be molecules containing other atoms as well. For example, the solvent substance (Bx) may contain nitrogen atoms, phosphorus atoms, and sulfur atoms. The solvent substance (Bx) may also contain halogen atoms other than fluorine atoms. However, from the viewpoint of improving oxidation stability, the solvent substance (Bx) preferably does not contain nitrogen atoms, phosphorus atoms, and sulfur atoms. In addition, from the perspective of reducing toxic gas species when a device containing a non-aqueous electrolyte rises abnormally and the non-aqueous electrolyte decomposes and gas is generated, the molecules of the solvent substance (Bx) are carbon atoms, hydrogen atoms, etc. , a molecule consisting only of oxygen atoms and fluorine atoms is preferable.

Specific examples of the solvent substance (Bx) include compounds having a structure in which one or more hydrogen atoms in a hydrocarbon ring or a ring containing an oxygen atom are substituted with a fluorine atom or an organic substituent containing a fluorine atom. However, in this application, the solvent substance and other substances are not limited by the manufacturing process thereof.

Preferred examples of the hydrocarbon ring include cyclopentane, cyclohexane, and cyclopentene. The ring containing an oxygen atom is a ring composed of a carbon atom, a hydrogen atom, and an oxygen atom, and preferable examples thereof include tetrahydrofuran and tetrahydropyran. Examples of substituents include halogen atoms such as fluorine atoms, alkyl groups, fluorinated alkyl groups, ether groups, ester groups, and hydroxyl groups.

Among the solvent substances (Bx), preferable examples of those having a ring structure and those having both a ring structure and a carbon-carbon unsaturated bond include 1,1,2,2,3,3,4-heptafluorocyclo Pentane (fluorination rate: 70%), 3,3,4,4,5,5-hexafluorocyclopentene (fluorination rate: 75%), and 1-methoxy-2,3,3,4,4,5 , 5-heptafluorocyclopentene (fluorination rate: 70%). Other examples of solvent substances (Bx) having carbon-carbon unsaturated bonds include CHF ₂ CF=CHCl (trade name "AMOLEA (registered trademark) AS-300", manufactured by AGC Corporation, fluorination rate: 60 %), and CF ₃ CH=CHCl (trade name "Serefin 1233Z", manufactured by Central Glass Co., Ltd., fluorination rate: 60%).

The boiling point of the solvent substance (Bx) is preferably within a desired temperature range in order to adjust physical properties such as favorable handling properties and generation of internal pressure. Specifically, the boiling point of the solvent substance (Bx) is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, even more preferably 90°C or higher, while preferably 170°C or higher. The temperature is preferably 150°C or lower, more preferably 150°C or lower.

It is preferable that the solvent substance (Bx) has no flash point. If the solvent substance (Bx) does not have a flash point, the entire non-aqueous electrolyte can easily also have no flash point. As a result, it is possible to reduce the risk of a fire occurring when the electrochemical device overheats for some reason and the non-aqueous electrolyte is released outside the device. "Having no flash point" means that it does not show a flash point at least in the flash point measurement method based on the tag sealing method (JIS K2265-1 (2007)), and more preferably the Cleveland open method (JIS K2265 -4 (2007)), it is evaluated that there is no flash point.

It is preferable that the solvent substance (Bx) has low reactivity with gases in the atmosphere. Specifically, it is preferable that the reactivity with gases (including water vapor) constituting the atmosphere is low. Since the solvent substance (Bx) has low reactivity with gases in the atmosphere, it is possible to reduce the danger when the non-aqueous electrolyte is released outside the device. Specifically, the proportion of molecules that are oxidized within 10 minutes after being released into the atmosphere at 25°C is 1% or less, or the proportion of molecules that are hydrolyzed is 1% or less, and more preferably both. preferable.

It is preferable that the solvent substance (Bx) has high solubility in water. The lower limit of solubility in water is preferably 10 ppm or more, more preferably 100 ppm or more. When it has such high water solubility, it can easily dissolve ionic components at high concentrations. The upper limit of solubility in water is not particularly limited, but may be, for example, 10,000 ppm or less.

The dielectric constant of the solvent substance (Bx) is preferably a large value. The relative permittivity (measurement frequency: 1 kHz) is preferably 2.0 or more, more preferably 5 or more, even more preferably 8 or more, even more preferably 10 or more. By employing the solvent substance (B) having a high dielectric constant, the range in which the electrolyte can maintain a compatible state becomes wider. The upper limit of the dielectric constant is not particularly limited, but may be, for example, 50 or less.

The proportion of the solvent substance (Bx) in 100 volume% of the non-aqueous electrolyte is 10 volume% or more, preferably 20 volume% or more. The solvent substance (Bx) has either a ring structure consisting of carbon atoms or a carbon-carbon unsaturated bond, has the above-mentioned specific fluorination rate, and is a solvent substance in the nonionic solvent component. By setting the ratio of (Bx) within the above-mentioned specific range, various desired effects can be obtained. Specifically, a high boiling point can be obtained even if the solvent substance (Bx) has a low molecular weight. Moreover, a non-aqueous electrolyte with high ion conductivity can be obtained, and in particular, the ion conductivity at low temperatures can be improved. Further, the viscosity of the non-aqueous electrolyte can be set within a desired low range. Furthermore, by increasing the proportion of the solvent substance (Bx) in the nonionic solvent component, the impregnation of the nonaqueous electrolyte into porous device components such as the electrode mixture layer and/or the separator is enhanced. be able to.

