JP2023064805A - Deactivator and deactivation method - Google Patents

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

The present disclosure relates to deactivators and methods of deactivation.

Conventionally, when recycling or discarding a non-aqueous secondary battery, a deactivation process is performed to deactivate the collected battery. As such a treatment, for example, it is possible to connect the recovered battery to a charging/discharging device and discharge it to 0 V, but in this case, the discharging sometimes takes a long time. In addition, when the collected battery is a battery after the operation of the current interrupting mechanism (CID), the battery itself could not be discharged. Therefore, it has been proposed to add a redox shuttle agent (for example, ferrocene) that exhibits an oxidation-reduction potential in the range of 3.0 to 4.5 V with respect to the oxidation-reduction potential of lithium inside the recovered battery (Patent Document 1). reference). As a result, the battery voltage of the non-aqueous secondary battery can be lowered to 0 V safely and quickly without using a charging/discharging device. In addition, conventionally, a method has been proposed in which the carbon of the electrode mixture is peeled off from the copper foil surface of the negative electrode sheet of the lithium ion battery using a release agent that is an aqueous solution (see, for example, Patent Documents 2 and 3). According to this method, the cost of recycling can be greatly reduced by recovering the copper foil and carbon using a release agent.

JP 2018-137137 A JP 2015-26566 A JP 2007-179774 A

However, when the non-aqueous secondary battery is deactivated using the redox shuttle agent of Patent Document 1, the secondary battery after deactivation is disassembled and reused, but the electrode mixture is separated. There is a problem that the treatment process is complicated because it is necessary to perform treatment separately. On the other hand, according to the peeling methods of Patent Documents 2 and 3, it was necessary to perform a separate deactivation treatment in addition to the peeling treatment. Moreover, since the deactivating agent described above is non-aqueous and the release agent is aqueous, they could not be mixed and used at the same time. Thus, there has been a demand for further simplification of the steps of deactivation treatment and electrode decomposition treatment.

The present disclosure has been made to solve such problems, and a main object thereof is to provide an inactivating agent and an inactivating method capable of simplifying the process.

As a result of intensive research to achieve the above-mentioned object, the present inventors have found that in a case where a carbon material is used as an electrode active material, the use of a solvent co-inserted between the layers makes the non-aqueous secondary battery inactive. In addition, the inventors have found that the separation and decomposition of the electrode mixture can be further promoted, and have completed the invention of the present disclosure.

That is, the deactivating agent of the present disclosure is
A deactivator for deactivating a non-aqueous secondary battery comprising 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 in Li reference potential;
a non-aqueous solvent co-inserted into the carbon material;
includes.

The inactivation method of the present disclosure also includes:
A deactivation method for deactivating a non-aqueous secondary battery including an electrode containing a carbon material as an active material,
An adding step of adding the deactivator for the non-aqueous secondary battery described above to the interior of the non-aqueous secondary battery.

With this deactivating agent and deactivating method, the process can be further simplified in the case where a carbon material is included as an electrode active material. The reason why such an effect is obtained is presumed as follows, for example. When a redox shuttle agent whose redox potential is lower than the potential of the positive electrode and higher than the potential of the negative electrode is added to a non-aqueous secondary battery in a charged state, the potential difference between each electrode and the redox shuttle agent is used as a driving force to promote discharge of the battery. Inactivation of the battery can be achieved. Furthermore, a solvent that co-inserts is used as a solvent for the redox shuttle agent, and as the discharge of the battery progresses, delamination due to co-insertion of the solvent into the active material of the carbon material progresses, and the current collector foil and the electrode mixture are separated. can be separated. For this reason, processes such as, for example, recycling can be simplified as compared with the case where the deactivation process and the electrode stripping process are performed separately.

FIG. 2 is a cross-sectional view showing an outline of the configuration of a non-aqueous secondary battery 20; Explanatory drawing which shows the mechanism by which a non-aqueous secondary battery is inactivated. Redox reactions using p-benzoquinone and 1,4-naphthoquinone. Explanatory drawing which shows the crystal structure of graphite. FIG. 10 is an X-ray diffraction measurement result obtained by recovering and measuring exfoliated powder in Experimental Example 1. FIG. Cyclic voltammetry measurement results of Experimental Examples 4 and 5. Discharge behavior of the battery after addition of the deactivator of Experimental Examples 6 and 7.

The deactivator for a non-aqueous secondary battery of the present disclosure is a deactivator that deactivates a non-aqueous secondary battery having an electrode containing a carbon material as an active material. The deactivating agent includes 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 in Li reference potential. Also, the non-aqueous solvent co-inserts into the carbon material. As used herein, a redox shuttle agent is intended to refer to an oxidizable and reducible compound capable of repeatedly transporting charge between a positive electrode and a negative electrode.

