Deactivating agents and deactivation methods

Abstract

To provide a novel deactivator and a novel method for deactivation for deactivating a non-aqueous secondary battery.SOLUTION: The deactivator of the present disclosure is a deactivator for deactivating a non-aqueous secondary battery, and includes: a redox shuttle agent including a fluorenone-based compound having a fluorenone core of which oxidation-reduction potential is a Li reference potential and is higher than that of a negative electrode active material of a non-aqueous secondary battery and is lower than that of a positive electrode active material of a non-aqueous secondary battery; and a non-aqueous solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to deactivating agents and deactivation methods. [Background technology]

[0002] Conventionally, when nonaqueous secondary batteries are recycled or disposed of, 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 to discharge. Furthermore, if the recovered batteries have a current interrupt device (CID) activated, they cannot be discharged at all. Therefore, it has been proposed to add a redox shuttle agent, such as ferrocene, viologen, or quinone, to the recovered batteries (see Patent Documents 1 and 2). This allows the battery voltage of nonaqueous secondary batteries to be lowered safely and quickly without using a charge / discharge device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-137137 [Patent Document 2] Japanese Patent Publication No. 2022-108831 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the deactivators described in Patent Documents 1 and 2 can deactivate non-aqueous secondary batteries, the types of redox shuttle agents have not yet been sufficiently investigated, and there has been a demand for new, better deactivators.

[0005] The present disclosure has been made to solve such problems, and a main object of the present disclosure is to provide a novel deactivating agent and deactivation method for deactivating non-aqueous secondary batteries. [Means for solving the problem]

[0006] As a result of extensive research to achieve the above-mentioned object, the present inventors have found that a nonaqueous secondary battery can be inactivated by using a fluorenone compound having a fluorenone skeleton as a redox shuttle agent of a deactivator, and have thus completed the invention of the present disclosure.

[0007] That is, the deactivating agent of the present disclosure is A deactivator for deactivating a non-aqueous secondary battery, a redox shuttle agent including a fluorenone compound having a fluorenone skeleton, the oxidation-reduction potential of which, 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; a non-aqueous solvent; It includes:

[0008] The inactivation method of the present disclosure also includes: A method for deactivating a non-aqueous secondary battery, comprising: The method includes adding the above-mentioned deactivator for non-aqueous secondary batteries to the inside of the non-aqueous secondary battery. [Effects of the Invention]

[0009] This deactivator and deactivation method can deactivate a nonaqueous secondary battery. The reason for this effect is presumably that the compound having a fluorenone skeleton contained in the deactivator receives electrons from the negative electrode and transfers them to the positive electrode, thereby promoting discharge of the nonaqueous secondary battery and reducing the battery capacity. [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] FIG. 1 is an explanatory diagram showing the oxidation-reduction reaction of fluorenone. [Figure 4] Cyclic voltammogram of Experimental Example 1. [Figure 5] Cyclic voltammogram of Experimental Example 8. [Figure 6] Graph showing the inactivation behavior of Experimental Examples 2 and 9. [Figure 7] Graph showing the inactivation behavior of Experimental Examples 2 to 6. [Figure 8] Graph showing the inactivation behavior of Experimental Examples 3 and 10. [Figure 9] Graph showing the inactivation behavior of Experimental Examples 3 and 11 DETAILED DESCRIPTION OF THE INVENTION

[0011] (deactivating agent) The passivator for a non-aqueous secondary battery of the present disclosure comprises a redox shuttle agent and a non-aqueous solvent. The redox shuttle agent is a compound whose oxidation-reduction potential, relative to the Li reference potential, is higher than that of the negative electrode active material of the non-aqueous secondary battery and lower than that of the positive electrode active material of the non-aqueous secondary battery. The redox shuttle agent comprises a fluorenone-based compound having a fluorenone skeleton. In this specification, the redox shuttle agent refers to a compound that can be oxidized and reduced and that can repeatedly transport charge between a positive electrode and a negative electrode. The non-aqueous solvent is a solvent capable of dissolving the redox shuttle agent.

