JP2022139980A - Recovery agent, recovery method for non-aqueous electrolyte secondary battery, and manufacturing method for non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a novel recovery method for a non-aqueous electrolyte secondary battery.SOLUTION: A recovery agent includes a solute having an aromatic hydrocarbon compound in a reduced state and a metal ion, a solvent that dissolves the solute, and an electrolyte. A recovery method of a non-aqueous electrolyte secondary battery includes a recovery step of injecting the recovery agent into the non-aqueous electrolyte secondary battery to recover the capacity of the non-aqueous electrolyte secondary battery.SELECTED DRAWING: None

Description

The present disclosure relates to a recovery agent, a recovery method for a non-aqueous electrolyte secondary battery, and a method for manufacturing a non-aqueous electrolyte secondary battery.

Conventionally, as a method for recovering the capacity of a non-aqueous electrolyte secondary battery whose capacity has deteriorated due to long-term storage or charge-discharge cycles, a third electrode is provided in addition to the positive electrode and the negative electrode, and the third electrode and the positive electrode are externally short-circuited. , a method of supplying carrier ions from the third electrode to the positive electrode has been proposed (see, for example, Patent Document 1).

JP 2016-076358 A

However, in Patent Literature 1, the incorporation of the third electrode causes a problem such as complicating the structure of the battery. Therefore, there has been a demand for a novel recovery method for non-aqueous electrolyte secondary batteries that can recover the capacity without using a third electrode.

The present disclosure has been made to solve such problems, and a main object thereof is to provide a novel recovery method for a non-aqueous electrolyte secondary battery.

As a result of intensive research to achieve the above object, the present inventors found that a solution containing a solute having a reduced aromatic hydrocarbon compound and metal ions and a solvent for dissolving this solute is prepared as a non-aqueous solution. It was found that the capacity was recovered by injecting it into an electrolytic solution secondary battery. In particular, it was found that if the recovery agent contains, in addition to the above-mentioned solute and solvent, an electrolytic solution such as that used in non-aqueous electrolyte secondary batteries, the capacity of the battery after recovery is further improved. I have completed the disclosure.

That is, the recovery agents disclosed herein are
A recovery agent for recovering the capacity of a non-aqueous electrolyte secondary battery using metal ions as carrier ions,
comprising a solute having an aromatic hydrocarbon compound in a reduced state and a metal ion, a solvent that dissolves the solute, and an electrolytic solution;
It is.

In addition, the recovery method for the non-aqueous electrolyte secondary battery disclosed in this specification includes:
A recovery method for recovering the capacity of a non-aqueous electrolyte secondary battery using metal ions as carrier ions,
A recovery step of injecting the recovery agent described above into the non-aqueous electrolyte secondary battery to recover the capacity of the non-aqueous electrolyte secondary battery;
includes.

Further, the method for manufacturing the non-aqueous electrolyte secondary battery disclosed in this specification includes:
A battery preparation step of preparing a non-aqueous electrolyte secondary battery with metal ions as carrier ions and having deteriorated capacity;
a recovery step of recovering the capacity of the non-aqueous electrolyte secondary battery by the recovery method for the non-aqueous electrolyte secondary battery described above;
includes.

This recovery agent, recovery method for non-aqueous electrolyte secondary batteries, and method for manufacturing non-aqueous electrolyte secondary batteries provide a novel recovery method for non-aqueous electrolyte secondary batteries and a non-aqueous electrolyte secondary battery using the same. A novel method for manufacturing a battery can be provided. The reason why such an effect is obtained is presumed as follows. For example, a recovery agent containing a solute having a reduced aromatic hydrocarbon compound and metal ions and a solvent for dissolving this solute acts directly on the positive electrode simply by being injected into the non-aqueous electrolyte secondary battery. This is presumed to be due to a recovery reaction that supplies electrons and metal ions to the positive electrode. In particular, a recovery agent containing an electrolytic solution in addition to the above-described solute and solvent further improves the capacity of the battery after recovery. The reason for this is presumed as follows. For example, a recovery agent containing an electrolyte has a higher solvation with respect to an aromatic hydrocarbon compound than a recovery agent that does not contain an electrolyte, and the reduced aromatic hydrocarbon compound easily separates metal ions. Therefore, when a recovery agent containing an electrolytic solution is used, the activation energy when electrons and metal ions are supplied to the positive electrode becomes small, and the supply of electrons and metal ions to the positive electrode is performed smoothly, resulting in efficient recovery. It is thought that the reaction progresses and the capacity of the battery after recovery is further improved.

