Container for non-aqueous electrolyte and method for storing non-aqueous electrolyte

Abstract

The present invention pertains to: a non-aqueous electrolyte container including a storage part made of austenitic stainless steel, wherein the storage part is provided with a passive layer on a contact surface with a non-aqueous electrolyte, the amount of chromium atoms in the surface of the passive layer is at least 40 mass% with respect to the total amount of iron atoms, chromium atoms, nickel atoms, and molybdenum atoms, and the non-aqueous electrolyte contains a specific sulfate compound; and a method for storing a non-aqueous electrolyte using said non-aqueous electrolyte container. The present invention can thus provide: a non-aqueous electrolyte container capable of suppressing the elution of iron into a non-aqueous electrolyte; and a method for storing a non-aqueous electrolyte using said non-aqueous electrolyte container.

Description

[Technical field]

[0001] The present disclosure relates to a container for a non-aqueous electrolyte and a method for storing a non-aqueous electrolyte. [Background technology]

[0002] In recent years, batteries, which are electrochemical devices, have been attracting attention as energy storage systems for small, high-energy density applications such as information-related equipment and communication equipment, i.e., personal computers, video cameras, digital cameras, mobile phones, smartphones, etc., as well as large-scale, power storage systems for power applications such as electric vehicles, hybrid vehicles, and fuel cell vehicle auxiliary power sources, power storage, etc. One candidate is non-aqueous electrolyte batteries, including lithium-ion batteries, which have high energy density and voltage and can provide high capacity, and research and development of these batteries is currently being actively conducted.

[0003] The nonaqueous electrolyte used in nonaqueous electrolyte batteries is often prepared by dissolving a fluorine-containing electrolyte such as lithium hexafluorophosphate (hereinafter also referred to as "LiPF6"), lithium bis(fluorosulfonyl)imide (hereinafter also referred to as "LiFSI"), or lithium tetrafluoroborate (hereinafter also referred to as "LiBF4") as a solute in a solvent such as a cyclic carbonate, a chain carbonate, or an ester, because this is suitable for obtaining batteries with high voltage and high capacity.

[0004] Furthermore, for the purpose of improving battery characteristics such as the cycle characteristics and output characteristics of non-aqueous electrolyte batteries, attempts have been made widely to add small amounts (usually 0.001% by mass or more and 10% by mass or less) of compounds called additives to the electrolyte, and dihalophosphates such as lithium difluorophosphate are known as such additives.

[0005] As containers used for storing and transporting such non-aqueous electrolyte solutions (hereinafter also referred to as "non-aqueous electrolyte containers"), containers made of stainless steel, which have excellent airtightness and durability, are generally used (for example, Patent Document 1). Since stainless steel has high corrosion resistance, even if the non-aqueous electrolyte comes into contact with air and becomes more corrosive, the container is unlikely to corrode to the extent that it interferes with use. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2015-74798 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, in an effort to improve the performance of batteries, further investigations have been made into the composition of non-aqueous electrolytes, in particular into additives used in non-aqueous electrolytes. The present inventors have been studying non-aqueous electrolyte compositions containing dihalophosphates such as lithium difluorophosphate as additives, and have found that it is preferable to use sulfate compounds such as ethylene sulfate as additives in combination. However, when a sulfate compound is used (particularly when a dihalophosphate and a sulfate compound are used in combination), if a conventional stainless steel container is used as a storage container for the non-aqueous electrolyte, it is unexpectedly found that a large amount of iron is dissolved into the non-aqueous electrolyte, which not only advances corrosion of the container, but also raises concerns that the concentration standard for metals that can be contained in the non-aqueous electrolyte cannot be met, and a new problem occurs in that a non-aqueous electrolyte battery using this non-aqueous electrolyte is prone to short circuiting.

[0008] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a container for a non-aqueous electrolyte that can suppress the elution of iron into the non-aqueous electrolyte. [Means for solving the problem]

[0009] In view of these problems, the inventors conducted intensive research and discovered that the elution of iron can be suppressed by forming a passive layer on the surface of the container, the container portion of which is made of austenitic stainless steel, that comes into contact with the non-aqueous electrolyte.

[0010] That is, the present inventors have found that the above object can be achieved by the following configuration.

[0011] <1> A container for a non-aqueous electrolyte having a storage portion, The housing is made of austenitic stainless steel, a passivation layer is provided on a surface of the container that comes into contact with the non-aqueous electrolyte; the amount of chromium atoms relative to the total amount of iron atoms, chromium atoms, nickel atoms, and molybdenum atoms on the surface of the passive layer is 40 mass% or more; The nonaqueous electrolyte container contains a compound represented by the following general formula (2):

[0012] [ka]

[0013] [In general formula (2), R 3 represents a hydrocarbon group having 2 to 5 carbon atoms. The hydrocarbon group may contain a heteroatom between the carbon atom-carbon atom bond. Any hydrogen atom in the hydrocarbon group may be substituted with a halogen atom. <2> The austenitic stainless steel is SUS304. <1> 2. A container for a non-aqueous electrolyte according to claim 1 . <3> <1> or <2> A method for storing a non-aqueous electrolyte using the container for the non-aqueous electrolyte described in claim 1. <4> The storage temperature of the non-aqueous electrolyte is 25°C or lower. <3> A method for storing the non-aqueous electrolyte solution according to claim 1. <5> Perform in an inert atmosphere <3> or <4> A method for storing the non-aqueous electrolyte solution according to claim 1. <6> The storage portion contains a nonaqueous electrolyte solution containing the compound represented by the general formula (2). <1> or <2> 2. A container for a non-aqueous electrolyte according to claim 1 . Effect of the Invention

