Inactivating agent for nonaqueous secondary battery and inactivating method for nonaqueous secondary battery

Abstract

Disclosed is an inactivating agent for inactivating a nonaqueous secondary battery, the inactivating agent including: a redox shuttle agent which has a redox potential higher than that of the negative electrode active material of the nonaqueous secondary battery and lower than that of the positive electrode active material of the nonaqueous secondary battery at the Li reference potential; and N-methyl-2-pyrrolidone.

Description

Deactivator for non-aqueous secondary battery and deactivation method for non-aqueous secondary battery

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

[0002] Conventionally, when recycling or disposing of nonaqueous secondary batteries, a deactivation process is performed to deactivate the recovered batteries. For example, one such 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) activated, 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, in such deactivation methods, the use of a phenothiazine-based compound as a redox shuttle agent 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 such as 1,2-dimethoxyethane, which has high solubility for phenothiazine and low viscosity, 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.

[0003] JP 2018-137137 A JP 2022-073888 A

[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.

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

[0007] That is, the deactivator for a nonaqueous secondary battery according to the present disclosure is a deactivator for deactivating a nonaqueous secondary battery, and includes: a redox shuttle agent having an oxidation-reduction potential, relative to Li reference potential, that 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.

[0008] The method for deactivating a nonaqueous secondary battery according to the present disclosure further comprises an adding step of adding the above-described deactivator for a nonaqueous secondary battery to the inside of the nonaqueous secondary battery.

[0009] This non-aqueous secondary battery deactivator and non-aqueous secondary battery deactivation method allows non-aqueous 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 a high concentration of the redox shuttle agent involved in the reaction can be maintained. This allows the redox shuttle to proceed smoothly even with a smaller amount of deactivator, resulting in more rapid battery deactivation.

[0010] 1 is a cross-sectional view showing an outline of the configuration of a nonaqueous secondary battery 20. An explanatory diagram showing the mechanism by which a nonaqueous secondary battery is deactivated. A graph showing changes in battery voltage in Experimental Examples 1 to 3. A graph showing changes in battery voltage in Experimental Examples 4 to 6. A graph showing changes in battery voltage in Experimental Examples 7 to 9. A graph showing changes in battery voltage in Experimental Examples 10 and 11.

[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] [Nonaqueous Secondary Battery] First, a nonaqueous secondary battery to be deactivated will be described. A nonaqueous secondary battery includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a nonaqueous ion-conducting medium interposed between the positive electrode and the negative electrode and conducting carrier ions. Examples of carrier ions include Group 1 element ions and Group 2 element ions. Examples of Group 1 element ions include lithium ions, sodium ions, and potassium ions. Examples of Group 2 element ions include magnesium ions and calcium ions. For ease of explanation, the following description will mainly focus on the case where the nonaqueous secondary battery is a lithium-ion secondary battery.

[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 it to the surface of a current collector, drying it, and compressing it to increase electrode density as needed. The positive electrode active material may have a redox potential relative to Li higher than that of the redox shuttle agent contained in the deactivator. The redox potential relative to Li is preferably 3.3 V or higher, and may be 3.4 V or higher, 3.8 V or higher, 4.0 V or higher, or 4.2 V or higher. Examples of the positive electrode active material include sulfides containing transition metal elements and oxides containing lithium and transition metal elements. Specifically, transition metal sulfides such as TiS2, TiS3, MoS3, and FeS2, Li, (1-x) MnO2 (0<x<1, etc., same below), Li (1-x) Lithium manganese composite oxides such as Mn2O4, Li (1-x) Lithium cobalt composite oxides such as CoO2, Li (1-x) Lithium nickel composite oxides such as NiO2, Li (1-x) Ni a Mn b O2 (a+b=1) and Li (1-x) Ni a Mn b Lithium nickel manganese composite oxides such as O4 (a + b = 2), Li (1-x) Ni a Co b Mn cLithium nickel cobalt manganese composite oxides such as LiO2 (a+b+c=1), lithium vanadium composite oxides such as LiV2O3, and transition metal oxides such as VO5 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 nickel vanadate 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 LiNiO. 1 / 3 Co 1 / 3 Mn 1 / 3 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 such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.). Examples of binders that can be used include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-containing rubber, as well as thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, and natural butyl rubber (NBR). Additionally, aqueous 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, or the like 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 combination. Application methods include roller coating (e.g., applicator roll), screen coating, doctor blade coating, spin coating, and bar coating. Any of these can be used to achieve any desired thickness and shape. Examples of current collectors include aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymers, and conductive glass. For the purpose of improving adhesion, conductivity, and oxidation resistance, aluminum and copper surfaces treated with carbon, nickel, titanium, or silver can also be used. These surfaces can also be subjected to oxidation treatment. The shape of the current collector may be a foil, a film, a sheet, a net, a punched or expanded material, a lath material, a porous material, a foam material, a formed material of a fiber group, etc. The thickness of the current collector is, for example, 1 to 500 μm.

