JP2023146133A - Recycling treatment method for carbon-containing material - Google Patents

Abstract

To provide a recycling treatment method for a carbon-containing material such as an electricity storage device that can reduce the amount of carbon dioxide released into the atmosphere.SOLUTION: A recycling treatment method for a carbon-containing material includes the steps of (a) placing a cathode in an electrolytic bath containing molten salt or near the top of the electrolytic bath outside of the electrolytic bath containing molten salt, (b) placing an anode in the electrolytic bath, (c) placing at least a part of an electricity storage device containing carbon as the material to be treated in the electrolytic bath, and (d) applying voltage between the anode and the cathode at which carbon is separated from the carbon-containing material in the electrolytic bath and deposited as solid carbon.SELECTED DRAWING: None

Description

The present invention relates to a method for recycling carbon-containing materials, and specifically to a method for recycling lithium secondary batteries, electric double layer capacitors, and other power storage devices.

Composite materials of carbon and lithium-containing transition metal oxides, such as lithium cobalt oxide and lithium nickel oxide, are used in power storage devices such as lithium secondary batteries. In order to recover rare metals such as cobalt from this composite material and reuse them as electrode materials, various recycling processing methods have been proposed.

For example, Japanese Patent Application Laid-Open No. 10-158751 (Patent Document 1) describes (1) roasting of used lithium secondary batteries for the purpose of easily recovering valuable metals from used lithium secondary batteries with good yield. A roasting process in which organic materials are removed by decomposition, combustion, or volatilization to obtain a roasted product; (2) a pulverization process in which the roasted product is crushed to obtain a pulverized product; (3) the pulverized product is sieved. (4) a sieving process to obtain a primary valuable metal concentrate, and (4) a melting process to remove aluminum other than valuable metals contained under the sieve to produce a secondary valuable metal concentrate. Methods for recovering valuable metals are described.

In addition, JP 2005-11698 A (Patent Document 2) describes cobalt, which is a positive electrode material for lithium secondary batteries, with the aim of recycling lithium secondary battery electrode materials in a simpler process and in a shorter time. Lithium oxide is subjected to a reduction reaction with metallic lithium in a molten lithium chloride salt to produce lithium oxide, and cobalt or cobalt oxide is precipitated and separated.Then, the lithium oxide is electrolyzed in a molten lithium chloride salt and the metallic lithium is used as a cathode. A recycling treatment method is described, which is characterized by precipitating and recovering the particles.

Japanese Patent Application Publication No. 10-158751 Japanese Patent Application Publication No. 2005-11698

By the way, the "2050 Carbon Neutrality Declaration" announced by the Japanese government in 2020 aims to realize a decarbonized society and reduce greenhouse gas emissions to virtually zero by 2050.

In the method described in Patent Document 1, when a used lithium secondary battery is roasted at a temperature of 350°C to 1000°C in the roasting process, a large amount of carbon contained in the positive electrode material is burned and released as carbon dioxide. be done. Further, the carbon remaining in the primary valuable metal concentrate is used in the melting process to reduce unreduced valuable metals in the primary valuable metal concentrate, is oxidized, and is released as carbon dioxide.

On the other hand, in the method described in Patent Document 2, as a pretreatment, the pulverized electrode material is directly wetted in a molten salt and oxygen or air is bubbled therein to oxidize the carbon and remove it from the composite material. The removed carbon changes to carbon dioxide, becomes a gas, is released, and is removed by a carbon dioxide absorbent or the like provided in the sealing gas circulation path.

As described above, in the method described in Patent Document 1, a large amount of carbon dioxide is generated during the roasting process and the melting process. In the method described in Patent Document 2, processing of carbon dioxide absorbed by a carbon dioxide absorbent or the like poses a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for recycling carbon-containing materials such as power storage devices, which can reduce the amount of carbon dioxide released into the atmosphere.