[0014] According to the present disclosure, it is possible to provide a container for a non-aqueous electrolyte that can suppress the elution of iron into the non-aqueous electrolyte, and a method for storing a non-aqueous electrolyte that uses the container for a non-aqueous electrolyte. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The configurations and combinations thereof in the following embodiments are examples, and addition, omission, substitution, and other modifications of the configurations are possible without departing from the spirit of the present disclosure. In addition, the present disclosure is not limited to the embodiments. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0016] [Non-aqueous electrolyte container] The non-aqueous electrolyte container (hereinafter also simply referred to as the "container") of the present disclosure is a container for a non-aqueous electrolyte having a storage portion made of austenitic stainless steel, and having a passivation layer on the surface of the storage portion that comes into contact with the non-aqueous electrolyte.

[0017] The container of the present disclosure has a passive layer on the surface of the storage portion that comes into contact with the nonaqueous electrolyte, and the amount of chromium atoms on the surface of the passive layer relative to the total amount of iron atoms, chromium atoms, nickel atoms, and molybdenum atoms is 40 mass% or more, and preferably 40 to 65 mass%. The passive film possessed by typical austenitic stainless steels is a thin oxide film that forms naturally on the surface of the stainless steel, and on the surface of the passive film, the amount of chromium atoms relative to the total amount of iron atoms, chromium atoms, nickel atoms, and molybdenum atoms is approximately 20 mass%. That is, the passive layer in the container of the present disclosure is a layer that is richer in chromium than the passive film in typical austenitic stainless steels. The amount of chromium atoms relative to the total amount of iron atoms, chromium atoms, nickel atoms, and molybdenum atoms on the surface of the passive layer can be quantified by, for example, Auger electron spectroscopy.

[0018] The term "having a passivation layer on the surface of the container that comes into contact with the non-aqueous electrolyte" means that at least a passivation layer is formed on the inner surface of the container that actually comes into contact with the non-aqueous electrolyte when the container is filled with the non-aqueous electrolyte and left to stand. The passivation layer is preferably formed on the entire inner surface of the container.

[0019] The formation of the passivation layer can be carried out by using at least one of acid cleaning and electrolytic polishing. Acid cleaning is a method of oxidizing the surface of stainless steel by, for example, immersing the stainless steel in a strong oxidizing agent such as nitric acid. Electrolytic polishing is a method of electrolytically polishing the surface of stainless steel by passing a direct current between the stainless steel as the anode (positive side) and the opposing cathode (negative side) via an electrolyte. In the container of the present disclosure, the passivation layer is preferably formed by acid washing, since the apparatus and operation are simple.

[0020] The container of the present disclosure may have a housing portion made of austenitic stainless steel, and may have an outer peripheral portion made of another material on the outside of the housing portion (the side opposite to the surface in contact with the non-aqueous electrolyte), for example. The material for forming the outer periphery is not particularly limited, but examples thereof include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, and polyamide resins such as nylon.

[0021] In addition, the container of the present disclosure may or may not have a lid, but it is preferable for it to have a lid from the viewpoint of improving airtightness and preventing deterioration of the nonaqueous electrolyte due to contact between the nonaqueous electrolyte and oxygen in the air during storage in the container. The material of the lid is not particularly limited, but it is preferably made of austenitic stainless steel, and it is more preferable that the inside surface of the lid (the surface facing the storage section) also has a passive layer similar to that described above.

[0022] Examples of austenitic stainless steels used in the housing of the container of the present disclosure include SUS304, SUS316, SUS316L, etc. SUS304, SUS316, and SUS316L are specified in the Japanese Industrial Standard JIS G 4305.

[0023] The corrosion resistance of stainless steel depends on the performance of the passive film that is formed. In the case of austenitic stainless steel, the main components that form this passive film are chromium (Cr) and molybdenum (Mo), and it is said that the higher the concentration of these elements, the denser the passive film becomes and the better the corrosion resistance becomes. It is also said that the effect of Mo concentration in improving the corrosion resistance of the passive film is about three times that of Cr concentration. There is a difference in the composition of the two steel types SUS304 and SUS316, with SUS304 containing approximately 18% Cr but no Mo. In contrast, SUS316 contains approximately 18% Cr and approximately 2% Mo, so SUS316 is generally considered to be a material with better corrosion resistance than SUS304.

[0024] However, when storing a non-aqueous electrolyte containing a combination of a sulfate compound represented by the general formula (2) and a dihalophosphate represented by the general formula (3) described below, a container having a storage portion made of SUS304 is surprisingly more effective at suppressing the elution of iron into the non-aqueous electrolyte than SUS316, and can be used preferably.

