Inactivating agent and inactivation method

Abstract

To simplify processes such as recycling treatment.SOLUTION: A deactivator according to the present disclosure for deactivating a non-aqueous secondary battery with an electrode including a carbon material as an active material includes: a redox shuttle agent having an oxidation-reduction potential 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 in Li reference potential; and a non-aqueous solvent co-inserted into the carbon material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to inactivating agents and inactivating methods. [Background technology]

[0002] Conventionally, when recycling or disposing of non-aqueous secondary batteries, deactivation treatment is performed to deactivate the recovered batteries. For example, this treatment can involve connecting the recovered batteries to a charge / discharge device and discharging them to 0V, but this can be time-consuming. Furthermore, if the recovered battery is one that has already undergone current interruption (CID) activation, discharge itself is impossible. Therefore, it has been proposed to add a redox shuttle agent (e.g., ferrocene) exhibiting an oxidation-reduction potential in the range of 3.0 to 4.5V relative to the lithium oxidation-reduction potential to the inside of the recovered battery (see Patent Document 1). This allows for the safe and rapid reduction of the battery voltage of non-aqueous secondary batteries to 0V without the use of a charge / discharge device. Additionally, a method has been proposed to remove carbon from the electrode composite material from the copper foil surface of the negative electrode sheet of a lithium-ion battery using an aqueous release agent (see, for example, Patent Documents 2 and 3). This method claims to significantly improve recycling costs by recovering the copper foil and carbon using the release agent. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-137137 [Patent Document 2] Japanese Patent Publication No. 2015-26566 [Patent Document 3] Japanese Patent Publication No. 2007-179774 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, when a non-aqueous secondary battery is deactivated using the redox shuttle agent described in Patent Document 1, the deactivated secondary battery is to be disassembled and reused, but it is necessary to perform a separate separation process for the electrode composite material, which presents a problem of a complicated processing step. On the other hand, according to the stripping methods of Patent Documents 2 and 3, a separate deactivation process is required in addition to the stripping process. Furthermore, since the above-mentioned deactivators are non-aqueous and the stripping agents are aqueous solutions, they could not be mixed and used simultaneously. Thus, there was a need to simplify the processes of deactivation and electrode disassembly.

[0005] This disclosure is made to solve these problems and primarily aims to provide an inactivating agent and an inactivating method that can simplify the process. [Means for solving the problem]

[0006] Through diligent research to achieve the above-mentioned objectives, the present inventors discovered that using a solvent co-inserted between layers in a system where carbon material is used as the electrode active material can deactivate non-aqueous secondary batteries and further promote the peeling and decomposition of the electrode composite material, thus completing the invention disclosed herein.

[0007] In other words, the inactivator disclosed herein is A deactivator for inactivating a non-aqueous secondary battery equipped with an electrode containing a carbon material as an active material, A redox shuttle agent 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 a Li reference potential, A non-aqueous solvent to be co-inserted into the carbon material, It includes.

[0008] Furthermore, the deactivation method of this disclosure is A method for deactivating a non-aqueous secondary battery equipped with electrodes containing a carbon material as an active material, The method includes an addition step of adding the above-mentioned deactivator for non-aqueous secondary batteries to the inside of the non-aqueous secondary battery. [Advantages of the Invention]

[0009] In this inactivator and inactivation method, in a material containing a carbon material as an electrode active material, the process can be further simplified. The reason for obtaining such an effect is presumably as follows, for example. When a redox shuttle agent having a redox potential lower than the positive electrode potential and higher than the negative electrode potential is added to a non-aqueous secondary battery in a charged state, the discharge of the battery proceeds using the potential difference between each electrode and the redox shuttle agent as a driving force, and the inactivation of the battery can be achieved. Further, a solvent that is co-inserted as a solvent of the redox shuttle agent is used. As the discharge of the battery proceeds, the peeling due to the co-insertion of the solvent into the active material of the carbon material also proceeds, and the current collector foil and the electrode binder can be separated. Therefore, compared with a case where the inactivation treatment and the electrode peeling treatment are performed separately, for example, the processes such as recycling treatment can be further simplified. [Brief Description of the Drawings]

[0010] [Figure 1] Cross-sectional view showing the schematic configuration of the non-aqueous secondary battery 20. [Figure 2] Explanatory drawing showing the mechanism by which the non-aqueous secondary battery is inactivated. [Figure 3] Redox reaction when p-benzoquinone and 1,4-naphthoquinone are used. [Figure 4] Explanatory drawing showing the crystal structure of graphite. [Figure 5] X-ray diffraction measurement results obtained by collecting and measuring the peeled powder of Experimental Example 1. [Figure 6] Cyclic voltammetry measurement results of Experimental Examples 4 and 5. [Figure 7] Discharge behavior of the battery after adding the inactivator of Experimental Examples 6 and 7. [Embodiments for Carrying Out the Invention]

[0011] The deactivator for non-aqueous secondary batteries described herein is a deactivator for deactivating a non-aqueous secondary battery equipped with electrodes containing a carbon material as an active material. This deactivator comprises a redox shuttle agent and a non-aqueous solvent. The redox shuttle agent has 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, based on the Li reference potential. The non-aqueous solvent is co-inserted into the carbon material. In this specification, a redox shuttle agent means an oxidizable and reducible compound that can repeatedly transport charge between the positive and negative electrodes.