As a result of extensive research, the present inventors discovered that a carbon-containing material containing carbon in a single form, such as a power storage device such as a lithium secondary battery, is placed in an electrolytic bath containing a molten salt, and an appropriate voltage is applied to the material. It has been found that by applying an electric current between the cathode and the anode, the carbon contained in the carbon-containing material can be separated from the carbon-containing material and precipitated as solid carbon. Processing using this electrochemical reaction does not involve combustion of carbon, so it is possible to reduce the amount of carbon dioxide released. Furthermore, by controlling the solid carbon produced to be highly pure carbon, it is also possible to recycle carbon.

Based on the above findings, the present invention is configured as follows.

The method for recycling carbon-containing materials according to the present invention includes:
(a) disposing a cathode near the top surface of the electrolytic bath in the electrolytic bath containing the molten salt or outside the electrolytic bath containing the molten salt;
(b) placing an anode in an electrolytic bath;
(c) disposing a carbon-containing material containing carbon in the form of a simple substance in an electrolytic bath as a material to be treated;
(d) applying a voltage between an anode and a cathode that causes carbon to be separated from the carbon-containing material in the electrolytic bath and deposited as solid carbon;

By doing so, it is possible to provide a method for recycling carbon-containing materials that can reduce the amount of carbon dioxide released into the atmosphere.

In the above method, in step (d), carbon in the carbon-containing material in contact with the anode in the electrolytic bath is oxidized to carbonate ions, and the carbonate ions are reduced on the cathode side in the electrolytic bath. Preferably, a voltage is applied between the anode and the cathode that results in solid carbon.

In the above method, the cathode is placed in an electrolytic bath, and in step (d) carbon in the carbon-containing material in contact with the cathode in the electrolytic bath is reduced to carbide ions (C ₂ ^2- ). Therefore, it is preferable to apply a voltage between the anode and the cathode in which carbide ions (C ₂ ^2- ) are oxidized to solid carbon on the anode side in the electrolytic bath.

In the above method, the carbon-containing material is preferably at least a part of the electricity storage device.

In the above method, it is preferable that at least a portion of the power storage device is a used power storage device that has been crushed or disassembled.

In the above method, the electricity storage device is preferably a non-aqueous secondary battery.

In the above method, the electrolytic bath is preferably placed in a sealable reaction vessel.

1 is a diagram schematically showing a system that performs a recycling processing method according to a first embodiment of the present invention. FIG. 2 is a diagram schematically showing a system that performs a recycling method according to a second embodiment of the present invention. It is a figure which shows typically the system which performs the recycling processing method of 3rd Embodiment of this invention.

Embodiments of the present invention will be described below based on the drawings.

<First embodiment>
As shown in FIG. 1, the recycling processing apparatus 1 of the first embodiment schematically illustrated includes a reaction vessel 10 accommodating an electrolytic bath 100, a basket-shaped anode 21, a cathode 22, an anode 21 and a cathode. 22 is connected to the power supply section 23. In this embodiment, both the anode 21 and the cathode 22 are placed in the electrolytic bath, but the cathode 22 may be placed outside the electrolytic bath 100 near the top surface of the electrolytic bath 100. Further, the reaction container 10 may be configured to be open or closed, and is preferably configured to be closed.

The electrolytic bath 100 uses a molten salt in which a metal oxide is dissolved in advance. By dissolving the metal oxide, oxide ions (O ^2- ) can be stably present in the electrolytic bath. Oxide ions (O ²⁻ ) may be supplied into electrolytic bath 100 in other ways.

Further, in the electrolytic bath 100, a carbon-containing material 400 containing carbon in the form of a single substance as a material to be treated is housed in a basket-shaped anode 21 and arranged. The carbon in the form of an element may be any known carbon in the form of an element, such as graphite, hard carbon, amorphous carbon, acetylene black, Ketjen black, activated carbon, and the like. The carbon-containing material containing carbon in the form of an element may be carbon itself in the form of an element, or may be an electrode material containing carbon in the form of an element as a part of its constituent elements, or an electrode material such as an electrode. It may be an electricity storage device including the material. More specifically, the carbon-containing material 400 is preferably one obtained by crushing or disassembling a used non-aqueous secondary battery or a non-aqueous secondary battery that became defective during factory production. Moreover, it is preferable that the non-aqueous secondary battery is a lithium secondary battery.