It is more preferable to set the proportion of the solvent substance (Bx) in 100 volume % of the non-aqueous electrolyte to a high value such as 50 volume % or more, since this can improve the safety of an electrochemical device containing the non-aqueous electrolyte. Specifically, since the volatility of the solvent in a highly concentrated electrolytic solution is generally suppressed, the internal pressure is unlikely to increase even if a device containing the electrolytic solution reaches a high temperature. Therefore, when an abnormality occurs inside the device, it is difficult for a user to detect the abnormality from the outside. Here, since the non-aqueous electrolyte contains the solvent substance (Bx), internal pressure can be generated at a temperature higher than a certain level, and the temperature at which the internal pressure is generated depends on the type and composition ratio of the solvent substance (Bx). Can be adjusted by selection. By using a non-aqueous electrolyte that has been adjusted to generate such internal pressure, if the electrochemical device overheats for some reason and the exterior is destroyed, the solvent substance (Bx) can be easily released outside the device. In this case, most of the electrolyte is lost, which makes it difficult for the ions to move, and the operation of the device slows down or stops, thereby ensuring high safety.

The non-aqueous electrolyte of the present invention contains, as a part of the solvent substance (B), a fluorine-containing solvent substance (C) which is a substance other than the solvent substance (Bx) (hereinafter also simply referred to as "solvent substance (C)"). ) may be included. The solvent substance (C) is a compound having a fluorination rate of 40% or more and containing neither a ring structure composed of carbon atoms nor a carbon-carbon unsaturated bond in the molecule. By including the solvent substance (C), it is possible to easily adjust the viscosity of the nonaqueous electrolyte to a desired range.

Examples of solvent substances (C) include various fluorinated alkanes and fluorinated ethers. Examples of fluorinated alkanes include the trade name "Vertrell XF" (manufactured by Mitsui Chemours Fluoro Products Co., Ltd., 2H,3H-decafluoropentane); 6000'' (CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH ₃ ) (manufactured by AGC). Examples of fluorinated ethers include the trade name "Opteon SF-10" (manufactured by Mitsui Chemours Fluoro Products Co., Ltd.); Fluoroethyl 2,2,2-trifluoroethyl ether); trade name "NOVEC7100" (CF ₃ CF ₂ CF ₂ CF ₂ OCH ₃ ), "NOVEC 7200" (CF ₃ (CF ₂ ) ₃ 0CH ₂ CH ₃ and CF ₃ C(-CF ₃ )(-F)CF ₂ OCH ₂ CH ₃ mixture), "NOVEC7300"(CF ₃ CF ₂ C(-OCH ₃ )(-F)C(-CF ₃ ) ₂ (-F)) , "NOVEC7500" and "NOVEC7600" (manufactured by 3M); and "Galden" (manufactured by Solvay, perfluoropolyether). _Further _examples _of _fluorinated _ethers _include _{CF3CHFCF2OCH2CF2CHF2} _, _{CHF2CF2CH2OCF2CHF2} _, _{CF3CHFCF2CH2OCHF2} _, _{CF3CHCF2OCH2CF2} _CF ₃ _{_} _{_} _{_} _{_} _, _{CF3CHFCF2OCH2CF3} _, _{CHF2CF2OCH2CF3} _, _{CF3CHFCF2OCH3} _, _{CF3CF2CH2OCHF2} _, _and _{CF3CH2OCH2CF3} _. _{_} _{_} _{_} _{_} _{_} _{_} _{_}

The proportion of the solvent substance (A) in 100 volume % of the non-aqueous electrolyte may be 25 to 85 volume %.

(Additive (P))
In some embodiments, the nonionic solvent component can include an additive (P) as a solvent material (A), a solvent material (B), or another nonionic solvent component. The additive (P) is one selected from the group consisting of a cyclic sulfate compound (PA), a vinyl ethylene carbonate compound (PB), and a cyclic fluorine compound having an unsaturated bond (PC). It can be more than that.

Examples of the cyclic sulfate compound (PA) include 1,3,2-dioxathiolane 2,2-dioxide (ethylene sulfate), 4-methyl-1,3,2-dioxathiolane 2,2-dioxide, and 1,3,2-dioxathiane 2,2-dioxide is mentioned.

Examples of the vinyl ethylene carbonate compound (PB) include compounds having a vinyl ethylene carbonate skeleton, such as 3-vinyl ethylene carbonate, 3,4-divinyl ethylene carbonate, and 3-ethynyl ethylene carbonate.

Examples of cyclic fluorine compounds (PC) having unsaturated bonds and ether bonds include 3,3,4,4,5,5-hexafluorocyclopentene and 1-methoxy-2,3,3,4,4 , 5,5-heptafluorocyclopentene.

When the nonionic solvent component contains the additive (P), the current efficiency of the device is improved, for example, in the case of a lithium ion battery, the coulombic efficiency during charging and discharging is improved. From the viewpoint of effectively obtaining such effects, the amount of additive (P) added is preferably 0.01% by weight or more, more preferably 0.05% by weight or more based on 100% by weight of the nonionic solvent component, On the other hand, it is preferably 10% by weight or less, more preferably 7% by weight or less.

