Method for producing precursor and method for producing positive electrode material

Abstract

In the present invention, a reducing agent containing at least one substance selected from the group consisting of iron metal and iron oxides is added to an oxide containing at least one valuable element selected from the group consisting of Ni, Co, and Mn and impurity elements constituted of copper and iron, thereby obtaining an oxide mixture. The oxide mixture is heated to reduce the oxide to thereby obtain a metal. The present invention obtains a leachate containing a valuable element and an impurity element by bringing the metal into contact with an acid solution. A sulfurizing agent is added to the leachate so as to cause copper to precipitate as copper sulfide, thereby obtaining a copper removal solution. An oxidizing agent is added to the copper removal solution so as to cause iron to precipitate as iron hydroxide, thereby obtaining a valuable element solution containing a valuable element. The valuable element solution, a complexing agent, and an alkaline aqueous solution are introduced into a reaction tank liquid to obtain a precipitate containing the valuable element.

Description

Method for manufacturing precursor and method for manufacturing cathode material

[0001] This invention relates to a method for producing a precursor and a method for producing a cathode material.

[0002] In recent years, the demand for lithium-ion batteries has been rapidly increasing due to the widespread adoption of smartphones, personal computers, and electric vehicles. In particular, the recent CO2 emissions... ２ From the perspective of reducing emissions, the demand for electric vehicles that do not use fossil fuels is expected to expand further in the future, and consequently, the demand for lithium-ion batteries is also expected to increase further.

[0003] Generally, lithium-ion batteries are composed of a combination of components such as a positive electrode material, a negative electrode material, and a separator, and also include an electrolyte. The positive electrode material of a lithium-ion battery is composed of an oxide (composite oxide) containing nickel (Ni), cobalt (Co), manganese (Mn), etc. The supply of metal elements such as Ni, Co, and Mn that make up the positive electrode material is not abundant on a global scale. For this reason, recovering these metal elements (valuable elements) from the positive electrode material of waste lithium-ion batteries is highly desirable from the perspective of effective resource utilization. Here, "waste lithium-ion batteries" refers to waste lithium-ion batteries (used products); defective lithium-ion batteries (those generated during the manufacturing process of lithium-ion batteries, etc.); etc.

[0004] When recovering valuable elements from the cathode material of waste lithium-ion batteries, it is necessary to perform pretreatment such as electrolyte removal, crushing, and pulverization before recovery. After such pretreatment, the cathode material is separated from the waste lithium-ion battery, and then the valuable elements are recovered from the separated cathode material.

[0005] One method for recovering valuable elements is dry processing. In dry processing (for example, Patent Document 1), a reducing agent is added to oxides (cathode material) separated from waste lithium-ion batteries, and then heated to obtain metal and slag. Subsequently, the metal containing valuable elements is recovered by separating the two.

[0006] Japanese Patent Publication No. 2021-95628

[0007] Metals obtained through dry processing may contain impurity elements in addition to valuable elements such as Ni and Co. Examples of impurity elements include copper (Cu) and iron (Fe) derived from waste lithium-ion batteries. When metals obtained through dry processing are reused as positive electrode material for lithium-ion batteries, the presence of impurity elements (Cu and Fe) can degrade battery performance. Therefore, it is desirable to remove impurity elements as much as possible.

[0008] The present invention has been made in view of the above points, and aims to provide a novel method for producing cathode material and its precursor for use in lithium-ion batteries. More specifically, the present invention aims to provide a novel method for recovering valuable elements such as Ni while removing impurity elements from oxides such as cathode material of waste lithium-ion batteries, and for producing a precursor and cathode material containing the recovered valuable elements.

[0009] As a result of diligent research, the inventors have found that the above objective can be achieved by adopting the following configuration, and have completed the present invention. That is, the present invention provides the following [1] to

[15] . [1] A method for producing a precursor for a positive electrode material used in a lithium-ion battery, comprising: adding a reducing agent containing at least one element selected from the group consisting of metallic iron and iron oxide to an oxide containing at least one valuable element selected from the group consisting of nickel, cobalt and manganese and impurity elements consisting of copper and iron to obtain a mixed oxide; reducing the oxide by heating the mixed oxide to obtain a metal; contacting the metal with an acid solution to obtain a leachate containing the valuable element and the impurity element; adding a sulfidating agent to the leachate to precipitate copper as copper sulfide; obtaining the leachate from which copper has been removed as a copper removal solution; adding an oxidizing agent to the copper removal solution to precipitate iron as iron hydroxide; obtaining the copper removal solution from which iron has been removed as a valuable element solution containing the valuable element; and introducing the valuable element solution, a complexing agent and an alkaline aqueous solution into a reaction vessel to obtain a precipitate containing the valuable element. [2] The method for producing the precursor according to [1], wherein the oxide is obtained from a waste lithium-ion battery. [3] A method for producing a precursor according to [1] or [2], wherein the metal is powdered and then brought into contact with the acid solution. [4] A method for producing a precursor according to any one of [1] to [3], wherein the iron oxide is ferrous oxide. [5] A method for producing a precursor according to any one of [1] to [4], wherein the temperature at which the mixed oxide is heated is 1450°C or higher. [6] A method for producing a precursor according to any one of [1] to [5], wherein the metal obtained by heating the mixed oxide contains the valuable element and the impurity element. [7] A method for producing a precursor according to any one of [1] to [6], wherein the acid solution contains an acid and an oxidizing agent for the acid solution, and the content of the oxidizing agent for the acid solution is 0.5% by volume or more relative to the acid. [8] A method for producing a precursor according to [7], wherein the oxidizing agent for the acid solution is hydrogen peroxide.[9] The method for producing a precursor according to any one of [1] to [8] above, wherein the amount of sulfiding agent added is 1.0 equivalent or more relative to the copper contained in the leachate, and when precipitation of the copper sulfide, the pH of the leachate to which the sulfiding agent has been added is 3.0 or less.

[10] The method for producing a precursor according to any one of [1] to [9] above, wherein the oxidizing agent is at least one oxidizing agent A selected from the group consisting of air and ozone, or at least one oxidizing agent B selected from the group consisting of hydrogen peroxide, hypochlorous acid and potassium permanganate, the amount of oxidizing agent A added is 0.1 vvm or more relative to the copper removal solution, the amount of oxidizing agent B added is 0.005 volume% or more relative to the copper removal solution, and when precipitation of the iron hydroxide, the pH of the copper removal solution to which the oxidizing agent has been added is 3.0 or more and 7.0 or less.

[11] The method for producing a precursor according to

[10] above, wherein the temperature of the copper removal solution to which the oxidizing agent has been added is 10°C or higher.

[12] A method for producing a precursor according to any one of [1] to

[11] above, wherein the reducing agent is at least one selected from the group consisting of dust, scale, sludge, and scrap.

[13] A method for producing a precursor according to any one of [1] to

[12] above, wherein the alkaline aqueous solution is an aqueous sodium hydroxide solution, and the complexing agent is at least one ammonium source selected from the group consisting of ammonia and ammonium salts.

[14] A method for producing a positive electrode material for use in a lithium-ion battery, comprising mixing a precursor obtained by a method for producing a precursor according to any one of [1] to

[13] above with a lithium-containing compound, and calcining the resulting mixture to obtain a calcined product containing the valuable element and lithium.

[15] A method for producing a positive electrode material according to

[14] above, wherein the lithium-containing compound is at least one selected from the group consisting of lithium hydroxide and lithium carbonate.

[0010] The present invention provides a novel method for manufacturing precursors and cathode materials.

[0011] This is a flowchart illustrating an example of a method for recovering valuable elements. This is a flowchart illustrating an example of a process for manufacturing precursors and cathode materials. This is an Ellingham diagram (standard free energy change-temperature diagram). This is a potential-pH diagram (S-H) for Cu and Ni. ２ (O system). Potential-pH diagram of Fe and Ni (O ２ -H ２ It is of the O type.

[0012] [Method for Manufacturing Precursors and Cathode Materials] The following describes a method for manufacturing cathode materials used in lithium-ion batteries (method for manufacturing cathode materials). The following description also describes a method for manufacturing precursors used in cathode materials (method for manufacturing precursors). First, as shown in Figure 1A, valuable elements are recovered from oxides such as cathode materials of waste lithium-ion batteries. That is, a solution of valuable elements containing valuable elements is obtained by subjecting the oxides to dry treatment and wet treatment. Then, as shown in Figure 1B, a precursor is manufactured using the obtained solution of valuable elements, and then the cathode material is manufactured.

[0013] Figure 1A is a flowchart illustrating an example of a method for recovering valuable elements. Based on Figure 1A, the method for recovering valuable elements will be outlined. In the dry treatment, first, a reducing agent, described later, is added to an oxide (Ni, Co, Mn, Cu, Fe) to obtain a mixed oxide. Next, the obtained mixed oxide is heated to reduce the oxide and obtain metal (Ni, Co, Mn, Cu, Fe) and slag. The two are separated as appropriate. Before the wet treatment, it is preferable to powder the obtained metal to obtain metal powder (Ni, Co, Mn, Cu, Fe). In the wet treatment, first, the metal (metal powder) is brought into contact with an acid solution to obtain a leachate (Ni, Co, Mn, Cu, Fe) and leachate residue. The two are separated as appropriate. Next, a sulfiding agent is added to the obtained leachate to precipitate copper sulfide (Cu) and obtain a copper removal solution (Ni, Co, Mn, Fe). The two are separated as appropriate. Then, an oxidizing agent is added to the copper removal solution to precipitate iron hydroxide (Fe) and obtain a solution of valuable elements (Ni, Co, Mn).

