Apparatus for manufacturing metallic lithium and method for manufacturing metallic lithium

Abstract

To manufacture metallic lithium more efficiently and easily. [Solution] The metallic lithium manufacturing apparatus comprises a deposition electrode that comes into contact with a non-aqueous electrolyte and deposits metallic lithium; a counter electrode that comes into contact with an aqueous electrolyte and contains an electrode material containing lithium, and is opposite to the deposition electrode; an oxygen removal unit that reduces or removes dissolved oxygen from the aqueous electrolyte; an ion conducting medium interposed between the deposition electrode and the counter electrode that separates the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions; and a control unit that uses the aqueous electrolyte treated in the oxygen removal unit to apply an electric current between the counter electrode and the deposition electrode, thereby depositing metallic lithium from the lithium on the counter electrode side onto the deposition electrode.

Description

[Technical Field]

[0001] This specification discloses a lithium metallic manufacturing apparatus and a method for manufacturing lithium metallic. [Background technology]

[0002] Currently, with the global shift to electric vehicles (EVs), the demand for lithium-ion batteries is surging, making the development of recycling technologies for used lithium-ion batteries an urgent necessity. However, among the valuable elements used in lithium-ion batteries, lithium is a difficult element to recover. Current methods for recycling lithium-ion batteries are broadly divided into dry methods, which separate lithium through oxidation-reduction or melting, and wet methods, which separate lithium through extraction using precipitation or solvents. In the dry method, lithium is oxidized and incorporated into the slag, so lithium must be extracted from the slag to recover it. Basic lithium compounds such as Li2O and LiOH have high solubility in water, while acidic lithium compounds such as LiF and LiPO4 have very low solubility in water. Therefore, in order to recover lithium, the slag must be adjusted so that it consists of highly basic lithium compounds. Currently, lithium is not recovered using the dry method.

[0003] On the other hand, in the wet method, lithium can only be recovered by extraction at a high pH, ​​so a method is used in which a large amount of sodium carbonate is added to produce lithium carbonate and then lithium is recovered. The lithium recovery rate by this method is about 80-90%, which is low compared to other valuable metals (Mn: 94-99%, Ni: 91-99%, Co: 95-99%) (see Non-Patent Literature 1). In addition, the process of evaporating water during Li2CO3 recovery consumes energy and produces a large amount of wastewater, which poses a problem of high environmental impact.

[0004] As a method for producing metallic lithium, for example, there has been proposed a method including an anode compartment containing an aqueous solution of an alkali metal salt, a cathode compartment, and a solid electrolyte that separates the anode compartment and the cathode compartment from each other, wherein at least a part of the surface of the solid electrolyte that contacts the anode compartment and / or at least a part of the surface of the solid electrolyte that contacts the cathode compartment has at least one ion conductive layer (see, for example, Patent Document 1). In this production apparatus, lithium dissolved in the aqueous solution can be taken out as metallic lithium. Further, as such a production apparatus, for example, there has been proposed an apparatus in which electrolysis is carried out using an anode that contacts a molten composition containing a lithium salt and a cathode separated from the molten composition by a solid electrolyte capable of conducting lithium ions (see, for example, Patent Document 2). In this production apparatus, metallic lithium can be taken out from a molten composition including those having a low lithium salt concentration.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the manufacturing apparatuses described in Patent Documents 1 and 2 use lithium ions or molten compositions dissolved in an aqueous solution as the source of metallic lithium, but other sources were not considered. Examples of lithium sources for lithium secondary batteries include positive electrode active materials, but producing metallic lithium from such electrode materials requires dissolving them in an aqueous solution or melting them at high temperatures, which is a time-consuming process. Furthermore, when electrode materials are used as raw materials for the production of metallic lithium, under certain conditions, the reaction may be inhibited, making it impossible to efficiently produce metallic lithium. Thus, there has been a desire for a more efficient and easier method of producing metallic lithium.

[0008] This disclosure has been made in view of these challenges, and its main objective is to provide a lithium metal manufacturing apparatus and a method for manufacturing lithium metal that can produce lithium metal more efficiently and easily. [Means for solving the problem]

[0009] Through diligent research to achieve the above-mentioned objectives, the present inventors discovered that by using a non-aqueous solvent at the deposition electrode, placing an electrode material at the counter electrode using an aqueous solvent, further reducing the amount of dissolved oxygen in this aqueous solvent, and applying a predetermined current, metallic lithium can be deposited on the deposition electrode more efficiently and easily. This led to the completion of the invention disclosed herein.

[0010] That is, the metallic lithium manufacturing apparatus of this disclosure, A lithium metal production apparatus for depositing metallic lithium, A deposition electrode in which metallic lithium is deposited upon contact with a non-aqueous electrolyte, The electrode material contains lithium and is in contact with an aqueous electrolyte, and includes a counter electrode facing the deposited electrode, An oxygen removal unit for reducing or removing dissolved oxygen from the aqueous electrolyte, An ion-conducting medium interposed between the deposition electrode and the counter electrode, which separates the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions, A control unit that applies an electric current between the counter electrode and the deposition electrode using the aqueous electrolyte system treated in the oxygen removal unit, thereby depositing metallic lithium from the lithium on the counter electrode onto the deposition electrode, It is something that is provided.

[0011] The present disclosure describes a method for producing metallic lithium. A method for producing metallic lithium, comprising: a deposition electrode that contacts a non-aqueous electrolyte and deposits metallic lithium; a counter electrode that contacts an aqueous electrolyte and contains an electrode material containing lithium, and is opposite to the deposition electrode; and an ion-conducting medium interposed between the deposition electrode and the counter electrode, which separates the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions, An oxygen removal step for reducing or removing dissolved oxygen from the aqueous electrolyte, A deposition step in which metallic lithium is deposited onto the deposition electrode from the lithium on the counter electrode by applying an electric current between the counter electrode and the deposition electrode using the aqueous electrolyte after the oxygen removal step, It includes. [Effects of the Invention]

[0012] This disclosure enables the production of metallic lithium more efficiently and easily. The reasons for these effects are presumed to be as follows. For example, in this metallic lithium production apparatus, the electrode material of a lithium secondary battery can be used directly as the supply source for the counter electrode. Furthermore, since an aqueous electrolyte is used for the counter electrode, it is easy to handle. In addition, by using an aqueous electrolyte with reduced dissolved oxygen, the decrease in the efficiency of metallic lithium production due to local corrosion in the electrode material can be further suppressed. Therefore, metallic lithium can be obtained more efficiently and easily with this metallic lithium production apparatus and method. [Brief explanation of the drawing]