(Ratio of nonionic solvent components)
The proportion of the nonionic solvent component in 100% by weight of the non-aqueous electrolyte is preferably 30% by weight or more, more preferably 40% by weight or more, while preferably 95% by weight or less, more preferably 90% by weight or less. be.

(Other optional ingredients)
The non-aqueous electrolyte of the present invention may contain arbitrary components in addition to the above-mentioned ionic components and non-ionic solvent components. For example, it may contain a polymer compound with a molecular weight of more than 1000. That is, while the solvent component usually has a molecular weight of 1000 or less, a polymer compound with a weight average molecular weight of more than 1000, preferably more than 10,000, which can be dissolved in the solvent component, is dissolved in the non-aqueous electrolyte. may exist. By including a polymer compound, the ionic conductivity and viscosity of the nonaqueous electrolyte may be adjusted to an appropriate range. From the viewpoint of adjusting the ionic conductivity and viscosity within appropriate ranges, the proportion of the polymer compound in 100% by weight of the non-aqueous electrolyte is preferably 50% by weight or less. Examples of polymer compounds include polyethylene oxide, polyethylene oxide-propylene oxide copolymers, and polyoxazoline polymers.

(Properties of non-aqueous electrolyte)
The non-aqueous electrolyte of the present invention preferably has no flash point. By not having a flash point, the safety of electrochemical devices containing non-aqueous electrolytes can be improved. A non-aqueous electrolyte having no flash point can be obtained by appropriately selecting non-flammable or low combustible solvent substances from the above-exemplified components as the solvent substance (A) and the solvent substance (B).

(Method for producing non-aqueous electrolyte)
The method for producing a non-aqueous electrolyte of the present invention is not particularly limited, and can be produced by mixing the components described above in an appropriate environment suitable for producing an electrolyte.

Although the order of mixing each component is not particularly limited, it is preferable that the ionic component and the solvent substance (A) are mixed first, and then the solvent substance (B) is further mixed into the resulting mixture. By mixing in this order, the ionic component can be quickly dissolved and precipitation of the ionic component can be suppressed. Alternatively, some of the components may be mixed in an amount larger than the target ratio, and then the components may be reduced by distilling off or the like. In addition, each component is encapsulated inside the device in a state in which a portion of each component is solid, and then the solids are dissolved and mixed inside the device, so that each component is mixed at the target ratio. A non-aqueous electrolyte can also be obtained. For example, part of the solvent substance (B) in a solid state is sealed inside a device along with other components in a liquid state, and then the solvent substance (B) is dissolved, and each component is mixed in a target ratio. A water electrolyte can be obtained.

(Applications of non-aqueous electrolyte: Electrochemical devices)
The electrochemical device of the present invention includes the non-aqueous electrolyte of the present invention described above. That is, the nonaqueous electrolyte of the present invention can be used as a component of an electrochemical device. Since the electrochemical device of the present invention contains the non-aqueous electrolyte of the present invention as an electrolyte, it can enjoy advantages such as high capacity retention, high operating performance at low temperatures, and high safety.

The electrochemical device of the present invention may include a device exterior and contents such as an electrode, a separator, and the nonaqueous electrolyte of the present invention, which are enclosed in a sealed space inside the device exterior. The electrodes and separators are not particularly limited, and known electrodes and separators that are suitable for the use of the device can be appropriately employed.

The non-aqueous electrolyte of the present invention can be of low risk in the event that it leaks out of the device for some reason. It is possible to have a mechanism that releases the seal by the exterior when the temperature rises above a threshold value, so that the operation can be stopped when an abnormality occurs. Such a threshold may be between 2 atmospheres and 10 atmospheres.

Specific examples of the electrochemical devices of the present invention include various non-aqueous primary batteries, secondary batteries, electric double layer capacitors, electric double layer transistors, electrochromic display materials, electrochemical luminescent elements, electrochemical actuators, and dye-sensitized solar cells. Examples of batteries include lithium primary batteries, lithium ion secondary batteries, lithium metal secondary batteries, sodium ion batteries, potassium ion batteries, magnesium ion batteries, aluminum ion batteries, fluoride ion batteries, and air batteries. The battery is particularly preferably a lithium ion primary battery or a lithium ion secondary battery.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the embodiments shown below, and may be implemented with arbitrary changes within the scope of the claims of the present invention and equivalents thereof.

In the following description, "%" and "part" representing amounts are based on mass unless otherwise specified. Further, the operations described below were performed at room temperature and normal pressure unless otherwise specified. In particular, the steps from preparing the electrolyte to sealing it into the battery were carried out in a dry room with a temperature of 25° C. and a dew point of −40° C. or lower, unless otherwise specified.

(Manufacturing example 1)
(P1-1. Preparation of preliminary high concentration electrolyte)
As a preliminary preparation, the ionic substances and solvent substances (A) shown in Table 1 are mixed in the proportions shown in Table 1 to prepare electrolytes (01) to (20) that do not contain the solvent substance (B). did. If the dissolution rate was slow at the temperature of 25° C. in the dry room, heating was performed.

