Methods for treating the positive electrode of non-aqueous electrolyte secondary batteries and methods for recovering valuable metals from metal composite oxides.

Abstract

This invention provides a method for processing the positive electrode of a non-aqueous electrolyte secondary battery, which can reduce phosphorus (P) in a metallic material at low cost, and a method for recovering valuable metals from a metal composite oxide, which can recover valuable metals with reduced impurities at low cost. The method for processing the positive electrode of a non-aqueous electrolyte secondary battery of this invention is a method for processing the positive electrode of a non-aqueous electrolyte secondary battery, the positive electrode having an Al-containing foil and an active material as a Ni and / or Co-containing metal composite oxide. The method includes: an addition step (S11), adding an oxide containing Ni and / or Co as an oxidant to the positive electrode; and a melting step (S12), melting the positive electrode with the added oxidant to oxidize and remove P contained in the positive electrode, thereby obtaining a metallic material containing Ni and / or Co.

Description

Technical Field

[0001] This invention relates to a method for processing the positive electrode of a non-aqueous electrolyte secondary battery and a method for recovering valuable metals from metal composite oxides. Background Technology

[0002] The demand for non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, used as power sources in hybrid and electric vehicles has increased dramatically in recent years. Along with this increased demand, the amount of used non-aqueous electrolyte secondary batteries, defective non-aqueous electrolyte secondary batteries, and processing waste generated during manufacturing is also on the rise. The electrodes of non-aqueous electrolyte secondary batteries, especially the positive electrode, contain valuable components such as nickel (Ni) and cobalt (Co). To effectively utilize resources, metal materials containing valuable components such as Ni and Co are recovered from non-aqueous electrolyte secondary batteries. The electrolyte used in lithium-ion secondary batteries typically uses a non-aqueous solvent mixed with LiPF6 (lithium hexafluorophosphate). The recovered metal materials contain phosphorus (P) as an impurity, and methods for reducing phosphorus content in these metal materials have been proposed.

[0003] For example, in Patent Document 1, as a method for recovering valuable metals from waste lithium-ion batteries, a method for performing a dephosphorization process is described. This dephosphorization process involves melting the waste lithium-ion battery, separating the slag from the resulting melt, recovering the metal material containing valuable metals, and then adding calcium oxide (CaO) while blowing oxygen into the metal material, thereby oxidizing and removing phosphorus from the metal material.

[0004] Patent document 2 describes a method for recovering valuable metals from waste lithium-ion batteries, which involves adding CaO as a flux to the pulverized battery material, melting the pulverized material together with the flux, thereby removing P into the flux and separating it as slag, thus reducing the P content in the metal material. Existing technical documents Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-091826 Patent Document 2: International Publication No. 2020 / 013294 Summary of the Invention The problem that the invention aims to solve

[0006] In the recycling method described in Patent Document 1, the need for a dephosphorization process increases recycling costs. Furthermore, the recycling methods described in Patent Documents 1 and 2 do not sufficiently reduce phosphorus content in the metallic materials.

[0007] Therefore, the object of the present invention is to provide a method for processing the positive electrode of a non-aqueous electrolyte secondary battery that can reduce phosphorus (P) in metallic materials at low cost, and a method for recovering valuable metals from metal composite oxides that can recover valuable metals with reduced impurities at low cost. Methods for solving problems

[0008] The present invention discloses a method for processing the positive electrode of a non-aqueous electrolyte secondary battery. The positive electrode has an Al-containing foil and an active material as a metal composite oxide containing Ni and / or Co. The processing method includes: an addition step, in which an oxide containing Ni and / or Co is added to the positive electrode as an oxidant; and a melting step, in which the positive electrode with the added oxidant is melted to oxidize and remove P contained in the positive electrode, thereby obtaining a metal material containing Ni and / or Co.

[0009] The present invention discloses a method for recovering valuable metals from a metal composite oxide containing valuable metals, comprising: a reducing agent addition step, wherein a reducing agent for reducing the valuable metal in the metal composite oxide is added to the metal composite oxide; an oxidizing agent addition step, wherein an oxide containing the valuable metal is added as an oxidizing agent to the metal composite oxide to which the reducing agent has been added; a melting step, wherein the metal composite oxide to which the reducing agent and the oxidizing agent have been added is melted to reduce the valuable metal in the metal composite oxide and simultaneously oxidize impurities contained in the metal composite oxide to obtain a melt containing the valuable metal and the oxide; and a separation step, wherein the oxide is separated from the melt to obtain the valuable metal. Invention Effects

[0010] According to the present invention, by adding oxides containing Ni and / or Co as oxidants to the positive electrode, the positive electrode with added oxidants is melted, thereby enabling the reduction of phosphorus (P) in metallic materials at low cost.