[0013] [Figure 1] A schematic diagram illustrating an example of the lithium metal manufacturing apparatus 10 of this disclosure. [Figure 2] A diagram showing the relationship between the concentration of the aqueous electrolyte salt, the applied current density, and the delithiation reaction efficiency. [Figure 3] Backscattered electron image of an aluminum current collector foil immersed in an aqueous electrolyte solution containing dissolved oxygen. [Figure 4] pH values ​​before and after immersion of aluminum current collector foil in an aqueous electrolyte solution containing dissolved oxygen. [Figure 5] The amount of dissolved oxygen in the aqueous electrolyte after air or nitrogen bubbling treatment. [Figure 6] pH values ​​before and after immersion of the LFP electrode and Al current collector in an aqueous electrolyte solution. [Figure 7] Measurement results obtained by immersing an LFP electrode in a 1M-LiNO3 aqueous solution with dissolved oxygen. [Figure 8] Measurement results obtained by immersing an LFP electrode in a 1M-LiNO3 aqueous solution after reducing dissolved oxygen. [Figure 9] Results of a study on galvanic corrosion in LFP electrodes. [Figure 10] Electrolysis measurement results of a cell using a 1M LiNO3 aqueous solution. [Figure 11] pH value and Al concentration before and after immersion of the LFP electrode and Al current collector in an aqueous electrolyte. [Figure 12] Electrolysis measurement results of a cell using a 0.5M-Li2SO4 aqueous solution. [Modes for carrying out the invention]

[0014] (Lithium metal manufacturing equipment) The lithium metal production apparatus described in this embodiment includes a housing portion, a deposition electrode, a non-aqueous electrolyte, a counter electrode, an aqueous electrolyte, an ion conduction medium, an oxygen removal portion, and a control portion. The deposition electrode is an electrode that contacts the non-aqueous electrolyte and on which metallic lithium is deposited. The counter electrode is an electrode that contacts the aqueous electrolyte and includes an electrode material containing lithium, and is an electrode facing the deposition electrode. The ion conduction medium is interposed between the deposition electrode and the counter electrode, separates the non-aqueous electrolyte and the aqueous electrolyte, and conducts lithium ions. The control portion deposits lithium on the counter electrode side as metallic lithium on the deposition electrode by applying a current between the deposition electrode and the counter electrode.

[0015] Examples of the electrode material serving as a lithium supply source include the positive electrode and negative electrode of a lithium secondary battery, among which the positive electrode is preferred. Examples of the lithium secondary battery include a lithium ion battery in which the negative electrode stores and releases lithium, a lithium secondary battery in which the negative electrode is lithium metal or a lithium alloy, and a hybrid capacitor. The electrode material may be the electrode material of the lithium secondary battery as it is, may be a fragmented electrode obtained by cutting the electrode material, or may be black mass as an active material concentrate produced in the recycling process of the lithium secondary battery. The active material serving as a lithium supply source is preferably a positive electrode active material, and examples of the positive electrode active material as a lithium source include sulfides containing a transition metal element, composite oxides containing lithium and a transition metal element, and the like. Specifically, transition metal sulfides such as TiS2, TiS3, MoS3, and FeS2, with the basic composition formula Li (1-x) MnO2 (0 < x < 1, etc., the same below), Li (1-x) Mn2O4, etc., lithium manganese composite oxides, with the basic composition formula Li (1-x) CoO2, etc., lithium cobalt composite oxides, with the basic composition formula Li (1-x) NiO2, etc., lithium nickel composite oxides, with the basic composition formula Li (1-x) Ni a Co b Mn cLithium nickel cobalt manganese composite oxides such as O2 (a + b + c = 1), lithium vanadium composite oxides with a basic composition formula such as LiV2O3, transition metal oxides with a basic composition formula such as V2O5, etc. can be used. As the lithium source, lithium iron phosphate (LiFePO4: LFP), etc. can be mentioned. Specifically, the lithium source includes LFP, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111), LiNi 0.5 Co 0.3 Mn 0.2 O2 (NCM532), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.5 Mn 1.5 O4, LiMn2O4, etc. can be mentioned. Note that the "basic composition formula" means that other elements may be included.

[0016] This electrode material may, for example, have a positive electrode active material of a lithium secondary battery and a current collector formed of a metal different from the positive electrode active material. Further, this positive electrode active material may contain lithium iron phosphate. Furthermore, the current collector may contain one or more of aluminum, nickel, and stainless steel. When the positive electrode active material is lithium iron phosphate and the current collector is aluminum or the like,异种金属接触腐食 (heterogeneous metal contact corrosion) etc. may occur, and the production efficiency may decrease due to the corrosion current when a current is applied. Therefore, the significance of introducing an oxygen removal part is high.

[0017] It should be noted that the term "异种金属接触腐食" in the original text seems to be a Japanese term which is directly translated here. It might be more accurately translated as "heterogeneous metal contact corrosion" in the context. Also, it's important to double-check the accuracy of the translation in the context of the patent content for any specific technical or domain-related nuances.The housing is a component that houses the deposition electrode, the counter electrode, and the ion-conducting medium. This housing is made of an insulating material that is stable in terms of temperature and potential during metallic lithium deposition, such as resin or ceramic. This housing is divided into a cathode chamber and an anode chamber by the ion-conducting medium. The cathode chamber houses the deposition electrode and a non-aqueous electrolyte. The anode chamber houses the counter electrode and an aqueous electrolyte. The anode chamber of this housing may be open to the atmosphere. When the housing is open to the atmosphere, it is preferable because it makes it easier to remove and store the electrode material, which is the lithium supply source.

[0018] The deposition electrode is a cathode from which metallic lithium is deposited. This deposition electrode is preferably made of at least one of copper and nickel, for example. Alternatively, this deposition electrode may be made of metallic lithium or a lithium alloy, or of a noble metal such as Pt or Au. This deposition electrode is preferably made of foil or a plate. The deposition electrode may be housed in a cathode chamber together with a non-aqueous electrolyte, for example. When the deposition of metallic lithium reaches a sufficient thickness, the deposition electrode is removed from the cathode chamber and the metallic lithium is separated.

[0019] The non-aqueous electrolyte is a lithium conductor, and preferably one containing a dissolved Li-containing salt. Examples of non-aqueous solvents for this electrolyte include ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), 1,3-dioxolane (DOL), and dimethoxyethane (DME). The Li-containing salt may be the same substance as the support salt used in lithium secondary batteries, such as LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiSbF6, LiSiF6, LiAlF4, LiSCN, LiClO4, LiCl, LiF, LiBr, LiI, and LiAlCl4. Among these, one or more selected from the group consisting of inorganic salts such as LiPF6, LiBF4, LiAsF6, and LiClO4, and organic salts such as LiCF3SO3, LiN(CF3SO2)2, and LiC(CF3SO2)3 are mentioned. Of these, lithium hexafluorophosphate (LiPF6) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are preferred as Li-containing salts. The concentration of the Li-containing salt is preferably 0.01 mmol / L (mM) or higher, more preferably 0.1 mM or higher, and may be 1 mM or higher. Furthermore, this concentration is preferably 4 M or lower, more preferably 2 M or lower, and may be 1 M or lower.

[0020] The counter electrode is adjacent to the electrode material of a lithium secondary battery, which is a source of metallic lithium. The counter electrode only needs to ensure electrical conductivity with respect to the lithium source, and may be biased toward the ion-conducting medium while the electrode material is disposed on the ion-conducting medium side. This counter electrode is preferably made of at least one of aluminum, titanium, and platinum. The counter electrode may also be a carbon electrode containing carbon. The shape of the counter electrode may be a plate, a mesh, or a porous body. When the counter electrode is biased toward the electrode material as a lithium source, it is preferable that it be mesh or porous so that excess aqueous electrolyte can be discharged from between it and the ion-conducting medium.