[0012] [Non-aqueous secondary battery] First, let's describe the non-aqueous secondary battery that is the target of deactivation. A non-aqueous secondary battery has electrodes that contain a carbon material as the active material. This non-aqueous secondary battery comprises a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous ion-conducting medium interposed between the positive and negative electrodes to conduct 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. The carbon material may be, for example, a graphite-based material and may be the negative electrode active material. In the following, for the sake of explanation, we will mainly describe the case where the non-aqueous secondary battery is a lithium-ion secondary battery in which the 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 any material as long as its redox potential based on Li is higher than that of the redox shuttle agent contained in the deactivator. However, it may be a material with a redox potential exceeding 3.0 V based on the Li reference potential, preferably 3.5 V or higher, more preferably 3.8 V or higher, and even more preferably 4.0 V or higher. 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) 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) 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 type 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, for example LiCoO2, LiNiO2, LiMnO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 is preferred.

[0014] As the conductive material for the positive electrode, for example, graphite such as natural graphite (scaly graphite, flake graphite) or artificial graphite, acetylene black, carbon black, Ketjenblack, carbon whiskers, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.) can be used. As the binder, for example, fluororesins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber, or thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, and natural butyl rubber (NBR) can be used. In addition, aqueous binders such as cellulose-based or aqueous dispersions of styrene-butadiene rubber (SBR) can be used. As the solvent, for example, organic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran can be used. Alternatively, a dispersant, thickener, etc., may be added to water, and the active material may be slurryed with latex such as SBR. As a thickener, for example, polysaccharides such as carboxymethylcellulose and methylcellulose can be used alone or as a mixture of two or more. As a coating method, for example, roller coating such as applicator roll coating, screen coating, doctor blade method, spin coating, and bar coating can be used, and any thickness and shape can be achieved using any of these. As a current collector, aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, conductive glass, etc., as well as aluminum and copper whose surfaces have been treated with carbon, nickel, titanium, or silver for the purpose of improving adhesion, conductivity, and oxidation resistance, can be used. For these, the surface can also be oxidized. As for the shape of the current collector, examples include foil, film, sheet, net, punched or expanded, lath, porous, foam, and fiber group formation. 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 a suitable solvent to form a paste-like negative electrode composite, applying and drying it on the surface of a current collector, and compressing it as needed to increase the electrode density, or by tightly bonding the negative electrode active material and the current collector. The negative electrode active material should have a redox potential with respect to Li that is lower than that of the redox shuttle agent contained in the deactivator, but it is preferable that the redox potential is less than 1.5V with respect to Li, more preferably 1.0V or less, and even more preferably 0.5V or less. Examples of negative electrode active materials include carbon materials capable of intercalating and releasing lithium ions. Examples of carbon materials include those having a layered structure, such as graphites. Examples of graphites include natural graphite (scaly graphite, flake graphite) and artificial graphite. Furthermore, the conductive material, binder, and solvent used in the negative electrode can be those exemplified for the positive electrode. The negative electrode current collector can be made of copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymers, conductive glass, Al-Cd alloys, etc., and for the purpose of improving adhesion, conductivity, and reduction resistance, materials such as copper with surfaces treated with carbon, nickel, titanium, or silver can also be used. These 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 is preferably made of copper. Since copper has an oxidation-reduction potential of about 3.0 to 3.5 V with respect to Li (see J. Electrochem. Soc. 144 (1997) 3476-3483, J. Mater. Chem. 21 (2011) 9891-9911, etc.), it is thought that copper dissolution will be suppressed if the negative electrode potential is kept below 3.0 V during deactivation, and the application of the deactivating agents and deactivation methods described later is particularly significant. When the leaching of copper from the negative electrode is suppressed, the deposition of copper at the positive electrode is also suppressed. Therefore, when recycling or disposing of non-aqueous secondary batteries after deactivation, there is no need to remove or recover the deposited material from the positive electrode, which is preferable because it allows for efficient recycling or disposal.