[Non-aqueous secondary battery]
First, the non-aqueous secondary battery to be deactivated will be described. A non-aqueous secondary battery includes an electrode containing a carbon material as an active material. This non-aqueous secondary battery includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous ion conductive medium interposed between the positive electrode and the negative electrode to conduct carrier ions. . Examples of carrier ions include Group 1 element ions and Group 2 element ions. Group 1 element ions include, for example, lithium ions, sodium ions, and potassium ions. Group 2 element ions include, for example, magnesium ions and calcium ions. The carbon material is, for example, a graphite-based material and may be a negative electrode active material. For convenience of explanation, 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 will be mainly explained below.

For the positive electrode, for example, a positive electrode active material, a conductive material, and a binder are mixed, and an appropriate solvent is added to make a paste-like positive electrode mixture. It may be formed by compression in order to increase the electrode density. The positive electrode active material may have an oxidation-reduction potential based on Li that is higher than the redox shuttle agent contained in the deactivator. A voltage of 3.5 V or more is preferable, a voltage of 3.8 V or more is more preferable, and a voltage of 4.0 V or more is even more preferable. A sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like can be used as the positive electrode active material. Specifically, transition metal sulfides such as TiS ₂ , TiS ₃ , MoS ₃ and FeS ₂ , Li _(1-x) MnO ₂ (0<x<1, etc., same below), Li _(1-x) Mn Lithium-manganese composite oxides such as _2O4 , Lithium-cobalt composite oxides such as Li _{(1-x) CoO2} , Lithium _- nickel composite oxides such as Li _{(1-x) NiO2} , Li _(1-x) Ni _Lithium -nickel _- manganese composite oxides such as _aMnbO2 (a+b= ₁ ) and Li _{( 1-x) NiaMnbO4 (} a+b=2 ₎ , Li _{(1-x) NiaCobMncO} Lithium-nickel-cobalt-manganese composite oxides such as ₂ (a+b+c=1), lithium-vanadium composite oxides such as LiV ₂ O ₃ , and transition metal oxides such as V ₂ O ₅ can be used. In addition, olivine-type lithium manganese phosphate compounds such as Li _{(1-x) MnPO4} , olivine-type lithium cobalt phosphate compounds such as Li _{(1-x) CoPO4} , Li _{(1-x) NiPO4} and the like. An olivine-type lithium nickel phosphate compound or the like can be used. Also, reverse spinel-type lithium manganese vanadate compounds such as Li _{(1-x) MnVO4} , reverse spinel-type lithium cobalt vanadate compounds such as Li _{(1-x) CoPO4} , Li _{(1-x) NiPO4} An inverse spinel type lithium nickel vanadate compound such as The positive electrode active material is preferably an oxide containing one or more of nickel, manganese, and cobalt, such as _LiCoO2 , _LiNiO2 , _LiMnO2 , LiNi1 _{/3Co1 /} 3Mn1 _{/ 3O2} etc. are preferable.

Examples of conductive materials for the positive electrode include graphite such as natural graphite (scale graphite, scale graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel , aluminum, silver, gold, etc.) can be used. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing resins such as fluororubber, thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene rubber (EPDM), and sulfone. Modified EPDM rubber, natural butyl rubber (NBR), and the like can be used. Cellulose-based or styrene-butadiene rubber (SBR) aqueous dispersions, which are water-based binders, can also be used. Examples of the solvent include organic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. can. Alternatively, a dispersant, a thickener, or the like may be added to water, and the active material may be slurried with a latex such as SBR. As the thickening agent, for example, polysaccharides such as carboxymethyl cellulose and methyl cellulose can be used singly or as a mixture of two or more. Application methods include, for example, roller coating such as applicator roll, screen coating, doctor blade method, spin coating, and bar coater, and any thickness and shape can be obtained using any of these methods. Current collectors include aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, and conductive glass. The surface of which is treated with carbon, nickel, titanium, silver, or the like can be used. For these, it is also possible to oxidize the surface. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded, lath, porous, foam, and fiber group formations. The current collector used has a thickness of, for example, 1 to 500 μm.