FIG. 2 is a schematic diagram showing an example of a non-aqueous electrolyte secondary battery 20; Explanatory drawing which shows an example of the scheme of a recovery reaction. 5 is a graph showing discharge capacities before and after capacity recovery in Experimental Examples 1 to 4; FIG. 10 is an ESR measurement result of the electrolyte solution of the battery after injection of the recovery agent in Experimental Example 2. FIG. ESR measurement results of the recovery agents of Experimental Examples 2 and 4. ESR measurement results of the recovery agents of Experimental Examples 1 and 2.

The recovery agent disclosed in this specification recovers the capacity of a non-aqueous electrolyte secondary battery. A recovery method for a non-aqueous electrolyte secondary battery disclosed in this specification is a method for recovering the capacity of a non-aqueous electrolyte secondary battery. Preferred embodiments of the recovery agent and the recovery method of the non-aqueous electrolyte secondary battery will be described below.

[Non-aqueous electrolyte secondary battery]
First, the non-aqueous electrolyte secondary battery to be recovered will be described. The non-aqueous electrolyte secondary battery is preferably a non-aqueous electrolyte secondary battery using metal ions as carrier ions. The non-aqueous electrolyte secondary battery may use, for example, group 1 ions such as lithium, sodium, and potassium, and group 2 ions such as magnesium, calcium, and strontium as carrier ions. Moreover, the non-aqueous electrolyte secondary battery may be an ion secondary battery such as a lithium ion secondary battery, or may be a metal secondary battery such as a lithium metal secondary battery. As an example, the case where the non-aqueous electrolyte secondary battery is a lithium ion secondary battery will be mainly described below.

A non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode may have a positive electrode active material capable of intercalating and deintercalating lithium ions. The negative electrode may have a negative electrode active material capable of intercalating and deintercalating lithium ions. The non-aqueous electrolyte may be interposed between the positive electrode and the negative electrode to conduct lithium ions.

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. 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 , and basic compositional formulas of Li _(1-x) MnO ₂ (0<x<1, etc., the same applies hereinafter) and Li _{(1 -x)} Lithium-manganese composite oxides such as Mn ₂ O ₄ , Lithium-cobalt composite oxides such as Li _(1-x) CoO ₂ with a basic composition formula, Li _(1-x) NiO ₂ with a basic composition formula, etc. a lithium-nickel composite oxide having a basic composition formula of Li _(1-x) Ni _a Co _b Mn _c O ₂ (a+b+c=1) or the like, a basic composition formula of LiV ₂ O ₃ Lithium vanadium composite oxides such as V 2 O 5 , transition metal oxides having a basic composition formula such as V ₂ O ₅ , and the like can be used. Among these, transition metal composite oxides of lithium such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ and LiV ₂ O ₃ are preferred. Further, Li _y Ni _(1-x) M _x O ₂ (where 0≦x≦0.5, 0<y<1.20, M is from the group consisting of Co, Al, Mn, Fe, Ti and B At least one selected element) is also preferable, and it may be used in combination with a lithium-manganese composite oxide having a spinel structure. It should be noted that the “basic composition formula” means that other elements may be included. The positive electrode active material may have an oxidation-reduction potential of 3.5 V or higher, 4.0 V or higher, or 4.5 V or higher based on Li metal.

In the positive electrode, the conductive material is, for example, graphite such as natural graphite (scale graphite, scale graphite) or artificial graphite, acetylene black, carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel , aluminum, silver, gold, etc.) or a mixture of two or more thereof can be used. Among these, carbon black and acetylene black are preferable as the conductive material from the viewpoint of electronic conductivity and coatability. The binder plays a role of binding the active material particles and the conductive material particles, and examples thereof include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing resin such as fluororubber, polypropylene, Thermoplastic resins such as polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of cellulose-based carboxymethyl cellulose (CMC), styrene-butadiene copolymer (SBR), polyvinyl alcohol, or the like, which is an aqueous binder, can also be used. Examples of solvents for dispersing the positive electrode active material, conductive material, and binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, and N,N-dimethylaminopropylamine. , ethylene oxide, and tetrahydrofuran can be used. 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. The basis weight of the positive electrode mixture is not particularly limited, but may be, for example, more than 5 mg/cm ² , 6 mg/cm ² or more, or 7 mg/cm ² or more. The basis weight of the positive electrode mixture may be, for example, 20 mg/cm ² or less. 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.