[0016] As the ion conducting medium, non-aqueous electrolytes containing supporting salts or non-aqueous gel electrolytes can be used. Examples of solvents for non-aqueous electrolytes include carbonate compounds, ester compounds, ether compounds, nitrile compounds, amide compounds, furan compounds, sulfolane compounds, and dioxolane compounds, which can be used individually or in mixtures. Specifically, examples of carbonate compounds include cyclic carbonate compounds such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, as well as linear 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. Furthermore, examples of ester compounds include cyclic ester compounds such as γ-butyllactone and γ-valerolactone, and linear 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; and examples of oxolane compounds include 1,3-dioxolane and methyldioxolane. These can be used individually or in combination. Of these, a mixture of cyclic carbonate compounds and linear carbonate compounds, such as DMC-EC, DEC-EC, and DMC-EMC-EC, is preferred as the solvent for the non-aqueous 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, which can be used individually or in combination.The supporting salt is preferably concentrated in the electrolyte at a concentration of 0.1 mol / L or more and 5 mol / L or less, and more preferably at a concentration of 0.5 mol / L or more and 2 mol / L or less. In addition, instead of a liquid 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 as the ion conducting medium.

[0017] This non-aqueous secondary battery may include a separator between the positive and negative electrodes. The separator is not particularly limited as long as its composition can withstand the operating range of the non-aqueous secondary battery, but examples include polymer nonwoven fabrics such as polypropylene nonwoven fabric, and thin microporous membranes of olefin resins such as polyethylene. These may be used individually or in combination.

[0018] The shape of this non-aqueous secondary battery is not particularly limited, but examples include coin-type, button-type, sheet-type, stacked-type, cylindrical-type, flat-type, and rectangular-type. It may also be a large type used in electric vehicles, etc. An example of a non-aqueous secondary battery is shown in Figure 1. Figure 1 is a schematic cross-sectional view showing the configuration of a coin-type non-aqueous secondary battery 20. As shown in Figure 1, the non-aqueous secondary battery 20 comprises a cup-shaped battery case 21, a positive electrode 22 having a positive electrode active material and provided at the bottom of the battery case 21, a negative electrode 23 having a negative electrode active material and provided at a position 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. This non-aqueous secondary battery 20 includes an ion-conducting medium 27 in which a lithium salt is dissolved in the space between the positive electrode 22 and the negative electrode 23. The negative electrode active material is a carbon material.

[0019] [Deactivating agent] Next, the deactivator will be described. The deactivator includes a redox shuttle agent and a non-aqueous solvent. The non-aqueous solvent included in the deactivator is not particularly limited as long as it is co-inserted into the carbon material, and examples include dimethyl sulfoxide (DMSO), 1,2-dimethoxyethane (DME), and propylene carbonate (PC), of which DMSO is more preferred.

[0020] The redox shuttle agent contained in the deactivator has an oxidation-reduction potential (AMD) that is higher than that of the negative electrode active material of the non-aqueous secondary battery to be deactivated, and lower than that of the positive electrode active material of the non-aqueous secondary battery to be deactivated, using Li as the reference potential. Furthermore, it is preferable that the AMD redox shuttle agent has an AMD redox potential of less than 3.0V. The oxidation-reduction potential of the AMD redox shuttle agent can be determined by cyclic voltammetry. Specifically, the AMD redox potential E0(V) of the AMD redox shuttle agent can be determined by cyclic voltammetry using the formula E0 = (Ea + Ec) / 2, where Ea(V) is the peak potential on the oxidation side and Ec(V) is the peak potential on the reduction side. If there are two or more AMD redox potentials within the potential window, it is preferable that all AMD redox potentials are less than 3.0V (preferably within the preferred range described later). Cyclic voltammetry is preferably performed on a measurement solution containing a non-aqueous solvent, a supporting salt, and the AMD redox shuttle agent. The non-aqueous solvent in the measurement solution may be the same type as the non-aqueous solvent of the target inactivator. Examples of supporting electrolytes in the measurement solution include inorganic salts such as LiPF6, LiBF4, LiAsF6, and LiClO4, and organic salts such as LiCF3SO3, LiN(CF3SO2)2, and LiC(CF3SO2)3, which can be used individually or in combination. The supporting electrolyte in the measurement solution may be the same type as the supporting salt of the non-aqueous secondary battery to be deactivated. The concentration of the supporting electrolyte in the measurement solution may be 0.1 mol / L or more and 5 mol / L or less, or 0.5 mol / L or more and 2 mol / L or less, or the same as the concentration of the supporting salt in the ion conduction medium of the non-aqueous secondary battery to be deactivated. The concentration of the redox shuttle agent in the measurement solution may be 1 mmol / L or more and less than or equal to the solubility, or 30 mmol / L or more and less than or equal to the solubility, or 50 mmol / L or more and 100 mmol / L or less. The concentration of the redox shuttle agent in the measurement solution may be the same as the concentration of the redox shuttle agent of the target inactivator.