For the negative electrode, for example, a negative electrode active material, a conductive material, and a binder are mixed, and an appropriate solvent is added to form a paste-like negative electrode mixture. It may be formed by compression in order to increase the electrode density, or may be formed by bonding the negative electrode active material and the current collector. The negative electrode active material may have an oxidation-reduction potential based on Li that is lower than the redox shuttle agent contained in the deactivator. 0 V or less is more preferable, and 0.5 V or less is even more preferable. Examples of negative electrode active materials include carbon materials capable of intercalating and deintercalating lithium ions. Carbon materials include, for example, those having a layered structure, such as graphites. Graphites include, for example, natural graphite (flake-like graphite, flake-like graphite) and artificial graphite. As the conductive material, binder, solvent, and the like used for the negative electrode, those exemplified for the positive electrode can be used. The current collector of the negative electrode includes copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc. For that purpose, for example, copper or the like whose surface is treated with carbon, nickel, titanium, silver, or the like can also be used. For these, it is also possible to oxidize the surface. A current collector having the same shape as that of the positive electrode can be used. Among these, the current collector of the negative electrode preferably contains copper. Copper has an oxidation-reduction potential of about 3.0 to 3.5 V relative to Li (J. Electrochem. Soc. 144 (1997) 3476-3483, J. Mater. Chem. 21 (2011) 9891-9911 etc.), it is considered that the elution of copper is suppressed if the negative electrode potential is kept below 3.0 V during deactivation, and the application of the deactivator and deactivation method described later is particularly significant. . When the elution of copper from the negative electrode is suppressed, the deposition of copper on the positive electrode is also suppressed. Therefore, when the non-aqueous secondary battery is recycled or discarded after deactivation, the precipitate is removed or recovered from the positive electrode. It is preferable because it is unnecessary and can be efficiently recycled or discarded.

A non-aqueous electrolytic solution containing a supporting salt, a non-aqueous gel electrolytic solution, or the like can be used as the ion-conducting medium. Examples of the solvent for the non-aqueous electrolytic solution include carbonate compounds, ester compounds, ether compounds, nitrile compounds, amide compounds, furan compounds, sulfolane compounds and dioxolane compounds, and these can be used alone or in combination. . Specifically, the carbonate compounds include cyclic carbonate compounds such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, 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. 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; and furan compounds. Examples 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 singly or in combination. Among them, the solvent for the non-aqueous electrolytic solution is preferably a mixed solution of a cyclic carbonate compound and a chain carbonate compound such as DMC-EC, DEC-EC, DMC-EMC-EC. 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 . Salts may be mentioned, and these may be used alone or in combination. The concentration of the supporting salt in the electrolytic solution is preferably 0.1 mol/L or more and 5 mol/L or less, more preferably 0.5 mol/L or more and 2 mol/L or less. As the ion-conducting medium, instead of the 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 may be used. can be used.

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 non-aqueous secondary batteries. These may be used alone, or may be used in combination.

The shape of the non-aqueous secondary battery is not particularly limited, and examples thereof include coin-type, button-type, sheet-type, laminate-type, cylindrical-type, flat-type, and square-type. Moreover, it is good also as a large sized thing used for an electric vehicle etc. An example of a non-aqueous secondary battery is shown in FIG. FIG. 1 is a cross-sectional view showing a schematic configuration of a coin-type non-aqueous secondary battery 20. As shown in FIG. As shown in FIG. 1, the non-aqueous secondary battery 20 includes 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, and a positive electrode having a negative electrode active material. A negative electrode 23 provided at a position opposite to 22 via a separator 24, a gasket 25 made of an insulating material, and a gasket 25 disposed in the opening of the battery case 21 and sealing the battery case 21 via the gasket 25. A sealing plate 26 is provided. 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 . Moreover, the negative electrode active material is a carbon material.

[Deactivator]
Next, the deactivator will be explained. Inactivating agents include redox shuttle agents and non-aqueous solvents. The non-aqueous solvent contained in the deactivator is not particularly limited as long as it co-inserts into the carbon material. Examples include dimethyl sulfoxide (DMSO), 1,2-dimethoxyethane (DME), propylene carbonate ( PC) and the like, among which DMSO is more preferable.

