Deactivator for nonaqueous secondary battery and method for deactivating nonaqueous secondary battery

Abstract

To deactivate a nonaqueous secondary battery more quickly with a smaller amount of deactivator.SOLUTION: A deactivator that deactivates a nonaqueous secondary battery includes: a redox shuttle agent whose oxidation-reduction potential, relative to a Li reference potential, is higher than that of a negative electrode active material of the nonaqueous secondary battery and lower than that of a positive electrode active material of the nonaqueous secondary battery; and N-Methyl-2-pyrrolidone.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a passivator for a non-aqueous secondary battery and a method for passivating a non-aqueous secondary battery. [Background technology]

[0002] Conventionally, when recycling or disposing of nonaqueous secondary batteries, a deactivation process is performed to deactivate the recovered batteries. For example, one possible process involves connecting the recovered batteries to a charge / discharge device and discharging them to 0 V. However, this process can take a long time. Furthermore, if the recovered batteries have a current interrupt device (CID), they cannot be discharged at all. Therefore, adding a redox shuttle agent such as a 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-based compound to the recovered batteries has been proposed (see Patent Document 1). This allows the battery voltage of nonaqueous secondary batteries to be safely and quickly reduced to 0 V without the use of a charge / discharge device. Furthermore, using a phenothiazine-based compound as a redox shuttle agent in such deactivation methods has been proposed (see Patent Document 2). This is said to enable more rapid deactivation of nonaqueous secondary batteries. In particular, when a deactivator in which phenothiazine is dissolved in a solvent with high solubility and low viscosity, such as 1,2-dimethoxyethane, is used, it is possible to achieve both a high concentration of phenothiazine and an improved diffusion rate, thereby enabling rapid deactivation with a small amount of deactivator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-137137 [Patent Document 2] Japanese Patent Publication No. 2022-073888 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although Patent Document 2 shows that a non-aqueous secondary battery can be quickly deactivated with a small amount of deactivator, it has been desired to deactivate a non-aqueous secondary battery more quickly with an even smaller amount of deactivator.

[0005] The present disclosure has been made to solve such problems, and a main object of the present disclosure is to deactivate a non-aqueous secondary battery more quickly with a smaller amount of deactivator. [Means for solving the problem]

[0006] As a result of extensive research to achieve the above-mentioned object, the present inventors have found that adding a deactivating agent containing a redox shuttle agent and N-methyl-2-pyrrolidone to the interior of a nonaqueous secondary battery quickly deactivates the nonaqueous secondary battery, and have thus completed the invention of the present disclosure.

[0007] That is, the deactivator for the nonaqueous secondary battery of the present disclosure is A deactivator for deactivating a non-aqueous secondary battery, a redox shuttle agent having an oxidation-reduction potential, relative to a Li reference potential, higher than that of a negative electrode active material of the nonaqueous secondary battery and lower than that of a positive electrode active material of the nonaqueous secondary battery; and N-methyl-2-pyrrolidone; It is something.

[0008] The method for deactivating a nonaqueous secondary battery according to the present disclosure further comprises: an addition step of adding the nonaqueous secondary battery deactivator described above to the inside of the nonaqueous secondary battery, It is something. [Effects of the Invention]

[0009] This nonaqueous secondary battery deactivator and nonaqueous secondary battery deactivation method allows nonaqueous secondary batteries to be deactivated more quickly with a smaller amount of deactivator. The reason for this effect is presumably that, for example, by using a deactivator containing N-methyl-2-pyrrolidone in addition to a redox shuttle agent, the spread of the deactivator within the battery can be suppressed, and the concentration of the redox shuttle agent involved in the reaction can be maintained at a high level, allowing the redox shuttle to proceed smoothly even with a smaller amount of deactivator, resulting in more rapid battery deactivation. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing the outline of the configuration of a nonaqueous secondary battery 20. FIG. [Figure 2] FIG. 2 is an explanatory diagram showing the mechanism by which a nonaqueous secondary battery is deactivated. [Figure 3] 1 is a graph showing changes in battery voltage in Experimental Examples 1 to 3. [Figure 4] 10 is a graph showing changes in battery voltage in Experimental Examples 4 to 6. [Figure 5] 10 is a graph showing changes in battery voltage in Experimental Examples 7 to 9. [Figure 6] 10 is a graph showing changes in battery voltage in Experimental Examples 10 and 11. DETAILED DESCRIPTION OF THE INVENTION

[0011] The nonaqueous secondary battery deactivator of the present disclosure contains a redox shuttle agent and N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), and is used to deactivate the nonaqueous secondary battery. The nonaqueous secondary battery to be deactivated may be either unused or used.

[0012] [Non-aqueous secondary battery] First, the non-aqueous secondary battery to be deactivated will be described. The non-aqueous secondary battery includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous ion conductive medium interposed between the positive electrode and the negative electrode for conducting carrier ions. Examples of the carrier ions include Group 1 element ions and Group 2 element ions. Examples of the Group 1 element ions include lithium ions, sodium ions, and potassium ions. Examples of the Group 2 element ions include magnesium ions and calcium ions. Hereinafter, for the sake of convenience of explanation, the case where the non-aqueous secondary battery is a lithium ion secondary battery will be mainly described.

[0013] The positive electrode may be formed by, for example, mixing a positive electrode active material, a conductive material, and a binder, adding an appropriate solvent to form a paste-like positive electrode mixture, applying and drying it on the surface of a current collector, and compressing it as necessary to increase the electrode density. The positive electrode active material may have a redox potential based on Li higher than that of the redox shuttle agent contained in the deactivator, but preferably has a redox potential of 3.3 V or more based on the Li standard potential, and may be 3.4 V or more, 3.8 V or more, 4.0 V or more, 4.2 V or more, etc. As the positive electrode active material, sulfides containing transition metal elements, oxides containing lithium and transition metal elements, etc. can be used. Specifically, transition metal sulfides such as TiS2, TiS3, MoS3, FeS2, Li (1-x) MnO2 (0 < x < 1, etc., the same hereinafter), Li (1-x) lithium manganese composite oxides such as Li (1-x) CoO2 and other lithium cobalt composite oxides, Li (1-x) lithium nickel composite oxides such as NiO2, Li (1-x) Ni a Mn b O2 (a + b = 1) or Li (1-x) Ni a Mn b lithium nickel manganese composite oxides such as Li (1-x) Ni a Co b Mn cLithium nickel cobalt manganese composite oxides such as O2 (a+b+c=1), lithium vanadium composite oxides such as LiV2O3, and transition metal oxides such as V2O5 can be used. (1-x) Olivine-type lithium manganese phosphate compounds such as MnPO4, Li (1-x) Olivine-type lithium cobalt phosphate compounds such as CoPO4, Li (1-x) Olivine-type lithium nickel phosphate compounds such as NiPO4, Li (1-x) Olivine-type lithium iron phosphate compounds such as FePO4 can be used. (1-x) Inverse spinel lithium manganese vanadate compounds such as MnVO4, Li (1-x) Inverse spinel lithium cobalt vanadate compounds such as CoPO4, Li (1-x) Inverse spinel lithium vanadate nickel compounds such as NiPO4 can be used. The positive electrode active material is preferably an oxide containing one or more of nickel, manganese, and cobalt, such as LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc. are preferred. Alternatively, the positive electrode active material is preferably a phosphate containing iron, such as LiFePO4.