[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 LiVO3. 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. Materials such as copper, nickel, stainless steel, titanium, aluminum, baked carbon, conductive polymers, conductive glass, and Al—Cd alloys can be used as the negative electrode current collector. Materials such as copper whose surfaces have been treated with carbon, nickel, titanium, or silver for the purpose of improving adhesion, conductivity, and reduction resistance can also be used. These surfaces can also be subjected to an oxidation treatment. The shape of the current collector can be the same as that of the positive electrode.

[0016] The ion-conducting medium can be a nonaqueous electrolyte solution containing a supporting salt, a nonaqueous gel electrolyte solution, or the like. Examples of solvents for nonaqueous electrolyte solutions 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 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 can be used alone or in combination. The concentration of the supporting salt in the electrolyte is preferably 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less. 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 nonaqueous 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 via a separator 24, a gasket 25 made 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 calculating the peak potential of the oxidation side determined by cyclic voltammetry as E pa [V], the peak potential on 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 reference potential. When the current collector is made of Cu or an alloy thereof, a redox shuttle agent having an oxidation-reduction potential of less than 3.0 V relative to the lithium reference potential is preferred because it can further suppress the elution of Cu.

[0021] Preferably, the redox shuttle agent 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 bond strength H s and the dispersion power D in the Hansen solubility parameters of the redox shuttle agent p , polarization force P p , hydrogen bond strength H p The distance R to NMP in the Hansen space was calculated using the following formula (1) using 0.5The Hansen solubility parameter (also referred to as 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 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 a Cartesian coordinate system. The solubility of substances with each other is estimated by the distance between the coordinates indicating the HSP of each substance, and it is said that the closer the coordinates are to each other, the more soluble the substance is, and the farther the coordinates are, the less soluble the substance is. For this reason, it is preferable that the redox shuttle agent has a small distance R from NMP in the Hansen space. In the redox shuttle agent, the above-mentioned distance R is, for example, 10.5 MPa. 0.5 It may be less than 10 MPa 0.5 It may be 9.5 MPa or less. 0.5 The Hansen solubility parameter is the value at 25°C. 2 = 4 × (D p -D s ) 2 + (P p -P s ) 2 + (H p -H s ) 2 ...Equation (1)

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

[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 carbon atoms, and even more preferably 6 or less carbon atoms. 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. The viologens preferably have 30 or less carbon atoms, more preferably 20 or less, and even more preferably 14 or less. Specific examples of the 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 to the cation of formula (2). - ), tetrafluoroborate anion (BF4 - ), pentafluoroarsine anion (AsF6 - ), perchlorate anion (ClO - ), Br - , Cl - , F - and inorganic anions such as trifluoromethanesulfonate anion (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]

[0028] A quinone compound is a compound having a structure in which the C—H 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 fewer carbon atoms, more preferably 14 or fewer, and even more preferably 10 or fewer. 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]

[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 pyrazine skeletons, as well as pyridazine skeletons and pyrimidine skeletons, which are isomers of pyrazine. Furthermore, diazabenzene compounds also include naphthyridine skeletons, such as quinoxaline skeletons, benzopyridazine (cinnoline) skeletons, quinazoline skeletons, and phthalazine skeletons, which are isomers of quinoxaline. In formulas (5) to (7), R 24 ~R 31are 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, 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 have been 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 derivatives thereof as a basic skeleton. Examples of quinoxaline compounds include quinoxaline and derivatives thereof as a basic skeleton. Examples of pyrazine compounds include pyrazine and derivatives thereof as a basic skeleton. When the number of aromatic rings increases, as in the case of quinoxaline and phenazine, the solubility in non-aqueous solvents may decrease, so quinoxaline and phenazine are preferred as redox shuttle agents.

[0031]

[0032] The fluorenone-based compound has a fluorenone skeleton in which two hydrogen atoms bonded to the carbon atom at position 9 of the fluorene are replaced with one oxo group (=O). The fluorenone-based compound includes fluorenone and its derivatives. The fluorenone derivative refers to a compound having a substituent other than hydrogen on a carbon atom other than the carbon at position 9 having the oxo group. This fluorenone-based compound may be represented by formula (8). In formula (8), R 32 ~R 39 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, 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 have been 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 39Two or more of the following may be bonded to form a ring. Examples of 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]

[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 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]