The redox shuttle agent contained in the inactivating agent has an oxidation-reduction potential at the Li reference potential, which is higher than the negative electrode active material of the non-aqueous secondary battery to be inactivated, and the non-aqueous system to be inactivated. It is lower than the positive electrode active material of the secondary battery. Moreover, this redox shuttle agent preferably has a Li reference potential of less than 3.0V. The redox potential of the redox shuttle agent can be determined by cyclic voltammetry. Specifically, the oxidation-reduction potential E ₀ (V) of the redox shuttle agent is obtained when Ea (V) is the peak potential on the oxidation side and Ec (V) is the peak potential on the reduction side obtained by cyclic voltammetry. , E ₀ =(Ea+Ec)/2. If there are two or more redox potentials within the potential window, it is preferred that all redox potentials be less than 3.0 V (preferably within the preferred range described below). Cyclic voltammetry is preferably performed on a measurement solution containing a non-aqueous solvent, a supporting salt and a redox shuttle agent. The non-aqueous solvent for the measurement solution may be of the same type as the non-aqueous solvent for the intended deactivator. Examples of the supporting electrolyte of _the measurement solution include _inorganic salts such as _LiPF6 , _LiBF4 , _LiAsF6 and _LiClO4 , _LiCF3SO3 , LiN( _CF3SO2 ) ₂ , LiC( _{CF3SO2 ) 3} , and organic salts such as these can be used alone or in combination. The supporting electrolyte of the measurement solution may be of the same type as the supporting electrolyte 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. may be the same as the concentration of the supporting salt in the ion-conducting medium. The concentration of the redox shuttle agent in the measurement solution may be 1 mmol/L or more and the solubility or less, 30 mmol/L or more and the solubility or less, 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 that of the target inactivating agent.

The redox shuttle agent preferably has an oxidation-reduction potential of less than 3.0 V, preferably 0.5 V or more and less than 3.0 V, more preferably 1.0 V or more and less than 3.0 V. A voltage of 5 V or more and 2.9 V or less is more preferable. Examples of the redox shuttle agent having an oxidation-reduction potential of less than 3.0 V relative to the Li reference potential include quinone analogues and viologen analogues. A quinone analog means quinone and a quinone derivative, and a viologen analog means a viologen and a viologen derivative. Viologens are compounds having a structure in which hydrocarbon groups are respectively bonded to two pyridine ring nitrogen atoms of a 4,4'-bipyridine skeleton.

A quinone analogue is a compound having a structure in which C—H groups on two carbon atoms of an aromatic hydrocarbon skeleton are each replaced with a C═O group. The quinone analog may have a 4- to 7-membered ring aromatic hydrocarbon skeleton, and preferably has a 6-membered ring aromatic hydrocarbon skeleton (having a benzoquinone structure). The quinone analog may have, for example, the p-benzoquinone structure of formula (q1) or the o-benzoquinone structure of formula (q2), and preferably has the p-benzoquinone structure of formula (q1). A quinone analog has a hydrocarbon group, a carboxyl group, an alkoxy group, a nitro group, an amino group, a halogen (F, Cl, Br, etc.) may have a structure in which a substituent such as Br is introduced. The hydrocarbon group is preferably, for example, a chain hydrocarbon group (which may be linear or branched) or a cyclic hydrocarbon group. Chain hydrocarbon groups include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decanyl group, undecanyl group and dodecanyl group; alkenyl groups such as groups, propenyl groups, butenyl groups, pentenyl groups, heptenyl groups, octenyl groups, nonenyl groups, decenyl groups, undecenyl groups and dodecenyl groups; The cyclic hydrocarbon group includes cycloalkyl groups such as cyclopropyl group, cyclopentyl group, cyclohexyl group and cycloheptyl group; and aryl groups such as phenyl group and naphthyl group. Moreover, these hydrocarbon groups may have substituents such as carboxyl groups, alkoxy groups, nitro groups, amino groups, and halogens (F, Cl, Br, etc.). Among these, the hydrocarbon group is preferably a straight-chain alkyl group, and preferably has no substituent. Each of the hydrocarbon groups preferably has 20 or less carbon atoms, more preferably 10 or less, and even more preferably 6 or less. When the quinone analogue has a plurality of substituents, the substituents may combine to form a ring. Examples of quinone analogs in which substituents are bonded to form a ring include naphthoquinone (1,4-naphthoquinone, 1,2-naphthoquinone, etc.), anthraquinone (9,10-anthraquinone, etc.), derivatives thereof, and the like. mentioned. The quinone analog preferably has 20 or less carbon atoms, more preferably 14 or less carbon atoms, and still more preferably 10 or less carbon atoms.

Specific examples of quinone analogues include 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)), 2,3-dichloro-1,4-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)), 1-nitro and anthraquinone (formula (q17)). Among these, the redox shuttle agent is preferably p-benzoquinone or 1,4-naphthoquinone.

More preferably, the inactivating agent contains one or more of p-benzoquinone and 1,4-naphthoquinone as a redox shuttle agent and DMSO as a non-aqueous solvent. In the combination of the redox shuttle agent and the non-aqueous solvent, the oxidized form and reduced form of the redox shuttle agent are stabilized by interaction with the non-aqueous solvent, and the redox shuttle agent is thought to exhibit more stable oxidation-reduction.