[0025] The shape of the container of the present disclosure is not particularly limited, and may be any shape, such as a bottle shape or a cylinder shape. The horizontal cross-sectional shape of the bottle-shaped container can be any shape, such as a circle, a polygon such as a triangular or octagonal shape, or the like. Among these, from the viewpoint of the strength and workability of the container, it is preferable that the horizontal cross-sectional shape is a circle. In addition, the cross-sectional area of ​​the container can be continuously changed in the vertical direction. For example, by making the cross-sectional area near the center in the height direction of the container smaller than those near both ends, a constricted structure can be formed by making a part of the container body (body) thinner, or a structure can be formed by providing unevenness on the container surface to make the container easier to grip.

[0026] The capacity of the container of the present disclosure is not particularly limited, but from the viewpoint of ease of handling, it is preferably 10 to 200,000 cm 3 is preferable, and 20 to 30,000 cm 3 More preferably, 50 to 1,000 cm 3 More preferably, 100 to 500 cm 3 The diameter of the body of the container is not particularly limited, but from the viewpoint of ease of handling, it is preferably 50 to 150 mm, and more preferably 60 to 100 mm.

[0027] [Non-aqueous electrolyte] The nonaqueous electrolyte to be stored using the nonaqueous electrolyte container of the present disclosure is not particularly limited except that it contains a compound represented by general formula (2), but it is a nonaqueous electrolyte containing a solute and a nonaqueous organic solvent, and may further contain commonly used additive components in any ratio. The effect of using the nonaqueous electrolyte container of the present disclosure is particularly pronounced when the nonaqueous electrolyte contains, in addition to the compound represented by general formula (2), a compound represented by general formula (3) described below as an additive.

[0028] <About solutes> The solute contained in the non-aqueous electrolyte is preferably an ionic salt, and examples of the solute include at least one cation selected from the group consisting of alkali metal ions and alkaline earth metal ions, and a hexafluorophosphate anion, a tetrafluoroborate anion, a trifluoromethanesulfonate anion, a fluorosulfonate anion, a bis(trifluoromethanesulfonyl)imide anion, a bis(pentafluoroethanesulfonyl)imide anion, a bis(fluorosulfonyl)imide anion, a (trifluoromethanesulfonyl)(fluorosulfonyl)imide anion, a bis(difluorophosphoric acid anion, a tetrafluoroborate anion, a trifluoromethanesulfonyl)imide anion, a bis(difluorophosphoric acid anion, a tetrafluoroborate anion, a trifluoromethanesulfonyl)(fluoro ... R (difluorophosphoric acid)imide anion, R (fluorosulfonyl)imide anion, and (difluorophospho R It is preferable that the anion pair is an ionic salt consisting of at least one anion pair selected from the group consisting of (trifluoromethanesulfonyl)imide anion and (trifluoromethanesulfonyl)imide anion.

[0029] In addition, the cation of the ionic salt that is the solute is lithium, sodium, potassium, or magnesium, and the anion is a hexafluorophosphate anion, a tetrafluoroborate anion, a trifluoromethanesulfonate anion, a bis(trifluoromethanesulfonyl)imide anion, a bis(fluorosulfonyl)imide anion, a bis(difluorophosphoric acid anion, a hexafluorophosphate anion, a tetrafluoroborate anion, a trifluoromethanesulfonate anion, a bis(difluorophosphoric acid anion, a hexafluorophosphate anion, a tetrafluoroborate anion, a trifluoromethanesulfonate anion, a bis(difluorophosphoric acid anion, a hexafluorophosphate anion, a tetrafluoroborate anion, a trifluoromethanesulfonate anion, a bis(difluorophosphoric acid anion, a hexafluorophosphate anion, a tetrafluoroborate anion, a trifluoromethanesulfonyl)imide ... R (difluorophosphoric acid)imide anion, and R From the viewpoints of high solubility in non-aqueous organic solvents and electrochemical stability, the anion is preferably at least one selected from the group consisting of (fluorosulfonyl)imide anions.

[0030] There is no particular restriction on the suitable concentration of these solutes, but the lower limit is 0.5 mol / L or more, preferably 0.7 mol / L or more, more preferably 0.9 mol / L or more, and the upper limit is 2.5 mol / L or less, preferably 2.2 mol / L or less, more preferably 2.0 mol / L or less. By setting the concentration to 0.5 mol / L or more, it is possible to suppress the deterioration of the cycle characteristics and output characteristics of the nonaqueous electrolyte battery due to the decrease in ion conductivity, and by setting the concentration to 2.5 mol / L or less, it is possible to suppress the deterioration of the cycle characteristics and output characteristics of the nonaqueous electrolyte battery due to the increase in viscosity of the nonaqueous electrolyte. In addition, these solutes may be used alone or in combination.

[0031] <Non-aqueous organic solvents> The type of nonaqueous organic solvent used in the nonaqueous electrolyte is not particularly limited, and any nonaqueous organic solvent can be used. Specifically, ethyl methyl carbonate (hereinafter also referred to as "EMC"), dimethyl carbonate (hereinafter also referred to as "DMC"), diethyl carbonate (hereinafter also referred to as "DEC"), methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2,2-trifluoroethyl ethyl carbonate, 2,2,2-trifluoroethyl propyl carbonate, bis(2,2,2-trifluoroethyl)carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl methyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl ethyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl propyl carbonate, bis(1,1,1,3,3,3-hexafluoro-1-propyl)carbonate , ethylene carbonate (hereinafter also referred to as "EC"), propylene carbonate (hereinafter also referred to as "PC"), butylene carbonate, fluoroethylene carbonate (hereinafter also referred to as "FEC"), difluoroethylene carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl 2-fluoropropionate, ethyl 2-fluoropropionate, diethyl ether, dibutyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, N,N-dimethylformamide, acetonitrile, propionitrile, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and γ-valerolactone.