[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 LiPF, LiBF, LiAsF, and LiClO, and organic salts such as LiCFSO, LiN(CFSO), and LiC(CFSO). 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 of the solvent other than NMP is preferably 50% by volume or less, 10% by volume or less, 1% by volume 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] [Deactivation 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 inside 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 the deactivator added may be 0.1 μL / mAh or more, 0.5 μL / mAh or more, or 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 the 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, a case in which the redox shuttle agent is phenothiazine is described as an example. Phenothiazine contained in the deactivator exists as a neutral molecule or a cation radical in the electrolyte (ionically conductive 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)), and the anion (PF6 - etc.) and stabilizes (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, by using a deactivator containing NMP 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 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 implemented as any one of the following items [1] to [6]. [1] A non-aqueous secondary battery deactivator, the non-aqueous secondary battery deactivator comprising: a redox shuttle agent having a redox potential, relative to Li, 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 non-aqueous secondary battery deactivator according to item [1], wherein the redox shuttle agent is a ferrocene-based compound or a phenothiazine-based compound. [3] The non-aqueous secondary battery deactivator according to item [1] or [2], containing 0.5 mol / L or more of the redox shuttle agent. [4] A non-aqueous secondary battery deactivator method, comprising: adding the non-aqueous secondary battery deactivator according to any one of items [1] to [3] to the inside of the non-aqueous secondary battery. [5] The method for deactivating a nonaqueous secondary battery according to [4], wherein the deactivator is added in an amount of less than 10 μL / mAh relative to the battery capacity of the nonaqueous secondary battery in the addition step. [6] The method for deactivating a nonaqueous secondary battery according to [4] or [5], wherein the elapsed time 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.

[0049] Examples using the deactivator for nonaqueous secondary batteries according to 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) Nonaqueous Secondary Battery As a nonaqueous 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 is 4.2 V relative to Li), acetylene black, and polyvinylidene fluoride (PVdF) mixed in a mass ratio of 93:4:3 was coated onto an aluminum current collector foil and vacuum dried at 120 °C to obtain a positive electrode. A negative electrode composite consisting of graphite (oxidation-reduction potential at full charge is 0.1 V relative to Li), carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR) mixed in a mass ratio of 98:1:1 was coated onto a copper current collector foil and vacuum dried 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 make the concentration 1 mol / L. A polyethylene separator was sandwiched between the obtained positive electrode and negative electrode, and 0.45 mL of an ion conductive 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) Deactivator A deactivating solution (deactivator) was prepared by dissolving phenothiazine in N-methyl-2-pyrrolidone (NMP) to a concentration of 1.0 mol / L.

[0052] (3) Inactivation Step A nonaqueous secondary battery in a fully charged state (voltage 4.1 V) was opened under an argon atmosphere, and 31.7 μL of inactivation solution was added. After the inactivation solution was added, 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 inactivation 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 deactivating solution was prepared by dissolving phenothiazine in NMP to a concentration of 3.0 mol / L. In Experimental Example 2, the amount of deactivating 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 deactivating 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 deactivating 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 elapsed time 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 decrease the diffusion rate of phenothiazine and thus decrease the battery discharge rate. 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 that of the improvement in the diffusion rate of phenothiazine due to the use of a low-viscosity solvent in Patent Document 2. The mechanism by which the discharge rate is improved by the use of NMP was thought to be a local increase in the phenothiazine concentration due to the suppression of the spread of the deactivator within the battery. The suppression of the spread of the deactivator 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 of 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 a similar effect could be obtained even if the redox shuttle agent was not a phenothiazine-based compound.

[0060] Furthermore, NMP could increase 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) Nonaqueous 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 polyethylene monolayer microporous membrane was prepared as a separator. The positive and negative electrodes were opposed to each other via a separator impregnated with approximately 0.45 mL of electrolyte solution 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 reach a fully charged state.

[0062] (2) Deactivator A deactivating solution (deactivator) was prepared by dissolving phenothiazine in N-methyl-2-pyrrolidone (NMP) to a concentration of 1.0 mol / L.

[0063] (3) Inactivation Step The battery was fully charged (voltage 3.75 V) and opened under an argon atmosphere, and 18.7 μL of inactivation solution was added. After the inactivation solution was added, 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 inactivation 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 deactivation 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 was the same as Experimental Example 7, 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 9, the amount of phenothiazine added per battery capacity was 1.9 μmol / mAh.

[0066] Experimental Example 10 was the same as Experimental Example 7, except that the deactivation 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 was the same as Experimental Example 7, except that the deactivation 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 elapsed time 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 in 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] The above results demonstrate 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 supplementary note, 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 NMP used in the present invention is as high as 86° C., and therefore it was presumed that the effect of improving the safety of the inactivation treatment step and the treated battery could also be obtained.

[0073]

[0074]

[0075] This application claims priority from Japanese Patent Application No. 2024-068889, filed on April 22, 2024, the entire contents of which are incorporated herein by reference.

[0076] The present invention is applicable to the field of the battery industry.

[0077] 20 nonaqueous 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, the deactivator comprising: a redox shuttle agent having an oxidation-reduction potential, relative to Li, 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 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. A method for deactivating a non-aqueous secondary battery, comprising: an adding step of adding the deactivator for a non-aqueous secondary battery according to claim 1 or 2 to the interior of the non-aqueous secondary battery.

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

6. 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 drops to 0.5 V or less is 30 hours or less.

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