The redox shuttle agent preferably has a solubility of 1 mmol/L or more, more preferably 30 mmol/L or more, and 50 mmol/L or more at 20° C. in the non-aqueous solvent contained in the deactivating agent. is more preferred. The higher the solubility of the redox shuttle agent, the higher the concentration of the redox shuttle agent in the deactivator. This is because it can be discharged in a short time. Since the quinone analogues and viologen analogues described above have relatively high solubility in non-aqueous solvents, if these are used as redox shuttle agents, the concentration of the redox shuttle agent contained in the inactivating agent can be increased. preferable. The redox shuttle agent may have a solubility of 1000 mmol/L or less, or 100 mmol/L or less at 20° C. in the non-aqueous solvent contained in the deactivating agent.

The concentration of the redox shuttle agent contained in the deactivator 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 the higher the concentration of the redox shuttle agent, the faster the battery with high energy density such as an electric vehicle (EV) can be discharged. The concentration of the redox shuttle agent contained in the inactivating agent may be below the solubility, or may be below 100 mmol/L.

The inactivating agent preferably does not contain a solute (for example, a supporting salt) other than the redox shuttle agent. Preferably. This is because the less the solute other than the redox shuttle agent is in the deactivator, the lower the viscosity tends to be, and the more rapidly deactivation proceeds. From this point of view, the inactivating agent preferably does not contain a supporting salt, but may contain a supporting salt. 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 . etc. The supporting salt may be the same as or different from the supporting salt contained in the ion-conducting medium of the non-aqueous secondary battery to be deactivated.

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

In the adding step, the above-described deactivator is added inside a non-aqueous secondary battery having an electrode containing a carbon material as an active material. Specifically, the deactivator is added so that the positive and negative electrodes of the non-aqueous secondary battery are in contact with the deactivator. The method of adding the deactivator is not particularly limited, but after the battery container is once opened and the deactivator is injected, it may be sealed again if necessary, or the battery container may be injected with a syringe from the outside. After injection, it may be sealed if desired. The adding step is preferably performed under an inert atmosphere such as an argon atmosphere.

The amount of the deactivator to be added may be appropriately selected according to the size of the non-aqueous secondary battery, and may be, for example, 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 the deactivator added may be, for example, 0.1% or more and 500% or less with respect to the volume [mL] of the ion conductive medium contained in the non-aqueous secondary battery to be deactivated. It may be 10% or more and 300% or less. The amount of the redox shuttle agent added to the non-aqueous secondary battery is, for example, 0.0001 mol/Ah or more per battery capacity [Ah] at full charge of the non-aqueous secondary battery to be deactivated. .1 mol/Ah or less, or 0.001 mol/Ah or more and 0.01 mol/Ah or less.

This addition step is preferably performed on a non-aqueous secondary battery having a negative electrode current collector containing copper. As described above, copper has an oxidation-reduction potential of about 3.0 to 3.5 V with respect to the Li reference potential, so during deactivation, if the negative electrode potential is kept below 3.0 V, the elution of copper is suppressed. It's for. Moreover, it is preferable that this adding step is performed for a non-aqueous secondary battery using graphite as a negative electrode active material. This is because the non-aqueous electrolyte co-inserts and is inserted into the layered structure to contribute to the decomposition of the electrode mixture. In addition, in this addition step, it is preferable to use a non-aqueous secondary battery having a remaining capacity SOC (State of charge) of 10% or more, or 20% or more, more preferably 50% or more, and still more preferably 80% or more. . When there are many lithium ions between the layers of the carbon material, such as when the SOC is 50% or more, coinsertion of the non-aqueous solvent easily proceeds due to interaction, which is preferable.

For example, the non-aqueous secondary battery after the addition step may be held stationary or may be held while being vibrated. The retention time may be a time determined empirically as the time until the inactivation is completed. It may be 200 hours or less.