[0011] According to the present invention, by adding a reducing agent and an oxidizing agent to a metal composite oxide containing valuable metals, and melting the metal composite oxide containing the reducing agent and oxidizing agent, it is possible to recover valuable metals with reduced impurities at low cost. Attached Figure Description

[0012] Figure 1 This is a perspective view of the non-aqueous electrolyte secondary battery used in the method for processing the positive electrode of the non-aqueous electrolyte secondary battery according to this embodiment. Figure 2 This is a flowchart illustrating the processing method of the positive electrode of a non-aqueous electrolyte secondary battery according to this embodiment. Figure 3 It is a graph showing the recovery rates of Ni, Co, Mn, and Al relative to the amount of NiO powder added, as well as the amount of P in the metallic material. Detailed Implementation

[0013] 1. Implementation Method The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0014] Figure 1 This is a perspective view of a non-aqueous electrolyte secondary battery 10 used in the method for processing the positive electrode of a non-aqueous electrolyte secondary battery according to this embodiment. The non-aqueous electrolyte secondary battery 10 is a previously used lithium-ion secondary battery used as a power source for vehicles such as electric vehicles or hybrid vehicles. In the following description, the case of a lithium-ion secondary battery as the non-aqueous electrolyte secondary battery 10 will be used as an example. However, the non-aqueous electrolyte secondary battery 10 is not limited to lithium-ion secondary batteries; it can also be a magnesium-ion secondary battery, a sodium-ion secondary battery, a potassium-ion secondary battery, a calcium-ion secondary battery, etc. The non-aqueous electrolyte secondary battery 10 is not limited to previously used batteries; it can also be an unused non-aqueous electrolyte secondary battery that was determined to be a defective product after manufacturing. Furthermore, in the method for processing the positive electrode of a non-aqueous electrolyte secondary battery according to this embodiment, the positive electrode to be processed can be a positive electrode taken from a used non-aqueous electrolyte secondary battery, a positive electrode taken from an unused non-aqueous electrolyte secondary battery, a positive electrode taken from processing waste (e.g., defective electrode bodies) from the manufacturing process of the non-aqueous electrolyte secondary battery, or processing waste from the manufacturing process of the positive electrode. The positive electrode to be processed may contain, for example, phosphorus (P) from an electrolyte such as LiPF6 (lithium hexafluorophosphate) described later, and impurities such as phosphorus (P) in the positive electrode material.

[0015] The non-aqueous electrolyte secondary battery 10 has electrodes (not shown) and a non-aqueous electrolyte (not shown) within a battery container 12. The battery container 12 is made of, for example, aluminum alloy. The battery container 12 includes a container body 14 and a cover 16. The container body 14 and the cover 16 are laser-welded. The container body 14 is formed into a bottomed rectangular tube shape, housing the electrodes and the non-aqueous electrolyte inside. The cover 16 is provided at an opening in the container body 14, sealing the container body 14. A safety valve 18, a positive terminal 20, and a negative terminal 22 are provided on the cover 16. The safety valve 18 is used to reduce the internal pressure of the non-aqueous electrolyte secondary battery 10. The positive terminal 20 is connected to the positive terminal (described later) via a positive lead (not shown). The negative terminal 22 is connected to the negative terminal (described later) via a negative lead (not shown).

[0016] The electrode body includes a positive electrode (not shown) and a negative electrode (not shown) wound together with a diaphragm (not shown) in between. The electrode body is not limited to the wound type described above, but can also be a stacked type in which a positive electrode, a negative electrode and a diaphragm are stacked.

[0017] The positive electrode has a positive current collector and a positive active material layer. The positive current collector is an aluminum (Al) foil (hereinafter also referred to as Al foil). The mass percentage of the positive current collector in the positive electrode is 5-25% by mass. The positive active material layer contains positive active material, binder, and conductive material. The mass percentages of the conductive material and binder in the positive active material layer are 0-30% by mass and 0-20% by mass, respectively, of the positive electrode.

[0018] As the positive electrode active material, any metal composite oxide containing nickel (Ni) and / or cobalt (Co) can be used. For example, the positive electrode active material can be selected from lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium nickel manganese composite oxide, lithium nickel cobalt aluminum composite oxide, lithium nickel cobalt manganese composite oxide, etc. In this embodiment, the positive electrode active material is a lithium nickel cobalt manganese composite oxide. Furthermore, in the case of a magnesium-ion secondary battery, any magnesium composite oxide can be used; in the case of a sodium-ion secondary battery, any sodium composite oxide can be used; in the case of a potassium-ion secondary battery, any potassium composite oxide can be used; and in the case of a calcium-ion secondary battery, any calcium composite oxide can be used.

[0019] The adhesive is a fluorine-based adhesive containing fluorine compounds such as polyvinylidene fluoride (PVDF). The conductive material is a carbon material such as graphite and carbon black.

[0020] The negative electrode has a negative current collector and a negative active material layer. For example, the negative current collector is copper (Cu) foil, and the negative active material is graphite. As a separator, a porous membrane or non-woven fabric made of resins such as polyethylene (PE) or polypropylene (PP) is generally used.