[0032] The nonaqueous organic solvent preferably contains at least one selected from the group consisting of cyclic carbonates and chain carbonates, which provides excellent cycle characteristics at high temperatures, and preferably contains an ester, which provides excellent input / output characteristics at low temperatures. Specific examples of the cyclic carbonate include EC, PC, butylene carbonate, FEC, and the like, and among these, at least one selected from the group consisting of EC, PC, and FEC is preferable. Specific examples of the chain carbonate include EMC, DMC, DEC, methyl propyl carbonate, ethyl propyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2,2-trifluoroethyl ethyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl methyl carbonate, and 1,1,1,3,3,3-hexafluoro-1-propyl ethyl carbonate, and among these, at least one selected from the group consisting of EMC, DMC, DEC, and methyl propyl carbonate is preferred. Specific examples of the ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl 2-fluoropropionate, and ethyl 2-fluoropropionate.

[0033] The non-aqueous electrolyte may contain a polymer. The polymer may be generally called a polymer solid electrolyte. The polymer solid electrolyte may contain a non-aqueous organic solvent as a plasticizer.

[0034] The polymer is not particularly limited as long as it is an aprotic polymer capable of dissolving the above solute and the additives described below. For example, a polymer having polyethylene oxide in the main chain or side chain, a homopolymer or copolymer of polyvinylidene fluoride, a methacrylic acid ester polymer, polyacrylonitrile, etc. are included. When a plasticizer is added to these polymers, aprotic nonaqueous organic solvents are preferred among the above nonaqueous organic solvents.

[0035] <About additives> From the viewpoints of improving the capacity retention rate after long-term cycles at high temperatures and suppressing an increase in resistance at low temperatures after high-temperature storage, the nonaqueous electrolyte contains a compound represented by the following general formula (2).

[0036] [ka]

[0037] [In general formula (2), R 3 represents a hydrocarbon group having 2 to 5 carbon atoms. The hydrocarbon group may contain a heteroatom between the carbon atom-carbon atom bond. Any hydrogen atom in the hydrocarbon group may be substituted with a halogen atom.

[0038] In general formula (2), R 3 R represents a hydrocarbon group having 2 to 5 carbon atoms. 3 Examples of the hydrocarbon group represented by include linear or branched alkylene groups, alkenylene groups, and alkynylene groups. R 3 When represents an alkylene group, specific examples of the alkylene group include an ethylene group, an n-propylene group, an i-propylene group, an n-butylene group, an s-butylene group, a t-butylene group, an n-pentylene group, and a -CH2CH(C3H7)- group. R 3 When represents an alkenylene group, specific examples of the alkenylene group include an ethenylene group and a propenylene group. R 3 When represents an alkynylene group, specific examples of the alkynylene group include an ethynylene group and a propynylene group.

[0039] R 3 The hydrocarbon group represented by may contain a heteroatom between the carbon atom and the carbon atom. Examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0040] R 3 Any hydrogen atom of the hydrocarbon group represented by may be substituted with a halogen atom. Examples of the hydrocarbon group in which any hydrogen atom is substituted with a fluorine atom include a tetrafluoroethylene group, a 1,2-difluoroethylene group, a 2,2-difluoroethylene group, a fluoroethylene group, and a (trifluoromethyl)ethylene group.

[0041] R 3is preferably an unsubstituted alkylene group having 2 to 3 carbon atoms, and more preferably an ethylene group.

[0042] The content of the compound represented by formula (2) in the non-aqueous electrolyte is preferably 0.01 mass% or more and 8.00 mass% or less, more preferably 0.05 mass% or more and 3.00 mass% or less, and even more preferably 0.1 mass% or more and 2.50 mass% or less, based on the total amount of the non-aqueous electrolyte.

[0043] The non-aqueous electrolyte may further contain commonly used additive components in any ratio.

[0044] The nonaqueous electrolyte preferably contains any of the compounds represented by the following general formulas (3) to (6) in addition to the compound represented by general formula (2), from the viewpoints of improving the capacity retention rate after long-term cycles at high temperature and suppressing an increase in resistance at low temperature after high-temperature storage.

[0045] [ka]

[0046] [In general formula (3), X 3 and X 4 Each independently represents a halogen atom. M2 + represents an alkali metal cation, an ammonium ion, or an organic cation.

[0047] In general formula (3), X 3 and X 4 represents a halogen atom. 3 and X 4 Examples of the halogen atom represented by include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., and a fluorine atom is preferable. X 3 and X 4 may be the same or different, but are preferably the same, and are preferably both fluorine atoms.

[0048] In general formula (3), M2 +represents an alkali metal cation, an ammonium ion, or an organic cation. M2 + Examples of the alkali metal cation represented by the formula (I) include a lithium cation, a sodium cation, and a potassium cation. M2 + is preferably an alkali metal cation, more preferably a lithium cation.