The mechanism by which the non-aqueous secondary battery is deactivated by this deactivation method is presumed as follows. FIG. 2 is an explanatory diagram showing a mechanism of non-aqueous secondary battery inactivation. 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 redox shuttle agent and the redox shuttle are released from the negative electrode using the potential difference between the positive electrode or the negative electrode and the redox shuttle agent as a driving force. Electron transfer from the agent to the positive electrode progresses, and the battery discharges. Specifically, the reduced form of the redox shuttle agent (RS _(red) in the figure) gives electrons to the positive electrode to become the oxidized form (RS _(ox) in the figure). and become a reductant repeatedly, and the battery discharges. When the positive electrode potential or the negative electrode potential becomes equal to the oxidation-reduction potential of the redox shuttle agent, the discharge of that electrode no longer progresses. Therefore, the positive electrode potential and the negative electrode potential finally become equal to the potential of the redox shuttle agent, and deactivation is completed. Note that "completion of deactivation" may mean that the non-aqueous secondary battery is discharged at least until the SOC of the non-aqueous secondary battery becomes 0%. If the SOC is discharged to 0%, the negative electrode potential is not too low, such as more than 1.5 V and less than 3.0 V at the Li reference potential, so gas is generated due to decomposition of the electrolyte, which is an ion conducting medium. It is less likely to occur, and the safety of the electrode itself is high. Therefore, recycling and disposal after deactivation can be safely performed. The lower the battery voltage after deactivation is, the less sparking is likely to occur, so it is preferable. FIG. 3 shows a specific example of redox reaction when p-benzoquinone or 1,4-naphthoquinone is used as the redox shuttle agent. In these reactions, one-electron reduction produces a radical anion, and two-electron reduction produces a dianion. FIG. 4 is an explanatory diagram showing the crystal structure of graphite. The co-inserting non-aqueous solvent is considered to be intercalated between the graphene layers shown in FIG. 4 and decompose this laminated structure, which is presumed to cause the electrode mixture to separate from the current collector. .

With the deactivating agent and the deactivating method described above, it is possible to further simplify processes such as recycling treatment in the case where the carbon material is included as the electrode active material. The reason why such an effect is obtained is presumed as follows, for example. When a redox shuttle agent whose redox potential is lower than the potential of the positive electrode and higher than the potential of the negative electrode is added to a non-aqueous secondary battery in a charged state, the potential difference between each electrode and the redox shuttle agent is used as a driving force to promote discharge of the battery. Inactivation of the battery can be achieved. Furthermore, a solvent that co-inserts is used as a solvent for the redox shuttle agent, and as the discharge of the battery progresses, delamination due to co-insertion of the solvent into the active material of the carbon material progresses, and the current collector foil and the electrode mixture are separated. can be separated. Therefore, the process can be simplified as compared with the case where the deactivation process and the electrode stripping process are performed separately.

It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms within the technical scope of the present disclosure.

For example, in the above-described embodiments, the redox shuttle agent preferably has an oxidation-reduction potential of less than 3.0 V with reference to lithium. As long as it is lower than the positive electrode active material of the battery, it is not particularly limited to this, and it may have an oxidation-reduction potential of 3.0 V or higher. For example, when the current collector foil is not Cu, a redox shuttle agent that exhibits an oxidation-reduction potential that matches the battery member may be used. The redox shuttle agent is not particularly limited to those having an oxidation-reduction potential of less than 3.0 V relative to Li as long as it functions as the redox agent. Examples include ferrocene, TEMPO-based compounds, and phenothiazine-based compounds. , other substances may be used. TEMPO-based compounds include, for example, 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), 4-acetamido-2,2,6,6-tetramethyl-1-piperidinyloxy (Ac-TEMPO) and the like. Examples of phenothiazine compounds include phenothiazine, 2-trifluoromethylphenothiazine, 2-methoxyphenothiazine, 10-methylphenothiazine, 2-ethylthiophenothiazine, 2-methylthiophenothiazine, 2-chlorophenothiazine, and 2-acetylphenothiazine. is mentioned.

Experimental examples will be described below in which the deactivating agent and the deactivating method for the non-aqueous secondary battery of the present disclosure are specifically investigated. Experimental Examples 1 and 3 to 6 correspond to Examples of the present disclosure, Experimental Example 2 corresponds to a Reference Example, and Experimental Example 3 corresponds to a Comparative Example.

(Electrode immersion experiment)
The electrode was immersed in a solvent, visual observation of electrode detachment behavior, and structural analysis of the powder after detachment were carried out. First, a lithium ion battery consisting of a graphite negative electrode and a LiNi _1/3 Co _1/3 Mn _1/3 O ₂ positive electrode was prepared as a test cell, and the graphite negative electrode used in the immersion experiment was fully charged. As a negative electrode, a slurry of graphite/carboxymethylcellulose/styrene-butadiene rubber (mass ratio 98:1:1) was coated on a copper foil as a current collector and vacuum-dried at 120°C. As a positive electrode, a slurry of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ /acetylene black/polyvinylidene fluoride (mass ratio 93:4:3) was applied to an aluminum foil as a current collector, and vacuumed at 120°C. Dried ones were used. Lithium hexafluorophosphate (LiPF ₆ ) was dissolved at a concentration of 1 mol/L in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (volume ratio 3:4:3) as an electrolytic solution. I used something. A polyethylene single-layer microporous membrane was used as a separator. The positive electrode and the negative electrode were opposed to each other via a separator impregnated with an electrolytic solution, and enclosed in a laminate film. This cell was subjected to two cycles of charge and discharge at a temperature of 20° C. and a voltage range of 3 to 4.1 V, and then charged to 4.1 V to be fully charged. The fully charged cell was disassembled in an argon atmosphere glove box, and the graphite negative electrode was washed with DMC. The washed graphite negative electrode was immersed in dimethyl sulfoxide (DMSO) and allowed to stand, and the presence or absence of peeling was visually observed (Experimental Example 1).