The negative electrode may be formed by adhering a negative electrode active material and a current collector. The material may be coated on the surface of the current collector, dried, and compressed to increase the electrode density, if necessary. Examples of negative electrode active materials include inorganic compounds such as lithium, lithium alloys and tin compounds, carbonaceous materials capable of intercalating and deintercalating lithium ions, composite oxides containing multiple elements, and conductive polymers. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, amorphous carbon, diamond-like carbon, fullerenes, carbon nanotubes, carbon nanohorns, and the like. is mentioned. Among them, graphites such as artificial graphite and natural graphite have an operating potential close to that of metallic lithium, can be charged and discharged at a high operating voltage, and suppress self-discharge when lithium salt is used as a supporting salt. Moreover, the irreversible capacity during charging can be reduced, which is preferable. Examples of composite oxides include lithium-titanium composite oxides and lithium-vanadium composite oxides. Among them, carbonaceous materials are preferable as the negative electrode active material from the viewpoint of safety. As the conductive material, binder, solvent, and the like used for the negative electrode, those exemplified for the positive electrode can be used. The negative electrode active material may have an oxidation-reduction potential of 1.0 V or less, 0.5 V or less, or 0.3 V or less based on Li metal. The basis weight of the negative electrode mixture may, for example, exceed 3 mg/cm ² or may be 4 mg/cm ² or more. The basis weight of the negative electrode mixture may be, for example, 15 mg/cm ² or less. 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.

The non-aqueous electrolyte may contain a supporting salt and an organic solvent. Examples of supporting electrolytes include inorganic salts such as LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiAlCl ₄ , LiBF ₄ and LiSbF ₆ , LiN(FSO ₂ ) ₂ (also referred to as LiFSI) and LiN(CF ₃ SO ₂ ) ₂ . (also called LiTFSI) and LiN( _C2F5SO2 ) _{2 (} also called _LiBETI ). These supporting salts may be used alone or in combination. The concentration of the supporting salt is preferably 0.1-2.0M, more preferably 0.8-1.2M. As the organic solvent, for example, an aprotic organic solvent can be used. Examples of such organic solvents include cyclic carbonates, chain carbonates, cyclic esters, cyclic ethers, chain ethers, and fluorinated derivatives thereof. Cyclic carbonates include, for example, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and the like. Examples of chain carbonates include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Cyclic esters include, for example, gamma-butyrolactone and gamma-valerolactone. Cyclic ethers include, for example, tetrahydrofuran and 2-methyltetrahydrofuran. Chain ethers include, for example, dimethoxyethane and ethylene glycol dimethyl ether. These may be used alone, or may be used in combination. In addition, as the nonaqueous electrolyte, nitrile solvents such as acetonitrile and propylnitrile, ionic liquids, gel electrolytes, and the like may be used. The non-aqueous electrolyte may contain additives such as film-forming agents and flame retardants.

The non-aqueous electrolyte secondary battery may have a separator between the positive electrode and the negative electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the non-aqueous electrolyte secondary battery. and thin microporous membranes such as fluororesins. These may be used alone, or may be used in combination.

The non-aqueous electrolyte secondary battery may have an openable and closable pouring port in a battery case containing the positive electrode, the negative electrode and the non-aqueous electrolyte. The recovery agent can be easily injected from the injection port.

The shape of the non-aqueous electrolyte secondary battery is not particularly limited, and examples thereof include coin type, button type, sheet type, laminated type, cylindrical type, flat type, and rectangular type. Also, it may be applied to a large-sized one used for an electric vehicle or the like. FIG. 1 is a schematic diagram showing an example of a non-aqueous electrolyte secondary battery 20. As shown in FIG. The non-aqueous electrolyte 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 negative electrode active material having a positive electrode 22. A negative electrode 23 provided at a position facing each other with a separator 24 interposed therebetween, 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 with the gasket 25 interposed therebetween. and has. In this nonaqueous electrolyte secondary battery 20 , the space between the positive electrode 22 and the negative electrode 23 is filled with a nonaqueous electrolyte 27 .

The non-aqueous electrolyte secondary battery may have an internal resistance exceeding 5 Ωcm ² , 7 Ωcm ² or more, or 10 Ωcm in a state where the capacity is not deteriorated (also referred to as a battery before deterioration). It may be ² or more. In non-aqueous electrolyte secondary batteries, such as batteries for electric vehicles, where the thickness of the electrode mixture and weight per unit area are large and the internal resistance is relatively high, the capacity and cycle capacity of the battery after recovery cannot be reduced by simply injecting the recovery agent. Since the retention rate is often low, it is highly significant to apply the recovery method of the non-aqueous electrolyte secondary battery of the present disclosure. The internal resistance of the battery before deterioration may be 50 Ωcm ² or less.

[Restoration agent]
Next, the recovery agent will be explained. The recovery agent includes a solute having a reduced aromatic hydrocarbon compound and metal ions, a solvent that dissolves the solute, and an electrolytic solution. The restorative agent may be a pre-prepared restorative agent or may be prepared in the preparation step of preparing the restorative agent. In the recovery agent, the reduced aromatic hydrocarbon compound and the metal ion may be dissociated or associated.

