Recycling methods for carbon-containing materials

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

[Technical Field]

[0001] This invention relates to a method for recycling carbon-containing materials, and more specifically, to a method for recycling lithium secondary batteries, electric double-layer capacitors, and other energy storage devices. [Background technology]

[0002] Composite materials of lithium-containing transition metal oxides and carbon, such as lithium cobalt oxide and lithium nickel oxide, are used in energy storage devices such as lithium secondary batteries. Various recycling methods have been proposed to recover rare metals such as cobalt from these composite materials and reuse them as electrode materials.

[0003] For example, Japanese Patent Publication No. 10-158751 (Patent Document 1) describes a method for recovering valuable metals from used lithium secondary batteries, which aims to recover valuable metals from used lithium secondary batteries in a simple and efficient manner, comprising: (1) a roasting step of roasting the used lithium secondary battery to decompose, burn, or volatilize and remove organic materials to obtain a roasted product; (2) a grinding step of grinding the roasted product to obtain a pulverized product; (3) a sieving step of sieving the pulverized product to obtain a primary valuable metal concentrate; and (4) a melting step of removing aluminum other than valuable metals contained below the sieve to produce a secondary valuable metal concentrate.

[0004] Furthermore, Japanese Patent Publication No. 2005-11698 (Patent Document 2) describes a recycling method for lithium secondary battery electrode materials, which aims to recycle them in a shorter time using a simpler process. This method involves reducing lithium cobalt oxide, which is the positive electrode material of a lithium secondary battery, together with metallic lithium in a lithium chloride molten salt to produce lithium oxide, which then precipitates and separates cobalt or cobalt oxide. Subsequently, the lithium oxide is electrolyzed in the lithium chloride molten salt to deposit and recover metallic lithium at the cathode. [Prior art documents] [Patent Documents]

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the "Carbon Neutrality Declaration in 2050" announced by the Japanese government in 2020, it aims to achieve a decarbonized society by 2050 and substantially reduce greenhouse gas emissions to zero.

[0007] In the method described in Patent Document No. 1, when the used lithium secondary battery is baked at a temperature of 350°C to 1000°C in the baking process, a large amount of carbon contained in the positive electrode material is burned and released as carbon dioxide. In addition, the carbon remaining in the primary valuable metal concentrate is used to reduce the un-reduced valuable metal in the primary valuable metal concentrate in the melting process and is oxidized and released as carbon dioxide.

[0008] On the other hand, in the method described in Patent Document No. 2, as a pretreatment, the pulverized electrode material is directly wetted in the molten salt and oxygen or air is bubbled through it to oxidize the carbon and remove it from the composite material. The removed carbon is changed into carbon dioxide and dissipated as a gas, and is removed by a carbon dioxide absorbent or the like provided in the seal gas circulation path.

[0009] Thus, in the method described in Patent Document No. 1, a large amount of carbon dioxide is generated in the baking process and the melting process. In the method described in Patent Document No. 2, the treatment of carbon dioxide absorbed by a carbon dioxide absorbent or the like becomes a problem.

[0010] Therefore, an object of the present invention is to provide a recycling method for carbon-containing materials such as power storage devices that can reduce the amount of carbon dioxide released into the atmosphere.

Means for Solving the Problems

[0011] As a result of diligent research, the inventors have discovered that by placing a carbon-containing material, such as a lithium-ion battery or other energy storage device, in an electrolytic bath containing molten salt and applying an appropriate voltage between the cathode and anode, the carbon contained in the carbon-containing material can be separated and deposited as solid carbon. This electrochemical reaction process does not involve the combustion of carbon, thus reducing the amount of carbon dioxide emitted. Furthermore, by controlling the process so that the resulting solid carbon is of high purity, it becomes possible to recycle the carbon.

[0012] Based on the above findings, the present invention is configured as follows.

[0013] The recycling method for carbon-containing materials according to the present invention is: (a) The step of placing a cathode in or near the upper surface of an electrolytic bath containing molten salt, either in or outside of an electrolytic bath containing molten salt, (b) The step of placing the anode in the electrolytic bath, (c) The step of placing a carbon-containing material containing carbon in a single form in an electrolytic bath as the material to be treated, (d) The process includes the step of applying a voltage between the anode and cathode such that carbon is separated from the carbon-containing material in the electrolytic bath and deposited as solid carbon.

