Deactivating agents and deactivation methods

Abstract

To inactivate a non-aqueous secondary battery more reliably.SOLUTION: A deactivator according to the present disclosure is a deactivator that deactivates a non-aqueous secondary battery, and includes a redox shuttle agent that is a hydroquinone-based compound containing a hydroquinone structure having an oxidation-reduction potential 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 at Li reference potential, 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 is to connect the recovered batteries to a charge / discharge device and discharge them to 0 V. However, this process can take a long time. Furthermore, if the recovered batteries have a current interrupt device (CID), they cannot be discharged at all. Therefore, it has been proposed to add a redox shuttle agent (e.g., ferrocene) that exhibits a redox potential in the range of 3.0 to 4.5 V relative to the redox potential of lithium to the recovered batteries (see Patent Document 1). This allows the battery voltage of a nonaqueous secondary battery to be safely and quickly reduced to 0 V without using a charge / discharge device. [Prior art documents] [Patent documents]

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

[0004] In a deactivation process for nonaqueous secondary batteries using a deactivator consisting of a redox shuttle agent and a nonaqueous solvent, the deactivator must be added to a limited space within the battery. However, reducing the amount of redox shuttle agent added reduces the battery's discharge rate and lengthens the deactivation time. Therefore, it is considered necessary to increase the concentration of the redox shuttle agent in the deactivator and reduce the amount of solution added. In contrast, Patent Document 1 uses a redox shuttle agent with a concentration in the range of 0.01 to 0.1 mmol / L, which requires the addition of a relatively large amount of deactivator to the nonaqueous secondary battery. A deactivator that can more reliably perform deactivation of nonaqueous secondary batteries is desired.

[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 that more reliably deactivates non-aqueous secondary batteries. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above-mentioned object, the present inventors have found that nonaqueous secondary batteries can be more reliably inactivated by using a compound having a hydroquinone structure as a redox shuttle agent, 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 that is a hydroquinone-based compound containing a hydroquinone structure whose oxidation-reduction potential, relative to a Li reference potential, is higher than that of a negative electrode active material of the nonaqueous secondary battery and lower than that of a positive electrode active material of the nonaqueous secondary battery; 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 enable more reliable deactivation of nonaqueous secondary batteries. The reason for this effect is presumed to be as follows: When a redox shuttle agent with a redox potential lower than the positive electrode potential and higher than the negative electrode potential is added to a charged nonaqueous secondary battery, the potential difference between each electrode and the redox shuttle agent serves as a driving force to discharge the battery, thereby deactivating the battery. Furthermore, in this disclosure, a hydroquinone-based compound containing a hydroquinone structure is used as the redox shuttle agent. Hydroquinone is a two-electron reduced form of p-benzoquinone and exhibits various redox mechanisms under the influence of protons. For example, there is a reaction formula in which a two-electron redox reaction occurs between p-benzoquinone and a dianion generated by desorbing a proton from hydroquinone, and another reaction formula in which a two-electron redox reaction occurs without desorbing a proton from hydroquinone. It is presumed that which mechanism prevails in the oxidation-reduction of hydroquinone varies depending on the composition and concentration of the coexisting solvent and supporting salt. However, since either of the oxidation-reduction reactions can be carried out in a variety of solvents, it is presumed that nonaqueous secondary batteries can be more reliably inactivated without being affected by the type of solvent. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing the outline of the configuration of a nonaqueous secondary battery 20. FIG. [Figure 2] FIG. 2 is an explanatory diagram showing the mechanism by which a nonaqueous secondary battery is deactivated. [Figure 3] 1 is a scheme showing an example of an oxidation-reduction reaction of a redox shuttle agent. [Figure 4] Discharge behavior after adding the passivating agents of Experimental Examples 1 and 2 to a fully charged evaluation cell. [Figure 5] 1 shows the discharge behavior after the deactivators of Reference Examples 1 and 2 were added to a fully charged evaluation cell. DETAILED DESCRIPTION OF THE INVENTION

[0011] (deactivating agent) The passivator for a non-aqueous secondary battery according to the present disclosure comprises a redox shuttle agent and a non-aqueous solvent. The redox shuttle agent is a hydroquinone-based compound containing a hydroquinone structure 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. 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.

[0012] [Non-aqueous 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 whose negative electrode active material is a carbon material.