[0021] The redox shuttle agent is preferably one whose oxidation-reduction potential is less than 3.0V on the Li-based potential, preferably between 0.5V and 3.0V, more preferably between 1.0V and 3.0V, and even more preferably between 1.5V and 2.9V. Examples of redox shuttle agents with an oxidation-reduction potential of less than 3.0V on the Li-based potential include quinone analogs and viologen analogs. Quinone analogs refer to quinones and quinone derivatives, and viologen analogs refer to viologens and viologen derivatives. Viologens are compounds having a structure in which hydrocarbon groups are bonded to two pyridine ring nitrogen atoms of a 4,4'-bipyridine skeleton.

[0022] Quinone analogs are compounds having a structure in which the CH groups on two carbon atoms of an aromatic hydrocarbon skeleton are each replaced with C=O groups. Quinone analogs may have an aromatic hydrocarbon skeleton with 4 to 7 membered rings, but those having an aromatic hydrocarbon skeleton with 6 membered rings (those having a benzoquinone structure) are preferred. Quinone analogs may have, for example, a p-benzoquinone structure of formula (q1) or an o-benzoquinone structure of formula (q2), but those having a p-benzoquinone structure of formula (q1) are preferred. Quinone analogs may have a structure in which a substituent such as a hydrocarbon group, carboxyl group, alkoxy group, nitro group, amino group, or halogen (F, Cl, Br, etc.) is introduced to one or more carbon atoms of the aromatic hydrocarbon skeleton that do not constitute a C=O group. Preferred hydrocarbon groups include, for example, linear hydrocarbon groups (which may be straight or branched) and cyclic hydrocarbon groups. Examples of linear hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decanyl, undecanyl, and dodecanyl groups; and alkenyl groups such as vinyl, propenyl, butenyl, pentenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups. Examples of cyclic hydrocarbon groups include cycloalkyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, and cycloheptyl groups; and aryl groups such as phenyl and naphthyl groups. These hydrocarbon groups may also have substituents such as carboxyl, alkoxy, nitro, amino, and halogens (F, Cl, Br, etc.). Of these, linear alkyl groups are preferred, and those without substituents are preferred. Each hydrocarbon group preferably has 20 or fewer carbon atoms, more preferably 10 or fewer, and even more preferably 6 or fewer. Quinone analogs, when having multiple substituents, may have substituents bonded together to form a ring. Examples of quinone analogs that have substituents bonded together to form a ring include naphthoquinones (such as 1,4-naphthoquinone and 1,2-naphthoquinone), anthraquinones (such as 9,10-anthraquinone), and their derivatives.The quinone analogs preferably have 20 or fewer carbon atoms, more preferably 14 or fewer, and even more preferably 10 or fewer.

[0023] [ka]

[0024] Quinone analogs include, specifically, p-benzoquinone (formula (q3)), methyl-p-benzoquinone (formula (q4)), 2,5-dimethyl-1,4-benzoquinone (formula (q5)), methoxybenzoquinone (formula (q6)), 2,5-dihydroxy-1,4-benzoquinone (formula (q7)), 1,4-naphthoquinone (formula (q8)), 2-methyl-1,4-naphthoquinone (formula (q9)), and 2,3-dichloro-1,4 Examples include naphthoquinone (formula (q10)), 2-hydroxy-1,4-naphthoquinone (formula (q11)), anthraquinone (formula (q12)), 2-methylanthraquinone (formula (q13)), 2-tert-butylanthraquinone (formula (q14)), 1-chloroanthraquinone (formula (q15)), 1,4-dihydroxyanthraquinone (formula (q16)), and 1-nitroanthraquinone (formula (q17)). Of these, p-benzoquinone and 1,4-naphthoquinone are preferred as redox shuttle agents.

[0025] [ka]

[0026] As the inactivating agent, it is more preferable to include one or more of p-benzoquinone and 1,4-naphthoquinone as the redox shuttle agent and DMSO as the non-aqueous solvent. In this combination of redox shuttle agent and non-aqueous solvent, the oxidized and reduced forms of the redox shuttle agent are stabilized by interaction with the non-aqueous solvent, and it is thought that the redox shuttle agent exhibits more stable oxidation-reduction.

[0027] The redox shuttle agent preferably has a solubility of 1 mmol / L or more, more preferably 30 mmol / L or more, and even more preferably 50 mmol / L or more, in the non-aqueous solvent contained in the inactivator at 20°C. This is because a higher solubility of the redox shuttle agent allows for a higher concentration of the redox shuttle agent in the inactivator, and a higher concentration of the redox shuttle agent in the inactivator allows for faster discharge of high-energy-density batteries, such as those used in electric vehicles (EVs). The quinone analogues and viologen analogues mentioned above have relatively high solubility in non-aqueous solvents, so using them as redox shuttle agents is preferable because it allows for a higher concentration of the redox shuttle agent in the inactivator. The redox shuttle agent may have a solubility of 1000 mmol / L or less, or 100 mmol / L or less, in the non-aqueous solvent contained in the inactivator at 20°C.