Experimental Example 2 was obtained by immersing the graphite electrode in DMSO without subjecting the graphite electrode to the charge cycle and full charge treatment, and visually observing the presence or absence of peeling. In addition, in the same manner as in Experimental Example 1, a test cell was prepared, and after two cycles of charging and discharging were brought to a fully charged state, the electrodes obtained by disassembling were used in the test cell. Experimental Example 3 was obtained by immersing the sample in a solution and visually observing the presence or absence of peeling.

(X-ray diffraction measurement)
In an argon atmosphere glove box, the powder separated from the current collector was collected by vacuum filtration and air-dried. The X-ray diffraction pattern of the recovered powder was measured using an X-ray diffractometer (Ultima IV manufactured by Rigaku Corporation) without exposure to air. The X-ray was CuKα, and the measurement range was 2θ=10 to 50°.

(Cyclic voltammetry measurement)
The redox properties of the redox shuttle agent in each solvent were measured by cyclic voltammetry to evaluate its performance as a deactivator for non-aqueous secondary batteries. 0.05 mol/L of p-benzoquinone or 1,4-naphthoquinone as a redox shuttle agent and 1 mol/L of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a supporting salt were dissolved in a DMSO solvent to prepare a measurement solution. . Experimental Example 4 uses p-benzoquinone as the redox shuttle agent, and Experimental Example 5 uses 1,4-naphthoquinone. A three-electrode H-type cell was fabricated using glassy carbon as the working electrode, metallic lithium as the counter electrode, and metallic lithium pressed against a nickel wire as the reference electrode. The current response was obtained when the potential was swept with Li/Li ⁺ . For cyclic voltammetry, an electrochemical measurement system (VMP3, manufactured by Biologic Inc.) was used, and the measurement conditions were a temperature of 20° C. and a potential sweep rate of 50 mV/sec.

(Battery deactivation evaluation)
Deactivation of the battery and detachment behavior of the negative electrode by addition of the deactivator were evaluated. As an inactivating agent, 0.05 mol/L of p-benzoquinone or 1,4-naphthoquinone dissolved in DMSO was used as experimental examples 6 and 7, respectively. The lithium ion secondary battery used for evaluation is the same as the test cell of Experimental Example 1. A battery in a fully charged state (voltage of 4.1 V) was unsealed in an argon atmosphere, and 1.268 mL of the above-mentioned deactivating liquid (equivalent to 10% of the battery capacity) was injected. The battery was resealed and the battery voltage change 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 state of peeling of the negative electrode was visually observed.

(Results and discussion)
Table 1 shows the results of the electrode immersion experiment. A graphite negative electrode taken out from a lithium ion secondary battery in a fully charged state (voltage 4.1 V) was immersed in DMSO, and as a result, the negative electrode mixture was peeled off from the copper foil (Experimental Example 1). FIG. 5 is an XRD pattern obtained by collecting the powder exfoliated by vacuum filtration of the solution and performing X-ray diffraction measurement. For comparison, the XRD pattern of the graphite powder used as the active material is also shown. A very sharp peak was confirmed at 2θ=26.6° in the XRD pattern of the graphite powder. This is the peak corresponding to the (002) plane of graphite. On the other hand, in the XRD pattern of the exfoliated powder in Experimental Example 1, the peak intensity corresponding to the (002) plane of graphite was very low. This suggests that the long-range order in the c-axis direction of graphite has been lost, and is the behavior seen when the graphene layer (see FIG. 4) is peeled off from graphite (Reference 1: Adv. Energy Mater. 7 (2017) 1700418.). In a lithium ion battery, exfoliation of graphene layers may occur, for example, when lithium ions are solvated and inserted (coinsert) between the graphene layers of graphite during charging. Coinsertion is believed to proceed when the absolute value of the solvation energy (negative value) between the solvent and lithium ions is large. An example using carbonate (PC) has been reported (Reference 2: J. Phys. Chem. C 114 (2010) 11680-11685.). Although the electrode detachment mechanism in Experimental Example 1 of the present invention is not clear, the XRD pattern suggested detachment of the graphene layer, and the detachment of the graphene layer was confirmed in a DMSO solvent that forms a stable solvation structure with lithium ions. Based on this, it was speculated that in Experimental Example 1, the composite material was peeled from the copper foil due to the peeling of the graphene layers due to co-intercalation.