[0021] The aqueous electrolyte is an electrolyte in which lithium ions diffuse. On the counter electrode side, an inexpensive and low environmental impact aqueous electrolyte can be used instead of an expensive non-aqueous electrolyte. The aqueous electrolyte of the counter electrode preferably contains cations and anions. It is preferable that, for example, lithium nitrate, lithium sulfate, lithium chloride, lithium carboxylate, etc. are dissolved in this aqueous electrolyte. In the aqueous electrolyte, the concentration of cations and anions is preferably 0.01 mM or more, more preferably 0.1 mM or more, and may be 1 mM or more. Also, this concentration is preferably 10 M or less, more preferably 5 M or less, and may be 2 M or less. Further, it is more preferable that the aqueous electrolyte of the counter electrode contains cations and anions of 0.1 M or more and 2 M or less. In this range, the aqueous electrolyte is easy to handle and preferable. Also, in this range, local corrosion of the electrode material is likely to occur, and the effect of further suppressing the decrease in the production efficiency of metallic lithium by reducing dissolved oxygen can be obtained.

[0022] The ion conduction medium may be a plate-like body that prevents short-circuiting between the deposition electrode and the counter electrode. This ion conduction medium is preferably a solid electrolyte. The solid electrolyte may be, for example, a garnet-type oxide containing at least Li, La, and Zr. This solid electrolyte has a basic composition of Li 7.0+x-y (La 3-x ,A x )(Zr 2-y ,T y )O 12 and may be such. However, A is one or more of Sr and Ca, T is one or more of Nb and Ta, and it satisfies 0 < x ≦ 1.0, 0 < y < 0.75. Alternatively, the solid electrolyte has a basic composition (Li 7-3z+x-y M z )(La 3-x A x )(Zr 2-y T y )O 12 or (Li 7-3z+x-y M z )(La 3-x A x )(Y 2-y T y )O12 It may be a garnet-type oxide represented by the formula. However, in the formula, element M is one or more of Al and Ga, element A is one or more of Ca and Sr, T is one or more of Nb and Ta, and 0≦z≦0.2, 0≦x≦0.2, and 0≦y≦2 may be assumed. In this basic composition formula, it is more preferable that 0.05≦z≦0.1 is satisfied. In this basic composition formula, it is more preferable that 0.05≦x≦0.1 is satisfied. Also, in this basic composition formula, it is more preferable that 0.1≦y≦0.8 is satisfied. Within such ranges, the ionic conductivity can be made more suitable.

[0023] Alternatively, as a solid electrolyte, for example, the common Li3N, also known as LISICON. 14 Zn(GeO4)4, Li sulfide 3.25 Ge 0.25 P 0.75 S4, perovskite type La 0.5 Li 0.5 TiO3, (La 2 / 3 Li 3x □ 1 / 3-2x )TiO3(□: atomic vacancy), garnet-type Li7La3Zr2O 12 LiTi2(PO4)3, also known as NASICON type, Li 1.3 M 0.3 Ti 1.7 Examples include (PO3)4(M=Sc,Al). Also, Li7P3S obtained from glass ceramics with a composition of 80Li2S·20P2S5(mol%). 11 Furthermore, Li, a sulfide-based substance with high conductivity. 10Ge2PS2 is another example. Examples of glass-based inorganic solid electrolytes include Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li4SiO4, Li2S-P2S5, Li3PO4-Li4SiO4, Li3BO4-Li4SiO4, and those using SiO2, GeO2, B2O3, and P2O5 as glass-based materials with Li2O as a network modifier. Other examples of thiolysicone solid electrolytes include Li2S-GeS2 systems, Li2S-GeS2-ZnS systems, Li2S-Ga2S2 systems, Li2S-GeS2-Ga2S3 systems, Li2S-GeS2-P2S5 systems, Li2S-GeS2-SbS5 systems, Li2S-GeS2-Al2S3 systems, Li2S-SiS2 systems, Li2S-P2S5 systems, Li2S-Al2S3 systems, LiS-SiS2-Al2S3 systems, and Li2S-SiS2-P2S5 systems. These solid electrolytes may also be formed in a plate shape and placed between the deposition electrode and the counter electrode.

[0024] The oxygen removal unit reduces or removes dissolved oxygen from an aqueous electrolyte, for example. This oxygen removal unit is not particularly limited as long as it can reduce or remove dissolved oxygen, but for example, it may reduce or remove dissolved oxygen from the aqueous electrolyte by bubbling an inert gas into the aqueous electrolyte. The oxygen removal unit may include a supply unit for supplying the inert gas and a flow pipe for circulating the inert gas to the aqueous electrolyte. Alternatively, the oxygen removal unit may have a cylinder containing the inert gas. The inert gas may be nitrogen or a noble gas. Examples of noble gases include He and Ar. Of these, nitrogen is preferred as the inert gas. The flow rate of the inert gas can be appropriately set according to the amount of aqueous electrolyte. The oxygen removal unit preferably reduces or removes the dissolved oxygen content of the aqueous electrolyte to 3 g / L or less. Reducing the dissolved oxygen content to 3 g / L or less further suppresses the occurrence of reactions other than metallic lithium deposition, thus enabling more efficient production of metallic lithium. A lower dissolved oxygen content is preferable, and a content closer to 0 g / L is preferable. The oxygen removal unit may be designed to remove dissolved oxygen at all times during the production of metallic lithium, or it may be designed to contain a sealed aqueous electrolyte and remove dissolved oxygen before the production of metallic lithium.

[0025] The control unit is a controller that controls the entire apparatus. The control unit may perform processes such as applying current between the deposition electrode and the counter electrode, and executing oxygen removal processes in the oxygen removal section. The control unit may apply current to the counter electrode and the deposition electrode at a current density of 8 mA / g or more and 380 mA / g or less per unit mass of active material contained in the electrode material. This applied current may be, for example, 25 mA / g or more, even more preferably 35 mA / g or more, and 45 mA / g or more per unit mass of active material. Furthermore, this applied current is preferably 300 mA / g or less, more preferably 200 mA / g or less, and even more preferably 80 mA / g or less. It is more preferable for the control unit to apply current at a current density of 25 mA / g or more and 80 mA / g or less per unit mass of active material contained in the electrode material.