[0012] [Non-aqueous secondary battery] First, a 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 conduction medium interposed between the positive electrode and the negative electrode and 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 having a carbon material as the negative electrode active material 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 composite material, applying and drying the composite material 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, and may have a redox potential exceeding 3.0 V based on the Li standard potential, preferably 3.5 V or more, more preferably 3.8 V or more, and even more preferably 4.0 V or more. 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, lithium cobalt composite oxides such as Li (1-x) NiO2, lithium nickel composite oxides such as 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 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 and the like are preferred.

[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, 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 aqueous dispersions of cellulose-based materials like carboxymethyl cellulose (CMC) and 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, dispersants, thickeners, etc. can be added to water, and the active material can 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 current collector may be in the form of a foil, film, sheet, net, punched or expanded, lath, porous, foamed, fiber group formed, 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 redox potential of the negative electrode active material is preferably 3.0 V or less, more preferably 2.0 V or less, and even more preferably 1.0 V or less, relative to the Li reference potential. Examples of negative electrode active materials include inorganic compounds such as lithium, lithium alloys, and tin compounds; carbon materials capable of absorbing and releasing lithium ions; composite oxides containing multiple elements; and conductive polymers. Examples of carbon materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Examples of composite oxides include Li4Ti5O 12Examples of the negative electrode active material include lithium titanium composite oxides such as LiV2O3 and lithium vanadium composite oxides such as LiV2O3. Of these, carbon 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. These surfaces can also be oxidized. The shape of the current collector can be the same as that of the positive electrode. Of these, the negative electrode current collector preferably contains copper. Since copper has a redox potential of approximately 3.0 to 3.5 V relative to Li (see, for example, J. Electrochem. Soc. 144 (1997) 3476-3483, J. Mater. Chem. 21 (2011) 9891-9911), it is believed that copper elution can be suppressed by maintaining the negative electrode potential at less than 3.0 V during passivation, and therefore the application of the passivating agent and passivation method described below is particularly significant. Suppressing copper elution from the negative electrode also suppresses copper deposition at the positive electrode, which is preferable because it eliminates the need to remove or recover deposits from the positive electrode when recycling or disposing of the nonaqueous secondary battery after passivation, allowing for efficient recycling or disposal.

[0016] Examples of the ion-conducting medium include a nonaqueous electrolyte solution containing a supporting salt and a nonaqueous gel electrolyte solution. Examples of solvents for nonaqueous electrolyte solutions include carbonate compounds, ester compounds, ether compounds, nitrile compounds, amide compounds, furan compounds, sulfolane compounds, and dioxolane compounds, which can be used alone or in combination. Specific examples of carbonate compounds include cyclic carbonate compounds such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, and chain carbonate compounds such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate. Examples of ester compounds include cyclic ester compounds such as γ-butyllactone and γ-valerolactone, and chain ester compounds such as methyl formate, methyl acetate, ethyl acetate, and methyl butyrate. Examples of ether compounds include dimethoxyethane, ethoxymethoxyethane, and diethoxyethane. Examples of nitrile compounds include acetonitrile and benzonitrile. Examples of amide compounds include dimethylacetamide (DMA) and dimethylformamide. Examples of furan compounds include tetrahydrofuran and methyltetrahydrofuran. Examples of sulfolane compounds include sulfolane and tetramethylsulfolane. Examples of oxolane compounds include 1,3-dioxolane and methyldioxolane. These compounds can be used alone or in combination. Among these, a mixture of a cyclic carbonate compound and a chain carbonate compound, such as DMC-EC, DEC-EC, or DMC-EMC-EC, is preferred as the solvent for the nonaqueous electrolyte. 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, and these 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] This nonaqueous secondary battery may include a separator between the positive electrode and the negative electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the nonaqueous secondary battery, but 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. In addition, it is preferable that either the positive electrode 22 or the negative electrode 23 of this nonaqueous secondary battery 20 contains SBR as a binder.