[0021] Non-aqueous electrolytes contain a non-aqueous solvent and a lithium salt (electrolyte) soluble in that non-aqueous solvent. Carbonates can be used as non-aqueous solvents, such as propylene carbonate (PC), ethylene carbonate (EC), butene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). These non-aqueous solvents can be used alone or in combination of two or more.

[0022] As electrolytes, phosphorus (P)-containing electrolytes such as LiPF6 (lithium hexafluorophosphate) can be used. Other electrolytes that can be used include LiBF4 (lithium tetrafluoroborate), LiTFSA (lithium trifluoromethanesulfonamide), and LiTFSI (lithium bis(trifluoromethane)sulfonylimide). These electrolytes can be used alone or in combination of two or more. The following explanation uses LiPF6 as an example.

[0023] like Figure 2As shown, the method for processing the positive electrode of the non-aqueous electrolyte secondary battery 10 is a method for processing the positive electrode of the non-aqueous electrolyte secondary battery having a positive electrode. The positive electrode has an Al-containing foil and an active material as a metal composite oxide containing Ni and / or Co. The method includes: a preparation step S10 for preparing the positive electrode; an addition step S11 for adding an oxide containing Ni and / or Co as an oxidant to the positive electrode; a melting step S12 for oxidizing and removing P contained in the positive electrode by melting the positive electrode with added oxidant to obtain a metal material containing Ni and / or Co; and a separation step S13 for separating the melt obtained from the melted positive electrode into a metal material containing Ni and / or Co and slag. Each step is described in detail below.

[0024] [Preparation Process] In preparation step S10, a sheet-shaped positive electrode is prepared by opening the battery container 12 and unwinding the taken-out wound electrode body. The sheet-shaped positive electrode is provided to the next step, namely the addition step S11. Alternatively, in preparation step S10, a discharge step to discharge the non-aqueous electrolyte secondary battery 10, an internal cleaning step to clean the inside of the battery container 12 of the discharged non-aqueous electrolyte secondary battery 10 with a cleaning solution, and a cutting step to cut the sheet-shaped positive electrode using a shredder or the like may also be performed. In this embodiment, the positive electrode prepared in preparation step S10 is taken from a used non-aqueous electrolyte secondary battery 10, but it is not limited to this; it may also be taken from an unused non-aqueous electrolyte secondary battery, a positive electrode taken from processing waste in the manufacturing process of the non-aqueous electrolyte secondary battery, or processing waste in the manufacturing process of the positive electrode. Preparation step S10 preferably only prepares the positive electrode. This is because if components other than the positive electrode (battery container 12, separator, negative electrode, etc.) are present in the melting process S12 described later, the reduction reaction will be hindered.

[0025] [Add process] In the addition step S11, an oxide containing Ni and / or Co is added to the positive electrode as an oxidant. The shape of the oxidant is not particularly limited; it can be in powder, block, or flake form, etc. For example, by placing the positive electrode and oxidant powder in a bag and vibrating it, the oxidant powder can adhere to the surface of the positive electrode. Alternatively, a mixer such as a stirrer, Henschel mixer, or Notta mixer can be used to mix the positive electrode and oxidant powder. The positive electrode with the added oxidant is then provided to the next step, the melting step S12.

[0026] The oxidant must be a substance that oxidizes P but is difficult to oxidize Ni and / or Co, which are the targets for recovery. It is an oxide containing an element that is more difficult to oxidize than P. "Elements more difficult to oxidize than P" refers to elements located above P in the Ellingham diagram, such as Ni and Co. The oxidant must be an oxide containing an element that is more difficult to oxidize than P, but it can also contain elements that are more easily oxidized than P. "Elements more easily oxidized than P" refers to elements located below P in the Ellingham diagram, such as Li. Even if the oxidant contains elements that are more easily oxidized than P, these elements will be oxidized and removed along with P in the melting process S12.

[0027] The oxidant contains at least one substance selected from the group consisting of NiO, CoO, Co2O3, Co3O4, NiMnCo composite oxide, NiMn composite oxide, MnCo composite oxide, NiCo composite oxide, and positive electrode active material materials containing Ni and / or Co composite oxides. The positive electrode active material material used as the oxidant can be selected from, for example, LiNi composite oxide, LiCo composite oxide, LiNiCo composite oxide, LiNiMn composite oxide, LiNiCoAl composite oxide, LiNiCoMn composite oxide, etc. The oxidant is preferably an oxide containing Ni and / or Co, which is the target for recovery. When the recovered metal material is used directly as a metal material for nickel-metal hydride batteries or for hydrogen storage, it is preferable that it does not contain components that would become pollutants, for example, it is preferable that the oxide does not contain metals other than Ni, Co, and Mn. The most preferred oxidant is NiO. Because Ni is Ni itself, which is the target for recovery, it can be recovered as Ni by being reduced by NiO. In this embodiment, NiO is used as the oxidant.

[0028] The amount of oxidant added relative to the positive electrode is based on the amount of residual Al remaining after the redox reaction of the active material and Al (as a reducing agent), in which all of the residual Al is oxidized. By adding an amount of oxidant in which all of the residual Al is oxidized, P can be reliably removed by oxidation.