(P1-2. Evaluation of presence or absence of precipitation)
After the electrolytes (01) to (20) were left in a 20°C environment for 3 days, the presence or absence of solid precipitation was evaluated. The results are shown in Table 1. Solid precipitation was observed in some electrolytes.

(P1-3. Impregnation evaluation)
A test was conducted to see if electrolytes (01) to (20) could be impregnated into a lithium ion battery separator. A polyolefin separator (manufactured by Polypore, product name "Celguard 2325"), which is commonly used as a lithium ion battery separator, was cut into strips with a width of 1 cm and a length of 5 cm, and the 1 cm tip was immersed in an electrolytic solution for 1 second to soak the separator. If the electrolyte penetrated into the site, it was evaluated as "impregnation", and if it did not, it was evaluated as "not impregnated". As a result, all cases were evaluated as not being impregnated.

LiFSI: Lithium bisfluorosulfonylimide (Li ⁺ (FSO ₂ ) ₂ N ⁻ )
LiTFSI: Lithium bistrifluoromethanesulfonylimide (Li ⁺ (CF ₃ SO ₂ ) ₂ N ⁻ )
LiBF4: Lithium tetrafluoroborate LiBr: Lithium bromide MgTFSI: Magnesium bistrifluoromethanesulfonylimide (Mg ²⁺ ((CF ₃ SO ₂ ) ₂ N ⁻ ) ₂ )
EMI-TFSI: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide

(Example 1 and Comparative Example 1)
Electrolytes (01) to (20) preliminarily prepared in Production Example 1, solvent substances (B) shown in Table 2, and other solvent substances (C) are mixed in the proportions shown in Table 2, Electrolytes (101-1) to (120) of Examples and electrolytes (201-1) to (211) of Comparative Examples were prepared. The obtained electrolyte solution was observed to evaluate whether it was uniformly dissolved. The results are shown in Table 2. In the examples, all electrolytic solutions were mixed uniformly, and no salt precipitation was observed. On the other hand, in some of the comparative examples, the electrolytic solution was separated into two layers.

The electrolytes of the obtained Examples and Comparative Examples were evaluated for the presence or absence of solid precipitation using the same procedure as in Production Example 1 (P1-2). The results are shown in Table 2. Although solid precipitation was observed in electrolytic solutions (10) to (12) and (14), no solid precipitation was observed in the electrolytic solutions of Examples, including those prepared using the electrolytic solutions (10) to (12) and (14). It was found that the liquid had high stability.

Electrolytes (102), (107-1) to (107-4) of Examples and electrolytes (202-1) to (202-3) and (207-1) to (207-3) of Comparative Examples In contrast, when adding a fluorine solvent substance (C) that does not have a cyclic structure or unsaturated bond instead of the solvent substance (B), it is either not compatible with the high concentration electrolyte, or even if it is compatible, it is not compatible with the high concentration electrolyte. It can be seen that the range of soluble composition is narrow.

Among the obtained electrolytes of Examples and Comparative Examples, those that did not separate into two layers in the solubility evaluation were evaluated for impregnation in the same procedure as in Production Example 1 (P1-3). From the comparison of the impregnating evaluations of electrolytes (101-1) to (101-3) and comparative electrolyte (201-1), when the addition of solvent substance (B) is 5% by volume, It was found that impregnation did not occur and impregnation occurred without problems if the amount was 10% by volume or more.

Solvent substance (Bx) addition amount: Addition ratio of solvent substance to the total volume % of the entire non-aqueous electrolyte (unit: volume %)
Other solvent substances: Types of solvent substances other than the solvent substance (Bx) added here.Other addition amount: Addition amount of other solvent substances. Addition ratio of the solvent substance to the total volume% of the entire non-aqueous electrolyte (unit: volume%)
B-1: 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name "Zeolora H", manufactured by Nippon Zeon Co., Ltd.)
B-2: 3,3,4,4,5,5-hexafluorocyclopentene B-3: 1-methoxy-2,3,3,4,4,5,5-heptafluorocyclopentene C-1: 2H, 3H-decafluoropentane (trade name: "Vertrell XF" manufactured by Mitsui Chemours Fluoro Products Co., Ltd.)
C-2: 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (trade name "Asahikulin AE-3000", manufactured by AGC)
C-3: 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether C-4: Product name "NOVEC7100" (manufactured by 3M)
C-5: Product name "NOVEC7200" (manufactured by 3M)
C-6: Product name “NOVEC7300” (manufactured by 3M)

(Example 2)
The viscosity of the electrolytic solution, which is a mixture of the electrolytic solution (08) prepared in Production Example 1 and the solvent substance (B-1) added at the concentration shown in Table 3, was measured. The measurement was carried out using an EMS viscometer (manufactured by Kyoto Electronics Industry Co., Ltd., EMS-1000S) in an environment of 25°C, keeping the electrolyte composition unchanged under sealed conditions and no moisture in the air mixed in. The measurement was made at a rotation speed of 1000 rpm. The viscosity measured by this measurement method is basically the same value as the value measured in accordance with JIS Z8803.