[0019] [Deactivating agent] Next, the deactivator will be described. The deactivator includes a redox shuttle agent and a non-aqueous solvent. The redox shuttle agent includes a fluorenone-based compound having at least a fluorenone skeleton. The fluorenone-based compound has a fluorenone skeleton in which two hydrogen atoms bonded to the carbon atom at position 9 of fluorene are substituted 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 (1). In formula (1), R 1 ~R 8 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 1 ~R 8 may each independently represent a hydrogen atom, an alkyl group, a phenyl group, an acetyl group, or a halogen atom. 1 ~R8 Four or more of R may be hydrogen. 1 ~R 8 Two or more of these may be bonded to form a ring.

[0020] [ka]

[0021] Examples of fluorenone compounds include fluorenone (formula (2)) as a basic skeleton, and its derivatives, such as 2-aminofluorenone (formula (3)), 2,7-dihydroxyfluorenone (formula (4)), 2-carboxyfluorenone (formula (5)), 2-nitrofluorenone (formula (6)), 2,7-dinitrofluorenone (formula (7)), benzo[B]fluorenone (formula (8)), and 2,7-dibromofluorenone (formula (9)). Formulas (3) to (9) show examples in which one or two amino groups, hydroxy groups, carboxy groups, nitro groups, benzo groups, or bromo groups are substituted as main substituents, but the substitution positions may be changed, and compounds may have three or more substituents at any positions.

[0022] [ka]

[0023] The redox shuttle agent preferably has an oxidation-reduction potential of less than 3.0 V relative to the Li potential. Fluorenone compounds are considered to have an oxidation-reduction potential of less than 3.0 V relative to the Li potential. The redox shuttle agent may have an oxidation-reduction potential of 2.9 V or less relative to the Li potential. The redox shuttle agent may have an oxidation-reduction potential of 0.5 V or more, 1.0 V or more, or 1.5 V or more relative to the Li potential. The redox shuttle agent can be determined by cyclic voltammetry. Specifically, the oxidation-reduction 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 pcWhen [V] is used, E0 = (E pa +E pc ) / 2. When there are two or more oxidation-reduction potentials within the potential window, it is preferable that all of the oxidation-reduction potentials are less than 3.0V.

[0024] The concentration of the redox shuttle agent contained in the deactivator is preferably higher, preferably 50 mmol / L or higher, more preferably 100 mmol / L or higher, even more preferably 200 mmol / L or higher, and may be 500 mmol / L or higher. A higher concentration of the redox shuttle agent is preferable because it allows high-energy density batteries, such as those used in electric vehicles (EVs), to be discharged in a shorter time. The concentration of the redox shuttle agent contained in the deactivator may be below the solubility limit, 5.0 mol / L or lower, or 2.0 mol / L or lower.

[0025] The deactivator may contain solutes other than the redox shuttle agent, but preferably does not contain any solutes. Even if the deactivator contains solutes other than the redox shuttle agent, the concentration is preferably less than 0.1 mmol / L or less than 0.01 mmol / L. The lower the solute content other than the redox shuttle agent in the deactivator, the lower the viscosity tends to be, leading to more rapid deactivation. Examples of solutes include the supporting salts described above. 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.

[0026] The non-aqueous solvent contained in the deactivating agent is not particularly limited as long as it dissolves the redox shuttle agent. This non-aqueous solvent is preferably one that can dissolve the redox shuttle agent more stably and with a high solubility. For example, an aprotic solvent is preferred, and a polar aprotic solvent having polarity is more preferred. Examples of this non-aqueous solvent include ethers such as tetrahydrofuran (THF), dioxolane, dioxane, diethyl ether (DEE), dimethoxyethane (DME), diglyme (G2), triglyme (G3), and tetraglyme (G4); carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC); sulfoxides such as dimethyl sulfoxide (DMSO); and amides such as dimethylformamide (DMF), dimethylacetamide (DMA), and hexamethylphosphoric triamide (HMPA). The non-aqueous solvent may be an ether or a carbonate, which is preferable from the viewpoint of recyclability because it allows the electrode mixture to be inactivated while maintaining the electrode structure without peeling off from the current collector foil.