[0014] In this way, it is possible to provide a recycling method for carbon-containing materials that can reduce the amount of carbon dioxide released into the atmosphere.

[0015] In the above method, in step (d), it is preferable to apply a voltage between the anode and cathode such that the 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 to solid carbon on the cathode side of the electrolytic bath.

[0016] In the above method, the cathode is placed in an electrolytic bath, and in step (d), the carbon in the carbon-containing material in contact with the cathode in the electrolytic bath is reduced to carbide ions (C2 2- ) becomes carbide ions (C2) on the anode side in the electrolytic bath. 2- It is preferable to apply a voltage between the anode and cathode such that the material is oxidized to solid carbon.

[0017] In the above method, it is preferable that the carbon-containing material is at least part of the energy storage device.

[0018] In the above method, it is preferable that at least a portion of the energy storage device is a crushed or disassembled used energy storage device.

[0019] In the above method, the energy storage device is preferably a non-aqueous secondary battery.

[0020] In the above method, it is preferable that the electrolytic bath is placed inside a sealable reaction vessel. [Brief explanation of the drawing]

[0021] [Figure 1] This figure schematically shows a system for performing the recycling process method according to the first embodiment of the present invention. [Figure 2] This figure schematically shows a system for performing the recycling process method according to a second embodiment of the present invention. [Figure 3] This figure schematically shows a system for performing the recycling process method according to the third embodiment of the present invention. [Modes for carrying out the invention]

[0022] Embodiments of this invention will be described below with reference to the drawings.

[0023] <First Embodiment> As shown in Figure 1, the schematically illustrated recycling apparatus 1 of the first embodiment comprises a reaction vessel 10 containing an electrolytic bath 100, a basket-shaped anode 21, a cathode 22, and a power supply unit 23 to which the anode 21 and cathode 22 are connected. In this embodiment, both the anode 21 and cathode 22 are placed in the electrolytic bath, but the cathode 22 may be placed outside the electrolytic bath 100, near the upper surface of the electrolytic bath 100. Furthermore, the reaction vessel 10 may be open or configured to be sealable, and it is preferable that it be sealable.

[0024] The electrolytic bath 100 uses a molten salt in which a metal oxide has been dissolved in advance. By dissolving the metal oxide, oxide ions (O 2- ) can be stably present in the electrolytic bath. 2- ) may be supplied into the electrolytic bath 100 by other means.

[0025] Furthermore, within the electrolytic bath 100, a carbon-containing material 400 containing carbon in its elemental form is housed and arranged in a basket-shaped anode 21 as the material to be treated. The elemental form of carbon may be, for example, known elements of carbon such as graphite, hard carbon, amorphous carbon, acetylene black, Ketjen black, or activated carbon. The carbon-containing material containing carbon in its elemental form may be carbon itself, or it may be, for example, an electrode material that includes elemental form of carbon as a component, or an energy storage device that includes such an electrode material. More specifically, the carbon-containing material 400 is preferably, for example, a used non-aqueous secondary battery or a non-aqueous secondary battery that has been crushed or decomposed during the factory production stage. The non-aqueous secondary battery is preferably a lithium secondary battery.

[0026] The power supply unit 23 applies a voltage between the basket-shaped anode 21 and cathode 22 so that the following reactions occur on the anode 21 and cathode 22 sides in the electrolytic bath 100.

[0027] The carbon-containing material of the workpiece to be processed, which is accommodated in the basket-shaped anode 21 and contacts the anode 21, undergoes the reactions of the following formulas (1) to (3). Reaction in the carbon-containing material: C (carbon-containing material) + 3O 2- → CO3 2- + 4e - (1) C (carbon-containing material) + 2O 2- [[ID=I4]]→ CO2 + 4e - (2) C (carbon-containing material) + O 2- → CO + 2e - (3) Among these, the main reaction is the formula (1).

[0028] When CO3 of the formula (1) 2- is reduced at the cathode, solid carbon is generated in the electrolytic bath according to the formula (4).

[0029] Cathode reaction: CO3 2- + 4e - → C (solid) + 3O 2- (4)

[0030] The oxide ions (O 2- ) generated at the cathode are reused in the oxidation reaction of the carbon-containing material shown by the formulas (1) to (3) and the oxidation reaction of the anode material in the following formulas (5) to (8).