A voltage is applied between the basket-shaped anode 21 and the cathode 22 by the power supply unit 23, so that the following reaction occurs on the anode 21 side and the cathode 22 side in the electrolytic bath 100.

In the carbon-containing material of the treated material housed in the basket-shaped anode 21 and in contact with the anode 21, the following reactions (1) to (3) occur.
Reactions with carbon-containing materials:
C (carbon-containing material) +3O ^2- →CO ₃ ^2- +4e ^- (1)
C (carbon-containing material) +2O ^2- →CO ₂ +4e ^- (2)
C (carbon-containing material) + O ^2- → CO + 2e ^- (3)
Among these, the main reaction is expressed by formula (1).

When CO ₃ ^2- in formula (1) is reduced at the cathode, solid carbon is produced in the electrolytic bath according to formula (4).

Cathode reaction: CO ₃ ^2- +4e ^- →C (solid) +3O ^2- (4)

The oxide ions (O ^2- ) generated at the cathode are caused by the oxidation reaction of the carbon-containing material shown in formulas (1) to (3) and the anode material in formulas (5) to (8) described below. is reused in the oxidation reaction.

When the cathode 22 is placed outside the electrolytic bath 100 near the top surface of the electrolytic bath 100, a discharge is generated between the cathode 22 and the top surface of the electrolytic bath 100. By this discharge, the carbonate ions shown in equation (4) are reduced and carbon fine particles are formed.

When the basket-shaped anode 21 is made of nickel ferrite or the like, it can function as an insoluble oxygen-generating anode. In this case, the reaction at the anode 21 (oxygen generating anode) is expressed by the following equation (5).
Anodic reaction (oxygen generating anode): 2O ^2- → O ₂ +4e ^- (5)

When carbon is used as the material for the basket-shaped anode 21, it can be used as an inexpensive current-carrying electrode, but the reaction at the anode 21 (carbon) is an oxidation reaction similar to that of the carbon-containing material that is the material to be treated.
Anodic reaction (carbon anode):
C (carbon electrode) +3O ^2- →CO ₃ ^2- +4e ^- (6)
C (carbon electrode) +2O ^2- →CO ₂ +4e ^- (7)
C (carbon electrode) + O ^2- → CO + 2e ^- (8)
These become side reactions (1) to (3).

Focusing on the carbon-containing material here, from equation (1), which is the main reaction at the anode, and equation (4), which is the cathode reaction, the overall reaction becomes the following equation, and carbon is precipitated from the carbon-containing material.

C (carbon-containing material) → C (solid) (9)

<Molten salt>
As the molten salt, alkali metal halides, alkaline earth metal halides, alkali metal carbonates, and alkaline earth metal carbonates can be used.

Examples of alkali metal halides include compounds such as LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI. can be used.

Examples _of alkaline earth metal halides include _MgF2 , _CaF2 , SrF2, _BaF2 , MgCl2, CaCl2, _SrCl2 , _BaCl2 , _MgBr2 , _{CaBr2 , SrBr2} , _BaBr2 , _{MgI2 , CaI2.} , SrI ₂ , BaI ₂ and the like can be used.

As the alkali metal carbonate, carbonates such as Li ₂ CO ₃ , Na ₂ CO ₃ and K ₂ CO ₃ can be used.

As the alkaline earth metal carbonate, carbonates such as MgCO ₃ , CaCO ₃ and BaCO ₃ can be used.

<Oxide ion (O ^2- )>
Oxide ions (O ^2- ) are previously supplied into the electrolytic bath. As the oxide ion (O ²⁻ ) source, alkali metal oxides and alkaline earth metal oxides can be used. As the alkali metal oxide, oxides such as Li ₂ O, Na ₂ O, K ₂ O, etc. can be used. As the alkaline earth metal oxide, oxides such as MgO, CaO, BaO, etc. can be used.