[0014] In this way, valuable elements (Ni, Co, Mn) can be recovered while removing impurity elements (Cu, Fe) from the oxide. Valuable elements can be easily recovered from the positive electrode material (oxide) of the waste lithium-ion battery with a high purity that enables reuse as raw materials for lithium-ion batteries.

[0015] Next, the method for recovering valuable elements will be described in more detail.

[0016] 〈Reduction target (oxide)〉 The reduction target is an oxide containing at least one valuable element selected from the group consisting of nickel (Ni), cobalt (Co), and manganese (Mn), and impurity elements such as copper (Cu) and iron (Fe). Specifically, for example, it is the positive electrode material of a waste lithium-ion battery. The valuable element may be at least one element selected from the group consisting of Ni and Co. By performing pretreatment such as removing the electrolyte solution, crushing, pulverizing, and sorting on the waste lithium-ion battery, the positive electrode material (oxide) is obtained.

[0017] 〈Addition of reducing agent (obtaining mixed oxide)〉 First, a reducing agent is added to the oxide that is the reduction target to obtain a mixed oxide, which is a mixture of the oxide and the reducing agent.

[0018] 〈Findings obtained by the inventors〉 The positive electrode material of a lithium-ion battery generally consists of oxides (complex oxides) such as LiNiO ２ , LiCoO ２ , LiMnO ２ etc. Considering the dry process thermodynamically, for example, LiNiO ２ and LiCoO ２ decompose as follows at high temperatures, and NiO and CoO are generated respectively. 2LiNiO ２ → Li ２ O + 2NiO + 1 / 2O ２ 2LiCoO ２ → Li ２ O + 2CoO + 1 / 2O ２

[0019] The standard free energy changes (ΔG ０ ) in the decomposition reactions of NiO and CoO are shown below respectively. NiO → Ni + 1 / 2O ０ ), are shown below respectively. NiO → Ni + 1 / 2O２ ΔG ０ =234900-84.68T[J] CoO→Co+1 / 2O ２ ΔG ０ = 235480 - 71.55T [J] Substances having a free energy change value lower than these standard free energy change values ​​at any high temperature can be used as reducing agents.

[0020] Incidentally, conventionally, substances with strong reducing power, such as carbonaceous materials, Al-containing materials, and Si-containing materials, are used as reducing agents. This is intended to avoid reduction failure. If the reducing power of the reducing agent is insufficient and reduction failure occurs, a portion of the cathode material is separated as slag in the form of oxides, and the content of valuable elements in the metal obtained by reducing the cathode material is reduced. However, when carbonaceous materials are used as reducing agents, CO ２ The amount generated is large. Also, when using Al-containing or Si-containing substances as reducing agents, the cost is high because the price of the reducing agent itself is relatively high. Therefore, CO ２ From the perspective of reducing waste generation and cost reduction, it is desirable to use a reducing agent other than those mentioned above. Therefore, the inventors investigated substances that are not carbonaceous, are relatively inexpensive and readily available, and could serve as new reducing agents. As a result, they found that metallic iron (Fe) or iron oxide is effective.

[0021] Standard free energy change (ΔG) of the decomposition reaction of iron oxide ０ The equation is as follows: FeO = Fe + 1 / 2O ２ ΔG ０ =264430-64.73T[J]Fe ３ O ４ =3FeO+1 / 2O ２ ΔG ０ =302370-108.15T[J]

[0022] Figure 2 is the Ellingham diagram (standard free energy change-temperature diagram). Referring to the standard free energy change and the Ellingham diagram (Figure 2) described above, the Fe / FeO equilibrium is less virtuous than the Ni / NiO equilibrium and the Co / CoO equilibrium, suggesting the possibility of reduction by Fe. Also, FeO / Fe ３ O ４ The equilibrium is less noble than the Ni / NiO equilibrium but more noble than the Co / CoO equilibrium. Therefore, it is expected that Ni will be recovered as a metal, and Co will remain in the slag. Specifically, the following reaction is expected: NiO + Fe → Ni + FeO: ΔG ０ =-29530-19.95T[J] CoO+Fe→Co+FeO:ΔG ０ =-28950-6.82T[J]

[0023] In the Ellingham diagram (Figure 2), the higher up a compound is, the more easily it is metallized. When Si or Al is used as a reducing agent, Mn is also easily metallized. Therefore, by using Fe (or FeO) as a reducing agent, it is possible to metallize only Ni and Co without metallizing Mn.

[0024] Reducing agent: For the reasons stated above, a reducing agent containing at least one of metallic iron (Fe) and iron oxide is used. As metallic iron (Fe), for example, scrap or granular iron used in steel mills may be used.

[0025] Iron oxides are generally ferrous oxide (FeO), also called wustite, and triiron tetroxide (FeO), also called magnetite. ３ O ４ ) and ferric oxide (Fe), also known as hematite ２ O ３Iron oxide is classified into three types. Of these, magnetite and hematite have higher standard free energy changes than wustite at the same temperature, and may not readily induce reduction reactions. For this reason, ferrous oxide (wustite) is preferred as iron oxide because it readily induces reduction reactions. Iron oxide may also be at least one of the dust, scale, and sludge (hereinafter referred to as "dust" for convenience) that are produced as by-products in the steelmaking process. Using dust as iron oxide is preferable from the viewpoint of effectively utilizing by-products of the steelmaking process and utilizing an inexpensive iron source.

[0026] 《Amount of Reducing Agent Added》 The amount required to reduce an oxide is called 1.0 equivalent. For example, when the reducing agent is metallic iron (Fe) or ferrous oxide (FeO), the reduction using 1.0 equivalent of the reducing agent is shown as follows: Fe + (NiO, CoO, MnO) → (Ni, Co, Mn) + FeO 3FeO + (NiO, CoO, MnO) → (Ni, Co, Mn) + Fe ３ O ４

[0027] When determining the amount of reducing agent to add, first, the content of NiO, CoO, and MnO in the oxide to be reduced is determined. Specifically, the content of Ni, Co, and Mn in the oxide to be reduced is measured and considered to be the content of NiO, CoO, and MnO, respectively. The content of Ni, Co, and Mn is measured using an energy-dispersive X-ray spectrometer (EDX).

[0028] The amount of reducing agent added is preferably 1.0 equivalent or more, more preferably 1.1 equivalents or more, even more preferably 1.2 equivalents or more, and particularly preferably 1.4 equivalents or more, because it helps to suppress insufficient reduction.

[0029] Incidentally, when a large amount of reducing agent is added to an oxide to avoid poor reduction, the amount of iron (Fe) contained in the resulting metal (product metal) tends to increase. Conventionally, when trying to reduce the Fe content in the product metal (for example, to 10% by mass or less), it is necessary to reduce the amount of reducing agent added (for example, to less than 1.1 equivalents), and in this case, it is difficult to suppress poor reduction. However, since Fe can be removed by wet treatment, the amount of reducing agent added can be increased (for example, to 1.1 equivalents or more), making it easier to suppress poor reduction.

[0030] Therefore, there is no particular upper limit to the amount of reducing agent to be added. However, from the viewpoint of easily removing Fe by wet treatment, it is preferable that the amount of Fe contained in the generated metal be small. Also, the effect saturates even if an excess of reducing agent is added. For this reason, the amount of reducing agent to be added is preferably 2.0 equivalents or less, and more preferably 1.8 equivalents or less.

[0031] <Heating of mixed oxides (acquisition of metals)> Next, the mixed oxide (a mixture of oxide and reducing agent) is heated. This reduces the oxide. Note that, in addition to the reducing agent, CaO and SiO are also used during heating. ２ Fluxes such as the following may be added. In other words, the mixed oxide may further contain flux. The equipment used for heating the mixed oxide is not particularly limited and includes conventionally known equipment such as electric furnaces, resistance furnaces, high-frequency melting furnaces, low-frequency melting furnaces, rotary kilns, vertical furnaces, and steelmaking furnaces.

[0032] <Heating Temperature> The heating temperature when heating the mixed oxide is preferably 1300°C or higher, more preferably 1350°C or higher, even more preferably 1400°C or higher, and particularly preferably 1450°C or higher, because it helps to suppress poor reduction. There is no particular upper limit, but the heating temperature is preferably 1800°C or lower, and more preferably 1700°C or lower.

[0033] 《Heating Atmosphere》 When heating mixed oxides, the atmosphere (heating atmosphere) can be, for example, nitrogen gas (N ２Suitable atmospheres include inert atmospheres such as a argon (Ar) atmosphere and a reducing atmosphere such as a carbon monoxide (CO) atmosphere.

[0034] 《Heating Time》 The heating time for the mixed oxide (heating time) is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more, because it helps to suppress poor reduction. There is no particular upper limit, but the heating time is preferably 6 hours or less, and more preferably 5 hours or less.