[0026] Next, a specific example of a metallic lithium production apparatus will be described using drawings. Figure 1 is a schematic explanatory diagram showing an example of a metallic lithium production apparatus 10 of this disclosure. As shown in Figure 1, the metallic lithium production apparatus 10 comprises a deposition electrode 11, a non-aqueous electrolyte 12, an ion conducting medium 13, an electrode material 14, a counter electrode 15, an aqueous electrolyte 16, a housing section 19, a control section 20, and an oxygen removal section 25. Note that any of the above-described configurations may be adopted for each component. The cathode chamber 21 contains the deposition electrode 11 and the non-aqueous electrolyte 12, and the anode chamber 22 contains the electrode material 14, the counter electrode 15, and the aqueous electrolyte 16, with each chamber separated by the ion conducting medium 13. The electrode material 14, which is a lithium supply source, is adjacent to the counter electrode 15. In addition, the generated metallic lithium is deposited on the surface of the deposition electrode 11. The ion-conducting medium 13 is a solid electrolyte that conducts lithium ions and isolates the non-aqueous electrolyte 12 from contact with the aqueous electrolyte 16. The containment section 19 may be open to the atmosphere at the top when bubbling is continued during the production of metallic lithium, or it may be sealed when electrode material is added after reducing the oxygen concentration by bubbling. The oxygen removal section 25 supplies an inert gas to the aqueous electrolyte 16 and performs a process to remove dissolved oxygen. The oxygen removal section 25 reduces or removes the amount of dissolved oxygen in the aqueous electrolyte to 3 g / L or less.

[0027] In the lithium metal production apparatus 10 configured in this way, lithium can be extracted from the counter electrode 15 by applying an electric current between the deposition electrode 11 and the counter electrode 15, thereby depositing lithium metal on the deposition electrode 11. The current density for this current application can be set appropriately considering the apparatus configuration and deposition efficiency, but it is preferably in the range of 8 mA / g or more and 380 mA / g or less, and more preferably in the range of 25 mA / g or more and 80 mA / g or less.

[0028] (Method of manufacturing metallic lithium) In this manufacturing method, for example, metallic lithium may be produced using the metallic lithium manufacturing apparatus described above. This metallic lithium manufacturing apparatus comprises a deposition electrode that comes into contact with a non-aqueous electrolyte and deposits metallic lithium; a counter electrode that comes into contact with an aqueous electrolyte and contains an electrode material containing lithium, and is opposite to the deposition electrode; an ion conducting medium interposed between the deposition electrode and the counter electrode, separating the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions; and an oxygen removal unit that reduces or removes dissolved oxygen from the aqueous electrolyte. This method for producing metallic lithium includes an oxygen removal step of reducing or removing dissolved oxygen from the aqueous electrolyte; and a deposition step of applying an electric current between the deposition electrode and the counter electrode using the aqueous electrolyte after the oxygen removal step, thereby depositing metallic lithium from the lithium on the counter electrode side onto the deposition electrode.

[0029] In the oxygen removal process, it is preferable to reduce or remove dissolved oxygen from the aqueous electrolyte by bubbling an inert gas into the aqueous electrolyte. The counter electrode may also include a positive electrode as the electrode material, comprising a positive electrode active material of a lithium secondary battery and a current collector formed of a different metal from the positive electrode active material. When the electrode material is a raw material for metallic lithium, localized corrosion may occur within the electrode material; therefore, the oxygen removal treatment can further suppress this corrosion. Furthermore, in this process, it is preferable that the aqueous electrolyte of the counter electrode contains cations and anions in concentrations of 0.1 M to 2 M. This range is preferable because the aqueous electrolyte is easy to handle. Also, within this range, localized corrosion of the electrode material is more likely to occur, and the effect of further suppressing the decrease in the efficiency of metallic lithium production due to reduced dissolved oxygen can be obtained. In the oxygen removal treatment, it is preferable to reduce or remove the amount of dissolved oxygen in the aqueous electrolyte to 3 g / L or less. Reducing the amount of dissolved oxygen to 3 g / L or less further suppresses the occurrence of reactions other than metallic lithium deposition, thus enabling more efficient production of metallic lithium. It is preferable that the amount of dissolved oxygen be as low as possible, and that it be as close to 0 g / L as possible.

[0030] In the deposition process, it is preferable that the counter electrode contains the positive electrode material of a lithium secondary battery as the electrode material. Furthermore, in this deposition process, it is preferable to apply a current in the range of 8 mA / g to 380 mA / g, and more preferably in the range of 25 mA / g to 80 mA / g, per active material contained in the electrode material. This deposition process can be carried out at room temperature, for example, between 20°C and 30°C. However, the deposition process may also be carried out at temperatures of 30°C or higher or 40°C or higher.

[0031] During the deposition process, the cell voltage increases when lithium is extracted from the electrode material (e.g., the positive electrode) contained in the anode chamber. Once this voltage increase is confirmed, the operator replaces the electrode material with a new one and continues the production of metallic lithium. This replacement of electrode material is repeated until the metallic lithium layer on the deposition electrode reaches the desired thickness. After this, the operator retrieves the deposition electrode in an atmosphere with a dew point of -38°C or lower, peels off the metallic lithium layer from the deposition electrode, and recovers the metallic lithium.

[0032] The metallic lithium manufacturing apparatus and method described above can produce metallic lithium more efficiently and easily. The reasons for these effects are presumed to be as follows. For example, in this metallic lithium manufacturing apparatus, the electrode material of a lithium secondary battery can be used directly as the supply source for the counter electrode. In addition, since an aqueous electrolyte is used for the counter electrode, it is easy to handle. Furthermore, by using an aqueous electrolyte with reduced dissolved oxygen, the decrease in the efficiency of metallic lithium production due to local corrosion in the electrode material can be further suppressed. Therefore, metallic lithium can be obtained more efficiently and easily with this metallic lithium manufacturing apparatus and method.

[0033] This metallic lithium production apparatus and method involves placing an electrode material, which serves as a lithium supply source, adjacent to the counter electrode in an anode chamber separated by an ion-conducting medium. A non-aqueous electrolyte is contained in the cathode chamber, also separated by the ion-conducting medium, along with the deposition electrode. Electrolysis, performed by applying current to the deposition electrode and counter electrode, extracts lithium ions from the lithium supply source, diffuses the ion-conducting medium, and deposits metallic lithium on the deposition electrode. This disclosure allows for the production of metallic lithium at room temperature and generates metallic lithium using only the energy equivalent to the charging voltage multiplied by the capacity of a lithium secondary battery, thus enabling significant energy savings. Furthermore, this disclosure is a method for electrochemically extracting lithium ions primarily from the positive electrode of used lithium secondary batteries, which are expected to see a rapid increase in demand, enabling the production of high-value-added metallic lithium. This method achieves significant energy savings by directly generating metallic lithium without the need for lithium carbonate or other intermediates. In addition, because it is possible to selectively extract only lithium ions from the electrode material serving as the lithium supply source, the contamination of lithium with other valuable elements during the recovery of other valuable elements in post-recycling processes can be reduced.

[0034] Here, we will explain, for example, the case in which an electrode using an aluminum metal current collector is used as a raw material for producing metallic lithium. Since the surface of aluminum metal is covered with an oxide film, the uniform corrosion rate in which the entire surface of the aluminum metal corrodes uniformly in a neutral aqueous solution is very slow. However, when it comes into contact with a dissimilar metal, localized corrosion can occur in which the oxide film is locally destroyed (see Figure 9C described later). In lithium-ion batteries, the positive electrode has an electrode composite material coated on an aluminum current collector, so in a Li salt aqueous solution, corrosion of the aluminum occurs due to contact between the aluminum and the electrode material, which can inhibit the delithiation reaction of the desired positive electrode active material. In this disclosure, in a method for electrochemically extracting lithium ions mainly from the positive electrode of a used lithium-ion battery, with the aim of producing high value-added metallic lithium, the occurrence of the corrosion reaction of the current collector can be suppressed by reducing or removing the amount of dissolved oxygen in the aqueous electrolyte, thereby enabling a smooth delithiation reaction from the positive electrode active material on which the electrode composite material is coated on the current collector.