[0049] [ka]

[0050] [In general formula (4), R 4 represents a hydrocarbon group having 2 to 6 carbon atoms. The hydrocarbon group may contain a heteroatom between the carbon atom-carbon atom bond. Any hydrogen atom in the hydrocarbon group may be substituted with a halogen atom.

[0051] In general formula (4), R 4 R represents a hydrocarbon group having 2 to 6 carbon atoms. 4 Examples of the hydrocarbon group represented by include linear or branched alkylene groups, alkenylene groups, and alkynylene groups. R 4 When represents an alkylene group, specific examples of the alkylene group include an ethylene group, an n-propylene group, an i-propylene group, an n-butylene group, an s-butylene group, a t-butylene group, an n-pentylene group, a -CHCH(CH)- group, and an n-hexylene group. R 4 When represents an alkenylene group, specific examples of the alkenylene group include an ethenylene group and a propenylene group. R 4 When represents an alkynylene group, specific examples of the alkynylene group include a propynylene group.

[0052] R 4 The hydrocarbon group represented by may contain a heteroatom between the carbon atom and the carbon atom. Examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0053] R 4 Any hydrogen atom of the hydrocarbon group represented by may be substituted with a halogen atom. Examples of the hydrocarbon group in which any hydrogen atom is substituted with a fluorine atom include a tetrafluoroethylene group, a 1,2-difluoroethylene group, a 2,2-difluoroethylene group, a fluoroethylene group, and a (trifluoromethyl)ethylene group.

[0054] R 4 is preferably an unsubstituted alkylene group having 3 to 4 carbon atoms, and more preferably a propylene group.

[0055] [ka]

[0056] [In general formulas (5) and (6), R 5 are each independently a substituent having at least one of an unsaturated bond and an aromatic ring.

[0057] Above R 5 is preferably a group selected from an alkenyl group, an allyl group, an alkynyl group, an aryl group, an alkenyloxy group, an allyloxy group, an alkynyloxy group, and an aryloxy group.

[0058] The alkenyl group is preferably an ethenyl group, the allyl group is preferably a 2-propenyl group, the alkynyl group is preferably an ethynyl group, and the aryl group is preferably a phenyl group, a 2-methylphenyl group, a 4-methylphenyl group, a 4-fluorophenyl group, a 4-tert-butylphenyl group, or a 4-tert-amylphenyl group.

[0059] The alkenyloxy group is preferably a vinyloxy group, the allyloxy group is preferably a 2-propenyloxy group, the alkynyloxy group is preferably a propargyloxy group, and the aryloxy group is preferably a phenoxy group, a 2-methylphenoxy group, a 4-methylphenoxy group, a 4-fluorophenoxy group, a 4-tert-butylphenoxy group, or a 4-tert-amylphenoxy group.

[0060] In addition, the three R 5 From the viewpoint of a high durability improving effect, it is preferable that at least two of the above be ethenyl groups, ethynyl groups, or both.

[0061] Specific examples of additives other than the compounds represented by the above general formulas (2) to (6) include cyclohexylbenzene, cyclohexylfluorobenzene, fluorobenzene (hereinafter sometimes referred to as FB), biphenyl, difluoroanisole, tert-butylbenzene, tert-amylbenzene, 2-fluorotoluene, 2-fluorobiphenyl, vinylene carbonate, dimethylvinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, methylpropargyl carbonate, ethylpropargyl carbonate, and dipropargyl carbonate. , maleic anhydride, succinic anhydride, methylenemethane disulfonate, dimethylenemethane disulfonate, trimethylenemethane disulfonate, methyl methanesulfonate, lithium tetrafluoroborate, lithium difluorobis(oxalato)phosphate (hereinafter sometimes referred to as LDFBOP), sodium difluorobis(oxalato)phosphate, potassium difluorobis(oxalato)phosphate, lithium difluorooxalatoborate (hereinafter sometimes referred to as LDFOB), sodium difluorooxalatoborate, potassium difluorooxalatoborate, bis( Oxalate ) Lithium borate, bis( Oxalate ) Sodium borate, bis( Oxalate )Examples of compounds that have an overcharge prevention effect, a negative electrode film forming effect, or a positive electrode protection effect include potassium borate, lithium tetrafluorooxalatophosphate (hereinafter, may be referred to as LTFOP), sodium tetrafluorooxalatophosphate, potassium tetrafluorooxalatophosphate, lithium tris(oxalato)phosphate, sodium tris(oxalato)phosphate, potassium tris(oxalato)phosphate, lithium ethylfluorophosphate (hereinafter, may be referred to as LEFP), lithium propylfluorophosphate, lithium fluorophosphate, ethenesulfonyl fluoride (hereinafter, may be referred to as ESF), trifluoromethanesulfonyl fluoride (hereinafter, may be referred to as TSF), methanesulfonyl fluoride (hereinafter, may be referred to as MSF), and phenyl difluorophosphate (hereinafter, may be referred to as PDFP).

[0062] The content of the additives other than the compound represented by formula (2) in the nonaqueous electrolyte is preferably 0.01 mass% or more and 8.00 mass% or less, more preferably 0.05 mass% or more and 3.00 mass% or less, and even more preferably 0.1 mass% or more and 2.50 mass% or less, based on the total amount of the nonaqueous electrolyte.