[0035] 《Products (metal and slag)》 By reducing the oxide (cathode material) that is the target of reduction, metal is produced. In other words, the valuable elements (Ni, Co, Mn) contained in the oxide are recovered as metal.

[0036] The metal obtained by the reduction of oxides (also called the "product metal") is an alloy containing valuable elements (Ni, Co, Mn) and impurity elements (Cu, Fe). The product metal may contain only one of the valuable elements (Ni, Co, Mn).

[0037] By reducing oxides (cathode materials), in addition to metals, slag may also be generated. Slag (also called "generated slag") may contain oxides such as FeO. In addition, generated slag may also contain oxides of valuable elements not included in the generated metal (e.g., MnO). When reducing oxides containing Mn, the Mn / MnO equilibrium may be replaced by the Fe / FeO equilibrium and FeO / Fe... ３ O ４ Because it is less efficient than equilibrium, it can suppress the incorporation of Mn into the resulting metal obtained by reduction. Separating Mn from the resulting metal by wet processing is computationally intensive. Suppressing the incorporation of Mn into the resulting metal and retaining Mn in the resulting slag is beneficial because it reduces this computational burden.

[0038] <Separation of Metal and Slag> Regarding the generated metal and slag obtained by the reduction of oxides, it is preferable to separate them before pulverizing the generated metal, as will be described later. The separation method is not particularly limited, and known methods can be used.

[0039] <Powdering of Metals (Obtaining Metal Powder)> Next, it is preferable to powder the resulting metal to obtain metal powder. In the wet process, as will be described later, first, leaching is carried out on the resulting metal using an acid solution. At this time, if the resulting metal is in the state obtained by the reduction of oxides, the leaching efficiency may be insufficient. For this reason, it is preferable to powder the resulting metal before carrying out leaching with an acid solution.

[0040] The smaller the particle size of the metal powder, the better the leaching efficiency. However, if the particle size of the metal powder is too small, handling may deteriorate and the risk of explosive reactions may increase. Therefore, these points should also be taken into consideration, and the particle size of the metal powder should be kept within an appropriate range. Specifically, for example, the particle size of the metal powder is preferably 250 to 6000 μm, and more preferably 300 to 5000 μm. The particle size is the median diameter (particle size at 50% cumulative value) on a volume basis in the particle size distribution determined by laser diffraction and scattering (the same applies hereinafter).

[0041] The method for pulverizing the generated metal is not particularly limited as long as the particle size of the resulting metal powder can be kept within an appropriate range. Examples include methods using grinding equipment such as jaw crushers and vibrating mills; atomization; and so on.

[0042] <Contact of metal with acid solution (obtaining leachate)> Next, the metal (metal powder) is brought into contact with the acid solution to leach out valuable elements (Ni, Co, Mn) and impurity elements (Cu, Fe). That is, a leachate containing valuable elements and impurity elements is obtained. The metal from which the valuable elements and impurity elements have leached out becomes a residue (leaching residue). There are no particular limitations on the method of contacting the metal with the acid solution, but examples include immersing the metal in the acid solution; spraying the metal with the acid solution; etc.

[0043] 《Solid-Liquid Ratio (Metal / Acid Solution)》 If the amount of acid solution in contact with the metal is too small (the amount of metal is too large relative to the amount of acid solution), some of the metal elements, such as valuable elements that have dissolved in the acid solution, may reach their saturation solubility and precipitate, resulting in insufficient leaching. For this reason, the ratio of the mass of the solid metal (in units: g) to the volume of the liquid acid solution (in units: mL) (also called the "solid-liquid ratio (metal / acid solution)") is preferably 1 / 5 or less, more preferably 1 / 7 or less, and even more preferably 1 / 10 or less. When the solid-liquid ratio (metal / acid solution) is 1 / 10, for example, 1 g of metal is immersed in 10 mL of acid solution. On the other hand, the solid-liquid ratio (metal / acid solution) is preferably 1 / 50 or more, more preferably 1 / 35 or more, and even more preferably 1 / 20 or more.

[0044] Acidic solutions: Acidic solutions that come into contact with metals must contain at least an acid.

[0045] (Acid) Examples of acids used in the acid solution include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid. These may be used individually or in combination of two or more. From the viewpoint of realizing "battery-to-battery" recycling, where waste lithium-ion batteries are recycled and reused as raw materials for lithium-ion batteries, it is preferable to use sulfuric acid as the acid. This is because valuable elements can be obtained in the form of sulfates, which are easily used as cathode materials for lithium-ion batteries. Chlorides may also be included in the sulfuric acid and used as the acid.

[0046] ((Acid Concentration)) The concentration of the acid (e.g., sulfuric acid) used in the acid solution (acid concentration) is preferably 0.1 mol / L or higher, more preferably 0.5 mol / L or higher, and even more preferably 1.0 mol / L or higher, because it can increase the rate of leaching. There is no particular upper limit, but the acid concentration is preferably 8.0 mol / L or lower, more preferably 6.0 mol / L or lower, even more preferably 4.0 mol / L or lower, and particularly preferably 3.0 mol / L or lower.

[0047] (Oxidizing agent for acid solution) The inventors have found that even when the solid-liquid ratio (metal / acid solution) and acid concentration are within the above-mentioned range, leaching may be insufficient. For this reason, it is preferable to add an oxidizing agent (oxidizing agent for acid solution) to the acid solution as a leaching accelerator. Examples of oxidizing agents for acid solutions include hydrogen peroxide, hypochlorous acid, potassium permanganate, and ozone. Of these, hydrogen peroxide and ozone are preferred because the use of hypochlorous acid and potassium permanganate may require complicated post-treatment of chlorine, potassium, manganese, etc.

[0048] ((Content of oxidizing agent for acid solution)) From the viewpoint of ensuring sufficient leaching, the content of the oxidizing agent for the acid solution (e.g., hydrogen peroxide) in the acid solution is preferably 0.5 volume% or more, more preferably 1.0 volume% or more, even more preferably 3.0 volume% or more, even more preferably 5.0 volume% or more, particularly preferably 6.0 volume% or more, and most preferably 6.9 volume% or more, relative to the acid (e.g., sulfuric acid). On the other hand, the content of the oxidizing agent for the acid solution (e.g., hydrogen peroxide) in the acid solution is preferably 15.0 volume% or less, more preferably 13.0 volume% or less, and even more preferably 10.0 volume% or less, relative to the acid (e.g., sulfuric acid).

[0049] <Contact Time> The contact time between the metal and the acid solution is preferably 0.5 hours or more, more preferably 0.8 hours or more, and even more preferably 1.0 hour or more, in order to ensure sufficient leaching. On the other hand, from the viewpoint of productivity, the contact time is preferably 3.0 hours or less, and more preferably 1.5 hours or less.

[0050] <Separation of leachate and leachate residue> As described later, it is preferable to separate the leachate and leachate residue before adding the sulfurizing agent to the leachate. The separation method is not particularly limited, and known solid-liquid separation methods can be employed.

[0051] <Addition of sulfiding agent (obtaining copper removal solution)> Next, a sulfiding agent is added to the leachate containing valuable elements (Ni, Co, Mn) and impurity elements (Cu, Fe) to precipitate the impurity element copper (Cu) as copper sulfide. In this way, a leachate from which copper (Cu) has been selectively removed is obtained as a copper removal solution.

[0052] Figure 3 shows the potential-pH diagram (S-H) of copper (Cu) and nickel (Ni). ２ It is an O-system. In Figure 3, copper (Cu) - sulfur (S) - water (H) ２ Figure 3 shows the region on the potential-pH diagram of system O) where precipitates of copper (Cu) and nickel (Ni) oxides (hydroxides) or sulfides form, taking solubility into account. Note that cobalt precipitates in a similar manner to nickel, so its illustration is omitted in Figure 3. As shown in Figure 3, in the region where the pH is 3.0 or less and the oxidation-reduction potential is low, copper (Cu) precipitates selectively. Although not shown in Figure 3, in this region, copper precipitates as copper(II) sulfide (CuS). By utilizing this, the copper (Cu) contained in the leachate is precipitated as copper(II) sulfide and selectively removed by making the leachate low pH and reducing. That is, a copper removal solution is obtained, which is an leachate from which copper (Cu) has been removed.

[0053] Sulfidating agents: Sulfur (S), hydrogen sulfide (H) are used as sulfidating agents added to the leachate. ２ S), sodium hydrogen sulfide (NaSH), sodium sulfide (Na ２ Examples include S), and these may be used individually or in combination of two or more. Of these, from the viewpoint of ease of handling, sulfur, sodium hydrogen sulfide, and sodium sulfide, which can be handled as solids or solutions, are preferred over hydrogen sulfide, which is a toxic gas. However, in all cases, hydrogen sulfide gas may be generated by the sulfurization reaction, so caution is required when carrying out the experiment.

[0054] The temperature of the leachate to which the sulfiding agent has been added (sulfidation temperature) is not particularly limited and may be, for example, at room temperature.