[0014] Examples of conductive materials that can be used for the positive electrode include graphite (e.g., natural graphite (e.g., scaly graphite, flake graphite) and artificial graphite), acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (e.g., copper, nickel, aluminum, silver, and gold). Examples of binders that can be used include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-containing rubber; thermoplastic resins such as polypropylene and polyethylene; ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, and natural butyl rubber (NBR). Water-based binders such as cellulose-based binders and aqueous dispersions of styrene butadiene rubber (SBR) can also be used. Examples of solvents that can be used include organic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. Alternatively, a dispersant, thickener, etc. may be added to water, and the active material may be slurried with a latex such as SBR. Examples of thickeners include polysaccharides such as carboxymethyl cellulose and methyl cellulose, either alone or in a mixture of two or more. Application methods include roller coating (e.g., applicator roll), screen coating, doctor blade coating, spin coating, and bar coating. Any of these methods can be used to obtain a desired thickness and shape. Current collectors can be made of aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymers, conductive glass, etc., as well as aluminum or copper whose surfaces have been treated with carbon, nickel, titanium, or silver to improve adhesion, conductivity, and oxidation resistance. These surfaces can also be subjected to oxidation treatment. Current collector shapes include foil, film, sheet, net, punched or expanded, lath, porous, foamed, and fibrous. Thicknesses of current collectors ranging from 1 to 500 μm are typically used.

[0015] The negative electrode may be formed, for example, by mixing a negative electrode active material, a conductive material, and a binder, adding an appropriate solvent to form a paste-like negative electrode mixture, applying it to the surface of a current collector, drying it, and compressing it to increase electrode density as needed. Alternatively, the negative electrode may be formed by closely adhering the negative electrode active material to the current collector. The negative electrode active material may have a redox potential relative to Li lower than that of the redox shuttle agent contained in the deactivator. Preferably, the redox potential is 3.0 V or less, more preferably 2.0 V or less, and even more preferably 1.0 V or less relative to Li. Examples of negative electrode active materials include inorganic compounds such as lithium, lithium alloys, and tin compounds; carbonaceous materials capable of absorbing and releasing lithium ions; composite oxides containing multiple elements; and conductive polymers. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Examples of composite oxides include Li4Ti5O 12 Examples of the negative electrode active material include lithium titanium composite oxides such as LiV2O3 and lithium vanadium composite oxides such as LiV2O3. Of these, carbonaceous materials such as graphite are preferred as the negative electrode active material. The conductive materials, binders, solvents, etc. used in the negative electrode can be the same as those exemplified for the positive electrode. For the negative electrode current collector, copper, nickel, stainless steel, titanium, aluminum, baked carbon, conductive polymers, conductive glass, Al-Cd alloys, etc. can be used. For the purpose of improving adhesion, conductivity, and reduction resistance, copper or other materials whose surfaces have been treated with carbon, nickel, titanium, silver, etc. can also be used. The surfaces of these materials can also be oxidized. The shape of the current collector can be the same as that of the positive electrode.

[0016] Examples of ion-conducting media include nonaqueous electrolytes containing a supporting salt and nonaqueous gel electrolytes. Examples of solvents for nonaqueous electrolytes include carbonate compounds such as cyclic carbonate compounds (e.g., ethylene carbonate) and chain carbonate compounds (e.g., dimethyl carbonate), ester compounds such as cyclic ester compounds (e.g., γ-butyrolactone) and chain ester compounds (e.g., methyl formate), ether compounds such as dimethoxyethane, nitrile compounds such as acetonitrile, furan compounds such as tetrahydrofuran, sulfolane compounds such as sulfolane, and dioxolane compounds such as 1,3-dioxolane. These compounds can be used alone or in combination. Examples of supporting salts include inorganic salts such as LiPF, LiBF, LiAsF, and LiClO, and organic salts such as LiCFSO, LiN(CFSO), and LiC(CFSO). These compounds can be used alone or in combination. The concentration of the supporting salt in the electrolyte is preferably 0.1 mol / L to 5 mol / L, more preferably 0.5 mol / L to 2 mol / L. As the ion-conducting medium, an ion-conducting polymer, an inorganic solid electrolyte, a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, or an inorganic solid powder bound by an organic binder can be used instead of a liquid ion-conducting medium.

[0017] The separator is not particularly limited as long as it has a composition that can withstand the range of uses of non-aqueous secondary batteries, and examples thereof include polymer nonwoven fabrics such as polypropylene nonwoven fabrics and thin microporous films of olefin resins such as polyethylene. These may be used alone or in combination.

[0018] The shape of this nonaqueous secondary battery is not particularly limited, and examples thereof include coin, button, sheet, laminate, cylindrical, flat, and prismatic types. Large-sized batteries for use in electric vehicles and the like may also be used. An example of a nonaqueous secondary battery is shown in FIG. 1. FIG. 1 is a cross-sectional view showing the schematic configuration of a coin-type nonaqueous secondary battery 20. As shown in FIG. 1, the nonaqueous secondary battery 20 includes a cup-shaped battery case 21, a positive electrode 22 having a positive electrode active material and disposed at the bottom of the battery case 21, a negative electrode 23 having a negative electrode active material and disposed opposite the positive electrode 22 with a separator 24 interposed therebetween, a gasket 25 formed of an insulating material, and a sealing plate 26 disposed at the opening of the battery case 21 and sealing the battery case 21 via the gasket 25. The nonaqueous secondary battery 20 includes an ion-conducting medium 27 containing a lithium salt dissolved in the space between the positive electrode 22 and the negative electrode 23.