[0027] [Inactivation method] Next, a method for deactivating the nonaqueous secondary battery using the deactivator described above will be described. This deactivation method includes an addition step of adding the deactivator described above to the interior 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. For example, the battery container may be opened once, the deactivator may be injected, and then resealed as needed. Alternatively, the deactivator may be injected from the outside of the battery container using a syringe and then sealed as needed. The addition step is preferably performed in an inert atmosphere such as an argon atmosphere.

[0028] In this addition step, the deactivator is preferably added in an amount of 0.1 mol / Ah or less relative to the capacity of the nonaqueous secondary battery. Because the internal space of a nonaqueous secondary battery is limited, a smaller amount of deactivator is preferred. This amount may be 0.01 mol / Ah or less, or 0.005 mol / Ah or less. The amount of redox shuttle agent relative to the capacity of the nonaqueous secondary battery may be 0.001 mol / Ah or more, 0.002 mol / Ah or more, or 0.003 mol / Ah or more. Adding an amount of 0.001 mol / Ah or more is preferable because it further shortens the time required for deactivation.

[0029] The amount of the deactivator added may be appropriately selected depending on the size of the nonaqueous secondary battery, and may be, for example, 0.01 mL to 10 mL, or 0.05 mL to 5.0 mL. The amount of the deactivator added may be, for example, 0.01% to 500% or 1% to 300% of the volume [mL] of the ion conductive medium contained in the nonaqueous secondary battery to be deactivated.

[0030] This addition step is preferably carried out on a nonaqueous secondary battery having a negative electrode current collector containing copper, because, as described above, copper has an oxidation-reduction potential of about 3.0 to 3.5 V relative to Li, and therefore, if the negative electrode potential is kept below 3.0 V during passivation, copper elution is suppressed.

[0031] The nonaqueous secondary battery to which the deactivator has been added may be held stationary or may be held while being shaken. The holding time may be a time empirically determined as the time required for deactivation to be completed, depending on the capacity of the nonaqueous secondary battery and the amount of deactivator added. The holding time may be, for example, 5 hours or more, 10 hours or more, or 20 hours or more, depending on the capacity of the nonaqueous secondary battery and the amount of deactivator added. The holding time may also be, for example, 100 hours or less, 50 hours or less, or 20 hours or less.

[0032] The mechanism by which this inactivation method inactivates a non-aqueous secondary battery is presumed to be as follows. Figure 2 is an explanatory diagram showing the mechanism by which a non-aqueous secondary battery is inactivated. When a redox shuttle agent (RS in the figure) that exhibits an oxidation-reduction potential lower than the positive electrode potential and higher than the negative electrode potential is added to the battery, the potential difference between the positive electrode or negative electrode and the redox shuttle agent serves as the driving force for electron transfer from the negative electrode to the redox shuttle agent and from the redox shuttle agent to the positive electrode, causing the battery to discharge. Specifically, the reduced form of the redox shuttle agent (RS in the figure) (red) ) donates electrons to the positive electrode to form the oxidized (ox) ), and the oxidized form of the redox shuttle agent receives electrons from the negative electrode to become the reduced form. This process repeats, resulting in the battery discharging. When the positive electrode potential or negative electrode potential becomes equal to the redox shuttle agent's oxidation-reduction potential, the discharge of that electrode stops. Therefore, the positive electrode potential and negative electrode potential eventually become equal to the potential of the redox shuttle agent, completing the deactivation process. Note that "deactivation is complete" may also refer to the nonaqueous secondary battery being discharged until its SOC reaches 0%. Discharging to 0% SOC prevents the negative electrode potential from being too low, for example, between 1.5 V and 3.0 V relative to the Li reference potential. This reduces the risk of gas generation due to decomposition of the electrolyte, which serves as an ion-conducting medium, and ensures the safety of the electrode itself. Therefore, recycling and disposal after deactivation can be carried out safely. A lower battery voltage after deactivation is preferable because it reduces the risk of sparks. For example, a voltage of 3.0 V or less is acceptable, with 1.2 V or less, 1.0 V or less, or 0.5 V or less being more preferred. Figure 3 is an explanatory diagram showing the oxidation-reduction reaction of fluorenone as a redox shuttle agent. When fluorenone is reduced, it becomes a ketyl radical in the first step, and is further reduced to become a dianion. Dianions are generally unstable, but the aromaticity of the five-membered ring of fluorenone is thought to stabilize it.