On the other hand, in Experimental Example 2 in which an uncharged graphite negative electrode was immersed in DMSO, the negative electrode mixture did not separate from the copper foil. This is probably because lithium ions do not exist in the graphite negative electrode and co-insertion does not proceed. Further, in Experimental Example 3, in which a fully charged graphite negative electrode was immersed in a carbonate-based mixed solvent (EC/DMC/EMC, volume ratio 3:4:3) used as an electrolyte solvent for lithium-ion batteries, the copper foil was removed from the negative electrode. Peeling of the compound material did not progress. This is thought to be because, as described in reference 2, the absolute values of the solvation energies (negative values) between EC, DMC, EMC and lithium ions are small and coinsertion does not proceed. As described above, it has been clarified that when a fully charged graphite negative electrode is immersed in DMSO, the electrode mixture is separated from the copper current collector foil due to the separation of the graphene layer of the graphite.

FIG. 6 shows the results of cyclic voltammetry measurements of p-benzoquinone and 1,4-naphthoquinone in DMSO solvent (Experimental Examples 4 and 5). In both cases, peaks corresponding to quinone oxidation and reduction were identified at potentials Ea and Ec. Since the standard redox potential E ₀ is equal to the midpoint of the peak oxidation potential Ea and the peak reduction potential Ec (Ea+Ec)/2, the standard redox potential E ₀ of p-benzoquinone and 1,4-naphthoquinone in DMSO is , the Li reference potential was 2.96 V and 2.77 V, respectively. Table 2 summarizes the standard oxidation-reduction potentials of Experimental Examples 4 and 5. In the cyclic voltammogram, several small peaks were confirmed in addition to the peaks of the potentials Ea and Ec. It was presumed that this is due to oxidation-reduction of a quinone dimer that proceeds as a side reaction (Reference 3: Anal. Chem. 86 (2014) 10917-10924).

FIG. 7 shows changes in battery voltage after adding a deactivating solution to a fully charged battery (voltage 4.1 V) (Experimental Examples 6 and 7). In both cases, after the addition of the deactivating liquid, the battery voltage decreased, that is, discharge proceeded. When a p-benzoquinone/DMSO solution was used as the deactivating liquid, the cell voltage dropped to 3 V after 2 hours and to 1 V after 17 hours. On the other hand, when a 1,4-naphthoquinone/DMSO solution was used as the deactivating solution, the battery voltage dropped to 3 V after 4 hours, to 1 V after 19 hours, and to nearly 0 V after 160 hours. When the inactivated batteries were disassembled and the negative electrodes were visually observed, the negative electrode mixture was peeled off from the copper foil in all cases. As described in Experimental Example 1, this was presumed to be due to the fact that the reaction between DMSO and the fully charged negative electrode progressed the exfoliation of the graphene layer of graphite. From the above, it was found that when the co-inserted DMSO was used as the solvent for the deactivator, the negative electrode mixture and the copper current collector foil could be separated simultaneously with the discharge of the battery.

It goes without saying that the present disclosure is by no means limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure.

INDUSTRIAL APPLICABILITY The present invention can be used in the field of battery industry.

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 (6)

A deactivator for deactivating a non-aqueous secondary battery comprising 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 in Li reference potential;
a non-aqueous solvent co-inserted into the carbon material;
An inactivating agent containing 2. The deactivator of Claim 1, wherein the non-aqueous solvent comprises dimethylsulfoxide. The inactivating agent according to claim 1 or 2, wherein the redox shuttle agent uses a quinone analogue. A deactivation method for deactivating a non-aqueous secondary battery including an electrode containing a carbon material as an active material,
An adding step of adding the non-aqueous secondary battery deactivator according to any one of claims 1 to 3 to the inside of the non-aqueous secondary battery,
A method for deactivating a non-aqueous secondary battery, comprising: 5. The deactivation method according to claim 4, wherein in said adding step, said non-aqueous secondary battery including graphite as a negative electrode active material is used. 6. The deactivation method according to claim 4, wherein said non-aqueous secondary battery having a remaining capacity SOC of 50% or more is used in said adding step.

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