[0019] [Deactivating agent] Next, the deactivating agent will be described. The deactivating agent includes a redox shuttle agent and NMP.

[0020] The redox shuttle agent is not particularly limited as long as it is an oxidizable and reducible compound that can repeatedly transport charge between a positive electrode and a negative electrode. The redox shuttle agent has a redox potential, relative to the Li reference potential, that is higher than that of the negative electrode active material of the nonaqueous secondary battery to be deactivated and lower than that of the positive electrode active material of the nonaqueous secondary battery to be deactivated. The redox shuttle agent preferably has a redox potential, relative to the Li reference potential, of 3.0 V to 4.2 V, more preferably 3.0 V to 4.0 V, and even more preferably 3.0 V to 3.8 V. The redox potential of the redox shuttle agent can be determined by cyclic voltammetry. Specifically, the redox potential of the redox shuttle agent is calculated by dividing the peak potential on the oxidation side determined by cyclic voltammetry by E pa [V], the peak potential of the reduction side is E pc When [V] is used, E0 = (E pa +E pc) / 2. This redox shuttle agent may have an oxidation-reduction potential of less than 3.0 V relative to the lithium potential. When the current collector is made of Cu or its alloy, a redox shuttle agent having an oxidation-reduction potential of less than 3.0 V relative to the lithium potential is preferred because it can further suppress Cu elution.

[0021] The redox shuttle agent preferably has high solubility in NMP. Using a redox shuttle agent with high solubility in NMP allows the preparation of a deactivator containing a high concentration of the redox shuttle agent, which is expected to accelerate deactivation and reduce the amount of deactivator used. As the energy density of batteries increases, the space available for injecting the deactivator often becomes smaller, making it desirable to reduce the amount of deactivator used. The solubility of the redox shuttle agent in NMP may be, for example, 0.5 mol / L or more, 1 mol / L or more, or 3 mol / L or more. The solubility of the redox shuttle agent in NMP may be, for example, 5 mol / L or less, or 4 mol / L or less. In this specification, solubility refers to solubility at 25°C.

[0022] The redox shuttle agent has a dispersion power D in the Hansen solubility parameters of NMP. s , polarization force P s , hydrogen bonding strength H s and the dispersion power D in the Hansen solubility parameters of the redox shuttle agent p , polarization force P p , hydrogen bonding strength H p The distance R from NMP in the Hansen space calculated using the following formula (1) is 10.5 MPa. 0.5It may be set to the following. The Hansen solubility parameter (also called HSP) was announced by Charles M Hansen and is known as an index of the solubility of substances with each other. The Hansen solubility parameter is composed of three numerical values: D (atomic dispersion force), P (molecular polarizability), and H (molecular hydrogen bonding force), and these three parameters are expressed as coordinates in a three-dimensional space (Hansen space) of an orthogonal coordinate system. The solubility of substances with each other is estimated by the distance between the coordinates indicating the HSP of each substance; the closer the coordinates are to each other, the easier the substance is to dissolve, and the farther the coordinates are from each other, the harder the substance is to dissolve. For this reason, it is preferable that the redox shuttle agent has a small distance R from NMP in the Hansen space. For a redox shuttle agent, the above-mentioned distance R is, for example, 10.5 MPa 0.5 It may be less than 10MPa 0.5 It may be less than 9.5MPa 0.5 The Hansen solubility parameter is the value at 25°C. R 2 =4×(D p -D s ) 2 +(P p -P s ) 2 +(H p -H s ) 2 Formula (1)

[0023] Examples of the redox shuttle agent include one or more of phenothiazine compounds, viologen compounds, quinone compounds, diazabenzene compounds, fluorenone compounds, ferrocene compounds, and TEMPO compounds.

[0024] The phenothiazine-based compound may be phenothiazine or a derivative of phenothiazine. Phenothiazine is a heterocyclic compound formed by condensing a benzene ring to each end of a thiazine. The phenothiazine-based compound may be a phenothiazine having a substituent introduced therein. The phenothiazine-based compound may be, for example, one represented by formula (1). In formula (1), R 1 ~R 9are functional groups that may be the same or different. Examples of functional groups include one or more of hydrogen, alkyl groups, aryl groups, acyl groups, alkoxy groups, alkylsulfanyl groups, hydroxyl groups, sulfone groups, nitro groups, amino groups, carboxyl groups, and halogens. The alkyl groups may have from 1 to 6 carbon atoms, may be linear or branched, or may be halogenated alkyl groups in which some or all of the hydrogen atoms are substituted with halogens. Examples of alkyl groups include methyl groups, ethyl groups, isopropyl groups, tert-butyl groups, and trifluoromethyl groups. The aryl groups may have from 6 to 12 carbon atoms. Examples of aryl groups include phenyl groups, tolyl groups, xylyl groups, mesityl groups, and naphthyl groups. The acyl groups may have from 1 to 7 carbon atoms. Examples of acyl groups include formyl groups, acetyl groups, and benzoyl groups. The alkoxy groups may have from 1 to 6 carbon atoms. Examples of alkoxy groups include methoxy groups, ethoxy groups, and phenoxy groups. The alkylsulfanyl group may have 1 to 6 carbon atoms. Examples of the alkylsulfanyl group include a methylsulfanyl group and an ethylsulfanyl group. Examples of the halogen include fluorine, chlorine, and bromine. In formula (1), R 1 ~R 9 may each independently represent a hydrogen atom, an alkyl group, a phenyl group, an acetyl group, or a halogen atom. 1 ~R 9 six or more of R may be hydrogen; 1 ~R 9Examples of the phenothiazine-based compound include phenothiazine, 2-trifluoromethylphenothiazine, 2-methoxyphenothiazine, 10-methylphenothiazine, 2-ethylthiophenothiazine, 2-methylthiophenothiazine, 2-chlorophenothiazine, 2-acetylphenothiazine, 10-ethylphenothiazine, 10-isopropylphenothiazine, 10-tert-butylphenothiazine, 10-acetylphenothiazine, 10-phenylphenothiazine, 3,7-dichloro-10-ethylphenothiazine, 3,7-dibromo-10-ethylphenothiazine, and 3,7-bis(trifluoromethyl)-10-ethylphenothiazine.