[0033] The deactivator and deactivation method described above can deactivate a nonaqueous secondary battery. The reason for this effect is presumably that, for example, the compound having a fluorenone skeleton contained in the deactivator receives electrons from the negative electrode and transfers them to the positive electrode, thereby promoting discharge of the nonaqueous secondary battery and reducing the battery capacity. In particular, the compound having a fluorenone skeleton is presumably capable of exhibiting reversible and stable oxidation-reduction within the battery, since the dianion produced by reduction on the negative electrode surface is stabilized by the aromaticity of the five-membered ring, thereby enabling rapid battery discharge regardless of the solvent. Furthermore, the compound having a fluorenone skeleton has a redox potential of 3 V vs. Li / Li + Therefore, the negative electrode potential after discharge is 3V vs. Li / Li + It is believed that this makes it possible to maintain the temperature at or below 100°C, thereby suppressing copper elution when copper is used in the negative electrode current collector. Furthermore, because compounds having a fluorenone skeleton have relatively high solubility in various non-aqueous solvents, it is possible to increase the concentration of the redox shuttle agent in the deactivator, and it is believed that a relatively small amount of deactivator can be used to deactivate a non-aqueous secondary battery.

[0034] 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.

[0035] For example, in the above-described embodiment, the nonaqueous secondary battery to be deactivated has been described as a lithium ion secondary battery, but is not particularly limited thereto, and may be a hybrid capacitor, a pseudo-electric double layer capacitor, a lithium or sodium alkali metal secondary battery, an alkali metal ion battery, or the like.

[0036] The present disclosure may be any of the following [1] to [7]. [1] A deactivator for deactivating a non-aqueous secondary battery, the deactivator comprising: a redox shuttle agent containing a fluorenone-based compound having a fluorenone skeleton, the redox potential of which, relative to Li, 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 a non-aqueous solvent. [2] The deactivator according to [1], wherein the fluorenone compound is represented by formula (1): [ka] [3] The inactivator according to [1] or [2], wherein the fluorenone-based compound is fluorenone or a fluorenone derivative. [4] The deactivating agent according to any one of [1] to [3], wherein the non-aqueous solvent contains one or more compounds selected from the group consisting of ethers, carbonates, sulfoxides, and amides. [5] The deactivating agent according to any one of [1] to [4], wherein the redox shuttle agent is dissolved in the non-aqueous solvent in an amount of 50 mmol / L to 5 mol / L. [6] A method for deactivating a nonaqueous secondary battery, the method comprising: adding the deactivator for a nonaqueous secondary battery according to any one of [1] to [5] to the inside of the nonaqueous secondary battery. [7] The method for deactivating a battery according to [6], wherein the nonaqueous secondary battery has a negative electrode current collector containing copper in the adding step. [Example]

[0037] Below, examples in which the deactivator and deactivation method for nonaqueous secondary batteries of the present disclosure were specifically examined are described as experimental examples. Experimental Examples 1 to 7 correspond to working examples of the present disclosure, Experimental Examples 8 and 9 correspond to reference examples, and Experimental Examples 10 and 11 correspond to comparative examples.

[0038] (Experimental Example 1) Fluorenone, a redox shuttle agent, was evaluated by cyclic voltammetry using an H-type cell. The measurement solution was prepared by dissolving 1.0 mol / L of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a supporting electrolyte and 50 mmol / L of fluorenone as a redox shuttle agent in N,N-dimethylacetamide (DMA). The working electrode was glassy carbon, the counter electrode was metallic lithium, and the reference electrode was a nickel wire with metallic lithium crimped on it. The measurement temperature was 20°C, and the potential range was 1.0 to 4.0 V vs. Li / Li. + The potential sweep rate was 50 mV / sec.