The measurement results are shown in Table 3. The electrolytic solution (08) without the addition of solvent substance (B-1) exhibited a viscosity of 60 cP at 25°C, and it was confirmed that the viscosity tended to decrease significantly as the amount of solvent substance (B-1) added increased. Ta. By lowering the viscosity, it is expected that the liquid will move more smoothly inside the electrochemical device.

(B-1) ratio: volume % of (B-1) in the volume % of the entire non-aqueous electrolyte.

(Example 3)
About the electrolytic solution (11) prepared in Production Example 1 and the electrolytic solution (111) of Example 1, which is an electrolytic solution prepared by adding 40% by volume of the solvent substance (B-1) to the electrolytic solution (11). Ionic conductivity was measured. The measurement was carried out in the temperature range of -20 to 80°C, and the measurement was carried out in the frequency range of 1M to 0.1Hz by the AC impedance method using an impedance analyzer manufactured by Solartron. The results are shown in Figure 1.

In the measurement of electrolytic solution (11), the ionic conductivity decreased significantly at temperatures below 40°C, and it was not possible to measure the ionic conductivity at temperatures below that. On the other hand, measurements of the electrolytic solution (111) showed good ionic conductivity even at low temperatures, indicating that the solvent substance (B) suppressed solidification of the electrolytic solution.

(Example 4)
Electrolyte solution (01) prepared in Production Example 1, and electrolyte solution in which 60% by volume of solvent substance (B-1), (B-2) or (C-3) was added to electrolyte solution (01). The ionic conductivity of the electrolytes (101-1), (101-4), and (201-2) of Example 1 was measured. The measurement was performed according to the same procedure as in Example 3, except that the temperature range was -20 to 10°C. The results are shown in Figure 2.

In the electrolytic solution (01), the ionic conductivity decreased significantly as the temperature decreased. In the electrolytic solutions (101-1) and (101-3), which are electrolytic solutions to which the solvent substance (B) was added, the ionic conductivity at low temperatures could be greatly improved. The degree of improvement was relatively greater in electrolyte solution (101-4) than in electrolyte solution (101-1). In the electrolytic solution (201-2), which is an electrolytic solution to which the solvent substance (C-3) was added, an improvement effect was observed at temperatures below 0°C, but it tended to get worse at temperatures above 0°C.

(Example 5)
Electrolyte solution (117-1) of Example 1, which is an electrolyte solution prepared in Production Example 1 and to which solvent substance (B-1) is added at a ratio of 10% by volume or 30% by volume. and (117-2) were evaluated for impregnation into electrodes.
Etched aluminum foil with a thickness of 30 μm was prepared as a base material. On the base material, a layer containing activated carbon, acetylene black, SBR (styrene-butadiene rubber) binder, and CMC (carboxymethylcellulose) as a thickener in a weight ratio of 90%, 5%, 3%, and 2%, respectively. An activated carbon electrode consisting of a base material and a composite material layer was prepared by pressing the layer. The area weight and density of the composite material layer were 6.1 mg/cm ² and 0.48 g/cm ³ .
The activated carbon electrode was cut out to form a 4×4 cm rectangular test electrode. 15 μl of the electrolytic solution was dropped onto the surface of the test electrode on the composite material layer side, and the manner in which the electrolytic solution permeated into the composite material layer was observed. The electrolytic solution gradually permeated into the composite material layer, and the time when the surface of the composite material layer lost its luster was defined as the end of impregnation, and the time taken from dropping to the end of impregnation was recorded.
In order to prevent volatilization of the electrolytic solution during the test, the dropping was performed in a glass petri dish with a lid, and the lid was placed immediately after the dropping. The times required for impregnation with electrolyte solution (17), electrolyte solution (117-1), and electrolyte solution (117-2) were 489 seconds, 182 seconds, and 75 seconds, respectively. From this, it was found that the impregnation rate into the electrode composite material layer was improved by adding the solvent substance (B).

(Example 6)
(6-1. Positive electrode)
Aluminum foil with a thickness of 20 μm was prepared as a current collector for the positive electrode. A layer containing 94%, 3%, and 3% by weight of lithium cobalt oxide (positive electrode active material), acetylene black, and PVDF (polyvinylidene fluoride) binder, respectively, is provided on the positive electrode current collector, and the layer is pressed. By doing so, a positive electrode composite material layer was formed, and a lithium ion positive electrode consisting of a positive electrode current collector and a positive electrode composite material layer was prepared. The fabric weight and density of the positive electrode composite material layer were 20 mg/cm ² and 3.0 g/cm ³ .

(6-2. Negative electrode)
A copper foil with a thickness of 10 μm was prepared as a current collector for the negative electrode. On the negative electrode current collector, a layer containing graphite (MAG-E manufactured by Hitachi Chemical Co., Ltd.), acetylene black, SBR binder, and CMC in a weight ratio of 97%, 0.5%, 1%, and 1.5%, respectively. A negative electrode composite material layer was formed by pressing the layer, and a lithium ion negative electrode consisting of a negative electrode current collector and a negative electrode composite material layer was prepared. The area weight and density of the negative electrode composite material layer were 10 mg/cm ² and 1.4 g/cm ³ .