[0031] When the cathode 22 is arranged near the upper surface of the electrolytic bath 100 outside the electrolytic bath 100, a discharge is generated between the cathode 22 and the upper surface of the electrolytic bath 100. By this discharge, the carbonate ions shown by the formula (4) are reduced and fine particles of carbon are formed.

[0032] When the material of the basket-shaped anode 21 is made of nickel ferrite or the like, it can function as an insoluble oxygen generation anode. In this case, the reaction at the anode 21 (oxygen generation anode) becomes the following formula (5). Anode reaction (oxygen generation anode): 2O 2- → O2 + + 4e - (5)

[0033] When carbon is used as the material for the basket-shaped anode 21, it can be used as an inexpensive conductive electrode, but the reaction at the anode 21 (carbon) is an oxidation reaction similar to that of the carbon-containing material being treated. Anode reaction (carbon anode): C (carbon electrode)+3O 2- →CO3 2- +4e - (6) C (carbon electrode)+2O 2- →CO2+4e - (7) C (carbon electrode) + O 2- →CO+2e - (8) These are side reactions of (1) to (3).

[0034] Focusing on the carbon-containing material, the overall reaction is given by the following equation, derived from equation (1), which is the main reaction at the anode, and equation (4), which is the reaction at the cathode, resulting in the deposition of carbon from the carbon-containing material.

[0035] C (carbon-containing material) → C (solid) (9)

[0036] <molten salt> Alkali metal halides, alkaline earth metal halides, alkali metal carbonates, and alkaline earth metal carbonates can be used as molten salts.

[0037] As alkali metal halides, 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.

[0038] As alkaline earth metal halides, compounds such as MgF2, CaF2, SrF2, BaF2, MgCl2, CaCl2, SrCl2, BaCl2, MgBr2, CaBr2, SrBr2, BaBr2, MgI2, CaI2, SrI2, and BaI2 can be used.

[0039] As alkali metal carbonates, carbonates such as Li2CO3, Na2CO3, and K2CO3 can be used.

[0040] As alkaline earth metal carbonates, carbonates such as MgCO3, CaCO3, and BaCO3 can be used.

[0041] <Oxide ions (O 2- )> Oxide ions (O 2- Oxide ions (O) are supplied to the electrolytic bath in advance. 2- Alkali metal oxides and alkaline earth metal oxides can be used as the source. Alkali metal oxides include oxides such as Li2O, Na2O, and K2O. Alkaline earth metal oxides include oxides such as MgO, CaO, and BaO.

[0042] As the electrolytic reaction progresses, oxide ions (O) in the electrolytic bath 2- When the amount of oxide ions (O) decreases and is depleted, the reaction in equation (1) stops, so the oxide ions (O) need to be used as appropriate. 2- ) needs to be replenished. Oxide ions (O 2- In addition to adding alkali metal oxides and alkaline earth metal oxides, another method to prevent the depletion of these substances is to blow carbon dioxide into the electrolytic bath.

[0043] In this case, carbon dioxide is oxide ions (O) in the electrolytic bath. 2- It reacts with ) and is absorbed into the electrolytic bath as carbonate ions, as shown in the following equation. CO2 + O 2- → CO3 2- (10)

[0044] To generate carbonate ions, 1 mole of oxide ions (O 2- ) consumes , but through the cathodic reduction reaction shown in equation (4), 1 mole of carbonate ions is converted to 3 moles of oxide ions (O 2- Because ) is generated, blowing carbon dioxide into the electrolytic bath results in oxide ions (O 2- This will replenish the supply.

[0045] <Processing temperature> There are no particular restrictions on the processing temperature (temperature of the electrolytic bath). However, at temperatures exceeding 900°C, thermal decomposition of the carbonate itself becomes significant, and the materials that can be used for the electrolytic cell become limited, making handling difficult. Therefore, a processing temperature of 250°C to 800°C is preferable. For example, when a mixed molten salt of LiCl-KCl molten chloride and K2CO3 is used as the molten salt, and LiO2 is used as the oxide ion source, a processing temperature of 450°C is preferable.

[0046] <Cathode> In the method for producing graphite particles according to the present invention, the cathode may be immersed in the electrolytic bath, or it may not be immersed in the electrolytic bath but placed outside the electrolytic bath near the upper surface of 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 upper surface of the electrolytic bath. By placing the cathode near the upper surface of the electrolytic bath without immersing it in the electrolytic bath, extremely fine carbon particles of sub-nanometer size or smaller can be formed.

