JP7398326B2 - Non-aqueous electrolyte and non-aqueous electrolyte battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte battery, and more specifically to a non-aqueous electrolyte containing a specific compound and a specific amount of ions of a specific element, and a non-aqueous electrolyte using this non-aqueous electrolyte. Regarding electrolyte batteries.

BACKGROUND ART In recent years, nonaqueous electrolyte batteries such as lithium secondary batteries have been put into practical use as in-vehicle power sources for driving electric vehicles and the like.

As a means to improve the battery characteristics of non-aqueous electrolyte batteries, many studies have been made in the fields of active materials for positive and negative electrodes and additives for non-aqueous electrolytes.

For example, Patent Document 1 discloses that, for the purpose of improving the initial charge capacity and input/output characteristics of a non-aqueous electrolyte secondary battery, at least one fluorosulfonate represented by M(FSO ₃ ) _x is contained. A non-aqueous electrolyte and a non-aqueous electrolyte secondary battery are disclosed in which LiPF ₆ is added to the non-aqueous electrolyte, and the ratio of the fluorosulfonate and LiPF ₆ is within a specific range.
Patent Document 2 discloses a nonaqueous electrolyte in which an electrolyte salt is dissolved in a nonaqueous solvent, with the aim of providing a nonaqueous electrolyte that can improve electrochemical properties over a wide temperature range, and a power storage device using the same. discloses a nonaqueous electrolyte characterized by containing 0.001 to 5% by mass of a specific acyclic lithium salt in the nonaqueous electrolyte, and a power storage device using the same.
Patent Document 3 aims to provide a nonaqueous electrolyte secondary battery in which a stable film is formed on the surface of a negative electrode active material (graphite material) and can exhibit higher battery performance, and the purpose is to provide a non-aqueous electrolyte secondary battery that can exhibit higher battery performance. A non-aqueous electrolyte secondary battery comprising: an electrode body containing: a non-aqueous electrolyte; Disclosed is a nonaqueous electrolyte ^secondary battery, characterized in that the graphite material has a coating film containing sulfur (S) atoms and charge carriers formed on the surface of the graphite material. has been done.
Patent Document 4 aims to provide a lithium ion secondary battery with excellent durability, and includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte. A lithium ion secondary battery is disclosed in which tungsten is present on the surface of the substance and lithium fluorosulfonate is added to the nonaqueous electrolyte. The document states that with the above structure, even if the battery is used for a long period of time, the metal elements attached to the surface of the positive electrode will not be eluted into the nonaqueous electrolyte, and low reaction resistance will be maintained over a long period of time. It is stated that a lithium-ion battery with excellent durability can be provided.

International Publication No. 2011/099585 International Publication No. 2013/168821 Japanese Patent Application Publication No. 2014-127313 Japanese Patent Application Publication No. 2015-037012

By adding lithium fluorosulfonate (FSO ₃ Li) to a nonaqueous electrolyte, the durability of a nonaqueous electrolyte battery tends to improve. On the other hand, according to studies conducted by the present inventors, it has been found that a battery containing a non-aqueous electrolyte containing FSO ₃ Li has insufficient charge storage characteristics in a high-temperature environment. Therefore, the present invention provides a non-aqueous electrolyte that can improve the charge storage characteristics of a non-aqueous electrolyte battery in a high-temperature environment, even though it contains FSO ₃ Li, and a non-aqueous electrolyte that is excellent in a high-temperature environment. The present invention provides a non-aqueous electrolyte battery having excellent charge storage characteristics.

As a result of intensive studies to solve the above problems, the present inventor has determined that a nonaqueous electrolytic solution containing FSO ₃ Li further contains iron ions, and the content of iron ions is within a specific range. The inventors have discovered that the charge storage characteristics of non-aqueous electrolyte batteries in high-temperature environments can be improved, and have arrived at the present invention.

That is, the present invention provides specific embodiments shown in [1] to [8] below.
[1] A non-aqueous electrolytic solution containing FSO ₃ Li and containing iron ions in an amount of 1 mass ppm or more and 100 mass ppm or less.
[2] The non-aqueous electrolytic solution according to [1], wherein the content of FSO ₃ Li is 0.001% by mass or more and 10.0% by mass or less.
[3] A non-aqueous electrolyte battery comprising a positive electrode and a negative electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte contains FSO ₃ Li and contains iron ions in an amount of 1 mass ppm or more. A non-aqueous electrolyte battery containing 100 mass ppm or less of a non-aqueous electrolyte.
[4] The positive electrode has a current collector and a positive electrode active material layer provided on the current collector, and the positive electrode active material is a metal oxide represented by the following compositional formula (1). 3], the nonaqueous electrolyte battery according to item 3.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ ...(1)
(In the above formula (1), a1, b1, c1 and d1 satisfy 0.90≦a1≦1.10, 0<b1<0.4, b1+c1+d1=1. M is Mn, Al, Mg, Zr , represents at least one element selected from the group consisting of Fe, Ti, and Er.)
[5] The positive electrode has a current collector and a positive electrode active material layer provided on the current collector, and the positive electrode active material is a metal oxide represented by the following compositional formula (2). 3], the nonaqueous electrolyte battery according to item 3.
Li _a2 Ni _b2 Co _c2 M _d2 O ₂ ...(2)
(In the above formula (2), a2, b2, c2 and d2 satisfy 0.90≦a2≦1.10, 0.4≦b2<1.0, b2+c2+d2=1. M is Mn, Al, Mg , represents at least one element selected from the group consisting of Zr, Fe, Ti, and Er.)
[6] The non-aqueous electrolyte battery according to any one of [3] to [5], wherein the positive electrode is an NMC positive electrode, and the content of nickel element in the NMC positive electrode is 30 mol% or more.
[7] The nonaqueous electrolyte battery according to [3], [5], or [6], wherein the positive electrode is an NMC positive electrode, and the content of nickel element in the NMC positive electrode is 40 mol% or more.
[8] The nonaqueous electrolyte battery according to any one of [3] to [7], wherein the content of FSO ₃ Li in the nonaqueous electrolyte is 0.001% by mass or more and 10.0% by mass or less. .

By using the non-aqueous electrolyte of the present invention, it is possible to obtain a non-aqueous electrolyte battery with improved charge storage characteristics in a high-temperature environment.

Embodiments of the present invention will be described in detail below. The following embodiments are examples (representative examples) of the present invention, and the present invention is not limited thereto. Moreover, the present invention can be implemented with arbitrary changes within the scope without departing from the gist thereof.

<1. Non-aqueous electrolyte>
The non-aqueous electrolytic solution according to one embodiment of the present invention contains FSO ₃ Li, and contains iron ions in an amount of 1 mass ppm or more and 100 mass ppm or less.
The non-aqueous electrolytic solution according to one embodiment of the present invention contains specific amounts of iron ions and FSO ₃ Li in the non-aqueous electrolytic solution, so that FSO ₃ ^- (fluorosulfonic acid ions) are arranged in the iron ions. It is presumed that the reduction resistance of iron ions increases due to the position or interaction, and the negative electrode reduction reaction is suppressed, thereby improving charge storage characteristics in a high-temperature environment.
Hereinafter, a non-aqueous electrolytic solution according to an embodiment of the present invention will be described in detail.

<1-1. FSO ₃ Li>
The non-aqueous electrolyte of this embodiment contains FSO ₃ Li.
The content of FSO ₃ Li in the non-aqueous electrolyte is preferably 0.001% by mass or more, more preferably 0.010% by mass or more, even more preferably 0.10% by mass or more, while the upper limit is not particularly limited. Although there is no limitation, it is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, even more preferably 5.0% by mass or less, particularly preferably 4.0% by mass or less, especially Preferably it is 3.0% by mass or less.
When the content of FSO ₃ Li in the nonaqueous electrolyte is 10.0% by mass or less, it is preferable because the negative electrode reduction reaction does not increase to the extent that the internal resistance of the nonaqueous electrolyte battery increases. When the content is 0.001% by mass or more, it is preferable because the effect of the present invention of containing FSO ₃ Li is produced. Therefore, within the above range, the negative electrode reduction reaction in a high-temperature environment is suppressed, so that the charge storage characteristics in a high-temperature environment can be improved.
FSO ₃ Li may be synthesized by a known method and used, or a commercially available product may be obtained and used. When measuring the amount of FSO ₃ Li in the electrolyte in a non-aqueous electrolyte battery, remove the component containing the non-aqueous electrolyte from the non-aqueous electrolyte battery, extract the non-aqueous electrolyte, and then measure. Bye. For example, extraction can be performed using a centrifuge, or the non-aqueous electrolyte can be extracted using an organic solvent. Add ice-cooled pure water to the extracted nonaqueous electrolyte, mix quickly, and immediately perform anion ion chromatography (e.g., Thermo Fisher Scientific, ICS-2000, column: AS23, eluent: 5.0 mM
Na ₂ CO ₃ /0.9mM NaHCO ₃ , Detection method: Detect SO ₄ ^2- ions separated using suppressor-equipped electrical conductivity detection method (12.5mM H ₂ SO ₄ ), and detect FSO ₃ ^- ions with SO ^From the calibration curve of ₄ ^2- ions, FSO ₃ - ions can be quantified by converting the molar sensitivity ratio [k(SO ₄ ^2- )/k(FSO ₃ ^- )]=2.0. The amount of FSO ₃ ⁻ ions in the non-aqueous electrolyte is regarded as the amount of FSO ₃ Li.