[0025] [ka]

[0026] The viologen-based compound may be a viologen or a derivative of a viologen. The viologen-based compound is a compound having a structure in which a hydrocarbon group is bonded to each of the two nitrogen atoms of the pyridine ring of a 4,4'-bipyridine skeleton, and has, for example, a structure of formula (2). In formula (2), R 10 and R 11are hydrocarbon groups that may be the same or different. The hydrocarbon group is preferably a linear or branched chain hydrocarbon group or a cyclic hydrocarbon group. Examples of the linear hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decanyl, undecanyl, and dodecanyl, and alkenyl groups such as vinyl, propenyl, butenyl, pentenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl. Examples of the cyclic hydrocarbon group include cycloalkyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, and cycloheptyl, and aryl groups such as phenyl and naphthyl. These hydrocarbon groups may have a substituent such as a carboxyl group, an alkoxy group, a nitro group, an amino group, or a halogen atom (e.g., F, Cl, or Br). Of these, the hydrocarbon group is preferably a linear alkyl group, and preferably has no substituent. Each hydrocarbon group preferably has 20 or less carbon atoms, more preferably 10 or less, and even more preferably 6 or less. In formula (2), R 12 ~R 19are functional groups which may be the same or different. The functional group may be, for example, hydrogen, or a substituent such as a hydrocarbon group, a carboxyl group, an alkoxy group, a nitro group, an amino group, or a halogen. The hydrocarbon group may be one or more of the hydrocarbon groups exemplified above. When a viologen compound has multiple substituents, the substituents may be bonded to each other to form a ring. Viologens preferably have 30 or less carbon atoms, more preferably 20 or less, and even more preferably 14 or less. Specific examples of this viologen compound include methyl viologen, ethyl viologen, propyl viologen, butyl viologen, pentyl viologen, hexyl viologen, heptyl viologen, and octyl viologen. Examples of viologen compounds include 1,1'-dimethyl-3,3'-[methylenebis(oxy)]-4,4'-bipyridinium, phenyl viologen, and 1-(4-aminophenyl)-1'-methyl-4,4'-bipyridinium. Viologen compounds contain hexafluorophosphate anion (PF6) as a counter anion of the cation of formula (2). - ), tetrafluoroborate anion (BF4 - ), pentafluoroarsine anion (AsF6 - ), perchlorate anion (ClO4 - ), Br - , Cl - , F - Inorganic anions such as trifluoromethanesulfonate (CF3SO3 - ), bis(trifluoromethanesulfonyl)imide anion (N(CF3SO2)2 - , TFSI), tris(trifluoromethylsulfonyl)methide anion (C(CF3SO2)3 - The counter anion may be the same as or different from the anion of the supporting salt of the nonaqueous secondary battery to be deactivated.

[0027] [ka]

[0028] A quinone compound is a compound having a structure in which the CH groups on two carbon atoms of an aromatic hydrocarbon skeleton are each replaced with a C=O group. The quinone compound may have a 4- to 7-membered aromatic hydrocarbon skeleton, and preferably has a 6-membered aromatic hydrocarbon skeleton (a benzoquinone structure). The quinone may have, for example, a p-benzoquinone structure of formula (3) or an o-benzoquinone structure of formula (4). In formulas (3) and (4), R 20 ~R 23 are functional groups which may be the same or different. Examples of functional groups include one or more of hydrogen, alkyl groups, aryl groups, acyl groups, alkoxy groups, alkylsulfanyl groups, hydroxyl groups, sulfonic groups, nitro groups, amino groups, carboxyl groups, and halogens. When a quinone compound has multiple substituents, the substituents may be bonded to each other to form a ring. Examples of quinone compounds in which the substituents are bonded to each other to form a ring include naphthoquinone (1,4-naphthoquinone, 1,2-naphthoquinone, etc.), anthraquinone (9,10-anthraquinone, etc.), and derivatives thereof. The quinone compound preferably has 20 or less carbon atoms, more preferably 14 or less, and even more preferably 10 or less. Specific examples of quinone compounds include p-benzoquinone, methyl-p-benzoquinone, 2,5-dimethyl-1,4-benzoquinone, methoxybenzoquinone, 2,5-dihydroxy-1,4-benzoquinone, 1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, anthraquinone, 2-methylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 1,4-dihydroxyanthraquinone, and 1-nitroanthraquinone.

[0029] [ka]

[0030] Diazabenzene compounds have a diazabenzene skeleton. Examples of diazabenzene compounds include those in which two benzene rings are replaced with nitrogen, and those in which an aromatic ring is further condensed to the diazabenzene skeleton. For example, compounds having a naphthyridine skeleton or a diazaanthracene skeleton, which have a skeleton in which two carbon atoms of an acene, such as naphthalene or anthracene, are replaced with nitrogen, and derivatives thereof. Examples of diazabenzene compounds include phenazine compounds and derivatives thereof (formula (5)), quinoxaline compounds and derivatives thereof (formula (6)), and pyrazine compounds and derivatives thereof (formula (7)). Diazabenzene compounds also include those having a pyrazine skeleton, as well as pyridazine and pyrimidine skeletons, which are isomers of pyrazine. Furthermore, diazabenzene compounds also include those having a naphthyridine skeleton, such as a quinoxaline skeleton, as well as benzopyridazine (cinnoline) skeletons, quinazoline skeletons, and phthalazine skeletons, which are isomers of quinoxaline. In formulas (5) to (7), R 24 ~R 31are functional groups that may be the same or different. Examples of functional groups include one or more of hydrogen, alkyl groups, aryl groups, acyl groups, alkoxy groups, alkylsulfanyl groups, hydroxyl groups, sulfone groups, nitro groups, amino groups, carboxyl groups, and halogens. The alkyl groups may have from 1 to 12 carbon atoms, may be linear or branched, or may be halogenated alkyl groups in which some or all of the hydrogen atoms are substituted with halogens. Examples of alkyl groups include methyl groups, ethyl groups, isopropyl groups, tert-butyl groups, and trifluoromethyl groups. The aryl groups may have from 6 to 12 carbon atoms. Examples of aryl groups include phenyl groups, tolyl groups, xylyl groups, mesityl groups, and naphthyl groups. The acyl groups may have from 1 to 7 carbon atoms. Examples of acyl groups include formyl groups, acetyl groups, and benzoyl groups. The alkoxy groups may have from 1 to 6 carbon atoms. Examples of alkoxy groups include methoxy groups, ethoxy groups, and phenoxy groups. The alkylsulfanyl group may have 1 to 6 carbon atoms. Examples of the alkylsulfanyl group include a methylsulfanyl group and an ethylsulfanyl group. Examples of the halogen include fluorine, chlorine, and bromine. R 24 ~R 31 , each independently may be hydrogen, an alkyl group, a phenyl group, an acetyl group, or a halogen. 24 ~R 31 Four or more of these may be hydrogen. Examples of phenazine compounds include phenazine and its derivatives as a basic skeleton. Examples of quinoxaline compounds include quinoxaline and its derivatives as a basic skeleton. Examples of pyrazine compounds include pyrazine and its derivatives as a basic skeleton. When the number of aromatic rings increases, such as in quinoxaline and phenazine, the solubility in non-aqueous solvents may decrease, so quinoxaline and phenazine are preferred as redox shuttle agents.