[0029] As a lower limit for the amount of oxidant added to oxidize P, it is not necessary to reach an amount in which all the remaining Al is oxidized. This is because the oxidation of P will partially begin even if Al remains in the recovered metal. Therefore, the lower limit for the amount of oxidant added to oxidize P is an amount in which the Al recovery rate shown in the following formula (1) is 3.0% or less, more preferably 0.2% or less, and even more preferably 0.01% or less. Al recovery rate (%) = (mass of molten Al metal) / (mass of molten Al metal before melting) ……………………………(1) In formula (1), metallic Al refers to Al with reducing ability, excluding Al in Al oxides. Unless otherwise specified, metallic Al will be simply referred to as Al in this specification. Furthermore, the Al used in the reduction of the positive electrode active material can be Al foil from the positive electrode, or it can be added separately as needed. The mass of metallic Al can be determined, for example, by performing ICP (Inductively Coupled Plasma) mass analysis.

[0030] Even with the addition of a large amount of oxidant, the removal efficiency of P is not affected, therefore there is no particular upper limit to the amount of oxidant added. However, if too much oxidant is added, some Co and / or Ni may be oxidized, and the amount of oxidant that does not contribute to the oxidation reaction increases. Therefore, the upper limit of the amount of oxidant added is the amount of the remaining Al as a reducing agent after the redox reaction of the active material and Al as a reducing agent, plus 25.0% of the amount of the remaining Al that is completely oxidized, more preferably plus 7.6%. If the amount of oxidant added is below this amount, the recovery rates of Ni and Co show high values ​​of about 80% or more for the former and 90% or more for the latter. In addition, the amount of remaining Al that is completely oxidized refers to the amount of Al recovery rate (%) of 0.01% or less. As a reducing agent, it is not limited to Al foil, and other reducing agents can also be used. In addition, the type of reducing agent is not limited to Al, as long as it is a substance that can reduce the metal complex oxide containing Ni and / or Co in the active material. The determination of the amount of reducing agent added is the same as in the case of Al. In addition, the recovery rate of the reducing agent is represented by the following formula (2). Reducing agent recovery rate (%) = (mass of reducing agent after melting) / (mass of reducing agent before melting) ……………………………(2)

[0031] Furthermore, based on the mass of the cathode, the lower limit of the amount of oxidant added relative to the cathode is preferably 50.0% by mass, more preferably 58.3% by mass, and even more preferably 66.7% by mass. If the amount of oxidant added is less than 50.0% by mass, the oxidation and removal of P will be insufficient. The more oxidant added, the greater the reduction in the amount of P (ppm) in the metal material described later. The amount of P in the metal material is 3500 ppm or less when the amount of oxidant added is 50.0% by mass or more, 3000 ppm or less when the amount of oxidant added is 58.3% by mass or more, and 10 ppm or less when the amount of oxidant added is 66.7% by mass or more. Even if a large amount of oxidant is added, it will not affect the removal effect of P, so the upper limit of the amount of oxidant added is not particularly limited. However, if the amount of oxidant added is too large, some Co and / or Ni may be oxidized, so the upper limit of the amount of oxidant added relative to the cathode is preferably 83.3% by mass, more preferably 71.7% by mass. Up to 71.7% by mass of oxidant, the recovery rates of Ni and Co were as high as 90% or more. When the amount of oxidant added exceeded 71.7% by mass, the recovery rates of Ni and Co tended to decrease, but even when the amount of oxidant added was 83.3% by mass, the recovery rates of Ni and Co remained as high as about 80%.

[0032] [Melting Process] In the melting process S12, the positive electrode containing an oxidant is melted to obtain a melt. For the melting process S12, LiNi is used. x Co y Mn z Taking the case where O2 is used as the positive electrode active material as an example, in the melting process S12, the Al foil contained in the positive electrode becomes a reducing agent, and the following reaction occurs. As a result of the reaction, an alloy containing Ni, Co, and Mn is obtained as a metallic material containing the metals constituting the metal composite oxide (Ni...). x Co y Mn z ). LiNi x Co y Mn z O₂ + Al → 1 / 2Li₂O + Ni x Co y Mn z +1 / 2Al2O3 In this embodiment, heat energy is imparted to the positive electrode from an external heating device (e.g., a high-frequency induction melting furnace), for example, melting the positive electrode at 1500°C. To make the alumina (Al2O3) a molten slag state, fluxing agents such as CaO may also be added.

[0033] The lithium nickel cobalt manganese composite oxide, used as the positive electrode active material, is reduced by Al foil, which acts as a reducing agent. P contained in the positive electrode is removed by oxidation with NiO, which acts as an oxidizing agent. As a result, alloys containing Ni, Co, and Mn with reduced P content in the metallic material can be recovered. However, Mn is partially oxidized by NiO, with a lower recovery rate than that of Ni and Co.