<1-2. Iron ion>
The non-aqueous electrolyte according to one embodiment of the present invention contains iron ions in an amount of 1 ppm or more and 100 ppm or less by mass. The valence of iron ions contained in the non-aqueous electrolyte may be divalent or trivalent. Further, the non-aqueous electrolyte according to an embodiment of the present invention may contain both divalent iron ions (Fe ²⁺ ) and trivalent iron ions (Fe ³⁺ ) in any ratio. In this specification, the content of iron ions in the non-aqueous electrolyte is the content of iron element ions in the non-aqueous electrolyte.
The content of iron ions in the nonaqueous electrolyte is usually 1 mass ppm or more, preferably 2 mass ppm or more, more preferably 3 mass ppm or more, still more preferably 5 mass ppm or more, and particularly preferably 10 mass ppm. ppm or more, particularly preferably 25 mass ppm or more, while the upper limit is usually 100 mass ppm or less, preferably 90 mass ppm or less, more preferably 80 mass ppm or less, still more preferably 70 mass ppm or less, particularly preferably It is 60 mass ppm or less.
When the iron ion content is higher than 100 mass ppm, the internal resistance of the non-aqueous electrolyte battery increases due to an increase in the negative electrode reduction reaction, whereas when it is lower than 1 mass ppm, the iron ion content increases. The effect becomes lower because the difference from the case without it becomes smaller.
The compounds serving as iron ion sources may be used alone or in combination of two or more in any combination and ratio. Compounds that serve as iron ion sources include Fe(EC) _n (PF ₆ ) _m (EC = ethylene carbonate ligand, n = 0 to 6, m = 2 to 3), tris(2,4-pentanedionate), ) Examples include Fe complexes such as iron and ferrocenes. Preferred examples of the ligand include elements constituting batteries, such as cyclic carbonates such as ethylene carbonate, propylene carbonate, and fluoroethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate, which are used as nonaqueous solvents. Examples include organic solvents such as chain carbonates; carboxylic acid esters such as methyl acetate; ether compounds; and sulfone compounds. In addition, compounds that serve as iron ion sources include Fe(CH ₃ COO) _n (n=2-3); Fe(CF ₃ COO) _n (n=2-3); Fe(FSO ₃ ) _n (n= 2-3); Fe(CF ₃ SO ₃ ) _n (n=2-3); FeSO ₄ ; iron halides such as iron chloride; and the like. Further, the iron ion may be eluted from battery components such as a positive electrode active material, a negative electrode active material, a positive electrode current collector, a negative electrode current collector, or an exterior body that may contain Fe.
Iron ions usually form a salt with a counter anion in a non-aqueous electrolyte. In this embodiment, a counter anion other than the FSO ₃ ⁻ ion may be coordinated with an iron ion to form a complex, or an iron ion and one or more counter anions may form a salt. . Preferable examples of the counter anion include elements constituting a battery, such as fluorophosphate ions such as PF ₆ ^- ions derived from LiPF ₆ and PO ₂ F ₂ ^- ions derived from LiPO ₂ F ₂ , and fluorophosphate ions derived from FSO ₃ Li. Examples include FSO ₃ ^- ion, fluoride ion, carbonate ion, carboxylate ion, sulfonate ion, sulfonylimide ion, (oxalate)borate ion, etc., and more preferably PF ₆ ^- ion, FSO ₃ ^- ion, or fluoride ion. Examples include compound ions. Among these, FSO ₃ ⁻ ion is particularly preferable because it has a higher coordination ability to iron ions than PF ₆ ⁻ ion.
In this embodiment, it is estimated that the FSO ₃ ^- ion coordinates with iron ions and suppresses the negative electrode reduction reaction in a high temperature environment, thereby improving charge storage characteristics in a high temperature environment. Ru. To measure the amount of iron ions in the electrolyte in a non-aqueous electrolyte battery, remove the component containing the non-aqueous electrolyte from the non-aqueous electrolyte battery, extract the non-aqueous electrolyte, and measure. good. For example, the non-aqueous electrolyte can be extracted using a centrifuge, or the non-aqueous electrolyte can be extracted using an organic solvent. Using the extracted non-aqueous electrolyte, iron elements, that is, iron ions, are quantified by inductively coupled radio frequency plasma emission spectroscopy (ICP-AES, for example, Thermo Fischer Scientific, iCAP 7600duo) using Li and acid concentration matching calibration curve method.

<1-3. Electrolyte>
The non-aqueous electrolytic solution of this embodiment usually contains an electrolyte as a component, like a general non-aqueous electrolytic solution. There are no particular limitations on the electrolyte used in the non-aqueous electrolyte of this embodiment, and any known electrolyte can be used. Hereinafter, specific examples of the electrolyte will be described in detail.
<1-3-1. Lithium salt>
As the electrolyte in the non-aqueous electrolyte of this embodiment, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and one or more arbitrary salts can be used, and specific examples include the following.

For example, lithium fluoroborate salts such as _LiBF4 ;
Lithium fluorophosphate salts such as LiPF ₆ and LiPO ₂ F ₂ ;
Lithium tungstate salts such as LiWOF ₅ ;
Carboxylic acid lithium salts such as CF ₃ CO ₂ Li;
Sulfonic acid lithium salts such as CH ₃ SO ₃ Li;
Lithium imide salts such as LiN( _FSO2 ) ₂ , _LiN ( _CF3SO2 ) ₂ ;
Lithium methide salts such as LiC(FSO ₂ ) ₃ ;
Lithium oxalate salts such as lithium difluorooxalatoborate;
Other fluorine-containing organic lithium salts such as LiPF ₄ (CF ₃ ) ₂ ;
etc.

In addition to the effect of improving charge storage characteristics in a high-temperature environment obtained by the present invention, lithium fluoroborate salts, lithium fluorophosphate salts, and lithium sulfonate salts can further enhance the effect of improving charge/discharge rate characteristics and impedance characteristics. , lithium imide salts, and lithium oxalate salts, and those selected from fluoroborate lithium salts, fluorophosphate lithium salts, lithium imide salts, and lithium oxalate salts are preferred.

The total concentration of these electrolytes in the nonaqueous electrolyte is not particularly limited, but is usually 8% by mass or more, preferably 8.5% by mass or more, and more preferably 9% by mass based on the total amount of the nonaqueous electrolyte. % or more. Moreover, the upper limit is usually 18% by mass or less, preferably 17% by mass or less, and more preferably 16% by mass or less. When the total concentration of the electrolyte is within the above range, the electrical conductivity becomes appropriate for battery operation, and therefore sufficient output characteristics tend to be obtained.

<1-4. Non-aqueous solvent>
The non-aqueous electrolytic solution of this embodiment, like a general non-aqueous electrolytic solution, usually contains a non-aqueous solvent that dissolves the above-mentioned electrolyte as its main component. There are no particular limitations on the nonaqueous solvent used here, and any known organic solvent can be used. Examples of the organic solvent include saturated cyclic carbonates, chain carbonates, carboxylic acid esters, ether compounds, and sulfone compounds. Although not particularly limited thereto, saturated cyclic carbonates, chain carbonates, or carboxylic acid esters are preferred, and saturated cyclic carbonates or chain carbonates are more preferred. These can be used alone or in combination of two or more. As the combination of two or more types of nonaqueous solvents, a combination of two or more types selected from the group consisting of saturated cyclic carbonates, chain carbonates, and carboxylic acid esters is preferable, and a combination of saturated cyclic carbonates or chain carbonates is more preferable. .

<1-4-1. Saturated cyclic carbonate>
Examples of the saturated cyclic carbonate include those having an alkylene group having 2 to 4 carbon atoms, and saturated cyclic carbonates having 2 to 3 carbon atoms are preferably used from the viewpoint of improving battery characteristics due to improved degree of lithium ion dissociation. . Further, the saturated cyclic carbonate may be a cyclic carbonate having a fluorine atom, such as monofluoroethylene carbonate.

Examples of the saturated cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Among these, ethylene carbonate and propylene carbonate are preferred, and ethylene carbonate, which is less likely to be oxidized and reduced, is more preferred. One type of saturated cyclic carbonate may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present invention, but the lower limit is usually 3% by volume or more, preferably 5% by volume, based on the total amount of the solvent in the non-aqueous electrolyte. % by volume or more. By setting this range, a decrease in electrical conductivity due to a decrease in the dielectric constant of the nonaqueous electrolyte can be avoided, and the large current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the nonaqueous electrolyte battery can be maintained within a good range. It becomes easier to The upper limit is usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less. Within this range, the oxidation/reduction resistance of the non-aqueous electrolyte tends to improve, and the stability during high-temperature storage tends to improve.
Incidentally, the volume % in the present invention means the volume at 25° C. and 1 atmosphere.

<1-4-2. Chain carbonate>
As the chain carbonate, one having 3 to 7 carbon atoms is usually used, and in order to adjust the viscosity of the electrolytic solution to an appropriate range, a chain carbonate having 3 to 5 carbon atoms is preferably used.

Specifically, the chain carbonates include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, Examples include isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butylethyl carbonate, isobutylethyl carbonate, t-butylethyl carbonate, and the like.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propylisopropyl carbonate, ethylmethyl carbonate, and methyl-n-propyl carbonate are preferred, and dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate are particularly preferred. be.

Furthermore, chain carbonates having a fluorine atom (hereinafter sometimes abbreviated as "fluorinated chain carbonates") can also be suitably used. The number of fluorine atoms that the fluorinated chain carbonate has is not particularly limited as long as it is 1 or more, but it is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethylmethyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.

Examples of the fluorinated dimethyl carbonate derivative include fluoromethylmethyl carbonate, difluoromethylmethyl carbonate, trifluoromethylmethyl carbonate, bis(fluoromethyl) carbonate, bis(difluoro)methyl carbonate, bis(trifluoromethyl) carbonate, and the like.

Examples of fluorinated ethylmethyl carbonate derivatives include 2-fluoroethylmethyl carbonate, ethylfluoromethyl carbonate, 2,2-difluoroethylmethyl carbonate, 2-fluoroethylfluoromethyl carbonate, ethyldifluoromethyl carbonate, and 2,2,2-trifluoromethyl carbonate. Examples include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

Examples of fluorinated diethyl carbonate derivatives include ethyl-(2-fluoroethyl) carbonate, ethyl-(2,2-difluoroethyl) carbonate, bis(2-fluoroethyl) carbonate, and ethyl-(2,2,2-trifluoroethyl) carbonate. ethyl) carbonate, 2,2-difluoroethyl-2'-fluoroethyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2'-fluoroethyl carbonate, 2,2, Examples include 2-trifluoroethyl-2',2'-difluoroethyl carbonate and bis(2,2,2-trifluoroethyl) carbonate.

One type of chain carbonate may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, based on the total amount of the solvent in the nonaqueous electrolyte. Moreover, it is usually 90 volume% or less, preferably 85 volume% or less, and more preferably 80 volume% or less. By setting the content of chain carbonate within the above range, it is possible to maintain the viscosity of the non-aqueous electrolyte in an appropriate range, suppress a decrease in ionic conductivity, and, in turn, make it easier to maintain the output characteristics of the non-aqueous electrolyte battery in a favorable range. Become. When two or more types of chain carbonates are used in combination, the total amount of chain carbonates may be made to satisfy the above range.

Furthermore, by combining ethylene carbonate in a specific content with a specific linear carbonate, battery performance can be significantly improved.

For example, when dimethyl carbonate and ethyl methyl carbonate are selected as specific chain carbonates, the content of ethylene carbonate is not particularly limited and can be set arbitrarily as long as it does not significantly impair the effects of the present invention. The content of dimethyl carbonate is usually 15% by volume or more, preferably 20% by volume, and usually 45% by volume or less, preferably 40% by volume or less, based on the total amount of the solvent. The content of ethyl methyl carbonate is usually 20 volume% or more, preferably 30 volume% or more, and usually 50 volume% or less, preferably 45 volume% or less, and the content of ethyl methyl carbonate is usually 20 volume% or more, preferably 30 volume% or more. , and usually 50% by volume or less, preferably 45% by volume or less. When the contents of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are within the above ranges, high temperature stability is excellent and gas generation tends to be suppressed.