[0047] Furthermore, by not immersing the electrodes in the electrolytic bath, impurities originating from the cathode substrate are less likely to be mixed into the electrolytic bath. In addition, since all the formed carbon particles are present in the electrolytic bath, the recovery of the carbon particles becomes easier.

[0048] Various materials can be used for the cathode, including iron, nickel, molybdenum, tantalum, tungsten, and other metals, their alloys, carbon materials such as glassy carbon and conductive diamond, conductive ceramics, and semiconducting ceramics. Furthermore, these materials can also be used as cathodes when formed as thin films on dissimilar materials.

[0049] <Anode> The anode structure is designed to retain the carbon-containing material to be treated in the electrolytic bath without dissipation, and to electrically contact the anode with the carbon-containing material. In addition to a general current-carrying electrode using carbon, the anode can also function as an insoluble oxygen-evolving anode.

[0050] As an insoluble oxygen-evolving anode, an insoluble electrode is used in which the surface of a substrate made of a metal such as Ti is coated with RuO2, IrO2, RhO2, or Ta2O5, and Ni X Fe 3-X Nickel ferrite represented by O4(X=0.1~2.0), or chemical formula: Ni X Co 1-X O(X=0.1~0.5 or formula: Ni X Co 3-X Conductive ceramic electrodes made of nickel-cobalt oxide represented as O4 (X=0.3~1.5), or conductive diamond electrodes, can be used.

[0051] <Solid carbon recovery> When recovering solid carbon, the electrolytic bath containing the solid carbon is transferred outside the reaction vessel and solidified into a salt at room temperature. The solidified salt is dissolved in water or warm water below 50°C, and the 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 obtained solid carbon can be recycled into graphite suitable for use as an electrode material, for example, by heat treatment.

[0052] In this way, various elements contained in carbon-containing materials such as energy storage devices can be continuously separated in a single reaction vessel or on a single recycling line.

[0053] As described above, the carbon-containing material recycling method according to the present invention does not require the burning of carbon by roasting the energy storage device when recycling an energy storage device as an example of a carbon-containing material, as in conventional methods. Therefore, the amount of carbon dioxide released into the atmosphere can be reduced. Furthermore, since there is no need to use a carbon dioxide adsorbent, the treatment of carbon dioxide adsorbed in the adsorbent is not a problem.

[0054] Furthermore, the carbon in carbon-containing materials can be recycled into high-purity solid carbon. For example, if the carbon in a carbon-containing material is present in the form of amorphous carbon, it is possible to produce 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 changes only in its crystal structure before and after the recycling process, without undergoing compound formation. Therefore, the electrolytic energy required for recycling can be kept low, as it is mainly limited to the energy consumed in the transformation of the crystal structure. Moreover, if the carbon in the carbon-containing material is graphite and the precipitate is also solid graphite, the energy required for recycling becomes even lower than when only the transformation of the crystal structure is involved. Thus, the recycling method of the present invention is also advantageous from the viewpoint of energy conservation.

[0055] In the first embodiment, the recycling process is preferably carried out under the following conditions: The molten salt is preferably LiCl-KCl. The processing temperature is preferably 300°C to 800°C, and more preferably 400°C to 500°C. The voltage between the cathode and anode is preferably greater than 0V and 4V or less, and more preferably 1.6V to 2.0V.

[0056] In the first embodiment, for example, an electrolytic bath at 450°C is prepared using 1 L of LiCl-KCl as the molten salt, crushed and decomposed lithium batteries are added to the electrolytic bath as a carbon-containing material, and solid carbon can be obtained by applying a voltage of 2.0 V between the anode and cathode.

[0057] In the first embodiment, it is possible to circulate unreactable gases such as Ar or N2 through the reaction vessel, and since it can be opened to the atmosphere, the apparatus structure is simple.

[0058] <Second Embodiment> As shown in Figure 2, the schematically illustrated recycling processing apparatus 2 of the second embodiment includes, similar to the recycling processing apparatus 1 of the first embodiment, a reaction vessel 10 containing an electrolytic bath 100, a basket-shaped anode 21, a cathode 22, and a power supply unit 23 to which the anode 21 and cathode 22 are connected. In this embodiment, both the anode 21 and cathode 22 are placed in the electrolytic bath, but the cathode 22 may be placed outside the electrolytic bath 100, near the upper surface of the electrolytic bath 100. In the electrolytic bath 100, a carbon-containing material 400 containing carbon in a single form is placed inside the basket-shaped anode 21 as the material to be processed.