[0035] It goes without saying that this disclosure is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of this disclosure.

[0036] This disclosure may be any of the following [1] to

[10] . [1] A lithium metal production apparatus for depositing metallic lithium, A deposition electrode in which metallic lithium is deposited upon contact with a non-aqueous electrolyte, The electrode material contains lithium and is in contact with an aqueous electrolyte, and includes a counter electrode facing the deposited electrode, An oxygen removal unit for reducing or removing dissolved oxygen from the aqueous electrolyte, An ion-conducting medium interposed between the deposition electrode and the counter electrode, which separates the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions, A control unit that applies an electric current between the counter electrode and the deposition electrode using the aqueous electrolyte system treated in the oxygen removal unit, thereby depositing metallic lithium from the lithium on the counter electrode onto the deposition electrode, A lithium metal manufacturing apparatus equipped with the following features. [2] The lithium metal production apparatus according to [1], wherein the oxygen removal unit reduces or removes dissolved oxygen from the aqueous electrolyte by bubbling an inert gas into the aqueous electrolyte. [3] The lithium metal production apparatus according to [1] or [2], wherein the oxygen removal unit reduces or removes the amount of dissolved oxygen in the aqueous electrolyte to 3 g / L or less. [4] A lithium metal manufacturing apparatus according to any one of [1] to [3], wherein the counter electrode comprises a positive electrode as the electrode material, having a positive electrode active material of a lithium secondary battery and a current collector formed of a metal different from the positive electrode active material. [5] The lithium metallic manufacturing apparatus according to [4], wherein the positive electrode active material comprises lithium iron phosphate, and the current collector comprises one or more of aluminum, nickel, and stainless steel. [6] The lithium metal production apparatus according to any one of [1] to [5], wherein the aqueous electrolyte of the counter electrode contains cations and anions in a concentration of 0.1 mol / L or more and 2 mol / L or less. [7] A metallic lithium manufacturing apparatus according to any one of [1] to [6], wherein metallic lithium is deposited on the deposition electrode from the lithium on the counter electrode side under any one or more of the conditions (1) to (4). (1) The control unit applies the current within a range of 8 mA / g or more and 380 mA / g or less per unit of active material contained in the electrode material. (2) The control unit applies the current within a range of 25 mA / g or more and 80 mA / g or less per unit of active material contained in the electrode material. (3) The counter electrode is made of at least one of aluminum, titanium, and platinum, and the deposition electrode is made of at least one of copper and nickel. (4) The non-aqueous electrolyte of the deposition electrode contains a Li-containing salt dissolved at a concentration of 0.01 mmol / L or more and 4 mol / L or less. [8] A method for producing metallic lithium, comprising: a deposition electrode that comes into contact with a non-aqueous electrolyte and deposits metallic lithium; a counter electrode that comes into contact with an aqueous electrolyte and contains an electrode material containing lithium, and is opposite to the deposition electrode; and an ion-conducting medium interposed between the deposition electrode and the counter electrode, which separates the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions, An oxygen removal step for reducing or removing dissolved oxygen from the aqueous electrolyte, A deposition step is performed in which metallic lithium is deposited onto the deposition electrode from the lithium on the counter electrode by applying an electric current between the counter electrode and the deposition electrode using the aqueous electrolyte after the oxygen removal step, A method for producing metallic lithium containing [the specified substance]. [9] The method for producing metallic lithium according to [8], wherein the oxygen removal step involves reducing or removing dissolved oxygen from the aqueous electrolyte by bubbling an inert gas into the aqueous electrolyte.

[10] The counter electrode includes as the electrode material a positive electrode having a positive electrode active material of a lithium secondary battery and a current collector formed of a metal different from the positive electrode active material, The method for producing metallic lithium according to [8] or [9], wherein the aqueous electrolyte of the counter electrode contains cations and anions in a concentration of 0.1 mol / L or more and 2 mol / L or less. [Examples]

[0037] The following describes experimental examples that specifically examine the manufacturing apparatus and manufacturing method of metallic lithium disclosed herein. Experimental Examples 2 and 5 correspond to embodiments of this disclosure, while Experimental Examples 1, 3, and 4 correspond to reference examples.

[0038] (1) Method for producing metallic lithium by electrolysis using LiNO3 and Li2SO4 aqueous solutions Solid electrolytes that are selective Li-ion conductors (Li2O-Al2O3-SiO2-P2O5-TiO2 system, LICGC) TMMetallic lithium was produced using a cell (Figure 1) with a separated anode and cathode chamber (AG-01; manufactured by Ohara Corporation). A 20 mm diameter Al plate was used as the counter electrode (anode) in contact with the positive electrode of a lithium secondary battery, and a 23 mm diameter Cu foil was used as the deposition electrode (cathode). Lithium was extracted from the positive electrode of the lithium-ion battery by electrolysis, and metallic lithium was deposited on the Cu foil. As a lithium supply source, the positive electrode of a lithium-ion battery with LiFe(PO4) (LFP) as the active material was used. This positive electrode has a structure in which the active material, conductive additive (HS-100), and binder (PVdF#7305) are kneaded in a ratio of 92:5:3 and coated on only one side of an aluminum current collector (basis weight of active material: 7-8 mg / cm³). 2 ). This LFP electrode was cut to a diameter of 19 mm to serve as the electrode. A 0.01 mM to 6 M LiNO3 aqueous solution or a 0.5 M Li2SO4 aqueous solution was injected into the anode chamber, and a non-aqueous electrolyte, lithium hexafluorophosphate (LiPF6) salt, was dissolved in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 3:4:3 to form an electrolyte solution (1M-LiPF6 / EC+DMC+EMC). The anode side was open to the atmosphere, and electrolysis was performed at a constant current with a current density of 23, 46, 68, or 91 mA / g per lithium ion positive electrode active material.

[0039] (2) Measurement of dissolved oxygen concentration in LiNO3 aqueous solution Pure water left in the atmosphere for one week, and 100 mM, 1 M, and 6 M LiNO3 aqueous solutions were prepared. These solutions were bubbled with air or N2 gas for 15 minutes, and the dissolved oxygen concentration of each solution was analyzed using a gas chromatograph / thermal conductivity detector (GC-TCD; Shimadzu Corporation).

[0040] (3) Immersion of Al current collector foil and LFP electrode in LiNO3 aqueous solution 19 mm diameter aluminum current collector foil and LFP electrodes were immersed in pure water and 2 mL of 1 mM, 1 M, and 6 M LiNO3 aqueous solutions at 25°C for 1 day.