<1-4-3. Ether compounds>
As the ether compound, chain ethers having 3 to 10 carbon atoms and cyclic ethers having 3 to 6 carbon atoms are preferred.

The ether compounds may be used alone or in combination of two or more in any desired ratio.
The content of the ether compound is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present invention, but it is usually at least 1% by volume, preferably at least 2% by volume, more preferably at least 2% by volume based on 100% by volume of the nonaqueous solvent. is 3% by volume or more, and usually 30% by volume or less, preferably 25% by volume or less, more preferably 20% by volume or less. When two or more types of ether compounds are used in combination, the total amount of the ether compounds may satisfy the above range. If the content of the ether compound is within the above-mentioned preferred range, it is easy to ensure the effect of improving the ionic conductivity resulting from the improvement in the degree of lithium ion dissociation of the chain ether and the reduction in viscosity. Furthermore, when the negative electrode active material is a carbonaceous material, the phenomenon in which chain ether is co-inserted with lithium ions can be suppressed, so that input/output characteristics and charge/discharge rate characteristics can be kept within appropriate ranges.

<1-4-4. Sulfone compounds>
The sulfone compound is not particularly limited, even if it is a cyclic sulfone or a chain sulfone, but in the case of a cyclic sulfone, the number of carbon atoms is usually 3 to 6, preferably 3 to 5, and in the case of a chain sulfone. , compounds having usually 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms are preferred. Further, the number of sulfonyl groups in one molecule of the sulfone compound is not particularly limited, but is usually 1 or 2.

Examples of the cyclic sulfone include monosulfone compounds such as trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones; disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones. Among them, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.

As the sulfolane, sulfolane or a sulfolane derivative (hereinafter, sulfolane may also be abbreviated as "sulfolane") is preferable. As the sulfolane derivative, one in which one or more of the hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring is substituted with a fluorine atom or an alkyl group is preferable.

One type of sulfone compound may be used alone, or two or more types may be used in combination in any combination and ratio.
The content of the sulfone compound is not particularly limited and may be arbitrary as long as it does not significantly impair the effects of the present invention, but is usually 0.3% by volume or more, preferably 0.3% by volume or more, based on the total amount of the solvent in the non-aqueous electrolyte. The content is 5% by volume or more, more preferably 1% by volume or more, and usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less. When two or more types of sulfone compounds are used in combination, the total amount of the sulfone compounds may satisfy the above range. If the content of the sulfone compound is within the above range, an electrolytic solution with excellent high-temperature storage stability tends to be obtained.

<1-4-5. Carboxylic acid ester>
The carboxylic acid ester is preferably a chain carboxylic ester, more preferably a saturated chain carboxylic ester. Further, the total number of carbon atoms in the carboxylic acid ester is usually 3 to 7, and carboxylic esters having 3 to 5 carbon atoms are preferably used from the viewpoint of improving battery characteristics due to improved output characteristics.

Examples of carboxylic acid esters include saturated chain carboxylic esters such as methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl pivalate, and ethyl pivalate, methyl acrylate, ethyl acrylate, methyl methacrylate, and methacrylic acid. Examples include unsaturated chain carboxylic acid esters such as ethyl. Among them, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl pivalate, and ethyl pivalate are preferred, and from the viewpoint of improving output characteristics, methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate are more preferred. One type of carboxylic acid ester may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the carboxylic acid ester is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present invention, but the lower limit is usually 3% by volume or more, preferably 5% by volume, based on the total amount of the solvent in the non-aqueous electrolyte. % by volume or more. By setting this range, a decrease in electrical conductivity due to a decrease in the dielectric constant of the nonaqueous electrolyte can be avoided, and the large current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the nonaqueous electrolyte battery can be maintained within a good range. It becomes easier to The upper limit is usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less. Within this range, the oxidation/reduction resistance of the non-aqueous electrolyte tends to improve, and the stability during high-temperature storage tends to improve.
Incidentally, the volume % in the present invention means the volume at 25° C. and 1 atmosphere.

<1-5. Fluorosulfonates other than FSO ₃ Li>
Counter cations of fluorosulfonates other than FSO ₃ Li (hereinafter simply referred to as "fluorosulfonates") are not particularly limited, but include sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR ¹³ Examples include ammonium represented by R ¹⁴ R ¹⁵ R ¹⁶ (wherein R ¹³ to R ¹⁶ each independently represent a hydrogen atom or an organic group having 1 to 12 carbon atoms).

Specific examples of fluorosulfonates include:
Examples include sodium fluorosulfonate, potassium fluorosulfonate, rubidium fluorosulfonate, and cesium fluorosulfonate.

The fluorosulfonate salts may be used alone or in combination of two or more in any combination and ratio. Further, the total content of fluorosulfonate and FSO ₃ Li in the entire nonaqueous electrolyte of this embodiment is usually 0.001% by mass or more, preferably 0.01% by mass in 100% by mass of the nonaqueous electrolyte. Above, more preferably 0.1% by mass or more, and usually 15% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, particularly preferably 2% by mass. The content is particularly preferably 1% by mass or less. When using two or more types of fluorosulfonate salts, the total amount of FSO ₃ Li and fluorosulfonate salts may satisfy the above range.
Within this range, swelling of the non-aqueous electrolyte battery due to charging and discharging can be suitably suppressed.

<1-6. Auxiliary agent>
The non-aqueous electrolytic solution of this embodiment may contain the following auxiliary agents within a range that achieves the effects of the present invention.
Unsaturated cyclic carbonates such as vinylene carbonate, vinylethylene carbonate or ethynylethylene carbonate;
Carbonate compounds such as methoxyethyl-methyl carbonate;
Spiro compounds such as methyl-2-propynyl oxalate;
Sulfur-containing compounds such as ethylene sulfite;
Isocyanate compounds such as diisocyanates having a cycloalkylene group such as 1,3-bis(isocyanatomethyl)cyclohexane;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone;
Hydrocarbon compounds such as cycloheptane;
Fluorine-containing aromatic compounds such as fluorobenzene;
Silane compounds such as tris(trimethylsilyl) borate;
Ester compounds such as 2-propynyl 2-(methanesulfonyloxy)propionate;
Lithium salts such as lithium ethylmethyloxycarbonylphosphonate;
Isocyanate esters such as triallyl isocyanurate;
etc. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity retention characteristics and cycle characteristics after high-temperature storage can be improved.

The content of the auxiliary agent is not particularly limited, and is arbitrary as long as it does not significantly impair the effects of the present invention. The content of the auxiliary agent is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and usually 5% by mass or more, based on the total amount of the nonaqueous electrolyte. It is at most 3% by mass, preferably at most 3% by mass, and more preferably at most 1% by mass. Within this range, the effect of the auxiliary agent is likely to be fully expressed, and high-temperature storage stability tends to be improved. When two or more types of auxiliary agents are used in combination, the total amount of the auxiliary agents may be made to satisfy the above range.

<2. Non-aqueous electrolyte battery>
A non-aqueous electrolyte battery according to an embodiment of the present invention is a non-aqueous electrolyte battery comprising a positive electrode and a negative electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte, and a non-aqueous electrolyte according to the embodiment. More specifically, a positive electrode has a current collector and a positive electrode active material layer provided on the current collector and is capable of occluding and releasing metal ions, and a current collector and a positive electrode active material layer provided on the current collector. The present invention includes a negative electrode having a negative electrode active material layer and capable of occluding and releasing metal ions, and a non-aqueous electrolytic solution containing FSO ₃ Li and containing iron ions in an amount of 1 mass ppm or more and 100 mass ppm or less.

<2-1. Battery configuration>
The non-aqueous electrolyte battery of this embodiment has the same structure as a conventionally known non-aqueous electrolyte battery except for the above-mentioned non-aqueous electrolyte. Usually, a positive electrode and a negative electrode are laminated via a porous membrane (separator) impregnated with the above-mentioned non-aqueous electrolyte, and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte battery according to the present embodiment is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

<2-2. Non-aqueous electrolyte>
As the non-aqueous electrolyte, the above-described non-aqueous electrolyte according to one embodiment of the present invention is used. Note that it is also possible to mix and use other non-aqueous electrolytes with the above-mentioned non-aqueous electrolytes without departing from the spirit of the present invention.

<2-3. Positive electrode>
In one embodiment of the present invention, the positive electrode includes a current collector and a positive electrode active material layer provided on the current collector.
The positive electrode used in the non-aqueous electrolyte battery of this embodiment will be described in detail below.

<2-3-1. Cathode active material>
The positive electrode active material used in the positive electrode will be explained below.
(1) Composition The positive electrode active material is lithium iron phosphate, lithium cobalt oxide, or a transition metal oxide containing at least Ni and Co, with Ni and Co accounting for 50 mol% or more of the transition metals. There is no particular restriction as long as it can chemically occlude and desorb metal ions, but for example, it is preferable to use a substance that can electrochemically occlude and desorb lithium ions, and contains lithium and at least Ni and Co. A transition metal oxide in which 60 mol% or more of the metals are Ni and Co is preferred. This is because Ni and Co have a redox potential suitable for use as a positive electrode material of a secondary battery and are suitable for high capacity applications.

The metal component of the lithium transition metal oxide preferably contains at least one element selected from the group consisting of Fe, Ni, and Co as an essential transition metal element, preferably Ni and Co, and other elements. Examples of the metal elements include Mn, V, Ti, Cr, Fe, Cu, Al, Mg, Zr, Er, etc., and Mn, Ti, Fe, Al, Mg, Zr, etc. are preferable. Specific examples of lithium transition metal oxides include, for example, LiFePO ₄ , LiCoO ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.80 Co _0.15 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , Li _1.05 Ni _0.33 Mn _0.33 Co _0.33 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , Li _{1 .05} Ni _0.50 Mn _0.29 Co _0.21 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ etc. .