[0034] [Separation Process] In separation step S13, the molten metal and molten slag are separated due to their difference in specific gravity and then cooled, thereby separating the metal material containing Ni, Co, and Mn from the slag. The Ni in the recovered metal material originates from the lithium nickel cobalt manganese composite oxide used as the positive electrode active material and NiO used as the oxidant. The Co and Mn in the metal material originate from the lithium nickel cobalt manganese composite oxide used as the positive electrode active material.

[0035] 2. Functions and Effects In the processing method for the non-aqueous electrolyte secondary battery according to this embodiment, an oxide containing Ni and / or Co is added as an oxidant to the positive electrode, causing the positive electrode with the added oxidant to melt. Since the P contained in the positive electrode is oxidized and removed by the oxidant, a dephosphorization process is not required, and the P in the metal material can be reduced at low cost. The Ni and / or Co contained in the oxidant can be recovered as metal material.

[0036] By setting the amount of oxidant added relative to the positive electrode to 50.0% by mass or more and 83.3% by mass or less, the phosphorus (P) content in the metal material can be reduced more reliably, and the decrease in the recovery rate of Ni and / or Co can be suppressed. By setting the amount of oxidant added to 66.7% by mass or more, the P content in the metal material can be reduced to less than 10 ppm, thus allowing the recovered metal material to be directly used as a metal material for nickel-metal hydride batteries or for hydrogen storage. If the P content in the recovered metal material is less than 650 ppm, it is considered that even if the recovered metal material is directly used as an electrode material for nickel-metal hydride batteries, it will not affect the battery performance.

[0037] 3. Example The following describes the experiments conducted to confirm the effectiveness of the present invention.

[0038] A pre-prepared non-aqueous electrolyte secondary battery was prepared, containing a wound electrode body and a non-aqueous electrolyte in a battery container 12. The composition of the positive electrode and the non-aqueous electrolyte in the prepared non-aqueous electrolyte secondary battery is shown below.

[0039] Positive electrode <Non-aqueous electrolyte> Non-aqueous solvent (DMC:EMC:PC): mass ratio 28:27:28 Electrolyte (LiPF6): 1M

[0040] In the experiment, firstly, the inside of the battery container 12 is cleaned by discharging the prepared non-aqueous electrolyte secondary battery, the battery container 12 is opened, and the taken-out wound electrode body is unwound and cut with a shredder, thereby preparing the positive electrode (preparation step S10).

[0041] Examples 1-10 show cathodes with added oxidant. In these examples, oxidant and CaO powder were added to the cathode by placing 30g of cathode, a predetermined amount of oxidant, and 11.1g of CaO powder into a pre-prepared bag and shaking it (addition step S11). NiO powder was used as the oxidant. The amount of NiO powder added was 10.0g in Examples 1 and 2, 15.0g in Examples 3 and 4, 17.5g in Examples 5 and 6, 20.0g in Examples 7 and 8, and 25.0g in Examples 9 and 10. CaO powder was added to bring the alumina to a molten slag state. Comparative Examples 1 and 2 show cathodes without added oxidant. In these examples, only CaO powder was added to the cathode by placing 30g of cathode and 8.0g of CaO powder into a pre-prepared bag and shaking it.

[0042] The positive electrodes of Examples 1 to 10 and Comparative Examples 1 and 2 were provided to the melting process S12 for experiments.

[0043] The cathodes of Examples 1-10, containing NiO powder as an oxidant, were placed in a high-frequency induction melting furnace. While nitrogen (N2) was introduced at a flow rate of 5 L / min, the furnace temperature was raised from room temperature to 1550°C and maintained for 20 minutes to melt the cathodes of Examples 1-10. The high-frequency induction melting furnace consisted of an alumina crucible for filling the cathodes of Examples 1-10, a carbon crucible containing the alumina crucible, and a high-frequency induction coil arranged along the outer periphery of the carbon crucible. After cooling the furnace temperature to room temperature, the alumina crucible was disassembled, and the metal material was removed.

[0044] The cathodes of Comparative Examples 1 and 2, without added oxidant, were placed in a high-frequency induction melting furnace. The air inside the furnace was purged to create a vacuum, and the temperature was raised from room temperature to 300°C and maintained for 90 minutes. Then, argon (Ar) gas was added to the furnace to create an Ar atmosphere, raising the furnace temperature to 1550°C and maintaining it for 20 minutes, causing the cathodes of Comparative Examples 1 and 2 to melt. After cooling the furnace to room temperature, the alumina crucible was disassembled, and the metal material was removed.