In the restorative agent, the aromatic hydrocarbon compound is preferably polyacene or polyphenyl. Polyacene is a compound having a structure in which a plurality of benzene rings are condensed, and includes naphthalene, anthracene, tetracene, pentacene, and the like. Polyphenyl is a compound having a structure in which a plurality of phenyl groups are linked by single bonds, and includes biphenyl, ortho-terphenyl, meta-terphenyl, para-terphenyl, paraquaterphenyl, paraquinkiphenyl and the like. Polyacene and polyphenyl may have a substituent on the aromatic ring and may contain a heteroatom in the aromatic ring. Examples of substituents include halogen atoms, alkyl groups, aryl groups, alkenyl groups, alkoxy groups, aryloxy groups, sulfonyl groups, amino groups, cyano groups, carbonyl groups, acyl groups, amide groups, and hydroxyl groups. Heteroatoms include nitrogen, oxygen, sulfur, and the like. Polyacenes containing heteroatoms in the aromatic ring include quinolines, chromenes, acridines, and the like. Polyphenyls containing heteroatoms in the aromatic ring include bipyridine and the like. In addition to those mentioned above, the aromatic hydrocarbon compound is preferably a compound in which a cycloalkane is bonded to an aromatic ring, such as cyclohexylbenzene. The aromatic hydrocarbon compound is preferably at least one of naphthalene, biphenyl, anthracene, ortho-terphenyl, and para-terphenyl, and more preferably at least one of naphthalene and biphenyl. The aromatic hydrocarbon compound may be, for example, one or more of formula (1) and formula (2). The aromatic hydrocarbon compound in a reduced state is, for example, the above-described aromatic hydrocarbon compound in a reduced state (also referred to as a reductant), such as a radical anion. The aromatic hydrocarbon compound in a reduced state may be, for example, one or more of the reductant of the compound of formula (1) and the reductant of the compound of formula (2).

In the recovery agent, the metal ion is not particularly limited, but may be, for example, the same kind of metal ion as the carrier ion of the non-aqueous electrolyte secondary battery. In the recovery agent, the metal ions may be, for example, one or more of alkali metal ions such as lithium ions, sodium ions and potassium ions, and alkaline earth metal ions such as magnesium ions, calcium ions and strontium ions.

The restorative agent may contain one or more compounds of Formula (3) and Formula (4) as a solute. In the compounds of formulas (3) and (4), the radical anion portion is the above-described reduced aromatic hydrocarbon compound, and the metal cation portion is the above-described metal ion.

In the recovery agent, the solvent dissolves the above-described solute, and is preferably liquid at room temperature. Solvents include, for example, aprotic solvents such as ether compounds. The ether compound may be any compound having an ether skeleton, and may be either a cyclic ether or a chain ether. The ether compound preferably has two or more ether groups in its molecule. The solvent may be one or more of tetrahydrofuran (THF), dimethoxyethane (DME), diethoxyethane (DEE), dioxolane (DOL), dioxane (DOX). Preferably, the solvent is one or more of tetrahydrofuran and dimethoxyethane.

The recovery agent may be obtained by adding an aromatic hydrocarbon compound and a metal in a metallic state instead of an ionic state into a solvent. For example, it may be obtained by one or more of formulas (5) and (6). More specifically, as shown in formulas (7) to (9), naphthalene, diphenyl, or terphenyl may be reacted with Li metal in a THF solvent. Further, according to the formulas (7) to (9), naphthalene, diphenyl, terphenyl and Li metal may be reacted in a DME solvent. This makes it possible to easily prepare a recovery agent containing a solute having a reduced aromatic hydrocarbon compound and metal ions and a solvent for dissolving this solute. The recovery agent may be prepared by adding a metal to a precursor obtained by adding an aromatic hydrocarbon compound to a solvent. The recovery agent may be prepared under an inert atmosphere such as an argon atmosphere or a nitrogen atmosphere. The recovery agent may be prepared in a low dew point environment such as -20°C or lower, -40°C or lower, or -60°C or lower. The recovery agent may be prepared by stirring a solvent, an aromatic hydrocarbon compound and a metal, in which case a stirrer or the like may be used. The solvent is dehydrated by distillation, immersion in molecular sieves, or the like, so that the water content is preferably 100 ppm or less before use.

The recovery agent described above is also called a recovery agent undiluted solution. In the recovery agent undiluted solution, the concentration of the solute (which may be the concentration of each of the reduced aromatic hydrocarbon compound and the metal ion) may be 0.05 mol/L or more and 1.1 mol/L or less, or 0.1 mol/L. 1.1 mol/L or more, or 0.5 mol/L or more and 1.0 mol/L or less. Also, this concentration may be less than or equal to the solubility. Further, the ratio M _A /M _B of the number of moles M _A (mol) of the reduced aromatic hydrocarbon compound contained in the recovery agent and the number of moles M _B (mol) of the metal ion is set to 1/1. However, it may be 1.1/1.0 to 1.0/1.1 or 1.2/1.0 to 1.0/1.2.