[0031] [ka]

[0032] Fluorenone compounds have a fluorenone skeleton in which two hydrogen atoms bonded to the carbon atom at position 9 of fluorene are replaced with one oxo group (=O). Fluorenone compounds include fluorenone and its derivatives. Fluorenone derivatives refer to compounds having a substituent other than hydrogen on a carbon atom other than the carbon at position 9 bearing the oxo group. This fluorenone compound may be represented by formula (8). In formula (8), R 32 ~R 39 are functional groups that may be the same or different. Examples of functional groups include one or more of hydrogen, alkyl groups, aryl groups, acyl groups, alkoxy groups, alkylsulfanyl groups, hydroxyl groups, hydroxyl groups, sulfone groups, nitro groups, nitroxy groups, amino groups, carboxyl groups, and halogens. The alkyl groups may have from 1 to 12 carbon atoms, may be linear or branched, or may be halogenated alkyl groups in which some or all of the hydrogen atoms are substituted with halogens. Examples of alkyl groups include methyl groups, ethyl groups, isopropyl groups, tert-butyl groups, and trifluoromethyl groups. The aryl groups may have from 6 to 12 carbon atoms. Examples of aryl groups include phenyl groups, tolyl groups, xylyl groups, mesityl groups, and naphthyl groups. The acyl groups may have from 1 to 7 carbon atoms. Examples of acyl groups include formyl groups, acetyl groups, and benzoyl groups. The alkoxy groups may have from 1 to 6 carbon atoms. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a phenoxy group. The alkylsulfanyl group may have 1 to 6 carbon atoms. Examples of the alkylsulfanyl group include a methylsulfanyl group and an ethylsulfanyl group. Examples of the halogen include fluorine, chlorine, and bromine. R 32 ~R 39 may each independently represent a hydrogen atom, an alkyl group, a phenyl group, an acetyl group, or a halogen atom. 32 ~R 39 Four or more of R may be hydrogen.32 ~R 39 Two or more of these may be bonded to form a ring. Fluorenone compounds include fluorenone as a basic skeleton and its derivatives such as 2-aminofluorenone, 2,7-dihydroxyfluorenone, 2-carboxyfluorenone, 2-nitrofluorenone, 2,7-dinitrofluorenone, benzo[B]fluorenone, and 2,7-dibromofluorenone.

[0033] [ka]

[0034] Examples of ferrocene-based compounds include ferrocene and its derivatives. Ferrocene is a compound having a structure in which two cyclopentadienyl groups are bonded to a central iron ion. The ferrocene-based compound may be one in which a substituent has been introduced into the cyclopentadienyl group of ferrocene. The ferrocene-based compound may be one represented by formula (9). Examples of functional groups include the functional groups exemplified for phenothiazine. In formula (9), R 40 ~R 49 may each independently represent a hydrogen atom, an alkyl group, a phenyl group, an acetyl group, an amino group, an acyl group, or a halogen atom. 40 ~R 49 six or more of R may be hydrogen; 40 ~R 49 Seven or more of the ferrocene-based compounds may be hydrogen atoms. Examples of the ferrocene-based compounds include ferrocene, acetylferrocene, aminoferrocene, benzoylferrocene, bromoferrocene, t-butylferrocene, butylferrocene, and decamethylferrocene. In the ferrocene-based compounds (e.g., formula (9)), the two cyclopentadienyl rings may be in a twisted conformation or an overlapping conformation.

[0035] [ka]

[0036] Examples of TEMPO compounds include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), N-(3,3,5,5-tetramethyl-4-oxypiperidyl)pyrene-1-carboxyamide (Pyrene-TEMPO), 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical (MeO-TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxybenzoate (BzO-TEMPO), and 4-acetamido-2,2,6,6-tetramethyl-1-piperidinyloxy (Ac-TEMPO).

[0037] The deactivator preferably contains the redox shuttle agent at a concentration of 0.1 mol / L or more, more preferably 0.5 mol / L or more, even more preferably 1 mol / L or more, and even more preferably 2 mol / L or more. The deactivator may contain the redox shuttle agent at a concentration of 5 mol / L or less, or may contain the redox shuttle agent at a concentration of 4 mol / L or less. The deactivator may contain the redox shuttle agent in an amount equal to or less than the solubility limit.

[0038] The deactivator preferably does not contain any solutes (e.g., supporting salts) other than the redox shuttle agent, and even if it does contain solutes other than the redox shuttle agent, the concentration is preferably less than 0.1 mmol / L or less than 0.01 mmol / L. Examples of supporting salts include inorganic salts such as LiPF6, LiBF4, LiAsF6, and LiClO4, and organic salts such as LiCF3SO3, LiN(CF3SO2)2, and LiC(CF3SO2)3. The supporting salt may be the same as or different from the supporting salt contained in the ionically conductive medium of the nonaqueous secondary battery to be deactivated.

[0039] The deactivator preferably does not contain any solvent other than NMP, and even if it contains a solvent other than NMP, the amount is preferably 50% by volume or less, 10% or less, 1% or less, etc. Examples of the solvent include non-aqueous solvents such as carbonate compounds, ester compounds, ether compounds, nitrile compounds, amide compounds, phosphate ester compounds, furan compounds, sulfolane compounds, and dioxolane compounds, and these can be used alone or in combination.

[0040] [Inactivation method] Next, a method for deactivating the non-aqueous secondary battery using the deactivator will be described. This deactivation method includes a step of adding the deactivator to the interior of the non-aqueous secondary battery.