As the electrolytic reaction progresses, the oxide ions (O ^2- ) in the electrolytic bath decrease and become depleted, and the reaction of formula (1) stops, so it is necessary to replenish the oxide ions (O ^2- ) as appropriate. . As a method for preventing the depletion of oxide ions (O ^2- ), in addition to adding the alkali metal oxides and alkaline earth metal oxides, there is also a method of blowing carbon dioxide into the electrolytic bath.

In this case, carbon dioxide reacts with oxide ions (O ^2- ) in the electrolytic bath, becomes carbonate ions shown in the following formula, and is absorbed into the electrolytic bath.
CO ₂ + O ^2- → CO ₃ ^2- (10)

To generate carbonate ions, 1 mole of oxide ions (O ^2- ) is consumed, but by the cathodic reduction reaction shown in equation (4), 3 moles of oxide ions (O ^2- ) are converted from 1 mole of carbonate ions. As a result, blowing carbon dioxide into the electrolytic bath replenishes oxide ions (O ^2- ).

<Processing temperature>
There is no particular restriction on the treatment temperature (bath temperature of the electrolytic bath). However, in a high temperature range exceeding 900°C, thermal decomposition of the carbonate itself becomes noticeable, and the materials that can be used for the electrolytic cell are limited, making handling difficult, so it is recommended that the treatment temperature be between 250°C and 800°C. preferable. For example, when a mixed molten salt of LiCl-KCl molten chloride and K ₂ CO ₃ is used as the molten salt and LiO ₂ is used as the oxide ion source, the treatment temperature is preferably 450°C.

<Cathode>
In the method for producing graphite particles according to the present invention, the cathode may be immersed in the electrolytic bath, or may be placed outside the electrolytic bath near the top surface of the electrolytic bath without being immersed in the electrolytic bath. That is, carbonate ions may be reduced on the surface of the cathode immersed in the electrolytic bath, or carbonate ions may be reduced by discharge electrons near the top surface of the electrolytic bath. By arranging the cathode near the top surface of the electrolytic bath without immersing it in the electrolytic bath, extremely fine carbon particles of subnanometer size or less can be formed.

Furthermore, by not immersing the electrode in the electrolytic bath, impurities derived from the cathode base material are less likely to be mixed into the electrolytic bath. Furthermore, since all the carbon particles formed are present in the electrolytic bath, recovery of the carbon particles is facilitated.

As the material of the cathode, various metals such as iron, nickel, molybdenum, tantalum, and tungsten, alloys thereof, carbon materials such as glassy carbon and conductive diamond, conductive ceramics, semiconducting ceramics, etc. can be used. Further, a thin film formed of these materials on a different material can also be used as a cathode.

<Anode>
The structure of the anode is such that the carbon-containing material, which is the material to be treated, is held in the electrolytic bath without being dissipated, and the anode and the carbon-containing material are brought into electrical contact. As for the function of the anode, in addition to a general current-carrying electrode using carbon, it can also serve as an insoluble oxygen-generating anode.

Examples of insoluble oxygen-generating anodes include insoluble electrodes in which the surface of a substrate made of a metal such as Ti is coated with RuO ₂ , IrO ₂ , RhO ₂ , Ta ₂ O ₅ , and Ni _X Fe _3-X O ₄ (X=0. 1 to 2.0), or compositional formula: Ni _X Co _1-X O (X=0.1 to 0.5) or formula: Ni _X Co _3-X O ₄ (X=0. A conductive ceramic electrode made of nickel cobalt oxide represented by 3 to 1.5) or a conductive diamond electrode can be used.

<Recovery of solid carbon>
When recovering solid carbon, the electrolytic bath containing solid carbon is transferred to the outside of the reaction vessel and solidified into salt at room temperature. The solidification salt is dissolved in water or hot water of 50°C or less, and solid carbon is suspended in the aqueous solution while applying ultrasound. The resulting suspension is filtered through a membrane filter, and the solid carbon deposited on the filter is dried. The solid carbon obtained can be recycled into graphite suitable for use in electrode materials, for example by heat treatment.

By doing so, various elements contained in a carbon-containing material such as an electricity storage device can be continuously separated in one reaction vessel or on one recycling processing line.