The electrolyte may be, for example, the non-aqueous electrolyte exemplified in the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery, and the organic solvent exemplified in the non-aqueous electrolyte and the supporting salt exemplified in the non-aqueous electrolyte. , may be included. The solvent of the electrolytic solution may be different from the solvent of the recovery agent stock solution. More preferably, it contains a cyclic carbonate and a chain carbonate. The solvent of the electrolytic solution may be one or more of ethylene carbonate, dimethyl carbonate, and ethylmethyl carbonate. The supporting salt of the electrolytic solution may be different from the solute of the recovery agent stock solution, and may be an inorganic salt such as LiPF ₆ or an organic salt such as LiFSI. The electrolyte may contain additives such as film-forming agents and flame retardants. The composition of the electrolyte may be the same as that of the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery to be recovered. In the recovery agent, the content of the electrolytic solution may be, for example, 10% by volume or more and 90% by volume or less, may be 20% by volume or more and 80% by volume or less, may be 30% by volume or more and 70% by volume or less, or may be 30% by volume. % or more and 60 volume % or less, or 30 volume % or more and 50 volume % or less. When preparing a recovery agent containing an electrolytic solution, the recovery agent stock solution and the electrolytic solution may be mixed, the recovery agent stock solution and the electrolytic solution may be stirred, or they may be stirred using a stirrer or the like. .

The recovery agent may have an oxidation-reduction potential higher than that of the negative electrode and lower than that of the positive electrode. The oxidation-reduction potential of the recovery agent may be, for example, 0.5 V or more and 2.5 V or less, 1.0 V or more and 2.0 V or less, or 1.2 V or more and 1.9 V or less based on Li metal. .

For the recovery agent, for example, one or more signals can be confirmed in the g value range of 1.996 or more and 2.020 or less as measured by an electron spin resonance (ESR) method. In such a recovery agent, it is considered that the aromatic hydrocarbon compound in a reduced state exists in a radical state. This g value is obtained by using the resonance frequency ν (Hz) and the magnetic field strength H (mT) obtained by ESR measurement, hν = gμ _B H (where h is Planck's constant (6.626176 × 10 ^-34 Js ), μ _B is derived using the Bohr magneton (9.274078×10 ⁻²⁴ JT ⁻¹ )) equation.

[Recovery method for non-aqueous electrolyte secondary battery]
Next, a recovery method for the non-aqueous electrolyte secondary battery will be described. This non-aqueous electrolyte secondary battery recovery method is a recovery method for recovering the capacity of the non-aqueous electrolyte secondary battery, and recovers the capacity of the non-aqueous electrolyte secondary battery using the recovery agent described above. a recovery step;

(Recovery process)
In this step, a recovery agent is injected into the non-aqueous electrolyte secondary battery to recover the capacity of the non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery to be recovered is a battery whose capacity has deteriorated (also referred to as a deteriorated battery). good too. A non-aqueous electrolyte secondary battery to be recovered may be an unused product or a used product. Even unused items may deteriorate in capacity due to long-term storage.

In this step, when injecting the recovery agent, the non-aqueous electrolyte secondary battery may be opened and the recovery agent may be injected and the opening may be closed, or the recovery agent may be injected into the non-aqueous electrolyte secondary battery. may be injected to close the perforation. When injecting the recovery agent, the injection may be performed under an inert atmosphere such as an argon atmosphere or a nitrogen atmosphere. The recovery agent may be injected so as to contact at least the positive electrode, but may be mixed with the non-aqueous electrolyte. The injection amount of the recovery agent can be appropriately determined according to the configuration of the non-aqueous electrolyte secondary battery, the degree of deterioration, and the like. The injection amount of the recovery agent may be, for example, 1% or more and 100% or less, or 10% or more and 75% or less, with respect to the volume [mL] of the nonaqueous electrolyte contained in the nonaqueous electrolyte secondary battery. Well, it may be 25% or more and 50% or less. In this step, the capacity of the non-aqueous electrolyte secondary battery may be recovered by allowing a predetermined time to elapse after the recovery agent is injected. At that time, it may be left still, shaken, or a voltage may be applied. This time may be, for example, 1 hour or more and 48 hours or less, 6 hours or more and 36 hours or less, or 12 hours or more and 24 hours or less.