[0059] Unlike the first embodiment, in the second embodiment, the reaction vessel 10 of the recycling processing apparatus 2 is configured to be sealed. Furthermore, it is equipped with a pressure monitoring unit 30 and a pressure adjustment unit 31, and if the pressure in the reaction vessel 10 rises above a predetermined level due to carbon dioxide and carbon monoxide generated by the side reaction, the carbon dioxide and carbon monoxide are discharged to the outside of the reaction vessel.

[0060] The power supply unit 23 applies a voltage between the anode 21 and the cathode 22 so that the following reactions (11) to (14) occur on the anode 21 and cathode 22 sides of the electrolytic bath 100.

[0061] In the carbon-containing material housed within the basket-shaped anode 21 and in contact with the anode 21 as the material to be treated, the following reactions (11) to (13) occur, as in the second embodiment. Reactions in carbon-containing materials: C (carbon-containing material) +3O 2- →CO3 2- +4e - (11) C (carbon-containing material) +2O 2- →CO2+4e - (12) C (carbon-containing material) + O 2- →CO+2e - (13)

[0062] Of these, the main reaction is (11), but in the second embodiment, the carbon dioxide generated in the side reaction equation (12) is also converted into carbonate ions.

[0063] As the carbon dioxide generated in equation (12) is released outside the bath, the pressure inside the reaction vessel increases, and accordingly, the carbon dioxide filling the reaction vessel and the oxide ions (O) in the electrolytic bath react. 2- The following reaction is promoted between ( ) and , and carbon dioxide is absorbed into the electrolytic bath 100. As a result, the pressure inside the reaction vessel decreases and is eventually maintained at a constant pressure. CO2 + O 2- → CO3 2- (14)

[0064] CO3 produced in equations (11) and (14) 2- It is reduced at the cathode according to equation (15), and solid carbon is produced in the electrolytic bath. Cathode reaction: CO3 2- +4e - →C(solid)+3O 2- (15)

[0065] Since the carbon dioxide generated by the side reaction is also added to the reduction reaction at the cathode, the current efficiency is higher in Embodiment 2 than in Embodiment 1.

[0066] In Embodiment 2, as in Embodiment 1, when an oxygen-evolving anode is used as the basket-shaped anode 21, the reaction at the anode 21 (oxygen-evolving anode) is given by the following equation (16). The oxygen-evolving anode is formed of nickel ferrite or diamond, for example. Anode reaction (oxygen-evolving anode): 2O 2- →O2+4e - (16)

[0067] Furthermore, since the reaction vessel is sealed in the second embodiment, the amount of carbon dioxide released into the atmosphere can be reduced compared to the first embodiment.

[0068] The other configurations and effects of the second embodiment are the same as those of the first embodiment.

[0069] In the second embodiment, the recycling process is preferably carried out under the following conditions: The molten salt is preferably LiCl-KCl. The processing temperature is preferably 300°C to 800°C, and more preferably 400°C to 500°C. The voltage between the cathode and anode is preferably greater than 0V and 4V or less, and more preferably 1.6V to 2.0V.

[0070] In the second embodiment, for example, an electrolytic bath at 450°C is prepared using 1 L of LiCl-KCl as the molten salt, crushed and decomposed lithium batteries are added to the electrolytic bath as a carbon-containing material, a voltage of 2.0 V is applied between the anode and cathode, and the pressure is controlled so that the pressure inside the reaction vessel containing carbon dioxide produced by the side reaction reaches 1 atm, thereby obtaining solid carbon.

[0071] <Third Embodiment> As shown in Figure 3, the schematically illustrated recycling apparatus 3 of the third embodiment includes, similar to the recycling apparatus 1 of the first embodiment, a reaction vessel 10 containing an electrolytic bath 100, an anode 21, a cathode 22, and a power supply unit 23 to which the anode 21 and cathode 22 are connected. In this embodiment, both the anode 21 and cathode 22 are placed in the electrolytic bath. A carbon-containing material 400 containing carbon in a standalone form is placed in the electrolytic bath 100 as the material to be processed.