As described above, in the method for recycling carbon-containing materials according to the present invention, unlike conventional methods, when recycling an electricity storage device as an example of a carbon-containing material, the electricity storage device is roasted to remove carbon. Since there is no need to burn it, the amount of carbon dioxide released into the atmosphere can be reduced. Further, since there is no need to use a carbon dioxide adsorbent, there is no problem in processing carbon dioxide adsorbed in the adsorbent.

Furthermore, the carbon in the carbon-containing material can be recycled to high purity solid carbon. For example, when carbon in a carbon-containing material is contained in the form of amorphous carbon, it is possible to generate solid carbon in the form of graphite, which is more functional and has higher utility and commercial value than amorphous carbon. In this case, the carbon differs only in its crystal structure before and after the recycling treatment without undergoing any compound formation. Therefore, the electrolytic energy required for recycling can be reduced because the energy consumed is mainly for converting the crystal structure. Further, if the carbon in the carbon-containing material is graphite and the precipitate is also solid graphite, the energy required for recycling is even smaller than if only a transformation of the crystal structure is involved. As described above, the recycling method of the present invention is also advantageous from the viewpoint of energy saving.

In the case of the first embodiment, specifically, it is preferable that the recycling process is performed under the following conditions. Preferably, the molten salt is LiCl-KCl. The treatment temperature is preferably 300°C or higher and 800°C or lower, more preferably 400°C or higher and 500°C or lower. The voltage between the cathode and the anode is preferably greater than 0V and less than or equal to 4V, more preferably greater than or equal to 1.6V and less than or equal to 2.0V.

In the first embodiment, for example, an electrolytic bath at 450° C. is prepared using 1 L of LiCl-KCl as a molten salt, a crushed and decomposed lithium battery is added as a carbon-containing material into the electrolytic bath, and an anode and a cathode are added. Solid carbon can be obtained by applying a voltage of 2.0 V between.

In the first embodiment, it is also possible to flow a gas that is difficult to react with, such as Ar or N ₂ , into the reaction container, and the device structure is simple because it can be opened to the atmosphere.

<Second embodiment>
As shown in FIG. 2, similarly to the recycling processing apparatus 1 of the first embodiment, the schematically illustrated recycling processing apparatus 2 of the second embodiment includes a reaction vessel 10 accommodating an electrolytic bath 100, and a basket-shaped recycling processing apparatus 2. , an anode 21 , a cathode 22 , and a power supply section 23 to which the anode 21 and the cathode 22 are connected. In this embodiment, both the anode 21 and the cathode 22 are placed in the electrolytic bath, but the cathode 22 may be placed outside the electrolytic bath 100 near the top surface of the electrolytic bath 100. In the electrolytic bath 100, a carbon-containing material 400 containing carbon in the form of a single substance as a material to be treated is housed in a basket-shaped anode 21.

Unlike the first embodiment, in the second embodiment, the reaction container 10 of the recycling processing apparatus 2 is configured to be airtight. Furthermore, it is equipped with a pressure monitoring section 30 and a pressure adjustment section 31, and when the pressure in the reaction vessel 10 becomes higher than a predetermined value due to carbon dioxide and carbon monoxide generated in a side reaction, carbon dioxide and carbon monoxide are removed from the reaction vessel 10. Discharge outside.

A voltage is applied between the anode 21 and the cathode 22 by the power supply unit 23, so that the following reactions (11) to (14) occur on the anode 21 side and the cathode 22 side in the electrolytic bath 100.

In the carbon-containing material housed in the basket-shaped anode 21 and in contact with the anode 21 as a material to be treated, the following reactions (11) to (13) occur as in the second embodiment.
Reactions with carbon-containing materials:
C (carbon-containing material) +3O ^2- →CO ₃ ^2- +4e ^- (11)
C (carbon-containing material) +2O ^2- →CO ₂ +4e ^- (12)
C (carbon-containing material) + O ^2- → CO + 2e ^- (13)

Among these, the main reaction is (11), but the second embodiment is characterized in that carbon dioxide generated in the side reaction equation (12) is also converted into carbonate ions.