[0041] (4) X-ray powder diffraction (XRD) measurement The active material phase of the LFP electrode before and after electrolysis was identified by XRD. An XRD instrument (Ultima IV; Rigaku) ​​was used, with CuKα X-rays, and measurements were performed under the following conditions: voltage 40kV, current 40mA, and scan rate 10° / min. The obtained XRD patterns were analyzed using XRD analysis software (JADE Pro; LightStone).

[0042] (5) SEM observation Scanning electron microscope (SEM) observations were performed using an SEM instrument (SU3500, Hitachi High-Tech) at an acceleration voltage of 15kV to observe the surfaces of the LFP electrode and Al current collector foil. Energy-dispersive X-ray spectroscopy (EDX) analysis was also performed.

[0043] (6) Inductively coupled plasma emission spectroscopy Quantitative analysis of Li, P, Fe, and Al in LFP electrodes or aqueous solutions after immersion in LFP powder was performed using inductively coupled plasma emission spectroscopy (ICP-OES) analysis (PS3520UIVDDII, Hitachi High-Tech Science).

[0044] [Experimental Examples 1-5] Experimental Example 1 involved using an LFP electrode as the Li supply source, a 1M-LiNO3 aqueous solution as the anode electrolyte, and no nitrogen bubbling treatment was performed on the aqueous electrolyte, with a current density of 45 mA / g per unit mass of active material. Experimental Example 2 was the same as Experimental Example 1 except that nitrogen bubbling treatment was performed on the aqueous electrolyte. Experimental Example 3 was the same as Experimental Example 1 except that the anode aqueous electrolyte was a 6M-LiNO3 aqueous solution. Experimental Example 4 was the same as Experimental Example 1 except that the anode aqueous electrolyte was a 0.5M-Li2SO4 aqueous solution. Experimental Example 5 was the same as Experimental Example 4 except that nitrogen bubbling treatment was performed on the aqueous electrolyte.

[0045] (7) Deliquidation reaction of LFP electrodes The lithium delithion reaction efficiency of LFP electrodes in the current density range of 2 to 91 mA / g and the concentration range of 0.01 mM to 6 M-LiNO3 aqueous solutions was calculated from the ICP analysis results of LFP electrodes after electrolysis. Figure 2 is a diagram showing the relationship between the concentration of the aqueous electrolyte salt, the applied current density, and the lithium delithion reaction efficiency. Figure 2 shows the mapping of the lithium delithion reaction efficiency of LFP electrodes against current density and LiNO3 concentration. At a current density of 91 mA / g, high lithium delithion reaction efficiency of over 80% was shown almost uniformly for LiNO3 aqueous solutions from 0.01 mM to 6 M. However, at a current density of 45 mA / g, the lithium delithion reaction efficiency decreased in the concentration range of 100 mM to 3 M-LiNO3, and the lowest lithium delithion reaction efficiency was 18% at a 1 M-LiNO3 concentration. From the above, it was found that there is a range of conditions, centered around a current density of 45 mA / g and a 1 M-LiNO3 concentration, in which the lithium delithion reaction is less likely to occur.

[0046] (8) Reaction of Al current collector foil alone with LiNO3 aqueous solution The oxidation-reduction potential of Al metal is -1.676 V vs. SHE, but because the surface of Al metal is covered with an oxide film, the uniform corrosion rate of the entire Al metal surface in a neutral aqueous solution is very slow. On the other hand, contact with precipitates or dissimilar metals, and Cl - It is known that the presence of halides such as NO3 can cause localized corrosion, in which the oxide film is locally destroyed [Yoshiyuki Otani, et al., "A Simple Explanation of Aluminum Corrosion ~The Relationship Between Oxide Film and Corrosion~", UACJ Technical Reports, 2016, 3, 52-56]. On the other hand, NO3 - Although ions are not considered to be significantly different from the corrosive properties of pure water [Goro Ito, "Corrosion of Aluminum", Light Metals, 1981, 31, 683-696.], NO3 -Since ions have oxidizing power, their corrosiveness may change at high concentrations. Therefore, we investigated the dependence of the Al corrosion reaction on LiNO3 concentration when an Al current collector foil was immersed in a LiNO3 aqueous solution. Figure 3 is a backscattered electron image of an Al current collector foil immersed in an aqueous electrolyte system with dissolved oxygen. Figure 4 shows the pH values ​​before and after immersion of the Al current collector foil in an aqueous electrolyte system with dissolved oxygen. As shown in Figure 3, when the LiNO3 concentration exceeded 1M, pitting corrosion was formed, and fine irregularities were observed across the entire surface. Also, as shown in Figure 4, the pH increased after immersion in pure water, while the pH decreased in the LiNO3 aqueous solution, and furthermore, the pH decreased as the concentration increased. The corrosion reaction of Al occurring in aqueous solution is expressed by the following equation [Yoichi Kojima, "The Story of Aluminum Corrosion", Furukawa-SkyReview, 2006, 2, 60-69.]. OH produced by reduction reaction (2) - The ions are formed by reaction equation (3) Al 3+ In some cases, Al(OH)3 is formed with ions, while in other cases, Al2O3 is produced by reaction equations (4) and (5). When Al(OH)3 is produced, the reaction in equation (4) does not occur, so the pH does not decrease. However, when Al2O3 is produced, the pH decreases due to reaction equation (4). After immersion in Al, the pH of pure water increases due to oxidation reaction (1) and reduction reaction (2), whereas the pH decreases in high-concentration LiNO3 aqueous solution, which is expected to be due to the occurrence of reaction equations (4) and (5) following the reduction reaction (2). From the above, it was found that Al corrosion occurs when Al is immersed in pure water and LiNO3 aqueous solution, and the corrosion reaction rate increases as the LiNO3 concentration increases.

[0047] [ka]

[0048] (9) Dissolved oxygen concentration in LiNO3 aqueous solution Figure 5 shows the results of measuring the dissolved oxygen content in aqueous electrolytes after air or nitrogen bubbling treatment. As shown in Figure 5, the dissolved oxygen concentration in aqueous solutions left in the atmosphere for one week and in aqueous solutions after air bubbling treatment decreased as the LiNO3 concentration of the aqueous solution increased. The dissolved oxygen concentrations after being left in the atmosphere were pure water: 9.1 ng / mL, 1M-LiNO3 aqueous solution: 7.5 ng / mL, and 6M-LiNO3 aqueous solution: 2.5 ng / mL. On the other hand, the dissolved oxygen concentration in the aqueous solution after N2 bubbling treatment was below the detection limit. From the above, it was found that dissolved oxygen in LiNO3 aqueous solutions can be removed by N2 bubbling.

[0049] (10) Effect of dissolved oxygen when LFP electrodes are immersed in 1M-LiNO3 aqueous solution The LFP electrode was immersed in a 1M-LiNO3 aqueous solution, which showed the lowest lithium removal reaction during electrolysis at a rate of 45 mA / g, and the changes in the LFP electrode were investigated. Two types of 1M-LiNO3 aqueous solutions were used: one containing dissolved oxygen without N2 gas bubbling treatment, and another in which the dissolved oxygen concentration was reduced by N2 gas bubbling treatment. Figure 6 shows the pH values ​​measured before and after immersion of the LFP electrode and Al current collector in the 1M-LiNO3 aqueous solution electrolyte. As shown in Figure 6, the pH of the aqueous solution without N2 gas bubbling treatment decreased significantly upon immersion of the LFP electrode. Therefore, under these conditions, it was considered that reactions (4) and (5) were promoted following reactions (1) and (2).