[0013] The positive electrode may be formed by mixing, for example, a positive electrode active material, a conductive material, and a binder, adding an appropriate solvent to form a paste-like positive electrode mixture, applying and drying it on the surface of a current collector, and compressing it as necessary to increase the electrode density. The positive electrode active material may be one having a redox potential based on Li higher than that of the redox shuttle agent contained in the inactivator, and may be one having 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 below), Li (1-x) lithium manganese composite oxides such as Li (1-x) CoO2, etc., lithium cobalt composite oxides such as Li (1-x) lithium nickel composite oxides such as NiO2, Li (1-x) Ni a Mn b O2 (a + b = 1) or Li (1-x) Ni a Mn b lithium nickel manganese composite oxides such as Li (1-x) Ni a Co b Mn c lithium nickel cobalt manganese composite oxides such as Li (1-x) O2 (a + b + c = 1), lithium vanadium composite oxides such as LiV2O3, transition metal oxides such as V2O5, etc. can be used. Also, Li (1-x) olivine-type lithium manganese phosphate compounds such as Li (1-x) olivine-type lithium cobalt phosphate compounds such as CoPO4, Li (1-x) olivine-type lithium nickel phosphate compounds such as NiPO4, etc. can be used. Also, Li (1-x) inverse spinel-type lithium manganese vanadate compounds such as 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 (e.g., natural graphite (e.g., scaly graphite, flake graphite) and artificial graphite), acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (e.g., copper, nickel, aluminum, silver, and gold). Examples of binders that can be used include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-containing rubber; thermoplastic resins such as polypropylene and polyethylene; ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, and natural butyl rubber (NBR). Water-based binders such as cellulose-based binders and aqueous dispersions of styrene butadiene rubber (SBR) can also be used. Examples of solvents that can be used include organic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. Alternatively, a dispersant, thickener, etc. may be added to water, and the active material may be slurried with a latex such as SBR. Examples of thickeners include polysaccharides such as carboxymethyl cellulose and methyl cellulose, either alone or in a mixture of two or more. Application methods include roller coating (e.g., applicator roll), screen coating, doctor blade coating, spin coating, and bar coating. Any of these methods can be used to obtain a desired thickness and shape. Current collectors can be made of aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymers, conductive glass, etc., as well as aluminum or copper whose surfaces have been treated with carbon, nickel, titanium, or silver to improve adhesion, conductivity, and oxidation resistance. These surfaces can also be subjected to oxidation treatment. Current collector shapes include foil, film, sheet, net, punched or expanded, lath, porous, foamed, and fibrous. Thicknesses of current collectors ranging from 1 to 500 μm are typically used.

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

[0016] Examples of 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.

[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 is, for example, a hydroquinone-based compound having a hydroquinone structure. The hydroquinone structure refers to a dihydric phenol structure having a six-membered aromatic hydrocarbon skeleton and two hydroxyl groups. The hydroquinone-based compound is a compound having a hydroquinone structure, including hydroquinone and its derivatives. The hydroquinone derivative refers to a compound having a substituent other than hydrogen on a carbon other than the carbon having a hydroxyl group. This hydroquinone-based compound may be represented by formula (1). Here, the functional group R in formula (1) 1 ~R 4 Examples of the substituents include hydrogen, hydrocarbon groups, carboxyl groups, alkoxy groups, nitro groups, amino groups, and halogens (F, Cl, Br, etc.). Examples of the hydrocarbon group include, for example, chain hydrocarbon groups and cyclic hydrocarbon groups. The chain hydrocarbon may be linear or branched. Examples of the chain 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 halogeno group (F-, Cl-, Br-, etc.). Of these, the hydrocarbon group is preferably a straight-chain alkyl group, and preferably has no substituent. Each hydrocarbon group preferably has 20 or less carbon atoms, more preferably 10 or less, and even more preferably 6 or less.

[0020] [ka]

[0021] Examples of hydroquinone compounds include those represented by formulas (2) to (16). Specifically, examples of compounds with a basic skeleton include hydroquinone (formula (2)) and its derivatives (formulas (5) to (8)), naphthohydroquinone (formula (3)) and its derivatives (formulas (9) to (12)), and anthrahydroquinone (formula 4) and its derivatives (formulas (13) to (16)). Since the number of aromatic rings in naphthohydroquinone and anthrahydroquinone can decrease solubility in non-aqueous solvents, hydroquinone and its derivatives (formulas (2), (5) to (8)) are more preferred as redox shuttle agents, with hydroquinone (formula (2)) being even more preferred. While formulas (5) to (16) each have one of the following main substituents: a methyl group, a methoxy group, a chloro group, or a nitro group, the substitution position may be changed, or two or more of the above-mentioned substituents may be present at any position.