[0028] The concentration of the redox shuttle agent in the inactivator is preferably 1 mmol / L or higher, more preferably 30 mmol / L or higher, and even more preferably 50 mmol / L or higher. This is because a higher concentration of the redox shuttle agent allows for faster discharge of high-energy-density batteries, such as those used in electric vehicles (EVs). The concentration of the redox shuttle agent in the inactivator may be below the solubility limit, or 100 mmol / L or lower.

[0029] The deactivator preferably does not contain solutes (e.g., supporting salts) other than the redox shuttle agent, and if it does contain solutes other than the redox shuttle agent, it is preferable that the amount is less than 0.1 mmol / L or less than 0.01 mmol / L. This is because, in deactivators, the less solute other than the redox shuttle agent there is, the lower the viscosity tends to be, and therefore deactivation proceeds more rapidly. From this viewpoint, it is preferable that the deactivator does not contain supporting salts, but it may contain supporting salts. Examples of supporting salts include inorganic salts such as LiPF6, LiBF4, LiAsF6, and LiClO4, and organic salts such as LiCF3SO3, LiN(CF3SO2)2, and LiC(CF3SO2)3. The supporting salt may be the same as or different from the supporting salt contained in the ion conduction medium of the non-aqueous secondary battery to be deactivated.

[0030] [Inactivation method] Next, a method for deactivating the non-aqueous secondary battery described above using the aforementioned deactivator will be explained. This deactivation method includes an addition step of adding the deactivator to the inside of the non-aqueous secondary battery.

[0031] In the addition step, the above-mentioned deactivator is added to the inside of a non-aqueous secondary battery having electrodes containing carbon material as an active material. Specifically, the deactivator is added so that it comes into contact with the positive and negative electrodes of the non-aqueous secondary battery. The method of adding the deactivator is not particularly limited, but the battery container may be opened and the deactivator injected, and then resealed if necessary, or it may be injected from outside the battery container with a syringe, and then sealed if necessary. The addition step is preferably carried out under an inert atmosphere such as an argon atmosphere.

[0032] The amount of inactivating agent to be added may be appropriately selected depending on the size of the non-aqueous secondary battery, for example, it may be 0.1 mL or more and less than 10 mL, or 0.5 mL or more and 5.0 mL or less. The amount of inactivating agent to be added may be, for example, 0.1% or more and 500% or 10% or more and 300% or less relative to the volume [mL] of the ion conduction medium contained in the non-aqueous secondary battery to be deactivated. The amount of redox shuttle agent to be added to the non-aqueous secondary battery may be, for example, 0.0001 mol / Ah or more and 0.1 mol / Ah or less, or 0.001 mol / Ah or more and 0.01 mol / Ah or less, per the fully charged battery capacity [Ah] of the non-aqueous secondary battery to be deactivated.

[0033] This addition step is preferably performed on non-aqueous secondary batteries having a negative electrode current collector containing copper. As mentioned above, copper has an oxidation-reduction potential of approximately 3.0 to 3.5V relative to the Li reference potential, so maintaining the negative electrode potential below 3.0V during deactivation suppresses the dissolution of copper. Furthermore, this addition step is preferably performed on non-aqueous secondary batteries using graphite as the negative electrode active material. This is because the non-aqueous electrolyte is co-inserted and is inserted into the layered structure, contributing to the decomposition of the electrode composite material. In addition, in this addition step, it is preferable to use a non-aqueous secondary battery with a remaining capacity (SOC) of 10% or more, or 20% or more, more preferably 50% or more, and even more preferably 80% or more. When there are many lithium ions present between the layers of carbon material, such as when the SOC is 50% or more, the co-insertion of the non-aqueous solvent proceeds more easily due to interactions, which is preferable.

[0034] The non-aqueous secondary battery after the additive step may be held at rest, for example, or held while being vibrated. The holding time may be determined empirically as the time until deactivation is complete, but for example, it may be 6 hours or more and 500 hours or less, 30 hours or more and 300 hours or less, or 50 hours or more and 200 hours or less.