[0041] In the addition step, a deactivator is added to the inside of the nonaqueous secondary battery. Specifically, the deactivator is added so that the deactivator comes into contact with the positive and negative electrodes of the nonaqueous secondary battery. The method for adding the deactivator is not particularly limited, and the deactivator may be added by opening the nonaqueous secondary battery or by using a syringe.

[0042] The amount of deactivator added may be, for example, 10 μL or more, 20 μL or more, or 30 μL or more, or 1000 μL or less, 100 μL or less, or 50 μL or less. When used in large batteries such as those for vehicles, the amount of deactivator added may be, for example, 1 mL or more, 5 mL or more, or 10 mL or more, or 1000 mL or less, 100 mL or less, or 50 mL or less. The amount of deactivator added may be, for example, 0.1% to 500% or 10% to 300% of the volume of the ion conductive medium contained in the nonaqueous secondary battery to be deactivated. The amount of deactivator added may be 0.1 μL / mAh or more, 0.5 μL / mAh or more, 1 μL / mAh or more, or 70 μL / mAh or less, 50 μL / mAh or less, 10 μL / mAh or less, or 5 μL / mAh or less, per battery capacity of the nonaqueous secondary battery. The amount of redox shuttle agent added to the nonaqueous secondary battery by adding a deactivator (hereinafter also referred to as the added amount of redox shuttle agent) may be, for example, 0.1 μmol / mAh or more, 0.5 μmol / mAh or more, or 1 μmol / mAh or more, or 7 μmol / mAh or less, or 6 μmol / mAh or less, per battery capacity of the nonaqueous secondary battery.

[0043] The time elapsed from the addition of the deactivator in the addition step until the battery voltage of the nonaqueous secondary battery reaches 0.5 V or less is preferably 30 hours or less, more preferably 25 hours or less, and even more preferably 20 hours or less.

[0044] The mechanism by which a non-aqueous secondary battery is deactivated by this deactivation method is presumed to be as follows. FIG. 2 is an explanatory diagram showing the mechanism by which a non-aqueous secondary battery is deactivated. In FIG. 2, as an example, a case in which the redox shuttle agent is phenothiazine is described. Phenothiazine contained in the deactivator exists as a neutral molecule or a cation radical in the electrolyte (ion-conducting medium of the non-aqueous secondary battery + non-aqueous solvent of the deactivator), and functions as a redox shuttle agent that alternates between radical and neutral states through the exchange of electrons between the positive and negative electrodes.

[0045] Specifically, when a deactivator is added to a non-aqueous secondary battery, phenothiazine, which exists as a neutral molecule, donates an electron to the positive electrode and becomes a cation radical (Figure 2(1)), which converts to an anion (PF6 - etc.) and it becomes stable (Figure 2 (2)). When electrons are supplied to the cation radical from the negative electrode, phenothiazine becomes a neutral molecule (Figure 2 (3)). At the same time as the electrons, Li ions are released from the negative electrode, and the Li ions pass through the separator and move to the positive electrode (Figure 2 (4)). By repeating the above process, the potential difference between the positive and negative electrodes eventually disappears, the battery voltage approaches 0 V, and deactivation is complete.

[0046] The deactivator and deactivation method described above enable nonaqueous secondary batteries to be deactivated more quickly with a smaller amount of deactivator. The reason for this effect is presumably that, for example, using a deactivator containing NMP in addition to a redox shuttle agent can suppress the spread of the deactivator within the battery, maintaining a high concentration of the redox shuttle agent involved in the reaction. This allows the redox shuttle to proceed smoothly even with a smaller amount of deactivator, resulting in faster battery deactivation.

[0047] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

[0048] The present disclosure may be any of the following [1] to [6]. [1] A deactivator for deactivating a non-aqueous secondary battery, the deactivator comprising: a redox shuttle agent having a redox potential, relative to a Li reference potential, that is higher than that of a negative electrode active material of the non-aqueous secondary battery and lower than that of a positive electrode active material of the non-aqueous secondary battery; and N-methyl-2-pyrrolidone. [2] The deactivator for a non-aqueous secondary battery according to [1], wherein the redox shuttle agent is a ferrocene-based compound or a phenothiazine-based compound. [3] The deactivator for a non-aqueous secondary battery according to [1] or [2], containing the redox shuttle agent at a concentration of 0.5 mol / L or more. [4] A method for deactivating a nonaqueous secondary battery, comprising: adding the deactivator for a nonaqueous secondary battery according to any one of [1] to [3] to the inside of the nonaqueous secondary battery. [5] The method for deactivating a nonaqueous secondary battery according to [4], wherein in the adding step, the deactivator is added so that the amount of the deactivator added relative to the battery capacity of the nonaqueous secondary battery is less than 10 μL / mAh. [6] The method for deactivating a nonaqueous secondary battery according to [4] or [5], wherein the time elapsed from the addition of the deactivator in the addition step until the battery voltage of the nonaqueous secondary battery becomes 0.5 V or less is 30 hours or less. [Example]

[0049] Examples using the deactivator for nonaqueous secondary batteries of the present disclosure will be described below as examples. Experimental Examples 1 to 2, 7 to 8, and 10 correspond to working examples, and Experimental Examples 3 to 6, 9, and 11 correspond to comparative examples.

[0050] [Experimental Example 1] (1) Non-aqueous secondary battery As a non-aqueous secondary battery, a lithium secondary battery having a voltage of 4.1 V and a capacity of 17 mAh was prepared as follows: LiNi 1 / 3 Co 1 / 3 Mn 1 / 3A positive electrode composite consisting of O2 (oxidation-reduction potential at full charge of 4.2 V vs. Li), acetylene black, and polyvinylidene fluoride (PVdF) in a mass ratio of 93:4:3 was coated onto an aluminum current collector foil and dried in vacuum at 120 °C to obtain a positive electrode. A negative electrode composite consisting of graphite (oxidation-reduction potential at full charge of 0.1 V vs. Li), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 98:1:1 was coated onto a copper current collector foil and dried in vacuum at 120 °C to obtain a negative electrode. An ion-conducting medium was prepared by mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of approximately 3:4:3 and adding LiPF6 as a lithium salt to the mixture to a concentration of 1 mol / L. A polyethylene separator was sandwiched between the obtained positive and negative electrodes, and 0.45 mL of an ion-conducting medium was impregnated into the separator, which was then sealed in a laminate film. The resulting cell was subjected to two charge-discharge cycles at a temperature of 25°C and a voltage range of 3.0 to 4.1 V, and then charged to 4.1 V to be fully charged.