When the pressure inside the reaction vessel increases as the carbon dioxide generated in equation (12) is released to the outside of the bath, the carbon dioxide filling the reaction vessel and the oxide ions (O ^{2 -} ), the following reaction is promoted, and carbon dioxide is absorbed into the electrolytic bath 100. As a result, the pressure inside the reaction vessel decreases and eventually remains constant.
CO ₂ + O ^2- → CO ₃ ^2- (14)

CO ₃ ^2- produced in equations (11) and (14) is reduced at the cathode according to equation (15), and solid carbon is produced in the electrolytic bath.
Cathode reaction:
CO ₃ ^2- +4e ^- →C (solid) +3O ^2- (15)

Since the carbon dioxide generated in the side reaction also participates in the reduction reaction at the cathode, the current efficiency is higher in the second embodiment than in the first embodiment.

In the second embodiment, as in the first embodiment, when an oxygen-generating anode is used as the basket-shaped anode 21, the reaction at the anode 21 (oxygen-generating anode) is expressed by the following equation (16). The oxygen evolution anode is formed by nickel ferrite or diamond, by way of example.
Anodic reaction (oxygen generating anode): 2O ^2- → O ₂ +4e ^- (16)

Further, in the second embodiment, since the reaction container is sealed, the amount of carbon dioxide released into the atmosphere can be reduced compared to the first embodiment.

The other configurations and effects of the second embodiment are the same as those of the first embodiment.

In the case of the second embodiment, specifically, it is preferable that the recycling process is performed under the following conditions. Preferably, the molten salt is LiCl-KCl. The treatment temperature is preferably 300°C or higher and 800°C or lower, more preferably 400°C or higher and 500°C or lower. The voltage between the cathode and the anode is preferably greater than 0V and less than or equal to 4V, more preferably greater than or equal to 1.6V and less than or equal to 2.0V.

In the second embodiment, for example, an electrolytic bath at 450° C. is prepared using 1 L of LiCl-KCl as a molten salt, a crushed and decomposed lithium battery is added as a carbon-containing material to the electrolytic bath, and an anode and a cathode are added. Solid carbon can be obtained by applying a voltage of 2.0 V during this period and controlling the pressure so that the pressure in the reaction vessel containing carbon dioxide generated by the side reaction is 1 atm.

<Third embodiment>
As shown in FIG. 3, similarly to the recycling processing apparatus 1 of the first embodiment, the schematically illustrated recycling processing apparatus 3 of the third embodiment includes a reaction vessel 10 containing an electrolytic bath 100, and an anode 21. , a cathode 22 , and a power supply section 23 to which the anode 21 and the cathode 22 are connected. In this embodiment, both anode 21 and cathode 22 are placed in an electrolytic bath. In the electrolytic bath 100, a carbon-containing material 400 containing carbon in the form of a single substance is arranged as a material to be treated.

The recycling processing apparatus 3 of the third embodiment is different from the first and second embodiments in that the cathode 22 is formed in a basket shape, and the carbon-containing material 400 is arranged inside the basket-shaped cathode 22. It is in contact with the cathode 22. Further, the electrolytic bath 100 contains carbide ions (C ₂ ^2- ), which are made by dissolving calcium carbide (CaC ₂ ) or the like in molten salt in advance.

A voltage is applied between the anode 21 and the cathode 22 by the power supply unit 23, so that the following reactions (17) to (18) occur on the anode 21 side and the cathode 22 side in the electrolytic bath 100.

Cathode reaction: 2C (carbon-containing material) + 2e ^- → C ₂ ^2- (17)
Anodic reaction: C ₂ ^2- → 2C (solid) + 2e ^- (18)

The other configurations and effects of the third embodiment are the same as those of the first embodiment.

In the case of the third embodiment, specifically, it is preferable that the recycling process is performed under the following conditions. Preferably, the molten salt is LiCl-KCl. The treatment temperature is preferably 300°C or higher and 800°C or lower, more preferably 400°C or higher and 500°C or lower. Assuming that all the raw material carbon is dissolved in the molten salt electrolytic bath, the carbon concentration is preferably 2 mol% to 20 mol%, more preferably 5 mol% to 15 mol%. The voltage between the cathode and the anode is preferably greater than 0V and less than or equal to 4V, more preferably greater than or equal to 1.6V and less than or equal to 2.0V.