[0035] The mechanism by which this deactivation method inactivates non-aqueous secondary batteries is presumed to be as follows. Figure 2 is an explanatory diagram showing the mechanism by which non-aqueous secondary batteries are inactivated. When a redox shuttle agent (RS in the figure), which has an oxidation-reduction potential lower than the positive electrode potential and higher than the negative electrode potential, is added to the battery, electron transfer proceeds from the negative electrode to the redox shuttle agent and from the redox shuttle agent to the positive electrode, driven by the potential difference between the positive or negative electrode and the redox shuttle agent, 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, forming an oxidizer (RS in the diagram). (ox) ) and the oxidized form of the redox shuttle agent receives electrons from the negative electrode and becomes a reduced form, and this process proceeds repeatedly, causing the battery to discharge. When the positive electrode potential or negative electrode potential becomes equal to the oxidation-reduction potential of the redox shuttle agent, 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, and inactivation is completed. Note that "inactivation is complete" may mean that the battery has been discharged until the SOC of the non-aqueous secondary battery is at least 0%. If the battery has been discharged until the SOC is 0%, the negative electrode potential is not too low, for example, more than 1.5V but less than 3.0V with a Li reference potential, so gas generation due to decomposition of the electrolyte, which is an ion conducting medium, is less likely to occur, and the safety of the electrode itself is high. Therefore, recycling and disposal after inactivation can be carried out safely. A lower battery voltage after inactivation is preferable because sparking is less likely to occur, for example, it may be 3.0V or less, and it is more preferable to be 1.2V or less, 1.0V or less, or 0.5V or less. Figure 3 shows specific examples of redox reactions when p-benzoquinone or 1,4-naphthoquinone is used as a redox shuttle agent. In these reactions, a radical anion is generated by one-electron reduction, and a dianion is generated by two-electron reduction. Figure 4 is an explanatory diagram showing the crystal structure of graphite. The non-aqueous solvent to be co-inserted is thought to be inserted between the layers of the graphene layer shown in Figure 4, and to decompose this layered structure, which is presumed to cause the electrode composite to detach from the current collector.

[0036] The deactivating agents and deactivation methods described above can simplify processes such as recycling when carbon materials are used as electrode active materials. The reason for this effect is presumed to be as follows: When a redox shuttle agent, whose oxidation-reduction potential is lower than the positive electrode potential and higher than the negative electrode potential, is added to a charged non-aqueous secondary battery, the potential difference between each electrode and the redox shuttle agent acts as a driving force, causing the battery to discharge and deactivate. Furthermore, since a co-insertion solvent is used as the solvent for the redox shuttle agent, as the battery discharges, the co-insertion of the solvent into the carbon material active material causes peeling, separating the current collector foil from the electrode composite. For this reason, the process can be simplified compared to methods that perform deactivation and electrode peeling separately.

[0037] It goes without saying that this disclosure is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of this disclosure.

[0038] For example, in the embodiments described above, it was stated that the redox shuttle agent preferably has an oxidation-reduction potential of less than 3.0V relative to the lithium reference potential. However, it is not limited to this, and an oxidation-reduction potential of 3.0V or higher may be used, as long as it is higher than that of the negative electrode active material of a non-aqueous secondary battery and lower than that of the positive electrode active material of a non-aqueous secondary battery. For example, when the current collector foil is not made of Cu, a redox shuttle agent exhibiting an oxidation-reduction potential that matches the battery components may be used. This redox shuttle agent is not particularly limited to one with an oxidation-reduction potential of less than 3.0V relative to the Li reference potential, as long as it functions as the above-mentioned oxidation-reduction agent. For example, other substances such as ferrocene, TEMPO compounds, and phenothiazine compounds may be used. Examples of TEMPO compounds include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), N-(3,3,5,5-tetramethyl-4-oxypiperidyl)pyrene-1-carboxamide (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-acetamide-2,2,6,6-tetramethyl-1-piperidinyloxy (Ac-TEMPO). Examples of phenothiazine compounds include phenothiazine, 2-trifluoromethylphenothiazine, 2-methoxyphenothiazine, 10-methylphenothiazine, 2-ethylthiophenothiazine, 2-methylthiophenothiazine, 2-chlorophenothiazine, and 2-acetylphenothiazine. [Examples]

[0039] The following describes experimental examples of specific studies on the deactivating agent and deactivation method for non-aqueous secondary batteries of this disclosure. Experimental Examples 1, 3-6 correspond to the embodiments of this disclosure, Experimental Example 2 corresponds to a reference example, and Experimental Example 3 corresponds to a comparative example.

[0040] (Electrode immersion experiment) The electrodes were immersed in a solvent, and the electrode peeling behavior was visually observed, followed by structural analysis of the powder after peeling. First, the graphite anode and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 A lithium-ion battery consisting of an O2 positive electrode was fabricated as a test cell, and the graphite negative electrode used for the immersion experiment was fully charged. For the negative electrode, a slurry of graphite / carboxymethylcellulose / styrene-butadiene rubber (mass ratio 98:1:1) was coated onto copper foil used as a current collector and vacuum-dried at 120°C. LiNi was used as the positive electrode. 1 / 3 Co 1 / 3 Mn 1 / 3 A slurry of O2 / acetylene black / polyvinylidene fluoride (mass ratio 93:4:3) was coated onto aluminum foil used as a current collector and vacuum-dried at 120°C. The electrolyte was a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (volume ratio 3:4:3) in which lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1 mol / L. A single-layer polyethylene microporous membrane was used as the separator. The positive and negative electrodes were placed opposite each other via a separator impregnated with the electrolyte, and sealed within a laminate film. This cell underwent two charge-discharge cycles at 20°C and a voltage range of 3-4.1V, then charged to 4.1V to a fully charged state. The fully charged cell was disassembled in an argon-atmosphere glove box, and the graphite negative electrode was cleaned with DMC. The cleaned graphite anode was immersed in dimethyl sulfoxide (DMSO) and left to stand, and the presence or absence of peeling was visually observed (Experimental Example 1).