[0063] The nonaqueous electrolyte preferably contains any of the compounds represented by the above general formulas (3) to (6) in addition to the compound represented by general formula (2), from the viewpoints of improving the capacity retention rate after long-term cycles at high temperature and suppressing an increase in resistance at low temperature after high-temperature storage, and more preferably contains both the compound represented by general formula (2) and the compound represented by general formula (3). The container of the present disclosure can particularly exhibit the effect of suppressing iron elution when storing a nonaqueous electrolyte solution containing both the compound represented by general formula (2) and the compound represented by general formula (3), which are useful for improving battery characteristics.

[0064] In addition, the battery may contain one or more of the following compounds: a lithium salt of a boron complex having an oxalic acid group, a lithium salt of a phosphorus complex having an oxalic acid group, a compound having an O=SF bond, and a compound having an O=PF bond. The battery may contain the above compounds, which is preferable not only for improving the capacity retention rate after a long-term cycle at high temperature and suppressing the increase in resistance at low temperature after high-temperature storage, but also for reducing the elution of Ni components from a Ni-containing electrode into the electrolyte when the electrode is used. It is more preferable that the lithium salt of the boron complex having an oxalic acid group is lithium difluorooxalatoborate and the lithium salt of the phosphorus complex having an oxalic acid group is at least one selected from the group consisting of lithium tetrafluorooxalatophosphate and lithium difluorobis(oxalato)phosphate, since this not only improves the capacity retention rate after long-term cycles at high temperatures and inhibits an increase in resistance at low temperatures after high-temperature storage, but also provides a particularly excellent effect in inhibiting the elution of Ni components from the positive electrode. Examples of the compound having the O=SF bond include lithium fluorosulfonate, lithium bis(fluorosulfonyl)imide, lithium (trifluoromethanesulfonyl)(fluorosulfonyl)imide, propyl fluorosulfate, phenyl fluorosulfate, 4-fluorophenyl fluorosulfate, 4-tert-butylphenyl fluorosulfate, 4-tert-amylphenyl fluorosulfate, ethenesulfonyl fluoride, trifluoromethanesulfonyl fluoride, methanesulfonyl fluoride, benzenesulfonyl fluoride, 4-fluorophenylsulfonyl fluoride, 4-tert-butylphenylsulfonyl fluoride, 4-tert-amylphenylsulfonyl fluoride, 2-methylphenylsulfonyl fluoride, and the like. Among these, at least one selected from the group consisting of lithium fluorosulfonate, lithium bis(fluorosulfonyl)imide, and lithium (trifluoromethanesulfonyl)(fluorosulfonyl)imide is particularly preferred because it can improve the capacity retention rate after long-term cycles at high temperatures, suppress the increase in resistance at low temperatures after high-temperature storage, and suppress the elution of Ni components from the positive electrode. Examples of the compound having the O=PF bond include the compound represented by the above general formula (3), such as lithium difluorophosphate, lithium ethyl fluorophosphate, bis(difluorophosphoric acid), R Lithium difluorophosphate, lithium ethyl fluorophosphate, bis(difluorophosphoric acid), lithium phenyl difluorophosphate, and phenyl difluorophosphate are particularly preferred. R At least one selected from the group consisting of lithium fluoride (III) imide and lithium fluoride (III) imide has some effect of improving the capacity retention rate after long-term cycles at high temperature, suppressing the increase in resistance at low temperature after high-temperature storage, and suppressing the elution of Ni components from the positive electrode, and is particularly preferred in terms of high productivity and low production cost compared to the above-mentioned lithium salt of a boron complex having an oxalic acid group, the lithium salt of a phosphorus complex having an oxalic acid group, and the compound having an O=SF bond. Some of the other additives mentioned above overlap with the solutes, but when used as additives, they are added at a lower concentration than the solute concentration mentioned above.

[0065] Furthermore, as in the case of a non-aqueous electrolyte battery called a polymer battery, the non-aqueous electrolyte may be quasi-solidified with a gelling agent or a crosslinked polymer.

[0066] The nonaqueous electrolyte container of the present disclosure is preferably a container for nonaqueous electrolyte containing a nonaqueous electrolyte containing the compound represented by the general formula (2) in a storage portion.

[0067] [How to store non-aqueous electrolyte] The present disclosure also relates to a method for storing a non-aqueous electrolyte using the above-mentioned container for a non-aqueous electrolyte. The non-aqueous electrolyte is filled in the storage portion of the container for a non-aqueous electrolyte and stored.

[0068] When the non-aqueous electrolyte is filled in the container, the filling rate is preferably 20 to 98% of the volume of the container, more preferably 30 to 97%, and even more preferably 50 to 95%. If the filling rate is less than 20%, the low boiling point solvent in the non-aqueous electrolyte is likely to volatilize, and the concentration of the high boiling point solvent increases, so that solid matter is likely to precipitate at the opening of the container, and the sealability may be reduced. On the other hand, if the filling rate exceeds 98%, the lid may easily come into contact with the non-aqueous electrolyte, or the internal pressure in the container may increase, and the sealability may be reduced. Therefore, the above-mentioned range of the filling rate is preferable. In addition, it is preferable to fill the non-aqueous electrolyte so that the top surface of the non-aqueous electrolyte to be filled is preferably 1 cm or more, more preferably 2 cm or more, and even more preferably 3 cm or more lower than the liquid inlet.