[0055] (Amount of sulfiding agent added) From the viewpoint of sufficiently removing copper contained in the leachate, the amount of sulfiding agent added is preferably 1.0 equivalent or more, more preferably 1.5 equivalents or more, and even more preferably 2.0 equivalents or more, relative to the amount of copper (Cu) contained in the leachate. On the other hand, if an excessive amount of sulfiding agent is added, the amount of sulfides (precipitates) of valuable elements (Ni, Co, etc.) will increase, and the amount of valuable elements that we want to remain in the resulting copper removal solution may decrease. From this viewpoint, the amount of sulfiding agent added is preferably 3.0 equivalents or less, more preferably 2.5 equivalents or less, and even more preferably 2.0 equivalents or less, relative to the amount of copper (Cu) contained in the leachate.

[0056] For example, when producing copper(II) sulfide (CuS) using 1.0 equivalent of sodium hydrogen sulfide (NaSH) as a sulfiding agent, 1 mol of sodium hydrogen sulfide (NaSH) is used for every 1 mol of copper (Cu) contained in the leachate.

[0057] 《Sulfidation pH》 When adding a sulfiding agent to the leachate to precipitate copper sulfide, if the pH of the leachate with the added sulfiding agent (sulfidation pH) is high, there is a possibility that the amount of valuable element sulfides (precipitates) that we want to retain in the copper removal solution will increase. For this reason, the sulfidation pH is preferably 3.0 or less, more preferably 2.0 or less, even more preferably 1.0 or less, and particularly preferably 0 (zero). The sulfidation pH can be adjusted, for example, by adding a pH adjusting agent to the leachate. The pH adjusting agent is not particularly limited, and examples include sulfuric acid and sodium hydroxide.

[0058] <Sulfidation Time> The time required for the copper contained in the leachate to react with the sulfidating agent to sulfide (sulfidation time) is preferably 0.1 hours or more, more preferably 0.2 hours or more, and even more preferably 0.3 hours or more. On the other hand, from the viewpoint of productivity, the sulfidation time is preferably 3.0 hours or less, more preferably 2.0 hours or less, and even more preferably 1.0 hour or less.

[0059] <Separation of copper sulfide and copper removal solution> As described later, it is preferable to separate the copper sulfide and the copper removal solution before adding the oxidizing agent to the copper removal solution. The separation method is not particularly limited, and known solid-liquid separation methods can be used.

[0060] <Addition of oxidizing agent (obtaining a solution of valuable elements)> Next, an oxidizing agent is added to the copper removal solution containing valuable elements (Ni, Co, Mn) and iron (Fe) to precipitate the impurity element iron (Fe) as iron hydroxide. In this way, a copper removal solution from which iron (Fe) has been selectively removed is obtained as a solution of valuable elements containing valuable elements (Ni, Co, Mn).

[0061] Figure 4 shows the potential-pH diagram (O) of iron (Fe) and nickel (Ni). ２ -H ２ It is an O system. In Figure 4, iron (Fe) - oxygen (O ２ ) - Water (H ２ Figure 4 shows the region on the potential-pH diagram of system O) where precipitates of iron (Fe) and nickel (Ni) oxides (hydroxides) form, taking solubility into account. Note that cobalt precipitates in a similar manner to nickel, so its illustration is omitted in Figure 4. As shown in Figure 4, in the region where the pH is between 3.0 and 7.0 and the oxidation-reduction potential is high, iron (Fe) precipitates selectively. Although not shown in Figure 4, in this region, iron precipitates as iron(III) oxide hydroxide (FeO(OH)). By utilizing this, by making the copper removal solution acidic to neutral and oxidizing, the iron (Fe) contained in the copper removal solution is precipitated as iron(III) oxide hydroxide and selectively removed. That is, a valuable element solution, which is a copper removal solution from which iron (Fe) has been removed, is obtained.

[0062] <Oxidizing Agent> Examples of oxidizing agents to be added to the copper removal solution include at least one oxidizing agent A selected from the group consisting of air and ozone; and at least one oxidizing agent B selected from the group consisting of hydrogen peroxide, hypochlorous acid, and potassium permanganate. Of these, air, hydrogen peroxide, and ozone are preferred because using hypochlorous acid and potassium permanganate may require complicated post-treatment for chlorine, potassium, manganese, etc.

[0063] (Amount of oxidizing agent added) From the viewpoint of sufficiently oxidizing the iron contained in the copper removal solution, the amount of oxidizing agent A (air, ozone), which is a gas, added is preferably 0.1 vvm or more, more preferably 0.3 vvm or more, and even more preferably 0.5 vvm or more, relative to the copper removal solution. On the other hand, the amount of oxidizing agent A added is preferably 5.0 vvm or less, more preferably 4.0 vvm or less, and even more preferably 3.0 vvm or less, relative to the copper removal solution.

[0064] The unit "vvm" represents the volume ratio of gas injected per minute relative to the liquid. For example, if the amount of oxidizing agent A added is 2vvm, then 2 liters of oxidizing agent A are injected per minute into 1 liter of copper removal solution.

[0065] For similar reasons, the amount of oxidizing agent B (hydrogen peroxide, hypochlorous acid, potassium permanganate) added is preferably 0.005% by volume or more, more preferably 0.015% by volume or more, even more preferably 0.050% by volume or more, and particularly preferably 0.100% by volume or more, relative to the copper removal solution. On the other hand, the amount of oxidizing agent B added is preferably 1.500% by volume or less, more preferably 1.000% by volume or less, even more preferably 0.500% by volume or less, and particularly preferably 0.300% by volume or less, relative to the copper removal solution.

[0066] <Oxidation Temperature> The inventors have found that using only the oxidizing agent described above may result in insufficient oxidation of the iron contained in the copper removal solution. Therefore, from the viewpoint of promoting oxidation, it is preferable to raise the temperature (oxidation temperature) of the copper removal solution to which the oxidizing agent has been added. Specifically, the oxidation temperature is preferably 10°C or higher, more preferably 30°C or higher, and even more preferably 50°C or higher. On the other hand, the oxidation temperature is preferably 90°C or lower, and more preferably 80°C or lower.

[0067] 《Oxidation pH》 When adding an oxidizing agent to a copper removal solution to precipitate iron hydroxide, if the pH of the copper removal solution with the oxidizing agent added (oxidation pH) is too low, precipitation may be difficult. For this reason, the oxidation pH is preferably 3.0 or higher, more preferably 3.7 or higher, even more preferably 4.0 or higher, and particularly preferably 4.5 or higher. On the other hand, if the oxidation pH is too high, the coprecipitation of valuable elements (such as Ni and Co) increases, and there is a concern that the amount of valuable elements to be retained in the resulting valuable element solution will decrease. For this reason, the oxidation pH is preferably 7.0 or lower, more preferably 6.0 or lower, and even more preferably 5.0 or lower. The oxidation pH can be adjusted, for example, by adding a pH adjusting agent to the copper removal solution. Examples of pH adjusting agents are not particularly limited, but include sulfuric acid and sodium hydroxide.

[0068] <Oxidation Time> The time required for the iron contained in the copper removal solution to react with the oxidizing agent (oxidation time) is preferably 0.3 hours or more, more preferably 0.5 hours or more, and even more preferably 1.0 hour or more. On the other hand, from the viewpoint of productivity, the oxidation time is preferably 3.0 hours or less, more preferably 2.0 hours or less, and even more preferably 1.5 hours or less.

[0069] 《Oxidizing Agents》 From the viewpoint of improving the reaction rate for forming iron hydroxide precipitates, oxidizing agents may be used in combination with the oxidizing agent described above. Examples of oxidizing agents include ferric oxide (Fe ２ O ３ At least one selected from the group consisting of ) and iron(III) oxide hydroxide (FeO(OH)), and the form of the oxidizing agent is preferably in powder form. The principle by which the reaction rate is improved by the oxidizing agent is catalytic action. Specifically, since the oxidizing agent tends to become negatively charged in aqueous solution (copper removal solution), Fe ２＋ It adsorbs ions, Fe ２＋ internal e － This weakens the connection with Fe ２＋ →Fe ３＋ +e － It is thought that the activation energy of this reaction (Fe oxidation reaction) is lowered, and the reaction is accelerated.

[0070] (Amount of oxidizing agent added) It is thought that the more oxidizing agent added, the larger the reaction surface area and the faster the Fe oxidation reaction. For this reason, the amount of oxidizing agent added is preferably 0.1 g / L or more, more preferably 0.5 g / L or more, and even more preferably 1.0 g / L or more, relative to the copper removal solution. On the other hand, if too much oxidizing agent is added, there is a concern that the coprecipitation of valuable elements (Ni, Co, etc.) will increase. For this reason, the amount of oxidizing agent added is preferably 40.0 g / L or less, more preferably 10.0 g / L or less, and even more preferably 5.0 g / L or less, relative to the copper removal solution.

[0071] (Particle size of oxidizing agent) If the particle size of the oxidizing agent is too small, the reaction surface area will be excessive, raising concerns about increased coprecipitation of valuable elements (Ni, Co, etc.). For this reason, the particle size of the oxidizing agent is preferably 0.1 μm or larger, more preferably 0.3 μm or larger, and even more preferably 0.5 μm or larger. On the other hand, if the particle size of the oxidizing agent is too large, the reaction surface area will be insufficient, and the desired effect may not be obtained. For this reason, the particle size of the oxidizing agent is preferably 3.0 μm or smaller, more preferably 2.0 μm or smaller, and even more preferably 1.0 μm or smaller.