[0041] Furthermore, in Experimental Example 2, the graphite electrode described above was immersed in DMSO without undergoing a charging cycle or full charging process, and the presence or absence of peeling was observed visually. Similarly to Experimental Example 1, a test cell was prepared, and after two charge-discharge cycles, it was brought to a fully charged state. The electrodes obtained from the disassembly were then immersed in the solvent (EC / DMC / EMC) used in the test cell, and the presence or absence of peeling was observed visually. This was Experimental Example 3.

[0042] (X-ray diffraction measurement) The powder detached from the current collector was collected by vacuum filtration in an argon-atmosphere glove box and air-dried. The X-ray diffraction pattern of the collected powder was measured using an X-ray diffractometer (Rigaku Ultima IV) in an air-free environment. The X-ray was CuKα, and the measurement range was 2θ = 10 to 50°.

[0043] (Cyclic voltammetry measurement) The redox shuttle properties in each solvent were measured by cyclic voltammetry to evaluate their performance as deactivators for non-aqueous secondary batteries. 0.05 mol / L of p-benzoquinone or 1,4-naphthoquinone was dissolved in DMSO solvent as the redox shuttle, and 1 mol / L of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was dissolved as the supporting salt to prepare the measurement solution. Experimental Example 4 used p-benzoquinone as the redox shuttle, and Experimental Example 5 used 1,4-naphthoquinone. A three-electrode H-type cell was constructed using glassy carbon as the working electrode, metallic lithium as the counter electrode, and nickel wire with metallic lithium crimped onto it as the reference electrode, with a voltage of 2.0~3.5V vs. Li / Li + The current response was obtained when the potential was swept. Cyclic voltammetry was performed using an electrochemical measurement system (VMP3, manufactured by Biologic), with measurement conditions of a temperature of 20°C and a potential sweep rate of 50 mV / sec.

[0044] (Battery deactivation evaluation) The deactivation of batteries and the delamination behavior of the negative electrode were evaluated by the addition of an inactivating agent. As the inactivating agent, p-benzoquinone or 1,4-naphthoquinone dissolved in DMSO at a concentration of 0.05 mol / L was used, and these were designated as Experimental Examples 6 and 7, respectively. The lithium-ion secondary battery used for evaluation was the same as the test cell in Experimental Example 1. A fully charged battery (voltage 4.1V) was opened under an argon atmosphere, and 1.268 mL of the above-mentioned inactivating solution (equivalent to 10% of the battery capacity) was injected. The battery was resealed, and the change in battery voltage was measured at a temperature of 20°C. After the measurement was completed, the battery was disassembled in an argon-atmosphere glove box, and the delamination state of the negative electrode was visually observed.

[0045] (Results and Discussion) Table 1 shows the results of the electrode immersion experiment. When a graphite negative electrode taken from a fully charged lithium-ion secondary battery (voltage 4.1V) was immersed in DMSO, the negative electrode composite material peeled off from the copper foil (Experimental Example 1). Figure 5 shows the XRD pattern obtained by X-ray diffraction measurement of the peeled powder recovered by vacuum filtration of the solution. For comparison, the XRD pattern of the graphite powder used as the active material is also shown. In the XRD pattern of the graphite powder, a very sharp peak was observed at 2θ = 26.6°. This peak corresponds to the (002) plane of graphite. On the other hand, in the XRD pattern of the powder peeled off in Experimental Example 1, the peak intensity corresponding to the (002) plane of graphite was significantly reduced. This suggests that the long-range order in the c-axis direction of the graphite was lost, which is the behavior observed when the graphene layer (see Figure 4) peels off from graphite (Reference 1: Adv. Energy Mater. 7 (2017) 1700418). In lithium-ion batteries, delamination of the graphene layer can occur, for example, when lithium ions are inserted (co-inserted) between the graphene layers of graphite while solvated during charging. Co-insertion is thought to proceed when the absolute value of the solvation energy (negative value) between the solvent and lithium ions is large, and examples have been reported using DMSO, 1,2-dimethoxyethane (DME), and propylene carbonate (PC) as the electrolyte solvent (Reference 2: J. Phys. Chem. C 114 (2010) 11680-11685). Although the electrode delamination mechanism in Experimental Example 1 of the present invention is not clear, given that delamination of the graphene layer was suggested by the XRD pattern, and that delamination of the graphene layer was confirmed in the DMSO solvent which forms a stable solvation structure with lithium ions, it was inferred that in Experimental Example 1, the composite material peeled off from the copper foil due to delamination of the graphene layer by co-insertion.