Particularly preferred is an embodiment in which the positive electrode active material is a transition metal oxide represented by the following compositional formula (1).
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ ...(1)
(In the above formula (1), a1, b1, c1 and d1 satisfy 0.90≦a1≦1.10, 0<b1<0.4, b1+c1+d1=1. M is Mn, Al, Mg, Zr , represents at least one element selected from the group consisting of Fe, Ti, and Er.)
In the compositional formula (1), it is preferable that 0.1≦d1<0.5.
Because the composition ratios of Ni and Co and other metal species are within specific ranges, transition metals are difficult to elute from the positive electrode, and even if they are eluted, Ni and Co will not remain in the non-aqueous secondary battery. This is because the negative effects of

Particularly preferred is an embodiment in which the positive electrode active material is a transition metal oxide represented by the following compositional formula (2).
Li _a2 Ni _b2 Co _c2 M _d2 O ₂ ...(2)
(In the above formula (2), a2, b2, c2 and d2 satisfy 0.90≦a2≦1.10, 0.4≦b2<1.0, b2+c2+d2=1. M is Mn, Al, Mg , Zr, Fe, T
Represents at least one element selected from the group consisting of i and Er. )
In compositional formula (2), it is preferable that the numerical value is 0.10≦d2<0.40. Moreover, it is preferable to show a numerical value of 0.50≦b2≦0.96.
Since Ni and Co are the main components and the composition ratio of Ni is larger than the composition ratio of Co, it is stable and can provide high capacity when used as a positive electrode in a non-aqueous electrolyte battery. Because it will be.

Particularly preferred is an embodiment in which the positive electrode active material is a transition metal oxide represented by the following compositional formula (3).
Li _a3 Ni _b3 Co _c3 M _d3 O ₂ ...(3)
(In formula (3), the numerical values are 0.90≦a3≦1.10, 0.50≦b3≦0.94, 0.05≦c3≦0.2, 0.01≦d3≦0.3. , b3+c3+d3=1.M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)
In compositional formula (3), it is preferable that the numerical value satisfies 0.10≦d3≦0.3.
This is because the positive electrode active material having the above composition makes it possible to obtain particularly high capacity when used as a positive electrode for a non-aqueous secondary battery.

Furthermore, two or more of the above positive electrode active materials may be used in combination. Similarly, at least one of the above positive electrode active materials and other positive electrode active materials may be mixed and used. Examples of other positive electrode active materials include transition metal oxides, transition metal phosphate compounds, transition metal silicate compounds, and transition metal borate compounds not listed above.
Among these, lithium-manganese composite oxides having a spinel-type structure and lithium-containing transition metal phosphoric acid compounds having an olivine-type structure are preferred. Specifically, examples of the lithium manganese composite oxide having a spinel structure include LiMn ₂ O ₄ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O ₄ and the like. This is because these lithium manganese composite oxides have the most stable structure, are less likely to release oxygen even in the event of an abnormality in a nonaqueous electrolyte battery, and are excellent in safety.
Further, as the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , manganese phosphates such as LiMnPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are replaced with Al, Ti. , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, and other metals substituted.
Among the lithium-containing transition metal phosphate compounds, lithium iron phosphate compounds are preferred. This is because iron is an extremely inexpensive metal with abundant resources, and is also less harmful. That is, among the above specific examples, LiFePO ₄ can be cited as a more preferable specific example.

In one embodiment of the present invention, the positive electrode is an NMC positive electrode, and the content of the nickel element in the NMC positive electrode is preferably 30 mol% or more, and the content of nickel element is 40 mol% or more in a non-aqueous electrolyte battery. It is more preferable from the viewpoint of increasing the capacity.
Here, in this specification, the NMC positive electrode means a positive electrode whose positive electrode active material includes nickel manganese cobalt (NMC) and is a material represented by the following formula (I).
Li _a Ni _b Co _c Mn _d O ₂ ...(I)
(In the above formula (I), a, b, c and d satisfy 0.90≦a≦1.10, b+c+d=1.)

(2) Surface coating It is also possible to use a cathode active material with a substance (hereinafter referred to as a "surface-adhering substance" as appropriate) attached to the surface of the cathode active material having a composition different from that of the substance constituting the main cathode active material. . Examples of surface-attached substances include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, Sulfates such as calcium sulfate and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; carbon; and the like.

These surface-adhering substances can be prepared, for example, by dissolving or suspending them in a solvent, impregnating them into the positive electrode active material, and then drying them, or by dissolving or suspending a surface-adhering substance precursor in a solvent and impregnating them into the positive electrode active material. It can be attached to the surface of the positive electrode active material by a method of reacting it by heating or the like after heating, or by a method of adding it to the positive electrode active material precursor and baking it at the same time. In addition, when attaching carbon, it is also possible to use a method of mechanically attaching carbonaceous matter in the form of activated carbon or the like afterwards.

The mass of the surface-attached substance adhering to the surface of the positive electrode active material is preferably 0.1 ppm or more, more preferably 1 ppm or more, and even more preferably 10 ppm or more, based on the mass of the positive electrode active material. Moreover, it is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.
The surface-attached substance can suppress the oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode active material, and can improve battery life. Further, when the amount of adhesion is within the above range, the effect can be fully exhibited, and the resistance will not increase easily without inhibiting the ingress and egress of lithium ions.

(3) Shape The positive electrode active material may have a particle shape. The shape of the positive electrode active material particles may be a lump, a polyhedron, a sphere, an ellipsoid, a plate, a needle, a column, etc., which are conventionally used. Moreover, primary particles aggregate to form secondary particles, and the shape of the secondary particles may be spherical or ellipsoidal.

(4) Method for manufacturing the positive electrode active material The method for manufacturing the positive electrode active material is not particularly limited as long as it does not go beyond the gist of the present invention, but there are several methods that can be used. method is used.
In particular, various methods can be considered to produce a spherical or ellipsoidal active material. For example, one method is to use a transition metal raw material such as a transition metal nitrate or sulfate, and raw materials of other elements as necessary. is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to prepare and collect a spherical precursor. After drying this as necessary, LiOH, Li ₂ CO ₃ , LiNO A method of obtaining an active material by adding a Li source such as _{No. 3} and firing at a high temperature can be mentioned.

In addition, as an example of another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, oxides, etc., and raw materials of other elements as necessary, are dissolved or pulverized and dispersed in a solvent such as water. Then, it is dried and molded using a spray dryer or the like to obtain a spherical or ellipsoidal precursor, and a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ is added thereto and fired at a high temperature to obtain an active material. can be mentioned.

As an example of yet another method, a transition metal raw material such as a transition metal nitrate, sulfate, hydroxide, or oxide, a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and other elements as necessary The active material is obtained by dissolving or pulverizing and dispersing the raw material in a solvent such as water, drying and molding it with a spray dryer, etc. to obtain a spherical or ellipsoidal precursor, and baking this at a high temperature to obtain the active material. Can be mentioned.

<2-3-2. Positive electrode structure and manufacturing method>
Below, the structure of the positive electrode used in the present invention and its manufacturing method will be explained.
(Production method of positive electrode)
The positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. A positive electrode using a positive electrode active material may be manufactured by any known method. For example, a positive electrode active material, a binder, and if necessary a conductive material, a thickener, etc., are mixed together in a dry manner and formed into a sheet, which is then pressed onto a positive electrode current collector, or these materials are mixed in a liquid medium. A positive electrode can be obtained by dissolving or dispersing the slurry in a slurry, applying it to a positive electrode current collector, and drying it to form a positive electrode active material layer on the current collector.

The content of the positive electrode active material in the positive electrode active material layer is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 99.9% by mass or less. Yes, and more preferably 99% by mass or less. When the content of the positive electrode active material is within the above range, a sufficient electrical capacity of the non-aqueous electrolyte battery can be ensured. Furthermore, the strength of the positive electrode is also sufficient. In this embodiment, the positive electrode active material powder (particles) may be used alone, or two or more types having different compositions or different powder physical properties may be used in any combination and ratio. When using two or more types of active materials in combination, it is preferable to use the composite oxide containing lithium and manganese as a powder component. Cobalt or nickel is an expensive metal with few resources, and in large batteries that require high capacity, such as those used in automobiles, the amount of active material used becomes large, which is not preferable from the point of view of cost. Therefore, in large batteries, it is desirable to use manganese as a main component as a cheaper transition metal in the positive electrode active material.

<Conductive material>
As the conductive material, any known conductive material can be used. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type, and may use 2 or more types together in arbitrary combinations and ratios.

The content of the conductive material in the positive electrode active material layer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1% by mass or more, and preferably 50% by mass or less. The content is more preferably 30% by mass or less, and even more preferably 15% by mass or less. When the content of the conductive material is within the above range, sufficient conductivity can be ensured. Furthermore, it is easy to prevent a decrease in battery capacity.

<Binder>
The binder used for producing the positive electrode active material layer is not particularly limited as long as it is a material that is stable to the non-aqueous electrolyte and the solvent used during electrode production.
In the case of the coating method, the binder is not particularly limited as long as it is a material that can be dissolved or dispersed in the liquid medium used during electrode manufacturing, but specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, and aromatic. Resin-based polymers such as group polyamides, cellulose, and nitrocellulose; Rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; Styrene/butadiene/styrene block copolymer or its hydrogenated product, EPDM (ethylene/propylene/diene terpolymer), styrene/ethylene/butadiene/ethylene copolymer, styrene/isoprene/styrene block copolymer, or Thermoplastic elastomeric polymers such as hydrogenated products; soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate copolymers, propylene/α-olefin copolymers, etc. ; Polyvinylidene fluoride (PV
dF), fluorinated polymers such as polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and tetrafluoroethylene/ethylene copolymer; polymer compositions having ionic conductivity for alkali metal ions (particularly lithium ions), etc. It will be done. Note that these substances may be used alone or in combination of two or more in any combination and ratio.

The content of the binder in the positive electrode active material layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, and preferably 80% by mass or less. The content is more preferably 60% by mass or less, even more preferably 40% by mass or less, and particularly preferably 10% by mass or less. When the ratio of the binder is within the above range, the positive electrode active material can be sufficiently retained and the mechanical strength of the positive electrode can be ensured, resulting in good battery performance such as cycle characteristics. Furthermore, it also helps avoid deterioration in battery capacity and conductivity.

<Liquid medium>
The liquid medium used to prepare the slurry for forming the positive electrode active material layer is capable of dissolving or dispersing the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. There is no particular restriction on the type of solvent as long as it is a solvent, and either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water, a mixed solvent of alcohol and water, and the like. Examples of organic solvents include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide , amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide; and the like. In addition, these may be used individually by 1 type, or may use 2 or more types together in arbitrary combinations and ratios.

<Thickener>
When using an aqueous solvent as the liquid medium for forming a slurry, it is preferable to form the slurry using a thickener and a latex such as styrene butadiene rubber (SBR). Thickeners are commonly used to adjust the viscosity of slurries.
The thickener is not limited as long as it does not significantly limit the effect of the present invention, but specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. etc. These may be used alone or in combination of two or more in any combination and ratio.

When using a thickener, the ratio of the thickener to the positive electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.6% by mass or more. Preferably, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. When the ratio of the thickener is within the above range, the coating properties of the slurry will be good, and the ratio of the active material in the positive electrode active material layer will be sufficient, which will reduce the problem of battery capacity reduction and the positive electrode. This makes it easier to avoid the problem of increased resistance between active materials.