Injection of the recovery agent in this step is considered to cause a recovery reaction as shown in FIG. 2, for example. FIG. 2 is an explanatory diagram showing an example of a recovery reaction scheme, and an explanatory diagram showing the scheme when the positive electrode active material is a lithium-transition metal composite oxide. As shown in FIG. 2, in the recovery agent, a solute having a radical anion of an aromatic hydrocarbon compound (Are.- in FIG. 2) and a metal ion (Li ⁺ in FIG. 2) acts as a reducing agent that donates electrons. By acting on the deteriorated positive electrode (Li _ny MeO ₂ in FIG. 2), electrons and metal ions are donated from the reducing agent to the positive electrode, and the capacity can be recovered. A zero-valent complex of an electrically neutral aromatic hydrocarbon compound and a lithium atom is considered to behave like metallic lithium. Therefore, when the above-mentioned zero-valent complex of lithium comes into contact with the deteriorated positive electrode, it supplies electrons and metal ions to the positive electrode and is incorporated into the positive electrode in a state of having battery activity, so that the capacity of the battery can be recovered. is considered possible. Even if metal ions are brought into contact with the deteriorated positive electrode in the form of a salt such as LiPF ₆ , such a capacity recovery effect cannot be obtained.

In this step, a recovery agent containing an electrolytic solution in addition to the solute and solvent described above is used, so that the capacity of the battery after recovery is further improved. The reason for this is presumed as follows. For example, a recovery agent containing an electrolyte has a higher solvation with respect to an aromatic hydrocarbon compound than a recovery agent that does not contain an electrolyte, and the radical anion of the aromatic hydrocarbon compound easily separates electrons and metal ions. Therefore, when a recovery agent containing an electrolytic solution is used, the activation energy when solute electrons and metal ions are supplied to the positive electrode becomes small, and the metal ions are smoothly supplied to the positive electrode, resulting in efficient recovery. It is thought that the reaction progresses and the capacity of the battery after recovery is further improved. In addition, when a recovery agent containing no electrolyte is injected into a non-aqueous electrolyte secondary battery, there is concern that the ionic conductivity of the non-aqueous electrolyte will decrease and the polarization overvoltage will increase. It is considered that the decrease in ionic conductivity and the increase in polarization overvoltage can be suppressed by using . In this way, the capacity of the non-aqueous electrolyte secondary battery is recovered, and a non-aqueous electrolyte secondary battery (also referred to as a recovered battery) with recovered capacity is obtained.

In the recovery agent and the recovery method of the non-aqueous electrolyte secondary battery described in detail above, the capacity of the non-aqueous electrolyte secondary battery can be recovered by injecting the recovery agent into the non-aqueous electrolyte secondary battery. . This recovery agent and recovery method for a non-aqueous electrolyte secondary battery can provide a novel recovery method that does not require a third electrode. In addition, in this recovery agent and recovery method for a non-aqueous electrolyte secondary battery, the capacity of the battery after recovery can be further improved by using the recovery agent containing the electrolyte.

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

For example, in the above-described embodiment, a method for recovering a non-aqueous electrolyte secondary battery has been described. It is possible to manufacture a new non-aqueous electrolytic secondary battery in which the is recovered. Therefore, the recovery method of the non-aqueous electrolyte secondary battery can also be said to be a manufacturing method of the non-aqueous electrolyte secondary battery. A non-aqueous electrolyte secondary battery may be manufactured using the recovery method for a non-aqueous electrolyte secondary battery described above. A method for manufacturing a non-aqueous electrolyte secondary battery includes a battery preparation step of preparing a non-aqueous electrolyte secondary battery with metal ions as carrier ions whose capacity has deteriorated, and the recovery method for the non-aqueous electrolyte secondary battery described above. and a recovery step of recovering the capacity of the non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery prepared in the battery preparation step can be the same as the deteriorated battery described in the above embodiment.

An example in which a lithium ion battery was recovered by the method for recovering a non-aqueous electrolyte secondary battery of the present disclosure will be described below as an example. Note that Experimental Examples 2 and 4 correspond to Examples, and Experimental Examples 1 and 3 correspond to Reference Examples. The present disclosure is by no means limited to the following examples, and it goes without saying that various aspects can be implemented as long as they fall within the technical scope of the present disclosure.