[0039] (Experimental Example 2) The deactivation behavior of lithium-ion batteries was evaluated using fluorenone as a redox shuttle agent. A 1.0 mol / L solution of fluorenone in dimethoxyethane (DME) was prepared as the deactivation solution. The lithium-ion batteries used for the evaluation were fabricated as follows: LiNi 1 / 3 Co 1 / 3 Mn 1 / 3A positive electrode was fabricated by coating aluminum foil with a positive electrode composite containing 93% by mass of O2, 4% by mass of acetylene black, and 3% by mass of polyvinylidene fluoride. A negative electrode was fabricated by coating copper foil with a negative electrode composite containing 98% by mass of graphite, 1% by mass of carboxymethyl cellulose, and 1% by mass of styrene-butadiene rubber. An electrolyte solution was prepared by dissolving 1.0 mol / L of LiPF6 in a mixed solvent (hereinafter referred to as the electrolyte solvent) containing 30% by volume of ethylene carbonate (EC), 40% by volume of dimethyl carbonate (DMC), and 30% by volume of ethyl methyl carbonate (EMC). A polyethylene monolayer microporous membrane was prepared as a separator. The positive and negative electrodes were placed facing each other with a separator impregnated with the electrolyte interposed between them and sealed in a laminate film. The lithium-ion battery had a capacity of approximately 17 mAh and contained approximately 1 mL of electrolyte (the same applies to Experimental Examples 3 to 7, 9 to 11 described below). The lithium-ion battery thus fabricated was subjected to two charge / discharge cycles in the voltage range of 3 to 4.1 V, and then charged to 4.1 V to reach a fully charged state. The fully charged battery was opened under an argon atmosphere, and 0.127 mL of the above-mentioned deactivation solution was injected. The battery was then resealed, and the voltage change was measured at a temperature of 25°C. The deactivated lithium-ion battery was disassembled under an argon atmosphere, and the electrode was removed. The electrode and metallic lithium were placed in a beaker containing an electrolyte prepared in the same manner as the electrolyte for the lithium-ion battery, and the voltage between the electrode and metallic lithium was measured with a tester.

[0040] (Experimental Example 3) The deactivation behavior was evaluated in the same manner as in Experimental Example 2, except that a deactivation solution prepared by dissolving 1.0 mol / L of fluorenone in the above-mentioned electrolyte solvent was used.

[0041] (Experimental Example 4) The inactivation behavior was evaluated in the same manner as in Experimental Example 2, except that a 1.0 mol / L solution of fluorenone in dimethyl sulfoxide (DMSO) was used as the inactivation solution.

[0042] (Experimental Example 5) The inactivation behavior was evaluated in the same manner as in Experimental Example 2, except that a 1.0 mol / L solution of fluorenone in N,N-dimethylacetamide (DMA) was used as the inactivation solution.

[0043] (Experimental Example 6) The inactivation behavior was evaluated in the same manner as in Experimental Example 2, except that a 1.0 mol / L solution of fluorenone in dimethyl carbonate (DMC) was used as the inactivation solution.

[0044] (Experimental Example 7) The redox potentials of fluorenone derivatives were calculated using density functional theory. The Gibbs free energy (ΔG OX ) and the Gibbs free energy of the reduced form (ΔG RED ) and calculate the target redox potential E from the following formula (A) assuming two-step one-electron reduction. abs was calculated as the absolute potential, where F is the Faraday constant 96485 C / mol. E abs =(ΔG OX -ΔG RED ) / F···(A) From the obtained absolute potential, the oxidation-reduction potential E relative to the lithium electrode was calculated using the following formula (B). RedOx was calculated. E RedOx [V vs. Li + / Li]=E abs -1.4 (B) Free energies were calculated using density functional theory in the Gaussian09 Revision E package, using B3LYP and 6-311++G(d,p) as functionals and basis sets, and incorporating solvation effects with a dielectric constant of 29.11 for the solvent using a continuum polarization model.

[0045] (Experimental Example 8) A measurement solution was prepared by dissolving 1.0 mol / L of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 50 mmol / L of benzophenone as supporting electrolytes in N,N-dimethylacetamide (DMA), and measurements were carried out in the same manner as in Experimental Example 1. The potential range was 0.5 to 4.0 V vs. Li / Li + It was decided.