[0051] (2) Inactivating agent An inactivating solution (inactivator) was prepared by dissolving phenothiazine in N-methyl-2-pyrrolidone (NMP) to a concentration of 1.0 mol / L.

[0052] (3) Inactivation process A nonaqueous secondary battery in a fully charged state (voltage 4.1 V) was opened under an argon atmosphere, and 31.7 μL of deactivating solution was added. After the addition of the deactivating solution, the battery was resealed, and the change in battery voltage was measured at a temperature of 25°C. In Experimental Example 1, the amount of deactivating solution added per battery capacity (17 mAh) was 1.9 μL / mAh, and the amount of phenothiazine added per battery capacity was 1.9 μmol / mAh.

[0053] [Experimental Example 2] The procedure was the same as in Experimental Example 1, except that the inactivation solution was prepared by dissolving phenothiazine in NMP to a concentration of 3.0 mol / L. In Experimental Example 2, the amount of inactivation solution added per battery capacity was 1.9 μL / mAh, and the amount of phenothiazine added per battery capacity was 5.6 μmol / mAh.

[0054] [Experimental Example 3] The procedure was the same as in Experimental Example 1, except that the deactivation solution was prepared by dissolving phenothiazine in 1,2-dimethoxyethane (DME) to a concentration of 1.0 mol / L. In Experimental Example 3, the amount of deactivation solution added per battery capacity was 1.9 μL / mAh, and the amount of phenothiazine added per battery capacity was 1.9 μmol / mAh.

[0055] [Experimental Example 4] The procedure was the same as in Experimental Example 1, except that a deactivating solution was prepared by dissolving phenothiazine in DME to a concentration of 0.1 mol / L, the amount of deactivating solution added was 1.268 mL, and the change in battery voltage was measured at a temperature of 20°C. In Experimental Example 4, the amount of deactivating solution added per battery capacity was 74.6 μL / mAh, and the amount of phenothiazine added per battery capacity was 7.5 μmol / mAh.

[0056] [Experimental Example 5] The procedure was the same as in Experimental Example 1, except that a deactivating solution was prepared by dissolving phenothiazine in triethylene glycol dimethyl ether (triglyme) to a concentration of 0.1 mol / L, the amount of deactivating solution added was 1.268 mL, and the change in battery voltage was measured at a temperature of 20° C. In Experimental Example 5, the amount of deactivating solution added per battery capacity was 74.6 μL / mAh, and the amount of phenothiazine added per battery capacity was 7.5 μmol / mAh.

[0057] [Experimental Example 6] The procedure was the same as in Experimental Example 1, except that a deactivating solution was prepared by dissolving phenothiazine in tetraethylene glycol dimethyl ether (tetraglyme) to a concentration of 0.1 mol / L, the amount of deactivating solution added was 1.268 mL, and the change in battery voltage was measured at a temperature of 20° C. In Experimental Example 6, the amount of deactivating solution added per battery capacity was 74.6 μL / mAh, and the amount of phenothiazine added per battery capacity was 7.5 μmol / mAh.

[0058] [Results and Discussion] Figure 3 shows the changes in battery voltage in Experimental Examples 1 to 3, and Figure 4 shows the changes in battery voltage in Experimental Examples 4 to 6. In Experimental Examples 1 to 6, after the addition of the deactivating solution, the battery voltage dropped to 0.1 V or less, indicating that the deactivating solution functioned in all cases. Table 1 summarizes the time elapsed from the addition of the deactivating solution until the battery voltage reached 0.5 V in Experimental Examples 1 to 6.

[0059] A comparison of Experimental Example 1 and Experimental Example 3 revealed that the battery discharge proceeded more quickly in Experimental Example 1. Since all experimental conditions were the same between Experimental Example 1 and Experimental Example 3 except for the solvent used in the deactivation solution, it was inferred that the difference in discharge rate was due to the difference in solvent. Comparing the viscosity of the solvents, the viscosity of NMP used in Experimental Example 1 was 1.65 cP, which was more than four times higher than the viscosity (0.41 cP) of DME used in Comparative Example 1. Based on the Stokes-Einstein equation, it was inferred that the use of NMP solvent would actually slow the diffusion rate of phenothiazine and reduce the discharge rate of the battery. Regarding this point, an investigation was conducted using Experimental Examples 4 to 6, and it was confirmed that when DME (viscosity 0.41 cP), triglyme (viscosity 1.96 cP), and tetraglyme (viscosity 3.3 cP) were used as the solvent for the deactivation solution, the discharge rate tended to decrease as the viscosity of the solvent increased. Therefore, it was speculated that the improvement in the discharge rate of a battery due to the use of NMP as a solvent for the deactivating solution was due to a mechanism different from the improvement in the diffusion rate of phenothiazine due to the use of a low-viscosity solvent in Patent Document 2. The mechanism for the improvement in the discharge rate due to the use of NMP was thought to be the local increase in the phenothiazine concentration due to the suppression of the spread of the deactivating agent within the battery. The suppression of the spread of the deactivating agent due to the use of NMP was speculated to be due to the high viscosity of NMP and the low wettability of NMP with the separator. It should be noted that the mechanism for this improvement in the discharge rate was speculated to be due to the difference in solvent, and it was confirmed in Experimental Examples 7 to 11 described below that similar effects could be obtained even if the redox shuttle agent was not a phenothiazine-based compound.

[0060] Furthermore, NMP was capable of increasing the concentration of phenothiazine to 3 mol / L or more. In Experimental Example 2, a phenothiazine / NMP solution with a concentration of 3 mol / L was investigated, and it was confirmed that, as shown in Figure 3, a further improvement in the discharge rate was possible with an increase in the phenothiazine concentration compared to the phenothiazine / NMP solution with a concentration of 1 mol / L (Experimental Example 1).