[0072] <Separation of iron hydroxide and valuable element solution> It is preferable to separate the iron hydroxide and the valuable element solution. The separation method is not particularly limited, and known solid-liquid separation methods can be used. The valuable elements in the valuable element solution obtained in this way can be used, for example, as a positive electrode material for lithium-ion batteries.

[0073] <Obtaining Valuable Element Precipitate> Figure 1B is a flowchart showing an example of the process for producing the precursor. Next, the valuable element solution obtained by the valuable element recovery method described above, a complexing agent, and an alkaline aqueous solution are introduced (dropwise) into the reaction vessel liquid, and a precipitate containing valuable elements (valuable element precipitate) is obtained by the so-called coprecipitation method, as shown in Figure 1B. Specifically, the valuable element precipitate is, for example, at least one selected from the group consisting of a composite hydroxide containing valuable elements and a composite oxide containing valuable elements. By using the coprecipitation method, the valuable elements (Ni, Co, Mn) can be uniformly dispersed at the atomic level. The obtained valuable element precipitate is filtered from the reaction vessel liquid, and washed with water and dried as necessary to obtain a cathode material precursor.

[0074] When obtaining a precipitate of valuable elements, an aqueous solution of the raw materials may be used instead of a solution of valuable elements. The aqueous solution of the raw materials is prepared by adding at least one selected from the group consisting of a nickel source, a cobalt source, and a manganese source to a solution of valuable elements. In the aqueous solution of the raw materials, the molar ratio of nickel content, cobalt content, and manganese content (Ni / Co / Mn) is preferably 1 / 1 / 1, 5 / 2 / 3, 6 / 2 / 2, or 8 / 1 / 1.

[0075] Nickel sources include nickel salts such as nickel sulfate, nickel carbonate, nickel nitrate, nickel acetate, and nickel chloride, and nickel sulfate (NiSO4). ４ ) is preferred. The cobalt source is, for example, a cobalt salt such as cobalt sulfate, cobalt carbonate, cobalt nitrate, cobalt acetate, or cobalt chloride, and cobalt sulfate (CoSO4) ４ ) is preferred. Manganese sources are, for example, manganese salts such as manganese sulfate, manganese carbonate, manganese nitrate, manganese acetate, and manganese chloride, and manganese sulfate (MnSO4) ４ ) is preferred. The nickel source, cobalt source, and manganese source are each preferably used in the form of aqueous solutions. In each aqueous solution, the concentrations (contents) of the nickel source, cobalt source, and manganese source are each preferably adjusted to the molar ratios described above.

[0076] The pH of the raw material aqueous solution is preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less. Furthermore, the pH of the raw material aqueous solution is, for example, 1 or more, and preferably 2 or more.

[0077] The dropping rate of the valuable element solution (raw material aqueous solution) is preferably 1.0 mL / min or more, and more preferably 2.5 mL / min or more. Furthermore, the dropping rate of the valuable element solution (raw material aqueous solution) is preferably 7.0 mL / min or less, and more preferably 5.5 mL / min or less.

[0078] Examples of complexing agents include ammonia (NH₃). ３ An ammonium source is selected from the group consisting of ammonium sulfate and ammonium salts. Examples of ammonium salts include ammonium sulfate, ammonium chloride, ammonium nitrate, and ammonium carbonate. Ammonia is preferred as the complexing agent that is the ammonium source. The ammonium source is preferably used in the form of an aqueous solution. In the aqueous solution, the concentration (content) of the ammonium source is preferably adjusted to the molar ratio described later.

[0079] The dropping rate of the complexing agent is preferably 0.1 mL / min or more, and more preferably 0.3 mL / min or more. Furthermore, the dropping rate of the complexing agent is preferably 1.0 mL / min or less, and more preferably 0.8 mL / min or less.

[0080] The molar ratio (NH₄) of the ammonium source (complexing agent) content relative to the total content of valuable elements (Ni, Co, Mn) in the raw material aqueous solution. ４ The molar ratio ( / (Ni + Co + Mn)) is preferably greater than 0, more preferably 2 or greater, and even more preferably 4 or greater. ４ The ratio of (Ni + Co + Mn) is preferably 20 or less, more preferably 15 or less, and even more preferably 12 or less.

[0081] As the alkaline aqueous solution, an aqueous solution of sodium hydroxide (NaOH) is preferred.

[0082] The reaction vessel liquid is the liquid inside the reaction vessel, and is an aqueous solution prepared, for example, by adding an alkaline aqueous solution such as an aqueous sodium hydroxide solution to pure water. The pH of the reaction vessel liquid is preferably 9.0 or higher, and more preferably 9.5 or higher. Furthermore, the pH of the reaction vessel liquid is preferably 12.0 or lower, and more preferably 11.5 or lower. The temperature of the reaction vessel liquid is preferably 30°C or higher, and more preferably 35°C or higher. Furthermore, the temperature of the reaction vessel liquid is preferably 60°C or lower, and more preferably 45°C or lower.

[0083] When obtaining the precipitate, it is preferable to stir the reaction vessel liquid using a stirring rod or the like. If the stirring speed (rotation speed of the stirring blade) is too slow, a homogeneous precipitate of valuable elements may not be obtained. On the other hand, if the stirring speed is too fast, the complexing agent (e.g., aqueous ammonia solution) may be scattered during stirring, destabilizing the reaction between the complexing agent and the aqueous raw material solution, and again, a homogeneous precipitate of valuable elements may not be obtained. In these cases, the precursor obtained by drying the precipitate of valuable elements does not become uniformly spheroidal, making it difficult to obtain a high tap density. Therefore, from the viewpoint of obtaining a high tap density, the stirring speed is, for example, 150 to 550 rpm, preferably 200 to 500 rpm, more preferably 250 to 450 rpm, and even more preferably 300 to 400 rpm. Note that the stirring speed may be changed during the process. For example, it may be possible to start with a slow stirring speed and change to a faster, more suitable stirring speed as the volume of liquid in the reaction vessel increases.

[0084] It is preferable to control the pH of the reaction vessel solution within the above range by adding an alkaline aqueous solution to the reaction vessel solution dropwise while adding the valuable element solution (aqueous solution of raw materials) and the complexing agent.

[0085] The obtained valuable element precipitate is preferably filtered from the reaction vessel liquid (solid-liquid separation), washed with water, and then dried. The drying temperature is preferably 90°C or higher, more preferably 95°C or higher. Furthermore, the drying temperature is preferably 120°C or lower, more preferably 110°C or lower. The drying time is preferably 5 hours or more, more preferably 8 hours or more. Furthermore, the drying time is preferably 15 hours or less, more preferably 12 hours or less.

[0086] As described above, for example, a precursor for the cathode material can be obtained by washing and drying the precipitate of valuable elements. In the precursor, the molar ratio of nickel content to the total content of valuable elements (Ni, Co, Mn) (Ni / (Ni+Co+Mn)) is preferably 0.3 or higher, and more preferably 0.4 or higher. Furthermore, this molar ratio (Ni / (Ni+Co+Mn)) is preferably 1.0 or lower, and more preferably 0.8 or lower.

[0087] The tap density of the precursor is 0.8 g / cm³. ３ The above is preferable, 1.0 g / cm³ ３ The above is more preferable, specifically 1.2 g / cm³. ３ The above is even more preferable. Furthermore, the tap density of the precursor is 1.8 g / cm³. ３ It may also be less than 1.5 g / cm³. ３ The following may also be true: Tap density is per 100 cm³ of standing volume. ３ The sample is placed in the container, and using a tapping device, it is tapped until the volume of the sample no longer decreases. Then, the mass of the sample (in grams) is measured against the volume of the sample (in centimeters). ３ This can be calculated by dividing by (the same applies below).

[0088] Precursor particle size D １０ The particle size D of the precursor is preferably 3.0 μm or larger, and more preferably 4.0 μm or larger. １０ The particle size of the precursor is preferably 10.0 μm or less, and more preferably 8.0 μm or less. ５０ The particle size D of the precursor is preferably 8.0 μm or larger, and more preferably 9.0 μm or larger. ５０ The particle size of the precursor is preferably 16.0 μm or less, and more preferably 14.0 μm or less. ９０ The particle size D of the precursor is preferably 12.0 μm or larger, and more preferably 14.0 μm or larger. ９０ Particle size D is preferably 24.0 μm or less, and more preferably 22.0 μm or less. １０ , particle size D ５０ and particle size D ９０ These are the particle sizes at which the cumulative frequency of the particle size distribution determined by laser diffraction and scattering methods accounts for 10%, 50%, and 90% of the volume, respectively (the same applies hereafter).

[0089] <Obtaining the Calcined Product> Figure 1B is a flowchart showing an example of the process for manufacturing a positive electrode material. Next, the obtained precursor is mixed with a lithium-containing compound, and the resulting mixture is calcined. In this way, as shown in Figure 1B, a calcined product containing valuable elements and lithium (a composite oxide containing valuable elements and lithium) is obtained. By appropriately crushing the obtained calcined product, a positive electrode material for use in lithium-ion batteries is obtained. The positive electrode material is also called a positive electrode active material.

[0090] The resulting cathode material is a composite oxide containing valuable elements (Ni, Co, Mn) and lithium (Li), and may further contain at least one element A selected from the group consisting of aluminum (Al), silicon (Si), titanium (Ti), zirconium (Zr), calcium (Ca), potassium (K), barium (Ba), strontium (Sr), and sulfur (S).