[0045] The compositional analysis results of the various metallic materials obtained by melting the cathodes of Examples 1-10 and Comparative Examples 1 and 2 are as follows: Figure 3 As shown. Figure 3 It is a graph showing the recovery rates of Ni, Co, Mn, and Al relative to the amount of NiO powder added, as well as the amount of P in the metallic material. Figure 3 The average value of the measured values ​​(N=2) from examples with the same amount of NiO powder added was plotted with NiO powder addition (g) as the horizontal axis, the recovery rates (%) of Ni, Co, Mn, and Al as the vertical axis on the left side of the paper, and the P content (ppm) in the metal material as the vertical axis on the right side of the paper. Furthermore, the P content in the cathode of Examples 1-10 before melting was in the range of 4500-10000 ppm. The recovery rates of Ni, Co, Mn, and Al were obtained by dividing the mass of each metal after melting by the mass of each metal before melting. Regarding the Ni recovery rate, it was obtained by dividing the mass of each metal after melting by the mass obtained by adding the Ni content in the Ni powder added as an oxidant to the Ni content in the cathode before melting. The mass of each metal before melting was determined by ICP (Inductively Coupled Plasma) mass analysis. Additionally, for some samples, the values ​​were calculated based on the mass percentage of the positive electrode active material in the cathode before melting and the composition of the positive electrode active material. The mass of each metal after melting and the phosphorus content in the metallic material were also determined by ICP quality analysis. Hitachi High-Tech Corporation's PS3520UVDDII or SPS3520UVDD was used for all ICP quality analyses.

[0046] Depend on Figure 3It was confirmed that the higher the amount of oxidant added, the greater the reduction in phosphorus (P). Up to 10g of oxidant added, Al recovery preferentially decreased, but the reduction in P was smaller. Conversely, when the amount of oxidant added exceeded 10g, i.e., when the Al recovery was less than 8.0%, the reduction in Al recovery became slow, while P decreased sharply. When the amount of oxidant added was 15g or more (Al recovery less than 1.6%), the P content was less than 3500ppm; when the amount of oxidant added was 17.5g or more (Al recovery less than 0.2%), the P content was less than 3000ppm; and when the amount of oxidant added was 20g or more (Al recovery less than 0.01%), the P content was less than 10ppm. It was confirmed that P contained in the cathode could be oxidized and removed by melting the cathode with added oxidant. Up to 20g of oxidant added (Al recovery less than 0.01%), the recovery rates of Ni and Co reached over 90%. When the amount of oxidant added exceeds 20g, the recovery rates of Ni and Co tend to decrease. This can be attributed to the partial oxidation of Ni and Co, as well as the increased amount of oxidant (NiO powder) that does not contribute to the oxidation reaction. However, even with an oxidant addition of 25g, the recovery rates of Ni and Co remain high at approximately 80%. Furthermore, the Al recovery rate is below 0.01% at the stage where 20g of oxidant is added, suggesting that the remaining Al is completely oxidized at that point. That is, the 25g oxidant addition is the amount obtained by adding 25% (5g) of the amount of the remaining Al that is completely oxidized to the 20g amount of Al that is completely oxidized. Additionally, it was observed that the Mn recovery rate decreases with a significant increase in the amount of oxidant added. The Mn recovery rate shows a similar trend to the decrease in P, decreasing sharply when the oxidant addition exceeds 10g. The Ellingham diagram shows the order of oxidizability as Al, Mn, P, Co, and Ni. In the melting process S12, even if there are unoxidized Al and Mn residues, the oxidation and removal of P will begin. It can be seen that after Al and Mn are fully oxidized and removed, the amount of P is also significantly reduced.

[0047] It was confirmed that when the metal material was removed from the disassembled alumina crucible, the more NiO powder was added, the darker the surface color of the slag became. This suggests that with the increase in the amount of NiO powder added, MnO2 precipitation occurred on the surface of the slag.

[0048] In summary, by setting the amount of oxidant added to 15 g (50.0% by mass) or more and 25 g (83.3% by mass) or less, it can be confirmed that the P content in the metallic material can be reduced to 3500–10 ppm while the recovery rate of Ni and Co is greater than 80%. By setting the amount of oxidant added to 17.5 g (58.3% by mass) or more and 20 g (66.7% by mass) or less, the P content in the metallic material can be further reduced to 3000–10 ppm, and the recovery rate of Ni and Co can be increased to greater than 95%. By setting the amount of oxidant added to 20 g (66.7% by mass) or more and 25 g (83.3% by mass) or less, the P content in the metallic material can be reduced to less than 10 ppm without reducing the recovery rate of Ni and Co, thus achieving sufficient dephosphorization.

[0049] In the above experiment, because a carbon crucible was used, the positive electrode was melted while N2 gas was introduced. However, if a crucible made of a material that is difficult to react with oxygen (such as alumina) is used, the positive electrode can also be melted in an atmospheric atmosphere.

[0050] 4. Variations This invention is not limited to the above-described embodiments, and appropriate modifications can be made within the scope of the spirit of this invention.

[0051] In the above embodiment, the melting process S12 uses an external heating device to melt the positive electrode, but the positive electrode can also be melted using the heat of reaction between the foil and the active material. The "reaction between the foil and the active material" refers to a high-temperature redox reaction that occurs when a mixture of a positive electrode current collector (Al metal) and a positive electrode active material (metal oxide) reacts, simultaneously reducing the metal oxide with Al metal; this is also known as the aluminothermic reaction. The positive electrode generates its own heat through the heat of reaction between the foil and the active material. "Self-heating" means that even without external heating (e.g., a high-frequency induction melting furnace) imparting heat to the positive electrode, its temperature rises due to the heat of reaction between the foil and the active material.