<Consolidation>
The positive electrode active material layer obtained by coating and drying the slurry on the current collector is preferably compacted by hand pressing, roller pressing, etc. in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1 g·cm ^-3 or more, more preferably 1.5 g·cm ^-3 or more, particularly preferably 2 g·cm ^-3 or more, and preferably 4 g·cm ^-3 or less, It is more preferably 3.5 g·cm ^-3 or less, particularly preferably 3 g·cm ^-3 or less.
When the density of the positive electrode active material layer is within the above range, the permeability of the non-aqueous electrolyte near the current collector/active material interface will not decrease, and the charge/discharge characteristics will be particularly good at high current densities. Become. Furthermore, the conductivity between active materials is less likely to decrease, and battery resistance is less likely to increase.

<Current collector>
There are no particular limitations on the material of the positive electrode current collector, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; carbonaceous materials such as carbon cloth and carbon paper. Among these, metal materials, particularly aluminum, are preferred.

In the case of metal materials, examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foamed metal, etc. In the case of carbonaceous materials, examples include carbon plate, Examples include carbon thin films and carbon cylinders. Among these, metal thin films are preferred. Note that the thin film may be formed into a mesh shape as appropriate.
The thickness of the current collector is arbitrary, but is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and preferably 1 mm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. preferable. When the thickness of the current collector is within the above range, the strength required for the current collector can be sufficiently ensured. Furthermore, handling properties are also improved.

Although the ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, it is preferably (thickness of the active material layer on one side immediately before pouring the non-aqueous electrolyte)/(thickness of the current collector). It is 150 or less, more preferably 20 or less, particularly preferably 10 or less, also preferably 0.1 or more, more preferably 0.4 or more, and particularly preferably 1 or more.
When the ratio of the thickness of the current collector to the positive electrode active material layer is within the above range, the current collector is less likely to generate heat due to Joule heat during high current density charging and discharging. Furthermore, the volume ratio of the current collector to the positive electrode active material becomes difficult to increase, and a decrease in battery capacity can be prevented.

<Electrode area>
From the viewpoint of increasing stability at high output and high temperature, it is preferable that the area of the positive electrode active material layer be larger than the outer surface area of the battery outer case. Specifically, the total area of the positive electrode relative to the surface area of the exterior of the non-aqueous electrolyte battery is preferably 20 times or more, more preferably 40 times or more, in terms of area ratio. In the case of a square shape with a bottom, the outer surface area of the outer case refers to the total area calculated from the length, width, and thickness of the case filled with the power generation element, excluding the protruding parts of the terminals. . In the case of a cylindrical shape with a bottom, the geometric surface area is approximated by assuming that the case portion filled with the power generation element excluding the protruding portion of the terminal is a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode composite material layer facing the composite material layer containing the negative electrode active material. , refers to the sum of the areas calculated for each surface separately.

<Discharge capacity>
When using the above non-aqueous electrolyte, the electric capacity of the battery element housed in one battery exterior of the non-aqueous electrolyte battery (the electric capacity when the battery is discharged from a fully charged state to a discharged state) is If it is 1 ampere hour (Ah) or more, the effect of improving low-temperature discharge characteristics becomes large, so it is preferable. Therefore, the discharge capacity of the positive electrode plate is preferably 3Ah (ampere hour) or more, more preferably 4Ah or more, and preferably 100Ah or less, more preferably 70Ah or less, and particularly preferably 70Ah or less when fully charged. Design to be 50Ah or less.

Within the above range, voltage drop due to electrode reaction resistance does not become too large when drawing a large current, and deterioration of power efficiency can be prevented. Furthermore, the temperature distribution due to heat generated inside the battery during pulse charging and discharging does not become too large, resulting in poor durability for repeated charging and discharging, and heat dissipation efficiency is poor in response to sudden heat generation during abnormalities such as overcharging and internal short circuits. It is possible to avoid this phenomenon.

<Thickness of positive electrode plate>
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity, high output, and high rate characteristics, the thickness of the positive electrode active material layer after subtracting the thickness of the current collector should be The thickness is preferably 10 μm or more, more preferably 20 μm or more, and preferably 200 μm or less, and more preferably 100 μm or less.

<2-4. Negative electrode>
In one embodiment of the present invention, the negative electrode includes a current collector and a negative electrode active material layer provided on the current collector.
The negative electrode active material used in the negative electrode will be described below. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions. Specific examples include carbonaceous materials having carbon as a constituent element, alloy materials, and the like. These may be used alone or in any combination of two or more.

<2-4-1. Negative electrode active material>
As described above, examples of the negative electrode active material include carbonaceous materials, alloy materials, and the like.

Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, (6) resin-coated graphite, etc. It will be done.

(1) Examples of natural graphite include scaly graphite, flaky graphite, soil graphite, and/or graphite particles obtained by subjecting these graphites as raw materials to processes such as spheroidization and densification. Among these, from the viewpoint of particle filling properties and charge/discharge rate characteristics, spherical or ellipsoidal graphite that has been subjected to spheroidization treatment is particularly preferred.

As the device used for the spheroidization process, for example, a device that repeatedly applies mechanical effects such as compression, friction, and shear force, mainly impact force but also particle interaction, to the particles can be used.

Specifically, the casing has a rotor with many blades installed inside it, and as the rotor rotates at high speed, it applies impact compression, friction, and shear forces to the raw material of natural graphite (1) introduced inside. It is preferable to use an apparatus that applies a mechanical action such as the above to perform a spheronization process. Moreover, an apparatus having a mechanism for repeatedly applying mechanical action by circulating the raw material is preferable.

For example, when performing spheronizing treatment using the above-mentioned apparatus, the circumferential speed of the rotating rotor is preferably set to 30 to 100 m/sec, more preferably 40 to 100 m/sec, and 50 to 100 m/sec. More preferably, it is set to seconds. Although the spheroidization process can be carried out by simply passing the raw material through, it is preferable to circulate or retain the material in the apparatus for 30 seconds or more, and it is preferable to perform the process by circulating or retaining the raw material in the apparatus for 1 minute or more. is more preferable.

(2) Artificial graphite includes coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin, etc. are heated at a temperature usually above 2500°C and usually below 3200°C. Examples include those manufactured by graphitizing at high temperature and pulverizing and/or classifying as necessary.

At this time, a silicon-containing compound, a boron-containing compound, or the like can also be used as a graphitization catalyst. Another example is artificial graphite obtained by graphitizing mesocarbon microbeads separated during the heat treatment process of pitch. Furthermore, artificial graphite in the form of granulated particles consisting of primary particles may also be mentioned. For example, a graphitizable carbonaceous material powder such as mesocarbon microbeads or coke, a graphitizable binder such as tar or pitch, and a graphitization catalyst are mixed, graphitized, and crushed as necessary. Examples include graphite particles obtained by aggregating or bonding a plurality of flat particles such that their orientation planes are non-parallel.

(3) Amorphous carbon is amorphous carbon that has been heat-treated at least once in a temperature range that does not cause graphitization (range 400 to 2200°C) using a graphitizable carbon precursor such as tar or pitch as a raw material. Examples include particles and amorphous carbon particles heat-treated using a non-graphitizable carbon precursor such as a resin as a raw material.

(4) Examples of carbon-coated graphite include those obtained as follows. Natural graphite and/or artificial graphite and a carbon precursor, which is an organic compound such as tar, pitch, or resin, are mixed and heat-treated at least once in the range of 400 to 2300°C. The heat-treated natural graphite and/or artificial graphite is used as core graphite, and this is coated with amorphous carbon to obtain a carbon-graphite composite. This carbon-graphite composite is listed as carbon-coated graphite (4).

Further, the composite form may be a form in which the entire or part of the surface of nuclear graphite is coated with amorphous carbon, or a form in which a plurality of primary particles are combined with carbon originating from the carbon precursor as a binder. It's okay. Alternatively, natural graphite and/or artificial graphite can be reacted with hydrocarbon gas such as benzene, toluene, methane, propane, aromatic volatiles, etc. at high temperature to deposit carbon on the graphite surface (CVD). The carbon graphite composite can be obtained.

(5) Examples of graphite-coated graphite include those obtained as follows. Natural graphite and/or artificial graphite and a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin are mixed and heat-treated at least once in a temperature range of about 2400 to 3200°C. Heat-treated natural graphite and/or artificial graphite is used as core graphite, and graphite-coated graphite (5) is obtained by covering the whole or part of the surface of the core graphite with a graphitized material.

(6) Resin-coated graphite is, for example, natural graphite and/or artificial graphite obtained by mixing natural graphite and/or artificial graphite with resin, etc., and drying at a temperature of less than 400°C as core graphite, and resin etc. It can be obtained by coating the nuclear graphite with

Furthermore, the carbonaceous materials (1) to (6) described above may be used alone or in combination of two or more in any combination and ratio.

Organic compounds such as tar, pitch, and resin used in the carbonaceous materials (2) to (5) above include coal-based heavy oil, DC-based heavy oil, cracked petroleum heavy oil, and aromatic hydrocarbons. , N-ring compounds, S-ring compounds, polyphenylene, organic synthetic polymers, natural polymers, thermoplastic resins, and thermosetting resins. Further, the raw material organic compound may be used after being dissolved in a low-molecular organic solvent in order to adjust the viscosity during mixing.

Furthermore, as the natural graphite and/or artificial graphite that is a raw material for nuclear graphite, natural graphite subjected to spheroidization treatment is preferable.

Next, the alloy material used as the negative electrode active material may be lithium alone, a single metal or alloy forming a lithium alloy, or their oxides, carbides, nitrides, silicones, etc., as long as they can absorb and release lithium. It may be any compound such as a compound, a sulfide or a phosphide, and is not particularly limited. The elemental metals and alloys forming the lithium alloy are preferably materials containing metals and metalloid elements of groups 13 and 14 (that is, excluding carbon), and more preferably elemental metals of aluminum, silicon, and tin, and materials containing these elements. It is an alloy or compound containing atoms, and more preferably one having silicon or tin as a constituent element, such as elemental metals of silicon and tin, and alloys or compounds containing these atoms.
One type of these may be used alone, or two or more types may be used in combination in any combination and ratio.

<Metal particles that can be alloyed with Li>
When using single metals and alloys forming lithium alloys, or compounds such as their oxides, carbides, nitrides, silicides, sulfides, or phosphides as negative electrode active materials, the metals that can be alloyed with Li are: It is in particle form. Methods for confirming that the metal particles are metal particles that can be alloyed with Li include identification of the metal particle phase by X-ray diffraction, observation of the particle structure by an electron microscope, EDX elemental analysis, and fluorescent X-ray analysis. Examples include elemental analysis.