[Experimental example 1]
(Non-aqueous electrolyte secondary battery (battery before deterioration))
For the positive electrode, 92 wt % of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM, manufactured by Toda Kogyo), 5 wt % of acetylene black (manufactured by Denka Co., Ltd.), and 3 wt % of polyvinylidene fluoride (manufactured by Kureha) were used. % of the positive electrode mixture was formed on one side of an aluminum current collector foil so as to have a basis weight of 7 mg/cm ² . For the negative electrode, a negative electrode mixture containing 98 wt% graphite (OMAC 1.5s, manufactured by Osaka Gas Chemicals), 1 wt% carboxymethyl cellulose (manufactured by Daicel), and 1 wt% styrene-butadiene rubber (manufactured by JSR) was used. A copper current collecting foil formed on one side so as to have a concentration of 4 mg/cm ² was used. The electrolytic solution used was a mixed solvent containing 30 vol% ethylene carbonate, 40 vol% dimethyl carbonate, and 30 vol% ethyl methyl carbonate, in which LiPF ₆ was dissolved to a concentration of 1.1M. . A polypropylene separator impregnated with 1 mL of electrolytic solution was sandwiched between the positive electrode and the negative electrode to prepare a laminate cell. This was used as the battery before deterioration. The electrode area of the cell was 10 cm ² for both the positive electrode and the negative electrode. When the resistance of the battery before deterioration was measured with a digital multimeter, the cell resistance was 10 Ωcm ² . In this non-aqueous electrolyte secondary battery, the discharge lower limit voltage was 3.0V and the charge upper limit voltage was 4.1V, which were determined according to the battery configuration.

(degraded battery)
In the produced laminate cell, by charging to a capacity (SOC = 50%) corresponding to 50% of the electric capacity of the cell in a voltage range of 3.0 V to 4.1 V, Li is extracted from the positive electrode and simulated A positive electrode with a reduced capacity was obtained (also referred to as a deteriorated positive electrode). After that, the cell was disassembled and the deteriorated positive electrode was taken out. Then, a laminate cell was produced in the same manner as the production of the battery before deterioration, except that the deteriorated positive electrode was used as the positive electrode. This was defined as a deteriorated battery. The deteriorated battery was CC-charged to 4.1 V at 0.9 mA, then CC-discharged to 3.0 V at 0.9 mA, and the discharge capacity at that time was measured.

(recovery agent)
Under an inert atmosphere, naphthalene is dissolved in a tetrahydrofuran (THF) solvent to a concentration of 1.0 mol/L, and then 1.0 mol/L of lithium metal is added and stirred to obtain the above formula (7). A dark green radical anion liquid composition (lithium naphthalenide + THF), which is a recovery agent stock solution, was prepared by the reaction shown and used as a recovery agent.

(Recovery of deteriorated batteries)
A portion of the deteriorated battery was opened in an argon atmosphere, 0.5 mL of a recovery agent was injected with a pipette, and the opening was closed and left for 24 hours (recovery treatment). Thus, the deteriorated battery was recovered to obtain a recovered battery.

(Evaluation of recovery battery)
The recovered battery was CC-charged at 0.9 mA in a voltage range from 3.0 V to 4.1 V, then CC-discharged at 0.9 mA to 3.0 V, and the discharge capacity at that time was measured.

[Experimental example 2]
Experimental Example 2 was the same as Experimental Example 1, except that a recovery agent prepared by mixing the recovery agent (recovery agent undiluted solution) of Experimental Example 1 and the following electrolytic solution at a volume ratio of 5:5 was used. Same. The electrolytic solution was prepared by dissolving LiFSI to a concentration of 1.1 M in a mixed solvent containing 30 vol % ethylene carbonate, 40 vol % dimethyl carbonate, and 30 vol % ethyl methyl carbonate.

[Experimental examples 3 and 4]
Experimental Example 3 was the same as Experimental Example 1, except that the solvent of the recovery agent undiluted solution was changed from the THF solvent to the dimethoxyethane (DME) solvent. Experimental Example 4 was the same as Experimental Example 2, except that the solvent of the recovery agent undiluted solution was changed from the THF solvent to the DME solvent.

[ESR measurement]
Various samples were subjected to electron spin resonance (ESR) measurement using an electron spin resonance apparatus, ELEXSYS-E500 manufactured by Bruker. The measurement was performed under the conditions shown in Table 1 by putting 50 μL of the sample in a quartz ESR cell for measuring an aqueous solution. The samples used were the electrolyte solution extracted from the battery immediately after the recovery agent was injected in Experimental Example 2, the electrolyte solution extracted from the battery after standing for 5 days after the recovery agent was injected in Experimental Example 2, the recovery agent of Experimental Example 1, and the electrolytic solution of Experimental Example 2. The recovery agent, the recovery agent of Experimental Example 4, was used. It is reported, for example, in J. Am. Chem. Soc. 1954, 76, 13, 3367-3369 that lithium naphthalenide exhibits activity on electron spin resonance.

[Experimental result]
The results of Experimental Examples 1 to 4 are summarized in Table 2. Further, the discharge capacities before and after the capacity recovery of Experimental Examples 1 to 4 are summarized in the graph of FIG. As shown in Table 2 and FIG. 3, in Experimental Examples 2 and 4 using the recovery agent containing the electrolytic solution, it was found that the capacity was recovered. Further, when comparing Experimental Examples 1 and 2 in which the solvent of the recovery agent undiluted solution is THF, Experimental Example 2 using the recovery agent containing the electrolytic solution has a larger recovery capacity, and the experiment in which the solvent of the recovery agent undiluted solution is DME. Comparing Examples 3 and 4, Experimental Example 4 using a recovery agent containing an electrolytic solution had a larger recovery capacity. From this, it was found that the use of the recovery agent containing the electrolytic solution further improved the capacity of the battery after recovery. The reason why such an effect can be obtained was considered using the ESR measurement results.