(6-3. Lithium ion secondary battery)
An aluminum tab was attached to the positive electrode current collector obtained in (6-1) by ultrasonic welding. A nickel tab was attached to the negative electrode current collector obtained in (6-2) by ultrasonic welding. A positive electrode and a negative electrode with tabs, and a separator (polyolefin separator with a thickness of 25 μm, trade name "Celguard #2325") are stacked to form (current collector for positive electrode) / (mixture material layer for positive electrode) / (separator) / (negative electrode). A laminate having a layer structure of (mixture material layer for negative electrode)/(current collector for negative electrode) was obtained.

An aluminum laminate bag with a polyethylene sealant was prepared. The laminate was placed in an aluminum laminate bag, and the electrolytic solution (118) prepared in Example 1 (LiFSI: propylene carbonate: vinyl ethylene carbonate = 1:4:1 (molar ratio), based on the total volume of the entire non-aqueous electrolyte The solvent substance (B-1) (volume ratio: 40 vol%) was injected, and the aluminum laminate bag was sealed. As a result, a lithium-ion secondary battery was completed.

(6-4. Charge/discharge test of lithium ion secondary battery)
The battery obtained in (6-3) was charged and discharged at a rate of 0.5C relative to the designed capacity in an environment of 25°C. As a result, in the voltage range of 4.2 to 3.0 V, the discharge capacity was 145 mAh/g per weight of the positive electrode active material, and repeated charging and discharging was possible. The capacity retention rate after 50 cycles with respect to the initial discharge capacity was as high as 94%.

(Comparative example 2)
(C2-1. Preparation of preliminary high concentration electrolyte)
A preliminary electrolyte solution (21) was prepared in the same manner as in the preparation of the electrolyte solution (18) in Production Example 1, except for the following changes.
- The molar ratio of the solvent substance (A) was changed from 4 propylene carbonate + 1 vinyl ethylene carbonate (molar ratio) to 6 propylene carbonate + 1 vinyl ethylene carbonate (molar ratio).
- The molar ratio of the solvent substance (A) to 1 mol of the ionic substance was changed from 5 mol to 7 mol.

(C2-2. Preparation of electrolyte solution)
Electrolyte solution (212) was prepared by the same operation as for preparing electrolyte solution (118) in Example 1, except for the following changes.
- Instead of the preliminary electrolyte (18), the preliminary electrolyte (21) prepared in (C2-1) was used.
In the obtained electrolytic solution (212), LiFSI: propylene carbonate: vinyl ethylene carbonate = 1:6:1 (molar ratio), and the volume of the solvent substance (B-1) with respect to the total volume of the entire non-aqueous electrolyte The ratio was 40 vol%.

(C2-3. Manufacture and evaluation of lithium ion secondary battery)
A lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 5 except for the following changes.
-In place of electrolyte (118), electrolyte (212) prepared in (C2-2) was used.
As a result, the discharge capacity was 144 mAh/g per weight of the positive electrode active material, and repeated charging and discharging was possible. The capacity retention rate after 50 cycles with respect to the initial discharge capacity was 91%, which was lower than in Example 5.

(Comparative example 3)
A lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 5 except for the following changes.
- In place of the electrolytic solution (118), the preliminary electrolytic solution (21) prepared in (C2-1) of Comparative Example 2 was used as it was.
As a result, the discharge capacity was 143 mAh/g per weight of the positive electrode active material, and repeated charging and discharging was possible. The capacity retention rate after 50 cycles with respect to the initial discharge capacity was 94%, which was lower than in Example 5.

(Example 7)
(7-1. Capacitor)
Two pieces of the activated carbon electrode obtained in Example 5 were cut out to a size of 3 x 4 cm to obtain test electrodes. An aluminum tab was attached to the end of each test electrode by ultrasonic welding. A sheet of paper with a thickness of 35 μm (manufactured by Nippon Kokoshi Kogyo, TF4535) was placed as a separator between the pair of test electrodes with tabs. A laminate having a layer structure of layer)/(base material) was obtained.

An aluminum laminate bag with a polyethylene sealant was prepared. The laminate was placed in an aluminum laminate bag, and the electrolytic solution (117-2) prepared in Example 1 (EMI-TFSI: propylene carbonate = 1:1 (mole ratio), volume ratio of the entire non-aqueous electrolyte 30 vol%) 600 μl of the solution was injected using a micropipette, and an aluminum laminate bag was sealed by heat-sealing to obtain a capacitor cell.

(7-3. Evaluation of capacitor)
A pair of plastic plates having sponge material on their surfaces were prepared, and these plates were placed facing each other with the sides having the sponge material facing inside, and the cells of the obtained capacitor were placed between them. A pressure mechanism was constructed by sandwiching these with clips from the outside of the plastic plate. In this state, charge and discharge the cell at a current value of 1A/g (current value per unit weight of activated carbon, which is the positive electrode active material) between 2.5V and 0V, and check whether charging and discharging is possible. was evaluated, and the discharge capacity at that time was measured. As a result, charging and discharging were possible. Furthermore, when only the electrolyte of this capacitor is changed to the preliminary electrolyte (17) produced in Production Example 1, the capacity developed is 90% of that of the capacitor of this example, and the solvent substance ( It was confirmed that the capacity per weight of activated carbon increased depending on the presence or absence of B). Although the mechanism by which the capacity increased is not clear, it is thought that due to the high permeability of the fluorinated solvent, there is a surface of the active material that cannot be penetrated by the electrolyte of the comparative example, and this is why it is used. .