[0046] (Experimental Example 9) The inactivation behavior was evaluated in the same manner as in Experimental Example 2, except that a solution of 1.0 mol / L of benzophenone dissolved in DME was used as the inactivation solution.

[0047] (Experimental Example 10) The deactivation behavior was evaluated in the same manner as in Experimental Example 2, except that 1.268 mL of a deactivation solution prepared by dissolving 50 mmol / L of methyl viologen in the above-mentioned electrolyte solvent was injected. The measurement temperature was 20°C.

[0048] (Experimental Example 11) The deactivation behavior was evaluated in the same manner as in Experimental Example 2, except that 1.268 mL of a deactivation solution prepared by dissolving 50 mmol / L of parabenzoquinone in the above-mentioned electrolyte solvent was injected. The measurement temperature was 20°C.

[0049] (Results and Discussion) Figure 4 shows the cyclic voltammogram of Experimental Example 1 (fluorenone). Two pairs of redox peaks were observed. These peaks were presumed to be due to the redox of fluorenone. The peak potential E pa , E pc From the value of , the standard oxidation-reduction potential E0 is calculated using the following formula (C). E0=(E pa +E pc ) / 2···(C) Using the above equation (C), the standard redox potential E0 of fluorenone in DMA solvent is 2.08 V vs. Li / Li + and 1.52V vs. Li / Li +Furthermore, no peaks due to reactions other than the oxidation-reduction of fluorenone (side reactions) were observed, suggesting that fluorenone exhibits stable oxidation-reduction in DMA solvent.

[0050] Figure 5 shows the cyclic voltammogram of Experimental Example 8 (benzophenone). In this case, too, two pairs of redox peaks were observed. These peaks are due to the redox of benzophenone, and the redox potential is 1.62 V vs. Li / Li. + and 1.04V vs. Li / Li + However, the peak intensity on the oxidation side was weaker than that on the reduction side, suggesting that the reversibility of the oxidation-reduction reaction was low.

[0051] Figure 6 shows the deactivation behavior of Experimental Example 2 (fluorenone / DME) and Experimental Example 9 (benzophenone / DME). A discharge reaction was observed in Experimental Example 2, but almost no discharge reaction was observed in Experimental Example 9. In Experimental Example 2, the SOC (State of Charge) of the battery reached 0% (voltage 3V) 5.3 hours after the addition of fluorenone, and 20 hours after the addition, the battery discharged to a voltage of approximately 1V. After disassembling the cell after discharge, the potentials of the positive and negative electrodes were measured, and were 3.67V vs. Li / Li, respectively. + and 2.58V vs. Li / Li + It was.

[0052] Figure 7 shows the deactivation behavior of Experimental Example 3 (fluorenone / electrolyte solvent (EC+DMC+EMC)). In Experimental Example 3, the SOC of the battery reached 0% after 13.5 hours, and the battery was further discharged to a voltage of approximately 1 V, confirming that the solution functions as a deactivating solution. After disassembling the cell after discharge, the potentials of the positive and negative electrodes were measured, and were 3.66 V vs. Li / Li, respectively. + and 2.77V vs. Li / Li + It was.

[0053] FIG. 7 also shows the deactivation behavior of Experimental Example 2 (fluorenone / DME), Experimental Example 4 (fluorenone / DMSO), Experimental Example 5 (fluorenone / DMA), and Experimental Example 6 (fluorenone / DMC). A discharge reaction was confirmed in all Experimental Examples 2 to 6, and it was confirmed that they functioned as a deactivator. After disassembling the cell after discharge, the potentials of the positive and negative electrodes were measured. In Experimental Example 4, the positive electrode was 3.68 V vs. Li / Li. + , negative electrode is 2.56V vs. Li / Li + In Experimental Example 5, the positive electrode was 3.66 V vs. Li / Li + , negative electrode is 2.72V vs. Li / Li + In Experimental Example 6, the positive electrode was 3.65 V vs. Li / Li + , negative electrode is 2.49V vs. Li / Li + It was.