[0091] The following describes each step in the manufacturing method of the cathode material in more detail.

[0092] First, the precursor and the lithium-containing compound are mixed to obtain a mixture. At this time, the molar ratio (Li / (Ni+Co+Mn)) of the lithium-constituted content of the lithium-containing compound to the sum of the nickel-constituted content of the precursor, the cobalt-constituted content of the precursor, and the manganese-constituted content of the precursor is preferably greater than 1.03, and more preferably 1.04 or greater. Furthermore, this molar ratio (Li / (Ni+Co+Mn)) is preferably less than 1.10, and more preferably 1.08 or less.

[0093] Suitable lithium-containing compounds include, for example, at least one selected from the group consisting of lithium hydroxide and lithium carbonate.

[0094] If the resulting cathode material contains element A as described above, a compound containing element A (hereinafter also referred to as "A-containing compound") may be further mixed into the mixture. Examples of A-containing compounds include, but are not limited to, hydroxides, oxides, chlorides, and salts of element A (e.g., sulfates, carbonates, nitrates, etc.). The amount of A-containing compound mixed can be adjusted as appropriate according to the desired composition.

[0095] Next, the mixture obtained by mixing is fired to obtain a fired product. At this time, it is preferable to pre-fire the mixture and then fire it. The firing temperature for pre-fire is preferably 400°C or higher, and more preferably 500°C or higher. Furthermore, the firing temperature for pre-fire is preferably 700°C or lower, and more preferably 680°C or lower. The firing temperature for the main firing is preferably 800°C or higher, and more preferably 900°C or higher. Furthermore, the firing temperature for the main firing is preferably 1000°C or lower, and more preferably 980°C or lower.

[0096] The atmosphere for calcination can be an oxidizing atmosphere (e.g., an atmospheric atmosphere) or a non-oxidizing atmosphere. An example of a non-oxidizing atmosphere is an atmosphere with an oxygen concentration of 10% by volume or less, and a specific example of this is a nitrogen atmosphere. The atmosphere for the final calcination can be an oxidizing atmosphere (e.g., an atmospheric atmosphere) or a non-oxidizing atmosphere.

[0097] The firing time for the preliminary firing is preferably 2 hours or more, and more preferably 3 hours or more. Furthermore, the firing time for the preliminary firing is preferably 48 hours or less, and more preferably 12 hours or less. The firing time for the main firing is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more. Furthermore, the firing time for the main firing is preferably 30 hours or less, more preferably 15 hours or less, and even more preferably 8 hours or less.

[0098] The calcined material may be washed with water. Washing with water removes any excess lithium that has not penetrated the interior. After washing, it is dried as appropriate. The calcined material may be further calcined at a temperature between 200°C and 800°C, or crushed. In this way, a positive electrode material for use in lithium-ion batteries is obtained.

[0099] The tap density of the positive electrode material is 1.0 g / cm³.３ The above is preferable, and 1.5 g / cm ３ or more is more preferable. Further, the tap density of the positive electrode material is 3.5 g / cm ３ or less may be used, and 3.0 g / cm ３ or less may be used.

[0100] The particle size D of the positive electrode material １０ is preferably 3.0 μm or more, and more preferably 4.0 μm or more. Further, the particle size D of the positive electrode material １０ is preferably 10.0 μm or less, and more preferably 8.0 μm or less. The particle size D of the positive electrode material ５０ is preferably 8.0 μm or more, and more preferably 9.0 μm or more. Further, the particle size D of the positive electrode material ５０ is preferably 16.0 μm or less, and more preferably 14.0 μm or less. The particle size D of the positive electrode material ９０ is preferably 12.0 μm or more, and more preferably 14.0 μm or more. Further, the particle size D of the positive electrode material ９０ is preferably 24.0 μm or less, and more preferably 22.0 μm or less.

[0101] A lithium ion battery generally includes a positive electrode, a negative electrode, and an ion conduction medium (for example, an electrolyte such as a non-aqueous electrolyte) that is interposed between the positive electrode and the negative electrode to conduct lithium ions, and may further include a separator. Using the obtained positive electrode material described above, a positive electrode is manufactured by a known method, and using the manufactured positive electrode, a lithium ion battery is manufactured. The manufactured lithium ion battery is excellent in discharge capacity and cycle characteristics.

[0102] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples described below.

[0103] [Test A] <Preparation of Positive Electrode Material> A positive electrode material of a used lithium ion battery was prepared. Specifically, pretreatment such as decomposition, discharge, and removal of the electrolyte was performed on the used lithium ion battery to separate the positive electrode material (oxide). The composition ratio (molar ratio) of nickel (Ni), cobalt (Co), and manganese (Mn) in the positive electrode material is shown in Table 1 below. The positive electrode material further contained copper (Cu) and iron (Fe) as impurity elements.

[0104]

[0105] <Preparation of Reducing Agents> Powders of graphite (C), metallic aluminum (Al), and FeSi were prepared as reducing agents. Furthermore, as additional reducing agents, powders of metallic iron (Fe) obtained by atomization, ferrous oxide (FeO), dust generated in the steelmaking process, and scale generated in the steelmaking process were prepared. The composition of the dust and scale is shown in Table 2 below. In Table 2 below, "M.Fe" indicates the amount of metallic Fe.

[0106]

[0107] <Addition of reducing agent and heating of mixed oxide> Place the prepared cathode material into an electric furnace with a heat size of 150 kg, and then add one of the reducing agents mentioned above, and flux (CaO, SiO ２ A mixed oxide was obtained by adding ( ). The obtained mixed oxide was heated under an Ar atmosphere. In this way, the cathode material was reduced. The heating time was 3 hours in all cases. The type of reducing agent used, the amount added (in equivalent units), and the heating temperature (in °C) are shown in Table 3 below.

[0108] The reduction rates (in mass%) are shown in Table 3 below. The reduction rate is the ratio of the amount of metal actually obtained to the amount of metal theoretically produced by the reduction reaction. As shown in Table 3 below, high reduction rates were observed in all examples. Relatively high reduction rates were also obtained when dust or scale was used as the reducing agent.

[0109] CO2 per 1 ton of positive electrode material ２ Amount generated (unit: kg-CO2) ２ The values ​​for CO2 / t are shown in Table 3 below. As shown in Table 3 below, the CO2 values ​​when metallic iron or iron oxide is used as a reducing agent are shown. ２ The amount of waste generated was lower in all cases compared to when graphite was used as a reducing agent.

[0110] The cost required for reduction per kilogram of cathode material was calculated relatively, using the case where graphite was used as the reducing agent as a baseline. The results are shown in Table 3 below. As shown in Table 3 below, the cost increased when Al or FeSi was used as the reducing agent, while the cost decreased when metallic iron or iron oxide was used.

[0111] Thus, by using metallic iron or iron oxide as a reducing agent, a high reduction rate can be maintained while reducing CO ２ We were able to reduce the amount of waste generated and lower costs.

[0112]

[0113] <Powdering of Metals> The composition of the metals and slag produced by the reduction of the cathode material was determined. Of the metals produced by the reduction of the cathode material, those having the composition shown in Table 4 below were powdered using a vibratory mill to obtain metal powder. The particle size of the obtained metal powder was 1100 μm.

[0114] <Contact between metal and acid solution> An acid solution was prepared by adding 7.0 volume% hydrogen peroxide as an oxidizing agent to sulfuric acid (concentration: 2.0 mol / L). A metal (metal powder) having the composition shown in Table 4 below was brought into contact with the prepared acid solution at a solid-liquid ratio of 1 / 10 (metal / acid solution) (contact time: 1.0 hour). Specifically, the metal powder was immersed in the acid solution. In this way, a leachate and leachate residue were obtained and separated. The concentration of each element in the leachate was determined using XRF (X-ray fluorescence) analysis, and the leaching rate (unit: mass%) of each element from the metal into the leachate was calculated. The results are shown in Table 4 below. As shown in Table 4 below, the leaching rate for each element was 100 mass%, indicating that all elements were successfully leached from the metal into the leachate.

[0115]

[0116] <Addition of Sulfidating Agent> The content of each element in the obtained leachate (unit: g / L) is shown in Table 5 below. Sodium hydrogen sulfide (NaSH) was added to the obtained leachate as a sulfidating agent and stirred at room temperature (25°C). The amount of sulfidating agent (sodium hydrogen sulfide) added was 2.0 equivalents relative to the Cu contained in the leachate. The pH of the leachate with the added sulfidating agent (sulfidation pH) was adjusted to 0 (zero) using sulfuric acid and sodium hydroxide as pH adjusters. In this way, the copper (Cu) contained in the leachate was reacted with the sulfidating agent and sulfidized (sulfidation time: 20 minutes), and precipitated as copper sulfide (copper(II) sulfide). Subsequently, the copper sulfide and the copper removal solution, which is the leachate from which copper has been removed, were separated. The content of each element in the copper removal solution (unit: g / L) was determined by ICP-AES (inductively coupled plasma atomic emission spectrometry). The results are shown in Table 5 below. Furthermore, for each element, the ratio of its content in the copper removal solution to its content in the leachate was determined as the residual rate a (unit: mass%). The results are shown in Table 5 below. As shown in Table 5 below, the Cu content in the copper removal solution is very low, indicating that Cu was removed from the leachate with very high efficiency.