[0022] [ka]

[0023] The non-aqueous solvent contained in the deactivating agent is preferably a solvent different from the carbonate compound. Examples of carbonate compounds include the cyclic carbonate compounds and chain carbonate compounds described above. This non-aqueous solvent preferably has a higher solubility for the redox shuttle agent and can dissolve it more stably. For example, an aprotic solvent is preferred, and a polar aprotic solvent is more preferred. Examples of this non-aqueous solvent include sulfoxides such as dimethyl sulfoxide (DMSO), amides such as dimethylformamide (DMF), dimethylacetamide (DMA), and hexamethylphosphoric triamide (HMPA), and ethers such as tetrahydrofuran (THF), dioxolane, dioxane, dimethyl ether (DME), diethyl ether (DEE), dimethoxyethane (G1), diglyme (G2), triglyme (G3), and tetraglyme (G4). Of these, DMSO is more preferred as the non-aqueous solvent.

[0024] The concentration of the redox shuttle agent contained in the deactivator is preferably higher, preferably 1.0 mol / L or higher, more preferably 2.0 mol / L or higher, even more preferably 2.5 mol / L or higher, and may be 3.0 mol / 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, or may be 5.0 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] [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 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.

[0027] 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.

[0028] The amount of deactivator added may be appropriately selected depending on the size of the nonaqueous secondary battery, and may be, for example, 0.005 mL to 50 mL, 0.01 mL to 10 mL, or 0.05 mL to 5.0 mL. The amount of 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.

[0029] The nonaqueous secondary battery after the addition step may be held stationary or held while being shaken. The holding time may be a time empirically determined as the time required for the 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, 6 hours to 500 hours, 30 hours to 300 hours, or 50 hours to 200 hours, although it depends on the capacity of the nonaqueous secondary battery and the amount of deactivator added.

[0030] 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.

[0031] Figure 3 shows an example of a redox reaction using a redox shuttle agent. Figure 3A shows reaction A, in which a proton is eliminated when hydroquinone is used; Figure 3B shows reaction B, in which a proton is not eliminated when hydroquinone is used; and Figure 3C shows reaction C, in which benzoquinone is used. Hydroquinone is a two-electron reduced form of p-benzoquinone, but it can undergo various redox mechanisms depending on the influence of the proton. For example, reaction A shows a two-electron redox reaction between p-benzoquinone and the dianion generated by the elimination of a proton from hydroquinone, while reaction B shows a two-electron redox reaction without the elimination of a proton from hydroquinone. It is believed that the mechanism that predominates in the redox reaction of hydroquinone depends on the composition and concentration of the coexisting solvent and supporting salt (Reference: Electrochim. Acta 81 (2012) 275-282). For example, when a redox shuttle agent is used in a carbonate compound, which is the electrolyte of a non-aqueous secondary battery, the redox reactions shown in Reactions A and C may become unstable. On the other hand, when hydroquinone is used as the redox shuttle agent, other reaction mechanisms, such as Reaction B, exist, and it is presumed that the redox reactions will proceed more stably even in the electrolyte of a non-aqueous secondary battery.

[0032] The deactivator and deactivation method described above can more reliably deactivate nonaqueous secondary batteries. The reason for this effect is presumed to be as follows: When a redox shuttle agent with a redox potential lower than the positive electrode potential and higher than the negative electrode potential is added to a charged nonaqueous secondary battery, the potential difference between each electrode and the redox shuttle agent serves as a driving force to discharge the battery, thereby deactivating the battery. Furthermore, in this embodiment, a hydroquinone-based compound containing a hydroquinone structure is used as the redox shuttle agent. Hydroquinone is a two-electron reduced form of p-benzoquinone and exhibits various redox mechanisms under the influence of protons. For example, there is Reaction Formula A ( FIG. 3A ), in which a two-electron redox reaction occurs between p-benzoquinone and a dianion generated by desorbing a proton from hydroquinone. There is also Reaction Formula B ( FIG. 3B ), in which a two-electron redox reaction occurs without desorbing a proton from hydroquinone. It is presumed that which mechanism prevails in the oxidation-reduction of hydroquinone varies depending on the composition and concentration of the coexisting solvent and supporting salt. However, since either of the oxidation-reduction reactions can be carried out in a variety of solvents, it is presumed that nonaqueous secondary batteries can be more reliably inactivated without being affected by the type of solvent.