[0069] When the nonaqueous electrolyte is stored using the above-mentioned nonaqueous electrolyte container, the storage temperature is preferably 25° C. or lower, from the viewpoint of suppressing elution of iron into the nonaqueous electrolyte, more preferably 5° C. or lower, and even more preferably −5° C. or lower.

[0070] In addition, the nonaqueous electrolyte in the container for nonaqueous electrolyte is preferably stored under an inert atmosphere from the viewpoint of preventing deterioration due to oxygen in the air, etc. That is, when there is a gas phase region in the storage section of the container for nonaqueous electrolyte that is not filled with the nonaqueous electrolyte, it is preferable that the region is replaced with an inert gas. Specifically, the oxygen concentration in the gas phase region is preferably 0.3% by volume or less, and more preferably 0.1% by volume or less.

[0071] By using the storage method of the present disclosure, the dissolution of iron into the nonaqueous electrolyte during storage in the container is suppressed, thereby suppressing corrosion of the container. Furthermore, when this nonaqueous electrolyte is used in a nonaqueous electrolyte battery, the occurrence of a short circuit can be suppressed. In addition, the nonaqueous electrolyte stored by the storage method of the present disclosure is less susceptible to deterioration due to iron elution, and is less likely to affect battery performance. Therefore, the performance of the nonaqueous electrolyte before storage, such as improved capacity retention after long-term cycles at high temperatures and suppressed increase in resistance at low temperatures after high-temperature storage, is maintained, and the nonaqueous electrolyte can be preferably used in nonaqueous electrolyte batteries. The storage method of the present disclosure is particularly effective in the case of a nonaqueous electrolyte solution containing the compound represented by the general formula (2) and the compound represented by the general formula (3) as additives. EXAMPLES

[0072] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these descriptions in any way.

[0073] [Preparation of non-aqueous electrolyte] <Preparation of non-aqueous electrolyte 1> A mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) was used as the nonaqueous organic solvent, and LiPF6, which was a solute, and each of the additives shown in Table 1 were dissolved in the solvent to prepare nonaqueous electrolyte solution 1 having the composition shown in Table 1. The above preparation was carried out while maintaining the liquid temperature in the range of 20 to 30°C.

[0074] <Preparation of non-aqueous electrolyte 2> Non-aqueous electrolyte solution 2 having the composition shown in Table 1 below was prepared in the same manner as non-aqueous electrolyte solution 1, except that ethylene sulfate was not added.

[0075] <Preparation of non-aqueous electrolyte 3> Nonaqueous electrolyte solution 3 having the composition shown in Table 1 below was prepared in the same manner as in the preparation of nonaqueous electrolyte solution 1, except that lithium difluorophosphate was not added.

[0076] In Table 1 below, the numerical values ​​for the nonaqueous organic solvent represent the volume ratios of EC, EMC, and DMC, the numerical values ​​for the solute represent the amount of the solute (mol / L) in the total amount of the nonaqueous electrolyte, and the numerical values ​​for the additive represent the concentration (mass%) of each additive component contained in the total amount of the nonaqueous electrolyte.

[0077] [Table 1]

[0078] 〔evaluation〕 The effects on the non-aqueous electrolyte and the container of storing the non-aqueous electrolyte in the container of the present disclosure were evaluated by storing test pieces made of austenitic stainless steels SUS304 or SUS316L in the non-aqueous electrolyte while immersed in the non-aqueous electrolyte and measuring the change in the iron atom concentration in the non-aqueous electrolyte before and after storage.

[0079] [Preparation of test pieces] The test pieces used were made of austenitic stainless steel SUS304 or SUS316L (both had dimensions of 20 mm×15 mm×3 mm). A SUS304 test piece that was not subjected to the passivation treatment described below was used as test piece 1. Furthermore, test piece 1 was immersed in 30% nitric acid at 50°C for 1 hour for passivation treatment, and the resulting test piece was used as test piece 2. Similarly, a SUS316L test piece was not subjected to the passivation treatment described below, and was taken as test piece 3. Furthermore, test piece 3 was immersed in 30% nitric acid at 50°C for 1 hour for passivation treatment, and this test piece was taken as test piece 4. Test pieces 1 to 4 were washed with acetone before the immersion test in the nonaqueous electrolyte solution, and further washed with ultrapure water (collected using a MILLIPORE Milli-Q Integral 15 manufactured by Merck) and then dried at 60° C. for 12 hours. The amount of chromium atoms relative to the total amount of iron atoms, chromium atoms, nickel atoms, and molybdenum atoms on the surface of the passive layer of each of the test pieces 1 to 4 was measured by Auger electron spectroscopy.

[0080] <Test Example 1> A 20 mL fluororesin bottle (PFA wide-mouth bottle (without inner stopper) manufactured by Sunplatec Co., Ltd.) was filled with 25 g of the nonaqueous electrolyte 1, and the prepared test piece 2 was immersed and stored. Storage was performed at 45°C for 16 days, 27 days, and one year. Storage at 45°C was performed by placing the bottle in a thermostatic chamber and controlling the environmental temperature. Note that the storage temperature of 45°C is outside the preferable storage temperature of "25°C or lower," but this was set for the sake of convenience in the accelerated corrosion test (accelerated test).