[0052] Because the aluminothermic reaction is accompanied by a large amount of heat, the reaction continues through self-heating (heat of reaction) after the temperature for sustained reaction is reached. One method to initiate the aluminothermic reaction is the aluminothermic process, where a positive electrode is placed in a crucible and ignited. Essentially, the aluminothermic reaction can proceed solely through this ignition, yielding a metallic material containing the metals that constitute the metal complex oxide. Furthermore, in the aluminothermic process, appropriate combustion aids can be used as needed. Alternatively, there are methods that utilize externally supplied high-temperature heat from devices such as electric arc melting or high-frequency induction melting furnaces. In this case, the positive electrode melts through self-heating (heat of reaction), and simultaneously, the heat from electric arc melting or high-frequency induction melting further melts the positive electrode.

[0053] The method for processing the positive electrode of the non-aqueous electrolyte secondary battery 10 may include, in addition to the preparation step S10, the addition step S11, the melting step S12, and the separation step S13, a heating step for heating the positive electrode. The heating step is performed between the preparation step S10 and the addition step S11, or between the addition step S11 and the melting step S12.

[0054] The heating process is described below. The heating apparatus for the heating process includes a furnace, a heating section, a thermometer, a gas supply section, a flow meter, and a control section. The furnace has an internal space for accommodating the positive electrode. The heating section heats the positive electrode disposed within the furnace. The thermometer measures the temperature within the furnace. The gas supply section supplies oxygen-containing gas (air in this example) into the furnace, creating an oxygen-containing atmosphere. The flow meter measures the flow rate of the air within the furnace. The control section controls the heating section based on the thermometer readings, causing the furnace to heat up at a predetermined rate to a pre-set heating temperature. The control section also controls the gas supply section based on the flow meter readings, controlling the flow rate of air supplied to the furnace. The control section controls the heating section and the gas supply section to maintain the heating temperature and flow rate for a predetermined time. This time of maintaining the heating temperature and flow rate is called the "holding time." Furthermore, the above heating apparatus is just one example. Therefore, the structure of the heating apparatus is not limited to the above structure and can be appropriately designed. For example, if a rotary kiln or similar device is used, continuous heating processing can be performed.

[0055] The heating process is described below. First, the sheet-shaped positive electrode is placed in a heat-resistant container. Next, the heating device is activated to raise the temperature inside the furnace to a preset heating temperature. The container with the positive electrode is placed inside the furnace, and air is supplied to the furnace at a predetermined flow rate. The heating temperature and flow rate are maintained until a preset holding time has elapsed. Alternatively, the container with the positive electrode can be placed inside the furnace before the heating device is activated.

[0056] The heat treatment is preferably performed at a temperature that prevents the foil from oxidizing. If the heating temperature is too high, the Al foil, which serves as the positive current collector, will oxidize. The oxidized Al foil cannot be used as a reducing agent in the melting process S12.

[0057] The heat treatment is preferably performed at a temperature at which the binder decomposes. If the heating temperature is too low, the binder will not decompose sufficiently, leaving binder residue at the positive electrode. When a positive electrode containing binder residue is provided to the melting process S12, the thermal decomposition and subsequent oxidation of the binder in S12 generate gases such as H2O, CO2, or CO oxides, which hinder the reduction reaction. These gases that hinder the reduction reaction are called reaction-inhibiting gases. Furthermore, the rapid expansion of the generated gases could potentially damage the furnace, posing a significant danger. By performing the heat treatment at a temperature at which the binder decomposes, a positive electrode with the binder removed can be provided to the melting process S12. Furthermore, the heat treatment is preferably performed at a temperature at which the conductive material is oxidized and removed.

[0058] The heat treatment is preferably performed at a temperature of 400°C or higher and 650°C or lower. By setting the heating temperature to 400°C or higher and 650°C or lower, the binder is reliably decomposed, and the oxidation of the Al foil is suppressed. Furthermore, if the heating temperature is too high, the Al in the positive electrode current collector may become a reducing agent, leading to an unexpected reduction reaction, which is dangerous. The heat treatment is more preferably performed at 450°C or higher and 600°C or lower, and even more preferably at 500°C or higher and lower than 600°C.

[0059] In the heating process, the foil is heated at a temperature that prevents oxidation, thereby inhibiting the formation of aluminum oxide on the Al foil surface and promoting the reduction reaction (aluminothermic reaction) in the melting process S12.

[0060] In the heating process, heating is performed at the temperature required to decompose the binder, which inhibits the generation of reaction-inhibiting gases in the S12 stage of the melting process and promotes the reduction reaction (aluminothermic reaction).