[0046] On the other hand, in Experimental Example 2, where an uncharged graphite anode was immersed in DMSO, the anode composite material did not detach from the copper foil. This is thought to be because lithium ions were not present in the graphite anode, and co-insertion did not proceed. Furthermore, in Experimental Example 3, where a fully charged graphite anode was immersed in a carbonate-based mixed solvent (EC / DMC / EMC, volume ratio 3:4:3) used as the electrolyte solvent for lithium-ion batteries, the anode composite material did not detach from the copper foil. This is thought to be because, as described in Reference 2, the absolute value of the solvation energy (negative value) between EC, DMC, EMC and lithium ions is small, and co-insertion does not proceed. In summary, it was found that when a fully charged graphite anode is immersed in DMSO, the electrode composite material detaches from the copper current collector foil due to the detachment of the graphene layer of the graphite.

[0047] [Table 1]

[0048] Figure 6 shows the cyclic voltammetry results of p-benzoquinone and 1,4-naphthoquinone in DMSO solvent (Experimental Examples 4 and 5). In both cases, peaks corresponding to the oxidation and reduction of the quinone were observed at potentials Ea and Ec. Since the standard redox potential E0 is equal to the midpoint of the oxidation peak potential Ea and the reduction peak potential Ec (Ea + Ec) / 2, the standard redox potentials E0 of p-benzoquinone and 1,4-naphthoquinone in DMSO were 2.96V and 2.77V, respectively, with Li as the reference potential. Table 2 summarizes the standard redox potentials for Experimental Examples 4 and 5. In addition to the peaks at potentials Ea and Ec, several small peaks were observed in the cyclic voltammogram. These were presumed to be due to the redox of quinone dimers proceeding as a side reaction (Reference 3: Anal. Chem. 86 (2014) 10917-10924).

[0049] [Table 2]

[0050] Figure 7 shows the change in battery voltage after adding an inactivating solution to a fully charged battery (voltage 4.1V) (Experimental Examples 6 and 7). In all cases, after adding the inactivating solution, the battery voltage decreased, i.e., discharge progressed. When a p-benzoquinone / DMSO solution was used as the inactivating solution, the battery voltage decreased to 3V after 2 hours and to 1V after 17 hours. On the other hand, when a 1,4-naphthoquinone / DMSO solution was used as the inactivating solution, the battery voltage decreased to 3V after 4 hours, to 1V after 19 hours, and to around 0V after 160 hours. When the batteries were disassembled after inactivation and the negative electrode was visually inspected, the negative electrode composite material had peeled off from the copper foil in all cases. This was presumed to be due to the peeling of the graphene layer of graphite caused by the reaction between DMSO and the fully charged negative electrode, as described in Experimental Example 1. From the above, it was found that when DMSO is co-inserted as the solvent for the deactivator, separation of the negative electrode composite and the copper current collector foil is possible simultaneously with the discharge of the battery.

[0051] It goes without saying that this disclosure is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of this disclosure. [Industrial applicability]

[0052] This invention is applicable to the field of the battery industry. [Explanation of Symbols]

[0053] 20 Non-aqueous secondary battery, 21 Battery case, 22 Positive electrode, 23 Negative electrode, 24 Separator, 25 Gasket, 26 Sealing plate, 27 Ion conducting medium.

Claims

1. A deactivator for inactivating a non-aqueous secondary battery equipped with an electrode containing a carbon material as an active material, A redox shuttle agent 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 a Li reference potential, The carbon material comprises a non-aqueous solvent, The non-aqueous solvent is an inactivating agent comprising one or more of dimethyl sulfoxide (DMSO), 1,2-dimethoxyethane (DME), and propylene carbonate (PC).

2. The inactivator according to claim 1, wherein the non-aqueous solvent comprises dimethyl sulfoxide.

3. The redox shuttle agent is an inactivator according to claim 1 or 2, wherein a quinone analog is used.

4. A method for deactivating a non-aqueous secondary battery equipped with electrodes containing a carbon material as an active material, 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, A method for deactivating non-aqueous secondary batteries, including the method described above.

5. The deactivation method according to claim 4, wherein the addition step uses the non-aqueous secondary battery having graphite as the negative electrode active material.

6. The deactivation method according to claim 4 or 5, wherein the addition step uses a non-aqueous secondary battery with a remaining capacity of 50% or more.

Images