[0081] After each storage period, the amount of iron atoms contained in the non-aqueous electrolyte 1 was measured using an ICP optical emission spectrometer (Agilent 5110 ICP-OES).

[0082] <Test Examples 2 to 4> Test Examples 2 to 4 were carried out in the same manner as Test Example 1, except that the test pieces used were changed to those shown in Table 2.

[0083] <Test Examples 5 to 8> Test Examples 5 to 8 were carried out in the same manner as Test Examples 1 to 4, except that the nonaqueous electrolyte used was changed to Nonaqueous Electrolyte Solution 2.

[0084] <Test Examples 9-12> Test Examples 9 to 12 were carried out in the same manner as Test Examples 1 to 4, respectively, except that the nonaqueous electrolyte used was changed to Nonaqueous Electrolyte Solution 3.

[0085] The results are shown in Table 2. The iron atom concentrations in the nonaqueous electrolytes 1 to 3 before storage in the containers were similarly measured, and the results are also shown in Table 2.

[0086] [Table 2]

[0087] The evaluation results shown in Table 2 confirm that the nonaqueous electrolyte containers of the examples of the present disclosure, in which the surfaces in contact with the nonaqueous electrolyte were passivated by acid cleaning, are able to significantly reduce the dissolution of iron into the nonaqueous electrolyte, compared to the comparative example containers that were not acid cleaned. In addition, when comparing SUS316L and SUS304, it was found that SUS304 had a higher iron elution inhibition effect even after storage for 27 days and after storage for one year, making it a more useful material. Furthermore, from the results of Test Examples 5 and 7, which are Reference Examples, it was found that the container of the present disclosure can suppress the elution of iron even in the storage of nonaqueous electrolyte 2 containing lithium difluorophosphate, which is a compound represented by general formula (3), but not containing ethylene sulfate, which is a compound represented by general formula (2). However, compared to the storage of nonaqueous electrolyte 1 containing both the compound represented by general formula (2) and the compound represented by general formula (3), and nonaqueous electrolyte 3 containing the compound represented by general formula (2) but not containing the compound represented by general formula (3), the difference in the amount of iron eluted into the nonaqueous electrolyte with or without acid washing was not large. From this, it was shown that the container of the present disclosure is preferably used for storing a nonaqueous electrolyte containing a compound represented by general formula (3), but has a high iron elution suppression effect in storing a nonaqueous electrolyte containing a compound represented by general formula (2), particularly in storing a nonaqueous electrolyte containing both the compound represented by general formula (2) and the compound represented by general formula (3), such as nonaqueous electrolyte 1. [Industrial Applicability]

[0088] According to the present disclosure, it is possible to provide a container for a non-aqueous electrolyte that can suppress the elution of iron into the non-aqueous electrolyte, and a method for storing a non-aqueous electrolyte that uses the container for a non-aqueous electrolyte.

[0089] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the disclosure. This application is based on a Japanese patent application (Patent Application No. 2019-105458) filed on June 5, 2019, the contents of which are incorporated herein by reference.

Claims

1. A container for a non-aqueous electrolyte having a storage portion, The housing is made of austenitic stainless steel, a passivation layer is provided on a surface of the container that comes into contact with the non-aqueous electrolyte; the amount of chromium atoms relative to the total amount of iron atoms, chromium atoms, nickel atoms, and molybdenum atoms on the surface of the passive layer is 40 mass% or more; The nonaqueous electrolyte container includes a compound represented by the following general formula (2) and a compound represented by the following general formula (3): 【Chemistry 1】 [In general formula (2), R ３ represents a hydrocarbon group having 2 to 5 carbon atoms. The hydrocarbon group may contain a heteroatom between a carbon atom-carbon atom bond. Any hydrogen atom in the hydrocarbon group may be substituted with a halogen atom. 【Chemistry 2】 [In formula (3), X 3 and X 4 each independently represent a halogen atom; M 2 + represents an alkali metal cation, an ammonium ion, or an organic cation.]

2. The nonaqueous electrolyte is selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2,2-trifluoroethyl ethyl carbonate, 2,2,2-trifluoroethyl propyl carbonate, bis(2,2,2-trifluoroethyl)carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl methyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl ethyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl propyl carbonate, bis(1,1,1,3,3,3-hexafluoro-1-propyl)carbonate, and ethylene carbonate. The container for non-aqueous electrolyte according to claim 1, which contains at least one non-aqueous organic solvent selected from the group consisting of butyl carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl 2-fluoropropionate, ethyl 2-fluoropropionate, diethyl ether, dibutyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, N,N-dimethylformamide, acetonitrile, propionitrile, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and γ-valerolactone.

3. 3. The container for a non-aqueous electrolyte according to claim 1, wherein the austenitic stainless steel is SUS304.

4. A method for storing a non-aqueous electrolyte, comprising using the container for the non-aqueous electrolyte according to any one of claims 1 to 3.

5. 5. The method for storing a non-aqueous electrolyte according to claim 4, wherein the storage temperature of the non-aqueous electrolyte is 25[deg.] C. or lower.

6. The method for storing a non-aqueous electrolyte according to claim 4 or 5, which is carried out in an inert atmosphere.

7. 3. The container for a non-aqueous electrolyte according to claim 1, wherein the container contains a non-aqueous electrolyte containing the compound represented by the general formula (2) and the compound represented by the general formula (3).

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