[0054] Figure 8 shows the deactivation behavior of Experimental Example 3 (fluorenone / electrolyte solvent (EC+DMC+EMC)) and Experimental Example 10 (methyl viologen / electrolyte solvent (EC+DMC+EMC)). In Experimental Example 10, it took 35 hours to discharge down to a voltage of 3 V. This confirmed that the use of fluorenone improved the discharge rate compared to methyl viologen.

[0055] FIG. 9 shows the deactivation behavior of Experimental Example 3 (fluorenone / electrolyte solvent (EC+DMC+EMC)) and Experimental Example 11 (parabenzoquinone / electrolyte solvent (EC+DMC+EMC)). In Experimental Example 11, almost no discharge reaction was observed. It has been confirmed that a deactivation solution using parabenzoquinone functions as a deactivation solution when N,N-dimethylacetamide is used as the solvent (Patent Publication No. 2022-108831). However, it was found that it does not function as a deactivation solution in carbonate solvents, which are commonly used as electrolytes for lithium-ion batteries. From this, it was inferred that when a deactivation solution containing parabenzoquinone is used in a lithium-ion battery containing a carbonate solvent in the electrolyte, the deactivation solution may be diluted by the carbonate solvent contained in the electrolyte, resulting in the inactivation failure. In contrast, when fluorenone was used, it was confirmed that the solution functions as a deactivation solution even in carbonate solvents, suggesting that such a risk does not exist.

[0056] From the above, it was found that the deactivation solution using fluorenone can rapidly discharge the battery voltage regardless of the solvent composition, and the negative electrode potential can be kept at 3 V vs. Li / Li. + It was presumed that copper elution could be suppressed by keeping the temperature below this range.

[0057] The calculation results of the redox potentials of fluorenone (the above formula (2)) and fluorenone derivatives (the above formulas (3) to (9)) are shown in Table 1. Compared with the experimental result of Experimental Example 1, the calculated redox potential of fluorenone was lower by about 0.3 V. However, regardless of the type of substituent, the first redox potential was 2.7 V vs. Li / Li. + or less and the second oxidation-reduction potential is 0.5V vs. Li / Li + The first oxidation-reduction potential of the fluorenone derivatives was the value reported in J.Phys.Org.Chem,24(2011)1119-1128 and ECS Transactions,89(1)(2019)49-59. From the above, the first oxidation-reduction potential of all fluorenone derivatives was 3.0 V vs. Li / Li + or less and the second oxidation-reduction potential is 0.5V vs. Li / Li+ It is considered that the above is the case, and it is presumed that the elution of copper can be suppressed even when used as a deactivating agent.

[0058] [Table 1]

[0059] 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. [Industrial Applicability]

[0060] The present disclosure is applicable to the field of the battery industry. [Explanation of symbols]

[0061] 20 non-aqueous secondary battery, 21 battery case, 22 positive electrode, 23 negative electrode, 24 separator, 25 gasket, 26 sealing plate, 27 ion conductive medium.

Claims

1. A deactivator for deactivating a non-aqueous secondary battery, a redox shuttle agent including a fluorenone compound having a fluorenone skeleton, the redox potential of which 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 relative to a Li reference potential; a non-aqueous solvent; A deactivating agent comprising:

2. The deactivator according to claim 1 , wherein the fluorenone-based compound is represented by formula (1): 【Chemistry 1】

3. The deactivator according to claim 1 , wherein the fluorenone-based compound is fluorenone or a fluorenone derivative.

4. The deactivating agent according to any one of claims 1 to 3, wherein the non-aqueous solvent contains one or more compounds selected from the group consisting of ethers, carbonates, sulfoxides, and amides.

5. 4. The deactivating agent according to claim 1, wherein the redox shuttle agent is dissolved in the non-aqueous solvent in a range of 50 mmol / L to 5 mol / L.

6. A method for deactivating a non-aqueous secondary battery, comprising: an addition step of adding the deactivator for a non-aqueous secondary battery according to any one of claims 1 to 3 to the inside of the non-aqueous secondary battery; An inactivation method comprising:

7. The deactivation method according to claim 6 , wherein the nonaqueous secondary battery has a negative electrode current collector containing copper in the addition step.

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