(Example 8)
(8-1. Capacitor)
A capacitor was obtained by the same operations as in Example 7 (7-1) and (7-2) except for the following changes.
・As the electrolyte, instead of the electrolyte (117-1) prepared in Example 1, the electrolyte (117-3) prepared in Example 1 (EMI-TFSI: propylene carbonate = 1:1 (molar ratio) , the volume ratio of the solvent substance (B-1) to the total volume of the entire non-aqueous electrolyte was 80 vol%).

(8-2. Shutdown performance of capacitor)
The resistance value (unit: Ω) of the capacitor obtained in (8-1) was measured by an AC impedance method (using an impedance analyzer manufactured by Solartron, measurement frequency 1 MHz to 0.01 Hz). The ambient temperature of the cell was raised from 25° C., and the relationship between temperature and resistance value was determined. Table 4 shows the relative measured values of the resistance value at each temperature, with the resistance value at 25° C. being 1.

It was confirmed that the resistance decreased as the temperature increased up to 70°C. This is understood to be because the viscosity of the electrolytic solution decreased as the temperature rose, and the ionic conductivity increased.
An increase in resistance was confirmed after 80°C. This is thought to be because the solvent substance (B) evaporated to a large extent and the amount of electrolyte solution was insufficient. It can be seen that the resistance value at 100° C. was more than 10 times the resistance value at 25° C., making it difficult to operate the device. In this test, since a large laminate cell was used, the outer packaging was not torn by the pressure of the evaporated solvent substance (B). However, it is also possible to design the sheath so that the pressure of the solvent substance (B) can rupture it if an abnormally high temperature occurs.

(Example 9)
The electrolytic solution (107-2) prepared in Example 1 was determined by the flash point measurement method in accordance with the tag sealing method (JIS K2265-1 (2007)) and the Cleveland open method (JIS K2265-4 (2007)). , the flash point was measured. No flash point was confirmed when measuring the flash point using the closed tag method, and when measuring the flash point using the Cleveland open method, the prescribed test could not be continued due to boiling of the solvent substance (B), resulting in an evaluation of no flash point. . It has been found that low flammability can be imparted to the electrolyte if the solvent substance (B) is non-flammable.

(Comparative example 4)
Combustibility was evaluated by taking 100 mg of the electrolytic solution (03) prepared in Production Example 1, placing it in a stainless steel dish with a diameter of 2 cm, applying a burner flame, and observing the state. As a result, it was observed that ignition occurred 5 seconds after the burner was applied, and combustion continued for 8 seconds.

(Example 10)
Combustibility was evaluated by taking 100 mg of the electrolytic solution (103) prepared in Example 1, placing it in a stainless steel dish with a diameter of 2 cm, applying a burner flame, and observing the state. As a result, it was observed that ignition occurred 7 seconds after the burner was applied, and combustion continued for 5 seconds.
By comparing Comparative Example 4 and Example 9, it was found that the ignitability and combustion time of the electrolytic solution can be reduced by adding the solvent substance (B-2) that does not have a flash point.

(Example 11)
(11-1. Positive electrode sheet)
In the production of the following positive electrode sheet and lithium ion secondary battery, the experiment was conducted by changing the temperature of the experimental environment to 18°C so that the melting point of the solvent substance (B-1) was below 20.5°C.
A poly(ethylene oxide-propylene oxide) copolymer (ethylene oxide unit:propylene oxide unit in molar ratio of 90:10) having a weight average molecular weight of 500,000 was added to the electrolytic solution (08) prepared in Production Example 1 at a concentration of 5% by weight. % and mixed to prepare an electrolytic solution (08-P). Weighed the electrolyte (08-P) to 10, PTFE (polytetrafluoroethylene) to 1, lithium cobalt oxide to 100, and acetylene black to 5 (weight ratio), and kneaded them well in a mortar. A cohesive clay-like composition was obtained. This composition was stretched thin to obtain a positive electrode sheet with a thickness of 100 μm.

(11-2. Manufacture of lithium ion secondary battery)
Aluminum foil with a thickness of 25 μm, the positive electrode sheet of this example obtained in (11-1), a separator with a thickness of 25 μm (manufactured by Polypore, product name “Celguard 2325”), and a Li metal foil with a thickness of 100 μm as a negative electrode. and a 25 μm thick copper foil were stacked in this order to obtain an electrode composite for a lithium ion secondary battery. The electrode composite was inserted into an aluminum laminate housing for the battery. At this point, the amount of electrolyte introduced into the battery was 200 mg, excluding the poly(ethylene oxide-propylene oxide) copolymer component. 50 mg of a solid mass of solvent substance (B-1) (melting point: 20.5° C.) was weighed out and gently placed in a location within the laminate housing that did not come into contact with the electrodes. After degassing by reducing the pressure to 0.15 atm for 1 minute, the opening at the end of the exterior was sealed with heat while maintaining the deaerated state to produce a lithium ion battery. No weight loss was observed before and after vacuum sealing.