[0117] <Addition of Oxidizing Agent> Next, the copper removal solution was diluted with water. The content of each element in the diluted copper removal solution (unit: g / L) is shown in Table 5 below. The reason for dilution was that in preliminary experiments, when an oxidizing agent was added to a model solution having a similar composition to the copper removal solution shown in Table 5 below, excessive precipitation occurred, making stirring impossible in some cases. Hydrogen peroxide was added as an oxidizing agent to the diluted copper removal solution and stirred. The amount of oxidizing agent (hydrogen peroxide) added was 0.020 volume% relative to the diluted copper removal solution. The pH (oxidation pH) of the copper removal solution with the added oxidizing agent was adjusted to 4.5 using sulfuric acid and sodium hydroxide as pH adjusters. The temperature (oxidation temperature) of the copper removal solution with the added oxidizing agent was set to 70°C and maintained at that temperature. In this way, the iron (Fe) contained in the copper removal solution was reacted with the oxidizing agent and oxidized (oxidation time: 1.0 hour), and precipitated as iron hydroxide (iron(III) oxide hydroxide). Subsequently, the iron hydroxide and the valuable element solution, which was the copper removal solution from which iron had been removed, were separated. The content of each element in the valuable element solution (unit: g / L) was determined by ICP-AES. The results are shown in Table 5 below. Furthermore, for each element, the ratio of the content in the valuable element solution to the content in the copper removal solution (diluted) was determined as the residual rate b (unit: mass%). The results are shown in Table 5 below. As shown in Table 5 below, the Fe content in the valuable element solution is very low, indicating that Fe was removed from the copper removal solution with very high efficiency.

[0118] Furthermore, for each element, the final residual rate in the valuable element solution was determined as the overall residual rate (unit: mass%) from residual rates a and b. The results are shown in Table 5 below. From the results shown in Table 5 below, it can be seen that by performing a dry treatment, then pulverizing the metal obtained by the dry treatment, and then performing a wet treatment, the valuable elements (Ni, Co, Mn) could be recovered with very high purity.

[0119]

[0120] [Test B] <Preparation of positive electrode material to metal pulverization> The preparation of the positive electrode material and the pulverization of the metal are the same as in Test A, so the explanation will be omitted.

[0121] <Contact between metal and acid solution> Multiple acid solutions were prepared by adding an oxidizing agent for the acid solution (hydrogen peroxide) to sulfuric acid (concentration: 2.0 mol / L) in the amounts (unit: volume%) shown in Table 6 below. Except for changing the amount of oxidizing agent added, the metal (metal powder) was brought into contact with the acid solution in the same manner as in Test A described above to obtain a leachate. Furthermore, the leaching rate (unit: mass%) of each element from the metal into the leachate was calculated in the same manner as in Test A described above. The results are shown in Table 6 below. As shown in Table 6 below, the leaching rate increased as the amount of oxidizing agent added for the acid solution increased. It was found that an amount of oxidizing agent for the acid solution (hydrogen peroxide) of 6.9 volume% or more is suitable for sufficiently leaching valuable metals (Ni, Co, Mn). However, when the amount added exceeds 6.9 volume%, the leaching rate plateaus. Therefore, from a cost perspective, it was found that within the scope of this embodiment, 6.9% by volume is a suitable amount of oxidizing agent (hydrogen peroxide) for the acid solution.

[0122]

[0123] <Addition of Sulfidating Agent> Sodium hydrogen sulfide (NaSH) was added as a sulfidating agent to the leachate shown in Table 5 above, in the amount (unit: equivalent) shown in Table 7 below, and the mixture was stirred. At this time, the sulfidation pH was adjusted to the value shown in Table 7 below. Except for changing the amount of sulfidating agent and the sulfidation pH, the copper contained in the leachate was precipitated as copper sulfide in the same manner as in Test A described above to obtain a copper removal solution. Furthermore, the Cu content (unit: mg / L), Ni residue rate (unit: mass%), and Co residue rate (unit: mass%) in the obtained copper removal solution were determined in the same manner as in Test A described above. The results are shown in Table 7 below. As shown in Table 7 below, in order to sufficiently remove copper, it is preferable to add 2.0 equivalents or more of sulfidating agent relative to the copper, but it was found that the Ni residue rate and Co residue rate decrease as the amount of sulfidating agent added increases. Furthermore, as shown in Table 7 below, as the sulfidation pH increased, copper removal became insufficient, and the residual rates of Ni and Co tended to decrease. From the above, it was found that within the scope of this embodiment, an amount of sulfidating agent added of 2.0 equivalents and a sulfidation pH of 0 (zero) were preferable.

[0124]

[0125] <Addition of Oxidizing Agent> First, the copper removal solution obtained in Test Example 7-4 of Table 7 above was diluted 5-fold. Next, hydrogen peroxide as an oxidizing agent was added to the copper removal solution (diluted) at the addition amounts (unit: volume %) shown in Table 8 below, and the mixture was stirred. At this time, the oxidation pH and oxidation temperature (unit: °C) were adjusted to the values shown in Table 8 below. Except for changing the addition amount of the oxidizing agent, oxidation pH, and oxidation temperature, iron contained in the copper removal solution was precipitated as iron hydroxide in the same manner as in Test A described above to obtain a valuable element solution. Note that no oxidation aid was used in both Test A and Test B. Further, in the same manner as in Test A described above, the Fe content (unit: mg / L) in the obtained valuable element solution, as well as the Ni residual rate (unit: mass %) and Co residual rate (unit: mass %) were determined. The results are shown in Table 8 below. As shown in Table 8 below, it was found that in order to sufficiently remove iron, it is preferable to set the oxidation pH to 6.0, or to set the oxidation pH to 4.5 or higher and add an oxidizing agent. Also, as shown in Table 8 below, as the oxidation pH increases, while iron is efficiently removed, the Ni residual rate and Co residual rate tend to decrease. From the above, it was found that within the scope of this example, the addition amount of the oxidizing agent (hydrogen peroxide) is preferably 0.030 volume %, and the oxidation pH is in the range of 4.5 to 5.0.

[0126]

[0127] [Test C] <Production of Precursors> Precursors 1 to 5 were produced as follows.

[0128] 《Precursor 1》 To the valuable element solution of Test Example 8-4 described in Table 8 above, nickel sulfate (NiSO ４ ) as a nickel source, cobalt sulfate (CoSO ４ ) as a cobalt source, and manganese sulfate (MnSO ４) was added. In this way, a raw material aqueous solution was prepared in which the content of valuable elements (Ni, Co, Mn) was 1.25 mol / L and the Ni / Co / Mn (molar ratio) was 6 / 2 / 2. 0.35 L of pure water, sodium hydroxide aqueous solution, and ammonia aqueous solution were added to the reaction vessel to prepare a reaction vessel solution with a pH of 11.0. The raw material aqueous solution, ammonia aqueous solution as a complexing agent (concentration: 28 mass%), and sodium hydroxide aqueous solution as an alkaline aqueous solution (concentration: 48 mass%) were added dropwise to the reaction vessel solution to obtain a precipitate (precipitate of valuable elements). More specifically, the raw material aqueous solution was added dropwise to the reaction vessel solution at a rate of 4.0 mL / min while the complexing agent was added dropwise at a rate of 0.8 mL / min. During the addition of the raw material aqueous solution and the complexing agent, the alkaline aqueous solution was also added dropwise to control the pH of the reaction vessel solution to 11.0. During this time, the reaction vessel liquid was stirred with a stirring blade, and the temperature of the reaction vessel liquid was controlled to 40°C. The stirring speed (rotation speed of the stirring blade) was initially set to 200 rpm, but was increased to 350 rpm as the volume of liquid in the reaction vessel increased. Next, the obtained precipitate was filtered and washed with water, and then dried in a dryer at 100°C for 10 hours. Thus, precursor 1 was obtained.

[0129] Precursor 2 was obtained in the same manner as Precursor 1, except that the composition of the raw material aqueous solution was changed to Ni / Co / Mn (molar ratio) = 5 / 2 / 3.

[0130] Precursor 3 was obtained in the same manner as Precursor 1, except that the composition of the raw material aqueous solution was changed to Ni / Co / Mn (molar ratio) = 1 / 1 / 1.

[0131] Precursor 4 was obtained in the same manner as Precursor 1, except that the dropping rate of the complexing agent was changed to 0.6 mL / min.

[0132] <Precursor 5> Without using the valuable element solutions listed in Table 8 above, a raw material aqueous solution with a Ni / Co / Mn (molar ratio) of 6 / 2 / 2 was prepared using nickel sulfate, cobalt sulfate, and manganese sulfate as reagents. Otherwise, Precursor 5 was obtained in the same manner as Precursor 1.

[0133] Precursor 6 was obtained in the same manner as Precursor 1, except that the stirring speed was kept at 200 rpm from the beginning until the end of stirring (it was not increased to 350 rpm).

[0134] Precursor 7 was obtained in the same manner as Precursor 1, except that the stirring speed was set to 500 rpm from the beginning until the end of stirring.