[0061] [Experimental Example 7] (1) Non-aqueous secondary battery A lithium secondary battery with a voltage of 3.75 V and a capacity of 10 mAh was prepared as follows: A positive electrode slurry mixture of LiFePO4 (with a redox potential of 3.85 V relative to Li when fully charged), acetylene black, and polyvinylidene fluoride (PVdF) in a mass ratio of 92:5:3 was applied to aluminum foil and vacuum-dried at 120°C to obtain a positive electrode. A negative electrode slurry mixture of graphite (with a redox potential of 0.1 V relative to Li when fully charged), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 98:1:1 was applied to copper foil and vacuum-dried at 120°C to obtain a negative electrode. Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:4:3, and lithium hexafluorophosphate (LiPF6) was dissolved as a lithium salt to a concentration of 1.0 mol / L to prepare an electrolyte solution. A single-layer microporous polyethylene membrane was prepared as a separator. The positive and negative electrodes were placed opposite each other with a separator impregnated with approximately 0.45 mL of electrolyte solution interposed between them and sealed in a laminate film. This cell was subjected to two charge-discharge cycles at a temperature of 25°C and a voltage range of 3.0 to 3.75 V, and then charged to 3.75 V to fully charge the cell.

[0062] (2) Inactivating agent An inactivating solution (inactivator) was prepared by dissolving phenothiazine in N-methyl-2-pyrrolidone (NMP) to a concentration of 1.0 mol / L.

[0063] (3) Inactivation process The battery was fully charged (voltage 3.75 V) and opened under an argon atmosphere, and 18.7 μL of deactivating solution was added. After the addition of the deactivating solution, the battery was resealed and the change in battery voltage was measured at a temperature of 25°C. In Experimental Example 7, the amount of deactivating solution added per battery capacity (10 mAh) was 1.9 μL / mAh, and the amount of phenothiazine added per battery capacity was 1.9 μmol / mAh.

[0064] [Experimental Example 8] The procedure was the same as in Experimental Example 7, except that the inactivation solution was prepared by dissolving phenothiazine in NMP to a concentration of 3.0 mol / L. In Experimental Example 8, the amount of phenothiazine added per battery capacity was 5.6 μmol / mAh.

[0065] [Experimental Example 9] The procedure was the same as in Experimental Example 7, except that the inactivation solution was prepared by dissolving phenothiazine in 1,2-dimethoxyethane (DME) to a concentration of 1.0 mol / L. In Experimental Example 9, the amount of phenothiazine added per battery capacity was 1.9 μmol / mAh.

[0066] [Experimental Example 10] The procedure was the same as in Experimental Example 7, except that the inactivation solution was prepared by dissolving ferrocene in NMP to a concentration of 0.5 mol / L. In Experimental Example 10, the amount of ferrocene added per battery capacity was 0.9 μmol / mAh.

[0067] [Experimental Example 11] The procedure was the same as in Experimental Example 7, except that the inactivation solution was prepared by dissolving ferrocene in DME to a concentration of 0.5 mol / L. In Experimental Example 11, the amount of ferrocene added per battery capacity was 0.9 μmol / mAh.

[0068] [Results and Discussion] Figure 5 shows the battery voltage changes for Experimental Examples 7 to 9, and Figure 6 shows the battery voltage changes for Experimental Examples 10 and 11. After the addition of the deactivating solution, the battery voltage dropped to 0.1 V or less in both the battery using LiFePO4 as the positive electrode active material and the battery using ferrocene as the redox shuttle agent, demonstrating that the deactivating solution functioned in both cases. Table 1 summarizes the time elapsed from the addition of the deactivating solution until the battery voltage reached 0.5 V in Experimental Examples 7 to 11.

[0069] A comparison of Experimental Examples 7 and 9 revealed that the discharge rate of a battery using a LiFePO4 positive electrode can be improved by using NMP as a solvent for the passivation solution, just as with a battery using a ternary positive electrode. Furthermore, as shown in Experimental Example 8, the use of NMP solvent makes it possible to increase the phenothiazine concentration up to 3 mol / L, thereby enabling a further improvement in the discharge rate.

[0070] A comparison of Experimental Examples 10 and 11 revealed that the discharge rate of a battery using ferrocene as a redox shuttle agent was improved by using NMP as the solvent for the passivation solution, just as in a battery using phenothiazine as a redox shuttle agent.

[0071] These results suggest that the use of NMP as a solvent can achieve both a high redox shuttle agent concentration and an improved battery discharge rate, and that nonaqueous secondary batteries can be deactivated more quickly with a smaller amount of deactivator. Furthermore, the use of NMP as a solvent was shown to provide the above-mentioned effects regardless of the type of positive electrode active material or redox shuttle agent.

[0072] Additionally, as a supplement, the flash points of the solvents (DME, tetrahydrofuran, N,N-dimethylacetamide, N,N-dimethylformamide) of the inactivation liquid proposed in the above-mentioned Patent Document 2 are -2°C, -14.5°C, 64°C, and 58°C, respectively, whereas the flash point of the NMP used in the present invention is as high as 86°C. Therefore, it is presumed that this will also have the effect of improving the safety of the inactivation treatment process and the batteries after treatment.

[0073] [Table 1]

[0074] [Table 2] [Industrial Applicability]

[0075] The present invention is applicable to the field of the battery industry. [Explanation of symbols]

[0076] 20 Non-aqueous secondary battery, 21 Case, 22 Positive electrode, 23 Negative electrode, 24 Separator, 25 Gasket, 26 Sealing plate, 27 Ion conducting medium.

Claims

1. A deactivator for deactivating a non-aqueous secondary battery, a redox shuttle agent having an oxidation-reduction potential, relative to a Li reference potential, higher than that of a negative electrode active material of the nonaqueous secondary battery and lower than that of a positive electrode active material of the nonaqueous secondary battery; and N-methyl-2-pyrrolidone; A deactivator for non-aqueous secondary batteries.

2. 2. The deactivator for a non-aqueous secondary battery according to claim 1, wherein the redox shuttle agent is a ferrocene-based compound or a phenothiazine-based compound.

3. The deactivator for a non-aqueous secondary battery according to claim 1 or 2, containing the redox shuttle agent at 0.5 mol / L or more.

4. an addition step of adding the nonaqueous secondary battery passivator according to claim 1 or 2 to the inside of the nonaqueous secondary battery; A method for deactivating a non-aqueous secondary battery.

5. 5. The method for deactivating a nonaqueous secondary battery according to claim 4, wherein in the adding step, the deactivator is added so that an amount of the deactivator added relative to a battery capacity of the nonaqueous secondary battery is less than 10 μL / mAh.

6. 5. The method for deactivating a nonaqueous secondary battery according to claim 4, wherein the time elapsed from the addition of the deactivator in the addition step until the battery voltage of the nonaqueous secondary battery becomes 0.5 V or less is 30 hours or less.

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