[0033] 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.

[0034] 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. [Example]

[0035] Below, examples in which the deactivator and deactivation method for non-aqueous secondary batteries of the present disclosure were specifically examined are described as experimental examples. Experimental Example 1 corresponds to an example of the present disclosure, and Experimental Example 2 corresponds to a comparative example.

[0036] (Experimental Example 1) The deactivation behavior of the battery due to the addition of a deactivator was evaluated. The evaluation cells were made of a negative electrode with graphite as the negative electrode active material and a LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 A lithium-ion battery was fabricated consisting of a cathode with O2 as the active material. The anode was made by coating a copper foil with a slurry mixture of graphite, carboxymethyl cellulose, and styrene butadiene rubber (mass ratio 98:1:1) and vacuum drying at 120°C. The cathode was made of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 A slurry mixture of O2, acetylene black, and polyvinylidene fluoride (mass ratio 93:4:3) was coated on aluminum foil and vacuum dried at 120°C. The nonaqueous electrolyte solution was a 1 mol / L solution of lithium hexafluorophosphate (LiPF6) in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (volume ratio 3:4:3). A polyethylene single-layer microporous membrane was used as the separator. The positive and negative electrodes were arranged facing each other with a separator impregnated with the electrolyte interposed between them and sealed in a laminate film to form an evaluation cell. This cell was subjected to two charge-discharge cycles at a temperature of 20°C over a voltage range of 3.0 to 4.1 V, and then charged to 4.1 V to reach a fully charged state. The battery capacity of this evaluation cell was 17 mAh. The battery was fully charged (voltage 4.1 V) and opened under an argon atmosphere. A deactivator was prepared by dissolving hydroquinone in dimethyl sulfoxide (DMSO) at a concentration of 2.5 mol / L. The amount of hydroquinone added relative to the battery capacity was 0.003 mol / Ah. This corresponds to a liquid volume of 0.021 mL for the battery capacity (17 mAh) used in Experimental Example 1. After adding the deactivator, the evaluation cell was resealed, and the change in battery voltage was measured at a temperature of 20°C.

[0037] (Experimental Example 2) Battery deactivation evaluation was carried out under the same conditions as in Experimental Example 1, except that p-benzoquinone dissolved in DMSO at a concentration of 2.5 mol / L was used as the deactivator.

[0038] (Reference example 1) Battery deactivation evaluation was carried out under the same conditions as in Experimental Example 1, except that hydroquinone dissolved in DMSO at a concentration of 0.05 mol / L was used as the deactivator and the amount of hydroquinone added relative to the battery capacity was 0.004 mol / Ah.

[0039] (Reference example 2) Battery deactivation evaluation was carried out under the same conditions as in Experimental Example 1, except that p-benzoquinone dissolved in DMSO at a concentration of 0.05 mol / L was used as the deactivator and the amount of p-benzoquinone added relative to the battery capacity was 0.004 mol / Ah.

[0040] (Results and Considerations) Figure 4 shows the discharge behavior after the deactivators of Experimental Examples 1 and 2 were added to a fully charged evaluation cell. Figure 5 shows the discharge behavior after the deactivators of Reference Examples 1 and 2 were added to a fully charged evaluation cell. Table 1 summarizes the concentrations and amounts of deactivators added for Experimental Examples 1 and 2 and Reference Examples 1 and 2, as well as the deactivation time required for the cell voltage to reach 1.0 V. As shown in Figure 4, in Experimental Example 1, in which a small amount of a high-concentration deactivator was added to the evaluation cell, the battery voltage gradually decreased from 4.1 V after the addition of the deactivator, reaching 3.0 V after 80 hours, 1.0 V after 120 hours, and nearly 0 V after 440 hours. In contrast, in Experimental Example 2, the discharge rate was very slow, and the battery voltage only decreased to 3.6 V 440 hours after addition. Furthermore, as shown in Figure 5, when a large amount of a low-concentration deactivator was added to the evaluation cell, in both Reference Examples 1 and 2, the battery voltage gradually decreased from 4.1 V after the addition of the deactivator and reached 1.0 V or less after 25 hours, and no difference was observed between hydroquinone and p-benzoquinone.