[0135] <Characteristics of Precursors> For each of the obtained precursors 1 to 5, the tap density and particle size (D) were determined by the method described above. １０ , D ５０ and D ９０ The following was calculated. The results are shown in Table 9 below.

[0136]

[0137] As shown in Table 9 above, precursors 1 to 5 showed higher tap densities compared to precursor 6, which was stirred at a stirring speed of 200 rpm, and precursor 7, which was stirred at a stirring speed of 500 rpm.

[0138] <Manufacturing of Cathode Materials> Cathode materials 1 to 10 were manufactured using the obtained precursors 1 to 5 as follows.

[0139] 《Cathode Material 1》 A mixture was obtained by mixing precursor 1 with lithium hydroxide as a lithium-containing compound. The molar ratio (Li / (Ni+Co+Mn)) during mixing was 1.075. The obtained mixture was calcined to obtain a calcined product. More specifically, the mixture was calcined at 650°C for 8 hours in an air atmosphere, and then calcined at 950°C for 3 hours in an air atmosphere. The obtained calcined product was roughly crushed using a mortar. The calcined product was not washed with water. Thus, cathode material 1 was obtained.

[0140] Cathode materials 2 to 5 were obtained in the same manner as for cathode material 1, except that precursor materials 2 to 5 were used for each.

[0141] Cathode material 6 was obtained in the same manner as cathode material 1, except that a mixture was obtained by mixing precursor 1 with lithium carbonate as a lithium-containing compound.

[0142] Cathode materials 7 to 10 were obtained in the same manner as for cathode material 6, except that precursors 2 to cathode material 5 were used for each.

[0143] <Characteristics and Evaluation of Cathode Materials> For the obtained cathode materials 1 to 10, the tap density and particle size (D) were determined by the method described above. １０ , D ５０ and D ９０ The following was determined. Furthermore, the charging capacity, discharging capacity, cycle characteristics, and discharge capacity after the cycle test were determined as follows. The results are shown in Table 10 below.

[0144] 《Test 1: Charging and Discharging Capacity》 A mixture was obtained by adding N-methyl-2-pyrrolidone to positive electrode material (90% by mass), acetylene black (5% by mass), and polyvinylidene fluoride (5% by mass) and kneading. The obtained mixture was applied to an aluminum current collector to form a coating film. The laminate of the coating film and the aluminum current collector was pressed using a roll press to achieve a density of 3.1 to 3.3 g / cm³. ３ The laminate was pressurized to the specified range. A 14 mm diameter disc was punched out from the pressurized laminate. The punched disc was vacuum-dried at 150°C for 10 hours. The vacuum-dried disc was used as the positive electrode. A lithium metal sheet was used as the negative electrode. A porous polyethylene membrane (thickness: 16 μm, manufactured by Seigen Materials Co., Ltd.) was used as the separator. 1 mole of LiPF was added to 1 L of a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) with a volume ratio (EC / DMC) of 1 / 1. ６ A non-aqueous electrolyte was obtained by dissolving the material. Using these positive electrode, negative electrode, separator, and non-aqueous electrolyte, a lithium-ion battery (test cell) for evaluation was fabricated in a glove box purged with argon. The fabricated test cell was charged and discharged at 25°C. Specifically, first, it was charged with a constant current of 0.05C, and when the voltage reached 4.3V, it was switched to constant voltage charging, and charging was terminated when the charging current dropped to 0.01C. Next, it was discharged with a constant current of 0.05C until the voltage reached 2.75V. In this way, the charging capacity (unit: mAh / g) and discharging capacity (unit: mAh / g) were determined.

[0145] 《Test 2 (Cycle Test): Cycle Characteristics》 First, the negative electrode was prepared. Specifically, pure water was added to artificial graphite (96.5% by mass), acetylene black (0.5% by mass), styrene-butadiene rubber (2% by mass), and carboxymethylcellulose (1% by mass) and kneaded to obtain a mixture. The obtained mixture was applied to a copper current collector to form a coating film. The laminate of the coating film and the copper current collector was pressed using a roll press to a density of 1.3 to 1.5 g / cm³. ３ The laminate was pressurized to maintain a certain range. A disc punched out from the pressurized laminate was used as the negative electrode. Except for the negative electrode, a lithium-ion battery (test cell) for evaluation was fabricated in the same manner as in Test 1 above. Using the fabricated test cell, 500 charge-discharge cycles (500 cycles) were repeated at 60°C with a current of 1.0C in the voltage range of 2.75 to 4.2V. From the obtained discharge capacity (unit: mAh / g), the cycle characteristics (unit: %) were determined using the following formula: Cycle characteristics = (Discharge capacity of the 500th cycle / Discharge capacity of the 1st cycle) × 100

[0146] 《Test 3: Discharge Capacity After Cycle Testing》 The positive electrode was removed from the test cell after the cycle test. Except for the removed positive electrode, a lithium-ion battery (test cell) for evaluation was prepared in the same manner as in Test 1 above. Using the prepared test cell, the discharge capacity (unit: mAh / g) was determined by charging and discharging in the same manner as in Test 1 above.

[0147]

[0148] As shown in Table 10 above, cathode materials 1 to 4, which use precursors 1 to 4 obtained using a valuable element solution, exhibited equivalent charging capacity, discharging capacity, cycle characteristics, and discharge capacity after cycle testing compared to cathode material 5, which did not use a valuable element solution. Furthermore, cathode materials 6 to 9, which use precursors 1 to 4 obtained using a valuable element solution, exhibited equivalent charging capacity, discharging capacity, cycle characteristics, and discharge capacity after cycle testing compared to cathode material 10, which did not use a valuable element solution.

Claims

1. A method for producing a precursor for a positive electrode material used in a lithium-ion battery, comprising: adding a reducing agent containing at least one element selected from the group consisting of metallic iron and iron oxide to an oxide containing at least one valuable element selected from the group consisting of nickel, cobalt and manganese, and impurity elements consisting of copper and iron, to obtain a mixed oxide; reducing the oxide by heating the mixed oxide to obtain a metal; contacting the metal with an acid solution to obtain a leachate containing the valuable element and the impurity element; adding a sulfidizing agent to the leachate to precipitate copper as copper sulfide, thereby obtaining the leachate from which copper has been removed as a copper removal solution; adding an oxidizing agent to the copper removal solution to precipitate iron as iron hydroxide, thereby obtaining the copper removal solution from which iron has been removed as a valuable element solution containing the valuable element; and introducing the valuable element solution, a complexing agent and an alkaline aqueous solution into a reaction vessel to obtain a precipitate containing the valuable element.

2. The method for producing the precursor according to claim 1, wherein the oxide is obtained from a waste lithium-ion battery.

3. A method for producing a precursor according to claim 1 or 2, wherein the metal is powdered and then brought into contact with the acid solution.

4. A method for producing a precursor according to any one of claims 1 to 3, wherein the iron oxide is ferrous oxide.

5. A method for producing a precursor according to any one of claims 1 to 4, wherein the temperature at which the mixed oxide is heated is 1450°C or higher.

6. A method for producing a precursor according to any one of claims 1 to 5, wherein the metal obtained by heating the mixed oxide contains the valuable element and the impurity element.

7. The method for producing a precursor according to any one of claims 1 to 6, wherein the acid solution contains an acid and an oxidizing agent for the acid solution, and the content of the oxidizing agent for the acid solution is 0.5% by volume or more relative to the acid.

8. The method for producing a precursor according to claim 7, wherein the oxidizing agent for the acid solution is hydrogen peroxide.

9. A method for producing a precursor according to any one of claims 1 to 8, wherein the amount of sulfiding agent added is 1.0 equivalent or more relative to the copper contained in the leachate, and when precipitating the copper sulfide, the pH of the leachate to which the sulfiding agent has been added is 3.0 or less.

10. A method for producing a precursor according to any one of claims 1 to 9, wherein the oxidizing agent is at least one oxidizing agent A selected from the group consisting of air and ozone, or at least one oxidizing agent B selected from the group consisting of hydrogen peroxide, hypochlorous acid and potassium permanganate, the amount of oxidizing agent A added is 0.1 vvm or more relative to the copper removal solution, the amount of oxidizing agent B added is 0.005 volume% or more relative to the copper removal solution, and when precipitation of iron hydroxide, the pH of the copper removal solution to which the oxidizing agent has been added is 3.0 or more and 7.0 or less.

11. The method for producing a precursor according to claim 10, wherein the temperature of the copper removal solution to which the oxidizing agent has been added is 10°C or higher.

12. The method for producing a precursor according to any one of claims 1 to 11, wherein the reducing agent is at least one selected from the group consisting of dust, scale, sludge, and scrap.

13. A method for producing a precursor according to any one of claims 1 to 12, wherein the alkaline aqueous solution is an aqueous solution of sodium hydroxide, and the complexing agent is at least one ammonium source selected from the group consisting of ammonia and ammonium salts.

14. A method for producing a positive electrode material for use in a lithium-ion battery, comprising: mixing a precursor obtained by a method for producing a precursor described in any one of claims 1 to 13 with a lithium-containing compound; and calcining the resulting mixture to obtain a calcined product containing the valuable element and lithium.

15. The method for producing a cathode material according to claim 14, wherein the lithium-containing compound is at least one selected from the group consisting of lithium hydroxide and lithium carbonate.

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