[0050] Figure 7 shows the measurement results when an LFP electrode was immersed in a 1M-LiNO3 aqueous solution with dissolved oxygen. Figure 7a is a photograph of the immersed electrode and the aqueous solution, Figure 7b is a backscattered electron image, and Figures 7c to 7f are the EDX measurement results for each element. Figure 8 shows the measurement results when an LFP electrode was immersed in a 1M-LiNO3 aqueous solution after reducing the dissolved oxygen. Figure 8a is a photograph of the immersed electrode and the aqueous solution, Figure 8b is a backscattered electron image, and Figures 8c to 8f are the EDX measurement results for each element. As shown in Figure 7a, white precipitates were attached to the surface of the LFP electrode after immersion in a 1M-LiNO3 aqueous solution (with dissolved oxygen), and the aqueous solution was also cloudy white. As shown in Figures 7c to 7f, Al and O were detected from the white precipitates on the electrode surface, and the pH of the electrolyte decreased after immersion, so the white precipitates were considered to be Al2O3. When the LiNO3 aqueous solution and the ambient atmosphere are in equilibrium, the reduction reaction of Al corrosion in the LiNO3 aqueous solution (2) will have a higher reaction rate if the partial pressure of oxygen in the ambient atmosphere and the dissolved oxygen concentration in the aqueous solution are high. Therefore, it was expected that Al corrosion would be suppressed by reducing the dissolved oxygen concentration. In fact, the pH of the 1M-LiNO3 aqueous solution (with N2 bubbling) after immersion of the LFP electrode did not decrease as much as in the case of an aqueous solution containing normal dissolved oxygen (without N2 bubbling), as shown in Figure 6. Furthermore, as shown in Figure 8, no white precipitates were found on the surface of the LFP electrode after immersion. From the above, it was found that dissolved oxygen accelerates the reaction rate of reaction equation (2) and promotes the formation of Al2O3 by reaction equations (4) and (5), while reducing dissolved oxygen slows down the reaction rate of equation (2) and suppresses the formation of Al2O3.

[0051] When Al current collector foil alone is immersed in a 1M-LiNO3 aqueous solution, the pH does not change much, whereas the pH of the LFP electrode drops significantly. This is presumed to be because galvanic corrosion is accelerated in the LFP electrode, which has a structure in which Al current collector foil and LFP powder are in contact [Yoichi Kojima, "The Story of Aluminum Corrosion", Furukawa-SkyReview, 2006, 2, 62-69.]. The reaction rate of galvanic corrosion of Al accelerates as the surface area of ​​the contacting metals increases. Since LFP powder, which is conductive due to its carbon coating, has a surface area orders of magnitude larger than that of Al current collector foil, the LFP electrode is a condition where galvanic corrosion is easily accelerated. Figure 9 shows the results of the study on galvanic corrosion in the LFP electrode, with Figure 9a being an explanatory diagram of the potential of each reaction, Figure 9b being a diagram of the relationship between the corrosion current and the electrode potential, and Figure 9c being an explanatory diagram of galvanic corrosion. The oxidation-reduction potentials of each reaction, and the potential of Al measured by immersion in a 1M-LiNO3 aqueous solution, are shown in Figure 9a. Furthermore, as shown in Figure 9b, since LFP has a higher potential than Al, the corrosion potential of Al increases upon contact with LFP. Therefore, the reduction of oxygen represented by reaction equation (2) (OH) - The reaction (formation of ) occurs rapidly on the LFP. As a result, as shown in Figure 9c, Al2O3 precipitates on the LFP by the reaction of equation (5). When dissolved oxygen is reduced, the reaction rate of equation (2) slows down, so the reduction reaction of Al also slows down, and Al corrosion is suppressed. Furthermore, since the corrosion potential of Al is lower than the oxidation-reduction potential of LFP, it was inferred that the oxidation reaction of Al is more likely to occur than the oxidation of LFP during electrolysis.

[0052] (11) Effect of dissolved oxygen on electrolysis (45 mA / g) in 1 M LiNO3 aqueous solution In an experiment immersing an LFP electrode in a 1M-LiNO3 aqueous solution, galvanic corrosion between Al and LFP was suppressed by reducing dissolved oxygen. Therefore, the effect of N2 bubbling at a rate of 45 mA / g in a cell using a 1M-LiNO3 aqueous solution was investigated. Experimental Example 1 was conducted without N2 bubbling, and Experimental Example 2 was conducted with N2 bubbling. Figure 10 shows the electrolysis measurement results of the cell using a 1M-LiNO3 aqueous solution, with Figure 10a showing the relationship between cell voltage and capacity, and Figure 10b showing the XRD measurement results of the electrodes, including Experimental Examples 1 and 2. As shown in Figure 10a, N2 bubbling resulted in almost no change in potential but an increase in capacity. Also, as shown in Figure 10b, under the 1M-LiNO3 aqueous solution conditions without N2 bubbling, the main phase after electrolysis was the LFP phase, and the Fe(PO4)(FP) phase was 0%. Therefore, it was inferred that the main reaction during electrolysis, which showed a capacity of 188 mAh / g up to 4.5V, was due to the corrosion reaction of Al. On the other hand, as shown in Figure 10b, in the aqueous solution after N2 bubbling, LFP was converted to the FP phase by electrolysis, and the proportion of the FP phase improved to 100%. However, since the capacity during electrolysis was 228 mAh / g, which significantly exceeded the theoretical capacity of 170 mAh / g, it is inferred that Al corrosion occurred as a side reaction with a capacity of 58 mAh / g. The pH after electrolysis without N2 bubbling was 3.83, while with N2 bubbling it was 4.18, indicating that the decrease in pH due to Al corrosion was reduced. From the above, it was found that reducing dissolved oxygen suppressed Al corrosion during electrolysis at a rate of 45 mA / g in a 1M-LiNO3 aqueous solution, and the deliquidation reaction of LFP occurred preferentially.