[0041] From the above, it was found that when a hydroquinone / DMSO solution is used as a deactivator, it is possible to quickly discharge the battery to a voltage of nearly 0 V, regardless of the concentration or amount of hydroquinone added. In particular, the effect was remarkable when the concentration of hydroquinone was increased and the amount of deactivator solution was reduced. The reason for this effect is thought to be the influence of the solvent composition and protons. For example, when Li + In the presence of p-benzoquinone, it is thought that while p-benzoquinone exhibits stable redox in DMSO, it does not exhibit reversible redox in the carbonate solvent of a nonaqueous electrolyte. Therefore, in Experiment 2, in which the amount of deactivator was reduced by increasing the concentration of p-benzoquinone, the carbonate solvent in the electrolyte likely reduced the reversibility of the p-benzoquinone redox reaction, resulting in a slower battery discharge rate. On the other hand, hydroquinone exhibits a redox reaction similar to that of p-benzoquinone (Figure 3A) as well as a redox reaction involving protons (Figure 3B). Hydroquinone is a two-electron reduced form of p-benzoquinone, but it exhibits various redox mechanisms depending on the proton. For example, there is Reaction A, in which a two-electron redox reaction occurs between p-benzoquinone and the dianion generated by deprotonation from hydroquinone, and Reaction B, in which a two-electron redox reaction occurs without deprotonation from hydroquinone. It is presumed that which mechanism predominates in the oxidation-reduction of hydroquinone depends on the composition and concentration of the coexisting solvent and supporting salt. In the hydroquinone / DMSO solution of Experimental Example 1, as the amount of deactivator solution was reduced, the amount of DMSO also decreased, and the reversibility of Reaction Formula A was reduced. On the other hand, in Experimental Example 1, when the solution volume was reduced by increasing the concentration of hydroquinone, the oxidation-reduction reaction of hydroquinone involving protons of Reaction Formula B predominates, and it is presumed that this makes it possible to discharge the battery to a voltage of 0 V more quickly and reliably.

[0042] Thus, it was found that a deactivator using a hydroquinone-based redox shuttle agent can more reliably deactivate nonaqueous secondary batteries, regardless of the concentration of the redox shuttle agent. Furthermore, because the capacity of nonaqueous secondary batteries to which a liquid agent can be added is limited, it is inferred that a higher concentration of the redox shuttle agent in the deactivator is preferable, and the content of the hydroquinone-based compound is 1 mol / L or more, more preferably 2 mol / L or more, and even more preferably 2.5 mol / L or more. Furthermore, because the capacity of nonaqueous secondary batteries to which a liquid agent can be added is limited, it is inferred that a smaller amount of redox shuttle agent added in the deactivator is preferable, and it is inferred that the amount of redox shuttle agent relative to the capacity of the nonaqueous secondary battery is 0.1 mol / Ah or less, more preferably 0.01 mol / Ah or less, and even more preferably 0.005 mol / Ah or less. Furthermore, it is believed that the same effects as those described above can be obtained if the redox shuttle agent has a hydroquinone structure, and that it may have any functional group as a substituent.

[0043] [Table 1]

[0044] 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]

[0045] The present invention is applicable to the field of the battery industry. [Explanation of symbols]

[0046] 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 that is a hydroquinone-based compound containing a hydroquinone structure, 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; The hydroquinone-based compound is a deactivator represented by formula (1). 【Chemistry 1】

2. The deactivator described in claim 1, wherein the hydroquinone-based compound is represented by any one of formulas (2) to (16). 【Chemistry 2】

3. The deactivator according to claim 1 or 2, comprising the hydroquinone compound at 1 mol / L or more.

4. The deactivating agent according to any one of claims 1 to 3, wherein the non-aqueous solvent is a solvent different from a carbonate compound.

5. 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 4 to the inside of the non-aqueous secondary battery; An inactivation method comprising:

6. The deactivation method according to claim 5 , wherein the amount of the redox shuttle agent added in the adding step is 0.1 mol / Ah or less relative to the capacity of the nonaqueous secondary battery.

7. 7. The deactivation method according to claim 5, wherein the amount of the redox shuttle agent added in the adding step is 0.001 mol / Ah or more relative to the capacity of the nonaqueous secondary battery.

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