In the third embodiment, for example, an electrolytic bath at 450° C. is prepared using 1 L of LiCl-KCl as a molten salt, a crushed and decomposed lithium battery is added as a carbon-containing material to the electrolytic bath, and an anode and a cathode are added. Solid carbon can be obtained by applying a voltage of 2.0 V between.

The present invention can be summarized as follows.

[1] The method for recycling carbon-containing materials according to the present invention includes:
(a) disposing a cathode near the top surface of the electrolytic bath in the electrolytic bath containing the molten salt or outside the electrolytic bath containing the molten salt;
(b) placing an anode in an electrolytic bath;
(c) disposing a carbon-containing material containing carbon in the form of a simple substance in an electrolytic bath as a material to be treated;
(d) applying a voltage between an anode and a cathode that causes carbon to be separated from the carbon-containing material in the electrolytic bath and deposited as solid carbon;

[2] In the method of [1] above, in step (d), carbon in the carbon-containing material that is in contact with the anode in the electrolytic bath is oxidized to carbonate ions, and on the cathode side in the electrolytic bath, carbon is oxidized to carbonate ions. It is preferable to apply a voltage between the anode and the cathode to reduce carbonate ions to solid carbon.

[3] In the method of [1] above, the cathode is placed in an electrolytic bath, and in step (d), carbon in the carbon-containing material in contact with the cathode in the electrolytic bath is reduced to form carbide ions ( It is preferable to apply a voltage between the anode and the cathode so ^{that the carbide ions (C 2 2-} ₎ ^become solid carbon by oxidation on the anode side in the electrolytic _bath .

[4] In the method described in any one of [1] to [3] above, the carbon-containing material is preferably at least a part of the electricity storage device.

[5] In the method of [4] above, it is preferable that at least a portion of the electricity storage device is a used electricity storage device that has been crushed or disassembled.

[6] In the method of [4] or [5] above, the electricity storage device is preferably a non-aqueous secondary battery.

[7] In the method described in any one of [1] to [6] above, the electrolytic bath is preferably placed in a sealable reaction vessel.

The embodiments and examples disclosed above should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and includes meanings equivalent to the claims and all modifications within the scope.

10: reaction vessel, 21: anode, 22: cathode, 100: electrolytic bath, 400: carbon-containing material.

Claims (7)

(a) disposing a cathode in an electrolytic bath containing a molten salt or near the top surface of the electrolytic bath outside the electrolytic bath containing a molten salt;
(b) placing an anode in the electrolytic bath;
(c) disposing a carbon-containing material containing carbon in the form of a simple substance in the electrolytic bath as a material to be treated;
(d) A method for recycling a carbon-containing material, comprising the step of applying a voltage between the anode and the cathode so that carbon is separated from the carbon-containing material in the electrolytic bath and deposited as solid carbon. In the step (d), the carbon in contact with the anode in the electrolytic bath is oxidized to carbonate ions, and the carbonate ions are reduced to solid carbon on the cathode side in the electrolytic bath. 2. The method of claim 1, comprising applying a voltage between the anode and the cathode. The cathode is disposed in the electrolytic bath, and in step (d), carbon in the carbon-containing material in contact with the cathode in the electrolytic bath is reduced to form carbide ions (C ₂ ^2- ). 2. The method according to claim 1, comprising applying a voltage between the anode and the cathode such that carbide ions (C ₂ ^2- ) are oxidized to become solid carbon on the anode side in the electrolytic bath. Method. The method according to any one of claims 1 to 3, wherein the carbon-containing material is at least a part of an electricity storage device. The method according to claim 4, wherein the at least part of the power storage device is a used power storage device that has been crushed or disassembled. The method according to claim 4 or 5, wherein the electricity storage device is a non-aqueous secondary battery. 7. A method according to any one of claims 1 to 6, wherein the electrolytic bath is arranged in a sealable reaction vessel.

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