[0053] (12) LiNO3 concentration dependence of galvanic corrosion of Al in LFP electrodes Figure 11 shows the pH value (Figure 11a) and Al concentration (Figure 11a) of the LFP electrode and Al current collector before and after immersion in the aqueous electrolyte. Even when the LFP electrode was immersed in a 6M LiNO3 aqueous solution with dissolved oxygen, the significant pH decrease observed at 1M did not occur, as shown in Figure 11a, and in Experimental Example 3, the proportion of the FP phase in the electrode after electrolysis was 100%. Analysis of the Al concentration in the LiNO3 aqueous solution after electrolysis showed that the concentration was lower at 6M than at 1M, as shown in Figure 11b, indicating that Al corrosion was suppressed at 6M compared to 1M. The factors that suppressed Al corrosion at 6M were the effect of dissolved oxygen and NO3. - The effect of ionic oxidizing power is a possible factor. GC-TCD analysis of the dissolved oxygen concentration in the LiNO3 aqueous solution after air bubbling revealed 7.45 g / L (1M) and 2.46 g / L (6M), with the 6M concentration being less than half that of the 1M concentration. Therefore, it is thought that a decrease in dissolved oxygen concentration leads to a decrease in the rate of oxygen reduction in Al corrosion, and consequently, a decrease in the oxidation reaction rate of Al elution. Furthermore, NO3 - Because ions function as oxidizing agents, Al metal dissolves in dilute nitric acid but not in concentrated nitric acid of approximately 18M. Although Al was also corroded by immersion in a 6M LiNO3 aqueous solution, the corrosion of Al may be suppressed compared to 1M because the conditions are more conducive to oxide film growth than at 1M. From the above, the relationship between dissolved oxygen concentration and NO3 - It was thought that the oxidizing power of the ions suppressed Al corrosion of the LFP electrode in the 6M-LiNO3 aqueous solution.

[0054] (13) Effect of dissolved oxygen on electrolysis in 0.5 ml i2SO4 aqueous solution We investigated whether galvanic corrosion between Al and LFP occurs in Li2SO4 aqueous solutions, similar to LiNO3 aqueous solutions, and whether Al corrosion is suppressed by reducing dissolved oxygen. Cells were assembled using two types of 0.5M-Li2SO4 aqueous solutions: without N2 bubbling (Experimental Example 4) and with N2 bubbling (Experimental Example 5), and electrolysis was performed at a rate of 45mA / g. Figure 12 shows the electrolysis measurement results of the cells using 0.5M-Li2SO4 aqueous solutions, with Figure 12a showing the relationship between voltage and capacitance, and Figure 12b showing the XRD measurement results of samples including Experimental Examples 4 and 5. As shown in Figure 12b, the electrode of the cell using the 0.5M-Li2SO4 aqueous solution without N2 bubbling remained at 66% FP phase, while the 0.5M-Li2SO4 aqueous solution with N2 bubbling converted to 100% FP phase. Therefore, it was found that even in an aqueous Li2SO4 solution, reducing dissolved oxygen suppresses Al corrosion and improves the efficiency of the Li-decarbonization reaction of the LFP electrode.

[0055] The experimental results described above demonstrate that the present disclosure of a method and apparatus for producing metallic lithium enables the production of metallic lithium using LFP, an electrode material for lithium secondary batteries, as a Li source. Furthermore, it was found that by further reducing the dissolved oxygen in the aqueous electrolyte, metallic lithium can be produced more efficiently using electrode materials in various states.

[0056] [Table 1]

[0057] It goes without saying that this disclosure is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of this disclosure. [Industrial applicability]

[0058] The metallic lithium production apparatus and metallic lithium production method disclosed herein are applicable to the technical field of regenerating and producing metallic lithium. [Explanation of Symbols]

[0059] 10 Metallic lithium production apparatus, 11 Deposition electrode, 12 Non-aqueous electrolyte, 13 Ion conducting medium, 14 Electrode material, 15 Counter electrode, 16 Aqueous electrolyte, 19 Containment section, 20 Control section, 21 Cathode compartment, 22 Anode compartment, 25 Oxygen removal section.

Claims

1. A lithium metal production apparatus for depositing metallic lithium, A deposition electrode in which metallic lithium is deposited upon contact with a non-aqueous electrolyte, The electrode material contains lithium and is in contact with an aqueous electrolyte, and includes a counter electrode facing the deposited electrode, An oxygen removal unit for reducing or removing dissolved oxygen from the aqueous electrolyte, An ion-conducting medium interposed between the deposition electrode and the counter electrode, which separates the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions, A control unit that applies an electric current between the counter electrode and the deposition electrode using the aqueous electrolyte system treated in the oxygen removal unit, thereby depositing metallic lithium from the lithium on the counter electrode onto the deposition electrode, A lithium metal manufacturing apparatus equipped with the following features.

2. The lithium metal production apparatus according to claim 1, wherein the oxygen removal unit reduces or removes dissolved oxygen from the aqueous electrolyte by bubbling an inert gas into the aqueous electrolyte.

3. The lithium metal production apparatus according to claim 1 or 2, wherein the oxygen removal unit reduces or removes the amount of dissolved oxygen in the aqueous electrolyte to 3 g / L or less.

4. The lithium metal manufacturing apparatus according to claim 1 or 2, wherein the counter electrode includes a positive electrode as the electrode material, having a positive electrode active material of a lithium secondary battery and a current collector formed of a metal different from the positive electrode active material.

5. The lithium metal production apparatus according to claim 4, wherein the positive electrode active material contains lithium iron phosphate, and the current collector contains one or more of aluminum, nickel, and stainless steel.

6. The lithium metal production apparatus according to claim 1 or 2, wherein the aqueous electrolyte of the counter electrode contains cations and anions in a concentration of 0.1 mol / L or more and 2 mol / L or less.

7. A metallic lithium manufacturing apparatus according to claim 1 or 2, wherein metallic lithium is deposited on the deposition electrode from the lithium on the counter electrode side under any one or more of the conditions (1) to (4). (1) The control unit applies the current in a range of 8 mA / g or more and 380 mA / g or less, where the current density per active material contained in the electrode material is 380 mA / g or less. (2) The control unit applies the current in a range of 25 mA / g or more and 80 mA / g or less per unit of active material contained in the electrode material. (3) The counter electrode is made of at least one of aluminum, titanium, and platinum, and the deposition electrode is made of at least one of copper and nickel. (4) The non-aqueous electrolyte of the deposition electrode contains a Li-containing salt dissolved at a concentration of 0.01 mmol / L or more and 4 mol / L or less.

8. A method for producing metallic lithium, comprising: a deposition electrode that contacts a non-aqueous electrolyte and deposits metallic lithium; a counter electrode that contacts an aqueous electrolyte and contains an electrode material containing lithium, and is opposite to the deposition electrode; and an ion-conducting medium interposed between the deposition electrode and the counter electrode, which separates the non-aqueous electrolyte and the aqueous electrolyte while conducting lithium ions, An oxygen removal step for reducing or removing dissolved oxygen from the aqueous electrolyte, A deposition step is performed in which metallic lithium is deposited onto the deposition electrode from the lithium on the counter electrode by applying an electric current between the counter electrode and the deposition electrode using the aqueous electrolyte after the oxygen removal step, A method for producing metallic lithium containing [the specified substance].

9. The method for producing metallic lithium according to claim 8, wherein the oxygen removal step reduces or removes dissolved oxygen from the aqueous electrolyte by bubbling an inert gas into the aqueous electrolyte.

10. The counter electrode includes a positive electrode as the electrode material, which has a positive electrode active material of a lithium secondary battery and a current collector made of a metal different from the positive electrode active material. The method for producing metallic lithium according to claim 8 or 9, wherein the aqueous electrolyte of the counter electrode contains 0.1 mol / L or more and 2 mol / L or less of cations and anions.

Images