FIG. 4 shows the ESR measurement results of the electrolyte solution extracted from the battery immediately after injection of the recovery agent in Experimental Example 2 and the electrolyte solution extracted from the battery after standing for 5 days after the injection of the recovery agent in Experimental Example 2. As shown in FIG. As shown in FIG. 4, a signal considered to be a naphthalenide anion radical was confirmed at the position of g=2.001 in both electrolytic solutions. This indicates that in lithium naphthalenide, the 2s1 electron, which is the outermost electron of lithium, is transferred to the naphthalenide ligand, but the naphthalenide ligand side is not a mere anion but an anion radical. It was speculated that

As shown in FIG. 4, the amplitude (intensity) of the signal, which is considered to be naphthalenide anion radical, decreased significantly after leaving for 5 days compared to immediately after injection of the recovery agent. It was speculated that this indicates that electrons of naphthalenide anion radicals were converted to 2s1 electrons of lithium, and that lithium was inserted into the positive electrode active material, resulting in a decrease in naphthalenide anion radicals.

FIG. 5 shows the ESR measurement results of the recovery agents of Experimental Examples 2 and 4. The signal of Experimental Example 2 ((1) in the figure) using THF solvent had a larger amplitude (intensity) than the signal of Experimental Example 4 ((2) in the figure) using DME solvent. It was speculated that this indicates that Experimental Example 4 using DME solvent has a greater solvation of naphthalenide.

FIG. 6 shows the ESR measurement results of the recovery agents of Experimental Examples 1 and 2. As shown in FIG. However, the recovery agent of Experimental Example 1 was adjusted to a low solute concentration of 10 mmol/L for convenience of measurement. The signal of Experimental Example 1 had a larger amplitude (intensity) than the signal of Experimental Example 2, and the ultrafine structure was clear. It was presumed that this indicates that the recovery agent of Experimental Example 2 had greater solvation with respect to naphthalenide than the recovery agent of Experimental Example 1 by adding the electrolytic solution. When the solvation to naphthalenide is large, lithium naphthalenide tends to release lithium ions and electrons. As a result, in Experimental Example 2, lithium ions were smoothly supplied to the positive electrode, recovery proceeded efficiently, and it is assumed that the battery capacity after recovery was improved as compared with Experimental Example 1 in which no electrolytic solution was added. rice field.

20 non-aqueous electrolyte secondary battery, 21 battery case, 22 positive electrode, 23 negative electrode, 24 separator, 25 gasket, 26 sealing plate, 27 non-aqueous electrolyte.

Claims (9)

A recovery agent for recovering the capacity of a non-aqueous electrolyte secondary battery using metal ions as carrier ions,
comprising a solute having an aromatic hydrocarbon compound in a reduced state and a metal ion, a solvent that dissolves the solute, and an electrolytic solution;
recovery agent. The solute has one or more of a reductant of the compound of formula (1) and a reductant of the compound of formula (2) as the aromatic hydrocarbon compound in the reduced state,
The restorative agent according to claim 1.

the solute has metal ions of the same type as the carrier ions;
The restorative agent according to claim 1 or 2. including one or more of tetrahydrofuran and dimethoxyethane as the solvent;
The recovery agent according to any one of claims 1 to 3. Containing a cyclic carbonate and a chain carbonate as the electrolytic solution,
The restorative agent according to any one of claims 1 to 4. The electrolyte contains the same type of electrolyte as the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery,
The restorative agent according to any one of claims 1 to 5. Containing the electrolytic solution in a range of 10% by volume or more and 90% by volume or less,
The recovery agent according to any one of claims 1-6. A recovery method for recovering the capacity of a non-aqueous electrolyte secondary battery using metal ions as carrier ions,
A recovery step of injecting the recovery agent according to any one of claims 1 to 7 into the non-aqueous electrolyte secondary battery to recover the capacity of the non-aqueous electrolyte secondary battery,
including,
A recovery method for a non-aqueous electrolyte secondary battery. A battery preparation step of preparing a non-aqueous electrolyte secondary battery with metal ions as carrier ions and having deteriorated capacity;
A recovery step of recovering the capacity of the non-aqueous electrolyte secondary battery by the recovery method for the non-aqueous electrolyte secondary battery according to claim 8;
A method for manufacturing a non-aqueous electrolyte secondary battery, comprising:

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