Any conventionally known metal particles that can be alloyed with Li can be used, but from the viewpoint of the capacity and cycle life of the non-aqueous electrolyte battery, the metal particles include, for example, Fe, Co, and Sb. , Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, As, Nb, Mo, Cu, Zn, Ge, In, Ti, and W. Preferably, it is a metal or a compound thereof. Moreover, an alloy consisting of two or more types of metals may be used, and the metal particles may be alloy particles formed of two or more types of metal elements. Among these, metals selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or metal compounds thereof are preferred.

Examples of the metal compound include metal oxides, metal nitrides, metal carbides, and the like. Furthermore, an alloy consisting of two or more metals may be used.

Among metal particles that can be alloyed with Li, Si or a Si metal compound is preferred. The Si metal compound is preferably a Si metal oxide. Si or a Si metal compound is preferable from the viewpoint of increasing the capacity of the battery. In this specification, Si or Si metal compounds are collectively referred to as Si compounds. Specific examples of the Si compound include SiO _x , SiN _x , SiC _x , SiZ _x O _y (Z=C, N), and the like. The Si compound is preferably a Si metal oxide, and the Si metal oxide is represented by the general formula SiO _x . This general formula SiO _x is obtained using Si dioxide (SiO ₂ ) and metal Si (Si) as raw materials, and the value of x is usually 0≦x<2. SiO _x has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals allow alkali ions such as lithium ions to enter and exit easily, making it possible to obtain batteries with high capacity. .

The Si metal oxide is specifically expressed as SiO _x , where x is 0≦x<2, more preferably 0.2 or more and 1.8 or less, and even more preferably 0. It is 4 or more and 1.6 or less, particularly preferably 0.6 or more and 1.4 or less. Within this range, the battery has a high capacity and at the same time it is possible to reduce the irreversible capacity due to the combination of Li and oxygen.

<Amount of oxygen contained in metal particles that can be alloyed with Li>
The amount of oxygen contained in the metal particles that can be alloyed with Li is not particularly limited, but is usually 0.01% by mass or more and 8% by mass or less, preferably 0.05% by mass or more and 5% by mass or less. The oxygen distribution within the particles may be present near the surface, within the particles, or uniformly within the particles, but oxygen is preferably present near the surface. When the amount of oxygen contained in the metal particles that can be alloyed with Li is within the above range, the strong bond between the metal particles and O (oxygen atoms) suppresses the volumetric expansion associated with secondary charging and discharging of the non-aqueous electrolyte battery. Moreover, it is preferable because it can provide a non-aqueous electrolyte battery with excellent cycle characteristics.

<Negative electrode active material containing metal particles and graphite particles that can be alloyed with Li>
The negative electrode active material may contain metal particles and graphite particles that can be alloyed with Li. The negative electrode active material may be a mixture in which metal particles that can be alloyed with Li and graphite particles are mixed in the state of independent particles, or metal particles that can be alloyed with Li can be mixed on the surface of graphite particles. /or it may be a complex existing internally.

The above-mentioned composite of metal particles and graphite particles that can be alloyed with Li (also referred to as composite particles) is not particularly limited as long as it contains metal particles and graphite particles that can be alloyed with Li. However, particles in which metal particles and graphite particles that can be alloyed with Li are integrated through physical and/or chemical bonding are preferable. A more preferable form is a state in which the metal particles and graphite particles that can be alloyed with Li are dispersed within the particles to the extent that the metal particles and graphite particles are present at least both on the surface of the composite particle and inside the bulk. It is in such a form that graphite particles are present to unite them through physical and/or chemical bonding. A more specific preferred form is a composite material composed of at least metal particles that can be alloyed with Li and graphite particles, wherein the graphite particles, preferably natural graphite, have a curved surface and a folded structure. The composite material (negative electrode active material) is characterized in that metal particles capable of alloying with Li are present in the gaps within the structure. Further, the gap may be a void, or a substance such as amorphous carbon, graphite material, resin, etc. that buffers the expansion and contraction of metal particles that can be alloyed with Li is present in the gap. It's okay.

<Content ratio of metal particles that can be alloyed with Li>
The content ratio of metal particles that can be alloyed with Li to the total of metal particles that can be alloyed with Li and graphite particles is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1. It is 0% by mass or more, more preferably 2.0% by mass or more. Also, usually 99% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, even more preferably 20% by mass or less, especially Preferably it is 15% by mass or less, most preferably 10% by mass or less. When the content ratio of metal particles that can be alloyed with Li is within this range, it is possible to control side reactions on the Si surface, and it is possible to obtain sufficient capacity in a non-aqueous electrolyte battery. preferable.

<Coverage rate>
In this embodiment, the negative electrode active material may be coated with a carbonaceous material or a graphite material. Among these, coating with an amorphous carbonaceous material is preferable from the viewpoint of acceptability of lithium ions. This coverage is usually 0.5% or more and 30% or less, preferably 1% or more and 25% or less, and more preferably 2% or more and 20% or less. The upper limit of the coverage rate is determined from the viewpoint of reversible capacity when the battery is assembled, and the lower limit of the coverage rate is determined from the viewpoint that the core carbonaceous material is uniformly coated with amorphous carbon and formed into strong granules. From the viewpoint of the particle size of the particles obtained when pulverized after firing, the above range is preferable.

Note that the coverage (content) of carbides derived from organic compounds in the finally obtained negative electrode active material is determined by the amount of negative electrode active material, the amount of organic compounds, and the residual amount measured by the micro method in accordance with JIS K 2270. It can be calculated using the following formula depending on the charcoal ratio.

Formula: Coverage rate (%) of carbide derived from organic compound = (mass of organic compound x residual carbon rate x 100)
/{mass of negative electrode active material + (mass of organic compound x residual carbon percentage)}

<Internal porosity>
The internal porosity of the negative electrode active material is usually 1% or more, preferably 3% or more, more preferably 5% or more, still more preferably 7% or more. Further, it is usually less than 50%, preferably 40% or less, more preferably 30% or less, even more preferably 20% or less. If this internal porosity is too small, the amount of liquid within the particles of the negative electrode active material tends to decrease in a non-aqueous electrolyte battery. On the other hand, if the internal porosity is too large, the interparticle gaps tend to decrease when used as an electrode. It is preferable that the lower limit of the internal porosity is in the above range from the viewpoint of charge/discharge characteristics, and the upper limit is in the above range from the viewpoint of diffusion of the non-aqueous electrolyte. Further, as described above, this gap may be a void, or a material such as amorphous carbon, graphite material, resin, etc. that buffers the expansion and contraction of metal particles that can be alloyed with Li may be used in the gap. They may exist or gaps may be filled with these.

<2-4-2. Configuration and manufacturing method of negative electrode>
For producing the negative electrode, any known method can be used as long as the effects of the present invention are not significantly impaired. For example, it is formed by adding a binder, a solvent, and if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, applying this to a current collector, drying it, and then pressing it. can do.

Further, the alloy material negative electrode can be manufactured using any known method. Specifically, negative electrode manufacturing methods include, for example, adding a binder, a conductive material, etc. to the negative electrode active material described above and then roll-molding it as it is to make a sheet electrode, or compression molding it to make a pellet electrode. Although methods such as coating, vapor deposition, sputtering, plating, etc. on a negative electrode current collector (hereinafter sometimes referred to as "negative electrode current collector"), the above-mentioned negative electrode A method of forming a thin film layer (negative electrode active material layer) containing an active material is used. In this case, a binder, a thickener, a conductive material, a solvent, etc. are added to the above-mentioned negative electrode active material to form a slurry, and this is applied to the negative electrode current collector, dried, and then pressed to increase the density. , forming a negative electrode active material layer on the negative electrode current collector;

Examples of the material of the negative electrode current collector include steel, copper, copper alloy, nickel, nickel alloy, stainless steel, and the like. Among these, copper is preferred, and copper foil is more preferably used, from the viewpoint of ease of processing into a thin film and cost.

The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. If the negative electrode current collector is too thick, the capacity of the nonaqueous electrolyte battery as a whole may decrease too much, while if it is too thin, it may become difficult to handle.

Note that in order to improve the binding effect with the negative electrode active material layer formed on the surface, the surfaces of these negative electrode current collectors are preferably roughened in advance. Surface roughening methods include blasting, rolling with a rough roll, coated abrasive paper to which abrasive particles are fixed, a grindstone, an emery buff, a machine that polishes the current collector surface with a wire brush equipped with a steel wire, etc. Examples include a mechanical polishing method, an electrolytic polishing method, a chemical polishing method, and the like.

Furthermore, in order to reduce the mass of the negative electrode current collector and improve the energy density per mass of the battery, a perforated negative electrode current collector such as expanded metal or punched metal can also be used. The mass of this type of negative electrode current collector can be freely changed by changing its aperture ratio. Further, when negative electrode active material layers are formed on both sides of this type of negative electrode current collector, peeling of the negative electrode active material layer becomes more difficult to occur due to the rivet effect through the holes. However, if the aperture ratio becomes too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, so that the adhesive strength may decrease on the contrary.

A slurry for forming a negative electrode active material layer is usually prepared by adding a binder, a thickener, etc. to the negative electrode material. Note that the "negative electrode material" in this specification refers to a material that is a combination of a negative electrode active material and a conductive material.

The content of the negative electrode active material in the negative electrode material is usually preferably 70% by mass or more, particularly 75% by mass or more, and usually 97% by mass or less, particularly preferably 95% by mass or less. If the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient, and if it is too large, the content of the conductive material is relatively insufficient, resulting in a lack of electricity as a negative electrode. It tends to be difficult to ensure conductivity. Note that when two or more negative electrode active materials are used together, the total amount of the negative electrode active materials may satisfy the above range.

Examples of the conductive material used for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. One type of these may be used alone, or two or more types may be used in combination in any combination and ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material also acts as an active material. The content of the conductive material in the negative electrode material is usually 3% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, preferably 25% by mass or less. If the content of the conductive material is too small, the conductivity tends to be insufficient, and if the content is too large, the content of the negative electrode active material etc. tends to be relatively insufficient, resulting in a tendency for the battery capacity and strength to decrease. In addition, when two or more electrically conductive materials are used together, the total amount of the electrically conductive materials may satisfy the above range.

As the binder used for the negative electrode, any material can be used as long as it is stable to the solvent and electrolyte used during electrode manufacture. Examples include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and the like. One type of these may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the binder is usually 0.5 parts by mass or more, preferably 1 part by mass or more, and usually 10 parts by mass or less, preferably 8 parts by mass or less, based on 100 parts by mass of the negative electrode material. . If the binder content is too low, the resulting negative electrode tends to lack strength, and if it is too high, the battery capacity and conductivity tend to be insufficient due to a relative lack of negative electrode active material, etc. becomes. In addition, when using two or more binders together, the total amount of the binders may satisfy the above range.