[0061] In the heating process, heating is performed at a temperature above 400°C and below 650°C, which suppresses the aluminothermic reaction during heat treatment, thereby improving safety. Heat treatment removes the binder and conductive materials, suppressing the generation of reaction-inhibiting gases in the S12 melting stage. Therefore, the reduction reaction (aluminothermic reaction) in the S12 melting stage is promoted.

[0062] In the above embodiment, Al foil of the positive current collector was used as a reducing agent, but Al powder, for example, can also be added as a reducing agent.

[0063] This invention is not limited to the treatment method of the positive electrode of non-aqueous electrolyte secondary batteries, but is a widely applicable technology for removing impurities that are more easily oxidized than the valuable metals in metal composite oxides and for recovering valuable metals from metal composite oxides containing valuable metals. For example, it can be used in primary batteries or in ores from mineral resources. Furthermore, the impurities are not limited to phosphorus (P); any substance that is more easily oxidized than the valuable metals in metal composite oxides can be an impurity. By using this invention, valuable metals with impurities such as P removed can be recovered. That is, the method for recovering valuable metals from metal composite oxides according to the present invention is a method for recovering valuable metals from metal composite oxides containing valuable metals, comprising: a reducing agent addition step, in which a reducing agent for reducing the valuable metal in the metal composite oxide is added to the metal composite oxide; an oxidizing agent addition step, in which an oxide containing the valuable metal is added as an oxidizing agent to the metal composite oxide to which the reducing agent has been added; a melting step, in which the valuable metal in the metal composite oxide is reduced by melting the metal composite oxide to which the reducing agent and the oxidizing agent have been added, while oxidizing the impurities contained in the metal composite oxide, to obtain a melt containing the valuable metal and the oxide; and a separation step, in which the oxide is separated from the melt to obtain the valuable metal. This method enables the recovery of valuable metals with reduced impurities from metal composite oxides at low cost. Symbol Explanation

[0064] 10: Non-aqueous electrolyte secondary batteries; S10: Preparation process; S11: Add a process; S12: Melting process; S13: Separation process.

Claims

1. A method for treating the positive electrode of a non-aqueous electrolyte secondary battery, wherein, The non-aqueous electrolyte secondary battery has a positive electrode, which comprises an Al-containing foil and an active material as a metal composite oxide containing Ni and / or Co. The method for processing the positive electrode of the non-aqueous electrolyte secondary battery includes: The addition process involves adding an oxide containing Ni and / or Co as an oxidant to the positive electrode; and The melting process involves melting the positive electrode to which the oxidant has been added, thereby oxidizing and removing P contained in the positive electrode to obtain a metallic material containing Ni and / or Co. The amount of oxidant added is the amount shown in formula (1) where the Al recovery rate is less than 3.0%. Equation (1): Al recovery rate (%) = (mass of molten Al metal) / (mass of molten Al metal) 2. A method for treating the positive electrode of a non-aqueous electrolyte secondary battery, wherein, The non-aqueous electrolyte secondary battery has a positive electrode, which comprises an Al-containing foil and an active material as a metal composite oxide containing Ni and / or Co. The method for processing the positive electrode of the non-aqueous electrolyte secondary battery includes: The addition process involves adding an oxide containing Ni and / or Co as an oxidant to the positive electrode; and The melting process involves melting the positive electrode to which the oxidant has been added, thereby oxidizing and removing P contained in the positive electrode to obtain a metallic material containing Ni and / or Co. The amount of oxidant added relative to the positive electrode is 50.0% by mass or more and 83.3% by mass or less.

3. The method for processing the positive electrode of a non-aqueous electrolyte secondary battery as described in claim 1 or 2, wherein, The oxidant contains at least one substance selected from the group consisting of NiO, CoO, Co2O3, Co3O4, NiMnCo composite oxide, NiMn composite oxide, MnCo composite oxide, NiCo composite oxide, and a combination of positive electrode active material materials containing Ni and / or Co composite oxides.

4. The method for processing the positive electrode of a non-aqueous electrolyte secondary battery as described in claim 1 or 2, wherein, The non-aqueous electrolyte secondary battery also has a non-aqueous electrolyte. The non-aqueous electrolyte has an electrolyte containing P.

5. The method for treating the positive electrode of a non-aqueous electrolyte secondary battery as described in claim 1 or 2, wherein, Prior to the addition step, a preparation step for preparing the positive electrode is also included.

6. A method for recovering valuable metals from metal composite oxides containing valuable metals, the method comprising: The reducing agent addition step involves adding a reducing agent to the metal composite oxide to reduce the valuable metal in the metal composite oxide; In the oxidant addition step, an oxide containing a valuable metal is added as an oxidant to the metal composite oxide in which the reducing agent has been added. The melting process involves melting the metal composite oxide with added reducing agent and oxidizing agent to reduce the valuable metal in the metal composite oxide and oxidize the impurities contained in the metal composite oxide, thereby obtaining a melt containing valuable metal and oxide. as well as The separation process separates the oxide from the melt to obtain the valuable metal.

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