[0072] In the third embodiment of the recycling processing apparatus 3, the difference from the first and second embodiments is that the cathode 22 is formed in a basket shape, and the carbon-containing material 400 is placed inside the basket-shaped cathode 22 and in contact with the cathode 22. In addition, the electrolytic bath 100 is a molten salt in which calcium carbide (CaC2) etc. is dissolved in advance, and carbide ions (C2 2- This includes )

[0073] The power supply unit 23 applies a voltage between the anode 21 and the cathode 22 so that the following reactions (17) to (18) occur on the anode 21 and cathode 22 sides of the electrolytic bath 100.

[0074] Cathode reaction: 2C (carbon-containing material) + 2e - →C2 2- (17) Anode reaction: C2 2- →2C(solid)+2e - (18)

[0075] The other configurations and effects of the third embodiment are the same as those of the first embodiment.

[0076] In the third embodiment, the recycling process is preferably carried out under the following conditions: The molten salt is preferably LiCl-KCl. The processing temperature is preferably 300°C to 800°C, and more preferably 400°C to 500°C. 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%, and more preferably 5 mol% to 15 mol%. The voltage between the cathode and anode is preferably greater than 0V and 4V or less, and more preferably 1.6V to 2.0V.

[0077] In the third embodiment, for example, an electrolytic bath at 450°C is prepared using 1 L of LiCl-KCl as the molten salt, crushed and decomposed lithium batteries are added to the electrolytic bath as a carbon-containing material, and solid carbon can be obtained by applying a voltage of 2.0 V between the anode and cathode.

[0078] The present invention can be summarized as follows:

[0079] [1] A method for recycling carbon-containing materials according to the present invention is: (a) The step of placing a cathode in or near the upper surface of an electrolytic bath containing molten salt, either in or outside of an electrolytic bath containing molten salt, (b) The step of placing the anode in the electrolytic bath, (c) The step of placing a carbon-containing material containing carbon in a single form in an electrolytic bath as the material to be treated, (d) The process includes the step of applying a voltage between the anode and cathode such that carbon is separated from the carbon-containing material in the electrolytic bath and deposited as solid carbon.

[0080] [2] In the method described in [1] above, it is preferable that in step (d), a voltage is applied between the anode and cathode such that the 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 to solid carbon on the cathode side in the electrolytic bath.

[0081] [3] In the method described in [1] above, the cathode is placed in an electrolytic bath, and in step (d), the carbon in the carbon-containing material in contact with the cathode in the electrolytic bath is reduced to carbide ions (C2 2- ) becomes carbide ions (C2) on the anode side in the electrolytic bath. 2- It is preferable to apply a voltage between the anode and cathode such that the material is oxidized to solid carbon.

[0082] [4] In the method according to any one of [1] to [3] above, the carbon-containing material is preferably at least part of the energy storage device.

[0083] [5] In the method described in [4] above, it is preferable that at least a portion of the energy storage device is a crushed or disassembled used energy storage device.

[0084] [6] In the method described in [4] or [5] above, the energy storage device is preferably a non-aqueous secondary battery.

[0085] [7] In the method according to any one of the above [1] to [6], it is preferable that the electrolytic bath is placed in a sealable reaction vessel.

[0086] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description and includes all variations in the meaning and scope equivalent to the claims. [Explanation of Symbols]

[0087] 10: Reaction vessel, 21: Anode, 22: Cathode, 100: Electrolytic bath, 400: Carbon-containing material.

Claims

1. (a) The step of placing a cathode in or near the upper surface of an electrolytic bath containing a molten salt, either in or outside the electrolytic bath containing a molten salt. (b) The step of placing an anode in the electrolytic bath, (c) The step of placing a carbon-containing material containing carbon in a single form in the electrolytic bath as the material to be treated, (d) The process includes the step of applying a voltage between the anode and the cathode such that carbon is separated from the carbon-containing material in the electrolytic bath and deposited as solid carbon, A method for recycling a carbon-containing material, wherein step (d) above includes applying a voltage between the anode and the cathode such that 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 according to claim 1, wherein the carbon-containing material is at least part of an energy storage device.

3. The method according to claim 2, wherein at least a portion of the energy storage device is a crushed or disassembled used energy storage device.

4. The method according to claim 2 or 3, wherein the energy storage device is a non-aqueous secondary battery.

5. The method according to any one of claims 1 to 4, wherein the electrolytic bath is located in a sealable reaction vessel.

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