Examples of the thickener used in the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. One type of these may be used alone, or two or more types may be used in combination in any combination and ratio. A thickener may be used as necessary, but when used, the content of the thickener in the negative electrode active material layer should generally be in the range of 0.5% by mass or more and 5% by mass or less. is preferred.

The slurry for forming the negative electrode active material layer is prepared by mixing the above negative electrode active material with a conductive material, a binder, and a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. Ru. Water is usually used as the aqueous solvent, but alcohols such as ethanol and organic solvents such as cyclic amides such as N-methylpyrrolidone may be used in combination in an amount of 30% by mass or less based on water. You can also do it. In addition, organic solvents include cyclic amides such as N-methylpyrrolidone; linear amides such as N,N-dimethylformamide and N,N-dimethylacetamide; aromatic hydrocarbons such as anisole, toluene, and xylene. alcohols such as butanol and cyclohexanol; among them, cyclic amides such as N-methylpyrrolidone;
, N-dimethylformamide, N,N-dimethylacetamide and the like are preferred. In addition, any one type of these may be used alone, or two or more types may be used in combination in any combination and ratio.

The obtained slurry is applied onto the above-mentioned negative electrode current collector, dried, and then pressed to form a negative electrode active material layer and obtain a negative electrode. The coating method is not particularly limited, and any known method can be used. The drying method is not particularly limited either, and known methods such as natural drying, heat drying, reduced pressure drying, etc. can be used.

<Electrode density>
The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g·cm ^-3 or more, and 1.2 g·cm ^-3 or more. is more preferably 1.3 g·cm ^-3 or more, particularly preferably 2.2 g·cm ^-3 or less, more preferably 2.1 g·cm ^-3 or less, and 2.0 g·cm ^-3 or less. More preferably, it is 1.9 g·cm ⁻³ or less. If the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles will be destroyed, resulting in an increase in the initial irreversible capacity of the non-aqueous electrolyte battery, or a decrease in the current collector/negative electrode active material. This may lead to deterioration of high current density charge/discharge characteristics due to decreased permeability of the non-aqueous electrolyte near the interface. Furthermore, if the density of the negative electrode active material is below the above range, the conductivity between the negative electrode active materials may decrease, battery resistance may increase, and the capacity per unit volume may decrease.

<2-5. Separator＞
A separator is usually interposed between the positive electrode and the negative electrode to prevent short circuits. In this case, the non-aqueous electrolytic solution of the present invention is usually used by impregnating the separator.

There are no particular restrictions on the material or shape of the separator, and any known material can be used as long as it does not significantly impair the effects of the present invention. Among them, resins, glass fibers, inorganic materials, etc., which are made of materials that are stable to the non-aqueous electrolyte of the present invention, and which are in the form of porous sheets or non-woven fabrics with excellent liquid retention properties are used. is preferred.

As materials for the resin and glass fiber separators, for example, polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, glass filters, etc. can be used. Among them, glass filters and polyolefins are preferred, and polyolefins are more preferred. One type of these materials may be used alone, or two or more types may be used in combination in any combination and ratio.

The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less. If the separator is too thin than the above range, the insulation properties and mechanical strength may decrease. Moreover, if the thickness is too thick than the above range, not only battery performance such as rate characteristics may deteriorate, but also the energy density of the non-aqueous electrolyte battery as a whole may decrease.

Furthermore, when using a porous material such as a porous sheet or nonwoven fabric as a separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, if it is too large than the above range, the mechanical strength of the separator tends to decrease and the insulation properties tend to decrease.

Further, the average pore diameter of the separator is also arbitrary, but it is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. When the average pore diameter exceeds the above range, short circuits tend to occur. Moreover, if it falls below the above range, the film resistance may increase and the rate characteristics may deteriorate.

On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. things are used.

As for the form, those in the form of a thin film such as nonwoven fabric, woven fabric, and microporous film are used. In the case of a thin film, one having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the independent thin film shape described above, a separator can be used in which a composite porous layer containing the inorganic particles is formed on the surface layer of the positive electrode and/or negative electrode using a resin binder. For example, a porous layer may be formed on both sides of the positive electrode using alumina particles having a 90% particle size of less than 1 μm and a fluororesin as a binder.

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure in which the above-mentioned positive electrode plate and negative electrode plate are interposed with the above-mentioned separator in between, and an electrode group in which the above-mentioned positive electrode plate and negative electrode plate are spirally wound with the above-mentioned separator interposed in between. Either is fine. The ratio of the volume of the electrode group to the internal battery volume (hereinafter referred to as electrode group occupancy) is usually 40% or more, preferably 50% or more, and usually 90% or less, and 80% or less. preferable. The lower limit of the electrode group occupancy is preferably within the above range from the viewpoint of battery capacity. In addition, the upper limit of the electrode group occupancy rate is set in order to secure the gap space, from the viewpoint of various characteristics such as the repeated charging and discharging performance of the battery and high temperature storage, and from the viewpoint of avoiding activation of the gas release valve that releases internal pressure to the outside. It is preferable to set it as the said range. If the gap space is too small, the battery's high temperature will cause the components to expand and the vapor pressure of the liquid electrolyte to increase, increasing the internal pressure, which will affect the battery's charge/discharge cycle performance and high-temperature storage. This may reduce properties or even activate a gas release valve that releases internal pressure to the outside.

[Current collection structure]
Although the current collection structure is not particularly limited, in order to more effectively achieve the improvement in discharge characteristics by the non-aqueous electrolyte described above, it is preferable to have a structure that reduces the resistance of wiring parts and joint parts. . When the internal resistance is reduced in this way, the effects of using the above-mentioned non-aqueous electrolyte are particularly well exhibited.

When the electrode group has the above-mentioned laminated structure, a structure in which the metal core portions of each electrode layer are bundled and welded to a terminal is preferably used. When the area of one electrode becomes large, the internal resistance becomes large, so it is also suitable to provide a plurality of terminals within the electrode to reduce the resistance. When the electrode group has the above-mentioned wound structure, the internal resistance can be lowered by providing a plurality of lead structures on each of the positive and negative electrodes and bundling them into a terminal.

[Protective element]
Protection elements include PTC (Positive Temperature Coefficient) elements, which increase resistance when abnormal heat generation or excessive current flows, thermal fuses, thermistors, and devices that prevent current flowing through the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation. Examples include a valve that shuts off (current cutoff valve). It is preferable that the protection element is selected so that it does not operate under normal use of high current, and from the viewpoint of high output, it is more preferable to use a design that does not lead to abnormal heat generation or thermal runaway even without the protection element.

[Exterior body]
The non-aqueous electrolyte battery of this embodiment is usually configured by housing the above-mentioned non-aqueous electrolyte, a negative electrode, a positive electrode, a separator, etc. in an exterior body (exterior case). There is no limit to this exterior body, and any known exterior body can be used as long as it does not significantly impair the effects of the present invention.

The material of the outer case is not particularly limited as long as it is stable to the non-aqueous electrolyte used. Specifically, metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, magnesium alloys, nickel, and titanium, or laminated films of resin and aluminum foil are preferably used.

For exterior cases using the above metals, the metals are welded together using laser welding, resistance welding, or ultrasonic welding to create a hermetically sealed structure, or the metals are caulked using a resin gasket. There are things that do. Examples of exterior cases using the above-mentioned laminate film include those in which resin layers are heat-sealed to each other to form a hermetically sealed structure. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when creating a sealed structure by heat-sealing a resin layer via a current collector terminal, the metal and resin are joined, so the intervening resin may be a resin with a polar group or a modified resin with a polar group introduced. Resin is preferably used.

Further, the shape of the exterior body is also arbitrary, and may be, for example, cylindrical, square, laminated, coin-shaped, large-sized, or the like.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Reference Examples, but the present invention is not limited to these Examples unless it exceeds the gist thereof.

[Preparation of EC solution containing Fe(PF ₆ ) ₂ ]
In an argon glove box, 0.25 g (2.0 mmol) of FeCl ₂ was weighed into a 50 mL beaker and suspended in acetonitrile (AN). While stirring this, 1.01 g (4.0 mmol) of AgPF ₆ was slowly added in small portions, followed by stirring at 40° C. for 6 hours. As the reaction progressed, a white solid of AgCl was produced. After leaving it as it is overnight, AgCl was filtered off and the obtained filtrate was concentrated under reduced pressure to obtain 1.09 g of a white solid of [Fe(AN) _n ](PF ₆ ) ₂ (n=0 to 6). Obtained. Approximately 3 g of ethylene carbonate (EC) melted at 45°C was added to 0.79 g of the obtained white solid to dissolve the solid, and by vacuuming at 40°C for 8 hours, AN, which was the coordinating solvent, was removed. was removed. The resulting insoluble components were filtered off to obtain 3.08 g of an EC solution containing Fe(PF ₆ ) ₂ .

[Preparation of positive electrode]
90 parts by mass of Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ as a positive electrode active material, 7 parts by mass of acetylene black as a conductive material, and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder. were mixed in an N-methylpyrrolidone solvent using a disperser to form a slurry. This was coated uniformly on one side of a 15 μm thick aluminum foil, dried, and then pressed to form a positive electrode.

[Preparation of negative electrode]
98 parts by mass of natural graphite, 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose 1% by mass) and an aqueous dispersion of styrene-butadiene rubber (styrene-butadiene rubber) as thickeners and binders. 1 part by mass (concentration 50% by mass) was added and mixed with a disperser to form a slurry. The obtained slurry was applied to both sides of a 10 μm thick copper foil, dried, and then pressed to form a negative electrode.

[Preparation of non-aqueous electrolyte]
Under a dry argon atmosphere, based on an EC solution containing Fe(PF ₆ ) ₂ , the iron ion concentration in the mixed solvent was as shown in Table 1, and the solvent composition was ethylene carbonate (EC) and ethyl methyl carbonate (EMC). , dimethyl carbonate (DMC) at a volume ratio of 3:4:3, LiPF ₆ was diluted with EC, EMC, and DMC, and thoroughly dried. 1 mol/L (12.3% by mass, (as a concentration in a non-aqueous electrolyte). Note that the non-aqueous electrolyte that does not contain Fe(PF ₆ ) ₂ is referred to as reference electrolyte 1. FSO ₃ Li was added to the Fe(PF ₆ ) ₂ -containing non-aqueous electrolyte solution prepared above or reference electrolyte 1, and the non-aqueous electrolyte of Examples 1-1 to 1-2 described in Table 1 below was prepared. Non-aqueous electrolyte solutions of Comparative Examples 1-2 and 1-3 were prepared. Comparative Example 1-1 is the reference electrolytic solution 1 itself. In addition, the non-aqueous electrolytes of Comparative Examples 1-4 and 1-5 were prepared without adding FSO ₃ Li. In the table, the content of FSO ₃ Li indicates the amount added, and the content of Fe element (iron ion) is a value determined based on the measurement results of inductively coupled radio frequency plasma emission spectroscopy (ICP-AES) described below. . In addition, "content (mass %)" and "content (mass ppm)" in the table are contents when reference electrolyte solution 1 is 100 mass %.