(11-3. Evaluation of lithium ion secondary battery)
Immediately after manufacturing, an attempt was made to charge the lithium ion secondary battery manufactured in (11-2) at a rate of 0.1C at 18°C, but no current flowed and charging was not possible. It was thought that it would not work as a battery because the separator was not impregnated with electrolyte.
Thereafter, this lithium ion secondary battery was heated to 25° C., and then charging was attempted at 25° C. at a rate of 0.1 C. Since charging was possible, the battery was charged to 4.2 V. Further charging and discharging showed a discharge capacity of 140mAh/g (Ah value per unit weight of lithium cobalt oxide, which is the positive electrode active material) in the voltage range of 4.2 to 3.0V, allowing repeated charging and discharging. Met.

After conducting the charge/discharge test, we disassembled the lithium ion secondary battery and observed the inside. We found that the solvent material (B-1) placed in a solid state had melted and become a uniform electrolyte, and the separator was wet with electrolyte. When the separator was peeled off from the positive electrode sheet, there was a feeling of sticking and a stringy appearance, suggesting that the polyethylene oxide-propylene oxide copolymer was dissolved. The positive electrode sheet maintained its initial shape without dissolving. Thus, the electrolyte of the present invention may be completed inside the device and may include a polymer.

Claims

A non-aqueous electrolyte containing an ionic component and a non-ionic solvent component,
The nonionic solvent component is
a hetero element-containing organic solvent substance (A) which is an organic compound with a fluorination rate of less than 40%;
and a fluorine-containing organic solvent substance (B), which is an organic compound with a fluorination rate of 40% or more,
The fluorine-containing organic solvent substance (B) contains a fluorine-containing organic solvent substance (Bx) which is a compound containing a ring structure composed of carbon atoms, a carbon-carbon unsaturated bond, or both of these in the molecule. including,
The proportion of the fluorine-containing organic solvent substance (Bx) in 100 volume% of the non-aqueous electrolyte is 10 volume% or more,
The molar amount of the hetero element-containing organic solvent substance (A) is within 5 times the cation amount of the ionic component,
Non-aqueous electrolyte.
The nonionic solvent component contains the hetero element-containing organic solvent substance (A), the fluorine-containing organic solvent substance (B), or an additive (P) as another nonionic solvent component,
The non-aqueous electrolyte according to claim 1, wherein the additive (P) is one or more selected from the group consisting of a cyclic sulfate compound, a vinyl ethylene carbonate compound, and a cyclic fluorine compound having an unsaturated bond.
the ionic component includes a fluorine-containing sulfonylimide anion,
The non-aqueous electrolyte according to claim 1, wherein the proportion of the imide anion to the anions constituting the ionic component is 50 mol% or more.
The non-aqueous electrolyte according to claim 3, wherein the fluorine-containing sulfonylimide anion is a bisfluorosulfonylimide anion.
the ionic component includes a boron anion,
The non-aqueous electrolyte according to claim 1, wherein the proportion of the boron anion to the anions constituting the ionic component is 50 mol% or more.
The non-aqueous electrolyte according to claim 1, wherein the ionic component includes an ionic liquid.
The nonaqueous electrolyte according to claim 1, wherein the nonionic solvent component contains acetonitrile as the hetero element-containing organic solvent substance (A).
A claim in which the nonionic solvent component contains, as the hetero element-containing organic solvent substance (A), one or more selected from the group consisting of ethylene carbonate, fluorinated ethylene carbonate, propylene carbonate, γ-butyrolactone, and sulfolane. Item 1. The non-aqueous electrolyte according to item 1.
The nonaqueous electrolyte according to claim 1, wherein the nonionic solvent component contains two or more kinds of compounds as the hetero element-containing organic solvent substance (A).
The nonionic solvent component includes a flame retardant solvent substance (AR) as the hetero element-containing organic solvent substance (A),
The flame retardant solvent substance (AR) is a compound (R1) which is a phosphoric acid ester or a phosphite ester and has 1 to 6 carbon atoms per molecule, and the hydrogen of the compound (R1) is partially removed. The non-aqueous electrolyte according to claim 1, which is one or more selected from the group consisting of a fluorinated compound (R2) and a compound having a phosphazene ring (R3).
The nonaqueous electrolyte according to claim 1, wherein the nonionic solvent component contains a substance having a carbon-carbon unsaturated bond as the fluorine-containing organic solvent substance (Bx).
The nonaqueous electrolyte according to claim 1, wherein the nonionic solvent component includes a substance having an ether bond as the fluorine-containing organic solvent substance (Bx).
The non-aqueous electrolyte according to claim 1, wherein the nonionic solvent component contains a fluorine-containing organic solvent substance (C) other than the fluorine-containing organic solvent substance (Bx) as the fluorine-containing organic solvent substance (B). liquid.
The non-aqueous electrolyte according to claim 1, which has no flash point.
An electrochemical device comprising the nonaqueous electrolyte according to any one of claims 1 to 14.
The non-aqueous electrolyte has a structure in which the non-aqueous electrolyte is sealed in a sealed space in the exterior, and the space is opened when the pressure in the space exceeds a threshold, and the threshold is 16. The electrochemical device according to claim 15, wherein the pressure is between 2 atmospheres and 10 atmospheres.