<Measurement of Fe element content in non-aqueous electrolyte>
100 μL (approximately 130 mg) of the non-aqueous electrolyte was collected. The fractionated non-aqueous electrolyte was weighed into a PTFE beaker, added with an appropriate amount of concentrated nitric acid, and subjected to wet decomposition on a hot plate.
The content of Fe element (iron ion) was measured using Li and acid concentration matching calibration curve method using Fischer Scientific, iCAP 7600duo).

[Manufacture of non-aqueous electrolyte secondary battery]
A battery element was produced by laminating the above positive electrode, negative electrode, and polyethylene separator in the order of negative electrode, separator, and positive electrode. This battery element was inserted into a bag made of a laminate film made of aluminum (40 μm thick) coated with a resin layer on both sides, with the positive and negative terminals protruding, and then the prepared non-aqueous electrolyte was poured into the bag. A laminate-type non-aqueous electrolyte secondary battery was produced by injecting the solution into the battery and vacuum-sealing it.

<Evaluation of non-aqueous electrolyte secondary batteries>
[Initial conditioning]
In a constant temperature bath at 25°C, the non-aqueous electrolyte secondary battery was heated to 4.2V at a current equivalent to 1/6C (1C refers to the current value that takes 1 hour to charge or discharge. The same applies hereinafter). After constant current-constant voltage charging (hereinafter referred to as CC-CV charging), the battery was discharged to 2.5V at 1/6C. CC-CV charging was performed at 1/6C to 4.1V. Thereafter, aging was performed at 60° C. for 12 hours. Thereafter, the battery was discharged to 2.5V at 1/6C to stabilize the non-aqueous electrolyte secondary battery. Furthermore, after performing CC-CV charging to 4.2V at 1/6C, initial conditioning was performed by discharging to 2.5V at 1/6C.

[Charge storage test]
After initial conditioning, the nonaqueous electrolyte secondary battery was again CC-CV charged to 4.2V at 1/6C, and then stored at high temperature at 60°C for 168 hours. After storing at high temperature and cooling the battery, calculate the discharge capacity when discharging the non-aqueous electrolyte secondary battery to 2.5V at 1/6C at 25℃, and calculate this as the "residual capacity (1 week)". And so. Table 1 below shows the remaining capacity of Examples 1-1 to 1-2 and Comparative Examples 1-1 to 1-5, when the remaining capacity (1 week) of Comparative Example 1-1 is 100. (1 week) values are shown.
After the charge storage test, the non-aqueous electrolyte secondary battery was again CC-CV charged to 4.2V at 1/6C, and then stored at high temperature at 60°C for 336 hours. The discharge capacity when the non-aqueous electrolyte secondary battery was discharged to 2.5V at 1/6C at 25°C was determined, and this was defined as the "residual capacity (2 weeks)". Table 1 below shows the remaining capacity of Examples 1-1 to 1-2 and Comparative Examples 1-1 to 1-5, when the remaining capacity (2 weeks) of Comparative Example 1-1 is 100. (2 weeks) Shows the value of remaining capacity (2 weeks).

A comparison between Comparative Example 1-1 and Comparative Example 1-2 showed that the remaining capacity of the battery increased when the electrolytic solution contained FSO ₃ Li. On the other hand, from Comparative Examples 1-1 to 1-3 and Example 1-1, even if the electrolytic solution contains FSO ₃ Li, if it contains iron ions exceeding a certain amount, the remaining capacity will decrease. It has been shown. On the other hand, from Examples 1-1 and 1-2, even when the electrolyte contains FSO ₃ Li and the same amount of iron ions as in Comparative Examples 1-4 and 1-5, , it was shown that the residual capacity was improved more than when FSO ₃ Li was contained alone. In addition, the remaining capacity after two weeks of storage shows that the deterioration of the non-aqueous electrolyte battery due to changes over time is suppressed by the electrolyte containing a specific amount of iron ions and FSO ₃ Li. It has been shown that when the aqueous electrolyte contains FSO ₃ Li and a specific amount of iron ions, the charge storage characteristics of a nonaqueous electrolyte secondary battery in a high-temperature environment are improved. Furthermore, from a comparison between Comparative Examples 1-2 and 1-3, it was found that when the amount of iron ions contained in the electrolyte solution is outside a specific range, the effect of adding FSO ₃ Li is impaired, and the non-aqueous electrolyte battery It can be seen that the remaining capacity of

<Example 2-1 to Example 2-6, Comparative Example 2-1 to Comparative Example 2-6>
[Preparation of positive electrode]
A positive electrode was produced in the same manner as in Example 1-1.

[Preparation of negative electrode]
A negative electrode was produced in the same manner as in Example 1-1.

[Preparation of non-aqueous electrolyte]
Performed using tris(2,4-pentanedionato)iron(III) (Fe(acac) ₃ ) or iron(III) trifluoromethanesulfonate (Fe(OTf) ₃ ) in place of Fe(PF ₆ ) ₂ FSO ₃ Li was added to the iron ion-containing non-aqueous electrolytic solution or reference electrolyte 1 prepared in the same manner as in Example 1-1, etc., and the non-aqueous electrolyte of Examples 2-1 to 2-6 shown in Table 2 below An aqueous electrolyte was prepared. Comparative Example 1-1 is the reference electrolytic solution 1 itself. In addition, the non-aqueous electrolytes of Comparative Examples 2-1 to 2-6 were prepared without adding FSO ₃ Li. In addition, "content (mass %)" and "content (mass ppm)" in the table are contents when reference electrolyte solution 1 is 100 mass %. In addition, in the table, the content of FSO ₃ Li indicates the amount added, and the content of Fe element (iron ion) is determined based on the measurement results of inductively coupled radio frequency plasma emission spectroscopy (ICP-AES), as in Example 1. This is the value calculated based on.

[Manufacture of non-aqueous electrolyte secondary battery]
A laminate type non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-1, except that the above-mentioned positive electrode, negative electrode, and non-aqueous electrolyte were used.

<Evaluation of non-aqueous electrolyte secondary batteries>
Initial conditioning and charge storage tests were conducted in the same manner as in Example 1-1. The remaining capacity (1 week) and remaining capacity (2 weeks) were determined in the same manner as in Example 1-1. Table 2 below shows the residual capacity (1 week) of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-6 when the residual capacity (1 week) of Comparative Example 1-1 is 100. 1 week), the remaining capacity of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-6 when the remaining capacity (2 weeks) of Comparative Example 1-1 is set to 100 (2 weeks) are shown together with the results of Comparative Example 1-1 and Comparative Example 1-2.

From Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-6, when the electrolytic solution contains a specific amount of iron ions and also contains FSO ₃ Li, FSO ₃ Li It was shown that the residual capacity was increased compared to the case of containing alone. Additionally, the remaining capacity after two weeks of storage showed that deterioration of non-aqueous electrolyte batteries due to changes over time was suppressed by the electrolyte containing a specific amount of iron ions and FSO ₃ Li. . That is, it was shown that the charge storage characteristics of a non-aqueous electrolyte secondary battery in a high-temperature environment are improved. From Examples 1-1 to 1-2 and 2-1 to 2-6, regardless of the valence of the iron ion and the type of counter anion, that is, regardless of the iron ion source, It has been shown that when the non-aqueous electrolyte contains FSO ₃ Li and a specific amount of iron ions, the charge storage characteristics of the non-aqueous electrolyte secondary battery in a high-temperature environment are improved.

For example, the shelf life of a battery is usually about 200 days for vehicle manufacturers. Since the difference in remaining capacity after storage for one week and two weeks increases over time, it can be said that the longer the storage period is, the more pronounced the effects of the present invention will be.

According to the present invention, it is possible to realize a non-aqueous electrolyte battery having excellent charge storage characteristics in a high-temperature environment, which is useful.
Furthermore, the non-aqueous electrolyte and non-aqueous electrolyte battery of the present invention can be used in various known applications using a non-aqueous electrolyte or a non-aqueous electrolyte battery. Specific examples include notebook computers, pen input computers, mobile computers, e-book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, headphone stereos, video movies, LCD televisions, handy cleaners, portable CDs, and mini discs. , transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, motorcycles, motorized bicycles, bicycles, lighting equipment, toys, game equipment, watches, power tools, strobes, cameras, home backups Examples include power sources, backup power sources for business offices, power sources for load leveling, natural energy storage power sources, and lithium ion capacitors.

Claims (6)

A non-aqueous electrolytic solution containing FSO ₃ Li, containing iron ions in an amount of 1 mass ppm or more and 100 mass ppm or less, and having an FSO ₃ Li content of 0.001 mass % or more and 10.0 mass % or less . A non-aqueous electrolyte battery comprising a positive electrode and a negative electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte, the non-aqueous electrolyte containing FSO ₃ Li and containing iron ions in an amount of 1 mass ppm or more and 100 mass ppm. A non-aqueous electrolyte battery , wherein the content of FSO ₃ Li in the non-aqueous electrolyte is 0.001% by mass or more and 10.0% by mass or less. The positive electrode has a current collector and a positive electrode active material layer provided on the current collector, and the positive electrode active material is a metal oxide represented by the following composition formula ( 1 ). The described non-aqueous electrolyte battery.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ ...(1)
(In the above formula (1), a1, b1, c1 and d1 satisfy 0.90≦a1≦1.10, 0<b1<0.4, b1+c1+d1=1. M is Mn, Al, Mg, Zr , represents at least one element selected from the group consisting of Fe, Ti, and Er.) The positive electrode has a current collector and a positive electrode active material layer provided on the current collector, and the positive electrode active material is a metal oxide represented by the following compositional formula ( 2 ). The described non-aqueous electrolyte battery.
Li _a2 Ni _b2 Co _c2 M _d2 O ₂ ...(2)
(In the above formula (2), a2, b2, c2 and d2 satisfy 0.90≦a2≦1.10, 0.4≦b2<1.0, b2+c2+d2=1. M is Mn, Al, Mg , represents at least one element selected from the group consisting of Zr, Fe, Ti, and Er.) The nonaqueous electrolyte battery according to any one of claims 2 to 4 , wherein the positive electrode is an NMC positive electrode, and the content of nickel element in the NMC positive electrode is 30 mol% or more. 6. The nonaqueous electrolyte battery according to claim 2 , wherein the positive electrode is an NMC positive electrode, and the content of nickel element in the NMC positive electrode is 40 mol% or more.